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Proceedings Paper

Dissimilar material combination in laser beam welding: reduction of distortion
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Paper Abstract

During welding the localized heat input results in high temperature gradients between the weld seam and the base material leading to residual stress. The residual stress is a result of two competing processes; thermal shrinkage of the material while cooling (resulting in tensile stress in the weld seam) and phase transformation induced volume expansion (resulting in compressive stress in the weld seam). Both processes superimpose to a resulting residual stress profile. To counteract the problems of residual stress and distortion, in the past few years low-transformation-temperature (LTT) materials have been successfully used as filler wire. Typically, LTT materials are highly alloyed Fe-based materials with levels of Cr and Ni that ensure that austenite transforms to martensite at reduced temperatures. This transformation is accompanied by large volumetric dilatation. The surrounding base material prevents this dilatation in the weld seam and compressive stress builds up while reducing residual stress and distortion. A way to use the LTT effect, other than using a LTT filler wire, is to combine dissimilar materials. By combining high alloy and low alloy materials a microstructure is formed in-situ that shows similar properties as a common LTT weld metal. The displacements after welding are always lower when using LTT filler material when compared to conventional wire, proving that LTT can be used to mitigate distortion during laser beam welding. In this paper the strain distribution by the use of digital image correlation is examined. The influence of dissimilar welding on the microstructure is considered and it is investigated whether the LTT effect can be reproduced with conventional filler wire.

Paper Details

Date Published: 2 March 2020
PDF: 14 pages
Proc. SPIE 11273, High-Power Laser Materials Processing: Applications, Diagnostics, and Systems IX, 112730B (2 March 2020); doi: 10.1117/12.2543866
Show Author Affiliations
Fatma Akyel, RWTH Aachen Univ. (Germany)
Simon Olschok, RWTH Aachen Univ. (Germany)
Uwe Reisgen, RWTH Aachen Univ. (Germany)

Published in SPIE Proceedings Vol. 11273:
High-Power Laser Materials Processing: Applications, Diagnostics, and Systems IX
Stefan Kaierle; Stefan W. Heinemann, Editor(s)

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