Q1: What's the real difference between 310 and 310S?
A: It all comes down to carbon. 310S stainless steel is the low-carbon version. Standard 310 allows up to 0.25% carbon, while 310S caps it at 0.08%. This single change makes 310S the safer choice for anything that gets welded or goes through repeated heating and cooling cycles, as it resists a common failure called "sensitization" where the material becomes prone to intergranular corrosion.
Q2: Which one handles heat better?
A: In terms of pure oxidation resistance in a hot furnace, they're nearly identical. Both work great up to about 1150°C. The slight difference is that standard 310's higher carbon can give it a minor edge in long-term creep strength at the absolute highest temperatures. But for 95% of applications, you won't see a performance gap. The trade-off is fabrication risk, not heat resistance.
Q3: We need to weld it. Does it matter which grade we use?
A: Absolutely. This is the most important decision point. Use 310S. Welding standard 310 can create a weak zone next to the weld that's susceptible to corrosion, especially if the part ever operates between 425-870°C or sees any moisture. 310S avoids this problem, making it the standard choice for any fabricated component. It saves you from needing costly post-weld heat treatments.
Q4: When would I ever choose standard 310?
A: Only in specific cases: for simple, unwelded parts that will live continuously at very high temperatures (like a solid cast furnace bracket) and where that tiny bit of extra creep strength is calculated to be necessary. Even then, many engineers now default to 310S for simplicity and supply chain consistency. If you're welding it, the choice is made for you: it's 310S stainless steel.
Q5: How do I make sure I'm actually getting 310S and not 310?
A: Check the paperwork. Your purchase order and the Mill Test Certificate (MTC) must say "310S". Then, on the MTC, look at the Carbon (C) content. It must read 0.08% or lower. If it's higher, you didn't get 310S. This is the only way to be sure.
Q6: Is one more expensive than the other?
A: The raw material cost is almost the same. The real cost difference comes later. Choosing 310 for a welded job might save a few dollars upfront but can cost thousands later in repairs, downtime, or early failure. 310S steelis the cost-effective choice when you consider the total project lifecycle and risk.
Q7: We deal with sulfurous atmospheres. Any advice?
A: Both resist sulfidation well due to their high chromium. However, if you have a welded component in that environment, the sensitized weld zone in standard 310 becomes a prime target for accelerated attack. For reliability, a welded part in a sulfidizing atmosphere is another strong reason to specify 310S.
Q8: Our old specs call for 310. Can we switch to 310S?
A: In almost all cases, yes—and you probably should. It's a direct upgrade in terms of fabricability and corrosion safety. 310S meets the same mechanical and high-temperature performance specs. The one exception would be a very specific, unwelded part designed explicitly around 310's marginal high-temperature creep advantage. For everything else, switching to 310S is a smart way to modernize your specs and reduce risk.
Q9: Can you help us decide for a tricky application?
A: Of course. Send us the details: what the part is, the operating temperature range, the atmosphere, and how it's made. Ronsco team give you a straight opinion on which grade makes the most sense. We can also supply material that's certified to both 310S and 310H specs if you need that extra assurance for high-temperature strength.
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