1、Designation: A255 10Standard 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. A number in parent
2、heses 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 Department of Defense.1. Scope1.1 These test methods cover the identification and descrip-tion of test m
3、ethods 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 test method to be used f
4、or 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 range of chemical composit
5、ions 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 temperature(Table 1). It is m
6、easured 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 hardness level.1.5 The val
7、ues stated in inch-pound units are to be regardedas the standard. The values given in parentheses are forinformation only.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-
8、priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E18 Test Methods for Rockwell Hardness of Metallic Ma-terialsE112 Test Methods for Determining Average Grain Size2.2 ASTM Adjuncts:ASTM Hardenability
9、Chart3END-QUENCH OR JOMINY TEST3. Description3.1 This test method covers the procedure for determiningthe hardenability of steel by the end-quench or Jominy test. Thetest consists of water quenching one end of a cylindrical testspecimen 1.0 in. in diameter and measuring the hardeningresponse as a fu
10、nction of the distance from the quenched end.4. Apparatus4.1 Support for Test SpecimenA fixture for supporting thetest specimen vertically so that the lower 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 thesta
11、ndard 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. X1.1.4.2 Water-Quenching DeviceA water-quenching deviceof suitable capacity to provide a vertical stream of water thatcan be controlled to a height of 2.5 in. (63.5 mm
12、) when passingthrough an orifice 0.5 in. (12.7 mm) in diameter. A tank ofsufficient capacity to maintain the water temperature require-ments of 6.3 with a small pump and control valves will be1These test methods are under the jurisdiction of ASTM Committee A01 onSteel, Stainless Steel and Related Al
13、loys and are the direct responsibility ofSubcommittee A01.15 on Bars.Current edition approved May 1, 2010. Published June 2010. Originallyapproved in 1942. Last previous edition approved in 2007 as A255 071. DOI:10.1520/A0255-10.2For referenced ASTM standards, visit the ASTM website, www.astm.org, o
14、rcontact 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 Charts (812 by 11 in. pads of 50 charts) areavailable from ASTM International Headquarters. Order Adjun
15、ct No. ADJA0255.Original adjunct produced in 1945.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.found satisfactory. The water-supply line shall also be providedwith a quick opening valve.5. Test Specimens5.1 Wrought SpecimensEnd-qu
16、ench specimens shall beprepared from rolled or forged stock and 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 s
17、pecimen shall be 1.0 in. (25.4mm) in diameter by 4.0 in. (101.6 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 no
18、rmalized inaccordance with 6.1 and of such size as to permit the 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 an
19、d theuser. The previous thermal history of the specimen tested 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. A graphiteor metal mold may be used to form
20、an overlength specimen 1.0in. (25.4 mm) in diameter which shall be 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 speci
21、mens are described inAppendix X1.6. Procedure6.1 NormalizingThe wrought 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 s
22、ample to improve machinabilityis permitted.6.2 HeatingPlace the specimen 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 im
23、portant to heat the specimen in such anatmosphere that practically 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
24、the specimen resting on the chips.6.2.1 Other methods consist of 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 graphit
25、e or carbon, or a layer of carbonaceousmaterial such as charcoal, 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 top
26、of the specimen. Repeat this procedure periodically, for ex-ample 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 in
27、position. The support for the specimen shall be dry at thebeginning 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 andt
28、he beginning of the quench should not be more than 5 s. Directthe stream of water, at a temperature of 40 to 85F (5 to 30C),against the bottom face of the specimen for not less than 10min. Maintain a condition of still air around the specimenduring cooling. If the specimen is not cold when removed f
29、romthe fixture, immediately quench it in water.6.4 Hardness MeasurementTwo 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 reproducibil
30、ity of results, and correlation withcooling rates in quenched bars.6.4.1 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 of thequenched structure takes place. Very light cuts with waterc
31、ooling 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:NOTE 35 % nitric acid (concentrated) and 95 % water by volume.NOTE 450 % hydrochloric acid (concentrat
32、ed) and 50 % water byvolume.Wash the sample in hot water. Etch in solution No. 1 untilblack. Wash in hot water. Immerse in solution No. 2 for3sandwash in hot water. Dry in air blast.TABLE 1 Normalizing and Austenitizing TemperaturesASteel Series Ordered CarbonContent, max, %NormalizingTemperature,F
33、(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, 98000.26 to 0.36, incl 1650 (900) 1600 (870)0.37 and over 1600 (870) 1550 (845)2300, 2500, 3300,4800, 93000.25 and und
34、er 1700 (925) 1550 (845)0.26 to 0.36, incl 1650 (900) 1500 (815)0.37 and over 1600 (870) 1475 (800)9200 0.50 and over 1650 (900) 1600 (870)AA variation of 610F (6C) from the temperatures in this table is permissible.BNormalizing and austenitizing temperatures are 50F (30C) higher for the6100 series.
35、A255 1026.4.1.1 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, the test specimen restson one of its flats on an anvil firmly atta
36、ched 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 the specimen in a V-block is notpermitted.6.4.2.1 The Rockwell test
37、er should periodically be checkedagainst standard test blocks. It is recommended that a test blockbe interposed between the specimen and the indenter to checkFIG. 1 Test Specimen in Support for Water QuenchingFIG. 2 Preferred Test SpecimenFIG. 3 Optional Test SpecimenA255 103the seating of the inden
38、ter and the specimen simultaneously.For general statements 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
39、 as well asproviding for accurate spacing between indentations. 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 foun
40、d that withreasonable operating care and a well-built 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 accuratel
41、y when testinglow-hardenability steels than when testing 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, ind
42、enter spacing should bemeasured immediately.6.4.4 Readings 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 hav
43、e been made is used as a base, the burrsaround the indentation 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 as
44、sist in thedetection of errors in specimen preparation 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
45、 specimenshould be tested.6.4.4.2 For reporting purposes, 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 whic
46、h the ordinatesrepresent HRC values and the abscissae 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
47、 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. Exam
48、ples of this method areJ416 in. (6.4 mm) = 47 HRC min, J716 in. (11.1 mm) = 50HRC max, and J516 in. (7.9 mm) = 3849 HRC.9. Report9.1 Report the following information that may be recordedon the ASTM hardenability chart:9.1.1 Previous thermal history of the specimen tested, in-cluding the temperature
49、of normalizing and austenitizing,9.1.2 Chemical Composition,9.1.3 ASTM grain size (McQuaid-Ehn) as determined byTest Methods E112, unless otherwise indicated, and9.1.4 A prominent notation on the standard hardenabilitychart if any of the test specimens listed in Appendix X1 areused.CALCULATION OF HARDENABILITY10. Introduction10.1 This method of Jominy Hardenability calculation fromthe chemical ideal diameter (DI) on a steel is based on theoriginal work of M. A. Grossman and provides increasedaccuracy by refinement of the carbon multiplying facto
