Last night I made a battery box out of thin sheet and welded a bracket to the middle of it. This warped the box so it stands up from the ground at one corner. I cut off the bracket but the box is still warped. What has happened to it to make it this shape?

This is due to shrinking when the metal is heated. This problem has recently been mentioned in a post about welding a patch into a floor.

if your going to weld thin sheet try dipping one end in a bucket of water to sink the heat away or turn the heat down and go slower, if its a long weld be sure to put stitches in it at opposite ends working towards the middle to prevent warping.

Welcome to the world of heat distortion. This is a real issue that always has to be dealt with, either by sucking the heat away with aluminum or copper blocks, less heat, or alternative approaches (riveting or brazing.)

To fix what you have, and now knowing that the metal strinks when welded, try heating the appropriate side to draw the problem surface back into alignment.

[Edited on 9/29/10 by kb58]

Thanks guys. I've made another but this time with less weld. The results are much better. Cheers.