2205双相不锈钢中厚板边部起皮缺陷机理研究

Study on edge peeling defect mechanism of medium and heavy plate for 2205 duplex stainless steel

利用扫描电镜观察了2205双相不锈钢中厚板边部起皮缺陷,缺陷部位氧化皮的成分和形态有明显的差别,缺陷掉落后,凹坑内主要富集Cr、O、C元素。研究表明:2205双相不锈钢中厚板边部起皮缺陷与连铸坯边部柱状晶及受力状态有关。由于柱状晶强度低、面缩率低,中厚板展宽过程中位于连铸坯边部的柱状晶在拉应力作用下柱状晶晶界产生微裂纹,尤其是在α和γ两相结合部位易产生微裂纹,微裂纹在随后的轧制中扩展。同时,随着变形的深入,连铸坯在展宽轧制时的不均匀变形使连铸坯宽面上、下角部金属逐步向钢板心部流动,分别内移至钢板上、下表面,角部被氧化的金属进入钢板基体。经两种因素共同作用,在后续的轧制过程中微裂纹逐步扩展,导致缺陷的产生。

The edge peeling defect of medium and heavy plate for 2205 duplex stainless steel was analyzed by SEM,then it found that the composition and morphology of oxide scale in defect position had obvious differences,and the Cr,O,C elements were mainly enriched in the steel pit after defects dropped out. The results show that the edge peeling defect of medium and heavy plate for 2205 duplex stainless steel is relative to columnar crystal and force status at the edge of continuous casting billet. Because of the low strength and the reduction of area of columnar crystal,the crystal boundary of the columnar crystal which located at the edge of the continuous casting billet was engendered the microcrack under the effect of the tensile stress during the spreading procedure of the medium and heavy plate. In especial,the microcrack easily engendered at the combination position of the α and γ phase,then the crack extended in the subsequent rolling procedure. Meanwhile,with the penetration of the deformation,the metal at the upper and lower corner positions of the side section for billet flowed to the core of the steel plate gradually under the effect of the in-homogeneous deformation during the spreading rolling procedure of the continuous casting billet,then separately moved to the upper and lower surfaces of the billet,and the oxidized metal of the corner position entered into the matrix of the steel plate. The microcrack was extended gradually during the subsequent rolling procedure under the combined action of the two factors,and formed the defect.