MIG welding Alloy - teach me!

[chairchild]

I've got this whimsical idea in my head, of modifying the alloy intake manifold for my car... but I don't have a TIG welder, and I don't fancy paying £100+ for someone else to weld it up for me.


I know to "set-up" a MIG welder for welding alloy, it needs:

1) a larger tip than the feed wire, as it expands. I've got a spare 0.6mm, 0.8mm, and a 1mm tip, so that's covered (the 1mm is unused too)

2) extend the liner to as close to the rollers as possible

3) minimal tension on the rollers, so as not to deform the wire

4) stainless wire brush, used ONLY for alloy, and nothing else


Now..gas, pure Argon I'm assuming?
And do I go for a positive or negative earth?


And if trying to weld a large lump of alloy (ie:the manifold!) adding supplemental heat in the form of a blowtorch/hob would be beneficial? But would using a gas flame as a heat source contaminate the metal? Or am I just worrying over nothing?

[workinprogress]

pure argon only or the welds will break

ali wire expands with heat as you say,,,so you may need to go up a size on your torch liner too

don't use any extra heat as this will contminate the weld,,,and only weld indoors in still air but have some form of mask on as the fumes will do nasty things to your lungs if you breathe a large amount.

use a darker setting on your head mask (or darker glass) as the arc is 3 times as bright as with steel and is very intense .

when you strike an arc,,,draw the torch back quickly to about 3 times the distance you would use with steel as the heat produced can travel back up the ali wire very quickly and burn the tip.

double your wire speed compared to steel for a given power setting,,,again,,,if you don't the wire will burn back.

experiment with scrap till your happy,,,and then take your time,,,measure twice,,,fabricate one

hope this hepls

[composimmonite]

Have you thought about using Durafix rods ?
www.durafix.co.uk/

Paul H

[chairchild]

workinprogress, excellent advice there! Any info on whether it's advantageous to have a positive or negative earth?

And I've only got a tiddler of a blowtorch - more suited to heating small bolts rather than heating up the whole manifold Plus the layout I've got planned, may be difficult to do if I'm basically soldering it on a large scale

[scruff]

It's very hard to do neatly.
A right pain to get things right and you need to move much faster than normal.

Good luck!

[MrSpeedy]

Generally speaking any MIG Ali welding is done using spool torches due to the difficulties in pushing the wire. I've always used Tig personally, but you always need to use AC current to keep the oxide off the weld pool so neg or pos earth is irrelevant.

[chairchild]

so... if going the MIG route, and persevering with the normal wire feed, would it be of benefit to rewire it to straight AC, rather than rectified?

Even though it'll only be 50Hz, and a 50:50 ratio, rather than the usual offset ratio that aids the "cleaning" portion, and a much higher frequency

[Clamity]

Just curious how much welding you are talking about. If it's a cash job, a couple of hours of tig at a local firm shouldn't come to £100, especially if you can jig everything up nicely so they can see exactly what you want doing first.

This thread is a bit of an education. I'd not really heard of mig welding non-ferrous. If it's hard to do though, why is it ever used instead of tig? That Durafix looks very interesting.

[chairchild]

because an AC TIG welder costs a bomb! lol

Overall layout will be:

A Rover L series diesel manifold:



With the top lopped off, and then the core from an old RX7 intercooler welded direct to the top



A tapered tube welded to the top open end,with a flange added to bolt on a 52mm Throttle body (nice and cheap - to be used as an emergency shutoff valve)

And around the intercooler, a water jacket added, to turn it into a fixed chargecooler




so yeah... quite a bit lol

[scruff]

The intercooler will be far too thin to MIG. it'll just melt and blow holes.
Tack with mig and then get it all TIG welded.

[chairchild]

hmmm....in that case, I may give those durafix rods a go?

£20 gets me five 45cm rods,and they don't even need to reach 400 degrees C to work.

[usedabused]

Personally I'd take that particular job to a pro but if you are adamant to do it yourself good on you and try here,

www.mig-welding.co.uk/forum/index.php

[optima21]

I used the durafix rods or one of the similar alloys when I fitted a new plenum to an inlet manifold (I cut the old one off). its usable, but needs some practice. previoously I've done model boilermaking and fabricated parts by silver soldering (between 600c and 850c). 400c might not seem that hot, but aluminium has high thermal conductivity, so you need a decent blowtorch and may struggle smaller DIY ones. also the type of burner makes a difference, on normal burners the air for combustion enters the burner itself, so if used in a confined corner the combustion gases can extinguish the flame. I use a primus sievert that has interchange burners etc and runs from a propane cylinder. like this one



they make what they call cyclone burners which are used in confined spaces and the burner, where the air enters the burner a few inches from where its burned (you can see the air entry hole on the right in the picture



another issue can be the thermal expansion, and movement between parts can be be an issue due to heating and cooling, so if you can screw, rivet or clam parts together it will help. if you overheat the durafix alloy, it can erode away the aluminium. the aluminium or alloy needs to be up to temperature and then the rod needs to be applied, they rods should not be heated directly.

and after my ramblings here's some pics of the manifold I modified

[chairchild]

usedabused - I like to try my hand at as many tasks as humanly possible Even if I screw it up, I'll have an appreciation of what's needed to do it in the future

And optima, those are the first real pictures I've seen of that stuff in use!



Had an idea to help semi-heat it, and that's stick it on a tabletop electric hob (you know the type) as that should help keep it at a minimum of about 200 degrees-ish. I suppose I can tempt my dad to lend me his bigger propane torch too

Really liking the idea of this stuff now. Now I just need to get myself a new manifold to fit to my car, before I can start to chop up the original


Cheers all!

[usedabused]

Fair play to you chairchild there does become a point during certain stages were actually having a go is more fun than the finished part.

Keep us posted and whatever you do register on welding forum they are a dry bunch but very friendly and knowledgeable about all kinds of metal witchcraft...........

[composimmonite]

I put the item needing work in the domestic oven to pre heat before using the Durafix rods - makes them a lot easier to use.
You can always use the Durafix rods to tack thinsg together ans then take to someone with a TIG to do the final welding.
BTW I've previously used Technoweld rods but no where as good as Durafix as you have to "scrub" the molten metal pool with a stainless rod whereas the Durafix is like soldering.

Paul H

[Clamity]

Apr 6, 2012 11:55:54 GMT optima21 said:

That's a very tidy bit of fabrication. Did you spend a bit of time getting the holes close fitting before soldering it all together? By that I mean can you bridge much in the way of a gap with the durafix?

Actually I had some techniweld sticks and found them a bit disappointing too. I used a bit of stainless bar with a chisel tip ground into it as a scraper tool, but the joints were pretty weak. Perhaps a stainless wire brush would have worked better.

[optima21]

yeah it was quite close fitting and yes the rods can be used for gap filling, but you need to be careful with temperature as its a bit like plumbing solder where it goes from a solid to a liquid over a temperature range. the heat also causes the fit to alter due to thermal expansion, so don't expect it be a machined tolerance when done.
The picture with me holding it might be slightly misreading as that was taken after I'd dressed and finished the inside of the plenum. the rest of the pictures are taken after the manifold cooled down.

Also I wouldnt like to use it for high strength applications despite the manufacturers claims.

before I modified that manifold, I had one that I cut the back off,ported the inside and then stuck the back on with fibreglass paste. I ran that manifold for a couple years without issue, but then again on a normally aspirated engine the plenum is under vaccum so the two haves are pulled together. if it was forced induction, I'd have used some re-inforcing plates before using the fibreglass paste.