Method for bonding a valve seat with a cylinder head

摘要

A method for bonding valve seats for intake and exhaust valves to an engine cylinder head. Valve seats are brazed to an aluminum cylinder head using an Al-Zn type brazing material and a fluoride type flux. The brazing material contains 70 to 90 % by weight of Zn. The brazing is preferably carried out at a temperature of 470 DEG to 520 DEG C. To allow the brazing material and flux to be present between the cylinder head and each valve seat, the cylinder head contains U-grooves formed around the opening of each intake or exhaust port. The U-groove consists of an annular step formed along the opening of the intake or exhaust port and a bank extended along the inner circumference of the step. The valve seats are placed in the U-grooves, which are then filled with the brazing material and flux, to carry out brazing of the valve seats onto the cylinder head. After completion of the brazing, the banks are removed to complete bonding of the valve seats to the cylinder head. In another method, a valve seat is directly bonded to a cylinder head by applying a fluoride type flux on the valve seat.