Research And Optimization Of Pipeline Steel’s LF And Deep Drawing Steel’s RH Refining Slag System

The LF and RH refining slag of X70and SPHE-B in210plant of VALIN LY STEEL is designed according to the experiences of other domestic manufacturers, the slag’s capacity of inclusion adsorption and desulfurization is low, the increasing nitrogen amount in LF refining is high, the present refining slag is unable to adapt to the fast pace of production in converter and the development of high quality varieties of steel.In this research, the X70’s LF and SPHE-B’s RH refining slag system is investigated in the field, the metallurgical properties of the present slag system and the quality of steel are evaluated, the influence factors of the metallurgical properties of slag are analyzed, from the three aspects of desulfurization, adsorption, preventing from increasing nitrogen, the refining slag composition of SPHE-B and X70is designed by theoretical analysis and calculation, and the metallurgical properties of the slag are tested in the laboratory, according to the results, the composition of slag system is modified, finally, the appropriate refining slag composition of X70and SPHE-B is acquired by industrial test.From the research, some conclusions were drew as follows:(1) strong oxidation resistance is the main reason of low rate of desulfurization in X70and increasing sulfur in SPHE-B, high content of CaO and low content of Al2O3is the reason of low adsorption ability and high amount of increasing nitrogen in X70, low content of Al2O3is the main reason of low adsorption rate in SPHE-B;(2)Through theoretical analysis and calculation, the composition of the finalslag of RH refining of SPHE-B is40-50%CaO,4-10%SiO2,6-8%MgO,20-25%Al2O3, FeO+MnO<10.0%,the composition of the final slag of LF refining of X70is50-55%CaO,8-10%SiO2,6-8%MgO,20-25%Al2O3,FeO+MnO<1.2%;(3)The result of the test of the metallurgical properties in the laboratory showed that:the melt temperature of the refining slag of SPHE-B、X70are1225℃、1335℃, the average desulfurization rate and deoxidation rate of the LF refining slag of X70are66.67%、80.19%%; the average desulfurization rate and deoxidation rate of the RH refining slag of SPHE-B are2.05%、95.75%,the results showed the designed refining slag of SPHE-B and X70had good metallurgical properties;(4) The results of industrial test showed:At the end of the RH refining of SPHE-B,[O]t≤0.0032%,the sulfur content remains unchanged; At the end of the LF refining of X70,[S]≤0.0015%,[O]t≤0.0035%,the increasing amount of nitrogen is less than0.0022%.Totally,there are40pieces of pictures,17sheets of tables and65pieces of references.