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303 Stainless Steel: Properties, Uses, and Advantages
- John
303 stainless steel is highly valued for its excellent machinability and reliable corrosion resistance. It’s a go-to material for components that require precise machining, such as fittings and fasteners. This article discusses the 303 stainless steel, covering its composition, properties, applications, and processing.
What Is 303 Stainless Steel?
303 stainless steel, also called AISI 303, belongs to the family of austenitic stainless steels. It comprises approximately 70% iron, 18% chromium, 8% nickel, and a minor quantity of sulfur. Sulfur improves workability and slightly reduces toughness and corrosion resistance. It is usually used in precision components and kitchen accessories.
303 Stainless Steel Equivalents
| Country/Region | Standard/Specification | Equivalent Grade |
| China | GB/T 1220, GB/T 20878 | 06Cr19Ni10S (or 303) |
| USA | ASTM A276, ASTM A581, ASTM A582 | 303 |
| EU | EN 10088-3 | X8CrNiS18-9 (1.4305) |
| Germany | DIN EN 10088-3 | X8CrNiS18-9 |
| Japan | JIS G4303 | SUS303 |
| England | BS EN 10088-3 | 303S21 |
303 Stainless Steel Subgroups
303Se
This variant includes selenium in its composition. That further improves machinability and allows for better surface finishes during machining operations. It is particularly useful in high-precision turning and milling processes that require superior surface quality.
303Cu
In this variant, copper is added to the composition to improve machinability even more. Additionally, the presence of copper provides slightly better corrosion resistance and increases the material’s ductility.
303XLD (Extra Low Carbon)
This variant is designed with a lower carbon content to improve its corrosion resistance, particularly in environments where the material might be susceptible to intergranular corrosion. At the same time, it retains the machinability of standard 303 stainless steel.
What Is the Chemical Composition of 303 Stainless Steel?
| Element | C | Si | Mn | P | S | Cr | Ni | N |
| wt% | ≤0.15 | ≤1.00 | ≤2.00 | ≤0.20 | ≥0.15 | 17-19 | 8-10 | ≤0.11 |
303 Stainless Steel Properties
Mechanical Properties
| Property | Typical Value |
| Yield Strength | 190-450 MPa |
| Tensile Strength | 500-750 MPa |
| Brinell Hardness (HB) | 190-240 HB |
| Rockwell Hardness (HRC) | 48-58 HRC |
| Vickers Hardness (HV) | 190-240 HV |
| Elongation | 35-50% |
| Elastic Modulus | 190-210 GPa |
303 Stainless Steel Hardness
303 stainless steel has moderate hardness. The typical Brinell hardness (HB) for 303 stainless steel ranges from 160 to 190. While its hardness cannot be increased through heat treatment, it can be slightly improved by cold working.
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Hardness of Stainless Steel
303 Stainless Steel Yield Strength
303 stainless steel has a typical yield strength of around 205 MPa (30,000 psi). It offers moderate strength and is best suited for applications requiring good machinability rather than high strength.
Physical Properties
| Property | Typical Value (Metric/Imperial) |
| Density | 7.90 g/cm³ (0.285 lb/in³) |
| Melting Point | 1400-1450 °C (2552-2642 °F) |
| Thermal Conductivity | 16.3 W/m·K (113 BTU/ft·h·°F) |
| Thermal Expansion | 17.3 µm/m·°C (9.61 µin/in·°F) |
| Electrical Conductivity | 1.4 x 10⁶ S/m (2.4% IACS) |
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.
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Is Stainless Steel Magnetic?
Corrosion Resistance
303 stainless steel offers decent corrosion resistance. It can perform well in environments with mild exposure to atmospheric conditions and weak acids. However, its resistance is lower than other stainless steel like 304. Because it contains sulfur content. That enhances its machinability but makes it easier to corrosion, particularly in chloride-rich or marine environments. It’s suitable for many applications but is not ideal for highly corrosive or harsh conditions.
Heat Resistance
303 stainless steel can handle temperatures up to 870°C (1600°F) during intermittent use and up to 925°C (1700°F) during continuous use. Its heat resistance is moderate. Therefore, it is not ideal for extremely high-temperature environments. Other stainless steels like 304 or 316 offer better heat resistance.
What Is the 303 Stainless Steel Used for?
This table outlines the applications of 303 stainless steel along with the reasons it is chosen for these uses.
| Application | Reason |
| Screws, Bolts, and Nuts | High machinability |
| Shafts and Gears | Smooth finishes and precision |
| Fittings | Precision machining |
| Valve Components | Ideal for complex parts |
| Electrical Components | Easy to machine |
What Are the Advantages and Disadvantages of 303 Stainless Steel?
The advantages of 303 stainless steel are as follows.
Excellent Machinability: 303 stainless steel is very easy to machine, making it ideal for producing precise parts quickly.
Good Corrosion Resistance: It performs well in mild environments, resisting rust and corrosion under everyday conditions.
Smooth Surface Finish: The material allows for a high-quality finish, which is important for parts that need to look good and fit well.
Here are the disadvantages of 303 stainless steel
Lower Corrosion Resistance: It’s not as resistant to corrosion as other stainless steels like 304 or 316, especially in harsh environments.
Poor Weldability: The added sulfur makes 303 less suitable for welding, as it can cause cracking.
Limited Formability: 303 is less flexible than other stainless steel, making it harder to bend or form into complex shapes.
303 Stainless Steel Heat Treatment
Annealing
During the annealing process, 303 stainless steel should be heated to around 1010-1120°C (1850-2050°F) and then rapidly cooled. This helps relieve internal stresses and improves its machinability.
It is crucial to avoid extended exposure to temperatures between 400-850°C (750-1560°F). Because this can lead to sensitization, making the steel more susceptible to corrosion.
Hardening
303 stainless steel cannot be hardened through heat treatment because it is an austenitic stainless steel. Its hardness is primarily controlled through cold working, not by heat treatment.
Stress Relief
If stress relief is needed, it’s usually done by heating the steel to a lower temperature, around 400-600°C (750-1110°F), followed by controlled cooling. However, care must be taken not to exceed these temperatures for too long, as it can negatively affect the material’s properties.
303 Stainless Steel Hot Working
303 stainless steel can be hot worked, but it requires careful control of temperatures. The ideal temperature range for hot working is between 950°C and 1200°C (1742°F to 2192°F). Heating above this range may cause excessive grain growth while working at lower temperatures can lead to cracking.
After hot working, it’s recommended to anneal the material to restore its corrosion resistance and mechanical properties.
303 Stainless Steel Cold Working
303 stainless steel is not ideal for cold working due to its higher sulfur content. When cold worked, it may become more brittle and prone to cracking. Small amounts of cold working can be done, but it should be limited to avoid damage.
303 Stainless Steel Cutting
Tool Wear
The added sulfur in 303 stainless steel improves machinability but can cause tools to wear out faster. It’s important to use high-quality, sharp tools and to monitor them regularly to maintain precision.
Cutting Speed
While 303 is easier to machine than other stainless steel, maintaining the right cutting speed is crucial. Going too fast can overheat and damage the material while going too slow can lead to an inefficient machining process.
Chip Control
The sulfur in 303 helps break up chips during machining, but it’s still important to manage chip removal carefully. If chips build up, they can damage the surface finish or the cutting tools.
Coolant Use
Using coolant is essential to keep the material and tools cool during machining. This helps avoid overheating, improves the surface finish, and extends the lifespan of the tools.
303 Stainless Steel Welding
303 stainless steel is not ideal for welding because of its sulfur content. The sulfur can cause cracking and poor weld quality. If welding is necessary, it’s best to use low heat and specialized welding techniques. Other stainless steels might be better suited for welding.
303 Stainless Steel Forming
303 stainless steel is less ductile than other stainless steel, which means it’s harder to bend or shape. It’s not ideal for applications that involve significant forming or bending.
Compare 303 Stainless Steel With Other Stainless Steel
303 VS 304 Stainless steel
- 303 contains added sulfur. It helps reduce friction during cutting and drilling. So 303 stainless steel is easier to machine than 304.
- 303 stainless steel has lower corrosion resistance than 304. The added sulfur in 303 slightly reduces its ability to resist corrosion. 304 is better suited for environments where moisture, chemicals, or salt exposure is a concern.
- 304 stainless steel performs better in welding applications. Welding 304 does not require any special precautions. It retains its strength and corrosion resistance after welding.
- 304 is more versatile. It is suited for kitchen equipment, food processing, and even medical devices.
303 VS 316 Stainless Steel
- 316 contains molybdenum, which helps protect against rust and pitting. So 316 has better corrosion resistance.
- 316 has higher toughness and 303 contains added sulfur. So 316 is more difficult to machine.
- 316 is more suitable for welding. It retains its strength and corrosion resistance after welding. 303 is not recommended for welding. Because the sulfur content can cause cracks and weaken the welds.
- 316 is usually used in marine, chemical, and medical industries. 303 is suitable for less corrosive environments.
Other Things About 303 Stainless Steel
Does 303 Steel Rust?
303 stainless steel can resist rust in normal conditions. However, it’s more likely to rust in tough environments, like places with high humidity, salt, or acids. So, while it doesn’t rust easily, it’s not as rust-resistant as some other types like 304 or 316.
Related Reading
Will Stainless Steel Rust and How Can You Solve It?
How to Clean and Polish Stainless Steel?
Is 303 SS Food Grade?
303 stainless steel is not deemed suitable for food-grade applications. The added sulfur, which makes it easier to machine, also reduces its corrosion resistance. This makes it less suitable for food-related applications.
For food grade, 304 or 316 stainless steel is a better choice because they offer higher corrosion resistance and are safer for food contact.
Is 303 Stainless Steel Medical Grade?
303 stainless steel is not medical grade. It has added sulfur for better machinability, but this also lowers its corrosion resistance. In medical applications high corrosion resistance and safety are crucial. 316 offers superior corrosion resistance and is more suitable for use in medical devices and implants.
Summary & Furthermore
This article briefly explains the definition, composition, applications, and other important aspects of 303 stainless steel. To learn more about stainless steel or other steel types, check out our blog or contact our metal experts.
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