Testing method of heat treatment hardness of the h

The hardness test method of tool heat treatment

surface heat treatment is divided into two categories, one is surface quenching and tempering heat treatment, and the other is chemical heat treatment. The hardness test methods are as follows:

1. Surface quenching and tempering heat treatment

surface quenching, tempering heat treatment is usually carried out 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 testing, and Rockwell 2, uneven installation of the main machine or surface Rockwell hardness tester can also be used. The selection of test force (scale) is related to the effective hardened layer depth and workpiece surface hardness. There are three kinds of durometers involved here

Vickers hardness tester is an important means to test the surface hardness of heat-treated workpieces. It can use a test force of 0.5 ~ 100kg to test the surface hardened layer as thin as 0.05mm. Its accuracy is the highest, and it can distinguish the small difference in the surface hardness of heat-treated workpieces. In addition, the effective hardened layer depth should also be tested by Vickers hardness tester. Therefore, it is necessary to equip a Vickers hardness tester for units that carry out surface heat treatment processing or use a large number of surface heat treated workpieces

the surface Rockwell hardness tester is also very suitable for testing the hardness of surface quenched workpieces. There are three scales for the surface Rockwell hardness tester. It can be used to test various surface hardened workpieces with an effective hardening depth of more than 0.1mm. Although the table can not only effectively reduce the carbon footprint in the production process, the accuracy of Rockwell hardness tester is not as high as that of Vickers hardness tester, but as a testing method for quality management and qualification inspection of heat treatment plants, it has been able to meet the requirements. Moreover, it also has the characteristics of simple operation, convenient use, low price, rapid measurement and direct reading of hardness value. Using the surface Rockwell hardness tester, it can quickly and non destructively detect the surface heat-treated workpieces in batches. This is of great significance for metal processing and machinery manufacturing plants

when the surface heat treatment hardening layer is thick, Rockwell hardness tester can also be used. When the thickness of the hardened layer of heat treatment is 0, especially the dispersion is uneven HRA scale can be used when the thickness of hardened layer is more than 0.8mm, and HRC scale can be used when the thickness of hardened layer is more than 0.8mm

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 the international standard ISO, American Standard ASTM and Chinese standard GB/T. These three conversion tables can be found in the technical data column of Shenyang Tianxing station

2. Chemical heat treatment

chemical heat treatment is to make the surface of the workpiece first infiltrate the atoms of one or more chemical elements on the high-temperature expansion surface, so as to change the chemical composition, structure and performance 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 main technical parameters of chemical heat treatment workpiece are the depth of hardened layer and surface hardness. The depth of hardened layer should be tested by Vickers hardness tester. Check the distance from the workpiece surface to the point where the hardness drops to 50HRC. This is the effective hardening depth

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 relatively thin, generally no more than 0.7mm. At this time, Rockwell hardness tester can no longer be used

3. Local heat treatment

if the local hardness requirements of parts are high, local quenching heat treatment can be carried out by means of induction heating. Such parts usually need to mark the location of local quenching heat treatment and local hardness value 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 hardening layer is shallow, the surface Rockwell hardness tester can be used to test the hrn hardness value