ISO 6507-1:1997 pdf download – Metallic materials – Vickers hardness test— Part 1: Test method
ISO 6507-1:1997 pdf download – Metallic materials – Vickers hardness test— Part 1: Test method.
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 sothat 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 specifiedvalue.The time from the initial application of the force until the full test force is reached shall not beless than 2 s nor greater than 8 s. For low-force hardness and microhardness tests, this time shall notexceed 10 s. For low-force hardness and microhardness tests, the approach speed of the indentershall 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 appliedwith 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 least2,5 times the mean diagonal length of the indentation in the case of steel, copper and copper alloysand at least three times the mean diagonal length of the indentation in the case of light metals, leadand tin and their alloys.
The distance between the centres of two adjacent indentations shall be at least three times the meandiagonal length of the indentation in the case of steel, copper and copper alloys, and at least six timesthe mean diagonal length in the case of light metals, lead and tin and their alloys. Ilf two adjacent
indentations differ in size, the spacing shall be based on the mean diagonal length of the largerindentation.
7.7 Measure the lengths of the two diagonals. The arithmetical mean of the two readings shall betaken for the calculation of the vickers hardness.
For flat surfaces, the difference between the lengths of two indentation diagonals should not begreater than 5 %. lf the difference is greater, this shall be stated in the test report.
8 Uncertainty of the results
The uncertainty of results is dependent on various parameters which may be separated into twocategories:
a)parameters depending on the Vickers hardness testing machine (including the uncertainty ofthe verification of the testing machine and of the calibration of the reference blocks);
b)parameters depending on the application of the test method (variation of the operatingconditions).
NOTE— In the absence of sufficient data on those parameters it is not possible, at present, to fix values ofaccuracy, but the uncertainty may approach approximately ± 10 % of the measured hardness values.
The test report shall include the following information:
a)reference to this part of ISO 6507;
blall details necessary for identification of the test piece;c)the result obtained;
dall operations not specified by this part of lSO 6507, or regarded as optional;e) details of any occurrence which may have affected the results;
f)the temperature of the test, if it is outside the range specified in 7.1.
1 A strict comparison of hardness values is only possible at identical tast forces.
2 There is no general process of accurately converting Vickers hardness into other scales of hardness or intotensile strength.Such conversions therefore should be avoided,unless a reliable basis for conversion can beobtained by comparison tests.
3 lt 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, theindentation should be made so that the diagonals are inclined at approximately 45° to the direction of cold-working.The specification for the product may indicate limits for the differences between the lengths of thetwo diagonals.
4 There is evidence that some materials may be sensitive to the rate of straining which causes small changes inthe value of the yield stress.The corresponding effect on the termination of the formation of an indentation canmake alterations in the hardness value.