Secondary refining's development

Development of secondary refining furnace technology

In order to homogenize the composition and temperature, the gas stirring process in the ladle appeared. The most striking is the adoption of secondary refining, which greatly improves the output and quality of steel. However, what is the main task and purpose of secondary refining? The composition of molten steel, decarburization, deslagging and refining of molten steel shall be adjusted according to the target of molten steel, molten steel melting, deslagging and refining.

The introduction of vacuum decarbonization makes it possible to greatly reduce the carbon content. At present, molten steel with carbon content of 20ppm can be obtained, and steel for special purposes is expected to contain carbon of 10ppm. It is expected that the P requirement for special purpose steel in the future will be reduced to 30ppm. Now, by removing s from molten iron and molten steel, the s content can reach 10ppm stably. At present, there is no need to take off s to a lower level. In the future, the nitrogen content of special steel is required to be 20ppm, and now the steel with a total oxygen content of 15ppm can be obtained. In the future, the minimum oxygen content is required to be about 10ppm. Through vacuum treatment, the hydrogen content can be reduced to about 1ppm.

The current steelmaking process is quite flexible, depending on the product range of the steelmaking plant. Generally, it starts with hot metal pre desulfurization, followed by converter steelmaking, and then vacuum treatment (RH treatment or ladle furnace degassing treatment). If necessary, the molten steel can be heated next. It can be heated in the ladle furnace or by aluminothermic method. At the end of secondary refining, calcium containing materials are added for inclusion modification treatment. Finally, molten steel is cast by continuous casting process.