Introduction to the types of carbon steel

Carbon steel is an iron-carbon alloy with a carbon content of 0.0218% to 2.11%. Generally also contains a small amount of silicon, manganese, sulfur, phosphorus. Generally, the higher the carbon content in carbon steel, the greater the hardness and the higher the strength, but the lower the plasticity.

Classification:

(1)  According to the purpose, carbon steel can be divided into three categories: carbon structural steel, carbon tool steel and free-cutting structural steel, and carbon structural steel is further divided into engineering construction steel and machine manufacturing structural steel;

(2)  According to the smelting method, it can be divided into open hearth steel and converter steel;

(3)  According to the deoxidation method, it can be divided into boiling steel (F), killed steel (Z), semi-killed steel (b) and special killed steel (TZ);

(4)  According to the carbon content, carbon steel can be divided into low carbon steel (WC ≤ 0.25%), medium carbon steel (WC0.25%-0.6%) and high carbon steel (WC>0.6%);

(5)  According to the quality of steel, carbon steel can be divided into ordinary carbon steel (higher phosphorus and sulfur content), high-quality carbon steel (lower phosphorus and sulfur content) and high-quality high quality steel (lower phosphorus and sulfur content) and special grade High quality steel.

Types:

Carbon structural steel:

Grade: Example Q235-A•F, means σs=235MPa.

Note on the grade: Q is the yield strength, A quality grade (with ABCD four grades), F boiling steel.

Features: low price, excellent process performance (such as weldability and cold formability).

Application: General engineering structure and general mechanical parts. For example, Q235 can be used to make bolts, nuts, pins, hooks and less important mechanical parts, as well as rebars, profiles, and steel bars in building structures.

High-quality carbon structural steel:

Grade: Example 45, 65Mn, 08F.

Note on grades: It directly represents the ten thousand percent of the carbon content of the metal.

Application: Non-alloy steel for manufacturing important mechanical parts is generally used after heat treatment.

Common steel grades and uses:

08F:low mass fraction of carbon, good plasticity, low strength, used for stamping parts such as automobile and instrument housing;

20:Good plasticity and weldability, used for parts with low strength requirements and carburized parts, such as hoods, welding containers, small shafts, nuts, washers and carburized gears, etc.;

45, 40Mn: after quenching and tempering, the comprehensive mechanical properties are good, and it is used for mechanical parts with large force, such as gears, connecting rods, machine tool spindles, etc.;

60, 65Mn steel has high strength; it is used to manufacture various springs, locomotive rims, and low-speed wheels.

Carbon tool steel:

Grade: For example, T12 steel means Wc=1.2% carbon tool steel.

Note for grades: T plus the thousandths of the carbon content of the metal.

Features: It belongs to eutectoid steel and hypereutectoid steel, with high strength, hardness and good wear resistance. It is suitable for manufacturing various low-speed cutting tools.

Common steel grades and uses:

T7, T8: Make parts that require toughness to withstand a certain impact. Such as sledgehammers, punches, chisels, woodworking tools, scissors.

T9, T10, T11: Manufacturing tools that require high hardness and high wear resistance with low impact. Such as taps, small drills, dies, hand saw blades.

T12, T13: Make tools that are immune to impact. Such as files, scrapers, razors, measuring tools.

Cast steel:

Grade: For example, ZG200-400, which means cast steel with σs=200MPa and σb=400MPa.

Performance: The casting performance is worse than that of cast iron, but the mechanical properties are better than that of cast iron.

Application: It is mainly used to manufacture relatively important mechanical parts with complex shapes and high requirements on mechanical properties, but it is difficult to form by forging and other methods in the process, such as gearbox casings of automobiles, couplers and couplings of locomotives and vehicles.