A smelting method for producing low-phosphorus steel from high-phosphorus molten iron

Abstract

The present invention belongs to the technical field of converter steelmaking, in particular to a smelting method for producing low-phosphorus steel from high-phosphorus molten iron, and belongs to the technical field of metallurgy. The present invention relates to a smelting method for producing low-phosphorus steel from high-phosphorus molten iron, wherein the converter scrap ratio is controlled at 15-25%, and the oxygen supply flow rate is controlled at 4.0-4.5Nm 3 / (min·t). The single slag method is adopted for smelting, and the molten iron is operated with slag. When the silicon content of molten iron is ≥0.25%, the amount of slag carried by molten iron is controlled at 5-10kg per ton of iron, and when the silicon content of molten iron is <0.25%, the amount of slag carried by molten iron is controlled at 10-20kg per ton of iron. The bottom blowing is turned on throughout the smelting process, and the bottom blowing flow rate is appropriately increased during the slag pouring and steel tapping stages. The feeding system and oxygen supply system of the smelting process are controlled synchronously. Finally, the phosphorus content of molten iron is 0.20-0.25%, and the phosphorus content of molten steel is <0.01%. The dephosphorization rate can reach more than 97%.

Description

Technical Field

[0001] The invention belongs to the technical field of converter steelmaking, in particular to a smelting method for producing low-phosphorus steel from high-phosphorus molten iron, and belongs to the technical field of metallurgy. Background Art

[0002] As steel enters an era of micro-profit or even negative profit, various steelmaking companies have strictly controlled the cost of steelmaking. The cost of raw materials such as molten iron and scrap steel accounts for more than 70% of the cost of steelmaking, and iron ore accounts for more than 50% of the cost of molten iron. Using some low-priced high-phosphorus ores instead of expensive high-quality iron ore can significantly reduce the cost of ironmaking, but it will cause the phosphorus content of molten iron to be too high. The phosphorus content of molten iron produced by a company in converter smelting is generally below 0.13%. In order to reduce production costs, high-phosphorus iron ore needs to be used. At that time, the phosphorus content of molten iron will be greater than 0.20%, which poses a great challenge to the steelmaking system. Based on this, it is urgent to develop a smelting process for producing low-phosphorus steel grades with high-phosphorus molten iron at low cost.

[0003] Low-phosphorus steel grades generally require the final phosphorus content of the converter to be controlled within 0.01%. In order to ensure that the final phosphorus content meets the standard and achieve low-phosphorus steelmaking in the converter, there are three common smelting methods: (1) Converter double-linked steelmaking, the final phosphorus content can be stably controlled within 0.006%, but this operation requires two converters, and the dephosphorization furnace requires the use of light and thin scrap steel to ensure the rapid melting of scrap steel under low temperature conditions, and the scrap steel ratio must be controlled within 10%; this process has complex production organization and poor economic efficiency. (2) Converter double-slag steelmaking, double-slag smelting is carried out in the same converter. The advantages of this process are: due to the pouring of phosphorus-rich slag, the dephosphorization efficiency is high, and the final phosphorus content of the converter can basically be stably controlled below 0.01%; Disadvantages: Long smelting cycle and large iron loss during slag pouring. (3) Steelmaking with single slag and large slag volume in converter: in one converter, the smelting conditions of high basicity, large slag volume and low temperature at the converter end point are controlled; advantages: relatively simple operation and relatively fast smelting rhythm; disadvantages: unstable dephosphorization effect. Due to equipment constraints and production needs, a company needs to adopt the single slag method. In view of this situation, it is of great significance to develop a smelting process of high-phosphorus hot metal single slag method and low-cost production of low-phosphorus steel grades. Patent CN 109280731 A "Method for producing converter end point P≤0.01% steel by smelting high-phosphorus hot metal with less slag", adopts single slag method for smelting low silicon and high phosphorus hot metal with silicon content of 0.14-0.26% and phosphorus content of 0.15-0.20%, requires the converter to keep slag as much as possible, when P2O5 in slag is less than 3.5%, the slag amount is controlled at 50-100%, when P2O5 in slag>3.5%, no slag is left; control the feeding system of smelting process (using lime, dolomite and sintered ore to make slag), oxygen supply system (using high-low-high-low gun position, oxygen blowing flow rate is 23800-24000m 3 / h) and bottom blowing system (preliminary 380Nm3 / h, mid-term 230Nm 3 / h, later stage Nm 3 / h); ultimately achieve smelting technology with slag consumption ≤50kg / t, final molten steel phosphorus content ≤0.01%, and dephosphorization rate ≥94%. Patent CN 108624735 B "A method for smelting low-phosphorus steel with low slag consumption based on high-silicon and high-phosphorus molten iron converter" is aimed at high-silicon and high-phosphorus molten iron with silicon content of 0.55-0.8% and phosphorus content of 0.17-0.22%. The single slag method is used for smelting, and the molten iron temperature is required to be greater than 1250℃ and the scrap ratio is greater than 25%. When the single slag method is used for smelting, when the P2O5 in the final slag is greater than 3.8%, no slag is left. When the P2O5 in the slag is 3.0-3.8 %, when the slag volume is greater than 10 tons, half slag retention is adopted, and when the slag volume is less than 8 tons, full slag retention is adopted; lime, dolomite, tailings and sludge balls are used for slag making in the smelting process, the new slag material is less than 70kg / t, the early slag basicity is controlled at 2.0, the terminal slag basicity is controlled at 3.2, and the final slag FeO is controlled at 14-20%; high gun position is used throughout the process to help slag, and the gun is pressed for 30s in the later stage; the early bottom blowing intensity is 0.05Nm 3 / t / min, medium term 0.03Nm 3 / t / min, later 0.05Nm 3 / t / min; finally, the smelting of low-phosphorus steel is realized. Compared with the above two patents, this patent has the following advantages: (1) There is no requirement for the silicon content of molten iron, and molten iron of all conventional silicon contents can be produced (the silicon content of molten iron of a certain company is basically distributed in 0.1-1.0%, with an average of 0.45%). (2) In order to improve the slag removal effect, the two patents both adopt slag retention operation, which has the disadvantages of being affected by the phosphorus pentoxide content in the slag, resulting in the inability to retain slag in the furnace, and excessive slag retention will lead to the deterioration of the slag splashing and furnace protection effect; this patent adopts the method of molten iron with slag to help slag removal. Since the molten iron slag is liquid molten slag, the slag has low alkalinity and high Al2O3, and its own melting point is low. The Al2O3 it carries can produce low-melting-point calcium aluminate with lime, which further helps slag removal. In addition, the phosphorus content in the molten iron slag is extremely low, which will not cause additional input of phosphorus content in the system, and can ensure that each furnace of steel can use molten iron slag to help slag removal. (3) This patent makes clear requirements on the bottom blowing flow rate during converter smelting and slag pouring and steel tapping. In particular, the use of large flow stirring method during slag pouring and steel tapping can further promote the dephosphorization effect and improve the dephosphorization efficiency. The total dephosphorization efficiency reaches more than 97%. Summary of the invention

[0004] The purpose of the present invention is to provide a smelting method for producing low-phosphorus steel from high-phosphorus molten iron, so as to achieve the purpose of producing low-phosphorus steel from high-phosphorus molten iron.

[0005] To achieve the purpose of the present invention, the technical solution adopted is:

[0006] A smelting method for producing low-phosphorus steel from high-phosphorus molten iron comprises the following steps (it should be noted that the following material percentages are all mass percentages):

[0007] (1) The smelting step includes: adding scrap steel and molten iron, controlling the scrap steel ratio of the converter to 15-25%, the phosphorus content in the molten iron to 0.2-0.25%, and controlling the slag content of the molten iron to 5-20 kg per ton of iron when the silicon content of the molten iron is ≥ 0.25%, otherwise controlling the slag content of the molten iron to 10-20 kg per ton of iron; and also includes the steps of oxygen blowing in the converter, slag making, slag pouring, steel tapping, and slag splashing to protect the furnace. The smelting step of the present invention adopts the molten iron slag operation, and controls the feeding system, oxygen supply system, and bottom blowing system of the smelting process to achieve efficient dephosphorization of the converter, as follows:

[0008] In the molten iron slag operation, the slag basicity is 1.0-1.3. More specifically, the composition of the molten iron slag is controlled to be: CaO: 35-40%, SiO2: 30-35%, MgO: 5-10%, Al2O3: 15-20%, P: 0.01%, and the others are inevitable impurities.

[0009] The oxygen supply system is as follows: from the start of blowing to the end of blowing, the oxygen supply is 15%, and the oxygen lance position is controlled at 1.4-1.5m; from blowing 15% to 45%, the oxygen lance position is controlled at 1.5-1.8m; from blowing 45% to 85%, the oxygen lance position is controlled at 1.7-2.0m; from blowing 85% to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m, and the oxygen supply intensity is controlled at 4.0-4.5Nm throughout the smelting process. 3 / t / min.

[0010] The feeding system includes: the basicity of the converter terminal slag is controlled at 3.0-4.5, the MgO content of the slag is controlled at 6.0-10.0%, and the FeO of the slag is controlled at 10.0-20.0%; lime and light-burned dolomite are used for slag making, oxygen blowing is 0-35%, and 50-70% of the slag making material is added at one time; oxygen blowing is 35-80% on the principle of small amounts and multiple batches, and the remaining slag making material is added; ore temperature is used for smelting process, and more than 60% of the total amount of ore is added before oxygen blowing is 35%, and the remaining material is added on the principle of small amounts and multiple batches during the drying period.

[0011] The bottom blowing system includes: the bottom blowing intensity is controlled at 0.03-0.05Nm from the beginning of oxygen blowing to 35% of oxygen blowing. 3 / t / min; During the process of blowing oxygen 35-85%, the bottom blowing intensity is controlled at 0.02-0.03Nm 3 / t / min; During the process of blowing oxygen from 85% to lifting the gun, the bottom blowing intensity is controlled at 0.03~0.05Nm 3 / t / min; the bottom blowing intensity during slag pouring and steel tapping is controlled at 0.05~0.08Nm 3 / t / min.

[0012] Furthermore, the final temperature of the converter is controlled at 1580-1620° C., and the final carbon content is controlled at 0.04-0.10%.

[0013] The technical advantage of the present invention is that for molten iron with a phosphorus content of 0.2 to 0.25%, the single slag method can be used to stably produce low-phosphorus steel with a phosphorus content of ≤0.01%. The present invention designs the corresponding slag amount of molten iron according to the different silicon content of molten iron, and uses liquid molten iron slag to help slag in the converter smelting process. The phosphorus content in the molten iron slag is extremely low, which will not cause additional input of the system's phosphorus content, ensuring that each furnace of steel can use the molten iron slag to help slag. The present invention also makes clear requirements on the bottom blowing flow rate during converter smelting and slag pouring and steel tapping, especially the use of large flow stirring in the slag pouring and steel tapping stage, which can further promote the dephosphorization effect and improve the dephosphorization efficiency, and the dephosphorization efficiency reaches more than 97%. DETAILED DESCRIPTION

[0014] The present invention is further described in detail below in conjunction with embodiments:

[0015] Example 1 (Low Silicon High Phosphorus Hot Metal)

[0016] 120t converter smelts LX72A steel. Raw materials: molten iron 118t, molten iron with slag 1770kg, molten iron temperature 1380℃, molten iron silicon 0.21%, molten iron phosphorus: 0.23%, scrap steel 32t.

[0017] Oxygen supply system: The oxygen supply flow rate during the entire smelting process is 33000Nm 3 / h; from the start of blowing to 15% oxygen supply, the oxygen lance position is controlled at 1.4-1.5m; from 15% to 45% oxygen is blown, the oxygen lance position is controlled at 1.5-1.8m; from 45% to 85% oxygen is blown, the oxygen lance position is controlled at 1.7-2.0m; from 85% oxygen is blown to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m.

[0018] Feeding system: blowing oxygen at 0-35%, adding 2500kg lime and 1300kg light-burned dolomite; blowing oxygen at 35-80%, adding 1700kg lime and 900kg light-burned dolomite in batches; the amount of ore added during the smelting process is 3000kg, of which 2000kg is added in the early stage, and the remaining ore is added in batches during the drying period.

[0019] Bottom blowing system: oxygen blowing 0-35%, bottom blowing flow rate 320Nm 3 / h; oxygen blowing 35-85%, bottom blowing flow rate controlled at 230Nm 3 / h; Blow oxygen 85% to lift the gun, bottom blowing flow rate controlled at 380Nm 3 / h; the bottom blowing intensity during slag pouring and steel tapping is controlled at 480Nm 3 / h.

[0020] The above method is used for smelting. The final converter temperature is 1615℃, the final carbon is 0.052%, the final phosphorus is 0.006%, the dephosphorization rate is 97.4%, the final slag basicity is 3.82, the final slag FeO is 17.2%, and the oxygen supply is 6320Nm 3 , oxygen supply time: 13.2min.

[0021] Example 2 (medium silicon high phosphorus molten iron)

[0022] 120t converter smelts LX72A steel. Raw materials: molten iron 118t, molten iron with slag 950kg, molten iron temperature 1385℃, molten iron silicon 0.52%, molten iron phosphorus: 0.22%, scrap steel 32t.

[0023] Oxygen supply system: The oxygen supply flow rate during the entire smelting process is 33000Nm 3 / h; from the start of blowing to 15% oxygen supply, the oxygen lance position is controlled at 1.4-1.5m; from 15% to 45% oxygen is blown, the oxygen lance position is controlled at 1.5-1.8m; from 45% to 85% oxygen is blown, the oxygen lance position is controlled at 1.7-2.0m; from 85% oxygen is blown to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m.

[0024] Feeding system: blowing oxygen at 0-35%, adding 3900kg lime and 1800kg light-burned dolomite; blowing oxygen at 35-80%, adding 2100kg lime and 1000kg light-burned dolomite in batches; the amount of ore added during the smelting process is 4000kg, of which 2500kg is added in the early stage, and the remaining ore is added in batches during the drying period.

[0025] Bottom blowing system: oxygen blowing 0-35%, bottom blowing flow rate 320Nm 3 / h; oxygen blowing 35-85%, bottom blowing flow rate controlled at 230Nm 3 / h; Blow oxygen 85% to lift the gun, bottom blowing flow rate controlled at 380Nm 3 / h; the bottom blowing intensity during slag pouring and steel tapping is controlled at 480Nm 3 / h.

[0026] The smelting method is as follows: the final converter temperature is 1612℃, the final carbon is 0.055%, the final phosphorus is 0.004%, the dephosphorization rate is 98.2%, the final slag basicity is 3.52, the final slag FeO is 15.2%, and the oxygen supply is 6280Nm 3 , oxygen supply time: 13.1min.

[0027] Example 3 (High silicon and high phosphorus molten iron)

[0028] 120t converter smelts LX72A steel. Raw materials: molten iron 118t, molten iron with slag 720kg, molten iron temperature 1410℃, molten iron silicon 0.85%, molten iron phosphorus: 0.24%, scrap steel 35t.

[0029] Oxygen supply system: The oxygen supply flow rate during the entire smelting process is 33000Nm 3 / h; from the start of blowing to 15% oxygen supply, the oxygen lance position is controlled at 1.4-1.5m; from 15% to 45% oxygen is blown, the oxygen lance position is controlled at 1.5-1.8m; from 45% to 85% oxygen is blown, the oxygen lance position is controlled at 1.7-2.0m; from 85% oxygen is blown to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m.

[0030] Feeding system: blowing oxygen at 0-35%, adding 5000kg lime and 2000kg light-burned dolomite; blowing oxygen at 35-80%, adding 3100kg lime and 1500kg light-burned dolomite in batches; the amount of ore added during the smelting process is 5200kg, of which 3200kg is added in the early stage, and the remaining ore is added in batches during the drying period.

[0031] Bottom blowing system: oxygen blowing 0-35%, bottom blowing flow rate 320Nm 3 / h; oxygen blowing 35-85%, bottom blowing flow rate controlled at 230Nm 3 / h; Blow oxygen 85% to lift the gun, bottom blowing flow rate controlled at 380Nm 3 / h; the bottom blowing intensity during slag pouring and steel tapping is controlled at 480Nm 3 / h.

[0032] Smelting by the above method, the final temperature of the converter is 1618℃, sampling before slag pouring: carbon 0.062%, phosphorus 0.0067%, dephosphorization rate: 97.2%; sampling after slag pouring: carbon 0.058%, phosphorus 0.0051%, dephosphorization rate: 97.9%; final slag basicity 3.27, final slag FeO: 14.7%, oxygen supply: 6410Nm 3 , oxygen supply time: 13.3min. Comparative Example 1 (molten iron without slag operation)

[0033] 120t converter smelts LX72A steel. Raw materials: molten iron 118t, molten iron with slag 0, molten iron temperature 1380℃, molten iron silicon 0.21%, molten iron phosphorus: 0.23%, scrap steel 32t.

[0034] Oxygen supply system: The oxygen supply flow rate during the entire smelting process is 33000Nm 3 / h; from the start of blowing to 15% oxygen supply, the oxygen lance position is controlled at 1.4-1.5m; from 15% to 45% oxygen is blown, the oxygen lance position is controlled at 1.5-1.8m; from 45% to 85% oxygen is blown, the oxygen lance position is controlled at 1.7-2.0m; from 85% oxygen is blown to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m.

[0035] Feeding system: blowing oxygen at 0-35%, adding 2500kg lime and 1300kg light-burned dolomite; blowing oxygen at 35-80%, adding 1700kg lime and 900kg light-burned dolomite in batches; the amount of ore added during the smelting process is 3000kg, of which 2000kg is added in the early stage, and the remaining ore is added in batches during the drying period.

[0036] Bottom blowing system: oxygen blowing 0-35%, bottom blowing flow rate 320Nm 3 / h; oxygen blowing 35-85%, bottom blowing flow rate controlled at 230Nm 3 / h; Blow oxygen 85% to lift the gun, bottom blowing flow rate controlled at 380Nm 3 / h; the bottom blowing intensity during slag pouring and steel tapping is controlled at 480Nm 3 / h.

[0037] The smelting method is as follows: the final converter temperature is 1615°C, the final carbon is 0.050%, the final phosphorus is 0.015%, the dephosphorization rate is 93.5%, the final slag basicity is 4.82, and the final slag FeO is 19.2%. Compared with Example 1, when the final slag basicity and oxidizability are higher, the dephosphorization rate is lower, and there is an obvious difficulty in slagging during the test. After the phosphorus content reaches the standard, the steel is tapped.

[0038] Comparative Example 2 (Compared with Example 1, the amount of slag in the molten iron is too large)

[0039] 120t converter smelts LX72A steel. Raw materials: molten iron 118t, molten iron with slag 3200kg, molten iron temperature 1380℃, molten iron silicon 0.21%, molten iron phosphorus: 0.23%, scrap steel 32t.

[0040] Oxygen supply system: The oxygen supply flow rate during the entire smelting process is 33000Nm 3 / h; from the start of blowing to 15% oxygen supply, the oxygen lance position is controlled at 1.4-1.5m; from 15% to 45% oxygen is blown, the oxygen lance position is controlled at 1.5-1.8m; from 45% to 85% oxygen is blown, the oxygen lance position is controlled at 1.7-2.0m; from 85% oxygen is blown to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m.

[0041] Feeding system: blowing oxygen at 0-35%, adding 2500kg lime and 1300kg light-burned dolomite; blowing oxygen at 35-80%, adding 1700kg lime and 900kg light-burned dolomite in batches; the amount of ore added during the smelting process is 3000kg, of which 2000kg is added in the early stage, and the remaining ore is added in batches during the drying period.

[0042] Bottom blowing system: oxygen blowing 0-35%, bottom blowing flow rate 320Nm 3 / h; oxygen blowing 35-85%, bottom blowing flow rate controlled at 230Nm 3 / h; Blow oxygen 85% to lift the gun, bottom blowing flow rate controlled at 380Nm 3 / h; the bottom blowing intensity during slag pouring and steel tapping is controlled at 480Nm 3 / h.

[0043] The above method is used for smelting. The final converter temperature is 1615℃, the final carbon is 0.052%, the final phosphorus is 0.012%, the dephosphorization rate is 94.8%, the final slag basicity is 3.12, the final slag FeO is 17.2%, and the oxygen supply is 6260Nm 3 , oxygen supply time: 13.1min. Compared with Example 1, when the amount of slag in the molten iron is too large, the slag in the smelting process is thinner, splashing occurs, and the basicity of the slag at the end of the converter is low, and the dephosphorization rate is reduced.

[0044] Comparative Example 3 (molten iron without slag operation, using traditional ore addition to help slag)

[0045] 120t converter smelts LX72A steel. Raw materials: molten iron 118t, molten iron with slag 0, molten iron temperature 1380℃, molten iron silicon 0.21%, molten iron phosphorus: 0.23%, scrap steel 32t.

[0046] Oxygen supply system: The oxygen supply flow rate during the entire smelting process is 33000Nm 3 / h; from the start of blowing to 15% oxygen supply, the oxygen lance position is controlled at 1.4-1.5m; from 15% to 45% oxygen is blown, the oxygen lance position is controlled at 1.5-1.8m; from 45% to 85% oxygen is blown, the oxygen lance position is controlled at 1.7-2.0m; from 85% oxygen is blown to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m.

[0047] Feeding system: blowing oxygen at 0-35%, adding 2500kg lime and 1300kg light-burned dolomite; blowing oxygen at 35-80%, adding 1700kg lime and 900kg light-burned dolomite in batches; the amount of ore added during the smelting process is 6200kg, of which 3900kg is added in the early stage, and the remaining ore is added in batches during the drying period.

[0048] Bottom blowing system: oxygen blowing 0-35%, bottom blowing flow rate 320Nm 3 / h; oxygen blowing 35-85%, bottom blowing flow rate controlled at 230Nm 3 / h; Blow oxygen 85% to lift the gun, bottom blowing flow rate controlled at 380Nm 3 / h; the bottom blowing intensity during slag pouring and steel tapping is controlled at 480Nm 3 / h.

[0049] The above method is used for smelting, and the final converter temperature is 1595°C, the final carbon is 0.040%, the final phosphorus is 0.012%, the dephosphorization rate is 94.8%, the final slag basicity is 4.38, and the final slag FeO is 20.3%. Compared with Example 1, the traditional method of adding ore to help slag formation has serious splashing during the smelting process, and the dephosphorization rate is slightly lower when the final slag basicity and oxidizability are higher and the final temperature is lower.

[0050] Comparative Example 4 (reducing the bottom blowing flow rate during slag pouring and steel tapping stage)

[0051] 120t converter smelts LX72A steel. Raw materials: molten iron 118t, molten iron with slag 720kg, molten iron temperature 1410℃, molten iron silicon 0.85%, molten iron phosphorus: 0.24%, scrap steel 35t.

[0052] Oxygen supply system: The oxygen supply flow rate during the entire smelting process is 33000Nm 3 / h; from the start of blowing to 15% oxygen supply, the oxygen lance position is controlled at 1.4-1.5m; from 15% to 45% oxygen is blown, the oxygen lance position is controlled at 1.5-1.8m; from 45% to 85% oxygen is blown, the oxygen lance position is controlled at 1.7-2.0m; from 85% oxygen is blown to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m.

[0053] Feeding system: blowing oxygen at 0-35%, adding 5000kg lime and 2000kg light-burned dolomite; blowing oxygen at 35-80%, adding 3100kg lime and 1500kg light-burned dolomite in batches; the amount of ore added during the smelting process is 5200kg, of which 3200kg is added in the early stage, and the remaining ore is added in batches during the drying period.

[0054] Bottom blowing system: oxygen blowing 0-35%, bottom blowing flow rate 320Nm 3 / h; oxygen blowing 35-85%, bottom blowing flow rate controlled at 230Nm 3 / h; Blow oxygen 85% to lift the gun, bottom blowing flow rate controlled at 380Nm 3 / h; the bottom blowing intensity during slag pouring and steel tapping is controlled at 120Nm 3 / h (anti-blocking mode).

[0055] The final temperature of the converter was 1617°C, the samples taken before slag pouring showed carbon 0.063%, phosphorus 0.0073%, and dephosphorization rate 97.0%, the samples taken after slag pouring showed carbon 0.062%, phosphorus 0.0071%, and dephosphorization rate 97.1%, the final slag basicity was 3.31, and the final slag FeO was 14.9%. In the slag pouring and steel tapping stage, the bottom blowing flow rate was reduced, and the dephosphorization amount was reduced by 0.0014% compared with Example 3.

[0056] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical solutions and concepts of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A smelting method for producing low-phosphorus steel from high-phosphorus molten iron, characterized in that: The steps include: (1) a smelting step, comprising: adding scrap steel and molten iron, controlling the scrap steel ratio of the converter to 15-25%, the phosphorus content in the molten iron to 0.2-0.25%, and controlling the slag content of the molten iron to 5-20 kg per ton of iron when the silicon content of the molten iron is ≥ 0.25%, otherwise controlling the slag content of the molten iron to 10-20 kg per ton of iron, and the slag basicity to 1.0-1.3; and also comprising the steps of oxygen blowing in the converter, slag making, slag pouring, steel tapping, and slag splashing to protect the furnace, while controlling the feeding system, oxygen supply system, and bottom blowing system of the smelting process to perform dephosphorization; The oxygen supply system is as follows: from the start of blowing to the end of blowing, the oxygen supply is 15%, and the oxygen lance position is controlled at 1.4-1.5m; from blowing 15% to 45%, the oxygen lance position is controlled at 1.5-1.8m; from blowing 45% to 85%, the oxygen lance position is controlled at 1.7-2.0m; from blowing 85% to the end of blowing, the oxygen lance position is controlled at 1.2-1.5m, and the oxygen supply intensity is controlled at 4.0-4.5Nm throughout the smelting process. 3 / t / min; The feeding system includes: during the smelting process, the basicity of the converter terminal slag is controlled at 3.0-4.5, the MgO content of the slag is controlled at 6.0-10.0%, and the FeO of the slag is controlled at 10.0-20.0%; lime and light-burned dolomite are used for slag making, oxygen is blown at 0-35%, and 50-70% of the slag making material is added at one time; oxygen is blown at 35-80% in small quantities and multiple batches, and the remaining slag making material is added; ore temperature is used in the smelting process, and more than 60% of the total amount of ore is added before oxygen is blown at 35%, and the remaining material is added in small quantities and multiple batches during the drying period; The bottom blowing system includes: the bottom blowing intensity is controlled at 0.03-0.05Nm from the beginning of oxygen blowing to 35% of oxygen blowing. 3 / t / min; During the process of blowing oxygen 35-85%, the bottom blowing intensity is controlled at 0.02-0.03Nm 3 / t / min; During the process of blowing oxygen from 85% to lifting the gun, the bottom blowing intensity is controlled at 0.03~0.05Nm 3 / t / min; the bottom blowing intensity during slag pouring and steel tapping is controlled at 0.05~0.08Nm 3 / t / min.

2. The smelting method for producing low-phosphorus steel from high-phosphorus molten iron according to claim 1, characterized in that: The composition of molten iron slag is controlled as follows: CaO: 35-40%, SiO2: 30-35%, MgO: 5-10%, Al2O3: 15-20%, P: 0.01%, and the others are unavoidable impurities.

3. The smelting method for producing low-phosphorus steel from high-phosphorus molten iron according to claim 1, characterized in that: The final temperature of the converter is controlled at 1580-1620°C, and the final carbon content is controlled at 0.04-0.10%.