Influence of heat treatment on mechanical properties and carbide morphology of tool steel manufactured by semi-solid processing

摘要

Tool steels, which are widely employed in the die and tool applications require excellent hardness, toughness and strength. The good combination of those mechanical properties is always exhibited by the martensite matrix with fine grain size and uniform precipitation distribution. In the conventional die manufacturing as shown in Fig. 1, the refinement of grain is achieved by dynamic recrystallization as the casting stock suffered from large strain induced by multi-pass hot forming process. Also, long soaking time before hot rolling is required to reduce segregation of hard precipitates. The conventional route consumes a large amount of energy and takes up quite long working hours. Thus, an innovative route with lower energy consumption and shorter working hours was needed to replace the conventional method. Here, innovative die manufacturing route by SIMA+SSP (Semi-solid Processing) is proposed as shown in Fig. 2. The spheroidal microstructure and flexile forming property of metal in semi-solid state proved that the semi-solid forming technology would be a potential candidate to take place of the high energy consuming multi-pass rolling or hot forging to complete the deformation of product and the refinement of microstructure. In this study, the feasibility of an innovative semi-solid route to achieve the refinement of tool steel was investigated experimentally.