Stainless Steel

Heat-resistant austenitic stainless steel with high silicon content (1.5–2.5%) for exceptional scaling resistance up to 1000°C. The silicon creates a protective SiO₂ layer supplementing the chromium oxide barrier. Excellent resistance to carburization and sulfidation. Used for furnace parts, burner nozzles, kiln furniture, hardening boxes, annealing baskets, and high-temperature industrial process components. Equivalent to AISI 309.

Heat-resistant austenitic stainless steel with 25% Cr and 21% Ni for outstanding oxidation resistance up to 1150°C in continuous service. Higher Si content (1.5-2.5%) enhances scaling resistance. Used for furnace parts, heat treatment baskets, muffles, radiant tubes, burner nozzles, thermocouple sheaths, and kiln furniture. The standard material for furnace construction. Similar to AISI 310/314. Not recommended for sulphur-containing atmospheres.

Heat-resistant duplex (austenitic-ferritic) stainless — 25Cr-4Ni-1.5Si. Si addition improves oxidation resistance at high temperature. Used for furnace components, burner nozzles, heat treatment fixtures, and kiln supports operating at 800-1000°C. Higher strength than fully austenitic heat-resistant grades at intermediate temperatures due to duplex structure.

Martensitic CrNi stainless — AISI 431. Best corrosion resistance of ALL martensitic stainless steels due to high Cr (15-17%) + Ni (1.5-2.5%). Hardenable to HRC 46-50. Used for shafts, bolts, valve stems, pump components, fasteners in marine/offshore environments. Also aerospace (WL4044) and medical instruments. Service to 400°C.

6% Mo super austenitic stainless steel — trade name 254 SMO (Outokumpu). PREN 42-44, equivalent to super duplex but fully austenitic = non-magnetic, better weldability, wider temperature range (-196 to +300°C). Strength nearly 2× that of 300-series stainless. Used for seawater systems, offshore oil/gas, FGD scrubbers, bleach plants, and desalination where super duplex is limited by temperature or magnetic concerns.

Super austenitic 6Mo+Cu stainless — Alloy 926 / Incoloy 25-6MO. Enhanced version of 904L with higher Mo (6-7%) and N (0.15-0.25%). PREN 41-48 — rivaling super duplex but fully austenitic. Ni 24-26% eliminates stress corrosion cracking. Used for seawater systems, FGD, phosphoric acid production, offshore hydraulics, and salt extraction. Service -196 to +400°C.

Basic martensitic stainless steel — 0.16-0.25% C + 12-14% Cr. Hardenable to HRC 48-52. THE workhorse martensitic stainless: cheap, available, and adequate corrosion resistance for mild environments. AISI 420 equivalent. Used for cutlery, surgical instruments, shafts, valve spindles, bolts, and turbine blades. Better corrosion resistance than X12Cr13 (1.4006/410) due to higher C and slight Cr advantage.

Martensitic creep-resistant stainless steel for high-temperature applications up to 600°C. V and Mo additions provide excellent creep rupture strength and high-temperature oxidation resistance. Hardenable to approximately 280 HB. Used for steam and gas turbine blades, high-temperature bolts, valve spindles, and fasteners in power generation. Standardized in EN 10302 (creep-resistant steels) and EN 10269 (high-temp fasteners).

Ti-stabilized ferritic stainless with Mo — 18% Cr + 2% Mo + Ti. Best pitting resistance in the ferritic family (PREN ~25, comparable to 316L austenitics). Ti stabilization prevents sensitization after welding. Used as cost-effective replacement for 316L in hot water systems, solar collectors, catering equipment, and automotive exhaust heat exchangers. No Ni = lower cost than austenitic.

Lean ferritic stainless with just 12% Cr and ~1% Ni — the cheapest stainless option. Also called "utility ferritic" or 3CR12. Lower corrosion resistance than 304 but much better than carbon steel. Magnetic, weldable (with precautions), and formable. Used where mild corrosion resistance at lowest cost is the goal: railway wagons, coal trucks, bus chassis, sugar mills, and architectural cladding in mild environments.

Low-cost utility ferritic stainless steel (12% Cr). A cost-effective alternative to 304 where full corrosion resistance is not required. Good weldability for a ferritic grade. Used for railway wagons, bus bodies, sugar industry, mining equipment, and structural applications.

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.

Low-carbon molybdenum-bearing austenitic stainless steel, widely known as AISI 316L. The Mo addition (2–2.5%) significantly improves resistance to pitting and crevice corrosion compared to 1.4301 (304). Low carbon content (max 0.03%) ensures resistance to intergranular corrosion after welding without post-weld heat treatment. Standard grade for pharmaceutical, petrochemical, chemical and marine applications. PREN 23–29.

Low-carbon austenitic stainless steel with 2.5-3.0% Mo — the higher-Mo variant of 1.4404 (316L). The increased Mo (vs 2.0-2.5% in 1.4404) provides superior pitting and crevice corrosion resistance in chloride environments. Ultra-low carbon (≤0.03%) prevents sensitization during welding. Used for chemical processing equipment, pharmaceutical vessels, offshore piping, marine hardware, and pulp & paper digesters where 1.4404 is borderline. Often specified in pharmaceutical/biotech where maximum corrosion resistance is required.

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.

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.

Super duplex stainless steel — SAF 2507 / UNS S32750. PREN >40 giving outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking in chloride environments including hot seawater. 50/50 austenite-ferrite microstructure. UTS >800 MPa — roughly 2x the strength of 316L. Used for offshore oil/gas, desalination, chemical tankers, flue gas desulfurization, and subsea equipment.

Super duplex stainless with W + Cu addition — trade name Zeron 100 (Rolled Alloys). PREN >41 — even higher than SAF 2507 (1.4410) due to tungsten contribution. Outstanding pitting, crevice, and stress corrosion cracking resistance in hot seawater and aggressive chlorides. Used for subsea oil/gas equipment, seawater desalination, FGD systems, and chemical tankers in the most aggressive chloride environments.

Nitrogen-strengthened low-carbon austenitic stainless steel — essentially 316LN. The N addition (0.12–0.22%) raises yield strength to ≥280 MPa (vs 200 for 316L) without sacrificing corrosion resistance or weldability. Preferred over 316L for pressure vessels and cryogenic applications where higher design stress is needed. Approved for ASME Section VIII. Used for chemical reactors, pharmaceutical vessels, cryogenic storage (LNG) and high-pressure piping.

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.

High-molybdenum austenitic stainless steel with 4.0-5.0% Mo — significantly higher than 316L (2.0-2.5%). Provides substantially improved resistance to pitting and crevice corrosion in chloride environments (PREN ~35, vs ~25 for 316L). Low carbon (≤0.03%) and N addition for sensitization resistance and strength. Used for chemical processing in aggressive chloride media, flue gas desulfurization, pulp & paper bleach plants, and seawater-cooled heat exchangers where 316L is insufficient but duplex is not desired.

The most widely used duplex stainless steel worldwide (SAF 2205 / UNS S31803/S32205). Austenitic-ferritic microstructure provides ~2× yield strength of 304/316 (≥450 MPa) with excellent resistance to stress corrosion cracking, pitting (PREN 33-38), and intergranular corrosion. Service temperature -50°C to 300°C. Used for oil & gas production tubing, chemical processing vessels, desalination plants, pulp & paper digesters, heat exchangers, and bridge structures. Weldable with ER2209 filler.

Super duplex stainless steel (SAF 2507 / UNS S32750) with 25% Cr, 7% Ni, 4% Mo, and high N for PREN ≥42. The highest corrosion resistance and strength among standard duplex grades — YS ≥550 MPa is ~2.5× that of 316L. Service temperature up to 300°C. Used for subsea oil & gas equipment (manifolds, trees, risers), desalination plants, flue gas cleaning, chemical tankers, and mining equipment in severe chloride environments. Requires careful welding to avoid sigma phase.