ABSTRACT
I. INTRODUCTI ON Aside from the purpose of rapid quenching, the formation of ribbon or wire directly from molten metals and alloys has long been an aim of engineers. Such processes can eliminate the elabora te mechanical reduct ion of cast ingots to small final di · mensions. The essence of the technology lies in the forma tion of the material fina l shape while still in the liquid state and the conservation of that shape on transformation to the solid state . In such processes di fficulty always exists, at the point of contact between the mel t stream to the cooling media. Because of the high fl uidi ty of melt , the stream shape can easi ly be disto rted or even disrupted so that the maintenance of the original ori fice or slot cross-sect ional shape by the melt is always quite diffi cult . Nevertheless, some successes have been achieved; examples of successful processes include planar-flow casting fo r ribbon formation and freejet casting fo r wire formation. An illustrative in troduction of various rapid quenching techniques is given by Jones [1]. In the case of ribbon fo rmation, a breakthrough happened when a process was invented in which. instead of trying to have the mel t maintain the cross-sectional shape of the slot as it was ejected into the cooling medium , the ribbon is formed out of a melt " puddle" on a fast -moving solid surface [2,3). The principle of this process, which will be described in some deta il in the next section , is based on the dragging out of a liquid boundary layer, which naturally takes the shape of a ribbon, out of the melt puddle. In the case of the direct wire fo rmation from the melt, the conservation of the circular cross-sectional shape of the melt formed by the orifice is essent ial. The break down of the shape is inevitable when solid coolant is used so that only semicircular or oblique cross-sectioned wire can be made in such a case . The melt extraction method (4] is one of such technique. Spinning of molten alloy while sur rounded by semimolten glass to keep the shape of liquid meta l via the high viscosity of glass is called the Taylor process (5]. While
this process may be used for some alloys, the reaction between the melt and glass which takes place in many cases limits the choice of metal and glass combinations to be spun . Also , the cooling rate of this wire casting process is reduced by the existence of low heat conductive glass around the metal wire during cooling. An innovative method by Ohnaka [6) which utilizes the nearly perfect laminar flow of liquid coolant inside a rotating drum as cooling medium allows preservation of the circular cross section of the orifice in the wire. This process is called the in-rotating liquid-spinning process (INROLISP).
