CN116814965A - A method and device for improving electroslag remelting production capacity - Google Patents

Abstract

The invention relates to a method and a device for improving the production capacity of electroslag remelting, wherein in the electrode remelting smelting operation, an induction heating coil is used for carrying out auxiliary heating on an electrode, so that the melting speed of the electrode in liquid slag is improved. The implementation of the invention can reduce the electric quantity consumption of the whole production system, and simultaneously can realize the improvement of the electroslag remelting production capacity, so that the production capacity is improved by 20-40% compared with the original electroslag remelting process.

Description

A method and device for improving electroslag remelting production capacity

Technical field

The invention belongs to the technical field of electroslag remelting smelting, and in particular relates to a method and device for improving electroslag remelting production capacity.

Background technique

The basic principle of electroslag remelting is that the electric current passes through the resistance heat generated by the liquid slag to gradually melt the metal electrode. The molten metal gathers into metal droplets, passes through the slag layer and enters the metal molten pool. Electroslag remelting has a good ability to remove non-metallic inclusions, and the steel and alloys that have been electroslag remelted have a high degree of cleanliness. 80 to 90% of the non-metallic inclusions contained in steel smelted by general methods can be removed after electroslag remelting. Electroslag steel ingots are forcibly cooled and solidified in a water-cooled crystallizer, so the steel ingots have a dense crystal structure and generally do not produce low-magnification defects such as shrinkage cavities and porosity. Because of the above advantages, electroslag remelting has become one of the main methods for producing high-quality steel and alloys. However, the biggest disadvantage of electroslag remelting is that the production capacity is relatively low, usually 0.3 to 0.8t/h. This is mainly because during the production of electroslag remelting, the electrodes are gradually melted through heat conduction based on the high temperature of the liquid slag. This thermal efficiency of heat conduction directly affects the melting rate of the electrode. In order to increase the temperature of the liquid slag, the thermal resistance is improved by improving the slag system, thereby increasing the slag temperature to accelerate the melting of the electrode. Slag systems with large thermal resistance usually have relatively large viscosity, which is not conducive to the removal of inclusions from molten steel. In addition, the large thermal resistance also requires more electrical energy to maintain the high temperature state of the liquid slag. In order to reduce power consumption, although the power grid system of electroslag remelting has been optimized to reduce the reactance of the connecting line and improve the power factor, the power consumption per ton of steel during the electroslag remelting process is still relatively high, generally between 1500 and 2000KW.h/ t.

The patent application number _201310166458 . , Al ₂ O ₃ : 20 to 30%, CaO: 20 to 30%, SiO ₂ : 5 to 10%. This slag system increases the viscosity of the electroslag remelting slag by adding CaO, which increases the resistance of the slag and improves the electroslag efficiency of the slag, thereby also achieving the effect of improving production capacity. However, this method increases the slag electroslag consumption by adjusting the slag composition, which will additionally increase the power consumption. In addition, the CaO added to the slag can easily absorb moisture from the air, causing the hydrogen content of the electroslag steel ingot to increase. Taken together, this application is not conducive to low-cost and stable production by adjusting the composition of the slag.

The reference document "Research on Second Generation Electroslag Metallurgical Processes" (Volume 10 Supplement of Journal of Materials and Metallurgy, 2011) provides a comprehensive discussion of the current electroslag remelting technology. Among them, the literature discusses the improvement of electroslag remelting production. The efficiency was discussed, and a new method was introduced, which used the electroslag pouring method to pour the molten steel smelted in the electric arc furnace from the tundish transition trough into the crystallizer containing molten and superheated alkaline synthetic slag to complete the ingot pouring. Although this method greatly improves production efficiency compared with the traditional electroslag remelting process, strictly speaking, this method is no longer an electroslag remelting process because the molten steel melted by the electric furnace is directly poured into the crystallizer containing slag. Within this process, this process will have a great adverse impact on the quality of the steel ingot. Firstly, this will inevitably have a relatively strong stirring effect on the slag in the crystallizer, which will easily cause slag entrainment and reduce the cleanliness of the steel ingot; secondly, it will greatly reduce the pouring time. The contact surface ratio between liquid molten steel and slag is not conducive to removing inclusions from the molten steel; thirdly, the amount of molten steel injected is much larger than that of traditional electroslag remelting, which is detrimental to the solidification structure of the steel ingot. Influence, it is easy to produce segregation and loose defects; the last point is that the molten steel melted by the electric furnace, in order to prevent the molten steel from freezing at too low a temperature during the pouring process, it will be heated to a very high temperature, that is, it must have a certain degree of superheat. Most of the heat will be lost by radiation during the pouring process, which is a waste of energy. Judging from a certain link alone, it seems that energy saving has been achieved. However, analyzing the energy usage of the entire system alone, it has not actually achieved the effect of reducing power consumption and reducing costs.

Based on the above background, the present invention proposes to pre-heat the electrode through induction heating based on the principle of electroslag remelting, thereby reducing the power consumption of the entire system, increasing the electrode melting rate, and improving the electroslag remelting production capacity. Effect.

Contents of the invention

The object of the present invention is to provide a method and device for improving the production capacity of electroslag remelting, which can not only reduce the power consumption of the entire production system, but also improve the production capacity of electroslag remelting so that the production capacity can be compared with the original The electroslag remelting process is improved by 20% to 40%.

In order to achieve the above objects, the present invention adopts the following technical solutions:

A method for improving electroslag remelting production capacity. The method is to auxiliary heat the electrode through an induction heating coil during the electrode remelting smelting operation, thereby increasing the melting speed of the electrode in the liquid slag.

Specific methods include:

1) Install the crystallizer on the bottom water tank and complete the normal process operations.

2) Swing the induction heating coil above the crystallizer, and make the induction heating coil and the center of the crystallizer on the same axis.

3) Pass the electrode into the crystallizer from the upper part of the induction heating coil, and make the gap between the induction heating coil and the electrode uniform;

4) Sprinkle the ignition slag on the bottom water tank, move the electrode downward until it contacts the ignition slag, and then energize it to ignite the arc. After the ignition slag is completely melted and the current and voltage are stable, put it into the crystallizer. slag;

The slag material is CaF ₂ -Al ₂ O ₃ -NaCl ternary slag system. The advantage of this slag system is that it has a low melting point and good conductivity. It is beneficial to the removal of inclusions at high temperatures. It can also significantly reduce power consumption and reduce costs. Effect. The disadvantage is that the resistance heat of this slag system is lower than that of conventional slag materials, which is not conducive to the melting of electrodes. However, the induction heating auxiliary function is used in this process to make up for the shortcomings of this slag system. The mass percentage of each component of the slag system that matches this process is: CaF ₂ is 65% to 80%, Al ₂ O ₃ is 15% to 30%, and NaCl is 5% to 10%. Since the melting rate of droplets is faster than conventional, in order to ensure that the falling droplets can fully contact the liquid slag, the amount of slag invested is increased by 1 to 3 times than conventional to ensure that the depth of the liquid slag pool is controlled at 100 to 300mm. .

5) After the slag material is put into the crystallizer, adjust the position of the induction heating coil, keep the distance between the bottom end surface of the induction heating coil and the liquid slag surface within the range of 20 to 50mm, start the induction heating coil to auxiliary heating of the electrode, and Adjust the power to control the heating temperature of the induction heating coil to the electrode to 20 to 50°C below the solidus temperature of the electrode steel; select the frequency of the induction heating coil according to the size of the heating electrode. The heated electrode gradually melts in the liquid slag and falls into the molten metal pool in the form of droplets. Under the water cooling of the crystallizer and the bottom water tank, the molten steel in the molten metal pool is gradually cooled and solidified to form an electroslag steel ingot.

6) After the electrode is completely melted, turn off the induction heating coil, move the induction heating coil out of the working position, and complete the electroslag remelting operation.

A device used in a method for improving electroslag remelting production capacity, including a crystallizer, an induction heating coil, and a bottom water tank. The crystallizer is placed above the bottom water tank. The induction heating coil is above the crystallizer and connected to the crystallizer. The center is on the same axis. During production operations, the electrode penetrates into the crystallizer from the upper part of the induction heating coil.

The induction heating coil is a single-turn solenoid structure, and the overall shape is round or square.

Considering that the melting rate of the electrode during the remelting process is usually 20~50mm/h, and the induction heating speed can reach the target heating temperature every minute, if a multi-turn induction heating coil is used, it will inevitably cause the electrode to enter the high-temperature liquid slag. During the melting process, some high-temperature areas are exposed to the outside for a long time, which will cause oxidation of the electrode surface in the high-temperature area, thereby reducing the cleanliness of the final steel ingot. At the same time, this part of the high-temperature area will continue to lose heat through radiation heat dissipation, which will significantly increase the cost of electricity. Taking a 10-turn coil as an example, the electricity consumption during electroslag remelting production will increase by about 15% compared with that without induction heating. . In order to solve these problems, the induction heating coil is designed as a single-turn solenoid structure to ensure that only a narrow area of the electrode surface is heated during the induction heating process, which can minimize the surface oxidation caused by the induction heating of the electrode. For cleanliness For steel types that require very high strength, a layer of aluminum oxide powder can also be painted on the surface of the electrode to prevent the surface from oxidizing due to high temperature. The use of a single-turn coil is beneficial to reducing heat loss. At the same time, in order to reduce heat loss and oxidation, the distance between the coil and the liquid slag surface is controlled within a small range of 20 to 50mm, ensuring that the coil can enter the liquid slag in the shortest time after heating the electrode. Inside the pool.

The specific shape of the induction heating coil is determined by the cross-sectional shape of the electrode being heated. The cross section of the coil solenoid is rectangular, the height of the induction heating coil is h, and the diameter of the induction heating coil is D. If the coil is rectangular, the diameter D of the coil is converted according to the diameter of the circle under the equivalent area, and the height-to-diameter ratio h/ The value range of D is 0.05~0.1. In order to prevent the electrode and the coil from contacting each other, the gap distance from the inner wall of the coil to the electrode surface is required to be controlled at 10 to 50 mm. The value range of the equivalent cross-sectional diameter of the electrode and the height-to-diameter ratio h/D of the coil can be designed according to the following range. When the equivalent cross-sectional diameter of the electrode is ≤100mm, the value of the height-to-diameter ratio h/D is 0.09~0.1; when 100mm <When the equivalent cross-sectional diameter of the electrode is ≤360mm, the height-to-diameter ratio h/D takes a value of 0.07 to 0.09; when the equivalent cross-sectional diameter of the electrode is >360mm, the height-to-diameter ratio h/D takes a value of 0.05 to 0.07. In order to have a good heating effect on electrodes of different sizes while ensuring that they are not melted, the adjustment range of the heating power of the induction heating coil is set to 10 to 300kW. During the induction heating process, the frequency of the coil has a great influence on the heating effect of the electrode. When high-frequency heating is used, the induced current is concentrated on the electrode surface due to the skin effect, causing the internal heating of the electrode to be slow. For large-sized electrodes, the heating The effect is not ideal. For smaller electrodes, high-frequency heating can quickly heat the electrode, which helps to improve the heating effect of the electrode. For this reason, during the heating process, an appropriate heating frequency should be selected according to the size of the heated electrode. In the present invention, the frequency of the coil is selected in the range of 50 to 1000 Hz. When the equivalent cross-sectional diameter of electrode (2) ≤ 100mm, the induction heating frequency adopts 800 ~ 1000Hz; when 100mm < the equivalent cross-sectional diameter of electrode (2) ≤ 360mm, the induction heating frequency adopts 200 ~ 800Hz; when the electrode (2) 2) When the equivalent cross-sectional diameter is >360mm, the induction heating frequency should be 50 to 200Hz.

Through the new design of the electroslag remelting process, the present invention has an auxiliary function of electromagnetic induction heating. Under this function, special slag materials are used. Compared with the existing electroslag remelting process, the present invention has Good beneficial effects are as follows:

1) Significantly reduces the power consumption per ton of steel during the electroslag process, reducing the power consumption from the original 1500 to 2000KW.h/t of steel to 1200 to 1400KW.h/t of steel;

2) The effective utilization rate of electric energy has been increased from the original average of 75% to an average of 85%, reducing production costs;

3) Through this method, the electroslag remelting production capacity can be increased from 0.3 to 0.8t/h to 0.6 to 1.5t/h.

Description of the drawings

Figure 1 is a schematic diagram of an induction heating electroslag remelting device.

Figure 2 is a schematic diagram of the appearance of the induction heating coil.

Figure 3 is a schematic cross-sectional view of the induction heating coil.

In the picture: 1-induction heating coil driving mechanism; 2-electrode; 3-crystallizer; 4-induction heating coil; 5-liquid slag; 6-metal liquid pool; 7-electroslag ingot; 8-bottom water tank.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention more clear, the specific implementation modes of the present invention will be further described below in conjunction with the examples. The following examples are used to specifically illustrate the content of the present invention. These embodiments are only general representations of the content of the present invention. Description does not limit the content of the invention.

The present invention uses induction heating to assist in heating up the electrode, thereby reducing the power consumption of the entire system, increasing the electrode melting rate, and improving the electroslag remelting production capacity.

The present invention uses an electroslag remelting device with an electrode induction heating function to complete the remelting smelting operation of the electrode, thereby increasing the melting speed of the electrode in the liquid slag and achieving the metallurgical effect of increasing production capacity. Now combined with the device The schematic diagram is explained as follows:

As shown in Figure 1, the device used in the embodiment of the present invention to improve the electroslag remelting production capacity includes a crystallizer 3, an induction heating coil 4, and a bottom water tank 8. The crystallizer 3 is placed above the bottom water tank 8, and the induction heating coil 4 is above the crystallizer 3 and on the same axis as the center of the crystallizer 3. During production operations, the electrode 2 penetrates into the crystallizer 3 from the upper part of the induction heating coil 4.

The induction heating coil 4 is driven by the induction heating coil holding mechanism 1 to complete the upward and downward and left and right adjustment movements to meet the adjustment of the position of the induction heating coil during production.

The induction heating coil 4 is a single-turn solenoid structure. As shown in Figure 3, the cross-section of the coil solenoid is rectangular, and its height-to-diameter ratio h/D ranges from 0.05 to 0.1. h is the height of the induction heating coil 4, and D is the diameter of the induction heating coil 4.

The process of the embodiment of the present invention is as follows:

Example 1:

Electroslag remelting H13 mold steel, electrode 2 has a diameter of 300mm, and electroslag ingot 7 has a diameter of 400mm. The specific process operation method is as follows:

According to the fact that the gap distance from the inner wall of the induction heating coil 4 to the surface of the electrode 2 is controlled at 10 to 50 mm and according to 100 mm < the equivalent cross-sectional diameter of the electrode ≤ 360 mm, the height-to-diameter ratio h/D of the induction heating coil 4 is 0.07 to 0.09. According to the process requirements, the diameter D of the induction heating coil 4 is a 360mm circular coil (as shown in Figure 2), the height of the coil solenoid is 27mm, and the induction heating frequency is 500Hz.

The specific process methods are as follows:

1) Install the crystallizer 3 on the bottom water tank 8 and complete the conventional process operations;

2) Swing the induction heating coil 4 above the crystallizer 3, and make the induction heating coil 4 and the center of the crystallizer 3 on the same axis;

3) Penetrate the electrode 2 from the upper part of the induction heating coil 4 and make the gap between the induction heating coil 4 and the electrode 2 even;

4) Sprinkle the ignition slag on the bottom water tank 8, move the electrode downward until it contacts the ignition slag, and then energize it to ignite the arc. After the ignition slag is completely melted and the current and voltage are stable, feed the electrode to the crystallizer. 3. Add CaF ₂ -Al ₂ O ₃ -NaCl ternary slag material. The mass percentages of CaF ₂ -Al ₂ O ₃ -NaCl in the slag are 75%, 19%, and 6% respectively, and the depth of liquid slag 5 is controlled at 150mm;

5) After the slag material is put into the crystallizer 3, adjust the position of the induction heating coil 4, keep the distance between the bottom end surface of the induction heating coil 4 and the surface of the liquid slag 5 within 50mm, and start the induction heating coil 4 to the electrode 2 Auxiliary heating is performed, and the heating temperature of the electrode 2 is controlled to 40°C below the solidus temperature of the electrode steel by adjusting the power.

6) After the electrode 2 is completely melted, turn off the induction heating coil 4, move the induction heating coil out of the working position, and complete the electroslag remelting operation.

Example 2:

Electroslag remelting Invar steel, the cross-section of electrode 2 is rectangular 300*1500mm, and the electroslag ingot 7 is 450*1000mm. The specific process operation method is as follows:

According to the shape and size of the electrode 2, a rectangular induction heating coil 4 is selected. The cross-section of electrode 2 is a rectangle of 300*1500mm, and the diameter of the equivalent area circle is 379mm. According to the process requirements that the gap distance from the inner wall of the induction coil to the surface of the electrode 2 is controlled at 10~50mm and when the equivalent cross-sectional diameter of the electrode is >360mm, the height-to-diameter ratio h/D of the induction heating coil 4 should be 0.05~0.07. The induction heating coil 4 uses a rectangular coil of 320*1520mm, the height of the coil solenoid is 25mm, and the induction heating frequency is 150Hz. The specific process methods are as follows:

1) Install the crystallizer 3 on the bottom water tank 8 and complete the conventional process operations;

2) Swing the induction heating coil 4 above the crystallizer 3, and make the induction heating coil 4 and the center of the crystallizer 3 on the same axis;

3) Penetrate the electrode 2 from the upper part of the induction heating coil 4 and make the gap between the induction heating coil 4 and the electrode 2 even;

4) Sprinkle the ignition slag on the bottom water tank 8, move the electrode 2 downward until it is in contact with the ignition slag, and then energize it to ignite the arc. After the ignition slag is completely melted and the current and voltage are stable, proceed to the crystallization The CaF ₂ -Al ₂ O ₃ -NaCl ternary slag material is put into the vessel 3. The mass percentages of CaF ₂ -Al ₂ O ₃ -NaCl in the slag are 77%, 18%, and 5% respectively, and the depth of liquid slag 5 is controlled at 200mm.

5) After the slag material is put into the crystallizer 3, adjust the position of the induction heating coil 4, keep the distance between the bottom end surface of the induction heating coil 4 and the surface of the liquid slag 5 within 45mm, and start the induction heating coil 4 to the electrode 2 Auxiliary heating is performed, and the heating temperature of the electrode 2 by the induction heating coil 4 is controlled to be 30°C below the solidus temperature of the electrode steel type.

6) After the electrode 2 is completely melted, turn off the induction heating coil 4, move the induction heating coil 4 out of the working position, and complete the electroslag remelting operation.

Example 3:

Electroslag remelting 9Cr18 bearing steel, the cross-section of electrode 2 is square 85*85mm, and the electroslag ingot 7 is 100*100mm. The specific process operation method is as follows:

According to the shape and size of the electrode 2, a square induction heating coil 4 is selected. The diameter of the equivalent area circle converted into a square with a cross-section of 85*85mm for electrode 2 is 96mm. According to the process requirements that when the gap distance from the inner wall of the induction coil to the surface of the electrode 2 is controlled at 10 to 50 mm and the equivalent cross-sectional diameter of the electrode is ≤ 100 mm, the height-to-diameter ratio h/D is 0.09 to 0.1, the induction heating coil 4 adopts 100 *100mm square coil, the height of the coil solenoid is 11mm, and the induction heating frequency is 900Hz.

The specific process methods are as follows:

1) Install the crystallizer 3 on the bottom water tank 8 and complete the conventional process operations;

2) Swing the induction heating coil 4 above the crystallizer 3, and make the induction heating coil 4 and the center of the crystallizer 3 on the same axis;

3) Penetrate the electrode 2 from the upper part of the induction heating coil 4 and make the gap between the induction heating coil 4 and the electrode 2 even;

4) Sprinkle the ignition slag on the bottom water tank 8, move the electrode 2 downward until it is in contact with the ignition slag, and then energize it to ignite the arc. After the ignition slag is completely melted and the current and voltage are stable, proceed to the crystallization The CaF ₂ -Al ₂ O ₃ -NaCl ternary slag material is put into the vessel 3. The mass percentages of CaF ₂ -Al ₂ O ₃ -NaCl in the slag are 72%, 21%, and 7% respectively, and the depth of liquid slag 5 is controlled at 240mm.

5) After the slag material is put into the crystallizer 3, adjust the position of the induction heating coil 4, keep the distance between the bottom end surface of the induction heating coil 4 and the surface of the liquid slag 5 at 50mm, and start the induction heating coil 4 to conduct the heating on the electrode 2 For auxiliary heating, the heating temperature of the electrode 2 by the induction heating coil 4 is controlled to 25°C below the solidus temperature of the electrode steel by adjusting the power.

6) After the electrode 2 is completely melted, turn off the induction heating coil 4, move the induction heating coil 4 out of the working position, and complete the electroslag remelting operation.

Claims (10)

1. A method for improving electroslag remelting production capacity is characterized in that in electrode remelting smelting operation, an induction heating coil is used for carrying out auxiliary heating on an electrode, so that the melting speed of the electrode in liquid slag is improved.

2. The method for improving the electroslag remelting production capacity according to claim 1, wherein the specific method comprises the following steps:

1) Installing the crystallizer on the bottom water tank, and completing the conventional process operation;

2) Placing an induction heating coil above the crystallizer, and enabling the induction heating coil and the center of the crystallizer to be positioned on the same axis;

3) Penetrating an electrode from the upper part of the induction heating coil into the crystallizer;

4) Spraying ignition slag on the bottom water tank, moving the electrode downwards to be in contact with the ignition slag, conducting electrifying ignition and arcing, and throwing slag into the crystallizer after the ignition slag is completely melted and the current and the voltage are stable;

5) Adjusting the position of an induction heating coil, keeping the distance between the bottom end surface of the induction heating coil and the slag surface within the range of 20-50 mm, starting the induction heating coil to carry out auxiliary heating on the electrode, and controlling the heating temperature of the induction heating coil on the electrode to be 20-50 ℃ below the solidus temperature of the electrode steel grade;

6) After the electrode is completely melted, the induction heating coil is closed, and the electroslag remelting operation is completed.

3. The method for improving the electroslag remelting production capacity according to claim 2, wherein the slag is CaF ₂ -Al ₂ O ₃ The NaCl ternary slag system has slag amount to ensure the depth of the liquid slag pool to be controlled in 100-300 mm.

4. A method for improving electroslag remelting production as claimed in claim 3, wherein the CaF ₂ -Al ₂ O ₃ The NaCl ternary slag system comprises the following components in percentage by mass: caF (CaF) ₂ 65％～80％、Al ₂ O ₃ 15％～30％、NaCl5％～10％。

5. The method for improving the electroslag remelting production capacity of claim 2, wherein the heating power of the induction heating coil is adjusted to be 10-300 kW; when the equivalent diameter of the cross section of the electrode is less than or equal to 100mm, the heating frequency of the induction heating coil is 800-1000 Hz; when the equivalent diameter of the cross section of the electrode is less than or equal to 360mm and is less than 100mm, the heating frequency of the induction heating coil is 200-800 Hz; when the equivalent diameter of the cross section of the electrode is more than 360mm, the induction heating frequency is 50-200 Hz.

6. A method for improving the electroslag remelting production capacity as claimed in claim 2, wherein the gap distance from the inner wall of the induction heating coil to the electrode surface is 10 to 50mm.

7. An apparatus for improving the productivity of electroslag remelting as claimed in any one of claims 1 to 6 wherein the apparatus comprises a crystallizer, an induction heating coil, and a bottom water tank, wherein the crystallizer is placed above the bottom water tank, the induction heating coil is above the crystallizer and is on the same axis as the center of the crystallizer, and the electrodes penetrate into the crystallizer from the upper part of the induction heating coil during the production operation.

8. The apparatus for improving electroslag remelting production of claim 7 wherein the induction heating coil is of a single turn solenoid construction, and is generally circular or square.

9. The apparatus for improving electroslag remelting production capacity as claimed in claim 8, wherein the cross section of the induction heating coil is rectangular, the value range of the height-diameter ratio h/D is 0.05-0.1, h is the height of the induction heating coil, and D is the diameter of the induction heating coil.

10. The apparatus for improving the productivity of electroslag remelting according to claim 9, wherein the range of values of the equivalent diameter of the cross section of the electrode and the ratio h/D of the height to diameter of the induction heating coil is designed as follows: when the equivalent diameter of the cross section of the electrode is less than or equal to 100mm, the value of the height-diameter ratio h/D is 0.09-0.1; when the equivalent diameter of the cross section of the electrode is less than or equal to 360mm and is less than 100mm, the value of the height-diameter ratio h/D is 0.07-0.09; when the equivalent diameter of the cross section of the electrode is more than 360mm, the value of the height-diameter ratio h/D is 0.05-0.07.