Effect of Casting Condition on Ripple Mark and Surface Crack of Roll-Cast Al-Mg Alloy

Abstract

Effect of casting conditions on ripple mark and surface crack of as-cast Al-4.7%Mg strip was investigated. A vertical type high speed twin roll caster was used. A casting speed was 30 m/min. Casting conditions were tip-shape of a back-dam plate, gap between a roll and the back dam plate and texture on the roll-surface. The texture on the roll-surface was useful to reduce the ripple mark. In bending test conducted to investigate surface crack of as-cast strip, the texture on the roll surface was effective to the reduce the crack. The position of the crack was not coin side with the position of the ripple mark. This result shows that there is no correlation between the ripple mark and the ductility or the strength of as-cast strip. Small roll load was effective to reduce the crack and degree of the ripple mark. Effect of the roll load on the ripple mark was discussed including solidification delay and seepage of Magnesium.