310 vs. 310H vs. 310S: How to Choose?
Apr 01, 2026
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If you are sourcing high-temperature stainless steel for furnace components, heat exchangers, petrochemical equipment, boilers, or heat treatment systems, choosing between grades 310, 310H, and 310S is a critical purchasing decision.
Although all three grades belong to the chromium-nickel (Cr-Ni) austenitic stainless steel family, their performance differences stem primarily from variations in carbon content. These differences directly affect the material's creep strength, weldability, resistance to carbide precipitation, and long-term service life in high-temperature environments.
What is 310 stainless steel?
Type 310 stainless steel (UNS S31000) is a high-chromium, high-nickel austenitic stainless steel designed specifically for high-temperature service. Its chemical composition typically includes 24.0%–26.0% chromium, 19.0%–22.0% nickel, and a maximum of 0.25% carbon; depending on the specific atmosphere, load, and component design, Grade 310 stainless steel can be used in continuous service environments at temperatures up to approximately 1100–1150°C (2010–2100°F). Common applications include industrial furnace components, heat treatment equipment, burners, kiln parts, and heat exchangers.
What is 310S stainless steel?
310S stainless steel (UNS S31008) is the low-carbon version of 310 stainless steel, specifically developed for high-temperature applications requiring good corrosion resistance after welding and fabrication. Its chemical composition includes 24.0%–26.0% chromium, 19.0%–22.0% nickel, and a maximum carbon content of 0.08%. The reduced carbon content helps inhibit chromium carbide precipitation during welding and heating, thereby lowering the risk of sensitization under appropriate service conditions. It is commonly used in the manufacture of furnace tubes, heat exchangers, burners, and welded thermal equipment.
What is 310H stainless steel?
310H stainless steel (UNS S31009) is a high-temperature austenitic stainless steel with controlled carbon content, specifically developed for applications requiring superior creep resistance and strength during long-term high-temperature service. It contains 24.0%–26.0% chromium, 19.0%–22.0% nickel, and 0.04%–0.10% carbon, with a maximum silicon content of 0.75%. Compared to 310S, the controlled carbon range imparts superior high-temperature strength, making the material suitable for furnace supports, pressure equipment, and components subjected to sustained thermal loads.
310 vs. 310H vs. 310S Stainless Steel: Key Differences
The primary difference between 310, 310H, and 310S stainless steels lies in their carbon content, which directly influences their respective maximum service temperatures, creep-rupture strengths, and welding characteristics. Standard 310 stainless steel (UNS S31000) has a carbon content of no more than 0.25%; 310H stainless steel (UNS S31009) has its carbon content controlled between 0.04% and 0.10%; and 310S stainless steel (UNS S31008) is a low-carbon variant with a carbon content not exceeding 0.08%. This lower carbon content helps minimize chromium carbide precipitation, sensitization, and intergranular corrosion, making the material suitable for equipment operating in the temperature range of approximately 425°C to 1100°C.
310 vs. 310H vs. 310S Stainless Steel:Chemical Compositions
| Grade | Carbon (C) | Manganese (Mn) | Silicon (Si) | Phosphorus (P) | Sulfur (S) | Chromium (Cr) | Nickel (Ni) | Nitrogen (N) |
|---|
| 310 | ≤ 0.25% | ≤ 2.00% | ≤ 1.50% | ≤ 0.045% | ≤ 0.030% | 24.00-26.00% | 19.00-22.00% | ≤ 0.10% |
| 310S | ≤ 0.08% | ≤ 2.00% | ≤ 1.50% | ≤ 0.045% | ≤ 0.030% | 24.00-26.00% | 19.00-22.00% | ≤ 0.10% |
| 310H | 0.04-0.10% | ≤ 2.00% | ≤ 1.50% | ≤ 0.045% | ≤ 0.030% | 24.00-26.00% | 19.00-22.00% | ≤ 0.10% |
310 vs. 310H vs. 310S Stainless Steel: Mechanical Properties
| Property | 310 | 310S | 310H |
|---|
| Tensile Strength | 515 MPa (75 ksi) | 515 MPa (75 ksi) | 515 MPa (75 ksi) |
| Yield Strength | 205 MPa (30 ksi) | 205 MPa (30 ksi) | 205 MPa (30 ksi) |
| Elongation | 40% | 40% | 40% |
| Hardness (Brinell) | 217 max | 217 max | 217 max |
| Hardness (Rockwell B) | 95 max | 95 max | 95 max |
| Hardness (Vickers) | 220 max | 220 max | 220 max |
| Modulus of Elasticity | 200 GPa (29,000 ksi) | 200 GPa (29,000 ksi) | 200 GPa (29,000 ksi) |
310 vs. 310H vs. 310S Stainless Steel: Weldability
Weldability is a primary reason why buyers choose 310S over 310 or 310H. 310S stainless steel has a maximum carbon content of 0.08%-significantly lower than the standard 310 grade (≤0.25%)-which reduces the risk of chromium carbide precipitation during welding and prolonged exposure to heat. This helps minimize sensitization and potential intergranular corrosion in welded structures. For equipment such as furnace tubes, heat exchangers, and welded heat-treatment systems-where post-weld corrosion resistance and manufacturing reliability are critical-310S is the safer choice.
310 vs. 310H vs. 310S Stainless Steel: High-Temperature Service Limits
| Feature | 310 (Standard) | 310H (High Carbon) | 310S (Low Carbon) |
| Max Service Temp (Oxidizing) | ~1150°C (2100°F) | ~1150°C (2100°F) | ~1150°C (2100°F) |
| Max Service Temp (Intermittent) | ~1035°C (1900°F) | ~1035°C (1900°F) | ~1035°C (1900°F) |
| Creep-Limited Temp Range | Moderate | High (Above 600°C) | Low to Moderate |
| Sensitization Temp Range | 425°C - 860°C | 425°C - 860°C | 425°C - 860°C |
| Primary Limitation | Ductility loss over time | Sigma phase embrittlement | Creep strength |
310 vs. 310H vs. 310S: How to Choose?
Choose Grade 310H if:
Operating temperatures continuously exceed 800°C to 1150°C.
Components support structural loads under thermal stress (e.g., boiler hangers, tube supports, thermowell tubes, thermal power piping).
Design specifications prioritize long-term creep-rupture resistance over post-weld corrosion resistance.
Choose Grade 310S if:
The component involves extensive welding or heavy plate thickness ($>6\text{ mm}$).
Operating temperatures cycle between 425°C and 1100°C, and post-weld solution annealing is impractical.
The application is exposed to moist high-temperature gases or chemical condensate where intergranular corrosion resistance is required.
Choose Standard Grade 310 if:
The material is used for non-welded or lightly welded fixtures, thin sheet parts, or general heat treatment trays operating under non-critical structural loads below 1000°C.
To help determine the specific materials suitable for your project, could you please specify:
What specific component or piece of equipment are you manufacturing (e.g., furnace tubes, welded supports, heat shields, etc.)?
Does the component require extensive welding during fabrication?
What are the expected operating temperatures and loads?
FAQ
Q: Can 310S directly replace 310H in high-stress furnace applications?
A: Generally, no. Although 310S offers better weldability, it lacks the creep strength characteristic of 310H. Substituting 310S for 310H in high-stress, high-temperature structural components could lead to premature creep deformation (such as sagging or elongation).
Q: Which grade should be selected for sulfur-containing environments?
A: 310S is usually the preferred choice in sulfur-bearing atmospheres. Its lower carbon content reduces the risk of intergranular corrosion, a form of corrosion that is often exacerbated by the presence of chromium carbides at grain boundaries.
Q: Is it safe to weld 310H using standard 310S welding consumables?
A: Welding is possible, but the weld joint may lose the creep strength advantage inherent to the 310H base metal. For critical high-temperature structural applications, it is recommended to use welding consumables that match the creep resistance properties of 310H.
Q: What is "sensitization," and why does it affect these steels differently?
A: Sensitization refers to the precipitation of chromium carbides at grain boundaries within the temperature range of 425°C to 860°C. Grades 310 and 310H are more susceptible to this phenomenon. In contrast, the low carbon content of 310S significantly delays or prevents this process, thereby maintaining better material integrity.
Q: What is "Sigma phase (σ-phase)" embrittlement?
A: All three grades are susceptible to this. When exposed to temperatures between 600°C and 900°C, all 310-series steels form "Sigma phase" (σ-phase)-an intermetallic compound that causes the steel to become brittle at room temperature. If equipment has operated within this temperature range, extreme caution must be exercised during handling or maintenance during shutdowns.
Q: Which grade is best suited for thermal cycling (frequent heating and cooling) conditions?
A: 310S is generally better suited for thermal cycling conditions. Its lower carbon content provides slightly better ductility, helping the material accommodate internal stresses caused by thermal expansion and contraction, thereby preventing cracking.
Q: Why do pressure vessel codes (such as ASME) typically require the use of 310H?
A: ASME and other pressure vessel codes require 310H because the "H" grade ensures a minimum carbon content, thereby guaranteeing creep-rupture performance. Standard 310 steel does not possess these guaranteed high-temperature strength specifications.
Q: If my furnace components deform over time, should I switch from 310S to 310H?
A: Yes. Deformation (creep) indicates that stress levels have exceeded the material's yield strength at that temperature. Switching to 310H offers superior creep resistance, helping components retain their shape for longer periods under the same operating conditions.
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