Harati Ebrahim, Karlsson Leif, Svensson Lars-Erik, Pirling Thilo, Dalaei Kamellia
Department of Engineering Science, University West, SE-461 86 Trollhättan, Sweden.
Institut Max von Laue-Paul Langevin, 6 rue Jules Horowitz, BP156, F-38042 Grenoble, France.
Materials (Basel). 2017 May 29;10(6):593. doi: 10.3390/ma10060593.
Evaluation of residual stress in the weld toe region is of critical importance. In this paper, the residual stress distribution both near the surface and in depth around the weld toe was investigated using neutron diffraction, complemented with X-ray diffraction. Measurements were done on a 1300 MPa yield strength steel welded using a Low Transformation Temperature (LTT) consumable. Near surface residual stresses, as close as 39 µm below the surface, were measured using neutron diffraction and evaluated by applying a near surface data correction technique. Very steep surface stress gradients within 0.5 mm of the surface were found both at the weld toe and 2 mm into the heat affected zone (HAZ). Neutron results showed that the LTT consumable was capable of inducing near surface compressive residual stresses in all directions at the weld toe. It is concluded that there are very steep stress gradients both transverse to the weld toe line and in the depth direction, at the weld toe in LTT welds. Residual stress in the base material a few millimeters from the weld toe can be very different from the stress at the weld toe. Care must, therefore, be exercised when relating the residual stress to fatigue strength in LTT welds.
评估焊趾区域的残余应力至关重要。本文采用中子衍射并辅以X射线衍射，研究了焊趾附近表面及深度方向的残余应力分布。测量是在使用低转变温度（LTT）焊材焊接的屈服强度为1300 MPa的钢上进行的。使用中子衍射测量了距表面仅39 µm处的近表面残余应力，并通过应用近表面数据校正技术进行评估。在焊趾处以及热影响区（HAZ）深入2 mm处，均发现表面0.5 mm范围内存在非常陡峭的表面应力梯度。中子结果表明，LTT焊材能够在焊趾处的所有方向上诱导近表面压缩残余应力。得出的结论是，在LTT焊缝的焊趾处，横向于焊趾线方向和深度方向均存在非常陡峭的应力梯度。距焊趾几毫米处的母材中的残余应力可能与焊趾处的应力有很大差异。因此，在将残余应力与LTT焊缝的疲劳强度相关联时必须谨慎。
