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Refractory Metals

Refractory Metals

Date posted: November 21, 2016 // Refractory Metals

Refractory metals are characterised by their exceptionally high resistance to both heat and wear. In addition, they are chemically inert with a high resistance to acids and oxidation, and are of relatively high density. The two definitions for the elements that qualify them for this label differ, but both are based upon their melting points. The more restrictive definition includes only those with a melting point of 2 200oC or greater, and is made up of just five elements – niobium, molybdenum, tantalum, tungsten and rhenium. A broader criterion accepts 2 000oC as the lower limit, in the process adding a further nine qualifiers that include titanium, vanadium and chromium.

Among the reasons that elements such as these are so highly prized is the property known as creep resistance – creep being the tendency for a material to deform at high temperatures. It is this property that, for example, makes them particularly suitable for the construction of jet engines or, not surprisingly, for the manufacture of the tools used in order to forge other elements that are not included among the refractory metals.

Although the more energy-efficient models are rapidly gaining favour, the tungsten wire filaments once used universally in the manufacture of electric light globes for every conceivable use are effective because of their high melting point. This coupled with their high resistance, allows them to be heated to the exceptionally high temperatures needed to produce incandescence without causing them to burn out in the process. For much the same reasons, it is also a good choice for use as a permanent electrode in the process known as tungsten inert gas welding. An even more common use and one that far more may be familiar with relies on its strength and density, rather than resistance, to heat when combined with carbon to form super-tough tungsten carbide drill bits.

 

Among the refractory metals that are most resistant to corrosion is tantalum; a property that has earned a number of roles within medicine and surgery, while the high capacitance of tantalum films has enabled the miniaturisation of previously bulky components for use in the circuitry of mobile phones and tablet PCs.

In addition to playing key roles in the lighting, semiconductor, smelting and welding industries, these elements have become equally important to the manufacture of glass, for use as protective coatings, and even in engine technology.

Labotec Industrial Technologies supplies South Africa’s industries with high-quality materials and finished components for use in a wide range of applications that require the use of refractory metals, including molybdenum, tungsten, niobium, tantalum and chromium.