低温度梯度结晶器的传热分析及工业应用试验

 结晶器内钢液凝固前沿温度梯度的降低可以阻碍柱状晶的生长、促进柱状晶向等轴晶的转变和提高等轴晶率，从而有利于铸坯组织的均质化。基于上述原理和结晶器传热计算，设计和制造了可用于降低钢液凝固前沿温度梯度的带隔热镀层的新型结晶器，并在方坯连铸机上进行了工业试验，分析了其对方坯凝固组织的影响。结果表明，低温度梯度结晶器可满足连铸生产要求；与传统结晶器相比，低温度梯度结晶器出口铸坯表面温度提高了108℃，相近拉速下该结晶器的平均热流密度相对更低，表明其减缓了钢液在凝固初期的传热，从而降低了凝固前沿的温度梯度；通过与低过热度、电磁搅拌技术相结合，低温度梯度结晶器生产的铸坯等轴晶率提高了8%～13%，中心偏析和缩孔严重程度明显降低。

Design and Industrial Application Trial for Low Temperature Gradient Mould Copper Tube

The growth of columnar grain could be restrained and the transformation from columnar grain to equiaxed grain would be promoted by decreasing temperature gradient on solidified front in the mould to increase equiaxed grain ratio, which was beneficial for homogenization of billet structure. Based on above-mentioned theory and mould heat transfer computation, a new mould with heat insulated coating for decreasing temperature gradient was designed and fabricated. Industrial trials were carried out on a billet caster using the mould. The effect of this technology on solidification structure of billet was analyzed. The result showed that the low temperature gradient could satisfy the need of continuous casting. The surface temperature of billet was increased by 108℃ and average heat flux was lower compared to traditional mould as the casting speed was similar, which indicated that heat transfer at the initial stages of solidification of molten steel had been restrained and therefore the temperature gradient on solidified front was decreased. The equiaxed grain ratio of billet produced by the low temperature gradient mould integrated with low superheat and EMBR technology was increased by 8%~13% and the severity of center segregation and cavitation had been reduced obviously.