We design 309/309S stainless steel plates for industries where temperatures exceed 1,000°F (538°C). Unlike standard 304/316L alloys, 309S (UNS S30908) leverages 22–24% chromium and 12–15% nickel to form a stable oxide layer that prevents scaling and carburization under cyclic heat up to 980°C. This ultra-low-carbon variant (≤0.08% C) eliminates weld decay, making it indispensable for fabricating integrated furnace systems, exhaust manifolds, and catalytic converters.

Key Performance Advantages

1. Unmatched Thermal Stability

• Oxidation Resistance: Withstands continuous service at 980°C and intermittent spikes to 1,150°C without spalling.

• Low Thermal Expansion: Coefficient of 16.0 × 10⁻⁶/°C (20–100°C) reduces stress cracking in thermal cycling.

• Creep Strength: 30% higher stress rupture life than 304 at 870°C.

2. Corrosion Resistance in Aggressive Media

• Resists sulfidation in fuel-rich combustion environments and nitric acid mixtures (≤20% concentration).

• Outperforms 316L in sulfur-containing atmospheres (e.g., coal-fired boilers, petrochemical crackers).

3. Mechanical Robustness

• Tensile Strength: ≥515 MPa

• Yield Strength: ≥205 MPa

• Elongation: ≥40%

• Hardness: ≤187 HB – ideal for machining flanges, nozzles, and brackets.

Technical Specifications: Chemistry & Properties

Table 1: Chemical Composition (Weight %)

*Note: 309 has identical composition but higher C (≤0.20%) for non-welded applications.*

Table 2: Mechanical & Thermal Properties

Global Price Analysis (2025 Q3)

*Note: Scrap 309S trades at $15,200–$19,000/ton, incentivizing recycling.*

Industry-Specific Applications

• Energy & Power:

  • Boiler baffles, burner nozzles, FGD scrubber liners

  • Nuclear fuel rod supports (resists neutron embrittlement)

• Petrochemical:

  • Ethylene cracker tubes, reformer furnace internals

• Waste Treatment:

  • Incinerator grates, ash conveyor systems (handles chlorides/sulfides)

• Automotive:

  • Turbocharger housings, exhaust manifolds

Precision Processing Guidelines

1. Welding:

   • Use AWS E309-16 electrodes with preheat to 150°C – prevents Cr-carbide precipitation.

   • Post-weld anneal at 1040°C for 1 hr/25 mm thickness.

2. Machining:

   • Carbide tools with TiN coating; coolant flow ≥20 L/min to avoid work hardening.

3. Heat Treatment:

   • Solution annealing: 1000–1050°C → rapid air/water quench.

Strategic Sourcing Advice

1. Avoid “Price-Only” Tenders: Low-cost suppliers often omit solution annealing, risking intergranular corrosion.

2. Certification Matters: Demand Mill Test Reports (MTRs) validating:

   • ASTM A240 compliance

   • Ferrite content ≤5% (ensures phase stability)

3. Why Luokaiwei?

   • Thickness Range: 0.5–80 mm (cold-rolled) / 20–200 mm (hot-rolled)

   • Surface Finishes: No. 4 brushed, 2B mill, #8 mirror for radiant heat reflection

   • Zero Lead Time: 12,000 tons of semi-finished stock for urgent Tier-1 projects.

5 Critical FAQs

1. Can 309S replace 314 stainless in kiln furniture?
   Yes – its lower silicon content (≤1.00% vs. 1.5–3.0% in 314) reduces embrittlement at 1,000°C.

2. How does scrap value impact total cost?
   309S scrap trades at $15,200–19,000/ton – our buyback program recoups 30–40% of initial CAPEX.

3. Is post-weld heat treatment mandatory?
   For cyclic >600°C service: yes. For ambient-temperature vessels: no.

4. What’s the max chlorides tolerance?
   ≤50 ppm in aqueous media – switch to 317L (>3% Mo) if chlorides exceed 100 ppm.

5. Do you supply ASME Section VIII-compliant plates?
   All our 309S plates carry ASME SA-240 certification for pressure vessel fabrication.