303 Stainless Steel vs. 304: What’s the Difference?
Oct 14, 2025
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When choosing stainless steel for machining or fabrication, two of the most common grades are AISI 303 and AISI 304. While both belong to the austenitic 18-8 stainless steel family, they serve very different purposes. Understanding their chemical composition, mechanical properties, corrosion resistance, and machinability is essential for making the right purchasing decision.
What is 303 stainless steel?
303 stainless steel is an austenitic stainless steel with added sulfur. It offers excellent machinability but offers less corrosion resistance than other grades, such as 304. Its primary applications include fasteners, screws, shafts, and other parts that require extensive machining.
What is 304 stainless steel?
304 stainless steel is the most common, versatile, and widely used grade of stainless steel, known as "18/8" for its ~18% chromium and ~8% nickel content. This austenitic alloy offers excellent corrosion resistance, is easy to clean and form, and resists heat, making it ideal for diverse applications, particularly in kitchens, food processing, and general hardware.
1. Chemical Composition
The main difference between 303 and 304 stainless steel lies in their sulfur content. Grade 303 contains added sulfur to improve machinability, while 304 remains cleaner and more corrosion-resistant.
| Element | AISI 303 (%) | AISI 304 (%) |
|---|---|---|
| Carbon (C) | ≤ 0.15 | ≤ 0.08 |
| Manganese (Mn) | ≤ 2.00 | ≤ 2.00 |
| Silicon (Si) | ≤ 1.00 | ≤ 1.00 |
| Phosphorus (P) | ≤ 0.20 | ≤ 0.045 |
| Sulfur (S) | 0.15–0.35 | ≤ 0.03 |
| Chromium (Cr) | 17.0–19.0 | 18.0–20.0 |
| Nickel (Ni) | 8.0–10.0 | 8.0–10.5 |
| Molybdenum (Mo) | - | - |
2. Mechanical Properties
| Property | AISI 303 | AISI 304 |
|---|---|---|
| Tensile Strength (MPa) | 620 min | 515–750 |
| Yield Strength (MPa) | 240 min | 205–290 |
| Elongation (%) | 40 | 40–60 |
| Hardness (HB) | 190 max | 183 max |
| Density (g/cm³) | 8.03 | 8.00 |
303 vs 304 stainless steel yield strength
The yield strength is the highest stress that can be implemented along the materials axis before the alloy initiates a change in shape. The yield strength offset at 0.2% for grade 304 is 290Mpa, whereas, for grade 303, the same value stands at 310 Mpa.
Corrosion Resistance Comparison
AISI 304 stainless steel demonstrates significantly superior corrosion resistance to AISI 303, particularly in environments containing chloride ions (≤200 ppm) or acidic media. Its stable chromium oxide passive film, supported by 18.0–20.0% chromium and 8.0–10.5% nickel with minimal sulfur content (≤0.03%), effectively resists pitting and crevice corrosion, enabling it to withstand short-term exposure to low-to-medium concentration hydrochloric acid, sulfuric acid, and seawater (e.g., food processing equipment, offshore platform structures).
In contrast, AISI 303 incorporates 0.15–0.35% sulfur to enhance machinability, which disrupts the uniformity of its passive film and increases susceptibility to intergranular corrosion. As a result, it is only recommended for mild conditions without strong corrosive agents or in dry atmospheric environments (e.g., non-exposed parts of general mechanical components).
Is 303 Stainless Steel Magnetic?
No. 303 stainless steel is generally considered non-magnetic in its annealed condition. This is typical for austenitic stainless steel.
Which is better, 303 or 304 stainless steel?
While 303 is less corrosion-resistant than 304, it still offers good resistance to oxidation when intermittently exposed to temperatures up to 1400°F. However, the sulfur content negatively impacts 303's weldability, making it prone to cracking.
Price and Availability (October 2025)
| Product | Material Grade | Size Range | Surface Finish | Approx. Price (USD/kg) |
|---|---|---|---|---|
| Stainless Steel Round Bar | 303 | Ø 6–200 mm | Bright, Peeled | $2.80–$3.10/kg |
| Stainless Steel Round Bar | 304 | Ø 6–200 mm | Bright, Pickled | $2.60–$2.90/kg |
| Stainless Steel Sheet | 304 | 0.3–6 mm | 2B, BA, No.1 | $2.50–$2.80/kg |
💡 Note: Prices vary depending on surface finish, order volume, and international freight costs. Gnee provides competitive factory pricing and customized cutting, polishing, and packaging services.
Why Choose Gnee
✅ Over 18 years of stainless steel manufacturing and export experience
✅ Complete product range: 303 / 304 bars, rods, sheets, and tubes
✅ ISO, SGS, BV certified materials ensuring quality compliance
✅ Advanced processing: CNC cutting, polishing, and surface treatment
✅ Professional packaging for moisture-proof and damage-free delivery
✅ Fast delivery time: 7–15 days depending on order quantity
ASTM Specification of Stainless Steel 303
Trade Name: 303 Se Stainless, 303 Se
ASTM A582 (Round Bars) 303 SS Condition B, 303 SS Condition A
ASTM A581 (Stainless Steel Wire)
ASTM A895 (plate, sheet, and strip)
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