Metallurgy ladle refining's introduction

Introduction to metallurgy ladle refining

Refining outside the furnace divides the traditional steelmaking into two steps. The first step is called primary refining, which is the melting, dephosphorization, decarburization and main alloying of the furnace charge in an oxidizing atmosphere; The second step is called refining. Deoxidation, desulfurization, inclusion removal, inclusion denaturation, fine adjustment of composition, control of molten steel temperature, etc. are carried out in vacuum, inert atmosphere or controllable atmosphere. Since the 1960s, various refining methods outside the furnace have appeared one after another. This technology has developed rapidly all over the world.

Out of furnace refining has become an indispensable link in the modern iron and steel production process. In particular, the combination of out of furnace refining and continuous casting is an important means to ensure the smooth operation of continuous casting production, expand continuous casting varieties and improve slab quality.

In the steelmaking production process, the use of converter (or electric furnace) - out of furnace refining - continuous casting has become a common mode of technical transformation in steel plants.

The processes of various out of furnace refining methods are different, and their common characteristics are: there is an ideal refining atmosphere, such as vacuum, inert gas or reducing gas; Using electromagnetic force and blowing inert gas to stir molten steel; In order to compensate the temperature drop loss of molten steel in the refining process, electric arc, plasma, chemical method and other heating methods are adopted.

Metallurgy ladle refining matching with continuous casting is to improve slab quality and ensure the stability of continuous casting process. Selecting appropriate refining method outside the furnace is an important means to prepare molten steel for continuous casting and provide qualified molten steel. Therefore, the selection of ladle refining equipment in combination with product quality requirements shall meet the following basic requirements:

1. Adjust the molten steel temperature to reach the pouring temperature range required by continuous casting;

2. Improve the cleanliness of molten steel, especially reduce the content of large inclusions in steel;

3. Reduce the gas content in steel (such as hydrogen and nitrogen content);

4. Reduce the content of harmful impurities (such as sulfur and phosphorus) in steel;

5. Homogenize the temperature and composition of molten steel, and fine tune the composition to make the chemical composition range of finished steel very narrow;

6. Change the shape and composition of inclusions in steel and improve the fluidity of molten steel;

7. Reduce the smelting load of the steelmaking furnace, shorten the smelting cycle and improve the productivity;

8. Ladle refining furnace becomes a "buffer" between steelmaking furnace and continuous casting machine, balancing the production rhythm between them, which is conducive to improving the productivity of continuous casting machine.