| 摘要 |
PURPOSE:To improve resistance to thermal fatigue strength without spoiling casting property and strength by a method wherein a tip, made of hypereutectic flake graphite cast iron having specific composition, is internal-chill cast in a valve bridge section, faced to a combustion chamber and located between suction valve and exhaust valve. CONSTITUTION:A suction port 5 and an exhaust port 6 are opened for the combustion chamber 4 in the cylinder head 1 and the suction valve 7 and the exhaust valve 8, opening and closing respective ports 5, 6, are arranged in the cylinder head 1 so as to be neighbored. The hypereutectic flake graphite cast iron tip 11 is internal-chill cast in the valve bridge section 1A between said ports 5, 6 in the cylinder head 1. Matrix 1B, except said tip 11, is cast by normal cast iron already known before. In this case, the composition of said tip 11 is specified that the equivalent amount of carbon is 4.3-4.6%, Mo is 0.3-0.8%, Cr is 0.05-0.40%, Mn is 0.1-1.5%, P is 0.1% or less, S is 0.1% or less and the balance is Fe. |
