Pickling, annealing and low temperature tempering of seamless steel tubes

Keywords: seamless steel pipe pickling, annealing and low temperature tempering
Pickling of seamless steel tubes is a very widely used method for removing grease. It uses the principle of emulsification, wetting and penetration of surfactants, and uses the mechanical peeling effect of acid to corrode metals to generate hydrogen to achieve the purpose of removing grease. Acidic cleaners can be used at low and medium temperatures. Generally, only liquid oil can be removed at low temperature, and oil and grease can be removed at medium temperature. Generally only suitable for soaking treatment.

Seamless steel tube before pickling

The purpose of annealing seamless steel tube is to eliminate structural defects, improve the structure, make the composition uniform and refine the grain, improve the mechanical properties of the steel, reduce the residual stress; at the same time, it can reduce the hardness, improve the plasticity and toughness, and improve the machinability. machinability. Therefore, annealing is not only to eliminate and improve the structural defects and internal stress left by the previous process, but also to prepare for the subsequent process. Therefore, annealing belongs to the heat treatment of semi-finished products, also known as preheat treatment. After a certain degree of cold deformation processing, the mechanical properties of the chilled seamless steel tube are improved. The deformation degree of the semi-cold state is smaller than that of the cold-processed carbon steel tube, and the mechanical properties are between the soft state and the cold state, which is suitable for light processing.

Unannealed seamless steel tube, annealed or not depends on the delivery status required by the customer

The structure obtained by low temperature tempering is tempered martensite. The purpose is to reduce the internal stress and brittleness of the quenched seamless steel tube under the premise of maintaining the high hardness and high wear resistance of the quenched seamless steel tube, so as to avoid cracking or premature damage during use. Mainly used for various high carbon cutting tools, measuring tools, cold stamping dies, rolling bearings and carburized parts, etc. The hardness after tempering is generally HRC58-6 medium temperature tempering (250-500 degrees). Fire trotter. Its purpose is to obtain high yield strength, elastic limit and high toughness of seamless steel tubes. Therefore, it is mainly used for the treatment of various springs and hot work dies. The hardness after tempering is generally HRC35-50.