2003 年 21 巻 2 号 p. 282-294
Laser welding process is widely used in industry. However, its use in joining dissimilar metals like steel and aluminium is recently suggested. Dissimilar joint between aluminium and steel is required to achieve reduced weight in structure with better strength, but formation of brittle intermetallic compounds(IMC)at the joint interface reduces the strength considerably. By controlling laser power and interaction time with the material, there is a possibility of achieving joints with reduced thickness of IMC.
In this work, laser roll bonding of aluminium and steel sheets was fundamentally investigated. As basis study, Time-Temperature-Phase(TTP)diagram was constructed for diffusion-bonded joints under different compressive pressures. Steel sheet was heated with CO2 laser beam, immediately followed by pressing it against the underlying aluminium sheet by means of a roll. Joints were made by inserting aluminium-brazing flux and shielding with argon gas to avoid surface oxidation. Temperature profiles across the section were simulated to identify suitable laser power and travel speed. The interfaces of joints were analyzed by using EPMA. Tensile shear strength of the joints was measured and the sheared surface was analyzed by XRD. There is an optimum range of laser power, travel speed and roll pressure in which appreciable joint strength results. It is found that reduction in the thickness of interface layer and hence improvement in the joint strength is possible by laser roll bonding process.