Stainless Steel Seamless Coil Tube — GB/T 14976 Fluid Transportation Grade
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. manufactures high-performance stainless steel seamless coil tubes (盘管/Coiltube) conforming to the Chinese National Standard GB/T 14976 — the definitive specification for seamless steel tubes intended for fluid transportation. These coil tubes are engineered to deliver superior corrosion resistance, mechanical integrity, and dimensional precision, making them ideal for applications involving the conveyance of gases, liquids, and slurries in industrial, chemical, and energy sectors.
As a coil-form product, this seamless tube offers the advantage of continuous, joint-free delivery, reducing installation labor, minimizing leak risk, and enabling efficient downstream forming operations such as bending, cutting, and welding without the need for intermediate splicing.
Material & Properties
The coil tubes are fabricated from austenitic and/or duplex stainless steel grades compliant with GB/T 14976 and corresponding international equivalents. Commonly available grades include:
- 304 (06Cr19Ni10) — General-purpose austenitic stainless steel with excellent corrosion resistance and formability.
- 304L (022Cr19Ni10) — Low-carbon variant resistant to intergranular corrosion in welded assemblies.
- 316 (06Cr17Ni12Mo2) — Molybdenum-enhanced grade offering superior resistance to pitting and crevice corrosion.
- 316L (022Cr17Ni12Mo2) — Low-carbon version of 316 for enhanced weldability and corrosion performance.
- 321 (06Cr18Ni11Ti) — Titanium-stabilized grade for elevated-temperature service.
- S31803 / 2205 Duplex — High-strength duplex grade for aggressive chloride environments.
Mechanical Performance Requirements
In accordance with GB/T 14976, the minimum mechanical properties are specified as follows:
- Tensile Strength (Rm): ≥ 520 MPa (typical for 304/316 grades)
- Yield Strength (Rp0.2): ≥ 205 MPa
- Elongation (A): ≥ 40% (minimum 30% for some grades)
- Hardness: ≤ 217 HBW (unless otherwise specified)
- Impact Energy: ≥ 47 J at −29°C (where applicable)
Specifications
| Parameter | Specification |
|---|---|
| Governing Standard | GB/T 14976 — Seamless steel tubes for fluid transportation |
| Product Form | Seamless coil tube (盘管/Coiltube) | Outer Diameter (OD) | 6 mm – 219 mm (custom sizes available upon request) |
| Wall Thickness (WT) | 0.5 mm – 18 mm (tolerance ±10% or ±0.1 mm, whichever is greater) |
| Coil Length | Typically 50 m – 500 m per coil (negotiable) |
| Surface Finish | Pickled and Passivated (2B / BA available) |
| End Condition | Plain ends, beveled ends, or cut-to-length segments |
| Hydrostatic Test Pressure | P = 2S × T × D / (D − 2T), minimum 5 MPa (per GB/T 14976) |
| Non-Destructive Testing (NDT) | 100% Eddy Current (ECT) or Ultrasonic Testing (UT) per standard |
| Temperature Range | −196°C to +600°C (grade-dependent) |
| Pressure Rating | Up to 40 MPa (PN40) depending on OD and WT |
| Packaging | Export-grade coil packaging with moisture barrier and wooden crating |
Manufacturing Process
The production of seamless coil tubes at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage process:
- Hot Rolling / Extrusion / Piercing: Stainless steel billets are heated to forging temperature (1,100–1,200°C) and pierced to produce seamless hollow sections, ensuring metallurgical homogeneity and the absence of weld seams.
- Hot Finishing: The hot-rolled tube undergoes hot sizing to achieve preliminary dimensional accuracy.
- Acid Pickling and Descaling: Surface oxide scale is removed using a controlled acid bath (HNO₃/HF mixture) to reveal a clean, corrosion-resistant base surface.
- Cold Drawing / Cold Sizing: Tubes are drawn through precision dies to achieve final OD and wall thickness dimensions with tight tolerances and improved surface finish.
- Coiling: The finished tube is wound into a continuous coil on a precision coiler, ensuring uniform coil diameter and tight layer-to-layer contact.
- Hydrostatic Testing: Every coil is subjected to 100% hydrostatic pressure testing per GB/T 14976 to verify wall integrity and detect internal defects.
- Non-Destructive Testing (NDT): Full-length eddy current testing (ECT) and/or ultrasonic testing (UT) is performed to detect internal and surface discontinuities. Magnetic Particle Inspection (MPI) is applied where applicable.
- Final Passivation and Surface Treatment: A final passivation treatment ensures maximum passive film formation for optimal corrosion resistance.
- Dimensional Inspection and Certification: Final OD, WT, and straightness are verified; mill test certificates (MTC) are issued per EN 10204 3.1 or 3.2.
Applications
GB/T 14976 seamless coil tubes are widely employed across multiple industries:
- Chemical & Petrochemical Processing: Conveyance of corrosive fluids, acids, alkalis, and hydrocarbons in process piping systems.
- Oil & Gas Industry: Downhole tubing, surface piping, and instrumentation lines in upstream and midstream operations.
- Food & Beverage Processing: Sanitary-grade fluid lines for dairy, brewing, and pharmaceutical applications (304/316L grades).
- Power Generation: Boiler tubes, superheater tubes, and condensate lines in thermal and nuclear power plants.
- Marine & Offshore: Seawater handling systems, ballast lines, and offshore platform piping.
- Automotive & Aerospace: Exhaust systems, fuel lines, and hydraulic circuit tubing.
- Water Treatment & Desalination: High-pressure feed lines and membrane housing tubes in reverse osmosis (RO) systems.
Quality Certifications & Assurance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring traceability, compliance, and reliability:
- GB/T 14976 Compliance: All products are manufactured and tested in strict accordance with the Chinese National Standard for seamless fluid transportation tubes.
- ISO 9001:2015: Certified Quality Management System ensuring consistent product quality and customer satisfaction.
- ISO 3834: Quality requirements for welding of metallic materials (where welded assemblies are involved).
- Mill Test Certificate (MTC): Every shipment is accompanied by an EN 10204 Type 3.1 or 3.2 certificate documenting chemical composition, mechanical properties, and test results.
- Hydrostatic Test Report: 100% inline hydrostatic testing with pressure, hold time, and pass/fail data recorded per coil.
- NDT Report: Full-length ECT/UT inspection reports available upon request, confirming freedom from internal and surface defects.
- Third-Party Inspection: Independent verification by SGS, BV, or TÜV available for international buyers.
Unique Selling Points
- Seamless Construction: Eliminates the risk of weld-induced corrosion initiation, ensuring maximum pressure containment and service life.
- Continuous Coil Format: Reduces material waste, minimizes installation joints, and enables efficient downstream processing.
- Full Traceability: Heat-number traceability from raw material to finished product, supported by comprehensive MTC documentation.
- Customization Capability: Flexible OD, WT, surface finish, and coil length configurations tailored to project-specific requirements.
- 100% Testing Coverage: Every coil undergoes hydrostatic, NDT, and dimensional verification — no sampling-only protocols.
- Competitive Lead Times: Strategic inventory management and production planning ensure reliable delivery schedules for domestic and export markets.
Wenzhou Jixing Metal Materials Co., Ltd. — Delivering precision-engineered stainless steel seamless coil tubes that meet the highest standards of fluid transportation performance, backed by rigorous quality assurance and global compliance.