Formation and control of midway crack in LDCC #br# Q235B steel slab with high casting speed
LAN Peng1,HAN Gengwei2,LI Liang1,WANG Pu1, JIANG Xianxun2,ZHANG Jiaquan1
(1. School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, China;
2. Department of Production and Technology, Jilin Jianlong Iron and Steel Co., Ltd., Jilin 132104, Jilin, China)
Abstract： The formation mechanism and influencing factors for midway crack in continuously cast Q235B slab by LDCC route were studied based on numerical modeling and strain calculation, and the strategy to control the slab quality at high casting speed was also developed according to the plant condition. It was found that the precision of roll gap and alignment was the key factor affecting the occurring of midway crack in Q235B slab, as the tensile strain induced by both roll gap fluctuation and roll misalignment was larger than 60%. The secondary cooling in initial zones of the caster also has significant influence. The strain by surface temperature rebound was about 40% at most. The total tensile strain at the solidification front was lowered by 20% when the cooling was strengthened and homogenized with positive deviation of the roll gap between neighboring rolls along pulling direction about 1.5 mm, while that effect was less obvious when the deviation decreases to 0.5 mm. The influence of roll gap precision became more prominent as the casting speed increased. Increasing the Mn/S to higher than 25 enable the shell to resist the additional strain from 1.5 mm positive deviation between neighboring rolls, ±0.5 mm roll misalignment and 50 ℃/m surface temperature rebounding. It was suggested that the total precision of the roll gap should be controlled to ±0.5 mm and the positive deviation of the roll gap between neighboring rolls should be within 0.5 mm to prevent the midway crack in Q235B steel by LDCC route with casting speed higher than 1.5 m/min.
兰鹏，韩庚维，李亮，王璞，蒋宪勋，张家泉. 直上钢Q235B板坯高拉速下中间裂纹的形成与调控[J]. 钢铁, 2019, 54(8): 144-153.
LAN Peng,HAN Gengwei,LI Liang,WANG Pu,. Formation and control of midway crack in LDCC #br# Q235B steel slab with high casting speed. Iron and Steel, 2019, 54(8): 144-153.
