Врсте нерђајућег челика: Свеобухватан водич

Увођење

Нехрђајући челик is a widely used material known for its exceptional properties such as durability, снага, and resistance to corrosion.

It is utilized across various industries, from construction and automotive to medical devices and kitchen appliances.

Selecting the appropriate type of stainless steel ensures optimal performance and longevity in different applications. This guide provides an in-depth overview of the different kinds of stainless steel, their characteristics, и одговарајуће апликације.

1. Шта је од нехрђајућег челика?

Stainless steel is an alloy made primarily of iron and at least 10.5% хром, giving it distinctive corrosion resistance. The addition of chromium allows for the formation of a thin, protective oxide layer on the steel surface, preventing rust and oxidation.

Other elements like nickel, молибден, and manganese may also be added to enhance specific properties such as strength, дуктилност, and resistance to heat and chemicals.

Common Properties of Stainless Steel:

• ‌Corrosion resistance‌: The chromium element in stainless steel reacts with oxygen to form a dense sodium chromate layer, which effectively reduces the probability of corrosion and makes stainless steel have good corrosion resistance‌.
• ‌Heat resistance‌: Stainless steel can maintain excellent physical and mechanical properties at high temperatures, has good heat resistance, and can maintain good physical and chemical properties in different temperature environments‌.
• ‌High strength‌: Stainless steel has high strength and can withstand greater pressure and tension‌.
• ‌Safety and hygiene‌: Stainless steel does not contain radioactive substances and will not cause any harm to the human body. It is suitable for food production equipment or production lines and other devices.
• ‌Beautiful surface‌: The surface of stainless steel is bright, Једноставно чишћење, and has low maintenance costs‌1.
• ‌Good machinability‌: Stainless steel can be formed and processed in a variety of ways, such as welding, cold processing, precision processing, итд.
• ‌Recyclability‌: Stainless steel materials can be recycled and have little impact on the environment.
• ‌Good elasticity and plasticity‌: Stainless steel materials have good elasticity and plasticity and are not prone to breakage‌.

These characteristics make stainless steel widely used in various fields, such as machinery, aviation, military industry, Хемијска индустрија, итд.

2. Types of Stainless Steel

Stainless steel is divided into five main families, each with unique microstructures and chemical compositions that impart distinct properties. Understanding these classifications is crucial for selecting the right material for various applications, from kitchen appliances to aerospace components. Here’s an in-depth look at each type:

1. Аустенитни од нехрђајућег челика

Структура:
Austenitic stainless steel has a face-centered cubic (ФЦЦ) кристална структура, which is stable at room temperature. This structure makes it non-magnetic and highly ductile.

Састав:
These steels typically contain 16-26% хром и 6-22% никл, with some grades also containing molybdenum or nitrogen to enhance corrosion resistance. Low carbon content (usually less than 0.1%) prevents carbide precipitation, which can cause intergranular corrosion.

Својства:
Austenitic stainless steels are known for their excellent corrosion resistance, especially in acidic and chloride-rich environments. They offer good formability and weldability, making them suitable for complex shapes and large structures. Међутим, they cannot be hardened by heat treatment; уместо тога, they are often cold-worked to increase strength.

Common Grades:

• 304: Also known as 18/8 нехрђајући челик, this is the most widely used grade due to its versatility and excellent corrosion resistance.
• 316: Contains molybdenum, which provides superior resistance to pitting and crevice corrosion in marine and chemical environments.
• 310: High temperature-resistant steel used in furnace parts and heat exchangers.

Апликације:
Austenitic stainless steels are found in a wide range of products, including kitchen sinks, Опрема за прераду хране, chemical tanks, and architectural facades.

2. Феритни од нехрђајућег челика

Структура:
Ferritic stainless steel has a body-centered cubic (БЦЦ) структура, similar to that of carbon steel, which makes it magnetic and less ductile than austenitic grades.

Састав:
Typically containing 10.5-30% chromium and very low carbon (мање од 0.1%), these steels have little to no nickel, making them more cost-effective than austenitic varieties.

Својства:
Ferritic stainless steels provide good corrosion resistance and are resistant to stress corrosion cracking. They have better thermal conductivity than austenitic grades but are less suitable for welding and forming.

Common Grades:

• 430: Commonly used in automotive trims and appliance panels due to its good corrosion resistance and formability.
• 409: Contains lower chromium content, offering moderate corrosion resistance, often used in automotive exhaust systems.

Апликације:
Ferritic stainless steels are often used in automotive applications, Индустријска опрема, и украсне украсе.

3. Мартензитни од нехрђајућег челика

Структура:
Martensitic stainless steel has a body-centered tetragonal (БЦТ) структура. It is magnetic and can be heat-treated to achieve high strength and hardness.

Састав:
These steels contain 12-18% хром, 0.1-1.2% угљеник, and little to no nickel. The high carbon content allows them to be hardened and tempered.

Својства:
Martensitic stainless steels are characterized by high strength, тврдоћа, and moderate corrosion resistance. They can be heat-treated to achieve a wide range of mechanical properties but are more brittle and less corrosion-resistant than other stainless steel families.

Common Grades:

• 410: General-purpose grade offering good corrosion resistance and high mechanical strength.
• 420: Often used for cutlery due to its ability to be polished to a high shine and maintained sharp edges.
• 440Ц: High carbon content makes it suitable for high-wear applications.

Апликације:
Martensitic stainless steels are used in knife blades, хируршки инструменти, шахтови, и вентили.

4. Дуплек нерђајући челик

Структура:
Duplex stainless steel has a mixed microstructure of austenite and ferrite, typically in a 50:50 ratio. This dual-phase structure gives it unique properties.

Састав:
Duplex steels typically contain 18-28% хром, 4.5-8% никл, и до 5% молибден, са ниским садржајем угљеника. The balanced composition reduces susceptibility to stress corrosion cracking and increases mechanical strength.

Својства:
These steels combine the best attributes of austenitic and ferritic grades, offering high strength, Одлична отпорност на корозију, и добра заварљивост. They perform well in harsh environments, such as those exposed to chloride and sulfuric acid.

Common Grades:

• 2205: The most widely used duplex grade, known for high strength and resistance to stress corrosion cracking.
• 2507: Super duplex grade offering even higher strength and corrosion resistance.

Апликације:
Duplex stainless steels are used in chemical processing, нафтне и гасне индустрије, Марине апликације, и измењивачи топлоте.

5. Падавине-отврдњавање (ПХ) Нехрђајући челик

Структура:
PH stainless steels have a unique microstructure that allows them to be heat-treated to achieve high strength and toughness. They start as austenitic or martensitic and undergo precipitation hardening to form fine particles that increase strength.

Састав:
These steels are alloyed with elements like aluminum, бакар, и титанијум, which form intermetallic compounds that precipitate during heat treatment.

Својства:
PH stainless steels offer a combination of high strength, Добра отпорност на корозију, and excellent mechanical properties. They can be heat-treated to various strength levels, making them versatile for many demanding applications.

Common Grades:

• 17-4 ПХ: The most widely used PH grade, combining high strength and moderate corrosion resistance.
• 15-5 ПХ: Offers improved toughness over 17-4 PH and is often used in aerospace applications.

Апликације:
PH stainless steels are used in aerospace components, high-performance valves, зупчаници, and other precision engineering parts.