ISO 6507-2:2018 download.Metallic materials — Vickers hardness test — Part 2: Verification and calibration of testing machines.
1 Scope
ISO 6507-2 specifies a method of verification and calibration of testing machines and diagonal measuring system for determining Vickers hardness in accordance with ISO 6507-1.
A direct method of verification and calibration is specified for the testing machine, indenter and the diagonal length measuring system. An indirect verification method using reference blocks Is specified for the overall checking of the machine.
If a testing machine is also to be used for other methods of hardness testing, it shall be verified independently for each method.
ISO 6507-2 is also applicable to portable hardness testing machines but not applicable to hardness testing machines based on different measurement principles, e.g. ultrasonic impedance method.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of ISO 6507-2. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 376, Metallic materials — Calibration offorce-proving mstruments used for the verification of uniaxial testing machines
ISO 6507-1, Metallic materials — Vickers hardness test — Part 1: Test method
ISO 6507-3, Metallic materials — Vickers hardness test — Part 3: Calibration of reference blocks
3 Terms and definitions
No terms and definitions are listed in ISO 6507-2.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
c) the test force can be applied and removed without shock, vibration or overshoot and in such a manner that the readings are not influenced;
d) the diagonal measuring system:
1) ii integral with the machine, the change from removing the test force to measuring mode does not influence the readings;
2) the illumination device of the measuring microscope produces uniform lighting of the whole observed field with enough contrast between the indentation and the surrounding surface to determine the boundary clearly:
3) the centre of the indentation is in the centre of the field of view. if necessary.
NOTE The criteria specified in ISO 6507-2 for the performance of the testing machine have been developed and refined over a significant period of time. When determining a specific tolerance that the machine needs to meet, the uncertainty associated with the use ol measuring equipment and/or reference standards has been incorporated within this tolerance and it would therefore be inappropriate to make any further allowance for this uncertainty by. for example, reducing the tolerance by the measurement uncertainty. This applies to all measurements made when performing a direct or indirect verification of the machine,
5 Direct verification
5.1 General
5.1.1 Direct verification shall be conducted in accordance with the schedule given in Oause 7.
5.12 Direct verification involves:
a) calibration of the test force;
b) verification of the indenter
c) calibration and verification aithe diagonal measuring system:
d) verification of the testing cycle.
5.1.3 Direct verification should be carried out at a temperature of 123 ± 5) C. If the verification is
made outside this temperature range, this shall be stated in the verification report
5.1.4 The instruments used for verification and calibration shalt be traceable to national standards.
5.2 Calibration of the test force
5.2.1 Each test force used within the working rangeof the testing machine shall be measured. Whenever the indenter position affects the applied force, this shall be done at not less than three positions of the plunger uniformly spaced throughout its range of movement during testing.
For testing machines whose test force is shown not to be influenced by the position of the plunger, e.g. closed-loop controlled loading system, the test force can be calibrated In one position.
5.2.2 The test force shall be measured by one of the following methods:
— by means of an elastic proving device in accordance with Iso 376, class I or better:
— by balancing against a force, accurate to ±0,2 %, applied by means of calibrated masses or another method with the same accuracy.
5.5 VerIfication of the testing cycle
The testing cycle shall be timed with equipment having a maximum expanded uncertainty of 1 s. The timing values obtained shall fall within the limits set for the testing cycle in ISO 6507-1.
5.6 UncertaInty of calIbration/verIficatIon
Uncertainty of the calibration/verification results shall be determined. An example is given in AnnezA.
6 IndIrect verification
6.1 General
6.1.1 Indirect verification shall he conducted in accordance with the schedule given in CJausel.
6.12 Indirect verification involves verification of the overall performance of the testing machine by means of reference blocks calibrated in accordance with ISO 6507.3.
6.1.3 Indirect verification should be carried out at a temperature of (23 t 5) C. If the verification is made outside this temperature range, this shall be reported In the verification report.
6.1.4 The instruments used for verification and calibration shall be traceable to national standards.
6.2 Test force and hardness levels
The testIng machine shall be verified by testing reference blocks that have been calibrated in accordance with ISO 6507-3. The blocks shall have been calibrated using the same test forces that the machine will use for future testing. When verifying more than one test force, at least two reference blocks shall be selected from the hardness ranges specified below for each test force that the machine wIll be verified. The set of blocks needed for verifying the machine for all the test forces shall be chosen so that at least one reference block from each hardness range is used for the verifications. When verifying testing machines using only one test lorce, three reference blocks shall be used, one from each of the three hardness ranges specified below. The hardness ranges should be chosen, when possible, to replicate the hardness levels most commonly tested when using the specific test forces.
— <2SOHV
— 400HVto600l-IV
— >700HV.