Stainless Steel grades

Austenitic stainless steel with the highest work-hardening rate of all 300-series grades. Lower Cr and Ni (17/7 vs 18/9 for 304) makes it metastable — cold working induces martensite transformation for extreme strength (UTS >1300 MPa in full-hard temper). THE stainless spring steel. Used for stainless springs, washers, clips, structural components requiring high strength + corrosion resistance, and railway car bodies.

Higher-carbon variant of 304 (C max 0.15% vs 0.08%). The original "18-8" stainless steel. Higher C gives better strength after cold work but makes it susceptible to intergranular corrosion after welding. Largely superseded by 304/304L but still specified for springs and high-strength cold-worked applications. Used for springs, screen cloth, architectural trim, and wire forms.

Free-machining austenitic stainless steel — the most machinable of all austenitic grades. 0.15-0.35% S (as MnS inclusions) provides excellent chip-breaking. Trade-off: lower corrosion resistance than 304, poor weldability (hot cracking risk), and not suitable for cold forming. Used for high-volume automatic lathe parts: fittings, valves, screws, shafts, and precision components.

The world's most widely used stainless steel — the original 18/8 austenitic. Good corrosion resistance in atmospheric, organic, and inorganic environments. Excellent formability and weldability. Not recommended for chloride-rich or marine environments (use 316L). Used in food processing, kitchen equipment, architecture, tanks, and general engineering.

The most widely used austenitic stainless steel. Excellent corrosion resistance, good formability and weldability. Standard choice for food processing, chemical, and architectural applications.

Low-carbon version of 304. Maximum 0.030% C prevents sensitization during welding — no post-weld heat treatment needed. The standard choice for welded structures in food, chemical, and pharmaceutical industries. Often dual-certified with 1.4301.

Nitrogen-enhanced low-carbon 304. The N addition (0.12-0.22%) increases yield strength ~40% over 304L without reducing corrosion resistance or weldability. Used for pressure vessels, storage tanks, and cryogenic applications where higher design stress is needed.

High-chromium austenitic stainless for high-temperature service. Better oxidation resistance than 304 due to higher Cr (22-24%) and Ni (12-14%). Maximum service temperature ~1000°C (intermittent). Used for furnace parts, heat exchangers, fluidized bed combustors, kiln liners, and boiler baffles.

High-chromium, high-nickel austenitic for the highest service temperatures among standard austenitics. Oxidation resistance to ~1100°C (continuous). Higher Cr/Ni than 309S. Used for furnace parts, radiant tubes, heat treatment baskets, kiln liners, and high-temperature flue gas equipment.

Standard-carbon austenitic stainless steel with molybdenum. Higher C than 316L (max 0.07% vs 0.03%) giving slightly higher strength. Same corrosion resistance as 316L. Used where welding is not required or post-weld solution annealing is possible.

Low-carbon austenitic stainless steel with molybdenum addition. Superior corrosion resistance to 304, especially against chlorides and pitting. Standard choice for chemical processing, marine, medical implants, and pharmaceutical equipment.

Nitrogen-enhanced low-carbon version of 316. The N addition (0.12-0.22%) increases yield strength by ~30% over 316L without losing corrosion resistance or weldability. Used for pressure vessels, nuclear components, and structural applications requiring higher design stress.

Titanium-stabilized austenitic stainless steel with molybdenum. Stabilization prevents sensitization during prolonged high-temperature exposure. Very popular in Germany for chemical, pharmaceutical, and food processing. Being replaced internationally by 316L (1.4404) for most applications.

Low-carbon austenitic with 3-4% Mo — higher Mo than 316L (2-3%). Better pitting and crevice corrosion resistance (PREN ~30 vs ~25). Used in aggressive chemical environments where 316L is borderline: pharmaceutical, dye production, and organic acid processing.

Titanium-stabilized austenitic stainless steel. Similar to 304 but with Ti addition to prevent carbide precipitation during welding and high-temperature service (up to 800°C). Used for aircraft exhaust manifolds, boiler casings, jet engine parts, and chemical processing.

Niobium-stabilized austenitic stainless steel. Nb forms NbC instead of CrC, preventing sensitization during welding or high-temp service (425-860°C). Alternative to 321 (Ti-stabilized). Used for welded structures in chemical processing, aircraft exhaust systems, and high-temp piping.

Super-austenitic stainless steel with high Mo and Cu content. Excellent resistance to sulfuric acid, phosphoric acid, and chloride environments. Bridges the gap between standard austenitics (316L) and nickel alloys (Inconel/Hastelloy). Used in chemical processing, oil & gas, and pharmaceutical.

Work-hardening austenitic stainless — AISI 301. Higher C (0.05-0.15%) than 301LN enables extreme cold-work strengthening to UTS 1300+ MPa in full-hard temper. THE spring-temper stainless: used for flat springs, retaining clips, conveyor belts, automotive structural parts, and rail car body panels. Corrosion resistance similar to 304 in annealed state.

Heat-resistant 25Cr-21Ni austenitic stainless — AISI 310S (low-C variant). Oxidation resistance to 1050°C continuous, 1150°C intermittent. Higher Cr+Ni than 304/316 = much better high-temperature scaling resistance. Used for furnace parts, radiant tubes, heat treatment fixtures, kiln linings, and thermocouple protection tubes. Also used in petrochemical cracker tubes.

Low-carbon 18/10 austenitic stainless — AISI 304L. C max 0.030% prevents sensitization after welding without stabilizing elements. THE welding-grade 304. Slightly higher Ni (10-12.5%) than 1.4301 (304) for better austenite stability. Used for welded vessels, piping, food equipment, and any 304 application requiring post-weld corrosion resistance without solution annealing.

High-Mo, high-Ni variant of 316L. Often specified for pharmaceutical and biotech cleanroom applications where delta-ferrite must be minimized (high Ni ensures fully austenitic structure). Also used in chemical processing and offshore. Often dual-certified with 1.4404.

Higher-alloy variant of 316L — Ni 12.5-15.0% (vs 10.0-13.0 for 1.4404) and Mo 2.5-3.0%. Guaranteed delta-ferrite free (essential for pharmaceutical/biotech electropolished surfaces). THE pharma and biotech process equipment stainless. Also used for chemical plant and food processing where maximum pitting resistance in the 316-family is needed.

Low-carbon nitrogen-enhanced austenitic Cr-Ni-Mo steel — AISI 316LN. Nitrogen (0.12-0.22%) boosts yield strength above 316L while maintaining weldability. Higher PREN than 316L for better pitting resistance. Charpy impact compliant to -196°C. ASME Section III approved for nuclear pressure boundary. Used for nuclear power piping, LNG cryogenic vessels, pharmaceutical equipment, and chemical plants.

High-Mo austenitic stainless — 4-5% Mo (vs 2-2.5% for 316L). N addition for strength and PREN. Superior pitting and crevice corrosion resistance in chloride environments compared to 316L/317L. PREN ~34-38. UNS S31726 / AISI 317LMN. Used for chemical plant, pharmaceutical equipment, pulp bleach plants, and FGD systems where 316L would fail. Resistant to intergranular corrosion even after welding.