A tungsten-boron stainless steel composite material and a method for manufacturing the same

Abstract

The application discloses a tungsten-boron stainless steel composite material and a preparation method thereof, and relates to the technical field of shielding materials, which comprises a boron-tungsten compound, wherein the boron-tungsten compound particles are dispersed in a stainless steel matrix. The tungsten-boron stainless steel composite material has high density of the dispersed boron-tungsten compound, tungsten is a heavy metal element with stable chemical properties and high gamma shielding efficiency; boron has a high neutron absorption cross section for medium and low energy neutrons, and is a high-efficiency neutron shielding component; the tungsten boride materials of various components have good compatibility with the stainless steel; at the sintering and other hot working temperatures of the stainless steel, the tungsten boride materials do not react with the stainless steel matrix; the boron-tungsten compound is dispersed in the stainless steel matrix, and the composite material prepared by the method has better neutron shielding performance and gamma shielding performance than traditional boron stainless steel.

Description

Technical Field

[0001] This invention relates to the field of shielding materials technology, specifically to a tungsten boron stainless steel composite material and its preparation method. Background Technology

[0002] Boron steel possesses a high neutron absorption cross section, while stainless steel exhibits excellent mechanical properties and gamma shielding capabilities. Therefore, boron steel is a high-performance structural-functional integrated material with significant application value in shielding engineering. Boron stainless steel, used as a structural material, can replace some shielding materials, reducing their weight and volume. However, at room temperature, the solid solubility of boron in stainless steel is limited. During heat treatment and cooling, boron precipitates at grain boundaries, forming continuous brittle phases of iron boride and chromium boride. Iron boride and chromium boride have relatively low boron density. If there is an excessive amount of brittle phases, a brittle phase network structure can form within the material, making the entire material brittle.

[0003] Currently, the boron content of commonly used boron cast steel generally does not exceed 0.8%, and the boron content of Grade A boron cast steel produced by powder metallurgy is no more than 3%. Therefore, boron embrittlement limits the increase of boron content in boron stainless steel, affecting its neutron absorption capacity. Thus, improving the neutron absorption capacity of boron stainless steel is one of the goals pursued by shielding material researchers.

[0004] Therefore, due to the problem of boron embrittlement, current boron steel composite materials still have the problem of low neutron shielding performance and gamma shielding performance. Summary of the Invention

[0005] Based on the problems existing in the background technology, the purpose of this invention is to provide a tungsten boron stainless steel composite material and its preparation method. In this tungsten boride stainless steel composite material, tungsten boride particles are dispersed in the stainless steel matrix, increasing the boron content in the boron carbide stainless steel composite material of the shielding material to more than 3%, and the tensile strength is higher than 300 MPa. At the same time, the density of the material increases, and the gamma shielding performance of the shielding material is improved. Compared with the existing boron steel composite material, the neutron shielding performance and gamma shielding performance of the tungsten boride stainless steel composite material are both improved.

[0006] This invention is achieved through the following technical solution:

[0007] In a first aspect, this application provides a tungsten-boron stainless steel composite material, comprising a boron-tungsten compound, wherein the boron-tungsten compound particles are dispersed within a stainless steel matrix.

[0008] Nuclear reactors are composite shielding fields for neutrons and gamma rays. Gamma ray shielding generally requires the use of high atomic number and high density materials, such as tungsten and lead. High-energy neutrons are generally first slowed down by scattering with materials with high scattering cross-sections, then slowed down by hydrogen-containing materials, and finally absorbed by materials with large neutron absorption cross-sections.

[0009] The tungsten-boron stainless steel composite material of this invention features a high density of boron and tungsten compounds in the dispersed phase. Tungsten is a chemically stable heavy metal element with high gamma shielding efficiency. Boron has a high neutron absorption cross section for medium and low-energy neutrons, making it a highly efficient neutron shielding component. Various tungsten boride materials exhibit good compatibility with stainless steel and do not react with the stainless steel matrix at the sintering and other hot working temperatures of stainless steel. By dispersing boron and tungsten compounds in the stainless steel matrix, a composite material with superior neutron and gamma shielding performance compared to traditional boron stainless steel can be prepared.

[0010] Stainless steel has a large scattering cross section for high-energy neutrons and a high high-energy neutron moderation efficiency. It also has good mechanical properties and corrosion resistance. Boron-tungsten stainless steel composite material integrates the high density and high efficiency of gamma shielding performance of tungsten, the neutron shielding performance of boron, the high-energy neutron moderation performance of stainless steel, corrosion resistance and good mechanical properties. It is a high-performance comprehensive shielding material that can reduce the weight and volume of the shielding body, which is of great significance for reducing the weight and volume of mobile reactors.

[0011] In the tungsten boride stainless steel composite material of this invention, tungsten boride particles are dispersed in the stainless steel matrix, increasing the boron content in the shielding material to more than 3%, while the density of the material increases, thus improving the gamma shielding performance of the shielding material. Compared with existing boron steel composite materials, the neutron shielding performance and gamma shielding performance of the tungsten boride stainless steel composite material are both improved.

[0012] Furthermore, the volume of the boron-tungsten compound is 10% to 50% of the total volume of the boron-tungsten compound and the stainless steel matrix.

[0013] Furthermore, the boron-tungsten compound includes any one or more combinations of tungsten monoboride, tungsten diboride, tungsten diboride, and tungsten pentaboride.

[0014] Furthermore, the borotungsten compound is tungsten monoboride.

[0015] Furthermore, the particle size of the boron-tungsten compound is 0.5 to 10 micrometers.

[0016] Furthermore, the average particle size of the boron-tungsten compound is 5 micrometers.

[0017] Furthermore, the stainless steel matrix is ​​304 stainless steel.

[0018] To ensure good mechanical properties, the matrix of the tungsten boron stainless steel composite material is made of 304 stainless steel. 304 stainless steel has good plasticity and corrosion resistance, which gives the boron carbide stainless steel composite material good corrosion resistance and mechanical properties, making it suitable for use as a structural material.

[0019] Furthermore, the density of the boron-tungsten stainless steel composite material is higher than 8.5 g / cm³. 3 .

[0020] Secondly, this application provides a method for preparing tungsten-boron stainless steel composite materials.

[0021] Includes the following steps:

[0022] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0023] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill.

[0024] Step 3: The mixture of tungsten boride powder and stainless steel powder obtained in Step 2 is sintered and rolled to obtain tungsten boride stainless steel composite material.

[0025] The purpose of using a high-energy ball mill to process tungsten boride powder and stainless steel powder is to mechanically alloy the tungsten boride powder and stainless steel powder, so that the tungsten boride powder is dispersed into the stainless steel matrix. Because commercially available tungsten boride powder has a small particle size and a high volume fraction in the composite material, it will form a structure in which tungsten boride encapsulates stainless steel particles, and a continuous brittle tungsten boride phase will be formed in the composite material, thus making the material brittle overall.

[0026] Furthermore, the sintering method can be any one of SPS sintering, hot pressing sintering, or hot isostatic pressing sintering.

[0027] Because the stainless steel powder has a chromium hydride passivation layer on its surface, which hinders the sintering of stainless steel, it is difficult to densify stainless steel. Therefore, it is necessary to use a pressure strengthening method for sintering, namely, the SPS sintering method, hot pressing sintering method, and hot isostatic pressing sintering method used in this application.

[0028] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0029] (1) The tungsten-boron stainless steel composite material of the present invention has a high density of various compounds of boron and tungsten in the dispersed phase. Tungsten is a chemically stable heavy metal element with high gamma shielding efficiency. Boron has a high neutron absorption cross section for medium and low energy neutrons and is a highly efficient neutron shielding component. Various components of tungsten boride materials have good compatibility with stainless steel. They do not react with the stainless steel matrix at the sintering and other hot working temperatures of stainless steel. By dispersing the compounds of boron and tungsten in the stainless steel matrix, a composite material with neutron shielding performance and gamma shielding performance superior to that of traditional boron stainless steel can be prepared.

[0030] (2) The boron-tungsten stainless steel composite material of the present invention integrates the high density and high efficiency gamma shielding performance of tungsten, the neutron shielding performance of boron, the high energy neutron moderation performance of stainless steel, corrosion resistance and good mechanical properties. It is a high-performance comprehensive shielding material that can reduce the weight and volume of the shielding body and is of great significance for reducing the weight and volume of mobile reactors.

[0031] (3) In the tungsten boride stainless steel composite material of the present invention, tungsten boride particles are dispersed in the stainless steel matrix, increasing the boron content in the shielding material to more than 3%, and at the same time increasing the density of the material, the gamma shielding performance of the shielding material is improved. Compared with the existing boron steel composite material, the neutron shielding performance and gamma shielding performance of the tungsten boride stainless steel composite material are both improved. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:

[0033] Figure 1 The image shows a SEM image of the tungsten-boron stainless steel composite material prepared in Example 1 of this invention, where 1 is a tungsten boride particle and 2 is the stainless steel matrix. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.

[0035] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0036] Example 1

[0037] This embodiment provides a tungsten boron stainless steel composite material, which is composed of tungsten boride particles dispersed in a stainless steel matrix, wherein the tungsten boride content is 40%, the balance is 304 stainless steel matrix, and the particle size of the tungsten boride particles is 0.5-5 micrometers.

[0038] The preparation method of this tungsten-boron stainless steel composite material is as follows:

[0039] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0040] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. The ball mill speed is 300 rpm and the ball milling time is 2 hours.

[0041] Step 3: The mixture of tungsten boride powder and stainless steel powder from Step 2 is subjected to hot pressing and sintering to obtain tungsten boride stainless steel composite material. The sintering conditions are: pressure 30 MPa, temperature 1100 degrees Celsius, and holding time 2 hours.

[0042] The tungsten boride stainless steel composite material prepared by the above method was subjected to microscopic examination using scanning electron microscopy. The results are as follows: Figure 1 As shown in the electron microscope image, tungsten boride is uniformly dispersed in the stainless steel matrix without forming a continuous brittle phase. There is no interfacial reaction between tungsten boride and stainless steel, indicating good compatibility.

[0043] Example 2

[0044] Based on Example 1, this example provides a tungsten-boron stainless steel composite material, which is composed of tungsten diboride particles dispersed in a stainless steel matrix, wherein the tungsten diboride content is 24%, the balance is 304 stainless steel matrix, the equivalent boron content is 3%, and the particle size of the tungsten diboride particles is 5 micrometers.

[0045] The preparation method of this tungsten-boron stainless steel composite material is as follows:

[0046] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0047] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. The ball mill speed is 300 rpm and the ball milling time is 2 hours.

[0048] Step 3: The mixture of tungsten boride powder and stainless steel powder from Step 2 is placed in a stainless steel sheath, vacuum-sealed, and then placed in an exothermic isostatic pressing furnace for hot isostatic pressing sintering at 1050 degrees Celsius for 1 hour at a pressure of 150 MPa, yielding the tungsten boride stainless steel composite material.

[0049] Example 3

[0050] Based on Example 1, this example provides a tungsten-boron stainless steel composite material, which is composed of tungsten boride particles dispersed in a stainless steel matrix, wherein the tungsten boride content is 50% and the balance is 304 stainless steel matrix, and the particle size of the tungsten boride particles is 5 micrometers.

[0051] The preparation method of this tungsten-boron stainless steel composite material is as follows:

[0052] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0053] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. The ball mill speed is 300 rpm and the ball milling time is 2 hours.

[0054] Step 3: Place the mixture of tungsten boride powder and stainless steel powder from Step 2 into a stainless steel sheath, perform vacuum sealing and welding, and then place it in an exothermic isostatic pressing furnace for hot isostatic pressing sintering at a temperature of 1050 degrees Celsius, a holding time of 1 hour, and a pressure of 150 MPa to obtain tungsten boride stainless steel composite material.

[0055] Example 4

[0056] Based on Example 1, this example provides a tungsten boron stainless steel composite material, which is composed of tungsten diboride particles dispersed in a stainless steel matrix, wherein the tungsten diboride content is 18%, the balance is 304 stainless steel matrix, and the particle size of the tungsten diboride particles is 5 micrometers.

[0057] The preparation method is as follows:

[0058] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0059] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. The ball mill speed is 300 rpm and the ball milling time is 2 hours.

[0060] Step 3: Place the mixture of tungsten boride powder and stainless steel powder from Step 2 into a stainless steel sheath, perform vacuum sealing and welding, and then place it in an exothermic isostatic pressing furnace for hot isostatic pressing sintering at a temperature of 1050 degrees Celsius, a holding time of 1 hour, and a pressure of 150 MPa to obtain tungsten boride stainless steel composite material.

[0061] Example 5

[0062] Based on Example 1, this example provides a tungsten boron stainless steel composite material, which is composed of tungsten pentaboride particles dispersed in a stainless steel matrix, wherein the tungsten pentaboride content is 50%, the balance is 304 stainless steel matrix, and the particle size of the tungsten pentaboride particles is 5 micrometers.

[0063] The preparation method of this tungsten-boron stainless steel composite material is as follows:

[0064] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0065] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. The ball mill speed is 300 rpm and the ball milling time is 2 hours.

[0066] Step 3: The mixture of tungsten boride powder and stainless steel powder from Step 2 is subjected to SPS sintering to obtain tungsten boride stainless steel composite material. The sintering conditions are: pressure 60 MPa, temperature 1100 degrees Celsius, and holding time 10 minutes.

[0067] Example 6

[0068] This embodiment provides a tungsten boron stainless steel composite material, which is composed of tungsten boride particles dispersed in a stainless steel matrix, wherein the tungsten boride content is 24% and the balance is 304 stainless steel matrix, and the particle size of the tungsten boride particles is 5 micrometers.

[0069] The preparation method of this tungsten-boron stainless steel composite material is as follows:

[0070] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0071] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. The high-energy ball mill speed is 400 rpm and the ball milling time is 4 hours.

[0072] Step 3: Place the mixture of tungsten boride powder and stainless steel powder from Step 2 into a stainless steel sheath, perform vacuum sealing and welding, and then place it in an exothermic isostatic pressing furnace for hot isostatic pressing sintering at a temperature of 1000 degrees Celsius, a holding time of 1 hour, and a pressure of 150 MPa to obtain tungsten boride stainless steel composite material.

[0073] Example 7

[0074] This embodiment provides a tungsten boron stainless steel composite material, which is composed of tungsten boride particles dispersed in a stainless steel matrix, wherein the tungsten boride content is 10%, the balance is 304 stainless steel matrix, and the particle size of the tungsten boride particles is 5 micrometers.

[0075] The preparation method of this tungsten-boron stainless steel composite material is as follows:

[0076] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0077] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. The high-energy ball mill speed is 400 rpm and the ball milling time is 4 hours.

[0078] Step 3: Place the mixture of tungsten boride powder and stainless steel powder from Step 2 into a stainless steel sheath, perform vacuum sealing and welding, and then place it in an exothermic isostatic pressing furnace for hot isostatic pressing sintering at a temperature of 1000 degrees Celsius, a holding time of 1 hour, and a pressure of 150 MPa to obtain tungsten boride stainless steel composite material.

[0079] Example 8

[0080] This embodiment provides a tungsten boron stainless steel composite material, which is composed of tungsten boride particles dispersed in a stainless steel matrix, wherein the tungsten boride content is 40% and the balance is 304 stainless steel matrix, and the average particle size of the tungsten boride particles is 10 micrometers.

[0081] The preparation method of this tungsten-boron stainless steel composite material is as follows:

[0082] Step 1: Weigh out a certain amount of tungsten boride and stainless steel powder according to the specified proportions;

[0083] Step 2: Put the weighed tungsten boride powder and stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. The ball mill speed is 300 rpm and the ball milling time is 2 hours.

[0084] Step 3: The mixture of tungsten boride powder and stainless steel powder from Step 2 is subjected to hot pressing and sintering to obtain tungsten boride stainless steel composite material. The sintering conditions are: pressure 30 MPa, temperature 1100 degrees Celsius, and holding time 2 hours.

[0085] The density, Cs137 gamma-ray attenuation coefficient, thermal neutron shielding efficiency (2mm), and fast neutron shielding efficiency of the tungsten-boron stainless steel composite materials prepared by the methods in Examples 1-8 were tested. The test results are shown in the table below, and are also compared with stainless steel and traditional boron stainless steel.

[0086]

[0087]

[0088] The test data in the table above show that the thermal neutron shielding performance and fast neutron shielding performance of the tungsten boride-stainless steel composite material are slightly better than those of traditional boron stainless steel, but its gamma shielding performance has a significant advantage over that of traditional boron stainless steel.

[0089] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tungsten boron stainless steel composite material, characterized in that, It includes tungsten diboride, wherein the tungsten diboride particles are dispersed in a stainless steel matrix; wherein the tungsten diboride content is 24%, the balance is 304 stainless steel matrix, the equivalent boron content is 3%, and the particle size of the tungsten diboride particles is 5 micrometers.

2. The tungsten boron stainless steel composite material according to claim 1, characterized in that, The density of the tungsten boron stainless steel composite material is 8.52 g / cm³. 3 .

3. A method for preparing the tungsten-boron stainless steel composite material according to any one of claims 1 to 2, characterized in that, Includes the following steps: Step 1: Weigh out tungsten diboride and 304 stainless steel powder separately according to the proportions; Step 2: Put the weighed tungsten diboride powder and 304 stainless steel powder from Step 1 into a high-energy ball mill and mix them using the high-energy ball mill. Step 3: The mixture of tungsten diboride powder and 304 stainless steel powder obtained in Step 2 is sintered to obtain tungsten diboride stainless steel composite material.

4. The method for preparing a tungsten-boron stainless steel composite material according to claim 3, characterized in that, The sintering method in step 3 can be any one of SPS sintering, hot pressing sintering, or hot isostatic pressing sintering.

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