Heat Rises and preheats your next bead

by geezer
(Canada)

I'm no welder by any stretch, but common sense tells me that your up hill method is better/has more pen. than a down hill weld cause the heat is traveling up and preheating ahead of you better than it would on down hill travel.

You could prove that out by quickly appling a torch to the middle of a vertical plate and measure the temp. diff. top & bottom.

My guess is the bottom will be cooler.

I enjoy your vid's and hope you make more of them.

Comments for
Heat Rises and preheats your next bead

Average Rating starstarstarstarstar

Click here to add your own comments

Feb 25, 2010
Rating
starstarstarstarstar 		To rebutt rons post on heat travel
by: geezer

Heat rises?
by: Ron

IMHO, heated air does rise because the heated air has the room to rise(air gets lighter as heated). The heat in metal, on the other hand, has nowhere to go, and not enough time to do it. So I don't think it makes to much difference, either weld up or down, the heat will just radiate out from the heat source until disipated in surrounding metal.

Ron

Ron ,I agree with some of your thinking, however you discount the effect of the hot gases that would naturally flow upward ahead of your weld preheating the material. This effect cannot happen in downward welding as the heat would rise back up over something already welded.

Jody's claim of reduced voltage required for the same penetration in upward travel would sustantiate this preheat effect.

To further simplify the issue, when you apply a torch to solder a pipe in the middle of a pipe. The solder will melt quite easily on the top of the pipe, but no so easily on the bottom of the pipe.

When you want to heat something up you apply the heat to the lowest point, Why ,cause heat rises better than it travels downward.
Feb 06, 2010
Rating
starstarstarstar 		Heat rises?
by: Ron

IMHO, heated air does rise because the heated air has the room to rise(air gets lighter as heated). The heat in metal, on the other hand, has nowhere to go, and not enough time to do it. So I don't think it makes to much difference, either weld up or down, the heat will just radiate out from the heat source until disipated in surrounding metal.

Ron

Click here to add your own comments

Return to mig welding techniques.