ASTM A753-21

Standard Specification for Wrought Nickel-Iron Soft Magnetic Alloys (UNS K94490, K94840, N14076, N14080)

ABSTRACT
This specification covers commonly used wrought nickel-iron soft magnetic alloys produced or supplied expressly for use in magnetic cores and other parts requiring high magnetic permeability, high electrical resistivity, low coercive field strength, and low core loss. This specification does not cover material produced by casting or by powder metallurgy techniques. These materials are capable of being produced in a wide variety of forms and conditions such as forging billet, hot-rolled plate, strip, and bar, cold-finished bars, cold-rolled sheep and strip, shaped bar and wire. Four specific alloy types containing nominally 45, 48, 76 and 80 nickel with various other elements are covered by this specification. The alloy chemistry requirements are listed. Magnetic property requirements for the different alloys, product forms and sizes are specified. Typical physical property data and useful heat treatment information are provided in appendices.
SCOPE
1.1 This specification covers commonly used wrought nickel-iron soft magnetic alloys produced or supplied expressly for use in magnetic cores and other parts requiring high magnetic permeability, high electrical resistivity, low coercive field strength, and low core loss.  
1.2 This specification covers materials supplied by a producer or converter to the form and physical condition desired for fabrication into parts that will later be given a final heat treatment to achieve the desired magnetic characteristics. It covers materials supplied in the form of forging billet; hot-rolled plate, strip, and bar; cold-finished bar; cold-rolled and annealed sheet and strip; shaped bar and wire; and wire.  
1.2.1 This specification does not cover either powder metallurgically produced or cast parts.  
1.2.2 This specification lists requirements for strip products having isotropic or semi-isotropic magnetic properties but does not include requirements for anisotropic or square hysteresis loop alloys or alloys processed to yield flattened hysteresis loops by use of heat treatments in an applied magnetic field.  
1.2.3 This specification does not cover alloys modified by the addition of elements such as sulfur and selenium to enhance machinability.  
1.3 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to customary (cgs-emu and inch-pound) units which are provided for information only and are not considered standard.  
1.3.1 There are selected values presented in two units, both of which are in acceptable SI units. These are differentiated by the word “, or,” as in “g/cm3, or, (kg/m3).” In addition, values for mean linear coefficient of expansion in Table X1.1 are shown solely in μm/m/°C in keeping with prior versions of this standard.  
1.4 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.  
1.5 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: 31-Jan-2021
• ICS: 77.120.40 - Nickel, chromium and their alloys
• Technical Committee: A06 - Magnetic Properties
• Drafting Committee: A06.02 - Material Specifications

Relations

• Refers: ASTM A484/A484M-24 - Standard Specification for General Requirements for Stainless Steel Bars, Billets, Shapes, and Forgings
• Effective Date: 01-Jan-2024
• Refers: ASTM A340-23a - Standard Terminology of Symbols and Definitions Relating to Magnetic Testing
• Effective Date: 01-Dec-2023
• Refers: ASTM A480/A480M-23b - Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip
• Effective Date: 01-Nov-2023
• Refers: ASTM A484/A484M-23a - Standard Specification for General Requirements for Stainless Steel Bars, Billets, Shapes, and Forgings
• Effective Date: 01-Sep-2023
• Refers: ASTM A484/A484M-23 - Standard Specification for General Requirements for Stainless Steel Bars, Billets, and Forgings
• Effective Date: 01-Mar-2023
• Refers: ASTM A484/A484M-20a - Standard Specification for General Requirements for Stainless Steel Bars, Billets, and Forgings
• Effective Date: 05-May-2020
• Refers: ASTM A340-19b - Standard Terminology of Symbols and Definitions Relating to Magnetic Testing
• Effective Date: 15-Oct-2019
• Refers: ASTM A480/A480M-19 - Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip
• Effective Date: 01-Sep-2019
• Refers: ASTM A484/A484M-19 - Standard Specification for General Requirements for Stainless Steel Bars, Billets, and Forgings
• Effective Date: 01-Sep-2019
• Refers: ASTM A340-19a - Standard Terminology of Symbols and Definitions Relating to Magnetic Testing
• Effective Date: 15-Jun-2019
• Refers: ASTM A340-19 - Standard Terminology of Symbols and Definitions Relating to Magnetic Testing
• Effective Date: 15-Feb-2019
• Refers: ASTM A484/A484M-18a - Standard Specification for General Requirements for Stainless Steel Bars, Billets, and Forgings
• Effective Date: 01-Nov-2018
• Refers: ASTM A480/A480M-18 - Standard Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip
• Effective Date: 01-Sep-2018
• Refers: ASTM A340-18 - Standard Terminology of Symbols and Definitions Relating to Magnetic Testing
• Effective Date: 01-Jun-2018
• Refers: ASTM A484/A484M-18 - Standard Specification for General Requirements for Stainless Steel Bars, Billets, and Forgings
• Effective Date: 01-Jan-2018

Overview

ASTM A753-21 specifies the requirements for wrought nickel-iron soft magnetic alloys, including the UNS designations K94490, K94840, N14076, and N14080. Published by ASTM International, this standard is essential for manufacturers and users who need materials with exceptional soft magnetic properties such as high permeability, high electrical resistivity, low coercivity, and low core loss. The alloys covered are intended for use in magnetic cores and similar applications where optimal magnetic characteristics are critical.

ASTM A753-21 covers a range of wrought product forms such as forging billets, hot-rolled plate, strip and bar, cold-finished bar, cold-rolled and annealed sheet and strip, shaped bar and wire, and wire. This specification excludes materials produced by casting or powder metallurgy.

Key Topics

• Alloy Types: Covers four main alloys with varying nickel content (nominally 45%, 48%, 76%, and 80%), each with specific property and composition requirements.
• Forms and Conditions: Materials are available in multiple wrought forms (e.g., billets, hot- and cold-rolled products, wire) tailored for further processing and final applications.
• Magnetic Properties:
  • High magnetic permeability for efficient energy transfer
  • High electrical resistivity to minimize eddy current loss
  • Low coercive field strength reducing energy loss in AC applications
  • Low core loss for improved efficiency
• Testing Requirements: Specifies test methods for measuring magnetic properties using ring-type specimens, and outlines acceptable test practices for both direct current (DC) and alternating current (AC) magnetic testing.
• Physical and Mechanical Properties: Appendices include typical data on density, electrical resistivity, saturation flux density, Curie temperature, hardness, yield strength, and tensile strength.

Applications

Wrought nickel-iron soft magnetic alloys manufactured under ASTM A753-21 are widely used in industries that demand high magnetic performance. Typical applications include:

• Magnetic Cores for transformers, inductors, and reactors, where high permeability and low loss are vital for performance and energy-efficiency.
• Electrical and Electronic Devices such as relays, magnetic shielding, sensors, and electromagnetic clutches.
• Rotating Machinery including motors and generators, benefiting from isotropic and semi-isotropic properties in thin strip grades.
• Instrumentation where precise magnetic properties are needed for signal fidelity in control systems and measurement equipment.

These alloys are selected for parts requiring both reliable soft magnetic behavior and good fabrication properties, making them essential for high-performance, precision components.

Related Standards

ASTM A753-21 references several other ASTM standards to ensure comprehensive control over magnetic material quality and testing:

• ASTM A34/A34M – Sampling and procurement testing of magnetic materials
• ASTM A340 – Terminology of symbols and definitions for magnetic testing
• ASTM A341/A341M, A596/A596M, A773/A773M, A772/A772M – Methods for direct and alternating current magnetic property tests
• ASTM A480/A480M, A484/A484M, A555/A555M – General requirements for plate, strip, bar, billets, and wire
• ASTM E527 – Unified Numbering System for metals and alloys
• ASTM E1019 – Methods for chemical analysis of nickel, iron, and related alloys

Users are encouraged to consult these related standards to ensure full compliance and optimal material performance when specifying or using nickel-iron soft magnetic alloys.

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Keywords: ASTM A753-21, nickel-iron magnetic alloys, soft magnetic materials, magnetic cores, high permeability, electrical resistivity, core loss, wrought alloys, magnetic property testing, UNS K94490, K94840, N14076, N14080.

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:A753 −21
Standard Specification for
Wrought Nickel-Iron Soft Magnetic Alloys (UNS K94490,
K94840, N14076, N14080)
This standard is issued under the fixed designation A753; 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 1.4 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This specification covers commonly used wrought
responsibility of the user of this standard to establish appro-
nickel-ironsoftmagneticalloysproducedorsuppliedexpressly
priate safety, health, and environmental practices and deter-
for use in magnetic cores and other parts requiring high
mine the applicability of regulatory limitations prior to use.
magnetic permeability, high electrical resistivity, low coercive
1.5 This international standard was developed in accor-
field strength, and low core loss.
dance with internationally recognized principles on standard-
1.2 This specification covers materials supplied by a pro-
ization established in the Decision on Principles for the
ducer or converter to the form and physical condition desired
Development of International Standards, Guides and Recom-
for fabrication into parts that will later be given a final heat
mendations issued by the World Trade Organization Technical
treatment to achieve the desired magnetic characteristics. It
Barriers to Trade (TBT) Committee.
covers materials supplied in the form of forging billet; hot-
2. Referenced Documents
rolled plate, strip, and bar; cold-finished bar; cold-rolled and
annealed sheet and strip; shaped bar and wire; and wire.
2.1 ASTM Standards:
1.2.1 This specification does not cover either powder met-
A34/A34M Practice for Sampling and Procurement Testing
allurgically produced or cast parts.
of Magnetic Materials
1.2.2 This specification lists requirements for strip products
A340 Terminology of Symbols and Definitions Relating to
havingisotropicorsemi-isotropicmagneticpropertiesbutdoes
Magnetic Testing
not include requirements for anisotropic or square hysteresis
A341/A341M Test Method for Direct Current Magnetic
loop alloys or alloys processed to yield flattened hysteresis
Properties of Soft Magnetic Materials Using D-C Per-
loops by use of heat treatments in an applied magnetic field.
meameters and the Point by Point (Ballistic)Test Methods
1.2.3 This specification does not cover alloys modified by A480/A480M Specification for General Requirements for
Flat-Rolled Stainless and Heat-Resisting Steel Plate,
theadditionofelementssuchassulfurandseleniumtoenhance
machinability. Sheet, and Strip
A484/A484M Specification for General Requirements for
1.3 The values stated in SI units are to be regarded as
Stainless Steel Bars, Billets, and Forgings
standard. The values given in parentheses are mathematical
A555/A555M Specification for General Requirements for
conversions to customary (cgs-emu and inch-pound) units
Stainless Steel Wire and Wire Rods
whichareprovidedforinformationonlyandarenotconsidered
A596/A596M Test Method for Direct-Current Magnetic
standard.
PropertiesofMaterialsUsingthePointbyPoint(Ballistic)
1.3.1 There are selected values presented in two units, both
Method and Ring Specimens
of which are in acceptable SI units. These are differentiated by
A772/A772M TestMethodforACMagneticPermeabilityof
3 3
the word “, or,” as in “g/cm , or, (kg/m ).” In addition, values
Materials Using Sinusoidal Current
for mean linear coefficient of expansion in Table X1.1 are
A773/A773M Test Method for Direct Current Magnetic
shown solely in µm/m/°C in keeping with prior versions of this
Properties of Low Coercivity Magnetic Materials Using
standard.
Hysteresigraphs
E527 Practice for Numbering Metals and Alloys in the
Unified Numbering System (UNS)
This specification is under the jurisdiction of ASTM Committee A06 on
Magnetic Properties, and is the direct responsibility of Subcommittee A06.02 on
Material Specifications. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Feb. 1, 2021. Published February 2021. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 1978. Last previous edition approved in 2013 as A753 – 08 (2013). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/A0753-21. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A753−21
E1019 Test Methods for Determination of Carbon, Sulfur, 6. Chemical Composition
Nitrogen, and Oxygen in Steel, Iron, Nickel, and Cobalt
6.1 The alloys shall conform to the requirements prescribed
Alloys by Various Combustion and Inert Gas Fusion
in Table 2. Since magnetic performance is paramount, analysis
Techniques
variations are permitted by mutual agreement between the user
and producer.
3. Terminology
6.2 Determination of metallic constituents and phosphorus
3.1 Except as noted in 3.1.1 below, the terms and symbols
shall be by a method(s) acceptable to both producer and user.
used in this specification are defined in Terminology A340.
Analysis of carbon and sulfur shall be done in accordance with
3.1.1 Permeability values listed in Table 4 and Table 5, are
Test Methods E1019.
relative permeabilities, that is, the absolute value divided by
the magnetic constant. Permeability values will not make
7. Form and Condition
further reference to the qualifying term, “relative.”
7.1 These materials are capable of being produced in a wide
4. Classification
variety of forms and conditions suitable for further manufac-
ture into specific magnetic articles. The desired form and
4.1 Four specific alloy types are covered in Table 1.
condition shall be specified and should be discussed with the
producer before ordering to assure receiving the appropriate
TABLE 1 Specific Alloy Types
product. Available forms and conditions are:
A B
Alloy Type UNS Number Nickel Range, %
7.1.1 ForgingBillet—Hotworked;hotworkedwithsurfaces
1 K94490 43.5 to 46.5
prepared by grinding.
2 K94840 47.0 to 49.0
3 N14076 75.0 to 78.0
7.1.2 Hot-Rolled Plate, Strip, and Bar—Hot-rolled; hot-
4 N14080 79.0 to 82.0
rolled and acid cleaned; hot-rolled and annealed; hot-rolled,
A
UNS refers to the Unified Numbering System, an alloy identification system
annealed, and acid cleaned; hot-rolled and mechanically
supported by ASTM. Refer to Practice E527 for details.
B cleaned; mechanical properties as specified.
Alloy Types 3 and 4 have additions of molybdenum, copper, and chromium to
improve magnetic performance.
7.1.3 Cold-Finished Bars—Cold-drawn; cold-drawn and
centerless ground; cold-drawn and annealed to specified me-
chanical properties.
4.2 Alloy Type 2 in thin-strip form (thickness less than or
7.1.4 Cold-Rolled Sheet and Strip—Cold-rolled; deep draw
equal to 0.51 mm (0.020 in.)) is available in two different
quality; cold-rolled and annealed to specified mechanical
grades. Grade 1 is semi-isotropic and is recommended for use
properties.
in transformer laminations. Grade 2 is isotropic and is recom-
7.1.5 Wire—Cold-drawn; cold-drawn and annealed to speci-
mended for use in rotating machinery laminations and mag-
fied mechanical properties.
netic shielding parts. These grades are the result of different
7.1.6 Shaped Bar and Wire—Cold-worked; cold-worked
mill processing (that is, cold-rolling and annealing) practices
and annealed to specified mechanical properties.
and cannot be created by changes in the final heat treatment
8. Magnetic Property Requirements—General
given to the laminations or parts.
Requirements
5. Ordering Information
8.1 Test Methods—Because of the extremely high magnetic
5.1 Orders for material conforming to this specification
permeabilities developed in these alloys after heat treatment,
shall include the following information:
the use of permeameters (Test Method A341/A341M)is
5.1.1 Reference to this specification and year of issue or
expressly forbidden. Allowable test methods are those using
revision.
ring-type specimens.
5.1.2 Alloy type (Section 4) and grade where appropriate.
5.1.3 Dimensions and tolerances (Section 12).
5.1.4 Quantity (weight or number of pieces as appropriate).
TABLE 2 Chemical Requirements (Weight Percent)
5.1.5 Form and condition (Section 7).
Alloy 1 Alloy 2 Alloy 3 Alloy 4
5.1.6 Magnetic property requirements if they are other than
UNS UNS UNS UNS
K94490 K94840 N14076 N14080
those listed in this specification.
5.1.7 Certification of chemical analysis and magnetic qual- Carbon, max. 0.05 0.05 0.05 0.05
Manganese, max. 0.80 0.80 1.5 0.80
ity evaluation.
Silicon, max. 0.50 0.50 0.50 0.50
5.1.8 Marking and packaging requirements.
Phosphorus, max. 0.03 0.03 0.02 0.02
Sulfur, max. 0.01 0.01 0.01 0.01
5.1.9 End Use—Whenever possible, the user should specify
Chromium 0.30 max. 0.30 max. 2.0-3.0 0.30 max.
whetherthematerialwillbemachined,blankedintoflatpieces,
Nickel 43.5-46.5 47.0-49.0 75.0-78.0 79.0-82.0
blanked and formed, deep drawn to shape, wound into a core,
Molybdenum 0.30 max 0.30 max. 0.50 max 3.5-6.0
Cobalt, max. 0.50 0.50 0.50 0.50
punched into laminations, or photo-etched. This will help the
Copper 0.30 max 0.30 max. 4.0-6.0 0.30 max.
producer to provide the most suitable material for the user’s
A
Iron balance balance balance balance
fabricating practices.
A
Iron is the balance by difference. Quantitative analysis of this element is not
5.1.10 Exceptions to this specification or special require-
required.
ments such as mechanical property requirements.
A753−21
8.2 Test Specimen—Whenever possible, test specimen size 10.3.1 For thicknesses not listed, the requirements shall be
and shape shall conform to those listed in Practice A34/A34M. determined by linear interpolation of data shown in Table 5.
Specimen shapes such as stacked laminations, solid rings, and 10.3.2 For thicknesses outside the ranges shown in Table 5,
spirally wound tape and wire cores are necessary for the most the ac magnetic property requirements shall be as mutually
accurate results. If, however, the product form or dimensions agreed between the producer and user.
precludes the use of a preferred test specimen, the specimen
11. Typical Physical and Mechanical Properties
shape and size shall be mutually agreed upon between the
11.1 Typicalphysicalandmechanicalpropertiesarelistedin
producer and user.
Appendix X1.
8.3 Density—The assumed densities of these materials for
purposes of magnetic testing shall be as in Table 3: 12.
...

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: A753 − 08 (Reapproved 2013) A753 − 21
Standard Specification for
Wrought Nickel-Iron Soft Magnetic Alloys (UNS K94490,
K94840, N14076, N14080)
This standard is issued under the fixed designation A753; 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 commonly used wrought nickel-iron soft magnetic alloys produced or supplied expressly for use in
magnetic cores and other parts requiring high magnetic permeability, high electrical resistivity, low coercive field strength, and low
core loss.
1.2 This specification covers materials supplied by a producer or converter to the form and physical condition desired for
fabrication into parts that will later be given a final heat treatment to achieve the desired magnetic characteristics. It covers
materials supplied in the form of forging billet; hot-rolled plate, strip, and bar; cold-finished bar; cold-rolled and annealed sheet
and strip; shaped bar and wire; and wire.
1.2.1 This specification does not cover either powder metallurgically produced or cast parts.
1.2.2 This specification lists requirements for strip products having isotropic or semi-isotropic magnetic properties but does not
include requirements for anisotropic or square hysteresis loop alloys or alloys processed to yield flattened hysteresis loops by use
of heat treatments in an applied magnetic field.
1.2.3 This specification does not cover alloys modified by the addition of elements such as sulfur and selenium to enhance
machinability.
1.3 The values stated in inch-poundSI units are to be regarded as standard. The values given in parentheses are mathematical
conversions to SI units thatcustomary (cgs-emu and inch-pound) units which are provided for information only and are not
considered standard.
1.3.1 There are selected values presented in two units, both of which are in acceptable SI units. These are differentiated by the
3 3
word “, or,” as in “g/cm , or, (kg/m ).” In addition, values for mean linear coefficient of expansion in Table X1.1 are shown solely
in μm/m/°C in keeping with prior versions of this standard.
1.4 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.
1.5 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.
This specification is under the jurisdiction of ASTM Committee A06 on Magnetic Properties, and is the direct responsibility of Subcommittee A06.02 on Material
Specifications.
Current edition approved May 1, 2013Feb. 1, 2021. Published July 2013February 2021. Originally approved in 1978. Last previous edition approved in 20082013 as
A753A753 – 08 (2013).–08. DOI: 10.1520/A0753-08R13.10.1520/A0753-21.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
A753 − 21
2. Referenced Documents
2.1 ASTM Standards:
A34/A34M Practice for Sampling and Procurement Testing of Magnetic Materials
A340 Terminology of Symbols and Definitions Relating to Magnetic Testing
A341/A341M Test Method for Direct Current Magnetic Properties of Soft Magnetic Materials Using D-C Permeameters and the
Point by Point (Ballistic) Test Methods
A480/A480M Specification for General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip
A484/A484M Specification for General Requirements for Stainless Steel Bars, Billets, and Forgings
A555/A555M Specification for General Requirements for Stainless Steel Wire and Wire Rods
A596/A596M Test Method for Direct-Current Magnetic Properties of Materials Using the Point by Point (Ballistic) Method and
Ring Specimens
A772/A772M Test Method for AC Magnetic Permeability of Materials Using Sinusoidal Current
A773/A773M Test Method for Direct Current Magnetic Properties of Low Coercivity Magnetic Materials Using Hysteresig-
raphs
E527 Practice for Numbering Metals and Alloys in the Unified Numbering System (UNS)
E1019 Test Methods for Determination of Carbon, Sulfur, Nitrogen, and Oxygen in Steel, Iron, Nickel, and Cobalt Alloys by
Various Combustion and Inert Gas Fusion Techniques
3. Terminology
3.1 The Except as noted in 3.1.1 below, the terms and symbols used in this specification are defined in Terminology A340.
3.1.1 Permeability values listed in Table 4 and Table 5, are relative permeabilities, that is, the absolute value divided by the
magnetic constant. Permeability values will not make further reference to the qualifying term, “relative.”
4. Classification
4.1 Four specific alloy types are covered in Table 1.
TABLE 1 Specific Alloy Types
A B
Alloy Type UNS Number Nickel Range, %
1 K94490 43.5 to 46.5
2 K94840 47.0 to 49.0
3 N14076 75.0 to 78.0
4 N14080 79.0 to 82.0
A
UNS refers to the Unified Numbering System, an alloy identification system
supported by ASTM. Refer to Practice E527 for details.
B
Alloy Types 3 and 4 have additions of molybdenum, copper, and chromium to
improve magnetic performance.
4.2 Alloy Type 2 in thin-strip form (thickness less than or equal to 0.020 in. (0.51 mm))0.51 mm (0.020 in.)) is available in two
different grades. Grade 1 is semi-isotropic and is recommended for use in transformer laminations. Grade 2 is isotropic and is
recommended for use in rotating machinery laminations and magnetic shielding parts. These grades are the result of different mill
processing (that is, cold-rolling and annealing) practices and cannot be created by changes in the final heat treatment given to the
laminations or parts.
5. Ordering Information
5.1 Orders for material conforming to this specification shall include the following information:
5.1.1 Reference to this specification and year of issue or revision.
5.1.2 Alloy type (Section 4) and grade where appropriate.
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.
A753 − 21
5.1.3 Dimensions and tolerances (Section 12).
5.1.4 Quantity (weight or number of pieces as appropriate).
5.1.5 Form and condition (Section 7).
5.1.6 Magnetic property requirements if they are other than those listed in this specification.
5.1.7 Certification of chemical analysis and magnetic quality evaluation.
5.1.8 Marking and packaging requirements.
5.1.9 End Use—Whenever possible, the user should specify whether the material will be machined, blanked into flat pieces,
blanked and formed, deep drawn to shape, wound into a core, punched into laminations, or photo-etched. This will help the
producer to provide the most suitable material for the user’s fabricating practices.
5.1.10 Exceptions to this specification or special requirements such as mechanical property requirements.
6. Chemical Composition
6.1 The alloys shall conform to the requirements prescribed in Table 2. Since magnetic performance is paramount, analysis
variations are permitted by mutual agreement between the user and producer.
6.2 Determination of metallic constituents and phosphorus shall be by a method(s) acceptable to both producer and user. Analysis
of carbon and sulfur shall be done in accordance with Test Methods E1019.
7. Form and Condition
7.1 These materials are capable of being produced in a wide variety of forms and conditions suitable for further manufacture into
specific magnetic articles. The desired form and condition shall be specified and should be discussed with the producer before
ordering to assure receiving the appropriate product. Available forms and conditions are:
7.1.1 Forging Billet—Hot worked; hot worked with surfaces prepared by grinding.
7.1.2 Hot-Rolled Plate, Strip, and Bar—Hot-rolled; hot-rolled and acid cleaned; hot-rolled and annealed; hot-rolled, annealed, and
acid cleaned; hot-rolled and mechanically cleaned; mechanical properties as specified.
7.1.3 Cold-Finished Bars—Cold-drawn; cold-drawn and centerless ground; cold-drawn and annealed to specified mechanical
properties.
TABLE 2 Chemical Requirements (Weight Percent)
Alloy 1 Alloy 2 Alloy 3 Alloy 4
UNS UNS UNS UNS
K94490 K94840 N14076 N14080
Carbon, max. 0.05 0.05 0.05 0.05
Manganese, max. 0.80 0.80 1.5 0.80
Silicon, max. 0.50 0.50 0.50 0.50
Phosphorus, max. 0.03 0.03 0.02 0.02
Sulfur, max. 0.01 0.01 0.01 0.01
Chromium 0.30 max. 0.30 max. 2.0-3.0 0.30 max.
Nickel 43.5-46.5 47.0-49.0 75.0-78.0 79.0-82.0
Molybdenum 0.30 max 0.30 max. 0.50 max 3.5-6.0
Cobalt, max. 0.50 0.50 0.50 0.50
Copper 0.30 max 0.30 max. 4.0-6.0 0.30 max.
A
Iron balance balance balance balance
A
Iron is the balance by difference. Quantitative analysis of this element is not
required.
A753 − 21
7.1.4 Cold-Rolled Sheet and Strip —Strip—Cold-rolled; deep draw quality; cold-rolled and annealed to specified mechanical
properties.
7.1.5 Wire—Cold-drawn; cold-drawn and annealed to specified mechanical properties.
7.1.6 Shaped Bar and Wire—Cold-worked; cold-worked and annealed to specified mechanical properties.
8. Magnetic Property Requirements—General Requirements
8.1 Test Methods—Because of the extremely high magnetic permeabilities developed in these alloys after heat treatment, the use
of permeameters (Test Method A341/A341M) is expressly forbidden. Allowable test methods are those using ring-type specimens.
8.2 Test Specimen—Whenever possible, test specimen size and shape shall conform to those listed in Practice A34/A34M.
Specimen shapes such as stacked laminations, solid rings, and spirally wound tape and wire cores are necessary for the most
accurate results. If, however, the product form or dimensions precludes the use of a preferred test specimen, the specimen shape
and size shall be mutually agreed upon between the producer and user.
8.3 Density—The assumed densities of these materials for purposes of magnetic testing shall be as in Table 3:
8.4 Heat Treatment—The heat treatment applied to the test specimen shall be mutually agreed upon between the producer and user.
If no such agreement exists, the heat treatment applied to the test specimen shall be chosen by the producer to exceed the magnetic
property requirements listed in Tables 4 and 5 of this specification. Refer to Appendix X2 for information on heat treatment of these
alloys.
9. dc Magnetic Property Requirements
9.1 dc magnetic testing shall be the only magnetic test method used for all product forms and sizes other than thin strip and sheet.
Thin sheet and strip is defined as flat-rolled product having a thickness of 0.020 in. (0.51 mm)0.51 mm (0.020 in.) or less.
9.2 Testing shall be conducted using either Test Method A596/A596M or Test Method A773/A773M.
9.3 The dc magnetic property requirements after appropriate heat treatment are shown in Table 4. The symbol d refers to the
minimum dimension such as thickness or diameter.
10. ac Magnetic Property Requirements (Thin Sheet and Strip Only)
10.1 ac magnetic testing shall be used for all strip and sheet with a thickness of 0.020 in. (0.51 mm)0.51 mm (0.020 in.) or less.
10.2 Testing shall consist of impedance permeability measured at 60Hz and shall be conducted using Test Method A772/A772M.
10.3 The ac magnetic property requirements after appropriate heat treatment are shown in Table 5.
10.3.1 For thicknesses not listed, the requirements shall be determined by linear interpolation of data shown in Table 5.
TABLE 3 Assumed Density
Assumed Density
3 3
Alloy Type UNS No. g/cm , or, (kg/m )
1 K94490 8.17 8170
1 K94490 8.17 (8170)
2 K94840 8.25 8250
2 K94840 8.25 (8250)
3 N14076 8.58 8580
3 N14076 8.58 (8580)
4 (4 % Mo) N14080 8.74 8740
4 (4 % Mo) N14080 8.74 (8740)
4 (5 % Mo) N14080 8.77 8770
4 (5 % Mo) N14080 8.77 (8770)
A753 − 21
TABLE 4 dc Magnetic Property Requirements
NOTE 1—The coercive field strength for Alloy Types 1 and 2 is determined from a maximum induction of 10 kG (1.0 T),magnetic flux density of 1.0
T (10 kG), while for Alloy Types 3 and 4 the coercive field strength is determined from a maximum induction of 5 kG (0.5 T).magnetic flux density of
0.5 T (5 kG).
Alloy Alloy Alloy Alloy
Type 1 Type 2 Type 3 Type 4
Product Form and Size Magnetic Property
UNS UNS UNS UNS
K94490 K94840 N14076 N14080
(Relative) Permeability at 40 G (14 mT), min . . . . . . . . . 35 000
Billet (all sizes) Permeability at 4 mT
. . . . . . . . . 35 000
Bar, Wire, Plate, Plate Coil (4
...