304H Austenitic Stainless Steel Coil Tube for High-Temperature Boiler Applications
Product Overview
Wenzhou Jixing Metal Materials Co., Ltd. presents its premium-grade 304H austenitic stainless steel coil tube, engineered specifically for demanding high-temperature industrial applications. As part of the austenitic general-purpose stainless steel family, this coil tube is distinguished by its elevated carbon content (≥0.04%) compared to standard 304 and 304L grades, delivering superior creep resistance and long-term structural integrity at elevated service temperatures. This makes it an ideal solution for boiler superheaters, high-temperature steam pipelines, and other thermal process systems where sustained performance under extreme conditions is critical.
Manufactured to the highest international standards, the 304H coil tube combines the excellent corrosion resistance and formability inherent to the 304 family with enhanced high-temperature mechanical properties, offering a unique balance of durability, reliability, and economic efficiency for power generation and petrochemical industries.
Material & Properties
The 304H grade is a high-carbon variant of the standard 304 austenitic stainless steel. The deliberate increase in carbon content to a minimum of 0.04% (compared to ≤0.08% in 304 and ≤0.03% in 304L) promotes the formation of stable carbon carbides, thereby reducing the susceptibility to intergranular carbide precipitation at elevated temperatures. This microstructural refinement directly translates to improved creep strength, thermal fatigue resistance, and extended service life in high-temperature environments.
Key Material Characteristics
- Carbon Content: ≥0.04% — optimized for high-temperature creep resistance
- Creep Strength: Significantly superior to 304 and 304L at temperatures above 600°C (1,112°F)
- Corrosion Resistance: Excellent resistance to oxidation, scaling, and general corrosion in high-temperature oxidizing atmospheres
- Formability: Maintains good ductility and weldability characteristic of austenitic stainless steels
- Non-magnetic: Retains austenitic structure — non-magnetic in the annealed condition
- Maximum Service Temperature: Up to 1,093°C (2,000°F) with sustained strength retention
Chemical Composition (ASTM/EN Equivalent)
| Element | Specification (wt%) |
|---|---|
| Carbon (C) | ≥0.04 – 0.10 |
| Chromium (Cr) | 18.0 – 20.0 |
| Nickel (Ni) | 8.0 – 10.5 |
| Manganese (Mn) | ≤2.0 |
| Silicon (Si) | ≤1.0 |
| Phosphorus (P) | ≤0.045 |
| Sulfur (S) | ≤0.030 |
| Iron (Fe) | Balance |
Specifications
| Parameter | Specification |
|---|---|
| Product Form | Coil Tube (盘管) |
| Material Grade | 304H (Austenitic — General Purpose) |
| Standard References | ASTM A213/A213M, ASME SA-213, EN 10216-5, GB/T 12771 |
| Outer Diameter Range | 6.0 mm (0.24 in) – 168.3 mm (6.63 in) |
| Wall Thickness Range | 0.5 mm (0.020 in) – 12.0 mm (0.472 in) |
| Coil Inner Diameter | 1,000 mm (39.4 in) – 3,000 mm (118.1 in) (customizable) |
| Coil Length | Up to 60 m (197 ft) per coil (custom lengths available) |
| Surface Finish | Bright annealed, pickled, or polished (as required) |
| Tolerance (OD) | ±0.05 mm to ±0.15 mm (per standard or custom) |
| Tolerance (Wall) | ±10% of nominal (or tighter per specification) |
| Delivery Condition | Annealed and pickled (solution treated) |
Manufacturing Process
The production of 304H coil tube at Wenzhou Jixing Metal Materials Co., Ltd. follows a rigorous multi-stage manufacturing process designed to ensure dimensional accuracy, microstructural integrity, and consistent mechanical performance:
- Raw Material Selection: High-purity 304H stainless steel billets or ingots are carefully selected, with strict control over carbon content (≥0.04%) and trace element composition to meet ASTM/EN specification requirements.
- Hot Rolling: Billets are heated to controlled temperatures and hot-rolled to preliminary dimensions, establishing the initial coil geometry with precise outer diameter and wall thickness control.
- Coil Winding: The hot-rolled tube is wound into coils of specified inner diameter, with careful handling to prevent mechanical deformation or surface damage.
- Solution Annealing: Coils undergo solution heat treatment at temperatures between 1,010°C and 1,150°C (1,850°F – 2,092°F), followed by rapid cooling, to achieve a fully austenitic microstructure and optimize mechanical properties.
- Pickling & Passivation: The annealed surface is pickled to remove oxide scale and subsequently passivated to form a protective chromium oxide layer, ensuring maximum corrosion resistance.
- Dimensional Inspection: Each coil undergoes comprehensive dimensional verification including outer diameter, wall thickness, straightness, and coil geometry checks using precision instrumentation.
- Non-Destructive Testing (NDT): Eddy current testing and hydrostatic pressure testing are performed to detect internal and surface defects, ensuring 100% quality assurance.
- Final Inspection & Packaging: Tubes pass final visual and dimensional inspection before being packaged for shipment with full traceability documentation.
Applications
The 304H coil tube is specifically engineered for high-temperature industrial applications where superior creep strength and long-term thermal stability are paramount. Primary applications include:
- Boiler Superheaters: Primary application — the enhanced creep resistance of 304H ensures reliable performance in furnace superheater sections operating at temperatures exceeding 600°C (1,112°F), significantly outperforming standard 304 and 304L grades.
- High-Temperature Steam Pipelines: Ideal for superheated steam lines in power plants, chemical processing facilities, and industrial heating systems where sustained thermal cycling is present.
- Heat Exchanger Tubing: Suitable for high-temperature heat exchangers in petrochemical, oil refining, and pharmaceutical industries requiring both thermal resistance and corrosion protection.
- Industrial Furnace Components: Used in furnace tubes, radiant sections, and convection banks where oxidation resistance at elevated temperatures is essential.
- Power Generation Equipment: Applied in waste-to-energy plants, cogeneration systems, and biomass boilers where continuous high-temperature operation is required.
- Chemical Processing: Suitable for high-temperature process piping and reactors handling mildly corrosive media at elevated temperatures.
Key Differentiator: The 304H grade's carbon content of ≥0.04% provides measurable improvement in high-temperature creep strength over 304 and 304L grades, extending service life in boiler superheater and high-temperature steam line applications by up to 30–50% under equivalent operating conditions.
Quality Certifications
Wenzhou Jixing Metal Materials Co., Ltd. maintains a comprehensive quality management system ensuring every 304H coil tube product meets or exceeds international standards. Certifications and compliance include:
- ISO 9001:2015 — Quality Management System Certification
- ISO 14001 — Environmental Management System
- ASTM A213/A213M — Standard Specification for Seamless Austenitic Stainless Steel Tubes for High-Pressure Boilers and Heat Exchangers
- ASME SA-213 — Boiler and Pressure Vessel Code compliance
- EN 10216-5 — European standard for austenitic stainless steel tubes
- GB/T 12771 — Chinese national standard for stainless steel welded and seamless tubes
- Mill Test Certificates (MTC/EN 10204 Type 3.1) — Provided with every shipment for full traceability
Every coil tube undergoes rigorous quality control at each production stage, from incoming raw material verification through final product inspection, ensuring consistent performance and full compliance with applicable international standards. Third-party inspection services are available upon request to provide additional assurance for critical applications.