Composite film, preparation method of composite film and flow controller

Abstract

The invention discloses a composite film, a preparation method of the composite film and a flow controller. The composite film is used for the feedback type flow controller and comprises a first film layer and a second film layer. In the thickness direction of the composite film, the first film layer comprises a first surface and a second surface which are oppositely arranged; the second thin film layers are laid on the first surface and the second surface; wherein the thermal expansion coefficient of the second thin film layer is smaller than that of the first thin film layer. According to the composite film, the preparation method of the composite film and the flow controller, at least the problem that in the prior art, a film on the flow controller is prone to deformation due to temperature change, and therefore normal operation and control precision of the flow controller are affected can be solved.

Description

Technical Field

[0001] The present invention relates to the technical field of precision transmission, and in particular to a composite film, a method for preparing the composite film, and a flow controller. Background Art

[0002] As the key control part of the liquid hydrostatic system, the composite film feedback flow controller plays a vital role in the operation of the system. Its main function is to accurately distribute the flow to the corresponding oil cavity according to the load condition of the support end. This process requires the flow controller to have a high degree of sensitivity to obtain the change information of the load on the support end in real time and accurately. The composite film feedback flow controller obtains the pressure data of the oil cavity through a complex and precise control mechanism, so as to scientifically and reasonably distribute the oil cavity flow, thereby ensuring that the liquid hydrostatic system maintains stable and efficient operation under different working conditions.

[0003] The flow controller is a precision control element. The diameter and thickness of the composite film directly determine its deformation and elastic properties under a specific pressure, which in turn affects the accuracy of flow control. Therefore, the diameter and thickness of the metal composite film are strictly required. In the prior art, the metal composite film of the flow controller is basically made of a single layer and a single material, which is greatly affected by temperature changes; this may cause the metal composite film to change due to temperature. Even under the same pressure, its deformation will be different from that at normal temperature, thereby affecting the normal operation of the flow controller and reducing the control accuracy of the flow controller. Summary of the invention

[0004] The main purpose of the present invention is to provide a composite film, a method for preparing the composite film and a flow controller, at least to solve the problem in the prior art that the film on the flow controller is easily deformed due to temperature changes, thereby affecting the normal operation and control accuracy of the flow controller.

[0005] According to one aspect of the present invention, there is provided a composite film, the composite film being used for a feedback flow controller, the composite film comprising:

[0006] A first film layer, along the thickness direction of the composite film, the first film layer comprising a first surface and a second surface arranged opposite to each other;

[0007] A second film layer, the first surface and the second surface are both covered with the second film layer;

[0008] Wherein, the thermal expansion coefficient of the second film layer is smaller than the thermal expansion coefficient of the first film layer.

[0009] Furthermore, the thickness of the composite film is [0.5, 1.0] mm, wherein the thickness of the first film layer is [0.2, 0.3] mm, and the thickness of the second film layer is [0.15, 0.2] mm.

[0010] Furthermore, the first film layer includes a stainless steel layer, and the second film layer includes an Invar layer.

[0011] Furthermore, the thermal expansion coefficient of the first film layer is [16,20]×10 -6 / ℃, the thermal expansion coefficient of the second film layer is [-0.1,2.0]×10 -6 / ℃.

[0012] Furthermore, the elastic modulus of the first film layer is [190, 196] GPa, and the elastic modulus of the second film layer is [130, 150] GPa.

[0013] Furthermore, the Poisson's ratio of the first film layer is [0.29, 0.31], and the Poisson's ratio of the second film layer is [0.27, 0.29].

[0014] According to another aspect of the present invention, a method for preparing a composite film is further provided. The method for preparing a composite film is used to prepare the composite film as claimed in claim 1, and the method for preparing a composite film comprises:

[0015] Step S1: preparing the second film layer and the first film layer with a specified thickness by a rolling process, and then performing surface treatment on the second film layer and the first film layer to remove oxide scale and oil stains on the surfaces of the second film layer and the first film layer;

[0016] Step S2: stacking the second film layer, the first film layer and the second film layer in sequence to form a composite film assembly, heating the composite film assembly to a predetermined temperature under a predetermined pressure, and welding the second film layer, the first film layer and the second film layer to form a composite film body;

[0017] Step S3: heat treating the composite film body to remove residual stress of the composite film body;

[0018] Step S4: mechanically processing the heat-treated composite film body to process the composite film body into the composite film that meets the design requirements;

[0019] Step S5: cleaning and inspecting the composite film to remove debris and oil stains on the surface of the composite film, and inspecting the quality of the composite film.

[0020] Furthermore, in the step S2, diffusion welding is used to weld the thin film assembly.

[0021] Further, in step S2, the predetermined pressure is [4,6] MPa; and / or the temperature is

[0022] [895,905]℃.

[0023] According to another aspect of the present invention, a flow controller is provided. The flow controller comprises the composite film mentioned above or the composite film prepared by the composite film preparation method mentioned above.

[0024] In the present invention, the second film layer is laid on the first surface and the second surface of the first film layer, and the thermal expansion coefficient of the second film layer is smaller than the thermal expansion coefficient of the first film layer. With such arrangement, after the composite film is installed in the body of the flow controller, the second film layer of the composite film is less affected by temperature than the single-layer, single-material metal film in the prior art, and the control accuracy of the flow controller can be improved. Specifically, under different temperature environments, the thermal expansion coefficient of the second film layer arranged on the opposite sides of the first film layer of the composite film is extremely low, so that the entire composite film can produce more stable deformation when subjected to the same pressure, thereby achieving more accurate control of the flow rate, and effectively reducing the flow control error caused by temperature changes. In addition, the composite film also ensures the normal operation of the flow controller. The composite film ensures that the deformation it undergoes is always within the allowable range, avoiding the problem of failure of the flow controller due to abnormal changes in the size of the composite film. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 It is a schematic diagram of the overall structure of the composite film disclosed in an embodiment of the present invention;

[0027] Figure 2 A schematic diagram of a composite film preparation method disclosed in an embodiment of the present invention;

[0028] Figure 3 The figure is a schematic diagram of the structure of a flow controller disclosed in an embodiment of the present invention.

[0029] The above drawings include the following reference numerals:

[0030] 10. Composite film; 101. First film layer; 102. Second film layer; 20. Flow controller; 201. Cover plate; 202. Sealing ring; 203. Main body. DETAILED DESCRIPTION

[0031] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0032] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0033] Unless otherwise specifically stated, the relative arrangement of the parts and steps described in these embodiments, numerical expressions and numerical values ​​do not limit the scope of the present invention. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, methods and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be regarded as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0034] As mentioned in the background technology, the metal film of the flow controller is basically made of a single layer and a single material, which is greatly affected by temperature changes; this may cause the metal film to change due to temperature, and even under the same pressure, its deformation will be different from that at normal temperature, thereby affecting the normal operation of the flow controller and reducing the control accuracy of the flow controller. The present application provides a composite film, which is made of a metal alloy of two materials, and the deformation of the composite film is small when the temperature changes, which is conducive to the normal operation of the flow controller and improves the control accuracy of the flow controller. The composite film of the present application will be introduced in detail in conjunction with the accompanying drawings.

[0035] like Figure 1As shown, according to an embodiment of the present application, a composite film 10 is provided. Specifically, the composite film 10 is used in a feedback flow controller, wherein the composite film 10 includes a first film layer 101 and a second film layer 102 .

[0036] In this embodiment, along the thickness direction of the composite film 10, the first film layer 101 includes a first surface and a second surface that are oppositely arranged, and the first surface and the second surface are both covered with a second film layer 102; wherein the thermal expansion coefficient of the second film layer 102 is smaller than the thermal expansion coefficient of the first film layer 101.

[0037] In the actual production process, the second film layer 102 is laid on the first surface and the second surface of the first film layer 101, and the thermal expansion coefficient of the second film layer 102 is less than the thermal expansion coefficient of the first film layer 101. In this way, after the composite film 10 is installed in the body 203 of the flow controller 20, the second film layer 102 of the composite film 10 is less affected by temperature than the single-layer, single-material metal film in the prior art, which can improve the control accuracy of the flow controller 20. Specifically, the thermal expansion coefficient of the second film layer 102 arranged on the opposite sides of the first film layer 101 of the composite film 10 is extremely low under different temperature environments, so that the entire composite film 10 can produce more stable deformation when subjected to the same pressure, thereby achieving more accurate control of the flow rate, and effectively reducing the flow control error caused by temperature changes. In addition, the composite film 10 also ensures the normal operation of the flow controller 20. The composite film 10 ensures that its deformation is always within the allowable range, avoiding the problem of failure of the flow controller 20 due to abnormal changes in the size of the composite film 10.

[0038] like Figure 1As shown, the thickness of the composite film 10 is [0.5, 1.0] mm. Exemplarily, the thickness of the composite film 10 can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 1.0 mm, etc. When the thickness of the composite film 10 is between 0.5 mm and 1.0 mm, the composite film 10 can be well installed in the flow controller 20 and improve the working efficiency. In addition, the composite film 10 in this thickness range can also balance the response speed and mechanical strength, which not only ensures a fast response, but also ensures that the composite film 10 is not easily damaged or deformed, thereby extending the service life of the composite film 10. In this embodiment, the thickness of the first film layer 101 is [0.2, 0.3] mm. Exemplarily, the thickness of the first film layer 101 can be 0.2 mm, 0.25 mm, 0.3 mm; the thickness of the second film layer 102 is [0.15, 0.2] mm. Exemplarily, the thickness of the second film layer 102 can be 0.15 mm, 0.2 mm, etc. In this embodiment, the thickness of the first film layer 101 is preferably 0.3 mm, and the thickness of the second film layer 102 is preferably 0.15 mm. In this configuration, since the elastic modulus of the second film layer 102 is smaller than that of the first film layer 101, the thickness of the second film layer 102 is set smaller than that of the first film layer 101, and after the first film layer 101 and the second film layer 102 are composited, the deformations generated between the first film layer 101 and the second film layer 102 are similar. At this time, the thickness of the composite film 10 is 0.6 mm, which can ensure that the composite film 10 can quickly improve the response speed without being easily deformed or damaged.

[0039] Furthermore, the first film layer 101 includes a stainless steel layer, and the second film layer 102 includes an Invar layer. The films in the prior art are single-layer and single-material, mostly stainless steel. In the present embodiment, the metal film sheet is obtained by laying Invar layers on both sides of the stainless steel layer and compounding them, which reduces the deformation of the composite film 10 caused by temperature changes. In the present embodiment, Invar is a special iron-nickel alloy with an extremely low thermal expansion coefficient and good mechanical properties. Compounding Invar and stainless steel combines the advantages of the two materials, which can further improve the control accuracy, response speed and stability of the flow controller 20.

[0040] Furthermore, the thermal expansion coefficient of the first film layer 101 is [16, 20]×10 -6 / ℃, the thermal expansion coefficient of the second film layer 102 is [-0.1, 2.0]×10 -6 / ℃. The film layer will change in size when the temperature changes, thus affecting the normal operation and control accuracy of the flow controller 20. When the thermal expansion coefficient of the film layer is low, the size of the film layer changes less when the temperature changes, which is conducive to maintaining a stable opening of the flow controller 20, thereby improving the accuracy of flow control; it is also conducive to maintaining the system stability and response speed of the flow controller 20; it is also conducive to extending the service life of the composite film 10, and vice versa. In the present application, the first film layer 101 is 304 stainless steel, and its thermal expansion coefficient under the influence of temperature can be 16×10 -6 / ℃、17×10 -6 / ℃、20×10 -6 / ℃, the first film layer 101 can maintain good stability at most temperatures; while the second film layer 102 is Invar, which has a very low thermal expansion coefficient, generally about 1.2×10 -6 / °C, the film layer can maintain high dimensional stability when the temperature changes, thereby improving the control accuracy of the flow controller 20. Therefore, the composite film 10 obtained by compounding Invar and stainless steel can effectively reduce the adverse effects of temperature changes on the composite film 10 and the flow controller 20.

[0041] Furthermore, the elastic modulus of the first film layer 101 is [190, 196] GPa, and the elastic modulus of the second film layer 102 is [130, 150] GPa. Exemplarily, the elastic modulus of the first film layer 101 may be 190 GPa, 192 GPa, 194 GPa, etc.; the elastic modulus of the second film layer 102 may be 130 GPa, 140 GPa, 150 GPa. In this embodiment, the elastic modulus of the composite film 10 affects the response speed of the composite film 10 in the flow controller 20, the mechanical stress of the composite film 10, and the temperature stability. The high elastic modulus of the first film layer 101 can ensure that the composite film 10 responds quickly when subjected to force, and improve the dynamic response speed of the composite film 10 in the flow controller 20. In this embodiment, after the first film layer 101 and the second film layer 102 are compounded, the elastic modulus of the composite film 10 is slightly lower than that of a single layer of stainless steel, but the low thermal expansion coefficient of the second film layer 102 can significantly improve the temperature stability of the composite film 10, thereby improving the comprehensive performance of the composite film 10 and reducing the deformation of the composite film 10 when the temperature changes.

[0042] Further, the Poisson's ratio of the first film layer 101 is [0.29, 0.31]. For example, the Poisson's ratio of the first film layer 101 can be 0.29, 0.30, 0.31, etc.; the Poisson's ratio of the second film layer 102 is [0.27, 0.29]. For example, the Poisson's ratio of the second film layer 102 can be 0.27, 0.28, 0.29, etc. In this embodiment, the Poisson's ratios of the first film layer 101 and the second film layer 102 are very close. By laying the second film layer 102 on the opposite sides of the first film layer 101 and compounding them, it is ensured that the response speed of the composite film 10 in the flow controller 20 remains basically unchanged, and the deformation of the composite film 10 under temperature changes is reduced, so that the flow controller 20 can control the flow change more accurately, and effectively reduce the flow control error caused by temperature.

[0043] In order to verify the technical effect of the composite film 10 of the present invention, the present invention provides the following specific embodiments and comparative examples:

[0044] Example 1

[0045] Invar layers were laid on opposite sides of the 304 stainless steel layer, and the film layers were composited using a diffusion welding process with an applied pressure of 5 MPa, a temperature of 900°C, and a holding time of 60 min to obtain a composite film 10. The composite film 10 was used to explore the effect of temperature changes on its deformation.

[0046] In this embodiment, no pressure is applied to the composite film 10, and the temperature varies in the range of 20°C to 40°C.

[0047] When the composite film 10 in this embodiment is used, the maximum deformation of the composite film 10 is 0.44 μm.

[0048] Example 2

[0049] The composite film 10 of Example 2 is the same as that of Example 1, except that, in this example, a pressure of 0.3 MPa is applied to the composite film 10 .

[0050] When the composite film 10 in this embodiment is used, the maximum deformation of the composite film 10 is 3 μm.

[0051] Example 3

[0052] The composite film 10 of Example 3 is the same as that of Example 2, except that in this example, the temperature variation range of the composite film 10 is 40° C. to 60° C.

[0053] When the composite film 10 in this embodiment is used, the maximum deformation of the composite film 10 is 2 μm.

[0054] Comparative Example 1

[0055] The temperature variation range and no pressure application in Comparative Example 1 are the same as those in Example 1, except that in this example, the film is a single layer of 304 stainless steel and does not need to be composited.

[0056] When the film in this embodiment is used, the maximum deformation of the film is 5 μm.

[0057] Comparative Example 2

[0058] The temperature variation range and applied pressure in Comparative Example 2 are the same as those in Example 2, except that in this example, the film is a single layer of 304 stainless steel.

[0059] When the film in this embodiment is used, the maximum deformation of the film is 11 μm.

[0060] Comparative Example 3

[0061] The temperature variation range and applied pressure in Comparative Example 3 are the same as those in Example 3, except that in this example, the film is a single layer of 304 stainless steel.

[0062] When the film in this embodiment is used, the maximum deformation of the film is 8 μm.

[0063] Table 1 obtained according to the above examples and comparative examples is as follows:

[0064] Serial number film Applied pressure (MPa) Temperature range (℃) Deformation(μm) Example 1 Composite film 0 20-40 0.44 Example 2 Composite film 0.3 20-40 3 Example 3 Composite film 0.3 40-60 2 Comparative Example 1 Single layer film 0 20-40 5 Comparative Example 2 Single layer film 0.3 20-40 11 Comparative Example 3 Single layer film 0.3 40-60 8

[0065] According to Table 1: By comparing Example 1 and Comparative Example 1, it can be known that when the composite film 10 and the single-layer 304 stainless steel film are not subjected to pressure, as the temperature changes, the deformation of the composite film 10 is smaller than that of the single-layer film.

[0066] By setting Example 1 and Comparative Example 1 and considering the effect of temperature change on the deformation of the film separately, the material selection of the film layer can be optimized, so that the most suitable material combination of the film layer can be selected to ensure that the film can maintain consistency under different temperature environments and extend the service life of the film.

[0067] By comparing Example 2 and Comparative Example 2, and Example 3 and Comparative Example 3, it can be seen that under the same pressure, as the temperature changes, the deformation of the composite film 10 is less than that of the single-layer 304 stainless steel film.

[0068] By comparing Example 2 and Example 3, and Comparative Example 2 and Comparative Example 3, it can be known that when the same pressure is applied to the composite film 10 and the single-layer film, as the temperature increases, the deformation of the composite film 10 is smaller than that of the single-layer film.

[0069] Specifically, the above situation occurs mainly because after the Invar layer is laid on the opposite sides of the 304 stainless steel layer, the composite film 10 has a high elastic modulus due to the characteristics of stainless steel, and Invar has an extremely low thermal expansion coefficient, which can significantly improve the temperature stability of the composite film 10. After the two are combined, the comprehensive performance of the composite film 10 is improved, so that under the same pressure, the deformation generated when affected by temperature is smaller than that of a single-layer, single-material film.

[0070] In summary, the present invention provides a second film layer 102 on both the first surface and the second surface of the composite film 10 which are arranged opposite to the first film layer 101, and the thermal expansion coefficient of the second film layer 102 is smaller than the thermal expansion coefficient of the first film layer 101. The influence of temperature change on the deformation of the composite film 10 is explored experimentally, and the experimental data is analyzed. The experimental results show that: in the case of no pressure, within the same temperature change range, the deformation of the composite film 10 is smaller than that of a single-layer, single-material 304 stainless steel film. Therefore, an invar layer is provided on both sides of the stainless steel layer to reduce the deformation of the composite film 10 under temperature change. And under the same pressure, as the temperature rises, the deformation of the composite film 10 is still smaller than that of a single-layer, single-material 304 stainless steel film. Therefore, the composite film 10 in this embodiment is less deformed under the same pressure under the condition of temperature change. When it is applied to the flow controller 20, the control accuracy of the flow controller 20 can be further improved and the normal operation of the flow controller 20 can be ensured.

[0071] according to Figure 2 As shown, the present application also provides a method for preparing a composite film, and the method for preparing a composite film is used to prepare the composite film 10 mentioned above. Specifically, the method for preparing a composite film in this embodiment includes:

[0072] Step S1: Prepare the second film layer 102 and the first film layer 101 with a specified thickness by a rolling process, and then perform surface treatment on the second film layer 102 and the first film layer 101 to remove the oxide scale and oil stain on the surface of the second film layer 102 and the first film layer 101

[0073] In step S1, the metal material (i.e., 304 stainless steel and Invar) is placed between the rollers and pressure is applied to cause plastic deformation and rolling to a specified thickness. In this embodiment, the thickness of the first film layer 101 is 0.3 mm, and the thickness of the second film layer 102 is 0.15 mm. It is worth noting that in this step, parameters such as rolling pressure, rolling speed, and rolling temperature need to be strictly controlled to ensure that the material thickness is uniform and the internal structure is uniform without defects that affect the material properties, such as cracks, delamination, etc. The rolled film material is then surface treated to remove impurities such as oxide scale, oil stains, etc. on the surface to improve the bonding strength between the layers of material in the subsequent composite process.

[0074] Step S2: stacking the second film layer 102, the first film layer 101 and the second film layer 102 in sequence to form a composite film assembly, heating the composite film assembly to a predetermined temperature under a predetermined pressure, and welding the second film layer 102, the first film layer 101 and the second film layer 102 to form a composite film body;

[0075] In this step, during the stacking process, it is necessary to ensure that the layers of film are tightly fitted without gaps and misalignments. Diffusion welding is used to weld the stacked three layers of film to form a composite film body. Diffusion welding is a welding process that causes atomic-level diffusion on the contact surfaces of two or more materials under high temperature and high pressure conditions. Diffusion welding can avoid pores, cracks and microstructural changes in the material. In this step, the stacked film assembly is placed in a diffusion welding device under a vacuum or protective atmosphere environment, a pressure of 4MPa to 6MPa is applied to fully contact the contact surfaces of the three layers of film, and the temperature is raised to 895°C to 905°C for 60 minutes. Under these conditions, atomic diffusion is facilitated. Specifically, in this embodiment, the pressure preferably applied is 5MPa and the temperature is 900°C. Under this control condition, the atoms between the layers of film can diffuse with each other to form a strong metallurgical bond.

[0076] Step S3: heat-treating the composite film body to remove residual stress of the composite film body.

[0077] In this step, heat treatment includes annealing, normalizing, quenching, tempering, surface quenching, etc. This treatment process is used to reduce or eliminate the internal stress generated by the material during the manufacturing process, prevent crack propagation or fatigue failure caused by stress concentration, and help maintain the dimensional stability of the prepared composite film body and avoid deformation. The specific heat treatment process is not limited in this application and is selected according to actual production needs. During the heat treatment process, it is necessary to control the heating temperature and cooling rate to avoid excessively high temperatures that lead to a decrease in the performance of the composite film body; it is also necessary to ensure that the composite film body is evenly heated and cooled to effectively eliminate the residual stress inside the composite film body.

[0078] Step S4: Mechanically process the heat-treated composite film body to form a composite film 10 that meets the design requirements.

[0079] According to the model of the flow controller 20, the composite film body is machined into a composite film 10 that meets the diameter requirements of the flow controller 20. In this process, high-precision processing equipment and tools are required to ensure that the dimensional accuracy and surface roughness of the composite film 10 meet the requirements.

[0080] Step S5 : cleaning and inspecting the composite film 10 to remove debris and oil stains on the surface of the composite film 10 , and inspecting the quality of the composite film 10 .

[0081] After processing is completed, the composite film 10 needs to be cleaned and inspected to remove processing debris and oil stains on the surface of the composite film 10, and the composite film 10 needs to be inspected using relevant methods and instruments to detect the dimensional accuracy (such as thickness and diameter), surface quality and composite quality of the composite film 10 to ensure that it meets product quality standards.

[0082] See also Figure 3 As shown, the present application also provides a flow controller 20. The flow controller 20 includes the above-mentioned composite film 10 or the composite film 10 prepared by the above-mentioned composite film preparation method. The flow controller 20 includes a cover plate 201, a sealing ring 202, a composite film 10 and a main body 203. Specifically, the composite film 10 is placed at the corresponding position of the main body 203 of the flow controller 20, and the sealing ring 202 is installed in the groove on the cover plate 201 of the flow controller 20. The flow controller 20 is fixed to the surface of the static pressure functional component by bolt connection and can be used for oil circulation. The advantages of using the composite film 10 of the above-mentioned embodiment in the flow controller 20 are as described above, and will not be repeated here.

[0083] It can be seen from the above embodiments that the present invention can at least achieve the following technical effects:

[0084] (1) The composite film provided by the present invention produces less deformation when affected by temperature changes than a single-layer, single-material metal film;

[0085] (2) In the method for preparing the composite film provided by the present invention, the composite film produced has a small deformation amount when affected by temperature;

[0086] (3) In the flow controller provided by the present invention, a composite film is installed inside the flow controller. Compared with the single-layer, single-material metal film in the prior art, under the same pressure conditions, when the temperature changes, the deformation of the composite film is smaller, thereby improving the control accuracy of the flow controller and ensuring the normal operation of the flow controller.

[0087] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0088] In addition, it should be noted that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. If not otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0089] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A composite film, wherein the composite film (10) is used for a feedback flow controller, characterized in that: The composite film (10) comprises: A first film layer (101), along the thickness direction of the composite film (10), the first film layer (101) comprising a first surface and a second surface arranged opposite to each other; A second film layer (102), wherein the first surface and the second surface are both covered with the second film layer (102); Wherein, the thermal expansion coefficient of the second film layer (102) is smaller than the thermal expansion coefficient of the first film layer (101).

2. The composite film according to claim 1, characterized in that The thickness of the composite film (10) is [0.5, 1.0] mm, wherein the thickness of the first film layer (101) is [0.2, 0.3] mm, and the thickness of the second film layer (102) is [0.15, 0.2] mm.

3. The composite film according to claim 1, characterized in that The first film layer (101) comprises a stainless steel layer, and the second film layer (102) comprises an Invar layer.

4. The composite film according to claim 1, characterized in that The thermal expansion coefficient of the first film layer (101) is [16, 20]×10 -6 / °C, the thermal expansion coefficient of the second film layer (102) is [-0.1, 2.0]×10 -6 / ℃.

5. The composite film according to claim 1, characterized in that The elastic modulus of the first film layer (101) is [190, 196] GPa, and the elastic modulus of the second film layer (102) is [130, 150] GPa.

6. The composite film according to claim 1, characterized in that: The Poisson's ratio of the first film layer (101) is [0.29, 0.31], and the Poisson's ratio of the second film layer (102) is [0.27, 0.29].

7. A method for preparing a composite film, characterized in that: The method for preparing the composite film is used to prepare the composite film (10) according to any one of claims 1 to 6, and the method for preparing the composite film comprises: Step S1: using a rolling process to prepare the second film layer (102) and the first film layer (101) having a specified thickness, and then performing surface treatment on the second film layer (102) and the first film layer (101) to remove oxide scale and oil stains on the surfaces of the second film layer (102) and the first film layer (101); Step S2: stacking the second film layer (102), the first film layer (101) and the second film layer (102) in sequence to form a composite film assembly, heating the composite film assembly to a predetermined temperature under a predetermined pressure, and welding the second film layer (102), the first film layer (101) and the second film layer (102) to form a composite film body; Step S3: heat treating the composite film body to remove residual stress of the composite film body; Step S4: mechanically processing the composite film body after the heat treatment to process the composite film body into the composite film (10) that meets the design requirements; Step S5: cleaning and inspecting the composite film (10) to remove debris and oil stains on the surface of the composite film (10), and detecting the quality of the composite film (10).

8. The method for preparing a composite film according to claim 7, characterized in that: In the step S2, the thin film assembly is welded by diffusion welding.

9. The method for preparing a composite film according to claim 7, characterized in that: In the step S2, the predetermined pressure is [4, 6] MPa; and / or the temperature is [895, 905] °C.

10. A flow controller, characterized in that: The flow controller (20) comprises the composite film (10) according to any one of claims 1 to 6 or the composite film (10) prepared by the method for preparing a composite film according to any one of claims 7 to 9.

Images