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以经济型双相不锈钢为例,通过金相试验和扫描电镜对热轧板表面缺陷进行分析。结果表明,缺陷呈细长形、沿轧制方向分布,缺陷内部已明显发生了二次氧化,证明缺陷在热轧前已形成。对连铸坯修磨前、后的表面质量进行分析,发现连铸坯皮下气孔是导致热轧板表面缺陷的主要原因。而皮下气孔是由于双相不锈钢在凝固过程中氮析出造成的,为此,采用低温快注、优化冷却和电磁搅拌的方法改善氮析出条件。现场应用后,双相不锈钢板坯因皮下气孔缺陷产生的报废率由10.6%下降到2%,产品质量得到显著改善。
Taking economical duplex stainless steel as an example, the surface defects of the hot rolled plate were analyzed by metallographic test and scanning electron microscope. The results show that the defects are slender, distributed along the rolling direction, the defects have obviously occurred within the secondary oxidation, to prove defects have been formed before hot rolling. The surface quality of the continuous casting slab before and after grinding was analyzed, and it was found that the sub-stomata of the continuous casting slab was the main cause of the surface defects of the hot rolled slab. The hypodermic pores are caused by the nitrogen precipitation during the solidification of duplex stainless steel. Therefore, the method of rapid cooling at low temperature, optimization of cooling and electromagnetic stirring is used to improve the conditions of nitrogen precipitation. After field application, the rejection rate of the duplex stainless steel slab due to the subcutaneous blowhole defect decreased from 10.6% to 2%, the quality of the product was significantly improved.