Rhe vacuum refining system with submerged lance and powder injection desulphurization method

Abstract

The present application relates to a kind of RH vacuum refining system with immersion lance and powder spraying desulfurization method, belong to metallurgical technical field.System includes RH vacuum refining equipment, wire feeding equipment, wherein RH vacuum refining equipment is equipped with temperature measuring oxygen sampling equipment, immersion lance.Powder spraying desulfurization method is by adding desulfurizer in vacuum refining process to remove sulfur in molten steel.The present application combines powder spraying lance and RH immersion tube, and inserts into ladle molten steel surface after spraying powder, utilizes the stirring kinetic energy of molten steel circulating flow between ladle and vacuum chamber and low oxygen condition formed by vacuum treatment, makes desulfurizing powder quickly and evenly dispersed in molten steel and reacts with sulfur element in molten steel, avoids powder being taken away by vacuum pumping, improves desulfurizing powder utilization rate, energy efficiency reduces, realizes converter tapping after not through LF furnace directly into RH refining desulfurization, with shorter process flow, prepares low-sulfur clean steel, reduces steel production cost, realizes clean steel efficient desulfurization.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology and relates to an RH vacuum refining system with an immersion spray gun and a powder spraying desulfurization method. Background Technology

[0002] The RH refining process was originally designed by the German companies Ruhrstahl and Heraeus using vacuum refining equipment. Initially used for dehydrogenation, it has now been developed into a multi-functional refining system capable of removing carbon, sulfur, phosphorus, oxygen, and inclusions, as well as heating and adjusting composition.

[0003] RH desulfurization is a technology that removes sulfur from molten steel under vacuum by adding a desulfurizing agent. It is a key process in steelmaking, achieving deep desulfurization of molten steel through RH vacuum refining units. It is mainly applied to steel grades with strict sulfur content requirements, such as ultra-low carbon steel and high-grade silicon steel (e.g., requiring ω(S) ≤ 0.005%). Its core principle is to utilize the thermodynamic and kinetic conditions of the vacuum environment to promote the desulfurization reaction. The desulfurizing agent reacts chemically with the sulfur in the molten steel to generate sulfides (such as CaS), which are then transferred to the slag. This transfer of sulfur from the molten steel to the slag phase achieves desulfurization. Common desulfurizing agents include CaO-CaF slag systems, and their desulfurization reaction is as follows: (CaO) + [S] = (CaS) + [O] The existing technologies for adding desulfurizing agents are usually the input method and the powder injection method. The input method involves directly adding the desulfurizing agent from the vacuum silo into the vacuum tank without additional equipment, which is less expensive. However, the desulfurization rate is relatively low, the stability is poor, and the lower tank and immersion pipe are severely corroded. When a large amount of desulfurizing agent is added, the steel is prone to freezing, which affects the circulation of molten steel. On the other hand, the powder injection method has the advantages of high desulfurization rate and simple operation, but the equipment cost is higher.

[0004] The RH-IJ ladle powder injection method, developed by Nippon Steel's Oita Plant in 1985, involves inserting a nitrogen-blowing powder injection pipe deep within the molten steel, below the RH circulating riser pipe in the ladle. This allows the injected desulfurizing powder to remain in the molten steel for a longer period. The injected powder not only desulfurizes but also creates conditions for the heterogeneous nucleation of CO bubbles. The powder-carrying gas flow enhances the stirring effect at the bottom of the ladle and in the vacuum chamber, increasing the circulating flow rate of the molten steel. The RH-IJ method can achieve a desulfurization rate of 70%–90%, and the [S] content in the molten steel can be reduced to 10 × 10⁻⁶. -4 %.

[0005] The RH-PB vacuum chamber powder injection method, developed by Nippon Steel's Nagoya plant in 1987, utilizes oxygen nozzles at the bottom of the RH-OB vacuum chamber to blow powder into the molten steel through OB nozzles, achieving a desulfurization rate of 70%–90%. It can achieve deep desulfurization down to [S] < 5 × 10⁻⁶. -4 %, deep dephosphorization to [P] < 30 × 10 -4%.

[0006] Traditional top-lance powder injection methods include the RH-KPB process developed by Kawasaki Steel in 1986, the RH-MFB process developed by Nippon Steel in 1992, the RH-PTB process developed by Sumitomo Corporation's Wakayama Plant in 1994, and the MESID process developed by Belgium's SIDMAR Steel Plant in 1994. All of these methods involve injecting desulfurizing agents (such as CaO powder) into the molten steel through a water-cooled top-lance nozzle in a vacuum chamber. This significantly expands the reaction interface area between the powder particles and the molten steel, thereby accelerating the desulfurization reaction and reducing the sulfur content in the steel. When the desulfurizing agent dosage is 5 kg / t and 8 kg / t, the final sulfur content in the molten steel is 5 × 10⁻⁶, respectively. -4 % and 1.3×10 -4 %~2.9×10 -4 %.

[0007] The equipment characteristics of the top-lance powder spraying method are: ① no lance clogging problem; ② no refractory material consumption for the lance; ③ low consumption of powder carrier gas. However, when the desulfurizing agent is sprayed into the surface of molten steel in the RH vacuum tank through the top lance, the desulfurizing powder will float to the top slag because of the difference in density between the desulfurizing agent and the molten steel, and the desulfurization rate is only 50% to 80%.

[0008] The latest RH powder injection desulfurization technology is the RH circulating pipe powder injection method, in which desulfurization powder is injected into molten steel from the riser pipe of the RH circulating pipe, and enters the vacuum tank along with the lifting gas and the upward molten steel. Its characteristics are: long powder-carrying bubble path and good dispersion; direct contact between powder and molten steel, good kinetic conditions, and high mass transfer efficiency; minimal impact of powder on refractory materials, and recycling into the top slag.

[0009] When using RH vacuum desulfurization, existing powder injection technology has the following advantages: ① RH vacuum smelting can reduce the oxygen activity in molten steel; ② It isolates the steel from air, preventing oxidation; ③ It has a short processing cycle, large production capacity, and good refining effect. The disadvantages are that the desulfurization powder enters the vacuum tank with the air bubbles, accelerating the consumption of refractory material at the bottom of the tank; and some powder is drawn into the vacuum pipes with the airflow, corroding and clogging the pipes; the specific gravity of the desulfurizing agent is much lower than that of the molten steel, causing the powder to easily accumulate on the surface of the vacuum tank, affecting the powder utilization rate.

[0010] Given the various unresolved issues with existing RH desulfurization technology, steelmaking production still follows the process: pre-treatment desulfurization of molten hot metal → BOF (Boiling-Off Foil) → tapping with slag blocking via sliding plate → aluminum addition for deoxidation → LF (Fluorescent Leachate) slag formation for desulfurization and alloy coarse adjustment → RH degassing and alloy fine adjustment → continuous casting. To achieve a shorter process flow, it is necessary to research better desulfurizing agent addition methods and equipment. Summary of the Invention

[0011] In view of this, the purpose of the present invention is to provide an RH vacuum refining system with an immersion spray gun and a powder spraying desulfurization method, which utilizes the low-oxygen smelting environment provided by RH vacuum refining to efficiently produce low-sulfur clean steel.

[0012] To achieve the above objectives, the present invention provides the following technical solution: An RH vacuum refining system with an immersion spray gun includes an RH vacuum refining device and a wire feeding device arranged sequentially in the process steps. The RH vacuum refining device includes an RH vacuum refining tank and a ladle arranged vertically opposite each other. The bottom of the RH vacuum refining tank is provided with an RH immersion pipe, and an immersion spray gun is provided between the riser and fallr of the RH immersion pipe. The powder outlet of the spray gun faces the ladle and extends below the surface of the molten steel in the ladle. The ladle is also provided with a temperature and oxygen determination sampling device for taking samples of molten steel to measure temperature and determine oxygen.

[0013] Optionally, the powder spraying gun includes a castable refractory material wrapped around its exterior, and the castable refractory material fills the space between the riser and fallr of the RH impregnation pipe; it also includes a powder spraying pipe, on the outside of which a directional round pipe, a supporting square pipe, and a connecting plate are sequentially fitted, wherein the connecting plate is disposed on the outer side of both ends of the supporting square pipe, and the supporting square pipe and the connecting plate are respectively provided with a plurality of refractory material anchoring claws on the side of the supporting square pipe and the connecting plate near the castable refractory material; the inner side of the connecting plate is welded to the supporting square pipe and the directional round pipe, and the outer side is welded to the riser and fallr.

[0014] Optionally, the directional round tube radially protrudes to support the square tube, and the protruding portion of the directional round tube is fixedly connected to the powder spray pipe by a set screw.

[0015] Optionally, the powder inlet of the powder spraying pipe is connected to a powder conveying pipe, and a cyclone powder distributor is provided at the connection point; wherein the powder conveying pipe includes a metal powder conveying hose, and the two ends of the metal powder conveying hose are respectively connected to the powder inlet of the powder spraying pipe and the powder spraying equipment.

[0016] Optionally, the powder spray gun is parallel to the radial axis of the RH impregnation tube, or is arranged at an acute angle to it.

[0017] Optionally, the powder outlet of the powder spray gun is flush with the ends of the riser and fallr tubes, or the powder outlet is embedded between the riser and fallr tubes.

[0018] Optionally, the RH vacuum refining tank is equipped with a vacuum pump and a lifting gas valve, so that after the RH vacuum refining tank is evacuated, the molten steel circulates between the ladle and the RH vacuum refining tank.

[0019] A powder injection desulfurization method using any of the above-mentioned RH vacuum refining systems with immersion spray guns includes the following steps: S1, the molten steel from the converter directly enters the RH vacuum refining equipment for vacuum refining treatment. The molten steel is transported from the ladle position to the processing position by the ladle transport vehicle. The ladle is lifted by the lifting device, so that the RH immersion pipe and powder spraying gun on the RH vacuum refining tank are inserted below the surface of the molten steel. The vacuum pump and lifting valve on the RH vacuum refining tank are turned on to evacuate the RH vacuum refining tank. After that, the molten steel begins to circulate between the ladle and the RH vacuum refining tank. S2, the temperature and oxygen determination and sampling operation is performed by the temperature and oxygen determination sampling equipment, and the amount of desulfurizer and other alloying elements added in this furnace is calculated based on the measured steel temperature data, steel free oxygen content data and steel sample composition data. S3, the molten steel is circulated under vacuum for 4-6 minutes, and after natural carbon deoxidation is achieved in the vacuum environment, the temperature and oxygen are measured and sampled again by a temperature and oxygen sampling device. After the free oxygen content of the molten steel reaches the expected range, the full amount of desulfurization powder is sprayed into the molten steel in the ladle by the powder spraying gun. S4, after the molten steel is circulated in a vacuum state for 10-14 minutes, other alloying elements are added into the RH vacuum refining tank through a vacuum feeding device; S5. After the molten steel is circulated in vacuum for 18-20 minutes, the temperature and oxygen are measured and sampled again by the temperature and oxygen sampling equipment. After the temperature and composition of the molten steel reach the expected range, the vacuum pump is gradually shut off and the ladle is lowered. When the RH immersion tube is about to leave the molten steel surface, the RH vacuum refining tank is purged to prevent the top slag from being drawn into the vacuum system. S6. After the ladle is lowered into position, the ladle transport vehicle transports the molten steel from the processing position to the wire feeding position. The wire feeding device feeds the specified length of calcium wire and other alloys into the molten steel. At the same time, argon gas is blown into the bottom of the ladle to stir it, causing impurities in the molten steel to float to the surface. After the wire feeding and stirring treatment is completed, the ladle transport vehicle transports the molten steel from the wire feeding position to the ladle lifting position, waiting for the ladle to be lifted into the continuous casting machine.

[0020] Optionally, in step S3, if the free oxygen content does not reach the specified value after the molten steel is circulated in a vacuum for 4-6 minutes and natural carbon deoxidation in a vacuum environment, a specified amount of aluminum particles are added to the RH vacuum refining tank by a vacuum feeding device for forced deoxidation.

[0021] Optionally, the molten steel after deoxidation and alloying with low-carbon aluminum killed steel in the converter can be directly desulfurized by powder injection without waiting for the natural carbon deoxidation stage to end when entering the RH vacuum refining process; the molten steel that fails to meet the standards after desulfurization in the LF furnace can be desulfurized again by spraying a certain amount of desulfurization powder into the ladle through a powder injection gun when entering the RH vacuum refining process, so as to obtain qualified ultra-low sulfur molten steel.

[0022] The beneficial effects of this invention are as follows: The RH desulfurization process using the system and method of this invention effectively removes sulfur from molten steel by adding a desulfurizing agent during vacuum refining, making it an important technology for producing ultra-low carbon steel and high-grade electrical steel. However, traditional RH refining desulfurization methods suffer from low desulfurization efficiency, and the desulfurizing agent corrodes vacuum pipes, shortening the lifespan of refractory materials.

[0023] Unlike Nippon Steel's RH-IJ ladle powder spraying method, this invention uses an RH immersion powder spraying gun to spray powder into the ladle. The RH immersion powder spraying gun is integrated with the two immersion tubes of the RH vacuum tank, and both are inserted below the molten steel surface for powder spraying and desulfurization. This eliminates the need for the RH-IJ ladle powder spraying gun and its lifting system, resulting in simpler equipment and easier maintenance and replacement. Furthermore, unlike Nippon Steel's RH-IJ ladle powder spraying gun with its nozzle facing upwards at the bottom of the ladle, this invention's RH immersion powder spraying gun is located at the top of the ladle with its nozzle facing downwards. The sprayed desulfurization powder directly enters the downward flow in the circulating pipe and is rapidly dispersed throughout the molten steel, improving desulfurization efficiency.

[0024] By efficiently utilizing the RH vacuum environment, a carbon-oxygen reaction naturally occurs to form low-oxygen molten steel, improving the utilization rate of desulfurization powder. Furthermore, by efficiently utilizing the stirring kinetic energy of the circulating flow of molten steel between the ladle and the vacuum chamber, the desulfurization powder is rapidly and uniformly dispersed in the molten steel and reacts with the sulfur element in the molten steel, minimizing the corrosion of refractory materials by the desulfurization agent and preventing the powder from being carried away by the vacuum pump, further improving the desulfurization efficiency.

[0025] This invention utilizes the dead zone of the top layer of molten steel inside the ladle around the immersion tube to restrict the return of sulfur from the surface oxide slag to the molten steel.

[0026] The new technology of this invention enables steel to be directly fed into the RH refining desulfurization furnace after being tapped from the converter without passing through the LF furnace, thus producing low-sulfur clean steel with a shorter process flow, reducing steelmaking production costs, and achieving efficient desulfurization of clean steel.

[0027] In addition, for mid-to-high-end steel grades, the system and method of this invention can achieve ultra-low sulfur production at low cost, reduce the pressure of hot metal pretreatment and converter sulfur control, improve production efficiency, and shorten smelting time.

[0028] Other advantages, objectives, and features of the invention will be set forth in part in the description which follows, and in part will be apparent to those skilled in the art from the following examination, or may be learned from practice of the invention. The objectives and other advantages of the invention can be realized and obtained through the following description. Attached Figure Description

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein: Figure 1A schematic diagram of the connection between the immersion powder spraying gun and the separate immersion tube at the bottom of the RH vacuum refining tank. Figure 2 for Figure 1 BB cross-sectional diagram; Figure 3 A schematic diagram of the connection between the immersion powder spraying gun and the integrated impregnation tube at the bottom of the RH vacuum refining tank; Figure 4 This is an enlarged schematic diagram of an integrated impregnation tube; Figure 5 for Figure 4 A schematic diagram of the CC cross-section; Figure 6 This is a schematic diagram of an immersion spray gun. Figure 7 for Figure 6 A schematic diagram of the AA cross-section; Figure 8 This is a schematic diagram showing the connection between the RH vacuum refining equipment and the powder spraying equipment.

[0030] Figure label: 1. Powder spraying gun, 1-1 casting refractory material, 1-2 powder spraying pipe, 1-3 refractory anchoring claw, 1-4 supporting square tube, 1-5 connecting plate, 1-6 directional round tube, 1-7 set screw, 2. powder conveying pipe, 2-1 cyclone powder distributor, 2-2 metal powder conveying hose, 3. RH impregnation pipe, 3-1 split impregnation pipe, 3-2 integrated impregnation pipe, 4. steel ladle, 5. RH vacuum refining equipment, 5-1 RH vacuum refining tank, 6. powder spraying equipment. Detailed Implementation

[0031] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0032] The accompanying drawings are for illustrative purposes only and are schematic diagrams, not actual pictures. They should not be construed as limiting the invention. To better illustrate the embodiments of the invention, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions. It is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0033] In the accompanying drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components. In the description of the present invention, it should be understood that if terms such as "upper," "lower," "left," "right," "front," and "rear" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the present invention 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, the terms used to describe positional relationships in the drawings are only for illustrative purposes and should not be construed as limiting the present invention. For those skilled in the art, the specific meaning of the above terms can be understood according to the specific circumstances.

[0034] Please see Figures 1 to 8 This is an RH vacuum refining system with an immersion spray gun, comprising an RH vacuum refining device 5 and a wire feeding device arranged sequentially in the process steps. The RH vacuum refining device 5 includes an RH vacuum refining tank 5-1 and a ladle 4 arranged vertically opposite each other. The bottom of the RH vacuum refining tank 5-1 is equipped with an RH immersion pipe 3, and an immersion spray gun 1 is installed between the riser and fallr pipes of the RH immersion pipe 3. The powder outlet of the spray gun 1 faces the ladle 4 and extends below the surface of the molten steel inside the ladle 4. The ladle 4 is also equipped with a temperature and oxygen determination sampling device for sampling, measuring temperature, and determining oxygen in the molten steel. The RH vacuum refining tank 5-1 is equipped with a vacuum pump and a lifting air valve, which, after evacuating the RH vacuum refining tank 5-1, allows the molten steel to circulate between the ladle 4 and the RH vacuum refining tank 5-1.

[0035] Furthermore, the powder spraying gun 1 is positioned between the riser and fallr of the RH immersion pipe 3. The powder spraying gun 1 is externally wrapped with cast refractory material 1-1, which fills the space between the riser and fallr of the RH immersion pipe 3. The powder outlet of the powder spraying gun 1 faces the ladle 4, and the powder inlet faces the lower part of the RH vacuum refining tank 5-1. The powder spraying gun 1 and the RH immersion pipe 3 are integrated and inserted together below the liquid surface of the ladle 4 to spray powder. This efficiently utilizes the stirring kinetic energy of the circulating flow of molten steel between the ladle 4 and the RH vacuum refining tank 5-1, allowing the powder to disperse rapidly and evenly in the molten steel and participate in the chemical reaction. The service life of the powder spraying gun 1 is the same as that of the RH immersion pipe 3, and it is put into and taken out of service together with the RH immersion pipe 3. The cast refractory material 1-1 on the outside of the powder spraying gun 1 and the refractory material of the RH immersion pipe 3 are manufactured as a single unit.

[0036] The powder spraying gun 1 also includes a powder spraying pipe 1-2. The powder spraying pipe 1-2 is sequentially fitted with a directional round pipe 1-6, a supporting square pipe 1-4, and a connecting plate 1-5. The connecting plate 1-5 is located on the outer sides of both ends of the supporting square pipe 1-4. The inner side of the connecting plate 1-5 is welded to the supporting square pipe 1-4 and the directional round pipe 1-6, and the outer side is welded to the ascending pipe and descending pipe. The supporting square pipe 1-4 and the connecting plate 1-5, near the casting refractory material 1-1, are respectively provided with several refractory material anchoring claws 1-3, which are cast integrally with the casting refractory material 1-1. The directional round pipe 1-6 protrudes radially from the supporting square pipe 1-4, and the protruding portion of the directional round pipe 1-6 is fixedly connected to the powder spraying pipe 1-2 by set screws 1-7.

[0037] The powder inlet of the powder spraying pipe 1-2 is connected to the powder conveying pipe 2, and a cyclone powder distributor 2-1 is provided at the connection to prevent powder blockage. The powder conveying pipe 2 includes a metal powder conveying hose 2-2, and the two ends of the metal powder conveying hose 2-2 are respectively connected to the powder inlet of the powder spraying pipe 1-2 and the powder spraying pipe of the powder spraying equipment 6.

[0038] The radial axes of the powder spraying gun 1 and the RH immersion tube 3 can be parallel or intersected at an acute angle. The powder outlet of the powder spraying gun 1 is inserted vertically or at a certain angle below the liquid surface of the ladle 4 to avoid contact with the refractory material of the ladle 4. The powder outlet of the powder spraying gun 1 is flush with the ends of the riser and downcomer pipes, or the powder outlet is embedded between the riser and downcomer pipes.

[0039] In some embodiments of the present invention, the RH impregnation tube 3 can be a split impregnation tube 3-1 or an integral impregnation tube 3-2. When it is an integral impregnation tube 3-2, the casting refractory 1-1 of the immersion powder spraying gun 1 and the refractory of the riser and fallr of the integral RH impregnation tube 3-2 are made into a whole.

[0040] Example 1 A steel plant produces high-grade electrical steel and uses the RH vacuum refining system with an immersion spray gun of this invention for powder spraying desulfurization, producing low-sulfur high-quality steel at low cost. The selected metallurgical equipment includes an RH vacuum refining unit 5, a powder spraying unit 6, a temperature and oxygen sampling device, and a wire feeding device. The immersion tube of the RH vacuum refining unit 5 includes an RH immersion spray gun 1 integrated with the immersion tube, capable of spraying powder into the ladle 4. In this embodiment, the RH immersion tube 3 is an integrated immersion tube 3-2. The following process method is used to produce low-sulfur clean steel: S1, the molten steel from the converter directly enters the RH vacuum refining equipment 5 for vacuum refining treatment. The molten steel is transported from the ladle position to the processing position by a ladle transport vehicle. The ladle 4 is lifted by the lifting device, so that the RH immersion pipe 3 and the powder spraying gun 1 on the RH vacuum refining tank 5-1 are inserted below the surface of the molten steel. The vacuum pump and lifting valve on the RH vacuum refining tank 5-1 are turned on to evacuate the RH vacuum refining tank 5-1. After that, the molten steel begins to circulate between the ladle 4 and the RH vacuum refining tank 5-1.

[0041] S2, the temperature and oxygen determination sampling equipment performs temperature and oxygen determination and sampling operations, and transmits the measured steel molten temperature data, steel molten free oxygen content data and steel sample composition data to the intelligent steelmaking management system. The intelligent steelmaking management system's static model calculates the amount of desulfurizer added and the amount of other alloying elements added for this furnace.

[0042] S3, under vacuum, the molten steel is circulated for 4-6 minutes, and after natural carbon deoxidation is achieved in the vacuum environment, the temperature and oxygen content is measured and sampled again by a temperature and oxygen sampling device. After the free oxygen content of the molten steel reaches the expected range, the full amount of desulfurization powder is injected into the molten steel in the ladle 4 by the powder injection gun 1. The amount of powder injected is 0.5-4 kg / t steel, and the desulfurization powder is a CaO-CaF2 system or a calcium aluminate system.

[0043] When the molten steel circulates under vacuum for 4-6 minutes and the free oxygen content does not reach the specified value after natural carbon deoxidation in the vacuum environment, a specified amount of aluminum particles are added to the RH vacuum refining tank 5-1 by the vacuum feeding device for forced deoxidation.

[0044] S4. After the molten steel is circulated in a vacuum state for 10-14 minutes, other alloying elements are added to the RH vacuum refining tank 5-1 through a vacuum feeding device.

[0045] S5. After the molten steel circulates under vacuum for 18-20 minutes, the temperature and oxygen are measured and sampled again by the temperature and oxygen sampling equipment. Once the temperature and composition of the molten steel reach the expected range, the vacuum pump is gradually shut off and the ladle 4 is lowered. When the RH immersion tube 3 is about to leave the molten steel surface, the RH vacuum refining tank 5-1 is purged to prevent the top slag from being drawn into the vacuum system.

[0046] S6. After the ladle 4 is lowered into position, the ladle transport vehicle transports the molten steel from the processing position to the wire feeding position. The wire feeding device feeds the specified length of calcium wire and other alloys into the molten steel. At the same time, argon gas is blown into the bottom of the ladle 4 to stir it, causing impurities in the molten steel to float to the surface. After the wire feeding and stirring treatment is completed, the ladle transport vehicle transports the molten steel from the wire feeding position to the ladle lifting position, waiting for the ladle 4 to be lifted into the continuous casting machine.

[0047] In this embodiment, the immersion powder spraying gun 1 is integrated with the RH immersion tube 3, and its service life is the same as that of the RH immersion tube 3. It is also connected to and de-energized along with the RH immersion tube 3. The immersion powder spraying gun 1 and the powder spraying pipe of the powder spraying equipment 6 are connected by a flexible metal hose at the bottom of the RH vacuum tank. The RH immersion powder spraying gun 1 consists of a metal nozzle wrapped with cast refractory material, and anchoring studs are welded to the outside of the metal nozzle to reinforce the connection with the cast refractory material.

[0048] The metal barrel of the RH immersion powder spraying gun 1 is welded and fixed together with the riser and fallr skeletons of the RH immersion tube 3, located between the riser and fallr of the RH immersion tube 3, with their center lines parallel to each other. The casting refractory of the RH immersion powder spraying gun 1 and the casting refractory of the RH immersion tube 3 are made as a whole.

[0049] The temperature- and oxygen-determining sampling equipment utilizes robotic intelligent equipment, greatly improving the working environment and reducing the labor intensity of operators. If the free oxygen content does not reach the specified value after the molten steel has circulated for 4-6 minutes and undergone natural carbon deoxidation in a vacuum environment, a specified amount of aluminum particles is added to the vacuum tank via a vacuum feeding device for forced deoxidation.

[0050] After being deoxidized and alloyed with low-carbon aluminum-killed steel in a converter, the molten steel can be directly desulfurized by powder injection without waiting for the natural carbon deoxidation stage to end when it enters the RH vacuum refining process. The molten steel that fails to meet the desulfurization standards after being desulfurized in the LF furnace can be desulfurized again by spraying a certain amount of desulfurization powder into the ladle 4 through the powder injection gun 1 when it enters the RH vacuum refining process, so as to obtain qualified ultra-low sulfur molten steel.

[0051] In this embodiment, the powder spraying equipment 6 uses argon as the carrier gas to transport the desulfurization powder in a dense phase.

[0052] In this embodiment 1, by adding a desulfurizing agent during the vacuum refining process and combining thermodynamic and kinetic control, the effective removal of sulfur from molten steel is achieved. This minimizes the stirring effect on the slag inside the ladle 4, allowing the injected refining powder to have a longer residence time in the molten steel, thus enhancing the stirring effect at the bottom of the ladle 4 and in the vacuum chamber. The injected powder can both desulfurize and create conditions for the heterogeneous nucleation of CO bubbles. The utilization rate of the desulfurizing agent is effectively improved, and the consumption of desulfurizing agent is reduced to less than 3 kg / t.

[0053] Example 2 A steel plant uses blast furnace hot metal to produce IF steel and aims to produce low-cost clean steel with a shorter process flow. The RH vacuum refining system with an immersion spray gun of this invention is used for powder injection desulfurization. The system includes an RH vacuum refining unit 5, a powder injection unit 6, a temperature and oxygen sampling device, and a wire feeding device. The immersion tube of the RH vacuum refining unit 5 includes an RH immersion spray gun 1 integrated with the immersion tube, capable of injecting powder into the ladle 4. In this embodiment, the RH immersion tube 3 is a split-type immersion tube 3-1. The following process method is used to produce low-sulfur clean steel: S1, the molten steel from the converter directly enters the RH vacuum refining equipment 5 for vacuum refining treatment. The molten steel is transported from the ladle position to the processing position by a ladle transport vehicle. The ladle 4 is lifted by the lifting device, so that the RH immersion pipe 3 and the powder spraying gun 1 on the RH vacuum refining tank 5-1 are inserted below the surface of the molten steel. The vacuum pump and lifting valve on the RH vacuum refining tank 5-1 are turned on to evacuate the RH vacuum refining tank 5-1. After that, the molten steel begins to circulate between the ladle 4 and the RH vacuum refining tank 5-1.

[0054] S2, the temperature and oxygen determination sampling equipment performs temperature and oxygen determination and sampling operations, and transmits the measured steel molten temperature data, steel molten free oxygen content data and steel sample composition data to the intelligent steelmaking management system. The intelligent steelmaking management system's static model calculates the amount of desulfurizer added and the amount of other alloying elements added for this furnace.

[0055] S3, under vacuum, the molten steel is circulated for 4-6 minutes, and after natural carbon deoxidation is achieved in the vacuum environment, the temperature and oxygen content is measured and sampled again by a temperature and oxygen sampling device. After the free oxygen content of the molten steel reaches the expected range, the full amount of desulfurization powder is injected into the molten steel in the ladle 4 by the powder injection gun 1. The amount of powder injected is 0.5-4 kg / t steel, and the desulfurization powder is a CaO-CaF2 system or a calcium aluminate system.

[0056] S4. After the molten steel is circulated in a vacuum state for 10-14 minutes, other alloying elements are added to the RH vacuum refining tank 5-1 through a vacuum feeding device.

[0057] S5. After the molten steel circulates under vacuum for 18-20 minutes, the temperature and oxygen are measured and sampled again by the temperature and oxygen sampling equipment. Once the temperature and composition of the molten steel reach the expected range, the vacuum pump is gradually shut off and the ladle 4 is lowered. When the RH immersion tube 3 is about to leave the molten steel surface, the RH vacuum refining tank 5-1 is purged to prevent the top slag from being drawn into the vacuum system.

[0058] S6. After the ladle 4 is lowered into position, the ladle transport vehicle transports the molten steel from the processing position to the wire feeding position. The wire feeding device feeds the specified length of calcium wire and other alloys into the molten steel. At the same time, argon gas is blown into the bottom of the ladle 4 to stir it, causing impurities in the molten steel to float to the surface. After the wire feeding and stirring treatment is completed, the ladle transport vehicle transports the molten steel from the wire feeding position to the ladle lifting position, waiting for the ladle 4 to be lifted into the continuous casting machine.

[0059] The casting refractory of the RH immersion powder spraying gun 1 is manufactured separately from the refractory materials of the riser and downcomer pipes. The RH immersion powder spraying gun 1 is located between the two RH immersion pipes 3, welded to the RH immersion pipes 3 via connecting plates 1-5, and vertically inserted into the molten steel surface. The bottom of the RH immersion powder spraying gun 1 generally does not extend beyond the end of the RH immersion pipe 3 to avoid contact with the refractory material of the ladle 4. The powder spraying equipment 6 in this plant uses argon as the carrier gas to transport the desulfurization powder in a dense phase.

[0060] This embodiment can achieve the following technical effects: (1) After deoxidation and alloying of low carbon aluminum killed silicon steel smelted by RH, the free oxygen activity in the molten steel is very low, which is conducive to desulfurization and no longer requires LF desulfurization, thus reducing production costs; (2) For steel grades that need to undergo RH decarburization treatment, although the slag in ladle 4 has a high oxidizing property, the slag in ladle 4 is located in the dead zone of the circulating flow of molten steel. During the RH treatment process, the desulfurizing agent is directly added to ladle 4 to react with the molten steel, which can avoid the influence of the oxidizing property of the slag in ladle 4. (3) The desulfurizing agent is circulated and stirred with the molten steel, and is more evenly dispersed in the molten steel, which is conducive to the reaction with sulfur in the molten steel.

[0061] (4) The desulfurization powder does not enter the vacuum pumping pipeline, thus reducing equipment maintenance costs.

[0062] Finally, it should be noted that 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 preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A RH vacuum refining system with an immersion spray gun, characterized in that: The equipment includes an RH vacuum refining device (5) and a wire feeding device arranged sequentially according to the process. The RH vacuum refining device (5) includes an RH vacuum refining tank (5-1) and a ladle (4) arranged opposite each other. The bottom of the RH vacuum refining tank (5-1) is provided with an RH immersion pipe (3). An immersion powder spraying gun (1) is provided between the riser and fallr of the RH immersion pipe (3). The powder outlet of the powder spraying gun (1) faces the ladle (4) and extends below the surface of the molten steel in the ladle (4). The ladle (4) is also provided with a temperature and oxygen determination sampling device for taking samples of molten steel for temperature and oxygen determination. The powder spraying gun (1) includes a castable refractory material (1-1) wrapped around the outside, and the castable refractory material (1-1) fills the space between the riser and the fallr of the RH impregnation pipe (3); it also includes a powder spraying pipe (1-2), and the powder spraying pipe (1-2) is sequentially fitted with a directional round pipe (1-6), a supporting square pipe (1-4), and a connecting plate (1-5), wherein the connecting plate (1-5) is located on the outer side of both ends of the supporting square pipe (1-4), and the supporting square pipe (1-4) and the connecting plate (1-5) are respectively provided with a plurality of refractory anchoring claws (1-3) on the side of the supporting square pipe (1-4) and the connecting plate (1-5) near the castable refractory material (1-1); the inner side of the connecting plate (1-5) is welded to the supporting square pipe (1-4) and the directional round pipe (1-6), and the outer side is welded to the riser and the fallr.

2. The RH vacuum refining system with an immersion spray gun according to claim 1, characterized in that: The directional round tube (1-6) radially protrudes from the supporting square tube (1-4), and the protruding part of the directional round tube (1-6) is fixedly connected to the powder spray pipe (1-2) by a set screw (1-7).

3. The RH vacuum refining system with an immersion spray gun according to claim 1, characterized in that: The powder inlet of the powder spray pipe (1-2) is connected to the powder conveying pipe (2), and a cyclone powder distributor (2-1) is provided at the connection point; wherein the powder conveying pipe (2) includes a metal powder conveying hose (2-2), and the two ends of the metal powder conveying hose (2-2) are respectively connected to the powder inlet of the powder spray pipe (1-2) and the powder spraying equipment (6).

4. The RH vacuum refining system with an immersion spray gun according to claim 1, characterized in that: The powder spray gun (1) is parallel to the radial axis of the RH impregnation tube (3), or is arranged at an acute angle to the radial axis of the tube.

5. The RH vacuum refining system with an immersion spray gun according to claim 1, characterized in that: The powder outlet of the powder spray gun (1) is flush with the ends of the riser and the fallr, or the powder outlet is embedded between the riser and the fallr.

6. The RH vacuum refining system with an immersion spray gun according to claim 1, characterized in that: The RH vacuum refining tank (5-1) is equipped with a vacuum pump and a lifting gas valve. After the RH vacuum refining tank (5-1) is evacuated, the molten steel circulates between the ladle (4) and the RH vacuum refining tank (5-1).

7. A method for powder injection desulfurization using an RH vacuum refining system with an immersion spray gun according to any one of claims 1 to 6, characterized in that: Includes the following steps: S1, the molten steel from the converter directly enters the RH vacuum refining equipment (5) for vacuum refining treatment. The molten steel is transported from the ladle position to the processing position by the ladle transport vehicle. The ladle (4) is lifted by the lifting device, so that the RH immersion pipe (3) and powder spraying gun (1) on the RH vacuum refining tank (5-1) are inserted below the surface of the molten steel. The vacuum pump and lifting valve on the RH vacuum refining tank (5-1) are turned on to evacuate the RH vacuum refining tank (5-1). After the molten steel begins to circulate between the ladle (4) and the RH vacuum refining tank (5-1); S2, the temperature and oxygen determination and sampling operation is performed by the temperature and oxygen determination sampling equipment, and the amount of desulfurizer and other alloying elements added in this furnace is calculated based on the measured steel temperature data, steel free oxygen content data and steel sample composition data. S3, under vacuum, the molten steel circulates for 4~6 minutes and achieves natural carbon deoxidation in the vacuum environment. Then, the temperature and oxygen are measured and sampled again by the temperature and oxygen sampling equipment. After the free oxygen content of the molten steel reaches the expected range, the full amount of desulfurization powder is sprayed into the molten steel in the ladle (4) by the powder spray gun (1). S4, after the molten steel is circulated under vacuum for 10-14 minutes, other alloying elements are added to the RH vacuum refining tank (5-1) through a vacuum feeding device; S5. After the molten steel circulates for 18-20 minutes under vacuum, the temperature and oxygen are measured and sampled again by the temperature and oxygen sampling equipment. After the temperature and composition of the molten steel reach the expected range, the vacuum pump is gradually shut off and the ladle (4) is lowered. When the RH immersion tube (3) is about to leave the molten steel surface, the RH vacuum refining tank (5-1) is purged with air to prevent the top slag from being drawn into the vacuum system. S6. After the ladle (4) is lowered into position, the ladle transport vehicle will transport the molten steel from the processing position to the wire feeding position. The wire feeding device will feed the alloy of a specified length into the molten steel. At the same time, argon gas will be blown into the bottom of the ladle (4) to stir it, so that the impurities in the molten steel will float to the surface. After the wire feeding and stirring treatment is completed, the ladle transport vehicle will transport the molten steel from the wire feeding position to the ladle lifting position, waiting for the ladle (4) to be lifted into the continuous casting machine.

8. The powder injection desulfurization method according to claim 7, characterized in that: In step S3, when the molten steel is circulated under vacuum for 4-6 minutes and the free oxygen content does not reach the specified value after natural carbon deoxidation under vacuum, a specified amount of aluminum particles are added to the RH vacuum refining tank (5-1) by the vacuum feeding device for forced deoxidation.

9. The powder injection desulfurization method according to claim 7, characterized in that: After the molten steel is deoxidized and alloyed by the converter smelting of low carbon aluminum killed steel, it can be directly desulfurized by powder injection without waiting for the natural carbon deoxidation stage to end when it enters the RH vacuum refining treatment. The molten steel that fails to meet the desulfurization standard after the LF furnace desulfurization treatment is desulfurized again by spraying a certain amount of desulfurization powder into the ladle (4) through the powder injection gun (1) when it enters the RH vacuum refining treatment, so as to obtain qualified ultra-low sulfur molten steel.

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