African Fusion March 2020

Arc-welding-based additive manufacturing

In this paper from the 72 nd IIW International Conference of Bratislava, Slovakia last year, A Josten of CarlCloosSchweißtechnik andMHöfemann of Salzgitter Mannesmann Forschung (SZMF) describe two possible applications of arc-welding-based additive manufacturing in automotive engineering with the goals of producing vehicles more efficiently and reducing the environmental impact of the vehicle production processes and the vehicles themselves. Arc-welding-based additive manufacturing for body reinforcement in automotive engineering

W elding no longer only means fusion welding or thermal coating. In recent times arc-welding-based additive manufacturing has becomemore important for generat- ing parts consisting of weld deposits. Cost-efficient and fast part production, plus their improvedmechanical properties are some of the arguments for arc-welding-based additive manufacturing [1]. So too, in automotive engineering this manufacturing process can help to reinforce body components by generating stiffening elements by deposition welding. Benefits of this simple and flex- ible method are more flexural rigidity even though comparatively less material volume is used and the ability to quickly modify and use the system for many other applications. In this study an advanced short arc welding process with low- heat input was chosen. Special feature of this process include a bidirectional wire motion during welding for a better drop separation and therefore almost no formation of spatter. These experimental welding trialswere subdivided into two fundamental topics. The first was to check the possibility of generating a gusset plate on zinc coated car body parts by additive manufacturing to reinforce a right angle of bent thin steel sheet. The second topic was to increase flexural rigidity of the sheet by depositing weld metal in a grid. Bend tests of the grid sheets indicated clearly increased flex- ural rigidity compared to the parent material. Even though the total heat input into one sheet is comparatively high, a carefully selectedwelding sequence alongwith a clamping device can keep warping to a minimum. The very stable arc can overcome previ- ous weld lines and results in good penetration especially at the intersection points. Transverse microsection examinations show generally good penetration and layer structure. Finally the welds are visually appealing. This production method and the results of this fun- damental study may be interesting for automotive engineering, and for other applications such as additive production of any components to reduce material expenditure if reinforcement or high rigidity is demanded.

Whilemany studies investigate(d) the properties of components that are generated by multi-layer applications such as these, this fundamental study is intended to show two possible applications of arc-based-additive manufacturing processes in automotive engineering with the usual goals of producing vehicles more ef- ficiently and reducing the environmental impact of the vehicle and its production. The aim is to show how these goals could be approached, what difficulties and limitations still exist at present and where further research work could be initiated. Introduction Arc-welding-based additive manufacturing, also known as ‘wire and arc additive manufacturing (WAAM)’, has become important for generating parts by depositing layers of material via fusion welding. Cost efficiency and fast part production, plus improved mechanical properties are some of the arguments for arc-welding- based additive manufacturing [1]. High deposition rates at lower investment and operating costs compared to powder-based pro- cesses are of particular interest for the production of large-volume components [2]. But in order to become more interesting as an arc process for increased use in the field of additivemanufacturing in research in- stitutes, for example, the development of energy-reduced digitally controlled short arc processes and the simplified use of industrial robots for torch manipulation was an important milestone for welding industries [1]. Additive manufacturing often means building up complete com- ponents by adding layer on layer. There are some processes that can be applied for this purpose. A categorisation according to feedstock (filler material) – which is deposited layer by layer – and heat source is shown in Figure 1. An arc-based process with an endless wire electrode, which is similar to the functional principle of GasMetal ArcWelding (GMAW), Wire and Arc Additive Manufacturing (WAAM) Categorization of processes for AM [3]

Figure 1: Categorisation of processes for Additive Manufacturing (AM) [3].

Figure 2: The functional principle of GMAW [4].

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March 2020

AFRICAN FUSION