The effect of surface preparation on the bond strength of Al-St strips in CRB process

•The influences of wire brushing and belt grinding preparation on aluminum clad steel strip have been discussed.•The surface state after preparation is important on the bonding strength in cold roll bonding process.•The metallic bonding of aluminum and steel is achieved in the crack of steel surface.•The cracks between brittle layer and substrate metal are the weak area of the interface.

The effect of surface preparation on the bond strength of Al-St clad strips in cold roll bonding (CRB) was investigated. For the purpose, the steel strip were prepared by two different way before the cold roll bonding, and evaluate the sample bonding strength by peeling test of the rolling deformation zone. The results show that, at the same reduction, bond strength of Al-St strip treated by belt grinding is higher than by wire brushing. The threshold reduction of Al-St strip treated by belt grinding (10%) is lower than by wire brushing (15%). The belt grinding treatment removes contamination such as oxide layer efficiently and has proper degree of surface hardened. The strip surface with thinner brittle layer and cleaner metal can create stronger bonding. A major feature of the bonding mechanism is that soft aluminum is extruded into the cracks on steel surface under normal roll pressure and contacts with underlying fresh steel metal so that the metallic bond between Al and Fe is formed. Meanwhile the mechanical biting from the blocks along the interface also contributes to the bonding strength.

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