IRON-BASED SINTERED ALLOY-MADE VALVE SHEET FOR INTERNAL COMBUSTION ENGINE AND MANUFACTURING METHOD THEREFOR

PROBLEM TO BE SOLVED: To provide an iron-based sintered alloy-made valve sheet for internal combustion engine having excellent abrasion resistance and excellent dropout resistance, and a manufacturing method therefor.SOLUTION: There is provided a valve sheet having a structure in which a tempered martensite phase having fine carbide with major axis:30 μm or less of 27 area% deposited is a matrix phase, and further hard particle in the matrix phase is dispersed with 31 to 80 area%, and a composition in which a matrix part containing the matrix phase, the hard particle or further a solid lubricant particle contains, by mass%, C:0.5 to 1.8%, further one or more kind selected from Mo, Cr, V and W of 10 to 50% as total, further one or more kind selected from Ni, Co, Cu, Si, S, Ca, F of 10 to 80% as total, and the balance Fe with inevitable impurities. Thereby, there is provided a valve sheet excellent in abrasion resistance and dropout resistance, and containing a large amount of hard particle at density:7.3 to 8.2 g/cm, radial strength:400 MPa or more.SELECTED DRAWING: None 【課題】優れた耐摩耗性と優れた耐脱落性を兼備する内燃機関用鉄基焼結合金製バルブシート及びその製造方法の提供。【解決手段】長径：30μm以下の微細炭化物を面積率で27％以下析出させた焼戻マルテンサイト相を基地相とし、さらに該基地相中に硬質粒子を、面積率で31〜80％分散させた組織とし、基地相および前記硬質粒子、あるいはさらに固体潤滑剤粒子を含む基地部が、質量％で、Ｃ：0.5〜1.8％を含み、さらに、Mo、Cr、Ｖ及びＷのうちから選ばれた１種又は２種以上を合計で10〜50％、更にNi、Co、Cu、Si、Ｓ、Ca、Ｆのうちから選ばれた１種又は２種以上を合計で10〜80％、含有し、残部Fe及び不可避的不純物からなる組成とする、バルブシート。これにより、密度：7.3〜8.2ｇ/cm３、圧環強さ：400MPa以上で、多量に硬質粒子を含有する、耐摩耗性及び耐脱落性に優れたバルブシート。【選択図】なし