A vanadium-containing molten iron converter smelting process

Abstract

This invention relates to a vanadium-containing molten iron converter smelting process, comprising: S1, pre-treating and desulfurizing vanadium-titanium molten iron; S2, placing the desulfurized molten iron into a vanadium extraction converter for vanadium extraction and dephosphorization; and S3, subjecting the vanadium-extracted and dephosphorized semi-steel to high-carbon smelting in a steelmaking converter, thereby obtaining pure molten steel with high carbon, high manganese, low nitrogen, low phosphorus, and low oxygen content. Unlike existing technologies in the field, this invention, through the design of the vanadium-containing molten iron process flow, achieves coordinated operation of each step, effectively avoiding problems such as insufficient heat source, high oxidizing properties, and difficulty in controlling phosphorus levels in the final molten steel during vanadium-containing molten iron smelting.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a vanadium-containing molten iron converter smelting process. Background Technology

[0002] Steel enterprises using vanadium-titanium magnetite for smelting typically employ a dual-process smelting method: desulfurization of the vanadium-containing molten iron, vanadium extraction in a converter, and steelmaking in a converter. The semi-steel obtained after desulfurization and vanadium extraction in this process has a carbon content of 3.4%–3.8%, with trace amounts of silicon and manganese, which are exothermic slag-forming elements. Typically, dephosphorization is not performed in the vanadium extraction converter. The temperature of the semi-steel after vanadium extraction fluctuates between 1380-1450℃, while the temperature of the semi-steel added to the steelmaking converter fluctuates between 1300-1350℃. Therefore, semi-steel converter steelmaking suffers from problems such as insufficient heat source, difficulty in dephosphorization, and severe deep blowing and supplementary blowing leading to high nitrogen content and low manganese content in key molten steel.

[0003] There are existing literature reports addressing the problems of high nitrogen content, low manganese content, and difficulty in dephosphorization in vanadium-containing molten iron steelmaking. For example, Chinese Patent 201810147755.2 discloses a method and apparatus for manganese alloying using manganese ore. Specifically, it discloses a method for reducing manganese in manganese ore using molten electrolysis. This technology involves adding 3-10 kg / ton of manganese ore to the slag and using electrolytic molten reduction to increase the manganese content in the molten steel by 0.1%-0.2% (by weight). However, this method requires high-quality manganese ore and has high industrial production costs.

[0004] Chinese Patent 202111447493.X discloses a method for controlling the nitrogen content of molten steel in a converter process, relating to the field of converter steelmaking technology. It solves the problem of high nitrogen increase in molten steel during the converter tapping process. Based on the TSC measurement results of the auxiliary lance in the later stage of converter blowing, the method controls the oxidizing properties of the molten steel at the endpoint within the required range while ensuring the first-time hit rate. Simultaneously, during tapping, deoxidation, and alloying, measures of "argon atmosphere protection + top slag coverage + delayed alloy addition + weak-to-strong + incomplete deoxidation" are adopted to maintain relative oxidizing properties in the molten steel and argon atmosphere protection throughout the process, reducing nitrogen absorption by the steel stream and nitrogen increase in the molten steel in the ladle during tapping. The method controls the nitrogen increase in molten steel at converter tapping to below 5 ppm, laying the foundation for the production of low-nitrogen steel. While there are many patent documents on improving converter dephosphorization efficiency, existing literature only covers methods for controlling the manganese, nitrogen, and phosphorus content of molten steel at the converter endpoint, and does not address smelting processes that simultaneously obtain low-nitrogen, low-phosphorus, and high-manganese steel. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a vanadium-containing molten iron converter smelting process. Through the design of the vanadium-containing molten iron process flow, the coordination and cooperation of each process are achieved, effectively avoiding problems such as insufficient heat source, high oxidizing properties, and difficulty in controlling phosphorus in the final molten steel during vanadium-containing molten iron smelting.

[0006] The technical solution adopted in this invention is as follows:

[0007] The vanadium-containing molten iron converter smelting process proposed in this invention includes the following steps:

[0008] S1. Pre-treatment of vanadium-titanium molten iron for desulfurization;

[0009] S2. The desulfurized molten iron is put into a vanadium extraction converter for vanadium extraction and dephosphorization.

[0010] S3. The semi-steel after vanadium removal and dephosphorization is smelted in a steelmaking converter with high carbon content to obtain pure molten steel with high carbon, high manganese, low nitrogen, low phosphorus and low oxygen content.

[0011] Preferably, in step S2, pre-dephosphorization is performed simultaneously with vanadium extraction, and oxygen is top-blown during vanadium extraction with a supply intensity of 1.0-2.0 m³ / s. 3 / (t·min), while blowing oxygen, add 5-10kg of lime for dephosphorization, control the carbon content of semi-steel between 3.4-3.8%, control the temperature of semi-steel between 1380-1450℃, and the dephosphorization rate ≥40%.

[0012] Preferably, in step S3, the specific process of high-carbon smelting is as follows: After vanadium extraction and dephosphorization, the semi-steel is added to the steelmaking converter, followed by the addition of slag-forming materials; high-magnesium lime and quicklime are added at the start of oxygen blowing, at amounts of 5-9 kg / t steel respectively; manganese ore is added 15-25 kg / t steel after 1-2 minutes of oxygen blowing; top-blown oxygen is supplied at an intensity of 2.5-3.5 m. 3 / t·min; bottom-blown argon gas, supply intensity of 0.1-0.2m³ / min. 3 / t·min; When the molten steel temperature is 1630-1660℃ and the final carbon content is between 0.30-0.60%, the steel is directly tapped to obtain pure molten steel with high carbon, high manganese, low nitrogen, low phosphorus, and low oxidizing properties.

[0013] Preferably, the manganese ore comprises the following chemical composition by weight percentage: TMn: 35%-45%; FexO: 10%-20%; SiO2: 12%-19%; CaO: 11%-15%; P≤0.050%; S≤0.30%; the balance being impurities, with a particle size between 5-20 mm.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] This invention effectively overcomes the problem of insufficient heat source for semi-steel due to its low auxiliary material consumption (less than 18 kg per ton of steel) and small temperature drop. At the same time, the use of dual dephosphorization alleviates the dephosphorization pressure in steelmaking converters, creating favorable conditions for obtaining pure molten steel with high carbon, high manganese, low nitrogen, low phosphorus, and low oxidizing properties. Meanwhile, the slag has a very low oxidizing TFe content, which has little impact on the furnace lining. The operation is simple and has obvious advantages. Attached Figure Description

[0016] Figure 1 This is a flowchart of the process of the present invention. Detailed Implementation

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] like Figure 1 As shown, the vanadium-containing molten iron converter smelting process proposed in this invention specifically includes the following steps:

[0019] S1. Pre-treatment of vanadium-titanium molten iron for desulfurization;

[0020] S2. The desulfurized molten iron is then placed into a vanadium extraction converter for vanadium extraction and dephosphorization. During vanadium extraction in the converter, pre-dephosphorization is performed simultaneously with vanadium extraction. Oxygen is top-blown during vanadium extraction, with a supply intensity of 1.0-2.0 m³ / h. 3 / (t·min), while blowing oxygen, add 5-10kg of lime for dephosphorization, control the carbon content of semi-steel between 3.4-3.8%, control the temperature of semi-steel between 1380-1450℃, and the dephosphorization rate ≥40%.

[0021] S3. The semi-steel after vanadium extraction and dephosphorization is subjected to high-carbon smelting in a steelmaking converter. The specific process is as follows: The semi-steel after vanadium extraction and dephosphorization is added to the steelmaking converter, followed by slag-forming materials; high-magnesium lime and quicklime are added at the beginning of oxygen blowing, at a rate of 5-9 kg / t steel; manganese ore is added 15-25 kg / t steel after 1-2 minutes of oxygen blowing; top-blown oxygen is supplied at an intensity of 2.5-3.5 m. 3 / t·min; bottom-blown argon gas, supply intensity of 0.1-0.2m³ / min. 3 / t·min; When the molten steel temperature is 1630-1660℃ and the final carbon content is between 0.30-0.60%, oxygen blowing is stopped and the steel is tapped directly to obtain pure molten steel with high carbon, high manganese, low nitrogen, low phosphorus, and low oxidizing properties.

[0022] The manganese ore comprises the following chemical composition by weight percentage: TMn: 35%-45%; FexO: 10%-20%; SiO2: 12%-19%; CaO: 11%-15%; P≤0.050%; S≤0.30%; the balance being impurities, with a particle size between 5-20 mm.

[0023] The working principle of this invention is as follows: First, in terms of process flow, the process of desulfurization before vanadium extraction is adopted. During the pre-treatment desulfurization, the desulfurization temperature is lower and the temperature drop is less, which can create heat source conditions for vanadium extraction in the converter. Second, the heat source (temperature and carbon) of the semi-steel can also be adjusted through the vanadium extraction process, which can ensure the heat source requirements of converter steelmaking.

[0024] From a technical perspective: Vanadium extraction in converters typically requires the addition of coolant. This invention, by adding coolant and lime, achieves both vanadium extraction and dephosphorization, significantly reducing the phosphorus content in the semi-finished steel (phosphorus is mainly removed in the steelmaking converter). Steelmaking converters primarily dephosphorize by adding auxiliary materials at room temperature (lime, high-magnesium lime, slag-forming agents, etc.). Reducing the phosphorus content in the semi-finished steel significantly reduces the amount of such cold materials needed, creating conditions for adding manganese ore to increase the manganese content in the molten steel. Secondly, the high-carbon extraction process offers better thermal efficiency. In the early and middle stages of converter smelting, rapid carbon oxidation leads to higher thermal efficiency and better denitrification. In the later stages of smelting, carbon levels decrease rapidly, but the heating rate is slower, resulting in lower thermal efficiency and a higher risk of nitrogen buildup. Therefore, the high-carbon extraction process is beneficial for improving converter thermal efficiency. Furthermore, the high-carbon extraction process, with its high carbon content at the converter endpoint and suitable temperature range, facilitates dephosphorization, and the lower oxidizability of the molten steel results in higher steel purity. In summary, the process of this invention can produce pure molten steel with high carbon, high manganese, low nitrogen, low phosphorus, and low oxidizing properties.

[0025] Compared with the existing process: vanadium-titanium molten iron → vanadium extraction in vanadium converter → semi-steel desulfurization → converter dephosphorization steelmaking;

[0026] The process of first extracting vanadium and then desulfurizing results in a large temperature drop during desulfurization, leading to a low temperature when the vanadium enters the steelmaking converter, which is not conducive to the utilization of thermal efficiency. Secondly, this process does not dephosphorize in the vanadium extraction converter. Dephosphorization in the steelmaking converter requires the addition of a large amount of auxiliary materials, resulting in a severe shortage of heat source in the converter and low thermal efficiency. The temperature can only be raised by iron oxide in the later stage of smelting, resulting in low carbon, high nitrogen, and high oxidizability of the molten steel. In addition, the molten steel does not contain manganese, has many oxidized inclusions, and has low purity.

[0027] The present invention will be further illustrated below through specific embodiments:

[0028] Example 1

[0029] A certain factory's 120t converter uses vanadium-titanium iron smelting. The production process is as follows: vanadium-titanium iron → iron pretreatment and desulfurization → vanadium extraction converter dephosphorization and vanadium extraction → semi-steel converter high-strength carbon steelmaking; the vanadium-containing iron has a phosphorus content of 0.08%, a vanadium content of 0.35%, and a carbon content of 4.0%; coolant and lime are added during vanadium extraction oxygen blowing, with 5 kg of lime added per ton of steel; oxygen is top-blown during vanadium extraction, with a gas supply intensity of 1.0 m³ / h. 3 The semi-steel was produced at a temperature of 1380℃ (t·min), and the vanadium content, phosphorus content, and carbon content were measured to be 0.04%, 0.04%, and 3.4%, respectively. The dephosphorized semi-steel was then fed into a steelmaking converter for smelting, with top-blown oxygen at an oxygen supply intensity of 2.5 m³ / min. 3 / t·min; bottom-blown argon gas, supply intensity of 0.1m 3 At the start of oxygen blowing, high-magnesium lime and quicklime are added. Both high-magnesium lime and quicklime are commonly used auxiliary materials in semi-steelmaking, and the addition amount is 5 kg / t steel. After 1 minute of oxygen blowing, manganese ore (the content of each component by weight percentage is as follows: TMn: 45%, FexO: 15%, SiO2: 15%, CaO: 14%, P: 0.020%, S: 0.10%, the rest are impurities, and the particle size is between 5-20 mm) is added at a rate of 20 kg / t steel. The oxygen lance is operated at a high position throughout the process, with the lance position controlled at 1.5-2.5 m, and measured by the auxiliary lance. When the steel temperature reaches 1630℃ and the carbon content reaches 0.45%, oxygen blowing is stopped and the steel is tapped. The resulting molten steel is pure molten steel with a manganese content of 0.79%, a nitrogen content of 0.0006%, a phosphorus content of 0.008%, and an oxygen content of 60 ppm, and the slag TFe content is only 10%.

[0030] Example 2

[0031] A certain factory's 120t converter uses vanadium-titanium iron smelting. The production process is as follows: vanadium-titanium iron → iron pretreatment and desulfurization → vanadium extraction converter dephosphorization and vanadium extraction → semi-steel converter high-strength carbon steelmaking; wherein, the phosphorus content of the vanadium-containing iron is 0.09%, the vanadium content is 0.38%, and the carbon content is 4.2%; coolant and lime are added during vanadium extraction oxygen blowing, with 10kg of lime added per ton of steel; oxygen is top-blown during vanadium extraction, with a gas supply intensity of 2.0m. 3 The semi-steel was produced at a temperature of 1450℃ (t·min), and the vanadium content was measured to be 0.04%, phosphorus content 0.041%, and carbon content 3.5%. The dephosphorized semi-steel was then fed into a steelmaking converter for smelting, with top-blown oxygen at an oxygen supply intensity of 3.5 m³ / min. 3 / t·min; bottom-blown argon gas, supply intensity of 0.2m 3At the start of oxygen blowing, high-magnesium lime and quicklime are added at a rate of 9 kg / t steel. After 2 minutes of oxygen blowing, manganese ore (with the following composition by weight percentage: TMn: 35%, FexO: 20%, SiO2: 19%, CaO: 15%, P: 0.020%, S: 0.10%, the remainder being impurities, particle size 5-20 mm) is added at a rate of 25 kg / t steel. The oxygen lance is operated at a high position throughout the process, with the lance position controlled at 1.5-2.5 m, measured by the auxiliary lance. When the steel temperature reaches 1660℃ and the carbon content reaches 0.30%, oxygen blowing is stopped and the steel is tapped. The resulting pure molten steel has a manganese content of 0.75%, a nitrogen content of 0.0007%, a phosphorus content of 0.007%, and an oxygen content of 68 ppm, and the slag TFe content is only 11%.

[0032] Matters not covered in this invention are common knowledge.

[0033] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A converter smelting process for vanadium-containing molten iron, characterized in that, The process includes the following steps: S1. Pre-treatment of vanadium-titanium molten iron for desulfurization; S2. The desulfurized molten iron is put into a vanadium extraction converter for vanadium extraction and dephosphorization. S3. The semi-steel after vanadium removal and dephosphorization is smelted in a steelmaking converter with high carbon content to obtain pure molten steel with high carbon, high manganese, low nitrogen, low phosphorus and low oxygen content. In step S3, the specific process of high-carbon smelting is as follows: Vanadium-removed and dephosphorized semi-steel is added to the steelmaking converter, followed by the addition of slag-forming materials; high-magnesium lime and quicklime are added at the start of oxygen blowing, at amounts of 5-9 kg / t steel respectively; manganese ore is added 15-25 kg / t steel after 1-2 minutes of oxygen blowing; top-blown oxygen is supplied at an intensity of 2.5-3.5 m. 3 / t·min; bottom-blown argon gas, supply intensity of 0.1-0.2m³ / min. 3 / (t·min); When the molten steel temperature is 1630-1660℃ and the final carbon content is between 0.30-0.60%, the steel is directly tapped to obtain pure molten steel with high carbon, high manganese, low nitrogen, low phosphorus, and low oxidizing properties. The manganese ore comprises the following chemical composition by weight percentage: TMn: 35%-45%; Fe x O: 10%-20%; SiO2: 12%-19%; CaO: 11%-15%; P ≤0.050%; S ≤0.30%; the balance is impurities, with a particle size between 5-20 mm. In step S2, pre-dephosphorization is carried out simultaneously with vanadium extraction. During vanadium extraction, oxygen is top-blown at a supply intensity of 1.0-2.0 m³ / s. 3 / (t·min), while blowing oxygen, add 5-10kg of lime for dephosphorization, control the carbon content of semi-steel between 3.4-3.8%, control the temperature of semi-steel between 1380-1450℃, and the dephosphorization rate ≥40%.

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