Precision Seamless Hygienic-Grade Stainless Steel Coil Tube — GB/T 3639
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. presents a premium-grade precision seamless stainless steel coil tube manufactured in strict accordance with the Chinese National Standard GB/T 3639 for precision seamless steel tubes. Engineered specifically for hygienic-grade applications, this coil tube delivers exceptional dimensional accuracy, superior surface finish, and rigorous cleanliness performance — making it the ideal choice for industries where contamination control, corrosion resistance, and mechanical integrity are non-negotiable.
The seamless construction eliminates weld seams entirely, ensuring uniform wall thickness, maximum pressure resistance, and zero risk of internal leakage pathways. Supplied in continuous coil form, the product offers enhanced processing efficiency, reduced material waste, and seamless integration into automated forming and fabrication lines.
Material & Properties
- Base Material: Austenitic stainless steel grades including 304 (06Cr19Ni10), 304L (022Cr19Ni10), 316 (06Cr17Ni12Mo2), 316L (022Cr17Ni12Mo2), and 321 (06Cr18Ni11Ti), among others conforming to GB/T 3639 material specifications.
- Manufacturing Method: Cold-drawn seamless — ensuring tight dimensional tolerances, smooth internal and external surfaces, and excellent mechanical homogeneity.
- Corrosion Resistance: Excellent resistance to atmospheric, aqueous, and chemical corrosion environments; 316/316L grades offer superior resistance to chlorides and acidic media.
- Mechanical Properties: High tensile strength, elongation, and hardness retention after cold working; suitable for both static and dynamic loading applications.
- Hygienic Surface Finish: Available in polished, electropolished, and sanitary-passivated finishes with surface roughness (Ra) as low as 0.2–0.4 μm, meeting FDA, 3-A, and EHEDG hygienic requirements.
Specifications
| Parameter | Specification / Range | Standard Reference |
|---|---|---|
| Standard | GB/T 3639 (Precision Seamless Steel Tubes) | GB/T 3639 |
| Product Form | Coil Tube (Continuous Coil) | — |
| Outer Diameter (OD) | Φ3.0 mm – Φ114.3 mm (custom sizes available) | GB/T 3639 |
| Wall Thickness | 0.3 mm – 8.0 mm (customizable) | GB/T 3639 |
| Dimensional Tolerance (OD) | ±0.05 mm to ±0.20 mm (precision grade) | GB/T 3639 |
| Dimensional Tolerance (WT) | ±5% to ±10% of nominal wall thickness | GB/T 3639 |
| Surface Roughness (Ra) | 0.2 μm – 1.6 μm (depending on finish grade) | Hygienic Grade |
| Available Grades | 304, 304L, 316, 316L, 321, 310S | GB/T 3639 |
| Coil Length | 10 m – 100 m (standard); custom lengths on request | — |
| Coil Inner Diameter | Φ100 mm – Φ500 mm (customizable) | — |
| End Condition | Plain ends, chamfered, or beveled | — |
| Surface Treatment | Passivated, polished, electropolished, sanitary cleaned | Hygienic Grade |
| Packaging | Wooden pallet with moisture-proof wrapping; protective end caps | — |
Manufacturing Process
The production of this precision hygienic-grade coil tube follows a rigorous multi-stage process to ensure every specification is met with uncompromising quality:
- Raw Material Selection: Only certified, traceable stainless steel billets and ingots from approved mills are used. Incoming material undergoes 100% chemical composition analysis via optical emission spectroscopy (OES) to verify grade compliance.
- Piercing & Hot Rolling: Billets are heated to controlled temperatures and pierced to produce seamless hollow tubes, eliminating any weld seam or discontinuity.
- Pilger Milling / Cross-Rolling: The hot-rolled tube is further reduced through pilger or cross-rolling mills to achieve near-final dimensions with high material efficiency.
- Cold Drawing: Tubes are cold-drawn through precision tungsten carbide dies and mandrels to achieve the tight dimensional tolerances required by GB/T 3639. Multiple drawing passes may be employed for ultra-precise tolerances.
- Coil Winding: Drawn tubes are wound onto precision coil reels with controlled tension to prevent kinking, deformation, or surface marking.
- Heat Treatment (Annealing): Solution annealing in a controlled atmosphere (protective gas or vacuum) restores full austenitic microstructure, relieves cold-work stresses, and ensures maximum corrosion resistance.
- Pickling & Passivation: Tubes are acid-pickled to remove oxide scale, followed by nitric acid or citric acid passivation to form a uniform, protective chromium oxide layer critical for hygienic performance.
- Surface Finishing: Mechanical polishing, electropolishing, or orbital polishing is applied as specified to achieve the required surface roughness (Ra ≤ 0.4 μm for hygienic grade).
- Hygienic Cleaning: Final cleaning with deionized water and approved detergents removes all particulate and ionic contamination. Tubes are sanitized to meet pharmaceutical and food-grade cleanliness standards.
- Quality Inspection: Every coil undergoes comprehensive inspection — dimensional verification (OD, WT, straightness), hydrostatic pressure testing, surface defect examination, and chemical analysis. Non-destructive testing (eddy current or ultrasonic) is available upon request.
- Packaging & Shipping: Coils are protected with moisture-proof wrapping, secured on wooden pallets, and shipped with full traceability documentation.
Applications
The hygienic-grade precision seamless stainless steel coil tube is designed for the most demanding applications across multiple industries:
- Food & Beverage Processing: Milk processing lines, beer and beverage brewing systems, juice and dairy equipment, CIP (Clean-in-Place) piping systems, and food-grade heat exchangers.
- Pharmaceutical & Biotechnology: Sterile fluid transfer systems, bioreactors, cleanroom piping, pharmaceutical water systems (WFI, purified water), and GMP-compliant processing equipment.
- Medical Devices: Fluid delivery tubing for infusion pumps, dialysis machines, endoscopy equipment, and medical instrument manufacturing.
- Chemical & Petrochemical: Corrosive chemical transfer lines, reactor internals, heat exchanger tubes, and process piping in aggressive chemical environments.
- Cosmetics & Personal Care: Processing lines for cosmetic formulations, essential oil distillation, and high-purity ingredient handling.
- Electronics & Semiconductor: Ultra-clean fluid lines, ultra-pure water (UPW) systems, and chemical vapor deposition (CVD) equipment.
- General Industrial: Precision instrumentation, hydraulic and pneumatic systems, and high-purity gas delivery lines.
Quality Certifications & Compliance
Wenzhou Jixing Metal Materials Co., Ltd. is committed to delivering products that meet the highest international and national quality standards. This hygienic-grade coil tube complies with the following:
- GB/T 3639 — Chinese National Standard for Precision Seamless Steel Tubes
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001 — Environmental Management System Certification
- GB/T 12771 — Seamless stainless steel tubes for hygienic applications (where applicable)
- EN 10217 / ASTM A312 — Equivalent international standard compliance available upon request
- 3-A Sanitary Standards — American Sanitary Foundation compliance for food-grade applications
- FDA 21 CFR 177.1550 — Food contact material compliance
- EHEDG — European Hygienic Engineering Design Group guidelines
Each shipment is accompanied by a full mill test certificate (MTC) including chemical composition, mechanical properties, dimensional inspection data, and traceability information. Third-party inspection (TPI) and customer witness testing (CWT) are available upon request.
Unique Selling Points
Precision Without Compromise: GB/T 3639 precision tolerances ensure consistent fit, reliable welding, and seamless integration into hygienic process systems.
Seamless Integrity: True seamless construction eliminates weld seams — the primary failure and contamination point in welded tubing — ensuring maximum pressure integrity and hygienic performance.
Hygienic-Grade Surface Excellence: Surface roughness as low as Ra 0.2 μm with full passivation and sanitization prevents bacterial adhesion, biofilm formation, and product contamination.
Coil Form Efficiency: Continuous coil supply reduces cutting waste, accelerates fabrication, and enables automated processing — significantly lowering total cost of ownership.
Full Traceability: Every coil is traceable from raw material mill certificate through final inspection, ensuring complete supply chain transparency and regulatory compliance.
Customization Capability: Flexible customization of dimensions, surface finish, coil configuration, and packaging to meet specific project requirements.