WO2020237866A1

WO2020237866A1 - Electromagnetic semi-continuous casting method for non-ferrous metal and alloy thereof

Info

Publication number: WO2020237866A1
Application number: PCT/CN2019/102803
Authority: WO
Inventors: 乐启炽; 王航; 贾永辉; 陈星瑞; 程春龙; 周雄
Original assignee: 东北大学
Priority date: 2019-05-29
Filing date: 2019-08-27
Publication date: 2020-12-03
Also published as: CN110076305B; CN110076305A

Abstract

An electromagnetic semi-continuous casting method for a non-ferrous metal and an alloy thereof, using an electromagnetic semi-continuous casting device for non-ferrous metal and alloy thereof. An outer side wall of a copper inner sleeve (11) of the device is provided with or not provided with a reinforcing rib; when the reinforcing rib is provided, the reinforcing rib and the copper inner sleeve (11) are an integrated structure; the reinforcing rib is composed of a plurality of annular bodies (13), or a plurality of rows of arc bodies (14) or a plurality of circular ring bodies (13) and a plurality of columnar bodies. The method involves: (1) passing in cooling water and introducing a metal melt into a crystallizer; (2) respectively supplying two groups of excitation coils (8) with an alternating current or a pulse current by means of a power supply, each forming a magnetic field with a phase difference of 90°, and the resulting phase difference magnetic field acting on the metal melt; and (3) performing casting.

Description

Electromagnetic semi-continuous casting method for non-ferrous metals and alloys thereof

Technical field

The invention belongs to the field of metal material preparation, and specifically relates to an electromagnetic semi-continuous casting method for non-ferrous metals and alloys thereof.

Background technique

Semi-continuous casting is currently the main method for preparing metal ingots in industrial production; traditional direct water-cooled semi-continuous casting (traditional DC method) is to evenly introduce molten metal into the crystallizer, under the action of water cooling the crystallizer A solid solidified shell is formed, and then the starter head drives the solidified part to move down at a certain speed. When the solidified part leaves the mold, it will be affected by the secondary cooling water, and the solidified layer of the ingot is also It moves slowly to the center and completely solidifies and crystallizes. As the molten metal continuously flows into the mold, the ingot is continuously solidified and formed in the mold; this method increases labor productivity, improves working conditions, and increases The length of the ingot is increased, and the geometric loss of the cutting head and the tail is reduced; however, the ingots produced by traditional semi-continuous casting have the disadvantages of coarse grains, severe segregation, and poor surface quality of the ingots, which make the material loss rate greatly increase.

In order to solve the various problems of the traditional DC method, new semi-continuous casting technologies have been developed at home and abroad, including low-groove casting, hot-top casting, air sliding and air curtain casting, low-level semi-continuous casting and field assisted casting, etc. Among them, the effect of applying an external field during the metal solidification process is the most significant; currently the external fields applied mainly include electromagnetic field and ultrasonic field, but the method of applying ultrasonic field is limited due to the large attenuation of ultrasonic in the melt and the direct ultrasonic rod A series of problems such as pollution caused by the effect on the melt have made it impossible to apply to industrial production on a large scale; and the electromagnetic casting technology has a series of advantages such as non-contact, pollution-free and significant refined solidification structure, which has been widely recognized by the industry.

The basic principle of electromagnetic casting technology is to pass an alternating current into the excitation coil to generate an alternating magnetic field. The alternating magnetic field acts on the molten metal through the inner sleeve of the mold, and induces current in the molten metal, induced current and alternating magnetic field The electromagnetic force generated by the function plays the role of stirring the melt, uniforming the flow field, temperature field and solute field of the melt, thereby making the crystal grain of the ingot refined and improving the surface quality. However, this technology has certain requirements for the crystallizer: (1) The permeability of the crystallizer should be good to ensure the electromagnetic pressure required for soft contact on the surface of the ingot; (2) The crystallizer should have a good cooling effect to ensure that the melt is crystallized A solidified shell of a certain thickness is formed in the vessel to avoid accidents such as pull-out; (3) The mold must have a certain strength, especially the yield strength, because the huge temperature gradient will produce great thermal stress, which is very easy Deformation and thermal stress cracks occur, causing damage to the mold.

At present, the copper inner sleeve can basically meet the requirements of good cooling effect and strength, but due to the high shielding of copper to the magnetic field, the alternating magnetic field generated by the excitation coil will be larger when passing through the copper inner sleeve of the mold Loss, the electromagnetic utilization rate is greatly reduced, resulting in a poor stirring effect of the electromagnetic field on the melt; in order to improve the permeability of the mold, some scholars have successively developed a slotted electromagnetic continuous casting mold. This kind of crystallizer cuts several gaps uniformly along the upper part of the crystallizer wall in a certain direction, so that the electromagnetic field can directly act on the melt through the gaps, thereby reducing the shielding effect of the crystallizer wall on the magnetic field. There are various types of slitting, including equal slitting, non-equal slitting, full-body slitting, non-full-body slitting and oblique slitting.

Chinese patents CN200710190961, CN200920266196.3, CN02265157.8, etc. show that opening a certain number of slits on the inner sleeve of the crystallizer can increase the intensity of the magnetic field in the crystallizer and greatly increase the permeability of the crystallizer. However, due to the existence of the slit, the slit mold has great defects: (1) The distribution of the magnetic field in the melt becomes more complicated, and the difference in electromagnetic force between the slit and the non-cut melt is more complicated. This difference is likely to cause the surface quality of the ingot to deteriorate and affect the metallurgical quality of the ingot; (2) The existence of slits destroys the integrity of the mold, greatly reduces the strength of the mold, and brings trouble to actual production. Stability factor; (3) The slit makes each metal layer of the mold wall independent of each other, and during the continuous casting process, the mold will produce thermal expansion and contraction effects under the action of high temperature, and the slit may be compressed or expanded The big trend leads to difficulties in the design of the cooling water circuit.

Considering the many shortcomings of the slotted mold, many researchers have turned their attention to the seamless electromagnetic casting mold. Seamless crystallizer can be divided into two design forms, one is segmented seamless crystallizer, and the other is integral seamless crystallizer. Chinese patent 201811273062.4 provides a two-stage copper alloy crystallizer with high permeability and soft contact. The upper part adopts high permeability copper alloy to increase the permeability, and the lower part adopts pure copper material. The thickness of the mould wall is 20mm-30mm. The connection between the lower part and the lower part is welded by pure copper TIG, but the mold has the difficulty of smooth connection between the two materials and the difference in thermal properties is likely to cause serious defects in the ingot; the integral seamless soft contact crystal The mold is filled with high-resistivity powder between high-conductivity copper or copper alloy, and processed by hot isostatic pressing into a whole; this kind of mold has improved strength, but it still has not solved the problem. Magnetic problem.

Summary of the invention

technical problem

The solution to the problem

Technical solutions

In view of the various problems existing in electromagnetic semi-continuous casting, such as the presence of slits in the inner sleeve of the mold to reduce the strength, the complicated magnetic field distribution in the melt, which easily deteriorates the surface quality, the limited range of electromagnetic field in the melt, and the utilization rate of the magnetic field. Inferior, the present invention provides an electromagnetic semi-continuous casting method for non-ferrous metals and their alloys, which adjusts the mold structure and reduces the thickness of the traditional copper inner sleeve so that the magnetic field generated by the excitation coil acts more on the molten metal Medium and uniform distribution to achieve technical goals such as refining the ingot grains, eliminating surface defects, reducing the segregation of alloy components, and improving surface quality.

The non-ferrous metal and its alloy electromagnetic semi-continuous casting method of the present invention adopts a non-ferrous metal and its alloy electromagnetic semi-continuous casting device, which includes a mold and an excitation coil system; the mold is composed of an upper cover plate, a mold shell, and a copper inner sleeve It is composed of the mold sealing water plate, the upper part of the mold shell is provided with a cooling water inlet, and the bottom of the copper inner sleeve is provided with two cold water spray holes; the excitation coil system is fixed in the cooling water tank between the mold shell and the copper inner sleeve. It is composed of fixing bolts, coil pressing plate, coil support block and excitation coil; among them, the outer side wall of the copper inner sleeve is provided with or without reinforcing ribs. When the reinforcing ribs are provided, the reinforcing ribs and the copper inner sleeve are an integral structure , The reinforcing rib is composed of multiple circular ring bodies, or composed of multiple rows of arc-shaped bodies, or formed by multiple circular ring bodies and multiple columnar bodies; the thickness of the side wall of the copper inner sleeve is 6 ~20mm; The excitation coils are divided into two groups, each of the two groups of excitation coils is connected in series, and each is connected to the power supply;

The method is:

(1) Pour cooling water into the cooling water tank, and the cooling water is sprayed from the second cold water nozzle; the molten metal is introduced into the mold to make the liquid level of the molten metal reach a predetermined height; the molten metal is non-ferrous Metal or non-ferrous metal alloy;

(2) The two sets of excitation coils are supplied with alternating current or pulse current through the power supply, so that each group of excitation coils generates a set of alternating electromagnetic signals or pulse electromagnetic signals, each forming a magnetic field; the two sets of excitation coils are connected The phase difference of the alternating current or pulse current is 90°, and the resulting phase difference magnetic field acts on the molten metal in the mold;

(3) Start the non-ferrous metal and its alloy electromagnetic semi-continuous casting device to cast the molten metal, and the second cold water sprayed from the second cold water nozzle to cool the ingot below the mold until the casting is completed.

In the above method, the vertical cross section of the reinforcing rib is rectangular, trapezoidal on the side or semicircle on the side; when the vertical cross section is rectangular, the lateral thickness along the copper inner sleeve outward is 3-9mm and the height is 6-20mm; When the vertical section is a trapezoid placed sideways, the upper side of the trapezoid is 3-10mm long, the lower side is 6-20mm long, and the height is 3-9mm; when the vertical section is semicircular, the semicircular diameter is 6-20mm.

In the above method, the vertical section of the inner space of the copper inner sleeve is an isosceles trapezoid or an inverted isosceles trapezoid, and the angle between the side of the isosceles trapezoid or the side of the inverted isosceles trapezoid and the axis is θ=1°~ 8°.

In the above method, the inner side wall of the copper inner sleeve is provided with a plating layer, and the plating layer is a chromium plating layer, a Ni-Fe plating layer, a Ni-Co alloy plating layer, a Ni-Fe-W-Co alloy plating layer or a Ni-P alloy plating layer.

In the above method, the material of the mold shell is steel, the material of the upper cover plate and the mold water sealing plate is paramagnetic stainless steel, and the paramagnetic stainless steel is 304 stainless steel, 321 stainless steel or 347 stainless steel.

In the above method, when the reinforcing rib is composed of multiple circular ring bodies, the vertical distance between two adjacent circular ring bodies is 15-50mm; when the reinforcing rib is composed of multiple rows of arc-shaped bodies, the distance between two adjacent rows of arc-shaped bodies The vertical spacing is 15-50mm, and the horizontal spacing between two adjacent arc-shaped bodies in each row of arc-shaped bodies is 5-25mm; when the stiffener is formed into a grid by multiple toroids and multiple cylindrical bodies, two adjacent ones The vertical spacing of the ring body is 15-50mm. The columnar body is divided into a long columnar body and a short columnar body. The two ends of the long columnar body are respectively connected with the uppermost ring body and the lowermost ring body, and the short columnar The two ends of the body are respectively connected with two adjacent ring bodies.

In the above method, the cross section of the secondary cold water nozzle is circular, with a diameter of 0.5 to 3.5 mm.

In the above method, in the two sets of excitation coils, the aspect ratio of the two sets of excitation coils is set to 1:N at the same time, or the aspect ratio of one of the excitation coils is 1:N, then the aspect ratio of the other set of excitation coils It is N:1, where N=1～5.

In the above method, the number of turns of the excitation coil is 30～150, and the distance between two adjacent excitation coils is 10～50mm; the turns ratio of the two groups of excitation coils is 1:N, where N=0.2～5; The individual excitation coils are arranged from top to bottom with the axis of the mold as the axis.

In the above method, each coil in the two sets of excitation coils is arranged in the same direction, that is, the alternating current flowing into each coil flows in the same direction to ensure that the magnetic field lines of the magnetic field generated by each coil are the same.

In the above method, when the metal melt is copper or copper alloy, the thickness of the side wall of the copper inner sleeve is 8-20 mm.

In the above method, when the diameter of the ingot is less than 150mm, the thickness of the side wall of the copper inner sleeve is at least 8mm, when the diameter of the ingot is between 150 and 300mm, the thickness of the side wall of the copper inner sleeve is at least 10mm, and when the ingot diameter is greater than At 300mm, the side wall thickness of the copper inner sleeve should be at least 12mm.

In the above method, when the metal melt is copper or copper alloy, the hole diameter of the secondary cold water nozzle is 1～3.5mm; when the metal melt is aluminum, magnesium, aluminum alloy or magnesium alloy, the diameter of the secondary cold water nozzle hole is 0.5～3.5mm. 2.5mm.

In the above method, when alternating current or pulse current is applied to the two sets of excitation coils, the current intensity is 50-200A and the frequency is 10-30Hz; when the pulse current is applied, the duty ratio is 10-30%.

The device and method of the invention have strong applicability to round ingots or slabs.

The device and method of the present invention are also applicable to electromagnetic semi-continuous casting of steel.

The main technical principle of the present invention is: in view of the shortcoming of the small magnetic field generated by a single coil in the traditional electromagnetic continuous casting process, the excitation coil is divided into two groups and the phase difference current with a phase difference of 90° is passed through the adjustment coil. The height and the axial distance between the coils can significantly increase the strength and action area of the magnetic field in the molten metal, and increase the electromagnetic utilization; for the traditional copper inner sleeve, the thickness of the inner sleeve is large, which makes the magnetic field loss in the inner sleeve larger The disadvantage of reducing the effect and the magnetic field strength in the melt is to reduce the thickness of the inner sleeve, and apply different forms and distributions of reinforcing ribs for different casting alloys to increase the strength of the inner sleeve; the above method can be significantly increased Acting on the strength of the magnetic field and the area of action of the melt, it produces fine-grained, uniform ingots with good surface quality.

The beneficial effects of the invention

Beneficial effect

Through the above technical features, the present invention can achieve the following positive effects:

(1) The thickness of the copper inner sleeve is smaller than that of the traditional inner sleeve, which significantly improves the permeability and the electromagnetic utilization rate. It has a positive effect on the semi-continuous casting of copper alloy, aluminum alloy, magnesium alloy, steel and other metals;

(2) It has strong applicability to cast alloys of different sizes, specifications and types, and the thickness of the inner sleeve can be changed according to the different types of alloys, and differently distributed reinforcing ribs can be applied to strengthen the strength of the inner sleeve;

(3) According to the characteristics of different casting alloys, the excitation coil can adjust the turns ratio and aspect ratio of the coil, adjust the position of the excitation coil, and adjust the parameters of the phase current applied by the coil (current intensity I, frequency f) , The generated differential phase magnetic field can effectively improve the electromagnetic utilization rate and have a large permeability of the melt, which has a positive effect on the uniform distribution of the magnetic field in the metal melt;

(4) The electromagnetic force acts on the metal melt, does not directly contact the melt, does not introduce other impurities, and does not pollute the metal melt;

(5) The device has compact structure, high safety, simple assembly and easy maintenance.

Brief description of the drawings

Description of the drawings

Figure 1 is a schematic diagram of the cross-sectional structure of the non-ferrous metal and its alloy electromagnetic semi-continuous casting device in embodiment 1 of the present invention; in the figure, 1. the upper cover plate of the mold, 2. the mold shell, 3. the cooling water inlet, and 4. Bolt, 5. Coil pressing plate, 6. Coil support block, 7. Mould sealing plate, 8. Excitation coil, 9. Fastening bolt, 10. Sealing ring, 11. Copper inner sleeve, 12. Second cold water spray hole , 13, torus body, 14, arc-shaped body, 15, long columnar body, 16, short columnar body;

Figure 2 is a schematic diagram of the copper inner sleeve structure in the embodiment of the present invention; in the figure, (a) the reinforcing rib is composed of multiple circular ring bodies; (b) the reinforcing rib is composed of multiple rows of arc-shaped bodies, each row of arc-shaped The body has a number of single arc-shaped bodies, and each row of arc-shaped bodies is staggered in the vertical direction; (c) the stiffener is composed of a plurality of circular ring bodies and a plurality of columnar bodies forming a grid shape, and the columnar body is a long columnar body; (d) ) The reinforcing rib is composed of a plurality of circular ring bodies and a plurality of columnar bodies, and the columnar body is a short columnar body;

Figure 3 is a schematic diagram of the cross-sectional structure of the reinforcing rib in the embodiment of the present invention; in the figure, (a) the vertical cross-section is rectangular; (b) the vertical cross-section is trapezoidal; (c) the vertical cross-section is semicircular;

Figure 4 is a schematic diagram of the arrangement of excitation coils in the embodiment of the present invention; among them: (a) is the arrangement of two groups of excitation coils in sequence; (b) is the arrangement of two groups of excitation coils alternately;

Figure 5 is a cloud diagram of the magnetic induction intensity distribution in the molten metal with different excitation coil length-to-width ratios in Example 1 of the present invention; in the figure, (a) the excitation coil length-to-width ratio is 4:1; (b) the excitation coil length-to-width ratio 2:1; (c) the aspect ratio of the excitation coil is 1:1; (d) the aspect ratio of the excitation coil is 1:2; (e) the aspect ratio of the excitation coil is 1:4;

Fig. 6 is the Lorentz force distribution cloud diagram during one cycle after the two sets of coils are applied with the same phase pulse current in the embodiment 1 of the present invention; in the figure, T is the period; (a) 0.2T, (b) 0.4T , (C) 0.6T, (d) 0.8T, (e) 1T;

Fig. 7 is the Lorentz force distribution cloud diagram during one cycle after the pulse currents with a phase difference of 90° are applied to the two sets of coils in Example 1 of the present invention; in the figure, T is the period; (a) 0.2T, (b ) 0.4T, (c) 0.6T, (d) 0.8T, (e) 1T;

8 is a schematic diagram of the arrangement of the distance between two cold water injection holes in an embodiment of the present invention; in the figure, d is the diameter of the second cold water injection hole, and L is the distance between two adjacent second cold water injection holes;

Figure 9 is a macroscopic structure diagram of a Φ300mm pure copper ingot prepared in the comparative test of Example 3 of the present invention and traditional DC casting; in the figure, (a) traditional DC casting; (b) Example 3 of the present invention;

Figure 10 is a photograph of the appearance of a Φ300mm pure copper ingot prepared in a comparative test of Example 3 of the present invention and traditional DC casting; in the figure, (a) traditional DC casting; (b) Example 3 of the present invention;

Figure 11 is a macroscopic structure diagram of the AZ31 magnesium alloy prepared in the comparative test of Example 2 of the present invention and traditional DC casting; in the figure, (a) traditional DC casting; (b) Example 2 of the present invention;

12 is a graph showing the macrosegregation curve of major elements in the radius direction of the AZ31 magnesium alloy prepared in a comparative test between Example 2 of the present invention and conventional DC casting; in the figure, (a) conventional DC casting; (b) Example 2 of the present invention.

Invention embodiment

Embodiments of the invention

The copper inner sleeve used in the embodiment of the present invention is composed of an upper flange and a side wall, and the upper flange and the side wall are an integral structure.

In the embodiment of the present invention, the thickness of the side wall of the copper inner sleeve is 6-20 mm.

In the embodiment of the present invention, the vertical cross section of the reinforcing rib is rectangular, trapezoidal on the side or semicircle on the side; the structure is shown in Figure 3; when the vertical cross section is rectangular, the lateral thickness along the outer side of the copper inner sleeve 3～9mm, height 6～20mm; when the vertical section is a trapezoid placed on the side, the upper side of the trapezoid is 3-10mm long, the lower side is 6-20mm, and the height is 3-9mm; when the vertical section is semicircular, semicircular The diameter is 6-20mm.

In the embodiment of the present invention, the inner side wall of the copper inner sleeve is provided with a plating layer, and the plating layer is a chromium plating layer, a Ni-Fe plating layer, a Ni-Co alloy plating layer, a Ni-Fe-W-Co alloy plating layer or a Ni-P alloy plating layer.

In the embodiment of the present invention, the material of the mold shell is steel, the material of the upper cover plate and the mold water sealing plate is paramagnetic stainless steel, and the paramagnetic stainless steel is 304 stainless steel, 321 stainless steel or 347 stainless steel.

In the embodiment of the present invention, when the reinforcing rib is composed of multiple circular ring bodies 13, the vertical distance between two adjacent circular ring bodies 13 is 15-50mm; when the reinforcing rib is composed of multiple rows of arc-shaped bodies 14, two adjacent The vertical spacing of the rows of arc-shaped bodies 14 is 15-50mm, and the horizontal spacing of two adjacent arc-shaped bodies 14 in each row of arc-shaped bodies 14 is 5-25mm; when the reinforcing rib is composed of multiple circular ring bodies 13 and multiple columnar bodies In the case of a grid, the vertical distance between two adjacent ring bodies is 15-50mm. The columnar body is divided into a long columnar body 15 and a short columnar body 16. The two ends of the long columnar body 15 are respectively connected with the uppermost ring The body is connected to the bottom ring body 13, and the two ends of the short cylindrical body 16 are respectively connected to two adjacent ring bodies 13; the structure is shown in FIG. 2.

In the embodiment of the present invention, the vertical section of the inner space of the copper inner sleeve is an isosceles trapezoid or an inverted isosceles trapezoid, and the angle between the side of the isosceles trapezoid or the inverted isosceles trapezoid and the axis is θ=1°～8 °; When the casting alloy is copper or copper alloy, the vertical section is an inverted isosceles trapezoid; when the casting alloy is aluminum, magnesium, aluminum alloy or magnesium alloy, the vertical section is an isosceles trapezoid.

In the two groups of excitation coils in the embodiment of the present invention, the aspect ratio of one group of excitation coils is 1:N, and the aspect ratio of the other group of excitation coils is N:1, where N=1～5; The number of turns is 30～150, the distance between two adjacent excitation coils is 10～50mm, the turns ratio of the two groups of excitation coils is 1:N, where N=0.2～5; each excitation coil in the two groups of excitation coils is monomer Arrange from top to bottom, and take the crystallizer axis as the axis.

In the embodiment of the present invention, each coil in the two sets of excitation coils is arranged in the same direction, that is, the alternating current flowing into each coil flows in the same direction, which ensures that the magnetic field lines of the magnetic field generated by each coil are the same.

In the embodiment of the present invention, when the number of excitation coils in each group of excitation coils exceeds 1, the excitation coils in each group are arranged up and down, as shown in Figure 4(a); or the individual excitation coils in each group of excitation coils alternate Arrangement, as shown in Figure 4(b).

In the embodiment of the present invention, when the metal melt is copper or copper alloy, the upper flange has a thickness of 10-20 mm; when the metal melt is aluminum, magnesium, aluminum alloy or magnesium alloy, the upper flange has a thickness of 6-15 mm.

In the non-ferrous metal and its alloy electromagnetic semi-continuous casting device of the present invention, when the diameter of the prepared ingot is less than 200 mm, the copper inner sleeve is not provided with reinforcing ribs.

The magnet wire used in the excitation coil in the embodiment of the present invention is a commercially available double-layer polyimide-fluorine 46 composite film-coated rectangular copper wire.

In the embodiment of the present invention, among the excitation coil monomers, the level of the lowest excitation coil monomer is higher than the height of the center of the liquid cavity of the molten metal in the mold.

In the embodiment of the present invention, when there is no molten metal inside the mold, the magnetic induction intensity inside the copper inner sleeve is 20-200 mT when the excitation coil generates a magnetic field.

In the embodiment of the present invention, the cross section of the second cold water nozzle hole is circular; when the metal melt is copper or copper alloy, the diameter of the second cold water nozzle hole is 1～3.5mm; when the metal melt is aluminum, magnesium, aluminum alloy or magnesium When alloying, the diameter of the second cold water nozzle hole is 0.5-2.5mm; when the metal melt is copper or copper alloy, the distance between two adjacent second cold water nozzle holes is 3 to 5 times the diameter of the second cold water nozzle hole; When the body is aluminum, magnesium, aluminum alloy or magnesium alloy, the distance between two adjacent secondary cooling water nozzle holes is 2 to 4 times the diameter of the secondary cooling water nozzle; the structure is shown in Figure 8.

In the embodiment of the present invention, when the metal melt is copper or copper alloy, the thickness of the side wall of the copper inner sleeve is 8-20 mm.

In the embodiment of the present invention, when the diameter of the ingot is less than 150mm, the thickness of the side wall of the copper inner sleeve is at least 8mm. When the diameter of the ingot is between 150 and 300mm, the thickness of the side wall of the copper inner sleeve is at least 10mm. When the diameter is greater than 300mm, the side wall thickness of the copper inner sleeve shall be at least 12mm.

In the embodiment of the present invention, when the metal melt is copper or copper alloy, the diameter of the second cold water nozzle hole is 1～3.5mm; when the metal melt is aluminum, magnesium, aluminum alloy or magnesium alloy, the diameter of the second cold water nozzle hole 0.5～2.5mm.

In the embodiment of the present invention, when alternating current is applied to the two sets of excitation coils, the current intensity is 50-200A and the frequency is 10-30Hz.

In the embodiment of the present invention, paramagnetic stainless steel is selected as the material of the upper cover plate and the sealing water plate, so that the phase difference magnetic field generated by the two sets of excitation coils can pass smoothly and the magnetic lines of force are not deformed. The material of the mold shell is ordinary steel, so that the magnetic field It is not easy to pass through the mold shell, reducing the loss of the magnetic field in the outside world.

In the embodiment of the present invention, because the thickness of the side wall of the copper inner sleeve is relatively thin, considering that there is a huge temperature gradient in the copper inner sleeve during the semi-continuous casting process, thermal deformation will occur. The cross-sectional shape and different forms of reinforcing ribs strengthen the strength of the inner sleeve.

In the embodiment of the present invention, the current used is a phase difference current. The phase difference currents are respectively fed into the two sets of excitation coils to generate a phase difference magnetic field to act on the metal melt; a set of excitation coils is fed with a current with an initial phase of 0° , The other set of coils is fed with a current with an initial phase of 90°; the axial distance between each excitation coil is adjusted by the height of the coil support block.

Example 1

The non-ferrous metal and its alloy electromagnetic semi-continuous casting device includes a mold and an excitation coil system; the structure is shown in Figure 1. The mold is composed of an upper cover plate 1, a mold shell 2, a copper inner sleeve 11, and a mold water sealing plate 7. The upper part of the mold shell 2 is provided with a cooling water inlet 3, and the bottom of the copper inner sleeve 11 is provided with two cold water spray holes 12;

The vertical section of the inner space of the copper inner sleeve 11 is an inverted isosceles trapezoid;

The upper part of the upper cover plate 1 of the mold is fixed to the upper flange of the copper inner sleeve 11 by bolts, and is connected in a sealed manner by a sealing ring 10;

The upper part of the mold shell 2 is fixedly connected with the upper cover plate 1 of the mold through the fastening bolt 9; the bottom of the mold shell 2 is fixedly connected with the mold water sealing plate 7 through the fastening bolt 9;

The mold water sealing plate 7 is ring-shaped, and is fixed with the mold shell 2 by fastening bolts 9 and is connected in a sealed manner by a sealing ring 10;

The excitation coil system is fixed in the cooling water tank between the mold shell 2 and the copper inner sleeve 11, and consists of a fixing bolt 4, a coil pressing plate 5, a coil support block 6 and an excitation coil 8;

The fixing bolt 4 is welded and fixed to the bottom of the mold shell 2; a number of coil pressing plates 5 are fixed on the fixing bolts 4; each excitation coil 8 and each coil support block 6 are arranged alternately up and down, and between two adjacent coil pressing plates 5 There is only one coil support block 6 between; the coil support block 6 and the excitation coil 8 are pressed and fixed by the fixing bolt 4, the coil pressing plate 5 and the bottom of the mold shell 2;

The outer side wall of the copper inner sleeve 11 is provided with reinforcing ribs 13. The reinforcing ribs 13 and the side walls of the copper inner sleeve 11 are an integral structure. The reinforcing ribs 13 are composed of multiple circular ring bodies, as shown in Figure 2(a). Show

The excitation coil 8 is divided into two groups, each of the two groups of excitation coils is connected in series, and each group is connected to a power source;

Using the above device, a numerical simulation of the magnetic field distribution in the magnesium alloy melt under different coil length-to-width ratios (4:1, 2:1, 1:1, 1:2, 1:4) was carried out. There are two sets of fixed excitation coils, the number of coil turns is 40 turns, one for each group. The two sets of coils are located at the center of the height of the magnesium alloy melt and the distance between the two sets of coils is 10mm. Pulse current with a phase of 0°, the lower coil is fed with a pulse current with an initial phase of 90°, and the electromagnetic parameters of the pulse current are set to current intensity I=80A, frequency f=20Hz, duty cycle D=20% ; The results of the numerical simulation are shown in Figure 5; the simulation results show that changing the aspect ratio of the coil can effectively change the size and distribution of the magnetic induction intensity in the melt; the smaller the coil aspect ratio, the smaller the magnetic induction intensity in the melt Decrease, but the distribution area in the melt increases and the uniformity of the distribution is better;

The two sets of coils are respectively fed with pulse currents of the same phase and pulse currents with a phase difference of 90°; numerical simulation of the Lorentz force distribution in the molten metal in the two cases, the Lorentz force distribution in one cycle Cloud diagrams are shown in Figure 6 and Figure 7; the number of turns of the two sets of coils is 40 turns, one for each set, the axial distance between the coils is 30mm, and the phase difference is 90°, the upper excitation coil flux Into the pulse current with the initial phase of 0°, the lower coil enters the pulse current with the initial phase of 90°, and the electromagnetic parameters of the pulse current are set to current intensity I=80A, frequency f=20Hz, and duty cycle D= 20%; the simulation results show that the Lorentz force in the melt does not change much when the unidirectional pulse current and the phase difference pulse current are applied, but under the action of the phase difference magnetic field, Lorentz force The maximum force will alternately change the center plane positions of the two sets of coils in the melt, which will make the flow field, temperature field and solute field in the melt more evenly distributed under the action of a unidirectional magnetic field, and significantly improve the metallurgical quality of the metal ingot; Therefore, the difference phase magnetic field under the same electromagnetic parameters has a better stirring effect on the molten metal than the unidirectional magnetic field.

Example 2

The structure of the device is the same as that of Embodiment 1, the difference is: the axial distance between the two coils is 20-40mm, the vertical section of the inner space of the copper inner sleeve is an isosceles trapezoid, the diameter is 320mm, the thickness is 8mm, and no reinforcement is provided. Rib, the current flowing into the excitation coil is harmonic current;

Use the above device to

For continuous casting of AZ31 magnesium alloy in the mold, the cooling water is first introduced into the cooling water tank, and the cooling water is sprayed from the second cooling water nozzle; the metal melt is introduced into the mold to make the level of the metal melt reach a predetermined height; The metal melt is a non-ferrous metal or a non-ferrous metal alloy;

The two sets of excitation coils are fed with harmonic currents of different initial phases through the power supply, so that each set of excitation coils generates a set of electromagnetic signals, and each forms a harmonic magnetic field; the phase difference of the alternating currents through the two sets of excitation coils is 90 °, the formed difference-phase harmonic magnetic field acts on the molten metal in the mold;

Start the non-ferrous metal and its alloy electromagnetic semi-continuous casting device for casting. The casting temperature is 720℃, the casting speed is 1.12mm/s, the cooling water volume is 10.5-12.5m ³ /h, and the intensity of the phase current is 50-80A. The frequency is 10～30Hz, the second cold water sprayed through the second cold water nozzle cools the ingot under the mold until the casting is completed;

The same magnesium alloy was prepared by traditional DC casting for comparative experiments; the macrostructure is shown in Figure 11, it can be seen from the figure that the columnar crystals of the traditional DC casting ingot are coarse, and the ingot grains obtained by the above method are fine and uniformly distributed; The comparison of the macro-segregation of the main elements in the ingot radius direction is shown in Figure 12. It can be seen from the figure that the macro-segregation of the ingot elements cast by the above method is smaller and more uniform than the traditional DC casting.

Example 3

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

(1) The stiffener is composed of 5 rows of arc-shaped bodies, as shown in Figure 2(b);

(2) Each group of excitation coils is composed of two excitation coils, the arrangement is shown in Figure 4(a); the axial distance of adjacent excitation coils is 30-50mm,

(3) The vertical section of the inner space of the copper inner sleeve is an inverted isosceles trapezoid, with a side wall thickness of 10mm;

Using the above device to prepare pure copper ingots,

The casting temperature is 1180℃, the casting speed is 4m/h, the cooling water pressure is 34～38m ³ /h, there are two sets of excitation coils fixed in the mold, the current intensity is 200A, the frequency is 20Hz, and the duty cycle is 20%;

Using traditional DC casting to prepare the same pure copper ingots for comparative experiments; the macrostructure photo is shown in Figure 9; it can be seen from the figure that the columnar crystals of the ingots obtained by the method of this embodiment are smaller, and the small equiaxed crystal regions are significantly increased; The appearance photo is shown in Fig. 10, which shows that the surface of the ingot obtained by traditional DC casting has obvious defects such as wrinkles, while the surface of the ingot obtained in this embodiment is smoother and has better surface quality.

Claims

An electromagnetic semi-continuous casting method for non-ferrous metals and their alloys is characterized in that an electromagnetic semi-continuous casting device for non-ferrous metals and their alloys is used. The device includes a mold and an excitation coil system; the mold is composed of an upper cover plate, a mold shell, and copper The cooling water inlet is provided on the upper part of the mold shell and the bottom of the copper inner sleeve is provided with two cold water spray holes; the excitation coil system is fixed between the mold shell and the copper inner sleeve for cooling In the water tank, it is composed of fixing bolts, coil pressing plate, coil support block and excitation coil; among them, the outer side wall of the copper inner sleeve is equipped with or without reinforcing ribs. When there are reinforcing ribs, the reinforcing ribs and the copper inner sleeve As a one-piece structure, the reinforcing rib is composed of multiple circular ring bodies, or composed of multiple rows of arc-shaped bodies, or composed of multiple circular ring bodies and multiple columnar bodies; the side wall of the copper inner sleeve The thickness is 6-20mm; the excitation coils are divided into two groups, each of the two groups of excitation coils is connected in series, and each is connected to the power source;

The method is:

(1) Pour cooling water into the cooling water tank, and the cooling water is sprayed from the second cold water nozzle; the molten metal is introduced into the mold to make the liquid level of the molten metal reach a predetermined height; the molten metal is non-ferrous Metal or non-ferrous metal alloy;

(2) The two sets of excitation coils are supplied with alternating current or pulse current through the power supply, so that each group of excitation coils generates a set of alternating electromagnetic signals or pulse electromagnetic signals, each forming a magnetic field; the two sets of excitation coils are connected The phase difference of the alternating current or pulse current is 90°, and the resulting phase difference magnetic field acts on the molten metal in the mold;

(3) Start the non-ferrous metal and its alloy electromagnetic semi-continuous casting device to cast the molten metal, and the second cold water sprayed from the second cold water nozzle to cool the ingot below the mold until the casting is completed.
An electromagnetic semi-continuous casting method for non-ferrous metals and their alloys according to claim 1, wherein the vertical cross section of the reinforcing ribs is rectangular, trapezoidal on the side or semicircular on the side; when the vertical section is When it is rectangular, the lateral thickness along the copper inner sleeve is 3-9mm and the height is 6-20mm; when the vertical section is a trapezoid placed on the side, the upper side of the trapezoid is 3-10mm long, the lower side is 6-20mm, and the height 3-9mm ; When the vertical section is a semicircle, the diameter of the semicircle is 6-20mm.
The electromagnetic semi-continuous casting method of non-ferrous metals and their alloys according to claim 1, wherein the vertical section of the inner space of the copper inner sleeve is an isosceles trapezoid or an inverted isosceles trapezoid, an isosceles trapezoid The angle between the side or the side of the inverted isosceles trapezoid and the axis is θ=1°～8°.
The electromagnetic semi-continuous casting method of non-ferrous metals and their alloys according to claim 1, wherein in the two sets of excitation coils, the aspect ratio of the two sets of excitation coils is set to 1:N at the same time, or one of them The aspect ratio of one group of excitation coils is 1:N, and the aspect ratio of another group of excitation coils is N:1, where N=1～5.
An electromagnetic semi-continuous casting method for non-ferrous metals and their alloys according to claim 1, wherein when the reinforcing rib is composed of a plurality of circular ring bodies, the vertical distance between two adjacent circular ring bodies is 15-50mm; When the reinforcing rib is composed of multiple rows of arc-shaped bodies, the vertical distance between two adjacent rows of arc-shaped bodies is 15-50mm, and the horizontal distance between two adjacent arc-shaped bodies in each row of arc-shaped bodies is 5-25mm; When a circular ring body and a plurality of columnar bodies form a grid, the vertical distance between two adjacent circular ring bodies is 15-50mm. The columnar body is divided into a long columnar body and a short columnar body. The two ends of the long columnar body They are respectively connected with the uppermost annular body and the lowermost annular body, and the two ends of the short columnar body are respectively connected with two adjacent annular bodies.
The electromagnetic semi-continuous casting method of non-ferrous metals and their alloys according to claim 1, characterized in that the number of turns of the excitation coil is 30-150, and the distance between two adjacent excitation coils is 10-50mm; The turns ratio of the coil is 1:N, where N=0.2-5; the individual excitation coils in the two sets of excitation coils are arranged from top to bottom, and the axis of the mold is taken as the axis.
An electromagnetic semi-continuous casting method for non-ferrous metals and their alloys according to claim 1, wherein when the diameter of the ingot is less than 150mm, the thickness of the side wall of the copper inner sleeve is at least 8mm, and when the diameter of the ingot is between 150 and 300mm In between, the side wall thickness of the copper inner sleeve is at least 10mm. When the ingot diameter is greater than 300mm, the side wall thickness of the copper inner sleeve is at least 12mm.