Paper Title
VERTICAL TWIN ROLL CASTING OF ALUMINUM ALLOY A7075 USING COPPER ROLLS

Abstract
This paper reports on the vertical twin roll casting of aluminum alloy A7075. Aluminum alloy A7075 belongs to the highest strength alloys and its sheets are produced by rolling and extrusion. It is used in the aerospace industry and for special applications, but it has a high susceptibility to solidification cracking and is difficult to obtain sheets easily. Twin-roll casting can produce thin sheets directly from molten metal, making it possible to produce plates other than conventional alloys for plates. In this study, thin sheets were produced using copper rolls with higher thermal conductivity than the iron rolls used in the previous study. The aim of this study is to fabricate good thin plates by using copper rolls with high thermal conductivity to cool and solidify the material more rapidly. The roll diameter was 200 mm. The initial roll gap was 0.5 mm and the pouring temperature was 700℃. The solidification length was 78 mm. The roll speed was mainly varied experimental conditions, and the value were from 1 m/min to 10 m/min for the investigation of the effects on the strip surface conditions. It was possible to produce A7075 strips by vertical twin roll strip casting process. Very large cracks occurred when thin sheets were produced using copper rolls at a roll peripheral speed of 5 m/min. This is thought to be due to the good continuity of the thin sheets produced, and the longer sheets hitting the bucket placed at the bottom of the experimental apparatus and jamming in the roll gap area. This problem can be solved by installing a guide using rollers at the bottom of the experimental apparatus.The sheet surface texture consisted of metallic luster and mud areas. Keywords - Aluminum Alloy A7075, Twin Roll Casting Process, Copper Rolls, Surface Condition, Strip Thickness.