High quality carbon structural steel

High quality carbon structural steel

Definition

High quality carbon structural Steel (GB/T699-2015) :

Steel contains no other alloy elements (except residual elements) except carbon (C) element and alloy elements containing a certain amount of silicon (Si) for deoxidation (generally not more than 0.40%) and manganese (Mn) (generally not more than 0.80% and up to 1.20%). Such steel must have both chemical composition and mechanical properties. The contents of sulfur (S) and phosphorus (P) are generally controlled below 0.035%. If it is controlled below 0.030%, it is called high quality steel, and "A" should be added after the grade, such as 20A; If P is controlled below 0.025% and S is controlled below 0.020%, it is called extra high quality steel, and "E" should be added after the grade to show the difference. For other residual alloying elements brought into steel by raw materials, such as chromium (Cr), nickel (Ni), copper (Cu), etc., the content of Cr≤0.25%, Ni≤0.30%, Cu≤0.25%. Some brands of manganese (Mn) content up to 1.40%, known as manganese steel.

This kind of steel depends on the adjustment of carbon content (C) to improve the mechanical properties of steel, therefore, according to the level of carbon content, this kind of steel can be divided into:

Low carbon steel - carbon content is generally less than 0.25%, such as 10, 20 steel, etc.

Medium carbon steel - carbon content is generally between 0.25 ~ 0.60%, such as 35, 45 steel, etc.

High carbon steel - carbon content generally greater than 0.60%. Such steel is not normally used to make steel pipes.

In fact, there is no clear limit to the carbon content between them.

This kind of steel output is larger, more widely used, generally rolled (forging) into round, square, flat and other profiles, plates and seamless steel pipe. It is mainly used for manufacturing general structure and mechanical structure parts and components as well as building structural parts and pipelines for conveying fluids. According to the requirements of use, sometimes need heat treatment (normalizing or tempering) after use.

Classification

High quality carbon structural steel can be divided into three types according to the carbon content: low carbon steel (C≤0.25%), medium carbon steel (C 0.25-0.6%) and high carbon steel (C> 0.6%).

According to different manganese content, high quality carbon structural steel can be divided into normal manganese content (0.25%-0.8% manganese content) and high manganese content (0.70%-1.20% manganese content), and the latter has better mechanical and machining properties.

1. Hot rolled sheet and strip of high-quality carbon structural steel

High quality carbon structural steel hot rolled sheet and strip used in automotive, aviation and other industries. The grade of its steel is boiling steel: 08F, 10F, 15F; Killed steel: 08, 08AL, 10, 15, 20, 25, 30, 35, 40, 45, 50. 25 and below are low carbon steel plates. 30 and above are medium carbon steel plates.

2. High quality carbon structural steel hot rolled thick steel plate and wide steel strip

High quality carbon structural steel hot rolled thick steel plates and wide steel strips are used in various mechanical structural parts. Its steel grade is low carbon steel including: 05F, 08F, 08, 10F, 10, 15F, 15, 20F, 20, 25, 20Mn, 25Mn, etc.; Medium carbon steel includes: 30, 35, 40, 45, 50, 55, 60, 30Mn, 40Mn, 50Mn, 60Mn, etc.; High carbon steel includes: 65, 70, 65Mn, etc.

Use

The sulfur and phosphorus content of high quality carbon structural steel is less than 0.035%, which is mainly used to manufacture more important parts. Generally used in the production of prestressed concrete steel wire, steel strand, anchor, as well as high strength bolts, steel castings of important structures, etc.

According to GB/T 699-1999, the grade of high-quality carbon structural steel is represented by two digits, that is, the millionth digit of the average carbon content in the steel. For example, steel No.20 represents high quality carbon steel with an average carbon content of 0.20%. For boiling steel, F is added to the tail, such as 10F, 15F, etc. 08, 10, 15, 20, 25 and other grades belong to low carbon steel, its plasticity is good, easy to draw, stamping, extrusion, forging and welding.

High quality carbon structural steel 08, 10, 15, 20, 25 and other grades belong to low carbon steel, its plasticity is good, easy to draw, stamping, extrusion, forging and welding. Among them, 20 steel is the most widely used, commonly used to manufacture screws, nuts, washers, small shafts, stamping parts, welding parts, and sometimes used to manufacture carburized parts. 30, 35, 40, 45, 50, 55 and other brands belong to the medium carbon steel, because of the pearlite content in the steel, its strength and hardness is higher than before, after quenching hardness can be significantly increased. Among them, 45 steel is the most typical. It not only has high strength and hardness, but also has good plasticity and toughness, that is, excellent comprehensive performance. 45 Steel is the most versatile in mechanical construction, commonly used in the manufacture of shafts, lead screws, gears, connecting rods, sleeves, keys, vital screws and nuts. Grades 60, 65, 70, 75 and so on belong to high carbon steel. They after quenching, tempering not only strength, hardness, and excellent elasticity, commonly used to manufacture small spring, spring, wire rope, roll, etc.