Effect of Argon Injection into the Down-Leg of RH on the Inclusion Removal in Industrial Trials

The novel industrial trial is conducted to investigate the effect of argon injection into the down-leg of the RH degasser on the inclusion removal. The ‘cold steel plate dipping’ is used to take samples of molten steel and argon bubbles from the RH ladle. The industrial CT detection and electron microscope observation are applied to analyze the bubble characteristics. The results show that the size of bubbles generated by argon injection in the down-leg ranges from 7 to 1430 μm. Among them, the number density of bubbles with a diameter of 60 μm is the largest, reaching 0.1 per mm3. After adopting the down-leg argon injection technology, the average oxygen activity at the end of the RH process decreases by 2.35 ppm, and the surface defects of cold-rolled sheets of all grades are reduced. Based on the theoretical analysis of bubble collision and adhesion to inclusions, the small-sized bubbles have a relatively high capture probability for inclusions smaller than 10 μm. Comprehensively analyzing the experimental results, it is found that the down-leg argon injection technology has an obvious effect on removing inclusions.