Development of secondary refining technology

Development of secondary refining technology

The secondary refining has the functions of making the temperature and composition of the molten steel uniform, adjusting the composition of the molten steel, degassing (decarburization, denitrification, dehydrogenation), deoxidation, desulfurization, dephosphorization, adjusting the temperature of the molten steel, and controlling the shape of inclusions. Currently, a variety of secondary refining processes that can be developed according to different functional requirements (molten steel stirring, powder injection, alloy addition, furnace atmosphere control, decompression and heating) are being developed.

During the period of rapid economic growth, the Japanese iron and steel conglomerate completed the steelmaking process consisting of "converter-secondary refining" as a means to improve the quality of converter steel in order to expand the steel grades that can be produced by the converter while increasing the converter's productivity. Established a mass production method for multi-variety, high-quality steel.

In addition, for the secondary refining in the electric furnace steelmaking, the LF method was developed to transfer the molten steel reduction period smelting operation of the electric furnace steelmaking, which has made a great contribution to improving the productivity of the electric furnace. At present, various secondary refining equipment has been applied in accordance with the electric furnace with multiple functions such as oxygen blowing and the requirements for high quality steel.

In the 1980s, with the increase in the proportion of refining treatment of high-purity steel represented by ultra-low carbon steel, the requirements for mass treatment of molten steel became higher and higher, and the treatment process was required to be simplified. With the improvement of various processing technologies, even in the secondary refining, additional processing functions appear to the existing processes, which speeds up the development of the reaction vessel from simple processing to intensive and multifunctional. In the secondary refining process, the temperature of molten steel will drop faster. Therefore, in order to reduce the load on the refractory materials of the converter after the tapping temperature rises, the equipment with the function of raising temperature has been actively developed and introduced.

In addition, in order to reduce the production cost of low-phosphorus steel, while introducing hot metal pretreatment technology, on the one hand, it optimizes the smelting function of the converter and secondary refining, and on the other hand, it develops various refining processes to achieve high purity and high purity. The production technology of clean molten steel has been developed rapidly.