I have a large casting that has a terible inclusion of slag in it. There was a lug that should be above this area but this failed and ripped a lot of material out with it. The casting is hollow and holds water at around 1.5-2 bar. I have had a new lug laser cut from 20mm and this will be bolted in place using the decent material either side of the slag. I need to plug the inclusion though to make a fairly flat surface and also to hopefully seal it. Cleaning/ grinding it will be nearly impossible I should think. I don't want to put any serious heat into ynd casting for fear of it cracking. Could I cast lead into this area to seal it off or is that a mental idea?