Stainless Steel Grades: Complete Comparison of 304, 316, 410, 430 & More
AISI/ASTM A240 (multiple UNS) · Published: 2026-07-25 · Updated: August 2026
Stainless steel grades are classified by their metallurgical microstructure into five families: austenitic (300 series and 200 series), ferritic (400 series, 430), martensitic (410, 420, 440), duplex (austenite + ferrite, 2205), and...
Stainless steel grades are classified by their metallurgical microstructure into five families: austenitic (300 series and 200 series), ferritic (400 series, 430), martensitic (410, 420, 440), duplex (austenite + ferrite, 2205), and precipitation-hardening (17-4PH, 15-5PH). Each family offers distinct combinations of corrosion resistance, strength, hardness, and magnetic properties suited to different applications. Austenitic grades (304, 316, 321, 347) are non-magnetic, non-heat-treatable, and offer the best combination of corrosion resistance and formability—they account for ~70% of all stainless production. 304-stainless-steel/">304 is the general-purpose grade; 316-stainless-steel/">316/316L adds molybdenum for chloride resistance; 321/347 are titanium/niobium-stabilized for high-temperature welded service. Ferritic grades (430, 409) are magnetic, lower-cost, and used for automotive exhausts, appliance interiors, and decorative trim where general corrosion resistance is sufficient. Martensitic grades (410, 420, 440C) are magnetic and hardenable by heat treatment—420 and 440C are used for cutlery, surgical instruments, and bearings. Duplex grades (2205, 2507) combine austenite and ferrite for ~2× the yield strength of 316 with superior chloride stress-corrosion cracking resistance—used in oil & gas, pulp & paper, and desalination. Precipitation-hardening grades (17-4PH, 15-5PH) achieve very high strength (1000+ MPa yield) through age-hardening, used in aerospace and high-performance applications. The Pitting Resistance Equivalent Number (PREN = %Cr + 3.3×%Mo + 16×%N) ranks chloride pitting resistance: 304 (PREN 18-20) < 316L (24-28) < 904L (35-43) < 254 SMO (43+) < 2507 super-duplex (42+). For marine immersion, specify PREN >32. For a complete cross-grade comparison with carbon and alloy steels, see our Steel Grade Comparison Guide.
Quick Facts
| Category | Stainless Steel |
| Standard | AISI/ASTM A240 (multiple UNS) |
| Density | 7.7-8.0 g/cm³ (grade-dependent) |
| Yield Strength | 170-1000 MPa (grade- and condition-dependent) |
| Tensile Strength | 485-1800 MPa (grade- and condition-dependent) |
Detailed Mechanical Properties
| Yield Strength Range | 170 MPa (annealed 316L) - 1100 MPa (aged 17-4PH) |
| Elongation Range | 12% (martensitic hardened) - 55% (austenitic annealed) |
| Hardness Range | 70 HB (annealed austenitic) - 60 HRC (hardened 440C) |
Physical Properties
| Density Range | 7.7 (martensitic) - 8.0 (austenitic) g/cm³ |
| Thermal Conductivity | 15-25 W/m·K (lower than carbon steel) |
| Electrical Resistivity | 0.000060-0.000078 Ω·cm |
| Specific Heat | 460-500 J/kg·K |
Global Equivalents & Cross-Reference
| Alternative Standard / Grade | Action |
|---|---|
| AISI 304 | Compare |
| AISI 316 | Compare |
| AISI 410 | Compare |
| AISI 430 | Compare |
| AISI 17-4PH | Compare |
| Duplex 2205 | Compare |
Heat Treatment & Processing
| Note | Austenitic grades cannot be hardened by heat treatment (only by cold work). Martensitic grades are hardened by quenching and tempering. PH grades are hardened by precipitation (age) hardening at 480-620°C. Duplex grades are solution-annealed at 1020-1100°C. |
Welding & Fabrication
| Note | Austenitic grades (304, 316, 321) have excellent weldability with proper filler selection (ER308L, ER316L). Ferritic grades require low heat input to avoid grain coarsening. Martensitic grades are difficult to weld and require preheat + PWHT. Duplex grades require controlled heat input and solution annealing after welding. |
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Frequently Asked Questions
What is the most common stainless steel grade?
AISI 304 (UNS S30400) is the most common, accounting for over 50% of global stainless production. Often called '18/8 stainless' for its 18% Cr and 8% Ni composition, 304 is the default for kitchen equipment, food processing, and architectural applications. <a href="/materials/304-stainless-steel/">304 stainless steel</a> covers full properties.
What is the difference between 304 and 316 stainless steel?
316 adds 2-3% molybdenum, dramatically improving resistance to chloride pitting. Choose 304 for indoor, freshwater, food, and mild chemical service. Choose 316/316L for marine, coastal, pharmaceutical, or any chloride-containing environment. 316 costs ~25-40% more than 304. See <a href="/materials/316-stainless-steel/">316 stainless steel</a> for full grade details.
What is the strongest stainless steel grade?
Precipitation-hardening grades like 17-4PH (UNS S17400) achieve yield strengths over 1000 MPa (145 ksi) after age-hardening, comparable to alloy steels like AISI 4340. Martensitic 440C achieves 1900+ MPa tensile in the hardened condition but with reduced corrosion resistance. Duplex 2507 super-duplex offers ~550 MPa yield with excellent corrosion resistance.
Which stainless steel is magnetic?
Ferritic (430, 409) and martensitic (410, 420, 440) grades are magnetic. Duplex grades (2205, 2507) are magnetic. Austenitic grades (304, 316, 321) are essentially non-magnetic when annealed but may become slightly magnetic after cold working. If strict non-magnetic behavior is required, specify 316L in the annealed condition.
What stainless steel is best for marine environments?
For atmospheric marine exposure (coastal), 316L (PREN 24-28) is the minimum recommendation. For splash zones or seawater immersion, specify a higher-PREN grade: duplex 2205 (PREN 35), super-austenitic 254 SMO (PREN 43), or nickel-based alloys like Inconel 625. 304 and 430 are not suitable for marine service.
References & International Standards
- ASTM International. Standard Specifications for Steel & Metal Alloys. astm.org
- International Organization for Standardization (ISO). Metallic Materials — Cross-Reference Database. iso.org
- American Iron and Steel Institute (AISI). Steel Grade Designations & Equivalents. steel.org
- European Committee for Standardization (CEN). EN Steel Standards & Numbering System. cencenelec.eu
Stainless & Corrosion-Resistant Steel — Engineering Reference
Stainless steels are defined by their chromium content (minimum 10.5%), which forms a self-healing passive layer of chromium oxide that resists corrosion. Grades are classified by microstructure: austenitic (300 series), ferritic (400 series), martensitic, and duplex.
ASTM A240/A276/A312, EN 10088, JIS G4304/G4305, GB/T 3280/4237
Food processing equipment, medical implants, chemical tanks, architectural cladding, marine hardware, pharmaceutical piping
For welded stainless fabrications, specify the low-carbon variant (304L, 316L) to prevent chromium carbide precipitation at grain boundaries, which causes intergranular corrosion (weld decay).