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Help CenterSteel Pipe & Tube & Precision Steel Pipe，DIN 2391、EN 10305-1、ASTM A519、ASTM A269、JIS G3445
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1. Product Overview
Precision Steel Tube, also known as cold-drawn / cold-rolled seamless precision bright tube, is high-precision special steel pipe produced from hot rolled seamless tube blanks through multi-pass cold drawing, cold rolling, bright annealing and finishing processes, in accordance with GB/T 3639-2021 national standard.
Compared with ordinary hot rolled steel pipes, it features ultra-tight dimensional tolerance, high internal and external surface finish, oxide-free surface and low residual stress. It can be directly used for hydraulic cylinders, air cylinders and precision mechanical parts without secondary turning or boring. It provides reliable high-pressure sealing performance and remains crack-free during cold bending, flaring and flattening. It is widely applied in high-precision manufacturing sectors including hydraulic & pneumatic systems, automobile manufacturing, construction machinery, automation equipment and precision instruments.
Core Forming Principle
After pickling, phosphating and saponification lubrication, tube blanks undergo cold plastic deformation through precision dies at room temperature to reduce outer diameter and evenly thin wall thickness. Bright annealing eliminates work hardening and internal stress to form uniform and dense metallographic structure. It achieves high dimensional accuracy and mirror-smooth inner surface simultaneously, preventing medium leakage and friction abrasion under high pressure.
2. Main Steel Grades & Applicable Working Conditions
2.1 Carbon Precision Steel Tube (For General Hydraulic & Structural Parts)
10#, 20#, 35#, 45#, Q355B
20#: Oil cylinders, air cylinders, conventional hydraulic pipelines with excellent plasticity for cold processing
45#: Mechanical sleeves and precision structural components with high strength and hardness after quenching & tempering
2.2 Alloy Precision Steel Tube (For Heavy Load, Wear Resistance & High Strength)
20Cr, 40Cr, 42CrMo, 16Mn, 20CrMnTi
40Cr / 42CrMo: Heavy-duty hydraulic cylinders for construction machinery, transmission sleeves and heavy-load precision parts, available for nitriding and quenching reinforcement
3. Applicable Standard System
Domestic Chinese Standards
GB/T 3639-2021 Cold-drawn or Cold-rolled Seamless Precision Steel TubesGB/T 17395 Steel tubes — Dimensions, shapes, masses and tolerancesGB/T 8162 Seamless steel tubes for structural purposesGB/T 8163 Seamless steel tubes for liquid service
International Export Standards
DIN 2391 (European standard for hydraulic precision tubes), EN 10305-1, ASTM A519, ASTM A269, JIS G3445
4. Complete Specification Parameters
Outer Diameter Range: 4mm–273mm; small hydraulic precision tubes Φ6/10/16/22/28/32/42/50/63mm; medium & large mechanical sleeves 89–273mm
Wall Thickness Range: 0.5mm–20mm; thin-wall bright tubes 0.5–4mm, medium-heavy wall cylinder tubes 5–20mm
Standard Fixed Length: 6m, 9m, 12m; customized length 3–15m available, short cut pieces can be supplied on demand
Pipe End Types
Plain End: For general assembly and welding
Deburred & Chamfered End: Specially for cylinder assembly, no sharp edges to scratch sealing components
Process Classification
Cold-drawn Precision Tube: Cost-effective, suitable for small and medium batches and structural parts
Cold-rolled Bright Precision Tube: Higher precision and smoother inner surface, preferred for high-pressure hydraulic systems
Dimensional Accuracy Grades (GB/T 3639)
Normal Grade: OD tolerance ±0.10mm, wall thickness tolerance ±10%
High Precision Grade: OD tolerance ±0.05mm, wall thickness tolerance ±5%, inner diameter reaches IT7~IT9 precision tolerance
Surface Roughness
Normal precision tube Ra ≤4μm; high-grade cold rolled bright tube Ra ≤2μm, inner wall free of drawing marks, oxide scale and pits
5. Complete Production Process
Incoming inspection of hot rolled tube blanks → Pickling for oxide scale removal → Phosphating & saponification lubrication → Multi-pass cold drawing / cold rolling forming → Bright annealing under oxygen-free atmosphere → Straightening & rounding → Fixed-length cutting → Deburring and chamfering on both ends → 100% Eddy Current Testing (ET) → Full dimensional inspection → Manual surface recheck → Anti-rust oil coating → Sealed with plastic end caps → Bundling, packaging and warehousing
6. Mandatory Full-Range Inspection (Pipe-by-Pipe Test)
6.1 Mechanical Property Tests
Tensile test: Yield strength, tensile strength, elongation after fracture; excellent plasticity under annealed delivery state
Flattening test: No cracks or peeling after flattening to 1/2 of original outer diameter
Flaring test: No cracking with 30° cone mandrel, flaring rate ≥15%
Cold bending test: No cracking or lamination after 90° bending
Hardness test: Two delivery states optional, soft annealed state and cold-drawn hard state
6.2 Non-Destructive Testing
Full coverage Eddy Current Testing (ET) to detect tiny internal & external surface cracks, scratches and lamination defects; Ultrasonic Testing (UT) is additionally conducted for hydraulic cylinder tubes.
6.3 Hydrostatic Pressure Test (Special for Hydraulic Tubes)
Pressure holding test carried out as customer requirements, stable pressure maintained at 3–30MPa without leakage, meeting cylinder sealing pressure requirements.
6.4 Appearance & Dimensional Inspection
Bright and clean internal & external surfaces, free of oxide layer, scabs, rolling marks and pits; outer diameter, wall thickness, inner diameter and straightness measured and recorded at multiple points for each tube.
7. Core Product Advantages
Ultra-high dimensional accuracy, greatly reducing machining costTolerance controlled within 0.03–0.05mm; cylinders can be directly assembled with sealing parts without boring or finish turning, cutting down machining procedures and material loss.
Mirror-smooth inner & outer surfaces, oxide-freeSealed bright annealing eliminates rust and oxide scale, keeping hydraulic oil clean to avoid valve blockage and oil seal abrasion.
Excellent plasticity for deep processingAnnealed tubes support arbitrary cold bending, flaring, reducing, welding, threading and nitriding heat treatment without cracking during forming.
Seamless integrated structure with zero leakage under high pressureWeld-free design ensures stable pressure resistance, free of pipe burst and leakage risks under long-term high-pressure circulation of hydraulic and pneumatic systems.
Low internal stress, stable dimension after formingMulti-pass annealing eliminates cold working stress; no deformation after processing and assembly, consistent dimension during long service life.
Full specification coverage & flexible customizationCustom thin-wall small OD tubes, heavy-wall large OD tubes, special lengths, special tolerances and special steel grades are available; small batch samples can be delivered quickly.
8. Main Application Fields
Hydraulic & Pneumatic Industry (Core Application)Hydraulic cylinder barrels, air cylinder tubes, high-pressure hydraulic pipelines, precision valve sleeves for hydraulic equipment
Automobile ManufacturingShock absorber tubes, transmission sleeves, engine precision oil tubes, chassis structural parts, sensor sleeves
Construction Machinery & Automation EquipmentHydraulic pipes for excavators & loaders, precision shaft sleeves for robots, linear bushing sleeves, automation equipment frames
General Machinery ManufacturingPrecision machine tool spindle sleeves, bearing bushes, gear blanks, precision instrument structural tubes
Energy & Petrochemical IndustrySmall heat exchange tube bundles, instrument impulse tubes, low-pressure clean fluid transmission pipes
Other IndustriesMedical equipment, precision structural tubes for fitness equipment, small marine hydraulic pipelines
9. Surface Protection, Packaging, Shipment & Lead Time
Factory ProtectionInternal and external surfaces coated with special anti-rust oil, plastic dustproof caps installed on both ends; export tubes wrapped with VCI volatile anti-rust paper and covered with blue waterproof woven cloth for moisture and rust prevention during sea transportation.
Loading Port: Tianjin Port, shipment available via Qingdao Port and Shanghai Port.
Lead Time
Regular stock carbon precision tubes (20#, 45#): 5–7 days
Alloy precision tubes (40Cr, 42CrMo) & high-precision cold rolled bright tubes: 8–12 days
Custom tubes with special tolerances, extra large/small outer diameter: 15–22 days
MOQ & Samples: Minimum order quantity 3 tons; 30cm test samples provided free of charge for material and pressure inspection.
10. Supporting Quality Assurance Documents
Complete set of original Chinese & English factory certificates:
Raw material chemical composition analysis report
Mechanical property test report (tensile, flattening, flaring)
Eddy current / ultrasonic non-destructive testing report
Hydrostatic pressure test record
Dimensional tolerance inspection data sheet
GB / DIN standard certificate, packing list, certificate of origin
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