Classification of carbon steel
According to the mass percentage of carbon:
Low-carbon steel (C: ≤ 0.25%) Also known as mild steel, low-carbon steel is easy to accept various processes such as forging, welding and cutting, and is commonly used in the manufacture of chains, rivets, bolts, and shafts.
Medium carbon steel (C: 0.25% <C ≤ 0.6%) has a variety of products such as killed steel, semi-static steel, and boiling steel. In addition to carbon, it can also contain a small amount of manganese (0.70% to 1.20%). According to product quality, it is divided into common carbon structural steel and high-quality carbon structural steel. Thermal processing and cutting performance is good, welding performance is poor. Strength and hardness are higher than that of low carbon steel, while plasticity and toughness are lower than low carbon steel. The hot-rolled and cold-drawn materials can be used without heat treatment, and can also be used after heat treatment. The medium carbon steel after quenching and tempering has good comprehensive mechanical properties. The highest hardness that can be achieved is about HB538, and the tensile strength σb is 600 to 1100 MPa. As a result, medium-carbon steels are most widely used in various applications of moderate-intensity level, and are used in large quantities for manufacturing various mechanical parts in addition to construction materials.
High-carbon steels (C: >0.6%) are often referred to as tool steels and contain more than 0.60% to 1.70% carbon, which can be hardened and tempered. Hammers, crowbars, etc. are made of steel with a carbon content of 0.75%; cutting tools such as drills, taps, reamers, etc. are made of steel with a carbon content of 0.90% to 1.00%. The higher the carbon content, the greater the hardness and strength, but the decrease in plasticity
(In addition, 2.1% to 4.5% carbon-containing carbon-carbon alloy is commonly referred to as cast iron.) 2. According to the quality of the steel (mainly impurities sulfur, phosphorus content):
Ordinary carbon steel (S s0.055%, P ≤ 0.045%) High-quality carbon steel (S ≤ 0.040%, P ≤ 0.040%)
High-quality high-quality carbon steel (S s 0.030%, P ≤ 0.035%) 3, by use:
Carbon structural steel: mainly used for bridges, ships, building components, machine parts and other carbon tool steel: mainly used for tools, molds, measuring tools, etc.
2. High-quality carbon structural steel: The steel number is expressed as the average mass of carbon. Such as 20 #, 45 # and so on. 20# means C: 0.20% (20/20). Uses: mainly used for manufacturing various machine parts
3. Carbon tool steel: The steel number is expressed in terms of the average mass of carbon, and is preceded by T. Such as T9, T12 and so on. T9 means C: 0.9% (9 parts per thousand). Uses: mainly used for the manufacture of various tools, measuring tools, molds, etc.
4. Cast steel: Cast steel grades are ZG in front of numbers, and numbers represent the average mass fraction in steel (in thousands of fractions). Such as ZG25, said that containing C: 0.25%. Uses: Mainly used for manufacturing parts with complex shapes and requiring certain strength, ductility and toughness, such as gears and couplings.