A low cost method of smelting an aluminium killed steel

Abstract

The application discloses a low-cost smelting method of aluminum killed steel and relates to the technical field of steel metallurgical manufacturing, and the technical points are as follows: S1, hot metal pretreatment: KR stirring desulfurization, the end-point sulfur content is less than or equal to 0.0030% after the treatment, and there is no scum on the surface of the hot metal; S2, converter smelting: the ratio of scrap steel to hot metal in the converter is 1:4-5, the converter bottom blowing flow is 500-800 m 3 / h, the aluminum-containing alloy and other alloys are sequentially added into the ladle during the converter tapping process, the converter end-point carbon content is 0.03%-0.04%, the converter end-point free oxygen content is 0.05%-0.07%, and the converter end-point sulfur content is less than or equal to 0.0050%; S3, LF refining: the LF refining furnace early-stage bottom blowing flow is 200-300 NL / min; and S4, continuous casting. The application solves the problem of low aluminum metal yield in the whole process of aluminum killed steel by adjusting the aluminum alloy adding process and the LF refining process.

Description

Technical Field

[0001] The present invention relates to the technical field of iron and steel metallurgy manufacturing, and in particular to a low-cost smelting method for aluminum-killed steel. Background Art

[0002] When smelting aluminum-killed steel, aluminum-containing alloys are added to the molten steel during the converter tapping process to deoxidize and alloy it. However, due to aluminum's low melting point, low density, and susceptibility to oxidation at high temperatures, aluminum burns off significantly during the converter tapping process and subsequent refining, resulting in low aluminum yields and high steelmaking costs. Furthermore, increased aluminum burn-off leads to an increase in Al2O3 inclusions, which can cause nodules on the submerged nozzle during the pouring process, further compromising ingot quality.

[0003] Patent CN106811575A discloses a device and method for improving the aluminum yield after the converter furnace. Using dedicated aluminum cake feeding equipment after the converter furnace, aluminum blocks or cakes are directly sunk into the molten steel according to a specific method. This prevents the aluminum blocks from floating up and coming into contact with slag or the atmosphere, which could cause them to burn. This improves the aluminum yield after the converter furnace and reduces production costs. However, this method requires additional equipment and relies on manual hanging of aluminum cakes, which limits its application scenarios, is complex to operate, and has low production efficiency.

[0004] Patent CN113584258A discloses a method for reducing aluminum loss during LF refining. By periodically adding the first and second batches of refining slag, the slag-making process is optimized to control the (CaO%) / (Al2O3%) ratio in the slag, reduce the mass transfer capacity of the oxidizing components in the slag, and weaken the redox reaction at the slag-steel interface, thereby reducing aluminum loss. However, the high-viscosity, high-solids slag produced by this method has poor desulfurization performance and weak inclusion absorption capacity, which weakens the slag's effectiveness. Given the current high cleanliness requirements for steel materials, this method is difficult to meet.

[0005] The existing technology mainly has the following problems: 1. The aluminum alloy addition process is unreasonable, and the recovery rate of metallic aluminum in the converter steelmaking process is low; 2. Slag formation and desulfurization reactions in the LF refining process lead to violent slag-metal reactions and large aluminum losses; 3. In the LF refining process, the ladle bottom blowing intensity is high, resulting in large aluminum losses; 4. The aluminum loss in the entire smelting process is large, resulting in a large number of inclusions and nodules in the continuous casting nozzle.

[0006] In view of this, this patent is applied for. Summary of the Invention

[0007] The purpose of the present invention is to solve the above problems and provide a low-cost smelting method for aluminum-killed steel. By adjusting the aluminum alloy addition process and LF refining process, the problem of low metal aluminum yield in the entire process of aluminum-killed steel is solved.

[0008] In order to achieve the above-mentioned object, the technical invention of the present invention is as follows: a low-cost smelting method of aluminum-killed steel, comprising the following steps:

[0009] S1. Hot metal pretreatment: KR stirring desulfurization, the end point sulfur content is ≤0.0030% after the treatment, and there is no slag on the surface of the hot metal;

[0010] S2. Converter smelting: The ratio of scrap steel to molten iron in the converter is 1:4-5, and the converter bottom blowing flow rate is 500-800m 3 / h, and ensure that no less than 4 bottom blowing holes are working at the same time, and the bottom blowing flow rate of a single hole is ≥125m 3 / h, aluminum alloy and other alloys are added to the ladle in sequence during the converter tapping process, the converter end point carbon content is 0.03%-0.04%, the converter end point free oxygen content is 0.05%-0.07%, and the converter end point sulfur content is ≤0.0050%;

[0011] S3, LF refining: After the ladle is placed, start the ladle bottom blowing with a flow rate of 200-300NL / min. After stirring for 5 minutes, take steel samples and slag samples for testing and temperature measurement. According to the alloy composition of the molten steel, adjust the composition to the target value;

[0012] S4. Continuous casting: The molten steel passes through the tundish, crystallizer and other processes to obtain qualified continuous casting billets.

[0013] The principles of the present invention are as follows: by slag-making in the converter steel-making process, the slag-making task of the LF process is advanced, and by desulfurization in the KR process, the desulfurization task is advanced. On the one hand, the better kinetic conditions of the converter steel-making process are utilized to rapidly slag-make, thereby reducing the loss of metallic aluminum during slag-making in the LF refining process. On the other hand, the loss of metallic aluminum due to the vigorous reaction of slag and gold during the LF refining and desulfurization process is reduced. The sulfur content at the converter end point is controlled to shorten the LF desulfurization time, thereby reducing the loss of aluminum due to the slag-gold reaction in the LF process. The timing of adding aluminum alloy and the ladle bottom blowing flow rate system are controlled to ensure that the aluminum alloy is in full contact with the molten steel and avoid exposure to air. At the same time, the ladle bottom blowing is used to remove oxidizing air in the ladle before the converter steel-making process. At the same time, during the steel-making process, appropriate kinetic conditions are controlled to promote the dissolution of aluminum in the aluminum alloy, thereby improving the yield of metallic aluminum during the converter steel-making process. By synergizing the bottom blowing flow rate control, alloy mixing, and power-on temperature increase during the LF refining process, the exposure time of the molten steel is reduced, the power supply efficiency is improved, the loss of metallic aluminum during the LF refining process is reduced, the number of inclusions is reduced, and the pouring performance of the molten steel is improved.

[0014] Preferably, in S2, after 1 / 18 of the steel has been tapped from the converter, the aluminum-containing alloy begins to be added to the ladle, and when 5 / 6 of the steel has been tapped, the addition of the aluminum-containing alloy is completed.

[0015] More preferably, in S2, the amount of aluminum alloy added per ton of steel is calculated according to the following formula: (free oxygen % at the converter end point*15+0.4) / aluminum content in the aluminum alloy.

[0016] Preferably, in S2, other alloys are added according to the lower limit of the target composition range after the aluminum alloy is initially added.

[0017] Preferably, in S2, lime is added in an amount of 1.5-3.5 kg / t after 1 / 9 of the steel has been tapped from the converter; and after tapping is completed, a slag surface deoxidizer is added in an amount of 1-2 kg / t. The slag surface deoxidizer comprises 30% Al, 15% Al2O3, 20% CaO, 20% CaF2, and the remainder is Fe.

[0018] Preferably, in S2, the ladle bottom blowing flow rate system during the converter tapping process is: 3 minutes before tapping: 500-600NL / min; during tapping: 300-400NL / min; after tapping: 100-200NL / min.

[0019] Preferably, in S3, after 5 minutes of refining treatment, the sulfur content in the molten steel is ≤0.003%, and the aluminum content is 0.05-0.08%.

[0020] More preferably, in S3, 5 minutes after the refining process starts, the steel slag composition is: T.Fe<1%, MnO<1%, Al2O325-35%, CaO 43-53%, SiO2 8-12%, MgO 6-10%.

[0021] Preferably, in S3, according to the temperature of the molten steel, the power is turned on to raise the temperature to the target temperature, and the bottom blowing flow rate is adjusted to 300-400NL / min during the power-on period.

[0022] More preferably, in S3, 0.2-0.3 kg / t of calcium carbide is added every 10 minutes of power supply.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention advances the slagging and desulfurization tasks of the LF process, controls the sulfur content at the converter end point, shortens the time for LF refining slagging and desulfurization, and thus reduces aluminum loss during the LF process.

[0025] 2. The present invention improves the yield of metallic aluminum in the LF refining process by controlling the timing of aluminum addition and the ladle bottom blowing flow rate.

[0026] 3. The present invention reduces the loss of metal aluminum in the entire process, reduces the number of inclusions, and improves the pouring performance of molten steel through the coordination of bottom blowing flow control, alloy mixing and power-on temperature increase during the LF refining process. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the present invention, the technical invention of the present invention will be further described in detail below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0028] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the embodiments.

[0029] Example 1

[0030] The low-cost smelting control method of aluminum-killed steel disclosed in the present invention is applied to low-alloy steel SPHC, the steel container volume is 180t, and its target composition is C: 0.03%-0.05%, Si≤0.03%, Mn: 0.12%-0.20%, Al: 0.02-0.06%, and S≤0.01%.

[0031] The process flow is KR desulfurization → converter smelting → LF refining → continuous pouring.

[0032] S1. Hot metal pretreatment: KR stirring desulfurization, the final sulfur content after treatment is 0.0026%, and there is no slag on the surface of the hot metal.

[0033] S2, converter smelting: converter top and bottom composite blowing, 4 bottom blowing holes working, single hole bottom blowing flow rate is 131m 3 / h、151m 3 / h、128m 3 / h、137m 3 / h. The converter scrap-to-hot metal ratio is 22%, the converter end-point carbon content is 0.035%, the converter end-point free oxygen content is 0.065%, and the converter end-point sulfur content is 0.0048%. The order of alloy addition during the converter tapping process is aluminum-containing alloys, followed by other alloys. After 10 tons of converter steel has been tapped, 253 kg of aluminum granules with a purity of 98% are added to the ladle. The addition of aluminum granules is complete after 150 tons of steel has been tapped. Other alloys are added after the aluminum alloy addition begins, according to the lower limit of the target composition range. After 20 tons of converter steel has been tapped, lime is added at a rate of 1.8 kg per ton of steel. Slag stoppers and slides are used during the converter tapping process, with a slag discharge rate of 1.8 kg per ton. After tapping is complete, a slag surface deoxidizer is added. The deoxidizer contains 30% Al, 15% Al₂O₃, 20% CaO, 20% CaF₂, and Fe as the remaining component. The addition rate is 1.1 kg per ton of steel. The ladle bottom blowing flow rate system during the converter tapping process is: 3 minutes before tapping: 558NL / min; during tapping: 321NL / min; after tapping: 145NL / min.

[0034] S3, LF Refining: After the molten steel is transferred to the ladle refining furnace, bottom blowing is initiated at a rate of 231 NL / min. After stirring for 5 minutes, steel and slag samples are taken and the temperature is measured. The sulfur content of the molten steel is 0.0028%, the aluminum content is 0.077%, and the slag composition is: T.Fe 0.55%, MnO 0.34%, Al2O3 32.2%, CaO 50.1%, SiO2 8.3%, and MgO 6.4%. The composition is adjusted to the target value based on the alloy composition of the molten steel. Based on the molten steel temperature, the power is applied to raise the temperature to the target, while the bottom blowing rate is adjusted to 387 NL / min. Every 10 minutes of power application, 40 kg of calcium carbide is added per ton of steel.

[0035] S4, continuous pouring, the molten steel passes through the tundish, crystallizer and other processes to obtain qualified continuous casting billets.

[0036] The finished product composition is C: 0.043%, Si: 0.017%, Mn: 0.16%, Al: 0.051%, S: 0.0025%.

[0037] The BOF tapping yield is calculated as follows: aluminum addition to the BOF tapping process / aluminum content of the molten steel arriving at the LF station * weight of the molten steel. The overall aluminum yield is calculated as follows: (aluminum addition to the BOF tapping process + aluminum wire feed during refining) / aluminum content of the finished product * weight of the molten steel.

[0038] In this embodiment, the recovery rate of metallic aluminum during the converter tapping process is above 56%, and the recovery rate of metallic aluminum in the entire process is 37%.

[0039] Example 2

[0040] The low-cost smelting control method of aluminum-killed steel disclosed in the present invention is applied to pipeline steel X80, the steel package input is 180t, and the finished product composition is C: 0.040%-0.065%, Si: 0.16%-0.24%, Mn: 1.6%-1.7%, S≤0.004%, Cr: 0.14%~0.18%, Ni: 0.11%-0.16%, Mo: 0.09%-0.13%, Nb: 0.045%-0.055%, Ti: 0.01%-0.02%, and Al: 0.02%-0.05%.

[0041] The process flow is KR desulfurization → converter smelting → LF refining → continuous pouring.

[0042] S1. Hot metal pretreatment: KR stirring desulfurization, the final sulfur content after treatment is 0.0019%, and there is no slag on the surface of the hot metal.

[0043] S2, converter smelting: converter top and bottom composite blowing, 5 bottom blowing holes working, single hole bottom blowing flow rate is 126m 3 / h、135m 3 / h、132m 3 / h、129m 3 / h、127m 3 / h. The ratio of converter scrap to molten iron is 21%, the converter end-point carbon content is 0.038%, the converter end-point free oxygen content is 0.055%, and the converter end-point sulfur content is 0.0031%. The order of alloy addition during the converter tapping process is aluminum-containing alloys, followed by other alloys. After 10 tons of converter steel has been tapped, 232 kg of aluminum cake with a purity of 95% is added to the ladle. When 150 tons of steel has been tapped, the addition of aluminum cake is complete. Other alloys are added according to the lower limit of the target composition range after the aluminum alloy is added. After 20 tons of converter steel has been tapped, lime is added at a rate of 2 kg per ton of steel. Slag plugs and slides are used during the converter tapping process, with a slag discharge rate of 1.8 kg / ton. After tapping is completed, a slag surface deoxidizer is added at a rate of 1.5 kg per ton of steel. The ladle bottom blowing flow rate system during the converter tapping process is: 3 minutes before tapping: 555NL / min; during tapping: 387NL / min; after tapping: 188NL / min.

[0044] S3, LF refining: Upon arrival, bottom blowing was initiated at a rate of 278 NL / min. After stirring for 5 minutes, steel and slag samples were collected and the temperature measured. The molten steel had a sulfur content of 0.0019% and an aluminum content of 0.066%. The slag composition was as follows: T.Fe 0.67%, MnO 0.58%, Al2O3 29.1%, CaO 47.3%, SiO2 9.2%, and MgO 10.1%. The alloy composition of the molten steel was adjusted to the target value. Based on the molten steel temperature, the power was applied to raise the temperature to the target. During this period, the bottom blowing rate was adjusted to 333 NL / min. Every 10 minutes of power application, 37 kg of calcium carbide was added to each ton of steel.

[0045] S4. Continuous pouring: The molten steel passes through the tundish, crystallizer and other processes to obtain qualified continuous casting billets.

[0046] The finished product composition is C: 0.063%, Si: 0.21%, Mn: 1.64%, S: 0.0018%, Cr: 0.16%, Ni: 0.14%, Mo: 0.11%, Nb: 0.049%, Ti: 0.013%, Al: 0.047%.

[0047] In this embodiment, the recovery rate of metallic aluminum during the converter tapping process is 54%, and the recovery rate of metallic aluminum in the entire process is 38%.

[0048] Comparative Example 1

[0049] An aluminum-killed steel with a finished product composition of C: 0.052%, Si: 0.013%, Mn: 0.23%, Al: 0.035%, and S: 0.0085%. The steel package volume is 180 tons, and the general process flow is converter smelting → LF refining → continuous casting.

[0050] Molten iron requirements: The sulfur content of molten iron is 0.0345%.

[0051] Converter smelting: Combined top and bottom blowing is performed in the converter. After converter blowing is completed, aluminum alloys, other alloys, and lime are added sequentially during the tapping process. When the converter tapping volume reaches 1 / 3, 237 kg of aluminum alloy is added to the ladle. Aluminum granules are added before tapping is complete. When the converter tapping volume reaches 1 / 3 ton, lime is added at a rate of 1.5 kg per ton of steel.

[0052] LF refining: After the molten steel was transferred to the ladle refining furnace, bottom blowing was initiated at a rate of 537 NL / min. After stirring for 5 minutes, steel and slag samples were taken and the temperature was measured. The sulfur content of the molten steel was 0.0248%, the aluminum content was 0.019%, and the metallic aluminum yield was 14.7%. The slag contained 5.2% T.Fe and 6.3% MnO, indicating strong oxidizing properties and lacking desulfurization and inclusion absorption capabilities. 456 kg of lime was then added to the ladle, followed by 50 kg of calcium carbide every 3-5 minutes. An appropriate amount of aluminum wire was also added, and the slag was stirred and slag was formed. After 20-25 minutes of adjustment, the slag reached the target slag structure, demonstrating desulfurization and inclusion absorption capabilities. An additional 300 kg of lime was added for desulfurization until the molten steel sulfur content reached the target value. The composition of the molten steel was then adjusted to the target value based on the alloy composition. Based on the molten steel temperature, the slag was heated to the target temperature. Under normal circumstances, the refining time for white slag formation is more than 20 minutes, and the refining time for white slag formation and desulfurization is more than 30 minutes. The aluminum content recovery rate of the whole process is 22.1%.

[0053] S4, continuous pouring, the molten steel passes through the tundish, crystallizer and other processes to obtain qualified continuous casting billets.

[0054] Comparative Example 2

[0055] An aluminum-killed steel with a steel container volume of 180 tons has a finished product composition of C: 0.038%, Si: 0.023%, Mn: 0.21%, Al: 0.032%, and S: 0.0067%. The general process flow is converter smelting → LF refining → continuous casting.

[0056] Molten iron requirements: The sulfur content of molten iron is 0.0223%.

[0057] Converter smelting: Combined blowing at the top and bottom of the converter. After the converter blowing is completed, aluminum alloys, other alloys, lime, etc. are added in sequence during the tapping process. After the converter tapping volume reaches 1 / 3, aluminum alloy is added to the ladle in an amount of 222kg; before the end of tapping, the aluminum particles are added. Other alloys are added according to the lower limit of the target composition range after the addition of aluminum alloy begins. After the converter tapping volume reaches 1 / 3t, lime is added in an amount of 1.8kg per ton of steel. The converter tapping process uses slag plugs and slides to block slag, and the slag discharge amount is ≤3kg / t. The ladle bottom blowing flow rate during the converter tapping process is 600NL / min.

[0058] LF refining: After the molten steel is transferred to the ladle refining furnace, bottom blowing is initiated at a rate of 555 NL / min. After stirring for 5 minutes, steel and slag samples are collected and the temperature is measured. The sulfur content of the molten steel is 0.0173%, the aluminum content is 0.019%, and the metallic aluminum yield is 15.7%. The slag contains 7.1% T.Fe and 8.6% MnO, indicating strong oxidizing properties and lacks the ability to desulfurize or absorb inclusions. 500 kg of lime is then added to the ladle, followed by 50 kg of calcium carbide every 3-5 minutes. The slag is stirred and slag is formed. After 20-25 minutes of adjustment, the slag reaches the target slag structure and possesses the ability to desulfurize and absorb inclusions. An additional 300 kg of lime is added for desulfurization until the sulfur content of the molten steel reaches the target value. The composition of the molten steel is then adjusted to the target value based on the alloy composition of the molten steel. The temperature is then raised to the target temperature based on the molten steel temperature. Under normal circumstances, the refining process takes over 20 minutes to produce white slag, and the refining and desulfurization process takes over 30 minutes. The yield of metallic aluminum in the entire process is 20.9%.

[0059] S4, continuous pouring, the molten steel passes through the tundish, crystallizer and other processes to obtain qualified continuous casting billets.

[0060] Comparative Example 3

[0061] An aluminum-killed steel with a ladle melt of 180t has a finished product composition of C: 0.052%, Si: 0.013%, Mn: 0.23%, Al: 0.037%, and S: 0.0098%. The general process flow is converter smelting → LF refining → continuous pouring.

[0062] Molten iron requirements: The sulfur content of molten iron is 0.0388%.

[0063] Converter smelting: Combined blowing in the converter top and bottom is performed. After converter blowing is completed, aluminum alloys, other alloys, and lime are added sequentially during the tapping process. After the converter tapping volume reaches 1 / 3, aluminum alloys are added to the ladle; aluminum granules are added before tapping is complete. Lime is added after the converter tapping volume reaches 1 / 3 ton, at a rate of 1.5 kg per ton of steel. Slag plugs and slides are used during the converter tapping process, with the amount of slag discharged ≤ 3 kg / ton.

[0064] LF refining: After the molten steel was transferred to the ladle refining furnace, bottom blowing was initiated at a rate of 537 NL / min. After stirring for 5 minutes, steel and slag samples were taken and the temperature was measured. The molten steel contained 0.0277% sulfur, 0.021% aluminum, and a metallic aluminum yield of 16.6%. The slag contained 5.2% T.Fe and 6.3% MnO, indicating strong oxidizing properties and insufficient desulfurization and inclusion absorption capabilities. 456 kg of lime was then added to the ladle, followed by 50 kg of calcium carbide every 3-5 minutes. The slag was stirred and slag was formed. After 20-25 minutes of slag adjustment, the slag reached the target slag structure, demonstrating desulfurization and inclusion absorption capabilities. An additional 300 kg of lime was added for desulfurization until the molten steel sulfur content reached the target value. The composition of the molten steel was then adjusted to the target value based on the alloy composition. The molten steel was heated to the target temperature, with a bottom blowing rate of 600 NL / min. Under normal circumstances, the refining and white slag production time is more than 20 minutes, and the refining and white slag production and desulfurization time is more than 30 minutes. The yield of metallic aluminum in the whole process is 23.3%.

[0065] S4, continuous pouring, the molten steel passes through the tundish, crystallizer and other processes to obtain qualified continuous casting billets.

[0066] Conclusion: It can be seen from Example 1 that the present invention shortens the time for LF refining slag making and desulfurization by advancing the slag making and desulfurization tasks of the LF process and controlling the sulfur content at the converter end point. The metal aluminum yield in the converter tapping process is increased from less than 20% to more than 50%, and the metal aluminum yield in the whole process is increased from less than 20% to 30%. The slag at the refining station is refined to achieve the target slag composition, the slag adjustment time is shortened by more than 15 minutes, the sulfur content at the LF refining station is reduced to meet the target requirements, the bottom blowing time is reduced, and the aluminum loss in the smelting process is further reduced. It can be seen from Example 2 that the present invention improves the metal aluminum yield in the LF refining process by controlling the timing of aluminum addition and the bottom blowing flow rate of the ladle. The metal aluminum yield in the converter tapping process is increased from less than 20% to more than 50%, and the metal aluminum yield in the whole process is increased from less than 25% to more than 35%. Refine the incoming slag to achieve the target slag composition, shorten the slag adjustment time by more than 15 minutes, refine the sulfur content of the incoming slag by LF to meet the target requirements, reduce the bottom blowing time, and further reduce the aluminum loss in the smelting process.

[0067] The above specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make non-creative modifications to the embodiments as needed. However, as long as they are within the scope of the claims of the present invention, they are protected by patent law.

Claims

1. A low-cost smelting method for aluminum-killed steel, characterized in that: The steps include: S1. Hot metal pretreatment: KR stirring desulfurization, the end point sulfur content is ≤0.0030% after the treatment, and there is no slag on the surface of the hot metal; S2. Converter smelting: The ratio of scrap steel to molten iron in the converter is 1:4-5, and the converter bottom blowing flow rate is 500-800m 3 / h, aluminum alloy and other alloys are added to the ladle in sequence during the converter tapping process, the converter end point carbon content is 0.03%-0.04%, the converter end point free oxygen content is 0.05%-0.07%, and the converter end point sulfur content is ≤0.0050%; wherein: The ladle bottom blowing flow rate system during the converter tapping process is: 3 minutes before tapping: 500-600NL / min; during tapping: 300-400NL / min; after tapping: 100-200NL / min; After 1 / 18 of the steel has been tapped from the converter, aluminum alloy is added to the ladle. When 5 / 6 of the steel has been tapped, the addition of aluminum alloy is completed. S3, LF refining: The bottom blowing flow rate of the LF refining furnace in the early stage is 200-300NL / min; S4. Continuous pouring.

2. A low-cost smelting method for aluminum-killed steel according to claim 1, characterized in that: In S2, the amount of aluminum alloy added per ton of steel is calculated according to the following formula: (free oxygen % at the converter end point*15+0.4) / aluminum content in aluminum alloy.

3. A low-cost smelting method for aluminum-killed steel according to claim 1, characterized in that: In S2, other alloys are added according to the lower limit of the target composition range after the aluminum-containing alloy is initially added.

4. A low-cost smelting method for aluminum-killed steel according to claim 1, characterized in that: In S2, after 1 / 9 of the converter has been tapped, lime is added in an amount of 1.5-3.5 kg / t; after tapping is completed, slag surface deoxidizer is added in an amount of 1-2 kg / t.

5. The low-cost smelting method of aluminum-killed steel according to claim 1, characterized in that: In S3, after 5 minutes of refining treatment, the sulfur content in the molten steel is ≤0.003%, and the aluminum content is 0.05-0.08%.

6. A low-cost smelting method for aluminum-killed steel according to claim 1, characterized in that: In S3, 5 minutes after the refining process begins, the slag composition is: T.Fe<1%, MnO<1%, Al2O325-35%, CaO43-53%, SiO28-12%, MgO6-10%.

7. A low-cost smelting method for aluminum-killed steel according to claim 1, characterized in that: In S3, according to the temperature of the molten steel, power is turned on to raise the temperature to the target temperature, and the bottom blowing flow rate is adjusted to 300-400NL / min during the power-on period.

8. A low-cost smelting method for aluminum-killed steel according to claim 7, characterized in that: In S3, 0.2-0.3 kg / t of calcium carbide is added every 10 minutes of power supply.