I don't think what you're doing is really smelting, which is producing metal from metallic ores. It sounds like what you want to do is remelting. Unfortunately, copper isn't easy to melt in its pure form; it takes a lot of heat (2000F+) to do that, more than most home-made furnaces can achieve. And casting it doesn't work too well either. I'd suggest you mix some tin into it (about 10% by weight), which would bring down the melting point and give you bronze ingots, which are more useful for casting.
If you don't know how to do this stuff, I'd strongly advise you to find someone who does, and have them show you, in person, what you need to know. There's a lot more to this than an email message or even a Youtube video will teach you, and what you don't know can kill you, when molten metal's involved.
Andrew Werby
United Artworks- Sculpture, Jewelry, Furniture,and other Art Objects, plus Art Resources, Techniques of Sculpture, Jewelry and Lapidary, an Online Bookstore, and a Custom Art Referral Network