超大断面宽厚板坯模铸技术

Mold Casting Technology for Jumbo Slab Ingots

超大断面宽厚板坯是制备大规格锻造坯料的重要基材,此类厚度超过500 mm、锭身无锥度的宽厚板坯只能采用模铸工艺制备。但因尺寸效应导致凝固过程和铸锭质量极难控制,易出现致密度低、宏观偏析严重、开裂等缺陷。在合理化锭型设计的基础上,分析在模铸工艺条件下各类锭型的凝固过程和内部质量。研究结果表明无锥度的锭型设计导致熔池形状呈U形,不利于铸锭形成自下而上的凝固过程,恶化芯部钢水的补缩条件。对疏松的计算结果进一步印证这一结论,且厚度越小,疏松缺陷分布范围越广、致密度越差。大截面宽厚板坯的厚度对应力影响较小。宽厚板坯的厚度和锥度对C元素的宏观偏析和V形偏析没有显著影响,而加快冷却速度可以显著加大成分均匀层的深度,抑制A形偏析的形成。

Jumbo slab as an essential material for making super-large metal forgings can be made only by the means of mold casting technique because of its thickness above 500 mm and its taper-free requirement.The size effect imposes extreme difficulty on control of solidification process and cast ingot quality.Defects,such as low density,serious macro-segregation and cracking,are prone to generate.Based reasonably designed ingot shapes,the solidification process and internal quality of various ingot shapes have been analyzed under mold casting technique The analysis result shows that the taper-free ingot design leads to a U-shaped molten pool that is not conductive to the formation of solidification from bottom to top and deteriorates the molten steel feeding condition.The porosity calculation results further confirm the analysis result and reveal that the smaller the thickness is,the wider the porosity defects spread an the lower the density is.The slab thickness has litter effect on the stress.The slab thickness and taper have no significant effect on the macro-segregation and V-shaped segregation of carbon element while accelerated cooling process can increase significantly the depth of the even layer of the carbon element and constrain the formation of A-shaped segregation.