WeldForming – a new inline process combination for the improvement of weld seam properties

Abstract

The arc welding process reduces the components’ prospective lifetime due to the high heat input and the resulting inhomogeneous crystalline structure. In order to compensate this disadvantage, subsequent treatment processes decoupled from the welding process are state of the art. This paper presents the novel process combination, WeldForming, which uses the heat generated during the welding process for a subsequent forming process in the seam area. The goal is to change the microstructure of the welded joint by using thermal forming processes right after the welding by inducing recrystallization processes in order to avoid the classic zone formation - coarse grain, fine grain and intercritical zones. The process development is based on numerical simulations. For the first time, a numerical model was developed in which a welding and a rolling process can be combined in a single simulation model, taking into account the microstructural changes. The necessary material model for the description of the microstructural changes (recrystallization behaviour) is based on thermophysical simulations. A novel approach was the development of a material model for the filler metal G4Si1 in its cast-like state, reflecting the microstructure developing during the solidification of the weld metal. By combining the knowledge gained from the thermophysical simulation and the numerical process simulation, a process window for the novel methodology of WeldForming could be identified. On the basis of this, a test setup was developed with which the functioning of WeldForming was proven.