Composition of valve
The valve is composed of valve head and stem. The valve head temperature is very high (intake valve 570 ~ 670k, exhaust valve 1050 ~ 1200k), and it also bears the pressure of gas, the force of valve spring and the inertia force of transmission components. Its lubrication and cooling conditions are poor, which requires that the valve must have certain strength, stiffness, heat resistance and wear resistance. Alloy steel (chromium steel, nickel chromium steel) is generally used for inlet valve, and heat-resistant alloy (silicon chromium steel) is used for exhaust valve. Sometimes, in order to save heat-resistant alloy, the exhaust valve head is made of heat-resistant alloy and the rod is made of chromium steel, and then the two are welded together.