GB/T 06Cr25Ni20 Stainless Steel: High-Temperature Austenitic Alloy for Corrosive and Oxidizing Environments
GB/T 06Cr25Ni20 (equivalent to AISI 310S) is a high-chromium, high-nickel austenitic stainless steel designed for extreme-temperature applications and corrosive environments. With a nominal composition of 25% chromium and 20% nickel, this grade offers superior oxidation resistance up to 1150°C (2100°F) while maintaining structural integrity in sulfur-containing and carburizing atmospheres. This article provides a technical breakdown of its chemical composition, mechanical properties, manufacturing process, industrial applications, and comparative advantages over similar high-temperature alloys.
1. Chemical Composition (GB/T 20878 & ASTM A240 Standards)
| Element | Content Range (wt%) | Functional Role |
|---|---|---|
| Carbon (C) | ≤ 0.08% | Minimized to prevent carbide precipitation and intergranular corrosion at high temperatures |
| Chromium (Cr) | 24.00 – 26.00% | Forms Cr₂O₃ passive layer; critical for oxidation resistance in air and sulfur-bearing gases |
| Nickel (Ni) | 19.00 – 22.00% | Stabilizes austenitic microstructure; enhances high-temperature strength and ductility |
| Manganese (Mn) | ≤ 2.00% | Improves hot workability; partial substitute for nickel in cost-sensitive applications |
| Silicon (Si) | ≤ 1.50% | Enhances oxidation resistance at temperatures above 800°C; strengthens passive film |
| Phosphorus (P) | ≤ 0.045% | Residual impurity; controlled to maintain weldability and toughness |
| Sulfur (S) | ≤ 0.030% | Minimized to prevent hot cracking during welding and high-temperature service |
| Iron (Fe) | Balance | Base matrix element; provides structural stability |
2. Mechanical Properties at Elevated Temperatures
| Property | Room Temperature | 500°C (932°F) | 800°C (1472°F) | 1000°C (1832°F) |
|---|---|---|---|---|
| Tensile Strength (MPa) | ≥ 520 | ≥ 415 | ≥ 140 | ≥ 70 |
| Yield Strength (MPa) | ≥ 205 | ≥ 170 | ≥ 95 | ≥ 45 |
| Elongation (%) | ≥ 40 | ≥ 30 | ≥ 25 | ≥ 20 |
| Modulus of Elasticity (GPa) | 193 | 175 | 140 | 100 |
*Values conform to GB/T 4237 and ASTM A240 standards for solution-annealed condition
3. Manufacturing and Heat Treatment Process
- Melting: Electric arc furnace (EAF) + argon oxygen decarburization (AOD) or vacuum oxygen decarburization (VOD) to achieve ultra-low carbon and high purity, critical for high-temperature performance.
- Hot Working: Forged or hot-rolled at 1150-1250°C with controlled cooling to prevent sigma phase formation; water quenching recommended for thick sections (>25mm).
- Cold Working: Limited to light forming due to high work-hardening rate; intermediate annealing at 1040-1120°C required for complex shapes.
- Solution Annealing: Heated to 1040-1150°C followed by rapid water quenching to dissolve chromium carbides and restore corrosion resistance.
- Surface Finishing: Pickling in nitric-hydrofluoric acid blend to remove scale; electropolishing optional for medical/pharmaceutical applications to achieve Ra < 0.5μm.
4. Key Industrial Applications
Petrochemical Processing
Reformer tubes, pyrolysis furnaces, and catalytic cracker components operating in hydrogen sulfide and carbon monoxide environments at 900-1100°C.
Thermal Processing Equipment
Annealing covers, radiant tubes, and muffle furnaces in heat treatment plants; resistant to carburization and nitriding atmospheres.
Power Generation
Boiler superheaters, exhaust systems, and flue gas desulfurization (FGD) components in coal-fired and waste-to-energy plants.
Aerospace & Defense
Jet engine exhaust systems, afterburner components, and missile parts requiring oxidation resistance at Mach 2+ velocities.
Glass Manufacturing
Regenerators, checkers, and molten glass contact parts in float glass production lines (resistant to alkali vapor corrosion).
Food & Pharmaceutical
High-temperature sterilization equipment and fluidized bed dryers where metal purity and corrosion resistance are critical.
5. Comparison with Competing High-Temperature Alloys
| Alloy | Max Continuous Service Temp. | Key Advantages | Limitations | Typical Applications |
|---|---|---|---|---|
| 06Cr25Ni20 (310S) | 1150°C | Best oxidation resistance in air; cost-effective for continuous high-temperature service | Limited strength above 1000°C; susceptible to sigma phase embrittlement | Furnace components, petrochemical equipment |
| 06Cr23Ni13 (309S) | 1050°C | Lower nickel content reduces cost; good for intermittent high-temperature exposure | Inferior oxidation resistance compared to 310S | Welding filler metal, heat shields |
| 253MA | 1150°C | Nitrogen-strengthened; higher creep resistance than 310S | Higher cost; limited availability in certain product forms | Reformer tubes, exhaust manifolds |
| Inconel 601 | 1250°C | Superior high-temperature strength; resistant to carburization | Significantly more expensive; difficult to machine | Aerospace, nuclear applications |
6. Engineering Considerations and Selection Guidelines
- Welding Requirements: Use ER310 or ER310S filler metal; preheat not required for thin sections (<6mm). Post-weld annealing recommended for critical applications to restore corrosion resistance.
- Thermal Cycling: Avoid repeated thermal shocks above 800°C; design for gradual temperature changes to prevent thermal fatigue cracking.
- Corrosive Environments: Not recommended for aqueous chloride solutions (risk of pitting/crevice corrosion); consider 316L or 904L for such conditions.
- Surface Preparation: Remove all contaminants before high-temperature service; residual oils or greases can cause localized corrosion.
- Certification: Verify material test reports (MTR) confirm compliance with GB/T 20878, ASTM A240, or EN 10095 standards for critical applications.
- Alternative Grades: For temperatures exceeding 1150°C, consider nickel-based alloys (e.g., Inconel 600/601) or ceramic-coated solutions.
7. Request a Technical Quote for 06Cr25Ni20 Stainless Steel
Require GB/T 06Cr25Ni20 (310S) stainless steel in custom dimensions or specific product forms (sheets, plates, pipes, or bars)? Our metallurgical experts provide tailored solutions for high-temperature applications with full certification and competitive pricing. Contact us with your technical specifications for a detailed quotation.