Single-sided electro-gas welding on sheet metal thickness jumps and irregular butt joint geometries [IGF-No. 17415 BR]

Responsible research institutes: Rostock University, Chair of Manufacturing Engineering (Prof. Wanner)

Time period: 01.03.2012 to 31.05.2014

Final report: CMT 28/2014


Motivation / Background

The challenge for the German shipyards to compete on the global market lies in the securing of market shares by using corresponding know-how and implementation of new and economic technologies, especially after the most recent shipyard crisis. In Germany, section butt welds are constructed by utilizing semi-automatic and automatic gas-shielded metal-arc welding, while in Asia they are often constructed with electro-gas welding. A characteristic of the joints constructed with electro-gas welding is the broad field of application for the lower hull as well as a relatively high weld volume.

Although precise machinery is used, there are still regularly deviations in the gaps of the sections of up to 10 mm. The increasing use of regular gas-shielded metal-arc welding could react to this problem. That, however, is very time consuming and inconvenient. By creating a variation of the ESG to solve this problem the production time and the inconvenience could be reduced greatly.

 

Summary of planned objectives and actions

The objective of this project is the creation of a single-sided electro-gas process on irregular butt welding. It shall combine the increase in production through one layered welding and the reduction of mistakes that an automatic process possesses. Different variations of wires (one wire, double wire and tandem) and oscillation shall also be examined.

Mistakes made during welding, especially in the semi-automatic regular gas-shielded metal-arc welding, are supposed to be minimized. Apart from the investigation of mechanical and technological quality grades, which are supposed to be verified under normal circumstances (e.g. in a shipyard), there is also a great demand to analyze the oscillation resistance.

A technology is to be developed that can weld different kinds of large gaps, sudden differences in sheet thickness and certain diagonals in the hull without pausing the process. To achieve this, not only must a new set of rules for the butt welding tracking in combination with a preferably automatic control of the process, but also an optimal weld deposit and rules be found, to guarantee enough notched impact strength in the joint, boundary line and the heat affected zone. In order to limit the amount of variables (material, sheet thickness, wires, energy input per unit length, gas backing, air gaps), the statistical experimental design should be used. By doing so it is possible to resort to older research and experiences on electro-gas welding.

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