the_fbi
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| posted on 1/4/07 at 03:14 PM |
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Arc welding with stainless
Had to plug up a pipe (EGR takeoff) on my tintops new stainless 4-1 manifold, given it was stainless I bought some stainless rods.
Had a real problem with them for some reason. Not sure if you're supposed to need more amps with stainless than mild, but whatever I did they
just wanted to do either nothing (ie. arc up but then just stopped) or stuck to the workpiece and glowed hot enough for their full length (enough to
see though the mask!).
So I gave up on that and used mild steel rods instead. OK so it'll rust, but its only a few blobs to hold a plug into the pipe.
The weird thing is, this weekend I had to cut/shut a 61mm stainless exhuast pipe (another part of the manifold) to shorten it do it clears the
floorpan.
Tried the rods again and they are fine. Due to the thin wall (1.25mm I'd guess) I had to do very short tacks throughout the whole circumference
then go back and fill in the holes, etc etc. But they were awesome.
Slightly suprised they were self chipping (ie. slag explodes and comes off as it cools), do stainless rods always do this?
Anyway, the real question is.....
At some point before Sept I need to redo my cut/shut to remove about another 15mm so its perfect (just wanted it back together this weekend!) and also
fit a CAT so it passes the MOT.
Whats the best way of welding it up next time. Its actually airtight this time and doesn't look bad at all. But should I really invest in a
Tig?
In actual fact the CAT part will be easy, as it'll be a lap joint, this was a butt joint so a lot more dodgy (less metal to play with).
I'm trying to justify buying a Tig but ideally I'd want an AC one to do ally too, but that'll double the price and all I'd use
it for would be an inlet manifold and I can buy one of those for the difference.
Basically, any benefit in my saving up over the next few months for a Tig to do the job, or if I managed with Arc this time should I just use that
still?
Other question is, should stainless Arc rods use the same settings as mild? I used about 90A this time for the small spots and it worked fine.
ta
Chris
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Confused but excited.
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| posted on 1/4/07 at 06:27 PM |
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Get the Tig set. You know you want to. 
Tell them about the bent treacle edges!
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mark chandler
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| posted on 1/4/07 at 06:29 PM |
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Buy a TIG, you know it makes sense.
In theory its easier as the material is a better quality but....
Welding stainless is tricky with arc as the flux must completely surrond the material, even with TIG if you do not back gas then the side facing away
has a poor finish.
So I guess arc with thin material will not be very successfull, thick material should be okay.
But then I have never tried stainless with ARC, only TIG.
Regards Mark
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gazza285
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| posted on 1/4/07 at 06:32 PM |
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If you have managed with the stainless rods I'd not bother with a TIG. Make sure that the rods are dry first, stick them in the oven for a bit
before you use them, and you shouldn't need any more amps than with mild. Be careful, as you have found, the slag will ping off and go anywhere,
many a welder has lifted the mask to get a bit of slag in the eye with stainless.
DO NOT PUT ON KNOB OR BOLLOCKS!
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907
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| posted on 1/4/07 at 07:28 PM |
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Hi
Stainless rods run best on a DC welder.
The difficulty you had in starting and maintaining the arc sounds like too low an open circuit voltage.
They burn with a deep cup so restarting a used cold rod is harder than a new rod.
90 amps would be a hottish setting for a 2.5mm rod or a cool setting for a 3.2mm.
You don't state what size rods you were using.
Bake rods at 200C for an hour before using them.
Hth
Paul G
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the_fbi
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| posted on 1/4/07 at 08:50 PM |
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quote:
Originally posted by 907
90 amps would be a hottish setting for a 2.5mm rod or a cool setting for a 3.2mm.
You don't state what size rods you were using.
I need to go check it was 90 then. They are only 2mm rods. Perhaps it was 70.
Then again, what the scale says and exactly what it is are probably 2 totally different things!
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907
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| posted on 1/4/07 at 09:00 PM |
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65 ish should be plenty, although like you say, every scale seems to differ.
I assume you are using an AC transformer type welder.
Paul G
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