1、Designation: B 312 09Standard Test Method forGreen Strength of Specimens Compacted from MetalPowders1This 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 of last revisi
2、on. 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 tomeasure the transverse rupture strength of a compacted butunsintered (gree
3、n) test specimen produced from lubricated orunlubricated metal powders or powder mixtures.1.2 Green strength is measured by a quantitative laboratoryprocedure in which the fracture strength is calculated from theforce required to break an unsintered test specimen supportedas a simple beam while subj
4、ected to a uniformly increasingthree-point transverse load under controlled conditions.1.3 This test method is a companion standard to TestMethod B 528 that covers the measurement of the transverserupture strength of sintered PM test specimens.1.4 With the exception of density values, for which theg
5、/cm3unit is the industry standard, and mass measurementsused to calculate density, the values stated in inch-pound unitsare to be regarded as the standard. The SI equivalents shown inparentheses have been converted in accordance with IEEE/ASTM Standard SI 10, may be approximate and are onlyincluded
6、for information.1.5 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-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use
7、.2. Referenced Documents2.1 ASTM Standards:2B 215 Practices for Sampling Metal PowdersB 243 Terminology of Powder MetallurgyB 528 Test Method for Transverse Rupture Strength ofMetal Powder SpecimensB 925 Practices for Production and Preparation of PowderMetallurgy (PM) Test SpecimensB 962 Test Metho
8、ds for Density of Compacted or SinteredPowder Metallurgy (PM) Products Using ArchimedesPrincipleE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodSI 10 American National Standard for Use of the Interna-tional System of Units (SI): The Modern Metric Syst
9、em3. Terminology3.1 Definitionsthe definitions of powder metallurgy (PM)terms used in this test method can be found in TerminologyB 243. Additional descriptive PM information is available inthe Related Material section of Vol 02.05 of the Annual Bookof ASTM Standards.4. Summary of Test Method4.1 Thr
10、ee rectangular test specimens are compacted to apredetermined green density from test portions of the metalpowder or powder mixture that is to be tested.4.2 Each unsintered bar is placed, in turn, in a test fixtureand subjected to a uniformly increasing transverse load undercontrolled conditions unt
11、il fracture occurs.4.3 The green strength or maximum flexural stress of eachspecimen is determined by calculation using the stress equationfor a simply supported beam with a concentrated mid-pointload.4.4 The green strength of the material being tested isreported as the arithmetic mean of the result
12、s of three indi-vidual tests at the measured green density rounded to thenearest 100 psi (0.5 MPa).5. Significance and Use5.1 The green strength value determined under the condi-tions specified by this test method is influenced by thecharacteristics of the powder, how it compacts under thespecified
13、conditions (i.e., the particle to particle bonding thatexists following compacting), and the lubrication system used.5.2 Knowledge of the green strength value is useful to theproduction, characterization and utilization of metal powdersin the manufacture of PM structural parts and bearings.1This tes
14、t method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.02 on Base Metal Powders.Current edition approved May 1, 2009. Published July 2009. Originally approvedin 1956. Last previous edition approved in 2
15、002 as B 312 96 (2002).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.1*A Summary of Changes section appears
16、 at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.3 The test for green strength of a compacted metal powdercan be used to:5.3.1 Relate the resistance of a pressed compact to breakageor damage due to handli
17、ng.5.3.2 Compare the quality of a metal powder or powdermixture from lot to lot.5.3.3 Determine the effect of the addition of a lubricant orother powders to a base powder.5.3.4 Evaluate powder mixing or blending variables.5.4 Factors that are known to influence the green strengthof a metal powder ar
18、e particle shape, particle size distributionand compressibility of the metal powder.5.5 The amount and type of lubricant or other additives andthe mixing procedures have a strong effect on the greenstrength of specimens produced from metal powder mixtures.6. Apparatus6.1 Analytical Balancea laborato
19、ry instrument with acapacity of at least 100 g suitable for determining the mass ofboth the test portion of powder and the green test specimen toan accuracy of 0.001 g.6.2 PM Tool Seta compacting die and punches capable ofproducing the test specimens; an example of which is shown inPractices B 925 a
20、s Laboratory Tooling Transverse RuptureTest Specimen.6.3 Universal Testing Machine or PM Compacting Pressapress with the ability to hold the PM tooling and apply theforce necessary to compact the test specimens to the targetgreen density.6.4 Outside Micrometers or Calipersinstruments capableof measu
21、ring from 0.000 to 1.250 in. (0.00 to 31.75 mm) withan accuracy 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 CompressionTesting Machine a fixture (Fig. 1) for locating the testspecimen and a press capable of applying a breakin
22、g load at acontrolled rate of approximately 20 lbf/min (90 N/min), andon which the force can be read to the nearest 0.1 lbf (0.5 N), or6.5.2 Constant Loading Beam Device, Metal Shot andScale a lever-arm laboratory device (Fig. 2), designed tocollect a controlled flow of metal shot that will produce
23、a forcewith a loading rate of approximately 20 lbf/min (90 N/min)on a pre-positioned test specimen until fracture occurs, and ascale with a capacity of at least 25 lb (10 kg) to determine themass to the nearest 0.01 lb (0.005 kg) of the shot that wasrequired.7. Test Specimen7.1 The recommended test
24、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 inPractices B 925 as Transverse Rupture Strength Test Specimen.7.2 Either the thin test specimen with a thickness 0.250 60.005 in. (6.35 6 0.13 mm) or the th
25、ick test specimen havinga thickness of 0.500 6 0.005 in. (12.70 6 0.13 mm) may beused as agreed to by the concerned parties.7.3 The top and bottom faces of the green compact shall beparallel within 0.001 in. (0.03 mm).FIG. 1 Example of Constant Loading Beam DeviceB3120927.4 The green density shall b
26、e within 6 0.05 g/cm3of thetarget green density that has been agreed to between theconcerned parties.8. Procedure8.1 Lubrication MethodThe lubrication system to be usedwhen compacting the test specimen shall be a matter ofagreement between the concerned parties. Compactibility andgreen density will
27、vary with the method chosen as well as thecare with which it is applied and affect the green strengthvalue.8.1.1 Lubricated metal powder mixtures should be tested inthe as-received condition.8.1.2 Unlubricated metal powder or powder mixtures maybe compacted with the aid of die-wall lubrication or an
28、admixed powder lubricant.8.1.2.1 If die-wall-lubrication is chosen, it shall be appliedprior to the compacting of each test specimen following theprocedures in Practices B 925.8.1.2.2 If an admixed lubricant is to be used; the type, grade,percentage and mixing procedure shall be agreed upon betweent
29、he concerned parties or shall closely follow accepted PMpractice.8.2 Powder SamplingUsing Eq 1, calculate the mass ofmetal powder that will be needed to produce one test specimenfrom the nominal dimensions and desired thickness at thetarget green density.M 5DG3 W 3 T 3 L0.061(1)where:M = mass of pow
30、der needed, g,DG= target green density, g/cm3,W = width of test specimen, in.,T = thickness of test specimen, in.,L = length of test specimen, in., and0.061 = conversion factor, in3to cm38.2.1 Following the recommendations in Practices B 215,take a gross sample of powder from the lot that is to be t
31、estedof sufficient quantity to produce a minimum of three testspecimens.8.2.2 From this gross sample, remove three test portions ofpowder that can be used to produce three test specimens of thedesired thickness at the target green density. Each test portionshall be within 0.02 g of the powder mass t
32、hat was calculated.8.3 Compacting ProcedureSet-up the PM Tooling in thecompacting press or the universal testing machine. Then, usingthe force that is necessary to produce the desired thickness atthe target green density, compact three test specimens from thethree test portions of powder following t
33、he compacting proce-dure in Practices B 925.8.3.1 Determine the mass of each test specimen to thenearest 0.001 g, measure the specimen dimensions to thenearest 0.001 in. (0.03 mm), number and identify the top ofeach specimen.8.3.2 Calculate the green density of each test specimenusing Eq 2. Record t
34、hese values to the nearest 0.01 g/cm3.DG5 0.061MW 3 T 3 L(2)where:DG= green density of the test specimen, g/cm3,0.061 = conversion factor, in3to 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 u
35、se Test Method B 962 to measure the green densityof the test specimens because of the possible effect of absorbed water onthe green strength value.8.4 Testing ProcedureSelect a set of three green testspecimens that are within 6 0.05 g/cm3of the target greendensity, and break each bar in turn using e
36、ither the TransverseRupture Test Fixture, or the Constant Loading Beam Device.FIG. 2 Transverse Rupture Test FixtureB312093USING THETRANSVERSE RUPTURE STRENGTH TESTFIXTURE8.4.1 Place the Transverse Rupture Test Fixture, Fig. 1,between the platens of the compression testing machine withthe movable up
37、per portion securely attached, (if possible), tothe upper platen.8.4.1.1 Locate each of the measured test specimens, in turn,centered lengthwise on the supporting rods of the test fixturewith the top face uppermost.8.4.1.2 Apply a uniformly increasing compressive load at arate of approximately 20 lb
38、f/min (90 N/min), until fractureoccurs. Record the force at fracture directly from the read-outon the testing machine for each test specimen as the breakingforce, P, in lbf (or N) to the nearest 0.1 lbf (0.5 N) for use infuture calculations.8.4.1.3 If the upper portion of the test fixture is not att
39、achedto the upper press platen, then the force in lbf (N), exerted bythe mass of the upper portion of the test fixture shall bedetermined and added to the read-out to determine the truebreaking force.USING THECONSTANT LOADING BEAM DEVICE8.4.2 Set up the Constant Loading Beam Device, Fig. 2,ona sturd
40、y laboratory table or bench and balance the lever armwith the empty collecting container hanging in place on thehook.8.4.2.1 Open the valve and adjust the flow rate of the shot toapproximately 20 lb/min (9 kg/min). Record the setting,empty and rehang the collecting container.8.4.2.2 Locate each of t
41、he measured test specimens, in turn,centered lengthwise on the supporting rods of the test fixturewith the top face uppormost.8.4.2.3 Open the valve to the predetermined setting andallow metal shot to flow into the collecting container untilfracture occurs.8.4.2.4 Stop the flow, empty the container
42、and determine themass 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 0.01lbf (0.5 N) using the following equation:P 5A 3 FB(3)where:P = force required to break the test specimen, lbf (N),A = length of lever arm A, in. (mm) see Fig. 2,B = len
43、gth of lever arm B, in. (mm) see Fig. 2, andF = force on the lever arm caused by the mass of the metalshot, lbf (N).When using in-lb units, F in lbf=Sinlb.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, o
44、btained from thestress equation in sec. 8.4.1.2, 8.4.1.3 or 8.4.2.5, calculate thegreen strength values for each of the test specimens as follows:GS 53 3 P 3 L2 3T23 W(4)where:GS = green strength, psi (MPa),P = Breaking force required to rupture, lbf (N)L = length of span between supports of test fi
45、xture, 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. (mm.)10. Report10.1 The general reporting format shall be : Green Strengthof a (nominal thickness) test specimen at (the measured) greendensity.10.1.1 The green strength
46、shall be reported in psi (or MPa)as the arithmetic mean of three individual test results roundedto the nearest 100 psi (or 0.5 MPa).10.1.2 The thickness of the test specimen that was used shallbe included in the report as a nominal value.10.1.3 The green density shall be reported as the average ofth
47、e three test specimens to the nearest 0.01 g/cm3.10.2 An alternative reporting method may be to graph thegreen strength as a function of green density using the resultsobtained at a minimum of three data points.10.3 The following information may also be reported tohelp interpret the test results:10.
48、3.1 Testing apparatus used, either the Transverse RuptureTest Fixture or The Constant Loading Beam Device.10.3.2 Powder type, brand, grade and lot identificationnumber.10.3.3 Composition of the powder mixture if other than abase powder.10.3.4 Lubrication system as well as type, brand andamount.10.3.
49、5 Apparent density, flow rate and sieve analysis of thepowder and the test methods used to determine these proper-ties.10.3.6 Compacting pressure used to achieve the targetgreen density.11. Precision and Bias311.1 The precision of this test method has been determinedfrom an interlaboratory study, (ILS) conducted on two ferrousmaterials by the Metal Powder Industries Federation in 2005 inwhich 32 laboratories participated. Practice E 691 was used toperform a statistical analysis of the data at the 95% confidencelevel.11.1.1 Repeatability Values, r, obtained when us
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