I. Overview of Cold Drawn Seamless Pipe
Cold-drawn seamless pipe is hot rolled seamless steel pipes made from hot rolled seamless steel tubes as billets, processed and molded at room temperature by cold drawing process.
Moreover, cold drawn seamless pipe offers core features such as the absence of welding seams, high dimensional accuracy (with tolerances controlled at 0.02–0.05 mm), and an excellent surface finish (with roughness Ra ≤ 1.6 μm).
In comparison with hot rolled pipes, the cold drawing process actively refines the grain structure through plastic deformation, enhances the material strength by 20%–30%, and reduces the risk of surface oxidation.
II. Cold finished seamless pipe national standards
| Country/Region | Standard Name | Standard Number | Scope of Application |
|---|---|---|---|
| China | For cold drawn or Cold-Rolled Seamless Pipes | GB/T 3639-2021 | For high-precision applications in mechanical structures, hydraulic equipment, and automotive components |
| Europe | Technical Delivery Conditions for Precision Steel Pipes Part 1: Cold Drawn Seamless Steel Pipes | EN 10305-1:2002 | For round-section seamless cold-drawn steel pipes 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 Pipes | ASTM A513 | For construction, machinery, and automotive industries |
| Japan | Cold Drawn Seamless steel pipe | 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 steel pipe production process
i. Billet preparation
Select high-quality billets (such as 20#, 45#, Q355B), remove the surface oxide scale by pickling, and ensure the quality of subsequent processing. This step is the basis for producing high-precision seamless carbon steel pipes.
ii. Cold drawing
Use multi-pass drawing, and the reduction rate is controlled at 10% to 40%. In order to reduce friction, phosphating lubrication technology is used to effectively improve dimensional accuracy and surface finish.
iii. Heat treatment process
Annealing treatment: annealing at 600-750℃ to eliminate internal stress and improve plasticity and toughness.
Normalizing treatment: normalizing at 850-950℃ to optimize the organizational structure and improve strength and hardness.
iv. Finishing process
The straightening machine ensures the straightness of the pipe, and the cutting equipment cuts it to the required length to ensure the flatness of the end face. Eddy current flaw detection is used to detect cracks ≥0.5mm to ensure that each seamless pipe is defect-free.
v. Surface treatment
Phosphating, galvanizing or anti-rust oil coating can be carried out according to needs to enhance corrosion resistance and surface adhesion. As a professional seamless steel pipe manufacturer, we strictly control every process to ensure stable and reliable products.
IV. Analysis of the core advantages of cold-drawn seamless pipes
i. High precision
The outer diameter tolerance of cold-drawn pipes is 5 times smaller than that of hot-rolled pipes, which is suitable for direct precision assembly of structural seamless pipe. Its surface finish is high, and the roughness can reach Ra≤1.6μm, ensuring good performance.
ii. Improved strength
Through cold drawing, the tensile strength of carbon steel seamless pipes can be increased to more than 600MPa, which is about 30% higher than the raw material strength, and the mechanical properties are optimized, which is suitable for high pressure and heavy load conditions.
iii. Material saving
Furthermore, the cold drawing process reduces the processing allowance by about 50%, achieves a finished product rate of over 95%, and effectively minimizes material waste while improving production efficiency and economic benefits.
iv. Strong versatility
Manufacturers can customize special-shaped sections according to customer needs—such as internal straight teeth, spiral grooves, and more—to meet diverse applications, and these products are widely used across various industries.
V. Comparison table of cold drawn seamless steel pipe and hot rolled seamless steel pipe
| Comparison Item | Cold-Drawn Seamless Pipe | Hot-Rolled Seamless Pipe |
|---|---|---|
| Dimensional Accuracy | High, with small outer diameter tolerance, suitable for precision assembly | Lower, with larger tolerance range, suitable for general purposes |
| Surface Quality | High smoothness, low roughness (Ra≤1.6μm) | Rougher surface, usually requires secondary processing |
| Mechanical Properties | Higher strength and hardness, suitable for high-pressure and heavy-load environments | General mechanical properties, suitable for medium and low-pressure use |
| Material Utilization | High, with less machining allowance, saving material | Larger machining allowance, more material waste |
| Application Scope | Precision machinery, hydraulic systems, automotive components, etc. | Structural piping, boiler tubes, general mechanical manufacturing |
| Price | Higher, due to complex processing technology | Lower, due to high production efficiency |
VI. Cold finished seamless pipe production process
Raw material preparation (pickling of steel billets) → Piercing and hot rolling to form rough pipes → Annealing treatment → Pickling and oiling → Multiple cold drawing passes to shape → Intermediate annealing (if required) → Heat treatment (normalizing or annealing) → Straightening → Non-destructive testing and hydrostatic testing → Cutting → Surface treatment (phosphating, galvanizing, or oiling) → Inspection and marking → Warehousing
VII. Classification of cold drawn seamless pipes
i. Classification by material
(1) Carbon steel cold drawn seamless pipes
For example, 20#, 45#, Q345, etc., are widely used in machinery and construction fields.
(2) Alloy steel cold drawn seamless pipes
Mainly used to manufacture boiler seamless pipes and high-pressure boiler pipes, with good high temperature resistance and corrosion resistance.
(3) Stainless steel cold drawn seamless pipes
Such as 304, 316L, suitable for chemical and food industries, with strong corrosion resistance.
ii. Classification by use
(1) Structural cold drawn seamless pipes
Mainly used in machinery manufacturing, building structures and automobile manufacturing, mostly common round seamless pipes.
(2) Cold drawn seamless pipes for fluid transportation
Used to transport fluids such as water, oil, and gas.
(3) Cold drawn seamless pipes for boilers and pressure vessels
Suitable for high temperature and high pressure environments, mainly for the manufacture of high-pressure boiler pipes.
(4) Hydraulic cold drawn seamless pipes
Used in hydraulic systems, requiring high precision and high strength.
iii. Classification by processing technology
(1) Cold drawn seamless pipe
Improve dimensional accuracy and surface quality through cold drawing.
(2) Cold rolled seamless pipe
Used for pipes with higher precision and thinner walls.
VIII. 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: Seamless steel pipe factory can provide plain ends, bevels or threads upon request.
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