Preparation method of metal hollow sphere

Abstract

The invention discloses a preparation method of a metal hollow sphere, which comprises the following steps of: 1, uniformly mixing two stages of non-spherical metal powder with different powder granularities as raw materials, and pressing to obtain a cubic or cylindrical green body; secondly, non-spherical metal powder with the fine powder granularity is adopted for preparing powder slurry, and the powder slurry is sprayed on the surface of the cubic or cylindrical green body to obtain a sprayed green body; 3, sintering the sprayed green body at high temperature to obtain a sintered green body; and fourthly, the sintered blank is placed in electrostatic suspension equipment to be subjected to high-temperature melting and heat preservation, and the metal hollow ball is obtained after rapid cooling. The porosity of the metal hollow sphere is regulated and controlled by selecting the non-spherical metal powder with the two-level granularity as the raw material, container-free and crucible-free near-net forming is achieved through the electrostatic suspension method, the metal hollow sphere with the hollow interior and the solid exterior and the sphere wall being a compact shell is obtained, the blank of the size of the metal hollow sphere from the micro-nano level to several millimeters is filled, and the metal hollow sphere is suitable for large-scale production. The material is suitable for the fields of energy absorption, damping vibration attenuation, explosion prevention, flame retardance, heat insulation and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of porous metal materials, and in particular relates to a method for preparing a metal hollow sphere. Background Art

[0002] After the metal hollow sphere is used as a unit body to prepare the structural material, it can be used in the fields of sound insulation, heat insulation, energy absorption, explosion protection, etc. At present, the metal hollow spheres that can be directly purchased on the market are mostly large in size (≥3mm), and the material is relatively limited. The hollow spheres are mostly welded into a whole sphere by splicing two hemispheres; the metal hollow spheres prepared by other methods, such as the template method, have porous sphere walls and low sphere strength; the hollow spheres prepared by the additive manufacturing method have a powder outlet hole on the surface of the sphere wall, which needs to be sealed by the process before use; the hollow spheres prepared by the atomization method and the replacement reaction sintering method are mostly micron- or nano-sized hollow spheres with small sizes. The post-processing process has a certain impact on the performance of the metal hollow spheres, and if the sphere wall is porous, it is not easy to use in the fields of energy absorption and vibration and explosion protection.

[0003] Based on the shortcomings of the above methods, it is necessary to provide a method for preparing metal hollow spheres. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a metal hollow sphere in view of the shortcomings of the above-mentioned prior art. The method realizes the regulation of the porosity of the metal hollow sphere by selecting non-spherical metal powders with two-level particle sizes as raw materials, and realizes near-net forming without a container or a crucible by adopting an electrostatic suspension method, thereby obtaining a metal hollow sphere with a solid inner surface and a dense shell as the sphere wall, thereby improving its strength, and solving the problem that the metal hollow sphere prepared by the prior art has low strength due to the porous sphere wall and limited size, which affects its performance.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for preparing a metal hollow sphere, characterized in that the method comprises the following steps:

[0006] Step 1: using two levels of non-spherical metal powders of different powder sizes as raw materials, mixing them evenly and then pressing them with a mold to obtain a cubic or cylindrical green body with a porous structure;

[0007] Step 2: using the non-spherical metal powder with a finer powder particle size in the raw material described in step 1, mixing it evenly with the low-concentration slurry to obtain a powder slurry, and then spraying the powder slurry evenly on the surface of the cubic or cylindrical green body obtained in step 1 to obtain a sprayed green body;

[0008] Step 3: placing the sprayed green body obtained in step 2 in a high temperature furnace for high temperature sintering to obtain a sintered green body;

[0009] Step 4: Place the sintered green body obtained in step 3 in an electrostatic suspension device for high-temperature melting and heat preservation, and obtain a metal hollow sphere after rapid cooling.

[0010] The above-mentioned method for preparing hollow metal spheres is characterized in that the two levels of non-spherical metal powders with different powder particle sizes in step one are non-spherical metal powders with powder particle sizes of 25μm to 44μm and 75μm to 125μm, or non-spherical metal powders with powder particle sizes of 44μm to 90μm and 106μm to 180μm.

[0011] The above-mentioned method for preparing hollow metal spheres is characterized in that the non-spherical metal powder in step 1 is stainless steel powder, titanium alloy powder or tungsten alloy powder.

[0012] The above-mentioned method for preparing a metal hollow sphere is characterized in that the porosity of the cubic or cylindrical green body in step 1 is 10% to 50%.

[0013] The above-mentioned method for preparing a metal hollow sphere is characterized in that the temperature of the high-temperature sintering in step 3 is 0.95T m , T m The melting point of the raw metal powder for the preparation of the spray green body. By controlling the high-temperature sintering temperature of the spray green body, the spray green body can achieve metallurgical bonding, and the raw material powders of different powder particle sizes in the spray green body form a certain strength at the overlapping points, thereby forming a channel for the powder melt to bridge each other in the subsequent electrostatic suspension smelting process in advance, which is beneficial to the formation of a dense spherical shell of the metal hollow sphere prepared later.

[0014] The above-mentioned method for preparing a metal hollow sphere is characterized in that the temperature of the high temperature melting in step 4 is 1.1T m ~1.3T m , T m The melting point of the raw metal powder for the preparation of the spray green body. By using a higher temperature than the melting point of the raw metal powder, it is ensured that the non-spherical metal powders of two levels of different powder sizes are both molten, so that the structure and composition of the large-particle powder after low superheating during the electrostatic suspension smelting process are uniform, and a metal hollow sphere with better performance is obtained.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The present invention mixes and presses non-spherical metal powders of two levels of particle size into a green body with pores, sprays non-metallic powder on the surface for high-temperature sintering, and then adopts an electrostatic suspension method to melt and cool to prepare a metal hollow sphere. The porosity of the metal hollow sphere is regulated by selecting non-spherical metal powders of two levels of particle size, and the electrostatic suspension method is adopted to achieve near-net forming without a container or a crucible, so as to obtain a metal hollow sphere with a hollow interior and a solid exterior and a dense shell as the sphere wall. The metal hollow sphere has high strength, and the sphere wall does not have a porous structure, and is suitable for energy absorption, damping and vibration reduction, explosion-proof flame retardancy, heat insulation and other fields.

[0017] 2. The present invention selects two-level particle size non-spherical metal powder as raw material, which not only realizes the controllability of porosity, but also facilitates compression molding through particle size grading. At the same time, in the subsequent high-temperature sintering molding process, the finer particle size non-spherical metal powder plays the role of low-temperature metallurgical bonding aid, promotes the sintering connection of the metal powder, and improves the integrity of the dense shell on the surface of the metal hollow sphere.

[0018] 3. The two-grade non-spherical metal powder raw material used in the present invention is relatively common and easy to purchase, and the inner cavity of the mold involved in the pressing molding is cylindrical or cubic, which is easy to implement, and the process is mature and the molding rate is high.

[0019] 4. The present invention adopts an electrostatic suspension method to prepare the metal hollow spheres, which not only achieves no crucible pollution, but also has no pollution to the microstructure and macrostructure of the metal hollow spheres, as well as the equipment and the use environment, and is green and environmentally friendly.

[0020] 5. The method of the present invention can realize the preparation of small-sized dense spherical wall metal hollow spheres, filling the size gap of metal hollow spheres from micro-nanoscale to several millimeters.

[0021] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a physical picture of the sintered green body prepared in Example 1 of the present invention.

[0023] Figure 2 This is a physical picture of the metal hollow sphere prepared in Example 1 of the present invention.

[0024] Figure 3 This is a photo of the metal hollow sphere prepared in Example 1 of the present invention after being cut in half.

[0025] Figure 4 This is a physical picture of the metallographic sample made by inlaying the metal hollow spheres prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] Example 1

[0027] This embodiment includes the following steps:

[0028] Step 1: Using non-spherical stainless steel powders with a powder size of 44 μm and 180 μm as raw materials, mixing them evenly in equal mass proportions and then pressing them using a mold to obtain a cubic green body with a porosity of 30%;

[0029] Step 2: using a non-spherical stainless steel powder with a powder particle size of 44 μm, and mixing it with a polyvinyl alcohol slurry with a mass concentration of 3% in a mass ratio of 1:4 to obtain a powder slurry, and then using a spray gun to evenly spray the powder slurry on the surface of the cubic green body obtained in step 1 to obtain a sprayed green body;

[0030] Step 3: Place the sprayed green body obtained in step 2 in a vacuum sintering furnace for high-temperature sintering at a temperature of 1200°C and a holding time of 1h to obtain a sintered green body. Figure 1 As shown;

[0031] Step 4: Place the sintered green body obtained in step 3 in an electrostatic suspension device, adjust the laser temperature to 1500°C for high-temperature melting and keep the temperature for 30 seconds, and then quickly cool to obtain a stainless steel hollow ball with a porosity of 10%. Figure 2 shown.

[0032] Figure 3 This is a photo of the metal hollow sphere prepared in this example after being cut in half. Figure 4 This is a metallographic sample of a hollow metal ball prepared in this embodiment. Figure 3 and Figure 4 It can be seen that the metal hollow sphere has a hollow inner and solid outer structure, and the sphere wall is a dense shell without a porous structure.

[0033] The non-spherical stainless steel powder in step 1 and step 2 of this embodiment can also be replaced by tungsten alloy powder.

[0034] Example 2

[0035] This embodiment includes the following steps:

[0036] Step 1: Using non-spherical TC4 titanium alloy powders with a powder size of 30 μm and 150 μm as raw materials, mixing them evenly in equal mass proportions and then pressing them using a mold to obtain a cylindrical green body with a porosity of 50%;

[0037] Step 2: Using non-spherical TC4 titanium alloy powder with a powder particle size of 30 μm, and mixing it with polyvinyl alcohol slurry with a mass concentration of 3% in a mass ratio of 1:3 to obtain a powder slurry, and then using a spray gun to evenly spray the powder slurry on the surface of the cylinder obtained in step 1 to obtain a sprayed green body;

[0038] Step 3: Place the sprayed green body obtained in step 2 in a vacuum sintering furnace for high-temperature sintering at a temperature of 1600° C. for a holding time of 2 h to obtain a sintered green body;

[0039] Step 4: Place the sintered body obtained in step 3 in an electrostatic suspension device, adjust the laser temperature to 1800° C. for high-temperature melting and keep the temperature for 1 minute, and obtain a TC4 titanium alloy hollow sphere with a porosity of 25% after rapid cooling.

[0040] Example 3

[0041] This embodiment includes the following steps:

[0042] Step 1: Use non-spherical tungsten alloy powders with a powder size of 25 μm and 125 μm as raw materials, mix them evenly in equal mass proportions, and then press them using a mold to obtain a cylindrical green body with a porosity of 10%;

[0043] Step 2: Use non-spherical tungsten alloy powder with a powder particle size of 25 μm, mix it with polyvinyl alcohol slurry with a mass concentration of 3% in a mass ratio of 1:3 to obtain powder slurry, and then use a spray gun to evenly spray the powder slurry on the surface of the cylinder obtained in step 1 to obtain a sprayed green body;

[0044] Step 3: Place the sprayed green body obtained in step 2 in a vacuum sintering furnace for high-temperature sintering at a temperature of 1900° C. for a holding time of 2 h to obtain a sintered green body;

[0045] Step 4: Place the sintered body obtained in step 3 in an electrostatic suspension device, adjust the laser temperature to 2200° C. for high-temperature melting and keep warm for 1 minute, and obtain a tungsten alloy hollow sphere with a porosity of 8% after rapid cooling.

[0046] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a hollow metal sphere, characterized in that: The method comprises the following steps: Step 1: using two levels of non-spherical metal powders of different powder sizes as raw materials, mixing them evenly and then pressing them with a mold to obtain a cubic or cylindrical green body with a porous structure; Step 2: using the non-spherical metal powder with finer powder particle size in the raw material described in step 1, mixing it with the low-concentration slurry to obtain a powder slurry, and then spraying the powder slurry evenly on the surface of the cubic or cylindrical green body obtained in step 1 to obtain a sprayed green body; Step 3: placing the sprayed green body obtained in step 2 in a high temperature furnace for high temperature sintering to obtain a sintered green body; Step 4: Place the sintered green body obtained in step 3 in an electrostatic suspension device for high-temperature melting and heat preservation, and obtain a metal hollow sphere after rapid cooling.

2. The method for preparing a hollow metal sphere according to claim 1, characterized in that: The two levels of non-spherical metal powders with different powder particle sizes in step 1 are non-spherical metal powders with powder particle sizes of 25μm to 44μm and 75μm to 125μm, or non-spherical metal powders with powder particle sizes of 44μm to 90μm and 106μm to 180μm.

3. The method for preparing a hollow metal sphere according to claim 1, characterized in that: The non-spherical metal powder in step 1 is stainless steel powder, titanium alloy powder or tungsten alloy powder.

4. The method for preparing a hollow metal sphere according to claim 1, characterized in that: The porosity of the cubic or cylindrical green body in step 1 is 10% to 50%.

5. The method for preparing a hollow metal sphere according to claim 1, characterized in that: The temperature of high temperature sintering in step 3 is 0.95T m , T m The melting point of the raw metal powder for the preparation of the spray green body.

6. The method for preparing a hollow metal sphere according to claim 1, characterized in that: The temperature of the high temperature melting in step 4 is 1.1T m ~1.3T m , T m The melting point of the raw metal powder for the preparation of the spray green body.

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