303 vs 304 Stainless Steel
Side-by-side comparison · Composition · Properties · Selection guide
303 and 304 share the same 18/8 austenitic base; the difference is sulfur. 303 adds ≥0.15% sulfur to form chip-breaking sulfide inclusions, roughly doubling machining rates — and the same inclusions cost it some corrosion resistance and essentially all of its weldability. The choice is therefore decided by how the part is manufactured, not by strength, which is nearly identical in the annealed condition.
Full datasheets:303 Stainless Steel·304 Stainless Steel
At a Glance
| 303 | 304 | |
|---|---|---|
| Type | Austenitic (free-machining) | Austenitic |
| UNS | S30300 | S30400 |
| Standard | ASTM A582 | ASTM A240/A240M |
| Density | 7.93 g/cm³ | 7.93 g/cm³ |
Corrosion Resistance and Service Limits
303
- General corrosion resistance comes from the chromium-rich passive film; nickel, molybdenum, nitrogen and copper change performance by grade.
- Check chlorides, temperature, crevices, deposits, process chemistry and cleaning conditions. A grade designation alone is not a service-life guarantee.
304
- General corrosion resistance comes from the chromium-rich passive film; nickel, molybdenum, nitrogen and copper change performance by grade.
- Check chlorides, temperature, crevices, deposits, process chemistry and cleaning conditions. A grade designation alone is not a service-life guarantee.
Fabrication and Heat Treatment
| Operation | 303 | 304 |
|---|---|---|
| Welding | Generally weldable with a qualified procedure and matching or over-alloyed filler where required; remove heat tint when corrosion service demands it. | Generally weldable with a qualified procedure and matching or over-alloyed filler where required; remove heat tint when corrosion service demands it. |
| Forming | Good ductility is typical, but rapid work hardening increases forming load and springback; bend radius and intermediate annealing depend on grade and reduction. | Good ductility is typical, but rapid work hardening increases forming load and springback; bend radius and intermediate annealing depend on grade and reduction. |
| Machining | Use rigid tooling, positive feeds and controlled heat because the material work-hardens; free-machining grades require separate corrosion and welding review. | Use rigid tooling, positive feeds and controlled heat because the material work-hardens; free-machining grades require separate corrosion and welding review. |
| Heat treatment | Solution annealing and rapid cooling restore the intended condition where applicable. Austenitic grades are not hardened by conventional quench-and-temper treatment. | Solution annealing and rapid cooling restore the intended condition where applicable. Austenitic grades are not hardened by conventional quench-and-temper treatment. |
Chemical Composition (wt%)
| Element | 303 | 304 |
|---|---|---|
| C | ≤0.15 | ≤0.08 |
| Mn | ≤2.00 | ≤2.00 |
| Si | ≤1.00 | ≤0.75 |
| Cr | 17.0–19.0 | 17.5–19.5 |
| Ni | 8.0–10.0 | 8.0–10.5 |
| P | ≤0.20 | ≤0.045 |
| S | ≥0.15 | ≤0.030 |
| Mo | ≤0.60 (optional) | — |
| N | — | ≤0.10 |
Mechanical Properties
| Property | 303 | 304 |
|---|---|---|
| Tensile strength (annealed, typical) | ≈620 MPa | — |
| Yield strength (0.2%, typical) | ≈240 MPa | — |
| Elongation (50 mm, typical) | ≈50% | — |
| Hardness | ≤262 HBW | ≤201 HBW |
| Tensile strength | — | ≥515 MPa (75 ksi) |
| Yield strength (0.2%) | — | ≥205 MPa (30 ksi) |
| Elongation (50 mm) | — | ≥40% |
Which One Should You Choose?
Choose 303 for:
- High-volume turned parts on screw machines and lathes
- Fittings, bushings and valve bodies where machining time dominates cost
- Tight-tolerance parts needing excellent surface finish off the tool
- Dry, indoor or oiled mechanical service
Choose 304 for:
- Anything that will be welded — 303 hot-cracks in the weld zone
- Deep drawing, bending and other heavy cold forming
- Chloride, outdoor or washdown exposure
- Food-contact and hygienic surfaces
Our verdict
Let the process route decide: if the part spends its life on a CNC lathe and stays dry, 303 pays for itself in cycle time. The moment welding, forming or meaningful corrosion exposure enters the drawing, specify 304 — the machining penalty is real but recoverable, while a cracked 303 weld or pitted food surface is not.
Cost and Availability
Compare the current stock position, mill route, minimum production quantity, processing yield, testing and delivered cost for 303 and 304 at quotation time. A fixed price ratio would be misleading because product form, size, condition and market timing can change the commercial result.
Do Not Substitute Without Review
Do not replace 303 with 304, or the reverse, from the grade name alone. Recheck chemistry, mechanical-property condition, product standard, dimensions, corrosion environment, welding procedure and project approval before substitution.
303 & 304 Products We Export
304 Stainless Steel Sheet
304/304L stainless steel sheet in 2B, BA, No.4 and mirror finish, in quotation-confirmed dimensions, cut to size, with ordered documentation.
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304 Stainless Steel Welded Pipe
304 welded stainless steel pipe and tube to ASTM A312, A249 and A554 — industrial, sanitary and polished decorative, round, square and rectangular sections.
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304 Stainless Steel Round Bar
304/304L stainless steel round bar, in quotation-confirmed dimensions, bright drawn h9/h11 or peeled, cut to length — machining stock with full heat traceability.
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Frequently Asked Questions
Are 303 and 304 the same strength?
Effectively yes in the annealed state — both sit around 500–620 MPa tensile with similar yield. 303 is only supplied as bar and never in heavily cold-worked tempers, so if you need strain-hardened strip or formed strength, 304 is the only option of the two.
How much faster does 303 machine than 304?
Shops typically run 60–100% higher cutting speeds with better chip control and longer tool life. On high-volume turned parts that often halves machine-hours per piece, which outweighs 303's modest bar-stock price premium.
Is 303 acceptable for food-contact parts?
It is best avoided on product-contact surfaces. The sulfide stringers can pit under acidic cleaning regimes and trap residues at the surface. Many food-machinery specs explicitly restrict free-machining grades; 304 or 316L are the compliant choices.
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Technical content updated: 2026-07-29
Organizational author: Tsingshan (Shandong) Iron & Steel Co., Ltd..Review method, status and limitations.