| 摘要 |
PURPOSE: Provided are iron-based sintered alloy and preparation of valve seat using the same, which are excellent in abrasion resistance and heat resistance against a high-powered engine, are applicable for use in a valve seat for a suction and exhaust valve of internal-combustion engine of all sorts. CONSTITUTION: The iron-based sintered alloy contains 0.5-2.0pts.wt. of Cr, 6.0-10.0pts.wt. of Mo, 0.1-2.0pts.wt. of Si, 9.0-14.0pts.wt. of Co, 0.5-2.0pts.wt. of Ni, 2.0-6.0pts.wt. of Cu, 0.6-1.2pts.wt. of C, 5.0-15.0pts.wt. of Pb and up to 3.0pts.wt. and the rest composed of iron. The iron-based sintered alloy is characterized by being distributed homogeneously Co-based hard phase and Mo-based hard phase over mixture matrix of sorbite and bainite. Preparation of valve seat using the iron-based sintered contains the steps of: i) mixing step that mix homogeneously the components of the iron-based sintered alloy; ii) compression-molding step that compression-mold the composition to make a molded article; iii) pre-sintering step that make the molded article sintered to give a little hardness at temperature that carbon is not diffused in mixture gas of N2 + H2 atmosphere; iv) cold forging step that inject the pre-sintered body into a mold and press it under a pressure of 10-15TON/cm2 at the upper and lower sides to make a matrix high-density by being increased density of the pre-sintered body; v) a second sintering step that sinter the cold gorging article under a temperature of not more than melting point in the mixture gas atmosphere to be diffused homogeneously to be joined the Co-based hard phase and the Mo-based hard phase over the matrix, and making the sorbite and the bainite formed by the matrix; vi) Pb impregnation step that impregnate Pb having excellent lubrication property into a void formed at the mixture matrix or the hard phases to be lubricated the sintered body; and then vii) barrel step that remove a wire after manufacturing.
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