Debate on the jobsite last week about pre-heating vs just letting it cool slow

We had a big argument on a tank repair job in Baton Rouge last Tuesday. Half the crew swears by pre-heating the plate to 300 before welding to fight cracking, but this old hand I work with says just let your passes cool naturally and it's fine. He showed me a repair he did on a 2-inch thick carbon steel head that never got pre-heated and has held 5 years now. I'm torn between the textbook and real-world results, any of you guys ever stop pre-heating and have it work out? What's your call?

2 comments

Log in to join the discussion

Log In

2 Comments

ivanb414mo ago

Have you ever tested a repair like that after five years yourself? I'm with you, man. Textbook stuff is usually built on worst-case scenarios, and sometimes real-world experience beats it out. I've seen plenty of pre-heated jobs crack anyway because the guy didn't control the interpass temp right. That old hand you work with probably just knows his steel and his technique, and that counts for a lot. I'd still pre-heat on anything over an inch or on tricky alloys, but for plain carbon steel a slow cool and good technique can absolutely work. It's all about knowing the risk you're taking and living with it.

0

thea_knight4mo ago

Real talk right there. Pre heat is a tool, not a magic fix, and I've seen guys follow the book to the letter and still get failures cause they rushed the post weld cool down. The old timers just have that feel for the metal that you can't get from a chart.

3