Last piece of advice before welding?

[Gamble97]

Tried welding an AN ftting on a valve cover and got it done but it didn't look pretty. Going to try and weld this AN fitting to this cast aluminum fuel rail tonight. Using the tig and 4043. Anything I should know or anything I should do prior to welding this?

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[sparky1987]

I woild heat up the rail and wire brush it so its clean 4043 is a good filler so just make sure you heat up the piece you're welding so it cooks some of the oils and impurities out and right before you weld it take a piece of scotch brite or a ss wire brush and brush the area where you're going to weld

 

[Bo0sTdTsI]

Ah u beat me but yea thats pretty much it for something like that. As long as its clean and on the right amperage you should be good. The pre heating is smart especially for welding on cast.

 

[Gamble97]

So something like this, how do you know what the right amperage is? I don't even know where to start or which side to concentrate the heat too.

I can't describe it, but cast aluminum welds funny. Also seems it likes to make pin holes.

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[sparky1987]

The pin holes come from the impurities in the cast. That's why you bake it or heat it up with a propane torch to cook the oils and garbage to the surface and then use a ss wire brush or scotch brite to clean the material. Correct amperage depends who you're talking to. I have my machine set at 200 amps and I use the foot pedel to control the puddle. General rule of thumb you want a puddle twice the diameter of the tungsten. Makes for a nice even weld.

 

[okcpopeman]

Ya that weld looks like it had lots of contamination. Prep is one of (if not THE) most important aspects to welding aluminum, especially cast!

 

[99gst_racer]

What are you using to clean the aluminum?

The aluminum that Mitsu used on the fuel rail, VC, and water necks kind of sucks to weld. We used denatured alcohol to clean it really well and that helped quite a bit.

 

[Gamble97]

I heated it up with a propane torch and used a wire brush. Guess I should have used some acetone as well or more heat with the propane torch.

Can or should I say 'should' you grind down cast aluminum welds? I know it's a no no for aluminum but is cast aluminum different?

 

[gixrman]

I've welded up cast and had to grind it down with a carbide bur and then reweld it to insure a good seal. A final wipe down with acetone and the tourch helps before the final pass.

 

[architechnik]

It also looks like you had good penetration on the fitting, but not the cast portion. The cast piece has so much aluminum that it's likely acting like a heat sink and pulling the heat away from where you want it.

Try bringing the temp of the entire cast piece up to temp before starting and use tongs to place it in a vice. Keep applying heat as necessary if things are taking too long. Make sure it's at least 300-500 F before you even start. If you have a laser temp reader you can lock on to the piece, that's your best option to keep track of the cast piece and see if it's losing heat too quickly.

 

[Gamble97]

Idk if my little propane torch will even get it to 300, but I'll try it next time. So do you think how it is now, it will hold say 100psi? or should I grind it down and just use the torch to go over it again? (no filler)

 

[architechnik]

Don't worry about the torch, use your stove. If you turn the heat up to 450 and let it bake for 15-20 minutes, that should prep it enough.

If you're using a little propane torch fitting that's pretty standard, grab some MAPP gas instead of just propane; it's the yellow can. It's kind of like premixed with oxygen and is far more efficient.

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I can't say for sure what kind of pressures that weld will hold because there's no real way to tell how well it's seated in the pictures. I would say bang it on something a few times and if it feels and sounds like it's one piece, you should be fine.

 

[Gamble97]

I'm going to the store later so I'll pick up some map gas. I know it burns hotter which is nice but it also smells worse. No big deal though.

 

[architechnik]

Yeah, it's got a slight smell to it, but it's expected when you're burning a bunch of crap off dirty parts anyway.

Just be sure to heat up a wide area when dealing with thick aluminum. It's hard to keep a single spot hot because of it's specific heat properties. It's used for cooling systems for a reason; it's great at moving heat to other places.

 

[Archer Fabrications]

your amperage looks to be up too high, welds are just cooking your materiel into crap or at least the filler. as everyone is saying, wire brush the rail keep it clean THEN weld preheating is good idea on cast material also because of the heat disapation