ISO 6507-1:1997 download free.Metallic materials – Vickers hardness test – Part 1 Test method.
The Vickers hardness test is specified in this part of ISO 6507 for lengths of indentation diagonals between 0,020 mm and 1,400 mm.
The force values in this part of ISO 6507 were calculated from kilogram force values. They were introduced before the SI-system was adopted. It was decided to keep the values based on the old units for this edition, but for the next revision it will be necessary to consider the advantage of introducing rounded values of test force and the consequence on the hardness scales.
NOTE — In general, decreasing the test force increases the scatter of results of the measurements. This is particularly true for low-force Vickers hardness tests and Vickers microhardness tests where the principal limitation will arise in the measurement of the diagonals of the indentation. For Vickers microhardness. the accuracy of determination of the mean diagonal length is unlikely to be better than ± 0,001 mm (see annex E).
For specific materials and/or products, particular International Standards exist.
2 Normative reference
The following standard contains provisions which, through reference in this text, constitute provisions of this part of ISO 6507. At the time of publication, the edition indicated was valid. All standards are subject to revision, and parties to agreements based on this part of ISO 6507 are encouraged to investigate the possibility of applying the most recent edition of the standard indicated below. Members of IEC and ISO maintain registers of currently valid International Standards.
ISO 6507-2:1997, Metallic materials — Vickers hardness test — Part 2: Verification of testing machines.
4.2 The Vickers hardness is denoted by the symbol HV preceded by the hardness value followed by
a) a number representing the test force (see table 3);
b) the duration of loading, in seconds, if different from the time specified in 7.4.
EXAMPLES
640 HV 30 = Vickers hardness of 640 determined with a test force of 294,2 N applied for 10 s to 15 s.
640 HV 30/20 Vickers hardness of 640 determined with a test force of 294,2 N applied for 20 s.
5 Testing machine
5.1 Testing machine, capable of applying a predetermined force or forces within the required range
of test forces, in accordance with ISO 6507-2.
5.2 Indenter, a diamond in the shape of a right pyramid with a square base, as specified in ISO 6507-2.
5.3 Measuring device, as specified in ISO 6507-2.
NOTE — A suggested procedure for monitoring the uncertainty of the hardness testing machine by the users is given in annex 0.
6 Test piece
6.1 The test shall be carried Out Ofl a surface which is smooth and even, free from oxide scale, foreign matter and, in particular, completely free from lubricants, unless otherwise specified in product standards. The finish of the surface shall permit accurate determination of the diagonal length of the indentation.
6.2 Preparation shall be carried out in such a way that any alteration of the surface hardness, due to heat or cold-working, for example, is minimized.
Due to the small depth of Vickers microhardness indentations, it is essential that special precautions are taken during preparation. It is recommended to use a polishing/electropolishing process which is suitable for the material parameters.
6.3 The thickness of the test piece or of the layer under test shall be at least 1,5 times the diagonal length of the indentation (see annex A).
No deformation shall be visible at the back of the test piece after the test.
6.4 For tests on curved surfaces, the corrections given in annex B, tables B.1 to B.6 shall be applied.
6.5 For test pieces of small cross-section or of irregular shape, it may be necessary to provide some
form of additional support.
7 Procedure
7.1 In general, the test is carried out at ambient temperature within the limits of 10 °C to 35 °C. Tests carried out under controlled conditions shall be made at a temperature of (23 ± 5) °C.
7.2 The following test forces (see table 3) shall be used.
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 is important that the test piece lies firmly on the support so that displacement cannot occur during the test.
7.4 Bring the indenter into contact with the test surface and apply the test force in a direction perpendicular to the surface, without shock or vibration, until the applied force attains the specified value. The time from the initial application of the force until the full test force is reached shall not be less than 2 s nor greater than 8 s. For low-force hardness and microhardness tests, this time shall not exceed 10 s. For low-force hardness and microhardness tests, the approach speed of the indenter shall not exceed 0,2 mm/s.
The duration of the test force shall be 10 s to 15 s.
For particular materials, a longer time for maintaining the force is provided; this time shall be applied with a tolerance of ± 2 s.
7.5 Throughout the test, the testing machine shall be protected from shock or vibration.
7.6 The distance between the centre of any indentation and the edge of the test piece shall be at least
2,5 times the mean diagonal length of the indentation in the case of steel, copper and copper alloys
and at least three times the mean diagonal length of the indentation in the case of light metals, lead
and tin and their alloys.
The distance between the centres of two adjacent indentations shall be at least three times the mean diagonal length of the indentation in the case of steel, copper and copper alloys, and at least six times the mean diagonal length in the case of light metals, lead and tin and their alloys. If two adjacent indentations differ in size, the spacing shall be based on the mean diagonal length of the larger indentation.
7.7 Measure the lengths of the two diagonals. The arithmetical mean of the two readings shall be taken for the calculation of the Vickers hardness.
For flat surfaces, the difference between the lengths of two indentation diagonals should not be greater than 5 %. If the difference is greater, this shall be stated in the test report.
9 Test report
The test report shall include the following information:
a) reference to this part of ISO 6507;
b) all details necessary for identification of the test piece;
c) the result obtained;
d) all operations not specified by this part of ISO 6507, or regarded as optional;
e) details of any occurrence which may have affected the resuits;
f) the temperature of the test, if it is outside the range specified in 7.1.
NOTES
1 A strict comparison of hardness values is only possible at identical test forces.
2 There is no general process of accurately converting Vickers hardness into other scales of hardness or into tensile strength. Such conversions therefore should be avoided, unless a reliable basis for conversion can be obtained by comparison tests.
3 It should be noted that for anisotropic materials, for example those which have been heavily cold•worked, there will be a difference between the lengths of the two diagonals of the indentation. Where possible, the indentation should be made so that the diagonals are inclined at approximately 450 to the direction of cold-working. The specification for the product may indicate limits for the differences between the lengths of the two diagonals.
4 There is evidence that some materials may be sensitive to the rate of straining which causes small changes in the value of the yield stress The corresponding effect on the termination of the formation of an indentation can make alterations in the hardness value.