Signature Vacuum, Meadville, USA, has recently shipped a tungsten carbide reclamation furnace to Kohsei Co., Ltd., in Japan. The furnace utilises the molten zinc reclamation process to produce friable tungsten carbide.
The reclamation of cobalt cemented carbide with zinc is based on the fact that cobalt is soluble in zinc. At 800°C, cobalt and zinc form a eutectic alloy pulling the cobalt from its cementing position in the carbide mixture.
The unit is a two zone horizontal vacuum furnace designed to operate under vacuum, partial pressure inert atmospheres and up to 5 psig. The furnace is capable of processing 1000 kg per cycle. The control system is designed to allow easy integration into a supervisory control system while still maintaining flexibility in operation. The entire unit is of a modular design to simplify upgrades and repairs.
Signature’s furnace processing concept incorporates two equal sets of crucibles in the vacuum furnace. One is in the heated zone, where the carbide is roasted in the molten zinc, connected by a flow tube to one in the cold zone. At the end of the roasting time, the zinc has evaporated from the heated crucible and condensed in the receiving crucible in the cold zone. The receiver crucible being pre-loaded with tungsten carbide parts is then placed in the heated zone for the next roasting cycle. In this way, the zinc is only handled once on the initial loading.