I finally understood why my old foreman was so picky about weld prep after a job in Toledo.

We were on a shutdown at the refinery there, and this guy, Frank, spent twenty minutes cleaning a single joint I'd already wire-wheeled. He said 'Kid, if you don't get every speck of mill scale off, that weld's gonna have a cold lap you can hide a dime in.' He showed me the difference on a test plate, and the penetration was night and day. Anyone else have a boss who drilled one specific thing into your head that you still think about years later?

3 comments

3 Comments

the_evan1mo ago

Remember that test plate he showed you? Did he ever explain what exactly the mill scale does to mess with the weld puddle, or was it just a "trust me, it's bad" kind of lesson? Always wondered about the science behind that specific failure.

alicesingh1mo ago

He just pointed at the burn marks and sighed... classic.

the_zara1mo ago

Mill scale acts like a barrier, it doesn't melt at the same temp as the base metal. The puddle can't fuse properly and just rolls over the top, leaving that cold lap. Frank was dead on about the dime.