Preparation method of large-size high-density tungsten-based composite shielding material

Abstract

The invention discloses a preparation method of a large-size high-density tungsten-based composite shielding material, which comprises the following steps: weighing tungsten powder, boron source powder and sintering aid powder in proportion, mixing the raw material powder, and putting into a ball mill for wet ball milling; drying, grinding and sieving the ball-milled powder; and the powder passing through the screen is loaded into a forming mold to be subjected to cold isostatic pressing, a tungsten-based composite material blank formed through pressing is put into a metal mold to be subjected to hot isostatic pressing, and the large-size high-density tungsten-based composite shielding material is successfully prepared through the powder metallurgy technology. The preparation method is high in process maturity, easy and convenient to operate and short in preparation period, long-time high-temperature sintering and high-temperature boriding treatment are not needed, and it is ensured that the large-size tungsten-based composite shielding material has high compactness through raw material powder particle size control and hot isostatic pressing sintering process optimization. The large-scale industrial production of the large-size tungsten-based composite shielding material is easy to realize, and the method has a wide commercial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of powder metallurgy technology, and particularly relates to a method for preparing large-size, high-density tungsten-based composite shielding materials. Background Technology

[0002] The development of the nuclear industry, nuclear medicine, and new nuclear fusion reactors has played a crucial role in my country's socio-economic and scientific development. However, while these nuclear facilities bring social and economic benefits, they also inevitably generate radiation of different energy levels, such as neutrons, gamma rays, and X-rays, posing direct or indirect harm to humans and the environment. Because neutrons and gamma rays have extremely strong penetrating power, their radiation hazards are the most significant among nuclear radiation rays. Therefore, developing a comprehensive shielding material that combines neutron and gamma-ray shielding properties has become an urgent need in the current development of nuclear technology.

[0003] Domestic and international organizations have conducted extensive research and application of nuclear radiation shielding materials. However, traditional shielding materials, such as shielding concrete, lead-boron polyethylene, and high-boron steel, suffer from drawbacks including large volume, poor workability and durability, weak neutron absorption capacity, toxicity, and low operating temperature, making it difficult to meet current demands for weight reduction. Therefore, it is crucial to develop a shielding material that is highly effective, safe, non-toxic, and possesses both comprehensive shielding performance and structural mechanical properties. Tungsten, with its excellent gamma-ray attenuation, high melting point, and high thermal conductivity, is the best choice for shielding materials. However, tungsten has a limited neutron capture cross-section, especially for thermal neutron energy. Therefore, it is necessary to add components with good thermal neutron absorption properties to the material to form a new material capable of effectively attenuating neutrons and gamma rays. Boron (B) has a high neutron self-absorption cross-section and, as a ceramic phase, possesses high hardness and strength, which can increase the material's thermal neutron absorption effect while also improving its strength. Therefore, adding a small amount of boron to tungsten-based materials can form a novel tungsten-based composite material capable of effectively attenuating neutrons and gamma rays. However, tungsten has a high melting point of 3400℃, while boron has a high melting point of 2076℃, and boron diffuses slowly in tungsten. Therefore, it is difficult to prepare uniformly doped boron-doped tungsten-based composite materials using existing processes. Therefore, there is an urgent need to provide a method for preparing high-density boron-doped tungsten-based composite materials. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a method for preparing large-size, high-density tungsten-based composite shielding materials. This invention employs powder metallurgy technology to mix tungsten powder, boron source powder, and sintering aid powder, followed by ball milling, cold isostatic pressing, and hot isostatic pressing, ultimately yielding large-size, high-density tungsten-based composite shielding materials.

[0005] This invention discloses a method for preparing large-size, high-density tungsten-based composite shielding material, comprising the following steps: Weigh out the tungsten powder, boron source powder, and sintering aid powder according to the mass percentage; Tungsten powder, boron source powder, and sintering aid powder are mixed and then placed in a ball mill for wet ball milling. The powder after ball milling is dried, ground, and sieved. The powder passing through the sieve is loaded into the molding die, and then the molding die is subjected to cold isostatic pressing. The pressed tungsten-based composite material blank is then placed into a metal mold, and the metal mold is then subjected to hot isostatic pressing to obtain the tungsten-based composite shielding material.

[0006] Furthermore, the amount of tungsten powder used is 93-96 wt%, the amount of boron source powder used is 2-4 wt%, and the amount of sintering aid powder used is 2-3 wt%.

[0007] Furthermore, the boron source powder is boron powder and / or boron carbide powder, and the sintering aid powder is cobalt powder and / or nickel powder.

[0008] Furthermore, the average particle size of the tungsten powder is 50 μm, and the average particle size of the boron source powder and sintering aid powder is 30 μm.

[0009] Furthermore, the wet ball milling process involves mixing tungsten powder, boron source powder, and sintering aid powder according to a specified ratio, placing them in a ball milling jar, adding alcohol, and adding zirconia milling balls at a ball-to-material ratio of 4:1 by mass, and milling at a speed of 200 r / min for 8 hours.

[0010] Furthermore, the ball-milled powder is dried, ground, and then passed through a 200-mesh sieve.

[0011] Furthermore, the ball-milled powder was dried in a 60°C oven for 3 hours.

[0012] Furthermore, the cold isostatic pressing process involves loading powder into a molding die, sealing the die under vacuum, and then placing it in a cold isostatic press for cold isostatic pressing. The pressing pressure is set to 100~300MPa, the holding time is 10~20min, and the depressurization speed is 3MPa / s.

[0013] Furthermore, the molding die is a hard rubber short tube die.

[0014] Furthermore, the hot isostatic pressing process involves placing the pressed tungsten-based composite material blank into a metal mold, sealing the mold under vacuum, and then placing it into a hot isostatic press for hot pressing and sintering. The hot pressing pressure is set to 100~200MPa, the holding time is 0.5~2h, the depressurization rate is 3MPa / s, and the sintering temperature is 1300~1500℃.

[0015] This invention provides a method for preparing large-size, high-density tungsten-based composite shielding materials. Compared with existing technologies, this invention has at least the following advantages: This invention successfully prepares large-size, high-density tungsten-based composite shielding materials using powder metallurgy technology. The preparation method of this invention has high process maturity, is simple to operate, and has a short preparation cycle. It does not require long-term high-temperature sintering and high-temperature boronizing treatment. The prepared tungsten-based composite shielding materials can be further scaled up in size according to actual needs. Through control of raw material powder particle size and optimization of the hot isostatic pressing process, the high density of the tungsten-based composite shielding materials can still be ensured. The preparation method of this invention is easy to realize for large-scale industrial production of large-size tungsten-based composite shielding materials and has broad commercial application prospects. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 The image shows the XRD pattern of the tungsten-based composite material prepared in Example 1 of this invention. Detailed Implementation

[0018] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0019] Unless otherwise specified, all temperatures mentioned herein are in degrees Celsius, and the preferred embodiments can be freely combined as needed. Those skilled in the art will understand that the data and parameters described in the examples are merely exemplary and do not constitute a limitation of the invention. All components used in the following examples and comparative examples are compounds known in the art, and all equipment used is equipment publicly known in the art. All components and equipment used in this invention can be obtained commercially or prepared using known techniques.

[0020] This invention provides a method for preparing large-size, high-density tungsten-based composite shielding material, comprising the following steps: Weigh out the tungsten powder, boron source powder, and sintering aid powder according to the mass percentage; Tungsten powder, boron source powder, and sintering aid powder are mixed and then placed in a ball mill for wet ball milling. The powder after ball milling is dried, ground, and sieved. The powder passing through the sieve is loaded into the molding die, and then the molding die is subjected to cold isostatic pressing. The pressed tungsten-based composite material blank is then placed into a metal mold, and the metal mold is then subjected to hot isostatic pressing to obtain the tungsten-based composite shielding material.

[0021] Preferably, the tungsten powder accounts for 93-96 wt%, the boron source powder accounts for 2-4 wt%, and the sintering aid powder accounts for 2-3 wt%. The boron source powder is preferably boron powder and / or boron carbide powder, and the sintering aid powder is preferably cobalt powder and / or nickel powder.

[0022] Preferably, the tungsten powder has an average particle size of 50 μm, and the boron source powder and sintering aid powder both have an average particle size of 30 μm.

[0023] Preferably, the wet ball milling process of the present invention is as follows: tungsten powder, boron source powder, and sintering aid powder weighed in proportion are mixed and placed in a ball milling jar, alcohol is added, and zirconium oxide milling balls are added at a mass ratio of 4:1. The mixture is then milled at a speed of 200 r / min for 8 hours.

[0024] Preferably, the ball-milled powder is dried, ground, and then passed through a 200-mesh sieve. More preferably, the ball-milled powder is dried in an oven at 60°C for 3 hours.

[0025] Preferably, the cold isostatic pressing process of the present invention involves loading powder into a molding die, sealing the die under vacuum, and then placing it in a cold isostatic press for cold isostatic pressing. The pressing pressure is set to 100~300MPa, the holding time to 10~20min, and the depressurization rate to 3MPa / s. The molding die is preferably a rigid rubber short tube mold.

[0026] Preferably, the hot isostatic pressing process of the present invention involves placing the pressed tungsten-based composite material blank into a metal mold, sealing the mold under vacuum, and then placing it in a hot isostatic press for hot pressing and sintering. The hot pressing pressure is set to 100~200MPa, the holding time to 0.5~2h, the depressurization rate to 3MPa / s, and the sintering temperature to 1300~1500℃. After hot isostatic pressing is completed, the tungsten-based composite material is removed after cooling to room temperature in the furnace. The metal mold is preferably a titanium alloy mold.

[0027] The technical principle of this invention for preparing large-size, high-density tungsten-based composite shielding materials is as follows: Through ball milling, cold isostatic pressing, and hot isostatic pressing, this invention achieves the composite molding of high-tungsten-content tungsten-based composite materials. For the application requirements of larger-size tungsten-based composite materials, larger-size hard rubber short tube molds can be selected. By controlling the particle size of the raw material powder, using sintering aids, and optimizing the hot isostatic pressing sintering process, high-density tungsten-based composite materials are sintered and prepared under high temperature and high pressure conditions. The resulting tungsten-based composite material has good mechanical properties.

[0028] The present invention will now be described in more detail with reference to exemplary embodiments. The following embodiments or experimental data are intended to illustrate the present invention by way of example, and those skilled in the art should understand that the present invention is not limited to these embodiments or experimental data.

[0029] Example 1 The preparation of large-size, high-density tungsten-based composite shielding materials includes the following steps: S1. Ingredients Weigh out 9.3 kg of tungsten powder, 0.4 kg of boron powder and 0.3 kg of nickel powder, wherein the average particle size of the tungsten powder is 50 μm, and the average particle size of the boron powder and nickel powder is 30 μm. S2. Wet ball milling Tungsten powder, boron powder, and nickel powder were mixed and placed in a ball mill jar. Alcohol was added until a mixed powder suspension was formed. Zirconia milling balls were added at a mass ratio of 4:1, and the mixture was milled at 200 r / min for 8 hours. After multiple batches of milling, the milling of all raw materials was completed. S3. Drying, grinding, and sieving The ball-milled powder was dried in a 60°C oven for 3 hours, then ground and passed through a 200-mesh sieve. S4. Cold isostatic pressing The powder passing through the sieve is loaded into a square rigid rubber short tube mold with a volume of 120mm×120mm×12mm. After the mold is vacuum sealed, it is placed in a cold isostatic press for cold isostatic pressing. The cold isostatic pressing pressure is 150MPa, the holding time is 15min, and the depressurization speed is 3MPa / s. S5. Hot isostatic pressing The pressed tungsten-based composite material blank is placed into a titanium alloy mold. After the mold is vacuum sealed, it is placed in a hot isostatic press for hot pressing and sintering. The hot isostatic pressing pressure is 200 MPa, the holding time is 0.5 h, the depressurization rate is 3 MPa / s, and the sintering temperature is 1500℃. After the hot isostatic pressing is completed, the tungsten-based composite material is taken out after cooling to room temperature with the furnace.

[0030] Example 2 The preparation of large-size, high-density tungsten-based composite shielding materials includes the following steps: S1. Ingredients Weigh out 9.3 kg of tungsten powder, 0.4 kg of boron carbide powder and 0.3 kg of nickel powder, wherein the average particle size of the tungsten powder is 50 μm, and the average particle size of the boron carbide powder and the nickel powder is 30 μm. S2. Wet ball milling Tungsten powder, boron carbide powder, and nickel powder were mixed and placed in a ball mill jar. Alcohol was added until a mixed powder suspension was formed. Zirconia milling balls were added at a ball-to-material ratio of 4:1 by mass, and the mixture was milled at 200 r / min for 8 hours. After multiple batches of milling, the milling of all raw materials was completed. S3. Drying, grinding, and sieving The ball-milled powder was dried in a 60°C oven for 3 hours, then ground and passed through a 200-mesh sieve. S4. Cold isostatic pressing The powder passing through the sieve is loaded into a square rigid rubber short tube mold with a volume of 120mm×120mm×12mm. After the mold is vacuum sealed, it is placed in a cold isostatic press for cold isostatic pressing. The cold isostatic pressing pressure is 100MPa, the holding time is 20min, and the depressurization speed is 3MPa / s. S5. Hot isostatic pressing The pressed tungsten-based composite material blank is placed into a titanium alloy mold. After the mold is vacuum sealed, it is placed in a hot isostatic press for hot pressing and sintering. The hot isostatic pressing pressure is 150 MPa, the holding time is 1 hour, the depressurization rate is 3 MPa / s, and the sintering temperature is 1400℃. After the hot isostatic pressing is completed, the tungsten-based composite material is taken out after cooling to room temperature with the furnace.

[0031] Example 3 The preparation of large-size, high-density tungsten-based composite shielding materials includes the following steps: S1. Ingredients Weigh out 9.4 kg of tungsten powder, 0.4 kg of boron powder and 0.2 kg of cobalt powder, wherein the average particle size of the tungsten powder is 50 μm, and the average particle size of the boron powder and cobalt powder is 30 μm. S2. Wet ball milling Tungsten powder, boron powder, and cobalt powder were mixed and placed in a ball mill jar. Alcohol was added until a mixed powder suspension was formed. Zirconia milling balls were added at a mass ratio of 4:1, and the mixture was milled at 200 r / min for 8 hours. After multiple batches of milling, the milling of all raw materials was completed. S3. Drying, grinding, and sieving The ball-milled powder was dried in a 60°C oven for 3 hours, then ground and passed through a 200-mesh sieve. S4. Cold isostatic pressing The powder passing through the sieve is loaded into a square rigid rubber short tube mold with a volume of 120mm×120mm×12mm. After the mold is vacuum sealed, it is placed in a cold isostatic press for cold isostatic pressing. The cold isostatic pressing pressure is 200MPa, the holding time is 15min, and the depressurization speed is 3MPa / s. S5. Hot isostatic pressing The pressed tungsten-based composite material blank is placed into a titanium alloy mold. After the mold is vacuum sealed, it is placed in a hot isostatic press for hot pressing and sintering. The hot isostatic pressing pressure is 100 MPa, the holding time is 2 hours, the depressurization rate is 3 MPa / s, and the sintering temperature is 1300℃. After the hot isostatic pressing is completed, the tungsten-based composite material is taken out after cooling to room temperature with the furnace.

[0032] Example 4 The preparation of large-size, high-density tungsten-based composite shielding materials includes the following steps: S1. Ingredients Weigh out 9.6 kg of tungsten powder, 0.2 kg of boron carbide powder and 0.2 kg of cobalt powder, wherein the average particle size of the tungsten powder is 50 μm, and the average particle size of the boron carbide powder and the cobalt powder is 30 μm. S2. Wet ball milling Tungsten powder, boron carbide powder, and cobalt powder were mixed and placed in a ball mill jar. Alcohol was added until a mixed powder suspension was formed. Zirconia milling balls were added at a mass ratio of 4:1, and the mixture was milled at 200 r / min for 8 hours. After multiple batches of milling, the milling of all raw materials was completed. S3. Drying, grinding, and sieving The ball-milled powder was dried in a 60°C oven for 3 hours, then ground and passed through a 200-mesh sieve. S4. Cold isostatic pressing The powder passing through the sieve is loaded into a square rigid rubber short tube mold with a volume of 120mm×120mm×12mm. After the mold is vacuum sealed, it is placed in a cold isostatic press for cold isostatic pressing. The cold isostatic pressing pressure is 300MPa, the holding time is 10min, and the depressurization speed is 3MPa / s. S5. Hot isostatic pressing The pressed tungsten-based composite material blank is placed into a titanium alloy mold. After the mold is vacuum sealed, it is placed in a hot isostatic press for hot pressing and sintering. The hot isostatic pressing pressure is 100 MPa, the holding time is 2 hours, the depressurization rate is 3 MPa / s, and the sintering temperature is 1500℃. After the hot isostatic pressing is completed, the tungsten-based composite material is taken out after cooling to room temperature with the furnace.

[0033] Comparative Example 1 This comparative example prepares a large-size, high-density tungsten-based composite shielding material. The difference between this comparative example and Example 1 is that nickel powder, a sintering aid, was not used in the raw materials. The rest of the preparation method is exactly the same as that of Example 1.

[0034] Comparative Example 2 This comparative example prepares a large-size, high-density tungsten-based composite shielding material. The difference between this comparative example and Example 1 is that the raw materials used are tungsten powder with an average particle size of 80 μm, boron powder with an average particle size of 50 μm, and nickel powder. The rest of the preparation method is exactly the same as that of Example 1.

[0035] Comparative Example 3 This comparative example prepares a large-size, high-density tungsten-based composite shielding material. The difference between this comparative example and Example 1 is that the ball milling speed is 100 r / min, while the rest of the preparation method is exactly the same as that of Example 1.

[0036] Comparative Example 4 This comparative example prepares a large-size, high-density tungsten-based composite shielding material. The difference between this comparative example and Example 1 is that the sintering temperature in the hot isostatic pressing process is 1200℃, while the rest of the preparation method is exactly the same as that in Example 1.

[0037] Chemical composition and density analysis of tungsten-based composite materials XRD analysis was performed on the tungsten-based composite shielding material prepared in Example 1. Figure 1 The image shows the XRD pattern of the tungsten-based composite shielding material in Example 1. Figure 1 It is known that W₂NiB₂ is also formed in the tungsten-based composite material in addition to elemental tungsten. This demonstrates that by using sintering aids, alloying of tungsten, boron, and the sintering aid metals is achieved during the sintering process, resulting in a tungsten-based composite material with higher density.

[0038] The density of the tungsten-based composite shielding materials prepared in Examples 1-4 and Comparative Examples 1-4 was tested and analyzed. The test results are shown in Table 1. In Table 1, density refers to the percentage of the measured density of the tungsten-based composite materials prepared in each example and comparative example relative to the density of the tungsten-based alloy with the same composition. It can be seen that the density of the tungsten-based composite shielding materials in Examples 1-4 is significantly better than that in Comparative Examples 1-4.

[0039] Table 1. Density test results of each embodiment and comparative example.

[0040] In Comparative Example 1, no sintering aids were used. Since both tungsten and boron have high melting points (tungsten melting point reaches 3400℃ and boron melting point reaches 2076℃) and the diffusion rate of boron in tungsten is extremely slow, it is difficult to form an alloy between tungsten and boron at the sintering temperature of 1500℃ and the holding time of 0.5h in Comparative Example 1. As a result, the density of the tungsten-based composite shielding material obtained will not meet the strength requirements of the material application.

[0041] The tungsten powder, boron powder, and nickel powder used in Comparative Example 2 had a relatively large average particle size. The density of the tungsten-based composite shielding material obtained after cold isostatic pressing and hot isostatic pressing was lower than that of the composite materials obtained in the embodiments of this invention. This demonstrates that the particle size of the raw material powder has a significant impact on the final density of the composite material. A larger average particle size of the raw material powder affects the reaction rate of the raw materials during the reaction process, making it impossible to ensure uniform alloying within the composite material blank during hot isostatic pressing, thus leading to a decrease in the density of the tungsten-based composite shielding material.

[0042] Although the average particle size of the raw material powders such as tungsten powder, boron powder and nickel powder used in Comparative Example 3 meets the preferred requirements of the present invention for the particle size of raw material powders, the ball milling speed is reduced, resulting in uneven powder mixing during the mixing process. As a result, the density of the tungsten-based composite shielding material obtained is still lower than that of the composite material obtained in the various embodiments of the present invention, indicating that the mixing uniformity of the raw material powders also has a significant impact on the density of the final composite material.

[0043] In Comparative Example 4, the sintering temperature was only 1200℃, which prevented sufficient alloying between tungsten, boron, and nickel. Consequently, the density of the tungsten-based composite shielding material prepared in Comparative Example 4 was lower than that of the composite materials in the embodiments of this invention. When the sintering temperature was increased to over 1500℃, experimental verification showed that the density of the composite material did not increase significantly further. Therefore, the preferred sintering temperature is 1300~1500℃.

[0044] All materials used in this invention are commercially available and can be purchased from retail sources. The above description is merely a preferred embodiment of the invention and is not intended to limit the invention. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A method for preparing a large-size, high-density tungsten-based composite shielding material, characterized in that, Includes the following steps: Weigh out the tungsten powder, boron source powder, and sintering aid powder according to the mass percentage; Tungsten powder, boron source powder, and sintering aid powder are mixed and then placed in a ball mill for wet ball milling. The powder after ball milling is dried, ground, and sieved. The powder passing through the sieve is loaded into the molding die, and then the molding die is subjected to cold isostatic pressing. The pressed tungsten-based composite material blank is then placed into a metal mold, and the metal mold is then subjected to hot isostatic pressing to obtain the tungsten-based composite shielding material.

2. The method for preparing tungsten-based composite shielding material according to claim 1, characterized in that, The proportion of tungsten powder used is 93-96 wt%, the proportion of boron source powder used is 2-4 wt%, and the proportion of sintering aid powder used is 2-3 wt%.

3. The method for preparing tungsten-based composite shielding material according to claim 2, characterized in that, The boron source powder is boron powder and / or boron carbide powder, and the sintering aid powder is cobalt powder and / or nickel powder.

4. The method for preparing tungsten-based composite shielding material according to claim 1, characterized in that, The average particle size of the tungsten powder is 50 μm, while the average particle size of the boron source powder and the sintering aid powder is 30 μm.

5. The method for preparing tungsten-based composite shielding material according to claim 1, characterized in that, The wet ball milling process involves mixing tungsten powder, boron source powder, and sintering aid powder according to a specified ratio, placing them in a ball milling jar, adding alcohol, and adding zirconia milling balls at a ball-to-material ratio of 4:1 by mass. The mixture is then milled at 200 r / min for 8 hours.

6. The method for preparing tungsten-based composite shielding material according to claim 1, characterized in that, The powder after ball milling is dried, ground, and then passed through a 200-mesh sieve.

7. The method for preparing tungsten-based composite shielding material according to claim 6, characterized in that, After ball milling, the powder was placed in a 60℃ oven and dried for 3 hours.

8. The method for preparing tungsten-based composite shielding material according to claim 1, characterized in that, The cold isostatic pressing process involves loading powder into a molding die, sealing the die under vacuum, and then placing it in a cold isostatic press for cold isostatic pressing. The pressing pressure is set to 100~300MPa, the holding time is 10~20min, and the depressurization speed is 3MPa / s.

9. The method for preparing tungsten-based composite shielding material according to claim 8, characterized in that, The molding die is a hard rubber short tube die.

10. The method for preparing tungsten-based composite shielding material according to claim 1, characterized in that, The hot isostatic pressing process involves placing the pressed tungsten-based composite material blank into a metal mold, sealing the mold under vacuum, and then placing it into a hot isostatic press for hot pressing and sintering. The hot pressing pressure is set to 100~200MPa, the holding time is 0.5~2h, the depressurization rate is 3MPa / s, and the sintering temperature is 1300~1500℃.

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