Failure Analysis And Process Optimization On The Cold Extrusion Dies Of Star Sets

For the star sets cold extruding die, the fracture failure was analyzed by the optical microscope, scanning electron microscope and the hardness tester. The paper analyzes and discusses the main reason for the failure of the mold, then proposes improvements.Brittle oxide and silicate inclusions are observed in the raw materials obtained mold by SEM. Continuity of the matrix is separated and mechanical properties of the material are reduced by these inclusion, which lead to decrease the life of the mold. The carbide exists in zonal distribution in raw materials, which is the underlying causes of cracks. The suggestions are presented as follows,(1) Inspecting the raw materials to ensure that there is less non-metallic inclusions in tissue. (2) Forging the raw materials again to smash the banding carbide in the organization.Banding carbides exist in raw materials, it is difficult to improve the morphology of carbide only by the heat treatment.The microstructure of the mold show that crack extends in the direction of carbide, and some carbides even distribute on the crack directly.In addition, there are some coarser grains in some areas due to slight overheated. By heat treatment process optimization, the results show that the properties of 1070℃ quenching and 200 ℃ tempering is better than that of the original 1130℃ quenching and 540℃.The structure of mold is also one of the main reasons to affect the life of the mold. If there are obvious corners and thickness on the mold, which can lead to stress concentration. The molds have no such problems, which are used the way of combination, indicating that the way can be a good solution to the problem of mold radial cracking.