JP5380264B2 - Method for melting metal ingots - Google Patents

Description

  The present invention relates to a method for melting a metal ingot by electron beam melting, and particularly relates to a method for efficiently adding an oxygen source constituting a metal titanium ingot.

  Titanium materials have been developed for use in recent years, and are widely used not only for aircraft applications but also for civilian purposes such as building materials, roads, and sporting goods.

  The titanium material is rarely used as pure titanium, and is usually used in the form of an alloy. Among alloys, titanium alloys configured by adding an alloy element such as oxygen or iron are known. When oxygen is added as a titanium alloy component, for example, when supplying sponge titanium to an electron beam melting furnace. In addition, a powdered oxide such as titanium oxide is often blended with titanium sponge and supplied to the melting furnace.

  However, powdered titanium oxide as described above is difficult to mix efficiently and uniformly with granular titanium sponge, and both raw materials are often unevenly distributed inside the raw material feeder or mixer. It has been difficult to supply a melting material having a uniform composition to an electron beam melting furnace.

  In response to such a problem, for example, by applying a powdered alloy raw material suspended in soda glass to the surface of the sponge titanium, the alloy component is held on the surface of the sponge titanium at a predetermined ratio. A technique for supplying coated sponge titanium to an electron beam melting furnace is disclosed (for example, see Patent Document 1). According to such a method, it is considered that the alloy composition in the sponge titanium can be configured to a desired composition.

  However, in this technique, since a third component other than the raw material such as soda glass and organic solvent is added, it is not necessarily an effective method for producing a high purity alloy ingot. Moreover, the said method includes the application | coating process of the alloy component to sponge titanium, and the room for examination is left also from the point of productivity.

  In addition, by heating granular titanium sponge with titanium oxide powder on the surface to high temperature in a vacuum and sintering the titanium oxide on the surface to sponge titanium, the powdery alloy component is efficiently applied to sponge titanium. A technique of blending is also known (see, for example, Patent Document 2).

  However, this method also includes a step of applying titanium oxide to the sponge titanium and a step of sintering, and the degree of freedom is limited in terms of equipment and time.

  There is also known a technique for supplying briquettes formed by mixing granular metal such as sponge titanium and alloy powder to an electron beam melting furnace or a VAR melting furnace (see Patent Document 3).

  However, the method of briquette molding by mixing granular metal such as sponge titanium and powdered oxide such as titanium oxide or iron oxide requires a briquette molding process, and there is room for improvement in terms of cost. Is left.

  Furthermore, from the same viewpoint as Patent Document 3, after preparing powdery titanium oxide by press molding, pellet-shaped titanium oxide fired into tablets is prepared, and a mixed raw material containing this and sponge titanium is dissolved by electron beam A technique for melting a metal titanium ingot by supplying it to a furnace is disclosed (for example, see Patent Document 4). In this method, the alloy components can be made uniform by adjusting the supply ratio of titanium sponge and titanium oxide pellets. Moreover, the scattering loss of titanium oxide when the raw material is charged into the hearth of the electron beam melting furnace can be effectively suppressed.

  However, the titanium oxide pellets baked in this way often dissolve and disappear in a relatively short time after being put into the molten titanium held in the hearth. There has been a demand for improvement because the fine titanium oxide pellets that have not been dissolved completely during the staying time and are not yet dissolved may be discharged into the mold as they are. In particular, when manufacturing a titanium alloy having a high oxygen content, the size and number of titanium oxide pellets to be supplied increase, and therefore undissolved titanium oxide pellets are likely to be a problem.

  As described above, in producing a titanium alloy containing oxygen as an alloy component, it has been difficult for the conventional technique to efficiently make the oxygen component uniform and increase the oxygen content.

Japanese Patent Laid-Open No. 01-156434 JP 2001-279345 A JP 2005-298855 A WO 2008-0708402

  As described above, an efficient method is desired in which titanium oxide is used as an alloy component, the composition in the titanium alloy is made uniform, and the oxygen content in the titanium alloy material is increased.

  The present invention has been made in view of the above problems, and provides a technique capable of efficiently dissolving oxide ingots added to granular metal raw materials in a method for melting metal ingots by electron beam melting. It is intended.

  In view of such circumstances, the inventors have intensively studied the means for solving the above problems based on the above viewpoints. When adjusting the oxygen content in the molten metal using an electron beam melting furnace, granular metal raw materials and oxides are used. It was found that the metal oxide can be uniformly dissolved without being left in the molten metal by introducing the mixture composed of the ingot obtained by firing the mixture into an electron beam melting furnace. The invention has been completed.

That is, the method for melting a metal ingot according to the present invention is obtained by firing a metal hydroxide having a primary particle size of 1.0 to 3.0 μm in a method for melting a metal ingot using an electron beam melting furnace. An ingot having a particle diameter of 0.1 to 5.0 mm or an ingot having a particle diameter of 1 to 5 mm obtained by firing a metal oxide having a primary particle diameter of 1.0 to 3.0 μm (hereinafter referred to as “oxidation”). A method of melting a metal ingot using a mixture of a granular metal raw material as a melting raw material .
The particle diameter d _p (mm) of the oxide ingot is a unit of the oxide ingot calculated by the relational expression (1) from the particle diameter d _f (μm) of the primary particles constituting the oxide ingot. The melting time a (min / mm) per diameter is defined by applying the equation (2) .
a = −b × d _f + c (1)
(Here, the coefficients b and c are constants determined as appropriate depending on the type of oxide ingot used for the raw material.)
d _p = t _m / a (2)
(Here, t _m (min) is the residence time of the oxide ingot in the electron beam melting furnace.)

  In the present invention, it is preferable that the oxide ingot is a clinker obtained by firing a metal hydroxide.

  In this invention, it is set as the preferable aspect that an oxide ingot is a granular granule comprised with the said oxide.

  In this invention, it is set as the preferable aspect that the purity of the ingot comprised with the said metal oxide is 3N or more.

  In this invention, it is set as the preferable aspect that the mixture of an oxide ingot and a granular metal raw material is supplied to the hearth molten metal hold | maintained in the hearth of the electron beam melting furnace.

  In this invention, it is set as the preferable aspect that the surface vicinity temperature of a hearth molten metal is heated and hold | maintained more than melting | fusing point of an oxide ingot.

  In this invention, it is set as the preferable aspect that the mixture of an oxide ingot and a granular metal raw material is supplied to a hearth molten metal while a fixed quantity is cut out from a rotary raw material charging device.

In the present invention, the particle diameter d _p (mm) of the oxide ingot is calculated from the particle diameter d _f (μm) of the primary particles constituting the oxide ingot by the relational expression (1). It is a preferred embodiment that the melting time a (min / mm) per unit diameter of the ingot is defined by applying the equation (2).
a = −b × d _f + c (1)
(Here, the coefficients b and c are constants determined as appropriate depending on the type of oxide ingot used for the raw material.)
d _p = t _m / a (2)
(Here, t _m (min) is the residence time of the oxide ingot in the electron beam melting furnace.)

  In the present invention, it is preferable that the oxide ingot is composed of titanium oxide or iron oxide.

  In this invention, it is set as the preferable aspect that the granular metal raw material is comprised by sponge titanium or titanium scrap.

  As described above, even when the oxide ingot specified by the present invention and the granular metal raw material are put into the molten metal in the hearth, the oxide ingot does not remain undissolved, and the oxygen content in the titanium metal is reduced. The effect that it can raise uniformly and effectively is produced. By using the method according to the present invention, not only can the oxygen content in the metal ingot be configured to a target level, but also the oxygen content distribution in the longitudinal direction of the metal ingot can be formed uniformly. There is an effect.

It is a graph which shows the relationship between the average particle diameter of the oxide ingot in this invention, and melt | dissolution time. It is a graph which shows the relationship between the primary particle diameter of the primary particle which comprises the oxide ingot in this invention, and a dissolution rate. It is a schematic cross section which shows the melting apparatus of the metal ingot which concerns on one Embodiment of this invention. It is a top view of the hearth and the casting_mold | template part in the melting apparatus of FIG.

Hereinafter, embodiments of the present invention will be described in detail.
The method for melting a metal ingot according to the present invention is characterized in that a mixture of an oxide ingot and a granular metal material is used as a melting material.

  In particular, in the present invention, it is preferable to use a granular granule composed of a clinker or a metal oxide obtained by firing a metal hydroxide.

By using the oxide ingot in the form as described above as an additive to the granular metal raw material, the oxygen content in the molten metal ingot can be increased uniformly and efficiently. is there.

  In the clinker obtained by baking the metal hydroxide at a high temperature, it is preferable to use a relatively fine clinker. Specifically, it is preferable to use 0.1 to 5.0 mm clinker as the raw material.

  The oxygen content required for the metal ingot to be melted in the present invention is in the range of 100 to 500 ppm. Therefore, the oxide ingot required to satisfy this is the weight of the granular metal raw material. The ratio is in the range of about 1/100 to 1/1000, which is very small.

  Therefore, in order to uniformly add to the granular metal raw material, the size of the oxide ingot added to the granular metal raw material is preferably as fine as possible, specifically 0.1 to 5.0 mm. The clinker is preferably used as the raw material.

  As a result, a material having a uniform composition can be supplied into the hearth of the electron beam melting furnace, and the composition of the metal ingot melted in the electron beam melting furnace can be made uniform. is there.

  In the present invention, various types of metal raw materials can be used as the granular metal raw material. For example, when the metal ingot to be melted is a metal titanium ingot, a sponge titanium or a titanium scrap chip-shaped raw material can be used.

  However, when the clinker as described above is used as the oxide ingot according to the present invention, it is preferable to use a porous titanium material such as sponge titanium.

  Prior to supplying the granular titanium oxide and granular titanium to the electron beam melting furnace, the granular titanium oxide is physically fixed in the gap of the sponge titanium by mixing in advance using a mixer. There is an effect that it is possible.

  As a result, the clinker filled in the rotary raw material feeder can be discharged to the hearth in the electron beam melting furnace with a high yield.

  On the other hand, when the oxygen content in the melted metal ingot is set high, the above-described titanium oxide clinker can be further granulated and processed into granules or pellets. . The pellet-shaped titanium oxide is preferably sized so as to approximate the particle size of granular titanium. Specifically, it is preferable to adjust in the range of 1 to 5 mm.

  Even in this case, it is preferable to mix both granular titanium and granular titanium oxide in advance before supplying the raw material to the electron beam melting furnace. As a result, the raw material in which the granular titanium oxide and the granular titanium raw material are uniformly mixed can be supplied to the electron beam melting furnace.

  In addition, as the oxide ingot according to the present invention, a titanium oxide granule produced by granulating fine titanium oxide produced by a chlorine method or a sulfuric acid method can also be used. Titanium oxide granules are made by adding a dispersing agent such as PVA to fine titanium oxide, granulating to a predetermined size with a granulator, dehydrating and drying, and then subjecting it to high temperature treatment, thereby oxidizing the oxide used in the present invention. It can also be used as an ingot. By using such a granulated body, there is an effect that the mixing state with a porous raw material such as sponge titanium can be remarkably improved.

  Therefore, the size of the granule constituting the granular titanium oxide is preferably in the range of 1 to 5 mm. By granulating in the size of the above-described range, there is an effect that the porous body formed on the surface of the sponge titanium can enter or be fixed. As a result, the rotary mixer can be efficiently discharged into the hearth of the electron beam melting furnace.

Next, preferable physical properties of each aspect of the oxide ingot are described below.
1) When the oxide ingot is a titanium oxide clinker It is preferable to use a titanium oxide clinker obtained by firing a hydroxide of titanium. The apparent density of the clinker is preferably in the range of 0.5 to 1.5 g / cm ³ .

On the other hand, when the apparent density of the granular titanium oxide is 1.5 g / cm ³ or more, the molten titanium can be efficiently brought into contact with the molten metal titanium held in the hearth. It is difficult to penetrate, and as a result, it can cause the complete dissolution of granular titanium oxide. For this reason, it is preferable to select and use the apparent density of the granular titanium oxide used for this invention so that it may become the range of 0.5-1.5 g / cm < ³ >.

  In addition, it is preferable to selectively use a primary particle constituting the clinker having a size in the range of 1.0 μm to 3.0 μm. When the size of the primary particles is less than 1.0 μm, it is preferable that the molten titanium hardly penetrates into the clinker when introduced into the molten metal titanium, resulting in a decrease in the dissolution rate of the clinker. Absent. On the other hand, when the size of the primary particles constituting the titanium oxide clinker exceeds 3.0 μm, the dissolution rate of the titanium oxide clinker is lowered, which is not preferable.

2) When the oxide ingot is a granulated body of titanium oxide Even when granular titanium oxide is used by granulating fine titanium oxide, the apparent density of the granulated body after granulation is The range is preferably the same as that of the titanium oxide clinker, and specifically, the range of 0.5 to 1.5 g / cm ³ is preferable.

  Moreover, it is preferable that the size of the titanium oxide granule composed of fine titanium oxide is also in the range of 1 to 5 mm.

  By composing the oxide ingot according to the present invention in the above-described range, it can be quickly dissolved when it is put into the molten metal titanium held in the hearth in the electrolytic beam melting furnace. There is an effect.

When a titanium oxide clinker is used as the oxide ingot according to the present invention, the particle size d _p (mm) of the clinker is the following (1) from the particle size of the primary particles d _f (μm) constituting the granular titanium oxide: The dissolution time a (min / mm) per clinker unit diameter calculated by the relational expression of the formula (2) is defined by applying the formula (2).
a = −b × d _f + c (1)
Here, the coefficients b and c are appropriately determined depending on the type of granular titanium oxide used as a raw material.
d _p = t _m / a (2)
Here, t _m is the residence time of the granular titanium oxide in the electron beam melting furnace (minutes).

  Here, the coefficients b and c included in the formula (1) are values determined depending on the type and dissolution conditions of granular titanium oxide. In the present invention, the coefficient b is 5 to 10, and the coefficient c. Is appropriately set within the range of 15-20. Here, a method for determining the coefficients b and c will be described below.

As the titanium oxide clinker, at least two types of granular titanium oxides having different primary particle diameters and different particle diameters after granulation are prepared. After melting and heating the titanium material placed in the electron beam melting furnace, the granular titanium oxide is individually charged therein, and the complete dissolution time of the granular titanium oxide, that is, the residence time t _m (min) Is measured to determine the dissolution rate a (min / mm) per unit time.

Next, with respect to the two granular titanium oxides, the dissolution rate a (min / mm) and the primary particle diameter d _f (μm) are plotted, and when the two points are connected, they are expressed by a linear relationship as shown in FIG. Can be obtained. Both the coefficients b and c in the equation (1) can be determined from the slope of the straight line and the intercept of the Y axis.

When the relationship is formulated, the dissolution rate a (min / mm) is determined as the slope of the straight line as shown in FIG. Furthermore, when the residence time in the molten metal in the hearth into which the titanium oxide is charged is determined, the particle diameter d _p (mm) of the granular titanium oxide to be charged into the hearth is determined from the equation (2). Is done.

  That is, the primary particle diameter of the titanium oxide clinker charged into the hearth is determined, and the residence time of the molten metal in the hearth is determined, whereby the particle diameter of the granular titanium oxide to be charged into the hearth can be determined. The granular titanium oxide determined in this manner has an effect that it can be efficiently dissolved without being left undissolved inside even when it is put into a hearth.

  The purity of the oxide ingot used in the present invention is preferably 3N or more, and more preferably 4N or more. By using the oxide ingot having the purity as described above, there is an effect that only the oxygen content can be effectively increased without reducing the purity of the molten metal ingot.

  It is preferable to heat-treat the oxide ingot according to the present invention in advance in a temperature range of about 110 to 300 ° C. prior to charging into the melting furnace. By performing such heat treatment, water in the titanium oxide can be separated and removed, and the bumping phenomenon caused by water vapor when the titanium oxide clinker is put into a melting furnace is effectively suppressed. There is an effect that it is possible.

  The temperature in the vicinity of the surface of the molten metal held in the hearth for supplying the oxide ingots as described above is preferably kept at a temperature equal to or higher than the melting point of the oxide ingots. By maintaining the surface temperature of the molten metal at the temperature as described above, there is an effect that it is possible to effectively suppress the residual frequency of the oxide agglomerates due to variations and fluctuations in operation.

  The oxide ingot used in the present invention is mixed with a granular metal raw material and mixed uniformly, and then the mixture is supplied into a molten metal titanium held in a hearth using a rotary mixer such as an Archimedes can. It is preferable.

  As the granular metal material, it is preferable to use a porous material such as sponge titanium, but instead of the sponge titanium, recycled materials such as pure titanium chips and forged pieces can also be used. By using the recycle material as described above, there is an effect that the raw material cost of the metal ingot to be melted can be reduced.

  The sponge titanium used as the granular metal material used in the present invention preferably uses a particle size range of 1 to 10 mm selectively. When the particle size of the sponge titanium is 1 mm or less, it is not preferable that the titanium sponge is scattered by the upward flow generated from the molten titanium and scattered outside from the hearth when it is put into the molten titanium held in the hearth.

On the other hand, when the particle size of the sponge titanium is 10 mm or more, which is the upper limit of the above range, it is not preferable because it cannot be completely dissolved in the molten metal titanium held in the hearth.
Therefore, it is preferable to selectively use a particle size range of 1 to 10 mm for titanium sponge, which is one of the preferred embodiments of the bulk metal used in the present invention.

  Next, a preferred method for melting an alloy ingot using the melting raw material described above will be described in detail with reference to FIG. In this embodiment, the case where the granular metal raw material is sponge titanium and the oxide ingot is a titanium oxide clinker composed of titanium oxide will be described below. FIG. 3 shows a configuration example of an electron beam melting furnace used in the present invention.

  The dissolution raw material 12 in this embodiment is a granular mixture composed of sponge titanium and titanium oxide clinker. The melted raw material 12 is filled in a cylindrical rotary raw material discharge device called an Archimedes can 10 and is continuously discharged to the raw material feeder 11 as the Archimedes can 10 rotates. The massive sponge titanium and granular titanium oxide constituting the melting raw material 12 are preferably mixed in advance using a mixer.

  The Archimedes can 10 is a horizontal rotation type raw material cutting device, and spiral ribs are disposed on the inner surface of the Archimedes can 10, and the Archimedes can 10 is filled with the ribs. The melting raw material 12 can be supplied to the electron beam melting furnace in a state close to the extrusion flow without back mixing. As a result, there is an effect that an ingot having a uniform raw material composition can be melted.

  The melted raw material 12 discharged to the raw material feeder 11 is supplied to a hearth 13 disposed downstream of the raw material feeder 11. The melting raw material 12 supplied to the hearth 13 stays in the molten metal 20 held in the hearth 13, but receives the electron beam irradiated on the surface of the molten metal 20 from the electron beam irradiation means 15 and the heat supply from the molten metal 20. Then, while staying in the molten metal 20 held in the hearth 13, the molten metal is completely dissolved and integrated with the molten metal 20.

  Further, as shown in FIG. 4, it is preferable to operate so that a guard zone 14 having an electron beam irradiation density higher than that of the remaining hearth region is provided on the downstream side of the molten metal 20 held in the hearth 13. .

  The irradiation density of the electron beam applied to the guard zone 14 is preferably 2-10 times larger than the density of the electron beam applied to the molten metal 20 in the hearth in the other region. It is preferable to irradiate 4 to 8 times larger. As a result, the temperature of the guard zone 14 can be maintained at a higher temperature than the other molten metal 20 in the hearth, and the molten raw material 12 can be reliably dissolved while staying in the hearth 13. There is an effect.

  By providing the guard zone 14, even when a part of the melted raw material 12 supplied to the molten metal 20 in the hearth 13 bypasses undissolved and tries to flow downstream, When entering, there is an effect that the melting raw material 12 to be bypassed is trapped and completely melted and integrated with the molten metal 20. The guard zone 14 is preferably irradiated with an electron beam so as to run in reverse to the flow of the molten metal 20 in the hearth 13.

  The melting raw material 12 is completely dissolved in the hearth 13 as described above, and discharged to the water-cooled mold 30 provided downstream of the hearth 13 to form the mold pool 21 in the water-cooled mold 30. The lower part of the mold pool 21 receives cooling from the water-cooled mold 30 to form an ingot 22. The ingot 22 formed by the water-cooled mold 30 is continuously drawn downward by the drawing means 31 engaged with the lower end portion of the ingot 22.

  As described above, according to the present invention, it is possible to effectively avoid unmelted oxide ingots supplied to the electron beam melting furnace, and as a result, oxygen content in the melted metal ingot The effect is that the amount can be maintained uniformly.

  In addition, it can replace with the said titanium oxide with respect to this invention, and the oxide ingot comprised from the iron oxide can also be used. Even in such a case, the molten metal in the hearth held in the electron beam melting furnace can be supplied uniformly and with a high yield, and as a result, an ingot having a uniform composition can be produced. is there.

  In addition, it is possible not only to avoid the residual and uneven distribution of the melted raw material in the raw material supply device, but also to effectively suppress the scattering of the raw material supplied from the raw material supply device to the molten metal in the hearth. As a result, there is also an effect that it is possible to effectively suppress a decrease in the discharge yield of the molten metal from the Archimedes can to the hearth.

  Thus, by using the oxide ingot according to the present invention as an oxygen source of the metal ingot to be melted, in the ingot to be melted without causing any undissolved residue in the hearth of the oxide ingot This makes it possible to make the components uniform and to effectively suppress component fluctuations.

Hereinafter, the present invention will be described in more detail by way of examples. The conditions of the examples and comparative examples were as follows.
1. Raw material 1) Sponge titanium Purity: 99.7%
Particle size: 25.4mm
Bulk density: 1.3 to 2.0 g / cm ³
2) Oxide ingot A (made by Toho Titanium Co., Ltd., TiO ₂ powder (trade name: HT0210) granulated with PVA)
Purity: 99.9%
Primary particle size: 2.3 μm
Particle size: 1 to 3 mm (after firing)
3) Oxide ingot B (manufactured by Sakai Chemical Co., Ltd., titanium oxide clinker manufactured by sulfuric acid method)
Purity: 99.9%
Primary particle size: 0.9μm
Particle size: 0.15 to 0.85 mm (after firing)

2. Melting device 1) Raw material supply device: Archimedes can (horizontal rotary supply device)
2) Melting furnace: Hearth-type electron beam melting furnace

3. Melting conditions 1) Melting power: 1100 to 1400 kW
2) Degree of vacuum: 1 × 10 ⁻⁵ to 8 × 10 ⁻³ Torr
3) Mold diameter: 660mm

[Example 1]
After the sponge titanium, which is a metal raw material, was held in a molten state in a button melting furnace, the oxide ingots A and B were supplied and the time required for complete dissolution was measured. At that time, it was 2000 degreeC when the temperature of Haas was measured with the radiation thermometer. The results are shown in Table 1. From Table 1, the relationship between the primary particle diameter (d _f ) and the dissolution rate (a) is expressed by the equation (3), and the diameter (d _p ) and dissolution time (t _m ) of the pellet composed of the primary particles The relationship was determined as shown in equation (4).
a = −6.4 × d _f +18.7 (min / mm) (3)
t _m = a × d _p (min) (4)

  Using the formalized relationship, an oxide ingot having a particle size corresponding to the residence time of the molten metal in the hearth required for the production rate of the titanium ingot is prepared, and is mixed homogeneously with spodite titanium to Archimedes. The can was filled and attached to the raw material supply device of the electron beam melting furnace.

  Next, 10 Archimedes cans were supplied to the hearth in the melting furnace to melt 10 metal titanium ingots having an increased oxygen content. When the oxygen content in the cross-section direction and the longitudinal direction of the melted ingot was investigated, the variation sufficiently satisfied the characteristics required for the product.

[Example 2]
In Example 1, an oxide ingot B (titanium oxide clinker) manufactured by the sulfuric acid method was prepared under the same conditions except that a titanium oxide clinker having a particle diameter of 1.5 mm with various primary particle diameters was prepared. The dissolution rate of titanium oxide clinker was investigated.

  As a result, when the diameter of the primary particles was in the range of 1.0 to 3.0 μm, the dissolution time tended to shorten as the diameter increased. However, when the primary particle diameter was reduced to 0.8 μm, which is less than 1.0 μm, the dissolution time tended to increase. On the other hand, with the titanium oxide clinker constituted with a primary particle diameter of 3.2 μm in which the primary particle diameter exceeded 3 μm, the complete dissolution time turned to a tendency to increase conversely. Therefore, in the said Example, it was confirmed that it is preferable to use the titanium oxide clinker comprised by the primary particle diameter of 1.0-3.0 micrometers.

[Comparative Example 1]
In Example 1, the relationship between the particle size and the dissolution time was simply determined without considering the size of the primary particles of the titanium oxide clinker. Next, an oxide ingot having a size corresponding to the melting rate performed in the electron beam melting furnace was prepared in the obtained relational expression, and supplied to the electron beam melting furnace to produce a metal ingot. As a result, the variation in oxygen content in the cross-section direction of the ingot was small. However, as for the oxygen content in the longitudinal direction of the ingot, a portion having an abnormally high oxygen content was observed in the middle portion of the ingot.

[Comparative Example 2]
In Example 1, after granulating titanium oxide produced by the sulfuric acid method, titanium oxide pellets fired at 1500 ° C. at a high temperature were put into an electron beam melting furnace. As a result, the melting time per unit diameter was smaller than that in Example 1. Because it doubled, it was abandoned for application to actual machines.

  The present invention is suitable for a technique for melting a metal ingot having a uniform alloy composition and excellent yield, and particularly suitable for melting a titanium alloy using an electron beam melting furnace.

10 ... Archimedes can,
11 ... Raw material feeder,
12 ... Raw material for dissolution,
13 ... Haas,
14 ... Guard zone,
15 ... Electron beam irradiation means,
20 ... molten metal,
21 ... Mould pool,
22 ... Ingot,
30 ... Water-cooled mold,
31 ... Extraction means.

Claims (9)

Ingots having a particle size of 0.1 to 5.0 mm obtained by firing a metal hydroxide having a primary particle size of 1.0 to 3.0 μm in a method for melting a metal ingot using an electron beam melting furnace Alternatively, an agglomerate having a particle diameter of 1 to 5 mm obtained by firing a metal oxide having a primary particle size of 1.0 to 3.0 μm (hereinafter sometimes referred to as “oxide agglomerate”) and a granular metal A method for melting a metal ingot using a mixture with a raw material as a melting raw material ,
The particle diameter d _p (mm) of the oxide ingot is calculated from the particle diameter d _f (μm) of the primary particles constituting the oxide ingot by the relational expression (1). A melting method for a metal ingot, characterized in that a melting time a (min / mm) per unit diameter is defined by applying the equation (2) .
a = −b × d _f + c (1)
(Here, the coefficients b and c are constants determined as appropriate depending on the type of oxide ingot used for the raw material.)
d _p = t _m / a (2)
(Here, t _m (min) is the residence time of the oxide ingot in the electron beam melting furnace.)   The method for melting a metal ingot according to claim 1, wherein the oxide ingot is a clinker obtained by firing a metal hydroxide.   2. The method for melting a metal ingot according to claim 1, wherein the oxide ingot is a granulated granule composed of a metal oxide.   The method for melting a metal ingot according to claim 1, wherein the purity of the ingot formed of the metal oxide is 3N or more.   The method for melting a metal ingot according to claim 1, wherein the mixture of the oxide ingot and the granular metal raw material is supplied to a hearth molten metal held in a hearth of an electron beam melting furnace.   2. The method for melting a metal ingot according to claim 1, wherein a temperature in the vicinity of the surface of the molten hearth is heated and maintained at a temperature equal to or higher than a melting point of the oxide ingot.   The molten metal ingot according to claim 1, wherein the mixture of the oxide ingot and the granular metal raw material is supplied to the hearth molten metal while being cut out from the rotary raw material charging device by a predetermined amount. Method. The method for melting a metal ingot according to any one of claims 1 to 7 , wherein the oxide ingot is made of titanium oxide or iron oxide. The method for melting a metal ingot according to any one of claims 1 to 7 , wherein the granular metal raw material is composed of sponge titanium or titanium scrap.

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