MATERIALS · STAINLESS STEEL
AISI 304 / 1.4301. SS304 is the standard 18/8 chromium-nickel austenitic stainless steel and the most widely used stainless grade. It resists corrosion well in most atmospheres, foods and many chemicals, welds and forms easily, and is essentially non-magnetic when annealed. It is harder to machine than 303 because it work-hardens and forms long, stringy chips.
DENSITY
8 g/cm³HARDNESS
215 HB maxTENSILE STRENGTH
500–700 MPaMACHINABILITY
Fair (45%)TURNING, CARBIDE
90–160 m/minCALCULATOR
Enter your part size and your own rates. Density and a starting cutting speed are filled in for this material.
EQUIVALENT GRADES
Nearest equivalents across standards. Check the exact standard on critical parts.
| Standard | Grade |
|---|---|
| AISI/SAE | 304 |
| UNS | S30400 |
| EN / W.Nr | X5CrNi18-10 / 1.4301 |
| IS | X04Cr19Ni9 (IS 6603) |
| JIS | SUS304 |
| BS | 304S31 (En58E) |
Also known as: 304, 1.4301, X5CrNi18-10, 18/8, SUS304, 304S31, En58E
CHEMICAL COMPOSITION
| Element | Weight % |
|---|---|
| C | ≤0.07 (EN 10088-3); ≤0.08 (ASTM) |
| Si | ≤1.00 |
| Mn | ≤2.00 |
| P | ≤0.045 |
| S | ≤0.030 |
| Cr | 17.5–19.5 (EN 10088-3); 18.0–20.0 (ASTM) |
| Ni | 8.0–10.5 |
| N | ≤0.10 |
MECHANICAL PROPERTIES
| Condition | Solution annealed bar, EN 10088-3 (up to 160 mm); ASTM A276 minimums in brackets |
| Tensile strength (MPa) | 500–700 (ASTM: 515 min) |
| Yield strength (MPa) | 190 min (ASTM: 205 min) |
| Elongation (%) | 45 min (ASTM: 40 min) |
| Hardness | 215 HB max |
| Density (g/cm³) | 8 |
MACHINING
| Turning, carbide (m/min) | 90–160 |
| Turning, HSS (m/min) | 20–30 |
| Machinability | Fair, 45% (AISI B1112 = 100% (published figures 42–45%)) |
304 work-hardens quickly and forms long, stringy chips. Use a rigid set-up and sharp positive-rake tools (around 10–16° rake and 6–8° clearance), and keep the feed and depth of cut large enough to cut beneath the hardened skin left by the previous pass; never let the tool dwell or rub. Chip-breaker inserts stop swarf wrapping round the work. Flood coolant is essential: water-soluble emulsion for carbide at higher speeds, sulphurised or chlorinated neat oil for heavy, slow HSS work. For long production runs, ask the mill for an improved-machinability 304 bar.
APPLICATIONS
INDUSTRIES THAT USE IT
PROCESSING
| Heat treatment | Cannot be hardened by heat treatment. Solution anneal at 1010–1120 °C and cool rapidly; avoid long exposure at 425–860 °C, which causes carbide precipitation (use 304L where this cannot be avoided). |
| Welding | Excellent by all standard fusion methods with or without filler; use 308 filler (308L for 304L), and anneal heavy welded sections of 304 for maximum corrosion resistance (not needed for 304L). |
| Supplied as | Round bar, Rod, Sheet, Strip, Plate, Pipe, Tube, Fittings and flanges |
QUESTIONS
Annealed 304 is austenitic and responds only negligibly to a magnet (relative permeability roughly 1.003–1.05). Cold work such as bending, drawing or forming can turn some of the structure into martensite, so worked areas may become slightly magnetic.
316 adds molybdenum, which improves resistance to pitting and crevice corrosion in chlorides. As a guide, 304 is considered resistant to potable water with up to about 200 mg/L chloride at room temperature, against about 1000 mg/L for 316. 316 costs more and is usually run slightly slower when machining.
304L has a lower carbon limit (0.030% max against 0.07–0.08%), which avoids chromium carbide precipitation next to welds, so heavy welded sections do not need post-weld annealing. 304L has slightly lower specified strength, and plate and pipe are often stocked dual-certified to both grades.
RELATED MATERIALS
STAINLESS STEEL
AISI 303 / 1.4305 · 8 g/cm³
STAINLESS STEEL
AISI 316 / 316L / 1.4401 / 1.4404 · 8 g/cm³
STAINLESS STEEL
AISI 410 / 1.4006 · 7.75 g/cm³
STAINLESS STEEL
AISI 630 (17-4 PH) / 1.4542 · 7.75 g/cm³
Data reviewed 2026-10-02 against:
Typical values for reference. Always check the mill certificate and the standard your customer specifies.
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