A tubular gradient porous metal element with high permeation flux and a preparation method thereof

Abstract

The application discloses a tubular gradient porous metal element with high permeation flux, which comprises a tubular support body with a large-pore structure and a precision control layer with a small-pore structure coated outside the support body, and no particle penetration phenomenon exists between the precision control layer and the support body. In addition, the application also discloses a preparation method of the tubular gradient porous metal element with high permeation flux. The support body blank is prepared by cold isostatic pressing, and then the precision control layer is sprayed by powder wet spraying. Through analysis of the fluid permeation resistance generation mechanism, the application eliminates the existing space of the permeation interaction layer from the microstructure level, eliminates the additional flow resistance caused by the permeation interaction layer generated by the existing process, greatly improves the permeation flux of the tubular gradient porous metal element, and the prepared tubular porous metal element has the advantages of large flux, small surface roughness and excellent blowback performance, and has a wide application prospect in the filtration and separation industry of modern industry.

Description

Technical Field

[0001] This invention belongs to the field of porous metal materials technology, specifically relating to a high-permeability tubular gradient porous metal element and its preparation method. Background Technology

[0002] Tubular porous elements, manufactured from powder particles through pressing, sintering, and processing, offer advantages such as large filtration area, good assembly performance, and high replaceability, making them the primary structural form for porous elements in modern industry. However, due to factors such as powder particle size and formability, traditional porous metal materials with uniform pore size struggle to achieve efficient separation of fine particles smaller than 2μm.

[0003] To address the challenge of efficiently separating fine particles, gradient porous metal materials have been developed based on traditional materials. This involves first preparing a large-pore support, followed by the fabrication of a precision control layer on the support surface using methods such as wet powder coating, sol-gel, or dip-coating, resulting in a gradient porous metal element with high filtration accuracy. However, in existing methods for preparing the large-pore support, the pressing pressure is applied to the support surface through a soft rubber sleeve, leading to an uneven and rough outer surface after sintering. Furthermore, the precision control layer requires surface modification with fine powder particles before its fabrication, resulting in a particle thickness far exceeding practical requirements. Ultimately, this causes the permeability of the gradient porous material to fall far short of theoretical values. These problems significantly reduce the permeation flux of the filter element, increasing the number of elements in the filtration system and causing issues such as excessive pressure differential per filter element, increased backflushing frequency, and reduced lifespan. Therefore, effectively improving the permeation flux of tubular gradient porous metal elements while ensuring filtration accuracy has become a major challenge limiting the further widespread application of gradient porous metal filter elements.

[0004] In preliminary research and analysis, the applicant discovered that the microstructure of existing gradient porous metal materials actually consists of three layers in the thickness direction. The innermost layer is a macroporous support, mainly used to provide mechanical strength. The outermost layer is a precision control layer with small pore size, used to achieve efficient interception of solid particles smaller than 2μm. The third layer is a permeation interaction layer formed by the intersection of the rough-surfaced macroporous support and the precision control layer. It is precisely the presence of the permeation interaction layer that causes an increase in the additional resistance of the gradient porous metal filter element, significantly reducing the material's permeation flux.

[0005] Therefore, there is a need to provide a tubular gradient porous metal element with high permeability flux and its preparation method. Summary of the Invention

[0006] The technical problem to be solved by this invention is to address the shortcomings of the prior art by providing a tubular gradient porous metal element with high permeability. This tubular gradient porous metal element consists of a support body with a high surface finish and a large pore structure, and a precision control layer with a small pore structure covering the support body. This eliminates the space for the existence of the permeation interaction layer at the microstructural level, preventing the additional resistance generated by the permeation interaction layer, and has the advantages of high permeability and easy backflush.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a high-permeability tubular gradient porous metal element, characterized in that the porous metal element includes a tubular support with a large pore structure and a precision control layer with a small pore structure covering the support body, wherein the surface roughness Ra of the large pore support body is ≤8μm, and there is no particle permeation phenomenon between the precision control layer and the support body.

[0008] The tubular gradient porous metal element of the present invention consists of a support body with a high surface finish and a large pore structure, and a precision control layer with a small pore structure covering the support body. The large pore support body in the tubular gradient porous metal element has a smooth surface, which eliminates the space for the existence of the permeation interaction layer at the microstructural level and prevents the additional resistance generated by the permeation interaction layer. When the surface roughness Ra of the support body is ≤8μm, the surface of the support body will not interact with the precision control layer, which has the advantages of high permeation flux and easy backflushing, and has broad application prospects in the filtration and separation industry of modern industry.

[0009] The aforementioned high-permeability tubular gradient porous metal element is characterized in that the porous metal element is made of stainless steel, nickel-based alloy, titanium, titanium alloy, or copper alloy. This invention, by controlling the material of the porous metal element, makes it suitable for various working conditions.

[0010] The aforementioned high-permeability tubular gradient porous metal element is characterized in that the wall thickness of the support body is 2mm to 3mm, and the thickness of the precision control layer is no greater than 30μm. In this invention, the overall strength of the high-permeability tubular gradient porous metal element is ensured by controlling the thickness of the support body. The filtration accuracy (minimum filtration particle size) of the high-permeability tubular gradient porous metal element in this invention is determined by the pore size (i.e., powder particle size) of the precision control layer. When the filtration accuracy is determined, i.e., the powder particle size of the precision control layer is constant, the permeability of the material is theoretically inversely proportional to the thickness of the precision control layer; that is, the thinner the precision control layer, the greater the permeability of the material. On the other hand, it has been found that 30μm is the critical size to ensure the integrity of the precision control powder layer structure. At this point, the precision control layer has been formed and its structure is complete; excessive thickness will cause a loss of material permeability.

[0011] The above-mentioned high-permeability tubular gradient porous metal element is characterized in that the average pore size of the large pore structure is 10μm to 30μm, and the average pore size of the small pore structure is no greater than 3μm.

[0012] In addition, the present invention provides a method for preparing a tubular gradient porous metal element with high permeability flux, characterized in that the method includes the following steps:

[0013] Step 1: Design and process the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve;

[0014] Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, put the metal powder into the cavity formed by the assembly of the rigid outer mold and the inner mold from the top. Then, under vibration, make the metal powder completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed.

[0015] Step 3: Use cold isostatic pressing to press the part to be formed obtained in step 2. After pressing, remove the lower positioning seal, the upper positioning seal and the inner mold in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold.

[0016] Step 4: Perform a high-temperature sintering on the tubular porous support blank that is attached to the inner wall of the rigid outer mold obtained in Step 3, and then remove the rigid outer mold to obtain the finished support.

[0017] Step 5: Using wet powder spraying, fine metal powder with an average particle size of no more than 20μm is uniformly coated onto the surface of the support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is performed to obtain a tubular gradient porous metal element with high permeability.

[0018] This invention analyzes the mechanism of permeation resistance generation in existing gradient structures, identifies the root cause of permeation resistance deviating from theoretical levels, and uses this theory as guidance to revolutionize the forming method of existing tubular porous metal materials. Specifically, during the forming of the support, the traditional process of using a soft rubber mold acting on the outer surface of the support is changed. Instead, a hard mold with a smooth surface interacts with the outer surface of the support, transferring the smooth surface to the surface in contact with the precision control layer. This forms a large-pore support with a smooth surface required for high permeation flux filtration elements, eliminating the additional permeation resistance formed by the permeation interaction layer. Under the premise of ensuring filtration accuracy, the permeation flux of tubular gradient porous elements is effectively improved.

[0019] The above method is characterized in that the material of the rigid outer mold in step one is heat-resistant steel, high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide, and the surface roughness Ra of the inner wall is ≤1.6μm. This invention ensures the strength of the rigid outer mold by controlling its material, thereby guaranteeing the structural characteristics of the support. Controlling the surface roughness of the inner wall of the rigid outer mold ensures the smoothness of the inner surface of the support, improving the performance of the high-permeability tubular gradient porous metal element.

[0020] The method described above is characterized in that the pressing pressure in step three is 80MPa to 200MPa, and the pressing time is 30s to 120s. This invention, by controlling the pressing parameters, enables the support to be initially pressed and shaped, thus ensuring the structural strength of the support.

[0021] The above method is characterized in that the temperature of the first high-temperature sintering in step four is 950℃~1350℃, and the time is 60min~180min. This invention ensures the structural strength of the support by controlling the parameters of high-temperature sintering to achieve initial sintering and shaping.

[0022] The above method is characterized in that the secondary high-temperature sintering in step five is carried out at a temperature of 900℃ to 1200℃ for 30 min to 60 min. This invention controls the parameters of high-temperature sintering to sinter the support and the precision control layer into a single unit, ensuring the performance of the high-permeability tubular gradient porous metal element.

[0023] The above method is characterized in that the permeation flux of the high-permeability tubular gradient porous metal element in step five is not less than 50m³. 3 / m 2 ·kPa·h.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] 1. This invention is based on the analysis of the fluid permeation resistance generation mechanism of gradient porous metal materials, eliminating the damage to membrane permeation performance caused by particle permeation. It improves the performance of existing gradient porous metal elements from the process level, solves the problem of insufficient permeation flux of existing tubular gradient porous metal elements, and improves the service performance of products with only minimal modifications to existing industrial production processes without changing the existing core equipment. In the design of filtration systems, the increased permeation flux of filter elements can significantly reduce the overall volume and energy consumption of filters.

[0026] 2. Compared with traditional elements, the tubular gradient porous metal element of the present invention can increase the permeation flux by 30% to 70% under the same precision. Under the same treatment capacity, it significantly reduces the amount of filter material used and the floor space of the filter, thus achieving energy saving, emission reduction and efficiency improvement.

[0027] 3. The preparation method of the present invention has a wide range of applications, is easy to operate, and has a high yield. It is especially suitable for the technical upgrading and transformation of existing large-scale production lines, and can significantly increase the added value of products without changing the existing core equipment.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the high-permeability tubular gradient porous metal element of the present invention.

[0030] Figure 2 This is a schematic diagram of the structure of the part to be formed obtained in step two of the present invention.

[0031] Explanation of reference numerals in the attached figures:

[0032] 1—Support body; 2—Precision control layer; 3—Rigid outer mold;

[0033] 4—Lower positioning seal; 5—Upper positioning seal; 6—Inner steel sleeve;

[0034] 7—Soft mold; 8—Metal powder. Detailed Implementation

[0035] Figure 1 This is a schematic diagram of the high-permeability tubular gradient porous metal element of the present invention. Figure 1 As can be seen from the above, the high permeability tubular gradient porous metal element of the present invention includes a support 1 with a large pore structure and a precision control layer 2 with a small pore structure covering the support 1.

[0036] Figure 2 This is a schematic diagram of the structure of the part to be formed obtained in step two of the present invention. Figure 2 As can be seen from the above, the mold in this invention includes a hard outer mold 3, an inner mold, and a lower positioning seal 4 and an upper positioning seal 5 for sealing the gap formed between the hard outer mold 3 and the inner mold; the inner mold is composed of an inner steel sleeve 6 and a soft mold 7 that precisely fits with the outer surface of the inner steel sleeve 6; the cavity formed after the hard outer mold 3, the inner mold, the lower positioning seal 4 and the upper positioning seal 5 are assembled is filled with metal powder 8.

[0037] Example 1

[0038] This embodiment includes the following steps:

[0039] Step 1: Design and manufacture the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve; the rigid outer mold is made of 310S heat-resistant steel, and the surface roughness of the inner wall is Ra = 0.6μm;

[0040] Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, fill the cavity formed by the assembly of the rigid outer mold and the inner mold with metal powder from the top. Then, under vibration, allow the metal powder to completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed. The metal powder is 316L stainless steel powder with a mesh size of -100 to +160.

[0041] Step 3: Using cold isostatic pressing, the part to be formed obtained in step 2 is pressed under a pressure of 180MPa and a time of 30s. After pressing, the lower positioning seal, the upper positioning seal and the inner mold are removed in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold.

[0042] Step 4: The tubular porous support blank obtained in Step 3, which is attached to the inner wall of the rigid outer mold, is subjected to a high-temperature sintering at a temperature of 1350℃ for 180 minutes. Then the rigid outer mold is removed to obtain the finished support.

[0043] Step 5: Using wet powder spraying, fine metal powder with an average particle size of 16μm is uniformly coated onto the surface of the finished support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is carried out at a temperature of 1200℃ for 60 minutes to obtain a tubular gradient porous metal element with high permeability. The fine metal powder is 316L stainless steel powder.

[0044] Testing revealed that the surface roughness of the support in the tubular gradient porous metal element prepared in this embodiment was 5.6 μm, the average pore size of the macroporous structure of the support was 30 μm, the average pore size of the microporous structure of the precision control layer was 1.8 μm, the wall thickness of the support was 2.5 mm, the thickness of the precision control layer was 30 μm, and there was absolutely no particle permeation between the precision control layer and the macroporous support, with a permeation flux of 92 m³ / s. 3 / m 2 The permeability is 45 mPa·h, meeting the petrochemical industry's demand for tubular stainless steel filter elements; additionally, porous elements prepared using the same metal powder as in this embodiment and conventional methods have a permeability of only 45 mPa·h. 3 / m 2With a permeation flux of ·kPa·h, the tubular gradient porous metal element prepared in this embodiment achieves 2.0 times that of the traditional method under the same filtration precision conditions.

[0045] In this embodiment, the material of the hard outer mold can also be a high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide.

[0046] Example 2

[0047] This embodiment includes the following steps:

[0048] Step 1: Design and process the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve; the rigid outer mold is made of alumina and the surface roughness Ra of the inner wall is 1.6μm;

[0049] Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, fill the cavity formed by the assembly of the rigid outer mold and the inner mold with metal powder from the top. Then, under vibration, allow the metal powder to completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed. The metal powder is 316L stainless steel powder with a mesh size of -100 to +220.

[0050] Step 3: Using cold isostatic pressing, the part to be formed obtained in step 2 is pressed under a pressure of 200MPa and a time of 60s. After pressing, the lower positioning seal, the upper positioning seal and the inner mold are removed in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold.

[0051] Step 4: The tubular porous support blank obtained in Step 3, which is attached to the inner wall of the rigid outer mold, is subjected to a high-temperature sintering at a temperature of 1300℃ for 120 minutes. Then the rigid outer mold is removed to obtain the finished support.

[0052] Step 5: Using wet powder spraying, fine metal powder with an average particle size of 13μm is uniformly coated onto the surface of the finished support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is carried out at a temperature of 1000℃ for 60 minutes to obtain a tubular gradient porous metal element with high permeability. The fine metal powder is 316L stainless steel powder.

[0053] Testing revealed that the surface roughness of the support in the tubular gradient porous metal element prepared in this embodiment was 4.3 μm, the average pore size of the macroporous structure of the support was 25 μm, the average pore size of the microporous structure of the precision control layer was 1.6 μm, the wall thickness of the support was 2 mm, the thickness of the precision control layer was 22 μm, and there was absolutely no particle permeation between the precision control layer and the macroporous support, with a permeation flux of 75 m³ / s. 3 / m 2 The permeability is 42 mPa·h, meeting the water treatment industry's requirements for tubular stainless steel filter elements; additionally, porous elements prepared using the same metal powder as in this embodiment and conventional methods have a permeability of only 42 mPa·h. 3 / m 2 With a permeation flux of ·kPa·h, the tubular gradient porous metal element prepared in this embodiment achieves 1.7 times that of the traditional method under the same filtration accuracy conditions.

[0054] In this embodiment, the material of the hard outer mold can also be a high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide.

[0055] Example 3

[0056] This embodiment includes the following steps:

[0057] Step 1: Design and process the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve; the rigid outer mold is made of heat-resistant steel, and the surface roughness of the inner wall is Ra = 0.6 μm;

[0058] Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, fill the cavity formed by the assembly of the rigid outer mold and the inner mold with metal powder from the top. Then, under vibration, allow the metal powder to completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed. The metal powder is 316L stainless steel powder with a mesh size of -200 to +280.

[0059] Step 3: Using cold isostatic pressing, the part to be formed obtained in step 2 is pressed under a pressure of 160MPa and a time of 40s. After pressing, the lower positioning seal, the upper positioning seal and the inner mold are removed in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold.

[0060] Step 4: The tubular porous support blank obtained in Step 3, which is attached to the inner wall of the rigid outer mold, is subjected to a high-temperature sintering at a temperature of 1250℃ for 120 minutes. Then the rigid outer mold is removed to obtain the finished support.

[0061] Step 5: Using wet powder spraying, fine metal powder with an average particle size of 15μm is uniformly coated onto the surface of the finished support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is carried out at a temperature of 1150℃ for 60 minutes to obtain a tubular gradient porous metal element with high permeability. The fine metal powder is 316L stainless steel powder.

[0062] Testing revealed that the surface roughness of the support in the tubular gradient porous metal element prepared in this embodiment was 7.3 μm, the average pore size of the macroporous structure of the support was 14 μm, the average pore size of the microporous structure of the precision control layer was 1.5 μm, the wall thickness of the support was 3 mm, the thickness of the precision control layer was 25 μm, and there was absolutely no particle permeation between the precision control layer and the macroporous support, with a permeation flux of 51 m³ / s. 3 / m 2 The permeability is ·kPa·h, meeting the water treatment industry's requirements for tubular stainless steel filter elements; additionally, porous elements prepared using the same metal powder as in this embodiment and conventional methods have a permeability of only 32m³. 3 / m 2 With a permeation flux of ·kPa·h, the tubular gradient porous metal element prepared in this embodiment achieves 1.6 times that of the traditional method under the same filtration precision conditions.

[0063] In this embodiment, the material of the hard outer mold can also be a high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide.

[0064] Example 4

[0065] This embodiment includes the following steps:

[0066] Step 1: Design and process the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve; the rigid outer mold is made of heat-resistant steel, and the surface roughness of the inner wall is Ra = 1.2 μm;

[0067] Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, fill the cavity formed by the assembly of the rigid outer mold and the inner mold with metal powder from the top. Then, under vibration, allow the metal powder to completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed. The metal powder is Inconel 625 nickel alloy powder with a mesh size of -100 to +200.

[0068] Step 3: Using cold isostatic pressing, the part to be formed obtained in step 2 is pressed under a pressure of 80MPa and a time of 120s. After pressing, the lower positioning seal, the upper positioning seal and the inner mold are removed in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold.

[0069] Step 4: The tubular porous support blank obtained in Step 3, which is attached to the inner wall of the rigid outer mold, is subjected to a high-temperature sintering at a temperature of 1200℃ for 120 minutes. Then the rigid outer mold is removed to obtain the finished support.

[0070] Step 5: Using wet powder spraying, fine metal powder with an average particle size of 14μm is uniformly coated onto the surface of the finished support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is carried out at a temperature of 1100℃ for 50 minutes to obtain a tubular gradient porous metal element with high permeability. The fine metal powder is Inconel 625 nickel alloy powder.

[0071] Testing revealed that the surface roughness of the support in the tubular gradient porous metal element prepared in this embodiment was 3.6 μm, the average pore size of the macroporous structure of the support was 26 μm, the average pore size of the microporous structure of the precision control layer was 1.6 μm, the wall thickness of the support was 2.5 mm, the thickness of the precision control layer was 24 μm, and there was absolutely no particle permeation between the precision control layer and the macroporous support, with a permeation flux of 88 m³ / s. 3 / m 2 The permeability is 42 mPa·h, meeting the petrochemical industry's demand for tubular stainless steel filter elements; additionally, porous elements prepared using the same metal powder as in this embodiment and conventional methods have a permeability of only 42 mPa·h. 3 / m 2 With a permeation flux of ·kPa·h, the tubular gradient porous metal element prepared in this embodiment achieves twice the permeation flux of traditional methods under the same filtration precision conditions.

[0072] In this embodiment, the material of the hard outer mold can also be a high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide.

[0073] Example 5

[0074] This embodiment includes the following steps:

[0075] Step 1: Design and process the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve; the rigid outer mold is made of heat-resistant steel, and the surface roughness of the inner wall is Ra = 1.2 μm;

[0076] Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, fill the cavity formed by the assembly of the rigid outer mold and the inner mold with metal powder from the top. Then, under vibration, allow the metal powder to completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed. The metal powder is TA1 titanium powder with a mesh size of -100 to +200.

[0077] Step 3: Using cold isostatic pressing, the part to be formed obtained in step 2 is pressed under a pressure of 120MPa and a time of 100s. After pressing, the lower positioning seal, the upper positioning seal and the inner mold are removed in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold.

[0078] Step 4: The tubular porous support blank obtained in Step 3, which is attached to the inner wall of the rigid outer mold, is subjected to a high-temperature sintering at a temperature of 950℃ for 60 minutes. Then the rigid outer mold is removed to obtain the finished support.

[0079] Step 5: Using wet powder spraying, fine metal powder with an average particle size of 15μm is uniformly coated onto the surface of the support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is performed at a temperature of 900℃ for 30 minutes to obtain a tubular gradient porous metal element with high permeability. The fine metal powder is TA1 titanium powder.

[0080] Testing revealed that the surface roughness of the support in the tubular gradient porous metal element prepared in this embodiment was 3.6 μm, the average pore size of the macroporous structure of the support was 10 μm, the average pore size of the microporous structure of the precision control layer was 2.4 μm, the wall thickness of the support was 2.4 mm, the thickness of the precision control layer was 22 μm, and there was absolutely no particle permeation between the precision control layer and the macroporous support, with a permeation flux of 51 m³ / s. 3 / m 2 The permeability is ·kPa·h, meeting the petrochemical industry's demand for tubular stainless steel filter elements; additionally, porous elements prepared using the same metal powder as in this embodiment and conventional methods have a permeation flux of only 22m. 3 / m 2 With a permeation flux of ·kPa·h, the tubular gradient porous metal element prepared in this embodiment achieves 2.3 times that of the traditional method under the same filtration precision conditions.

[0081] In this embodiment, the material of the hard outer mold can also be a high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide.

[0082] Example 6

[0083] This embodiment includes the following steps:

[0084] Step 1: Design and process the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve; the rigid outer mold is made of heat-resistant steel, and the surface roughness of the inner wall is Ra = 0.8 μm;

[0085] Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, fill the cavity formed by the assembly of the rigid outer mold and the inner mold with metal powder from the top. Then, under vibration, allow the metal powder to completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed. The metal powder is TC4 titanium alloy powder with a mesh size of -100 to +160.

[0086] Step 3: Using cold isostatic pressing, the part to be formed obtained in step 2 is pressed under a pressure of 150MPa and a time of 80s. After pressing, the lower positioning seal, the upper positioning seal and the inner mold are removed in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold.

[0087] Step 4: The tubular porous support blank obtained in Step 3, which is attached to the inner wall of the rigid outer mold, is subjected to a high-temperature sintering at a temperature of 1000℃ for 100 minutes. Then the rigid outer mold is removed to obtain the finished support.

[0088] Step 5: Using wet powder spraying, fine metal powder with an average particle size of 15μm is uniformly coated onto the surface of the finished support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is carried out at a temperature of 900℃ for 30 minutes to obtain a tubular gradient porous metal element with high permeability. The fine metal powder is TC4 titanium alloy powder.

[0089] Testing revealed that the surface roughness of the support in the tubular gradient porous metal element prepared in this embodiment was 3.6 μm, the average pore size of the macroporous structure of the support was 14 μm, the average pore size of the microporous structure of the precision control layer was 2.2 μm, the wall thickness of the support was 2.4 mm, the thickness of the precision control layer was 21 μm, and there was absolutely no particle permeation between the precision control layer and the macroporous support, with a permeation flux of 72 m³ / s. 3 / m 2 The permeability is ·kPa·h, meeting the petrochemical industry's demand for tubular stainless steel filter elements; additionally, porous elements prepared using the same metal powder as in this embodiment and conventional methods have a permeation flux of only 33m³. 3 / m 2With a permeation flux of ·kPa·h, the tubular gradient porous metal element prepared in this embodiment achieves 2.1 times that of the traditional method under the same filtration accuracy conditions.

[0090] In this embodiment, the material of the hard outer mold can also be a high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide.

[0091] Example 7

[0092] This embodiment includes the following steps:

[0093] Step 1: Design and process the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve; the rigid outer mold is made of heat-resistant steel, and the surface roughness of the inner wall is Ra = 1.2 μm;

[0094] Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, fill the cavity formed by the assembly of the rigid outer mold and the inner mold with metal powder from the top. Then, under vibration, allow the metal powder to completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed. The metal powder is H59 copper alloy powder with a mesh size of -60 to +100.

[0095] Step 3: Using cold isostatic pressing, the part to be formed obtained in step 2 is pressed under a pressure of 100MPa and a time of 90s. After pressing, the lower positioning seal, the upper positioning seal and the inner mold are removed in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold.

[0096] Step 4: The tubular porous support blank obtained in Step 3, which is attached to the inner wall of the rigid outer mold, is subjected to a high-temperature sintering at a temperature of 1100℃ for 140 minutes. Then the rigid outer mold is removed to obtain the finished support.

[0097] Step 5: Using wet powder spraying, fine metal powder with an average particle size of 15μm is uniformly coated onto the surface of the finished support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is carried out at a temperature of 900℃ for 30 minutes to obtain a tubular gradient porous metal element with high permeability. The fine metal powder is H59 copper alloy powder.

[0098] Testing revealed that the surface roughness of the support in the tubular gradient porous metal element prepared in this embodiment was 3.6 μm, the average pore size of the macroporous structure of the support was 16 μm, the average pore size of the microporous structure of the precision control layer was 2.1 μm, the wall thickness of the support was 2.4 mm, the thickness of the precision control layer was 20 μm, and there was absolutely no particle permeation between the precision control layer and the macroporous support, with a permeation flux of 82 m³ / s. 3 / m 2 The permeability is 39 mPa·h, meeting the petrochemical industry's demand for tubular stainless steel filter elements; additionally, porous elements prepared using the same metal powder as in this embodiment and conventional methods have a permeability of only 39 mPa·h. 3 / m 2 With a permeation flux of ·kPa·h, the tubular gradient porous metal element prepared in this embodiment achieves 2.1 times that of the traditional method under the same filtration accuracy conditions.

[0099] In this embodiment, the material of the hard outer mold can also be a high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide.

[0100] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the technical essence of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A high-permeability tubular gradient porous metal element, characterized in that, The porous metal element includes a tubular support with a large pore structure and a precision control layer with a small pore structure covering the support. The surface roughness Ra of the support is ≤8μm, and there is no particle penetration between the precision control layer and the support.

2. The high-permeability tubular gradient porous metal element according to claim 1, characterized in that, The porous metal element is made of stainless steel, nickel-based alloy, titanium, titanium alloy, or copper alloy.

3. The high-permeability tubular gradient porous metal element according to claim 1, characterized in that, The wall thickness of the support is 2mm to 3mm, and the thickness of the precision control layer is no more than 30μm.

4. The high-permeability tubular gradient porous metal element according to claim 1, characterized in that, The average pore size of the large pore structure is 10μm to 30μm, and the average pore size of the small pore structure is no greater than 3μm.

5. A method for preparing a high-permeability tubular gradient porous metal element as described in any one of claims 1 to 4, characterized in that, The method includes the following steps: Step 1: Design and process the mold; the mold includes a rigid outer mold, an inner mold, and a lower positioning seal and an upper positioning seal to seal the gap formed between the rigid outer mold and the inner mold; the inner mold consists of an inner steel sleeve and a soft mold that precisely fits the outer surface of the inner steel sleeve; Step 2: Insert the inner mold from the mold designed and processed in Step 1 into the rigid outer mold, then fix the lower positioning seal. Next, put the metal powder into the cavity formed by the assembly of the rigid outer mold and the inner mold from the top. Then, under vibration, make the metal powder completely fill the entire cavity. Finally, fix the upper positioning seal to obtain the part to be formed. Step 3: Use cold isostatic pressing to press the part to be formed obtained in step 2. After pressing, remove the lower positioning seal, the upper positioning seal and the inner mold in sequence to obtain a tubular porous support blank attached to the inner wall of the hard outer mold. Step 4: Perform a high-temperature sintering on the tubular porous support blank that is attached to the inner wall of the rigid outer mold obtained in Step 3, and then remove the rigid outer mold to obtain the finished support. Step 5: Using wet powder spraying, fine metal powder with an average particle size of no more than 20μm is uniformly coated onto the surface of the support obtained in Step 4 to form a precision control layer. Then, a second high-temperature sintering is performed to obtain a tubular gradient porous metal element with high permeability.

6. The method according to claim 5, characterized in that, The material of the hard outer mold mentioned in step one is heat-resistant steel, high-temperature alloy, molybdenum or molybdenum alloy, alumina, zirconium oxide or silicon oxide, and the surface roughness Ra of the inner wall is ≤1.6μm.

7. The method according to claim 5, characterized in that, The pressing pressure in step three is 80MPa~200MPa, and the time is 30s~120s.

8. The method according to claim 5, characterized in that, The temperature for the first high-temperature sintering in step four is 950℃~1350℃, and the time is 60min~180min.

9. The method according to claim 5, characterized in that, The secondary high-temperature sintering in step five is performed at a temperature of 900℃~1200℃ for 30min~60min.

10. The method according to claim 5, characterized in that, The permeability flux of the high-permeability tubular gradient porous metal element mentioned in step five is not less than 50m. 3 / m 2 ·kPa·h.

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