DIN2391 ST52 Cold Drawn High Precision Pipe

DIN2391 ST52 cold drawn precision tubes are seamless steel tubes made to tight dimensional and surface tolerances. They are pulled through a die in the cold state, which tightens the outside diameter, straightens the tube, and leaves the bore smooth and consistent. That finish is what lets the tube hold position under high pressure and still bend or form without cracking - the reason it turns up in hydraulic cylinders, machine tools, and automotive parts.

What "DIN2391 ST52" Actually Means

DIN 2391 is the German standard for seamless precision steel tubes supplied in the cold-drawn condition. ST52 (material 1.0580) is the grade, with a minimum yield strength around 355 MPa - the same level as the European grade E355 under EN 10305-1, which you will see quoted in many EU specs. Because the tube is drawn cold rather than finished hot, its tolerances and surface quality sit well above a standard seamless pipe.

DIN2391 ST52 Cold Drawn Precision Steel Pipe Specification

Delivery Conditions: BK, BKW, BKS, GBK, NBK

The letter after the condition tells you what heat treatment the tube received after drawing, and that decides how much you can bend or weld it later:

BK (+C) - cold finished, no heat treatment. Highest strength, but not meant for further cold forming.

BKW (+LC) - finished with a light final pass; allows slight forming.

BKS (+SR) - stress relieved, so drawing residual stress is lowered.

GBK (+A) - annealed; softer and easier to machine or bend.

NBK (+N) - normalized; best overall ductility and weldability.

Choose the condition from what you will do to the tube in your own shop - cut, bend, or weld.

Honing and Bore Finish

For hydraulic and pneumatic cylinders the inside of the tube matters more than the outside. After drawing, the bore can be honed to H7–H9 tolerance with a surface finish of Ra 0.4–0.8 µm, so the piston seal rides without scoring the wall. If only the outside needs to be precise, a cold-drawn tube without honing is usually enough and costs less.

Typical Applications

Hydraulic and pneumatic cylinders

Injection moulding and machine tool frames

Automotive drive and steering components

Bearings and precision sleeves

General mechanical engineering under pressure

How to Order

Give us the grade, outer diameter, wall thickness, length, delivery condition, and end finish, and we will quote against stock or production. Other grades such as E355 are available on request.

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Test and inspection

Q: How can I get the price?

A: Send the grade, outer diameter, wall thickness, length, quantity, and delivery condition. We quote against stock or production lead time.

Q: Do you inspect the finished tubes?

A: Yes. QC checks every production step and the finished tubes before shipment - dimensions, surface, and hydrostatic or ultrasonic testing as the application requires.

Q: What is your delivery time?

A: Stock items ship within 7 days. Made-to-order tubes take about 15 days, depending on size and condition.

Q: How are the tubes packaged?

A: Tubes are bundled, fitted with plastic end caps, separated by inner and outer steel protective rings, then secured with metal strapping and wooden supports inside the container.

Q: What is the difference between BK and NBK?

A: BK is cold finished with no heat treatment - strongest but hard to form. NBK is normalized after drawing, giving the best ductility and weldability. Pick BK when you only machine it; pick NBK when you need to bend or weld.

Q: Is honing included as standard?

A: No. Cold-drawn tubes ship as drawn; honing to H7–H9 / Ra 0.4–0.8 µm is a separate operation for cylinder bores. Tell us if your application needs the honed bore.

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