Improving Global Quality of Life

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.
154 Improving Global Quality of Life Through Optimum Use and Innovation of Welding and Joining Technologies