Fri, 27 Jul 2018 02:10:27 +0000
Prevention of heat treatment deformation
The deformation causes of precision and complex molds are often complex, but we can reduce and control the deformation of molds by mastering the deformation rules, analyzing the reasons for the deformation, and adopting different methods to prevent the deformation of molds. Generally speaking, the heat treatment deformation of precision and complex molds can be prevented by the following methods.
(1) select materials reasonably. For the precision complex die, the micro-deformation die steel with good material (such as cavity-quenched steel) should be selected, the mould steel with severe carbide segregation should be properly forged and tempered, and the large and unforged die steel can be treated with solid solution double refinement.
(2) the mold structure design should be reasonable, the thickness should not be too large, the shape should be symmetrical, the deformation rule should be mastered for the mold with large deformation, and the machining allowance should be reserved.
(3) preheat treatment should be carried out for precision and complex molds to eliminate the residual stress generated during machining.
(4) reasonable selection of heating temperature and control of heating speed. For precision complex molds, slow heating, preheating and other methods of balanced heating can be adopted to reduce the deformation of heat treatment of molds.
(5) on the premise of ensuring the hardness of the mold, precooling, graded cooling and quenching or temperature-quenching process shall be adopted as far as possible.
(6) for precision and complex molds, vacuum heating and quenching and deep cooling treatment after quenching shall be adopted as far as possible when conditions permit.
(7) for some precision and complex molds, the precision of the molds can be controlled by preheat treatment, aging heat treatment and nitrogen conditioning heat treatment.
(8) when repairing the defects of mold sand holes, air holes, wear and other defects, cold welding machine and other equipment with little thermal influence shall be selected to avoid deformation during repair.
In addition, correct heat treatment process operation (such as hole plugging, hole binding, mechanical fixation, proper heating method, correct choice of cooling direction of mold and movement direction in cooling medium, etc.) and reasonable tempering heat treatment process are also effective measures to reduce the deformation of precision and complex molds.