High Guality Steel Smelting Technology Optimization And Composition Controlling

With the development of automotive industry, high-rise buildings, bridges,engineering machinery, especially the emergence of energy and resources crisis, the improvement of steel quality is demanded. The steel quality has been become an important means to improve enterprise competitiveness, in which, the high value-added products become the key of enterprise survival. Therefore, it is significant to produce excellent high quality steel by optimizing smelting process and controlling the composition of steel,which not only has important economic benefits, but also important social benefits.In accordance with the requirements of the steel smelting, combining with the characteristics of tooling equipment, the smelting technology of different level of high steel grade line were determined.The smelting process of the steel, whos carbon content is between 0.04% and 0.08%is as followed: hot metal desulphurization pretreatment of steel- converter smelting- LF refining furnace- RH refining furnace- slab continuous casting; That of the steel, whos carbon content is small than 0.04% is as followed: hot metal desulphurization pretreatment of steel- smelting converter- RH refining furnace- LF refining furnace- slab continuous casting; That of the steel, whos carbon content is small than 0.0040% is as followed: hot metal desulphurization pretreatment of steel- LF- converter smelting furnace temperature control- RH refining furnace- slab continuous casting.According to the different smelting process, by optimizing smelting process, the low carbon content canbe obtained and the composition is uniform in converter. The carburization quantity is controlled within 0.015% in LF furnace refining process. RH decarbonization process is controlled to take off the carbon content within 24 ppm. The control from refining carbon end to the finished product, the carbon content is controlled within 20 ppm. The carbon content control in high grade steel smelting meet the requirements of different steel grade.The method of double slag dephosphorization process in converter is determined,which make the dephosphorization efficiency secured. The finished phosphorus indifferent level high grade steel can be controlled to achieve a good level and the smelting demand of various steel is meeted, which provides the technical support for the mass production.During the process of high grade steel smelting, the sulfur content is 20-40 ppm after the hot metal desulphurization by controlling the powder spraying desulphurization pretreatment, in which the grilled slag effect is strictly controlled in molten iron. In order to prevent and reduce resulfurization, the sulfur content can be controlled lower at 77 ppm after finished steel liquid in converter. The sulfur content in the steel can be controlled between 7 to 24 ppm according to the demand of the steel grade by deep desulfurization of LF furnace smelting process, which can meet the needs of the mass production.By optimizing the process and the full process control technology, the gas content in steel can be secured. The level of high hydrogen content in steel can be controlled in 1.3ppm. The RH dehydrogenation rate can reach 77.5% to 80.3%. The nitrogen content in the steel can be controlled in 40 ppm.