There is uneven deformation in the seamless steel pipe during cold drawing, which generates additional stress. After cold drawing, this additional stress becomes residual stress and remains in the pipe. Boiler tubes can be used in pipelines, thermal equipment, machinery industry, petroleum geological exploration, containers, chemical industry and special purposes. The degree of uneven deformation of the seamless steel pipe determines the size and distribution of its residual stress.
The cold drawing deformation of seamless steel pipe is determined by its deformation characteristics. Steel pipes are divided into cold-galvanized steel pipes and hot-dip galvanized steel pipes. Cold-galvanized steel pipes have been banned, and the latter has been advocated by the state to be temporarily usable. In the 1960s and 1970s, developed countries in the world began to develop new pipes and gradually banned galvanized pipes. Steel plates are classified according to professional use, such as plates for oil drums, enamel plates, bulletproof plates, etc.; according to surface coating, there are galvanized sheets, tinned sheets, lead-plated sheets, plastic composite steel sheets, etc. Steel pipe anti-corrosion is a type of coating with drying oil as the main film-forming substance. It is characterized by easy production, good brushability, good wettability to the surface, low price, and flexible paint film; but the paint film dries slowly, soft, poor mechanical properties, acid and alkali resistance, water resistance and water resistance. Organic solvents are poor. Drying oil is often combined with antirust pigments to form antirust paint, which is used in atmospheric environments with low corrosion resistance requirements. Since there is no mandrel involved in the processing of the pipe wall during the empty drawing process, and the thickness of the pipe wall does not change much after deformation, resulting in great differences in the deformation conditions and deformation states of the inner and outer layers of the seamless steel pipe, resulting in uneven deformation.
During the deformation process, since the metal near the inner surface of the seamless steel pipe first enters a plastic deformation state, and the metal is not affected by the resistance generated by friction when it flows in the axial direction, the inhomogeneity of its axial deformation along the wall thickness direction appears, As a result, the natural extension of the outer layer of the seamless steel pipe is significantly lower than that of the inner layer. Seamless steel pipes are steel pipes made of a single piece of metal with no seams on the surface, called seamless steel pipes. According to the production method, seamless pipes are divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes, extruded pipes, and jacking pipes. In this way, the axial and tangential additional tensile deformation and additional tensile stress generated in the outer layer of the seamless steel pipe reach the maximum value; on the contrary, the axial and tangential additional compressive deformation and compressive stress generated in the inner layer of the seamless steel pipe also When the maximum value is reached, the additional stress remains in the tube as residual stress after deformation.
