Classification by steel quality
According to the quality of steel, it can be divided into ordinary carbon steel and high-quality carbon steel.
(1) Ordinary carbon structural steel, also known as ordinary carbon steel, has wide restrictions on carbon content, performance range and content of phosphorus, sulfur and other residual elements. In China and some countries, it is divided into three categories according to the guaranteed conditions of delivery: Class A steel (Class A steel) is steel that guarantees mechanical properties. Type B steels (Type B steels) are steels with guaranteed chemical composition. Special steel (C-type steel) is a steel that guarantees both mechanical properties and chemical composition, and is often used to manufacture more important structural parts. China produces and uses the most A3 steel with a carbon content of about 0.20% (Class A No. 3 steel), which is mainly used for engineering structures.
Some carbon structural steels also add a small amount of aluminum or niobium (or other carbide-forming elements) to form nitride or carbide particles to limit grain growth, strengthen the steel, and save steel. In China and some countries, in order to meet the special requirements of professional steel, the chemical composition and properties of ordinary carbon structural steel have been adjusted, and a series of professional steel of ordinary carbon structural steel (such as bridges, buildings, steel bars, steel for pressure vessels, etc.).
(2) Compared with ordinary carbon structural steel, high-quality carbon structural steel has lower content of sulfur, phosphorus and other non-metallic inclusions. According to the different carbon content and use, this kind of steel is roughly divided into three categories:
① Less than 0.25% C is low carbon steel, especially 08F, 08Al with carbon content less than 0.10%, etc., which are widely used as deep drawing parts such as automobiles and cans because of their good deep drawing and weldability. ……Wait. 20G is the main material for making ordinary boilers. In addition, low carbon steel is also widely used as carburizing steel for machinery manufacturing.
②0.25～0.60%C is medium carbon steel, which is mostly used in the quenched and tempered state to make parts in the machinery manufacturing industry.
③More than 0.6%C is high carbon steel, which is mostly used in the manufacture of springs, gears, rolls, etc.
According to the different manganese content, it can be divided into ordinary manganese content (0.25-0.8%) and higher manganese content (0.7-1.0% and 0.9-1.2%) two steel groups. Manganese can improve the hardenability of steel, strengthen ferrite, and improve the yield strength, tensile strength and wear resistance of steel. Usually, "Mn" is added after the grade of steel with high manganese content, such as 15Mn, 20Mn, to distinguish it from carbon steel with normal manganese content.
Classification by use
According to the use, it can be divided into carbon structural steel and carbon tool steel.
Carbon tool steel The carbon content is between 0.65 and 1.35%. After heat treatment, high hardness and high wear resistance can be obtained. It is mainly used to manufacture various tools, cutting tools, molds and measuring tools (see tool steel).
Carbon structural steel is divided into 5 grades according to the yield strength of steel:
Q195, Q215, Q235, Q255, Q275
Each grade is divided into A, B, C, and D grades due to different quality. There are at most four grades, and some have only one. In addition, there are differences in the deoxidation methods of steel smelting.
Deoxygenation method notation:
F - boiling steel
b - semi-killed steel
Z - killed steel
TZ - special killed steel

Classified by process
Round steel is divided into three types: hot rolled, forged and cold drawn. The size of hot rolled round bar is 5.5-250 mm. Among them: small round bars of 5.5-25 mm are mostly supplied in bundles of straight strips, which are often used as steel bars, bolts and various mechanical parts; round bars larger than 25 mm are mainly used for the manufacture of mechanical parts and billets of seamless steel pipes Wait.
Classification by chemical composition
Carbon steel can be divided into low carbon steel, medium carbon steel and high carbon steel according to chemical composition (that is, carbon content).
(1) Low carbon steel
Also known as mild steel, low carbon steel with carbon content from 0.10% to 0.30% is easy to accept various processing such as forging, welding and cutting, and is often used in the manufacture of chains, rivets, bolts, shafts, etc.
(2) Medium carbon steel
Carbon steel with a carbon content of 0.25% to 0.60%. There are killed steel, semi-killed steel, boiling steel and other products. 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 ordinary carbon structural steel and high-quality carbon structural steel. Good thermal processing and cutting performance, poor welding performance. The strength and hardness are higher than those of low carbon steel, while the plasticity and toughness are lower than those of low carbon steel. Hot-rolled and cold-drawn materials can be used directly without heat treatment, or they can be used after heat treatment. The quenched and tempered medium carbon steel has good comprehensive mechanical properties. The highest hardness that can be achieved is about HRC55 (HB538), and σb is 600-1100MPa. Therefore, among various uses of medium strength level, medium carbon steel is the most widely used, in addition to being used as a building material, it is also widely used in the manufacture of various mechanical parts.
(3) High carbon steel
Often called tool steel, it has a carbon content from 0.60% to 1.70% and 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%.

Chengdu Jinyongcheng Metal Products Co., Ltd. The company's main business is an enterprise engaged in the wholesale and retail of steel products. The company mainly provides raw materials for the manufacturing industry, and special-shaped products can be customized.
Chengdu Jinyongcheng Metal Products Co., Ltd. was established on October 24, 2017. Its registered office is located in Building 1, No. 366, East Sixth Road, Checheng, Chengdu Economic and Technological Development Zone (Longquanyi District), Sichuan Province. The legal representative is Liao Yong. The business scope includes production and sales: mechanical equipment, metal products, auto parts; sales: steel, mechanical and electrical products, electronic appliances, Wujinjiaodian, rubber products, building materials, electronic products, metal structural parts, non-ferrous metals (subject to approval according to law) Business activities can only be carried out after the approval of the relevant departments; without the relevant administrative license (approval), no business activities shall be carried out).

Yong Liao

289584567@qq.com

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