Casting Conditions and Solidification Characteristics of Sn-Zn Alloys

Sn-Zn합금의 주조조건과 응고특성

An investigation has been conducted to describe solidification characteristics in Sn-Zn binary system and Sn-Zn-Ag ternary system added by Ag produced by the continuous casting process using heated mold as a basic study for developing Pb-free solder materials. To obtain the continuous casting rods with mirror surface and near net shape at higher casting speed, water flow rates must be increased and mold temperature must be lowered. However, surface tearing in the casting rods occured at lower continuous casting speed while break out occured at higher continuous casting speed even if optimum conditions such as water flow rate and heated mold temperature are determined. Primary ${\alpha}Sn$ and eutectic structure in unidirectioally solidified Sn-Zn alloys were finer with increased casting speed. But, directionality may not be expected for primary Zn in hypereutectic Sn-Zn alloy. It was found that the addition of $0.2{\sim}0.8%$ Ag promoted the growth of primary ${\alpha}Sn$ dendrites. The changes of tensile strength and elongation in Sn-Zn binary alloys were not observed while the increase of tensile strength and the decrease of elongation in Sn-Zn-Ag ternary alloys were observed with increased casting speed.