IIW White Paper

and assessment. Multi-material design of welded structures can be considered as a key technology for the future. Respective IIW Working Units have already responded to this development.

Many of the high performance stainless steel, nickel base alloy and aluminium base alloy filler metals are sensitive to solidification cracking, liquation cracking and/or ductility dip cracking. Understanding of these various forms of “hot cracking” is still largely incomplete, which limits application of these alloys. The International Institute of Welding has provided, and continues to provide, a major resource for attacking these problems. The IIW pioneered both the measurement of diffusible hydrogen in welds and in understanding of the phenomenon of hydrogen induced cracking. Indeed, the international standard for measurement of diffusible hydrogen, ISO 3690, is a direct product of the collaboration of experts within IIW Commission II. Likewise, ISO TR 17844 Welding – Comparison of standardised methods for the avoidance of cold cracks provides guidance on selection of pre-heat temperatures for various conditions of restraint and various levels of diffusible hydrogen. The weld shrinkage restraint influences the cold cracking susceptibility of a joint by a respective stress increase and also changes the hot cracking tendency. A challenge for the IIW in future will be to transfer the knowledge about shrinkage restraint effects to respective weldability and cracking tests, in order to develop more realistic weldability testing procedures. This would represent a major step forward to reach the final goal of a consistent transfer of the results from laboratory weldability tests to real components and vice versa.

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Through Optimum Use and Innovation of Welding and Joining Technologies

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