1 Department of Management Engineering, Technical University of Denmark
During the present work crack testing concerning small and fast solidifying laser welds in austenitic stainless steel has been studied. A set of methods has been applied to investigate alloy properties, including ·Application of known information to predict solidification phases from the alloy composition. ·Weld metal solidification rate measurements for prediction of phases. ·Various crack tests to assess the crack susceptibility of alloys. ·A combination of the above for selection of suitable, weldable alloys. The possibility of using such specific methods for alloys and applications has been investigated and recommendations are given. From studies of literature it is found that the austenitic stainless steels have lowest crack susceptibility by a solidification course leaving approximately 15% rest ferrite in the weld metal. The alloys properties and the solidification rate determines the amount of ferrite and they have great influence on the crack susceptibility. Newer research has presented data to predict solidification phases and these have been incorporated in the work. Tests of the solidification rate measurement by the remelt technique have not been clear. The results have been compared to the crack behaviour, but do not show an expected correlation between the crack resistance and the solidification rate. The employment of pulsed seams is therefore assessed not to be usable in the present selection methods. From evaluation of several crack tests, the Weeter spot weld test has been chosen to form a basis for the development of a practicable method to select specific alloys for welding applications. A new test, the Groove test has been developed, which has reduced the time consumption and lightened the analysis effort considerably. The Groove test showed results in good compliance with the Weeter test.