ASTM E112 Grade 5+ Fine-Grain Stainless Steel Coil Tube
Product Overview
The Wenzhou Jixing Fine-Grain Stainless Steel Coil Tube is a precision-engineered coil (盘管) product manufactured with rigorous microstructural control to achieve an ASTM E112 grain size rating of Grade 5 or finer. This advanced metallurgical specification ensures superior mechanical performance, enhanced fatigue resistance, and uniform corrosion protection — making it a premium choice for demanding industrial applications where long-term reliability and structural integrity are paramount.
Wenzhou Jixing Metal Materials Co., Ltd leverages state-of-the-art metallurgical processing and quality control systems to deliver coil tubes with consistently fine-grained microstructures. The controlled grain architecture is not merely a specification checkbox — it is the foundation upon which the tube's entire performance envelope is built.
Material & Metallurgical Properties
The defining characteristic of this product is its tightly controlled grain size, evaluated and certified in accordance with ASTM E112. The grain size rating is maintained at Grade 5 or finer (≥ G5), meaning the average grain diameter is approximately 63 micrometers or smaller. This fine-grained structure delivers measurable and significant advantages over standard-grade coil tubes:
- Enhanced Yield and Tensile Strength: According to the Hall–Petch relationship, finer grains increase the number of grain boundaries, which act as barriers to dislocation motion. This directly translates to higher yield strength and tensile strength at equivalent compositions.
- Superior Ductility and Impact Toughness: Fine-grained microstructures maintain excellent elongation and reduce the ductile-to-brittle transition temperature, ensuring reliable performance in low-temperature and cyclic-loading environments.
- Extended Fatigue Life: The refined grain structure significantly improves resistance to low-cycle and high-cycle fatigue failure, making these tubes ideal for applications involving repeated thermal or mechanical cycling.
- Uniform Corrosion Resistance: A homogeneous fine-grain distribution ensures consistent chromium and alloy element segregation at the microstructural level, promoting uniform passive film formation and reducing the risk of localized intergranular or pitting corrosion.
- Improved Formability: Fine grains reduce anisotropy and promote more uniform deformation during cold working, enabling tighter coil diameters and more complex geometries without cracking or thinning.
Specifications
| Parameter | Specification | Test Standard |
|---|---|---|
| Product Type | Stainless Steel Coil Tube (盘管) | — |
| Grain Size Rating | ≥ ASTM E112 Grade 5 (G5 or finer) | ASTM E112 |
| Average Grain Diameter | ≤ 63 μm | ASTM E112 |
| Microstructural Homogeneity | Uniform grain distribution, no abnormal grain growth | ASTM E112 / Internal QC |
| Available Grades | 304, 304L, 316, 316L, 321, 310S, 904L, 2205 (Duplex) | ASTM / EN / GB |
| Outer Diameter Range | 3.0 mm – 50.8 mm (customizable) | — |
| Wall Thickness Range | 0.3 mm – 3.0 mm (customizable) | — |
| Coil Diameter | Standard and custom coil diameters available | — |
| Surface Finish | Pickled & Passivated (P&P), BA, Mill Finish | ASTM A967 |
| Manufacturing Method | Seamless (Piercing / Hot Rolled / Cold Drawn) | ASTM A213 / A269 |
| Solution Annealing | 1050°C – 1150°C, water quench | Internal Process Spec |
| Intergranular Corrosion | ASTM A262 Practice E / Practice A | ASTM A262 |
| Product Standard | ASTM A213, ASTM A269, EN 10216-5, GB/T 12771 | — |
Manufacturing Process
Achieving a consistent ASTM E112 Grade 5+ grain structure requires precise control at every stage of the manufacturing pipeline. Wenzhou Jixing employs a multi-stage process to ensure metallurgical quality:
- Raw Material Selection: High-purity stainless steel billets and ingots are sourced from certified suppliers with strict chemical composition control. Residual element levels (S, P, N, O) are minimized to prevent unwanted grain boundary segregation and abnormal grain growth.
- Piercing & Hot Rolling: Billets are heated to precise temperatures and pierced into seamless hollow bars. Hot rolling parameters — including rolling temperature, reduction ratio, and cooling rate — are carefully optimized to establish a favorable starting microstructure.
- Intermediate Annealing: Strategic annealing cycles are applied between cold working passes to relieve residual stresses and promote controlled recrystallization, preventing grain coarsening while maintaining formability.
- Cold Drawing & Coiling: Tubes are cold-drawn to final dimensions and wound into coils. The controlled cold work introduces beneficial dislocation density, which aids in achieving fine recrystallized grains during final annealing.
- Final Solution Annealing: Tubes are heated to 1050°C–1150°C and rapidly quenched. This step dissolves carbides, homogenizes the microstructure, and establishes the target fine-grained austenitic (or duplex) structure. The annealing temperature and cooling rate are precisely calibrated to achieve G5 or finer grain ratings.
- Pickling & Passivation: A pickling and passivation treatment removes surface scale and contaminants, forming a uniform chromium-rich passive oxide layer for enhanced corrosion resistance.
- Microstructural Verification: Each production lot undergoes grain size evaluation per ASTM E112 using optical microscopy and/or electron backscatter diffraction (EBSD). Only lots meeting or exceeding the G5 specification are released for shipment.
Applications
The superior mechanical and corrosion performance of the fine-grain coil tube makes it suitable for a wide range of demanding applications:
- Heat Exchangers & Boilers: Coil tubes with fine grains withstand repeated thermal cycling and resist stress corrosion cracking in high-temperature service environments.
- Automotive Exhaust Systems: Enhanced fatigue life and high-temperature strength make these tubes ideal for catalytic converter substrates and exhaust manifold components.
- Petrochemical & Refinery Equipment: Uniform corrosion resistance and mechanical strength ensure reliable performance in aggressive chemical processing environments.
- Food & Pharmaceutical Processing: Hygienic surface finish and resistance to intergranular corrosion meet stringent sanitary requirements (FDA / 3-A compliant).
- Medical Device Manufacturing: Fine-grain 316L coil tubes are used in implantable devices, surgical instruments, and medical tubing where biocompatibility and fatigue resistance are critical.
- Marine & Offshore Engineering: Duplex and super-austenitic grade coil tubes with controlled grain structure offer outstanding resistance to chloride pitting and crevice corrosion.
- Power Generation: Steam generator tubes and superheater coils benefit from the extended fatigue life and thermal stability provided by fine-grain microstructures.
- Aerospace Components: Precision-formed coil tubes used in fuel lines, hydraulic systems, and structural components where weight optimization and fatigue performance are essential.
Quality Certifications & Assurance
Wenzhou Jixing Metal Materials Co., Ltd maintains a comprehensive quality management system and holds the following certifications to ensure product excellence:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001 — Environmental Management System Certification
- ISO 45001 — Occupational Health & Safety Management System
- EN 10204 3.1 — Third-party certified material test certificates available upon request
- ASTM E112 Grain Size Certification — Every production lot is accompanied by documented grain size evaluation results
- NACE MR0175 / ISO 15156 — Available for sour service applications (H₂S environments)
- PED 2014/68/EU — Pressure Equipment Directive compliance for European market
- NSF / FDA — Compliance for food-grade and medical applications
Wenzhou Jixing Commitment: Every coil tube produced undergoes rigorous metallurgical verification, including ASTM E112 grain size analysis, mechanical testing (tensile, hardness, impact), and corrosion resistance evaluation (ASTM A262, ASTM G48). Full traceability from raw material to finished product is maintained through batch-coded documentation and digital quality records.
Unique Selling Points
- Guaranteed Fine Grain Structure: ASTM E112 Grade 5+ certification on every lot — not a nominal specification, but a verified and documented metallurgical guarantee.
- Superior Fatigue Performance: Fine-grain microstructures deliver 20–40% improvement in fatigue life compared to standard grain-size coil tubes, reducing maintenance intervals and total cost of ownership.
- Uniform Corrosion Resistance: Homogeneous grain distribution ensures consistent passive film formation across the entire tube surface, eliminating weak points for localized attack.
- Enhanced Formability: Fine grains reduce deformation anisotropy, enabling more complex forming operations and tighter tolerances during downstream fabrication.
- Full Traceability: Complete documentation from mill heat number through final inspection, supporting regulatory compliance and quality audits.
- Customization Capability: Flexible sizing, grading, and finishing options to meet specific application requirements, supported by experienced technical engineering staff.