Effect of Refining Outside the Furnace On Refractory Materials
Long time high temperature, vacuum. The refining outside the furnace is mostly carried out under vacuum, the degree of vacuum is 666.6~3999.7Pa, and refractory material is easy to evaporate under high temperature vacuum. Due to the long processing time outside the furnace refining, the heat loss of the molten steel is large. In order to compensate the heat loss of the refining outside the furnace, the heating temperature outside the furnace is heated (arc, oxygen or aluminum oxide) or the tapping temperature is increased,(1650~1750℃), this will accelerate the role of refractory materials and slag and molten steel, and the slag will intensify the erosion of refractory materials.
Erosion of slag. In the refining process outside the furnace, the alkalinity and viscosity of the slag vary greatly. Taking the VOD furnace as an example, the acidification slag is in the initial stage of refining, the alkalinity of the slag is 0.5~1, and the middle and late stages of refining are converted into high alkalinity slag. The alkalinity of the slag is 2.0~3.0, even reaching 4.0~5.0. In this case, the refractory material is not only eroded by the acid slag and the low alkalinity slag, but also by the erosion of the high alkalinity slag.
Infiltration of slag. The slag refined outside the furnace belongs to CaO-Al2O3-FeO slag. The slag has good fluidity and low viscosity. The slag will solidify under the high temperature and penetrate into the deep part of the lining refractory brick to form a thick metamorphic layer. Due to the performance and composition of the metamorphic layer, especially the linear expansion coefficient is very different from the original brick layer, structural peeling and damage will occur when subjected to thermal shock.
Strong scouring and wear of slag and molten steel. In the refining process outside the furnace, the molten steel and slag have a very serious effect on the scouring wear of the refractory. Taking the RH furnace as an example, the circulating speed of the molten steel is 80 to 100 t/min, and the flow rate in the dip tube is 1 to 1.5 m/s.
Thermal shock damage caused by sudden temperature changes. Since the refining equipment outside the furnace is non-continuous, the temperature change between the two operations is severe, and the temperature difference reaches 500~800 ℃. After a sharp thermal shock, cracks are formed on the working surface of the refractory material, causing the hot surface to be peeled off.
