Method of machining a leaf spring

Abstract

The application relates to a processing method of a plate spring and belongs to the technical field of spring processing. The processing method of the plate spring comprises the following steps: S1, first, straightening the plate spring raw material through a measuring tool, and then sharpening the edges of the plate spring raw material through a file; S2, bending the material processed in the step S1 through a bending machine, and adjusting the position and angle of a bending die; S3, correcting the material bent in the step S2 through a lathe clamp, and observing whether cracks and pits exist on the product; S4, performing stress annealing treatment on the material corrected in the step S3; S5, performing turning and milling processing on the material subjected to the annealing treatment in the step S4 through a machine tool; and S6, performing aging heat treatment on the material subjected to the machining in the step S4. Therefore, the product quality, the processing efficiency and the qualified rate of the plate spring are improved.

Description

Technical Field

[0001] This invention belongs to the field of spring processing technology, and specifically relates to a method for processing leaf springs. Background Technology

[0002] Leaf springs are special, irregularly shaped springs made from nuclear-grade nickel-based high-temperature alloy sheets. They are mainly used in nuclear fuel assemblies in nuclear reactors and play a crucial role in the entire nuclear reaction process. Leaf springs require extremely high precision in their geometric dimensions, form and position tolerances, and appearance quality. However, existing leaf spring manufacturing methods struggle to guarantee product quality, resulting in low processing efficiency and low yield rates. Summary of the Invention

[0003] This invention provides a method for processing leaf springs to solve the above-mentioned technical problems.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A method for processing a leaf spring includes the following steps:

[0005] S1. First, straighten the leaf spring raw material using measuring tools, and then blunt its sharp edges using a file:

[0006] S2. The material processed in step S1 is bent using a bending machine, while adjusting the position and angle of the bending die.

[0007] S3. Use a lathe to perform full-shape straightening on the material bent in step S2, and observe whether there are cracks and pits on the product;

[0008] S4. Perform stress annealing on the material corrected in step S3;

[0009] S5. The material after annealing in step S4 is machined and milled using a machine tool;

[0010] S6. Perform aging heat treatment on the material after machining in step S4.

[0011] Optionally, in step S2, the dimensions of the bending die are controlled within ±30°, while the positioning support of the product rotates with the flow of material when the die head is pressed down.

[0012] Optionally, in step S3, the material is observed for cracks and pits using a 5x magnifying glass, while the straightening process is non-impact straightening.

[0013] Optionally, in step S1, the raw material is a nickel-based high-temperature alloy, and the raw material is arranged to be cut along the rolling direction.

[0014] Optionally, in step S5, the cutting speed is 30-50 m / min during the cutting process, the cutting method is layered spiral cutting, each layer is 0.1-0.3 mm, and the feed rate is 60-80 m / min.

[0015] Optionally, in step S5, after each processing step is completed, the cutting fluid and metal shavings on the product surface are washed with clean water.

[0016] Optionally, in step S5, the perpendicularity of the processed product is less than 0.2 mm, its flatness is less than 0.2 mm, and its dimensional tolerance is 0.05 mm.

[0017] Optionally, step S6 is as follows:

[0018] S601. Use ultrasonic cleaning to clean the product and the heating furnace to ensure the cleanliness of the heating environment.

[0019] S602. Preheat the furnace to 800°C for 1 hour.

[0020] S603. Place the product flat on the tray, and the products should not be stacked.

[0021] S604. First, raise the temperature in the heating furnace to 720°C and hold it for 8 hours. Then, cool it down to 620°C at a rate of 55°C / H. Next, hold the product at 620°C for 8 hours and fill it with inert gas. Finally, cool the temperature in the heating furnace to below 150°C before removing it from the furnace.

[0022] Optionally, after aging heat treatment, the product's mechanical properties include a tensile strength ≥1240MPa and a grain size of grade 5 or higher.

[0023] As can be seen from the above technical solution, the beneficial effect of the leaf spring processing method provided by the present invention is as follows: by straightening the raw material of the leaf spring and blunting its sharp edges, then bending the material, then performing full-shape straightening and stress annealing on the bent material, then processing the material by a machine tool, and finally performing aging heat treatment on the material. This solves the technical problems of existing leaf spring processing methods, such as difficulty in guaranteeing product quality, low processing efficiency, and low pass rate. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 A process flow diagram of a leaf spring processing method provided in an embodiment of the present invention;

[0026] Figure 2 A process flow diagram of heat treatment provided for an embodiment of the present invention. Detailed Implementation

[0027] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0028] 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.

[0029] 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. Therefore, a feature defined as "first" or "second" may 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.

[0030] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0031] Example

[0032] Leaf springs are special, irregularly shaped springs made from nuclear-grade nickel-based high-temperature alloy sheets. They are mainly used in nuclear fuel assemblies in nuclear reactors and play a crucial role in the entire nuclear reaction process. Leaf springs require extremely high precision in their geometric dimensions, form and position tolerances, and appearance quality. However, existing leaf spring manufacturing methods struggle to guarantee product quality, resulting in low processing efficiency and low yield rates.

[0033] To solve the above-mentioned technical problems, this embodiment provides a method for processing a leaf spring, including the following steps:

[0034] S1. First, straighten the leaf spring raw material using measuring tools, and then blunt its sharp edges using a file:

[0035] S2. The material processed in step S1 is bent using a bending machine, while the position and angle of the bending die are adjusted.

[0036] S3. Use a lathe to straighten the material after bending in step S2, and observe whether there are cracks and pits on the product.

[0037] S4. Perform stress annealing on the material after correction in step S3;

[0038] S5. The material after annealing in step S4 is machined and milled using a machine tool;

[0039] S6. Perform aging heat treatment on the material after machining in step S4.

[0040] It should be noted that the leaf spring is made of nuclear-grade nickel-based superalloy GH4169, which has good yield strength and creep resistance.

[0041] Based on the above, in step S1, the leaf spring raw materials are first laid out and cut along the rolling direction. The raw materials are then clamped and fixed using pliers and jigs to ensure stability during straightening. Next, the leaf spring raw materials are ground to the required dimensions using a flat grinding method, and the cutting fluid on their surface is removed with clean water. Then, the edges of the leaf spring raw materials are processed and polished using a file or grinding wheel to blunt them, minimizing the impact on the appearance quality of the leaf spring material during bending.

[0042] Based on the above, in step S2, due to the high yield strength of nuclear-grade nickel-based superalloys, product springback is easily caused during bending, making it difficult to guarantee product dimensions. Therefore, the elastic modulus must be fully considered when designing the bending die, and it must be verified and corrected multiple times to control its angle dimension within ±30°.

[0043] It should be specifically noted that during bending, when the upper die head presses down, the material flows with the die, which can damage the product's appearance. Therefore, special modifications are needed to the bending die so that when the die head presses down, the product's positioning support rotates along with the material flow. This eliminates relative movement between the product and the die, preventing friction and ensuring the product's appearance and quality.

[0044] Based on the above, in step S3, it is first necessary to observe whether the leaf spring raw material has appearance problems such as cracks and pits through a 5x magnifying glass, and then use a lathe to perform full-shape correction on the product.

[0045] It is important to clarify that non-impact straightening must be used during the straightening process. Non-impact straightening is used to change the shape of metal workpieces without using impact force. Compared with traditional impact forming processes (such as hammering, stamping, etc.), non-impact straightening has lower noise, vibration, and energy consumption. If impact straightening is used, it will cause quality risks such as cracks, pitting, and overlap in the leaf spring raw materials.

[0046] Based on the above, in step S4, although the nickel-based superalloy of the leaf spring raw material has high strength and hardness, it is brittle and prone to cracking and fracture. Stress annealing is used to remove residual stress and change the material's plastic deformation capacity, thereby improving the material's toughness and ductility and preventing cracking and fracture during subsequent processing.

[0047] Based on the above, in step S5, the machine tool mainly performs turning on the material's external dimensions and width, milling on the sides, and machining the elastic retention area and chamfers. Each part is machined with a dedicated fixture. To ensure the overall dimensions of the product and the current machining dimensions, the fixture design must guarantee both clamping force and prevent surface quality issues such as pinch marks and indentations.

[0048] It should be specifically noted that, due to the excellent high-temperature strength and hardness of nickel-based superalloys, and the high temperatures generated during machining, the cutting coating is prone to burning. Therefore, the end mill material in this embodiment is tungsten-cobalt cemented carbide, featuring parabolic flutes, unequally divided teeth, a controllable clearance angle design, and a surface ceramic coating to avoid resonance caused by machining chatter affecting surface quality and geometric dimensions. This embodiment uses Denuke's Denucool-SM8410 high-temperature alloy-specific cutting fluid, with a cutting speed of 30-50 m / min, a layered helical cutting method, each layer being 0.1-0.3 mm thick, and a feed rate of 60-80 m / min. The tool condition needs to be periodically checked during machining. Furthermore, after each machining operation, the surface of the leaf spring raw material must be cleaned with water to remove any cutting fluid and other contaminants.

[0049] Based on the above, in step S6, nickel-based superalloys are particularly sensitive to hot working processes, therefore the aging heat treatment includes the following steps:

[0050] S601. Clean the product with ultrasonic waves (there must be no impurities such as paint, powder, or lubricating oil), and clean the heating furnace to ensure the cleanliness of the heating environment. The heating furnace must not contain sulfur, phosphorus, lead, or other low-melting-point metals, otherwise it will affect the brittleness of the nickel-based high-temperature alloy.

[0051] S602. Preheat the furnace to 800°C for 1 hour.

[0052] S603. Place the product flat on the tray, and the products should not be stacked. When placing the product, you can also place the furnace sample and place it in the coldest and hottest part of the furnace.

[0053] S604. First, raise the temperature in the heating furnace to 720°C and hold it for 8 hours. Then, lower the temperature to 620°C at a rate of 55°C / H. Next, hold the product at 620°C for 8 hours and fill it with inert gas. Finally, cool the temperature in the heating furnace to below 150°C before removing it from the furnace.

[0054] It should be specifically noted that the surface quality of the material after aging heat treatment remains unchanged in terms of color and deformation. Its mechanical properties include a tensile strength ≥1240MPa and a grain size of grade 5 or higher.

[0055] In summary, after actual testing, compared with existing leaf spring processing methods, the processing method provided by this invention, processed through the above steps, increases production efficiency by 20% and first-pass yield from 80% to 98%. Therefore, the leaf springs processed by the method provided by this invention exhibit superior mechanical properties. It solves the technical problems of existing leaf spring processing methods, such as difficulty in guaranteeing product quality, low processing efficiency, and low yield. The leaf springs processed by the method provided by this invention have excellent dimensional accuracy, behavioral tolerances, and appearance quality. This improves the service life of the leaf springs and reduces costs.

[0056] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope described in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for processing a leaf spring, characterized in that, Includes the following steps: S1. First, the leaf spring raw material is straightened using measuring tools, and then its sharp edges are blunted using a file. S2. The material processed in step S1 is bent using a bending machine, while adjusting the position and angle of the bending die. S3. Use a lathe to perform full-shape straightening on the material bent in step S2, and observe whether there are cracks and pits on the product; S4. Perform stress annealing on the material corrected in step S3; S5. The material after annealing in step S4 is machined and milled using a machine tool; S6. Perform aging heat treatment on the material after machining in step S5; In step S2, the size of the bending die is controlled within ±30°, and the positioning support of the product rotates with the flow of material when the die head is pressed down. In step S3, the material is observed for cracks and pits using a 5x magnifying glass, while the straightening process is non-impact straightening.

2. The processing method of a leaf spring according to claim 1, characterized in that, In step S1, the raw material is a nickel-based high-temperature alloy, and the raw material is arranged to be cut along the rolling direction.

3. The processing method of a leaf spring according to claim 1, characterized in that, In step S5, the cutting speed during machining is 30-50 m / min, the cutting method is layered spiral cutting, each layer is 0.1-0.3 mm, and the feed rate is 60-80 m / min.

4. The processing method of a leaf spring according to claim 3, characterized in that, In step S5, after each processing step is completed, the cutting fluid and metal shavings on the product surface are washed with clean water.

5. A method for processing a leaf spring according to claim 4, characterized in that, In step S5, the perpendicularity of the processed product is less than 0.2 mm, its flatness is less than 0.2 mm, and its dimensional tolerance is 0.05 mm.

6. A method for processing a leaf spring according to claim 1, characterized in that, The process of step S6 is as follows: S601. Use ultrasonic cleaning to clean the product and the heating furnace to ensure the cleanliness of the heating environment. S602. Preheat the furnace to 800°C for 1 hour. S603. Place the product flat on the tray, and the products should not be stacked. S604. First, raise the temperature in the heating furnace to 720°C and hold it for 8 hours. Then, lower the temperature to 620°C at a rate of 55°C / H. Next, hold the product at 620°C for 8 hours and fill it with inert gas. Finally, cool the temperature in the heating furnace to below 150°C before removing it from the furnace.

7. A method for processing a leaf spring according to claim 6, characterized in that, After aging heat treatment, the product's mechanical properties include a tensile strength ≥1240MPa and a grain size of grade 5 or higher.

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