304 Stainless Steel (UNS S30400)
The general-purpose 18-8 stainless: 75 ksi annealed bar, cold-worked bolts to 160 ksi, non-magnetic, and resistant to water, food and most mild chemicals.
What 304 Stainless is.
Type 304 is the most widely used stainless steel. Its 18 percent chromium and 8 percent nickel give a stable austenitic structure that is easily machined, formed and welded, non-magnetic when annealed, and resistant to atmospheric, fresh-water and food-service corrosion. For fasteners it is ordered as commercial 304 to ASTM F593, in annealed, cold-worked or strain-hardened conditions, or as ASTM A193 B8 when the job is a pressure-retaining flange.
We machine 304 bolts, studs, nuts, washers and components from certified A276 bar, and cold work or strain harden to the F593 condition specified. If your order calls up A193 B8 or A320 B8, use those pages; the material is the same but the testing and marking rules differ.
Chemical composition.
| Element | Symbol | Min % | Max % |
|---|---|---|---|
| Carbon | C | — | 0.08 |
| Manganese | Mn | — | 2.00 |
| Phosphorus | P | — | 0.045 |
| Sulfur | S | — | 0.030 |
| Silicon | Si | — | 1.00 |
| Chromium | Cr | 18.0 | 20.0 |
| Nickel | Ni | 8.0 | 11.0 |
Values per ASTM A276/A276M-17 Tables 1 and 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team.
Mechanical properties.
| Condition and nominal diameter (in.) | Tensile strength, min (ksi) | Yield strength 0.2% offset, min (ksi) | Elongation, min (%) | Reduction of area, min (%) | Hardness |
|---|---|---|---|---|---|
| Condition A (annealed), hot finished — all | 75 | 30 | 40 | 50 | — |
| Condition A, cold finished — ½ and under | 90 | 45 | 30 | 40 | — |
| Condition A, cold finished — over ½ | 75 | 30 | 30 | 40 | — |
| Condition B (cold worked) — ¾ and under | 125 | 100 | 12 | 35 | — |
| Condition B — over ¾ to 1 | 115 | 80 | 15 | 35 | — |
| Condition B — over 1 to 1¼ | 105 | 65 | 20 | 35 | — |
| Condition B — over 1¼ to 1½ | 100 | 50 | 24 | 45 | — |
| Condition B — over 1½ to 1¾ | 95 | 45 | 28 | 45 | — |
| Condition S (strain hardened) — 2 and under | 95 | 75 | 25 | 40 | — |
| Condition S — over 2 to 2½ | 90 | 65 | 30 | 40 | — |
| Condition S — over 2½ to 3 | 80 | 55 | 30 | 40 | — |
Values per ASTM A276/A276M-17 Tables 1 and 2 (verified against the specification). Confirm the edition called out on your purchase order with our estimating team. Condition B applies to 202, 302, 304, 304N, 316, 316N, 304L and 316L; Condition S to 304, 304N, 316, 316N, 304L and 316L.
| F593 condition · marking | Nominal diameter (in.) | Tensile strength (ksi) | Yield strength, min (ksi) | Rockwell hardness |
|---|---|---|---|---|
| AF (annealed after forming) · F593A | ¼ to 1½ | 65 to 85 | 20 | B85 max |
| A (annealed) · F593B | ¼ to 1½ | 75 to 100 | 30 | B65 to B95 |
| CW1 (cold worked) · F593C | ¼ to ⅝ | 100 to 150 | 65 | B95 to C32 |
| CW2 (cold worked) · F593D | ¾ to 1½ | 85 to 140 | 45 | B80 to C32 |
| SH1 (strain hardened) · F593A | ¼ to ⅝ | 120 to 160 | 95 | C24 to C36 |
| SH2 (strain hardened) · F593B | ¾ to 1 | 110 to 150 | 75 | C20 to C32 |
| SH3 (strain hardened) · F593C | 1⅛ to 1¼ | 100 to 140 | 60 | B95 to C30 |
| SH4 (strain hardened) · F593D | 1⅜ to 1½ | 95 to 130 | 45 | B90 to C28 |
Values per ASTM F593-24 Table 2, full-size tests (verified against the specification). Yield is 0.2 % offset; hardness is Rockwell. Machined-specimen limits differ slightly.
Specifications that apply.
How 304 Stainless ships from Houston.
- Hex and heavy hex bolts and cap screws
- Full-thread studs and threaded rod
- Socket head cap and set screws
- Hex, jam and lock nuts
- Washers and spacers
- Machined components from certified bar
304 Stainless fasteners we make.
Every item is manufactured to your drawing or standard in 304 Stainless, imperial or metric, with an EN 10204 3.1 certificate.
What is 304 stainless steel?
304 is the basic austenitic stainless steel: about 18 percent chromium for corrosion resistance and 8 to 11 percent nickel to hold the austenitic structure at room temperature. That structure is what makes the alloy non-magnetic, tough at cryogenic temperatures and impossible to harden by heat treatment. Strength comes from cold work instead, which is why the F593 conditions range from 75 ksi annealed to 160 ksi strain hardened in small sizes.
304 versus A193 B8
They are the same chemistry. A193 B8 adds the heat-treatment classes, the per-lot testing and the marking that pressure-vessel and piping codes require, and it is what an ASME flange drawing will call for. Commercial 304 to F593 is the right specification for general machinery, structures and equipment where the drawing simply says stainless. If the order is unclear, we supply B8 Class 1, which satisfies both.
Galling and thread lubrication
Austenitic threads gall when run dry under load. We supply 304 fasteners with anti-seize, PTFE coating or silver-plated nuts on request, and can pair 304 bolts with 316 or Nitronic 60 nuts where the joint is assembled repeatedly.
Testing, certification and marking
- Tensile and hardness tested per lot on the finished product
- Grade or marking symbol F593A to F593D and manufacturer's identification on every piece
- EN 10204 3.1 material test report with heat number and chemistry; 3.2 witness available
- PMI verification and intergranular corrosion testing (ASTM A262) arranged on request
Recent 304 Stainless jobs.
304L Stainless Steel (UNS S30403)
304 with carbon held to 0.030 percent so welds and heat-affected zones do not sensitize — the choice for welded assemblies and parts that will be heated in service.
ASTM A276 bar · ASTM F593 bolts316 Stainless Steel (UNS S31600)
The marine and chemical-plant stainless: 2 to 3 percent molybdenum for pitting and crevice resistance in chlorides, with the same strength tables as 304.
ASTM A193 / ASME SA-193ASTM A193 Grade B8 Class 1 (304 Stainless)
304 stainless bolting — Class 1 for corrosion resistance and cryogenic-to-1500 °F service, Class 2 strain hardened to 125 ksi for strength.