To eliminate such a fear that an oxide film and any impurities or the like are left behind in a weld zone at a time when a valve seat is welded to a cylinder head by means of resistance heating, thereby making a good welding job achievable, and to make improvements in heat transfer from the valve seat to the cylinder head.
A countersink 3 is formed in an opening edge part of an exhaust hole 2 of a cylinder heat, and the peripheral surface 7 of the junction of a valve seat 5 is formed into a head-cut cone, while plural pieces of projecting bars 8 facing nearly in the radial direction are installed in the peripheral surface 7 in advnace, and these projecting bars 8 are forcibly pressed to the countersink 3, energizing the cylinder heat 1 and the valve seat 5 with an electric current, then these junctions is subjected to resistance heating, and the valve seat 5 is pressed toward the cylinder heat 1 under pressure as fusing the cylinder head 1, whereby an oxide film or the like made up in an inner circumferential surface of the countersink 3 is broken down by the projecting bars 8, and further the resistance heating welding is carried out as discharging the broken pieces from the junction along each of respective grooves 9.
KANZAKI TATSUO
ASANUMA HIROAKI
