Preventing failures in the manufacture or operation of petrochemical reactors made from creep-resistant, low-alloy steels such as 13CrMoV9-10 still requires research, despite over 60 years of investigation into the field of stress relief cracking. Welding this steel grade requires care. This is due to its low toughness and high strength in the as-welded condition if not heat treated after welding, combined with an increased susceptibility to cracking during stress relaxation. Previous research on cracking has focused on metallurgical factors; little knowledge has been gained on cracking under real-life restraint conditions. In this work, the influence of welding heat control on cracking was investigated by simulating the manufacturing conditions prevailing in the construction of petrochemical reactors using a weld mockup. Cracks formed during post-weld heat treatment in a temperature range between 300 ℃ and 500 ℃. Compared to small scale samples, the toughness of the restrained welds was significantly lower. SEM and TEM analyses of the samples revealed early ageing due to precipitation of carbides during post-weld heat treatment under restraint. An overview of how a comprehensive assessment of the integrity of submerged arc welded CrMoV steels can be achieved is provided. This chapter is adapted from the following open access articles published under the CC BY 4.0 license: Kromm, A., Lausch, T., Schroepfer, D. et al. Influence of welding stresses on relief cracking during heat treatment of a creep-resistant 13CrMoV steel: part I—effect of heat control on welding stresses and stress relief cracking. Weld World 64, 807–817 (2020). https://doi.org/10.1007/s40194-020-00875-6 Kromm, A., Lausch, T., Schroepfer, D. et al. Influence of welding stresses on relief cracking during heat treatment of a creep-resistant 13CrMoV steel Part II: mechanisms of stress relief cracking during post weld heat treatment. Weld World 64, 819–829 (2020). https://doi.org/10.1007/s40194-020-00881-8