1、Designation: A 756 94 (Reapproved 2001)Standard Specification forStainless Anti-Friction Bearing Steel1This standard is issued under the fixed designation A 756; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revi
2、sion. 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 the requirements forchromium-carbon bearing quality stainless steel to be used inthe manufacture of
3、anti-friction bearings.1.2 Supplementary Requirements of an optional nature areprovided and when desired shall be so stated in the order.1.3 The values stated in inch-pound units are to be regardedas the standard.2. Referenced Documents2.1 ASTM Standards:A 484/A 484M Specification for General Requir
4、ements forStainless Steel Bars, Billets, and Forgings2A 751 Test Methods, Practices, and Terminology forChemical Analysis of Steel Products2E 45 Test Methods for Determining the Inclusion Contentof Steel3E 381 Test Method of Macroetch Testing Steel Bars, Billets,Blooms, and Forgings3E 1019 Test Meth
5、ods for Determination of Carbon, Sulfur,Nitrogen, and Oxygen in Steel and in Iron, Nickel, andCobalt Alloys4E 1077 Test Method for Estimating the Depth of Decarbur-ization of Steel Specimens32.2 Other Standard:SAE J418a Grain Size Determination of Steel53. Ordering Information3.1 Orders for material
6、 under specification should includethe following information:3.1.1 Quantity,3.1.2 Grade identification,3.1.3 Specification designation and year of issue,3.1.4 Dimensions, shape, and3.1.5 Supplementary Requirements, if desired.4. Process4.1 The steel shall be made by a process that is capable ofprovi
7、ding a high-quality product meeting the requirements ofthis specification.5. Chemical Composition5.1 Typical examples of chemical compositions are shownin Table 1. Other compositions may be specified.5.2 An analysis of each heat of steel shall be made by thesteel manufacturer in accordance with Test
8、 Methods A 751.The chemical composition thus determined shall conform tothe requirements specified in Table 1 for the ordered grade orto requirements agreed upon between the manufacturer and thepurchaser.5.3 Product analysis may be made by the purchaser inaccordance with Test Methods A 751. Permissi
9、ble variations inproduct analysis shall be made in accordance with Specifica-tion A 484/A 484M.6. Dimensions, Mass, and Permissible Variations6.1 The size and shape of the material shall be agreed uponbetween manufacturer and purchaser.6.2 Dimensional tolerances for hot-rolled or hot-rolled andannea
10、led bars, in straight lengths or coils, and cold-finishedbars 0.500 in. (12.7 mm) and larger in diameter furnished underthis specification shall conform to the requirements specified inthe latest edition of Specification A 484/A 484M.6.3 Dimensional tolerances for cold-finished coils for balland rol
11、ler material shall be as shown in Table 2.6.4 Coil tolerances also apply to cold-finished straightlengths under 0.500 in. (12.7 mm) in diameter.7. Quality Tests7.1 The supplier shall be held responsible for the quality ofthe material furnished and shall make the necessary tests toensure this quality
12、. The supplier shall be required to report onthe results of the macroetch and microinclusion rating testsdetailed below. Quality tests shown in 7.2 through 7.4 arebased upon procedures established in Test Methods E 45.7.2 SamplingSamples taken in accordance with the fol-lowing paragraphs shall be ob
13、tained from 4 by 4-in. (102 by102-mm) rolled billets or forged sections. Tests may be made1This specification is under the jurisdiction of ASTM Committee A01 on Steel,Stainless Steel and Related Alloys and is the direct responsibility of SubcommitteeA01.28 on Bearing Steels.Current edition approved
14、June 15, 1994. Published August 1994. Originallypublished as A 75678. Last previous edition A 75693.2Annual Book of ASTM Standards, Vol 01.03.3Annual Book of ASTM Standards, Vol 03.01.4Annual Book of ASTM Standards, Vol 03.05.5Available from Society of Automotive Engineers, 400 Commonwealth Drive,Wa
15、rrendale, PA 15096.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.on smaller or larger sections by agreement with the purchaser.A minimum 3 to 1 reduction of rolled billets or forged sectionsis required for strand cast products.7.2.
16、1 For top poured products, a minimum of six samplesrepresenting the top and bottom of first, middle, and last usableingots shall be examined.7.2.2 For bottom poured products, a minimum of sixsamples shall be examined and they shall represent the top andbottom of three ingots. One ingot shall be take
17、n at randomfrom the first usable plate poured, one ingot, at random, fromthe usable plate poured nearest to the middle of the heat, andone ingot, at random, from the last usable plate poured. Whentwo usable plates constitute a heat, two of the sample ingotsshall be selected from the second usable pl
18、ate poured. Where asingle usable plate constitutes a heat, any three random ingotsmay be selected. Other methods of sampling shall be as agreedupon between the manufacturer and the purchaser.7.2.3 For strand cast products, a minimum of six samplesrepresenting the first, middle, and last portion of t
19、he heat castshall be examined. At least one sample shall be taken fromeach strand.7.3 MacroetchSpecimens representative of cross sectionsof billets shall be macroetched and rated in accordance withTest Method E 381 acid and water (1:1) at 160 to 180F (71 to82C). Such specimens shall not exceed S 2,
20、R 2, and C 2 ofTest Method E 381.7.4 Inclusion RatingThe specimens shall be38 by34 in.(9.5 by 19.1 mm) and shall be taken from an area halfwaybetween the center and outside of the billet. The polished faceshall be longitudinal to the direction of rolling. The scale usedfor rating the specimens shall
21、 be the Jernkontoret chartdescribed in Method A of Test Methods E 45, Plate III. Plate Iis to be used for inclusion exceeding a rating of 212 . Fieldswith sizes or numbers of all types of inclusions intermediatebetween configurations shown on the chart shall be classifiedas the lesser of the rating
22、number. The worst field of eachinclusion type from each specimen shall be recorded as therating for the specimen. Two thirds of all specimens and at leastone from each ingot tested, as well as the average of allspecimens, shall not exceed the rating specified in Table 3.8. Response to Heat Treatment
23、8.1 Specimens with sections38 in. (9.5 mm) in thickness,cut from a bar, billet, or forging, shall be placed in a furnacethat is at 1875 6 10F (1023.8 6 5.5C), allowed to heat to1875 6 10F, held at heat 25 min, and cooled in still air.Hardness of such specimens shall be not lower than 58 HRC.8.2 Samp
24、les heat treated as in 8.1 shall show a fracture grainsize of No. 6 or finer. (See SAE J418a.)9. Decarburization and Surface Imperfections9.1 Decarburization and surface imperfections shall notexceed the limits specified in Table 4 and Table 5. Decarbur-ization shall be measured using the microscopi
25、cal methodsdescribed in Test Method E 1077.10. Microstructure and Hardness10.1 The material shall be free of excessive carbide segre-gation.10.2 When annealing is specified in the order, the steel shallhave a completely spheroidized microstructure and a hardnessas specified in Table 6.10.3 Small siz
26、es where Rockwell B scale hardness readingsare impractical shall show a maximum tensile strength of115 000 psi (792 mPa).11. Inspection11.1 The manufacturer shall afford the purchasers inspectorall reasonable facilities necessary to satisfy him that thematerial is being produced and furnished in acc
27、ordance withthis specification. Mill inspection by the purchaser shall notinterfere unnecessarily with the manufacturers operations. AllTABLE 1 Chemical CompositionElement 440C 440C MODCarbon 0.95 to 1.10 1.00 to 1.10Manganese, max 1.00 0.30 to 1.00Phosphorus, max 0.025 0.025Sulfur, max 0.025 0.025S
28、ilicon, max 1.00 0.20 to 1.00Chromium 16.00 to 18.00 13.00 to 15.00Nickel, max 0.75 0.75Copper, max 0.50 0.50Molybdenum 0.40 to 0.65 3.75 to 4.25TABLE 2 Dimensional Tolerances for Cold-Finished CoilsSize, in. (mm) Total Tolerance, in. (mm)Through 0.096 (2.44) 0.002 (0.05)Over 0.096 to 0.270 (2.44 to
29、 6.86), incl 0.003 (0.08)Over 0.270 to 0.750 (6.86 to 19.1), incl 0.004 (0.10)TABLE 3 Inclusion RatingRating UnitsType Thin Series Heavy SeriesA 2.0 1.5B 2.5 1.5C 2.0 1.5D 2.0 1.0TABLE 4 Decarburization and Surface Imperfections for Coils and Bars for Balls and RollersSize, in. (mm)Decarburization o
30、r Surface Imperfections per Side, max, in. (mm)Hot-Rolled or Hot-Rolled AnnealedCold-FinishedAnnealedThrough 0.250 (6.35) 0.005 (0.13) 0.003 (0.08)Over 0.250 (6.35) to 0.500 (12.7), incl 0.006 (0.15) 0.004 (0.10)Over 0.500 (12.7) to 0.750 (19.1), incl 0.008 (0.20) 0.006 (0.15)Over 0.750 (19.1) to 1.
31、000 (25.4), incl 0.010 (0.25) 0.008 (0.20)A 756 94 (2001)2tests and inspections shall be made at the place of manufacture,unless otherwise agreed to.12. Certification and Reports12.1 Upon request of the purchaser in the contract or order,a manufacturers certification that the material was manufac-tu
32、red and tested in accordance with this specification, togetherwith a report of the test results, shall be furnished at the timeof the shipment.SUPPLEMENTARY REQUIREMENTSOne or more of the Supplementary Requirements described below apply when included in thepurchasers order or contract. When so inclu
33、ded, a Supplementary Requirement shall have the sameforce as if it were in the body of the specification. Supplementary Requirements details not fullydescribed shall be agreed upon between the purchaser and the supplier, but shall not negate any of therequirements in the body of the specification.S1
34、. Residual ElementsS1.1 The purchaser may specify that the analysis of tita-nium, aluminum, and/or oxygen (Test Methods E 1019) beprovided by agreement with the steel manufacturer. Thenumber and location of samples shall be by agreement betweenthe purchaser and manufacturer.S2. Calcium AdditionsS2.1
35、 Intentional additions of calcium or calcium alloys fordeoxidation or inclusion shape control are not permitted unlessspecifically approved by the purchaser. The use oflime orfluorspar, or both, in the steelmaking slag is acceptable.S3. Magnetic Particle MethodS3.1 The purchaser may specify that the
36、 magnetic particlemethod described be used in addition to the microinclusionrating system described in 7.4. The magnetic particle methodmeasures bearing steel cleanliness by evaluating the totallength of macroinclusions for a stated area or per unit area.Results are commonly expressed in millimetres
37、 per squaremetre.S3.2 SamplingSee 7.2.S3.3 Test specimens shall be straight cylinder quarter sec-tion samples prepared and examined in accordance with themagnetic particle method of Test Methods E 45.S3.4 For purposes of calculation, an inclusion length shallbe taken as the mean length of the length
38、 bracket into which itfalls; that is, an inclusion in the116 to18 -in. bracket shall betaken as being332 in. in length. The sum of all lengths for eachspecimen shall be determined and expressed as total length perarea inspected. The average total length per area inspected ofall six specimens shall n
39、ot exceed 200 mm /m2(or equivalent).S4. Sample Reduction RatioS4.1 For the sampling described in 7.2, the purchaser mayspecify that he reduction ratio from as-cast section to testsection be provided.TABLE 5 Decarburization and Surface Imperfections for Bars and TubesSize, in. (mm)Decarburization or
40、Surface Imperfections per Side, max, in. (mm)Hot-Rolled BarsHot-Rolled Annealed Cold-Finished AnnealedBars Tubes Bars TubesThrough 1.000 (25.4) 0.012 (0.31) 0.015 (0.38) 0.012 (0.31) 0.012 (0.31) 0.010 (0.21)Over 1.000 (25.4) to 2.000 (50.8), incl 0.017 (0.43) 0.022 (0.56) 0.020 (0.51) 0.015 (0.38)
41、0.014 (0.36)Over 2.000 (50.8) to 3.000 (76.2), incl 0.025 (0.64) 0.030 (0.76) 0.030 (0.76) 0.025 (0.64) 0.019 (0.48)Over 3.000 (76.2) to 4.000 (101.6), incl 0.035 (0.89) 0.045 (1.14) 0.035 (0.89) 0.024 (0.61)Over 4.000 (101.6) to 5.000 (127.0), incl 0.055 (1.40) 0.065 (1.65) 0.040 (1.02) 0.028 (0.71
42、)TABLE 6 Maximum Hardness for Annealed MaterialMaximum HardnessProduct Condition Brinell RockwellCoils hot-rolled-annealed . . . 25 HRCBars and tubes hot-rolled-annealed 255 HB . . .Coils, bars, and tubes cold-drawn-annealed 255 HB 100 HRBCoils, bars, and tubes annealed-cold-drawn as agreed upon bet
43、ween the purchaser and the manufacturerA 756 94 (2001)3ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent
44、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 technical committee and must be reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either
45、for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hear
46、ing 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 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(www.astm.org).A 756 94 (2001)4
