Welding Practice

[Matt@RFR]

Oh, I think it's more bad in theory than anything, since, by the time you drop your gun, flip your hood up, grab a rag and slap it on, the tack is allready cool enough to not do any damage.



The theory is that weld material shrinks as it cools, which causes warpage. The faster it cools, the more pronounced the shrinkage becomes.

I proved this to myself years ago when building big big tanks:

If the tank was big enough to need more than one plate for the wrapper, I'd have to weld two plates together (butt welds), then roll that into the round wrapper. Well, mild steel plate is not square, straight, or anything else from the factory, so I had to burn the sides to fit, and would allways come up with gaps.

So I tack'd as much of the seem as I could, and where I had gaps, I'd run a weld right up to where the gap was, stop, throw all my **** off and dump a 5 gallon bucket of water on it....and watched the gap close!!! Lesson learned.

Example of a big tank: 30,000 gallons, 30-something feet tall and something like 15' in diameter. Fun stuff! Bottom wrapper was 1/4" plate, middle and top wrappers were 3/16".

[MuscleRodz]

Quenching a weld also hardens it. If it cools too fast in certain alloys especially 4130 will make the weld so hard it will become brittle and break on impact. You do not want to temper (harden) a weld in most applications, especially rollbars.

Mike