A method for preparing high-density titanium alloy billets using a high proportion of recycled scrap

Abstract

This invention discloses a method for preparing high-density titanium alloy billets using a high proportion of recycled scrap, belonging to the field of titanium alloy billet preparation technology. The method includes: process calculation and batching, material pretreatment, weighing and mixing of small-particle materials, high-density billet forming, and billet stacking. This invention overcomes the technical bottleneck of high-proportion scrap pressing by combining small-particle materials with ultra-high tonnage rapid pressing, effectively addressing problems such as poor billet uniformity and poor forming effect, reducing billet density from the usual less than 3.0 g / cm³. 3 Increased to 3.2g / cm 3 The above represents a qualitative leap from difficult-to-form to high-density forming. While ensuring that the addition ratio is not less than 60%, strict particle size control and mixing process guarantee the uniformity of composition. The high-density billet improves the conductivity and melting stability of the electrode, reduces splashing during the melting process, and thus improves the metallurgical quality of titanium ingots.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy billet preparation technology, and relates to the high-value utilization of recycled titanium alloy scrap, specifically to a method for preparing high-density titanium alloy billets from a high proportion of recycled scrap. Background Technology

[0002] Titanium and titanium alloys are widely used in aerospace, chemical, and medical fields due to their excellent properties. The production process generates a large amount of recyclable materials such as machining chips and milling chips. Driven by both green manufacturing and cost control of titanium materials, the use of titanium alloy chips generated during machining as recycled materials for remelting has become an important development direction for the industry. Achieving efficient and high-proportion recycling of these high-value chips is of great significance for reducing the cost of titanium materials, saving strategic resources, and promoting the circular economy.

[0003] Currently, the conventional technical route for preparing electrode blanks from recycled titanium alloy scrap involves mixing a small amount (≤30%) of recycled scrap with sponge titanium, master alloys, etc., and then pressing them into shape. However, existing recycled scrap briquetting processes face significant technical bottlenecks when used in high-proportion applications: (1) High proportion of scrap material is difficult to press: When the proportion of recycled titanium scrap material exceeds 30%, due to the small and thin scrap material, large specific surface area and high elastic recovery rate, traditional presses are difficult to achieve effective densification, and the resulting billet has low density (usually <3.0 g / cm³). 3 Furthermore, its high looseness makes it prone to breakage and slag shedding during transportation, stacking, or furnace loading, failing to meet the requirements of EB smelting for electrode structural integrity and large-scale industrial recycling.

[0004] (2) Poor compatibility of material particle size and proportion: Existing processes often use large-particle sponge titanium (0.83-25.4 mm) mixed with intermediate alloy with larger particle size. After mixing with fine and thin scrap, the fluidity is poor and the filling is uneven, resulting in large fluctuations in pressing density and serious composition deviation, which affects the consistency of subsequent melting.

[0005] (3) Insufficient automation and engineering: Most briquetting production lines rely on manual feeding, demolding and stacking, which is inefficient and easily introduces pollution; the mold cavity design does not take into account the thermal expansion of the mold generated during high-frequency pressing, which often leads to mold jamming, cracking and other faults when the blank is demolded, which restricts the large-scale and stable application of high proportion of recycled materials.

[0006] The aforementioned problems severely limit the proportion of recycled titanium alloy materials added to high-end ingots, making it difficult to achieve the synergistic goal of "cost reduction + quality improvement + greening". Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing high-density titanium alloy billets with a high proportion of recycled scrap, which aims to overcome the technical problem that the poor material flowability and large elastic rebound caused by the excessive proportion of scrap make it difficult to achieve high-density and high-stability forming of the billet.

[0008] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A method for preparing high-density billets with a high proportion of recycled titanium alloy scrap, the method specifically includes the following steps: Step 1, Process Calculation and Ingredient Preparation: Based on the target alloy composition and the known average composition of the recycled titanium alloy scrap, calculate the amount of each element that needs to be supplemented; considering the burn-off rate of easily burnable elements during the smelting process, excessive supplementation is required; based on the calculation results, proportion the other materials and the recycled titanium alloy scrap.

[0009] Step 2, Material Pretreatment: All materials (i.e., other materials and recycled titanium alloy scrap) are dried. After drying, the materials are transferred to a dry environment to cool and store for later use to prevent secondary moisture absorption.

[0010] Step 3: Weighing and mixing small-particle materials: Weigh each component material after drying according to the calculation results in step one; mix the weighed materials evenly and then package them into portions, and then transport them to the loading position of the electrode block hydraulic press.

[0011] Step 4, high-density billet forming: Step 4.1, feeding and pressing: accurately feed a portion of the pre-packaged material into the mold cavity.

[0012] Step 4.2, primary compaction: The main pressure head is rapidly pressed down and pressure is maintained.

[0013] Step 4.3, burr removal: When the main pressure head presses down for the second time to demold the blank, the annular auxiliary pressure head fixed above the pressure head presses down simultaneously to neatly remove the burrs generated by the lateral flow of material on the circumference of the blank that was previously pressed and pushed out of the mold cavity.

[0014] Step 4.4, Demolding: Eject the formed blank horizontally and smoothly from the bottom of the mold.

[0015] Step 5, stacking the billets: Grab the prepared billet, place it in the silo and stack it; until the silo is full.

[0016] The present invention also has the following technical features: Specifically and optionally, in step one, the proportion of recycled titanium alloy scrap added during preparation is ≥60wt%; preferably 70-80wt%.

[0017] More preferably, in step one, when the target alloy is titanium alloy TC4, the proportion of recycled titanium alloy scrap added during preparation is 80 wt%; when the target alloy is titanium alloy TA15, the proportion of recycled titanium alloy scrap added during preparation is 70 wt%.

[0018] Specifically, in step one, the weight range of a single billet is 1.2 to 2.5 kg, and the weight of a single batch of materials should be 1.6 to 2.0 kg.

[0019] Specifically and optionally, in step one, when the target alloy is titanium alloy TC4 titanium alloy, other materials include: grade 0 sponge titanium, Al-V65 master alloy, aluminum granules, iron granules, and titanium dioxide powder.

[0020] Specifically and optionally, in step one, when the target alloy is titanium alloy TA15, other materials include: grade 0 sponge titanium, Al-Mo60 master alloy, aluminum granules, sponge zirconium, and titanium dioxide powder.

[0021] Specifically, in step two, the drying conditions are: drying at 180–280°C for 3–6 hours. Preferably, the drying conditions are: drying at 220–240°C for 4–5 hours.

[0022] Specifically, in step three, among the other materials, the particle size of the sponge titanium is 3-12.7 mm, the aluminum particles are < φ6*6 mm, and the particle size of the intermediate alloy is < 4 mm. Preferably, the aluminum particles are approximately φ2*2 mm, and the particle size of the intermediate alloy is < 3 mm.

[0023] Specifically, in step three, when weighing the dried components, an electronic scale with an accuracy of ±0.2g / kg is used.

[0024] Specifically, in step three, the mixing conditions are: mixing at a rotation speed of 20–40 r / min for at least 20 seconds. Preferably, the mixing conditions are: mixing at a rotation speed of 24 r / min for 25 seconds.

[0025] Specifically, in step 4.1, the mold cavity height is ≥400mm, the lower part height is ≥50mm, and the discharge end is a flared opening. Preferably, in step 4.1, the mold cavity height is 450mm, the lower part height is 70mm, and the discharge end is a flared opening with a taper of 1:50.

[0026] Specifically, in step 4.2, the pressure used by the main pressure head is 620-650 tons, and the pressure holding time is 3-5 seconds; the pressing time of a single block is controlled within 30 seconds.

[0027] Specifically, in step five, the hopper is 6000mm long and 640-700mm wide.

[0028] Specifically, in step five, during stacking, six columns of blanks are placed in each layer; the second layer of blanks is offset from the first layer by 1 / 3 of the blank diameter in the length direction, forming a stable staggered structure.

[0029] The beneficial technical effects of this invention compared to the prior art are as follows: (I) This invention breaks through the technical bottleneck of high-proportion scrap pressing molding by combining small-particle materials with ultra-high tonnage rapid pressing, effectively overcoming problems such as poor billet uniformity and poor molding effect, and reducing billet density from the usual less than 3.0 g / cm³. 3 Increased to 3.2g / cm 3 The above represents a qualitative leap from difficult-to-form to high-density forming. While ensuring that the addition ratio is not less than 60%, strict particle size control and mixing process guarantee the uniformity of composition. The high-density billet improves the conductivity and melting stability of the electrode, reduces splashing during the melting process, and thus improves the quality of titanium ingots.

[0030] (II) The automation and intelligence levels of the process flow of this invention are significantly improved. From material portioning and feeding to precise stacking by robotic arms, the entire process is automated, making it particularly suitable for large-scale production of small single-weight billets, thus improving production efficiency, consistency, and safety. Targeted mold designs, such as the flared mold cavity, reduce demolding resistance and jamming risk for high-density billets. The synchronous burr removal function eliminates the need for subsequent separate cleaning processes, allowing billets to be directly stacked and optimizing production cycle time. The staggered stacking scheme ensures safety during the smelting preparation stage, stabilizing the billet column structure and avoiding safety hazards caused by rolling or tipping during hoisting and furnace loading. Attached Figure Description

[0031] Figure 1 This is a flowchart of the high-density billet preparation process.

[0032] Figure 2 This is a picture of the actual weighing and mixing equipment.

[0033] Figure 3 Demonstrates billet forming and burr removal Figure 4 The comparison shows the effect of burr removal (left: no burrs removed; right: burrs removed).

[0034] Figure 5 The process of stacking billets was demonstrated.

[0035] Figure 6 This is a photograph of the actual materials in the silo.

[0036] The technical solution of the present invention will be further described below with reference to the embodiments. Detailed Implementation

[0037] It should be noted that, unless otherwise specified, all raw materials and equipment used in this invention are those known in the art. For example, the electrode block hydraulic press is an electrode block hydraulic press known in the prior art.

[0038] To prepare a material with high density (≥3.2 g / cm³) while maintaining a recycled scrap content of ≥60%. 3 This invention utilizes the following technical approach to produce small, single-weight electrode blanks that are structurally complete, uniformly composed, and suitable for automated continuous production, in order to meet the requirements of subsequent smelting processes: First, based on the proportion of recycled scrap (≥60%, mass fraction) and the target composition, calculate the required ratio and weight of sponge titanium and various intermediate alloys (such as aluminum granules, aluminum vanadium, etc.), and determine the weight range of a single billet to be 1.2 to 2.5 kg.

[0039] Second, the material is dried at 180-280℃ to completely remove surface adsorbed moisture, ensuring that there is no gas leakage interference during the pressing process, and eliminating the impact of moisture on the accuracy of symmetry and the internal quality of the billet.

[0040] Third, based on the calculation results, adopt the following... Figure 2 The equipment shown weighs the dried materials. To achieve high-density pressing, the particle size of the materials needs to be carefully controlled: sponge titanium particles are 3–12.7 mm, aluminum particles are < φ6*6 mm, and intermediate alloy particles are < 4 mm. The weighed materials are mixed at a mixing speed of 20–40 r / min for at least 20 seconds. After uniform mixing, the materials are transported to the feeding system.

[0041] Fourth, use a hydraulic press with a nominal pressure ≥ 500 tons for electrode block pressing. The mold cavity height is ≥ 400 mm, the pressing time for a single block is controlled within 30 seconds, the holding time is ≥ 3 seconds, and the diameter of the formed blank is φ90~120 mm. Through high-tonnage rapid pressing, the density of the blank reaches ≥ 3.2 g / cm³. To facilitate demolding and reduce material jamming, the lower half of the mold cavity is designed as a flared shape with a larger bottom and a smaller top, reducing demolding resistance. At the same time, a secondary pressure head that can press down synchronously is fixed above the press head on the outside, used to remove burrs around the circumference of the blank immediately after pressing (such as...). Figure 3 and Figure 4 As shown in the figure, this achieves neat edges on the billet to facilitate subsequent stacking.

[0042] Fifth, a robotic arm is used to automatically pick up the pressed blanks and stack them into a dedicated hopper. The width of the hopper should be less than or equal to the product of the blank diameter and (number of fabric rows + 0.5). During stacking, if... Figure 5 As shown, each layer of billet is required to be staggered by about 1 / 3 of the diameter to form a stable staggered structure and prevent the material from tipping over during transfer or smelting preparation.

[0043] Following the above technical ideas and solutions, the following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0044] Example 1 This embodiment provides a method for preparing high-density billets from high-proportion recycled titanium alloy scrap. The method employs... Figure 1 The process shown uses TC4 recycled scrap, sponge titanium, vanadium aluminum, aluminum granules, iron granules, and titanium dioxide to prepare a billet with a scrap addition ratio of 80% and a single weight of 2.0 kg.

[0045] In this embodiment, the target composition of the smelted TC4 titanium alloy is: aluminum: 6.2 wt%, vanadium: 4.0 wt%, iron: 0.18 wt%, oxygen: 0.18 wt%, with the balance being titanium.

[0046] The method specifically includes the following steps: Step 1, Process Calculation and Ingredient Preparation: First, based on the target alloy composition and the known average composition of 80% TC4 recycled scrap (6.20% aluminum, 4.15% vanadium, 0.18% iron, and 0.18% oxygen), the required amounts of each element to be added were calculated. Considering that aluminum is an easily burned-out element during the smelting process (approximately 20% burn-out rate), an excess supplement is necessary. The calculation shows that the following should be added: approximately 334g of grade 0 sponge titanium (particle size 3-12.7mm), approximately 21g of Al-V65 master alloy (particle size <3mm), approximately 42g of aluminum particles (particle size φ2*2mm), approximately 1g of iron particles (particle size <2mm), and approximately 2g of titanium dioxide powder, mixed with 1.6kg of TC4 recycled scrap, for a total weight of approximately 2.0kg.

[0047] Step 2, Material Pretreatment: All materials (TC4 recycled scrap, sponge titanium, intermediate alloy, etc.) were placed in a vacuum drying oven and dried at 220°C for 4 hours to completely remove physically adsorbed moisture. After drying, the materials were transferred to a dry environment to cool and store for later use to prevent secondary moisture absorption.

[0048] Step 3: Weighing and mixing small-particle materials: Inside the drying room, using an electronic scale with an accuracy of ±0.2 g / kg, each component of the dried material was weighed according to the calculation results in step one. All the weighed materials were poured into a mixer and mixed at 24 r / min for 25 seconds to ensure uniform composition. The mixed material was then dispensed into dedicated 2.0 kg / portion hoppers and transported by an automatic conveyor belt to the loading position of a 600-ton electrode block hydraulic press.

[0049] Step 4, high-density billet forming: Step 4.1, Feeding and Pressing: The mechanical feeding system precisely feeds one portion of the mixture (2.0 kg) into the mold cavity. The mold cavity is 450 mm high, with a flared opening at the bottom that is 70 mm high and has a taper of 1:50.

[0050] Step 4.2, primary compaction: The main pressure head presses down rapidly at a pressure of 650 tons, with a pressure holding time of 5 seconds.

[0051] Step 4.3, burr removal: When the main pressure head demolds the blank, the annular auxiliary pressure head fixed above the pressure head presses down synchronously to neatly remove the burrs (flashes) generated by the lateral flow of material on the circumference of the blank that was previously pressed and pushed out of the mold cavity.

[0052] Step 4.4, Demolding: The ejection mechanism smoothly ejects the formed blank laterally from the lower end of the flared opening. Due to the flared opening design, demolding is smooth without jamming or damage to the blank.

[0053] The pressed blank has a diameter of φ110mm and a height of approximately 63mm. The measured density of the blank after molding is 3.3 g / cm³, with no burrs on the edges and a complete structure.

[0054] Step 5, stacking the billets: A robotic arm picks up the prepared billets and places them into a dedicated transfer hopper. The hopper is 6000mm long and 700mm wide (<110mm * (6 columns + 0.5)), with 6 columns of billets stacked per layer. During stacking, the second layer of billets is offset from the first layer by approximately 37mm (≈1 / 3 of the diameter) in the length direction, forming a stable staggered structure. This process is repeated until the hopper is full. A single hopper can hold 2100 billets (7 layers × 6 columns * 50 sections), and the transfer process is free from tipping over or collision damage.

[0055] Improvement effect of Example 1: The TC4 billet produced using the above process, after testing, exhibits a stable density between 3.4 and 3.5 g / cm³, with significantly higher integrity than low-density billets prepared using traditional methods. The billet has a regular shape, no visible burrs, and good compositional uniformity. When used in subsequent EB melting production, the process is smooth with no abnormal splashing, and the final ingot has a uniform composition, fully meeting the requirements of aerospace-grade TC4 ingot standards.

[0056] Example 2 This embodiment provides a method for preparing high-density billets from high-proportion recycled titanium alloy scrap. The method employs... Figure 1 The process shown uses TA15 recycled scrap, sponge titanium, vanadium aluminum, molybdenum aluminum, aluminum granules, sponge zirconium, and titanium dioxide to prepare a billet with a scrap addition ratio of 70% and a single weight of 1.6 kg.

[0057] In this embodiment, the target composition of the smelted TA15 titanium alloy is: aluminum: 6.8 wt%, molybdenum: 1.7 wt%, vanadium: 2.25 wt%, zirconium: 2.25 wt%, oxygen: 0.12 wt%, with the balance being titanium.

[0058] The method specifically includes the following steps: Step 1, Process Calculation and Ingredient Preparation: Based on the known composition of 70% TA15 recycled scrap (consistent with the target composition) and a 20% Al element loss rate, the replenishment amount was calculated. The proportions are: 1.12 kg of TA15 recycled scrap, approximately 417 g of grade 0 sponge titanium (3-12.7 mm), approximately 4 g of Al-V65 master alloy (<3 mm), approximately 14 g of Al-Mo60 master alloy (<3 mm), approximately 32 g of aluminum granules (φ2*2 mm), approximately 11 g of sponge zirconium (<3 mm), approximately 2 g of titanium dioxide powder, for a total weight of approximately 1.6 kg.

[0059] Step 2, Material Pretreatment: As in Example 1, all materials were vacuum dried at 240°C for 5 hours.

[0060] Step 3: Weighing and mixing small-particle materials: After accurately weighing according to the formula, put the mixture into the mixer and mix for 25 seconds. The evenly mixed material is then divided into 1.6kg / portion hoppers for later use.

[0061] Step 4, high-density billet forming: Step 4.1: Load the material into the mold. The mold cavity height is 450mm, and the lower part is a flared opening with a height of 70mm and a taper of 1:50.

[0062] Step 4.2: Press down with 620 tons of pressure and hold for 3 seconds.

[0063] Step 4.3: Remove burrs using the synchronous auxiliary pressure head.

[0064] Step 4.4: Eject and demold to obtain a blank with a diameter of φ100mm.

[0065] Step 5, stacking the billets: A robotic arm picks up the prepared billets and places them into a dedicated transfer hopper. The hopper is 6000mm long and 640mm wide (<100mm * (6 columns + 0.5)), with 6 columns of billets stacked per layer. During stacking, the second layer of billets is offset from the first layer by approximately 33mm (≈1 / 3 of the diameter) in the length direction, forming a stable staggered structure. This process is repeated until the hopper is full. A single hopper can hold 2100 billets (7 layers × 6 columns * 50 sections), and the transfer process is free from tipping over or collision damage.

[0066] Improvement effect of Example 2: The density of TA15 billets produced using the above process reaches 3.3-3.4 g / cm³. 3 The material has a dense structure. After being used in EB smelting, the composition analysis of the ingots showed that the contents of each major element (Al, Mo, V, Zr) deviated from the target values ​​within ±0.2%, the oxygen content was stable in the range of 0.11-0.13%, the macroscopic structure of the ingot was uniform, and there were no defects such as high or low density inclusions, which met the requirements for TA15 alloy ingots for aerospace applications. This method achieves a high proportion and high quality of recycling of TA15 alloy recycled materials.

Claims

1. A method for preparing high-density billets with a high proportion of recycled titanium alloy scrap, characterized in that, The method specifically includes the following steps: Step 1, Process Calculation and Ingredient Preparation: Based on the target alloy composition and the known average composition of the recycled titanium alloy scrap, calculate the amount of each element that needs to be added; considering the burn-off rate of easily burnable elements during the smelting process, an over-addition is required; based on the calculation results, proportion the other materials and the recycled titanium alloy scrap. Step 2, Material Pretreatment: Dry all materials, and then transfer them to a dry environment to cool and store them for later use to prevent secondary moisture absorption. Step 3: Weighing and mixing small-particle materials: Weigh each component material after drying according to the calculation results in step one; mix the weighed materials evenly and then package them into portions, and then transport them to the loading position of the electrode block hydraulic press. Step 4, high-density billet forming: Step 4.1, Feeding and Pressing: Precisely feed a portion of the pre-packaged material into the mold cavity; Step 4.2, primary compaction: The main pressure head rapidly presses down and maintains pressure; Step 4.3, burr removal: When the main pressure head demolds the blank, the annular auxiliary pressure head fixed above the pressure head presses down synchronously to neatly remove the burrs generated by the lateral flow of material on the circumference of the blank that was previously pressed and pushed out of the mold cavity. Step 4.4, Demolding: Gently eject the formed blank horizontally from the bottom of the mold; Step 5, stacking the billets: Grab the prepared billet, place it in the silo and stack it; until the silo is full.

2. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step one, the proportion of recycled titanium alloy scrap added during preparation is ≥60wt%.

3. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step one, the target alloy is either TC4 titanium alloy or TA15 titanium alloy.

4. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step one, the weight of a single blank ranges from 1.2 to 2.5 kg.

5. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step two, the drying conditions are: drying at 180–280℃ for 3–6 hours.

6. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step three, other materials include: sponge titanium, aluminum granules, and master alloy; wherein, the sponge titanium granules have a particle size of 3 to 12.7 mm, the aluminum granules are < φ6*6 mm, and the master alloy granules have a particle size of < 4 mm.

7. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step three, the mixing conditions are: mix at a speed of 20-40 r / min for at least 20 seconds.

8. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step 4.1, the mold cavity height is ≥400mm, the lower part height is ≥50mm, and the discharge end is a flared opening.

9. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step 4.2, the pressure used by the main pressure head is 620-650 tons, and the pressure holding time is 3-5 seconds; the pressing time of a single block is controlled within 30 seconds.

10. The method for preparing high-density billets with a high proportion of recycled titanium alloy scrap as described in claim 1, characterized in that, In step five, during stacking, six columns of blanks are placed in each layer; the second layer of blanks is offset from the first layer by 1 / 3 of the blank diameter in the length direction, forming a stable staggered structure.

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