We supply seamless precision steel tube to DIN 2391 in St35, St45 and St52. Cold drawing gives a tight wall tolerance and a smooth surface, so the tube can go straight into machining or pressure lines.
Price: quoted per specification. Steel prices move with the raw material market, so every quotation is confirmed at the time of order.
Specifications
- Standard: DIN 2391 seamless precision steel tube
- Steel grade: St35, St45, St52
- Delivery condition: BK, BKW, BKS, GBK, NBK
- Size range: Outside diameter 4-80 mm, wall 0.6-10 mm, quoted to drawing
Drawn pipe, cold drawn tube, seamless cold drawn: the process names
DIN 2391 tube is bought under at least four different process names, and the buyer usually picks the one their own shop uses rather than the one on the standard. They all describe tube that has been pulled through a die after the hollow shell was made, but they are not identical products.
| Name in the enquiry | What it actually is | Seam | Where it comes from |
|---|---|---|---|
| drawn pipe, drawn steel pipe | Loose trade wording for any cold drawn tube, sized as pipe or tube | Either | Maintenance, plant buyers |
| cold drawn tube, cold drawn steel tube | Tube reduced in diameter and wall by drawing, then annealed | Either | Machine shops, distributors |
| seamless cold drawn tube, CDS | Pierced shell drawn over a plug or mandrel, no weld anywhere | None | UK and EU drawings, hydraulic work |
| drawn over mandrel, DOM | Welded tube drawn over a mandrel, flash removed | Welded, drawn | US drawings, shock absorber bodies |
| welded and drawn tubing | Same as DOM, written the long way | Welded, drawn | SAE J525 buyers |
| DIN 2391 tube | Seamless precision tube to the German standard | None | European drawings |
The distinction that matters commercially is the first three against the last three. A drawn pipe enquiry can be satisfied by either route, so it is worth confirming whether the part is pressure-loaded or simply machined: the seamless route costs more and is only worth it where the seam would be a liability.
DIN 2391 and the standards it is compared with
DIN 2391 has been superseded by EN 10305-1, but the two are quoted side by side on European drawings, and American buyers often arrive with an ASTM or SAE number instead. The table places the usual alternatives next to each other.
| Standard | Product | Seam | Typical use |
|---|---|---|---|
| DIN 2391 | Seamless precision steel tube, cold drawn | None | Hydraulic and pneumatic lines, machined parts |
| EN 10305-1 | Seamless cold drawn precision tube (E235, E355) | None | The current European replacement for DIN 2391 |
| DIN 2393 / EN 10305-2 | Welded precision tube, cold drawn | Welded, drawn | Shock absorber bodies, bushes, medium pressure |
| ASTM A519 | Seamless carbon and alloy mechanical tubing | None | 1020, 1045, 4130 machined parts |
| ASTM A513 Type 5 | Electric resistance welded, drawn over mandrel | Welded, drawn | DOM tubing, 0.5-2.5 inch |
| SAE J524 | Seamless low carbon tubing | None | Automotive lines and fittings |
| SAE J525 | Welded and cold drawn low carbon tubing | Welded, drawn | Automotive parts where a seam is acceptable |
In practice the choice between DIN 2391 and A519 is a choice of market rather than of steel: both are seamless and cold drawn, and the difference sits in the grade list, the tolerance tables and the certificate language a customer expects. We draw to both, and a single order can carry a DIN 2391 certificate and an A519 grade if the drawing asks for it.
Delivery conditions: BK, BKW, BKS, GBK, NBK
| Symbol | Condition | What it means for the part |
|---|---|---|
| BK | Cold drawn, no heat treatment after the last draw | Hardest and strongest, least ductile |
| BKW | Cold drawn and soft annealed | Soft enough to flare, bend or swage |
| BKS | Cold drawn and stress relieved | Straighter and more stable, keeps most of the strength |
| GBK | Annealed, straightened, then cold drawn | Good surface and straightness at moderate strength |
| NBK | Normalised | Uniform structure for parts that will be welded |
EN 10305-1 writes the same conditions as +C, +LC, +SR, +A and +N. The condition is normally fixed by what happens next: a tube that will be honed is supplied BK or GBK, a tube that will be bent is supplied BKW, and a tube that will be welded is supplied NBK.
Typical applications
- Hydraulic and pneumatic lines
- Machined bushes, pins and shafts
- Precision mechanical parts
Sizes and tolerances
| Item | Range | Note |
|---|---|---|
| Outside diameter | 4-80 mm | Outside this range quoted as a special draw |
| Wall thickness | 0.6-10 mm | Wall to drawing where the OD allows |
| OD tolerance | +-0.05 to +-0.10 mm | Set by the final draw |
| Wall tolerance | +-10 percent | Closer where the bore is honed afterwards |
| Length | 4-7 m random, or fixed | Cut to length with deburred ends on request |
| Delivery condition | BK, BKW, BKS, GBK, NBK, or +C to +N | Condition chosen for the next operation |
Where the drawing gives an ID and a wall rather than an OD, the draw schedule is set from the bore, because on a cylinder or a bushing the bore is the working surface and the outside is only a boundary.
FAQ
Is DIN 2391 still valid, or must I quote EN 10305-1?
EN 10305-1 replaced DIN 2391 and is the standard to quote on new drawings. DIN 2391 is still widely accepted, and the tube and the certificate are the same, so an older drawing does not need to be rewritten.
What is the difference between drawn pipe and drawn tube?
Only the sizing convention. Pipe is ordered by nominal bore and schedule, tube by outside diameter and wall. The mill product can be identical, and the same drawing can be quoted either way.
Can I get DIN 2391 tube with an A519 grade?
Yes, on request. The draw schedule, the tolerances and the certificate are agreed separately, so a customer who needs a 4130 or 1045 grade with a European tolerance table can have both on one document.
Which condition should I order for bending?
BKW, or an annealed condition. Hard drawn BK tube bends to a larger radius and cracks more easily on tight bends, especially at a wall below about 1.5 mm.
Do you supply honed or SRB tube in DIN 2391?
Yes. Cylinder tube is supplied cold drawn with a honing allowance, or honed and SRB to Ra 0.2-0.4 µm, and the bore is measured at both ends and in the middle.
Standard reference: see our DIN 2391 standard page for grades, delivery conditions and tolerances.
Quality and packing: tubes are protected with anti-rust oil and packed seaworthy, in wooden cases where agreed. Each lot is tested for chemical composition, yield and tensile strength, flattening, elongation and dimensions, with visual inspection and NDT available on request.
Request a quotation: send your size list or drawing through our contact page. We reply within one working day with price, tolerance and lead time.