Ultralow-manganese industrial pure iron and preparation method thereof

Abstract

The invention relates to ultralow-manganese industrial pure iron and a preparation method thereof, and belongs to the technical field of steel smelting. Comprising the following steps: (1) blast furnace smelting; (2) KR desulfurization; (3) smelting in a converter; (4) LF + RH refining; and (5) continuous casting. In the step (1), a central coke adding mode is adopted for blast furnace smelting, coke is added in the center of a blast furnace, and an inverted V-shaped soft melting zone is formed; blast furnace molten iron adopts a low-silicon smelting method; the physical heat of molten iron is not less than 1600 DEG C, and the basicity R2 of slag is controlled to be 1.35; in the step (3), during converter smelting, an oxygen lance nozzle is arranged in a mode that one hole is formed in the center and five holes are formed in the periphery at equal intervals, the center Mach number is 2.06, and the Mach number of the five holes in the periphery is 2.07; in the step (4), high-oxygen demanganization is adopted in LF refining; and deep demanganization is adopted in RH refining. According to the method, the purity of iron in a finished casting blank is 99.94% or above, the content of gas impurity elements (nitrogen and oxygen) is only 4.3 ppm, the total content of other elements is 3.5 ppm, and batch production of ultralow-manganese industrial pure iron smelting is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of steel smelting, and particularly relates to an extra-low manganese industrial pure iron and a preparation method thereof. Background Art

[0002] Industrial pure iron is a special alloy steel with a very low carbon content. It has excellent properties such as low coercivity, good thermal and electromagnetic properties, soft texture, and good toughness. Industrial pure iron is an important raw material for smelting precision alloys, superalloys, extra-low carbon stainless steels, electrothermal alloys, new energy batteries, etc., and is widely used in telecommunications, the electronics industry, measurement, remote control, etc. The process of extra-low manganese pure industrial pure iron has become a very important research and breakthrough problem in the steel industry, reflecting the industrial level and comprehensive strength of a steel enterprise, and is of great significance to scientific research, industry, and engineering. Among them, the content of gas impurity elements (nitrogen and oxygen) in industrial pure iron is only 4.3 ppm, and the total content of the remaining elements is 3.5 ppm.

[0003] Extra-low manganese pure industrial pure iron is a special alloy steel with extremely low impurity content. As a special material required for the development of high-tech industries, it has more excellent corrosion resistance, magnetic and electrical properties than traditional pure iron and iron-based materials, and has broad application prospects in many fields such as aerospace, energy, and new semiconductors. However, in the current production process, industrial pure iron is easily contaminated by impurities, and it is of great significance to achieve continuous batch production of pure industrial pure iron.

[0004] After retrieval, a super-low carbon and extra-low manganese industrial pure iron and a preparation method thereof are disclosed in Chinese Patent CN113774277B. Its components and weight percentage contents are as follows: Its chemical composition and weight percentage contents are: C: ≤0.002%, Mn: ≤0.035%, Si: ≤0.010%, Al: ≤0.020%, P: ≤0.015%, S: ≤0.005%, Nb: ≤0.030%, Ti: ≤0.030%, Cu: ≤0.020%, Cr: ≤0.020%, Mo: ≤0.020%, V: ≤0.030%, N: ≤0.0040%, T[O] ≤0.008%, and the balance is Fe and inevitable inclusions. However, in the pure iron prepared by the above patent, the total content of other elements is still relatively high, and it is impossible to prepare industrial pure iron with higher purity. Summary of the Invention

[0005] Aiming at the problem that industrial pure iron is prone to be contaminated by impurities during production in the existing production of industrial pure iron, the present invention provides an ultra-low manganese industrial pure iron and its preparation method to solve the above problems. The present invention aims to control and reduce elements such as manganese, silicon, carbon, phosphorus, sulfur, and copper. For blast furnace molten iron, a low-silicon smelting method is adopted to ensure a low silicon content under the condition of long-term stable physical heat of the molten iron; the blast furnace burden distribution system is strictly implemented to control various parameters such as the coke ratio of the blast furnace; the KR desulfurization, converter smelting, and LF+RH refining processes are controlled, and finally ultra-low manganese industrial pure iron is obtained to realize the batch production of ultra-low manganese industrial pure iron smelting. The ultra-low manganese pure iron mentioned usually refers to the content of manganese in pure iron w(Mn) ≤ 0.015%.

[0006] The technical solution of the present invention is as follows: In the first aspect, the present invention provides a preparation method of ultra-low manganese industrial pure iron, including the following steps: (1) Blast furnace smelting; (2) KR desulfurization; (3) Converter smelting; (4) LF+RH refining; (5) Continuous casting.

[0007] Among them, in step (1), the blast furnace smelting adopts the method of adding coke in the center. Coke is added in the center of the blast furnace to form an inverted "V"-shaped softening-melting zone, improving the liquid permeability and gas permeability of the hearth; for the blast furnace molten iron, a low-silicon smelting method is adopted to ensure low silicon without low heat under the condition of long-term stable physical heat of the molten iron. For the thermal regime control of the molten iron, the physical heat ≥ 1600 °C, and the slag basicity R2 is controlled according to 1.35 to inhibit the reduction of silicon; In step (3), during converter smelting, a "5+1" hole Laval nozzle is adopted, and the oxygen lance nozzle is arranged in a way that there is 1 hole in the center and 5 equidistant holes around it. The Mach number in the center is 2.06, and the Mach number of the 5 holes around is 2.07; In step (4), high-oxygen de-manganese is adopted in LF refining; deep de-manganese is adopted in RH refining.

[0008] Furthermore, in blast furnace smelting, high-quality iron ore is used, MT (total moisture) ≤ 3.0%, TFe ≥ 65%, P ≤ 0.050%, S ≤ 0.005%, TiO2 ≤ 0.02%, MnO ≤ 0.05%; Coke quality control standard: A d ≤ 12.3%, S t ，d ≤ 0.69%, CSR ≥ 71%, CRI is 20% - 23%, M 40 ≥ 87%, M 10 ≤ 5.4%, average particle size 45 - 50 mm; Sinter quality control standard: TFe ≥ 57.5%, FeO 10.0 - 10.5%, RDI +315 mm ≥ 67%, T ≥ 80%, R2 is controlled at 1.85 - 1.95. Improve the stability rate of the quality of raw fuels.

[0009] Furthermore, in blast furnace smelting, the coke ratio of the blast furnace is 339 kg / t, the coal ratio is 143 kg / t, the fuel ratio is 490 kg / t, the blast volume is 7335 m 3 / min, the oxygen enrichment rate is 3.9%, the blast temperature is 1240 °C, and the w(Mn) of the tapped hot metal is ≤0.023% and w(Si) is ≤0.040%.

[0010] Furthermore, during KR desulfurization, stirring and slag skimming desulfurization are carried out. 3000 kg of desulfurizer is added and stirred for 15 minutes. After desulfurization of the hot metal, w(S) ≤0.002%, and after desulfurization, the slag is skimmed until the bright surface of the hot metal is ≥98%.

[0011] Furthermore, 210 tons of hot metal are charged into the converter. The temperature of the charged hot metal is ≥1350 °C, 40 tons of scrap steel are used, and there are no iron blocks mixed in the scrap steel. All high-quality steel sheet materials without copper elements are used.

[0012] Furthermore, during converter smelting, it is divided into the early stage, the middle stage, and the late stage. Among them, the time in the early stage is 3 minutes; the time in the middle stage is 3 - 10 minutes; the time in the late stage is 10 - 12 minutes.

[0013] Furthermore, in the early stage of converter smelting, the oxygen flow rate is 20000 - 23000 m 3 / h, the bottom blowing flow rate is 240 - 260 m 3 / h, the lance position of the oxygen lance is 2600 mm, 4000 kg of lime, 1500 kg of raw dolomite, and 1200 kg of mill scale are added to ensure that slag is formed as soon as possible in the early stage to accelerate the oxidation reaction. The large impact area of the high lance position oxygen jet enhances the stirring of the molten steel and the slag, and accelerates the oxidation of manganese in the early stage. At the 3rd minute, the lance is lifted to stop smelting, and slag is poured out to remove a large amount of MnO and P2O5 in the slag, ensuring the removal of most of the manganese elements and effective dephosphorization in the molten steel in the early stage.

[0014] Furthermore, in the middle stage of converter smelting, the oxygen flow rate is 47000 - 49000 m 3 / h, the bottom blowing flow rate is 480 - 500 m 3 / h, the lance position of the oxygen lance is 2200 mm, 4000 kg of lime, 1000 kg of raw dolomite, and 800 kg of mill scale are added. The kinetic and thermodynamic conditions of the converter molten bath are sufficient. As the oxidation reaction continues, the molten steel is stirred evenly and the temperature of the molten bath gradually rises, removing manganese, phosphorus, and residual sulfur elements in the molten steel.

[0015] Furthermore, in the late stage of converter smelting, the oxygen flow rate is 53000 - 55000 m 3 / h, the bottom blowing flow rate is 320 - 340 m 3 / h, the lance position of the oxygen lance is 1800 mm, 500 kg of lime, 200 kg of raw dolomite, and 200 kg of mill scale are added. In the later stage of smelting, the bottom blowing flow rate is reduced to carry out a weak stirring mode to prevent manganese elements from returning to the molten steel. At the same time, to prevent the de-manganese rate from decreasing under high-temperature conditions, the converter end temperature is controlled at 1590 - 1620 °C, and the end oxygen activity is 0.080 % - 0.110 %, so as to ensure that w(Mn) ≤ 0.04 %, w(Si) ≤ 0.010 %, w(C) ≤ 0.04 %, w(P) ≤ 0.005 %, w(S) ≤ 0.007 %, w(Cu) ≤ 0.008 % at the end point.

[0016] Further, the high-oxygen de-manganese includes: the transfer and isolation time is 23 minutes, the LF tapping temperature ≥ 1520 °C, 450 kg of flux and 1000 kg of lime are added for the first heating, and the heating time is 7 minutes to ensure the fluidity of the slag. The bottom blowing argon gas flow rate in the ladle is 30 - 80 m 3 / h, and the stirring time is 5 minutes; 500 kg of lime is added for the second heating, the heating time is 5 minutes, and the bottom blowing argon gas flow rate in the ladle is 30 - 80 m 3 / h, and the stirring time is 3 minutes. Utilize the high oxidability characteristics of the converter end molten steel to further remove manganese elements in the LF refining furnace, and w(Mn) ≤ 0.020 % at the LF end point.

[0017] Further, the deep de-manganese includes: the transfer and isolation time is 20 minutes; the set flow rate range of the circulating gas lifting gas in the early stage of deep de-manganese is 80 - 120 m 3 / h, and the set flow rate range of the circulating gas lifting gas in the middle and later stages is 80 - 200 m 3 / h, and the cycle time is 15 minutes. Oxygen blowing is carried out for temperature rise according to an oxygen-aluminum ratio of 1:1.3. After the temperature rise is completed, the vacuum degree is controlled below 0.25 kPa. To make the inclusions float up sufficiently, the time from the end of oxygen blowing to breaking the vacuum is ensured to be more than 10 minutes. w(Mn) ≤ 0.015 % for deep de-manganese, and the tapping temperature is 1580 °C. 200 m of calcium wire is fed, the soft blowing flow rate is 100 L / minute, and the soft blowing time is 8 minutes.

[0018] Further, in step (5), during casting, the tundish starting pouring tonnage ≥ 40 tons, and an argon blowing stopper rod and a double-blowing upper nozzle are used. The argon gas flow rates of the stopper rod and the upper nozzle are controlled according to 4 - 8 L / minute.

[0019] On the second aspect, the present invention provides an ultra-low manganese industrial pure iron prepared by the above method, with the following composition: Mn ≤ 0.015 %, Si ≤ 0.010 %, C ≤ 0.008 %, P ≤ 0.007 %, S ≤ 0.007 %, Cu ≤ 0.008 %, the content of gas impurity elements (nitrogen and oxygen) ≤ 4.3 ppm, the total content of the remaining elements is 3.5 ppm, and Fe ≥ 99.94 %.

[0020] The beneficial effects of the present invention are as follows: In the preparation method of ultra-low manganese industrial pure iron provided by the present invention, during blast furnace smelting, by adopting the blast furnace burden distribution method and the central coke charging method, the gas permeability and liquid permeability of the hearth can be improved, smooth operation can be promoted, which is beneficial to increasing production and saving coke; by controlling blast furnace smelting parameters such as blast furnace coke ratio, coal ratio, and fuel ratio, the furnace temperature stability rate can be greatly improved, so as to reduce the fuel consumption of the blast furnace, and at the same time, the cost of the steelmaking process can also be reduced. KR desulfurization can reduce sulfur elements and improve the purity of molten steel. Controlling the temperature of the hot metal entering the furnace provides reasonable physical heat guarantee for converter smelting; the converter oxygen supply adopts the method of staged oxygen supply, which reduces the overoxidation of molten steel and improves the purity of molten steel. LF refining + RH refining further reduces the manganese content to reach the level of industrial pure iron. The protective casting of the continuous caster can control the content of gas impurity elements (nitrogen and oxygen) ≤ 4.3 ppm. The preparation method of ultra-low manganese industrial pure iron provided by the present invention can achieve an iron purity in the finished casting billet of more than 99.94%, wherein the content of gas impurity elements (nitrogen and oxygen) is only 4.3 ppm, and the total content of the remaining elements is 3.5 ppm, realizing the batch production of ultra-low manganese industrial pure iron smelting. Specific embodiments

[0021] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts shall fall within the protection scope of the present invention.

[0022] Example 1 A preparation method of ultra-low manganese industrial pure iron includes the following steps: (1) Blast furnace smelting The blast furnace burden distribution adopts the central coke charging method, and coke is added to the center of the blast furnace to form an inverted "V" - shaped soft melting zone. The imported high-quality ore is used as the iron ore added, and its standard content is MT (total moisture) ≤ 3.0%, TFe ≥ 65%, P ≤ 0.050%, S ≤ 0.005%, TiO2 ≤ 0.02%, MnO ≤ 0.05%. The quality control standards for the added coke are: A d ≤ 12.3%, S t ，d ≤ 0.69%, CSR ≥ 71%, CRI is 20% - 23%, M 40 ≥ 87%, M 10 ≤ 5.4%, and the average particle size is 45 - 50 mm. The quality control standards for the added sinter ore are: TFe ≥ 57.5%, FeO 10.0% - 10.5%, RDI +315mm ≥ 67%, T ≥ 80%, R2 is controlled at 1.85. Improve the stability rate of the quality of raw fuels.

[0023] The blast furnace hot metal adopts a low-silicon smelting method to ensure low silicon and not low heat under the condition of long-term stable physical heat of the hot metal. For the control of the thermal regime of the hot metal, the physical heat is 1600 °C, the basicity of the slag R2 is controlled according to 1.35 to inhibit the reduction of silicon. The coke ratio of the blast furnace is 339 kg / t, the coal ratio is 143 kg / t, the fuel ratio is 490 kg / t, the blast volume is 7335 m 3 / min, the oxygen enrichment rate is 3.9%, the blast temperature is 1240 °C, and the w(Mn) of the tapped hot metal is 0.023% and w(Si) is 0.040%.

[0024] (2)KR desulfurization The tapped hot metal is subjected to KR stirring and slag skimming for desulfurization. 3000 kg of desulfurizer is added and stirred for 15 minutes. After desulfurization of the hot metal, w(S) is 0.002%, and after desulfurization, the slag is skimmed until 98% of the hot metal surface is bright.

[0025] (3)Converter smelting The hot metal from step (2) is transferred to the converter. The amount of hot metal charged into the furnace is 210 tons, and the temperature of the hot metal charged into the furnace is 1350 °C. 40 tons of scrap steel is used. The scrap steel does not contain iron blocks and all uses high-quality steel sheet materials without copper elements. The converter uses a newly designed "5 + 1" hole Laval nozzle. The oxygen lance nozzle is arranged with 1 hole in the center and 5 holes equidistantly arranged around it. The Mach number in the center is 2.06, and the Mach number of the 5 holes around is 2.07. In the first 3 minutes of the early stage of converter smelting, the oxygen flow rate is 20000 m 3 / h, the bottom blowing flow rate is 240 m 3 / h, the oxygen lance position is 2600 mm. 4000 kg of lime, 1500 kg of calcined dolomite, and 1200 kg of mill scale are added to ensure slag formation as soon as possible in the early stage to accelerate the oxidation reaction. The large impact area of the high lance position oxygen jet enhances the stirring of the molten steel and the slag, accelerating the oxidation of manganese in the early stage. At the 3rd minute, the lance is lifted to stop smelting and slag is poured out to remove a large amount of MnO and P2O5 in the slag, ensuring the removal of most of the manganese elements in the molten steel and effective dephosphorization in the early stage. In the middle stage of converter smelting from 3 to 10 minutes, the oxygen flow rate is 47000 m 3 / h, the bottom blowing flow rate is 480 m 3 / h, the oxygen lance position is 2200 mm. 4000 kg of lime, 1000 kg of calcined dolomite, and 800 kg of mill scale are added. The kinetic and thermodynamic conditions of the converter molten pool are sufficient. As the oxidation reaction continues, the molten steel is stirred evenly and the temperature of the molten pool gradually rises, removing manganese, phosphorus, and residual sulfur elements in the molten steel. In the later stage of converter smelting from 10 to 12 minutes, the oxygen flow rate is 53000 m 3 / h, the bottom blowing flow rate is 320 m 3 / h, the lance position is 1800 mm. Add 500 kg of lime, 200 kg of raw dolomite, and 200 kg of mill scale. In the later stage of smelting, reduce the bottom blowing flow rate to carry out a weak stirring mode to prevent the manganese element from returning to the molten steel. At the same time, to prevent the de-manganese rate from decreasing under high-temperature conditions, control the converter end temperature at 1590 °C and the end oxygen activity at 0.080%, so as to ensure that w(Mn) ≤ 0.04%, w(Si) ≤ 0.010%, w(C) ≤ 0.04%, w(P) ≤ 0.005%, w(S) ≤ 0.007%, w(Cu) ≤ 0.008% at the end.

[0026] (4)LF+RH refining LF refining, high-oxygen de-manganese, the transfer and isolation time is 23 minutes, the LF tapping temperature is 1520 °C. Add 450 kg of flux and 1000 kg of lime for the first heating. The heating time is 7 minutes to ensure the fluidity of the slag. The bottom blowing argon gas flow rate in the ladle is 30 m 3 / h, and the stirring time is 5 minutes; add 500 kg of lime for the second heating, the heating time is 5 minutes, the bottom blowing argon gas flow rate in the ladle is 30 m 3 / h, and the stirring time is 3 minutes. Utilize the high oxidizability of the converter end molten steel to further remove the manganese element in the LF refining furnace. w(Mn) ≤ 0.020% at the LF end.

[0027] RH refining, deep de-manganese, the transfer and isolation time is 20 minutes. For deep de-manganese, the set flow rate of the circulating gas lifting gas in the early stage is 80 m 3 / h, and the set flow rate of the circulating gas lifting gas in the middle and later stages is 80 m 3 / h, and the cycle time is 15 minutes. Blow oxygen to raise the temperature according to an oxygen-aluminum ratio of 1:1.3. After the temperature raising is completed, control the vacuum degree below 0.25 kPa. To make the inclusions float up sufficiently, the time from the end of blowing oxygen to breaking the vacuum is 10 minutes. w(Mn) ≤ 0.015% for deep de-manganese, and the tapping temperature is 1580 °C. Feed 200 m of calcium wire, the soft blowing flow rate is 100 L / minute, and the soft blowing time is 8 minutes.

[0028] (5)Continuous casting The continuous casting machine is protected by casting. The ladle opening weight is 40 tons. Use an argon blowing stopper and a double-blow upper nozzle. The argon gas flow rates of the stopper and the upper nozzle are controlled at 4 L / minute.

[0029] Conduct component detection on the prepared ultra-low manganese industrial pure iron. The specific results are as follows: w(Mn) 0.015%, w(Si) 0.010%, w(C) 0.008%, w(P) 0.007%, w(S) 0.007%, w(Cu) 0.008%. Among them, the content of gas impurity elements (nitrogen and oxygen) is 4.3 ppm, the total content of the remaining elements is 3.5 ppm, and the purity of the industrial pure iron is 99.94422%.

[0030] Example 2 A preparation method of ultra-low manganese industrial pure iron, comprising the following steps: (1) Blast furnace smelting The blast furnace burdening adopts the center-adding coke method, adding coke at the center of the blast furnace to form an inverted "V"-shaped soft melting zone. The imported high-quality ore is used as the iron ore, and its standard content is MT (total moisture) ≤ 3.0%, TFe ≥ 65%, P ≤ 0.050%, S ≤ 0.005%, TiO2 ≤ 0.02%, MnO ≤ 0.05%. The quality control standards for the added coke are: A d ≤ 12.3%, S t ，d ≤ 0.69%, CSR ≥ 71%, CRI is 20% - 23%, M 40 ≥ 87%, M 10 ≤ 5.4%, average particle size 45 - 50 mm. The quality control standards for the added sinter are: TFe ≥ 57.5%, FeO 10.0% - 10.5%, RDI +315 mm ≥ 67%, T ≥ 80%, R2 is controlled at 1.95. Improve the quality stability rate of the raw fuels.

[0031] The blast furnace hot metal adopts the low-silicon smelting method to ensure low silicon without low heat under the long-term stable physical heat of the hot metal. For the control of the hot metal thermal regime, the physical heat is 1610 °C, the slag basicity R2 is controlled according to 1.35 to inhibit the reduction of silicon. The blast furnace coke ratio is 339 kg / t, the coal ratio is 143 kg / t, the fuel ratio is 490 kg / t, the air volume is 7335 m 3 / min, the oxygen enrichment rate is 3.9%, the blast temperature is 1240 °C, and the w(Mn) of the tapped hot metal is 0.019% and w(Si) is 0.035%.

[0032] (2) KR desulfurization Perform KR stirring and slag skimming desulfurization on the tapped hot metal, add 3000 kg of desulfurizer, stir for 15 minutes, and after desulfurization of the hot metal, w(S) is 0.001%, and after desulfurization, skim the slag to 100% of the bright surface of the hot metal.

[0033] (3) Converter smelting Transfer the hot metal in step (2) to the converter. The amount of hot metal charged into the furnace is 210 tons, the temperature of the hot metal charged into the furnace is 1400 °C, and 40 tons of scrap steel are used. There are no iron blocks doped in the scrap steel, and all are high-quality steel sheet materials without copper elements. The converter adopts the designed new type of "5 + 1" hole Laval nozzle, and the oxygen lance nozzle is arranged in a way of 1 hole in the center and 5 equidistant holes around. The Mach number in the center is 2.06, and the Mach number of the 5 holes around is 2.07. In the first 3 minutes of the early stage of converter smelting, the oxygen flow rate is 23000 m 3 / h, and the bottom blowing flow rate is 260 m 3 / h, the lance position is 2,600 mm, 4,000 kg of lime, 1,500 kg of raw dolomite, and 1,200 kg of mill scale are added to ensure slag formation as soon as possible in the early stage to accelerate the oxidation reaction. The oxygen jet at a high lance position has a large impact area, enhancing the stirring of the molten steel and slag, accelerating the oxidation of manganese in the early stage. At the 3rd minute, the lance is lifted to stop smelting, and slag is poured out to remove a large amount of MnO and P2O5 in the slag, ensuring the removal of most manganese elements and effective dephosphorization from the molten steel in the early stage. During the middle stage of converter smelting, from 3 to 10 minutes, the oxygen flow rate is 49,000 m 3 / h, the bottom blowing flow rate is 500 m 3 / h, the lance position is 2,200 mm, 4,000 kg of lime, 1,000 kg of raw dolomite, and 800 kg of mill scale are added. The kinetic and thermodynamic conditions of the converter bath are sufficient. As the oxidation reaction continues, the molten steel is evenly stirred and the bath temperature gradually rises, removing manganese, phosphorus, and residual sulfur elements from the molten steel. During the late stage of converter smelting, from 10 to 12 minutes, the oxygen flow rate is 55,000 m 3 / h, the bottom blowing flow rate is 340 m 3 / h, the lance position is 1,800 mm, 500 kg of lime, 200 kg of raw dolomite, and 200 kg of mill scale are added. In the late stage of smelting, the bottom blowing flow rate is reduced to the weak stirring mode to prevent manganese elements from returning to the molten steel. At the same time, to prevent the reduction of the de-manganese rate under high-temperature conditions, the converter end temperature is controlled at 1,620 °C and the end oxygen activity is 0.110%, so as to ensure that w(Mn)≤0.04%, w(Si)≤0.010%, w(C)≤0.04%, w(P)≤0.005%, w(S)≤0.007%, w(Cu)≤0.008% at the end point.

[0034] (4)LF + RH refining For LF refining, high-oxygen de-manganese, the transfer and separation time is 23 minutes, the LF tapping temperature is 1,530 °C, 450 kg of flux and 1,000 kg of lime are added for the first heating, and the heating time is 7 minutes to ensure the fluidity of the slag. The argon gas flow rate at the bottom of the ladle is 80 m 3 / h, the stirring time is 5 minutes; for the second heating, 500 kg of lime is added, the heating time is 5 minutes, the argon gas flow rate at the bottom of the ladle is 80 m 3 / h, the stirring time is 3 minutes. Utilizing the high oxidizability of the converter end molten steel, manganese elements are further removed in the LF refining furnace, and w(Mn)≤0.020% at the LF end.

[0035] For RH refining, deep de-manganese, the transfer and separation time is 20 minutes. The set flow rate of the circulating gas for lifting in the early stage is 120 m 3 / h, and the set flow rate of the circulating gas for lifting in the middle and late stages is 120 m 3 / h, cycle time is 15 minutes. Oxygen blowing is carried out for heating up according to an oxygen-aluminum ratio of 1:1.3. After the heating-up is completed, the vacuum degree is controlled below 0.25 kpa. To make the inclusions float up sufficiently, the time from the end of oxygen blowing to breaking the vacuum is 12 minutes. For deep de-manganese, w(Mn) ≤ 0.015 %, and the tapping temperature is 1595 °C. 200 m of calcium wire is fed, the soft blowing flow rate is 100 L / minute, and the soft blowing time is 8 minutes.

[0036] (5)Continuous casting For the continuous caster, protective casting is carried out. The ladle tapping tonnage for the tundish start-up is 45 tons. An argon-blowing stopper rod and a double-blowing upper nozzle are used, and the argon gas flow rates of the stopper rod and the upper nozzle are controlled at 8 L / minute.

[0037] The prepared ultra-low manganese industrial pure iron is subjected to composition detection, and the specific results are as follows: w(Mn) 0.013 %, w(Si) 0.008 %, w(C) 0.006 %, w(P) 0.005 %, w(S) 0.005 %, w(Cu) 0.006 %. Among them, the content of gas impurity elements (nitrogen and oxygen) is 4.1 ppm, the total content of the remaining elements is 3.3 ppm, and the purity of the industrial pure iron is 99.95626 %.

[0038] Example 3 A preparation method of ultra-low manganese industrial pure iron includes the following steps: (1)Blast furnace smelting For the blast furnace burden distribution, the center-adding coke method is adopted. Coke is added at the center of the blast furnace to form an inverted "V"-shaped softening-melting zone. The imported high-quality iron ore added has the following standard contents: MT (total moisture) ≤ 3.0 %, TFe ≥ 65 %, P ≤ 0.050 %, S ≤ 0.005 %, TiO2 ≤ 0.02 %, MnO ≤ 0.05 %. The quality control standards for the added coke are: A d ≤ 12.3 %, S t ，d ≤ 0.69 %, CSR ≥ 71 %, CRI is 20 % - 23 %, M 40 ≥ 87 %, M 10 ≤ 5.4 %, average particle size 45 - 50 mm. The quality control standards for the added sinter are: TFe ≥ 57.5 %, FeO 10.0 % - 10.5 %, RDI +315 mm ≥ 67 %, T ≥ 80 %, R2 is controlled at 1.90. Improve the stability rate of the quality of the raw fuels.

[0039] For the blast furnace hot metal, a low-silicon smelting method is adopted to ensure low silicon without low heat under the condition of long-term stable physical heat of the hot metal. For the control of the hot metal thermal regime, the physical heat is 1605 °C, the furnace slag basicity R2 is controlled according to 1.35 to inhibit the reduction of silicon. The blast furnace coke ratio is 339 kg / t, the coal ratio is 143 kg / t, the fuel ratio is 490 kg / t, and the blast volume is 7335 m3 per minute, oxygen enrichment rate 3.9%, blast temperature 1240 °C, and the tapped hot metal has w(Mn) 0.021% and w(Si) 0.038%.

[0040] (2)KR desulfurization The tapped hot metal is subjected to KR stirring and slag skimming for desulfurization. 3000 kg of desulfurizer is added and stirred for 15 minutes. After desulfurization of the hot metal, w(S) is 0.0015%, and after desulfurization, the slag is skimmed until 99% of the hot metal surface is bright.

[0041] (3)Converter smelting The hot metal from step (2) is charged into the converter. The amount of hot metal charged is 210 tons, and the temperature of the charged hot metal is 1380 °C. 40 tons of scrap steel is used, and there are no iron blocks mixed in the scrap steel. All high-quality steel plates without copper element are used. The converter uses a newly designed "5 + 1" hole Laval nozzle. The oxygen lance nozzle is arranged with 1 hole in the center and 5 equally spaced holes around it. The Mach number in the center is 2.06, and the Mach number of the 5 holes around is 2.07. In the first 3 minutes of the early stage of converter smelting, the oxygen flow rate is 21000 m 3 / h, the bottom blowing flow rate is 245 m 3 / h, the oxygen lance position is 2600 mm, 4000 kg of lime, 1500 kg of raw dolomite, and 1200 kg of mill scale are added to ensure slag formation as soon as possible in the early stage to accelerate the oxidation reaction. The large impact area of the high lance position oxygen jet enhances the stirring of the molten steel and slag, accelerating the oxidation of manganese in the early stage. At the 3rd minute, the lance is lifted to stop smelting, and slag is poured out to remove a large amount of MnO and P2O5 in the slag, ensuring the removal of most of the manganese elements and effective dephosphorization in the molten steel in the early stage. In the middle stage of converter smelting from 3 to 10 minutes, the oxygen flow rate is 48000 m 3 / h, the bottom blowing flow rate is 490 m 3 / h, the oxygen lance position is 2200 mm, 4000 kg of lime, 1000 kg of raw dolomite, and 800 kg of mill scale are added. The kinetic and thermodynamic conditions of the converter bath are sufficient. With the continuous progress of the oxidation reaction, the molten steel is stirred evenly and the bath temperature gradually rises, removing manganese, phosphorus, and residual sulfur elements in the molten steel. In the late stage of converter smelting from 10 to 12 minutes, the oxygen flow rate is 54000 m 3 / h, the bottom blowing flow rate is 330 m 3 / h, the oxygen lance position is 1800 mm, 500 kg of lime, 200 kg of raw dolomite, and 200 kg of mill scale are added. In the late stage of smelting, the bottom blowing flow rate is reduced to a weak stirring mode to prevent manganese elements from returning to the molten steel. At the same time, to prevent the reduction of the de-manganese rate under high temperature conditions, the converter end temperature is controlled at 1600 °C and the end oxygen activity is 0.090%, so as to ensure that at the end, w(Mn) ≤ 0.04%, w(Si) ≤ 0.010%, w(C) ≤ 0.04%, w(P) ≤ 0.005%, w(S) ≤ 0.007%, w(Cu) ≤ 0.008%.

[0042] (4)LF + RH refining LF refining, high - oxygen de - manganese, transfer - interval time is 23 minutes, the temperature of LF furnace at charging is 1525 °C. 450 kg of flux and 1000 kg of lime are added for the first heating, and the heating time is 7 minutes to ensure the fluidity of the slag. The flow rate of argon gas blown from the bottom of the ladle is 50 m 3 / h, and the stirring time is 5 minutes; 500 kg of lime is added for the second heating, the heating time is 5 minutes, the flow rate of argon gas blown from the bottom of the ladle is 50 m 3 / h, and the stirring time is 3 minutes. Utilize the high - oxidizing property of the molten steel at the end of the converter to further remove manganese elements in the LF refining furnace, and w(Mn) at the end of LF ≤ 0.020 %.

[0043] RH refining, deep de - manganese, transfer - interval time is 20 minutes. The set flow rate of the circulating gas for lifting in the early stage is 100 m 3 / h, and the set flow rate of the circulating gas for lifting in the middle and late stages is 100 m 3 / h, and the circulation time is 15 minutes. Oxygen is blown for temperature rise according to the oxygen - aluminum ratio of 1:1.3. After the temperature - rising ends, the vacuum degree is controlled below 0.25 kpa. To make the inclusions float up sufficiently, the time from the end of oxygen - blowing to breaking the vacuum is 11 minutes. For deep de - manganese, w(Mn) ≤ 0.015 %, and the tapping temperature is 1580 °C. 200 m of calcium wire is fed, the soft - blowing flow rate is 100 L / minute, and the soft - blowing time is 8 minutes.

[0044] (5)Continuous casting The continuous caster is protected by casting. The ladle - opening tonnage of the tundish is 43 tons. The argon - blowing stopper rod and double - blown upper nozzle are adopted, and the argon gas flow rates of the stopper rod and the upper nozzle are controlled at 6 L / minute.

[0045] The composition of the prepared ultra - low - manganese industrial pure iron is detected, and the specific results are as follows: w(Mn) 0.014 %, w(Si) 0.009 %, w(C) 0.007 %, w(P) 0.006 %, w(S) 0.006 %, w(Cu) 0.007 %. Among them, the content of gas impurity elements (nitrogen and oxygen) is 4.2 ppm, and the total content of the remaining elements is 3.4 ppm. The purity of the industrial pure iron is 99.95024 %.

[0046] Comparative example According to the method disclosed in Patent CN113774277B, ultra - low - manganese industrial pure iron is prepared, including the following steps: (1)KR desulfurization of hot metal: More than two slag - skimming treatments are carried out, and it is required that the residence time between every two slag - skimmings is not less than 8 min; the exposed surface is not less than 90 %; S in the hot metal after desulfurization ≤ 0.001 %; the proportion of hot metal is 86 % - 87 %, and the rest is low - sulfur scrap steel.

[0047] (2) Carry out converter smelting, which is carried out in the following three stages: The first stage: from the start of blowing to 30% of the total smelting duration. In this stage, control the lance height of the oxygen lance at 2.3 - 2.4 m; Add active lime at 14.8 - 18.5 kg / ton of steel and add light burned dolomite at 14.2 - 18.2 kg / ton of steel; control the molten steel temperature at 1320 - 1350 °C at the end of this paragraph; adopt the double slag method and pour the slag once; The second stage: from the end of the first stage to 85% of the total smelting duration. In this stage, control the lance height of the oxygen lance at 2.0 - 2.2 m; add active lime at 18.0 - 21.8 kg / ton of steel; when blowing reaches the end of this stage, control the molten steel temperature at 1520 - 1550 °C and control the C content in the molten steel at 0.4% - 0.6%; The third stage: from the end of the second stage to the blowing end point: in this stage: control the lance height of the oxygen lance at 1.9 - 2.0 m; add pellet ore at 4.0 - 5.0 kg / ton of steel; when blowing reaches the end point, control the molten steel temperature at 1600 - 1620 °C, control the C content in the molten steel at ≤0.035%, and control the free oxygen content in the molten steel at 0.0500% - 0.0800%; carry out tapping, and adopt the double slag blocking mode during tapping and strictly prohibit slag from flowing into the ladle during converter tapping.

[0048] (3) Carry out ladle furnace treatment: add active lime at 2.0 - 3.0 kg / ton of steel in the ladle; control the total treatment time at 30 - 50 min and the total heating time at 15 - 30 min. When the ladle furnace treatment ends: control the free oxygen content in the molten steel at 0.0550% - 0.0850%, control the molten steel temperature at 1620 - 1630 °C, and reduce the Mn content in the molten steel by 0.008% - 0.015%.

[0049] (4) Carry out vacuum furnace decarburization treatment: in this stage: adopt top lance oxygen blowing to reduce the Mn content in the molten steel by 0.005% - 0.010%; control the oxygen blowing amount at 1.0 - 1.8 Nm 3 / ton of steel; control the vacuum pure degassing time not less than 8 min, control the vacuum circulation time at 20 - 28 min, and control the vacuum degree at ≤50 Pa; when the vacuum treatment ends: control the temperature at 1581 - 1591 °C, control the free oxygen content in the molten steel at 0.0010% - 0.0020% after deoxidation with aluminum pellets, control the total oxygen T[O] in the molten steel ≤0.0050%, and C ≤0.0010% after treatment; add 40Al modifying agent at 0.7 - 1.1 kg / ton of steel after the vacuum treatment ends.

[0050] (5) Continuously cast into billets according to the conventional method.

[0051] The composition of the prepared extra-low manganese industrial pure iron was detected, and the specific results are as follows: w(Mn) 0.018%, w(Si) 0.005%, w(C) 0.014%, w(P) 0.010%, w(S) 0.004%, w(Cu) 0.014%. The content of gas impurity elements (nitrogen and oxygen) was 35 ppm, and the purity of the pure industrial pure iron was 99.935%.

[0052] It can be seen from the comparison that the purity of the industrial pure iron prepared in Examples 1 to 3 of the present invention is above 99.94%, which is significantly higher than that of the industrial pure iron prepared in the comparative example. Especially for the content of gas impurities, the total amount of gas impurities in Examples 1 to 3 is below 4.3 ppm, while the nitrogen content in the comparative example is 17 ppm and the oxygen content is 18 ppm; both are higher than the detection values of Examples 1 to 3.

[0053] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, those of ordinary skill in the art can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention. / Any person skilled in the art within the technical scope disclosed by the present invention can easily think of changes or substitutions, which should all be covered by the protection scope of the present invention.

Claims

1. A preparation method of ultra-low manganese industrial pure iron, characterized in that It includes the following steps: (1) Blast furnace smelting; (2) KR desulfurization; (3) Converter smelting; (4) LF+RH refining; (5) Continuous casting; Among them, in step (1), the blast furnace smelting adopts the method of adding coke in the center. Coke is added in the center of the blast furnace to form an inverted "V" - shaped softening - melting zone. The hot metal in the blast furnace adopts the method of low - silicon smelting. The physical heat of the hot metal is ≥1600 °C, and the basicity R2 of the slag is controlled at 1.35; In step (3), during converter smelting, the oxygen lance nozzle is arranged with 1 hole in the center and 5 equidistant holes around it. The Mach number in the center is 2.06, and the Mach number of the 5 holes around is 2.07; In step (4), LF refining adopts high - oxygen de - manganese, and RH refining adopts deep de - manganese.

2. The preparation method of an extra-low manganese industrial pure iron according to claim 1, characterized in that, In blast furnace smelting, high-quality iron ore is used, with MT ≤ 3.0%, TFe ≥ 65%, P ≤ 0.050%, S ≤ 0.005%, TiO2 ≤ 0.02%, and MnO ≤ 0.05%; Coke quality control standards: A d ≤ 12.3%, S t ，d ≤ 0.69%, CSR ≥ 71%, CRI is 20% - 23%, M 40 ≥ 87%, M 10 ≤ 5.4%, average particle size 45 - 50 mm; Sinter quality control standards: TFe ≥ 57.5%, FeO 10.0% - 10.5%, RDI +315 mm ≥ 67%, T ≥ 80%, R2 is controlled at 1.85 - 1.

95.

3. The preparation method of an extra-low manganese industrial pure iron according to claim 1, characterized in that, The coke ratio of the blast furnace is 339 kg / t, the coal ratio is 143 kg / t, the fuel ratio is 490 kg / t, the blast volume is 7335 m 3 / min, the oxygen enrichment rate is 3.9%, the blast temperature is 1240 °C, and the Mn content of the tapped hot metal is ≤0.023% and the Si content is ≤0.040%.

4. The preparation method of an extra-low manganese industrial pure iron according to claim 1, characterized in that, During converter smelting, it is divided into the early stage, the middle stage and the late stage. Among them, the time of the early stage is 3 minutes; the time of the middle stage is 3 - 10 minutes; the time of the late stage is 10 - 12 minutes.

5. The preparation method of an ultra-low manganese industrial pure iron according to claim 4, characterized in that, During the early stage of converter smelting, the oxygen flow rate is 20,000 - 23,000 m 3 / h, the bottom blowing flow rate is 240 - 260 m 3 / h, the lance position of the oxygen lance is 2,600 mm, 4,000 kg of lime, 1,500 kg of raw dolomite, and 1,200 kg of mill scale are added. At the 3rd minute, the lance is lifted to stop smelting and slag is poured out.

6. The preparation method of an extra-low manganese industrial pure iron according to claim 4, characterized in that, During the middle stage of converter smelting, the oxygen flow rate is 47,000 - 49,000 m 3 / h, the bottom blowing flow rate is 480 - 500 m 3 / h, the lance position of the oxygen lance is 2,200 mm, 4,000 kg of lime, 1,000 kg of raw dolomite, and 800 kg of mill scale are added.

7. The preparation method of an extra-low manganese industrial pure iron according to claim 4, characterized in that, During the later stage of converter smelting, the oxygen flow rate is 53000 - 55000 m 3 / h, the bottom blowing flow rate is 320 - 340 m 3 / h, the lance position of the oxygen lance is 1800 mm, 500 kg of lime, 200 kg of raw dolomite, and 200 kg of mill scale are added. The converter end temperature is controlled at 1590 - 1620 °C, and the end oxygen activity is 0.08% - 0.110%. The contents of each component at the converter end are: Mn ≤ 0.04%, Si ≤ 0.010%, C ≤ 0.04%, P ≤ 0.005%, S ≤ 0.007%, Cu ≤ 0.008%.

8. The preparation method of an ultra-low manganese industrial pure iron according to claim 1, characterized in that, High-oxygen de-manganese includes: transfer time of 23 minutes, LF tapping temperature ≥ 1520 °C, adding 450 kg of flux and 1000 kg of lime during the first heating, heating time of 7 minutes to ensure slag fluidity, ladle bottom blowing argon gas flow rate of 30 - 80 m 3 / h, stirring time of 5 minutes; adding 500 kg of lime during the second heating, heating time of 5 minutes, ladle bottom blowing argon gas flow rate of 30 - 80 m 3 / h, stirring time of 3 minutes, further removing manganese element in the LF refining furnace by utilizing the high oxidizability characteristics of the converter end molten steel, and the Mn content at the LF end ≤ 0.020%.

9. The preparation method of an extra-low manganese industrial pure iron as claimed in claim 1, wherein Deep de-manganization includes: residence time of 20 minutes, the set flow rate range of the circulating gas lift gas in the early stage of deep de-manganization is 80 - 120 m 3 / h, and the circulating gas lift gas in the middle and late stages is 80 - 200 m 3 / h, cycle time of 15 minutes; oxygen blowing for temperature increase is carried out according to an oxygen-to-aluminum ratio of 1:1.

3. After the temperature increase ends, the vacuum degree is controlled below 0.25 kpa, and the time from the end of oxygen blowing to breaking the vacuum is ensured to be more than 10 minutes; for deep de-manganization, Mn ≤ 0.015 %, tapping temperature is 1580 °C; 200 m of calcium wire is fed, soft blowing flow rate is 100 L / minute, and soft blowing time is 8 minutes.

10. An ultra-low manganese commercial pure iron obtained by using the preparation method according to any one of claims 1-9, characterized in that, The composition is as follows: Mn≤0.015 %, Si≤0.010 %, C≤0.008 %, P≤0.007 %, S≤0.007 %, Cu≤0.008%, the content of gas impurity elements is ≤4.3 ppm, the total content of the remaining elements is 3.5 ppm, and Fe≥99.94 %.