A metal surface constant pressure nanometer strengthening device and a strengthening method

Abstract

The application discloses a metal surface constant pressure nanometer strengthening device and a strengthening method, and relates to the technical field of metal surface nanometer strengthening. The device has better fault tolerance, can deepen the depth of the metal nanometer layer, and can improve the precision of surface nanometerization. The metal surface constant pressure nanometer strengthening device comprises a tool shank, a constant air pressure assembly, a tool support and a nanometer strengthening tool which are sequentially connected from top to bottom. A pressure sensor is arranged between the tool shank and the constant air pressure assembly. The upper end of the tool shank is connected with a vertical machining center. The lower end of the nanometer strengthening tool is in contact with a workpiece for rolling. The nanometer strengthening tool can make the surface of the workpiece locally plastically deform to generate dislocation nanometer refined grains. The constant air pressure assembly can provide constant pressure for the nanometer strengthening tool. The pressure sensor can detect the pressure between the nanometer strengthening tool and the workpiece in real time. The application also provides a strengthening method based on the above metal surface constant pressure nanometer strengthening device.

Description

Technical Field

[0001] This application relates to the field of metal surface nano-strengthening technology, and in particular to a constant pressure nano-strengthening device and method for metal surfaces. Background Technology

[0002] Roller burnishing is a plastic forming method that uses roller burnishing tools to apply pressure to the surface of a workpiece, causing the surface metal to plastically flow and fill in depressions, thereby reducing surface roughness. Because the surface metal undergoes plastic deformation, the surface grains become finer, forming a residual stress layer, which improves properties such as wear resistance, hardness, and corrosion resistance.

[0003] Traditional rolling devices and methods have certain drawbacks. For example, Chinese patent "A Method for Preparing Gradient Nanostructured Metal Sheets" (Publication No.: CN114406600A) discloses a method for preparing gradient nanostructured metal sheets. This method uses a rolling spherical cutting tool to reciprocate and roll the surface of the metal sheet, moving it sequentially through each pass. The surface layer of the metal sheet undergoes localized, intense plastic deformation, resulting in grain refinement and the formation of a gradient nanostructure. However, this method places high demands on the machining of the spherical cutting tool and the tool holder. During processing, the spherical cutting tool inevitably wears and deforms, significantly affecting machining accuracy. Furthermore, the spherical cutting head makes point contact with the workpiece, resulting in low machining efficiency. Another example is Chinese patent "A Method for Preparing Gradient Metal Materials Using Hydraulic Controlled Pressure" (Publication No.: CN116536492A), which discloses a method for preparing gradient metal materials using hydraulic controlled pressure. However, this method suffers from drawbacks such as slow hydraulic control response, inability to adjust in real time, poor fault tolerance, and susceptibility to leakage. In addition, traditional rolling methods not only have the above-mentioned drawbacks, but are also insufficient for deep nano-strengthening of metal surfaces, and even have limited nano-strengthening precision. Summary of the Invention

[0004] The embodiments of this application provide a constant pressure nano-strengthening device and method for metal surfaces, which not only has better fault tolerance, but also can deepen the metal nanolayer and improve the precision of surface nano-sizing.

[0005] To achieve the above objectives, one embodiment of this application provides a constant pressure nano-strengthening device for metal surfaces, comprising a tool holder, a constant pressure assembly, a tool holder, and a nano-strengthened tool connected sequentially from top to bottom; a pressure sensor is provided between the tool holder and the constant pressure assembly; the upper end of the tool holder is connected to a vertical machining center; the lower end of the nano-strengthened tool contacts and rolls against the workpiece; the nano-strengthened tool can cause localized plastic deformation on the surface of the workpiece to generate dislocation nano-refined grains; the constant pressure assembly can provide constant pressure to the nano-strengthened tool; and the pressure sensor can detect the pressure between the nano-strengthened tool and the workpiece in real time.

[0006] Furthermore, the tool holder is a U-shaped holder; the nano-reinforced tool is a wheel structure with a central hole, and a reinforcing head is provided in the middle of the wheel rim of the nano-reinforced tool. The reinforcing head is a protrusion that surrounds the wheel rim in the circumferential direction; the nano-reinforced tool is connected to the U-shaped holder through a connecting shaft assembly; the nano-reinforced tool and the connecting shaft assembly are rotatably connected by a bearing.

[0007] Furthermore, the nano-reinforced cutting tool is provided with two bearing mounting holes, and a bearing is installed in the bearing mounting holes; the outer ring of the bearing is connected to the nano-reinforced cutting tool, and the inner ring is connected to the connecting shaft assembly.

[0008] Furthermore, both ends of the connecting shaft assembly are connected to the tool holder by screws; the connecting shaft assembly is provided with an external thread section, and a nut is connected to the external thread section, which can axially limit the two bearings.

[0009] Furthermore, the constant pressure assembly includes an air pump, a booster pump, a pressure regulating valve, a constant pressure air tank, and a piston cylinder connected in sequence; the fixed end of the piston cylinder is connected to the tool holder via a pressure sensor, and the telescopic end is connected to the tool support via a connecting plate; the air pump provides a base pressure; the booster pump increases the pressure; the pressure regulating valve stabilizes the output pressure of the booster pump; and the constant pressure air tank buffers the pressure changes caused by the extension and retraction of the piston cylinder.

[0010] Furthermore, the reinforcing head protrudes directly from the rim or through a rounded chamfer; the cross-section of the reinforcing head is a semicircle; the diameter of the semicircle d≤6mm; and the maximum diameter D of the rim of the nano-reinforced tool is 20mm.

[0011] Furthermore, the surface of the workpiece is either a plane or a curved surface.

[0012] Furthermore, the material of the workpiece is aluminum alloy, copper alloy, stainless steel, GCr15, bearing steel or mold steel.

[0013] On the other hand, embodiments of this application also provide a strengthening method based on the above-mentioned constant pressure nano-strengthening device for metal surfaces, including the following steps: S1, the workpiece is mounted on a clamping mechanism, and the tool holder is mounted on a vertical machining center; S2, the vertical machining center is started, and the vertical machining center drives the tool holder to move downward. While the strengthening head is pressed into the workpiece, the pressure is measured by a pressure sensor; S3, the nano-strengthening tool reciprocates in the horizontal direction at a tool speed V2. After each reciprocation, the clamping mechanism drives the workpiece to move a preset distance D in the horizontal direction at a workpiece speed V1. The directions of the workpiece speed V1 and the tool speed V2 are perpendicular to each other, and the overall machining process presents a serpentine trajectory; S4, step S3 is repeated until the nano-strengthening of the workpiece surface is completed, forming a deep gradient nano-layer.

[0014] Further, in step S3, the preset distance D = 0.015mm to 0.05mm; the rolling depth is 0.01mm to 0.1mm; V1 = D*V2 / L; where L is the workpiece length; V2 ≥ 2000mm / min.

[0015] This application has the following advantages over the prior art:

[0016] 1. The constant pressure nano-strengthening device for metal surfaces in this application embodiment utilizes the principle of constant pressure coordination by setting a constant air pressure component between the support and the tool holder. This makes the nano-strengthening device elastic, the processing process more gentle, and has better fault tolerance, which can deepen the depth of the metal nano-layer. Furthermore, by setting a pressure sensor between the tool holder and the constant air pressure component to detect the pressure value in real time, the accuracy of surface nano-strengthening is further improved, and the adaptability is better. The telescopic piston cylinder allows the processing objects to be extended from planar structures to curved structures, thus expanding the scope of application.

[0017] 2. The constant pressure component in the constant pressure nano-strengthening device for metal surfaces in this application includes an air pump, a booster pump, a pressure regulating valve, a constant pressure tank, and a piston cylinder; the extension and retraction end of the piston cylinder is provided with a connecting plate, and the tool holder is mounted on the connecting plate; the air pump can provide basic air pressure; the booster pump can increase air pressure; the pressure regulating valve can stabilize the output air pressure of the booster pump; the constant pressure tank is used to buffer the air pressure change caused by the displacement of the piston cylinder, and has a simple structure and stable performance.

[0018] 3. The nano-strengthening tool in the constant pressure nano-strengthening device for metal surfaces in this application embodiment can increase the depth of the processed nano-layer by 2 to 4 times compared with traditional tools, and the deformation layer influence can reach more than 2000μm. The nano-strengthening effect and efficiency, as well as the surface finish, are significantly improved. The surface finish can reach below 0.02 in laboratory tests.

[0019] 4. In the constant pressure nano-strengthening device for metal surfaces in this application embodiment, the nano-strengthening tool is axially limited by the bearing through the nut, which is beneficial for the nano-strengthening tool to maintain structural stability and high precision under high-speed rotation. In addition, since the smaller the cross-sectional diameter of the strengthening head, the greater the pressure on the surface of the workpiece, the better the nano-strengthening effect. Therefore, the strengthening device in this application embodiment forms a deeper gradient nano-layer on the metal surface by making the maximum value D of the rim of the nano-strengthening tool ≤ 20 mm and the cross-sectional diameter d of the strengthening head ≤ 6 mm.

[0020] 5. The nano-strengthening tool in the constant pressure nano-strengthening device for metal surfaces in this application embodiment can be replaced with a hard-strengthening tool head according to the characteristics and shape of the processed area, so as to perform local fine processing, which further increases the applicability and practicality of the device and saves costs. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 This is a three-dimensional structural diagram of Embodiment 1 of this application;

[0023] Figure 2 This is a left view of Embodiment 1 of this application;

[0024] Figure 3 for Figure 2 AA section view;

[0025] Figure 4 This is a schematic diagram of the structure of the nano-reinforced cutting tool in Embodiment 1 of this application;

[0026] Figure 5 This is a top view of the relative movement trajectory of the nano-reinforced tool and the workpiece in Embodiment 1 of this application;

[0027] Figure 6 This is a schematic diagram of the structure of the nano-reinforced cutting tool in Embodiment 1 of this application;

[0028] Figure 7 This is a schematic diagram showing the maximum value of the rim and the diameter of the reinforcing head section of the nano-reinforced tool in Embodiment 1 of this application;

[0029] Figure 8This is a comparison of the stress-strain curves of stainless steel round bars with diameters of 3mm and 6mm after nano-rolling in Example 1 of this application, and coarse-grained material CG of the same size.

[0030] Figure 9 The above are CG fatigue SN curves of stainless steel 3mm diameter round bars and 6mm diameter round bars after nano-rolling and the same size coarse-grained material.

[0031] Figure 10 This is a graph showing the relationship between the tensile strength and fatigue ratio of the workpiece in Embodiment 1 of this application;

[0032] Figure 11 This is a schematic diagram of the structure of the nano-reinforced cutting tool in Embodiment 2 of this application;

[0033] Figure 12 This is a schematic diagram showing the maximum value of the rim and the diameter of the reinforcing head section of the nano-reinforced tool in Embodiment 2 of this application;

[0034] Figure 13 The tensile engineering stress-strain curve of the workpiece made of Ti in Embodiment 2 of this application;

[0035] Figure 14 The microhardness and corresponding microhardness microstructure of the cross section of the workpiece made of Ti in Example 2 of this application after nanostructuring;

[0036] Figure 15 This is a thermal stability diagram of the structure of the workpiece made of Ni in Embodiment 2 of this application. Detailed Implementation

[0037] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0039] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation", "connection" and "joining" should be interpreted broadly, for example, they can refer to fixed connections, detachable connections, or integral connections; those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0040] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" can explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0041] Example 1:

[0042] Reference Figures 1 to 7 The embodiments of this application provide a constant pressure nano-strengthening device for metal surfaces, including a tool holder 1, a pressure sensor 2, a constant air pressure assembly, a tool holder 3, and a nano-strengthened tool 4.

[0043] Tool holder 1 is existing technology and will not be described in detail here. The upper end of tool holder 1 is mounted on the tool clamping structure of the vertical machining center, and the lower end is connected to tool support 3 via a constant pressure assembly. The constant pressure assembly can provide constant pressure for the nano-reinforced tool 4. A pressure sensor 2 is provided between the constant pressure assembly and tool holder 1, which can detect the pressure between the nano-reinforced tool 4 and the workpiece 15 in real time.

[0044] The tool holder 3 is a U-shaped holder with two free ends. The nano-reinforced tool 4 is connected to the tool holder 3 via a connecting shaft assembly, and the two are rotatably connected by a bearing. The lower end of the nano-reinforced tool 4 contacts and rolls against the workpiece 15 to cause localized plastic deformation on the surface of the workpiece 15, generating dislocation nano-refined grains.

[0045] The nano-reinforced cutting tool 4 is a wheel-type structure with a central hole. A reinforcing head 5 is located in the center of its rim, and the reinforcing head 5 is a protrusion that surrounds the rim circumferentially and protrudes directly from it. The cross-section of the reinforcing head 5 is semi-circular, with a diameter d = 6 mm. The maximum diameter of the rim of the nano-reinforced cutting tool 4 is D = 20 mm. Depending on the characteristics and shape of the area being processed, the nano-reinforced cutting tool 4 can be replaced with a hard-reinforced cutting head for localized fine machining, further increasing the applicability and practicality of this device while saving costs.

[0046] Two bearing mounting holes are provided on both ends of the central hole, and bearings 6 are installed in the bearing mounting holes. The outer ring of bearing 6 is interference-fitted with the inner wall of the bearing mounting hole, and the inner ring is connected to the connecting shaft assembly.

[0047] For ease of installation, the connecting shaft assembly includes a pin 7 and a shouldered bushing 8 fitted onto the middle section of the pin 7. The pin 7 has an external thread section, on which a nut 9 is connected. The nut 9 provides axial restraint for the two bearings 6. The two ends of the pin 7 are connected to the two free ends of the tool holder 3 by screws 10.

[0048] The constant pressure assembly includes, in sequence, an air pump (not shown), a booster pump (not shown), a pressure regulating valve (not shown), a constant pressure air tank (not shown), and a piston cylinder 11. The fixed end of the piston cylinder 11 is connected to the tool holder 1, and the telescopic end is provided with a connecting plate 12, on which the tool holder 3 is mounted. The air pump provides the base pressure, the booster pump increases the pressure, the pressure regulating valve stabilizes the output pressure of the booster pump, and the constant pressure air tank buffers the pressure changes caused by the displacement of the piston cylinder 11.

[0049] The surface of the workpiece 15 can be flat or curved, and the material can be aluminum alloy, copper alloy, stainless steel, GCr15, bearing 6 steel, or mold steel. Specifically, in Embodiment 1, the workpiece 15 has a curved surface structure and is made of 316 stainless steel.

[0050] Figure 8 The figure shows the stress-strain curves of 316 stainless steel material with a diameter of 3mm and 6mm after nano-rolling and coarse-grained material CG in Example 1. As shown in the figure, the material has a better yield limit. It can be seen from the stress-strain curve that the yield strength of the material has increased from 250MPa before nano-rolling to about 750MPa after nano-rolling.

[0051] Figure 9 The figure shows the fatigue SN curves of 316 stainless steel materials with 3mm and 6mm diameter nano-rolling after nano-rolling, compared to the coarse-grained material. As shown in the figure, at 300MPa, the coarse-grained material only has 10 fatigue cycles. 3 After nano-sizing, the fatigue cycle count is increased to >10. 7 .

[0052] Figure 10 The graph shows the relationship between tensile strength and fatigue ratio. As shown in the figure, the nanomaterial properties of 316 stainless steel are significantly improved.

[0053] Example 2:

[0054] Reference Figure 11 and Figure 12 The only difference between Example 2 and Example 1 is that the reinforcing head 5 protrudes through a rounded chamfer. It should be noted that, in this case, the object of Example 2, i.e., the surface of the workpiece 15, has a planar structure and is made of pure Ti.

[0055] Figure 13The figures show the tensile stress-strain curves of the workpiece 15 made of Ti in Example 2. Curve A corresponds to a CG coarse-grained titanium tube with a wall thickness of 2 mm. Curve B corresponds to a nano-sized GNG titanium tube with a wall thickness of 2 mm. Curve C corresponds to a nano-sized GNG titanium tube with a wall thickness of 1.5 mm. After nano-sizing, the yield strength of the titanium alloy is increased from approximately 460 MPa to approximately 650 MPa.

[0056] Figure 14 The figure shows the microhardness and corresponding microstructure of the cross-section of a titanium (Ti) workpiece after nano-sizing. As shown, the hardness of the gradient nanolayers of the titanium alloy varies from 440 at the outermost layer to 150 at the core, while the original hardness of the substrate is 150. This demonstrates that nano-sizing significantly improves the hardness of Ti.

[0057] In summary, after using the nano-strengthening device of the present invention for nano-strengthening treatment of metal surfaces, the surface quality is better, the roughness can be lower than 0.02, and the nano-layer depth can be deeper, reaching 1000-2000um.

[0058] When the object of Example 2, namely the workpiece 15, has a curved surface and is made of Ni, refer to... Figure 15 This illustrates the thermal stability of the nanoscale grain structure on the surface of the workpiece. Specifically, (A) is a grain size versus temperature curve after annealing for 1 hour.

[0059] (B) is a TEM image of the nickel nanostructured sample. (C) is a TEM image of the nickel nanostructured sample after annealing at 500°C for 1 hour. As shown in the figures, the stress intensity is significantly improved after the metal surface is nano-strengthened using the nano-strengthening device of this application. This set of figures illustrates that the nanostructure has excellent thermal stability.

[0060] The above embodiments demonstrate that the nano-strengthening device of this application not only has better fault tolerance and can deepen the metal nanolayer, improve the precision of surface nano-sizing, but also has adaptability, and the processing objects can be extended from planar structures to curved structures.

[0061] Reference Figure 1 and Figure 5 The embodiments of this application also provide a strengthening method based on the above-mentioned constant pressure nano-strengthening device for metal surfaces, comprising the following steps:

[0062] S1. The workpiece 15 is mounted on the clamping mechanism, and the tool holder 1 is mounted on the vertical machining center.

[0063] S2. Start the vertical machining center. The vertical machining center drives the tool holder 1 to move downward. At the same time, the reinforcing head 5 presses into the workpiece 15 and the pressure is measured by the pressure sensor 2.

[0064] S3. The nano-reinforced cutting tool 4 reciprocates horizontally at a tool speed V2. After each reciprocation, the clamping mechanism drives the workpiece 15 to move a preset distance D horizontally at a workpiece speed V1. The directions of the workpiece speed V1 and the cutting tool speed V2 are perpendicular to each other, and the overall machining process follows a serpentine trajectory. The preset distance D = 0.02 mm; the rolling depth is 0.01 mm to 0.1 mm; V1 = 0.02 mm * V2 / L; L is the workpiece length; V2 = 2000 mm / min.

[0065] S4. Repeat step S3 until the nano-reinforcement of the surface of the workpiece 15 is completed, forming a deep gradient nanolayer.

[0066] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions within the technical scope 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 metal surface constant pressure nanometer strengthening device, characterized in that, The application relates to a nano-reinforced tool, which comprises, from top to bottom, a tool handle, a constant air pressure assembly, a tool support and a nano-reinforced tool; a pressure sensor is arranged between the tool handle and the constant air pressure assembly; the upper end of the tool handle is connected with a vertical machining center; the lower end of the nano-reinforced tool is in contact with a workpiece for rolling; the nano-reinforced tool can cause local plastic deformation of the surface of the workpiece to generate dislocation nano-fined grains; the constant air pressure assembly can provide constant pressure for the nano-reinforced tool; and the pressure sensor can detect the pressure between the nano-reinforced tool and the workpiece in real time. The tool support is a U-shaped support; the nano-reinforced tool is in a wheel type structure with a central hole; a reinforcing head is arranged in the middle of the rim of the nano-reinforced tool; the reinforcing head is a protrusion which is circumferentially arranged on the rim; the cross section of the reinforcing head is a semicircle; the diameter d of the semicircle is less than or equal to 6 mm; and the maximum diameter D of the rim of the nano-reinforced tool is less than or equal to 20 mm. The constant air pressure assembly comprises, in sequence, an air pump, a pressure booster, an air pressure regulating valve, a constant pressure tank and a piston cylinder; the fixed end of the piston cylinder is connected with the tool handle through the pressure sensor, and the telescopic end is connected with the tool support through a connecting plate; the air pump can provide basic air pressure; the pressure booster can increase air pressure; the air pressure regulating valve can stabilize the output air pressure of the pressure booster; and the constant pressure tank is used for buffering the air pressure change caused by the extension and retraction of the piston.

2. The apparatus for constant pressure nanonreinforcement of metal surfaces according to claim 1, characterized in that, The nano-reinforced tool is connected with the U-shaped support through a connecting shaft assembly; the nano-reinforced tool and the connecting shaft assembly are rotationally connected through bearings.

3. The apparatus for constant pressure nanonreinforcement of metal surfaces according to claim 2, characterized in that, Two bearing mounting holes are arranged in the nano-reinforced tool, and bearings are arranged in the bearing mounting holes; the outer ring of the bearing is connected with the nano-reinforced tool, and the inner ring is connected with the connecting shaft assembly.

4. The apparatus for constant pressure nanonreinforcement of metal surfaces according to claim 3, characterized in that, The two ends of the connecting shaft assembly are connected with the tool support through screws; an external thread section is arranged on the connecting shaft assembly, a nut is connected on the external thread section, and the nut can axially limit the two bearings.

5. The apparatus for constant pressure nanonreinforcement of metal surfaces according to claim 4, characterized in that, The reinforcing head directly protrudes from the rim or protrudes through a circular arc chamfer.

6. The apparatus for constant pressure nanonreinforcement of metal surfaces according to claim 5, characterized in that, The surface of the workpiece is a plane or a curved surface.

7. The apparatus for constant pressure nanonreinforcement of metal surfaces according to claim 6, characterized in that, The material of the workpiece is aluminum alloy, copper alloy, stainless steel, GCr15, bearing steel or die steel.

8. A method of strengthening based on the metal surface constant pressure nanometer strengthening device according to any one of claims 1-7, characterized in that, The method comprises the following steps: S1, mounting the workpiece on a clamping mechanism and mounting the tool handle on a vertical machining center; S2, starting the vertical machining center, driving the tool handle to move downward, and measuring the pressure through the pressure sensor while the reinforcing head is pressed into the workpiece; S3, the nano-reinforced tool reciprocates along the horizontal direction at a tool speed V2, after each reciprocation, the clamping mechanism drives the workpiece to move along the horizontal direction at a workpiece speed V1 for a preset distance D, the directions of the workpiece speed V1 and the tool speed V2 are perpendicular to each other, and the overall machining process presents a snake-shaped trajectory; S4, repeating step S3 until the nano-reinforcement of the surface of the workpiece is completed, and a deep gradient nano layer is formed. The preset distance D in the step S3 is 0.015 mm to 0.05 mm; the rolling depth is 0.01 mm to 0.1 mm; V1=D*V2 / L; wherein, L is the length of the workpiece; V2≥2000 mm / min.

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