First thin aluminium welds

[FranV8]

Well, had to reposition a peg on a simple nose stand for a boat trolley that I'd made in ally, frustrating at first then got an okay (but not pretty) result.

Then thought, for some fun. I'd got some scrap aluminium sheet that was old lagging cladding from work, for practice. It's 1mm thick, so chucked in a 1.6mm tungsten, cut the sheet with my £15 Argos air nibbler, then first had a go at a lap joint, then thought I'd do the butt joint. Pleased with the results, but not full penetration on the butt weld. Think I'd get away with knocking up a couple of underbonnet tanks in 2mm ?

Opinions welcomed gratefully!

PS - Anyone spot the touchdowns...

 

[Engineer]

Before making tanks its a good idea to be able to make full penetration welds on thin materials, which is not particularly easy and will take quite a bit of practice. If you are using 2mm and dont linish the welds, then tanks would probably hold without full pen, but far better if you do have properly done welds.

 

[FranV8]

Thanks Engineer. What do you think is a good way to get more pen? Just more current, more time building a bigger pool or do I need to leave a gap between the two materials? I got scared of blowing through so I didn't allow the keyhole to form and fill into that.

 

[Engineer]

You need to get keyhole, and practice this on scrap material till you are getting proper full pen weld all the time.

 

[hotrodder]

You don't need a keyhole on thin material but it's harder to judge what's going on without. If you're keyholing it and make a mistake you're more likely to end up with a mess, judging pen without a keyhole will take some practice as the signs the weldpool gives are subtle. It's quite hard to describe... pool size is obviously one clue but it'll also get shinier and sink almost imperceptably. If you just touch the wire to the pool (as you would with say stainless) at this stage the result will probably be either LOF (if you're on the cool side of perfect) or a heavy root with an underfilled cap (if on the hot side). You need to positively feed a little wire into the pool. It's quite a fine line to walk and when you get 'it' you'll probably find that (initially at least) stop/starts will be inconsitant- either very obvious to look at or with LOF if they're virtually invisible

Think I'd get away with knocking up a couple of underbonnet tanks in 2mm ?

Only one way to find out! Before you dive in with an expansion tank or the like i'd knock up a small tank that you can leak test or better yet hydraulic test. If you're welds are consistantly air tight then that's half the battle. Typically with automotive stuff it's the mouting tabs/brackets that are more prone to failure- virtually always from fatigue sometimes from welding defects, sometimes poor design

 

[FranV8]

Thanks chaps, most useful. Tonight I was going to practice a bit more on the 1mm, but I was doing mild steel still finishing off a bench/tool cupboard I'm making (which went well, very happy, was using the pedal, and swapping feet and hands at one point!)

Hotrodder, I might even knock up a small atmospheric tank that's on my Corvette. The other tank I want to make is a copy of a late model mod, where GM put a small plastic pressurised expansion tank up near the top of the firewall. I think this'll make the system less prone to minor airlocks that seem to dog the earlier (C4) models.

Looks like I'll need to do a few more practice runs of going to both extremes (LOF and underfill!) to find the right balance.

Engineer - I hadn't planned on linishing the welds off, but you're right, getting the right penetration is the best way to go, so that's what I'll aim for.