Calcium wire feeding device for small vacuum induction furnace and working method thereof

Abstract

The present application belongs to the technical field of steel metallurgy, and particularly relates to a calcium wire feeding device for a small vacuum induction furnace and a working method thereof. The calcium wire feeding device comprises a first vacuum chamber and a second vacuum chamber. The first vacuum chamber and the second vacuum chamber are communicated and separated by a movable vacuum isolation plate. An electric hoist is fixedly installed in the second vacuum chamber. A counterweight is connected to a hoisting end of the electric hoist. A cap is connected below the counterweight. A plurality of calcium wires are clamped to the bottom end of the cap through fixing blocks. A vacuum induction furnace is installed in the first vacuum chamber. The top of the vacuum induction furnace is covered by the cap, so as to isolate the molten steel in the induction furnace from the first vacuum chamber. The induction furnace and the refractory cap form a closed space, which can reduce the phenomenon that calcium elements boil and evaporate into the vacuum chamber, improve the calcium partial pressure in the closed space, and increase the amount of calcium elements dissolved into the molten steel. Therefore, the influence of the continuous vacuum extraction process on the calcium element recovery rate can be reduced.

Description

Technical Field

[0001] This invention belongs to the field of iron and steel metallurgy technology, and particularly relates to a small vacuum induction furnace calcium feeding wire device and its working method. Background Technology

[0002] Before new steel grades in the steel industry are put into mass production, they must undergo multiple heats and small-scale laboratory tests to produce small steel ingots, which are then rolled or forged to take samples for various performance tests and analyses. Product performance is not only affected by the research and development process, but the control of the experimental production process also has a significant impact on the test data. Therefore, it is particularly important to improve the accuracy of the control of the molten steel composition as much as possible.

[0003] Ca is widely used in steelmaking processes to remove Al2O3 inclusions and has a certain deoxidation effect. However, Ca has a boiling point of only 1484℃, which is lower than the temperature of molten steel. Under the continuous vacuum environment in a vacuum induction furnace, Ca is easily boiled and volatilized when added to molten steel. The existing process increases the calcium content by adding calcium alloys to the vacuum induction furnace from the silo. However, since the density of calcium alloys is lower than that of steel, the calcium alloys easily melt on the surface of the molten steel and boil and volatilize, and are then removed by the vacuum equipment. The calcium recovery rate is only 1-4%, which is low and unstable.

[0004] In the steelmaking industry of large-tonnage converters, the calcium content in molten steel is generally controlled by feeding calcium wire into the molten steel using a wire feeder. The calcium wire consists of a steel shell and calcium powder. By rapidly feeding the calcium wire (feeding speed of more than 2.5 m / s) into the depths of the molten steel, the calcium recovery rate can be improved, reaching more than 20%. However, the wire feeder is a large piece of equipment and is not suitable for vacuum experimental furnaces of 100-200 kg class. Moreover, it is difficult to maintain a vacuum state during the calcium wire feeding process, which can easily cause the molten steel to be oxidized.

[0005] Chinese invention patent application CN110777231A discloses a vacuum furnace wire feeding device, which includes a drive device and a transmission device. The drive device includes a counter, a motor, and a reducer. The transmission device includes a drive shaft, a drive wheel, and a pressure wheel. The counter is mounted on the motor and is used to obtain the number of rotations of the motor rotor. The rotor is connected to the input shaft of the reducer, and the output shaft of the reducer is connected to one end of the drive shaft. The drive wheel is connected to the other end of the drive shaft. The pressure wheel is arranged adjacent to the drive wheel, and a transmission channel is defined between the pressure wheel and the drive wheel. This invention has a relatively complex design structure, is difficult to maintain, has limited wire feeding speed, relatively low efficiency, and has high requirements for the size and shape of the fed wire, resulting in poor operational flexibility and smoothness.

[0006] Chinese invention patent application CN108559860B discloses an apparatus and method for efficient desulfurization in vacuum induction melting of nickel-based alloys. This invention includes a vacuum induction furnace and a feeding and wire feeding device located above the furnace cover. Magnesium or calcium cored wire is inserted into the molten pool of the vacuum induction furnace through this device for desulfurization. However, this invention lacks an effective calculation or measurement method and control mechanism for the precise amount of wire added, resulting in insufficient accuracy in the feeding process. Summary of the Invention

[0007] The purpose of this invention is to provide a small vacuum induction furnace calcium feeding wire device and its working method to solve the problems existing in the prior art.

[0008] The technical solution adopted by the present invention to solve its technical problem is: a small experimental vacuum induction furnace calcium wire feeding device, including a first vacuum chamber and a second vacuum chamber. The first vacuum chamber and the second vacuum chamber are connected and separated by a movable vacuum isolation plate. An electric hoist is fixedly installed in the second vacuum chamber. A counterweight is connected to the hoist's lifting end. A cap is connected below the counterweight. Several calcium wires are clamped to the bottom of the cap by a fixing block. A vacuum induction furnace is installed in the first vacuum chamber.

[0009] Furthermore, the counterweight is a cylindrical iron block with a hook welded to the top. The counterweight is attached to the lifting end of the electric hoist via the hook, and an internally threaded pipe is welded to the bottom of the counterweight.

[0010] Furthermore, the cap is made of magnesia-carbon refractory material and is spherical. The bottom diameter of the cap matches the top opening of the vacuum induction furnace. A steel external thread rod is embedded at the top of the cap, and the cap is connected to the internal thread tube of the counterweight through the external thread rod. A fixed circular groove is opened at the center of the bottom end of the cap.

[0011] Furthermore, the fixing block is a frustum-shaped wooden block, and the calcium wire is secured to the inner wall of the fixing groove at the bottom of the cap through the fixing block.

[0012] A method for operating a small-scale vacuum induction furnace calcium wire feeding device for experimental use includes the following steps:

[0013] (1) Calculate the amount of calcium line fed using the feeding amount calculation formula, and calculate the total length of calcium line using the total length calculation formula;

[0014] (2) Cut the calcium wire into several pieces of appropriate length according to the total length of the calcium wire, and then use a fixing block to clamp the cut calcium wire onto the inner wall of the fixing groove at the bottom of the cap. Use a hammer to tap the fixing block to clamp the calcium wire.

[0015] (3) Connect the counterweight and cap in sequence, evacuate the second vacuum chamber, open the vacuum isolation plate to connect the first and second vacuum chambers, turn on the electric hoist, lower the cap and cover the vacuum induction furnace, and feed the calcium wire into the molten steel in the vacuum induction furnace of the first vacuum chamber.

[0016] (4) After the calcium wire is fed in for 5-10 seconds, start the electric hoist again to raise the cap back into the second vacuum chamber and close the vacuum isolation plate, thus ending the calcium wire feeding.

[0017] Furthermore, the formula for calculating the feed amount in step (1) is:

[0018] L=ω Ca ×m 钢 ×1000 / (η×K);

[0019] Where L is the calcium feeding volume, in meters (m);

[0020] ω Ca The target value for the percentage of calcium by mass in molten steel, in %

[0021] m 钢 This refers to the weight of the molten steel, in kg.

[0022] η represents the calcium recovery rate, expressed as a percentage.

[0023] K represents the weight of calcium in a unit of calcium line, expressed in g / m.

[0024] Furthermore, the formula for calculating the total length in step (1) is: L0 = nL1 + L;

[0025] Where L is the calcium feeding amount;

[0026] L0 is the total length of the calcium line;

[0027] n is the number of calcium wires;

[0028] L1 is the distance from the top surface of the fixed circular groove to the surface of the molten steel.

[0029] Furthermore, in step (2), the length L2 of the cut calcium wire is greater than L1 and less than the distance L3 from the top surface of the fixed circular groove to the inner wall of the bottom surface of the vacuum induction furnace.

[0030] The present invention has the following beneficial effects:

[0031] 1. This invention isolates the molten steel inside the induction furnace from the first vacuum chamber by covering the top of the vacuum induction furnace with a cap, thus forming a sealed space between the induction furnace and the refractory cap. This reduces the phenomenon of calcium boiling and volatilizing into the vacuum chamber, increases the partial pressure of calcium in the sealed space, and thus increases the amount of calcium dissolved into the molten steel. This reduces the impact of continuous vacuuming on the calcium recovery rate.

[0032] 2. This invention further expands the functionality of the first vacuum chamber used for vacuum melting and the second vacuum chamber used for sampling in the prior art, giving them the function of feeding calcium wire, without requiring damage or modification to the existing equipment, thus reducing technical transformation costs.

[0033] 3. Compared with existing industrial calcium wire feeding machines, this invention is suitable for small experimental furnaces and can feed calcium wires in a vacuum environment, thereby improving the recovery rate of calcium.

[0034] 4. This invention controls the amount of calcium wire fed through the formulas for calculating the amount of feed and the total length, thereby improving the accuracy of calcium wire feeding.

[0035] 5. The present invention uses a method of feeding a wire-type calcium alloy into molten steel to increase calcium content. After being fed deep into the molten steel, the steel shell on the outer surface of the calcium wire melts, thereby reducing the boiling volatilization rate of calcium and increasing the calcium recovery rate. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the structure of the present invention.

[0037] Figure 2 This is a schematic diagram of the connection structure between the cap and the calcium wire of the present invention.

[0038] Figure 3 This is a schematic cross-sectional view of the vacuum induction furnace position during calcium wire feeding according to the present invention.

[0039] The components are: 1. First vacuum chamber; 2. Second vacuum chamber; 3. Vacuum isolation plate; 4. Electric hoist; 5. Counterweight; 6. Cap; 7. Fixing block; 8. Calcium wire; 9. Vacuum induction furnace; 10. Hook; 11. Internally threaded pipe; 12. Externally threaded rod; 13. Fixed circular groove; 14. Molten steel. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0041] Example 1:

[0042] like Figure 1-3 As shown, a small-scale vacuum induction furnace for feeding calcium wires for experimental use includes a first vacuum chamber 1 and a second vacuum chamber 2. The first vacuum chamber 1 and the second vacuum chamber 2 are connected and separated by a movable vacuum isolation plate 3. An electric hoist 4 is fixedly installed in the second vacuum chamber 2. A counterweight 5 is connected to the hoist 4 at its lifting end. A cap 6 is connected below the counterweight 5. Several calcium wires 8 are clamped to the bottom of the cap 6 by a fixing block 7. A vacuum induction furnace 9 is installed in the first vacuum chamber 1.

[0043] The counterweight 5 is a cylindrical iron block. The bottom diameter of the counterweight 5 can be set to 100-150mm, and the height to 50-100mm, depending on the actual situation. A hook 10 is welded to the top of the counterweight 5, which is then attached to the lifting end of the electric hoist 4. An internally threaded pipe 11 is welded to the bottom of the counterweight 5. The counterweight 5 is used to increase the lifting weight of the calcium wire 8, enhancing its stability during descent. In this embodiment, the bottom diameter of the counterweight 5 is 120mm, and the height is 60mm.

[0044] The cap 6 is made of magnesia-carbon refractory material and is spherical. The cap 6 is used to cover the upper opening of the vacuum induction furnace 9, thereby isolating the molten steel 14 inside the induction furnace and isolating the vacuum induction furnace 9 into a sealed control, thus preventing calcium from boiling and evaporating into the first vacuum chamber 1, thereby increasing the partial pressure of calcium in the sealed space, which in turn increases the amount of calcium dissolved into the molten steel, thereby reducing the impact of continuous vacuuming process on the calcium recovery rate. To ensure that the cap 6 has sufficient strength and that the fixing groove 13 has sufficient height to hold the calcium wire 8, the height of the cap 6 is 100-150mm. The bottom diameter of the cap 6 matches the upper opening of the vacuum induction furnace 9. In this embodiment, the spherical height of the cap 6 is 120mm. A steel external threaded rod 12 is embedded at the top of the cap 6. The cap 6 is connected to the internal threaded tube 11 of the counterweight block 5 through the external threaded rod 12. A fixing groove 13 is opened at the center of the bottom end of the cap 6. The fixing groove 13 is used to hold the calcium wire 8. Therefore, sufficient space is needed to accommodate the calcium wire 8 and the fixing block 7. The diameter of the fixing groove 13 is 60-70mm and the height of the fixing groove 13 is 50-60mm. In this embodiment, the diameter of the fixing groove 13 is 65mm and the height is 55mm.

[0045] The fixing block 7 is a frustum-shaped wooden block. The function of the fixing block 7 is to hold the calcium wire 8 onto the inner wall of the fixing groove 13. The fixing block 7 needs to enter the fixing groove 13 and hold the calcium wire 8. Therefore, the upper surface diameter of the fixing block 7 is 30-50mm, the lower surface diameter is 45-60mm, and the height of the fixing block 7 is 30-50mm. In this embodiment, the upper surface diameter of the fixing block 7 is 40mm, the lower surface diameter is 50mm, and the height is 35mm.

[0046] It should be noted that, Figure 1 The connection method of each structure of the present invention is described. Each structure is not drawn according to the actual size. In reality, the volume of the second vacuum chamber 2 is large enough to accommodate the connected electric hoist 4, counterweight 5, cap 6, fixing block 7, and calcium wire 8.

[0047] Example 2:

[0048] like Figure 1-3 As shown, this embodiment provides a working method for a small-scale vacuum induction furnace calcium feeding device for testing. This embodiment is based on Embodiment 1.

[0049] In this embodiment, the target value ω of the calcium content by mass in molten steel 14 is... Ca It is 0.006%, and the molten steel weighs 14 m. 钢 The weight is 225 kg; the calcium recovery rate η is 10%; the weight of calcium K contained in unit calcium line 8 is 130 g / m.

[0050] A method for operating a small-scale vacuum induction furnace calcium wire feeding device for experimental use includes the following steps:

[0051] (1) The feeding amount of calcium line 8 is calculated using the formula for calculating the feeding amount of calcium line 8. The calculation results are as follows:

[0052] L=0.006%×225kg×1000 / (10%×130g / m)=1.04m;

[0053] The total length of calcium wire 8 is calculated according to the formula for calculating the total length of calcium wire 8. Since the weight of molten steel 14 is determined, the liquid level of molten steel 14 is also determined. Therefore, the distance L1 from the top surface of the fixed circular groove 13 to the liquid surface of molten steel 14 is also determined. In this embodiment, L1 = 86.6 mm. That is, when calcium wire 8 is fixed in the fixed circular groove 13, in order to ensure a stable fixation, the upper end of calcium wire 8 rests on the top surface of the fixed circular groove 13. After the cap 6 is placed on the vacuum induction furnace 9, the lower part of calcium wire 8 enters the molten steel 14. The upper part of calcium wire 8 is 86.6 mm above the liquid surface of molten steel 14. This part cannot be included in the feeding amount of calcium wire 8.

[0054] In this embodiment, the distance L3 from the top surface of the fixed circular groove 13 to the inner wall of the bottom surface of the vacuum induction furnace 9 is 500mm. If the length L2 of a single calcium wire 8 is greater than 500mm, the cap 6 will not be able to cover the top opening of the vacuum induction furnace 9. If it is equal to 500mm, the cap 6 will also not be able to cover the top opening of the vacuum induction furnace 9 due to a certain deviation. Therefore, L2 should be less than 500mm. The deeper the calcium wire 8 is immersed in the molten steel 14, the better the feeding effect of the calcium wire 8. Therefore, L2 must be greater than the distance L1 from the top surface of the fixed circular groove 13 to the surface of the molten steel 14.

[0055] In this embodiment, the feed amount of calcium wire 8 is 1.04m. If n is 1 or 2, it means using one calcium wire 8 with a length of 1.3m or two calcium wires of 0.65m each. Then L2 is greater than 500mm, which will cause the cap 6 to be unable to cover the top of the vacuum induction furnace 9. When n is 3, L2 is 86.6 + 1.04 / 3 = 433mm, which meets the condition that L2 is greater than L1 and less than L3. Therefore, when n is 3, the total length of calcium wire 8 is L0 = nL1 + L = 3 × 0.433m + 1.04m = 1.3m.

[0056] Of course, n can also be greater than 3, but considering the immersion depth of calcium line 8 or the feeding effect of calcium line 8, it is better to take a value of 3. The specific value also needs to be determined based on other factors. For example, there may be 4 calcium lines 8 of suitable length on site. In order to save costs, a value of 4 can also be taken.

[0057] (2) Cut the 1.3m calcium wire 8 into 3 pieces of 433mm each, and then use the fixing block 7 to clamp the cut calcium wire 8 onto the inner wall of the fixing groove 13 at the bottom of the cap 6. Use a hammer to tap the fixing block 7 to clamp the calcium wire 8 tightly.

[0058] It should be noted that the cutting length of calcium wire 8 can be adjusted according to the actual situation. For example, if there are two 450mm calcium wires 8 on site, in order to save costs, it is sufficient to cut another 400mm calcium wire 8.

[0059] (3) Connect the counterweight 5 and the cap 6 in sequence. After evacuating the second vacuum chamber 2, open the vacuum isolation plate 3 to connect the first vacuum chamber 1 and the second vacuum chamber 2. Turn on the electric hoist 4 to lower the cap 6 and cover the vacuum induction furnace 9. The calcium wire 8 is fed into the molten steel 14 in the vacuum induction furnace 9 of the first vacuum chamber 1.

[0060] (4) After the calcium wire 8 is fed in for 8 seconds, the electric hoist 4 is started again, so that the cap 6 rises back into the second vacuum chamber 2 and the vacuum isolation plate 3 is closed, thus ending the feeding of the calcium wire 8.

[0061] The calcium content in the molten steel 14 was measured to be 0.0068%, and the calculated calcium recovery rate was 11.3%, significantly higher than the recovery rate (1-4%) achieved by adding calcium alloys to the vacuum induction furnace 9 via a hopper in existing processes. This is due to two main reasons: First, this invention uses a method of feeding a wire-type calcium alloy into the molten steel to increase calcium content. The steel shell on the outer surface of the calcium wire 8 melts only after it has been fed deep into the molten steel, thus reducing the boiling and volatilization rate of calcium and increasing the calcium recovery rate. Second, during operation, the refractory cap 6 covers the top of the vacuum induction furnace 9, isolating the molten steel 14 from the first vacuum chamber 1. This creates a sealed space between the furnace and the cap, reducing the boiling and volatilization of calcium into the first vacuum chamber 1 and increasing the partial pressure of calcium in this sealed space. This increases the amount of calcium dissolved in the molten steel, thus reducing the impact of continuous vacuuming on the calcium recovery rate.

[0062] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the concept and scope of the present invention. Various modifications and improvements made to the technical solutions of the present invention by those skilled in the art without departing from the inventive concept should fall within the protection scope of the present invention.

[0063] The technologies, shapes, and structures not described in detail in this invention are all known technologies.

Claims

1. A method for operating a calcium wire feeding device for a small experimental vacuum induction furnace, characterized in that, The experimental small vacuum induction furnace calcium wire feeding device includes a first vacuum chamber and a second vacuum chamber. The first vacuum chamber and the second vacuum chamber are connected and separated by a movable vacuum isolation plate. An electric hoist is fixedly installed in the second vacuum chamber. A counterweight is connected to the hoist's lifting end. A cap is connected below the counterweight. Several calcium wires are clamped to the bottom of the cap by a fixing block. A vacuum induction furnace is installed in the first vacuum chamber. The counterweight is a cylindrical iron block with a hook welded to the top. The counterweight is attached to the lifting end of the electric hoist via the hook. An internally threaded pipe is welded to the bottom of the counterweight. The cap is made of magnesium-carbon refractory material. The cap is spherical and the bottom diameter of the cap matches the top opening of the vacuum induction furnace. A steel external thread rod is embedded at the top of the cap. The cap is connected to the internal thread tube of the counterweight through the external thread rod. A fixed circular groove is opened at the center of the bottom of the cap. The fixing block is a frustum-shaped wooden block, and the calcium wire is clamped to the inner wall of the fixing groove at the bottom of the cap through the fixing block; The operating method of the experimental small vacuum induction furnace calcium wire feeding device includes the following steps: (1) Calculate the amount of calcium line fed using the feeding amount calculation formula, and calculate the total length of calcium line using the total length calculation formula; (2) Cut the calcium wire into several pieces of appropriate length according to the total length of the calcium wire, and then use a fixing block to clamp the cut calcium wire onto the inner wall of the fixing groove at the bottom of the cap. Use a hammer to tap the fixing block to clamp the calcium wire. (3) Connect the counterweight and the cap in sequence, evacuate the second vacuum chamber, open the vacuum isolation plate to connect the first vacuum chamber and the second vacuum chamber, turn on the electric hoist, lower the cap and cover the vacuum induction furnace, and feed the calcium wire into the molten steel in the vacuum induction furnace of the first vacuum chamber. (4) After the calcium wire is fed in for 5-10 seconds, start the electric hoist again to raise the cap back into the second vacuum chamber and close the vacuum isolation plate, thus ending the calcium wire feeding.

2. The operating method of the experimental small vacuum induction furnace calcium wire feeding device according to claim 1, characterized in that, The formula for calculating the feeding amount in step (1) is: L=ω Ca ×m 钢 ×1000 / ( ×K); Where L is the calcium feeding volume, in meters (m); ω Ca The target value for the percentage of calcium by mass in molten steel, in % m 钢 This refers to the weight of the molten steel, in kg. The calcium recovery rate is expressed as % . K represents the weight of calcium in a unit of calcium line, expressed in g / m.

3. The operating method of the experimental small vacuum induction furnace calcium wire feeding device according to claim 2, characterized in that, The formula for calculating the total length in step (1) is: L0 = nL1 + L; Where L is the calcium feeding amount; L0 is the total length of the calcium line; n is the number of calcium wires; L1 is the distance from the top surface of the fixed circular groove to the surface of the molten steel.

4. The operating method of the experimental small vacuum induction furnace calcium wire feeding device according to claim 3, characterized in that, In step (2), the length L2 of the cut calcium wire is greater than L1 and less than the distance L3 from the top surface of the fixed circular groove to the inner wall of the bottom surface of the vacuum induction furnace.

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