Study On The Mechanism Of Promoting Iron Carbide Formation By Oxides Additives

In this paper, the resent research status of iron carbide preparation and all kinds of effects on formation of iron carbide, such as reaction temperature, gas pressure, reaction atmosphere, microstructure of raw material, additive, etc,are summarized elaborately. The effect of 1%V2O3,1%TiO2 additive on iron carbide formation by two steps was studied by thermogravimetric analysis experiments in H2-CO-CO2 mixtures at 853K~973K. The conclusions are as follows:(1)With temperature increasing, the rate of reduction reaction increases but the rate of carburization reaction decreases quickly at 853K~973K, which nearly reaches zero at the temperature of 973K. XRD analysis indicates iron carbide is not available in the product.(2)In this experiment conditions. Being compared with specimens without additive, 1%TiO2 additive has weakly promoting effects on reduction reaction process, however, it has suppressive effects on carburization reaction process; 1%V2O3 additive has no influence on reduction reaction, and obviously promoting effect on the rate of carburization reaction and the conversion rate of the end of carburization reaction. The effect of 1%V2O3 additive on the conversion rate of the end of carburization reaction becomes more obvious with the increase of temperature.(3)It is reasonable that the reaction kinetics is analyzed with the shrinking core model. It is found that the rate limit step of reduction and carburization reactions are the interfacial reaction and the V2O3 additive has a promoting effect on it.(4)Adding 1%V2O3, the amount of mesopore and large pores of sample increase at the end of reduction reaction, leading to specific surface area and pore volume increased, surface activity of reduced iron increase, which benefits carburization reaction gas adsorption in the reduction iron, thus contributing to the carburization reaction.