Best aluminium for welding?

[GeorgeB]

For aluminium sheet, metalsupermarkets.com offer the following grades:

- 1050
- 5005
- 5083
- 5083O
- 5251
- 6082
- NS4

These numbers mean nothing to me! Which grade(s) is/are best for TIG or MIG welding?

Are any of them near-pure aluminium or are they all alloys of some kind?

Is welding best suited to near-pure aluminium?

 

[shenion]

I would think you would want to select the grade on what it is used for.

 

[oilcooled :)]

http://www.metalsupermarkets.com/catalog/ALUMINUM/PLATE

look under the list of grades it give a good explanation?

 

[hotrodder]

1050 is commercially pure aluminium the rest are alloys. All are weldable and all are softened/weakened by welding (with the exception of 5083O which is already annealed and in it's softest, weakest form). All aluminium has a suffix that goes with the basic alloy explained here, the O after 5083 indicating it's annealed

1050 is very soft, formable and weak
5xxx series are aluminium alloys with magnesium as the primary alloying element (NS4 is 5251, just a different designation system). They are not heat treatable but significantl harder and stronger than 1050.
6082 is an aluminium, magnesium, silicon alloy. Stronger again and heat treatable. Maximum tensile strength around 48000psi, annealed around 18000 psi. Welding it results in a complex HAZ (which is softer and weaker containing annealed and 'overaged' areas). Strength in the HAZ after welding could be as low as 20000 - 24000 psi, best case scenario maybe approaching 30000psi if the welder knows what they're doing and doesn't overheat everything

As Shenion said the grade used depends on many things- service environment as corrosion properties vary, the amount of shaping needed as some alloys aren't very formable i.e. prone to cracking when bent etc

 

[GeorgeB]

Thank you for so much help. I still can't find any product guidelines at metalsupermarkets.

I'm thinking of 2 applications for aluminium:

1. A sheet to curve round into a cylinder shape about 2ft diameter. The cheapest which won't crack would be best. No welding needed.

2. A sheet to make into a box for an oil-immersed welder like an Oxford. I'd bend it into a box shape (so it's creased at the corners - better not crack!) and weld one seam. And then weld on a bottom plate, plus a flange all round the edge at the top. Just like an Oxford welder. The aim is to get the weight down but do you think aluminium is suited to this? It's still a heavy load with the oil and transformer.

 

[brightspark]

the casing for welder would be best made out of steel sheet easyer stronger and cheaper to work . its the core and copper windings +the weight of the oil that makes them heavy

 

[oilcooled :)]

george just out of curiosity, how in the name of god did you get hold of a oil immersed welder with no tank, or are you making a oil welder? aluminium sounds hard to work with. steel would be far easier welded. paint outside, oil will keep inside good

 

[GeorgeB]

george just out of curiosity, how in the name of god did you get hold of a oil immersed welder with no tank, or are you making a oil welder? aluminium sounds hard to work with. steel would be far easier welded. paint outside, oil will keep inside good

I need 3 boxes filled with oil for 3 different, existing transformers that I seek to re-house.

 

[oilcooled :)]

ah i c, i like that, your always trying to modify things george, u would make a good engineer, u seem to be an ambitious one anyway

 

[hotrodder]

Aluminium is around a 1/3 the density of steel but it's also around a 1/3 the stiffness (elastic deflection) regardless of alloy, even those that are stronger than mild steel. This is part of the reason why say an aluminium bike frame uses very differently sized tubes to a steel frame. In the case of a simple flat sided box the shape is against you i.e. unless you can put some shape into the flat areas to stiffen them up (roll beads into it, diamond/cross brake it) you're not going to save any weight. Even if you were to do this together with either thinner sheet steel or with a switch to ally the weight savings will be so insignificant it won't be noticable as already said

Aluminium is quite a different beast compared with steel properties wise (fatigue limit for example) and needs more attention to detail and care when fabricating with the stuff i.e. mistakes/sloppy workmanship that's trivial/cosmetic with mild steel WILL bite you with aluminium, it WILL crack if bent on too tight a radius and/or if grain direction is not accounted for when laying out bends for example

 

[GeorgeB]

Aluminium is around a 1/3 the density of steel

Many thanks for a very helpful post. I think aluminium is out then, as a sheet material for the tanks of oil immersed welders. It looks like I need to use mild steel, but I'll chance my luck at using thinner sheet than Oxford did. It should be easier to bend into a box shape, for a start.