摘要
近年来在汽车轻量化大趋势及成本控制的压力下,诸多车企将汽车板减薄至0.65 mm左右后,加工制作冲压变形大部件时钢板冲压开裂缺陷(俗称“针眼”)显著增加,其主要发生于连铸交接坯轧制的钢板。对薄规格高品质汽车钢板冲压开裂问题开展了研究,通过采用扫描电镜和能谱分析分别对开裂缺陷部位进行高倍观察和成分分析,同时运用数值模拟方法研究了炉炉连浇过程接续炉次钢水进入中间包后的流动和混合特征。研究发现造成汽车板冲压开裂的夹杂物主要分为2类,一类为条、块状Al_(2)O_(3)夹杂物,另一类为CaO·2Al_(2)O_(3)、CaO·6Al_(2)O_(3)类钙铝酸盐夹杂物。交接坯轧制的汽车板中Al_(2)O_(3)夹杂物和钙铝酸盐类夹杂物较正常坯多,主要原因为接续炉次开浇时刻中间包内少量钢水裸露被氧化和少量覆盖渣混入钢液。开发了板坯连铸炉炉连浇过程交接坯长度预测模型,并通过对混浇过程产生的铸坯取样分析验证了模型的适用性。钢板轧制发生冲压开裂的交接坯主要是中间包出口处接续炉次钢水质量分数达到20%~80%时间段内所浇铸形成的铸坯,采用“双挡墙+双挡坝”控流结构的中间包产生交接坯时间最短,为7.33 min。根据以上研究结果进行了工业试验,并且对30个浇次的实际生产数据进行了跟踪和统计,按照之前的交接坯降级策略需要降级84块铸坯,通过策略优化,仅降级了38块铸坯,降级量由之前的41.38%减少至18.72%,而所生产薄规格汽车板的“针眼”状冲压开裂发生率没有增加,仍保持在每万件2.5起以下的先进控制水平。
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 Al_(2)O_(3)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%.
作者
张涛
王新华
吴忠有
李金波
高福彬
刘俊山
ZHANG Tao;WANG Xinhua;WU Zhongyou;LI Jinbo;GAO Fubin;LIU Junshan(Hansteel Co.,Ltd.,HBIS Group,Handan 056015,Hebei,China)
出处
《钢铁》
CAS
CSCD
北大核心
2023年第10期75-84,共10页
Iron and Steel
基金
国家重点研发计划资助项目(2021YFB3401001)。
关键词
汽车板
针眼缺陷
非金属夹杂物
连铸交接坯
钢液混合
automobile steel sheet
cracking defect
non-metallic inclusion
transition slabs in continuous casting
steel mixing
