Super304H & HR3C Seamless Stainless Steel Coil Tube for Ultra-Supercritical Boiler Superheaters

Product Overview

Wenzhou Jixing Metal Materials Co., Ltd. supplies high-performance seamless stainless steel coil tubes engineered specifically for the superheater sections of ultra-supercritical (USC) coal-fired power generation boilers. Operating in demanding environments where steam temperatures reach 600–620 °C (1,112–1,148 °F) and pressures range from 25–30 MPa (3,626–4,351 psi), these coil tubes represent a critical component in the thermal efficiency chain of next-generation power plants. The product line leverages advanced austenitic stainless steel alloys—Super304H and HR3C—to deliver exceptional creep strength, thermal fatigue resistance, and oxidation performance under sustained high-temperature service conditions.

Material & Properties

The coil tubes are fabricated from two premier alloy grades selected for their superior metallurgical characteristics in ultra-high-temperature steam environments:

Super304H (UNS S31040)

HR3C (UNS S31324)

Specifications

Parameter Specification
Product Type Seamless Stainless Steel Coil Tube
Material Grades Super304H (UNS S31040) / HR3C (UNS S31324)
Outer Diameter (OD) 26.7 mm – 48.3 mm (1.05" – 1.90")
Wall Thickness 3.0 mm – 5.5 mm (0.118" – 0.217")
Coil Inner Diameter (ID) 800 mm – 1,500 mm (31.5" – 59.1")
Coil Length Customizable; typically 100 m – 300 m (328 – 984 ft) per coil
Operating Steam Temperature 600 – 620 °C (1,112 – 1,148 °F)
Operating Pressure 25 – 30 MPa (3,626 – 4,351 psi)
Surface Finish Mill finish / Polished (Ra ≤ 0.8 μm available)
End Condition Plain end, beveled, or threaded as specified
Heat Treatment Solution annealed and water/quenched (1050 – 1150 °C)
Applicable Standards ASTM A312, ASTM A213, EN 10216-5, GB/T 14976, JIS G3459
Delivery Condition Coiled, packaged on wooden pallets with protective wrapping

Manufacturing Process

The production of these high-performance coil tubes follows a rigorous multi-stage manufacturing protocol to ensure dimensional accuracy, metallurgical homogeneity, and mechanical reliability:

  1. Raw Material Selection: Vacuum-induction melted (VIM) + argon-oxygen decarburization (AOD) refined ingots or billets are selected to ensure ultra-low impurity levels (S ≤ 0.015%, P ≤ 0.025%).
  2. Hot Rolling / Piercing: Billets are heated to 1,100–1,200 °C and hot-rolled through a continuous piercing mill to produce seamless hollow blanks with precise wall-to-diameter ratios.
  3. Hot Finishing: The hot-finished tubes undergo reeling and sizing to achieve the target outer diameter and wall thickness within ±10% tolerance.
  4. Heat Treatment: Solution annealing at 1,050–1,150 °C followed by rapid quenching to dissolve carbides and maximize austenite stability and creep resistance.
  5. Cold Drawing / Cold Pilgering: Tubes are cold-worked through precision dies to achieve tight dimensional tolerances (±0.05 mm on wall thickness) and improved surface finish.
  6. Pickling & Passivation: Acid pickling (HNO₃ + HF blend) removes scale, followed by passivation to establish a protective chromium oxide film.
  7. Coiling: Finished tubes are coiled on precision mandrels using CNC-controlled coiling equipment to maintain uniform curvature without plastic deformation.
  8. Non-Destructive Testing (NDT): Each coil undergoes 100% ultrasonic testing (UT) for internal defects, eddy current testing (ECT) for surface/subsurface flaws, and hydrostatic pressure testing per ASTM A312.

Applications

These Super304H and HR3C seamless coil tubes are purpose-engineered for the following demanding power generation applications:

Why Coil Tubes? Coil tube construction eliminates longitudinal weld seams found in welded alternatives, providing uniform stress distribution, superior fatigue resistance, and easier field installation through cold-bending into final geometry without heat treatment.

Quality Certifications & Testing

Wenzhou Jixing Metal Materials Co., Ltd. maintains comprehensive quality assurance programs aligned with international standards:

Key Verification Tests Performed:

  1. Creep Rupture Testing: Long-term creep strength verified at 600 °C, 620 °C, and 650 °C per ASTM E139 / ISO 204.
  2. Oxidation/Scale Growth Testing: Isothermal oxidation exposure at 700 °C for 1,000+ hours to validate scale adhesion and spalling resistance per ASTM G182.
  3. Tensile & Hardness Testing: Room temperature and elevated temperature (600 °C) tensile properties per ASTM E8 / ASTM E21.
  4. Impact Testing: Charpy V-notch impact energy at operating temperature per ASTM E23.
  5. Chemical Analysis: Spectrometric verification of full alloy composition with certified mill analysis reports.
  6. Grain Structure & Inclusion Analysis: Metallographic examination to confirm austenitic grain size (ASTM E112) and cleanliness.

Unique Selling Points