Casting for low pressure, HT300 gray iron for medium and low pressure, and 35 and 45 steel for medium and high pressure. When the cylinder head itself is the guide sleeve of the piston rod, the best choice for the cylinder head is cast iron. At the same time, brass, bronze and other wear-resistant materials should melt on the guide surface of the rolled tube. If the structure of the guide sleeve is pressed into the guide sleeve, the guide sleeve should be wear-resistant cast iron, bronze or brass. Common materials for pistons are wear-resistant cast iron, gray cast iron (HT300, HT350), steel and aluminum alloy. The coaxiality tolerance value of the piston and piston rod should be 0.03mm.
The commonly used materials are seamless steel tubes 20, 35 and 45, and the rolled tubes are honed or rolled to meet the roughness requirements within 0.4m. Twenty steel pipes can be used for low-pressure cylinders, and forty-five steel pipes for high-pressure cylinders.
There are two types of piston rods: solid rod and hollow rod. One end of the hollow piston rod needs to be used for welding and heat treatment. The solid piston rod material for heat treatment is 3545 steel, and the hollow piston rod material is 3545 seamless steel pipe. After rough machining, the piston rod is quenched and tempered 229 ~ 255Hb, if necessary, the hardness is 45 ~ 55 ℃, after high frequency quenching treatment, quenching treatment in India.