In the carbide industry, valuable materials such as tungsten carbide and cobalt are used, for example, in indexable inserts, drills and milling cutters. These raw materials are expensive, sometimes scarce and only available in a few regions. The recycling of used carbide products is therefore becoming increasingly important.
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A tried and tested process is the so-called thermal zinc process: In this process, hard metal scrap is heated together with zinc in a furnace
heated in a furnace. The zinc diffuses into the cobalt binder, causing the carbide to break up and disintegrate into a porous, easily crushable mass. After the zinc has evaporated, a powder structure remains, which serves as the starting point for new hard metal products.
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In one customer’s process, two separate crucibles are used, which are coupled together via a hollow connector. One contains the zinc, the other the hard metal scrap. The weak point of the system was at the transitions between the crucibles. crucibles and the connector: Zinc vapor could escape uncontrolled, with negative consequences for process reliability, material yield and system components.
The existing design did not allow for a permanent seal. A reliable, easy-to-implement solution was needed at short notice and without system conversion.
The aim was to create a functioning seal between the connector and the crucible without changing the existing system. The requirements were:
Graphite Materials impressed with its fast and non-binding consultation and developed a suitable concept based on a temperature-resistant soft felt within a few days. soft feltwhich was flexibly adapted to the geometry and inserted into the transition area.
By using the soft felt seal, it was possible to significantly improve the sealing of the system. Based on the process parameters and component geometry, a simple but highly effective solution was developed that not only reduces zinc loss but also extends the service life of the system components.
Soft felt seals (red) on the crucibles
Tungsten and cobalt, in particular, can be recovered from carbide scrap.
Depending on the material, other metals such as titanium, tantalum, or niobium may also be present.
Rising prices for cemented carbide and valuable raw materials are making the recovery of cemented carbide increasingly attractive from an economic standpoint.
At the same time, unreliable supply chains are increasing the pressure to use existing raw materials efficiently and become less dependent on imports.
Graphite components are indispensable for many recycling processes due to their high temperature resistance, thermal conductivity, and chemical resistance.
They ensure reliable plant operation even at high process temperatures.