ISO 6507-3:2018 pdf download – Metallic materials – Vickers hardness test — Part 3: Calibration of reference blocks
ISO 6507-3:2018 pdf download – Metallic materials – Vickers hardness test — Part 3: Calibration of reference blocks.
Measurement uncertainty analysis is a useful tool to help determine sources of error and to understand differences between measured values. This annex gives guidance on uncertainty estimation but the values derived are for information only, unless sperifically Instructed otherwise by the customer. The criteria specified in this document ror the performance of the testing machine have been developed and refined over a significant period or time. When determining a specific tolerance that the machine needs to meet, the uncertainty associated with the use of 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. In each case, it is simply the measured value resulting from the use of the specified measuring equipment and/or reference standards that Is used Lu assess whether or not the machine complies with this document. However, there may be special circumstances where reducing the tolerance by the measurement uncertainty is appropriate. This should only be done by agreement of the parties involved.
The metrological chain necessary to define and disseminate hardness scales is described in ISO 6507-1.
A.2 Direct verification of the hardness-calibration machine
A.2.1 Calibration of the test force
See ISO 6507-2.
A.2.2 Calibration of the diagonal measuring device
See ISO 6507.2.
A.2.3 Verification of the indenter
See ISO 6507-2.
A.2.4 Verification of the test cycle
See ISO 6507-2.
A.3 Indirect verification of the hardness-calibration machine
NOTE In this annex, the index certiuicd reference material” (CRM) means, according to the definitions of the hardness testing standards. hardness reference block’.
By the indirect verification with primary hardness-reference blocks calibrated by the national-level calibration agency (see ISO 6507-1), the overall function of the hardness calibration machine is checked and the repeatability, as well as the deviation of the hardness-calibration machine from the actual hardness value, are determined.
The reference blocks shall be free of magnetism. It is recommended that the manufacturer shall ensure that the blocks. if made of steel, have been demagnetized at the end of the manufacturing process (before calibration).
4.5 Flatness and parallelism
The maximum deviation in flatness of the test and support surfaces shall not exceed 0.005 mm. The maximum error In parallelism shall not exceed 0.010 mm in 50 mm.
4.6 Surface roughness
The test surface shall be free from scratches that interfere with the measurement of the indentations. The test surface roughness. R1., shall not exceed 0,05 urn.1’1 The bottom support surface shall be a finely ground finish or better.
4.7 Prevention of the regrind of the test surface
To verify that no material has been subsequently removed from the reference block, its thickness at the time of calibration shall be marked on the reference block to the nearest 0,01 mm or an Identifying mark shall be made on the test surface Isee Clause 9 e)].
5 Calibration machine
In addition to fulfilling the general requirements specified in ISO 6507-2, the calibration machine shall also meet the requirements given in 52 to 5..
NOTE The criteria specified In this document for the performance of the ealtbrntlon 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 of 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 verification of the calibration machine.
5.2 Direct verification
The calibration machine shall be verified directly at intervals not exceeding 12 months. Direct verification involves
a) verification of the test force,
b) verification of the indenter,
c) calibration and verification of the diagonal measuring system, and
d) verification of the testing cycle; If this is not possible, at least the force versus time behaviour.
5.3 Traceability of verification instruments
The instruments used for verification and calibration shall be traceable to national standards.