Stainless Steel Coil Tube — Offline Batch Solution Treatment (Full-Length Furnace Annealing)
Product Overview
The Stainless Steel Coil Tube with Offline Batch Solution Treatment is a premium-grade austenitic stainless steel tube supplied in coil form, processed through a full-length offline solution annealing cycle. This advanced heat treatment methodology involves loading the entire continuous length of the coiled tube into a controlled-atmosphere furnace simultaneously, ensuring uniform thermal exposure across the full product length. This approach represents the highest standard of solution treatment available in the stainless steel tube industry, delivering superior mechanical homogeneity and complete elimination of cold-work-induced residual stresses.
Manufactured by Wenzhou Jixing Metal Materials Co., Ltd., this product combines the flexibility and material efficiency of coil-form tube with the metallurgical integrity achieved through batch offline solution treatment, making it ideal for demanding industrial and structural applications where property consistency is critical.
Material & Properties
Available Grades
- Austenitic Grades: 304 (UNS S30400/S30408), 304L (UNS S30403), 316 (UNS S31600/S31608), 316L (UNS S31603), 321 (UNS S32100/S32101), 310S (UNS S31008)
- Super-Austenitic Grades: 904L (UNS N08904), 2205 Duplex (UNS S32205) — upon request
Key Metallurgical Properties Post-Solution Treatment
- Complete Grain Homogenization: Full-length furnace exposure ensures uniform grain structure from coil start to coil end
- Zero Residual Stress: The batch solution treatment eliminates 100% of cold-work residual stresses introduced during cold drawing and forming operations
- Optimized Corrosion Resistance: Complete carbon solution into the austenitic matrix maximizes resistance to intergranular corrosion (IGC) and pitting
- Superior Formability: Fully annealed condition provides maximum ductility for downstream cold forming, bending, and machining
- Uniform Hardness Distribution: Typical hardness of 80–100 HRB across the entire coil length, with minimal variation (±5 HRB)
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Product Form | Coil Tube (Coiltube) | — |
| Outer Diameter (OD) | 6.0 mm – 108.0 mm | ASTM A554 / GB/T 12771 |
| Wall Thickness | 0.5 mm – 4.0 mm | ASTM A554 / GB/T 12771 |
| Coil Length | 50 m – 150 m (typical) | — |
| Coil Inner Diameter | 200 mm – 400 mm | — |
| Surface Finish | No. 1, 2B, BA, Mirror (upon request) | ASTM A473 |
| Solution Treatment Temperature | 1050°C – 1150°C (grade-dependent) | ASTM A554 §10.3 |
| Quenching Method | Water quench / Air quench (grade-dependent) | — |
| Residual Stress Level | ≤ 15 MPa (effectively zero) | — |
| Tensile Strength (Rm) | 520 – 700 MPa (grade-dependent) | ASTM A580 |
| Yield Strength (Rp0.2) | ≥ 205 MPa (minimum) | ASTM A580 |
| Elongation (A) | ≥ 40% | ASTM A580 |
| Applicable Standards | ASTM A554, ASTM A580, GB/T 12771, EN 10217-7, JIS G3459 | — |
Manufacturing Process
Process Flow
- Raw Material Procurement: Selection of certified stainless steel strip or seamless tube blanks from approved mills, with full chemical composition verification.
- Cold Forming / Drawing: Strip is cold-formed into tube shape or seamless tube is cold-drawn to final dimensions, introducing controlled cold work.
- Coiling: The formed tube is wound into coil form for efficient storage and downstream processing.
- Offline Batch Solution Treatment (Core Process):
- The entire coiled length of tube is loaded into a continuous atmosphere furnace in a single batch
- Furnace is heated to the specified solution temperature (1050–1150°C) under inert atmosphere (N₂ or argon) or vacuum to prevent oxidation
- Uniform temperature distribution is maintained across the full furnace volume via multi-zone temperature control (±5°C accuracy)
- Soaking time is held for a minimum of 1 hour per 25 mm of wall thickness to ensure complete carbon dissolution
- Rapid quenching (water or controlled air) follows immediately to retain the fully austenitic, solution-treated microstructure
- Pickling & Passivation: Post-quench surface cleaning removes any scale or oxide, followed by passivation to restore the chromium oxide protective layer.
- Quality Inspection: Comprehensive dimensional, mechanical, and metallurgical testing including hardness mapping along the coil length, tensile testing, intergranular corrosion testing (ASTM A262 Practice E), and spectrographic analysis.
- Packaging & Delivery: Coils are wrapped in protective film or paper, crated, and prepared for shipment with full mill test certificates.
Advantages of Offline Batch Solution Treatment
Why Offline Batch Processing is Superior to Continuous In-Line Annealing:
- Complete Residual Stress Elimination: Unlike continuous annealing lines which may leave localized stress concentrations at transition zones, the batch furnace ensures every point along the tube experiences identical thermal history
- Maximum Property Uniformity: The entire coil receives homogeneous treatment, resulting in the most uniform mechanical and corrosion properties achievable
- Flexibility for Custom Temperatures: Batch furnaces allow precise control of solution temperature for each specific grade without line reconfiguration
- Accommodates All Coil Lengths: No limitation on coil length or diameter, unlike continuous furnaces with fixed processing widths
Applications
- Food & Beverage Processing Equipment: Hygienic piping systems, heat exchangers, and CIP (Clean-In-Place) systems requiring maximum corrosion resistance and uniform wall integrity
- Chemical & Pharmaceutical Industry: Process piping, reactor components, and transfer lines handling aggressive media
- Automotive Industry: Exhaust system components, fuel lines, and structural tubing requiring stress-free material for precise forming
- Architecture & Construction: Structural railings, handrails, and decorative elements where consistent mechanical properties are essential for safety
- Medical Devices: Surgical instrument tubing, implant components, and medical equipment housings
- Energy Sector: Solar thermal absorber tubes, nuclear fuel cladding precursors, and power generation components
- Precision Engineering: Hydraulic cylinders, pneumatic components, and optical instrument housings
Quality Certifications
- ISO 9001:2015 — Quality Management System
- ISO 14001:2015 — Environmental Management System
- EN 10204 3.1 — Inspection Certificates (Mill Test Reports)
- EN 10204 3.2 — Inspection Certificates (Third-Party Inspection Available)
- ASTM A554 — Standard Specification for Cold-Drawn Austenitic Stainless Steel Tubing for Chemical and Similar Severe Service
- ASTM A580 — Standard Specification for Mechanical Properties of Cold-Formed Stainless Steel Bars, Rods, Wire, and Tubular Products
- GB/T 12771 — Chinese National Standard for Stainless Steel Tubes for Fluid Transport
- EN 10217-7 — European Standard for Tubes for Mechanical and Structural Purposes
- Third-Party Inspection: SGS, Bureau Veritas, TÜV Rheinland (available upon request)
Unique Selling Points
- 100% Residual Stress Elimination — Achieved through full-length batch furnace treatment, unmatched by continuous processing methods
- Industry-Leading Property Uniformity — Hardness variation of ≤ ±5 HRB across the entire coil length
- Maximum Corrosion Performance — Complete carbon solution ensures optimal resistance to intergranular and pitting corrosion
- Superior Downstream Formability — Fully annealed, stress-free condition enables complex cold forming without cracking
- Flexible Customization — Wide range of grades, dimensions, surface finishes, and coil configurations available