ASTM E18-22

Standard Test Methods for Rockwell Hardness of Metallic Materials

SIGNIFICANCE AND USE
4.1 The Rockwell hardness test is an empirical indentation hardness test that can provide useful information about metallic materials. This information may correlate to tensile strength, wear resistance, ductility, and other physical characteristics of metallic materials, and may be useful in quality control and selection of materials.  
4.2 Rockwell hardness tests are considered satisfactory for acceptance testing of commercial shipments, and have been used extensively in industry for this purpose.  
4.3 Rockwell hardness testing at a specific location on a part may not represent the physical characteristics of the whole part or end product.  
4.4 Adherence to this standard test method provides traceability to national Rockwell hardness standards except as stated otherwise.
SCOPE
1.1 These test methods cover the determination of the Rockwell hardness and the Rockwell superficial hardness of metallic materials by the Rockwell indentation hardness principle. This standard provides the requirements for Rockwell hardness machines and the procedures for performing Rockwell hardness tests.  
1.2 This test method includes requirements for the use of portable Rockwell hardness testing machines that measure Rockwell hardness by the Rockwell hardness test principle and can meet all the requirements of this test method, including the direct and indirect verifications of the testing machine. Portable Rockwell hardness testing machines that cannot meet the direct verification requirements and can only be verified by indirect verification requirements are covered in Test Method E110.  
1.3 This standard includes additional requirements in the following annexes:    
Verification of Rockwell Hardness Testing Machines  
Annex A1  
Rockwell Hardness Standardizing Machines  
Annex A2  
Standardization of Rockwell Indenters  
Annex A3  
Standardization of Rockwell Hardness Test Blocks  
Annex A4  
Guidelines for Determining the Minimum Thickness of a
Test Piece  
Annex A5  
Hardness Value Corrections When Testing on Convex
Cylindrical Surfaces  
Annex A6  
1.4 This standard includes nonmandatory information in the following appendixes that relates to the Rockwell hardness test.    
List of ASTM Standards Giving Hardness Values Corresponding
to Tensile Strength  
Appendix X1  
Examples of Procedures for Determining Rockwell
Hardness Uncertainty  
Appendix X2  
1.5 Units—At the time the Rockwell hardness test was developed, the force levels were specified in units of kilograms-force (kgf) and the indenter ball diameters were specified in units of inches (in.). This standard specifies the units of force and length in the International System of Units (SI); that is, force in Newtons (N) and length in millimeters (mm). However, because of the historical precedent and continued common usage, force values in kgf units and ball diameters in inch units are provided for information and much of the discussion in this standard refers to these units.  
1.6 The test principles, testing procedures, and verification procedures are essentially identical for both the Rockwell and Rockwell superficial hardness tests. The significant differences between the two tests are that the test forces are smaller for the Rockwell superficial test than for the Rockwell test. The same type and size indenters may be used for either test, depending on the scale being employed. Accordingly, throughout this standard, the term Rockwell will imply both Rockwell and Rockwell superficial unless stated otherwise.  
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.  
1.8 This international standard was developed in accordance with internationally recognized p...

General Information

• Status: Published
• Publication Date: 30-Apr-2022
• ICS: 77.040.10 - Mechanical testing of metals
• Technical Committee: E28 - Mechanical Testing
• Drafting Committee: E28.06 - Indentation Hardness Testing

Relations

• Refers: ASTM A370-24 - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 01-Mar-2024
• Refers: ASTM B36/B36M-23 - Standard Specification for Brass Plate, Sheet, Strip, And Rolled Bar
• Effective Date: 01-Oct-2023
• Refers: ASTM B103/B103M-23 - Standard Specification for Phosphor Bronze Plate, Sheet, Strip, and Rolled Bar
• Effective Date: 01-Oct-2023
• Refers: ASTM B19-20 - Standard Specification for Cartridge Brass Sheet, Strip, Plate, Bar, and Disks
• Effective Date: 01-Apr-2020
• Refers: ASTM B152/B152M-19 - Standard Specification for Copper Sheet, Strip, Plate, and Rolled Bar
• Effective Date: 01-Oct-2019
• Refers: ASTM B103/B103M-19 - Standard Specification for Phosphor Bronze Plate, Sheet, Strip, and Rolled Bar
• Effective Date: 01-Oct-2019
• Refers: ASTM A1038-19 - Standard Test Method for Portable Hardness Testing by the Ultrasonic Contact Impedance Method
• Effective Date: 01-Oct-2019
• Refers: ASTM A370-19 - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 01-Jul-2019
• Refers: ASTM B130-19 - Standard Specification for Commercial Bronze Strip for Bullet Jackets
• Effective Date: 01-Apr-2019
• Refers: ASTM B36/B36M-18 - Standard Specification for Brass Plate, Sheet, Strip, And Rolled Bar
• Effective Date: 01-Oct-2018
• Refers: ASTM A370-17a - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 15-Nov-2017
• Refers: ASTM A1038-17 - Standard Test Method for Portable Hardness Testing by the Ultrasonic Contact Impedance Method
• Effective Date: 01-Nov-2017
• Refers: ASTM A370-17 - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 01-Jan-2017
• Refers: ASTM A370-15 - Standard Test Methods and Definitions for Mechanical Testing of Steel Products
• Effective Date: 01-Nov-2015
• Refers: ASTM B103/B103M-15 - Standard Specification for Phosphor Bronze Plate, Sheet, Strip, and Rolled Bar
• Effective Date: 15-May-2015

Overview

ASTM E18-22: Standard Test Methods for Rockwell Hardness of Metallic Materials defines procedures and requirements for determining the Rockwell and Rockwell superficial hardness of metallic materials. As an internationally recognized standard published by ASTM International, ASTM E18-22 is essential for ensuring the repeatability, accuracy, and traceability of Rockwell hardness tests across global industries. The standard is widely used for material selection, quality control, and acceptance testing in the manufacture and commercial trade of metals.

Key Topics

• Rockwell Hardness Test Principle
  The Rockwell hardness test is an empirical indentation test, measuring the depth of penetration under a major and a minor force. It uses either a diamond spheroconical indenter or a tungsten carbide (or steel) ball.

• Scale Selection
  ASTM E18-22 covers multiple Rockwell and Rockwell superficial scales, suited to different metals and material thicknesses. The selection of scale depends on factors such as material type, thickness, and expected hardness range.

• Testing Equipment
  The standard details requirements for both stationary and portable Rockwell hardness testing machines, including verification protocols for machine and indenter performance.

• Verification and Calibration
  Routine direct and indirect verification ensure traceability to national standards and accurate measurements.

• Test Specimen Requirements
  Recommendations for surface preparation, specimen thickness, and support are included to minimize errors and ensure representative results.

• Test Procedures
  ASTM E18-22 specifies the test cycle, indentation spacing, ambient test temperatures, and reporting requirements for consistent and objective hardness measurements.

Applications

• Quality Control
  Rockwell hardness testing is a staple in quality assurance for incoming and outgoing metal shipments. Consistency in hardness measurements directly impacts product performance.

• Material Selection and Specification
  Hardness often correlates with other material properties like tensile strength, wear resistance, and ductility, aiding in selecting the right material for engineering applications.

• Acceptance Testing
  The standard is widely accepted for acceptance testing in commercial transactions, providing a transparent and standardized method for buyers and sellers.

• Process Monitoring
  Manufacturers use Rockwell hardness results to monitor and control heat treatments, surface hardening, and other metallurgical processes.

• On-Site and Field Testing
  Portable Rockwell hardness testers, governed by this standard, allow for in-situ hardness measurement of large or immobile parts, enhancing flexibility and reducing downtime.

Related Standards

ASTM E18-22 references several other standards for mechanical testing and hardness measurement, including:

• ASTM A370 - Mechanical Testing of Steel Products
• ASTM E92 - Vickers and Knoop Hardness of Metallic Materials
• ASTM E110 - Portable Rockwell and Brinell Hardness Testers
• ASTM E140 - Hardness Conversion Tables for Metals
• ISO 6508-1 - Metallic Materials-Rockwell Hardness Test
• SAE J417 - Hardness Tests and Conversions

Practical Value

Compliance with ASTM E18-22 ensures reliable and comparable Rockwell hardness data, which supports improved material performance, regulatory compliance, and supply chain confidence. By standardizing test methods and verifications, ASTM E18-22 minimizes ambiguities, supports traceability, and enhances the integrity of materials testing in critical applications such as automotive, aerospace, construction, and manufacturing.

For users looking to ensure consistent and internationally traceable Rockwell hardness results, adherence to ASTM E18-22 is essential for effective materials management and quality assurance.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E18 − 22 An American National Standard
Standard Test Methods for
1,2
Rockwell Hardness of Metallic Materials
ThisstandardisissuedunderthefixeddesignationE18;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope* kilograms-force (kgf) and the indenter ball diameters were
specified in units of inches (in.). This standard specifies the
1.1 These test methods cover the determination of the
units of force and length in the International System of Units
Rockwell hardness and the Rockwell superficial hardness of
(SI); that is, force in Newtons (N) and length in millimeters
metallic materials by the Rockwell indentation hardness prin-
(mm). However, because of the historical precedent and
ciple. This standard provides the requirements for Rockwell
continued common usage, force values in kgf units and ball
hardness machines and the procedures for performing Rock-
diameters in inch units are provided for information and much
well hardness tests.
of the discussion in this standard refers to these units.
1.2 This test method includes requirements for the use of
1.6 The test principles, testing procedures, and verification
portable Rockwell hardness testing machines that measure
procedures are essentially identical for both the Rockwell and
RockwellhardnessbytheRockwellhardnesstestprincipleand
Rockwell superficial hardness tests.The significant differences
canmeetalltherequirementsofthistestmethod,includingthe
betweenthetwotestsarethatthetestforcesaresmallerforthe
directandindirectverificationsofthetestingmachine.Portable
Rockwell superficial test than for the Rockwell test. The same
Rockwellhardnesstestingmachinesthatcannotmeetthedirect
type and size indenters may be used for either test, depending
verification requirements and can only be verified by indirect
on the scale being employed. Accordingly, throughout this
verification requirements are covered in Test Method E110.
standard, the term Rockwell will imply both Rockwell and
1.3 This standard includes additional requirements in the
Rockwell superficial unless stated otherwise.
following annexes:
1.7 This standard does not purport to address all of the
Verification of Rockwell Hardness Testing Machines Annex A1
safety concerns, if any, associated with its use. It is the
Rockwell Hardness Standardizing Machines Annex A2
responsibility of the user of this standard to establish appro-
Standardization of Rockwell Indenters Annex A3
Standardization of Rockwell Hardness Test Blocks Annex A4
priate safety, health, and environmental practices and deter-
Guidelines for Determining the Minimum Thickness of a Annex A5
mine the applicability of regulatory limitations prior to use.
Test Piece
1.8 This international standard was developed in accor-
Hardness Value Corrections When Testing on Convex Annex A6
Cylindrical Surfaces
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
1.4 Thisstandardincludesnonmandatoryinformationinthe
following appendixes that relates to the Rockwell hardness Development of International Standards, Guides and Recom-
test. mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
List of ASTM Standards Giving Hardness Values Appendix X1
Corresponding
to Tensile Strength
2. Referenced Documents
Examples of Procedures for Determining Rockwell Appendix X2
Hardness Uncertainty
2.1 ASTM Standards:
A370Test Methods and Definitions for Mechanical Testing
1.5 Units—At the time the Rockwell hardness test was
of Steel Products
developed, the force levels were specified in units of
A623Specification for Tin Mill Products, General Require-
ments
These test methods are under the jurisdiction of ASTM Committee E28 on A623MSpecification for Tin Mill Products, General Re-
Mechanical Testing and are the direct responsibility of Subcommittee E28.06 on
quirements [Metric]
Indentation Hardness Testing.
Current edition approved May 1, 2022. Published May 2022. Originally
approved in 1932. Last previous edition approved in 2020 as E18–20. DOI:
10.1520/E0018-22 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
In this test method, the term Rockwell refers to an internationally recognized contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
type of indentation hardness test as defined in Section 3, and not to the hardness Standards volume information, refer to the standard’s Document Summary page on
testing equipment of a particular manufacturer. theASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E18−22
A883Test Method for Ferrimagnetic Resonance Linewidth ISO/IEC 17011Conformity Assessment—General Require-
and Gyromagnetic Ratio of Nonmetallic Magnetic Mate- ments for Accreditation Bodies Accrediting Conformity
rials Assessment Bodies
A956/A956MTest Method for Leeb Hardness Testing of ISO/IEC 17025General Requirements for the Competence
Steel Products of Testing and Calibration Laboratories
A1038Test Method for Portable Hardness Testing by the 2.4 Society of Automotive Engineers (SAE) Standard:
Ultrasonic Contact Impedance Method SAE J417Hardness Tests and Hardness Number Conver-
B19Specification for Cartridge Brass Sheet, Strip, Plate, sions
Bar, and Disks
3. Terminology and Equations
B36/B36MSpecification for Brass Plate, Sheet, Strip, And
Rolled Bar
3.1 Definitions:
B96/B96MSpecification for Copper-Silicon Alloy Plate, 3.1.1 calibration—determination of the values of the sig-
Sheet, Strip, and Rolled Bar for General Purposes and
nificant parameters by comparison with values indicated by a
Pressure Vessels reference instrument or by a set of reference standards.
B103/B103M Specification for Phosphor Bronze Plate,
3.1.2 standardization—to bring in conformance to a known
Sheet, Strip, and Rolled Bar
standard through verification or calibration.
B121/B121MSpecification for Leaded Brass Plate, Sheet,
3.1.3 verification—checking or testing to assure confor-
Strip, and Rolled Bar
mance with the specification.
B122/B122MSpecification for Copper-Nickel-Tin Alloy,
3.1.4 Rockwell hardness test—an indentation hardness test
Copper-Nickel-Zinc Alloy (Nickel Silver), and Copper-
using a verified machine to force a diamond spheroconical
Nickel Alloy Plate, Sheet, Strip, and Rolled Bar
indenter or tungsten carbide (or steel) ball indenter, under
B130Specification for Commercial Bronze Strip for Bullet
specifiedconditions,intothesurfaceofthematerialundertest,
Jackets
andtomeasurethedifferenceindepthoftheindentationasthe
B134/B134MSpecification for Brass Wire
force on the indenter is increased from a specified preliminary
B152/B152MSpecification for Copper Sheet, Strip, Plate,
test force to a specified total test force and then returned to the
and Rolled Bar
preliminary test force.
B370Specification for Copper Sheet and Strip for Building
Construction
3.1.5 Rockwell superficial hardness test—sameastheRock-
B647Test Method for Indentation Hardness of Aluminum
wellhardnesstestexceptthatsmallerpreliminaryandtotaltest
Alloys by Means of a Webster Hardness Gage
forces are used with a shorter depth scale.
E29Practice for Using Significant Digits in Test Data to
3.1.6 Rockwell hardness number—a number derived from
Determine Conformance with Specifications
the net increase in the depth of indentation as the force on an
E74Practices for Calibration and Verification for Force-
indenter is increased from a specified preliminary test force to
Measuring Instruments
a specified total test force and then returned to the preliminary
E92Test Methods for Vickers Hardness and Knoop Hard-
test force.
ness of Metallic Materials
3.1.7 Rockwell hardness machine—a machine capable of
E110Test Method for Rockwell and Brinell Hardness of
performing a Rockwell hardness test and/or a Rockwell super-
Metallic Materials by Portable Hardness Testers
ficial hardness test and displaying the resulting Rockwell
E140Hardness Conversion Tables for Metals Relationship
hardness number.
Among Brinell Hardness, Vickers Hardness, Rockwell
3.1.7.1 Rockwell hardness testing machine—a Rockwell
Hardness, Superficial Hardness, Knoop Hardness, Sclero-
hardness machine used for general testing purposes.
scope Hardness, and Leeb Hardness
E384Test Method for Microindentation Hardness of Mate-
3.1.7.2 Rockwell hardness standardizing machine—a Rock-
rials
well hardness machine used for the standardization of Rock-
E691Practice for Conducting an Interlaboratory Study to
well hardness indenters, and for the standardization of Rock-
Determine the Precision of a Test Method
well hardness test blocks. The standardizing machine differs
from a regular Rockwell hardness testing machine by having
2.2 American Bearings Manufacturer Association Stan-
tighter tolerances on certain parameters.
dard:
ABMA 10-1989Metal Balls
3.1.7.3 portable Rockwell hardness testing machine—a
Rockwell hardness testing machine that is designed to be
2.3 ISO Standards:
ISO 6508-1Metallic Materials—Rockwell Hardness Test— transported, carried, set up, and operated by the users, and that
measures Rockwell hardness by the Rockwell indentation
Part 1: Test Method (scalesA, B, C, D, E, F, G, H, K, N,
T) hardness test principle.
3.1.7.4 movable Rockwell hardness testing machine—a
Rockwell hardness testing machine that is designed to be
Available from American Bearing Manufacturers Association (ABMA), 2025
M Street, NW, Suite 800, Washington, DC 20036.
5 6
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St., Available from Society of Automotive Engineers (SAE), 400 Commonwealth
4th Floor, New York, NY 10036, http://www.ansi.org. Dr., Warrendale, PA 15096-0001, http://www.sae.org.
E18−22
moved to different locations on a moveable frame, table or
similar support that is integral to the testing machine (for
example, securely fixed to a rolling table), or a Rockwell
hardness testing machine that is designed to move into testing
positionpriortoatest,(forexample,securelyfixedtoamoving
support arm), and has been previously verified to ensure that
such a move will not affect the hardness result.
3.2 Equations:
¯
3.2.1 The average H of a set of n hardness measurements
H , H ,…, H is calculated as:
1 2 n
H 1H 1…1H
1 2 n
¯
H 5 (1)
n
3.2.2 The error E in the performance of a Rockwell hard-
FIG. 1 Rockwell Hardness Test Method (Schematic Diagram)
ness machine at each hardness level, relative to a standardized
scale, is determined as:
¯
E 5 H 2 H (2) Step 1—The indenter is brought into contact with the test
STD
specimen, and the preliminary test force F is applied. After
where:
holding the preliminary test force for a specified dwell time,
¯
= average of n hardness measurements H , H ,…, H
H
1 2 n
the baseline depth of indentation is measured.
made on a standardized test block as part of a
Step 2—The force on the indenter is increased at a
performance verification, and
controlled rate by the additional test force F to achieve the
H = certified average hardness value of the standardized
STD
total test force F. The total test force is held for a specified
test block.
dwell time.
3.2.3 The repeatability R in the performance of a Rockwell Step 3—The additional test force is removed, returning to
hardness machine at each hardness level, under the particular the preliminary test force. After holding the preliminary test
verification conditions, is estimated by the range of n hardness force for a specified dwell time, the final depth of indentation
measurements made on a standardized test block as part of a is measured. The Rockwell hardness value is derived from the
performance verification, defined as: difference h in the final and baseline indentation depths while
under the preliminary test force. The preliminary test force is
R 5 H 2 H (3)
max min
removed and the indenter is removed from the test specimen.
where:
5.1.1 There are two general classifications of the Rockwell
H = highest hardness value, and
test: the Rockwell hardness test and the Rockwell superficial
max
H = lowest hardness value.
hardness test. The significant difference between the two test
min
classifications is in the test forces that are used. For the
4. Significance and Use
Rockwellhardnesstest,thepreliminarytestforceis10kgf(98
4.1 The Rockwell hardness test is an empirical indentation
N)andthetotaltestforcesare60kgf(589N),100kgf(981N),
hardnesstestthatcanprovideusefulinformationaboutmetallic
and 150 kgf (1471 N). For the Rockwell superficial hardness
materials. This information may correlate to tensile strength,
test, the preliminary test force is 3 kgf (29 N) and the total test
wear resistance, ductility, and other physical characteristics of
forces are 15 kgf (147 N), 30 kgf (294 N), and 45 kgf (441 N).
metallic materials, and may be useful in quality control and
5.1.2 Indenters for the Rockwell hardness test include a
selection of materials.
diamond spheroconical indenter and tungsten carbide ball
indenters of specified diameters.
4.2 Rockwell hardness tests are considered satisfactory for
5.1.2.1 Steelindenterballsmaybeusedonlyfortestingthin
acceptance testing of commercial shipments, and have been
sheet tin mill products specified in Specifications A623 and
used extensively in industry for this purpose.
A623M using the HR15T and HR30T scales with a diamond
4.3 Rockwellhardnesstestingataspecificlocationonapart
spot anvil. Testing of this product may give significantly
maynotrepresentthephysicalcharacteristicsofthewholepart
differing results using a tungsten carbide ball as compared to
or end product.
historical test data using a steel ball.
4.4 Adherence to this standard test method provides trace-
NOTE 1—Previous editions of this standard have stated that the steel
abilitytonationalRockwellhardnessstandardsexceptasstated
ballwasthestandardtypeofRockwellindenterball.Thetungstencarbide
otherwise.
ball is considered the standard type of Rockwell indenter ball. The use of
tungsten carbide balls provide an improvement to the Rockwell hardness
5. Principles of Test and Apparatus
testbecauseofthetendencyofsteelballstoflattenwithuse,whichresults
in an erroneously elevated hardness value. The user is cautioned that
5.1 Rockwell Hardness Test Principle—The general prin-
Rockwell hardness tests comparing the use of steel and tungsten carbide
ciple of the Rockwell indentation hardness test is illustrated in
ballshavebeenshowntogivedifferentresults.Forexample,dependingon
Fig. 1. The test is divided into three steps of force application
the material tested and its hardness level, Rockwell B scale tests using a
and removal. tungsten carbide ball indenter have given results approximately one
E18−22
Rockwell point lower than when a steel ball indenter is used.
designation.Whenaballindenterisused,thescaledesignation
is followed by the letter “W” to indicate the use of a tungsten
5.1.3 The Rockwell hardness scales are defined by the
carbide ball or the letter “S” to indicate the use of a steel ball
combinations of indenter and test forces that may be used.The
(see 5.1.2.1).
standard Rockwell hardness scales and typical applications of
5.2.3.1 Examples:
the scales are given in Tables 1 and 2. Rockwell hardness
valuesshallbedeterminedandreportedinaccordancewithone
64 HRC = Rockwell hardness number of 64 on Rockwell C scale
of these standard scales.
81 HR30N = Rockwell superficial hardness number of 81 on the Rockwell
30N scale
5.2 Calculation of the Rockwell Hardness Number—During
a Rockwell test, the force on the indenter is increased from a
72 HRBW = Rockwell hardness number of 72 on the Rockwell B scale
preliminary test force to a total test force, and then returned to
using a tungsten carbide ball indenter
thepreliminarytestforce.Thedifferenceinthetwoindentation
5.2.4 Areported Rockwell hardness number or the average
depth measurements, while under the preliminary test force, is
value of Rockwell hardness measurements shall be rounded in
measured as h (see Fig. 1).
accordance with Practice E29 with a resolution no greater than
5.2.1 The unit measurement for h is mm. From the value of
the resolution of the hardness value display of the testing
h, the Rockwell hardness number is derived. The Rockwell
machine. Typically, the resolution of a Rockwell hardness
hardness number is calculated as:
number should not be greater than 0.1 Rockwell units.
5.2.1.1 For scales using a diamond spheroconical indenter
(see Tables 1 and 2): NOTE 2—When the Rockwell hardness test is used for the acceptance
testing of commercial products and materials, the user should take into
h
account the potential measurement differences between hardness testing
RockwellHardness 5100 2 (4)
0.002
machines allowed by this standard (see Section 10, Precision and Bias).
Because of the allowable ranges in the tolerances for the repeatability and
h
error of a testing machine, as specified in the verification requirements of
RockwellSuperficialHardness 5100 2 (5)
0.001
AnnexA1, one testing machine may have a test result that is one or more
hardness points different than another testing machine, yet both machines
where h is in mm.
can be within verification tolerances (see Table A1.3). Commonly for
5.2.1.2 Forscalesusingaballindenter(seeTables1and2):
acceptance testing, Rockwell hardness values are rounded to whole
numbers following Practice E29. Users are encouraged to address round-
h
RockwellHardness 5130 2 (6) ing practices with regards to acceptance testing within their quality
0.002
management system, and make any special requirements known during
contract review.
h
RockwellSuperficialHardness 5100 2 (7)
0.001
5.3 Rockwell Testing Machine—The Rockwell testing ma-
chine shall make Rockwell hardness determinations by apply-
where h is in mm.
ing the test forces and measuring the depth of indentation in
5.2.2 The Rockwell hardness number is an arbitrary
accordance with the Rockwell hardness test principle.
number, which, by method of calculation, results in a higher
5.3.1 SeetheEquipmentManufacturer’sInstructionManual
number for harder material.
for a description of the machine’s characteristics, limitations,
5.2.3 Rockwellhardnessvaluesshallnotbedesignatedbya
and respective operating procedures.
numberalonebecauseitisnecessarytoindicatewhichindenter
and forces have been employed in making the test (see Tables 5.3.2 The Rockwell testing machine shall automatically
1 and 2). Rockwell hardness numbers shall be quoted with a
convert the depth measurements to a Rockwell hardness
scale symbol representing the indenter and forces used. The number and indicate the hardness number and Rockwell scale
hardness number is followed by the symbol HR and the scale by an electronic device or by a mechanical indicator.
TABLE 1 Rockwell Hardness Scales
Scale Total Test Dial
Indenter Typical Applications of Scales
Symbol Force, kgf Figures
B ⁄16-in. (1.588-mm) ball 100 red Copper alloys, soft steels, aluminum alloys, malleable iron, etc.
C diamond 150 black Steel, hard cast irons, pearlitic malleable iron, titanium, deep case hardened steel, and other
materials harder than B100.
A diamond 60 black Cemented carbides, thin steel, and shallow case-hardened steel.
D diamond 100 black Thin steel and medium case hardened steel, and pearlitic malleable iron.
E ⁄8-in. (3.175-mm) ball 100 red Cast iron, aluminum and magnesium alloys, bearing metals.
F ⁄16-in. (1.588-mm) ball 60 red Annealed copper alloys, thin soft sheet metals.
G ⁄16-in. (1.588-mm) ball 150 red Malleable irons, copper-nickel-zinc and cupro-nickel alloys. Upper limit G92 to avoid possible
flattening of ball.
H ⁄8-in. (3.175-mm) ball 60 red Aluminum, zinc, lead.
K ⁄8-in. (3.175-mm) ball 150 red
L ⁄4-in. (6.350-mm) ball 60 red
M ⁄4-in. (6.350-mm) ball 100 red Bearing metals and other very soft or thin materials. Use smallest ball and heaviest load that does
P ⁄4-in. (6.350-mm) ball 150 red not give anvil effect.
R ⁄2-in. (12.70-mm) ball 60 red
S ⁄2-in. (12.70-mm) ball 100 red
V ⁄2-in. (12.70-mm) ball 150 red
E18−22
TABLE 2 Rockwell Superficial Hardness Scales
Scale Symbols
Total Test Force,
1 1 1 1
N Scale, Diamond T Scale, ⁄16-in. W Scale, ⁄8-in. X Scale, ⁄4-in. Y Scale, ⁄2-in.
kgf (N)
Indenter (1.588-mm) Ball (3.175-mm) Ball (6.350-mm) Ball (12.70-mm) Ball
15 (147) 15N 15T 15W 15X 15Y
30 (294) 30N 30T 30W 30X 30Y
45 (441) 45N 45T 45W 45X 45Y
5.4 Indenters—The standard Rockwell indenters are either 5.5.6 Special anvils or fixtures, including clamping fixtures,
diamond spheroconical indenters or tungsten carbide balls of may be required for testing pieces or parts that cannot be
1 1 1
1.588 mm ( ⁄16 in.), 3.175 mm ( ⁄8 in.), 6.350 mm ( ⁄4 in.), or supported by standard anvils. Auxiliary support may be used
12.70 mm ( ⁄2 in.) in diameter. Indenters shall meet the for testing long pieces with so much overhang that the piece is
requirementsdefinedinAnnexA3.Steelballindentersmaybe not firmly seated by the preliminary force.
used in certain circumstances (see 5.1.2.1).
5.6 Verification—Rockwell testing machines shall be veri-
5.4.1 Dust, dirt, or other foreign materials shall not be
fied periodically in accordance with Annex A1.
allowed to accumulate on the indenter, as this will affect the
5.7 Test Blocks—Test blocks meeting the requirements of
test results.
Annex A4 shall be used to verify the testing machine in
NOTE 3—Indenters certified to revision E18-07 or later meet the
accordance with Annex A1.
requirements of this standard.
NOTE 4—Test blocks certified to revision E18-07 or later meet the
requirements of this standard.
5.5 Specimen Support—Aspecimensupportor“anvil”shall
NOTE 5—It is recognized that appropriate standardized test blocks are
be used that is suitable for supporting the specimen to be
not available for all geometric shapes, or materials, or both.
tested.Theseatingandsupportingsurfacesofallanvilsshallbe
5.8 Use of Portable Rockwell Hardness Testing Machines:
clean and smooth and shall be free from pits, deep scratches,
and foreign material. Damage to the anvil may occur from 5.8.1 A fixed-location Rockwell hardness testing machine
may not be capable of testing certain samples because of the
testing too thin material or accidental contact of the anvil by
theindenter.Iftheanvilisdamagedfromanycause,itshallbe samplesizeorweight,samplelocation,accessibilityofthetest
point or other requirements. In these circumstances, the use of
repaired or replaced. Anvils showing the least visibly percep-
tible damage may give inaccurate results, particularly on thin a portable Rockwell hardness testing machine is an acceptable
method to test these samples. This method allows the use of a
material.
portable Rockwell hardness testing machine as follows.
5.5.1 Common specimen support anvils should have a
5.8.1.1 The portable Rockwell hardness testing machine
minimum hardness of 58 HRC. Some specialty support anvils
require a lower material hardness. shall meet the requirements of this method, including the test
principle, apparatus, indenters, applied forces, test procedures
5.5.2 Flat pieces should be tested on a flat anvil that has a
smooth, flat bearing surface whose plane is perpendicular to and the direct and indirect verifications of the testing machine
(except as indicated in Table A1.1). Test Method E110 covers
the axis of the indenter.
5.5.3 Small diameter cylindrical pieces shall be tested with portable Rockwell hardness testing machines that cannot be
directly verified or cannot pass direct verification but meet the
a hard V-grooved anvil with the axis of the V-groove directly
other requirements of this method.
undertheindenter,oronhard,parallel,twincylindersproperly
5.8.1.2 Aportable Rockwell hardness testing machine shall
positioned and clamped in their base.These types of specimen
supports shall support the specimen with the apex of the beusedonlywhentestingcircumstancesmakeitimpracticalto
cylinder directly under the indenter. use a fixed-location Rockwell hardness testing machine. In
5.5.4 For thin materials or specimens that are not perfectly such cases, it is recommended that an agreement or under-
flat, an anvil having an elevated, flat “spot” 3 mm ( ⁄8 in.) to standing be made between all parties involved (for example,
12.5mm( ⁄2in.)indiametershouldbeused.Thisspotshallbe testing service and customer) that a portable Rockwell hard-
polished smooth and flat. Very soft material should not be ness testing machine will be used instead of a fixed-location
Rockwell hardness testing machine (see 5.8.1.)
tested on the “spot” anvil because the applied force may cause
the penetration of the anvil into the under side of the specimen 5.8.1.3 The portable Rockwell hardness testing machine
regardless of its thickness. shallmeasurehardnessbytheRockwellhardnesstestprinciple
5.5.5 Whentestingthinsheetmetalwithaballindenter,itis (see 5.1). Portable hardness testing machines or instruments
recommended that a diamond spot anvil be used. The highly that measure hardness by other means or procedures different
polished diamond surface shall have a diameter between 4.0 thantheRockwellhardnesstestprinciple,suchasthosedefined
inTestMethodsA883,A956/A956M,A1038orB647,produce
mm(0.157in.)and7.0mm(0.2875in.)andbecenteredwithin
0.5 mm (0.02 in.) of the test point. converted Rockwell hardness values and do not comply with
this method.
5.5.5.1 CAUTION: A diamond spot anvil should only be
used with a maximum total test force of 45 kgf (441 N) and a 5.8.2 Daily Verification of portable hardness testing
ball indenter. This recommendation should be followed except machines—Portable hardness testing machines are susceptible
when directed otherwise by material specification. to damage when they are transported or carried from one test
E18−22
site to another. Therefore, in addition to complying with the requirements are specified in 9.4 and 9.5 when reporting
daily verification requirements specified in 7.1 and AnnexA1, corrected hardness values.
NOTE 7—Atable of correction values to be applied to test results made
a daily verification shall be performed at each test worksite
on spherical surfaces is given in ISO 6508-1.
wherethehardnesstestsaretobemadejustpriortomakingthe
hardness tests. The verification shall be performed with the 6.5 Whentestingsmalldiameterspecimens,theaccuracyof
portable hardness testing machine oriented as closely as the test will be seriously affected by alignment between the
practical to the position that it will be used. It is recommended indenter and the test piece, by surface finish, and by the
that the daily verification be repeated occasionally during straightness of the cylinder.
testing and after testing is completed.
7. Test Procedure
5.8.3 Additional reporting requirements when using a por-
table Rockwell hardness testing machine are given in 9.2. 7.1 A daily verification of the testing machine shall be
performed in accordance with A1.5 prior to making hardness
5.8.4 Portable hardness testing machines by the nature of
tests. Hardness measurements shall be made only on the
theirapplicationmayinduceerrorsthatcouldinfluencethetest
calibrated surface of the test block.
results. To understand the differences in results expected
7.1.1 The results of a daily verification shall comply with
between portable and fixed-location Rockwell hardness testing
the current values specified in Table A1.3 regardless of any
machines, the user should compare the results of the precision
maximum error E value marked on the test block (see Note 8).
and bias studies given in Section 10 and in Test Method E110.
NOTE8—Differenteditionsofthismethodhaverevisedsomemaximum
6. Test Piece
error E values given in Table A1.3. Consequently, the maximum error E
valuesmarkedonolderstandardizedtestblocksmaynotreflectthecurrent
6.1 For best results, both the test surface and the bottom
values.
surface of the test piece should be smooth, even and free from
7.2 Rockwellhardnesstestsshouldbecarriedoutatambient
oxide scale, foreign matter, and lubricants. An exception is
temperature within the limits of 10°C to 35°C (50°F to
made for certain materials such as reactive metals that may
95°F). Users of the Rockwell hardness test are cautioned that
adhere to the indenter. In such situations, a suitable lubricant
the temperature of the test material and the temperature of the
such as kerosene may be used. The use of a lubricant shall be
hardness tester may affect test results. Consequently, users
defined on the test report.
should ensure that the test temperature does not adversely
6.2 Preparation shall be carried out in such a way that any
affect the hardness measurement.
alteration of the surface hardness of the test surface (for
7.3 Thetestpieceshallbesupportedrigidlysothatdisplace-
example, due to heat or cold-working) is minimized.
ment of the test surface is minimized (see 5.5).
6.3 The thickness of the test piece or of the layer under test
7.4 Test Cycle—This standard specifies the Rockwell test
should be as defined in tables and presented graphically in
cycle by stating recommendations or requirements for five
AnnexA5.Thesetablesweredeterminedfromstudiesonstrips
separate parts of the cycle. These parts are illustrated for a
of carbon steel and have proven to give reliable results. For all
Rockwell C scale test in Fig. 2, and defined as follows:
other materials, it is recommended that the thickness should
(1) Contact Velocity, v —Thevelocityoftheindenteratthe
A
exceed 10 times the depth of indentation. In general, no
point of contact with the test material.
deformationshouldbevisibleonthebackofthetestpieceafter
(2) Preliminary Force Dwell Time, t —The dwell time
PF
the test, although not all such marking is indicative of a bad
beginning when the preliminary force is fully applied and
test.
ending when the first baseline depth of indentation is
6.3.1 Special consideration should be made when testing
measured, (also see 7.4.1.3).
parts that exhibit hardness gradients; for example, parts that
(3) Additional Force Application Time, t —The time for
TA
were case-hardened by processes such as carburizing,
applying the additional force to obtain the full total force.
carbonitriding, nitriding, induction, etc. The minimum thick-
(4) Total Force Dwell Time, t —The dwell time while the
TF
ness guidelines given in Annex A5 only apply to materials of
total force is fully applied.
uniform hardness, and should not be used to determine the
(5) Dwell Time for Elastic Recovery, t —The dwell time at
R
appropriate scale for measuring parts with hardness gradients.
the preliminary force level, beginning when the additional
The selection of an appropriate Rockwell scale for parts with
force is fully removed, and ending when the second and final
hardness gradients should be made by special agreement.
depth of indentation is measured.
NOTE 6—A table listing the minimum effective case depth needed for
7.4.1 The standard Rockwell test cycle is specified in Table
different Rockwell scales is given in SAE J417.
3. The test cycle used for Rockwell hardness tests shall be in
6.4 When testing on convex cylindrical surfaces, the result accordance with these test cycle values and tolerances (see
may not accurately indicate the true Rockwell hardness; Note 9), with the following exceptions.
therefore, the corrections given in AnnexA6 shall be applied. 7.4.1.1 Precautions for Materials Having Excessive Time-
For diameters between those given in the tables, correction Dependent Plasticity (Indentation Creep)—In the case of
factorsmaybederivedbylinearinterpolation.Testsperformed materials exhibiting excessive plastic flow after application of
on diameters smaller than those given in Annex A6 are not the total test force, special considerations may be necessary
acceptable. Corrections for tests on spherical and concave since the indenter will continue to penetrate. When materials
surfacesshouldbethesubjectofspecialagreement.Additional require the use of a longer total force dwell time than for the
E18−22
t
PA
1t . For testing machines that apply the preliminary force
PF
t in1sorless,thisadjustmenttothepreliminaryforcedwell
PA
time value t is optional.
PF
NOTE 9—It is recommended that the test cycle to be used with the
hardnessmachinematch,ascloselyaspossible,thetestcycleusedforthe
indirect verification of the hardness machine. Varying the values of the
testing cycle parameters within the tolerances of Table 3 can produce
different hardness results.
7.5 Test Procedure—There are many designs of Rockwell
hardness machines, requiring various levels of operator con-
trol. Some hardness machines can perform the Rockwell
hardness test procedure automatically with almost no operator
influence, while other machines require the operator to control
most of the test procedure.
7.5.1 Bring the indenter into contact with the test surface in
a direction perpendicular to the surface and, if possible, at a
velocity within the recommended maximum contact velocity
v .
A
7.5.2 Apply the preliminary test force F of 10 kgf (98 N)
fortheRockwellhardnesstestor3kgf(29N)fortheRockwell
superficial hardness test.
7.5.3 Maintain the preliminary force for the specified pre-
liminary force dwell time t .
PF
7.5.4 At the end of the preliminary force dwell time t ,
PF
immediately establish the reference position of the baseline
depth of indentation (see manufacturer’s Instruction Manual).
FIG. 2 Schematic of Force-Time Plot (a) and Indenter Depth-Time 7.5.5 Increase the force by the value of the additional test
Plot (b) of an HRC Test Illustrating the Test Cycle Parts
force F needed to obtain the required total test force F for a
given hardness scale (see Tables 1 and 2).The additional force
TABLE 3 Test Cycle Tolerances
F shall be applied in a controlled manner within the specified
Test Cycle Parameter Tolerance
application time range t .
TA
Indenter contact velocity, v (recommended) #2.5 mm/s
A
7.5.6 Maintain the total force F for the specified total force
Dwell time for preliminary force, t (when the time to apply 0.1 s to 4.0
PF
dwell time t .
the preliminary force t $ 1 s, then calculate this parameter s
TF
PA
t
PA
as 1t ) 7.5.7 Removetheadditionaltestforce F whilemaintaining
PF 1
Time for application of additional force, t 1.0 s to 8.0
TA
the preliminary test force F .
s
Dwell time for total force, t 2.0 s to 6.0 7.5.8 Maintain the preliminary test force F for an appro-
TF 0
s
priatetimetoallowelasticrecoveryinthetestmaterialandthe
Dwell time for elastic recovery, t 0.2 s to 5.0
R
stretch of the frame to be factored out.
s
7.5.9 At the end of the dwell time for elastic recovery,
immediately establish the final depth of indentation (see
manufacturer’s Instruction Manual). The testing machine shall
standardtestcyclestatedinTable3,thisshouldhespecifiedin
calculate the difference between the final and baseline depth
the product specification. In these cases, the actual extended
measurements and indicate the resulting Rockwell hardness
totalforcedwelltimeusedshallberecordedandreportedafter
value. The Rockwell hardness number is derived from the
the test results (for example, 65 HRFW, 10 s).
differential increase in depth of indentation as defined in Eq 4,
7.4.1.2 Therearetestingconditionsthatmayrequirethatthe
Eq 5, Eq 6, and Eq 7.
indenter contact velocity exceed the recommended maximum
statedinTable3.Theusershouldensurethatthehighercontact
7.6 Throughout the test, the apparatus shall be protected
velocitydoesnotcauseashockoroverloadwhichwouldaffect
from shock or vibration that could affect the hardness mea-
thehardnessresult.Itisrecommendedthatcomparisontestsbe
surement result.
made on the same test material using a test cycle within the
7.7 After each change, or removal and replacement, of the
requirements stated in Table 3.
indenterortheanvil,atleasttwopreliminaryindentationsshall
7.4.1.3 For testing machines that take1sor longer to apply
the preliminary force t , the preliminary force dwell time be made to ensure that the indenter and anvil are seated
PA
properly. The results of the preliminary indentations shall be
value t shall be adjusted before comparing the parameter
PF
with the tolerances of Table 3 by adding to it one half of t as disregarded.
PA
E18−22
NOTE 11—ASTM standards giving approximate hardness-tensile
7.8 After each change of a test force or removal and
strength relationships are listed in Appendix X1.
replacement of the indenter or the anvil, it is strongly recom-
mended that the operation of the machine be checked in
9. Report
accordance with the daily verification method specified in
9.1 The test report shall include the following information:
Annex A1.
9.1.1 The Rockwell hardness number. All reports of Rock-
7.9 Indentation Spacing—The hardness of the material im-
well hardness numbers shall indicate the scale used. The
mediately surrounding a previously made indentation will
reported number shall be rounded in accordance with Practice
usually increase due to the induced residual stress and work-
E29 (see 5.2.4 and Note 2),
hardening caused by the indentation process. If a new inden-
9.1.2 The total force dwell time, if outside the specified
tation is made in this affected material, the measured hardness
standard test cycle tolerances (see Table 3), and
value will likely be higher than the true hardness of the
9.1.3 The ambient temperature at the time of test, if outside
material as a whole. Also, if an indentation is made too close
thelimitsof10to35°C(50to95°F),unlessithasbeenshown
to the edge of the material or very close to a previously made
not to affect the measurement result.
indentation, there may be insufficient material to constrain the
9.2 Reporting Portable Testing Machine Hardness Values—
deformation zone surrounding the indentation. This can result
WhenusingaportableRockwellhardnesstestingmachine,the
in an apparent lowering of the hardness value. Both of these
measured hardness number shall be reported in accordance
circumstances can be avoided by allowing appropriate spacing
with 9.1, and appended with a /P to indicate that it was
between indentations and from the edge of the material.
determined by portable Rockwell hardness testing machine.
7.9.1 The distance between the centers of two adjacent
For example:
indentations shall be at least three times the diameter d of the
40HRC/P=Rockwellhardnessnumberof40ontheRockwell
indentation (see Fig. 3).
C scale.
7.9.2 The distance from the center of any indentation to an
72 HRBW/P = Rockwell hardness number of 72 on the
edge of the test piece shall be at least two and a half times the
Rockwell B scale with a tungsten carbide ball indenter.
diameter of the indentation (see Fig. 3).
9.3 Reporting Converted Hardness Values—Whenreporting
8. Conversion to Other Hardness Scales or Tensile
hardness values that have been converted from one type of
Strength Values
hardness test or hardness scale to another type of hardness test
8.1 There is no general method of accurately converting the or hardness scale, the original measurement number and test
RockwellhardnessnumbersononescaletoRockwellhardness scale shall also be reported (see E140).
numbers on another scale, or to other types of hardness 9.3.1 A common historical practice is to report the con-
numbers,ortotensilestrengthvalues.Suchconversionsare,at vertedhardnessvaluefollowedbythemeasuredhardnessvalue
best, approximations and, therefore, should be avoided except giveninparentheses.Forexample:353HBW(38HRC),where
for special cases where a reliable basis for the approximate 353 HBW is the converted hardness value and 38 HRC is the
original measurement value.
conversion has been obtained by comparison tests. Additional
requirements are specified in 9.3 and 9.5 when reporting 9.3.2 Otherformatsforreportingconvertedhardnessvalues,
such as data tables, may be used, however, the original
converted hardness values.
NOTE10—TheStandardHardnessConversionTablesforMetals,E140,
measurement number and test scale shall also be reported and
give approximate conversion values for specific materials such as steel,
clearly identified.
austenitic stainless steel, nickel and high-nickel alloys, cartridge brass,
9.4 Reporting Curvature Corrected Hardness Values—
copperalloys,andalloyedwhitecastirons.TheRockwellhardnessdatain
the conversion tables of E140 was determined using steel ball indenters.
When reporting Rockwell hardness test values that have been
corrected for testing on cylindrical or spherical surfaces (see
6.4), the following information shall be indicated in the test
report or documented in the test lab/customer contract or
agreement:
–the test values are corrected due to testing on a curved
surface,
–the source of correction value, if other than the correction
tables given in Annex A6 for convex cylindrical surfaces.
9.5 Since all converted or curvature-corrected hardness
values are considered approximate, the reported hardness
values shall be rounded in accordance with the Rounding
Method of Practice E29 and should have no more significant
digits than is given for the data in the applicable conversion or
FIG. 3 Schematic of Minimum Indentation Spacing correction table.
E18−22
7, 8
TABLE 4 Results of the Precision and Bias Study
10. Precision and Bias
Average
10.1 Precision—A Rockwell hardness precision and bias Test Block Sr SR r R
PB PB
Hardness
study was conducted in 2000 in accordance with Practice
Data from 2000 study
E691. Tests were performed in the following six Rockwell
62.8 HRA 62.50 0.164 0.538 0.459 1.506
73.1 HRA 73.04 0.138 0.358 0.387 1.002
scales:HRA,HRC,HRBS,HR30N,HR30TS,andHRES.The
83.9 HRA 84.54 0.085 0.468 0.238 1.309
testsintheHRBS,HR30TSandHRESscalesweremadeusing
25.0 HRC 24.99 0.335 0.440 0.937 1.232
steel ball indenters.Atotal of 18 Rockwell scale hardness test
45.0 HRC 45.35 0.156 0.259 0.438 0.725
65.0 HRC 65.78 0.153 0.389 0.427 1.089
blocks of the type readily available were used for this study.
45.9 HR30N 46.75 0.299 2.489 0.837 6.969
Test blocks at three different hardness levels (high, medium,
64.0 HR30N 64.74 0.248 0.651 0.694 1.822
andlow)ineachscaleweretestedthreetimeseach.Theresults
81.9 HR30N 82.52 0.195 0.499 0.547 1.396
Data from 2006 study
from the first study are filed under ASTM Research Report
7,8 40 HRBW 43.90 0.492 0.668 1.378 1.871
RR:E28-1021.
60 HRBW 61.77 0.663 0.697 1.855 1.953
95 HRBW 91.09 0.250 0.292 0.701 0.817
10.2 Starting with version E18-05, this standard changed
62 HREW 64.07 0.346 0.675 0.970 1.890
fromtheuseofsteelballstocarbideballsforallscalesthatuse
81 HREW 81.61 0.232 0.406 0.649 1.136
a ball indenter. Due to this change, a second study was 100 HREW 96.22 0.177 0.322 0.497 0.901
22 HR30TW 18.33 0.702 0.901 1.965 2.522
conducted in 2006. The second study was performed in
56 HR30TW 58.0 0.476 0.517 1.333 1.447
accordance with Practice E691 and was identical to the initial
79 HR30TW 81.0 0.610 0.851 1.709 2.382
study except it was limited to the HRBW, HR30TW, and
HREW scales, all of which use carbide ball indenters. The
results from that study are filed underASTM Research Report
nesstestersondifferentdays.Whencomparingtwotestresults
RR:E28-1022.
made under these conditions, a measurement difference of less
10.3 A total of 14 different labs participated in the two than the R value for that Rockwell scale is an indication that
PB
the results may be equivalent.
studies. Eight participated in the first study and nine in the
second study. Three labs participated in both studies. The labs
10.7 Any judgments based on 10.5 and 10.6 would have an
chosen to participate in this study were a combination of
approximately 95% probability of being correct.
commercial testing labs (6), in-house labs (5) and test block
10.8 This precision and bias study was conducted on a
manufacturer’s calibration labs (3). Each lab was instructed to
selected number of the most commonly used Rockwell scales.
testeachblockinthreespecificlocationsaroundthesurfaceof
For Rockwell
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: E18 − 20 E18 − 22 An American National Standard
Standard Test Methods for
1,2
Rockwell Hardness of Metallic Materials
This standard is issued under the fixed designation E18; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
This standard has been approved for use by agencies of the U.S. Department of Defense.
1. Scope*
1.1 These test methods cover the determination of the Rockwell hardness and the Rockwell superficial hardness of metallic
materials by the Rockwell indentation hardness principle. This standard provides the requirements for Rockwell hardness machines
and the procedures for performing Rockwell hardness tests.
1.2 This test method includes requirements for the use of portable Rockwell hardness testing machines that measure Rockwell
hardness by the Rockwell hardness test principle and can meet all the requirements of this test method, including the direct and
indirect verifications of the testing machine. Portable Rockwell hardness testing machines that cannot meet the direct verification
requirements and can only be verified by indirect verification requirements are covered in Test Method E110.
1.3 This standard includes additional requirements in the following annexes:
Verification of Rockwell Hardness Testing Machines Annex A1
Rockwell Hardness Standardizing Machines Annex A2
Standardization of Rockwell Indenters Annex A3
Standardization of Rockwell Hardness Test Blocks Annex A4
Guidelines for Determining the Minimum Thickness of a Annex A5
Test Piece
Hardness Value Corrections When Testing on Convex Annex A6
Cylindrical Surfaces
1.4 This standard includes nonmandatory information in the following appendixes that relates to the Rockwell hardness test.
List of ASTM Standards Giving Hardness Values Appendix X1
Corresponding
to Tensile Strength
Examples of Procedures for Determining Rockwell Appendix X2
Hardness Uncertainty
1.5 Units—At the time the Rockwell hardness test was developed, the force levels were specified in units of kilograms-force (kgf)
and the indenter ball diameters were specified in units of inches (in.). This standard specifies the units of force and length in the
International System of Units (SI); that is, force in Newtons (N) and length in millimeters (mm). However, because of the historical
These test methods are under the jurisdiction of ASTM Committee E28 on Mechanical Testing and are the direct responsibility of Subcommittee E28.06 on Indentation
Hardness Testing.
Current edition approved Feb. 1, 2020May 1, 2022. Published March 2020May 2022. Originally approved in 1932. Last previous edition approved in 20192020 as
E18 – 19.E18 – 20. DOI: 10.1520/E0018-2010.1520/E0018-22
In this test method, the term Rockwell refers to an internationally recognized type of indentation hardness test as defined in Section 3, and not to the hardness testing
equipment of a particular manufacturer.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E18 − 22
precedent and continued common usage, force values in kgf units and ball diameters in inch units are provided for information
and much of the discussion in this standard refers to these units.
1.6 The test principles, testing procedures, and verification procedures are essentially identical for both the Rockwell and
Rockwell superficial hardness tests. The significant differences between the two tests are that the test forces are smaller for the
Rockwell superficial test than for the Rockwell test. The same type and size indenters may be used for either test, depending on
the scale being employed. Accordingly, throughout this standard, the term Rockwell will imply both Rockwell and Rockwell
superficial unless stated otherwise.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of
regulatory limitations prior to use.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
A370 Test Methods and Definitions for Mechanical Testing of Steel Products
A623 Specification for Tin Mill Products, General Requirements
A623M Specification for Tin Mill Products, General Requirements [Metric]
A883 Test Method for Ferrimagnetic Resonance Linewidth and Gyromagnetic Ratio of Nonmetallic Magnetic Materials
A956A956/A956M Test Method for Leeb Hardness Testing of Steel Products
A1038 Test Method for Portable Hardness Testing by the Ultrasonic Contact Impedance Method
B19 Specification for Cartridge Brass Sheet, Strip, Plate, Bar, and Disks
B36/B36M Specification for Brass Plate, Sheet, Strip, And Rolled Bar
B96/B96M Specification for Copper-Silicon Alloy Plate, Sheet, Strip, and Rolled Bar for General Purposes and Pressure Vessels
B103/B103M Specification for Phosphor Bronze Plate, Sheet, Strip, and Rolled Bar
B121/B121M Specification for Leaded Brass Plate, Sheet, Strip, and Rolled Bar
B122/B122M Specification for Copper-Nickel-Tin Alloy, Copper-Nickel-Zinc Alloy (Nickel Silver), and Copper-Nickel Alloy
Plate, Sheet, Strip, and Rolled Bar
B130 Specification for Commercial Bronze Strip for Bullet Jackets
B134/B134M Specification for Brass Wire
B152/B152M Specification for Copper Sheet, Strip, Plate, and Rolled Bar
B370 Specification for Copper Sheet and Strip for Building Construction
B647 Test Method for Indentation Hardness of Aluminum Alloys by Means of a Webster Hardness Gage
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E74 Practices for Calibration and Verification for Force-Measuring Instruments
E92 Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materials
E110 Test Method for Rockwell and Brinell Hardness of Metallic Materials by Portable Hardness Testers
E140 Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness,
Superficial Hardness, Knoop Hardness, Scleroscope Hardness, and Leeb Hardness
E384 Test Method for Microindentation Hardness of Materials
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
2.2 American Bearings Manufacturer Association Standard:
ABMA 10-1989 Metal Balls
2.3 ISO Standards:
ISO 6508-1 Metallic Materials—Rockwell Hardness Test—Part 1: Test Method (scales A, B, C, D, E, F, G, H, K, N, T)
ISO/IEC 17011 Conformity Assessment—General Requirements for Accreditation Bodies Accrediting Conformity Assessment
Bodies
ISO/IEC 17025 General Requirements for the Competence of Testing and Calibration Laboratories
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American Bearing Manufacturers Association (ABMA), 2025 M Street, NW, Suite 800, Washington, DC 20036.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
E18 − 22
2.4 Society of Automotive Engineers (SAE) Standard:
SAE J417 Hardness Tests and Hardness Number Conversions
3. Terminology and Equations
3.1 Definitions:
3.1.1 calibration—determination of the values of the significant parameters by comparison with values indicated by a reference
instrument or by a set of reference standards.
3.1.2 standardization—to bring in conformance to a known standard through verification or calibration.
3.1.3 verification—checking or testing to assure conformance with the specification.
3.1.4 Rockwell hardness test—an indentation hardness test using a verified machine to force a diamond spheroconical indenter or
tungsten carbide (or steel) ball indenter, under specified conditions, into the surface of the material under test, and to measure the
difference in depth of the indentation as the force on the indenter is increased from a specified preliminary test force to a specified
total test force and then returned to the preliminary test force.
3.1.5 Rockwell superficial hardness test—same as the Rockwell hardness test except that smaller preliminary and total test forces
are used with a shorter depth scale.
3.1.6 Rockwell hardness number—a number derived from the net increase in the depth of indentation as the force on an indenter
is increased from a specified preliminary test force to a specified total test force and then returned to the preliminary test force.
3.1.7 Rockwell hardness machine—a machine capable of performing a Rockwell hardness test and/or a Rockwell superficial
hardness test and displaying the resulting Rockwell hardness number.
3.1.7.1 Rockwell hardness testing machine—a Rockwell hardness machine used for general testing purposes.
3.1.7.2 Rockwell hardness standardizing machine—a Rockwell hardness machine used for the standardization of Rockwell
hardness indenters, and for the standardization of Rockwell hardness test blocks. The standardizing machine differs from a regular
Rockwell hardness testing machine by having tighter tolerances on certain parameters.
3.1.7.3 portable Rockwell hardness testing machine—a Rockwell hardness testing machine that is designed to be transported,
carried, set up, and operated by the users, and that measures Rockwell hardness by the Rockwell indentation hardness test
principle.
3.1.7.4 movable Rockwell hardness testing machine—a Rockwell hardness testing machine that is designed to be moved to
different locations on a moveable frame, table or similar support that is integral to the testing machine (for example, securely fixed
to a rolling table), or a Rockwell hardness testing machine that is designed to move into testing position prior to a test, (for
example, securely fixed to a moving support arm), and has been previously verified to ensure that such a move will not affect the
hardness result.
3.2 Equations:
¯
3.2.1 The averageH of a set of n hardness measurements H , H , …, H is calculated as:
1 2 n
H 1H 1…1H
1 2 n
¯
H 5 (1)
n
3.2.2 The error E in the performance of a Rockwell hardness machine at each hardness level, relative to a standardized scale, is
determined as:
¯
E 5 H 2 H (2)
STD
Available from Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
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where:
¯
= average of n hardness measurements H , H , …, H made on a standardized test block as part of a performance
H
1 2 n
verification, and
H = certified average hardness value of the standardized test block.
STD
3.2.3 The repeatability R in the performance of a Rockwell hardness machine at each hardness level, under the particular
verification conditions, is estimated by the range of n hardness measurements made on a standardized test block as part of a
performance verification, defined as:
R 5 H 2 H (3)
max min
where:
H = highest hardness value, and
max
H = lowest hardness value.
min
4. Significance and Use
4.1 The Rockwell hardness test is an empirical indentation hardness test that can provide useful information about metallic
materials. This information may correlate to tensile strength, wear resistance, ductility, and other physical characteristics of
metallic materials, and may be useful in quality control and selection of materials.
4.2 Rockwell hardness tests are considered satisfactory for acceptance testing of commercial shipments, and have been used
extensively in industry for this purpose.
4.3 Rockwell hardness testing at a specific location on a part may not represent the physical characteristics of the whole part or
end product.
4.4 Adherence to this standard test method provides traceability to national Rockwell hardness standards except as stated
otherwise.
5. Principles of Test and Apparatus
5.1 Rockwell Hardness Test Principle—The general principle of the Rockwell indentation hardness test is illustrated in Fig. 1. The
test is divided into three steps of force application and removal.
Step 1—The indenter is brought into contact with the test specimen, and the preliminary test force F is applied. After holding
the preliminary test force for a specified dwell time, the baseline depth of indentation is measured.
Step 2—The force on the indenter is increased at a controlled rate by the additional test force F to achieve the total test force
F. The total test force is held for a specified dwell time.
FIG. 1 Rockwell Hardness Test Method (Schematic Diagram)
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Step 3—The additional test force is removed, returning to the preliminary test force. After holding the preliminary test force
for a specified dwell time, the final depth of indentation is measured. The Rockwell hardness value is derived from the difference
h in the final and baseline indentation depths while under the preliminary test force. The preliminary test force is removed and the
indenter is removed from the test specimen.
5.1.1 There are two general classifications of the Rockwell test: the Rockwell hardness test and the Rockwell superficial hardness
test. The significant difference between the two test classifications is in the test forces that are used. For the Rockwell hardness
test, the preliminary test force is 10 kgf (98 N) and the total test forces are 60 kgf (589 N), 100 kgf (981 N), and 150 kgf (1471
N). For the Rockwell superficial hardness test, the preliminary test force is 3 kgf (29 N) and the total test forces are 15 kgf (147
N), 30 kgf (294 N), and 45 kgf (441 N).
5.1.2 Indenters for the Rockwell hardness test include a diamond spheroconical indenter and tungsten carbide ball indenters of
specified diameters.
5.1.2.1 Steel indenter balls may be used only for testing thin sheet tin mill products specified in Specifications A623 and A623M
using the HR15T and HR30T scales with a diamond spot anvil. Testing of this product may give significantly differing results using
a tungsten carbide ball as compared to historical test data using a steel ball.
NOTE 1—Previous editions of this standard have stated that the steel ball was the standard type of Rockwell indenter ball. The tungsten carbide ball is
considered the standard type of Rockwell indenter ball. The use of tungsten carbide balls provide an improvement to the Rockwell hardness test because
of the tendency of steel balls to flatten with use, which results in an erroneously elevated hardness value. The user is cautioned that Rockwell hardness
tests comparing the use of steel and tungsten carbide balls have been shown to give different results. For example, depending on the material tested and
its hardness level, Rockwell B scale tests using a tungsten carbide ball indenter have given results approximately one Rockwell point lower than when
a steel ball indenter is used.
5.1.3 The Rockwell hardness scales are defined by the combinations of indenter and test forces that may be used. The standard
Rockwell hardness scales and typical applications of the scales are given in Tables 1 and 2. Rockwell hardness values shall be
determined and reported in accordance with one of these standard scales.
5.2 Calculation of the Rockwell Hardness Number—During a Rockwell test, the force on the indenter is increased from a
preliminary test force to a total test force, and then returned to the preliminary test force. The difference in the two indentation
depth measurements, while under the preliminary test force, is measured as h (see Fig. 1).
5.2.1 The unit measurement for h is mm. From the value of h, the Rockwell hardness number is derived. The Rockwell hardness
number is calculated as:
5.2.1.1 For scales using a diamond spheroconical indenter (see Tables 1 and 2):
h
Rockwell Hardness 5 100 2 (4)
0.002
TABLE 1 Rockwell Hardness Scales
Scale Total Test Dial
Indenter Typical Applications of Scales
Symbol Force, kgf Figures
B ⁄16-in. (1.588-mm) ball 100 red Copper alloys, soft steels, aluminum alloys, malleable iron, etc.
C diamond 150 black Steel, hard cast irons, pearlitic malleable iron, titanium, deep case hardened steel, and other
materials harder than B100.
A diamond 60 black Cemented carbides, thin steel, and shallow case-hardened steel.
D diamond 100 black Thin steel and medium case hardened steel, and pearlitic malleable iron.
E ⁄8-in. (3.175-mm) ball 100 red Cast iron, aluminum and magnesium alloys, bearing metals.
F ⁄16-in. (1.588-mm) ball 60 red Annealed copper alloys, thin soft sheet metals.
G ⁄16-in. (1.588-mm) ball 150 red Malleable irons, copper-nickel-zinc and cupro-nickel alloys. Upper limit G92 to avoid possible
flattening of ball.
H ⁄8-in. (3.175-mm) ball 60 red Aluminum, zinc, lead.
K ⁄8-in. (3.175-mm) ball 150 red
L ⁄4-in. (6.350-mm) ball 60 red
M ⁄4-in. (6.350-mm) ball 100 red Bearing metals and other very soft or thin materials. Use smallest ball and heaviest load that does
P ⁄4-in. (6.350-mm) ball 150 red not give anvil effect.
R ⁄2-in. (12.70-mm) ball 60 red
S ⁄2-in. (12.70-mm) ball 100 red
V ⁄2-in. (12.70-mm) ball 150 red
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TABLE 2 Rockwell Superficial Hardness Scales
Scale Symbols
Total Test Force,
1 1 1 1
N Scale, Diamond T Scale, ⁄16-in. W Scale, ⁄8-in. X Scale, ⁄4-in. Y Scale, ⁄2-in.
kgf (N)
Indenter (1.588-mm) Ball (3.175-mm) Ball (6.350-mm) Ball (12.70-mm) Ball
15 (147) 15N 15T 15W 15X 15Y
30 (294) 30N 30T 30W 30X 30Y
45 (441) 45N 45T 45W 45X 45Y
h
Rockwell Superficial Hardness 5 100 2 (5)
0.001
where h is in mm.
5.2.1.2 For scales using a ball indenter (see Tables 1 and 2):
h
Rockwell Hardness 5 130 2 (6)
0.002
h
Rockwell Superficial Hardness 5 100 2 (7)
0.001
where h is in mm.
5.2.2 The Rockwell hardness number is an arbitrary number, which, by method of calculation, results in a higher number for
harder material.
5.2.3 Rockwell hardness values shall not be designated by a number alone because it is necessary to indicate which indenter and
forces have been employed in making the test (see Tables 1 and 2). Rockwell hardness numbers shall be quoted with a scale symbol
representing the indenter and forces used. The hardness number is followed by the symbol HR and the scale designation. When
a ball indenter is used, the scale designation is followed by the letter “W” to indicate the use of a tungsten carbide ball or the letter
“S” to indicate the use of a steel ball (see 5.1.2.1).
5.2.3.1 Examples:
64 HRC = Rockwell hardness number of 64 on Rockwell C scale
81 HR30N = Rockwell superficial hardness number of 81 on the Rockwell
30N scale
72 HRBW = Rockwell hardness number of 72 on the Rockwell B scale
using a tungsten carbide ball indenter
5.2.4 A reported Rockwell hardness number or the average value of Rockwell hardness measurements shall be rounded in
accordance with Practice E29 with a resolution no greater than the resolution of the hardness value display of the testing machine.
Typically, the resolution of a Rockwell hardness number should not be greater than 0.1 Rockwell units.
NOTE 2—When the Rockwell hardness test is used for the acceptance testing of commercial products and materials, the user should take into account the
potential measurement differences between hardness testing machines allowed by this standard (see Section 10, Precision and Bias). Because of the
allowable ranges in the tolerances for the repeatability and error of a testing machine, as specified in the verification requirements of Annex A1, one testing
machine may have a test result that is one or more hardness points different than another testing machine, yet both machines can be within verification
tolerances (see Table A1.3). Commonly for acceptance testing, Rockwell hardness values are rounded to whole numbers following Practice E29. Users
are encouraged to address rounding practices with regards to acceptance testing within their quality management system, and make any special
requirements known during contract review.
5.3 Rockwell Testing Machine—The Rockwell testing machine shall make Rockwell hardness determinations by applying the test
forces and measuring the depth of indentation in accordance with the Rockwell hardness test principle.
5.3.1 See the Equipment Manufacturer’s Instruction Manual for a description of the machine’s characteristics, limitations, and
respective operating procedures.
5.3.2 The Rockwell testing machine shall automatically convert the depth measurements to a Rockwell hardness number and
indicate the hardness number and Rockwell scale by an electronic device or by a mechanical indicator.
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5.4 Indenters—The standard Rockwell indenters are either diamond spheroconical indenters or tungsten carbide balls of 1.588 mm
1 1 1 1
( ⁄16 in.), 3.175 mm ( ⁄8 in.), 6.350 mm ( ⁄4 in.), or 12.70 mm ( ⁄2 in.) in diameter. Indenters shall meet the requirements defined
in Annex A3. Steel ball indenters may be used in certain circumstances (see 5.1.2.1).
5.4.1 Dust, dirt, or other foreign materials shall not be allowed to accumulate on the indenter, as this will affect the test results.
NOTE 3—Indenters certified to revision E18E18-07-07 or later meet the requirements of this standard.
5.5 Specimen Support—A specimen support or “anvil” shall be used that is suitable for supporting the specimen to be tested. The
seating and supporting surfaces of all anvils shall be clean and smooth and shall be free from pits, deep scratches, and foreign
material. Damage to the anvil may occur from testing too thin material or accidental contact of the anvil by the indenter. If the
anvil is damaged from any cause, it shall be repaired or replaced. Anvils showing the least visibly perceptible damage may give
inaccurate results, particularly on thin material.
5.5.1 Common specimen support anvils should have a minimum hardness of 58 HRC. Some specialty support anvils require a
lower material hardness.
5.5.2 Flat pieces should be tested on a flat anvil that has a smooth, flat bearing surface whose plane is perpendicular to the axis
of the indenter.
5.5.3 Small diameter cylindrical pieces shall be tested with a hard V-grooved anvil with the axis of the V-groove directly under
the indenter, or on hard, parallel, twin cylinders properly positioned and clamped in their base. These types of specimen supports
shall support the specimen with the apex of the cylinder directly under the indenter.
5.5.4 For thin materials or specimens that are not perfectly flat, an anvil having an elevated, flat “spot” 3 mm ( ⁄8 in.) to 12.5 mm
( ⁄2 in.) in diameter should be used. This spot shall be polished smooth and flat. Very soft material should not be tested on the “spot”
anvil because the applied force may cause the penetration of the anvil into the under side of the specimen regardless of its
thickness.
5.5.5 When testing thin sheet metal with a ball indenter, it is recommended that a diamond spot anvil be used. The highly polished
diamond surface shall have a diameter between 4.0 mm (0.157 in.) and 7.0 mm (0.2875 in.) and be centered within 0.5 mm (0.02
in.) of the test point.
5.5.5.1 CAUTION: A diamond spot anvil should only be used with a maximum total test force of 45 kgf (441 N) and a ball
indenter. This recommendation should be followed except when directed otherwise by material specification.
5.5.6 Special anvils or fixtures, including clamping fixtures, may be required for testing pieces or parts that cannot be supported
by standard anvils. Auxiliary support may be used for testing long pieces with so much overhang that the piece is not firmly seated
by the preliminary force.
5.6 Verification—Rockwell testing machines shall be verified periodically in accordance with Annex A1.
5.7 Test Blocks—Test blocks meeting the requirements of Annex A4 shall be used to verify the testing machine in accordance with
Annex A1.
NOTE 4—Test blocks certified to revision E18-07 or later meet the requirements of this standard.
NOTE 5—It is recognized that appropriate standardized test blocks are not available for all geometric shapes, or materials, or both.
5.8 Use of Portable Rockwell Hardness Testing Machines:
5.8.1 A fixed-location Rockwell hardness testing machine may not be capable of testing certain samples because of the sample
size or weight, sample location, accessibility of the test point or other requirements. In these circumstances, the use of a portable
Rockwell hardness testing machine is an acceptable method to test these samples. This method allows the use of a portable
Rockwell hardness testing machine as follows.
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5.8.1.1 The portable Rockwell hardness testing machine shall meet the requirements of this method, including the test principle,
apparatus, indenters, applied forces, test procedures and the direct and indirect verifications of the testing machine (except as
indicated in Table A1.1). Test Method E110 covers portable Rockwell hardness testing machines that cannot be directly verified
or cannot pass direct verification but meet the other requirements of this method.
5.8.1.2 A portable Rockwell hardness testing machine shall be used only when testing circumstances make it impractical to use
a fixed-location Rockwell hardness testing machine. In such cases, it is recommended that an agreement or understanding be made
between all parties involved (for example, testing service and customer) that a portable Rockwell hardness testing machine will
be used instead of a fixed-location Rockwell hardness testing machine (see 5.8.1.)
5.8.1.3 The portable Rockwell hardness testing machine shall measure hardness by the Rockwell hardness test principle (see 5.1).
Portable hardness testing machines or instruments that measure hardness by other means or procedures different than the Rockwell
hardness test principle, such as those defined in Test Methods A883, A956A956/A956M, A1038 or B647, produce converted
Rockwell hardness values and do not comply with this method.
5.8.2 Daily Verification of portable hardness testing machines—Portable hardness testing machines are susceptible to damage
when they are transported or carried from one test site to another. Therefore, in addition to complying with the daily verification
requirements specified in 7.1 and Annex A1, a daily verification shall be performed at each test worksite where the hardness tests
are to be made just prior to making the hardness tests. The verification shall be performed with the portable hardness testing
machine oriented as closely as practical to the position that it will be used. It is recommended that the daily verification be repeated
occasionally during testing and after testing is completed.
5.8.3 Additional reporting requirements when using a portable Rockwell hardness testing machine are given in 9.2.
5.8.4 Portable hardness testing machines by the nature of their application may induce errors that could influence the test results.
To understand the differences in results expected between portable and fixed-location Rockwell hardness testing machines, the user
should compare the results of the precision and bias studies given in Section 10 and in Test Method E110.
6. Test Piece
6.1 For best results, both the test surface and the bottom surface of the test piece should be smooth, even and free from oxide scale,
foreign matter, and lubricants. An exception is made for certain materials such as reactive metals that may adhere to the indenter.
In such situations, a suitable lubricant such as kerosene may be used. The use of a lubricant shall be defined on the test report.
6.2 Preparation shall be carried out in such a way that any alteration of the surface hardness of the test surface (for example, due
to heat or cold-working) is minimized.
6.3 The thickness of the test piece or of the layer under test should be as defined in tables and presented graphically in Annex A5.
These tables were determined from studies on strips of carbon steel and have proven to give reliable results. For all other materials,
it is recommended that the thickness should exceed 10 times the depth of indentation. In general, no deformation should be visible
on the back of the test piece after the test, although not all such marking is indicative of a bad test.
6.3.1 Special consideration should be made when testing parts that exhibit hardness gradients; for example, parts that were
case-hardened by processes such as carburizing, carbonitriding, nitriding, induction, etc. The minimum thickness guidelines given
in Annex A5 only apply to materials of uniform hardness, and should not be used to determine the appropriate scale for measuring
parts with hardness gradients. The selection of an appropriate Rockwell scale for parts with hardness gradients should be made
by special agreement.
NOTE 6—A table listing the minimum effective case depth needed for different Rockwell scales is given in SAE J417.
6.4 When testing on convex cylindrical surfaces, the result may not accurately indicate the true Rockwell hardness; therefore, the
corrections given in Annex A6 shall be applied. For diameters between those given in the tables, correction factors may be derived
by linear interpolation. Tests performed on diameters smaller than those given in Annex A6 are not acceptable. Corrections for tests
on spherical and concave surfaces should be the subject of special agreement. Additional requirements are specified in 9.4 and 9.5
when reporting corrected hardness values.
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NOTE 7—A table of correction values to be applied to test results made on spherical surfaces is given in ISO 6508-1.
6.5 When testing small diameter specimens, the accuracy of the test will be seriously affected by alignment between the indenter
and the test piece, by surface finish, and by the straightness of the cylinder.
7. Test Procedure
7.1 A daily verification of the testing machine shall be performed in accordance with A1.5 prior to making hardness tests.
Hardness measurements shall be made only on the calibrated surface of the test block.
7.1.1 The results of a daily verification shall comply with the current values specified in Table A1.3 regardless of any maximum
error E value marked on the test block (see Note 8).
NOTE 8—Different editions of this method have revised some maximum error E values given in Table A1.3. Consequently, the maximum error E values
marked on older standardized test blocks may not reflect the current values.
7.2 Rockwell hardness tests should be carried out at ambient temperature within the limits of 1010 °C to 35 °C (50(50 °F to 95 °F).
Users of the Rockwell hardness test are cautioned that the temperature of the test material and the temperature of the hardness tester
may affect test results. Consequently, users should ensure that the test temperature does not adversely affect the hardness
measurement.
7.3 The test piece shall be supported rigidly so that displacement of the test surface is minimized (see 5.5).
7.4 Test Cycle—This standard specifies the Rockwell test cycle by stating recommendations or requirements for five separate parts
of the cycle. These parts are illustrated for a Rockwell C scale test in Fig. 2, and defined as follows:
(1) Contact Velocity, v —The velocity of the indenter at the point of contact with the test material.
A
FIG. 2 Schematic of Force-Time Plot (a) and Indenter Depth-Time Plot (b) of an HRC Test Illustrating the Test Cycle Parts
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(2) Preliminary Force Dwell Time, t —The dwell time beginning when the preliminary force is fully applied and ending when
PF
the first baseline depth of indentation is measured, (also see 7.4.1.3).
(3) Additional Force Application Time, t —The time for applying the additional force to obtain the full total force.
TA
(4) Total Force Dwell Time, t —The dwell time while the total force is fully applied.
TF
(5) Dwell Time for Elastic Recovery, t —The dwell time at the preliminary force level, beginning when the additional force
R
is fully removed, and ending when the second and final depth of indentation is measured.
7.4.1 The standard Rockwell test cycle is specified in Table 3. The test cycle used for Rockwell hardness tests shall be in
accordance with these test cycle values and tolerances (see Note 9), with the following exceptions.
7.4.1.1 Precautions for Materials Having Excessive Time-Dependent Plasticity (Indentation Creep)—In the case of materials
exhibiting excessive plastic flow after application of the total test force, special considerations may be necessary since the indenter
will continue to penetrate. When materials require the use of a longer total force dwell time than for the standard test cycle stated
in Table 3, this should he specified in the product specification. In these cases, the actual extended total force dwell time used shall
be recorded and reported after the test results (for example, 65 HRFW, 10 s).
7.4.1.2 There are testing conditions that may require that the indenter contact velocity exceed the recommended maximum stated
in Table 3. The user should ensure that the higher contact velocity does not cause a shock or overload which would affect the
hardness result. It is recommended that comparison tests be made on the same test material using a test cycle within the
requirements stated in Table 3.
7.4.1.3 For testing machines that take 1 s or longer to apply the preliminary force t , the preliminary force dwell time value t
PA PF
t
PA
shall be adjusted before comparing the parameter with the tolerances of Table 3 by adding to it one half of t as 1t . For testing
PA PF
machines that apply the preliminary force t in 1 s or less, this adjustment to the preliminary force dwell time value t is optional.
PA PF
NOTE 9—It is recommended that the test cycle to be used with the hardness machine match, as closely as possible, the test cycle used for the indirect
verification of the hardness machine. Varying the values of the testing cycle parameters within the tolerances of Table 3 can produce different hardness
results.
7.5 Test Procedure—There are many designs of Rockwell hardness machines, requiring various levels of operator control. Some
hardness machines can perform the Rockwell hardness test procedure automatically with almost no operator influence, while other
machines require the operator to control most of the test procedure.
7.5.1 Bring the indenter into contact with the test surface in a direction perpendicular to the surface and, if possible, at a velocity
within the recommended maximum contact velocity v .
A
7.5.2 Apply the preliminary test force F of 10 kgf (98 N) for the Rockwell hardness test or 3 kgf (29 N) for the Rockwell
superficial hardness test.
7.5.3 Maintain the preliminary force for the specified preliminary force dwell time t .
PF
TABLE 3 Test Cycle Tolerances
Test Cycle Parameter Tolerance
Indenter contact velocity, v (recommended) #2.5 mm/s
A
Dwell time for preliminary force, t (when the time to apply 0.1 to 4.0 s
PF
the preliminary force t $ 1 s, then calculate this parameter
PA
t
PA
as 1t )
PF
Dwell time for preliminary force, t (when the time to apply 0.1 s to 4.0
PF
the preliminary force t $ 1 s, then calculate this parameter s
PA
t
PA
as 1t )
PF
Time for application of additional force, t 1.0 to 8.0 s
TA
Time for application of additional force, t 1.0 s to 8.0
TA
s
Dwell time for total force, t 2.0 to 6.0 s
TF
Dwell time for total force, t 2.0 s to 6.0
TF
s
Dwell time for elastic recovery, t 0.2 to 5.0 s
R
Dwell time for elastic recovery, t 0.2 s to 5.0
R
s
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7.5.4 At the end of the preliminary force dwell time t , immediately establish the reference position of the baseline depth of
PF
indentation (see manufacturer’s Instruction Manual).
7.5.5 Increase the force by the value of the additional test force F needed to obtain the required total test force F for a given
hardness scale (see Tables 1 and 2). The additional force F shall be applied in a controlled manner within the specified application
time range t .
TA
7.5.6 Maintain the total force F for the specified total force dwell time t .
TF
7.5.7 Remove the additional test force F while maintaining the preliminary test force F .
1 0
7.5.8 Maintain the preliminary test force F for an appropriate time to allow elastic recovery in the test material and the stretch
of the frame to be factored out.
7.5.9 At the end of the dwell time for elastic recovery, immediately establish the final depth of indentation (see manufacturer’s
Instruction Manual). The testing machine shall calculate the difference between the final and baseline depth measurements and
indicate the resulting Rockwell hardness value. The Rockwell hardness number is derived from the differential increase in depth
of indentation as defined in Eq 4, Eq 5, Eq 6, and Eq 7.
7.6 Throughout the test, the apparatus shall be protected from shock or vibration that could affect the hardness measurement result.
7.7 After each change, or removal and replacement, of the indenter or the anvil, at least two preliminary indentations shall be made
to ensure that the indenter and anvil are seated properly. The results of the preliminary indentations shall be disregarded.
7.8 After each change of a test force or removal and replacement of the indenter or the anvil, it is strongly recommended that the
operation of the machine be checked in accordance with the daily verification method specified in Annex A1.
7.9 Indentation Spacing—The hardness of the material immediately surrounding a previously made indentation will usually
increase due to the induced residual stress and work-hardening caused by the indentation process. If a new indentation is made
in this affected material, the measured hardness value will likely be higher than the true hardness of the material as a whole. Also,
if an indentation is made too close to the edge of the material or very close to a previously made indentation, there may be
insufficient material to constrain the deformation zone surrounding the indentation. This can result in an apparent lowering of the
hardness value. Both of these circumstances can be avoided by allowing appropriate spacing between indentations and from the
edge of the material.
7.9.1 The distance between the centers of two adjacent indentations shall be at least three times the diameter d of the indentation
(see Fig. 3).
7.9.2 The distance from the center of any indentation to an edge of the test piece shall be at least two and a half times the diameter
of the indentation (see Fig. 3).
FIG. 3 Schematic of Minimum Indentation Spacing
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8. Conversion to Other Hardness Scales or Tensile Strength Values
8.1 There is no general method of accurately converting the Rockwell hardness numbers on one scale to Rockwell hardness
numbers on another scale, or to other types of hardness numbers, or to tensile strength values. Such conversions are, at best,
approximations and, therefore, should be avoided except for special cases where a reliable basis for the approximate conversion
has been obtained by comparison tests. Additional requirements are specified in 9.3 and 9.5 when reporting converted hardness
values.
NOTE 10—The Standard Hardness Conversion Tables for Metals, E140, give approximate conversion values for specific materials such as steel, austenitic
stainless steel, nickel and high-nickel alloys, cartridge brass, copper alloys, and alloyed white cast irons. The Rockwell hardness data in the conversion
tables of E140 was determined using steel ball indenters.
NOTE 11—ASTM standards giving approximate hardness-tensile strength relationships are listed in Appendix X1.
9. Report
9.1 The test report shall include the following information:
9.1.1 The Rockwell hardness number. All reports of Rockwell hardness numbers shall indicate the scale used. The reported
number shall be rounded in accordance with Practice E29 (see 5.2.4 and Note 2),
9.1.2 The total force dwell time, if outside the specified standard test cycle tolerances (see Table 3), and
9.1.3 The ambient temperature at the time of test, if outside the limits of 10 to 35 °C (50 to 95 °F), unless it has been shown not
to affect the measurement result.
9.2 Reporting Portable Testing Machine Hardness Values—When using a portable Rockwell hardness testing machine, the
measured hardness number shall be reported in accordance with 9.1, and appended with a /P to indicate that it was determined by
portable Rockwell hardness testing machine,machine. For example:
40 HRC/P = Rockwell hardness number of 40 on the Rockwell C scale.
72 HRBW/P = Rockwell hardness number of 72 on the Rockwell B scale with a tungsten carbide ball indenter.
9.3 Reporting Converted Hardness Values—When reporting hardness values that have been converted from one type of hardness
test or hardness scale to another type of hardness test or hardness scale, the original measurement number and test scale shall also
be reported (see E140).
9.3.1 A common historical practice is to report the converted hardness value followed by the measured hardness value given in
parentheses. For example: 353 HBW (38 HRC), where 353 HBW is the converted hardness value and 38 HRC is the original
measurement value.
9.3.2 Other formats for reporting converted hardness values, such as data tables, may be used, however, the original measurement
number and test scale shall also be reported and clearly identified.
9.4 Reporting Curvature Corrected Hardness Values—When reporting Rockwell hardness test values that have been corrected for
testing on cylindrical or spherical surfaces (see 6.4), the following information shall be indicated in the test report or documented
in the test lab/customer contract or agreement:
–the test values are corrected due to testing on a curved surface,
–the source of correction value, if other than the correction tables given in Annex A6 for convex cylindrical surfaces.
9.5 Since all converted or curvature-corrected hardness values are considered approximate, the reported hardness values shall be
rounded in accordance with the Rounding Method of Practice E29 and should have no more significant digits than is given for the
data in the applicable conversion or correction table.
E18 − 22
7,8
10. Precision and Bias
10.1 Precision—A Rockwell hardness precision and bias study was conducted in 2000 in accordance with Practice E691. Tests
were performed in the following six Rockwell scales: HRA, HRC, HRBS, HR30N, HR30TS, and HRES. The tests in the HRBS,
HR30TS and HRES scales were made using steel ball indenters. A total of 18 Rockwell scale hardness test blocks of the type
readily available were used for this study. Test blocks at three different hardness levels (high, medium, and low) in each scale were
7,8
tested three times each. The results from the first study are filed under ASTM Research Report RR:E28-1021.
10.2 Starting with version E18-05, this standard changed from the use of steel balls to carbide balls for all scales that use a ball
indenter. Due to this change, a second study was conducted in 2006. The second study was performed in accordance with Practice
E691 and was identical to the initial study except it was limited to the HRBW, HR30TW, and HREW scales, all of which use
carbide ball indenters. The results from that study are filed under ASTM Research Report RR:E28-1022.
10.3 A total of 14 different labs participated in the two studies. Eight participated in the first study and nine in the second study.
Thre
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