1、Designation: B 331 95 (Reapproved 2002)Standard Test Method forCompressibility of Metal Powders in Uniaxial Compaction1This standard is issued under the fixed designation B 331; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the y
2、ear 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 test method covers determination of compressibil-ity of metal powders as measured by the extent to which
3、theycan be densified in a specified die under controlled conditions.1.2 The values stated in inch-pound units are to be regardedas the standard. The SI equivalents are in parentheses and maybe approximate.1.3 This standard does not purport to address all of thesafety concerns, if any, associated wit
4、h its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:B 215 Practices for Sampling Finished Lots of Metal Pow-ders2B 243 T
5、erminology of Powder Metallurgy2B 328 Test Method for Density, Oil Content, and Intercon-nected Porosity of Sintered Powder Metal Structural Partsand Oil-Impregnated Bearings23. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod refer to Terminology B 243.4. Summary of Test M
6、ethod4.1 The test method consists of compacting a sample ofmetal powder in a confining die, ejecting it from the die, andmeasuring its green density. The powder is subjected touniaxial loading in a standardized die of rectangular or ofround cross section.5. Significance and Use5.1 The compressibilit
7、y obtained is a measure of a materialcharacteristic inherent in the powder. The test method is usefulas a quality control test in the evaluation and manufacturingcontrol of metal powder production, and as an acceptance testfor shipment of metal powder lots.5.2 Results may be affected by test conditi
8、ons such as thetype amount, and method of lubrication, dwell time, and diematerial. They may not necessarily agree with results obtainedunder production conditions.6. Apparatus6.1 Die and Two Steel PunchesThe die should be made ofcemented carbide, or alternatively of tool steel. The set may bedesign
9、ed either for rectangular compacts or round compacts.Fig. 1 illustrates typical rectangular tooling and Fig. 2 illus-trates typical round tooling.6.2 Compression Testing Machine or Hydraulic PowderCompacting Press, capable of applying an adequate load withan accuracy of at least 61.0 %.6.3 Balance,
10、suitable for weighing at least 100 g to thenearest 0.01 g.6.4 Micrometer, or other suitable measuring device formeasuring the dimensions of the compacts to the nearest0.0002 in. (0.005 mm).7. Sampling7.1 A quantity of powder capable of producing the requirednumber of test specimens (see 9.1 and Sect
11、ion 11) shall beobtained in accordance with Practices B 215.8. Preparation of Apparatus8.1 Lubrication is necessary to assist the ejection of thecompacted test specimen from the die. Either die wall lubrica-tion or powder lubrication may be used.8.1.1 Unlubricated Powder may be tested in a die withl
12、ubricated walls. Apply to the die walls a mixture of a lubricantin a volatile organic liquid. After any excess liquid has drainedaway, allow the solution adhering to the walls to evaporateleaving a thin layer of lubricant.NOTE 1An example of such a mixture is 100 g of zinc stearate in 1 Lof methyl a
13、lcohol.8.1.2 An alternative way of testing powder not containing alubricant is to use an otherwise unlubricated die after thor-oughly mixing into the powder a sufficient amount of a suitablelubricant.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder P
14、roducts and is the direct responsibility of Subcom-mittee B09.02 on Base Metal Powders.Current edition approved Feb. 15, 1995. Published April 1995. Originallypublished as B 331 58T. Last previous edition B 331 85 (1990).2Annual Book of ASTM Standards, Vol 02.05.1Copyright ASTM International, 100 Ba
15、rr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8.1.3 Lubricated Powder, received already mixed with suf-ficient lubricant should be tested in an otherwise unlubricateddie.8.2 Compressibility may vary according to the method oflubrication, type, and amount of lubricant.
16、8.3 The parties shall agree on the method, amount, and typeof lubricant.9. Procedure9.1 Powder Sample MassThe powder sample mass shallbe such as to result in a rectangular compact 0.240 to 0.260 in.thick (6.1 to 6.6 mm) or a round compact 0.27 to 0.29 in. (6.9to 7.4 mm) thick. For a powder whose com
17、pressibility is notknown, it may be necessary to adjust the powder mass based onthe specimen thickness obtained in an initial test.9.2 CompactionThe specimen shall be made using adouble action pressing process. One example of this type ofcompaction is as follows:9.2.1 Insert the lower punch into the
18、 die cavity. Position thedie cavity to the desired filling height using supporting spacersbetween the die and the lower press platen. Pour the powdersample into the die cavity taking care to ensure that the powderis uniformly distributed. Insert the upper punch and then applyand release a preliminar
19、y pressure of approximately 5000 psi(35 MPa). Remove the spacers supporting the die. If the die issupported by springs, or in some similar way, it is unnecessaryto apply the preliminary pressure. Apply the final pressure. InNOTE 1The dimensions for the cavity shall be 0.500 6 0.004 in. wide (12.70 6
20、 0.10 mm) by 1.250 6 0.004 in. long (31.75 6 0.10 mm). The matingparts shall fit freely and should be finished to 4 RMS, or better, to dimensions of 0.0005 in. (0.013 mm) to 0.001 in. (0.025 mm) smaller than the bottomof the die cavity, in each dimension. The dimensions given in the drawing typify t
21、he die cavity and punch within the stated tolerance, at the nominal widthand length dimensions, permitting die wall to punch clearances of 0.00025 to 0.0005 in. (0.006 mm to 0.013 mm) at each of the four sides of the die,at the bottom of the die. The outer ring may be AISI H-11 steel hardened to 45
22、to 48 HRC. The punches may be AISI A-7 steel hardened to 60 to 62HRC. The die insert should be die grade tungsten carbide.FIG. 1 Example of Tooling to Produce Rectangular Test PieceB 3312special cases where the results may be affected by the rate ofpressure application, a rate not exceeding 60 000 p
23、si/min (415MPa/min) is recommended.9.2.2 Release the pressure as soon as the maximum pressureis attained, because pressure dwells of as little as 10 s canincrease iron powder compressibility by 0.3 %.9.3 Ejectionthe compact is then either ejected from thedie or exposed via a withdrawal process, in a
24、ccordance withthe type of apparatus used. For the commonly used punch anddie systems described in 9.2, the part is ejected by pushingback the die with the aid of two spacer blocks, or the like. Theblocks should be longer than the combined length of the upperpunch and the formed part. If possible, re
25、move the upper punchby hand. If not possible, perform ejection with blocks until thepunch clears the die, remove the punch, and continue to ejectthe test piece until it clears the die. Carefully deburr test pieceswith fine emery paper.9.4 MeasurementsWeigh the compact to the nearest 0.01g. Measure i
26、ts dimensions to the nearest 0.0002 in. (0.005mm). Compacts may not have top and bottom surfaces that areexactly parallel and care must be taken in determining anaverage thickness.9.5 Compacting PressuresSamples of powder may bepressed either at a single specified pressure or at a series ofspecified
27、 pressures. In the latter case, the densities obtained canbe utilized for drawing the compressibility curve of thepowder, such as, a graph of density as a function of thecompacting pressure. Alternatively, by trial and error, thepowder may be compacted to a specified green density and thecompacting
28、pressure taken as a measure of its compressibility.9.6 For the method selected in 9.5, repeat 9.2-9.4 twicemore.NOTE 1The outer ring may be AISI H-11 steel hardened to 45 to 48 HRC. The punches may be AISI A-7 steel hardened to 60 to 62 HRC. The dieinsert should be die grade tungsten carbide. Mating
29、 parts should be fitted and lapped to 4 RMS or better.FIG. 2 Example of Tooling to Produce Round Test PieceB 331310. Calculations10.1 Calculate the density of the green compact as follows:10.1.1 For round compacts:rg5 Green density, g/cm35 4/p32.54!3! 3 M/d23 t!5 0.0777 M/d23 t! (1)where:M = mass of
30、 compact, g,d = diameter of compact, in., andt = thickness of compact, in.Where the test specimen is measured in mm, the equation is:rg5 Green density, g/cm35 4/p! 3 1000 3 M! d23 t!5 1273 M/d23 h! (2)10.1.2 For rectangular compacts:rg5 Green density, g/cm35 1/2.54!33 M/L 3 W 3 t!5 0.0610 M/L 3 W 3
31、T! (3)where:M = mass of compact, g,L = length of compact, in.,W = width of compact in., andt = thickness of compact, in.Where the test specimen is measured in mm, the equation is:rg5 Green density, g/cm35 1000 M/L 3 W 3 t! (4)10.2 Alternatively, the density of the green compact may becalculated by t
32、he water immersion method of Test MethodB 328.11. Report11.1 Report the compressibility as the average of threedensity measurements, calculated to the nearest 0.01 g/cm3.Report also the individual density measurements and thecompacting pressure rounded to the nearest 0.5 tsi.11.2 Alternatively, repo
33、rt the compressibility curve of thepowder as a graph drawn through points representing a singledetermination, at not less than four compacting pressures or,draw the line through points representing the average of threedeterminations at three compacting pressures.11.3 If the alternative method of com
34、pacting to a specifiedgreen density is used, report the compressibility as the com-pacting pressure, with its precision, and the individual pres-sures. Report also the specified green density used.11.4 Report the compact thickness, and type, amount, andmethod of lubrication. (For die wall lubricatio
35、n, specify theamount of lubrication as the weight percent dissolved in thesolvent. Where admixed lubricant is used, the type and amountused shall be indicated).11.5 Report whether the method used for determination ofdensity was as prescribed in 10.1 or 10.2.12. Precision and Bias312.1 For the densit
36、y determination method of 10.1, ferrousand nonferrous powders, the repeatability interval, r, is 0.025g/cm3. On the basis of test error alone, the difference inabsolute value of individual test results obtained in the samelaboratory on the same material will be expected to exceed0.025 g/cm3only abou
37、t 5 % of the time.12.2 For the density determination method of 10.1, thereproducibility interval, R, for ferrous and nonferrous powdersis 0.07 g/cm3. On the basis of test error alone, the difference inabsolute value between individual test results obtained in twodifferent laboratories on the same ma
38、terial will be expected toexceed R only about 5 % of the time. Thus, if a largerdifference is found, there is reason to question one or both testresults.12.3 No precision data for this test method are available,based on 10.2, the use of Test Method B 328 for densitydetermination.12.4 No statement ca
39、n be made about bias, because there areno accepted standard or reference powders for compressibilitytesting.13. Keywords13.1 compressibility; metal powderASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard.
40、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 technical committee and must be reviewed ev
41、ery 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 consideration at a meeting of theresponsible tech
42、nical 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 Harbor Drive, PO Box C700, West Conshohoc
43、ken, 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).3Supporting data are available from ASTM Headquarters. Request RR:B09-1002.B 3314
