1、Designation: B312 09B312 14Standard Test Method forGreen Strength of Specimens Compacted from MetalPowders1This standard is issued under the fixed designation B312; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last r
2、evision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This standard covers a test method that may be used to measure the transverse rupture strength of a compacted butunsintered
3、 (green) test specimen produced from lubricated or unlubricated metal powders or powder mixtures.1.2 Green strength is measured by a quantitative laboratory procedure in which the fracture strength is calculated from the forcerequired to break an unsintered test specimen supported as a simple beam w
4、hile subjected to a uniformly increasing three-pointtransverse load under controlled conditions.1.3 This test method is a companion standard to Test Method B528 that covers the measurement of the transverse rupturestrength of sintered PM test specimens.1.4 With the exception of density values, the v
5、alues for density and the mass used to determine density, for which the g/cmuseof the gram per cubic centimeter (g/cm3 unit ) and gram (g) units is the industry standard, and mass measurements used to calculatedensity, the values stated longstanding industry practice, the values in inch-pound units
6、are to be regarded as the standard. The SIequivalents shown in parentheses have been converted in accordance withvalues given in parentheses are mathematicalconversions to SI units IEEE/ASTM SI 10, may be approximate and are only included for information. that are provided forinformation only and ar
7、e not considered standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prio
8、r to use.2. Referenced Documents2.1 ASTM Standards:2B215 Practices for Sampling Metal PowdersB243 Terminology of Powder MetallurgyB528 Test Method for Transverse Rupture Strength of Powder Metallurgy (PM) SpecimensB925 Practices for Production and Preparation of Powder Metallurgy (PM) Test Specimens
9、B962 Test Methods for Density of Compacted or Sintered Powder Metallurgy (PM) Products Using Archimedes PrincipleE691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test MethodIEEE/ASTM SI 10 American National Standard for Metric Practice3. Terminology3.1 Definition
10、sthe definitions of powder metallurgy (PM) terms used in this test method can be found in Terminology B243.Additional descriptive PM information is available in the Related Material section of Vol 02.05 of the Annual Book of ASTMStandards.4. Summary of Test Method4.1 Three rectangular test specimens
11、 are compacted to a predetermined green density or at a specified compacting pressure fromtest portions of the metal powder or powder mixture that is to be tested.1 This test method is under the jurisdiction ofASTM Committee B09 on Metal Powders and Metal Powder Products and is the direct responsibi
12、lity of Subcommittee B09.02on Base Metal Powders.Current edition approved May 1, 2009June 1, 2014. Published July 2009July 2014. Originally approved in 1956. Last previous edition approved in 20022009 asB312 96B312 09. (2002). DOI: 10.1520/B0312-09.10.1520/B0312-14.2 For referencedASTM standards, vi
13、sit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM stand
14、ard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM
15、 is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14.2 Each unsintered bar is placed, in turn, in a test fixture and subjected to
16、 a uniformly increasing transverse load undercontrolled conditions until fracture occurs.4.3 The green strength or maximum flexural stress of each specimen is determined by calculation using the stress equation fora simply supported beam with a concentrated mid-point load.4.4 The green strength of t
17、he material being tested is reported as the arithmetic mean of the results of three individual tests atthe measured green density or at the specified compacting pressure rounded to the nearest 100 psi (0.5 MPa).5. Significance and Use5.1 The green strength value determined under the conditions speci
18、fied by this test method is influenced by the characteristicsof the powder, how it compacts under the specified conditions (i.e., the particle to particle bonding that exists followingcompacting), and the lubrication system used.5.2 Knowledge of the green strength value is useful to the production,
19、characterization and utilization of metal powders in themanufacture of PM structural parts and bearings.5.3 The test for green strength of a compacted metal powder can be used to:5.3.1 Relate the resistance of a pressed compact to breakage or damage due to handling.5.3.2 Compare the quality of a met
20、al powder or powder mixture from lot to lot.5.3.3 Determine the effect of the addition of a lubricant or other powders to a base powder.5.3.4 Evaluate powder mixing or blending variables.5.4 Factors that are known to influence the green strength of a metal powder are particle shape, particle size di
21、stribution andcompressibility of the metal powder.5.5 The amount and type of lubricant or other additives and the mixing procedures have a strong effect on the green strengthof specimens produced from metal powder mixtures.6. Apparatus6.1 Analytical Balancea laboratory instrument A balance readable
22、to 0.001 g with a minimum capacity of at least 100 gsuitable to be used for determining the mass of both the test portion of the powder and the green test specimen to an accuracy of0.001 the nearest 0.01 g.6.2 PM Tool Seta compacting die and punches capable of producing the test specimens; an exampl
23、e of which is shown inPractices B925 as Laboratory Tooling Transverse Rupture Test Specimen.6.3 Universal Testing Machine or PM Compacting Pressa press with the ability to hold the PM tooling and apply the forcenecessary to compact the test specimens to the target green density.6.4 Outside Micromete
24、rs or Calipersinstruments capable of measuring from 0.000 to 1.250 in. (0.00 to 31.75 mm) with anaccuracy of 0.001 in. (0.03 mm).6.5 Either of the following sets of testing apparatus:6.5.1 Transverse Rupture Test Fixture and Compression Testing Machinea fixture (Fig. 1) for locating the test specime
25、n anda press capable of applying a breaking load at a controlled rate of approximately 20 lbf/min (90 N/min), and on which the forcecan be read to the nearest 0.1 lbf (0.5 N), or6.5.2 Constant Loading Beam Device, Metal Shot and Scale a lever-arm laboratory device (Fig. 2), designed to collect acont
26、rolled flow of metal shot that will produce a force with a loading rate of approximately 20 lbf/min (90 N/min) on apre-positioned test specimen until fracture occurs, and a scale with a capacity of at least 25 lb (10 kg) to determine the mass tothe nearest 0.01 lb (0.005 kg) of the shot that was req
27、uired.7. Test Specimen7.1 The recommended test specimen is an unsintered, (green), rectangular compact having dimensions of 0.500 in. (12.70 mm)wide by 1.250 in. (31.75 mm) long as specified in Practices B925 as Transverse Rupture Strength Test Specimen.7.2 Either the thin test specimen with a thick
28、ness 0.250 6 0.005 in. (6.35 6 0.13 mm) or the thick test specimen having athickness of 0.500 6 0.005 in. (12.70 6 0.13 mm) may be used as agreed to by the concerned parties.7.3 The top and bottom faces of the green compact shall be parallel within 0.001 in. (0.03 mm).7.4 The green density shall be
29、within 6 0.05 g/cm3 of the target green density that has been agreed to between the concernedparties.B312 1428. Procedure8.1 Lubrication MethodThe lubrication system to be used when compacting the test specimen shall be a matter of agreementbetween the concerned parties. Compactibility and green den
30、sity will vary with the method chosen as well as the care with whichit is applied and affect the green strength value.8.1.1 Lubricated metal powder mixtures should be tested in the as-received condition.8.1.2 Unlubricated metal powder or powder mixtures may be compacted with the aid of die-wall lubr
31、ication or an admixedpowder lubricant.8.1.2.1 If die-wall-lubrication is chosen, it shall be applied prior to the compacting of each test specimen following theprocedures in Practices B925.FIG. 1 Example of Constant Loading Beam DeviceTransverse Rupture Test FixtureFIG. 2 Transverse Rupture Test Fix
32、tureExample of Constant Loading Beam DeviceB312 1438.1.2.2 If an admixed lubricant is to be used; the type, grade, percentage and mixing procedure shall be agreed upon betweenthe concerned parties or shall closely follow accepted PM practice.8.2 Powder SamplingUsing Eq 1, calculate the mass of metal
33、 powder that will be needed to produce one test specimen fromthe nominal dimensions and desired thickness at the target green density.M5DG 3W3T3L0.061 (1)where:M = mass of powder needed, g,DG = target green density, g/cm3,W = width of test specimen, in.,T = thickness of test specimen, in.,L = length
34、 of test specimen, in., and0.061 = conversion factor, in3 to cm38.2.1 Following the recommendations in Practices B215, take a gross sample of powder from the lot that is to be tested ofsufficient quantity to produce a minimum of three test specimens.8.2.2 From this gross sample, remove three test po
35、rtions of powder that can be used to produce three test specimens of thedesired thickness at the target green density. Each test portion shall be within 0.02 g of the powder mass that was calculated.8.3 Compacting ProcedureSet-up the PM Tooling in the compacting press or the universal testing machin
36、e. Then, using theforce that is necessary to produce the desired thickness at the target green density, compact three test specimens from the three testportions of powder following the compacting procedure in Practices B925.8.3.1 Determine the mass of each test specimen to the nearest 0.0010.01 g, m
37、easure the specimen dimensions to the nearest0.001 in. (0.03 mm), number and identify the top of each specimen.8.3.2 Calculate the green density of each test specimen using Eq 2. Record these values to the nearest 0.01 g/cm3.DG 50.061 MW3T3L (2)where:DG = green density of the test specimen, g/cm3,0.
38、061 = conversion factor, in3 to cm3 ,M = mass of the test specimen, g,W = width of test specimen, in.,T = thickness of test specimen, in., andL = length of test specimen, in.NOTE 1Do not use Test Method B962 to measure the green density of the test specimens because of the possible effect of absorbe
39、d water on the greenstrength value.8.4 Testing ProcedureSelect a set of three green test specimens that are within 6 0.05 g/cm3 of the target green density, andbreak each bar in turn using either the Transverse Rupture Test Fixture, or the Constant Loading Beam Device.USING THETRANSVERSE RUPTURE STR
40、ENGTH TEST FIXTURE8.4.1 Place the Transverse Rupture Test Fixture,Fig. 1, between the platens of the compression testing machine with the movableupper portion securely attached, (if possible), to the upper platen.8.4.1.1 Locate each of the measured test specimens, in turn, centered lengthwise on the
41、 supporting rods of the test fixture withthe top face uppermost.8.4.1.2 Apply a uniformly increasing compressive load at a rate of approximately 20 lbf/min (90 N/min), until fracture occurs.Record the force at fracture directly from the read-out on the testing machine for each test specimen as the b
42、reaking force, P, inlbf (or N) to the nearest 0.1 lbf (0.5 N) for use in future calculations.8.4.1.3 If the upper portion of the test fixture is not attached to the upper press platen, then the force in lbf (N), exerted by themass of the upper portion of the test fixture shall be determined and adde
43、d to the read-out to determine the true breaking force.USING THECONSTANT LOADING BEAM DEVICE8.4.2 Set up the Constant Loading Beam Device, Fig. 2, on a sturdy laboratory table or bench and balance the lever arm withthe empty collecting container hanging in place on the hook.8.4.2.1 Open the valve an
44、d adjust the flow rate of the shot to approximately 20 lb/min (9 kg/min). Record the setting, emptyand rehang the collecting container.8.4.2.2 Locate each of the measured test specimens, in turn, centered lengthwise on the supporting rods of the test fixture withthe top face uppormost.B312 1448.4.2.
45、3 Open the valve to the predetermined setting and allow metal shot to flow into the collecting container until fractureoccurs.8.4.2.4 Stop the flow, empty the container and determine the mass of the shot, S, to the nearest 0.01 lb (0.005 kg).8.4.2.5 Calculate the breaking force, P, to the nearest 0.
46、01 lbf (0.5 N) using the following equation:P5A3FB (3)where:P = force required to break the test specimen, lbf (N),A = length of lever arm A, in. (mm) see Fig. 2,B = length of lever arm B, in. (mm) see Fig. 2, andF = force on the lever arm caused by the mass of the metal shot, lbf (N).When using in-
47、lb units, F in lbf = S in lb.When using SI units, F in N = 9.8 times S in kg.where:S = mass of the metal shot, lb (kg)9. Calculations9.1 Using the breaking force values, P, obtained from the stress equation in sec. 8.4.1.2, 8.4.1.3 or 8.4.2.5, calculate the greenstrength values for each of the test
48、specimens as follows:GS5 33P3L23T 23W (4)where:GS = green strength, psi (MPa),P = Breaking force required to rupture, lbf (N)L = length of span between supports of test fixture, in. (mm), (see Fig. 1) to the nearest 0.001 in. (0.03 mm)W = width of specimen, in. (mm), andT = thickness of specimen, in
49、. (mm.)10. Report10.1 The general reporting format shall be : Green Strength of a (nominal thickness) test specimen at (the measured) greendensity.density or at the specified compacting pressure.10.1.1 The green strength shall be reported in psi (or MPa) as the arithmetic mean of three individual test results rounded tothe nearest 100 psi (or 0.5 MPa).10.1.2 The thickness of the test specimen that was used shall be included in the report as a nominal value.10.1.3 The green density shall be reported as the average of the three test specimens to the nearest
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