Optimization of welding thickness on casting-steel surface for production of forging die

Abstract

There are many drawbacks of traditional mold manufacturing technology, especially for dies used on large-scale hydraulic press, such as poor forging penetration, high difficulty of open die-forging process of modules, inferior hardness after heat treatment, high cost, massive waste of invalid forging dies, and so on. Therefore, a new method of mold making is put forward in this paper, which is to do surface welding on casting-steel. The FEM simulation experiments were done to establish a simplified finite element model of the surface welding mold based on JXZG casting-steel. Then, the thermal cycle curve method was used to simulate the surface welding and tempering process. Meanwhile, the temperature field and residual stress field under different welding thickness were analyzed. The finite element modal of landing gear used in a large civil aircraft was established, and then elastic-plastic finite element method was utilized to simulate the forming process of billet and to analyze the temperature field and residual stress distribution of different time. The results demonstrated that FEM could simulate the actual process of surface welding on casting-steel effectively. The equivalent stress close to welding line decreased when the welding thickness inclined, and then it leveled out when the welding thickness was 15 mm; on contrary, the equivalent stress far from welding line increased when the welding thickness declined and the impact of weld pass on casting-steel matrix enlarged which increased the possibility of defects when the casting-steel was used. In sum, when the impact of welding thickness and the cost of mold making are taken into consideration, 16 mm was chosen as the optimal surface welding thickness under given working conditions of landing gear.