Classification of heat treatment and test method of hardness

In view of the situation that the Brinell, Rockwell and Vickers hardness machines can not be used to test the hardness of large and heavy workpieces after heat treatment, this paper analyzes and discusses how to select the correct hardness testing methods to avoid quality problems.

Classification of heat treatment and test method of hardness

1. The hardness of heat-treated workpieces shall be tested by hardness tester. Phr series portable surface Rockwell hardness tester is very suitable for testing the hardness of surface heat-treated workpieces. It can test all kinds of surface heat-treated workpieces whose effective depth is more than 0.1mm. Easy to operate, easy to use, low price, direct reading hardness value.

2. The surface heat treatment can be divided into two categories, one is surface quenching heat treatment, the other is chemical heat treatment. The hardness test method is as follows: chemical heat treatment is to infiltrate one or several chemical elements into the workpiece surface, so as to change the chemical composition, texture and performance of the workpiece surface. After quenching and low temperature tempering, the surface of workpiece has high hardness, wear resistance and contact fatigue strength, while the core of workpiece has high strength and toughness.

3. The main technical parameters of the chemical heat treatment workpiece are the hardening depth and surface hardness. The depth of the hardened layer should be measured by Vickers hardness tester. Check the distance from the workpiece surface to the point where the hardness drops to 50HRC. This is that the surface hardness test of the effective hardening depth chemical heat treatment workpiece is similar to that of the surface quenching heat treatment workpiece, which can be tested by Vickers hardness tester, surface Rockwell hardness tester or Rockwell hardness tester, but the thickness of the nitriding thickness is relatively thin, generally no more than 0.7mm, at this time, Rockwell hardness tester can no longer be used. If the local hardness of parts is required to be high, induction heating and other methods can be used for local quenching heat treatment. 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. Rockwell hardness tester can be used to test HRC hardness. If the hardening layer of heat treatment is shallow, surface Rockwell hardness tester can be used to test hrn hardness.