Hydraulic cylinder components and materials

Under normal circumstances, the hydraulic cylinder is composed of the rear end cover, cylinder, piston, piston rod and front end cover and other main parts.

In order to prevent the working medium from leaking out of the cylinder or from the high pressure chamber to the low pressure chamber, a sealing device (sealing ring) is arranged between the cylinder and the end cover, the piston and the piston rod, the piston and the cylinder, the piston rod and the front end cover. A dustproof device is also provided on the outside of the front end cover.

In order to prevent the piston from impacting the end cap when it moves rapidly to the end of the stroke, the end of the cylinder can also be provided with a buffer device. If necessary, in order to exhaust, but also set the exhaust device.

The material selection of each part of the cylinder should be based on the working condition of the cylinder, and the material will affect the quality of the cylinder.

1. Cylinder

The commonly used material is 20, 35, 45 seamless steel pipe, and the steel pipe has been honed or rolled to achieve the roughness requirements within 0.4μm. The low pressure cylinder can use 20 steel pipe, and the high pressure cylinder can use 45 steel pipe. The wall thickness of the cylinder should be calculated and selected strictly according to the design pressure, considering the use of working conditions to set the safety factor, if the impact + alternating load, the safety factor should be selected higher, if the wall thickness is thin, the cylinder is prone to heating deformation, or even blasting.

2. Piston rod

The piston rod has two kinds of solid rod and hollow rod, and one end of the hollow piston rod needs to be set aside for welding and heat treatment. The solid piston rod material is 35, 45 steel, and the hollow piston rod material is 35, 45 seamless steel pipe. After roughing the piston rod, the hardness is adjusted to 229~285HB, and if necessary, the hardness is 45~55HRC after high-frequency quenching.

The piston rod is very critical surface treatment, conventional chromium plating layer 2 to 3 wires, some applications need 3 to 5 wires. Some manufacturers rely on low price competition coating thickness is very low rather than no thickness, the piston rod is easy to rust. The coating is measured with a coating thickness gauge.

3. Cylinder head

Low pressure castings, medium and low pressure with HT300 gray iron, medium and high pressure with 35, 45 steel. When the cylinder head itself is the guide sleeve of the piston rod, the cylinder head is best cast iron. At the same time, brass, bronze or other wear-resistant materials should be fused on the guide surface. If the guide sleeve is pressed into the cylinder head, the guide sleeve shall be wear-resistant cast iron, bronze or brass.

4. Piston

Commonly used materials are wear-resistant cast iron, gray cast iron (HT300, HT350), steel and aluminum alloy. The coaxial tolerance of the piston and piston rod shall be 0.03mm