Research On Technologies Of Deoxidization And Inclusion Control Of Rolling Steel

It is required to improve the roller quality along with the rapid developing of steel rolling technique, speed and automated level of rolling mills. The problem how to improve the operating life of roller to satisfying the desire of rolling mills has been a new subject which roller manufactories will research. In recent years, production technology of significant wearing roller used in metallurgy industry of China has been wider advanced, but there is still sizeable disparity compared to developed countries.At present, Sino Steel Xingtai Machinery& Mill Roll CO. LTD is the top-rank special roller manufacturer which dominates at production capacity and variety specification of roller in our nation. Basing on the above condition, the subject research is retrofitting LF-VD processing of steel-casting foundry in order to improve quality of molten steel further. Because the roll steel contains definite magnitude alloying agent, various inclusions could format and precipitate which result in bad effects to performance of roll. The thesis presumptive and predictive inclusion formatting and precipitating from roll steel in current technology and system of the factory basing on the thermodynamics and dynamics calculation; illuminate the effect about inclusion formatting in various smelting process by stereoscan energy spectrum analysis and microscopic examination which could analyze the qualitative including pattern, component, size of inclusion; improve the level of deoxidize system in current craft thought using different deoxidizing agent in order to improve the degas level of smelting process, especially to reduce the dissolved oxygen and total oxygen of steel in a greater degree. The conclusions of paper are following:(1) In the process of LF-VD, the major inclusions are oxide, sulfide and oxide-sulfide complexes in melting process; a small amount nitrides including TiN, TiC and VN format and precipitate in the coagulating process after casting; the average diameter of inclusion in finished steel is less than 3μm, and the diameters of above 95% inclusions are less than 10μm that only a few ones are greater than 10μm.(2)Using aluminum for deoxidizing could achieve low oxygen content, and Al2O3 inclusion will generate much more easily. But when a will be below 2×10-6, increasing quantity of Al continuingly is futility. Simultaneity, a small amount of MgO and will generate.(3) In refining process, the main Ti-inclusion are TiO(s); during the solidifying process because of V, Ti and N enrichment in steel, it is better for TiN, TiC and VN generating.(4) In wire feeding operating, final deoxidize operating and vacuum process are preferable for deoxidizing, but during alloying operating oxygen content is increasing largely; The increment of soft flowing and time expanding are better for rising and exhausting inclusions, but the flow ratio should be control well in order to avoid secondary oxygenizing.(5) It is obvious that the method using Al deoxidizer instead of Si-Al-Ba deoxidizer which reduces the initial dissolved oxygen content, is better for controlling the oxygen content in refining process. And it is effective to reduce the quantity of slag during refining process.