CN103406520A - Consumable stirrer added device and method for producing large homogeneous electro-slag re-melting steel ingots - Google Patents

Abstract

A device and method for preparing large-scale homogeneous electroslag remelting steel ingots with a consumable stirrer, the device includes a crystallizer, a consumable electrode, a cooling water circulation system, a lifting arm and an electric control device, and a consumable electrode control device and a consumable agitator, the consumable agitator includes a stirring shaft and a stirring blade, and the stirring blade is fixedly connected to the stirring shaft, and the material of the agitator is the same as that of the final large homogeneous electroslag remelted steel ingot; The stirring shaft is connected to the output shaft of the reducer through a coupling device; the stirring blade is a sheet structure that gradually thickens from the top of the blade to the root of the blade, and the stirring blade is fixedly connected to the stirring shaft in a single-layer and multi-piece manner; the lifting cross arm control The consumable stirrer enters and exits the crystallizer; the rotation of the consumable stirrer of the present invention drives the rotational flow of molten steel at the solidification front of the steel ingot, which can break the primary dendrites at the solidification front, enter the melt to form new crystal nuclei, and strengthen the compact structure properties, and inhibit the segregation of metal elements.

Description

Device and method for preparing large homogeneous electroslag remelted steel ingot with additional consumable stirrer

technical field

The invention relates to the technical field of solidification technology for large electroslag remelted steel ingots in the metallurgical industry, and in particular to a device and method for preparing large homogeneous electroslag remelted steel ingots with an additional consumable stirrer.

Background technique

In recent years, with the rapid development of the electric power industry, nuclear industry and petrochemical industry, the demand for large castings and forgings is increasing, and the quality requirements for large castings and forgings are also getting higher and higher. Large steel ingots are the early products of large castings and forgings, and their quality is particularly important for improving the quality of large castings and forgings. In the electroslag remelting crystallizer, the solidification process of the steel ingot is a typical directional solidification process, that is, it has the heat transfer characteristics of one side heating and one side cooling. This directional solidification structure can basically eliminate the segregation and segregation of the electroslag remelting steel ingot Shrinkage and other defects. However, the solidification process of large electroslag remelted steel ingots is very long, ranging from tens of hours to hundreds of hours depending on the tonnage of the ingot, and the solute redistribution is sufficient, resulting in the enrichment of low melting point and low density elements such as carbon and phosphorus at the solidification front , plus other physical processes, such as the influence of hot solute convection, etc., make the chemical composition of different regions of the steel ingot uneven, resulting in macro-segregation and micro-segregation; An air gap will be formed between the walls of the crystallizer. The existence of the air gap will reduce the thermal conductivity between the steel ingot and the mold wall, and the speed of heat transfer from the steel ingot will be affected, so that the heat flow from the mold will decrease, and the solidification speed of the steel ingot will decrease. This phenomenon is more serious with the enlargement of steel ingots. Speeding up the cooling of steel ingots and suppressing segregation of steel ingots are the only ways to increase production efficiency and improve the quality of steel ingots.

The alloying elements in the steel ingot are evenly distributed in the molten steel at the initial stage of electroslag remelting, but in the conventional solidification process, due to the different solubility of the alloying elements in the solid-liquid phase and the natural convection of the molten steel caused by the temperature difference, some alloying elements are often in the molten steel. The solidification front precipitates and is gradually displaced to the hot core area of molten steel to enrich and form macro segregation. The segregation and shrinkage porosity of large electroslag remelted steel ingots are the bottlenecks that restrict the quality of high-end equipment such as steam turbine rotors. Although domestic and foreign metallurgical fields have recently made some progress in the formation mechanism of segregation, such as the determination of segregation types and segregation locations, the progress in segregation control measures has been slow, and there are almost no effective measures to suppress or eliminate macro segregation inside large steel ingots. And shrinkage and other defects.

Contents of the invention

Aiming at the problems existing in the prior art, the present invention provides a device and method for preparing large-scale homogeneous electroslag remelted steel ingots by adding a consumable stirrer.

The idea of the invention is to change the flow mode of uncondensed molten steel during the solidification process of the steel ingot, and solve the problem of macroscopic and microscopic segregation of alloy components produced during the solidification process of large electroslag remelted steel ingots. Based on the principle of stirring solidification to suppress solidification segregation proposed by M.C. Flemings (professor of MIT in the United States), the consumable stirrer inserted after the pouring of large steel ingots is not only a cold source, but also a power source for driving molten steel flow, which can reduce superheat and accelerate the solidification of the ingot. By controlling the displacement and rotation speed of the consumable stirrer, the purpose of homogenizing the alloy composition of the steel ingot and compacting the central structure during the solidification process is achieved.

Technical scheme of the present invention is;

A device for preparing large homogeneous electroslag remelting steel ingots with an additional consumable stirrer, including a crystallizer, a consumable electrode, a cooling water circulation system, a lifting cross arm, an electric control device and a consumable electrode control device, and the bottom water tank is fixed On the operation platform, the crystallizer is placed on the bottom water tank of the cooling water circulation system, the main pole on one side of the operation platform is connected to the lifting cross arm, and the electric control device is fixed on the lifting cross arm. The electric control device includes a control motor and a reducer, the control motor is fixed on the lifting cross arm, the output end of the control motor is connected to the input end of the reducer, and the device also includes a consumable stirrer;

The consumable stirrer includes a stirring shaft and a stirring blade, and the stirring blade is fixedly connected to the stirring shaft, and the material of the stirrer is the same as that of the finally prepared large homogeneous electroslag remelted steel ingot;

The stirring shaft is connected with the output shaft of the reducer through a shaft coupling;

The stirring blade is a sheet structure gradually thickened from the top of the blade to the root of the blade, and the stirring blade is fixedly connected to the stirring shaft in a single-layer multi-piece manner;

The end of the lifting cross arm connected with the main pole is a sliding end, and there are several rollers on the inner wall of the sliding end, and the rollers drive the sliding end to move up and down along the main pole to control the consumable stirrer to enter and exit the crystallizer.

There are no less than two consumable electrodes, and the rotation diameter of the stirring shaft is smaller than the pole center circle diameter of each consumable electrode.

The consumable stirrer is located in the center of the crystallizer, and the consumable stirrer stirs in the crystallizer and is consumed by continuous melting.

The stirring shaft is tapered from top to bottom.

The length of the stirring shaft exceeds one-third of the length of the consumable electrode, and the stirring shaft extends into the bottom of the molten metal pool of the crystallizer, and the height of the stirring blades from the root to the top is less than the pole center circle of each consumable electrode radius.

The method for preparing a large homogeneous electroslag remelting steel ingot using the device for preparing a large homogeneous electroslag remelting steel ingot using the additional consumable agitator comprises the following steps:

Step 1: Pass cooling water into the crystallizer from the water inlet of the bottom water tank, and then put electrode slag or pre-melted slag into the crystallizer;

Step 2: Immerse the consumable electrode into the slag pool of the crystallizer through the conductive cross arm and pass a strong current to melt the consumable electrode. After the consumable electrode melts, the steel droplets fall to the bottom of the mold through the slag layer, The molten steel gradually accumulated at the bottom of the mold forms a molten metal pool, which is then cooled by the water wall of the mold and gradually solidifies to form a steel ingot;

Step 3: When the height of the steel ingot in the crystallizer is equivalent to the radius of the crystallizer, control the lifting cross arm to put the consumable agitator from the upper part of the crystallizer through the gap between the consumable electrodes into the liquid metal molten pool through the slag pool , and placed in the center of the crystallizer;

Step 4: Control the consumable agitator to start rotating and stirring. The linear speed of the consumable agitator blade rotation is equivalent to the convection velocity of the molten metal in the liquid metal molten pool;

Step 5: The consumable stirrer moves up with the rise of the molten metal pool, and the motor controls the consumable stirrer to rotate and gradually move up. The speed of the consumable stirrer is synchronized with the speed at which the steel ingot is solidified from the bottom of the crystallizer upwards ;

Step 6: When the slag pool moves up to the top of the crystallizer and the melting of the consumable electrode is completed, stop energizing the consumable electrode. At this time, remove the consumable electrode and the rest of the consumable agitator from the crystallizer, and cool the water circulation system keep running.

Step 7: When the steel ingot is completely cooled, the cooling water circulation system is closed, and the preparation of a large homogeneous steel ingot is completed.

Beneficial effect:

The consumable stirrer of the device of the present invention can be used as a cold source to accelerate the cooling and heat transfer speed of the steel ingot, and shorten the solidification time of the steel ingot, and at the same time, the melting of the consumable stirrer is equivalent to increasing the melting rate; The ingredients meet the requirements, so after self-consumption and melting during the stirring process of the consumable agitator, it is equivalent to adopting a qualified steel dense structure at the center of a large steel ingot to eliminate defects such as looseness; the rotation of the consumable agitator drives the rotation of the molten steel at the front of the ingot solidification Flow can break the primary dendrites at the solidification front, enter the melt to form new crystal nuclei, strengthen the compactness of the structure, and inhibit the segregation of metal elements.

Description of drawings

Fig. 1 is a schematic structural diagram of a consumable agitator according to a specific embodiment of the present invention, wherein (a) is a schematic structural diagram of a consumable agitator with a 2-piece straight plate structure, and (b) is a 3-piece agitating blade (c) is a structural schematic diagram of a consumable agitator with a 4-piece straight plate structure with stirring blades;

Figure 2 is a schematic diagram of the device structure for preparing large-scale homogeneous electroslag remelted steel ingots using a consumable stirrer according to a specific embodiment of the present invention, (a) is a consumable stirrer in which the stirring blades of the stirrer are 2-piece straight plate structure Schematic diagram of the structure, (b) is a structural schematic diagram of a consumable stirring device with a 3-piece straight plate structure for the stirring blades of the agitator, (c) is a consumable stirring device with a 4-piece straight plate structure for the stirring blades of the agitator Schematic;

Fig. 3 is a schematic diagram of the process of preparing a large homogeneous electroslag remelting steel ingot by a consumable agitator according to a specific embodiment of the present invention, where (a) is the initial stage of electroslag remelting just inserting a consumable electrode into the molten slag Schematic diagram, (b) is a schematic diagram of inserting the consumable chamber stirrer into the liquid metal molten pool when the height of the ingot is equal to the diameter of the crystallizer, (c) is the slag pool rising to the top of the crystallizer, and the consumable electrode and the Schematic diagram of consumable stirrer, (d) is a schematic diagram of electroslag remelting and expecting the steel ingot to be completely cooled;

Fig. 4 is the flow chart of the method for preparing large-scale homogeneous electroslag remelted steel ingot with additional consumable stirrer of the specific embodiment of the present invention;

Among them, 1-crystallizer, 2-consumable electrode, 3-water outlet of crystallizer, 4-water inlet of crystallizer, 5-bottom water tank, 6-water inlet and outlet of bottom water tank, 7-reducer output shaft, 8-method Blue plate, 9-stirring shaft, 10-stirring blade, 11-slag pool, 12-metal molten pool, 13-steel ingot, 14-cooling water seam of crystallizer wall, 15-conductive cross arm, 16-reducer, 17- Control motor, 18-lifting cross arm, 19-gripper, 20-hydraulic equipment, 21-main pole, 22-side pole, 23-operating platform.

Detailed ways

The specific implementation manners of the present invention will be described in detail below in conjunction with the accompanying drawings.

The device for preparing large-scale homogeneous electroslag remelting steel ingots with the additional consumable agitator of this embodiment, as shown in Figure 2 (a) to (c), includes a crystallizer 1, a consumable electrode 2, a cooling water circulation system, a lifting Cross arm 18 and electric control device, consumable electrode control device and consumable stirrer.

The slag pool 11 inside the crystallizer 1 contains electrode slag or pre-melted slag, and the state of the molten metal pool 12 is liquid. During the electroslag remelting process, molten steel droplets from the consumable electrode 2 pass through the slag pool 11 Falling to the bottom of the crystallizer 1 , the molten steel gradually accumulated at the bottom of the crystallizer 1 forms a molten metal pool 12 , and then is cooled by the water wall of the crystallizer and gradually solidifies to form the steel ingot 13 .

The crystallizer water cooling system includes a crystallizer wall cooling water slot 14 , a crystallizer water inlet 4 , a crystallizer water outlet 3 and a bottom water tank 5 , and the bottom water tank 5 is provided with a bottom water tank inlet and outlet 6 .

The bottom water tank 5 is fixed on the operation platform 23, the crystallizer 1 is placed on the bottom water tank 5 of the cooling water circulation system, the main pole 21 on the side of the operation platform 23 is connected to the lifting cross arm 18, and the electric control device is fixed on the lifting cross arm 18 on.

The electric control device comprises a control motor 17 and a speed reducer 16, the control motor 17 is fixed on the lifting cross arm 18, the output end of the control motor 17 is connected to the input end of the speed reducer 16, and the speed reducer 16 is used to control the motion speed of the stirring shaft 9, The lifting movement of the lifting cross arm 18 is controlled by the control room.

There are no less than two consumable electrodes 2, and the consumable electrodes 2 are evenly distributed in a ring with the center of the crystallizer 1 as the center of the circle.

The consumable stirrer includes a stirring shaft 9 and a stirring blade 10, and the stirring blade 10 is fixedly connected to the stirring shaft 9. The material of the stirrer is the same as that of the final large-scale homogeneous electroslag remelted steel ingot finished product, and the composition It meets the requirements, and the consumable stirrer itself is also continuously consumed during the molten steel stirring process. The consumable stirrer is located in the center of the crystallizer 1, and the consumable stirrer stirs in the crystallizer 1 and is consumed by continuous melting.

Due to the shallow liquid metal molten pool in electroslag remelting, it is not suitable to design the stirring blade as a multi-layer or inclined type. The agitator with straight blades is used to stir in the liquid metal molten pool to make the molten steel generate horizontal rotating flow and accelerate the steel ingot. Cooling, flattening the shape of the molten pool, and inhibiting the segregation of the steel ingot; at the same time, the loss of the agitator itself is equivalent to increasing its melting speed.

The stirring blade 10 is a flaky structure gradually thickened from the top of the blade to the root of the blade, and the stirring blade 10 is fixedly connected to the stirring shaft 9 in a single-layer multi-piece manner, and the number of blades can be 2-4. The material and amount of the stirring blade 10 are determined according to the total heat of the prepared large homogeneous electroslag remelting ingot molten steel, that is, the stirring blade 10 is consumed as much as possible after the stirring is completed. The inclination angle of the stirring blade 10 relative to the stirring shaft 9 is 20°-70°, and the cone angle of the stirring shaft 9 and the thickness expansion angle of the stirring blade 10 are both 9°-20°. As shown in Figure 1, the stirring blade in (a) is a 2-piece straight plate structure, the stirring blade in (b) is a 3-piece straight plate structure; the stirring blade in (c) is a 4-piece straight plate type structure; the stirring shaft 9 is tapered from top to bottom, and the stirring shaft 9 is connected to the output shaft of the reducer through a coupling device. In this embodiment, the coupling device is a flange 8, which is used to connect the output shaft 7 of the reducer and stirring shaft 9.

The length of the stirring shaft 9 exceeds one-third of the length of the consumable electrode 2, and the stirring shaft 9 extends into the bottom of the molten metal pool of the crystallizer 1, and the height of the stirring blade 10 from the root to the top is smaller than that of the respective consumable electrodes 2 The radius of the polar circle formed by the center of the bottom surface, that is, the rotation diameter of the agitator should ensure that it can enter and leave the central area between the respective consumption electrodes 2;

The end that the lifting cross arm 18 is connected with the main vertical rod 21 is a sliding end, and the inner wall of the sliding end has some rollers, and the rollers drive the sliding end to move up and down along the main vertical rod 21 to control the consumable agitator to enter and exit the crystallizer 1.

The consumable electrode control device includes a hydraulic device 20, a conductive cross arm 15 and a holder 19, as shown in Figure 2 (a) to (c), one end of the conductive cross arm 15 is connected to the side stand on the side of the operating platform 23 Rod 22 is connected, and the other end of conductive cross arm 15 is equipped with gripper 19, and one end that is connected with side upright bar 22 of conductive cross arm 15 is sliding end, and this sliding end inner wall has some rollers, and gripper 19 clamps from The consumption electrode 2; the roller at the sliding end of the conductive cross arm 15 drives the sliding end to move up and down along the side pole 22.

The method for preparing large-scale homogeneous electroslag remelted steel ingots by using the described device, as shown in Figure 4, comprises the following steps:

Step 1: Pass cooling water into the crystallizer from the water inlet of the bottom water tank, and then put electrode slag or pre-melted slag into the crystallizer;

Step 2: Immerse the consumable electrode into the slag pool of the crystallizer through the conductive cross arm and pass a strong current to melt the consumable electrode. After the consumable electrode melts, the steel droplets fall to the bottom of the mold through the slag layer, The molten steel gradually accumulated at the bottom of the mold forms a molten metal pool, which is then cooled by the water wall of the mold and gradually solidifies to form a steel ingot;

Step 3: When the height of the steel ingot in the crystallizer is equivalent to the radius of the crystallizer, control the lifting cross arm to put the consumable agitator from the upper part of the crystallizer through the gap between the consumable electrodes into the liquid metal molten pool through the slag pool , and placed in the center of the crystallizer;

Step 4: Control the consumable agitator to start rotating and stirring. The linear speed of the consumable agitator blade rotation is equivalent to the convection velocity of the molten metal in the liquid metal molten pool;

Step 5: The consumable stirrer moves up with the rise of the molten metal pool, and the motor controls the consumable stirrer to rotate and gradually move up. The speed of the consumable stirrer is synchronized with the speed at which the steel ingot is solidified from the bottom of the crystallizer upwards ;

Step 6: When the slag pool moves up to the top of the crystallizer and the melting of the consumable electrode is completed, stop energizing the consumable electrode. At this time, remove the consumable electrode and the rest of the consumable agitator from the crystallizer, and cool the water circulation system keep running.

Step 7: When the steel ingot is completely cooled, the cooling water circulation system is closed, and the preparation of a large homogeneous steel ingot is completed.

The above process of preparing large homogeneous electroslag remelting steel ingots is shown in Figure 3(a)~(d), where (a) represents the initial stage of electroslag remelting just inserted into the electrode slag material or pre-melted slag material Consumable electrode, (b) means that when the height of the steel ingot is equal to the diameter of the crystallizer, a consumable stirrer is inserted into the liquid metal molten pool, (c) means that the slag pool rises to the top of the mold, and the consumable electrode and the self-consumable electrode are about to be retrieved Consumption of the stirrer, (d) indicates that the electroslag remelting end expects the ingot to cool completely.

Claims (6)

1. A device for preparing large-scale homogeneous electroslag remelting steel ingots with a consumable stirrer, including a crystallizer, a consumable electrode, a cooling water circulation system, a lifting arm, an electric control device, and a consumable electrode control device. The water tank is fixed on the operation platform, the crystallizer is placed on the bottom water tank of the cooling water circulation system, the main pole on one side of the operation platform is connected to the lifting cross arm, and the electric control device is fixed on the lifting cross arm. The electric control device includes The control motor and the reducer, the control motor is fixed on the lifting cross arm, the output end of the control motor is connected to the input end of the reducer, and it is characterized in that it also includes a consumable stirrer; The consumable stirrer includes a stirring shaft and a stirring blade, and the stirring blade is fixedly connected to the stirring shaft, and the material of the stirrer is the same as that of the finally prepared large homogeneous electroslag remelted steel ingot; The stirring shaft is connected with the output shaft of the reducer through a shaft coupling; The stirring blade is a sheet structure gradually thickened from the top of the blade to the root of the blade, and the stirring blade is fixedly connected to the stirring shaft in a single-layer multi-piece manner; The end of the lifting cross arm connected with the main pole is a sliding end, and there are several rollers on the inner wall of the sliding end, and the rollers drive the sliding end to move up and down along the main pole to control the consumable stirrer to enter and exit the crystallizer. 2. The device for preparing large-scale homogeneous electroslag remelted steel ingots with an additional consumable stirrer according to claim 1, characterized in that: the rotation diameter of the stirring shaft is smaller than the diameter of the polar circle formed by the center of each consumable electrode bottom surface . 3. The device for preparing large-scale homogeneous electroslag remelted steel ingots with an additional consumable stirrer according to claim 1, characterized in that: the consumable stirrer is located at the center of the crystallizer, and the consumable stirrer stirs in the crystallizer And continue to melt and consume. 4. The device for preparing large-scale homogeneous electroslag remelted steel ingots with an additional consumable stirrer according to claim 1, characterized in that: the stirring shaft is tapered from top to bottom. 5. The device for preparing large-scale homogeneous electroslag remelted steel ingots with an additional consumable stirrer according to claim 1, is characterized in that: the length of the stirring shaft exceeds 1/3rd of the length of the consumable electrode, and The stirring shaft extends into the bottom of the liquid metal molten pool of the crystallizer, and the height of the stirring blades from the root to the top is smaller than the radius of the polar circle formed by the center of the bottom surface of each consumable electrode. 6. adopt the method for preparing large-scale homogeneous electroslag remelting steel ingot by the device that adopts additional consumable agitator described in claim 1 to prepare large-scale homogeneous electroslag remelting steel ingot, it is characterized in that: comprise the steps: Step 1: Pass cooling water into the crystallizer from the water inlet of the bottom water tank, and then put electrode slag or pre-melted slag into the crystallizer; Step 2: Immerse the consumable electrode into the slag pool of the crystallizer through the conductive cross arm and pass a strong current to melt the consumable electrode. After the consumable electrode melts, the steel droplets fall to the bottom of the mold through the slag layer, The molten steel gradually accumulated at the bottom of the mold forms a molten metal pool, which is then cooled by the water wall of the mold and gradually solidifies to form a steel ingot; Step 3: When the height of the steel ingot in the crystallizer is equivalent to the radius of the crystallizer, control the lifting cross arm to put the consumable agitator from the upper part of the crystallizer through the gap between the consumable electrodes into the liquid metal molten pool through the slag pool , and placed in the center of the crystallizer; Step 4: Control the consumable agitator to start rotating and stirring. The linear speed of the consumable agitator blade rotation is equivalent to the convection velocity of the molten metal in the liquid metal molten pool; Step 5: The consumable stirrer moves up with the rise of the molten metal pool, and the motor controls the consumable stirrer to rotate and gradually move up. The speed of the consumable stirrer is synchronized with the speed at which the steel ingot is solidified from the bottom of the crystallizer upwards ; Step 6: When the slag pool moves up to the top of the crystallizer and the melting of the consumable electrode is completed, stop energizing the consumable electrode. At this time, remove the consumable electrode and the rest of the consumable agitator from the crystallizer, and cool the water circulation system continue to run; Step 7: When the steel ingot is completely cooled, the cooling water circulation system is closed, and the preparation of a large homogeneous steel ingot is completed.

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