What is DIN 2391 ST52 Pipe?

DIN 2391 is the German standard for cold drawn precision seamless steel pipes. To make these pipes hot rolled pipes are drawn through a die at room temperature. This cold working method makes tight dimensional tolerances and a smooth surface finish that hot rolling can't achieve.

ST52 is a high-strength grade within this standard. The designation means minimum tensile strength of approximately 520 MPa. Under current EN standards, this grade is now called S355. The old ST52 name persists in the industry because it has been used for decades.

When your hydraulic cylinder or pneumatic actuator faces high working pressures, the pipes wall must contain that force. Higher yield strength means you can use thinner walls or achieve higher pressure ratings with the same wall. Either way, you get a better strength-to-weight ratio.

Applications

DIN 2391 ST52 pipes serve precision applications requiring high strength:

Hydraulic Cylinders

These pipes are used in cylinder barrels for hydraulic rams and actuators. The high yield strength handles working pressures up to 250-350 bar depending on dimensions. Precision bore tolerances ensure proper piston seal contact. The cold drawn surface gives adequate finish for many applications, or the pipe can be honed for critical service.

Pneumatic Systems

Air cylinders and pneumatic actuators use ST52 pipes for their strength and dimensional accuracy. Pneumatic pressures are lower than hydraulic, but the precision tolerances remain important for seal life and smooth operation. Automation equipment, packaging machines, and assembly systems rely on pneumatic cylinders made from this material.

Frequently Asked Questions

  • What is the equivalent of ST52 pipe?

    ST52 equals S355 or E355 in current EN standards. In ASTM terms, it is close to A519 Grade 1026 for mechanical tubing. The key property is 355 MPa minimum yield strength. Different standards use different naming but the material performance is similar.

  • What are the pressure ratings for ST52 seamless pipes?

    Pressure rating depends on pipe dimensions and safety factor. A typical 50mm OD x 5mm wall ST52 pipe handles approximately 280 bar working pressure with standard safety factor. Smaller diameter thick-wall pipes rate higher. Always calculate based on your specific dimensions.