Effect of Recrystallization and Partial Melting Method on Microstructural Evolution of SKD61 Tool Steel in Semi-solid State

摘要

The microstructural evolution and basic refinement mechanism of the semi-solid-state SKD 61 tool steel fabricated by recrystallization and partial melting (RAP) method were investigated experimentally. The effects of different parameters in RAP processing were systematically clarified to achieve the grain refinement of cast SKD61 steel in the semi-solid state. Results showed that, the microstructure of RAP processed specimen were finer and more globular than the microstructure of starting material. The distribution of finer solid particles in the RAP processed specimen was affected by the distribution of strain during predeformation. Uniform and spherical solid particles inclined to locate in the regions suffered from larger strain. The specimens subjected to a plastic predeformation at a lower temperature have a more uniform and spherical semi-solid microstructure than those specimens undergoing predeformation with the same reduction at higher temperatures. In addition, the grain refinement mechanism of SKD61 tool steel processed by RAP method was discussed.