ASTM A956-12
(Test Method)Standard Test Method for Leeb Hardness Testing of Steel Products
Standard Test Method for Leeb Hardness Testing of Steel Products
SIGNIFICANCE AND USE
5.1 Hardness of a material is a poorly defined term that may have many meanings depending on the type of test performed and the expectations of the person involved. The Leeb hardness test is of the dynamic or rebound type, which primarily depends both on the plastic and on the elastic properties of the material being tested. The results obtained are indicative of the strength and dependent on the heat treatment of the material tested.
5.2 The Leeb hardness test is a superficial determination only measuring the condition of the surface contacted. The results generated at that location do not represent the part at any other surface location and yield no information about the material at subsurface locations.
SCOPE
1.1 This test method covers the determination of the Leeb hardness of steel, cast steel, and cast iron (Part A), including the methods for the verification of Leeb hardness testing instruments (Part B), and the calibration of standardized test blocks (Part C). Note 1—The original title of this standard was “Standard Test Method for Equotip Hardness Testing of Steel Products.”1
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.
1.3 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 and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: A956 − 12
Standard Test Method for
1
Leeb Hardness Testing of Steel Products
This standard is issued under the fixed designation A956; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope shaped tungsten carbide, silicon nitride, or diamond tipped
impact body, multiplied by 1000.
1.1 This test method covers the determination of the Leeb
hardness of steel, cast steel, and cast iron (Part A), including ReboundVelocity
L 5 31000
the methods for the verification of Leeb hardness testing ImpactVelocity
instruments (Part B), and the calibration of standardized test
The Leeb hardness number is followed by the symbol HL
blocks (Part C).
with one or more suffix characters representing the type of
NOTE 1—The original title of this standard was “Standard Test Method impact device.
1
for Equotip Hardness Testing of Steel Products.”
3.1.3 Leeb hardness test—a dynamic hardness test method
1.2 The values stated in inch-pound units are to be regarded
using a calibrated instrument that impacts a spherically shaped
as standard. The values given in parentheses are mathematical
tungsten carbide, silicon nitride, or diamond tipped body with
conversions to SI units that are provided for information only
a fixed velocity (generated by a spring force) onto a surface of
and are not considered standard.
the material under test.The ratio of the rebound velocity to the
impactvelocityoftheimpactbodyisameasureofthehardness
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the of the material under test.
responsibility of the user of this standard to establish appro-
3.1.4 surface finish—all references to surface finish in this
priate safety and health practices and determine the applica-
test method are defined as surface roughness (that is, Ra =
bility of regulatory limitations prior to use.
average roughness value, AA = arithmetic average).
3.1.5 verification—checking or testing the instrument to
2. Referenced Documents
ensure conformance with this test method.
2
2.1 ASTM Standards:
E691Practice for Conducting an Interlaboratory Study to
4. Summary of Test Method
Determine the Precision of a Test Method
4.1 During a hardness test, an impact body with a spheri-
cally shaped tungsten carbide, silicon nitride, or diamond tip
3. Terminology
impacts under spring force, the test surface from which it
3.1 Definitions:
rebounds. The impact and rebound velocities are measured
3.1.1 calibration—determination of the values of the sig-
when the impact body is approximately 1 mm from the test
nificant operating parameters of the instrument by comparison
surface.Thisisaccomplishedbymeansofapermanentmagnet
with values indicated by a reference instrument or by a set of
mounted in the impact body which, during the test, moves
reference standards.
through a coil in the impact device and induces an electric
3.1.2 Leeb hardness number—anumberequaltotheratioof
voltage on both the impact and rebound movements. These
thereboundvelocitytotheimpactvelocityofa3-mmor5-mm
induced voltages are proportional to the respective impact and
(based on the type of impact device) diameter spherically
rebound velocities. The quotient of these measured voltage
values derived from the impact and rebound velocities, multi-
plied by the factor 1000 produces a number which constitutes
1
This test method is under the jurisdiction of ASTM Committee A01 on Steel,
the Leeb hardness value.
Stainless Steel and RelatedAlloys and is the direct responsibility of Subcommittee
A01.06 on Steel Forgings and Billets.
Current edition approved Nov. 15, 2012. Published December 2012. Originally
5. Significance and Use
approved in 1996. Last previous edition approved in 2006 as A956–06.
5.1 Hardnessofamaterialisapoorlydefinedtermthatmay
Leeb and Equotip are registered trademarks used with permission of Proceq SA.
DOI: 10.1520/A0956-12.
have many meanings depending on the type of test performed
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
andtheexpectationsofthepersoninvolved.TheLeebhardness
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
test is of the dynamic or rebound type, which primarily
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. depends both on the plastic and on the elastic properties of the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1
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A956 − 12
material being tested.The result
...
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: A956 − 06 A956 − 12
Standard Test Method for
1
Leeb Hardness Testing of Steel Products
This standard is issued under the fixed designation A956; 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.
1. Scope*Scope
1.1 This test method covers the determination of the Leeb hardness of steel, cast steel, and cast iron (Part A), including the
methods for the verification of Leeb hardness testing instruments (Part B), and the calibration of standardized test blocks (Part C).
1
NOTE 1—The original title of this standard was “Standard Test Method for Equotip Hardness Testing of Steel Products.”
1.2 The values stated in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units that are provided for information only and are not considered standard.
1.3 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 and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2
2.1 ASTM Standards:
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions:
3.1.1 calibration—determination of the values of the significant operating parameters of the instrument by comparison with
values indicated by a reference instrument or by a set of reference standards.
3.1.2 Leeb hardness number—a number equal to the ratio of the rebound velocity to the impact velocity of a 3-mm or 5-mm
(based on the type of impact device) diameter tungsten carbide ball spherically shaped tungsten carbide, silicon nitride, or diamond
tipped impact body, multiplied by 1000.
Rebound Velocity
L 5 31000
Impact Velocity
The Leeb hardness number is followed by the symbol HL with one or more suffix characters representing the type of impact
device.
3.1.3 Leeb hardness test—a dynamic hardness test method using a calibrated instrument that impacts a spherically shaped
carbide ball tungsten carbide, silicon nitride, or diamond tipped body with a fixed velocity (generated by a spring force) onto a
surface of the material under test. The ratio of the rebound velocity to the impact velocity of the impact body is a measure of the
hardness of the material under test.
3.1.4 surface finish—all references to surface finish in this test method are defined as surface roughness (that is, Ra = average
roughness value, AA = arithmetic average).
3.1.5 verification—checking or testing the instrument to ensure conformance with this test method.
4. Summary of Test Method
4.1 During a hardness test, an impact body with a spherically shaped tungsten carbide carbide, silicon nitride, or diamond tip
impacts under spring force, the test surface from which it rebounds. The impact and rebound velocities are measured when the
1
This test method is under the jurisdiction of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys and is the direct responsibility of Subcommittee A01.06
on Steel Forgings and Billets.
Current edition approved Sept. 1, 2006Nov. 15, 2012. Published September 2006December 2012. Originally approved in 1996. Last previous edition approved in 20022006
as A956 – 02.A956 – 06.
Leeb and Equotip are registered trademarks used with permission of Proceq SA. DOI: 10.1520/A0956-06.10.1520/A0956-12.
2
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM 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
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A956 − 12
impact body is approximately 1 mm from the test surface. This is accomplished by means of a permanent magnet mounted in the
impact body which, during the test, moves through a coil in the impact device and induces an electric voltage on both the impact
and rebound movements. These induced voltages are proportional to the respective impact and rebound velocities. The quotient
of these mea
...
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