Cold processing of steel

At room temperature or below the recrystallization temperature, through mechanical force, the steel produces the required permanent plastic deformation, and the process of obtaining the required sheet or section steel is called cold processing, including cutting, punching, drilling, planing and other cutting processing. Cold-rolled coil plate and cold-tied steel plate are the products obtained by further processing of hot-tied coil plate or hot-tied sheet light strip steel cold binding machine. Cold-formed thin-wall steel and molded steel plates, which are widely used in light steel structures, are also transversely pressed; Made of cold bending or binding. The basic material of parallel steel wire bundle, steel strand or steel wire rope, such as high-strength steel wire, is made of heat-treated high-quality carbon structural steel plates after many continuous cold drawing.

After cold working, the steel has different degrees of plastic deformation, the metal grain elongates along the deformation direction, the local grain breaks, the dislocation density increases, and the participating stress increases. Steel after cooling processing, will produce partial or overall hardening.

Local or integral hardening, that is, the strength and hardness of the steel is increased locally or as a whole, but the plasticity and toughness are reduced, this phenomenon is called cold hardening (or strain hardening). Cold-drawn high-strength steel wire makes full use of the cold hardening phenomenon and is widely used in suspension cable structures. In the strength checking calculation of cold-formed thin-wall steel structure, the strength increase caused by cold bending effect can be used conditionally. However, for steel members with complex sections, they cannot be used. On the contrary, steel becomes brittle due to cold hardening, which often becomes the cause of brittle fracture of steel structures. Therefore, for more important structures, the occurrence of local cold work hardening should be avoided as far as possible.