1.2.1.2.1.3 Shipyard - Building - Hull - Welding - Aluminium Welding - Consumables
 


 

Hull - Welding - Aluminium Welding - Consumables (last update 6/10/06)
      Fig. 2.1.3a Welding wire. We use exclusively ESAB Autrod 5183 wire (formerly Autorod 18.16) (also known under SFA/AWS A5.10; ER5183; EN ISO 18273 and S Al 5183 (AlMg4,5Mn0,7(A)). It comes with all the Lloyds approvals of conformity and is used by majority of aluminium shipyards (source: Aluland - Design Service)
Diameters of 1.0 1.2 and 1.6mm are used. Fig. 2.1.3 is no exaggeration, that’s how we do store wire over weekends and after purchase. Relative humidity below 5% does make a difference on longevity of the wire.
        Fig. 2.1.3b Shielding gas. At the beginning, we experimented with Argon/Helium gas mixtures (30% He). It is supposed to provide (and it does) a little better penetration characteristics (particularly for filled welds) due to better thermal conductivity of He. However, we have found that pure Argon is actually much easier to weld with. And as far as we could find, no-body else really bothers about Ar/He mixtures in real life. Moreover, our sinergy-lines on the ESAB welding machine do not support Ar/He mixtures. Ar/He mixture is generally recommended only for special use and/or machine welding. What is important, however, is a dew point bellow -50C (our supplier provides about -70C to -90C) - in practice it means 5N product.
        Fig. 2.1.3c Stainless steel brushes. All of the aluminium-oxide prior and after the welding is brushed off mechanically. Due to the possible contamination issues, only stainless steel brushes are recommended by various authors (and also being used by us). Being about three times more expensive they do not last a minute longer than ordinary steel - and the consumption is high. See also Fig. 4.3.2. We use various types of hand and machine brushes. If you are in the EU, a good supplier of first quality and relatively cheap stainless brushes is KART, actually last longer than original Bosh brushes! (within the limited number of samples we had a chance to test ourselves).
      Fig. 2.1.3d Abrasives. It is good idea to have abrasives designed for aluminium; the steel abrasives get clogged in no time. What also works okay are the abrasives designed for stone work. I believe that we were told the aluminium oxide based works best...it is also rather important to keep the cutting (brushing) speeds - meaning having the speed adjustable grinders is important as is mentioned in handtools section.

Fig. 2.1.3e Carbide Burrs, Aluminium is machined best with carbide tools (again, it pays of to have carbide designed for aluminium (structurally) and designed for cutting aluminium mechanically. For back chipping, edge forming and weld cleaning we mostly use the straight grinder (Fig. 4.3.1) with carbide burrs from MAFord. The middle one (conical) on the picuture is the most beloved.

For weld back-chipping we also use a home-made carbide back-chipping tool (see Fig. 4.3.5). Details of the carbide bids will be pusblished in next section.

  Fig. 2.1.3f Degreaser. This is THE issue. Actually nobody really suggests anything reasonable, some books on aluminium welding would only say use 'industrial degreaser'! In general, the alu-plant probably use a silicon based greaser when rolling the plates which is not easy to get rid of. To my shame I have forgot all my organic chemistry background, but in principle, polar solvents such as acetone or alcohol based solvents are useless. What works relatively well are the non-polar 'aliphatic' light paraffin based hydrocarbons, but then only when you give it some time, i.e. minutes, which you dont have when you want to wipe the weld. Probably the best would be aromatic hydrocarbons, such as benzene, or non-aromatic trichlorethen, however, both are rather well known carcinogen compounds. SO, likely the second best choice is Toluene. It seems to work relatively fast (i.e. heavy wiping). However, it causes headache after prolonged exposure. Our solution: clean with toluene and mechanically remove the oxide and the grease together with rotating stainless brush (see also Fig. 4.3.2). The brush is then immersed in light paraffin based solvent over night to clean the build up grease deposits. This seems to work just fine and we dont seem to have problem here.

Fig. 2.1.3g Phosphoric acid (update (06/10/2006) A single most important recent introduction to our consumables portfolio thanks to Kevin Morin from metalboatsociety.com. The phosphoric acid gets rid off all the surface rolled-in oxides and also all associated absorbed grease in this surface layer mentioned above. This is EXCELLENT stuff and very highly recommended (see example of results). Needless to say the extra safety precautions has to be taken, but it’s well balanced by the benefits it provides. Minimum need for wire-brushing (only gentle hand brushing just before welding), degreasing and surface preparation of large plates. Saving on time is enormous and also getting rid of all that associated aluminium oxide dust from wire-brushing process is highly beneficial. Cost saving on stainless brushes is also not negligible.
We dilute 85% Phosphoric acid with water 3:1 (mix acid to water, not the other way!), and then apply by normal painting brush. Within few minutes all the surface oxides are gone and what is left is washed-down with fresh water. After drying the plate is ready for welding. PS: expect price about 3-4 euros/liter, some international chem. suppliers such as Aldrich are willing to rip you off with 50 euro price tag for exactly the same stuff.

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