西气东输二线工程用X80螺旋埋弧焊管热影响区性能分析

对西气东输二线工程用X80级φ1219 mm×18.4 mm螺旋埋弧焊管热影响区夏比冲击韧性和维氏硬度进行了统计分析.结果表明:X80螺旋埋弧焊管热影响区具有优良的力学性能,不同钢厂产品之间性能差异较小;热影响区夏比冲击功低于管体母材130 J;硬度低于母材15～24 HV10,存在明显的热影响区"软化"现象.随着钢级...     

高强度管线钢焊接性研究现状

为了进一步提高我国高强度管线钢的焊接水平,促进管线工程以及焊接技术的发展,根据目前我国管道工程的发展, 讨论了高强度管线钢存在的焊接性问题,主要针对焊缝金属的强韧化匹配问题、冷裂纹问题以及HAZ的脆化问题的研究现状进行了总结。同时,结合存在的焊接性问题提出了相应的预防措施,建议提高焊接接头的韧性可以通过成分、工艺两方面因素来考虑;防止冷裂纹产生可从氢含量、淬硬组织、应力三个方面进行控制;提高焊接热影响区的韧性,可以采用激光焊、超窄间隙GMA焊、脉冲MAG焊等低热输入的焊接方法。     

高Nb X80管线钢焊接热影响区显微组织与韧性

为研究Nb含量对焊接热影响区微观组织和性能的影响,采用熔化极气体保护焊(gas metal arc welding,GMAW)和手工焊条电弧焊(shielded metal arc welding,SMAW)对0.055%Nb和0.075%Nb含量的X80钢管进行环焊. 采用夏比冲击试验和金相分析方法,研究热影响区的微观组织差异和夏比冲击韧性. 并借助扫描电镜和超高温激光共聚焦显微镜分析不同Nb含量X80管体的微观组织对热影响区性能的影响. 结果表明,在0 ℃和−20 ℃时,0.075%Nb和0.055%Nb的X80钢管GMAW环焊接头热影响区均具有较高的冲击韧性,其平均冲击吸收能量均高于150 J. 其中0.055%Nb略高于0.075%Nb的GMAW环焊接头热影响区夏比冲击吸收能量;焊接热输入较低时,0.055%Nb低于0.075%Nb的X80环焊接头粗晶区的韧脆转变温度,具有更好的低温韧性. 焊接热输入较高时,0.075%Nb的X80环焊接头粗晶区具有更高的上平台冲击吸收能量,且上平台温度和韧脆转变温度也更低,其低温韧性也更优异;还发现了X80环焊接头热影响区的冲击韧性不仅与热输入量和热影响区马氏体−奥氏体组织(M-A)的形状、大小、分布有关,而且还受管体中Nb含量、原始的强度与韧性、微观组织状态的遗传影响.

     

Application of instrumented indentation technique for enhanced fitness-for-service assessment of pipeline crack

While most in-field non-destructive technologies for structural integrity diagnosis focus on precise crack detection, a novel instrumented indentation technique for non-destructively determining tensile properties in fields is introduced here. The goal of this work is to apply the newly-developed indentation technique to in-field fitness-for-service (FFS) assessment of linepipe cracks. As one step to verify its applicability, tensile properties in base metal and girth weldement of API-X65-graded linepipe were evaluated by this indentation technique and provided for construction of material-specific failure assessment diagrams (FADs). Results are discussed in terms of the accuracy of the indentation data and how the FAD assessment results are affected by the variation in local tensile properties measured by indenting small target regions such as heat-affected zones (HAZs). Based on the results, we suggest that the indentation technique may be useful for reducing possible difficulties in flaw assessment (arising from the use of incorrect tensile properties) by providing reliably practical data for FAD construction.     

Irradiation embrittlement monitoring of WWER-440/213 TYPE RPVs

In the paper the main goals and progress of the surveillance specimen programme for the RPVs WWER-440/213 in Jaslovské Bohunice V-2 and Mochovce NPPs are presented. At Jaslovské Bohunice V-2, the standard surveillance specimen programme (SSSP) was finished and so-called ‘Extended Surveillance Specimen Programme’ (ESSP) was prepared on the base of its critical analysis. For first two units of the Mochovce NPP completely new programmes of irradiation embrittlement monitoring called ‘Modern Surveillance Specimen Programme’ is prepared. It is based on the experience with SSSP and ESSP as well as the recommendations of IAEA experts. This programme will serve for Mochovce NPP during all planned service life. The experience of ESSP application on the 3rd and 4th units in Jaslovské Bohunice V-2 NPP are presented in the paper too.     

Effect of microstructure inhomogeneity on hydrogen embrittlement susceptibility of X80 welding HAZ under pressurized gaseous hydrogen

Hydrogen embrittlement (HE) of high-grade pipeline welded joint is a threat to hydrogen gas transport. In this research, slow strain rate tension (SSRT) tests in high-pressure hydrogen gas, combined with hydrogen permeation tests and microstructure analysis were conducted on X80 steel, intercritical heated-affected zone (ICHAZ), fine-grained heat-affected zone (FGHAZ) and coarse-grained heat-affected zone (CGHAZ). The change of HE susceptibility from high to low was CGHAZ, FGHAZ, ICHAZ, and base metal. Microstructure was the important factor influencing hydrogen permeation and susceptibility to HE. Susceptibility to HE was increased in the order of “fine-grained massive ferrite (MF) and acicular ferrite (AF)”, “fine-grained granular bainite (GB) and MF”, “coarse-grained GB and bainite ferrite (BF) embedded with martensite-austenite (M-A) constitute”. The fine-grained MF and AF in base metal with lower hydrogen diffusivity can impede the embrittlement behaviour, while the coarse-grained GB and BF with higher hydrogen diffusivity in CGHAZ increased its susceptibility to HE.     

Grain refinement of HAZ in multi-pass welding

A technique named Impacting Trailed Welding (ITW) was proposed, aimed at refining the grain size of the HAZ in multi-pass welding. The key idea of ITW is to obtain a large deformation in the HAZ during one weld pass, and get it recrystallized during the next weld pass. Theoretical analysis suggests that the deformed HAZ can get completely recrystallized and the degree of the successive grain growth is lower than the normal grain growth, so that the grains can be dramatically refined. The average grain size was reduced by a factor 2 through the application of the ITW technique, and remained close to the grain size of the base material. The results are consistent with the theoretical analysis.     

焊接热影响区针状铁素体的形核长大及其对组织的细化作用

通过观察焊接热循环冷却过程中不同温度取样直接淬火后的微观组织,研究了焊接热影响区(HAZ)晶内针状铁素体(IAF)的形核长大过程,论证了针状铁素体分割原奥氏体晶粒及细化晶内组织的机理.Auger电子能谱(AES)证实,在TiOx-MnS型复合夹杂物边界附近存在贫Mn区,IAF易于在这类复合夹杂物上形核,单个复合夹杂物能...