Reimann Brake Ramp for planar flow casting processes and analysis of ribbon gluing

Abstract

Planar flow casting is a rapid solidification process used to manufacture thin, metallic ribbons, and foil. Liquid metal is forced through a nozzle against a heat-sink wheel, and it rapidly solidifies into thin ribbons. A puddle of molten metal, held by surface tension, forms between the nozzle and wheel. This study examines a well-defined periodic surface defect called herringbone (HB), which is commonly produced when casting zirconium based alloys. The presence of this defect is related to processing conditions and puddle dynamics. Its formation has been correlated with the pinning of the liquid puddle at the nozzle edge. Here, the uniformity of thickness along a ribbon was successfully controlled (over a length of 50 m) using the Reimann Brake Ramp, which reduces the wheel speed at the start of the cast. For the alloy used in this study, the variation in the dimensionless thickness parameter, τ/G, with the Euler number (Eu=ΔP/ρU2) at assigned values of B/G followed an allometric scaling, with an exponent value close to the theoretical value of 1/3. Furthermore, the nozzle inclination was related to the ribbon thickness, τ, and the ribbon quality. Moreover, a newly developed automatized melt spinner permitted monitoring and controlling of the process parameters, elucidating the gluing phenomenon of the ribbon observed during the starting phase. The ribbon gluing was influenced by the puddle geometry, the recirculation in the puddle, and later, to the ribbon cooling rate. Within these results, high-quality ribbons with control thickness over a considerable length are achieved.

Keywords

• Planar flow casting
• Amorphous metallic glass
• Melt puddle
• Herringbone defect
• Ribbon gluing
• Cooling rate