Stainless Steel Seamless Coil Tube — GB/T 14976 Fluid Transport Specification
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd (Product Code No. 70), this seamless stainless steel coil tube (Coiltube) is produced in strict accordance with the Chinese National Standard GB/T 14976 — the general technical specification for seamless steel tubes intended for fluid transport. This standard governs the manufacturing quality, mechanical performance, and testing protocols for seamless tubes used in conveying fluids such as water, gas, oil, and various industrial process media under moderate pressure and temperature conditions.
Product Overview
The Stainless Steel Seamless Coil Tube is a precision-engineered tubular product supplied in coiled form, offering superior flexibility in downstream processing compared to straight-length seamless tubes. The coil configuration enables efficient storage, transportation, and on-site forming operations, making it ideal for applications requiring cutting, bending, and welding into custom geometries without the need for additional straightening processes.
Designed under the fluid transport category of GB/T 14976, this product is specifically engineered for the reliable conveyance of liquids and gases in industrial, municipal, and commercial systems. The seamless construction eliminates longitudinal weld seams, providing uniform wall integrity and enhanced resistance to internal pressure and corrosion — critical advantages in demanding fluid transport environments.
Unique Selling Points
- Seamless Construction: Absence of longitudinal weld seams ensures homogeneous material continuity, superior pressure resistance, and improved fatigue life under cyclic loading conditions.
- Coil Form Supply: Delivered in continuous coil configuration for maximum material utilization, reduced cutting waste, and simplified handling logistics.
- GB/T 14976 Compliance: Fully certified against the Chinese national standard for seamless fluid transport tubes, ensuring traceability and regulatory acceptance across domestic and international markets.
- Comprehensive Quality Assurance: Every production batch undergoes hydrostatic pressure testing, non-destructive testing (NDT), and mechanical property verification to guarantee dimensional accuracy and metallurgical integrity.
Material & Properties
The Seamless Coil Tube is available in a range of austenitic and ferritic stainless steel grades conforming to GB/T 14976 material specifications. The primary grades include:
- 06Cr19Ni10 (304): General-purpose austenitic stainless steel with excellent corrosion resistance, formability, and weldability.
- 022Cr19Ni10 (304L): Low-carbon variant of 304 offering enhanced resistance to sensitization during welding.
- 06Cr17Ni12Mo2 (316): Molybdenum-alloyed austenitic grade providing superior resistance to pitting and crevice corrosion in chloride environments.
- 022Cr17Ni12Mo2 (316L): Low-carbon 316 with improved weldability and post-weld corrosion performance.
- 06Cr13 (410) / 12Cr13 (420): Martensitic grades for applications requiring higher hardness and wear resistance.
Mechanical Properties (Typical Values per GB/T 14976)
- Tensile Strength (Rm): ≥ 520 MPa (austenitic grades)
- Yield Strength (Rp0.2): ≥ 205 MPa (austenitic grades)
- Elongation (A): ≥ 40% (as-delivered condition)
- Hardness (HBW): ≤ 217 (annealed condition)
- Operating Temperature Range: −196 °C to +870 °C (grade-dependent)
Specifications
| Parameter | Specification |
|---|---|
| Standard | GB/T 14976 — Seamless Steel Tubes for Fluid Transport |
| Product Type | Stainless Steel Seamless Coil Tube (盘管 / Coiltube) |
| Manufacturing Method | Hot-rolled (HR) / Cold-drawn (CD) / Cold-rolled (CR) seamless |
| Outer Diameter (OD) | 6 mm – 219 mm (custom sizes available upon request) |
| Wall Thickness | 0.5 mm – 12 mm (tolerance per GB/T 14976 dimensional requirements) |
| Coil Weight | Typically 1 – 5 tons per coil (adjustable per customer requirement) |
| Surface Finish | Pickled & Passivated (P&P) / Polished / 2B Finish |
| End Condition | Plain end / Beveled end / Custom-cut per coil length |
| Material Grades | 304, 304L, 316, 316L, 310S, 321, 410, 420, 430 and others |
| Hydrostatic Test | 100% pressure-tested per GB/T 14976 requirements |
| Non-Destructive Testing (NDT) | Electromagnetic (ET) / Ultrasonic (UT) inspection on all coils |
| Heat Treatment | Solution annealing (1050 – 1150 °C) followed by rapid cooling |
| Packaging | Coiled, wrapped in moisture-proof film, secured with steel strapping |
Manufacturing Process
The production of Stainless Steel Seamless Coil Tubes adheres to a rigorously controlled multi-stage manufacturing workflow, ensuring compliance with every clause of GB/T 14976:
- Billet Preparation: High-purity stainless steel billets are sourced from certified mills and subjected to incoming inspection for chemical composition and surface quality.
- Hot Piercing (Pilot Milling): Heated billets are pierced through a pilot mill to produce seamless hollow tubes (tubes), establishing the initial bore geometry.
- Hot Rolling / Elongation: The pierced tubes undergo hot rolling or elongation on a rolling mill to achieve the target outer diameter and wall thickness within specified tolerances.
- Heat Treatment (Solution Annealing): Tubes are heated to 1050–1150 °C in a controlled-atmosphere furnace followed by rapid quenching (air or water) to dissolve carbides, homogenize microstructure, and restore full austenitic corrosion resistance.
- Pickling & Passivation: Surface scale and oxidation are removed via acid pickling, followed by passivation treatment to form a stable chromium oxide protective layer.
- Cold Drawing / Cold Rolling (if applicable): For tighter dimensional tolerances and improved surface finish, tubes may undergo cold drawing or cold rolling to achieve final OD, wall thickness, and mechanical properties.
- Coiling: Finished tubes are coiled onto a coiling reel at controlled tension to produce continuous coil lengths suitable for downstream processing.
- Quality Inspection: Every coil undergoes mandatory hydrostatic pressure testing, electromagnetic or ultrasonic non-destructive testing (NDT), dimensional verification, and mechanical property sampling.
- Packaging & Dispatch: Coils are wrapped in protective moisture-proof film, secured with steel strapping, and labeled with full traceability information including heat number, grade, dimensions, and test certificates.
Applications
The Seamless Stainless Steel Coil Tube conforming to GB/T 14976 serves a broad spectrum of fluid transport applications across multiple industries:
- Petrochemical & Oil/Gas Industry: Conveyance of crude oil, refined petroleum products, natural gas, and process chemicals under moderate pressure conditions.
- Food & Beverage Processing: Transfer of potable water, dairy products, beer, and food-grade fluids requiring hygienic, corrosion-resistant piping systems.
- Pharmaceutical Manufacturing: Fluid distribution in drug production lines, cleanroom environments, and sanitary processing equipment.
- Municipal Water Supply & Wastewater: Distribution of potable water and conveyance of treated effluent in urban infrastructure networks.
- Power Generation: Feedwater lines, condenser tubes, and auxiliary fluid circuits in thermal and nuclear power plants.
- Automotive & Machinery: Hydraulic lines, fuel delivery systems, and exhaust components requiring durable stainless steel tubing.
- Heat Exchangers & Boilers: Fabrication of tube bundles, shell-and-tube heat exchangers, and boiler components requiring seamless integrity.
- Structural & Architectural Applications: Decorative railings, furniture components, and structural framing in marine and coastal environments.
Quality Certifications & Testing Protocols
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system ensuring that every batch of Seamless Stainless Steel Coil Tube meets or exceeds the requirements of GB/T 14976. The following testing and certification protocols are applied:
Hydrostatic Pressure Testing
All coils are subjected to 100% hydrostatic pressure testing in accordance with GB/T 14976 specifications. The test pressure is calculated based on the material grade, tube dimensions, and a safety factor, ensuring that every section of the tube can withstand internal fluid pressure without leakage or deformation. This is the primary integrity verification method for seamless fluid transport tubes.
Non-Destructive Testing (NDT)
- Electromagnetic Testing (ET): Applied to detect surface and near-surface defects such as cracks, laps, and inclusions along the full coil length.
- Ultrasonic Testing (UT): Employed for volumetric inspection to identify internal discontinuities, wall thickness variations, and subsurface anomalies.
Mechanical Property Verification
Sample coupons extracted from each heat number are tested for tensile strength, yield strength, elongation, and hardness to confirm compliance with the mechanical performance requirements specified in GB/T 14976 for the respective material grade.
Chemical Composition Analysis
Spectrometric analysis (OES) and wet chemical testing are performed on each production heat to verify that the chemical composition falls within the allowable ranges defined by the applicable material grade specification.
Certification & Traceability
- Mill Test Certificate (MTC): Issued for every shipment, providing full traceability from raw material heat number through manufacturing and testing records.
- GB/T 14976 Compliance Declaration: Formal certification of conformity with the Chinese National Standard for seamless fluid transport tubes.
- ISO 9001 Quality Management System: The manufacturing facility operates under an ISO 9001-certified quality management framework.
- Batch Traceability: Each coil is marked with a unique identification code linking it to its production heat, inspection records, and test results.
Note: All specifications, dimensions, and material grades are subject to customer-specific requirements and may be customized upon request. Wenzhou Jixing Metal Materials Co., Ltd provides full technical support for project-specific applications and offers sample testing and pre-shipment inspection services to ensure customer satisfaction and project compliance.