Front bushing for construction machinery and manufacturing method therefor

Abstract

The present invention provides a front bushing for construction machinery and a manufacturing method therefor, in which a copper alloy is laminated on at least one of opposite end portions of the inner circumferential surface of the bushing, so that, even when bending of a pin is induced during a high-load operation and a concentrated load is generated at an edge portion of the inner circumferential surface of the bushing, the copper alloy is deformed to reduce contact surface pressure, thereby preventing seizure, wear, and galling of the bushing.

Description

Front bushing for construction machinery and method of manufacturing the same

[0001] The present invention relates to a front bushing for construction machinery and a method for manufacturing the same, and more specifically, to a front bushing for construction machinery and a method for manufacturing the same in which a copper alloy is laminated on at least one of the two ends of the inner circumferential surface of the bushing, so that even when bending of the pin is induced during high-load work and a concentrated load occurs at the corner of the inner circumferential surface of the bushing, the copper alloy can deform and reduce the contact surface pressure, thereby preventing joints, wear, and adhesion of the bushing.

[0002] In the front of the excavator, power is transmitted to most drive components using sliding bearings in the form of pin and bushing joints. The durability of the pin and bushing joint structure is determined by appropriate strength design and fatigue and wear characteristics. Furthermore, due to the nature of high-load, low-speed operation, the machine operates in a boundary lubrication state that is vulnerable to friction, wear, and adhesion; therefore, wear resistance and lubricity are critical.

[0003] Conventionally, to maintain lubrication performance, methods such as periodically injecting grease into the friction surfaces of the pin and bushing joints or surface-hardening the friction surfaces to improve wear resistance were used.

[0004] However, despite ensuring the wear resistance and lubricity of these pin and bushing joints, bending of the pin is induced when the excavator performs high-load operations due to the temporary high load applied to the front drive section. Consequently, contact between the pin and the bushing occurs only on the localized surface of the corners rather than on the entire inner circumference of the bushing. As a result, the surface pressure caused by the localized concentrated load applied to the pin and the bushing exceeds the limiting surface pressure of the pin and the bushing, leading to adhesive wear and noise at the contact surface.

[0005] These issues cause failures in pin and bushing joints, which consequently become a major cause of reduced excavator lifespan. Furthermore, the noise generated at the work site due to the joints leads to customer dissatisfaction.

[0006] The present invention aims to provide a front bushing for construction machinery and a method for manufacturing the same, which can prevent joints, wear, and adhesion of the bushing by allowing the copper alloy to deform and reduce contact pressure even when a concentrated load occurs at the corner of the inner surface of the bushing due to bending of the pin during high-load work, by laminating a copper alloy on at least one of the two ends of the inner surface of the bushing.

[0007] The technical problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention belongs from the description below.

[0008] One embodiment of the present invention for solving the above problem provides a front bushing for a construction machine having a pin disposed inside, characterized in that a copper alloy layer is laminated and provided on at least one of one end and the other end of the inner circumferential surface of the bushing.

[0009] According to an embodiment, the remaining portion of the bushing excluding the copper alloy layer may be made of steel.

[0010] According to an example, the copper alloy layer may contain 55 wt% or more of Cu and have a hardness of HRB 70 or higher.

[0011] According to an embodiment, the inner surface of the bushing provided with the copper alloy layer may have a constant inner diameter over the entire length of the bushing.

[0012] According to an embodiment, at least one of the end portion and the other end portion of the inner surface of the bushing is provided with a machined portion machined in the depth direction, and the copper alloy layer may be laminated on the machined portion.

[0013] According to an embodiment, the area of ​​the copper alloy layer provided at one end or the other end of the inner surface of the bushing may correspond to 10% to 30% of the total area of ​​the inner surface of the bushing.

[0014] According to the embodiment, the thickness of the copper alloy layer may be within 5 mm.

[0015] According to an embodiment, the inner surface of the bushing is provided with one or more dimples or one or more grooves, and the total area of ​​the one or more dimples or the total area of ​​the one or more grooves may correspond to 20% to 30% of the total area of ​​the inner surface of the bushing.

[0016] According to an embodiment, when a concentrated load is applied to at least one of the end portion and the other portion of the inner surface of the bushing by the pin, the copper alloy layer may be plastically deformed so that the contact area with the pin increases.

[0017] One embodiment of the present invention for solving the above problem provides a method for manufacturing a front bushing for construction machinery in which a pin is disposed inside, comprising: a step of providing an initial bushing made of steel material; a step of forming a processed portion by processing at least one of one end and the other end of the inner circumferential surface of the initial bushing in the depth direction; and a step of laminating a copper alloy layer on the processed portion.

[0018] According to an embodiment, after the lamination step, the method may further include a step of surface polishing the inner surface of the bushing so that the inner surface of the bushing has a constant inner diameter over the entire length of the bushing.

[0019] According to an embodiment, after the surface polishing step, the step of forming one or more dimples or one or more grooves on the inner circumference of the bushing may be further included.

[0020] According to an embodiment, in the stacking step, the copper alloy layer may be stacked by a Direct Energy Deposition (DED) method or a laser cladding method.

[0021] According to an embodiment, when the copper alloy layer is laminated by the DED method or the laser cladding method, the copper alloy layer may contain a base material component within 30%.

[0022] According to an embodiment, in the lamination step, the copper alloy layer may be laminated by pressing or joining a separately manufactured copper alloy ring to the processed part.

[0023] According to an example, the copper alloy layer may contain 55 wt% or more of Cu and have a hardness of HRB 70 or higher.

[0024] According to an example, in the lamination step, the copper alloy layer can be laminated with a thickness of 5 mm or less.

[0025] According to the present invention, a copper alloy is laminated at at least one of the two ends of the inner circumferential surface of a bushing, so that even when bending of the pin is induced during high-load operation and a concentrated load occurs at the corner of the inner circumferential surface of the bushing, the copper alloy deforms, thereby reducing the contact surface pressure. More specifically, when a concentrated load is applied to at least one of the two ends of the inner circumferential surface of the bushing by the pin, the copper alloy layer is plastically deformed so that the contact area with the pin increases, thereby allowing the concentrated load to be distributed over a wide area.

[0026] Accordingly, friction, wear, and adhesion of the bushings can be prevented. This can extend the lifespan of the bushings and, ultimately, the construction machinery, and prevent noise generated at the work site due to friction.

[0027] In addition, since copper alloys have superior lubricity compared to steel, anti-seizure properties can also be improved.

[0028] The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description of the invention or the claims.

[0029] FIG. 1 is a perspective view illustrating a front bushing for construction machinery according to one embodiment of the present invention.

[0030] Figure 2 is a schematic diagram showing a cross-section of Figure 1.

[0031] Figure 3 is a schematic diagram showing the state in which bending of the pin is induced in Figure 2.

[0032] FIG. 4 is a schematic diagram showing the flow of a method for manufacturing a front bushing for construction machinery according to one embodiment of the present invention.

[0033] FIGS. 5a to 5d are cross-sectional views showing the bushings after each of steps S1 to S3 and S5 of FIG. 4.

[0034] Figure 6 is a schematic diagram showing an example of step S3 of Figure 4.

[0035] Hereinafter, preferred embodiments of the front bushing for construction machinery and the method for manufacturing the same according to the present invention will be described with reference to the attached drawings.

[0036] Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intention or practice of the user or operator; additionally, the following embodiments are not intended to limit the scope of the present invention but are merely exemplary details of the components presented in the claims of the present invention.

[0037] To clearly explain the present invention, parts unrelated to the description have been omitted, and the same reference numerals are used for identical or similar components throughout the specification. Throughout the specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may additionally include other components.

[0038] In addition, components referred to as '~parts' throughout the specification may consist of two or more components combined into a single component, or a single component may be divided into two or more components based on more detailed functions. Furthermore, each component described below may additionally perform some or all of the functions performed by other components in addition to its primary function, and it goes without saying that some of the primary functions performed by each component may be exclusively performed by other components.

[0039]

[0040] First, a front bushing (10) for a construction machine according to one embodiment of the present invention will be described with reference to FIGS. 1 to 3.

[0041] For example, if the construction machine is an excavator, the front bushing (10) can be assembled to the front boom of the excavator. A pin (20) is placed inside the bushing (10), and the bushing (10) moves in an oscillating motion while making curved contact with the pin (20). This allows the front boom of the excavator to be driven.

[0042] When the excavator performs high-load work, bending of the pin (20) may be induced as a temporary high load is applied to the drive part of the front boom. In this case, contact between the pin (20) and the bushing (10) occurs only at the corners rather than at the front surface of the inner circumference of the bushing, and as a result, a localized concentrated load may be applied to the corners of the bushing (10).

[0043] To prevent this, the present invention is characterized by having a copper alloy layer (100) laminated and provided on at least one of the end portion and the other end portion of the inner surface of the bushing (10). In this embodiment, a copper alloy layer (100) is provided on both the end portion and the other end portion of the inner surface of the bushing (10).

[0044] The bushing (10) is basically made of steel. That is, the rest of the bushing (10), excluding the copper alloy layer (100), is made of steel.

[0045] As shown in FIG. 2, the inner surface of the bushing (10) equipped with a copper alloy layer (100) has a constant inner diameter over the entire length of the bushing. That is, the height of the inner surface where the copper alloy is laminated and the inner surface where the copper alloy is not laminated are the same. To this end, one end and the other end of the inner surface of the bushing (10) are each provided with a machined portion (150) machined in the depth direction, and the copper alloy layer (100) is laminated on the machined portion (150).

[0046] At this time, it is preferable that the area of ​​the copper alloy layer (100) provided at one end or the other end of the inner surface of the bushing (10) corresponds to 10% to 30% of the total area of ​​the inner surface of the bushing (10). Since this is based on one end of the bushing (10), if the copper alloy layer (100) is provided at both the one end and the other end of the inner surface of the bushing (10) as in the present embodiment, the total area of ​​the copper alloy layer (100) will correspond to 20% to 60% of the total area of ​​the inner surface of the bushing (10).

[0047] Table 1 below shows a comparison of load-carrying performance according to the stacking area of ​​the copper alloy layer (100) over the entire inner surface area of ​​the bushing (10) at one end of the bushing (10). For each comparative example and embodiment, the results are obtained by conducting evaluations under normal load conditions and corner concentrated load conditions. The test surface pressure was set to operate with a maximum contact stress of 344 MPa under normal load conditions where the pin (20) contacts the entire inner surface of the bushing (10), and a maximum contact stress of 1000 MPa under corner concentrated load conditions of the bushing (10) caused by bending of the pin (20). The test operation was set to a 90° oscillating motion at a rotational speed of 1 m / min, and the test was repeated for 200,000 cycles.

[0048] As can be seen in Table 1, if the area of ​​the copper alloy layer (100) provided at one end of the bushing (10) is less than 10% of the total area of ​​the inner surface of the bushing (10), there is a risk that the bent pin (20) will come into contact with the boundary portion (corner of the processed portion (150)) between the copper alloy layer (100) and the remaining steel portion, and as a result, stress exceeding the limit surface pressure may be applied.

[0049] On the other hand, if the area of ​​the copper alloy layer (100) provided at one end of the bushing (10) exceeds 30% of the total area of ​​the inner surface of the bushing (10), the normal load-bearing capacity (load-carrying capacity) is reduced due to the reduction in the steel area of ​​the inner surface of the bushing, and there is a concern that the durability of the bushing (10) may be reduced.

[0050] In this way, when the laminated area of ​​the copper alloy layer (100) corresponds to 10% to 30%, no problems of jointing, wear, and adhesion of the bushing (10) occur under both normal load conditions and corner concentrated load conditions.

[0051] Classification Lamination Area Lamination Depth Corner Concentrated Load Condition Normal Load Condition Evaluation Comparison Yes Steel Bushing 0% 0mm No abnormalities caused by joints, wear, or partial adhesion Fail Comparison Example Copper Alloy Bushing 0% 0mm No abnormalities caused by joints or partial wear (insufficient load-bearing capacity) Example 1 Copper Alloy Laminated Bushing 10% 10mm No abnormalities caused by partial wear or adhesion at the boundary between copper alloy and steel Fail Example 2 20% No abnormalities caused by 10mm Pass Example 3 30% No abnormalities caused by 10mm Pass Example 4 40% No abnormalities caused by 10mm Fail

[0052]

[0053] In addition, it is preferable that the thickness (t) of the copper alloy layer (100) be within 5 mm. That is, the copper alloy layer (100) has a thickness of 5 mm or less in the depth direction based on the inner surface of the bushing (10). This is because plastic deformation caused by contact load with the pin (20), which will be explained in detail later, occurs within 5 mm, and if it exceeds 5 mm, there is a risk that the bushing (10) will break during high-strength work due to insufficient strength of the bushing (10) caused by the reduction in steel thickness.

[0054] In this embodiment, a 5mm thick processed portion (150) is processed on the inner surface of the bushing (10), and then a copper alloy layer (100) is laminated to a thickness of 5mm on the processed portion (150).

[0055] Table 2 below shows a comparison of load-carrying performance according to the stacking thickness of the copper alloy layer (100). For each comparative example and embodiment, the results are based on evaluations conducted under normal load conditions and corner concentrated load conditions, and the test conditions are the same as those in Table 1 above.

[0056] As can be seen in Table 2, when the laminate thickness of the copper alloy layer (100) is within 5 mm, no problems of jointing, wear, and adhesion of the bushing (10) occur under both normal load conditions and corner concentrated load conditions.

[0057] Classification Lamination Area Lamination Thickness Corner Concentrated Load Condition Normal Load Condition Evaluation Comparison Yes Steel Bushing 0% 0mm No defects caused by joints, wear, or partial adhesion Fail Comparison Yes Copper Alloy Bushing 0% 0mm No defects caused by joints or partial wear (insufficient load-bearing capacity) Fail Example 1 Copper Alloy Laminated Bushing 20% ​​No defects caused by 1mm or more Pass Example 2 20% No defects caused by 5mm or more Pass Example 3 20% No defects caused by 10mm or more Part breakage (insufficient bushing strength) Fail

[0058]

[0059] Copper alloy materials have excellent embeddability and conformability, which are properties required for bearings. As a result, when a concentrated load is applied to at least one end and the other end of the inner circumference of the bushing (10) by the pin (20) as shown in FIG. 3, the copper alloy layer (100) is plastically deformed by the load so that the contact area with the pin (20) increases.

[0060] More specifically, the copper alloy layer (100) of the bushing (10) is subjected to compressive stress due to the load when contacted by the bending of the pin (20). At this time, the copper alloy undergoes plastic deformation in proportion to the applied load level due to its low hardness and high ductility characteristics, and as a result, as shown in FIG. 3, the length of the inner surface of the bushing (10) in contact with the pin (20) increases, thereby increasing the contact area. Consequently, the load is not concentrated only on the two end corners of the bushing (10) but can be distributed over a wide area by the deformed copper alloy layer (100), and the limiting surface pressure between the bushing (10) and the pin (20) can be avoided. Additionally, since the copper alloy has superior lubricity compared to steel, it can improve anti-seizure properties.

[0061] In particular, it is desirable that the copper alloy layer (100) contains at least 55 wt% Cu and has a hardness of HRB 70 or higher. Specifically, the copper alloy layer (100) contains at least 55 wt% Cu, and the remainder may contain additive elements such as Zn, Al, and Fe. In addition, if the hardness is lower than HRB 70, excessive wear may occur due to insufficient wear resistance of the bushing (10), so the hardness of the copper alloy layer (100) must be HRB 70 or higher. Table 3 below shows some examples of copper alloy chemical compositions, and results show that excessive wear occurs when the hardness is lower than HRB 70.

[0062] Classification Copper Alloy Chemical Composition (wt%) Hardness (HRB) Test Result Evaluation CuZnSnAlMnFeNi Wear Depth (mm) Surface Example 1 Remainder 22~280~0.25.0~7.52.5~5.02.0~4.00~0.510000.45 Normal Pass Example 2 Remainder 0~0.5-9~11-0.8~1.5-720.77 Normal Pass Example 3 Remainder 0~0.312~15--0~0.20~1.0642.30 Excessive Wear Fail

[0063]

[0064] Here, Example 1 is made of high-strength brass equivalent to CAC304, Example 2 is made of aluminum bronze equivalent to C95300, and Example 3 is made of phosphor bronze equivalent to CAC503.

[0065] If the bushing (10) is not manufactured by laminating a copper alloy layer (100) onto a steel material as in the present invention, but the entire bushing is made of copper alloy, the load-bearing capacity of the bushing is lower than that of a steel bushing, making it unsuitable for application to excavators for high-load work. (See Tables 1 and 2)

[0066] In addition, when a copper alloy layer (100) is not laminated and provided on one end and the other end of the inner surface of the bushing (10) as in the present invention, but rather a sloped structure is applied in advance to one end and the other end of the inner surface of the bushing (10), the pin (20) comes into contact with the sloped structure of the bushing (10) when the pin (20) bends, so the limit surface pressure may not be exceeded. However, since the degree of bending of the pin (20) varies depending on the size and load of the excavator, the difficulty of processing is high because individual design is required for the sloped dimensions according to each condition. Furthermore, when a load exceeding the prediction is applied, adhesive wear and joint problems still occur.

[0067] In some cases, the inner surface of the bushing (10) may also be provided with one or more dimples or one or more grooves. The dimples or grooves provide functions for storing and supplying grease, collecting wear particles, and increasing load-bearing capacity. As shown in FIG. 1, in this embodiment, a plurality of dimples (200) are provided on the inner surface of the bushing (10). At this time, it is preferable that the total area of ​​the plurality of dimples (200) corresponds to 20% to 30% of the total area of ​​the inner surface of the bushing (10).

[0068]

[0069] Next, with reference to FIG. 4, a method for manufacturing a front bushing for construction machinery according to one embodiment of the present invention will be described.

[0070] A method for manufacturing a front bushing for construction machinery according to one embodiment of the present invention comprises the steps of: providing an initial bushing (10') made of steel material (S1); forming a processed portion (150) by processing at least one of the end portion and the other end portion of the inner surface of the initial bushing (10') in the depth direction (S2); laminating a copper alloy layer (100) on the processed portion (150) (S3); surface polishing the inner surface of the bushing (10) so that the inner surface of the bushing (10) has a constant inner diameter over the entire length of the bushing (10) (S4); and forming one or more dimples (200) or one or more grooves on the inner surface of the bushing (10) (S5).

[0071] FIG. 5a shows an initial bushing (10') made of steel material. FIG. 5b shows a state in which a processing section (150) is processed at one end and the other end of the inner circumference of the initial bushing (10'). FIG. 5c shows a state in which a copper alloy layer (100) is laminated on the processing section (150). FIG. 5d shows a state in which a plurality of dimples (200) are formed on the inner circumference of the bushing (10).

[0072] In particular, the step (S3) of laminating a copper alloy layer (100) on a processing part (150) can be performed by various methods.

[0073] For example, in the deposition step (S3), the copper alloy layer (100) can be deposited by a Direct Energy Deposition (DED) method or a laser cladding method. Here, the DED method is one of the metal 3D printing methods, which involves depositing materials by melting and bonding them using energy such as a high-power laser, electron beam, or plasma arc while spraying metal powder or wire directly onto the surface of an object. Additionally, the laser cladding method is one of the surface modification methods, which involves manufacturing a coating layer by melting powder or wire using a high-power laser and continuously depositing it. In this way, by using a high-power laser beam to melt the copper alloy powder and simultaneously weld it to the steel base material while depositing it, the bonding force with the steel base material of the bushing can be secured.

[0074] When a copper alloy layer (100) is laminated by a DED method or a laser cladding method, the copper alloy layer (100) may contain a base material component within 30%. Specifically, during the DED or laser cladding process, the coating material is melted by a laser and coated onto the steel base material of the bushing, and at the same time, the steel base material is partially melted by the heat input from the laser. As a result, the melted steel base material is mixed with the coating material, and thus the copper alloy layer (100) contains a steel base material component within 30%. The steel base material component mixed in the copper alloy layer (100) may be formed into a needle-like or spherical microstructure within the copper alloy layer (100).

[0075] However, it is not limited to this, and as another physical method, in the lamination step (S3), the copper alloy layer (100) may be laminated by separately manufacturing a copper alloy ring (100') being pressed or bonded to the processing part (150). FIG. 6 shows the state before the separately manufactured copper alloy ring (100') is pressed or bonded to the processing part (150).

[0076] As seen above, it is preferable that the copper alloy layer (100) contains 55 wt% or more of Cu and has a hardness of HRB 70 or higher. Additionally, in the lamination step (S3), it is preferable that the copper alloy layer (100) be laminated with a thickness of 5 mm or less, and the area of ​​the copper alloy layer (100) provided at one end or the other end of the inner circumference of the bushing (10) is preferably 10% to 30% of the total area of ​​the inner circumference of the bushing (10).

[0077] The present invention is not limited to the specific embodiments and descriptions described above, and various modifications can be made by anyone with ordinary knowledge in the technical field to which the present invention pertains without departing from the essence of the invention as claimed in the claims, and such modifications fall within the scope of protection of the present invention.

[0078] The present invention relates to a front bushing for construction machinery and a method for manufacturing the same, and more specifically, to a front bushing for construction machinery and a method for manufacturing the same in which a copper alloy is laminated on at least one of the two ends of the inner circumferential surface of the bushing, so that even when bending of the pin is induced during high-load work and a concentrated load occurs at the corner of the inner circumferential surface of the bushing, the copper alloy can deform and reduce the contact surface pressure, thereby preventing joints, wear, and adhesion of the bushing.

Claims

1. In a front bushing for construction machinery in which a pin is disposed internally, A front bushing for construction machinery, characterized in that a copper alloy layer is laminated and provided on at least one of the end portion and the other portion of the inner surface of the bushing.

2. In Paragraph 1, A front bushing for construction machinery, characterized in that the remaining part of the bushing, excluding the copper alloy layer, is made of steel.

3. In Paragraph 1, A front bushing for construction machinery, characterized in that the copper alloy layer contains 55 wt% or more of Cu and has a hardness of HRB 70 or more.

4. In Paragraph 1, A front bushing for construction machinery, characterized in that the inner surface of the bushing provided with the copper alloy layer has a constant inner diameter over the entire length of the bushing.

5. In Paragraph 4, A front bushing for construction machinery, characterized in that at least one of the one end and the other end of the inner surface of the bushing is provided with a machined portion machined in the depth direction, and the copper alloy layer is laminated on the machined portion.

6. In Paragraph 1, A front bushing for construction machinery, characterized in that the area of ​​the copper alloy layer provided at one end or the other end of the inner circumferential surface of the bushing corresponds to 10% to 30% of the total area of ​​the inner circumferential surface of the bushing.

7. In Paragraph 1, A front bushing for construction machinery, characterized in that the thickness of the copper alloy layer is within 5 mm.

8. In Paragraph 1, A front bushing for construction machinery, characterized in that the inner surface of the bushing is provided with one or more dimples or one or more grooves, and the total area of ​​the one or more dimples or the total area of ​​the one or more grooves corresponds to 20% to 30% of the total area of ​​the inner surface of the bushing.

9. In Paragraph 1, A front bushing for construction machinery, characterized in that when a concentrated load is applied to at least one of the end portion and the other end portion of the inner circumferential surface of the bushing by the pin, the copper alloy layer is plastically deformed to increase the contact area with the pin.

10. A method for manufacturing a front bushing for construction machinery in which a pin is disposed internally, Step of providing an initial bushing made of steel; A step of forming a machined portion by machining at least one of the end portion and the other end portion of the inner surface of the initial bushing in the depth direction; and A method for manufacturing a front bushing for construction machinery, comprising the step of laminating a copper alloy layer on the above-mentioned processed portion.

11. In Paragraph 10, A method for manufacturing a front bushing for construction machinery, further comprising: a step of surface polishing the inner surface of the bushing after the above lamination step, so that the inner surface of the bushing has a constant inner diameter over the entire length of the bushing.

12. In Paragraph 11, A method for manufacturing a front bushing for construction machinery, further comprising the step of forming one or more dimples or one or more grooves on the inner circumference of the bushing after the above-mentioned surface polishing step.

13. In Paragraph 10, A method for manufacturing a front bushing for construction machinery, characterized in that, in the above lamination step, the copper alloy layer is laminated by a Direct Energy Deposition (DED) method or a laser cladding method.

14. In Paragraph 13, A method for manufacturing a front bushing for construction machinery, characterized in that when the copper alloy layer is laminated by the above DED method or the above laser cladding method, the copper alloy layer contains a base material component mixed within 30%.

15. In Paragraph 10, A method for manufacturing a front bushing for construction machinery, characterized in that, in the above-mentioned lamination step, the copper alloy layer is laminated by pressing or joining a separately manufactured copper alloy ring to the processed part.

16. In Paragraph 10, A method for manufacturing a front bushing for construction machinery, characterized in that the copper alloy layer contains 55 wt% or more of Cu and has a hardness of HRB 70 or more.

17. In Paragraph 10, A method for manufacturing a front bushing for construction machinery, characterized in that, in the above lamination step, the copper alloy layer is laminated to a thickness of 5 mm or less.

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