Fastener cold extrusion knowledge

The processing method of cold heading is to use the principle of plastic deformation of metal materials. At room temperature, the cold metal wire is put into the mold cavity of the cold heading machine, and under a certain external force and speed, the metal wire is forced to produce plastic flow.

Through the gap between the male mold and the female mold or the outlet of the female mold, the hollow, semi-hollow, or upsetting, diameter reduction and edge trimming can be used to obtain the desired shape and size. The essence of cold heading is metal plastic deformation.

The most difficult part in the plastic deformation process is the hollow long part, which is also a well-known difficulty in the cold heading industry. In the 1990s, limited by cold forging equipment, wire and heat treatment conditions, the aspect ratio (the ratio of the rod length to the inner hole diameter) could only reach 3-5 times.

However, with the continuous development of the industry, it has now reached 8-11 times. This is a bottleneck commonly believed by all cold forging people. Later, through continuous process improvements in equipment structure and mold design, the trial-produced length-to-diameter ratio reached 16 The length of hollow parts is expected to reach about 20 times in the future.