BS ISO 22394-2010 Hardmetals - Knoop hardness test《硬质合金 努普显微硬度试验》.pdf

1、BS ISO22394:2010ICS 77.040.10; 77.160NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBRITISH STANDARDHardmetals Knoophardness testThis British Standardwas published under theauthority of the StandardsPolicy and StrategyCommittee on 30 April2010. BSI 2010ISBN 978 0 580 65692 7Am

2、endments/corrigenda issued since publicationDate CommentsBS ISO 22394:2010National forewordThis British Standard is the UK implementation of ISO 22394:2010.The UK participation in its preparation was entrusted to TechnicalCommittee ISE/65, Sintered metal components.A list of organizations represente

3、d on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisionsof a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunityfrom legal obligations.BS ISO 22394:2010Re

4、ference numberISO 22394:2010(E)ISO 2010INTERNATIONAL STANDARD ISO22394First edition2010-02-01Hardmetals Knoop hardness test Mtaux-durs Essai de duret Knoop BS ISO 22394:2010ISO 22394:2010(E) PDF disclaimer This PDF file may contain embedded typefaces. In accordance with Adobes licensing policy, this

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9、l. + 41 22 749 01 11 Fax + 41 22 749 09 47 E-mail copyrightiso.org Web www.iso.org Published in Switzerland ii ISO 2010 All rights reservedBS ISO 22394:2010ISO 22394:2010(E) ISO 2010 All rights reserved iiiContents Page Foreword iv Introduction.v 1 Scope1 2 Normative references1 3 Principle1 4 Symbo

10、ls and designations.1 5 Apparatus.3 6 Test pieces .3 7 Procedure.3 8 Expression of results4 9 Test report4 10 Significance .4 Annex A (informative) Investigation regarding the demand of an International Standard for a Knoop hardness test for hardmetals.5 Annex B (informative) Comparison of important

11、 test procedures in Vickers and Knoop hardness tests 15 Bibliography16 BS ISO 22394:2010ISO 22394:2010(E) iv ISO 2010 All rights reservedForeword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing

12、 International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liais

13、on with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2. The main task of te

14、chnical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at least 75 % of the member bodies casting a vote. Attention is dr

15、awn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. ISO 22394 was prepared by Technical Committee ISO/TC 119, Powder metallurgy, Subcommittee SC 4, Sampling and testing

16、 methods for hardmetals. BS ISO 22394:2010ISO 22394:2010(E) ISO 2010 All rights reserved vIntroduction Many metallurgical problems require the determination of hardness over very small areas. The special shape of the Knoop indenter makes it possible to place indentations much closer together than wi

17、th a square Vickers indentation, e.g. to measure a steep hardness gradient. For a given long diagonal length, the depth and area of the Knoop indentation are known to be only 15 % of what they would be for a Vickers indentation with the same diagonal length. Both Vickers and Knoop hardness tests wer

18、e performed for a range of hardmetals, in order to investigate whether a specific International Standard is really required and if it compensates the limitations of the Vickers hardness test currently used. Knoop hardness tests were carried out independently in three institutes (KATS, Jinil Co., Seo

19、ul University) over a period of four months. The results of this test (see Annex A) show that this new International Standard regarding the Knoop hardness test is necessary. BS ISO 22394:2010BS ISO 22394:2010INTERNATIONAL STANDARD ISO 22394:2010(E) ISO 2010 All rights reserved 1Hardmetals Knoop hard

20、ness test 1 Scope This International Standard specifies the method of the Knoop hardness test for hardmetals. 2 Normative references The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references

21、, the latest edition of the referenced document (including any amendments) applies. ISO 4545-1, Metallic materials Knoop hardness test Part 1: Test method ISO 4545-2, Metallic materials Knoop hardness test Part 2: Verification and calibration of testing machines ISO 4545-4, Metallic materials Knoop

22、hardness test Part 4: Table of hardness values 3 Principle Forcing a diamond indenter, in the form of a rhombic-based pyramid with specified angles between opposite faces at the vertex, into the surface of a test piece and measuring the long diagonal of the indentation left in the surface after remo

23、val of the test force, F, in accordance with ISO 4545-1. 4 Symbols and designations 4.1 The Knoop hardness, HK, is given by the quotient obtained by dividing the test force F by the projected area Apof the indentation as represented by numerical value Equation (1): 222p21HK 0,102 0,102 0,102 1,4510,

24、07028tan22tan2F FF FFgAcd d dd= = = = = (1) where g is the acceleration due to gravity, in metres per second squared (m/s2), with a constant of 9,806 65; F is the test force, in newtons(N); pA is the projected area of the permanent indentation, in square millimetres (mm2); BS ISO 22394:2010ISO 22394

25、:2010(E) 2 ISO 2010 All rights reservedc is an indenter constant which equals tan22tan2, ideally with a constant of c = 0,0702 8; d is the length of the long indentation diagonal, in millimetres (mm) (see Figure 1); is the angle with a value of 172,5 (see Figure 2); is the angle with a value of 130

26、(see Figure 2). The indentation of d is assumed to be a rhombic-based pyramid with a base area as shown in Figure 1 and having, at the vertex, the same angles as the indenter (see Figure 2). Figure 1 Projected area of the indentation produced by the Knoop indenter Figure 2 Knoop indenter 4.2 The Kno

27、op hardness is denoted by the symbol HK preceded by the hardness value and supplemented by a number representing the test force. EXAMPLE 1 Use of the SI unit (GPa): 10 GPa HK 9,807 = Knoop hardness of 10 GPa, determined with a test force of 9,807 N (1 kgf). EXAMPLE 2 Use of the Knoop hardness number

28、 (no units specified): 1 000 HK 1 = Knoop hardness number of 1 000, determined with a test force of 9,807 N (1 kgf). EXAMPLE 3 The duration of loading, in seconds (s), if different from the time specified in 7.4: 1 000 HK 1 = Knoop hardness number of 1 000, determined with a test force of 9,807 N (1

29、 kgf) applied for 10 s to 15 s; 1 000 HK 1/20 = Knoop hardness number of 1 000, determined with a test force of 9,807 N (1 kgf) applied for 20 s. BS ISO 22394:2010ISO 22394:2010(E) ISO 2010 All rights reserved 35 Apparatus 5.1 The testing machine, in accordance with ISO 4545-2, should meet the follo

30、wing requirements: a) the indentation force should be calibrated to be within 1 % of the nominal value; b) the indenter should be vertically lowered on the surface of the test specimen at a rate lower than 0,1 mm/s. 5.2 Indenter, a diamond in the shape of a rhombic-based pyramid, as specified in ISO

31、 4545-2. 5.3 Measuring device 5.3.1 The measuring device shall permit an estimation of the diagonal of the indentation to within 0,2 m. 5.3.2 The device for measuring the diagonal of the indentation shall be calibrated against an accurately ruled line scale (stage micrometer) or device of equivalent

32、 accuracy. The errors of the line scale shall be known within an uncertainty of 0,2 m. 5.3.3 The verification of the measuring device shall be carried out in accordance with ISO 4545-2. 6 Test pieces 6.1 The thickness of the layer removed from the surface of the test piece shall be not less than 0,2

33、 mm. The test shall be carried out on a surface which is free from foreign matter and, in particular, completely free from lubricants. The test surface shall be ground and polished with fine diamond cloths in order to avoid experimental difficulties and errors owing to rough surface. Preparation sha

34、ll be carried out in such a way that any alteration of the surface hardness, for example, due to heat or cold working, is minimized. In determining the hardness of a test piece with a curved surface, a flat surface shall be provided on the test piece on which the hardness test is carried out. The te

35、st-piece surface and support surface shall be parallel to obtain symmetrical indentations. 6.2 The prepared test piece shall be at least 10 times as thick as the indentation depth expected under the chosen force. 7 Procedure 7.1 The test is normally carried out at a temperature of 23 C 5 C. If the t

36、est is carried out at a temperature outside this range, it shall be noted in the test report. 7.2 The test force shall be lower than 490,3 N (50 kgf). 7.3 The test piece shall be placed on a rigid support. The support surfaces shall be clean and free from foreign matter (scale, oil, dirt, etc.). It

37、is important that the test piece be firmly supported so that displacement cannot occur during the test. Focus the measuring microscope so that the specimen surface can be observed. 7.4 The indenter shall approach the surface within the velocity range of 15 m/s to 70 m/s. The time from the initial ap

38、plication of force until the full test force is reached shall not be less than 5 s nor greater than 10 s. The duration of the test force shall be from 10 s to 15 s. 7.5 Throughout the test, the apparatus shall be protected from shock or vibration. 7.6 If possible, at least three hardness determinati

39、ons shall be made on a test piece. BS ISO 22394:2010ISO 22394:2010(E) 4 ISO 2010 All rights reserved7.7 The distance between the limit of any indentation and the edge of the test piece shall be at least 2 times the short diagonal of the indentation. The distance between the limits of two adjacent in

40、dentations shall be at least 2,5 times the short diagonal of the indentation. If two adjacent indentations differ in size, the spacing shall be based on the short diagonal of the larger indentation. 7.8 The satisfactory condition of the indenter shall be verified frequently. Any irregularities in th

41、e shape of the indentation may show the poor condition of the indenter. If the examination of the indenter confirms this, then the test shall be rejected and the indenter renewed. 7.9 Measure the length of the long diagonal to within 0,2 m for less than 50 m, or to within 0,5 m for equal to or more

42、than 50 m. The length is used for the calculation of the Knoop hardness number. If one leg (one-half) of the long diagonal is more than 10 % longer than the other, or if the ends of the diagonals are not both in the field of focus, the surface of the test piece may not be normal to the axis of the i

43、ndenter. Align the test piece surface properly and make another indentation. 7.10 Attention is drawn to ISO 4545-4, which contains conversion tables for use in tests made on flat surfaces. 8 Expression of results Report the arithmetical mean of the hardness values obtained, rounded to the nearest 10

44、 HK. 9 Test report The test report shall include the following information: a) a reference to this International Standard; b) all details necessary for identification of the test sample; c) the result obtained; d) all options not specified by this International Standard, or regarded as optional; e)

45、details of any occurrence which may have affected the result. 10 Significance Knoop hardness measurements can be useful in studies of hardness gradients over small regions. However, the values should not be directly compared with Vickers hardness values. This is an ongoing subject of research (Refer

46、ence 3 in the Bibliography) and recommendations cannot yet be given as to good practice for comparison values. BS ISO 22394:2010ISO 22394:2010(E) ISO 2010 All rights reserved 5Annex A (informative) Investigation regarding the demand of an International Standard for a Knoop hardness test for hardmeta

47、ls A.1 Test procedure Hardmetal samples employed in this test are commercially available insert materials, the compositions of which are listed in Table A.1. The test loads applied are 1 kg to 50 kg. Tests to examine the distance effect (see Figures A.1 to A.4) were performed exclusively under 1 kg

48、and 30 kg. Table A.1 Composition of the test pieces used Test-piece number Composition Hardness (HRA) 1 WC-6%Coa92 to 92,6 2 WC-12%Coa90 to 90,8 3 TiCN(WC/MoC/TaC)-17%(Ni/Co)a 92,4 to 93 aPercentages are mass fractions. Both Vickers and Knoop hardness tests were performed in order to compare the two

49、 tests employed in hardmetals. Both tests were made at various loads of 5 kg to 50 kg, and 7 readings were taken under a given condition. Indentations were separated at a sufficient distance so as not to be influenced by each other. Knoop hardness values were measured while increasing the distance from the adjacent indentation as well as while increasing the distance from the edge of the sample. The distance is expressed in terms of number of tim