Method for preparing Ti80 titanium alloy flat ingot based on electron beam cold hearth furnace smelting high return material

Abstract

The application discloses a method for preparing Ti80 titanium alloy flat ingot based on an electron beam cold bed furnace and high return material melting and casting, uses Ti80 titanium alloy return material as raw material, uses VAR ingot cutting material as VAR compensation material, and optimizes the material distribution structure, so that the EB melting element burning loss is precisely controlled, the Ti80 titanium alloy flat ingot with qualified and controllable components is prepared by using a large proportion of Ti80 titanium alloy return material, the component unevenness problem under the high return material ratio is solved, and core technical support is provided for short process manufacturing of Ti80 plate.

Description

Technical Field

[0001] This invention relates to the field of Ti80 titanium alloy smelting technology, and more specifically, to a method for preparing Ti80 titanium alloy flat ingots based on electron beam cold hearth furnace smelting and casting of high-return material. Background Technology

[0002] Ti80 titanium alloy possesses comprehensive properties such as high strength, high toughness, weldability, and corrosion resistance, making it widely used in the manufacture of ship components such as pressure hulls for deep-sea submersibles and load-bearing structural parts. Plates are the primary product form. Currently, the conventional production route for Ti80 plates involves three vacuum arc remelting (VAR) processes – forging – hot rolling. This route suffers from long production cycles and high costs. Furthermore, Ti80 scrap is increasingly being generated, especially from ingots, forgings, and plate cuttings. However, effective utilization methods for Ti80 scrap are currently lacking. Developing methods to utilize Ti80 scrap as return material to reduce raw material costs, and achieving "forging-free" processing to lower overall processing costs, are key to expanding the application of Ti80 titanium alloys in the marine field.

[0003] The recycling industry has explored various methods for reusing titanium and titanium alloy scrap. For example, electron beam cold hearth furnaces (EB furnaces) are used to melt scrap and prepare ingots. EB furnace melting uses an electron beam as the heat source and a water-cooled copper crucible as the cooling bed. The kinetic energy of high-speed electrons is converted into heat energy, melting, refining, and casting the metal into ingots. This effectively removes high- and low-density inclusions, yielding high-purity titanium and titanium alloys, suitable for scrap recycling. However, due to the high vacuum working environment of the EB furnace, controlling the volatilization of smelting elements and the uniformity of ingot composition remains a significant technical challenge. Reports have mentioned using electron beam cold hearth furnaces to melt pure titanium and low-alloy titanium alloy flat ingots (such as TC4), then heating and directly rolling them into plates. This significantly shortens the production cycle, and the overall plate yield can reach over 75%. Chinese patent CN120099294B proposes a method for preparing titanium alloy flat ingots using a dual-stage vacuum consumable solidification furnace and an EB furnace, primarily addressing the issue of TC4 recycled material. However, this technology is currently unsuitable for smelting and preparing complex Ti80 alloy (Ti-6Al-3Nb-2Zr-1Mo) flat ingots. Although the solidification furnace can rapidly melt the raw materials to prepare ingots with preliminary mixed components, the open molten pool leads to Al volatilization, making composition control difficult. Furthermore, the composition compensation material is located at the bottom of the solidification furnace crucible. For high-melting-point, high-density components such as Mo, Nb, and Zr, the diffusion of high-melting-point components is slow, making it difficult to ensure that these elements achieve high uniformity on the macroscopic scale of the ingot, potentially leading to segregation defects. Therefore, currently, solidification furnace smelting is prone to volatilization, and the composition of high-alloy ingots fluctuates significantly. Using the smelted ingots directly as raw materials for the EB furnace carries the risk of exacerbating the uneven composition of the final ingot. Chinese patent CN120099295B proposes that TC4 recycled material (proportion ≥50%) + raw material compensation, layered briquetting, and EB furnace smelting can prepare high-performance two-phase titanium alloys (TC4+Cr, Fe) at low cost. Similarly, for Ti80 alloy, using recycled material + intermediate alloy as raw material (with AlNb, AlMo, Al or other elemental metals) for direct EB smelting, the multi-element and multi-state coexisting raw material has problems such as difficulty in controlling Al composition, difficulty in homogenizing high melting point components such as Mo, Nb, and Zr, and poor stability during long-term smelting.

[0004] In summary, while the EB furnace has the potential to recycle and remelt Ti80 titanium alloy scrap, the chemical composition and performance requirements of Ti80 alloy dictate its unique characteristics during EB furnace remelting. The main challenges stem from three aspects: element volatilization loss control (primarily Al) and compensation, inclusion control, and process stability. Element volatilization is a dynamic process, influenced by factors such as vacuum level, molten pool temperature, and melting rate. Simple batching calculations cannot accurately compensate for volatilization losses, easily leading to gradients in Al content at the head, middle, and tail of the ingot (with more severe volatilization at the tail due to the longer melt residence time during the feeding stage). Although the EB furnace can remove most inclusions through cold hearth refining, if the initial contamination of the scrap is severe or the melting process is inappropriate, residual risks remain. These inclusions are the source of cracks, seriously affecting the reliability of ship components. EB melting parameters such as electron beam power, scanning mode, melting rate, and vacuum level interact with each other. Inappropriate process window settings can affect molten pool stability, consequently impacting refining efficiency and solidification structure, potentially leading to ingot cracks or cold shuts. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing Ti80 titanium alloy flat ingots based on electron beam cold hearth furnace melting and casting of high-return material. This method uses Ti80 titanium alloy return material as raw material, VAR casting as compensating material, and optimizes the material distribution structure to precisely control the element loss during EB melting. This enables the preparation of Ti80 titanium alloy flat ingots with qualified and controllable composition using a large proportion of Ti80 titanium alloy return material, solving the problem of uneven composition under high return material ratios and providing core technical support for short-process manufacturing of Ti80 plates.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing Ti80 titanium alloy flat ingots based on electron beam cold hearth furnace casting of high-return material, comprising the following steps:

[0008] S1, determine the composition and quality of the Ti80 titanium alloy return material, and perform cutting and surface treatment;

[0009] The amount of the recycled Ti80 titanium alloy added is 30-70% of the EB raw material;

[0010] S2. Based on the target composition of Ti80 titanium alloy flat ingot, the VAR compensation material composition is obtained by using sponge titanium, Al-Mo master alloy, Al-Nb master alloy, Al wire and sponge to obtain VAR compensation material.

[0011] The Al content in the VAR compensation material is calculated according to the following formula:

[0012] ;

[0013] In the formula, [Al] represents the target Al content in Ti80 titanium alloy flat ingots, in %; m1 represents the total weight of the Ti80 titanium alloy return material, in kg; [Al]1 represents the average Al content of the Ti80 titanium alloy return material, in %; m2 represents the weight of the VAR compensation material, in kg; [Al]2 represents the weight percentage of Al in the VAR compensation material, in %; and χ represents the volatility coefficient of Al during electron beam melting, ranging from 13% to 19%.

[0014] S3. After mixing the VAR compensation material, press it into a consumable electrode, then perform vacuum consumable arc melting, and obtain a VAR ingot after exiting the furnace. After the composition is tested and meets the internal control requirements, cut it into VAR ingot cutting blocks.

[0015] S4, Ti80 titanium alloy return material and VAR ingot cutting block are used as EB raw materials, and after being misaligned and paired, they are put into the feed hopper of the electron beam cold hearth furnace. Then the electron beam cold hearth furnace is sealed and vacuumed and leak checked.

[0016] S5, confirm the graphic positions of each electron gun in the electron beam cooling bed, and melt the base material in the cooling bed to make a solidified shell;

[0017] S6, start the feeding system, push the material in the feeding hopper to the cooling bed for melting and refining, and then the refined titanium liquid flows into the crystallizer. After the titanium liquid fills the crystallizer, the ingot pulling begins.

[0018] The melting rate is 350~500 kg / h, and the residence time of the titanium liquid in the electron beam cold bed refining zone is 150~200 seconds; the ingot pulling speed is controlled at 150~200 mm / h.

[0019] S7. After the casting is completed, the tail of the ingot is rapidly fed back. After the feeding is completed, it is cooled. Then the electron beam cold hearth furnace is opened, and the Ti80 titanium alloy flat ingot is taken out from the crystallizer.

[0020] Preferably, in step S1:

[0021] The composition and mass of each type of Ti80 titanium alloy return material were obtained by chemical analysis or spectroscopic analysis, and the average Al content of the Ti80 titanium alloy return material was calculated.

[0022] The surface treatment includes shot blasting, acid and alkali washing, cleaning, and drying.

[0023] Preferably, in step S2:

[0024] The target composition of the Ti80 titanium alloy flat ingot, by mass percentage, is as follows: Al: 5.7~6.5%, Nb: 2.7~3.3%, Zr: 1.8~2.3%, Mo: 1.0~1.5%, 0<Si≤0.10%, 0<Fe≤0.25%, 0<C≤0.10%, 0<N≤0.05%, 0<H≤0.010%, O: 0.05~0.10%, with the balance being Ti and unavoidable impurities;

[0025] Preferably, in step S3:

[0026] After the electrodes are placed into the vacuum arc furnace, the vacuum level is evacuated to 1×10⁻⁶. -2 Below Torr, the leakage rate should be controlled to ≤0.1 Torr •L / S;

[0027] The vacuum self-consuming arc melting process is divided into three stages: arc initiation, steady-state melting, and capping. In the arc initiation stage, the melting current is 1.5~3 kA. In the steady-state melting stage, the melting current is gradually increased to 10~11 kA within 3~5 minutes. In the capping stage, the melting current decreases in a stepwise manner to 6~7 kA, 4~5 kA, and 1~2 kA, respectively, and each step is maintained for 5~10 minutes.

[0028] The internal control requirements are as follows: Al: [Al]1±0.5%, Nb: 2.7~3.3%, Zr: 1.8~2.3%, Mo: 1.0~1.5%, 0<O≤0.07%.

[0029] Preferably, in step S4:

[0030] During the vacuuming process, the vacuum level of the electron beam cold hearth furnace is controlled to be ≤8×10⁻⁶. -3 Torr;

[0031] During the leak detection, ensure that the leakage rate of the electron beam cold hearth furnace is ≤5 Torr•L / S.

[0032] Preferably, in step S5, when making the solidified shell, the power of electron guns 1 to 4 is 120 to 150 kW.

[0033] Preferably, in step S6: the material is melted using electron guns #1 to #4, with the melting power controlled at 100 to 240 kW and the scanning frequency at 180 to 200 Hz; the molten titanium liquid enters the refining zone, where electron gun #5 is used to refine the titanium liquid, with the refining power controlled at 100 to 160 kW; the refined titanium liquid overflows into the crystallizer, and electron guns #6 to #7 are turned on to heat the titanium liquid. Before the titanium liquid fills the bottom of the crystallizer, the power of electron guns #6 to #7 is 150 to 200 kW, and after filling the entire crystallizer, the power of electron guns #6 to #7 is increased to 200 to 320 kW.

[0034] Preferably, in step S6:

[0035] During the refining process, the surface temperature of the molten pool in the refining zone is stabilized at 150~300℃ above the alloy liquidus line.

[0036] During the casting process, the liquid level in the crystallizer is controlled at 5-10 mm from the edge of the crystallizer by adjusting the power of each electron gun.

[0037] Preferably, in step S7, the compensation time is 10-20 minutes.

[0038] The method for preparing Ti80 titanium alloy flat ingots based on electron beam cold hearth furnace casting of high-return material provided by the present invention has the following beneficial effects:

[0039] 1. This invention adopts the method of Ti80 titanium alloy return material classification and detection → VAR compensation material smelting → staggered material distribution (to ensure that the element content on each cross section is similar). By quantitatively controlling the burning loss through Al element compensation, combined with staggered material distribution, the composition of the molten pool and the element uniformity of the ingot cross section are ensured, thus solving the problem of compositional inhomogeneity under high return material ratio.

[0040] 2. This invention controls the element loss of Ti80 return material in the EB furnace by controlling the electron beam power and scanning strategy in the EB zone. It also strictly controls the power of the electron gun, scanning frequency, melting speed, melting pool depth and residence time of titanium liquid in the refining zone to achieve full alloying and refining, while ensuring the effective removal of high and low density inclusions.

[0041] 3. This invention achieves the preparation of titanium alloy flat ingots with qualified and controllable composition using a large proportion of Ti80 recycled material through VAR casting composition compensation and EB smelting purification-forming synergistic process. This provides raw materials for the short-process manufacturing of Ti80 plates, which meets the current industrial demand for green metallurgy and high-end equipment materials. It is particularly suitable for the industrial mass production of low-cost Ti80 titanium alloys for ships and marine equipment. Attached Figure Description

[0042] Figure 1 This is a process flow diagram of the method for preparing Ti80 titanium alloy flat ingots based on electron beam cold hearth furnace melting and casting of high-return material according to the present invention;

[0043] Figure 2 This is a schematic diagram of the material distribution in the feeding zone and melting zone of the electron beam cold hearth furnace of the present invention; positions 1 to 7 are the scanning areas corresponding to electron guns #1 to #7, 8 is the electron beam cold hearth furnace, 9 is the crystallizer, and 10 is the feeding hopper. Detailed Implementation

[0044] To better understand the above-mentioned technical solutions of the present invention, the technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0045] Combination Figure 1 As shown, this invention provides a method for preparing Ti80 titanium alloy flat ingots based on electron beam cold hearth furnace casting of high-return material, comprising the following steps:

[0046] S1. Determine the composition and quality of the Ti80 titanium alloy return material, and perform cutting and surface treatment.

[0047] In this step, chemical analysis or spectroscopic analysis is used to obtain the composition of each type of Ti80 titanium alloy return material, especially the Al content; the mass of each type of Ti80 titanium alloy return material is recorded, and the average Al content of the Ti80 titanium alloy return material is calculated accordingly.

[0048] (1)

[0049] In the formula, [Al]1 represents the average Al content of the recycled Ti80 titanium alloy, in percentages (%).

[0050] m i The weight of the i-th type of return material is in kg.

[0051] [Al] i The percentage of Al by weight in the i-th type of recycled material, in % (%).

[0052] In this step, the amount of Ti80 titanium alloy recycled material added is 30-70% of the EB raw material.

[0053] Surface treatment of Ti80 titanium alloy return material includes shot blasting (black skin material), acid and alkali washing, cleaning and drying.

[0054] S2. Based on the target composition of Ti80 titanium alloy flat ingot, the VAR compensation material composition is obtained. The VAR compensation material is obtained by mixing sponge titanium, Al-Mo master alloy, Al-Nb master alloy, Al wire and sponge.

[0055] This step mainly determines the VAR compensation material. The target composition of Ti80 titanium alloy flat ingots is as follows by mass percentage: Al: 5.7~6.5%, Nb: 2.7~3.3%, Zr: 1.8~2.3%, Mo: 1.0~1.5%, 0<Si≤0.10%, 0<Fe≤0.25%, 0<C≤0.10%, 0<N≤0.05%, 0<H≤0.010%, O: 0.05~0.10%, with the balance being Ti and unavoidable impurities.

[0056] The Al content in the VAR compensation material is calculated according to the following formula:

[0057] (2)

[0058] In the formula, [Al] represents the target Al content in Ti80 titanium alloy flat ingots, in units of %; m1 represents the total weight of Ti80 titanium alloy return material, in units of kg; [Al]1 represents the average Al content of Ti80 titanium alloy return material, in units of %; m2 represents the weight of VAR compensation material, in units of kg; [Al]2 represents the weight percentage of Al in VAR compensation material, in units of %; and χ represents the volatility coefficient of Al during electron beam melting, ranging from 13% to 19%.

[0059] Based on production experience with Ti-6Al-4V EB ingots, it is known that Al has a high saturated vapor pressure and a volatilization rate of 13%~19% during the smelting process; while Nb, Zr, and Mo have low saturated vapor pressures and their volatilization is negligible. In addition, the oxygen increase during the smelting process is 0.01~0.03%, the nitrogen increase is 0.003~0.004%, and other impurity elements are not increased.

[0060] The weight m2 of the VAR compensation material is determined based on the weight m1 of the Ti80 titanium alloy return material and the proportion of Ti80 titanium alloy return material in the EB raw material. Based on the target [Al] content in the Ti80 titanium alloy flat ingot, the weight m1 of the Ti80 titanium alloy return material, and the average Al content of the Ti80 titanium alloy return material, the weight percentage of Al in the VAR compensation material [Al]2 is determined according to formula (2).

[0061] Based on the above calculations, VAR compensation material was obtained by mixing sponge titanium, Al-Mo master alloy, Al-Nb master alloy, Al wire and sponge.

[0062] S3. After mixing the VAR compensation material, press it into a consumable electrode, then perform vacuum consumable arc melting, and obtain a VAR ingot after exiting the furnace. After the composition is tested and meets the internal control requirements, cut it into VAR ingot cutting blocks.

[0063] In this step, the VAR compensation material is mixed and pressed into a consumable electrode. After the electrode is loaded into a vacuum consumable furnace, it is evacuated to a vacuum level of 1×10⁻⁶. -2 Below Torr, the leakage rate should be controlled to ≤0.1 Torr •L / S.

[0064] Vacuum arc remelting (VAR) is divided into three stages: arc initiation, steady-state melting, and capping. In the arc initiation stage, the melting current is 1.5–3 kA, forming a stable discharge arc, and the consumable electrode begins to melt. In the steady-state melting stage, the melting current and time are controlled, gradually increasing the melting current to 10–11 kA within 3–5 minutes. In the capping stage, the melting current decreases in steps to 6–7 kA, 4–5 kA, and 1–2 kA, maintaining each step for 5–10 minutes. Through this vacuum arc remelting process, VAR ingots with dimensions of φ300–450 × 1000–1400 mm can be obtained.

[0065] The VAR ingot is leveled with a riser, and its surface is cleaned (removing surface inclusions and cracks). It is then cut in half axially. Samples are taken from the head and tail of the ingot for composition testing. The composition must meet the following internal control requirements: Al: [Al] 1±0.5%, Nb: 2.7~3.3%, Zr: 1.8~2.3%, Mo: 1.0~1.5%, 0<O≤0.07%. If the VAR ingot does not meet the above internal control requirements, the quality of the VAR compensation material and the Ti80 titanium alloy return material should be adjusted appropriately to ensure that the [Al] content of the Ti80 titanium alloy flat ingot is met.

[0066] S4, Ti80 titanium alloy return material and VAR ingot cutting block are used as EB raw materials, and after being misaligned and paired, they are put into the feed hopper of the electron beam cold hearth furnace. Then the electron beam cold hearth furnace is sealed and vacuumed and leak checked.

[0067] This step optimizes the fabric structure. Ti80 titanium alloy recycled material and VAR ingot cutting blocks are used as EB raw materials, and they are arranged according to a specific pattern. Specifically, this can be achieved using… Figure 2 The staggered pairing method shown ensures that the proportion of Ti80 titanium alloy return material in each cross section reaches 50-70%, thereby ensuring that the element content in each cross section is similar, which is beneficial to improving the uniformity of composition during melting.

[0068] After placing the Ti80 titanium alloy recycled material and VAR ingot cutting blocks into the feed hopper of the electron beam cooling furnace, the electron beam cooling furnace is sealed, and the furnace is evacuated to a vacuum degree ≤8×10⁻⁶. -3 Torr, and then during leak detection, ensure that the leakage rate of the electron beam cold hearth furnace is ≤5 Torr•L / S. This operation not only ensures the stable operation of the electron gun, but also reduces the increase of oxygen and nitrogen during the melting process.

[0069] S5, confirm the graphic positions of each electron gun in the electron beam cooling bed, and melt the base material in the cooling bed to make a solidified shell;

[0070] In this step, before melting and casting, it is necessary to... Figure 2The positions of the electron guns within the electron beam cooling bed are confirmed; if the positions of all electron guns are accurate (i.e., the boundaries of each electron gun's shape are within...), then... Figure 2 If the boundary position of the scanning area corresponding to the electron gun is shown, the power of electron guns 1 to 4 is increased to 120 to 150 kW to heat and melt the base material in the cooling bed to make a solidified shell; otherwise, the electron guns with errors in the graphic position are adjusted until the graphic position of all electron guns is accurate before the electron guns are turned on.

[0071] S6, start the feeding system, push the material in the feeding hopper to the cooling bed for melting and refining, and then the refined titanium liquid flows into the crystallizer. After the titanium liquid fills the crystallizer, the ingot pulling begins.

[0072] This step is smelting, the core of which is to control the volatilization of elements and the degree of refining by controlling process parameters. The specific parameters involved include melting rate (which determines refining time), power and distribution, and ingot pulling rate.

[0073] The melting rate is represented by M, with units of kg / h. The core of the M value is balancing efficiency and mass. To ensure effective removal of inclusions, the titanium melt must have sufficient residence time in the refining zone. Therefore, M needs to be controlled to be ≤ (V × ρ × 3600) / t, where t is the refining time (s); V is the volume of the molten pool in the refining zone (m³); and ρ is the melt density (~4100 kg / m³). During the smelting of Ti80 titanium alloy, in order to achieve full alloying and efficient removal of high / low density inclusions (such as TiN and Mo segregation) and to achieve ultra-low interstitial element content, the molten pool surface should be (10-15) mm from the upper edge of the cooling bed. For Ti80 titanium alloy return material, the refining time needs to be controlled at 150-200 seconds. Compared to virgin material, the refining time of Ti80 titanium alloy return material is extended to achieve full alloying and refining, while ensuring sufficient settling of high-density inclusions (HDI) and effective flotation and evaporation of low-density inclusions (LDI). In this invention, the melting rate is 350~500 kg / h, and the residence time of the titanium liquid in the electron beam cold bed refining zone is 150~200 seconds.

[0074] The input power of the electron beam cold hearth furnace is P≈ (k × M) / η.

[0075] Wherein, k: melting specific energy, in kW•h / kg, is a core empirical parameter. Generally, for VAR furnaces, k ranges from 0.5 to 1.0 kW·h / kg; for conventional titanium alloys, the melting specific energy ranges from 1 to 2.5 kW·h / kg; however, for Ti80 titanium alloys, due to the presence of high-melting-point elements Mo and Nb, the melting specific energy k is relatively high. However, excessively high specific energy (increasing power and accelerating melting rate) will lead to excessively high molten pool temperature, exacerbating the burn-off of volatile elements such as aluminum (Al), thus disrupting composition control. Drawing on early experience in pure titanium ingot production and to avoid excessive metal burn-off caused by excessive energy, this invention uses a melting specific energy k value of 1.8 to 2.2 kW·h / kg.

[0076] η is the electron beam thermal efficiency, with an empirical value typically ranging from 0.55 to 0.75, which is related to the equipment condition and vacuum level.

[0077] Based on the selection of the above key parameters, the input power range of the electron beam cold hearth furnace is 1000~1600 kW.

[0078] The power distribution in each zone of the electron beam cold hearth furnace can be further refined, as follows:

[0079] The melting zone rapidly melts the solid raw materials (Ti80 titanium alloy return material and VAR ingot cutting blocks) into droplets, which then flow into the refining zone. The power in the refining zone is typically 40%–60% of the total power. In this invention, this power is supplied by electron guns #1–4, each with an energy distribution of 100–240 kW and a scanning frequency of 180–200 Hz. The depth of the molten pool within the melting zone is controlled within the range of d–(10–15) mm, where d is the cooling bed depth. The power is dynamically adjusted according to the feeding rate.

[0080] The refining zone receives molten metal, maintaining a sufficiently large and stable molten pool to ensure refining and alloying are completed within a refining time (≥150 s); the power of the refining zone is typically 10-20% of the total power. In this invention, the power of the refining zone is supplied by the #5 electron gun, with a power range of 100-160 kW and a scanning frequency of 180-200 Hz, uniformly heating the entire surface of the molten pool. By adjusting the inflow rate of the molten zone and the cooling intensity of the water-cooled copper bed, the depth of the molten pool is stably controlled within the range of d-(10-15) mm, where d is the depth of the cooling bed.

[0081] The surface temperature of the molten pool in the refining zone is monitored using an infrared thermometer and stabilized at 150-300°C above the alloy liquidus line (for Ti80 titanium alloy, the surface temperature of the molten pool in the refining zone is approximately 1750-1900°C). This temperature ensures fluidity to facilitate the separation of inclusions while avoiding excessive heating that could lead to volatilization.

[0082] The function of the crystallization zone is to guide the refined melt into the crystallizer. Electron guns compensate for heat loss as the melt flows into the crystallizer, ensuring a stable liquid surface and sequential solidification. Its power is typically 30-40% of the total power. In this invention, the power of the crystallization zone is provided by electron guns #6 and #7, which are used to sweep the surface of the molten pool in the crystallizer, ensuring that the titanium melt fully and evenly fills the entire crystallizer while maintaining the quality of the ingot head. Before the titanium melt covers the bottom of the crystallizer, the power of electron guns #6 and #7 is 150-200 kW; after covering the entire crystallizer, the power increases to 200-320 kW.

[0083] During the above-mentioned melting and casting process, the motion control and power adjustment of the electron gun must be precisely synchronized to ensure the stability and uniformity of the melting and refining process, while ensuring that the melting speed of the material matches the casting speed. During the casting process, the casting speed = melting speed / crystallizer cross-section. Based on experience, the casting speed is controlled at 150~200mm / h. By adjusting the melting speed, the liquid level in the crystallizer can be controlled at 5~10mm from the edge of the crystallizer to ensure the stability and reliability of the casting quality.

[0084] S7. After the casting is completed, the tail of the ingot is rapidly fed back. After the feeding is completed, it is cooled. Then the electron beam cold hearth furnace is opened, and the Ti80 titanium alloy flat ingot is taken out from the crystallizer.

[0085] After the melting and casting is completed, the feeding is stopped and electron guns 1 to 4 are turned off. When there is no titanium liquid flowing at the gate scanned by electron gun 5, electron gun 5 is turned off. Electron guns 6 to 7 are used to feed the flat ingot formed in the crystallizer. In order to eliminate the excessive volatilization of Al during the feeding of the ingot tail, a rapid feeding process is adopted during melting and casting, with a feeding time of 10 to 20 minutes.

[0086] After feeding is completed, the ingot is cooled. After cooling, the electron beam cold hearth furnace is opened, and the Ti80 titanium alloy flat ingot is taken out from the crystallizer.

[0087] Example

[0088] The target composition of the Ti80 titanium alloy flat ingot cast in this embodiment is: Al: 5.7~6.5%, Nb: 2.7~3.3%, Zr: 1.8~2.3%, Mo: 1.0~1.5%, 0<Si≤0.10%, 0<Fe≤0.25%, 0<C≤0.10%, 0<N≤0.05%, 0<H≤0.010%, O 0.05~0.10%, with the balance being Ti and unavoidable impurities.

[0089] Combination Figure 1 As shown in this embodiment, the method for preparing Ti80 titanium alloy flat ingots based on electron beam cold hearth furnace melting and casting of high-return material is as follows:

[0090] The quality and composition of each type of Ti80 titanium alloy return material were analyzed using chemical analysis or spectroscopic analysis. The weights of the Ti80 titanium alloy return material blocks from the three heats were 1380, 2400, and 2800 kg, respectively. The main chemical compositions were as follows: Heat No. 1: Al 5.7%, Nb 3.2%, Zr 1.9%, Mo 1.4%; Heat No. 2: Al 6.1%, Nb 2.8%, Zr 2.0%, Mo 1.0%; and Heat No. 3: Al 6.3%, Nb 3.1%, Zr 2.2%, Mo 1.3%.

[0091] The average Al content of the Ti80 titanium alloy recycled material calculated according to formula (1) is 6.1%, Nb content is 3.0%, Zr content is 2.0%, and Mo content is 1.2%.

[0092] The design of Ti80 titanium alloy flat ingots involves 60% recycled material, resulting in a total material weight of 10,966 kg. The required VAR compensation material weight is 4,386 kg.

[0093] Substituting the median value of [Al] of 6.1 from the target composition of Ti80 titanium alloy flat ingot into formula (2), and taking the value of χ as 13%, the target value of Al in the VAR compensation material is calculated as: Al: 9.1%. Considering that the saturated vapor pressure of Nb, Zr, and Mo is low and volatilization is negligible, the value of the target composition of Ti80 titanium alloy flat ingot is taken as the median value, that is, Nb 3.0%, Zr 2.1%, Mo 1.3%, and other elements are not included.

[0094] The VAR compensation material is made from sponge titanium, Al-Mo master alloy, Al-Nb master alloy, Al wire, and sponge zirconium. After mixing the above materials, they are pressed into a consumable electrode with a diameter of φ316 mm and loaded into a crystallizer with a diameter of φ423 mm.

[0095] After the consumable electrode is installed in the vacuum consumable furnace, a vacuum process is performed until the vacuum level inside the furnace reaches 1×10⁻⁶. - 2 Below Torr, the leakage rate is ≤0.1 Torr •L / S.

[0096] Vacuum self-consuming arc melting includes three stages: arc initiation, steady-state melting, and capping.

[0097] During the arc initiation stage, the melting current is controlled at 1.5~3kA to form a stable discharge arc, and the consumable electrode begins to melt. During the melting stage, the melting current is gradually increased to 10~11 kA within 3~5 minutes, and melting is carried out normally to the predetermined weight. After reaching the predetermined weight, the melting current is reduced in steps to 6, 4, and 1 kA, with each step maintained for 5~10 minutes; after cooling, the VAR ingot with dimensions of φ423×1200 mm is obtained by breaking the void.

[0098] The VAR ingot was leveled with risers, and its surface was cleaned (removing surface inclusions and cracks). Samples were taken from both ends for chemical composition analysis. The results showed Al 9.2%, Nb 3.0%, Zr 2.0%, Mo 1.3%, and O 0.05%, meeting the internal control requirements for chemical composition (i.e., Al: 9.05~9.45%, Nb: 2.7~3.3%, Zr: 1.8~2.3%, Mo: 1.0~1.5%, O < O ≤ 0.06%). The VAR ingot was then cut into small pieces along the axis and radial direction for use in the EB furnace charging.

[0099] Following the steps described above, seven VAR primary casting ingots were smelted as raw materials for EB ingots. The main element content range of the obtained VAR casting ingots was Al 9.1-9.4%, Nb 2.9-3.1%, Zr 1.9-2.2%, Mo 1.1-1.4%, and O 0.05-0.06%, which meets the internal control requirements for the chemical composition of furnace VAR casting ingots.

[0100] The Ti80 titanium alloy return material and VAR ingot cutting block are arranged in a "misaligned" structure. Figure 2 The materials are arranged in a way that ensures that the returned material occupies approximately 60% of the area on each cross-section.

[0101] Seal the electron beam cold hearth furnace and evacuate it to 8×10⁻⁶. -3 The leakage rate of the electron beam cold hearth furnace is then tested to ensure that it does not exceed 5 Torr • L / S.

[0102] Before casting, confirm the pattern position of the electron guns and ensure that the image boundary positions of each electron gun are aligned with the target area. Figure 2 The boundary positions of the corresponding electron gun scanning areas are consistent.

[0103] The feeding system is activated, pushing the EB raw material from the hopper into the melting zone. The power of electron guns #1-#4 is sequentially increased to 150±20kW, the scanning frequency is controlled at 180-200 Hz, and the melting rate is maintained at 450±20 kg / h. The depth of the Ti80 titanium alloy molten pool in the melting zone is stably controlled within the range of 55-60mm (cooling bed depth d=70mm). The molten material flows into the refining zone, and the power of electron gun #5 is controlled at 130±30kW. By adjusting the inflow rate in the melting zone and the cooling intensity of the water-cooled copper bed, the depth of the molten pool is stably controlled within the range of 55-60 mm. The molten material resides in the refining zone for approximately 160 seconds to achieve sufficient alloying and refining. After the refined melt overflows into the crystallizer in the crystallization zone, electron guns #6 and #7 are gradually heated to gradually heat the molten titanium. At this stage, the power of electron guns #6 and #7 is 160-200 kW. Once the molten titanium has filled the entire crystallizer, the power of guns #6 and #7 is increased to 250±50 kW for casting, ensuring the molten titanium fully and evenly fills the entire crystallizer to guarantee the quality of the ingot. The crystallizer dimensions are 1525×355 mm.

[0104] During the casting process, the casting speed is controlled at 150~200mm / h; the liquid level in the crystallizer is controlled at 5~10mm from the edge of the crystallizer.

[0105] After the ingot is melted and cast, the feeding is stopped and electron guns 1 to 4 are turned off. When there is no titanium liquid flowing at the gate scanned by electron gun 5, electron gun 5 is turned off. Electron guns 6 to 7 are used to feed the flat ingot formed in the crystallizer for 15 minutes.

[0106] After feeding, the ingot was cooled for 3 hours. Finally, the electron beam cold hearth furnace was opened, and the Ti80 titanium alloy flat ingot with dimensions of 350×1520×4400mm was taken out of the crystallizer. Four points along the length of the ingot were selected for elemental analysis (Al, Nb, Zr, Mo, Fe, Si, C, N, H, O). The results are shown in Table 1.

[0107] The data in Table 1 show that the Ti80 flat ingot prepared by the method of the present invention exhibits excellent uniformity and ultra-high purity in chemical composition over a length of 4.4 meters, specifically as follows: (1) The main alloying elements have good uniformity along the length of the ingot, confirming the effectiveness of "misaligned material distribution and quantitative compensation". Al (the most difficult volatile element to control): the content fluctuates between 5.72% and 6.30%, with a range of only 0.58%; this not only falls completely within the internal control target (5.7~6.5%), but also the fluctuation range is much smaller than the deviation of >1% that may occur in conventional processes. This proves the effectiveness of the strategy of "return material classification and detection → VAR compensation material smelting → misaligned material distribution" and the Al element feedforward compensation model based on the burning loss law, solving the problem of composition uniformity under a high proportion of return material. (2) Refractory elements Mo and Nb: The Mo content range is 0.07%, and the Nb content range is 0.12%. This indicates that the refractory elements have also been fully homogenized, proving the sufficiency of VAR pre-alloying and the effectiveness of EB melting, and avoiding high-density segregation. (3) The purity reaches an ultra-high level. Gaseous elements: The O content is stable at 0.06% (O≤0.15% in Table 1 GBT3620.1-2016), the N content is stable at 0.004% (N≤0.05% in Table 1 GBT3620.1-2016), and the H content is less than 0.002%. This indicates that the entire melting and solidification process is under excellent protection, and the high vacuum environment of the EB furnace effectively removes the gas. Other impurities: The contents of impurities such as Fe, Si, and C are also far below the standard limits, proving that through precise power ratio and scanning control, a stable and uniform molten pool temperature field and flow field are formed, which not only ensures the uniform distribution of alloying elements, but also provides sufficient thermodynamic and kinetic conditions for inclusions to float / sink and for gas to escape.

[0108] In summary, the data in Table 1 proves that this invention, through an innovative system process, has successfully achieved precise control over the chemical composition of large-size, highly alloyed Ti80 flat ingots under a high return material ratio, thus achieving the predetermined goal of "high uniformity and high purity".

[0109] Table 1

[0110]

[0111] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A method of producing Ti80 titanium alloy slabs based on electron beam cold hearth melting of high return material, characterized in that: It comprises the following steps: S1, determining the composition and mass of Ti80 titanium alloy return material, and cutting and surface treatment; The adding amount of the Ti80 titanium alloy return material is 30-70% of the EB raw material; S2, obtaining VAR compensation material composition according to the target composition of Ti80 titanium alloy slab, and using sponge titanium, Al-Mo intermediate alloy, Al-Nb intermediate alloy, Al wire and sponge zirconium for batching to obtain VAR compensation material; The Al composition in the VAR compensation material is calculated according to the following formula: ； In the formula, [Al] is the target composition of Al in the Ti80 titanium alloy slab, in %; m1 is the total weight of the Ti80 titanium alloy return material, in kg; [Al]1 is the average Al content of the Ti80 titanium alloy return material, in %; m2 is the weight of the VAR compensation material, in kg; [Al]2 is the weight percentage content of Al in the VAR compensation material, in %; χ is the volatilization coefficient of Al during electron beam melting, and the value range is 13%-19%; The target composition of the Ti80 titanium alloy slab is as follows in mass percentage: Al: 5.7-6.5%, Nb: 2.7-3.3%, Zr: 1.8-2.3%, Mo: 1.0-1.5%, 0≤Si≤0.10%, 0≤Fe≤0.25%, 0≤C≤0.10%, 0≤N≤0.05%, 0≤H≤0.010%, O: 0.05-0.10%, and the balance is Ti and unavoidable impurities; S3, pressing the mixed VAR compensation material into consumable electrode, then performing vacuum consumable arc melting, obtaining VAR ingot after tapping, and performing composition detection, and cutting into VAR ingot cutting block after meeting the internal control requirements; The internal control requirements are as follows: Al: [Al]1±0.5%, Nb: 2.7-3.3%, Zr: 1.8-2.3%, Mo: 1.0-1.5%, and 0≤O≤0.07%; S4, taking the Ti80 titanium alloy return material and the VAR ingot cutting block as EB raw material, placing them into the feeding bin of the electron beam cold hearth furnace after staggered pairing, then sealing the electron beam cold hearth furnace, and performing vacuumizing and leak detection; S5, confirming the pattern position of each electron gun in the electron beam cold hearth, and melting the bedding material in the cold hearth to make a solidified skull; S6, starting the feeding system, pushing the material in the feeding bin to the cold hearth, performing melting and refining, then flowing the refined titanium liquid into the crystallizer, and starting to draw ingot after the titanium liquid fills the crystallizer; The melting rate is 350-500 kg / h, the residence time of the titanium liquid in the electron beam cold hearth refining zone is 150-200 seconds, and the ingot drawing speed is controlled at 150-200 mm / h; S7, after the melting and casting are completed, quickly supplementing the tail part of the ingot, cooling after the supplementing is completed, then opening the electron beam cold hearth furnace, and taking out the Ti80 titanium alloy slab from the crystallizer.

2. The method of producing Ti80 titanium alloy ingot based on electron beam cold hearth furnace melting of high return material according to claim 1, characterized in that: In step S1: The composition of each type of Ti80 titanium alloy return material is obtained by chemical analysis or spectral analysis, and the mass is recorded, and the average Al content of the Ti80 titanium alloy return material is calculated; The surface treatment comprises shot blasting, acid and alkali washing, cleaning and drying treatment.

3. The method of producing Ti80 titanium alloy ingot based on electron beam cold hearth furnace melting of high return material according to claim 1, characterized in that: In step S3: After the electrode is loaded into the vacuum consumable furnace, vacuum is drawn to 1 x 10 -2 Torr, and the leakage rate is controlled to be ≤ 0.1 Torr • L / S. The vacuum consumable arc melting is divided into three stages of starting arc, steady melting and capping; in the starting arc stage, the melting current is 1.5-3 kA; in the steady melting stage, the melting current is gradually increased to 10-11 kA within 3-5 min; in the capping stage, the melting current is decreased to 6-7 kA, 4-5 kA and 1-2 kA in a step manner, and each step is kept for 5-10 min.

4. The method of producing Ti80 titanium alloy ingot based on an electron beam cold hearth furnace with high return material according to claim 1, characterized in that: In step S4: During the vacuumizing process, the vacuum degree of the electron beam cold bed furnace is controlled to be ≤8×10 -3 Torr. In the leakage detection, the air leakage rate of the electron beam cold hearth furnace is ensured to be ≤5 Torr•L / S.

5. The method of producing Ti80 titanium alloy ingot based on electron beam cold hearth furnace melting of high return material according to claim 4, characterized in that: In step S5, when the solidified shell is made, the power of the 1-4# electron guns is 120-150 kW.

6. The method of producing Ti80 titanium alloy ingot based on an electron-beam cold hearth furnace with high return material according to claim 1, characterized in that: In step S6: the material is melted by the 1-4# electron guns, the melting power is controlled to be 100-240 kW, and the scanning frequency is 180-200 Hz; the melted titanium liquid enters the refining zone, the 5# electron gun is used to refine the titanium liquid, and the refining power is controlled to be 100-160 kW; the refined titanium liquid overflows into the crystallizer, the 6-7# electron guns are turned on to heat the titanium liquid, before the titanium liquid spreads over the bottom of the crystallizer, the power of the 6-7# electron guns is 150-200 kW, and after the titanium liquid spreads over the entire crystallizer, the power of the 6-7# electron guns is increased to 200-320 kW.

7. The method of producing Ti80 titanium alloy ingot based on an electron beam cold hearth furnace melting of high return material according to claim 1, characterized in that: In step S6: In the refining process, the surface temperature of the refining zone molten pool is stabilized at 150-300 ℃ above the alloy liquidus; In the ingot drawing process, the liquid level height in the crystallizer is controlled to be 5-10 mm away from the edge of the crystallizer by adjusting the power of each electron gun.

8. The method of producing Ti80 titanium alloy ingot based on an electron-beam cold hearth furnace with high return material according to claim 1, characterized in that: In step S7, the feeding time is 10-20 min.

Images