CN112481535B

CN112481535B - Magnesium alloy ingot and preparation method thereof

Info

Publication number: CN112481535B
Application number: CN202011218613.4A
Authority: CN
Inventors: 康心锴; 刘宝龙; 曾钢; 肖宏超; 黄硕
Original assignee: Aerospace Science and Industry Changsha New Materials Research Institute Co Ltd
Current assignee: Aerospace Science and Industry Changsha New Materials Research Institute Co Ltd
Priority date: 2020-11-04
Filing date: 2020-11-04
Publication date: 2022-12-09
Anticipated expiration: 2040-11-04
Also published as: CN112481535A

Abstract

The invention aims to provide a magnesium alloy ingot and a preparation method thereof, aiming at the components with the mass percentage of alloy: al:3.5-5.0%, zn:2.0-3.5%, the sum of Al content and Zn content is: al + Zn is more than or equal to 6% and less than or equal to 8%, mn:0.1-0.8%, RE:0.01-0.80%, ca:0.001-0.090%, fe is less than or equal to 0.005%, si is less than or equal to 0.05%, cu is less than or equal to 0.005%, ni is less than or equal to 0.005%, the total content of impurities is less than or equal to 0.1%, and the balance is Mg. The invention combines mechanical stirring refining and gas stirring refining, obviously improves the cleanliness of the melt and the distribution uniformity of alloy elements in the melt through low-temperature standing, and finally prepares the novel high-ductility medium-strength magnesium alloy cast rod with uniform structure, fine crystal grains, less internal defects and high surface quality.

Description

Magnesium alloy ingot and preparation method thereof

Technical Field

The invention belongs to the technical field of metal materials and metallurgy, and particularly relates to a novel high-ductility medium-strength magnesium alloy semi-continuous casting method and an ingot prepared by the method.

Background

The magnesium alloy is the lightest metal structural material in practical application, the density of the magnesium alloy is only 2/3 of that of aluminum alloy and 1/4 of that of steel, and meanwhile, the magnesium alloy has the advantages of high specific strength and specific stiffness, good thermal conductivity, excellent electromagnetic shielding and damping performances, good cutting processability and the like. Therefore, the magnesium alloy is an ideal lightweight structural material, and has a very wide application market in the fields of aerospace, automobiles, rail transportation, 3C and the like.

Pure magnesium has low absolute strength, and an alloying method is usually needed to be adopted to add alloying elements such as Al, zn, ca, mn or rare earth elements into pure magnesium to increase the strength of the pure magnesium, for example, adding Al and Zn with appropriate contents into the pure magnesium can effectively improve the mechanical property and the processing property of magnesium alloy, which is one of the important reasons that Mg-Al-Zn series magnesium alloy becomes the most common commercial magnesium alloy, but the proportion of the alloying elements Al and Zn has great influence on the mechanical property and the processing deformation of the magnesium alloy.

The novel high-ductility medium-strength magnesium alloy is independently designed and developed by adjusting the content of Al and Zn elements and adding a proper amount of rare earth elements such as Gd, Y and the like in the earlier stage of the team, and after deformation processing and aging treatment, the tensile strength is more than or equal to 330MPa, the yield strength is more than or equal to 240MPa, and the elongation is more than or equal to 20%. The magnesium has large solidification interval and small heat capacity, so that the magnesium alloy is easy to generate casting defects such as cracks, uneven filling, segregation and the like in the smelting process, meanwhile, the addition of different elements greatly changes the liquid-solid phase line in the cooling process of the magnesium alloy, the solid-liquid state has great influence on the solidification process of the magnesium alloy in the casting process, and the addition of rare earth elements can also influence the segregation and the structural uniformity. Therefore, it is necessary to develop a casting process of high ductility medium strength magnesium alloy for Al and Zn addition.

The invention discloses a novel high-ductility medium-strength magnesium alloy developed based on autonomous design, and a novel casting process flow is developed aiming at the magnesium alloy. The casting process flow can reduce the probability of defects such as inclusions and the like and obviously improve the yield of large-size magnesium alloy cast rods; on the other hand, the mechanical property of the material can be effectively improved, and the application range of the magnesium alloy material is expanded. By adopting the technical scheme, the magnesium alloy ingot with uniform structure, refined crystal grains, flat and smooth surface and less internal defects is successfully prepared, and the ingot quality is effectively improved.

Disclosure of Invention

In view of this, the invention aims to provide a casting preparation method of a high-ductility medium-strength magnesium alloy, which adopts an improved semicontinuous casting process to overcome the defects of coarse grains, segregation, cold shut and the like easily occurring in the magnesium alloy in the casting process, so as to inhibit macroscopic segregation, improve the quality and yield of an ingot and provide guarantee for subsequent deformation processing.

The invention provides a semi-continuous casting method of magnesium alloy, which comprises the following components in percentage by mass: 3.5 to 5.0 percent

Zn：2.0-3.5％

The sum of the Al content and the Zn content is as follows: al + Zn is more than or equal to 6 percent and less than or equal to 8 percent

Mn：0.1-0.8％

RE：0.01-0.80％

Ca：0.001-0.090％

Other inevitable impurity elements and the balance of magnesium.

The RE refers to rare earth elements.

The preparation process also comprises the following steps:

(1) Preparing raw materials with corresponding proportion according to the mass percentage of the components of the magnesium alloy, and baking and preheating the raw materials;

(2) Sequentially adding the raw materials into a smelting furnace for smelting, wherein the smelting temperature is 660-790 ℃;

(3) After the raw materials are completely melted, adjusting the temperature of the melt to 700-720 ℃, and carrying out mechanical stirring refining for 30-70min at a mechanical stirring speed of 100-160r/min; then, heating the melt to 730-750 ℃, keeping the temperature for 20-50min, removing oxidized slag on the surface layer of the melt, introducing argon to the bottom of the melt, stirring and refining the gas for 15-60min, wherein the gas flow is 20-40L/h;

(4) After refining is finished, standing the melt, cooling to 620-650 ℃, preserving heat for 2-6h, and then heating the melt to 670-700 ℃;

(5) And (3) draining the melt into an inner cavity of a crystallizer through a splitter plate, wherein when the casting is stable, the temperature of the melt in the crystallizer is 650-675 ℃, the ingot pulling speed is 30-90mm/min, and the cooling water flow is 60-90L/min, so that the magnesium alloy ingot is obtained.

Further, after mechanical stirring and refining in the step (3), uniformly spreading a covering agent on the surface of the melt, and then heating.

Further, in the step (5), the height of the melt from the top of the crystallizer is 40-70mm, the depth of the liquid cavity is 30-80mm, and finally the magnesium alloy ingot with the diameter phi of 100-500mm is obtained.

Furthermore, the magnesium alloy material comprises inevitable impurity elements such as Fe, si, cu, ni and the like, wherein Fe is less than or equal to 0.005%, si is less than or equal to 0.05%, cu is less than or equal to 0.005%, ni is less than or equal to 0.005%, and the total content of impurities is not more than 0.1%.

Further, the mass percent of the alloy component Al is 4.0-5.0%.

Further, the mass percent of the alloy component Zn is 2.0-3.0%.

Further, the sum of the Al content and the Zn content of the alloy components is as follows: al and Zn are more than or equal to 6.5 percent and less than or equal to 8.0 percent.

Further, the mass percent of Mn in the alloy component is 0.2-0.6%.

Furthermore, the RE element of the alloy component comprises Gd, Y or a mixed element of the Gd and the Y, and the mass percentage is 0.05-0.50%.

When Gd and Y are mixed as the alloy component RE, the mass ratio of Gd: Y = (0.01 to 100): 1 is further provided.

Further, the mass percentage of the alloy component Ca is 0.002-0.060%.

In the step (1), selecting appropriate raw materials according to alloy components is a conventional means of a person skilled in the art, the addition form of Mg, al and Zn elements can be a pure metal ingot or an intermediate alloy, and the addition form of Mn, RE and Ca is an intermediate alloy. Further preferably, in the step (1), high-purity magnesium ingots, high-purity aluminum ingots, high-purity zinc ingots, al-Mn intermediate alloys, mg-RE intermediate alloys and Mg-Ca intermediate alloys are selected as raw materials.

Further, in order to remove moisture, reduce the hydrogen content of the cast rod and ensure the casting quality, the raw materials are placed in a drying furnace or a smelting furnace for baking and preheating. Preferably, the raw materials are put into a drying furnace for baking and preheating, wherein the preheating temperature is 150-250 ℃, and the time is 30-120min.

In the step (2), the dried high-purity aluminum ingot, the high-purity zinc ingot, the Al-Mn intermediate alloy, the Mg-RE intermediate alloy and the Mg-Ca intermediate alloy are sequentially put into a smelting furnace for smelting, and argon is introduced for stirring after raw materials are added each time. Furthermore, in order to prevent the melt from being oxidized and burnt, the covering agent is uniformly scattered on the surface of the melt every time the raw materials are added.

Further, after the added raw materials are completely melted, the surface is subjected to slag skimming. And after slagging off, putting a stirring paddle into the melt, simultaneously adding a covering agent into the furnace, starting the stirring paddle to carry out mechanical stirring refining, wherein the refining time is 30-60min, and the mechanical stirring speed is 120-160r/min. The mechanical stirring can ensure that the alloy liquid is dispersed more fully, is beneficial to the uniform dispersion of alloy elements in the melt, and reduces the tendency of the macrosegregation of the cast ingot.

Furthermore, in order to improve the smelting quality, a layer of covering agent is uniformly scattered on the surface of the melt after mechanical stirring and refining.

Further, in order to ensure the stability of the temperature, the temperature of the melt is raised to 730-745 ℃, and the temperature is kept for 20-40min after the temperature is raised. And after the heat preservation time is up, removing surface oxidation slag inclusion, introducing argon gas to the bottom of the melt, stirring the melt, adding a covering agent, and carrying out gas stirring refining, wherein the refining time is 20-50min, and the gas flow is 30-40L/h. In the upwelling process of the melt, the argon can discharge part of slag inclusion in the melt and gas brought in by stirring to the surface, and meanwhile, under the stirring action of the argon, the covering agent can fully wrap impurities in the melt to sink or float to the surface, so that the components of the melt are more uniform in all directions, particularly in the height direction, and the macroscopic segregation is effectively reduced under the combined action of the covering agent and the melt.

And (5) further, standing the melt in the step (4), cooling to 620-640 ℃, and then preserving heat for 2-4h. The inclusion can completely float on the upper layer of the melt or precipitate at the bottom of the melt by cooling and standing for a long time, the content of the impurity Fe element in the melt is greatly reduced, the cleanliness of the melt is improved, and the quality of a final product is further improved. In addition, the temperature reduction can obviously reduce the burning loss of RE and Ca elements in the melt, and good element yield is obtained after casting.

In the step (5), argon or nitrogen is introduced to extrude the melt out of the smelting furnace, and in order to ensure that the cross section of the inner cavity of the crystallizer is uniformly filled with the melt, the melt is preferably guided to flow into the inner cavity of the crystallizer through a splitter plate, and meanwhile, inert gas is introduced above the liquid level of the melt to protect the melt and prevent oxidation.

Preferably, the diameter of the semi-continuous casting splitter disc is as follows: the diameter phi of the cast ingot is 100-250mm, and the diameter phi of the diverter disc is 50-120mm; the diameter of the cast ingot is 250-400mm, and the diameter of the diverter disc is 120-180mm; the diameter of the cast ingot is 400-500mm, and the diameter of the diverter disc is 180-220mm.

Preferably, the stable ingot pulling speed of the semi-continuous casting provided by the invention is as follows: the diameter of the casting blank is phi 100-250mm, and the ingot pulling speed is 70-90mm/min; the diameter phi is 250-400mm, and the ingot pulling speed is 40-70mm/min; the diameter phi is 400-500mm, and the ingot pulling speed is 30-40mm/min.

The invention also provides a magnesium alloy ingot, which is obtained by adopting the preparation method.

Has the advantages that:

1. the invention firstly adopts a method of combining mechanical stirring refining and gas stirring refining for refining, so that the melt is more fully refined, the alloy components in the melt are more uniformly dispersed, and the generation of inclusions is reduced.

2. The invention adopts long-time cooling and standing, obviously improves the melt quality and the yield of RE and Ca elements, reduces the investment of high-price Mg-RE and Mg-Ca master alloy, and ensures the high quality and lower cost of the casting rod material.

3. By adopting the improved semi-continuous casting process, the defects of coarse grains, segregation, cold shut and the like easily generated in the magnesium alloy in the casting process are overcome, so that the macrosegregation is inhibited, the quality and yield of the cast ingot are improved, and the guarantee is provided for the subsequent deformation processing.

Drawings

FIG. 1 is a picture of a magnesium alloy ingot with a diameter of 270mm prepared by the method.

FIG. 2 is a picture of a magnesium alloy ingot with a diameter of 355mm prepared by the method.

FIG. 3 is a picture of a magnesium alloy ingot with a diameter of 170mm prepared by the method.

FIG. 4 is an optical microstructure of a magnesium alloy prepared by the present invention and having a diameter of 270 mm.

Detailed Description

The present invention will be described in detail with reference to specific examples. The following examples will aid those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any manner. It should be noted that variations and modifications can be made by persons skilled in the art without departing from the spirit of the invention. All falling within the scope of the present invention.

All reagent starting materials are commercially available in the following examples.

The optical microstructure of the ingot in example 1 was measured by a metallographic microscope.

Example 1:

according to the component content Al:4.3%, zn:2.8%, mn:0.2%, gd:0.53%, Y:0.02%, ca:0.036 percent, and the balance being the component requirement of Mg, and sequentially adding a high-purity magnesium ingot, a high-purity aluminum ingot, a high-purity zinc ingot, an Al-Mn intermediate alloy, an Mg-RE intermediate alloy and an Mg-Ca intermediate alloy into a smelting furnace. After the raw materials are completely melted, adjusting the temperature of the melt to 700 ℃, mechanically stirring and refining for 60min at a mechanical stirring speed of 120r/min, then heating the melt to 730 ℃, preserving heat for 30min, stirring and refining for 60min with gas at a gas flow rate of 20L/h, standing and cooling the melt to 620 ℃ after the gas refining, preserving heat for 4h, then heating to 670 ℃, and preparing for semi-continuous casting. The semi-continuous casting ingot-pulling speed is 60mm/min, the cooling water flow is 65L/min, a magnesium alloy cast rod with the diameter of 270mm is cast, the surface quality is high, cracks and obvious cold shut are avoided, the microstructure is uniform, as shown in figures 1 and 4, ultrasonic flaw detection is carried out after the ingot blank surface layer is skinned, and the statistical result of the yield which can reach the A-level flaw detection standard is shown in table 1.

Example 2:

according to the component content Al:3.5%, zn:3.5%, mn:0.4%, gd:0.12%, Y:0.20%, ca:0.051 percent of magnesium ingot, high-purity aluminum ingot, high-purity zinc ingot, al-Mn intermediate alloy, mg-RE intermediate alloy and Mg-Ca intermediate alloy are added into the smelting furnace in sequence according to the component requirements of Mg for the rest. After the raw materials are completely melted, adjusting the melt temperature to 712 ℃, mechanically stirring and refining for 40min at a mechanical stirring speed of 150r/min, then heating the melt to 730 ℃, keeping the temperature for 30min, stirring and refining for 35min with gas at a gas flow rate of 30L/h, standing and cooling the melt to 640 ℃ after the gas refining, keeping the temperature for 3h, then heating to 700 ℃, and preparing for semi-continuous casting. The semi-continuous casting ingot-pulling speed is 50mm/min, the cooling water flow is 80L/min, a magnesium alloy cast rod with the diameter of 355mm is cast, the surface quality of an ingot blank is high, no crack exists, and obvious cold shut is achieved, as shown in figure 2. The statistical results of the yield which can reach the A-level flaw detection standard are shown in Table 1 after the ingot blank is skinned on the surface layer and is subjected to ultrasonic flaw detection.

Example 3:

according to the component content Al:5%, zn:2.8%, mn:0.3%, gd:0.13%, ca:0.023 percent and the balance of Mg according to the requirements of components, and sequentially adding a high-purity magnesium ingot, a high-purity aluminum ingot, a high-purity zinc ingot, an Al-Mn intermediate alloy, an Mg-RE intermediate alloy and an Mg-Ca intermediate alloy into a smelting furnace. After the raw materials are completely melted, adjusting the temperature of the melt to 710 ℃, mechanically stirring and refining for 50min at a mechanical stirring speed of 120r/min, then heating the melt to 740 ℃, preserving heat for 30min, stirring and refining for 50min with gas at a gas flow rate of 30L/h, standing and cooling the melt to 630 ℃ after the gas refining, preserving heat for 4h, then heating to 690 ℃, and preparing for semi-continuous casting. The semi-continuous casting ingot-pulling speed is 80mm/min, the cooling water flow is 65L/min, magnesium alloy cast rods with the diameter of 170mm are cast, and the surface quality of ingot blanks is high, cracks do not exist, and obvious cold shut is achieved, as shown in figure 3. The statistical results of the yield which can reach the A-level flaw detection standard are shown in Table 1 after the ingot blank is skinned.

Comparative example 1:

according to the component content Al:4.3%, zn:2.8%, mn:0.2%, gd:0.53%, Y:0.02%, ca:0.036 percent, and the balance of Mg, and adding a high-purity magnesium ingot, a high-purity aluminum ingot, a high-purity zinc ingot, an Al-Mn intermediate alloy, an Mg-RE intermediate alloy and an Mg-Ca intermediate alloy into a smelting furnace in sequence. And after the raw materials are completely melted, adjusting the temperature of the melt to 740 ℃, keeping the temperature for 30min, stirring and refining the gas for 50min, keeping the gas flow rate at 30L/h, standing the melt after the gas refining, cooling to 630 ℃, keeping the temperature for 4h, then heating to 690 ℃, and preparing for semi-continuous casting. The semi-continuous casting ingot-pulling speed is 60mm/min, the cooling water flow is 65L/min, and a magnesium alloy cast rod with the diameter of 270mm is cast. The statistical results of the yield which can reach the A-level flaw detection standard are shown in Table 1 after the ingot blank is subjected to ultrasonic flaw detection after the surface layer is turned into a skin, and the comparison shows that the ultrasonic flaw detection results in the ingot blank after casting without mechanical stirring and refining in comparative example 1 are obviously inferior to those in examples 1-3.

Comparative example 2:

according to the component content Al:4.3%, zn:3.1%, mn:0.3%, gd:0.23%, ca:0.042 percent and the balance of Mg, and adding a high-purity magnesium ingot, a high-purity aluminum ingot, a high-purity zinc ingot, an Al-Mn intermediate alloy, an Mg-RE intermediate alloy and an Mg-Ca intermediate alloy into the smelting furnace in sequence. And after the raw materials are completely melted, adjusting the melt temperature to 710 ℃, mechanically stirring and refining for 50min at a mechanical stirring speed of 120r/min, standing and cooling the melt to 630 ℃ after mechanical stirring and refining, preserving heat for 4h, and then heating to 690 ℃ to prepare semi-continuous casting. The semi-continuous casting ingot-pulling speed is 60mm/min, the cooling water flow is 65L/min, and a magnesium alloy cast rod with the diameter of 270mm is cast. The ultrasonic flaw detection test is carried out after the surface layer of the ingot blank is turned into a skin, the statistical result of the yield which can reach the A-level flaw detection standard is shown in the table 1, and the comparison shows that the ultrasonic flaw detection result in the ingot blank after the comparative example 2 is stirred, refined and cast without gas is obviously inferior to that in the examples 1-3.

Comparative example 3:

according to the component content Al:4.3%, zn:2.8%, mn:0.2%, gd:0.53%, Y:0.02%, ca:0.036 percent, and the balance of Mg, and adding a high-purity magnesium ingot, a high-purity aluminum ingot, a high-purity zinc ingot, an Al-Mn intermediate alloy, an Mg-RE intermediate alloy and an Mg-Ca intermediate alloy into a smelting furnace in sequence. After the raw materials are completely melted, adjusting the temperature of the melt to 700 ℃, mechanically stirring and refining for 60min at a mechanical stirring speed of 120r/min, then heating the melt to 730 ℃, keeping the temperature for 30min, stirring and refining for 60min with gas at a gas flow rate of 20L/h, standing and cooling the melt to 620 ℃ after the gas refining, keeping the temperature for 1h, then heating to 670 ℃, and preparing for semi-continuous casting. The speed of semi-continuous casting ingot pulling is 60mm/min, the cooling water flow is 65L/min, and magnesium alloy cast rods with phi 270mm are cast. The ultrasonic flaw detection test is carried out after the ingot blank is skinned on the surface layer, the statistical result of the yield which can reach the A-level flaw detection standard is shown in the table 1, and the comparison shows that the standing and heat preservation time of the comparative example 3 is short, and the ultrasonic flaw detection result in the ingot blank after casting is obviously inferior to that of the examples 1-3.

TABLE 1 ultrasonic testing results of examples and comparative examples

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made to the present invention by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A semi-continuous casting method of magnesium alloy is characterized in that: the selected magnesium alloy comprises the following components in percentage by mass: al:3.5-5.0%, zn:2.8-3.5%, the sum of Al content and Zn content is: al + Zn is more than or equal to 6% and less than or equal to 8%, mn:0.1-0.8%, RE:0.01-0.80%, ca:0.001-0.090%, other inevitable impurity elements and the balance of magnesium, wherein RE refers to rare earth elements;

the semi-continuous casting method comprises the following steps:

(3) When the raw materials are completely melted, adjusting the temperature of the melt to 700-720 ℃, and mechanically stirring and refining for 30-70min at a mechanical stirring speed of 100-160r/min; then, heating the melt to 730-750 ℃, keeping the temperature for 20-50min, removing oxidized slag on the surface layer of the melt, introducing argon to the bottom of the melt, stirring and refining the gas for 15-60min, wherein the gas flow is 20-40L/h;

(4) After refining is finished, standing the melt, cooling to 620-640 ℃, preserving heat for 2-4h, and then heating the melt to 670-700 ℃;

(5) Guiding the melt into an inner cavity of a crystallizer through a splitter plate, wherein when the casting is stable, the temperature of the melt in the crystallizer is 650-675 ℃, the ingot pulling speed is 30-90mm/min, and the cooling water flow is 60-90L/min, so as to obtain a magnesium alloy ingot;

the impurity elements comprise Fe, si, cu and Ni, wherein Fe is less than or equal to 0.005%, si is less than or equal to 0.05%, cu is less than or equal to 0.005%, ni is less than or equal to 0.005%, the total content of the impurity elements is not more than 0.1%, the rare earth elements comprise Gd, Y or a mixed element of the Gd and the Y, the mass percentage is 0.05-0.50%, and when the Gd and the Y are mixed, the mass ratio of the Gd to the Y is (0.01-100) = (0.01-100): 1).

2. The method of claim 1, wherein: in the step (5), the height of the melt from the top of the crystallizer is 40-70mm, the depth of the liquid cavity is 30-80mm, and finally the magnesium alloy ingot with the diameter phi of 100-500mm is obtained.

3. The method of claim 1, wherein: the mass percentage of Al in the magnesium alloy is 4.0-5.0%, and the sum of the Al content and the Zn content in the magnesium alloy is as follows: al and Zn are more than or equal to 6.5 percent and less than or equal to 8.0 percent, the mass percent of Mn in the magnesium alloy is 0.2 to 0.6 percent, and the mass percent of Ca in the magnesium alloy is 0.002 to 0.060 percent.

4. The method of claim 1, wherein: in the step (3), after the added raw materials are completely melted, slagging off the surface, putting a stirring paddle into the melt after slagging off, simultaneously adding a covering agent into the furnace, starting the stirring paddle to carry out mechanical stirring refining, wherein the refining time is 30-60min, and the mechanical stirring speed is 120-160r/min.

5. The method of claim 1, wherein: in the step (3), the melt is heated to 730-745 ℃, the temperature is kept for 20-40min after the temperature is reached, the surface oxidation slag inclusion is removed after the temperature keeping time is reached, argon is introduced to the bottom of the melt to stir the melt, meanwhile, a covering agent is added to stir and refine the gas, the refining time is 20-50min, and the gas flow is 30-40L/h.

6. The method of claim 1, wherein: in the step (5), introducing argon or nitrogen to extrude the melt from the smelting furnace, introducing the melt into an inner cavity of a crystallizer through a splitter plate, and simultaneously introducing inert gas above the liquid level of the melt to protect the melt and prevent oxidation; the diameter of the cast ingot is phi 100-250mm, and the diameter of the diverter disc is phi 50-120mm; the diameter of the cast ingot is 250-400mm, and the diameter of the diverter disc is 120-180mm; the diameter of the cast ingot is 400-500mm, and the diameter of the diverter disc is 180-220mm.

7. The method of claim 1, wherein: the diameter of the casting blank is phi 100-250mm, and the ingot pulling speed is 70-90mm/min; the diameter phi is 250-400mm, and the ingot pulling speed is 40-70mm/min; the diameter phi is 400-500mm, and the ingot pulling speed is 30-40mm/min.

8. A magnesium alloy ingot produced by the method according to any one of claims 1 to 7.