JP2003136222A - METHOD FOR MANUFACTURING Ni-BASE SUPERALLOY INGOT COMPOSED OF LITTLE COMPONENT SEGREGATION AND UNIFORMLY FINE CRYSTAL GRAIN - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an Ni-base superalloy ingot composed of little component segregation and uniformly fine crystal grains, which is used as a blank for manufacturing forged parts used for gas turbine such as a jet engine for aircraft, e.g. a turbine disk, a turbine shaft, etc. SOLUTION: In this manufacturing method, a shallow pool 5 of the molten Ni-base superalloy ingot is formed by remelting a VIM ingot obtained by high frequency induction vacuum melting or an ESR ingot 2 obtained by electro-slag remelting after the high frequency induction vacuum melting using an electron beam 3. Then, after adding metal powder 4 while holding a molten metal state having a prescribed temperature by irradiating the shallow pool 5 of the molten Ni-based superalloy with an electron beam 31, the Ni-base superalloy ingot composed of little component segregation and uniformly fine crystal grains is immediately manufactured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to forged parts used for gas turbines such as aircraft jet engines, for example,
The present invention relates to a method for producing a Ni-base superalloy ingot, which is a raw material for producing turbine disks, turbine shafts, and the like, and which has small segregation of components and is composed of uniformly fine crystal grains.

[0002]

2. Description of the Related Art In general, the destruction of forged parts such as turbine disks and turbine shafts in aircraft jet engines leads to fatal engine failure and loss of many lives. Has been paid. As an alloy for producing forged parts such as turbine disks and turbine shafts, a Ni-base superalloy (super alloy) excellent in high temperature strength and high temperature corrosion resistance is currently used. Udimet 720LI is a typical Ni-based superalloy.
(Trade name, mass% Cr: 16.0%, Co: 14.7)
%, Mo: 3.0%, W: 1.3%, Al: 2.5%,
Ti: 5.0%, C: 0.03%, B: 0.03%, Z
r: 0.03%, Ni: component composition consisting of the balance) is known. Then, in order to manufacture these forged parts such as turbine disks and turbine shafts, an ingot obtained by high-frequency vacuum melting of a Ni-base superalloy (hereinafter, an ingot obtained by high-frequency vacuum melting is referred to as "VIM ingot").
Or a Ni-based superalloy by high-frequency vacuum melting and vacuum casting, and an ingot obtained by further remelting electroslag (hereinafter, the ingot obtained by remelting electroslag is referred to as "ESR ingot").
Is further vacuum arc remelted to form an ingot with less impurities and inclusions, and this ingot is slab-forged and then forged repeatedly to form a billet with a small component segregation and a uniform fine structure. The billet is die-forged into a predetermined shape and finally heat-treated such as aging.

[0003]

The Ni-base superalloy ingot obtained by remelting the VIM ingot or ESR ingot by vacuum arc inevitably has a coarse crystal structure, and further, the central part of the ingot cannot be avoided. The difference in the component composition between the outer periphery and the outer periphery causes a relatively large component segregation, and in particular, the component segregation becomes large in an ingot of a Ni-base superalloy containing a large amount of Al and Ti and having a high volume ratio of the γ'phase. In order to manufacture a billet, which is a material for a forged part in a jet engine, from the Ni-based superalloy ingot obtained by the conventional vacuum arc remelting, it is necessary to increase the number of times of forging, which requires time and cost. . Therefore, a Ni-base superalloy ingot having a small component segregation and uniform fine crystal grains is produced, and a billet is manufactured using the Ni-based superalloy ingot having a small component segregation and uniform fine crystal grains. Has attempted to reduce the number of forgings for billet manufacturing.

[0004]

Therefore, the present inventors also
Studies were conducted to produce a Ni-base superalloy ingot having a small compositional segregation and uniform crystal grains. As a result, the VIM ingot or ESR ingot is electron beam remelted in place of the conventional vacuum arc remelting to form a shallow pool of Ni-base superalloy melt, and metal powder is added to this shallow melt pool and then immediately solidified. The resulting Ni-based superalloy ingot can be cleaned to the same degree as the Ni-based superalloy ingot obtained by the conventional method of vacuum-melt remelting the VIM ingot or ESR ingot. Compared to a Ni-based superalloy ingot obtained by a conventional method of remelting an ingot or an ESR ingot by a vacuum arc, the segregation between the central portion and the peripheral portion of the ingot is small and Ni consisting of remarkably uniform crystal grains is formed. The result of the study was that a base superalloy ingot could be obtained.

The present invention has been made on the basis of the results of such research. (1) VIM ingot or E
The SR ingot is re-melted with an electron beam to form a shallow pool of the Ni-base superalloy melt, and the metal powder is added to the shallow pool of the Ni-base superalloy melt immediately after solidification. The method has a feature in a method for producing a Ni-based superalloy ingot composed of crystal grains.

The shallow pool of the Ni-base superalloy melt obtained by electron beam remelting is likely to be cooled and solidified in a short time, and may be solidified before the metal powder is added. Therefore, a shallow pool of a Ni-based superalloy melt obtained by electron beam melting is subjected to electron beam irradiation, metal powder is added while the entire pool is kept in a molten state at a desired temperature, and then electron beam irradiation is stopped. Therefore, it is preferable to solidify immediately.

Therefore, according to the present invention, (2) a VIM ingot or an ESR ingot is remelted with an electron beam to form a shallow pool of a Ni-base superalloy melt, and the shallow pool of the Ni-base superalloy melt is irradiated with an electron beam. Then, the metal powder is added immediately after the metal powder is added while maintaining the molten metal state.
Method for producing i-based superalloy ingot, (3) VIM ingot or ESR ingot is remelted with an electron beam to form a shallow pool of Ni-based superalloy molten metal, and an electron beam is applied to the shallow pool of the Ni-based superalloy molten metal. The present invention is characterized by a method for producing a Ni-base superalloy ingot which has a small component segregation and is composed of uniformly fine crystal grains which are solidified immediately after metal powder is added while irradiating and maintaining the entire pool in a molten state.

If the surface area of the shallow pool of the molten Ni-base superalloy obtained by electron beam remelting is large, it may not be possible to irradiate the entire surface of the pool with the electron beam at one time. In such a case, a part of the shallow pool of the Ni-based superalloy melt obtained by electron beam melting is irradiated with an electron beam to maintain a part of the shallow pool in a molten state at a desired temperature, Move the electron beam irradiation position and the metal powder addition position while adding the metal powder to the part in the state, thereby adding the metal powder to the entire surface of the pool, then stopping the electron beam irradiation and immediately solidifying. Preferably. To move the electron beam irradiation position and the metal powder addition position over the entire surface of the pool, rotate the electron beam gun for electron beam irradiation and the hopper that stores the metal powder horizontally or in parallel. The pool formed at the upper end of the ingot may be rotated by rotating the ingot obtained by solidification, and the electron beam gun and the hopper storing the metal powder may be horizontally rotated or moved. The pool formed at the upper end of the ingot may be moved in parallel while rotating, and in any case, the electron beam gun and the hopper storing the metal powder may be moved relative to the pool formed at the upper end of the ingot. You can move it to.

Therefore, according to the present invention, (4) a VIM ingot or an ESR ingot is remelted with an electron beam to form a shallow pool of a Ni-base superalloy melt, and the shallow pool of the Ni-base superalloy melt is partially formed on a surface thereof. A part of the molten metal is maintained by irradiating it with an electron beam
A method for producing a Ni-base superalloy ingot consisting of fine crystal grains with small component segregation that is applied to the entire pool surface by moving the operation of immediately solidifying after adding metal powder to the i-base superalloy melt Is.

The metal powder added to the Ni-base superalloy melt is preferably a Ni-base superalloy powder having the same composition as the composition of the VIM ingot or ESR ingot, but it is added to the Ni-base superalloy melt. The metal powder is not limited to the Ni-based superalloy powder having the same composition as that of the VIM ingot or the ESR ingot.
The metal powder added to the base superalloy melt may be a Ni base superalloy powder having a component composition deviating from the component composition of the VIM ingot or ESR ingot. Further, it may be a mixed powder obtained by mixing element powders of the elements forming the VIM ingot or ESR ingot. The addition amount of these metal powders is 10% by volume or less with respect to the volume of the final ingot, and it is necessary to add them so as not to deviate from the desired component composition of the Ni-based superalloy. The grain size of the metal powder added to the Ni-based superalloy melt differs depending on the target crystal grain size of the Ni-based superalloy ingot and is not particularly limited, but the grain size is 16 to 65 μm. preferable.

Therefore, according to the present invention, (5) the metal powder to be added to the molten Ni-base superalloy is a Ni-base superalloy powder, the component described in (1), (2), (3) or (4) above. A method for producing a Ni-base superalloy ingot having small segregation and uniform fine crystal grains, (6) The metal powder added to the Ni-base superalloy melt has the same composition as the Ni-base superalloy melt. The powder (1), (2),
(3) or (4), which is characterized by the method for producing a Ni-based superalloy ingot which has a small component segregation and is composed of uniformly fine crystal grains.

The preferable temperature of the pool of the Ni-base superalloy melt to which the metal powder is added is preferably controlled within the range of the surface temperature exceeding the solidus temperature to the liquidus temperature + 30 ° C. The reason is unfavorable because the melt solidifies below the solidus temperature and the effect of forming fine crystal grains due to addition of the metal powder disappears, while the liquidus temperature + 30 ° C.
This is because it is not preferable to add the metal powder at a temperature exceeding the above range, because the metal powder serving as the nucleus of crystal generation melts and disappears, or the crystal grains grow large. Therefore, according to the present invention, (7) the surface temperature of the pool of the Ni-based superalloy molten metal to which the metal powder is added exceeds the solidus temperature.
A Ni-based superalloy ingot, which has a small component segregation and is composed of uniformly fine crystal grains according to (1), (2), (3) or (4), which is controlled within a range of liquidus temperature + 30 ° C. It is characterized by a manufacturing method.

The Ni-base superalloy used in the present invention may be a Ni-base superalloy of any composition, but the Ni-base superalloy ingot produced by the method of the present invention is used as a turbine disk in an aircraft jet engine. ,
Considering that it is used as a material for forged parts such as turbine shafts, in mass%, Cr: 5.0 to 30.0%,
Co: 1.0-30.0%, Mo: 0.5-20.0
%, W: 0.5 to 15.0%, Nb: 0.5 to 10.0
%, Al: 0.1 to 8.0%, Ti: 0.1 to 8.0
%, Fe: 40% or less (including 0), Mn:
2.0% or less (including 0), Si: 2.0% or less (including 0), C: 0.01 to 0.3%,
B: 0.001 to 0.1%, and Zr: 0.
01-1.0%, Hf: 0.01-5.0%, Ta:
A Ni-base superalloy containing 0.5 to 10.0% and one or more of Re: 0.01 to 6.0% with the balance being Ni and inevitable impurities. Is preferred.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a Ni-base superalloy ingot of the present invention, which has a small component segregation and is composed of uniformly fine crystal grains, will be described with reference to the drawings. FIG. 1 is a schematic sectional view of a melting and casting apparatus for carrying out this method. Figure 1
1, 1 is a water-cooled copper mold, 2 is a VIM ingot or ESR ingot, 21 is a Ni-based superalloy ingot obtained by remelting an electron beam, 3 is an electron beam for remelting, 31 is an electron beam for irradiation, and 4 is Metal powder, 5 is VI
A pool of a Ni-based superalloy melt obtained by remelting an M ingot or an ESR ingot with an electron beam, 6 is a cooling water circulation cavity, 7 is a hopper for supplying metal powder, 8
Is a Ni-based superalloy melt obtained by remelting with an electron beam.

The VIM ingot or ESR ingot 2 is melted by the electron beam 3, the obtained Ni-base superalloy melt 8 is filled in the water-cooled copper mold 1 to form a shallow pool 5, and metal powder is poured from above the pool 5. 4 is added to generate fine nuclei and immediately solidifies to form a part of the ingot having fine crystal grains, and at the same time, the solidified portion is pulled out in the A direction and rotated in the B direction as necessary, and the ingot is rotated. 21 is formed. The depth of the pool 5 is preferably shallow, and preferably in the range of 0.5 to 10 mm. The reason for this is that if the depth of the pool 5 is less than 0.5 mm, the solidification time is too short to solidify before adding the metal powder.
This is because when it exceeds 0 mm, the action of adding metal powder to the inside of the pool to generate fine nuclei does not work.

As the electron beam, two electron beam guns (not shown) are used in FIG. 1, but one electron beam gun is used to melt the VIM ingot or ESR ingot 2 and to melt the Ni-base superalloy melt. The surface irradiation of the pool 5 can be alternately repeated. Further, the electron beam can be narrowed or dispersed by a magnetic field and further bent, so that the electron beam can be installed at any position.

Example 1 Ni-16.0% Cr-14.7% Co-3.0% Mo
-1.3% W-2.5% Al-5.0% Ti-0.03
% C-0.03% B-0.03% N in the composition of Zr
The i-base superalloy is subjected to high-frequency vacuum melting, vacuum casting to produce a VIM ingot, and the obtained VIM ingot is further electroslag-melted to produce an ESR ingot.
This ESR ingot is 70KW as shown in Fig. 1.
Melted by the electron beam of
A water-cooled copper mold having a cavity of m is filled to form a molten metal pool having a depth of 2 mm in the water-cooled copper mold, and the molten metal pool is irradiated with a 70 KW electron beam from another electron beam gun on the pool surface. Surface temperature of 1350 ℃ (=
Liquid-phase temperature + 15 ° C) A molten Ni-based superalloy powder having an average particle diameter of 32 μm and the same composition as the ESR ingot is added to a pool in a molten state while solidifying the molten state at the same time. The solidified ingot was drawn out from the solidified ingot water-cooled copper mold while being rotated at a rotation speed of 10 rpm and a drawing speed of 2 mm / min to prepare a Ni-base superalloy ingot having a diameter of 200 mm and a height of 500 mm. .

Conventional Example 1 The ESR ingot prepared in Example 1 was melted by a normal vacuum arc to obtain a diameter of 200 mm and a height of 500.
A Ni-based superalloy ingot having dimensions of mm was prepared.

Thus, the Ni-base superalloy ingots obtained in Example 1 and Conventional Example 1 were divided into two parts on the plane including the axis, and the bottom and top of the ingot were divided into the central portion and the central portion of the cross section of the ingot. The component composition and average crystal grain size in the middle and outer peripheral portions were measured, and the results are shown in Tables 1 and 2.

[0020]

[Table 1]

[0021]

[Table 2]

From the results shown in Tables 1 and 2, the crystal grains of the Ni-base superalloy ingot shown in Table 1 obtained in Example 1 are the same as those of the Ni-base superalloy ingot obtained in Conventional Example 1 shown in Table 2. It can be seen that it is much more uniform and fine than the alloy ingot. In addition, N is generally used as a material for turbine disks, turbine shafts, etc. in aircraft jet engines.
The i-based superalloy ingot needs to have a small amount of component segregation in the central portion and the outer peripheral portion of the ingot, and particularly needs to have a small amount of component segregation of the component composition in the central portion and the outer peripheral portion of Al and Ti, which are easily segregated. However, the Ni-based superalloy ingot obtained in Example 1 has a maximum difference of 0.2% in composition between the central portion and the outer peripheral portion, whereas the Ni-based superalloy ingot obtained in Conventional Example 1 has a maximum difference of 0.2%. The difference in the concentration of Ti in the top portion of the Ni was 0.5%, and the Ni-based superalloy ingot obtained in Example 1 was the Ni obtained in Conventional Example 1.
It can be seen that the segregation of the components is significantly less than that of the base superalloy ingot.

Example 2 The VIM ingot produced in Example 1 was melted with an electron beam of 70 KW as shown in FIG. 1, and the resulting melt was filled in a water-cooled copper mold having a cavity with an inner diameter of 200 mm and water-cooled. A molten metal pool with a depth of 2 mm was formed in the copper mold, and a 70 KW electron beam was irradiated onto the pool surface from another electron beam gun in this molten metal pool so that the surface temperature of the pool was 1350 ° C. (= liquidus temperature + 15 ℃) while maintaining the molten state, the Ni-base superalloy powder having an average particle size of 2 μm and the same composition as the ESR ingot is added to the pool, and the solidified ingot is rotated at the same time. Speed: 10 rpm, drawing speed: 2 mm / m
Diameter: 200 mm, height: 500 m by pulling out from a solidified ingot water-cooled copper mold while rotating in
A Ni-based superalloy ingot having a size of m was prepared.

Conventional Example 2 The VIM ingot produced in Example 1 was melted in a usual vacuum arc to obtain a diameter of 200 mm and a height of 500.
A Ni-based superalloy ingot having dimensions of mm was prepared.

Thus, the Ni-base superalloy ingots obtained in Example 2 and Conventional Example 2 were divided into two parts along the plane including the shaft, and the bottom and top of the ingot were divided into the central portion and the central portion of the cross section of the ingot. When the component composition and the average crystal grain size in the outer peripheral middle portion and the outer peripheral portion were measured,
Almost the same results as those shown in Tables 1 and 2 were obtained.

[0026]

According to the method of the present invention, it is possible to obtain a Ni-base superalloy ingot which has a small component segregation depending on the location of the ingot and is composed of uniformly fine crystal grains throughout the ingot. Therefore, the number of ingot forging operations can be reduced. A Ni-based superalloy containing a large amount of Al and Ti and having a high volume fraction of the γ'phase, which has been said to be able to be produced only by the powder metallurgical method, has a small component segregation and is a uniform fine crystal throughout. It has an excellent industrial effect such that an ingot made of grains can be produced.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional explanatory view for explaining a method for producing a Ni-base superalloy ingot which has a small component segregation and is composed of uniformly fine crystal grains according to the present invention.

[Explanation of symbols]

1: Water-cooled copper mold, 2: VIM ingot or ESR ingot, 21: Ni-based superalloy ingot obtained by remelting electron beam, 3: Electron beam for remelting, 31: Electron beam for irradiation, 4: Metal powder 5, Ni-based superalloy molten metal pool, 6: Cooling water flow cavity, 7: Hopper,
8: Ni-base superalloy melt obtained by remelting with electron beam.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) B22D 11/041 B22D 11/041 E 21/00 21/00 C 23/02 23/02 23/06 23 / 06 27/20 27/20 B F01D 5/28 F01D 5/28 25/00 25/00 FL // C22C 19/05 C22C 19/05 C (72) Inventor Hiroaki Kikuchi 1230 Kamihideya, Okegawa, Saitama Prefecture Mitsubishi Material Co., Ltd. Okegawa Works F-term (reference) 3G002 AA07 AA11 AA13 AB07 AB08 AB09 4E004 MB14 MB20 NB04 NC10

Claims (7)

[Claims] 1. An ingot (hereinafter referred to as VIM ingot) or N obtained by high-frequency vacuum melting of a Ni-base superalloy.
An ingot (hereinafter referred to as an ESR ingot) obtained by high-frequency vacuum melting an i-base superalloy and then remelting the electroslag was re-melted with an electron beam to form a shallow pool of the Ni-base superalloy melt. A method for producing a Ni-base superalloy ingot having a small component segregation and uniform fine grains, characterized in that a metal powder is added to a shallow pool of a Ni-base superalloy melt and then immediately solidified. 2. A VIM ingot or an ESR ingot is remelted with an electron beam to form a shallow pool of a Ni-base superalloy melt, and the shallow pool of the Ni-base superalloy melt is irradiated with an electron beam to maintain the molten metal state. However, a method for producing a Ni-base superalloy ingot, which has a small component segregation and is composed of uniform fine grains, characterized by solidifying immediately after adding metal powder. 3. A VIM ingot or ESR ingot is remelted with an electron beam to form a shallow pool of a Ni-base superalloy melt, and the entire pool of the shallow pool of the Ni-base superalloy melt is irradiated with an electron beam to melt the entire pool. A method for producing a Ni-base superalloy ingot, which is characterized by adding metal powder while maintaining the state, and then immediately solidifying the powder, which has a small component segregation and is composed of uniformly fine crystal grains. 4. A VIM ingot or an ESR ingot is remelted with an electron beam to form a shallow pool of a Ni-base superalloy melt, and a partial surface of the shallow pool of the Ni-base superalloy melt is irradiated with an electron beam to form a shallow pool. Part is kept in a molten state, the metal powder is added to this partially molten Ni-base superalloy and then immediately solidified, and the operation is carried out on the entire surface of the pool. Segregation is small and uniform. A method for producing a Ni-based superalloy ingot composed of fine crystal grains. 5. The metal powder added to the Ni-based superalloy melt is
A Ni-based superalloy powder as claimed in claim 1,
2. A method for producing a Ni-based superalloy ingot, which comprises crystal grains having a small component segregation and uniform fineness as described in 2, 3 or 4. 6. A metal powder to be added to a Ni-based superalloy melt,
A Ni-based superalloy powder having the same composition as that of the molten Ni-based superalloy.
A method for producing a Ni-base superalloy ingot which has a small component segregation and is composed of uniformly fine crystal grains. 7. The surface temperature of a shallow pool of a Ni-base superalloy melt to which metal powder is added is controlled within a range from a temperature exceeding a solidus temperature to a liquidus temperature + 30 ° C. 5. The method for producing a Ni-base superalloy ingot according to claim 1, 2, 3 or 4, which has a small component segregation and is composed of uniformly fine crystal grains.