S355Jr cold drawn seamless square tube Dimensions: What Sizes Are Available?

2025-11-26 08:16:18

S355Jr Cold Drawn seamless square tube: Available Dimensions and Technical Specifications

Introduction to S355Jr Steel Grade

S355Jr is a European standard structural steel grade that offers excellent mechanical properties and weldability, making it highly suitable for various construction and engineering applications. The "J" designation indicates that this steel grade has guaranteed impact strength at 20°C below zero, while the "r" suffix signifies its suitability for rolled products. When processed into Cold drawn seamless square tubes, S355Jr combines the material's inherent strength with the precision of cold drawing technology, resulting in components with superior dimensional accuracy, surface finish, and mechanical properties.

Cold drawn seamless square tubes made from S355Jr steel are particularly valued in applications requiring high strength-to-weight ratios, structural integrity, and resistance to dynamic loads. The cold drawing process enhances the steel's mechanical properties through work hardening while maintaining excellent internal soundness due to the seamless manufacturing method.

Manufacturing Process Overview

The production of S355Jr cold drawn seamless square tubes involves several critical steps:

1. Steel Making: The process begins with carefully controlled steel production to achieve the precise chemical composition required for S355Jr grade.

2. Hot Rolling: The steel is hot-rolled into round billets, which serve as the starting material for tube production.

3. Piercing: The round billet is heated and pierced to create a hollow shell (mother tube) using a rotary piercing mill.

4. Cold Drawing: The mother tube undergoes cold drawing through a series of dies to achieve the desired square shape and dimensions. This process significantly improves:

- Dimensional accuracy

- Surface finish quality

- Mechanical properties through work hardening

- Wall thickness consistency

5. Heat Treatment: Some tubes may undergo stress relieving or other heat treatments depending on final application requirements.

6. Finishing: Final processes include straightening, cutting to length, surface treatment, and rigorous quality inspections.

The cold drawing process is particularly important as it allows for the production of tubes with tighter tolerances and better surface finishes compared to hot-finished products, while also increasing yield strength through strain hardening.

Standard Dimensions of S355Jr Cold Drawn Seamless Square Tubes

The available dimensions for S355Jr cold drawn seamless square tubes typically follow European standards (EN) and international specifications. While manufacturers can produce custom sizes, the most commonly available standard dimensions include:

Wall Thickness Range

- Minimum: 1.0 mm

- Maximum: 30.0 mm

- Common thicknesses: 1.5 mm, 2.0 mm, 2.5 mm, 3.0 mm, 4.0 mm, 5.0 mm, 6.0 mm, 8.0 mm, 10.0 mm

Outer Dimension Range (Square Tube Sides)

- Small sizes: 10 mm × 10 mm to 50 mm × 50 mm

- Medium sizes: 50 mm × 50 mm to 150 mm × 150 mm

- Large sizes: 150 mm × 150 mm to 300 mm × 300 mm

- Common sizes include:

- 20×20 mm

- 25×25 mm

- 30×30 mm

- 40×40 mm

- 50×50 mm

- 60×60 mm

- 70×70 mm

- 80×80 mm

- 90×90 mm

- 100×100 mm

- 120×120 mm

- 150×150 mm

- 200×200 mm

Length Options

- Standard lengths: 3000 mm, 6000 mm, 12000 mm

- Custom lengths available up to 18000 mm

- Tolerance on length: typically ±50 mm for standard lengths

Dimensional Tolerances

Cold drawn seamless square tubes maintain exceptionally tight tolerances:

- Outer dimensions: typically ±0.3 mm to ±1.0% of nominal size depending on dimensions

- Wall thickness: ±7.5% to ±10% of nominal thickness

- Straightness: ≤1.5 mm per meter length

- Squareness: ≤1.0% of outer dimension

Mechanical Properties of S355Jr Cold Drawn Seamless Square Tubes

The cold drawing process enhances the mechanical properties of S355Jr steel. Typical values include:

- Yield Strength (ReH): Minimum 355 MPa (can exceed 400 MPa after cold working)

- Tensile Strength (Rm): 470-630 MPa

- Elongation at Break (A): ≥22% (depending on thickness)

- Impact Energy (KV): ≥27 J at -20°C

- Hardness: 140-180 HB (Brinell Hardness)

These properties make S355Jr cold drawn seamless square tubes suitable for demanding structural applications where both strength and toughness are required.

Chemical Composition Requirements

The chemical composition of S355Jr steel is strictly controlled to ensure consistent performance:

- Carbon (C): ≤0.24%

- Silicon (Si): ≤0.55%

- Manganese (Mn): ≤1.60%

- Phosphorus (P): ≤0.035%

- Sulfur (S): ≤0.035%

- Aluminum (Al): ≥0.020% (for grain refinement)

- Nitrogen (N): ≤0.009% (if Al content is <0.020%)

The balanced composition ensures good weldability, formability, and toughness while maintaining the required strength levels.

Surface Quality and Finish

Cold drawn seamless square tubes offer superior surface quality compared to hot-finished products:

- Surface Finish: Smooth, with typical roughness (Ra) between 0.8-3.2 μm

- Surface Defects: Free from cracks, laps, and other harmful imperfections

- Decarburization: Minimal, typically <0.05 mm depth

- Scale: Virtually free from mill scale due to cold drawing process

The excellent surface finish often eliminates the need for additional machining in many applications, reducing production costs.

Available Heat Treatment Conditions

Depending on application requirements, S355Jr cold drawn seamless square tubes can be supplied in different conditions:

1. As-Drawn: The standard delivery condition with work-hardened properties

2. Stress Relieved: Heated to 550-650°C to relieve internal stresses without significantly affecting mechanical properties

3. Normalized: Heated to 890-950°C followed by air cooling to refine grain structure

4. Quenched and Tempered: For applications requiring enhanced mechanical properties

International Standards and Equivalent Grades

S355Jr cold drawn seamless square tubes comply with various international standards:

- European Standards: EN 10210-1, EN 10210-2

- International Equivalents:

- ASTM: A500 Grade C (similar but not identical)

- JIS: STKR490

- GB/T: Q355B (Chinese standard)

While these grades may have similar mechanical properties, the chemical compositions and testing requirements may differ slightly between standards.

Technical Advantages of Cold Drawn Seamless Square Tubes

The combination of S355Jr steel and cold drawing technology offers numerous technical benefits:

1. Enhanced Strength: Cold working increases yield and tensile strength

2. Precision Dimensions: Tight tolerances for high-accuracy applications

3. Excellent Surface Quality: Smooth finish reduces friction and improves appearance

4. Superior Straightness: Critical for precision assemblies

5. Improved Internal Soundness: Seamless construction eliminates weld defects

6. Consistent Wall Thickness: Important for structural integrity

7. Better Machinability: Compared to hot-finished tubes

8. Increased Fatigue Resistance: Beneficial for dynamic load applications

Common Applications

S355Jr cold drawn seamless square tubes find applications across various industries:

1. Construction: Structural frameworks, support columns, trusses

2. Mechanical Engineering: Machine frames, hydraulic cylinders, bearing housings

3. Automotive: Chassis components, roll cages, suspension parts

4. Material Handling: Conveyor systems, lifting equipment

5. Energy Sector: Wind turbine components, oil and gas equipment

6. Transportation: Railway components, trailer frames

7. Industrial Machinery: Robotic arms, production line equipment

Quality Control and Testing

Reputable manufacturers implement rigorous quality control measures:

1. Chemical Analysis: Spectrometry to verify composition

2. Mechanical Testing: Tensile, impact, and hardness tests

3. Dimensional Checks: Precise measurement of all parameters

4. Non-Destructive Testing: Ultrasonic, eddy current, or hydrostatic testing

5. Visual Inspection: Surface quality assessment

6. Metallographic Examination: Grain structure analysis when required

Packaging and Handling

Proper packaging ensures product integrity during transportation and storage:

- Protective Coatings: Oil or other corrosion inhibitors

- Bundling: Secured with steel straps to prevent damage

- End Protection: Plastic caps or other protection for tube ends

- Marking: Clear identification of grade, size, and heat number

- Storage Recommendations: Dry conditions, off the ground, covered when outdoors

Factors Affecting Dimension Selection

When selecting the appropriate size of S355Jr cold drawn seamless square tube, consider:

1. Load Requirements: Static and dynamic forces

2. Safety Factors: Industry-specific design factors

3. Connection Methods: Welding, bolting, or other joining techniques

4. Corrosion Considerations: Potential need for increased wall thickness

5. Weight Limitations: Especially in mobile applications

6. Fabrication Requirements: Bending, machining, or other processes

7. Cost Optimization: Balancing performance with material costs

Customization Options

While standard sizes are readily available, manufacturers can provide:

- Special Sizes: Outside standard dimension ranges

- Modified Tolerances: Tighter than standard when required

- Special Ends: Beveled, threaded, or other prepared ends

- Surface Treatments: Phosphating, painting, or other coatings

- Special Testing: Additional quality verification

Comparison with Other Steel Grades

S355Jr offers distinct advantages compared to other common structural steels:

- vs. S235Jr: Higher strength (355 vs. 235 MPa yield strength)

- vs. S275Jr: Better impact toughness at low temperatures

- vs. Carbon Steels: Superior weldability and toughness

- vs. Stainless Steels: More cost-effective for many structural applications

Environmental Considerations

S355Jr steel is 100% recyclable without quality degradation. The cold drawing process is more energy-efficient than many alternative manufacturing methods, resulting in a lower carbon footprint compared to hot-finished products.

Future Trends in Tube Manufacturing

The industry continues to evolve with:

1. Improved Process Control: For even tighter tolerances

2. Advanced Alloy Development: For enhanced properties

3. Automated Inspection: Using AI and machine vision

4. Sustainable Practices: Reduced energy consumption and waste

5. Digital Integration: For traceability and quality assurance

Conclusion

S355Jr cold drawn seamless square tubes offer an exceptional combination of mechanical properties, dimensional precision, and surface quality. With a wide range of standard sizes available from 10×10 mm up to 300×300 mm and wall thicknesses from 1.0 mm to 30.0 mm, these tubes meet the requirements of diverse industrial applications. The cold drawing process enhances the inherent qualities of S355Jr steel, making these tubes particularly suitable for critical structural components where strength, precision, and reliability are paramount.

When selecting S355Jr cold drawn seamless square tubes, engineers should carefully consider the dimensional requirements, mechanical property needs, and application conditions to specify the most appropriate size and wall thickness. The availability of both standard and custom dimensions ensures that optimal solutions can be found for virtually any structural or mechanical application requiring high-quality square tubing.