**3. Roll bonding**

Cold roll bonding (CRB) is a solid phase method of bonding similar or dissimilar metal sheets by rolling at room temperature, which has been widely employed in the production of large multilayer composite sheets and foils. Cold pressure welding by rolling (CRB) is a sort of pressure welding or solid-state welding technology in which bonding is created by joint plastic deformation of the metals to be welded, suggesting that the degree of deformation is one of the major criteria [7]. CRB can be applied to a wide range of materials, cold bonding also works effectively with materials that cannot be fused by standard fusion. Rolling generates the high interfacial pressure required for bonding between two metal parts. Tensile shear test, slide shear test, multistep shear test, peeling test, and T-peel test is some of the procedures used to assess the bond strength of layered materials. Many investigations on the parameters influencing bonding have been conducted to understand the mechanisms of the complicated nature of bonding and the process conditions that have been established empirically [38]. The roll bonding parameters to be considered are, the type of metal under consideration, the amount of deformation, the bonding temperature, the amount of pressure applied, the bonding time, the metal purity, the lattice structure, the surface preparation conditions, the geometry of the deformation zone (shape factor), the stacking sequence, the number of layers, the layer thickness, and the type of post-heat treatment, which have been reported in the literature. The removal of contaminated layers from the surface using chemical and mechanical treatments is critical in the CRB process (surface preparation).

### *Joining by Forming of Sheet Metals DOI: http://dx.doi.org/10.5772/intechopen.102098*

This usually entails washing and prepping surfaces to eliminate any impurities (bonding barriers) from the surfaces of the two metals to be bonded.

The complicated nature of the bonding mechanism involved in the roll bonding process has been the subject of numerous recent research studies [39]. Due to significant work-hardening by scratch-brushing, the metal surface gets hardened to a depth [40]. The cover layer fracture when exposed to sufficient surface expansions. Fracturing due to high interface pressure opens up new crack surfaces. Extrusion begins when the normal pressure is high enough and the surface expansion (or crack width) is significant. A connection is established when the asperities of the decovered virgin material of the two opposing surfaces make contact. This is the first bonding process mentioned [41]. The materials like aluminum, copper is easy to cold roll bond. Gold, silver, and platinum are other FCC metals that can be cold-bonded easily [7]. The bonding characteristics of hexagonal metals, such as magnesium, cadmium, and zirconium, are inferior to those of FCC materials.

Some of the applications of roll bonded sheet metal parts are, Al-Cu roll bonded sheets used in cooking utensils, heat exchangers, roof and wall plates. Al-Fe bonded sheets are used for electric heater reflectors, automobile silencers. Al roll bonded to stainless steel is used in automobile trims, Al-Steel-Al sheets used in the automobile exhaust system. Ti-Stainless steel-Ni found applications in the bipolar electrode in the fuel cell, Cu to Stainless steel bonded sheets have been widely used in communicator plate, and so on.
