ASTM F1537-20

Standard Specification for Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants (UNS R31537, UNS R31538, and UNS R31539)

ABSTRACT
This specification covers the chemical, mechanical, and metallurgical requirements for three wrought cobalt-28chromium-6molybdenum alloys used for surgical implants. The properties specified apply specifically to wrought bar, rod, and wire. The alloys shall conform to the prescribed chemical requirements. Two tension and two bend tests shall be performed on each sample lot to determine tensile properties. Bar, rod, and wire conforming to this specification shall have a homogeneous microstructure with an average grain size of ASTM No. 5 or finer when measured.
SCOPE
1.1 This specification covers the chemical, mechanical, and metallurgical requirements for three wrought cobalt-28chromium-6molybdenum alloys used for surgical implants. The properties specified apply specifically to wrought bar, rod, and wire.  
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used independently of the other, and values from the two systems shall not be combined.  
1.3 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.

General Information

• Status: Published
• Publication Date: 29-Feb-2020
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.12 - Metallurgical Materials

Relations

• Replaces: ASTM F1537-11 - Standard Specification for Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants (UNS R31537, UNS R31538, and UNS R31539)
• Effective Date: 01-Mar-2020
• Refers: ASTM E8/E8M-24 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Jan-2024
• Refers: ASTM F799-19 - Standard Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Forgings for Surgical Implants (UNS R31537, R31538, R31539)
• Effective Date: 15-May-2019
• Refers: ASTM E18-18 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Jul-2018
• Refers: ASTM E18-17 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Jul-2017
• Refers: ASTM E8/E8M-16 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 15-Jul-2016
• Refers: ASTM E8/E8M-15 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Feb-2015
• Refers: ASTM E8/E8M-13 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Jun-2013
• Refers: ASTM E18-12 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Dec-2012
• Refers: ASTM E112-12 - Standard Test Methods for Determining Average Grain Size
• Effective Date: 15-Nov-2012
• Refers: ASTM F75-12 - Standard Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants (UNS R30075)
• Effective Date: 15-May-2012
• Refers: ASTM E8/E8M-11 - Standard Test Methods for Tension Testing of Metallic Materials
• Effective Date: 01-Dec-2011
• Refers: ASTM E18-11 - Standard Test Methods for Rockwell Hardness of Metallic Materials
• Effective Date: 01-Nov-2011
• Refers: ASTM F799-11 - Standard Specification for Cobalt-28Chromium-6Molybdenum Alloy Forgings for Surgical Implants (UNS R31537, R31538, R31539)
• Effective Date: 01-Jun-2011
• Refers: ASTM E112-10 - Standard Test Methods for Determining Average Grain Size
• Effective Date: 01-Nov-2010

Overview

ASTM F1537-20 specifies the chemical, mechanical, and metallurgical requirements for three types of wrought cobalt-28chromium-6molybdenum alloys, designated as UNS R31537, UNS R31538, and UNS R31539. These alloys are predominantly used in the production of surgical implants and are supplied in the form of bar, rod, or wire. The standard outlines rigorous criteria to ensure the material’s quality, performance, and consistency, especially as it relates to biocompatibility and structural integrity crucial for medical applications.

These provisions aim to ensure that implantable medical devices are manufactured using high-performing, reliable materials that are suitable for long-term contact with human tissue and bone.

Key Topics

• Material Composition: The standard defines precise chemical requirements for each alloy type, focusing on elements such as cobalt, chromium, molybdenum, carbon, aluminum, lanthanum, nickel, iron, silicon, manganese, and nitrogen.
• Mechanical Properties: Tensile strength, yield strength, elongation, reduction in area, and typical hardness values are clearly specified for all delivered conditions: annealed, hot-worked, and warm-worked.
• Microstructure Requirements: Products must demonstrate a homogeneous microstructure with grain size ASTM No. 5 or finer, ensuring consistent behavior in medical use.
• Ultrasonic Inspection: Stringent ultrasonic inspection protocols are mandatory for specific sizes of bar, rod, and wire, promoting defect-free materials in safety-critical surgical implants.
• Testing and Certification: Detailed procedures for mechanical and chemical property verification, along with certification requirements, help ensure traceability and quality assurance throughout manufacturing and procurement.
• Unit of Measure and Documentation: Provides guidance for using SI or inch-pound units consistently and specifies the requirements for ordering and certifying material.

Applications

• Surgical Implants: The predominant use is in medical device manufacturing, particularly for implants that require long-term compatibility with body tissues such as orthopedic rods, pins, and wires.
• Medical Device Fabrication: The standard supports manufacturers in producing implantable devices that demand high strength, excellent corrosion resistance, and biocompatibility.
• Forging Stock: Wrought bar, rod, or wire meeting this specification can serve as input material for further forging operations in compliance with related standards, extending application across a range of surgical components.
• Consistent Quality for Critical Applications: Adoption of ASTM F1537-20 helps ensure the safety and efficacy of medical implants by standardizing the production and inspection of base materials, promoting confidence among device manufacturers and regulators.

Related Standards

For comprehensive compliance and integration into manufacturing processes, ASTM F1537-20 references or aligns with several related documents:

• ASTM E8/E8M – Test Methods for Tension Testing of Metallic Materials
• ASTM E18 – Test Methods for Rockwell Hardness of Metallic Materials
• ASTM E29 – Practice for Using Significant Digits in Test Data
• ASTM E112 – Test Methods for Determining Average Grain Size
• ASTM E354 – Chemical Analysis of High-Temperature Alloys
• ASTM F75 – Specification for Cobalt-28Chromium-6Molybdenum Alloy Castings for Surgical Implants
• ASTM F799 – Specification for Forgings of Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants
• ISO 5832-12 – International equivalent for metallic implant materials
• ISO 9001, AMS 2248, AMS 2269, AMS 2630 – Additional quality and material standards referenced for chemical analysis, quality systems, and ultrasonic inspection

By following ASTM F1537-20, manufacturers can ensure that cobalt-chromium-molybdenum alloys used in surgical implants consistently meet the demanding requirements of the medical sector, supporting patient safety and regulatory compliance.

Keywords: ASTM F1537-20, cobalt alloys, surgical implants, cobalt-28chromium-6molybdenum, medical device standards, implant materials, biomedical alloys, wrought bar rod wire.

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:F1537 −20
Standard Specification for
Wrought Cobalt-28Chromium-6Molybdenum Alloys for
Surgical Implants (UNS R31537, UNS R31538, and UNS
R31539)
This standard is issued under the fixed designation F1537; 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* F75 Specification for Cobalt-28 Chromium-6 Molybdenum
Alloy Castings and Casting Alloy for Surgical Implants
1.1 This specification covers the chemical, mechanical, and
(UNS R30075)
metallurgical requirements for three wrought cobalt-
F799 Specification for Cobalt-28 Chromium-6 Molybdenum
28chromium-6molybdenum alloys used for surgical implants.
Alloy Forgings for Surgical Implants (UNS R31537,
The properties specified apply specifically to wrought bar, rod,
R31538, R31539)
and wire.
IEEE/ASTM SI 10 American National Standard for Metric
1.2 The values stated in either SI units or inch-pound units
Practice
are to be regarded separately as standard. The values stated in
2.2 Aerospace Material Specifications:
each system are not necessarily exact equivalents; therefore, to
AMS 2248 Chemical CheckAnalysis Limits, Corrosion and
ensure conformance with the standard, each system shall be
Heat Resistant Steels and Alloys, Maraging and Other
used independently of the other, and values from the two
Highly-Alloyed Steels, and Iron Alloys
systems shall not be combined.
AMS 2269 Chemical CheckAnalysis Limits, Nickel, Nickel
1.3 This international standard was developed in accor-
Alloys and Cobalt Alloys
dance with internationally recognized principles on standard-
AMS 2630 Inspection, Ultrasonic Product over 0.5 Inch
ization established in the Decision on Principles for the
(12.7 mm) Thick
Development of International Standards, Guides and Recom-
2.3 ISO Standards:
mendations issued by the World Trade Organization Technical
ISO 5832–12 Implants for Surgery—Metallic Materials—
Barriers to Trade (TBT) Committee.
Part 12: Wrought Cobalt-Chromium-Molybdenum Alloy
ISO 6892 Metallic Materials - Tensile Testing at Ambient
2. Referenced Documents
Temperature
2.1 ASTM Standards:
ISO 9001 Quality Management Systems—Requirements
E8/E8M Test Methods for Tension Testing of Metallic Ma-
terials 3. Terminology
E18 Test Methods for Rockwell Hardness of Metallic Ma-
3.1 Definitions of Terms Specific to This Standard:
terials
3.1.1 lot—the total number of mill products produced from
E29 Practice for Using Significant Digits in Test Data to
the same melt heat under the same conditions at essentially the
Determine Conformance with Specifications
same time.
E112 Test Methods for Determining Average Grain Size
E354 Test Methods for Chemical Analysis of High-
4. Ordering Information
Temperature,Electrical,Magnetic,andOtherSimilarIron,
4.1 Inquiries and orders for material under this specification
Nickel, and Cobalt Alloys
shall include the following information:
4.1.1 Quantity;
This specification is under the jurisdiction of ASTM Committee F04 on
4.1.2 ASTM designation, alloy number, and date of issue;
Medical and Surgical Materials and Devices and is the direct responsibility of
4.1.3 Mechanical properties (see Section 7);
Subcommittee F04.12 on Metallurgical Materials.
4.1.4 Units to be certified – SI or inch pound;
Current edition approved March 1, 2020. Published April 2020. Originally
approved in 1994. Last previous edition approved in 2011 as F1537 – 11. DOI:
10.1520/F1537-20.
2 3
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Available from Society of Automotive Engineers (SAE), 400 Commonwealth
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Dr., Warrendale, PA 15096-0001, http://www.sae.org.
Standards volume information, refer to the standard’s Document Summary page on Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
the ASTM website. 4th Floor, New York, NY 10036, http://www.ansi.org.
*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
F1537−20
4.1.5 Form (bar, rod or wire); 6.2.1 Acceptance or rejection of a heat or lot of material
4.1.6 Applicable dimensions including size, thickness, may be made by the purchaser on the basis of this product
width, and length (exact, random, or multiples) or drawing analysis.
number; 6.2.2 Product analysis tolerances do not broaden the speci-
4.1.7 Condition (see Section 5); fied heat analysis requirements but cover variations between
4.1.8 Special tests (if any); and laboratories in the measurement of chemical content. Product
4.1.9 Other requirements. analysis limits shall be as specified in Table 2.
5. Materials and Manufacture
7. Mechanical Requirements
5.1 Product shall be furnished as specified below:
7.1 Tensile Properties:
5.1.1 The annealed condition is typically supplied as a hot
7.1.1 Perform at least two tension tests from each lot.
rolled and annealed product.
Should any of these test pieces not meet the specified
5.1.2 Thehotworkedconditionistypicallysuppliedasahot
requirements, test two additional test pieces representative of
rolled and unannealed product.
thesamelot,inthesamemanner,foreachfailedtestpiece.The
5.1.3 The warm worked condition is typically supplied as a
lot shall be considered in compliance only if all additional test
thermomechanically processed product to achieve a strain-
pieces meet the specified requirements.
hardened structure.
7.1.2 Tensile test results for which any specimen fractures
outside the gauge length shall be considered acceptable, if both
6. Chemical Requirements
the elongation and reduction of area meet the minimum
6.1 Thecobalt-28chromium-6molybdenumalloysshallcon-
requirements specified. Refer to subsections 7.11.4 and 7.11.5
form to the chemical requirements prescribed in Table 1. The
of Test Methods E8/E8M.
supplier shall not ship material that is outside the limits
7.1.3 The mechanical properties of test specimens shall
specified in Table 1 for the applicable alloy.
conform to the requirements specified in Table 3.
6.1.1 Requirements for the major and minor elemental
7.2 Hardness:
constituents are listed in Table 1. Also listed are important
7.2.1 Hardness values shall be determined in accordance
residual elements.Analysis for elements not listed in Table 1 is
with Test Methods E18.
not required to verify compliance with this specification.
7.2.2 Hardness values are for information only and shall not
6.1.2 All commercial metals contain small amounts of
be used as a basis for rejection.
elements other than those which are specified. It is neither
practical nor necessary to specify limits for unspecified
8. Microstructure Requirements
elements, whether residual elements or trace elements, that can
8.1 Bar, rod, and wire conforming to this specification shall
bepresent.Theproducerispermittedtoanalyzeforunspecified
have a homogeneous microstructure with an average grain size
elementsandispermittedtoreportsuchanalyses.Thepresence
of ASTM No. 5 or finer when measured in accordance with
of an unspecified element and the reporting of an analysis for
Test Methods E112.
that element shall not be a basis for rejection.
6.1.3 Intentional elemental additions other than those speci-
9. Ultrasonic Inspection
fied in Table 1 are not permitted.
9.1 For finished thicknesses 6.35 mm [0.250 in.] and
6.2 Product Analysis—The product analysis is either for the
greater, inspection shall be per AMS 2630 Class A1. Equiva-
purpose of verifying the composition of a heat or lot or to
lent test methods may be substituted when agreed to by
determine variations in the composition within the heat.
purchaserandsupplier.AMS2630indicatesaminimumsizeof
TABLE 1 Chemical Composition
Composition % (mass/mass) A,B
TABLE 2 Product Analysis Tolerances
Element Alloy 1 Alloy 2 Alloy 3
Element Permissible Variation Under the Minimum
UNS R31537 UNS R31538 UNS R31539
Limit or Over the Maximum Limit, % (mass/
(Low Carbon) (High Carbon) (Dispersion C
mass)
Strengthened)
Carbon 0.02
min max min max min max Aluminum#0.50 0.05
Carbon . 0.14 0.15 0.35 . 0.14
Aluminum >0.50 up to 1.00 0.10
Aluminum . . . . 0.30 1.00 Lanthanum 0.01
Lanthanum . . . . 0.03 0.20
Chromium 0.30
Chromium 26.0 30.0 26.0 30.0 26.0 30.0 Molybdenum 0.15
Molybdenum 5.0 7.0 5.0 7.0 5.0 7.0 Nickel 0.05
Nickel . 1.0 . 1.0 . 1.0 Iron 0.03
Iron . 0.75 . 0.75 . 0.75 Silicon 0.05
Silicon . 1.0 . 1
...

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: F1537 − 11 F1537 − 20
Standard Specification for
Wrought Cobalt-28Chromium-6Molybdenum Alloys for
Surgical Implants (UNS R31537, UNS R31538, and UNS
R31539)
This standard is issued under the fixed designation F1537; 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*
1.1 This specification covers the chemical, mechanical, and metallurgical requirements for three wrought cobalt-28chromium-
6molybdenum alloys used for surgical implants. The properties specified apply specifically to wrought bar, rod, and wire.
1.2 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values givenstated
in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.each
system are not necessarily exact equivalents; therefore, to ensure conformance with the standard, each system shall be used
independently of the other, and values from the two systems shall not be combined.
1.3 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:
E8/E8M Test Methods for Tension Testing of Metallic Materials
E18 Test Methods for Rockwell Hardness of Metallic Materials
E29 Practice for Using Significant Digits in Test Data to Determine Conformance with Specifications
E112 Test Methods for Determining Average Grain Size
E354 Test Methods for Chemical Analysis of High-Temperature, Electrical, Magnetic, and Other Similar Iron, Nickel, and
Cobalt Alloys
F75 Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants (UNS
R30075)
F799 Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Forgings for Surgical Implants (UNS R31537, R31538,
R31539)
IEEE/ASTM SI 10 American National Standard for Metric Practice
2.2 Aerospace Material Specifications:
AMS 2248 Chemical Check Analysis Limits, Corrosion and Heat Resistant Steels and Alloys, Maraging and Other
Highly-Alloyed Steels, and Iron Alloys
AMS 2269 Chemical Check Analysis Limits, Nickel, Nickel Alloys and Cobalt Alloys
AMS 2630 Inspection, Ultrasonic Product over 0.5 Inch (12.7 mm) Thick
2.3 ISO Standards:
ISO 5832–12 Implants for Surgery—Metallic Materials—Part 12: Wrought Cobalt-Chromium-Molybdenum Alloy
ISO 6892 Metallic Materials - Tensile Testing at Ambient Temperature
ISO 9001 Quality Management Systems—Requirements
This specification is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.12 on Metallurgical Materials.
Current edition approved Nov. 15, 2011March 1, 2020. Published December 2011April 2020. Originally approved in 1994. Last previous edition approved in 20082011
as F1537 – 08.F1537 – 11. DOI: 10.1520/F1537-11.10.1520/F1537-20.
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 Society of Automotive Engineers (SAE), 400 Commonwealth Dr., Warrendale, PA 15096-0001, http://www.sae.org.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
*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
F1537 − 20
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 lot—the total number of mill products produced from the same melt heat under the same conditions at essentially the same
time.
4. Ordering Information
4.1 Inquiries and orders for material under this specification shall include the following information:
4.1.1 Quantity,Quantity;
4.1.2 ASTM designation, alloy number, and date of issue,issue;
4.1.3 Mechanical properties (See(see Section 7),);
4.1.4 Units to be certified – SI or inch pound;
4.1.5 Form (bar, rod or wire),wire);
4.1.6 Applicable dimensions including size, thickness, width, and length (exact, random, or multiples) or drawing number,
number;
4.1.7 Condition (See(see Section 5),);
4.1.8 Special tests (if any),any); and
4.1.9 Other requirements.
5. Materials and Manufacture
5.1 Product shall be furnished as specified below:
5.1.1 The annealed condition is typically supplied as a hot rolled and annealed product.
5.1.2 The hot worked condition is typically supplied as a hot rolled and unannealed product.
5.1.3 The warm worked condition is typically supplied as a thermomechanically processed product to achieve a strain-hardened
structure.
6. Chemical Requirements
6.1 The cobalt-28chromium-6molybdenum alloys shall conform to the chemical requirements prescribed in Table 1. The
supplier shall not ship material that is outside the limits specified in Table 1 for the applicable alloy.
6.1.1 Requirements for the major and minor elemental constituents are listed in Table 1. Also listed are important residual
elements. Analysis for elements not listed in Table 1 is not required to verify compliance with this specification.
6.1.2 All commercial metals contain small amounts of elements other than those which are specified. It is neither practical nor
necessary to specify limits for unspecified elements, whether residual elements or trace elements, that can be present. The producer
is permitted to analyze for unspecified elements and is permitted to report such analyses. The presence of an unspecified element
and the reporting of an analysis for that element shall not be a basis for rejection.
6.1.3 Intentional elemental additions other than those specified in Table 1 are not permitted.
6.2 Product Analysis—The product analysis is either for the purpose of verifying the composition of a heat or lot or to determine
variations in the composition within the heat.
6.2.1 Acceptance or rejection of a heat or lot of material may be made by the purchaser on the basis of this product analysis.
TABLE 1 Chemical Composition
Composition % (mass/mass)
Element Alloy 1 Alloy 2 Alloy 3
UNS R31537 UNS R31538 UNS R31539
(Low Carbon) (High Carbon) (Dispersion
Strengthened)
min max min max min max
Carbon . 0.14 0.15 0.35 . 0.14
Aluminum . . . . 0.30 1.00
Lanthanum . . . . 0.03 0.20
Chromium 26.0 30.0 26.0 30.0 26.0 30.0
Molybdenum 5.0 7.0 5.0 7.0 5.0 7.0
Nickel . 1.0 . 1.0 . 1.0
Iron . 0.75 . 0.75 . 0.75
Silicon . 1.0 . 1.0 . 1.0
Manganese . 1.0 . 1.0 . 1.0
Nitrogen . 0.25 . 0.25 . 0.25
A
Cobalt Balance Balance Balance
A
Approximately equal to the difference of 100 % and the sum percentage of the
other specified elements. The percentage of cobalt difference is not required to be
reported.
F1537 − 20
6.2.2 Product analysis tolerances do not broaden the specified heat analysis requirements but cover variations between
laboratories in the measurement of chemical content. Product analysis limits shall be as specified in Table 2.
7. Mechanical Requirements
7.1 Tensile Properties:
7.1.1 Perform at least two tension tests from each lot. Should any of these test pieces not meet the specified requirements, test
two additional test pieces representative of the same lot, in the same manner, for each failed test piece. The lot shall be considered
in compliance only if all additional test pieces meet the specified requirements.
7.1.2 Tensile test results for which any specimen fractures outside the gauge length shall be considered acceptable, if both the
elongation and reduction of area meet the minimum requirements specified. Refer to subsections 7.11.4 and 7.11.5 of Test Methods
E8/E8M.
7.1.3 The mechanical properties of test specimens shall conform to the requirements specified in Table 3.
7.2 Hardness:
7.2.1 Hardness values shall be determined in accordance with Test Methods E18.
7.2.2 Hardness values are for information only and shall not be used as a basis for rejection.
8. Microstructure Requirements
8.1 Bar, rod, and wire conforming to this specification shall have a homogeneous microstructure with an average grain size of
ASTM No. 5 or finer when measured in accordance with Test Methods E112.
9. Ultrasonic Inspection
9.1 For finished thicknesses 0.250 in. (6.35 mm)6.35 mm [0.250 in.] and greater, inspection shall be per AMS 2630 Class A1.
Equivalent test methods may be substituted when agreed to by purchaser and supplier. AMS 2630 indicates a minimum size of
0.500 in. (12.7 mm).12.7 mm [0.500 in.]. The use of this specification to a minimum size of 0.250 in. (6.35 mm)6.35 mm [0.250
in.] is done with agreement of producer and user members of the committee.
9.2 For finished thicknesses less than 0.250 in. (6.35 mm)6.35
...