Method for improving damping loss factor of high damping structure stainless steel fiber sintered body

Abstract

The application discloses a method for improving the damping loss factor of high-damping structure stainless steel fiber sintered body, which comprises the following steps: adding lubricating oil on the outer surface of the high-damping structure stainless steel fiber sintered body. In the test process, the wire diameter of the stainless steel fiber, the porosity of the sintered body and the added amount of the lubricating oil are controlled, the relative movement between the fibers is improved, and then the damping loss factor of the stainless steel felt is improved.

Description

Technical Field

[0001] This invention belongs to the field of stainless steel fiber technology, and particularly relates to a method for improving the damping loss factor of high-damping stainless steel fiber sintered bodies. Background Technology

[0002] Currently, commonly used damping and vibration reduction materials are polymer rubbers. They possess advantages such as a large damping loss factor, excellent vibration reduction effect, and wide application range. However, their disadvantages include difficulty in application under harsh conditions, such as high temperature, high pressure, oil contamination, sunlight, and susceptibility to aging under prolonged use. The vibration reduction mechanism of polymer rubber is that when the rubber is subjected to external cyclic loads, the deformation of the long polymer chains and the friction between the molecular chains generate heat, consuming energy and thus achieving damping and vibration reduction. Synthesized rubber cannot be further modified; that is, once the rubber is synthesized, the damping is determined. Therefore, rubber modification is achieved through formulation, synthesis process, and curing process.

[0003] Currently, metal rubber is a type of spring-like vibration damping material with damping properties. It is prepared by hand-weaving and molding fine metal spring filaments into an elastic, porous material. It is a complex spring structure with advantages such as high load-bearing capacity, impact resistance, and corrosion resistance, making it suitable for high-pressure working environments. The damping energy dissipation mechanism of metal rubber involves dry friction between the metal filaments after being subjected to force, converting energy into frictional heat and dissipating it. Metal rubber is typically prepared using millimeter-sized fine metal spring filaments. Due to the relatively large filament diameter (usually in the millimeter range) and small specific surface area, the frictional energy dissipation between the metal filaments is much higher than that of a single spring, but its damping is still relatively low, incomparable to that of rubber. Furthermore, the processing involves hand-weaving and cold molding, thus the consistency of metal rubber product quality urgently needs to be addressed.

[0004] Based on the energy dissipation mechanism of friction, materials with high-friction structures, i.e., high-damping materials, can be designed and fabricated. In fibrous porous materials, a large number of interwoven fibers exist, providing the possibility for friction between them. When a fibrous porous material is subjected to external forces, such as vibration, friction between the fibers can occur, thereby converting energy into heat and dissipating it. Due to the large fiber content, the energy dissipation is significant; therefore, this structure containing a large number of fibers is a high-damping structure. To be a vibration damping material, it must not only possess damping characteristics but also a certain compressive strength to dissipate energy under vibration. Therefore, selecting fibers with excellent properties is crucial.

[0005] Stainless steel fiber has the characteristics of high strength, wear resistance and bending resistance. It can maintain its original performance even in oxygen environment with high temperature of 400-500℃ for a long time. It is completely resistant to acids, alkalis and organic solvents and can be used for a long time in harsh environments. It is a type of fiber material with excellent performance.

[0006] Stainless steel fibers are typically micron-sized fibers. They offer a huge specific surface area, forming high-damping structures. In contrast, general non-metallic fibers have poor load-bearing capacity and are unsuitable as vibration damping materials. Metal spring wires used in metal rubber typically have millimeter-sized diameters, providing a smaller specific surface area and failing to achieve high-friction, i.e., high-damping structures. Stainless steel fibers can be processed through molding, sintering, and other processes to produce products with stable properties, ensuring performance in practical applications. Currently, among numerous fiber materials, stainless steel fiber is the preferred choice.

[0007] However, during the sintering process, stainless steel felt forms sintering joints, where fibers are linked together. While these joints increase the strength of the sintered body, they reduce the relative movement between fibers, decreasing friction and thus reducing damping performance. The number of sintering joints is generally controlled by adjusting the sintering temperature and time, but the effect of locally excessively high temperatures during sintering cannot be completely avoided; therefore, sintering joints are unavoidable. Furthermore, the interlocking and overlapping of fibers also cause localized overall movement in the stainless steel fiber felt sintered body (hereinafter referred to as SFB), further reducing inter-fiber friction and damping. Even under conditions where strict control of sintering temperature and time is necessary to ensure strength, sintering joints are still unavoidable. Therefore, it is urgent to find other methods to improve damping performance. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention proposes a method for improving the damping loss factor of high-damping stainless steel fiber sintered bodies. By adding a lubricant to the stainless steel fiber felt sintered body, the relative motion between fibers is improved, thereby increasing the damping loss factor of the stainless steel felt.

[0009] This invention breaks through the previous view that improvements could only be made to the product manufacturing process. Research on the sintered SFB (Stainless Steel Fiber) product reveals that the friction between the fibers can be further improved after sintering, enhancing damping performance and thus improving the vibration reduction performance of SFB. This is because, due to its high-damping internal structure, when external vibration energy is transmitted into the stainless steel felt, dry friction between the stainless steel fibers occurs, converting the vibration energy into heat energy for dissipation. Simultaneously, high-temperature sintering yields a high-strength sintered body capable of withstanding heavy loads, broadening its application range. By improving the friction between the metal fibers, the damping loss factor of the stainless steel fiber felt is increased, further enhancing the damping performance of SFB. This invention provides a core material for the production of high-performance vibration dampers.

[0010] SFB (Stainless Steel Fiber) is typically prepared using a molding and sintering method. This involves laying, pressing, sintering, and shaping stainless steel fibers to obtain the sintered stainless steel fiber body (SFB). Its microstructure consists of interwoven metal fibers with a large internal surface area, forming a high-damping structure. When subjected to load, the friction between the fibers is very strong, creating a high-friction structure. The heat generated by friction is dissipated as heat, converting mechanical energy into damping; therefore, SFB possesses high damping performance.

[0011] Previous understanding of overcoming frictional damping typically involved increasing pressure or surface roughness to improve damping, neglecting relative motion. In reality, frictional damping only occurs when relative motion is present. For SFB structures, without relative motion, there can be no inter-fiber friction to dissipate energy, thus preventing damping. Only when relative motion exists between the fibers can friction occur, resulting in damping. This invention overcomes this previous bias by adding a lubricant to increase relative motion, thereby enhancing the damping effect.

[0012] To achieve the above objectives, the present invention provides the following technical solution:

[0013] A method for improving the damping loss factor of a high-damping stainless steel fiber sintered body is provided by dripping lubricating oil onto the outer surface of the high-damping stainless steel fiber sintered body.

[0014] Furthermore, the porosity of the high-damping stainless steel fiber sintered body is 40-95%. Porosity is a key parameter controlling compressive strength; the higher the porosity, the lower the compressive strength, and vice versa. Therefore, based on the needs, the actual compressive strength requirements should be met first, and then a smaller stainless steel fiber diameter should be selected; that is, the smaller the diameter, the greater the damping. This invention requires high compressive strength for the SFB (sulfuric acid fiber sintered body). For example, if it can be used in water depths of 1000m and in underwater vehicles, a compressive strength of 10MPa is required, and a porosity of less than 71% is sufficient to meet the compressive strength requirement. If even greater compressive strength is required, then a smaller porosity is needed. The higher the porosity, the larger the voids within the SFB, and the lower the compressive strength. Therefore, the porosity can be designed according to actual conditions. The higher the porosity, the fewer fibers per unit volume, the lower the probability of friction between fibers, and the lower the damping. Under the condition of meeting the compressive strength requirements, a smaller porosity should be selected as much as possible to ensure greater friction and obtain higher damping.

[0015] Furthermore, the stainless steel fibers used in the high-damping stainless steel fiber sintered body have a diameter of 3-100 micrometers. Because micrometer-sized fibers have a large specific surface area and a large frictional area between fibers, high damping is guaranteed. The smaller the stainless steel fiber diameter, the higher the price. Currently, the diameter of stainless steel fibers produced on a large scale can reach 3 micrometers. Based on cost considerations, this invention controls the stainless steel fiber diameter range to be above 3 micrometers, i.e., 3-100 micrometers.

[0016] Furthermore, due to the high porosity of SFB, which can reach over 95%, and the fact that most of SFB is void, it can accommodate a large amount of other media, thus fulfilling the prerequisite for adding lubricating oil. Therefore, this invention controls the amount of lubricating oil to be 20-100% of the pore volume of the high-damping stainless steel fiber sintered body.

[0017] Furthermore, the lubricating oil includes No. 32, No. 150, and No. 320 lubricating oil. When using the lubricating oil, the dripping method is as follows: drip the lubricating oil onto the surface of the high-damping stainless steel fiber sintered body, and let it stand for 2-3 hours after the lubricating oil has completely penetrated.

[0018] Compared with the prior art, the present invention has the following advantages and technical effects:

[0019] Inside the sintered SFB, defects, dryness, and lack of lubrication appear on the fiber surface due to high temperature. This invention uses lubricating oil to treat the SFB, which can increase the lubrication force between the stainless steel fibers, causing the fibers to slip relative to each other under the action of force, increasing the friction between the fibers, thereby further improving the damping of the SFB and obtaining high-damping material properties. Attached Figure Description

[0020] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:

[0021] Figure 1 This is a schematic diagram of the structure of the stainless steel fiber sintered body (SFB) prepared in Example 1 of the present invention. Detailed Implementation

[0022] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0023] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0024] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0025] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0026] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0027] All raw materials used in the following embodiments of the present invention are commercially available.

[0028] In the following embodiments of the present invention, the stainless steel fibers used in the high-damping structure stainless steel fiber sintered body have a diameter of 3-100 micrometers, preferably 6 micrometers, and a fiber length of 20-40 mm.

[0029] The lubricating oil used in this invention can be of different grades, but for ease of addition, a lubricating oil with lower viscosity is generally selected. It can be evenly dripped onto the surface of the high-damping stainless steel fiber sintered body, and after complete penetration, left to stand for 2-3 hours until it is uniform before use. - In the following embodiments of this invention, a lubricating oil with lower viscosity, namely No. 32, No. 150, and No. 320 lubricating oil, is preferred.

[0030] The present invention controls the amount of lubricating oil to be 20-100% of the pore volume of the high-damping stainless steel fiber sintered body, preferably 20%, 30%, 60%, 90% or 100%.

[0031] The present invention controls the porosity of the high-damping stainless steel fiber sintered body to be 40-95%, preferably 65-75%, more preferably 65%, 70% or 75%.

[0032] The following embodiments are further illustrations of the technical solution of the present invention.

[0033] Example 1 – 65% porosity SFB + 60% volume of No. 150 lubricating oil

[0034] SFB short fibers with a diameter of 6μm and an average fiber length of 30mm were used as raw materials. The raw materials were randomly and uniformly laid, initially pressed (pressure 5±0.1MPa), and sintered at 1100±10℃ for 3±0.5h. After sintering, according to the porosity requirements, a second pressing was performed (pressure 16±0.1MPa) to obtain SFB samples with a porosity of 65% (compressive strength of 13.5MPa) and a thickness of 4.02mm.

[0035] The added lubricant was general-purpose No. 150 lubricant, and the amount added was 30% (volume percentage) of the SFB void volume. The loss factor of the SFB was tested before and after adding the lubricant. It was found that the SFB damping loss factor was 0.025 before adding the lubricant, and 0.0714 after adding the lubricant, which is an increase of 185.6% compared with the unlubricated state.

[0036] Figure 1 This is a schematic diagram of the stainless steel fiber sintered body (SFB) prepared in Example 1 of the present invention. As can be seen from the figure, the SFB has a porous fiber structure, with metal fibers interlaced and superimposed, and a large number of voids. When vibration excitation is transmitted to the SFB, energy is consumed through the mutual friction of the internal fibers, thereby playing a vibration damping role.

[0037] Example 2 – 70% porosity SFB + 30% by volume No. 320 lubricating oil

[0038] The preparation method of the SFB sample is the same as in Example 1, except that it is subjected to secondary pressing (pressure of 13±0.1MPa) to obtain an SFB sample with a porosity of 70% (compressive strength of 11.3MPa) and a thickness of 3.75mm.

[0039] The added lubricant was general-purpose No. 320 lubricant, and the amount added was 30% (volume percentage) of the SFB void volume. The loss factor of the SFB was tested before and after adding the lubricant. It was found that the SFB damping loss factor before adding the lubricant was 0.0492, and the SFB damping loss factor after adding the lubricant was 0.0748, which was 52.0% higher than before adding the lubricant.

[0040] Example 3 – 75% porosity SFB + 90% volume of No. 32 lubricating oil

[0041] The preparation method of the SFB sample is the same as in Example 1, except that the primary pressing (pressure of 3±0.1MPa) and secondary pressing (pressure of 6±0.1MPa) are used to obtain an SFB sample with a porosity of 75% (compressive strength of 4.4MPa) and a thickness of 3.44mm.

[0042] The added lubricant was general-purpose No. 32 lubricant, and the amount added was 90% (volume percentage) of the SFB void volume. The loss factor of the SFB was tested before and after adding the lubricant. It was found that the SFB damping loss factor was 0.0570 before adding the lubricant, and 0.0700 after adding the lubricant, which is 22.8% higher than before adding the lubricant.

[0043] Example 4 – 70% porosity SFB + 20% by volume No. 150 lubricating oil

[0044] The preparation method of the SFB sample is the same as in Example 1, except that it is subjected to secondary pressing (pressure of 13±0.1MPa) to obtain an SFB sample with a porosity of 70% (compressive strength of 11.3MPa) and a thickness of 3.75mm.

[0045] The added lubricant was general-purpose No. 150 lubricant, and the amount added was 20% (volume percentage) of the SFB void volume. The loss factor of the SFB was tested before and after adding the lubricant. It was found that the SFB damping loss factor before adding the lubricant was 0.0492, and the SFB damping loss factor after adding the lubricant was 0.0550, which was an increase of 11.8% compared with the unlubricated state.

[0046] Example 5 – 70% porosity SFB + 60% by volume No. 150 lubricating oil

[0047] The preparation method of the SFB sample is the same as in Example 1, except that it is subjected to secondary pressing (pressure of 13±0.1MPa) to obtain an SFB sample with a porosity of 70% (compressive strength of 11.3MPa) and a thickness of 3.75mm.

[0048] The added lubricant was general-purpose No. 150 lubricant, and the amount added was 60% (volume percentage) of the SFB void volume. The loss factor of the SFB was tested before and after adding the lubricant. It was found that the SFB damping loss factor was 0.0492 before adding the lubricant, and 0.0620 after adding the lubricant, which is 26.2% higher than before adding the lubricant.

[0049] Example 6 – 70% porosity SFB + 90% volume of No. 150 lubricating oil

[0050] The preparation method of the SFB sample is the same as in Example 1, except that it is subjected to secondary pressing (pressure of 13±0.1MPa) to obtain an SFB sample with a porosity of 70% (compressive strength of 11.3MPa) and a thickness of 3.75mm.

[0051] The added lubricant was general-purpose No. 150 lubricant, and the amount added was 70% (volume percentage) of the SFB void volume. The loss factor of the SFB was tested before and after adding the lubricant. It was found that the SFB damping loss factor before adding the lubricant was 0.0492, and the SFB damping loss factor after adding the lubricant was 0.0770, which was 56.5% higher than before adding the lubricant.

[0052] Example 7 – 70% porosity SFB + 100% volume of No. 150 lubricating oil

[0053] The preparation method of the SFB sample is the same as in Example 1, except that it is subjected to secondary pressing (pressure of 13±0.1MPa) to obtain an SFB sample with a porosity of 70% (compressive strength of 11.3MPa) and a thickness of 3.75mm.

[0054] The added lubricant was general-purpose No. 150 lubricant, and the amount added was 100% (volume percentage) of the SFB void volume. The loss factor of the SFB was tested before and after adding the lubricant. It was found that the SFB damping loss factor before adding the lubricant was 0.0492, and the SFB damping loss factor after adding the lubricant was 0.0740, which was 50.4% higher than before adding the lubricant.

[0055] In summary, the voids in the SFB structure provide space for adding lubricating oil, which effectively improves the relative movement between fibers in the SFB. Factors affecting SFB damping include porosity, fiber diameter, and the amount of lubricating oil added. Excessive porosity results in a smaller damping loss factor because a larger porosity means fewer fibers per unit volume, reducing friction. Conversely, insufficient porosity reduces the friction space between fibers, decreasing relative movement and thus damping. Therefore, there is an optimal porosity value. Porosity can be designed based on pressure requirements; for pressures greater than 10 MPa, the porosity should be less than 71%, allowing for designs with higher pressure resistance. The porosity used in this invention is selected within the range of 40-95%. Smaller stainless steel fiber diameters result in a larger damping loss factor because smaller diameters mean more fibers per unit volume, a larger specific surface area, increased dry friction, and thus increased friction loss. Fiber diameters can be selected from 3-100 micrometers. Thickness has little effect on the damping loss factor. Lubricants of varying viscosities, such as different grades of lubricating oil, can be used. As the principle suggests, adding lubricating oil to the porous structure of SFB can improve inter-fiber friction, reduce overall fiber movement, and thus increase inter-fiber friction. The amount of lubricating oil used is 20-100% by volume of the SFB pores.

[0056] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for improving the damping loss factor of high-damping stainless steel fiber sintered bodies, characterized in that, Lubricating oil was dripped onto the outer surface of the high-damping stainless steel fiber sintered body. The porosity of the high-damping stainless steel fiber sintered body is 40-95%. The diameter of the stainless steel fibers used in the high-damping stainless steel fiber sintered body is 3-100 micrometers. The amount of lubricating oil used is 20-100% of the pore volume of the high-damping stainless steel fiber sintered body. The lubricating oil type includes one of No. 32, No. 150 and No. 320; When using lubricating oil, the dripping method is as follows: drip the lubricating oil onto the surface of the high-damping stainless steel fiber sintered body, and let it stand for 2-3 hours after the lubricating oil has completely penetrated.

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