Diffusion construction forming method for inhibiting metal segregation

Abstract

The invention discloses a diffusion construction forming method for inhibiting metal segregation, and relates to the technical field of metal materials. A diffusion construction forming method for inhibiting metal segregation comprises the following steps that a small blank is prefabricated, wherein metal raw materials are mixed and prefabricated into the small blank; surface cleaning: the small blank is subjected to machining and acid pickling, and a clean blank is obtained; stacking the blanks: stacking the blanks into a regular hexahedron to form a stack; wrapping: completely wrapping the stack with a metal foil material, and vacuumizing the interior of a sheath; diffusion bonding: carrying out hot isostatic pressure bonding on the sheath stacking body; and cutting machining, wherein burrs are removed through mechanical cutting, and the shape is cut out. According to the invention, the problems of forming requirements of large blanks of high-density-difference refractory metal alloys and the like are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal materials, and particularly relates to a diffusion construction forming method for suppressing metal segregation. Background Art

[0002] The metal blanking process is an important link in material processing, directly affecting the subsequent processing performance and part quality. At present, the mainstream metal blanking methods are mainly melting casting and powder metallurgy, which have their own advantages in different application scenarios and are widely used in the fields of industrial production and high-performance material manufacturing. Melting casting is widely used in the metal manufacturing field due to its simple preparation process and low cost, but it has extremely limited effects on refractory metals. Powder metallurgy is more suitable for refractory metals and has the characteristics of easy composition regulation, controllable porosity, and near-net shaping, and has always received much attention. However, for metal alloys with large differences in components such as tungsten-aluminum alloy, niobium-aluminum alloy, tungsten-copper alloy, tungsten-nickel alloy, and titanium-tantalum alloy, it is difficult to avoid the problem of composition segregation in these two processes. Taking the melting and powder metallurgy of titanium-tantalum alloy as an example: in melting, on the one hand, the buoyancy effect in the melt will cause the low-density titanium element (4.51 g / cm 3 ) to float, and the high-density tantalum element (16.60 g / cm 3 ) to sink, resulting in uneven solute distribution during solidification. On the other hand, during the high-temperature melting process, the titanium component with a lower boiling point (3530 °C) is very close to the melting point of tantalum (3020 °C) and is very easy to vaporize and escape from the melt pool, further exacerbating the segregation of the tantalum component; while in the powder metallurgy process, on the one hand, due to the large density difference of the components, unevenness is likely to occur during powder mixing, and on the other hand, there are differences in the diffusion rates of different element particles during the sintering process. Usually, the high-density elements diffuse slowly (the intrinsic diffusion coefficient of titanium is about 5 times that of tantalum) and are easily enriched in specific areas, further exacerbating the composition segregation. Composition segregation will cause problems such as increased precipitation of the second phase of the material, uneven performance, and poor processing performance, seriously affecting its processability and service performance. Therefore, suppressing segregation is crucial during the preparation process of refractory metals.

[0003] To solve the problem of composition segregation in the casting process, scholars have adopted technologies such as multiple melting, mechanical stirring, addition of nucleating agents, rapid cooling, and suspension casting during casting to optimize the solidification process. Although these methods can achieve remarkable effects in the preparation of conventional alloys, due to the fact that refractory metals containing components such as tungsten, molybdenum, tantalum, and niobium usually require higher energy consumption and higher production costs, these processes face great challenges in actual production. At the same time, as the ingot size increases, the composition segregation intensifies, and additional heat treatment, densification, or surface strengthening processes are required, further increasing the process complexity and cost; these methods are difficult to avoid the relatively high porosity and micro-defects of the castings, resulting in a decrease in the density of the material and damage to the mechanical properties and stability.

[0004] In addition, scholars have applied multiple sintering combination processes and techniques such as pre-sintered parts covered with powder. However, the combined sintering process requires the preparation of pre-sintered parts first, and then powder is covered layer by layer and multiple sinterings are needed. The workload is large, and with the increase in the number of sinterings, abnormal grain growth is likely to occur in local areas, resulting in imbalance of the material structure and properties. In addition, advanced additive manufacturing technologies such as selective laser melting and laser metal deposition have significant advantages in avoiding composition segregation, improving material uniformity and overall performance. However, their high manufacturing costs and limited production capacity have become the main obstacles to their further popularization and application in industrial production. As a large billet preparation method based on diffusion bonding, hot pressing can effectively improve the uniformity of the microstructure. This method is commonly used for metal material connection. Previously, patents such as "Method for forming homogeneous metal structure" (201511026272.X), "Method for forming metal structure" (201511027492.4), "Method for forming layered multi-column stacked metal structure" (201511029143.6) applied by the Institute of Metal Research, Chinese Academy of Sciences, and "Modular metal forming method" (201710839240.4) applied by the China Institute of Atomic Energy used the upsetting method to forge and weld multiple billets to achieve the forming of large billets. However, these methods require upsetting in multiple directions to reduce the voids between billets. If the same multiple pressurizations are used in combination with small billets to reduce the overall segregation degree, uneven deformation is also likely to occur during hot deformation, resulting in uneven structure and properties. However, through the isotropic gas action of high temperature and high pressure, hot isostatic pressing (HIP) technology can not only completely eliminate the internal pores and micro-defects of materials under the action of atomic diffusion, but also significantly improve the tissue uniformity and comprehensive performance of materials, and is expected to become a technical solution for us to solve the segregation control problem in the preparation process of large-sized billets of refractory metals.

[0005] To sum up, the billets prepared by the existing processes are difficult to meet the forming requirements of large-sized billets of refractory metal alloys with large density differences; although the new methods improved on the original technology by scientists to overcome the segregation problem have been improved to some extent, they are still not sufficient to achieve uniform forming of refractory metals with large density differences, and at the same time, there are problems such as complex processes, high costs, long cycles and poor component performance. Therefore, it is urgent to develop a new forming process that can simply and effectively suppress the segregation of refractory metal billets to meet the urgent needs of a new generation of high-reliability equipment in China for high-performance, high-precision and large-size integrated components. Summary of the Invention

[0006] The technical problem to be solved by the present invention is that the billets prepared by the process are difficult to meet the forming requirements of large billets of refractory metal alloys with large density differences, the process is complex, the cost is high, the cycle is long, and the performance of the components is poor. The purpose is to provide a diffusion build-up forming method for suppressing metal segregation, which solves the problems such as the forming requirements of large billets of refractory metal alloys with large density differences.

[0007] The present invention is realized by the following technical solutions:

[0008] A diffusion build-up forming method for suppressing metal segregation, comprising the following steps:

[0009] Preparing small billets: Mixing metal raw materials and prefabricating them into small billets;

[0010] Surface cleaning: Subjecting the small billets to machining and pickling to obtain cleaned billets;

[0011] Stacking billets: Stacking the billets to form a stacked body;

[0012] Jacketing: Completely wrapping the stacked body with metal foil, and then evacuating the inside of the jacket;

[0013] Diffusion bonding: Performing hot isostatic pressing on the jacketed stacked body;

[0014] Cutting and machining: Removing burrs and cutting into shape by mechanical cutting.

[0015] As a possible design, the above-mentioned machining and pickling of the small billets specifically involve first grinding the surface of the small billets, then machining on a milling machine, and finally pickling.

[0016] As a possible design, the above-mentioned prefabrication of small billets is carried out by powder metallurgy sintering, hot isostatic pressing, melting or 3D printing to make billets.

[0017] As a possible design, the above-mentioned billets include refractory metals, and the refractory metals include binary alloys and multi-element alloys containing refractory elements such as tungsten, molybdenum, tantalum, niobium, chromium and / or vanadium.

[0018] As a possible design, the height of the above-mentioned small billets is 1×10 2 ~5×10 2 mm, and the bottom surface area is 1×10 6 ~5×10 6 mm 2 .

[0019] As a possible design, the above-mentioned stacking method of the billets includes flat billets stacked flat, strip billets stacked in parallel arrays, strip billets stacked in vertical arrays, strip billets stacked vertically and staggeredly, other shaped billets stacked staggeredly or other shaped billets stacked in arrays.

[0020] As a possible design, the above-mentioned metal foil material includes steel, titanium alloy or superalloy.

[0021] As a feasible design solution, the above-mentioned vacuum pumping treatment can be operated as follows: reserve a small hole at the top of the jacket, and immediately seal the small hole by welding after the vacuum pumping operation is completed.

[0022] As a possible design, when the stack after the above-mentioned jacket is subjected to hot isostatic pressing, it is carried out in an inert atmosphere, the hot pressing pressure range is 0-1000 MPa, the treatment temperature is 800-2000 °C, and the pressure is applied for 0.5-30 hours;

[0023] The inert atmosphere includes nitrogen and / or argon.

[0024] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0025] By using diffusion bonding of small-sized homogeneous preforms, the present invention solves the problem of composition segregation in the preparation process of refractory metal large billets, realizes the homogenization of metal alloys. Specifically, by using air pressure to pressurize the preforms, densification and metallurgical bonding are achieved, so that the large metal billets prepared by this method are firmly bonded and the internal structure is uniform, providing a high-quality material basis for subsequent processing and forming. Moreover, the method of the present invention is simple and efficient, saving production costs, and providing technical support for the economic feasibility and production efficiency of large components of refractory metals. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings. In the drawings:

[0027] Figure 1 is one of the billet stacking methods of the present invention;

[0028] Figure 2 is the second billet stacking method of the present invention;

[0029] Figure 3 is the third billet stacking method of the present invention;

[0030] Figure 4 is the fourth billet stacking method of the present invention;

[0031] Figure 5 is the fifth billet stacking method of the present invention;

[0032] Figure 6 Schematic diagram of hot isostatic pressing diffusion bonding for the present invention Specific implementation manners

[0033] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments and drawings. The illustrative implementation manners of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For the reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0034] A diffusion construction forming method for suppressing metal segregation includes the following steps:

[0035] S1. Preparing small billets: Mixing metal raw materials and prefabricating them into small billets.

[0036] In some embodiments of the present invention, the above-mentioned preparation of small billets is carried out by powder metallurgy sintering, hot isostatic pressing, melting or 3D printing blanking. Powder metallurgy sintering, hot isostatic pressing, melting or 3D printing blanking can effectively eliminate the pores between metal powder particles, make the material reach higher density and uniformity, thereby improving the strength and hardness of the material and improving its wear resistance and corrosion resistance.

[0037] The above-mentioned powder metallurgy sintering is specifically to mix metal powders, cold press them into shape, and then sinter them in an inert gas atmosphere at 800 - 1200 °C for 1 - 3 h to obtain small billets.

[0038] The above-mentioned melting is specifically to mix metal powders, vacuum arc melt them at 2500 - 3500 °C to obtain a uniform alloy liquid, and then pour the alloy liquid into a mold and cool it at 10 - 30 °C / min to obtain small billets.

[0039] In some embodiments of the present invention, the above-mentioned refractory metals include binary alloys and multi-element alloys containing refractory elements such as tungsten, molybdenum, tantalum, niobium, chromium and / or vanadium.

[0040] In some embodiments of the present invention, the height of the above-mentioned small billets is 1×10 2 ~5×10 2 mm, and the bottom surface area is 1×10 6 ~5×10 6 mm 2 . At this size, it can ensure that the prefabricated billets have an insignificant segregation effect.

[0041] S2. Surface cleaning: Subjecting the small billets to machining and pickling to obtain clean billets.

[0042] Remove surface oxides and burrs by surface cleaning.

[0043] The above-mentioned machining and pickling include surface grinding, milling machine processing and pickling in sequence.

[0044] Preferably, the surface roughness of the cleaned blank is not greater than Ra3.2.

[0045] S3. Blank stacking: The blanks are stacked and placed into a regular hexahedron to form a stacking body.

[0046] In some embodiments of the present invention, the above-mentioned blank stacking placement method includes flat stacking of flat blanks, parallel array stacking of strip blanks, vertical array stacking of strip blanks, vertical staggered stacking of strip blanks, staggered stacking of other special-shaped blanks, or other special-shaped blank array stacking.

[0047] S4. Wrapping: The stack is completely wrapped with metal foil, and then the inside of the wrapping is vacuumed.

[0048] In some embodiments of the present invention, the metal foil includes steel, titanium alloy and high-temperature alloy.

[0049] S5. Diffusion bonding: hot isostatic pressing the sheath stack.

[0050] In some embodiments of the present invention, when the stack after the jacket is subjected to hot isostatic pressing, it is carried out in an inert atmosphere, the hot pressing pressure ranges from 0 to 1000 MPa, the processing temperature is 800 to 2000° C., and the pressing is applied for 0.5 to 30 hours;

[0051] The inert atmosphere includes nitrogen and / or argon.

[0052] S6. Cutting: The pressed sheets are mechanically cut to remove burrs and cut into shapes.

[0053] Example 1

[0054] A diffusion-building molding method for suppressing metal segregation, wherein the target product of this example is a tungsten-copper alloy billet block with a size of 500 mm×200 mm×2000 mm, comprises the following steps:

[0055] Prefabrication of small billets: Copper powder and tungsten powder are divided into 11 batches and fully mixed, and then put into a cold pressing mold for cold pressing to prepare 11 billets with a size of 550 mm × 250 mm × 250 mm; the prepared billets are then placed in a high-temperature furnace, the sintering temperature is set to 1000°C, and the temperature is maintained for 2 hours. After the sintering is completed, 11 billets are taken out to obtain prefabricated billets;

[0056] Surface cleaning: The small billets are polished on the surface, machined by a milling machine, and pickled to obtain clean billets with dimensions of 520 mm × 220 mm × 220 mm;

[0057] Stacking of billets: The 11 processed prefabricated billets are stacked in the Figure 1 shown manner, so that the surfaces of the billets are in flat and close contact with each other;

[0058] Jacketing: The stacked billets are wrapped with thin steel plates, and the joints of the thin steel plates are welded to form a jacket; The stacked billets are completely wrapped with metal foil, and then the inside of the jacket is evacuated;

[0059] Diffusion bonding: The jacketed stack is placed in a hot isostatic pressing furnace, set at a temperature of 1500 °C in an argon atmosphere, and kept at a pressure of 100 MPa for 2 hours to ensure high density and uniformity of the alloy. The hot isostatic pressing method is as Figure 6 shown;

[0060] Cutting and processing: The rough edges are removed and the shape is intercepted by mechanical cutting to cut into tungsten-copper alloy billet blocks with dimensions of 500 mm × 200 mm × 2000 mm.

[0061] Example 2

[0062] A diffusion bonding forming method for suppressing metal segregation. The target product of this example is a titanium-tantalum alloy billet block with dimensions of 500 mm × 500 mm × 500 mm, including the following steps:

[0063] Prefabricating small billets: The titanium powder and tantalum powder are divided into 10 batches and fully mixed. The mixed powder is loaded into a high-temperature melting furnace and melted by the vacuum arc melting method. The melting temperature is set at 3100 °C. At this temperature, titanium and tantalum are completely melted and fully mixed to form a uniform alloy liquid. The alloy liquid is poured into a graphite mold preheated to 500 °C, and the cooling rate is controlled at 20 °C / min. After cooling to room temperature, 100 prefabricated small billets with dimensions of 530 mm × 65 mm × 65 mm are prefabricated;

[0064] Surface cleaning: The small billets are polished on the surface, machined by a milling machine, and pickled to remove the surface oxide layer and rough edges, obtaining clean billets, and the dimensions of each billet are controlled at 520 mm × 60 mm × 60 mm;

[0065] Stacking of billets: The 100 processed prefabricated billets are stacked in the Figure 3 shown manner, so that the surfaces of the billets are in flat and close contact with each other;

[0066] Jacketing: The stack is wrapped with thin steel plates, the joints of the thin steel plates are welded, and then the inside of the jacket is evacuated;

[0067] Diffusion bonding: Place the blank in a hot isostatic pressing furnace, set the temperature to 1000 °C in an argon environment, and hold the pressure at 200 MPa for 2 hours to ensure high density and uniformity of the alloy. The hot isostatic pressing method is as Figure 6 shown;

[0068] Cutting process: Remove the burrs and cut into the desired shape by mechanical cutting, and cut the titanium-tantalum alloy blank into blocks of 500 mm × 500 mm × 500 mm.

[0069] Example 3

[0070] A diffusion bonding forming method for suppressing metal segregation. The target product of this example is an aluminum-tungsten alloy blank with dimensions of 500 mm × 500 mm × 500 mm, and the method includes the following steps:

[0071] Preparing small blanks: Divide the copper powder and tungsten powder into multiple batches for thorough mixing, then load them into a cold pressing mold for cold pressing to form multiple blanks with unequal but equal bottom surfaces. Place the prepared blanks in a high-temperature furnace, set the sintering temperature to 1000 °C, and maintain this temperature for 2 hours. After sintering, cool to room temperature and take out the blanks to obtain the prefabricated small blanks;

[0072] Surface cleaning: Polish, mill, and pickle the small blanks to obtain clean blanks with dimensions of 520 mm × 220 mm × 220 mm;

[0073] Stacking the blanks: Stack the processed prefabricated blanks in the Figure 5 shown manner so that the surfaces of the blanks are in flat and close contact with each other;

[0074] Jacketing: Wrap the stack with thin steel plates, weld the joints of the thin steel plates, and then evacuate the inside of the jacket;

[0075] Diffusion bonding: Transfer the blank to a hot isostatic pressing furnace, set the temperature to 1800 °C in a nitrogen environment, and hold the pressure at 100 MPa for 2 hours to ensure high density and uniformity of the alloy. The hot isostatic pressing method is as Figure 6 shown;

[0076] Cutting process: Remove the burrs and cut into the desired shape by mechanical cutting, and cut the aluminum-tungsten alloy blank into blocks of 500 mm × 500 mm × 500 mm.

[0077] The above specific embodiments further elaborate on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A diffusion structure forming method for suppressing metal segregation, characterized in that: The steps include: Prefabrication of small billets: Mixing metal raw materials and prefabricating them into small billets; Surface cleaning: The small blanks are machined and pickled to obtain clean blanks; Billet stacking: The billets are stacked and placed into a regular hexahedron to form a stacking body; Wrapping: Completely wrap the stack with metal foil; Diffusion bonding: hot isostatic pressing is performed on the package stacking bodies; Cutting: Mechanical cutting to remove burrs and cut into shapes.

2. A diffusion structure forming method for suppressing metal segregation according to claim 1, characterized in that: The prefabrication of the small-sized billet is carried out by powder metallurgy sintering, hot isostatic pressing, melting or 3D printing.

3. A diffusion structure forming method for suppressing metal segregation according to claim 1, characterized in that: The blank includes a refractory metal, including binary alloys and multinary alloys containing refractory elements of tungsten, molybdenum, tantalum, niobium, chromium and / or vanadium.

4. A diffusion structure forming method for suppressing metal segregation according to claim 1, characterized in that: The height of the small blank is 1×10 2 ~5×10 2 mm, the bottom area is 1×10 6 ~5×10 6 mm 2 .

5. The diffusion structure forming method for suppressing metal segregation according to claim 1, characterized in that: The blank stacking placement method includes flat stacking of flat blanks, parallel array stacking of strip blanks, vertical array stacking of strip blanks, vertical staggered stacking of strip blanks, staggered stacking of other special-shaped blanks, or array stacking of other special-shaped blanks.

6. The diffusion structure forming method for suppressing metal segregation according to claim 1, characterized in that: The metal foil material includes steel, titanium alloy or high temperature alloy.

7. The diffusion structure forming method for suppressing metal segregation according to claim 1, characterized in that: When the sheath stack body is subjected to hot isostatic pressing, it is carried out in an inert atmosphere, the hot pressing pressure ranges from 0 to 1000 MPa, the processing temperature is 800 to 2000° C., and the pressing time is 0.5 to 30 hours; The inert atmosphere includes nitrogen and / or argon.

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