Recently, it has become increasingly difficult for only a single metallic material to meet the demand, which asks for the effective characteristics, such as corrosion-resistance, high strength and electric conductivity, at the same time. The development of clad material, which consists of two or more metals, has arisen, in which the clad material has developed advanced functional properties by utilizing the property of each metal. Clad bars have been manufactured by swaging, hydrostatic extrusion, groove rolling methods and so on. However, it is difficult to produce the clad bar with a high dimensional accuracy efficiently. The development of a method for manufacturing a clad bar with diffusion bonding interface by hot rolling has been highly sought.
In this paper, first, the diffusion bonding methods by hot working, such as hydrostatic extrusion, groove rolling and rotary rolling methods, are studied comparatively. Next, in the diffusion bonding method by rotary rolling, the combination of metallic material, the feature of diffusion bonding, the metal flow at bonding portion and the thickness of the diffusion layer are investigated in detail. This diffusion bonding method can be carried out by the heavy reduction rolling which is a symmetric working method.