Study On Improving The Synthetic Properties Of Medium-chromium Cast Iron

In this paper, the development history and actuality of wear-resisting material at home and aboard are reviewed and the reasons why medium-chromium cast iron shows bad synthetic properties are profoundly analyzed. Then, on the basis of profound analysis of key technology and influence factors of medium-chromium cast iron production, according to the tenet of improving its mechanical properties and wear resistance, the influences of chemical composition, heat treatment, modified treatment and speed of cooling on the structure and properties of medium-chromium cast iron were investigated, so as to produce medium-chromium cast iron with high property and low price and provide the theory gist for its use under impact condition.Through the research of the influences of carbon content, Si/C ratio, manganese content, we ascertained their better content and found the phenomenon of silicon-chromium segregation in matrix. We also found that proper heat treatment could improve the structure and properties of medium-chromium cast iron remarkably and ascertained that its better quenching temperature and tempering temperature were 950 ℃ and 400 ℃, respective. The experiment results showed the structure was refined and the properties were enhanced after adding modificator, such as rare-earth ferrosilicon. low-carbon ferrochromium or compound modificator, and the modified effect of compound modificator was better than that of its any group component. By increasing the speed of cooling, the dendrite arm spacing of austenite, especially the secondary dendrite arm spacing, could be decreased evidently, which was advantaged to improve the synthetic mechanical properties.The properties of metal mold cast samples as-cast were obviously better than those of sand mold cast ones heat-treat condition, which could be the theory basis for the application of medium-chromium cast iron as-cast. The properties of metal mold cast medium-chromium cast iron approximated those of Ni-Hard4, so it was possible that Ni-Hard4 would be replaced by metal mold cast medium-chromium cast iron through improving foundry technique further.