Molten steel refining method adopting RH vacuum refining system

Abstract

The invention provides a molten steel refining method adopting an RH vacuum refining system, and the RH refining process comprises the following steps: pretreatment: after a steel ladle enters an RH refining station, inserting an RH dip pipe below the liquid level of molten steel; vacuum refining is conducted, specifically, vacuumizing is conducted, argon is blown into an ascending pipe of the RH dip pipe, when the pressure in a vacuum chamber reaches 20-200 Pa, the ascending pipe of the RH dip pipe is adjusted to lift the gas flow, and when the pressure in the vacuum chamber reaches the ultimate vacuum and the gas flow can be stably lifted, vacuum refining is completed; the inclined angle between each argon blowing hole and the horizontal plane is 30 degrees; alloying is conducted, specifically, the molten steel is alloyed in the RH vacuum refining treatment process; after alloying is completed, the components of the molten steel are detected, and if soft blowing treatment needs to be conducted on the molten steel, soft blowing is conducted on the molten steel; and if soft blowing is not needed, the RH refining of the molten steel is completed. The inclination angle of the argon blowing gas hole is changed, the lifting force of the blown gas to the molten steel is increased, then the circulating flow of the molten steel in the RH is increased, the cleanliness of the molten steel is improved, and therefore the steel product quality is improved.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy refining, and in particular to a molten steel refining method using an RH vacuum refining system. Background Art

[0002] Vacuum refining is an essential process equipment for steelmaking production and the development of high-end steel varieties. The common process equipment for traditional vacuum refining includes VD / VOD and RH. RH has more advantages in producing high-quality clean steel and is more suitable as a buffer link in contemporary high-efficiency converters and continuous casting production. It has become an indispensable refining facility for the production of high-end special steels, cold-rolled automotive plates, electrical steel and other varieties. In the past three years, RH has accounted for about 70% of the newly added vacuum refining in China.

[0003] RH technology has the advantages of short processing cycle and large production capacity. RH refining technology adopts the principle of vacuum degassing, which can effectively remove harmful gases such as hydrogen and nitrogen in molten steel. By optimizing the RH production process and equipment performance, the RH production efficiency can be further improved. After the molten steel enters the workstation, the immersion tube is first immersed in the molten steel, and then the vacuum pump is started to evacuate. Under the action of atmospheric pressure, the molten steel enters the vacuum tank from the immersion tube. The riser blows argon into the molten steel through the argon tube, so that the molten steel enters from the riser and flows to the downcomer through the lower part of the vacuum tank. This cycle is repeated continuously to purify the molten steel. Among them, the opening position and distribution method of the argon tube on the immersion tube on the ascending side have a great influence on the purification of the molten steel, but the traditional argon tube is mainly single-layer distribution and double-layer distribution, but the overall distribution structure is single, and the holes are evenly opened at the lower level.

[0004] Patent application number 202122630321.8: discloses an argon blowing hole distribution structure of the immersion tube on the rising side of the RH tube, including: a rising tube, the rising tube is a circular cylindrical structure built by upper ring bricks and lower ring bricks, the upper ring bricks are arranged below the vacuum tank, the lower ring bricks are connected below the upper ring bricks, a ladle is arranged below the lower ring bricks, and the lower ring bricks are provided with a plurality of argon blowing holes, the argon blowing holes are divided into a first layer of argon blowing holes and a second layer of argon blowing holes, both layers of argon blowing holes are evenly distributed along the circumference of the rising tube, and the first layer of argon blowing holes and the second layer of argon blowing holes are staggered. The beneficial effects of the utility model are: fully stirring the molten steel and shortening the vacuum cycle time; it can effectively reduce the erosion of the molten steel on the riser ring bricks, especially the upper ring bricks that are severely eroded, and improve the service life of the immersion tube. This patent mainly changes the distribution structure of the argon blowing holes of the immersion tube on the rising side, but only staggers the upper and lower layers of argon holes, and does not involve an increase in the circulation flow rate.

[0005] Patent application number 202210820851.5: Provides an RH refining furnace and a method for shortening the RH treatment cycle, the RH refining furnace comprising: a ladle (1) for containing molten steel, the bottom of the ladle (1) being provided with a bottom blowing port (11); a vacuum chamber (2) located above the ladle (1) and provided with an ascending pipe (21), a descending pipe (22) and a vacuum chamber (23), the tube wall of the ascending pipe (21) being provided with a side blowing port (211); a first blowing device (3) being fluidically connected to the side blowing port (211); and a second blowing device (4) being fluidically connected to the bottom blowing port (11). When used for RH treatment, a driving gas is blown into the vacuum chamber through the second blowing device of the ladle, and the driving gas cooperates with the side blowing driving gas, thereby effectively increasing the RH saturated circulation flow rate, reducing the mixing time, increasing the degassing and decarburization rates, accelerating the alloying, and shortening the RH treatment cycle. This patent mainly increases the circulation flow rate by providing a bottom blowing port at the bottom of the ladle and a side blowing port on the wall of the riser, and the bottom blowing and side blowing work together. This patent increases the blowing volume and increases the difficulty of the immersion tube modification.

[0006] Patent with application number 201720297987.7: This patent relates to the field of steelmaking and refining technology in metallurgical engineering, in particular to a pressure circulation degassing device, including a furnace body, the furnace body is cylindrical, a gas release device is provided on one side of the furnace body, two risers and downcomers for molten steel circulation are provided at the lower end of the furnace body, a skirt cover is provided on the furnace body, the risers and downcomers extend through the skirt cover to the interior of the ladle, the ladle is located directly below the furnace body, the outer diameter of the ladle intersection is consistent with the outer diameter of the skirt cover, the outer edge of the skirt cover is locked with the ladle through a pressure sealing lock, and the vacuuming process of conventional RH vacuum pumps at various levels is eliminated, and investment and energy consumption are greatly reduced; the pressure circulation degassing equipment can increase the rising stroke of bubbles in the molten steel between the outlet plane of the air-permeable bricks and the surface of the furnace body molten pool, and the bubbles stay in the molten steel for a long time, and the skirt cover of the pressure circulation degassing equipment can isolate the air and keep warm, reducing heat loss. This patent provides a skirt cover on the furnace body, and locks the outer edge of the skirt cover with a pressure seal lock and a ladle, making equipment modification more difficult.

[0007] Patent application number 202322281310.2: This patent relates to the technical field of RH refining furnaces, and provides a blowing hole arrangement structure of a riser pipe of an RH refining furnace, comprising: a pipe body, a plurality of blowing holes corresponding to the upper and lower functions of the outer surface of the pipe body, and the plurality of blowing holes are evenly divided into two groups, and also comprising: a plurality of connecting tubes, which are evenly divided into two groups and fixedly installed on one side of the two groups of blowing holes close to the outer surface of the pipe body. When the utility model is in use, the gas filtered by the filter plate enters the interior of the connecting tube, which is conducive to the removal of impurities contained in the gas and improves product quality. After the filter plate is taken out, it is cleaned or replaced, and then the filter plate is connected back to the mounting block, and then the mounting block is installed into the interior of the connecting tube, which is conducive to ensuring the normal use of the function of filtering impurities in the air. After the filtered gas passes through the ventilation chamber, it enters the blowing hole under the dredging action of the connecting tube, and finally enters the interior of the pipe body, which is conducive to avoiding the connection of multiple external air pipes. The blowing holes of the patent are evenly divided into two groups, and their arrangement is the same as the distribution of the inserted tube argon small tubes currently used in steel mills. A filter plate is added to filter the gas, but the distribution of the blowing holes is not improved.

[0008] Based on the above analysis, in order to not increase the cost, this patent proposes a new RH tube riser argon blowing hole distribution structure, which increases the circulation flow rate of molten steel during RH refining. Summary of the invention

[0009] According to the above technical problem that the distribution of argon blowing holes on the riser in the existing RH refining affects the circulation flow of molten steel, a molten steel refining method using an RH vacuum refining system is provided. The present invention mainly changes the inclination angle of the argon blowing holes of the immersion tube riser, thereby increasing the lifting gas flow of the riser and significantly increasing the circulation flow of molten steel in the RH.

[0010] The technical means adopted by the present invention are as follows:

[0011] A method for refining molten steel using an RH vacuum refining system, comprising: subjecting the molten steel to a converter smelting process, an LF refining process, an RH refining process and a continuous casting process to obtain pure molten steel;

[0012] The RH refining process comprises:

[0013] Pretreatment: After the ladle enters the RH refining station, the RH immersion tube is inserted below the liquid steel level;

[0014] Vacuum refining: Evacuate the chamber, blow argon into the RH immersion tube riser, and when the pressure in the vacuum chamber reaches 20-200Pa, adjust the RH immersion tube riser to increase the gas flow rate. When the pressure in the vacuum chamber reaches the ultimate vacuum and the gas flow rate can be stably increased, vacuum refining is completed;

[0015] The inclination angle of the argon blowing hole to the horizontal plane is 30°;

[0016] Alloying: Alloying of molten steel during RH vacuum refining;

[0017] After alloying is completed, determine whether soft blowing is required according to the steel grade processing requirements. If soft blowing is required, the molten steel is soft-blown; if soft blowing is not required, complete the RH refining of the molten steel.

[0018] Furthermore, the immersion tube is immersed in the molten steel to a depth of 500-700 mm; and the lifting gas flow rate of the immersion tube riser is controlled within 1000-1400 NL / min.

[0019] Furthermore, when the molten steel is soft-blown, the soft-blowing time is not less than 5 minutes, and the argon blowing flow rate is controlled at 30-70NL / min.

[0020] Furthermore, the argon blowing holes of the immersion tube riser are distributed in two rows in a staggered manner, and the two rows of argon blowing holes are inclined upward at 30 degrees to the horizontal plane.

[0021] Furthermore, after the alloying of the molten steel is completed, the RH breaks through the air, and the RH immersion tube is lifted to the outside of the molten steel liquid surface.

[0022] Further, after the RH refining process, the molten steel is transported to the continuous casting process for processing.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The present invention is proposed based on the background of traditional RH refining and smelting process. It uses the current RH refining equipment to change the inclination angle of the argon blowing hole to 30°, indirectly increasing the lifting force of the blown gas on the molten steel, thereby increasing the circulation flow of the molten steel in the RH. The method is simple and reliable, with strong feasibility. The circulation flow is significantly increased during the RH smelting process, and the cleanliness of the molten steel is improved, thereby improving the quality of steel products.

[0025] The present invention solves the problem of increasing the circulation flow of molten steel without increasing costs or significantly modifying equipment, thereby improving product quality and providing reference and guidance for the production of high-quality clean steel. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0027] Figure 1It is a diagram of the RH refining process in the present invention.

[0028] Figure 2 It is a vacuum device in the existing RH refining process.

[0029] Figure 3 for Figure 2 Main view.

[0030] Figure 4 for Figure 3 Enlarged view of point A in the middle.

[0031] Figure 5 It is a schematic diagram of the argon blowing hole in the present invention. DETAILED DESCRIPTION

[0032] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0034] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0035] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps described in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be regarded as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0036] like Figure 1-3 As shown, the present invention provides a method for refining molten steel using an RH vacuum refining system, comprising the steps of: the molten steel undergoing a converter smelting process, an LF refining process, an RH refining process and a continuous casting process to obtain pure molten steel;

[0037] The RH refining process comprises:

[0038] After the ladle enters the RH refining station, the RH immersion tube is inserted under the liquid steel surface, and the RH immersion tube is immersed to a depth of 500-700mm; then the vacuum is evacuated until the pressure in the vacuum chamber reaches 20-200Pa, and the gas flow rate of the RH immersion tube riser is adjusted to increase. When the pressure in the vacuum chamber reaches the ultimate vacuum and the gas flow rate is increased stably, vacuum refining is completed. Among them, the gas flow rate of the immersion tube riser is controlled at 1000-1400NL / min;

[0039] During the RH vacuum treatment, alloying is carried out according to the requirements of the molten steel composition. After the RH treatment is completed, the air is broken and the rising RH immersion tube is lifted to the outside of the molten steel surface. According to the steel grade treatment requirements, it is confirmed whether the molten steel needs to be soft-blown. If soft-blowing is required, the soft-blowing time shall not be less than 5 minutes, and the argon blowing flow rate shall be controlled at 30-70NL / min to avoid the slag surface being exposed.

[0040] After the RH refining process, the molten steel is transported to the continuous casting process for processing.

[0041] The argon blowing holes of the immersion tube riser described in the method are distributed in two rows in a staggered manner, and the two rows of argon blowing holes are inclined upward by 30 degrees.

[0042] Example 1

[0043] For 120t ladle, when producing heavy rail steel.

[0044] After the ladle enters the RH refining station, the modified RH immersion tube is inserted under the steel liquid surface, and the RH immersion tube is immersed to a depth of 550mm; then the vacuum is evacuated until the pressure in the vacuum chamber reaches 67Pa, and the gas flow rate of the RH immersion tube riser is adjusted to 1200NL / min;

[0045] During the RH vacuum treatment, alloying is performed according to the requirements of the steel liquid composition. After the RH treatment is completed, the vacuum is broken and the RH immersion tube is lifted out of the steel liquid surface. According to the steel grade treatment requirements, the steel liquid is soft-blown for no less than 5 minutes, and the argon blowing flow rate is controlled at 50NL / min.

[0046] After the RH refining process, the molten steel is transported to the continuous casting process for processing.

[0047] Example 2

[0048] After the ladle enters the RH refining station, the modified RH immersion tube is inserted under the steel liquid surface, and the RH immersion tube is immersed to a depth of 550mm; then the vacuum is evacuated until the pressure in the vacuum chamber reaches 67Pa, and the gas flow rate of the RH immersion tube riser is adjusted to 1200NL / min;

[0049] During the RH vacuum treatment, alloying is performed according to the requirements of the steel liquid composition. After the RH treatment is completed, the vacuum is broken and the RH immersion tube is lifted out of the steel liquid surface. According to the steel grade treatment requirements, the steel liquid is soft-blown for no less than 5 minutes, and the argon blowing flow rate is controlled at 50NL / min.

[0050] After the RH refining process, the molten steel is transported to the continuous casting process for processing.

[0051] The use of this immersion tube significantly improves the circulation efficiency of the molten steel. Under the same processing time, the number of circulations of the molten steel in the ladle is increased, which is more conducive to the floating of inclusions and the degassing of the molten steel, thereby improving the quality of the produced steel products.

[0052] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for refining molten steel using an RH vacuum refining system, characterized in that: The molten steel is subjected to a converter smelting process, a LF refining process, a RH refining process and a continuous casting process to obtain pure molten steel; The RH refining process comprises: Pretreatment: After the ladle enters the RH refining station, the RH immersion tube is inserted below the liquid steel level; Vacuum refining: Evacuate the chamber, blow argon into the RH immersion tube riser, and when the pressure in the vacuum chamber reaches 20-200Pa, adjust the RH immersion tube riser to increase the gas flow rate. When the pressure in the vacuum chamber reaches the ultimate vacuum and the gas flow rate can be stably increased, vacuum refining is completed; The inclination angle of the argon blowing hole to the horizontal plane is 30°; Alloying: Alloying of molten steel during RH vacuum refining; After alloying is completed, determine whether soft blowing is required based on the steel grade requirements. If soft blowing is required, the molten steel is soft-blown; if soft blowing is not required, complete the RH refining of the molten steel.

2. The method for refining molten steel using the RH vacuum refining system according to claim 1, characterized in that: The depth of the immersion pipe immersed in the molten steel is 500-700 mm; the lifting gas flow rate of the immersion pipe riser is controlled within 1000-1400NL / min.

3. The method for refining molten steel using the RH vacuum refining system according to claim 1, characterized in that: When soft blowing the molten steel, the soft blowing time shall not be less than 5 minutes, and the argon blowing flow rate shall be controlled at 30-70NL / min.

4. The method for refining molten steel using the RH vacuum refining system according to claim 1, characterized in that: The argon blowing holes of the immersion tube riser are distributed in two rows in a staggered manner, and the two rows of argon blowing holes are inclined upward at 30 degrees to the horizontal plane.

5. The method for refining molten steel using the RH vacuum refining system according to claim 1, characterized in that: After the alloying of the molten steel is completed, the RH breaks through the air, and the RH immersion tube is lifted to the outside of the molten steel liquid surface.

6. A method for refining molten steel using an RH vacuum refining system, characterized in that: After the RH refining process, the molten steel is transported to the continuous casting process for processing.

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