Research On Carbothermal Reduction And Strengthening Of Sea Sand Ore

Titanium dioxide is the main component of electrode covering,which plays an important role in slagging fluxes on welding electrodes.Marine placer,also known as ilmenite placer,is very rich in mineral reserves.And the reduced ilmenite product of marine placer contains both TiO2 and Fe,which possess slag forming capacity by TiO2 and restrike of arc property by Fe.Thus,marine placers are suitable for producing reduced ilmenite for coating material of welding electrode.In the present study,the reduced ilmenite for welding electrodes was prepared from Australian marine placers via direct reduction.The reduction behavior of marine placer-coal composites and strengthening experiments were systematically investigated,respectively.The carbothermic reduction behavior of marine placer-coal composites were investigated using isothermal reduction experimental methods.The following conclusions are obtained:(1)Four stages were observed in the carbothermic reduction of the marine placer-coal composites.The release of the volatiles in coal occurred at the first stage(?600?),and the solid-solid reduction and gas-solid reduction occurred at the second(600-960 0C)and third stages(960-1450?),respectively.The reduction rate of iron oxide at the third stage was higher than that at the second stage because of the high carbon gasification rate.A slowdown in the total mass loss occurred at approximately 1450? at the fourth stage.(2)When the temperature was below 1100?,the reduction products of ilmenite(FeTiO3)is ferrous oxide(FeO),iron(Fe)and titanium dioxide(TiO2),while iron oxide(Fe2O3)were reduced to FeO and Fe.The reduction process of the marine placer that exceeded 1100? can be written as:FeTiO3?FeTi2O5?Fe+TiO2.Ferrosilicon(Si-Fe)and aluminum(Al)were chosen as the additive to enhance the carbothermic reduction of marine placer.The following conclusions are obtained:(1)The additional Si-Fe and Al can obviously increase the reduction rate of the mixtures,and the corresponding products easily exceeded the technical requirement since the lower content of FeO.(2)The reaction mechanism was proposed for the carbothermic reduction of the marine placer-coal mixture with Al.When the temperature was higher than 960?,the heat release of the aluminothermic reduction increases the temperature in the neighboring area.This increase in temperature facilitates the gasification reaction and promotes the carbothermic reduction rate of marine placer.(3)The addition of Si-Fe facilitates the nucleation and coalescence of metallic iron formed by reduction.