Gamma-TiAl alloy cast ingot containing high-melting-point alloy elements and VAR preparation method of gamma-TiAl alloy cast ingot

Abstract

The invention belongs to the technical field of gamma-TiAl alloy cast ingot preparation, and relates to a gamma-TiAl alloy cast ingot containing high-melting-point alloy elements and a VAR preparation method of the gamma-TiAl alloy cast ingot, and the VAR preparation method specifically comprises the following steps: step 1, determining the components of a pre-alloy electrode bar according to the target components of the gamma-TiAl alloy cast ingot, and determining the size of the pre-alloy electrode bar and the size of a matched aluminum pipe; 2, a pre-alloyed cast ingot is prepared through a VAR smelting method; step 3, processing the pre-alloyed cast ingot into a pre-alloyed electrode bar; step 4, assembling the pre-alloyed electrode bar and an aluminum tube to obtain a composite electrode; and 5, the composite electrode is smelted through a VAR smelting method, and the gamma-TiAl alloy cast ingot is prepared. According to the method, the problems that an existing gamma-TiAl alloy ingot containing high-melting-point alloy elements is difficult to prepare, high in cost, low in production efficiency and the like can be solved, and the prepared ingot is uniform in component and free of any infusible substance.

Description

Technical Field

[0001] This invention belongs to the field of γ-TiAl alloy ingot preparation technology, and relates to a γ-TiAl alloy ingot containing high melting point alloying elements and its VAR preparation method, which is particularly suitable for the production and preparation of γ-TiAl alloy ingots required in fields such as precision casting and bar stock preparation. Background Technology

[0002] γ-TiAl alloy is a lightweight high-temperature structural material with high specific strength, high specific stiffness, high creep resistance, and high oxidation resistance. Within the service temperature range of 650℃ to 900℃, it is replacing high-temperature alloys in the aerospace field to reduce the weight of components due to its near-high-temperature alloy performance and low density. It has been successfully applied to the low-pressure turbine blades of many types of internationally advanced aero engines.

[0003] With the gradual application of γ-TiAl alloys, their alloy composition has been continuously optimized. New alloys incorporate high-melting-point elements such as Nb, Mo, Ta, and W to improve their room temperature and high-temperature performance. However, the addition of these high-melting-point elements presents challenges for alloy ingot casting. The melting point of γ-TiAl alloys is between 1450 and 1550°C, lower than that of pure titanium and other elements. Using the VAR method to prepare ingots easily leads to the formation of infusible materials. High-melting-point elements such as Nb, Mo, Ta, and W are often processed through aluminum-containing master alloys, whose melting points are close to those of pure titanium. This results in the formation of high-melting-point ingots using the VAR method for γ-TiAl alloys containing master alloys with these high-melting-point elements, resulting in high-density inclusions in the master alloy. This is a serious quality problem in ingots. Currently, the preparation of γ-TiAl alloy ingots containing high-melting-point elements often employs induction solidification melting (i.e., suspension melting), which can produce ingots free of HTi and master alloy infusible materials. However, induction melting equipment is expensive, and the maximum mass of a single melt is only 114 kg (based on TC4 alloy). This results in high costs and low production efficiency for ingots prepared using this method, severely hindering the industrial production of γ-TiAl alloy ingots containing high-melting-point alloying elements. VAR melting technology, on the other hand, is a commonly used method for producing ordinary titanium alloys. It has advantages such as mature equipment technology, a large number of existing equipment, and high production efficiency. If the problems of HTi and intermediate alloy infusibles in the VAR melting process for preparing γ-TiAl alloy ingots containing high-melting-point alloying elements can be overcome, it will facilitate the efficient and low-cost industrial production of this alloy ingot product, promoting the further application of the alloy.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a γ-TiAl alloy ingot containing high melting point alloying elements and its VAR preparation method, so as to solve the problems of difficult preparation, high cost and low production efficiency of existing γ-TiAl alloy ingots containing high melting point alloying elements.

[0006] To achieve the above objectives, the present invention provides the following technical solution: On the one hand, see Figure 1 As shown, this invention provides a method for preparing γ-TiAl alloy ingots containing high-melting-point alloying elements using VAR, specifically including the following steps: Step 1: Determine the composition of the pre-alloyed electrode rod based on the target composition of the γ-TiAl alloy ingot, and determine the size of the pre-alloyed electrode rod and the size of the matching aluminum tube. Step 2: Prepare pre-alloyed ingots using the VAR melting method; Step 3: Process the pre-alloyed ingot into a pre-alloyed electrode rod; Step 4: Assemble the pre-alloyed electrode rod with the aluminum tube to obtain a composite electrode; Step 5: The composite electrode is smelted using the VAR melting method to obtain a γ-TiAl alloy ingot.

[0007] Specifically, the process of determining the composition of the pre-alloyed electrode based on the target composition of the γ-TiAl alloy ingot in step 1 is as follows: The target composition of the γ-TiAl alloy ingot is defined as follows: In terms of mass percentage: It is at least one element selected from Nb, Mo, W, and Ta; Other elements in the γ-TiAl alloy ingot besides Ti, Al, Nb, Mo, W, and Ta; The composition ratio of the pre-alloyed electrode rod is: In terms of mass percentage: of which, The outer diameter of the aluminum tube. The outer diameter of the pre-alloyed electrode rod. The density of the aluminum tube, The density of the pre-alloyed electrode rod is 4.4~5.0 g / cm³. 3 , , , represents the compensation coefficients for each element in the pre-alloyed electrode rod.

[0008] Specifically, in step 1, the dimensions of the pre-alloyed electrode rod are as follows: diameter Φ70~Φ80mm, length 2000~2500mm.

[0009] Furthermore, in step 1, the length of the aluminum tube is 50-150 mm shorter than the length of the pre-alloyed electrode rod, the inner diameter of the aluminum tube is greater than or equal to the diameter of the pre-alloyed electrode rod used in conjunction with it, the outer diameter is Φ90-Φ110 mm, and the length is 2000-2500 mm.

[0010] Specifically, the relevant parameters for preparing the pre-alloyed ingot using the VAR melting method in step 2 are as follows: The melting process is repeated 2 to 3 times. The vacuum degree before melting is ≤1Pa, the air leakage rate during melting is ≤1Pa / min, the melting current is 5 to 15kA, the melting voltage is 25 to 35V, and the diameter of the resulting pre-alloyed ingot is 440 to 560mm.

[0011] Specifically, the process of machining the pre-alloyed ingot into a pre-alloyed electrode rod in step 3 is as follows: First, the pre-alloyed ingot is forged using a free forging machine at T... β ~T β Bars with diameters of Φ100~Φ180mm are drawn in a temperature range of +150℃, and then rolled using a two-roll mill at T... β ~T β The bar stock is rolled into a pre-finished product at a temperature range of +150℃, with a diameter larger than the target finished product diameter. A total machining allowance of 3~5mm is reserved. Finally, the surface of the bar stock is machined and processed until its diameter and length meet the requirements of the target design dimensions.

[0012] Specifically, in step 4, the pre-alloyed electrode rod is assembled with the aluminum tube to obtain a composite electrode. The specific assembly process is as follows: First, thoroughly clean the outer surface of the pre-alloyed electrode rod and the inner and outer surfaces of the matching aluminum tube. Then, insert the pre-alloyed electrode rod into the aluminum tube, ensuring the bottom of the pre-alloyed electrode rod is flush with the lower end of the aluminum tube, and the upper end of the pre-alloyed electrode rod protrudes from the aluminum tube. Finally, simultaneously machine through holes in the aluminum tube and the pre-alloyed electrode rod at a position 100-150mm from the upper end of the aluminum tube. Use pins made of the same material as the pre-alloyed electrode rod to fix the pre-alloyed electrode rod and the aluminum tube, thus forming a composite electrode. When assembling the composite electrode, use in-furnace welding to weld the exposed pre-alloyed electrode rod at the upper end of the composite electrode to the auxiliary electrode used for VAR melting, and then perform VAR melting.

[0013] Specifically, the melting process parameters of the composite electrode in step 5 are as follows: The melting process is carried out in 3 stages. The vacuum degree before melting is ≤0.8Pa, the leakage rate during melting is ≤0.8Pa / min, the melting current is 2~5kA, and the melting voltage is 26~34V.

[0014] Specifically, high-melting-point alloying elements include one or more of Nb, Mo, W, and Ta.

[0015] On the other hand, the present invention also provides a γ-TiAl alloy ingot containing high melting point alloying elements, wherein the γ-TiAl alloy ingot is prepared by some or all of the preparation methods described above, and the diameter of the γ-TiAl alloy ingot is Φ280~Φ320mm.

[0016] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: 1) This invention addresses the problem of unmelted HTi and master alloy in γ-TiAl alloy ingots containing high-melting-point alloying elements during VAR melting. Drawing on successful experience with high-melting-point element titanium alloys, a step-by-step alloying method is proposed: first, HTi with similar melting points is alloyed with a high-melting-point element master alloy during the pre-alloying ingot melting stage; then, aluminum and other elements are added during the γ-TiAl alloy ingot melting stage. This avoids mutual interference when high and low melting-point elements are alloyed simultaneously, fundamentally eliminating the formation of high-melting-point unmelted matter. This effectively solves the problem of unmelted matter in γ-TiAl ingots containing high-melting-point alloying elements prepared using VAR, thereby improving the melting uniformity of γ-TiAl ingots containing high-melting-point alloying elements.

[0017] 2) This invention innovatively designs a composite electrode structure of "pre-alloyed electrode rod + peripheral aluminum tube". This structure places the pre-alloyed electrode rod at the center, with the aluminum tube located outside the pre-alloyed electrode rod. Utilizing the characteristic of the electric arc concentrating at the core of the composite electrode during VAR melting, orderly melting of the pre-alloyed electrode rod and the aluminum tube is achieved during melting. Furthermore, the composite electrode uses mechanical pins to connect the aluminum tube and the pre-alloyed electrode rod, replacing the easily cracked dissimilar metal welding method, resulting in reliable connection and simple assembly. Simultaneously, by designing the upper pre-alloyed electrode rod to be longer than the aluminum tube, it facilitates welding and fixing to the auxiliary electrode, further improving the overall integrity of the electrode and the stability of the melting process. Attached Figure Description

[0018] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A flowchart of a VAR preparation method for γ-TiAl alloy ingots containing high melting point alloying elements provided by the present invention; Figure 2 This is an X-ray inspection result of the γ-TiAl alloy ingot prepared in Example 1 of the present invention; Figure 3 This is an X-ray inspection result of the γ-TiAl alloy ingot prepared in Example 2 of the present invention; Figure 4 This is an X-ray inspection result of the γ-TiAl alloy ingot prepared in Example 3 of the present invention; Figure 5 This is a schematic diagram of the composite electrode structure in this invention. Detailed Implementation

[0021] Exemplary embodiments will now be described in detail. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples consistent with some aspects of the invention as detailed in the appended claims.

[0022] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0023] Example 1 This embodiment provides an alloy ingot with a nominal composition of Ti-28.6Al-9Nb-2.4Mo-0.03B (mass fraction, %). The high-melting-point alloying elements in this alloy ingot include Nb and Mo. The VAR preparation method specifically includes the following steps: Step 1: Determine the composition of the pre-alloyed electrode rod based on the nominal composition of the γ-TiAl alloy ingot, and determine the dimensions of the pre-alloyed electrode rod and the matching aluminum tube; specifically: The pre-alloyed electrode rod is designed with a diameter of 75mm and a length of 2500mm, and the matching aluminum tube has an outer diameter of 90mm, an inner diameter of 75mm, and a length of 2400mm. The target composition of the γ-TiAl alloy ingot is: Ti-28.6Al-9Nb-2.4Mo-0.03B, i.e. For Nb and Mo elements; For element B; The composition ratio of the pre-alloyed electrode rod is: ,in, The outer diameter of the aluminum tube is 90mm. The outer diameter of the pre-alloyed electrode rod is 75 mm. The density of the aluminum tube is taken as 2.7 g / cm³. 3 , The density of the pre-alloyed electrode rod is 4.4~5.0 g / cm³. 3 , , , This represents the compensation coefficient for the influence of environmental factors, process conditions, etc., on the various elements in the pre-alloyed electrode rod. In this embodiment, , , The values ​​were 0.43 (Al), -0.05 (Nb), -0.02 (Mo), and 0.005 (B), respectively.

[0024] After calculation using the above formula, the composition ratio of the pre-alloyed electrode rod is Ti-9.75Al-11.38Nb-3.03Mo-0.04B (mass fraction, %).

[0025] Step 2: Prepare pre-alloyed ingots using the VAR melting method, with the following parameters: The melting process was carried out twice. Before the first melting, the vacuum degree was 0.8 Pa, the leakage rate during melting was 0.5 Pa / min, the melting current was 8.5 kA, and the melting voltage was 27.5 V. Before the second melting, the vacuum degree was 0.5 Pa, the leakage rate during melting was 0.3 Pa / min, the melting current was 9.5 kA, and the melting voltage was 28.5 V. The diameter of the pre-alloyed ingot was Φ440 mm.

[0026] Step 3: Process the pre-alloyed ingot into a pre-alloyed electrode rod. The specific process is as follows: The T value of the pre-alloyed material was measured. β The phase transformation point is 965℃. First, the pre-alloyed ingot is drawn at 1000℃ using a free forging machine to obtain a Φ100mm bar billet. Then, the bar is rolled at 1050℃ using a two-roll mill to obtain a Φ78mm bar. Finally, the bar is sized and its surface is machined using a machining method until its diameter and length meet the target design size requirements, i.e., Φ75mm×2500mm.

[0027] Step 4: Assemble the pre-alloyed electrode rod with the aluminum tube to obtain the composite electrode. The specific assembly process is as follows: First, thoroughly clean the outer surface of the pre-alloyed electrode rod and the inner and outer surfaces of the matching aluminum tube. Then, insert the pre-alloyed electrode rod into the aluminum tube, ensuring the bottom of the pre-alloyed electrode rod is flush with the lower end of the aluminum tube, leaving the upper end of the pre-alloyed electrode rod protruding from the aluminum tube. Finally, simultaneously machine through holes in both the aluminum tube and the pre-alloyed electrode rod at a position 100mm from the upper end of the aluminum tube. Use pins made of the same material as the pre-alloyed electrode rod to fix the pre-alloyed electrode rod and the aluminum tube, thus forming a composite electrode. See [link to documentation]. Figure 5 After welding the auxiliary electrode and the composite electrode using an in-furnace welding method, the composite electrode is then subjected to VAR melting.

[0028] Step 5: The composite electrode is smelted using the VAR melting method to obtain a γ-TiAl alloy ingot. The relevant process parameters are as follows: The melting process was repeated three times. The first melting process involved a vacuum of 0.72 Pa, a leakage rate of 0.62 Pa / min, a melting current of 2.8 kA, and a melting voltage of 28.5 V. The second melting process involved a vacuum of 0.65 Pa, a leakage rate of 0.51 Pa / min, a melting current of 3.2 kA, and a melting voltage of 29.0 V. The third melting process involved a vacuum of 0.53 Pa, a leakage rate of 0.31 Pa / min, a melting current of 3.5 kA, and a melting voltage of 30.0 V. The resulting γ-TiAl alloy ingot had a diameter of Φ320 mm. (See [reference needed]). Figure 2 As shown in Table 1 below, the ingot has a uniform composition and contains no unmeltable material.

[0029] Table 1. Compositional uniformity of γ-TiAl alloy ingots (wt.%) .

[0030] Example 2 This embodiment provides an alloy ingot with a nominal composition of Ti-31.28Al-4.49Nb-8.74Ta (mass fraction, %). The high-melting-point alloying elements in this alloy ingot include Nb and Ta. The VAR preparation method specifically includes the following steps: Step 1: Determine the composition of the pre-alloyed electrode rod based on the nominal composition of the γ-TiAl alloy ingot, and determine the dimensions of the pre-alloyed electrode rod and the matching aluminum tube; specifically: The pre-alloyed electrode rod is designed to have a diameter of 70 mm and a length of 2150 mm, and the matching aluminum tube has an outer diameter of 90 mm, an inner diameter of 70 mm, and a length of 2000 mm. The target composition of the γ-TiAl alloy ingot is: Ti-31.28Al-4.49Nb-8.74Ta, i.e. For Nb and Ta elements; After calculation using the above formula, where, Take +0.54, By taking -0.03 (Nb) and -0.07 (Ta) respectively, the composition ratio of the pre-alloyed electrode rod can be obtained as Ti-6.04Al-6.14Nb-11.95Ta.

[0031] Step 2: Prepare pre-alloyed ingots using the VAR melting method, with the following parameters: The melting process was carried out in three stages. The first melting stage involved a vacuum of 0.86 Pa, a leakage rate of 0.71 Pa / min, a melting current of 13.5 kA, and a melting voltage of 33.5 V. The second melting stage involved a vacuum of 0.72 Pa, a leakage rate of 0.53 Pa / min, a melting current of 14.2 kA, and a melting voltage of 34.5 V. The third melting stage involved a vacuum of 0.45 Pa, a leakage rate of 0.31 Pa / min, a melting current of 15.0 kA, and a melting voltage of 35.0 V. The resulting pre-alloyed ingot had a diameter of Φ520 mm.

[0032] Step 3: Process the pre-alloyed ingot into a pre-alloyed electrode rod. The specific process is as follows: The T value of the pre-alloyed material was measured. β The phase transformation point is 925℃. First, the pre-alloyed ingot is drawn at 1000℃ using a free forging machine to obtain a Φ140mm bar billet. Then, the bar is rolled at 1050℃ using a two-roll mill to obtain a Φ74mm bar. Finally, the bar is sized and its surface is machined using a machining method until its diameter and length meet the target design size requirements, i.e., Φ70mm×2150mm.

[0033] Step 4: Assemble the pre-alloyed electrode rod with the aluminum tube to obtain the composite electrode. The specific assembly process is as follows: First, clean the outer surface of the pre-alloyed electrode rod and the inner and outer surfaces of the matching aluminum tube. Then, insert the pre-alloyed electrode rod into the aluminum tube, making the bottom of the pre-alloyed electrode rod flush with the bottom of the aluminum tube, and expose the top of the pre-alloyed electrode rod from the aluminum tube. Finally, machine through holes simultaneously on the aluminum tube and the pre-alloyed electrode rod at a position 150mm from the top of the aluminum tube. Use pins made of the same material as the pre-alloyed electrode rod to fix the pre-alloyed electrode rod and the aluminum tube together to form a composite electrode. After welding the auxiliary electrode and the composite electrode using an in-furnace welding method, perform VAR melting on the composite electrode.

[0034] Step 5: The composite electrode is smelted using the VAR melting method to obtain a γ-TiAl alloy ingot. The relevant process parameters are as follows: The melting process was repeated three times. The first melting process involved a vacuum level of 0.67 Pa, a leakage rate of 0.53 Pa / min, a melting current of 3.7 kA, and a melting voltage of 29.5 V. The second melting process involved a vacuum level of 0.69 Pa, a leakage rate of 0.51 Pa / min, a melting current of 4.5 kA, and a melting voltage of 31.5 V. The third melting process involved a vacuum level of 0.42 Pa, a leakage rate of 0.36 Pa / min, a melting current of 5.0 kA, and a melting voltage of 33.5 V. The resulting γ-TiAl alloy ingot had a diameter of Φ280 mm. (See [reference needed]). Figure 3 As shown in Table 2 below, the ingot has a uniform composition and contains no unmeltable material.

[0035] Table 2. Compositional uniformity of γ-TiAl alloy ingots (wt.%) .

[0036] Example 3 This embodiment provides an alloy ingot with a nominal composition of Ti-28.24Al-6.85Mn-2.29W (mass fraction, %), wherein the high-melting-point alloying element in the alloy ingot includes W, and its VAR preparation method specifically includes the following steps: Step 1: Determine the composition of the pre-alloyed electrode rod based on the nominal composition of the γ-TiAl alloy ingot, and determine the dimensions of the pre-alloyed electrode rod and the matching aluminum tube; specifically: The pre-alloyed electrode rod is designed to be Φ80mm in size and 2250mm in length, and the matching aluminum tube is designed to be 100mm in outer diameter, 80mm in inner diameter, and 2200mm in length. The target composition of the γ-TiAl alloy ingot is: Ti-28.24Al-6.85Mn-2.29W, i.e. For W elements; For Mn elements; Similarly, after calculation using the above formula Take +0.53, Take 0 (W), If we take +1.34 (Mn), then the composition ratio of the pre-alloyed electrode rod is Ti-4.55Al-10.5Mn-3.06W.

[0037] Step 2: Prepare pre-alloyed ingots using the VAR melting method, with the following parameters: The melting process was carried out in three stages. The first melting stage involved a vacuum of 0.96 Pa, a leakage rate of 0.86 Pa / min, a melting current of 9.5 kA, and a melting voltage of 28.7 V. The second melting stage involved a vacuum of 0.63 Pa, a leakage rate of 0.42 Pa / min, a melting current of 10.5 kA, and a melting voltage of 30.0 V. The third melting stage involved a vacuum of 0.32 Pa, a leakage rate of 0.21 Pa / min, a melting current of 12.0 kA, and a melting voltage of 31.5 V. The resulting pre-alloyed ingot had a diameter of Φ560 mm.

[0038] Step 3: Process the pre-alloyed ingot into a pre-alloyed electrode rod. The specific process is as follows: The T value of the pre-alloyed material was measured. β The phase transformation point is 785℃. First, the pre-alloyed ingot is drawn at 850℃ using a free forging machine to obtain a Φ180mm bar billet. Then, the bar is rolled at 900℃ using a two-roll mill to a Φ85mm bar. Finally, the bar is sized and its surface is machined using a machining method until its diameter and length meet the target design dimensions, i.e., Φ80mm×2250mm.

[0039] Step 4: Assemble the pre-alloyed electrode rod with the aluminum tube to obtain the composite electrode. The specific assembly process is as follows: First, clean the outer surface of the pre-alloyed electrode rod and the inner and outer surfaces of the matching aluminum tube. Then, insert the pre-alloyed electrode rod into the aluminum tube, making the bottom of the pre-alloyed electrode rod flush with the bottom of the aluminum tube, and expose the top of the pre-alloyed electrode rod from the aluminum tube. Finally, simultaneously machine through holes in the aluminum tube and the pre-alloyed electrode rod at a position 120mm from the top of the aluminum tube. Use pins made of the same material as the pre-alloyed electrode rod to fix the pre-alloyed electrode rod and the aluminum tube together to form a composite electrode. After welding the auxiliary electrode and the composite electrode using an in-furnace welding method, perform VAR melting on the composite electrode.

[0040] Step 5: The composite electrode is smelted using the VAR melting method to obtain a γ-TiAl alloy ingot. The relevant process parameters are as follows: The melting process was repeated three times. The first melting was performed with a vacuum of 0.53 Pa, a leakage rate of 0.67 Pa / min, a melting current of 2.0 kA, and a melting voltage of 26.0 V. The second melting was performed with a vacuum of 0.56 Pa, a leakage rate of 0.51 Pa / min, a melting current of 3.5 kA, and a melting voltage of 27.5 V. The third melting was performed with a vacuum of 0.25 Pa, a leakage rate of 0.39 Pa / min, a melting current of 4.0 kA, and a melting voltage of 28.5 V. The resulting γ-TiAl alloy ingot had a diameter of Φ280 mm. (See [reference needed]). Figure 4 As shown in Table 3 below, the ingot has a uniform composition and contains no unmeltable material.

[0041] Table 3. Compositional uniformity of γ-TiAl alloy ingots (wt.%) In summary, the γ-TiAl alloy ingots with high melting point elements prepared by this invention have uniform composition and no high melting point unmelting substances. Furthermore, the preparation cost is low and the production efficiency is high. This invention enables the large-scale industrial preparation of γ-TiAl alloy ingots with high melting point elements and can be successfully applied to the production of precision castings, bars, plates, and other related products.

[0042] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0043] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for preparing γ-TiAl alloy ingots containing high-melting-point alloying elements using VAR, characterized in that, Specifically, the following steps are included: Step 1: Determine the composition of the pre-alloyed electrode rod based on the target composition of the γ-TiAl alloy ingot, and determine the size of the pre-alloyed electrode rod and the size of the matching aluminum tube. Step 2: Prepare pre-alloyed ingots using the VAR melting method; Step 3: Process the pre-alloyed ingot into a pre-alloyed electrode rod; Step 4: Assemble the pre-alloyed electrode rod with the aluminum tube to obtain a composite electrode; Step 5: The composite electrode is smelted using the VAR melting method to obtain a γ-TiAl alloy ingot.

2. The method for preparing VAR of γ-TiAl alloy ingots containing high-melting-point alloying elements according to claim 1, characterized in that, In step 1, the specific process of determining the composition of the pre-alloyed electrode based on the target composition of the γ-TiAl alloy ingot is as follows: The target composition of the γ-TiAl alloy ingot is defined as follows: In terms of mass percentage: It is at least one element selected from Nb, Mo, W, and Ta; Other elements in the γ-TiAl alloy ingot besides Ti, Al, Nb, Mo, W, and Ta; The composition ratio of the pre-alloyed electrode rod is: In terms of mass percentage: of which, The outer diameter of the aluminum tube. The outer diameter of the pre-alloyed electrode rod. The density of the aluminum tube, The density of the pre-alloyed electrode rod is 4.4~5.0 g / cm³. 3 , , , represents the compensation coefficients for each element in the pre-alloyed electrode rod.

3. The method for preparing VAR of γ-TiAl alloy ingots containing high-melting-point alloying elements according to claim 1, characterized in that, In step 1, the dimensions of the pre-alloyed electrode rod are as follows: diameter Φ70~Φ80mm, length 2000~2500mm.

4. The method for preparing VAR of γ-TiAl alloy ingots containing high-melting-point alloying elements according to claim 3, characterized in that, In step 1, the length of the aluminum tube is 50-150 mm shorter than the length of the pre-alloyed electrode rod. The inner diameter of the aluminum tube is greater than or equal to the diameter of the pre-alloyed electrode rod used in conjunction with it, the outer diameter is Φ90-Φ110 mm, and the length is 2000-2500 mm.

5. The method for preparing VAR of γ-TiAl alloy ingots containing high-melting-point alloying elements according to claim 1, characterized in that, In step 2, the relevant parameters for preparing the pre-alloyed ingot using the VAR melting method are as follows: The melting process is repeated 2 to 3 times. The vacuum degree before melting is ≤1Pa, the air leakage rate during melting is ≤1Pa / min, the melting current is 5 to 15kA, the melting voltage is 25 to 35V, and the diameter of the resulting pre-alloyed ingot is 440 to 560mm.

6. The method for preparing VAR of γ-TiAl alloy ingots containing high-melting-point alloying elements according to claim 1, characterized in that, In step 3, the specific process of processing the pre-alloyed ingot into a pre-alloyed electrode rod is as follows: First, the pre-alloyed ingot is forged using a free forging machine at T... β ~T β Bars with diameters of Φ100~Φ180mm are drawn in a temperature range of +150℃, and then rolled using a two-roll mill at T... β ~T β The bar stock is rolled into a pre-finished product at a temperature range of +150℃, with a diameter larger than the target finished product diameter. A total machining allowance of 3~5mm is reserved. Finally, the surface of the bar stock is machined and processed until its diameter and length meet the requirements of the target design dimensions.

7. The method for preparing VAR of γ-TiAl alloy ingots containing high-melting-point alloying elements according to claim 1, characterized in that, In step 4, the pre-alloyed electrode rod is assembled with the aluminum tube to obtain the composite electrode. The specific assembly process is as follows: First, clean the outer surface of the pre-alloyed electrode rod and the inner and outer surfaces of the matching aluminum tube. Then, insert the pre-alloyed electrode rod into the aluminum tube, making the bottom of the pre-alloyed electrode rod flush with the bottom of the aluminum tube, and expose the top of the pre-alloyed electrode rod from the aluminum tube. Finally, machine through holes simultaneously on the aluminum tube and the pre-alloyed electrode rod at a position 100-150mm from the top of the aluminum tube. Use pins made of the same material as the pre-alloyed electrode rod to fix the pre-alloyed electrode rod and the aluminum tube together to form a composite electrode.

8. The method for preparing VAR of γ-TiAl alloy ingots containing high-melting-point alloying elements according to claim 1, characterized in that, In step 5, the melting process parameters for the composite electrode are as follows: The melting process is carried out in 3 stages. The vacuum degree before melting is ≤0.8Pa, the leakage rate during melting is ≤0.8Pa / min, the melting current is 2~5kA, and the melting voltage is 26~34V.

9. The method for preparing VAR of γ-TiAl alloy ingots containing high-melting-point alloying elements according to claim 1, characterized in that, High-melting-point alloying elements include one or more of Nb, Mo, W, and Ta.

10. A γ-TiAl alloy ingot containing high-melting-point alloying elements, characterized in that, The γ-TiAl alloy ingot is prepared by the preparation method according to any one of claims 1 to 9, and the diameter of the γ-TiAl alloy ingot is Φ280~Φ320mm.

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