In my opinion there are two things that should be changed to the matallurgy crafting system.
1) In physics there is something called conservation of mass. If one iron ore weighs 6 (whatever) and I put it in the furnace I obtain molten iron that weighs like 4, I think. This makes sense as I have separated the iron from the impurities. However, If I proceed to make an ingot out of the molten iron, I obtain an ingot that weighs like, 1.5. Why would I throw away molten iron? This does not make sense to me because I think the cast iron should weigh as much as the molten iron put into the cast. This is what completely boggles my mind though: When the ingot is melted back to molten iron, somehow, by the power of Talad I guess, the molten iron weighs 4 again. My suggestion would be to have the same weights for molten iron and iron ingots, and stocks would, of course, be a multiple of that. This way no laws of physics are broken.
2) Currently the only way to make steel stock is by combining original iron ore and coal lumps which makes it very impractical and also wouldn't make sense in the real world. It makes much more sense to me to combine coal lumps with molten iron. This way steel stocks and iron ingots become a way of storing iron for making steel. It just makes more sense to me.
Just a thought.