PURPOSE: To enhance a life and to reduce a cost to a layer extent by using a dot pin made of a high-speed steel having specific composition of materials and physical properties.
CONSTITUTION: A dot pin in use is made of high-speed steel powder containing 1.4-2.0% C, 8-4.5% Cr, 8% or more Mo, 4% or more W, 3.0-5.5% V and 7.8-12% Co by weight with a W equivalent (W%+2Mo%) of 19.5-25 and has a wire diameter of 0.1-0.4mm by a cold wire drawing, a hardness of Hv 870-950, and an anti-folding force of 500kg/mm2 or more. A part of the carbon C is taken into solid solution in a substrate; the other is bound with W, M, O, Cr, V, and the like to form a carbide, which enhances hardness and increase wear resistance. A part of the tungsten W forms a double carbide (M6C) and imparts wear resistance; the other is taken into solid solution in the substrate to obtain resistance to softening at high temp.. The molybdenum Mo has properties approximately similar to the W and corresponds to W=2Mo. A part of the chromium Cr forms a carbide (M23C6); the other is taken into solid solution in the substrate to impart self-hardening properties to the steel to improve the hardenability.
NAGAO ICHIRO
KIMORI YOSHIO
KOBE STEEL LTD