Last night my son wanted to do some welding on a friends snowmobile. As I don't yet have heat in my shop and it was around 10 degrees in my shop, I asked him to not do any welding till we had heat in the shop as I was concerned that running the welder in cold temps was not good for it. I assume that internal parts of the welder (coils, etc...) might be more prone to failure in extreame temps. Any thoughts on that...or is it no harder on the welder to be run in cold weather as in warm???
Outside temperature does not make a difference to the welder itself...you may want to pre-heat the part to be welded though to get the chill out of it. We have a Lincoln Ranger 9 gas powered welder mounted in the back of a pick -up and it is used all year. When I say get the chill out I mean up to maybe 100 deg. F. Could probably be done with a small propane torch if you don't have O/A set-up
I wouldn't worry too much about the welder, other than to let it idle for a few minutes before and after use-- before to let it warm a little and drive any moisture out, after to let it cool (always a good idea)
The weld, on the other hand, I would worry about. A few questions first: what process? What filler? How experienced is your son? What is the part being welded? Is it safety critical?
Now, general info, presuming mild steel: Low temp welding can be tough to get right: the part should be preheated for a good distance from where the weld will be done. The cooling rate of the weld must be held down to avoid cracking. The faster the cooling, the harder and more brittle the weld. The surrounding metal will also be embrittled. With sufficient preheat, the cooling rate will be reduced, as will thermal stresses in the weld area that will promote cracks. If you must do this without preheat (no torch or other means) in a pinch, grind the area immediately before welding,and let the grinding heat warm the material, and lay a cover bead to refine and anneal the weld. Grinding the cover down may also be used to help anneal the weld. Other metals should also be preheated to reduce cooling stresses, as well as to insure that there is sufficient fusion.