What is carbon steel? What are the characteristics?
Carbon steel is the earliest and largest basic material in modern industries. In the world's industrial countries, while working hard to increase the output of low -alloy high -strength steel and alloy steel, they also pay great attention to improving the quality of carbon steel and expanding the variety and use scope.
The current proportion of carbon steel production in the total steel output of various countries is maintained at about 80%. It is not only widely used in construction, bridges, railways, vehicles, ships, and various mechanical manufacturing industries, but also in modern petrochemical industry in modern times. In terms of ocean development and other aspects, it is also used in large quantities.
The carbon content is less than 2.11%. Except for iron, manganese, phosphorus, sulfur and other impurities such as silicon, manganese, phosphorus, and sulfur within limited editions, iron carbon alloys do not contain other alloy elements. The carbon content for industrial carbon steel is generally 0.05%~ 1.35%. The performance of carbon steel mainly depends on carbon content. Increased carbon content, the strength and hardness of the steel increase, and the plasticity, toughness and weldability are reduced. Compared with other steel, carbon steel is used earliest, low in cost, wide performance range, and maximum dosage. It is suitable for water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with water, steam, air, hydrogen, ammonia, nitrogen and petroleum products with a temperature of -30-425 ° C. The commonly used plates include WC1, WCB, ZG25 and high -quality steel 20, 25, 30 and low alloy structure steel 16MN.
1. Carbon structure steel
Main use: various projects. Generally, air -cooled supply is usually used after hot rolling. Users generally do not need to be used directly. This type of steel is divided into five levels according to its yield strength level.
Name: Sign symbol Q+minimum σs value — level symbol+deoxylonicity symbols such as: Q235AF
Level symbols: A, B, C, D (Glass D has reached high -quality steel level)
2. High -quality carbon structure steel
Main use: important parts. You can adjust the mechanical properties of the parts by heat treatment. The state of the factory can be air -cooled after hot rolling, or it can be annealing, positive fire and other states. According to the national standards (GB/T699-1999, it is divided into three quality grades: high-quality steel, high-quality high-quality steel A and special high-quality steel E.
Naming: Use two digits to represent, two digits indicate the amount of carbon content in the steel. Such as: 45 Steel WC = 0.45%
Common card numbers: 08F, 10#, 15#, 20#, 35#, 45#, 60#, etc.
3. Carbon tool steel (WC = 0.65% ~ 1.35% is high carbon steel)
Main use: make a variety of small tools. For quenching and low temperature recovery treatment, high hardness and high wear resistance can be performed. It is divided into two categories: high -quality and high -quality high -quality level.
Naming: 1000 times the sign of the symbol T+carbon content. Such as: T10 WC = 1.0%
Advanced high -quality high -quality level adds A at the tail of the steel number, such as T10A
4. Casting carbon steel parts for general engineering (cast steel)
Main use: difficult parts formed with methods such as forging and other methods and high mechanical performance requirements;
Name: Sign symbol zg+minimum σs value-minimum σb value, such as: zg340-640
display method
Number: Q+Number+Quality Grade Symbol · Typening Method Symbol
For example: q235a · f
Among them, Q represents the yield strength, 235 represents the value of the yield strength, A means the quality level is A -level, and f means boiling steel.
Q235A · F -indicates that the yield strength is 235N/mm2;
Chemical impact
The performance of carbon steel mainly depends on the carbon content and micro -tissue of steel. In the state of annealing or hot -rolled, the strength and hardness of the steel are increased with the increase in carbon content, and the plasticity and impact toughness decreased. Welding and cold curvature deterioration. Therefore, steel for engineering structure often limits carbon content. Residual elements and impurities in carbon steels such as manganese, silicon, nickel, phosphorus, sulfur, oxygen, nitrogen, etc., also affect the performance of carbon steel. These effects sometimes strengthen each other and sometimes offset each other.
Processing performance
Most of the carbon steel uses oxygen -turning furnaces to smell, and high -quality carbon steel is also produced in an arc furnace. Depending on the degree of deoxidation of the steelmaking process, carbon steel can be divided into semi -static steel, boiling steel, and semi -semi -static steel between the two. The impact of the smelting method on the performance of steel is mainly used through the purity of steel. Through vacuum treatment, out -of -furnace refining, and blowing technology, people can obtain higher purity steel, which significantly improves the quality of carbon steel.
The plastic processing process of carbon steel is usually divided into heat processing and cold processing. After heat processing, the short bubbles and loose defects in the steel ingots are welded to make the tissue of the steel. At the same time, thermal processing can destroy the casting tissue and refine the grains. Make the forging steel more mechanical performance than the casting state. The steel processed by cold, with the degree of deformation of the cold plastic, increased strength and hardness, and decreased plasticity and toughness. In order to improve the material rate, continuous steel casting technology is widely used.
Manufacturing process
The smelting of carbon steel is usually carried out in the turntable and flat furnace. Generally smelting ordinary carbon steel, while flat furnaces can smell all kinds of high -quality steel. Oxygen top blowing technology has developed rapidly, and there is a trend to replace the flat furnace steelmaking. Inject the refined steel fluid into the steel ingot mold, and get various steel ingots. The steel ingots are processed into steel plates, steel bands, steel strips and various section -shaped steel after forging or rolling. Carbon steel is generally used directly in hot rolled state. When used to manufacture tools and various machine parts, heat treatment is required according to the requirements of the use; as for cast steel parts, most of them must be treated.