Method for manufacturing tial alloy casting material, tial alloy casting material, moving blade for jet engine, and turbine wheel

Abstract

This method for manufacturing a TiAl alloy casting material includes: a melting step in which a source material that includes Ti and Al is melted into a molten metal; a deoxidation material adding step in which a deoxidation material that includes Ca is added to one or both of the source material and the molten metal, said deoxidation material being added such that the concentration of Ca in the total mass of the the source material and the molten metal is 0.2 mass% to 1.0 mass%; and a deoxidation step in which, by heating the molten metal that includes the deoxidation material and maintaining the molten state, fumes that include a reaction product of the Ca and oxygen in the molten metal are produced, and the oxygen in the molten metal is removed.

Description

Manufacturing method of TiAl alloy casting material, TiAl alloy casting material, jet engine rotor blade and turbine wheel

[0001] The present invention relates to a method for manufacturing a TiAl alloy cast material, a TiAl alloy cast material, a jet engine rotor blade, and a turbine wheel. This application claims priority to Japanese Patent Application No. 2022-050457, filed on March 25, 2022, the contents of which are incorporated herein by reference.

[0002] Ni-based superalloys have traditionally been used as materials for jet engine rotor blades and turbine wheels for passenger car turbochargers. In recent years, TiAl alloys have been attracting attention as a new material for use in these components. The density of TiAl alloys is about half that of Ni-based superalloys. Therefore, even if the components are large, they can be lighter in weight, which contributes greatly to improving engine efficiency and reducing fuel consumption and carbon dioxide emissions through weight reduction.

[0003] In TiAl alloy components used in jet engine rotor blades and turbine wheels, the impurity concentration in the TiAl alloy forming the components is naturally specified. Regarding oxygen, the most likely impurity to be mixed in, the content in the TiAl alloy is specified to be, for example, 0.12 mass% or less. If the oxygen content in the TiAl alloy exceeds 0.12 mass%, the impact resistance of the TiAl alloy component decreases, and problems such as breakage of the component during use become more likely to occur.

[0004] Jet engine rotor blades and turbine wheels made of TiAl alloys are usually produced by casting TiAl alloy cast materials, which are made from titanium sponge, aluminum particles, and / or master alloy ingots made from these metal element raw materials.

[0005] Currently, when casting TiAl alloy casting materials for jet engine blades and turbine wheels, the following manufacturing method is used to obtain products with a sufficiently low oxygen content that satisfies the TiAl alloy composition regulations. Specifically, a vacuum melting furnace is used to melt raw materials in a vacuum or in an inert gas atmosphere, preventing oxygen from being mixed into the molten raw materials. Furthermore, melting raw materials in a water-cooled copper crucible prevents oxygen from being mixed into the molten metal.

[0006] When melting metal materials such as iron-based and Ni-based alloys, oxide ceramic crucibles are generally used. However, since the molten TiAl alloy is active, when melted in an oxide ceramic crucible, oxygen is mixed into the molten metal from the crucible, resulting in a high oxygen concentration in the cast material.

[0007] Furthermore, when casting TiAl alloy casting materials for jet engine blades and turbine wheels, raw materials with low oxygen content are used to obtain products with a sufficiently low oxygen content that meet the TiAl alloy composition specifications. Specifically, low-oxygen metal element raw materials and / or low-oxygen master alloy ingots (cast metals) made from low-oxygen metal element raw materials are used.

[0008] A master alloy ingot with a low oxygen content is usually produced by the following casting method: the raw materials for the master alloy ingot are melted in a water-cooled copper crucible placed in a vacuum melting furnace under a vacuum or inert gas atmosphere.

[0009] Patent Document 1 describes a method for producing a TiAl alloy ingot by melting Ti and Al as melting raw materials in a ceramic crucible by high-frequency induction melting and casting the resulting molten metal into a mold. Patent Document 1 also describes a method for producing a TiAl alloy ingot by melting Ti and Al as melting raw materials in a ceramic crucible by high-frequency induction melting and casting the resulting molten metal into a mold. ２ O ３ It is described that by using SiO2 as the material of the ceramic crucible, the amount of oxygen generated by decomposition of the ceramic crucible during melting can be suppressed, and the concentration of oxygen mixed into the TiAl alloy can be suppressed.

[0010] Patent Document 2 describes a method for producing an ingot of a TiAl-based alloy, in which the oxygen content of the Ti raw material is 800 ppm or less, the oxygen content of the Al raw material is 100 ppm or less, and if other alloying components are Cr, V, or Nb, the oxygen content of those components is 2000 ppm or less, and if other alloying components are Mn, the oxygen content of those components is 3000 ppm or less. Patent Document 2 describes melting the alloy raw materials and then solidifying them to produce a primary ingot whose composition has been adjusted in advance, which is then melted in a water-cooled copper crucible. Patent Document 2 also describes storing the alloy material in an inert gas atmosphere to protect it from surface oxidation and other effects.

[0011] Patent Document 3 describes a method for producing a high-purity TiAl-based intermetallic compound, in which high-purity Ti having an oxygen content of 200 ppm or less and high-purity Al having a purity of 99.99 wt % or more are used as base materials, and the base materials are melted to reduce the oxygen content to 0.03% or less, cast, and then annealed. Patent Document 3 also describes repeating melting and solidification on a copper hearth multiple times.

[0012] Patent Document 4 describes a method for producing a TiAl-based intermetallic compound alloy by melting raw materials consisting of 48 to 70 atomic % titanium and 30 to 52 atomic % aluminum in a calcia crucible. Patent Document 4 also describes a method in which the titanium raw material is heated in a vacuum and degassed beforehand, and then the titanium and aluminum raw materials are charged into the crucible and melted by a vacuum induction melting method.

[0013] Non-Patent Document 1 describes that Ti alloys were induction melted in a water-cooled copper crucible and deoxidized by adding a Ca alloy to the melt. Non-Patent Document 1 also describes that, as a result of analyzing an ingot obtained by deoxidizing a TiAl master alloy containing 0.16 mass% of oxygen using an AlCa alloy as a deoxidizer, deoxidization was achieved to O=0.02% when Ca was ≥ 0.3%.

[0014] Japanese Unexamined Patent Publication No. 2011-36877 (A) Japanese Unexamined Patent Application No. 2009-113060 (A) Japanese Unexamined Patent Publication No. 3-193839 (A) Japanese Unexamined Patent Application No. 3-199330 (A)

[0015] Tomoki Shibata and Noboru Demukai, Deoxidation of TiAl, Electric Steel Making, Vol. 64, No. 1, February 1993, pp. 32-39

[0016] In the conventional techniques, when producing a TiAl alloy casting material having a sufficiently low oxygen content, it has been necessary to use a special device that melts raw materials using a water-cooled copper crucible installed in a vacuum melting furnace under a vacuum or inert gas atmosphere, and / or to use special raw materials having a low oxygen content. Therefore, there is a demand for more options for devices and raw materials that can be used when producing a TiAl alloy casting material having a sufficiently low oxygen content.

[0017] The present invention has been made in view of the above circumstances, and aims to provide a method for producing a TiAl alloy cast material having a sufficiently low oxygen content, which is highly versatile and can be used with a variety of equipment and raw materials, a TiAl alloy cast material having an oxygen content of 0.12 mass % or less, and a jet engine rotor blade and turbine wheel made of a TiAl alloy cast material having an oxygen content of 0.12 mass % or less.

[0018] [1] A method for producing a TiAl alloy casting material, comprising: a melting step of melting raw materials containing Ti and Al to obtain a molten metal; a deoxidizing agent adding step of adding a deoxidizing agent containing Ca to either or both of the raw materials and the molten metal, wherein the deoxidizing agent is added so that the Ca concentration in the total mass of the raw materials and the deoxidizing agent is 0.2 mass% to 1.0 mass%; and a deoxidizing step of heating the molten metal containing the deoxidizing agent and maintaining it in a molten state, thereby generating fumes containing a reaction product of oxygen in the molten metal and Ca, thereby removing oxygen from the molten metal.

[0019] [2] The method for producing a TiAl alloy casting material according to [1], characterized in that the deoxidizer is an AlCa alloy.

[0020] [3] The method for producing a TiAl alloy casting material according to [1] or [2], wherein the melting step is a step of melting the raw materials in an oxide ceramic crucible, the deoxidizing agent adding step is either or both of a step of putting the deoxidizing agent into the oxide ceramic crucible together with the raw materials and a step of adding the deoxidizing agent to the molten metal placed in the oxide ceramic crucible, and the deoxidizing step is characterized in that the molten metal containing the deoxidizing agent placed in the oxide ceramic crucible is heated and melted.

[0021] [4] The method for producing a TiAl alloy casting material according to [1] or [2], wherein the deoxidizing agent adding step is a step of putting the deoxidizing agent together with the raw materials into an oxide ceramic crucible installed in a vacuum melting furnace, the melting step is a step of melting the raw materials in the oxide ceramic crucible installed in the vacuum melting furnace under an Ar atmosphere after the deoxidizing agent adding step, and the deoxidizing step is a step of heating and melting the molten metal containing the deoxidizing agent in the oxide ceramic crucible installed in the vacuum melting furnace under an Ar atmosphere.

[0022] [5] The oxide ceramic crucible is placed in an atmospheric melting furnace with an air atmosphere, and the melting step includes a mold placing step of placing a funnel-shaped mold with a wider opening facing the oxide ceramic crucible so as to cover the opening of the oxide ceramic crucible, an atmosphere substitution step of supplying Ar gas into the oxide ceramic crucible, and a heating step of heating the oxide ceramic crucible, and the deoxidizing material adding step includes a step of putting the deoxidizing material into the oxide ceramic crucible together with the raw materials, and a step of adding the deoxidizing material to the molten metal placed in the oxide ceramic crucible through the funnel-shaped mold. and a step of adding a deoxidizing agent to the ceramic crucible, the deoxidizing step being performed in the funnel-shaped mold. In the deoxidizing step, the molten metal containing the deoxidizing agent is heated and melted in the ceramic crucible having an opening covered by the funnel-shaped mold, the fumes in the ceramic crucible are discharged through the funnel-shaped mold, and after the deoxidizing step, the atmospheric melting furnace is turned upside down with the ceramic crucible and the funnel-shaped mold integrated together, and the molten metal is poured from the ceramic crucible into the funnel-shaped mold and cooled.

[0023] [6] The method for producing a TiAl alloy casting material according to any one of [1] to [5], wherein the raw material contains either or both of TiAl alloy cutting chips and TiAl alloy casting scrap.

[0024] [7] A TiAl alloy casting material containing 0.04% to 0.10% by mass of oxygen and 0.01% to 0.03% by mass of Ca. [8] A TiAl alloy casting material containing 31.9% to 34.2% by mass of Al, 4.0% to 5.4% by mass of Nb, 2.3% to 3.0% by mass of Cr, 0.04% to 0.12% by mass of oxygen, 0.01% to 0.07% by mass of Ca, and the balance consisting of Ti and impurities.

[0025] [9] A jet engine blade comprising the cast TiAl alloy material according to [7] or [8].

[10] A turbine wheel comprising the cast TiAl alloy material according to [7] or [8].

[0026] The method for producing a TiAl alloy casting material of the present invention includes the steps of: melting raw materials containing Ti and Al to obtain a molten metal; adding a deoxidizer containing Ca to either or both of the raw materials and the molten metal so that the Ca concentration in the total mass of the raw materials and the deoxidizer is 0.2 to 1.0 mass%; and heating the molten metal containing the deoxidizer and maintaining it in a molten state to generate fumes containing reaction products of oxygen in the molten metal and Ca, thereby removing oxygen from the molten metal. Therefore, by pouring the molten metal after the deoxidization step into a mold and cooling it, a TiAl alloy casting material with a sufficiently low oxygen content can be obtained.

[0027] Therefore, according to the method for producing a cast TiAl alloy material of the present invention, a cast TiAl alloy material with a sufficiently low oxygen content can be obtained without using special equipment or special raw materials with a low oxygen content, and a variety of equipment and raw materials can be used. For example, even if the raw materials contain poor quality raw materials with a high oxygen content, or if the molten metal contains oxygen mixed in from the oxide ceramic crucible and / or the atmosphere, the method for producing a cast TiAl alloy material of the present invention can produce a cast TiAl alloy material with a sufficiently low oxygen content.

[0028] Fig. 1 is a process diagram for explaining an example of a method for manufacturing the TiAl alloy cast material of the present embodiment. Fig. 2 is a process diagram for explaining an example of a method for manufacturing the TiAl alloy cast material of the present embodiment. Fig. 3 is a process diagram for explaining an example of a method for manufacturing the TiAl alloy cast material of the present embodiment. Fig. 4 is a process diagram for explaining an example of a method for manufacturing the TiAl alloy cast material of the present embodiment. Fig. 5 is a process diagram for explaining an example of a method for manufacturing the TiAl alloy cast material of the present embodiment. Fig. 6 is a process diagram for explaining an example of a method for manufacturing the TiAl alloy cast material of the present embodiment.

[0029] The present inventors have conducted extensive research to solve the above problems, as described below. Specifically, to obtain a TiAl alloy casting material with a sufficiently low oxygen content, a special device is used to melt raw materials using a water-cooled copper crucible installed in a vacuum melting furnace under a vacuum or inert gas atmosphere, resulting in high initial capital investment and operating costs. Furthermore, the use of a water-cooled copper crucible limits the amount of molten metal that can be melted, resulting in a small number of casting materials that can be cast in one batch, resulting in insufficient productivity. Furthermore, when a water-cooled copper crucible is used, the molten metal is easily overheated to a low temperature, which can easily cause poor flow during casting and result in a low yield of non-defective products.

[0030] In order to solve the problems that arise when using a water-cooled copper crucible, it is conceivable to use, instead of the water-cooled copper crucible, an oxide ceramic crucible, which is generally used when melting metal materials such as iron-based and Ni-based alloys. When an oxide ceramic crucible is used, a larger amount of molten metal can be melted and the superheat temperature of the molten metal can also be increased compared to when a water-cooled copper crucible is used.

[0031] However, molten TiAl alloys are highly reactive. Therefore, when raw materials containing Ti and Al are melted in an oxide ceramic crucible, oxygen from the material of the oxide ceramic crucible is mixed into the molten raw materials. As a result, the TiAl alloy casting material obtained after casting has a high oxygen content. For this reason, it has not been possible to use an oxide ceramic crucible to produce a TiAl alloy casting material with a sufficiently low oxygen content.

[0032] In order to reduce the initial investment and operating costs, it is possible to use an atmospheric melting furnace instead of a vacuum melting furnace. However, when an atmospheric melting furnace is used, oxygen from the atmosphere is mixed into the melted raw materials. As a result, the TiAl alloy casting material obtained after casting has a high oxygen content.

[0033] Furthermore, when special raw materials with low oxygen content are used to obtain TiAl alloy casting materials with a sufficiently low oxygen content, the raw materials are expensive and special equipment is required for storing the raw materials. Furthermore, when a master alloy ingot with low oxygen content is produced as a raw material with low oxygen content, a special device is required to melt the raw materials using a water-cooled copper crucible installed in a vacuum melting furnace under a vacuum or inert gas atmosphere.

[0034] On the other hand, there is a demand for the use of TiAl alloy scrap as a raw material for TiAl alloy castings. Examples of TiAl alloy scrap include TiAl alloy cutting chips and / or TiAl alloy casting scrap. Examples of TiAl alloy cutting chips include cutting chips generated during the production of components such as jet engine rotor blades from TiAl alloy castings. Examples of TiAl alloy casting scrap include casting scrap consisting of parts that do not become TiAl alloy casting products, such as runners generated during precision casting of TiAl alloys using lost-wax casting.

[0035] However, TiAl alloy scrap has a high oxygen content. Specifically, organic matter such as coolant and cutting oil adheres to the TiAl alloy cutting chips. Because the organic matter adheres firmly to the TiAl alloy cutting chips, it is difficult to sufficiently reduce the oxygen content even if the TiAl alloy cutting chips are washed with an organic solvent. Furthermore, TiAl alloy casting scrap usually contains oxygen that is mixed in due to the reaction between a mold made of oxide ceramic and the molten raw material. Therefore, TiAl alloy casting scrap also has a high oxygen content. For these reasons, it has been difficult with conventional techniques to produce TiAl alloy casting materials with a sufficiently low oxygen content using raw materials containing TiAl alloy scrap.

[0036] In recent years, the production volume of TiAl alloy components has been rapidly expanding. In particular, the use of jet engine blades made of TiAl alloys has been expanding worldwide, and their production volume has been increasing. However, the cost of jet engine blades made of current TiAl alloys is several times higher than that of jet engine blades made of Ni-based superalloys. For this reason, there is a strong demand for reducing the cost of TiAl alloy castings used for jet engine blades.

[0037] Therefore, the present inventors have conducted extensive research to solve the above problems and to realize a versatile manufacturing method for TiAl alloy castings that can produce TiAl alloy castings with a sufficiently low oxygen content using not only a special device that melts raw materials using a water-cooled copper crucible installed in a vacuum melting furnace under a vacuum or inert gas atmosphere, but also a variety of devices, such as a device equipped with an oxide ceramic crucible installed in an atmospheric melting furnace or a vacuum melting furnace, and a variety of raw materials, such as TiAl alloy scrap, while focusing on deoxidizers for the melting raw materials.

[0038] As a result, it was found that it is sufficient to add a deoxidizer to either or both of the raw materials and the molten metal so that the Ca concentration in the total mass of the raw materials and the deoxidizer containing Ca is 0.2 mass % to 1.0 mass %, and then heat the molten metal containing the deoxidizer and maintain it in a molten state. Ca is an element that bonds more easily with oxygen than Ti and Al. Therefore, by heating the molten metal and maintaining it in a molten state, the Ca in the molten metal reacts with the oxygen in the molten metal to form CaO, CaTiO ３ , CaAl ２ O ４ These reaction products are discharged from the molten metal as fumes, and as a result, oxygen in the molten metal is removed along with Ca.

[0039] Furthermore, the present inventors have confirmed that by adding a deoxidizer containing Ca so that the Ca concentration in the total mass of the raw materials and the deoxidizer is within the above range, a cast TiAl alloy material with a sufficiently low oxygen content and excellent impact resistance can be obtained without using special equipment or special raw materials with a low oxygen concentration, and have arrived at the present invention. Specifically, by using the method of adding a deoxidizer containing Ca to achieve the above concentration, as shown in the examples described below, a cast TiAl alloy material with a sufficiently low oxygen content can be obtained even when using an equipment using a general-purpose melting furnace and oxide ceramic crucible that are commonly used for melting metal materials, or when using raw materials including TiAl alloy scrap with a high oxygen concentration.

[0040] The method for producing a TiAl alloy cast material, the TiAl alloy cast material, the jet engine rotor blade, and the turbine wheel of the present invention will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments.

[0041] [Method of Manufacturing Cast TiAl Alloy Material] In this embodiment, an example of a method of manufacturing a cast TiAl alloy material will be described using an apparatus equipped with an oxide ceramic crucible 2 installed in an atmospheric melting furnace 1. Figures 1 to 7 are process diagrams illustrating an example of a method of manufacturing a cast TiAl alloy material according to this embodiment. In Figures 1 to 6, reference numeral 1 denotes the atmospheric melting furnace, and reference numeral 2 denotes the oxide ceramic crucible.

[0042] A known atmospheric melting furnace can be used as the atmospheric melting furnace 1. In this embodiment, a reversing furnace (rollover furnace) type is used as the atmospheric melting furnace 1. As shown in FIG. 1, the atmospheric melting furnace 1 has a substantially cylindrical accommodation section 1a that is open at the top. The atmospheric melting furnace 1 has a furnace wall 1b and a high-frequency coil 4 that is installed within the furnace wall 1b and heats an oxide ceramic crucible 2. As shown in FIG. 1, the oxide ceramic crucible 2 is installed within the accommodation section 1a.

[0043] A known oxide ceramic crucible can be used as the oxide ceramic crucible 2. It is preferable to use a chemically stable oxide ceramic as the material for the oxide ceramic crucible 2. Specifically, calcia or yttria is preferable, and calcia is more preferable because it is a material that is less likely to contain inclusions. By using an oxide ceramic crucible 2 made of calcia or yttria, the amount of oxygen that is mixed into the melting raw material 3a (molten metal) from the oxide ceramic crucible 2 can be suppressed. Therefore, even if the amount of Ca-containing deoxidizer added to the raw material 3 or the melting raw material 3a is small, the oxygen content in the TiAl alloy cast material obtained after casting can be sufficiently reduced.

[0044] [Melting Step] [Deoxidizer Addition Step] The manufacturing method of the TiAl alloy cast material of this embodiment includes a melting step. In the melting step, a raw material 3 is melted to obtain a molten raw material 3a (molten metal). In this embodiment, the raw material 3 is melted in an oxide ceramic crucible 2 installed in an atmospheric melting furnace 1 in an air atmosphere. As will be described later, the raw material 3 is melted after the opening of the oxide ceramic crucible 2 is covered with a funnel-shaped mold 5 and an argon atmosphere is created inside the oxide ceramic crucible 2. Argon can be supplied into the oxide ceramic crucible 2 using, for example, a gas supply pipe 7 inserted into the oxide ceramic crucible 2 via the funnel-shaped mold 5, as will be described later.

[0045] 1, in the melting step, a portion of the raw material 3 is placed in an oxide ceramic crucible 2. Further, the entire amount of the deoxidizing material containing Ca is added to the oxide ceramic crucible 2, and then the raw material 3 is melted.

[0046] (Raw Material) Raw material 3 includes Ti and Al. Raw material 3 may contain, in addition to Ti and Al, one or more additive elements selected from, for example, Nb, Cr, Mo, V, Mn, W, Fe, Si, C, and B. The composition of raw material 3 can be determined appropriately depending on the application of the TiAl alloy cast material obtained after casting. Raw material 3 may contain, for example, 31.9 to 34.2 mass% Al, 4.0 to 5.4 mass% Nb, 2.3 to 3.0 mass% Cr, 0.1 to 0.5 mass% oxygen, with the balance being Ti and impurities.

[0047] The raw material 3 contains impurities at a concentration within a range that will not interfere with the intended use of the resulting TiAl alloy cast material. For example, when casting a TiAl alloy cast material to be used as a jet engine blade or turbine wheel, the impurities contained in the raw material 3 are preferably within a content range that satisfies the TiAl alloy composition specifications (material specifications for each product) of the resulting TiAl alloy cast material.

[0048] The composition of the raw material 3 does not match the composition of the TiAl alloy cast material obtained after casting. Specifically, this is because, in the manufacturing process of the TiAl alloy cast material, there are elements that increase by being mixed into the raw material 3a from the oxide ceramic crucible 2 in contact with the raw material 3a, the atmosphere, etc., elements that increase by adding a deoxidizing material containing Ca, and elements that decrease by being emitted from the raw material 3a as fumes.

[0049] In the manufacturing method of the TiAl alloy cast material of this embodiment, Ti and Al, which are the main elements of the TiAl alloy, are hardly mixed in from the equipment or atmosphere, or are hardly discharged during the manufacturing process. Therefore, there is almost no increase or decrease in the amount of Ti during the manufacturing process of the TiAl alloy cast material. Therefore, the mass of Ti used as raw material 3 and the mass of Ti contained in the TiAl alloy cast material obtained after casting can be considered to be the same. On the other hand, the amount of Al increases by using an AlCa alloy as a deoxidizer containing Ca in the manufacturing process of the TiAl alloy cast material, and the amount of Al increases by using an AlCa alloy as a deoxidizer containing Ca in the deoxidation process. ２ O ４These are reduced by being expelled from the molten metal as fumes such as:

[0050] Furthermore, in the manufacturing method of the TiAl alloy cast material of this embodiment, Nb and Cr, which may be contained as additive elements in the raw material 3, are hardly mixed in from the equipment or atmosphere, or discharged during the manufacturing process, just like Ti. Therefore, there is almost no increase or decrease in the amounts of Nb and Cr during the manufacturing process of the TiAl alloy cast material. Therefore, the masses of Nb and Cr used as the raw material 3 and the masses of Nb and Cr contained in the TiAl alloy cast material obtained after casting can be considered to be the same.

[0051] For example, if the composition of raw material 3 is 31.9 to 34.2 mass% Al, 4.0 to 5.4 mass% Nb, 2.3 to 3.0 mass% Cr, 0.1 to 0.5 mass% oxygen, with the balance being Ti and impurities, then after casting, a TiAl alloy cast material containing 31.9 to 34.2 mass% Al, 4.0 to 5.4 mass% Nb, 2.3 to 3.0 mass% Cr, 0.04 to 0.12 mass% oxygen, and 0.01 to 0.07 mass% Ca, with the balance being Ti and impurities, is easily obtained, which is preferable. A TiAl alloy cast material having such a composition has excellent impact resistance, and also has good machinability, tensile strength, and creep strength, making it suitable for use as a material for jet engine rotor blades and turbine wheels.

[0052] The Al content in the raw material 3 can be, for example, 31.9 to 34.2 mass %, and preferably 32.9 to 33.8 mass %, because this improves the impact resistance, tensile strength, and creep strength of the TiAl alloy cast material obtained after casting.

[0053] The Nb content in raw material 3 can be, for example, 4.0% by mass to 5.4% by mass, and preferably 4.4% by mass to 5.0% by mass. This is because the TiAl alloy cast material obtained after casting has good oxidation resistance. The Cr content in raw material 3 can be, for example, 2.3% by mass to 3.0% by mass, and preferably 2.5% by mass to 2.8% by mass. This is because the TiAl alloy cast material obtained after casting has good ductility. When raw material 3 contains 4.4% by mass to 5.0% by mass of Nb and 2.5% by mass to 2.8% by mass of Cr in addition to Ti and Al, a TiAl alloy cast material having better impact resistance, machinability, tensile strength, and creep strength can be obtained.

[0054] The shape of the raw material 3 is not particularly limited, and examples thereof include titanium sponge, Al particles (pellets), Nb flakes, Cr particles, and other metal element raw materials, and / or master alloy ingots (cast metals) made using these metal element raw materials.

[0055] The raw material 3 may contain TiAl alloy scrap. Examples of TiAl alloy scrap include TiAl alloy cutting chips and TiAl alloy casting scrap. Examples of TiAl alloy cutting chips include cutting chips generated during the production of components such as jet engine rotor blades from TiAl alloy casting materials. Examples of TiAl alloy casting scrap include casting scrap consisting of parts that do not become TiAl alloy casting products, such as runners generated during precision casting of TiAl alloys using lost-wax casting.

[0056] When TiAl alloy cutting chips are used as the raw material 3, it is preferable to use the raw material after washing organic substances such as coolant and cutting oil adhering to the TiAl alloy cutting chips with an organic solvent such as acetone in order to further reduce the oxygen content in the TiAl alloy cast material obtained after casting. Known methods such as using an ultrasonic cleaner can be used as a method for washing the TiAl alloy cutting chips with an organic solvent. When TiAl alloy casting scraps are used as the raw material 3, it is preferable to use the raw material after pickling the surface in order to further reduce the oxygen content in the TiAl alloy cast material obtained after casting.

[0057] (Ca-containing deoxidizer) As the Ca-containing deoxidizer, for example, simple Ca may be used, or an AlCa alloy, CaF ２ , CaCl ２ It is also possible to use a Ca-containing compound such as the above. As the Ca-containing deoxidizer, it is preferable to use an AlCa alloy, since it is a solid and therefore easy to handle, does not require special considerations for storage, and does not require special considerations for safety. As the AlCa alloy, since there is little fluctuation in the Ca content during the manufacturing process of the AlCa alloy and it can be manufactured stably, it is preferable to use an AlCa alloy whose Ca content in the AlCa alloy is 3% by mass to 20% by mass, more preferably 10% by mass or 5% by mass, and even more preferably 5% by mass.

[0058] The Ca-containing deoxidizer is added so that the Ca concentration in the total mass of the raw material 3 and the deoxidizer is 0.2 to 1.0 mass%. The amount of the Ca-containing deoxidizer added can be appropriately determined within the above range depending on the composition of the raw material 3, the composition range of the target TiAl alloy cast material, and conditions such as the atmosphere, temperature, and time for heating the melted raw material 3a containing the deoxidizer. By adding the Ca-containing deoxidizer so that the Ca concentration in the total mass of the raw material 3 and the deoxidizer is within the above range, a TiAl alloy cast material containing 0.04 to 0.12 mass% oxygen and 0.01 to 0.07 mass% Ca and having excellent impact resistance can be obtained after casting. In the method for producing a TiAl alloy cast material of this embodiment, the Ca concentration in the total mass of the raw material 3 and the deoxidizer is set to 0.2 mass% or more, so that the effect of adding the deoxidizer is fully obtained and the oxygen content of the TiAl alloy cast material obtained after casting is 0.12 mass% or less. Also, the Ca concentration in the total mass of the raw material 3 and the deoxidizer is set to 1.0 mass% or less, so that the residual Ca content in the TiAl alloy cast material obtained after casting is 0.07 mass% or less.

[0059] The deoxidizer containing Ca may be added so that the Ca concentration in the total mass of the raw material 3 and the deoxidizer is 0.4% to 0.8% by mass. By setting the amount of the deoxidizer containing Ca within the above range and appropriately adjusting conditions such as the composition of the raw material 3 and the atmosphere, temperature, and time for heating the melted raw material 3a containing the deoxidizer, a TiAl alloy cast material containing 0.04% to 0.10% by mass of oxygen and 0.01% to 0.03% by mass of Ca after casting and having better impact resistance can be obtained. The deoxidizer containing Ca may be added so that the Ca concentration in the total mass of the raw material 3 and the deoxidizer is 0.55% to 0.65% by mass.

[0060] 2, a funnel-shaped mold 5 is placed on the furnace wall 1b of the atmospheric melting furnace 1 with its wider opening facing the oxide ceramic crucible 2 so as to cover the opening of the oxide ceramic crucible 2 (mold placement step). The wider opening of the funnel-shaped mold 5 functions as a sprue for pouring the molten raw material 3a into the funnel-shaped mold 5 in the casting step described below. It is preferable to use a funnel-shaped mold 5 whose internal volume is larger than the volume of the raw material 3.

[0061] The funnel-shaped mold 5 may be made of a known material used in producing TiAl alloy castings. Specifically, the funnel-shaped mold 5 may be a mold made of cast iron, carbon steel, or the like, having a two-part structure with the inner surface coated with a ceramic such as zircon to prevent reaction with the molten raw material 3a. While the present embodiment has been described using a mold as the funnel-shaped mold 5, lost-wax casting may also be performed using a ceramic mold made of alumina, silica, mullite, zirconia, or the like as the funnel-shaped mold 5. Lost-wax casting can produce a TiAl alloy casting material having a shape similar to that of the final product.

[0062] 2, it is preferable to install a simple sealant 6 made of cement or the like at the contact area between the funnel-shaped mold 5 and the furnace wall 1b of the atmospheric melting furnace 1. This prevents air from entering the oxide ceramic crucible 2 from the contact area between the funnel-shaped mold 5 and the furnace wall 1b of the atmospheric melting furnace 1.

[0063] Next, a gas supply pipe 7 is inserted through the narrower opening of the funnel-shaped mold 5, and Ar gas is supplied into the oxide ceramic crucible 2 through the gas supply pipe 7 (atmosphere replacement step). Ar gas is heavier than air. Therefore, when Ar gas is supplied into the oxide ceramic crucible 2, the Ar gas accumulates at the bottom of the oxide ceramic crucible 2, and the air is discharged through the funnel-shaped mold 5. As a result, the atmosphere inside the funnel-shaped mold 5 and the oxide ceramic crucible 2 is replaced with an Ar atmosphere, and it is possible to prevent the melted raw material 3a obtained by melting the raw material 3 from coming into contact with the air.

[0064] Thereafter, the oxide ceramic crucible 2 is heated using a high-frequency coil 4 installed in the atmospheric melting furnace 1, and the raw material 3 is melted to obtain a molten raw material 3a (heating step) as shown in Fig. 3. In this embodiment, even after the atmosphere inside the funnel-shaped mold 5 and the oxide ceramic crucible 2 has been replaced with an Ar atmosphere, it is preferable to continue supplying Ar gas into the oxide ceramic crucible 2 until immediately before the lid 5a is placed on the narrower opening of the funnel-shaped mold 5 (see Fig. 5). This effectively prevents oxygen from being mixed into the molten raw material 3a, thereby further reducing the oxygen content in the TiAl alloy cast material obtained after casting.

[0065] In the melting step of this embodiment, it is preferable to melt the raw material 3 while observing the interior of the oxide ceramic crucible 2 visually or with a camera through the narrower opening of the funnel-shaped mold 5. This makes it possible to confirm the state of melting of the raw material 3 and whether or not all of the raw material 3 has melted.

[0066] Next, in the melting step of this embodiment, as shown in FIG. 4, a funnel 8 is placed in the narrower opening of the funnel-shaped mold 5, and the remaining raw material 3 is added to the oxide ceramic crucible 2 in one or more batches through the funnel 8 and the funnel-shaped mold 5.

[0067] In the manufacturing method of the TiAl alloy cast material of this embodiment, a case has been described in which a portion of the raw materials 3 is placed in the oxide ceramic crucible 2 and melted to form a molten metal, and then the remaining raw materials 3 are added to the oxide ceramic crucible 2 in one or more divided batches, but it is also possible to place all of the raw materials 3 in the oxide ceramic crucible 2 and then melt the raw materials 3, or to place a portion of the raw materials 3 in the oxide ceramic crucible 2 and melt it while adding the remaining raw materials 3 in one or more divided batches to the oxide ceramic crucible 2. When the raw materials 3 are added to the oxide ceramic crucible 2 in multiple batches, different raw materials 3 may be added each time, or the same raw materials may be added in some of the multiple batches, or the same raw materials may be added each time, and this can be determined appropriately depending on the composition and shape of the raw materials 3, etc.

[0068] In the method for producing a TiAl alloy cast material of this embodiment, the entire amount of the Ca-containing deoxidizer is placed in the oxide ceramic crucible 2 together with the raw materials 3, but the Ca-containing deoxidizer may be added to the raw materials 3a (molten metal) placed in the oxide ceramic crucible 2 via the funnel-shaped mold 5. In the method for producing a TiAl alloy cast material of this embodiment, the Ca-containing deoxidizer may be added to the raw materials 3 and / or the raw materials 3a in multiple batches. That is, a portion of the Ca-containing deoxidizer may be placed in the oxide ceramic crucible 2 together with the raw materials 3, and the remaining Ca-containing deoxidizer may be added to the raw materials 3a placed in the oxide ceramic crucible 2 in one or multiple batches via the funnel-shaped mold 5.

[0069] [Deoxidation Step] In this embodiment, after confirming that all of the raw material 3 has been melted, in the deoxidation step, the raw material 3a containing a deoxidizer is heated and melted in an oxide ceramic crucible 2 whose opening is covered with a funnel-shaped mold 5, and the molten state is maintained. This homogenizes the components contained in the raw material 3a. At the same time, fumes containing reaction products of oxygen and Ca in the raw material 3a are generated and discharged through the funnel-shaped mold 5, thereby removing oxygen from the raw material 3a.

[0070] The time for which the deoxidizing material-containing melting raw material 3a is heated and held in a molten state is preferably 2 to 10 minutes, more preferably 3 to 5 minutes, after all of the raw materials 3 have been melted to form the deoxidizing material-containing melting raw material 3a. Holding the deoxidizing material-containing melting raw material 3a in a molten state for 2 minutes or longer allows the reaction between oxygen and Ca in the melting raw material 3a to proceed sufficiently. As a result, the generation of fumes containing reaction products of oxygen and Ca in the melting raw material 3a is promoted, further enhancing the effect of removing oxygen from the melting raw material 3a. Holding the deoxidizing material-containing melting raw material 3a in a molten state for 10 minutes or less allows the oxygen content in the TiAl alloy cast material obtained after casting to be reduced without impairing the productivity of the TiAl alloy cast material.

[0071] The temperature at which the melting raw material 3a containing the deoxidizer is heated and maintained in a molten state is preferably 1650°C to 1750°C, and more preferably 1675°C to 1725°C. If the temperature at which the melting raw material 3a containing the deoxidizer is maintained in a molten state is 1650°C or higher, the reaction between oxygen and Ca in the melting raw material 3a is promoted, and the generation of fumes containing reaction products is promoted, thereby making the effect of removing oxygen from the melting raw material 3a more pronounced. If the temperature at which the melting raw material 3a containing the deoxidizer is heated and maintained in a molten state is 1750°C or lower, the reaction between the oxide ceramic crucible 2 and the melting raw material 3a is suppressed, which is preferable.

[0072] In this embodiment, it is preferable to carry out the deoxidation step by heating the raw material 3 in the oxide ceramic crucible 2 using the high-frequency coil 4, melting the raw material 3 contained in the oxide ceramic crucible 2 to form the molten raw material 3a containing the deoxidizer, and then continuing to heat the molten raw material 3a to maintain the molten state of the molten raw material 3a. This allows for efficient production of a TiAl alloy casting material.

[0073] In this embodiment, after the deoxidation step, a lid 5a is placed on the narrower opening of the funnel-shaped mold 5, as shown in Fig. 5. The lid 5a may be made of, for example, cast iron or carbon steel, and its inner surface may be coated with ceramic such as zircon to prevent reaction with the molten raw materials 3a.

[0074] In this embodiment, as shown in Fig. 6, the atmospheric melting furnace 1 is then turned upside down with the oxide ceramic crucible 2 and the funnel-shaped mold 5 integrated, and the molten raw material 3a is poured from the oxide ceramic crucible 2 into the funnel-shaped mold 5 and cooled (casting step). This produces a TiAl alloy cast material 3b. As shown in Fig. 7, the TiAl alloy cast material 3b is then removed from the funnel-shaped mold 5 and cut into a product portion 3c consisting of a portion that will become a product and a reusable portion 3e consisting of a portion that will not become a product due to the formation of shrinkage cavities 3d. The reusable portion 3e is TiAl alloy casting scrap and can be reused as the raw material 3 for the TiAl alloy cast material 3b.

[0075] (Other Examples) The method for producing a TiAl alloy cast material according to this embodiment is not limited to the above-described embodiment. For example, in the above-described embodiment, an example of a method for producing a TiAl alloy cast material has been described using an apparatus including an oxide ceramic crucible 2 installed in an atmospheric melting furnace 1 as shown in Fig. 1, but a vacuum melting furnace may be used instead of the atmospheric melting furnace. A known vacuum melting furnace may be used, for example, a general vacuum induction melting furnace (VIM furnace).

[0076] When a vacuum melting furnace is used, the following method is preferably used. That is, in the deoxidizer addition step, the entire amount of the deoxidizer is placed in an oxide ceramic crucible installed in the vacuum melting furnace together with the raw materials. Then, the vacuum melting furnace is evacuated and Ar gas is supplied to replace the atmosphere inside the vacuum melting furnace with an Ar gas atmosphere. Then, in the melting step, the entire amount of the raw materials is melted in the oxide ceramic crucible installed in the vacuum melting furnace in the Ar atmosphere to obtain a molten metal.

[0077] When a vacuum melting furnace is used, it is preferable to melt the raw material 3 while observing the inside of the oxide ceramic crucible 2 through a quartz window installed in the vacuum induction melting furnace using a camera installed in the upper part of the vacuum induction melting furnace. This makes it possible to confirm the melting state of the raw material 3 and whether or not all of the raw material 3 has melted. Thereafter, in the deoxidation step, oxygen in the molten metal is removed by heating the molten metal containing the deoxidizer in the oxide ceramic crucible installed in the vacuum melting furnace in an Ar atmosphere and maintaining the molten state.

[0078] The method for producing a TiAl alloy cast material according to this embodiment includes the steps of: adding a deoxidizer containing Ca to either or both of a raw material 3 containing Ti, Al, and various additive elements and a melting raw material 3a obtained by melting the raw material 3, such that the Ca concentration in the total mass of the raw material 3 and the deoxidizer is 0.2 to 1.0 mass%; and deoxidizing the melting raw material 3a containing the deoxidizer by heating and maintaining the melting raw material 3a in a molten state to generate fumes containing a reaction product of Ca and oxygen in the melting raw material 3a. Therefore, the TiAl alloy cast material obtained by the casting step after the deoxidizing step contains 0.04 to 0.12 mass% oxygen and 0.01 to 0.07 mass% Ca and has excellent impact resistance.

[0079] Therefore, according to the method for producing a cast TiAl alloy material of this embodiment, a cast TiAl alloy material with a sufficiently low oxygen content can be obtained without using special equipment or special raw materials with a low oxygen content. Specifically, the method for producing a cast TiAl alloy material of this embodiment can use various equipment, such as an equipment equipped with an oxide ceramic crucible 2 installed in an atmospheric melting furnace 1 or a vacuum melting furnace, and various raw materials, such as TiAl alloy cutting chips and TiAl alloy casting scrap with a high oxygen content, without any restrictions.

[0080] [Cast TiAl Alloy] The cast TiAl alloy of this embodiment contains 0.04% to 0.10% by mass of oxygen and 0.01% to 0.03% by mass of Ca. Because the oxygen content is 0.10% by mass or less and the Ca content is 0.03% by mass or less, the cast TiAl alloy of this embodiment has excellent impact resistance. Furthermore, because the oxygen content is 0.04% by mass or more, the amount of Ca-containing deoxidizer used can be reduced when the cast TiAl alloy is produced using the method for producing the cast TiAl alloy of this embodiment. As a result, the Ca content in the cast TiAl alloy can be reduced to 0.03% by mass or less. Furthermore, because the Ca content is 0.01% by mass or more, the amount of Ca-containing deoxidizer available can be ensured when the cast TiAl alloy is produced using the method for producing the cast TiAl alloy of this embodiment, and the deoxidizing effect of adding the deoxidizer can be fully achieved. Therefore, various devices, such as a device equipped with an oxide ceramic crucible 2 installed in an atmospheric melting furnace 1 or a vacuum melting furnace, and various raw materials, such as TiAl alloy cutting chips and TiAl alloy casting scraps, can be used.

[0081] The TiAl alloy cast material of this embodiment may contain 31.9 to 34.2 mass% Al, 4.0 to 5.4 mass% Nb, 2.3 to 3.0 mass% Cr, 0.04 to 0.12 mass% oxygen, 0.01 to 0.07 mass% Ca, and the balance consisting of Ti and impurities. Such a TiAl alloy cast material has excellent impact resistance, as well as good machinability, tensile strength, and creep strength, and is therefore suitable for use as a material for jet engine blades and turbine wheels.

[0082] The TiAl alloy cast material of this embodiment may contain 32.9 to 33.8 mass% Al, 4.4 to 5.0 mass% Nb, 2.5 to 2.8 mass% Cr, 0.04 to 0.12 mass% oxygen, 0.01 to 0.07 mass% Ca, and the balance consisting of Ti and impurities. Such a TiAl alloy cast material has superior impact resistance, as well as superior machinability, tensile strength, and creep strength, making it particularly suitable as a material for jet engine blades and turbine wheels.

[0083] The TiAl alloy casting materials of this embodiment can be produced by using the above-mentioned method for producing the TiAl alloy casting materials of this embodiment, by appropriately changing conditions such as the composition of the raw material 3, the type and amount of the deoxidizer containing Ca, and the atmosphere, temperature, and time for heating the melted raw material 3a containing the deoxidizer.

[0084] [Jet engine rotor blade] [Turbine wheel] The jet engine rotor blade and turbine wheel of this embodiment are made of the Al alloy cast material of this embodiment. Therefore, they have excellent impact resistance. The jet engine rotor blade and turbine wheel of this embodiment can be manufactured by cutting the Al alloy cast material of this embodiment using, for example, a known method. TiAl alloy cutting chips generated when cutting the TiAl alloy cast material are casting scrap and can be reused as raw material 3 for TiAl alloy cast material 3b.

[0085] The above describes the embodiments of the present invention in detail, but each configuration and combination thereof in each embodiment is an example, and additions, omissions, substitutions, and other modifications of the configurations are possible within the scope that does not deviate from the spirit of the present invention.

[0086] Experimental Example 1 An atmospheric melting furnace 1 of the reversing furnace (rollover furnace) type shown in Figure 1 was used, and an oxide ceramic crucible 2 made of calcia was placed inside the atmospheric melting furnace 1. Metal element raw materials were prepared, consisting of titanium sponge (trade name: TST-1; manufactured by Toho Titanium Co., Ltd.), Al particles (pellets) (manufactured by Furuuchi Chemical Co., Ltd.), Nb flakes (manufactured by Rare Metallic Co., Ltd.), and Cr particles (manufactured by Furuuchi Chemical Co., Ltd.). In addition, an AlCa alloy with a Ca content of 5 mass% was prepared as a Ca-containing deoxidizer.

[0087] Each of the above metal element raw materials was weighed to obtain a raw material containing 33.4 mass% Al, 4.8 mass% Nb, 2.7 mass% Cr, with the remainder being Ti and impurities. A deoxidizer containing Ca was added to the raw material to obtain the deoxidizer-containing raw material of Experimental Example 1 containing 0.10 mass% Ca. That is, the Al content in the deoxidizer-containing raw material of Experimental Example 1 is the ratio of the total amount of Al particles contained in the deoxidizer-containing raw material and the amount of Al in the AlCa alloy. Then, 500 g of the deoxidizer-containing raw material of Experimental Example 1 was placed in an oxide ceramic crucible 2.

[0088] Next, as shown in Figure 2, the funnel-shaped mold 5 was placed on the furnace wall 1b of the atmospheric melting furnace 1 with the wider opening facing the oxide ceramic crucible 2 so as to cover the opening of the oxide ceramic crucible 2 (mold placement step). The funnel-shaped mold 5 was a mold made of carbon steel with a two-part structure whose inner surface was coated with zircon paint (trade name: Okapaint 308; manufactured by Okazaki Mining Products Co., Ltd.). Next, as shown in Figure 2, a sealing material 6 made of cement was placed at the contact area between the funnel-shaped mold 5 and the furnace wall 1b of the atmospheric melting furnace 1.

[0089] Next, a gas supply pipe 7 was inserted into the narrower opening of the funnel-shaped mold 5, and Ar gas was supplied into the oxide ceramic crucible 2 through the gas supply pipe 7 (atmosphere replacement step). The supply of Ar gas into the oxide ceramic crucible 2 was continued until just before the lid 5a was placed on the narrower opening of the funnel-shaped mold 5 (see FIG. 5). Thereafter, the oxide ceramic crucible 2 was heated using a high-frequency coil 4 installed in the atmospheric melting furnace 1, and the deoxidizer-containing raw material was melted to obtain a melted raw material 3a, as shown in FIG. 3 (heating step).

[0090] The interior of the oxide ceramic crucible 2 was observed using a camera through the narrower opening of the funnel-shaped mold 5, and it was confirmed that all of the deoxidizer-containing raw material had melted. The oxide ceramic crucible 2 was then continuously heated, and the molten state of the deoxidizer-containing molten raw material 3a after all of the deoxidizer-containing raw material had melted was maintained at 1700°C for 3 minutes (deoxidation step). Thereafter, as shown in Fig. 5, a lid 5a was placed on the narrower opening of the funnel-shaped mold 5. The lid 5a was made of carbon steel, the inner surface of which was coated with zircon paint (trade name: Okapaint 308, manufactured by Okazaki Mining Products Co., Ltd.).

[0091] 6, the funnel-shaped mold 5 and the atmospheric melting furnace 1 were integrated, and the furnace 1 was then turned upside down, and the raw material 3a was poured from the ceramic oxide crucible 2 into the funnel-shaped mold 5 and cooled (casting step). This resulted in a TiAl alloy cast material 3b of Experimental Example 1, which was a substantially cylindrical ingot having a diameter of 40 mm and a length of 100 mm.

[0092] "Experimental Examples 2 to 5" The same raw materials as in Experimental Example 1 were weighed out, and the same Ca-containing deoxidizer as in Experimental Example 1 was added to the raw materials to obtain deoxidizer-containing raw materials containing Ca in the amounts (addition amounts) shown in Table 1. Except for this, the same procedures as in Experimental Example 1 were carried out to obtain TiAl alloy cast materials 3b of Experimental Examples 2 to 5, which were approximately cylindrical ingots having a diameter of 40 mm and a length of 100 mm.

[0093] "Experimental Example 6" A TiAl alloy cast material 3b of Experimental Example 6, which was a substantially cylindrical ingot having a diameter of 40 mm and a length of 100 mm, was obtained in the same manner as Experimental Example 1, except that the raw material of Experimental Example 1 was used instead of the deoxidizer-containing raw material of Experimental Example 1.

[0094] Experimental Example 7: TiAl alloy cutting chips and TiAl alloy casting scrap were prepared, each having the same Ti, Al, Nb, and Cr contents as the raw material in Experimental Example 1. The TiAl alloy cutting chips were ultrasonically cleaned using acetone before use. The TiAl alloy casting scrap was surface-pickled before use.

[0095] Of the metal element raw materials used as the raw material for Experimental Example 1, 25 mass % was TiAl alloy cutting chips and 25 mass % was TiAl alloy casting scrap, which were used as the raw material for Experimental Example 7. A TiAl alloy cast material 3b for Experimental Example 7, which was a substantially cylindrical ingot having a diameter of 40 mm and a length of 100 mm, was obtained in the same manner as Experimental Example 1, except that the same Ca-containing deoxidizer as in Experimental Example 1 was added to the raw material for Experimental Example 7 to form a deoxidizer-containing raw material for Experimental Example 7 containing 0.10 mass % Ca.

[0096] "Experimental Examples 8 to 11" The same raw materials as in Experimental Example 7 were weighed, and the same Ca-containing deoxidizer as in Experimental Example 1 was added to the raw materials to obtain deoxidizer-containing raw materials containing Ca in the amounts (addition amounts) shown in Table 1. Except for this, the same procedures as in Experimental Example 7 were carried out to obtain TiAl alloy cast materials 3b of Experimental Examples 8 to 11, which were approximately cylindrical ingots having a diameter of 40 mm and a length of 100 mm.

[0097] "Experimental Example 12" A TiAl alloy cast material 3b of Experimental Example 12, which was a substantially cylindrical ingot having a diameter of 40 mm and a length of 100 mm, was obtained in the same manner as Experimental Example 7, except that the raw material of Experimental Example 7 was used instead of the deoxidizer-containing raw material of Experimental Example 7.

[0098] Experimental Example 13 A vacuum induction melting furnace (VIM furnace) was used instead of the atmospheric melting furnace 1 shown in Fig. 1, and an oxide ceramic crucible 2 made of calcia similar to that of Experimental Example 1 was placed in the vacuum induction melting furnace. Then, 500 g of the deoxidizer-containing raw material of Experimental Example 1 was placed in the oxide ceramic crucible 2 in the same manner as in Experimental Example 1.

[0099] Next, the vacuum melting furnace was evacuated and Ar gas was supplied to replace the atmosphere inside the vacuum melting furnace. Subsequently, an induction heating device installed in the vacuum induction melting furnace was used to heat and melt the deoxidizer-containing raw material in the oxide ceramic crucible 2 to obtain the melted raw material 3a (heating step). A camera installed above the vacuum induction melting furnace was used to observe the interior of the oxide ceramic crucible 2 through a quartz window installed in the vacuum induction melting furnace, and it was confirmed that all of the deoxidizer-containing raw material had melted. The oxide ceramic crucible 2 was then continuously heated, and the molten state of the melted raw material 3a containing the deoxidizer after all of the deoxidizer-containing raw material had melted was maintained at 1700°C for 3 minutes (deoxidation step).

[0100] Thereafter, the raw material 3a was poured from the oxide ceramic crucible 2 into a mold having a cylindrical inner surface and placed in a vacuum melting furnace, and cooled (casting step), thereby obtaining a TiAl alloy cast material 3b of Experimental Example 13, which was a substantially cylindrical ingot having a diameter of 40 mm and a length of 100 mm.

[0101] "Experimental Examples 14 to 17" The same raw materials as in Experimental Example 1 were weighed out, and the same Ca-containing deoxidizer as in Experimental Example 1 was added to the raw materials to obtain deoxidizer-containing raw materials containing Ca in the amounts (addition amounts) shown in Table 2. Except for this, the same procedures as in Experimental Example 13 were carried out to obtain TiAl alloy cast materials 3b of Experimental Examples 14 to 17, which were approximately cylindrical ingots having a diameter of 40 mm and a length of 100 mm.

[0102] "Experimental Example 18" A TiAl alloy cast material 3b of Experimental Example 18, which was a substantially cylindrical ingot having a diameter of 40 mm and a length of 100 mm, was obtained in the same manner as Experimental Example 13, except that the raw material of Experimental Example 1 was used instead of the deoxidizer-containing raw material of Experimental Example 1.

[0103] "Experimental Example 19" A TiAl alloy cast material 3b of Experimental Example 19, which was a substantially cylindrical ingot having a diameter of 40 mm and a length of 100 mm, was obtained in the same manner as in Experimental Example 13, except that the deoxidizer-containing raw material of Experimental Example 7 was used.

[0104] "Experimental Examples 20 to 23" The same raw materials as in Experimental Example 7 were weighed, and the same Ca-containing deoxidizer as in Experimental Example 1 was added to the raw materials to obtain deoxidizer-containing raw materials containing Ca in the amounts (addition amounts) shown in Table 2. Except for this, the same procedures as in Experimental Example 13 were carried out to obtain TiAl alloy cast materials 3b of Experimental Examples 20 to 23, which were approximately cylindrical ingots having a diameter of 40 mm and a length of 100 mm.

[0105] "Experimental Example 24" A TiAl alloy cast material 3b of Experimental Example 24, which was a substantially cylindrical ingot having a diameter of 40 mm and a length of 100 mm, was obtained in the same manner as in Experimental Example 13, except that the raw material of Experimental Example 7 was used instead of the deoxidizer-containing raw material of Experimental Example 7.

[0106] Tables 1 and 2 show the type of melting furnace used in the production of the TiAl alloy cast materials of Experimental Examples 1 to 24, the material of the crucible, the atmosphere in the crucible while heating the crucible, the amount of Ca added (Ca concentration in the deoxidizer-containing raw material), the amount of TiAl alloy cutting chips added (the content in the deoxidizer-containing raw material excluding the deoxidizer), and the amount of TiAl alloy casting scrap added (the content in the deoxidizer-containing raw material excluding the deoxidizer) for the TiAl alloy cast materials of Experimental Examples 1 to 24. Tables 1 and 2 also show the classification of the TiAl alloy cast materials of Experimental Examples 1 to 24 as invention examples and comparative examples.

[0107] [Measurement of oxygen content and Ca content] The TiAl alloy cast materials 3b of Experimental Examples 1 to 24 obtained in this manner were analyzed using an infrared absorption apparatus (product name: EMGA-930; manufactured by HORIBA) to determine the oxygen content. The TiAl alloy cast materials 3b of Experimental Examples 1 to 24 were also analyzed using a high-frequency inductively coupled plasma (ICP) optical emission spectrometer (product name: ICP-OES; manufactured by HORIBA) to determine the Ca content. The results are shown in Tables 1 and 2.

[0108] [Charpy Impact Test] The TiAl alloy cast materials 3b of Experimental Examples 1 to 24 were each subjected to a heat treatment at 1200°C for 4 hours. These heat treatment conditions are those typically used in hot isostatic pressing (HIP) for manufacturing jet engine blades made of TiAl alloys. Subsequently, a 55 mm long test piece with a square cross section measuring 10 mm long and 10 mm wide was taken from the center of each TiAl alloy cast material 3b, and a Charpy impact test was performed at room temperature. The results are shown in Tables 1 and 2.

[0109] In the Charpy impact test, a small testing machine with a capacity of 7.5 J (product name: mpact tester; manufactured by Toyo Seiki Co., Ltd.) was used to reduce measurement error. Furthermore, if notches were made in the test specimens, the impact values ​​of all experimental examples would be very small, making it difficult to clearly evaluate the differences between the individual experimental examples. For this reason, notches were not made in the test specimens.

[0110] (Evaluation Criteria Value) The Charpy impact values ​​of the TiAl alloy cast materials 3b of Experimental Examples 1 to 24 were 2.0 J / cm ２ The evaluation standard values ​​for the Charpy impact value of the TiAl alloy cast material were determined based on the test results shown below.

[0111] A conventional TiAl alloy casting material for use in jet engine blades was produced by the following method: A raw material consisting of 33.4 mass% Al, 4.8 mass% Nb, 2.7 mass% Cr, 0.08 mass% oxygen, and the remainder Ti and impurities was melted using a water-cooled copper crucible installed in a vacuum melting furnace under a vacuum atmosphere, and the melt was poured into the same mold as in Experimental Example 13, which was also installed in the vacuum melting furnace, and cooled. In this manner, three TiAl alloy casting materials for evaluation were produced, each being a roughly cylindrical ingot with a diameter of 40 mm and a length of 100 mm.

[0112] The three resulting cast TiAl alloys for evaluation were subjected to a Charpy impact test in the same manner as in Experimental Example 1. As a result, the Charpy impact value was 2.0 J / cm ２ ~2.5 J / cm ２From this, it can be seen that the Charpy impact value of the TiAl alloy cast material was within the range of 2.0 J / cm ２ If the Charpy impact strength is equal to or greater than 2.0 J / cm, it can be evaluated that the cast TiAl alloy has impact resistance properties equivalent to those of conventional cast TiAl alloys used for jet engine blades. ２ That's all.

[0113]

[0114]

[0115] As shown in Tables 1 and 2, the TiAl alloy cast materials of the invention, to which a deoxidizer was added so that the Ca concentration in the total mass of the raw material and the deoxidizer was 0.2 to 1.0 mass%, all had an oxygen content of 0.12 mass% or less, which is the specified value (company specification), and a Ca content within the range of 0.01 to 0.07 mass%. Furthermore, the Charpy impact values ​​of all of the TiAl alloy cast materials of the invention were above the evaluation standard value of 2.0 J / cm. ２ From the above, it was confirmed that the impact resistance was equal to or greater than that of conventional TiAl alloy cast materials used for jet engine rotor blades.

[0116] From this, it was confirmed that by using raw materials whose oxygen content is within the range of 0.175 mass% to 0.284 mass% in TiAl alloy casting materials (Experimental Examples 6, 12, 18, and 24) produced without adding a deoxidizer, and by using a manufacturing method that differs only in that a deoxidizer is added so that the Ca concentration in the total mass of the raw materials and the deoxidizer is 0.2 mass% to 1.0 mass%, it is possible to obtain TiAl alloy casting materials containing 0.04 mass% to 0.10 mass% oxygen and 0.01 mass% to 0.03 mass% Ca.

[0117] Furthermore, from the results of Experimental Examples 1 to 24, it was confirmed that by adding a deoxidizer so that the Ca concentration in the total mass of the raw materials and the deoxidizer is 0.2 mass % to 1.0 mass %, it is possible to use a variety of devices and raw materials, such as a production method using an apparatus equipped with an oxide ceramic crucible 2 installed in an atmospheric melting furnace 1 and maintaining an Ar reflux atmosphere inside the crucible while the crucible is being heated, a production method using an apparatus equipped with an oxide ceramic crucible 2 installed in a vacuum melting furnace and maintaining an Ar atmosphere inside the crucible while the crucible is being heated, and a method using raw materials including TiAl alloy cutting chips and TiAl alloy casting scrap.

[0118] More specifically, in Experimental Examples 1 and 13, the Ca concentration in the total mass of the raw material and the deoxidizer was 0.1 wt %, so the deoxidizing effect of Ca was insufficient and the oxygen content exceeded the specified value. As a result, the Charpy impact value was 2.0 J / cm, which was the evaluation standard value. ２ In Experimental Examples 5 and 17, the Ca concentration in the total mass of the raw material and the deoxidizer was 1.1 wt %, so the oxygen concentration was low but the Ca content was high. As a result, the Charpy impact value was less than the evaluation standard value of 2.0 J / cm ２ The value was less than

[0119] In Experimental Examples 7 and 19, which used raw materials containing TiAl alloy cutting chips and TiAl alloy casting scrap, the Ca concentration in the total mass of the raw materials and the deoxidizer was 0.1 wt %, similar to Example 1 and Experimental Example 13, so the deoxidizing effect of Ca was insufficient and the oxygen content exceeded the specified value. As a result, the Charpy impact value was 2.0 J / cm, which was the evaluation standard value. ２ The value was less than

[0120] In Experimental Examples 11 and 23, which used raw materials containing TiAl alloy cutting chips and TiAl alloy casting scrap, the Ca concentration in the total mass of the raw materials and deoxidizer was 1.1 wt %, similar to Experimental Examples 5 and 17. Therefore, although the oxygen concentration was low, the Ca content was high. As a result, the Charpy impact value was 2.0 J / cm, which was the evaluation standard value. ２ The value was less than

[0121] A TiAl alloy casting material with a sufficiently low oxygen content can be obtained without using special equipment or special materials.

[0122] REFERENCE SIGNS LIST 1 atmospheric melting furnace 1a container 1b furnace wall 2 oxide ceramic crucible 3 raw material 3a melting raw material 3b TiAl alloy casting material 3c product portion 3d shrinkage cavity 3e reuse portion 4 high frequency coil 5 funnel-shaped mold 5a lid 6 sealing material 7 gas supply pipe 8 funnel

Claims

1. A melting step of melting a raw material containing Ti and Al to obtain a molten metal; a deoxidizing material adding step of adding a deoxidizing material containing Ca to either one or both of the raw material and the molten metal, the deoxidizing material being added so that a Ca concentration in a total mass of the raw material and the deoxidizing material is 0.2 mass% to 1.0 mass%; a deoxidization process for removing oxygen from the molten metal by heating the molten metal containing the deoxidizing material and maintaining the molten state to generate fumes containing a reaction product of the oxygen in the molten metal and Ca.

2. 2. The method for producing a TiAl alloy casting material according to claim 1, wherein the deoxidizer is an AlCa alloy.

3. The melting step is a step of melting the raw material in an oxide ceramic crucible, the deoxidizing material adding step is either or both of a step of putting the deoxidizing material into the oxide ceramic crucible together with the raw material and a step of adding the deoxidizing material to the molten metal put in the oxide ceramic crucible; 3. The method for producing a TiAl alloy casting material according to claim 1, wherein in the deoxidizing step, the molten metal containing the deoxidizing material placed in the oxide ceramic crucible is heated and melted.

4. The deoxidizing material adding step is a step of putting the deoxidizing material together with the raw material into an oxide ceramic crucible installed in a vacuum melting furnace, the melting step is a step of melting the raw material in the oxide ceramic crucible installed in the vacuum melting furnace in an Ar atmosphere after the deoxidizing material adding step, 3. The method for producing a TiAl alloy casting material according to claim 1, characterized in that in the deoxidization process, the molten metal containing the deoxidizer is heated and melted in the oxide ceramic crucible installed in the vacuum melting furnace in an Ar atmosphere.

5. The oxide ceramic crucible is placed in an atmospheric melting furnace having an air atmosphere; The melting step includes a mold setting step of setting a funnel-shaped mold so that a wider opening of the funnel-shaped mold faces the oxide ceramic crucible so as to cover the opening of the oxide ceramic crucible, an atmosphere replacement step of supplying Ar gas into the oxide ceramic crucible, and a heating step of heating the oxide ceramic crucible, the deoxidizing material adding step is either or both of a step of putting the deoxidizing material into the oxide ceramic crucible together with the raw material and a step of adding the deoxidizing material to the molten metal put in the oxide ceramic crucible through the funnel-shaped mold; In the deoxidization step, the molten metal containing the deoxidizing material is heated and melted in the oxide ceramic crucible, the opening of which is covered by the funnel-shaped mold, and the fumes in the oxide ceramic crucible are discharged through the funnel-shaped mold; 4. The method for producing a TiAl alloy casting material according to claim 3, further comprising the steps of: after the deoxidation step, turning the atmospheric melting furnace upside down while the oxide ceramic crucible and the funnel-shaped mold are integrated together; and pouring the molten metal from the oxide ceramic crucible into the funnel-shaped mold and cooling the molten metal.

6. 3. The method for producing a TiAl alloy casting material according to claim 1, wherein the raw material contains either one or both of TiAl alloy cutting chips and TiAl alloy casting scrap.

7. A TiAl alloy casting material containing 0.04% by mass to 0.10% by mass of oxygen and 0.01% by mass to 0.03% by mass of Ca.

8. A TiAl alloy casting material comprising 31.9% by mass to 34.2% by mass of Al, 4.0% by mass to 5.4% by mass of Nb, 2.3% by mass to 3.0% by mass of Cr, 0.04% by mass to 0.12% by mass of oxygen, 0.01% by mass to 0.07% by mass of Ca, and the balance being Ti and impurities.

9. A jet engine rotor blade, comprising the TiAl alloy cast material according to claim 7 or 8.

10. A turbine wheel, comprising the TiAl alloy cast material according to claim 7 or 8.