Carbon structural steel and low alloy structural steel, hot-rolled thick steel plate and steel strip (GB/T3274-1988)

Carbon Structural Steels and Low Alloy Structural Steels Hot Rolled Thick Plates and Steel Strips

　　Carbon Structural Steels and Low Alloy Structural Steels Hot Rolled Thick Plates and Steel Strips (GB/T3274—1988) is a standard used to define and measure characteristics of carbon structural steels and low alloy structural steels hot-rolled thick plates and steel strips.

　　GB/T3274—1988 covers specification on hot rolled thick steel plates and strips. It applies to carbon structural steels and low-alloy structural steels hot rolled thick plates and steel strips with a nominal thickness greater than 5mm. Steel grades includes: Q235, Q275, Q345, Q390, 16Mn, 09CuPCrNi-A, Q295NH and so on. It also provides requirements for chemical composition, mechanical properties, heat treatment, surface property, specification and delivery conditions for hot rolled thick plates.

　　To maintain high quality standards of steel, production processes are strictly monitored throughout the entire process from raw material to finished products. Each type of steel is strictly inspected according to the standards. The surface inspection checks the surface defect and strip quality; and chemicical analysis ensures the chemical composition of steel is up to the requirements. Dimensions of steel plates and strips are also tested to ensure that they are correct.

　　When producing hot rolled thick plates and steel strips, rolling is one of the most important processes. Mill rollers are used to reduce the thickness of steel slabs and the finished thickness of steel plates can reach up to more than 60mm. Heat treatment after rolling is necessary to further improve mechanical properties of steel plates and strips and make them harder and stronger.

　　Carbon Structural Steels and Low Alloy Structural Steels Hot Rolled Thick Plates and Steel Strips (GB/T3274—1988) outlines requirements for production quality, inspection and acceptance criteria, and delivery conditions for hot rolled thick steel plates and strips. This standard is important for the steel industry and ensure good materials are used to produce high quality steel components for various industries.

Carbon structural steels and low alloy structural steels are the two major types of steel stipulated by the engineering structure state standard GB/T3274-1988. Carbon structural steels are the most widely used and are mainly used to make engineering structures that require good strength, ductility, impact resistance and welding performance. Low alloy structural steel is also widely used, and is often used to make engineering structures that require relatively high strength, such as large welded pressure vessels and ships. Hot-rolled thick plates and strips are made of these two kinds of steel.

Carbon structural steel has greater strength and hardness, but lower plasticity and weldability than low alloy structural steel, so it is difficult to be used to make components with complex shapes, but it is suitable for making large parts or small components without complicated shapes. Low alloy structural steel has better plasticity, toughness, fatigue and corrosion resistance than carbon structural steel, so it can be used to make steel structures with complicated shapes.

Hot rolled thick steel plates and strips are commonly used for tanks, boilers, pipelines and offshore platforms because of their good mechanical properties and weldability. The plates and strips used for tanks and boilers are often made of low-alloy structural steel, while the pipelines and offshore platforms are often composed of carbon structural steel or low-alloy structural steel. The carbon structural steel and low-alloy structural steel required for the production of hot-rolled thick steel plates and strips shall conform to the standard of GB/T3274-1988. Hot-rolled thick steel plates and strips should meet the size range, shape and weight tolerance requirements stipulated by the standard, as well as the mechanical properties, chemical composition and heat treatment technical requirements of the standard.