| RH vacuum furnace has many characteristics such as great refining function, high treatment capacity, short treatment cycle and the high cleanliness of molten steel after treatment. It has been widely used all over the world. It has poor working conditions because of the high speed flushing of air flow and molten steel for a long time. Among all the equipment that make up RH vacuum furnace, immersion tubes soak in molten steel long, their inner walls get the flushing of high speed air flow and molten steel, and their outer walls suffer from the erosion of molten slag and thermal shock, so their working conditions are the worst and their life spans are generally short. These restrict the development of the RH vacuum furnace technique.Because the life spans of the immersion tubes of the RH vacuum furnace in Shougang Qiangang Steel are generally short, the productivities of molten steel treatment of RH vacuum furnace are greatly limited, so the popularization of the RH techniques in Qiangang Steel is limited. These caused great wasting of resources and heavy economic losses. This paper tries to study in the corrosion mechanism and thermal distortion analysis of the immersion tubes for solving the low life span problem of RH immersion tubes in Qiangang Steel. The study looks into the following four parts:Part ? first introduces the design features of RH vacuum furnace and the Bottleneck in limiting its technical development. And then introduces current situation at home and abroad, finds out the gap on the service life of RH vacuum furnace between Shougang Qiangang Steel and the other outstanding steelworks at home and abroad, and raises the issue on Improving Service Life of Immersion Tubes for RH Vacuum Furnace.Part ? looks into the Corrosion mechanism of the inside Magnesia-Chrome Brick and outside castable of the immersion tubes and finds the causes on damage of immersion tubes with characteristics of Qiangang Steel RH techniques, the service conditions of immersion tubes and slag corrosion experiment in the lab, using SEM?EDS and XRD as analyzing tools.Part III creates the analysis on thermal distortion finite element analysis of immersion tubes of RH refining furnace with the study about thermal distortion on the composite structure "refractory bricks-steel shell-castable" of immersion tubes. And it reforms partly on the structure of steel shell of immersion tubes according the analysis result.Part IV puts emphasis on the field use of the RH vacuum furnace, improves the spray-repair vehicle of the immersion tubes in Qiangang steel, optimizes gunning mode, presents technology for swift replacing of the vacuum chamber of the RH vacuum furnace. The end of the study summarizes the whole paper and looks into the future, and indicates with actual data that:the above method can raise the life span from average 70 heats per year in 2007 to 112 heats quarterly in 2013, the highest is 154 heats quarterly. It makes 8 heats continuous casting of the X80 pipeline steel and 5 heats continuous casting of SDC06 ultra-low carbon steel come true. It has reached the international advanced level on single-station RH vacuum furnace. |
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