The website has a separate section "Steel grades" with a detailed technical description of different types of steel grades, including their designation according to different numbering systems, chemical composition, mechanical properties and corrosion resistance.
Different numbering systems and standards are used to clearly identify and distinguish various grades of stainless steel. These systems and standards provide information about the chemical composition, structure, and properties of the steel, making them essential tools for selecting and using stainless steel in specific applications.
In general, stainless steel, also known as inox, is a corrosion-resistant type of steel with high strength and heat resistance. Its wide range of applications in various industries is due to its complex of unique properties, including:
- Strength and durability: This material is distinguished by its resistance to mechanical loads, making it indispensable in structures operated in harsh conditions.
- Hygiene: Ease of cleaning and disinfection makes stainless steel an ideal choice for medical equipment and the food industry.
- Aesthetic appearance: Inox has an attractive silvery sheen that blends perfectly with modern architectural and design solutions.
Stainless Steel Marking Systems
There are numerous stainless steel marking systems, each using its own designations for different grades.
- AISI: This system is used in the United States and other countries.
- JIS: This system is used in Japan.
- V2A and V4A: Used in some countries, outdated.
- Classification of steels A2-A5.
- GOST: This system is used in Russia and other CIS countries.
Stainless steel is represented by a wide range of grades, each with a unique set of characteristics. The most common is the grade containing 18% chromium and 10% nickel. Changes in the content of certain elements in the steel composition affect its corrosion resistance, mechanical properties, and other characteristics, such as weldability.
In particular, a significant decrease in the nickel content leads to a change in the steel structure: instead of only the austenitic phase, areas with austenitic and ferritic phases appear (duplex stainless steel).
Different numbering systems are used to clearly identify and distinguish these grades.
AISI System
Developed by the American Iron and Steel Institute (AISI) and used worldwide.
The marking includes a number, to which letter designations can be added, depending on the composition of the steel.
- 200: austenitic steel with chromium, nickel, and manganese
- 300: austenitic steel with chromium and nickel
- 400: ferritic and martensitic chromium-containing steel grades
- Letter designations:
- L: low-carbon alloy
- Ti: titanium alloy
- Four-digit numbers are used to mark new grades of duplex stainless steel (for example, 2205 - steel 1.4462).
Shortened Grade Designation
This system uses letters and numbers to indicate the chemical composition of the steel.
- X: high-alloy alloy
- 2: carbon content in hundredths of a percent (0.02%)
- Cr: chromium content (17%)
- Ni: nickel content (12%)
- Mo: molybdenum content (2%)
This marking system corresponds to AISI 316 L and DIN 1.4404.
Classification of A2-A5 Steels
A2, A3, A4, and A5 steels belong to the group of carbon structural steels of ordinary quality. They are classified by the mass fraction of carbon in their composition:
- A2: contains 0.05-0.12% carbon
- A3: contains 0.12-0.20% carbon
- A4: contains 0.17-0.25% carbon
- A5: contains 0.25-0.32% carbon
V2A and V4A Designations
The designations V2A and V4A steel were used more than 100 years ago and were introduced to denote the first experimental grades of stainless steel. "V" stands for "Versuch", translated from German as "testing" or "trial", and "A" stands for austenitic steel. V2A means CrNi alloy, and V4A means CrNiMo alloy. These designations are still used to denote stainless steel in some countries.
Standard EN ISO 3506-1:2009 (mechanical properties of fasteners, bolts, screws and rivets made of corrosion-resistant stainless steel) uses the marking from A1 to A5 to denote austenitic stainless steel. These markings indicate different alloy compositions, not corrosion properties.
For example, grade 1.4401 belongs to group A4, and grade 1.4571 belongs to group A5. However, both grades of stainless steel have practically the same corrosion resistance.
Most often, the designations A2 and A4 are used for a group of stainless steel grades that have a certain corrosion resistance. However, this is not entirely accurate, since these designations do not provide information about the alloy composition and, accordingly, about some properties of the material, such as weldability.
In Europe, martensitic and ferritic steels are classified according to the EN 10028 system, which uses a alphanumeric designation.
Martensitic steels are designated by the letter M, followed by a number indicating the nominal strength class (in MPa). For example:
- M270 - martensitic steel with a nominal strength of 270 MPa
- M350 - martensitic steel with a nominal strength of 350 MPa
Ferritic steels are designated by the letter F, followed by a number indicating the nominal yield strength (in MPa). For example:
- F250 - ferritic steel with a nominal yield strength of 250 MPa
- F300 - ferritic steel with a nominal yield strength of 300 MPa
In addition to the basic designation, the marking may also include other symbols indicating:
- Delivery conditions: for example, A - annealed, N - normalized, Q - quenched and tempered
- Chemical composition: for example, Mn4 - 4% manganese, CrMoV - chromium, molybdenum and vanadium
- Other properties: for example, Z35 - increased strength at low temperatures.
Stainless Steel Processing and Technological Properties
Stainless steel can be subjected to various types of processing, making it a flexible material for the production of a wide range of products. Some of the most common processing methods include:
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Hot working: This method involves heating the steel to a high temperature and then forging, rolling, or stamping it to the desired shape.
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Cold working: This method involves deforming the steel at room temperature using processes such as bending, cutting, or stamping.
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Welding: Stainless steel can be welded using various methods such as arc welding, gas welding, and laser welding.
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Passivation: This process involves treating the steel surface with chemicals to remove oxides and other contaminants, making it more resistant to corrosion.
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Finishing: Stainless steel can be polished, sanded, etched, or coated with various coatings to give it the desired appearance.
The technological properties of stainless steel depend on its composition and processing. Some of the most important properties include:
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Strength: Stainless steel has high tensile, compressive, and shear strength.
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Hardness: Stainless steel can be soft, hard, or semi-hard, depending on its composition and processing.
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Toughness: Stainless steel can be tough or brittle, depending on its composition and processing.
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Heat resistance: Stainless steel can withstand high temperatures without losing strength and corrosion resistance.
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Weldability: Stainless steel can be welded using various methods.
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Machinability: Stainless steel can be machined using various methods such as cutting, milling, drilling, and grinding.
Selecting the Stainless Steel Grade
When selecting stainless steel, it is important to consider factors such as:
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Operating conditions: Consider whether the steel will be exposed to aggressive environments such as chemicals, seawater, or high temperatures.
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Required properties: Determine which properties, such as strength, hardness, toughness, or heat resistance, are critical for your application.
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Processing method: Choose a grade of steel that is suitable for the processing method you plan to use.
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Cost: Compare the prices of different grades of steel to find the most cost-effective solution.
It is important to know the correspondence of stainless steel grades in different marking systems in order to correctly select the material for a specific application.
Applications of Stainless Steels
Stainless steel is used in a wide range of industries due to its unique properties. Some of the most common applications include:
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Food industry: Stainless steel is used for the production of food processing equipment, utensils, tableware, and other items that come into contact with food. Its corrosion resistance and hygiene make it an ideal material for use in this industry.
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Construction: Stainless steel is used for reinforcing concrete, manufacturing facade panels, roofing materials, stairs, railings, and other building elements. Its strength, durability, and aesthetic appearance make it a popular choice for architects and designers.
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Medicine: Stainless steel is used for the production of surgical instruments, implants, medical equipment, and other products used in surgery, dentistry, and other medical procedures. Its corrosion resistance, biocompatibility, and ease of cleaning make it an indispensable material for medical applications.
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Chemical industry: Stainless steel is used for the production of tanks for storing and transporting chemicals, as well as for the production of equipment for chemical processes. Its corrosion resistance and wear resistance make it resistant to aggressive chemical environments.
Advantages of using stainless steel:
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Corrosion resistance: Stainless steel is highly resistant to corrosion from water, air, chemicals, and other aggressive environments. This makes it an ideal material for use in applications where corrosion is a major concern, such as in the food industry, chemical industry, and marine environments.
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Strength and durability: Stainless steel is strong and durable, making it able to withstand high stresses and harsh conditions. It is also resistant to wear and tear, making it a long-lasting material for a variety of applications.
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Hygiene: Stainless steel is easy to clean and disinfect, making it a hygienic material for use in applications where cleanliness is critical, such as in the food industry and medical field.
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Aesthetic appeal: Stainless steel has a sleek and attractive appearance, making it a popular choice for architectural and design applications. It is available in a variety of finishes, such as polished, brushed, and satin, to suit different aesthetic preferences.
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Recyclability: Stainless steel is a recyclable material, making it an environmentally friendly choice. It can be recycled repeatedly without losing its quality, reducing its environmental impact.
Disadvantages of using stainless steel:
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Higher cost: Stainless steel is generally more expensive than other metals, such as carbon steel or aluminum. This can make it a less cost-effective choice for some applications.
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Difficulty in machining: Stainless steel can be more difficult to machine than other metals, such as carbon steel. This can increase manufacturing costs and make it more challenging to create complex shapes.
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Magnetic properties: Some grades of stainless steel are magnetic, which can be a drawback in certain applications, such as those involving sensitive electronic equipment.
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Sensitivity to chlorides: Stainless steel can be susceptible to corrosion in environments with high chloride concentrations, such as seawater or road salt. Specific grades of stainless steel are developed to withstand these environments.
Overall, stainless steel is a versatile and valuable material with a wide range of applications. Its unique combination of corrosion resistance, strength, durability, hygiene, and aesthetic appeal makes it a popular choice for a variety of industries and applications. However, it is important to consider the cost, machining difficulty, magnetic properties, and chloride sensitivity when selecting stainless steel for a specific application.
Please note that the information provided here is intended for general informational purposes only and should not be construed as professional engineering advice. When selecting materials for specific applications, it is always advisable to consult with qualified engineers and material specialists.