Inspection items and methods of heat treatment

This paper summarizes the experience of using indentation hardness test and conductivity test methods of commonly used aluminum alloy materials and steel parts in foreign subcontracting production, and discusses how to effectively control and prevent the heat treatment deformation of parts through examples, so as to make the heat treated parts meet the requirements of engineering design drawings.

Inspection items and methods of heat treatment

1. When the heat treatment parts enter the factory, the corresponding heat treatment inspection records attached by the supplier shall be inspected to confirm whether the records meet the relevant technical requirements.

2. Selection principle of hardness testing instrument:

(1) Cast iron products (gray iron, ductile iron, etc.) shall be tested by Brinell hardness tester or Vickers and Leeb hardness tester, but not by Rockwell or surface Rockwell hardness tester.

(2) All kinds of steel parts can choose appropriate testing instruments according to product characteristics: Brinell, Rockwell, Vickers or Leeb hardness tester, etc.

(3) For thin-walled parts (with thickness less than 2mm) and non-ferrous metals, Vickers, Richter or surface Rockwell hardness tester shall be used, but Brinell hardness tester shall not be used for testing.

3. In order to get more accurate test results, the test parts of the parts shall be polished and polished, and the surface finish shall be above Ra1.6. (when testing finished parts or parts that are not allowed to be polished on the surface, surface grinding shall not be carried out first and surface inspection shall not be affected directly on the parts. If the test result is unqualified, destructive grinding test shall be carried out. If it is qualified after grinding, it shall be determined as qualified.)

4. In principle, each part shall be tested for at least four points, and the average value shall be taken as the evaluation result. (except for parts that are small or cannot take multiple points)

5. When decarburization occurs on the surface of heat treated parts, the surface of parts shall be ground to a depth of 0.5-2mm before testing.