Carbon steel revealed: core material for industrial applications

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. 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 (high phosphorus and sulfur content), high-quality carbon steel (low phosphorus and sulfur content), high-grade high-quality steel (lower phosphorus and sulfur content) and special high-quality steel.

Types

Carbon structural steel

Grade: For example, Q235-A·F, indicating σs=235MPa.

Grade annotation: Q is yield strength, A is quality grade (there are four grades, ABCD), and F is boiling steel.

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

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

High-quality carbon structural steel

Grade: For example, 45, 65Mn, 08F.

Grade annotation: directly indicates the ten thousandth of the carbon content of the metal.

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

Common steel grades and uses:

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

20, good plasticity and weldability, used for parts with low strength requirements and carburized parts, such as hoods, welded containers, small shafts, nuts, washers and carburized gears;

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

60 and 65Mn steels have high strength; they are used to manufacture various springs, motorcycle wheel rims, and low-speed wheels.

Carbon tool steel

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

Grade annotation: T plus the thousandth of the metal carbon content.

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

Common steel grades and uses:

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

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

T12, T13: Make tools that are not subject to impact. Such as files, scrapers, razors, and measuring tools.

Cast steel

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

Performance: Casting performance is worse than cast iron, but mechanical properties are better than cast iron.

Application: Mainly used to manufacture important mechanical parts with complex shapes, high mechanical properties, and difficult to form by forging and other methods, such as automobile gearbox housings, locomotive vehicle couplers and couplings, etc.

Specific Advantages of Carbon Steel

‌High strength‌: Carbon steel has excellent strength and can withstand heavy loads and forces, making it suitable for applications requiring high strength‌

High hardness: The hardness of carbon steel mainly depends on its carbon content. The higher the carbon content, the greater the hardness. This gives carbon steel significant advantages in manufacturing wear-resistant parts, cutting tools and molds‌

‌Good corrosion resistance‌: Through appropriate surface treatment, such as plating or coating, the corrosion resistance of carbon steel can be significantly improved to adapt to general corrosive environments‌

‌Weldability‌: Carbon steel is easy to weld, and can be processed and formed at lower temperatures after welding, making it suitable for structural parts that require welding‌

Cost advantage‌: Compared with other alloy steels, the manufacturing cost of carbon steel is more affordable because its main ingredients are carbon and iron which are widely and easily available‌

Examples of carbon steel applications in different fields

Machinery manufacturing: Carbon steel is widely used in the manufacture of machine tools, bearings, transmission parts, etc. due to its high strength and good processing performance

Construction engineering: Carbon steel is used in skeleton structures, bridges and reinforced concrete in construction engineering due to its high strength and good weldability

Automobile manufacturing: Carbon steel is widely used in construction machinery such as automobiles, trucks, excavators, etc. due to its high strength and wear resistance

Mining industry: Carbon steel is used in the production of mining equipment, mine supports and drilling tools, etc. due to its high strength and wear resistance