Heat treatment of seamless pipe refers to a seamless steel pipe thermal processing process that changes the chemical composition and organization of the surface or interior of the seamless steel pipe to obtain the required properties by means of heating, heat preservation and cooling.
The reasons for the deformation of seamless steel pipes are often complex, but as long as the law of deformation is mastered, the causes are analyzed, and different methods are used to prevent the deformation of seamless steel pipes, it can be reduced and controlled. Generally speaking, the heat treatment deformation of seamless steel pipes can be prevented by the following methods.
(1) Reasonable material selection. For seamless steel pipes, micro-deformation die steels (such as air-quenched steels) with good materials should be selected. Die steels with serious carbide segregation should be reasonably forged and quenched and tempered. For larger and unforgeable die steels, solid solution double refinement heat treatment can be carried out.
(2) The structural design of the seamless steel pipe should be reasonable, the thickness should not be too disparate, and the shape should be symmetrical. For the mold with large deformation, the deformation law should be mastered, and the processing allowance should be reserved. For large, precise and complex molds, a combined structure can be used.
(3) The seamless steel pipe should be pre-heated to eliminate the residual stress generated during machining.
(4) Reasonably select the heating temperature and control the heating speed. For seamless steel pipes, slow heating, preheating and other balanced heating methods can be adopted to reduce the heat treatment deformation of seamless steel pipes.
(5) Under the premise of ensuring the hardness of seamless steel pipes, pre-cooling, graded cooling quenching or warm quenching processes should be adopted as much as possible.
(6) For seamless steel pipes, if conditions permit, vacuum heating quenching and cryogenic treatment after quenching should be used as much as possible.
(7) For some sophisticated and complex molds, pre-heat treatment, aging heat treatment, quenching and tempering nitriding heat treatment can be used to control the precision of seamless steel pipes.
(8) When repairing defects such as trachoma, pores, and wear of seamless steel pipes, use cold welding machines and other repair equipment with small thermal impact to avoid deformation during the repair process.
In addition, correct heat treatment process operation (Such as hole plugging, hole binding, mechanical fixation, suitable heating method, correct selection of the cooling direction of the seamless steel pipe and the direction of movement in the cooling medium, etc.) and reasonable tempering heat treatment process are also effective measures to reduce the deformation of seamless steel pipes.
The reasons for the deformation of seamless steel pipes are often complex, but as long as the law of deformation is mastered, the causes are analyzed, and different methods are used to prevent the deformation of seamless steel pipes, it can be reduced and controlled. Generally speaking, the heat treatment deformation of seamless steel pipes can be prevented by the following methods.
(1) Reasonable material selection. For seamless steel pipes, micro-deformation die steels (such as air-quenched steels) with good materials should be selected. Die steels with serious carbide segregation should be reasonably forged and quenched and tempered. For larger and unforgeable die steels, solid solution double refinement heat treatment can be carried out.
(2) The structural design of the seamless steel pipe should be reasonable, the thickness should not be too disparate, and the shape should be symmetrical. For the mold with large deformation, the deformation law should be mastered, and the processing allowance should be reserved. For large, precise and complex molds, a combined structure can be used.
(3) The seamless steel pipe should be pre-heated to eliminate the residual stress generated during machining.
(4) Reasonably select the heating temperature and control the heating speed. For seamless steel pipes, slow heating, preheating and other balanced heating methods can be adopted to reduce the heat treatment deformation of seamless steel pipes.
(5) Under the premise of ensuring the hardness of seamless steel pipes, pre-cooling, graded cooling quenching or warm quenching processes should be adopted as much as possible.
(6) For seamless steel pipes, if conditions permit, vacuum heating quenching and cryogenic treatment after quenching should be used as much as possible.
(7) For some sophisticated and complex molds, pre-heat treatment, aging heat treatment, quenching and tempering nitriding heat treatment can be used to control the precision of seamless steel pipes.
(8) When repairing defects such as trachoma, pores, and wear of seamless steel pipes, use cold welding machines and other repair equipment with small thermal impact to avoid deformation during the repair process.
In addition, correct heat treatment process operation (Such as hole plugging, hole binding, mechanical fixation, suitable heating method, correct selection of the cooling direction of the seamless steel pipe and the direction of movement in the cooling medium, etc.) and reasonable tempering heat treatment process are also effective measures to reduce the deformation of seamless steel pipes.
