热处理对超(超)临界锅炉TP347H弯管组织和性能的影响

Effect of Heat Treatment on Microstructure and Properties of TP347H Elbow

以超(超)临界锅炉广泛使用的TP347H奥氏体耐热不锈钢为研究对象,选取规格为φ50.8 mm×4.5 mm的TP347H管子,在800℃下弯曲成为弯曲半径为85.5 mm的180°弯管。采用硬度试验、双环电化学动电位再活化法(DL-EPR)试验、金相试验、扫描电镜试验和晶间腐蚀试验,研究不同固溶处理制度对在800℃弯管后的TP347H钢管组织和性能的影响。研究结果表明:TP347H钢管在800℃弯管变形后,发生明显的加工硬化(229 HB),其硬度随固溶温度的升高而降低,1150℃固溶时硬度达到164 HB。800℃弯管的再活化率比原始钢管及固溶处理后的弯管高2个数量级,达到0.2755,晶间腐蚀敏感性大,易发生晶间腐蚀,晶间腐蚀试验结果表明在800℃弯管弯曲后产生裂纹。经高温固溶后,弯管的再活化率迅速下降,固溶温度低于1100℃时,再活化率(R_(a)0.0022)呈下降趋势,固溶温度高于1100℃时,再活化率(R_(a)0.0046)又开始上升。固溶处理能够显著降低800℃弯管的晶间腐蚀敏感性。

TP347H austenitic heat-resistant stainless steel widely used in ultra(supercritical)boiler was taken as the research object,and the specification of φ50.8 mm×4.5 mm TP347H pipe was bent to a 180°bend with a bending radius of 85.5mm at 800℃.The effect of different solution treatment on microstructure and property of bending TP347H steel tube at 800℃ was studied by using hardness test,double loop-electrochemical potentioknetic reactivation(DL-EPR)test,microscopic test,scanning electron microscopy test,intergranular corrosion test.The results showed that the TP347H tube after bending deformation at 800℃ has obvious work-hardening(229 HB),the hardness decreased with the increase of the solid solution temperature.The hardness reached 164 HB at 1150℃.The reactivation rate of bending tube at 800℃ was 2 orders of magnitude higher than that of the original steel tube and the solid solution treatment bending tube.Intergranular corrosion of bending tube at 800℃ was sensitive.The results of intergranular corrosion test showed that cracks appeared after bending at 800℃.After high temperature solid solution,the reactivation rate of elbow decreased rapidly.When the solution temperature was lower than 1100℃,the reactivation rate(R_(a)0.0022)decreased.When the solution temperature was higher than 1100℃,the reactivation rate(R_(a)0.0046)began to rise again.Solid solution treatment could significantly reduce the intergranular corrosion sensitivity of bending tube at 800℃.