Investigation of HAC-Susceptibility of Multi-Layer Welds with the “Bead Bend Test” Procedure and Examples

A new test method called “Bead Bend Test” for evaluation of the hydrogen-assisted cold cracking — (HAC) susceptibility of multi-layer welds will be presented. The main advantage of this test is the possibility of evaluation of weldments that are established by using real welding procedures. Also, different on-site stress conditions can be taken into account by variation of the clamping system. The test results can be used for theoretical investigations, but also for practical recommendations regarding the necessary minimum interpass temperatures to prevent HAC under consideration of the plate thickness, the materials strength level, and the diffusible hydrogen content of the weld metal. As an example, the HAC behaviour of high strength cellulosic pipeline weldments are discussed. An additional feature of this test procedure is the HAC evaluation of joints built up by a combination of different electrode types; e.g., cellulosic and basic types which are shown in a second example.