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DIN 2391 Precision Steel Pipe

OD Range :

10 mm ～ 120 mm

WT Range :

1 mm ～ 15 mm

Length :

3 m ～ 12 m

Tolerance :

Outer Diameter: ±0.1 to 0.3 mm; Wall Thickness: ±0.05 to 0.2 mm; Length: ±5 mm

Material :

ST35, ST45, ST52

Standard :

DIN 2391

Surface :

Bright Annealed, Pickled, Anti-rust Oil Coating

Application :

Hydraulic Cylinders, Mechanical Components, Automotive Industry, Pneumatic Systems, Precision Machining

Introduction :

DIN 2391 precision steel tubes are cold-drawn seamless steel tubes characterized by high dimensional accuracy and a smooth surface finish, making them suitable for mechanical and hydraulic systems with strict requirements regarding dimensions and surface quality.

I. Overview of DIN 2391 Precision Steel Tubes

DIN 2391 precision steel tubes are cold-drawn, seamless precision steel tubes characterized by high dimensional accuracy, a smooth surface finish, and excellent mechanical properties.
These products are primarily utilized in mechanical engineering, hydraulic systems, automotive components, and precision industrial equipment—specifically in applications where strict requirements regarding dimensional tolerances and surface quality are paramount.

Key Features:

High Precision: Features tight tolerances on outer diameter and wall thickness, making it suitable for high-precision machining operations.
Superior Surface Finish: Undergoes bright annealing or pickling treatments, resulting in a smooth surface that facilitates further processing or coating applications.
Stable Performance: The cold-drawing process ensures uniform and reliable mechanical properties.
Diverse Material Options: Common steel grades include ST35, ST45, and ST52, corresponding to E235, E255, and E355, respectively.

II. Common Materials and Distinctions for DIN 2391 Precision Steel Tubes

Material / Grade	DIN Equivalent	Main Properties	Typical Applications	Differences & Features
ST35	E235	Medium yield strength, good ductility	General mechanical parts, hydraulic tubes	Moderate strength, easy to process, low cost
ST45	E255	Higher yield strength, moderate hardness	Hydraulic cylinders, mechanical structures	Stronger than ST35, suitable for medium pressure applications
ST52	E355	High yield strength, excellent toughness	High-pressure hydraulic systems, automotive parts	Best combination of strength and toughness, ideal for high-pressure or critical components
16Mn	16Mn	Good comprehensive mechanical properties	Industrial mechanical pipes, pressure vessels	Good pressure resistance, suitable for structural and pressure applications
C45	C45	High carbon steel, high hardness	Mechanical shafts, precision components	High strength and wear resistance, but lower ductility

III. Mechanical Properties of Common Materials for DIN 2391 Precision Steel Tubes

Material / Grade	Yield Strength (MPa)	Tensile Strength (MPa)	Elongation (%)	Hardness (HB)	Typical Applications
ST35 / E235	235 ± 10	360 – 510	≥ 25	120 – 160	General mechanical parts, hydraulic tubes
ST45 / E255	255 ± 10	410 – 560	≥ 23	140 – 180	Hydraulic cylinders, mechanical structural components
ST52 / E355	355 ± 15	510 – 680	≥ 20	160 – 200	High-pressure hydraulic systems, automotive parts
16Mn	235 – 355	430 – 600	≥ 20	140 – 190	Industrial mechanical pipes, pressure vessels
C45	430 – 530	580 – 700	≥ 16	170 – 210	Mechanical shafts, precision components

IV. Application Fields of DIN 2391 Precision Steel Tubes

Hydraulic and Pneumatic Systems
Suitable for equipment such as hydraulic cylinders, hydraulic rods, and pneumatic cylinders. These applications demand high precision and smooth surface finishes to ensure high-pressure sealing integrity and fluid operation.
Precision Machinery and Automotive Industry
Suitable for machine tool guide rods, mechanical components, automotive hydraulic parts, transmission shafts, and similar items. These applications require high precision, high strength, and pressure-resistance capabilities.
Industrial Equipment, Heavy Industry, and Energy Sector
Suitable for automated machinery, hydraulic components for cranes, pressure piping, boilers, and gas equipment. These applications require robust pressure-bearing capacity, stable mechanical properties, and high processing precision.

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DIN 2391 Precision Steel Tube Dimensions Table

Outer Diameter (mm)	Wall Thickness (mm)	Length (m)	Dimensional Tolerance (OD / WT / Length)	Common Materials
10	1, 1.5, 2	3 – 12	±0.1 / ±0.05 / ±5	ST35, ST45
12	1, 1.5, 2, 2.5	3 – 12	±0.1 / ±0.05 / ±5	ST35, ST45
14	1, 1.5, 2, 2.5, 3	3 – 12	±0.15 / ±0.1 / ±5	ST35, ST45
15	1, 1.5, 2, 2.5, 3	3 – 12	±0.15 / ±0.1 / ±5	ST35, ST45
16	1, 1.5, 2, 2.5, 3, 3.5	3 – 12	±0.15 / ±0.1 / ±5	ST35, ST45
18	1.5, 2, 2.5, 3, 3.5, 4	3 – 12	±0.15 / ±0.1 / ±5	ST35, ST45
20	1.5, 2, 2.5, 3, 3.5, 4	3 – 12	±0.15 / ±0.1 / ±5	ST35, ST45
22	2, 2.5, 3, 3.5, 4, 5	3 – 12	±0.15 / ±0.1 / ±5	ST35, ST45, ST52
25	2, 2.5, 3, 3.5, 4, 5, 6	3 – 12	±0.15 / ±0.1 / ±5	ST35, ST45, ST52
28	2.5, 3, 3.5, 4, 5, 6, 7	3 – 12	±0.2 / ±0.15 / ±5	ST45, ST52
30	3, 3.5, 4, 5, 6, 7, 8	3 – 12	±0.2 / ±0.15 / ±5	ST45, ST52
32	3, 3.5, 4, 5, 6, 7, 8	3 – 12	±0.2 / ±0.15 / ±5	ST45, ST52
35	3, 3.5, 4, 5, 6, 7, 8	3 – 12	±0.2 / ±0.15 / ±5	ST45, ST52
38	3, 3.5, 4, 5, 6, 7, 8, 9	3 – 12	±0.2 / ±0.15 / ±5	ST45, ST52
40	3, 4, 5, 6, 7, 8, 9	3 – 12	±0.2 / ±0.15 / ±5	ST45, ST52
42	3, 4, 5, 6, 7, 8, 9	3 – 12	±0.2 / ±0.15 / ±5	ST45, ST52
45	4, 5, 6, 7, 8, 9, 10	3 – 12	±0.2 / ±0.15 / ±5	ST52
48	4, 5, 6, 7, 8, 9, 10	3 – 12	±0.2 / ±0.15 / ±5	ST52
50	4, 5, 6, 7, 8, 9, 10	3 – 12	±0.2 / ±0.15 / ±5	ST52
55	5, 6, 7, 8, 9, 10, 11	3 – 12	±0.25 / ±0.2 / ±5	ST52
60	5, 6, 7, 8, 9, 10, 11, 12	3 – 12	±0.25 / ±0.2 / ±5	ST52
65	5, 6, 7, 8, 9, 10, 11, 12	3 – 12	±0.25 / ±0.2 / ±5	ST52
70	6, 7, 8, 9, 10, 11, 12	3 – 12	±0.25 / ±0.2 / ±5	ST52
75	6, 7, 8, 9, 10, 11, 12	3 – 12	±0.25 / ±0.2 / ±5	ST52
80	6, 7, 8, 9, 10, 11, 12, 13	3 – 12	±0.25 / ±0.2 / ±5	ST52
85	7, 8, 9, 10, 11, 12, 13, 14	3 – 12	±0.3 / ±0.2 / ±5	ST52, 16Mn
90	7, 8, 9, 10, 11, 12, 13, 14	3 – 12	±0.3 / ±0.2 / ±5	ST52, 16Mn
95	8, 9, 10, 11, 12, 13, 14	3 – 12	±0.3 / ±0.2 / ±5	ST52, 16Mn
100	8, 9, 10, 11, 12, 13, 14, 15	3 – 12	±0.3 / ±0.2 / ±5	ST52, 16Mn
110	9, 10, 11, 12, 13, 14, 15	3 – 12	±0.3 / ±0.2 / ±5	ST52, 16Mn
120	10, 11, 12, 13, 14, 15	3 – 12	±0.3 / ±0.2 / ±5	ST52, 16Mn

DIN 2391 Precision Steel Tube Standard Overview

1. Standard Title

DIN 2391 – German Industrial Standard, specifically for cold-drawn seamless precision steel tubes.

2. Types

DIN 2391-1 / T: Seamless cold-drawn steel tubes, typically used in mechanical and hydraulic systems
DIN 2391-2 / E: Cold-drawn precision steel tubes for pressure applications

3. Dimensions and Tolerance Requirements

Outer Diameter: 10 – 120 mm
Wall Thickness: 1 – 15 mm
Length: 3 – 12 m (Cut-to-length available)
Outer Diameter Tolerance: ±0.1 – ±0.3 mm
Wall Thickness Tolerance: ±0.05 – ±0.2 mm

4. Material Grades

Standard: ST35 (E235), ST45 (E255), ST52 (E355)
Special: 16Mn, C45 (for high-pressure or high-hardness applications)

5. Manufacturing Requirements

Cold-drawn or cold-rolled process
Surface Treatment: Bright annealing, pickling, anti-rust oil application
Dimensional accuracy and mechanical properties must comply with the requirements of the DIN 2391 standard.

6. Corresponding International Standards

Partially corresponds to EN 10305-1 (Cold Drawn Steel Tubes for Mechanical and Hydraulic Applications)
Meets the requirements for hydraulic, pneumatic, precision mechanical, and industrial equipment applications.

DIN 2391 Precision Steel Tube Production Process

1. Raw Material Preparation:
Selection of high-quality round steel bars or steel tube billets, followed by chemical composition analysis.

2. Pre-treatment:
Heating of the steel billets and removal of surface impurities.

3. Cold Drawing:
Drawing through a cold drawing machine to achieve the required outer diameter, wall thickness, and dimensional precision.

4. Straightening and Cutting:
Straightening of the steel tubes and cutting to specified lengths.

5. Heat Treatment:
Bright annealing to enhance toughness and improve surface finish.

6. Surface Treatment:
Pickling or application of anti-rust oil to ensure a smooth, rust-resistant surface.

7. Testing and Inspection:
Verification of dimensional tolerances, mechanical properties, and surface quality.

8. Packaging and Shipment:
Packaging in accordance with customer requirements, accompanied by an inspection report.

Inspection Category	Inspection Content	Standard Requirements / Range
Dimensional Inspection	Outer diameter, wall thickness, length	OD: ±0.1 – ±0.3 mm, WT: ±0.05 – ±0.2 mm, Length: ±5 mm
Mechanical Properties	Yield strength, tensile strength, elongation, hardness	Must comply with material specifications (ST35 / ST45 / ST52 / 16Mn / C45)
Surface Quality	Surface finish, cracks, pits, shrinkage cavities	Smooth and clean surface, free from cracks, pits, or defects; compliant with bright annealed or pickled standards
Chemical Composition	Content of C, Mn, P, S, Si, etc.	Must comply with DIN 2391 material standards (ST35, ST45, ST52, 16Mn, C45)
Additional Testing	Hydraulic test, pressure test, material certification	According to customer or standard requirements; MTC (Mill Test Certificate) and inspection reports available

Q1. What are the common material grades for DIN 2391 precision steel tubes?

Common material grades include ST35 / E235, ST45 / E255, ST52 / E355, 16Mn, and C45.
ST35 and ST45 are suitable for general mechanical and hydraulic applications, offering moderate strength and ease of machining.
ST52 and 16Mn are suitable for high-pressure and high-strength applications, such as automotive hydraulic components and industrial equipment.
C45 is suitable for mechanical parts requiring high hardness and wear resistance.

Q2. What is the size range for DIN 2391 precision steel tubes?

Outer Diameter: 10 mm – 120 mm
Wall Thickness: 1 mm – 15 mm
Length: 3 m – 12 m (Cut-to-length available)
Dimensional Tolerances: Outer Diameter ±0.1–0.3 mm, Wall Thickness ±0.05–0.2 mm, Length ±5 mm

Q3. Which industries and applications are suitable for DIN 2391 precision steel tubes?

They are primarily applied in:
Hydraulic and pneumatic systems (hydraulic cylinders, pneumatic cylinders)
Precision machinery and automotive components (machine tool guide rods, transmission shafts)
Industrial equipment and heavy industry (automated machinery, pressure piping, boilers)
They are suitable for applications requiring high precision, high pressure resistance, and a superior surface finish.

Q4. What surface treatments are available for DIN 2391 precision steel tubes?

Common surface treatments include:
Bright Annealing: Improves toughness and results in a smooth surface finish
Pickling: Removes surface scale (oxides)
Anti-rust Oil Coating: Prevents rusting during storage and transportation

Q5. What are the inspection standards for DIN 2391 precision steel tubes?

The main inspection items include:
Dimensional Inspection: Outer diameter, wall thickness, length, and tolerances
Mechanical Properties: Yield strength, tensile strength, elongation, and hardness
Chemical Composition: C, Mn, P, S, Si, etc.
Surface Quality: Surface finish, absence of cracks, pits, or shrinkage cavities
Material Test Certificates (MTC)** and inspection reports can be provided.

Q6. Can DIN 2391 precision steel tubes be customized?

Yes. Based on customer requirements, the following can be provided:
Fixed lengths
Special outer diameters and wall thicknesses
Special material grades
Special surface treatments
Even after customization, the tubes strictly adhere to the DIN 2391 precision steel tube standard, guaranteeing dimensional accuracy and mechanical properties.