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Help CenterSteel Pipe & Tube & Precision Steel Tube，10#, 20#, 45#, Q345B、20Cr、40Cr、20CrMo
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1. Product Overview
Precision seamless steel tube is high-precision seamless pipe manufactured from premium carbon and alloy steel billets through multi-pass cold drawing / cold rolling, bright annealing and precision finishing. Its core advantages include ultra-tight dimensional tolerance, oxide-free smooth inner wall, uniform wall thickness, and excellent roundness & straightness. It can be directly used for hydraulic cylinders, precision machinery, automotive components and other applications without secondary turning or honing.
Divided into cold-drawn precision tube and cold-rolled precision tube, it offers 5–10 times higher dimensional accuracy and significantly lower surface roughness than ordinary hot-rolled seamless pipes, with better pressure sealing performance. It is a high-precision pipe dedicated to high-end equipment manufacturing.
2. Applicable Standards
Domestic Standards
GB/T 3639-2021 Seamless Cold-Drawn or Cold-Rolled Precision Steel Tubes (Main Standard)
GB/T 17395 General Tolerance Standard for Steel Pipe Dimensions
GB/T 8162 Seamless Steel Tubes for Structural Purposes
International Export Standards
DIN 2391, EN 10305-1/4, ASTM A519, ISO 4394
Supporting Certifications
SGS material test report, ET eddy current NDT report, hydrostatic test certificate, original Mill Test Certificate (MTC)
3. Main Material Grades
3.1 Carbon Steel (Hydraulic & General Machinery)
10#, 20#, 45#, Q345B (equivalent to DIN ST35 / ST52)
3.2 Alloy Steel (High-Strength Wear-Resistant Structural Parts)
20Cr, 40Cr, 20CrMo, 42CrMo, 35CrMo
3.3 US Standard Export Grades
SAE1020, SAE1045, 4130 chromoly alloy
4. Heat Treatment Delivery Conditions
BK Cold Drawn Hard State: No heat treatment after cold working, high hardness and strength, suitable for light machining
BKS Stress-Relieved Annealing: Eliminates internal cold working stress, deformation-resistant, ideal for bending and flaring
NBK Bright Annealed (Mainstream for Hydraulic Tubes): Oxide-free annealing under protective atmosphere, mirror-bright inner and outer walls, clean bore, directly used for cylinders and high-pressure oil circuits
GBK Full Annealed: Best ductility, suitable for heavy bending and stamping forming
5. Complete Production Process
Qualified round billet peeling → Heating and piercing into hot-rolled hollow tube → Pickling, phosphating and saponification lubrication → Multi-pass cold drawing / cold rolling to reduce outer diameter and wall thickness → Degreasing and cleaning → Bright annealing (NBK) → Precision straightening → Sizing and rounding → Inner and outer wall polishing → Eddy current NDT → Precision dimension inspection → Hydrostatic pressure test for each tube → High-pressure inner bore flushing to remove impurities → Anti-rust oil coating → Plastic end caps sealing → Steel strip bundling / wooden pallet warehousing
6. Core Technical Parameters
6.1 Size Range
Outer Diameter (OD): 4mm ~ 325mm
Wall Thickness (WT): 0.5mm ~ 20mm, thin-wall and heavy-wall customized available
Standard Fixed Length: 6m, 5.8m; customized length 1–12m, 6m / 12m popular for export
End Finish: Plain cut, chamfered, deburred, threaded machining
6.2 High Precision Tolerance (Premium Grade)
OD Tolerance: ±0.03 ~ ±0.05mm
ID Tolerance: IT7–IT11 precision grade, within ±0.035mm
Wall Thickness Tolerance: ±5%, while ordinary seamless pipes are only ±10%~15%
Straightness: ≤0.5mm/m, minimal ovality
6.3 Surface Roughness
Inner and outer wall Ra: 0.2–3.2μm, NBK bright annealed tube inner bore Ra ≤0.8μm
Free of oxide scale, scratches, pits and rust, no extra pickling or honing required for hydraulic systems
6.4 Pressure and Forming Performance
Hydrostatic Test: Hold 1.5× design pressure for 10s without leakage, hydraulic tubes withstand 25–35MPa
Formability: No deformation after cold bending, no cracking during flaring and flattening, excellent weldability
Internal Cleanliness: Free of rolling impurities and iron filings, suitable for precision hydraulic valve groups and avoids oil circuit blockage
7. Core Product Advantages
Ultra-high dimensional accuracy, greatly reduces machining costWith strict tolerance control, pipes can be directly assembled after delivery, saving boring and precision turning procedures, machining time and consumables.
Bright and clean inner bore, high-pressure leak-proofNBK oxide-free surface reduces fluid resistance, no impurity shedding, ensuring long-term leak-proof performance for oil cylinders and hydraulic pipelines.
Uniform and stable mechanical properties, wide processing adaptabilityMultiple heat treatment options available, suitable for bending, stamping, turning, welding and secondary heat treatment without cracking.
Uniform wall thickness and high concentricity, balanced pressure bearingMulti-pass cold rolling eliminates wall thickness deviation, no local stress concentration under high pressure, with high burst safety factor.
Smooth and bright surface, direct exposed assembly availableNo extra polishing needed, suitable for automation equipment housings and precision supports.
Full-size stock available, customized deep processing supportedHoning, chamfering, cutting, tapping, black phosphating, galvanizing and other one-stop processing services available.
8. Main Application Fields
8.1 Hydraulic and Pneumatic Industry (Core Application)
Hydraulic cylinder barrels, high-pressure hydraulic tubing, pneumatic cylinders, precision pipelines for hydraulic valves, hydraulic systems for construction machinery
8.2 Automobile Manufacturing
Automotive transmission shafts, steering system pipes, shock absorber cylinders, engine high-pressure fuel pipes, chassis precision structural parts
8.3 General Precision Machinery
Spindle sleeves for automation equipment, bearing bushes, precision gear blanks, machine tool guide tubes, instrument and equipment housings
8.4 Construction and Mining Machinery
Hydraulic props, jack cylinders, high-pressure pipelines for excavators, high-strength precision transmission pipes
8.5 Aerospace and New Energy Equipment
Hydraulic pipelines for energy storage systems, lightweight precision structural parts for aerospace, precision supports for photovoltaic equipment
8.6 Chemical, Food and Medical Equipment
Clean medium transmission pipelines, laboratory instrument pipes, medical device structural pipes
9. Packaging, Shipment and Lead Time
Packaging Methods
Small diameter thin precision tubes: Tightly bundled with steel strips, plastic dust-proof caps at both ends, wrapped with anti-rust waterproof film
Medium and large diameter precision tubes: Single pipe wrapped with anti-rust woven cloth, sealed pipe ends to prevent collision
Export packaging: Fixed by IPPC fumigated wooden pallets, suitable for 20GP / 40HC container sea transportation
2. Delivery Warehouse: Spot goods shipped directly from Tianjin Port
3.Lead Time: 5–7 days for regular NBK bright annealed stock goods; 10–18 days for customized orders of special alloys, extra heavy wall thickness and deep processing
4.Payment Term: 30% TT advance deposit, balance settled before shipment, L/C letter of credit is not accepted.
10. Full Factory Inspection Items
Spectral chemical composition analysis of raw materials, strictly control harmful impurities S and P
Full inspection of outer diameter, inner diameter, wall thickness, length and straightness, re-measured by micrometer at multiple points
100% eddy current ET NDT to detect internal microcracks and lamination defects
Hydrostatic tightness pressure test for every single tube
Tensile, hardness, flattening and flaring mechanical performance tests
Random inspection of inner wall roughness and cleanliness
Original Mill Test Certificate, factory certificate and third-party SGS authoritative test report provided
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