【摘要】 本文利用着色探伤、低倍检验、金相分析、显微硬度及电子探针等方法，分析了某化肥厂一段转化炉炉管沿异种纲焊接融合区的爆裂事故。研究结果表明：４Ｃｒ２５Ｎｉ２０钢与１（１／４）Ｃｒ（１／２）Ｍｏ钢焊接融合区，在５００℃左右， 近２００００小时的运行中，１（１／４）Ｃｒ（１／２）Ｍｏ钢接近融合线部位，由于碳向焊缝扩散而发 生脱碳现象，沿异种钢的融合线折出薄壳状脆性碳化物相，融合区硬度升高，这是导 致融合区韧性下降，引起炉管沿融合线断裂的主要原因。更多还原

【Abstract】 Tubes of 1hc primary reformer furnace of an ammonia plant were exam- inated through dye penetrate; macro and micrometall-ographic; microhardness and micro-probe tests. The results ofs the examinations show that after 20000 hrs of operation at 500℃, the carbons of the 1(1/4)Cr(1/2)Mo Stecl diffused from heat affected zone to the welded fusion boundaryl the 1(1/4)Cr(1/2)Mo Stee1 side of the welded fusion boundary was decarburized and a thin shell-like brittle carbide was precipitated along the fusion boundary of the welding seam; the hardness of the welded fusion zone was incrcased. Theseare the reason of the brittle cracks along the welded fusion zone. Cracks started from the root of the welding seam.更多还原