The material conveying system inputs raw materials such as sinter (fired by sintering plant), coke, limestone, etc. into the distribution system at the top of the blast furnace, and the distribution system evenly distributes them into the furnace according to a certain proportion. The hot air system blows wind into the blast furnace, and the coke burns to form a certain high-temperature (1 150- 1200℃) chemical atmosphere, and the iron oxide in the sinter undergoes reduction reaction at this temperature and environment.
Part of the oxygen in the ore forms carbon dioxide and part becomes carbon monoxide. Part of the impurity gas is discharged at high temperature and enters the dust removal and purification system and the blast furnace gas recovery system. Useless carbon dioxide is discharged and carbon monoxide is recovered and reused. Iron in ore is reduced to liquid molten iron at high temperature.
Hot metal is also called pig iron. Pig iron can be divided into three categories: one is steel for steelmaking (SI content is less than1.25%); One is cast iron for casting machine parts and tools (silicon content is greater than1.25%); There is also an iron alloy (mainly ferromanganese and ferrosilicon).
Steelmaking:
Essentially, it is a smelting process of heating molten iron (pig iron), adding different elements, and reducing the carbon content of iron to 0.2- 1.7% by blowing oxygen. It can make various steels with different textures. If manganese is added, manganese steel will be refined; Adding nickel, chromium and titanium will make the steel less prone to rust.
Extended data:
Iron-carbon alloys are divided into steel and pig iron, and steel is an iron-carbon alloy with carbon content of 0.03% ~ 2%. Carbon steel is the most commonly used common steel, which is easy to smelt, easy to process and low in price, and can meet the use requirements in most cases, so it is widely used. According to the different carbon content, carbon steel is divided into low carbon steel, medium carbon steel and high carbon steel. With the increase of carbon content, the hardness of carbon steel increases and the toughness decreases.
Alloy steel is also called special steel. Adding one or more alloying elements on the basis of carbon steel changes the structure and properties of steel, thus having some special properties, such as high hardness, high wear resistance, high toughness and corrosion resistance. The alloying elements often added in steel are silicon, tungsten, manganese, chromium, nickel, molybdenum, vanadium, titanium and so on.
Alloy steel resources are quite rich, except for chromium and cobalt deficiency and low manganese grade, tungsten, molybdenum, vanadium, titanium and rare earth metals are in high reserves. At the beginning of 2 1 century, the proportion of alloy steel in the total steel output will increase greatly.
Iron-carbon alloy with carbon content of 2% ~ 4.3% is called pig iron. Pig iron is hard and brittle, but it is resistant to compression and wear. According to the different forms of carbon in pig iron, it can be divided into white iron, gray iron and ductile iron. The carbon in white iron is distributed in the form of Fe3C, and the fracture is silvery white. It is hard and brittle, so it can't be machined. It is the raw material for steelmaking, so it is also called steelmaking pig iron.
The fracture of gray cast iron with carbon distributed in flake graphite is silver gray, which is easy to cut, cast and wear-resistant. If carbon is distributed in spherical graphite, it is called ductile iron, and its mechanical properties and machinability are close to those of steel. Special cast iron can be obtained by adding special alloying elements to cast iron. If chromium is added, the wear resistance can be greatly improved, which has a very important application under special conditions.
Source of carbon in steel: One of the raw materials for ironmaking is iron ore, the main component is Fe2O3, and there is no carbon. The second raw material for ironmaking is coke. In the process of ironmaking, part of coke remains in molten iron, resulting in carbon in molten iron. Iron and steel are produced by smelting pig iron from iron ore.
The process of steelmaking with pig iron as raw material is mainly the process of carbon removal. Carbon cannot be completely removed, and steel needs a certain amount of carbon to achieve the best performance.
Through smelting equipment
(1) converter steel converter-blown steel can be divided into bottom blowing, side blowing, top blowing, air blowing and pure oxygen blowing. According to the different lining, it can be divided into acidic and alkaline.
⑵ Open hearth steel The steel refined by open hearth furnace can be divided into acidic steel and alkaline steel according to the different lining materials. Generally, open hearth steel is mostly alkaline.
(3) Electric furnace steel The steel refined by electric furnace includes electric furnace steel, induction furnace steel and vacuum induction furnace steel. Alkaline EAF steel is produced in large quantities in industry.
According to the quality of steel
(1) Ordinary steel contains many impurity elements, such as carbon structural steel, low-alloy structural steel, etc. The sulfur content ws is generally ≤ 0.05% and the phosphorus content WP is ≤ 0.045%.
(2) High-quality steel contains less impurity elements, and the contents of sulfur, phosphorus, ws and wp are generally ≤0.04%, such as high-quality carbon structural steel, alloy structural steel, carbon tool steel and alloy tool steel, spring steel and bearing steel.
(3) High-quality steel contains few impurity elements, with sulfur content ws generally less than 0.03% and phosphorus content WP less than 0.035%, such as alloy structural steel and tool steel. High-grade and high-quality steel is usually marked with the symbol "A" or the Chinese character "Gao" after the steel number for identification.
References:
Baidu encyclopedia-steel