| 摘要 |
PROBLEM TO BE SOLVED: To provide a valve seat made of an iron-based sintered alloy which is used in a state of being cast-wrapped into a cylinder head made of a light metal alloy. SOLUTION: The valve seat 1 is made of an iron-based sintered alloy obtained by integrating the two layers of a face surface side layer 11 and a seating surface side layer 12. The face surface side layer has a composition where hard grains are dispersed into the base phase and 0.2-1.5% C and 1.5-40.0% Co are contained, which is the composition having a shrinkage amount higher than that in the seating surface side layer. Further, the layer may be a high speed steel based composition of a specified composition. The ratio of the layer thicknesses of the face surface side layer to that of the sealing surface side layer is adjusted to a prescribed range. In this way, upon sintering, by the shrinkage of the face surface side layer, as the outer circumferential face of the valve seat is left sintered without working it, the outer circumferential face of the valve seat can be formed in a taper shape having a desired taper angle in which the diameter of the face surface side is made smaller than that of the seating surface side. Further, in addition to the above composition, the face surface side layer and the seating surface side layer may contain at least one kind selected from Ni, W, V, Mo, Si, Mn, Cr or the like. COPYRIGHT: (C)2011,JPO&INPIT
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