Stainless Steel Seamless Coil Tube — GB/T 14976 Fluid Transport Grade

Product Overview

The Seamless Coil Tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd is a precision-engineered stainless steel tubing product designed specifically for fluid transport applications. Conformity to GB/T 14976 (General Technical Conditions for Seamless Steel Tubes for Fluid Transport) ensures that every coil tube meets the rigorous Chinese National Standard governing seamless fluid tubes. This product is supplied in continuous coil form, offering superior handling efficiency, minimal material waste, and compatibility with automated forming and processing lines.

The coil tube is fabricated from high-grade austenitic and duplex stainless steels, providing excellent corrosion resistance, mechanical integrity, and long-term service life under demanding fluid conveyance conditions. Each coil is subjected to comprehensive quality assurance protocols including hydrostatic pressure testing, non-destructive testing (NDT), and mechanical property verification.

Material & Properties

Stainless steel coil tubes conforming to GB/T 14976 are typically produced from the following material grades:

• 304 / 06Cr19Ni10 (UNS S30408) — General-purpose austenitic grade with excellent corrosion resistance and formability.
• 304L / 022Cr19Ni10 (UNS S30403) — Low-carbon variant suitable for welding applications and sensitization-sensitive environments.
• 316 / 06Cr17Ni12Mo2 (UNS S31608) — Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion.
• 316L / 022Cr17Ni12Mo2 (UNS S31603) — Low-carbon 316 variant for enhanced weldability and intergranular corrosion resistance.
• 321 / 06Cr18Ni11Ti (UNS S32108) — Titanium-stabilized grade for high-temperature service and stress corrosion resistance.
• 310S / 06Cr25Ni20 (UNS S31008) — High-temperature austenitic grade for extreme thermal environments.

Key material properties include:

• Corrosion Resistance: Excellent resistance to atmospheric, chemical, and aqueous corrosive environments.
• Mechanical Strength: High tensile strength with adequate ductility for forming and bending operations.
• Weldability: Good to excellent weldability depending on grade selection.
• Temperature Range: Serviceable from cryogenic temperatures up to 870 °C (1600 °F) depending on grade.
• Hygiene: Smooth interior surface suitable for food-grade and pharmaceutical fluid transport.

Specifications

Parameter	Specification
Applicable Standard	GB/T 14976 — Seamless Steel Tubes for Fluid Transport
Product Form	Continuous Coil (Coil Tube)
Outer Diameter (OD)	6.0 mm – 168.3 mm (customizable upon request)
Wall Thickness	0.5 mm – 6.0 mm (tolerance ±10% per GB/T 14976)
Coil Length	3,000 m – 10,000 m per coil (standard); custom lengths available
Coil Weight	Typically 500 kg – 2,500 kg per coil
Surface Finish	Mill Finish / Bright Annealed / Pickled & Passivated
Surface Roughness (Ra)	≤ 0.5 μm (Bright Annealed); ≤ 0.8 μm (Mill Finish)
End Condition	Plain Cut / Beveled / Custom per customer specification
Material Grades	304, 304L, 316, 316L, 321, 310S, 2205, 904L, and others
Tolerance (OD)	±0.5% (Precision); ±1.0% (Standard)
Tolerance (Wall)	±10%
Coil Packaging	Wooden reel or steel pallet with protective wrapping
Hydrostatic Test Pressure	≥ 20 MPa (or as specified per GB/T 14976 requirements)
NDT Methods	Electromagnetic Testing (ET) / Eddy Current Inspection

Manufacturing Process

The production of seamless coil tubes at Wenzhou Jixing Metal Materials Co., Ltd follows a rigorous, multi-stage manufacturing sequence:

1. Raw Material Selection: Certified stainless steel billets or bars are procured from qualified mills with full material traceability and chemical composition verification.
2. Piercing & Hot Rolling: Billets are heated to forging temperature and pierced to produce seamless hollow bars (HMB), which are then hot-rolled to near-final dimensions.
3. Intermediate Heat Treatment: Hot-rolled tubes undergo solution annealing (austenitization) to restore ductility and achieve uniform microstructure prior to cold working.
4. Cold Drawing / Cold Pilgering: Tubes are cold-drawn through precision dies to achieve exact dimensional tolerances, superior surface finish, and enhanced mechanical properties.
5. Bright Annealing: Cold-worked tubes are annealed in a controlled atmosphere (protective gas) furnace to relieve residual stresses, restore full austenitic properties, and achieve a clean, oxide-free bright surface.
6. Pickling & Passivation: Tubes are chemically pickled to remove any residual scale or discoloration, followed by passivation treatment to establish a stable chromium oxide protective film.
7. Coiling: Finished tubes are wound onto reels using precision coiling equipment to ensure uniform tension and prevent surface damage or deformation.
8. Quality Inspection: Each coil undergoes comprehensive testing including hydrostatic pressure testing, electromagnetic non-destructive testing (NDT), dimensional verification, and mechanical property testing.
9. Packaging & Dispatch: Coils are packaged on protective reels with appropriate moisture and corrosion protection for safe transport and storage.

Applications

GB/T 14976 seamless stainless steel coil tubes find extensive application across multiple industries:

• Chemical Processing: Transport of aggressive chemical media, acids, alkalis, and process fluids in chemical plants and refineries.
• Food & Beverage Industry: Hygienic fluid transfer lines for dairy, brewing, and food processing equipment where sanitary requirements are paramount.
• Pharmaceutical & Biotechnology: Clean fluid transfer systems requiring high purity and resistance to contamination.
• Oil & Gas: Downhole tubing, flow lines, and processing equipment components in upstream and midstream operations.
• Petroleum Refining: Crude oil and refined product transfer lines, heat exchanger tubing, and distillation column internals.
• Heat Exchanger Manufacturing: Seamless coil tubes are ideal for automated heat exchanger tube fabrication, enabling efficient U-bend forming and tube sheet insertion.
• Pressure Vessel & Equipment Fabrication: Internal piping and structural tubing for pressure vessels and process equipment.
• Automotive & Aerospace: Fuel lines, hydraulic systems, and structural tubing in demanding mechanical applications.
• Water Treatment & Desalination: Brackish water and seawater transport systems requiring long-term corrosion resistance.
• Medical Equipment: Tubing for medical gas delivery, sterilization systems, and diagnostic equipment.

Quality Certifications & Compliance

Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system ensuring full compliance with international and national standards:

• GB/T 14976 — Chinese National Standard for Seamless Steel Tubes for Fluid Transport (primary governing standard)
• GB/T 12771 — Chinese National Standard for Stainless Steel Tubes for Fluid Transport (supplementary reference)
• ISO 9001:2015 — Quality Management System certification ensuring consistent product quality and process control
• ISO 14001 — Environmental Management System certification demonstrating environmental responsibility
• ASME / ASTM Standards — Available upon request for international project compliance
• EN 10217 / EN 10216 — European standards available for European market requirements

Quality Assurance Protocols include:

• Hydrostatic Pressure Testing: Every coil is subjected to hydrostatic pressure testing at a minimum of 20 MPa to verify weld integrity and structural soundness, ensuring zero leakage under operational conditions.
• Non-Destructive Testing (NDT): Electromagnetic testing (ET) and eddy current inspection are performed to detect internal and surface defects without damaging the product, ensuring freedom from cracks, seams, and inclusions.
• Mechanical Property Verification: Tensile testing, hardness testing, and impact testing are conducted on representative samples to confirm compliance with specified mechanical requirements.
• Chemical Composition Analysis: Spectroscopic verification of alloy composition to ensure material grade conformity.
• Dimensional Inspection: Precision measurement of outer diameter, wall thickness, straightness, and coil geometry.
• Mill Test Certificates (MTC): Full traceability documentation including EN 10204 3.1 material certificates provided with every shipment.

Unique Selling Points

• Full Standard Compliance: Complete adherence to GB/T 14976 ensures reliability and acceptance across all fluid transport applications in the Chinese and international markets.
• Continuous Coil Format: Eliminates butt-weld joints inherent in straight-length tubing, reducing potential failure points and improving system integrity.
• Automated Processing Compatibility: Coil form enables seamless integration with automated tube forming, bending, and fabrication equipment, significantly reducing production costs and lead times.
• Superior Surface Quality: Bright annealed finish with low surface roughness provides enhanced corrosion resistance and facilitates easy cleaning in hygienic applications.
• Comprehensive Testing Regime: Triple-layer quality assurance through hydrostatic testing, NDT, and mechanical property verification ensures zero-defect delivery.
• Material Traceability: Full chemical and mechanical traceability from raw material to finished product with EN 10204 3.1 certification.
• Customization Capability: Flexible customization of dimensions, material grades, surface finishes, and packaging to meet specific customer requirements.

Note: All products are manufactured under strict quality control protocols. Specific dimensions, tolerances, and material grades should be confirmed in writing prior to order placement. Wenzhou Jixing Metal Materials Co., Ltd reserves the right to update specifications in accordance with evolving standards and technological advancements.