1, The hardness of the heat treatment workpiece is tested by the hardness tester. PHR series portable surface Rockwell hardness tester is very suitable for testing the hardness of surface heat treatment workpiece, can test the effective depth of more than 0.1mm surface heat treatment workpiece. Simple operation, easy to use, low price, can directly read the hardness value.
2, The surface heat treatment is divided into two categories, one is the surface quenching and tempering heat treatment, the other is the chemical heat treatment, the hardness test method is as follows: chemical heat treatment is to make the surface of the workpiece into one or several chemical elements of the atom, thereby changing the chemical composition, organization and performance of the surface of the workpiece. After quenching and low temperature tempering, the workpiece surface has high hardness, wear resistance and contact fatigue strength, and the core of the workpiece has high strength and toughness.
3. The main technical parameters of the chemical heat treatment workpiece are the depth of the hardened layer and the surface hardness. The depth of the hardened layer is still tested by the Vickers hardness tester. Measure the distance from the surface of the workpiece to the point at which the hardness drops to 50HRC. This is the effective hardening depth of the surface hardness test of chemical heat treatment workpiece and surface hardening heat treatment workpiece hardness test is similar, can be used to test Vickers hardness tester, surface Rockwell hardness tester or Rockwell hardness tester, but the thickness of nitrided thickness is thinner, generally not greater than 0.7mm, then can no longer use Rockwell hardness tester. Parts if the local hardness requirements are high, can be used induction heating and other ways for local hardening heat treatment, such parts are usually marked on the drawing of the local hardening heat treatment location and local hardness value. The hardness test of the part should be carried out in the specified area. Rockwell hardness tester can be used to test HRC hardness value. If the heat treatment hardening layer is shallow, Rockwell hardness tester can be used 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. The hardness test can be used by Vickers hardness tester, Rockwell or surface Rockwell hardness tester. The selection of the test force (scale) is related to the effective hardening layer depth and the workpiece surface hardness. There are three kinds of hardness gauges involved. 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 surface hardening layer as thin as 0.05mm thick, its accuracy is the highest, can distinguish the small difference in the surface hardness of the workpiece. In addition, the depth of the effective hardening layer is also measured 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, The surface Rockwell hardness tester is also very suitable for testing the hardness of surface hardening workpiece, the surface Rockwell hardness tester has three kinds of scales to choose from. A wide range of surface hardened workpieces with an effective hardening depth of more than 0.1mm can be tested. Although the precision of the surface Rockwell hardness tester is not as high as the Vickers hardness tester, it has been able to meet the requirements as a testing means for quality management and qualification inspection of heat treatment plants. Moreover, it also has the characteristics of simple operation, convenient use, low price, rapid measurement, can directly read the hardness value, etc., the use of surface Rockwell hardness tester can be used for a batch of surface heat treatment workpiece for rapid and non-destructive piece by piece detection. This is important for metal processing and machinery manufacturing plants. When the surface heat treatment hardening layer is thicker, 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 is more than 0.8mm, the HRC scale can be used.
6, Vickers, Rockwell and surface Rockwell three hardness values can be easily converted to each other, converted into standards, drawings or user needs hardness values. The corresponding conversion table has been given in the international standard ISO, the American standard ASTM and the Chinese standard GB/T.