低碳钢和中碳钢连铸方坯初始凝固的对比研究

以低碳钢和中碳钢为研究对象,围绕不同连铸工艺参数对方坯初始凝固行为的影响,利用CA-FE耦合模型模拟实际连铸过程结晶器内方坯的初始凝固行为,考察拉速和过热度对方坯出结晶器坯壳厚度的影响,对比二者出结晶器横截面枝晶微观形貌.研究表明:过热度和拉速增加均能使出结晶器坯壳厚度下降,而拉速的影响更为显著.不同钢种在相同条件下出结晶器坯壳厚度下降梯度不同.过热度越低柱状晶越致密细小,利于提高连铸坯质量,拉速对柱状晶的影响相对较小.由于出结晶器坯壳安全厚度限制,过热度取15℃,低碳钢拉速不能超过2.2 m·min-1,中碳钢拉速不能超过2.5 m·min-1,据此针对不同钢种设计不同拉速可提高连铸效率.同时,模型结果显示低碳钢出结晶器时刻柱状晶更为发达. 

Comparative study on the initial solidification behavior of continuous casting billets between low-carbon steel and medium-carbon steel

Low-carbon steel and medium-carbon steel were taken as the objects of research in this paper. In order to study the effects of process parameters on the initial solidification behavior of continuously cast billets,a CA-FE coupled method was used to simulate the initial solidification behavior of billets in the mold during practical continuous casting. The dependences of initial billet shell thickness at the exit of the mold upon superheat and casting speed were investigated and the microstructure morphologies of the two steels were compared at the same time. It is shown that the shell thickness decreases with increasing superheat and casting speed,while the casting speed has a more significant impact. The shell thickness of different steels decreases at different gradients under the same condition. The lower the superheat temperature,the more compact the columnar crystals will be,which is useful to improve the quality of continuous casting billets,while the casting speed has less influence. With the constraint of shell thickness at the exit of the mold,the superheat is taken to be 15℃,and the casting speeds of low-carbon steel and medium-carbon steel could not surpass 2.2m·min-1 and 2.5 m·min-1,respectively. According to this result,we can design the optimum drawing speeds for different steel grades to improve the efficiency of continuous casting. Moreover,the model results show that the columnar crystals of low-carbon steel is more developed than those of medium-carbon steel.