The reasons for the deformation of carbon seamless steel pipes are often complicated, but as long as we master the laws of deformation, analyze the causes, and use different methods to prevent the deformation of the mold, it can be reduced and controlled. In general, the heat treatment deformation of seamless steel pipes can be prevented by the following methods.
(1) Reasonable selection of materials. For seamless steel pipes, micro-deformation die steels (such as air-quenched steels) with good quality should be selected, and die steels with serious carbide segregation should be reasonably forged and quenched and tempered. Refinement heat treatment.
(2) The design of the mold structure should be reasonable, the thickness of the seamless steel pipe should not be too large, and the shape should be symmetrical. For the mold with large deformation, the deformation law should be mastered, and the machining allowance should be reserved. For large and seamless steel pipes, a combined structure can be used.
(3) The seamless steel pipe should be pre-heated to eliminate the residual stress generated during the machining process.
(4) Reasonably select the heating temperature and control the heating speed. For the seamless steel pipe, slow heating, preheating and other balanced heating methods can be adopted to reduce the heat treatment deformation of the mold.
(5) On the premise of ensuring the hardness of the mold, try to use pre-cooling, graded cooling and quenching or warm quenching processes.
(6) For seamless steel pipes, vacuum heating and quenching and cryogenic treatment after quenching should be used as far as possible.
(7) For some sophisticated and complex molds, pre-heat treatment, aging heat treatment, and quenching and tempering nitriding heat treatment can be used to control the accuracy of the mold.
(8) When repairing mold blisters, pores, wear and other defects, use cold welding machines and other repair equipment with little thermal impact to avoid deformation during the repair process.
If the local hardness of the parts is high, the local quenching heat treatment can be carried out by means of induction heating. For such parts, the location of the local quenching heat treatment and the local hardness value are usually marked on the drawings.