2101节镍双相不锈钢立式连铸板坯的组织转变

Microstructure Transformation Process of Lean Duplex Stainless Steel 2101 in Vertical Continuous Casting Slab

分析了2101双相不锈钢实际铸坯的宏观晶粒分布和微观组织转变。结果表明,2101双相不锈钢的柱状晶向等轴晶转变(CET转变)发生在二冷2区末端距铸坯表面25 mm处。在此区域内适当降低铸坯表面冷却强度有助于减小坯壳内部温度梯度促进CET转变,提高铸坯的等轴晶率和扩大角部的等轴晶区域;对微观组织的分析发现,在二冷6区之后提高冷却强度可调整铸坯中心形成的奥氏体形态,有利于晶内及晶界处奥氏体细化和减小晶界处针状奥氏体组织的数量和尺寸,从而在一定程度上提高铸坯的热变形能力。

The macro grain size distribution and microstructure change of the slab of Lean duplex stainless steel 2101 was investigated. It was concluded that columnar equiaxed crystal transformation(CET) occurred in the location, where is at the end of section No.2 of the secondary cooling zone with 25 mm from the slab surface. Decreasing the slab surface cooling strength in this zone will reduce internal temperature gradient in the shell, and promote CET transition, improve the rate of equiaxial crystal and expand the equiaxial zone at the corner. The results of microstructure analysis show that behind the section No. 6 in secondary cooling zone the morphology of austenite formed in the core of the billet can be adjusted by increasing the cooling intensity, which is also beneficial to the refinement of austenite morphology in the grain and at the grain boundary. Size of the acicular austenite structure at the grain boundary can be reduced, so as to improve the heat deformation ability of the billet.