Porous, spattery welds

From a SIP TurboMIG 105.

I know it's cheap and not very powerful, but seem to be getting very poor welds on car bodywork. The gas supplied is CO2, would I be better off with Argon ?

The welds seem fine when welding onto 1mm mild steel test pieces, and even with the shield gas on 'high' still seem to be getting porosity and spatter.

Any ideas ?

Tks

Paul.

Reply to
zymurgy
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Have you got a good earth connection? Are you working in a breezy environment? If it's a dual welder, have you got the polarity right? Are you cleaning the workpiece thoroughly?

Reply to
Rob Morley

Well, I earthed it to the bit I was welding on, rather than the bit I was welding 'to'.

Yes, outside, but made sure the shield gas was on max. Hence my coomment about CO2 shield. I'm told this is quite a 'cold' gas and tends to keep the weld temperature down. Has anyone tried Argon on a DIY rig ?

It's not a gas/gasless, only a gas, as I was told i'd get better quality welds with gas. The gasless i'm assured is like an arc welder and needs the slag cleaning ..

I suppose it wouldn't be beyond the realms of possibility to change polarity and try it gasless.

Well, the body was a bit rusty and a bit thin. But this was in a 'test' area if you see what I mean :)

Thanks for the help,

Paul.

Reply to
zymurgy

Pure argon isn't used for steel - argon/CO2 mix makes it easier to work on thin sheet without burning through, but when I tried it after using CO2 for a while I found I wasn't getting enough heat into the weld for decent penetration - it's just a matter of getting used to the different characteristics.

I mostly use gasless these days and there doesn't often seem to be any accumulation of slag - certainly nothing that requires anything more than a quick scrub with a wire brush.

Probably a bit tricky if it wasn't designed that way - I was going to try it with my old welder, but I ended up getting a new dual welder instead.

Welding rust isn't easy, and will never produce brilliant results - that's my excuse anyway.

:-)

Reply to
Rob Morley

Cut back to clean, rust-free metal. Welding to rust in near impossible, and won't give a strong joint. Try Argon/CO2 mix, something like BOC's "Argonshield" works very well. I usually earth the car's body when doing bodywork repairs, not the work, as it's usually too fiddly to get a great big croc clip onto a small piece of plate. Do you have input/output pressure guages on the gas bottle's regulator? If so set it for about 10 -15 PSI static pressure (when not welding) - this will drop when you push the trigger. Have you experimented with wire-feed rate and power settings? If these are miles out for the material you're welding you'll get poor results.

Alan.

Reply to
Alan

Yes - get some Argoshield Light (or similar), an argon/co2 mix.

Trying to use pure CO2 is probably the main cause of poor welds by UK hobbyist MIG welders.

Reply to
dingbat

Hm, thanks for this. yes, welded fine on test pieces. Will give argon/CO2 a go. What's best to use pure CO2 on ?

Also is there such a thing as stainless MIG wire for welding stainless steel or am I being hopelessly optimistic !?

Thanks

Paul.

Reply to
zymurgy

AFAIK it's not best for anything, just cheap.

You can get stainless MIG wire but (depending on the grade of stainless) it can be difficult to get a good result.

Reply to
Rob Morley

Thin steel in dip transfer mode. _But_ you're working a much more difficult process here and the risk is that it will turn into globular transfer mode instead (which is bad and the usual cause of "pigeon crap" welds). If you have a sophisticated machine with a pulsed mode, then CO2 is a useful shield gas. If you don't, then I wouldn't touch it.

Reply to
Andy Dingley

Changed Gas, (Now on an 80% argon and 20% CO2 mix) and now i'm getting plenty of metal into the weld, but it's blobby and i'm getting poor melting of the donor metal to the existing metal. Seems to be blobbing up on each side of the join, but not flowing into each other.

I think I may have the torch too close to the workpiece, but moving it back doesn't help any.

Any (more) ideas ?

Thanks all,

Rgds,

Paul.

Reply to
zymurgy

Increase the power or reduce the feed rate?

Reply to
Rob Morley

Use the Spinal Tap technique. Turn all the dials up to 11 (ESPECIALLY the feed rate) and do some practice. Kick the thing into spray transfer mode and learn to do it all properly for technique while it's working in the easy regime. Get a wheelbarrow full of scrap (1/8" or 1/4") and go for it. Only then (at least one wheelbarrow of small plates converted to a single lump) start turning things down and learning to work in dip transfer mode, or with lower currents.

Increasing wire feed rate (if machine current is adequate) also _increases_ the current and heat production, simply from having more metal available as a charge carrier. It's not like gas welding where heat is independent of wire mass and you can "over-fill" a weld.

A book like Gibson's "Practical Welding" is handy too. The theory is easy, but important, and the rest is practice and forcing yourself to really study the results (including doing nick-break tests).

Reply to
dingbat

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