超超临界火电用Super304H不锈钢管的组织分析

Microstructure analysis of Super304H steel pipe used for ultra-super-critical boiler

分析了Super304H不锈钢成品管和穿孔后133 mm毛管的显微组织。在Super304H不锈钢成品管组织中能观测到蠕虫状物相和较粗大的Nb化物,经电镜和XRD分析,可以确认蠕虫状物相是高温铁素体相,含量在6%－8%;穿孔后133 mm毛管组织中,存在少量的δ铁素体,但由于量很少,在X射线衍射分析时检测不到。结果表明,成品管中存在较多的δ铁素体主要是在从133 mm毛管到成品管生产过程中形成的,因此要降低软化处理和固溶处理的温度,既可减少δ铁素体相的量,也可减少粗大的Nb化物,保证最终钢管产品质量和提高产品合格率。

Microstructure of the finished Super304H austenitic stainless steel pipe and the perforated 133 mm raw pipe was analyzed.A lot of worm-like phase and niobium compounds were observed in the finished pipe,but little in the raw pipe.The worm-like phase was determined as δ-ferrite by XRD.The analysis results show that the δ-ferrite in finished Super304H pipe generates in the course of heat treatment within the process of 133 mm raw pipe to finished pipe because of the too high treating temperatures.So the solution temperature and softening temperature should be reduced respectively which not only can decrease δ-ferrite but also refine niobium compounds,and ensure the quality of finished pipes and increase the percentage of pass.