Cold processing of steel pipes (such as cold drawn seamless tubes) includes methods such as cold rolling, cold drawing, cold tension reduction and spinning, which are the main methods for producing precision thin-walled and high-strength pipes. Among them, cold rolling and cold drawing are commonly used high-efficiency production methods for cold processing of steel pipes.
Compared with hot rolling, cold working has the following advantages:
It can produce large-diameter and thin-walled pipes; high geometric precision; high surface finish; it is helpful for grain refinement, and with the corresponding heat treatment system, high comprehensive mechanical properties can be obtained.
It can produce various special-shaped and variable-section characteristics and some materials with narrow thermal processing temperature range, low high-temperature toughness and good room temperature plasticity. The outstanding advantage of cold rolling is that it has a strong ability to reduce the wall, and can significantly improve the performance, dimensional accuracy and surface quality of incoming materials.
The area reduction rate of cold drawing is lower than that of cold rolling, but the equipment is simpler, the cost of tooling is less, the production is flexible, and the range of product shapes and specifications is also larger. Therefore, it is necessary to combine cold rolling and cold drawing methods reasonably on site. In recent years, cold tension reduction, welded pipe cold processing, and ultra-long pipe cold drawing technology can increase the output of the unit. Expand the range of varieties and specifications, improve the quality of welds, and provide suitable pipe materials for cold rolling and cold drawing. In addition, warm processing has received much attention in recent years, usually induction heating to 200 ℃ ~ 400 ℃, to improve the plasticity of the tube billet. The maximum elongation of warm rolling is about 2 to 3 times that of cold rolling; Increased by 30%, making it possible for some metals with low plasticity and high strength to be finished.
Although the specification range, dimensional accuracy, surface quality and microstructure of cold-worked tubes are superior to those of hot-rolled tubes, there are four problems in its production: high cycle times, long production cycle, large metal consumption and complex intermediate treatment process.
Due to the different materials, technical conditions and specifications of various steel pipes, the production process and
The process system is also different, but in general it consists of the following three main processes:
1) Pre-treatment for cold working, including preparations in three aspects: size, shape, structure and surface state;
2) Cold working, including cold drawing, cold rolling and spinning;
3) Finishing of finished products, including heat treatment, cutting, straightening and inspection of finished products.
