When it comes to stainless steel, understanding the differences between various grades can be crucial for selecting the right material for your project. Two commonly compared grades are 303 and 304 stainless steel. Both have unique properties and are used in different applications, so let’s dive into what sets them apart.
What is 303 Stainless Steel?
303 stainless steel is an austenitic stainless steel known for its excellent machinability. It contains about 17-19% chromium, 8-10% nickel, and 0.15-0.35% sulfur, which enhances its ability to be easily cut and shaped. It is commonly used in manufacturing components like screws and bolts where precise machining is crucial. Although it offers good corrosion resistance, it is less resistant than 304 stainless steel.
303 Stainless Steel Properties and Composition
Key properties include:
Physical Properties
| Property | 303 Stainless Steel |
|---|---|
| Density | 8.03 g/cm³ |
| Melting Point | 1400-1450°C |
| Specific Heat | 0.50 J/g·°C |
| Thermal Conductivity | 16.3 W/m·K |
| Electrical Resistivity | 0.73 µΩ·cm |
| Magnetic Properties | Non-magnetic |
Mechanical Properties
| Property | 303 Stainless Steel |
|---|---|
| Tensile Strength | 90,000 psi (620 MPa) |
| Yield Strength | 30,000 psi (210 MPa) |
| Elongation | 40% |
| Hardness (Rockwell B) | 90-95 HB |
| Modulus of Elasticity | 28,000,000 psi (193 GPa) |
| Poisson’s Ratio | 0.27 |
Chemical Composition
| Element | Percentage |
|---|---|
| Iron (Fe) | Balance |
| Chromium (Cr) | 17.0 – 19.0% |
| Nickel (Ni) | 8.0 – 10.0% |
| Sulfur (S) | 0.15 – 0.35% |
| Phosphorus (P) | 0.15 – 0.35% |
| Carbon (C) | Up to 0.15% |
| Manganese (Mn) | Up to 2.0% |
What is 303 Stainless Steel Equivalent To?
303 stainless steel is known for its machinability and is equivalent to several other stainless steel grades depending on the standards and regions. Here are some common equivalents:
| Standard | Equivalent Grade | Country/Region |
|---|---|---|
| AISI | 303 | United States |
| EN | 1.4305 | Europe |
| JIS | SUS303 | Japan |
| UNS | S30300 | United States |
| DIN | 1.4305 | Germany |
| BS | 303S31 | United Kingdom |
303 Stainless Steel Price Per Pound?
As of 2024, the approximate price for 303 stainless steel is typically between $3.00 and $6.00 per pound. The price of 303 stainless steel can vary based on factors such as the form (e.g., bar, sheet, plate), size, quantity, and market conditions.
Is 303 or 304 More Expensive?
Typically, 304 stainless steel is more expensive than 303 stainless steel. 304 stainless steel contains higher amounts of chromium and nickel compared to 303, which increases its cost.
Is 303 Stainless Steel Corrosion Resistant Steel?
303 stainless steel is corrosion resistant, but not as much as 304 stainless steel. It offers good resistance to corrosion in many environments, but it is less effective in highly corrosive environments compared to 304 due to its lower chromium and nickel content. It is prone to corrosion and cracking in chloride environments above 60 ℃.
Is 303 Stainless Steel Magnetic?
303 stainless steel is generally non-magnetic in its annealed (heat-treated) state. However, it can become slightly magnetic if it is cold-worked or machined. This magnetic property is due to the presence of ferrite in the structure that can develop during processing.
Will a Magnet Stick to 303 Stainless Steel?
A magnet may stick slightly to 303 stainless steel, especially if it has been cold-worked or machined. However, 303 stainless steel is generally considered non-magnetic in its annealed state.
What is 303 Stainless Steel Good For?
303 stainless steel is well-suited for applications where ease of machining is a priority. Its key advantages make it ideal for:
- Precision machined parts (screws, bolts, nuts)
- Automotive components
- Aerospace parts
- Industrial equipment (valves, pumps)
- Medical devices
303 Stainless Steel vs 304
Here’s a comparison of 303 and 304 stainless steel:
| Property | 303 Stainless Steel | 304 Stainless Steel |
|---|---|---|
| Corrosion Resistance | Good, but less than 304; suitable for most general environments | Excellent; better for harsh environments and exposure to chemicals |
| Machinability | Excellent; designed for easy machining | Good; not as easy to machine as 303 |
| Strength | Similar to 304; tensile strength around 90,000 psi (620 MPa) | Similar; tensile strength around 70,000 psi (480 MPa) |
| Composition | 17-19% Chromium, 8-10% Nickel, 0.15-0.35% Sulfur, 0.15% Carbon | 18-20% Chromium, 8-10.5% Nickel, up to 0.08% Carbon |
| Magnetic Properties | Generally non-magnetic; can be slightly magnetic if cold-worked | Generally non-magnetic |
| Applications | Precision machining components like screws and fittings | Widely used in food processing, chemical processing, and construction |
Which is Better, 303 or 304 Stainless Steel?
303 is often used in applications where high-speed machining is essential, such as in the manufacturing of components like screws, bolts, and fittings. 304 is ideal for applications requiring high corrosion resistance and is frequently used in the food industry, chemical processing, and construction.
Which is Stronger, 303 Stainless Steel or 304?
304 stainless steel is generally stronger than 303 stainless steel. While 303 has a tensile strength of about 90,000 psi (620 MPa), 304 typically has a lower tensile strength of around 70,000 psi (480 MPa) but can be work-hardened to enhance strength.
Which is Easier to Machine 303 or 304?
303 stainless steel is easier to machine than 304 stainless steel. This is because 303 is specifically alloyed with sulfur and phosphorus, which improve its machinability by reducing friction and heat during cutting.
Which is Softer 303 or 304 Stainless Steel?
303 stainless steel is generally softer than 304 stainless steel. This is due to its higher sulfur content, which improves machinability but results in a lower hardness compared to 304 stainless steel.
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Conclusion
In summary, both 303 and 304 stainless steel have their unique advantages. Choosing between them depends on your specific needs—whether you prioritize machinability or corrosion resistance. By understanding these properties, you can make an informed decision and select the right material for your project.
More resources:
410 Stainless Steel vs 304: Source — BOYI
304 vs 316 Stainless Steel: Source — BOYI
FAQ
303 stainless steel is not easily hardened. Unlike some other stainless steel grades, 303 is designed primarily for machinability rather than hardness. It cannot be significantly hardened through heat treatment.
303 stainless steel is resistant to rust and corrosion in many environments, but it is not immune. It generally performs well in mild environments, but it can rust if exposed to harsh conditions, chemicals, or prolonged moisture.
303 stainless steel is commonly used in applications where ease of machining is crucial. It is ideal for precision machined parts such as screws, bolts, and nuts.
316 stainless steel excels in corrosion resistance, particularly in aggressive environments, while 303 stainless steel is favored for its machinability and is used in less corrosive conditions.
303 stainless steel is generally not heat-treated to increase hardness. For applications requiring heat treatment to improve hardness, other stainless steel grades, such as 17-4 PH or 440C, would be more suitable.
303 stainless steel can be welded, but it is not ideal for welding due to its high sulfur content, which can lead to welding challenges. The sulfur in 303 improves machinability but can cause issues such as reduced weld quality and increased susceptibility to cracking.
Catalog: Materials Guide
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
