Preparation method of stainless steel fiber powder

Abstract

The invention belongs to the field of material preparation, and particularly relates to a preparation method of stainless steel fiber powder, which mainly utilizes the principle that after austenitic stainless steel is charged with hydrogen, dislocation rings appear, brittle hydrides are generated, hydrogen atoms permeate into stainless steel crystal lattices and gather in a stress concentration area, so that the toughness and ductility of the material are obviously reduced, and the material is easier to crush. The stainless steel fiber powder prepared by a novel process combining hydrotreating and ball milling is reasonably designed, the ultra-short stainless steel fiber powder with a specific length-diameter ratio can be prepared in a short time by optimizing the preparation process, the fiber length is 30-100 microns, the average length is 60 microns, and the diameter of the ultra-short stainless steel fiber powder is 10-20 microns. The specific fiber powder can be used for large-porosity precise porous sintering materials, metal film material functional additives, fiber reinforcement and electromagnetic radiation prevention, high-end precise 3D printing materials and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of materials, and particularly relates to a method for preparing stainless steel fiber powder. Background Art

[0002] Stainless steel fibers (typically with diameters ranging from 4μm to 1μm, with submicron sizes in the future) combine the fineness and flexibility of fibers with the high strength, high elastic modulus, excellent electrical and thermal conductivity, corrosion resistance, and wear resistance of metals, making them a new type of functional material. Currently, stainless steel fiber powder can be used in high-porosity precision porous sintered materials for filtration and separation, as well as for sound absorption and vibration reduction. It is also used in the semiconductor and biopharmaceutical industries, as a functional additive for metal membrane materials such as electromagnetic shielding and stealth coatings, and as an organic fiber additive. Fiber reinforcement also protects against electromagnetic radiation and eliminates static electricity. It is also used in high-end precision 3D printing materials. For example, stainless steel fiber, one of the most stable high-temperature dielectric materials, can be used as a filter medium by laying stainless steel powder with a certain aspect ratio into a felt and sintering it into a porous product. Due to its narrow pore diameter distribution, it offers high permeability, high humidity resistance, corrosion resistance, high dust-carrying capacity, and easy cleaning, making it suitable for filtering a variety of gases and liquids. Compared to traditional filter materials, stainless steel fiber exhibits outstanding corrosion resistance in harsh environments such as high temperatures and strong acids.

[0003] At present, the large-scale production of stainless steel fibers adopts the cutting method. The stainless steel fiber bundle is tensioned by a traction mechanism and continuously cut by a high-speed rotating cutting knife. However, due to equipment factors, the size of the prepared short fibers is limited, and the fiber length in the stainless steel fibers is difficult to reach below 100μm. At present, domestic mechanical cutting can usually cut stainless steel fibers to 3-6mm (some precision equipment can reach 1-2mm). However, the filtration effect of fibers of this length used as filter elements is poor. The smaller the length of the stainless steel fiber, for example, the filter element prepared from stainless steel fiber powder with a length of micron has advantages such as a more intricate network structure, a smaller effective pore size and gradient distribution, and a high specific surface area to enhance adsorption capacity, and has a better filtration effect. Filter elements prepared from stainless steel fiber powder are more likely to produce a large number of tortuous channels, forcing the fluid to detour in the filter element, increasing the chance of contact between pollutants and fibers, and significantly increasing the probability of particulate matter being physically intercepted, especially small particles are more difficult to "detour" through. The prior art has not yet disclosed a method for preparing stainless steel fiber powder with a micron length. Summary of the Invention

[0004] In view of this, the present invention discloses a method for preparing stainless steel fiber powder, the specific scheme is as follows:

[0005] The present invention discloses a method for preparing stainless steel fiber powder, which specifically comprises the following steps:

[0006] S1. Place the stainless steel long fiber into a hydrogenation furnace to hydrogenate the stainless steel long fiber;

[0007] S2. The hydrogenated stainless steel long fibers were cut using a cutting machine to a cutting length of 1-2 mm to obtain stainless steel fibers;

[0008] S3 using a dispersant to disperse the cut stainless steel fibers, and then the stainless steel fibers are washed and dried;

[0009] S4. The stainless steel fibers obtained in step S3 are placed in a planetary ball mill for ball milling to obtain stainless steel fiber powder.

[0010] As a supplement to the technical solution of the present invention, in step S1, the hydrogenation treatment of the stainless steel long fiber is specifically as follows: first, the stainless steel long fiber is placed in a hydrogenation furnace, and then the hydrogenation furnace is filled with hydrogen. Then the furnace temperature is raised from room temperature to 700°C-750°C at a heating rate of 3-5°C / min, the holding time is 0.5-1.5h, and the furnace is cooled; the hydrogen absorption pressure during the hydrogen absorption process is ensured to be 0.15-0.2MPa, and the hydrogen pressure in the furnace during cooling is: 0-0.05MPa. The solubility of hydrogen in metals generally increases with increasing pressure (following Sieverts' law), resulting in more hydrogen atoms entering the stainless steel lattice or defects. High pressure may promote the diffusion of hydrogen, especially at high temperatures, hydrogen atoms are more likely to migrate to grain boundaries, dislocations and other areas, exacerbating the local enrichment of hydrogen. The above process is based on the principle that a large number of dislocation loops and brittle hydrides appear after austenitic stainless steel is charged with hydrogen. This allows hydrogen atoms to penetrate the stainless steel lattice and accumulate in stress concentration areas, resulting in a significant decrease in the material's toughness and ductility, making it easier to crush during the subsequent ball milling process. However, when the hydrogen absorption pressure is less than 0.15MPa as specified in this application, the performance of the stainless steel fiber material will not change much, affecting the subsequent ball milling time. When the hydrogen absorption pressure is greater than 0.2MPa as specified in this application, there will be too many hydrogen atoms inside the stainless steel fiber, the material performance will deteriorate too much, and ball milling will aggravate the fiber powderization. Therefore, it is crucial to reasonably adjust the hydrogen absorption pressure.

[0011] Too high a temperature in the hydrogenation furnace will cause carbide precipitation, affecting the overall performance of the stainless steel long fiber. Too low a temperature will easily lead to poor hydrogen absorption effect. Therefore, within the temperature range of 700℃-750℃, it is possible to ensure that the technical effect of hydrogenation treatment is maximized without destroying the austenite phase.

[0012] Through the above process, the hydrogen atom concentration inside the stainless steel fiber is reduced to 10-20ppm, which greatly reduces the toughness of the stainless steel fiber and increases the brittleness of the stainless steel, enabling the subsequent ball milling treatment to achieve the best effect.

[0013] As a supplement to the technical solution of the present invention, in step S3, since the stainless steel fibers are slender (less than 10 microns in diameter), the fibers are easily entangled and adhered due to friction or electrostatic adsorption during cutting. Therefore, they must be separated by dispersion treatment after cutting to avoid fiber agglomeration and affect the subsequent ball milling effect. The specific dispersion treatment process is: sodium hexametaphosphate (NaPO3)6, polyethylene glycol (PEG) and polyvinyl alcohol (PVA) are weighed in a mass ratio of 4:2:1, and the three are thoroughly mixed to obtain a mixed powder. Subsequently, the mixed powder is dissolved in deionized water with a mass percentage of 3%-5%, placed on a magnetic stirrer, and stirred at a constant speed for 1 hour to obtain a uniformly dispersed dispersant solution. The cut stainless steel fibers are then placed in a dispersant solution and dispersed using ultrasonic vibration, and stirred with a stirrer at a speed of 60r / min for 1h, so that the stainless steel fibers are evenly dispersed. The present application uses a composite dispersant to achieve a synergistic effect. The dispersant contains a hydrophilic group that can reduce the surface tension of the liquid, making the fiber easier to wet. The fiber surfaces are charged with the same charge, preventing the fibers from approaching each other through Coulomb repulsion. Dispersant molecules adsorb on the fiber surface to form a lubricating layer, reducing the friction coefficient. At the same time, the synergistic effect of stirring and ultrasound can achieve better fiber dispersion.

[0014] Preferably, the polyethylene glycol is polyethylene glycol-4000. While solid at room temperature, polyethylene glycol-4000 has good water solubility, dissolving rapidly (better than PEG-6000) while avoiding the fluidity issues of liquid PEG, making it more suitable as a dispersant. Compared to low-molecular-weight PEG (such as PEG-400, which is highly hygroscopic), PEG-4000 is more stable and less prone to moisture absorption and agglomeration, facilitating storage and processing.

[0015] Preferably, the polyvinyl alcohol is polyvinyl alcohol-2488. Polyvinyl alcohol-2488 has a higher degree of polymerization (DP), resulting in better dispersion stability. The higher molecular weight (DP) of 2400 gives it a thicker steric barrier, effectively isolating particles and reducing aggregation. The 88% alcoholysis degree (partial alcoholysis) retains a certain amount of acetoxy groups, making it both hydrophilic and hydrophobic, allowing for faster dissolution in cold water and more efficient wetting of particle surfaces.

[0016] The dispersed stainless steel fibers are then rinsed and filtered under a filter screen to rinse the dispersant attached to the surface of the stainless steel fibers. The stainless steel fibers are then placed in deionized water and stirred for 10-15 minutes. The above process can be repeated multiple times, at least twice, to remove the dispersant attached to the surface of the stainless steel fibers.

[0017] The rinsed and filtered stainless steel fibers were then air-dried and placed in a blast drying oven. Hot air was blown out by a circulating fan to remove water from the fiber surface. The hot air temperature was 100° C. and the blowing was continued for 5 hours.

[0018] As a supplement to the technical solution of the present invention, in step S4, the ball milling process is specifically to place the dried stainless steel long fibers in a planetary ball mill and ball mill the cut fibers. The ball milling medium is paraffin wax, which can significantly reduce the direct collision ability of the steel balls and avoid the cold welding technical problem of the stainless steel fibers during the ball milling process. The air-dried stainless steel fibers are placed in the ball mill for ball milling at a speed of 180-210 r / min, a ball milling time of 0.5-1.5 hours, a ball-to-material ratio of 4:(1-2), and a ratio of 3:4:3 of large (diameter 115-125 mm), medium (diameter 75-85 mm), and small (diameter 35-45 mm) stainless steel balls in the ball mill. Finally, stainless steel short fibers with different aspect ratios are obtained. Under a specific ball-to-material ratio and speed, the grinding balls fall to form a "waterfall motion", and the impact and grinding work synergistically, resulting in the highest crushing efficiency, uniform particle size distribution, and moderate energy consumption. Stainless steel fiber powder with a length range of 30 μm to 100 μm can be produced.

[0019] The above-mentioned ball-to-material ratio is the optimal ratio. Under the condition of a certain hydrogen atom concentration in the stainless steel fiber, when the ball-to-material ratio is too large, it is easy to cause the stainless steel fiber powder to be completely broken and form a powdery structure. When the ball-to-material ratio is too small, it is easy to cause low ball milling efficiency. Under the above-mentioned ball-to-material ratio conditions, the rotation speed is set. When the rotation speed is lower than 180r / min, a "cascading motion" will be formed. When it is higher than 210r / min, centrifugal movement causes the grinding balls to rotate against the wall, and the impact and grinding effects are weakened. Under a specific ball-to-material ratio, rotation speed, and ball milling time, the stainless steel fiber is just crushed into fiber powder, avoiding insufficient fiber crushing due to short time, and the fiber will not be crushed into powder due to too long time.

[0020] Through the limitations of the above-mentioned ball milling process, the austenitic stainless steel fiber can realize the transformation of austenite to martensite under room temperature conditions through mechanical driving force during the ball milling process. Due to the combined effects of its body-centered cubic (BCC) structure, supersaturated solid solution of carbon, high-density dislocations and phase transformation stress, the hardness and strength of martensite will be improved, thereby improving the hardness and strength of the fiber powder.

[0021] As a preferred technical solution of the present invention, under the conditions of the above-mentioned ball milling process parameters, the ball milling speed is preferably 200-210 r / min, which can achieve an optimal proportion of martensite structure.

[0022] As a preferred technical solution of the present invention, it also includes step S5. ball milling medium removal treatment, placing the ball-milled stainless steel fibers in cyclohexane or carbon tetrachloride solution to remove paraffin, and then placing them in a blast drying oven for drying for 4-6 hours to obtain stainless steel fiber powder with a length of 30 to 100 μm.

[0023] As a preferred technical solution of the present invention, step S6 of dehydrogenation treatment is also included: the stainless steel fiber powder is placed in a box-type resistance furnace and heated to 300-400°C at a rate of 5°C / min for annealing for 2-3 hours in air to promote the diffusion and escape of hydrogen atoms. The removal of hydrogen restores the fiber powder's brittleness and improves its toughness.

[0024] Beneficial effects: The present invention overcomes the technical difficulty that the current cutting method cannot achieve the preparation of superconducting stainless steel fiber powder. Through ball milling treatment after hydrogenation, the large-scale production of stainless steel fiber powder can be achieved. The prepared stainless steel fiber powder has a length between 30μm and 100μm and can be widely used in large-porosity precision porous sintered materials, functional additives for metal film materials, organic fiber additives, fiber reinforcement and prevention of electromagnetic radiation, and high-end precision 3D printing materials, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a process flow chart for the preparation of stainless steel fiber powder.

[0026] Figure 2 (a) is a photo of the stainless steel fiber after cutting in Example 1.

[0027] Figure 2 (b) is the SEM image of the stainless steel long fiber powder after cutting in Example 1.

[0028] Figure 2 (c) is the XRD pattern of the stainless steel fiber after cutting in Example 1.

[0029] Figure 2 (d) Actual photo of the stainless steel fiber powder of Example 1.

[0030] Figure 2 (e) SEM image of the stainless steel fiber powder of Example 1.

[0031] Figure 2 (f) XRD pattern of stainless steel fiber powder in Example 1.

[0032] Figure 3 (a) is the SEM image of the surface scanning analysis of stainless steel fiber powder;

[0033] Figure 3 (b) Distribution of C atoms in the SEM image of the surface scanning analysis of stainless steel fiber powder.

[0034] Figure 3 (c) Distribution of Fe atoms in the SEM image of the surface scanning analysis of stainless steel fiber powder.

[0035] Figure 3(d) Distribution of Cr atoms in the SEM image of the surface scanning analysis of stainless steel fiber powder.

[0036] Figure 3 (e) S atom distribution in the SEM image of the surface scanning analysis of stainless steel fiber powder.

[0037] Figure 3 (f) is the distribution of Ni atoms in the SEM image of the surface scanning analysis of stainless steel fiber powder.

[0038] Figure 3 (g) is the distribution of Mn atoms in the SEM map of the surface scanning analysis of stainless steel fiber powder.

[0039] Figure 3 (h) is the distribution of Si atoms in the SEM image of the surface scanning analysis of stainless steel fiber powder.

[0040] Figure 3 (i) Distribution of Cu atoms in the SEM image of the surface scanning analysis of stainless steel fiber powder.

[0041] Figure 4 This is the XRD pattern of the stainless steel fiber powder prepared in Example 2 of the present application.

[0042] Figure 5 (a) SEM image of stainless steel fiber powder at low hydrogen absorption pressure;

[0043] Figure 5 (b) is the SEM image of stainless steel fiber powder at high hydrogen absorption pressure.

[0044] Figure 6 (a) is a photo of the dispersion effect of stainless steel fiber powder when PEG dispersant is used alone;

[0045] Figure 6 (b) is a photo of the dispersion effect of stainless steel fiber powder when using the patented composite dispersant.

[0046] Figure 7 (a) is the SEM image of the stainless steel fiber powder prepared in Comparative Example 4;

[0047] Figure 7 (b) is the SEM image of the stainless steel fiber powder prepared in Example 3;

[0048] Figure 7 (c) is the SEM image of the stainless steel fiber powder prepared in Example 1;

[0049] Figure 7 (d) is the SEM image of the stainless steel fiber powder prepared in Comparative Example 5. DETAILED DESCRIPTION

[0050] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0051] Example 1

[0052] S1. Hydrogenation of Stainless Steel Fibers: First, place a 4mm diameter stainless steel fiber in a hydrogenation furnace and fill it with hydrogen. The furnace temperature is then raised from room temperature to 700°C at a heating rate of 5°C / min, held for 0.5h, and cooled. The hydrogen absorption pressure is 0.15MPa, and the hydrogen pressure during cooling is 0.01MPa.

[0053] S2. Cutting of stainless steel long fibers: First, cut the hydrogenated stainless steel fibers on a cutting machine at a cutting speed of 400 times / min and a cutting length of 1-2 mm. Figure 2 (a) to Figure 2 As shown in (c), there is almost no martensite in the cut stainless steel long fiber.

[0054] S3. Dispersion of stainless steel fibers: Sodium hexametaphosphate (NaPO3)6, polyethylene glycol-4000 (PEG-400) and polyvinyl alcohol-2488 (PVA-2488) were weighed in a mass ratio of 4:2:1, and the three were thoroughly mixed to obtain a mixed powder. Subsequently, the mixed powder was dissolved in deionized water at a mass percentage of 3%, placed on a magnetic stirrer, and stirred at a constant speed for 1 hour to obtain a uniformly dispersed dispersant solution. The cut stainless steel fibers were then placed in the dispersant solution and dispersed using ultrasonic vibration, and stirred with a stirrer at a speed of 60r / min for 1 hour to uniformly disperse the stainless steel fibers.

[0055] The dispersed stainless steel fibers were rinsed and filtered under a filter sieve, and then the stainless steel fibers were placed in deionized water and stirred for 11 minutes. The above process can be repeated twice.

[0056] The rinsed and filtered stainless steel fibers were then air-dried and placed in a blast drying oven. Hot air was blown out by a circulating fan to remove water from the fiber surface. The hot air temperature was 100° C. and the blowing was continued for 5 hours.

[0057] S4. Ball Milling of Stainless Steel Fibers: Place the dried stainless steel fibers in a planetary ball mill and ball mill the cut fibers using paraffin wax as the milling medium. Mill the hydrogenated, 1-2 mm stainless steel fibers in the mill at a speed of 205 rpm for 60 minutes, using a ball-to-material ratio of 4:1. The ratio of large, medium, and small steel balls is 3:4:3, with the large ball diameter being 120 mm, the medium ball diameter being 80 mm, and the small ball diameter being 40 mm. This results in stainless steel short fibers with varying aspect ratios.

[0058] S5. Removal of ball milling media: The ball milled stainless steel fibers are placed in cyclohexane or carbon tetrachloride solution to remove paraffin wax, and then placed in a forced air drying oven for 4 hours to obtain stainless steel fiber powder with a certain aspect ratio.

[0059] The stainless steel fiber powder prepared by this method is mainly composed of Fe, Cr, Ni, Mn, Si and Mo. The elements are evenly distributed and no macro segregation phenomenon has been found. The proportions are the same as those of the original materials. Figure 3 (a) to Figure 3 As shown in (i), it shows that the stainless steel fiber powder prepared by this method has a uniform composition, which is a prerequisite for ensuring fiber performance.

[0060] S6. Dehydrogenation Treatment: The stainless steel fiber powder was placed in a box-type resistance furnace and heated to 350°C at a rate of 5°C / min for 2 hours in air to promote the diffusion and release of hydrogen atoms. After dehydrogenation, the stainless steel fiber powder was prepared into a filter element, and its tensile strength was tested, which was found to be 50 MPa.

[0061] like Figure 2 (d) to Figure 2 As shown in (f), the length of the ball-milled stainless steel fiber powder ranges from 30 to 100 μm, resulting in an aspect ratio between 7 and 25, and an average length of 60 μm. The stainless steel fiber powder is composed of a dual phase of martensite (FCC) and austenite (BCC). The surface of the fiber powder is relatively smooth, similar to the morphology of long fibers, but some small protrusions can be found on the surface of the fiber powder. These protrusions are caused by the combined effects of drawing, hydroannealing, and ball milling.

[0062] Example 2

[0063] S1. Hydrogenation of Stainless Steel Fibers: First, place a 4mm diameter stainless steel fiber in a hydrogenation furnace and fill it with hydrogen. The furnace temperature is then raised from room temperature to 700°C at a heating rate of 5°C / min, held for 0.5h, and cooled. The hydrogen absorption pressure is 0.16MPa, and the hydrogen pressure during cooling is 0.02MPa.

[0064] S2. Cutting of stainless steel long fibers: First, cut the hydrogenated stainless steel fibers on a cutting machine at a cutting speed of 400 times / min and a cutting length of 1-2 mm.

[0065] S3. Dispersion of stainless steel fibers: Sodium hexametaphosphate (NaPO3)6, polyethylene glycol-4000 (PEG-400) and polyvinyl alcohol-2488 (PVA-2488) were weighed in a mass ratio of 4:2:1, and the three were thoroughly mixed to obtain a mixed powder. Subsequently, the mixed powder was dissolved in deionized water at a mass percentage of 4%, placed on a magnetic stirrer, and stirred at a constant speed for 1 hour to obtain a uniformly dispersed dispersant solution. The cut stainless steel fibers were then placed in the dispersant solution and dispersed using ultrasonic vibration, and stirred with a stirrer at a speed of 60r / min for 1 hour to uniformly disperse the stainless steel fibers.

[0066] The dispersed stainless steel fibers were rinsed and filtered under a filter sieve, and then the stainless steel fibers were placed in deionized water and stirred for 12 minutes. The above process can be repeated twice.

[0067] The rinsed and filtered stainless steel fibers were then air-dried and placed in a blast drying oven. Hot air was blown out by a circulating fan to remove water from the fiber surface. The hot air temperature was 100° C. and the blowing was continued for 5 hours.

[0068] S4. Ball Milling of Stainless Steel Fibers: Place the dried stainless steel fibers in a planetary ball mill and mill the cut fibers using paraffin wax as the milling medium. Mill the hydrogenated, cut stainless steel fibers (1-2 mm in diameter) at a speed of 190 rpm for 60 minutes, using a ball-to-material ratio of 4:1. The ratio of large, medium, and small steel balls is 3:4:3, with the large ball diameter being 120 mm, the medium ball diameter being 80 mm, and the small ball diameter being 40 mm. This results in stainless steel short fibers with varying aspect ratios.

[0069] S5. Removal of ball milling media: The milled stainless steel fibers are placed in cyclohexane or carbon tetrachloride solution to remove paraffin wax, and then placed in a blast drying oven for drying for 4 hours. The final obtained stainless steel fiber powder has a certain aspect ratio. Compared with Example 1, the ball milling speed in this embodiment is lower, such as Figure 4 As shown in Figure 3, the martensite content is lower after ball milling.

[0070] S6. Dehydrogenation Treatment: Place the stainless steel fiber powder in a box-type resistance furnace and heat it to 350°C at a rate of 5°C / min for 2 hours in air to promote the diffusion and release of hydrogen atoms. After dehydrogenation, the stainless steel fiber powder is prepared into a filter element with a tensile strength of 50 MPa.

[0071] Example 3

[0072] S1. Hydrogenation of Stainless Steel Fibers: First, place a 4mm diameter stainless steel fiber in a hydrogenation furnace and fill it with hydrogen. The furnace temperature is then raised from room temperature to 700°C at a heating rate of 5°C / min, held for 0.5h, and cooled. The hydrogen absorption pressure is 0.2MPa, and the hydrogen pressure during cooling is 0.03MPa.

[0073] S2. Cutting of stainless steel long fibers: First, cut the hydrogenated stainless steel fibers on a cutting machine at a cutting speed of 400 times / min and a cutting length of 1-2 mm.

[0074] S3. Dispersion of stainless steel fibers: Sodium hexametaphosphate (NaPO3)6, polyethylene glycol-4000 (PEG) and polyvinyl alcohol-2488 (PVA) were weighed in a mass ratio of 4:2:1, and the three were thoroughly mixed to obtain a mixed powder. Subsequently, the mixed powder was dissolved in deionized water at a mass percentage of 5%, placed on a magnetic stirrer, and stirred at a constant speed for 1 hour to obtain a uniformly dispersed dispersant solution. The cut stainless steel fibers were then placed in the dispersant solution and dispersed using ultrasonic vibration, and stirred with a stirrer at a speed of 60r / min for 1 hour to uniformly disperse the stainless steel fibers.

[0075] The dispersed stainless steel fibers were rinsed and filtered under a filter sieve, and then the stainless steel fibers were placed in deionized water and stirred for 14 minutes. The above process can be repeated twice.

[0076] The rinsed and filtered stainless steel fibers were then air-dried and placed in a blast drying oven. Hot air was blown out by a circulating fan to remove water from the fiber surface. The hot air temperature was 100° C. and the blowing was continued for 5 hours.

[0077] S4. Ball Milling of Stainless Steel Fibers: Place the dried stainless steel fibers in a planetary ball mill and mill the cut fibers using paraffin wax as the milling medium. Mill the hydrogenated, cut stainless steel fibers (1-2 mm in diameter) at a speed of 210 rpm for 30 minutes, using a ball-to-material ratio of 4:1. The ratio of large, medium, and small steel balls is 3:4:3, with the large ball diameter being 120 mm, the medium ball diameter being 80 mm, and the small ball diameter being 40 mm. This results in stainless steel short fibers with varying aspect ratios.

[0078] S5. Removal of ball milling media: The ball milled stainless steel fibers are placed in cyclohexane or carbon tetrachloride solution to remove paraffin wax, and then placed in a forced air drying oven for 4 hours to obtain stainless steel fiber powder with a certain aspect ratio.

[0079] S6. Dehydrogenation treatment: Place the stainless fiber powder in a box-type resistance furnace and heat it to 350℃ at a rate of 5℃ / min for annealing for 2 hours in air to promote the diffusion and escape of hydrogen atoms. After dehydrogenation, the stainless fiber powder is prepared into a filter element with a tensile strength of 50MPa.

[0080] Comparative Example 1

[0081] The difference between this comparative example and implementation 1 is only in step S1.

[0082] S1. Hydrogenation of Stainless Steel Fibers: First, place a 4mm diameter stainless steel fiber in a hydrogenation furnace and fill it with hydrogen. The furnace temperature is then raised from room temperature to 700°C at a heating rate of 5°C / min, held for 0.5h, and cooled. The hydrogen pressure is 0.05MPa, and the hydrogen pressure during cooling is 0.01MPa.

[0083] like Figure 5 (a) shows the stainless steel fiber powder prepared in the comparative example. The stainless steel fiber prepared in this comparative example has a hydrogen atom concentration of about 7-8 ppm due to hydrogenation treatment, which directly affects the ball milling treatment, resulting in the stainless steel fiber powder after ball milling not being completely broken.

[0084] Comparative Example 2

[0085] The difference between this comparative example and implementation 1 is only in step S1.

[0086] S1. Hydrogenation of Stainless Steel Fibers: First, place a 4mm diameter stainless steel fiber in a hydrogenation furnace and fill it with hydrogen. The furnace temperature is then raised from room temperature to 700°C at a heating rate of 5°C / min, held for 0.5h, and cooled. The hydrogen pressure is 0.5MPa, and the hydrogen pressure during cooling is 0.01MPa.

[0087] like Figure 5 (b) shows the stainless steel fiber powder prepared in the comparative example. The stainless steel prepared in this comparative example has a hydrogen atom content of 30 ppm due to hydrogenation treatment, which directly affects the ball milling process, resulting in the stainless steel fiber powder being in powder form after ball milling.

[0088] Comparative Example 3

[0089] The difference between this comparative example and implementation 1 is only in step S3.

[0090] S3. Dispersion of stainless steel fibers: The stainless steel fibers cut in step S2 were placed in a simple 3% PEG solution, placed on a magnetic stirrer, and stirred at a constant speed for 1 hour to obtain a uniformly dispersed dispersant solution. The cut stainless steel fibers were then placed in the dispersant solution and dispersed using ultrasonic vibration, and stirred with a stirrer at a speed of 60 r / min for 1 hour. The dispersion effect was poor and agglomeration occurred. The comparison diagram of the dispersion treatment of this comparative example and Example 1 is shown in FIG. Figure 6 As shown, Figure 6 (a) is the stainless steel fiber after dispersion treatment in this comparative example, and it can be clearly seen that there is agglomeration problem. Figure 6 (b) shows the stainless steel fibers after dispersion treatment in Example 1. It can be clearly seen that the fibers are evenly dispersed without agglomeration.

[0091] Comparative Example 4

[0092] The difference between this comparative example and implementation 1 is that the only difference is that step S4

[0093] S4. Ball Milling of Stainless Steel Fibers: Place the dried stainless steel fibers in a planetary ball mill and ball mill the cut fibers using paraffin wax as the milling medium. Mill the hydrogenated, 1-2 mm stainless steel fibers at a speed of 210 rpm for 20 minutes, using a 4:1 ball-to-material ratio and a 3:4:3 ratio of large, medium, and small steel balls to obtain stainless steel short fibers with varying aspect ratios.

[0094] Comparative Example 5

[0095] The difference between this comparative example and implementation 1 is that the only difference is that step S4

[0096] S4. Ball Milling of Stainless Steel Fibers: Place the dried stainless steel fibers in a planetary ball mill and mill the cut fibers using paraffin wax as the milling medium. Mill the hydrogenated, 1-2 mm stainless steel fibers in the mill at a speed of 210 rpm for 120 minutes, using a ball-to-material ratio of 4:1 and a ratio of large, medium, and small steel balls of 3:4:3. Stainless steel short fibers with varying aspect ratios are obtained.

[0097] Combined with Example 1, Example 2, Comparative Example 4 and Comparative Example 5, the length and morphology of the stainless steel fiber powder are affected by the ball milling time. Figure 7 (a) is the SEM image of the stainless steel fiber powder prepared in Comparative Example 4, Figure 7 (b) is the SEM image of the stainless steel fiber powder prepared in Example 1, Figure 7 (c) is the SEM image of the stainless steel fiber powder prepared in Example 3. Figure 7(d) is an SEM image of the stainless steel fiber powder prepared in Comparative Example 4. It can be seen that the stainless steel fibers prepared with milling times between 30 and 60 minutes have relatively good length and morphology, meeting the requirements for fiber powder. At 20 minutes, the majority of the fibers are well over 150 μm in length. At 120 minutes, most of the fibers have become powdered, and some have become flattened.

[0098] Comparative Example 6

[0099] The difference between this comparative example and implementation 1 is that step S6, dehydrogenation treatment, is not performed.

[0100] The stainless steel fiber powder after ball milling is directly prepared into a filter element, and its tensile strength is 31MPa.

[0101] The performance comparison of the stainless steel fiber powder prepared in Examples 1-3 and Comparative Examples 1-6 is shown in the following table:

[0102] Table 1. Comparison of stainless steel fiber powder performance under different processes

[0103]

[0104] It can be clearly seen from the above table that the martensite content of the stainless steel fiber powder in Example 2 is lower than that in Example 1, resulting in a decrease in the strength of the final stainless steel fiber powder.

[0105] Since there is no final dehydrogenation treatment in Example 6, the strength of the filter element prepared therefrom is significantly lower.

[0106] The above description is only a preferred specific implementation method of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing stainless steel fiber powder, characterized in that: The following steps are involved: S1. Place the stainless steel long fiber into a hydrogenation furnace to hydrogenate the stainless steel long fiber; S2. The hydrogenated stainless steel long fibers were cut using a cutting machine to a cutting length of 1-2 mm to obtain stainless steel fibers; S3 using a dispersant to disperse the cut stainless steel fibers, and then the stainless steel fibers are washed and dried; S4. The stainless steel fibers obtained in step S3 are placed in a planetary ball mill for ball milling to obtain stainless steel fiber powder.

2. The method for preparing stainless steel fiber powder according to claim 1, characterized in that: The hydrogenation treatment in step S1 is specifically as follows: placing the stainless steel long fiber into a hydrogenation furnace, then filling the hydrogenation furnace with hydrogen, heating the furnace temperature from room temperature to 700°C-750°C at a heating rate of 5°C / min, holding the temperature for 0.5-1.5h, and finally cooling the furnace; the pressure in the furnace during the heating and holding stages is 0.15-0.2MPa, and the pressure in the furnace during the cooling stage is 0-0.05MPa.

3. The method for preparing stainless steel fiber powder according to claim 1, characterized in that: In step S3, the dispersant is an aqueous solution prepared by dissolving sodium hexametaphosphate, polyethylene glycol, and polyvinyl alcohol in water at a mass percentage of 3%-5%, and the mass ratio of sodium hexametaphosphate, polyethylene glycol, and polyvinyl alcohol in the dispersant is 4:2:1; The polyethylene glycol is specifically polyethylene glycol-4000, and the polyvinyl alcohol is specifically polyvinyl alcohol-2488.

4. The method for preparing stainless steel fiber powder according to claim 1, wherein: In step S3, the dispersion treatment is specifically to place the cut stainless steel fibers into a dispersant, perform ultrasonic vibration, and stir with a stirrer at a rotation speed of 60 r / min for 1 hour.

5. The method for preparing stainless steel fiber powder according to claim 3, characterized in that: In step S3, the stainless steel fiber is cleaned by placing the stainless steel fiber on a filter screen and rinsing the dispersant attached to the surface of the stainless steel fiber. The stainless steel fiber is then placed in deionized water and stirred for 10-15 minutes. The above rinsing and stirring steps are performed at least twice.

6. The method for preparing stainless steel fiber powder according to claim 3, characterized in that: In step S3, the stainless steel fiber is dried as follows: the washed and filtered stainless steel fiber is placed in a blast drying oven, and hot air is blown out by a circulating fan to remove water from the fiber surface. The hot air blown out by the circulating fan has a temperature of 100° C. and is blown continuously for 5 hours.

7. The method for preparing stainless steel fiber powder according to claim 1, characterized in that: In step S4, the ball milling treatment is specifically as follows: the stainless steel fiber is placed in a ball mill for ball milling at a rotation speed of 180-210 r / min, a ball milling time of 0.5-1.5 h, a ball-to-material ratio of 4:(1-2), and the ratio of large, medium and small steel balls in the ball mill is 3:4:

3.

8. The method for preparing stainless steel fiber powder according to claim 7, characterized in that: The ball mill has a rotation speed of 200-210 r / min.

9. The method for preparing stainless steel fiber powder according to claim 7, characterized in that: In the step S4, the ball milling medium is paraffin wax; and the step S5 is further included. The stainless steel fiber powder obtained by ball milling is placed in cyclohexane or carbon tetrachloride solution to remove the paraffin wax, and then placed in a blast drying oven for drying for 4-6 hours.

10. The method for preparing stainless steel fiber powder according to claim 9, characterized in that: The method further includes step S6. placing the stainless steel fiber powder into a box-type resistance furnace, heating the powder to 300-400° C. at a rate of 5° C. / min for annealing, the annealing time being 2-3 hours, and the medium being air.

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