Production Practice of Ultra-Low Carbon Steel H1T in 150 mm×150 mm Small Billet

In order to solve the problems of high blooming cost of the traditional process route for ultra-low carbon steel H1T， including preprocessing， converter， RH， bloom/ingot continuous casting， and blooming， and the frequent blockage of nozzle in the process of continuous casting which leads to production interruption， a 150 mm×150 mm billet continuous casting production process has been developed. The process control has been focused on the blockage of continuous casting nozzle， and the changes of composition， slag system， and inclusions during the production process have been analyzed. The industrial production practice shows that the product of ultra-low carbon steel H1T has been successfully produced by adopting the process of adding aluminum for deoxidation in converter tapping， LF slag basicity > 10， top slag （FeO + MnO） ≤ 2%， stirring argon flow > 600 L/min to ensure desulfurization， RH process with oxygen blowing for deep decarburization under 65 Pa， and calcium treatment of molten steel. And the number of continuous heats has reached 10 heats.