| 摘要 |
PROBLEM TO BE SOLVED: To provide an end mill composed of fine-particulate tungsten carbide base cemented carbide having high strength and high toughness, by which the cutting edge faces of the end faces and outer circumferential edges exhibit excellent chipping resistance, particularly, under the heavy cutting conditions, e.g. of deep cutting and high rate feeding in steel or the like. SOLUTION: In an end mill composed of a cutting edge part in which the end faces are used as cutting edge faces, and also, outer circumferential edges are formed and a shank part, in which at least the cutting edge part in the cutting edge part and the shank part is composed of fine tungsten carbide particles in which the growth of the particles is suppressed by the incorporation of Cr, and, in structural observation by a scanning type electron microscope, also composed of a tungsten base cemented carbide composed of a dispersed phase occupying 75 to 95 area %, and the balance bonding phase essentially consisting of Co and also containing solid solution Cr with inevitable impurities, and, in which, as for the contents of Co and Cr, Co: 4 to 15 mass %, and Cr: 0.1 to 3 mass % are satisfied by the ratios occupied to the whole, a diffusion extra-thin layer of Co and Cr is formed on the surface parts of the fine tungsten carbide particles composing the dispersed phase of the fine-particulate tungsten carbide base cemented carbide.
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