Preparation method of large recycled titanium alloy sintered part

Abstract

The invention discloses a preparation method of a large powder titanium alloy return scrap sintered part, and belongs to the field of powder metallurgy titanium alloys. The method comprises the following steps: by taking coarse powder return scrap generated by atomization powder preparation as a raw material, calculating the proportion of powder with different oxygen contents, mixing, filling into a cylindrical sheath formed by rolling and welding a titanium alloy plate, and carrying out vacuum sintering to obtain a preformed blank; placing the preformed blank in the center of a larger-size sheath, filling powder around the preformed blank, and performing vacuum sintering again; and the nested sintering process is repeated, the size is increased layer by layer, and finally the large powder titanium alloy return scrap electrode is prepared. The process is simple, the cost is low, hot isostatic pressing equipment is not needed, efficient recycling and reusing of the titanium alloy coarse powder can be achieved, the method is suitable for cyclic utilization of the 3D printing waste powder, and remarkable economic and environmental benefits are achieved.

Description

Technical Field

[0001] This invention belongs to the field of titanium metallurgy, specifically relating to a method for preparing large titanium alloy recycled material sintered parts. Background Technology

[0002] Titanium metal possesses a series of advantages, including low density, high strength, good corrosion resistance, and high biocompatibility, making it a promising material for applications in aerospace, marine, medical, and chemical industries. However, the high production cost of titanium alloys limits their large-scale application, primarily due to the complex hot working process (accounting for approximately 50% of the total cost) and low material utilization (20-50%). Furthermore, obtaining complex-shaped titanium products often requires further processing, resulting in significant waste of titanium material. 3D printing, which can directly print finished parts from powder with minimal additional processing, significantly improves material utilization and is widely used in titanium alloy products. Currently, various powder preparation methods and processes in 3D printing generate large amounts of coarse powder particles. These spherical powders have poor pressing properties, making them unsuitable for traditional powder metallurgy pressing and sintering. During vacuum melting, titanium alloy powder can be sucked away by the vacuum pump, leading to production accidents. With the large-scale application of 3D printing technology in industrial production, the recycling and reuse of waste generated from 3D printing has become a widely concerned issue. Hot isostatic pressing (HIP) is generally used to heat-press the coarse powder generated during 3D printing into titanium alloy profiles for reuse.

[0003] However, due to the high cost of hot isostatic pressing equipment and its high operating costs, the cost of recycling and reusing coarse powder is higher than that of using virgin material, which in turn affects the recycling and reuse of recycled titanium alloy powder. How to achieve low-cost use of recycled material is the key issue we are currently facing.

[0004] For example, Chinese patent CN119501071A discloses a method for recycling titanium alloy powder used in additive manufacturing. This method uses spherical titanium alloy powder of the same grade with a particle size of 15-300μm as raw material. The powder-filled sleeve is placed in a hot isostatic pressing furnace, evacuated, and pressurized. The pressure is maintained at 90-110MPa, the temperature at 600-650℃, and the holding time is 1-2h. The sleeve size reaches φ500-1000×800-2000mm. Due to the heat transfer limitation, it is difficult to directly sinter ultra-large billets at such a large size, which easily produces black core and affects the sintering quality. At the same time, due to the large shrinkage of the powder sintered billet, excessive stress is easily generated, which leads to the cracking of the billet. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing large titanium alloy recycled material sintered parts that is flexible in process, low in cost, and suitable for large-scale production, as well as the high-quality sintered parts obtained therefrom.

[0006] In a first aspect, the present invention provides a method for preparing large titanium alloy recycled material sintered parts, the core of which lies in adopting a "layer-by-layer nested sintering" strategy.

[0007] In a second aspect, the present invention provides a large titanium alloy sintered part prepared by the above method. The sintered part is dense and has uniform composition and structure, and can be directly used as an electrode for vacuum melting or a near-net-shape structural blank.

[0008] The technical solution of this invention: A method for preparing large titanium alloy recycled material sintered parts includes: A. Prepare bag sleeves of different sizes; B. Fill the smallest sac with recycled titanium alloy material and sinter it to obtain a preform; C. The preform is placed in a larger enclosure and filled with titanium alloy powder, and then sintered to obtain a larger preform. D. Repeat step C until the sintered part of the final size is obtained.

[0009] The cladding is made of titanium alloy, and the composition of the recycled titanium alloy material is the same as that of the titanium alloy cladding. After sintering, the cladding does not need to be removed.

[0010] Hot isostatic pressing sintered titanium alloy recycled material and cladding are used.

[0011] The packages are sorted according to their size, and the size difference between adjacent packages is determined by the pressure of the hot isostatic pressing equipment.

[0012] The titanium alloy recycled material is a coarse powder of titanium alloy returned material. After setting the oxygen content of the titanium alloy sintered parts, the coarse powder of titanium alloy returned material with different oxygen contents is weighed and mixed evenly.

[0013] Titanium alloy recycled material is a mixture of powder and block material. After calculating the oxygen content of the block material, powder with different oxygen contents is prepared.

[0014] Micron or nano-reinforcing phases are added to titanium alloy powder as reinforcing phases.

[0015] The beneficial effects of this invention are: Flexible process and low cost: Existing vacuum sintering furnaces or hot isostatic pressing equipment can be used. By using a step-by-step nesting method, the limitation of the equipment cavity on the size of one molding can be overcome, avoiding dependence on ultra-large single hot isostatic pressing equipment and significantly reducing equipment investment and operating costs.

[0016] High material adaptability: It can be compatible with the processing of mixed recycled materials with different oxygen contents and particle sizes (from powder to small pieces), and can accurately control the composition of the final product (especially the oxygen content) through calculation and batching, so as to achieve high-value targeted recycling of recycled materials.

[0017] High product quality: The layer-by-layer sintering process facilitates gradual stress release, reducing the risk of cracking during one-time sintering of large-sized blanks. The cladding material is consistent with the internal material composition and is sintered together, forming a metallurgically bonded whole with no interface defects and good structural integrity.

[0018] The application prospects are broad: the large integral sintered parts prepared are particularly suitable as consumable electrodes for vacuum consumable arc melting, fundamentally solving the problems of powder and slag shedding of traditional bundled electrodes. They can also be used as preforms for large forgings or rolled parts. Attached Figure Description

[0019] Figure 1 A schematic diagram of the layer-by-layer sintering structure of the present invention. Detailed Implementation

[0020] Example 1 (corresponding to the basic method of claim 1) This embodiment demonstrates the preparation of a large TC4 titanium alloy electrode rod using a vacuum sintering method.

[0021] Prepare the sheaths: Prepare three cylindrical sheaths made of 2mm thick TC4 titanium plates, welded together, with the following dimensions: Small size sleeve: inner diameter Φ100 mm, height 200 mm, wall thickness 2 mm.

[0022] Medium-sized sleeve: inner diameter Φ150 mm, height 300 mm, wall thickness 2 mm.

[0023] Large size sleeve: inner diameter Φ200 mm, height 400 mm, wall thickness 2 mm.

[0024] All the packaging sleeves have one end welded and sealed, and the other end has an opening for filling with powder.

[0025] Raw material preparation: Coarse powder with a particle size of 50-150 μm generated during the preparation of TC4 titanium alloy by gas atomization was selected as recycled material.

[0026] Primary sintering: Coarse powder is filled into a small sleeve, vibrated to compact it, and then the open end is welded and sealed. The sealed sleeve is placed in a vacuum sintering furnace, heated to 1000℃ at 10℃ / min, and held at this temperature for 3 hours under a vacuum degree better than 1×10⁻² Pa. It is then cooled in the furnace at 5℃ / min to below 200℃ before being removed from the furnace. A dense primary preform (Φ100 mm×200 mm) is obtained.

[0027] Secondary nested sintering: The primary preform is placed in the center of the medium-sized sleeve, and the surrounding annular gap is filled with the same TC4 coarse powder. After vibration to compact, the sleeve is sealed. A second sintering process is performed using the exact same sintering process as in step 3 to obtain the secondary preform (Φ150 mm × 300 mm).

[0028] Three-stage nested sintering and finished product: The secondary preform is placed in the center of the large casing, surrounded by coarse powder, sealed, and then sintered again using the same process. After sintering, the caps at the ends of the casing are removed to obtain a large TC4 integral sintered electrode rod with final dimensions of Φ200 mm × 400 mm. Ultrasonic testing showed no internal cracks, holes, or other defects.

[0029] Example 2 (corresponding to claim 2: homogeneous sheath) Based on Example 1, the cladding material and recycled material were standardized to industrial pure titanium TA2. The recycled material was obtained by crushing TA2 machining chips. The cladding was made of 1.5 mm thick TA2 plate. The sintering process was adjusted to 950℃ / 2h. After sintering, the cladding and the internal material were completely bonded. Wire cutting samples were taken from the sintered part, and metallographic observation and microhardness testing were performed at the interface between the cladding and the core. No obvious interface was found, and the hardness values ​​transitioned uniformly, indicating that a good metallurgical bond had been formed. The cladding did not need to be removed and participated in subsequent melting as part of the electrode.

[0030] Example 3 (corresponding to claim 3: hot isostatic pressing sintering) This embodiment uses hot isostatic pressing (HIP) as the sintering method.

[0031] The coarse powder of TC4 return material is packed into a small titanium alloy sleeve (Φ80 mm×150 mm) and sealed.

[0032] The cladding is placed in a hot isostatic pressing furnace and processed under the conditions of 1000℃ / 150 MPa / holding for 3 hours to obtain a fully dense primary preform.

[0033] The primary preform is placed in the center of the inner sleeve (Φ120 mm×250 mm), filled with powder, and then sealed. A second hot isostatic pressing is then performed with the same parameters.

[0034] Repeat the above process, using a large sleeve (Φ180 mm × 350 mm) for a third hot isostatic pressing.

[0035] The final product is a large TC4 sintered part with a diameter of 180 mm and a density of nearly 99.5%.

[0036] Example 4 (corresponding to claim 4: dimensional gradient design) Within the framework of hot isostatic pressing (HIP), a sequence of cladding dimensions was designed for the working chamber size and ultimate pressure (200 MPa) of a specific type of HIP equipment. To ensure sufficient densification of each newly filled powder layer under pressure, the inner diameter difference between adjacent cladding layers was set to 40 mm. The specific sequence was: Φ100 mm → Φ140 mm → Φ180 mm → Φ220 mm. Each sintering stage used parameters of 1050℃ / 180 MPa / 2.5 hours. Through four-stage sintering, an ultra-large, highly dense sintered part with a diameter of Φ220 mm × 500 mm was successfully prepared. Testing showed good bonding between layers with no delamination.

[0037] Example 5 (corresponding to claim 5: oxygen content control) This example demonstrates how to control the oxygen content of the final product through ingredient mixing.

[0038] There are two different sources of TC4 return feed coarse powder: Powder A (from a process with good inert atmosphere protection): Oxygen content is 0.08 wt.%. Powder B (partially oxidized or recycled powder from complex sources): Oxygen content is 0.18 wt.%. The objective is to prepare a large electrode with an oxygen content of 0.12 wt.%. Based on mass balance calculations, the required mass mixing ratio of powder A to powder B is 2:1.

[0039] Weigh the two powders precisely according to this ratio, place them in a V-type mixer and mix for 2 hours to ensure uniformity.

[0040] A Φ200 mm electrode was prepared using the vacuum sintering and nesting process (three-stage) as described in Example 1.

[0041] Oxygen content analysis was performed on samples taken from different parts of the finished electrode. The average value was 0.119 wt.% and the range was 0.008 wt.%, indicating that the oxygen content was precisely controlled and evenly distributed.

[0042] Example 6 (corresponding to claim 6: powder-block mixture) This embodiment processes a mixed raw material that includes blocky recycled material.

[0043] Composition of recycled materials: TC4 blocky recycled material (derived from scrapped parts, cleaned and crushed into 5-10 mm pieces): oxygen content 0.10 wt.%. TC4 fine powder (-325 mesh): Oxygen content 0.20 wt.% The target finished product has an oxygen content of 0.15 wt.%. Let the mass of the block material be M_b and the mass of the powder material be M_p. Solving the equation, we get M_b : M_p = 1 : 1.

[0044] The block material and powder are loaded into a bag and vibrated to mix, so that the fine powder fully fills the gaps between the blocks and adheres to the surface of the blocks.

[0045] Due to the presence of bulk material, the filling density is relatively high. A high sintering temperature of 1100℃ was used, followed by vacuum sintering for 4 hours and a two-stage nesting process, ultimately yielding a sintered part with a diameter of 150 mm. Metallographic analysis shows that the sintering interface between the bulk material and the powder material has good bonding and a uniform microstructure.

[0046] Example 7 (corresponding to claim 7: adding a reinforcing phase) This embodiment aims to prepare sintered parts of particle-reinforced titanium matrix composites.

[0047] Matrix: TC4 return material coarse powder.

[0048] Reinforcing phase: nano-TiC powder (average particle size 50 nm), added at 1.0 wt.% of the matrix mass.

[0049] The TC4 powder and TiC powder were mixed in a planetary ball mill for 4 hours under argon protection to achieve uniform dispersion of nanoparticles.

[0050] Sintered parts were prepared using a three-stage vacuum sintering process similar to that in Example 1.

[0051] Performance tests show that, compared with pure TC4 sintered parts without added reinforcing phase, the sintered parts prepared in this embodiment have an increased room temperature hardness of approximately 18% and an increased high-temperature compressive strength at 600°C of approximately 25%.

Claims

1. A method for preparing large titanium alloy recycled material sintered parts, characterized in that... include: A. Prepare bag sleeves of different sizes; B. Fill the smallest sac with recycled titanium alloy material and sinter it to obtain a preform; C. The preform is placed in a larger enclosure and filled with titanium alloy powder, and then sintered to obtain a larger preform. D. Repeat step C until the sintered part of the final size is obtained.

2. The method for preparing large recycled titanium alloy sintered parts according to claim 1, characterized in that: The cladding is made of titanium alloy, and the composition of the recycled titanium alloy material is the same as that of the titanium alloy cladding. After sintering, the cladding does not need to be removed.

3. The method for preparing large recycled titanium alloy sintered parts according to claim 1, characterized in that: Hot isostatic pressing sintered titanium alloy recycled material and cladding are used.

4. The method for preparing large recycled titanium alloy sintered parts according to claim 3, characterized in that: The sheaths are sorted according to size, and the size difference between adjacent sheaths meets the requirements for heat conduction and pressure conduction.

5. The method for preparing large recycled titanium alloy sintered parts according to claim 1, characterized in that: The titanium alloy recycled material is a coarse powder of titanium alloy returned material. After setting the oxygen content of the titanium alloy sintered parts, the coarse powder of titanium alloy returned material with different oxygen contents is weighed and mixed evenly.

6. The method for preparing large recycled titanium alloy sintered parts according to claim 1, characterized in that: Titanium alloy recycled material is a mixture of powder and block material. After calculating the oxygen content of the block material, powder with different oxygen contents is prepared.

7. The method for preparing large recycled titanium alloy sintered parts according to claim 1, characterized in that: Micron or nano-reinforcing phases are added to titanium alloy powder as reinforcing phases.

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