厚壁TP347钢管焊接接头再热裂纹敏感性试验研究  

Study on reheat cracking susceptibility of welded joint of thick-wall TP347 piping

作　　者：王建军[1,2] 李冬毓 俞树荣 WANG Jianjun;LI Dongyu;YU Shurong(Lanzhou University of Technology,Lanzhou 730050,China;Sinopec Fifth Construction Co.,Ltd.,Guangzhou 510180,China)

机构地区：[1]兰州理工大学,兰州730050 [2]中石化第五建设有限公司,广州510180

出　　处：《压力容器》2022年第7期15-24,共10页Pressure Vessel Technology

基　　金：国家重点研发计划项目“石化企业污染防控与修复工程技术体系构建与示范”(2018YFC1803305)。

摘　　要：随着石油化工加氢系列装置大型化,用于装置高温高压部位的厚壁TP347钢管焊接接头在热处理后,以及管道使用一段时间后,焊接接头出现再热裂纹的问题比较突出。目前缺乏对高温下厚壁TP347焊接接头残余应力松弛、材料演化损伤等方面的深入研究。针对以上问题,开展了厚壁TP347钢管焊接接头900℃高温恒载试验和750~900℃温度区间高温慢拉伸试验。结果表明:厚壁TP347钢管焊接接头在900℃时的再热裂纹临界断裂应力为24 MPa,该应力已远低于80%母材高温屈服强度,说明该温度下焊接接头具有较高的再热裂纹敏感性;高温慢拉伸试验结果表明:850~900℃区间焊接接头具有较高再热裂纹敏感性,750~800℃焊接接头稍微具有再热裂纹敏感性,随着温度升高,再热裂纹敏感性增大。采用光学金相、扫描电镜以及能谱分析等微观方法进行研究分析,发现厚壁TP347钢管焊接接头具有较高再热裂纹敏感性,这是因为高温加速了Cr, Nb, Mn, Si等元素向晶界扩散,晶界聚集析出大量的碳化物,降低了晶界的塑性。因厚壁管道具有较大的焊接残余应力,高温下,在应力作用下晶界产生孔洞,孔洞合并导致了裂纹沿着晶界扩展。With the tendency of petrochemical hydrogenation series units to large scale, the welded joints of thick-walled TP347 steel pipe used in high temperature and high pressure parts of the units have a prominent problem of reheat cracks after heat treatment or after a period of time of service.At present, there is lack of in-depth research on residual stress relaxation and material evolution damage of thick-walled TP347 welded joints at high temperature.To solve the above problems, 900 ℃ high temperature dead load test and 750~900 ℃ high temperature slow tensile test were carried out for welded joints of thick-walled TP347 steel pipe.The results show that the critical fracture stress of reheat crack is 24 MPa at 900 ℃,which is much lower than 80% of the base metal′s high temperature yield strength, indicating that the welded joint has high sensitivity to reheat crack at this temperature.The high temperature and slow tensile test results show that the joints welded in the temperature range of 850~900 ℃ have high reheat crack sensitivity, and the joints welded in the temperature range of 750~800 ℃ have slight reheat crack sensitivity, and the reheat crack sensitivity increases with the increase of temperature.By using optical metallography, scanning electron microscopy and energy spectrum analysis, it is found there is high reheat crack sensitivity of welded joints of thick-walled TP347 steel tubes, this is because the high temperature accelerates the diffusion of Cr, Nb, Mn, Si and other elements to grain boundaries, where a large amount of carbide precipitates, which reduces the plasticity of grain boundaries.Due to the large welding residual stress in the thick-walled pipeline, pores are generated in the grain boundary under the action of stress at high temperature, and the combination of pores leads to the crack propagation along the grain boundary.

关 键 词：TP347钢 再热裂纹 恒载试验 慢拉伸试验 析出相 

分 类 号：TH140.7[一般工业技术—材料科学与工程] TG406[机械工程—机械制造及自动化]