Abstract：Many automobile enterprises recently decreased the thickness of the steel sheet to about 0.65 mm,which resulted in a remarkable increase of cracking defects when large deformation is applied,particularly on the steel sheets produced from the transition slabs in continuous casting. The cracking of the thin gauge automobile sheets were investigated by the high-magnification observation,and composition analysis of the cracking were carried out by scanning electron microscopy and energy spectrum analysis. The flow and mixing characteristics of the molten steel in succeeding heat entered the tundish were analyzed by numerical simulation,and the results find out that the cracking was caused mainly inclusions of Al2O3 and calcium aluminates. More cracking occurred on steel sheets made from the transition slabs mainly due to a small amount of liquid steel being oxidized and a few tundish slag drops involved in the liquid steel at the time when the succeeding heat starts casting. The prediction model of the transient slab length was developed,and the applicability of the mathematical model was verified by sampling and analyzing the mixed-casting slabs. The cracking occurred mainly on sheets of the slabs cast within the time when the mass percent of the steel of the succeeding heat reached 20%-80% at the exit of the tundish. The tundish with the flow control structure of double weirs and double dams has the shortest time to produce the transition slabs and the time is 7.33 min. Industrial experiments were carried out based on the research results,and the actual production data of 30 casting sequences were tracked. According to the previous downgrade strategy of transition slabs,84 slabs needed to be downgraded,but through optimization,only 38 transition slabs should be downgraded. The amount of degradation was reduced from 41.38% to 18.72%,while the stamping cracking rate did not increase,and remained the advanced control level at less than 0.025%.
张涛, 王新华, 吴忠有, 李金波, 高福彬, 刘俊山. 薄规格高品质汽车板交接坯降级策略的优化[J]. 钢铁, 2023, 58(10): 75-84.
ZHANG Tao, WANG Xinhua, WU Zhongyou, LI Jinbo, GAO Fubin, LIU Junshan. Optimization research on downgrade strategy of transition slabs of thin size and high quality automobile sheet[J]. Iron and Steel, 2023, 58(10): 75-84.
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