Porous iron and method for producing the same

Abstract

The application belongs to the field of metal materials, and discloses a preparation method of porous iron, and specifically comprises the following steps: step 1: granulating iron powder, PMMA powder and carbon powder to obtain granulated powder; step 2: mixing the granulated powder obtained in step 1 with solid wax which is solid at room temperature to obtain a molding material; step 3: performing compression molding on the molding material obtained in step 2 to obtain a green body; and step 4: performing degreasing, combustion, reduction and sintering on the green body obtained in step 3 to obtain finished product porous iron. Through the operation of granulating raw materials first and then mixing with PE wax, the finished product has a greater improvement in the pore effect at the macro and micro levels.

Description

Technical Field

[0001] This invention belongs to the field of metallic materials, specifically relating to a porous iron and its preparation method. Background Technology

[0002] Porous metallic materials are a rapidly developing new type of functional material. They have the characteristics of good permeability, large specific surface area, good energy absorption and shock absorption performance, and low thermal and electrical conductivity. They can be made into filters, silencers, catalyst carriers, electrodes, etc., and are widely used in machinery, medicine, metallurgy, environmental protection and other fields.

[0003] Among existing technologies for preparing porous iron, the most common is the traditional powder metallurgy method. This involves mixing raw materials with a pore-forming agent, molding the mixture, and then removing the pore-forming agent through thermal decomposition or hot leaching before finally sintering to obtain porous iron. However, using traditional pore-forming agents often results in incomplete removal, leading to problems such as low porosity and uneven pore size in the finished product. Furthermore, simply mixing the raw materials with the pore-forming agent directly causes uneven pore distribution.

[0004] Therefore, the technical problem to be solved in this case is: how to prepare porous iron materials with better porosity through the synergistic effect between granulation process and pore-forming agent. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing porous iron. This method uses PMMA powder, carbon powder, and solid wax as pore-forming agents to achieve pore formation inside the granulated powder and between the granulated powders, which can significantly improve the porosity of porous iron.

[0006] In addition, the present invention also provides porous iron prepared based on the above method.

[0007] To achieve this objective, the present invention employs the following technical solution:

[0008] A method for preparing porous iron specifically includes the following steps:

[0009] Step 1: Granulate iron powder, PMMA powder, and carbon powder to obtain granulated powder;

[0010] Step 2: Mix the granulated powder obtained in Step 1 with solid wax that is solid at room temperature to obtain molding material;

[0011] Step 3: Press the molding material obtained in Step 2 into shape to obtain a green blank;

[0012] Step 4: Degrease, burn, reduce, and sinter the green body obtained in Step 3 to obtain the finished porous iron.

[0013] The research in this invention revealed that granulating the raw materials before mixing them with solid wax has the following effects: Firstly, granulation ensures a very uniform distribution of the pore-forming agents PMMA powder and carbon powder. The PMMA powder guarantees good porosity in the product, while the carbon powder acts as a low-temperature support and a high-temperature combustion pore-forming agent. After the PMMA powder is removed, the material maintains its complete structure and is ultimately burned off, further enhancing the porosity of the product at the microscopic level. Secondly, the use of solid wax makes the particles more evenly distributed, which is beneficial for improving the uniformity of the product's pores. Furthermore, the solid wax is also removed at the final stage, resulting in macroscopic pores between the particles. The porous iron product obtained by this invention exhibits significantly improved porosity at both the microscopic and macroscopic levels.

[0014] Preferably, the iron powder is spherical with a particle size of 5-45 μm; the PMMA powder is spherical with a particle size of 20-300 μm; the carbon powder is spherical with a particle size of 20-300 μm; and the solid wax, which is solid at room temperature, is spherical with a particle size of 5-250 μm.

[0015] In some embodiments of the present invention, the particle size (particle size, diameter) of the iron powder is 5um, 10um, 15um, 20um, 25um, 30um, 35um, 40um or 45um.

[0016] In some embodiments of the present invention, the particle size of PMMA powder is 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 120um, 140um, 160um, 180um, 200um, 220um, 240um, 260um, 280um, or 300um.

[0017] In some embodiments of the present invention, the particle size of the toner is 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 120um, 140um, 160um, 180um, 200um, 220um, 240um, 260um, 280um, or 300um.

[0018] In some embodiments of the present invention, the particle size of the solid wax is 5um, 10um, 20um, 30um, 40um, 50um, 60um, 70um, 80um, 90um, 100um, 120um, 140um, 160um, 180um, 200um, 220um, 240um, or 250um.

[0019] Preferably, the granulation operation involves adding iron powder, PMMA powder, and carbon powder to a PVA solution for granulation, wherein the PVA solution is an aqueous solution with a concentration of 3-14 wt%.

[0020] The total volume ratio of the iron powder, PMMA powder, and carbon powder to the volume ratio of the PVA solution is 1:2 to 3.

[0021] Preferably, the iron powder, PMMA powder, carbon powder, and solid wax are present in the following quantities by volume percentage:

[0022]

[0023] In this invention, the porosity of porous iron is the volume ratio of iron powder in all raw materials. Through the method of this invention, porous iron with a porosity of 50% to 95% can be prepared.

[0024] Preferably, the molding process in step 3 is cold pressing, with a pressure of 50MPa to 300MPa.

[0025] Preferably, the degreasing temperature in step 4 is 95℃~130℃ for 0.5~2h, and 250℃~280℃ for 1~3h, in an air atmosphere.

[0026] Preferably, the combustion temperature in step 4 is 700℃~1050℃, the duration is 1~3h, and the atmosphere is an air atmosphere.

[0027] Preferably, the reduction temperature in step 4 is 850℃~1050℃, the duration is 1~3h, and the atmosphere is hydrogen or carbon monoxide atmosphere.

[0028] Preferably, the sintering temperature in step 4 is 1150℃~1400℃, the sintering time is 2~5h, and the atmosphere is an inert gas atmosphere.

[0029] Preferably, the solid wax is paraffin wax or PE wax.

[0030] Meanwhile, a porous iron was also disclosed, which was prepared by the porous iron preparation method described above.

[0031] The beneficial effects of this invention are

[0032] By first granulating the raw materials and then mixing them with solid wax, the following effects are achieved: Firstly, granulation ensures a very uniform distribution of the pore-forming agents PMMA powder and carbon powder. The PMMA powder guarantees good porosity in the product, while the carbon powder acts as a low-temperature support and a high-temperature combustion pore-forming agent. After the PMMA powder is removed, the material maintains its complete structure and is ultimately burned off, further enhancing the porosity of the product at the microscopic level. Secondly, the use of PE wax makes the particles more evenly distributed, which is beneficial for improving the uniformity of the product's pores. Furthermore, the solid wax is ultimately removed, resulting in macroscopic pores between the particles. The porous iron product obtained by this invention exhibits significantly improved porosity at both the microscopic and macroscopic levels. Attached Figure Description

[0033] Figure 1 Here is a SEM image of the finished product from Example 1;

[0034] Figure 2 Here is a SEM image of the finished product from Example 2;

[0035] Figure 3 This is a SEM image of the finished product from Example 3. Detailed Implementation

[0036] 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 only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] Example 1

[0038] Prepare raw materials with a porosity of 95% as follows: 50% vol, 150 μm PMMA powder; 35% vol, 100 μm carbon powder; 10% vol, 50 μm PE wax powder; and 5% vol, 15 μm iron powder.

[0039] The PMMA powder has a molecular weight of 500,000 to 1,000,000 and is manufactured by Arkema Altuglas.

[0040] Granulation: PMMA powder, carbon powder, and iron powder are granulated using an 8wt% PVA solution as a solvent. The volume ratio of solvent to powder is 1:2. The final drying moisture content is controlled between 1wt% and 3wt% to obtain granulated powder.

[0041] Mixing: Mix the granulated powder and PE wax powder with a V-type mixer for 3 hours to obtain the molding material.

[0042] Cold pressing: The molding material is loaded into the mold and cold pressed for 5 minutes with a hydraulic press at a pressure of 70 MPa to obtain the green blank.

[0043] Degreasing and combustion: The green billet is placed in a muffle furnace and heated at a rate of 5℃ / min in air atmosphere, held at 110℃ for 0.5h, held at 260℃ for 2h, heated to 900℃ in air atmosphere and held for 2h, and then cooled to room temperature in the furnace to obtain degreased oxidized material.

[0044] Reduction and sintering: The degreased oxidized material is placed in an atmosphere furnace, hydrogen is continuously introduced, the temperature is raised to 950℃ and held for 2 hours, then nitrogen is continuously introduced and the temperature is raised to 1200℃ and held for 3 hours. The material is then cooled with the furnace to obtain the finished product.

[0045] See finished product SEM image Figure 1 .

[0046] Example 2

[0047] Prepare raw materials with 80% porosity: 40% vol, 300 μm PMMA powder, 35% vol, 300 μm carbon powder, 5% vol, 250 μm PE wax powder, and 20% vol, 45 μm iron powder.

[0048] The PMMA powder has a molecular weight of 500,000 to 1,000,000 and is manufactured by Arkema Altuglas.

[0049] Granulation: PMMA powder, carbon powder, and iron powder are granulated using 14wt% PVA solution as solvent. The volume ratio of solvent to powder is 1:2.5. The final drying moisture content is controlled between 1wt% and 3wt% to obtain granulated powder.

[0050] Mixing: Mix the granulated powder and PE wax powder with a V-type mixer for 3 hours to obtain the molding material.

[0051] Cold pressing: The molding material is loaded into the mold and cold pressed for 3 minutes with a hydraulic press at a pressure of 300MPa to obtain the green blank.

[0052] Degreasing and combustion: The green billet is placed in a muffle furnace and heated at a rate of 5℃ / min in air atmosphere, held at 130℃ for 0.5h, held at 280℃ for 1h, heated to 1050℃ in air atmosphere and held for 1h, and then cooled to room temperature in the furnace to obtain degreased oxidized material.

[0053] Reduction and sintering: The degreased oxidized material is placed in an atmosphere furnace, and carbon monoxide is continuously introduced. The temperature is raised to 1050℃ and held for 1 hour. Then, argon gas is continuously introduced and the temperature is raised to 1400℃ and held for 2 hours. The material is then cooled with the furnace to obtain the finished product.

[0054] See finished product SEM image Figure 2 .

[0055] Example 3

[0056] Prepare raw materials with a porosity of 50% as follows: 30% vol, 20 μm PMMA powder; 15% vol, 20 μm carbon powder; 5% vol, 5 μm PE wax powder; and 50% vol, 5 μm iron powder.

[0057] The PMMA powder has a molecular weight of 500,000 to 1,000,000 and is manufactured by Arkema Altuglas.

[0058] Granulation: PMMA powder, carbon powder, and iron powder are granulated using 3wt% PVA solution as solvent. The volume ratio of solvent to powder is 1:3. The final drying moisture content is controlled between 1wt% and 3wt% to obtain granulated powder.

[0059] Mixing: Mix the granulated powder and PE wax powder with a V-type mixer for 3 hours to obtain the molding material.

[0060] Cold pressing: The molding material is loaded into the mold and cold pressed for 8 minutes with a hydraulic press at a pressure of 50 MPa to obtain the green blank.

[0061] Degreasing and combustion: The green billet is placed in a muffle furnace and heated at a rate of 5℃ / min in air atmosphere. It is held at 95℃ for 2 hours, then at 250℃ for 3 hours, and then heated to 700℃ in air atmosphere for 3 hours. It is then cooled to room temperature in the furnace to obtain the degreased oxidized material.

[0062] Reduction and sintering: The degreased oxidized material is placed in an atmosphere furnace, and carbon monoxide is continuously introduced. The temperature is raised to 850°C and held for 3 hours. Then, argon gas is continuously introduced and the temperature is raised to 1150°C and held for 5 hours. The material is then cooled in the furnace to obtain the finished product.

[0063] See finished product SEM image Figure 3 .

[0064] Comparative Example 1

[0065] Prepare raw materials with a porosity of 50%: 30% vol, 20 μm PMMA powder, 20% vol, 20 μm carbon powder, and 50% vol, 5 μm iron powder.

[0066] The PMMA powder has a molecular weight of 500,000 to 1,000,000 and is manufactured by Arkema Altuglas.

[0067] Granulation: PMMA powder, carbon powder, and iron powder are granulated using 8wt% PVA solution as solvent and the volume ratio of solvent to powder is 1:3. The final drying moisture content is controlled at 1wt% to 3wt% to obtain granulated powder.

[0068] Cold pressing: The granulated powder is loaded into the mold and cold pressed for 5 minutes with a hydraulic press at a pressure of 70 MPa to obtain the green body.

[0069] Degreasing and combustion: The green billet is placed in a muffle furnace and heated at a rate of 5℃ / min. It is held at 110℃ for 0.5h, at 260℃ for 2h, and at 900℃ for 2h. It is then cooled to room temperature with the furnace to obtain the degreased oxidized material.

[0070] Reduction and sintering: The degreased oxidized material is placed in an atmosphere furnace, hydrogen is continuously introduced, the temperature is raised to 950℃ and held for 2 hours, then nitrogen is continuously introduced and the temperature is raised to 1200℃ and held for 3 hours. The material is then cooled with the furnace to obtain the finished product.

[0071] Comparative Example 2

[0072] Prepare raw materials with a porosity of 50%: 35% vol, 20 μm PMMA powder, 15% vol, 5 μm PE wax powder, and 50% vol, 5 μm iron powder.

[0073] The PMMA powder has a molecular weight of 500,000 to 1,000,000 and is manufactured by Arkema Altuglas.

[0074] Granulation: PMMA powder and iron powder are granulated using 8wt% PVA solution as solvent and the volume ratio of solvent to powder is 1:3. The final drying moisture content is controlled at 1wt% to 3wt% to obtain granulated powder.

[0075] Mixing: Mix the granulated powder and PE wax powder with a V-type mixer for 3 hours to obtain the molding material.

[0076] Cold pressing: The granulated powder is loaded into the mold and cold pressed for 5 minutes with a hydraulic press at a pressure of 70 MPa to obtain the green body.

[0077] Degreasing and combustion: The green billet is placed in a muffle furnace and heated at a rate of 5℃ / min in air atmosphere, held at 110℃ for 0.5h, held at 260℃ for 2h, heated to 900℃ in air atmosphere and held for 2h, and then cooled to room temperature in the furnace to obtain degreased oxidized material.

[0078] Reduction and sintering: The degreased oxidized material is placed in an atmosphere furnace, hydrogen is continuously introduced, the temperature is raised to 950℃ and held for 2 hours, then nitrogen is continuously introduced and the temperature is raised to 1200℃ and held for 3 hours. The material is then cooled with the furnace to obtain the finished product.

[0079] Comparative Example 3

[0080] It is largely the same as Example 1, except that PMMA powder is not added to the raw materials.

[0081] Performance testing

[0082] SEM testing equipment: Zeiss Sigma 300 field emission scanning electron microscope (Germany)

[0083] Carbon measuring device model: LECO-844 carbon-sulfur analyzer (USA)

[0084] Refer to Table 1 for specific test data.

[0085] Table 1 Performance test data for each sample

[0086]

[0087] Conclusion Analysis:

[0088] Analysis of the test data from Examples 1-3 shows that, according to the technical solution of the present invention, which involves granulating the raw materials and then mixing them with solid wax, the difference between the measured porosity of the obtained products and the porosity set during the preparation of the raw materials is extremely small when preparing porous iron with different porosities. The smallest difference is 0.2% in Example 3. In the technical solution of the present invention, carbon powder serves as a skeletal support and a combustion pore-forming agent. The carbon content in the products of Examples 1-3 is very low, only about 10 ppm, and the structure of the products is very complete without any collapse. It can be seen that, using the technical solution of the present invention, the products prepared have almost no pore-forming agent residue, and the porosity effect is unexpected.

[0089] Comparative Example 1, based on Example 3, omits the addition of PE wax powder. As can be seen from the data, its porosity is only 45.7%. This is because PE wax is the first pore-forming agent to be removed during the degreasing stage. During the removal process, it also makes PMMA powder easier to remove. Without PE wax powder, PMMA powder residue will remain and cannot be completely removed, resulting in an increase in carbon content and a decrease in porosity in the finished product.

[0090] Comparative Example 2, based on Example 3, omits the addition of carbon powder. As mentioned above, carbon powder acts as a skeletal support and a combustion pore-forming agent, which can improve the strength of the product and further enhance the porosity. Without the use of carbon powder, the strength of the material is insufficient, and the prepared porous iron product directly exhibits collapse.

[0091] Comparative Example 3, based on Example 3, omitted the addition of PMMA powder, resulting in experimental failure.

[0092] In summary, in the technical solution of this invention, PMMA powder, PE wax powder, and toner are all indispensable and must be used together to exert a synergistic effect. In addition, granulation operation is required to achieve the objective of this invention.

[0093] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing porous iron, characterized in that, Specifically, the following steps are included: Step 1: Granulate iron powder, PMMA powder, and carbon powder to obtain granulated powder; Step 2: Mix the granulated powder obtained in Step 1 with solid wax that is solid at room temperature to obtain molding material; Step 3: Press the molding material obtained in Step 2 into shape to obtain a green blank; Step 4: Degrease, burn, reduce, and sinter the green body obtained in Step 3 to obtain porous iron; The contents of the iron powder, PMMA powder, carbon powder, and solid wax are as follows: Iron powder 5~50 vol% PMMA powder 30~50% vol% Toner 15~35 vol% Solid wax 5~10 vol% The solid wax is PE wax; The combustion temperature described in step 4 is 700℃~1050℃, the duration is 1~3h, and the atmosphere is air. The reduction temperature in step 4 is 850℃~1050℃, the duration is 1~3h, and the atmosphere is hydrogen or carbon monoxide atmosphere. The sintering temperature in step 4 is 1150℃~1400℃, the duration is 2~5h, and the atmosphere is an inert gas atmosphere.

2. The preparation method according to claim 1, characterized in that, The iron powder is spherical with a particle size of 5~45um; the PMMA powder is spherical with a particle size of 20~300um; the carbon powder is spherical with a particle size of 20~300um; and the solid wax is spherical with a particle size of 5~250um.

3. The preparation method according to claim 1, characterized in that, The molding process described in step 3 is cold pressing, with a pressure of 50MPa to 300MPa.

4. The preparation method according to claim 1, characterized in that, The degreasing temperature in step 4 is 95℃~130℃ for 0.5~2h, and 250℃~280℃ for 1~3h, in an air atmosphere.

5. A porous iron, characterized in that, It is prepared by the porous iron preparation method as described in any one of claims 1 to 4.

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