阅读说明：本技术 一种高密度含硼复合材料制备方法 (Preparation method of high-density boron-containing composite material ) 是由 王健 马书旺 吕政� 杨志民 杨剑 梁秋实 张国松 毛昌辉 于 2019-11-07 设计创作，主要内容包括：本发明涉及一种高密度含硼复合材料制备方法,属于屏蔽材料技术领域。该复合材料的组成为：钨的质量分数为30％～85％,硼化物质量分数为0.8～10％,其余为铁或钢基体。钨粉经酒精湿磨分散处理并干燥,将钨粉和硼化物与一定比例金属粉末混合分散；经过冷等静压、真空除气、热等静压烧结以及机加工等工序,即可制备得到高密度含硼复合屏蔽材料。本发明的工艺,避免了铸造过程中硼元素与铁元素生成聚集在晶界处连续分布的网状硼化物的过程,硼化物仍然呈现均匀颗粒状分布,改善了材料的力学性能。添加钨颗粒,进一步提高复合材料密度和γ射线屏蔽性能,是一种兼具优异中子、γ射线屏蔽性能和力学性能的新型结构功能一体化复合屏蔽材料。(The invention relates to a preparation method of a high-density boron-containing composite material, belonging to the technical field of shielding materials. The composite material comprises the following components: the mass fraction of tungsten is 30-85%, the mass fraction of boride is 0.8-10%, and the balance is iron or steel matrix. Wet grinding and dispersing tungsten powder by alcohol, drying, and mixing and dispersing the tungsten powder, boride and metal powder according to a certain proportion; the high-density boron-containing composite shielding material can be prepared through the procedures of cold isostatic pressing, vacuum degassing, hot isostatic pressing sintering, machining and the like. The process of the invention avoids the process that boron and iron elements generate the net boride which is gathered at the grain boundary and continuously distributed in the casting process, the boride is still uniformly distributed in a granular shape, and the mechanical property of the material is improved. The tungsten particles are added, so that the density and the gamma ray shielding performance of the composite material are further improved, and the composite material is a novel structural and functional integrated composite shielding material with excellent neutron and gamma ray shielding performance and mechanical performance.)

1. A high-density boron-containing composite shielding material is characterized in that: the composite material comprises the following components: the mass fraction of tungsten is 30-85%, the mass fraction of boride is 0.8-10%, and the balance is iron or steel matrix.

2. The high density boron-containing composite shielding material of claim 1, wherein: the boride is B₄C、ZrB₂And HfB₂One or more of them.

3. The high density boron-containing composite shielding material of claim 1, wherein: the iron or steel substrate is Fe, FeNi, 304L or 316L stainless steel substrate.

4. A preparation method of a high-density boron-containing composite shielding material comprises the following steps:

(1) tungsten powder pretreatment: placing tungsten powder in a mixer, mixing with ethanol as a mixing medium, and then carrying out vacuum drying to obtain pretreated tungsten powder;

(2) preparing materials: taking tungsten powder, boride powder and iron or steel powder obtained by pretreatment as raw materials, and weighing and proportioning 30-85% by mass of the tungsten powder, 0.8-4.0% by mass of the boride powder and the balance of iron or steel matrix powder;

(3) powder mixing: uniformly mixing the raw material powder by adopting a mixer under the protection of argon to obtain composite powder;

(4) cold isostatic pressing: carrying out cold isostatic pressing on the composite powder, and isolating a hydraulic medium (wear-resistant hydraulic oil) from the mixed powder by using a rubber sheath;

(5) vacuum degassing: placing the cold isostatic pressing billet in a prefabricated stainless steel sheath, preserving heat at a certain temperature, and sealing after the billet sheath reaches a certain vacuum degree;

(6) hot isostatic pressing: and carrying out hot isostatic pressing sintering, then cooling along with the furnace, and removing the skin by machining to obtain the high-density boron-containing composite shielding material.

5. The method of preparing a high density boron-containing composite shielding material of claim 4, wherein: the boride is B₄C、ZrB₂And HfB₂One or more of the above; the iron or steel matrix powder is Fe, FeNi, 304L stainless steel or 316L stainless steel powder.

6. The method of preparing a high density boron-containing composite shielding material of claim 4, wherein: the purity of the tungsten powder is more than 99.9%, and the particle size is 4-12 mu m; in the tungsten powder pretreatment, a double-cone mixer is adopted, the weight ratio of grinding balls to powder is 1: 0.5-1: 2, the mixing time is 8-12 hours, and the vacuum drying time is 8-12 hours; and (3) drying the boride powder and the matrix powder at 120 ℃ for 8-10 hours in vacuum.

7. The method of preparing a high density boron-containing composite shielding material of claim 4, wherein: in the powder mixing process, the adopted mixer is a double-cone mixer, the weight ratio of the grinding balls to the powder is 1: 0.5-1: 2, and the mixing time is 10-24 hours.

8. The method of preparing a high density boron-containing composite shielding material of claim 4, wherein: the cold isostatic pressure is 50 MPa-200 MPa, and the pressure maintaining time is 10 min-40 min.

9. The method of preparing a high density boron-containing composite shielding material of claim 4, wherein: the cold isostatic pressing billet is arranged in a stainless steel sheath, and the vacuum degree is lower than 1 multiplied by 10 at the temperature of 500-700 DEG C^-2Sealing under the condition of Pa; the degassing time is not less than 10 hours.

10. The method of preparing a high density boron-containing composite shielding material of claim 4, wherein: the hot isostatic pressing sintering temperature is 800-1300 ℃, the heat preservation time is 2-4 hours under the pressure of 100-200 MPa, and the heating rate is not higher than 10 ℃/min.

Technical Field

The invention relates to a preparation method of a high-density boron-containing composite material, in particular to a nuclear radiation protection boron-containing high-density composite shielding material and a preparation method thereof, and particularly relates to a neutron and gamma ray radiation protection material and a powder metallurgy preparation method thereof, belonging to the technical field of shielding materials.

Background

With the increasing severity of the world energy crisis and the increasing prominence of environmental issues, the development and application of nuclear energy technology become the hot spot and core of new energy development. The high boron steel and the high boron stainless steel have good neutron absorption performance, gamma ray shielding performance and structural performance, and are widely concerned, so that the high boron steel and the high boron stainless steel are applied to nuclear radiation protection shielding materials, spent fuel storage materials, reactor control materials and the like.

The neutron shielding performance of high-boron steel and high-boron stainless steel mainly depends on the content of boron element. At present, the boron content of high-boron steel and high-boron stainless steel is 0.1-3.0 wt%, and the apparent density of boron element is about 0.008-0.230 g/cm³And the solid solubility of boron element in Fe is very low, and along with the increase of boron content, the boron element is precipitated at the grain boundary in the form of boride, so that the toughness of boron steel is sharply reduced, and the phenomenon of boron brittleness is formed.

Chinese patent (CN 101284306B) introduces a jet deposition preparation method, the prepared boron steel has uniform and fine structure, and borides are dispersed and distributed in high boron steel, but the method has the problems of longer process flow, high manufacturing cost, low density and mechanical property and the like through atomization powder spraying, sintering forming and other processes. The Chinese patent (CN 106435401A) and the Chinese patent (CN 106378459A) adopt atomization spray to prepare powder, and respectively adopt preparation processes of powder rolling-sintering and hot isostatic pressing-rolling forming, so that the segregation of elements is reduced, and the comprehensive mechanical property is good. The Chinese patent (CN 102051531A) adopts chemical component adjustment and adopts a mode of smelting, rapid cooling and multiple forging and hot rolling to prepare the high-boron austenitic stainless steel, thereby realizing the refinement of as-cast microstructure and improving the hot processing performance of steel.

The scheme can realize the adjustment of the microstructure and the mechanical property of the high boron steel, but is limited by the characteristics of a steel or stainless steel matrix, has very limited shielding property aiming at gamma rays and aims at⁶⁰The linear attenuation coefficient of Co gamma ray is about 0.38-0.41 cm^-1To aim at¹³⁷The linear attenuation coefficient of the Cs gamma ray is about 0.52-0.57 cm^-1Further improvement in the gamma ray shielding performance is difficult to achieve. The development requirements of new generation small reactors, movable reactors, ADS reactors and other novel reactors on miniaturization and integration of shielding materials are difficult to meet.

Disclosure of Invention

The invention aims to provide a novel high-density boron-containing composite material aiming at the defects of low boron element content and limited gamma ray shielding performance of the existing boron steel and high-boron steel materials, and the material has the advantages of high density, excellent gamma ray shielding performance, high boron content and good mechanical property.

The invention is realized by the following technical scheme:

a high density boron-containing composite shielding material, the composition of the composite material: the mass fraction of tungsten is 30-85%, the mass fraction of boride is 0.8-10%, and the balance is iron or steel matrix.

Further, the mass fraction of tungsten is 40-75%; furthermore, the mass fraction of tungsten is 50-70%.

Further, the mass fraction of boride is 0.8-5%.

Preferably, the boride is B₄C、TiB₂、ZrB₂And HfB₂One or more of the above; the iron or steel substrate is Fe, FeNi, 304L or 316L stainless steel substrate.

A preparation method of a high-density boron-containing composite shielding material comprises the following steps:

(1) pretreatment: placing tungsten powder in a mixer, mixing with ethanol as a mixing medium, and then carrying out vacuum drying to obtain pretreated tungsten powder; respectively vacuum drying boride powder and iron or steel matrix powder;

(2) preparing materials: taking tungsten powder, boride powder and iron or steel matrix powder obtained by pretreatment as raw materials, and weighing and proportioning 30-85% by mass of the tungsten powder, 0.8-10.0% by mass of the boride powder and the balance of the iron or steel matrix powder;

(3) powder mixing: uniformly mixing the raw material powder by adopting a mixer under the protection of argon to obtain composite powder;

(4) cold isostatic pressing: carrying out cold isostatic pressing on the composite powder, and isolating a hydraulic medium (wear-resistant hydraulic oil) from the mixed powder by using a rubber sheath;

(5) vacuum degassing: placing the cold isostatic pressing billet in a prefabricated stainless steel sheath, preserving heat at a certain temperature, and sealing after the billet sheath reaches a certain vacuum degree;

(6) hot isostatic pressing: and carrying out hot isostatic pressing sintering, then cooling along with the furnace, and removing the skin by machining to obtain the high-density boron-containing composite shielding material.

In the step (1), the purity of the tungsten powder is more than 99.9%, and the particle size is 4-12 μm; in the tungsten powder pretreatment, a double-cone mixer is adopted as a mixer, the weight ratio of grinding balls to powder is 1: 0.5-1: 2, the mixing time is 8-12 hours, and the vacuum drying time is 8-12 hours. And (3) drying the boride powder and the matrix powder at the temperature of 120 ℃ for 8-10 hours in vacuum.

In the step (2), the boride is B₄C、TiB₂、ZrB₂And HfB₂One or more of the above; the iron or steel matrix powder is Fe, FeNi, 304L stainless steel or 316L stainless steel powder.

In the step (3), in the powder mixing process, the adopted mixer is a double-cone mixer, the weight ratio of the grinding balls to the powder is 1: 0.5-1: 2, and the mixing time is 10-24 hours.

In the step (4), the cold isostatic pressure is 50 MPa-200 MPa, and the pressure maintaining time is 10 min-40 min.

In the step (5), the cold isostatic pressing billet is arranged in a pre-manufactured stainless steel sheath, and the vacuum degree is lower than 1 multiplied by 10 at the temperature of 500-700 DEG C^-2Sealing under the condition of Pa; the degassing time is not less than 10 hours.

In the step (6), the hot isostatic pressing sintering temperature is 800-1300 ℃, the heat preservation time is 2-4 hours under the pressure of 100-200 MPa, the heating rate is not higher than 10 ℃/min, the composite material is formed by furnace cooling, and the surface iron or stainless steel sheet is turned off by a lathe to obtain the high-density boron-containing composite shielding material.

According to the invention, through the processes of powder mixing, cold isostatic pressing, vacuum degassing and hot isostatic pressing, the composite molding of the high volume fraction functional phase and the matrix is realized, the comprehensive mechanical properties such as strength and toughness of the high volume fraction iron-based composite material are obviously improved, and the application range of the high volume fraction iron-based composite material is expanded. The molding performance of the composite material is improved by optimizing the proportion of the particle sizes of the matrix and the reinforcing phase powder; the powder is mixed for multiple times, so that the dispersibility of the reinforcing phase in the matrix is improved; the tungsten powder is subjected to dispersion pretreatment, so that the tungsten powder is changed into monodisperse particles from an agglomerated chain, and the sintering activity and the dispersion uniformity of the tungsten powder in the composite material are improved. The density of the high-density boron-containing composite shielding material prepared by the process is more than 99%, and the density is 10-15 g/cm according to different components³Room temperature tensile strength of 350-960 MPa, yield strength of 350-840 MPa, and room temperature impact toughness of 4-19 j.cm^-2The apparent density of boron element is 0.08-0.40 g/cm³The neutron and gamma ray shielding capability is obviously improved compared with boron steel, and the composite material is excellent in comprehensive performance and has great application potential.

Drawings

FIG. 1 shows an embodiment of the present invention1 preparation of B₄And (3) a section scanning electron microscope microscopic microstructure photo of the C/W/FeNi high-density boron-containing composite shielding material.

FIG. 2 is B prepared according to example 2 of the present invention₄And (3) a section scanning electron microscope microscopic microstructure photo of the C/W/Fe high-density boron-containing composite shielding material.

Detailed Description

The preparation process of the high-density boron-containing composite material comprises the following steps: wet grinding, dispersing and drying tungsten powder by alcohol, drying boride and metal matrix powder, and mixing and dispersing the tungsten powder, the boride and a certain proportion of metal powder; the high-density boron-containing composite shielding material can be prepared through the procedures of cold isostatic pressing, vacuum degassing, hot isostatic pressing sintering, machining and the like.

The preparation process of the high-density boron-containing composite shielding material comprises the following steps:

(1) placing tungsten powder in a double-cone mixer, mixing the tungsten powder with ethanol as a mixing medium for 10 hours at a weight ratio of grinding balls to powder of 1:1, and vacuum-drying for 10 hours to obtain pretreated tungsten powder; the purity of tungsten powder particles is more than 99%, and the particle size is 4-12 mu m;

(2) mixing the pretreated tungsten powder obtained in the step (1) by mass percent of 30-85%, boride by mass percent of 0.8-4.0%, and the balance of pure Fe, FeNi, 304L or 316L stainless steel powder; the boride being B₄C、ZrB₂、HfB₂One or more of the above; carrying out vacuum drying on boride powder and matrix powder for 8-10 hours at 120 ℃;

(3) uniformly mixing the powder by using a double-cone mixer under the protection of argon, wherein the weight ratio of the grinding balls to the powder is 1:1, and the mixing time is 10-24 hours, so as to obtain composite powder;

(4) carrying out cold isostatic pressing on the composite powder obtained in the step (3), and isolating a hydraulic medium (wear-resistant hydraulic oil) from the mixture by using a rubber sheath, wherein the cold isostatic pressing pressure is 50-200 MPa, and the pressure maintaining time is 10-40 min;

(5) putting the cold isostatic pressing billet obtained in the step (4) into a pre-manufactured stainless steel sheath, and keeping the vacuum degree below 1 multiplied by 10 at 500-700 DEG C^-2Pa conditionSealing;

(6) and (3) preserving the heat for 3 hours under the conditions that the temperature is 800-1300 ℃ and the pressure is 100-200 MPa by using a hot isostatic pressing sintering method, cooling along with a furnace to realize the molding of the composite material, wherein the heating rate is not higher than 10 ℃/min, and turning off the surface iron sheet by using a lathe to obtain the high-density boron-containing composite shielding material.

Example 1:

in the embodiment, the tungsten particle reinforced iron-based composite material comprises 55 mass percent of tungsten and 0.85 mass percent of B₄C and 44.15% FeNi70 powder, the preparation method of the high-density boron-containing composite material is carried out according to the following steps:

weighing 5.5kg of tungsten powder, mixing the tungsten powder with a stainless steel grinding ball and ethanol as a mixing medium for 10 hours by using a double-cone mixer, and drying the tungsten powder for 10 hours in vacuum to obtain pre-dispersion treated tungsten powder, wherein the mass ratio of the stainless steel grinding ball to the tungsten powder is 1: 1; carrying out vacuum drying on boride powder and matrix powder for 8 hours at 120 ℃ in advance; 5500g of tungsten powder subjected to pre-dispersion treatment, 85g of boron carbide powder and 4415g of carbonyl Fe3Ni7 powder are mixed, a double-cone mixer is used for mixing for 8 hours under the protection of argon gas, and stainless steel balls are added and mixed for 8 hours under the protection of argon gas in a ball-to-material ratio of 1:1 to obtain composite powder. A rubber sheath is adopted to isolate a hydraulic medium (anti-wear hydraulic oil) from the composite powder, and the preforming of the composite powder is realized under the cold isostatic pressing conditions of 100MPa of pressure and 15min of pressure maintaining time. Placing the cold-pressed billet in a pre-made stainless steel sheath at 500 deg.C and vacuum degree lower than 1 × 10^-2And sealing under the condition of Pa, wherein the degassing time is not less than 10 hours. Heating to 800 ℃ at a heating rate of 10 ℃/min, and preserving heat for 3 hours under the hot isostatic pressing condition with the pressure of 140-150 MPa. And cooling to room temperature along with the furnace, and turning off the surface iron sheet by using a lathe to obtain the high-density boron-containing composite shielding material.

Obtained B₄The density of the C/W/FeNi composite material is 99.9 percent, the section microstructure of the composite material is shown in figure 1, the composite material has compact structure and uniform distribution of the reinforcing phase, and the density of the composite material reaches 12.09g/cm³Tensile strength at room temperature of 960MPa, yield strength of 830MPa, and impact toughness of 17.5j/cm²Apparent density of boron element of 0.08g/cm³，⁶⁰The linear attenuation coefficient of Co gamma-ray can reach 0.62cm^-1To aim at¹³⁷Linear attenuation coefficient of Cs gamma ray is about 0.97cm^-1Compared with boron steel, the improvement is more than 50%.

Example 2:

referring to the process conditions and steps of example 1, the high-density boron-containing composite shielding material is prepared by using the following raw materials in percentage by mass: 61.15%, B₄C: 0.85%, carbonyl Fe: 38 percent. The present embodiment is different from embodiment 1 in that: the matrix powder is carbonyl iron powder, and the dosages of the mixed tungsten powder and the carbonyl iron powder are 6115g and 3800g respectively. The hot isostatic pressing temperature was 900 ℃.

Cross-sectional microstructure of the composite Material referring to FIG. 2, prepared B₄The density of the C/W/Fe composite material reaches 11.94g/cm³Tensile strength at room temperature of 500MPa, yield strength of 475MPa and impact toughness of 6.2j/cm²Apparent density of boron element of 0.08g/cm³，⁶⁰The linear attenuation coefficient of Co gamma-ray can reach 0.60cm^-1To aim at¹³⁷Linear attenuation coefficient of Cs gamma ray is about 0.95cm^-1Compared with boron steel, the improvement is more than 50%.

Example 3:

referring to the process conditions and steps of example 1, the high-density boron-containing composite shielding material is prepared by using the following raw materials in percentage by mass: 67%, B₄C: 1.1%, 316L stainless steel: 31.9 percent. The present embodiment is different from embodiment 1 in that: the matrix powder is 316L stainless steel powder, and the dosage of the mixed tungsten powder, the boron carbide powder and the 316L stainless steel powder is 6700g, 110g and 3190g respectively. The hot isostatic pressing temperature was 900 ℃.

Preparation of B₄The density of the C/W/316L composite material reaches 12.30g/cm³Room temperature tensile strength of 420MPa, yield strength of 380MPa, and impact toughness of 5.1j/cm²Apparent density of boron element is 0.10g/cm³。

Example 4:

referring to the process conditions and steps of example 1, the high-density boron-containing composite shielding material is prepared by using the following raw materials in percentage by mass: 65% and zirconium boride: 5.3%, 316L stainless steel: 29.7 percent. The present embodiment is different from embodiment 1 in that: the base powder is 316L stainless steel powder, the boride powder is zirconium boride, and the dosages of the mixed tungsten powder, the zirconium boride powder and the 316L stainless steel powder are 6500g, 530kg and 2970g respectively. The hot isostatic pressing temperature was 900 ℃.

Prepared ZrB₂The density of the/W/316L composite material reaches 12.04g/cm³Room temperature tensile strength of 475MPa, yield strength of 390MPa, impact toughness of 4.8j/cm²Apparent density of boron element of 0.12g/cm³。

The invention has the advantages that the powder metallurgy solid phase sintering process is adopted, the process that boron and iron generate the net boride which is gathered at the grain boundary and continuously distributed in the casting process is avoided, the boride is still uniformly distributed in a granular shape, and the mechanical property of the material is improved. Tungsten particles are added in the process of the composite material, so that the density and the gamma ray shielding performance of the composite material are further improved, and the composite material is a novel structure-function integrated composite shielding material with excellent neutron and gamma ray shielding performance and mechanical performance.