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Tack Welding Stainless


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#1 KatoKid

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Posted 12 February 2011 - 07:45 AM

Ok, call out to all you welders out there.

I need to modify my factory BMW stainless steel headers slightly to fit so will need to buy some stainless mandrel bends and then cut to fit and then tack weld in place so I can take the pipes to someone who can TIG them properly for me.

Ive got a good Lincholn MIG but dont want the expense of having to buy wire and gas just for a few tacks so have few questions about the best and cheapest way of doing this:
1. Is there such a thing as gasless stainless MIG wire?
2. Can I use normal argoshield mild steel gas with stainless wire just for tacking.
3. Will normal steel wire and gas allow me just to tack? If yes will it cause problems when they go to TIG properly latter?

Any other suggestions on how to get this done?

Thanks.

David

#2 Sirpent

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Posted 12 February 2011 - 07:53 AM

David

I have a gasless mig welder which Im happy to loan you as Im in no need of it at the moment.

In answer to you questions.

A gasless mig welder uses flux cored wire which technically replaces the gas when a current is passed through it.

You can buy CIG stainless flux cored wire at Bunnings, and Super Cheap, 0.8 and 0.9 from memory.

Im heading up to Ferntree Gully this arvo so more than happy to lend you my kit if you like.

Cheers

John

#3 luvemfast

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Posted 12 February 2011 - 07:57 AM

I would have thought that you'd be ok to tack with argoshield and S/S wire.
But John thinks there is flux cored wire, that would be better

#4 handsandwhich

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Posted 12 February 2011 - 08:07 AM

Answers to your questions.

1. Yes, but highly expensive and probably would need to buy a whole roll
2. Yes, but unless this is ground out later, this is the part that will rust out first.
3. Yes and shouldn't be too much of an issue as long as the welds are not porous.

I'd say make sure you put some anti spatter spray on the bits you don't want to have any weld spatter on. Even if you are just going to do little tacks.

Try to get the thickest walled tubing you can get, (or match the existing tubing) to help minimize cracking due to the expansion and contraction of the stainless.

#5 Wayne G

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Posted 12 February 2011 - 09:43 AM

when I worked in an exhaust shop making stainless systems, we used the mig with mild wire to spot the system together and then finished the job with stainless TIG. We never had any problems or complaints.

#6 luvemfast

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Posted 12 February 2011 - 11:02 AM

when I worked in an exhaust shop making stainless systems, we used the mig with mild wire to spot the system together and then finished the job with stainless TIG. We never had any problems or complaints.

Perfect answer for you Dave

#7 KatoKid

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Posted 12 February 2011 - 11:37 AM

Thanks all, especially Wayne G.

Wayne, assume you use normal argoshield with the steel wire when tacking?

Further to the subject, can anyone recommend a source for stainless mandrel bends in Melbourne?

#8 handsandwhich

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Posted 12 February 2011 - 02:05 PM

http://stores.ebay.c...fsub=1734755012

#9 Wayne G

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Posted 12 February 2011 - 09:20 PM

0.8mm mild wire, normal argoshield, no problems. I did my own 4wd exhaust out of 2.5 inch stainless and welded the entire system that way. No problems with extended beach work, surface rust on welds when paint wore off.

Don't overthink it and you will be fine, if the engineering I see on your thread is any indication. Looks really good!

#10 zzzzed

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Posted 13 February 2011 - 12:31 AM

when welding stainless pipe in the past i have used an arc welder with stainless rods with good results it even surprised me how good the welds came up.
this being said i would go the tig path if i had the option 

#11 nat0_240_chevZ

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Posted 14 February 2011 - 11:56 AM

yep, mild steel tack will be fine to hold it together.
these can be ground out if you want to be anal, after tacking with SS , ie tack mith mn, then shop to tack with ss then grind out ms tacks, then fulle weld.
but asd wayne has said, for an exhaust wont be a problem.
just prep or chamfer the joint halves for some decent peno.
try atlas specialty metals for bends.
thats where i buy some here for work, but the adel branch
nat0

#12 DaMuffinman

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Posted 15 March 2012 - 09:34 PM

Hi bud just reading urn post and thought id add my two cents  . so  if ur just taking it should be fine. but remember stainless has very fast heat cycles. so if it is going to see alot of heat and needs to be strong. it will need to be ground out before the real welding begins. again just my two cents. i have made a couple of ss manifolds and know to do it right the first time.
Good luck.

#13 handsandwhich

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Posted 16 March 2012 - 06:41 AM

Hi bud just reading urn post and thought id add my two cents  . so  if ur just taking it should be fine. but remember stainless has very fast heat cycles. so if it is going to see alot of heat and needs to be strong. it will need to be ground out before the real welding begins. again just my two cents. i have made a couple of ss manifolds and know to do it right the first time.
Good luck.


Yes a lot of very careful planning must have gone into doing this job and maybe, just maybe he might be ready to attempt to do this 13 months after the original question was raised.

#14 jamo240

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Posted 16 March 2012 - 07:14 AM

Hey Dave...do you want me to bring my TIG to your place and do them for you? If you prefer, I have a roll of stainless MIG wire you can borrow to tack them and then I will TIG them for you if you want. You can borrow my bottle of argon if you want too.

I've got some sources for bends too..the guy i use most at the moment is in mulgrave not far from Monash Uni.

#15 KatoKid

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Posted 16 March 2012 - 02:52 PM

Thanks Jamo.

Will take you up on your offer when the time comes....a long way off yet though. Im going to splurge and by a proper 2 post hoist soon so that all the undercar stuff can be done a lot easier...especially the zorst.

#16 jamo240

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Posted 16 March 2012 - 06:02 PM

No probs Dave...least I can do. Let me know when and we'll do it.

CHeers

Jamo

#17 jamo240

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Posted 16 March 2012 - 06:09 PM

OH...and on the questions you asked, you can used SS wire with argoshield. Argoshield is a MAG gas (Metal Active Gas) meaning the gas takes part in the welding process rather than just shielding it as is the case with argon (MIG = Metal Inert Gas). The purpose of the CO2 blend is to both reduce the cost of the gas (important when you're using a lot), and also to reduce spatter...I don't know how the chemistry works, but that is what it does.

You can also tack with mild steel wire and weld up with SS later, but obviously you will end up with a part of the weld that will rust. Just get a small roll of SS (or borrow mine) and use in your MIG/MAG machine with argoshield, then TIG it all so it's neat.

Cheers

Jamo

#18 Zedman240®

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Posted 16 March 2012 - 07:15 PM

Does the gas also keep oxygen out of the weld? I thought that was the reason for the shielding gas..

#19 jamo240

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Posted 16 March 2012 - 07:23 PM

Yes Dimitri...that is what it does, but blended gases are used as active gases to take part in the welding process as well as shield it...they do both jobs at the same time. Purely inert gases (argon, helium) are used as a straight shield.

Cheers






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