Hydraulic pipe

steelfor hydraulic systemsfor mining applications

Product overview

The ST52 Bored Tube is a seamless steel tube with precision internal boring to deliver tight inner-diameter tolerances, high roundness and consistent wall thickness. Manufactured from ST52 low-alloy structural steel, it is designed for large-diameter hydraulic cylinder barrels and other heavy-duty hydraulic components used in construction, mining and material-handling equipment.

Key product data

• Model： Bored Tube
• Brand： EAST AI
• Material： ST52 (ST52.3 / ST52.4 available)
• ID range： 50 mm – 800 mm
• OD range： 80 mm – 1000 mm
• Max length： up to 8000 mm

Material properties of ST52 steel

ST52 (DIN 2391 / EN 1.0570 S355) offers a balanced combination of tensile strength, ductility and machinability. It provides good weldability and impact resistance suitable for hydraulic cylinder applications.

Chemical composition (typical %):

Carbon (C) ≤ 0.22
Silicon (Si) ≤ 0.55
Manganese (Mn) ≤ 1.60
Phosphorus (P) ≤ 0.025
Sulfur (S) ≤ 0.025

Mechanical properties:

Tensile strength: 490 – 630 MPa
Yield strength: ≥ 355 MPa
Elongation: ≥ 20%
Impact energy: ≥ 27 J (at 20°C)

Manufacturing process

• Raw material preparation：Selection and inspection of ST52 seamless pipes for surface quality, dimensions and chemistry.
• Boring：Deep-hole/boring machining to achieve specified inner diameter, roundness and wall thickness.
• Heat treatment (optional)：Normalization or quench & temper (Q+T) to enhance hardness, strength and fatigue performance.
• Surface finishing：Inner surface ground/finished to Ra ≤ 0.8 μm to reduce friction and extend seal life.
• Inspection：Ultrasonic testing, dimensional and straightness checks, hardness and tensile verification.

Dimensional range and technical specifications

Material grade: ST52 / ST52.3 / ST52.4
Inner diameter (ID): 50 mm – 800 mm
Outer diameter (OD): 80 mm – 1000 mm
Length: up to 8000 mm
Surface roughness: Ra ≤ 0.8 μm
Roundness tolerance: ≤ 0.03 mm
Straightness: ≤ 1:1000
Heat treatment: Normalized / Q+T optional

Key advantages

• High strength and load capacity for high-pressure hydraulic systems.
• Precision inner surface reduces piston wear and improves sealing.
• Tight dimensional tolerances and straightness for consistent performance over long lengths.
• Good machinability and weldability for secondary operations (grooving, porting, flanging, threading).
• Enhanced fatigue life with optional heat treatment and protective coatings.

Applications

• Hydraulic cylinder barrels for excavators, loaders and mining machinery.
• Heavy-duty mobile and industrial hydraulic systems requiring large-diameter cylinders.
• Custom hydraulic components and repair/replacement barrels.

Quality control and testing

100% ultrasonic flaw detection; dimensional tolerance verification; hardness and tensile testing; surface finish inspection. All test records are documented and traceable.

Packaging and delivery

Internal and external anti-rust oil, protective film and woven wrapping, export wooden or steel crates, fumigation-free packing and pallet options. Stock availability and lead times vary by dimension and are provided on request.

Commercial designation / Technical specifications

• Denomination: ST52 Bored Tube
• Brand: EAST AI
• Material: ST52 (ST52.3 / ST52.4)
• ID range: 50 mm – 800 mm
• OD range: 80 mm – 1000 mm
• Max length: up to 8000 mm
• Inner surface: Ra ≤ 0.8 μm
• Roundness tolerance: ≤ 0.03 mm
• Straightness: ≤ 1:1000
• Tensile strength: 490 – 630 MPa
• Yield strength: ≥ 355 MPa
• Optional heat treatment: Normalized or Q+T