Question about using a different grade of rod on old boiler plate

I was talking to a guy named Ray at the supply house in Erie last week. He's been welding since the 70s. I was picking up my usual 7018 for a patch job on a feedwater heater. He asked about the base metal thickness and when I said it was that old 3/4 inch stuff, he just shook his head. He told me, 'On that vintage plate, you're fighting carbon migration. Try a 7024 for the first pass to butter it, then go back with your 7018.' I'd never heard that before, always just used 7018 for everything. I tried it on the job yesterday and the bead laid in so much smoother, way less spatter. It made me realize I might be using the right rod but not always in the right order. Has anyone else had to switch up their rod sequence for older steel?

3 comments

3 Comments

ray3634d ago

That point about carbon migration on old plate is key. I read an old procedure from a shipyard that said the same thing. They called it a buttering pass with a mild rod to make a buffer layer. The high carbon in the old steel can mess with your first bead if you go straight in with 7018. Using that 7024 first sort of seals the deal, then you can build on it with your stronger rod. It's one of those old school tricks that got lost for a lot of people.

derek9944d ago

Old school tricks are the best. I learned about buttering passes the hard way on a tractor frame repair, ended up with a bead full of cracks like a dry riverbed. My boss just shook his head and handed me a box of 7024.

blairtaylor4d ago

Honestly, do you think that buffer layer also helps with the stress from the different expansion rates between old and new metal?