LF furnace steelmaking method and steel material manufacturing method

Abstract

The present invention relates to the technical field of steelmaking, and discloses an LF furnace steelmaking method and a steel manufacturing method. An LF furnace steelmaking method comprises: after the ladle reaches the LF furnace, power is supplied after slag addition is completed, and after the electrode is stable, iron oxide scale is added into the molten steel so that the instantaneous value of oxygen content on the surface of the molten steel increases by 30 to 50 ppm after the iron oxide addition is completed, so that the slag foams, thereby increasing the slag thickness. The steel manufacturing method comprises the above-mentioned LF furnace steelmaking method. The LF furnace steelmaking method provided in the embodiment of the present application achieves a good submerged arc effect by adding iron oxide to increase the slag thickness, thereby saving electricity and ensuring the quality of steel.

Description

Technical Field

[0001] The present invention relates to the technical field of steelmaking, and in particular to an LF furnace steelmaking method and a steel material manufacturing method. Background Art

[0002] LF furnace, or ladle refining furnace, is the main refining equipment outside the furnace in steel production. LF furnace generally refers to the refining furnace in the steel industry. It is actually a special form of electric arc furnace. In the LF furnace process of steel mills, lime and bauxite are generally added to the steel after the converter is tapped, and lime is added after the LF furnace. In the refining process, lime and fluorite can be appropriately added according to the quality of the buried arc.

[0003] The following problems exist in the steelmaking process of LF furnace: Taking 120 tons of steel made in LF furnace as an example, 1 ton of slag material without foaming is about 9 cm thick, which always leads to poor arc submergence. Generally, 1.6 tons of slag and 14 cm thick slag are required to ensure good arc submergence effect. If more slag material is added to improve the arc submergence effect, the slag material cost will increase; if the amount of slag material added is too small, the slag material thickness will be small, resulting in poor arc submergence, which will slow down the heating speed and lead to high power consumption.

[0004] Another way to increase the slag thickness is to add something containing a foaming agent, such as calcium carbide (calcium carbide), silicon carbide, and aluminum calcium carbon, but these materials have to be purchased from outside and are more expensive.

[0005] In view of this, this application is hereby filed. Summary of the invention

[0006] The object of the present invention is to provide a LF furnace steelmaking method and a steel manufacturing method, aiming to improve at least one of the problems mentioned in the background art.

[0007] The present invention is achieved in that:

[0008] In a first aspect, an embodiment of the present application provides a LF furnace steelmaking method, comprising:

[0009] The ladle reaches the LF furnace, and power is supplied after slag addition is completed. After the electrode is stable, iron oxide scale is added to the molten steel to increase the instantaneous value of oxygen content on the surface of the molten steel by 30 to 50 ppm after the iron oxide is added, causing the slag to foam, thereby increasing the slag thickness.

[0010] In an optional implementation manner, when the steel type to be refined is rebar, the amount of iron oxide scale added is 30 to 50 kg per 120 tons of molten steel.

[0011] In an optional embodiment, power is supplied twice during the entire steelmaking process of the LF furnace. The first power supply is started after the slag is added, and the first sampling is carried out after slag melting, and the second power supply is carried out until leaving the station.

[0012] In an optional embodiment, power is supplied three times throughout the LF furnace steelmaking process. The first power supply starts after slag addition is completed, and the first sampling is carried out after slag melting and the second power supply is carried out. The third power supply is carried out after the second sampling until leaving the station.

[0013] In an optional embodiment, after the first sampling is completed, the chemical composition of the molten steel is adjusted according to the first sampling result. Before adjusting the chemical composition of the molten steel, the argon flow rate is 15-35m 3 / h; when adjusting the chemical composition of molten steel, the argon flow rate is controlled to be 60~100m 3 / h.

[0014] In an optional embodiment, after the chemical composition of the molten steel is adjusted, the temperature is increased to 10-15° C. higher than the outlet temperature, and then deoxidation is performed.

[0015] In an optional embodiment, the deoxidation method is to add 20-30 kg of ferrosilicon powder per 120 tons of molten steel, and the argon flow rate during the deoxidation process is 60-100 m 3 / h.

[0016] In an optional embodiment, secondary sampling is performed after deoxidation is completed. If the secondary sampling results show that the chemical composition of the molten steel matches the target value, the chemical composition of the molten steel will no longer be adjusted. If the secondary sampling results show that the chemical composition of the molten steel deviates from the target value, the chemical composition of the molten steel will be adjusted again.

[0017] In an optional embodiment, a third power transmission is performed, and the time required to heat the molten steel to the outlet temperature is greater than 300 seconds; lime and fluorite are added to the molten steel during the third power transmission process, with the amount of lime added being 80 to 100 kg per 120 tons of molten steel, and the amount of fluorite added being 30 to 40 kg per 120 tons of molten steel.

[0018] In a second aspect, the present invention provides a method for manufacturing steel, comprising the LF furnace steelmaking method according to any one of the aforementioned embodiments.

[0019] The present invention has the following beneficial effects:

[0020] The LF furnace steelmaking method provided in the present application adds iron oxide to the ladle after power supply starts, so that the oxygen content in the molten steel increases by 30 to 50 ppm. On the one hand, it makes the slag foam, increases the slag thickness, improves the arc submergence effect, and increases the heating rate, thereby achieving the effect of saving electricity. On the other hand, since the slag material put into the molten steel has poor heat transfer properties, it takes a certain amount of time for the electrode conduction temperature to reach the molten steel. After the iron oxide is put in, the heat transfer rate is increased to achieve the effect of saving electricity. Therefore, in the LF furnace steelmaking process, the effect of saving electricity can be achieved by adding iron oxide to the molten steel.

[0021] Therefore, the LF furnace steelmaking method provided in the present application can achieve a good submerged arc effect by adding iron oxide to increase the slag thickness under the premise of adding a small amount of slag, thereby saving electricity and ensuring the quality of steel. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0023] The LF furnace steelmaking method and steel manufacturing method provided in the embodiments of the present application are described in detail below.

[0024] The LF furnace steelmaking method provided in the embodiment of the present application comprises:

[0025] The ladle reaches the LF furnace, and power is supplied after slag addition is completed. After the electrode is stable, iron oxide scale is added to the molten steel to increase the instantaneous value of oxygen content on the surface of the molten steel by 30 to 50 ppm after the iron oxide is added, causing the slag to foam, thereby increasing the slag thickness.

[0026] In the LF furnace steelmaking method provided in the embodiment of the present application, iron oxide scale is added into the ladle after power supply starts, so that the oxygen content in the molten steel increases by 30-50ppm, which, on the one hand, makes the slag foam, increases the slag thickness, improves the arc submergence effect, and increases the heating rate, thereby achieving the effect of saving electricity; on the other hand, since the slag material put into the molten steel has poor heat transfer properties, it takes a certain amount of time for the electrode conduction temperature to reach the molten steel, and after the iron oxide is put into the ladle, the heat transfer rate is increased to achieve the effect of saving electricity. Therefore, in the LF furnace steelmaking process, the effect of saving electricity can be achieved by adding iron oxide into the molten steel.

[0027] For steel mills, the most abundant thing is iron oxide scale, which can be found everywhere, whether in steelmaking, refining, continuous casting, water treatment, slag pool, etc. Therefore, if iron oxide scale is to be used inside the steel mill, it only needs to be collected and packaged in bags to ensure that it is dry when used.

[0028] Oxide scale is used for some steel types that have low requirements for oxygen control of molten steel, or steel types that need a certain oxygen content, such as screw mosquito steel, Q195LB wire drawing steel, 1215MS free-cutting steel, etc. Taking screw mosquito steel as an example, the process does not have high requirements for slag-making and arc-burying, as long as the arc can be buried, so the designed slag volume is small, converter slag washing + LF refining furnace = 1 ton, and the phenomenon of poor arc-burying, slow heating, high power consumption, and large electrode loss often occurs. Oxide scale contains oxygen, which can make the slag foam, thereby increasing the slag thickness and improving the arc-burying effect. It can be applied to steel types such as rebar that have low requirements for oxygen control.

[0029] Therefore, the LF furnace steelmaking method provided in the embodiment of the present application can achieve a good arc submergence effect by adding oxidized iron scale to increase the slag thickness under the premise of adding a small amount of slag, thereby saving electricity and ensuring the quality of steel. The oxidized iron scale used does not need to be purchased from outside, and can be found everywhere in the steel plant, and its cost can be almost ignored. Therefore, the LF furnace steelmaking method provided in the present application also has the advantage of low cost.

[0030] Specifically, in the LF furnace steelmaking method provided in the embodiment of the present application, the number of power transmissions can be 1, 2 or 3. Generally speaking, the fewer the number of power transmissions, the more power is saved in theory, but currently due to equipment limitations, it is difficult to achieve the target value of the molten steel temperature at the LF furnace outlet with one power transmission. Therefore, 2 or 3 power transmissions are usually adopted at present.

[0031] The specific plan for two power transmissions is as follows, taking rebar as an example:

[0032] After the converter taps out steel, lime and bauxite are added. After the ladle arrives at the LF furnace, lime is added again to reach the target value of the total slag volume, and then the first power supply is carried out. The power supply wattage is adjusted according to different steel types and refining amounts. Taking Shaoguan Iron and Steel Plant as an example, it is generally adjusted between 4-11 levels;

[0033] During the first power supply process, the argon flow rate into the LF furnace is 15-35m 3 / h(5-15m 3 / h is soft blowing argon, 15-35 is weak blowing argon, 35-45m 3 / h is normal steelmaking argon, 45-60m 3 / h is strong blowing argon, 60-100m 3 In this application, soft blowing argon or weak blowing argon is used to reduce the fluidity of the slag and reduce the arc light from spreading outside the slag. The argon flow rate can be 15m 3 / h、20m 3 / h、25m 3 / h、30m 3 / h or 35m 3 / h.

[0034] After the electrode is stable, add 30-50kg (for example, 30kg, 40kg or 50kg) of scale oxide to the molten steel for every 120 tons of molten steel. After the addition is completed, the instantaneous value of the oxygen content in the upper layer of the molten steel will increase by about 30-50ppm. Generally, aluminum deoxidizer is not added to the screw mosquito steel converter, and alloy deoxidation is entirely relied on. There will be 10-30ppm of oxygen in the LF furnace refining. During the refining process, the oxygen is also maintained at 15-25ppm. The scale oxide is added by hand, and the scale oxide contains oxygen. A bag of 10kg scale oxide can increase oxygen by 10ppm, and 30-50kg scale oxide can increase oxygen by 30-50ppm. Due to the addition of scale oxide, the oxygen content in the molten steel increases, the slag foams, the layer thickness increases, the arc submergence effect is improved, and the heating rate is increased, thereby achieving the effect of saving electricity.

[0035] The present application can reduce the transfer of oxygen from the upper molten steel to the lower molten steel through argon control. The increase in oxygen content is an instantaneous oxygen value measured by the inventor using an oxygen meter after hand-throwing iron oxide scale in practice. The empirical value is that 10 ppm of oxygen can be increased for every 10 kg of iron oxide thrown in. Generally, when hand-throwing iron oxide scale, you can hear the sound of slag foaming. When foaming, it will make a gurgling sound, and when it is not foaming, it will make a sizzling sound of electric current.

[0036] It should be noted that, in the present application, the amount of iron oxide scale added is mainly for rebar. When the method provided in the present application is applied to the refining of other steel grades, the amount of iron oxide scale added will be different depending on the specific steel grade composition.

[0037] As the first power supply continues, the temperature of the molten steel rises, and the lime and other substances added to the molten steel melt. When the melting of the lime and other substances is completed, slagging is completed, and the first sampling is carried out after slagging.

[0038] After the composition of the sample taken for the first time comes out, it needs to be coordinated with the alloy and deoxidized, which will reduce the oxygen content in the slag and prevent the slag from foaming. When the temperature rises later, the submerged arc effect will be relatively poor. Therefore, according to the production rhythm, the first power-on heating time should be as long as possible to reduce the later heating time.

[0039] After the first sampling is completed, the second power supply is carried out. After the first sampling result comes out, the chemical composition of the molten steel is adjusted according to the first sampling result. Before adjusting the chemical composition of the molten steel, the argon flow rate is 15-35m 3 / h(e.g. 15m 3 / h、20m 3 / h、25m 3 / h、30m 3 / h or 35m 3 / h); when adjusting the chemical composition of molten steel, the argon flow rate is controlled to be 60~100m 3 / h(e.g. 60m 3 / h、70m3 / h、80m 3 / h、90m 3 / h or 100m 3 / h).

[0040] It should be noted that before adjusting the chemical composition of molten steel, weak argon blowing of 15 to 35 m 3 / h, which is determined by the size of the bottom blowing of the ladle. For a ladle with good bottom blowing permeability, 15 to 20 m 3 / h argon flow rate; for bottom blowing ladles with poor air permeability, 30-35m 3 / h argon flow rate. The principle of selecting the amount of argon is to choose a reasonable value between the downward heat transfer rate of the molten steel and the oxidation rate of the molten steel by the oxidized slag. When the argon is controlled to a weak blowing state, the reaction interface between the slag and the molten steel is small, and the heat is transferred through the iron oxide in the slag, which achieves the purpose of both heating the molten steel and reducing the oxidation of the molten steel elements. In order to save electricity, the argon control is mainly weak and soft to maintain the foaming of the slag; and in the later stage, in order to achieve better deoxidation of the slag surface, a larger slag gas (argon 60~100m 3 / h), promoting the reaction between ferrosilicon powder and slag surface.

[0041] After the chemical composition of the molten steel is adjusted, the temperature is raised to 10-15°C (e.g. 10°C, 12°C or 15°C) higher than the exit temperature, and then deoxidation is carried out. The deoxidation method is to add 20-30kg (e.g. 20kg, 25kg or 30kg) of ferrosilicon powder per 120 tons of molten steel, and the argon flow rate during the deoxidation process is 60-100m 3 / h(e.g. 60m 3 / h、70m 3 / h、80m 3 / h、90m 3 / h or 100m 3 / h).

[0042] Adding an appropriate amount of ferrosilicon powder to reduce the slag can avoid high oxygen in the slag, which will continue to oxidize the elements in the molten steel, resulting in unstable composition of the molten steel and affecting the quality of the molten steel. If ferrosilicon powder is not added, the manganese oxide and iron oxide in the slag will be relatively high. The slag with oxygen will still oxidize the elements of the molten steel, but at a slower speed. If an oxidation reaction occurs in the continuous casting crystallizer, it will cause the liquid level to fluctuate, and the corresponding ingot cannot be shipped normally. After the alloy is prepared, only a small amount of elements are oxidized into the slag, and the amount of ferrosilicon powder to reduce these elements is certain. Adding too much ferrosilicon powder beyond the required amount will only cause a waste of raw materials and increase costs.

[0043] In order to improve the heating efficiency in the early stage, the oxidation method is used to heat up. In the later stage, ferrosilicon powder and alloy are used to reduce the molten steel, reduce the oxides in the slag, and ensure the quality of the molten steel. Large amounts of argon gas stirring are required to allow the steel-slag to react fully.

[0044] After deoxidation is completed, secondary sampling is carried out. If the secondary sampling results show that the chemical composition of the molten steel matches the target value, the chemical composition of the molten steel will no longer be adjusted. If the secondary sampling results show that the chemical composition of the molten steel deviates from the target value, the chemical composition of the molten steel will be adjusted again.

[0045] If there is no need to adjust the chemical composition again and the temperature of the molten steel after deoxidation just meets the outlet temperature, there is no need to supply power three times; if the chemical composition needs to be adjusted again, the temperature of the molten steel just meets the outlet temperature after adjusting the chemical composition, there is no need to supply power three times.

[0046] The specific scheme of three-way power transmission with rebar is:

[0047] The tertiary power transmission scheme is basically the same as the secondary power transmission scheme, the only difference is:

[0048] If the chemical composition does not need to be adjusted again and the temperature of the molten steel after deoxidation is lower than the outlet temperature, power must be supplied for the third time until the temperature rises to the outlet temperature; if the chemical composition needs to be adjusted again, the temperature of the molten steel after the adjustment is lower than the outlet temperature, power must be supplied for the third time until the temperature rises to the outlet temperature.

[0049] If the time required for the molten steel to reach the outlet temperature after the third power transmission is more than 300 seconds, lime and fluorite are added to the molten steel during the third power transmission process. The amount of lime added is 80-100 kg per 120 tons of molten steel, and the amount of fluorite added is 30-40 kg per 120 tons of molten steel. If the time required for the molten steel to reach the outlet temperature is less than 300 seconds, it is not necessary to add lime and fluorite. The reason is: Take the production of 120 tons of rebar at Shaoguan Iron and Steel Plant as an example. After stirring, there is no foaming in the slag, and the thickness is the same as when no iron oxide scale is added, which is only about 9 cm. There will also be a phenomenon of poor arc submergence. When the power is sent at 4 gears, the temperature can only rise by 5°C per minute. Compared with the 6°C rise per minute before the first sampling, 300 seconds, 5°C less, which means that one more minute of power is sent, and the power consumption in one minute is 180 degrees. Calculated at 0.68 yuan per degree of electricity, the cost is 122 yuan, while 100 kilograms of lime are 40 yuan, and 40 kilograms of fluorite are 72 yuan. The power consumption and the total price of slag are not much different. Therefore, if the temperature rises within 300 seconds in the later stage, no slag can be added.

[0050] The present application also provides a method for manufacturing steel, which includes the LF furnace steelmaking method provided in the present application. Therefore, the method for manufacturing steel has low energy consumption and good economic benefits.

[0051] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0052] Example 1

[0053] This embodiment provides a LF furnace steelmaking method, which is implemented in Shaoguan Iron and Steel Plant with three-time power transmission operation. The LF furnace produces 120 tons of rebar, and the LF furnace outlet temperature is 1560℃±5℃. Specifically:

[0054] After the converter taps out steel, 300kg lime and 500kg bauxite are added. After the ladle arrives at the LF furnace, 200kg lime is added until the total slag volume reaches 1000kg. The temperature of the molten steel at the station is 1525℃, and then the first power supply is carried out. The first power supply is adjusted to level 4, corresponding to an active power of 12500KW.

[0055] After the electrode is stable, add 40 kg of iron oxide scale into the molten steel.

[0056] As the first power supply lasted for 350 seconds, the temperature of the molten steel increased, and after the slag was melted, the first sampling was carried out. The temperature was measured at 1550℃.

[0057] After the first sampling is completed, the second power transmission is carried out. The second power transmission is adjusted to level 4, corresponding to an active power of 12500KW. The first sampling results show that other elements such as carbon, silicon, and manganese are very close to the target range of the composition. According to experience, the operator can adjust the composition of the molten steel to the target value at one time. Therefore, in this embodiment, after the first sampling results come out, the operator adjusts the composition of the molten steel to the target value at one time. Then the temperature is raised for 250 seconds, and the temperature of the molten steel rises to 1575℃, and then 20kg of ferrosilicon powder is added to the molten steel for deoxidation.

[0058] Before adjusting the chemical composition of molten steel, the argon flow rate is controlled to 30m 3 / h, start adjusting the chemical composition of the molten steel and then adjust the argon flow rate to 100m 3 / h. During the process of adjusting the chemical composition, the argon flow rate is 100m 3 / h and stir for 3 minutes to make it uniform. After mixing, adjust the argon gas to 10m 3 / hThe temperature was measured again and the temperature was 1558℃.

[0059] After the adjustment is completed, the third power supply is carried out. The third power supply is adjusted to level 4, corresponding to an active power of 12500KW. The temperature rises to 1565℃ in 70 seconds, and then the ladle leaves the station.

[0060] Compared with the method without adding scale oxide, the method provided in this embodiment adopts 4-speed power transmission, consumes 3 kWh of electricity per second, and the total power transmission time is 350+250=600 seconds. The temperature of molten steel rises by 60°C, and the power consumption is 600*3=1800 kWh. The temperature rises by 6°C per minute. If scale oxide is not added, the temperature rises by 5.5°C per minute, and the power consumption is 60*60 / 5.5=654.5 seconds, and the power consumption is 654.5*3=1963.6 kWh. Compared with the method without adding scale oxide, the power saving is 1963.6-1800=163.6 kWh. Based on the industrial electricity consumption of 1 kWh / yuan, the cost is reduced by 163.6 yuan.

[0061] Note: Because the last 70 seconds were spent on reduction operation, the thickness of the slag layer was the same as that without the addition of iron oxide scale, so the power consumption was the same.

[0062] Example 2

[0063] The operation method of this embodiment is basically the same as that of embodiment 1, except that the argon control of the process is changed. After the first sampling, before adjusting the chemical composition of the molten steel according to the sampling results, the argon flow rate is controlled to 20m 3 / h.

[0064] In this embodiment, the argon gas flow rate is controlled to be 20m 3 / h, the steel and slag transfer speed is relative to 30m 3 / h, it will be slower, and the heat released by the electrode will be sucked away by the dust collector above because it is not transferred downward in time.

[0065] Example 3

[0066] The operation method of this embodiment is basically the same as that of embodiment 1, except that the argon control of the process is changed. After the first sampling, before adjusting the chemical composition of the molten steel according to the sampling results, the argon flow rate is controlled to 45m 3 / h.

[0067] In this embodiment, the argon gas flow rate is controlled to be 45m 3 / h, the argon flow rate is too large. On the one hand, the reaction of the hand-thrown iron oxide scale with the molten steel is accelerated, oxidizing the silicon element in the molten steel, resulting in an increase in the consumption of ferrosilicon alloy when the metal is matched; on the other hand, the iron oxide reacts with the molten steel, and the amount of iron oxide in the slag is reduced, which leads to weakened foaming and further reduced slag thickness.

[0068] Comparative Example 1

[0069] The operation method of this comparative example is basically the same as that of Example 1, except that the weight of the oxidized iron scale thrown in by hand is changed. In this example, 20 kg of oxidized iron scale is thrown in by hand, and the corresponding instantaneous value increase of oxygen content on the surface of the molten steel is about 20 ppm.

[0070] The original 9 cm slag has a low degree of foaming. After foaming, it is only 9.5-11 cm, and the submerged arc effect is poor. Using the 4-level heating efficiency, the temperature rises by about 5.6℃ per minute. The saving is 60*60*3 / 5.6-1800=128.5 kWh of electricity, and the cost is reduced by 128.5 yuan.

[0071] Comparative Example 2

[0072] The operation method of this comparative example is basically the same as that of Example 1, except that the weight of the oxidized iron scale thrown in by hand is changed. In this example, 70 kg of oxidized iron scale is thrown in by hand, and the corresponding instantaneous value increase of oxygen content on the surface of the molten steel is about 70 ppm.

[0073] The slag foaming will be better, and the slag thickness can reach 15 cm. It is beneficial to reduce power consumption, but if the dosage continues to increase, there will be no obvious effect on reducing power consumption, because the heating efficiency of the 4th gear will not exceed 6.5°C at most, so based on the slag thickness of 15 cm, the temperature rises by about 6.3°C per minute, and the power consumption saved is 60*60*3 / 6.3-1800=-85.7 kWh, which is 85.7 yuan more than Example 2. However, due to the increase in oxygen content, the amount of hand-thrown ferrosilicon powder in the later stage needs to be increased by 30kg. The price of ferrosilicon powder is 5,000 yuan / ton, and 30 kg is 150 yuan. Therefore, the increase in the amount of iron oxide scale can reduce power consumption, but the cost of deoxidation in the later stage increases, and the comprehensive cost cannot reach the lowest.

[0074] In summary, the LF furnace steelmaking method provided by the present application adds iron oxide to the ladle after power supply starts, so that the oxygen content in the molten steel increases by 30 to 50 ppm. On the one hand, it makes the slag foam, increases the slag thickness, improves the arc submergence effect, and increases the heating rate, thereby achieving the effect of saving electricity. On the other hand, since the slag put into the molten steel has poor heat transfer properties, it takes a certain amount of time for the electrode conduction temperature to reach the molten steel. After the iron oxide is put in, the heat transfer rate is increased to achieve the effect of saving electricity. Therefore, in the LF furnace steelmaking process, the effect of saving electricity can be achieved by adding iron oxide to the molten steel.

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A LF furnace steelmaking method, characterized in that: Used for refining rebar, including: After the converter is tapped, 300kg of lime and 500kg of bauxite are added for every 120 tons of molten steel. When the ladle reaches the LF furnace, 200kg of lime is added for every 120 tons of molten steel until the total slag amount is 1000kg. After the slag is added, power is supplied. After the electrode is stable, iron oxide scale is added to the molten steel to increase the instantaneous value of oxygen content on the surface of the molten steel by 30-50ppm after the iron oxide is added, so as to cause slag foaming and increase the slag thickness. The dosage of the iron oxide scale is 30-50 kg per 120 tons of molten steel; During the steelmaking process of the LF furnace, power is supplied twice. The first power supply is started after the slag is added, and the first sampling is carried out after the slag is melted, and the second power supply is carried out until the steel leaves the station; or, during the steelmaking process of the LF furnace, power is supplied three times. The first power supply is started after the slag is added, and the first sampling is carried out after the slag is melted, and the second power supply is carried out, and the third power supply is carried out after the second sampling until the steel leaves the station; After the first sampling is completed, the chemical composition of the molten steel is adjusted according to the first sampling result. Before adjusting the chemical composition of the molten steel, the argon flow rate is 15-35m 3 / h; when adjusting the chemical composition of molten steel, the argon flow rate is controlled to be 60~100m 3 / h.

2. The LF furnace steelmaking method according to claim 1, characterized in that: After the chemical composition of the molten steel is adjusted, the temperature is raised to 10 to 15°C higher than the outlet temperature, and then deoxidation is carried out.

3. The LF furnace steelmaking method according to claim 2, characterized in that: The deoxidation method is to add 20-30 kg of ferrosilicon powder to every 120 tons of molten steel, and the argon flow rate during the deoxidation process is 60-100 m 3 / h.

4. The LF furnace steelmaking method according to claim 3, characterized in that: After deoxidation is completed, secondary sampling is carried out. If the secondary sampling results show that the chemical composition of the molten steel matches the target value, the chemical composition of the molten steel will no longer be adjusted. If the secondary sampling results show that the chemical composition of the molten steel deviates from the target value, the chemical composition of the molten steel will be adjusted again.

5. The LF furnace steelmaking method according to claim 1, characterized in that: The third power transmission is carried out, and the time required for the molten steel to be heated to the outlet temperature is greater than 300 seconds; during the third power transmission process, lime and fluorite are added to the molten steel, the amount of lime added is 80-100 kg for every 120 tons of molten steel, and the amount of fluorite added is 30-40 kg for every 120 tons of molten steel.

6. A method for manufacturing steel, characterized in that: The method comprises the LF furnace steelmaking method as described in any one of claims 1 to 5.