Skipping the pre-heat step on a quarter-inch steel job didn't lead to disaster

Last week, I was working on a repair for a small storage tank built from quarter-inch steel. The code book called for pre-heating the joint before any welding. I decided to skip that step because we were running behind and the shop temperature was already high. After I finished the weld, we did a dye penetrant test and it came back clean with no signs of cracking. I have handled a few similar jobs on light gauge steel this way and all passed inspection. Most folks in our trade would call this reckless and insist on pre-heat for every weld. But from my view, it is an extra step that is not always necessary, especially with thinner materials. I am curious if others have found this to be true or if I just got lucky.

3 comments

3 Comments

chen.faith1mo ago

Ever hear old timers say codes are for the worst metal?

aarona961mo ago

You mentioned thinner materials, but what about the actual steel mix? I've seen two pieces of the same thickness act totally different. One was just plain mild steel and welded fine cold, the other had some extra alloys in it for toughness and immediately got a tiny crack. The spec sheet called for the same pre-heat, but the metal itself was the real problem. Sometimes the code is covering for bad or inconsistent metal quality, lol.

king.grant25d ago

My old foreman in Texas used to say the code is a safety net for the worst batch from the mill. I mean, you can have two sheets with the same stamp that act like totally different metals. It just shows how much the base material matters, no matter what the paper says.