The development of secondary refining furnace

In order to homogenize the composition and temperature, a gas stirring process in the ladle appeared. The most striking thing is the use of secondary refining, which greatly improves the output and quality of steel.

However, what is themain taskand purpose of secondary refining? Separate molten steel and slag phase during tapping and continuous casting, deoxidize molten steel, perform alloying according to the end target, adjust injection temperature, improve the cleanliness of molten steel, denaturation of inclusions, Removal of [H] and [N] dissolved in molten steel, decarburization, desulfurization, and uniform molten steel composition and temperature.

The introduction of vacuum decarburization makes it possible to significantly reduce the carbon content. At present, molten steel with a carbon content of 20 ppm is available, and it is expected that steel for special purposes can reach 10 ppm. It is expected that P for special purpose steel will drop to 30ppm in the future.

Now, by removing S from molten iron and molten steel, the S content can reach 10ppm stably. Currently, there is no need to drop s to a lower level. In the future,special steel requires a nitrogen content of 20ppm. Now steel with a total oxygen content of 15ppm can be obtained. In the future, the minimum oxygen content is required to be about 10ppm. Vacuum treatmentcan reduce the hydrogen content to about 1ppm.

The current steelmaking process is quite flexible and depends on the product range of the steelmaking plant. Generally, it starts with the pre-desulfurization of molten iron, followed by converter steelmaking.

Then vacuum treatment (RH treatment or ladle furnace degassing treatment), if necessary, the molten steel can also be heated. It can be heated in the ladle furnace or the aluminothermic method. At the end of the secondary refining, calcium-containing materials are added for inclusion denaturation treatment. Finally, the molten steel is cast using a continuous casting process.