304 is the everyday stainless. It covers food equipment, kitchen work, architectural trim, tanks, enclosures and general fabrication, and it is the most widely produced stainless steel there is. It forms well, welds well and resists most indoor and outdoor corrosion without any coating. We source 304 and 304L in sheet, plate, bar, tube and pipe, and arrange the cut to size.
What 304 stainless is
304 is an austenitic stainless steel, often called 18-8 for its nominal 18% chromium and 8% nickel. The chromium forms a thin oxide film that protects the surface and heals itself when scratched. The nickel keeps the structure austenitic, which makes it tough, ductile and non-magnetic in the annealed condition.
It cannot be hardened by heat treatment, only by cold work. 304L is the low-carbon version, and most 304 sold today is dual certified 304/304L, meeting both.
304 stainless properties
| Property | Value | What it means in the shop |
|---|---|---|
| Tensile strength | 75 ksi minimum | Stronger than mild steel in tension |
| Yield strength | 30 ksi minimum | Low yield: easy to form, but work hardens fast |
| Hardness | 92 HRB maximum | Annealed; gets harder wherever you bend or cut it |
| Density | 0.289 lb/in³ (8.0 g/cm³) | Slightly heavier than carbon steel |
| Weldability | Excellent | Use 304L or dual cert for heavy welded sections |
| Machinability | Fair to poor | Work hardens; keep the tool cutting, never rub |
| Corrosion resistance | Very good | Pits in chlorides, salt water and pool chemicals |
Minimums per ASTM A240 for annealed 304. Mill certs show actual tested values.
Typical uses
- Food and beverage equipment, tables, sinks and hoods
- Tanks, hoppers and process piping for non-chloride service
- Architectural trim, railings and signage
- Enclosures, brackets and hardware
- Exhaust parts and general fabrication
Common finishes and conditions
2B is the standard cold-rolled sheet finish: smooth, gray and slightly reflective. #4 is a directional brushed finish used on appliances, trim and anything customers see; it usually comes with PVC film to protect it. #8 is a mirror finish, and BA (bright annealed) is a smoother, more reflective mill finish than 2B.
Plate is usually hot rolled, annealed and pickled (HRAP, also called No. 1 finish), which is duller and rougher. Bar commonly comes cold finished or turned and polished. Stainless sheet gauges differ from carbon steel gauges, so confirm thickness in decimals on the sheet metal gauge chart.
304 vs 316 stainless
316 adds 2–3% molybdenum, which gives it much better resistance to chlorides: salt water, coastal air, de-icing salts, pool chemicals and many process chemicals. 304 is the right call for indoor work, food service and most outdoor work away from the coast. 316 typically costs more because of the molybdenum and higher nickel. If the part will see salt or chlorides, pay for 316; otherwise 304 does the job.
| 304 | 316 | |
|---|---|---|
| Chromium / nickel / moly (nominal) | 18 / 8 / 0% | 17 / 10–14 / 2–3% |
| Tensile / yield (A240 min) | 75 / 30 ksi | 75 / 30 ksi |
| Chloride and salt resistance | Moderate | Better |
| Typical service | Indoor, food, general outdoor | Marine, coastal, chemical, pharma |
| Matching filler | 308L | 316L |
Welding and machining 304
304 welds well with TIG, MIG or stick. Use 308L filler. Heat between about 800 and 1,500 °F can pull carbon out as chromium carbides at grain boundaries, which leaves the weld zone prone to corrosion. That is why heavy welded parts use 304L or dual-certified material. Keep heat input low to limit distortion, and clean or passivate heat tint on anything that must stay rust-free.
304 work hardens as you cut, so a dull tool or a light rubbing pass makes the next cut harder. Use sharp carbide, positive rake, steady feed and plenty of coolant. If a part is all machining and no welding, 303 machines much better, though it does not weld well.