ISO HARDNESS STANDARDS INDENTATION HARDNESS TESTS AND HARDNESS STANDARD BLOCKS

摘要

ISO standards for hardness are established from metrological standards for force, length, etc. and daily control requirements via hardness standard blocks. The authors have already stated that the unification of loading speed via ISO standards is important both industrially and economically. In consideration of the international importance of ISO standards for hardness testing, the authors review the current ISO specifications in this report, particularly their definition of loading speed, tolerances for Rockwell reference loads, and other test-block requirements, based on our own experiments. Although it may be necessary to have continuous experimental findings using various hardness testers and test blocks, the following conclusions can be said at present. (1) As a result of reviewing the basis of defining test force application, it can be generally concluded that LRT would be more appropriate than the indentation velocity as a basis of defining the test force application for indentation hardness tests. (2) Considering the experiment results and the present situation concerning testing machine and method, the tolerances for the first and second reference loads for Rockwell hardness should be specified independently, and it may be necessary to loosen the tolerance for the second reference load. (3) In the future, it is hoped that the test load tolerances for overall indentation hardness tests will be reviewed by studying the method of testing the dynamic load being applied during hardness testing, rather than the checking mass of weight or static load. (4) As regards the ISO requirement for hardness block thickness, it is desirable that that for micro Vickers blocks should be 5 mm or more, and that for non-ferrous HR blocks should be 7 mm or more, based on a through consideration of the characteristics of individual testing methods, test forces, and block materials, as is the case with JIS standards. (5) It has been confirmed that high-precision hardness blocks play an important role in the experimental verification of various aspects of hardness testing.