Extrusion Microstructure And Properties Of Hypereutectic High Chromium Cast Iron Semi-solid Rheological

Semi-solid slurries of hypereutectic high chromium cast iron were prepared by inclined cooling plate method and were squeezed by self designed mould directly. The influence of pressure, dwell time and temperature of mould to the macroquality, microstructure and mechanical properties of the casting are investigated in this thesis.The technological parameters affected the internal quality of the casting a lot. When the temperature of the mould was too low, the casting had cracks. When the temperature of the mould was too high, the freezing time of the casting extended and there would be shrinkage holes and shrinkage porosity in the casting because the casting unfroze in dwell time. When the pressure was little, there would be big shrinkage holes in the casting. With the pressure increasing, shrinkage holes would be lessen and even diminished. When the dwell time was short, there would be shrinkage holes and shrinkage porosities in the casting. As the dwell time increased, the shrinkage holes would be diminished and the shrinkage porosities would be reduced.According to the casting got from the semi-solid extrusion. From the top to down, the primary carbide grew all along, the quantity of grains in unit area reduced and the shape gene hoisted and then descended. The uniformity of microstructure in axial direction was poor. From the margin to the centre of the casting, the uniformity of microstructure in horizontal direction was fine. The pressure and dwell time affect the uniformity of microstructure not too obvious but the temperature of the mould affect it a lot. When the temperature of the mould was too high, it would cause the uniformity of the microstructure of the casting descended obviously.By semi-solid squeeze casting, the mechanical properties of the casting were all improved to some extend than the general castings. In all semi-solid castings, as the temperature of the mould hoisted, the rigidity and the wear ability of the casting were hoisted all along; the impact tenacity was first hoisted and then depressed. As the pressure increased, the rigidity, the wear ability and the impact tenacity of the casting were hoisted all along. As the dwell time extended, the rigidity and the wear ability of the casting was hoisted all along, the impact tenacity was first hoisted and then depressed.