Keeping the “Bends” down

If you heat it, it will warp. Keep that in mind. Almost any form of welding will result in some distortion or stress imparted to the metal. Many people are unaware that a single pass weld that is “hot and heavy” typically will cause the metal to draw up considerably toward the welded side. Welding tubing, particularly thin gauge material is particularly susceptible to drawing and bowing. When metal is heated during welding, several physical changes occur. There is one part surrounding the weld that is much cooler than the immediate vicinity, so you have the same piece of metal expanding and contracting at different rates.

The piece to be welded will have to bend to conform to the cooling weld metal. This is characteristic of all metals. Some resist the change in structure that results more than other because they rapidly conduct heat, but even the best metal alloy will be affected somewhat. Add to that with certain metals change the grain structure quite radically right at the root of the weld, you have a recipe for trouble. So what to do? Well, keep the welds as small and as thin as possible with a smaller rod. Take two or three passes at a lower amperage with plenty of cool down during the interpass period. A single heavy weld isn’t a good idea. Resist the temptation, and you will be better off. This will allow a fine quality weld to be made, even if several passes need to be added. Also, pre bowing or bending of the part at the seam is a good idea, so that when the weld is completed, the metal has pulled itself into a perfect level position. This may take some practice, but if you prebend the metal in the opposite way it wants to pull before the welding starts, you’ll save a lot of wasted effort.

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