STE460钢厚焊缝残余应力的中子衍射研究

管道焊接残余应力是影响管道安全和使用寿命的关键因素。中子衍射是唯一无损检测厚钢焊缝结构完整性的方法。本文主要采用中子衍射谱仪，辅以显微镜和硬度分析仪研究40 mm厚STE460钢管钨极惰性气体保护焊得的焊缝的残余应力分布、微观形貌、维氏硬度等。研究结果表明，焊缝的残余应力最高达670 MPa，非常接近STE460钢抗拉强度极限，而热影响区内的残余应力很小。全峰半高宽分析表明，焊缝区域塑性形变程度较低。整个焊缝不同区域的晶体显微照片表明其皆是均匀细晶。沿着焊缝方向和垂直焊缝方向的维氏硬度几乎一致，均在（200~250）HV02范围内。分析测试结果不仅满足工业应用里的电站基础结构建设和其他非破坏性残余应力评估装置校准的需求，并能增加对STE460钢厚截面焊缝的认知。

Residual Stress Characterization in Thick STE460 Steel Welding Seam Using Neutron Diffraction

The residual stress within the weld is a key factor affecting the safety and the life performance of welded pipelines. The only method to validate structural integrity in thick steel welds non destructively is neutron diffraction. Therefore, the residual stress distribution of a tungsten inert gas weld in a 40 mm thick pipe made of STE460 steel was investigated using neutron diffraction. In addition, microscopy and hardness measurements were used to analyze morphology and micro hardness. The results show high residual stress up to 670 MPa in the weld, reaching nearly the ultimate tensile strength of STE460 steel, whereas only moderate residual stresses are found in the heat affected zone. Analysis of the width of the reflection profiles (full width at half maxima) indicates a low degree of plastic deformation in the weld region. The grain of the whole weld is almost uniform fine crystal grains in different areas. The hardness across the weld and through weld are quite homogenous, with hardness values in the range of （200-250）HV02. This kind of welded pipe fittings is widely used for foundation structures of wind power plants and transport of oil and gas. The results not only meet engineering requirements, but also will be used to calibrate devices for non destructive evaluation methods like magnetic Barkhausen noise, ultrasonic and eddy current testing, which are used for the residual stress and crack detection in the industrial process. Furthermore, these results can increase understanding of STE460 steel thick section welds.