Open hearth steel: including carbon steel and low alloy steel. According to the different lining materials, it can be divided into acid and alkaline open hearth steels.
converter steel: including carbon steel and low alloy steel. According to different oxygen blowing positions, there are three kinds of converter steels: bottom blowing, side blowing and oxygen top blowing.
electric furnace steel: mainly alloy steel. According to the different types of electric furnaces, there are four kinds of electric arc furnace steel, induction furnace steel, vacuum induction furnace steel and electroslag furnace steel.
boiling steel, killed steel and semi-killed steel: they are distinguished according to the degree of deoxidation and pouring system.
2. Classification by chemical composition:
Carbon steel is an alloy of iron and carbon. It is reported that in addition to iron and carbon, it contains elements such as silicon, manganese, phosphorus and sulfur. According to the different carbon content, it can be divided into low carbon (C <: .25%), medium carbon (C: .25%-.6%) and high carbon (C >: .6%) three kinds of steel. Steel with carbon content less than .4% is called industrial pure iron.
ordinary low-alloy steel: a small amount of alloying elements (such as silicon, calcium, titanium, niobium, boron and rare earth elements, etc., the total amount of which is not more than 3%) are added on the basis of low-carbon ordinary carbon steel. And the steel grade with better comprehensive performance can be obtained.
alloy steel: it is a kind of steel containing one or more appropriate alloying elements, which has good and special properties. According to the total content of alloying elements, it can be divided into low alloys (total <: 5%), medium alloy (total amount of alloy is 5%-1%) and high alloy (total amount >: 1%) three kinds of steel.
3. Classification by use:
Structural steel: There are two types of construction steel and mechanical steel according to different uses. Construction steel is used to build boilers, ships, bridges, factories and other buildings. Mechanical steel is used to make machines or mechanical parts.
tool steel: high carbon steel and medium carbon steel used for manufacturing various tools, including carbon tool steel, alloy tool steel and high-speed tool steel.
special steel: special-purpose steel with special physical and chemical properties, including stainless and acid-resistant steel, heat-resistant steel, electrothermal alloy and magnetic materials.
Common smelting methods
1. Converter steelmaking:
A steelmaking method mainly using liquid pig iron as raw material without external heat source. Its main feature is to use the physical heat of liquid pig iron in converter and the heat generated by the chemical reaction of various components in pig iron, such as carbon, manganese, silicon and phosphorus, with oxygen sent into the furnace as smelting heat source to make steel. In addition to molten iron, there are slagging materials (lime, Shi Ying, fluorite, etc.); In order to adjust the temperature, scrap steel and a small amount of cold pig iron and ore can also be added. Converter can be divided into alkaline (lined with magnesia or white clouds) and acidic (lined with siliceous materials) according to the properties of refractory lining. According to the part of gas blowing into the furnace, it is divided into bottom blowing and top blowing and side blowing; According to the gas used, it is divided into air converter and oxygen converter. Acidic converter can not remove sulfur and phosphorus from pig iron, so it must use high-quality pig iron, so its application scope is limited. Basic converter is suitable for steelmaking with high phosphorus pig iron, which has achieved great development in western Europe. Air-blown converter steel has not been popularized in the world because of its high nitrogen content, limited raw materials and inability to mix more scrap steel. Oxygen top-blown converter came out in 1952, and now it has become the main steelmaking method in the world. On the basis of oxygen top-blown converter steelmaking, in order to blow high phosphorus pig iron, oxygen top-blown converter steelmaking with lime powder has appeared. With the successful development of oxygen bottom blowing tuyere technology, in 1967, Germany and France built oxygen bottom blowing converters respectively. In 1971, after the introduction of this technology in the United States, a converter with bottom blowing oxygen and lime powder was developed for smelting phosphorus-containing pig iron. In 1975, France and Luxembourg successfully developed the converter steelmaking method of top-bottom combined blowing.
2. oxygen top-blown converter steelmaking:
converter steelmaking method with pure oxygen blowing molten iron from the top of converter to make steel, or LD method; In the United States, it is usually called BOF method, also known as BOP method. It is the main method of modern steelmaking. The furnace is an upright crucible-shaped container, and an upright water-cooled oxygen gun is inserted into the furnace from the top to supply oxygen. The furnace body can tilt. The charge is usually molten iron, scrap steel and slagging materials; A small amount of cold pig iron and iron ore can also be added. High-pressure pure oxygen (containing more than O 299.5%) is blown downward from the top of the molten pool by oxygen lance to remove silicon, manganese, carbon and phosphorus in molten iron by oxidation, and dephosphorization and desulfurization are carried out by slagging. The heat generated by the oxidation of various elements heats the liquid metal in the molten pool and makes the molten steel reach the current chemical composition and temperature. It is mainly used for smelting non-alloy steel and low-alloy steel; But through refining, it can also be used to smelt alloy steel such as stainless steel.
3. Oxygen bottom-blown converter steelmaking:
A converter steelmaking method in which oxygen is blown into the molten pool in the furnace through an oxygen nozzle at the bottom of the converter to smelt molten iron into steel. Its characteristics are: The height and diameter of the furnace are relatively small; The furnace bottom is flat and can be quickly disassembled and replaced; The tuyere, distributor system and oxygen supply system on the furnace body are used to replace the oxygen lance system of oxygen top-blown converter. The metal yield of oxygen bottom-blown converter is 1% ~ 2% higher than that of oxygen top-blown converter because of its smooth blowing, less splashing, less soot and low iron oxide content in slag. Powder slagging material is used, because the particles are fine and the specific surface is large, which increases the reaction interface, so the slagging is fast and is beneficial to desulfurization and dephosphorization. This method is especially suitable for blowing medium phosphorus pig iron, so it is most widely used in western Europe.
4. Continuous steelmaking:
A steelmaking method in which raw materials (molten iron and scrap steel) are continuously added from one end of the furnace regardless of the number of heats, and finished products (molten steel) are continuously discharged from the other end of the furnace. The idea of continuous steelmaking process appeared as early as the 19th century. Because of the potential advantages of this process, such as small equipment, simple and stable process, many countries have made a large number of experiments of various methods for decades, including tank method, spray method and foam method, but so far they have not been put into industrial production.
5. Mixed steelmaking:
A steelmaking method in which one furnace is used for steelmaking, another electric furnace is used for smelting reduced slag or reduced slag and alloy, and then mixed at a certain height. This method can improve the quality of steel by treating steelmaking water from open hearth furnace, converter and electric furnace. Rushing and mixing can increase the contact area between slag and steel, accelerate chemical reaction, deoxidize and desulfurize, and have the function of adsorbing and polymerizing gases and inclusions, thus improving the purity and quality of steel.
6. Combined blowing converter steelmaking:
On the basis of top-blowing and bottom-blowing oxygen converter steelmaking methods, a new steelmaking method is developed by combining their advantages and overcoming their disadvantages, that is, blowing different gases at the bottom of the original top-blowing converter to improve the stirring of molten pool. At present, most countries in the world use this steelmaking method, and have developed various types of combined blowing converter steelmaking technologies, such as BSC-BAP method, which is developed by British Steel Company and uses air +N2 or Ar2 as bottom blowing gas and N2 as cooling gas. The KMS method developed by Klokner-Max Metallurgical Plant in Germany, which uses natural protective bottom gun and injects coal and oxygen into the molten pool from the bottom, the K-BOP method developed by Kawasaki Iron and Steel Company in Japan, which blows oxygen mixed lime powder accounting for 3% of the total oxygen into the molten pool from the bottom, and the LD-OB method developed by Nippon Steel Company, which blows oxygen accounting for 1%-2% of the total oxygen from the bottom and cools the bottom nozzle with propane or natural gas, etc.
7. Top-blown oxygen open-hearth steelmaking:
Since the mid-195s, 1 ~ 5 water-cooled oxygen lances have been inserted into the melting chamber from the top of the furnace to directly blow oxygen into the molten pool. This method improves the dynamic conditions of molten pool reaction, changes the thermal effect of carbon-oxygen reaction from endothermic to exothermic, and improves the thermal conditions. Productivity has been greatly improved.
8. EAF steelmaking:
A steelmaking method that uses the thermal effect of electric arc to melt metals and other materials. Three-phase AC arc furnace for steelmaking is the most common direct heating arc furnace. In the process of steelmaking, because there is no gas in the furnace, an oxidizing or reducing atmosphere and conditions can be formed according to the process requirements, so it can be used to smelt high-quality non-alloy steel and alloy steel. According to the furnace capacity per ton, EAF can be divided into ordinary power EAF, high power EAF and ultra-high power EAF. The purpose of developing EAF steelmaking to high power and ultra-high power is to shorten smelting time, reduce power consumption, improve productivity and reduce costs. With the appearance of high-power and ultra-high-power electric furnaces, electric arc furnaces have become melters, and all refining processes are carried out in refining devices. In recent ten years, DC arc furnace has developed rapidly because of low electrode consumption, small voltage fluctuation and low noise, and can be used to smelt high-quality steel and ferroalloy.
9. STB method:
The original text is Sumitomo Top and Bottom Blowing Process, which is a top-bottom combined blowing converter steelmaking method developed by Sumitomo Metal Company of Japan. This method combines the advantages of oxygen top-blown converter steelmaking and oxygen bottom-blown converter steelmaking. When it is used for blowing low carbon steel, the dephosphorization effect is good and the cost is significantly reduced. The bottom blowing gases used are O2, CO2, N2, etc. On the basis of STB method, STB-P method of injecting powder from the top was developed, which further improved the dephosphorization conditions of high carbon steel and was used to refine stainless steel.
1. RH method:
Also known as circulating vacuum treatment. Developed by German Ruhrstahl/Heraeus Company * * *. There are two conduits below the vacuum chamber, into which molten steel is inserted. After vacuumizing, molten steel rises to a certain height, and then inert gases Ar are blown into the riser to drive molten steel to enter the vacuum chamber for vacuum treatment, and then flow back to the ladle through the other conduit. The vacuum chamber is equipped with an alloying feeding system. This method has become the main vacuum treatment method for molten steel in large capacity ladle (> ＞8t).
11. RH-OB:
RH oxygen blowing method. Oxygen Blowing is added to the vacuum cycle degassing (RH) method to raise the temperature. For refining stainless steel, decarburization reaction can be preferentially carried out under reduced pressure; When used for refining ordinary steel, the load of converter can be reduced. Aluminum can also be used to raise the temperature.
12. OBM-S method:
The original text is Oxygen Bottom Maxhutte—Scarp, which is an oxygen bottom-blown converter steelmaking method with natural gas or propane as the cooling medium of the bottom-blown oxygen lance, which was invented by the Maxhutte-Klockner factory in Germany. OBM-S is to install a side oxygen lance on the furnace cap of OBM oxygen bottom-blown converter, and the bottom oxygen lance blows gas and natural gas to preheat the scrap steel, so as to increase the scrap steel ratio.
13. NK-CB method:
The original text is NKK Combined Blowing System, which is a top-bottom combined blowing converter steelmaking method established by Japan Steel Pipe Company in 1973, that is, a small amount of gases (Ar, CO2, N2) are blown from the bottom of the furnace at the same time of top blowing, so as to strengthen the stirring of steel slag and control the partial pressure of CO in molten steel. This method adopts perforated brick nozzle, which can reduce the cost when it is used to smelt low carbon steel. It is beneficial to dephosphorization when it is used to smelt high carbon steel. This method should be combined with hot metal pretreatment process
14. MVOD: < P > A water-cooled oxygen lance is added to the equipment of VAD method, so that it can be blown with oxygen to decarburize in vacuum. Because decarburization in vacuum is an exothermic reaction, the vacuum heating measures of VAD method can be omitted. The operation process is the same as VOD method.
15. LF method:
Ladle Furnace is a ladle furnace refining method developed by Japan Special Steel Company (Datong Special Steel Company) in 1971. Its equipment and technology are composed of argon stirring, submerged arc heating and alloy feeding system. The advantages of this process are: the chemical composition and temperature of molten steel can be accurately controlled; Reduce the content of inclusions; The yield of alloy elements is high. LF furnace has become an indispensable external refining equipment between steelmaking furnace and continuous casting machine.
16. LD steelmaking method:
In p>1952, Linz Plant of Austrian Steel and Donawitz Plant of Austrian Alpine Mining and Metallurgy Company were the first to successfully develop the oxygen top-blown converter steelmaking method in industry, and were named after the first letters of the two plants. This law was quickly popularized all over the world after it came out. The United States calls this method BOF or BOP method, which is the abbreviation of Basic Oxygen Furnace or Process. See oxygen top blowing and converter for details.
17. LD-OTB method:
The original text is LD-ox gyen top an bottom process, which is a top-bottom combined blowing converter steelmaking process developed by Kakogawa Plant of Kobe Steel Company. It is characterized by the use of a special bottom blowing single-ring slit nozzle (SA nozzle), so that the bottom blowing body can be controlled in a wide range. Inert gas is blown into the bottom.
18. LD-HC method:
The original text is LD-Hainaut Saubre CRM, which is a top-bottom combined blowing converter steelmaking method developed by Belgium for blowing high-phosphorus hot metal, that is, LD+ bottom blowing oxygen and protecting the nozzle with hydrocarbons.
19. LD-AC method:
The original text is LD-Arbed-Centre National, which is a steel-making method developed by French Iron and Steel Research Institute, and is used for blowing high-phosphorus hot metal.
2. KS method:
The original Klockner Steelmaking is a converter steelmaking process with 1% solid material and oxygen injection at the bottom. The bottom blowing oxygen ratio is 6% ~ 1%.
21. K-ES method:
The electric arc furnace steelmaking method, which combines bottom blowing gas technology, secondary combustion technology and pulverized coal injection technology, is a technology jointly developed by Tokyo Steelmaking Company of Japan and Kiokner Company of Germany, and can replace electricity with coal.
22. FINKL—VAD method:
Arc heating ladle degassing method or vacuum arc degassing method. It is characterized in that an arc heating device is additionally arranged on the cover of the vacuum chamber, and argon gas is used for stirring under vacuum. The degassing effect of this method is stable, and it can be desulfurized, decarburized and added with a large number of alloys. The equipment is mainly composed of vacuum chamber, arc heating system, alloy feeding device, vacuum pumping system and hydraulic system.
23. DH method:
A vacuum treatment device developed by Dortmund Horder United Metallurgical Company in Germany. In the vacuum chamber lined with refractory material, a conduit with refractory lining is inserted into the ladle, and the vacuum chamber or ladle is lowered and lifted periodically, so that a part of molten steel enters the vacuum chamber and returns to the ladle after treatment. The upper part is provided with an alloying device and a vacuum heating and heat preservation device. At present, this kind of equipment is no longer built.
24. CLU method:
A method for refining stainless steel. Its principle is the same as AOD method, and the object point is to use steam instead of argon. This method was successfully developed by French Creusot-Loire company and Swedish Uddeholm company, and was put into production in 1973. Steam decomposes into H2 and O2 after contacting with molten steel; H2 reduces the partial pressure of CO.. At the same time, the decomposition reaction is endothermic, so the temperature rise of molten steel can be suppressed. However, the oxidation burning loss of chromium is more serious than that of AOD method.
25. CAS method:
The original text is composition adjustment.