ASTM A255-2010(2018) Standard Test Methods for Determining Hardenability of Steel.pdf

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1、Designation: A255 10 (Reapproved 2018)Standard Test Methods forDetermining Hardenability of Steel1This standard is issued under the fixed designation A255; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.

2、A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These test methods cover the identification and

3、 descrip-tion of test methods for determining the hardenability of steels.The two test methods include the quantitative end-quench orJominy Test and a method for calculating the hardenability ofsteel from the chemical composition based on the original workby M. A. Grossman.1.2 The selection of the t

4、est method to be used for deter-mining the hardenability of a given steel shall be agreed uponbetween the supplier and user. The Certified Material TestReport shall state the method of hardenability determination.1.3 The calculation method described in these test methodsis applicable only to the ran

5、ge of chemical compositions thatfollow:Element Range, %Carbon 0.100.70Manganese 0.501.65Silicon 0.150.60Nickel 1.50 maxChromium 1.35 maxMolybdenum 0.55 maxCopper 0.35 maxVanadium 0.20 max1.4 Hardenability is a measure of the depth to which steelwill harden when quenched from its austenitizing temper

6、ature(Table 1). It is measured quantitatively, usually by noting theextent or depth of hardening of a standard size and shape of testspecimen in a standardized quench. In the end-quench test thedepth of hardening is the distance along the specimen from thequenched end which correlates to a given har

7、dness level.1.5 The values stated in inch-pound units are to be regardedas standard. The values given in parentheses are mathematicalconversions to SI units that are provided for information onlyand are not considered standard.1.6 This standard does not purport to address all of thesafety concerns,

8、if any, associated with its use. It is theresponsibility 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 intern

9、ationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2E18 Te

10、st Methods for Rockwell Hardness of Metallic Ma-terialsE112 Test Methods for Determining Average Grain Size2.2 ASTM Adjuncts:ASTM Hardenability Chart3END-QUENCH OR JOMINY TEST3. Description3.1 This test method covers the procedure for determiningthe hardenability of steel by the end-quench or Jominy

11、 test.Thetest consists of water quenching one end of a cylindrical testspecimen 1.0 in. in diameter and measuring the hardeningresponse as a function of the distance from the quenched end.4. Apparatus4.1 Support for Test SpecimenA fixture for supporting thetest specimen vertically so that the lower

12、end of the specimenis a distance of 0.5 in. (12.7 mm) above the orifice of thewater-quenching device. A satisfactory type of support for thestandard 1.0-in. (25.4-mm) specimen is shown in Fig. 1.NOTE 1A suitable support for other sizes and shapes of specimens isshown in Fig. X1.1.1These test methods

13、 are under the jurisdiction of ASTM Committee A01 onSteel, Stainless Steel and Related Alloys and are the direct responsibility ofSubcommittee A01.15 on Bars.Current edition approved Sept. 1, 2018. Published September 2018. Originallyapproved in 1942. Last previous edition approved in 2014 as A25510

14、 (2014). DOI:10.1520/A025510R18.2For referenced 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.3Standard ASTM Hardenability

15、Charts (812 by 11 in. pads of 50 charts) areavailable from ASTM International Headquarters. Order Adjunct No. ADJA0255.Original adjunct produced in 1945.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke

16、n, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organizat

17、ion Technical Barriers to Trade (TBT) Committee.14.2 Water-Quenching DeviceAwater-quenching device ofsuitable capacity to provide a vertical stream of water that canbe controlled to a height of 2.5 in. (63.5 mm) when passingthrough an orifice 0.5 in. (12.7 mm) in diameter. A tank ofsufficient capaci

18、ty to maintain the water temperature require-ments of 6.3 with a small pump and control valves will befound satisfactory. The water-supply line shall also be providedwith a quick opening valve.5. Test Specimens5.1 Wrought SpecimensEnd-quench specimens shall beprepared from rolled or forged stock and

19、 shall represent the fullcross section of the product. If negotiated between the supplierand the user, the end-quench specimen may be prepared froma given location in a forged or rolled product or from acontinuous cast billet. The test specimen shall be 1.0 in. (25.4mm) in diameter by 4.0 in. (101.6

20、 mm) in length, with meansfor hanging it in a vertical position for end quenching.Dimensions of the preferred specimen and of an optionalspecimen (Note 2) are given in Figs. 2 and 3. The specimenshall be machined from a bar previously normalized inaccordance with 6.1 and of such size as to permit th

21、e removalof all decarburization in machining to 1.0 in. round. The end ofthe specimen to be water cooled shall have a reasonablysmooth finish, preferably produced by grinding. Normalizingmay be waived by agreement between the supplier and theuser. The previous thermal history of the specimen tested

22、shallalways be recorded.5.2 Cast SpecimensA separately cast end-quench speci-men may be used for non-boron steels. Cast specimens are notsuitable for boron steel grades due to erratic results.Agraphiteor metal mold may be used to form an overlength specimen 1.0in. (25.4 mm) in diameter which shall b

23、e cut to the standardspecimen size. The mold may also be used to form a 1.25-in.(31.8-mm) diameter specimen which shall be machined to thefinal specimen size. Cast tests need not be normalized.NOTE 2Other sizes and shapes of test specimens are described inAppendix X1.6. Procedure6.1 NormalizingThe w

24、rought product from which thespecimen is to be prepared shall be normalized to ensure properhardening characteristics. The sample shall be held at thetemperature listed in Table 1 for 1 h and cooled in air.Tempering of the normalized sample to improve machinabilityis permitted.6.2 HeatingPlace the s

25、pecimen in a furnace that is at thespecified austenitizing temperature (Table 1) and hold at thistemperature for 30 min. In production testing slightly longertimes up to 35 min may be used without appreciably affectingresults. It is important to heat the specimen in such anatmosphere that practicall

26、y no scaling and a minimum ofdecarburization takes place. This may be accomplished byheating the specimen in a vertical position in a container withan easily removable cover containing a layer of cast-iron chipswith the bottom face of the specimen resting on the chips.6.2.1 Other methods consist of

27、placing the specimen in anappropriately sized hole in a graphite block or placing thespecimen in an upright tube attached to a flat base, both of aheat-resistant metal, with the collar projecting for a tong hold.Place a disk of graphite or carbon, or a layer of carbonaceousmaterial such as charcoal,

28、 in the bottom of the tube to preventscaling.6.2.2 For a particular fixture and furnace, determine the timerequired to heat the specimen to the austenitizing temperatureby inserting a thermocouple into a hole drilled axially in the topof the specimen. Repeat this procedure periodically, for ex-ample

29、 once a month, for each combination of fixture andfurnace.6.3 QuenchingAdjust the water-quenching device so thatthe stream of water rises to a free height of 2.5 in. (63.5 mm)above the 0.5-in. (12.7-mm) orifice, without the specimen inposition. The support for the specimen shall be dry at thebeginni

30、ng of each test. Then place the heated specimen in thesupport so that its bottom face is 0.5 in. above the orifice, andturn on the water by means of the quick-opening valve. Thetime between removal of the specimen from the furnace andthe beginning of the quench should not be more than 5 s. Directthe

31、 stream of water, at a temperature of 40 to 85 F (5 to30 C), against the bottom face of the specimen for not lessthan 10 min. Maintain a condition of still air around thespecimen during cooling. If the specimen is not cold whenremoved from the fixture, immediately quench it in water.6.4 Hardness Mea

32、surementTwo flats 180 apart shall beground to a minimum depth of 0.015 in. (0.38 mm) along theentire length of the bar and Rockwell C hardness measure-ments made along the length of the bar. Shallower grounddepths can affect reproducibility of results, and correlation withcooling rates in quenched b

33、ars.TABLE 1 Normalizing and Austenitizing TemperaturesASteel SeriesOrderedCarbonContent,max, %NormalizingTemperature,F (C)AustenitizingTemperature,F (C)1000, 1300, 1500,3100, 4000, 41000.25 and under 1700 (925) 1700 (925)4300, 4400, 4500,4600, 4700, 5000,5100, 6100,B8100, 8600, 8700,8800, 9400, 9700

34、,98000.26 to 0.36,incl1650 (900) 1600 (870)0.37 and over 1600 (870) 1550 (845)2300, 2500, 3300,4800, 93000.25 and under 1700 (925) 1550 (845)0.26 to 0.36,incl1650 (900) 1500 (815)0.37 and over 1600 (870) 1475 (800)9200 0.50 and over 1650 (900) 1600 (870)AA variation of 10 F (6 C) from the temperatur

35、es in this table is permissible.BNormalizing and austenitizing temperatures are 50 F (30 C) higher for the 6100series.A255 10 (2018)26.4.1 The preparation of the two flats must be carried outwith considerable care. They should be mutually parallel andthe grinding done in such a manner that no change

36、 of thequenched structure takes place. Very light cuts with watercooling and a coarse, soft-grinding wheel are recommended toavoid heating the specimen. In order to detect tempering due togrinding, the flat may be etched with one of the followingetchant solutions:FIG. 1 Test Specimen in Support for

37、Water QuenchingFIG. 2 Preferred Test SpecimenFIG. 3 Optional Test SpecimenA255 10 (2018)3NOTE 35 % nitric acid (concentrated) and 95 % water by volume.NOTE 450 % hydrochloric acid (concentrated) and 50 % water byvolume.Wash the sample in hot water. Etch in solution No. 1 untilblack. Wash in hot wate

38、r. Immerse in solution No. 2 for3sandwash in hot water. Dry in air blast.6.4.1.1 The presence of lighter or darker areas indicates thathardness and structure have been altered in grinding. If suchchanges caused by grinding are indicated, new flats may beprepared.6.4.2 When hardness tests are made, t

39、he test specimen restson one of its flats on an anvil firmly attached to the hardnessmachine. It is important that no vertical movement be allowedwhen the major load is applied. The anvil must be constructedto move the test specimen past the penetrator in accurate stepsof116 in. (1.5 mm). Resting th

40、e specimen in a V-block is notpermitted.6.4.2.1 The Rockwell tester should periodically be checkedagainst standard test blocks. It is recommended that a test blockbe interposed between the specimen and the indenter to checkthe seating of the indenter and the specimen simultaneously.For general state

41、ments regarding the use of test blocks andsurface conditions, reference should be made to 4.7 and 5.2,respectively, of Test Methods E18.6.4.3 Exercise care in registering the point of the indenter inrelationship to the quenched end of the specimen as well asproviding for accurate spacing between ind

42、entations. A low-power measuring microscope is suitable for use in determiningthe distance from the quenched end to the center of the firstimpression and in checking the distance from center to centerof the succeeding impressions. It has been found that withreasonable operating care and a well-built

43、 fixture, it is practicalto locate the center of the first impression 0.0625 6 0.004 in.(1.5 6 0.10 mm) from the quenched end. The variationsbetween spacings should be even smaller. Obviously, it is moreimportant to position the indenter accurately when testinglow-hardenability steels than when test

44、ing high-hardenabilitysteels. The positioning of the indenter should be checked withsufficient frequency to provide assurance that accuracy require-ments are being met. In cases of lack of reproducibility or ofdifferences between laboratories, indenter spacing should bemeasured immediately.6.4.4 Rea

45、dings shall be taken in steps of116 in. (1.6 mm) forthe first 16 sixteenths (25.4 mm), then 18, 20, 22, 24, 28, and32 sixteenths of an inch. Values below 20 HRC are notrecorded because such values are not accurate. When a flat onwhich readings have been made is used as a base, the burrsaround the in

46、dentation shall be removed by grinding unless afixture is used which has been relieved to accommodate theirregularities due to the indentations.6.4.4.1 Hardness readings should preferably be made ontwo flats 180 apart. Testing on two flats will assist in thedetection of errors in specimen preparatio

47、n and hardnessmeasurement. If the two probes on opposite sides differ bymore than 4 HRC points at any one position, the test should berepeated on new flats, 90 from the first two flats. If the retestalso has greater than 4 HRC points spread, a new specimenshould be tested.6.4.4.2 For reporting purpo

48、ses, hardness readings should berecorded to the nearest integer, with 0.5 HRC values roundedto the next higher integer.7. Plotting Test Results7.1 Test results should be plotted on a standard hardenabil-ity chart prepared for this purpose, in which the ordinatesrepresent HRC values and the abscissae

49、 represent the distancefrom the quenched end of the specimen at which the hardnessdeterminations were made. When hardness readings are takenon two or more flats, the values at the same distance should beaveraged and that value used for plotting. A facsimile of thestandard ASTM hardenability chart3on which typical harden-ability curves have been plotted is shown in Fig. 4.8. Index of Hardenability8.1 The hardenability of a steel can be designated by aspecific HRC hardness value or HRC hardness value range ata given Jominy (“J”) distance. Examples of