EA039285B1 - Method for producing metal ingot - Google Patents

Abstract

A method for producing a metal ingot by using an electron-beam melting furnace including an electron gun capable of controlling a radiation position of an electron beam, and a hearth that accumulates a molten metal of a metal raw material, in which, in a downstream region between an upstream region in which the metal raw material is supplied onto the surface of the molten metal and a first side wall, an irradiation line is disposed so as to block a lip portion and so that two end portions are positioned in the vicinity of the side wall of the hearth. A first electron beam is radiated onto the surface of the molten metal along the irradiation line, and the first electron beam is radiated along the irradiation line. By this means, the surface temperature (T2) of the molten metal along the irradiation line is made higher than the average surface temperature (T0) of the entire surface of the molten metal in the hearth, and a molten metal flow from the irradiation line toward upstream that is a direction toward the opposite side to the first side wall is formed in an outer layer of the molten metal.

Description

The field of technology to which the invention belongs

The present invention relates to a method for producing a metal ingot in which a metal raw material is melted using an electron beam melting process.

Prerequisites for the creation of the invention

Ingot of commercially pure titanium or titanium alloy, etc. produced by melting titanium raw materials such as titanium sponge or waste. Examples of methods for melting metal raw materials (hereinafter simply raw materials) such as titanium raw materials include a vacuum arc remelting process, a plasma arc melting process, and an electron beam melting process. In the electron beam melting process, a raw material is melted by directing an electron beam onto a solid raw material in an electron beam melting furnace (hereinafter also referred to as an EB furnace). In order to prevent scattering of electron beam energy, the melting of raw materials by electron beam irradiation in an EL furnace is performed in a vacuum chamber. Molten titanium (hereinafter also referred to as molten metal), which is a molten raw material, is refined in a furnace bath and then solidified in a mold to form a titanium ingot. According to the electron beam melting process, since the irradiation position of the electron beam, which is the heat source, can be precisely controlled by electromagnetic force, heat can also be sufficiently supplied to the molten metal near the mold. Therefore, it is possible to produce an ingot without degrading its surface quality.

An EL furnace typically includes a raw material supply portion that supplies raw materials such as a titanium sponge, one or a plurality of electron guns for melting the supplied raw material, a bath (for example, a water-cooled copper bath) for accumulating the molten raw material, and a mold for forming an ingot. by cooling the molten titanium poured into it from the bath. EL furnaces are roughly classified into two types according to differences in bath configurations. In particular, the EL furnace 1A, which includes a melting bath 31 and a cleaning bath 33, as illustrated in FIG. 1 and an EL furnace 1B that only includes a cleaning bath 30 as illustrated in FIG. 2 are two different types of EL furnace.

EL furnace 1A illustrated in FIG. 1 includes a raw material supply portion 10, electron guns 20a to 20e, a melting bath 31 and a cleaning bath 33, and a casting mold 40. The solid raw material 5 that is introduced into the melting bath 31 from the raw material supply portion 10 is irradiated by the electron guns 20a and 20b to thereby melt the raw material and obtain molten metal 5c. The molten raw material (molten metal 5c) in the melting bath 31 flows into a purification bath 33 which communicates with the melting bath 31. In the purification bath 33, the temperature of the molten metal 5c is maintained or increased by irradiating the molten metal 5c with electron guns 20c and 20d. Through this, impurities contained in the molten metal 5c are removed and the like, and the molten metal 5c is purified. Thereafter, the purified molten metal 5c flows into the mold 40 from the spout portion 33a provided at the end portion of the purification bath 33 . The molten metal 5c solidifies in the mold 40, thereby producing an ingot 50. A bath consisting of a melting bath 31 and a cleaning bath 33, as shown in FIG. 1 is also referred to as a long bath.

On the other hand, the EL furnace 1B shown in FIG. 2 includes raw material supply portions 10A and 10B, electron guns 2OA-2OD, a cleaning bath 30, and a mold 40. A bath that only consists of a cleaning bath 30 is also referred to as a short bath, in contrast to the long bath shown in FIG. . 1. In the EL furnace 1B, which uses a short bath, the solid raw material 5, which is placed on the raw material supply portions 10A and 10B, is melted by electron beams that are emitted from the electron guns 20A and 20B, and the molten raw material 5 is dripped into the molten metal 5c, located in the cleaning bath 30, from the raw material supply parts 10A and 10B. Thus, the melt bath 31 illustrated in FIG. 1 can be removed from the EL furnace 1B illustrated in FIG. 2. In addition, in the cleaning bath 30, the temperature of the molten metal 5c is maintained or increased by irradiating electron beams from the electron gun 20C over a wide range over the entire surface of the molten metal 5c. Through this, impurities contained in the molten metal 5c are removed and the like, and thus the molten metal 5c is purified. Thereafter, the purified molten metal 5c flows into the mold 40 from the spout portion 36 provided at the end portion of the purification bath 30, and an ingot 50 is produced.

In the case of producing an ingot using a bath and a mold through an electron beam melting process as described above, if impurities enter the ingot, they will cause cracks in the ingot. Therefore, there is a need to develop an electron beam melting technology that can ensure that impurities do not enter the molten metal that flows into the mold from the bath. The impurities originate mainly from raw materials and are classified into two types, namely, HRP (high density inclusions) and GNP (low density inclusions). GDP is, for example, an impurity in which tungsten is the main component, and the density of GDP is greater than that of molten titanium. On the other hand, GNP is an impurity in which nitrided titanium and the like are the main component. The internal part of the GNP is in a porous state, so the density of the GNP is less than the density of molten titanium.

- 1 039285

On the inner surface of the water-cooled copper bath, a hardened layer is formed, which is molten titanium, solidified from contact with the bath surface. This cured layer is known as the scull. Among the aforementioned impurities, since the HPFs have a high relative density, they are deposited in the molten metal (molten titanium) in the bath and adhere to the surface of the scull and thereby are trapped, and therefore the probability of the HPFs entering the ingot becomes low. On the other hand, since the density of the GNP is less than the density of the molten titanium, the main part of the GNP floats to the surface of the molten metal inside the bath. While the GNP float to the surface of the molten metal, nitrogen diffuses into the molten metal and dissolves in it. In the case of using the long tub shown in FIG. 1, since the residence time of the molten metal in the long bath can be increased, it becomes easier to cause impurities such as GNP to dissolve in the molten metal compared to the case of using a short bath. On the other hand, in the case of using a short bath, as shown in FIG. 2, since the residence time of the molten metal in a short bath is shorter compared to a long bath, the probability that impurities will not be dissolved in the molten metal is high compared to using a long bath. In addition, in the case of GNPs that have a high nitrogen content, since their dissolution temperature is high, the probability that the GNPs are dissolved in the molten metal during the residence time in normal operation is extremely low.

Therefore, for example, Patent Document 1 discloses a titanium metal electron beam melting method in which the surface of the molten metal in the bath is scanned with an electron beam in a direction opposite to the direction in which the molten metal flows into the mold, and the average temperature of the molten metal in a region adjacent with an outlet for molten metal in the bath, maintained equal to or higher than the melting point of impurities. According to the technique disclosed in Patent Document 1, by scanning the electron beam in a zigzag manner in the opposite direction of the molten metal flow, an attempt is made to push back impurities that float on the surface of the molten metal so that they do not enter the mold.

List of documents

Prior Art Patent Documents

Patent Document 1: JP2004-232066A.

non-patent document

Non-Patent Document 1: Tao Meng, Factors influencing the fluid flow and heat transfer in electron beam melting of Ti-6A1-4V, (2009).

Summary of the Invention Technical Problem

However, according to the method disclosed in the above-mentioned Patent Document 1, since the electron beam is scanned in the opposite direction of the molten metal flow, there is a possibility that impurities further downstream of the molten metal from the electron beam irradiation position will enter the mold. . In addition, further downstream of the molten metal relative to the electron beam irradiation position, the molten metal flow accelerates towards the mold, and thus the residence time of the molten metal in the bath is reduced, and there is a possibility that the impurity removal rate will decrease. In addition, when impurities are present further downstream of the molten metal from the electron beam irradiation position, the risk of them entering the mold with the molten metal stream is increased. For these reasons, there is a possibility that the impurities contained in the molten metal inside the bath, in particular the GNP floating on the surface of the molten metal 5c, will flow into the mold from the bath and end up in the ingot which is formed in the mold. Therefore, there is a need for a method for producing a metal ingot, which, by preventing impurities such as GNR from flowing out of the bath into the mold, can prevent impurities from entering the ingot.

The object of the present invention, which has been made in view of the above problem, is to provide a new and improved method for producing a metal ingot, which can inhibit the ingress of impurities contained in the molten metal in the furnace bath into the ingot.

Solution

In order to solve the above problem, according to a certain point of view of the present invention, there is provided a method for producing a metal ingot by using an electron beam furnace having an electron gun capable of controlling an electron beam irradiation position and a bath that accumulates molten metal from a metal raw material, the metal ingot contains a total of 50 wt.% or more of at least one metal element selected from the group consisting of titanium, tantalum, niobium, vanadium, molybdenum and

- 2 039285 zirconium, in which, among the plurality of side walls of the bath, which accumulates molten metal from metal raw materials, the first side wall is a side wall provided with a part of the drain toe for flowing molten metal from the bath into the mold; the irradiation line is located in the downstream region between the upstream region in which the metal raw material is supplied to the surface of the molten metal and the first side wall, so that the irradiation line blocks a part of the drain spout, and the two end parts of the irradiation line are located in close proximity to the side bath walls; the first electron beam is radiated to the surface of the molten metal along the irradiation line; and the radiation of the first electron beam along the irradiation line increases the surface temperature (T2) of the molten metal on the irradiation line above the average surface temperature (T0) of the entire surface of the molten metal in the bath, and forms a reverse flow of molten metal in the outer layer of the molten metal, directed in the opposite direction to the first side wall away from the irradiation line.

According to the present invention, by emitting an electron beam along the irradiation line, as described above, on the surface of the molten metal in the bath, impurities from the bath are prevented from flowing into the mold, and impurities can be prevented from entering the ingot.

The two end parts of the irradiation line are located near the first side wall.

The two end parts of the irradiation line are located at the inner surface of the side wall or in the area separated from the inner surface of the side wall by 5 mm or less.

The flow of molten metal may be the flow from the irradiation line, which reaches the side wall, which runs essentially perpendicular to the first side wall.

The irradiation line may have a convex shape that protrudes from the part of the drain sock in the opposite direction.

The irradiation line may have a V-shape or a circular arc shape having a diameter equal to or greater than the width of the outlet of the spout portion.

The irradiation line may have a T-shape that includes a first straight portion along the first side wall between the two end portions and a second straight portion that extends substantially perpendicular to the first straight portion away from the first side wall.

The irradiation line may be in the form of a straight line along the first side wall between the two end portions.

The flow of molten metal may be a reverse flow from the irradiation line that is directed centrally from a pair of side walls that face each other and extend substantially perpendicular to the first side wall of the bath.

The irradiation line may have a convex shape that protrudes towards the spout part.

The irradiation line may be U-shaped, which includes the first straight part along the first side wall between the two end parts, as well as the second straight part and the third straight part from the two end parts of the first straight part, which extend respectively along the side walls. which face each other and extend substantially perpendicular to the first side wall of the tub.

The second electron beam may be radiated to a stagnation position of the molten metal flow that results from the emission of the first electron beam along the irradiation line.

A plurality of first electron beams may be emitted along an irradiation line using a plurality of electron guns such that the paths of the first electron beams intersect or overlap at the surface of the molten metal.

The bath may be configured to include only a cleaning bath in which the metal raw material is melted in the raw material supply part, drips from the raw material supply part into the bath, and the metal raw material is cleaned in the molten metal inside the cleaning bath.

The bath may be a multi-stage bath in which a plurality of divided baths are combined and arranged in series, wherein in each of the divided baths a first electron beam is irradiated onto the surface of the molten metal along an irradiation line which is positioned such that the irradiation line blocks a portion of the spout in the downstream region. flow, and the two end parts of the irradiation line are located in close proximity to the side wall of the divided bath.

In addition, the metal raw material may contain 50 wt.% or more of elemental titanium.

Useful effects of the invention

According to the present invention described above, impurities contained in the molten metal in the furnace bath can be inhibited from entering the ingot.

Brief description of the drawings

Fig. 1 is a schematic diagram illustrating an electron beam furnace that includes a long bath.

Fig. 2 is a schematic diagram illustrating an electron beam furnace,

- 3 039285 which includes a short tub.

Fig. 3 is a schematic diagram illustrating an electron beam furnace (short bath) which carries out the method for producing a metal ingot according to the first embodiment of the present invention.

Fig. 4 is a plan view illustrating one example of an irradiation line and supply lines in a bath according to the first embodiment of the present invention.

Fig. 5 is a partial cross section along line I-I shown in FIG. four.

Fig. 6 is a plan view illustrating one example of a molten metal flow that is generated when an electron beam is emitted along an irradiation line according to the method for manufacturing a metal ingot of the first embodiment of the present invention.

Fig. 7 is a plan view illustrating one example of an irradiation line according to the first embodiment of the present invention.

Fig. 8 is an explanatory drawing illustrating another example of an irradiation line according to the first embodiment of the present invention.

Fig. 9 is a plan view illustrating one example of a molten metal flow that is generated when an electron beam is emitted along an irradiation line according to the method for producing a metal ingot of the second embodiment of the present invention.

Fig. 10 is a plan view illustrating the shape of an irradiation line according to the second embodiment of the present invention.

Fig. 11 is a plan view illustrating one example of a molten metal flow that is generated when an electron beam is emitted along an irradiation line according to the method for manufacturing a metal ingot of the third embodiment of the present invention.

Fig. 12 is a plan view illustrating one example of an irradiation line and supply lines in a bath according to a fourth embodiment of the present invention.

Fig. 13 is a plan view illustrating one example of a molten metal flow that is generated when an electron beam is emitted along an irradiation line according to the method for manufacturing a metal ingot of the fourth embodiment of the present invention.

Fig. 14 is a plan view illustrating one example of an irradiation line according to the fourth embodiment of the present invention.

Fig. 15 is a plan view illustrating one example of an irradiation line according to the fourth embodiment of the present invention.

Fig. 16 is a plan view illustrating a V-shaped irradiation path which is a modification of the irradiation line according to the fourth embodiment of the present invention.

Fig. 17 is a plan view illustrating a circular arc-shaped irradiation path which is a modification of an irradiation line according to the fourth embodiment of the present invention.

Fig. 18 is a plan view illustrating a U-shaped irradiation path which is a modification of the irradiation line according to the fourth embodiment of the present invention.

Fig. 19 is a schematic plan view illustrating one example of a multi-stage bath configuration.

Fig. 20 is an explanatory drawing illustrating a simulation result according to Example 1.

Fig. 21 is a flow line diagram illustrating the flow of molten metal according to Example 1.

Fig. 22 is an explanatory drawing illustrating a simulation result according to Example 2.

Fig. 23 is an explanatory drawing illustrating a simulation result according to Example 3.

Fig. 24 is an explanatory drawing illustrating a simulation result according to Example 4.

Fig. 25 is an explanatory drawing illustrating the irradiation lines of Example 5.

Fig. 26 is an explanatory drawing illustrating a simulation result according to Example 5.

Fig. 27 is an explanatory drawing illustrating the irradiation line of Example 6.

Fig. 28 is an explanatory drawing illustrating a simulation result according to Example 6.

Fig. 29 is an explanatory drawing illustrating the irradiation line of Example 7.

Fig. 30 is an explanatory drawing illustrating a simulation result according to Example 7.

Fig. 31 is an explanatory drawing illustrating the simulation result with

- 4 039285 according to example 8.

Fig. 32 is an explanatory drawing illustrating a simulation result according to Example 9.

Fig. 33 is an explanatory drawing illustrating a simulation result according to Example 10.

Fig. 34 is an explanatory drawing illustrating a simulation result according to Example 11.

Fig. 35 is an explanatory drawing illustrating a simulation result according to Example 12.

Fig. 36 is an explanatory drawing illustrating a simulation result according to Example 13.

Fig. 37 is an explanatory drawing illustrating a simulation result according to Comparative Example 1.

Fig. 38 is an explanatory drawing illustrating the irradiation line of Comparative Example 2.

Fig. 39 is an explanatory drawing illustrating a simulation result according to Comparative Example 2.

Fig. 40 is an explanatory drawing illustrating the irradiation lines of Comparative Example 3.

Fig. 41 is an explanatory drawing illustrating a simulation result according to Comparative Example 3.

Fig. 42 is an explanatory drawing illustrating the irradiation line of Comparative Example 4.

Fig. 43 is an explanatory drawing illustrating a simulation result according to Comparative Example 4.

Fig. 44 is an explanatory drawing illustrating the test result of an example relating to the behavior of a molten metal flow.

Fig. 45 is an explanatory drawing illustrating the test result of an example of an electron beam for GNP dissolution acceleration.

Description of Embodiments

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that in the present description and the accompanying drawings, constituent members having essentially the same functional configuration are denoted by the same reference symbols, and their repeated description is omitted.

1. First Embodiment.

First, a method for producing a metal ingot according to the first embodiment of the present invention will be described.

1.1. Configuration of an electron beam melting furnace.

First with reference to FIG. 3, the configuration of the electron beam furnace for carrying out the metal ingot production method according to the present embodiment will be described. Fig. 3 is a schematic diagram illustrating the configuration of an electron beam furnace 1 (hereinafter referred to as an EB furnace 1) according to the present embodiment.

As shown in FIG. 3, the EL furnace 1 includes a pair of raw material supply portions 10A and 10B (hereinafter referred to generally as raw material supply portion 10), a plurality of electron guns 20A to 20E (hereinafter collectively referred to as electron guns 20), a cleaning bath 30, and a foundry form 40. Thus, the EL furnace 1 according to the present embodiment includes only one cleaning bath 30 as a bath, and the bath structure in question is referred to as a short bath. It should be noted that although the method for producing a metal ingot of the present invention can be preferably applied to the short bath EV furnace 1 as shown in FIG. 3, the metal ingot production method of the present invention is also applicable to the EL furnace 1A, which has a long bath as shown in FIG. one.

The purification bath 30 (hereinafter referred to as bath 30) is a device for purifying molten metal 5c from metal raw material 5 (hereinafter referred to as raw material 5) and simultaneously accumulating molten metal 5c to thereby remove impurities contained in the molten metal 5c. The bath 30 according to the present embodiment is, for example, a water-cooled copper bath having a rectangular shape. A spout part 36 is provided in a side wall at the end of one side in the longitudinal direction (Y direction) of the vat 30. The spout part 36 is an outlet for flowing molten metal 5c from the vat 30 into the mold 40.

The mold 40 is a device for cooling and solidifying molten metal 5c from raw material 5 to thereby produce a metal ingot 50 (for example, titanium ingot or

- 5 039285 titanium alloy current). The mold 40, for example, is a water-cooled copper mold having a rectangular tubular appearance. The mold 40 is positioned under the spout 36 of the tub 30 and cools the molten metal 5c pouring into it from the tub 30 above the mold 40. As a result, the molten metal 5c within the mold 40 gradually solidifies towards the bottom of the mold 40 , and a solid ingot 50 is formed.

The raw material supply part 10 is a device for supplying the raw material 5 to the bath 30. The raw material 5 is, for example, titanium raw material such as titanium sponge or waste. In the present embodiment, for example, as illustrated in FIG. 3, a pair of feed portions 10A and 10B are provided above a pair of long side walls of the tub 30. The solid feed 5 supplied from outside is placed in the feed portions 10A and 10B, and electron beams from the electron guns 20A and 20B are emitted onto the feed 5.

Thus, in the present embodiment, to supply the raw material 5 to the bath 30, the solid raw material 5 is melted by emitting electron beams on the raw material 5 in the raw material supply portion 10, and the molten raw material 5 (molten metal) drips into the molten metal 5c in the bath 30 from the inner edges parts 10 supply of raw materials. In other words, the raw material 5 is fed into the bath 30 by first pre-melting the raw material 5 outside the bath 30 and then allowing the molten metal to drip into the molten metal 5c in the bath 30. supply of raw materials to the surface of the molten metal 5c in the bath 30, correspond to the supply lines 26, which will be described later (see Fig. 4).

It should be noted that the method for supplying the raw material 5 is not limited to the dripping described in the above example. For example, the solid raw material 5 can be directly introduced, as it is, into the molten metal 5c in the bath 30 from the raw material supply portion 10. The introduced solid raw material 5 is then melted into the high temperature molten metal 5c, and thereby added to the molten metal 5c. In this case, the introduction lines, which are the positions at which the solid raw material 5 is introduced into the molten metal 5c in the bath 30, correspond to the supply lines 26, which will be described later (see FIG. 4).

To carry out the electron beam melting process, the electron guns 20 emit electron beams on the raw material 5 or the molten metal 5c. As shown in FIG. 3, the EL furnace 1 according to the present embodiment includes, for example, electron guns 20A and 20B for melting the solid raw material 5 that has been supplied to the raw material supply portion 10, the electron gun 20C for maintaining the temperature of the molten metal 5c in the bath 30 , an electron gun 20D for heating molten metal 5c at the top inside the mold 40, and an electron gun 20E for preventing impurities from flowing out of the bath 30. Each of the electron guns 20A to 20E is capable of controlling the electron beam irradiation position. Therefore, electron guns 20C and 20E are capable of projecting electron beams to desired positions on the surface of molten metal 5c in bath 30.

The electron guns 20A and 20B emit electron beams on the solid raw material 5 placed on the raw material supply portion 10 to thereby heat and melt the raw material 5. The electron gun 20C heats the molten metal 5c and maintains the molten metal 5c at a predetermined temperature by emitting an electron beam in a wide range onto the surface of the molten metal 5c in the bath 30. The electron gun 20D emits an electron beam onto the surface of the molten metal 5c in the mold 40 to thereby heat the molten metal 5c at its top and maintain the molten metal 5c at the top while predetermined temperature so that the molten metal 5c at the top of the mold 40 does not solidify. The electron gun 20E emits an electron beam in a focused manner along the irradiation line 25 (see FIG. 4) on the surface of the molten metal 5c in the bath 30 in order to prevent impurities from flowing out of the bath 30 into the mold 40.

Thus, the present embodiment is characterized in that it prevents impurities from escaping by, for example, emitting (emission lines) an electron beam in a focused manner along the irradiation line 25 on the surface of the molten metal 5c using the electron gun 20E. This characteristic will be described in detail later. It should be noted that in the EL furnace 1 according to the present embodiment, the electron gun 20E for the emission line shown in FIG. 3 is provided separately from other 2OA-2OD electron guns. Due to this, when other electron guns 20A to 20D are used to melt the raw material 5 and maintain the temperature of the molten metal 5c, linear irradiation by the electron gun 20E can be continued at the same time, so that the surface temperature of the molten metal 5c at the irradiation line position can be prevented from decreasing. However, the present invention is not limited to this example. For example, the electron beam can be emitted along the irradiation line 25 using one or more of the existing electron guns 20A and 20B for melting raw materials or electron guns 20C and 20D for maintaining the temperature of the molten metal, without additional installation of the electron gun 20E for linear irradiation. Due to this quantity

- 6 039285 The number of electron guns installed in the EL furnace 1 can be reduced, the cost of the equipment can be reduced, and the existing electron guns can be used efficiently.

1.2. Scheme of a method for the production of a metal ingot.

Next, with reference to FIG. 3-6, a flowchart of a method for producing a metal ingot by an electron beam melting process according to the first embodiment of the present invention will be described. Fig. 4 is a plan view illustrating one example of an irradiation line 25 and a supply line 26 in a bath 30 according to the present embodiment. Fig. 5 is a partial cross section along line I-I shown in FIG. 4. FIG. 6 is a plan view illustrating one example of a molten metal flow that is generated when an electron beam is emitted along an irradiation line according to the metal ingot production method of the present embodiment. It should be noted that the top views of FIG. 4 and 6 correspond to the bath 30 of the electron beam furnace 1 shown in FIG. 3.

The purpose of the metal ingot production method according to the present embodiment is to prevent the impurities contained in the molten metal (molten metal 5c) obtained by melting the solid raw material 5 from flowing out into the mold 40 from the bath 30 when producing the metal ingot 50 commercially pure titanium or titanium alloy, etc. According to the metal ingot production method of the present embodiment, specifically, a titanium raw material as a metal raw material is taken as an object, and the metal ingot production method solves the problem of preventing the occurrence of a situation in which the GNP, which among all the impurities contained in the titanium raw material, has density less than the density of molten titanium metal (molten titanium) fall into the titanium or titanium alloy ingot 50 . It should be noted that although the following describes the case in which the electron beam furnace 1 with a short bath, as illustrated in FIG. 3, the present invention is not limited to this example, and can also be applied to the long bath electron beam furnace 1A illustrated in FIG. one.

In order to solve the above problem, in the method for producing a metal ingot according to the present embodiment, as illustrated in FIG. 4, the raw material 5 is fed into the molten metal 5c inside the bath 30 through the supply lines 26, which are adjacent to the side walls 37A and 37B on the long sides of the bath 30. In addition, an electron beam is emitted along the irradiation line 25, which is positioned to block part 36 of the drain sock relative to the surface of the molten metal 5c, which is in the bath 30.

The supply lines 26 are imaginary lines representing the positions at which the raw material 5 is supplied from outside the bath 30 to the molten metal 5c in the bath 30. The supply lines 26 are located on the surface of the molten metal 5c at positions along the respective inner surfaces of the side walls 37A and 37B of the bath 30.

In the present embodiment, the molten raw material 5 drips into the bath 30 from the inner edge portions of the raw material supply portion 10 located at the top of the side walls 37A and 37B on the long sides of the bath 30, as illustrated in FIG. 3. Therefore, the respective supply lines 26 are located on the surface of the molten metal 5c in the bath 30 under the inner edge portions of the raw material supply portion 10, and are in the form of lines along the inner surface of the respective side walls 37A and 37B. It should be noted that the supply lines 26 do not need to have a strictly straight shape along the inner surfaces of the side walls 37A, 37B and 37C of the bath 30, and, for example, they can be in the form of a dotted line, the shape of a dotted line, a curvilinear shape, a wavy line shape, a zigzag a shape, a double line shape, a ribbon shape, a polygonal line shape, and the like.

The irradiation line 25 (corresponding to the irradiation line of the present invention) is an imaginary line that is a path of positions at which an electron beam (corresponding to the first electron beam of the present invention) is emitted in a focused manner onto the surface of the molten metal 5c in the bath 30. The irradiation line 25 is located on the surface molten metal 5c so that it blocks the spout portion 36. The two end portions e1 and e2 of the irradiation line 25 are located near the side wall 37A, 37B, 37C or 37D (hereinafter referred to as the side wall(s) 37) of the tub 30. The irradiation line 25 need not be strictly straight, and may, for example, have a dotted line shape, a dotted line shape, a curvilinear shape, a wavy line shape, a zigzag shape, a double line shape, a ribbon shape, a polygonal line shape, and the like.

The location of the irradiation line 25 and the supply line 26 will now be described in more detail. As illustrated in FIG. 4, the rectangular tub 30 according to the present embodiment has four side walls 37A, 37B, 37C, and 37D. The pair of side walls 37A and 37B that face each other in the X direction constitute a pair of long sides of the tub 30 and are parallel to the longitudinal direction (Y direction) of the tub 30. In other words, among the side walls 37, the side walls 37A and 37B extend substantially , perpendicular to the side wall 37D, in which the spout portion 36 is provided. In addition, a pair of side walls 37C and 37D, which

- 7 039285 face each other in the Y direction, make up a pair of short sides of the tub 30, and are parallel to the width direction (X direction) of the tub 30. Here, the term essentially perpendicular comes from the fact that the tub that is commonly used is rectangular , and one side wall and another side wall adjacent to that side wall intersect substantially perpendicularly. In other words, the term substantially perpendicular does not mean a strictly perpendicular condition, and a margin of error is allowed within the range in which use as a bathtub is normally possible. The permissible angular deviation from the perpendicular state can be, for example, within a range of 5°.

A spout part 36 for flowing molten metal 5c from the pool 30 into the mold 40 is provided in a side wall 37D which is one of the short sides. On the other hand, the spout portion 36 is not provided in the three side walls 37A, 37B, and 37C, which are side walls different from the side wall 37D. Therefore, the side wall 37D corresponds to the first side wall provided with the spout portion, and the side walls 37A, 37B, and 37C correspond to the side walls in which the spout portion 36 is not provided.

In the example illustrated in FIG. 4, two straight feed lines 26 are located along the side walls 37A and 37B on the surface of the molten metal 5c in the bath 30. In addition, the irradiation line 25 is positioned to block the downstream spout portion 36 in the longitudinal direction (Y direction). bath 30 relative to the lines 26 supply. In the present invention, that area in the longitudinal direction (Y direction) of the tub 30 which includes the supply lines 26 and does not contact the spout part 36 is referred to as the antecedent area S2. In addition, that region in the longitudinal direction (Y direction) of the tub 30 which is located between the preceding region S2 and the side wall 37D in which the spout portion 36 is provided is referred to as the subsequent region S3. In the following description, the area inside the bathtub 30 is described in such a way that it is divided into the previous area S2 and the next area S3 by a straight line that connects the end points on the two supply lines 26 from the part 36 of the drain sock.

The irradiation line 25 is located in the subsequent region S3. The two end portions e1 and e2 of the irradiation line 25 are located near the side wall 37A, 37B, 37C or 37D of the bath 30. In the example illustrated in FIG. 4, the end portions e1 and e2 are located near the side wall 37D. As used herein, the phrase end parts e1 and e2 located near the side wall 37 means that the end parts e1 and e2 are located on the inner surface of the side wall 37 or in the region in which the distance x from the inner surface of the side wall 37 is not more than 5 mm. The first electron beam is emitted to the corresponding area. It should be noted that a hardened layer, called the skull 7, which is the solidified molten metal 5c, is formed on the inner surface of the walls 37 of the bath 30 (see Fig. 5 and 6). The formation of the ledge 7 near the side walls 37 is not a problem and the first electron beam can be radiated onto the ledge 7.

In the present embodiment, a special temperature gradient is formed on the surface of the molten metal 5c in the bath 30 by emitting an electron beam in a focused manner along the irradiation line 25 on the surface of the molten metal 5c as mentioned above, and thereby controlling the flow of the molten metal 5c. Next, the temperature distribution on the surface of the molten metal 5c in the bath 30 will be described.

Generally, in the electron beam melting process, in order to prevent the molten metal 5c from solidifying in the bath 30, the electron beam is evenly irradiated, for example, by the electron gun 20C, to the heat-holding irradiation region 23, which occupies a wide surface area of the molten metal 5c, to thereby maintain the temperature. of the molten metal 5c in the bath 30. By performing such heat-holding electron beam emission, the entire molten metal 5c accumulated in the bath 30 is heated, and the average surface temperature T0 (hereinafter referred to as the molten metal surface temperature T0) of the entire surface of the molten metal 5c is maintained at a predetermined level. The surface temperature of the molten metal T0 is, for example, in the range from 1923 K (melting point of the titanium alloy) to 2323 K, and preferably is in the range from 1973 to 2273 K.

In the present embodiment, electron beams are emitted onto the solid raw material 5 at the aforementioned raw material supply portion 10 by the electron guns 20A and 20B to melt the raw material 5, and the high temperature molten metal flows down to the positions of the molten metal supply lines 26 5c in the bath 30, to thereby supply the raw material 5 to the bath 30. Therefore, among all the molten metal 5c in the bath 30, impurities such as GNP contained in the raw material 5 are mainly present near the supply lines 26 . In addition, since high-temperature molten metal is supplied continuously or intermittently to the supply lines 26, a high temperature region (see region S1 in FIG. 5) having a surface temperature T1 higher than the above-mentioned molten metal surface temperature T0 is formed near the supply lines 26 . Surface temperature T1 (hereinafter referred to as feed temperature T1) of molten metal 5c on lines 26

- 8 039285 supply is approximately the same as the temperature of the molten metal that drips from the raw material supply portion 10 into the bath 30, and is higher than the above-mentioned molten metal surface temperature T0 (T1>T0). The feed temperature T1 is, for example, within the range 1923-2423 K and preferably within the range 1973-2373 K.

In addition, according to the metal ingot production method of the present embodiment, apart from irradiating the above-mentioned heat holding electron beam to the molten metal 5c heat holding irradiation area 23, the electron beam is irradiated in a focused manner by the electron gun 20E to the molten metal 5c along the irradiation line 25. By such concentrated electron beam emission, a high temperature region having a surface temperature T2 that is higher than the aforementioned molten metal surface temperature T0 is formed in the downstream region S3 and blocks the spout portion 36. The surface temperature T2 (hereinafter referred to as the irradiation line temperature T2) of the molten metal 5c in the irradiation line 25 is higher than the above-mentioned molten metal surface temperature T0 (T2>T0). In addition, in order to more reliably suppress the leakage of impurities, the temperature of the irradiation line T2 is preferably higher than the above-mentioned feed temperature T1 (T2>T1>T0). The temperature of the irradiation line T2 is, for example, within the range of 1923 to 2473 K, and preferably is within the range of 1973-2423 K.

Thus, according to the method for manufacturing the metal ingot of the present embodiment by emitting an electron beam along the irradiation line 25 on the surface of the molten metal 5c, a high temperature region of the molten metal 5c is also formed near the irradiation line 25, not only near the supply lines 26. Due to this, as illustrated in FIG. 6, in the outer molten metal layer 5c, the molten metal flow 61 (corresponding to the molten metal flow of the present invention) can be forcibly generated from the irradiation line 25 in the opposite direction (i.e., the Y direction) which is the direction from the side wall 37D. In particular, the generated molten metal stream 61 can be constantly maintained by maintaining the temperature of the molten metal 5c above the temperature T0 at arbitrary positions of the irradiation line 25 .

The molten metal 5c that accumulates in the bath 30 is cleaned while in the bath 30 and then flows out of the spout portion 36 into the mold 40. As illustrated in FIG. 6, in the central part in the width direction (X direction) in the bath 30, the molten metal flow 60, which flows along the longitudinal direction (Y direction) of the bath 30, is formed from the vicinity of the side wall 37C, which is one of the short sides, and flows to the part 36 drain sock. Through this flow of molten metal 60, the molten metal 5c that has accumulated inside the bath 30 flows out of the spout portion 36 into the mold 40. The impurities are categorized into IGR (not shown), which have a high relative density compared to the molten metal 5c, and IRR 8 which have a low relative density compared to molten metal 5c. HPFs that have a high relative density settle in the molten metal 5c and adhere to the scull 7 that is formed on the surface of the bottom of the tub 30, and hence the probability of the HPFs flowing into the mold 40 from the spout portion 36 becomes low. On the other hand, a large part of the VNP 8, which have a low relative density, floats to the surface of the molten metal 5c and, as illustrated in FIG. 5 moves with the flow in the outer layer of molten metal 5c.

According to the method for producing a metal ingot of the present embodiment, an electron beam is irradiated to the surface of the molten metal 5c in the bath 30 along the irradiation line 25, which has two end portions e1 and e2 located at the side wall 37 of the bath 30 so as to block the pouring spout part 36 . Due to this, Marangoni convection is created by means of a temperature gradient on the surface of the molten metal 5c, and as illustrated in FIG. 6, in the outer layer of molten metal 5c, a reverse flow of the outer layer of molten metal 5c (molten metal flow 61) from the irradiation line 25 is formed. The molten metal stream 61 prevents the HLR 8 from flowing into the mold 40, causing the HLR 8, which float on the surface of the molten metal 5c in the bath 30, to move away from the spout portion 36 .

When a temperature gradient occurs at the surface of the fluid, there is also a surface tension gradient in the fluid, which causes convection to form in the fluid. Such convection in a fluid medium is called Marangoni convection. In the main metals, of which titanium is a representative, Marangoni convection is a flow from an area of high temperature to an area of low temperature.

Next, a case will be considered in which, when the raw material 5 drips along the supply lines 26 into the molten metal 5c in the bath 30, as illustrated in FIG. 4, the temperature of the molten metal (raw material supply temperature T1) which drips along the supply lines 26 is already higher than the temperature T0 of the molten metal accumulated in the bath 30. In this case, as illustrated

- 9 039285 but in FIG. 5, the region S1 near the supply lines 26 onto which the molten raw material 5 (molten metal) drips is a high temperature region in which the temperature is higher than the temperature of the molten metal 5c in other regions. Therefore, as illustrated in FIG. 5 and 6, in the outer layer of molten metal 5c, a molten metal flow 63 is formed from the region S1 to the side wall 37B and a molten metal flow 62 is formed from the region S1 to the central part in the width direction (X direction) of the bath 30.

Thus, as illustrated in FIG. 6, the VNP 8 contained in the molten metal that drips on the supply line 26 moves with the molten metal flow 62 to the center portion in the width direction (X direction) of the bath 30, and also moves with the molten metal flow 63 to the side wall 37B of the bath 30 The molten metal streams 62 that flow toward the central portion of the pool 30 from each of the left and right supply lines 26 collide at the central portion in the width direction of the pool 30, thereby forming a stream of molten metal 60 (see FIG. 6) toward the portion 36 spout along the longitudinal direction (Y-direction) of the bath 30. As a result, the SNR 8 floating in the molten metal 5c also moves with the molten metal flow 60 and flows towards the spout part 36. Therefore, in order to ensure that impurities, such as RNR 8, do not flow from spout portion 36 into mold 40, it is preferable that an outer layer of molten metal flow 5c be formed that repels RNR entrained by molten metal flow 60 towards portion 36 drain sock, in the opposite direction, and thus keeps the GNP away from part 36 of the drain sock.

Therefore, according to the production method of the metal ingot of the present embodiment, as illustrated in FIG. 4 and 6, an electron beam is irradiated onto the molten metal surface 5c along a V-shaped irradiation line 25, the two end portions e1 and e2 of which are located near the side wall 37D, and which protrudes rearward to block the spout portion 36. Due to this, the surface temperature T2 of the molten metal 5c in the area around the irradiation line 25 is increased, and a surface temperature gradient of the molten metal 5c is formed between the area around the irradiation line 25 and the irradiation area 23 to keep heat. As a result, Marangoni convection occurs and, as illustrated in FIG. 6, a reverse flow 61 of molten metal from the irradiation line 25 occurs in the outer layer of molten metal 5c. By means of this molten metal flow 61, the flow of impurities such as GNR is controlled, and the impurities that have flowed to the spout portion 36 are pushed back to a position that is farther from the irradiation line 25 . In this way, impurities can be prevented from escaping from the spout portion 36 .

Here, for example, by giving the irradiation line 25 a shape that protrudes away from the spout, such as a V-shape as illustrated in FIG. 4 and 6, Marangoni convection can be created such that the flow 61 of molten metal to the spout portion 36 flows towards the side walls 37A and 37B of the tub 30. In other words, in FIG. 6, the molten metal flow 61 is a flow that is directed in the opposite direction (away from the spout part 36) in the Y-axis direction, and also from the spout part 36 in the X-axis direction. Thus, the molten metal flow 61 moves impurities such as as GNPs that float on the surface of the molten metal 5c in areas near the supply lines 26, in the opposite direction from the irradiation line 25, and also to the side walls 37A and 37B of the bath 30.

Some of the HLRs 8 moving towards the side walls 37A and 37B adhere to the scull 7 formed on the inner surfaces of the side walls 37 of the bath 30 and therefore no longer travel in the molten metal 5c in the bath 30. Alternatively, the HLRs 8 gradually dissolve as they circulate within the bath 30. Particularly, since the molten metal 5c in the immediate vicinity of the irradiation line 25 is at a high temperature, the melting of the HPR 8 is accelerated. Thus, when the electron beam is emitted along the irradiation line 25, impurities are not only blocked and trapped in the irradiation line 25, but the impurities are also trapped by the skull 7 formed on the inner surfaces of the side walls 37A and 37B, or the dissolution of nitrided titanium, etc. is accelerated, which is the main component of the GNP 8, and thus the leakage of impurities from the spout portion 36 can be prevented.

Thus, according to the method for manufacturing the metal ingot of the present embodiment, the electron beam is emitted along the irradiation line 25 which is downstream of the supply lines 26 . This forms a reverse flow of molten metal 61 from the high temperature region of the molten metal 5c near the irradiation line 25, and as a result, impurities such as GNP that flowed towards the spout portion 36 are pushed back from the spout portion 36. Therefore, the leakage of impurities from the bath 30 into the mold 40 can be prevented. As a result, impurities can be prevented from entering the ingot.

1.3. The location of the irradiation line.

Next, the location of the irradiation line 25 along which the electron beam is emitted in a focused manner will be described in detail.

In the method for producing a metal ingot according to the present embodiment,

- 10 039285, as illustrated in FIG. 4, the electron beam is emitted along the irradiation line 25, which is located in the downstream region S3 between the upstream region S2, which includes the supply lines 26, and the side wall 37D. The supply lines 26 are imaginary lines representing the positions at which the molten metal of the raw material 5 drips into the molten metal 5c in the bath 30. The irradiation line 25 is an imaginary line that corresponds to the travel path of the electron beam that is emitted by the linear irradiation electron gun 20E.

In the method for producing a metal ingot according to the present embodiment, as illustrated in FIG. 6, the irradiation line 25 has a V-shape which has two end portions e1 and e2 located at the side wall 37D and which protrudes backward to block the spout portion 36. When the electron beam is emitted onto the surface of the molten metal 5c along this irradiation line 25, a reverse flow 61 of molten metal from the irradiation line 25 is formed. As a result, the molten metal stream 60 flowing to the spout portion 36 is pushed back, and it becomes possible to prevent impurities such as GNR from flowing out of the pool 30 into the mold 40.

Here, it is preferable to suitably position the irradiation line 25 so that the molten metal flow 60 from the center of the bath 30 to the spout 36 does not pass through the irradiation line 25 and flow to the spout 36. Therefore, according to the production method of the metal ingot of the present embodiment, the irradiation line 25 is used to securely separate the previous area S2 in which the supply lines 26 are located and the spout portion 36. To this end, the two end parts e1 and e2 of the irradiation line 25 are located near the side wall 37. The phrase end parts e1 and e2 are located near the side wall 37 means that the end parts e1 and e2 are located on the inner surface of the side wall 37 or in the area in which the distance x from the inner surface of the side wall 37 is not more than 5 mm. When the end portions e1 and e2 are inside the above region, impurities such as GNP do not pass through the space between the side wall 37 and the end portions e1 and e2 of the irradiation line 25, and the flow path from the preceding region S2 to the spout portion 36 can be reliably blocked. . It should be noted that, as mentioned above, the formation of the ledge 7 near the side walls 37 is not a problem, and the first electron beam can be radiated onto the ledge 7.

In addition, it is necessary that the width b of the irradiation line 25 in the X direction in FIG. 4 (hereinafter referred to as the width of the irradiation line) was at least larger than the opening width b ₀ of the spout portion 36 . If the width b of the irradiation line is smaller than the width b ₀ of the opening of the spout part 36, there is a possibility that the flow of the outer layer of molten metal 5c from the previous region S2 to the spout part 36 will occur in the part in which the electron beam is not emitted, and the ERR will flow into the mold 40. It should be noted that the width b of the irradiation line may be smaller than the width of the pool 30, and the time required for a single scan of the irradiation line 25 increases with increasing width b of the irradiation line. When the time required for a single scan of the irradiation line 25 is increased, the flow 61 of molten metal to the side walls of the bath 30 generated by the electron beam emission is weakened, and the probability of outflow of the IRR to the spout portion 36 is increased.

In addition, the irradiation line height h, which is the height at which the irradiation line 25 protrudes backward, is determined in consideration of the molten metal flow 61 generated by the emission of the corresponding electron beam and the scanning time. Here, the height h of the irradiation line is equal to the distance from the top of the irradiation line 25 to the point of intersection between the straight line that connects the two end portions e1 and e2 of the irradiation line 25 and the straight line passing in the Y direction through the top of the irradiation line 25. As the height h of the irradiation line increases, the degree to which the molten metal stream 61 formed by the electron beam emission along the irradiation line 25 having the V-shape illustrated in FIG. 4 becomes a flow towards the side walls 37A and 37B of the bath 30, but on the other hand, the time required for a single scan of the irradiation line 25 increases. Therefore, it is preferable to set the height h of the irradiation line so that the time required for scanning becomes as short as possible while maintaining the direction of the molten metal flow 61 towards the side walls 37A and 37B.

In the method for producing a metal ingot according to the present embodiment, the position of the top of the irradiation line 25 is not limited to the position on a straight line that passes through the width center of the pool 30 (hereinafter also referred to as the center line) as illustrated in FIG. 4. However, it is desirable that the top of the irradiation line 25 and the center of the opening width of the spout portion 36 be on the center line of the tub 30, as illustrated in FIG. 4. By positioning the top of the irradiation line 25 on the center line, as illustrated in FIG. 6, the molten metal flow 61 can be made symmetrical about the center line. By emitting an electron beam in this way, the flow of the outer layer is melted

The metal 5c can be oriented towards the side walls 37A and 37B, which are a short distance from the irradiation line 25, and the likelihood of impurities such as GNP adhering to the skull 7 can be increased.

As long as the electron beam irradiation line 25 of the metal ingot production method according to the present embodiment has a convex shape that protrudes backward from the spout portion 36, the irradiation line 25 may have a shape other than the V-shape shown in FIG. 4. For example, the irradiation line 25 may have a curvilinear shape such as a parabola. Alternatively, the irradiation line 25 may have, for example, a substantially semi-circular arc shape, as illustrated in FIG. 7. In this case, the arc-shaped irradiation line 25 has a diameter that is equal to or greater than the opening width bo of the spout portion 36 . In particular, as illustrated in FIG. 7, the arc-shaped irradiation line 25 is set so that its center is on a straight line passing through the center of the opening width of the spout part 36, and so that it is part of a circle having a diameter equal to or greater than the opening width bo of the spout part 36 sock.

In this case, also similarly to FIG. 4, when the temperature of the raw material 5 which drips onto the supply line 26 is higher than the temperature of the molten metal 5c which is already accumulated in the bath 30, molten metal streams are formed which correspond to the molten metal streams 60, 61 and 62 shown in FIG. 6. In other words, the molten metal streams from the raw material 5 that drip onto the respective supply lines 26 flow toward the center in the width direction (X direction) of the bath 30, and these molten metal streams 62 collide with each other at the center in the width direction (direction X) baths 30 and thereby form a stream 60 of molten metal which flows to the spout part 36.

In addition, the irradiation line 25 is set so that the two end portions e1 and e2 are located near the side wall 37D, and the irradiation line 25 blocks the spout portion 36. The electron beam is irradiated onto the surface of the molten metal 5c along the irradiation line 25 which is thus defined. Due to this, Marangoni convection occurs, and the flow 60 of molten metal, which flows to the part 36 of the spout, is directed back to the side walls 37A and 37B. As a result, the HPR sticks to the scull 7 formed on the side walls 37 of the tub 30, and thus the HPR can be prevented from moving through the molten metal 5c. Alternatively, the GNPs may also be dissolved by circulation through the molten metal 5c that has accumulated in the bath 30.

It should be noted that, the actual irradiation position at which the electron beam is emitted to the irradiation line 25 need not be exactly on the irradiation line 25. It is sufficient that the actual irradiation position at which the electron beam is emitted is approximately on the irradiation line 25, which is set as the target, and no problems arise as long as the actual path of the electron beam is within the allowable deviation range from the irradiation line 25, which is set as the target. In addition, the two end parts e1 and e2 of the irradiation line 25 are located near the inner surface of the side wall 37 of the tub 30. The phrase end parts e1 and e2 are located near the side wall 37 means that the end parts e1 and e2 are located on the inner surface of the side wall 37 or in a region in which the distance x from the inner surface of the side wall 37 is not more than 5 mm. The end portions e1 and e2 of the irradiation line 25 are set in this area, and the electron beam is emitted along the irradiation line 25, and the formation of the ledge 7 on the inner surface of the side walls 37 of the tub 30 is not a problem, and the electron beam can be radiated to the ledge 7.

In addition, in the method for producing a metal ingot according to the present embodiment, if the location of the electron beam irradiation line 25 is such that inside the succeeding region S3, the two end portions e1 and e2 are near the side wall 37 (either of 37A, 37B, 37C, and 37D ) and the irradiation line 25 blocks the spout portion 36 (so that the preceding region S2 and the spout portion 36 are securely separated by the irradiation line 25), the irradiation line 25 may have any arbitrary shape. The forms illustrated in Fig. 4 and 7 are merely illustrative examples, and the form in which the irradiation line 25 is separated from the side wall 37D more than in the above examples is also acceptable.

For example, as illustrated in FIG. 8, in the case where the preceding region S2 containing the supply lines 26 is located upstream in the longitudinal direction of the tub 30, the succeeding region S3 between the preceding region S2 and the side wall 37D is wider than in the case illustrated in FIG. 4. However, since it is possible to position the irradiation line 25 at any position, as long as it is in the subsequent region S3, as illustrated in FIG. 8, it is also possible to arrange the irradiation line 25 in the central part in the longitudinal direction of the bath 30. In this case, the two end parts e1 and e2 of the irradiation line 25 can be located at the side walls 37A and 37B. From the point of view of more reliably preventing the EPR 8 from flowing into the mold 40 from the bath 30, it is preferable to position the two end portions e1 and e2 of the irradiation line 25 against the side wall 37D in which the spout portion 36 is provided, as illustrated in FIG. 4 etc. Due to this, the scanning distance of the electron beam is shortened, and

- 12 039285 the time required for a single scan of the irradiation line 25 can be reduced. As a result, the temperature of the molten metal 5c in the irradiation line 25 can be effectively increased, and the molten metal return flow 61 from the irradiation line 25 can be formed earlier in the outer layer of the molten metal 5c.

1.4. Electron beam settings for linear irradiation.

Next, the settings of the electron beam for linear irradiation (the first electron beam) which is emitted in a focused manner along the above-mentioned irradiation line 25 will be described.

In order to push back the molten metal stream 62 from the supply lines 26 (see FIG. 6) away from the outlet of the bath 30 by means of the molten metal stream 61 away from the irradiation line 25 (see FIG. 6), as mentioned above, it is preferable to suitably set the irradiation conditions such as the amount of heat transfer, the scanning speed, and the heat flux distribution of the electron beam for linear irradiation.

The amount of heat transferred [W] of the electron beam is a parameter that influences the temperature increase of the molten metal 5c in the irradiation line 25, as well as the rate of the Marangoni convection flow (molten metal flow 61) that is generated due to the temperature increase in question. If the electron beam heat transfer amount is small, the molten metal flow 61 which overcomes the total molten metal flow 5c cannot be formed. Accordingly, the larger the electron beam heat transfer amount, the better, and for example, the heat transfer amount may be in the range of 0.150.60 [MW].

The scanning speed [m/s] of the electron beam is a parameter that affects the speed of the aforementioned molten metal flow 61 . When the electron beam is emitted along the irradiation line 25, the irradiation line 25 on the surface of the molten metal 5c is repeatedly scanned by the electron beam emitted from the electron gun 20E. If the scanning speed of the electron beam is then low, then the irradiation line 25 will have places that are not irradiated by the electron beam for a long time. At these locations, the surface temperature of the molten metal 5c will decrease rapidly, and the flow rate 61 of molten metal that occurs at these locations will also decrease. In such a case, it will be difficult to suppress the molten metal flow 60 by the molten metal flow 61, and the possibility that the molten metal flow 60 will pass through the irradiation line 25 will increase. Therefore, the scanning speed of the electron beam is preferably as high as possible, and is, for example, within the range of 1.0-20.0 [m/s].

The distribution of the heat flux generated by the electron beam on the surface of the molten metal 5c is a parameter that affects the amount of heat transferred to the molten metal 5c by the electron beam. The heat flux distribution corresponds to the size of the electron beam aperture. The smaller the aperture of the electron beam, the greater the degree of steepness of the distribution of the heat flux transmitted to the molten metal 5c. The heat flow distribution on the surface of the molten metal 5c, for example, is described by the following formula (1) (see, for example, non-patent document 1). The following formula (1) shows that the heat flux decreases exponentially according to the distance from the electron beam spot.

Expression 1

z. x f ( ^χ - ^χ ο) ² + (y-YoA q(t, x, y) = q ₀ exp----------l ^2σ ) (1) if qdxdy = Q

J Jail surface (2) where (x, y) represents the position of the molten metal surface, (xo, yo) represents the electron beam spot, and σ represents the standard deviation of the heat flux distribution. In addition to this, qo is the heat flux in the electron beam spot. When the amount of heat transferred by the electron gun is Q, as illustrated in the above formula (2), q ₀ is set so that the total sum of the heat flow q over the entire surface of the molten metal inside the bath becomes Q.

As for these parameters, their values can be determined, for example, by heat flow simulation or the like. and positioned to redirect molten metal flow 60 from the center of bath 30 to spout 36 upstream of irradiation line 25 by Marangoni convection which is generated by electron beam radiation along irradiation line 25. Specifically, the electron beam emission conditions for linear irradiation can be set such that the temperature (irradiation line temperature T2) of the high temperature region near the irradiation line 25 becomes higher than the temperature (surface temperature of the molten metal TO) of the heat-holding irradiation region 23, as illustrated in FIG. 6.

It should be noted that the aforementioned radiation conditions, such as the amount of heat transferred, scanning speed, and electron beam heat flux distribution for linear irradiation

- 13 039285 The values are limited to the characteristics of the equipment that emits the electron beam. Accordingly, when setting the electron beam emission conditions, it is advantageous to make the amount of heat transfer as large as possible, the scanning speed to be as high as possible, and the heat flux distribution to be as narrow as possible (i.e., to make the aperture of the electron beam as small as possible) within the equipment performance range. In addition, the emission of the electron beam through the irradiation line 25 may be performed by a single electron gun or a plurality of electron guns. In addition, the electron gun 20E exclusively for linear irradiation (see FIG. 3) can be used as the electron gun for the linear irradiation described here, or alternatively, electron guns designed for other purposes, such as electron guns, can be used for linear irradiation. guns 20A and 20B for melting raw materials or electron guns 20C and 20D for maintaining the temperature of the molten metal (see Fig. 3).

1.5. Summary.

The method for producing a metal ingot according to the first embodiment of the present invention has been described above. According to the present embodiment, an electron beam is irradiated onto the surface of the molten metal 5c in the bath 30 along an irradiation line 25, the two end portions e1 and e2 of which are located against the side wall 37 of the bath 30, and which is positioned to block the spout portion 36 of the spout. Due to this, Marangoni convection is created by means of a temperature gradient on the surface of the molten metal 5c, and as illustrated in FIG. 6, in the outer molten metal layer 5c, a reverse flow of the outer molten metal layer 5c (molten metal flow 61) from the irradiation line 25 is formed. Accordingly, by means of the molten metal stream 61, the molten metal stream 60 passing through the central part of the bath 30 to the spout part 36 can be pushed back upstream of the irradiation line 25, and impurities such as GNP can flow out of the bath 30 into the mold 40 8 floating in the molten metal 5c can be prevented. The molten metal 5c which is pushed back inside the bath 30 melts while circulating through the molten metal 5c in the bath 30 or is captured by the skull 7.

In addition, the irradiation line 25 is formed to have a convex shape protruding backwards, as illustrated in FIG. 4 and 7. In this way, the flow 60 of molten metal to the spout part 36 can be directed towards the side walls 37A and 37B of the bath 30 from the irradiation line 25 of the flow 61 of molten metal. As a result, the EOR 8 floating in the outer layer of molten metal 5c may adhere to the scull 7 on the inner surface of the side walls of the bath 30. In addition, it is also possible to dissolve the EOR 8 while they are circulating through the molten metal 5c in the bath 30. By this, the occurrence of a situation in which impurities flow from the pool 30 into the mold 40 and enter the ingot 50 can be prevented.

Furthermore, according to the metal ingot production method of the present embodiment, since there is no need to change the shape of the existing bath 30, this method can be easily carried out and special maintenance is also not required.

In conventional titanium alloy production methods, it is customary to remove impurities by keeping the molten metal for a long time in the bath, thereby dissolving the GNP in the molten metal, while causing the GNP to adhere to the scull formed on the surface of the bottom of the bath. Therefore, a long bath has traditionally been used to thereby ensure sufficient residence time of the molten metal in the bath. However, according to the metal ingot production method of the present embodiment, since impurities can be suitably removed even when the residence time of the molten metal in the bath is relatively short, it is possible to use a short bath. Accordingly, by using a short bath in the EL furnace 1, heating costs such as electricity consumption can be reduced, and the production cost of the EL furnace 1 can be reduced accordingly. In addition, when using a short bath instead of a long bath, the amount the scull 7 formed in the tub can be reduced. Therefore, the output can be improved.

2. Second embodiment.

Next, a method for producing a metal ingot by an electron beam melting process according to the second embodiment of the present invention will be described.

In the method for producing a metal ingot by the electron beam melting process according to the present embodiment, the shape of the electron beam irradiation line 25 differs from the first embodiment. The following will mainly describe the differences between the metal ingot production method and the first embodiment, and a detailed description of settings and processing similar to the metal ingot production method according to the first embodiment will be omitted. It should be noted that although the following description also describes the case in which the short bath electron beam furnace 1 illustrated in FIG. 3, the present invention is not limited to this example, and can also be applied to the long bath electron beam furnace illustrated in FIG. one.

- 14 039285

2.1. Scheme of the method for the production of a metal ingot.

In the method for producing a metal ingot by an electron beam melting process according to the present embodiment, the irradiation line 25 has a T-shape, which includes a first straight portion L1 along the side wall 37D between two end portions e1 and e2, and a second straight the portion L2 that extends backwards substantially perpendicular to the first straight portion L1. The spout portion 36 is blocked by the first straight portion L1. By radiating the electron beam along the irradiation line 25 having this shape, the VNPs floating in the outer layer of molten metal 5c are prevented from flowing out of the pool 30 into the mold 40.

The present embodiment will now be described in more detail based on FIG. 9 and 10. FIG. 9 is a plan view illustrating one example of an irradiation line 25 in a metal ingot production method according to the present embodiment, and also illustrates molten metal flows on the surface of molten metal 5c in bath 30. FIG. 10 is a plan view illustrating one example of an irradiation line 25 in a metal ingot production method according to the present embodiment. It should be noted that the top view in Fig. 9 corresponds to the bath 30 of the electron beam furnace 1 shown in FIG. 3. In addition, in FIG. 10, description of the scull that forms on the inner surface of the side walls 37 of tub 30 will be omitted.

In the present embodiment, as illustrated in FIG. 9 and 10, the irradiation line 25 is T-shaped, and the electron beam is emitted along the irradiation line 25. In this case, similar to the case in which the electron beam is emitted along the irradiation line 25 illustrated in the first embodiment, a temperature gradient is also generated between the heat-holding irradiation region 23 and the region near the irradiation line 25, and Marangoni convection occurs. As a result of the occurrence of Marangoni convection, a reverse flow 61 of molten metal from the line 25 of irradiation is formed, and the RNPs are pushed back.

Fig. 9 illustrates the flow of molten metal 5c when the temperature of the feedstock 5 that drips into the molten metal 5c along the supply lines 26 is higher than the temperature of the molten metal 5c that has already accumulated in the bath 30. Marangoni convection is a flow from the region high temperature to low temperature area. Therefore, the raw material 5, which drips into the molten metal 5c along the supply lines 26, is carried along by the molten metal flow 62 and moves toward the center portion in the width direction (X direction) of the bath 30, and is also carried along by the molten metal flow 63 towards the side walls 37A and 37B of the bath. 30. The molten metal streams 62 that flow toward the center portion of the pool 30 from each of the left and right supply lines 26 collide at the center portion in the width direction of the pool 30, thereby forming a stream of molten metal 60 toward the spout portion 36 along the longitudinal direction ( direction Y) of the bath 30. As a result, the VPR 8, floating in the molten metal 5c, also moves with the flow of molten metal 60 and flows to the part 36 of the drain sock. By forming the flow of the outer layer of molten metal 5c, which repels the WLR, which are moving with the flow of molten metal 60 towards the spout part 36, in the opposite direction, and thus keeps the WLR away from the spout part 36, it is possible to prevent impurities such as WLR from flowing out. 8 from spout part 36 to mold 40.

In the method for producing a metal ingot according to the present embodiment, as illustrated in FIG. 9, when the molten metal flow 60 towards the spout part 36 approaches the spout part 36, the molten metal flow 60 reaches a region in which an electron beam is emitted along the T-shaped irradiation line 25 onto the surface of the molten metal 5c. The irradiation line 25 consists of a first straight portion L1 which is substantially parallel to the side wall 37D and which blocks the spout portion 36, and a second straight portion L2 which extends backward from approximately the center of the first straight portion L1. The two end portions e1 and e2 of the first straight portion L1 are located near the side wall 37D.

The temperature of the molten metal T2 in the region near the irradiation line 25 along which the electron beam is emitted increases compared to the temperature T0 of the irradiation region 23 to keep heat. Therefore, Marangoni convection occurs and a reverse flow 61 of molten metal from the irradiation line 25 is formed. Due to the occurrence of Marangoni convection, as illustrated in FIG. 9, the molten metal stream 60 towards the spout portion 36 is pushed back by the molten metal stream 61 that originates at the irradiation line 25 and becomes a stream that flows towards and reaches the side walls 37A and 37B of the tub 30. Due to this, after the RNP, entrained by the stream 60 of the molten metal to the part 36 of the drain sock, will move to the side walls 37A and 37B of the tub 30, the RNP stick to the ledge 7 formed on the side walls of the tub 30, and stop moving. Alternatively, the RNPs entrained on the surface of the molten metal 5c are dissolved during circulation through the bath 30.

Thus, according to the metal ingot manufacturing method of the present embodiment, an electron beam is emitted along the T-shaped irradiation line 25 . Due to this, it is formed

- 15 039285 return flow of molten metal from the irradiation line 25. As a result, the ROP in the molten metal 5c can be prevented from flowing out of the bath 30 into the mold 40. Therefore, the occurrence of a situation in which impurities flow from the bath 30 into the mold 40 and enter the ingot 50 can be prevented.

2.2. The location of the irradiation line.

When the irradiation line 25 is in a T-shape, electron beams can be emitted along the irradiation line 25 using, for example, three electron guns. In other words, as illustrated in FIG. 10, the electron beams may be emitted along the irradiation lines d1 and d3 constituting the first straight portion L1 and the irradiation line d2 constituting the second straight portion L2, respectively.

As for the first rectilinear portion L1 along the side wall 37D, which is substantially parallel to the width direction (X direction) of the bath 30, electron beams are emitted to it using two electron guns. The irradiation line d1 and the irradiation line d3 have a common end and are substantially collinear. The control accuracy of the electron beam irradiation position is reduced by the evaporation of a volatile valuable metal such as aluminum, especially in the case of metal alloy melting. Accordingly, in order to reliably block the spout portion 36 with electron beam radiation along the first straight portion L1, it is preferable that one end of the irradiation line d1 and one end of the irradiation line d3 overlap each other. In particular, by overlapping the irradiation line d1 and the irradiation line d3 by 5 mm or more, even when the accuracy of controlling the positions of the electron beams with respect to the irradiation line 25 decreases, a gap can be prevented between the irradiation line d1 and the irradiation line d3.

The length b ₂ of the irradiation line of the first rectilinear part L1 (i.e. the sum of the lengths of the irradiation lines d1 and d3 in Fig. 10) is determined taking into account the height h _{2 of} the second rectilinear part L2 of the irradiation line, which will be described later, or the amount of heat transferred by electronic beams emitted from electron guns. The length b ₂ of the irradiation line is set so that it is at least greater than the opening width of the spout part 36 . If the length b ₂ of the irradiation line is less than the width of the opening of the spout part 36, there is a possibility that a flow of molten metal is formed from the previous region S2 of the bath 30 to the spout part 36 in the part that is not irradiated by the electron beam, and the ERR will flow from tub 30 into the mold 40. Therefore, it is desirable to make the length b ₂ of the irradiation line at least greater than the width of the opening of the spout part 36.

In addition, the length b ₂ of the irradiation line may be less than the width of the pool 30, and the time required for a single scan of the first straight portion L1 illustrated in FIG. 9 increases with increasing length b2 of the irradiation line. If the time required for a single scan of the irradiation line 25 is increased, the flow 61 of molten metal to the side walls of the bath 30 created by the electron beam will become weaker, and the probability of passing through the spout portion 36 of the spout 36 will increase. It is also desirable that the respective lengths of the irradiation lines d1 and d3, which constitute the first straight portion L1, be approximately the same. By this, the scanning distance of each electron beam can be uniformly reduced, and the temperature of the molten metal 5c in the first straight portion L1 can be uniformly increased. It should be noted that the number of electron guns that emit an electron beam onto the first straight portion L1 is not limited to that used in this example, and may be 1 or may be 3 or more.

In addition, with regard to the second straight portion L2, the electron beam may be radiated to it, for example, by one electron gun. Although the number of electron guns that emit an electron beam along the second straight portion L2 may be greater than one, generally, since the scanning distance in this case is shorter than for the first straight portion L1, it is possible to adequately emit the electron beam along the second straight portion L2 with using one electron gun. The height h ₂ of the irradiation line of the second straight part L2 is also determined taking into account the length b ₂ of the irradiation line of the first straight part L1 or the amount of heat transferred by the electron beam emitted by the electron gun. The larger the height h ₂ of the irradiation line, the longer the time required to scan the irradiation line 25 once, and the smaller the degree of increase in the temperature of the molten metal 5c in the second straight portion L2. Therefore, the height h2 of the irradiation line is set so that the time required for scanning can be made as short as possible and the temperature of the molten metal 5c can be effectively increased. It should be noted that it is desirable that the height h2 of the irradiation line is within a range of values equivalent to approximately 2/5-3/5 of the length b ₂ of the irradiation line.

In the case of irradiating the electron beam to the surface of the molten metal 5c in the bath 30 along the above-mentioned T-shaped irradiation line 25, it is desirable to set the width center of the opening of the spout part 36, the midpoint of the first straight part L1 and the second straight part L2 on the center line of the bath 30, as illustrated in fig. 10. Due to this, the flow of races

- 16 039285 molten metal 5c in the bath 30 can be made approximately symmetrical about the center line. In addition, the flow of molten metal in the electron beam irradiation line 25 may be directed towards the side walls 37A and 37B that are in the vicinity of the irradiation line 25. Due to this, the likelihood of impurities such as GNP adhering to the skull 7 can be increased.

It should be noted that, the actual irradiation position at which the electron beam is emitted to the irradiation line 25 need not be strictly on the irradiation line 25. It is sufficient that the actual irradiation position at which the electron beam is emitted is approximately on the irradiation line 25, which is set as the target, and no problems arise as long as the actual path of the electron beam is within the allowable deviation range from the irradiation line 25, which is set as the target. In addition, the two end portions e1 and e2 of the first straight portion L1 of the electron beam path in the present embodiment are located near the inner surface of the side wall of the tub 30. The phrase end portions e1 and e2 are located near the side wall 37 means that the end portions e1 and e2 are located on the inner surface of the side wall 37 or in a region where the distance x from the inner surface of the side wall 37 is not more than 5 mm. The end portions e1 and e2 of the irradiation line 25 are set in this area, and the electron beam is emitted along the irradiation line 25, and the formation of the ledge 7 on the inner surface of the side walls 37 of the tub 30 is not a problem, and the electron beam can be radiated to the ledge 7.

In addition, with regard to the electron beams emitted from the respective electron guns, similarly to the first embodiment, the radiation conditions such as the amount of heat to be transferred, the scanning speed, and the heat flux distribution of the electron beam are limited by the characteristics of the equipment that emits the electron beam. Accordingly, when setting the electron beam emission conditions, it is preferable to make the amount of heat transferred by the electron beam as large as possible, the scanning speed to be as high as possible, and the heat flow distribution to be as narrow as possible (i.e., to make the aperture of the electron beam as small as possible) within the performance range of the equipment.

In this case, the irradiation line 25 in the metal ingot production method according to the present embodiment is composed of a first straight portion L1 and a second straight portion L2. The molten metal stream 61, which is formed by irradiating electron beams along the T-shaped irradiation line 25, is formed when the streams formed by the first straight portion L1 and the second straight portion L2 overlap each other. Therefore, the method for emitting electron beams along the T-shaped irradiation line 25 is determined based on at least one of the length b ₂ of the irradiation line and the height h ₂ of the irradiation line, as well as the amount of heat transmitted by the electron gun. The surface flow vector of molten metal 5c towards the side walls 37 of the bath 30 from the irradiation line 25 can be determined by setting the above values.

Specifically, in the case where the amount of heat transmitted by the electron beam emitted along the first straight portion L1 is greater than the amount of heat transmitted by the electron beam emitted along the second straight portion L2, the flow to the side wall 37C which faces the portion 36 bath sock drain 30, will be stronger. On the other hand, when the amount of heat transferred by the electron beam emitted along the second straight portion L2 is greater than the amount of heat transferred by the electron beam emitted along the first straight portion L1, the flows to the side walls 37A and 37B of the bath 30 will be stronger. Thus, the orientation of the molten metal flow from the electron beam irradiation position to the side walls 37 of the bath 30 may be determined by the ratio between the radiant force of the electron beam(s) to the first straight portion L1 and the radiant force of the electron beam to the second rectilinear portion L2.

For example, if the amount of heat transferred by the electron guns used is approximately the same, the method of irradiating the irradiation line 25 can be determined based only on the ratio between the length b ₂ of the irradiation line and the height h ₂ of the irradiation line. In this case, for example, the scan distances of the respective electron guns (i.e., the lengths of the irradiation lines d1, d2 and d3) can be made approximately the same, and the corresponding parameters can be set so that the scan rates and heat flux distributions also become approximately the same. . In other words, the length b2 of the irradiation line is made equal to twice the height h2 of the irradiation line.

In addition, in the case where the amounts of heat transmitted by the electron guns used differ from each other, it is sufficient to determine the irradiation method of the irradiation line 25, taking into account the length b2 of the irradiation line and the height h2 of the irradiation line, and the amount of heat transmitted by the respective electron guns, so that the flow of molten metal 60 to the spout portion 36 is pushed back by the flow of molten metal 61 to the side walls 37A and 37B of the tub 30.

- 17 039285

Further, according to the electron beam emitting method of the present embodiment, the molten metal flow 61 is formed by overlapping the flows formed by the first straight portion L1 and the second straight portion L2. Therefore, compared with the case where the electron beam is emitted along the irradiation line 25 illustrated in the first embodiment, the speed at which the HLRs are directed towards the side walls 37 of the tub 30 can be increased, and the probability of the HLRs sticking to the ledge 7 can be further increased. . Accordingly, even if at least any one value among the heat transfer amount, the scanning speed and the heat flux distribution of each electron gun is smaller than the settings for the electron gun that emits the electron beam along the irradiation line 25 illustrated in the first embodiment , it is possible to obtain an effect that is equal to or greater than that of the first embodiment.

Thus, by emitting electron beams along the irradiation line 25 as described in the metal ingot production method according to the present embodiment, it is possible to move the flow on the surface of the molten metal 5c to the spout part 36 back in the direction from the irradiation line 25 to the side walls 37A and 37B of the tub 30. By doing so, the RNPs that have flowed to the spout portion 36 can be directed towards the side walls 37 of the tub 30 and trapped by the ledge 7 on the side walls 37 of the tub 30. Alternatively, the RNPs can also be dissolved by circulating through the molten metal 5c in bath 30. Due to this, the occurrence of a situation in which the GNR flows out of the bath 30 into the mold 40 and enters the ingot can be prevented.

It should be noted that the irradiation line 25 is not particularly limited, and any arbitrary shape can be used as long as the irradiation line 25 is such that, within the succeeding region S3, two end portions e1 and e2 are located near the side wall 37 (either of 37A, 37B, 37C and 37D) and the irradiation line 25 blocks the spout part 36 (so that the previous region S2 and the spout part 36 are securely separated by the irradiation line 25). For example, the line 25 irradiation may be located in the Central part in the longitudinal direction of the tub 30 or may be located near the part 36 of the drain sock. From the point of view of more reliable prevention of the outflow of WNP from the tub 30 into the mold 40, the irradiation line 25 is preferably located as close as possible to the drain sock portion 36 .

2.3. Summary.

The method for producing a metal ingot according to the second embodiment of the present invention has been described above. According to the present embodiment, the irradiation line 25 has a T-shape that includes a first straight portion L1 along the side wall 37D between two end portions e1 and e2, and a second straight portion L2 that extends backwards substantially perpendicular to the first rectilinear part of L1. By emitting electron beams along the irradiation line 25 having this shape, the flow of molten metal towards the spout portion 36 can be pushed back at the irradiation line 25 and directed towards the side walls 37 of the bath 30. may adhere to the ledge 7 on the side walls 37 of the bath 30. Alternatively, the WNR may also be dissolved by circulating through the molten metal 5c in the bath 30. By doing so, a situation arises in which the WNR flows out of the bath 30 into the mold 40 and enters the ingot, can be prevented.

In addition, according to the production method of the metal ingot of the present embodiment, since the molten metal stream 61 which is generated by the electron beam emission along the irradiation line 25 is formed by superimposing the streams generated by the electron beam emission along the respective positions of the first straight portion L1 and the second straight part L2, the molten metal flow 61 is a strong flow. Therefore, GNP can be reliably captured by the ledge. In addition, it is also possible to reduce the amount of heat transferred, the scanning speed, or the heat distribution of the electron gun.

Furthermore, according to the metal ingot production method of the present embodiment, since there is no need to change the shape of the existing bath 30, this method can be easily carried out and special maintenance is also not required.

In conventional titanium alloy manufacturing processes, it is common to remove impurities by holding the molten metal for a long time in the bath, thereby dissolving the WNP in the molten metal while causing the WNP to adhere to the scull formed on the surface of the bottom of the bath. Therefore, a long bath has traditionally been used to thereby ensure sufficient residence time of the molten metal in the bath. However, according to the metal ingot production method of the present embodiment, since impurities can be suitably removed even when the residence time of the molten metal in the bath is relatively short, it is possible to use a short bath. Accordingly, by using the short bath in the EL furnace 1, heating costs such as electricity consumption can be reduced, and accordingly, production costs can be reduced.

- 18 039285 on the EL furnace 1. In addition, when using a short bath instead of a long bath, the amount of ledge 7 formed in the bath can be reduced. Therefore, the output can be improved.

3. Third embodiment.

Next, a method for producing a metal ingot according to the third embodiment of the present invention will be described.

In the metal ingot production method according to the present embodiment, although the shape of the irradiation line 25 is approximately the same as in the metal ingot production method according to the first embodiment, the number of electron guns that emit electron beams is different from the first embodiment. The difference between the metal ingot production method and the first embodiment is mainly described below, and a detailed description of settings and processing similar to the metal ingot production method according to the first embodiment is omitted. Note that, although the following description also describes the case in which the short bath electron beam furnace 1 illustrated in FIG. 3, the present invention is not limited to this example, and can also be applied to the long bath electron beam furnace 1A illustrated in FIG. one.

Next, a method for emitting electron beams in a metal ingot production method according to the present embodiment will be described with reference to FIG. 11. FIG. 11 is a plan view illustrating one example of an irradiation line 25 in a metal ingot production method according to the present embodiment.

In the method for producing a metal ingot according to the present embodiment, as illustrated in FIG. 11, similarly to the first embodiment illustrated in FIG. 4, the irradiation line 25 has a convex shape which protrudes backward from the spout portion 36. In particular, the irradiation line 25 has a V-shape, for example. The V-shaped irradiation line 25 illustrated in FIG. 11 is composed of a first straight portion and a second straight portion which extend toward the center of the tub 30 from the corner portions at the two ends of the side wall 37D on which the spout portion 36 is provided. The end portion e1 of the first straight portion is disposed at one end of the side wall 37D, and the end portion e2 of the second straight portion is disposed at the other end of the side wall 37D.

The emission of electron beams along the first straight part and the second straight part is performed by different electron guns. In other words, the electron beams are emitted along the V-shaped irradiation line 25 of the two electron guns. For example, in the case where the emission range of the electron beam is limited, for example, by the space occupied by the equipment, and hence the emission along the V-shaped irradiation line 25 illustrated in FIG. 4 cannot be performed using a single electron gun as in the first embodiment, electron beams can be emitted using a plurality of electron guns as in the present embodiment.

Meanwhile, the electron beams are emitted along the irradiation line 25 using two electron guns so that the respective paths of the electron beams cross or overlap on the surface of the molten metal 5c. For example, in the part (at the top of the V-shaped part) in which the first straight part and the second straight part are connected, as illustrated in FIG. 11, electron beams can be emitted so that these parts of a straight line intersect. In other words, the first straight part and the second straight part are connected so that the first straight part and the second straight part intersect and are not connected at the end parts opposite to the end parts e1 and e2 at the side wall 37D.

In the case of melting of the metal alloy, the precision of the electron beam irradiation position control is reduced by the evaporation of a volatile valuable metal such as aluminum. Electron beam melting of raw materials in an EL furnace is performed in a vacuum chamber, and if the volatile valuable metal is evaporated, the vacuum degree inside the vacuum chamber deteriorates and the straightness of the electron beam decreases. As a result, it becomes difficult to control the electron beam irradiation position with high precision. In such a situation, it will be difficult to accurately perform irradiation using two electron guns along the V-shaped irradiation line 25 in which two straight portions are connected together by one pair of ends, as illustrated in FIG. 4. In addition, if a gap occurs between these two straight portions, the probability that a flow is formed on the surface of the molten metal 5c from the gap to the spout portion 36, and that the IRR will flow to the spout portion 36, will increase.

Therefore, in the case of emitting electron beams using two electron guns, the two end portions e1 and e2 are located at the side wall 37, and the irradiation line 25 is positioned to block the spout portion 36. In addition, in order to reliably prevent the ERR in the molten metal 5c in the bath 30 from flowing out of the spout portion 36, the paths of the electron beams emitted by the two electron guns are made to intersect. Thereby,

- 19 039285 even if the accuracy of controlling the positions of the electron beams is degraded to some extent, because the first straight part and the second straight part intersect, no gap is formed between them, and the IRR in the molten metal 5c in the bath 30 does not flow out of the pouring spout part 36 . In particular, the likelihood of the IRR flowing out to the spout part 36 can be further reduced by increasing the length from the intersection point to the end part to 5 mm or more in both the first straight part and the second straight part.

The first straight portion and the second straight portion may be connected at a position different from their end portions. For example, in a state in which the straightness of the electron beams is maintained, as illustrated in FIG. 11, the first straight portion and the second straight portion may be joined at a position that is 1/4 of the half-width D of the tub 30 in the width direction of the tub 30 (i.e., at a position where D1 =D/4). It should be noted that if it is possible to control the position of the electron beam with high precision, the respective lengths of the first straight portion and the second straight portion can be made equal to the length from the respective corner portion of the tub 30 to the intersection point, and the V-shaped irradiation line 25 can be in which two rectilinear parts are joined together at their ends, as illustrated in FIG. four.

It is also possible to use two electron guns when the irradiation line 25 has a shape other than a V-shape. For example, the irradiation line 25 may have a curvilinear shape, such as a parabola, in which the apex is on the center line of the tub 30. Alternatively, the irradiation line 25 may have a substantially semi-circular shape, as illustrated in FIG. 7. In such cases, it is also sufficient to block the molten metal flow path 5c between the preceding region S2 and the spout portion 36, causing the electron beam paths to intersect at the portion where the irradiation lines join. In addition, in the case of using three or more electron guns, it is also sufficient that the paths of the electron beams emitted by the different electron guns intersect at the part where the irradiation paths join.

4. Fourth Embodiment.

Next, a method for producing a metal ingot according to the fourth embodiment of the present invention will be described.

4.1. Scheme of the method for the production of a metal ingot.

In the method for producing a metal ingot according to the present embodiment, the irradiation line, which is located on the surface of the molten metal in the pool, is in the form of a straight line that is substantially parallel to the width direction of the pool. The flow path of the molten metal to the spout part, through which the molten metal from the pool flows into the mold, is blocked by emitting an electron beam along the above-mentioned irradiation line. Due to this, the RUR, which are impurities floating on the surface of the molten metal, are pushed back into the bath so that the RUR does not flow into the mold from the spout part. GNPs that are pushed back into the bath dissolve while in the bath. As a result, the GNR can be prevented from flowing into the mold.

The method for producing a metal ingot according to the present embodiment will now be described in more detail based on FIG. 12 and 13. FIG. 12 is a plan view illustrating the irradiation line 25 according to the metal ingot production method of the present embodiment. Fig. 13 is an explanatory drawing illustrating a molten metal flow that is generated on the surface of the molten metal 5c when an electron beam is emitted along the irradiation line 25 illustrated in FIG. 12. It should be noted that the top view of FIG. 12 corresponds to the bath 30 of the electron beam furnace 1 shown in FIG. 3. It should be noted that although the following description also describes the case in which the short bath electron beam furnace 1 illustrated in FIG. 3, the present invention is not limited to this example, and can be applied to the long bath electron beam furnace 1A illustrated in FIG. one.

In the method for producing a metal ingot according to the present embodiment, the two end portions e1 and e2 are located near the side wall 37 of the bath 30, and the irradiation line 25 is located on the surface of the molten metal 5c in the bath 30 so that it blocks the spout nose portion 36. In particular, as illustrated in FIG. 12, the irradiation line 25 is in the form of a straight line which is substantially parallel to the width direction of the tub 30 between the two end portions e1 and e2. The end portions e1 and e2 of the irradiation line 25 are positioned near the side wall 37D, in which the spout portion 36 is provided. The irradiation line 25 illustrated in FIG. 12 has approximately the same length as the opening width of the spout portion 36. The irradiation line 25 is disposed in the succeeding region S3 between the preceding region S2, which includes the supply lines 26, and the side wall 37D.

The electron beam is irradiated onto the surface of the molten metal 5c along the irradiation line 25 having the shape described above. Due to this, Marangoni convection is created by means of a temperature gradient on the surface of the molten metal 5c, and as illustrated in FIG. 13, in

- 20 039285 outer layer of molten metal 5c, a reverse flow of the outer layer of molten metal 5c (molten metal stream 61) from the irradiation line 25 is formed. Next, a case will be considered in which, when the raw material 5 drips along the supply lines 26 into the molten metal 5c in the bath 30, the temperature of the molten metal (feed temperature of the raw material T1) that drips along the supply lines 26 is higher than the molten metal temperature T0 accumulated in the bath 30. In this case, the areas near the supply lines 26 onto which the molten raw material 5 (molten metal) drips are high temperature areas in which the temperature is higher than the temperature of the molten metal 5c in other areas. Therefore, as illustrated in FIG. 13, molten metal 5c in areas near the supply lines 26 flows from the supply lines 26 to the center portion in the width direction (X direction) of the pool 30, and a molten metal stream 62 is formed in the outer layer of the molten metal 5c.

It should be noted that although not shown in FIG. 13, molten metal 5c in areas near the supply lines 26 also flows from the supply lines 26 to the side walls 37A and 37B in the width direction (X direction) of the bath 30, as illustrated in FIG. 5 and a molten metal stream (molten metal stream 63 in FIG. 5) is formed in the outer layer of molten metal 5c. The RNP 8 contained in the molten metal that has dripped onto the supply line 26 is carried along by the molten metal stream (molten metal stream 63 in FIG. 5), moves towards the side walls 37A and 37B of the tub 30, and adheres to the skull 7 formed on the inner surfaces. side walls 37A and 37B, and thus are caught.

The molten metal streams 62 that flow toward the center portion of the pool 30 from each of the left and right supply lines 26 collide at the center portion in the width direction of the pool 30, thereby forming a stream of molten metal 60 toward the spout portion 36 along the longitudinal direction (Y direction). ) baths 30. As a result, the VNP 8, floating in the molten metal 5c, also move with the stream of molten metal 60 and flow to the part 36 of the drain sock. In order to ensure that contaminants, such as BPR 8, do not flow from the spout portion 36 into the mold 40, it is preferred that an outer layer of molten metal flow 5c be formed that repels the PPR entrained by the molten metal flow 60 towards the spout portion 36 , in the opposite direction, and thereby keeps the GNP away from the part 36 of the drain sock.

Therefore, in the method for producing a metal ingot according to the present embodiment, as illustrated in FIG. 12 and 13, two end portions e1 and e2 are positioned near the side wall 37D, and an irradiation line 25 in the form of a straight line is positioned on the surface of the molten metal 5c so as to block the spout portion 36. The temperature of the molten metal in the region near the irradiation line 25 becomes higher than the temperature of the molten metal in the irradiation region 23 for heat retention. Therefore, Marangoni convection occurs and a reverse flow 61 of molten metal from the irradiation line 25 is formed. The molten metal stream 61 is a stream that pushes back the RPGs 8 carried by the molten metal stream 60 towards the spout part 36 in the central part in the width direction of the tub 30. By means of the molten metal stream 61, the PRTs 8 that flowed towards the spout part 36 are pushed back. from the irradiation line 25 and flow to the inside of the bath 30. The RNGs 8, which have been pushed back to the inside of the bath 30, are entrained in the flow on the surface of the molten metal 5c and dissolve as they circulate through the bath 30. Alternatively, after the BLRs 8 have moved to the side walls 37A and 37B of tub 30, they stick to the ledge 7 formed on the side walls of tub 30 and no longer move.

Thus, in the method for producing a metal ingot according to the present embodiment, an electron beam is emitted along an irradiation line 25, the two end portions e1 and e2 of which are located near the side wall 37, and which is positioned to block the spout portion 36. This forms a reverse flow of molten metal 61 from the region of high temperature of the molten metal 5c near the irradiation line 25, and impurities such as GNP that flowed towards the spout part 36 are pushed back from the spout part 36. Accordingly, the impurities in question can be prevented from flowing out of the bath 30 into the mold 40. As a result, the occurrence of a situation in which impurities enter the ingot can be prevented.

4.2. The location of the irradiation line.

In the metal ingot production method according to the present embodiment, the irradiation line 25 is in the form of a straight line. Due to this, the scanning distance of the electron beam can be reduced. As a result, the occurrence of a situation in which the GNP 8 in the molten metal 5c passes through the spout portion 36 and flows out of the pool 30 into the mold 40 can be prevented.

As illustrated in FIG. 12 and 13, when the shape of bathtub 30 in plan view is rectangular, it is desirable to position the irradiation line 25 along the side wall 37D. The side wall 37D is substantially parallel to the width direction (X direction) of the bath 30.

- 21 039285 nod in the central part in the direction of the width of the pool 30, thereby forming the flow of molten metal 60 to the spout portion 36 along the longitudinal direction (Y direction) of the pool 30. The flow of molten metal 60 is essentially parallel to the longitudinal direction of the pool 30. Accordingly , by positioning the irradiation line 25 along the side wall 37D of the tub 30, the flow of molten metal 5c to the spout portion 36 (molten metal flow 60) can be effectively suppressed. In addition, a reverse flow 61 of molten metal from the irradiation line 25 is formed. As a result of this, the VNP 8, which are entrained by the flow of molten metal 5c and flow towards the spout part 36, can be pushed back from the spout part 36 by the flow of molten metal 61 into the interior of the bath 30.

It suffices that the irradiation line 25 is located at least in the subsequent area S3 between the previous area S1, which includes the supply lines 26, and the side wall 37D. In order to more reliably prevent impurities from escaping, as illustrated in FIG. 12 and 13, it is preferred that the irradiation line 25 be located at the inlet stream to the spout portion 36. In this case, the length of the irradiation line 25 is made at least equal to or greater than the width of the opening of the spout part 36. Preferably, the length of the irradiation line 25 is approximately the same as the width of the opening of the spout portion 36. Due to this, the scanning distance of the electron beam emitted along the irradiation line 25 can be made as short as possible. As a result, even when the electron beam scanning speed is reduced, the molten metal flow 61 generated by the electron beam emission along the irradiation line 25 is slightly weakened. Accordingly, since the RNRs 8 are securely pushed back into the tub 30 before they can enter the spout portion 36, the RNRs 8 do not leak out of the tub 30.

The arrangement of the irradiation line 25 in the metal ingot production method according to the present embodiment is also applicable to a long puddle, not only to a short puddle, as illustrated in FIG. 12 and 13. An example of a case in which the irradiation line 25 having the shape of a straight line is used in a long bath that includes a melting bath 31 and a purification bath 33 (hereinafter referred to as long baths 31 and 33) is illustrated in FIG. 14 and 15. It should be noted that in FIG. 14 and 15, the melting bath 31 and the cleaning bath 33 are shown for convenience in such a way that the melting bath 31 and the cleaning bath 33 are modeled as one bath. For example, as illustrated in FIG. 14, similar to FIG. 12 and 13, an irradiation line 25 having the shape of a straight line with a length that is approximately equal to the width of the opening of the spout part 36 is located at the inlet of the spout part 36. The two end portions e1 and e2 of the irradiation line 25 are positioned near the side wall 37D, and the irradiation line 25 is positioned to block the spout portion 36 of the sock. Due to this, similarly to Fig. 12 and 13, the EORs 8 that flow to the spout portion 36 along with the molten metal 5c are held back at the irradiation line 25 and pushed back. Therefore, the ERT 8 remains in the long vats 31 and 33, and the ERT 8 can be reliably prevented from flowing out of the long vats 31 and 33 into the mold 40.

In addition, in the case of long baths 31 and 33, it is also preferable to arrange the irradiation line 25 in the subsequent region S3 between the preceding region S2, including the raw material supply region 28 into which the raw material 5 drips, and the side wall 37D. As illustrated in FIG. 14 and 15, in the long vats 31 and 33, the raw material supply area 28 into which the raw material 5 drips is usually located at the farthest position in the longitudinal direction (Y direction) of the long vats 31 and 33. In other words, the raw material supply region 28 is located near side wall 37C, which is opposite the spout part 36 in the longitudinal direction of the long tubs 31 and 33. Accordingly, for example, as illustrated in FIG. 15, the irradiation line 25 may be located in the longitudinal center of the long baths 31 and 33. The longitudinal center position of the long baths 31 and 33 is the position in the subsequent region S3, which is downstream of the preceding region S2, which includes itself area 28 supply of raw materials. In this case, the two end portions e1 and e2 of the irradiation line 25 are located near the side walls 37A and 37B. Due to this, it is possible to prevent the passage of the VNP 8 through the irradiation line 25 and their outflow to the drain part 36 of the sock.

It should be noted that the actual irradiation position at which the electron beam is emitted to the irradiation line 25 need not be exactly on the irradiation line 25 . It is sufficient that the actual irradiation position at which the electron beam is emitted is approximately on the irradiation line 25, which is set as the target, and no problems arise as long as the actual path of the electron beam is within the allowable deviation range from the irradiation line 25, which is set as the target. In addition, the phrase end parts e1 and e2 located near the side wall 37 means that the end parts e1 and e2 are located on the inner surface of the side wall 37 or in the area in which the distance x from the inner surface of the side wall 37 is not more than 5 mm. The end portions e1 and e2 of the irradiation line 25 are set in this area, and the electron beam is emitted along the irradiation line 25, and forming a scull 7 on the inner surface of the side walls 37 of the long baths 31 and 33 is not a problem, and the electron beam can be radiated to the scull 7.

- 22 039285

In addition, with regard to the electron beams emitted from the respective electron guns, similarly to the first embodiment, the radiation conditions such as the amount of heat to be transferred, the scanning speed, and the heat flux distribution of the electron beam are limited by the characteristics of the equipment that emits the electron beam. Accordingly, when setting the electron beam emission conditions, it is preferable to make the amount of heat transferred by the electron beam as large as possible, the scanning speed to be as high as possible, and the heat flow distribution to be as narrow as possible (i.e., to make the aperture of the electron beam as small as possible) within the performance range of the equipment.

4.3. Acceleration of GNP dissolution.

In the method for producing a metal ingot according to the present embodiment, by blocking the spout part 36 by the irradiation line 25, the HLRs 8 are kept inside the bath 30, and the HLRs 8 are dissolved as they circulate inside the bath. Due to this, the occurrence of a situation in which the GNR flows out of the bath 30 into the mold 40 can be prevented. Thus, as long as the EOR 8 is not dissolved, there is a possibility that the EOR 8 may leak out of the bath 30 into the mold 40. Therefore, in order to reduce the likelihood of the EOR 8 flowing out of the bath 30 into the mold 40, it is necessary accelerate the dissolution of the HLRs 8 that are present in the bath 30. To this end, an electron beam to accelerate the dissolution of the HLRs (corresponding to the second electron beam of the present invention) may be emitted onto the surface of the molten metal 5c in the bath 30.

An electron beam to accelerate the dissolution of the GNP, for example, may be radiated to a stagnation position of the molten metal flow 5c. VNP 8 tend to stagnate in a stagnant position in the flow of molten metal 5c. Thus, the GNP 8 inside the bath can be dissolved more quickly by emitting an electron beam to accelerate the dissolution of the GNP in the position in which they stagnate. It should be noted that there is no need to continuously emit an electron beam to accelerate the dissolution of the GNP, and it is sufficient to appropriately emit an electron beam to accelerate the dissolution of the GNP at the stagnation position in the molten metal flow 5c in which the GNP 8 stagnates. electron gun to emit an electron beam to accelerate the dissolution of the GNP, a separate electron gun to accelerate the dissolution of the GNP (not shown in the drawings) can be used, or alternatively electron guns for other purposes, such as electron guns 20A and 20B for melting raw materials or electron guns 20C and 20D to maintain the temperature of the molten metal (see Fig. 3) can also be used to accelerate the dissolution of the GNP. The position of the stagnation in the molten metal flow 5c can be determined in advance by simulation or the like. The stagnation position can be determined by performing simulation based on the position and shape of the irradiation line 25, as well as the amount of heat to be transferred and the scanning speed of the electron beam, etc., which are set as described above.

4.4. Modification.

Next, one modification of the fourth embodiment will be described. Examples have been described above in which the irradiation line 25 on the surface of the molten metal 5c in the bath 30 is in the form of a straight line in which the two end portions e1 and e2 are located near the side walls 37 so as to block the spout portion 36 as illustrated in FIG. 12 and 13. However, the present invention is not limited to these examples. Even if the shape of the irradiation line 25 differs from that in the example illustrated in FIG. 12 or 13, the molten metal flow path to spout portion 36 that allows molten metal 5c in pool 30 to flow into mold 40 may be blocked and BRT 8 may be pushed back into pool 30.

For example, the irradiation line 25 may have a convex shape that protrudes toward the drain portion 36 of the sock. In particular, as illustrated in FIG. 16, the irradiation line 25 may be V-shaped, the two end portions e1 and e2 of which are located near the side walls 37A and 37B, and which protrude towards the spout portion 36. Due to this, since the spout part 36 is blocked, it is possible to prevent the GNP 8 in the molten metal 5c from flowing out to the spout part 36 . In addition, by emitting an electron beam along the irradiation line 25, a reverse flow of molten metal 5c from the irradiation line 25 can be generated. As a result, the VNP 8 can be pushed back into the tub 30.

Alternatively, as illustrated in FIG. 17, the irradiation line 25 may be in the form of an arc of a circle, the two end portions e1 and e2 of which are located near the side walls 37A and 37B, and which protrude towards the spout portion 36. In this case, too, since the spout part 36 is blocked, it is possible to prevent the VNR 8 in the molten metal 5c from flowing out to the spout part 36 . In addition, by emitting an electron beam along the irradiation line 25, a reverse flow of molten metal 5c from the irradiation line 25 can be generated. As a result, the VNP 8 can be pushed back inside the tub 30.

In addition, the irradiation line 25 may have a U-shape convex to the spout portion 36. For example, as illustrated in FIG. 18, the U-shaped irradiation line 25 includes a first straight portion L1, a second straight portion L2, and a third straight

- 23 039285 part L3. The first straight portion L1 is located substantially parallel to the side wall 37D between the two end portions e1 and e2. The first straight portion L1 is positioned to block the spout portion 36 . The second straight portion L2 and the third straight portion L3 are arranged to extend substantially perpendicular to the two ends of the first straight portion L1 along a pair of side walls 37A and 37B that face each other. The two end portions e1 and e2 of the irradiation line 25 are positioned near the side walls 37A and 37B of the tub 30. Due to this, since the spout part 36 is blocked, it is possible to prevent the RNP 8 in the molten metal 5c from flowing out to the spout part 36. In addition, by emitting an electron beam along the irradiation line 25, a reverse flow of molten metal 5c from the irradiation line 25 can be generated. As a result, the VNP 8 can be pushed back inside the tub 30.

Note that, in the U-shaped irradiation line 25, the angle at which the first straight portion L1 and the second straight portion L2 are connected, and the angle at which the first straight portion L1 and the third straight portion L3 are connected may be right angles, as illustrated in fig. 18, or may be rounded.

Also in the modification, the actual irradiation position at which the electron beam is irradiated to the irradiation line 25 need not be strictly on the irradiation line 25. It is sufficient that the actual irradiation position at which the electron beam is emitted is approximately on the irradiation line 25, which is set as the target, and no problems arise as long as the actual path of the electron beam is within the allowable deviation range from the irradiation line 25, which is set as the target. In addition, the phrase end parts e1 and e2 located near the side wall 37 means that the end parts e1 and e2 are located on the inner surface of the side wall 37 or in the area in which the distance x from the inner surface of the side wall 37 is not more than 5 mm. The end portions e1 and e2 of the irradiation line 25 are set in this area, and the electron beam is emitted along the irradiation line 25, and the formation of the ledge 7 on the inner surface of the side walls 37 of the tub 30 is not a problem, and the electron beam can be radiated to the ledge 7.

In addition, with respect to each irradiation line 25 illustrated in FIG. 16-18, the electron beam may be emitted along the irradiation line 25 using a single electron gun, or the electron beams may be emitted along the irradiation line 25 using a plurality of electron guns.

In addition, in the case where the irradiation line 25 is located as illustrated in FIG. 16-18, when the electron beam is emitted along the corresponding irradiation line 25, a reverse flow of molten metal 5c is formed from the irradiation line 25 toward the center in the width direction (X direction) of the pool 30. In other words, the molten metal flow 5c is formed in the direction towards the center from the side walls 37A and 37B on the side of the irradiation line 25 that is farther from the spout. Meanwhile, the temperature of the molten metal in the region near the irradiation line 25 is higher than the temperature of the molten metal in the irradiation region 23 for heat retention. Accordingly, Marangoni convection occurs and a flow 61 of molten metal is formed towards the center from the side walls 37A and 37B of the bath 30.

In this case, stagnation may occur in the molten metal flow 5c at the center in the width direction of the bath 30. Therefore, an electron beam to accelerate the dissolution of the IRR can be emitted to the stagnation position of the molten metal flow 5c. VNP 8 tend to stagnate in the position of stagnation of the flow of molten metal. By emitting an electron beam to accelerate the dissolution of the GNP at this position, the stagnation of the GNP 8 in the bath can be dissolved more rapidly.

4.5. Summary.

The method for producing a metal ingot according to the present embodiment has been described above. According to the present embodiment, on the surface of the molten metal 5c in the bath 30, the two end portions e1 and e2 of the irradiation line 25 are located at the side walls 37, and the irradiation line 25 is positioned so as to block the spout portion 36 of the spout. This blocks the molten metal flow path to the spout portion 36 that allows the molten metal to flow out of the pool 30 into the mold. As a result, the VNP 8 are delayed at the inlet of the part 36 of the drain sock. VNP 8 continue to circulate inside the bath 30, and thus dissolve. By doing this, it is possible to prevent the EGR 8 contained in the molten metal 5c from flowing out of the spout portion 36 into the mold 40.

In addition, due to the rectilinear shape of the irradiation line 25, the scanning distance of the electron beam can be reduced. Therefore, even if the electron beam scanning speed is reduced, the molten metal flow 5c generated by the electron beam emission along the irradiation line 25 is slightly weakened. Accordingly, since the RNRs 8 are securely pushed back into the tub 30 before they can enter the spout portion 36, the RNRs 8 do not leak out of the tub 30.

In addition, because the irradiation line 25 is in the form of a straight line, the control of the electron gun(s) becomes simple, and the number of electron guns used

- 24 039285 guns can be kept to a minimum.

Moreover, according to the metal ingot production method of the present embodiment, since there is no need to change the shape of the existing bath 30, this method can be easily carried out and special maintenance is also not required.

In conventional titanium alloy production methods, it is customary to remove impurities by keeping the molten metal for a long time in the bath, thereby dissolving the GNP in the molten metal, while causing the GNP to adhere to the scull formed on the surface of the bottom of the bath. Therefore, a long bath has traditionally been used to thereby ensure sufficient residence time of the molten metal in the bath. However, according to the metal ingot production method of the present embodiment, since impurities can be suitably removed even when the residence time of the molten metal in the bath is relatively short, it is possible to use a short bath. Accordingly, by using a short bath in the EL furnace 1, heating costs such as electricity consumption can be reduced, and the production cost of the EL furnace 1 can be reduced accordingly. In addition, when using a short bath instead of a long bath, the amount the scull 7 formed in the tub can be reduced. Therefore, the output can be improved.

5. Location of the irradiation line in a multistage bath.

Although the cases have been described above in which the metal ingot manufacturing methods according to the above-described embodiments are applied to the short puddle 30 illustrated in FIG. 3, or to the long tubs 31 and 33 illustrated in FIG. 1, the present invention is not limited to these examples. For example, the bath to which the method of producing a metal ingot according to the present invention is applied may be a multi-stage bath in which a plurality of separated baths are combined and arranged in series. For example, as illustrated in FIG. 19, a two-stage bath 30 can be obtained by combining and sequencing the first bath 30A and the second bath 30B.

Similar to tub 30 illustrated in FIG. 4, for example, the first bath 30A (corresponding to the divided bath of the present invention) is a device for cleaning the molten metal 5c of the raw material 5 that drips along the supply lines 26 and accumulating the molten metal 5c to thereby remove the impurities contained in the molten metal 5c. The first tub 30A is a rectangular tub and is composed of four side walls 37A, 37B, 37C, and 37D. A spout part 36 is provided in the side wall 37D of the first tub 30A. The molten metal 5c of the first pool 30A that flows out of the spout portion 36 accumulates in the second pool 30B.

The second bath 30B (corresponding to the divided bath of the present invention) is a device for purifying the molten metal 5c that comes from the first bath 30A and accumulating the molten metal 5c, thereby removing impurities contained in the molten metal 5c. The second tub 30B is also a rectangular tub and consists of four side walls 37A, 37B, 37C, and 37D. A spout part 36 is provided in the side wall 37D of the second tub 30B. The molten metal 5c of the second pool 30B that flows out of the spout portion 36 flows into the mold 40.

In this type of two-stage bath 30, which consists of two separated baths, in each of the first bath 30A and the second bath 30B, the two end portions e1 and e2 of the irradiation line 25 are located against the side wall 37, and the irradiation line 25 is positioned to block part 36 drain sock. In each of the first bath 30A and the second bath 30B, a reverse flow 61 of molten metal from the irradiation line 25 is formed by emitting an electron beam onto the surface of the molten metal 5c along the irradiation line 25. As a result, the flow of molten metal 5c to the spout portion 36 is pushed back, and thus impurities such as GNR can be prevented from flowing from the first pool 30A to the second pool 30B, and from the second pool 30B to the mold 40.

It should be noted that although the multi-stage bath illustrated in FIG. 19 is a two-stage bath, the present invention is not limited to this example. A multi-stage bath may be a three- or more-stage bath in which three or more separated baths are combined and arranged in series. In this case, too, in each divided tub, the two end portions of the irradiation line are positioned near the side wall, and the irradiation line is positioned so that it blocks a portion of the spout. The reverse flow of molten metal from the irradiation line is created by emitting an electron beam onto the surface of the molten metal along the irradiation line. By this, the flow of molten metal to the downspout part can be pushed back, and in this way impurities such as GNR can be prevented from flowing out into the bath or into the mold in the next stage.

Examples

Next, examples of the present invention will be described. The following examples are just specific examples to test the effects of the present invention, and the present invention is not limited to the following examples.

- 25 039285 (1) Examples of linear irradiation.

First, with references to Table. 1 and FIG. 20-43, examples will be described in which simulation was performed to test the GNP removal effect by linear irradiation according to the first to fourth embodiments of the present invention described above.

With regard to the present examples, in examples 1-8, 11-13 and comparative examples 1, 3 and 4, the flow of molten metal in the bath 30 was simulated for the case in which titanium alloy was used as the raw material 5, and the electron beam was emitted along the irradiation line 25 on the molten titanium alloy metal 5c which has accumulated in the short bath illustrated in FIG. 3. The temperature distribution of the molten metal 5c in the bath 30, the behavior of the SHR and the amount of the SHF flowing out of the bath 30 were established. In addition, in Examples 9 and 10 and Comparative Example 2, the flow of molten metal in the baths 31 and 33 was simulated at the time when The electron beam was radiated along the irradiation line 25 onto the molten titanium alloy metal 5c which had accumulated in the long bath illustrated in FIG. one.

In Example 1, as illustrated in FIG. 4, the two end portions e1 and e2 of the V-shaped irradiation line 25 were located at the side wall 37D, and the V-shaped irradiation line 25 was positioned to cover the spout portion 36, and the electron beam was emitted along the irradiation line 25.

In Example 2, as illustrated in FIG. 7, the two end portions e1 and e2 of the arcuate irradiation line 25 were located at the side wall 37D, and the arcuate irradiation line 25 was positioned to cover the spout portion 36, and the electron beam was emitted along the irradiation line 25.

In Example 3, as illustrated in FIG. 10, the two end portions e1 and e2 of the T-shaped irradiation line 25 were located at the side wall 37D, and the T-shaped irradiation line 25 was positioned to cover the spout portion 36, and the electron beam was emitted along the irradiation line 25.

Examples 4 and 5 are examples of the case in which electron beams are emitted to the irradiation line 25 using two electron guns. In Example 4, as illustrated in FIG. 11, the two end portions e1 and e2 of the V-shaped irradiation line 25 were located at both ends of the side wall 37D, and the V-shaped irradiation line 25 was positioned to cover the spout portion 36, and electron beams were emitted along the irradiation line 25. In Example 5, as illustrated in FIG. 25, although the irradiation line 25 was located similarly to that shown in FIG. 11 (Example 4), the scanning direction of the electron beams has been changed. The amount of heat transferred by the electron beams of the two electron guns used in each of Example 4 and Example 5 was 0.125 [MW], respectively.

In Example 6, as illustrated in FIG. 27, the two end portions e1 and e2 of the V-shaped irradiation line 25 were located at both ends of the side wall 37D, and the V-shaped irradiation line 25 was positioned to cover the spout portion 36, and the electron beam was emitted along the irradiation line 25.

In Example 7, as illustrated in FIG. 29, the two end portions e1 and e2 of the V-shaped irradiation line 25 were located at both ends of the side wall 37D, and the V-shaped irradiation line 25 was positioned to cover the spout portion 36, and the electron beam was emitted along the irradiation line 25. In example 7, the top Q of the V-shape was located at a position that deviated from the center in the direction of the width of the tub 30.

In example 8, as illustrated in FIG. 12, the two end portions e1 and e2 of the straight-line irradiation line 25 were located at the side wall 37D, and the irradiation line 25 was positioned to cover the spout portion 36, and the electron beam was emitted along the irradiation line 25.

In Example 9, as illustrated in FIG. 14, in the long baths 31 and 33, the two end portions e1 and e2 of the straight-line irradiation line 25 were located at the side wall 37D, and the irradiation line 25 was positioned to cover the spout portion 36, and the electron beam was emitted along the line 25 irradiation.

In example 10, as illustrated in FIG. 15, in the long baths 31 and 33, the two end portions e1 and e2 of the straight-line irradiation line 25 were located at both ends of the side wall 37D, and the irradiation line 25 was located at the center in the longitudinal direction of the long baths 31 and 33, and the electron beam was emitted along the line 25 exposure.

In example 11, as illustrated in FIG. 16, the two end portions e1 and e2 of the V-shaped irradiation line 25 were located at the side walls 37A and 37B, and the V-shaped irradiation line 25, which protruded to the spout part 36, was positioned so as to cover the spout part 36, and the electronic the beam was emitted along the irradiation line 25 .

In example 12, as illustrated in FIG. 17, the two end portions e1 and e2 of the arcuate irradiation line 25 were located at the side walls 37A and 37B, and the arcuate irradiation line 25, which protruded to the spout portion 36, was positioned to cover the spout portion 36, and the electron beam was emitted along the line. 25 irradiation.

In Example 13, as illustrated in FIG. 18, two end parts e1 and e2 of the U-shaped line 25

- 26 039285 irradiations were located at the side walls 37A and 37B, and the U-shaped irradiation line 25, which protruded to the spout part 36, was positioned to cover the spout part 36, and the electron beam was emitted along the irradiation line 25.

On the other hand, as Comparative Example 1, a similar simulation was performed for the case in which the heat-holding electron beam was irradiated to the irradiation region 23 to hold the heat of the molten metal 5c in the bath 30, and in which linear irradiation along the irradiation lines 25, 25 was not performed.

In Comparative Example 2, the method disclosed in Patent Document 1, which was described above, was simulated. In other words, as illustrated in FIG. 38, the zigzag irradiation line 25 was placed on the surface of the molten metal 5s in the long baths 31 and 33, and the electron beam was emitted along the irradiation line 25.

In Comparative Example 3, as a comparison with Example 4, as illustrated in FIG. 40, the electron beams were emitted along the V-shaped irradiation line 25 in which the lines did not cross at the top. It should be noted that the amount of heat transferred by each electron beam of the two electron guns used in Comparative Example 3 was 0.125 MW, respectively.

In Comparative Example 4, as a comparison with Example 3, as illustrated in FIG. 42, the electron beams were emitted along three straight lines of the T-shaped irradiation line 25 in which the three straight lines did not intersect. The irradiation line 25 illustrated in FIG. 42 consisted of a first straight portion L1 and a second straight portion L2 along the side wall 37D in which a spout nose portion 36 was provided, and a third straight portion L3 perpendicular to the side wall 37D. The first straight portion L1, the second straight portion L2, and the third straight portion L3 did not contact each other. It should be noted that the amount of heat transferred by the electron beams emitted along the first straight part L1 and the second straight part L2 was 0.05 MW, respectively, and the amount of heat transferred by the electron beam emitted along the third straight part L3 of the part was 0. 15 MW. In addition, the scanning speed of the electron beam along the first straight part L1 and the second straight part L2 was 2.9 m/s, and the scanning speed of the electron beam along the third straight part L3 was 3.6 m/s.

Simulation conditions of these examples are shown in table. one.

Table 1

Amount of heat transferred by electron beam [MW] Electron beam scanning speed [m/s] Electron Beam Heat Flow Distribution(o[m]) Irradiation path shape Example 1 0.25 1.8 0.02 V shape Example 2 0.35 1.7 0.02 Arc shape Example 3 dl :0.09 d2:0.15 d3:0.09 2.94 0.013 T-shape Example 4 0.125 1.8 0.02 V shape Example 5 0.125 1.8 0.02 V shape Example 6 0.25 1.8 0.02 V shape Example 7 0.25 1.8 0.02 V shape Example 8 0.25 1.6 0.02 Rectilinear shape Example 9 0.25 1.6 0.02 Rectilinear shape Example 10 0.25 2.0 0.02 Rectilinear shape Example 11 0.30 1.8 0.02 V shape Example 12 0.25 1.8 0.02 Arc shape Example 13 0.30 1.8 0.02 U shape Comparative - - - (No exposure)

- 27 039285

example 1 Comparative Example 2 0.25 1.9 0.02 Zigzag Comparative Example 3 0.125 1.8 0.02 V shape Comparative Example 4 LI :0.05 L2:0.05 L3:0.15 Ll:2.9 L2:2.9 L3:3.6 0.02 T-shape

For each simulation, a transient was calculated as the flow and temperature of the molten metal 5 s change at each time point depending on the scanning of the electron beam. Modeling was performed based on the assumptions that the GNP is titanium nitride, the grain size of titanium nitride is 3.5 mm, and the density of titanium nitride is 10% less than the density of the molten metal 5c.

The simulation results for Examples 1-13 and Comparative Examples 1-4 are described below. Fig. 20-24, 26, 28, and 30-36 show simulation results for Examples 1-13, respectively, and FIG. 37, 39, 41 and 43 show the simulation results for Comparative Examples 1-4, respectively.

Fig. 20, 22-24, 26, 28 and 30-36 and FIG. 37 , 39 , 41 and 43 show the temperature distribution on the surface of the molten metal 5c in the bath and the behavior of the VNR that flow on the surface of the molten metal 5c at the time when the irradiation position of the electron beam for linear irradiation that is emitted along the irradiation line 25 is in a representative position. In the temperature distribution diagrams on the left side of the above-mentioned FIGS. 20, 22-24, 26, 28, and 3036 and 37, 39, 41, and 43, the high temperature region marked with a circle indicates the position of the electron beam irradiation relative to the irradiation line 25 at a given time, the two upper and lower ribbon-like high temperature portions mean two supply lines 26, and the low temperature part near the inner surface of the bath indicates that part in which the scull 7 is formed. In addition, in the flow diagrams on the right side of FIG. 20, 22-24, 26, 28 and 30-36 and 37, 39, 41 and 43 flow lines having a non-linear shape indicate the flow path of the WNP.

Example 1

In Example 1, as illustrated in FIG. 20, a high temperature region was formed along the irradiation line 25 blocking the spout part 36, and a molten metal flow 61 was formed from the irradiation line 25 to the opposite side of the spout part 36. Therefore, as illustrated in FIG. 20 , all of the EOR that flowed from the supply lines to the spout part 36 moved with the molten metal flow 61 to the side walls 37A and 37B, and there was no flow line that passed through the spout part 36 and further into the mold. 40. Thus, it was found that the RNP in the tub 30 was pushed back and did not flow out of the spout portion 36 into the mold 40. FIG. 21 shows the direction and strength of the flow of molten metal 5c at respective locations near the irradiation line 25 in Example 1. Based on FIG. 21, it was also found that a strong flow of molten metal 5c was generated at high speed from the irradiation line 25 in the opposite direction of the spout part 36 and towards the side walls 37A and 37B.

Example 2

As illustrated in FIG. 22, in Example 2, similarly to Example 1, a high temperature region was also formed along the irradiation line 25 blocking the spout part 36, and a molten metal flow 61 was formed from the irradiation line 25 to the opposite side of the spout part 36. Therefore, all of the EGR that flowed from the supply lines to the spout 36 moved with the molten metal stream 61 to the side walls 37A and 37B, and there was no flow line that passed through the spout 36 and further into the mold. 40. Thus, it was found that the GNR in the tub 30 was pushed back and did not flow out of the spout portion 36 into the mold 40.

Example 3

In Example 3, similarly to Examples 1 and 2, as illustrated in FIG. 23, a high temperature area was also formed along the irradiation line 25 blocking the spout part 36, and a molten metal flow 61 was formed from the irradiation line 25 to the opposite side of the spout part 36. Therefore, all of the EGR that flowed from the supply lines to the spout 36 moved with the molten metal stream 61 to the side walls 37A and 37B, and there was no flow line that passed through the spout 36 and further into the mold. 40. Thus, it was found that the GNR in the tub 30 was pushed back and did not flow out of the spout portion 36 into the mold 40.

Examples 4 and 5.

In Examples 4 and 5, electron beams were emitted along the irradiation line 25 using two electron guns. In example 4, two electron guns emitted electron beams along the irradiation line 25 so that these electron beams were at the top of the V-shape at the same

- 28 039285 point in time. In addition, in Example 5, two electron guns emitted electron beams along the irradiation line 25 so that when the electron beam from one of the electron guns was at the top of the V-shape, the electron beam from the other electron gun was at the center of the line. irradiation. Fig. 24 shows the simulation result of Example 4, and FIG. 26 shows the simulation result of example 5.

Both in the case of Example 4 and in the case of Example 5, as illustrated in FIG. 24 and 26, similarly to Examples 1 to 3, a high temperature region was formed along the irradiation line 25 blocking the spout part 36, and a molten metal flow 61 was formed from the irradiation line 25 away from the spout part 36. Therefore, all of the EGR that flowed from the supply lines to the spout 36 moved with the molten metal stream 61 to the side walls 37A and 37B, and there was no flow line that passed through the spout 36 and further into the mold. 40. Thus, it was found that the GNR in the tub 30 was pushed back and did not flow out of the spout portion 36 into the mold 40.

Examples 6 and 7.

In Examples 6 and 7, although the V-shaped irradiation line 25 was arranged similarly to Example 1, the V-shape was different from Example 1. However, in Examples 6 and 7, similarly to Examples 1 to 5, as illustrated in FIG. 28 and 30, a high temperature region was also formed along the irradiation line 25 blocking the spout portion 36, and a molten metal flow 61 was formed from the irradiation line 25 to the opposite side of the spout portion 36. Therefore, all of the EGR that flowed from the supply lines to the spout 36 moved with the molten metal stream 61 to the side walls 37A and 37B, and there was no flow line that passed through the spout 36 and further into the mold. 40. Thus, it was found that the GNR in the tub 30 was pushed back and did not flow out of the spout portion 36 into the mold 40.

Examples 8-10.

In examples 8-10, the irradiation line 25 was in the form of a straight line. Fig. 31 shows the simulation result of Example 8, FIG. 32 shows the simulation result of Example 9, and FIG. 33 shows the simulation result of Example 10. The method of arranging the straight irradiation line 25 or the bath used differed between Examples 8-10. However, in Examples 8-10, similarly to Examples 1-7, as illustrated in FIG. 31-33, a high temperature region was also formed along the irradiation line 25 blocking the spout portion 36, and a molten metal flow 61 was formed from the irradiation line 25 to the opposite side of the spout portion 36. Therefore, all of the EGR that flowed from the supply lines to the spout 36 moved with the molten metal stream 61 to the side walls 37A and 37B, and there was no flow line that passed through the spout 36 and further into the mold. 40. Thus, it was found that the IRR in the tub 30 was pushed back and did not flow out of the spout portion 36 into the mold 40. It should be noted that based on FIG. 31-33, it has been found that there are stagnation positions in which the GNRs stagnate near the end portions of the irradiation line 25. Thereafter, these RNPs are entrained by the flow of molten metal in the bath and circulate through the interior of the bath. However, even if these RNPs once again reach the irradiation line 25, after they stagnate in the same positions, they circulate through the inside of the bath once again. These GNPs dissolve during circulation through the interior of the bath. Alternatively, an electron beam to promote the dissolution of the GNP may also be emitted at stagnant positions.

Examples 11-13.

In examples 11-13, the irradiation line 25 had a convex shape protruding in the direction of the spout part 36. Fig. 34 shows the simulation result of Example 11, FIG. 35 shows the simulation result of Example 12, and FIG. 36 shows the simulation result of Example 13. The convex shape of the irradiation line 25 differed between Examples 11-13. However, in Examples 11-13, similarly to Examples 1-10, as illustrated in FIG. 34-36, a high temperature region was also formed along the irradiation line 25 blocking the spout portion 36, and a molten metal flow 61 was formed from the irradiation line 25 to the opposite side of the spout portion 36. Therefore, all of the RNP that flowed from the supply lines to the spout part 36 moved with the molten metal flow 61 in the opposite direction of the spout part 36, and there was no flow line that passed through the spout part 36 and further into the mold 40. Thus, it was found that the GNR in the tub 30 was pushed back and did not flow out of the spout portion 36 into the mold 40.

It should be noted that based on FIG. 34-36, it was found that similarly to examples 8-10, between the irradiation line 25 and the supply lines 26, there are stagnation positions in which the RNRs stagnate in the center in the direction of the width of the bath 30. Thereafter, these RRTs are entrained by the flow of molten metal in the bath and circulate through the inside of the bath. However, even if these RNPs once again reach the irradiation line 25, after they stagnate in the same positions, they circulate through the inside of the bath once again. These GNPs dissolve during circulation through the interior of the bath. Alternatively, an electron beam to accelerate the dissolution of the GNP can also

- 29 039285 be emitted in the stagnant position. In addition, based on the simulation results of Examples 8-13, it was found that the stagnation positions at which the GNPs tend to stagnate can be controlled by changing the location and shape of the irradiation lines 25 .

It should be noted that in Examples 1 to 13, the respective electron beams were emitted so that the irradiation line 25 blocked the spout portion 36 of the sock. However, it is possible to appropriately change the location of the irradiation line 25, provided that the amount of heat to be transferred, the scanning speed, and the heat flux distribution of the electron beam are set appropriately, the end portions e1 and e2 of the irradiation line 25 are located on the side wall 37 of the bath 30, and the electron beam is emitted so as to block the flow path between the upstream region S2, including the supply lines 26 and the spout portion 36 . In such a case, it is obvious that the behavior of the GNP will be similar to the behavior illustrated in the above examples 1-13.

Comparative example 1.

In Comparative Example 1, no electron beam was emitted along the irradiation line 25 . Therefore, as illustrated in FIG. 37 , the RER flowed freely from the high temperature areas of the supply lines 26 to the central part of the bath 30, was carried along by the molten metal flow 60 in the central part of the bath 30, and a large amount of the RUR passed through the spout portion 36 and flowed into the mold.

Comparative example 2.

Comparative Example 2 is a simulation result of the method described in the above-mentioned Patent Document 1. In other words, as illustrated in FIG. 38, the electron beam scanned in a zigzag manner in the opposite direction of the flow of molten metal towards the mold on the surface of the molten metal 5c in the baths 31 and 33. As illustrated in FIG. 38, the irradiation line 25 had a zigzag shape along the longitudinal direction of the baths 31 and 33. The raw material 5 was introduced from the raw material supply region 28 from the far side in the longitudinal direction of the bath (i.e., from the opposite side of the spout). For convenience, melting bath 31 and cleaning bath 33 have been modeled as one bath.

In Comparative Example 2, as illustrated in FIG. 39, as the RTI moved from the raw material supply region 28 to the spout portion 36, the RNP gradually collected in the spout portion 36 and flowed out into the mold 40. Although in Comparative Example 2, the simulation was performed for the case in which a long tub was used, the RNP crossed irradiation line 25, and it can be easily assumed that the IRR would also flow into the mold if a short bath was used.

Comparative example 3.

In Comparative Example 3, as illustrated in FIG. 40, since the first straight portion and the second straight portion did not intersect, there was a place where the electron beam was not emitted near the center line of the bath 30. Therefore, as illustrated in FIG. 41, the RNP passed through this non-irradiated location and flowed through the spout portion 36 into the mold 40.

Comparative example 4.

In Comparative Example 4, as illustrated in FIG. 42, since the first straight portion L1, the second straight portion L2, and the third straight portion L3 did not intersect, there was a place where no electron beam was emitted near the inlet of the spout portion 36 of the tub 30. Therefore, as illustrated in FIG. 43, the RNP passed through this non-irradiated location and flowed out through the spout portion 36 into the mold 40.

The simulation results of Examples 1-13 and Comparative Examples 1-4 have been described above. Based on these simulation results, it can be said that it has been confirmed that by concentrated electron beam emission along the irradiation line 25, as illustrated in Examples 1 to 13, the molten metal flow is generated in the opposite direction of the spout part 36 from the irradiation line 25, and it is possible to prevent the GNR from passing through the spout portion 36 and flowing into the mold.

(2) An example of the behavior of a molten metal flow.

In the present example, the behavior of the molten metal flow with respect to the V-shaped irradiation line 25 according to the first embodiment and the irradiation line 25 according to the second embodiment was determined. In this case, Example 1 (V-shaped irradiation line 25) and Example 3 (T-shaped irradiation line 25) of the above examples were compared. For each simulation, a transient was calculated as the flow and temperature of the molten metal change at each instant of time depending on the scanning of the electron beam. In the present example, the electron guns used in Examples 1 and 3 were set up as shown in Table 1 below. 2. With regard to Example 3, three electron guns were used, and the T-shaped irradiation line 25 was formed so that the ratio (h2/b2) between the length of the irradiation line (b2) and the height of the irradiation line (h2) was 2/5.

- 30 039285

table 2

The amount of heat transferred by the electronic Electron Beam Scanning Speed Heat flux distribution of the electron beam Irradiation path shape beam [MW] [m/s] (o[m]) Example 1 0.25 3.7 0.02 V shape Example 3 dl :0.05 ¢12:0.15 ¢13:0.05 dl:2.9 ¢12:3.6 ¢13:2.9 0.02 T-shape

Fig. 44 shows the molten metal surface flow rate distribution and the maximum molten metal surface flow rate, and also shows the ratio of the total molten metal flow rate to the side wall 37A through the line segment AB from the vicinity of the spout portion 36. It should be noted that the ratio of the total flow rate is the ratio of the value represented by the product of the average flow rate of the molten metal by the length of the linear segment AB.

When comparing the flow rate distribution of the molten metal surface for Examples 1 and 3, it was found that although the flow rate of molten metal to the side wall 37A from the vicinity of the spout portion 36 is high in both Example 1 and Example 3, as illustrated in FIG. 44, the flow velocity is higher in Example 3 compared to Example 1. The maximum flow velocity in Example 3 was 0.13 m/s, while in Example 1 the maximum flow velocity was 0.11 m/s. In addition, the ratio of the velocity of the total molten metal flow that passed through the line segment AB parallel to the side wall 37 of the pool, which is shown in the velocity distribution of the surface of the molten metal in FIG. 44 also had a higher value in example 3 compared to example 1.

Thus, it was found that, compared with Example 1, in which the surface flow of molten metal to one side wall was formed as a result of the occurrence of a single Marangoni convection, a surface flow of molten metal with a higher speed was formed in Example 3, in which the surface flow was formed as a result of the occurrence of two Marangoni convections.

(3) An example of an electron beam to accelerate the dissolution of GNP.

Then, for the above example 8, a simulation of the case was performed in which an electron beam was used to accelerate the dissolution of the GNP. The present simulation also calculated the transient as the flow and temperature of the molten metal 5c change at each time point depending on the scanning of the electron beam. The simulation was performed on the assumption that the GNP is titanium nitride, the grain size of titanium nitride is 5 mm, and the density of titanium nitride is 10% less than the density of the molten metal 5c.

In the present example, first using one electron gun to prevent the outflow of the GNP, as illustrated in FIG. 12, an irradiation line 25 having a straight shape, the two end portions of which e1 and e2 were located on the side wall 37D in which the spout portion 36 is provided, was positioned to block the spout portion 36. The amount of heat transferred by the electron beam to prevent the outflow of the EOR was set to 0.25 MW, the scanning speed was set to 1.6 m/s, and the standard deviation of the heat flux distribution was 0.02 m. stagnation positions of the molten metal flow using two electron guns to accelerate the dissolution of the EOR in the bath 30, which were different from the electron gun to prevent the outflow of the EOR. At the same time, the time period of the emission of the electron beam by each electron gun to prevent the expiration of the EOR was set to 1 s, and the emission position of the corresponding electron beam was fixed at the position of stagnation of the molten metal flow. The amount of heat transferred by each electron beam to accelerate the dissolution of the WNP was set to 0.25 MW, and the standard deviation of the heat flow distribution was 0.02 m.

The simulation result is shown in Fig. 45. FIG. 45 shows the temperature distribution and behavior of the RTI for the surface of the molten metal in the bath 30 for four time intervals from the occurrence of the RTR in the molten metal 5c. In the temperature distribution diagrams on the left side of Fig. 45, a high temperature region near the spout portion 36 marked with a circle indicates the position of electron beam irradiation relative to the irradiation line 25 at a given time, and the circled regions of the high temperature supply lines 26 near the ends of the spout portion 36 indicate the positions of the electron beams for acceleration. dissolution of GNP at the appropriate time. In addition, the two upper and lower ribbon-like high temperature portions denote two supply lines 26, and the low temperature portion near the inner surface of the bath denotes the portion in which the scull 7 has formed. In addition to this, on the right in FIG. 45 shows the positions of the GNP for the corresponding time intervals.

- 31 039285

As illustrated in FIG. 45, the RTIs that were near the supply lines 26 0.8 seconds after the occurrence of the RTRs in the molten metal moved through the interior of the bath 30 over time. 27.7 seconds after the appearance of the RTI in the molten metal, a plurality of the RTRs were in the positions (stagnation positions of the molten metal flow) indicated by circles in the diagrams showing the behavior of the RTR. 27.8 s after the appearance of the VNP in the molten metal, electron beams were emitted for 1 s to these resulting groups of VNP using two electron guns to accelerate the dissolution of the VNP. As a result, VNPs were dissolved 28.8 s after the appearance of VNPs in the molten metal. Thus, it has been shown that by determining the stagnation points in the molten metal flow and emitting electron beams to the corresponding stagnation positions in the molten metal flow, it is possible to confidently dissolve the WNP at an early stage.

While the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to the examples described above. Obviously, a person skilled in the art will be able to develop various examples of changes and modifications within the technical idea described in the attached claims, and it should be understood that such examples will naturally belong to the technical scope of the present invention.

The above have mainly given examples of producing a titanium ingot 50 using a bath 30 and a mold 40, in which the metal raw material 5 that is the object of melting for the metal ingot production method of the present embodiments is, for example, a raw material of titanium or a titanium alloy. However, the method for producing a metal ingot of the present invention is also applicable to those cases in which a metal raw material other than a titanium raw material is melted and an ingot is produced from the corresponding metal raw material. In particular, the method for producing a metal ingot of the present invention is also applicable to the case of producing an active metal ingot with a high melting point, in which the ingot can be produced using an electron gun capable of controlling an electron beam irradiation position and an electron beam furnace having a bath that accumulates molten metal from metallic raw materials such as tantalum, niobium, vanadium, molybdenum or zirconium. In other words, the present invention can be particularly effectively applied to the case of producing an ingot containing the respective mentioned elements in a total amount of 50 mass% or more.

In addition, the shape of the bath to which the metal ingot production method according to the present embodiment is applied is not limited to a rectangular shape. For example, the method for producing a metal ingot according to the present embodiment is also applicable to a tub having a shape other than a rectangular one, in which the side walls of the tub have a curved shape such as elliptical or oval.

List of reference designations.

- Electron-beam melting furnace (EL-furnace),

- metal raw material, c - molten metal,

- garnisage,

- GNP,

10A, 10B - part of the supply of raw materials,

20A, 20V - electron gun for melting raw materials,

20C, 20D - electron gun for maintaining the temperature of the molten metal,

20E - electron gun for linear irradiation,

- irradiation area for keeping warm,

- irradiation line,

- supply line,

- cleaning bath,

- part of the drain sock,

37A, 37B, 37C - side wall, in which part of the drain sock is not provided,

D - first side wall,

- casting shape,

- ingot,

61, 62, 63 - flow of molten metal.

Claims (15)

1. A method for producing a metal ingot containing a total of 50 wt.% or more of at least one metal element selected from the group consisting of titanium, tantalum, niobium, vanadium, molybdenum and zirconium, by using an electron beam furnace having an electronic a gun configured to control the position of electron beam irradiation, - 32 039285 and a bath that accumulates molten metal from metal raw materials, and among the plurality of side walls of the bath that accumulates molten metal from metal raw materials, the first side wall is a side wall provided with a spout part for flowing molten metal from the bath into a mold; the irradiation line is located between the upstream area in which the metal raw material is supplied to the surface of the molten metal and the first side wall, so that the first electron beam that is radiated to the surface of the molten metal along the irradiation line blocks the part of the drain spout from the area in which metal raw material is fed to the surface of the molten metal, and the two end parts of the irradiation line are located in close proximity to the side wall of the bath; moreover, the two end parts of the irradiation line are located at the inner surface of the side wall or in the area spaced from the inner surface of the side wall by 5 mm or less; and by radiating the first electron beam along the irradiation line, the surface temperature (T2) of the molten metal on the irradiation line is increased above the average surface temperature (T0) of the entire surface of the molten metal in the bath and a reverse flow of molten metal is formed in the outer layer of the molten metal, directed in the opposite direction from the first side wall side, away from the irradiation line. 2. The method for producing a metal ingot according to claim 1, wherein the two ends of the irradiation line are located in close proximity to the first side wall. 3. A method for producing a metal ingot according to claim 1 or 2, wherein the molten metal flow is from an irradiation line that extends to a side wall of side walls that extends substantially perpendicular to the back of a first side wall of a plurality of side walls. bath walls. 4. A method for producing a metal ingot according to any one of claims 1 to 3, wherein the irradiation line has a convex shape that protrudes from the part of the spout in the opposite direction. 5. The metal ingot production method according to claim 4, wherein the irradiation line is V-shaped or circular arc-shaped having a diameter equal to or greater than the width of the outlet of the spout part. 6. A method for producing a metal ingot according to any one of claims 1 to 3, wherein the irradiation line has a T-shape that includes a first straight portion along the first side wall between the two end portions and a second straight portion that extends along the essentially perpendicular to the first straight part in the opposite direction from the first side wall. 7. A method for manufacturing a metal ingot according to claim 1 or 2, wherein the irradiation line is in the form of a straight line along the first side wall between the two end portions. 8. A method for producing a metal ingot according to claim 1 or 2, wherein the flow of molten metal is a flow from the irradiation line in the opposite direction from the first side wall, and is a flow towards the center from a pair of side walls that face each other and that pass, substantially perpendicular to the opposite side of the first side wall of the plurality of side walls. 9. The method for producing a metal ingot according to claim 8, wherein the irradiation line has a convex shape protruding from the reverse side to a portion of the spout. 10. The method for producing a metal ingot according to claim 8, wherein the irradiation line has a U-shape, containing the first straight part along the first side wall between the two end parts and the second straight part and the third straight part from the two end parts of the first straight part, which pass, respectively, along a pair of side walls that face each other and that extend substantially perpendicularly in the opposite direction from the first side wall of the plurality of side walls. 11. A method for producing a metal ingot according to any one of claims 8 to 10, wherein the second electron beam is radiated to a stagnation position of the molten metal flow that results from the emission of the first electron beam along the irradiation line. 12. A method for manufacturing a metal ingot according to any one of claims 1 to 11, wherein a plurality of first electron beams are emitted along an irradiation line using a plurality of electron guns so that the paths of the first electron beams intersect or overlap at the surface of the molten metal. 13. The method of producing a metal ingot according to any one of paragraphs.1-12, in which the bath contains only one cleaning bath; and the metal raw material is melted in the raw material supply part, the molten metal raw material drips from the raw material supply part into the bath, and the metal raw material in the molten metal is cleaned inside the cleaning bath. - 33 039285 14. A method for producing a metal ingot according to any one of claims 1 to 12, wherein the bath is a multi-stage bath in which a plurality of separated baths are combined and arranged in series; and in each of the divided baths, the first electron beam is irradiated to the surface of the molten metal along the irradiation line, which is located in such a way that the irradiation line blocks part of the downspout in the downstream region, and the two end parts of the irradiation line are located in close proximity to the side wall of the divided baths. 15. A method for producing a metal ingot according to any one of claims 1 to 14, wherein the metal raw material contains 50 wt% or more of elemental titanium.