Patent ID: 7089902

Claim:
A valve seat, press-fitted into a cylinder head of an internal combustion engine containing an iron-based sintered alloy, comprising: a valve-seating section; and a head-seating section. wherein the valve-seating section and the head-seating section are monolithically formed by a sintering process and form a double layer structure. the valve-seating section includes a first iron-based sintered alloy member that has a porosity of 10 to 25 percent by volume and a sintered density of 6.1 to 7.1 g/cm 3 and contains hard particles dispersed in a matrix phase, and the head-seating section includes a second iron-based sintered alloy member that has a porosity of 10 to 20 percent by volume and a sintered density of 6.4 to 7.1 g/cm 3 , wherein the hard particles contain at least one selected from the group consisting of C, Cr, Mo, Co, Si, Ni, S, and Fe, and the content of the hard particles in the first iron-based sintered alloy member is 5 to 40 percent by area.