For higher operational temperatures and pressures required in petrochemical plants, the modified 13CrMoV9-10 steel was developed providing high resistance against creep and compressed hydrogen. Extreme care during the welding procedure is necessary for this steel, attributed to low toughness, high strength in as-welded state, and increased susceptibility to stress relief cracking (SRC) during post-weld heat treatment (PWHT). Previous research of SRC in creep-resistant steels discussed mainly thermal and metallurgical factors. Few previous findings addressed the influences of welding procedure on crack formation during PWHT considering real-life manufacturing conditions. These investigations focus on effects of welding heat control on stresses during welding and subsequent PWHT operations close to realistic restraint and heat dissipation conditions using a special 3D testing facility, which was presented in parts I and II of this contribution. Part III addresses investigations on residual stress evolution affecting crack formation and discusses the transferability of results from large-scale testing to laboratory-scale. Experiments with test set-ups at different scales under diverse rigidity conditions and an assessment of the residual stresses of the weld-specimens using X-ray (surface near) and neutron diffraction analysis (bulk) were performed. This study aims to provide a way of investigating the SRC behaviour considering component-specific residual stresses via small-scale testing concepts instead of expensive weld mock-ups.

为了满足石化厂所需的更高工作温度和压力，开发了改性的13CrMoV9-10钢，以提供对蠕变和压缩氢的高抵抗力。这种钢在焊接过程中需要格外小心，这归因于其低韧性，刚焊接状态下的高强度以及在焊后热处理（PWHT）过程中对应力消除裂纹（SRC）的敏感性增加。先前关于抗蠕变钢中SRC的研究主要讨论了热学和冶金学因素。考虑到实际制造条件，以前的发现很少涉及焊接工艺对PWHT期间裂纹形成的影响。这些研究着重于焊接热控制对焊接过程中应力的影响，以及随后的PWHT操作（使用特殊的3D测试设备，接近于实际的约束和散热条件），这在本贡献的第I部分和第II部分中进行了介绍。第三部分讨论了影响裂纹形成的残余应力演变的研究，并讨论了从大规模测试到实验室规模的结果的可移植性。进行了在不同的刚性条件下以不同比例进行测试设置的实验，并使用X射线（靠近表面）和中子衍射分析（批量）评估了焊接试样的残余应力。