国内外均已积累相当多的实例,说明弯管的蠕变断裂寿命远低于直管。金相分析表明,炉外高温弯管的蠕变断裂属于沿晶空洞型蠕变断裂,裂纹起始于弯管外弧外壁表面沿轴向延伸。弯管与其相联结的直管在相同的工况下运行,具有相同的材料,相同的温度和起仃机次数,显然工况、材料因素不能说明裂纹起始位置和方向的规律性。 A considerable number of examples have been accumulated both at home and abroad, indicating that the creep rupture life of elbows is much lower than that of straight pipe. Metallographic analysis shows that the creep rupture at high temperature outside the furnace belongs to the creep rupture along the crystal cavity and the crack begins to extend axially along the outer wall surface of the elbow. Elbow pipe and its associated straight pipe running under the same conditions, with the same material, the same temperature and the number of Ding Ding machine, apparently operating conditions, material factors can not explain the crack initiation position and direction of the regularity.