A method for preparing iron-based metal hollow spheres

Abstract

The application discloses a preparation method of iron-based metal hollow spheres, and belongs to the technical field of porous metal materials. The method comprises the following steps: coating stainless steel powder on the surface of anhydrous calcium chloride spherical particles by mechanical mixing with anhydrous ethanol as a binder to obtain composite particles, and then sequentially drying, sintering and ultrasonic cleaning to obtain the iron-based metal hollow spheres; the sintering comprises the following steps: first, drying the composite particles and then keeping the temperature at 750 DEG C for 60-120 min; then keeping the temperature at 800 DEG C for 30-120 min; finally, increasing the temperature to 1100 DEG C-1200 DEG C and keeping the temperature for 120-180 min. The preparation method has the advantages of controllable process, high product yield, low cost, mass production and the like. In addition, the pore size, wall thickness and particle size of the iron-based metal hollow spheres prepared by the method can be flexibly controlled, and the metal hollow spheres have high surface density, good sphericity and high strength.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of porous metal materials, and particularly relates to a preparation method of iron-based metal hollow spheres. BACKGROUND

[0002] Due to uneven distribution of pores and macroscopic hole defects of traditional foam metals and light components, the performance repeatability and qualified rate of samples are low. Hollow sphere composite foam metal material is a new type of multifunctional light composite material, and the advantages of flexible controllable pore distribution, excellent and stable mechanical properties have become a research hotspot of existing porous metals.

[0003] Metal hollow spheres play an important role in the preparation of hollow sphere composite foam metal, and hollow sphere particles with uniform hole wall thickness and controllable particle size are the key to excellent performance of composite foam metal material. The hollow sphere particles with uniform / gradient metal and pores form a composite foam metal material through sintering / casting means, which has flexible controllable pores, few defects, high specific strength / stiffness, impact resistance, heat insulation and other properties, and has broad application prospects in the fields of automobile industry, aerospace, military industry.

[0004] At present, the preparation methods of metal hollow spheres mainly include melt atomization method, additive manufacturing method and mechanical stamping and welding method. The hollow spheres prepared by the melt atomization method have small size, the process is difficult to control, and the yield is low; the additive manufacturing method can obtain metal hollow spheres with flexible and controllable pores and wall thickness, but the production cycle is long, the cost is high, and mass production is not suitable; the mechanical stamping and welding method mainly prepares large-size metal hollow spheres, and the process is complex. The above methods have limitations in size control, yield and scale production of hollow spheres, and cannot meet the industrial application requirements of composite foam metal, resulting in less research and application of hollow sphere composite foam metal. SUMMARY

[0005] In view of the shortcomings of the prior art, the application provides a preparation method of iron-based metal hollow spheres

[0006] To achieve the above purpose, the technical scheme adopted by the application is as follows:

[0007] A preparation method of iron-based metal hollow spheres, using anhydrous ethanol as a binder, composite particles are obtained by coating stainless steel powder on the surface of anhydrous calcium chloride through mechanical mixing, and then dried, sintered and ultrasonic treated in sequence to obtain iron-based metal hollow spheres; the sintering includes the following steps: first, heat preservation at 750 DEG C for 60-120 min to make the metal particles pre-bonded and ensure that the hollow spheres have a certain strength; then heat preservation at 800 DEG C for 30-120 min to make the pore-forming template flow out as much as possible; finally, heat preservation at 1100 DEG C-1200 DEG C for 120-180 min.

[0008] Anhydrous calcium chloride is easily leached out of the metal shell after high-temperature melting, with minimal impact on the matrix. The foamed steel prepared with it exhibits excellent mechanical properties. In addition, anhydrous calcium chloride is highly soluble in water but insoluble in ethanol. Therefore, anhydrous ethanol can be used as a binder for coating anhydrous calcium chloride with metal powder, providing favorable conditions for the preparation of low-cost, high-performance iron-based hollow metal spheres.

[0009] As a preferred embodiment of the present invention, stainless steel powder and anhydrous calcium chloride are mixed, and then anhydrous ethanol is added. The composite particles of stainless steel powder coated with anhydrous calcium chloride are obtained by mechanical mixing.

[0010] In a preferred embodiment of the present invention, the anhydrous calcium chloride is in the form of spherical particles with a melting point of 782°C.

[0011] In a preferred embodiment of the present invention, the mass of the ethanol is 3% to 5% of the mass of the stainless steel powder.

[0012] As a preferred embodiment of the present invention, the composite particles of stainless steel powder coated with anhydrous calcium chloride are dried at 40°C to 80°C for 60 to 120 minutes to remove ethanol.

[0013] In a preferred embodiment of the present invention, the sintering heating rate is less than 5°C / min, and the sintering is carried out under argon gas.

[0014] As a preferred embodiment of the present invention, the stainless steel powder is a gas-atomized 200, 300, or 400 series stainless steel powder.

[0015] In a preferred embodiment of the present invention, the volume fraction ratio of stainless steel powder to anhydrous calcium chloride is 5-3:5-7. The wall thickness and size of the hollow spheres are controlled by adjusting the ratio of stainless steel powder to anhydrous calcium chloride and the size of anhydrous calcium chloride.

[0016] In a preferred embodiment of the present invention, the crucible used for sintering comprises a first crucible, a second crucible, and a third crucible stacked sequentially from bottom to top. This multi-layered crucible arrangement improves yield. A perforated plate is placed in each of the three crucible layers, and the dried composite particles are evenly spread on each perforated plate, preventing adhesion between particles during high-temperature sintering and secondary contamination of the hollow spheres by anhydrous calcium chloride flow. The three crucible layers are identical in size, and the bottom inner diameter of the upper crucible matches the top outer diameter of the lower crucible, ensuring the sealing of each crucible cavity and reducing particle oxidation. The three crucible layers are identical in size and stacked, with each layer having an independent cavity.

[0017] In a preferred embodiment of the present invention, the outer diameter of the perforated plate is fitted to the inner diameter of the crucible.

[0018] As a preferred embodiment of the present invention, the crucible used for sintering further includes a crucible lid, which is stacked on top of the third crucible, and the size of the crucible lid matches that of the third crucible.

[0019] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention uses stainless steel powder, anhydrous calcium chloride, and anhydrous ethanol as raw materials, and prepares iron-based metal hollow spherical particles through processes such as mixing, drying, sintering, and cleaning. The preparation method has advantages such as controllable process, high yield, low cost, and mass production capability, providing prerequisites for the preparation of hollow spherical composite foam metals, and also providing technical support for the development and industrial application of composite foam metals. Furthermore, the pore size, wall thickness, and particle size of the iron-based metal hollow spheres prepared by this invention can be flexibly controlled, and the metal hollow spheres have high surface density, good sphericity, and high strength. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the preparation process of iron-based hollow metal spheres.

[0021] Figure 2 This is a diagram of the perforated plate structure.

[0022] Figure 3 This is a front view of the crucible.

[0023] Figure 4 This is a reverse structural diagram of the crucible.

[0024] Figure 5 This is a diagram of a combination of a single-layer crucible and an orifice plate.

[0025] Figure 6 This is a structural diagram of a crucible stack, where a is the first layer of crucibles, b is the second layer of crucibles, c is the third layer of crucibles, and d is the crucible lid. Detailed Implementation

[0026] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0027] Example 1

[0028] A method for preparing an iron-based hollow metal sphere includes the following steps:

[0029] (1) Atomized 304 stainless steel powder with an average particle size of 400 mesh and anhydrous calcium chloride spherical particles with an average particle size of 6-8 mesh are mixed in a volume ratio of 2:3 and placed in a V-type mixer for uniform mixing. During the mixing process, 4% of the total amount of metal powder is added with anhydrous ethanol. The mixing time is 60 min to obtain composite particles in which steel powder is uniformly coated with anhydrous calcium chloride particles. The melting point of the anhydrous calcium chloride spherical particles is 782℃.

[0030] (2) The composite particles were placed in a drying oven to remove anhydrous ethanol. The drying temperature was 60℃ and the drying time was 120min.

[0031] (3) Spread the dried composite particles evenly in a special crucible (e.g., Figure 5 As shown, sintering is carried out in an argon atmosphere: During the sintering process, the temperature is first held at 750℃ for 120 minutes to allow the metal particles to pre-bond and ensure that the hollow spheres have a certain strength. The temperature is then held at 800℃ for 60 minutes to allow anhydrous calcium chloride to flow out of the particle shell as much as possible. Finally, the temperature is raised to 1100℃ and sintered for 120 minutes. The heating rate during the sintering process is 4℃ / min.

[0032] (4) The sintered spherical particles are placed in an ultrasonic cleaner filled with deionized water for ultrasonic cleaning and multiple water bath heating cleaning to remove residual calcium chloride in the hollow spheres; after further drying, 304 stainless steel hollow sphere particles are obtained.

[0033] The 304 stainless steel hollow spheres prepared in Example 1 had a diameter of 2.6 mm to 3.6 mm, a wall thickness of 0.22 mm to 0.28 mm, and a density of 1.3 g / cm³. 3 ~2.0g / cm 3 The hollow spheres have uniform dimensions and a yield rate of 95%. The foamed steel blocks made from these hollow spheres have high compressive strength, reaching 65MPa to 70MPa.

[0034] Example 2

[0035] A method for preparing an iron-based hollow metal sphere includes the following steps:

[0036] (1) Atomized 430 stainless steel powder with an average particle size of 400 mesh and anhydrous calcium chloride spherical particles with a particle size of 6-8 mesh are mixed in a volume ratio of 3:7. The mixture is placed in a V-type mixer and mixed evenly. During the mixing process, 4% of the total amount of metal powder is added with anhydrous ethanol. The mixing time is 60 min to obtain composite particles in which steel powder is uniformly coated with anhydrous calcium chloride particles. The melting point of the anhydrous calcium chloride spherical particles is 782℃.

[0037] (2) The composite particles were placed in a drying oven to remove anhydrous ethanol. The drying temperature was 40℃ and the drying time was 60min.

[0038] (3) Spread the dried composite particles evenly in a specially made crucible (e.g., Figure 5(As shown) and sealed with iron powder, and sintered in an argon atmosphere: During the sintering process, first, the temperature was held at 750℃ for 60 minutes to allow the metal particles to pre-bond and ensure that the hollow sphere has a certain strength. Then, the temperature was held at 800℃ for 30 minutes to allow anhydrous calcium chloride to flow out of the particle shell as much as possible. Finally, the temperature was raised to 1200℃ and sintered for 120 minutes. The heating rate during the sintering process was 4℃ / min.

[0039] (4) The sintered spherical particles are placed in an ultrasonic cleaner filled with deionized water for ultrasonic cleaning and multiple water bath heating cleaning to remove residual calcium chloride in the hollow spheres; after further drying, 430 stainless steel hollow sphere particles are obtained.

[0040] The 430 stainless steel hollow spheres prepared in Example 2 had a diameter of 2.4 mm to 3.5 mm, a wall thickness of 0.16 mm to 0.23 mm, and a density of 1.0 g / cm³. 3 ~1.1g / cm 3 The hollow spheres have uniform dimensions and a yield rate of 93%. The foamed steel blocks made from these hollow spheres have high compressive strength, reaching 60MPa to 70MPa.

[0041] Example 3

[0042] A method for preparing an iron-based hollow metal sphere includes the following steps:

[0043] (1) Atomized 304 stainless steel powder with an average particle size of 400 mesh and anhydrous calcium chloride spherical particles with an average particle size of 6-8 mesh are mixed in a volume ratio of 5:5 and placed in a V-type mixer for uniform mixing. During the mixing process, 5% of the total amount of metal powder is added with anhydrous ethanol. The mixing time is 60 min to obtain composite particles in which steel powder is uniformly coated with anhydrous calcium chloride particles. The melting point of the anhydrous calcium chloride spherical particles is 782℃.

[0044] (2) The composite particles were placed in a drying oven to remove anhydrous ethanol. The drying temperature was 80℃ and the drying time was 120min.

[0045] (3) Spread the dried composite particles evenly in a special crucible (e.g., Figure 5 As shown, sintering is carried out in an argon atmosphere: During the sintering process, the temperature is first held at 750℃ for 120 minutes to allow the metal particles to pre-bond and ensure that the hollow spheres have a certain strength. The temperature is then held at 800℃ for 120 minutes to allow anhydrous calcium chloride to flow out of the particle shell as much as possible. Finally, the temperature is raised to 1200℃ and sintered for 180 minutes. The heating rate during the sintering process is 4℃ / min.

[0046] (4) The sintered spherical particles are placed in an ultrasonic cleaner filled with deionized water for ultrasonic cleaning and multiple water bath heating cleaning to remove residual calcium chloride in the hollow spheres; after further drying, 304 stainless steel hollow sphere particles are obtained.

[0047] The 304 stainless steel hollow spheres prepared in Example 3 had a diameter of 2.7 mm to 3.8 mm, a wall thickness of 0.30 mm to 0.37 mm, and a density of 2.3 g / cm³. 3 ~3.1g / cm 3 The hollow spheres have uniform dimensions and a yield rate of 90%. The foamed steel blocks made from these hollow spheres have high compressive strength, reaching 77MPa to 85MPa.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for producing iron-based metal hollow spheres, characterized by, The stainless steel powder is coated on the surface of anhydrous calcium chloride by mechanical mixing with anhydrous ethanol as a binder to obtain composite particles, and then the iron-based metal hollow spheres are obtained by drying, sintering and ultrasonic treatment in sequence; the sintering comprises the following steps: The dried composite particles are first kept at 750 DEG C for 60-120 min, then kept at 800 DEG C for 30-120 min, and finally heated to 1100 DEG C-1200 DEG C for 120-180 min; The sintering uses a crucible which comprises a first layer of crucible, a second layer of crucible and a third layer of crucible which are stacked from bottom to top in sequence; a hole plate is placed in each layer of crucible, and the dried composite particles are uniformly laid on each layer of hole plate; the three layers of crucible are of the same size, and each layer of crucible has an independent cavity.

2. The method of claim 1, wherein the iron-based metal hollow sphere is prepared by the steps of: The stainless steel powder and anhydrous calcium chloride are mixed, and then anhydrous ethanol is added to obtain composite particles of stainless steel powder coated with anhydrous calcium chloride. ​ 3. The method of claim 1, wherein the iron-based metal hollow sphere is prepared by the steps of: The anhydrous calcium chloride is spherical particles with a melting point of 782 DEG C. ​ 4. The method of claim 1, wherein the iron-based metal hollow sphere is prepared by the steps of: The mass of the anhydrous ethanol is 3-5% of the mass of the stainless steel powder. ​ 5. The method of claim 1, wherein the iron-based metal hollow sphere is prepared by the steps of: The composite particles are dried at 40 DEG C-80 DEG C for 60-120 min. ​ 6. The method of claim 1, wherein the iron-based metal hollow sphere is prepared by the steps of: The sintering has a heating rate of less than 5 DEG C / min, and is carried out under argon. ​ 7. The method of claim 1, wherein the iron-based metal hollow sphere is prepared by the steps of: The stainless steel powder is gas-atomized 200, 300 or 400 series stainless steel powder. ​ 8. The method of claim 1, wherein the iron-based metal hollow sphere is prepared by the steps of: The volume fraction ratio of the stainless steel powder to the anhydrous calcium chloride is 5-3:5-7. ​ 9. The method for preparing iron-based hollow metal spheres as described in claim 1, characterized in that, The sintering uses a crucible which further comprises a crucible cover stacked above the third layer of crucible, and the crucible cover is matched with the third layer of crucible in size to realize sealing of the crucible.

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