There are three types of hardness testing standards for well furnace, including Vickers, Rockwell and surface Rockwell. According to the same way of heat treatment, the hardness test methods of surface quenching reheating heat treatment furnace and chemical heat treatment furnace are also different.
The main technical parameters of chemical heat treatment workpiece are hardening layer and surface hardness. The hardened layer shall be tested by Vickers hardness tester. Check the distance from the workpiece surface to the point where the hardness drops to 50HRC. This is hardening.
Chemical heat treatment is to infiltrate one or more atoms of chemical elements into the workpiece surface, so as to change 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, while the core of the workpiece has high strength and toughness.
The surface hardness test of chemical heat treatment workpiece is similar to that of surface quenching heat treatment workpiece. Vickers hardness tester, surface Rockwell hardness tester or Rockwell hardness tester can be used to test, but the thickness of nitriding thickness is thin, generally no more than 0.7mm. At this time, Rockwell hardness tester can no longer be used.
If the local hardness requirements of parts are high, local quenching heat treatment can be carried out by means of induction heating. For such parts, the location of local quenching heat treatment and local hardness value shall be marked on the drawing. The hardness test of parts shall be carried out in the designated area. The hardness testing instrument can use Rockwell hardness tester to test the HRC hardness value. If the heat treatment hardened layer is shallow, the surface Rockwell hardness tester can be used to test the hrn hardness value.
The surface quenching and reheating heat treatment of well furnace is usually carried out by induction heating or flame heating. The main technical parameters are surface hardness, local hardness and hardened layer. Vickers hardness tester, Rockwell or surface Rockwell hardness tester can be used for hardness testing. The selection of test force (scale) is related to the hardness of hardened layer and workpiece surface. There are three kinds of durometer involved here.
Vickers hardness tester is an important means to test the surface hardness of heat-treated workpiece. It can use the test force of 0.5 ~ 100kg to test the surface hardened layer as thin as 0.05mm. Its accuracy is high and can distinguish the small difference of workpiece surface hardness. In addition, the hardened layer should also be tested by Vickers hardness tester. Therefore, it is necessary to equip a Vickers hardness tester for units that conduct surface heat treatment or use surface heat treatment workpieces in large quantities.
The surface Rockwell hardness tester is also very suitable for testing the hardness of surface hardened workpieces. There are three scales for the surface Rockwell hardness tester. It can test various surface hardened workpieces with hardening depth of more than 0.1mm. Although the accuracy of the surface Rockwell hardness tester is not as high as that of the Vickers hardness tester, it can meet the requirements as a testing means for quality management and qualification inspection of the heat treatment plant. Moreover, it also has the characteristics of simple operation, convenient use, low price, rapid measurement and direct reading of hardness value. The surface Rockwell hardness tester can be used to quickly and nondestructive test the surface heat treated workpieces in batches one by one. This is of great significance for metal processing and machinery manufacturing factories.
Rockwell hardness tester can also be used when the surface heat treatment hardening layer of well furnace is thick. When the thickness of the hardened layer is 0.4 ~ 0.8mm, HRA scale can be used. When the thickness of the hardened layer exceeds 0.8mm, HRC scale can be used.
Vickers, Rockwell and surface Rockwell hardness values can be easily converted into standards, drawings or hardness values required by users. The corresponding conversion tables have been given in international standard ISO, American Standard ASTM and Chinese standard GB / T.
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