304 steel (S30400): properties, composition, equivalents

304 stainless steel (UNS S30400, 18-8): 18 % Cr, 8 % Ni, ≤ 0.08 % C. 205 MPa (30 ksi) yield, 515 MPa (75 ksi) tensile, non-magnetic, food-safe. Composition, properties, 304 vs 304L vs 316, and 1.4301/SUS304 equivalents.

What is 304?

Type 304 is the world's default stainless steel: an austenitic alloy of 18 % chromium and 8 % nickel (hence '18-8'), with carbon held at 0.08 % max, listed as UNS S30400 in ASTM A240 (plate), A276 (bar), A312 (pipe) and a dozen other product standards. It resists oxidizing acids, food media, most organic chemicals and ordinary atmospheres; it forms, draws and welds easily; it is non-magnetic, hygienic and tough to cryogenic temperatures. Roughly half of all stainless steel made is 304 or its low-carbon twin 304L.

Minimum properties are modest — 205 MPa (30 ksi) yield and 515 MPa (75 ksi) tensile — but the alloy work-hardens strongly, so cold-rolled tempers up to 1275 MPa are available, and typical annealed sheet actually tests at 260–300 MPa yield. Strength is retained to about 800 °C (oxidation limit ≈ 870 °C continuous), and there is no ductile-to-brittle transition.

Its limits are chloride pitting and stress-corrosion cracking above ~60 °C in chloride solutions — the reasons 316 exists — and sensitization when slowly cooled through 500–800 °C after welding thick sections, which is why 304L (C ≤ 0.03 %) is specified for heavy weldments. EN 1.4301, JIS SUS304, GB 06Cr19Ni10 and GOST 08Kh18N10 are identical for procurement.

304 chemical composition

ASTM A240/A240M-22 Table 1 (S30400). Bar per A276 uses the same limits with Si ≤ 1.00. Compare EN 1.4301: Cr 17.5–19.5, C ≤ 0.07, S ≤ 0.015.

304 mechanical properties

ASTM A240 Table 2; A276 Table 2; A666 for temper-rolled sheet. Minimum values; typical annealed 2B sheet tests at 260–300 MPa yield and 600–650 MPa tensile.

Impact toughness

304 requires a minimum Charpy V-notch energy of 100 J at -196 °C (typical). No transition temperature; 304 is a standard cryogenic material down to liquid-helium temperatures (ASME allows use to −254 °C / −425 °F without impact testing in most product forms).

304 equivalent grades

Identical = same composition and mechanical limits within rounding. Near = one limit differs (e.g. carbon max or impact temperature). Functional = interchangeable for most uses after an engineering check. Full cross-reference for 304 →

Old and superseded designations

Product forms and tolerance standards

Product forms: sheet, strip and plate (ASTM A240), bar and shapes (A276, A479), seamless and welded pipe (A312 TP304), tube (A269, A249), fittings (A403), flanges (A182 F304), forgings, wire, fasteners (F593), castings as CF8 (A351).

Dimensional tolerances: sheet/plate: ASTM A480 (thickness, flatness, finish Nos. 1, 2B, 2D, BA, 3, 4, 7, 8); bar: ASTM A484; pipe: ASTM A999 / ASME B36.19.

Key property values

304 stainless steel yield strength

Minimum 205 MPa (30 ksi) annealed; typical 260–300 MPa. Cold-finished bar ≥ 310 MPa; temper-rolled sheet ¼ hard ≥ 515 MPa, ½ hard ≥ 760 MPa, full hard ≥ 965 MPa (A666).

304 tensile strength

Minimum 515 MPa (75 ksi); typical 600–650 MPa annealed; up to 1275 MPa (185 ksi) full-hard sheet.

304 hardness

Annealed max 201 HB / 92 HRB (≈ 210 HV); typical 150–180 HB. Cold work raises it to 30–40 HRC. Not hardenable by heat treatment.

Corrosion resistance

PREN = Cr + 3.3 Mo + 16 N ≈ 18–20. Resists nitric acid to 65 %, organic acids, alkalis, fresh water, food and dairy media; pits in chloride solutions above ~200 ppm at elevated temperature and is susceptible to chloride SCC above 60 °C. Atmospheric: excellent inland, tea-staining near the coast.

High-temperature use

Continuous oxidation limit ≈ 870 °C (925 °C intermittent). For creep-rated service above 525 °C, ASME requires 304H (C ≥ 0.04 %). Sensitization risk on long exposure at 425–860 °C for 304 (not 304L).

Physical properties

Density 8.0 g/cm³ (0.289 lb/in³), E = 193 GPa (28 × 10⁶ psi), thermal expansion 17.2 × 10⁻⁶/K (0–100 °C), conductivity 16.2 W/m·K, resistivity 0.72 µΩ·m, specific heat 500 J/kg·K, magnetic permeability 1.02 max annealed.

Heat treatment

Solution anneal 1010–1120 °C (1850–2050 °F), water quench or rapid air cool. Stress relief 400–450 °C for cold-worked parts (below the sensitization range). Never slow-cool through 500–800 °C.

Weldability

Excellent weldability by GTAW, GMAW, SMAW, SAW, laser and resistance welding without preheat; filler ER308/ER308L (AWS A5.9) or E308L-16. Interpass ≤ 150 °C (300 °F); keep heat input moderate to limit distortion (expansion 50 % above carbon steel). For sections > 6 mm in corrosive service use 304L base and 308L filler, or solution-anneal after welding. Purge pipe roots with argon.

Machining, forming and heat treatment

Machinability ≈ 45 % of B1112 (work-hardens; use sharp positive-rake carbide, 60–120 m/min, steady feed, no dwelling); 303 is the free-machining alternative. Forming: outstanding deep-drawability and stretch formability; spring-back and required press force are about 1.5× carbon steel; use lubricants to avoid galling. Finishes per A480: No. 1 (hot-rolled), 2D, 2B (standard cold-rolled), BA, No. 3/4 (brushed), No. 7/8 (polished).

Typical applications

• Kitchen sinks, cookware, cutlery, food-service and restaurant equipment
• Food, beverage, dairy and pharmaceutical process equipment, tanks and piping
• Architectural panels, handrails, column covers (inland and urban)
• Chemical containers, water tanks, heat exchangers for non-chloride service
• Automotive and truck trim, exhaust components, fuel tanks
• Cryogenic vessels and LNG equipment (with 304L)
• Fasteners (A2-70 / ASTM F593 Group 1), springs (temper-rolled 301/304)

304 compared with related grades

Frequently asked questions

Related grades

Verified against ASTM A240/A240M-22; ASTM A240/A240M-22 Tables 1–2; ASTM A276/A276M-23; ASTM A666-15; ASME BPVC II-D (temperature limits). Last checked: September 2026.