Every tube is defined by its post-drawing heat-treatment state: NBK, BK, GBK, or BKV. The order confirmation specifies diameter, wall thickness, tolerance class, and inspection certificate together.
| Delivery condition | Condition | Diameter range | Wall thickness | Tolerance | Standard |
|---|---|---|---|---|---|
| NBK | Normalised annealed | Ø 6–120 mm | 0,5–10 mm | D4 / T3 | DIN 2391 · EN 10305-1 |
| BK | Cold drawn, hard | Ø 6–70 mm | 0,5–6 mm | D4 / T3 | DIN 2391 · EN 10305-1 |
| GBK | Annealed after drawing | Ø 25–120 mm | 2–12 mm | D4 / T3 | DIN 2391 · EN 10305-1 |
| BKW | Normalised annealed | Ø 6–60 mm | 0,5–5 mm | D4 / T3 | EN 10305-2 |
| BKV | Stress relieved | Ø 6–40 mm | 0,5–4 mm | D4 / T4 | EN 10305-4 |
| QT | Quenched + tempered | Ø 20–120 mm | 3–15 mm | D4 / T3 | EN 10216-3 |
Table values are indicative industry-typical examples — confirmed against your product range at the quotation stage.
DIN 2391
Cold-drawn precision steel tubes; grades St 37-4, St 45, St 52.
EN 10305-1
Seamless cold-drawn tubes, tight dimensional tolerances.
EN 10305-4
Seamless precision tubes for hydraulic and pneumatic lines.
EN 10216-3
Seamless tubes for pressure purposes; non-alloy and alloy grades.
