Full-Length Offline Solution Annealed Stainless Steel Coil Tube
Product Overview
This premium-grade stainless steel coil tube is distinguished by its offline batch solution annealing process, in which the entire continuous length of tubing is loaded into a high-temperature furnace for uniform heat treatment. Unlike conventional segment-based or induction annealing methods, this whole-tube furnace treatment eliminates 100% of residual stresses accumulated during cold forming and drawing, delivering the most homogeneous mechanical properties, corrosion resistance, and dimensional consistency along the full tube length. Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product represents the highest tier of solution-annealed coil tubing available in the market.
Material & Properties
The coil tube is fabricated from austenitic stainless steel grades including 304, 304L, 316, 316L, 321, 310S, and custom alloy specifications. Following the offline batch solution annealing process, the material achieves optimal microstructural homogeneity with fully dissolved carbides in solid solution, ensuring superior resistance to intergranular corrosion and stress corrosion cracking.
- Mechanical Properties: Fully uniform tensile strength, yield strength, and elongation values across the entire tube length with zero variation between heat-treated zones.
- Corrosion Resistance: Maximum pitting and crevice corrosion resistance due to complete carbide precipitation prevention through uniform solution treatment.
- Microstructure: Fully austenitic, stress-free grain structure with no martensitic transformation or strain-induced hardening.
- Surface Condition: Consistent surface finish (2B, BA, or polished) maintained throughout the annealing cycle without localized discoloration.
Specifications
| Parameter | Specification |
|---|---|
| Material Grades | 304, 304L, 316, 316L, 321, 310S, 904L, Custom Alloys |
| Outer Diameter | 3.0 – 108.0 mm (1/8" – 4") |
| Wall Thickness | 0.3 – 6.0 mm (0.012" – 0.236") |
| Tube Length | Coil wound, typically 1,000 – 5,000 m per coil |
| Coil Inner Diameter | 300 – 500 mm (12" – 20") |
| Surface Finish | 2B, BA (Bright Annealed), Polished (#4, #8) |
| Tolerance (OD) | ±0.05 mm to ±0.10 mm depending on OD range |
| Tolerance (WT) | ±0.02 mm to ±0.05 mm depending on WT range |
| Solution Annealing Temperature | 1,010 – 1,150 °C (1,850 – 2,102 °F), grade-dependent |
| Standard | ASTM A213/A269, ASME SA-213/SA-269, EN 10216-5, GB/T 14976 |
Manufacturing Process
The offline batch solution annealing process represents a fundamentally superior approach compared to inline or segment-based annealing methods. The manufacturing sequence is as follows:
- Raw Material Selection: Virgin stainless steel wire rod or seamless tube blanks sourced from certified mills, subjected to incoming material inspection (chemical composition analysis, mechanical testing).
- Tube Forming: Cold-drawn or cold-rolled forming of the coil tube to the target outer diameter and wall thickness specifications. This stage introduces residual stresses into the material.
- Coil Winding: The formed continuous tube is wound into a large coil of the required diameter and length, ready for batch heat treatment.
- Offline Batch Solution Annealing (Key Step): The entire coil tube assembly is carefully loaded into a large-capacity controlled-atmosphere furnace. The furnace is heated to the grade-specific solution temperature (typically 1,010–1,150 °C) and held for a calibrated soak time to ensure complete dissolution of carbide precipitates throughout the entire tube cross-section and length. The coil is then rapidly quenched (water or air quench depending on grade) to lock the microstructure in the fully austenitic, stress-free state.
- Pickling & Passivation: Post-annealing surface cleaning to remove any oxide scale, followed by passivation treatment to restore the full chromium oxide protective layer.
- Quality Inspection: Comprehensive testing including hardness measurement, tensile testing, corrosion testing (ASTM A262), dimensional verification, and visual/surface inspection.
Why Offline Batch Solution Annealing Matters: When the entire tube length is treated simultaneously in a single furnace cycle, there is no thermal gradient along the tube axis. This eliminates the property variations inherent in segment-by-segment annealing methods, where overlapping treatment zones or transition areas can create weak points. The result is a tube with truly uniform properties from coil end to coil end — critical for applications where mechanical reliability and corrosion resistance must be guaranteed at every point along the tube.
Applications
Due to the exceptional uniformity and stress-free condition achieved through offline batch solution annealing, this coil tube is specified for the most demanding applications:
- Heat Exchangers & Condensers: Shell-and-tube heat exchangers, air coolers, and condensers in petrochemical, power generation, and HVAC systems where uniform wall integrity is critical.
- Chemical Processing: Reactor internals, piping systems, and heat transfer surfaces in aggressive chemical environments requiring maximum corrosion resistance.
- Pharmaceutical & Food Processing: Sanitary tubing, CIP/SIP systems, and hygienic heat exchangers where surface uniformity and corrosion resistance are paramount.
- Nuclear & Energy: Instrument tubing and control systems requiring certified, traceable, and uniform material properties.
- Automotive & Aerospace: Precision tubing for fuel systems, hydraulic lines, and structural components where stress-free material eliminates risk of stress corrosion cracking.
- Medical Devices: Tubing for medical equipment and implant-adjacent components requiring biocompatible, uniformly processed stainless steel.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains rigorous quality management systems and holds the following certifications:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001 — Environmental Management System Certification
- ISO 45001 — Occupational Health & Safety Management System Certification
- PED (CE) — Pressure Equipment Directive Compliance for EU Market
- NACE MR0175 — Compliance for sour service applications (where applicable)
- Mill Test Certificates (MTC) — Full EN 10204 3.1 or 3.2 certificates provided with every shipment
Unique Selling Points
- 100% Residual Stress Elimination: The offline batch solution annealing process guarantees complete removal of all cold-work-induced residual stresses — a level of stress relief unattainable with inline or segment annealing methods.
- Maximum Property Uniformity: Zero variation in mechanical properties along the tube length, ensuring reliable performance at every point, not just at sampled test locations.
- Superior Corrosion Resistance: Complete carbide dissolution in a single uniform thermal cycle maximizes resistance to sensitization, intergranular corrosion, and stress corrosion cracking.
- Full Traceability: Each coil is individually heat-treated and documented, enabling complete batch traceability from raw material through final heat treatment.
- Consistent Surface Quality: Uniform annealing eliminates localized discoloration, surface embrittlement, or differential oxidation that can occur with segment-based methods.
- Custom Grade & Dimension Flexibility: Available in a wide range of stainless steel grades, diameters, and wall thicknesses to meet specific application requirements.