1、Designation: A838 02 (Reapproved 2013)A838 18Standard Specification forFree-Machining Ferritic Stainless Soft Magnetic Alloy Barfor Relay Applications1This standard is issued under the fixed designation A838; the number immediately following the designation indicates the year oforiginal adoption or,
2、 in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers free-machining ferritic stainless soft magnetic alloy
3、produced or supplied expressly incold-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
4、 covered. The primary constituents are shown in Table 1. These types have corrosion resistancesimilar to AISI Type 430F and Type 430F, Specification A582/A582M.1.3 This specification covers only these alloy types supplied in cold-finished bars in cross-sectional shapes such as rounds,squares, hexago
5、ns, and octagons with diameters (diagonals) greater than or equal to 0.250 in. (6.35 mm)6.35 mm (0.250 in.) andless than or equal to 1.625 in. (41.28 mm).41.5 mm (1.63 in.).21.4 Certain cold-finished round bar products are capable of being supplied mill annealed to required magnetic properties sucha
6、s low coercivity. The size range that can be mill annealed is from 0.250 to 1.625 in. (6.35 to 41.28 mm).6.35 to 41.5 mm (0.250to 1.63 in.). Other products of these alloys cannot be mill annealed to produce equivalently low coercivity; hence, the finalmachined parts should be heat treated as recomme
7、nded by the producer.1.5 The values stated in customary (cgs-emu and inch-pound) SI units are to be regarded as standard. The values given inparentheses are mathematical conversions to SI customary (cgs-emu and inch-pound) units which are provided for informationonly and are not considered standard.
8、1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability ofregulatory limitations prior to use.1
9、.7 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Tra
10、de (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3A34/A34M Practice for Sampling and Procurement Testing of Magnetic MaterialsA340 Terminology of Symbols and Definitions Relating to Magnetic TestingA341/A341M Test Method for Direct Current Magnetic Properties of Soft Magnetic Materials U
11、sing D-C Permeameters and thePoint by Point (Ballistic) Test MethodsA582/A582M Specification for Free-Machining Stainless Steel BarsA596/A596M Test Method for Direct-Current Magnetic Properties of Materials Using the Ballistic Method and Ring SpecimensA773/A773M Test Method for Direct Current Magnet
12、ic Properties of Low Coercivity Magnetic Materials Using Hysteresig-raphs1 This specification is under the jurisdiction of ASTM Committee A06 on Magnetic Properties and is the direct responsibility of Subcommittee A06.02 on MaterialSpecifications.Current edition approved May 1, 2013Oct. 1, 2018. Pub
13、lished July 2013October 2018. Originally approved in 1985. Last previous edition approved in 20072013 asA838 02 (2007).(2013). DOI: 10.1520/A0838-02R13.10.1520/A0838-18.2 Other product forms can be supplied to the chemistries listed in this specification; however, all other requirements shall be sub
14、ject to negotiation between the producerand the user.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This doc
15、ument 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. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as
16、 appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1E1019 Test Methods for Determination of Carbon, Sulfur,
17、Nitrogen, and Oxygen in Steel, Iron, Nickel, and Cobalt Alloys byVarious Combustion and Inert Gas Fusion Techniques2.2 Other Standard:IEC Publication 60404-7 Methods of Measurement of the Coercivity of Magnetic Materials in an Open Magnetic Circuit43. Terminology3.1 The terms and symbols used in thi
18、s specification are defined in Terminology A340.4. Classification4.1 Two specific alloy types are covered:4.2 Grades, Alloy Type 1The standard grades of this alloy type are distinguished by the as-supplied condition, coercivity,coercive field strength, and nominal mechanical hardness and are listed
19、in Table 2.4.3 Grades, Alloy Type 2The standard grades of this alloy type are distinguished by the as-supplied condition, coercivity,coercive field strength, and nominal mechanical hardness and are listed in Table 3.5. Ordering Information5.1 Purchase orders for material under this specification sha
20、ll include the following information to adequately describe thedesired 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.
21、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, and5.1.9 Exceptions to the specification or special requirements.6. Chemical Composition6.1 The material shall co
22、nform to the requirements prescribed 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 Condition7.1 Cold Finished Bars
23、Cold drawn; cold drawn and centerless ground; cold drawn and precision ground; mill annealed andcenterless ground; mill annealed and precision ground.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.TABLE 1 Alloy TypesAl
24、loy Type Nominal Composition, Weight PercentCarbon Chromium Silicon Sulfur Iron1 0.05 17.5 0.50 0.30 balance2 0.05 17.5 1.25 0.30 balanceTABLE 2 Grades for Alloy Type 1Grade As-Supplied Condition1 mill annealed2 mill annealed3 unannealed, cold drawnA838 1828. Magnetic Property Requirements8.1 Genera
25、lMaterial supplied under terms of this specification shall be tested using either ring, permeameter, or coercimetertest methods. Only the coercive field strength (HccB) is subject to specification. Since coercimeters saturate the test specimen beforemeasurement of the coercive field strength, two di
26、fferent sets of coercive field strength requirements, one for ring and permeametertesting and one for coercimeter testing, are given. Unless specified in the purchase order, coercimeter testing shall be the standardtest method.8.2 Test SpecimenTest specimen size and shape shall be in accordance with
27、 the requirements listed in Practice A34/A34M.If tests on heat-treated specimens are requested, all machining operations shall be performed before heat treatment. Thecross-sectional area of all specimen types shall be determined by measurement with a micrometer or calipers.8.3 Magnetic Test Specimen
28、 Heat TreatmentWhen specified on the purchase order, the annealed magnetic properties (alsoreferred to as the magnetic capability) rather than the as-supplied magnetic properties shall be determined. The heat treatment tobe used to assess the magnetic capability should be specified by the user. If n
29、ot, the following heat treatment procedure (full anneal)shall be used.8.3.1 AtmosphereHigh vacuum or very dry hydrogen (dew point less than 60C).8.3.2 Soak Temperature (Alloy Type 1)815 6 25C.8.3.3 Soak Temperature (Alloy Type 2)850 6 25C.8.3.4 Soak Time2-h minimum.8.3.5 CoolingFurnace cool (50 to 1
30、00C/h) to 400C 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 parallelto the bar axis is preferred. Testing of ring or link specimens shall b
31、e in accordance with Test Methods A596/A596M orA773/A773M. Testing of bar specimens on a permeameter shall be in accordance with either Test Methods A341/A341M orA773/A773M.8.4.2 RequirementsThe coercive field strength, when measured from a maximum magnetic flux density of 10.0 kG (1.00T),1.0 T (10
32、kG), shall meet the requirements listed in Table 5. Full-anneal requirements refer to specimens heat treated inaccordance with 8.3.8.5 Coercimeter Testing:8.5.1 Coercimeter testing is permitted provided it can be demonstrated that the maximum magnetic flux density induced in thespecimen exceeds 13 k
33、G (1.30 T)1.3 T (13 kG) and that the equipment and procedures used satisfy the requirements of IECPublication 60404-7.8.5.2 Any machining before testing shall be done with due care, and only enough material shall be removed to permit insertionof the test specimen into the coercimeter.8.5.3 Requireme
34、ntsThe coercive field strength shall meet the requirements listed in Table 6. Full-anneal requirements referto specimens heat treated in accordance with 8.3.9. Dimensions and Tolerances9.1 Dimensions and tolerances shall be as mutually agreed upon between the user and the producer.10. Certification1
35、0.1 When specified in the purchase order or contract, the user shall be furnished certification that samples representing eachlot have been either tested or inspected as directed in this specification and the requirements have been met. When specified in thepurchase order or contract, a report of te
36、st results shall be furnished.11. Packaging and Package Marking11.1 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 andgrade, or pro
37、ducers brand name, or a combination thereof, heat number, and material size. Each heat supplied on a given ordermust be identified separately and packaged separately.12. Keywords12.1 coercive field strength; coercivity; ferritic stainless steel; free-machining; relayTABLE 3 Grades for Alloy Type 2Gr
38、ade As-Supplied Condition1 mill annealed2 unannealed, cold drawnA838 183TABLE 4 Chemical RequirementsAlloy Type Carbon, max Manganese,max Silicon Phosphorus,max Sulfur Chromium Molybdenum,max Nickel, max Iron1 0.065 0.80 0.30/0.70 0.030 0.25/0.40 17.25/18.25 0.50 0.60 bal2 0.065 0.80 1.00/1.50 0.030
39、 0.25/0.40 17.25/18.25 0.50 0.60 balTABLE 5 DC Coercive Field Strength (Hc) RequirementsRing and Permeameter TestingAlloy Type Grade Bar Diameter Range, in. (mm) Hc, max1 1 $0.250 (6.35) #0.6875 (17.46) 2.30 Oe (183 A/m)0.6875 (17.46) #1.625 (41.28) 3.00 Oe (239 A/m)1 2 $0.250 (6.35) #0.6875 (17.46)
40、 4.70 Oe (374 A/m)0.6875 (17.46) #1.625 (41.28) 5.00 Oe (398 A/m)1 3 $0.250 (6.35) #1.625 (41.28) 7.00 Oe (557 A/m)1 full anneal (all grades) $0.250 (6.35) #1.625 (41.28) 2.20 Oe (175 A/m)2 1 $0.250 (6.35) #0.6875 (17.46) 2.60 Oe (207 A/m)0.6875 (17.46) #1.625 (41.28) 2.80 Oe (223 A/m)2 2 $0.250 (6.
41、35) #1.625 (41.28) 7.00 Oe (557 A/m)2 full anneal (all grades) $0.250 (6.35) #1.625 (41.28) 2.60 Oe (207 A/m)TABLE 5 DC Coercive Field Strength (HcB) RequirementsRing and Permeameter TestingAlloy Type Grade Bar Diameter Range, mm (in.) HcB, max1 1 $6.35 (0.250) # 17.5 (0.689) 180 A/m (2.3 Oe)17.5 (0
42、.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
43、 (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 (Hc) RequirementsCoercimeter TestingAlloy Type Grade Bar Diameter Range, in. (mm) Hc, max1 1 $0.250 (6.35) #0.
44、6875 (17.46) 2.90 Oe (231 A/m)0.6875 (17.46) #1.625 (41.28) 3.60 Oe (286 A/m)1 2 $0.250 (6.35) #0.6875 (17.46) 6.00 Oe (477 A/m)0.6875 (17.46) #1.625 (41.28) 6.60 Oe (525 A/m)1 3 $0.250 (6.35) #1.625 (41.28) 8.50 Oe (676 A/m)1 full anneal (all grades) $0.250 (6.35) #1.625 (41.28) 2.80 Oe (223 A/m)2
45、1 $0.250 (6.35) #0.6875 (17.46) 3.40 Oe (271 A/m)0.6875 (17.46) #1.625 (41.28) 3.60 Oe (286 A/m)2 2 $0.250 (6.35) #1.625 (41.28) 8.50 Oe (676 A/m)2 full anneal (all grades) $0.250 (6.35) #1.625 (41.28) 3.40 Oe (271 A/m)TABLE 6 Coercive Field Strength (HcB) RequirementsCoercimeter TestingAlloy Type G
46、rade Bar Diameter Range, mm (in.) HcB, max1 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)
47、 $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 184APPENDIX(Nonmandatory Information)X1
48、. TYPICAL PHYSICAL, MAGNETIC, AND MECHANICAL PROPERTIESX1.1 Typical physical and magnetic properties are listed in Table X1.1 for the two alloy types contained in this specification.Magnetic property data shown were measured on 0.250-6.35- to 0.375-in. (6.35-9.52-mm (0.250- to 9.52-mm)0.375-in.) dia
49、metermill-annealed (Grade 1both types) bar using a Fahy Permeameter in accordance with Test Method A341/A341M. Larger-diameter bars will yield lower maximum permeabilities and residual inductions due to limitations associated with testinglarge-diameter, relatively high-permeability bars on a permeameter. Typical mechanical property data other than hardness forGrade 1 of both alloy types is shown in Table X1.2. Typical hardness ranges are given in Table X1.3. The data provided are forinformation only and are not requirements in this specification and n
