異径双ロールキャスターで鋳造したAl-Mg合金板のインライン熱間圧延

A model experiment for in-line hot rolling was proposed, and its effectiveness in reducing surface cracking and improving the mechanical properties of cast strips of AC7A Al-Mg alloy was investigated. The strips were cast using an unequal-diameter twin-roll caster at 60 m/min. The strips had a width of 100 mm, and were immediately cut to a length of 200 mm and hot rolled at temperatures of 300, 350, 400, 450 and 500°C. The temperature of the strip surface was measured using a K-type thermocouple. The center area in the width direction of the strips was hot rolled. The thickness of the as-cast strips was 2 mm, and the width of the rolled region was 20 mm. The roll diameter was 70 mm, and the rolling speed was 15 m/min. The thickness reduction caused by hot rolling ranged from 19 to 42%. Surface cracking was reduced by the in-line hot rolling process. The hot-rolled strips were cold rolled down to a thickness of 0.5 mm and then annealed, and tensile tests were conducted. The in-line hot rolling process induced shear deformation of the microstructure. The most appropriate conditions for in-line hot rolling of AC7A were a thickness reduction of 27% and a temperature of 350°C, judging from the tensile strength and elongation results.