High-carbon ferromanganese and a method for producing the same

Abstract

This invention relates to the field of ferroalloy smelting technology and discloses a high-carbon ferromanganese and its preparation method, comprising the following steps: raw material pretreatment; converter preheating and bottom material laying: pretreated high-grade manganese ore, lime, and coke powder are mixed and added as bottom material to the CLU converter for preheating; iron addition and initial reduction: high-carbon ferromanganese is added to the converter, and graphite fragments are added, and initial reduction is carried out under a pure argon atmosphere; atmosphere control and second-stage reduction: when the carbon content of the molten iron drops to 5.0-5.8%, the reblowing gas is switched to a mixed gas of argon, CO, and CH4, and the remaining high-grade manganese ore, silicon carbide, ferrosilicon manganese alloy, and supplementary coke powder are added in batches, while adjusting the slag composition; endpoint judgment and iron tapping. The high-carbon ferromanganese of this invention has precise composition and high purity, and the preparation method is characterized by high efficiency, low consumption, greenness, and high manganese recovery rate, enabling the industrial-scale production of high-carbon ferromanganese.

Description

Technical Field

[0001] This invention relates to the field of ferroalloy smelting technology, specifically to a high-carbon ferromanganese and its preparation method. Background Technology

[0002] High-carbon ferromanganese, an indispensable core alloy raw material in the steel industry, is widely used in steel smelting as a deoxidizer and alloying additive, effectively improving the strength, hardness, and wear resistance of steel. Currently, the production of high-carbon ferromanganese mainly employs the electric furnace method and the converter method. The electric furnace method uses manganese ore and coke as raw materials, carrying out reduction smelting in an electric arc furnace. Although the process is mature, it suffers from high energy consumption, long smelting cycles, and large fluctuations in carbon content, making it difficult to meet the stringent requirements of modern high-end steel smelting for the stability of alloy raw material composition. While the converter method improves production efficiency to some extent, the thermodynamic competition between carbon oxidation and manganese reduction during smelting leads to incomplete slag-metal reaction, increasing chemical and mechanical manganese loss in the slag, reducing the overall manganese recovery rate, and exacerbating emissions of carbon dioxide and other gases during the blowing process, impacting environmental benefits. Therefore, avoiding these phenomena is key to solving the problem. For example, the invention patent with announcement number CN111304437B discloses a method for preparing high-carbon ferromanganese using high-manganese slag. The method is simple and easy to control, and the high-carbon ferromanganese obtained meets the national standard requirements. However, the manganese recovery rate is not high, which leads to an increase in the loss of manganese in the slag. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high-carbon ferromanganese and its preparation method. The high-carbon ferromanganese of the present invention has accurate composition and high purity, and the preparation method has the characteristics of high efficiency, low consumption, greenness and high manganese recovery rate, which can realize the industrial production of high-carbon ferromanganese.

[0004] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing high-carbon ferromanganese, comprising the following steps: (1) Raw material pretreatment; (2) Converter preheating and bottom material laying: The pretreated high-grade manganese ore, lime and coke powder are mixed and added to the CLU converter as bottom material for preheating; (3) Adding iron and initial reduction: Add high-carbon manganese molten iron to the converter and add graphite fragments, and carry out initial reduction under a pure argon atmosphere; (4) Atmosphere control and second-stage reduction: When the carbon content of molten iron drops to 5.0-5.8%, the re-blowing gas is switched to a mixture of argon, CO and CH4. The remaining high-grade manganese ore, silicon carbide, silicomanganese alloy and supplementary coke powder are added in batches. Magnesium oxide powder and alumina powder are added simultaneously to adjust the slag composition. (5) Endpoint judgment and tapping: When the carbon content of the molten iron reaches 6.0-8.0% and the manganese content reaches 65-82%, tap the iron.

[0005] Further, in step (1), the specific steps of raw material pretreatment are as follows: high-grade manganese ore is crushed to a particle size of 3-5mm, and silicon manganese alloy is crushed to a particle size of 2-3mm. Then, together with graphite powder, silicon carbide and lime, they are dried at 110-150℃ for 4-6 hours. After drying, they are stored in different moisture-proof warehouses. Coke powder, magnesium oxide powder and alumina powder are also stored in different moisture-proof warehouses for later use.

[0006] Further, in step (2), the specific steps of converter preheating and bottom material laying are as follows: the pretreated high-grade manganese ore, lime and coke powder are mixed evenly and added to the CLU converter as bottom material, and gas is introduced to preheat to 950-1050℃ for 2-2.5h.

[0007] Furthermore, the high-grade manganese ore, lime, and coke powder are present in a mass ratio of 4.5-5.5:1.8-2.2:2.8-3.2.

[0008] In the above steps, a high-temperature, porous initial reaction bed with preliminary alkalinity is formed by preheating the converter and the composite bottom material composed of manganese ore, lime, and coke. Preheating can significantly reduce thermal shock and temperature drop when molten iron is added later, avoiding damage to the furnace body and interruption of the molten pool reaction. The pre-mixed bottom material provides an immediate source of manganese, slag-forming agent, and reducing agent for the subsequent initial reduction reaction. At the same time, the early mixing of lime and manganese ore can initially build an alkaline environment, inhibit the early dissolution loss of MnO, and ensure the rapid start-up and stable progress of the reaction.

[0009] Further, in step (3), the specific steps of iron addition and initial reduction are as follows: High-carbon manganese molten iron at a temperature of 1310-1330℃ is added to the converter, with the amount of iron added being 80-100 times the total mass of the bottom material. Immediately after iron addition, graphite fragments of 3-5% of the iron addition amount are added. The converter top and bottom re-blowing system is started, and pure argon gas is introduced at a flow rate of 100-120 Nm³. 3 / h, time 40-50min.

[0010] Furthermore, the initial carbon content of the high-carbon manganese molten iron is 6.5-7.5%.

[0011] In the above steps, high-temperature, high-carbon, high-manganese molten iron is added to provide the main molten metal and initial carbon source. Graphite fragments are added to further increase carbon content and as a solid reducing agent. The smelting is carried out under the protection of pure argon gas. The core purpose is to selectively reduce the manganese oxides in the base material and the molten pool by using the carbon in the molten iron and graphite fragments without introducing an oxidizing atmosphere and avoiding the oxidation of carbon and manganese. At the same time, the strong stirring effect of argon gas is used to homogenize the composition of the molten pool, promote the floating of non-metallic inclusions, and dissipate dissolved hydrogen in the molten pool to the maximum extent, creating conditions for subsequent deep reduction and obtaining high-purity molten iron.

[0012] Further, in step (4), the specific steps of atmosphere control and second-stage reduction are as follows: when the carbon content of the molten iron drops to 5.0-5.8% as monitored online, the reblowing gas is switched to a mixture of argon, CO, and CH4, and the volume ratio of the three is controlled to be (6.5-7.5):(1.8-2.2):(0.8-1.2). Under the condition that the working pressure in the furnace is 90-110 kPa, the partial pressure of CO is controlled to be 20-30 kPa. The feeding system adds the remaining high-grade manganese ore, silicon carbide, ferrosilicon manganese alloy, and supplementary coke powder in 2-4 batches. The total addition amounts are 10-16%, 1.5-3.5%, 0.8-2.5%, and 0.8-2.5% of the iron content, respectively, with a batch interval of 25-35 minutes. Magnesium oxide powder and alumina powder are added simultaneously to adjust the slag composition, control the slag basicity to 1.5-1.8, and ensure that the content of magnesium oxide powder in the slag is 4-6% and the content of alumina powder is 2-4%.

[0013] Furthermore, the temperature of the molten iron is controlled at 1590-1660℃ throughout the entire process, and the reduction time is 55-85 minutes.

[0014] In the above steps, when the carbon content of the molten iron drops to the thermodynamic critical point of 5.0-5.8%, the gas is switched to a mixture of argon, CO, and CH4 in a specific ratio. Argon provides stirring power, promotes slag-metal mass transfer, purifies the furnace atmosphere, and isolates oxidizing gases. By controlling the partial pressure of CO, further carbon oxidation can be precisely suppressed thermodynamically. CH4 is decomposed into C and H2 at high temperature, replenishing highly active carbon atoms in situ. This provides a sufficient carbon source for the deep reduction of manganese and achieves precise adjustment of the final carbon content. The hydrogen produced by the decomposition can quickly escape from the molten pool under the action of high temperature and argon stirring. Combined with the subsequent settling process, the hydrogen content in the molten iron can be effectively controlled. Adding cold materials in batches can avoid the sudden drop in molten pool temperature and deterioration of the reaction interface caused by adding a large amount of cold materials at once, keeping the reduction reaction stable and efficient. Simultaneously adding magnesium oxide powder and aluminum oxide powder to adjust the slag system can promote the formation of high-melting-point spinel phase, significantly reduce the solubility of MnO in the slag phase, reduce the chemical loss of manganese, and optimize the fluidity of the slag to ensure mass transfer efficiency.

[0015] Furthermore, in step (5), the specific steps for determining the endpoint and tapping iron are as follows: when the carbon content of the molten iron reaches 6.0-8.0% and the manganese content reaches 65-82% through the online monitoring system, the blowing and feeding are stopped, and the iron is tapped after standing for 8-15 minutes to obtain high-carbon manganese ferromanganese.

[0016] This invention also protects a high-carbon ferromanganese, which is prepared by any one of the preparation methods described above. The high-carbon ferromanganese has the following chemical composition by mass fraction: Mn 65-82%, C 6-8%, Si 0.5-2.0%, P 0.03-0.1%, with the balance being Fe and unavoidable impurities; wherein the hydrogen content is 3-8 ppm and the non-metallic inclusion content is 0.005-0.02%.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: The high-carbon ferromanganese prepared by this invention exhibits strong compositional uniformity, with carbon content fluctuations within the range of ≤±0.3% and manganese content fluctuations within the range of ≤±1.2%. This addresses the industry pain points of traditional processes, such as difficulty in precisely controlling carbon content and large compositional fluctuations, and is more suitable for the stringent requirements of modern high-end steel smelting for the stability of alloy raw materials. By using a pure argon atmosphere for initial reduction in the first stage, the high-carbon ferromanganese molten iron itself undergoes a reduction reaction with the pretreated substrate, preventing premature oxidation of the initial carbon. At the critical node where the carbon content drops to 5.0-5.8%, the re-blowing gas is precisely switched to a mixture of argon, CO, and CH4, and the CO partial pressure is controlled. This thermodynamically suppresses further carbon oxidation, while CH4 decomposition replenishes the active carbon source. This allows the final carbon content to steadily recover and remain within the high carbon range of 6.0-8.0%, simultaneously achieving efficient reduction and recovery of manganese. This successfully resolves the core contradiction of "carbon preservation" and "manganese enhancement" in high-carbon ferromanganese smelting. By optimizing the preheating of the bottom charge and adding cold charge in batches, the sudden drop in molten pool temperature and the "shelling" phenomenon in the furnace caused by the concentrated addition of cold charge can be effectively alleviated, ensuring sufficient slag-metal reaction, significantly reducing the chemical and mechanical loss of manganese in the slag, improving the overall recovery rate of manganese, and increasing the utilization rate of scarce manganese resources. At the same time, the sufficient preheating of the converter and bottom charge reduces the energy consumption for heating the molten pool after iron addition, and the batch feeding and optimized slag system make the reaction more stable and rapid, avoiding large fluctuations in temperature and composition, thereby shortening the smelting cycle and achieving efficient, energy-saving, and stable production, with significant economic benefits and environmental advantages. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0019] Testing method: Refer to the GB / T5686.1-2022 standard to test the manganese (Mn) content in ferromanganese; Refer to the GB / T223.69-2008 standard to test the carbon (C) content in ferromanganese; Refer to the GB / T5686.2-2022 standard to test the silicon (Si) content in ferromanganese; Refer to the GB / T5686.4-2022 standard to test the phosphorus (P) content in ferromanganese; Refer to the GB / T223.73-2008 standard to test the iron (Fe) content in ferromanganese; Refer to the GB / T223.82-2018 standard to test the hydrogen (H) content in ferromanganese; Refer to the GB / T10561-2023 standard to test the non-metallic inclusion content in ferromanganese; Calculation of manganese recovery rate: According to the total input of manganese in raw materials (the sum of manganese contents in high-grade manganese ore, high-carbon ferromanganese hot metal, and silicomanganese alloy) and the total output of manganese in products (product quality × manganese content), it is calculated according to the formula "manganese recovery rate = (total output of manganese / total input of manganese) × 100%"; Calculation of energy consumption per ton of iron: Through the electric energy meter and gas flow meter supporting the converter, respectively, count the electric energy (kWh) and gas volume (m 3 ) consumed during the smelting process. Convert the gas volume into equivalent electric energy according to the calorific value (1m 3 gas ≈ 1kWh electric energy). Divide the total energy consumption by the product quality (ton) to obtain the energy consumption per ton of iron; Statistics of smelting time: Start timing from the preheating of the converter and stop timing until the tapping is completed, record the total smelting time, accurate to 1 minute.

[0020] Example 1 (1) High-grade manganese ore (chemical composition (mass fraction) is Mn 52%, P 0.06%, FeO 2.5%) was crushed to a particle size of 4 mm, and ferrosilicon manganese alloy (Si to Mn mass ratio of about 2:1) was crushed to a particle size of 2.5 mm. Then, together with graphite crushed (fixed carbon content of 99%, particle size of 0.8 mm), silicon carbide (SiC purity of 95%, particle size of 0.2 mm), and lime (effective CaO content of 86%, particle size of 2 mm), it was dried at 120℃ for 4 h. After drying, it was stored in different moisture-proof warehouses. Coke powder (fixed carbon content of 89%, particle size of 0.08 mm), magnesium oxide powder (MgO purity of 91%, particle size of 0.075 mm), and alumina powder (Al2O3 purity of 96%, particle size of 0.08 mm) were also stored in different moisture-proof warehouses for later use.

[0021] (2) Weigh 100kg of pretreated high-grade manganese ore, 40kg of lime and 60kg of coke powder, mix them evenly and add them to the CLU converter as bottom material. The total mass of the bottom material is 200kg. Preheat the gas to 1000℃ for 2.2h.

[0022] (3) Add 20 tons of high-carbon manganese molten iron at 1320℃ to the converter. The initial carbon content of the high-carbon manganese molten iron is 7.0%. Immediately after the iron is added, add 800 kg of graphite fragments, start the converter top and bottom blowing system, and introduce pure argon gas at a flow rate of 110 Nm³. 3 / h, time 45min.

[0023] (4) When the carbon content of the molten iron drops to 5.2% as monitored online, the re-blowing gas is switched to a mixture of argon, CO, and CH4, with the volume ratio of the three controlled at 7:2:1. Under the condition that the working pressure in the furnace is 100 kPa, the partial pressure of CO is adjusted to 25 kPa. 2400 kg of high-grade manganese ore, 500 kg of silicon carbide, 200 kg of ferrosilicon, and 200 kg of coke powder are added in three batches through the feeding system, with a batch interval of 30 min. 1000 kg of magnesium oxide powder and 400 kg of alumina powder are added simultaneously to adjust the slag composition, control the slag basicity to 1.6, and ensure that the content of magnesium oxide powder in the slag is 5% and the content of alumina powder is 3%. The temperature of the molten iron is controlled at 1630℃ and the reduction time is 70 min throughout this step.

[0024] (5) When the carbon content of the molten iron reaches 7.2% and the manganese content reaches 78.3% through the online monitoring system, stop blowing and feeding, let it stand for 12 minutes and then tap the iron to obtain high carbon manganese ferromanganese.

[0025] Testing revealed that the high-carbon ferromanganese, by mass fraction, comprises: Mn 78.3%, C 7.2%, Si 1.52%, P 0.08%, with the balance being Fe and unavoidable impurities; the hydrogen content is 7.1 ppm, and the non-metallic inclusion content is 0.016%; the manganese recovery rate is 88.6%, the energy consumption per ton of iron is 615 kWh, and the total smelting time is 127 min.

[0026] Example 2 (1) High-grade manganese ore (chemical composition (mass fraction) is Mn 55%, P 0.05%, FeO 2.2%) was crushed to a particle size of 4 mm, and ferrosilicon manganese alloy (Si to Mn mass ratio is about 2:1) was crushed to a particle size of 2.5 mm. Then, together with graphite crushed (fixed carbon content is 99.2%, particle size is 0.6 mm), silicon carbide (SiC purity is 96%, particle size is 0.15 mm), and lime (effective CaO content is 87%, particle size is 2 mm), it was dried at 150℃ for 6 h. After drying, it was stored in different moisture-proof warehouses. Coke powder (fixed carbon content is 90%, particle size is 0.06 mm), magnesium oxide powder (MgO purity is 92%, particle size is 0.075 mm), and alumina powder (Al2O3 purity is 96%, particle size is 0.082 mm) were also stored in different moisture-proof warehouses for later use.

[0027] (2) Weigh 105kg of pretreated high-grade manganese ore, 42kg of lime and 63kg of coke powder, mix them evenly and add them to the CLU converter as bottom material. The total mass of the bottom material is 210kg. Gas is introduced to preheat to 1030℃ and the preheating time is 2.4h.

[0028] (3) Add 18 tons of high-carbon manganese molten iron at 1320℃ to the converter. The initial carbon content of the high-carbon manganese molten iron is 7.5%. Immediately after the iron is added, add 900 kg of graphite fragments, start the converter top and bottom blowing system, and introduce pure argon gas at a flow rate of 115 Nm³. 3 / h, time 45min.

[0029] (4) When the carbon content of the molten iron drops to 5.5% as monitored online, the re-blowing gas is switched to a mixture of argon, CO, and CH4, with the volume ratio of the three controlled at 7:2:1. Under the condition that the working pressure in the furnace is 105 kPa, the partial pressure of CO is adjusted to 28 kPa. 2340 kg of high-grade manganese ore, 540 kg of silicon carbide, 225 kg of ferrosilicon, and 198 kg of coke powder are added in three batches through the feeding system, with a batch interval of 30 min. At the same time, 1100 kg of magnesium oxide powder and 450 kg of alumina powder are added to adjust the slag composition, control the slag basicity to 1.7, and make the magnesium oxide powder content in the slag 5.2% and the alumina powder content 3.5%. The temperature of the molten iron is controlled at 1640℃ and the reduction time is 75 min throughout this step.

[0030] (5) When the carbon content of the molten iron reaches 7.8% and the manganese content reaches 81.5% through the online monitoring system, stop blowing and feeding, let it stand for 14 minutes and then tap the iron to obtain high carbon manganese ferromanganese.

[0031] Testing revealed that the high-carbon ferromanganese, by mass fraction, comprises: Mn 81.5%, C 7.8%, Si 1.6%, P 0.07%, with the balance being Fe and unavoidable impurities; the hydrogen content is 6.8 ppm, and the non-metallic inclusion content is 0.014%; the manganese recovery rate is 89.5%, the energy consumption per ton of iron is 610 kWh, and the total smelting time is 134 min.

[0032] Example 3 (1) High-grade manganese ore (chemical composition (mass fraction) is Mn 48%, P 0.07%, FeO 2.8%) was crushed to a particle size of 4 mm, and ferrosilicon alloy (Si to Mn mass ratio is about 2:1) was crushed to a particle size of 3 mm. Then, together with graphite crushed (fixed carbon content is 98.5%, particle size is 1 mm), silicon carbide (SiC purity is 95%, particle size is 0.3 mm), and lime (effective CaO content is 85%, particle size is 2 mm), it was dried at 120℃ for 4 h. After drying, it was stored in different moisture-proof warehouses. Coke powder (fixed carbon content is 88%, particle size is 0.09 mm), magnesium oxide powder (MgO purity is 90%, particle size is 0.08 mm), and alumina powder (Al2O3 purity is 95%, particle size is 0.088 mm) were also stored in different moisture-proof warehouses for later use.

[0033] (2) Weigh 95kg of pretreated high-grade manganese ore, 38kg of lime and 57kg of coke powder, mix them evenly as base material and add them to the CLU converter. The total mass of the base material is 190kg. Preheat the gas to 980℃ for 2 hours.

[0034] (3) Add 16 tons of high-carbon manganese molten iron at 1320℃ to the converter. The initial carbon content of the high-carbon manganese molten iron is 6.5%. Immediately after the iron is added, add 480 kg of graphite fragments, start the converter top and bottom blowing system, and introduce pure argon gas at a flow rate of 105 Nm³. 3 / h, time 45min.

[0035] (4) When the carbon content of the molten iron drops to 5.0% as monitored online, the re-blowing gas is switched to a mixture of argon, CO, and CH4, with the volume ratio of the three controlled at 7:2:1. Under the condition that the working pressure in the furnace is 95 kPa, the partial pressure of CO is adjusted to 22 kPa. 1760 kg of high-grade manganese ore, 320 kg of silicon carbide, 144 kg of ferrosilicon, and 144 kg of coke powder are added in three batches through the feeding system, with a batch interval of 30 min. 900 kg of magnesium oxide powder and 380 kg of alumina powder are added simultaneously to adjust the slag composition, control the slag basicity to 1.5, and ensure that the content of magnesium oxide powder in the slag is 4.8% and the content of alumina powder is 2.5%. The temperature of the molten iron is controlled at 1610℃ and the reduction time is 65 min throughout this step.

[0036] (5) When the carbon content of the molten iron reaches 6.2% and the manganese content reaches 66.8% through the online monitoring system, stop blowing and feeding, let it stand for 11 minutes and then tap the iron to obtain high carbon manganese ferromanganese.

[0037] Testing revealed that the high-carbon ferromanganese, by mass fraction, comprises: Mn 66.8%, C 6.2%, Si 1.5%, P 0.09%, with the balance being Fe and unavoidable impurities; the hydrogen content is 7.5 ppm, and the non-metallic inclusion content is 0.018%; the manganese recovery rate is 85.8%, the energy consumption per ton of iron is 620 kWh, and the total smelting time is 121 min.

[0038] Example 4 (1) High-grade manganese ore (chemical composition (mass fraction) is Mn 53%, P 0.05%, FeO 2.4%) was crushed to a particle size of 4 mm, and ferrosilicon manganese alloy (Si to Mn mass ratio is about 2:1) was crushed to a particle size of 2.5 mm. Then, together with graphite crushed (fixed carbon content is 99%, particle size is 0.8 mm), silicon carbide (SiC purity is 96%, particle size is 0.2 mm), and lime (effective CaO content is 86.5%, particle size is 2 mm), it was dried at 120℃ for 5 h. After drying, it was stored in different moisture-proof warehouses. Coke powder (fixed carbon content is 89%, particle size is 0.08 mm), magnesium oxide powder (MgO purity is 91%, particle size is 0.075 mm), and alumina powder (Al2O3 purity is 96%, particle size is 0.08 mm) were also stored in different moisture-proof warehouses for later use.

[0039] (2) Weigh 102.5 kg of pretreated high-grade manganese ore, 41 kg of lime and 61.5 kg of coke powder, mix them evenly and add them to the CLU converter as bottom material. The total mass of the bottom material is 205 kg. Preheat the gas to 1010℃ for 2.3 h.

[0040] (3) Add 19 tons of high-carbon manganese molten iron at 1320℃ to the converter. The initial carbon content of the high-carbon manganese molten iron is 7.2%. Immediately after the iron is added, add 760 kg of graphite fragments, start the converter top and bottom blowing system, and introduce pure argon gas at a flow rate of 112 Nm³. 3 / h, time 48min.

[0041] (4) When the carbon content of the molten iron drops to 5.3% as monitored online, the re-blowing gas is switched to a mixture of argon, CO, and CH4, with the volume ratio of the three controlled at 6.8:2.1:1.1. Under the condition that the working pressure in the furnace is 110 kPa, the partial pressure of CO is adjusted to 30 kPa. 2470 kg of high-grade manganese ore, 475 kg of silicon carbide, 190 kg of ferrosilicon, and 190 kg of coke powder are added in 4 batches through the feeding system, with a batch interval of 25 min. 1050 kg of magnesium oxide powder and 420 kg of alumina powder are added simultaneously to adjust the slag composition, control the slag basicity to 1.8, and ensure that the content of magnesium oxide powder in the slag is 5.8% and the content of alumina powder is 3.8%. The temperature of the molten iron is controlled at 1650℃ and the reduction time is 80 min throughout this step.

[0042] (5) When the carbon content of the molten iron reaches 7.5% and the manganese content reaches 79.8% through the online monitoring system, stop blowing and feeding, let it stand for 13 minutes and then tap the iron to obtain high carbon manganese ferromanganese.

[0043] Testing revealed that the high-carbon ferromanganese, by mass fraction, comprises: Mn 79.8%, C 7.5%, Si 1.5%, P 0.07%, with the balance being Fe and unavoidable impurities; the hydrogen content is 6.5 ppm, and the non-metallic inclusion content is 0.012%; the manganese recovery rate is 89.0%, the energy consumption per ton of iron is 605 kWh, and the total smelting time is 138 min.

[0044] Example 5 (1) High-grade manganese ore (chemical composition (mass fraction) is Mn 50%, P 0.06%, FeO 2.7%) was crushed to a particle size of 4 mm, and ferrosilicon manganese alloy (Si to Mn mass ratio is about 2:1) was crushed to a particle size of 2.5 mm. Then, together with graphite crushed (fixed carbon content is 98.8%, particle size is 0.9 mm), silicon carbide (SiC purity is 95%, particle size is 0.25 mm), and lime (effective CaO content is 85.5%, particle size is 2 mm), it was dried at 140℃ for 5 h. After drying, it was stored in different moisture-proof warehouses. Coke powder (fixed carbon content is 88%, particle size is 0.09 mm), magnesium oxide powder (MgO purity is 90.5%, particle size is 0.08 mm), and alumina powder (Al2O3 purity is 95.5%, particle size is 0.085 mm) were also stored in different moisture-proof warehouses for later use.

[0045] (2) Weigh 97.5 kg of pretreated high-grade manganese ore, 39 kg of lime and 58.5 kg of coke powder, mix them evenly and add them to the CLU converter as bottom material. The total mass of the bottom material is 195 kg. Preheat the gas to 970°C for 2.1 h.

[0046] (3) Add 17 tons of high-carbon manganese molten iron at 1320℃ to the converter. The initial carbon content of the high-carbon manganese molten iron is 6.8%. Immediately after the iron is added, add 680 kg of graphite fragments, start the converter top and bottom blowing system, and introduce pure argon gas at a flow rate of 108 Nm³. 3 / h, time 45min.

[0047] (4) When the carbon content of the molten iron drops to 5.1% as monitored online, the re-blowing gas is switched to a mixture of argon, CO, and CH4, with the volume ratio of the three controlled at 7.2:1.9:0.9. Under the condition that the working pressure in the furnace is 90 kPa, the partial pressure of CO is adjusted to 20 kPa. 1870 kg of high-grade manganese ore, 340 kg of silicon carbide, 120 kg of ferrosilicon, and 170 kg of coke powder are added in two batches through the feeding system, with a batch interval of 35 min. At the same time, 950 kg of magnesium oxide powder and 360 kg of alumina powder are added to adjust the slag composition, control the slag basicity to 1.5, and make the magnesium oxide powder content in the slag 4.2% and the alumina powder content 2.2%. The temperature of the molten iron is controlled at 1600℃ and the reduction time is 60 min throughout this step.

[0048] (5) When the carbon content of the molten iron reaches 6.5% and the manganese content reaches 70.2% through the online monitoring system, stop blowing and feeding, let it stand for 10 minutes and then tap the iron to obtain high carbon manganese ferromanganese.

[0049] Testing revealed that the high-carbon ferromanganese, by mass fraction, comprises: Mn 70.2%, C 6.5%, Si 1.5%, P 0.06%, with the balance being Fe and unavoidable impurities; the hydrogen content is 7.8 ppm, and the non-metallic inclusion content is 0.019%; the manganese recovery rate is 86.5%, the energy consumption per ton of iron is 618 kWh, and the total smelting time is 118 min.

[0050] Comparative Example 1 The main difference between this comparative example and Example 5 is the atmosphere control and addition method in step (4). Specifically, when the carbon content of the molten iron drops to 5.1% as monitored online, instead of switching to a mixed gas of Ar, CO, and CH4, pure argon is maintained and the flow rate is increased to 120 Nm. 3 / h. Meanwhile, instead of adding in batches, a total of 1870 kg of high-grade manganese ore, 340 kg of silicon carbide, 120 kg of ferrosilicon-manganese alloy, and 170 kg of coke powder were added all at once. All other steps and parameters were the same as in Example 5.

[0051] According to the test results, the chemical composition of the ferromanganese prepared in this comparative example, by mass fraction, includes: Mn 69.2%, C 5.8%, Si 1.5%, P 0.08%, with the balance being Fe and unavoidable impurities; the hydrogen content is 8.5 ppm, the non-metallic inclusion content is 0.045%; the manganese recovery rate is 83.5%, the energy consumption per ton of iron is 640 kWh, and the total smelting time is 188 min.

[0052] Comparative Example 2 The main difference between this comparative example and Example 5 is that the slag composition in step (4) is adjusted without adding magnesium oxide powder and aluminum oxide powder, and only lime is used to adjust the slag basicity. The specific operation is as follows: when the carbon content of the molten iron drops to 5.1% as monitored online, the re-blowing gas is switched to a mixture of argon, CO, and CH4, and the volume ratio of the three is controlled to be 7.2:1.9:0.9. Under the condition that the working pressure in the furnace is 90 kPa, the CO partial pressure is adjusted to 20 kPa. The following materials are added in two batches through the feeding system: a total of 1870 kg of high-grade manganese ore, 340 kg of silicon carbide, 120 kg of ferrosilicon manganese alloy, and 170 kg of coke powder, with a batch interval of 35 min. Only lime is added to adjust the slag basicity to 1.5, and magnesium oxide powder and aluminum oxide powder are not added. The molten iron temperature is controlled at 1600℃ and the reduction time is 60 min throughout this step. Other steps and parameters are the same as in Example 5.

[0053] According to the test results, the chemical composition of the ferromanganese prepared in this comparative example, by mass fraction, includes: Mn 67.5%, C 6.3%, Si 1.6%, P 0.07%, with the balance being Fe and unavoidable impurities; the hydrogen content is 8.2 ppm, the non-metallic inclusion content is 0.038%; the manganese recovery rate is 81.2%, the energy consumption per ton of iron is 635 kWh, and the total smelting time is 125 min.

[0054] The comparison shows that in Comparative Example 1, the lack of switching the reblowing gas to a mixture of argon, CO, and CH4 resulted in insufficient thermodynamic inhibition of CO partial pressure, leading to intensified carbon oxidation and a decrease in the carbon content of ferromanganese. Furthermore, the one-time addition of cold material resulted in incomplete slag-metal reaction and insufficient time for inclusions to float, thus increasing the content of non-metallic inclusions. This necessitated a longer time to restore the temperature and complete the reaction, leading to a surge in energy consumption and time. In Comparative Example 2, the absence of magnesium oxide powder and aluminum oxide powder prevented the formation of a high-melting-point spinel phase, resulting in increased MnO dissolution and loss in the slag, which in turn reduced the manganese recovery rate and increased the content of non-metallic inclusions.

[0055] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0056] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

[0057] Those skilled in the art should understand that the above descriptions are merely several specific embodiments of the present invention, and not all embodiments.

Claims

1. A method for preparing high-carbon ferromanganese, characterized in that, Includes the following steps: (1) Raw material pretreatment; (2) Converter preheating and bottom material laying: The pretreated high-grade manganese ore, lime and coke powder are mixed and added to the CLU converter as bottom material for preheating; (3) Adding iron and initial reduction: Add high-carbon manganese molten iron to the converter and add graphite fragments, and carry out initial reduction under a pure argon atmosphere; (4) Atmosphere control and second-stage reduction: When the carbon content of molten iron drops to 5.0-5.8%, the re-blowing gas is switched to a mixture of argon, CO and CH4. The remaining high-grade manganese ore, silicon carbide, silicomanganese alloy and supplementary coke powder are added in batches. Magnesium oxide powder and alumina powder are added simultaneously to adjust the slag composition. (5) Endpoint judgment and tapping: When the carbon content of the molten iron reaches 6.0-8.0% and the manganese content reaches 65-82%, tap the iron.

2. The method for preparing high-carbon ferromanganese according to claim 1, characterized in that, In step (1), the specific steps of raw material pretreatment are as follows: crush high-grade manganese ore to a particle size of 3-5 mm, crush silicon manganese alloy to a particle size of 2-3 mm, and then dry it together with graphite crushed, silicon carbide and lime at 110-150℃ for 4-6 hours. After drying, store them in different moisture-proof warehouses. Coke powder, magnesium oxide powder and alumina powder are also stored in different moisture-proof warehouses for later use.

3. The method for preparing high-carbon ferromanganese according to claim 1, characterized in that, In step (2), the specific steps of converter preheating and bottom material laying are as follows: the pretreated high-grade manganese ore, lime and coke powder are mixed evenly and added to the CLU converter as bottom material, and gas is introduced to preheat to 950-1050℃ for 2-2.5h.

4. The method for preparing high-carbon ferromanganese according to claim 3, characterized in that, The high-grade manganese ore, lime, and coke powder are mixed in a mass ratio of 4.5-5.5:1.8-2.2:2.8-3.

2.

5. The method for preparing high-carbon ferromanganese according to claim 1, characterized in that, In step (3), the specific steps for iron addition and initial reduction are as follows: High-carbon manganese molten iron at a temperature of 1310-1330℃ is added to the converter, with the amount of iron added being 80-100 times the total mass of the bottom material. Immediately after iron addition, graphite fragments of 3-5% of the iron addition amount are added. The converter top and bottom re-blowing system is started, and pure argon gas is introduced at a flow rate of 100-120 Nm³. 3 / h, time 40-50min.

6. The method for preparing high-carbon ferromanganese according to claim 5, characterized in that, The initial carbon content of the high-carbon manganese molten iron is 6.5-7.5%.

7. The method for preparing high-carbon ferromanganese according to claim 1, characterized in that, In step (4), the specific steps of atmosphere control and second-stage reduction are as follows: when the carbon content of molten iron drops to 5.0-5.8% as monitored online, the reblowing gas is switched to a mixture of argon, CO, and CH4, and the volume ratio of the three is controlled to be (6.5-7.5):(1.8-2.2):(0.8-1.2). Under the condition that the working pressure in the furnace is 90-110 kPa, the partial pressure of CO is controlled to be 20-30 kPa. The remaining high-grade manganese ore, silicon carbide, ferrosilicon alloy and supplementary coke powder are added in 2-4 batches through the feeding system. The total addition amount is 10-16%, 1.5-3.5%, 0.8-2.5% and 0.8-2.5% of the iron content, respectively. The batch interval is 25-35 min. Magnesium oxide powder and alumina powder are added simultaneously to adjust the slag composition, control the slag basicity to be 1.5-1.8, and make the content of magnesium oxide powder in the slag 4-6% and the content of alumina powder 2-4%.

8. The method for preparing high-carbon ferromanganese according to claim 7, characterized in that, Throughout this step, the molten iron temperature is controlled at 1590-1660℃, and the reduction time is 55-85 minutes.

9. The method for preparing high-carbon ferromanganese according to claim 1, characterized in that, In step (5), the specific steps for determining the endpoint and tapping iron are as follows: when the carbon content of the molten iron reaches 6.0-8.0% and the manganese content reaches 65-82% through the online monitoring system, stop blowing and feeding, let it stand for 8-15 minutes and then tap the iron to obtain high-carbon manganese ferromanganese.

10. A high-carbon ferromanganese compound, characterized in that, The high-carbon ferromanganese is prepared by the preparation method according to any one of claims 1-9. The chemical composition of the high-carbon ferromanganese, by mass fraction, includes: Mn 65-82%, C 6-8%, Si 0.5-2.0%, P 0.03-0.1%, with the balance being Fe and unavoidable impurities; wherein the hydrogen content is 3-8 ppm and the non-metallic inclusion content is 0.005-0.02%.