Stainless Steel Coil Tube with Advanced Ultrasonic Testing (UT) Quality Assurance
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. is a leading manufacturer and supplier of high-grade stainless steel coil tubes (coiltube), engineered for demanding industrial applications requiring superior mechanical integrity and corrosion resistance. Our coil tube products are supplied in continuous coil form, offering significant advantages in fabrication efficiency, material utilization, and cost-effectiveness compared to straight-length tube deliveries.
The hallmark of our product line is the rigorous implementation of Pulse Reflection Ultrasonic Testing (UT) as a primary quality assurance method. This advanced non-destructive testing (NDT) technique enables comprehensive verification of wall thickness uniformity and detection of internal deep-layer defects — including laminations, cracks, inclusions, and voids — throughout the entire cross-section of the tube. This makes our coil tubes the preferred choice for thick-wall and seamless tube applications where internal quality verification is critical to service life and safety.
Material & Properties
Available Grades
- 304 / 304L (UNS S30400 / S30403): General-purpose austenitic stainless steel with excellent corrosion resistance, formability, and weldability.
- 316 / 316L (UNS S31600 / S31603): Molybdenum-enhanced austenitic grade offering superior resistance to chlorides, acids, and pitting corrosion.
- 321 (UNS S32100): Titanium-stabilized austenitic grade resistant to intergranular corrosion, suitable for elevated-temperature service.
- 310S (UNS S31008): High-temperature austenitic grade with exceptional oxidation resistance up to 1150°C (2092°F).
- 304H / 316H: High-carbon austenitic grades designed for high-temperature creep resistance in power generation and petrochemical applications.
- 2205 Duplex (UNS S31803): High-strength duplex stainless steel with superior resistance to chloride stress corrosion cracking.
- Custom grades available upon request including 904L, 2507 Super Duplex, 316Ti, and Alloy 6.
Key Mechanical Properties (Typical for 304 Grade)
- Tensile Strength: ≥ 520 MPa (75,400 psi)
- Yield Strength: ≥ 205 MPa (29,700 psi)
- Elongation: ≥ 40% (ASTM A270)
- Hardness: ≤ 220 HB (annealed condition)
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | 6.0 mm – 219.1 mm (0.24 in – 8.63 in) | ASTM A269 / A270 / A312 |
| Wall Thickness | 0.5 mm – 12.7 mm (0.020 in – 0.500 in) | ASTM A269 / A270 |
| Coil Length | Custom, typically 50 m – 200 m (164 ft – 656 ft) | Per customer requirement |
| Coil Inner Diameter | 152 mm – 305 mm (6 in – 12 in) | Custom available |
| Tolerance – OD | ± 0.05 mm – ± 0.5 mm (± 0.002 in – ± 0.020 in) | ASTM A213 / ASME B16.19 |
| Tolerance – Wall Thickness | ± 10% (minimum ± 0.05 mm / ± 0.002 in) | ASTM A269 |
| Surface Finish | Pickled & Passivated (P&P), No. 1, 2B, or custom | ASTM A478 |
| Heat Treatment | Annealed (Solution Annealed) | ASTM A478 |
| End Condition | Plain ends, beveled ends, or custom | Per customer specification |
| Delivery Condition | Coiled (continuous coil) | — |
| NDT Method | Pulse Reflection Ultrasonic Testing (UT) | ASTM E164 / E127 / EN 10229 |
Manufacturing Process
Production Workflow
- Raw Material Selection: Only certified stainless steel billets or strip from approved mills are procured, with full mill test certificates (MTC) verified against chemical composition requirements per ASTM or EN standards.
- Coil Forming / Cold Rolling: High-precision cold rolling mills form the stainless steel strip into seamless coil tubes with controlled dimensional tolerances and uniform wall thickness.
- Piercing & Stretch Reducing (for seamless coil): Hot-rolled seamless tubes undergo piercing and stretch-reducing processes to achieve precise OD and wall thickness in coil configuration.
- Solution Annealing: Tubes are annealed in protective atmosphere furnaces at temperatures of 1050°C – 1150°C (1922°F – 2092°F) followed by controlled cooling to restore full austenitic microstructure and maximum ductility.
- Pickling & Passivation: Surface oxides and scale are removed through controlled acid pickling, followed by passivation treatment to establish a protective chromium oxide film, ensuring optimal corrosion resistance.
- Dimensional Inspection: Each coil undergoes automated laser and caliper-based dimensional measurement to verify OD, wall thickness, and straightness tolerances.
- Ultrasonic Testing (UT) – Pulse Reflection Method: The coil is passed through automated ultrasonic testing systems operating on the pulse reflection principle. High-frequency ultrasonic transducers emit pulses into the tube wall; reflected signals from internal interfaces and defects are analyzed to measure wall thickness and detect volumetric flaws at any depth.
- Final Inspection & Packing: Coils are inspected, labeled with heat numbers and traceability information, and packed in protective wooden crates or steel bands for shipment.
Ultrasonic Testing (UT) – Pulse Reflection Method: Our Quality Differentiator
"The Pulse Reflection Ultrasonic Testing method is the gold standard for internal quality verification of thick-wall and seamless stainless steel tubes, providing non-destructive, 100% coverage inspection capability unmatched by any other NDT technique."
Technical Capabilities of Our UT System
- Wall Thickness Measurement: Accurate measurement of wall thickness at any point along the coil length, with resolution down to 0.05 mm (0.002 in), ensuring compliance with tight tolerance specifications.
- Deep-Internal Defect Detection: Detection of volumetric defects — including center-line segregation, laminations, cracks, inclusions, and voids — at any depth within the tube wall, with sensitivity to defect sizes as small as 0.5 mm (0.020 in).
- 100% Inline Inspection: Every meter of coil tube is tested, not merely sampled, providing comprehensive quality assurance and complete traceability.
- Full-Circumference Coverage: Multi-element transducer arrays ensure 360° coverage around the tube circumference during continuous coil movement.
- Automatic Data Logging: All UT results are digitally recorded, archived, and available for customer review, enabling full traceability from raw material to finished product.
- Compliance with International Standards: Testing procedures conform to ASTM E164, ASTM E127, EN 10229, and ISO 22539.
Why Pulse Reflection UT for Thick-Wall & Seamless Tubes?
For thick-wall tubes (wall thickness > 3 mm / 0.118 in) and seamless tube products, the pulse reflection ultrasonic method is the preferred and industry-standard NDT technique for internal quality verification. Unlike eddy current testing, which is limited to surface and near-surface defect detection, the pulse reflection UT method penetrates the entire wall thickness, providing:
- Unmatched sensitivity to internal volumetric defects at any depth
- Precise quantitative wall thickness measurement without contact
- No consumables or coupling agent requirements for contact UT probes
- Repeatability and objectivity through automated digital signal processing
- Acceptance/rejection criteria based on quantifiable defect amplitude and size thresholds
Applications
Industries Served
- Chemical & Petrochemical Processing: Reactor tubes, heat exchanger tubes, process piping, and transfer lines requiring resistance to aggressive chemicals and high pressures.
- Oil & Gas: Downhole tubing, wellhead assemblies, subsea piping, and offshore platform structural tubing.
- Power Generation: Boiler tubes, superheater tubes, condenser tubes, and nuclear-grade piping components.
- Food & Pharmaceutical: Sanitary process tubing, CIP/SIP-compatible piping, and hygienic heat exchangers.
- Marine & Offshore: Ballast water system tubing, seawater cooling circuits, and desalination plant components.
- Aerospace: Hydraulic tubing, fuel system lines, and structural tubing requiring certified internal quality.
- Medical Devices: Endoscope tubing, implant-grade tubing, and surgical instrument components.
- Automotive: Exhaust system tubing, fuel lines, and emissions control components.
- Construction & Architecture: Decorative railings, structural bracing, and architectural tubing.
Key Application Advantages of Coil Tube Delivery
- Eliminates butt-weld joints during fabrication, reducing leak paths and improving structural integrity
- Significantly reduces fabrication labor time and material waste (up to 30% savings)
- Enables automated tube processing through coil-fed tube cutting, bending, and forming machines
- Optimized for high-volume production runs and repetitive manufacturing operations
Quality Certifications & Compliance
Company Certifications
- ISO 9001:2015 – Quality Management System
- ISO 14001 – Environmental Management System
- ISO 45001 – Occupational Health & Safety Management System
- ISO 3834-2 – Welding Quality Requirements
- NACE SP0169 / NACE SP0287 – Corrosion Engineering Certification
Product Standards Compliance
- ASTM A269: Standard Specification for Seamless and Wrought Stainless Steel Tube, Pipe, and Fittings for Chemical and Allied Applications
- ASTM A270: Standard Specification for Cold-Rolled or Cold-Drawn Seamless and Wrought Austenitic Stainless Steel Tubes for Chemical and Allied Purposes
- ASTM A312: Standard Specification for Austenitic Stainless Steel Seamless, Welded, and Heavy-Walled Collected-Grain Tubes for High-temperature Service
- EN 10216-5: Heat-Exchange Tubes and Condensers — Seamless Tubes of Austenitic and Austenitic-Ferritic (Duplex) Steels
- ASME B16.19: Dimensions and Tolerances for Stainless Steel Tubing
- ASME BPV Code: Section I, Section VIII Div. 1 & 2 (for pressure vessel applications)
- EN 10229: Non-destructive testing of steel products — Ultrasonic testing of seamless tubes
NDT Certification
All ultrasonic testing personnel at Wenzhou Jixing Metal Materials Co., Ltd. are certified to ASNT Level II (minimum) or SNT-TC-1A Level II standards, with regular recertification and proficiency testing to maintain compliance with ASTM E164 and EN 10229 requirements. UT equipment is calibrated using certified reference blocks (V1, V2, V3 per EN 10229-2) prior to each production run.
Unique Selling Points
- 100% UT Inspection with Pulse Reflection Method: Every coil tube undergoes full-length, full-circumference ultrasonic inspection — not sampling — providing absolute confidence in internal quality.
- Thick-Wall Tube Expertise: Specialized UT capabilities for wall thicknesses up to 12.7 mm (0.500 in), making our products ideal for high-pressure and critical-service applications.
- Seamless Internal Quality Assurance: The pulse reflection UT method is the definitive technique for verifying the internal integrity of seamless tubes, eliminating concerns about weld-related defects entirely.
- Digital Traceability: Complete digital UT data records for every coil, enabling post-delivery quality review and regulatory audit compliance.
- Custom Coil Configuration: Flexible coil lengths, diameters, and delivery formats tailored to customer fabrication requirements.
- Multi-Grade Capability: Broad inventory of stainless steel grades from standard austenitic to super duplex and specialty alloys.
- Cost-Effective Coil Delivery: Up to 30% material savings and significant fabrication time reduction compared to straight-length tube.
Ordering Information
Wenzhou Jixing Metal Materials Co., Ltd. welcomes inquiries for custom specifications. Please provide the following details for a