JP2000087152A - CONSUMABLE ELECTRODE FOR INGOT OF Ti-Al INTERMETALLIC COMPOUND AND ITS PRODUCTION - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a consumable electrode capable of imparting strength to the connecting parts of the electrode and increasing the size of the ingot of a Ti-Al base intermetallic compd. SOLUTION: This is a consumable electrode for the ingot of a Ti-Al base intermetallic compd. obtd. by plurally connecting briquettes obtd. by cylindrically compression molding a melted raw material and used for vacuum arc melting and the weld zones connecting the briquettes are composed of sponge titanium only. In the consumable electrode 1, it is desirable that the outer peripheral parts 2c provided over the whole circumferences of the upper ends and lower ends of the external layer parts 2c of the briquettes 2 are composed of sponge titanium only and the connection of the briquettes is executed by welding them in the circumferential direction. Moreover, it is also desirable that belt-like parts 2a plurally provided in the longitudinal direction of the outermost circumferential face of the external layer parts of the briquettes are composed of sponge titanium only and the connection of the briquettes is executed by welding them in the longitudinal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a consumable electrode used in a vacuum arc melting method, and more particularly, to a TiAI-based material used as a gas turbine component for a material such as wings and cases in the fields of power generation, ships and aircraft. The present invention relates to a consumable electrode for producing an ingot of an intermetallic compound.

[0002]

2. Description of the Related Art A TiAl-based intermetallic compound comprising titanium (Ti) and aluminum (Al) in a molar ratio of about 1: 1 is
Its specific gravity is as light as about 3.8, and it has the property of maintaining high strength up to about 800 ° C. Therefore, it is attracting attention as an excellent lightweight heat-resistant structural material, and is being developed for practical use in a wide range of fields. In particular, regarding the improvement of energy efficiency in gas turbines such as aircraft engines, it is necessary to achieve high temperature (high output) and light weight at the same time. Ti with higher specific strength and specific elastic modulus than
Expectations for Al-based intermetallic compounds are great.

[0003] However, Ni-based alloys are mainly used as materials for parts used in large quantities, large-sized parts, or parts having complicated shapes, and TiAl-based intermetallic compounds have not been able to be used as substitutes for these materials. . This, as described above,
Despite the excellent properties of TiAl-based intermetallic compounds, the material cost is high and the manufacturing cost is high, and the manufacturing process for large materials has not been established. This is because its spread has been delayed due to difficulties in performing such tasks.

In order to promote the use of TiAl-based intermetallic compounds, it is necessary to develop a technique for enlarging the casting soul (ingot) as a material. If it is possible to increase the size of the ingot, it will be possible to reduce the manufacturing cost due to the increase in the unit weight of the lot, and at the same time, it will be effective to deal with the manufacture of large parts. However, there has been a limit in increasing the size of ingots of TiAl-based intermetallic compounds,
The limit of ingots manufactured to date is 300 mm in diameter or 200 kg in weight, and it has been impossible to manufacture large ingots of TiAl-based intermetallic compounds exceeding these limits.

FIG. 5 is a diagram schematically illustrating a process of manufacturing a consumable electrode used for vacuum arc melting. Usually, the titanium material produced as a melting raw material is a sponge-like or needle-like granular material, and is processed into a consumable electrode 1 serving as an anode electrode when melting in an arc melting furnace 4 to produce an ingot. You. Specifically, titanium sponge, which is a melting raw material, is formed into a columnar briquette 2 which is compression-molded by a compression press, and a plurality of these are connected by an electrode welding machine 5 to be processed into a consumable electrode 1. When a desired consumable electrode 1 is produced, it is vacuum-melted in an arc melting furnace 4 to produce an ingot.

When manufacturing a large ingot of a TiAl-based intermetallic compound, a briquette obtained by compression-molding a mixture of titanium and aluminum sponge, which is a melting raw material, by a compression press, and then welding a plurality of briquettes to form a consumable electrode In some cases, it may be difficult to ensure the strength of the electrode to withstand its own weight at the welded portion. When subjected to vacuum arc melting in such a state, the consumable electrode may be deformed or dropped off during the melting process, not only interrupting the production but also causing a serious accident.

[0007] The above-mentioned problem that the consumable electrode is deformed or falls off frequently occurs in the process of dissolving the consumable electrode for ingots of TiAl-based intermetallic compounds. It was considered difficult to dissolve, and as a result, it was difficult to produce a cast soul of a TiAl-based intermetallic compound having a maximum weight exceeding 300 kg.

Conventionally, as a means for ensuring the strength of the welded portion of the consumable electrode for ingots of TiAl-based intermetallic compounds, a mixture of molten raw materials is compression molded in a state of being enclosed in a pure titanium tube.
Attempts have been made to produce a compact (briquette) as coated with pure titanium and then weld a plurality of these to produce consumable electrodes. However, if this means is directly applied to the production of large ingots, the pure titanium tube buckles during compression molding, resulting in an inconsistent shape of the molded body, making it impossible to manufacture consumable electrodes and reducing the yield. In addition, there is a problem that the production cost is increased in preparing the pure titanium tube for covering the briquette, and the production cost of the consumable electrode is greatly increased. For this reason, the method of coating briquettes with pure titanium tubes described above is applied only to small ingots at the laboratory level, and is not applied to industrial ingot production.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a conventional TiAl
It was made in view of the problems that occur when manufacturing large ingots of base intermetallic compounds, and improves the briquette connection structure when manufacturing consumable electrodes that manufacture ingots of TiAl base intermetallic compounds. Accordingly, an object of the present invention is to provide a large casting of a TiAl-based intermetallic compound by providing a welded portion serving as a connection portion of an electrode with sufficient strength to hold the weight of a consumable electrode.

[0010]

Means for Solving the Problems The present inventor has made various studies in order to solve the above-mentioned problems. As a result, the welding weight of the consumable electrode used in the casting of the TiAl-based intermetallic compound is reduced by the weight of the electrode. The following findings (a) and (b) could be obtained as to the reason why the strength that could maintain the strength could not be secured.

(A) In the case where titanium (1680 ° C.) and aluminum (660 ° C.) having melting points greatly different from each other coexist in the welded portion, the penetration during welding may be uneven, or the aluminum may be evaporated. Welding defects are likely to occur. Due to these welding defects, the strength of the welded portion is significantly reduced.

(B) The heat input during welding causes fusion of coexisting titanium and aluminum, and the welded portion becomes a TiAl-based intermetallic compound, but cracks occur in the intermetallic compound with subsequent solidification shrinkage. Therefore, the strength of the welded portion is extremely reduced.

Based on the findings of (a) and (b) above, in order to prevent a decrease in the strength of the welded portion, it was repeatedly examined whether or not a connection structure containing no aluminum can be employed in the welded portion of the briquette. As a result, the present inventors have found a specific method for forming a welded portion consisting of titanium sponge alone in order to connect consumable electrodes even in a briquette obtained by compression-molding a raw material for dissolving titanium sponge and aluminum.
The present invention has been developed based on such circumstances, and the following (1) consumable electrode for ingot of TiAl-based intermetallic compound and (2) consumable electrode for ingot of TiAl-based intermetallic compound The gist is a method for manufacturing an electrode.

(1) A consumable electrode for an ingot of a TiAl-based intermetallic compound used for vacuum arc melting by connecting a plurality of briquettes obtained by compression-molding a molten raw material into a cylindrical shape, wherein a welding portion connecting the briquettes is A consumable electrode for an ingot of a TiAl-based intermetallic compound, characterized in that the electrode is composed only of titanium sponge.

In the above consumable electrode, the outer edge provided over the entire circumference of the upper and lower ends of the outer layer portion of the briquette is formed only of titanium sponge, and the briquettes are preferably connected by welding in the circumferential direction ( (See FIG. 1). Further, it is also desirable that the plurality of strips provided in the longitudinal direction of the outermost peripheral surface of the outer layer portion of the briquette are made of only sponge titanium, and the briquettes are connected by welding in the longitudinal direction (see FIG. 2).

(2) A plurality of briquettes obtained by compression-molding a molten raw material into a cylindrical shape are connected to each other, and TiAl is formed by a vacuum arc melting method.
A method for producing a consumable electrode for an ingot of a base intermetallic compound, wherein, when the briquettes are connected, a portion consisting only of titanium sponge is welded.
This is a method for producing a consumable electrode for an ingot of an Al-based intermetallic compound.

In the above-described method for producing a consumable electrode, the outer edge provided over the entire circumference of the upper and lower ends of the outer layer portion of the briquette is formed only of titanium sponge, and the outer edge is welded in the circumferential direction. It is desirable to connect the briquettes by. It is also preferable that a plurality of strips provided in the longitudinal direction of the outermost peripheral surface of the outer layer portion of the briquette are made of only sponge titanium, and the briquettes are connected by welding the strips in the longitudinal direction.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Target TiAl-Based Intermetallic Compound The present invention is directed to a normal TiAl-based intermetallic compound, for example, a TiAl-based intermetallic compound having an aluminum content of 30% by weight or more. In addition, as a raw material for forming briquettes, in addition to titanium sponge and aluminum, various mother alloys (Al-Mo, Al-V, Al-Nb, Al-C
r, Fe-B, etc.) or a single substance can be added as an alloy component. Therefore, all currently used TiAl-based intermetallic compounds can be an object of the present invention.

There is no particular limitation on the particle size of the titanium sponge used as the melting raw material, and any particle size may be used as long as it is suitable for ensuring the strength of the briquette itself to be compression molded according to the capacity of the press equipment. There is no particular limitation on the aluminum used as the raw material for melting, and the shape may be granular or plate-shaped as long as the dimensions are appropriate for securing the strength of the briquette itself according to the capacity of the press equipment.

2. Structure of Consumable Electrode The consumable electrode targeted by the present invention is obtained by connecting a plurality of briquettes obtained by compression-molding a molten raw material by welding. As described above, a state in which titanium and aluminum coexist in the welded portion. Need to be avoided. For this reason, the welded portion to which the briquette is connected is made of only sponge titanium. In the consumable electrode of the present invention, it is not necessary to specify the details of the structure as long as the welded portion is composed of only titanium sponge. However, in order to secure sufficient strength, the embodiment shown in FIGS. It is desirable to adopt.

FIG. 1 is a view showing a configuration example of a consumable electrode for ingots of a TiAl-based intermetallic compound of the present invention. As shown in FIG. 1, the briquette 2 constituting the consumable electrode 1 is composed of an inner layer 2a and an outer layer 2b, and the inner layer 2a is composed of a mixture of titanium sponge, aluminum and other alloy additives. You. On the other hand, the outer layer portion 2b of the briquette is made of a mixture of sponge titanium and aluminum and, if necessary, other alloy additives.
An outer edge 2c is provided at the upper end and the lower end over the entire circumference, and the outer edge 2c is formed only of titanium sponge.

When the briquette 2 is connected, the outer edge portion 2c at the upper end and the lower end of the outer layer portion is welded in the circumferential direction as a welding portion. As described above, since the outer edge portion 2c made of only sponge titanium is used as the welded portion, the connection of the consumable electrode 1 can secure sufficient strength.

FIG. 2 is a view showing another configuration example of the consumable electrode for ingot of the TiAl-based intermetallic compound of the present invention. As in the case of FIG. 1, the bracket 2 constituting the consumable electrode 1
It is composed of an inner layer portion 2a and an outer layer portion 2b, and a plurality of strips 2d are provided on the outermost peripheral surface of the outer layer portion 2b in the longitudinal direction of the electrode (four places in the figure). The inner layer 2a of the briquette 2 is composed of a mixture of titanium sponge, aluminum and other alloy additives, and the outer layer 2b is composed of a mixture of titanium sponge and aluminum and, if necessary, other alloy additives. The band-shaped portion 2d provided on the outermost peripheral surface of the outer layer portion is formed only of titanium sponge.

The briquette 2 shown in FIG. 2 is connected by longitudinally welding a band 2d provided on the outermost peripheral surface of the outer layer. For this reason, since the welding part which connects a briquette will be comprised only from sponge titanium, sufficient intensity | strength can be ensured.

The inner layer and the outer layer of the briquette used in the present invention are composed of a mixture of sponge titanium and aluminum, and other alloy additives are filled in the inner layer in principle. Depending on the form and characteristics, the outer layer of the briquette may be filled.

Regarding the outer diameter of the target briquette,
The gap with the inner wall of the water-cooled copper mold of the arc melting furnace is set appropriately so that the consumable electrode is stably melted.
The filling height and the compression height of the briquette are set in consideration of the capacity of the press equipment so that the strength of the compression-molded briquette itself is sufficiently ensured.

The thickness ratio of the inner layer portion and the outer layer portion of the briquette,
Furthermore, the width of the outer edge portion provided over the entire circumference of the upper end and lower end of the outer layer portion and the width of the plurality of band-shaped portions provided in the longitudinal direction of the outermost peripheral surface thereof, the penetration depth during welding,
It is appropriately designed according to the bead width or the weight of the consumable electrode. In that case, as a more rational design, the strength of the welded part is not required as much as the lower part of the consumable electrode,
The briquette structure and welding method can be changed according to the electrode position.

3. FIG. 3 shows a method of filling a molten raw material using a separator in order to produce a briquette constituting the consumable electrode shown in FIG. 1 in steps (a) and (b). FIG.
FIG. 1 shows the structure of a separator assembled inside the press die inner wall indicated by a dashed line. The specific filling procedure of the melted raw material will be described in Examples below, but a separator that forms an inner layer portion of a previously prepared briquette is described.
3a and a separator 3c forming an outer edge are arranged in a mold to divide a portion to be filled with a melted raw material. After filling the melted raw materials, the separators 3a and 3c are removed.

FIG. 4 is a view for explaining a method of filling a molten raw material using a separator for producing the briquette constituting the consumable electrode shown in FIG. Similarly, a specific filling procedure of the melting raw material will be described in an example described later, but inside the press mold inner wall, a separator 3a forming an inner layer portion of the briquette and a separator 3d forming a strip portion are assembled. Thus, the briquette constituting the consumable electrode shown in FIG. 2 is manufactured.

As for the welding of the electrodes, as shown in FIG. 5 described above, a plurality of compression-molded briquettes were arranged on a predetermined holding table, and the entire holding table was charged into a vacuum chamber and replaced with argon gas. Later, it is usually welded by TIG welding. At the time of TIG welding of the electrode, either the circumferential direction or the longitudinal direction may be used as long as the strength of the welded portion can be ensured. Furthermore, spot welding may be added if the welded portion is made of only sponge titanium. Further, if necessary, a welding rod of pure titanium may be used, and the strength of the welded portion may be further improved by overlaying.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention and the effects thereof will be described in detail based on Embodiments 1 and 2.

Example 1 In Example 1, an ingot of a TiAl-based intermetallic compound having the components shown in Table 1 was produced.
Therefore, the electrode structure shown in FIG.
In addition, a consumable electrode in which ten briquettes having a height of 200 mm were connected was manufactured. Since the weight per briquette is 50 kg, the total weight of the consumable electrode is approximately 500 kg.

[0033]

[Table 1]

As shown in FIG. 1, the briquette 2 has a two-layer structure of an inner layer 2a and an outer layer 2b, and further has an outer edge 2c over the entire circumference of the upper and lower ends of the outer layer 2b. The outer diameter of the inner layer portion 2a is 200 mm, and titanium sponge, granular aluminum, and A1-Mo as a mother alloy are filled as a melting raw material. The outer edge 2c provided at the upper and lower ends of the outer layer portion 2b had an inner diameter of 270 mm and a width (height from the end face) of 50 mm. The outer layer portion 2b is filled with titanium sponge and granular aluminum as a raw material for melting, while the outer edge portion 2c is filled only with titanium sponge.

In the case of filling the molten material into the press die, a method of filling the molten material using the separator shown in FIGS. 3A and 3B is employed. First, as shown in FIG. 3A, a separator 270 having a diameter of 270 mm and a separator 3a having a diameter of 200 mm are concentrically placed on the bottom surface of a press die. Next, only sponge titanium between the separator 3c and the inner wall of the press mold, a mixture of sponge titanium and granular aluminum between the separator 3a and the separator 3c, sponge titanium, granular aluminum and Al- The mixture of Mo is filled by a predetermined weight calculated in advance. Thereafter, the separator 3c is removed, and a mixture of titanium sponge and granular aluminum is filled between the separator 3a and the inner wall of the press die by a predetermined weight calculated in advance.

Next, as shown in FIG. 3 (b), the separator 3c is filled with a mixture of sponge titanium and granular aluminum, and is installed again. Then, only sponge titanium is placed between the separator 3c and the inner wall of the press mold,
A mixture of titanium sponge and granular aluminum is filled between 3a and separator 3c by a predetermined weight calculated in advance. After filling the melted raw materials, separator 3a and separator 3c
And take out.

The melted raw material filled in the press mold is compression-molded under a press condition of a maximum load of 1500 tons, and processed into a cylindrical briquette. Next, the outer edges of the upper and lower ends of the ten briquettes were TIG-welded in the circumferential direction, and the welded portions were connected with sufficient strength to produce predetermined consumable electrodes.

Using the consumable electrode thus produced, a dissolution current of 5 k
Under the melting conditions of A, 10 ^-2 to 10 ^-3 Torr within 450 mm inside diameter of mold
Arc melting in a vacuum of 440mm in outer diameter and 800mm in height
Thus, a consumable electrode for ingots of a TiAl-based intermetallic compound weighing 475 kg was manufactured. In this vacuum arc melting process, it was confirmed that the consumable electrode was not dropped or deformed during melting, and that the melting state was good.

Example 2 Also in Example 2, a consumable electrode was manufactured to manufacture an ingot of a TiAl-based intermetallic compound having the composition shown in Table 1 above. Since the size and weight of the briquette used for this were the same as in Example 1, the total weight of the consumable electrode was approximately 500 kg.

Since the consumable electrode having the structure shown in FIG. 2 is manufactured, the briquette 2 has a two-layer structure of the inner layer portion 2a and the outer layer portion 2b, and a plurality of strips provided in the longitudinal direction of the outermost peripheral surface of the outer layer portion 2b A section 2d is provided. The outer diameter of the inner layer part 2a is 200 mm, and is filled with titanium sponge, granular aluminum, iron powder, Fe-B and A1-V as melting raw materials. Further, the band-shaped portions 2d provided on the outermost peripheral surface of the outer layer portion 2b are four places at equal intervals in the circumferential direction, and the inner diameter of the bottom surface is 270 mm,
The width was 100 mm. The outer layer portion 2b is filled with titanium sponge and granular aluminum as a dissolving raw material, while the strip portion 2d is filled only with titanium sponge.

In the case of filling the molten material into the press die, the method for filling the molten material described with reference to FIG. 4 is employed.
First, a separator 3d having a diameter of 270 mm and a separator 3a having a diameter of 200 mm are installed concentrically on the bottom surface of a press die.
Next, the width between the separator 3d and the inner wall of the press mold is 10
Fill the four strips of 0mm only with titanium sponge,
The mixture of titanium sponge and granular aluminum is filled into four portions having a width of 135 mm at other portions. The space between the separator 3d and the separator 3a is filled with a mixture of titanium sponge and granular aluminum. Further, the interior of the separator 3a is filled with titanium sponge, granular aluminum, iron powder, Fe-B and A1-V to form an inner layer. After filling the melted raw material, the separator 3a and the separator 3d are extracted.

As in the case of Example 1, the melted raw material filled in the press die is compression-molded under a press condition of a maximum load of 1500 tons to process a cylindrical briquette. To connect ten briquettes, the strips of each briquette were TIG-welded in the longitudinal direction, and the welded portions were connected with sufficient strength to produce a predetermined consumable electrode.

Using the produced consumable electrode, a dissolution current of 5 k
Under the melting conditions of A, 10 ^-2 to 10 ^-3 Torr within 450 mm inside diameter of mold
Arc melting in a vacuum of 440 mm in outer diameter and 800 in height
A consumable electrode for ingot of a TiAl-based intermetallic compound having a weight of 475 kg was manufactured. At this time, it was confirmed that there was no falling or deformation of the consumable electrode during melting, and a favorable arc melting state.

[0044]

According to the consumable electrode for an ingot of a TiAl-based intermetallic compound and the method of manufacturing the same according to the present invention, a welded portion serving as a connecting portion of the electrode has sufficient strength to hold the weight of the consumable electrode. As a result, falling off or deformation during melting due to insufficient strength of the welded portion can be prevented. Therefore,
It is now possible to dissolve large-weight consumable electrodes that were previously impossible to dissolve, and it is possible to increase the size of ingots of TiAl-based intermetallic compounds, thereby improving productivity and manufacturing at low cost be able to. Thus, widespread use of TiAl-based intermetallic compounds in products can be expected.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration example of a consumable electrode for an ingot of a TiAl-based intermetallic compound of the present invention.

FIG. 2 is a view showing another configuration example of the consumable electrode for ingot of a TiAl-based intermetallic compound of the present invention.

FIG. 3 is a view for explaining a method of filling a molten raw material using a separator for producing a briquette constituting the consumable electrode shown in FIG.

FIG. 4 is a diagram illustrating a method of filling a molten raw material using a separator for producing a briquette constituting the consumable electrode shown in FIG.

FIG. 5 is a diagram schematically illustrating a manufacturing process of a consumable electrode used for vacuum arc melting.

[Explanation of symbols]

 1: Consumable electrode, 2: Briquette 2a: Inner layer, 2b: Outer layer, 2c: Outer edge, 2d: Strip 3, 3a, 3c, 3d: Separator 4: Arc melting furnace, 5: Electrode welding machine

Claims (6)

[Claims] A consumable electrode for an ingot of a TiAl-based intermetallic compound used for vacuum arc melting by connecting a plurality of briquettes obtained by compression-molding a molten raw material into a cylindrical shape, wherein a welding portion connecting the briquettes is a sponge. A consumable electrode for an ingot of a TiAl-based intermetallic compound, characterized by being constituted only by titanium. 2. The briquette inner layer comprises a mixture of titanium sponge, aluminum and other alloy additives, while the briquette outer layer comprises sponge titanium and aluminum and optionally other alloy additives. It is composed of a mixture, but the outer edge provided over the entire circumference of the upper and lower ends of the outer layer portion is formed only of titanium sponge, and the briquettes are connected by welding the outer edge in the circumferential direction. The consumable electrode for an ingot of a TiAl-based intermetallic compound according to claim 1, wherein 3. The briquette inner layer comprises a mixture of titanium sponge, aluminum and other alloy additives, while the briquette outer layer comprises sponge titanium and aluminum and, if necessary, other alloy additives. Although composed of a mixture, a plurality of strips provided in the longitudinal direction of the outermost peripheral surface of the outer layer portion are formed only of titanium sponge, and connection of these briquettes is performed by welding the strips in the longitudinal direction. The consumable electrode for an ingot of a TiAl-based intermetallic compound according to claim 1, characterized in that: 4. A method for producing a consumable electrode for an ingot of a TiAl-based intermetallic compound by connecting a plurality of briquettes obtained by compression-molding a molten raw material into a cylindrical shape by a vacuum arc melting method.
A method for producing a consumable electrode for ingots of a TiAl-based intermetallic compound, comprising welding a portion composed of only titanium sponge when connecting the briquettes. 5. The briquette inner layer comprises a mixture of titanium sponge, aluminum and other alloy additives, while the briquette outer layer comprises titanium sponge and aluminum and, if necessary, other alloy additives. The outer edge portion provided over the entire circumference of the upper and lower ends of the outer layer portion is made of only a sponge titanium, and the briquettes are connected by welding the outer edge portion in the circumferential direction. The method for producing a consumable electrode for an ingot of a TiAl-based intermetallic compound according to claim 4. 6. The briquette inner layer is composed of a mixture of titanium sponge, aluminum and other alloy additives, while the briquette outer layer is formed of titanium sponge and aluminum and, if necessary, other alloy additives. Along with being composed of a mixture, a plurality of strips provided in the longitudinal direction of the outermost peripheral surface of the outer layer portion are formed only of sponge titanium, and the briquettes are connected by welding the strips in the longitudinal direction. The method for producing a consumable electrode for an ingot of a TiAl-based intermetallic compound according to claim 4.