The product to be treated is kept immersed in a solution of sulfur-containing alkali metal salt at room temperature, and the product to be treated is used as an anode (+), and an iron sulfide layer of several μm is formed on the surface of the treated product through an electrochemical reaction. Iron sulfide has characteristics such as self-lubricating and oil-retaining properties, and has the effect of suppressing burns and abnormal wear of various iron sliding parts.

1. During the heat treatment process, too much or too little heat convection, or heating in the air or in the atmosphere, will affect the heat treatment process, resulting in deformation.

2. During the cooling process, due to the different cooling rates of each section of the material, a temperature difference is formed in each section, so that the volume shrinkage of each part of the material is different, so that thermal stress is formed. In addition, during the quenching process, during the transformation of the material from supercooled austenite to martensite, there is a change in specific volume, which forms a structural stress and causes phase transformation deformation.

3. The chemical composition of the heat treatment process itself, raw material defects, original group, heating factors, cooling factors, etc. may cause cracks in the material during the heat treatment process.