1Cr5Mo Radiant Coil Tube — Heat-Resistant Steel for Tube Furnace Applications
Product Overview
The 1Cr5Mo Radiant Coil Tube (Product Code: 958) is a premium heat-resistant alloy steel coil tube manufactured by Wenzhou Jixing Metal Materials Co., Ltd, specifically engineered for use in tube-type heating furnaces (管式加热炉) as radiant heating elements. These coil tubes are designed to operate under extreme thermal cycling conditions, where sustained exposure to high-temperature flue gases and thermal radiation demands exceptional oxidation resistance, thermal fatigue strength, and dimensional stability.
The coil tube configuration provides an extended heating surface area within a compact furnace footprint, enabling efficient and uniform heat transfer to process gases or materials. The 1Cr5Mo (1.5Cr-0.5Mo equivalent, Chinese GB/T standard designation) alloy system offers a superior balance of cost-effectiveness and performance for moderate-to-high temperature radiant applications, typically operating in the range of 600°C to 900°C.
Material & Properties
Chemical Composition (GB/T 5310 / ASTM A213 T11 Equivalent)
| Element | C | Si | Mn | P | S | Cr | Mo | Fe |
|---|---|---|---|---|---|---|---|---|
| Content (%) | 0.08–0.12 | 0.17–0.37 | 0.30–0.60 | ≤0.025 | ≤0.025 | 1.25–1.65 | 0.40–0.60 | Balance |
Mechanical & Physical Properties
| Property | Specification | Test Condition |
|---|---|---|
| Tensile Strength (UTS) | ≥ 485 MPa | Room Temperature |
| Yield Strength (0.2% Offset) | ≥ 245 MPa | Room Temperature |
| Elongation (A50mm) | ≥ 20% | Room Temperature |
| Impact Energy (Charpy V) | ≥ 41 J | −20°C |
| Thermal Conductivity | 27–30 W/(m·K) | 600°C |
| Linear Thermal Expansion | 11.5–12.0 × 10⁻⁶/K | 20–800°C |
| Maximum Service Temperature | 900°C (short-term 950°C) | Continuous Operation |
| Creep Strength (10,000 h, 1% Rupture) | ≥ 55 MPa | 750°C |
| Oxidation Resistance | Weight loss ≤ 0.5 mg/cm² | 800°C, 100 h air exposure |
Key Alloying Effects
- Chromium (1.25–1.65%): Forms a stable Cr₂O₃ protective oxide scale, providing primary resistance against high-temperature oxidation and sulfidation in furnace atmospheres.
- Molybdenum (0.40–0.60%): Enhances solid-solution strengthening, improves creep resistance at elevated temperatures, and stabilizes the ferritic matrix against grain growth during prolonged thermal exposure.
- Carbon (0.08–0.12%): Provides baseline strength through carbide precipitation (M₇C₃, M₂₃C₆), while remaining low enough to maintain weldability and ductility.
Specifications
| Parameter | Specification | Standard Reference |
|---|---|---|
| Outer Diameter (OD) | Φ38 mm, Φ45 mm, Φ51 mm, Φ57 mm, Φ60 mm (custom available) | GB/T 5310 / ASTM A213 |
| Wall Thickness (WT) | 2.0–5.0 mm (typical: 3.0 mm) | — |
| Coil Inner Diameter (ID) | Φ600 mm – Φ1200 mm | — |
| Coil Length | 15–100 m (continuous coil) | — |
| Bend Radius (Minimum) | ≥ 4 × OD | GB/T 12451 |
| Surface Finish | Hot-rolled / Pickled & Oiled / Annealed Bright | — |
| End Preparation | Plain cut / Beveled / Threaded / Flanged | — |
| Welding Process | GTAW (Gas Tungsten Arc Welding) / SAW (Submerged Arc Welding) | GB/T 12467 |
| Heat Treatment | Normalizing + Tempering (see Process section) | GB/T 16259 |
| Delivery Condition | Hot-rolled & Normalized / Annealed | — |
| Applicable Standards | GB/T 5310, GB/T 14976, ASTM A213/A213M, JIS G3463 | — |
| Weight (Typical, Φ51×3.0 mm, 50 m coil) | ≈ 310 kg | — |
Manufacturing Process
1. Raw Material Selection & Incoming Inspection
Hot-rolled seamless steel tubes conforming to GB/T 5310 or ASTM A213 T11 grade are sourced from certified mills. Each batch undergoes spectrographic verification (OES) for chemical composition, ultrasonic testing (UT) for internal defects, and hydrostatic pressure testing for wall integrity.
2. Coil Forming & Bending
Seamless tubes are cold- or warm-bent into the required coil geometry using hydraulic or mechanical bending machinery. The minimum bend radius is maintained at ≥ 4 × OD to prevent wall thinning and ovality exceeding 5% of nominal OD. Multi-pass bending ensures uniform springback compensation.
3. Weld Fabrication (Radiant Coil Assembly)
Segmental tubes are joined using GTAW (Gas Tungsten Arc Welding) with matching filler wire (ER80S-A2 or equivalent 1Cr5Mo composition). Weld parameters are optimized to minimize heat input (≤ 1.5 kJ/mm) and prevent excessive grain coarsening in the Heat-Affected Zone (HAZ). Multi-layer, multi-pass welding is employed for wall thicknesses exceeding 3.0 mm.
4. Weld Heat Treatment — Critical Process Step
Weld Heat Treatment (焊后热处理) is the defining quality-determining step for 1Cr5Mo radiant coil tubes. Due to the alloy's susceptibility to HAZ softening and temper embrittlement, a controlled post-weld heat treatment cycle is mandatory:
- Preheating: Localized preheating to 200–250°C to reduce residual stress and prevent cold cracking.
- Heating Rate: Controlled at ≤ 100°C/h up to 600°C, then ≤ 50°C/h to the final temperature.
- Soak Temperature: 780–820°C (normalizing range) held for 2 h + 1 h per 25 mm of wall thickness.
- Soak Duration: Minimum 2 hours to ensure complete austenitization and homogenization of the HAZ microstructure.
- Cooling: Controlled furnace cooling at ≤ 80°C/h to 600°C, followed by air cooling below 400°C. Alternatively, direct quenching to tempering temperature (620–680°C) is acceptable per GB/T 16259.
- Tempering: 620–680°C for 2–4 hours to relieve residual stresses and restore ductility.
The heat treatment cycle is executed in a continuous belt furnace or box-type resistance furnace with ±10°C temperature uniformity. Thermocouple instrumentation at multiple points along the weld length ensures full cycle verification. Thermal cycling simulation (500 cycles, 200°C–850°C) is performed on witness coupons to validate HAZ integrity.
5. Non-Destructive Testing (NDT)
- Dye Penetrant Testing (PT): 100% coverage of all weld seams per GB/T 18851.
- Ultrasonic Testing (UT): 100% of welds per GB/T 11345, Level II inspector qualification.
- Hardness Testing: HAZ hardness ≤ 285 HV to prevent brittle fracture susceptibility.
- Dimensional Inspection: OD, wall thickness, coil geometry, and springback verification.
6. Final Inspection & Packaging
Coil tubes are cleaned, passivated (for surface oxidation removal), and packaged with moisture-absorbent desiccants. Each coil is labeled with heat number, mill certificate reference, and dimensional data.
Applications
- Petrochemical Tube Furnaces: Radiant sections of reformer furnaces, cracker furnaces, and hydrogen production units in refineries.
- Chemical Process Heaters: High-temperature process heating for polymerization reactors, ethylene oxide converters, and sulfur recovery units.
- Petrochemical Crude Oil Heaters: Pre-heating and vaporization of heavy hydrocarbon feedstocks.
- Industrial Boilers: Superheater and reheater tubes in high-pressure steam generation systems.
- Power Generation: Waste heat recovery coils in gas turbine combined cycle plants.
- Steel Industry: Heating coils in continuous annealing lines and heat treatment furnaces.
Quality Certifications & Compliance
| Certification / Standard | Description |
|---|---|
| ISO 9001:2015 | Quality Management System — Manufacturing & Supply |
| ISO 3834-2 | Quality Requirements for Fusion Welding of Metallic Materials |
| ASME BPV Code | Boiler and Pressure Vessel Code — Section I & VIII (where applicable) |
| EN 10204 3.1 | Material Test Certificate — Inspection Report with Test Data |
| NACE MR0175 / ISO 15156 | Resistance to Sulfide Stress Cracking (for sour service qualification) |
| API 5CT / API 5L | API Monogram (where applicable for energy sector supply) |
| GB/T 5310 | Chinese National Standard — Seamless Steel Tubes for High-Pressure Boilers |
| GB/T 16259 | Chinese National Standard — Heat Treatment of Steel Tubes |
Unique Selling Points
- Specialized Weld Heat Treatment Expertise: Proprietary thermal cycling protocols developed through extensive field experience in tube furnace coil tube fabrication, ensuring HAZ microstructural integrity and long-term creep resistance.
- Full Traceability: Every coil tube is traceable to its heat number, mill certificate, weld procedure qualification record (WPS/PQR), and heat treatment cycle log.
- Custom Coil Geometry: Flexible manufacturing capability for non-standard coil configurations, bend radii, and end preparations tailored to specific furnace designs.
- Thermal Cycling Validation: Witness coupon thermal cycling testing (500+ cycles) provides empirical proof of fatigue resistance, exceeding typical industry qualification requirements.
- Multi-Standard Compliance: Simultaneous conformance to Chinese GB, American ASTM/ASME, and European EN standards enables global project deployment without requalification.
Technical Notes & Recommendations
Important: The weld heat treatment of 1Cr5Mo coil tubes is not merely a residual stress relief operation. Inadequate heat treatment results in HAZ softening (hardness drop of 20–40 HV), carbide network formation at grain boundaries, and premature creep rupture. Wenzhou Jixing Metal Materials Co., Ltd. adheres to the principle that "the weld is only as good as its heat treatment", implementing full-spectrum thermal monitoring and post-treatment microstructural verification (metallographic examination at 500× magnification) on every production lot.
For detailed engineering data sheets, material test certificates (MTC), and weld procedure specifications (WPS), contact Wenzhou Jixing Metal Materials Co., Ltd. directly for project-specific technical documentation.