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Help CenterSteel Pipe & Tube & Precision Seamless Steel Tube，10#、20#、35#、45#、16Mn(Q345B)、40Cr、42CrMo、27SiMn
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Precision Seamless Steel Tube Product Specification
1. Product Overview
Precision seamless bright steel tube is processed from premium carbon steel and alloy steel billets via cold drawing, cold rolling and bright annealing. Complying with GB/T3639-2021, DIN2391 and ASTM A519 standards, it features oxide-free inner & outer surfaces, ultra-tight dimensional tolerance and superior surface finish. No secondary turning or polishing is required for direct machining and assembly.
Core Advantages
High dimensional precision: Outer diameter tolerance ±0.05~±0.3mm, wall thickness tolerance ±5%~±10%, ultra-precision grade up to ±0.03mm with strictly controlled concentricity and ovality.
Smooth surface: Inner & outer surface roughness Ra≤0.4~1.6μm, free from peeling, cracks, pits and oxide scales.
Stable mechanical property: Uniform grain structure after annealing, no cracking during cold bending, flaring and flattening, excellent pressure resistance and fatigue resistance for leak-proof service.
Easy deep processing: Available for threading, drilling, bending and heat treatment to lower clients’ machining cost.
2. Applicable Standards
Domestic Standards
GB/T3639-2021 Cold Drawn & Cold Rolled Precision Seamless Steel Tubes, GB/T699 Quality Carbon Structural Steel, GB/T3077 Alloy Structural Steel, GB/T8713 Precision Steel Tubes for Hydraulic & Pneumatic Cylinders.
International Standards
DIN2391, EN10305, ASTM A519, JIS G3445 to meet inspection requirements for global export.
3. Common Grades, Chemical Composition & Mechanical Property
Available grades: 10#, 20#, 35#, 45#, 16Mn(Q345B), 40Cr, 42CrMo, 27SiMn; customized special materials acceptable.
| Grade | C(%) | Si(%) | Mn(%) | S/P(max,%) | Tensile Strength(MPa) | Yield Strength(MPa) | Elongation(%) |
|---|---|---|---|---|---|---|---|
| 20# | 0.17~0.24 | 0.17~0.37 | 0.35~0.65 | 0.035 | 410~550 | ≥245 | ≥25 |
| 45# | 0.42~0.50 | 0.17~0.37 | 0.50~0.80 | 0.035 | ≥600 | ≥355 | ≥16 |
| 42CrMo | 0.38~0.45 | 0.17~0.37 | 0.50~0.80 | 0.035 | ≥1080 | ≥885 | ≥12 |
Note: Strict control on harmful impurities Sulphur and Phosphorus to guarantee welding and forging performance.
Delivery Condition
NBK (Annealed): Stress-relieved bright annealing, soft property ideal for bending & flaring, preferred for hydraulic cylinder barrels.
BK (Cold Finished): Non-annealed after cold rolling, high hardness & wear resistance for high-strength sleeves.
NBK+N (Normalized): Medium strength for general structural components.
4. Dimension Specifications
Size Range
Outer Diameter (OD): φ4mm~φ120mm for regular stock; extra small/large sizes upon customization
Wall Thickness (WT): 0.5mm~12mm
Standard Length: 4m~6m; fixed-cut, multiple-length & special length from 100mm to 12m available, length tolerance ±5mm
Shape Index
Straightness ≤0.3~0.5mm/m, smooth burr-free end face with deburring treatment.
5. Production Flow
Raw billet incoming inspection → surface peeling & defect removal → heating & piercing into hollow shell → pickling, phosphating & saponification for lubrication → multi-pass cold rolling/cold drawing → degreasing & cleaning → bright non-oxidation annealing → straightening & finishing → NDT inspection (Eddy Current + Hydrostatic Test) → full dimensional check → marking, rust-proof packing → finished product warehousing.
6. Application Fields
Hydraulic & Pneumatic Industry: Cylinder barrels, pneumatic tubes, high-pressure hydraulic piping (mainly 20# & 45# annealed tube for zero leakage).
Automobile Manufacturing: Shock absorber sleeves, steering shaft sleeves, transmission shafts, engine bushings (45#,40Cr).
Precision Machinery: Guide pillars, bearing sleeves, automation equipment frames, mould fittings.
Construction Machinery: Hydraulic pipelines, precision sleeves, cylinder accessories.
Petrochemical & Instrument: Precision impulse tubing for gauges, low-pressure process pipelines.
General Structure: Precision steel frames, rebar couplers, small pressure vessel fittings.
7. Quality Inspection Items
Physical & Chemical Test: Spectrum analysis for chemical composition, tensile test, hardness test.
Dimensional Inspection: Laser measurement for OD, wall thickness, roundness and straightness.
Non-Destructive Test: Eddy current test for inner crack detection, hydrostatic pressure test from 6MPa to 30MPa on request.
Process Test: Flattening, flaring and cold bending test to ensure no cracking during forming.
8. Packing & Lead Time
Packing: Small tubes bundled with anti-rust oil & woven bag; large tubes individually wrapped with waterproof film for ocean shipment against moisture & rust.
Lead Time: In-stock items ship within 5~7 working days.
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