Regular Article

Study on the utilization of supersaturation degree in Al deoxidation to improve cleanliness and control of Al₂O₃ inclusions in ultra-low carbon steel

¹ School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 Xue-yuan Road, Hai-dian District, Beijing 100083, PR China
² Chinese Academy of Environmental Planning, Ministry of Ecological Environment, 10 Dayangfang, Beiyuan Road, Chaoyang District 100012, PR China
³ Research Institute of Technology of Shougang Group, #69 Yang-zhuang Road, Shi-jing-shan District, Beijing 100043, PR China
⁴ Steelmaking Plant of Beijing Shougang Co. Ltd, Qian-an City, Hebei Province 100041, PR China

^* e-mail: jiangmin@ustb.edu.cn

Received: 27 December 2020
Accepted: 5 February 2021

Abstract

Effects of supersaturation degree (S) in Al deoxidation on cleanliness and alumina inclusions in steel were studied. If enough Al was added to steel, higher initial dissolve oxygen before Al deoxidation resulted in higher steel cleanliness. In the experiments, with the rise of [mass% O] from 102 ppm to 340 ppm and 931 ppm, logS in steel melts were increased from 4.8, to 7.0 and 8.8, respectively. As a result, total oxygen (T.O) was decreased to 25 ppm, 22 ppm and 21 ppm, respectively. Based on the results, important influence of supersaturation degree on the formation of Al₂O₃ was revealed. At lower S, Al₂O₃ would be singular and smaller particles ≤ 5 µm that was difficult to be removed. However, Al₂O₃ would exist as large clusters in steel at higher S, which can be efficiently removed. By utilizing the findings in laboratory, RH refining of ultra-low-carbon steel was optimized. Steel cleanness and control of inclusions were improved. As a result, surface defects in cold rolling sheets caused by Al₂O₃ inclusions were effectively minimized.