Rheocasting system for ultra-low carbon steel

Abstract

The utility model discloses a kind of RH smelting systems of ultra-low carbon steel, including sequentially interconnected ladle and vacuum tank, the vacuum tank is connected with vacuum pipeline, the outlet end of vacuum pipeline is connected with pretreatment device, waste gas is discharged after being handled by pretreatment device, vacuum tank is located above ladle, vacuum tank is located above the ladle, vacuum tank is provided with riser, downcomer, one end of riser and one end of downcomer respectively extend into the ladle, another end is respectively communicated with the vacuum cavity of vacuum tank, three-way loop pipe is fixedly connected in the position of riser, vacuum sealing cavity is arranged in the position of downcomer, vacuum sealing cavity is arranged in the periphery of downcomer, riser, downcomer uses asymmetric structure arrangement, wherein, the length of riser is greater than the length of downcomer. The utility model is suitable for controlling gas inclusion ([N], [O]) in steel and preventing carbonization, nitrogen absorption pure steel production process.

Description

Technical Field

[0001] This utility model belongs to the field of iron and steel metallurgy technology, specifically relating to an RH smelting system for ultra-low carbon steel. Background Technology

[0002] The RH process is an important ladle refining method with a series of advantages, including short processing cycle, large production capacity, good refining effect, and ease of operation, and has been widely used in steelmaking production. To date, the RH process has evolved from a single degassing device into a multi-functional ladle refining system that incorporates vacuum decarburization, oxygen blowing decarburization, powder injection desulfurization, temperature compensation, and uniform temperature and composition. Moreover, with the advancement of technology and the expansion of refining functions, it has shown significant advantages in the production of ultra-low carbon steel. It is an indispensable out-of-furnace treatment device in modern steel plants. Ensuring the utilization rate of RH equipment and improving the processing capacity and ratio of RH are urgent issues to be addressed. Existing technologies still face the following technical bottlenecks in the RH refining of ultra-low carbon steel: insufficient decarburization precision; traditional natural decarburization is difficult to stably reduce the carbon content to below 200ppm; forced oxygen blowing is prone to causing excessive CO reaction, resulting in steel splashing and refractory loss in the vacuum tank; conflict in composition control: improper timing of deoxidation alloying can easily cause secondary oxidation or carbon increase (such as the carbon content rebounding due to the later addition of coolant); uncontrollable element burn-off; lack of quantitative compensation models for the burn-off of elements such as manganese and silicon during the top lance oxygen blowing process; and low composition hit rate.

[0003] In existing technologies, the coordinated control of top-lance oxygen blowing parameters (flow rate, timing) with circulating gas and vacuum degree lacks a systematic procedure, resulting in poor production stability of ultra-low carbon steel and a pass rate of less than 80%.

[0004] In view of the above factors, an RH smelting system for ultra-low carbon steel is provided, which is suitable for the production process of pure steel that controls gas inclusions ([N], [O]) in steel and prevents carbon increase and nitrogen absorption. Utility Model Content

[0005] The purpose of this invention is to provide an RH smelting system for ultra-low carbon steel to solve the problems mentioned in the background art.

[0006] The purpose of this utility model is achieved through the following technical solution: an RH smelting system for ultra-low carbon steel, comprising a ladle furnace and a vacuum tank connected in sequence, wherein the vacuum tank is connected to a vacuum pipeline, and the outlet end of the vacuum pipeline is connected to a pretreatment device, and the waste gas treated by the pretreatment device is discharged externally.

[0007] The vacuum trough is located above the ladle furnace. The vacuum trough is equipped with an ascending pipe and a descending pipe. One end of the ascending pipe and one end of the descending pipe extend into the ladle furnace, and the other end is connected to the vacuum chamber of the vacuum trough.

[0008] A three-way circulation pipe is fixedly connected to the location of the riser pipe, and a vacuum sealing cavity is provided at the location of the downcomer pipe, with the vacuum sealing cavity located on the periphery of the downcomer pipe.

[0009] Furthermore, the riser and downcomer are arranged in an asymmetrical structure, wherein the length of the riser is greater than the length of the downcomer.

[0010] Furthermore, the vacuum sealing cavity and the downcomer are integrally formed to create a vacuum channel between the vacuum sealing cavity and the downcomer;

[0011] A spaced support block is provided between the vacuum sealing cavity and the downcomer tube, and the support block is positioned above the molten steel.

[0012] Furthermore, the vacuum sealing cavity and the downcomer are made of non-fired magnesia spinel bricks, and the support blocks are made of non-fired magnesia spinel bricks and are evenly distributed along the circumference of the downcomer.

[0013] Furthermore, a top gun is provided on the top of the vacuum tank, and the top gun is an MFB top gun.

[0014] Furthermore, the flow rate of the MFB top gun is ≤1800 Nm³. 3 / h, vacuum degree <0.27kPa.

[0015] An application method for an RH smelting system for ultra-low carbon steel includes the following steps:

[0016] Equipment pre-inspection: Confirm the accuracy of the temperature and oxygen determination equipment, the start-up time of pump 1B ≤ 4 minutes, the maximum vacuum degree ≤ 0.10 kPa, and the immersion tube orifice diameter = 600 mm; Cleaning operation: Before smelting, clean the vacuum tank with two heats of low-carbon aluminum killed steel to remove cold steel from the hot bending tube; Ladle management: Cast low-carbon aluminum killed steel in the first two ladles to ensure that there is no residual steel residue at the ladle mouth / bottom;

[0017] Precise control of alloying: Early stage of decarburization: add low-carbon ferromanganese (control [Mn] ≤ 0.20%) and phosphorus-sulfur adjuster; Deoxidation constraint: aluminum is strictly prohibited during decarburization; after decarburization, add aluminum and circulate for 2 minutes before adding other alloys or ≤ 800 kg of coolant; Aluminum compensation calculation: the aluminum content in FeTi must be taken into account when adding aluminum;

[0018] The application methods of the RH smelting system include: smelting of ultra-low carbon aluminum-killed steel ([C] target ≤150ppm)

[0019] Step 1: Preprocessing

[0020] The tank was cleaned with two furnaces of SPHC steel (low carbon aluminum killed) to remove the cold steel from the vacuum tank. The start-up time of pump 1B was confirmed to be 3.8 minutes, the diameter of the impregnation tube was 602 mm, and the temperature measuring gun error was ±2℃.

[0021] Step 2: Top Gun Decision

[0022] Open the MFB top gun gas valve (gas flow rate 30-50 m³ / h), ignite the gas, and gradually adjust the gas opening to a gas flow rate of 100-200 m³ / h. Adjust the oxygen flow rate to 100-150 m³ / h. Place the gun below the indoor baking position below the waiting point for blowing.

[0023] The initial state is: [O] = 380ppm, [C] = 350ppm, T = 1585℃ (target T~R~ = 1600℃). [O] low, [C] high, T low → execute top gun decarburization + heating.

[0024] Step 3: Forced decarbonization

[0025] A three-way circulation pipe is fixedly connected to the riser pipe, allowing 1500 NL / min of circulation gas to be introduced, and 1750 Nm of oxygen is blown in by the MFB top lance. 3 / h, decarburization complete: [C] = 120ppm, vacuum degree 18kPa;

[0026] Step 4: Deoxidation and alloying

[0027] In step 3 above, after a 2-minute delay, aluminum is added for deoxidation. The aluminum replenishment is calculated according to the formula G = 1.0 × Q (Q = 15 Nm). 3 →Add 15kg of aluminum), continuously circulate for 2 minutes, then add electrolytic manganese to compensate for manganese loss (oxygen blowing rate 200Nm). 3 →Manganese loss 0.016% →Replenish manganese 120kg);

[0028] Step 5: Chemical heating

[0029] Heating trigger conditions: ① Deoxidized steel: Start when the difference between the target temperature T~R~ and the actual temperature T~front~ is >10℃; ② Undeoxidized steel: Add Al / Si deoxidation first before heating.

[0030] ΔT ~ net ~ = 1605 - 1585 = 20℃ → Oxygen blowing rate Q = 20 × 10 = 200 Nm 3 The circulating gas flow rate was 1200 NL / min, the vacuum degree was 4.5 kPa, and the final temperature of the molten steel was 1608℃.

[0031] Step 6: Pure degassing*

[0032] The circulating gas flow rate was 2000 NL / min, the vacuum was 0.08 kPa, and the duration was 8 min. The final composition was: [C] = 135 ppm, [O] = 12 ppm, [Mn] = 0.35%, and the target was hit.

[0033] An application method for an RH smelting system for ultra-low carbon steel includes the following steps:

[0034] Equipment pre-inspection: Confirm the accuracy of the temperature and oxygen determination equipment, the start-up time of pump 1B ≤ 4 minutes, the maximum vacuum degree ≤ 0.10 kPa, and the immersion tube orifice diameter = 600 mm; Cleaning operation: Before smelting, clean the vacuum tank with two heats of low-carbon aluminum killed steel to remove cold steel from the hot bending tube; Ladle management: Cast low-carbon aluminum killed steel in the first two ladles to ensure that there is no residual steel residue at the ladle mouth / bottom;

[0035] Precise control of alloying: Early stage of decarburization: add low-carbon ferromanganese (control [Mn] ≤ 0.20%) and phosphorus-sulfur adjuster; Deoxidation constraint: aluminum is strictly prohibited during decarburization; after decarburization, add aluminum and circulate for 2 minutes before adding other alloys or ≤ 800 kg of coolant; Aluminum compensation calculation: the aluminum content in FeTi must be taken into account when adding aluminum;

[0036] The application methods of RH smelting systems also include: ultra-low carbon aluminum-silicon killed steel ([C] target ≤180ppm);

[0037] Step 1: Decision-making with the gun on the ground

[0038] Open the MFB top gun gas valve (gas flow rate 30-50 m³ / h), ignite the gas, and gradually adjust the gas opening to a gas flow rate of 100-200 m³ / h. Adjust the oxygen flow rate to 100-150 m³ / h. Place the gun below the indoor baking position below the waiting point for blowing.

[0039] The initial state is: [O] = 550ppm, [C] = 280ppm, T = 1590℃ (target T~R~ = 1605℃). According to the decision table: [O] high, [C] low, T low → execute natural decarbonization + top gun heating.

[0040] Step 2: Natural decarbonization

[0041] Three-way circulation pipe, circulating gas 2000NL / min, vacuum degree 0.25kPa, decarburization 15min → [C]=170ppm;

[0042] Step 3: Deoxygenate first, then raise the temperature

[0043] Fe-Si pre-deoxidation is added to prevent peroxidation; ΔT ~ net ~ = 1610 - 1590 = 20℃ → oxygen blowing rate Q = 200 Nm 3Add aluminum and silicon according to G = 0.75 × Q (add 150 kg of Al-Si alloy), and add silicon according to the burn-off table: [Si] = 0.18% → burn-off rate 0.015% → add 30 kg of silicon, the endpoint [C] = 175 ppm, T = 1607℃, [Si] = 0.22% meets the standard.

[0044] An application method for an RH smelting system for ultra-low carbon steel, with carbon content control accuracy of ±15ppm (original ±50ppm), manganese loss during heating process reduced by 35%, and [N] ≤25ppm and [O] ≤15ppm in steel.

[0045] The application method of an RH smelting system for ultra-low carbon steel is applicable to the production process of pure steel that controls gas inclusions ([N], [O]) in ultra-low carbon steel ([C] < 200ppm) and prevents carbon increase and nitrogen absorption.

[0046] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0047] This invention is applicable to the production process of pure steel that controls gas inclusions ([N], [O]) in steel and prevents carbon gain and nitrogen absorption.

[0048] This invention adds low-carbon ferromanganese (Mn ≤ 0.20%) and phosphorus-sulfur modifiers in the early stage of decarburization to constrain deoxidation. Aluminum is strictly prohibited during the decarburization process. After decarburization is completed, aluminum is added and the system is circulated for 2 minutes before adding other alloys or ≤ 800 kg of coolant. Aluminum compensation is calculated, and the aluminum content in FeTi must be taken into account when adding aluminum.

[0049] The device and method of this invention achieve carbon content control accuracy of ±15ppm (previously ±50ppm), and reduce manganese loss during the heating process by 35%. ③ [N] in steel is ≤25ppm, and [O] is ≤15ppm, ensuring a 30% extension of the refractory life in the vacuum tank. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the overall connection of this utility model;

[0051] Figure 2 This is a schematic diagram of the condenser connected in series according to this utility model;

[0052] Figure 3 This is a cross-sectional schematic diagram of the condenser of this utility model. Detailed Implementation

[0053] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0054] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0055] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0056] like Figure 1-3 As shown, an RH smelting system for ultra-low carbon steel includes a ladle furnace 1 and a vacuum tank 2 connected in sequence. The vacuum tank 2 is connected to a vacuum pipe 3, and the outlet end of the vacuum pipe 3 is connected to a pretreatment device 4. The waste gas treated by the pretreatment device 4 is discharged externally.

[0057] The vacuum tank 2 is located above the ladle furnace 1. The vacuum tank 2 is equipped with an ascending pipe 5 and a descending pipe 6. One end of the ascending pipe 5 and one end of the descending pipe 5 extend into the ladle furnace 1, and the other end is connected to the vacuum chamber of the vacuum tank 2.

[0058] A three-way circulation pipe 7 is fixedly connected to the position of the riser pipe 5, and a vacuum sealing cavity 8 is provided at the position of the downcomer pipe 6, with the vacuum sealing cavity 8 located on the periphery of the downcomer pipe 6.

[0059] To facilitate the adsorption of slag at the bottom during use, the riser pipe 5 and the downcomer pipe 6 are arranged in an asymmetrical structure, wherein the length of the riser pipe 5 is greater than the length of the downcomer pipe 6.

[0060] In order to facilitate the isolation of air flow by setting up a vacuum sealing cavity 8 during use, the vacuum sealing cavity 8 and the downcomer 5 are integrally formed to form a vacuum channel between the vacuum sealing cavity 8 and the downcomer 5;

[0061] A spaced support block is provided between the vacuum sealing cavity and the downcomer 5, and the support block is located above the molten steel.

[0062] To enhance durability during use, the riser 5, vacuum sealing cavity, and downcomer 6 are made of non-fired magnesia spinel bricks. The support blocks, also made of non-fired magnesia spinel bricks, are evenly distributed around the circumference of the downcomer 6. The riser 5 and downcomer 6 have different inner diameters, with the inner diameter of the downcomer 6 being larger than that of the riser 5.

[0063] In order to facilitate the cooling of exhaust gas during use and to adsorb the trace dust contained in the exhaust gas by water, the pretreatment device 4 includes a gas cooler 9 and a condenser 10 connected in series, and three condensers 10 are provided.

[0064] Gas cooler 9 is a prior art disclosure. The gas cooler is a ventilation tank with an outer wall composed of cooling water pipes. When the exhaust gas passes through the tank, the flow rate drops sharply. Dust is deposited in the ash discharge pipe at the bottom of the tank under the action of gravity, while the cleaner gas exchanges heat with the water-cooled pipe wall, thereby cooling the exhaust gas.

[0065] At least two stages of steam jet pumps are connected in series with the steam jet pump installed on the adjacent condenser 10 at the connection position between the vacuum pipeline 3 and the gas cooler 9.

[0066] A steam jet pump is installed on the adjacent condenser 10. Exhaust gas and steam enter from the bottom of the tank and then exit from the top. During the rising process, the gas comes into full contact with the water curtain sprayed from the water spray nozzle, which cools the exhaust gas. The trace dust contained in the exhaust gas is adsorbed by the water, while the steam is cooled and turned into water before being discharged.

[0067] The condenser 10 consists of a ventilated tank and a spray layer distributed in the upper and middle parts of the tank. The spray layer includes several spray pipes arranged at intervals, and nozzles are provided on the spray pipes. The spray layer is connected to an external pipeline and sprays spray liquid by pumping.

[0068] The top of the vacuum tank 2 is provided with a top gun 11, which is an MFB top gun;

[0069] The MFB top gun flow rate is ≤1800 Nm. 3 / h, vacuum degree <0.27kPa.

[0070] An application method for an RH smelting system for ultra-low carbon steel includes the following steps:

[0071] Equipment pre-inspection: Confirm the accuracy of the temperature and oxygen determination equipment, the start-up time of pump 1B ≤ 4 minutes, the maximum vacuum degree ≤ 0.10 kPa, and the immersion tube orifice diameter = 600 mm; Cleaning operation: Before smelting, clean the vacuum tank with two heats of low-carbon aluminum killed steel to remove cold steel from the hot bending tube; Ladle management: Cast low-carbon aluminum killed steel in the first two ladles to ensure that there is no residual steel residue at the ladle mouth / bottom;

[0072] Precise control of alloying: Early stage of decarburization: add low-carbon ferromanganese (control [Mn] ≤ 0.20%) and phosphorus-sulfur adjuster; Deoxidation constraint: aluminum is strictly prohibited during decarburization; after decarburization, add aluminum and circulate for 2 minutes before adding other alloys or ≤ 800 kg of coolant; Aluminum compensation calculation: the aluminum content in FeTi must be taken into account when adding aluminum;

[0073] The application methods of the RH smelting system include: smelting of ultra-low carbon aluminum-killed steel ([C] target ≤150ppm)

[0074] Step 1: Preprocessing

[0075] The tank was cleaned with two furnaces of SPHC steel (low carbon aluminum killed) to remove the cold steel from the vacuum tank. The start-up time of pump 1B was confirmed to be 3.8 minutes, the diameter of the impregnation tube was 602 mm, and the temperature measuring gun error was ±2℃.

[0076] Step 2: Top Gun Decision

[0077] Open the MFB top gun gas valve (gas flow rate 30-50 m³ / h), ignite the gas, and gradually adjust the gas opening to a gas flow rate of 100-200 m³ / h. Adjust the oxygen flow rate to 100-150 m³ / h. Place the gun below the indoor baking position below the waiting point for blowing.

[0078] The initial state is: [O] = 380ppm, [C] = 350ppm, T = 1585℃ (target T~R~ = 1600℃). [O] low, [C] high, T low → execute top gun decarburization + heating.

[0079] Step 3: Forced decarbonization

[0080] A three-way circulation pipe is fixedly connected to the riser pipe, allowing 1500 NL / min of circulation gas to be introduced, and 1750 Nm of oxygen is blown in by the MFB top lance. 3 / h, decarburization complete: [C] = 120ppm, vacuum degree 18kPa;

[0081] Step 4: Deoxidation and alloying

[0082] In step 3 above, after a 2-minute delay, aluminum is added for deoxidation. The aluminum replenishment is calculated according to the formula G = 1.0 × Q (Q = 15 Nm). 3→Add 15kg of aluminum), continuously circulate for 2 minutes, then add electrolytic manganese to compensate for manganese loss (oxygen blowing rate 200Nm). 3 →Manganese loss 0.016% →Replenish manganese 120kg);

[0083] Step 5: Chemical heating

[0084] Heating trigger conditions: ① Deoxidized steel: Start when the difference between the target temperature T~R~ and the actual temperature T~front~ is >10℃; ② Undeoxidized steel: Add Al / Si deoxidation first before heating.

[0085] ΔT ~ net ~ = 1605 - 1585 = 20℃ → Oxygen blowing rate Q = 20 × 10 = 200 Nm 3 The circulating gas flow rate was 1200 NL / min, the vacuum degree was 4.5 kPa, and the final temperature of the molten steel was 1608℃.

[0086] Step 6: Pure degassing

[0087] The circulating gas flow rate was 2000 NL / min, the vacuum was 0.08 kPa, and the duration was 8 min. The final composition was: [C] = 135 ppm, [O] = 12 ppm, [Mn] = 0.35%, and the target was hit.

[0088] Element burn-off compensation table

[0089]

[0090] Full-process timing control (RH-E mode)

[0091]

[0092]

[0093] Aluminum consumption calculation model:

[0094] Low carbon aluminum killed steel G = 1.0 × Q Medium and low carbon aluminum-silicon killed steel G = (0.7 - 0.8) × Q High-carbon aluminum-silicon killed steel G = 0.6 × Q

[0095] An application method for an RH smelting system for ultra-low carbon steel includes the following steps:

[0096] Equipment pre-inspection: Confirm the accuracy of the temperature and oxygen determination equipment, the start-up time of pump 1B ≤ 4 minutes, the maximum vacuum degree ≤ 0.10 kPa, and the immersion tube orifice diameter = 600 mm; Cleaning operation: Before smelting, clean the vacuum tank with two heats of low-carbon aluminum killed steel to remove cold steel from the hot bending tube; Ladle management: Cast low-carbon aluminum killed steel in the first two ladles to ensure that there is no residual steel residue at the ladle mouth / bottom;

[0097] Precise control of alloying: Early stage of decarburization: add low-carbon ferromanganese (control [Mn] ≤ 0.20%) and phosphorus-sulfur adjuster; Deoxidation constraint: aluminum is strictly prohibited during decarburization; after decarburization, add aluminum and circulate for 2 minutes before adding other alloys or ≤ 800 kg of coolant; Aluminum compensation calculation: the aluminum content in FeTi must be taken into account when adding aluminum;

[0098] The application methods of RH smelting systems also include: ultra-low carbon aluminum-silicon killed steel ([C] target ≤180ppm);

[0099] Step 1: Decision-making with the gun on the ground

[0100] Open the MFB top gun gas valve (gas flow rate 30-50 m³ / h), ignite the gas, and gradually adjust the gas opening to a gas flow rate of 100-200 m³ / h. Adjust the oxygen flow rate to 100-150 m³ / h. Place the gun below the indoor baking position below the waiting point for blowing.

[0101] The initial state is: [O] = 550ppm, [C] = 280ppm, T = 1590℃ (target T~R~ = 1605℃). According to the decision table: [O] high, [C] low, T low → execute natural decarbonization + top gun heating.

[0102] Step 2: Natural decarbonization

[0103] Three-way circulation pipe, circulating gas 2000NL / min, vacuum degree 0.25kPa, decarburization 15min → [C]=170ppm;

[0104] Step 3: Deoxygenate first, then raise the temperature

[0105] Fe-Si pre-deoxidation is added to prevent peroxidation; ΔT ~ net ~ = 1610 - 1590 = 20℃ → oxygen blowing rate Q = 200 Nm 3 Add aluminum and silicon according to G = 0.75 × Q (add 150 kg of Al-Si alloy), and add silicon according to the burn-off table: [Si] = 0.18% → burn-off rate 0.015% → add 30 kg of silicon, the endpoint [C] = 175 ppm, T = 1607℃, [Si] = 0.22% meets the standard.

[0106] Element burn-off compensation table

[0107]

[0108] Full-process timing control (RH-E mode)

[0109]

[0110]

[0111] Aluminum consumption calculation model:

[0112] Low carbon aluminum killed steel G = 1.0 × Q Medium and low carbon aluminum-silicon killed steel G = (0.7 - 0.8) × Q High-carbon aluminum-silicon killed steel G = 0.6 × Q

[0113] An application method for an RH smelting system for ultra-low carbon steel, with carbon content control accuracy of ±15ppm (original ±50ppm), manganese loss during heating process reduced by 35%, and [N] ≤25ppm and [O] ≤15ppm in steel.

[0114] An application method for an RH smelting system for ultra-low carbon steel is applicable to the production process of pure steel that controls gas inclusions ([N], [O]) in ultra-low carbon steel ([C] < 200ppm) and prevents carbon increase and nitrogen absorption.

[0115] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0116] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. An RH smelting system for ultra-low carbon steel, characterized in that: It includes a ladle furnace (1) and a vacuum tank (2) connected in sequence. The vacuum tank (2) is connected to a vacuum pipe (3). The outlet end of the vacuum pipe (3) is connected to a pretreatment device (4). The waste gas treated by the pretreatment device (4) is discharged outside. The vacuum tank (2) is located above the ladle furnace (1). The vacuum tank (2) is equipped with an ascending pipe (5) and a descending pipe (6). One end of the ascending pipe (5) and one end of the descending pipe (6) extend into the ladle furnace (1), and the other end is connected to the vacuum chamber of the vacuum tank (2). The riser (5) is fixedly connected to a three-way circulation pipe (7), and the faller (6) is provided with a vacuum sealing cavity (8), which is located around the faller (6).

2. The RH smelting system for ultra-low carbon steel according to claim 1, characterized in that: The riser (5) and the faller (6) are arranged in an asymmetrical structure, wherein the length of the riser (5) is greater than the length of the faller (6).

3. The RH smelting system for ultra-low carbon steel according to claim 2, characterized in that: The vacuum sealing cavity (8) and the downcomer (6) are integrally formed to form a vacuum channel between the vacuum sealing cavity (8) and the downcomer (6); A spaced support block is provided between the vacuum sealing cavity and the downcomer (6), and the support block is located above the molten steel.

4. The RH smelting system for ultra-low carbon steel according to claim 3, characterized in that: The riser (5), vacuum sealing cavity and the fallr (6) are made of non-fired magnesia spinel bricks, and the support blocks are made of non-fired magnesia spinel bricks and are evenly distributed along the circumference of the fallr (6).

5. The RH smelting system for ultra-low carbon steel according to claim 4, characterized in that: The pretreatment device (4) includes gas coolers (9) and condensers (10) connected in series, and three condensers (10) are provided; The condenser (10) consists of a ventilated tank and a spray layer distributed in the upper and middle parts of the tank. The spray layer includes several spray pipes arranged at intervals, and nozzles are provided on the spray pipes. The spray layer is connected to an external pipeline and sprays spray liquid by pumping.

6. The RH smelting system for ultra-low carbon steel according to claim 5, characterized in that: The top of the vacuum tank (2) is provided with a top gun (11), and the top gun (11) is an MFB top gun; The MFB top gun has a flow rate of ≤1800 Nm³ / h and a vacuum degree of <0.27 kPa.

Images