Seeking welding advice/info

[guest18]

Hi Gang,
To give some background... I used to be able to weld. Loved gas welding and endured stick and mig welding. Despite this I have a nice little SIP Migmate 100 (not enough money for oxy acetelene!)
SWMBO needs some altar fires constructed for the Guides so guess who has just returned to the world of light fabrication after *cough cough* years of not touching a welder...

Anyway, I've got some 3mm thick angle and I've cut and ground the first sections ready to be welded, and today I rescued my mig from my parents back shed. Amazingly it still had gas in and all worked, but damn my welding is crap!!

So a question to those who know... I've had a play on some of the scrap and:
I have set it to max power and I could do solid (but UGLY) but joints, they seemed to lack any decent penetration though, although they are solid enough to withstand attack with a 2lb hammer I then tried turning up the wire speed and it seemed to help a little but when I welded a run on the surface it still seemed to be on the surface and not *in* the metal, I also couldn't see any indication of the weld on the underside.
So should I turn the wire speed up to maximum or is the welder just not powerful enough?

It's not critical, they're not going to go through an mot or anything(!) but I have some standards and if I'm going to do somethign I like to do a decent job... also it's annoying me that I seem to have forgotten how to do something I used to quite enjoy! Anyone able to advise?

Cheers,
Smudge

[Steve H]

Smudge, you not going to get much in the way of through penetration of 3mm steel with a 100 amp MIG (I usually use my 160 amp at its highest setting) . If it were me I would slow down the wire speed and move the gun across the work piece a lot slower, this should get more heat into the weld. Since it doesnt have to be pretty. you might be better of buying a cheap arc welder which should give better penetration than the MIG which tends to need higher current to achive the same weld. It also has the benefit that you dont have to buy bottles and it can weld outside easily and you dont have to shield the work piece to stop the gas blowing away.
This site is quite useful http://www.mig-welding.co.uk/tutorial.htm

[guest18]

Cheers Steve, Having thought about it the slower wires speed occurred to me this mornign too I'll try it tonight, I seem to remember that 100amp mig was rated to 3.5mm steel hence why I gave it a go, no matter, the price of welders has come shockingly low (compared to when I bought mine!!) so I'll maybe price up a punchy arc welder instead...
Will try the mig again tonight though as it's already there and doesn't cost me!

[Steve H]

Apparently the thickness quotes for most welders are rather optimistic. The other advantage of using a stick welder is that the final weld tends to be more 'honest'. When I first started in MIG the welds looked good but when cut open had little penetration, the worst when the joint just fell apart after being put in the cooling tank !. MIG can be very deceptive unlike stick.