Stainless steel welding with a MIG?

[voucht]

Hi,
The DIY stores sell welding wire for MIG for stainless steel welding. I thought you could only weld stainless steel with a TIG, but if the wire does exist, it means that it should be possible with a MIG, no?

I need to weld the stainless steel tubes of my exhaust system, and giving them to a professional welder will cost me a lot of money again.

Shall I try with my MIG, or do you guys absolutely not recommend it? If it is a yes, will my shield gas (Argon + 18% CO2 + 0.03% NO) work for that?

Thank you :)

[Talonmotorsport]

Yes you can MIG stainless with your current gas how ever it's not as soft as mild steel so it needs a lot of heat. I would suggest turning the amps up and the wire feed down and instead of trying to do long runs take it slow, I would tack space tack space grind flush then fill the spaces that way you know you've sealed the join. It would also help if you match the grade of stainless to the filler wire but I think you have enough to worry about already.

[alga]

AFAIK you need pure argon to properly shield stainless. However, at worst you'll have a rusting seam.

[Talonmotorsport]

You only need 100% Argon if you are MIG welding Ali which is a whole new world of ball ache. The seam won't rust if you use Co2/Argon mix on stainless but you will get spatter which will make a mess of the surrounding material the same as welding mild. The reason TIG is prefered over MIG on stainless is it pre-heats as you go as material like 316 is hard stuff. Tig is used in production welding of stainless as there's no need to clean the weld up after it's been done, with most of it being on show in things like kitchens and bits of boat which saves time and money.

[flyerncle]

Welded stainless with normal wire and Co2 before with no probs,not pretty but effective and for an exhaust that will get bloody hot will it matter.

[Talonmotorsport]

You need to use mild filler wire for joining mild to mild , stainless for stainless to stainless and so on. As your making an exhaust system it will go through constant heat changes, it will just end up shearing off after a while if you try mixing mild and stainless.

[K4KEV]

While you most certainly can weld dissimilar steels Phil is right the only way they work is when they are similar or have a dedicated filler/spool of wire mild on stainless will not last for two reasons one has a different expand contract rate to the other this is a perfect recipe for stress fracture especially on an exhaust ie hot cold hot cold the other fact is that it will rust along that seam even some stainless mig wires will rust as well, as the heat involved changes their properties, I would try to get grade 316 better still 316H or even better again would be 316Ti which contains a small amount of Titanium which helps with the weld boundry.
At minimum you want 316 for it to look and perform better

[flyerncle]

Were you a welder in another existence ?. :p

[K4KEV]

Austin & Pickergill time served plater.... ah built ships me:D

[flyerncle]

WF and JR Sheperd,drove the wagon that took the scrap away,same one that featured on Spender .;)

[Dualist]

High heat, low feed as you need to spray transfer the filler wire, also a high helium tri-mix gas will help with heat transfer.
Easy to get cold lap or zero penetration with a home mig but still doable, if you can get your hands on a synoptic mig and it'll be sweet, wire is bloody expensive too.

[flyerncle]

Glue the bugger ? :p

[voucht]

Thank you guys. That is lot of very good informations and tips you gave there.

I've been thinking about it all the past week. Now, I have cut my stainless steel elbows and tubes and they are ready to be assembled. But when I see the price of the stainless steel welding wire, I'm wondering if it worth spending this money without being sure of the result and its quality.

So I'm going to talk to the welder I know next week, and see how much he would charge. After all, it is only 3 junctions to be welded.

Thank a lot.

[TheArf]

Tig weld it and use pure argon, and if you can rig a second outlet from your Argon supply, tape off one end of the pipe and push trough some small holes, then put your second Argon supply in from the other end and seal it inside either with masking tape on manufacture a bug that allows you to feed argon inside to purge the air out of the weld area. This greatly improves the quality of the weld.

Arfon

[baz-r]

for mig welding stainless steels you really need argon or argon/oxygen (max 2%oxy) for 1-6mm
helium/argon/co2 blend for very thin to 3mm
argon/co2(2.5%) is ok for 3-11mm

i worked for a welding and ind gas supplyer

[voucht]

Thanks Arfon and Baz for the inputs. I think this thread can be useful to forum members in the future with all these very good infos.

I finally cut my stainless tubes and bring them to a professional welder I know with my motorbike muffler. He did a very fine job in one day, for only £30, which is much cheaper than a stainless wire roll (and a new gas mix!)
Here is the result, and I'm very happy with it.

http://farm6.staticflickr.com/5550/11225680304_d9687406a5_z.jpg (http://www.flickr.com/photos/99498333@N06/11225680304/)
2013-12-03_10-50-07 (http://www.flickr.com/photos/99498333@N06/11225680304/) par Voucht71 (http://www.flickr.com/people/99498333@N06/), sur Flickr

http://farm6.staticflickr.com/5477/11225684106_0b120e33dd_z.jpg (http://www.flickr.com/photos/99498333@N06/11225684106/)
2013-12-04_14-02-04 (http://www.flickr.com/photos/99498333@N06/11225684106/) par Voucht71 (http://www.flickr.com/people/99498333@N06/), sur Flickr

http://farm4.staticflickr.com/3825/11225772143_3c4fa21956_z.jpg (http://www.flickr.com/photos/99498333@N06/11225772143/)
2013-12-04_14-38-14 (http://www.flickr.com/photos/99498333@N06/11225772143/) par Voucht71 (http://www.flickr.com/people/99498333@N06/), sur Flickr

More pictures and a follow up about the muffler mounting at the end of this thread:
http://www.haynes.co.uk/forums/showthread.php?t=12974

Thanks a lot to all of you for your help :)

[TheArf]

Hellfire Sylvain what is that a muffler for an A380 its' chuffin huge.
Going back to the gas mixes, no I didn't sell it, I just used it on chemical pipework, and my other half has a food mixer but it doesn't make her a baker.

hey ho

Arfon

[voucht]

It IS huge !

Well, it has an integrated cat converter, so that also explains why. And I'm so glad I didn't have to insert one of these ugly cat converter in the exhaust line!

I'm curious to see how it will look on the finished car which will, if I succeed, have a mixed retro and modern look, so it could be actually pretty cool :cool:

Thanks.