BN1TL不锈钢连铸坯组织对鳞折缺陷形成影响及试验验证

Influence of microstructure for BN1TL stainless steel continuous casting billet on formation of scale defects and experimental verification

节镍奥氏体不锈钢热轧板及冷轧板表面的鳞折问题严重影响了产品的合格率。以BN1TL不锈钢连铸坯作为研究对象,分析了BN1TL不锈钢凝固组织的特点,并通过冷装炉方式下的热轧模拟试验验证了连铸坯组织与鳞折缺陷的相关性。试验结果表明,BN1TL不锈钢的凝固组织以柱状晶为主,晶粒尺寸由表层至芯部逐渐增大,柱状晶晶界存在铬的碳化物析出。同时该特点的凝固组织由于存在大量晶间析出,导致晶界弱化严重,经过热轧后易生成鳞折缺陷,并且影响整个轧制工艺流程。热轧模拟试验结果表明,材料在粗轧时即产生鳞折缺陷,精轧时缺陷得到扩展。减小在粗轧时的道次压下量可以减少鳞折缺陷的生成,改善板坯表面质量。

The scaling problem on the surface of hot-rolled or cold-rolled nickel-saving austenitic stainless steel affects the qualification rate of products seriously. The characteristics of solidification structure for BN1TL stainless steel were studied by BN1TL stainless steel continuous casting billet. The correlation between structure of continuous casting billet and the scale defect was verified by simulation test of hot rolling in cold charging furnace. It can be found from experimental results that the solidification structure of BN1TL stainless steel is mainly columnar crystals, and the grain size gradually increases from surface to core. The chromium carbide precipitation is observed in the grain boundary of columnar crystals, which leads to serious grain boundary weakening, therefore, the scale defects are easily to be produced during hot rolling and would affect the whole rolling process. The results of simulation show that the scale defect occurs during rough rolling and expanded during finish rolling. Reduce the pass reduction of rough rolling is a useful way to inhibit the production of scale defects and improve the quality of billet surface.