Abstract: An iron-based sintered alloy material for a valve seat having improved wear resistance and reduced opposite aggressibility to a mating valve. The iron-based sintered alloy material contains 10% to 20% by area of first hard particles and 15% to 35% by area of second hard particles dispersed in a base matrix phase, the first and the second hard particles accounting for 25% to 55% by area in total. The first hard particles are composed of a cobalt-based intermetallic compound and have a size of 10 to 150 ?m and a hardness of at least 500HV0.1 and less than 800HV0.1. The second hard particles are composed of a cobalt-based intermetallic compound and have a size of 10 to 150 ?m and a hardness of at least 800HV0.1 and less than 1100HV0.1. Solid lubricant particles may also be dispersed in the base matrix phase.

Abstract: A valve seat, press-fitted into a cylinder head of an internal combustion engine, containing an iron-based sintered alloy, includes a valve-seating section and a head-seating section. 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/cm3 and contains hard particles dispersed in a matrix. 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/cm3.

Abstract: An iron-based sintered alloy material for a valve seat having improved wear resistance and reduced opposite aggressibility to a mating valve. The iron-based sintered alloy material contains 10% to 20% by area of first hard particles and 15% to 35% by area of second hard particles dispersed in a base matrix phase, the first and the second hard particles accounting for 25% to 55% by area in total. The first hard particles are composed of a cobalt-based intermetallic compound and have a size of 10 to 150 ?m and a hardness of at least 500HV0.1 and less than 800HV0.1. The second hard particles are composed of a cobalt-based intermetallic compound and have a size of 10 to 150 ?m and a hardness of at least 800HV0.1 and less than 1100HV0.1. Solid lubricant particles may also be dispersed in the base matrix phase.

Abstract: A valve seat, press-fitted into a cylinder head of an internal combustion engine, containing an iron-based sintered alloy, includes a valve-seating section and a head-seating section. 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/cm3 and contains hard particles dispersed in a matrix. 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/cm3.

Abstract: An iron-base sintered alloy material for a valve sheet is a material in which a hard particle composed of one or more elements selected from C, Cr, Mo, Co, Si, Ni, S and Fe is dispersed in a base matrix phase, a porosity is 12 to 25% by volume ratio, and a density after sintering is 6.1 to 6.9 g/cm3. Thereby, production of iron oxide at operation of an internal combustion engine is accelerated, and the abrasion resistance is remarkably improved. It is preferable that a base matrix portion containing a base matrix phase and the hard particle has the composition containing a total of 10.0 to 40.0% of one or more selected from Ni, Cr, Mo, Cu, Co, V, Mn, W and C, and the balance substantially Fe. It is preferable that a solid lubricant particle of one or more selected from a sulfide and a fluoride is firther dispersed in a base matrix phase at 0.3 to 3.5% by area ratio.

Abstract: An iron-based sintered alloy material for a valve seat, in which hard particles are dispersed in a base matrix phase, is characterized in that the base matrix phase is comprised of 5 to 40 vol. % of a pearlite phase and 10 to 40 vol. % of a high-alloy diffused phase and particles having hardness of Hv 600 to 1300 and particle diameter of 10 to 150 &mgr;m are dispersed as the hard particles, by the amount of 10 to 30 vol. %, in the base matrix phase. The hard particles are preferably at least one type of particles selected from the group consisting of intermetallic compound particles of Mo—Ni—Cr—Si—Co; intermetallic compound particles of Cr—Mo—Co; Fe—Mo alloy particles; and carbide-precipitated particles.

Abstract: A valve seat made of an iron base sintered alloy for internal combustion engines comprises of hard particles of hardness 700-1300 Hv dispersed by 3-20% by volume in a matrix phase comprising comprising of a 5-40% psarlite phase, a 20-60% fine carbide dispersed phase, and a 5-20% high alloy diffusd phase. The hard paricles are preferably selected from a group of Mo--Ni--Cr--Si--Co intermetallic compound particles, Cr--Mo--Co intermetallic compound particles, and Fe--Mo alloy particles. The iron base sinteed alloy is conpised of, by weight, C: 0.2-2.0%, Cr: 1.0-9.0%, Mo: 1.0-9.0%, Si: 0.1-1.0%, W: 1.0-50%, V: 0.2-3.0%, one or more Cu, Co and Ni of 0.5-10.0% in total, and the remainder substantial Fe.

Abstract: The invention is directed to a joined type valve seat which is joined into the cylinder head of an aluminum alloy in an internal combustion engine by resistance welding and, in particular, to an improved joined type valve seat superior in strength, rigidity, and abrasion resistance, whereby no cracks are caused when running the engine or when joining the valve seat to the engine block by resistance welding. The valve seat is made of a material having a tensile strength of 300 MPa or above, a radial crushing strength of 500 MPa or above, an elongation of 0.6% or more, a thermal conductivity of 15 W/(m.multidot.K) or above, a coefficient of thermal expansion of 10.times.10-.sup.6 (1/K) or above, and an electric resistivity of 50 .mu..OMEGA..multidot.cm or below.

Abstract: A secondary hardening type high temperature wear-resistant sintered alloy body comprising 0.4 to 15 wt. % of at least one species of metal carbide forming element which is selected from the group consisting of W, Mo, V, Ti, Nb, Ta and B; 5 to 35 wt. % of at least one species of austenite forming element which is selected from the group consisting of Ni, Co, Cu, and Cr; 0.2 to 1.2 wt. % of C; and 0.04 to 0.2 wt. % of Al consisting essentially the remainder of Fe, wherein the alloy body contains an austenite phase which is capable of martensitic transformation.

Abstract: A secondary hardening type high temperature wear-resistant sintered alloy body comprising 0.4 to 15 wt. % of at least one species of metal carbide forming element which is selected from the group consisting of W, Mo, V, Ti, Nb, Ta and B; 5 to 35 wt. % of at least one species of austenite forming element which is selected from the group consisting of Ni, Co, Cu, and Cr; 0.2 to 1.2 wt. % of C; and 0.04 to 0.2 wt % of the remainder consisting essentially of Fe wherein the alloy body contains an austenite phase which is capable of martensitic transformation.