ASTM A838 - 24 继电器用易切削铁素体不锈软磁合金技术规范

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Designation: A838 −24
Standard Speciﬁcation for
Free-Machining Ferritic Stainless Soft Magnetic Alloy Bar
for Relay Applications
1
This standard is issued under the ﬁxed designation A838; 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 free-machining ferritic stain-
less soft magnetic alloy produced or supplied expressly in
cold-ﬁnished bar form for use in magnetic cores and other parts
requiring a high permeability, low-coercivity stainless steel.
1.1.1 This speciﬁcation does not cover either cast parts or
parts produced by powder metallurgy techniques.
1.2 Two speciﬁc alloy types are covered. The primary
constituents are shown in Table 1. These types have corrosion
resistance similar to AISI Type 430F and Type 430F, Speciﬁ-
cation A582/A582M.
1.3 This speciﬁcation covers only these alloy types supplied
in cold-ﬁnished bars in cross-sectional shapes such as rounds,
squares, hexagons, and octagons with diameters (diagonals)
greater than or equal to 6.35 mm (0.250 in.) and less than or
equal to 41.5 mm (1.63 in.).
2
1.4 Certain cold-ﬁnished round bar products are capable of
being supplied mill annealed to required magnetic properties
such as low coercivity. The size range that can be mill annealed
is from 6.35 mm to 41.5 mm (0.250 in. to 1.63 in.). Other
products of these alloys cannot be mill annealed to produce
equivalently low coercivity; hence, the ﬁnal machined parts
should be heat treated as recommended by the producer.
1.5 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.
1.6 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 appro-
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
1.7 This international standard was developed in accor-
dance with internationally recognized principles on standard-
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
3
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 Per-
meameters and the Point by Point (Ballistic) Test Methods
A582/A582M Speciﬁcation for Free-Machining Stainless
Steel Bars
A596/A596M Test Method for Direct-Current Magnetic
Properties of Materials Using the Point by Point (Ballistic)
Method and Ring Specimens
A773/A773M Test Method for Direct Current Magnetic
Properties of Low Coercivity Magnetic Materials Using
Hysteresigraphs
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
2.2 Other Standard:
IEC 60404-7:2019 Magnetic materials – Part 7: Methods of
measurement of the coercivity (up to 160 kA/m) of
magnetic materials in an open magnetic circuit
4
1
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, 2024. Published May 2024. Originally
approved in 1985. Last previous edition approved in 2018 as A838 – 18. DOI:
10.1520/A0838-24.
2
Other product forms can be supplied to the chemistries listed in this speciﬁ-
cation; however, all other requirements shall be subject to negotiation between the
producer and the user.
3
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.
4
Available from American National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
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.
1

3. Terminology
3.1 The terms and symbols used in this speciﬁcation are
deﬁned in Terminology A340.
4. Classiﬁcation
4.1 Two speciﬁc alloy types are covered:
4.2 Grades, Alloy Type 1—The standard grades of this alloy
type are distinguished by the as-supplied condition, coercive
ﬁeld strength, and nominal mechanical hardness and are listed
in Table 2.
4.3 Grades, Alloy Type 2—The standard grades of this alloy
type are distinguished by the as-supplied condition, coercive
ﬁeld strength, and nominal mechanical hardness and are listed
in Table 3.
5. Ordering Information
5.1 Purchase orders for material under this speciﬁcation
shall include the following information to adequately describe
the desired product:
5.1.1 Reference to this speciﬁcation and year of issue/
revision.
5.1.2 Alloy type and grade (Section 4),
5.1.3 Form and condition,
5.1.4 Dimensions and tolerances (Section 9),
5.1.5 Quantity (weight or number of pieces),
5.1.6 Magnetic property requirements if other than shown in
this speciﬁcation.
5.1.7 Certiﬁcation of analysis or magnetic quality
evaluation, or both, if needed,
5.1.8 Marking and packaging, and
5.1.9 Exceptions to the speciﬁcation or special require-
ments.
6. Chemical Composition
6.1 The material shall conform to the requirements pre-
scribed in Table 4.
6.2 Determination of metallic constituents shall be by a
method acceptable to both the producer and the user. Analysis
of carbon, nitrogen, sulfur, and oxygen shall be done in
accordance with Test Methods E1019.
7. Form and Condition
7.1 Cold Finished Bars—Cold drawn; cold drawn and
centerless ground; cold drawn and precision ground; mill
annealed and centerless ground; mill annealed and precision
ground.
8. Magnetic Property Requirements
8.1 General—Material supplied under terms of this speciﬁ-
cation shall be tested using either ring, permeameter, or
coercimeter test methods. Only the coercive ﬁeld strength
(H
cB
) is subject to speciﬁcation. Since coercimeters saturate the
test specimen before measurement of the coercive ﬁeld
strength, two different sets of coercive ﬁeld strength
requirements, one for ring and permeameter testing and one for
coercimeter testing, are given. Unless speciﬁed in the purchase
order, coercimeter testing shall be the standard test method.
8.2 Test Specimen—Test specimen size and shape shall be in
accordance with the requirements listed in Practice A34/
A34M. If tests on heat-treated specimens are requested, all
machining operations shall be performed before heat treatment.
The cross-sectional area of all specimen types shall be deter-
mined by measurement with a micrometer or calipers.
8.3 Magnetic Test Specimen Heat Treatment—When speci-
ﬁed on the purchase order, the annealed magnetic properties
(also referred to as the magnetic capability) rather than the
as-supplied magnetic properties shall be determined. The heat
treatment to be used to assess the magnetic capability should be
speciﬁed by the user. If not, the following heat treatment
procedure (full anneal) shall be used.
8.3.1 Atmosphere—High vacuum or very dry hydrogen
(dew point less than −60 °C).
8.3.2 Soak Temperature (Alloy Type 1)—815 °C 625 °C.
8.3.3 Soak Temperature (Alloy Type 2)—850 °C 625 °C.
8.3.4 Soak Time—2 h minimum.
8.3.5 Cooling—Furnace cool (50 °C ⁄h to 100°C/h) to
400 °C then cool to room temperature at any convenient rate.
8.4 dc Ring and Permeameter Testing:
8.4.1 Either ring or permeameter test methods may be used.
For ring testing, a link-type specimen with its long edge
parallel to the bar axis is preferred. Testing of ring or link
specimens shall be in accordance with Test Methods A596/
A596M or A773/A773M. Testing of bar specimens on a
permeameter shall be in accordance with either Test Methods
A341/A341M or A773/A773M.
8.4.2 Requirements—The coercive ﬁeld strength, when
measured from a maximum magnetic ﬂux density of 1.0 T
(10 kG), shall meet the requirements listed in Table 5. Full-
anneal requirements refer to specimens heat treated in accor-
dance with 8.3.
8.5 Coercimeter Testing:
TABLE 1 Alloy Types
Alloy Type Nominal Composition, Weight Percent
Carbon Chromium Silicon Sulfur Iron
1 0.05 17.5 0.50 0.30 balance
2 0.05 17.5 1.25 0.30 balance
TABLE 2 Grades for Alloy Type 1
Grade As-Supplied Condition
1mill annealed
2 mill annealed
3 unannealed, cold drawn
TABLE 3 Grades for Alloy Type 2
Grade As-Supplied Condition
1 mill annealed
2 unannealed, cold drawn
A838 − 24
2

8.5.1 Coercimeter testing is permitted provided it can be

demonstrated that the maximum magnetic ﬂux density induced

in the specimen exceeds 1.3 T (13 kG) and that the equipment

and procedures used satisfy the requirements of IEC 60404-7.

8.5.2 Any machining before testing shall be done with due

care, and only enough material shall be removed to permit

insertion of the test specimen into the coercimeter.

8.5.3 Requirements—The coercive ﬁeld strength shall meet

the requirements listed in Table 6. Full-anneal requirements

refer to specimens heat treated in accordance with 8.3.

9. Dimensions and Tolerances

9.1 Dimensions and tolerances shall be as mutually agreed

upon between the user and the producer.

10. Certiﬁcation

10.1 When speciﬁed in the purchase order or contract, the

user shall be furnished certiﬁcation that samples representing

each lot have been either tested or inspected as directed in this

speciﬁcation and the requirements have been met. When

speciﬁed in the purchase order or contract, a report of test

results shall be furnished.

11. Packaging and Package Marking

11.1 Packaging and package marking shall be subject to

agreement between the user and the producer.

11.2 Material furnished under this speciﬁcation shall be

identiﬁed by the name or symbol of the producer, by alloy type

and grade, or producer’s brand name, or a combination thereof,

heat number, and material size. Each heat supplied on a given

order must be identiﬁed separately and packaged separately.

12. Keywords

12.1 coercive ﬁeld strength; coercivity; ferritic stainless

steel; free-machining; relay

TABLE 4 Chemical Requirements

Alloy Type Carbon, max Manganese,

max Silicon Phosphorus,

max Sulfur Chromium Molybdenum,

max Nickel, max Iron

1 0.065 0.80 0.30/0.70 0.030 0.25/0.40 17.25/18.25 0.50 0.60 bal

2 0.065 0.80 1.00/1.50 0.030 0.25/0.40 17.25/18.25 0.50 0.60 bal

TABLE 5 DC Coercive Field Strength (H

) Requirements—Ring and Permeameter Testing

Alloy Type Grade Bar Diameter Range, mm (in.) H

, max

1 1 $6.35 (0.250) #17.5 (0.689) 180 A/m (2.3 Oe)

>17.5 (0.689) #41.5 (1.63) 240 A/m (3.0 Oe)

1 2 $6.35 (0.250) #17.5 (0.689) 370 A/m (4.7 Oe)

>17.5 (0.689) #41.5 (1.63) 400 A/m (5.0 Oe)

1 3 $6.35 (0.250) #41.5 (1.63) 560 A/m (7.0 Oe)

1 full anneal (all grades) $6.35 (0.250) #41.5 (1.63) 180 A/m (2.3 Oe)

2 1 $6.35 (0.250) #17.5 (0.689) 210 A/m (2.6 Oe)

>17.5 (0.689) #41.5 (1.63) 220 A/m (2.8 Oe)

2 2 $6.35 (0.250) #41.5 (1.63) 560 A/m (7.0 Oe)

2 full anneal (all grades) $6.35 (0.250) #41.5 (1.63) 210 A/m (2.6 Oe)

TABLE 6 Coercive Field Strength (H

) Requirements—Coercimeter Testing

Alloy Type Grade Bar Diameter Range, mm (in.) H

, max

1 1 $6.35 (0.250) #17.5 (0.689) 230 A/m (2.9 Oe)

>17.5 (0.689) #41.5 (1.63) 290 A/m (3.6 Oe)

1 2 $6.35 (0.250) #17.5 (0.689) 480 A/m (6.0 Oe)

>17.5 (0.689) #41.5 (1.63) 530 A/m (6.7 Oe)

1 3 $6.35 (0.250) #41.5 (1.63) 680 A/m (8.5 Oe)

1 full anneal (all grades) $6.35 (0.250) #41.5 (1.63) 220 A/m (2.8 Oe)

2 1 $6.35 (0.250) #17.5 (0.689) 270 A/m (3.4 Oe)

>17.5 (0.689) #41.5 (1.63) 290 A/m (3.6 Oe)

2 2 $6.35 (0.250) #41.5 (1.63) 680 A/m (8.5 Oe)

2 full anneal (all grades) $6.35 (0.250) #41.5 (1.63) 270 A/m (3.4 Oe)

A838 − 24

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标签： #易切削 #铁素体 #软磁合金

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ASTM A838-2024 Standard Specification for Free-Machining Ferritic Stainless Soft Magnetic Alloy Bar for Relay Applications 继电器用易切削铁素体不锈软磁合金技术规范

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