Tungsten Carbide Rolls

by KI-HONG, CHO

Publisher - TeaguTec Ltd

Category - General Novel

Tungsten carbide rolls are produced by a powder metallurgical process. The tungsten carbide rolls are made of "cemented carbide," that is, a tungsten carbide and a binding material, such as cobalt metal powder, that helps to "cement" the powder metal together. Small additions of other elements may be added for WC grain size control or other specialized purposes. Three binder metal powders are most commonly used: cobalt (for maximum toughness and abrasive wear resistance), nickel (for enhanced resistance to corrosive attack) and alloys of cobalt, nickel and chromium (for corrosion resistance and toughness). Tungsten carbide rolls proved to be the ultimate answer for hot rolling steel rods at high speeds. Compared to cast iron rolls, tungsten carbide rolls operated 10 to 15 times as long between pass groove changes. The application of tungsten carbide to hot rolling steel rods permitted rapid growth in the output rates of rod mills. In practical applications of rolls, roll may be subjected to repeated cyclic loading. Dynamic strength properties, such as fatigue strength, fatigue crack nucleation, propagation behavior and threshold stress for fatigue crack growth are important parameters. Apart from mechanical fatigue, thermal and environmental fatigue are also of importance. Some important parameters controlling thermal crack initiation are flow stress in tension, Young’s modulus, coefficient of thermal expansion and thermal conductivity. This presentation shows experimental results relating to the influence of binder composition on the growth of thermal fatigue cracks and corrosion resistance in the tungsten carbide roll material.

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