Steel Pipe & Tube & Precision Steel Pipe,10#/20#、35#/45#、40Cr/42CrMo、16Mn (Q345)
Detailed Description of Precision Steel Tube
1. Product Definition
Precision steel tube, also known as precision bright seamless steel tube, is a high-precision seamless steel pipe manufactured from high-quality carbon steel, alloy steel or stainless steel through cold drawing, cold rolling and bright annealing. It features no oxide layer on inner and outer walls, extremely tight dimensional tolerances and high surface finish, which can be directly used for precision assembly and high-pressure working conditions.
2. Executive Standards
National Standard: GB/T 3639-2021 (Cold-drawn & Cold-rolled Precision Seamless Steel Tubes), GB/T 8713 (Steel Tubes for Hydraulic and Pneumatic Systems)
International Standards: DIN 2391-2 (European Standard), ASTM A519 (American Standard)
Tolerance Grades: Grade D4 (Outer Diameter: ±0.05mm), Grade D3 (Outer Diameter: ±0.10mm), etc.
3. Common Materials & Properties
| Material | Main Composition | Characteristics & Applications |
|---|---|---|
| 10# / 20# | Low carbon steel (C ≤ 0.23%) | Good toughness and machinability, widely used for hydraulic and pneumatic components |
| 35# / 45# | Medium carbon steel (C=0.32~0.50%) | High strength, applied to mechanical structures, shaft parts and oil cylinders |
| 40Cr / 42CrMo | Chromium alloy steel | Excellent wear resistance and high strength, suitable for gears, bearing parts and high-pressure components |
| 16Mn (Q345) | Low-alloy high-strength steel | Good low-temperature toughness, used for engineering machinery and structural parts |
4. Dimensions & Specifications
Outer Diameter: 4–120mm (Common range: 6–89mm)
Wall Thickness: 0.5–30mm (Common range: 1.5–20mm)
Length: Standard length 6m, customized fixed length available (1–7m)
Tolerance (Grade D4):
Outer Diameter: ±0.05mm
Wall Thickness: ±5%
Straightness: ≤0.2mm/m
Surface Roughness: Ra ≤ 0.8μm
5. Manufacturing Process
Raw material preparation: Hot-rolled seamless steel tube or steel billet
Cold working: Multi-pass cold rolling and cold drawing to reduce diameter and wall thickness for higher precision
Heat treatment: Bright annealing to eliminate internal stress and restore ductility
Finishing: Straightening, nondestructive testing, cutting and polishing
Inspection: Dimensional check, surface inspection, mechanical property test, hydraulic/pneumatic pressure test
6. Key Performance Characteristics
High precision: Outer diameter tolerance up to ±0.05mm, uniform wall thickness and minimal ovality
High surface finish: No oxide layer on inner and outer walls; suitable for electroplating and direct assembly
High pressure resistance & leak-proof: Maximum bearing pressure up to 100MPa; no cracks after cold bending, flaring and flattening
Superior mechanical properties: Tensile strength 600–800MPa, good toughness and fatigue resistance
Stable performance: Uniform metal structure and consistent quality in mass production
7. Main Application Fields
Hydraulic & pneumatic systems: Oil cylinders, air cylinders, high-pressure tubing and valve parts
Precision machinery: Main shafts, guide rails, bearing sleeves and gear blanks
Automotive industry: Shock absorbers, steering columns, half shafts and fuel injection nozzles
Aerospace: Precision structural parts and hydraulic pipelines
Energy & petrochemical industry: High-pressure boiler tubes and instrument tubes for fluid transportation
Other fields: Medical equipment, electronic devices and military parts
8. Difference from Ordinary Seamless Steel Tube
Ordinary seamless steel tube: Mainly hot-rolled, outer diameter tolerance ±12.5%, with oxide scale on surface. Low precision, for general pipeline and structural support.
Precision steel tube: Processed by cold rolling/drawing and fine finishing, tight tolerance and bright oxide-free surface. High precision, for high-end equipment and hydraulic systems.
9. Packaging & Delivery
Packaging: Coated with anti-rust oil, wrapped with plastic film and woven bags or wooden cases; both ends sealed
Delivery condition: Annealed (soft state) or quenched & tempered (hard state)
Quality documents: Material certificate, dimensional inspection report, mechanical property report and nondestructive testing report
10. Purchasing Guidelines
Confirm applicable standards: Prioritize GB/T 3639-2021 Grade D4 or DIN 2391-2
Select proper material: 20# for hydraulic parts, 45# for structural parts, 42CrMo for high-pressure parts
Confirm tolerance requirements: ±0.05mm for ultra-high precision, ±0.10mm for regular use
Check surface quality: Ra ≤ 0.8μm, free from cracks, pits and oxide scale
Verify mechanical indicators: Tensile strength, yield strength, elongation and hardness shall comply with relevant standards
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