Stainless Steel Coil Tube for Cracking Furnace Radiation Sections
Product Overview
The Stainless Steel Coil Tube (Product No. 708) manufactured by Wenzhou Jixing Metal Materials Co., Ltd. is a precision-engineered rolled coil tube specifically designed for use in cracking furnace radiation sections (Radiant Coil Tubes). These coil tubes are critical components in petrochemical steam cracking processes, where hydrocarbon feedstocks are thermally decomposed to produce ethylene, propylene, and other olefinic monomers. The product is engineered to withstand extreme thermal cycling, high-temperature oxidation, and mechanical stresses associated with continuous bending operations in industrial furnaces.
This product line reflects advanced metallurgical engineering principles, incorporating lessons learned from Bending Analysis and Improvement Measures for Cracking Furnace Radiation Coil Tubes — a comprehensive technical study addressing deformation behavior, stress distribution, and structural integrity under operational conditions.
Material & Properties
The coil tubes are fabricated from high-performance austenitic and austenitic-ferritic stainless steel grades optimized for high-temperature service. Key material grades include:
- 310S (ASTM TP310H) — Chromium-Nickel austenitic stainless steel with superior hot strength and oxidation resistance up to 1150°C
- 309 (ASTM TP309) — Enhanced creep resistance for severe thermal environments
- 347 (ASTM TP347H) — Stabilized with niobium to prevent intergranular corrosion
- 321 (ASTM TP321H) — Titanium-stabilized austenitic grade for elevated temperature applications
Key Mechanical Properties (at 1000°C):
- Creep Strength: ≥ 15 MPa at 1000°C for 10,000 hours
- Oxidation Rate: ≤ 0.1 mg/dm²·h at 1000°C
- Thermal Expansion Coefficient: 17–19 × 10⁻⁶ /°C
- Thermal Conductivity: 30–35 W/m·K at 1000°C
- Yield Strength (RT): ≥ 205 MPa
- Tensile Strength (RT): ≥ 520 MPa
Specifications
| Parameter | Specification | Standard |
|---|---|---|
| Outer Diameter (OD) | Φ50.8 mm – Φ152.4 mm | ASTM A213 / ASME SA-213 |
| Wall Thickness | 1.5 mm – 6.0 mm | ASTM A213 |
| Bending Radius | R ≥ 3D (D = outer diameter) | Company Specification |
| Coil Length | Custom (typically 100 m – 500 m per coil) | Customer Requirement | Surface Finish | Pickled & Passivated (Ra ≤ 0.8 μm) | ASTM A403 |
| Temperature Range | -50°C to 1150°C | — |
| Pressure Rating | Up to 2.5 MPa (operating) | ASME B31.3 |
| End Condition | Plain end, beveled end, or thread-protected | Customer Specification |
| Heat Treatment | Solution Annealed at 1050–1150°C, followed by water quench | ASTM A213 |
| Coil Packing | Corrosion-inhibited, shrink-wrapped, palletized | ISO 15489 |
Manufacturing Process
The production of these coil tubes follows a rigorously controlled multi-stage manufacturing process:
- Slit Coil Preparation — Hot-rolled stainless steel strip is slit to precise width and annealed to achieve uniform grain structure and mechanical properties.
- Pipe Forming — The strip is rolled into a tubular blank using high-precision forming rolls with controlled reduction ratios to minimize residual stress.
- Welding — A continuous longitudinal seam is welded using TIG (Tungsten Inert Gas) or Plasma Arc Welding (PAW) with internal gas shielding to ensure weld integrity and minimize oxide inclusion.
- Heat Treatment — Welded tubes undergo solution annealing (1050–1150°C) followed by rapid quenching to dissolve carbides and restore full austenitic microstructure.
- Pickling & Passivation — Surface oxide scale is removed via acid pickling, followed by passivation treatment to form a protective chromium oxide film.
- Bending & Forming — Tubes are bent to specified radii using hydraulic or mechanical bending equipment. Bending analysis ensures controlled strain distribution, preventing cracking or ovalization. Improvement measures include preheating to 400–500°C during bending for grades requiring elevated-temperature forming, and the use of internal mandrels to maintain circularity.
- Coiling — Finished tube is coiled onto precision-wound reels with protective spacing to prevent surface damage.
- Quality Inspection — Each coil undergoes ultrasonic testing (UT), eddy current inspection (ECI), dimensional verification, and hydrostatic pressure testing.
Bending Analysis & Improvement Measures
A critical differentiator of this product is the integration of advanced bending deformation analysis into the manufacturing workflow. Key technical findings include:
- Strain Distribution: During bending, the outer fiber experiences tensile strain while the inner fiber undergoes compressive strain. Excessive strain can lead to cracking or wrinkling. Finite Element Analysis (FEA) is employed to predict strain levels and optimize bend radii.
- Residual Stress Management: Post-bending stress relief annealing at 550–650°C reduces residual stresses to below 100 MPa, enhancing long-term fatigue life.
- Material Workability Enhancement: Pre-heating during the bending process reduces the forming force requirement by 30–40% and extends the forming window, particularly for 310S grade which has limited cold-formability.
- Ovalization Control: The use of internal mandrels and multi-roll bending systems limits cross-sectional ovalization to ≤ 2% of the nominal diameter.
Applications
These stainless steel coil tubes are predominantly used in the following industrial applications:
- Petrochemical Steam Cracking Furnaces — Radiation sections (radiant coils) where temperatures reach 1100–1150°C
- Ethylene Cracker Furnaces — Transfer lines and radiant coils in naphtha or ethane cracking units
- Propylene Production Units — Propylene oxide and polypropylene precursor cracking processes
- Pyrolysis Gas Oil (PGO) Cracking — Heavy hydrocarbon feedstock decomposition
- Hydrogen Production — Steam-methane reforming (SMR) radiant tubes
- Ammonia Synthesis Plants — High-temperature shift converters
- Specialty Chemical Processing — Chlor-alkali and fluorine chemistry equipment
Quality Certifications & Standards Compliance
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring compliance with international standards:
- ISO 9001:2015 — Quality Management Systems
- ISO 3834-2 — Quality requirements for welding of metallic materials
- ASTM A213 / A269 — Seamless and welded austenitic stainless steel tubing
- ASME SA-213 — Boilers and pressure vessel tubing
- EN 10216-5 — European standard for welded stainless steel tubes
- JIS G3459 — Japanese Industrial Standard for austenitic stainless steel tubes
- API 5CT / API 5L — American Petroleum Institute standards (where applicable)
- Third-Party Inspection (TPI) — Available upon customer request (e.g., SGS, Bureau Veritas, DNV)
Unique Selling Points
- Engineering-Driven Design: Incorporates validated bending analysis and improvement protocols directly into the production process, reducing field failure rates.
- Extended Service Life: Optimized heat treatment and passivation extend operational life by 20–35% compared to industry averages.
- Custom Coil Configuration: Flexible coil lengths, bend radii, and end preparations tailored to specific furnace designs.
- Full Traceability: Heat-number traceability from raw material to finished product with complete mill test certificates (MTC).
- Technical Support: Dedicated metallurgical engineering team available for application-specific consultation and failure analysis.
Note: All specifications are subject to verification against applicable ASTM, ASME, and EN standards. Custom specifications may be developed in consultation with Wenzhou Jixing Metal Materials Co., Ltd. engineering personnel. Material certifications conform to EN 10204 Type 3.1.