Abstract: A valve seat is produced by (a) using, as a raw material powder for forming a matrix, an Fe-based alloy powder with an average particle size of 20 to 50 &mgr;m, and using, as a raw material powder for forming a hard dispersion phase, a Co-based alloy powder with an average particle size of 20 to 50 &mgr;m, (b) conducting solid phase sintering, under vacuum, of a pressed compact formed from a mixed powder generated by mixing the Co-based alloy powder into the Fe-based alloy powder in sufficient quantity to account for 25 to 35% by weight of the combined weight with the Fe-based alloy powder, and causing the Co, Cr and Si components of the Co-based alloy powder to diffuse and migrate into the matrix, and the Fe component of the Fe-based alloy powder to diffuse and migrate concurrently into the hard dispersion phase, thereby markedly improving adhesion of the hard dispersion phase to the matrix, and forming, as a result, an Fe-based sintered alloy substrate with a porosity of 10 to 20%, and comprising an Fe&mdas

Abstract: A valve seat is produced by (a) using, as a raw material powder for forming a matrix, an Fe-based alloy powder with an average particle size of 20 to 50 &mgr;m, and using, as a raw material powder for forming a hard dispersion phase, a Co-based alloy powder with an average particle size of 20 to 50 &mgr;m, (b) conducting solid phase sintering, under vacuum, of a pressed compact formed from a mixed powder generated by mixing the Co-based alloy powder into the Fe-based alloy powder in sufficient quantity to account for 25 to 35% by weight of the combined weight with the Fe-based alloy powder, and causing the Co, Cr and Si components of the Co-based alloy powder to diffuse and migrate into the matrix, and the Fe component of the Fe-based alloy powder to diffuse and migrate concurrently into the hard dispersion phase, thereby markedly improving adhesion of the hard dispersion phase to the matrix, and forming, as a result, an Fe-based sintered alloy substrate with a porosity of 10 to 20%, and comprising an Fe&mdas

Abstract: Prior to welding together two overlapped plated steel sheets 4 and 5 by laser lap welding that irradiates parts of the plated steel sheets (4, 5) extending on a weld line (Lw), slits (4b) are formed intermittently in the upper plated steel sheet (4) with a laser beam (L). Subsequently, a welding head (1) is moved along the weld line (Lw) while the upper plated steel sheet (4) is pressed against the lower plated steel sheet (5) by pressure rollers. Parts of the upper plated steel sheet (4) extending on the weld line (Lw) and not provided with the slits (4b) are irradiated with the laser beam to laser-weld the plated steel sheets (4, 5) together. A vapor of the component of the coating layers coating the joining surfaces (4a, 5a) of the plated steel sheets (4, 5) produced from the coating layers by the heat produced by the laser beam is discharged through the slits (4b).

Abstract: Prior to welding together two overlapped plated steel sheets 4 and 5 by laser lap welding that irradiates parts of the plated steel sheets (4, 5) extending on a weld line (Lw), slits (4b) are formed intermittently in the upper plated steel sheet (4) with a laser beam (L). Subsequently, a welding head (1) is moved along the weld line (Lw) while the upper plated steel sheet (4) is pressed against the lower plated steel sheet (5) by pressure rollers. Parts of the upper plated steel sheet (4) extending on the weld line (Lw) and not provided with the slits (4b) are irradiated with the laser beam to laser-weld the plated steel sheets (4, 5) together. A vapor of the component of the coating layers coating the joining surfaces (4a, 5a) of the plated steel sheets (4, 5) produced from the coating layers by the heat produced by the laser beam is discharged through the slits (4b).

Abstract: A valve guide member for internal combustion engines is formed of an Fe-based sintered alloy having excellent wear and abrasion resistance, consisting essentially, by weight %, of 1 to 4% C, 1.5 to 6% Cu, 0.1 to 0.8% P, and if required 0.05 to 1% Mo, and the balance of Fe and inevitable impurities, the Fe-based sintered alloy having a structure having a matrix formed mainly of pearlite, in which are dispersed hard Fe--C--P compounds and free graphite, or alternatively hard Fe--C--P compounds, carbides, and free graphite when the alloy contains Mo, the free graphite including 0.5 to 10 area % coarse free graphite having a particle diameter of 70 to 500 .mu.m.