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高温螺栓断裂可分为裂纹起始和裂纹缓慢扩展、裂纹临界失稳扩展两个阶段:裂纹的起始有较长的孕育期,多在螺纹第一扣底开始,裂纹由沿晶蠕变空洞链构成,第一阶段裂纹断口为沿晶开裂,晶界面布满孔洞,显示蠕变断裂的特征;第二阶段为瞬时过载断裂,显示准解理断口。由螺栓切取的缺口拉伸试样,呈缺口强化,断口为穿晶韧窝状;冲击韧性a_K≈0.8～5公斤米/厘米~2,断口为准解理,证明短时载荷不能形成沿晶空洞,空洞是在高温、长时间应力作用下形成的。
High-temperature bolt failure can be divided into crack initiation and crack propagation slowly, and crack propagation in two critical stages: the beginning of the crack has a longer period of inception, and the more the first buckling begins, the crack creeps from the intergranular cavity Chain. The fracture in the first stage is cracked along the grain and the grain boundary is covered with holes, showing the characteristics of creep rupture. The second stage is the instantaneous overload fracture, showing quasi-cleavage fracture. The notch tensile specimens cut by bolts showed a notch reinforcement and the fracture was a translucent dimple. The impact toughness a_K≈0.8 ~ 5 kg m / cm ~ 2 and the fracture surface was quasi-cleavage, which proved that the short-time load could not form along the crystal Holes and voids are formed under the action of high temperature and prolonged stress.