Assessment of cold cracking tests for low transformation temperature martensitic stainless steel multipass welds

Abstract

In the last decades, low-carbon soft‐martensitic stainless steels have been widely used by heavy industries such as hydraulic turbine and pipeline manufacturing. Their good corrosion resistance, high mechanical strength, and good cavitation erosion resistance combined with their relatively good weldability explain this success. However, arc welding operations of thick plates still require significant preheating to avoid cold cracking. From a practical point of view, this requirement can complicate manufacturing operations and limit the use of these alloys for some applications. It thus becomes important to assess their cold cracking susceptibility in order to reduce preheating temperature. The discrepancy between industrial observations in multipass welds and the results obtained from the standardized cold cracking test such as Tekken and GBOP (gapped bead-on-plate) tests led to a modification of the GBOP test as presented here. In order to reproduce the behavior of industrial cold cracks, a comparison between Tekken and GBOP tests was set up for the assessment of the cold cracking susceptibility of multipass 13%Cr‐4%Ni soft martensitic stainless steels welded with 410NiMo filler alloy. A two‐bead GBOP test was proposed. This modification is necessary because the low martensitic transformation temperature of the 13%Cr‐4%Ni stainless steels reverses the residual stress in the weld, preventing the possibility of cold cracking. A second bead is needed to induce tensile stress in the first bead so that crack may be generated as in industrial conditions. The relevance of these modifications is presented and discussed using contour method residual stress measurements and acoustic emission crack detection.