Mig welding

[Aussie Mike]

I think the point here is that there are several different welding technologies out there and they all have their strengths and weaknesses.

I agree with Stengun on the stick welder for heavier stuff. The penitration you get on heavier materials with a good stick welder is peerless. Getting a Tig torch that will run cool enough for long enough to weld heavier stuff is a problem. With a Tig you are also in very close proximity to the weld pool and this can become uncomfortable with higher current.

Tig is better than stick for lighter materials because there is far more control of the weld pool, less heat into the material surrounding the weld and less chance of impurities in the weld. Both of these processes are fairly slow though with the need to constantly change electrodes with the stick and the slow progress the weld pool makes with a Tig.

Mig is a great compromise between the two. You have reasonably high current capabilities and can get good penitration on medium heavy materials. The shielding gass makes for a clean weld. If your Mig is well set up and with good technique you can make a very good weld with minimal heat into the surrounding material. This is one of the reasons they are popular for the thin sheet of car panels. Control of the weld pool is much better than stick and starting your arc and getting your weld pool going is easier than both stick and Tig. I would much rather do a vertical/up or over head weld with a Mig. The reel of filler wire means that Mig is a fairly fast process without need to change electrodes etc. Also by adjusting your voltage/feed rate and how fast you move the torch you can lay down a good strong weld quite quickly.

One thing about Mig though is that you can easily do a weld that looks good but has hardly any penitration. Cold lapping is where the molten metal from the weld pool laps up and over the cold metal you are welding. Ths can happen if you are pushing your weld pool to quickly and it doesn't get a chance to melt right into the root of the weld. You end up with a weld bead that looks OK on the outside but is just crap underneath. I did the Australian Depart of Labour certifiication for Mig welding and we would do different types of Mig welds in all positions and then break the welds with a 100 ton press to see what's going on inside. It was very interesting to see the results of a weld that you though was perfect turn out to be rubbish. It makes you realy concentrate on your setup and technique.

We are fortunate enough to have 240 single phase power in Australia so you can run a fairly decent machine in your home workshop. I have a 220A Mig and a 125A Tig in my workshop and they both get a regular work out. 250A is about the biggest machine we can run off a single phase but if I want to do anything heavier a friend has a 350A 3phase Mig and a stick plant about the same current. The Tig I find is great on jobs like exhaust tubing, headers etc or stainles steel and chrome molly. The Mig is great for general fabrication and bodywork. I've been trusting my life to my welds for years and will continue to do so.

If you are serious about welding in your home workshop the best advice I can give you with whatever welding technique you chose is to go to a trade school or night class. Learn the proper techniques from a pro and then practice, practice, practice.

Cheers