My neighbor's fireplace has an opening to the outdoors for cleaning out ashes. It has a cast iron frame, but the door is missing. They have askedme to weld it shut, since they don't use it, but my only portable welder is a 120 v flux core "MIG." What will happen if I try to weld cast iron to steel with this? All I need is enough strength to keep a 4"x4" cover from falling off. Strength and safety are not involved.