Can anybody recommend a good web article on how to Mig weld.

I’m not too bad but it always seems more like luck than judgement when i get a good weld.
It would be nice to know the relationships between wire feed rate/current/material thicknes,type/co2 flow rates...etc...

I guess this has been covered before so please excuse me asking again

Thanks

liam's guide attached

Damn must be quicker in future, Tim beat me to it... was gonna post the same thing.

I found that document quite useful

Cheers

i like the ripping silk and sizzling bacon bit!

You can read all you like, you cannot beat someone good showing you - thats how I started. You can do everything by the book and still end up with a dodgy weld, with an instructor, he will notice the bad weld and show you how to avoid it in future.

Try your local tech for evening classes, quite a good social thing with pints afterwards!!

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Originally posted by JoelP
i like the ripping silk and sizzling bacon bit!

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Practice is the only way to get good at MIG welding. Once you know the basics of setting the machine up you can get good quite fast. Go to your local muffler shop and get some off cuts - while you are there ask for some pointers on setting the mig up and getting a good weld. (these guys do it all day in all sorts of positions so they are usually pretty good).
If you know what a good weld looks like then you know what to aim for.
Use two hands to hold the gun at all times, brace yourself and hold the nozzle with the non trigger hand - yes you will need a glove. Direct the gun with your gloved hand and keep a smooth and even run all the way through the weld - dont stop 1/2 way. If it looks like a good weld then it probably is, penetration is the key, no point just laying down a run on top of the steel. Practice on the offcuts of exhaust tube and then cut the weld in half to see what kind of penetration you are getting. Crank up the volts to get more. (Pulling the nozzle away from the steel as you are welding will lower the power and heat if its getting too hot).
Remember - you wouldnt want to hit something and have your chassis fall apart cause your welds are shit! The chassis will save your life in a crash - if you cant weld properly then get someone experienced to do the chassis!
Practice, practice, practice.

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Originally posted by wok
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Direct the gun with your gloved hand
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Basically, there are only two major adjustments on a MIG welder, voltage and wire feed speed. For a given wire diameter, current is dependent on wire feed speed, you can chart current vs wire speed. Voltage is related to arc length; if you suddenly pull the torch away from the work, the wire stickout will increase to maintain the same arc length.

generally speaking, a thicker material of the same type requires more current, or multiple passes, to weld. Steels of various alloys require approximately the same currents and voltage, aluminum of various alloys susbstantiall different currents, etc.

Use of alternate shield gas will affect the depth of penetration for a given bead width. Must use Helium, argon. or helium argon blends for aluminum; argon, argon carbon dioxide blends, or straight carbon dioxide for steels and steel derivayives like stainless.

Exotics require straight helium.

Flow rate- can affect the penetration of the weld given the same gas composition. generally (because I'm cheap), i use the lowest flow rate to secure good arc shielding and adjust other parameters to get good penetration.

Hope this is enough different from Liam's (it's been a while since I've read it) that it's additional, not redundant infornmation.

Julian wrote:


It would be nice to know the relationships between wire feed rate/current/material thicknes,type/co2 flow rates...etc...