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Help CenterSteel Pipe & Tube & Precision Steel Pipe，40Cr、42CrMo、35CrMo、20Cr、27SiMn、12Cr1MoV、Cr5Mo、Cr9Mo、10#、20#、35#、45#、16Mn(Q345B/C/D)
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1. Product Profile
Precision seamless bright steel tubes are fabricated from premium round steel billets or hot rolled seamless pipes via cold rolling, cold drawing, bright annealing, precision straightening and full non-destructive inspection. Distinct from standard hot rolled pipes, they feature micron-level dimensional accuracy, mirror flawless inner and outer surfaces free of oxide scale, reliable leak-proof pressure resistance and outstanding cold forming performance without cracking. Customers can conduct direct assembly without secondary turning or boring, making them indispensable core tubing for hydraulic pneumatic systems, automotive components, precision machinery and engineering machinery.
2. Applicable Implementation Standards
Domestic Chinese Standards
GB/T 3639-2020 Cold Drawn & Cold Rolled Precision Seamless Steel Tubes for General Mechanical Structures
GB/T 8713 Precision Seamless Steel Tubing for Hydraulic and Pneumatic Cylinders
GB/T 8162 Structural Seamless Steel Tubes; GB/T 8163 Seamless Steel Tubes for Fluid Conveyance
International Export Standards
German Standard: DIN 2391-2
European Standard: EN 10305-1, EN 10305-4 (Specialized hydraulic pipeline specification)
American Standard: ASTM A519, ASTM A179
Japanese Standard: JIS G3459
3. Common Material Grades (Regular Stock, Custom Special Alloys Available)
Carbon Structural Steel (Cost-efficient for general hydraulic & mechanical applications)
10#, 20#, 35#, 45#, 16Mn (Q345B/C/D)
Alloy Structural Steel (High tensile strength, wear resistant, suitable for heavy load working conditions)
40Cr, 42CrMo, 35CrMo, 20Cr, 27SiMn, 12Cr1MoV, Cr5Mo, Cr9Mo
Stainless Steel Precision Tubing (Anti-corrosion, ideal for new energy cooling pipelines)
304, 316L (Produced against custom orders)
4. Full Manufacturing Process Flow
Round steel billet → Hot piercing to form hollow shell → Pickling to remove oxide skin → Phosphating & saponification lubrication → Multi-pass cold rolling / cold drawing for diameter & wall reduction → Bright annealing (relieve internal stress & enhance surface smoothness) → Precision straightening → Fixed-length cutting → Double-sided internal & external cleaning + air purging → Eddy current & ultrasonic non-destructive testing → Full dimensional inspection (outer diameter, inner diameter, wall thickness, straightness, concentricity) → Anti-rust oil coating → Bundling & warehouse storage
5. Core Technical Indicators & Performance Advantages
1. Ultra-Tight Dimensional Tolerance (Core Competitive Edge)
Outer diameter tolerance: ±0.05 ~ ±0.20mm (divided into standard, high-precision and ultra-precision grades)
Inner diameter tolerance: H8 / H9 precision fit, minimum tolerance reaches ±0.03mm
Consistent wall thickness: ±3% ~ ±8%, minimal wall eccentricity, stable pressure bearing capacity
Straightness: ≤0.1mm per meter, concentricity ≤0.1mm, no bending distortion
Standard Dimension Range: OD 8–650mm, ID 4–500mm, wall thickness 1–100mm
Custom Length: 2000–12000mm, non-standard cut lengths supported
2. Premium Surface Finish
Inner and outer surfaces free of oxide scale, peeling, pits, cracks and surface blemishes
Inner wall roughness Ra ≤0.4–0.8μm, low fluid flow resistance, excellent sealing without oil leakage
Bright annealed delivery condition with uniform silvery metallic surface, no secondary polishing required
3. Superior Machinability & Mechanical Properties
High pressure tightness: Zero leakage under high-pressure working environments, compatible with high-pressure hydraulic systems
Excellent formability: No cracking or deformation during cold bending, flaring, flattening and stamping processes
Stable mechanical indicators: Uniform tensile strength and yield strength; customizable delivery states including annealed, normalized and stress-relieved
Lightweight design: Over 30% weight reduction versus solid round bars with identical bending & torsion resistance, cutting raw material consumption and processing labor costs
4. Four Optional Delivery Conditions
+C Cold Hardened State: High hardness and tensile strength, for structural parts without secondary bending forming
+LC Cold Softened State: Excellent ductility, supports flaring, bending and stamping operations
+SR Stress Relief Annealing: Eliminates residual cold working stress, maintains stable geometry during long-term service
+A Full Bright Annealed State: Optimal toughness, designated for hydraulic cylinders and pneumatic barrels
6. Precision Grade Classification & Corresponding Application Scenarios
| Precision Grade | Outer Diameter Tolerance | Wall Thickness Tolerance | Applicable Industries |
|---|---|---|---|
| Standard Grade | ±0.50mm | ±10% | General mechanical frames, low-pressure fluid pipelines |
| Medium High Grade | ±0.30mm | ±8% | Ordinary automotive spare parts, standard machine tools |
| High Precision Grade | ±0.20mm | ±5% | Hydraulic cylinders, pneumatic cylinders, shock absorber tubes |
| Ultra-Precision Grade | ±0.10mm | ±3% | Aviation fittings, precision measuring instruments, new energy equipment |
7. Major Application Sectors
Hydraulic & Pneumatic Equipment (Largest Application Field)Excavators, injection molding machines, hydraulic jacks, hydraulic station cylinder barrels, air cylinder tubes, high-pressure oil pipelines, solenoid valve housings. Smooth inner surfaces reduce hydraulic fluid loss and guarantee stable sealing performance.
Automotive Manufacturing IndustryEngine high-pressure fuel pipes, brake fluid tubes, shock absorber casings, steering tie rods, transmission sleeves, cooling pipelines for new energy battery packs.
General Precision MachineryMachine tool spindle sleeves, bearing retainers, gear bushings, tooling fixtures, precision instrument enclosures.
Construction & Mining MachineryHydraulic support pipes, lifting equipment cylinder barrels, mine high-pressure delivery tubes, heavy-load mechanical structural components.
Other Application FieldsRail transit equipment, medical apparatus, petrochemical fluid transmission, aviation precision fittings, agricultural machinery components.
8. Complete Factory Inspection Items
Dimensional Inspection: Batch sampling via coordinate measuring machines, micrometers and wall thickness gauges
Non-Destructive Testing: Eddy current & ultrasonic scanning to detect internal cracks and laminations
Mechanical Performance Tests: Tensile, flattening, flaring and hardness tests with official mechanical test reports issued
Metallographic Examination: Microstructure analysis for annealed tubing
Hydrostatic Pressure Test: Mandatory pressure holding test with zero leakage (required for cylinder pipes)
Spectroscopic Material Analysis: Batch chemical composition certification provided for every shipment
9. Packaging & Anti-Corrosion Protection
Small short-size tubes: Wrapped with plastic protective film, packed in woven bags, plastic end caps installed on both ends for dust and rust prevention
Large diameter thick-wall tubes: Coated with anti-rust oil, bundled with steel strapping, equipped with end protective covers
Export sea freight packaging: Wrapped with moisture-proof stretch film, loaded into wooden crates or pallets to prevent seawater corrosion and collision damage during ocean transit
10. Core Product Advantages Summary
Cost Saving & Production Efficiency Boost: Ultra-precise dimensions remove customer-side boring and polishing processes, lowering expenses on cutting tools, labor and raw material waste
Extended Service Lifespan: Uniform wall thickness and defect-free inner walls effectively avoid pipe burst and leakage under high pressure operation
Compatibility with Automated Machining: Compliant straightness and concentricity allow direct processing on CNC lathes
Global Export Eligibility: Fully compliant with mainstream European and American industrial standards; complete set of inspection documents facilitates customs clearance worldwide
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