Penetration: Moving slow or upping power?

[Sphinx]

Quick question for everybody:
Working on car bodywork for example, is it better practice to have a lower setting and move slowly or a higher power (and wire speed) and move a bit quicker?
I've tried both on my thin pieces of practice steel and find I can get seemingly good penetration on either setting and a neat weld, but which is better? Is one method better for strength of join? or minimising warping etc?

Thanks guys.

 

[fingers99]

As long as you get the penetration, the technique -- especially on car bodywork -- isn't going to matter overmuch. Do whichever you feel more comfortable with (but expect this to change with time).

As the essence to MIG is speed, I'd be inclined to up the power, but this can be scary at first.

 

[Sphinx]

Thanks for the swift reply. I just tried on some scrap steel the same thickness as the the car bodywork and found that the lower power (the lowest on my SIP) was much better when it came to edges. I've been using setting 2 with wire speed 2 (the wire speed automatically increases with power) but found that all was well untill I got to an edge where it just burnt away.
Now I've tried setting 1 with wire speed 2 (just over 3 for vertical welding) and if I slow down a bit I still get good penetration and it doesn't burn the edge completely away when I get to it.
However...with moving slower, it means you're welding a lot longer so my concern is excess heat. I guess only time will tell as I try different things though.

 

[Marty2005]

You should aim to get your travel speed, voltage and wire feed speed in some sort of equilibrium as it were. Generally think of increasing the voltage as increasing the heat. Thicker steel=more heat=more voltage. Set the wire speed to get that nice crackling sound, not so fast that the wire is banging into the steel and not so slow so that it burns back to the tip and get your travel speed to around 1cm a second. Well that's what my night school tutor told me anyway! Obviously different situations demand different techniquoes

 

[Sinister]

I was welding on my truck today and found that with less stick out I was able to get better penetration at the same voltage and wire speed.