Investigation Of Preparing Titanium Carbonitride From Titanium-bearing Blast Furnace Slag And Its Application

The situation for utilizing of titanium-bearing blast furnace slag comprehensively in Panzhihua Iron and Steel Company is systematically reviewed, then the carbonitridation of titanium-bearing slag is brought up to produce Ti(C, N) for refractories. Moreover, the residual slag can be used for cement, pavement, etc. after Ti(C, N) is separated from carbonitrized slags. So it may be an innovative approach for the comprehensive utilization of titanium-bearing blast furnace slag in Panzhihua Iron and Steel Company. The research work is summarized as follows: First, the thermodynamic analysis shows that reaction between titanates in slag, C and N2 occurs to produce TiN at 1200℃and TiC at 1300℃. The temperature range of 1300～1500℃is selected to treat the slag.Second, based on thermodynamic analysis, carbothermal reduction process was carried out in argon and nitrogen atmosphere for the pre-molten slag of TiO2-CaO-SiO2-Al2O3-MgO system according to titanium-bearing blast furnace slags in Panzhihua Iron and Steel Company. The phase evolution and microstructure of the products were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). It was found that the final products mainly consist of TiC in argon atmosphere and Ti(C, N) (mainly TiN) in nitrogen atmosphere. The grain size of TiC in argon atmosphere are less about 1～4μm than that of Ti(C, N) in nitrogen atmosphere in the same of experiment condition.Third, carbothermal reduction experiment was carried out for titanium-bearing blast furnace slag in Panzhihua Iron and Steel Company in nitrogen atmosphere at high temperature. The effects of nitriding temperature, isothermal treatment time and carbon content on formation and grain size of Ti(C, N) were studied by XRD, SEM and electron probe micro-analysis (EPMA). The results showed the better technical conditions are that nitriding temperature is 1450℃, isothermal treatment time is 2 hours, and carbon ratio is 1. The average grain size of Ti(C, N) is about 2μm in this experiment condition. Based on the above, the effect of additives such as K2CO3, CaF2 and Fe2O3 on the formation and grain growth of Ti(C, N) was studied. The results show that all the additives could modify the liquid slag properties and promote effectively the grain growth of Ti(C, N). Among them, Fe2O3 is the most effective additive and the agglomerate of Ti(C, N) grain grew up as its amount increased. Its maximum size reached up to 23μm. Meanwhile, the minimum grain size was found in the samples where no additive was added.Fourth, the effects of titanium-bearing blast furnace slag in Panzhihua Iron and Steel Company on the physical properties of ramming refractory and its slag resistance at 1450℃for 3 hours were investigated in blast furnace trough. The results showed titanium-bearing blast furnace slag in Panzhihua Iron and Steel Company could improve the physical properties of ramming refractories in blast furnace trough and slag resistance effectively.