[plain ol Bill]

When welding boiler tubes keep a few pieces of ER309 in your trick bag. Sometimes when welding new material to old tubes that have cooked in that boiler for many years you will find some you just cannot seem to get a root pass in without porosity. Clean it up and put the root in with 309 - problem solved. Old Indian trick

[rake]

If you got caught doing that at the shipyard I worked at you would have been fired on the spot
and escorted off the base in handcuffs.

[Otto Nobedder]

I do this often on the (non-code) outer vessels on vacuum jackets when I have to work in the carbon-steel sections.

Works a treat!.

BTW, welding carbon to carbon in 6gr using 309 is a common (civilian) shipyard test, even though it's not practiced. It proves you can weld damn near anything.

Steve S