A device and method for complex electromagnetic regulation of ingot solidification structure and defects in vacuum-insulated ingate, and application thereof

Abstract

The application discloses a device and method for complex electromagnetic regulation and control of solidification structure and defects of large ingot by vacuum insulating riser, and application thereof. The device comprises the following steps: assembling the lower end of the ingot mold and the bottom mold together to form the main part of the ingot mold, installing the riser device on the upper end of the ingot mold, ensuring that the riser liquid and the heating slag in the vacuum riser can be kept in liquid state within a set time by using the insulating condition formed by the vacuum riser, and setting the cooling medium flow channel of the bottom mold to radiate the lower half of the liquid in the ingot mold, and the electromagnetic stirring device is also set outside the vacuum riser, the helical alternating magnetic field generated by the helical electromagnetic stirrer is used to drive the riser liquid to produce helical motion according to the rotating direction of the magnetic field, and the liquid in the ingot mold is driven to rotate, so that the electromagnetic force induced rotational flow stirring is realized. The application can reduce or even eliminate the solidification defects of the large ingot, obtain the large ingot billet with excellent metallurgical quality, and obtain the metal material product with excellent quality through subsequent processing.

Description

TECHNICAL FIELD

[0001] The present application relates to a new method and device for regulating the solidification structure and defects of a large steel ingot and its application, which can greatly reduce or even eliminate the solidification defects of a large steel ingot, such as refining grains, reducing or eliminating porosity / shrinking, reducing macro and micro segregation, etc., and belongs to the fields of metallurgy, casting, solidification, large-scale castings and forgings, tool steels, special steels, high-temperature alloys, non-ferrous alloy manufacturing, etc. BACKGROUND

[0002] At present, the large steel ingot casting is carried out by top pouring or bottom pouring, the molten steel is poured into the ingot mold and the riser, and the rice husk ash or heat-generating insulating slag powder is placed on the upper part of the molten steel in the riser, and the heat in the molten steel is mainly dissipated through the ingot mold. After the molten steel is completely solidified, the steel ingot is taken out of the ingot mold and then enters the subsequent processes such as forging, rolling, drawing, heat treatment, etc. However, with the expansion of the size of the ingot or the increase of the ingot height, the heat dissipation and solidification speed of the molten steel in the ingot mold becomes slower, and the developed dendritic structure is formed when the molten steel solidifies, which easily forms dendrite bridging, prevents the molten steel above from being replenished, and finally forms porosity and shrinkage, which are located in the center or upper part of the steel ingot, or even in the lower part, rather than in the riser area, resulting in the degradation of the whole steel ingot or even the scrap; the developed dendrites block the upward floating of large particles inclusions, which are left in the steel and form crack sources, causing great safety hazards to the final service performance of the steel; the developed dendrites also cause serious macro and micro segregation; the channels formed by the melting of the dendrites also cause the upward or downward movement of the molten steel, forming channel segregation; the developed dendrites and the uneven solidification rate also cause great stress in the steel ingot, which may cause cracking of the steel ingot in severe cases; the high-carbon steel or alloy also forms coarse and reticular carbides between the dendrites, which seriously affect the service performance and safety of the steel ingot and also significantly affect the economic benefits of the enterprise.

[0003] To solve the solidification defects of large ingot, the existing process adopts water-cooled ingot mold, electromagnetic stirring outside the ingot mold, electromagnetic oscillation coil on the top of the riser, or high-temperature demolding light pressing, ultrasonic oscillation, setting the ingot mold vibration table and other methods, but the effect is very small, or the metallurgical defects cannot be eliminated. Using water-cooled ingot mold, due to the shrinkage of the solidified steel ingot, an air gap and thermal resistance are formed between the steel ingot and the ingot mold, so the water-cooled mold still cannot solve the problem, and the water cooling of the ingot mold will accelerate the radial heat dissipation and promote the rapid growth of the radial dendrites, eventually form a bridge, prevent the replenishment of the upper liquid steel and form more serious porosity and shrinkage. When the electromagnetic stirring is added outside the ingot mold, the magnetic field cannot penetrate due to the use of cast iron material for the ingot mold, and a small part of the cast steel material. Even if a stainless steel ingot mold is used, due to the wall thickness of more than 100 mm of the ingot mold and the thick shell of the solidified steel ingot of more than hundreds of mm, it is difficult for the magnetic field to penetrate to the un-solidified liquid steel area in the core of the ingot to form effective stirring. Adding an alternating magnetic field coil with water cooling on the top of the riser can form a crystallization rain effect through the induced electromagnetic oscillation effect, but due to the limited action distance and safety hazards, it still cannot solve the solidification defect problem in the middle of the ingot. The external ultrasonic vibration can effectively refine the grains, but how to solve the problem of erosion of the ultrasonic amplitude rod by the liquid steel and the resistance in the high-temperature liquid steel is still a world problem at present, and the ultrasonic wave has directionality and limited action depth in the liquid steel. The method of high-temperature demolding light pressing needs to spray water on the top of the riser, and although it is expected to solve part of the porosity and shrinkage during the light pressing process, it cannot solve the macro-segregation and inclusion defects, and there is also a potential risk of un-solidified liquid steel spouting, so there is no industrial application at present. The method of using the whole ingot mold vibration is only suitable for the top pouring mode. Vibration can cause the grain settlement of part of the ingot mold nucleation and the fracture and settlement of part of the dendrite tip, but as the size of the ingot increases, the weight of the ingot mold is as heavy as ten tons or even dozens of tons, and the weight of the ingot is also dozens of tons or even hundreds of tons. How to vibrate such a huge ingot system is a great technical difficulty, and there is also a great risk of leakage of steel, and the whole vibration also cannot solve the heat transfer and dendrite bridging in the center of the ingot, and finally cannot eliminate the solidification defects of the large ingot. Therefore, the solidification defect problem of the large ingot is a common problem faced by steel casting enterprises and many non-ferrous alloy ingot casting enterprises, and the existing means is difficult to solve, and new solutions and means are urgently needed. SUMMARY

[0004] In order to solve the prior art problems, the purpose of the present application is to overcome the shortcomings of the prior art, provide a device, method and application of vacuum heat-insulating riser composite electromagnetic regulation and control of large ingot solidification structure and defects, the present application strengthens the heat preservation of the ingot mold riser area, adopts the method of riser with vacuum interlayer and heat preservation layer, maximally reduces the convection, conduction and radiation heat transfer of the molten steel in the riser area; at the same time, a cover plate with vacuum interlayer and heat preservation layer is installed above the riser, so that the heat insulation in the riser area is realized, and the molten steel in the riser area can keep liquid state before the solidification of the lower ingot, which is equivalent to forming a hot top above the main body of the ingot; at the same time, a spiral conical rotating magnetic field stirrer is arranged in the riser area, the molten steel in the riser is stirred to produce spiral motion, which drives the rotation of the unsolidified molten steel in the center area of the ingot, and further affects the temperature gradient, dendrite growth, inclusion floating, temperature field and flow field of the molten steel in the center of the ingot. At the bottom of the ingot mold, a strengthened cooling measure is arranged to cool the bottom mold by water or compressed gas, so that the ingot is sequentially solidified from bottom to top, and the porosity and shrinkage hole are left at the upper end of the riser area. By using the above method, the solidification defects of the large ingot are finally reduced or even eliminated, the large ingot billet with excellent metallurgical quality is obtained, and after subsequent forging and rolling, drawing and heat treatment, products such as pipe, bar, wire, plate and strip with excellent quality can be obtained.

[0005] In order to achieve the above-mentioned purposes, the present application adopts the following inventive concept:

[0006] The application discloses a control method for vacuum riser heat-insulation electromagnetic homogenization of a large steel ingot, wherein a riser mold is changed into a non-magnetic stainless steel material, and the riser mold is made into a vacuum sandwich structure, which can effectively prevent heat convection and conduction; a heat-insulation blanket with high temperature resistance and extremely low thermal conductivity is pasted on the inner side of the riser mold, and then heat-insulation bricks with excellent heat-insulation performance are placed, so that the heat conduction of the riser liquid in the radial direction can be maximally prevented; a riser cover with a thick heat-insulation layer is further arranged on the upper part of the riser mold, heat-insulation bricks are arranged on the bottom of the riser cover, and heat-insulation blankets with high temperature resistance are arranged between the heat-insulation bricks and the riser cover for heat insulation; the arrangement of the riser cover with the thick heat-insulation layer can also maximally reduce the heat dissipation of the top of the liquid in the riser; the ingot mold has a large heat dissipation area, so the heat dissipation speed is relatively fast, and even faster than the bottom mold of the steel ingot, so that the dendrite bridging is easily formed at the ingot mold body; from the perspective of reducing the solidification defects and promoting the floating of inclusions, the formation of the solidification from bottom to top of the steel ingot is the best mode; the cooling medium channel is arranged at the bottom mold of the steel ingot, the cooling medium is introduced into the bottom mold of the steel ingot after the pouring of the liquid steel is completed, and the bottom mold of the steel ingot is formed into a strong heat dissipation condition, so that the directional solidification from bottom to top of the liquid in the ingot mold can be ensured; in order to further control the solidification of the liquid in the ingot mold, a variable frequency spiral electromagnetic stirrer is arranged outside the vacuum riser mold; since the vacuum riser mold is made of stainless steel and has good heat-insulation characteristics, the spiral magnetic field generated by the spiral electromagnetic stirrer can drive the long-time un-solidified liquid in the vacuum riser mold to generate spiral rotation, and drive the un-solidified liquid in the center of the steel ingot below the riser to generate spiral rotation; the spiral rotation of the liquid at the position can break the dendrites of the solidification front, form fine crystal nucleus precipitation, form crystal nucleus proliferation, and is expected to refine the dendrites and even form non-dendritic crystals, which are low in columnar crystals and even form equiaxed crystals; the spiral rotation can also break the dendrites about to bridge, form a through feeding channel, and ensure that the liquid above can be fully fed; the spiral rotation can also promote the inclusions removed from the liquid and the solidification front to collide, grow and float, and can also take the inclusions at the dendrite front away, into the center liquid and float, and improve the cleanliness of the liquid; the rotation of the liquid in the center of the steel ingot can reduce and homogenize the temperature gradient in the steel ingot, and then form an in-situ growth condition and a large number of equiaxed crystals; in addition, the nearly adiabatic heat-insulation condition formed by the riser mold and the strong cooling condition of the steel ingot base can form good sequential solidification characteristics and good feeding performance; the dendrite breaking and the crystal nucleus precipitation of the mold wall caused by the rotation of the liquid in the center of the steel ingot form a crystallization rain effect, so that the entire steel ingot can form a large range of equiaxed crystals, and the last solidification region of the steel ingot is completely reserved at the top end of the riser region, so that the solidification defects of the large steel ingot and the macro and micro segregation can be completely solved; the yield and the good product rate can be greatly improved, and the riser cutting ratio can be greatly reduced or even eliminated.

[0007] According to the above-mentioned application concept, the application adopts the following technical scheme:

[0008] The device for regulating the solidification structure and defects of large ingot by complex electromagnetic control of vacuum heat-insulating riser comprises a main body part of ingot mold for loading molten steel in the ingot mold to be solidified, which is formed by assembling the lower end of the ingot mold and the bottom mold together; and a riser device installed on the upper end of the ingot mold, wherein the riser device adopts a vacuum riser, the inside of the vacuum riser comprises a riser vacuum cavity, a riser heat-insulating blanket and riser heat-insulating bricks are arranged in sequence on the inner wall of the vacuum riser to form a riser inner wall, a riser top brick is arranged at the opening of the top end of the riser inner wall to close the top end, the upper surface of the riser top brick is provided with riser heat-insulating cotton and a riser cover in sequence to form a closed structure for heat insulation and sealing of the top end of the vacuum riser; and the lower surface of the riser top brick and the surface of the riser heat-insulating brick form a riser inner wall surface which directly contacts with the molten steel and slag, and the riser shape is formed to accommodate the molten steel and slag; the heat-insulating condition formed by the vacuum riser ensures that the molten steel and slag in the vacuum riser can remain in liquid state for a set time.

[0009] A bottom mold cooling medium flow channel is further arranged in the bottom mold, cooling medium is supplied to the bottom mold cooling medium flow channel through a bottom mold cooling medium inlet, and the cooling medium in the bottom mold cooling medium flow channel is discharged through a bottom mold cooling medium outlet to form a cooling cycle of the cooling medium for the bottom mold, thereby radiating the lower half of the molten steel in the ingot mold and forming a shallow concave initial solidification interface of the molten steel in the ingot mold; a bottom mold port refractory nozzle is further arranged in the middle of the bottom mold.

[0010] An electromagnetic force stirring device is further arranged outside the vacuum riser, which comprises a spiral electromagnetic stirrer, and the spiral electromagnetic stirrer generates a spiral alternating magnetic field to drive the molten steel in the riser to move spirally in the rotating direction of the molten steel, thereby driving the molten steel in the ingot mold to rotate and realizing the induced stirring of the molten steel in the riser driven by the electromagnetic force.

[0011] The self-bottom-up heat radiation condition and solidification sequence of the molten steel in the ingot mold are formed to obtain a shallow concave or even flat solidification interface, thereby regulating the solidification structure and defects of the large ingot.

[0012] The device of the application is applied to the homogenization of large ingot and the control of solidification defects, and mainly comprises a bottom injection pipe for loading molten steel, a strong cooling ingot bottom mold, an ingot mold, a vacuum riser mold, a vacuum riser mold cover, a spiral electromagnetic stirrer, a variable frequency power supply, a riser heat-insulating brick, heat-insulating materials and the like.

[0013] Preferably, the weight of the molten steel in the ingot mold is 1-1000 tons according to the volume of the ingot mold; preferably, the inner diameter of the ingot mold is 200-5000 mm, and the height of the ingot mold is 1-10 meters; preferably, the volume of the vacuum riser is 10-30% of the volume of the ingot mold; and preferably, the material of the ingot mold is at least one of cast iron, cast steel, stainless steel, water-cooled copper plate, graphite and other refractory materials.

[0014] Preferably, the inner cavity of the riser insulating brick has a horizontal cross-section shape of a circle with a 5°-10° inverted taper for easy demolding.

[0015] Preferably, the cooling medium flow channel in the ingot bottom mold has a cross-section shape of a circle, a square, a plate, a T shape or other special shapes, and is filled with at least one of cooling water, cooling oil, low-melting-point liquid metal, or at least one of compressed air, carbon dioxide, hydrogen, helium, nitrogen, argon, water vapor and other inert gases, or liquid medium of the above-mentioned gases.

[0016] Preferably, the vacuum riser and the riser cover adopt a vacuum heat insulation mechanism, and the vacuum degree in the vacuum cavity of the riser is in the range of 10 -4 Pa~4000Pa, preferably, the riser insulating blanket or the riser cover insulating cotton adopts at least one of zirconium silicate, aluminum oxide fiber, and carbon fiber felt, and preferably, the riser insulating brick and the riser top brick adopt at least one of silica, magnesia, mixed fiber material, aluminum oxide, magnesium oxide, and hollow sphere bonded body of silicon oxide;

[0017] Preferably, the vacuum cavity of the vacuum riser and the riser cover can be single-layer or multi-layer, and the vacuum layer and the riser insulating blanket layer, the radiation-proof layer or the riser insulating cotton layer can also be arranged alternately.

[0018] Preferably, the spiral electromagnetic stirrer is a full-enclosing type or a half-enclosing type or a double half-circle enclosing type which is sleeved on the periphery of the vacuum riser;

[0019] Preferably, the spiral electromagnetic stirrer is further provided with a cooling device, including a stirrer cooling water outlet and a stirrer cooling water inlet, and the spiral electromagnetic stirrer is cooled by circulating cooling water;

[0020] Preferably, the magnetic field mode is a single-spiral rotation type, a multi-spiral rotation type or a positive and negative rotation spiral rotation type with variable frequency and variable duty cycle;

[0021] Preferably, the rotation speed is 0-3000 revolutions per minute, the spiral frequency is 0-1000 Hz, the magnetic field frequency is 0-1000 Hz, the effective magnetic field strength is 0-3000 mT, and the duty cycle is 1-100%; the variable frequency current is provided by a variable frequency power supply, or a rotating permanent magnet or a superconducting magnet is used to generate; the power supply is supplied through a stirrer power supply interface; the variable frequency power supply is 2-phase, 3-phase or multi-phase, the current frequency is 0-1000 Hz, the current intensity is 0-30000 A, the output voltage is 0-1000 V, and the duty cycle is 1-100%; the angle between the spiral magnetic field and the ingot axis is 10-90°.

[0022] Preferably, the vacuum riser material adopts at least one of nickel-based superalloy, corrosion-resistant non-magnetic steel, nickel-chromium alloy 316L stainless steel, 304 stainless steel, 201 stainless steel, 321 stainless steel.

[0023] A method for regulating solidification structure and defects of large steel ingot by a vacuum heat-insulating riser composite electromagnetic device;

[0024] The spiral electromagnetic stirrer generates a spiral alternating magnetic field, which drives the riser liquid steel to generate spiral motion, drives the liquid steel in the ingot mold to rotate, thereby breaking dendrites, forming crystal nucleus proliferation, preventing dendrite bridging, promoting feeding, promoting inclusion aggregation and floating, driving inclusions away from the solidification interface, homogenizing temperature and reducing temperature gradient to form endogenous growth conditions, forming large-range equiaxed crystal or fine dendritic structure, reducing or even eliminating macrosegregation and stress;

[0025] At the same time, in order to strengthen the heat dissipation of the liquid steel in the ingot mold bottom plate, a bottom mold cooling medium flow channel is arranged in the bottom mold, and the heat is taken away from the bottom mold by the cooling medium, while the vacuum riser is in heat-insulating insulation, and the heating effect of the heating slag on the surface of the liquid steel is utilized to form a heat dissipation condition and a solidification sequence from bottom to top of the liquid steel in the ingot mold, so that a good shallow concave solidification interface is obtained, and even a unidirectional solidification structure is obtained, thereby reducing and eliminating solidification defects.

[0026] Preferably, the liquid steel in the ingot mold is poured by bottom pouring or top pouring, or is poured by open pouring or under inert atmosphere.

[0027] An application of a vacuum heat-insulating riser composite electromagnetic device for regulating solidification structure and defects of large steel ingot, which utilizes the vacuum heat-insulating riser composite electromagnetic device for regulating solidification structure and defects of large steel ingot, characterized in that the metal melt in the ingot mold is at least one of low-carbon steel, medium-carbon steel, high-carbon steel, alloy steel, special steel, high-temperature alloy, aluminum alloy, titanium alloy, copper alloy, zinc alloy, magnesium alloy, high-entropy alloy, or other alloy that needs to be produced by ingot casting, or at least one of semiconductors such as silicon and germanium that have melt conduction, or at least one of conductive metals, conductive oxides and salt melts.

[0028] Compared with the prior art, the present application has the following obvious and substantial characteristics and advantages:

[0029] 1. The vacuum heat-insulating riser structure provided in the present application can maximize the heat dissipation of the riser sidewall and top, and can keep the liquid steel in the riser in liquid state for a long time, forming a hot top, which is beneficial to the feeding of the solidifying liquid steel.

[0030] 2. The vacuum heat-insulated riser mold of the present application is made of non-magnetic high-temperature-resistant material, can effectively penetrate into a spiral magnetic field, drive the steel liquid to generate spiral rotation, and drive the rotation of the steel liquid in the center region of the ingot mold, thereby effectively affecting the solidification process of the steel liquid in the ingot mold;

[0031] 3. The vacuum heat-insulated riser structure of the present application can maintain the steel liquid in the riser as liquid for a long time due to excellent heat-insulating effect, provides unique conditions for applying a spiral electromagnetic field, and can ensure sufficient magnetic field penetration depth in the steel liquid;

[0032] 4. The steel ingot bottom mold strong heat-dissipation structure of the present application, in combination with the vacuum heat-insulated riser mold and the heat-insulated riser mold cover, can form a bottom-up solidification mode, can prevent the dendrite bridging caused by the radial solidification of the steel liquid in the ingot mold to the greatest extent, and thus can effectively avoid the porosity and shrinkage holes in the steel ingot;

[0033] 5. The present application applies spiral rotating stirring flow to the steel liquid in the vacuum riser area, which can drive the rotation of the steel liquid in the ingot mold region at the lower end of the riser due to the horizontal and axial components, can break the dendrites to form nucleation multiplication, prevent dendrite bridging, promote feeding, promote the aggregation and floating of inclusions, drive the inclusions away from the solidification interface, homogenize the temperature and reduce the temperature gradient to form ingrowth conditions, form large-area equiaxed crystal or fine dendrite structure, reduce or even eliminate macrosegregation and stress, and thus can obtain a large steel ingot with grain refinement, even equiaxed crystal, uniform composition, uniform structure, uniform stress, high density, and high cleanliness, can cut off the riser less or even not, and thus can greatly improve the yield;

[0034] 6. The present application is not only suitable for the solidification defect control of various steel ingots, but also suitable for the solidification defect control of high-temperature alloys, aluminum alloys, titanium alloys, magnesium alloys, copper alloys, high-entropy alloys, and various conductive melts, and has wide application. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Figure 1 is a structure schematic diagram of the device for controlling the solidification structure and defects of a large steel ingot by the vacuum heat-insulated riser composite electromagnetic regulation of the first embodiment of the present application. DETAILED DESCRIPTION

[0036] The present application is suitable for controlling various steel liquids, and is also suitable for high-temperature alloys, titanium alloys, copper alloys, aluminum alloys, magnesium alloys, zinc alloys, various conductive melts, non-metallic melts, and the like.

[0037] The above scheme is further described in combination with specific examples, and the preferred embodiments of the present application are described in detail as follows:

[0038] Embodiment 1

[0039] In this embodiment, as shown in Figure 1 A device for regulating the solidification structure and defects of a large ingot by electromagnetic control of the vacuum-insulated riser is provided. The lower end of the ingot mold 11 and the bottom mold 14 are assembled together to form the main body of the ingot mold, which is used to load the molten steel 12 in the ingot mold to be solidified. The riser device is installed on the upper end of the ingot mold 11. The riser device uses a vacuum riser 4, which includes a riser vacuum cavity 5 inside. The riser vacuum cavity 4 is provided with a riser insulating blanket 7 and a riser insulating brick 8 in sequence on the inner wall of the vacuum riser 4 to form the inner wall of the riser. The riser top brick 3 is provided on the top of the inner wall of the riser to close the opening. The upper surface of the riser top brick 3 is provided with a riser cover insulating cotton 2 and a riser cover 1 in sequence to form a closed structure, which insulates and closes the top of the vacuum riser 4. The lower surface of the riser top brick 3 and the surface of the riser insulating brick 8 form the inner wall surface of the riser refractory brick, which directly contacts with the molten metal and slag. The riser forms a shape to contain the riser molten steel 9 and the heating slag 6. The insulating condition formed by the vacuum riser 4 ensures that the riser molten steel 9 and the heating slag 6 inside the vacuum riser 4 can remain in liquid state for a set time;

[0040] A bottom mold cooling medium flow channel 15 is also provided in the bottom mold 14. Cooling medium is supplied to the bottom mold cooling medium flow channel 15 through the bottom mold cooling medium inlet 13, and the cooling medium in the bottom mold cooling medium flow channel 15 flows out through the bottom mold cooling medium outlet 17, forming a cooling cycle of the cooling medium for the bottom mold 14. The lower half of the molten steel 12 in the ingot mold is cooled to form an initial solidification ingot 18 with a shallow concave solidification interface. A bottom mold port refractory nozzle 16 is also provided in the middle of the bottom mold 14.

[0041] An electromagnetic stirring device is also provided outside the vacuum riser 4, which includes a helical electromagnetic stirrer 22. The helical electromagnetic stirrer 22 generates a helical alternating magnetic field, which drives the riser molten steel 9 to move in a helical shape according to the rotation direction of the molten steel 10, and drives the molten steel 12 in the ingot mold inside the ingot mold 11 to rotate, realizing electromagnetic force-induced rotational flow stirring.

[0042] The molten steel 12 in the ingot mold 11 forms a heat dissipation condition and a solidification sequence from bottom to top, obtaining a shallow concave solidification interface, thereby regulating the solidification structure and defects of the large ingot.

[0043] In this embodiment, the helical electromagnetic stirrer 22 is also provided with a cooling device, which includes a stirrer cooling water outlet 19 and a stirrer cooling water inlet 21. The helical electromagnetic stirrer 22 is cooled by circulating water.

[0044] In this embodiment, as shown in Figure 1, the method for realizing the object of the application adopts vacuum ladle composite electromagnetic regulation of solidification structure and defects of large steel ingot, and is realized by a special device, which mainly consists of a ladle cover 1, a ladle top brick 3, a vacuum ladle 4, a ladle insulating brick 8, a steel ingot mold 11, a bottom mold 14, and a spiral electromagnetic stirrer 22, wherein the vacuum ladle 4 is made of non-magnetic 316L stainless steel. In the implementation of the application, the steel ingot mold 11 and the bottom mold 14 are assembled on a special bottom pouring plate, the vacuum cavity 5 of the vacuum ladle 4 is evacuated to a vacuum degree of not less than 10 -2 Pa, the vacuum ladle 4 is pasted with a ladle insulating blanket 7 and a ladle insulating brick 8, the inner cavity of the vacuum ladle 4 is circular, the inner cavity of the ladle insulating brick 8 is also circular and has a 5°-10° inverted taper to facilitate demolding. The entire set of inner cavities of the vacuum ladle 4 containing the ladle insulating blanket 7 and the ladle insulating brick 8 is baked through by natural gas or coal gas and kept at a surface temperature of the inner cavity of the ladle insulating brick 8 of 800℃, then the entire set of the ladle is placed on the upper opening of the steel ingot mold 11, and the sealing between the bottom of the vacuum ladle 4 and the upper opening of the steel ingot mold 11 is made by refractory fiber cotton or refractory clay. The volume of molten steel in the cavity formed by the steel ingot mold 11, the vacuum ladle 4 and the bottom mold 14 is 18 tons, and the inner cavity of the steel ingot mold 11 is 16 deformed and has an equivalent diameter of 1100mm. The molten steel of H13 die steel is poured into the cavity formed by the bottom mold 14, the steel ingot mold 11 and the vacuum ladle 4 by a bottom pouring method through a refractory nozzle 16 of the bottom mold, when the molten steel reaches a certain position in the inner cavity of the vacuum ladle 4, the heating slag 6 is scattered onto the upper surface of the ladle molten steel 9 in the inner cavity of the vacuum ladle 4, and the ladle top brick 3 is covered, the upper opening of the ladle insulating brick 8 and the upper surface of the vacuum ladle 4 are flush or slightly lower than the ladle top brick 3. Then the ladle cover 1 containing the ladle cover insulating cotton 2 is covered on the vacuum ladle 4, the contact surface is sealed by refractory ceramic cotton, and the refractory ceramic cotton at the top of the upper opening of the steel ingot mold 11 and the upper opening of the vacuum ladle 4 is pressed and sealed by the self-weight of the ladle cover 1 and the vacuum ladle 4. Then the cooling circulating water is circulated into the stirrer cooling water inlet 21 and the stirrer cooling water outlet 19 of the spiral electromagnetic stirrer 22, the cooling circulating water pressure is not less than 0.15Mpa, and the cooling water flow is not less than 20m 3 / hr, the temperature rise of the cooling circulating water should not exceed 20℃. Then, place the spiral electromagnetic stirrer 22 on the side of the vacuum riser 4 using a rail or bracket and center it. Adjust the input current of the spiral electromagnetic stirrer 22 to 500A and the frequency to 50Hz through the stirrer power interface 20. At this time, the spiral alternating electromagnetic field generated in the spiral electromagnetic stirrer 22 will drive the riser molten steel 9 to generate spiral stirring motion in the direction of steel molten steel rotation 10, and then drive the molten steel 12 in the ingot mold 11 to rotate. This can avoid the formation of dendrite bridging in the center of the molten steel 12 in the ingot mold, and can promote dendrite fragmentation to form crystal nuclei and increase, reduce the temperature gradient at the solidification interface front, thereby refining the solidification structure of the ingot in the ingot mold 11, achieving homogenization and fine grain refinement, suppressing or even eliminating macro segregation, and can also promote the collision growth of endogenous inclusions discharged from the solidification front and float to the top of the riser molten steel 9 for removal of the hot slag. Compressed air is introduced into the bottom mold cooling medium inlet 13. The inlet pressure of the compressed air is 1.5 MPa. The compressed air flows through the bottom mold cooling medium channel 15, which fully cools the bottom mold 14 and the molten steel 12 in the ingot mold from the bottom. Then the compressed air flows out through the bottom mold cooling medium outlet 17 to be vented or vented after heat exchange. Due to the heat insulation and heat preservation effects of the vacuum riser 4, riser insulation blanket 7, riser insulation brick 8, riser vacuum cavity 5, riser top brick 3, riser cover insulation cotton 2, and riser cover 1, as well as the heat replenishment effect of the heating slag 6, the riser molten steel 9 in the inner cavity of the vacuum riser 4 can always be kept in a liquid state. This facilitates the penetration of the stirring magnetic field in the spiral electromagnetic stirrer 22 into the interior, forming an effective spiral stirring of the molten steel rotation direction 10. Ultimately, this controls the solidification structure of the steel ingot and eliminates solidification defects. The spiral electromagnetic stirrer 22 is kept running until all the molten steel in the steel ingot mold 11 and the vacuum riser 4 is solidified, ultimately obtaining a large steel ingot with no loose shrinkage cavities, uniform composition, fine grains, and high cleanliness.

[0045] The device of the embodiment realizes the heat insulation condition of the vacuum riser 4, and then ensures that the riser liquid steel 9 inside the vacuum riser 4 can be in liquid state for a long time. A helical electromagnetic stirrer 22 is arranged outside the vacuum riser 4. The helical electromagnetic stirrer 22 generates a helical alternating magnetic field, which drives the riser liquid steel 9 to generate helical motion, and drives the ingot mold liquid steel 12 inside the ingot mold 11 to rotate, so that the dendrites can be broken to form crystal nucleus proliferation, prevent dendrite bridging to promote feeding, promote the aggregation and growth of inclusions to float up, drive the inclusions at the solidification front away from the solidification interface, homogenize the temperature and reduce the temperature gradient to form endogenous growth conditions, form large range equiaxed crystal or fine dendritic structure, reduce or even eliminate macrosegregation, eliminate stress, and thus obtain a large ingot with grain refinement, even equiaxed crystal, uniform composition, uniform structure, uniform stress, high density and high cleanliness. The ingot can be cut less or even not cut, and thus the yield can be greatly improved. Meanwhile, in order to strengthen the heat dissipation of the liquid steel at the bottom plate of the ingot mold 11, a bottom mold cooling medium flow channel 15 is arranged in the bottom mold 14. The heat is taken away from the bottom mold 14 by the cooling medium, while the vacuum riser 4 is in heat insulation and heat preservation. At the same time, the heating effect of the heating slag 6 is utilized, which is beneficial to the formation of the heat dissipation condition and solidification sequence of the ingot mold liquid steel 12 in the ingot mold 11 from bottom to top, and finally a good shallow concave solidification interface can be obtained, even a unidirectional solidification structure, which is helpful to eliminate solidification defects.

[0046] Embodiment Two

[0047] The embodiment is basically the same as Embodiment One, and the difference is that:

[0048] In the embodiment, the device in Embodiment One is adopted, but after the helical electromagnetic stirrer 22 is applied, the current in the helical electromagnetic stirrer 22 is adjusted to 1000 A and the frequency is 8 Hz, and the adjustment is kept until the ingot is completely solidified.

[0049] The helical electromagnetic stirrer 22 generates a helical alternating magnetic field, which drives the riser liquid steel 9 to generate helical motion, and drives the ingot mold liquid steel 12 inside the ingot mold 11 to rotate, so that the dendrites can be broken to form crystal nucleus proliferation, prevent dendrite bridging to promote feeding, promote the aggregation and growth of inclusions to float up, drive the inclusions at the solidification front away from the solidification interface, homogenize the temperature and reduce the temperature gradient to form endogenous growth conditions, form large range equiaxed crystal or fine dendritic structure, reduce or even eliminate macrosegregation, eliminate stress; meanwhile, in order to strengthen the heat dissipation of the liquid steel at the bottom plate of the ingot mold 11, a bottom mold cooling medium flow channel 15 is arranged in the bottom mold 14. The heat is taken away from the bottom mold 14 by the cooling medium, while the vacuum riser 4 is in heat insulation and heat preservation. At the same time, the heating effect of the heating slag 6 is utilized, which is beneficial to the formation of the heat dissipation condition and solidification sequence of the ingot mold liquid steel 12 in the ingot mold 11 from bottom to top, and finally a good shallow concave solidification interface can be obtained, even a unidirectional solidification structure, which is helpful to eliminate solidification defects.

[0050] Example 3

[0051] This example is basically the same as the above examples, and the particularity is that:

[0052] In this example, the device in Example 1 is used, but after applying the helical electromagnetic stirrer 22, the current in the helical electromagnetic stirrer 22 is adjusted to 1000 A and the frequency is 8 Hz until the steel ingot is completely solidified. But pour into 7075 aluminum alloy liquid, until the aluminum alloy ingot is completely solidified, so as to obtain large 7075 aluminum alloy ingot with no loose shrinkage, uniform composition, grain refinement, high cleanliness.

[0053] Comparative Example

[0054] The device in Example 1 is used, but the helical electromagnetic stirrer 22 is not applied, and the solidification of the steel ingot is maintained. Although a large steel ingot without significant loose shrinkage can be obtained, the grain structure is relatively coarse, and the problem of excessive inclusions cannot be solved.

[0055] From the above examples and comparative examples, it can be seen that the method for complex electromagnetic regulation of the solidification structure and defects of a large ingot by the vacuum-insulated riser of the above examples, which is implemented by the special device thereof, the special device is mainly composed of a riser cover 1, a riser top brick 3, a vacuum riser 4, a riser insulating brick 8, an ingot mold 11, a bottom mold 14, and a helical electromagnetic stirrer 22, and the vacuum riser 4 is made of non-magnetic 316L stainless steel. The stainless steel vacuum riser 4 with a vacuum interlayer is adopted, the riser insulating blanket 7 and the riser insulating brick 8 are arranged in the inner cavity of the vacuum riser 4, the riser cover 1 with the riser cover insulating cotton 2 and the riser top brick 3 are further arranged on the top of the vacuum riser 4, so as to realize the heat insulation condition of the vacuum riser 4, and then ensure that the riser liquid steel 9 in the vacuum riser 4 can be in liquid state for a long time. The helical electromagnetic stirrer 22 is arranged on the outside of the vacuum riser 4, the helical electromagnetic stirrer 22 generates a helical alternating magnetic field, drives the riser liquid steel 9 to generate helical motion, drives the ingot mold liquid steel 12 in the ingot mold 11 to rotate, so as to break the dendrites to form nucleation proliferation, prevent dendrite bridging to promote feeding, promote the aggregation and growth of inclusions to float up, drive the inclusions before solidification away from the solidification interface, homogenize the temperature and reduce the temperature gradient to form an endogenous growth condition, form a large range of equiaxed crystal or fine dendritic structure, reduce or even eliminate macrosegregation, eliminate stress, and thus obtain a large ingot with grain refinement, even equiaxed crystal, uniform composition, uniform structure, uniform stress, high density, and high cleanliness, which can be less or even not cut off the riser, so as to greatly improve the yield. At the same time, in order to strengthen the heat dissipation of the liquid steel in the bottom plate of the ingot mold 11, the bottom mold cooling medium flow channel 15 is arranged in the bottom mold 14, the heat is taken away from the bottom mold 14 by the cooling medium, the vacuum riser 4 is in heat insulation and heat preservation, and the heating effect of the heating slag 6 is utilized, which is beneficial to the formation of the heat dissipation condition and the solidification sequence of the ingot mold liquid steel 12 in the ingot mold 11 from bottom to top, and finally a good shallow concave solidification interface and even a unidirectional solidification structure can be obtained, which is helpful to the elimination of solidification defects.

[0056] The above describes the embodiments of the present application in combination with the drawings, but the present application is not limited to the above examples, and various changes can be made according to the purpose of the invention and creation of the present application. Any change, modification, replacement, combination or simplification made according to the spirit and principles of the technical solutions of the present application shall be an equivalent replacement manner, as long as it meets the purpose of the present application and does not deviate from the technical principles and inventive concept of the present application.

Claims

1. A device for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser and composite electromagnetic control, comprising assembling the lower end of a steel ingot mold (11) and a bottom mold (14) together to form the main body of the steel ingot mold, used to load molten steel (12) into the steel ingot mold to be solidified; and installing a riser device at the upper end of the steel ingot mold (11), characterized in that: The riser device adopts a vacuum riser (4), and the vacuum riser (4) includes a riser vacuum chamber (5). A riser insulation blanket (7) and a riser insulation brick (8) are sequentially arranged on the inner wall of the vacuum riser (4) to form the inner wall of the riser. A riser top brick (3) is set at the top opening of the inner wall of the riser for sealing. A riser cover insulation cotton (2) and a riser cover (1) are sequentially arranged on the upper surface of the riser top brick (3) to form a closed structure, which provides heat insulation and sealing to the top of the vacuum riser (4). The lower surface of the riser top brick (3) and the surface of the riser insulation brick (8) form the inner wall surface of the riser refractory brick that is in direct contact with the molten metal slag, forming the riser shape to accommodate the riser molten steel (9) and the exothermic slag (6). The heat insulation conditions formed by the vacuum riser (4) ensure that the riser molten steel (9) and the exothermic slag (6) inside the vacuum riser (4) can remain in a liquid state for a set time. A cooling medium flow channel (15) is also provided in the bottom mold (14). Cooling medium is supplied to the cooling medium flow channel (15) through the cooling medium inlet (13) and the cooling medium flows out through the cooling medium outlet (17), forming a cooling cycle of cooling medium to the bottom mold (14), which dissipates heat to the lower half of the molten steel (12) in the ingot mold, so that the molten steel (12) in the ingot mold forms an initial solidified ingot (18) with a shallow concave solidification interface; a refractory nozzle (16) is also provided in the middle of the bottom mold (14). A magnetic stirring device is also provided on the outside of the vacuum riser (4), including a spiral electromagnetic stirrer (22). The spiral alternating magnetic field generated by the spiral electromagnetic stirrer (22) drives the riser molten steel (9) to generate a spiral motion in the direction of steel molten steel rotation (10), which drives the molten steel (12) in the steel ingot mold (11) to rotate, thereby realizing electromagnetic force-induced swirling stirring. By forming heat dissipation conditions and solidification sequence from bottom to top through the molten steel (12) in the ingot mold (11), a concave solidification interface is obtained, thereby controlling the solidification structure and defects of the large steel ingot.

2. The device for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser composite electromagnetic control according to claim 1, characterized in that: Based on the volume of the ingot mold (11), the weight of the molten steel (12) that can be contained in the ingot mold is 1-1000 tons; the inner diameter of the ingot mold (11) is 200-5000 mm, and the height of the ingot mold (11) is 1-10 meters; the volume of the vacuum riser (4) is 10-30% of the volume of the ingot mold (11); the material of the ingot mold (11) is at least one of cast iron, cast steel, copper, graphite, and other refractory materials.

3. The device for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser composite electromagnetic control according to claim 1, characterized in that: The horizontal cross-sectional shape of the inner cavity of the riser insulation brick (8) is circular, and it has a 5°~10° inverted taper for easy demolding.

4. The device for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser composite electromagnetic control according to claim 1, characterized in that: The cross-section of the cooling medium flow channel (15) in the bottom mold (14) of the steel ingot is circular, square or T-shaped. At least one of cooling water and cooling oil, or at least one of compressed air, carbon dioxide, hydrogen, helium, nitrogen, argon or water vapor is introduced into the cooling channel.

5. The device for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser composite electromagnetic control according to claim 1, characterized in that: The vacuum riser (4) and riser cover (1) adopt a vacuum insulation mechanism, and the vacuum degree in the riser vacuum chamber (5) is 10. -4 Pa~4000Pa, the riser insulation blanket (7) and riser cover insulation cotton (2) are made of at least one of zirconium silicate and alumina, and the riser insulation brick (8) and riser top brick (3) are made of at least one of alumina, magnesium oxide and silica hollow sphere binder; Alternatively, the vacuum layer and riser insulation blanket (7), riser insulation cotton (2) or radiation shielding layer of the vacuum riser (4) and riser cover (1) can be arranged alternately.

6. The device for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser composite electromagnetic control according to claim 1, characterized in that: The spiral electromagnetic stirrer (22) is either a fully enclosed type or a semi-enclosed type that surrounds the vacuum riser (4); The spiral electromagnetic stirrer (22) is also equipped with a cooling device, including a stirrer cooling water outlet (19) and a stirrer cooling water inlet (21), which uses cooling water to circulate and cool the spiral electromagnetic stirrer (22); The magnetic field mode is a single-helix rotation type, a multi-helix rotation type, or a forward and reverse helical rotation type with variable frequency and variable duty cycle; The rotation speed is 0-3000 rpm, the spiral frequency is 0-1000 Hz, the magnetic field frequency is 0-1000 Hz, the effective magnetic field strength is 0-3000 mT, and the duty cycle is 1-100%. The frequency conversion current is provided by the frequency conversion power supply, or generated by a rotating permanent magnet or a superconducting magnet. The power supply is supplied through the stirrer power interface (20). The frequency conversion power supply used is three-phase or multi-phase, the current frequency is 0-1000 Hz, the current strength is 0-30000 A, the output voltage is 0-1000 V, and the duty cycle is 1-100%. The angle between the spiral magnetic field and the steel ingot axis is 10-90°.

7. The device for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser composite electromagnetic control according to claim 1, characterized in that: The vacuum riser (4) is made of at least one of the following: non-magnetic nickel-based high-temperature alloy and corrosion-resistant non-magnetic steel.

8. A method for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser and composite electromagnetic control system, comprising the apparatus for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser and composite electromagnetic control system as described in claim 1, characterized in that: Using the spiral alternating magnetic field generated by the spiral electromagnetic stirrer (22), the riser molten steel (9) is driven to generate a spiral motion, which drives the molten steel (12) in the ingot mold (11) to rotate, thereby breaking dendrites, forming crystal nucleus proliferation, preventing dendrite bridging and promoting feeding, promoting the aggregation, growth and floating of inclusions, driving inclusions at the solidification front away from the solidification interface, homogenizing the temperature and reducing the temperature gradient to form endogenous growth conditions, forming a large-scale equiaxed crystal or fine dendritic structure, reducing or even eliminating macroscopic segregation and eliminating stress; Meanwhile, in order to enhance the heat dissipation of molten steel in the bottom plate of the ingot mold (11), a cooling medium flow channel (15) is set in the bottom mold (14). The cooling medium carries away heat from the bottom mold (14), while the vacuum riser (4) is insulated. At the same time, the heating effect of the heating slag (6) located on the surface of the molten steel is utilized to make the molten steel (12) in the ingot mold (11) form a heat dissipation condition and solidification sequence from bottom to top, thereby obtaining a good shallow concave solidification interface, or even obtaining a unidirectional solidification structure, reducing and eliminating solidification defects.

9. The method for controlling the solidification structure and defects of large steel ingots using a vacuum-insulated riser composite electromagnetic control according to claim 8, characterized in that: The steel liquid (12) in the steel ingot mold is poured in an open pouring or in an inert atmosphere, using either bottom pouring or top pouring.

10. An application of a vacuum-insulated riser composite electromagnetic control method for solidification structure and defects of large steel ingots, utilizing the device for vacuum-insulated riser composite electromagnetic control of solidification structure and defects of large steel ingots as described in claim 1, characterized in that: The molten metal in the ingot mold (11) is at least one of the following: low carbon steel, medium carbon steel, high carbon steel, aluminum alloy, titanium alloy, copper alloy, zinc alloy, and magnesium alloy.

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