ASTM A838-02

Standard Specification for Free-Machining Ferritic Stainless Soft Magnetic Alloy Bar for Relay Applications

SCOPE
1.1 This specification covers free-machining ferritic stainless 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 . These types have corrosion resistance similar to AISI Type 430F and Type 430F, Specification A 582/A 582M.
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 0.250 in. (6.35 mm) and less than or equal to 1.625 in. (41.28 mm).
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 0.250 to 1.625 in. (6.35 to 41.28 mm). 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 customary (cgs-emu and inch-pound) units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units which are provided for information only and are not considered standard.

General Information

• Status: Historical
• Publication Date: 09-Oct-2002
• ICS: 77.140.40 - Steels with special magnetic properties
• Technical Committee: A06 - Magnetic Properties
• Drafting Committee: A06.02 - Material Specifications

Relations

• Replaced By: ASTM A838-02(2007) - Standard Specification for Free-Machining Ferritic Stainless Soft Magnetic Alloy Bar for Relay Applications
• Effective Date: 01-May-2007

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: A 838 – 02
Standard Specification for
Free-Machining Ferritic Stainless Soft Magnetic Alloy Bar
for Relay Applications
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.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
TABLE 1 Alloy Types
1. Scope
Nominal Composition, Weight Percent
1.1 This specification covers free-machining ferritic stain-
Alloy Type
Carbon Chromium Silicon Sulfur Iron
less soft magnetic alloy produced or supplied expressly in
1 0.05 17.5 0.50 0.30 balance
cold-finishedbarformforuseinmagneticcoresandotherparts 2 0.05 17.5 1.25 0.30 balance
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.
A 340 Terminology of Symbols and Definitions Relating to
1.2 Two specific alloy types are covered. The primary
Magnetic Testing
constituents are shown in Table 1. These types have corrosion
A 341/A 341M Test Method for Direct Current Magnetic
resistance similar to AISI Type 430F and Type 430F, Specifi-
Properties of Materials Using dc Permeameters and the
cation A582/A582M.
Ballistic Test Method
1.3 Thisspecificationcoversonlythesealloytypessupplied
A 582/A582M Specification for Free-Machining Stainless
in cold-finished bars in cross-sectional shapes such as rounds,
Steel Bars
squares, hexagons, and octagons with diameters (diagonals)
A 596/A 596M Test Method for Direct Current Magnetic
greater than or equal to 0.250 in. (6.35 mm) and less than or
Properties of Materials Using the Ballistic Method and
equal to 1.625 in. (41.28 mm).
Ring Specimens
1.4 Certain cold-finished round bar products are capable of
A773/A773M Test Method for dc Magnetic Properties of
being supplied mill annealed to required magnetic properties
Materials Using Ring and Permeameter Procedures with
suchaslowcoercivity.Thesizerangethatcanbemillannealed
dc Electronic Hysteresigraphs
is from 0.250 to 1.625 in. (6.35 to 41.28 mm). Other products
E1019 Test Methods for Determination of Carbon, Sulfur,
ofthesealloyscannotbemillannealedtoproduceequivalently
Nitrogen, and Oxygen in Steel and in Iron, Nickel, and
low coercivity; hence, the final machined parts should be heat
Cobalt Alloys
treated as recommended by the producer.
2.2 Other Standard:
1.5 The values stated in customary (cgs-emu and inch-
IEC Publication 60404-7 Methods of Measurement of the
pound) units are to be regarded as standard. The values given
Coercivity of Magnetic Materials in an Open Magnetic
in parentheses are mathematical conversions to SI units which
Circuit
are provided for information only and are not considered
standard.
3. Terminology
3.1 The terms and symbols used in this specification are
2. Referenced Documents
defined in Terminology A340.
2.1 ASTM Standards:
A 34/A 34M Practice for Sampling and Procurement Test-
4. Classification
ing of Magnetic Materials
4.1 Two specific alloy types are covered:
4.2 Grades,AlloyType1—Thestandardgradesofthisalloy
type are distinguished by the as-supplied condition, coercivity,
This specification is under the jurisdiction of ASTM Committee A06 on
and nominal mechanical hardness and are listed in Table 2.
Magnetic Properties and is the direct responsibility of Subcommittee A06.02 on
Materials Specifications.
Current edition approved Oct. 10, 2002. Published November 2002. Originally
published as A838–85. Last previous edition A838/A838–97.
2 4
Other product forms can be supplied to the chemistries listed in this specifi- Annual Book of ASTM Standards, Vol 01.03.
cation; however, all other requirements shall be subject to negotiation between the Annual Book of ASTM Standards, Vol 03.05.
producer and the user. Available from American National Standards Institute, 25 W. 43rd St., 4th
Annual Book of ASTM Standards, Vol 03.04. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
A838–02
TABLE 2 Grades for Alloy Type 1
8.2 TestSpecimen—Testspecimensizeandshapeshallbein
Grade As-Supplied Condition accordance with the requirements listed in Practice A34/
A34M. If tests on heat-treated specimens are requested, all
1 mill annealed
2 mill annealed
machiningoperationsshallbeperformedbeforeheattreatment.
3 unannealed, cold drawn
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-
4.3 Grades,AlloyType2—Thestandardgradesofthisalloy
fied on the purchase order, the annealed magnetic properties
type are distinguished by the as-supplied condition, coercivity,
(also referred to as the magnetic capability) rather than the
and nominal mechanical hardness and are listed in Table 3.
as-supplied magnetic properties shall be determined. The heat
treatmenttobeusedtoassessthemagneticcapabilityshouldbe
5. Ordering Information
specified by the user. If not, the following heat treatment
5.1 Purchase orders for material under this specification
procedure (full anneal) shall be used.
shall include the following information to adequately describe
8.3.1 Atmosphere—High vacuum or very dry hydrogen
the desired product:
(dew point less than −60°C).
5.1.1 Reference to this specification and year of issue/
8.3.2 Soak Temperature (Alloy Type 1)—815 6 25°C.
revision.
8.3.3 Soak Temperature (Alloy Type 2)—850 6 25°C.
5.1.2 Alloy type and grade (Section 4),
8.3.4 Soak Time—2-h minimum.
5.1.3 Form and condition,
8.3.5 Cooling—Furnacecool(50to100°C/h)to400°Cthen
5.1.4 Dimensions and tolerances (Section 9),
cool to room temperature at any convenient rate.
5.1.5 Quantity (weight or number of pieces),
8.4 dc Ring and Permeameter Testing:
5.1.6 Magneticpropertyrequirementsifotherthanshownin
8.4.1 Either ring or permeameter test methods may be used.
this specification.
For ring testing, a link-type specimen with its long edge
5.1.7 Certification of analysis or magnetic quality evalua-
parallel to the bar axis is preferred. Testing of ring or link
tion, or both, if needed,
specimens shall be in accordance with Test Methods A596/
5.1.8 Marking and packaging, and
A596M or A773/A773M. Testing of bar specimens on a
5.1.9 Exceptions to the specification or special require-
permeameter shall be in accordance with either Test Methods
ments.
A341/A341M or A773/A773M.
6. Chemical Composition 8.4.2 Requirements—The coercive field strength, when
measured from a maximum flux density of 10.0 kG (1.00 T),
6.1 The material shall conform to the requirements pre-
shall meet the requirements listed in Table 5. Full-anneal
scribed in Table 4.
requirements refer to specimens heat treated in accordance
6.2 Determination of metallic constituents shall be by a
with 8.3.
method acceptable to both the producer and the user.Analysis
8.5 Coercimeter Testing:
of carbon, nitrogen, sulfur, and oxygen shall be done in
8.5.1 Coercimeter testing is permitted provided it can be
accordance with Test Methods E1019.
demon
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