WO2007052433A1

WO2007052433A1 - Apparatus for melting metal and method for manufacturing metal

Info

Publication number: WO2007052433A1
Application number: PCT/JP2006/319490
Authority: WO
Inventors: Norio Yamamoto; Masayasu Ito; Takeshi Shiraki
Original assignee: Toho Titanium Co., Ltd.
Priority date: 2005-11-02
Filing date: 2006-09-29
Publication date: 2007-05-10
Also published as: JP5074197B2; US20090223646A1; JPWO2007052433A1

Abstract

Provided is a method for melting metal materials, by which melting failure and surface defects formed on an initial melting portion at the time of starting to melt a metal ingot are suppressed. An apparatus for melting metal is provided with a hearth for melting a material metal and a mold for manufacturing the metal ingot by applying the molten metal to the mold. The apparatus is characterized in that a base for pulling out the ingot is provided at a bottom section of the mold, a recessed section is provided at a discretionary part on the base surface, and the base surface portion surrounding the recessed section is inclined toward the recessed section.

Description

Specification

Apparatus and method for melting metal

Technical field

The present invention relates to an apparatus for melting a metal material and a method for producing a metal using the apparatus, and in particular, when producing an ingot of a metal material in an electron beam melting furnace or a plasma arc melting furnace, The present invention relates to a technology for suppressing melting defects and surface defects in a formed ingot site.

Background art

A metal material is irradiated with an electron beam under a vacuum atmosphere using a melting furnace in which a water-cooled copper crucible is disposed in a melting furnace and a water-cooled base movable downward is disposed at the bottom of the crucible. There is known a technique for producing an ingot of the metal material by continuously or intermittently pulling down the water-cooling base while pouring or dripping the metal material into the water-cooling base.

At the start of melting, a molten metal (hereinafter sometimes referred to as “molten metal”) is in direct contact with the water-cooled base, and the contact portion force solidification starts. As the supply of molten metal advances, the molten metal deposits and solidifies on almost the entire surface of the water cooling base. Next, the metal material deposited on the water-cooled base is irradiated with an electron beam to melt the entire surface, and the force water-cooled base is pulled downward. As the melt surface descends as the water-cooled base is pulled downward, the electron beam melted melt is further supplied. In this manner, the molten metal is continuously supplied while the water-cooled base is pulled downward, and metal ingots are continuously produced.

The surface of the water-cooled base is flat, and when the poured molten metal falls onto the water-cooled base, it solidifies in a short time on the spot. Furthermore, when the next molten metal falls on the solidified metal, the molten metal flows in any direction and solidifies in a short time. In the early stage of melting, such dropping and solidification of the molten metal to the water-cooled base occur repeatedly. For this reason, defective melting portions and surface defects are formed in the ingot portion generated at the initial stage of melting (hereinafter sometimes referred to as "initial molten metal portion"), particularly in the ingot portion at the contact surface with the water-cooled base. Since these defects may be an obstacle in the processing steps performed in the post process, they may be cut in advance. Or removed by cutting. While this has reduced the yield of ingots, improvements have been sought.

[0005] In order to suppress such defects, a technique is known in which the initial molten metal portion is maintained in a molten state at all times by irradiating the electron beam immediately after the molten metal falls onto the water-cooling base. In this case, when the molten metal falls onto the water-cooled base and the molten metal is irradiated with the electron beam to form and maintain the molten metal, solidification of the molten metal proceeds while setting the irradiation position. there were.

[0006] To address this problem, a technique has been devised to suppress solidification of the initial molten metal portion by irradiating an electron beam to a wide surface including the molten metal dropping portion on the water-cooled base. Although partial solidification of the initial molten metal part can be temporarily suppressed, it may be covered with the molten metal, and the electron beam may be directly irradiated to the water-cooled base surface to melt away the water-cooled base surface. Was required.

As a method of solving the above problems, a metal block material of the same grade as the metal to be melted is disposed in advance on a water-cooled base, and the upper surface of the material is irradiated with an electron beam to form a sufficient molten metal surface. After that, a technique for starting dissolution is disclosed (see, for example, Patent Document 1). According to this method, it is possible to solve the problem that the molten metal solidifies by the time the electron beam is irradiated to the dropping part of the molten metal and the problem that the water cooling base is damaged by irradiating the electron beam to the range including the dropping part. Only the method of starting the supply of the molten metal to the crucible after forming the molten metal surface on the top of the metal block placed in the water-cooled base is disclosed, but there is no description on the method of forming the initial molten metal part. . Therefore, since it is necessary to dispose the metal block on the water-cooled base to remove a considerable portion of the metal block, there is a problem that the yield is lowered and the cost required for the removal occurs.

Further, a water-cooled base having a bowl-shaped portion capable of engaging with the ingot is provided at the bowl-shaped bottom portion, and the molten metal is dropped to the water-cooled base to engage the wedge-shaped portion with the initial molten metal portion of the ingot. A technique is disclosed for continuously producing an ingot by pulling the water-cooled base downward after joining and solidifying the ingot (see, for example, Patent Document 2).

Patent Document 1: Japanese Patent Application Laid-Open No. 2000-274957

Patent Document 2: Japanese Patent Application Laid-Open No. 2000-153345 Disclosure of the invention

Problem that invention tries to solve

[0010] At the same time, in the disclosure of Patent Document 2 described above, there is no description regarding the method of forming the initial molten metal portion or the method of avoiding the occurrence of defects in the initial molten metal portion. Thus, no effective measures have been taken yet for the above-mentioned problems concerning the formation of the initial molten metal part in the production of metal ingots.

The present invention has been made in view of the above situation, and aims to solve the problems remaining in the prior art as described above and to produce an ingot with a high yield. That is, the present invention provides a method of melting a metal material in which the melting defects and surface defects of the initial molten metal portion generated at the start of melting are suppressed.

Means to solve the problem

[0012] As a result of intensive studies to solve the problems remaining in the above-mentioned prior art, the present inventor uses a melting furnace in which a formed ingot bow I is placed at the bottom of a water-cooled copper crucible. And by providing a slope on the surface of the base surrounding the recess provided on the surface of the water-cooled base, it has been found that the molten metal dropped or dropped in the mold can be concentrated in the recess provided on the water-cooled base. It came to

That is, the present invention is a metal melting apparatus including a hearth for melting a raw material metal and a crucible for pouring the molten metal to produce a metal ingot, and the bottom of the crucible is provided with: A base for pulling out the ingot is provided, and a recess is provided in any part of the surface of the base, and the base surface surrounding the recess among the base surface is characterized by being inclined toward the recess.

The present invention is further characterized in that a recess is further provided at the bottom of the recess provided on the surface of the base. Furthermore, the drawing base is configured to be divisible so that the ingot formed on the drawing base for drawing the ingot can be drawn from the base. .

Effect of the invention

[0015] According to the metal melting apparatus of the present invention having the above configuration, the base surface of the bowl-shaped bottom portion Since the other part of the surface of the base is inclined toward the recess provided in the case, when the molten metal poured from the hearth first reaches the base, it is led to the inclination and is first caused to flow into the recess, and so on. Since the molten metal supplied is sequentially filled from the concave portion and is solidified by cooling, it is possible to effectively suppress the generation of surface defects and defective melting portions in the initial molten metal portion of the metal ingot to be formed. is there.

Furthermore, the molten metal can be reduced to the bottom of the recess provided on the surface of the base, and the generation of the surface defects and the defective melting can be further reduced. .

Furthermore, since the ingot drawing base is configured to be dividable, the ingot produced on the base can be easily extracted after melting is completed. is there.

According to the conventional method, the defective portion of the initial molten metal portion is cut and removed by the conventional method! However, according to the present invention, as described above, the surface defect and melting failure of the initial molten metal portion Since almost no part is generated, the yield of the ingot can be enhanced as compared with the conventional method. Brief description of the drawings

FIG. 1 is a schematic cross-sectional view of an electron beam melting apparatus according to the present invention.

FIG. 2 is a schematic cross-sectional view showing a modified example of the water-cooling base of the present invention.

FIG. 3 is a schematic cross-sectional view showing another modification of the water-cooled base of the present invention.

FIG. 4 is a schematic cross-sectional view showing another modification of the water-cooled base of the present invention.

FIG. 5 is a schematic cross-sectional view showing another modification of the water-cooled base of the present invention.

FIG. 6 is a schematic cross-sectional view showing a conventional water-cooled base.

Explanation of sign

[0020] 1 Raw material supply means

2 sponge titanium

3 Nose

4 Molten metal

5 square

6 Electron beam irradiation means 7a to 7e water-cooled base (example of the present invention)

7f water cooling base (conventional example)

71 Base slope

72 Base recess

73 Reverse Taper

74 Base bottom

75 Sloped bottom

76 Horizontal bottom

77 Sloped bottom

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a preferred embodiment in melting a metal titanium ingot using a hearth electron beam melting furnace using sponge titanium as a melting material. The code | symbol 1 is a raw material supply means for supplying the sponge titanium 2 which is a raw material. At the downstream side of the raw material supply means 1, a hose 3 made of water-cooled copper is provided, and the hearth 3 holds a molten metal 4 which also has a molten titanium power. A bowl 5 is provided downstream of the hearth 3, and since the hearth 3 is arranged in an inclined manner, the molten metal 4 can flow from the hearth 3 into the bowl 5 It has become. Electron beam irradiation means 6 is provided above the hearth 3 and the crucible 5, and the molten metal 4 can be brought into a molten state by irradiating with a force electron beam.

A water-cooling base 7 a is provided at the bottom of the bowl 5. As shown in FIG. 1, the water-cooled base 7a is formed with a base recess 72 at the center, and a base slope 71 is formed around the base recess 72 so as to be inclined toward the base recess 72. Furthermore, the base recess 72 is composed of a reverse taper portion 73 and a base bottom portion 74 forming the side wall of the base recess 72. As shown in the figure, the reverse taper portion 73 is inclined from the vertical direction, and is configured such that the angle formed by the reverse taper portion 73 and the base bottom portion 74 is an acute angle! .

Next, the operation of this hearth electron beam melting furnace will be described. At the bottom of Hearth 3 before titanium dissolution starts, a solid layer of titanium called a skull (not shown) is placed. First, the molten metal 4 is formed by irradiating an electron beam here. Subsequently, sponge titanium 2 is supplied to the substrate 3 by the raw material supply means 1, and the sponge titanium 2 is melted by irradiation of the electron beam and integrated with the molten metal 4. Next, the molten metal 4 flows in the hearth 3 and is refined, and then flows into the crucible 5.

The molten metal 4 flowing into the crucible 5 reaches the water cooling base 7 a disposed at the bottom of the crucible 5. Among the molten metal 4 that reached the water-cooled base 7a, the molten metal 4 that reached the base recess 72 was cooled by the base bottom 74 and solidified after a while, and that that reached the base inclined portion 71 was the base inclined portion 71. The inclination quickly causes the base recess 72 to flow and solidify as well. In this way, the molten metal reaching any point on the base can be introduced into the base recess 72 and solidified. Further, the molten metal 4 is supplied to fill the molten metal to such an extent that it covers the inclined base portion 71 and is solidified to form an initial molten metal portion of the titanium ingot. Immediately after the molten metal is first supplied to the base recess 72, the molten metal tends to solidify in a short time because the water-cooled base is not sufficiently heated by the heat of the molten metal and is in a low temperature state. It is in. Therefore, it is preferable to increase the irradiation output of the electron beam.

After the initial molten metal portion covering the base concave portion 72 and the base inclined portion 71 is formed, the water cooling base 7a is pulled downward to enlarge the space above the wedge 5, and further supply of the molten metal 4 to this space. To continue. In this manner, the molten metal is gradually cooled and solidified from the lower part to the upper part of the mold by continuously drawing the molten metal 4 into the mold 5 while pulling the water-cooling base 7a downward. Titanium ingot can be manufactured. At this time, since the reverse tapered portion 73 in the base concave portion 72 is engaged with the initial molten metal portion of the titanium ingot, the titanium ingot is pulled downward so that the initial molten metal portion and the water cooling base 72 do not separate. It is

Next, other preferable modifications of the components of the present invention will be described.

It is preferable that the base slope portion of the water-cooling base of the present invention be configured to be inclined from the periphery to the center.

When the molten metal is titanium, the inclination angle of the base inclination portion is preferably in the range of 2 to 10 ° with respect to the horizontal surface. By forming the base inclined portion at an angle in this range, the supplied molten metal can be uniformly distributed to the central portion of the water cooling base. Can. If the inclination angle is less than 2 °, it will be difficult to rapidly distribute to any part of the water cooling base due to the viscosity of molten titanium, and if the inclination angle exceeds 10 °, it will occupy in the ingot to be melted. Since the ratio of the initial molten metal part is increased, the processing yield may be reduced. The lower limit 2 ° of the inclination angle range is the case where the metal to be melted is titanium, and the lower limit differs depending on the viscosity when other metals are melted.

As another embodiment of the present invention, sponge titanium is disposed on a water-cooled base in advance, and it is irradiated with an electron beam to be melted therein and poured into a hearth recess to form an initial molten metal part. You may. According to such an aspect, since the sponge titanium covers the water-cooled hearth, it is possible to suppress the damage of the water-cooled hose due to the irradiation of the electron beam when forming the initial molten metal part.

[0029] FIG. 2 shows another embodiment according to the present invention. That is, it is a modified example of the water cooling base 7a in FIG. In the water-cooled base 7b, the bottom of the base recess 72 is not horizontal, and the center is provided with a sloped portion 75 which is inclined toward the center. According to the water cooling base 7b having such a configuration, it is possible to suppress solidification at a random point of the molten metal flowing first and guide the molten metal to the center in the base recess and to solidify sequentially. become.

[0030] FIG. 3 shows still another preferred! /-Aspect of the water-cooled base 7a! /. The water cooling base 7 c further comprises an inclined portion 75 and a horizontal portion 76. With such a recess configuration, the bottom of the initial molten metal portion of the formed ingot can form a gentle convex portion, and is easier to handle than the initial molten metal portion manufactured by the water-cooled base 7b shown in FIG. It becomes.

[0031] FIG. 4 shows a further preferable aspect of the water-cooled base 7a! /, Representing the aspect! /, The water-cooled base 7d is a force in which the bottom 77 of the base recess 72 is flat. It has the same structure. According to the water-cooled base 7d having such a configuration, the molten metal flowing into the base can be introduced along the inclination direction of the bottom portion of the base concave portion 72 and the molten metal flowing into the hearth. As a result, solidification of the molten metal proceeds sequentially from the lowermost end of the bottom portion 77, and as a result, it is possible to produce a healthy ingot in which the formation of macro defects in the solidified portion of the molten metal disappears.

The water-cooling base according to the present invention shown in FIG. 5 is rectangular, and shows a plan view as viewed from above. That is, the ingot melted in the embodiment of the present invention has a rectangular cross section. This implementation In the embodiment, the base concave portion 72 is characterized by being formed in a trapezoidal shape. Further, a straight line L-L 'represents the wedge-shaped parting line. It is characterized in that the water-cooled base 7e can be divided into two parts (7e-a, 7e-b) with the dividing line as a boundary. In particular, it is preferable that the lower base of the trapezoid be positioned on the dividing line side. At this time, there is no particular limitation as long as each side connecting the upper and lower bases of the trapezoid is open at the top, but it is practical to set the angle of each side to the horizontal line in the range of 30 to 60 °. Above preferred.

With this arrangement, after a predetermined amount of ingot is melted, the water-cooled base 7e-a is separated from 7e-b, and then the ingot placed on the upper surface of the water-cooled base 7e is removed. By sliding in a direction orthogonal to the straight line LL ′, the ingot formed with the fitting portion in the recess can be separated from the water cooling base 7e.

It is preferable that the division structure of the water cooling base described above is applied to the water cooling bases 7 a to 7 d described above. By adopting such a divided structure, it is possible to easily extract the ingot melted and produced by the water cooling base.

The horizontal cross sections of the water-cooled bases 7a to 7e can be applied not only to the rectangular shape described above, but also to the case of melting a circular ingot.

By disposing the water-cooled bases 7a to 7e as described above in the crucible 5 prior to melting, the molten metal having the hearth force introduced therein is suitably led to the concave portion to carry out the initial molten metal portion and the water-cooled portion. While the engagement of the base can be made strong, the ingot melted after the end of melting can be pulled out reliably by the water-cooling base force.

Example

Hereinafter, the power of the present invention will be described in more detail by way of examples. These are merely examples of the embodiments of the present invention and do not limit the present invention.

[Example 1]

The water-cooled base 7c shown in FIG. 3 was attached to the wedge 5 of the electron beam melting apparatus shown in FIG. Subsequently, the hearth 3 was irradiated with an electron beam and at the same time, the sponge titanium 2 was supplied to the nose 3 to form a molten metal 4 which was supplied to the crucible 5 to melt the titanium ingot. After the molten ingot was cooled, the water cooling base 7c was cut to obtain a titanium ingot. Cut ingot The structure at the bottom was sound and of quality that could be subjected to hot forging as it is. The yield of the recovered titanium ingot is 98% of the theoretical yield from the input material.

[Example 2]

Ingot was melted under the same conditions except using 7d instead of the water-cooled base 7c used in Example 1. As a result, the yield of the recovered titanium ingot was 98% of the theoretical yield from the input material.

[Comparative Example]

Using the conventional water-cooled base 7f shown in FIG. 6, titanium ingot was melted under the same conditions as in Example 1. The melted titanium ingot was cut off by water cooling base force. When the cut surface of the separated titanium ingot was examined, a portion with insufficient melting was found, and the portion was cut and removed. As a result, the yield of net titanium ingot remained at 95%.

Industrial applicability

The method of electron beam melting of a metal material according to the present invention makes it possible to suppress melting defects and surface defects in the initial molten metal portion of the ingot, so that the yield of manufacturing metal ingots is significantly improved. it can.

Claims

The scope of the claims

[I] A metal melting apparatus comprising: a hearth for melting a raw material metal; and a mold for pouring the melted metal to produce a metal ingot;

At the bottom of the bowl, a base for drawing an ingot is provided.

A recess is provided in any part of the base surface,

The base surface of the base surface surrounding the recess is inclined toward the recess.

V, a metal melting apparatus characterized in that.

[2] The metal melting apparatus according to claim 1, wherein the inclination angle of the base surface inclined toward the recess is in the range of 2 to 10 °.

[3] The concave portion comprises a bottom and a side wall, and the side wall is inclined from the vertical direction, and an angle formed between the bottom and the side wall is an acute angle. Dissolution device for metals as described in.

[4] The metal melting apparatus according to any one of claims 1 to 3, wherein a recess is further provided at the bottom of the recess.

[5] The metal melting apparatus according to claim 4, wherein a bottom surface of the recess provided at the bottom of the recess is inclined in an arbitrary direction with respect to a horizontal surface.

[6] The drawing base is configured to be dividable so that the ingot formed on the ingot drawing base can be drawn out from the base. Metal container device according to any of the.

[7] The apparatus for melting a metal according to any one of claims 1 to 6, wherein the base is made of water-cooled copper.

[8] The apparatus for melting a metal according to any one of claims 1 to 7, wherein the apparatus for melting a metal is an electron beam melting furnace or a plasma arc melting furnace.

[9] The above-mentioned metal is titanium, zirconium or tantalum, characterized in that

The metal melting apparatus as described in any one of 8.

[10] A method for producing a metal comprising using the apparatus for dissolving a metal according to any one of claims 1 to 9.

[II] The metal is titanium, zirconium or tantalum. The manufacturing method of the metal as described in.