RH refining furnace and production method thereof

Abstract

The invention relates to an RH refining furnace and a production method thereof, and belongs to the technical field of steelmaking production in the metallurgical industry. According to the technical scheme, the device comprises a vacuum chamber (1), dipping pipes (2) at the bottom of the vacuum chamber, at least one ascending pipe (21) and at least one descending pipe (22) which are matched with the dipping pipes (2), and lifting air blowing-in pipe stop valves on the ascending pipe (21) and the descending pipe (22), the number of the dipping pipes (2) at the bottom of the vacuum chamber is not less than three, and the number of the ascending pipe (21) or the descending pipe (22) is both at least one. The sectional area of a molten steel ascending channel limited by the ascending pipe (21) is equal to the sectional area of a molten steel descending channel limited by the descending pipe (22); the device has the beneficial effects that the switching control of the working modes of the dip pipes can be realized, so that each dip pipe can be used as an ascending pipe and a descending pipe in different refining furnaces, and the service life of each dip pipe can be obviously prolonged.

Description

Technical Field

[0001] The invention relates to an RH refining furnace and a production method thereof, belonging to the technical field of steelmaking production in the metallurgical industry. Background Art

[0002] The RH process, a method for refining molten steel outside the furnace, was jointly designed and developed by Ruhrstahl and Heraeus in Germany. The RH process is a key method for refining molten steel outside the furnace, providing degassing, decarburization, and deoxidation, as well as homogenizing the composition and temperature of the molten steel and promoting the floating of non-metallic inclusions.

[0003] An immersion tube is provided at the bottom of the RH vacuum refining furnace. There are generally two immersion tubes, one for rising and one for falling. Argon can be blown into the rising tube. During the refining of molten steel in the RH vacuum refining furnace, the immersion tube is first inserted into the molten steel in the ladle, and the vacuum chamber is evacuated. Then, argon is blown into the molten steel from the lower part of the rising tube as a driving gas, so that the apparent density of the molten steel in the rising tube is lower than that in the falling tube. Driven by the argon bubbles, the molten steel in the rising tube rises with the argon bubbles into the vacuum chamber, thereby undergoing degassing, decarburization, and deoxidation reactions. After refining in the vacuum chamber is completed, the molten steel in the vacuum chamber flows back to the ladle from the falling tube under the action of gravity.

[0004] In RH refining, erosion and damage to the dip tube are a major cost issue. Currently, improvements to the refractory material used to extend the tube's service life are common. Furthermore, steel companies currently primarily improve RH refining efficiency by increasing the refining furnace's circulation flow rate. This approach consumes significant amounts of argon and increases erosion of the dip tube, leading to increased production costs. Furthermore, the extent to which this circulation flow rate can be increased is limited. To meet the production requirements of high-quality steel grades, RH refining efficiency needs to be further improved. Summary of the Invention

[0005] The object of the present invention is to provide an RH refining furnace and a production method thereof, which can realize the switching control of the working mode of the immersion tube, so that each immersion tube can be used as an ascending tube and a descending tube in different refining furnaces, which can significantly extend the service life of each immersion tube and solve the problems existing in the background technology.

[0006] The technical solution of the present invention is:

[0007] An RH refining furnace comprises a vacuum chamber, an immersion pipe at the bottom of the vacuum chamber, an ascending pipe and a downpipe configured with the immersion pipe, and lift gas blowing pipe shut-off valves on the ascending pipe and the downpipe. The number of immersion pipes at the bottom of the vacuum chamber is not less than three, there is at least one ascending pipe or one downpipe, and the cross-sectional area of the molten steel ascending channel defined by the ascending pipe is equal to the cross-sectional area of the molten steel descending channel defined by the downpipe.

[0008] There are three immersion pipes at the bottom of the vacuum chamber, and the three immersion pipes are arranged in a triangle.

[0009] The three dip tubes are arranged in an equilateral triangle.

[0010] There are two risers and one downpipe configured with the three immersion tubes. The cross-sectional area of the molten steel rising channel defined by the two risers is equal to the cross-sectional area of the molten steel descending channel defined by the one downpipe.

[0011] There is one riser and two downcomers configured with the three immersion tubes. The cross-sectional area of the molten steel rising channel defined by one riser is equal to the cross-sectional area of the molten steel descending channel defined by the two downcomers.

[0012] There are four dipping tubes at the bottom of the vacuum chamber, and the four dipping tubes are arranged in a quadrilateral.

[0013] The four dip tubes are arranged in a square.

[0014] There is one riser and three downcomers configured with the four immersion tubes. The cross-sectional area of the molten steel rising channel defined by one riser is equal to the cross-sectional area of the molten steel descending channel defined by the three downcomers.

[0015] There are two risers and two downcomers configured with the four immersion tubes. The cross-sectional area of the molten steel rising channel defined by the two risers is equal to the cross-sectional area of the molten steel descending channel defined by the two downcomers.

[0016] There are three risers and one downpipe configured with the four immersion tubes. The cross-sectional area of the molten steel rising channel defined by the three risers is equal to that of the molten steel descending channel defined by the one downpipe.

[0017] A RH refining furnace production method adopts an RH refining furnace defined above. During the refining process, the rising tube and downpipe switching nodes should be selected between adjacent smelting furnaces, and multi-furnace switching or single-furnace switching should be performed according to the online use time of the refining furnace.

[0018] For a newly-commissioned vacuum furnace, during the initial period of 0-300 minutes of use, the riser and downcomer should be switched after each heat of steel is smelted; for a vacuum furnace that is used for 301-1500 minutes, the riser and downcomer should be switched after continuous smelting of ≥2 heats; for a vacuum furnace that is smelted for more than 1500 minutes, the riser and downcomer should be switched after the smelting of a single or multiple heats is completed. The switching of the riser and downcomer is accomplished by opening or closing the shut-off valve of the lifting gas blowing pipe.

[0019] The beneficial effects of the present invention are as follows: the present invention can realize the switching control of the working mode of the immersion tube by configuring a lifting gas blowing tube for each immersion tube, so that each immersion tube can be used as a riser and downcomer in different refining furnaces, avoiding the problems of rapid erosion rate and short service life caused by long-term single mode operation of the immersion tube, and can significantly extend the service life of each immersion tube and reduce production costs; and the switching of the working mode of the immersion tube also leads to a change in the flow direction of molten steel in the vacuum chamber, which can avoid the problem that the refractory material of the inner wall of the vacuum chamber at certain positions is subjected to long-term erosion by molten steel and requires frequent repairs. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a structural schematic diagram of the RH refining furnace with two immersion tubes of the present invention;

[0021] Figure 2 It is a structural schematic diagram of the RH refining furnace with three immersion tubes of the present invention;

[0022] Figure 3 The structure of the RH refining furnace with four immersion tubes of the present invention is shown as follows Figure 1 ;

[0023] Figure 4 The structure of the RH refining furnace with four immersion tubes of the present invention is shown as follows Figure 2 ;

[0024] In the figure: vacuum chamber 1, immersion pipe 2, ascending pipe 21, descending pipe 22. DETAILED DESCRIPTION

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

[0026] Refer to the attached Figure 1-4 A RH refining furnace includes a vacuum chamber 1, an immersion pipe 2 at the bottom of the vacuum chamber, an ascending pipe 21 and a downcomer 22 configured with the immersion pipe, and a lifting gas blowing pipe cut-off valve on the ascending pipe 21 and the downcomer 22. The number of the immersion pipes 2 at the bottom of the vacuum chamber is not less than three, there is at least one ascending pipe 21 or one downcomer 22, and the cross-sectional area of the molten steel ascending channel defined by the ascending pipe 21 is equal to the cross-sectional area of the molten steel descending channel defined by the downcomer 22.

[0027] Example 1

[0028] The RH refining furnace comprises a vacuum chamber 1 and a dip tube 2 at the bottom of the chamber. Each dip tube 2 is equipped with a lift gas injection pipe. The structures of the vacuum chamber 1 and dip tube 2, their mounting structure at the bottom of the chamber 1, and the installation structure of the lift gas injection pipe are all conventional in the art and will not be described in detail here. Argon is used as the lift gas, but other inert gases suitable for molten steel refining production can also be used.

[0029] like Figure 1 There are two dip tubes 2, and both are equipped with a lifting gas injection pipe. Each lifting gas injection pipe is equipped with a shut-off valve. In actual production, the lifting gas injection pipes of the two dip tubes 2 can be turned on and off to realize that one of the dip tubes 2 serves as an ascending pipe 21 and the other dip tube 2 serves as a descending pipe 22. Obviously, by turning the lifting gas injection pipes on and off, the working mode of the two dip tubes 2 can be switched. For example, in a certain refining heat, the first dip tube 2 serves as the ascending pipe 21 and the second dip tube 2 serves as the descending pipe 22. In the next refining heat, the first dip tube 2 serves as the descending pipe 22 and the second dip tube 2 serves as the ascending pipe 21.

[0030] Example 2

[0031] like Figure 2 , there are 3 dip tubes 2. Obviously, there are two possible situations:

[0032] (1) It includes two ascending tubes 21 and one descending tube 22; wherein, preferably, the two ascending tubes 21 have the same cross-sectional area, that is, the two ascending tubes 21 have the same inner diameter, and the inner diameters of the two ascending tubes 21 are defined as D1, and the inner diameter of the descending tube 22 is defined as D2, then, 2π(D1 / 2) 2 =π(D2 / 2) 2 ;

[0033] (2) It includes one ascending pipe 21 and two descending pipes 22; wherein, preferably, the two descending pipes have the same cross-sectional area, that is, the two descending pipes have the same inner diameter. The inner diameters of the two descending pipes are defined as D3, and the inner diameter of the ascending pipe 21 is defined as D4. Then, 2π(D3 / 2) 2 =π(D4 / 2) 2 .

[0034] Preferably, the three immersion tubes 2 are arranged in a triangle; further preferably, the three immersion tubes 2 are designed to be distributed in an equilateral triangle, and the central axis of the vacuum chamber 1 passes through the center of the equilateral triangle, which can ensure the reliability of the molten steel circulation and avoid the occurrence of small molten steel circulation in a local area and disrupting the normal production of the refining furnace.

[0035] In this embodiment, three immersion tubes 2 are provided. In the scheme comprising two riser tubes 21 and one downcomer 22, the two riser tubes 21 correspondingly form two ascending steel streams. These two ascending steel streams can generate convection impact and collision within the vacuum chamber 1 or within the downcomer 22, significantly improving the degassing effect and efficiency of the molten steel within the vacuum chamber 1. They can also effectively promote mass transfer and metallurgical reactions in the molten steel, thereby achieving better impurity removal and molten steel purification. In the scheme comprising one riser tube 21 and two downcomers 22, the two downcomers correspondingly form two descending steel streams. This not only allows the ascending steel stream to have multi-directional flow within the vacuum chamber 1, but also improves the vacuum refining effect of the dispersed flow of the molten steel. On the other hand, the two descending steel streams can effectively stir the molten steel in the ladle, effectively promoting mass transfer and metallurgical reactions in the molten steel, and thus improving the quality of the molten steel.

[0036] Example 3

[0037] like Figure 3 and Figure 4 , there are 4 dip tubes 2. Obviously, there are three possible situations:

[0038] (1) It includes one ascending pipe 21 and three descending pipes 22;

[0039] (2) comprising two ascending pipes 21 and two descending pipes 22;

[0040] (3) including three ascending pipes 21 and one descending pipe 22;

[0041] Preferably, the four immersion tubes 2 are arranged in a quadrilateral; further preferably, the four immersion tubes 2 are arranged in a square, and the central axis of the vacuum chamber 1 passes through the center of the square, which can ensure the reliability of the molten steel circulation.

[0042] Among them, it is better to have two ascending pipes 21 and two descending pipes 22. Further preferably, the two ascending pipes 21 have the same lumen cross-sectional area, and the two descending pipes 22 have the same lumen cross-sectional area, that is, the two ascending pipes 21 have the same inner diameter, and the two descending pipes have the same inner diameter. The inner diameters of the two ascending pipes 21 are both defined as D5, and the inner diameters of the two descending pipes 22 are both defined as D6. Then, 2π(D5 / 2) 2 =2π(D6 / 2) 2

[0043] Further preferably, the two rising pipes 21 are arranged diagonally, and the two downcomers 22 are arranged diagonally; the two rising pipes 21 correspondingly form two rising steel flows, which can produce convection impact and collision in the vacuum chamber 1, and the two rising steel flows on the diagonal produce a head-on collision effect, which can significantly improve the degassing effect and efficiency of the molten steel in the vacuum chamber 1, and can effectively promote mass transfer and metallurgical reactions in the molten steel, and can obtain better impurity removal effect and molten steel purification degree; the two downcomers correspondingly form two descending steel flows, which can better stir the molten steel in the ladle, and can also effectively promote mass transfer and metallurgical reactions in the molten steel, which is beneficial to improving the quality of the molten steel. In another possibility, the above-mentioned four immersion tubes 2 may produce two relatively independent cycles, that is, one of the rising steel flows continuously descends through one of the downcomers 22, and the other rising steel flow continuously descends through the other downcomer 22. Obviously, this mode can still ensure the reliability and refining effect of RH refining, but this situation is still avoided in this embodiment. Accordingly, by adjusting the lifting air flow in the two rising tubes 21, the flow rate and kinetic energy of the two rising steel flows can be controlled, so that the two rising steel flows can at least partially collide with each other.

[0044] The production method of the above-mentioned RH refining furnace comprises:

[0045] Determine the working mode switching node of the immersion pipe 2;

[0046] At the working mode switching node of the immersion pipe 2, the shut-off valve of the lifting gas blowing pipe configured for the current riser 21 is closed, and the shut-off valve of the lifting gas blowing pipe configured for the current downcomer 22 is opened.

[0047] It can be understood that the so-called working mode of the immersion pipe 2 includes the working mode of the riser 21 and the working mode of the downcomer 22, and the working mode of the immersion pipe 2 is switched at the working mode switching node, that is, between the working mode of the riser 21 and the working mode of the downcomer 22.

[0048] In the above method, preferably, the working mode switching node of the immersion tube 2 is located between two adjacent refining heats, that is, when the working mode of the immersion tube 2 is switched, there is no molten steel in the vacuum chamber 1, which can ensure production safety.

[0049] The above production method is applicable to both an RH refining furnace with two immersion tubes 2 and an RH refining furnace with three or more immersion tubes 2.

[0050] This production method, through the switching control of the working mode of the immersion tube 2, enables each immersion tube 2 to be used as a riser 21 and a downcomer 22 in different refining furnaces, avoiding the problems of rapid erosion and short service life caused by the immersion tube 2 running in a single mode for a long time, thereby significantly extending the service life of each immersion tube 2 and reducing production costs; and the switching of the working mode of the immersion tube 2 also leads to a change in the flow direction of the molten steel in the vacuum chamber 1, which can avoid the problem that the refractory material on the inner wall of the vacuum chamber 1 at certain positions is subjected to the erosion of the molten steel for a long time and needs frequent repairs.

[0051] Based on the above method, the switching node of the riser 21 and downcomer 22 is selected between adjacent smelting heats, and multi-furnace switching or single-furnace switching is performed according to the online use time of the refining furnace. Generally, for a newly online vacuum furnace, during the initial use period of 0-300 minutes, the switch should be made after each heat of steel smelting is completed; the golden life of the refractory material is 301-1500 minutes of use in the vacuum furnace, when the refractory material performance is stable and continuous smelting of ≥2 heats can be completed, and the riser 21 and downcomer 22 are switched. After the vacuum furnace smelting time is greater than 1500 minutes, the riser 21 and downcomer 22 are switched after the completion of single or multiple heats of smelting, depending on the corrosion of the refractory material and the immersion tube in the furnace. The riser 21 and downcomer 22 are switched by opening and closing the shut-off valve of the lifting gas inlet pipe.

[0052] Based on the above method, for the double immersion tube mode, in the initial 0-300min use of the vacuum furnace, after each batch of steel smelting is completed, the original riser gas shut-off valve is closed and the original downcomer gas shut-off valve is opened to achieve the effect of interactive use of the immersion tube riser and downcomer; the vacuum furnace is used for 301-1500min, which is the golden life period of refractory use. After continuous smelting of 3-5 batches, the immersion tube riser and downcomer are used alternately; after the vacuum furnace smelting time is greater than 1500min, according to the corrosion of the refractory and immersion tube in the furnace, the riser and downcomer are switched after the smelting of a single furnace or multiple furnaces.

[0053] Based on the above method, when there are three immersion tubes with relatively small inner diameters, and the immersion tubes include one riser and two downers, during the initial 0-300 minutes of vacuum furnace operation, after each heat of steel smelting is completed, the riser and downers are used alternately. During the 301-1500 minutes of vacuum furnace operation, which is the golden lifespan of refractory materials, the riser and downers are used alternately after 2-3 consecutive heats of smelting. After the vacuum furnace smelting time exceeds 1500 minutes, the riser and downers are switched after the completion of a single or multiple heats of smelting, depending on the corrosion of the refractory materials and the immersion tubes in the furnace.

[0054] Based on the above method, when there are four immersion tubes, the inner diameter of the immersion tube is relatively small, and two risers and two downers are preferably used. The distribution pattern refers to Example 3. In the initial use of the vacuum furnace (0-300 minutes), after each heat of steel smelting is completed, the immersion tube riser and downer are used alternately. The vacuum furnace is used for 301-1500 minutes, which is the golden life of refractory use. After 2-3 continuous smelting, the immersion tube riser and downer are used alternately. After the vacuum furnace smelting time is greater than 1500 minutes, the use of the riser and downer is switched after the completion of a single or multiple heats of smelting, depending on the corrosion of the refractory and immersion tube in the furnace.

[0055] Based on the above method, the erosion of the refractory materials in the furnace is monitored through the vacuum camera in the vacuum tank, and the inner diameter of the immersion tube is also monitored. Generally, the erosion rate of the downcomer and the upper refractory materials is more serious than that of the riser. Therefore, when the inner diameter of a single immersion tube is larger than that of other immersion tubes, this immersion tube should be used more as a riser in the future.

[0056] Based on the above method, a variety of molten steel circulation modes can be achieved, and these modes can be switched online during production, significantly improving the production flexibility of the RH refining furnace. By switching the molten steel circulation mode, the occurrence of small circulations can be avoided, and the appropriate molten steel circulation mode can be adaptively selected based on factors such as steel grade and molten steel quality, fully ensuring the molten steel refining effect. Obviously, the above method can also effectively extend the service life of each immersion tube 2 and reduce the continuous erosion of molten steel on specific areas of the vacuum chamber 1.

[0057] Therefore, preferably, the molten steel circulation mode switching node is located within a single refining heat.

Claims

1. An RH refining furnace comprising a vacuum chamber (1), an immersion pipe (2) at the bottom of the vacuum chamber, an ascending pipe (21) and a descending pipe (22) arranged with the immersion pipe (2), and a lifting gas blowing pipe shut-off valve on the ascending pipe (21) and the descending pipe (22), characterized in that: The number of the immersion tubes (2) at the bottom of the vacuum chamber is not less than three, the number of the riser (21) or the downcomer (22) is at least one, and the cross-sectional area of the molten steel rising channel defined by the riser (21) is equal to the cross-sectional area of the molten steel descending channel defined by the downcomer (22).

2. The RH refining furnace according to claim 1, characterized in that: There are three immersion pipes (2) at the bottom of the vacuum chamber, and the three immersion pipes (2) are arranged in an equilateral triangle.

3. The RH refining furnace according to claim 2, characterized in that: There are two riser tubes (21) and one downpipe (22) configured with the three immersion tubes (2). The cross-sectional area of the molten steel rising channel defined by the two riser tubes (21) is equal to the cross-sectional area of the molten steel descending channel defined by the one downpipe (22).

4. The RH refining furnace according to claim 2, characterized in that: There is one riser (21) and two downcomers (22) configured with the three immersion tubes (2). The cross-sectional area of the molten steel rising channel defined by the one riser (21) is equal to the cross-sectional area of the molten steel descending channel defined by the two downcomers (22).

5. The RH refining furnace according to claim 1, characterized in that: There are four immersion pipes (2) at the bottom of the vacuum chamber, and the four immersion pipes (2) are arranged in a quadrilateral.

6. The RH refining furnace according to claim 5, characterized in that: There is one riser (21) and three downcomers (22) configured for the four immersion tubes (2). The cross-sectional area of the molten steel rising channel defined by the one riser (21) is equal to the cross-sectional area of the molten steel descending channel defined by the three downcomers (22).

7. The RH refining furnace according to claim 5, characterized in that: There are two riser tubes (21) and two downcomers (22) configured with the four immersion tubes (2). The cross-sectional area of the molten steel rising channel defined by the two riser tubes (21) is equal to the cross-sectional area of the molten steel descending channel defined by the two downcomers (22).

8. The RH refining furnace according to claim 5, characterized in that: There are three risers (21) and one downcomer (22) configured with the four immersion tubes (2). The cross-sectional area of the molten steel rising channel defined by the three risers (21) is equal to the cross-sectional area of the molten steel descending channel defined by the one downcomer (22).

9. A RH refining furnace production method, characterized in that: An RH refining furnace as defined in any one of claims 1 to 8 is used. During the refining process, the switching nodes of the riser (21) and the downcomer (22) should be selected between adjacent smelting furnaces, and multi-furnace switching or single-furnace switching should be performed according to the online use time of the refining furnace.

10. The RH refining furnace production method according to claim 9, characterized in that: For a newly-installed vacuum furnace, during the initial period of 0-300 minutes of use, the riser (21) and the downcomer (22) should be switched after each furnace of steel is smelted; for a vacuum furnace used for 301-1500 minutes, the riser (21) and the downcomer (22) should be switched after smelting ≥ 2 furnaces continuously; for a vacuum furnace smelting time of > 1500 minutes, the riser (21) and the downcomer (22) should be switched after smelting of a single furnace or multiple furnaces, wherein the switching of the riser (21) and the downcomer (22) is completed by opening or closing the shut-off valve of the lifting gas blowing pipe.

Images