ASTM B312-1996(2002) Standard Test Method for Green Strength for Compacted Metal Powder Specimens《金属粉末密压试样未烧结强度的标准试验方法》.pdf

1、Designation: B 312 96 (Reapproved 2002)Standard Test Method forGreen Strength for Compacted Metal Powder Specimens1This standard is issued under the fixed designation B 312; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year

2、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 the greenstrength of unsintered compacted metal powder specimens bysubjec

3、ting them to a uniformly increasing transverse loadingunder controlled conditions. The term green strength, as usedherein, defines the stress, calculated from the flexure formula,required to break a specimen as a simple beam supported nearthe ends and applying the force midway between the fixed line

4、center of the supports.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 with its use. It is theresponsibility of the use

5、r 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 243 Terminology of Powder Metallurgy23. Terminology3.1 Definitions of powder metallurgy (P/M) terms can befound

6、 in Terminology B 243. Additional descriptive informa-tion is available in the Related Material section of Vol 02.05 ofthe Annual Book of ASTM Standards.4. Summary of Test Method4.1 The powder to be tested is pressed in a die to theconfiguration of a bar having a standard rectangular shape inthe pre

7、ssing direction and to one of two thicknesses. Either thepowder to be pressed contains lubricant or the surfaces of thedie are lubricated at each pressing.4.2 The pressed test specimens width, thickness, and den-sity are determined. The load necessary to fracture the bar isdetermined by applying a u

8、niformly increasing force to thespecimen while supporting it in the prescribed three-point bendtest fixture.4.3 Green strength or maximum fiber stress of the materialunder test is determined by calculation using the equation fora simply supported beam with a concentrated load.5. Significance and Use

9、5.1 The test for green strength of a compacted metal powderis useful as a:5.1.1 Method to relate the resistance of a pressed compact tobreakage or damage due to handling.5.1.2 Means of quality comparison of metal powder, lot tolot.5.1.3 Method of determining the effect of additions to a basepowder.5

10、.2 Significant variations in green strength will occur if thedensity tolerance of the pressed bar is exceeded.6. Apparatus6.1 Punches and Die (see Fig. 1), for producing a testspecimen having a nominal die dimension of 0.500 in. (12.70mm) wide by 1.250 in. (31.75 mm) long.6.2 Compression Testing Mac

11、hine or Powder Press, capableof applying the required pressure to produce, and break ifdesired, the standard test specimen.6.3 Balance, suitable for weighing to an accuracy of 0.01 g.6.4 Micrometers, capable of measuring from 0.0 to 1.25 in.(0.0 to 31.8 mm) with an accuracy of 0.001 in. (0.03 mm).6.

12、5 Either of the following testing apparatus:6.5.1 Constant Loading Beam Device as shown in Fig. 2,capable of measuring the breaking force on the test specimento the nearest 0.1 lbf (0.5 N).6.5.2 Transverse Rupture Test Fixture as shown in Fig. 3,for use with a compression testing machine to locate t

13、he testbar so the breaking force can be measured to the nearest 0.1 lbf(0.5 N).7. Test Specimen7.1 The test specimen has nominal dimensions of 0.500 in.(12.70 mm) wide by 1.250 in. (31.75 mm) long by either 0.250in. (6.35 mm) or 0.500 in. (12.70 mm) thick. The green densityshall be within 60.05 g/cm

14、3of the target.1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Productsand is the direct responsibility of Subcommit-tee B09.02 on Base Metal Powders.Current edition approved Sept. 10, 1996. Published December 1996. Originallypublished as B 312 56 T

15、. Last previous edition B 312 82 (1988)e1.2Annual Book of ASTM Standards, Vol 02.05.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.8. Procedure8.1 For lubricated powders follow the instructions startingin Section 8.2. The method of

16、lubrication of the powders shallbe standardized since green strength, green density, and com-pactibility will vary with the method chosen and the care withwhich it is applied. The method of lubrication shall be a matterof agreement between the parties concerned. Unlubricatedpowder may be tested in a

17、 die with lubricated walls. Apply tothe die walls a lubricant mixture (for example, a mixture of 100g of zinc stearate in one liter of methyl alcohol. Warning: Thismixture is flammable and should be used in a suitable, wellventilated area.) After any excess liquid has drained away,allow the die wall

18、s to dry, and fill with the powder being tested,as described in 8.2 and 8.3.8.2 Determine from Table 1 the approximate mass ofpowder to be used to make a test specimen 0.250 6 0.005 in.(6.356 0.13 mm) or 0.500 6 0.005 in. (12.7 6 0.13 mm) thickby 0.500 in. (12.7 mm) wide by 1.250 in. (31.7 mm) long.

19、 SeeFig. 4. Weigh this charge to 60.02 g.8.3 The specimen is prepared using a double action pressingprocess. One example of this type of compaction is as follows:With the lower punch inserted in the die cavity, pour thepowder into the die cavity taking care that the powder isuniformly distributed. A

20、pply pressure from both ends by meansof the following arrangement: Insert the upper punch, andplace the die, supported on two spacers, between the platens ofthe press. Apply a preliminary pressure of 5000 psi (34 MPa)to the upper punch, while the die barrel is supported by thespacers; then release t

21、he pressure and remove the spacers. Withthe spacers removed, apply the final compacting pressure at arate of 60 000 6 5000 psi (414 6 34 MPa)/min.8.4 Use a compacting pressure that will produce the correctthickness of 0.250 6 0.005 in. (6.35 6 0.13 mm) or 0.500 60.005 in. (12.7 6 0.13 mm).8.5 After

22、ejection from the die, weigh the specimen to thenearest 0.01 g, measure the specimen dimensions to the nearest0.001 in. (0.03 mm), and identify the top of the specimen.Calculate the density of the green specimen. If the specimendensity is within the tolerance, place the specimen in thetransverse rup

23、ture test fixture or the constant loading beamdevice perpendicular to the supporting rods with the topuppermost. In the case of the transverse rupture test fixture,place the loaded fixture between the platens of the compressiontesting machine set for an initial crosshead velocity of approxi-mately 0

24、.1 in./min and apply a uniformly increasing force at arate of approximately 20 lbf (89 N)/min until rupture occurs.Record the breaking force in lbf (or N) to the nearest 0.1 lbf(0.5 N). When using the constant loading beam device (Fig. 2),shot is allowed to flow into a suitable container at a rate t

25、hatwill produce approximately 20 lbf (89 N)/min on the specimen.The mass of the shot is determined to the nearest gram (0.0022lb) and the breaking force in lbf (or N) is calculated to thenearest 0.1 lbf (0.5 N) as follows:P 5 AX/B (1)where:P = force on test specimen, lbf (N),A = length A, in. (mm),B

26、 = length B, in. (mm), andX = mass of shot, lb (kg) to the nearest 0.0022 lb (1 g)required to rupture.9. Calculations9.1 Calculate the green strength as follows:S 53PL2t2w(2)where:S = green strength, psi (MPa),P = force required to rupture, lbf (N),L = length of specimen span of fixture, in. (mm),w

27、= width of specimen, in. (mm), andt = thickness of specimen, in. (mm).10. Report10.1 The green strength shall be reported in pounds-forceper square inch (or megapascals) as the average of threeindividual results to the nearest 100 psi (or .5 MPa). Theaverage green density shall always be reported wi

28、th the greenstrength. The nominal thickness of the test specimen should beindicated where necessary for clarity. The lubrication methodshall also be reported.11. Precision and Bias311.1 The following criteria should be used to judge accept-ability of individual results at the 95 % confidence level f

29、or the3Supporting data are available from ASTM Headquarters.NOTE 1The dimensions for the cavity shall be 0.500 6 0.004 in. wide(12.70 6 0.10 mm) by 1.250 6 0.004 in. long (31.75 6 0.10 mm). Themating parts shall fit freely and should be finished to a 4 in. (N3) or betterto dimensions of 0.0005 in. (

30、0.013 mm) to 0.0010 in. (0.025 mm) smallerthan the die cavity in each dimension. The dimensions given in thedrawing typify the die cavity and punch within the stated tolerance at thenormal width and length.FIG. 1 Example of Tooling to Produce the Test SpecimenB 31220.250 in. thick specimen. Repeatab

31、ility and reproducibilitydata for the 0.500 in. specimen are not available.NOTE 1This precision statement is different from the statements inother B09 test methods because it describes the repeatability and repro-ducibility of individual values, not the averages of groups of test values.11.1.1 The r

32、epeatability interval, r, is estimated by thefollowing equation: r = 0.037 S + 78, where S = greenstrength, (psi). Duplicate individual results by the same opera-tor should be considered suspect if they differ by more than r.11.1.2 The reproducibility interval, R, is estimated by thefollowing equati

33、on: R = 0.13 S + 220. The individual resultsobtained by each of two laboratories should not be consideredsuspect unless they differ by more than R.11.2 The bias of the green strength test can not be estab-lished because there is no standard available for comparison.12. Keywords12.1 constant loading

34、beam device; green strength; P/M;powder metallurgy; unsintered compactASTM 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 a

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37、ved 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 Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of

38、 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).FIG. 2 Example of Constant Loading Beam DeviceFIG. 3 Transverse Rupture Test FixtureTABLE 1 Mass of Powder to Obtain Green Density for TestSpecimenGreen Density, g/cm3Mass of Powder, gFor 0.250 in. Thickness For 0.500 in. Thickness6.0 15.5 31.06.2 16.0 32.06.4 16.5 33.06.6 17.0 34.06.8 17.5 35.07.0 18.0 36.07.2 18.5 37.07.4 19.0 38.07.6 19.5 39.0FIG. 4 Transverse Rupture Test SpecimenB 3123