The effects of solidification conditions on the formability of the twin-roll cast AA1050 strip

Abstract

Twin-roll casting (TRC) is a continuous sheet metal casting process, which was developed as an alternative to the conventional “ingot casting and hot mill method” of sheet metal production. Unlike the latter method, TRC combines the solidification of liquid metal and hot rolling at a single stage, thereby saving considerable energy, manpower and consumables. In the current work, the effects of three important solidification parameters on the formability behaviour of the twin-roll cast AA1050 sheet were studied. The parameters investigated were the casting speed, the casting gauge and the diameter of caster rolls. Initially, specimens of different parameter groups were cold rolled and annealed to same thicknesses and 0 temper condition from the as-cast state. Followingly, a series of intrinsic and simulative formability tests, including the uniaxial tensile test, Brinell hardness test, Erichsen test and dome stretching tests were performed. Using grid strain analysis method on the dome stretching test specimens and the uniaxial tensile test specimens, forming limit diagram (FLD) characterization was carried out. Microstructural study was conducted on the as-cast and 0-condition samples. Within the framework of the current study, the cold rolling machine in the Materials Laboratory was revised into a twin-roll caster and casting trials were performed. The microstructure of the samples obtained from the prototype caster was compared with the typical microstructure obtained from an industrial caster. It was observed from the test results that, changes in all three solidification parameters caused variations in formability, while the change in caster roll diameter caused the most significant changes. Moreover, test group samples cast at a small roll diameter illustrated a remarkably different microstructure, compared to the samples of the other test groups.