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 the atom that penetrates the surface of a workpiece into one or more chemical elements, thereby changing the chemical composition, organization, and properties of the surface of the workpiece. After quenching and tempering at low temperature, the surface of the workpiece has high hardness, wear resistance and contact fatigue strength, while the core of the workpiece has high toughness.
The main technical parameters of the chemical heat treatment workpiece are the depth of the hardened layer and the surface hardness. Depth of hardened layer is still measured by Vickers hardness tester. The distance from the surface of the workpiece to the point where the hardness drops to 50HRC is detected. This is the effective hardening depth of chemical heat treatment of the workpiece surface hardness test and surface hardening heat treatment workpiece hardness testing is similar, can use Vickers hardness tester, surface Rockwell hardness tester or Rockwell hardness tester to detect, but the thickness of nitriding thicker Thin, generally not more than 0.7mm, then Rockwell hardness tester can no longer be used.
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 hardened layer depth. Vickers hardness tester can be used for hardness test, Rockwell or Rockwell hardness tester can also be used. The choice of test force (scale) is related to the effective hardened layer depth and the surface hardness of the workpiece. There are three hardness scales involved here.
Vickers hardness tester is an important means to test the surface hardness of the heat treatment workpiece, it can use 0.5 to 100kg of test force, test thin to 0.05mm thick surface hardening layer, its accuracy is the highest, can distinguish the heat treatment workpiece surface hardness The slight difference. In addition, the effective hardened layer depth is also detected by the Vickers hardness tester. Therefore, it is necessary to provide a Vickers hardness tester for the unit that performs the surface heat treatment process or uses a large number of surface heat-treated workpieces.
Surface Rockwell hardness tester is also very suitable for testing the hardness of surface quenched workpieces. The surface Rockwell hardness tester can be selected with three scales. It is possible to test various hardened workpieces with an effective hardening depth of more than 0.1 mm. 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 control and inspection of the heat treatment plant. Moreover, it also has the characteristics of simple operation, convenient use, low price, rapid measurement, direct reading of hardness value, etc., and the use of surface Rockwell hardness tester can quickly and non-destructively detect each piece of surface heat-treated workpieces. This is important for metal processing and machinery manufacturing plants.
Rockwell hardness tester can also be used when the surface heat treatment hardening layer is thick. When the heat-treated hardened layer thickness is 0.4-0.8mm, the HRA ruler can be used. When the hardened layer thickness exceeds 0.8mm, the HRC ruler can be used.
The three hardness values ​​of Vickers, Rockwell, and Rockwell can be easily converted to each other and converted to standard, drawing, or user-desired hardness values. Corresponding conversion tables are given in the International Standard ISO, American Standard ASTM and Chinese Standard GB/T. The three conversion tables can be found in the technical information section of the Shenyang Star Website.
3, local heat treatment
If the local hardness of the part is required to be higher, the partial quenching heat treatment may be performed by means of induction heating. Such parts usually have the location of the local quenching heat treatment and the local hardness value on the drawing. Hardness testing of parts is performed within the specified area. The hardness tester can use Rockwell hardness tester to test the HRC hardness value. If the heat treatment hardened layer is lighter, the Rockwell hardness tester can be used to test the HRN hardness value.
1, chemical heat treatment
Chemical heat treatment is the atom that penetrates the surface of a workpiece into one or more chemical elements, thereby changing the chemical composition, organization, and properties of the surface of the workpiece. After quenching and tempering at low temperature, the surface of the workpiece has high hardness, wear resistance and contact fatigue strength, while the core of the workpiece has high toughness.
The main technical parameters of the chemical heat treatment workpiece are the depth of the hardened layer and the surface hardness. Depth of hardened layer is still measured by Vickers hardness tester. The distance from the surface of the workpiece to the point where the hardness drops to 50HRC is detected. This is the effective hardening depth of chemical heat treatment of the workpiece surface hardness test and surface hardening heat treatment workpiece hardness testing is similar, can use Vickers hardness tester, surface Rockwell hardness tester or Rockwell hardness tester to detect, but the thickness of nitriding thicker Thin, generally not more than 0.7mm, then Rockwell hardness tester can no longer be used.
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 hardened layer depth. Vickers hardness tester can be used for hardness test, Rockwell or Rockwell hardness tester can also be used. The choice of test force (scale) is related to the effective hardened layer depth and the surface hardness of the workpiece. There are three hardness scales involved here.
Vickers hardness tester is an important means to test the surface hardness of the heat treatment workpiece, it can use 0.5 to 100kg of test force, test thin to 0.05mm thick surface hardening layer, its accuracy is the highest, can distinguish the heat treatment workpiece surface hardness The slight difference. In addition, the effective hardened layer depth is also detected by the Vickers hardness tester. Therefore, it is necessary to provide a Vickers hardness tester for the unit that performs the surface heat treatment process or uses a large number of surface heat-treated workpieces.
Surface Rockwell hardness tester is also very suitable for testing the hardness of surface quenched workpieces. The surface Rockwell hardness tester can be selected with three scales. It is possible to test various hardened workpieces with an effective hardening depth of more than 0.1 mm. 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 control and inspection of the heat treatment plant. Moreover, it also has the characteristics of simple operation, convenient use, low price, rapid measurement, direct reading of hardness value, etc., and the use of surface Rockwell hardness tester can quickly and non-destructively detect each piece of surface heat-treated workpieces. This is important for metal processing and machinery manufacturing plants.
Rockwell hardness tester can also be used when the surface heat treatment hardening layer is thick. When the heat-treated hardened layer thickness is 0.4-0.8mm, the HRA ruler can be used. When the hardened layer thickness exceeds 0.8mm, the HRC ruler can be used.
The three hardness values ​​of Vickers, Rockwell, and Rockwell can be easily converted to each other and converted to standard, drawing, or user-desired hardness values. Corresponding conversion tables are given in the International Standard ISO, American Standard ASTM and Chinese Standard GB/T. The three conversion tables can be found in the technical information section of the Shenyang Star Website.
3, local heat treatment
If the local hardness of the part is required to be higher, the partial quenching heat treatment may be performed by means of induction heating. Such parts usually have the location of the local quenching heat treatment and the local hardness value on the drawing. Hardness testing of parts is performed within the specified area. The hardness tester can use Rockwell hardness tester to test the HRC hardness value. If the heat treatment hardened layer is lighter, the Rockwell hardness tester can be used to test the HRN hardness value.
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