汽车用双相钢铸坯成分偏析的研究

为了找到连铸工艺条件对双相钢铸坯内部偏析的影响规律和双相钢带状组织的成因,对双相钢DP780铸坯的内部偏析开展了研究。采用原位分析、钻屑成分检测、光学显微镜和扫描电镜等试验设备和检测方法,分析了中间包过热度、拉速对铸坯宏观偏析的影响,分析了二冷比水量、中间包过热度对一次、二次枝晶间距的影响,并研究了铸坯枝晶偏析对热轧板带状组织的影响,明确了双相钢带状组织产生的机理和控制措施。结果表明,过热度小于30 ℃时,双相钢铸坯中心偏析级别可以控制在C1.0级以下水平,中心等轴晶比例最高可达到12.25%。拉速对铸坯中心等轴晶比例影响不大。降低中间包过热度、提高二冷比水量可以减少双相钢铸坯内部一次枝晶间距和二次枝晶间距。

Research of slab segregation of dual phase steel for automobiles

The research of slab internal segregation of DP780 was carried out for finding the influence of process conditions of continuous casting and the cause of banded structure.Test equipments and test methods of original pisition analysis,drilling cutting composition testing,optical microscope and scanning electron microscopy(SEM)were used,the influence of tundish superheat,casting speed on slab macrosegregation was analyzed,the influence of secondary cooling ratio and tundish superheat on primary and secondary dendrite spacing was analyzed,and the influence of slab dendrite segregation on banded structure of hot rolled plate was studied,mechanism and countermeasures has been clear about banded structure happening of dual phase steel.The results showed that the degree of superheat was less than 30℃,the level of slab center segregation of dual phase steel could be controlled under C1.0,center equiaxial grain ratio could reach 12.25%.Casting speed had little influence on the center equiaxial grain ratio of slab.Primary and secondary dendrite spacing of dual phase steel slab were reduced by reducing superheat and improving secondary cooling ratio.