Hard inspection method for chemical heat treatment and surface quenching and tempering
Surface heat treatment is divided into two categories, one is chemical heat treatment and the other is surface quenching and tempering heat treatment. The hardness test method is as follows:
1. Chemical heat treatment
Chemical heat treatment is to make the workpiece surface infiltrate one or several chemical elements of the atom, thereby changing the workpiece surface chemical composition, organization and performance.After quenching and tempering, the surface of the workpiece has high hardness, wear resistance and contact fatigue strength, and the core of the workpiece has high toughness.
The main technical parameters of chemical heat treatment workpiece are the depth of hardened layer and surface hardness.The depth of the hardened layer is still determined by a vickers hardness tester.Detect the distance from the surface of the workpiece to the point where the hardness is reduced to 50HRC.This is the effective depth of hardening chemical heat treatment of workpiece surface hardness testing and surface heat treatment quenching hardness testing, can use vickers hardness tester, surface rockwell hardness tester or rockwell hardness tester to test, only the thickness of nitriding thick thin, generally not more than 0.7 mm, is no longer using rockwell hardness tester.
2. Surface quenching and tempering heat treatment
Surface quenching and tempering heat treatment is usually performed by induction heating or flame heating.The main technical parameters are surface hardness, local hardness and effective depth of hardened layer.The hardness test can be done by vickers hardness tester, or by rockwell hardness tester or surface rockwell hardness tester.The selection of test force (scale) is related to effective hardening depth and workpiece surface hardness.There are three types of durometer involved here.
The vickers hardness tester is an important means to test the surface hardness of the heat-treated workpiece. It can choose the test force of 0.5 ~ 100kg to test the surface hardening layer of the workpiece thin to 0.05mm thick. It has the highest accuracy and can distinguish the slight difference of the surface hardness of the heat-treated workpiece.In addition, the effective depth of the hardening layer is also detected by the vickers hardness tester, so it is necessary to have a vickers hardness tester for the units that conduct surface heat treatment or use a large number of surface heat treatment workpieces.
The surface rockwell hardness tester is also very suitable for testing the hardness of surface hardened workpiece.Various surface hardened workpieces whose effective hardening depth exceeds 0.1mm can be tested.Although the precision 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 qualified inspection in the heat treatment plant.In addition, it is easy to operate, easy to use, low price, rapid measurement and direct reading of hardness values. By using the surface rockwell hardness tester, it can be used to quickly and nondestructive testing of the surface heat treatment workpieces.This is of great significance to metal processing and machinery manufacturing plants.
When the surface heat treatment hardening layer is thicker, the rockwell hardness tester can also be used.HRA scale can be used when the thickness of heat treatment hardening layer is between 0.4 and 0.8mm, and HRC scale can be used when the thickness of hardening layer is over 0.8mm.
The three hardness values of vickers, rockwell and surface rockwell can be easily converted into standard, drawing or required by the user.Corresponding conversion tables are given in ISO, ASTM and GB/T.These three conversion tables can be found in the technical data column of shenyang tianxing website.
3. Local heat treatment
For parts with high local hardness requirements, local quenching heat treatment can be carried out by induction heating, etc. Such parts usually need to indicate the location of local quenching heat treatment and local hardness value on the drawing.The hardness test of the part should be carried out in the designated area.The hardness tester can use the rockwell hardness tester to test the HRC hardness value. For example, the surface rockwell hardness tester can be used to test the HRN hardness value if the hardening layer of heat treatment is shallow.