company news about SPHEROIDIZING ANNEALING PROCESS OF CHQ WIRES FOR MAKING FASTENERS

The steel used for manufacturing fasteners and connectors (such as bolts, nuts, screws, rivets, etc.) with cold heading processing method is called cold heading steel, simplified as CHQ wire.

Cold heading is the process of utilizing metal plastic forming at room temperature. Using cold heading technology to manufacture fasteners not only has high efficiency and good quality, but also saves materials and has low costs. However, the cold heading process requires high quality of raw materials.

Cold heading performance is one of the important properties of cold heading steel. The main properties that cold heading steel should possess are good cold formability; For cold heading steel deformation, it is necessary to have as little resistance as possible and as high deformation capability as possible. For this reason, it is generally required that the yield strength ratio of cold heading steel be between 0.5 and 0.65, and the cross-sectional shrinkage rate be >50%. In addition, to avoid surface cracking during cold heading, it is required that the surface quality of the steel be good, and the decarburization of the steel surface should be minimized as much as possible. High quality carbon steel is often used. If the carbon steel content of the steel is more than 0.25%, spheroidization annealing heat treatment should be carried out to improve the cold heading performance of the steel.

Spheroidization annealing furnace helps to provide an annealing process performed to spheroidize carbides in steel. The main purpose is to generate a spheroidized structure, which is the steel structure with best plasticity and lowest hardness. The steel is heated to 20-30 ℃ higher than Ac1 degree, and kept heat insulation for a period of time, and then slowly cooled to obtain a structure of spherical or granular carbides uniformly distributed on the ferrite matrix.

With the spheroidizing annealing process, the CHQ wire can be used to produce high strength fasteners such as 8.8 Grade, 10.9 Grade fasteners.