What is 303 stainless steel?
303 stainless steel is a free-machining austenitic stainless steel. Sulfur or selenium is added to its composition, giving it excellent machinability and making it suitable for machining precision parts on automatic lathes. Due to the presence of sulfur, its corrosion resistance is lower than that of 304 stainless steel, especially in chloride environments or at temperatures exceeding 50°C, where pitting corrosion is more likely to occur. 303 stainless steel is commonly used to manufacture bolts, nuts, bearings, pump and valve assemblies, and other mechanical parts requiring high machinability and surface finish.
What is 304 stainless steel?
304 stainless steel is a commonly used austenitic stainless steel. Its chemical composition typically contains 18% chromium and 8% nickel, hence it is often referred to as "18-8" stainless steel. Due to its excellent corrosion resistance, heat resistance, and good mechanical properties (such as formability and weldability), it is widely used in many fields, including food processing, construction, chemical industry, and household goods.
Chemical composition standard
|
Grade |
C | Mn | Si | P | Cr | Mo | Ni | Se | S | |
| 303 |
Min Max |
– 0.15 |
– 2.00 |
– 1.00 |
– 0.20 |
17.0 19.0 |
– – |
8.0 10.0 |
– |
0.15 – |
Mechanical performance standards
|
Grade |
TS(Mpa) | YS 0.2% yield point(Mpa) | Elongation | Hardness | |
| Rockwell Hardness(HRB) |
Brinell Hardness(HB) |
||||
| 303 | 650(typical) | 300(typical) | 45(typical) | – |
262(Max) |
|
Note:ASTM A582 only specifies the hardness. The above tensile properties are for reference only. Stretched rods up to 25.4mm in diameter have higher strength values and lower elongation. |
|||||
Physical properties (annealed state)
|
Grade |
Density(kg/m³) | Elastic Modulus(Gpa) | Average expansion coefficient | Thermal conductivity |
Specific heat 0-100°C(J/kg.k) |
Resistance(nΩ.m) | |||
| 0-100°C(um/m/°C) | 0-315°C(um/m/°C) | 0-538°C(um/m/°C) | 100°C(w/m.k) | 500°C(w/m.k) | |||||
| 303 | 7900 | 193 | 17.3 | 17.8 | 18.4 | 16.3 | 21.5 | f00 |
720 |
Corrosion Resistance:
303 stainless steel exhibits good corrosion resistance in mildly corrosive environments, but due to the addition of sulfur, its corrosion resistance, weldability, and formability are lower than those of 304 stainless steel. In chloride environments above 50°C, 303 stainless steel is susceptible to stress corrosion cracking. 303 stainless steel is not suitable for small-radius bending processes and cannot be hardened by heat treatment.
Machinability:
SUS304 and SUS303 have a thermal conductivity of 16.3 W/m·K, lower than the approximately 50 W/m·K of steel. Therefore, the cutting edge temperature tends to rise, limiting machining speed. The tool will not last long.
In SUS303, MnS reduces the fracture energy of the machined part, thereby reducing cutting resistance and increasing tool holding force. Furthermore, SUS304 chips are difficult to separate and easily get caught in the tool, while SUS303 chips separate easily, making it easier to machine deep holes. TIG welding and plasma welding can be used for welding.
If you have project requirements for 303/303se stainless steel bars, please feel free to place an order. GNEE Stainless Steel is an independent stocker and processor of 303/303se stainless steel. With a large inventory and excellent processing capabilities, we can meet the needs of most projects, whether it's stock products or custom-made products. We offer: stock sizes of plates and sheets, stock lengths of round bars, fixed-length plates and sheets, fixed-length round bars, cold forming of plates, sheets, and round bars, and any other necessary processing services. For any questions, please email Mail:es@gescosteel.com
