Toverify hardness testersto be in good working,with a given standard(ISO,JIS...)
1. 5tandard Blocks
To control various industrial hardness testers, it is important to verify all related factors , including indenters,static and dynamic loads, indentation measurement ,and sample pieces.Hardness blocks allow overall controlof these complicatedfactors in the field. Therfore,it is imperativethat a uniform surface hardness is displayed by all our test blocks,that the main factors of secular change are eliminated and,if possible, that the characteristics of their materialsare similar to those of materials in practical use.Our company, which was established in 1939 by 8hoichi Yamamoto , is the first dedicated manufacturer of standard test blocks in Japan,and has maintained its reputation as the bestand the foremost company in this field.
2. 150 9001 Quality 5ystem
We received a certificate dated December 26,1997,issued by Japan Quality Assurance Organization (JQA) , stating that Yamamoto's quality management system for hardness blocks complies with the requirements of the following
standards. The registercertificate No. is JQA-2078 180 9001-2000/ JI8 Q 9001:2000.
3. Characteristics of Our Hardness Blocks
Table 1 (back) shows detailed specifications of our test blocks and their materials.
Materials and manufacturing process To maintain one highly uniformsurface hardness , strict quality control of materials must be ensured for each test method. Our blocks are first cutfrom a plate material to avoid being affected bycenter segregation.Next,after machining to the required shapes ,heat treatment is carefully applied to the blocks to get a stable microstructure and the required hardness level. For such cases,a very accurate conversion relationship has beenalready obtained especially between 8hore hardness (H8), which is the Japanese original standa, and Vickers hardness(HV) values using eutectoid carbon steel.After heat treatment is completed , the blocks are ground , lapped,and then undergo a through
polishing process,followed by wet buffingto improve measuring precision and achieve the most accurateand consistent hardness
available in the world. Care is taken so that the surfece is not adversely affected,which could result in surface hardness irregularities ,and a routine microscopic structureinspection is performed as requiredacross the finished test surface for possiblevariations caused in the processes.
Hardness measurement of standard blocks Each 20-block lot that hasundergone heat
treatment and other finishing processes is suected to hardnesstests to checkfor variations in hardness,and to determinereliable,measurement-based reference values.
2. Integrated Precision of Hardness Testersand Hardness Blocks
Force, indenter,indentation measurement and
movement conditions, etc.,should be separately inspected to metrically verify the integrated
precision of hardnesstesters.
Industrial adjustments of these conditions
focus upon 180 standards.
On the other hand,indirect verification of a tester with test blocks is used to integrally verify these respective conditions . It is quite natural, therefore,the uncertainty factor due to the material to be additionally considered,aswell
as metrical accuracy values . We do our utmost in material selection, heat treatment,and other
processes to achieve the world's highest accuracy.(8ee Table 2.)
3. Best Use of Test Blocks
Choice of test blocks
Normally,the general accuracy of a tester needs to be indirectly verif ied with blocks for at least the three ranges -high,middle,andlow ranges of scales - in which a tester isbeing used. Routine inspections should be peormed with blocks in the high frequencyranges in use.