AISI 310S is the low-carbon version of Type 310, a high-alloy chromium-nickel austenitic stainless steel developed for elevated-temperature service. The key difference is carbon: Type 310 permits up to 0.25% C, while 310S is limited to 0.08% C under ASTM A240. The lower carbon level makes 310S particularly useful for welded furnace structures, piping, heat exchangers, and other fabricated components where carbide precipitation and weld-zone corrosion must be controlled. :contentReference[oaicite:0]{index=0}

What Does the “S” in 310S Mean?

The “S” in 310S is commonly used to distinguish the low-carbon version of Type 310. It is not a separate stainless family. The chromium and nickel ranges remain essentially the same, while the maximum carbon content is substantially reduced.

Under ASTM A240, Type 310 allows carbon up to 0.25%, whereas Type 310S limits carbon to 0.08%. This lower carbon level reduces the amount of carbon available to form chromium carbides during welding or prolonged exposure in sensitizing temperature ranges. :contentReference[oaicite:2]{index=2}

Why Low Carbon Matters for Welding

During welding, the heat-affected zone can experience temperatures that allow chromium carbides to form at grain boundaries. If this occurs to a significant degree, chromium can become locally depleted near those boundaries, potentially reducing resistance to intergranular corrosion after exposure to a corrosive environment.

Reducing carbon limits the amount of carbon available for carbide formation. As a result, 310S is commonly preferred when a 310-series component must be welded and then exposed to demanding thermal conditions. Technical references describe the lower carbon level as beneficial for reducing carbide precipitation during welding. :contentReference[oaicite:3]{index=3}

310S can be welded using common stainless-steel welding processes, including TIG and other arc-welding methods. Filler selection should be based on the welding procedure, joint design, service temperature, and applicable code rather than the grade name alone. :contentReference[oaicite:4]{index=4}

310S vs 310: Strength, Weldability and Temperature

The two grades share the same basic high-chromium/high-nickel design. The trade-off is that the lower carbon level of 310S can reduce its high-temperature strength relative to the higher-carbon 310 grade. This is why the choice should be based on fabrication method as well as service temperature.

Published technical data also note that the lower carbon content can reduce high-temperature strength compared with Type 310. Therefore, 310S should not simply be described as a universally “better” version; it is a different optimization of the same alloy family. :contentReference[oaicite:5]{index=5}

Why 310S Is Common in Real Procurement

In practical fabrication, many high-temperature components are assembled by welding rather than machined from a single piece. Furnace shells, tubes, heat exchangers, supports, ducts, and other thermal structures often contain multiple welded joints.

For these applications, the lower carbon limit provides a useful fabrication advantage without sacrificing the fundamental 25Cr-20Ni heat-resistant design. This is why 310S is frequently specified for welded thermal equipment. It is better to describe it as a common practical choice for welded applications rather than claim that every 310-series order is 310S.

AISI 310S Data Card

The following data provide a concise purchasing and engineering reference. Exact limits should be checked against the product form and governing specification.

The ASTM A240 reference values for 310S include a minimum tensile strength of 515 MPa, minimum yield strength of 205 MPa, and minimum elongation of 40%. The same source lists a maximum hardness of 95 HRB for plate, sheet, and strip covered by that specification. :contentReference[oaicite:6]{index=6}

310S High-Temperature Performance

The alloy is designed around its high chromium and nickel content. Chromium supports the formation of a protective oxide scale, while nickel stabilizes the austenitic structure. In suitable oxidizing atmospheres, 310S provides strong resistance to scaling and oxidation at elevated temperatures.

Technical references commonly place its useful oxidation-resistant service around the 1000–1100°C range, but there is no single temperature that applies to every application. Dry-air exposure, thermal cycling, mechanical loading, sulfur-containing gases, moisture, and component geometry can all change the practical limit. :contentReference[oaicite:7]{index=7}

310S Applications

The low-carbon grade is particularly useful where high-temperature performance must be combined with welded fabrication. Common applications include:

These applications are consistent with published material references, which list furnace engineering, furnace tubes, burners, heat exchangers, and air heaters among typical uses. :contentReference[oaicite:8]{index=8}

310S Plate and Coil Procurement

For flat products, ASTM A240 is a key specification for chromium and chromium-nickel stainless steel plate, sheet, and strip. A complete purchase description should include the grade, product standard, thickness, width, length or coil size, surface finish, condition, quantity, and inspection requirements.

For buyers who need multiple stainless grades or customized product forms, stainless steel products can be sourced according to the required grade, dimensions, surface condition, and certification requirements. Teda Ganghua provides stainless-steel sourcing and processing support for industrial buyers, including plate, sheet, coil, pipe, tube, bar, and related requirements.

310S Equivalents and Designations

310S is identified under several international designation systems. The most important purchasing identifiers are shown below.

EN 1.4845 and UNS S31008 are widely used identifiers for this low-carbon 310-series grade. However, “equivalent” should not be interpreted as permission to substitute one standard automatically. Chemical limits, mechanical requirements, product dimensions, testing, and delivery conditions should be checked against the project specification. :contentReference[oaicite:9]{index=9}

Is 310S More Expensive Than 310?

Both grades contain essentially the same high levels of chromium and nickel, so their raw-alloy basis is very similar. The lower carbon requirement of 310S can affect production and availability, but the actual quotation depends on product form, thickness, quantity, surface finish, processing, certification, and market conditions.

For this reason, there is no universal price rule stating that one grade is always more expensive than the other. Buyers should compare quotations using the same specification, dimensions, surface condition, quantity, and certification requirements.

Key Takeaways

• 310S is the low-carbon version of Type 310.
• Its ASTM A240 carbon limit is ≤0.08%, compared with ≤0.25% for Type 310.
• Chromium remains approximately 24–26% and nickel 19–22%.
• The lower carbon level is useful for welded fabrication and carbide-precipitation control.
• 310 can provide higher high-temperature strength, while 310S is often preferred where welding is a major part of fabrication.
• UNS S31008 and EN 1.4845 are important international identifiers.
• ASTM A240 is commonly used for 310S plate, sheet, and strip.
• Service temperatures around 1000–1100°C require application-specific evaluation of atmosphere, creep, oxidation, and thermal cycling.

Frequently Asked Questions

1. What does AISI 310S mean?

AISI 310S is the low-carbon version of Type 310 austenitic heat-resistant stainless steel. Its UNS designation is S31008, and its EN material number is 1.4845.

2. What is the carbon content of 310S?

For ASTM A240 Type 310S, the maximum carbon content is 0.08%. This is substantially lower than the 0.25% maximum specified for Type 310. :contentReference[oaicite:10]{index=10}

3. Is 310S better than 310 for welding?

310S is generally preferred when welded fabrication is important because its lower carbon content reduces the potential for chromium carbide precipitation during thermal exposure. However, the final grade should be selected according to the welding procedure and service requirements.

4. What is the maximum temperature for 310S?

Technical references commonly cite approximately 1000–1100°C for suitable high-temperature oxidation service, but the actual allowable temperature depends on atmosphere, mechanical loading, thermal cycling, and exposure time. It should not be treated as one universal design limit. :contentReference[oaicite:11]{index=11}

5. What is the difference between 310S and 310H?

310S is the low-carbon grade intended to improve fabrication and welding characteristics, while 310H is a higher-carbon version intended to provide stronger high-temperature mechanical performance in specified applications. The required grade should therefore be selected according to whether weldability or elevated-temperature strength is the dominant requirement.