Effect of Pre-Rolling Heat Treatments on the Bond Strength of Cladded Galvanized Steels in a Cold Roll Bonding Process

摘要

In the present study, the improvement of the bond strength of galvanized steel sheets in the cold roll bonding process is investigated. Zn-Fe intermetallic compounds are employed as an intermediate layer. The galvanized low-carbon steel is cold roll bonded. Prior to the roll bonding, the sheets are heat treated in the temperature range from 450 to 550 degrees C. The influence of the heat treatment on the bond strength is investigated. It is found that the use of the pre-rolling annealing increases the bond strength. The highest average value is observed after a treatment at temperatures in the range from 450 to 500 degrees C. Higher temperatures, however, reduce the bond strength. The bond is analyzed by optical and scanning electron microscopy (SEM) and evaluated in a tensile shear test. The interaction between iron and zinc is considered to be responsible for the improved bond strength. The presence of intermetallic compounds in the interface zone forms a brittle layer, which is required to create juvenile surfaces due to local fracturing during the roll bonding.