Open hearth steel: including carbon steel and low alloy steel. According to different lining materials, it can be divided into acid open hearth steel and alkaline open hearth steel.
Converter steel: including carbon steel and low alloy steel. According to different oxygen blowing positions, there are three kinds of converter steel: bottom blowing, side blowing and oxygen top blowing.
Electric furnace steel: mainly alloy steel. According to different types of electric furnaces, it can be divided into four types: electric furnace steel, induction furnace steel, vacuum induction furnace steel and electroslag furnace steel.
Boiling steel, killed steel and semi-killed steel: differentiated by deoxidation degree and gating system.
2, according to the chemical composition classification:
Carbon steel: It is an alloy of iron and carbon. Besides iron and carbon, it also contains elements such as silicon, manganese, phosphorus and sulfur. According to the different carbon content, it can be divided into three types of low carbon steel (C0.60%). Steel with carbon content below 0.04% is called industrial pure iron.
Ordinary low alloy steel: A steel with better comprehensive properties is obtained by adding a small amount of alloying elements (such as silicon, calcium, titanium, niobium, boron and rare earth elements). The total amount does not exceed 3%), based on low-carbon ordinary carbon steel.
Alloy steel: It is a kind of steel containing one or more appropriate alloying elements and has good special properties. According to the total content of alloying elements, it can be divided into three types: low alloy (total 10%) steel.
3, according to the purpose of classification:
Structural steel: according to different uses, it can be divided into two types: construction steel and mechanical steel. Building steel is used to build boilers, ships, bridges, factories and other buildings. Mechanical steel is used to manufacture 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 steel with special physical and chemical properties, including stainless acid-resistant steel, heat-resistant steel, electrothermal alloy and magnetic material.
Common smelting methods
1, converter steelmaking:
A steelmaking method using liquid pig iron as raw material without external heat source is mainly characterized in that the physical heat of liquid pig iron in a converter and the heat generated by the chemical reaction of various components in pig iron such as carbon, manganese, silicon and phosphorus with oxygen fed into the furnace are used as the melting heat source for steelmaking. In addition to molten iron, there are slagging materials (lime, timely, fluorite, etc. ). In order to adjust the temperature, scrap steel and a small amount of cold pig iron and ore can also be added. According to the properties of refractory lining, converters can be divided into alkaline converters (lined with magnesia or dolomite) and acidic converters (lined with siliceous materials). According to the gas blown into the furnace, it is divided into bottom blowing, top blowing and side blowing; According to the gas used, it can be divided into air converter and oxygen converter. Acid converter can't remove sulfur and phosphorus from pig iron, so its application range is limited. Basic converter is suitable for steelmaking with high phosphorus pig iron, which has made great progress in western Europe. Air-blown converter steel has not been popularized in the world because of its high nitrogen content, limited raw materials and no scrap, and now it has become the main steelmaking method in the world. On the basis of oxygen top-blown converter steelmaking, lime powder is introduced to smelt high phosphorus pig iron. With the successful development of oxygen bottom blowing port technology, Germany and France built oxygen bottom blowing converters in 1967 respectively. 197 1 After the technology was introduced into the United States, the lime powder oxygen bottom-blown converter was developed.
2, oxygen top-blown converter steelmaking:
A converter steelmaking method, or LD method, uses pure oxygen to blow molten iron from the top of the converter to form steel; In the United States, it is usually called BOF method, also known as BOP method. This 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 be tilted. 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. Blowing high-pressure pure oxygen (containing more than 99.5% O _ 2O) from the top of the molten pool with an oxygen lance, oxidizing to remove silicon, manganese, carbon and phosphorus from molten iron, and slagging for dephosphorization and desulfurization. The heat generated by the oxidation of various elements heats the liquid metal in the molten pool, making the molten steel reach the current chemical composition and temperature. Mainly used for smelting non-alloy steel and low alloy steel. But alloy steel such as stainless steel can also be smelted by refining.
3, oxygen bottom blowing converter steelmaking:
The invention relates to a converter steelmaking method, which blows oxygen to a molten pool in the furnace through an oxygen nozzle at the bottom of the converter to smelt molten iron into steel. The height and diameter of the furnace are relatively small; The furnace bottom is flat and can be quickly disassembled and replaced; The oxygen lance system of oxygen top-blown converter is replaced by tuyere, distributor system and oxygen supply system on the furnace body. Oxygen bottom-blown converter has the advantages of smooth blowing, less splashing, less smoke and dust, low iron oxide content in slag, and higher metal yield 1% ~ 2% than oxygen top-blown converter. Using powdery slagging materials, because the particles are fine and the specific surface is large, the reaction interface is increased, so slagging is fast, which 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 and finished products (molten steel) are continuously discharged from the other end of the furnace. The idea of continuous steelmaking process appeared as early as19th century. Because of its potential advantages such as small equipment and simple and stable process, many countries have carried out a lot of experiments on various methods for decades, among which the main methods are tank method, spray method and foam method.
5, mixed steelmaking:
A steelmaking method in which one furnace is used for steelmaking, and the other 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 the steelmaking water of open hearth furnace, converter and electric furnace. Mixing can increase the contact area of slag steel, accelerate chemical reaction, deoxidize and desulfurize, and has 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-blown and bottom-blown oxygen converter steelmaking methods, combining their advantages and overcoming their disadvantages, a new steelmaking method is developed, that is, blowing different gases at the bottom of the original top-blown converter to improve the stirring of molten pool. At present, most countries in the world have adopted this steelmaking method and developed various types of combined blowing converter steelmaking technology. Common steelmaking methods-BSC-BAP method with air +N2 or Ar2 as the bottom blowing gas and N2 as the cooling gas developed by British Iron and Steel Company, KMS method with natural protection bottom gun developed by Klokner-Max Metallurgical Plant in Germany, K-BOP method developed by Kawasaki Iron and Steel Company in Japan, which blows oxygen mixed lime powder accounting for 30% of the total oxygen into the molten pool from the bottom, and Nippon Steel Company.
7, top blowing oxygen open hearth steelmaking:
Since the mid-1950s, the steelmaking method of 1 ~ 5 water-cooled oxygen lance was adopted in open hearth production, and oxygen was directly blown 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, electric arc furnace steelmaking:
A steelmaking method for smelting metals and other materials by using the thermal effect of electric arc. Three-phase AC arc furnace for steelmaking is the most common directly heated arc furnace. In the process of steelmaking, because there is no gas in the furnace, oxidation or reduction 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 capacity of each ton of EAF, EAF can be divided into ordinary EAF, high-power EAF and super-high-power EAF. The development of electric arc furnace to high-power and ultra-high-power electric arc furnace aims at shortening smelting time, reducing power consumption, improving productivity and reducing cost. With the emergence of high-power and ultra-high-power electric arc furnaces, electric arc furnaces have become melting furnaces, 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. Set-top box method:
The original text is Sumitomo top-bottom combined 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 to blow low carbon steel, the dephosphorization effect is good and the cost is obviously reduced. The bottom blowing gas used is O2, CO2, N2, etc. On the basis of STB method, STB-P method of top powder spraying was developed, which further improved the dephosphorization performance of high carbon steel.
10, relative humidity method:
Also known as circulating vacuum treatment, it was jointly developed by German Ruhrstahl/Heraeus Company. There are two conduits under the vacuum chamber into which molten steel is injected. After vacuumizing, the molten steel rises to a certain height, then inert gas Ar is blown into the riser to drive the molten steel into the vacuum chamber for vacuum treatment, and then the molten steel flows back to the ladle through another conduit. The vacuum chamber is equipped with an alloy supply system. This method has become the main vacuum of large capacity (> > 80t) molten steel.
1 1、RH—OB:
RH oxygen blowing method is to add oxygen blowing to vacuum cycle degassing (RH) method to raise the temperature. For refining stainless steel, decarburization reaction can be preferentially carried out under reduced pressure. When it is used to refine ordinary steel, the load of converter can be reduced, and aluminum can also be added to increase the temperature.
12, OBM-S method:
The original text is oxygen bottom blowing Maxhutte—Scarp, which is an oxygen bottom blowing converter steelmaking method with natural gas or propane as cooling medium. OBM-S is to install a side-blown oxygen lance on the cover of OBM oxygen bottom-blown converter, and the bottom-blown oxygen lance blows gas and natural gas to preheat the scrap steel, thus achieving the purpose of improving 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 gas (Ar, CO2, N2) is blown from the bottom of the furnace while top blowing, so as to strengthen the stirring of steel slag and control the partial pressure of CO in molten steel. This method uses perforated brick nozzle to smelt low carbon steel, which can reduce the cost. Using it to smelt high carbon steel is beneficial to dephosphorization. This method should be combined with hot metal pretreatment process.
14、MVOD:
The method of adding a water-cooled oxygen gun to the equipment of VAD method to make it blow oxygen under vacuum to decarbonize. Because decarburization under 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:
The original text is ladle furnace, which is a ladle furnace refining method developed by Japan Special Steel Company (Datong Special Steel Company) in 197 1 year. Its equipment and technology are composed of argon stirring, submerged arc heating and alloy supply 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 alloying elements is high. LF furnace has become an indispensable refining equipment between steelmaking furnace and continuous casting machine.
16, converter steelmaking method:
1952, Linz Plant of Austrian Iron and Steel Company and Donowitz Plant of Austrian Alps Mining and Metallurgy Company were the first to successfully develop oxygen top-blown converter steelmaking process in industry, and were named after the initials of these two plants. After this method came out, it quickly spread all over the world. This method is called BOF or BOP method in the United States, which is the abbreviation of alkaline oxygen furnace or process. See oxygen top blowing for details.
17, laser diode OTB method:
The original text is LD-OX Gyen top-bottom process, which is a top-bottom combined blowing converter steelmaking process developed by Ogawa Plant of Kobe Steel Works. It is characterized by the adoption of a special bottom blowing single-ring slit nozzle (SA nozzle), which enables the bottom blower to be controlled in a wide range and blow inert gas 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:
LD-Arbed-Centre National is a top blowing oxygen and lime powder steelmaking method developed by French Iron and Steel Research Institute, which is used to blow high phosphorus hot metal.
20, KS method:
The original steelmaking in Klokner was a bottom-blown oxygen converter steelmaking process, with solid material 100%. The proportion of bottom blowing oxygen is 60% ~ 100%.
2 1, 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, which can replace electricity with coal.
22, FINKL—VAD method:
The arc heating ladle degassing method or vacuum arc degassing method is characterized in that an arc heating device is added to the cover of the vacuum chamber, and argon is used for stirring under vacuum. This method has a stable degassing effect and can be used for desulfurization, decarbonization and adding a large number of alloys. The equipment is mainly composed of vacuum chamber, arc heating system, alloy supply device, vacuum pumping system and hydraulic system.
23, DH method:
Vacuum treatment device developed by hoddle United Metallurgical Company in Dortmund, Germany. A vacuum chamber lined with refractory material (the lower part of which is equipped with a conduit lined with refractory material) is inserted into the ladle, and the vacuum chamber or ladle is periodically lowered and lifted, so that a part of molten steel enters the vacuum chamber and returns to the ladle after treatment. The upper part is equipped with alloying device and vacuum heating and heat preservation device. At present, this equipment has not been built.
24, CLU method:
A method for refining stainless steel. Its principle is the same as that of AOD method, and its purpose is to replace argon with steam. This method was successfully developed by French Creusot-Loire company and Swedish Uddeholm company, and put into production in 1973. After contacting with molten steel, steam is decomposed into H2 and O2. H2 reduces the partial pressure of CO, and 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, casting method:
The original text is sealed argon blowing to adjust the composition, which is an out-of-furnace refining method for fine-tuning the alloy composition under argon sealing. In this method, argon is blown from the bottom of the ladle, slag is discharged, the submerged hood is lowered, argon is blown continuously, and then fine-tuning alloy components are added. Its advantages are accurate composition control and high alloy yield.
26, CAS-OB method:
The original text is sealed argon blowing to adjust the composition, which is an external refining method of adding oxygen lance to casting equipment. In addition to fine-tuning the alloy composition, aluminum can also be added and oxygen can be blown to raise the temperature (chemical thermal method), and the heating rate is 5 ~ 13℃/min. This method can accurately control the temperature of molten steel within 3℃, which is beneficial to continuous casting production.
27.ASEA-SKF method:
Ladle refining method developed in Sweden. It adopts low-frequency electromagnetic stirring, atmospheric arc heating, ladle slagging refining, vacuum degassing at another station, and oxygen lance, which can blow oxygen to reduce pressure and decarbonize. In order to improve the refining effect, argon can also be blown at the bottom of the ladle through porous bricks, and alloy can be added to adjust the composition of molten steel.
28, AOD method:
Argon-oxygen decarbonization is the main refining method for smelting low carbon stainless steel. 1964 was successfully developed by American carbide company, and 1968 was used in actual production. Its metallurgical principle is to dilute CO with Ar to reduce its partial pressure and achieve vacuum effect. So that carbon is removed to a very low level. The furnace body and transmission device of AOD are similar to that of converter. Air holes are placed on the side wall near the furnace bottom, and mixed gas of Ar+O2 is blown into the furnace. The raw material is molten steel in the primary melting furnace. The blowing process is divided into oxidation stage, reduction stage and refining stage. It has become the main production process of stainless steel.
Special metallurgical method
Include electroslag remelting, vacuum metallurgy, plasma metallurgy, electron beam melting, zone melting and other steelmaking methods. If some high-tech or special-purpose steels require ultra-high purity, special metallurgical methods can be used for refining when ordinary steelmaking methods and external refining cannot meet the requirements.
Electroslag remelting (ESR): A refining process in which molten steel is cast or forged into electrodes and then remelted with slag resistance, also known as ESR. Its heat source comes from slag resistance heat. During remelting, the consumable electrode is immersed in the slag, and the current passes through the ionized slag, so that the temperature of the slag is much higher than the melting point of the molten consumable electrode. The consumable electrode inserted into the slag melts to form droplets, which pass through the slag pool by their own weight. The obtain slag is washed and refine, and then enters a metal melting pool under that condition of reduce air pollution. Forming a thin slag skin between the ingot and the crystallizer wall not only slows down the radial cooling, but also improves the surface quality of the finished ingot. With the help of water cooling at the bottom of the mold, it solidifies into a remelted ingot with less axial crystallization tendency and segregation, thus improving the hot working plasticity.
Plasma metallurgy: metallurgical process with plasma as heat source, that is, using plasma gun to convert electric energy into heat energy in directional plasma jet. Plasma jet has the characteristics of stable arc, concentrated heat and extremely high temperature. The working temperature of some plasma guns is as high as 5000 ~ 20000℃. Plasma gun can use inert gas (Ar) and reducing gas (H2) as media to achieve different metallurgical purposes. Plasma furnace can be used for high temperature melting.
Jet metallurgy: in order to accelerate the physical and chemical reaction between liquid metal and materials, powder materials are sent into liquid metal by gas jet to complete metallurgical reaction, also known as powder jet metallurgy. This technology is widely used in hot metal pretreatment and ladle refining to achieve the purpose of desulfurization, deoxidation, composition fine-tuning and inclusion denaturation. This technology has fast reaction speed and high material utilization rate.
Regional melting: a process of refining metals by using the solubility difference of impurity elements in liquid and solid phases proposed by W.G.Pfann in 1952. Its working principle is: assuming that a small piece of metal in a uniform solid metal bar melts into liquid, if this small piece of liquid area moves slowly from left to right, the impurities will be redistributed every time it moves, which is equivalent to driving the impurities to the right. After doing this many times,
Vacuum metallurgy: metallurgical process under the condition of less than 0. 1MPa to ultra-high vacuum [133.3x (< 760 ~10-12) pa], including refining, melting, remelting, refining, forming and heat treatment of metals and alloys. The main purposes are: ① to reduce. (2) reducing the content of gases or volatile impurities dissolved in metals; ③ Promote the chemical reaction with gaseous products; (4) Avoid pollution caused by refractory containers and meet the requirements of high-performance metal materials and new metal materials. With the need of producing new high-performance metal materials such as electrothermal materials, electrical alloys, soft magnetic alloys and high-temperature nickel-based alloys, various vacuum melting methods have been developed, including vacuum resistance melting, vacuum induction melting, vacuum arc remelting, electron beam melting and electroslag remelting.
Vacuum arc melting: the process of remelting metals and alloys by arc heating under vacuum (10-2 ~/kloc-0-1pa), also known as VAR method. The technological process is as follows: using a water-cooled copper crucible as a positive electrode, connecting a molten consumable electrode to a virtual electrode that enters the furnace body through sliding sealing as a negative electrode, and inputting a low-voltage DC current to strike an arc between the electrode and the bottom of the crucible. Metals and alloys are remelted by arc heating. With the melting of consumable electrode, consumable electrode is remelted into remelted ingot with uniform composition, dense structure, high purity and less segregation by controlling the descending speed of electrode. It is not only used to remelt active metals and heat-resistant refractory metals, but also used to remelt high-temperature alloys and special steels with strict requirements.
Vacuum electron beam melting: under high vacuum (133.3x10-4 ~133.3x10-8pa), the material to be melted (as anode) is bombarded by an electron gun, and then it is dropped into a water-cooled copper crystallizer to solidify into ingots. Ingots are continuously extracted by mechanical devices.
Vacuum resistance melting: a melting method that uses the heat generated by current passing through a conductor as a heat source. Generally, indirect heating is adopted, and heat energy is transferred to the materials in the furnace through an electric heater. The atmosphere in the resistance furnace can be inert or protective as required. Vacuum resistance furnace can be designed as melting furnace or heat treatment furnace.
Vacuum induction melting: the process of melting metals and alloys by induction electrothermal effect in vacuum. Select the power frequency according to the charge and capacity. It can be divided into high frequency (> 104 Hz), intermediate frequency (50 ~ 104 Hz) and power frequency (50 or 60Hz). Induction furnaces are divided into two categories: cored (closed tank) and coreless (crucible). The latter has high melting temperature and low electrothermal efficiency, and is suitable for melting special steel and nickel-based alloy. Vacuum induction melting is widely used to produce superalloy, high strength steel and ultra-high strength steel.
Steelmaking process
Slagging: the operation of adjusting slag composition, alkalinity, viscosity and reaction ability in iron and steel production. The purpose is to smelt metal with required composition and temperature through slag-metal reaction. For example, the slagging and oxygen blowing operation of oxygen top-blown converter is to generate slag with sufficient fluidity and alkalinity, so that sulfur and phosphorus can be reduced below the upper limit of planned steel grade, and the amount of splashing and slag overflow during oxygen blowing can be reduced as much as possible.
Slag tapping: Slag tapping or scraping operation in the smelting process according to different smelting conditions and purposes. If the single slag method is used for smelting, the oxidation slag must be scraped off at the end of oxidation; When making reducing slag by double slag method, all original oxide slag must be discharged to prevent phosphorus from flowing back.
Molten pool stirring: providing energy to the molten metal pool to make the molten metal and slag move, so as to improve the kinetic conditions of metallurgical reaction. The stirring of molten pool can be realized by gas, machinery and electromagnetic induction.
Electric furnace bottom blowing: according to the process requirements, N2, Ar, CO2, CO, CH4, O2 and other gases are blown into the furnace molten pool to accelerate melting and promote metallurgical reaction process. Bottom blowing process can shorten smelting time, reduce power consumption, improve dephosphorization and desulfurization operations, increase the amount of residual manganese in steel, improve the yield of metals and alloys, make the composition and temperature of molten steel more uniform, and thus improve the quality of steel.
Melting period: The melting period of steelmaking is mainly open hearth and electric furnace steelmaking. The melting period is called from the start of electrifying the electric arc furnace to the complete melting of the charge, and the melting period is called from the completion of molten iron to the complete melting of the charge in the open hearth furnace. The task of the melting period is to melt and raise the temperature of the burden as soon as possible, and slag is formed during the melting period.
Oxidation stage and decarbonization stage: the oxidation stage of common EAF steelmaking usually refers to the process stage from charge dissolution, sampling analysis to removal of oxide slag. Some people think that it started with blowing oxygen or adding ore to decarburize. The main task of oxidation stage is to oxidize carbon and phosphorus in molten steel. Removing gas and impurities; The molten steel is heated uniformly. Decarburization is an important operation process in the oxidation stage. In order to ensure the purity of steel, decarburization is required to be greater than 0.2%. With the development of external refining technology, oxidation refining of EAF is mostly carried out in ladle or refining furnace.
Refining period: During steelmaking, some elements and compounds harmful to steel quality are selected into gas phase or discharged or floated into slag through chemical reaction, thus being removed from molten steel.
Reduction period: in the steelmaking operation of ordinary high-power electric arc furnace, the period from the end of oxidation to tapping is usually called reduction period. Its main task is to produce reduced slag for diffusion, deoxidation, desulfurization, chemical composition control and temperature regulation. At present, the reduction period has been cancelled for steelmaking operations of high-power and ultra-high-power electric arc furnaces.
Refining outside the furnace: the steelmaking process of moving molten steel in the steelmaking furnace (converter, electric furnace, etc.). ) to another container for refining, also known as secondary metallurgy. Therefore, the steelmaking process is divided into two steps: primary smelting: melting, dephosphorization, decarbonization and main alloying of the burden in the furnace with oxidizing atmosphere. Refining: degassing, deoxidation and desulfurization of molten steel in the container by vacuum, inert gas or reducing atmosphere. Remove inclusions and fine-tune components, etc. The advantages of two-step steelmaking are: improving steel quality, shortening smelting time, simplifying technological process and reducing production cost. There are many kinds of refining outside the furnace, which can be roughly divided into two kinds: atmospheric refining and vacuum refining. According to different treatment methods, it can be divided into ladle treatment type and ladle refining type
Molten steel stirring: the stirring of molten steel during refining outside the furnace. It homogenizes the composition and temperature of molten steel and promotes metallurgical reaction. Most metallurgical reactions are interfacial reactions, and the diffusion speed of reactants and products is the limiting link of these reactions. The metallurgical reaction speed of molten steel at rest is very slow, for example, it takes 30-60 minutes for desulfurization of molten steel at rest in electric furnace; When refining in the furnace, it only takes 3 ~ 5 minutes to desulfurize the stirred molten steel. When molten steel is at rest, inclusions are removed by floating, and the removal speed is slow. When stirring molten steel, the removal rate of inclusions increases exponentially, which is related to the intensity and type of stirring, the characteristics and concentration of inclusions.
Ladle wire feeding: the method of deep desulfurization, calcium treatment and carbon-aluminum fine-tuning of molten steel by feeding deoxidized, desulfurized and fine-tuned powder wrapped in iron sheet, such as Ca-Si powder, or directly feeding aluminum wire and carbon wire. It also has the functions of purifying molten steel and improving the shape of nonmetallic inclusions.
Ladle treatment: short for ladle treatment external refining. Its characteristics are short refining time (about 10 ~ 30 minutes), single refining task, simple process operation and less equipment investment. With degassing, desulfurization, composition control, change the shape of inclusions in molten steel and other devices, such as vacuum cycle degassing (RH, DH), vacuum argon blowing (ladle).
Ladle refining: short for ladle refining outside the furnace. Its characteristics are that the refining time is longer than that of ladle treatment (about 60 ~ 180 minutes), and it has many refining functions, and there is a heating device to compensate the temperature drop of molten steel. Suitable for refining all kinds of high alloy steel and special performance steel (such as ultra-pure steel). Vacuum oxygen blowing decarburization (VOD), vacuum arc heating degassing (VAD), vacuum arc heating degassing (VAD), etc. Similarly, there is argon-oxygen decarbonization (AOD).
Inert gas treatment: inert gas is blown into molten steel, which does not participate in metallurgical reaction, but each small bubble rising in molten steel is equivalent to a "small vacuum chamber" (the partial pressure of H2, N2 and CO in the bubble is close to zero), which has the function of "gas washing". The principle of stainless steel production by out-of-furnace refining method is to apply the balance between carbon, chromium and temperature under different CO partial pressures. Oxygen is added to inert gas for refining and decarbonization.
Pre-alloying: the operation process of adding one or more alloying elements to molten steel to meet the requirements of finished steel composition specification is called alloying. In most cases, deoxidation and alloying are carried out at the same time, and some deoxidants added to steel are consumed in deoxidation and converted into deoxidation products to be discharged; The other part is absorbed by molten steel and plays an alloying role. Before the deoxidation operation is completely completed, the alloying effect of the alloy added at the same time with the deoxidizer is absorbed by molten steel, which is called prealloying.
Composition control: the operation to ensure that the composition of finished steel meets the standard requirements. Composition control runs through every link from batching to tapping, but the key point is to control the composition of alloy elements. For high-quality steel, it is often required to accurately control the composition in a narrow range. Generally, under the premise of not affecting the performance of steel, it is controlled according to the middle and lower limits.
Silicon addition: At the end of blowing, the silicon content in molten steel is extremely low. In order to meet the requirements of various steel grades for silicon content, a certain amount of silicon must be added in the form of alloy. As the consumption part of deoxidizer, it also increases the silicon in molten steel. The amount of silicon added should be accurately calculated and should not exceed the allowable range of steel blowing.
Terminal control: control to make the chemical composition and temperature of metal meet the planned tapping requirements at the end of steelmaking and blowing in oxygen converter. There are two methods for endpoint control: carburizing method and carbon drawing method.
Tapping: tapping operation when the temperature and composition of molten steel meet the specific requirements of steelmaking varieties. When tapping, attention should be paid to prevent slag from flowing into ladle. During tapping, additives for adjusting the temperature, composition and deoxidation of molten steel are added to the ladle or tapping stream.