Study On Generation And Microstructure Of Oxidation Film For High Chrome Cast Steel/iron Roller

The roller is one of the most consumed parts in the production for the rolled steel products.Formation and peeling of the oxide film of roller during the service process have a direct impact on the consumption of roller and the quality of rolled products.Therefore,it is of great significance to study the formation rules and microstructure of oxide film of different roller materials,which can help to formulate the rolling regulations and water cooling specifications,furthermore,to reduce the consumption of rollers and improve the quality of rolled products.In this thesis,the oxidation behaviors of high-Cr cast steel and high-Cr cast iron during continuous heating and isothermal processes have been studied by means of DSC,in-situ oxidation observation and oxidation weight increase,and then the phase structure and surface morphology have been studied by means of XRD and SEM.Meanwhile,the effect of air and vapour environment have been studied.the aim is to provide reference data for an company to reasonably select roller and formulate cooling process specification.Continuous heating results by DSC show that the high chromium cast steel begins to oxidize when the increase of heating temperature,but the oxidation weight gain rate slows down or even decreases when the temperature is higher than 500?.While,the temperature for high chromium cast iron is at about 400?.When heating temperature gets to 650⁷00?,the oxidation weight gain rate of the two materials began to increase.In situ observation results show that when the temperature reaches about 300?,the oxide film of the two materials form in the matrix and grows with the increase of temperature,but no oxide film forms on the carbide surface.In air atmosphere,the growth of oxide film with holding time appears parabolic pattern.As the temperature is lower than 600?,the oxidation weight increase small with the increase of temperature,however,when the temperature is higher than 600?,the oxidation weight quickly increases with the increase of temperature.The oxide film preferentially forms in the matrix,and the oxide film is mainly Fe₂O₃.The oxidation is accelerated significantly in the vapor environment,and the Fe₃O₄ phase would appears in the oxide film with the increase of the oxidation time.In-situ oxidation observation show that the oxide film preferentially forms in the matrix and the growth of oxide film around eutectic carbide was slightly higher than that of the matrix.All results of DSC continuous heating,isothermal oxidation,in-situ oxidation observation and cyclic heating oxidation show that the oxidation resistance of high chromium cast iron is higher than that of high chromium cast steel.