What are the requirements of materials for large hydraulic cylinders?

There are two categories of large-scale hydraulic cylinders: those with large bore diameters and those with large tonnages. These cylinders are characterized by their large cylinder diameters, long individual strokes, large volumes, and high weights. They are also capable of providing significant pulling force or thrust. Due to the challenges and costs associated with processing large hydraulic presses, material selection is a critical aspect of designing and manufacturing such cylinders. An incorrect choice of materials can result in substantial economic losses.

1. Material requirements for each part

The primary components of a large hydraulic cylinder include the hydraulic cylinder barrel, cylinder bottom, cylinder head, hydraulic piston rod (chrome plated bar), piston, earrings or flange, and mounting bases.

The materials commonly used for each part of a large hydraulic cylinder, in the absence of special working environments, are as follows:

Hydraulic cylinder barrel, also known as hydraulic cylinder tube, is typically made from 1020 seamless steel pipe, ST52.3 seamless steel pipe, or 1045 seamless steel pipe. For extra-large hydraulic cylinders, a higher strength steel such as SAE 4140 steel or 1045 steel may be required to make the hydraulic cylinder barrel.
Hydraulic piston rods are usually made from 1045 steel or St52 steel. When the hydraulic cylinder is subject to significant impact and vibration, alloy materials such as 27SiMn steel or 4140/42CrMo may be used.
Integral pistons are typically made from 1035 steel or 1045 steel. Assembled pistons are often made from materials such as gray cast iron, wear-resistant cast iron, or aluminum alloy. For special requirements, bronze, brass, or nylon wear-resistant sleeves can be installed on the outside of the steel piston blank.
The cylinder head material depends on the working pressure. High-strength cast iron (HT200) is suitable for working pressures of up to P10MPa, while seamless steel pipe is used for pressures up to P20MPa. Cast steel or forged steel is used for pressures exceeding P20MPa.

2. Special working conditions & environment

1)Typically, ST52, 1045 steel, or a higher grade of steel is utilized for the cylinder barrel. The hydraulic cylinder barrel is constructed from a honed tube with a surface roughness capable of achieving 0.4. The inner hole’s surface has a uniform grid honing pattern, allowing the piston to form a uniform oil film during reciprocating motion along the cylinder barrel’s surface.

2) The piston rod is typically subjected to quenching and tempering to achieve a hardness of HB241-286. The surface of the piston rod should also be plated with hard chrome, with a thickness of 0.02-0.05 mm or meet the requirements of HRC55-65. Additionally, the surface should be polished to achieve a high level of cleanliness, ranging from 0.4um to 0.2um.