Iron-based composite foam material and preparation method thereof

Abstract

The invention relates to an iron-based composite foam material and a preparation method thereof, and belongs to the technical field of metal-based composite materials. The invention provides an iron-based composite foam material which is composed of an iron matrix and a hollow sphere, and the diameter of the hollow sphere is 500 microns to 15 millimeters. The volume fraction of the hollow sphere is 40%-70%. Besides, the invention further provides a pneumatic pressure infiltration method for preparing the iron-based composite foam material, the method overcomes the problem that the existing mechanical pressure infiltration and mechanical stirring method is not suitable for high-melting-point material forming at present, and the method has the advantages of being easy to operate, good in hollow sphere integrity, uniform and adjustable in pore structure, compact in matrix and the like. Good application prospects are realized in the fields of large impact load resistance, explosion prevention, energy absorption, heat insulation and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal matrix composites, in particular to an iron-based composite foam material and a preparation method thereof. BACKGROUND

[0002] Most materials in nature are not completely dense, but contain a large number of pores. When the volume fraction of pores exceeds the volume fraction of solid phase, the material has many unique combinations of properties. It is not only light in weight, high in specific strength, but also has the functions of impact energy absorption, damping and vibration reduction. For example, animal bones, trees, corals and the like, such a material is called a porous material.

[0003] With the rapid development of advanced material preparation and forming technology, metals can also be processed into porous structures, among which foam metal is an important porous material. It has excellent mechanical properties such as light weight, high specific strength, high specific stiffness, and special functions such as impact energy absorption, heat insulation, vibration and noise reduction, electromagnetic shielding, etc. It is a structural and functional integrated material with excellent performance. At present, foam aluminum is the most widely researched and commercialized, but the internal structure of traditional foam aluminum is not uniform and has local defects, which has a great influence on its dynamic performance. Its mechanical properties such as strength, stiffness, elongation are low, the compressive strength is generally less than 5MPa, and the compression yield platform is low, which is difficult to apply to large impact energy load working conditions.

[0004] In recent years, a kind of metal matrix composite foam material composed of hollow spheres and metal matrix has attracted widespread attention from scholars at home and abroad. Studies have shown that this new type of metal matrix composite foam material has significantly improved mechanical properties due to the presence of hollow sphere particles. At present, the research on aluminum-based composite foam material is the most extensive, but in some special working conditions such as high temperature resistance, explosion prevention, fire prevention, etc. The application of aluminum-based composite foam material is greatly limited. In comparison, steel materials, as an important material widely used in industry, have the advantages of low cost, high mechanical properties, high temperature resistance, corrosion resistance, good weldability, and good compatibility with steel structures. In particular, iron-based composite foam material has more advantages in resisting large energy impact, which is unmatched by light metal matrix foam material. Therefore, the development of iron-based composite foam material and its preparation method is conducive to meeting the expanding application requirements.

[0005] Patent No. CN103614586A discloses a preparation method of Al2O3 hollow sphere / aluminum porous composite material. The method is to put Al2O3 hollow sphere into a mold, then pour molten metal into the preheated mold, close the mold and drive the liquid metal to the gap between the hollow sphere particles by mechanical extrusion, and obtain Al2O3 hollow sphere / aluminum porous composite material after solidification. In this method, metal pressure head and metal mold cavity are used, which is only suitable for the forming of low melting point metal materials. The temperature of molten steel sometimes reaches 1500℃, and the invention is not suitable for the preparation of iron-based composite foam. Patent No. CN108486400A discloses a metal-based hollow sphere composite foam material and a preparation method thereof. The method is to add hollow spheres into aluminum liquid after tackifying treatment by mechanical stirring, and obtain a composite foam material after the aluminum liquid solidifies. The stirring process used in this process is only suitable for low melting point materials such as aluminum alloy, and is also difficult to be used for the preparation of high melting point metal composite foam materials. In addition, the surface tension and density of steel liquid are much larger than those of aluminum melt, and the hollow spheres will float a lot in the steel liquid, which is difficult to disperse uniformly. Therefore, it is necessary to develop a preparation process suitable for high melting point iron-based composite foam material, and to ensure the uniformity of ceramic hollow spheres, so as to expand the application field of metal-based composite foam material. SUMMARY

[0006] In one aspect, the present application provides an iron-based composite foam material, which is composed of an iron-based matrix and ceramic hollow spheres. The ceramic hollow spheres are uniformly distributed in the matrix. The diameter of the ceramic hollow spheres is between 500 microns and 15 millimeters. The volume fraction of the ceramic hollow spheres is between 40% and 70%.

[0007] The iron-based matrix includes one of stainless steel, carbon steel, alloy steel, high-temperature alloy and cast iron.

[0008] The ceramic hollow spheres are made of one or more of oxide ceramic, nitride ceramic and carbide ceramic. Preferably, the ceramic hollow spheres are made of one or more of alumina ceramic, zirconia ceramic, silicon nitride ceramic and tungsten carbide ceramic.

[0009] In another aspect, the present application provides a gas pressure infiltration method for preparing an iron-based composite foam material, which includes the following steps:

[0010] (1) preparing a high-temperature-resistant cavity capable of accommodating ceramic hollow spheres, filling the ceramic hollow spheres into the cavity, and setting a ceramic filter screen at the bottom of the ceramic hollow spheres to prevent the hollow spheres from floating and moving during the forming process;

[0011] (2) starting the vacuum pump of the pressure infiltration equipment, opening the vacuum valve, and then starting the lower zone heater to preheat the cavity and the ceramic hollow spheres;

[0012] (3) After the ceramic hollow sphere preform reaches the set temperature, the upper zone induction heater of the infiltration equipment is started to melt the metal in the crucible into a metal liquid, and the metal liquid is poured into the mold cavity after a period of heat preservation and standing;

[0013] (4) The vacuum valve of the equipment is closed, and the pressurizing valve is opened to fill the preheated mold cavity with the molten metal liquid, and drive it into the tiny pores around the hollow sphere particles;

[0014] (5) After the mold filling is completed, a certain pressure is maintained for a period of time to eliminate defects in the casting, then the heating device is turned off, the metal liquid is solidified after pressure relief, the furnace cavity is opened to take out the casting, and an iron-based composite foam material is obtained.

[0015] Further, the high-temperature-resistant mold cavity in step (1) can be made of oxide ceramic, preferably made of one or more of alumina, magnesia, and zirconia;

[0016] Further, the ceramic filter screen in step (1) can be one of an alumina ceramic filter screen and a zirconia ceramic filter screen.

[0017] Further, the vacuum degree in step (2) is less than 10x10 -3 Pa, and the heating temperature of the mold cavity and the ceramic hollow sphere is 1000-1500℃. Preferably, the heating temperature is 1200-1400℃.

[0018] Further, the metal smelting temperature in step (3) is 1350-1580℃.

[0019] Further, the mold filling pressure in step (4) is 0.05-2MPa, and the compressed gas is high-purity argon or nitrogen.

[0020] Further, the pressure holding time in step (5) is 60-180s.

[0021] The ceramic hollow sphere / iron-based composite foam material of the present application retains the structural characteristics of the hollow sphere, the hollow spheres are uniformly distributed in the matrix, and the particle reinforcement mechanism is introduced to improve the mechanical properties of the material. This iron-based composite foam material has the advantages of low density, structure design, and high specific strength. In addition, the material has the advantages of low cost, high temperature resistance, corrosion resistance, good weldability, excellent steel structure compatibility, etc. In particular, the iron-based composite foam material has advantages in resisting high-energy impact, which is unmatched by light metal-based foam materials.

[0022] The preparation method of the ceramic hollow sphere / iron-based composite foam material of the present application is convenient to operate, overcomes the problem that the current mechanical infiltration and mechanical stirring method is not suitable for forming of high melting point materials, and the gas infiltration method adopted by the present application has the characteristics of low pressurization rate and stable pressure, which is beneficial to prevent the ceramic hollow sphere from being damaged in the infiltration process. In addition, the gas infiltration process adopted by the present application realizes the filling, crystallization and feeding of the metal melt under controllable pressure, which can effectively eliminate defects such as shrinkage cavity and shrinkage porosity in the metal matrix of the composite foam material. Therefore, the iron-based composite foam material prepared by the gas infiltration method of the present application has a series of advantages such as simple operation, good hollow sphere integrity, uniform and adjustable pore structure, and dense matrix, and has good application prospect in the fields of resisting large impact load, explosion-proof energy absorption, heat insulation and the like. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a structure schematic view of the gas pressure infiltration device for preparing the iron-based composite foam material of the present application.

[0024] Figure 2 It is a physical map of the iron-based composite foam material of the present application.

[0025] Figure 3 It is a quasi-static compression stress-strain curve diagram of the iron-based composite foam material of the present application.

[0026] In the figure: 1, upper zone induction heater; 2, steel liquid; 3, crucible; 4, high-temperature-resistant cavity; 5, filter screen; 6, ceramic hollow sphere; 7, lower zone heater; 8, pressurized gas tank; 9, vacuum pump; 10, iron-based composite foam material. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be clearly and completely described below.

[0028] The features and properties of the present application will be further described in detail below in combination with embodiments.

[0029] Embodiment 1:

[0030] In combination with Figure 1 the present embodiment, the preparation method of the alumina hollow sphere reinforced iron-based composite foam is realized according to the following steps:

[0031] (1) Fill the alumina ceramic hollow sphere 6 with a particle size of 5.12 mm into the high-temperature-resistant cavity 4, so that it is tightly packed, and place the 20 ppi alumina filter screen 5 on the top of the hollow sphere.

[0032] (2) Start the vacuum pump 9 of the infiltration equipment, and use the vacuum pump 9 to exhaust the air inside the furnace cavity, so that the vacuum degree reaches 6x10 -3Pa, start the lower zone heater 7, set the heating temperature to 1300°C, and keep it for 2h.

[0033] (3) Start the upper zone induction heater 1 of the infiltration equipment, melt the CF-8 austenitic stainless steel in the crucible 3, when the temperature reaches 1500°C, keep it for 20 minutes, and then pour it into the mold cavity;

[0034] (4) Close the vacuum valve of the equipment, open the pressurizing valve, and when the pressure reaches 0.1 MPa, make the molten steel 2 fill the preheated mold cavity, and drive it into the tiny pores around the hollow sphere particles.

[0035] (5) After the mold filling is completed, keep the pressure for 80s to eliminate the defects in the casting, then close the heating device, wait for the metal liquid to solidify and form, release the pressure, open the furnace cavity, and take out the casting to obtain the iron-based composite foam material 10.

[0036] Example 2:

[0037] In combination with Figure 1 the drawings, the preparation method of the aluminum oxide hollow sphere reinforced iron-based composite foam of the present embodiment is realized according to the following steps:

[0038] (1) Fill the aluminum oxide ceramic hollow spheres 6 with a particle size of 4.05 mm into the high-temperature mold cavity 4, make them compactly packed, and place the 20 ppi aluminum oxide filter screen 5 on the top of the hollow spheres.

[0039] (2) Start the vacuum pump 9 of the infiltration equipment, use the vacuum pump 9 to exhaust the air inside the furnace cavity, so that the vacuum degree reaches 6×10 -3 Pa, start the lower zone heater 7, set the heating temperature to 1350°C, and keep it for 2h.

[0040] (3) Start the upper zone induction heater 1 of the infiltration equipment, melt the CF-8 austenitic stainless steel in the crucible 3, when the temperature reaches 1550°C, keep it for 20 minutes, and then pour it into the mold cavity;

[0041] (4) Close the vacuum valve of the equipment, open the pressurizing valve, and when the pressure reaches 0.3 MPa, make the molten steel 2 fill the preheated mold cavity, and drive it into the tiny pores around the hollow sphere particles.

[0042] (5) After the mold filling is completed, keep the pressure for 100s to eliminate the defects in the casting, then close the heating device, wait for the metal liquid to solidify and form, release the pressure, open the furnace cavity, and take out the casting to obtain the iron-based composite foam material 10.

[0043] Example 3:

[0044] In combination with Figure 1 the drawings, the preparation method of the aluminum oxide hollow sphere reinforced iron-based composite foam of the present embodiment is realized according to the following steps:

[0045] (1) Fill the alumina ceramic hollow spheres 6 with a particle size of 3.02 mm into the high-temperature-resistant cavity, make it compactly packed, and place the 15 ppi alumina filter screen 5 on the top of the hollow spheres.

[0046] (2) Start the vacuum pump 9 of the infiltration equipment, use the vacuum pump 9 to exhaust the air inside the furnace cavity, so that the vacuum degree reaches 3 x 10 -3 Pa, start the lower zone heater 7, set the heating temperature to 1350℃, and keep it for 2h.

[0047] (3) Start the upper zone induction heater of the infiltration equipment, melt the CF-8 austenitic stainless steel in the crucible 3, when the temperature reaches 1580℃, keep it for 20 minutes, and then pour it into the mold cavity;

[0048] (4) Close the vacuum valve of the equipment, open the pressurizing valve, and when the pressure reaches 0.8 MPa, make the molten steel 2 fill the preheated mold cavity, and drive it into the tiny pores around the hollow sphere particles.

[0049] (5) After the filling is completed, keep the pressure for 100s to eliminate the defects in the casting, then turn off the heating device, wait for the metal liquid to solidify and form, then release the pressure, open the furnace cavity, and take out the casting, to obtain the iron-based composite foam material 10.

[0050] Figure 2 The physical map of the iron-based composite foam material prepared in Example 1 to Example 3. By observation, it can be clearly seen that the hollow spheres are uniformly distributed in the iron-based matrix, the hollow sphere structure is complete, and no phenomenon of steel liquid penetrating into the hollow sphere inside is found. The iron-based composite foam material in the physical map shows a good overall morphology, fully showing the maturity and stability of the preparation process.

[0051] Figure 3 The stress-strain curves of the iron-based composite foam material prepared in Example 1 to Example 3 under quasi-static compression conditions are shown. From the figure, it can be obviously found that the iron-based composite foam material experiences three typical stages during compression: initial elastic zone, platform zone and compaction zone. Table 1 is the quasi-static compression performance of the iron-based composite foam material, and Table 2 is the energy absorption value of the iron-based composite foam material. The compression stress-strain curve and performance data show that the ceramic hollow sphere reinforced iron-based composite foam material has high compression strength, energy absorption capacity and specific energy absorption, which is significantly higher than that of commercial aluminum foam material, and has good application prospect in the field of resisting large impact load and explosion energy absorption.

[0052] Table 1 Quasi-static compression performance of iron-based composite foam material

[0053] Test sample Hollow sphere outer diameter mm Density g / cm 3 ]]> yield strength MPa platform stress MPa Platform strain [%] Example 1 5.12 3.59 56.68 161.21 40.22 Example 2 4.05 3.38 65.12 153.83 41.03 Example 3 3.02 3.27 67.11 150.21 44.55

[0054] Table 2 Energy absorption values for iron-based syntactic foams

[0055] Test sample Hollow sphere outer diameter mm Density g / cm 3 ]] Volume energy absorption MJ / m 3 ]] mass absorption kj / kg Example 1 5.12 3.59 54.51 14.91 Example 2 4.05 3.38 53.91 16.67 Example 3 3.02 3.27 63.02 18.84

[0056] The application is not restricted to the described embodiments. The application extends to any novel one, or any new combination, of the features disclosed in this specification, and to any novel method or process, or any new combination, disclosed in this specification.

[0057] Obviously, the above-mentioned embodiments of the application are only examples for clearly illustrating the application, and are not intended to limit the embodiments of the application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art, and it is impossible to enumerate all the embodiments here. Any obvious changes or variations derived from the technical solutions of the application still fall within the protection scope of the application.

Claims

1. An iron-based composite foam material, characterized by, The composite material is composed of an iron base and ceramic hollow spheres, which are uniformly distributed in the iron base.

2. The iron-based composite foam material of claim 1, wherein, The ceramic hollow spheres have a diameter of 500 microns to 15 millimeters, and a volume fraction of 40% to 70%.

3. The iron-based composite foam material of claim 1, wherein, The iron base comprises one of stainless steel, carbon steel, alloy steel, high-temperature alloy and cast iron; and the ceramic hollow spheres are one or more of oxide ceramic, nitride ceramic and carbide ceramic.

4. A gas pressure infiltration method for preparing an iron-based composite foam material, comprising the following steps: (1) preparing a high-temperature-resistant cavity capable of containing ceramic hollow spheres, filling the ceramic hollow spheres into the cavity, and setting a ceramic filter screen at the bottom of the ceramic hollow spheres to prevent the hollow spheres from floating and moving during the molding process; (2) starting the vacuum pump of the infiltration equipment, opening the vacuum valve, and then starting the lower heating body to preheat the cavity and the ceramic hollow spheres; (3) after the ceramic hollow sphere preform reaches the set temperature, starting the upper induction heater of the infiltration equipment to melt the metal in the crucible into a metal liquid, and keeping the metal liquid for a period of time, and then pouring the metal liquid into the cavity after the metal is fully melted; (4) closing the vacuum valve of the equipment and opening the pressurizing valve to make the molten metal liquid fill the preheated cavity and drive it into the tiny pores around the hollow sphere particles; (5) after the filling is completed, keeping the pressure for a period of time to eliminate defects in the casting, then closing the heating device, and after the metal liquid solidifies and forms, releasing the pressure, opening the furnace cavity to take out the casting, and obtaining the iron-based composite foam material.

5. The gas pressure infiltration method for preparing an iron-based composite foam material according to claim 4, wherein the high-temperature-resistant cavity in step (1) is made of oxide ceramic, preferably one or more of alumina, magnesia and zirconia.

6. The gas pressure infiltration method for preparing iron-based composite foam material according to claim 4, wherein the vacuum degree in step (2) is less than 10 x 10 -3 The heating temperature of the mold cavity and the ceramic hollow spheres is 1000-1500°C. Preferably, the heating temperature is 1200-1400°C.

7. The gas pressure infiltration method for preparing an iron-based composite foam material according to claim 4, wherein the metal smelting temperature in step (3) is 1350°C to 1580°C.

8. The gas pressure infiltration method for preparing an iron-based composite foam material according to claim 4, wherein the filling pressure in step (4) is 0.05 MPa to 2 MPa, and the compressed gas is high-purity argon or nitrogen.

9. The gas pressure infiltration method for preparing an iron-based composite foam material according to claim 4, wherein the pressure keeping time in step (5) is 60 to 180 seconds.

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