ASTM B406-1996(2005) Standard Test Method for Transverse Rupture Strength of Cemented Carbides《硬质合金横向断裂强度的标准试验方法》.pdf

1、Designation: B 406 96 (Reapproved 2005)Standard Test Method forTransverse Rupture Strength of Cemented Carbides1This standard is issued under the fixed designation B 406; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of

2、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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This test method2covers the determin

3、ation of thetransverse rupture strength of cemented carbides.1.2 The values stated in inch-pound units are to be regardedas the standard. The SI values in parentheses are provided forinformation only.1.3 This standard does not purport to address the safetyconcerns, if any, associated with its use. I

4、t is the responsibilityof the user of this standard to establish appropriate safety andhealth practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:3B 276 Test Method for Apparent Porosity in CementedCarbides2.2 ISO Standard:4ISO-33

5、27 HardmetalsDetermination of Transverse Rup-ture Strength3. Significance and Use3.1 This test method is used as a means of determining thequality of cemented carbide grade powders by measuring theirsintered strength. It is performed on test specimens prepared tospecified shape, dimensions, and surf

6、ace finish; test specimensmay be prepared from finished parts if size permits. There is noknown standard material for this test method. The transverserupture strength of cemented carbides is not a design value.3.1.1 Most commercial cemented carbides have mechanicalbehavior that is best classified as

7、 brittle (negligible ductility).Fracture strengths are dependent on internal or surface flaws.Examples of incoherent internal flaws are macropores, Type Bporosity (see Test Method B 276), and inclusions of foreignparticles. Such flaws are randomly distributed spatially and insize within the sintered

8、 material. This imparts a statisticalnature to any transverse rupture strength measurement.3.1.2 The stress distribution in a beam in three-point loadingis non-uniform. It increases linearly along the span to amaximum at the center, and varies linearly through any sectionfrom compression on the top

9、to tension on the bottom. Themaximum tensile stress therefore occurs at center span in thebottom most fibers of the sample, and is defined as thetransverse rupture strength at failure. Failure is initiated at arandom flaw site, which is most probably not coincident withthe maximum stress. This impar

10、ts an additional statisticalnature to transverse rupture strength measurements.4. Apparatus4.1 Either a specially adapted machine for applying the loador a special fixture suitable for use with a conventionalload-applying machine may be used. In either case, theapparatus shall have the following par

11、ts:4.1.1 Two ground-cemented-carbide cylinders 0.250 60.001 in. (6.35 6 0.02 mm) in diameter, at least 0.500 in. (13mm) in length with the long axes parallel, and center to centerspacing of 0.563 6 0.005 in. (14.3 6 0.1 mm).4.1.2 Amovable member (free to move substantially only ina line perpendicula

12、r to the plane established by the axes of thetwo cylinders) containing a 0.4 6 0.05-in. (10 6 1.3-mm)cemented-tungsten-carbide ball or a ground-cemented-carbidecylinder of the same dimensions as, and with axis parallel to,those of the two previously mentioned cylinders (see 4.1.1).This ball or cylin

13、der shall be so positioned that movements ofthe member will cause the ball or cylinder to contact aspecimen placed on the two lower cylinders at the midpoint ofthe span between them.4.1.3 The apparatus shall be so constructed that the appli-cation of a sufficient load to the movable member to effect

14、breaking of a specimen will not cause appreciable deflection ofthe line of movement of the movable member and the planeestablished by the two fixed cylinders. The apparatus shall becapable of applying sufficient load to break the specimen. Theapparatus shall be capable of registering the load requir

15、ed1This test method is under the jurisdiction of ASTM Committee B09 on MetalPowders and Metal Powder Products and is the direct responsibility of Subcom-mittee B09.06 on Cemented Carbides.Current edition approved Oct. 1, 2005. Published October 2005. Originallyapproved in 1963. Last previous edition

16、 approved in 2000 as B 406 96 (2000).2This test method is comparable to ISO-3327.3For 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

17、 onthe ASTM website.4Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.(within 61 % of the load) to break the specimen. Thecement

18、ed-tungsten-carbide ball and cylinders shall not showpermanent deformation after use.5. Specimen Size5.1 The cemented carbide specimens shall be ground to thefollowing dimensions: 0.200 6 0.010 in. (5.00 6 0.25 mm)thick by 0.250 6 0.010 in. (6.25 6 0.25 mm) wide by 0.750 in.(19.0 mm) minimum long.6.

19、 Specimen Preparation6.1 Specimens shall be ground to a surface finish of 15 in.(0.381 m) rms maximum on four sides, and to the tolerancesspecified in Section 5. All grinding marks shall be parallel tothe length, 0.750 in. (19.05 mm), axis. Opposite ground facesshall be parallel within 0.001 in. (0.

20、0254 mm). The two facesthat are perpendicular to the length axis need not be ground.Careful grinding techniques should be used to prevent variousforms of surface cracking (flaws) that will degrade the mea-sured strength. Long-established practice recommends the useof soft resin bonded diamond wheels

21、, and copious quantities ofcoolant. For surface grinding, no pass shall exceed 0.0005 in.(0.0127 mm) in depth.6.2 The four edges of the specimen representing the inter-section of the ground faces shall be chamfered or honed to amaximum of 0.010 in. (0.25 mm) by 45 degrees. Any grindingmarks shall be

22、 parallel to the long axis of the specimen.6.3 Each specimen shall be measured to within 0.001 in.(0.02 mm) in both directions perpendicular to the length axis.Adjacent ground sides shall be at right angles to each otherwithin 2 degrees.6.4 Each specimen shall be visually inspected after grind-ing.

23、Any specimen on which cracks, chips, or obvious struc-tural defects appear on the ground surfaces shall be eliminatedfrom the test.7. Procedure7.1 Visually examine the cylinders and ball in the fixture forcracks, chips, deformation, or misalignment and check themovable member for freedom of movement

24、. Correct anydefects prior to use.7.2 Place a properly prepared and measured specimen onthe fixture with the long axis perpendicular to the cylinders andwith the 0.250-in. (6.25-mm) face resting on the two cylinders.Then adjust the movable member so that the ball or uppercylinder contacts the specim

25、en without substantial impact. If aball is used, place the specimen so that the ball touches themidpoint of the specimen width. Apply the load at a rate notexceeding 350 lbf/s (1.5 kN/s). Fracture should occur withinthe middle one third of the span between the supportingcylinders on the tension side

26、 of the specimen. Record thenumber of pounds required to cause fracture.7.3 Perform all tests at room temperature but not lower than65F (18C).7.4 Five specimens shall be tested.8. Calculation8.1 Calculate the transverse rupture strength as follows:S 5 3PL/2bh2(1)where:S = transverse rupture strength

27、, psi (MPa),P = load, lb (N) required to fracture,L = length of span, in. (mm),b = specimen width, in. (mm), andh = specimen thickness, in. (mm).9. Report9.1 One, but only one, of the five values obtained will beconsidered invalid if its deviation from the mean of the otherfour values is excessive a

28、s determined by the following:9.1.1 Take the average of the other four values.9.1.2 Find the deviation of the values from the average.9.1.3 Total the four deviations.9.1.4 If the value omitted has a greater deviation than thetotal of the four other deviations, it is dropped. Otherwise, allfive value

29、s must be considered valid.9.1.5 Example:Values Determined,psiDeviation fromAverage of 4180 000 20 000200 000 0205 000 5 000215 000 15 000150 000 (50 000)Average of 5 190 000 40 000Average of 4 200 000The last value is dropped. Had it been 160 000 to 240 000psi, it would have to be included in the a

30、verage.9.2 Report the transverse rupture strength as the mean of thevalid values. Also report the standard deviation of these validvalues. If less than five valid values are used in calculating themean, the number of valid values used in the calculation of themean and the standard deviations of thes

31、e valid values are to bereferenced in the report.10. Precision and Bias10.1 The statistical nature of transverse rupture strength incemented carbide was discussed in 3.1. This causes theprecision and bias of the test to be inseparable from statisticalnature of the material behavior. This dilemma is

32、compensatedfor by requiring the reporting of the standard deviation of thetest values.11. Keywords11.1 cemented carbides; fracture strength; hardmetals;tensile stress; transverse rupture strengthB 406 96 (2005)2ASTM International takes no position respecting the validity of any patent rights asserte

33、d in connection with any item mentionedin this standard. 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 th

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35、careful consideration at a meeting of theresponsible technical 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 Internat

36、ional, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, 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).B 406 96 (2005)3