1、Designation: A 838 02 (Reapproved 2007)Standard Specification forFree-Machining Ferritic Stainless Soft Magnetic Alloy Barfor Relay Applications1This standard is issued under the fixed designation A 838; the number immediately following the designation indicates the year oforiginal adoption or, in t
2、he case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This specification covers free-machining ferritic stain-less soft magnetic alloy pro
3、duced or supplied expressly incold-finished bar form for use in magnetic cores and other partsrequiring a high permeability, low-coercivity stainless steel.1.1.1 This specification does not cover either cast parts orparts produced by powder metallurgy techniques.1.2 Two specific alloy types are cove
4、red. The primaryconstituents are shown in Table 1. These types have corrosionresistance similar to AISI Type 430F and Type 430F, Specifi-cation A 582/A 582M.1.3 This specification covers only these alloy types suppliedin cold-finished bars in cross-sectional shapes such as rounds,squares, hexagons,
5、and octagons with diameters (diagonals)greater than or equal to 0.250 in. (6.35 mm) and less than orequal to 1.625 in. (41.28 mm).21.4 Certain cold-finished round bar products are capable ofbeing supplied mill annealed to required magnetic propertiessuch as low coercivity. The size range that can be
6、 mill annealedis from 0.250 to 1.625 in. (6.35 to 41.28 mm). Other productsof these alloys cannot be mill annealed to produce equivalentlylow coercivity; hence, the final machined parts should be heattreated as recommended by the producer.1.5 The values stated in customary (cgs-emu and inch-pound) u
7、nits are to be regarded as standard. The values givenin parentheses are mathematical conversions to SI units whichare provided for information only and are not consideredstandard.2. Referenced Documents2.1 ASTM Standards:3A 34/A 34M Practice for Sampling and Procurement Test-ing of Magnetic Material
8、sA 340 Terminology of Symbols and Definitions Relating toMagnetic TestingA 341/A 341M Test Method for Direct Current MagneticProperties of Materials Using D-C Permeameters and theBallistic Test MethodsA 582/A 582M Specification for Free-Machining StainlessSteel BarsA 596/A 596M Test Method for Direc
9、t-Current MagneticProperties of Materials Using the Ballistic Method andRing SpecimensA 773/A 773M Test Method for dc Magnetic Properties ofMaterials Using Ring and Permeameter Procedures withdc Electronic HysteresigraphsE 1019 Test Methods for Determination of Carbon, Sulfur,Nitrogen, and Oxygen in
10、 Steel and in Iron, Nickel, andCobalt Alloys2.2 Other Standard:IEC Publication 60404-7 Methods of Measurement of theCoercivity of Magnetic Materials in an Open MagneticCircuit43. Terminology3.1 The terms and symbols used in this specification aredefined in Terminology A 340.4. Classification4.1 Two
11、specific alloy types are covered:4.2 Grades, Alloy Type 1The standard grades of this alloytype are distinguished by the as-supplied condition, coercivity,and nominal mechanical hardness and are listed in Table 2.4.3 Grades, Alloy Type 2The standard grades of this alloytype are distinguished by the a
12、s-supplied condition, coercivity,and nominal mechanical hardness and are listed in Table 3.1This specification is under the jurisdiction of ASTM Committee A06 onMagnetic Properties and is the direct responsibility of Subcommittee A06.02 onMaterial Specifications.Current edition approved May 1, 2007.
13、 Published June 2007. Originallyapproved in 1985. Last previous edition approved in 2002 as A 838 02.2Other product forms can be supplied to the chemistries listed in this specifi-cation; however, all other requirements shall be subject to negotiation between theproducer and the user.3For referenced
14、 ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.
15、,4th Floor, New York, NY 10036, http:/www.ansi.org.TABLE 1 Alloy TypesAlloy TypeNominal Composition, Weight PercentCarbon Chromium Silicon Sulfur Iron1 0.05 17.5 0.50 0.30 balance2 0.05 17.5 1.25 0.30 balance1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 194
16、28-2959, United States.5. Ordering Information5.1 Purchase orders for material under this specificationshall include the following information to adequately describethe 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
17、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 inthis specification.5.1.7 Certification of analysis or magnetic quality evalua-tion, or both, if needed,5.1.8 Marking and packaging, and5.1.
18、9 Exceptions to the specification or special require-ments.6. Chemical Composition6.1 The material shall conform to the requirements pre-scribed in Table 4.6.2 Determination of metallic constituents shall be by amethod acceptable to both the producer and the user. Analysisof carbon, nitrogen, sulfur
19、, and oxygen shall be done inaccordance with Test Methods E 1019.7. Form and Condition7.1 Cold Finished BarsCold drawn; cold drawn andcenterless ground; cold drawn and precision ground; millannealed and centerless ground; mill annealed and precisionground.8. Magnetic Property Requirements8.1 General
20、Material supplied under terms of this speci-fication shall be tested using either ring, permeameter, orcoercimeter test methods. Only the coercive field strength (Hc)is subject to specification. Since coercimeters saturate the testspecimen before measurement of the coercive field strength,two differ
21、ent sets of coercive field strength requirements, onefor ring and permeameter testing and one for coercimetertesting, are given. Unless specified in the purchase order,coercimeter testing shall be the standard test method.8.2 Test SpecimenTest specimen size and shape shall be inaccordance with the r
22、equirements listed in Practice A 34/A 34M. If tests on heat-treated specimens are requested, allmachining 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 He
23、at TreatmentWhen speci-fied on the purchase order, the annealed magnetic properties(also referred to as the magnetic capability) rather than theas-supplied magnetic properties shall be determined. The heattreatment to be used to assess the magnetic capability should bespecified by the user. If not,
24、the following heat treatmentprocedure (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 100C/h
25、) to 400C thencool 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 edgeparallel to the bar axis is preferred. Testing of ring or linkspecimens shall be in acc
26、ordance with Test Methods A 596/A 596M or A 773/A 773M. Testing of bar specimens on apermeameter shall be in accordance with either Test MethodsA 341/A 341M or A 773/A 773M.8.4.2 RequirementsThe coercive field strength, whenmeasured from a maximum flux density of 10.0 kG (1.00 T),shall meet the requ
27、irements listed in Table 5. Full-annealrequirements refer to specimens heat treated in accordancewith 8.3.8.5 Coercimeter Testing:8.5.1 Coercimeter testing is permitted provided it can bedemonstrated that the maximum flux density induced in thespecimen exceeds 13 kG (1.30 T) and that the equipment a
28、ndprocedures used satisfy the requirements of IEC Publication60404-7.8.5.2 Any machining before testing shall be done with duecare, and only enough material shall be removed to permitinsertion of the test specimen into the coercimeter.8.5.3 RequirementsThe coercive field strength shall meetthe requi
29、rements listed in Table 6. Full-anneal requirementsrefer to specimens heat treated in accordance with 8.3.9. Dimensions and Tolerances9.1 Dimensions and tolerances shall be as mutually agreedupon between the user and the producer.TABLE 2 Grades for Alloy Type 1Grade As-Supplied Condition1 mill annea
30、led2 mill annealed3 unannealed, cold drawnTABLE 3 Grades for Alloy Type 2Grade As-Supplied Condition1 mill annealed2 unannealed, cold drawnTABLE 4 Chemical RequirementsAlloy Type Carbon, maxManganese,maxSiliconPhosphorus,maxSulfur ChromiumMolybdenum,maxNickel, max Iron1 0.065 0.80 0.30/0.70 0.030 0.
31、25/0.40 17.25/18.25 0.50 0.60 bal2 0.065 0.80 1.00/1.50 0.030 0.25/0.40 17.25/18.25 0.50 0.60 balA 838 02 (2007)210. Certification10.1 When specified in the purchase order or contract, theuser shall be furnished certification that samples representingeach lot have been either tested or inspected as
32、directed in thisspecification and the requirements have been met. Whenspecified in the purchase order or contract, a report of testresults shall be furnished.11. Packaging and Package Marking11.1 Packaging and package marking shall be subject toagreement between the user and the producer.11.2 Materi
33、al furnished under this specification shall beidentified by the name or symbol of the producer, by alloy typeand grade, or producers brand name, or a combination thereof,heat number, and material size. Each heat supplied on a givenorder must be identified separately and packaged separately.12. Keywo
34、rds12.1 coercive field strength; coercivity; ferritic stainlesssteel; free-machining; relayAPPENDIX(Nonmandatory Information)X1. TYPICAL PHYSICAL, MAGNETIC, AND MECHANICAL PROPERTIESX1.1 Typical physical and magnetic properties are listed inTable X1.1 for the two alloy types contained in this specif
35、ica-tion. Magnetic property data shown were measured on 0.250-to 0.375-in. (6.35- to 9.52-mm) diameter mill-annealed (Grade1both types) bar using a Fahy Permeameter in accordancewith Test Method A 341/A 341M. Larger-diameter bars willTABLE 5 DC Coercive Field Strength (Hc) RequirementsRing and Perme
36、ameter TestingAlloy Type Grade Bar Diameter Range, in. (mm) Hc, max11$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)12$0.250 (6.35) #0.6875 (17.46) 4.70 Oe (374 A/m)0.6875 (17.46) #1.625 (41.28) 5.00 Oe (398 A/m)13$0.250 (6.35) #1.625 (41.28) 7.00 Oe (5
37、57 A/m)1 full anneal (all grades) $0.250 (6.35) #1.625 (41.28) 2.20 Oe (175 A/m)21$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)22$0.250 (6.35) #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)TAB
38、LE 6 Coercive Field Strength (Hc) RequirementsCoercimeter TestingAlloy Type Grade Bar Diameter Range, in. (mm) Hc, max11$0.250 (6.35) #0.6875 (17.46) 2.90 Oe (231 A/m)0.6875 (17.46) #1.625 (41.28) 3.60 Oe (286 A/m)12$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
39、 (525 A/m)13$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)21$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)22$0.250 (6.35) #1.625 (41.28) 8.50 Oe (676 A/m)2 full anneal (all grades
40、) $0.250 (6.35) #1.625 (41.28) 3.40 Oe (271 A/m)TABLE X1.1 Typical Physical and Magnetic PropertiesProperty Alloy Type 1 Alloy Type 2Density, g/cm3(kg/m3) 7.62 (7620) 7.59 (7590)Electrical resistivity, V-cm (V-mm) 60.0 (600) 76.0 (760)Mean coefficient of thermal expansion,(0649C) (m/m/C)(11.9) (11.9
41、)Curie temperature, C 671 660Saturation flux density, kG (T) 15.5 (1.55) 15.2 (1.52)(Relative) maximum permeability 2300 2350Residual induction,AkG (T) 7.54 (0.754) 7.42 (0.742)Coercive field strength,AOe (A/m) 1.80 (143) 1.64 (130)AResidual induction and coercive field strength are determined from
42、a maximum flux density of 10 kG (1.0 T).A 838 02 (2007)3yield lower maximum permeabilities and residual inductionsdue to limitations associated with testing large-diameter, rela-tively high-permeability bars on a permeameter. Typical me-chanical property data other than hardness for Grade 1 of botha
43、lloy types is shown in Table X1.2. Typical hardness ranges aregiven in Table X1.3. The data provided are for informationonly and are not requirements in this specification and need notbe measured.ASTM International takes no position respecting the validity of any patent rights asserted in connection
44、 with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible t
45、echnical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful conside
46、ration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr
47、 Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website
48、(www.astm.org).TABLE X1.2 Typical Mechanical PropertiesGrade 1Property Alloy Type 1 Alloy Type 20.2 % yield strength, ksi (MPa) 45 (310) 50 (350)Ultimate tensile strength, ksi (MPa) 75 (520) 78 (540)Percent elongation in 2 in. (50.8 mm) 20 30Percent reduction in area 60 60TABLE X1.3 Typical HardnessAlloy Type Grade Typical Hardness1 1 75 to 82 HRB1 2 82 to 91 HRB1 3 85 HRB at midradius92 HRB at surface2 1 80 to 88 HRB2 2 85 HRB at midradius92 HRB at surfaceA 838 02 (2007)4
