303 stainless steel is 300-series of austenitic stainless steel. It contains a combination of elements such as chromium, nickel and small amounts of sulphur and phosphorus. This special composition gives 303 stainless steel unique properties that make it suitable for a wide variety of applications.
One of the key properties of 303 material stainless steel is its excellent machinability. Due to the presence of sulphur in its composition, the material has an enhanced chip-breaking capacity during machining. As a result, manufacturers can achieve high-quality surface finishes and precise tolerances when using 303 stainless steel.
In addition to its machinability, 303 alloy stainless steel exhibits good corrosion resistance. Its high chromium content helps prevent oxidation and corrosion in mildly corrosive environments. However, it may not be able to withstand certain chemicals or highly corrosive conditions compared to other grades such as 316 or 304.
Because of these properties, 303 stainless steel can be used in a variety of industries including aerospace, automotive, medical device manufacturing, and food processing. Equipment Manufacturing. It is commonly used for components such as shafts, pins, fasteners, valves, fittings and bushings that require machinability and moderate corrosion resistance.
303 Stainless Steel Composition
| Element | Percent |
|---|---|
| Carbon (C) | 0.10 |
| Chromium (Cr) | 17.00 – 19.00 |
| Manganese (Mn) | 2.00 |
| Silicon (Si) | 1.00 |
| Phosphorous (P) | 0.20 |
| Sulphur (S) | 0.015 min |
| Nickel (Ni) | 8.00 – 10.00 |
| Iron (Fe) | Balance |
303 Stainless Steel Mechanical properties
- Tensile strength: ≥520 MPa
- Yield strength (σ0.2): ≥205 MPa
- Elongation（δ5）: ≥40%
- Hardness: ≤187HB; ≤90HRB; ≤200HV
303 Stainless Steel Physical Properties
| Physical Properties | Value |
|---|---|
| 303 stainless steel density, g/cm3 (lb/in.3) | 7.9 (0.29) |
| Melting point, °C (°F) | 1400-1450 (2550-2590) |
| Specific heat capacity, J/kg·K (Btu/lb ·°F) | 500 (0.12) at 20℃ |
| Electrical resistivity, μΩ·m | 0.72 at 20℃ |
| Magnetic permeability | 1.02 (Approximate) |
| Elastic modulus, GPa (106 psi) | 193 (28) |
| Thermal conductivity, W/m·K (Btu/ft · h ·°F) | 16.2 (9.4) at 100 °C (212 °F) |
| 21.5 (12.4) at 500 °C (932 °F) | |
| Coefficient of thermal expansion, 10-6/K (μin./in. ·°F) | 17.2 (9.6) at 0-100 ℃ (32-212 °F) |
| 17.8 (9.9) at 0-315 ℃ (32-600 °F) | |
| 18.4 (10.2) at 0-538 ℃ (32-1000 °F) |
303 Stainless Steel Equivalent
- UNS S30300
- EN 1.4305
303 Stainless Steel Properties
Excellent Machinability
303 Stainless Steel is known for its excellent machinability, making it a popular choice for many industries. One of the key properties of 303 grade is its high sulphur content, which enhances its machinability. This allows for faster machining speeds and longer tool life.
Corrosion Resistance
In addition to its machinability, 303 stainless steel exhibits good corrosion resistance. It resists atmospheric conditions as well as mild chemicals, acids and alkalis. This makes it suitable for a variety of applications where exposure to corrosive environments is expected.
Non-magnetic
303 stainless steel is non-magnetic, and stainless steel 303 remains non-magnetic even after extensive machining.
Strength and Toughness
In addition, this stainless steel has good strength and toughness. Its tensile strength is comparable to other austenitic steel grades, but its yield strength is slightly lower. Its combination of strength and machinability makes it ideal for applications that require both mechanical properties and ease of fabrication.
It is important to note that while stainless steel 303 has many desirable properties, it has limitations compared to some other grades. For example, it may not be suitable for applications requiring high temperatures or extreme corrosion resistance.
Applications
Stainless steel 303 is a versatile and widely used material for a variety of industries. Its unique combination of mechanical properties, corrosion resistance, and workability make it well-suited for many different applications.
One common use for SS 303 is in the manufacture of fittings and fasteners. Due to its excellent machinability, it can be easily machined into screws, bolts, nuts and other hardware components. The material’s high strength and durability ensure reliable performance in demanding applications.
In addition to fittings and fasteners, stainless steel 303 is commonly used in the production of shafts, valves, gears, bushings and other precision components. Its corrosion resistance makes it suitable for use in harsh environments where it may come into contact with chemicals or moisture.
In addition, AISI 303 also has a place in the food processing industry. Because it does not react with most types of food substances, it is commonly used in the manufacture of equipment such as conveyor belts or parts that come into contact with food.
Another interesting application for 303 material stainless steel is in the automotive industry. The alloy has excellent strength-to-weight characteristics, making it ideal for the production of fuel injector components or exhaust systems.
Specifications
- ASTM A582/A582M: Standard Specification for Free-Machining Stainless Steel Bars
- ASTM A581/A581M: Standard Specification for Free-Machining Stainless Steel Wire and Wire Rods
- ASTM A895: Standard Specification for Free-Machining Stainless Steel Plate, Sheet, and Strip
- ASTM A959: Standard Guide for Specifying Harmonized Standard Grade Compositions for Wrought Stainless Steels
- ASTM A473: Standard Specification for Stainless Steel Forgings
- ASTM A314: Standard Specification for Stainless Steel Billets and Bars for Forging
Forms
303 Stainless Steel vs 304
Carbon content
Stainless steel 30 has a higher carbon content (about 0.3 per cent), while 304 stainless steel has a lower carbon content (about 0.08 per cent). The higher carbon content makes stainless steel 303 harder in cold working, easier to cut and form, but also more prone to rust.
Nickel content
304 stainless steel contains a higher nickel content (about 8%), which gives it better overall corrosion resistance, especially against oxidising media. In contrast, stainless steel 303 has a lower nickel content (about 6%) and its corrosion resistance is slightly inferior to 304.
Machinability
Due to the higher carbon content, stainless steel 303 shows better cutting performance and hardness in machining, which is suitable for manufacturing precision parts and application scenarios that require good cutting performance. While 304 stainless steel due to higher nickel content, its machining performance is slightly worse, but easier to form and weld.
Corrosion resistance
304 stainless steel provides excellent protection in many standard environments due to its high nickel content and good overall corrosion resistance. stainless steel 303, while also providing good corrosion resistance in most cases, may not be as corrosion resistant as 304 due to its higher carbon content in certain extreme conditions, such as high temperatures or environments with strong corrosive media.
Uses
303 stainless steel is commonly used in the manufacture of parts that require good cutting performance, such as nuts, bolts, springs and valves. While 304 stainless steel is widely used in food processing, chemical, medical and construction industries, especially in the higher requirements for corrosion resistance.
FAQ
303 stainless steel is not a food-grade stainless steel. Although stainless steel 303 can be used in certain applications, it does not meet the criteria for food-grade stainless steel. Food grade stainless steel needs to meet specific heavy metal migration indicators and stainless steel 303 is mainly used in applications requiring easy cutting and high surface finish and is unsuitable for food contact.
303 stainless steel and 304 stainless steel have their advantages and disadvantages, and the choice depends on the specific application scenario. 304 stainless steel is superior in terms of rust protection, corrosion resistance and versatility. In contrast, stainless steel 303 is better in machinability and resistance to high-temperature bonding.
Stainless steel 303 is mainly used where easy cutting and high surface finish are required. It is an austenitic, free-machining stainless wear-resistant acid steel, it exhibits good cutting properties and resistance to high-temperature bonding. stainless steel 303 is particularly suitable for producing automatic lathes, bolts and nuts, as these applications require a material with good machinability and surface finish.