Nowadays, the technology of double metal composite tube has been developed quickly in many countries, especially in Japan, America, UK, and former Russia. Main processes are seamless composite and casting, welding, outer coating metal, laser coating composite and so on. The popular process is nested mechanical metal at present, but there aren`t many consumers due to the limitation of this tube, the reason as follows: first is the joint of tube haven`t been solved well, so the advantage of composite haven`t been taken. Adopting technology of centrifugal casting and rolling to produce double metal products can overcome the problem above and will become the tendency of national and international in the future.
