welding thin to thick steel

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Hi everyone, I could do with a bit of advice about a problem I have welding thin steel (usually about 1mm) to thicker steel (usually about 3 or 4mm). Not enough heat and the weld doesn't take to the thicker stuff, too much heat and the thin metal blows (I'm using the thinnest wire and an Argon/CO2 mix). Any sensible advice would be much appreciated.
Reply:hello and welcome. 1mm is roughly 20 ga. 3mm would be almost 1/8". That's a tough challenge with mig, especially if your fit up isn't absolutely perfect. Joint design is also going to play a part in how well this works.Trying to run continuous beads will most likely be tough. Small short welds concentrated mostly on the heavy stock and washed over onto the thin stuff is going to be your best bet with typical equipment. Move around as much as possible to keep heat input down. A pulsed mig might be able to help you with doing these, but we are talking about a pretty significant investment in equipment.A better option might be tig. Tig gives you more control when welding thinner materials..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:You could also look into Oxy- Acetylene if you have the equipment or have someone show you.
Reply:The trick in MIGing thick to thin is dwell time.You have to point the torch at the thick stuff until you get a puddle then swing onto the thin stuff just long enough to complete the joining. Do only one or two cycles and stop. Move at least double the distance weled away and do a new stich. Then fill in, doing only small stitches at a time.Pardon the blasphemy, but have you considered bolting?Be wary of The Numbers: Figures don't lie,. but liars can figure.Welders:2008 Lincoln 140 GMAW&FCAW2012 HF 165 'toy' GTAW&SMAW1970's Cobbled together O/A