T91钢长时高温运行后塑韧性变化趋势研究

通过对某机组运行长达13万h的T91钢高温再热器管进行系列冲击试验,结合运行6万h的T91钢试样和原始管段试验结果,研究T91钢管长期高温运行后的塑韧性变化趋势.研究结果表明,随着运行时间的增加,T91钢的脆性转变温度(FA TT)出现了明显的上升趋势,表明运行过程中材料塑韧性下降；T91钢长期高温运行后(13万h)试验温度0℃以上时冲击断口表现为100％剪切断裂,韧性断裂为主；裂纹扩展过程中均只产生裂纹稳定扩展,与断口的解理断裂率为0％一致；随冲击试验温度的升高,3种试样的裂纹扩展能量Wp均增加,在相同温度下原始管段的裂纹扩展能量Wp最大.

DUCTILITY AND TOUGHNESS VARYING TENDENCY OF T91-STEEL AFTER LONG-TIME OPERATING AT HIGH TEMPERTURE

T91 steel pipes were investigated by series impact tests of T91-steel-made high temperature reheater pipes which had been running for 130 000 hours,combined with test results of the original pipes and T91-steel samples which had 60 000 hours of operation.Results show that,with the increasing running time,fracture appearance transition temperatrue(FATT) of T91 steel rose obviously,this indicates that there is a decrease in ductility and toughness of material during the running.After long time(130 000 h) operation at high temperature,T91 steel presents 100% shear fracture on the impact fracture surface when the test temperature was above 0 ℃,and the ductile fracture dominates.During the crack propagation process,only stable crack growth occurs,this is consistent with the cleavage fracture rate of the fracture surface(which is 0).As the temperature of impact test rising,crack propagation energy Wp of all 3 samples increases,and the original pipe’s is the maximum when its test temperature is the same as the other two.