I. Overview of Cold Drawn Seamless Tubes.
Cold drawn seamless tubes are high-precision tubes made from hot rolled seamless steel tubes as billets, processed and molded at room temperature by cold drawing process.
Its core features are no welding seam, high dimensional accuracy (tolerance can be controlled at 0.02-0.05mm) and excellent surface finish (roughness Ra≤1.6μm).
Compared with hot rolled tubes, the cold drawing process refines the grain structure through plastic deformation, which improves the material strength by 20%-30% and reduces the risk of surface oxidation.
II. Detailed information of standards in different countries or regions:
| Country/Region | Standard Name | Standard Number | Scope of Application |
|---|---|---|---|
| China | Precision Seamless Steel Pipe for Cold Drawing or Cold Rolling | GB/T 3639-2021 | For high-precision applications in mechanical structures, hydraulic equipment, and automotive components |
| Europe | Technical Delivery Conditions for Precision Steel Tubes Part 1: Cold Drawn Seamless Steel Tubes | EN 10305-1:2002 | For round-section seamless cold-drawn steel tubes in hydraulic and pneumatic systems |
| Europe | Technical Delivery Conditions for Precision Steel Tubes Part 4: Cold Drawn Seamless Steel Tubes for Hydraulic and Pneumatic Systems | EN 10305-4:2016 | For hydraulic and pneumatic systems |
| United States | Cold Drawn Seamless Steel Tubes | ASTM A513 | For construction, machinery, and automotive industries |
| Japan | Cold Drawn Seamless Steel Tubes | JIS G3467 | For precision machinery and hydraulic equipment |
| International | Technical Delivery Conditions for Precision Steel Tubes | ISO 1127:2016 | For various industrial applications |
III. Cold-drawn seamless pipe production process
(1) Billet preparation:
Select 20#, 45#, Q355B and other high-quality steel billets, by pickling to remove oxidized skin, to ensure that the surface of the billet is clean, ready for subsequent processing.
(2) Cold Drawing and Forming:
Through multi-stage drawing (reduction rate of 10%-40%), with phosphate lubrication to reduce friction, to ensure the dimensional accuracy and surface quality of the pipe in the cold drawing process.
(3) Heat treatment:
Annealing: annealing treatment at 600-750℃ to eliminate internal stress and improve the plasticity and toughness of the material.
Normalizing: Normalizing treatment at 850-950℃ to optimize the mechanical properties of the material and improve the strength and hardness.
(4) Finishing process:
Straightening: Straighten the pipe by straightening equipment to ensure the straightness of the pipe.
Cutting: Cut according to the required length to ensure the cut end surface is flat.
Eddy current flaw detection: Conduct eddy current flaw detection to detect cracks ≥ 0.5mm to ensure that the pipe is free from cracks and other defects.
(5) Surface treatment:
Phosphating: carry out phosphating treatment to improve the corrosion resistance and adhesion of the pipe surface.
Galvanizing: carry out galvanizing treatment to further enhance the corrosion resistance of the pipe.
Coating with anti-rust oil: Coat with anti-rust oil to prevent the pipe from rusting during storage and transportation.
IV.Cold Drawn Seamless Tubes Core Advantages Analysis:
(1) Excellent precision
OD tolerance is 5 times smaller than that of hot rolled tubes, which can be directly used for precision assembly.
High surface finish, roughness Ra≤1.6μm.
(2) Strength Improvement
Tensile strength reaches over 600MPa, 30% higher than raw material.
Optimized mechanical properties, suitable for high pressure and heavy load environment.
(3) Material saving
Processing allowance reduced by 50%, yield rate over 95%.
Reduce material waste, improve productivity and economic efficiency.
(4) Versatility
Supports customized shaped cross sections, such as internal straight teeth, spiral grooves, etc..
Satisfy special application requirements, suitable for a wide range of industries.
V. Common Specification Table
| Parameter | Range | Tolerance Requirement | Applicable Standard |
|---|---|---|---|
| Outer Diameter (mm) | 6-630 | ±0.1-0.5 mm | GB/T 3639 |
| Wall Thickness (mm) | 0.5-35 | ±5%-10% | GB/T 32957 |
| Length (m) | 1-12 (customizable) | ±50 mm | DIN 2445 |
| Inner Diameter Precision | IT8-IT10 grade | Roundness ≤0.05 mm | EN 10305 |
VI. Quality control points
(1) Composition testing:
Use spark spectrometer to ensure the chemical composition (e.g. C, Mn, Cr, etc.) is in accordance with GB/T 222 standard.
(2) Mechanical test:
Tensile test: in accordance with GB/T 228.1 standard to verify tensile strength and yield strength.
Impact test: conducted in accordance with GB/T 229 standards to assess the toughness of the material.
(3) Non-destructive testing:
Ultrasonic testing: Uses ultrasonic waves to detect internal defects, detecting defect sizes ≥5% of wall thickness.
Magnetic particle inspection: Used to detect defects such as cracks on the surface and near surface.
(4) Dimensional sampling:
Real-time monitoring of outer diameter using laser calibrator, sampling rate ≥5%.
Measure the inner and outer diameters, wall thickness and other dimensions root by root to ensure compliance with the accuracy requirements.
(5) Surface Quality Inspection:
Visually inspect the internal and external surfaces root by root under sufficient lighting conditions to ensure that there are no defects such as cracks and pockmarks.
The surface roughness Ra should meet the standard requirements, and the roughness of the outer surface is not more than 4μm for the steel pipe with outer diameter ≤260mm.
(6) Heat treatment quality control:
Annealing and normalizing process need to be strictly controlled to optimize the mechanical properties and eliminate internal stress.
(7) Packaging and anti-rust treatment:
Steel pipes in heat-treated condition shall be treated with anti-rust treatment before leaving the factory, generally coated with neutral oil.
VII. Cold-drawn seamless pipe size specification table
| Parameter | Range | Tolerance | Unit | Notes |
|---|---|---|---|---|
| Outer Diameter (OD) | 6 mm - 630 mm | ±0.1 mm - ±0.5 mm | mm | Tolerance varies with diameter size; larger diameters have larger tolerances. |
| Wall Thickness (WT) | 0.5 mm - 35 mm | ±5% - ±10% | mm | Thinner walls have smaller tolerances, while thicker walls have larger tolerances. |
| Length (L) | 1 m - 12 m | ±50 mm | m | Special lengths can be customized according to customer requirements. |
| Inner Diameter Precision | IT8 - IT10 grade | Roundness ≤0.05 mm | mm | Applicable for high-precision applications. |
| Surface Roughness | - | Ra ≤ 0.8 μm | μm | Cold drawing process ensures surface smoothness. |
| End Processing | - | Flat end, beveling, or threading available | - | Customizable according to customer requirements. |
Description:
Outside Diameter (OD): ranges from 6 mm to 630 mm with tolerances of ±0.1 mm to ±0.5 mm, depending on OD size.
Wall Thickness (WT): 0.5 mm to 35 mm with tolerances of ±5% to ±10%, tighter tolerances for thin-walled tubes.
Length (L): standard lengths from 1 m to 12 m with tolerances of ±50 mm, customized on request.
I.D. accuracy: accuracy classes from IT8 to IT10 with roundness tolerances of ≤0.05 mm for high-precision applications.
Surface roughness: Cold-drawing process guarantees surface roughness Ra ≤ 0.8 μm.
End machining: Flat ends, beveling or threading are available upon request.
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