Mon, 22 Oct 2018 08:12:55 +0000
Surface quenching and tempering heat treatment
Surface quenching and tempering heat treatment is usually carried out by induction heating or flame heating. The main technical parameters are surface hardness, local hardness and effective hardened layer depth. Hardness testing can be done with Vivtorinox hardness tester or Rockwell or surface Rockwell hardness tester. The selection of test force (ruler) is related to the depth of effective hardened layer and the hardness of workpiece surface. There are three kinds of hardness gauges.
1. Vickers hardness tester is an important means to test the surface hardness of heat-treated workpiece. It can choose the test force of 0.5-100kg to test the surface hardening layer which is thin to 0.05mm thick. Its precision is the highest. It can distinguish the small difference of surface hardness of heat-treated workpiece. In addition, the effective hardening depth should also be measured by Vickers hardness tester, so it is necessary to equip a Vickers hardness tester for surface heat treatment processing or a large number of surface heat treatment workpieces.
2. Surface Rockwell hardness tester is also very suitable for testing the hardness of surface hardened workpiece. There are three kinds of scales for surface Rockwell hardness tester. All kinds of hardened parts with effective hardening depth exceeding 0.1mm can be tested. Although the accuracy of the surface Rockwell hardness tester is not as high as that of the Vickers hardness tester, it has been able to meet the requirements as a means of quality management and qualification inspection in heat treatment plants. Moreover, it has the characteristics of simple operation, convenient use, low price, rapid measurement, and can directly read the hardness value. The surface Rockwell hardness tester can be used to detect batches of surface heat treatment workpieces rapidly and nondestructively. This is of great significance for Metalworking and machinery manufacturing plants.
Three. When the surface heat treatment hardening layer is thicker, the Rockwell hardness tester can also be adopted. HRA scale can be used when the thickness of heat treatment hardened layer is between 0.4 mm and 0.8 mm, and HRC scale can be used when the thickness of hardened layer exceeds 0.8 mm.
The hardness values of Vickers, Rockwell and Surface Rockwell can be easily converted into standard, drawings or hardness values required by users. The corresponding conversion tables have been given in international standard ISO, American Standard ASTM and China standard GB/T.