Microstructure and Properties of Cast Iron by Semi-Solid Die Casting Process

Abstract

Semi-solid cast irons were pressure-cast by using vertical and horizontal die casting machines. Series of experiments were carried out on flaky graphite cast irons. In the rheocasting method, semi-solid slurry (fraction solid is about 0.2) was subjected to the vertical die casting machine. Flat plates of 6 mm thick were produced. Surface quality, microstructure of product and die temperature were investigated. The reduction of heat shock of the die was also ensured. In the thixocasting method, as the raw materials, sand mold cast irons were heated to have a solid fraction of 0.2 and then die cast. Flat plates of 6mm thick were produced. The microstructure obtained after die casting was found to be primary austenite (ferrite and pearlite at room temperature) distributing in the structure and it was also found that the liquid phase section became austenite-cementite eutectic. When this eutectic was heat-treated, the cementite shortly changed to fine graphite spheres. The mechanical properties of the tested cast irons were improved by die casting and post heat treatment.