Bonding enhancement of cold rolling Al/steel composite plates via self-nano film modification

Abstract

Al/steel composite plates have wide application prospects. However, obtaining high bonding strength using the roll bonding method is difficult because the properties of aluminum and steel are quite different. In this study, an innovative process of producing high bonding strength Al/steel composite plates by using an oxidation treatment on steel surface and cold rolling is proposed. Results reveal that the steel side oxidation treatment can effectively improve the bonding strength of Al/steel composite plates. Compared with the surface treatment without oxidation, the shear strength of “wire brush grinding + steel side oxidation” and “belt grinding + steel side oxidation” can be increased by at least 3 times, and the shear strength is 95 and 100 MPa, respectively, at the reduction rate of 60 % in single pass of cold rolling. The mechanism analysis shows the brittle oxide on the surface of the steel plate forms a crack during the rolling process. A fresh metal bonding zone forms under rolling pressure because as the fresh metal inside the aluminum is squeezed into the side cracks of the steel, a high-strength bond is formed with the fresh metal inside the steel. Although the crack in the oxide-bonding area is small, it also undergoes mechanical interlock and element diffusion. This situation is conducive to the improvement of the bonding strength of Al/steel composite plates.