Fast solution heat treatment of high strength aluminum alloy sheets in radiant heating furnace during hot stamping

Abstract Lightweight of automobile has drawn increasing attention due to the demand for energy saving and emission reduction. High strength aluminum alloy sheet shows great potential in the automobile industry for its high strength and low density. Hot stamping has been developed for high strength aluminum alloy to improve the formability and reduce the springback. However, the solution time of this technology is too long. In order to reduce the solution time, several experiments have been carried out. The heating curves of bare sheets and BN or graphite coated sheets in radiant heating furnace were measured and the theoretical heating efficiency was calculated. The results showed that the heating efficiency was improved about 7.4 times with BN coating and 9.2 times with graphite coating depending on the heating temperature, so the heating rates of the coated sheets were faster than that of bare sheets. Further, hot stamping of bare and coated sheets was carried out and the mechanical properties of hot stamped sheets were tested. Hot stamping results showed that the solution time of 6061 and 7075 decreased from 10 min to 5 min by spraying BN or graphite on the sheets, reducing the solution time by 50%.