WO2021012350A1 - Device and method for magnesium alloy semi-continuous casting by applying combination frequency ultrasound - Google Patents

Abstract

A device and a method for magnesium alloy semi-continuous casting by applying combination frequency ultrasound. The device comprises a tundish (17), a first ultrasound generating device being fixed on a side wall or a bottom plate of the tundish (17), a second ultrasound generating device being provided in the tundish (17), and front end faces of ultrasound radiation rods of the two ultrasound generating devices being located in the tundish (17). The method comprises: (1) smelting a magnesium alloy melt; (2) preheating a tundish (17), a pipette (8) and two ultrasound irradiation rods; (3) delivering the refined magnesium alloy melt to the tundish (17), and turning on two ultrasound generators; (4) turning on a crystallizer (2); and (5) turning on a flow control valve (34) after completion of the application of the combination frequency ultrasound waves, delivering the magnesium alloy melt to the crystallizer (2) for semi-continuous casting.

Description

Device and method for applying group frequency ultrasound to semi-continuous casting of magnesium alloy Technical field

The invention belongs to the field of light alloy smelting, and particularly relates to a device and a method for applying group frequency ultrasound to perform semi-continuous casting of magnesium alloys.

Background technique

As the lightest structural metal material, magnesium alloy is widely used in the fields of 3C, aerospace, and high-speed trains. It has the advantages of high specific strength, high specific modulus, and good shock absorption performance. However, due to its low heat capacity and low solidification Defects such as developed dendrites, severe segregation and low ingot strength caused by latent heat have caused poor processing and formability and limited the application of magnesium alloys. Therefore, high-strength, fine-grained homogeneous magnesium alloy ingots have become a research hotspot in the field of magnesium alloys. .

The semi-continuous casting method has become the main method of magnesium alloy ingot production due to its high efficiency and low production cost. However, the low heat conduction rate of magnesium alloy makes the temperature difference between the center and the edge of the ingot large, developed dendrites and uneven structure.

Early crystal refinement techniques include Zr modification, carbon modification, and master alloy modification. However, due to strict requirements on alloy composition, the application of modification refiners is restricted; in recent years, the application of electromagnetic fields has changed the solidification behavior The technology has been developed rapidly. Since the former Soviet Union Getselev applied excitation coils on the basis of DC semi-continuous casting in the 1960s, the electromagnetic casting process has continued to develop; the low-frequency electromagnetic semi-continuous casting developed by Northeastern University has made certain progress. However, the skin effect of the applied electromagnetic field makes the effective area limited and the stirring intensity is low, which makes it difficult to improve the structure and performance of large-size ingots.

Ultrasonic field, as a mechanical wave with short stroke, high efficiency and strong stability, has been used in the field of non-ferrous metal smelting to improve the quality of ingots. At present, most scholars believe that the cavitation effect and sound flow effect produced by the ultrasonic field can promote the formation of The nucleus achieves the purpose of grain refinement; among them, Shanghai University (2004) invented a side power ultrasonic introduction method to improve the metal solidification structure; Tsinghua University (2008) invented a top introduction ultrasonic processing device, which can refine Grain size and uniform composition; At present, most casting equipment mainly uses single-frequency ultrasound, but due to the unstable resonance frequency and serious attenuation of the ultrasonic in the melt, the ultrasonic cavitation range is limited to the vicinity of the end face of the radiating rod. It is only suitable for small-size ingot production; due to the limited sound wave superposition effect of a single ultrasonic field, the cavitation intensity is limited. Therefore, the combined frequency ultrasonic field is increased by controlling the frequency of the two rows of sound waves, the group frequency ultrasonic insertion method, and the ultrasonic power. Acoustic wave coupling strength in the melt, thereby obtaining high-strength, fine-grained and homogeneous magnesium alloy ingots in semi-continuous casting.

Summary of the invention

technical problem

The solution to the problem

Technical solutions

The purpose of the present invention is to provide a device and method for applying group frequency ultrasound for semi-continuous casting of magnesium alloys. Two ultrasonic generating devices are adopted to change the insertion mode of the ultrasonic radiation rod by introducing the group frequency ultrasonic field, and adjust the ultrasonic frequency and power. Realize the coupling and superposition of acoustic waves, enhance the effects of cavitation and acoustic current, improve the structure of magnesium alloy, and improve the quality of ingots.

The device for semi-continuous casting of magnesium alloy by applying group frequency ultrasound of the present invention includes a smelting furnace, a tundish and a crystallizer. A pipette is arranged between the melting furnace and the tundish, and a chute is arranged between the tundish and the crystallizer; The top of the vessel is provided with a protective gas ring pipe, the inside of the protective gas ring pipe is connected with the protective gas source through the pipeline, and the protective gas ring pipe is provided with an outlet hole facing the axis of the crystallizer; the side wall or the bottom plate of the tundish A first ultrasonic generating device is fixed, and a second ultrasonic generating device is provided in the tundish. The first ultrasonic generating device is composed of a first ultrasonic radiation rod, a first ultrasonic guide rod and a first ultrasonic transducer. The device is composed of a second ultrasonic radiating rod, a second ultrasonic guide rod and a second ultrasonic transducer. The first ultrasonic transducer and the second ultrasonic transducer are respectively connected to the first ultrasonic generator and the second ultrasonic generator; The front ends of an ultrasonic radiating rod and a second ultrasonic radiating rod are both located inside the tundish, and the first ultrasonic radiating rod is located below the second ultrasonic radiating rod; when the first ultrasonic generating device is fixed on the side wall of the tundish, the first ultrasonic generating device An ultrasonic radiating rod is perpendicular to the axis of the second ultrasonic radiating rod; when the first ultrasonic generating device is fixed on the bottom plate of the tundish, the axes of the first ultrasonic radiating rod and the second ultrasonic radiating rod coincide; the second transducer is fixed On the sliding block, the sliding block is sleeved outside the cross beam, and the cross beam is assembled with the lifting device; the sliding block, the cross beam, and the lifting device form an ultrasonic supporting device.

In the above device, the ultrasonic transducer is a piezoelectric ceramic transducer or a magnetostrictive transducer; the piezoelectric ceramic transducer includes a transducer box, a metal diaphragm and a titanate piezoelectric ceramic material. The transducer The box body is provided with an air inlet and an air outlet for circulating cooling gas. The upper and lower ends of the titanate piezoelectric ceramic material are respectively connected to a metal diaphragm, and the two metal diaphragms are connected to the two poles of the ultrasonic generator through a cable. ; The magnetostrictive transducer includes a transducer box and a ferrite terbium magnetostrictive material. The transducer box is provided with a water inlet and a water outlet for the circulation of cooling water, and the cable is wound in turn on the ferrite terbium magnetostrictive material. On each telescopic rod of the telescopic material, the two ends of the cable are respectively connected with the two poles of the ultrasonic generator.

In the above device, the first ultrasonic transducer and the second ultrasonic transducer are respectively connected to the first waveguide rod and the second waveguide rod through an aviation joint connector; the first waveguide rod and the second waveguide rod are respectively connected to the first ultrasonic wave A radiating rod and a second ultrasonic radiating rod.

The internal space of the above-mentioned tundish is an inverted truncated cone shape, and the inclination angle of the side wall of the truncated cone shape (the angle between the side generatrix and the axis of the truncated cone) is 3°-10°.

The above-mentioned tundish includes a furnace body and a cover. The inner wall of the furnace is provided with an inner lining, the outer wall is covered with a heat preservation sleeve, and the tundish water port at the lower part of the furnace body is provided with a flow control valve; the cover is composed of two parts, one of which is The material is asbestos, and the other part is made of tempered glass for observing the inside of the tundish; the part of the cover made of asbestos is equipped with a feed port and a pipette assembly.

The above-mentioned crystallizer includes an inner sleeve, an outer sleeve, a bottom plate, a water sealing plate and a top plate; the top of the inner sleeve is provided with an oil distribution device, and the bottom is provided with two cold water outlets; the side wall of the outer sleeve is provided with a water inlet; Starter head; the gap between the starter head and the inner wall of the inner sleeve is filled with asbestos; the upper part of the inner sleeve is hermetically connected with the top plate, and the lower part is hermetically connected with the sealing plate; the upper part of the outer sleeve is hermetically connected with the top plate, and the lower part is sealed with the outside of the bottom plate Connection; the inside of the bottom plate is connected with the sealing water plate; the space between the inner sleeve and the outer sleeve is the cooling water cavity.

The outer wall of the above-mentioned melting furnace and the pipette is equipped with a heat preservation device, and is equipped with a thermocouple for temperature measurement.

The method of applying group frequency ultrasound for semi-continuous casting of magnesium alloy of the present invention adopts the above-mentioned device and carries out the following steps:

1. Melt the magnesium alloy melt in the smelting furnace. After the magnesium alloy melt is evenly stirred, the slagging treatment is carried out, and the No. 2 flux is sprinkled into the melt for refining. After the refining is completed, the magnesium alloy is allowed to stand for 10-15 minutes. The temperature of the melt is 30～80℃ above the liquidus line of magnesium alloy;

2. Preheat the tundish, pipette, the first ultrasonic radiation rod and the second ultrasonic radiation rod to a temperature of 30～80℃ above the liquidus of the magnesium alloy, and the preheating time is more than 30min; The second ultrasonic radiation rod is inserted into the tundish;

3. Transport the refined magnesium alloy melt into the tundish through a pipette; then turn on the first ultrasonic generator and the second ultrasonic generator, and the ultrasonic power is respectively passed through two ultrasonic transducers and two ultrasonic guide rods It is transmitted to two ultrasonic radiating rods, and the ultrasonic is emitted through the two ultrasonic radiating rods, combined to form a group frequency ultrasonic wave, and applied to the magnesium alloy melt; the frequency of the ultrasonic radiating rods emitted by the two ultrasonic radiating rods is 15～300kHz, and two The frequency difference of the ultrasonic waves emitted by the ultrasonic radiating rod is 1～60kHz;

4. Insert the starter head into the crystallizer, and fill the gap between the starter head and the inner wall of the crystallizer with asbestos; pass cooling water into the cooling water cavity of the crystallizer, and the cooling water is from the second cold water outlet discharge;

5. When the applied ultrasonic time of the group frequency to the magnesium alloy melt reaches or exceeds 2 min, open the flow control valve of the tundish, and transport the magnesium alloy melt in the tundish to the mold through the chute for semi-continuous casting. Until made into magnesium alloy ingot.

In the above method, when the prepared magnesium alloy ingot is an AZ series magnesium alloy, the temperature difference ΔT between the temperature of the magnesium alloy melt and the liquidus temperature of the magnesium alloy in step 1 is 30°C≤ΔT＜50°C; When the magnesium alloy ingot is a ZK series magnesium alloy or RE series magnesium alloy, the temperature difference ΔT between the temperature of the magnesium alloy melt and the magnesium alloy liquidus temperature in step 1 is 50°C≤ΔT≤80°C;

In the above method, when the first ultrasonic radiating rod and the second ultrasonic radiating rod are preheated, the temperature is measured by an infrared temperature measuring gun.

In step 3 above, when the volume of the magnesium alloy melt in the tundish reaches more than 70% of the volume of the tundish, the first ultrasonic generator and the second ultrasonic generator are turned on. At this time, the first radiating rod is located in the magnesium alloy melt. Inside, the bottom end of the second radiating rod is located 20-50mm below the liquid surface.

In the above method, when the ultrasonic transducer is a piezoelectric ceramic transducer, the transducer box of the piezoelectric ceramic transducer is provided with one or more titanate piezoelectric ceramic materials, and each titanate piezoelectric ceramic material The upper and lower ends of the ceramic material are connected with a metal diaphragm, and the two metal diaphragms connected with the same titanate piezoelectric ceramic material are respectively connected to the two poles of an ultrasonic generator through a cable; when the ultrasonic transducer is magnetostrictive In the case of the transducer, the transducer box of the magnetostrictive transducer is provided with one or more ferrite terbium magnetostrictive materials. The front and rear ends of each ferrite terbium magnetostrictive material are connected to one The two poles of the ultrasonic generator are connected.

In the above method, when the first ultrasonic generator and the second ultrasonic generator are turned on, and when the ultrasonic transducer is a piezoelectric ceramic transducer, the piezoelectric is controlled by passing cooling gas air into the transducer box. The temperature of the ceramic transducer is less than or equal to 40℃; when the first ultrasonic generator and the second ultrasonic generator are turned on, and when the ultrasonic transducer is a magnetostrictive transducer, cooling is passed into the transducer box Water, to control the temperature of the magnetostrictive transducer ≤40℃.

In the above method, the diameter of the magnesium alloy ingot

Among them, when the diameter of the prepared magnesium alloy ingot

In the device used for semi-continuous casting of magnesium alloy by applying group frequency ultrasound, the first ultrasonic generating device is fixed on the side wall of the tundish, the first ultrasonic radiating rod is located below the second ultrasonic radiating rod, and the first ultrasonic radiating rod The vertical distance between the second ultrasonic radiating rod and the second ultrasonic radiation rod is 50-100mm; when the diameter of the prepared magnesium alloy ingot

When using a device that applies group frequency ultrasound for semi-continuous casting of magnesium alloys, a first ultrasonic generating device is fixed on the bottom plate of the tundish, the first ultrasonic radiating rod is located below the second ultrasonic radiating rod, and the first ultrasonic radiating rod The vertical distance between the second ultrasonic radiation rod and the second ultrasonic radiation rod is more than 100mm.

In the above method, when semi-continuous casting is performed, the casting speed is 0.3 to 3 mm/s.

In the above step 4, the protective gas is continuously sprayed to the top of the crystallizer through the protective gas ring pipe on the top of the crystallizer; the lubricant oil is applied to the inner wall of the crystallizer through the oil distribution system of the crystallizer.

The above-mentioned protective gas is a mixed gas of CO ₂ and SF ₆ , in which the volume percentage of CO ₂ is 70-85%.

The principle of the present invention is: the resonance frequency in the single-frequency ultrasonic field is affected by the high temperature of the melt, resulting in frequency drift, and is affected by the viscosity of the melt. The cavitation range is limited to the end face, and it is difficult to achieve ultrasound to the entire melt. Processing: Under the condition that the total power remains the same, the group frequency ultrasound adjusts the frequency f and power of the two rows of sound waves by increasing the number of radiating rods and the application method, enhancing the nonlinear coupling of the sound waves, and improving the range of melt cavitation and air To improve the strength, large-size magnesium alloy ingots with uniform structure and excellent performance can be obtained in semi-continuous casting.

The beneficial effects of the invention

Beneficial effect

The device and method of the present invention can adjust the frequency and power of the two rows of ultrasonic waves by changing the spatial distribution of the ultrasonic rods, realize the nonlinear superposition of sound waves in the melt, and solve the limitations caused by problems such as frequency drift and sound pressure attenuation , The cavitation range is enhanced, and the cavitation intensity is increased; the simultaneous action of group frequency ultrasound (n≥2) can be realized; the magnetostrictive transducer is made of TbFe ₂ (terbium iron) material, and its saturation magnetostrictive stress ratio Nickel is 50-60 times larger, which can be used to make high-power sound sources; the inside of the tundish is inverted truncated cone shape, which is good for the tundish slag removal treatment; the cover of the tundish is good for heat preservation, reducing oxidation, and observing the height of the tundish melt; The sleeve can reduce the heat loss of the magnesium alloy melt in the tundish.

The device and method of the present invention are suitable for non-ferrous metals such as magnesium, aluminum, copper, etc., and refine the ingot structure by enhancing the cavitation and acoustic current effects.

Brief description of the drawings

Description of the drawings

Fig. 1 is a schematic flow chart of a method for applying group-frequency ultrasound to semi-continuously casting a magnesium alloy in an embodiment of the present invention;

2 is a schematic diagram of the structure of a device for applying group-frequency ultrasound for semi-continuous casting of magnesium alloy in an embodiment of the present invention;

Figure 3 is a schematic diagram of the structure of the crystallizer in Figure 1;

4 is a schematic diagram of the structure of a part of the intermediate package in Embodiment 1 of the present invention;

FIG. 5 is a schematic diagram of a partial structure of the intermediate package in Embodiment 2 of the present invention;

6 is a schematic diagram of a top view structure of a cover of a tundish in an embodiment of the present invention;

Figure 7 is a schematic diagram of the second ultrasonic transducer structure in embodiments 1 and 2 of the present invention; in the figure, (a) is a magnetostrictive transducer, (b) is a piezoelectric ceramic transducer;

8 is a schematic diagram of the structure of the second ultrasonic transducer in embodiments 3 and 4 of the present invention; in the figure, (a) is a magnetostrictive transducer, (b) is a piezoelectric ceramic transducer;

In the picture: 1. Starter head, 2. Crystallizer, 3. Protective gas ring tube, 4. Chute, 5. Melting furnace, 6. Beam, 7. Transducer fixing plate, 8. Pipette, 9. Slider, 10, second ultrasonic transducer, 11, second ultrasonic guide rod, 12, second ultrasonic radiation rod, 13, pillar, 14, screw, 15, handwheel, 16, base, 17, tundish, 18. Asbestos, 19, oil distribution device, 20, inner sleeve, 21, cooling water chamber, 22, top plate, 23, mold water inlet, 24, outer sleeve, 25, bottom plate, 26, sealing water plate, 27, second cold water Outlet, 28, tundish lining, 29, tundish furnace body, 30, insulation sleeve, 31, first ultrasonic radiation rod, 32, first ultrasonic guide rod, 33, first ultrasonic transducer, 34, control Flow valve, 35, asbestos cover part, 36, tempered glass cover part, 37, transducer water inlet, 38, magnetostrictive transducer box, 39, magnetostrictive transducer cable interface, 40, Transducer water outlet, 41, magnetostrictive transducer cable, 42, ferrite terbium magnetostrictive material, 43, transducer air inlet, 44, piezoelectric ceramic transducer box, 45, piezoelectric Ceramic transducer cable interface, 46, piezoelectric ceramic transducer cable, 47, metal diaphragm, 48, titanate piezoelectric ceramic material, 49, transducer air outlet;

9 is a schematic diagram of the sampling position of the tensile sample of the magnesium alloy ingot prepared in the embodiment of the present invention;

10 is a diagram of the cavitation area of the traditional single-frequency ultrasonic field and group-frequency ultrasonic numerical simulation software in Embodiment 1 of the present invention;

Figure 11 is a metallographic structure diagram of magnesium alloy ingots prepared in different ways in Example 1 of the present invention; in the figure (a) is no ultrasound, (b) is 15kHz single-frequency ultrasound, and (c) is group-frequency ultrasound;

12 is a comparison diagram of the tensile strength of magnesium alloy ingots prepared in different ways in Example 1 of the present invention;

Figure 13 is a metallographic structure diagram of magnesium alloy ingots prepared in different ways in Example 2 of the present invention; in the figure (a) is no ultrasound, (b) is 15kHz single-frequency ultrasound, and (c) is group-frequency ultrasound;

14 is a comparison diagram of the tensile strength of magnesium alloy ingots prepared in different ways in Example 2 of the present invention.

Invention embodiment

Embodiments of the invention

The power variation range of the ultrasonic generating device in the embodiment of the present invention is 0-2000W.

In the embodiment of the present invention, the preheating method of the first ultrasonic radiation rod and the second ultrasonic radiation rod is acetylene block preheating. In the embodiment of the present invention, oil grooves and oil seepage seams are arranged in the inner sleeve of the crystallizer, which facilitates smooth demolding during the casting process, and is set according to the patent application document with the publication number CN106944598.

The oil distribution device in the embodiment of the present invention is set according to the patent application document with the publication number CN106944598. When semi-continuous casting is performed in the embodiment of the present invention, the cooling water flow rate is 15 to 800 L/min;

In the embodiment of the present invention, the transducer fixing plate is welded and fixed on the slider.

In the embodiment of the present invention, when the transducer is a magnetostrictive transducer, the cable used in the box is a waterproof cable.

In the embodiment of the present invention, the front end face of the ultrasonic radiating rod is an end face of the ultrasonic radiating rod away from the ultrasonic guide rod.

The amount of flux No. 2 (barium flux) in the embodiment of the present invention is based on the flame extinguishing caused by the combustion of metallic magnesium after being added.

In the embodiment of the present invention, when the diameter of the magnesium alloy ingot is 30-200mm, the ultrasonic frequency emitted by the first ultrasonic radiating rod and the second ultrasonic radiating rod ≤40kH; when the diameter of the magnesium alloy ingot exceeds 200mm, the first The frequency of ultrasonic waves emitted by an ultrasonic radiating rod and a second ultrasonic radiating rod is greater than 40kHz.

The terbium ferrite magnetostrictive material of the magnetostrictive transducer in the embodiment of the present invention is composed of a plurality of ferrite terbium magnetostrictive rods, and the same cable is wound on each ferrite terbium magnetostrictive rod.

The setting method of the magnetostrictive transducer in the embodiment of the present invention is set according to the patent application document with publication number CN102205312A, and the setting method of the piezoelectric ceramic transducer is set according to the patent application document with publication number CN204035003U; the first ultrasonic transducer The structure of the device is the same as that of the second ultrasonic transducer.

In the embodiment of the present invention, the beam 6 is slidably connected to the pillar 13 through a sleeve. One end of the beam 6 is assembled on a manual lifting device including a screw 14 and a hand wheel 15. A bevel gear is installed between the hand wheel 15 and the screw 14; 13 The bottom is fixed on the base 16; when the lifting operation is carried out, the bevel gear assembled with the hand wheel 15 is rotated by rotating the hand wheel 15, and the bevel gear is raised and lowered along the screw 14 (screw), driving the beam 6 up and down along the pillar 13 mobile.

In the embodiment of the present invention, the diameter of the gas outlet hole on the protective gas ring pipe is 8-16mm, and the inner diameter of the protective gas ring pipe is 20-40mm. When the protective gas is sprayed, the flow rate of the protective gas is 4-6m/s. The air pressure is 0.2～0.8MPa.

The ultrasonic guide rod and the ultrasonic radiation rod in the embodiment of the present invention are both commercially available products.

The numerical simulation software in the embodiment of the present invention is COMSOL.

The equipment used for observing metallographic structure in the embodiment of the present invention is Olympus X53.

In the embodiment of the present invention, the front end surfaces of the first ultrasonic radiating rod and the second ultrasonic radiating rod are coated with a ZrO ₂ coating to extend the service life of the radiating rod.

In the embodiment of the present invention, when the magnesium alloy melt is transported to the tundish through the pipette, the magnesium alloy melt is pressed into the tundish through the pipette by sealing and pressurizing the melting furnace.

In the embodiment of the present invention, the AZ series magnesium alloy adopts an example grade of AZ80 magnesium alloy or AZ31 magnesium alloy, the ZK series magnesium alloy adopts an example grade of ZK60 magnesium alloy, and the RE series magnesium alloy adopts an example grade of Mg-Sm magnesium alloy. .

In the embodiment of the present invention, the protective gas is continuously sprayed to the top of the crystallizer through the protective gas ring pipe on the top of the crystallizer; the lubricant oil is applied to the inner wall of the crystallizer through the oil distribution system of the crystallizer; the protective gas is CO ₂ and SF ₆ The mixed gas of which the volume percentage of CO ₂ is 70-85%.

The preheating time in the embodiment of the present invention is the holding time after the temperature reaches the preheating target temperature.

The method flow of the embodiment of the present invention is shown in FIG. 1.

Example 1

The structure of the device for applying group frequency ultrasound for semi-continuous casting of magnesium alloy is shown in Figure 2. It includes a smelting furnace 5, a tundish 17 and a crystallizer 2. A pipette 8 is provided between the smelting furnace 5 and the tundish 17, and the tundish There is a chute 4 between 17 and the crystallizer 2; a protective gas ring pipe 3 is provided on the top of the crystallizer 2, and the inside of the protective gas ring pipe 3 is connected to a protective gas source through a pipe, and the protective gas ring pipe 3 is provided with an air outlet, The air outlet faces the axis of the crystallizer;

The structure of the tundish is shown in Fig. 4, a first ultrasonic generating device is fixed on the side wall, and a second ultrasonic generating device is arranged in the tundish. The first ultrasonic generating device is composed of a first ultrasonic radiation rod 31 and a first ultrasonic guide rod. 32 and the first ultrasonic transducer 33, the second ultrasonic generating device is composed of the second ultrasonic radiation rod 12, the second ultrasonic guide rod 11 and the second ultrasonic transducer 10, the first ultrasonic transducer and the second ultrasonic The transducers are respectively connected to the first ultrasonic generator and the second ultrasonic generator; the front ends of the first ultrasonic radiating rod 31 and the second ultrasonic radiating rod 12 are both located inside the tundish, and the first ultrasonic radiating rod 31 is located in the second ultrasonic radiating Below the rod 12;

The axis of the first ultrasonic radiating rod 31 and the second ultrasonic radiating rod 12 are perpendicular;

The second transducer 10 is fixed on the transducer fixing plate 7, the transducer fixing plate 7 is fixed on the slider 9, the slider 9 is sleeved outside the beam 6, and the beam 6 is assembled with the lifting device; the slider 9 , Cross beam 6, lifting device constitutes an ultrasonic support device;

The ultrasonic transducer is a magnetostrictive transducer, the structure is shown in Figure 7(a); the magnetostrictive transducer includes a magnetostrictive transducer box 38 and a terbium ferrite magnetostrictive material 42, which is magnetostrictive The telescopic transducer box 38 is provided with a transducer water inlet 37 and a transducer water outlet 40 for circulating cooling water. The magnetostrictive transducer cable 41 is wound in turn on each of the ferrite terbium magnetostrictive materials 42 On the telescopic rod, the two ends of the magnetostrictive transducer cable 41 are respectively connected to the two poles of the ultrasonic generator through the magnetostrictive transducer cable interface 39;

The first ultrasonic transducer 33 and the second ultrasonic transducer 10 are respectively connected to the first waveguide rod 32 and the second waveguide rod 11 through an aviation joint connector; the first waveguide rod 32 and the second waveguide rod 11 are respectively connected to the first waveguide rod by threads An ultrasonic radiating rod 31 and a second ultrasonic radiating rod 12;

The inner space of the tundish is an inverted truncated cone shape with a side wall inclination angle of 3°～10°;

The front ends of the first ultrasonic radiating rod and the second ultrasonic radiating rod are coated with a ZrO ₂ coating;

The tundish includes a tundish furnace body 29 and a cover. The inner wall of the tundish furnace body 29 is provided with a tundish lining 28, the outer wall is covered with an insulating sleeve 30, and the tundish water port at the lower part of the tundish furnace body 29 is provided with a flow control Valve 34;

The cover structure is shown in Figure 6 and consists of two parts. One part is made of asbestos, called asbestos cover part 35, and the other part is made of tempered glass, called tempered glass cover part 36, which is used to observe the inside of the tundish. Situation: The part of the cover made of asbestos is equipped with a feed port and the pipette 8 is assembled together;

The structure of the mold 2 is shown in Figure 3, including an inner sleeve 20, an outer sleeve 24, a bottom plate 25, a water sealing plate 26 and a top plate 22; the top of the inner sleeve 20 is provided with an oil distribution device 19, and the bottom is provided with two cold water outlets 27; A water inlet 22 is provided on the side wall of 24;

There is a starter head 1 under the mold 2; the gap between the starter head 1 and the inner wall of the inner sleeve 20 is filled with asbestos 18; the upper part of the inner sleeve 20 is sealed with the top plate 22, and the lower part is sealed with the water sealing plate 26; The upper part of 24 is hermetically connected with the top plate 22, and the lower part is hermetically connected with the outside of the bottom plate 25; the inside of the bottom plate 25 is hermetically connected with the water sealing plate 26; the space between the inner sleeve 20 and the outer sleeve 24 is the cooling water cavity 21;

The outer walls of the melting furnace 5 and the pipette 8 are equipped with heat preservation devices, and are equipped with thermocouples for temperature measurement;

The method is;

preparation

AZ80 magnesium alloy ingot;

The magnesium alloy melt is smelted in the smelting furnace. After the magnesium alloy melt is evenly stirred, the slagging treatment is carried out, and the No. 2 flux is sprinkled into the melt for refining. After the refining is completed, the magnesium alloy melt is left for 10 minutes. It is 40℃ above the liquidus line of magnesium alloy;

Preheat the tundish, the pipette, the first ultrasonic radiation rod and the second ultrasonic radiation rod to a temperature of 40°C above the liquidus of the magnesium alloy, and the preheating time is 30 minutes; the first ultrasonic radiation rod and the second ultrasonic radiation rod The preheating method of the second ultrasonic radiation rod is preheating of the acetylene block; insert the preheated second ultrasonic radiation rod into the tundish; when the first ultrasonic radiation rod and the second ultrasonic radiation rod are preheated, the infrared temperature measuring gun is used Temperature measurement; control the temperature of the magnetostrictive transducer ≤40℃ by passing cooling water into the transducer box; the vertical distance between the first ultrasonic radiating rod and the second ultrasonic radiating rod is 80mm;

The refined magnesium alloy melt is transported into the tundish through a pipette; then the first ultrasonic generator and the second ultrasonic generator are turned on, and the ultrasonic power is transmitted to the tundish through two ultrasonic transducers and two ultrasonic guide rods. Two ultrasonic radiating rods, and the two ultrasonic radiating rods emit ultrasonic waves to form a group frequency ultrasonic wave, which is applied to the magnesium alloy melt; the two ultrasonic radiating rods emit ultrasonic waves at 15kHz and 20kHz respectively; when the tundish When the volume of the magnesium alloy melt reaches more than 70% of the tundish volume, the first ultrasonic generator and the second ultrasonic generator are turned on. At this time, the first radiating rod is located in the magnesium alloy melt, and the bottom end of the second radiating rod is located in the liquid. 20mm below the surface;

Insert the starter head into the crystallizer, fill the gap between the starter head and the inner wall of the inner sleeve of the crystallizer with asbestos; pass cooling water into the cooling water cavity of the crystallizer, and the cooling water is discharged from the second cold water outlet;

When the time of applying the group frequency ultrasonic wave to the magnesium alloy melt reaches 2min, open the flow control valve of the tundish, and transport the magnesium alloy melt in the tundish to the mold through the chute, and conduct semi-continuous casting until it is made into magnesium Alloy ingot

Take a sample of the manufactured magnesium alloy ingot for testing. The sampling position is shown in Figure 9; the metallographic structure is shown in Figure 11(c); the above experiment is repeated without applying ultrasonic waves to obtain the magnesium alloy ingot The metallographic structure of the magnesium alloy ingot is shown in Figure 11(a); a single ultrasonic wave is applied, the ultrasonic frequency is 15kHz, and the above experiment is repeated, and the metallographic structure of the magnesium alloy ingot obtained is shown in Figure 11(b); , The structure grain under the group frequency ultrasonic application method is more uniform and finer, and the columnar crystal area of the ingot is greatly reduced;

The magnesium alloy ingots obtained by the above three methods were tested for tensile strength, and the results are shown in Figure 12;

Using numerical simulation software to analyze the cavitation area, the result is shown in Figure 10. It can be seen from the figure that compared with the single-frequency ultrasonic field, the cavitation range generated by the group-frequency ultrasonic field is larger and the action range is wider;

Example 2

The structure of the device for applying group-frequency ultrasound for semi-continuous casting of magnesium alloy is the same as that of Example 1, and the difference lies in:

(1) The structure of the tundish is shown in Figure 5, and the first ultrasonic generating device is fixed on the bottom plate;

(2) The axes of the first ultrasonic radiating rod 31 and the second ultrasonic radiating rod 12 coincide;

(3) The ultrasonic transducer is a piezoelectric ceramic transducer, the structure is shown in Figure 7(b); the piezoelectric ceramic transducer includes a piezoelectric ceramic transducer box 44, two metal diaphragms 47 and titanium Acid piezoelectric ceramic material 48. The piezoelectric ceramic transducer box 44 is provided with a transducer air inlet 43 and a transducer air outlet 49 for circulating cooling gas. The upper and lower two of the titanate piezoelectric ceramic material 48 The end faces are respectively connected to a metal diaphragm 47, the two metal diaphragms 47 are respectively connected to one end of the piezoelectric ceramic transducer cable 46, and the other end of the two piezoelectric ceramic transducer cables 46 passes through the piezoelectric ceramic transducer cable. The interface 45 is connected to the two poles of the ultrasonic generator;

(4) The internal space of the tundish is an inverted truncated cone shape with a side wall inclination of 8°;

The method is the same as in Example 1, the difference is:

(1) Preparation

AZ31 magnesium alloy ingot;

(2) After refining, let it stand for 15 minutes, and the temperature of the magnesium alloy melt is 30°C above the magnesium alloy liquidus;

(3) Tundish, pipette, first ultrasonic radiation rod and second ultrasonic radiation rod are preheated to the same temperature of magnesium alloy melt;

(4) Control the temperature of the piezoelectric ceramic transducer ≤40℃ by passing cooling gas air into the transducer box;

(5) The vertical distance between the first ultrasonic radiating rod and the second ultrasonic radiating rod is 120mm;

(6) The bottom end of the second radiating rod is located 50mm below the liquid surface;

The method of sampling and testing is the same as that in Example 1. The metallographic structure is shown in Figure 13(c); the above experiment is repeated without applying ultrasonic waves, and the metallographic structure of the magnesium alloy ingot obtained is shown in Figure 13(a). Show; Using a single ultrasonic wave, ultrasonic frequency 20kHz, repeat the above experiment, the metallographic structure of the magnesium alloy ingot obtained is shown in Figure 13 (b); as can be seen from the figure, the microstructure grains under the group frequency ultrasonic application method It is more uniform and smaller, and the columnar crystal area of the ingot is greatly reduced;

The magnesium alloy ingots obtained by the above three methods are tested for tensile strength, and the structure is shown in Figure 14.

Example 3

The structure of the device for applying group-frequency ultrasound for semi-continuous casting of magnesium alloy is the same as that of Example 1, and the difference lies in:

The structure of the ultrasonic transducer is shown in Figure 8(a), and two sets of terbium ferrite magnetostrictive materials are arranged in each transducer box;

The method is the same as in Example 1, the difference is:

(1) Preparation

ZK60 magnesium alloy ingot;

(2) The temperature of the magnesium alloy melt after refining is 50°C above the magnesium alloy liquidus;

(3) Tundish, pipette, first ultrasonic radiating rod and second ultrasonic radiating rod are preheated to the same temperature of magnesium alloy melt; the vertical distance between first ultrasonic radiating rod and second ultrasonic radiating rod is 50mm

(4) The frequencies of the ultrasonic waves emitted by the two ultrasonic radiating rods are 20kHz and 35kHz respectively; the bottom end of the second radiating rod is located 40mm below the liquid surface.

Example 4

The structure of the device for applying group-frequency ultrasound to semi-continuous casting of magnesium alloy is the same as that in Example 2. The difference lies in:

The structure of the ultrasonic transducer is shown in Figure 8(b); two sets of titanate piezoelectric ceramic materials are arranged in each transducer box;

The method is the same as in Example 2, the difference is:

(1) Preparation

Mg-Sm magnesium alloy ingot;

(2) The temperature of the magnesium alloy melt after refining is 60°C above the magnesium alloy liquidus;

(3) Tundish, pipette, first ultrasonic radiating rod and second ultrasonic radiating rod are preheated to the same temperature of magnesium alloy melt; the vertical distance between first ultrasonic radiating rod and second ultrasonic radiating rod is 150mm

(4) The frequencies of the ultrasonic waves emitted by the two ultrasonic radiating rods are 80kHz and 140kHz respectively; the bottom end of the second radiating rod is located 30mm below the liquid surface.

Claims (8)

1. A device for applying group frequency ultrasound for semi-continuous casting of magnesium alloys includes a melting furnace, a tundish and a crystallizer. A pipette is arranged between the melting furnace and the tundish, and a chute is arranged between the tundish and the crystallizer; The top of the vessel is provided with a protective gas annular tube, the inside of the protective gas annular tube is connected with the protective gas source through a pipeline, and the protective gas annular tube is provided with an air outlet, which faces the axial direction of the crystallizer; it is characterized by: the side wall of the tundish Or a first ultrasonic generating device is fixed on the bottom plate, and a second ultrasonic generating device is arranged in the tundish. The first ultrasonic generating device is composed of a first ultrasonic radiation rod, a first ultrasonic guide rod and a first ultrasonic transducer. The second ultrasonic generating device is composed of a second ultrasonic radiation rod, a second ultrasonic guide rod and a second ultrasonic transducer. The first ultrasonic transducer and the second ultrasonic transducer are respectively connected to the first ultrasonic generator and the second ultrasonic generator. The front end faces of the first ultrasonic radiation rod and the second ultrasonic radiation rod are located inside the tundish, and the first ultrasonic radiation rod is located below the second ultrasonic radiation rod; when the first ultrasonic generating device is fixed on the side wall of the tundish When the axis of the first ultrasonic radiating rod is perpendicular to the axis of the second ultrasonic radiating rod; when the first ultrasonic generating device is fixed on the bottom plate of the tundish, the axes of the first ultrasonic radiating rod and the second ultrasonic radiating rod coincide; The energy device is fixed on the sliding block, the sliding block is sleeved outside the cross beam, and the cross beam is assembled with the lifting device; the sliding block, the cross beam and the lifting device form an ultrasonic supporting device.
2. The device for applying group frequency ultrasound for semi-continuous casting of magnesium alloy according to claim 1, wherein the ultrasonic transducer is a piezoelectric ceramic transducer or a magnetostrictive transducer; piezoelectric ceramics The transducer includes a transducer box, a metal diaphragm and a titanate piezoelectric ceramic material. The transducer box is provided with an air inlet and an air outlet for circulating cooling gas. The upper and lower two of the titanate piezoelectric ceramic material Each end surface is connected to a metal diaphragm, and the two metal diaphragms are respectively connected to the two poles of the ultrasonic generator through a cable; the magnetostrictive transducer includes a transducer box and a ferrite terbium magnetostrictive material. The transducer box The body is provided with a water inlet and a water outlet for circulating cooling water, the cable is wound on each telescopic rod of the ferrite terbium magnetostrictive material in turn, and the two ends of the cable are respectively connected with the two poles of the ultrasonic generator.
3. The device for applying group frequency ultrasound for semi-continuous casting of magnesium alloys according to claim 1, characterized in that the inner space of the tundish is in the shape of an inverted truncated cone, and the inclination angle of the side wall of the truncated cone is 3°-10 °.
4. The device for applying group frequency ultrasound for semi-continuous casting of magnesium alloys according to claim 1, wherein the tundish includes a furnace body and a cover, the inner wall of the furnace is provided with an inner lining, and the outer wall is covered with Insulation jacket, a flow control valve is arranged on the tundish water port at the lower part of the furnace body; the cover is composed of two parts, one of which is made of asbestos, and the other is made of tempered glass for observing the inside of the tundish; the cover is made of asbestos Part of it is equipped with a feeding port and a pipette assembly.
5. A method for applying group frequency ultrasound for semi-continuous casting of magnesium alloys, which is characterized in that the device according to claim 1 is used, and the following steps are performed:

   (1) The magnesium alloy melt is smelted in a smelting furnace. After the magnesium alloy melt is evenly stirred, the slag is removed. The second flux is sprinkled into the melt for refining. After the refining is completed, let it stand for 10-15 minutes. The temperature of the alloy melt is 30～80℃ above the liquidus line of the magnesium alloy;

   (2) Preheat the tundish, pipette, first ultrasonic radiating rod and second ultrasonic radiating rod to a temperature of 30～80℃ above the liquidus of the magnesium alloy, and the preheating time is more than 30min; Insert the heated second ultrasonic radiation rod into the tundish;

   (3) The refined magnesium alloy melt is transported into the tundish through a pipette; then the first ultrasonic generator and the second ultrasonic generator are turned on, and the ultrasonic power is passed through two ultrasonic transducers and two ultrasonic guides respectively. The rod is transmitted to two ultrasonic radiating rods, and the ultrasonic waves are emitted through the two ultrasonic radiating rods, and combined to form a group frequency ultrasonic wave, which is applied to the magnesium alloy melt; the frequency of the two ultrasonic radiating rods is 15～300kHz, and The frequency difference of the ultrasonic waves emitted by each ultrasonic radiating rod is 1～60kHz;

   (4) Insert the starter head into the crystallizer, and fill the gap between the starter head and the inner wall of the crystallizer with asbestos; pass cooling water into the cooling water cavity of the crystallizer, and the cooling water is discharged from the second cold water Drain outlet

   (5) When the applied ultrasonic time of the group frequency to the magnesium alloy melt reaches or exceeds 2 minutes, open the flow control valve of the tundish, and transport the magnesium alloy melt in the tundish to the mold through the chute for semi-continuous casting. , Until made into magnesium alloy ingot.
6. The method of applying group frequency ultrasound for semi-continuous casting of magnesium alloy according to claim 5, characterized in that in step (3), when the volume of magnesium alloy melt in the tundish reaches more than 70% of the volume of the tundish , Turn on the first ultrasonic generator and the second ultrasonic generator. At this time, the first radiating rod is located in the magnesium alloy melt, and the bottom end of the second radiating rod is located 20-50mm below the liquid surface.
7. The method of applying group frequency ultrasound for semi-continuous casting of magnesium alloy according to claim 5, characterized in that in step (3), when the first ultrasonic generator and the second ultrasonic generator are turned on, and when the ultrasonic is changed When the energy device is a piezoelectric ceramic transducer, the temperature of the piezoelectric ceramic transducer is controlled to be less than or equal to 40℃ by passing cooling gas into the transducer box; when the first ultrasonic generator and the second ultrasonic generator are turned on When the ultrasonic transducer is a magnetostrictive transducer, the temperature of the magnetostrictive transducer is controlled to be ≤40°C by passing cooling water into the transducer box.
8. The method of applying group frequency ultrasound for semi-continuous casting of magnesium alloy according to claim 5, characterized in that the diameter of the magnesium alloy ingot

   

   Among them, when the diameter of the prepared magnesium alloy ingot

   

   In the device used for semi-continuous casting of magnesium alloy by applying group frequency ultrasound, the first ultrasonic generating device is fixed on the side wall of the tundish, the first ultrasonic radiating rod is located below the second ultrasonic radiating rod, and the first ultrasonic radiating rod The vertical distance between the second ultrasonic radiating rod and the second ultrasonic radiating rod is 50-100mm; when the diameter of the prepared magnesium alloy ingot

   

   When using a device that applies group frequency ultrasound for semi-continuous casting of magnesium alloys, a first ultrasonic generating device is fixed on the bottom plate of the tundish, the first ultrasonic radiating rod is located below the second ultrasonic radiating rod, and the first ultrasonic radiating rod The vertical distance between the second ultrasonic radiation rod and the second ultrasonic radiation rod is more than 100mm.

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