as someone else said, dont try beads, do tacks, what i like to do it do a tack about every 6-8 inchs and keep working my way around until its solidly welded in, it'll save you from the warping and burning thru. Do the same when you grind welds, skip from spot to spot, you can build up more than enough heat from grinding to have the same warping happen as welding if you stay in one spot too long.