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浙江某水电厂4水轮机转轮为铸焊结构,型号为HL200-LT-250。叶片材料为ZG0Cr13Ni6MoRe。上冠、下环材料为ZG20SiMn,用A207焊条把14片叶片与上冠下环焊接而成。 1978年安装时就曾发现转轮叶片上有11条裂纹,当时由制造厂进行了补焊。运行6967小时后,发现14只叶片又产生了长短不一的裂纹共194条,其中11号叶片近上冠焊缝熔合线附近4～7mm处的裂纹最长,占叶片宽度的2/3(图1);断口具有发亮的金属光泽,其形貌成颗粒状,裂纹无分叉;从微观上看,裂纹是沿原奥氏体晶界断裂。为此,进行了补焊。但运行2172h后,发现11号叶片上根部又有开裂,头部裂穿。于是再进行第二次补焊,运行450h后,仍在上部开裂,头
Zhejiang Hydropower Plant 4 turbine runner cast welding structure, model HL200-LT-250. Leaf material ZG0Cr13Ni6MoRe. On the crown, the material under the ring ZG20SiMn, with A207 electrode to 14 leaves and the crown under the ring welded together. In 1978, it was found that there were eleven cracks on the runner blades when repairs were made by the manufacturer. After 6,967 hours of operation, a total of 194 cracks were found in 14 blades, of which the cracks at 4 ~ 7mm near the weld line near the top of the No. 11 blade were the longest, accounting for 2/3 of the blade width Fig. 1). The fracture has shiny metallic luster and its morphology is grainy with no bifurcation. From the microscopic point of view, the fracture is along the original austenite grain boundaries. To this end, carried out welding repair. However, after 2172h of operation, it was found that there was another crack in the root of No. 11 leaf and the head was cracked. So again for the second welding, after running 450h, still cracking in the upper head