Fundamental Research On Slagless Steelmaking Process

Steel enterprises are under severe pressure with the over-capacity of domestic steel output in China. Slagless Steelmaking Process such as MURC double slag process has been adopted by some domestic enterprises for the purpose of adapting to the new steel environment, reducing the production cost, improving the enterprice competitive ability. Some Slagless Steelmaking Process such as MURC double-slag process generate less slag by reuse of decarbon slag and the typical technological process are as following:desilication and dephosphorus?pouring dephosphorous slag?decarbon?tapping and slag remaining. Compared to the traditonal steelmaking operation, Less-slag Steelmaking Operation has been widely applied because of the less slag output and raw materials consumption and the higher utilization rate of raw materials which benefits to the energy consumption and pollution reduction. The problems that the dephosphorous rate of dephosphorous period was so explosively unstable and that the low-basicity dephosphorization slag have potential effect on corrosion of refractory were studied in this thesis. The dephosphorous slags of different dephosphorous ratio were observed and analysised, and the distribution of phosphorous in slag were studied in this thesis. Also, the factors influencing the distribution between solid and liquid phase were studied. The corrosion behavior of low-basicity dephosphorization slag on magnesia refractory was investigated by static crucible method.The dephosphorous slags of different dephosphorous rate were observed and analysised. It can be found that phosphorous was mainly enriched in the 2CaO·SiO2 particles of the slag with high dephosphorous rate in dephosphorous period. However there was not much solid phase in the slag with low dephosphorous rate in which phosphorous was mainly spread in the liquid phase uniformly.Then some of slags were heat-treated and it can be found that the basicity of observed area increased while phosphorous in liquid phase decreased which means undissolve CaO existed in phosphorous slag.The factors influencing the distribution ratio between solid and liquid phase were studied by preparing different conten slags. It can be found that Lp increased with the increasing content of (%SiO2)+(%P2O5) and (FetO) before it reached the maximum and then LPS/i began to decrease. The value of (%Sio2)+(%P2O5) and (FetO) were 20% and 70% respectively at the maximum. LpS/i has little change with the ratio of 2CaO·SiO2 particles.The corrosion behavior of low-basicity dephosphorization slag on magnesia refractory was investigated by static crucible method. The results are as following:the corrosion behavior of magnesia crucible by high-basicity slag is primarily strucrural spalling caused by the penetration of slag at the solid-liquid interface. The corrosion by low-basicity dephosphorization slag is primarily erosion and dissolution through the crack of crucible which cause the crucible particles at the interface. When Fe2O3 ?20% in slag, low melting point solid solution with high FetO forms at the interface which intensifies the erosion. The increase of basicity and the content of MgO can relief the corrosion of crucible by dephosphorization slag.