Theoretical And Experimental Research On Titanium Removing In The Hot Metal Pretreatment

With the improvement of steel quality, higher demand for reducing the titanium content in steel should be satisfied. For steels like bearing steel, cord steel, spring steel and so on, the titanium content should be no more than15X10-6. As it is quite difficult to lower the titanium content in the process of steelmaking, a better method of removing titanium should be developed. In this paper, a new method of removing titanium in the hot metal pretreatment process has been introduced. The following content is included:The oxidation behavior of some elements, such as Ti, Si, Mn, C and P, in the titanium removing process; Study on the slag-metal reaction; Research on the activity of TiO2in the slag; The kinetics of titanium removing reaction in the hot metal pretreatment; Study on titanium removing behavior using three kinds of agents (sinter, pellets, iron concentrate) and the top blowing oxygen; Study on industrial applications of the titanium removing process in hot metal pretreatment. The main creativities are the calculation of TiO2activity and the choice of titanium removing agents.In this paper, the following results are given:(1) Through thermodynamic calculations it can be concluded that there is equilibrium relationship between the content of Ti and Si in liquid iron; The content of Mn decreases with the reduction of Ti; There is no direct relationship between the content of P and Ti and that the oxidation of C is mainly affected by temperature.(2) Based on coexistence theory, a model used for calculating the activity of TiO2in the titanium removing slag(SiO2-TiO2-CaO-MgO-FeO-MnO) is proposed. Increasing the basicity and improving the content of MgO, FeO, MnO in the slag can help to lower the activity of TiO2. By improving the activity of FeO in slag, lowering temperature and decreasing the activity coefficients of TiO2in slag, Ti distribution ratio between slag and iron would be improved.(3) The kinetic equation titanium removing process in hot metal pretreatment is established. It can be calculated that it is the mass transfer of Ti in molten iron that determines the reaction speed in the first four minutes of titanium removing process.(4) Tests of using three solid titanium removing agents indicate that under the condition of lkg/t titanium removing agent and lmin, using different agent can get different titanium removing rate. The order of titanium removing rate (from the largest one to smallest one) is sinter, pellets and iron concentrate.(5) The experiments of using top-blown oxygen as a way of removing titanium show that the average rate of titanium removing can be up to71.3%. The titanium removing rate will go up with the decrease of temperature and the increase of the amount of titanium removing agent and the amount of oxygen.(6) Industrial application of the titanium removing process shows that the lowest content of titanium in molten iron is0.0016%and the highest titanium removing rate can reach95.7%when using sinter as titanium removing agent. Meanwhile, the lowest content of titanium is0.0033%and the highest titanium removing rate is86.64%when using iron concentrate as titanium removing agent.