Roll bonding starts with two or more coils of cold finished strips of different metals or alloys. The metals are cleaned chemically, then abraded by a brushing operation to eliminate oxides and other surface impurities.

The cleaned metals are rolled under very high pressure, which reduces their thickness and bonds the metals together. As their surfaces are extended, typically by more than five times that of their original area, the atomic lattices of the metals merge, sharing electrons between mating surfaces.

Coils of bonded strip are heat treated to “relax” the materials and to extend diffusion of the electrons of one material into the other at the bond interface. Impurities that become gaseous when heated diffuse into the metals; nondiffusible impurities consolidate by spheroidization.

 

Anatomy of a metallurgical bond.

Clad metals are joined by a roll bonding and thermal treatment process that produces a metallurgical bond as the lattice structures of the metals are forced into conformance with each other. High pressure, producing massive deformation of the metals, causes a sharing of electrons at the interface, which produces a bond on the atomic level. No intermediate layers such as adhesives or braze metal are involved.