I. Overview of cold drawn seamless pipe:
- Cold-drawn seamless pipe is a high-precision pipe with hot-rolled seamless pipe as billet and processed at room temperature by cold-drawn process.
- Its core features are no weld, high dimensional accuracy (tolerance can be controlled at 0.02-0.05mm) and excellent surface finish (roughness Ra≤1.6μm).
- Compared to hot-rolled tubes, the cold drawing process refines the grain structure through plastic deformation, increasing the strength of the material by 20%-30% while reducing the risk of surface oxidation.
II. Details of standards in different countries or regions:
| Country | Standard Name | Standard Number | Applicable Scope |
|---|---|---|---|
| China | Cold drawn or cold-rolled precision seamless steel tube | GB/T 3639-2021 | For high-precision applications such as mechanical structures, hydraulic equipment, and automobile parts |
| Europe | Technical delivery conditions for seamless steel tubes for precision purposes — Part 1: Cold drawn tubes | EN 10305-1:2002 | For circular-section seamless cold drawn steel tubes for hydraulic and pneumatic systems |
| Europe | Technical delivery conditions for seamless steel tubes for precision purposes — Part 4: Cold drawn tubes for hydraulic and pneumatic systems | EN 10305-4:2016 | For hydraulic and pneumatic systems |
| USA | Cold drawn seamless steel tube | ASTM A513 | For industries such as construction, machinery, and automobiles |
| Japan | Cold drawn seamless steel tube | JIS G3467 | For precision machinery, hydraulic equipment, etc. |
| International Standard | Technical delivery conditions for seamless steel tubes for precision purposes | ISO 1127:2016 | For various industrial applications |
III. Cold-drawn seamless pipe production process
(1) Blank preparation:
• Select 20#, 45#, Q355B and other high-quality billets, and remove the oxide skin after pickling to ensure that the surface of the billet is clean and ready for subsequent processing.
(2) Cold drawing molding:
• Through multiple draws (reduction rate 10%-40%), combined with phosphate lubrication to reduce friction and ensure dimensional accuracy and surface quality during cold drawing.
(3) Heat treatment:
• Annealing: Annealing at 600-750 ° C to eliminate internal stress and improve the plasticity and toughness of the material.
• Normalizing: Normalizing at 850-950℃ to optimize the mechanical properties of the material and improve strength and hardness.
(4) Finishing:
• Straightening: The pipe is straightened by straightening equipment to ensure the straightness of the pipe.
• Cutting: Cut according to the required length to ensure that the cutting end face is flat.
• Eddy current inspection: Perform eddy current inspection to detect cracks ≥0.5mm to ensure that the pipe has no cracks and other defects.
(5) Surface treatment:
• Phosphating: phosphating is carried out to improve the corrosion resistance and adhesion of the pipe surface.
• Galvanizing: Galvanizing is performed to further improve the corrosion resistance of the pipe.
• Apply anti-rust oil: Apply anti-rust oil to prevent the pipe from rusting during storage and transportation.
IV. Core advantage analysis of cold-drawn seamless pipe:
(1) Excellent accuracy
• Outer diameter tolerance is 5 times smaller than that of hot rolled pipe, which can be used directly for precision assembly.
• High surface finish, roughness Ra≤1.6μm.
(2) Strength improvement
• Tensile strength of more than 600MPa, 30% higher than raw materials.
• Optimized mechanical properties for high pressure and heavy load environments.
(3) Material saving
• The processing allowance is reduced by 50%, and the yield exceeds 95%.
• Reduce material waste, improve production efficiency and economic benefits.
(4) Versatility
• Support custom shaped cross sections, such as internal straight teeth, spiral grooves, etc.
• Meet special application requirements, suitable for a variety of industries.
V. Common specification sheet
| Parameter | Range | Tolerance Requirements | Applicable Standard |
|---|---|---|---|
| Outer Diameter (mm) | 6-630 | ±0.1-0.5mm | GB/T 3639 |
| Wall Thickness (mm) | 0.5-35 | ±5%-10% | GB/T 32957 |
| Length (m) | 1-12 (Customizable) | ±50mm | DIN 2445 |
| Inner Diameter Accuracy | IT8-IT10 Grade | Roundness ≤0.05mm | EN 10305 |
VI. Quality control points
(1) Component testing:
• Use a spark spectrometer to ensure that the chemical composition (such as C, Mn, Cr, etc.) complies with GB/T 222.
(2) Mechanical test:
• Tensile test: According to GB/T 228.1 standard, verify tensile strength and yield strength.
• Impact test: In accordance with GB/T 229 standard, assess the toughness of the material.
(3) Non-destructive testing:
• Ultrasonic detection: Using ultrasonic detection of internal defects, detected defect size ≥ 5% of the wall thickness.
• Magnetic particle detection: used to detect surface and near-surface cracks and other defects.
(4) Size sampling inspection:
• Use a laser caliper to monitor the outer diameter in real time, with a sampling rate of ≥5%.
• Root by root measurement of inner and outer diameter, wall thickness and other dimensions to ensure that the accuracy requirements are met.
(5) Surface quality inspection:
• Visually inspect the inside and outside surfaces one by one under sufficient lighting conditions to ensure that there are no cracks, pitting and other defects.
• Surface roughness Ra should meet the requirements of the standard, the outer diameter of the steel pipe ≤260mm, the outer surface roughness is not greater than 4μm.
(6) Heat treatment quality control:
• Annealing and normalizing processes are strictly controlled to optimize mechanical properties and eliminate internal stresses.
(7) Packaging and anti-rust treatment:
• The steel pipe in the heat treatment state should be treated with rust prevention before leaving the factory, and generally coated with neutral oil.
