Comparison Of 309S And 310S: High-Chromium Vs Ultra-High-Chromium-Nickel High-Temperature Oxidation-Resistant Austenitic Stainless Steel

309S and 310S are both high-temperature oxidation-resistant austenitic stainless steels, with the core difference being chromium and nickel content (310S: Cr=24.00-26.00%, Ni=19.00-22.00%; 309S: Cr=22.00-24.00%, Ni=12.00-15.00%). The ultra-high chromium-nickel content of 310S further improves high-temperature oxidation resistance and creep strength, making them suitable for different ultra-high temperature service conditions.

Core Parameter Comparison

Parameter	309S Stainless Steel	310S Stainless Steel
Chemical Composition (wt%)	C≤0.08, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=22.00-24.00, Ni=12.00-15.00, Fe=Balance	C≤0.08, Si≤1.00, Mn≤2.00, P≤0.045, S≤0.030, Cr=24.00-26.00, Ni=19.00-22.00, Fe=Balance
Mechanical Properties (Annealed)	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤217HB	Tensile Strength ≥515MPa, Yield Strength ≥205MPa, Elongation ≥40%, Hardness ≤217HB
Service Temperature	-196℃ to 1050℃ (continuous service)	-196℃ to 1150℃ (continuous service)
High-Temperature Creep Strength (1000℃)	Creep rupture strength (1000h) ≥20MPa	Creep rupture strength (1000h) ≥35MPa
Equivalent Grades	SUS309S (JIS), EN 1.4828, UNS S30908	SUS310S (JIS), EN 1.4845, UNS S31008

Key Performance Differences: 1. High-temperature oxidation resistance: 310S's ultra-high chromium-nickel content forms a more dense and stable Cr₂O₃-NiO composite oxide film, which can resist oxidation at 1150℃; 309S's oxidation resistance is insufficient above 1050℃, and the oxide film is prone to aging and peeling. 2. High-temperature creep strength: At 1000℃, 310S's 1000h creep rupture strength is 75% higher than 309S, with better long-term structural stability under ultra-high temperature and stress. 3. Corrosion resistance: Both are suitable for high-temperature oxidizing atmospheres; 310S has better corrosion resistance in high-temperature mixed gas atmospheres (such as flue gas containing SO₂, NOx) due to higher nickel content. 4. Cost: 310S is 40-60% more expensive than 309S. 5. Formability: Both have good formability, but 310S's higher alloy content leads to higher deformation resistance and requires higher forming temperature.

Applicable Scenario Distinction: 309S is suitable for high-temperature oxidation-resistant components below 1050℃, such as industrial furnace liners (≤1050℃), high-temperature flue gas pipelines, heat treatment furnace fixtures and boiler combustion chamber components. 310S is suitable for ultra-high temperature oxidation-resistant stress-bearing components, such as ultra-high temperature furnace liners (1050-1150℃), petrochemical cracking furnace tubes, waste incinerator high-temperature components, and high-temperature sintering equipment parts.

Practical Q&A

Q1: Why can 310S be used at 1150℃ while 309S cannot? A1: 310S's chromium content (24-26%) and nickel content (19-22%) are higher than 309S; the composite oxide film formed by high chromium and nickel has stronger high-temperature stability, which can prevent internal metal oxidation and erosion at 1150℃; 309S's oxide film will decompose and peel off above 1050℃, leading to rapid component failure.

Q2: What is the difference in service life between 309S and 310S in ultra-high temperature furnace liners? A2: In 1100℃ oxidizing atmosphere, 310S's service life is ≥5 years, while 309S's service life is ≤1 year; 309S will experience obvious oxidation thinning and embrittlement at this temperature, which cannot meet long-term service requirements.

Q3: Can 310S be used in high-temperature corrosive mixed gas environments? A3: Yes. Its high nickel content improves resistance to high-temperature sulfide corrosion and nitrate corrosion; it is suitable for high-temperature flue gas containing SO₂, NOx and other corrosive gases, while 309S is prone to pitting corrosion in such environments.

Q4: What welding materials are used for 309S and 310S? A4: 309S uses ER309L welding wire, and 310S uses ER310L welding wire; both need to control welding heat input (≤200J/mm) to avoid grain coarsening; post-weld passivation treatment is recommended to improve the compactness of the oxide film.

Q5: How to select between 309S and 310S? A5: Choose 309S if the service temperature is ≤1050℃ and cost is a concern; choose 310S if the service temperature is 1050-1150℃, or if ultra-high temperature creep resistance and mixed gas corrosion resistance are required, regardless of cost.