Well I finished the week off by trying to weld a plug into a old (75 yrs or so ) heating radiator, the boss told me too use 309L SMAW and a couple hundred degrees preheat. That failed miserably so I cleaned everything off and tried a higher preheat temperature and allowed the heat to soak for a minute before welding. Well it was a total failure, I did notice the second time around that the base metal appeared to be evaporating as the arc approached, very strange behaviour indeed. On Both attempts the weld cracked as soon as welding stopped even with preheat around 500F, and it appeared as though the weld could be pulled off by hand.
I am starting to think the radiators may be unweldable or possibly just difficult. Monday I will attempt the repair with a Cast Iron rod. failing that I will suggest a threaded plug instead of a welded in one.
I was hoping that someone here may have successfuly repaired one of these old radiators and would be willing to share their technique. I will only have a hour monday to make another attempt before the owner tells them it can not be welded, and I would like to actually make this work,,,very stubborn!!
Thanks for any help or suggestions,( except solar heating )
John