A melt processing device and method for preparing ultra-large aluminum alloy ingots

Abstract

The present invention discloses a melt processing device and method for preparing super-large aluminum alloy ingots. The device is mainly composed of an annular electromagnetic melt processor, a hot top, a crystallizer, a crystallizer water tank, a graphite ring, an ingot guide and a lifting mechanism; the annular electromagnetic melt processor is placed in the crystallizer, concentric with the crystallizer, and a line port and a connecting mechanism are arranged on its top, and it is connected to the lifting structure, and can be moved up and down in the height direction of the crystallizer through the lifting mechanism, and positioned at a corresponding position in the crystallizer; the lower end of the hot top is sealed and connected to the crystallizer through a graphite ring; the crystallizer water tank is arranged on the periphery of the crystallizer. The device is used for melt processing, and in the semi-continuous casting process, the annular electromagnetic melt processor is applied to the alloy melt to achieve effective uniformity of the temperature field and composition field of the super-large volume alloy melt, and to achieve effective control of the melt flow, so as to prepare high-quality super-large aluminum alloy ingots with uniform and fine structure and uniform composition.

Description

Technical Field

[0001] The invention belongs to the field of metal material processing, and in particular relates to a melt processing device and method for preparing ultra-large aluminum alloy ingots. Background Art

[0002] Ultra-large aluminum alloy ingots play a vital role in major fields such as aerospace, rail transportation, national defense and military industry, and have very broad application prospects. Large-sized aluminum alloy ingots using ordinary semi-continuous casting have problems such as coarse and uneven organization, component segregation, looseness, cracking, etc., with low yield and difficult to guarantee quality, and cannot meet the performance requirements of subsequent processing procedures for aluminum alloy ingots, especially ultra-large high-quality and high-strength aluminum alloy ingots. The uneven temperature field, component field and stress field during the solidification of aluminum alloy melt are one of the main factors leading to such problems. With the super-large size of the ingot, the temperature difference between the core and the edge of the melt increases during the casting process, the liquid cavity is deeper, the flow is complex, and the alloy elements cannot be evenly distributed on the metallurgical size under non-equilibrium solidification conditions. In addition, the temperature distribution at the front of the solid-liquid interface is inconsistent with the temperature gradient, the grain growth rate is different, the growth overlap of dendrites in the mushy zone and the flow of intercrystalline liquid phase and many other factors affect the ingot structure, which ultimately leads to coarse and uneven organization, segregation, looseness, cracking and other problems.

[0003] There are many methods currently proposed to solve the above problems. Among them, electromagnetic field has the characteristics of high cleanliness, high energy density, high reliability, high controllability and high automation level. It has gradually become an important technical means to improve the quality of ingots, stabilize operations, and expand the range and specifications of products in the process of efficient continuous casting. It is an important research direction and approach in the field of external field control of metal material forming. However, due to the electromagnetism skin effect, the induced current density generated by alternating electromagnetic induction decays exponentially from the surface to the center of the ingot. Therefore, the improvement of the ingot structure and performance by stirring is mainly concentrated in the surface range, and the uniformity of the composition is difficult to control. For this reason, many beneficial explorations have been carried out at home and abroad.

[0004] Chinese patent CN 106925730 B discloses a preparation device and method for large-scale fine-grained homogeneous aluminum alloy ingots. The principle is to set an electromagnetic processor outside the crystallizer and a central cooler inside the melt. The two are coupled to form an annular space to stir the aluminum alloy melt, so that the uniformity of the temperature field and the composition field of the large-volume melt is greatly improved, and fine-grained homogeneous aluminum alloy ingots within Φ500mm can be prepared. However, as the size of the ingot increases, the electromagnetic field applied outside the crystallizer decays severely, and the improvement of the uniformity of the temperature field and the composition field during the melt stirring process will be greatly limited. Chinese patent CN 106623832 B discloses a method of directly immersing an electromagnetic processor into the alloy melt and applying an electromagnetic field from the inside of the melt to treat the alloy melt. Since the stirring treatment is carried out from the inside of the melt to the outside, the magnetic field decays little, and the internal and external temperature uniformity of the large-volume melt can be significantly improved. This method can realize the preparation of aluminum alloy ingots with a specification of Φ800mm. However, as the ingot specifications continue to increase, the size of the electromagnetic processor placed inside the melt also increases accordingly. The melt in the core area cannot be stirred by the electromagnetic field, and the function and effect of the electromagnetic treatment are greatly reduced. Summary of the invention

[0005] In order to overcome the shortcomings of the current preparation of super-large aluminum alloy ingots, the purpose of the present invention is to provide a melt processing device for preparing super-large aluminum alloy ingots. By using the device for melt processing during the casting process, super-large aluminum alloy ingots with fine structure and uniform composition can be obtained.

[0006] Another object of the present invention is to provide a melt processing method for preparing ultra-large aluminum alloy ingots using the device.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] A melt processing device for preparing super-large aluminum alloy ingots mainly consists of an annular electromagnetic melt processor, a hot top, a crystallizer, a crystallizer water tank, a graphite ring, an ingot guide and a lifting mechanism; the annular electromagnetic melt processor is placed in the crystallizer, concentric with the crystallizer, a line port and a connecting mechanism are arranged on the top of the annular electromagnetic melt processor, and is connected to the lifting mechanism, and can be moved up and down in the height direction of the crystallizer through the lifting mechanism and positioned at a corresponding position in the crystallizer; the lower end of the hot top is sealed and connected to the crystallizer through a graphite ring; the crystallizer water tank is arranged on the periphery of the crystallizer.

[0009] The main function of the annular electromagnetic melt processor is to simultaneously apply electromagnetic field and cooling temperature control effects to the alloy melt outside and inside the annular processor. Its overall shape is an annular cylindrical hollow structure, which is mainly composed of an upper cavity, a lower cavity, an inner electromagnetic coil, an outer electromagnetic coil, a temperature control unit, a cooling end, and a cooling medium; the upper cavity and the lower cavity are divided into independent spaces by a partition; the inner electromagnetic coil and the outer electromagnetic coil are placed in the upper cavity, the inner electromagnetic coil is placed on the inner side of the upper cavity, and the outer electromagnetic coil is placed on the outer side of the upper cavity; the temperature control unit is coated on the periphery of the upper cavity; the cooling end is arranged at the lower part of the lower cavity; the upper cavity, the lower cavity and the temperature control unit are respectively filled with cooling medium, and realize circulating cooling with the outside world.

[0010] The annular electromagnetic melt processor divides a large volume of melt into an external melt processing area and an internal melt processing area. The annular electromagnetic melt processor has an outer diameter of 500-1000 mm, an inner diameter of 200-600 mm, and a height of 100-500 mm.

[0011] The inner electromagnetic coil and the outer electromagnetic coil can be a rotating electromagnetic generator, a traveling wave electromagnetic generator or a spiral electromagnetic generator, respectively. The two sets of electromagnetic coils act independently and are composed of two sets of polygonal silicon steel yokes and two sets of coil groups wound with enameled copper wires, which respectively produce stirring shear and flow control effects on the melt in the inner and outer melt processing zones of the annular electromagnetic melt processor. The melt in the inner and outer melt processing zones of the annular electromagnetic melt processor is coupled with electromagnetic stirring and cooling by the cooling unit to achieve the purpose of uniform temperature field component field, and flush the bottom cooling end to promote nucleation, refine grains, and realize the casting of high-quality ultra-large aluminum alloy ingots.

[0012] The ampere-turns of the outer electromagnetic coil of the annular electromagnetic melt processor are 5000-40000 At, the ampere-turns of the inner electromagnetic coil are 2000-30000 At, the frequency is 0.5-50 Hz, and the shear rate of the inner and outer electromagnetic coils is 10-1000 mm / s.

[0013] The temperature control unit is composed of a temperature control layer, an insulation layer and a thermocouple. The main function of the temperature control layer is to keep the melt temperature of the inner melt processing zone and the melt temperature of the outer melt processing zone consistent through different cooling media and flow rates. The temperature control layer is composed of two layers of high-temperature resistant heat-conductive materials, and a spiral tube is arranged inside, and the cooling medium is passed through the spiral tube. The main function of the insulation layer is to prevent the melt from directly contacting the shell and protect the internal and external electromagnetic coils from being damaged by the high-temperature melt. The insulation layer is made of high-temperature resistant insulation ceramics and is arranged between the temperature control layer and the upper shell constituting the upper cavity. The thickness is controlled by the specific specifications of the temperature control layer. The thermocouple is arranged in the temperature control layer to detect and control the temperature.

[0014] The temperature control unit is annular and smoothly transitions with the cooling end of the lower cavity. The thickness of the temperature control unit is 5 to 15 mm. The number of spirals of the spiral tube of the temperature control unit is 3 to 30, and the spiral pitch is 1 to 8 mm. During the operation of the spiral tube, the cooling medium passes through the cooling medium, which reaches the bottom of the temperature control unit from the connection line ports at different positions, and is discharged from the outlet after heat exchange in the spiral tube.

[0015] The cooling end is semicircular with an outer diameter of 300-1000mm. A cooling pipe and a thermocouple are arranged inside. The cooling pipe is connected to the outside through the upper and lower cavities via a connecting mechanism. The thermocouple is arranged in the lower cavity and close to the cooling end, and is connected to the outside through the upper and lower cavities via a connecting mechanism. The cooling end is made of high temperature resistant heat conductive materials, such as graphite, steel, copper, molybdenum, titanium and their composite materials.

[0016] The cooling medium is various fluids such as air, nitrogen, argon, water, oil, etc. The cooling medium flow rate is 0-1000L / min, and the cooling intensity is 100-4000W / (m 2 •k).

[0017] The main principle of the present invention is: to apply an annular electromagnetic melt processor from the inside to the large-volume alloy melt in the semi-continuous casting process, and to divide the melt into an external melt processing area and an internal melt processing area by using the structure of the annular electromagnetic melt processor itself, and to adjust the position of the annular electromagnetic melt processor by applying different electromagnetic fields - spiral magnetic field, rotating magnetic field, and traveling wave magnetic field, to drive the melt flow in the two regions of the solidification process, and to achieve precise control of the uniformity of the temperature field and composition field of the ultra-large-volume alloy melt in the continuous casting process by uniformly cooling the inner and outer walls. Under the action of the inner and outer sets of electromagnetic coils of the annular electromagnetic melt processor, the melt in the inner and outer melt processing areas is effectively processed respectively, generating a multi-dimensional strong shear motion, avoiding the uneven stirring caused by the skin effect due to the excessive volume of the melt and the many problems caused by it. In addition, due to the different electromagnetic forces on the solid and liquid phases, a speed difference is generated between the solid and liquid phases, making the concentration boundary layer of the secondary distribution of the solute extremely thin, the dendrites are broken, the nucleation core is increased, the temperature gradient and the composition supercooling at the interface of the crystal nucleus are uniform, the grains are in a relatively uniform environment, the growth of dendrites is inhibited, and the formation of equiaxed crystals is beneficial; at the same time, the inner and outer electromagnetic coils can accelerate the downward movement of the melt in the internal melt processing area, and increase the cooling intensity during the solidification process of the ingot by flushing the cooling end at the bottom of the melt processor, inhibiting the melt from flowing along the wall of the crystallizer and the solidification front to the center of the ingot, reducing the depth of the liquid cavity, promoting melt heat transfer and uniformity, and promoting nucleation, thereby preparing high-quality ultra-large-size aluminum alloy ingots.

[0018] Based on the above device, the melt processing method of the present invention for preparing ultra-large aluminum alloy ingots using the above device comprises the following steps:

[0019] (1) In the semi-continuous casting process, the hot top and the ingot are first preheated to the set temperature, and the refined alloy melt reaches the crystallizer through the launder. The melt level rises, and continuous casting begins. The ingot slowly descends, and the cooling water flow rate slowly increases, so that the casting process enters a stable state;

[0020] (2) After the casting process enters a stable state, a cooling medium is introduced into the annular electromagnetic field melt processor, and the annular electromagnetic melt processor is immersed in a designated position above the graphite ring in the crystallizer through a lifting mechanism. At this time, the structure of the annular melt processor divides the melt into two parts: an external melt processing area and an internal melt processing area. The cooling end reaches the set designated position, so that the temperature control unit, the cooling end and the melt exchange heat, thereby realizing forced cooling of the alloy melt;

[0021] (3) Turn on the inner electromagnetic coil and the outer electromagnetic coil, adjust the parameters of the inner electromagnetic coil and the outer electromagnetic coil, and perform strong shear stirring treatment on the alloy melt in the inner and outer melt processing zones to make the melt composition and temperature uniform; adjust the flow rate of the cooling medium in the temperature control unit and the cooling end so that the cooling intensity of the temperature control unit and the cooling end reaches the set parameters, and the temperature of the alloy melt in the inner and outer melt processing zones reaches the specified temperature;

[0022] (4) Before the end of casting, turn off the inner and outer electromagnetic coils, lift the lifting mechanism, lift the annular electromagnetic melt processor above the crystallizer water tank, turn off the cooling medium, and clean and maintain the annular electromagnetic melt processor;

[0023] (5) After the casting is completed, an ultra-large aluminum alloy ingot is obtained.

[0024] The annular electromagnetic melt processor is placed at the core of the super-large melt through a lifting mechanism, and the bottom of the cooling end is located 2 to 200 mm above the graphite ring.

[0025] The cooling intensity of the electromagnetic melt processor is 500-5000W / (m 2 •k), the cooling intensity of the temperature control layer unit is 200~2000 W / (m 2 •k), keep the temperature of the internal and external melt stable.

[0026] The melt processing device and method for preparing super-large aluminum alloy ingots of the present invention are provided with an annular electromagnetic melt processing device on a semi-continuous casting platform, so that the ingots are subjected to uniform cooling and electromagnetic shearing treatment during the semi-continuous casting process, the melt flow state is adjusted, and the uniformity of the temperature field and the composition field during the solidification process is improved. The present invention can be used to prepare aluminum alloy round ingots with a diameter greater than 900 mm, such as super-large aluminum alloy ingots with a diameter of 1400 mm, in semi-continuous casting equipment.

[0027] The beneficial effects of the present invention are mainly reflected in:

[0028] 1. Compared with the traditional semi-continuous casting method, the present invention places an annular electromagnetic melt processor inside the crystallizer. The electromagnetic field generated can achieve stirring and shearing effects on the melt inside and outside the annular structure simultaneously or selectively, change the melt flow state in a targeted manner, and generate multi-dimensional strong shear flow in the melt, driving the internal melt to flush the cooling end multiple times to promote nucleation, thereby achieving effective control of the flow of ultra-large volume melts, and effectively avoiding the problem of uneven temperature field and composition field caused by the shear dead zone in the core melt when ordinary electromagnetic stirring is used to process ultra-large volume melts.

[0029] 2. The present invention places an annular melt processor inside the crystallizer during the semi-continuous casting process, cleverly combines uniform cooling and electromagnetic treatment in the crystallizer, and controls the position of the melt processor, the temperature control units on the inner and outer walls, the cooling end, and the interaction of the inner and outer electromagnetic coils to improve the uniformity of the temperature field and composition field and the flow condition of the ultra-large volume melt, increase the cooling intensity during the solidification process, reduce the temperature difference between the core and the edge, reduce the liquid cavity depth, promote the nucleation of the core melt, achieve a fine and uniform solidification structure, significantly reduce component segregation, and reduce the tendency of thermal cracking.

[0030] 3. Compared with the traditional semi-continuous casting method, the method of the present invention has high feasibility, good flexibility, good adaptability, convenient controllable processing of super-large melt, good implementation effect, easy to realize industrial production, and the cost of production equipment, especially the cost of super-large ingot casting equipment, is significantly reduced. The prepared super-large ingot has good surface quality and fine and uniform structure, which greatly reduces the subsequent homogenization and processing costs, has a fast casting speed, and significantly improves the production efficiency and yield rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a structural schematic diagram of the main parts of the melt processing device of the present invention.

[0032] Figure 2 It is a cross-sectional view of the annular electromagnetic melt processor of the present invention.

[0033] Figure 3 It is a schematic structural diagram of the melt and the annular electromagnetic melt processor when the melt device of the present invention is observed from top to bottom, wherein the annular electromagnetic melt processor only shows a partial structure.

[0034] Figure 4 It is a liquid phase fraction diagram of Φ1400mm 2219 aluminum alloy ingot prepared by the method of the present invention and conventional semi-continuous casting.

[0035] Figure 5 a is the microstructure of Φ1400mm 2219 aluminum alloy ingot prepared by ordinary semi-continuous casting; Figure 5b is the microstructure of Φ1400mm 2219 aluminum alloy ingot prepared by the method of the present invention.

[0036] Figure 6 The invention discloses the radial component distribution of a 2219 aluminum alloy ingot having a diameter of 1400 mm prepared by the method of the invention and conventional semi-continuous casting.

[0037] Reference numerals

[0038] 1 lifting mechanism 2 hot top 3 crystallizer 4 melt 5 crystallizer water tank 6 ring electromagnetic melt processor

[0039] 7 graphite ring 8 ingot 9 ingot guide 10 connection mechanism and line port 11 temperature control layer 12 spiral tube

[0040] 13-1 Thermocouple 13-2 Thermocouple 14 Insulation layer 15-1 Upper shell 15-2 Lower shell

[0041] 16 External electromagnetic coil 17 Internal electromagnetic coil 18 Cooling end 19 External melt processing area

[0042] 20 internal melt processing area 21 external electromagnetic coil yoke 22 internal electromagnetic coil yoke 23 cooling medium DETAILED DESCRIPTION

[0043] The present invention can be implemented according to the following examples, but is not limited thereto. These examples are only intended to illustrate the implementation process of the present invention, and are not intended to limit the scope of the present invention in any way. In the following examples, various processes and methods not described in detail are conventional methods known in the art.

[0044] like Figure 1 As shown, the melt treatment device for preparing high-quality super-large aluminum alloy ingots of the present invention mainly comprises an annular electromagnetic melt processor 6, a hot top 2, a crystallizer 3, a crystallizer water tank 5, a graphite ring 7, a starter ingot 9 and a lifting mechanism 1; during the casting process, the annular electromagnetic melt processor 6 is placed in the crystallizer 3, concentric with the crystallizer 3, a line port and a connecting mechanism are arranged on the top of the annular electromagnetic melt processor 6, and connected with the lifting mechanism 1, and can be moved up and down in the height direction of the crystallizer 3 through the lifting mechanism, and positioned at a corresponding position in the crystallizer 3. The hot top 2 is arranged above the crystallizer 3, the lower end of the hot top 2 is sealed and connected to the crystallizer 3 through the graphite ring 7, the starter ingot 9 is located below the crystallizer 3, the annular electromagnetic melt processor 6 is located above the semi-continuous casting platform, is placed in the crystallizer 3 during the casting process, the electromagnetic melt processor 6 is clamped by the lifting mechanism 1, and the crystallizer water tank 5 is arranged on the periphery of the crystallizer 3.

[0045] The number of annular electromagnetic melt processors is 6, such as Figure 2 , 3As shown, its overall shape is an annular cylindrical hollow structure, which is divided into an upper and lower cavity with independent closed spaces by a partition, and is set at an appropriate position in the center height direction of the crystallizer 3; the upper cavity is surrounded by an upper shell 15-1, and the lower cavity is surrounded by a lower shell 15-2. The inner electromagnetic coil 17 and the outer electromagnetic coil 16 are placed in the upper cavity, the inner electromagnetic coil 17 is placed on the inner side of the upper cavity, and the outer electromagnetic coil 16 is placed on the outer side of the upper cavity. The corresponding circuit is connected to the external device through the circuit port 10 of the upper cavity top cover. The inner and outer electromagnetic coils 16 and 17 are two sets of independent rotating electromagnetic stirrers, and the stirring method can be rotating electromagnetic stirring and spiral stirring. The two sets of electromagnetic coils act independently, and are composed of two sets of polygonal silicon steel yokes and two sets of coil groups wound with waterproof copper wires, which respectively shear and stir the inner and outer melts, change the flow of large-volume melts, and implement intervention and regulation of the melt flow field, further improve the uniformity of organizational components, refine grains, reduce segregation, and reduce thermal tendency. The cooling medium 23 is introduced into the upper cavity from the inlet pipe on the top cover and flows out from the outlet pipe on the top cover after circulation, so as to circulate and cool the inner and outer electromagnetic coils 16 and 17.

[0046] The inner and outer walls of the annular electromagnetic melt processor 6 are respectively covered with a set of temperature control units, which are covered on the periphery of the upper cavity and are composed of a temperature control layer 11, a spiral tube 12, an insulating layer 14 and a thermocouple 13-1; the temperature control unit of the annular electromagnetic melt processor 6 close to the melt is cylindrical, composed of an outer temperature control layer 11 and an inner insulating layer 14, and smoothly transitions with the cooling end 18 of the lower cavity; the inner diameter of the annular electromagnetic melt processor 6 is 200-600mm, the outer diameter is 500-1000mm, and the inner and outer walls are respectively flush with the cooling end 18, the thickness of the inner and outer walls are respectively 5-20mm, the temperature control layer is made of high-temperature resistant heat-conductive material, and the insulating layer is a high-temperature resistant heat-insulating material.

[0047] The temperature control layer 11 is provided with spiral tubes 12 in a multi-spiral manner, which are arranged in a multi-spiral layout from the line port from the radial position to the bottom of the temperature control layer, and are discharged in the reverse direction after heat exchange. They are made of materials with good thermal conductivity, such as copper, steel, titanium, and their alloys and composite materials; the inner diameter of the spiral tube 12 is 2 to 10 mm, the thickness is 0.5 to 3 mm, the number of spirals of the spiral tube 12 is 3 to 30, and the spiral pitch is 1 to 8 mm. The inlet of the spiral tube 12 is set at different positions at the bottom of the cooling end, and the cooling medium 23 is passed during the working process. The cooling medium 23 reaches the bottom of the temperature control layer 11 from the connection line port 10 at different positions, and is discharged from the outlet after spiral heat exchange, so that the overall melt temperature is evenly distributed. The insulation layer 14 is made of high-temperature resistant insulation material, such as ceramic fiber, to prevent heat transfer to the upper cavity from damaging the electromagnetic coil. Multiple sets of replaceable thermocouples 13-1 are set on the temperature control unit to measure the monitoring equipment and melt temperature.

[0048] The annular electromagnetic melt processor 6 of the present invention is composed of two cavities, upper and lower, and a cooling end 18 is arranged at the lower part of the lower cavity. The cooling end 18 is a semicircular hollow structure, with an outer diameter of 500-1000mm, an inner diameter of 200-600mm, a cross-sectional diameter of 300mm, and a thickness the same as that of the lower shell 15-2. It is made of high-temperature resistant heat-conductive materials, such as graphite, copper, molybdenum, titanium and their composite materials; the cooling end 18 is located at the bottom of the annular electromagnetic melt processor 6, and multiple groups of pipes are evenly distributed through the upper cavity to realize the AC heat exchange of the cooling medium. The thermocouple 13-2 is arranged in the lower cavity and is close to the bottom position of the cooling end, and is connected to the outside through the upper and lower cavities through the connecting mechanism. The cooling medium 23 enters from the upper line port 10 of the annular electromagnetic melt processor 6, passes through the upper cavity and flows through different positions in the cooling end 18, exchanges heat with the cooling end 18 to cool the melt 4, and then flows out through the upper cavity, which can realize the continuous dynamic uniform cooling of the melt 4 at the cooling end 18. The melt 4 continuously flushes the bottom of the cooling end 18 to cool and nucleate, improves the flow condition of the liquid cavity paste zone, reduces the degree of component segregation and the flow condition of floating crystals, and realizes continuous dynamic uniform cooling and shrinkage feeding of the melt 4.

[0049] The melt treatment method for preparing super-large aluminum alloy ingots using the device of the present invention is as follows: an annular electromagnetic melt processor 6 is arranged above the semi-continuous casting platform, and during the casting process, it is immersed from above the hot top 2 into a suitable position in the middle of the crystallizer 3, and uniform cooling and electromagnetic stirring are applied to the melt 4 from the inside of the melt. During the semi-continuous casting process, the hot top 2 and the ingot 9 are first preheated, and the refined alloy melt 4 enters the hot top 2 and the crystallizer 3. The melt level rises, continuous casting begins, the ingot slowly descends, the cooling water flow slowly increases, and the casting process enters a stable state. The cooling medium is introduced to immerse the annular electromagnetic melt processor 6 into the crystallizer 3 through the lifting mechanism 1, and the cooling end 18 is controlled to be located at the corresponding position of the crystallizer 3, so that the heat-conducting shell at the bottom of the cooling end 18 exchanges heat with the melt, thereby realizing forced cooling treatment of the alloy melt; the cooling medium 23 is introduced into the temperature control layer 11, and the thermocouple 13-1 detects the melt temperature to realize real-time monitoring of the temperature of the external and internal melts, and current is applied to the electromagnetic coils 16 and 17, which are turned on individually or in full to generate electromagnetic stirring, and the melt is divided into an external melt processing area 19 and an internal melt processing area 20 by using the annular structure of the electromagnetic stirrer to realize uniform stirring of a large volume of melt.

[0050] Example 1

[0051] An aluminum processing enterprise prepares Φ1400mm 2219 aluminum alloy ingots and has strict requirements on the uniformity of the internal structure and composition of the ingots. The average grain size of the cross section must be better than level 3, the grain size deviation must be controlled within 8%, and the alloy element segregation rate must be controlled within 5%.

[0052] The present invention is used to produce 2219 aluminum alloy round ingots with a diameter of 1400 mm. The schematic diagram of the device structure is as follows Figure 1-3 As shown. The annular electromagnetic melt processor 6 is arranged on the casting platform. The annular electromagnetic melt processor 6 has an outer diameter of 750 mm, an inner diameter of 360 mm, and a height of 300 mm. The annular electromagnetic melt processor 6, the hot top 2, and the crystallizer 3 are concentric. The bottom end of the annular electromagnetic melt processor 6 is flush with the bottom end of the crystallizer 3. The crystallizer water tank 5 is arranged on the periphery of the crystallizer 3. The electromagnetic stirring method adopts two sets of independent electromagnetic coils 16 and 17. The wires are connected to the external power supply through the connection mechanism line port 10.

[0053] The temperature control layer 11 of the outer wall temperature control unit of the annular electromagnetic melt processor 6 is made of high-temperature resistant heat-conducting material titanium, with an outer diameter of 750mm and a thickness of 20mm. The spiral tube 12 arranged inside is made of pure copper, with an inner diameter of 5mm, a thickness of 1mm, a spiral number of 3, and a spiral pitch of 5mm; the insulation layer of the outer wall temperature control unit is made of high-temperature resistant heat-insulating ceramic, with an outer diameter of 730mm and a thickness of 10mm. The temperature control layer 11 of the inner wall of the electromagnetic melt processor 6 is made of high-temperature resistant heat-conducting material titanium, with an outer diameter of 340mm and a thickness of 10mm. The heat-conducting tube arranged inside is made of pure copper, with an inner diameter of 5mm, a thickness of 1mm, a spiral number of 3, and a spiral pitch of 5mm; the insulation layer 13 of the inner wall temperature control unit is made of high-temperature resistant heat-insulating ceramic, with an outer diameter of 320mm and a thickness of 10mm. The lower cooling end 18 has an outer diameter of 750mm, an inner diameter of 320mm, a cross-sectional diameter of 280mm, and is made of titanium alloy.

[0054] During the continuous casting process, the melt 4 enters the crystallizer 3, the continuous casting equipment is started, and the annular electromagnetic melt processor 6 is turned on after the casting enters a stable state. The cooling medium is air, and the cooling water flow rate is 40m 3 / h, the water pressure is stable at 3kPa.

[0055] The specific process is as follows: First, the hot top 2, the crystallizer 3 and the ingot 9 are fully preheated to 250°C, and high-purity aluminum is used as the bottom. The high-temperature melt 4 (750°C) that has been degassed online and filtered at multiple stages is injected into the crystallizer 3 through the hot top 2. When the liquid level of the melt 4 is 230mm away from the top of the hot top 2, the continuous casting equipment is started, the casting speed is slowly increased to 20mm / min, and the cooling water flow is gradually increased to 40m 3 / h, wait for the casting to enter a stable state, at this time, the pouring temperature is about 710℃, control the introduction of cooling medium 23 such as air to cool the melt, immerse the melt processor with a dried surface below the melt surface, and keep the bottom of the cooling end 50mm above the graphite ring, and maintain the cooling intensity at 1500W / (m 2·k), and then turn on the outer electromagnetic coil and the inner electromagnetic coil respectively. The external electromagnetic parameters are frequency 20Hz, current intensity 50A, and ampere-turns 10000At; the internal electromagnetic parameters are frequency 5Hz, current intensity 40A, and ampere-turns 6000At. The outer electromagnetic coil and the inner electromagnetic coil stir the external and internal melts respectively to ensure that the shear rate is 190mm·s -1 Around, slow down the upward movement of the center of the liquid cavity, change the flow of the melt in the liquid cavity, and smooth the liquid cavity until the end of the casting process. During the production process, the temperature of the cooling end 18 is stabilized at 645℃, and the temperature control unit controls the internal and external melt temperatures to remain at around 665℃.

[0056] By comparing the 2219 aluminum alloy Φ1400mm round ingot prepared by the present invention and conventional semi-continuous casting, the simulation results Figure 4 It shows that the liquid cavity of the ingot using the method of the present invention becomes shallower, the liquid cavity is significantly flatter, the flow condition is controllable, and it has a significant improvement effect on improving the uniformity of grains and component segregation. The quality inspection results are as follows Figure 5 -a and Figure 5 -b and Figure 6 As shown, Figure 5 a represents the structure of the 2219 aluminum alloy ingot prepared by ordinary semi-continuous casting, and b represents the structure of the 2219 aluminum alloy ingot prepared by the present invention. The cross-sectional structure of the ingot prepared by the present invention is fine and uniform, the average grain size is 478 μm, and the overall grain size is better than grade 3; Figure 6 It is shown that compared with the conventional semi-continuous casting, the uniformity of the alloy element Cu in the ingot prepared by the present invention is significantly improved, and the segregation rate of the Cu element is 4.8%. Therefore, the composition uniformity of the ingot prepared by the present invention is greatly improved, meeting the technical requirements.

[0057] The defects of coarse and uneven structure, component segregation, cracking, etc. in the preparation of super-large aluminum alloy ingots by traditional semi-continuous casting are achieved. The present invention applies a ring-shaped electromagnetic melt processor to the alloy melt during the semi-continuous casting process to achieve effective uniformity of the temperature field and component field of the super-large volume alloy melt, and achieves effective control of the melt flow, so as to prepare high-quality super-large aluminum alloy ingots with uniform and fine structure and uniform composition. The present invention has a simple structure, a feasible method, high adaptability, significant effect, no need for special preparation of crystallizer equipment, high production efficiency, and is easy to combine with large-scale industrial automation production. It has broad industrial application prospects in the manufacturing of major structural parts such as aerospace, rail transportation, and ships.

Claims

1. A melt processing device for preparing ultra-large aluminum alloy ingots, characterized in that: The device mainly consists of an annular electromagnetic melt processor, a hot top, a crystallizer, a crystallizer water tank, a graphite ring, a guide ingot and a lifting mechanism; the annular electromagnetic melt processor is placed in the crystallizer, concentric with the crystallizer, a line port and a connecting mechanism are arranged on the top of the annular electromagnetic melt processor, and is connected to the lifting mechanism, and can be moved up and down in the height direction of the crystallizer through the lifting mechanism and positioned at a corresponding position in the crystallizer; the lower end of the hot top is sealed and connected to the crystallizer through a graphite ring; the crystallizer water tank is arranged on the periphery of the crystallizer; The overall shape of the annular electromagnetic melt processor is an annular cylindrical hollow structure, which is mainly composed of an upper cavity, a lower cavity, an inner electromagnetic coil, an outer electromagnetic coil, a temperature control unit, a cooling end, and a cooling medium; the upper cavity and the lower cavity are divided into independent spaces by a partition; the inner electromagnetic coil and the outer electromagnetic coil are placed in the upper cavity, the inner electromagnetic coil is placed on the inner side of the upper cavity, and the outer electromagnetic coil is placed on the outer side of the upper cavity; the temperature control unit is wrapped around the outer periphery of the upper cavity; the cooling end is arranged at the lower part of the lower cavity; the upper cavity, the lower cavity and the temperature control unit are respectively filled with cooling medium, and realize circulating cooling with the outside; The inner electromagnetic coil and the outer electromagnetic coil are respectively a rotating electromagnetic generator, a traveling wave electromagnetic generator or a spiral electromagnetic generator; the two sets of electromagnetic coils act independently, and are composed of two sets of polygonal silicon steel yokes and two sets of enameled copper wire wound coil groups, which respectively produce stirring shear and flow control effects on the melt in the inner and outer melt processing zones of the annular electromagnetic melt processor; The annular electromagnetic melt processor divides a large volume of melt into an external melt processing area and an internal melt processing area. The annular electromagnetic melt processor has an outer diameter of 500-1000 mm, an inner diameter of 200-600 mm, and a height of 100-500 mm.

2. The melt processing device for preparing super-large aluminum alloy ingots according to claim 1 is characterized in that: The temperature control unit consists of a temperature control layer, an insulation layer and a thermocouple. The temperature control layer is composed of two layers of high-temperature resistant heat-conductive materials, with a spiral tube arranged inside, and a cooling medium is passed through the spiral tube; the insulation layer is made of high-temperature resistant insulation ceramics, and is arranged between the temperature control layer and the upper shell constituting the upper cavity. The thermocouple is arranged in the temperature control layer to detect and control the temperature.

3. The melt processing device for preparing super-large aluminum alloy ingots according to claim 2 is characterized in that: The temperature control unit is annular and has a smooth transition with the cooling end of the lower cavity. The thickness of the temperature control unit is 5 to 15 mm. The number of spirals of the spiral tube of the temperature control unit is 3 to 30, and the spiral pitch is 1 to 8 mm. The cooling medium passes through the spiral tube during operation. The cooling medium reaches the bottom of the temperature control unit from the connection line ports at different positions, and is discharged through the outlet after heat exchange in the spiral tube.

4. The melt processing device for preparing super-large aluminum alloy ingots according to claim 2 is characterized in that: The cooling end is semicircular with an outer diameter of 300 to 1000 mm, and a cooling pipe and a thermocouple are arranged inside. The cooling pipe is connected to the outside through the upper and lower cavities via a connecting mechanism; the thermocouple is arranged in the lower cavity and close to the cooling end, and is connected to the outside through the upper and lower cavities via a connecting mechanism; the cooling end is made of high-temperature resistant heat-conductive material, and the high-temperature resistant heat-conductive material is graphite, steel, copper, molybdenum, titanium or a composite material of multiple thereof.

5. The melt processing device for preparing super-large aluminum alloy ingots according to claim 1, characterized in that: The cooling medium is air, nitrogen, argon, water or oil, the cooling medium flow rate is 0-1000L / min, and the cooling intensity is 100-4000W / (m 2 •k).

6. The melt processing device for preparing super-large aluminum alloy ingots according to claim 1, characterized in that: The ampere-turns of the outer electromagnetic coil of the annular electromagnetic melt processor are 5000-40000 At, the ampere-turns of the inner electromagnetic coil are 2000-30000 At, the frequency is 0.5-50 Hz, and the shear rate of the inner and outer electromagnetic coils is 10-1000 mm / s.

7. A melt processing method for preparing ultra-large aluminum alloy ingots using the device according to any one of claims 1 to 6, characterized in that: (1) In the semi-continuous casting process, the hot top and the ingot are first preheated to the set temperature, and the refined alloy melt reaches the crystallizer through the launder. The melt level rises, and continuous casting begins. The ingot slowly descends, and the cooling water flow rate slowly increases, so that the casting process enters a stable state; (2) After the casting process enters a stable state, a cooling medium is introduced into the annular electromagnetic field melt processor, and the annular electromagnetic melt processor is immersed in a designated position above the graphite ring in the crystallizer through a lifting mechanism. At this time, the structure of the annular melt processor divides the melt into two parts: an external melt processing area and an internal melt processing area. The cooling end reaches the set designated position, so that the temperature control unit, the cooling end and the melt exchange heat, thereby realizing forced cooling of the alloy melt; (3) Turn on the inner electromagnetic coil and the outer electromagnetic coil, adjust the parameters of the inner electromagnetic coil and the outer electromagnetic coil, and perform strong shear stirring treatment on the alloy melt in the inner and outer melt processing zones to make the melt composition and temperature uniform; adjust the flow rate of the cooling medium in the temperature control unit and the cooling end so that the cooling intensity of the temperature control unit and the cooling end reaches the set parameters, and the temperature of the alloy melt in the inner and outer melt processing zones reaches the specified temperature; (4) Before the end of casting, turn off the inner and outer electromagnetic coils, lift the lifting mechanism, lift the annular electromagnetic melt processor above the crystallizer water tank, turn off the cooling medium, and clean and maintain the annular electromagnetic melt processor; (5) After the casting is completed, an ultra-large aluminum alloy ingot is obtained.

8. The melt processing method according to claim 7, characterized in that: The annular electromagnetic melt processor is placed at the core of the super-large melt through a lifting mechanism, and the bottom of the cooling end is located 2 to 200 mm above the graphite ring.

9. The melt processing method according to claim 7, characterized in that: The cooling intensity of the electromagnetic melt processor is 500-5000W / (m 2 •k), the cooling intensity of the temperature control layer unit is 200~2000 W / (m 2 •k), keep the temperature of the internal and external melt stable.

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