Abstract: The relationship between microstructure and mechanical behaviors of the grey iron specimens after various thermal histories, prepared based on the casting process of ingot mould, is studied. It is found that there is an abnormal temperature range near 673 K in which the tensile strength increases with temperature increasing, and it should be related to the internal friction variation resulted from the thermal pretreatment. The difference of microstructure and mechanical properties of as-cast and heat pretreated specimens is revealed, and that matches the mould failure status during ingot casting. From the experiment, it is shown that the tensile strengths of the specimens after keeping 1 073 K for 3 hours pretreatment are improved obviously at all test temperatures. Moreover, the tensile strengths of the specimens after cyclic thermal load drop with the numbers of the thermal cycle pretreatment increasing. The failure mechanisms of grey iron ingot mould and reasonable suggestions to improve its service life are proposed.

Key words: cast iron;ingot moulds;microstructure;mechanical behaviors