A smelting process for semi-steel with hot compensation and deep desulphurization

Abstract

The present application belongs to metallurgical technical field, disclose a kind of to half steel hot compensation and deep desulphurization smelting process, the process is through vanadium extraction converter deep vanadium extraction process, furnace after vanadium slag process, half steel LF furnace hot compensation process, half steel LF furnace deep desulphurization process, half steel converter smelting process etc., the present application is after vanadium-containing hot metal is entered factory, not to hot metal pretreatment desulphurization, also not to half steel through pretreatment desulphurization, avoid the vanadium slag loss caused by pretreatment slagging;Vanadium extraction converter uses deep vanadium extraction process, cooling intensity is big, oxygen supply time is long, half steel carbon content and residual vanadium are low, ensure vanadium oxidation rate and recovery rate, maximum utilization of vanadium resources;Half steel tank uses refining ladle, avoid the problem of long time of ladle pouring process, guarantee the safety of LF furnace temperature rise;Half steel is deep desulphurization while LF hot compensation, desulphurization effect is good, cost is low;LF furnace hot compensation can adjust half steel hot compensation temperature according to half steel temperature and carbon content, solve the influence of half steel carbon content fluctuation, create favorable conditions for subsequent converter steelmaking.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to a smelting process for thermal compensation and deep desulfurization of semi-steel. Background Technology

[0002] Vanadium-titanium magnetite is smelted in a blast furnace to obtain vanadium-containing molten iron. To extract vanadium from this molten iron, a common domestic process is the double-tank converter process. This involves first extracting vanadium in the molten iron in a converter to produce semi-steel, which is then used for further steelmaking in the converter. The difference between vanadium extraction steelmaking and converter steelmaking lies in the converter's primary objective: "vanadium extraction with carbon retention." This is achieved by adding coolant to control the molten pool temperature, inhibiting the carbon-oxygen reaction, and ensuring that the vanadium in the molten iron is rapidly and completely oxidized into the slag, while minimizing the oxidation of carbon in the molten iron to provide sufficient heat for heating during steelmaking. However, vanadium extraction steelmaking also places a burden on steelmaking production due to the high sulfur load in the molten iron.

[0003] Semi-steel is a "chemically cold" intermediate product in steelmaking. The temperature of semi-steel after vanadium extraction in the converter is generally between 1350℃ and 1400℃, and the carbon content is generally between 3.2% and 4.0%. However, the tapping temperature of steelmaking in the converter is mostly above 1660℃. The converter heat is insufficient for semi-steel steelmaking, resulting in slow slag formation, poor dephosphorization and desulfurization, overblowing at the end of steelmaking, strong oxidizing properties of molten steel, and high sulfur load, all of which have a significant impact on converter steelmaking. Therefore, it is necessary to reduce the sulfur content of semi-steel, perform thermal compensation on semi-steel, and stabilize its quality.

[0004] In existing technologies, to eliminate the adverse effects of fluctuations in the sulfur mass fraction of vanadium-containing molten iron, the process involves vanadium-containing molten iron → pretreatment desulfurization → vanadium extraction in a converter → semi-steel converter steelmaking. However, vanadium loss occurs during the pretreatment desulfurization and slag removal process. To address this, Panzhihua Iron and Steel Group (Pangang) adopted a process of vanadium-containing molten iron → vanadium extraction in a converter → vanadium slag removal after the vanadium extraction furnace → pretreatment desulfurization → semi-steel converter steelmaking. This process avoids vanadium loss caused by pretreatment desulfurization and slag removal to some extent, but it also leads to a large temperature drop after semi-steel desulfurization. Furthermore, the unstable quality of the semi-steel, affected by fluctuations in its mass fraction, causes difficulties in subsequent converter smelting.

[0005] In existing technologies, to address the problems of insufficient heat in semi-steelmaking, slow slag formation during the steelmaking process, poor P and S removal effects, overblowing at the steelmaking endpoint, and strong oxidizing properties of molten steel, heat-raising agents such as coke, anthracite, silicon carbide, or ferrosilicon are added during semi-steelmaking for heat compensation. However, the process of using heat-raising agents for heat compensation has contradictions such as large amounts of heat-raising agents added, low utilization rate, low thermal efficiency, and increased steelmaking costs.

[0006] The invention with patent number CN 113088612 A discloses a method for pretreatment and desulfurization of molten iron using an LF furnace. The method involves transporting the molten iron ladle to the slag removal position, removing the top slag from the ladle, adding desulfurizing slag agent to the ladle in the LF furnace, blowing gas from the bottom of the ladle, pouring the molten iron from the ladle into the ladle, adding the desulfurizing slag agent, and then electrically stirring and desulfurizing. Afterward, the molten iron is sent to a mixing furnace or converter, mixed with qualified molten iron for smelting. This method has the advantage of low investment costs.

[0007] Patent CN107164604 A discloses a method for maintaining the temperature of molten iron in a ladle refining furnace. This method, when the molten iron cannot be returned for further processing, involves placing it into a ladle and using a bottom-blowing system to maintain the temperature of the ladle in the refining furnace. Once the converter system recovers, the maintained molten iron is added to the converter for normal smelting. This invention solves the problems of molten iron remaining in the ladle for extended periods without processing when the converter system malfunctions during production, and the formation of lumps in the ladle due to prolonged ladle stagnation.

[0008] The invention with patent number CN 115449592 A discloses a method for efficient heating and raising the temperature of molten scrap steel in an LF furnace. This method achieves the goals of improving the heating and raising rate and thermal efficiency of molten scrap steel in an LF furnace by using electrically heated converter tail slag in the LF furnace of the ladle to form slag, controlling the amount of slag-forming material added, controlling the three stages of heating and raising the temperature of the LF furnace in the ladle, and adjusting the flow rate of weak bottom blowing stirring gas and controlling the diameter of the bright ring on the liquid surface.

[0009] However, all of the above technologies involve pre-desulfurization or heating of molten iron in an LF furnace. In actual implementation, these technologies all require repeated ladle handling or hoisting, resulting in long processing times. Compared with the injection method and KR method for pre-desulfurization of molten iron in an LF furnace, the cost of pre-desulfurization in an LF furnace is higher. These technologies cannot meet the requirement of deep desulfurization while simultaneously providing thermal compensation for semi-steel in vanadium-containing molten iron. Using an LF furnace for pre-desulfurization or heating of molten iron cannot solve the problems of large fluctuations in carbon content and temperature in semi-steel, leading to unstable quality. The technologies are not very practical for on-site operation and cannot solve the problem of unstable quality of semi-steel caused by fluctuations in carbon content. Summary of the Invention

[0010] The purpose of this invention is to solve the technical problems existing in the smelting of semi-steel in the prior art, and to provide a smelting process for thermal compensation and deep desulfurization of semi-steel.

[0011] To achieve the above objectives, the present invention adopts the following technical solution:

[0012] A smelting process for heat compensation and deep desulfurization of semi-steel includes the following steps:

[0013] Step 1) Vanadium-containing molten iron with C≥3.6% and V≥0.15% is added to a vanadium extraction converter for vanadium extraction smelting, and a coolant is added at a rate of 30-120 kg / t of steel. The oxygen supply time is extended to 4-8 minutes, and a semi-steel with a C content of 2.2%-3.0%, residual V≤0.03%, and a temperature between 1330℃ and 1400℃ is finally obtained.

[0014] Step 2) Set up a slag remover at the LF furnace refining station. After the semi-steel is discharged, lift the semi-steel ladle into the ladle car at the LF furnace refining station to remove the vanadium slag that enters the semi-steel ladle when the vanadium is discharged into the semi-steel for recycling.

[0015] Step 3) After slag removal, argon is blown, temperature is measured, and samples are taken at the LF furnace processing station. The semi-steel is heated by electricity, and the temperature of the semi-steel is obtained between 1450℃ and 1550℃ through thermal compensation.

[0016] Step 4) Desulfurization is carried out simultaneously with thermal compensation in the LF furnace to reduce sulfur content in the semi-steel to 0.010%–0.040%.

[0017] Step 5) The semi-steel obtained in Step 4 is added to the steelmaking converter. Lime and raw dolomite are added to the molten steel in the converter for blowing to obtain qualified molten steel. After alloying, the steel is treated at the argon blowing station and then cast on the continuous casting machine.

[0018] Furthermore, in step 1), the coolant is one or a combination of several of the following: scrap steel, vanadium-containing pig iron blocks, iron oxide pellets, vanadium-titanium pellets, and ore.

[0019] Furthermore, the semi-steel can in step 2) uses a refined steel ladle.

[0020] Furthermore, in step 3), when implementing the heat compensation process, the semi-steel temperature is 1450℃ as the benchmark. When the temperature is lower than 1450℃, the semi-steel temperature is raised to 1450℃ through LF furnace heat compensation. Based on the semi-steel C content of 3.0%, the semi-steel heat compensation temperature is increased by 6℃ for every 0.1% decrease in the C content of the semi-steel.

[0021] Furthermore, in step 5, depending on the requirements of the steel grade being smelted, the molten steel can be alloyed and then refined in an external refining equipment before being cast on a continuous casting machine.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] This invention avoids pre-treatment and desulfurization of vanadium-containing molten iron upon arrival at the plant, as well as pre-treatment and desulfurization of semi-steel, thus preventing vanadium slag loss caused by pre-treatment slag removal. The vanadium extraction converter employs a deep vanadium extraction process, resulting in high cooling intensity, long oxygen supply time, and low carbon content and residual vanadium in the semi-steel, ensuring vanadium oxidation and recovery rates and maximizing vanadium resource utilization. The semi-steel ladle uses a refined steel ladle, avoiding the time-consuming ladle-turning process and ensuring the safety of LF furnace heating. The semi-steel undergoes deep desulfurization simultaneously with LF heat compensation, achieving good desulfurization effect and low cost. The LF furnace heat compensation temperature can be adjusted according to the semi-steel temperature and carbon content, resolving the impact of carbon content fluctuations on the quality stability of the semi-steel and creating favorable conditions for subsequent converter steelmaking. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] A smelting process for heat compensation and deep desulfurization of semi-steel includes the following steps:

[0027] Step 1) Vanadium-containing molten iron with C≥3.6% and V≥0.15% is added to a vanadium extraction converter for vanadium extraction smelting, and a coolant is added at a rate of 30-120 kg / t of steel. The oxygen supply time is extended to 4-8 minutes, and a semi-steel with a C content of 2.5%-3.0%, residual V≤0.03%, and a temperature between 1330℃ and 1400℃ is finally obtained.

[0028] Step 2) Install a slag remover at the LF furnace refining station. After the semi-steel is discharged, hoist the semi-steel ladle into the ladle car at the LF furnace refining station to remove the vanadium slag that enters the semi-steel ladle during the vanadium extraction process for recycling. The semi-steel ladle uses a refining ladle.

[0029] Step 3) After slag removal, argon is blown, temperature is measured, and samples are taken at the LF furnace processing station. The semi-steel is then heated by electricity, and a temperature between 1450℃ and 1550℃ is obtained through thermal compensation. During the thermal compensation process, a semi-steel temperature of 1450℃ is used as a baseline. If the temperature is lower than 1450℃, the LF furnace thermal compensation raises the semi-steel temperature to 1450℃. With a carbon content of 3.0% as a baseline, for every 0.1% decrease in carbon content, the semi-steel thermal compensation temperature increases by 6℃.

[0030] Step 4) While compensating for the LF furnace heat, lime and fluorite are added for desulfurization, reducing the sulfur content in the semi-steel to 0.010%–0.040%.

[0031] Step 5) The semi-steel obtained in Step 4 is added to the steelmaking converter. Lime and raw dolomite are added to the molten steel in the converter for blowing to obtain qualified molten steel. After alloying, the steel is treated at the argon blowing station and then cast on the continuous casting machine.

[0032] Example 1:

[0033] Step 1) A certain factory's 60-ton converter smelts vanadium-titanium magnetite ore into vanadium-containing molten iron through a blast furnace. After the molten iron is transported to the steel plant via a molten iron ladle, it does not undergo pre-treatment for desulfurization, thus avoiding the loss of vanadium slag and the temperature drop during the process caused by slag removal during pre-treatment.

[0034] 3.2t of vanadium-containing pig iron blocks and 57t of vanadium-containing molten iron were charged into the vanadium extraction converter. The mass fraction of each element in the vanadium-containing molten iron is shown in Table 1. The remainder consists of iron and unavoidable impurities.

[0035] Oxygen is then blown into the converter through an oxygen lance for smelting. After blowing oxygen for 1 minute, a coolant is added. The coolant is iron oxide balls, and the amount added is 35 kg / t of steel.

[0036] Oxygen supply intensity is 2.8 Nm 3 The process was controlled by a t·min control. Due to the high cooling intensity and long low-temperature cooling time of the molten pool, the carbon-oxygen reaction was inhibited, and the oxygen supply time was extended. At 5 min 19 s of blowing, the furnace flame was observed; the carbon flame was initially visible. The oxygen lance was immediately lifted, and the temperature was measured at 1356℃. After the semi-steel was produced, samples were taken for testing, yielding semi-steel with a C content of 2.53% and a residual V content of 0.029%. The specific composition of the semi-steel and V slag is shown in Table 2. By using a vanadium-extraction converter for deep vanadium extraction, enhancing the cooling intensity, and extending the oxygen supply time, the V oxidation rate of the V-containing molten iron reached 88.4%, maximizing the utilization of vanadium resources.

[0037] Step 2) After tapping the semi-steel, the semi-steel ladle is hoisted into the ladle car of the LF furnace refining station by an overhead crane. The semi-steel ladle uses a refined steel ladle. After tapping, it can be directly hoisted into the refining platform for processing in the LF furnace without the need to transfer the ladle or break the steel, which reduces waste and saves process time. In addition, the refined steel ladle ensures the safety of the LF furnace for heating and desulfurization.

[0038] Step 3) After the vanadium slag is removed, argon is blown and the temperature is measured at the LF furnace treatment station. The semi-steel molten steel is heated by high-power submerged arc heating. With the semi-steel carbon content of 3.0% as the benchmark, the semi-steel heat compensation temperature increases by 6°C for every 0.1% decrease in the semi-steel carbon content. The semi-steel carbon content of this furnace steel is 2.53%, so the corresponding heat compensation temperature increases by 28°C. Finally, the semi-steel temperature is compensated to 1478°C through LF furnace heat compensation. Even if the semi-steel carbon content is low, the heat compensation process increases the semi-steel temperature, ensuring that the thermal balance during converter steelmaking is not affected.

[0039] Step 4) While the LF furnace is undergoing thermal compensation, lime and fluorite are added to rapidly form white slag for desulfurization. In this example, the steel grade being smelted is 20CrMoH gear steel. According to the requirement that S ≤ 0.020% for steel grades, the S in the semi-steel is reduced to 0.015%. Since the iron oxide content in the semi-steel is low, the amount of slag fed into the converter is small, which is conducive to rapid slag formation in the LF furnace, resulting in high desulfurization efficiency and low cost.

[0040] Step 5: The processed semi-steel is hoisted from the refining ladle car onto the transfer ladle car, which then enters the converter bay. After adding 10.8 tons of scrap steel to the steelmaking converter, the semi-steel is added. 15 kg / t of active lime and 15 kg / t of raw dolomite are added to the molten steel in the converter to obtain qualified molten steel. After alloying, the steel is stirred by argon blowing and then subjected to RH vacuum treatment for ladle refining before being cast into a continuous casting machine. Because the semi-steel has a low carbon content after thermal compensation, the corresponding temperature increase and low sulfur content result in stable semi-steel quality. This avoids the strong oxidizing properties of the molten steel caused by over-blowing, providing favorable conditions for the steelmaking converter.

[0041] Comparative Example 1:

[0042] A certain factory's 60-ton converter produces vanadium-containing molten iron from vanadium-titanium magnetite smelted in a blast furnace. The molten iron is then transported to a steel plant via a ladle and subjected to vanadium extraction and steelmaking according to the process flow of vanadium-containing molten iron → pretreatment desulfurization → converter vanadium extraction → semi-steel converter steelmaking.

[0043] After the vanadium-containing molten iron ladle enters the plant, it is hoisted into the desulfurization station and desulfurized using the KR method. The steel grade being smelted is HRB400E. According to the requirement that the S content of the steel grade is ≤0.040%, the S content of the semi-steel is reduced to 0.035%. After desulfurization, slag removal is necessary. Since the vanadium slag is removed from the desulfurization slag, some vanadium slag is lost.

[0044] 1.2t of vanadium-containing pig iron blocks and 57t of vanadium-containing molten iron were charged into the vanadium extraction converter. The mass fraction of each element in the vanadium-containing molten iron is shown in Table 1. The remainder consists of iron and unavoidable impurities.

[0045] Oxygen is blown into the converter through an oxygen lance for smelting. After blowing oxygen for 1 minute, a coolant is added. The coolant is iron oxide pellets, and the amount added is 12 kg / t of steel.

[0046] Oxygen supply intensity is 2.8 Nm 3 / t.min control, due to the low cooling intensity of the process, the short low-temperature cooling time of the molten pool, the rapid temperature rise, the fast carbon-oxygen reaction, and the shortened oxygen supply time, when blowing for 3 minutes and 40 seconds, observe the furnace mouth flame. When the carbon flame is initially raised, immediately lift the oxygen lance and measure the temperature at 1362℃. After the semi-steel is produced, take a sample for testing and obtain a semi-steel with a C content of 3.67% and a residual V content of 0.052%. The specific composition of the semi-steel and V slag is shown in Table 2.

[0047] To ensure that the carbon content in the semi-steel is not too low, and to avoid insufficient heat in the subsequent steelmaking converter, the oxidation time of V was shortened, and the oxidation rate of V element only reached 79.2%.

[0048] To avoid insufficient heat in the steelmaking converter when tapping semi-steel, 1.6 kg / t of Fe-Si alloy is added to the molten iron ladle. After tapping, the semi-steel ladle is hoisted from the molten iron pit to the converter platform by an overhead crane. The semi-steel ladle is filled with molten iron, and the semi-steel is also contained in the molten iron ladle. The process of setting up the ladle and hoisting it back and forth takes a long time. The semi-steel is cold and easily sticks to the molten iron ladle. Adding Fe-Si alloy increases costs.

[0049] After adding 3.2 tons of scrap steel to the steelmaking converter, the semi-steel is added. Then, 15 kg / t of active lime, 12 kg / t of lightly calcined dolomite, 3.5 kg / t of slag-reducing agent, and 3.5 kg / t of carbonaceous exothermic agent are added to the molten steel to obtain qualified molten steel. After alloying, the steel is stirred with argon blowing, and the temperature and composition are finely adjusted before being cast into a continuous casting machine. Due to insufficient heat in the semi-steel steelmaking converter, slag formation is slow, dephosphorization and sulfur removal are poor, and over-blowing and strong oxidizing properties of the molten steel occur at the end of the steelmaking process, resulting in high-quality, low-cost molten steel. Even with the addition of carbonaceous exothermic agent, its limited thermal efficiency has little effect on improving the overall heat of the steelmaking converter.

[0050] Example 2:

[0051] Step 1) A certain factory's 120-ton converter smelts vanadium-titanium magnetite ore into vanadium-containing molten iron through a blast furnace. After the molten iron is transported to the steel plant via a molten iron ladle, it does not undergo pretreatment for desulfurization, thus avoiding the loss of vanadium slag and the loss of temperature drop during the process caused by slag removal during pretreatment.

[0052] 4.5t of light scrap steel and 125t of vanadium-containing molten iron were charged into the vanadium-containing converter. The mass fraction of each element in the vanadium-containing molten iron is shown in Table 1. The remainder consists of iron and unavoidable impurities.

[0053] Oxygen is blown into the converter through an oxygen lance for smelting. After blowing oxygen for 1 minute, a coolant is added. The coolant consists of iron oxide pellets and titanium-containing ore pellets. The amount of iron oxide pellets added is 50 kg / t of steel, and the amount of vanadium-titanium ore added is 15 kg / t of steel.

[0054] Oxygen supply intensity is 2.9 Nm 3 The process was controlled at / t.min. Due to the high cooling intensity and long low-temperature cooling time of the molten pool, the carbon-oxygen reaction was inhibited, and the oxygen supply time was extended. At 7 minutes and 9 seconds of blowing, the furnace flame was observed; the carbon flame was initially visible. The oxygen lance was immediately lifted, and the temperature was measured at 1342℃. After the semi-steel was produced, samples were taken for testing, yielding semi-steel with a C content of 2.78% and a residual V content of 0.025%. The specific composition of the semi-steel and V slag is shown in Table 2. By using a vanadium-extraction converter for deep vanadium extraction, enhancing the cooling intensity, and extending the oxygen supply time, the V oxidation rate of the V-containing molten iron reached 92.2%, maximizing the utilization of vanadium resources.

[0055] Step 2) After tapping the semi-steel, the semi-steel ladle is hoisted into the ladle car of the LF furnace refining station by an overhead crane. The semi-steel ladle uses a refined steel ladle. After tapping, it can be directly hoisted into the refining platform for processing in the LF furnace without the need to transfer the ladle or break the steel, which reduces waste and saves process time. In addition, the refined steel ladle ensures the safety of the LF furnace for heating and desulfurization.

[0056] A slag remover is installed at the LF furnace refining station to remove vanadium slag that enters the semi-steel ladle during vanadium extraction for recycling, thus minimizing vanadium slag waste.

[0057] Step 3) After the vanadium slag is removed, argon is blown and the temperature is measured at the LF furnace treatment station. The semi-steel molten steel is heated by high-power submerged arc heating. Based on a semi-steel carbon content of 3.0%, the semi-steel heat compensation temperature increases by 6°C for every 0.1% decrease in the semi-steel carbon content. The semi-steel carbon content of this furnace steel is 2.78%, so the corresponding heat compensation temperature increases by 13°C. Finally, the semi-steel temperature is compensated to 1463°C through LF furnace heat compensation. Even if the semi-steel carbon content is low, the heat compensation process increases the semi-steel temperature, ensuring that the thermal balance during converter steelmaking is not affected.

[0058] Step 4) While the LF furnace is undergoing thermal compensation, lime and fluorite are added to rapidly form white slag for desulfurization. In this example, the steel grade being smelted is HRB400E. According to the requirement that the S content of the steel grade is ≤0.040%, the S content of the semi-steel is reduced to 0.035%. Since the iron oxide content of the semi-steel is low, the amount of slag fed into the converter is small, which is conducive to rapid slag formation in the LF furnace, resulting in high desulfurization efficiency and low cost.

[0059] Step 5) The processed semi-steel is hoisted from the refining ladle car onto the transfer ladle car, which then drives into the converter bay. After adding 10.8 tons of scrap steel to the steelmaking converter, the semi-steel is added. 15 kg / t of active lime, 15 kg / t of raw dolomite, and a small amount of slagging agent are added to the molten steel in the converter to obtain qualified molten steel. After alloying, the steel is treated at the argon blowing station before being cast into a continuous casting machine. Because the semi-steel has a low carbon content after thermal compensation, the corresponding temperature increase and low sulfur content result in stable semi-steel quality. This avoids the strong oxidizing properties of the molten steel caused by over-blowing, providing favorable conditions for the steelmaking converter.

[0060] Comparative Example 2:

[0061] A certain factory's 120-ton converter produces vanadium-containing molten iron from vanadium-titanium magnetite smelted in a blast furnace. The molten iron is then transported to a steel plant via a ladle and subjected to vanadium extraction and steelmaking according to the process flow of vanadium-containing molten iron → vanadium extraction in converter → pre-treatment and desulfurization of semi-steel → steelmaking in converter of semi-steel.

[0062] 3.2t of light scrap steel and 125t of vanadium-containing molten iron were charged into the vanadium-containing converter. The mass fraction of each element in the vanadium-containing molten iron is shown in Table 1. The remainder consists of iron and unavoidable impurities.

[0063] Oxygen is blown into the converter through an oxygen lance for smelting. After blowing oxygen for 1 minute, a coolant is added. The coolant consists of iron oxide pellets and titanium-containing ore pellets. The amount of iron oxide pellets added is 10 kg / t of steel, and the amount of titanium-containing ore added is 5 kg / t of steel.

[0064] Oxygen supply intensity is 2.9 Nm 3 / t.min control, due to the low cooling intensity of the process, the short low-temperature cooling time of the molten pool, the rapid temperature rise, the fast carbon-oxygen reaction, and the shortened oxygen supply time, when blowing for 4min32s, observe the furnace mouth flame. When the carbon flame is initially raised, immediately lift the oxygen lance and measure the temperature at 1389℃. After the semi-steel is produced, take a sample for testing and obtain a semi-steel with a C content of 3.12% and a residual V content of 0.05%. The specific composition of the semi-steel and V slag is shown in Table 2.

[0065] To ensure that the carbon content in the semi-steel is not too low, and to avoid insufficient heat in the subsequent steelmaking converter, the oxidation time of V was shortened, and the oxidation rate of V element only reached 83.9%.

[0066] To prevent insufficient heat in the steelmaking converter when tapping semi-steel, 1.6 kg / t of Fe-Si alloy is added to the molten iron ladle. After tapping, the ladle is lifted from the molten iron pit onto the converter platform by an overhead crane and then to the desulfurization station. Because the semi-steel is stored in a molten iron ladle, the ladle-setting and reciprocating lifting processes are time-consuming. Furthermore, the low temperature of the semi-steel makes it prone to sticking to the molten iron ladle. Adding the Fe-Si alloy increases costs.

[0067] After the semi-steel is tapped, the molten iron ladle is hoisted into the desulfurization station and desulfurized using the KR method. The steel grade being smelted is HRB400E. According to the requirement that the S content of the steel grade is ≤0.040%, the S content of the semi-steel is reduced to 0.035%. After desulfurization, slag removal is necessary. Since vanadium slag is removed from the desulfurization slag, some vanadium slag is lost.

[0068] After adding 2.8 tons of scrap steel to the steelmaking converter, the semi-steel is added. 15 kg / t of active lime, 15 kg / t of raw dolomite, 3.5 kg / t of slag-reducing agent, and 3.5 kg / t of carbonaceous exothermic agent are added to the molten steel in the converter to obtain qualified molten steel. After alloying, the steel is treated at the argon blowing station before being cast into a continuous casting machine. Due to insufficient heat in the semi-steel steelmaking converter, slag formation is slow during the steelmaking process, resulting in poor P and S removal. Over-blowing at the end of the steelmaking process and strong oxidizing properties of the molten steel lead to high-quality, low-cost molten steel. Even with the addition of carbonaceous exothermic agent, its limited thermal efficiency has little effect on improving the overall heat of the steelmaking converter.

[0069] Table 1 shows the main elemental composition of vanadium-containing molten iron in the example:

[0070]

[0071] Table 2 shows the main components of the semi-steel and vanadium slag in the example:

[0072]

[0073] Regarding the vanadium content in semi-steel, because this invention employs a deep vanadium extraction process, under essentially the same molten iron conditions, the oxidation rate of vanadium obtained using this invention is approximately 10% higher than that of the comparative example, and the vanadium slag obtained by the method of this invention has a higher grade.

[0074] Furthermore, comparing Examples 1 and 2 with Comparative Examples 1 and 2, it can be seen that, according to the process flow of the present invention, when the C of the semi-steel is controlled at a low level, the temperature of the semi-steel is increased accordingly through LF furnace heat compensation, which can obtain a better vanadium extraction effect and a more stable semi-steel quality.

[0075] Whether comparing Example 1 with Comparative Example 1 or Example 2 with Comparative Example 2, the smelting process of deep desulfurization of semi-steel while undergoing LF furnace heat compensation is superior to the desulfurization effect of hot metal pretreatment or semi-steel pretreatment; it avoids vanadium loss caused by desulfurization slag removal; it avoids the problems of long process time and large temperature drop caused by ladle rewinding; and the semi-steel smelting does not require the addition of a temperature-raising agent, which greatly reduces costs.

Claims

1. A smelting process for thermal compensation and deep desulfurization of semi-steel, characterized in that, Includes the following steps: Step 1) Vanadium-containing molten iron with C≥3.6% and V≥0.15% is added to a vanadium extraction converter for vanadium extraction smelting, and a coolant is added at a rate of 30-120 kg / t of steel. The oxygen supply time is extended to 4-8 min, and a semi-steel with a C content of 2.2%-3.0%, residual V≤0.03%, and a temperature between 1330℃ and 1400℃ is finally obtained. Step 2) Set up a slag remover at the LF furnace refining station. After the semi-steel is discharged, lift the semi-steel ladle into the ladle car at the LF furnace refining station to remove the vanadium slag that enters the semi-steel ladle when the vanadium is discharged into the semi-steel for recycling. Step 3) After slag removal, argon is blown, temperature is measured, and samples are taken at the LF furnace processing station. The semi-steel is heated by electricity, and the temperature of the semi-steel is obtained between 1450℃ and 1550℃ through thermal compensation. When implementing the heat compensation process, a semi-steel temperature of 1450℃ is used as the baseline. If the temperature is lower than 1450℃, the semi-steel temperature is raised to 1450℃ through LF furnace heat compensation. Based on a semi-steel carbon content of 3.0%, for every 0.1% decrease in the carbon content of the semi-steel, the heat compensation temperature of the semi-steel is increased by 6℃. Step 4) Desulfurization is carried out simultaneously with thermal compensation in the LF furnace to reduce sulfur content in the semi-steel to 0.010%–0.040%. Step 5) The semi-steel obtained in Step 4 is added to the steelmaking converter. Lime and raw dolomite are added to the molten steel in the converter for blowing to obtain qualified molten steel. After alloying, the steel is treated at the argon blowing station and then cast on the continuous casting machine.

2. The smelting process for heat compensation and deep desulfurization of semi-steel according to claim 1, characterized in that: In step 1), the coolant is one or a combination of several of the following: scrap steel, vanadium-containing pig iron blocks, iron oxide pellets, vanadium-titanium pellets, and ore.

3. The smelting process for heat compensation and deep desulfurization of semi-steel according to claim 1, characterized in that: The semi-steel tank in step 2) uses a refined steel ladle.

4. The smelting process for thermal compensation and deep desulfurization of semi-steel according to claim 1, characterized in that: In step 5, depending on the requirements of the steel grade being smelted, the molten steel can be alloyed and then refined in an external refining equipment before being cast on a continuous casting machine.

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