Abstract
The factors that affect the stability of the melt stream during the casting of wire directly from the melt have been investigated. It is shown that the criticality of process parameters centres mostly on the forces imposed on the melt stream at confluence with the cooling water. The analysis of these forces indicated that the shear component of the disturbance is dependent on the ratio of the velocity of the melt stream (vm) to that of the cooling water (vw) in accord with results obtained from previous experiments. The role of oxide-forming elements in widening the process parameters range is attributed to the increased stability of the melt stream due to the additional shear force resistance offered by the solid oxide layer. The roles of Cr and Si oxides in stabilising the melt stream are confirmed by X-ray photoelectron spectroscopy (XPS) of wire indicating the presence of these oxides on fresh as-cast wires. Melt superheat and nozzle clearance distance are not strictly stream stability factors, but rather their role in glass formation prescribes optimal limits for fully amorphous wire.
Highlights
The ability to cast wire directly from melt provides such an obvious production process advantage that it has long attracted attention
We have explored the development of direct casting in a multi-stream mode [35,36] where it was demonstrated that the productivity of wire production could be increased through multi-streaming without adversely affecting the wire forming and vitrification processes
The casting conditions when using laser drilled multiple nozzles were summarised earlier [35]. These are concerned largely with stabilising the melt jets and maintaining their geometry in the transition from liquid melt to solid metallic glass wire. Each of these process parameters are considered as to how they affect the melt stream stability and how they determine the critical limits in the wire casting process
Summary
The ability to cast wire directly from melt provides such an obvious production process advantage that it has long attracted attention. This process has potential for scale up, but inconsistency in products after several attempts required the clarification of the many varied factors that affect the melt stream stability and, the quality of the cast metallic glass wires It represents the only method by which larger diameters of up to 150 μm glassy wires can be produced directly from melt. It is hoped that an understanding of such problems would contribute to new developments in the process and alloy selection for multi-stream casting of metallic glass wires directly from melt Such relatively thick metallic glass wires are known for their magnetic bi-stability and very high strength. It is expected that a high volume production would promote their use as structural reinforcement and possible magnetic applications
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