General Alloy Structural Steel in China – Uses, Grades and Mechanical Properties
General alloy structural steel is an important category of engineering materials which are produced in accordance with Chinese national standards (GB/T 1591–2008) and are designed for fabrication into wrought products. Due to the use of alloying elements, such steel has been developed to offer good strength and toughness properties, as well as good fatigue, corrosion and creep resistance.
Common grades of general alloy structural steel include Q235B, Q345B, Q345C, Q345D, Q345E, Q390, Q420, and Q460. These are broadly divided into low-alloy and high-alloy structural steel grades. In terms of chemical composition and mechanical properties, each grade has its own distinct details.
Q235B is a low-alloy structural steel with a small content of carbon, silicon and sulfur. It has moderate strength and good machinability and cold formability in general. It is used for the mechanical structure of buildings, bridges and ships, as well as corrugated sheets.
Q345B is a low-alloy structural steel with medium carbon content, very good cold formability and weldability and moderate strength and toughness. It has a high strength-to-weight ratio and is used for building frames and various load-bearing components.
Q345C is a low-alloy structural steel with low carbon content, excellent weldability and good formability. It is used for ships and marine engineering structures, as well as offshore oil production equipment.
Q345D is a medium-alloy structural steel with low carbon content, good formability and weldability, good mechanical strength and toughness, and high strength-to-weight ratio. It is used for structural components and various load-bearing components.
Q345E is a medium-alloy structural steel with medium carbon content, excellent weldability and formability, and excellent mechanical strength and toughness. It is suitable for the manufacture of general purpose structural components, shipbuilding equipment and offshore platforms.
Q390 is a high-strength low-alloy structural steel with medium carbon content, good welding performance, and good formability and toughness. It is used for bridges, tall buildings, transmission towers, and general structural components.
Q420 is a low-alloy structural steel with medium-high carbon content and good weldability and formability. It is suitable for heavy industrial constructions, crane and forklift columns, buildings and bridge constructions, transmission towers and railways, as well as all kinds of components.
Q460 is a medium-high carbon content, low-alloy structural steel with excellent weldability, good formability, high strength and low ductility. Its excellent mechanical properties make it suitable for applications such as manufacturing parts for cranes and goods hoists, large girders and high-pressure columns.
In terms of mechanical properties, the general alloy structural steel grades all possess strengths in the range of 235–630 MPa, and elongation between 16–22%. They are all suitable for transportation of goods or building materials, and their use is based on the actual requirements of a project.
In summary, general alloy structural steel is a very important engineering material and is widely used in many industries. It is available in a variety of grades, each of which has its own unique properties. Careful consideration should be given to the properties of each grade when selecting the alloy for a particular engineering application.
