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为了阐明双辊浇铸过程中凝固组织形成的机制,使用一台小型双辊连铸机对SUS304奥氏体不锈钢进行了连铸实验。铸带中有两种凝固组织,即柱状枝晶区和等轴晶区。随辊面和液态金属间接触时间的增加,铸带厚度枝晶区深度增大,而等轴晶区几乎不变。增加初始辊缝尺寸,仅使等轴晶区扩大。另外,已弄清了钢液过热和结晶辊承支力对形成凝固组织的影响。 钢液在与两结晶辊相接触时凝固的表层内形成柱状枝晶区。铸带剩余的未凝固层离开轧辊咬合后在缓慢的冷却速率下形成的是等轴晶区。根据实验结果和对铸带内热传递的理论分析,得出结论:在钢液过热相当高且轧辊支承力很小时,随着铸带离开轧辊时其表面的传热系数急剧减小,游离晶在枝晶凝固界面前沿优先长大,从而形成了等轴晶。
In order to clarify the formation mechanism of solidified structure during twin-roll casting, a continuous casting experiment was conducted on SUS304 austenitic stainless steel using a small twin-roll continuous casting machine. There are two kinds of solidification organizations in the belt, that is dendritic columnar zone and equiaxed zone. With the increase of contact time between roller surface and liquid metal, the depth of dendritic zone of belt thickness increases, but the equiaxed zone almost does not change. Increase the initial roll gap size, only to expand the equiaxed zone. In addition, the influence of molten steel overheating and bearing capacity of crystal roller on the formation of solidified structure has been clarified. The molten steel forms a columnar dendrite zone in the surface layer that solidifies when it comes into contact with the two crystallization rolls. The remaining unconsolidated layer of the strip forms an equiaxed zone at a slow cooling rate after leaving the nip. According to the experimental results and the theoretical analysis of the heat transfer in the belt, it is concluded that when the molten steel is overheated and the supporting force of the roller is very small, the heat transfer coefficient of the surface decreases sharply as the belt leaves the roller. Dendrite solidification front of the interface grow preferentially, forming an equiaxed crystal.