Welding Tips and Tricks

My neighbor has aluminum 4” irrigation wheel lines. He has several of the main pipes which are called torque tubes, many have been damaged and he has several pieces which need to be welded into 20 – 30’ sections.
I looking for recommendations on getting the pipe welded straight!
Some of the equipment I have;
Lincoln square wave 175 AC, DC welder Tig
12” X 36” lathe
20’ Angle Iron

I was thinking about cutting a slot about 5’ from the end of the Angle Iron; using this opening to weld the torque tubes together.
Another thought was to put a Torque Tube piece into the lathe, then set up some type of table/rollers and try to weld pieces together.

So what have you seen, recommendations, suggestions?
Thanks, Paul Kingsbury

a pice of pipe that fits snugly inside maybe? put it under were you will be welding the joint and it should keep it str8, dont be silly and use plastic pipe tho

BUG-

Go to "youtube" and look up "tools for pipe fitters"-and all the other stuff they have going on there. You 'should' be able to set up something that will work from the applications used there. Typically, you need one (or two) linear braces that will square the pipes to each other; strapped or clamped firmly as to restrict against any movement.-- at least a 4' span on opposite sides of the pipe [24" either side of the weld] Tack-weld 3/4" welds at four opposite points at the root of the BEVELED ENDS --grind the tacks to the minimum threshold of the root. Run the root pass from one tack all the way to the opposite one. Go back to where you started, overlapping 1/2" of that point, weld "up" the other side to the end of your first pass and over- lap again to fuse the roots as one. The next pass should "hotter" than the root pass, the two fusion points should be fused into the "hot pass" [without stopping at those points as before]. The remaining filler passes should be a little 'cooler'. The last pass should be 1/32" to 1/16" over the surface of the pipe. Grind flush if needed.

The reason I suggest 'two braces if possible' . All material can be curved in some way. Especially in long stretches [of pipe] that might be sagging by their own weight/length. By~which: If the tack welds produce any stresses that tweak the joint out of square, thats what you'll get.
Angle iron is handy and dandy, use it. Just as BurninRod suggested, watch out for burrs, slag-ends from cutting etc,, they will throw the "fit-up" off line.

Hey man, what i do to fit up pipe is get a long piece of angle iron and weld it to my bench or put it in a vice, anything you can do to get it to stay stable, then simply lay the pieces of pipe on it and they should fit up just perfectly. If they don't then it's because of a dent or something sticking out on one of them so just twist the one that isn't laying flat until it does, or have someone push down the close end into the angle iron and they will line up perfectly while you tack them.
cheers