Optimized welding processes for the repair and strengthening of structures made of old mild steels

Abstract

When repairing or reinforcing existing structures made of old mild steel, the preferred joining method may be welding rather than bolting, as is usually the case. Due to the specific properties of old mild steels, special problems have to be considered. The weldability of old mild steels is particularly influenced by their highly scattering chemical composition, existing inclusions and their distribution in the component as well as their limited material toughness. The first results of a research project at the Dresden University of Applied Sciences concerning the weldability of old rimmed mild steels have already been presented at Eurosteel 2017. This paper presents the findings of continued investigations, e.g. the use of other filler materials or out‐of‐position welding. The welding parameters were adjusted so that the toughness of the HAZ is better than in the unaffected base material. Additionally, the suitability of flux‐cored wire welding of old mild steels was investigated. This welding process enables a more economical production of large seam lengths. Unfortunately, the realized process parameters are very stringent, as the higher energy density of this process quickly leads to coarse grain formation in the HAZ and thus to a reduction in toughness.