A bimetallic composite self-lubricating bushing and a preparation method thereof

Abstract

This invention discloses a bimetallic composite self-lubricating bushing and its preparation method, comprising an outer layer and an inner layer. The outer layer is made of steel, and the inner layer is made of copper alloy. The inner wall of the outer layer is provided with multiple mating grooves, which are arranged in multiple layers along the axial direction of the outer layer. Adjacent mating grooves are spaced apart, and each layer includes multiple annularly spaced mating grooves. The inner layer is located within the mating grooves. Each mating groove includes a tip and a tail. The tips of adjacent mating grooves face opposite directions, and the distance between two adjacent mating grooves is the same as the groove width. The multi-layer mating groove structure of this invention, through centrifugal casting, achieves bimetallic interlocking and increases the metallurgical bonding area of ​​the staggered triangular straight mating groove structure with adjacent layers of tips facing opposite directions, significantly improving the interfacial bonding force of the bimetallic composite bushing.

Description

Technical Field

[0001] This invention relates to the field of metal bushing technology, and more specifically, to a bimetallic composite self-lubricating bushing and its preparation method. Background Technology

[0002] As wind turbines become larger and more offshore, the requirements for lubrication bushings in wind power transmission systems are extremely high. Bimetallic bushings with a steel outer shell and a copper inner shell have become core components of wind turbine yaw and pitch systems. Currently, the industry mainstream uses centrifugal casting to prepare them. This relies on molten copper liquid to tightly adhere to the inner surface of the steel bushing under centrifugal force, forming a metallurgical bond through atomic diffusion. However, traditional flat interfaces rely on only a single metallurgical bond, resulting in an interfacial shear strength of only 150-200 MPa. Under low-speed, heavy-load, and high-impact conditions in wind power, fatigue cracks are easily generated and propagated, ultimately leading to the overall peeling of the copper layer. The insufficient bonding strength of the steel-copper interface makes delamination failure likely. Therefore, a technical solution is needed to address these issues. Summary of the Invention

[0003] The purpose of this invention is to overcome the shortcomings of the prior art, increase the interfacial bonding force of bimetals, and provide a bimetallic composite self-lubricating bushing and its preparation method.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] This invention discloses a bimetallic composite self-lubricating bushing, comprising an outer layer and an inner layer. The outer layer is made of steel, and the inner layer is made of copper alloy. The inner wall of the outer layer is provided with multiple mating grooves. The mating grooves are arranged in multiple layers along the axial direction of the outer layer, with adjacent layers of mating grooves spaced apart. Each layer includes multiple annularly spaced mating grooves, and a portion of the inner layer is located within the mating grooves.

[0006] Furthermore, the joint groove includes a tip and a tail, the tips of two adjacent joint grooves face opposite directions, and the spacing between two adjacent joint grooves is the same as the groove width c of the joint groove.

[0007] Furthermore, the depth h of the joint groove is 0.3 to 0.8 mm, the ratio of the circumferential length a of the joint groove to the circumference of the inner side surface of the outer layer is 1:25 to 1:30, and the ratio of the width b of the joint groove to the axial length of the outer layer is 1:15 to 1:20.

[0008] Furthermore, the inner layer is made of CuSn12Ni2-C alloy.

[0009] This invention also discloses a preparation method for preparing the above-mentioned bimetallic composite self-lubricating bushing, comprising the following steps:

[0010] S1. Outer layer pre-machining: The alloy steel billet is rough-machined into the outer layer steel billet of the bushing to remove forging stress;

[0011] S2, Gutter machining: The inner wall of the outer steel billet made in S1 is machined using laser.

[0012] S3. Surface pretreatment: The inner surface of the outer steel billet with the bonding groove processed in S2 is ultrasonically vacuum cleaned to remove slag and oxide layer, and copper infiltration activation treatment is carried out in a vacuum environment.

[0013] S4. Centrifugal casting: The outer steel billet processed in S3 is fixed in a vertical centrifugal casting machine, and molten copper alloy liquid is poured into the outer steel billet. After cooling, a bimetallic composite billet is obtained.

[0014] S5. Gradient heat treatment: The bimetallic composite billet formed in S4 is subjected to stress normalizing, outer layer and inner layer heat treatment in sequence.

[0015] S6. Finished product processing: The bimetallic composite blank processed in S5 is subjected to rough turning, semi-finish turning and fine grinding in sequence to remove the copper layer processing allowance, and then vacuum pressure impregnation with composite solid lubricant to finally obtain the finished bushing.

[0016] Furthermore, in step S4, the amount of copper alloy cast, m, is calculated according to the following formula:

[0017]

[0018] in, The density of copper alloy, For the volume of the copper layer in the base layer of the mortise, For the total volume of the bonding groove, This is a shrinkage correction factor, with a value ranging from 2.2% to 3.2%.

[0019] Furthermore, in step S4, the... The calculation formula is:

[0020]

[0021] in, , The thickness of the copper layer in the finished bushing. Allowance for copper layer processing, The inner diameter of the outer layer. This is the axial length of the bushing.

[0022] Furthermore, in step S4, the... The calculation formula is:

[0023]

[0024] in, The circumferential length of the groove is [missing information]. The axial width of the groove is... For the depth of the joint groove, This represents the total number of circumferential joint grooves. Where L is the total number of axial grooves, and L is the axial length of the bushing. This represents the total number of intersections of the groove in the circumferential and axial directions.

[0025] Furthermore, in step S4, the formula for calculating the centrifugal speed of the outer steel billet is:

[0026]

[0027] in, This is the corrected centrifugal acceleration. The radius of the inner surface of the copper blank is . The calculation formula is:

[0028]

[0029]

[0030] in, The corrected thickness of the copper blank. The calculation formula is:

[0031]

[0032] in, For the reference centrifugal acceleration of a flat interface, To incorporate the correction factor for the resistance of the slot filling, The value ranges from 1.15 to 1.5.

[0033] Furthermore, in step S4, the inner layer casting temperature and the outer layer preheating temperature are calculated:

[0034]

[0035]

[0036] in, The temperature of the copper alloy liquid. For the corrected casting overheating, This is the preheating temperature of the outer steel billet.

[0037] The beneficial effects of this invention are:

[0038] 1. The multi-layer bonding groove structure of the present invention uses an interlaced triangular straight bonding groove structure with two adjacent layers having opposite tips. Through centrifugal casting, bimetallic interlocking and metallurgical bonding area are achieved, which significantly improves the interfacial bonding force of the bimetallic composite bushing. This structure can simultaneously restrict the axial and circumferential slippage of the copper layer, thereby increasing the contact area of ​​the bimetallic interface and having higher interfacial bonding strength and fatigue resistance.

[0039] 2. Based on the centrifugal casting bimetallic composite structure of the designed bonding groove, this invention reduces the calculation error of centrifugal casting volume by incorporating the copper layer processing allowance and the total volume of the bonding groove into the calculation of the overall casting volume. By optimizing the centrifugal speed through the filling resistance correction coefficient of the bonding groove, it ensures that the copper liquid completely fills the dead corner of the bonding groove, thereby reducing the circumferential thickness uniformity error of the bushing copper layer and improving the yield of bushing production. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of one embodiment.

[0041] Figure 2 This is a schematic diagram of the outer layer in this embodiment.

[0042] Figure 3 This is a schematic diagram of a connecting groove in this embodiment.

[0043] Reference numerals: 1. Outer layer; 11. Joint groove; 12. Outer annular groove; 13. Through hole; 2. Inner layer; 21. Lubrication pit. Detailed Implementation

[0044] The technical solutions in this embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0045] like Figures 1 to 3As shown, this embodiment discloses a bimetallic composite self-lubricating bushing, including an outer layer 1 and an inner layer 2. The outer layer 1 is made of 42CrMo steel, and the inner layer 2 is made of copper alloy. The inner layer 2 is made of CuSn12Ni2-C copper alloy, with 0.1% rare earth La added for micro-alloying to improve wear resistance and fatigue resistance. The outer layer 1 includes an outer ring groove 12 and multiple through holes 13. The outer ring groove 13 is located at the axial center of the outer layer 1, and the multiple through holes 13 are arranged in a ring within the range of the outer ring groove 12. The through holes 13 connect to the inner surface of the outer layer 1. The outer ring groove 12 and the through holes 13 facilitate oil injection into the bushing. The inner surface of the bushing is provided with an inner ring groove corresponding to the outer ring groove 12, which can store oil and disperse lubricating oil. The friction working surface of the inner layer 2 is machined with multiple evenly distributed lubrication pits 21 for storing lubricant and improving self-lubricating performance.

[0046] The inner wall of the outer layer 1 is provided with multiple bonding grooves 11. The bonding grooves 11 are provided in multiple layers along the axial direction of the outer layer 1. The bonding grooves 11 of adjacent layers are arranged at intervals. Each layer includes multiple annularly spaced bonding grooves 11. The tips of adjacent layers of bonding grooves 11 face opposite directions, forming an interlocking structure. This structure can restrict the axial and circumferential slippage of the inner layer 2, making the interface bonding more stable. Part of the inner layer 2 is located in the bonding grooves 11. The inner layer 2 is filled and bonded in the bonding grooves 11 by centrifugal casting, forming an interlocking structure. It forms a gradient metallurgical bonding interface with the inner wall of the outer layer 1, increasing the bonding contact area of ​​the two metal layers and increasing the bonding force of the two metal layers.

[0047] like Figure 3 As shown, the joint groove 11 is scissor-shaped, including a tip and a tail. The tip is a circumferentially protruding sharp angle, and the tail consists of two separate sharp angles. The distance between two adjacent joint grooves 11 is the same as the groove width c of the joint groove 11, ensuring a reasonable distance between the joint grooves 11 and making the interlocking of the inner and outer layers more uniform. The depth h of the joint groove 11 is 0.3 to 0.8 mm. The ratio of the circumferential length a of the joint groove 11 to the circumference of the inner side surface of the outer layer 1 is 1:25 to 1:30. The ratio of the width b of the joint groove 11 to the axial length of the outer layer 1 is 1:15 to 1:20, ensuring the number of joint grooves 11. A small number of joint grooves 11 has little impact on the bonding strength of the double-layer metal, while a large number of joint grooves 11 will affect the interlocking bonding volume between the outer layer 1 and the inner layer 2. A small distance between the joint grooves 11 affects the firmness of the bonding interface.

[0048] This embodiment also discloses a preparation method for preparing the above-mentioned bimetallic composite self-lubricating bushing, comprising the following steps:

[0049] S1. Outer layer pre-machining: Select 42CrMo alloy steel forgings, rough machine them into outer layer steel billets for bushings, and leave a 3mm machining allowance for the outer circle, inner hole and end face. Place the steel billet in a heating furnace, heat it to 600℃ and hold it for 4 hours. Cool it to room temperature with the furnace to remove forging stress. Then, finish machine the inner hole of the steel billet to the specified size, and leave a 1mm machining allowance for the outer circle and end face.

[0050] S2. Joining groove processing: The above-mentioned joining groove 11 is processed on the inner surface of the outer steel billet using a nanosecond laser processing machine. The depth accuracy of the joining groove is controlled to be ±0.02mm and the groove width accuracy is ±0.01mm. After processing, the slag on the inner surface of the steel billet is blown away with compressed air.

[0051] S3. Surface Pretreatment: Place the steel billet with the machined joint groove from S2 into an ultrasonic cleaner and ultrasonically clean it with anhydrous ethanol for 20 minutes to remove surface oil and dust. After removal, place it into a vacuum furnace and evacuate it to 1×10⁻⁶. -2 Pa, heated to 500℃ and held for 30 minutes, is subjected to copper infiltration activation treatment to form a pure copper activation layer with a thickness of about 1 micrometer on the inner surface of the steel billet, which improves the interfacial wettability of the inner surface of the outer layer.

[0052] S4. Centrifugal Casting: Fix the outer steel billet processed in S3 onto the mold of a vertical centrifugal casting machine, seal both ends, and pour molten copper alloy liquid into the outer steel billet. Calculate the amount of copper alloy to be poured according to the following formula:

[0053]

[0054] in, The density of copper alloy, For the volume of the copper layer in the base layer of the mortise, For the total volume of the bonding groove, This is a shrinkage correction factor, with a value ranging from 2.2% to 3.2%.

[0055] In this embodiment Shrinkage correction factor .

[0056] Raw base copper layer volume The calculation formula is:

[0057]

[0058] in, , The thickness of the copper layer in the finished bushing. Allowance for copper layer processing, The inner diameter of the outer layer. This is the axial length of the bushing.

[0059] The thickness of the finished copper layer in this embodiment Copper layer processing allowance Therefore, the thickness of the base copper layer of the blank Substitute into the calculation .

[0060] In step S4, the The calculation formula is:

[0061]

[0062] in, The circumferential length of the groove is [missing information]. The axial width of the groove is... For the depth of the joint groove, This represents the total number of circumferential joint grooves. Where L is the total number of axial grooves, and L is the axial length of the bushing. This represents the total number of intersections of the groove in the circumferential and axial directions.

[0063] In this embodiment, axial setting Layer bonding grooves, with each layer circumferentially set There are several joint grooves. Substituting the values ​​into the formula, the volume of a single joint groove is calculated as follows: The total length after deducting overlap is ,therefore This embodiment reduces the calculation error of centrifugal casting volume by incorporating the copper layer processing allowance and the total volume of the bonding groove into the calculation of the overall casting volume.

[0064] Calculate the centrifugal speed during casting using the following formula:

[0065]

[0066] in, This is the corrected centrifugal acceleration. The radius of the inner surface of the copper blank is . The calculation formula is:

[0067]

[0068]

[0069] in, The corrected thickness of the copper blank. The calculation formula is:

[0070]

[0071] in, For the reference centrifugal acceleration of a flat interface, To incorporate the correction factor for the resistance of the slot filling, The value ranges from 1.15 to 1.5.

[0072] The centrifugal acceleration of the flat interface reference in this embodiment Combined with the groove filling resistance correction coefficient Therefore, the corrected centrifugal acceleration is .

[0073] The thickness of the copper layer blank is The inner surface radius of the copper layer blank Substituting into the formula, the centrifugal speed is calculated. .

[0074] The casting temperature of the copper alloy and the preheating temperature of the steel billet are matched according to the following rules, and the inner layer casting temperature and outer layer preheating temperature are calculated as follows:

[0075]

[0076]

[0077] in, The temperature of the copper alloy liquid. For the corrected casting overheating, This refers to the preheating temperature of the outer steel billet;

[0078] When the ratio of groove depth to width is 0.3 to 0.5, ;

[0079] When the ratio of groove depth to width is 0.5 to 0.8, ;

[0080] When the ratio of groove depth to width is 0.3 to 0.5, ;

[0081] When copper layer processing allowance At that time, the casting temperature was too high. It can reduce the temperature by 5-10℃ and the centrifugal speed n can be reduced by 5%-8%. By optimizing the centrifugal speed through the combination tank filling resistance correction coefficient, it can ensure that the copper liquid completely fills the dead corner of the combination tank, reduce the error of the circumferential thickness uniformity of the copper layer of the bushing, and improve the yield of bushing production.

[0082] Preheat the steel billet to 660℃, start the centrifugal casting machine, increase the speed to 362r / min and keep it stable, pour the CuSn12Ni2-C copper alloy liquid molten to 1075℃ into the inner hole of the steel billet at a uniform speed, the casting time is about 15s, after casting is completed, keep the speed rotating for 5min, then slowly stop the machine and let it cool naturally to room temperature to obtain a bimetallic composite billet.

[0083] S5. Gradient heat treatment: The bimetallic composite billet formed by S4 is placed in a heating furnace, heated to 860℃ and held for 3 hours, then air-cooled to room temperature for stress relief normalizing treatment. Subsequently, it is heated to 850℃ and held for 2 hours, then oil-quenched, and then heated to 580℃ and held for 4 hours, and air-cooled to room temperature to complete the integrated heat treatment of steel substrate tempering and copper alloy aging. After treatment, the hardness of the steel substrate is HB290~310, and the hardness of the copper alloy layer is HB130~140.

[0084] S6. Finished product processing: The bimetallic composite blank processed in S5 is subjected to rough turning, semi-finish turning and fine grinding in sequence to remove the copper layer processing allowance. The lubrication pits 21 are processed on the copper alloy friction working surface using femtosecond laser. Two or three lubrication pits 21 are arranged radially along the circumference and spaced apart from each other. Vacuum pressure is applied to impregnate the composite solid lubricant to finally obtain the finished bushing.

[0085]

[0086] As shown in the table above, the test results of the finished product in this embodiment are compared with those of the traditional bushing. The interfacial shear strength of the bimetallic composite self-lubricating bushing prepared in this embodiment is ≥290MPa, which is more than 45% higher than that of the traditional flat interface bushing. The yield rate of mass production is ≥95%.

[0087] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A bimetallic composite self-lubricating bushing, characterized in that, It includes an outer layer (1) and an inner layer (2). The outer layer (1) is made of steel, and the inner layer (2) is made of copper alloy. The inner wall of the outer layer (1) is provided with multiple joint grooves (11). The joint grooves (11) are provided in multiple layers along the axial direction of the outer layer (1). The joint grooves (11) of adjacent layers are arranged at intervals. Each layer includes multiple annularly spaced joint grooves (11). Part of the inner layer (2) is located in the joint grooves (11).

2. The bimetallic composite self-lubricating bushing according to claim 1, characterized in that, The connecting groove (11) includes a tip and a tail. The tips of two adjacent connecting grooves (11) face opposite directions. The distance between two adjacent connecting grooves (11) is the same as the groove width c of the connecting groove (11).

3. The bimetallic composite self-lubricating bushing according to claim 1, characterized in that, The depth h of the connecting groove (11) is 0.3 to 0.8 mm, the ratio of the circumferential length a of the connecting groove (11) to the circumference of the inner side surface of the outer layer (1) is 1:25 to 1:30, and the ratio of the width b of the connecting groove (11) to the axial length of the outer layer (1) is 1:15 to 1:

20.

4. The bimetallic composite self-lubricating bushing according to claim 1, characterized in that, The inner layer (2) is made of CuSn12Ni2-C alloy.

5. A preparation method for preparing the bimetallic composite self-lubricating bushing according to any one of claims 1 to 4, characterized in that, Includes the following steps, S1. Outer layer pre-machining: The alloy steel billet is rough-machined into the outer layer steel billet of the bushing to remove forging stress; S2, Gutter machining: The inner wall of the outer steel billet made in S1 is machined using laser. S3. Surface pretreatment: The inner surface of the outer steel billet with the bonding groove processed in S2 is ultrasonically vacuum cleaned to remove slag and oxide layer, and copper infiltration activation treatment is carried out in a vacuum environment. S4. Centrifugal casting: The outer steel billet processed in S3 is fixed in a vertical centrifugal casting machine, and molten copper alloy liquid is poured into the outer steel billet. After cooling, a bimetallic composite billet is obtained. S5. Gradient heat treatment: The bimetallic composite billet formed in S4 is subjected to stress normalizing, outer layer and inner layer heat treatment in sequence. S6. Finished product processing: The bimetallic composite blank processed in S5 is subjected to rough turning, semi-finish turning and fine grinding in sequence to remove the copper layer processing allowance, and then vacuum pressure impregnation with composite solid lubricant to finally obtain the finished bushing.

6. The preparation method according to claim 5, characterized in that, In step S4, the amount of copper alloy cast m is calculated according to the following formula: in, The density of copper alloy, For the volume of the copper layer in the base layer of the mortise, For the total volume of the bonding groove, This is a shrinkage correction factor, with a value ranging from 2.2% to 3.2%.

7. The preparation method according to claim 6, characterized in that, In step S4, the The calculation formula is: in, , The thickness of the copper layer in the finished bushing. Allowance for copper layer processing, The inner diameter of the outer layer. This is the axial length of the bushing.

8. The preparation method according to claim 6, characterized in that, In step S4, the The calculation formula is: in, The circumferential length of the groove is [missing information]. The axial width of the groove is... For the depth of the joint groove, This represents the total number of circumferential joint grooves. Where L is the total number of axial grooves, and L is the axial length of the bushing. This represents the total number of intersections of the groove in the circumferential and axial directions.

9. The preparation method according to claim 7, characterized in that, In step S4, the formula for calculating the centrifugal speed of the outer steel billet is: in, This is the corrected centrifugal acceleration. The radius of the inner surface of the copper blank is . The calculation formula is: in, The thickness of the copper blank, after correction The calculation formula is: in, For the reference centrifugal acceleration of a flat interface, To incorporate the correction factor for the resistance of the slot filling, The value ranges from 1.15 to 1.

5.

10. The preparation method according to claim 5, characterized in that, In step S4, the inner layer casting temperature and the outer layer preheating temperature are calculated: in, The temperature of the copper alloy liquid. For the corrected casting overheating, This is the preheating temperature of the outer steel billet.

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