FOCUS ON WELDING
Design , material and filler material
Welding wire production at MIGAL . CO .
The entire process chain was checked using a pressure vessel in the form of a pipe branch . As per the design template , the branch ( additively applied area up to the stub ) was formed on a conventionally manufactured base pipe with a cut-out provided for this purpose . This is known as a hybrid component , because the substrate material to be welded on will become an integral part of the pressure vessel .
“ We decided to use aluminium as the material . We use the naturally hardened wrought alloy in plant construction because of its excellent low-temperature toughness , down to minus 273 ° C . Welding the material is challenging , however . It ’ s not just the choice of process and the process parameters that are crucial to the result , but also the choice of filler material ,” explained Martin Lohr , Linde Engineering .
The filler material plays a key role in metal 3D printing , as tight tolerances apply both to the diameter and to the chemical composition , with the aim being to include as little hydrogen as possible . Furthermore , the wire must be free of inclusions and neatly wound onto a spool to ensure that the manufacturing process runs smoothly .
“ The carbon footprint of the welding wire is an important environmental aspect , because it ’ s relevant in terms of the climate impact ,” pointed out engineer , Robert Lahnsteiner , CEO of MIGAL . CO , adding : “ Ours is 3.8kg CO₂ per kilogram of aluminium , which amounts to less than a quarter of the international average .”
Finite element method model ( FEM ) of the pressure vessel in the form of a pipe branch .
component and pressure testing ; as well as full documentation of the process chain , at their respective locations . A binding additive manufacturing procedure specification ( AMPS ) was subsequently created .
“ The entire value chain , including all the monitoring details , is considered in the draft standard for prEN 13445-14 , and in the previously published DIN / TS 17026 . This ensures that the fundamental safety requirements defined in Pressure Equipment Directive 2014 / 68 / EU can be met ,” confirmed Dr . Kati Schatz , Linde Engineering , outlining what is in the forthcoming standard .
“ All the details are included . This applies particularly to the material requirements ; design ; qualification of the additive process ; manufacturing and testing ; as well as acceptance and documentation . There is hardly any difference between this procedure and that for conventionally manufactured pressure vessels . Even though it has yet to provide the ‘ presumption of conformity ’ of the intended harmonised standard , and there will still be revisions , the specification can nevertheless serve as a guide for all those involved in the additive manufacturing process of pressure equipment ,” she added .
Material
Wall thickness / DED thickness [ mm ]
Outer diameter [ mm ]
Designing the component and selecting the process
The aim was to optimise the transition from the base pipe of the pressure vessel to the stub , in terms of both flow and topology . The design resulted in the following wall thicknesses : 8mm for the base pipe , 14mm for the transition from base pipe to branch , and 5mm for the branch .
Selecting the DED process
The essential requirements for the DED ( Direct Energy Deposition ) process ( also known as the wire arc additive manufacturing
Base pipe Transition Branch
EN AW-5083 / AlMg4.5Mn
Al 5183 / AlMg4.5Mn
Al 5183 / AlMg4.5Mn
8 14 5
273 273 / 168 168
Above : Material , wall thickness and outer diameter of the pipe branch .
66 | ismr . net | ISMR December 2024 / January 2025