Smelting method for homogeneous ultra-high strength titanium alloy ingots

Abstract

This invention discloses a method for melting homogeneous ultra-high strength titanium alloy ingots, belonging to the field of titanium alloy technology. To ensure the uniformity of elements in the ultra-high strength titanium alloy ingots, this invention provides a method for melting homogeneous ultra-high strength titanium alloy ingots, comprising: electrode block thickness H and pressing density ρ satisfying H≤k / (ρ-ρ0), welding to obtain a consumable electrode; the consumable electrode undergoes three melting processes, with the current I2 in the stable melting stage of the second melting process satisfying: I2≥α×I1, I2≥β×I ‑ The rated value is ≥10 min for the third melting and feeding process, and the melting current decrease rate is >1.2 kA / min. This invention ensures the stability of the consumable electrode during the first melting by controlling the particle size of the raw materials and designing the electrode block thickness; the second melting process uses an ultra-high limiting current process to reduce inclusion defects; and the third melting process uses an ultra-fast current interruption feeding process to make the ingot composition uniform, resulting in a high-quality, homogeneous, ultra-high-strength titanium alloy ingot.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis technology, specifically relating to a method for smelting homogeneous ultra-high strength titanium alloy ingots. Background Technology

[0002] Ultra-high strength titanium alloys refer to those with a room temperature strength greater than 1100 MPa and a fracture toughness of 55 MPa·m. 1 / 2 The above refers to titanium alloys. With the rapid development of aerospace vehicles, the performance and demand for ultra-high strength titanium alloys are becoming increasingly higher. CN120989434A discloses a 1500MPa grade titanium alloy bar and its preparation method. It originally designed a near-β type ultra-high strength titanium alloy with a composition system of Ti-V-Mo-Al-Zr-Cr-Nb-Fe. After processing, its room temperature strength is greater than 1500MPa and its elongation is greater than 6%, which can meet the requirements of modern high-level aircraft for large aerospace structural components. In this method, the raw material is pressed into an electrode block, welded to obtain a consumable electrode, and subjected to three vacuum consumable melting processes to obtain a titanium alloy ingot. The three vacuum consumable melting processes all use a sinusoidal AC stabilizing current. The specific process is as follows: First time: vacuum degree ≤2Pa, arc ignition to stable melting time ≤30min, average melting rate ≤5kg / min; Second and third times: vacuum degree ≤1.5Pa, arc ignition to stable melting time ≤25min, average melting rate ≤4kg / min.

[0003] However, the aforementioned Ti-V-Mo-Al-Zr-Cr-Nb-Fe ultra-high-strength titanium alloy, due to its multi-component design, exhibits significant differences in the melting points and densities of its elements, making it prone to macroscopic segregation and inclusion defects during solidification. This poses a significant challenge to controlling the compositional uniformity and microstructural stability of the ingot. Specifically, the electrode blocks are formed by pressing loose alloy raw materials, and their density is affected by the quality and particle size of the raw materials. If the electrode blocks do not meet the density requirements, they will break off and enter the molten pool, forming defects. The inventors discovered these problems in actual production. Therefore, based on CN120989434A, this invention improves the preparation process of homogeneous ultra-high-strength titanium alloy ingots.

[0004] CN115772616A discloses an ultra-high strength titanium alloy for aerospace structural components, which is composed of the following components by mass percentage: Al 4.0%~6.0%, Cr 4.0%~6.0%, Zr 2.0%~4.0%, Nb 0.5%~1.5%, (Mo+V) / Cr=(1~1.5):1, Mo / V=1:(0.5~1.3), with the balance being Ti and unavoidable impurities; in its preparation method, the raw materials are mixed and then subjected to three vacuum consumable arc melting processes, but the specific melting operations are not disclosed.

[0005] CN121294946A discloses an ultra-high strength titanium alloy for aerospace structural components, which is composed of the following components by mass percentage: Al: 5.5wt%~6.2wt%, V: 3.5wt%~4.2wt%, Mo: 1.2wt%~1.8wt%, Cr: The composition is as follows: Fe: 0.4wt%~0.6wt%, Si: 0.08wt%~0.12wt%, rare earth elements: 0.05wt%~0.15wt%, Hf: 0.1wt%~0.3wt%, Ta: 0.2wt%~0.5wt%, B: 0.005wt%~0.015wt%, with the remainder being Ti and unavoidable impurities; the rare earth elements are at least one of Nd and Er; the preparation method involves smelting in a vacuum arc furnace, which includes a first smelting, a second smelting, a third smelting, and a fourth smelting, wherein the vacuum degree of the first smelting is controlled at 8.0 × 10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1620~1680℃, and the melting time is 35~38min; the vacuum degree of the second melting is controlled at 4.0×10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1580~1620℃, and the melting time is 30~32min; the vacuum degree of the third melting is controlled at 2.0×10⁻⁶. -4 The arc ignition current is below Pa, the melting temperature is 1530~1570℃, and the melting time is 25~28min; the vacuum degree of the fourth melting is controlled at 1.0×10⁻⁶. -4 Below Pa, the arc ignition current is 1800~2000A, the melting temperature is 1500~1520℃, and the melting time is 20~22min.

[0006] CN117107113A discloses a Ti-Al-V-Mo-Cr-Zr-Nb metastable β-titanium alloy, comprising 3.8%~4.6% aluminum, 5.7%~6.5% vanadium, 4.2%~5.2% molybdenum, 3.0%~3.7% chromium, 1.0%~2.2% zirconium, ≤1.0% niobium, ≤0.05% carbon, ≤0.05% nitrogen, ≤0.015% hydrogen, and ≤0.15% oxygen, with the balance being titanium and impurity elements. The preparation method involves three vacuum arc remelting processes to prepare the components of the Ti-Al-V-Mo-Cr-Zr-Nb metastable β-titanium alloy into a titanium alloy ingot with uniform microstructure and chemical composition. However, the specific smelting operation is not disclosed.

[0007] CN119663051A discloses a Ti-V-Zr-Cr-Al series ultra-high strength near-β titanium alloy, which comprises, by mass percentage, 5.0~5.5% Al, 11.0~11.5% V, 2.5~3.0% Cr, 4.5~5.0% Zr, with the balance being Ti and unavoidable impurity elements; it is produced by two melting processes in a conventional vacuum arc furnace to form alloy ingots.

[0008] However, the above methods also cannot solve the problems of CN120989434A. For example, if the particle size of the smelting raw materials is not strictly controlled, it will easily affect the pressing of the electrode block. Electrode blocks with uneven particle size are prone to looseness and are easy to fall off during the first smelting, forming metallurgical defects. In order to strictly control the thickness of the electrode block, it will easily affect the density of the electrode block, and it will also be easy to fall off during the first smelting, forming metallurgical defects. During the smelting process, the refractory inclusions are not melted sufficiently, which affects the quality of the ingot and may cause cracks in the product. In addition, the uniformity of the ingot composition is easily deteriorated during the cooling process.

[0009] Therefore, in response to the urgent need for ultra-high strength titanium alloys, it is necessary to develop a new smelting method for homogeneous ultra-high strength titanium alloy ingots. Summary of the Invention

[0010] To meet the urgent demand for ultra-high strength titanium alloys in the aerospace industry, this invention ensures the stability of the consumable electrode during the first VAR melting process by selecting smelting raw materials, controlling the particle size of the raw materials, and designing the thickness of the electrode block. During the second VAR melting process, a high-temperature molten pool can be formed under extremely high current, completely melting refractory inclusions and causing them to lose their original form as heterogeneous cores, dispersing them in solid solution within the titanium alloy. During the third VAR melting process, rapid cooling is beneficial to the uniformity of the smelting composition. Accordingly, the current is rapidly cut off during the final feeding process to ensure uniform composition of the ingot. Based on these measures, the uniformity of elements in the ultra-high strength titanium alloy ingot can be guaranteed. Therefore, a melting method for homogeneous ultra-high strength titanium alloy ingots is proposed.

[0011] This invention provides a method for smelting homogeneous ultra-high strength titanium alloy ingots, comprising the following steps:

[0012] A. Select raw materials based on the chemical composition of the ultra-high strength titanium alloy ingot, then weigh and batch them; the composition system of the ultra-high strength titanium alloy ingot is Ti-V-Mo-Al-Zr-Cr-Nb-Fe, and its chemical composition by mass percentage is: V 5.5~6.5%, Mo 4.5~5.5%, Al 3.0~4.0%, Zr 2.5~3.5%, Cr 1.5~2.5%, Nb 1.5~2.5%, Fe 0.9~1.1%, with the balance being Ti and unavoidable impurities; or, its chemical composition by mass percentage is: V 3.5~4.5%, Mo 4.5~5.5%, Al 3.0~4.0%, Zr 2.5~3.5%, Cr 1.5~2.5%, Nb 1.5~2.5%, Fe 0.4~0.6%, with the balance being Ti and unavoidable impurities;

[0013] B. Press the raw materials prepared in step A according to the specified proportions into multiple electrode blocks. The thickness H of each electrode block and its pressing density ρ satisfy the following relationship: H≤k / (ρ-ρ0), where k is a coefficient with a value ranging from 100 to 250 mm·g / cm³. 3 ρ0 is the reference density, with a value ranging from 3.1 to 3.4 g / cm³. 3 H is in mm, and the compression density ρ ranges from 3.4 to 4.0 g / cm³. 3 After pressing, multiple electrode blocks are welded together to obtain a consumable electrode.

[0014] C. The consumable electrode from step B is melted for the first time. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The current I1 in the stable melting stage is 14~16.5kA. After melting, the electrode is cooled and removed from the furnace to obtain a primary ingot.

[0015] D. The ingot from step C is subjected to a second melting process. The melting process is divided into an arc initiation stage, a stable melting stage, and a feeding stage. The stable melting stage adopts an ultra-high limiting current process, specifically, the current I2 in the stable melting stage satisfies: I2≥α×I1, and I2≥β×I - Rated, α is the current amplification factor, ranging from 1.1 to 2.0, β is the rated load factor, ranging from 0.85 to 0.98, I - Rated is the rated output current of the main power supply of the vacuum self-consuming electric arc furnace used. After melting, cooling and tapping out of the furnace, a secondary ingot is obtained.

[0016] E. The secondary ingot from step D is subjected to a third melting process. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The current during the stable melting stage is I3. The feeding process adopts an ultra-fast current interruption feeding process with a feeding time ≥10min and a melting current decrease rate >1.2kA / min. After the melting process is completed, the ingot is cooled and then taken out of the furnace to obtain a tertiary ingot.

[0017] After post-processing, the three ingots from steps F and E yield a homogeneous ultra-high strength titanium alloy ingot.

[0018] In the above-mentioned smelting method, in step A, the raw materials are sponge titanium, aluminum briquettes, sponge zirconium, Al-60Cr, Ti-50Nb, Ti-32Mo, Al-85V, and Ti-30Fe.

[0019] In the above-mentioned smelting method, in step A, the raw materials contain sponge titanium with a particle size of 3~12.7mm, aluminum granules with a particle size of 8~13mm, sponge zirconium with a particle size of 1~18mm, Al-60Cr with a particle size of 1~6mm, Ti-50Nb with a particle size of 1~6mm, Ti-32Mo with a particle size of 1~6mm, Al-85V with a particle size of 1~6mm, and Ti-30Fe with a particle size of 1~6mm.

[0020] In the above smelting method, in step B, each electrode block is mixed by alternating clockwise and counterclockwise rotation.

[0021] In the above smelting method, in step B, the electrode block is a cylinder with a diameter of Φ450~500mm and a height equal to its thickness.

[0022] In the above smelting method, in step B, 110mm≤H≤k / (ρ-ρ0).

[0023] In the above smelting method, in step C, the vacuum degree is ≤1.5Pa.

[0024] In the above smelting method, in step C, the arc ignition time is ≤25min.

[0025] In the above smelting method, in step C, the feeding time is ≥15min.

[0026] In the above smelting method, in step C, the arc stabilizing current is AC, with a magnitude of 3~9A.

[0027] In the above smelting method, in step C, the cooling process involves a power-off cooling time of ≥8 hours.

[0028] In the above smelting method, in step D, the vacuum degree is ≤1.5Pa.

[0029] In the above smelting method, in step D, the arc ignition time is ≤25min.

[0030] In the above smelting method, in step D, the feeding time is ≥15min.

[0031] In the above smelting method, in step D, the arc stabilizing current is AC, with a magnitude of 5~10A.

[0032] In the above smelting method, step D involves cooling with a power outage for ≥8 hours.

[0033] In the above smelting method, in step D, I - The rated value ranges from 39 to 40 kA.

[0034] In the above smelting method, in step D, I2 ≥ α × I1 and I2 ≥ β × I - rated, and I2 - rated.

[0035] In the above smelting method, in step E, the vacuum degree is ≤1.2Pa.

[0036] In the above smelting method, in step E, the arc ignition time is ≤25min.

[0037] In the above smelting method, in step E, the arc stabilizing current is AC, with a magnitude of 6~12A.

[0038] In the above smelting method, in step E, the cooling process involves a power-off cooling time of ≥8 hours.

[0039] In the above smelting method, in step E, the value of I3 ranges from 24.5 to 28.5 kA.

[0040] In the above-mentioned smelting method, step F includes post-processing such as flattening and surface finishing.

[0041] The beneficial effects of this invention are:

[0042] This invention achieves a dense and compact electrode by carefully selecting smelting raw materials, controlling the particle size of the raw materials, and designing the electrode block thickness, ensuring the stability of the consumable electrode during the first VAR melting process. In the second VAR melting process, an ultra-high limiting current process significantly increases the molten pool temperature, allowing inclusions to melt and disperse in the ingot, thereby reducing inclusion defects. In the third VAR melting process, an ultra-fast current-cutting feeding process is employed to rapidly solidify the ingot, resulting in a homogeneous ingot composition. This invention improves the compositional uniformity and controls shrinkage cavities in ultra-high-strength titanium alloys, enabling stable industrial production of high-quality, homogeneous ultra-high-strength titanium alloy ingots. After processing, these ingots can meet the requirements of modern high-performance aircraft and have broad application prospects. Attached Figure Description ​

[0043] Figure 1 This is a schematic diagram of the ultra-fast current interruption compensation of the present invention.

[0044] Figure 2 This is a schematic diagram of traditional shrinkage compensation. Detailed Implementation

[0045] Specifically, a method for smelting a homogeneous ultra-high strength titanium alloy ingot includes the following steps:

[0046] Step 1: This involves an ultra-high-strength titanium alloy with a composition system of Ti-V-Mo-Al-Zr-Cr-Nb-Fe. Its chemical composition, by mass percentage, is: V 5.5~6.5%, Mo 4.5~5.5%, Al 3.0~4.0%, Zr 2.5~3.5%, Cr 1.5~2.5%, Nb 1.5~2.5%, Fe 0.9~1.1%, with the balance being Ti and unavoidable impurities; or, its chemical composition, by mass percentage, is: V 3.5~4.5%, Mo 4.5~5.5%, Al 3.0~4.0%, Zr 2.5~3.5%, Cr 1.5~2.5%, Nb 1.5~2.5%, Fe 0.4~0.6%, with the balance being Ti and unavoidable impurities; based on the composition of ultra-high strength titanium alloy, the raw materials selected are: sponge titanium, aluminum briquettes, sponge zirconium, Al-60Cr, Ti-50Nb, Ti-32Mo, Al-85V, and Ti-30Fe; the raw materials are selected to remove hard-core titanium, foamed titanium, etc., with the following requirements: sponge titanium particle size 3~12.7mm, aluminum briquettes particle size 8~13mm, sponge zirconium particle size 1~18mm, Al-60Cr particle size 1~6mm, Ti-50Nb particle size 1~6mm, Ti-32Mo particle size 1~6mm, Al-85V particle size 1~6mm, and Ti-30Fe particle size 1~6mm.

[0047] Step Two: Mix the raw materials from Step One according to the specified ratio and press them into multiple electrode blocks. The mixing of each electrode block is performed by alternating clockwise and counterclockwise rotation. The thickness H (mm) of each electrode block and its pressing density ρ (g / cm³) are... 3 The following relationship must be satisfied: H ≤ k / (ρ-ρ0), where k is a coefficient with a value ranging from 100 to 250 mm·g / cm³. 3 ρ0 is the reference density, with a value ranging from 3.1 to 3.4 g / cm³. 3 Generally speaking, H ≥ 110 mm (i.e., 110 mm ≤ H ≤ k / (ρ - ρ0)), and the value of ρ ranges from 3.4 to 4.0 g / cm³. 3 After pressing and welding multiple electrode blocks, a consumable electrode is obtained.

[0048] Step 3: The consumable electrode from Step 2 is melted for the first time. The vacuum degree is ≤1.5Pa. The melting is divided into an arc ignition stage, a stable melting stage, and a feeding stage. The arc ignition time is ≤25min. The current I1 in the stable melting stage is 14~16.5kA. The feeding time is ≥15min. The arc stabilization current is AC, with a value of 3~9A. After melting, the power is cut off and the cooling time is ≥8h. After exiting the furnace, a primary ingot is obtained.

[0049] Step 4: The ingot from Step 3 is subjected to a second melting process. The vacuum degree is ≤1.5Pa. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The arc-starting time is ≤25min. The stable melting stage adopts the "ultra-high limiting current process". Specifically, the current I2 in the stable melting stage satisfies: I2≥α×I1 and I2≥β×I - Rated, α is the current amplification factor, ranging from 1.1 to 2.0, β is the rated load factor, ranging from 0.85 to 0.98, I - Rated refers to the rated output current of the main power supply of the vacuum self-consuming electric arc furnace used, I. - The rated value typically ranges from 39 to 40 kA, and generally speaking, I² < I. - Rated, feeding time ≥15min, arc stabilization current uses AC current, magnitude is 5~10A, power off cooling time after melting ≥8h, after tapping out of furnace, secondary ingot is obtained.

[0050] Step 5: The secondary ingot from Step 4 is subjected to a third melting process. The vacuum degree is ≤1.2Pa. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The arc-starting time is ≤25min. The current I3 in the stable melting stage ranges from 24.5 to 28.5kA. The feeding process adopts the "rapid current interruption feeding process", the schematic diagram of which is shown below. Figure 1 As shown, the feeding time is ≥10min, and the melting current decrease rate is >1.2kA / min. The arc stabilization current is AC, with a magnitude of 6~12A. After melting, the power is cut off and the cooling time is ≥8h. Three-stage ingots are obtained after exiting the furnace.

[0051] Step Six: After flattening and surface polishing the three ingots from Step Five, a homogeneous ultra-high strength titanium alloy ingot is obtained.

[0052] This invention, based on the Ti-V-Mo-Al-Zr-Cr-Nb-Fe system described in CN120989434A, improves the smelting process. Therefore, this invention is applicable to smelting and preparing titanium alloy ingots with the following composition by mass percentage: V 5.5~6.5%, Mo 4.5~5.5%, Al 3.0~4.0%, Zr 2.5~3.5%, Cr 1.5~2.5%, Nb 1.5~2.5%, Fe 0.9~1.1%, with the balance being Ti and unavoidable impurities. Furthermore, experiments have shown that this invention is also applicable to titanium alloy ingots with other Ti-V-Mo-Al-Zr-Cr-Nb-Fe system compositions, for example, with the following chemical composition by mass percentage: V 3.5~4.5%, Mo 4.5~5.5%, Al 3.0~4.0%, Zr 2.5~3.5%, Cr 1.5~2.5%, Nb 1.5~2.5%, Fe 0.4~0.6%, balance Ti and unavoidable impurities.

[0053] In this invention, experiments have shown that electrode blocks pressed from raw materials with suitable particle size are denser, more stable during the first melting, reduce the risk of chipping, and ensure uniform ingot composition, thus avoiding metallurgical defects. If the raw material particle size is uneven, the pressed electrode blocks are prone to edge chipping, corner chipping, and loosening, posing a risk of chipping during the first melting. Therefore, this invention strictly controls the raw material particle size according to the aforementioned requirements.

[0054] In this invention, to ensure the quality of the consumable electrode after welding, making it more stable during the first melting process, reducing the risk of sharding, ensuring uniform ingot composition, and avoiding metallurgical defects, it is necessary to synergistically limit the thickness and density of the electrode block. Through experimentation, the mutual limiting relationship between the electrode block thickness and density in this invention is determined by the formula: H ≤ k / (ρ - ρ0), controlling the density of the pressed electrode block within a certain range, while simultaneously controlling the thickness within a certain range; wherein, the pressing density ρ needs to be controlled within the range of 3.4~4.0 g / cm³. 3 Within the range; in addition, the thickness of the electrode block and the pressing density affect each other, so the present invention requires special control of the thickness of the electrode block and the pressing density, but the other specifications of the electrode block are the same as those of conventional processes. For example, in the field, a single electrode block is generally a cylinder with a diameter of Φ450~500mm and a height equal to the thickness. At this time, based on the specifications of each electrode block, the number of electrode blocks can be determined according to common knowledge in the field. Then, all these electrode blocks are welded together to obtain a consumable electrode.

[0055] In this invention, the function of the current in the stabilizing melting stage is to generate high temperature, causing the electrode to heat up and melt into a liquid phase; the function of the arc stabilizing current is to generate a magnetic field, causing the liquid metal to rotate.

[0056] In this invention, the second melting process employs an "ultra-high limiting current process," generating extremely high temperatures in the molten pool. This completely melts the refractory inclusions, causing them to lose their original form as heterogeneous nuclei and disperse into the titanium alloy in a solid solution, significantly improving alloy quality and reducing problems such as cracking. The second melting process requires the current I2 in the second stable melting stage to be greater than the current I1 in the first stable melting stage, but with a limit close to the rated current I of the melting equipment. - The electrode diameter for the second melting process is larger than that for the first melting process, requiring a larger melting current. Therefore, I2 must be greater than I1, and the larger the second melting current, the better. However, I2 cannot exceed the rated current of the equipment. - Therefore, the current rating is set close to the device's limiting current. Thus, this invention innovatively requires I2 ≥ β × I, building upon the conventional process requirement of I2 ≥ α × I1. - rated, naturally I² < I - Rated. Based on actual production, the value range of α is 1.1~2.0, and the value range of β is 0.85~0.98. - The rated range is determined based on the smelting equipment. For example, in this embodiment of the invention, the range is 39~40kA. Better smelting equipment can also be used. - The rating will be higher.

[0057] In conventional processes, the time for the first and second feeding cycles is ≥15 minutes, and the time for the third feeding cycle is ≥60 minutes. Figure 2 As shown; however, this invention requires the third feeding time to be ≥10 min, and the melting current decrease rate to be >1.2 kA / min. It employs an ultra-fast current-interruption feeding process, using rapid cooling to quickly solidify the ingot, thereby ensuring uniform ingot composition, such as... Figure 1 As shown.

[0058] The following specific embodiments will be provided to explain the solution of the present invention. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0059] Example 1

[0060] This embodiment relates to an ultra-high strength titanium alloy with a composition system of Ti-V-Mo-Al-Zr-Cr-Nb-Fe.

[0061] Step 1: Based on the composition of the ultra-high strength titanium alloy: V 6.0%, Mo 5.0%, Al 3.5%, Zr 3.0%, Cr 2.0%, Nb 2.0%, Fe 1.0%, with the balance being Ti and unavoidable impurities; select the following raw materials: sponge titanium, aluminum briquettes, sponge zirconium, Al-60Cr, Ti-50Nb, Ti-32Mo, Al-85V, and Ti-30Fe; select the raw materials, removing hard-core titanium, foamed titanium, etc., with the following requirements: sponge titanium particle size 3~12.7mm, aluminum briquettes particle size 8~13mm, sponge zirconium particle size 1~18mm, Al-60Cr particle size 1~6mm, Ti-50Nb particle size 1~6mm, Ti-32Mo particle size 1~6mm, Al-85V particle size 1~6mm, and Ti-30Fe particle size 1~6mm.

[0062] Step Two: Mix the raw materials from Step One according to the specified ratio and press them into multiple electrode blocks (each electrode block is a cylinder with a diameter of Φ470mm and a height equal to its thickness H). The mixing of each electrode block is performed by alternating clockwise and counterclockwise rotation. The thickness H (mm) of each electrode block is related to its pressing density ρ (g / cm³). 3 The following relationship must be satisfied: H≤120 / (3.8-3.2)=200mm, where k is a coefficient with a value range of 100~250mm·g / cm. 3 ρ0 is the reference density, with a value ranging from 3.1 to 3.4 g / cm³. 3 Finally, H was determined to be 190mm. Multiple electrode blocks were pressed and welded to obtain a consumable electrode.

[0063] Step 3: The consumable electrode from Step 2 is melted for the first time under a vacuum of 1.5 Pa. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The arc-starting time is 23 min, the current I1 in the stable melting stage is 16 kA, the feeding time is 15 min, and the arc-stabilizing current is AC with a magnitude of 6 A. After the melting is completed, the power is cut off and the cooling time is 8 h. After exiting the furnace, a primary ingot is obtained.

[0064] Step 4: The ingot from Step 3 is subjected to a second melting process under a vacuum of 1.3 Pa. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The arc-starting time is 23 minutes. The stable melting stage employs an "ultra-high limiting current process," specifically, the stable melting current I2 satisfies: I2 ≥ 1.5 × 16 kA = 24 kA, and I2 ≥ 0.93 × 40 kA = 37.2 kA, I2 < 40 kA. α is the current amplification factor, ranging from 1.1 to 2.0, and β is the rated load factor, ranging from 0.85 to 0.98. -The rated output current of the main power supply of the vacuum self-consuming electric arc furnace used is 40kA. The final I2 is determined to be 38kA. The compensation time is 15min. The arc stabilization current is AC with a magnitude of 8A. The power-off cooling time after melting is 8h. After exiting the furnace, a secondary ingot is obtained.

[0065] Step 5: The secondary ingot from Step 4 is smelted for the third time under a vacuum of 1.0 Pa. The smelting process is divided into an arc-starting stage, a stable smelting stage, and a feeding stage. The arc-starting time is 23 min, the stable smelting current is 28 kA, and the feeding stage adopts the "rapid current interruption feeding process" with a feeding time of 16 min and a smelting current decrease rate of 1.8 kA / min. The stable arc current is AC with a magnitude of 10 A. After the smelting is completed, the power is cut off and the cooling time is 8 h. After exiting the furnace, the tertiary ingot is obtained.

[0066] Step Six: After flattening and surface polishing the three ingots from Step Five, a homogeneous ultra-high strength titanium alloy ingot is obtained, which is then subjected to flaw detection and composition analysis.

[0067] Testing revealed that the elemental composition of V was within the range of 0.15%, Mo within 0.2%, Al within 0.18%, Zr within 0.16%, Cr within 0.15%, Nb within 0.2%, and Fe within 0.15%. The ultra-high strength titanium alloy ingots smelted using this invention exhibited excellent compositional uniformity, free from inclusions, porosity, and other defects. Following the subsequent process described in CN120989434A, titanium alloy bars were obtained, and their mechanical properties were tested to show a tensile strength of 1556 MPa and an elongation of 10%, achieving both high uniformity and excellent mechanical properties.

[0068] Example 2

[0069] This embodiment relates to an ultra-high strength titanium alloy with a composition system of Ti-V-Mo-Al-Zr-Cr-Nb-Fe.

[0070] Step 1: Based on the composition of the ultra-high strength titanium alloy: V 6.0%, Mo 4.5%, Al 4.0%, Zr 3.0%, Cr 2.0%, Nb 2.5%, Fe 1.0%, with the balance being Ti and unavoidable impurities; select the following raw materials: sponge titanium, aluminum briquettes, sponge zirconium, Al-60Cr, Ti-50Nb, Ti-32Mo, Al-85V, and Ti-30Fe; select the raw materials, removing hard-core titanium, foamed titanium, etc., with the following requirements: sponge titanium particle size 3~12.7mm, aluminum briquettes particle size 8~13mm, sponge zirconium particle size 1~18mm, Al-60Cr particle size 1~6mm, Ti-50Nb particle size 1~6mm, Ti-32Mo particle size 1~6mm, Al-85V particle size 1~6mm, and Ti-30Fe particle size 1~6mm.

[0071] Step Two: Mix the raw materials from Step One according to the specified ratio and press them into multiple electrode blocks (each electrode block is a cylinder with a diameter of Φ470mm and a height equal to its thickness H). The mixing of each electrode block is performed by alternating clockwise and counterclockwise rotation. The thickness H (mm) of each electrode block is related to its pressing density ρ (g / cm³). 3 The following relationship must be satisfied: H≤140 / (3.9-3.1)=175mm, where k is a coefficient, with a value ranging from 100 to 250 mm·g / cm. 3 ρ0 is the reference density, with a value ranging from 3.1 to 3.4 g / cm³. 3 Finally, H was determined to be 175mm. Multiple electrode blocks were pressed and welded to obtain a consumable electrode.

[0072] Step 3: The consumable electrode from Step 2 is melted for the first time under a vacuum of 1.5 Pa. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The arc-starting time is 23 min, the current I1 in the stable melting stage is 16 kA, the feeding time is 15 min, and the arc-stabilizing current is AC with a magnitude of 6 A. After the melting is completed, the power is cut off and the cooling time is 8 h. After exiting the furnace, a primary ingot is obtained.

[0073] Step 4: The ingot from Step 3 is subjected to a second melting process under a vacuum of 1.3 Pa. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The arc-starting time is 23 minutes. The stable melting stage employs an "ultra-high limiting current process," specifically, the stable melting current I2 satisfies: I2 ≥ 1.5 × 16 kA = 24 kA, and I2 ≥ 0.93 × 40 kA = 37.2 kA, I2 < 40 kA. α is the current amplification factor, ranging from 1.1 to 2.0, and β is the rated load factor, ranging from 0.85 to 0.98. - The rated output current of the main power supply of the vacuum self-consuming electric arc furnace used is 40kA. The final I2 is determined to be 38kA. The compensation time is 15min. The arc stabilization current is AC with a magnitude of 8A. The power-off cooling time after melting is 8h. After exiting the furnace, a secondary ingot is obtained.

[0074] Step 5: The secondary ingot from Step 4 is smelted for the third time under a vacuum of 1.0 Pa. The smelting process is divided into an arc-starting stage, a stable smelting stage, and a shrinkage stage. The arc-starting time is 23 min, the stable smelting current is 28 kA, and the shrinkage is achieved using a "rapid current-cutting shrinkage process" with a shrinkage time of 14 min and a current decrease rate of 2 kA / min. The stable arc current is AC with a magnitude of 10 A. After the smelting process is completed, the power is cut off and the cooling time is 8 h. After exiting the furnace, a tertiary ingot is obtained.

[0075] Step Six: After flattening and surface polishing the three ingots from Step Five, a homogeneous ultra-high strength titanium alloy ingot is obtained, which is then subjected to flaw detection and composition analysis.

[0076] Testing revealed the following elemental variations: V 0.16%, Mo 0.18%, Al 0.20%, Zr 0.16%, Cr 0.15%, Nb 0.18%, and Fe 0.15%. The ultra-high strength titanium alloy ingots smelted using this invention exhibited excellent compositional uniformity, free from inclusions, porosity, and other defects. Following the subsequent process described in CN120989434A, titanium alloy bars were obtained, and their mechanical properties were tested to show a tensile strength of 1545 MPa and an elongation of 10.5%, achieving both high uniformity and excellent mechanical properties.

[0077] Comparative Example 1

[0078] The only difference from Example 1 is that in step five, "the feeding process adopts the 'rapid current interruption feeding process,' the feeding time is 16 minutes, and the melting current decrease rate is 1.8 kA / min" is changed to "the feeding process adopts the 'normal feeding process'" (e.g., Figure 1 The feeding time is 80 min, the melting current decrease rate is 0.35 kA / min, and the rest of the process is the same.

[0079] The test results showed that the elemental variation was 0.24% for V, 0.25% for Mo, 0.26% for Al, 0.25% for Zr, 0.24% for Cr, 0.28% for Nb, and 0.2% for Fe. The increased elemental variation indicates a decrease in compositional uniformity.

Claims

1. A method for smelting homogeneous ultra-high strength titanium alloy ingots, characterized in that: Includes the following steps: A. Select raw materials based on the chemical composition of the ultra-high strength titanium alloy ingot, then weigh and batch them; the composition system of the ultra-high strength titanium alloy ingot is Ti-V-Mo-Al-Zr-Cr-Nb-Fe, and its chemical composition by mass percentage is: V 5.5~6.5%, Mo 4.5~5.5%, Al 3.0~4.0%, Zr 2.5~3.5%, Cr 1.5~2.5%, Nb 1.5~2.5%, Fe 0.9~1.1%, with the balance being Ti and unavoidable impurities; or, its chemical composition by mass percentage is: V 3.5~4.5%, Mo 4.5~5.5%, Al 3.0~4.0%, Zr 2.5~3.5%, Cr 1.5~2.5%, Nb 1.5~2.5%, Fe 0.4~0.6%, with the balance being Ti and unavoidable impurities; B. Press the raw materials prepared in step A according to the specified proportions into multiple electrode blocks. The thickness H of each electrode block and its pressing density ρ satisfy the following relationship: H≤k / (ρ-ρ0), where k is a coefficient with a value ranging from 100 to 250 mm·g / cm³. 3 ρ0 is the reference density, with a value ranging from 3.1 to 3.4 g / cm³. 3 H is in mm, and the compression density ρ ranges from 3.4 to 4.0 g / cm³. 3 After pressing, multiple electrode blocks are welded together to obtain a consumable electrode. C. The consumable electrode from step B is melted for the first time. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The current I1 in the stable melting stage is 14~16.5kA. After melting, the electrode is cooled and removed from the furnace to obtain a primary ingot. D. The ingot from step C is subjected to a second melting process. The melting process is divided into an arc initiation stage, a stable melting stage, and a feeding stage. The stable melting stage adopts an ultra-high limiting current process, specifically, the current I2 in the stable melting stage satisfies: I2≥α×I1, and I2≥β×I - Rated, α is the current amplification factor, ranging from 1.1 to 2.0, β is the rated load factor, ranging from 0.85 to 0.98, I - Rated is the rated output current of the main power supply of the vacuum self-consuming electric arc furnace used. After melting, cooling and tapping out of the furnace, a secondary ingot is obtained. E. The secondary ingot from step D is subjected to a third melting process. The melting process is divided into an arc-starting stage, a stable melting stage, and a feeding stage. The current during the stable melting stage is I3. The feeding process adopts an ultra-fast current interruption feeding process with a feeding time ≥10min and a melting current decrease rate >1.2kA / min. After the melting process is completed, the ingot is cooled and then taken out of the furnace to obtain a tertiary ingot. After post-processing, the three ingots from steps F and E yield a homogeneous ultra-high strength titanium alloy ingot.

2. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 1, characterized in that: In step A, the raw materials are sponge titanium, aluminum briquettes, sponge zirconium, Al-60Cr, Ti-50Nb, Ti-32Mo, Al-85V, and Ti-30Fe.

3. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 2, characterized in that: In step A, the raw materials contain titanium sponge with a particle size of 3-12.7 mm, aluminum granules with a particle size of 8-13 mm, zirconium sponge with a particle size of 1-18 mm, Al-60Cr with a particle size of 1-6 mm, Ti-50Nb with a particle size of 1-6 mm, Ti-32Mo with a particle size of 1-6 mm, Al-85V with a particle size of 1-6 mm, and Ti-30Fe with a particle size of 1-6 mm.

4. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 1, characterized in that: At least one of the following must be met: In step B, each electrode block is mixed by alternating clockwise and counterclockwise rotation; In step B, the electrode block is a cylinder with a diameter of Φ450~500mm and a height equal to its thickness.

5. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 1, characterized in that: In step B, 110mm≤H≤k / (ρ-ρ0).

6. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 1, characterized in that: At least one of the following must be met: In step C, the vacuum degree is ≤1.5 Pa; In step C, the arc initiation time is ≤25 min; In step C, the compensation time is ≥15 min; In step C, the arc-stabilizing current is AC, with a magnitude of 3~9A; In step C, the cooling time is ≥8 hours after power failure.

7. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 1, characterized in that: At least one of the following must be met: In step D, the vacuum degree is ≤1.5 Pa; In step D, the arc initiation time is ≤25 min; In step D, the compensation time is ≥15 min; In step D, the arc-stabilizing current is AC, with a magnitude of 5~10A; In step D, the cooling time is ≥8 hours after power failure.

8. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 1, characterized in that: At least one of the following must be met: In step D, I - The value of rated ranges from 39 to 40 kA; In step D, I2 ≥ α × I1, and I2 ≥ β × I - rated, and I2 - rated.​ 9. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 1, characterized in that: At least one of the following must be met: In step E, the vacuum degree is ≤1.2 Pa; In step E, the arc initiation time is ≤25 min; In step E, the arc-stabilizing current is AC, with a magnitude of 6~12A; In step E, the cooling time is ≥8 hours after power failure; In step E, the value of I3 ranges from 24.5 to 28.5 kA.

10. The smelting method for homogeneous ultra-high strength titanium alloy ingots according to claim 1, characterized in that: In step F, the post-processing includes flattening and surface finishing.

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