Optimization of the melting behaviour of filling-alloyed, high-chromium cored wires in GMAW

The alloy composition of filling-alloyed flux-cored wires is achieved by adjusting the filling components while keeping the wire tube material constant. The advantage of this type of flux-cored wire is the more economical and flexible manufacturing process. A disadvantage is that due to the high alloy concentrations in the filling, micro-scale segregation can occur in the melt pool. The reason for this is the separate melting of the wire sheath and the filling, which is typical for flux-cored wires. As a result, the melting of the filling is often incomplete, so that solid particles are transferred into the melt pool and precipitate as micro-segregations occur. Within this work, it was investigated whether, and to what extent, the melting behaviour of filling-alloyed flux-cored wires can be influenced by the targeted adaptation of the wire temperature. For this purpose, different methods to influence the wire temperature were developed. The methods were validated on the one hand by analysing the melting process using high-speed images. On the other hand, individual droplets of the melted filler material were separated and evaluated metallographically.
Overall, it was found that the micro-segregations in the weld metal could be reduced up to 84 % with increasing wire temperature.