[hotdat]

Hi just want to know what can be achieved in the way of MIG welding stainless steel tubing? And how it is achieved?

[Otto Nobedder]

Welcome!

Define "tubing". What size, wall thickness (or scd. if pipe), and to what purpose.

MIG can actually achieve very high quality. In thicker sections, it's spray-arced to make ASME code welds that pass x-ray.

If you're building a handrail or banister, you can achieve excellent results, as well.

The advice will depend on the material, the purpose, and the equipment you intend to use.

Steve S

[hotdat]

Thanks Steve

I have access to an unlimited supply of 316 and 304 tubing removed from industrial food processing equipment I am unsure on wall thickness exactly but is perfect for building my own custom exhaust systems

My weling machine Uin Mig 175 about 8 year's old and is not an inverter type.

John

[weldin mike 27]

Another Aussie? You'll find a few of us here.

[TRACKRANGER]

Another Aussie? You'll find a few of us here.

(Only good ones, or course!)

[hotdat]

Ahh good to see a few of us on hear dont blame you guy's so much useful information better than anyone or anything I have come across before.

So Im a bit of a noob when it comes to anything other than mild steel and working for a local scrappy now I have access to a huge variety of materials for next to nothing so time to take full advantage of this.

Saving up for an entry level AC/DC TIG at the moment, something thats available locally that I can learn on doing a few custom automotive parts for my projects at home. Which brings me back to my original question.

As I haven't yet bought a tig and my 4x4 is in need of a new exhaust can I get long lasting and good quality welds on 316 or 304 stainless pipe around 2mm thick using my old uinimig 175. With the right gas and wire combo. My local welding suppy store could not give me any answers as he is an engineer not a welder. I can't seem to find any information on MIG welding stainless steel on the net though maybe im looking in the wrong places. Any help would be greatly appreciated

[Otto Nobedder]

I do MIG on 304SS regularly. Usually on thicker sections, but I can do pipe down to sch. 5, which is under 2mm in the sizes I work with. Your unimig 175 will handle it fine. The wire of choice for 304 (and 316 for your purpose) is 308/308L/308LSi (any of those 3 designations will do). The gas should be a helium/argon blend, with "Tri-Mix" (90%He, 7.5%Ar, 2.5%CO2) being the most commonly available gas, at least in the U.S. It "can" be done with 75/25 Ar/CO2, but with less attractive and potentially more brittle welds resulting.

The weld settings will depend on the wire diameter, material thickness, and your skill/comfort level.

Steve S

[GarryH]

You would bleed at the cost to buy a He tri-mix in Aus.

Just to put it into perspective, in Aus most exhaust shops just weld stainless exhausts with ER70S-6, their normal MIG wire.

Some will TIG them properly, but it is uncommon unless for show or race cars. Terrible I know, but that is reality in the industry here. I TIG my own for the race cars.

I had a little bit of success with MIG on exhausts but have gone back to TIG with purging because they say I am OCD.

gh

[Otto Nobedder]

GarryH, not all SS welding is exhaust pipe...

Steve S

[hotdat]

Gary I can not even find any tri mix locally where do I find it and whats it cost? I have an account with BOC gas but nothing on there website seems to be close to tri mix.

I have mig welded a few stainless exhausts on old junk cars with ER-70 seem to hold up ok but I am concerned with them cracking on spots that deal with high heat and the sudden introduction of water.

Also I want to be able to do some welds on other components that I can leave raw or grind and polish and not be worried about rust setting in.

[weldin mike 27]

http://www.boc.com.au/shop/en/au-boc-in ... nshield-66 brush with clean ss brush and all will be sweet. Don't over think it.

[weldin mike 27]

The gasses we have here may be different, but you will have no problem

[hotdat]

So its that simple Mike? 308 wire and stainshield for a good quality no rust weld.

I did see that gas and thought being called stainshield and stainless is what its designed for, it would be the best gas I could get my hands on for what I want to achieve. Although its much different to tri mix.

A friend of mine is bringing around a bottle of straight argon (unsure on exactly what it is) but he says thats all he uses with stainless wire and has no problem. But he is a farmer and not a welder. Whats the down side to this?

[Otto Nobedder]

100% argon performs poorly on short-circuit MIG. It's commonly used for spray-arc MIG on aluminum.

I've never attempted spray-arc stainless with 100% argon, but since blends like 90/10 Ar/ CO2 and 98/2 Ar/O2 are common, it may work. You should be aware that spray-arc on stainless works in flat positions only, you would need pulse capabilities for other positions.

I once accidentally attempted short-circuit MIG with straight argon when my helper hooked up the wrong bottle. I got black globular low-penetration welds, and quickly realized the bottle change was the only thing different from previous "good" welds.

If you are using an innershield wire, straight argon "may" have less negative effects depending on the flux in the wire.

Steve S

[weldin mike 27]

It's not necessarily that easy, but it is not super hard. Trial and error, you'll be fine.

[weldin mike 27]

Try dropping into a joint that welds ss and check what they are using, so you can see all the steps, and results

[hotdat]

Excellent thanks for all the info sounds like pure argon is not the way to go.

Im getting some machine work done tomorrow at a place that builds alot of fuel tankers. I will pick there brains and maybe they will show me how they do it.

And if all else fails I will get myself a bottle of stainshield from BOC and some 308 and have a play.

[weldin mike 27]

Let us know how you go.

[hotdat]

Ok spoke to one of the guys at the engineering place.

His advice was just to use stainless wire he didn't specify exactly what type of wire though, and my bottle of Argoshield will be fine for what I want to achieve.

If I wanted a much cleaner looking weld go for the Stainshield but he said if I want to get fussy I can buy acids to take the colouring out of it if I wanted to. And if im grinding on it use a new clean flap disk or what ever I am using only to be used for stainless and nothing else as not to introduce contaminants that will cause it to rust.

I found some stainless 307lsi wire laying around the work shop so I cant wait to have a play around when I get a chance. It sounds like welding up stainless exhausts is a simple task. But im going to do a few test welds using my Argoshield and to see what i can achieve for my cosmetic parts.

[hotdat]

For the non Australians wondering what Argosheild and Stainshield gas is.

Just noticed the Argosheild I have contains Oxygen. Introducing oxygen to the weld puddle would cause the weld to rust wouldn't it?

[Otto Nobedder]

Given those two options, my preference would be the Stainshield, but for exhaust tubing, you will likely be pleased with the Argoshield. Exhaust tube being thin by nature, I'd think the 1% H2 in the Stainshield would make heat control an issue. The Argoshield, on the other hand, will likely give you a dark weld surface due to the O2 content, but very aggressive wire-wheel treatment with a grinder (new SS wire wheel) should polish that up reasonably well while leaving your bead appearance (mostly) intact. SS exhaust will discolour some naturally, anyway.

Still, nothing beats a He/Ar mix for SS, but in many places it has priced itself out as an option.

By the way, a co-worker and I experimented with pure He for SS MIG. POOR results. The other stuff is there for a reason.

Steve S

[hotdat]

Thanks Steve so this grade of Stainshield would be better?

[Otto Nobedder]

Stainshield 69 sounds like an excellent compromise, especially for thinner sections. As long as it's affordable.

I have unlimited access to helium, so I forget what it costs folk who have to buy it.

That 0.9% O2 will give you some heat, so expect to move quickly, but I'd have no fear of welding tube with that blend.
Thinner wire and lower setting are your friend.

Steve S

[weldin mike 27]

I'm not sure if we can get helium mixes easily over here. I have seen a helium mix once (ask me how I know) but it was a very specific application

[weldin mike 27]

Maybe alushield