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The DIN 2391-1 St45 Honed Seamless Steel Tube is a premium precision honed tube specifically engineered for hydraulic cylinder applications, where smooth inner surface, tight tolerance, and high strength are critical. Manufactured using advanced cold drawn seamless steel tube technology, this product delivers a superior Ra ≤ 0.8 μm inner surface finish and H7–H10 tolerance, ensuring optimal sealing performance and reduced friction. Widely used in hydraulic systems, engineering machinery, and industrial equipment, the St45 honed tube offers excellent durability, pressure resistance, and long service life. As a reliable seamless steel tube supplier, we provide customized sizes, strict quality control, and global export solutions to meet demanding international standards.
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DIN 2391 ST45 Pipe Specification
| Property | Value |
|---|---|
| Material | St45 Steel |
| Standard | DIN 2391-1 |
| Grade | Precision honed tube |
| Outer Diameter | 6 mm to 100 mm |
| Wall Thickness | 1 mm to 10 mm |
| Length | Customizable (Up to 12 meters) |
| Surface Finish | Honed, Cold Drawn |
| Tensile Strength | 450 MPa |
| Yield Strength | 300 MPa |
| Elongation | ≥ 20% |
| Hardness | HB 150-250 |
DIN 2391 ST45 Tube Chemical Composition Standard
| Grade | C | Si | Mn | P max | S max |
| Din 2391 St45 | ≤0.21 | ≤0.35 | ≥0.4 | 0.025 | 0.025 |
ST45 Steel Seamless Pipe Mechanical Properties
| Cold drawn(Mandatory) | Cold drawn(Soft) | Cold Drawn and Stress Release | Anneal | Normalizing | ||||||||
| BK1) | BKW1) | (BKS) | (GBK)1) | (NBK)1) | ||||||||
| Grade | Tensile | Elongation | Tensile | Elongation | Tensile | Yield point | Elongation | Tensile | Elongation | Tensile | Yield point | Elongation |
| N/mm2 | % | N/mm2 | % | N/mm2 | N/mm2 | % | N/mm2 | % | N/mm2 | N/mm2 | % | |
| St45 | 580 | 5 | 520 | 8 | 520 | 375 | 12 | 390 | 21 | 440~570 | 255 | 21 |
Toleracne of DIN 2391 ST 45 Smls Pipe
| Outer Diameter Tolerance | 4-30 | 31-40 | 41-50 | 51-60 | 61-70 | 71-80 | 81-90 | 91-100 |
| ±0.08 | ±0.15 | ±0.20 | ±0.25 | ±0.30 | ±0.30 | ±0.40 | ±0.45 | |
| Wall thickness Tolerance | ±10% | |||||||
DIN 2391 St45 Seamless Precision Steel Tubes Pipe Size Chart
| 1/8" IPS(.405" O.D.) | 3 1/2" IPS( 4.000" O.D.) |
|---|---|
| SCH 40, 80 | SCH 10, 40, 80, 160, XXH |
| 1/4" IPS(.540" O.D.) | 4" IPS(4.500" O.D.) |
| SCH 10, 40, 80 | SCH 10, 40, 80, 160, XXH |
| 3/8" IPS(.675" O.D.) | 5" IPS( 5.563" O.D.) |
| SCH 10, 40, 80 | SCH 10, 40, 80, 160, XXH |
| 1/2" IPS(.840" O.D.) | 6" IPS(6.625" O.D.) |
| SCH 5, 10, 40, 80, 160, XXH | SCH 5, 10, 40, 80, 120, 160, XXH |
| 3/4" IPS(1.050" O.D.) | 8 " IPS(8.625" O.D.) |
| SCH 10, 40, 80, 160, XXH | SCH 5, 10, 40, 80, 120, 160, XXH |
| 1" IPS:(1.315′ O.D.) | 10" IPS(10.750" O.D.) |
| SCH 5, 10, 40, 80, 160, XXH | SCH 10, 20, 40, 80 (.500), TRUE 80(.500) |
| 1-1/4" IPS(1.660" O.D.) | 12" IPS(12.750" O.D.) |
| SCH 10, 40, 80, 160, XXH | SCH 10, 20, 40(.375), TRUE40(.406), SCH80(.500) |
| 1-1/2" IPS(1.900" O.D.) | 14" IPS(14.000" O.D.) |
| SCH 10, 40, 80, 160, XXH | SCH10 (.188), SCH40 (.375) |
| 2" IPS(2.375" O.D.) | 16" IPS(16.000" O.D.) |
| SCH 10, 40, 80, 160, XXH | SCH10(.188), SCH40(.375) |
| 2 1/2" IPS(2.875" O.D.) | 18" IPS (18.000" O.D.) |
| SCH 10, 40, 80, 160, XXH | SCH-40 (.375) |
| 3" IPS( 3.500" O.D.) | |
| SCH 5, 10, 40, 80, 160, XXH |
ST45 DIN 2391 Carbon Steel Welded Tube Size
| Wall | Sizes ( O.D.) |
|---|---|
| .010 | 1/16" , 1/8" , 3/16" |
| .020 | 1/16" , 1/8" , 3/16" , 1/4" , 5/16" , 3/8" |
| .012 | 1/8" |
| .016 | 1/8" , 3/16" |
| .028 | 1/8" , 3/16" , 1/4" , 5/16" , 3/8" , 1/2" , 3/4" , 1" , 1 1/2" , 2" |
| .035 | 1/8" , 3/16" , 1/4" , 5/16" , 3/8" , 7/16" , 1/2" , 16" , 5/8" , 3/4" , 7/8" , 1" , 1 1/4" , 1 1/2" , 1 5/8" , 2" , 2 1/4" |
| .049 | 3/16" , 1/4" , 5/16" , 3/8" , 1/2" , 16" , 5/8" , 3/4" , 7/8" , 1" , 1 1/8" , 1 1/4" , 1 1/2" , 1 5/8" , 2" , 2 1/4" |
| .065 | 1/4" , 5/16" , 3/8" , 1/2" , 16" , 5/8" , 3/4" , 7/8" , 1" , 1 1/4" , 1 1/2" , 1 5/8" , 1 3/4" , 2" , 2 1/2" , 3" |
| .083 | 1/4" , 3/8" , 1/2" , 5/8" , 3/4" , 7/8" , 1" , 1 1/4" , 1 1/2" , 1 5/8" , 1 7/8" , 2" , 2 1/2" ,3" |
| .095 | 1/2" , 5/8" , 1" , 1 1/4" , 1 1/2" , 2" |
| .109 | 1/2" , 3/4" , 1" , 1 1/4" , 1 1/2" , 2" |
| .120 | 1/2" , 5/8" , 3/4" , 7/8" , 1" , 1 1/4" , 1 1/2" , 2" , 2 1/4" , 2 1/2" , 3" |
| .125 | 3/4" , 1" , 1 1/4" , 1 1/2" , 2" , 3" , 3 1/4" |
| .134 | 1" |
| .250 | 3" |
| .375 | 3 1/2" |
Tolerance of Steel ST 45 Cold Finished Tube
| Outer diameter and wall Thickness | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Execution | Size Range | OD Tolerance | Wall tolerance | ||||||
| Hot-rolled Tube | OD – 80 mmOD > 80 mmWall < 12 mmWall - 12 mm | ± 0.4 mm± 0.5 % of OD | ± 0.7 mm± (5 % x wallthickness + 0.1 mm) | ||||||
| Hot-rolled peeled tube | All sizesWall < 12 mmWall - 12 mm | + 0.25/- 0 mm | ± 0.8 mm± (5 % x wall thickness+ 0.2 mm) | ||||||
| Cold Worked tubecold-rolled or cold-drawn | OD < 40 mmOD 40 - 80 mmOD > 80 Wall Thickness< 6 mm Wall Thickness6 - 8 mm Wall Thickness > 8 | + 0.30/- 0 mm*+ 0.35/- 0 mm*+ 0.40/- 0 mm* | ± 0.30 mm± 0.35 mm± 0.40 m | ||||||
DIN 2391 ST45 Carbon Steel Seamless Pipe Heat Treatment
| Heat Treatment Process | Stress Relieving | Quenching & Tempering | Annealing | Normalizing |
|---|---|---|---|---|
| Temperature Range | 550°C to 650°C |
550°C to 650°C (tempering) 900°C to 950°C (quenching) |
600°C- 650°C | 850°C - 900°C |
Features & Benefits
Precision Manufacturing: Achieved through advanced cold-drawing and honing processes, ensuring tight dimensional tolerances for exact fit.
High-Strength Performance: With a tensile strength of up to 450 MPa, ideal for high-pressure applications.
Durability in Harsh Environments: The St45 steel provides excellent wear resistance, even in aggressive hydraulic and industrial environments.
Smooth Surface Finish: Honed to perfection, reducing friction and increasing the efficiency of machinery and equipment.
Customization: Available in a wide range of sizes and lengths to suit specific applications.
Applications
Hydraulic Cylinders – Essential for applications requiring smooth, high-performance tubes.
Precision Machinery – Ideal for manufacturing parts where dimensional accuracy is critical.
Automotive Systems – Used in hydraulic and pneumatic applications within vehicle systems.
Industrial Equipment – Common in pumps, valves, and other heavy machinery components.
Inspection & Quality Assurance
100% Dimensional Inspection: Ensures the tube meets exact specifications.
Surface Roughness Testing: Guarantees a smooth, defect-free surface finish (Ra ≤ 0.8 µm).
Third-Party Certification: All tubes are inspected and certified by independent quality assurance agencies.
Hydrostatic Testing: Each tube is tested under high pressure to ensure leak-proof performance.
Frequently Asked Questions (FAQ)
Q1: What does "St45" mean in the product name?
A: "St45" is the German steel grade designation per DIN standards. It signifies a carbon steel with a minimum tensile strength of 45 kgf/mm² (approximately 440 MPa). It is comparable to AISI 1045 or C45 carbon steel.
Q2: Why is the honed inner surface so important?
A: The honed surface is crucial for several reasons:
It provides an ideal surface for piston seals, ensuring a perfect seal and preventing fluid leakage.
It minimizes friction and wear on the seals and the tube itself, extending the service life of the entire cylinder.
It helps retain oil on the surface, improving lubrication.
Q3: Can these tubes be welded directly?
A: Yes, the St45 grade steel has good weldability. However, proper welding procedures must be followed to avoid introducing stresses or distortions that could affect the precision of the tube. Post-weld heat treatment may be recommended for critical applications.
Q4: What is the difference between a honed tube and a standard seamless tube?
A: A standard seamless tube has a relatively rough internal surface from the drawing process. A honed tube undergoes an additional abrasive process (honing) that smooths and finishes the inner diameter to a precise, cross-hatched pattern, making it ready for use as a cylinder barrel without further machining.
Q5: How are the tube ends protected during shipping?
A: To preserve the critical honed inner surface from corrosion and damage, the tubes are cleaned, oiled, and the ends are sealed with plastic or metal caps/plugs.
Q6: Do you offer custom sizes and tolerances?
A: While we stock standard sizes as per DIN 2391-1, we can often accommodate requests for custom outer diameters, wall thicknesses, and lengths. Please contact our sales team with your specific requirements.
Q7: What is the difference between St45 and other steel grades used for honed tubes?
A: St45 steel provides a good balance of strength, durability, and machinability, making it a common choice for hydraulic tubes. Compared to other materials like St52, it is typically more affordable but still offers sufficient strength for most applications.
Q8: Can the St45 honed seamless steel tube be used in high-pressure hydraulic systems?
A: Yes, these tubes are designed for high-pressure applications, ensuring reliable performance even under extreme conditions.
Q9: What are the available sizes for DIN 2391-1 St45 honed seamless steel tubes?
A: Our tubes range from 6 mm to 100 mm in diameter and can be customized to specific lengths up to 12 meters.
Contact Us
For more details on our DIN 2391-1 St45 Honed Seamless Steel Tubes, or to request a quote, please contact us via email at [office@dongmjd.com] or call [+8615769214734]. We're happy to provide additional information and help you select the best tube for your needs.
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