Alloy Steel
Alloy Steel
Alloy steel is made by adding one or more alloying elements (such as chromium, nickel, molybdenum, tungsten, vanadium, titanium, zirconium, cobalt, aluminum, copper, etc.) to carbon steel to improve its performance.
The Role of Alloying Elements
- Strengthening ferrite:
When alloying elements dissolve into ferrite, they produce a solid solution strengthening effect, increasing the strength and hardness of alloy steel. For example, elements like silicon and manganese can significantly enhance the strength of ferrite.
- Forming alloy carbides:
Alloying elements can combine with carbon to form various alloy carbides, such as chromium carbide and tungsten carbide. These alloy carbides have high hardness, good wear resistance, and are relatively stable at high temperatures, which can improve the wear resistance and red hardness (the ability to maintain hardness at high temperatures) of alloy steel.
Classification
By the content of alloying elements:
– Low-alloy steel: The total content of alloying elements is less than 5%. It has relatively high strength, good toughness, and welding performance, and has better comprehensive properties than carbon steel. It is often used to manufacture structural components such as bridges, ships, and pressure vessels.
– Medium-alloy steel: The total content of alloying elements is between 5% and 10%. The strength, toughness, and wear resistance of this type of alloy steel are relatively balanced. It is often used to manufacture high-strength mechanical parts such as shafts and gears.
– High-alloy steel: The total content of alloying elements is greater than 10%. It has special physical and chemical properties. For example, stainless steel (with a relatively high chromium content) has good corrosion resistance, and heat-resistant steel can maintain stable performance in high-temperature environments. They are used to manufacture chemical equipment, medical devices, and components of aircraft engines.
By application:
– Alloy structural steel: Used to manufacture various mechanical parts and engineering structural components, such as quenched and tempered steel (used to manufacture parts that bear multiple loads) and carburized steel (used to manufacture parts with high hardness requirements on the surface and good toughness in the core).
– Alloy tool steel: Mainly used to manufacture various cutting tools, dies, and measuring tools. For example, high-speed steel has high hardness, red hardness, and wear resistance, and is used to manufacture cutting tools; cold work die steel is used to manufacture dies that deform metals in a cold state.
– Special performance alloy steel: This includes stainless steel, heat-resistant steel, and wear-resistant steel. Stainless steel can resist the corrosion of media such as the atmosphere, water, acids, alkalis, and salts; heat-resistant steel can maintain good mechanical properties and antioxidant properties at high temperatures; wear-resistant steel has high wear resistance and is often used to manufacture parts subject to severe wear.
Performance Characteristics
Excellent mechanical properties:
The mechanical properties of alloy steel, such as strength, hardness, toughness, and fatigue strength, are better than those of carbon steel. For example, alloy structural steel can reach very high levels of strength and toughness after appropriate heat treatment, meeting the needs of various complex working conditions.
- Good special properties:
It has special physical and chemical properties, such as corrosion resistance, heat resistance, and wear resistance. For instance, stainless steel can effectively resist the erosion of corrosive media in chemical and food processing fields; heat-resistant steel functions well in high-temperature environments such as high-temperature furnaces and engine hot-end components.
- Good hardenability:
The addition of alloying elements improves the hardenability of steel, enabling alloy steel to obtain a deeper hardened layer during quenching, thus enhancing the overall performance of the part.
