Cold-drawn round steel tubes deliver precise dimensional tolerances, smooth surface finishes, and increased tensile strength through cold-drawing reduction processes. As high-performance cold drawn seamless mechanical tubing, these products are applied primarily in hydraulic cylinders, automotive components, and precision machinery where standard hot-rolled tubes fail to meet dimensional and mechanical thresholds. Available in seamless and welded variants, tailored to specific pressure and structural requirements.
Specifications
|
Parameter |
Technical Standard / Range |
|
Manufacturing Standards |
DIN EN 10305-1 (Seamless), DIN EN 10305-2 (Welded), ASTM A519, JIS G3445 |
|
Outer Diameter (OD) |
10 mm – 150 mm |
|
Wall Thickness (WT) |
1 mm – 15 mm |
|
Length |
Fixed length 3m–6m, or random length (customizable up to 12m) |
|
Delivery Conditions (Heat Treatment) |
+C (BK), +LC (BKW), +SR (BKS), +A (GBK), +N (NBK) |
|
Straightness |
(\le 1.0 \text{ mm / 1000 mm}) (higher precision available upon request) |
|
Surface Finish |
Ra (\le 0.8 , \mu\text{m}) (inner/outer surfaces cleaned and phosphated/oiled for anti-corrosion) |
Material & Manufacturing
Steel Grades
• Carbon Steels: E235, E355 (including DIN EN 10305-1 E355+N steel tubes), SAE 1020, SAE 1045, ST35, ST45, ST52
• Alloy Steels: 25CrMo4, 42CrMo4, 20MnV6
Manufacturing Process
• Raw Material Preparation: High-frequency welded or hot-rolled seamless mother tubes inspected for surface defects.
• Surface Treatment: Acid pickling and phosphating to remove scale and apply a solid lubricant carrier.
• Cold Drawing: Drawing through tungsten carbide dies and over mandrels to exact OD, ID, and wall thickness dimensions.
• Thermal Stress Relief: Controlled atmosphere annealing furnaces to eliminate residual stresses and achieve required mechanical properties (+N / +SR).
• Straightening & Cutting: Multi-roll precision straightening followed by deburring and
Quality Inspection
Every production lot undergoes rigorous metallurgical and dimensional testing in accordance with ISO 9001 and IATF 16949 protocols:
Dimensional Verification: Laser OD/ID micrometers and air gauging for concentricity and wall thickness uniformity.
Non-Destructive Testing (NDT): Eddy current testing performed 100% inline to detect longitudinal and transverse defects.
Mechanical Testing: Tensile strength, yield strength, elongation, and flattening/flaring tests conducted per sample batch.
Metallographic Analysis: Grain size and decarburization depth evaluation via optical microscopy.
Traceability: Each bundle is stamped with heat numbers and issued with an EN 10204 3.1 Mill Test Certificate (MTC).
Applications
Fluid Power: Hydraulic and pneumatic cylinders for construction machinery, material handling equipment, and agricultural machinery.
Automotive: Steering columns, drive shafts, fuel injection lines, and shock absorber tubes.
Mechanical Engineering: Roller bearings, textile machinery spindles, and high-stress structural components.
Customization & Supply
Custom Tolerances:
Special drawing dies available for tight-tolerance requirements (e.g., ISO H8/H9 for inner diameter).
Cut-to-Length:
Precision cutting with tolerance down to (\pm 0.5 \text{ mm}).
Packaging:
VCI anti-rust paper wrapping, bundled with steel strips, and packed in wooden crates or woven bags to prevent transit damage.
Lead Time:
Standard stock items: 2–3 weeks. Custom production runs: 4–6 weeks.
Frequently Asked Questions
Q: What is the difference between +C (BK) and +N (NBK) delivery conditions?
A: +C (BK) means cold-drawn unheated, resulting in high mechanical strength and lower elongation, suitable for direct machining. +N (NBK) means normalized after cold drawing, relieving internal stress, stabilizing grain structure, and providing uniform mechanical properties suitable for bending and flanging.
Q: Do you provide seamless or welded cold-drawn tubes?
A: We supply both. Seamless cold-drawn tubes (DIN EN 10305-1) suit high-pressure hydraulic applications. Cold-drawn welded tubes (DIN EN 10305-2) offer precise outer/inner dimensions for structural and general mechanical uses at optimized costs.
Q: What corrosion protection is applied during shipping?
A: Tubes are coated with anti-rust oil inside and outside after cleaning. For ocean freight or long-term storage, VCI anti-rust film wrapping and waterproof packaging can be applied upon request.
Q: Can you supply tubes with honed inner surfaces for hydraulic cylinders?
A: Yes. We offer cold-drawn tubes with roller-burnished or honed IDs, achieving surface roughness Ra (\le 0.4 , \mu\text{m}), ready for direct piston seal assembly.
Q: What minimum order quantity (MOQ) is required for custom steel grades or dimensions?
A: MOQ typically starts at 3 metric tons per size for custom production runs. Smaller trial quantities may be accommodated if matching active rolling schedules.
Q: What inspection documentation accompanies the shipment?
A: Every shipment includes an EN 10204 3.1 Mill Test Certificate detailing chemical composition, mechanical test results, dimensional inspection data, and heat treatment logs.
Request a Quote
Submit your specifications to receive a technical proposal and commercial quotation within 24 hours.
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RFQ Details Template:
Steel Grade (e.g., E355+N / SAE 1020):
Outer Diameter (OD) & Wall Thickness (WT) / Inner Diameter (ID):
Length & Quantity:
Delivery Condition (e.g., +N, +C):
Target Port / Destination:
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