Improving the Cleanness of Low‐Carbon Tube Steel Under Steel Plant Conditions

Reducing the number of nonmetallic inclusions in high‐quality steel rolled products is of great importance for all steel plants. One of the ways to decrease the size and quantity of alumina and silicate nonmetallic inclusions could be suppressing their formation during steel tapping from the BOF converter to the ladle. This could be achieved by changing part of the aluminum for alternative deoxidizers which do not remain in crude steel. Steel deoxidation with the help of calcium and carbon compounds may allow for a drastic decrease in the quantity of alumina nonmetallic inclusions because of the positive effect on their solubility in liquid steel as well as redundant oxygen removal as a gas in CO and CO 2 compounds. Another way to eliminate endogenous Al and Si inclusions is to create favorable thermodynamic conditions to maximize the transfer of nonmetallic inclusions into slag during subsequent ladle furnace treatment. Establishing an optimum range of slag basicity may allow to suppress the harmful spinel inclusions. The effect of calcium carbide preliminary deoxidation during pouring of the semifinished product from BOF converter on the content of nonmetallic inclusions in flat‐rolled product has been analyzed. It has been shown that partial replacement of aluminum with calcium carbide during deoxidation of crude steel by BOF tapping together with liquid slag basicity control during ladle furnace treatment allows to reduce content of nonmetallic inclusions in low‐carbon steel.