Definition and Classification of Alloy Structural Steel
Alloy structural steel is a kind of special steel which is made of various kinds of alloy materials. It is widely used in the construction of bridges, ships, vehicles, boilers, high pressure vessels, oil and gas pipelines, and large steel structure components. Steel alloy structural steel is characterized by its special chemical composition, specific physical and mechanical properties, and specific processing performance, which can meet the needs of different structural components and engineering structures with different functions.
In general, alloy structural steel can be divided into several categories according to its composition and applications.
According to the composition of the alloy, there are high-carbon alloy structural steel, medium-carbon alloy structural steel and low-carbon alloy structural steel three categories. Among them, high-carbon alloy structural steel contains more alloying elements such as manganese, nickel and chromium and has the properties of higher strength and toughness, superior wear resistance, good corrosion resistance and higher fatigue strength. Medium-carbon alloy structural steel contains less alloy elements compared to high-carbon alloy structural steel and has better weldability, higher strength at low temperatures and stable performance. Low-carbon alloy structural steel is made of highly pure steel and has low carbon content so it can be welded and heat-treated, while maintaining good mechanical strength and toughness.
In terms of characteristics and applications, alloy structural steel can be divided into general purpose structural steel, atmospheric corrosion resistant structural steel and special purpose structural steel. General-purpose structural steel can resist external loads and has good ductility and welding performance. Atmospheric corrosion resistant structural steel is mainly used in humid environment with high oxygen content, such as bridges and atmospheric pipelines, and can resist atmospheric corrosion. Special purpose structural steel, due to its special properties, is suitable for special applications and is generally used in special industries such as aerospace, petrochemical and marine industries.
At present, there are many types of alloy structural steel, of which the most representative ones are 10-25CrNi2MoV steel, 4140 steel and 4130 steel. 10-25CrNi2MoV steel is mainly used for medium-sized and large components, such as forgings, shafts, high-pressure vessels and steam turbine blades. It has superior comprehensive mechanical properties, excellent corrosion resistance and good toughness. 4140 steel is mainly used for small and medium-sized mechanical components, such as machine tools, oil and gas pipelines, agricultural machinery and connecting rods. It has high strength and toughness and good processability. 4130 steel is mainly used to manufacture car and motorcycle parts, shafts and other components. It has good overall performance and machinability and is often used in general-purpose structural steel parts.
In short, alloy structural steel can be divided into several categories according to its composition and applications. Each category has its own characteristics and applications, enabling different kinds of components to be manufactured according to different needs. Therefore, alloy structural steel has been widely used in various engineering structures, from bridges and ships to automobiles and aerospace structures.
