WO2021012351A1

WO2021012351A1 - Device and method for combined-frequency ultrasound semi-continuous casting of magnesium alloy

Info

Publication number: WO2021012351A1
Application number: PCT/CN2019/102808
Authority: WO
Inventors: 乐启炽; 宁少晨; 陈星瑞; 胡成路; 李小强; 宝磊
Original assignee: 东北大学
Priority date: 2019-07-19
Filing date: 2019-08-27
Publication date: 2021-01-28
Also published as: CN110216250B; CN110216250A

Abstract

A device and method for combined-frequency ultrasound semi-continuous casting of a magnesium alloy, the device comprising a tundish (16), which is internally provided with two ultrasound generating devices, the front end face of an ultrasound irradiation rod of each ultrasound generating device being located in the tundish (16); a transducer and a support device are assembled together; and the support device is a lifting support device or a variable angle support device. The method comprises: (1) smelting a magnesium alloy melt; (2) preheating the tundish (16), a pipette (8) and the two ultrasound irradiation rods; inserting the ultrasound irradiation rods into the tundish (16), or inserting same into the tundish (16) after an included angle is adjusted; (3) conveying the magnesium alloy melt to the tundish (16), and starting up the ultrasound generating devices; (4) starting up a crystallizer (5); and (5) conveying the magnesium alloy melt in the tundish (16) into the crystallizer (5), and performing semi-continuous casting.

Description

Group frequency ultrasonic magnesium alloy semi-continuous casting device and method

Technical field

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

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 thermal conductivity 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, but the electromagnetic field is applied The skin effect makes the area of action limited and the stirring intensity is low, making 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. Only suitable for small size ingot production.

Summary of the invention

technical problem

The solution to the problem

Technical solutions

The purpose of the present invention is to provide a frequency-group ultrasonic magnesium alloy semi-continuous casting device and method, aiming at the existing single-frequency ultrasonic resonance frequency drift, severe sound pressure attenuation, and low cavitation intensity, which are insufficient to fully utilize the ultrasonic field in the melting of magnesium alloy. The advantage of the body is that two ultrasonic generating devices are used, and group-frequency ultrasound is applied through the control device to realize the coupling and superposition of sound waves, enhance the effect of cavitation and acoustic current, improve the magnesium alloy structure, and improve the quality of ingots.

The group frequency ultrasonic magnesium alloy semi-continuous casting device of the present invention 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; There is a protective gas ring tube, the inside of the protective gas ring tube is connected with the protective gas source through the pipeline, the protective gas ring tube is provided with an air outlet, and the air outlet faces the axis of the crystallizer; the tundish is provided with a first ultrasonic generating device and The second ultrasonic generating device is composed of a first ultrasonic radiating rod, a first ultrasonic guide rod and a first ultrasonic transducer, and the second ultrasonic generating device is composed of a second ultrasonic radiating rod, a second ultrasonic guide rod and The second ultrasonic transducer consists of the first ultrasonic transducer and the second ultrasonic transducer respectively connected to the first ultrasonic generator and the second ultrasonic generator; the front ends of the first ultrasonic radiating rod and the second ultrasonic radiating rod are both Located inside the tundish; the first transducer and the second transducer are assembled with the supporting device; the supporting device is a lifting supporting device or a variable angle supporting device; the lifting supporting device is composed of a slider, a beam and a lifting device , The two sliders are respectively fixedly connected with the first ultrasonic transducer and the second ultrasonic transducer, the two sliders are sleeved outside a cross beam, and the cross beam is assembled with the lifting device; the variable angle support device includes a cross beam and a guide rod , Lifting device and angle adjusting device; the driving motor of the lifting device is fixed on the cross beam, the screw rod assembled with the driving electrode passes through the cross beam and is connected with the cross beam by thread, and the bottom of the screw is connected to one end of the two connecting rods through a bearing; A support rod with a dovetail groove is fixed at the other end of each connecting rod, and a horizontal channel is provided in the dovetail groove for the horizontal movement of the axle; two guide rods respectively pass through a connecting rod and are slidably connected with the connecting rod; The sliders are respectively slidably connected with a dovetail groove, each slider is fixed with a pawl, and a ratchet gear matched with each pawl is sleeved on the axle, and each axle passes through a slider and a horizontal channel, and It is slidably connected to the sliding block, and the other end of each axle is fixed with a handwheel; the lower part of each ratchet is fixedly connected to a fixing frame; the two fixing frames are respectively fixedly connected to the first transducer and the second transducer; The connecting rod, the supporting rod, the sliding block, the hand wheel, the ratchet wheel and the pawl constitute an angle adjusting 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 water inlets and outlets for circulating cooling water. The front and rear of the ferrite terbium magnetostrictive material The two ends are respectively connected with the two poles of the ultrasonic generator through cables.

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 frequency group ultrasonic magnesium alloy semi-continuous casting method of the present invention adopts the above-mentioned device and performs 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 first ultrasonic radiating rod and the second ultrasonic radiating rod are inserted into the tundish through the lifting device, or the first ultrasonic radiating rod and the second ultrasonic radiating rod are adjusted to the included angle of 10°-30° through the angle adjusting device, and The intersection of the axes of the two ultrasonic radiating rods is located below the two ultrasonic radiating rods, then preheated, and then inserted into the tundish through the lifting device;

3. Transport the magnesium alloy melt into the tundish through a pipette; then turn on the first ultrasonic generator and the second ultrasonic generator, and the alternating current signals generated by the two ultrasonic generators are converted into two ultrasonic transducers. The corresponding mechanical vibration is transmitted to two ultrasonic radiating rods through the two ultrasonic radiating rods, and ultrasonic waves are emitted through the two ultrasonic radiating rods, combined to form a group frequency ultrasonic wave, and applied to the magnesium alloy melt; two of the ultrasonic radiating rods emit The frequency of the ultrasonic wave is 15～300kHz, and the difference of the ultrasonic frequency emitted by the two ultrasonic radiating rods 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 the above step 3, 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 and second radiating rods The bottom end 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, 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 of the same total power, the group frequency ultrasound increases the number and spatial distribution of the radiating rods through the supporting device, adjusts the frequency and power of the two rows of sound waves, enhances the nonlinear coupling of the sound waves, and enhances the range of melt cavitation. Cavitation strength, so that 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 of the present invention uses the frequency and power of two ultrasonic radiating rods, or the angle of two ultrasonic radiating rods at the same time, realizes the nonlinear superposition of sound waves in the melt, and solves the limitations caused by problems such as frequency drift and sound pressure attenuation The cavitation range is enhanced, and the cavitation intensity is increased; cooling air cooling or water cooling device is used to maintain the temperature of the ultrasonic transducer; the magnetostrictive transducer is made of TbFe ₂ (terbium iron) material, and its saturation magnetostrictive stress It is 50-60 times larger than nickel and can be used to make high-power sound sources; the structure of the tundish is conducive to the slag removal treatment of the tundish; the cover of the tundish is conducive to heat preservation, reducing oxidation, and observing the height of the tundish melt.

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 structural diagram of a group frequency ultrasonic magnesium alloy semi-continuous casting device in embodiment 1 of the present invention;

Figure 2 is a side view of Figure 1;

3 is a schematic diagram of a part of the structure of the variable angle support device in Embodiment 2 of the present invention;

Figure 4 is a partial enlarged view of the ratchet part of Figure 3; in the figure, (a) is the left ratchet part, (b) is the right ratchet part;

5 is a schematic diagram of a cross-sectional structure and a top view structure of a tundish in an embodiment of the present invention; in the figure, the left picture is a cross-sectional structure, and the right picture is a top view structure;

Figure 6 is a schematic diagram of the structure of the crystallizer in an embodiment of the present invention;

Figure 7 is a schematic diagram of the cross-sectional structure of the ultrasonic transducers in

embodiments

1 and 2 of the present invention, in the figure (a) is a magnetostrictive transducer, and (b) is a piezoelectric ceramic transducer;

Figure 8 is a schematic diagram of the cross-sectional structure of the ultrasonic transducers in

embodiments

3 and 4 of the present invention, in the figure (a) is a magnetostrictive transducer, and (b) is a piezoelectric ceramic transducer;

In the figure, 1. Starter head, 2. Magnesium alloy ingot, 3. Magnesium alloy melt, 4. Mold water inlet, 5. Mold, 6. Protective gas ring pipe, 7. Melting furnace, 8. Move Liquid pipe, 9, lifting support device pillar, 10, lifting support device screw, 11, lifting support device beam, 12, first ultrasonic transducer, 13, first ultrasonic guide rod, 14, first ultrasonic radiation rod, 15 , Transducer fixing plate, 16, tundish, 17, chute, 18, lifting support device slider, 19, tundish cover, 20, lifting support device base, 21, variable angle support device base, 22, connecting rod , 23, variable angle support device pillar, 24, support rod, 25, guide rod, 26, variable angle support device screw, 27 variable angle support device beam, 28, drive motor, 29, bevel gear, 30, bearing, 31, Variable angle support device slider, 32, variable angle support device handwheel, 33, ratchet wheel, 34, dovetail groove, 35, fixed frame, 36, pawl, 37, insulation sleeve, 38, tundish furnace body, 39, middle Bag lining, 40, asbestos cover part, 41, tempered glass cover part, 42, asbestos, 43, oil distribution device, 44, inner sleeve, 45, cooling water chamber, 46, top plate, 48, outer jacket, 49, Bottom plate, 50, sealing plate, 51, second cold water outlet, 52, transducer water inlet, 53, magnetostrictive transducer box, 54, magnetostrictive transducer cable interface, 55, transducer Water outlet, 56, magnetostrictive transducer cable, 57, ferrite terbium magnetostrictive material, 58, transducer air inlet, 59, piezoelectric ceramic transducer box, 60, piezoelectric ceramic transducer Device cable interface, 61, piezoelectric ceramic transducer cable, 62, metal diaphragm, 63, titanic acid piezoelectric ceramic material, 64, transducer air outlet, 65, flow control valve, 66, lifting support device handwheel ；

Fig. 9 is a schematic diagram of a semi-continuous casting process of a group frequency ultrasonic magnesium alloy in an embodiment of the present invention;

Figure 10 is a graph showing the sound pressure fluctuation of single-frequency ultrasound and group-frequency ultrasound in Example 2 of the present invention. In the figure, the left picture shows two kinds of single-frequency ultrasound, and the right picture shows the group-frequency ultrasound;

Figure 11 is a diagram of the cavitation area of the traditional single-frequency ultrasonic field and group-frequency ultrasound numerical simulation software in Example 2 of the present invention; in the figure, the left picture is 20kHz, the middle picture is 15kHz, and the right picture is the group-frequency ultrasound;

Figure 12 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 20kHz single-frequency ultrasound, (c) is 15kHz single-frequency Ultrasound, (d) is group frequency ultrasound;

Fig. 13 is a comparison diagram of 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, when the lifting support device is adopted, the transducer fixing plate 15 is welded and fixed on the lifting support device slider 18; when the variable angle support device is adopted, the transducer fixing plate is welded and fixed on the fixing frame.

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 surface of the ultrasonic radiating rod is the end surface of the ultrasonic radiating rod away from the ultrasonic guide rod, that is, the bottom end surface.

The amount of flux No. 2 (barium flux) in the embodiment of the present invention is based on the extinguishment of the flame produced by burning metallic magnesium after addition.

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, when the lifting support device is used, the lifting support device beam 11 is slidably connected to the lifting support device pillar 9 through a sleeve, and one end of the lifting support device beam 11 is assembled on the lifting support device screw 10 and the lifting support device handwheel. On the manual lifting device of 66, a bevel gear is installed between the lifting support device hand wheel 66 and the lifting support device screw 10; the bottom of the lifting support device pillar 9 is fixed on the lifting support device base 20; when the lifting operation is performed, the lifting support device The hand wheel 66 rotates to rotate the bevel gear assembled with the lifting support device hand wheel 66. The bevel gear moves up and down along the lifting support device screw 10 (screw), driving the lifting support device beam 11 to move up and down along the lifting support device pillar 9; When adjusting the horizontal position, move the lifting support device slider 18 to adjust the distance between the two ultrasonic radiation rods.

In the embodiment of the present invention, when a variable angle support device is used, the variable angle support device beam 27 is fixed on two variable angle support device pillars 23, and the bottom of the variable angle support device pillar 23 is fixed on the variable angle support device base 21; During the lifting operation, the bevel gear 29 is driven to rotate by the drive motor 28, so that the variable-angle supporting device screw 26 is raised and lowered, and the bearing 30 is driven to rise and fall, thereby driving the connecting rod 22 and the supporting rod 24 to move up and down along the guide rod 25 to adjust the two ultrasonic radiation rods. When adjusting the horizontal position, move the variable angle support device slider 31 to slide along the dovetail groove 34 to adjust the distance between the two ultrasonic radiation rods; when performing the angle adjustment operation, rotate the variable angle support device handwheel 32, The ratchet wheel 33 is rotated to reach the required angle and is positioned by the pawl 36, so that each fixing frame 35 drives the respective connected ultrasonic transducers to rotate, so that the two ultrasonic radiation rods form a required angle.

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. 9.

Example 1

The structure of the group frequency ultrasonic magnesium alloy semi-continuous casting device is shown in Figure 1 and Figure 2. It includes a smelting furnace 7, a tundish 16 and a crystallizer 5. A pipette 8 is provided between the smelting furnace 7 and the tundish 16, and the tundish A chute 17 is provided between 16 and the crystallizer 5;

The top of the crystallizer 5 is provided with a protective gas ring pipe 6, the inside of the protective gas ring pipe 6 is connected to a protective gas source through a pipe, and the protective gas ring pipe 6 is provided with an air outlet, which faces the axis of the crystallizer;

The tundish is provided with a first ultrasonic generating device and a second ultrasonic generating device. The first ultrasonic generating device is composed of a first ultrasonic radiation rod 14, a first ultrasonic guide rod 13, and a first ultrasonic transducer 12. The device has the same structure as the first ultrasonic generating device, and the first ultrasonic transducer 12 and the second ultrasonic transducer are respectively connected to the first ultrasonic generator and the second ultrasonic generator;

The front ends of the first ultrasonic radiation rod 14 and the second ultrasonic radiation rod are both located inside the tundish 16; the first transducer 12 and the second transducer are assembled with the supporting device;

The support device is a lifting support device, which is composed of a lifting support device slider 18, a lifting support device beam 11 and a lifting device. The two lifting support device sliders 18 are respectively fixed with a transducer fixing plate 15 and the two transducers are fixed. The plate 15 is respectively fixedly connected with the first ultrasonic transducer 12 and the second ultrasonic transducer, the two lifting support device sliders 18 are sleeved outside a lifting support device beam 11, and the lifting support device beam 11 is assembled with the lifting device ；

The two ultrasonic transducers are piezoelectric ceramic transducers, the structure is shown in Figure 7(b), including the piezoelectric ceramic transducer box 59, the metal diaphragm 62 and the titanate piezoelectric ceramic material 63. The ceramic transducer box 59 is provided with a transducer air inlet 58 and a transducer air outlet 64 for circulating cooling gas. The upper and lower ends of the titanate piezoelectric ceramic material 63 are respectively connected to a metal diaphragm 62, Two metal diaphragms 62 are respectively connected to one end of a piezoelectric ceramic transducer cable 61, and the other ends of the two piezoelectric ceramic transducer cables 61 are respectively connected to two poles of the ultrasonic generator;

The first ultrasonic transducer 12 and the second ultrasonic transducer are respectively connected to the first waveguide rod 13 and the second waveguide rod through an aviation joint connector; the first waveguide rod 13 and the second waveguide rod are respectively connected to the first ultrasonic radiation through threads Rod 14 and a second ultrasonic radiating rod;

The inner space of the tundish 16 is in the shape of an inverted truncated cone, and the inclination angle of the side wall of the truncated cone is 10°;

The structure of the tundish is shown in Figure 5, including a tundish furnace body 38, a tundish cover 19 is provided on the top, a tundish lining 39 is provided on the inner wall of the tundish furnace body 38, and the outer wall is covered with an insulation sleeve 37. A flow control valve 65 is provided on the tundish water port at the lower part of the furnace body 38; the structure of the tundish cover 19 is shown in the right figure of Figure 5, and consists of two parts, one of which is made of asbestos, called the asbestos cover part 40, and the other Part of the material is tempered glass for observing the inside of the tundish, called the tempered glass cover part 41; the part of the tundish cover 19 made of asbestos is provided with a feed port and a pipette 8 assembled together;

The front ends of the first ultrasonic radiating rod 14 and the second ultrasonic radiating rod are coated with a ZrO ₂ coating;

The structure of the crystallizer is shown in Figure 6, including an inner sleeve 44, an outer sleeve 48, a bottom plate 49, a water sealing plate 50 and a top plate 46; the top of the inner sleeve 44 is provided with an oil distribution device 43, and the bottom is provided with two cold water outlets 54; A mold water inlet 4 is provided on the side wall of the mold; a starter head 1 is provided under the mold 6; the gap between the starter head 1 and the inner wall of the inner sleeve 44 is filled with asbestos 42; the upper part of the inner sleeve 44 is sealed with the top plate 46 Connected, the lower part is sealed to the sealing plate 50; the upper part of the outer shell 48 is sealed to the top plate 46, and the lower part is sealed to the outside of the bottom plate 49; the inside of the bottom plate 49 is sealed to the sealing plate 50; between the inner sleeve 44 and the outer shell 48 The space is the cooling water cavity 45;

The outer walls of the melting furnace 7 and the pipette 8 are equipped with heat preservation devices, and are equipped with thermocouples for temperature measurement;

The method is:

Prepare φ=100mm AZ31 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; Enter the cooling gas air to control the temperature of the piezoelectric ceramic transducer ≤40℃;

The magnesium alloy melt is transported into the tundish through a pipette, the axes of the two ultrasonic radiation rods are parallel; then the first ultrasonic generator and the second ultrasonic generator are turned on, and the alternating current signals generated by the two ultrasonic generators are passed through two ultrasonic generators respectively. One ultrasonic transducer is converted into corresponding mechanical vibration, which is transmitted to two ultrasonic radiating rods through two ultrasonic guide rods, and ultrasonic waves are emitted through the two ultrasonic radiating rods, combined to form group-frequency ultrasonic waves, and applied to the magnesium alloy melt; The first ultrasonic radiating rod and the second ultrasonic radiating rod emit ultrasonic waves at 15kHz and 20kHz, respectively; 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. Ultrasonic generator, the bottom ends of the first radiating rod and the second radiating rod are located 50mm below the liquid 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.

Example 2

The structure of the device is the same as that of embodiment 1, the difference is:

(1) The supporting device is a variable angle supporting device. The structure is shown in Figures 3 and 4, including the variable angle supporting device beam 27, the guide rod 25, the lifting device and the angle adjusting device; the driving motor 28 of the lifting device is fixed at the variable angle The supporting device beam 27, the variable angle supporting device screw 26 assembled with the driving electrode 28 passes through the variable angle supporting device beam 27 and is connected to the variable angle supporting device beam 27 by threads. The bottom of the variable angle supporting device screw 26 is connected to the bearing 30 One end of the two connecting rods 22 is connected; the other end of each connecting rod 22 is fixed with a support rod 24 with a dovetail groove 34, and a horizontal channel is provided in the dovetail groove 34 for the horizontal movement of the wheel shaft; the two guide rods 25 respectively pass through Pass a connecting rod 22 and slidably connect with the connecting rod 22; two variable-angle support device sliders 31 are respectively slidably connected with a dovetail groove 34, and each variable-angle support device slider 31 is fixed with a pawl 36, and A ratchet gear 33 matched with each pawl 36 is sleeved on the axle. Each axle passes through a variable angle support device slider 31 and a horizontal channel, and is slidably connected to the variable angle support device slider 31. Each axle A variable angle support device handwheel 32 is fixed at the other end of the, the lower part of each ratchet 33 is fixedly connected to a fixing frame 35; the two fixing frames 35 are respectively fixedly connected to the first transducer 12 and the second transducer; The rod 22, the support rod 24, the variable angle support device slider 31, the variable angle support device handwheel 32, the ratchet gear 33 and the pawl 36 constitute an angle adjustment device;

(2) The ultrasonic transducer is a magnetostrictive transducer, the structure is shown in Figure 7(a), including the magnetostrictive transducer box 53 and the terbium ferrite magnetostrictive material 57, the magnetostrictive transducer The transducer box 53 is provided with a transducer water inlet 52 and a transducer water outlet 55 for circulating cooling water; the magnetostrictive transducer cable 56 is wound on each telescopic rod of the terbium ferrite magnetostrictive material 57 in turn , Both ends of the magnetostrictive transducer cable 56 are respectively connected to the two poles of the ultrasonic generator through the magnetostrictive transducer cable interface 54;

(3) The inner space of the tundish is inverted truncated cone shape, and the inclination angle of the side wall of the truncated cone shape is 5°;

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

(1) Prepare φ=150mm AZ80 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 radiating rod and second ultrasonic radiating rod are preheated to the same temperature of magnesium alloy melt; before preheating, first ultrasonic radiating rod and second ultrasonic radiating rod are adjusted by angle The device is adjusted to an angle of 30°, and the intersection of the axes of the two ultrasonic radiation rods is located below the two ultrasonic radiation rods, and then preheated, and then inserted into the tundish through the lifting device;

(4) Insert the preheated first ultrasonic radiating rod and second ultrasonic radiating rod into the tundish through the lifting device; when the first ultrasonic radiating rod and the second ultrasonic radiating rod are preheated, the temperature is measured by an infrared thermometer ; Control the temperature of the magnetostrictive transducer ≤40℃ by passing cooling water into the transducer box;

(5) The frequencies of ultrasonic waves emitted by the first and second ultrasonic radiating rods are 20kHz and 35kHz respectively; the bottom ends of the first and second radiating rods are located 20mm below the liquid surface;

Comparing the single-frequency sound pressure formed by the ultrasonic wave emitted by a single radiating rod with the sound pressure of the above-mentioned group frequency ultrasound, the result is shown in Figure 10, it can be seen that the sound pressure fluctuation caused by the group frequency ultrasound is more obvious;

Using numerical simulation software to analyze the cavitation area, the results are shown in Figure 11. 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;

Take a sample of the made magnesium alloy ingot and test its metallographic structure as shown in Figure 12(d); using the method without ultrasonic waves, repeat the above experiment, the metallographic structure of the magnesium alloy ingot obtained is shown in Figure 12(a) ) Is shown; using a single ultrasonic wave, ultrasonic frequency 15kHz and 20kHz, repeat the above experiment, the metallographic structure of the magnesium alloy ingot obtained is shown in Figure 12 (b) and Figure 12 (c); as can be seen from the figure, The structure grains under the application method of group frequency ultrasound are more uniform and finer, and the columnar crystal area of the ingot is greatly reduced;

The magnesium alloy ingots obtained by the above four methods were tested for tensile strength, and the results are shown in Figure 13.

Example 3

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

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

(1) Prepare φ=100mm ZK60 magnesium alloy ingot;

(2) The temperature of the magnesium alloy melt is 50°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) The frequencies of ultrasonic waves emitted by the first and second ultrasonic radiating rods are 30kHz and 35kHz respectively; the bottom ends of the first and second radiating rods are located 30mm below the liquid surface.

Example 4

The structure of the device is the same as that of the second embodiment, the difference lies in:

The structure of the ultrasonic transducer is shown in Figure 8(a), and two sets of titanic acid piezoelectric ceramic materials are arranged in each transducer box;

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

(1) Preparation of φ=220mm Mg-Sm magnesium alloy ingot;

(2) The temperature of the magnesium alloy melt is 70°C above the liquidus of the magnesium alloy;

(3) Tundish, pipette, first ultrasonic radiating rod and second ultrasonic radiating rod are preheated to the same temperature of magnesium alloy melt; before preheating, first ultrasonic radiating rod and second ultrasonic radiating rod are adjusted by angle Adjust the device to an angle of 10°;

(4) The frequencies of ultrasonic waves emitted by the first and second ultrasonic radiating rods are 45kHz and 100kHz, respectively; the bottom ends of the first and second radiating rods are located 35mm below the liquid surface.

Claims

A group frequency ultrasonic magnesium alloy semi-continuous casting device, comprising 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 crystallizer is arranged There is a protective gas ring pipe, the inside of the protective gas ring pipe is connected with the protective gas source through the pipeline, the protective gas ring pipe is provided with an air outlet, and the air outlet faces the direction of the crystallizer axis; it is characterized in that the first ultrasonic wave is provided in the tundish The first ultrasonic generating device is composed of a first ultrasonic radiating rod, a first ultrasonic guide rod and a first ultrasonic transducer, and the second ultrasonic generating device is composed of a second ultrasonic radiating rod and a second ultrasonic transducer. The guide rod and the second ultrasonic transducer are composed, the first ultrasonic transducer and the second ultrasonic transducer are respectively connected to the first ultrasonic generator and the second ultrasonic generator; the first ultrasonic radiating rod and the second ultrasonic radiating rod The front end faces are all located inside the tundish; the first transducer and the second transducer are assembled with the support device; the support device is a lifting support device or a variable angle support device; the lifting support device consists of a slider, a beam and The lifting device is composed of two sliding blocks respectively fixedly connected with the first ultrasonic transducer and the second ultrasonic transducer, the two sliding blocks are sleeved outside a beam, and the beam and the lifting device are assembled together; the variable angle support device includes a beam , Guide rod, lifting device and angle adjusting device; the driving motor of the lifting device is fixed on the cross beam, the screw rod assembled with the driving electrode passes through the cross beam and is connected with the cross beam by thread, and the bottom of the screw is connected with the two connecting rods through the bearing One end is connected; the other end of each connecting rod is fixed with a support rod with a dovetail groove, and a horizontal channel is provided in the dovetail groove for the horizontal movement of the axle; two guide rods respectively pass through a connecting rod and are slidably connected with the connecting rod ; Two sliders are respectively connected to a dovetail groove slidingly, each slider is fixed with a pawl, and a ratchet gear matched with each pawl is sleeved on the axle, and each axle passes through a slider and horizontal The channel is slidably connected with the slider, the other end of each axle is fixed with a handwheel; the lower part of each ratchet is fixedly connected with a fixing frame; the two fixing frames are respectively connected with the first transducer and the second transducer Fixed connection; connecting rod, support rod, sliding block, hand wheel, ratchet wheel and pawl constitute an angle adjusting device.
The frequency-group ultrasonic magnesium alloy semi-continuous casting device according to claim 1, wherein the ultrasonic transducer is a piezoelectric ceramic transducer or a magnetostrictive transducer; a piezoelectric ceramic transducer Including the transducer box, metal diaphragm and 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 end faces of the titanate piezoelectric ceramic material are respectively A metal diaphragm is connected, 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 terbium ferrite magnetostrictive material. The transducer box is provided with There are water inlets and water outlets for circulating cooling water, and the front and rear ends of the ferrite terbium magnetostrictive material are respectively connected to the two poles of the ultrasonic generator through cables.
A group frequency ultrasonic magnesium alloy semi-continuous casting device according to claim 1, wherein 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 cone is 3°-10°.
The frequency-group ultrasonic magnesium alloy semi-continuous casting device according to claim 1, characterized in that 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 an insulating sleeve, A flow control valve is provided 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 part of the cover made of asbestos is equipped with The inlet is assembled with the pipette.
A semi-continuous casting method for frequency-group ultrasonic magnesium alloy, which is characterized in that the device according to claim 1 is adopted and carried out in the following steps:

(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; The heated first ultrasonic radiating rod and the second ultrasonic radiating rod are inserted into the tundish through the lifting device, or the first ultrasonic radiating rod and the second ultrasonic radiating rod are adjusted to the included angle of 10°-30° through the angle adjusting device. And the intersection of the axes of the two ultrasonic radiation rods is located below the two ultrasonic radiation rods, and then preheated, and then inserted into the tundish through the lifting device;

(3) The 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 AC signals generated by the two ultrasonic generators are converted by two ultrasonic transducers respectively For corresponding mechanical vibration, it is transmitted to two ultrasonic radiating rods through two ultrasonic radiating rods, and ultrasonic waves are emitted through the two ultrasonic radiating rods, combined to form a group frequency ultrasonic wave, and applied to the magnesium alloy melt; two of the ultrasonic radiating rods The frequency of transmitting ultrasonic waves is 15～300kHz, and the frequency difference of the ultrasonic waves emitted by two ultrasonic radiating rods 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.
The method for semi-continuous casting of magnesium alloy with group frequency ultrasonic according to claim 5, characterized in that in step (3), when the volume of the magnesium alloy melt in the tundish reaches more than 70% of the volume of the tundish, the second is turned on An ultrasonic generator and a second ultrasonic generator. At this time, the bottom ends of the first radiating rod and the second radiating rod are located 20-50mm below the liquid surface.
The method for semi-continuous casting of a group-frequency ultrasonic magnesium alloy according to claim 5, wherein in step (3), when the first ultrasonic generator and the second ultrasonic generator are turned on, and when the ultrasonic transducer is In the case of piezoelectric ceramic transducers, the temperature of the piezoelectric ceramic transducer is controlled to be less than or equal to 40℃ by passing cooling gas air into the transducer box; when the first ultrasonic generator and the second ultrasonic generator are turned on, and 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.