A method for preparing large-size copper-iron alloy ingot

Abstract

A method for preparing a large-sized copper-iron alloy ingot is provided, which adopts continuous or semi-continuous casting, and adopts the following treatments during the casting process: (1) component alloying: adding an alloying modifier to the copper-iron alloy melt, the alloying modifier is composed of a mixture of copper-calcium alloy, copper-aluminum alloy, copper-manganese alloy and copper-cobalt alloy, and the composition weight percentage of the alloyed ingot obtained after adding the alloying modifier is as follows: 0.002~0.01wt.% calcium, 0.02~0.12wt.% aluminum, 0.05~1.0 wt.% manganese, 0.01-0.2wt.% cobalt, 15-80wt.% iron, and the balance copper; (2) adding a nucleating agent: continuously adding a rare earth nucleating agent to the molten pool during the casting process, wherein the rare earth nucleating agent is composed of a mixture of a copper-cerium alloy and a copper-scandium alloy, and the mass percentage of the rare earth nucleating agent is: 6-13wt.% cerium, 10-35wt.% scandium, and the balance copper; (3) strong magnetic field suppression: applying a strong magnetic field around the crystallizer, including a constant magnetic field and a pulsed magnetic field. The present invention can effectively improve the uniformity of the distribution of iron elements and iron-rich phases in large-sized ingots through the above-mentioned treatment measures.

Description

Technical Field

[0001] The invention belongs to the technical field of copper alloys, and in particular relates to a method for preparing a large-size copper-iron alloy ingot. Background Art

[0002] Copper-iron (Cu-Fe) alloys, as a new generation of high-strength conductive copper alloys, offer advantages such as high strength, electrical conductivity, thermal conductivity, electromagnetic shielding, and low cost, and hold promising prospects for development. However, high-iron Cu-Fe alloys (15.0-80.0 wt.%) exhibit a wide solidus-liquidus temperature range, preferential precipitation of the iron phase, and low iron density. This leads to significant variations in the distribution of the iron-rich phase within the ingot during selective crystallization and dendritic solidification, resulting in severe iron segregation. This compositional segregation becomes increasingly severe as the cross-sectional size of the ingot increases. Furthermore, because segregation occurs in the direction opposite to gravity (the iron-rich phase floats upward), the longer the ingot (casting in the direction of gravity), the more severe the segregation. This can lead to unacceptable compositional segregation in the ingot and severe cracking, scaling, and breakage during subsequent rolling.

[0003] Powder metallurgy is the primary method for preparing high-iron copper-iron alloys. Copper and iron powders are uniformly mixed, extruded, sintered, and then rolled to produce a billet. However, powder metallurgy is costly, and because the powder sintering temperature is below the alloy's melting point, the resulting alloy structure is less dense than that obtained by casting. Consequently, the material's final processing properties fail to fully demonstrate the alloy's unique properties.

[0004] Therefore, it is necessary to propose a new method for the preparation of large-sized copper-iron alloy ingots to effectively improve the uniformity of the distribution of iron elements and iron-rich phases in large-sized ingots. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing large-sized copper-iron alloy ingots, which effectively improves the uniformity of the distribution of iron elements and iron-rich phases in large-sized ingots by alloying the components, adding nucleating agents and adopting strong magnetic field suppression.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a large-sized copper-iron alloy ingot, using continuous or semi-continuous casting, and adopting the following treatments during the casting process:

[0007] (1) Component alloying treatment: an alloying modifier is added to the melt of the copper-iron alloy, wherein the alloying modifier is a mixture of copper-calcium alloy, copper-aluminum alloy, copper-manganese alloy and copper-cobalt alloy. The composition of the alloyed ingot obtained after adding the alloying modifier is as follows: 0.002-0.01 wt.% calcium, 0.02-0.12 wt.% aluminum, 0.05-1.0 wt.% manganese, 0.01-0.2 wt.% cobalt, 15-80 wt.% iron, and the balance is copper;

[0008] (2) Adding a nucleating agent: A rare earth nucleating agent is continuously added to the molten pool during the casting process. The rare earth nucleating agent is composed of a mixture of a copper-cerium alloy and a copper-scandium alloy. The mass percentage of the rare earth nucleating agent is: 6-13wt.% cerium, 10-35wt.% scandium, and the balance is copper;

[0009] (3) Strong magnetic field suppression: A strong magnetic field is applied around the crystallizer, including a constant magnetic field and a pulsed magnetic field, with the constant magnetic field located above the pulsed magnetic field;

[0010] (31) The constant magnetic field is formed by a strong magnet or electromagnet arranged around the crystallizer. The upper edge of the constant magnetic field is flush with the top surface of the crystallizer. The distribution height of the constant magnetic field is less than the height of the crystallizer, and the constant magnetic field intensity B = 0.01~0.05T / mm. The physical meaning of B is the average magnetic field intensity on the maximum symmetrical dimension length in the cross-section direction of the crystallizer, that is, B = H / L, where H is the total intensity of the constant magnetic field and L is the maximum symmetrical dimension length. When the crystallizer is a rectangular parallelepiped, L is half the length of the long side of the crystallizer cross section. When the crystallizer is a cylinder, L is the radius of the crystallizer cross section.

[0011] (32) The pulsed magnetic field is formed by connecting a pulsed current to a coil located at the exit of the crystallizer and having a high-iron-content ingot as the iron core. The pulsed magnetic field intensity applied to the melt is 0.1~0.3T and the frequency is 5.5~9.5Hz.

[0012] As an embodiment, the alloying modifier comprises the following components by weight: 5-10 wt.% calcium, 20-30 wt.% aluminum, 20-30 wt.% manganese, 20-30 wt.% cobalt, and the balance is copper.

[0013] As an embodiment, the alloying modifier has a particle size of 1 to 3 cm and a purity of ≥99%.

[0014] As an embodiment, the rare earth nucleating agent is added by a wire feeding method, wherein the rare earth nucleating agent is coated with a thin copper strip to form a rare earth wire, and the rare earth wire is slowly fed into the molten pool of the crystallizer through a stopper rod with a central opening, and a protective gas is filled in the central hole of the stopper rod. The amount of rare earth nucleating agent added is 0.02~0.06% of the mass of the copper-iron alloy.

[0015] As an embodiment, the rare earth nucleating agent is added in an amount of 0.05% by mass of the copper-iron alloy.

[0016] As an embodiment, the particle size of the rare earth nucleating agent is 50-100 mesh and the purity is ≥99%.

[0017] As an embodiment, the distribution height of the constant magnetic field is greater than 150 mm.

[0018] As an embodiment, the distribution height of the constant magnetic field is 180 mm, and the constant magnetic field intensity B is 0.20 T / mm.

[0019] As an embodiment, the pulse magnetic field strength is 0.2T and the frequency is 6.0 Hz.

[0020] As an embodiment, during the casting process, the casting temperature superheat is controlled at 90-130° C., and the casting speed is 40-80 mm / min.

[0021] The beneficial effects of the present invention are as follows: the method for preparing a large-sized copper-iron alloy ingot with uniform structure and its application provided by the present invention can effectively improve the uniformity of the distribution of iron elements and iron-rich phases in the large-sized ingot.

[0022] The alloying modifier in the present invention can refine and spheroidize the iron phase dendrites, especially the secondary dendrite arms, and promote the secondary dendrite arms to easily undergo melting fracture when the iron-rich phase dendrites recalcify during the solidification process, thereby breaking and refining the iron phase dendrite structure.

[0023] The addition of nucleating agents is mainly achieved by adding rare earth elements to the alloy solution, using heterogeneous nucleation to increase the number of nuclei per unit volume of the iron-rich phase, thereby reducing the size of the iron-rich phase dendrites. Among them, the scandium element significantly promotes the heterogeneous nucleation ability of the iron phase during the solidification process of the copper-iron alloy, and the use of rare earth wire fed from the center hole of the stopper rod can ensure the uniform composition of the nucleating additive.

[0024] The strong magnetic field applied around the crystallizer can give magnetic attraction to the iron-rich phase precipitated in the two-phase region during the solidification process, pulling the iron phase precipitated in the center of the crystallizer toward the edge of the crystallizer to prevent the iron content in the edge area of ​​the ingot from being too low; the pulsed electromagnetic field applied below the crystallizer provides a traction force along the direction of gravity to the iron-rich phase in the solution, which is used to balance the buoyancy generated by the density difference between the iron phase and the copper solution, thereby preventing the iron-rich phase from floating up during solidification. At the same time, the pulsed electric field also provides a force on the microscopic iron phase. After the secondary dendrite arms are refined under the action of the alloying modifier, the fragile dendrite arms are simultaneously subjected to the sudden pulsed electromagnetic force ( Figure 6 The electromagnetic force of the pulsed magnetic field suddenly increases with the sudden increase of current, which can produce an exciting effect on the dendrites, inducing dendrite fracture and tissue fragmentation, which will improve the refinement and distribution uniformity of the iron-rich phase structure, thereby achieving the homogenization of the iron element composition in large-sized copper-iron alloy ingots and obtaining high-quality ingots.

[0025] In addition, the present invention proposes to adopt high superheat casting, which can increase the distribution range of the solid-liquid two-phase region in the crystallizer and ensure sufficient fluidity of the precipitated iron phase melt.

[0026] The maximum segregation degree of the iron element in the cross section of the copper-iron alloy ingot produced by casting according to the present invention can be reduced by up to 30%, and the segregation degree at the head and tail of the ingot in the casting direction can be reduced by up to 40%. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0028] Figure 1 Schematic diagram of the process of adding the nucleating agent in the present invention;

[0029] Figure 2 Schematic diagram of applying a constant-intensity magnetic field around the crystallizer in the present invention;

[0030] Figure 3 It is a top view schematic diagram of the continuous casting of square billets;

[0031] Figure 4 It is a top view schematic diagram of the continuous casting of cylindrical billets;

[0032] Figure 5 Schematic diagram of simultaneously applying a constant magnetic field and a pulsed magnetic field outside the crystallizer in the present invention;

[0033] Figure 6 The current waveforms are those of traditional harmonic electromagnetic stirring and pulsed electromagnetic stirring;

[0034] Figure 7 Schematic diagram of the method for selecting measurement points on the cross section of the slab;

[0035] Markings in the figure: 1. Tundish, 2. Crystallizer, 3. Stopper rod, 4. Rare earth wire, 5. Submerged nozzle, 6. Alloy melt, 7. Argon gas, 8. Constant magnetic field, 9. Ingot, 10. Pulsed magnetic field. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and examples, but they are not intended to limit the invention in any way.

[0037] Example 1: A method for preparing a large-sized copper-iron alloy ingot using a semi-continuous casting method. The ingot has a slab cross-section of 420 mm x 160 mm and an iron content of 20 wt %. In other embodiments, a continuous casting method may also be used.

[0038] During the casting process, the following treatments are adopted: component alloying, nucleating agent addition and strong magnetic field suppression.

[0039] In the first treatment, component alloying refers to adding an alloying modifier to the copper-iron alloy melt after the copper-iron alloy is melted. The alloying modifier is composed of a mixture of copper-calcium alloy, copper-aluminum alloy, copper-manganese alloy and copper-cobalt alloy. The composition of the alloying modifier by mass percentage is: 7wt.% calcium, 25wt.% aluminum, 25wt.% manganese, 25wt.% cobalt, and the balance is copper. The particle size of the alloying modifier is 1-3cm, and the purity is 99% or above. In this embodiment, the particle size of the alloying modifier is 2cm and the purity is 99%. The composition of the alloyed ingot prepared after the alloying modifier is added to the copper-iron alloy melt is: 0.003wt.% calcium, 0.03wt.% aluminum, 0.07wt.% manganese, 0.09wt.% cobalt, 20wt.% iron, and the balance is copper.

[0040] In the second process, a rare earth nucleating agent is continuously added to the molten pool during the casting process. The agent is composed of a copper-cerium alloy and a copper-scandium alloy, with the weight percentage of the rare earth nucleating agent being 20% ​​cerium, 20% scandium, and the balance copper. The rare earth nucleating agent is in the form of alloy particles with an 80-mesh particle size and a purity of 99.5%. The rare earth nucleating agent is formed by coating a thin copper ribbon to form a rare earth wire. The rare earth nucleating agent is added during the casting process according to the casting speed, with the addition amount being 0.05% of the copper-iron alloy weight.

[0041] The rare earth nucleating agent is added by wire feeding method. Figure 1 As shown, a rare earth wire 4, formed into a wire, is slowly fed through a stopper rod 3 with a central opening. Argon gas 7 is filled into the center hole of the stopper rod 3, surrounding the rare earth wire 4 to provide gas protection and pressure balance, preventing the alloy melt from overflowing. Specifically, the stopper rod 3 is inserted into the alloy melt in the tundish 1 or head box above the crystallizer 2, aligning with the submerged nozzle 5 at the bottom. Protected by the argon gas 7, the rare earth wire 4 is slowly fed through the center opening of the stopper rod 3 into the submerged nozzle 5 below, where it is melted by the alloy melt and enters the melt of the crystallizer 2.

[0042] In the third technical treatment, Figure 2As shown, a constant magnetic field 8 is applied to the melt in the mold by placing strong magnets or electromagnets around the mold 2. With the top of the mold 2 as the zero point, the distribution height of the constant magnetic field 8 is -180 mm, and the lowest end of the constant magnetic field 8 is higher than the bottom of the mold 2. The intensity of the constant magnetic field 8 is B = 0.02 T / mm, where B is the average magnetic field intensity along the maximum symmetrical dimension of the cross-section of the mold 2. B = H / L, where H is the total intensity of the constant magnetic field and L is the maximum symmetrical dimension. For example, if the mold 2 is rectangular, L is half the length of the long side of the mold cross-section. For another example, if the mold is cylindrical, L is the radius of the mold cross-section.

[0043] like Figure 5 As shown, in addition to the constant magnetic field applied around the crystallizer 2, a pulsed magnetic field 10 is also provided at the outlet position at the bottom of the crystallizer 2. The pulsed magnetic field 10 is formed by passing a pulsed current through a coil with a high-iron-content ingot as the iron core. A pulsed magnetic field 10 of 0.2 T is applied to the melt in the crystallizer 2, and the frequency of the pulsed magnetic field 10 is 6.0 Hz.

[0044] During the casting process, the casting temperature and casting speed also affect the internal quality of the ingot. To obtain a uniform iron composition and iron-rich phase structure, the casting temperature superheat is controlled between 90 and 130°C and the casting speed is between 40 and 80 mm / min. In this embodiment, the casting temperature superheat is controlled at 110°C and the casting speed is 40 mm / min.

[0045] Example 2: This example adjusts some parameters based on Example 1. The adjusted parameters are:

[0046] (1) The alloying modifier comprises the following components by weight: 5 wt.% calcium, 20 wt.% aluminum, 20 wt.% manganese, 30 wt.% cobalt, and the balance copper;

[0047] (2) The composition of the alloyed ingot prepared by adding the alloying modifier to the copper-iron alloy melt is: 0.002 wt.% calcium, 0.02 wt.% aluminum, 0.05 wt.% manganese, 0.02 wt.% cobalt, 15 wt.% iron, and the balance is copper;

[0048] (3) The alloying modifier has a particle size of 1 cm and a purity of 99.5%;

[0049] (4) The composition of the rare earth nucleating agent is 6 wt.% cerium, 10 wt.% scandium, and the balance is copper;

[0050] (5) The particle size of the rare earth nucleating agent is 50 mesh and the purity is 99%;

[0051] (6) The amount of the rare earth nucleating agent added is 0.02% of the mass of the copper-iron alloy;

[0052] (7) The height of the strong magnet or electromagnet is 170 mm;

[0053] (8) The constant magnetic field strength B is 0.01 T / mm;

[0054] (9) The pulsed magnetic field strength is 0.1 T and the frequency is 7.0 Hz;

[0055] (10) The casting temperature superheat is 85℃ and the casting speed is 60mm / min.

[0056] Example 3: This example adjusts some parameters based on Example 1. The adjusted parameters are:

[0057] (1) The alloying modifier comprises the following components by weight: 10 wt.% calcium, 30 wt.% aluminum, 30 wt.% manganese, 20 wt.% cobalt, and the balance copper;

[0058] (2) The composition of the alloyed ingot prepared by adding the alloying modifier to the copper-iron alloy melt is: 0.01wt.% calcium, 0.12wt.% aluminum, 1.0wt.% manganese, 0.2wt.% cobalt, 80wt.% iron, and the balance is copper;

[0059] (3) The alloying modifier has a particle size of 3 cm and a purity of 99.2%;

[0060] (4) The composition of the rare earth nucleating agent is 13 wt.% cerium, 35 wt.% scandium, and the balance is copper;

[0061] (5) The particle size of the rare earth nucleating agent is 100 mesh and the purity is 99.5%;

[0062] (6) The amount of the rare earth nucleating agent added is 0.06% of the mass of the copper-iron alloy;

[0063] (7) The height of the strong magnet or electromagnet is 210 mm;

[0064] (8) The constant magnetic field strength B is 0.05 T / mm;

[0065] (9) The pulsed magnetic field strength is 0.3 T and the frequency is 9.0 Hz;

[0066] (10) The casting temperature superheat is 120℃ and the casting speed is 70mm / min.

[0067] In addition, in this embodiment, the casting billet is a round billet with a size of φ200 mm, and the corresponding crystallizer is a cylindrical crystallizer.

[0068] The technical effects of the method adopted in the present invention are further illustrated by several comparative examples below.

[0069] Comparative Example 1: Semi-continuous casting was used to produce copper-iron alloy ingots of the same dimensions as in Example 3, with an iron content of 20 wt%. The casting process omitted the three treatments described in this invention, namely, alloying, nucleating agent addition, and strong magnetic field suppression. The casting temperature was superheated to 80°C, and the casting speed was 40 mm / min.

[0070] Comparative Example 2: Semi-continuous casting was used to cast copper-iron alloy ingots of the same dimensions as in Example 1, with an iron content of 20 wt %. During the casting process, only the alloying treatment described in Example 1 was used, without the addition of a nucleating agent or the strong magnetic field suppression measures. The casting temperature was controlled at a superheat of 110°C, and the casting speed was 40 mm / min.

[0071] Comparative Example 3: Semi-continuous casting was used to cast copper-iron alloy ingots of the same dimensions as in Example 1, with an iron content of 20 wt%. During the casting process, only the nucleating agent addition described in Example 1 was employed, without alloying or strong magnetic field suppression. The casting temperature was controlled at a superheat of 110°C, and the casting speed was 40 mm / min.

[0072] Comparative Example 4: Semi-continuous casting was used to cast copper-iron alloy ingots of the same dimensions as in Example 1, with an iron content of 20 wt%. During the casting process, only the strong magnetic field suppression measures described in Example 1 were employed, without alloying or adding a nucleating agent. The casting temperature was controlled at a superheat of 110°C, and the casting speed was 40 mm / min.

[0073] Comparative Example 5: Based on Comparative Example 4, only a constant magnetic field is applied.

[0074] Comparative Example 6: Based on Comparative Example 4, only the pulsed magnetic field is applied.

[0075] The maximum segregation of the iron element in the cross section and the segregation at the head and tail of the large-sized copper-iron alloy ingots prepared in the above-mentioned embodiments and comparative examples are calculated and analyzed below. The results are shown in Table 1.

[0076] Maximum segregation degree P of the cross section of the ingot h The calculation method of (max) is: Figure 7 As shown, samples are taken at intervals along the center line of the ingot in the width direction of the cross section of the ingot. The distances between the sampling points are equal and the sampling points are marked as A 1 、 A 2 、 A 3 、 A4 … A i , i ≥3, measure the iron content at each sampling point by spectroscopic or chemical methods, and then calculate P according to formula (1) h (max);

[0077] (1)

[0078] Among them, the average =( A 1 + A 2 + A 3 +…… A i ) / i .

[0079] The head-tail segregation degree P of the ingot z The calculation method of (max) is:

[0080] (2)

[0081] in, A j is the average iron content of the cross section of the ingot, j Indicates the head or tail of the billet, so when calculating the average iron content at the head or tail of the billet, A j Can be written as A 头 or A 尾 , =( A 头 + A 尾 ) / 2.

[0082] Table 1 Maximum segregation of copper-iron alloy ingot composition

[0083]

[0084] As can be seen from the above table, the maximum segregation degree of iron element composition in the copper-iron alloy ingot prepared by the present invention is reduced by up to 29.5% in the cross section and by up to 39.3% at the head and tail of the ingot compared with Comparative Example 1, and the segregation of iron element composition in large-size ingots is effectively controlled.

[0085] Specifically, Comparative Example 1 does not adopt the three treatment methods described in the present invention, so both the maximum segregation degree of the cross section and the segregation degree of the head and tail of the ingot are higher than those of Examples 1-3, and are also higher than those of other comparative examples.

[0086] In Comparative Examples 2-6, only one of the three treatment methods described in the present invention is adopted, and the maximum segregation degree of the cross section of the ingot and the segregation degree at the head and tail of the ingot are higher than those in Examples 1-3. This shows that the treatment measures of the present invention can effectively improve the uniformity of the distribution of iron elements and iron-rich phases in large-size ingots.

[0087] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Those skilled in the art should understand that the specific implementation methods of the present invention can be modified or replaced with equivalents with reference to the above embodiments. Any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention are within the scope of protection of the pending claims.

Claims

1. A method for preparing large-sized copper-iron alloy ingots by continuous or semi-continuous casting, characterized in that: The following treatments are used during the casting process: (1) Component alloying treatment: an alloying modifier is added to the melt of the copper-iron alloy, wherein the alloying modifier is a mixture of copper-calcium alloy, copper-aluminum alloy, copper-manganese alloy and copper-cobalt alloy. The composition of the alloyed ingot obtained after adding the alloying modifier is as follows: 0.002-0.01 wt.% calcium, 0.02-0.12 wt.% aluminum, 0.05-1.0 wt.% manganese, 0.01-0.2 wt.% cobalt, 15-80 wt.% iron, and the balance is copper; (2) Adding a nucleating agent: A rare earth nucleating agent is continuously added to the molten pool during the casting process. The rare earth nucleating agent is composed of a mixture of a copper-cerium alloy and a copper-scandium alloy. The mass percentage of the rare earth nucleating agent is: 6-13wt.% cerium, 10-35wt.% scandium, and the balance is copper; (3) Strong magnetic field suppression: A strong magnetic field is applied around the crystallizer, including a constant magnetic field and a pulsed magnetic field, with the constant magnetic field located above the pulsed magnetic field; (31) The constant magnetic field is formed by a strong magnet or electromagnet arranged around the crystallizer. The upper edge of the constant magnetic field is flush with the top surface of the crystallizer. The distribution height of the constant magnetic field is less than the height of the crystallizer, and the constant magnetic field intensity B = 0.01~0.05T / mm. The physical meaning of B is the average magnetic field intensity on the maximum symmetrical dimension length in the cross-section direction of the crystallizer, that is, B = H / L, where H is the total intensity of the constant magnetic field and L is the maximum symmetrical dimension length. When the crystallizer is a rectangular parallelepiped, L is half the length of the long side of the crystallizer cross section. When the crystallizer is a cylinder, L is the radius of the crystallizer cross section. (32) The pulsed magnetic field is formed by connecting a pulsed current to a coil located at the exit of the crystallizer and having a high-iron-content ingot as the iron core. The pulsed magnetic field intensity applied to the melt is 0.1~0.3T and the frequency is 5.5~9.5Hz.

2. The method for preparing a large-sized copper-iron alloy ingot according to claim 1, wherein: The alloying modifier comprises the following components by weight: 5-10 wt.% calcium, 20-30 wt.% aluminum, 20-30 wt.% manganese, 20-30 wt.% cobalt, and the balance is copper.

3. The method for preparing a large-sized copper-iron alloy ingot according to claim 1, wherein: The alloying modifier has a particle size of 1-3 cm and a purity of ≥99%.

4. The method for preparing a large-sized copper-iron alloy ingot according to claim 1, wherein: The rare earth nucleating agent is added by a wire feeding method, wherein the rare earth nucleating agent is coated on a thin copper strip to form a rare earth wire, and the rare earth wire is slowly fed into the molten pool of the crystallizer through a stopper rod with a central hole, and a protective gas is filled into the central hole of the stopper rod. The amount of rare earth nucleating agent added is 0.02-0.06% of the mass of the copper-iron alloy.

5. The method for preparing a large-sized copper-iron alloy ingot according to claim 4, characterized in that: The rare earth nucleating agent is added in an amount of 0.05% of the mass of the copper-iron alloy.

6. The method for preparing a large-sized copper-iron alloy ingot according to claim 1 or 4, characterized in that: The particle size of the rare earth nucleating agent is 50-100 meshes, and the purity is ≥99%.

7. The method for preparing large-sized copper-iron alloy ingots according to claim 1, characterized in that: The distribution height of the constant magnetic field is greater than 150 mm.

8. The method for preparing large-sized copper-iron alloy ingots according to claim 7, characterized in that: The distribution height of the constant magnetic field is 180 mm, and the constant magnetic field intensity B is 0.20 T / mm.

9. The method for preparing large-sized copper-iron alloy ingots according to claim 1, characterized in that: The pulse magnetic field intensity is 0.2 T and the frequency is 6.0 Hz.

10. The method for preparing large-sized copper-iron alloy ingots according to claim 1, characterized in that: During the casting process, the casting temperature superheat is controlled at 90~130℃, and the casting speed is 40~80mm / min.

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