Castable and preparation method of RH furnace alloy chute containing castable

Abstract

The invention discloses a castable and a preparation method of an RH furnace alloy chute containing the castable. The castable comprises the following raw materials in parts by weight: 8-12 parts of 70 alumina, 65-75 parts of 85 alumina, 2-5 parts of silica fume, 4-6 parts of aluminate cement, 5-8 parts of activated alumina micropowder, 2-4 parts of steel fibers, less than or equal to 1 part of a water reducing agent and less than or equal to 1 part of explosion-proof fibers. The preparation method of the RH furnace alloy chute specifically comprises the following steps: (1) preparing a castable; (2) manufacturing an inner-layer steel plate of the alloy chute plate capable of being cooled by air; (3) manufacturing an outer-layer steel plate of the alloy chute plate capable of being air-cooled; (4) sealing and welding; (5) arranging a barometer, a butterfly valve and a standby passage; and (6) manufacturing a positioning ring of the alloy chute plate capable of being cooled by air, and carrying out pouring construction. The service life of the alloy feed opening can be prolonged, so that the repair frequency of an RH furnace can be reduced, the refining efficiency of a steel mill is improved, and meanwhile, the refractory material loss and the operating cost of a refractory material enterprise are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy, and more particularly to a casting material and a preparation method of an RH furnace alloy chute containing the casting material. Background Art

[0002] RH vacuum degassing refining method, namely molten steel vacuum cycle degassing method, is a molten steel refining method designed and developed by Ruhrstahl and Hereaeus. It is an important process for molten steel refining at present, which can realize functions such as degassing, decarburization, desulfurization, and adjustment of alloy content. The RH furnace is divided into several parts, including hot bending pipe, upper trough, alloy feeding port, middle trough, lower trough and immersion pipe. During smelting, alloy blocks fall from the silo and are introduced into the RH furnace through the alloy feeding port to achieve the purpose of adjusting the alloy composition. With the gradual increase in the output of various steel varieties, the amount of alloy added has increased significantly, from 100-200kg per furnace in the past to hundreds or thousands of kilograms per furnace, resulting in an increase in the passive impact loss of refractory materials at the alloy feeding port. Since the alloy feeding port is generally located in the middle of the upper trough, and the upper trough bricks have a long service life and a long replacement cycle, if the refractory materials at the alloy feeding port need to be replaced frequently due to alloy impact, it will not only affect the production efficiency of the steel plant, but also increase the loss of refractory materials.

[0003] Chinese patent document CN207512211U discloses "a self-flowing alloy chute for a refining furnace". Its construction plan is to use a complete set of iron molds as the lining of the chute. However, in this plan, the strength of the metal plate of the barrel steel structure will be reduced at high temperatures, and the chute plate will be more easily worn out under the scouring of a large amount of alloy, which is not conducive to long-term use.

[0004] Chinese patent document CN202415608U discloses "an alloy chute for a vacuum circulating degassing furnace", which uses a solid metal plate laid on the upper surface of the refractory material in the alloy feeding barrel. The length of the chute is determined by the impact point of the added alloy. However, in this scheme, the refractory material below the impact point is exposed to the impact of the alloy, and there is no alloy chute plate in other directions, which has no protective effect on the refractory material in the uncovered area.

[0005] Therefore, how to increase the service life of the alloy feeding port refractory material, thereby improving the production efficiency of the steel plant is an urgent problem that technical personnel in this field need to solve. Summary of the invention

[0006] In view of this, the object of the present invention is to provide a castable and a method for preparing an RH furnace alloy chute containing the same, which is used for an RH furnace alloy feeding port and improves the service life of the alloy chute plate.

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A casting material, comprising the following raw materials in parts by weight: 8-12 parts of 70 alumina, 65-75 parts of 85 alumina, 2-5 parts of microsilica powder, 4-6 parts of aluminate cement, 5-8 parts of activated alumina powder, 2-4 parts of steel fiber, ≤1 part of water reducing agent and ≤1 part of explosion-proof fiber;

[0009] The 85 alumina includes the following raw materials in percentage by mass: 8-5mm 85 alumina 14%-20%, 5-3mm 85 alumina 15%-20%, 3-1mm 85 alumina 12%-17%, 1-0mm 85 alumina 24%-28% and 0.06-0.074mm 85 alumina 20%-27%.

[0010] Furthermore, the mass fraction of Al2O3 in the above-mentioned 70 alumina is ≥70%.

[0011] Furthermore, the mass fraction of Al2O3 in the above-mentioned 85 alumina is ≥85%.

[0012] Furthermore, the mass fraction of SiO2 in the above-mentioned microsilica powder is ≥92%.

[0013] Furthermore, the mass fraction of Al2O3 in the above-mentioned aluminate cement is 71.0%-71.8%.

[0014] Furthermore, the mass fraction of Al2O3 in the above-mentioned activated alumina powder is ≥99.5%.

[0015] Furthermore, the water reducing agent is at least one of sodium hexametaphosphate, sodium tripolyphosphate and Castament FS20 (a water reducing agent for low-cement refractory castables containing microsilica).

[0016] The further beneficial effect of adopting the above method is that the sodium hexametaphosphate and Castament FS20 in the water reducer selected by the present invention can effectively improve the fluidity of the aluminum-silicon castable, and improve the operability of on-site construction when the feed opening is narrow; the fluidity of the aluminum-silicon castable mixed with sodium tripolyphosphate is weaker than that of hexametaphosphate and FS20, and is more suitable for situations where the feed opening is wide, the amount of water added by on-site workers fluctuates greatly, or the mixing personnel change frequently.

[0017] A method for preparing an RH furnace alloy chute containing the above-mentioned castable comprises the following steps:

[0018] (1) According to the weight proportions of the above castables, 1-0 mm 85 bauxite, 0.06-0.074 mm 85 bauxite, microsilica powder, aluminate cement, activated alumina powder, water reducer and explosion-proof fiber are weighed and premixed, and then 70 bauxite, 8-5 mm 85 bauxite, 5-3 mm 85 bauxite, 3-1 mm 85 bauxite and steel fiber are added and stirred to obtain the castable, which is then bagged for later use;

[0019] (2) To make the inner steel plate of the air-cooled alloy chute plate, use a 8-10 mm thick steel plate to roll it into a ring steel plate with an inner diameter of 360 mm, and evenly weld 8-12 serpentine partition steel plates with a height of 15-20 mm and a width of 10-20 mm on its outer diameter circular surface;

[0020] (3) Making an outer steel plate of an air-cooled alloy chute plate, whose inner diameter differs from the outer diameter of the inner steel plate by 20-23 mm, opening 8-12 holes with a width of 15-20 mm on a 5-8 mm thick steel plate, whose opening positions and sizes correspond to the positions of the serpentine partitions, the opening length is less than or equal to the partition length of 5-10 mm, and the width is less than or equal to the partition steel plate by 2-3 mm, then rolling the steel plate into an annular steel plate, and putting it outside the inner steel plate, so that the opening position coincides with the position of the corresponding length partition, and then welding the partition and the outer steel plate into a whole;

[0021] (4) Use annular steel plates to seal and weld the top and bottom of the inner and outer steel plates. The top annular steel plate is reserved for air-cooling air inlet and air-cooling air return pipe openings. The air inlet pipe and the air return pipe are welded to both sides of the partition respectively;

[0022] (5) A pressure gauge, a butterfly valve and a spare passage are set at the front end of the air inlet and the air return port. The air inlet and the air return port are respectively connected to the gas source and the soft connection direction pipeline of 2-4 lifting gas pipelines arranged at an interval of 180°-90°, so that they can be used as air-cooled gas sources. The spare passage is used as a second passage directly connected to 2-4 lifting gas pipes when the air tightness of the alloy chute is damaged. When there is a difference between the pressure gauges of the air inlet pipe and the air return pipe, the butterfly valve opens the spare passage to make the lifting gas directly connected to the nearest soft connection of the argon gas pipe;

[0023] (6) Use 10mm round steel to make the positioning ring of the air-cooled alloy chute plate, whose inner diameter is 3-5mm larger than the outer diameter of the alloy chute plate. Wrap 2 circles of 1mm thick yellow paper around the outer wall of the alloy chute plate, build the alloy discharge port door frame, cover the door frame with wooden boards on the outside of the door frame, and then use support rods to support the wooden boards. Install the air-cooled alloy chute plate, pass through the positioning ring so that the bottom is against the door frame brick, and the top is welded to the docking flange for fixation. Casting construction, after baking in the RH furnace, put it on the line for use. The damaged alloy discharge port chute plate can be split and repaired for secondary use.

[0024] The present invention adopts an air-cooled metal chute, which has an air-cooling channel reserved inside, an air inlet and an air return port are arranged at the top, and a barometer is connected outside the air return port to measure the gas pressure in the air return port pipeline. A butterfly valve and a spare passage are arranged at the front end of the air inlet and the end of the barometer outside the air return port, which are used to directly connect the lifting gas soft sleeve in case of damage to the alloy chute plate and gas leakage. In abnormal cases, even if the argon gas in the spare passage cannot blow away the refluxed molten steel, the normal circulation of the molten steel can be guaranteed when 2-4 argon gas pipes are blocked, and the smooth production of the steel plant can continue to be guaranteed.

[0025] The air-cooled gas source uses the same source gas in the argon tube of the RH furnace ascending immersion tube arranged oppositely. Its advantage is that the lifting gas cools the alloy chute plate, making it resistant to alloy impact in a high-temperature working environment, which can directly increase the service life of the alloy discharge port. The lifting gas source itself increases in temperature during the cooling process, and then is blown into the ascending tube through the argon tube to lift the molten steel. The heated gas moves faster, which is more conducive to the circulation of molten steel.

[0026] The backup passage connects the three-way pipe outside the air inlet and the air return port. A ball valve is installed in the three-way pipe to ensure that the backup passage is normally in a closed state. When the air pressure outside the air return port is lower than the threshold value, the air inlet pipe, the air return port and the alloy chute passage are closed, and the backup passage is opened to prevent the pressure in the argon pipe from being too low, resulting in the reflux of molten steel in the immersion tube and blocking the argon pipe.

[0027] In order to extend the life of the alloy feeding port, the refractory materials in the alloy feeding barrel of the RH furnace are constructed with steel fiber castables, and two positioning rings are set inside the steel shell to keep the relative position of the alloy chute plate fixed to prevent the chute plate from jumping and damaging the external refractory materials when the alloy is added.

[0028] In order to achieve air cooling of the alloy chute plate, 8-10mm thick steel plates are used in the inner diameter direction, and 5-8mm thick steel plates are used in the outer diameter direction. 8-12 partitions with a height of 15-20mm and a width of 15-20mm are evenly distributed between the two layers of steel plates, so that the space separated by the two steel plates can be arranged in a serpentine shape.

[0029] In summary, the advantages of the RH furnace alloy chute of the present invention are: first, the service life of the alloy feeding port is improved, the refractory cost is reduced, and the production efficiency of the steel plant is improved; second, the air flow velocity of the air-cooled gas that takes away the heat of the alloy chute plate will be increased when it is blown in the riser, which is beneficial to increase the circulation speed of molten steel and improve the refining efficiency; third, the air-cooled alloy chute can be replaced and repaired and reused, and the production cost is low; third, the alloy feeding port is used in the same construction as the casting material, which is easy to operate and saves work hours; finally, the influence of the heated lifting gas on the ring bricks of the riser immersion tube will be reduced, and the peeling near the argon gas pipe mouth of the riser immersion tube will be reduced to a certain extent.

[0030] Furthermore, in the above step (1), the premixing device is a conical premixer, and the time is 3-5 minutes; the stirring device is a planetary forced mixer, and the time is 3-5 minutes.

[0031] Furthermore, in the above step (2), one of the serpentine partition steel plates divides the alloy chute plate into two parts that are not connected to each other on the left and right, and one end of the interval of the remaining serpentine partition steel plates starts at the top or bottom, and the other end is 50-100mm away from the edge of the inner steel plate, which is the length of the partition steel plate.

[0032] It can be seen from the above technical solution that compared with the prior art, the beneficial effects of the present invention are as follows:

[0033] The present invention can increase the service life of the alloy feeding port, thereby reducing the repair frequency of the RH furnace, improving the refining efficiency of the steel plant, and reducing the refractory loss and the operating cost of the refractory enterprise. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is the overall structural diagram of the alloy chute of the RH furnace;

[0035] Figure 2 This is a schematic diagram of the structure of the air inlet pipe, air return pipe, dividing partition and serpentine partition in the RH furnace alloy chute. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. 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.

[0037] Example 1

[0038] Castable material, including the following raw materials by weight: 12kg of 70 alumina, 70.75kg of 85 alumina, 3kg of microsilica powder, 5kg of aluminate cement, 6kg of activated alumina powder, 3kg of steel fiber, 0.15kg of sodium hexametaphosphate and 0.1kg of explosion-proof fiber;

[0039] The 85 alumina includes the following raw materials in percentage by mass: 8-5mm 85 alumina 14%, 5-3mm 85 alumina 15.5%, 3-1mm 85 alumina 17%, 1-0mm 85 alumina 26.5% and 0.06-0.074mm 85 alumina 27%;

[0040] The mass fraction of Al2O3 in 70 alumina is 70.8%;

[0041] The mass fraction of Al2O3 in 85 alumina is 85.2%;

[0042] The mass fraction of SiO2 in microsilica powder is 92.5%;

[0043] The mass fraction of Al2O3 in aluminate cement is 71.7%;

[0044] The mass fraction of Al2O3 in the activated alumina powder is 99.6%.

[0045] Example 2

[0046] The preparation method of the RH furnace alloy chute containing the castable of Example 1 is as follows: Figure 1-2 As shown, the specific steps include:

[0047] (1) According to the weight of the castable in Example 1, 1-0 mm 85 bauxite, 0.06-0.074 mm 85 bauxite, microsilica powder, aluminate cement, activated alumina powder, sodium hexapolyphosphate and explosion-proof fiber were weighed, added to a conical premixer and premixed for 3 min, then transferred to a planetary forced mixer, 70 bauxite, 8-5 mm 85 bauxite, 5-3 mm 85 bauxite, 3-1 mm 85 bauxite and steel fiber were added, stirred for 4 min, and the castable was obtained and bagged for standby use;

[0048] (2) To make the inner steel plate of the air-cooled alloy chute plate, a 10 mm thick steel plate is rolled into a ring steel plate with an inner diameter of 360 mm. Ten serpentine partition steel plates with a height of 17 mm and a width of 20 mm are evenly distributed and welded on the outer diameter circular surface. One of the serpentine partition steel plates divides the alloy chute plate into two parts that are not connected to the left and right. The other serpentine partition steel plates have one end starting from the top or bottom, and the other end is 100 mm away from the edge of the inner steel plate as the length of the partition steel plate;

[0049] (3) The outer steel plate of the alloy chute plate that can be air-cooled is made, and its inner diameter is 20 mm different from the outer diameter of the inner steel plate. Ten holes with a width of 15 mm are opened on the 5 mm thick steel plate. The position and size of the holes correspond to the position of the serpentine partition. The length of the holes is less than or equal to the length of the partition 5 mm, and the width is less than or equal to the partition steel plate 3 mm. Then, the steel plate is rolled into a ring-shaped steel plate and put on the outer layer of the inner steel plate so that the position of the holes coincides with the position of the partition of the corresponding length. Then, the partition and the outer steel plate are welded into a whole;

[0050] (4) Use annular steel plates to seal and weld the top and bottom of the inner and outer steel plates. The top annular steel plate is reserved for air-cooling air inlet and air-cooling air return pipe openings. The air inlet pipe and the air return pipe are welded to both sides of the partition respectively;

[0051] (5) A pressure gauge, a butterfly valve and a spare passage are set at the front end of the air inlet and the air return port. The air inlet and the air return port are respectively connected to the gas source and the soft connection direction pipeline of four lifting gas pipelines arranged at 90° intervals, so that they can be used as air-cooled gas sources. The spare passage is used as a second passage directly connected to the four lifting gas pipes when the air tightness of the alloy chute is damaged. When there is a difference between the pressure gauges of the air inlet pipe and the air return pipe, the butterfly valve opens the spare passage, so that the lifting gas is directly connected to the nearest soft connection of the argon gas pipe;

[0052] (6) Use 10mm round steel to make the positioning ring of the air-cooled alloy chute plate, whose inner diameter is 4mm larger than the outer diameter of the alloy chute plate. Wrap 2 circles of 1mm thick yellow paper around the outer wall of the alloy chute plate, build the alloy discharge port door frame, cover the door frame with wooden boards on the outside of the door frame, and then use support rods to support the wooden boards. Install the air-cooled alloy chute plate, pass through the positioning ring so that the bottom is against the door frame brick, and the top is welded to the docking flange for fixation. Casting construction, after baking in the RH furnace, put it on line for use. The damaged alloy discharge port chute plate can be split and repaired for secondary use.

[0053] According to the test, the service life of the RH furnace alloy chute prepared in Example 2 is increased from the original 500 overhauls to 900-1000 overhauls, which reduces the frequency of repairs and improves the refining efficiency of the steel plant.

[0054] Since the RH furnace alloy chute lining bricks prepared in Example 2 are not directly eroded by a large amount of alloy, the impact on the alloy discharge port door frame bricks is greatly reduced, so that the life of the alloy discharge port door frame and the surrounding side wall working layer bricks is simultaneously improved, thereby increasing the company's profits.

[0055] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A casting material, characterized in that: The raw materials include the following parts by weight: 8-12 parts of 70 alumina, 65-75 parts of 85 alumina, 2-5 parts of microsilica powder, 4-6 parts of aluminate cement, 5-8 parts of activated alumina powder, 2-4 parts of steel fiber, ≤1 part of water reducing agent and ≤1 part of explosion-proof fiber; The 85 alumina comprises the following raw materials in percentage by mass: 8-5mm 85 alumina 14%-20%, 5-3mm 85 alumina 15%-20%, 3-1mm 85 alumina 12%-17%, 1-0mm 85 alumina 24%-28% and 0.06-0.074mm 85 alumina 20%-27%.

2. A casting material according to claim 1, characterized in that: The mass fraction of Al2O3 in the 70 alumina is ≥70%.

3. A casting material according to claim 1, characterized in that: The mass fraction of Al2O3 in the 85 alumina is ≥85%.

4. A casting material according to claim 1, characterized in that: The mass fraction of SiO2 in the microsilica powder is ≥92%.

5. A casting material according to claim 1, characterized in that: The mass fraction of Al2O3 in the aluminate cement is 71.0%-71.8%.

6. A casting material according to claim 1, characterized in that: The mass fraction of Al2O3 in the activated alumina micropowder is ≥99.5%.

7. A casting material according to claim 1, characterized in that: The water reducing agent is at least one of sodium hexametaphosphate, sodium tripolyphosphate and Castament FS20.

8. A method for preparing an RH furnace alloy chute containing the castable as claimed in claim 1, characterized in that: The specific steps include: (1) According to the weight proportions of the castable material of claim 1, first weigh 1-0 mm 85 bauxite, 0.06-0.074 mm 85 bauxite, microsilica powder, aluminate cement, activated alumina powder, water reducer and explosion-proof fiber, premix, then add 70 bauxite, 8-5 mm 85 bauxite, 5-3 mm 85 bauxite, 3-1 mm 85 bauxite and steel fiber, stir to obtain the castable, and bag it for later use; (2) To make the inner steel plate of the air-cooled alloy chute plate, use a 8-10 mm thick steel plate to roll it into a ring steel plate with an inner diameter of 360 mm, and evenly weld 8-12 serpentine partition steel plates with a height of 15-20 mm and a width of 15-20 mm on its outer diameter circular surface; (3) Making an outer steel plate of an air-cooled alloy chute plate, whose inner diameter differs from the outer diameter of the inner steel plate by 20-23 mm, opening 8-12 holes with a width of 15-20 mm on a 5-8 mm thick steel plate, whose opening positions and sizes correspond to the positions of the serpentine partitions, the opening length is less than or equal to the partition length of 5-10 mm, and the width is less than or equal to the partition steel plate by 2-3 mm, then rolling the steel plate into an annular steel plate, and putting it outside the inner steel plate, so that the opening position coincides with the position of the corresponding length partition, and then welding the partition and the outer steel plate into a whole; (4) Use annular steel plates to seal and weld the top and bottom of the inner and outer steel plates. The top annular steel plate is reserved for air-cooling air inlet and air-cooling air return pipe openings. The air inlet pipe and the air return pipe are welded to both sides of the partition respectively; (5) A pressure gauge, a butterfly valve and a spare passage are set at the front end of the air inlet and the air return port. The air inlet and the air return port are respectively connected to the gas source and the soft connection direction pipeline of 2-4 lifting gas pipelines arranged at an interval of 180°-90°, so that they can be used as air-cooled gas sources. The spare passage is used as a second passage directly connected to 2-4 lifting gas pipes when the air tightness of the alloy chute is damaged. When there is a difference between the pressure gauges of the air inlet pipe and the air return pipe, the butterfly valve opens the spare passage to make the lifting gas directly connected to the nearest soft connection of the argon gas pipe; (6) Use 10mm round steel to make the positioning ring of the air-cooled alloy chute plate, whose inner diameter is 3-5mm larger than the outer diameter of the alloy chute plate. Wrap 2 circles of 1mm thick yellow paper around the outer wall of the alloy chute plate, build the alloy discharge port door frame, cover the door frame with wooden boards on the outside of the door frame, and then use support rods to support the wooden boards. Install the air-cooled alloy chute plate, pass through the positioning ring so that the bottom is against the door frame brick, and the top is welded to the docking flange for fixation. Casting construction, after baking in the RH furnace, put it on the line for use. The damaged alloy discharge port chute plate can be split and repaired for secondary use.

9. The method for preparing an RH furnace alloy chute according to claim 8, characterized in that: In step (1), the premixing device is a conical premixer, and the time is 3-5 minutes; the stirring device is a planetary forced mixer, and the time is 3-5 minutes.

10. The method for preparing an RH furnace alloy chute according to claim 8, characterized in that: In step (2), one of the serpentine partition steel plates divides the alloy chute plate into two parts that are not connected to each other on the left and right. One end of the interval of the remaining serpentine partition steel plates starts at the top or bottom, and the other end is 50-100mm away from the edge of the inner steel plate, which is the length of the partition steel plate.

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