Screw Heat treatment
Cold forging bolts are usually made of materials with hardness suitable for plastic processing. Materials with high carbon content or alloying elements are not easy to process because of their hard material. Therefore, some materials need to be annealed to soften the material. Most materials can not meet the required strength in cold forging. Heat treatment is the treatment after cold forging and pressing. It can make the bolt have the required strength and mechanical properties. It is the most important process in the bolt manufacturing process.
Bolts can be classified into various strength grades according to their position and use. According to the respective standards of JIS, ISO and automobile manufacturers, mechanical properties such as hardness and tensile strength can be specified according to each strength grade. In order to make the formed bolts have the required mechanical properties, heat treatment (quenching and tempering) was carried out.