Preparation method of TC4 titanium alloy cast ingot

Abstract

The invention discloses a preparation method of a TC4 titanium alloy cast ingot. The preparation method comprises the following steps: determining a used residual waste component range according to target components of the TC4 titanium alloy cast ingot; the residual waste materials and the aluminum bars are evenly arranged in a feeding groove of the electron beam cold bed furnace; primary smelting is conducted through an electron beam cold bed furnace, and a primary cast ingot is prepared; and the primary cast ingot is smelted through a vacuum consumable electric arc furnace, and the TC4 titanium alloy cast ingot is prepared. Before material distribution, the loss amount in Al element smelting is calculated, and supplementation is carried out during material distribution, so that excessive loss of the Al element in EB smelting is made up, and the ingot casting quality is improved; the aluminum bars are uniformly distributed in the feeding groove, so that the burning loss of the aluminum element is balanced, the aluminum element in the cast ingot is uniformly distributed, and the phenomenon of macrosegregation is improved.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy ingots, and in particular to a method for preparing a TC4 titanium alloy ingot. Background Art

[0002] With the widespread application of titanium alloy products in aerospace, medical equipment, high-end equipment manufacturing and many other fields, the amount of TC4 waste materials generated in the production process is also increasing. These TC4 waste materials need to be recycled and reused in order to effectively reduce production costs. Electron beam cold bed melting technology is used for efficient melting and refining of TC4 waste materials due to its high vacuum, high energy density, and good controllability of the molten pool temperature.

[0003] In the prior art, due to the influence of high temperature and vacuum environment, aluminum will volatilize during the electron beam cold bed melting of TC4 waste. In order to offset the volatilization of aluminum and ensure that the composition of the final ingot meets the requirements, pure aluminum raw materials need to be added. The existing method of adding pure aluminum raw materials leads to increased production costs, difficulty in process control, and difficulty in achieving uniform distribution of aluminum during the ingot melting process. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects in the prior art and provide a method for preparing a TC4 titanium alloy ingot.

[0005] To achieve the above object, the technical solution of the present invention is as follows: A method for preparing a TC4 titanium alloy ingot comprises the following steps: Determine the composition range of TC4 scrap material according to the target composition range of TC4 titanium alloy ingot; The TC4 scrap material and the aluminum rod are evenly arranged in a feed trough of an electron beam cooling hearth furnace; the TC4 scrap material and the aluminum rod in the feed trough are melted by the electron beam cooling hearth furnace to prepare a primary ingot; The primary ingot is melted by a vacuum consumable arc furnace to prepare the TC4 titanium alloy ingot.

[0006] Furthermore, the step of melting the TC4 scrap material and the aluminum rod located in the feed trough by the electron beam cooling hearth furnace comprises: melting the TC4 scrap material and the aluminum rod located in the feed trough by the electron gun of the electron beam cooling hearth furnace; the electron gun comprises a first electron gun, a second electron gun and a third electron gun; the first electron gun is used to melt the scrap material into titanium liquid; the second electron gun is used to refine the titanium liquid; the titanium liquid enters the crystallizer of the electron beam cooling hearth furnace to form a molten pool, and the third electron gun is used to heat the surface of the molten pool.

[0007] Furthermore, the first scanning image of the first electron gun is spiral-shaped; and the second scanning image of the second electron gun switches between square and T-shaped.

[0008] Furthermore, the first scanning areas of the four first electron guns are symmetrically arranged about the cooling bed of the electron beam cooling bed furnace; and the second scanning area of ​​the second electron gun coincides with the central axis of the cooling bed.

[0009] Furthermore, the third electron gun includes a first gun and a second gun, the third scanning area of ​​the first gun is circular, the center of the third scanning area coincides with the center of the crystallizer, and the fourth scanning area of ​​the second gun is annular and located between the edge of the crystallizer and the third scanning area.

[0010] Furthermore, the ingot pulling speed for melting through the electron beam cooling furnace is 10-15 mm / min.

[0011] Furthermore, the length of the aluminum rod is 50-100 mm; the dimensions of the feed trough are 5000-6000 mm in length, 600-800 mm in width, and 400-600 mm in height.

[0012] Furthermore, the cross section of the aluminum rod is multi-deformed.

[0013] Furthermore, the mass of the aluminum rod accounts for 0.7-1.0% of the sum of the mass of the aluminum rod and the TC4 waste material. The total amount of aluminum rod added is calculated and divided into a plurality of aluminum rods of equal length and diameter by weight.

[0014] Furthermore, before the step of evenly arranging the TC4 scrap and the aluminum rods in the feed trough of the electron beam cooling furnace, the step further includes: pickling the aluminum rods to remove the oxide layer of the aluminum rods.

[0015] Placing recycled materials and aluminum bars in the feed trough to form recycled material layers and aluminum bar layers, so that the recycled material layers and aluminum bar layers are arranged alternately and spaced apart, and both the bottom layer and the top layer of the feed trough are recycled material layers; The recycled material layer has recycled material blocks or scraps of a certain height piled up in a stacking or gap-filling manner; the aluminum rod layer has a plurality of parallel aluminum rods, the aluminum rods are densely filled with recycled materials, and the aluminum rods are arranged in a direction parallel to the length of the feed trough; the aluminum rods with calculated weight are distributed into several layers in the height direction of the feed trough, and the aluminum rods in each layer are evenly distributed in an array in the horizontal direction.

[0016] The diameter of the primary ingot is 650 mm, and a crucible with a diameter of 720 mm is used to perform secondary VAR melting on the primary ingot, with a melting current of 25-29KA and a melting voltage of 30-35V; finally, a finished ingot with a diameter of 700±10 mm is obtained.

[0017] Furthermore, when the primary ingot is melted by a vacuum consumable arc furnace, an electromagnetic stirring device is used during the melting process to enhance melt convection and promote uniform distribution of alloy elements; the electromagnetic stirring includes an electromagnetic stirring coil arranged outside the water jacket of the vacuum consumable arc furnace, the electromagnetic stirring coil is connected to a power supply, and the metal liquid in the titanium alloy molten pool is moved by adjusting the current size and direction of the electromagnetic stirring coil, and the current is 10-20A.

[0018] Furthermore, during a melting process in the electron beam cooling hearth furnace, the electron beam cooling hearth furnace is provided with a crystal oscillator and a mechanical connecting device, the mechanical connecting device is connected to the bottom support of the electron beam cooling hearth furnace, the mechanical connecting device is connected to the crystal oscillator, and the mechanical vibration generated by the crystal oscillator drives the bottom support to oscillate at a corresponding frequency and amplitude through the mechanical connecting device to move the metal liquid in the titanium alloy molten pool.

[0019] The advantages and beneficial effects of the present invention are as follows: a preparation method of a TC4 titanium alloy ingot of the present invention accurately analyzes and calculates the loss of Al element in the EB smelting process before feeding, and makes corresponding supplements during feeding, thereby compensating for the excessive loss of Al element in the EB smelting process, thereby maintaining the Al element content in the ingot formed after smelting and casting within a preset range, thereby improving the quality of the ingot; and by evenly distributing the aluminum rods in the internal space of the feed trough, the burning loss of the aluminum element is more balanced, the aluminum element is evenly distributed in the ingot, thereby improving the phenomenon of macro segregation. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the preparation process of the present invention; Figure 2 is a schematic cross-sectional view of a feed trough in the present invention; Figure 3 is a top view of the feed trough in the present invention; Figure 4 It is a cross-sectional shape diagram of the aluminum rod in the present invention; Figure 5 is the scanning trajectory diagram of the first electron gun; Figure 6 is the T-shaped scanning trajectory diagram of the second electron gun; Figure 7 is the directional scanning trajectory diagram of the second electron gun; Figure 8 is a scanning area diagram of the third electron gun; Fig. 9 It is a schematic diagram of the ingot casting steps of the electron beam cooling hearth furnace; Fig.10 It is a location diagram for sampling the two ingot products in the present invention; Fig.11 It is a schematic diagram of the placement of wedges in the VAR furnace of the present invention; Fig.12 This is a schematic diagram of the structure of the wedge block in the VAR furnace of the present invention. Figure 1 ; Fig.13 This is a schematic diagram of the structure of the wedge block in the VAR furnace of the present invention. Figure 2 ; In the figure: 1, feed trough; 2, aluminum rod; 3, recycling material layer; 4, aluminum rod layer; 5, TC4 scrap material; 6, scanning track of the first electron gun; 7, T-shaped scanning track of the second electron gun; 8, square scanning track of the second electron gun; 9, third scanning area; 10, fourth scanning area; 11, melting area; 12, cooling bed; 13, refining area; 14, crystallization area; 31, wedge; 32, bottom plate; 33, first side plate; 34, second side plate; 35, rib plate; 36, scale line; 37, weight reduction hole; 38, consumable electrode; 39, crystallizer; DETAILED DESCRIPTION

[0021] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0022] A method for preparing a TC4 titanium alloy ingot, such as Figure 1 As shown, the following steps are included: Determine the composition range of TC4 scrap material according to the target composition range of TC4 titanium alloy ingot; The TC4 scrap material and the aluminum rod are evenly arranged in a feed trough of an electron beam cooling hearth furnace; the TC4 scrap material and the aluminum rod in the feed trough are melted by the electron beam cooling hearth furnace to prepare a primary ingot; The primary ingot is melted by a vacuum consumable arc furnace to prepare the TC4 titanium alloy ingot.

[0023] The preparation method of the TC4 titanium alloy ingot provided in the present application realizes the efficient utilization of the waste materials by accurately determining the composition range of the TC4 waste materials according to the target composition range of the TC4 titanium alloy ingot. Compared with the traditional method of directly using high-cost pure aluminum raw materials to offset the volatilization loss of the aluminum element, the present application offsets the volatilization loss of the aluminum element by adding aluminum rods. The traditional method usually uses the method of adding aluminum beans to supplement the Al element, which requires the addition and pressing of aluminum beans and sponge titanium to form electrodes; in this embodiment, the Al element is supplemented in the form of aluminum rods, so there is no need to add sponge titanium, thereby increasing the amount of TC4 waste materials added, and then achieving the effect of improving the recovery ratio.

[0024] Evenly arranging TC4 scrap and aluminum rods helps to form a stable molten pool during electron beam cold bed smelting, making heat transfer and material melting more uniform. This effectively solves the problem of uneven distribution of aluminum elements in traditional pure aluminum raw materials due to differences in melting rate and diffusion behavior during smelting, ensures that aluminum elements are evenly distributed in the molten pool, and prepares TC4 titanium alloy ingots with highly uniform distribution of aluminum elements, thereby improving the overall quality and performance uniformity of the ingots.

[0025] Furthermore, the step of melting the TC4 scrap material and the aluminum rod located in the feed trough by the electron beam cooling hearth furnace comprises: melting the TC4 scrap material and the aluminum rod located in the feed trough by the electron gun of the electron beam cooling hearth furnace; the electron gun comprises a first electron gun, a second electron gun and a third electron gun; the first electron gun is used to melt the scrap material into titanium liquid; the second electron gun is used to refine the titanium liquid; the titanium liquid enters the crystallizer of the electron beam cooling hearth furnace to form a molten pool, and the third electron gun is used to heat the surface of the molten pool.

[0026] By setting up the first electron gun to melt the TC4 waste material into titanium liquid, and the second electron gun to refine the titanium liquid, the division of labor and cooperation in the melting and refining processes is realized. The first electron gun can quickly melt the waste material with appropriate power and scanning mode to form a preliminary titanium liquid. Subsequently, the second electron gun deeply refines the titanium liquid to remove impurity elements (such as interstitial impurities such as oxygen, nitrogen, carbon and other trace harmful elements) to ensure the purity of the titanium liquid. This collaborative working method makes the refining process more efficient and thorough, and can effectively improve the purity of TC4 titanium alloy ingots.

[0027] The third electron gun heats the surface of the molten pool and accurately controls the temperature distribution on the surface of the molten pool to maintain an appropriate temperature gradient on the surface of the molten pool. During the crystallization process, the uniform temperature gradient helps to promote the uniform solidification rate of the ingot, avoid the phenomenon of uneven solidification caused by rapid local temperature changes, and cause problems such as composition and organizational segregation, improve the uniformity of the ingot composition, improve the overall quality of the ingot, reduce the generation of internal defects, and enhance the reliability of the ingot in subsequent processing and use.

[0028] Furthermore, the first scanning image of the first electron gun is spiral, and the scanning movement trajectory of the first electron gun during rotation scanning is as follows: Figure 5 As shown, the first electron gun is Figure 5 During the moving process of the track shown, a circular scan is made to form a spiral reciprocating scanning track, thereby forming a spiral covering scan to scan and melt the raw material without dead angles; the second scanning image of the second electron gun switches between square and T-shape. When performing the refining operation, a square scanning image is used, such as Figure 7As shown; when the titanium liquid begins to flow toward the crystallizer, the scanning image switches to a T shape, as shown Figure 6 shown.

[0029] By designing the scanning image of the first electron gun into a spiral shape, a larger range of scanning can be achieved, ensuring that the TC4 scrap is heated evenly during the melting process, accelerating the melting process of the scrap, and providing sufficient and uniform titanium liquid raw materials for subsequent refining and crystallization processes.

[0030] The scanning image of the second electron gun has the function of switching between square and T-shape. When the refining operation is mainly carried out, a square scanning image is used. At this time, the electron beam can be concentrated in a specific area of ​​the molten pool, and the titanium liquid is deeply refined with a higher energy density, effectively removing the impurity elements therein and improving the purity of the titanium liquid. When the titanium liquid begins to flow to the crystallizer, the scanning image switches to a T-shape. The characteristic of the T-shaped scanning image is that it can cover the key area from the molten pool to the overflow port of the crystallizer. By effectively heating this area, it ensures that the titanium liquid maintains good fluidity in the process of flowing to the crystallizer, and prevents the overflow port from being blocked due to temperature reduction or impurity accumulation, thereby ensuring the continuity and stability of the entire smelting and crystallization process, and helping to obtain high-quality, internally uniform and defect-free TC4 titanium alloy ingots.

[0031] Furthermore, the first scanning areas of the four first electron guns are symmetrically arranged about the cooling bed of the electron beam cooling bed furnace; and the second scanning area of ​​the second electron gun coincides with the central axis of the cooling bed.

[0032] The symmetrical arrangement of the four first scanning areas enables the TC4 scrap to be irradiated with a relatively balanced electron beam at all locations on the cooling bed, so that the raw materials are heated evenly during the melting process, avoiding uneven melting caused by local overheating or overcooling, which is beneficial to improving the melting efficiency and ensuring the stability of the quality of the titanium liquid. The second scanning area of ​​the second electron gun coincides with the central axis of the cooling bed. When the second electron gun performs a refining operation on the titanium liquid, this overlapping layout design allows the refining process to radiate evenly around the central axis of the cooling bed, ensuring that the titanium liquid in the entire molten pool can be fully and evenly refined.

[0033] Furthermore, the third electron gun includes a first gun and a second gun, and the third scanning area of ​​the first gun is circular, such as Figure 8 As shown, the center of the third scanning area coincides with the center of the crystallizer, and the fourth scanning area of ​​the second gun is annular and located between the edge of the crystallizer and the third scanning area.

[0034] In the electron gun setting of the electron beam cooling furnace, the third electron gun is composed of the first gun and the second gun. The third scanning area of ​​the first gun is circular, and the center of the circle coincides with the center of the crystallizer. In this way, when the first gun heats the surface of the molten pool, it can transfer heat to the periphery more evenly with the center of the crystallizer as the center, thereby heating the central area of ​​the molten pool.

[0035] The fourth scanning area of ​​the second gun is annular, and its position is between the edge of the crystallizer and the third scanning area of ​​the first gun, that is, surrounding the outside of the center area of ​​the molten pool. This annular scanning area forms a clever combination with the circular scanning area of ​​the first gun.

[0036] In the actual process of heating the molten pool surface, the combination of the annular and circular scanning areas can cover the entire molten pool surface more comprehensively and evenly than heating by relying solely on the circular scanning area. Fig. 9 As shown, all parts of the molten pool surface can obtain appropriate and uniform heat supply, thereby effectively improving the uniformity of the molten pool surface temperature, creating a good and stable thermal environment for the crystallization process of the titanium alloy in the molten pool, helping to ensure uniform crystallization rate and uniform and dense ingot structure, and ultimately improving the quality of TC4 titanium alloy ingots.

[0037] Furthermore, the ingot pulling speed for melting through the electron beam cooling furnace is 10-15 mm / min.

[0038] The ingot pulling speed affects the height and stability of the molten pool level, as well as the solidification process of the ingot. If the ingot pulling speed is too fast, the molten pool level will drop too quickly, which may cause the aluminum rod to be partially exposed on the surface of the molten pool, affecting its melting and composition uniformity; if the ingot pulling speed is too slow, the molten pool level may be too high, increasing the pressure and temperature gradient in the molten pool, and easily causing defects such as shrinkage cavities and cracks. Therefore, the ingot pulling speed should be reasonably adjusted according to factors such as the smelting rate, molten pool size, and ingot specifications to ensure that the molten pool level remains stable, so that the aluminum rods are melted and evenly mixed in a suitable molten pool environment, and at the same time ensure that the ingot can form a good organizational structure during the solidification process.

[0039] Furthermore, the length of the aluminum rod is 50-100 mm; the dimensions of the feed trough are 5000-6000 mm in length, 600-800 mm in width, and 400-600 mm in height.

[0040] By setting the length of the aluminum rod to 50-100mm and matching it with a feed trough with specifications of 5000-6000mm long, 600-800mm wide and 400-600mm high, its melting efficiency is improved and melting uniformity is ensured. Specifically, reducing the length of the aluminum rod will significantly increase its surface area to volume ratio. When melting in an electron beam cold hearth furnace, the electron beam acts on the aluminum rod. The larger surface area to volume ratio means that the aluminum rod can absorb heat more efficiently, thereby accelerating the melting speed and making it easier to achieve rapid melting.

[0041] At the same time, when processing aluminum bars, it is important to ensure the consistency of their dimensions, that is, to keep the length and other dimensions of each section of aluminum bars as close as possible. In this way, during the entire smelting process, the heat received by each section of aluminum bars and their own melting behavior will be relatively similar, avoiding uneven heating and asynchronous melting caused by differences in aluminum bar sizes. This plays an extremely important role in achieving uniformity in the entire smelting process and helps to ultimately obtain TC4 titanium alloy ingots with excellent quality and uniform composition.

[0042] Furthermore, the cross section of the aluminum rod is deformed, such as Figure 4 shown.

[0043] Since the surface curvature of the cylinder is the same, the angle between the electron beam and the aluminum rod surface will change during the scanning process, resulting in uneven energy absorption, which in turn affects the melting speed and uniformity. Especially in the area near the bottom and top of the cylinder, the incident angle of the electron beam is large, the energy absorption is relatively small, and the melting lag may occur.

[0044] The polygon is used to change the reflection and absorption characteristics of the electron beam on the surface of the aluminum rod, making the heat distribution more uniform, so as to achieve rapid and uniform melting of the aluminum rod during the smelting process and improve the uniformity of the ingot composition.

[0045] Furthermore, the mass of the aluminum rod accounts for 0.7-1.0% of the sum of the mass of the aluminum rod and the TC4 scrap material. By precisely controlling the addition of aluminum rods to 0.7-1.0%, on the one hand, it avoids the problem of composition deviation caused by adding too much or too little aluminum rods, ensuring that the aluminum content in the final ingot meets the expected standard; on the other hand, this precise addition control method helps to improve the uniformity of aluminum elements in the entire TC4 titanium alloy ingot. During smelting, a reasonable proportion of aluminum rods allows the aluminum element to be evenly distributed in the molten pool, and then in subsequent processes such as crystallization, it ensures that the aluminum content in various parts of the ingot tends to be consistent, thereby improving the overall quality of the ingot.

[0046] Furthermore, before the step of evenly arranging the TC4 scrap and the aluminum rods in the feed trough of the electron beam cooling hearth furnace, the step also includes: pickling the aluminum rods to remove the oxide layer of the aluminum rods. During smelting, the aluminum rods with an oxide layer may cause uneven release and distribution of the aluminum element. After the oxide layer is removed by pickling, the aluminum rods can melt more smoothly in the smelting environment of the electron beam cooling hearth furnace, and the aluminum element can be more evenly integrated into the molten metal formed by the TC4 scrap, thereby effectively improving the uniformity of the aluminum element in the entire TC4 titanium alloy ingot, which helps to obtain an ingot product with stable quality and excellent performance.

[0047] Specifically, dilute sulfuric acid with a mass fraction of 10%-20% or dilute hydrochloric acid with a mass fraction of 5%-15% is used for pickling. The pickling temperature range is 40-60°C. The pickling time is 10-30 minutes. Reasonable pickling temperature and pickling time can accelerate the reaction speed and improve the pickling efficiency.

[0048] Example: A method for preparing a TC4 titanium alloy ingot, with a recovery rate of 99.3% and a total input material of 6 tons.

[0049] 5955kg of surface-treated block TC4 recycled materials are used, and the remaining 45kg are aluminum materials. The residual waste materials of the block TC4 recycled materials are cleaned and dried, and the chemical composition analysis is as follows (mass percentage): Fe: 0.12-0.18; C: <0.03; N: <0.02; H: <0.006; O: 0.09-0.15; Al: 5.85-6.45; V: 3.95-4.35.

[0050] The above cleaning process is specifically as follows: the titanium alloy blocks or scraps to be recycled are classified by brand, and the recycled materials are cleaned to remove the oxide layer and oil stains on the surface; the recycled materials are classified and sampled by batches, and chemical analysis is performed to establish a raw material batching database as a basis for batching; Aluminum rod preparation: select aluminum with a purity greater than 99.8% to melt and cast into aluminum rods, so that the aluminum rods are evenly distributed in the feed trough to compensate for the loss of aluminum elements; The weight percentage of each element of the target ingot product is as follows: Fe: 0.12-0.18; C: <0.03; N: <0.02; H: <0.006; O: 0.09-0.15; Al: 5.85-6.45; V: 3.95-4.35; Then, check and retrieve the scrap materials that meet the above target composition from the established raw material ingredient database, and select the TC4 scrap materials with element composition (mass percentage) in the range of: 0.12-0.18; C: <0.03; N: <0.02; H: <0.006; O: 0.09-0.15; Al: 5.85-6.45; V: 3.95-4.35 from the previously classified and cleaned TC4 recycled scrap materials as the raw materials for ingots.

[0051] Since aluminum elements volatilize in large quantities during electron beam cold bed melting, aluminum rods 2 are selected and evenly distributed in the internal space of the feed trough 1 to compensate for the loss of aluminum elements; the aluminum rods 2 are arranged as follows: Figure 2 , 3 As shown; the amount of each raw material used is determined according to the target composition of the ingot and the weight of the ingot specification. Taking into account that a large amount of Al will volatilize during the smelting process, the amount of Al rod added is determined according to the loss of Al element. In the subsequent feeding process, the Al element needs to be supplemented accordingly.

[0052] Specifically, according to data summary and analysis, when the total smelting power of the EB furnace is 3000-3500KW, the loss of Al element is 0.7-0.8%, and the total weight of the ingot is 3000-6000kg, then the supplementary amount of aluminum element is 21-48kg; in this embodiment, the supplementary amount of aluminum element is made into aluminum rod 2, and specifically, the specifications of the aluminum rod 2 are: diameter 8-20mm, length 50-100mm. The addition amount of the aluminum rod 2 is 0.7-1.0% of the total weight of the raw materials of the ingot; the total addition amount of the aluminum rod 2 is calculated and divided into a number of aluminum rods 2 of equal length and diameter by weight.

[0053] Material distribution: recycled materials and aluminum rods 2 are placed in the feed trough 1, and TC4 waste materials with elemental composition in the above-mentioned range are selected and piled into the feed trough, which form recycled material layers 3 and aluminum rod 2 layers respectively with the aluminum rods, so that the recycled material layers 3 and the aluminum rod 2 layers are staggered and arranged, and the bottom and top layers of the feed trough 1 are both recycled material layers 3; the size specifications of the feed trough 1 are 5000-6000mm in length, 600-800mm in width, and 400-600mm in height.

[0054] The specific stacking form of the recycled materials and aluminum bars 2 in the feed trough 1 is as follows: Figure 2As shown in the figure, a cross-sectional schematic diagram of the feed trough 1 is shown; as shown in the figure, the recycled material layer 3 is piled with recycled material blocks or scraps of a certain height in the form of stacking and gap filling; when actually feeding, the waste material can be piled up to the top of the feed trough 1, and a layer of recycled material layer 3 is first laid on the lowest layer, and then a layer of aluminum rods 2 is laid on it, and a plurality of aluminum rods 2 are arranged in parallel in the aluminum rod 2 layer, and the space between two adjacent aluminum rods 2 is also densely filled with recycled materials, and the aluminum rods 2 are arranged in a direction parallel to the length of the feed trough 1, as shown in FIG. Figure 2 , 3 As shown, in the cross-sectional direction of the feed trough, the aluminum bars 2 between each aluminum bar layer are staggered, and on each aluminum bar layer, the joint ends of the aluminum bars are also staggered; in this way, the feeding of the Al element can be continuous and stable during smelting in the EB furnace, thereby making the distribution of the Al element more uniform; in actual settings, the optional specifications of the aluminum bars are: 8-20mm in diameter and 50-100mm in length. When the feed trough is 5000-6000mm long, 600-800mm wide, and 400-600mm high, 4-10 layers of aluminum bars can be set, and the width spacing of each layer of aluminum bars can be 100-200mm. According to the above-mentioned calculated weight, the aluminum bars 2 are distributed in several layers in the height direction of the feed trough 1, and the aluminum bars 2 in each layer are evenly distributed in an array in the horizontal direction. This distribution method makes the aluminum element evenly distributed in the horizontal direction, and as the electron gun melts the material layer by layer downward, the Al element can be supplemented at each melting depth, so that the Al element is evenly distributed in three-dimensional space, and thus the metal liquid melted in the cooling bed contains a uniform Al element.

[0055] EB furnace smelting, put the feed trough 1 into the EB cooling bed furnace feeding system, start smelting when the vacuum degree of the feed chamber is ≤0.6Pa and the vacuum degree of the smelting chamber is ≤0.1Pa, and the vacuum degree of the smelting chamber meets ≤0.5Pa during the smelting process. After the TC4 titanium alloy residue is bombarded by the electron beam and melted into titanium liquid, it flows into the crystallizer crucible for solidification through the melting cooling bed and the refining cooling bed, and then the ingot is pulled to the ingot pulling chamber through the ingot pulling system and cooled with the furnace before being taken out of the furnace to obtain a primary ingot with a diameter of 650mm. There are a total of seven electron guns in the EB furnace, No. 1-7, and the power of the electron gun is 280~440kV.

[0056] During the smelting process, guns 1-4 are used to melt the raw materials in the left and right feed tanks, gun 5 is used to refine the titanium liquid in the cooling bed, and guns 6-7 are used to heat the surface of the molten pool in the crystallizer so that the titanium liquid in the molten pool can be continuously solidified. The power distribution of each gun in EB smelting is shown in Table 1.

[0057] Table 1 Serial number Melting power ratio 1-4 60-70% 5 10-15% 6-7 20-25% VAR furnace smelting: After the primary ingot is cooled and taken out of the furnace, the ingot bottom starter is cut off, the riser flash is removed, and then it is placed in a VAR furnace for secondary smelting to obtain a finished ingot. The ingot smelted in the EB furnace is smelted twice in a crucible with a diameter of 720, with a smelting current of 25-29KA and a smelting voltage of 30-35V; finally, a finished ingot with a diameter of 700±10mm is obtained.

[0058] When secondary melting is carried out in a VAR furnace, Figure 11-13 As shown, the specific process is as follows: multiple wedges are evenly placed between the top edge of the consumable electrode and the crystallizer cylinder, and one end of each wedge with an angle b is inserted into the gap between the consumable electrode and the crystallizer cylinder. By adjusting the position of the consumable electrode, multiple wedges are at the same horizontal height to achieve a uniform gap between the consumable electrode and the crystallizer. The consumable electrode is located at the center of the crystallizer. Since the material of the first side plate and the second side plate of the bottom plate is the same as the alloy material for vacuum consumable arc melting, foreign matter is prevented from being brought into the crystallizer during the furnace loading process to cause pollution to the melting; since the material is an alloy, the structural strength is improved, and the positioning device can avoid deformation that causes uneven gap between the consumable electrode and the crystallizer, affecting melting safety and ingot quality; it is also avoided that during the welding process of the consumable electrode and the auxiliary electrode, the positioning device is prevented from spontaneously igniting at high temperature, resulting in increased air pressure in the crystallizer, affecting welding safety.

[0059] Specifically, the length L1 of the wedge 31 is 200-300 mm, the width L2 is 80-150 mm, and the thickness L3 is 80-150 mm.

[0060] Specifically, the included angle a between the bottom plate 32 and the first side plate 33 is in the range of 90°-150°, and the included angle b between the bottom plate 32 and the second side plate 34 is in the range of 15°-45°; Specifically, the bottom plate 32, the first side plate 33 and the second side plate 34 are integrally formed; Considering that there are many specifications of the crystallizer 39 and the consumable electrode 38, and the sizes of different specifications are also different, in order to ensure that the wedge 31 can be effectively used, the size of the wedge 31 and the sizes of the angle a and the angle b are also various, so that the staff can select a suitable wedge 31 according to the specifications of the crystallizer 39 and the consumable electrode 38. At the same time, the raw material of the wedge 31 is mainly taken from the titanium alloy plate in the waste material, and the titanium alloy plate is appropriately processed according to its own size to make it a wedge 31 that meets the above requirements.

[0061] Specifically, the wedge 31 also includes two ribs 35, and the two ribs 35 are symmetrically arranged on both sides of the bottom plate 32; the ribs 35 are triangular, and the three sides of the ribs 35 are respectively connected to the bottom plate 32, the first side plate 33 and the second side plate 34. Considering that the bottom plate 22, the first side plate 33 and the second side plate 34 alone cannot form a closed structure of the wedge 31, ribs 55 are welded on both sides thereof, so that the wedge 31 has a closed structure as a whole, thereby improving the overall strength of the wedge 31.

[0062] Specifically, the ribs 35 are provided with scale lines 36 with marking functions in the vertical direction; the scale lines 36 are used to observe the insertion depth of the wedges 31. When the scale lines 36 on the bottom plates 32 of the plurality of wedges 31 are at the same vertical distance from the top edge of the consumable electrode 38, it means that the plurality of wedges 31 are at the same horizontal height, thereby achieving the purpose of improving positioning accuracy.

[0063] Specifically, the scale lines are laser etched, chemically etched or mechanically engraved, which improves the clarity and wear resistance of the scale lines and makes them less likely to wear out or become blurred during the use of the wedge.

[0064] Specifically, the corners of the wedge 31 are chamfered; in order to prevent the wedge 31 from causing scratches to the operator during use, and to reduce the scratches on the surface of the consumable electrode 38 and the crystallizer 39 during the insertion and adjustment of the wedge 31, chamfers are set at the corners of the wedge 31, and the chamfer radius ranges from 0.5mm to 3mm.

[0065] Specifically, the bottom plate 32 , the first side plate 33 and the second side plate 34 are all provided with weight-reducing holes 37 ; in order to reduce the weight of the wedge 31 itself, a plurality of weight-reducing holes 37 are provided thereon.

[0066] Table 2 Ingot 1 composition test results

[0067] Table 3 Ingot 2 composition test results

[0068] Two ingots were prepared through the above steps, and the ingot components were tested after peeling and sampling. Specifically, Fig.10 As shown, chip-shaped and block-shaped analysis samples were taken from the head H, upper TOP, middle M, lower B, and bottom Tail of the ingot side surface for chemical composition analysis; the test results are shown in the table. Through the above sampling analysis, it can be seen that the main elements of the ingot are evenly distributed and meet the relevant standard requirements, and the impurity element content also meets the relevant standard requirements and is evenly distributed. The Al element is fully homogenized, realizing the efficient recovery of titanium alloy scrap.

[0069] As an implementation method for enhancing the mixing effect of the elements in the molten pool and reducing element segregation during smelting, the specific method is as follows: In the VAR furnace smelting, electromagnetic stirring is used during the smelting process to enhance melt convection and promote uniform distribution of alloy elements; the electromagnetic stirring includes an electromagnetic stirring coil arranged outside the water jacket, the coil is connected to a power supply, and is provided with a sensor and a controller to monitor and adjust the magnetic field strength and direction, and the characteristics of the magnetic field are controlled by adjusting the current size and direction to make the metal liquid in the titanium alloy molten pool move.

[0070] During VAR furnace smelting, the electromagnetic stirring equipment is set around the molten pool and outside the crucible. When set, the coil is kept at an appropriate distance from the molten pool to ensure that the magnetic field can effectively penetrate the molten pool. Specifically, the electromagnetic stirring includes an electromagnetic stirring coil set outside the water jacket, the coil is connected to a power supply, and a sensor and a controller are provided to monitor and adjust the magnetic field strength and direction, and the characteristics of the magnetic field are controlled by adjusting the power supply frequency and current to make the metal liquid in the titanium alloy molten pool move.

[0071] Titanium alloy liquids themselves are not ferromagnetic, which means they are not directly attracted or repelled by magnetic fields like ferromagnetic materials. However, titanium alloy liquids are good conductors and can generate eddy currents under the action of a rotating magnetic field through the electromagnetic induction effect, which is then driven by the Lorentz force.

[0072] According to the electromagnetic induction effect, when a rotating magnetic field acts on a conductive titanium alloy molten pool, an eddy current will be induced in the molten pool. This is based on Faraday's law of electromagnetic induction, that is, a changing magnetic field will generate an electromotive force in a conductor, thereby forming a current. The expression is: E = −N × ΔB / Δt Where: E is the induced electric field; ΔB is the change in magnetic field; t is the time interval; N represents the number of coil turns.

[0073] The induced eddy current interacts with the rotating magnetic field to generate the Lorentz force; the expression of the Lorentz force is: F=J×B Where: F is the Lorentz force; J is the current density; B is the magnetic field strength.

[0074] The force generated by the Lorentz force in the molten pool causes the liquid in the molten pool to start moving. Since the rotating magnetic field is continuously changing, the flow of the liquid also exhibits a rotating characteristic. This rotating flow helps to mix the different components in the molten pool, thereby reducing element segregation and improving the uniformity of the alloy.

[0075] A rotating magnetic field is generated by a set of coils. These coils are usually arranged in a certain arrangement (such as a three-phase coil). By passing an alternating current, a time-varying rotating magnetic field can be generated around the molten pool. The rotating magnetic field induces eddy currents in the conductive titanium alloy molten pool. The induced eddy currents interact with the rotating magnetic field to generate Lorentz force. The Lorentz force causes the liquid in the molten pool to start moving, forming a rotating flow.

[0076] The greater the magnetic field intensity, the stronger the Lorentz force generated and the better the stirring effect. The current frequency affects the speed of change of the rotating magnetic field, which in turn affects the generation and flow pattern of eddy currents. The geometry of the molten pool (such as diameter and depth) affects the distribution and flow pattern of eddy currents. The higher the conductivity of the titanium alloy, the stronger the induced eddy current and the better the stirring effect. Eddy currents are generated under the action of the rotating magnetic field through the electromagnetic induction effect, and then driven by the Lorentz force to achieve stirring of the metal liquid. This process effectively improves the uniformity of the composition in the molten pool and reduces element segregation.

[0077] Specifically: Electromagnetic stirring is used in the VAR smelting process to enhance melt convection and promote uniform distribution of alloy elements. The electromagnetic stirring includes an electromagnetic induction coil arranged outside the crucible, the coil is connected to a power source, and is provided with a sensor and a controller to monitor and adjust the magnetic field strength and direction. The characteristics of the magnetic field are controlled by adjusting the current size and direction to make the metal liquid in the titanium alloy molten pool move.

[0078] Setting of electromagnetic stirring structure: one or more sets of electromagnetic coils are installed around the outside of the melting crucible. An adjustable current source is equipped as a power control system, which can change the current size and direction, thereby adjusting the direction and strength of the magnetic field. The electromagnetic stirring system should have a fast response capability to accurately control the stirring effect.

[0079] Since the electromagnetic coil generates heat when working, an effective cooling system is required to ensure that the coil will not be damaged by overheating. High-temperature resistant and high-strength copper alloy or silver-copper alloy is used to ensure that the coil can withstand high temperatures and maintain good conductivity when energized. The cooling system uses forced water cooling to ensure that the coil temperature does not exceed the safe working range. Cooling water flow rate: Each coil segment must have a cooling water flow rate of at least 20 L / min to maintain the low temperature of the coil. Temperature sensors, position sensors and other equipment are installed to monitor the status of the molten pool and feed back information to the control system to achieve automated operation.

[0080] During the smelting process, the parameters of the smelting process are guided by monitoring the magnetic field of the electromagnetic stirring. The specific relationship between the electromagnetic field intensity and the smelting current includes the following: 1. Electromagnetic field strength and melt convection: Strong magnetic field: If the monitored electromagnetic field strength is higher than expected, this may mean that the stirring effect is too strong, which may cause excessive turbulence in the melt, affect the uniformity of the composition and increase the risk of pore formation. At this time, you should consider reducing the melting current or changing the frequency to weaken the stirring effect.

[0081] Weak magnetic field: On the contrary, if the electromagnetic field strength is insufficient, the melt convection is insufficient and cannot effectively promote the mixing of components and the floating of inclusions. At this time, the stirring force can be enhanced by appropriately increasing the melting current or adjusting the frequency.

[0082] 2. Electromagnetic field strength and melting rate: The melting current directly affects the energy input of the arc, which in turn affects the melting rate. High current can accelerate the melting speed, but it also leads to stronger electromagnetic effects. Therefore, it is necessary to find a balance point that can ensure sufficient melting rate without causing adverse effects due to excessively strong electromagnetic fields.

[0083] 3. Electromagnetic field strength and temperature distribution: Appropriate electromagnetic stirring helps to homogenize the temperature distribution of the molten pool. If abnormal electromagnetic field strength is detected in certain areas (such as locally too strong or too weak), the temperature uniformity can be improved by fine-tuning the melting current or changing the position of the electromagnetic coil.

[0084] Specific adjustment examples: For example, in a VAR melting process, real-time monitoring shows that the electromagnetic field intensity is too high, resulting in violent fluctuations on the melt surface, which may be caused by excessive melting current. At this time, the following measures can be taken: Reduce melting current: Gradually reduce the current until the melt surface fluctuations are observed to return to normal, while paying close attention to changes in the melting rate to ensure that it still meets production needs.

[0085] Stirring cycle: If reducing the current is not enough to solve the problem, you can also adjust the stirring cycle. By adjusting the direction of the current, you can control the forward or reverse stirring of the molten metal in the molten pool. The stirring cycle determines the flow state of the molten metal in the molten pool. The flow state in the molten pool can affect the mixing uniformity of the melt and the solidification process.

[0086] Optimize cooling conditions: In conjunction with the above adjustments, check that the cooling system is working properly to ensure that the ingot cooling rate is appropriate to avoid internal stress and cracks caused by rapid cooling.

[0087] On the basis of real-time monitoring of electromagnetic field intensity, by precisely controlling other key parameters such as the magnitude and direction of the melting current, more precise quality control can be achieved during the melting process, thereby improving the quality and consistency of titanium alloy ingots. This real-time adjustment not only relies on process monitoring technology and automated control systems, but also requires technical accumulation and practical experience support.

[0088] Electromagnetic stirring control: Electromagnetic stirring is used during the smelting process to improve the fluidity of the alloy liquid and promote the homogenization of the composition. It should be noted that the stirring intensity should be carefully controlled in the early and late stages of smelting to avoid composition segregation or inclusion problems caused by excessive stirring. In addition, in order to adapt to the new composition range, especially in controlling the oxygen (O) and nitrogen (N) content, the stirring intensity can be appropriately reduced at the end of smelting to help remove gas and reduce oxide inclusions.

[0089] Initial start-up: Soon after the start of smelting, when the molten pool is initially formed but not completely melted, the electromagnetic stirring system is started. At this time, a lower current intensity is used.

[0090] Stabilization period: As the smelting process progresses, the current intensity is gradually increased to generate sufficient eddy current movement inside the molten pool to promote uniform distribution of alloy elements.

[0091] Late adjustment: Before the end of smelting, appropriately reduce the current intensity and reduce the stirring intensity, which will help form a denser organizational structure and prevent component segregation caused by excessive stirring. The current direction and intensity of electromagnetic stirring can be flexibly adjusted according to the actual conditions of the molten pool to achieve the best stirring effect.

[0092] Furthermore, during a smelting operation in an electron beam cooling furnace, a crystal oscillator and a mechanical connection device are provided. The mechanical connection device is connected to the bottom support of the electron beam cooling furnace. The mechanical connection device is controlled by a signal of the crystal oscillator. The oscillation signal generated by the crystal oscillator drives the bottom support to oscillate at a corresponding frequency and amplitude through the mechanical connection device, thereby improving the distribution of alloy components and promoting the uniform distribution of chemical elements in the ingot. Specifically, the advantages include the following: 1. Enhance convection diffusion The vibration of the molten pool surface will drive the flow of the liquid inside the entire molten pool, forming convection. This convection effect is stronger than natural convection, which can make the alloy elements in the molten pool diffuse faster in the liquid. The alloy elements that were originally unevenly distributed in the molten pool will migrate from the high-concentration area to the low-concentration area under the action of convection, thus gradually achieving uniform distribution.

[0093] 2. Breaking the concentration gradient The combination of a crystal oscillator and a mechanical connection device is set up, and its vibration can break the concentration gradient formed by the alloy elements in the molten pool. In the absence of vibration, the alloy elements may form local areas of uneven concentration due to factors such as density differences, resulting in uneven material properties. Through the strong stirring effect generated by vibration, these areas of uneven concentration are broken, and the alloy elements are more fully mixed, ultimately achieving a uniform distribution of alloy elements in the entire molten pool, improving the quality and performance of the titanium alloy.

[0094] In actual use, the mechanical connection device is used to transmit the oscillation signal generated by the crystal oscillator to the bottom bracket of the electron beam cooling furnace (EB furnace). The design of such a device needs to consider several key factors, including vibration frequency, amplitude, force transmission efficiency and compatibility with existing equipment. Specifically, the mechanical connection device in this embodiment can be connected by direct coupling. For example, direct coupling can be achieved by fixing the oscillator directly to the base through a rigid mechanical arm or rod. This approach ensures maximum energy transfer efficiency. Setup: Choose appropriate materials to ensure strength and heat resistance while avoiding deformation or failure in high temperature environments. The connection points should be designed to withstand repeated stress cycles.

[0095] Due to the high temperature inside the EB furnace, effective insulation must be considered to prevent heat from being transferred to the oscillator and other sensitive components and causing failure.

[0096] Specifically, in some embodiments, a piezoelectric crystal oscillator with an operating frequency of 100 Hz and a maximum amplitude of ±1 mm is used to control the action of any of the above mechanical connection devices. During the smelting process, we set the starting oscillation frequency to 80 Hz and the amplitude to 0.5 mm, and allow the control system to flexibly adjust these parameters at different stages of smelting.

[0097] Install the crystal oscillator in a location relatively far from the high temperature area to protect it from thermal damage. It can be fixed on a sturdy bracket, which is connected to the furnace body through thermal insulation. Use a dedicated driver power supply to power the crystal oscillator, and equip it with a microprocessor or PLC (programmable logic controller) to accurately control the oscillation frequency and amplitude. This control system should have real-time monitoring capabilities and automatically adjust parameters according to changes in the melting process.

[0098] During the smelting process, the control system will dynamically adjust the working state of the oscillator according to the data fed back by the sensor. For example, if the solute distribution in the molten pool is uneven, the mixing effect can be improved by increasing the oscillation intensity; conversely, if it is found that the oscillation causes too much fluctuation, the amplitude can be appropriately reduced. Other key parameters such as the molten pool temperature and ingot pulling speed are monitored to ensure that they are coordinated with the oscillation conditions.

[0099] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a TC4 titanium alloy ingot, characterized in that: The following steps are involved: Determine the composition range of TC4 scrap material according to the target composition range of TC4 titanium alloy ingot; The TC4 scrap material and the aluminum rod are evenly arranged in a feed trough of an electron beam cooling hearth furnace; the TC4 scrap material and the aluminum rod in the feed trough are melted by the electron beam cooling hearth furnace to prepare a primary ingot; The primary ingot is melted by a vacuum consumable arc furnace to prepare the TC4 titanium alloy ingot.

2. The method for preparing the TC4 titanium alloy ingot according to claim 1, characterized in that: The step of melting the TC4 scrap material and the aluminum rod located in the feed trough by the electron beam cooling hearth furnace comprises: melting the TC4 scrap material and the aluminum rod located in the feed trough by the electron gun of the electron beam cooling hearth furnace; the electron gun comprises a first electron gun, a second electron gun and a third electron gun; the first electron gun is used to melt the scrap material into titanium liquid; the second electron gun is used to refine the titanium liquid; the titanium liquid enters the crystallizer of the electron beam cooling hearth furnace to form a molten pool, and the third electron gun is used to heat the surface of the molten pool; the ingot pulling speed of the electron beam cooling hearth furnace for melting is 10-15mm / min.

3. The method for preparing the TC4 titanium alloy ingot according to claim 2, characterized in that: The first scanning image of the first electron gun is spiral; the second scanning image of the second electron gun switches between square and T-shape; during refining operation, a square scanning image is used, and when the titanium liquid begins to flow toward the crystallizer, the scanning image switches to T-shape.

4. The method for preparing the TC4 titanium alloy ingot according to claim 3, characterized in that: The first scanning areas of the four first electron guns are symmetrically arranged about the cooling bed of the electron beam cooling bed furnace; the second scanning area of ​​the second electron gun coincides with the central axis of the cooling bed.

5. The method for preparing the TC4 titanium alloy ingot according to claim 4, characterized in that: The third electron gun includes a first gun and a second gun. The third scanning area of ​​the first gun is circular, and the center of the third scanning area coincides with the center of the crystallizer. The fourth scanning area of ​​the second gun is annular and is located between the edge of the crystallizer and the third scanning area.

6. The method for preparing a TC4 titanium alloy ingot according to any one of claims 1 to 5, characterized in that: The length of the aluminum rod is 50-100 mm; the size of the feed trough is 5000-6000 mm in length, 600-800 mm in width, and 400-600 mm in height; the cross section of the aluminum rod is multi-deformable.

7. The method for preparing a TC4 titanium alloy ingot according to any one of claims 1 to 5, characterized in that: The mass of the aluminum rod accounts for 0.7-1.0% of the sum of the mass of the aluminum rod and the TC4 waste material.

8. The method for preparing a TC4 titanium alloy ingot according to any one of claims 1 to 5, characterized in that: Before the step of evenly arranging the TC4 scrap and the aluminum rods in the feed slot of the electron beam cooling furnace, the method further includes: pickling the aluminum rods to remove the oxide layer of the aluminum rods.

9. A method for preparing a titanium alloy ingot with a high recovery ratio according to any one of claims 1 to 5, characterized in that: When the primary ingot is melted by a vacuum consumable arc furnace, an electromagnetic stirring device is used during the melting process to enhance melt convection and promote uniform distribution of alloy elements; the electromagnetic stirring includes an electromagnetic stirring coil arranged outside the water jacket of the vacuum consumable arc furnace, the electromagnetic stirring coil is connected to a power supply, and the metal liquid in the titanium alloy molten pool is moved by adjusting the current size and direction of the electromagnetic stirring coil, and the current is 10-20A.

10. A method for preparing a titanium alloy ingot with a high recovery ratio according to any one of claims 1 to 5, characterized in that: During a melting process in an electron beam cooling hearth furnace, the electron beam cooling hearth furnace is provided with a crystal oscillator and a mechanical connection device, the mechanical connection device is connected to the bottom support of the electron beam cooling hearth furnace, the mechanical connection device is connected to the crystal oscillator, and the mechanical vibration generated by the crystal oscillator drives the bottom support to oscillate at a corresponding frequency and amplitude through the mechanical connection device to move the metal liquid in the titanium alloy molten pool.

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