Cast can be welded using a cast iron suitable rod on a stick welder mig welding on cast I have done but u have to control the cooling process with oxy acetylene to stop weld fracture far from easy to do
not read all the replies before but after drilling literally thousands of holes in steel over the years use a dot punch then either use a 4mm then 8 and finally 10mm drill bits or 5mm then 10mm if 3 bits is too much work
drill bits on steel don't waste your time on cheap drills I would use...