Tungsten carbide, grinding

A wide apphcation of electrochemical grinding is the production of tungsten carbide [12070-12-1] cutting tools (see Carbides Tool materials). ECG is also useful in the grinding of fragile parts such as hypodermic needles and thinwaH tubes. 

Tungsten carbide (WC) is extremely hard and resistant to high temperatures. When cemented to tools, it is as hard as corundum (aluminum oxide) and makes excellent grinding surfaces and cutting edges for machine tools. 

The panels were all releaded and restored by Dieter Goldkuhle of Reston, Va. When the individual panes were separated, corners of those selected for analysis were cleaned with a tungsten carbide burr grinding... 

Microcline, albite and labradorite were obtained from Ward s Canada Limited. Cleaved crystal fragments and 60 mesh-sized samples were ultrasonically cleaned prior to use. Powdered samples (particle size < 25 ym) were prepared by grinding in a tungsten carbide ball mill, wet-sieving and washing in water. 

There are many types of mechanical grinding equipment available ball mills, ball and mortar sets, planetary mortars, impact mills, etc. These are available in a variety of materials steels, porcelain, agate, mullite, silicon carbide, tungsten carbide and others. Prices range from 200 to about 2,000. Unfortunately, the cost increases rather markedly as one goes to the harder materials, especially the carbides. 

Commonly used types of grinding media are carbon steel, stainless steel, chrome steel, tungsten carbide, ceramic, or zirconia. Ball mills produce up to 50 ton/hr of powder substantially passing a 200-mesh screen. Temperature control can be achieved by the use of jacketed ball mills through which a heat transfer fluid is circulated. 

The CRM 062 consisted of freshly picked olive twigs from Pescara (Italy). After washing, the twigs were air-dried on a plastic lattice positioned ca. 40 cm above a layer of polythene. The leaves were removed by threshing with wooden rods and collected from the polythene ground sheet. Grinding took place in a tungsten carbide hammer mill. 

After a coarse grinding (to a particle size of 2-10 mm) in a stainless steel mill, the material was packed in polythene lined containers and shipped to the Joint Research Centre of Ispra (Italy) for further processing. The material was then ground in a tungsten carbide mill. A fraction of the particles of 90-200 pm was sieved out this fraction was chosen in order to eliminate possible fine clay-like particles. 

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