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Help CenterDIN 2391 Seamless Precision Steel Tube-Hengzhihui Cold Drawn / Cold Rolled – ST35, ST45, ST52 BK, BKW, NBK Delivery Conditions
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DIN 2391 Seamless Precision Steel Tube-Hengzhihui
Cold Drawn / Cold Rolled – ST35, ST45, ST52
OD 6~204mm | WT 1~18mm | BK, BKW, NBK Delivery Conditions
Product Overview
Our DIN 2391 seamless precision steel tubes are manufactured by cold drawing or cold rolling processes for hydraulic cylinders, pneumatic systems, and precision mechanical applications. These tubes offer high dimensional accuracy, excellent surface finish, and consistent mechanical properties.
⚠️ Important Note: DIN 2391 has been withdrawn and replaced by EN 10305-1. We supply this standard for legacy replacement, maintenance, and retrofit projects .
Key Specifications:
Standard: DIN 2391-1 / DIN 2391-2 (withdrawn – replaced by EN 10305-1)
Grades: ST35 (E235), ST45 (E255), ST52 (E355 – most popular)
Outer Diameter: 6mm – 204mm (Standard Stock: 19mm – 89mm)
Wall Thickness: 1mm – 18mm
Length: 3m – 12m (Custom lengths available)
Manufacturing Process: Cold Drawn / Cold Rolled (Seamless)
Delivery Conditions: BK, BKW, BKS, GBK, NBK
Surface Finish: As-drawn / Bright / Oiled / Phosphated
✅ DIN 2391 compliant – Supplied to withdrawn standard for legacy projects
✅ Cold drawn / cold rolled – Precision manufacturing process
✅ ST52 in stock – Most popular grade for hydraulic cylinders
✅ Multiple delivery conditions – BK, BKW, NBK – match to application
✅ 100% NDT and hydrostatic testing available – Guaranteed integrity
✅ EN 10204 Type 3.1 MTC provided with heat number
✅ Factory direct – Competitive pricing and fast delivery
Steel Grade Overview
| Grade | EN 10305 Equivalent | Yield (MPa) | Tensile (MPa) | Delivery Condition | Application |
|---|---|---|---|---|---|
| ST35 | E235 | ≥235 | 340-480 | BK, NBK | General precision engineering |
| ST45 | E255 | ≥255 | 410-550 | BK, NBK | Higher strength applications |
| ST52 | E355 | ≥355 | 490-640 | BK, NBK | Hydraulic cylinders – most popular |
💡 ST52 is the most commonly requested grade for hydraulic cylinder applications .
Delivery Conditions – DIN 2391
| Symbol | Description | Application | Surface |
|---|---|---|---|
| BK (+C) | Cold drawn / as-drawn | Maximum strength | Dull |
| BKW (+LC) | Cold drawn + light finishing | Chrome plating prep | Bright |
| BKS (+SR) | Stress relieved | Dimensional stability | Dull |
| GBK (+A) | Annealed | Soft, machinable | Dull |
| NBK (+N) | Normalized | Good strength + ductility | Dull/satin |
💡 NBK (normalized) is the most popular delivery condition for hydraulic cylinders – good strength with excellent ductility and weldability .
Chemical Composition
| Grade | C max | Si max | Mn max | P max | S max |
|---|---|---|---|---|---|
| ST35 | 0.17 | 0.35 | 0.40 | 0.025 | 0.025 |
| ST45 | 0.21 | 0.35 | 0.40 | 0.025 | 0.025 |
| ST52 | 0.22 | 0.55 | 1.60 | 0.025 | 0.025 |
💡 Low carbon content ensures excellent weldability and good formability for bending, flaring, and flattening operations .
Mechanical Properties – ST52 (Most Popular)
| Condition | Tensile (MPa) | Yield (MPa) | Elongation (%) | Surface |
|---|---|---|---|---|
| BK | 560-780 | ≥450 | ≥10 | Dull |
| NBK | 490-640 | ≥355 | ≥22 | Dull/satin |
| BKW | 520-700 | ≥400 | ≥14 | Bright |
💡 ST52 NBK provides the best combination of strength (≥355 MPa yield) and ductility for hydraulic cylinders .
Dimensional Tolerances – DIN 2391 Precision Tubes
| OD (mm) | Standard Tolerance (mm) | High Precision (mm) |
|---|---|---|
| 6-30 | ±0.08 | ±0.03 |
| 31-40 | ±0.15 | ±0.05 |
| 41-50 | ±0.20 | ±0.08 |
| 51-60 | ±0.25 | ±0.08 |
| 61-80 | ±0.30 | ±0.10 |
💡 High precision tolerances are available upon request – ideal for applications requiring ultra-tight dimensional accuracy .
Manufacturing Process – Cold Drawing / Cold Rolling
Cold Drawing Process for Precision Tubes:
Hot rolled tubes are pickled to remove scale
Cold drawing precisely reduces the diameter – achieves tight tolerances
Heat treatment – BK (as-drawn), BKW (finish drawn), NBK (normalized) as specified
Straightening – ensures straightness for hydraulic applications
Precision cutting – to exact customer length
100% NDT and hydrostatic testing – guarantees integrity
Grade Selection – Hydraulic Cylinder Applications
| Application | Recommended Grade | Delivery Condition | Key Feature |
|---|---|---|---|
| General precision parts | ST35 | NBK | Economical |
| Hydraulic cylinders (standard) | ST52 | NBK | Most popular |
| High strength hydraulics | ST52 | BK | Maximum strength |
| Chrome plated piston rods | ST52 | BKW | Bright surface |
| Machined components | ST35 | GBK | Soft, machinable |
| Welded assemblies | ST52 | NBK | Good weldability |
DIN 2391 vs EN 10305-1
| Feature | DIN 2391 (Withdrawn) | EN 10305-1 (Current) |
|---|---|---|
| Status | Withdrawn (2003) | Current |
| Grade naming | ST35, ST45, ST52 | E235, E255, E355 |
| Technical content | Equivalent | Equivalent |
| Delivery conditions | BK, BKW, BKS, GBK, NBK | +C, +LC, +SR, +A, +N |
💡 For new projects, we recommend EN 10305-1 – DIN 2391 is supplied for legacy replacement projects only .
Key Applications – Legacy Precision Tubes
| Industry | Application | Recommended Grade |
|---|---|---|
| Hydraulics | Cylinder barrels | ST52 NBK |
| Hydraulics | Piston rods | ST52 BKW |
| Pneumatics | Cylinder tubes | ST35 NBK |
| Automotive | Shock absorber tubes | ST35 |
| Machine Building | Guide tubes, shafts | ST52 |
Why Choose Our DIN 2391 Precision Tubes?
| Advantage | Description |
|---|---|
| Legacy standard support | Supply to withdrawn DIN 2391 for replacement projects |
| ST52 NBK in stock | Most popular hydraulic grade – ready to ship |
| Multiple delivery conditions | BK, BKW, BKS, GBK, NBK – all available |
| High precision tolerances | OD tolerances as tight as ±0.03mm |
| Full traceability | EN 10204 3.1 MTC with heat number |
| In-house processing | Cutting, honing, phosphating, bending |
Contact for Quote
📧 Email: yjhtrade@gmail.com
📞 WhatsApp: +86 15106174543
🌐 Website: /
Contact Person: Alice Yuan
Reply within 24 hours.
Tags: DIN 2391 Precision Steel Tube Cold Drawn Tube ST52 ST35 Hydraulic Cylinder Tube German Standard
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