Stainless steel, due to its various excellent properties and wide range of applications, plays a crucial role in modern society’s industries, construction, environmental protection, sanitation, and other sectors.
Due to its versatility, durability, and cost-effectiveness, stainless steel production has been increasing year by year worldwide.
Although stainless steel shares some common characteristics, its main components include iron, chromium, nickel, molybdenum, and other metals, with the price fluctuations of nickel and chromium significantly impacting the price of stainless steel.
The first step in choosing the best option when using stainless steel is to identify the alloy that best suits your product.
Let’s take a look at common types and considerations.
Types of Stainless Steel
Austenitic Stainless Steel
- Characteristics: Contains a higher amount of chromium (16%-26%) and nickel (typically more than 8%), sometimes includes molybdenum, offering excellent corrosion resistance and toughness. It is non-magnetic and can be strengthened through cold working.
- Applications: Widely used in food processing equipment, chemical equipment, building decorations, etc. Common grades include 304, 316, and 321.
Ferritic Stainless Steel
- Characteristics: Contains a higher amount of chromium (10.5%-30%) and typically no nickel. It is cost-effective with moderate corrosion resistance, magnetic, and poor weldability.
- Applications: Used in automotive exhaust systems, washing machines, kitchenware, decorative materials, etc. Common grades include 430 and 409.
Martensitic Stainless Steel
- Characteristics: Contains higher carbon, providing higher strength and hardness, but lower corrosion resistance. It can be hardened through heat treatment and is magnetic.
Applications: Primarily used for manufacturing tools, bearings, surgical instruments, etc. Common grades include 410, 420, and 440C.
Duplex Stainless Steel
- Characteristics: Combines the characteristics of both austenitic and ferritic stainless steels, providing high strength and excellent corrosion resistance, particularly resistant to chloride stress corrosion cracking.
- Applications: Widely used in marine, oil, and chemical industries. Common grades include 2205 and 2507.
Precipitation Hardening Stainless Steel
- Characteristics: Achieves extremely high strength and hardness through heat treatment while maintaining good corrosion resistance.
- Applications: Widely used in aerospace, nuclear industries, medical devices, and other high-strength applications. Common grades include 17-4PH and 15-5PH.
These stainless steel types are suitable for different applications depending on their chemical composition and performance characteristics, meeting various needs from daily life to industrial production.
Stainless Steel Grades
Stainless steel grades are standardized numbers or names used to classify and identify different types of stainless steel materials. Grades are distinguished based on chemical composition and performance characteristics, helping users understand properties like corrosion resistance, strength, toughness, and weldability to select the right material for their applications.
Naming System for Stainless Steel Grades:
U.S. Standards (ASTM/SAE)
The U.S. system typically uses three or five digits, for example, 304, 316, and 410. The first two digits indicate the major type (e.g., 300 series for austenitic stainless steel), and the last three digits specify the exact composition of the steel.
Example: 304 refers to an austenitic stainless steel with 18% chromium and 8% nickel.
European Standards (EN/ISO)
The European system uses a combination of letters and numbers, typically starting with “X” followed by numbers indicating the alloy composition.
Example: X5CrNi18-10 refers to stainless steel containing about 18% chromium and 10% nickel.
Chinese Standards (GB)
The Chinese system uses a format of “Number + Steel,” such as 06Cr19Ni10, where “06” indicates a carbon content of less than 0.06%, “Cr” represents 19% chromium, and “Ni” represents 10% nickel.
Common Stainless Steel Series and Grades
300 Series Stainless Steel (Austenitic)
Characteristics: Non-magnetic, with main alloying elements chromium and nickel, sometimes molybdenum to enhance corrosion resistance. Offers excellent corrosion resistance, weldability, and formability, with moderate strength. Cannot be hardened by heat treatment but can be strengthened through cold working.
- 304: The most common austenitic stainless steel, containing 18% chromium and 8% nickel, suitable for general applications such as food processing equipment and building materials.
- 304L: A low-carbon version of 304 with better weldability, used in chemical equipment.
- 316: Contains molybdenum (about 2-3%), providing enhanced resistance to chloride corrosion, suitable for marine, chemical, and pharmaceutical industries.
- 316L: A low-carbon version of 316, with better weldability, suitable for highly corrosion-resistant environments.
- 321: Contains titanium to prevent carbide precipitation during welding, suitable for high-temperature environments.
400 Series Stainless Steel (Ferritic and Martensitic)
Characteristics: Typically high in chromium, low or no nickel, thus more cost-effective. Ferritic stainless steel is magnetic with moderate corrosion resistance, suitable for environments with less corrosion. Martensitic stainless steel can be hardened by heat treatment, offering high strength but lower corrosion resistance.
Common Grades:
- 410 (Martensitic): High strength and good wear resistance, used in tools, surgical instruments, valves, etc.
- 420 (Martensitic): High carbon content and strong hardness, used in knives and surgical instruments.
- 430 (Ferritic): Moderate corrosion resistance and cost-effective, commonly used in household appliances, kitchenware, and automotive decorations.
- 409 (Ferritic): Good high-temperature resistance, primarily used in automotive exhaust systems.
200 Series Stainless Steel (Austenitic)
Characteristics: Typically high in chromium, low or no nickel, thus more cost-effective. Ferritic stainless steel is magnetic with moderate corrosion resistance, suitable for environments with less corrosion. Martensitic stainless steel can be hardened by heat treatment, offering high strength but lower corrosion resistance.
Common Grades:
- 410 (Martensitic): High strength and good wear resistance, used in tools, surgical instruments, valves, etc.
- 420 (Martensitic): High carbon content and strong hardness, used in knives and surgical instruments.
- 430 (Ferritic): Moderate corrosion resistance and cost-effective, commonly used in household appliances, kitchenware, and automotive decorations.
- 409 (Ferritic): Good high-temperature resistance, primarily used in automotive exhaust systems.
200 Series Stainless Steel (Austenitic)
Characteristics: Replaces nickel with manganese and nitrogen, making it more cost-effective. Corrosion resistance is slightly lower than 300 series, with moderate strength suitable for milder corrosive environments.
Common Grades:
- 201: Contains less nickel, with slightly lower corrosion resistance, widely used in low-cost alternatives to 304, such as kitchenware and tableware.
- 202: Similar to 201 but with slightly higher strength and corrosion resistance, used in similar applications.
Duplex Stainless Steel
Characteristics: Combines the properties of both austenitic and ferritic stainless steels, offering higher strength and excellent corrosion resistance. Particularly resistant to chloride stress corrosion cracking, with good weldability. Its strength is twice that of 300 series but with higher cost.
Common Grades:
- 2205: The most common duplex stainless steel, with excellent resistance to pitting and stress corrosion cracking, suitable for marine, chemical, and shipbuilding industries.
- 2507: Super duplex stainless steel with even better corrosion resistance, used in highly corrosive environments.
Precipitation Hardening Stainless Steel
Characteristics: Achieves very high strength through heat treatment while maintaining good corrosion resistance. Suitable for applications that require high strength and lighter materials.
Common Grades:
- 17-4PH (630): High strength and good corrosion resistance, widely used in aerospace, nuclear, and oil and gas industries.
- 15-5PH: Similar to 17-4PH, but with better toughness, commonly used in aerospace, chemical, and marine industries.
High Alloy Stainless Steel
Characteristics: Contains high levels of chromium, nickel, and other elements (such as molybdenum and titanium), specifically designed for extremely corrosive or high-temperature environments.
Common Grades:
- 254 SMO: A super-austenitic stainless steel containing 6% molybdenum, offering excellent resistance to pitting and crevice corrosion, ideal for seawater treatment and highly corrosive environments.
- Alloy 904L: Contains high chromium, nickel, and molybdenum, offering outstanding resistance to acidic corrosion, suitable for chemical processing.
Conclusion
Different stainless steel series and grades, based on their alloy compositions and processing methods, have varying degrees of corrosion resistance, strength, and physical properties, making them suitable for a range of industrial applications. The choice of the appropriate stainless steel grade depends on specific use conditions, environments, and cost considerations.
SSM provides stainless steel pipes, fittings, flanges, fasteners, plates, and bars. For any technical inquiries or procurement needs, please contact us.
