Classification and hardness testing methods for heat treatment plants

1. The hardness of the heat treated workpiece is tested by a hardness tester. PHR series portable surface Rockwell hardness tester is very suitable for detecting the hardness of surface heat treatment workpieces, and can test various surface heat treatment workpieces with an effective depth of more than 0.1mm. Simple operation, easy to use, low price, can directly read the hardness value.
2. Surface heat treatment is divided into two categories, one is surface quenching tempering heat treatment, the other is chemical heat treatment, and its hardness test method is as follows: chemical heat treatment is to make the surface of the workpiece penetrate into one or several chemical element atoms, thereby changing the chemical composition, structure and properties of the workpiece surface. After quenching and low-temperature tempering, the surface of the workpiece has high hardness, wear resistance and contact fatigue strength, and the core of the workpiece has high toughness.
3. The main technical parameters of chemical heat treatment workpieces are hardened layer depth and surface hardness. The depth of the hardened layer should still be detected with a Vickers hardness tester. Detects the distance from the surface of the workpiece to the point where the hardness drops to 50HRC. This is the effective hardening depth chemical heat treatment workpiece surface hardness test and surface quenching heat treatment workpiece hardness test is similar, can be used Vickers hardness tester, surface Rockwell hardness tester or Rockwell hardness tester to detect, but nitriding thickness thickness is thinner, generally not more than 0.7mm, then Rockwell hardness tester can no longer be used. If the local hardness of the part is high, the local quenching heat treatment can be carried out by induction heating and other methods, and such parts usually have to mark the location and local hardness value of the local quenching heat treatment on the drawing. The hardness test of the part is carried out in the specified area. Hardness testing instrument can use Rockwell hardness tester to test HRC hardness value, such as heat treatment hardening layer is shallow, can use surface Rockwell hardness tester to test HRN hardness value.
4. 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 hardening layer depth. Hardness testing can be done using Vickers hardness tester, or Rockwell or surface Rockwell hardness tester. The choice of test force (ruler) is related to the depth of the effective hardened layer and the surface hardness of the workpiece. Three types of hardness testers are involved here. Vickers hardness tester is an important means to test the surface hardness of heat treatment workpiece, it can choose 0.5~100kg test force, test the thickness of 0.05mm thick surface hardening layer, its accuracy is the highest, can distinguish the slight difference in workpiece surface hardness. In addition, the effective hardening layer depth is also tested by the Vickers hardness tester, so it is necessary to equip a Vickers hardness tester for units that perform surface heat treatment processing or use a large number of surface heat treatment workpieces.
5. Surface Rockwell hardness tester is also very suitable for testing the hardness of surface quenching workpieces, and there are three scales to choose from the surface Rockwell hardness tester. Various case-hardened workpieces with an effective hardening depth of more than 0.1mm can be tested. Although the accuracy of the surface Rockwell hardness tester is not as high as the Vickers hardness tester, it can meet the requirements as a means of quality management and qualification inspection of heat treatment plants. Moreover, it also has the characteristics of simple operation, easy to use, low price, rapid measurement, and direct reading of hardness value, and the use of surface Rockwell hardness tester can be used to quickly and non-destructive piece-by-piece testing of batch surface heat treatment workpieces. This is of great importance for metalworking and machine-building plants. When the surface heat treatment hardened layer is thick, a Rockwell hardness tester can also be used. When the thickness of the hardened layer is 0.4~0.8mm, the HRA scale can be used, and when the thickness of the hardened layer exceeds 0.8mm, the HRC scale can be used.
6. The three hardness values of Vickers, Rockwell and surface Rockwell can be easily converted into standards, drawings or hardness values required by users. The corresponding conversion tables are given in the international standard ISO, the American standard ASTM and the Chinese standard GB/T.