Abstract
Investigations of the weldability of metals often deal with hot cracking, as one of the most dreaded imperfections during weld fabrication. The hot cracking investigations presented in this paper were carried out as part of a study on the development of low transformation temperature (LTT) weld filler materials. These alloys allow to mitigate tensile residual stresses that usually arise during welding using conventional weld filler materials. By this means, higher fatigue strength and higher lifetimes of the weld can be achieved. However, LTT weld filler materials are for example, high-alloyed Cr/Ni steels that are susceptible to the formation of hot cracks. To assess hot cracking, we applied the standardized modified varestraint transvarestraint hot cracking test (MVT), which is well appropriate to evaluate different base or filler materials with regard to their hot cracking susceptibility. In order to consider the complete material volume for the assessment of hot cracking, we additionally applied microfocus X-ray computer tomography (µCT). It is shown that by a suitable selection of welding and MVT parameter the analysis of the complete 3D hot crack network can provide additional information with regard to the hot cracking model following Prokhorov. It is now possible to determine easy accessible substitute values (e.g., maximum crack depth) for the extent of the Brittleness Temperature Range (BTR) and the minimum critical strain .
Highlights
The aim to achieve lightweight constructions and higher load capacities at the same time leads to an increased use of high-strength steels
We focused our investigation on a Cr/Ni based low transformation temperature (LTT) alloy (e.g., References [1,41]) that shows a conspicuous hot cracking characteristic [23]
The filler material was deposited into the groove of the Modified Varestraint Transvarestraint (MVT) specimen by automated gas metal arc (GMAW) welding using six layers while the low alloyed high strength steel S960Q was used as substrate
Summary
The aim to achieve lightweight constructions and higher load capacities at the same time leads to an increased use of high-strength steels To exploit their full strength potential, welding these components on their own strength level is a major challenge. The second effect is that the phase transformation austenite to martensite leads to an increase of weld volume, which is hindered by the base material This counteracts the restrained thermal shrinkage of the weld and shifts the residual stress distributions towards compression. To mitigate welding induced tensile residual stresses, post-weld treatments can be applied with the objective to increase the fatigue resistance, as for example, shot peening, hammering or heat treatments.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
