A laser cladding repair process for a crankshaft crankpin

Abstract

The present application relates to the technical field of laser cladding, and particularly relates to a laser cladding repair process for a crankshaft crank web, comprising the following steps: S1, pretreating a to-be-repaired part on the crankshaft crank web; S2, clamping the crankshaft in a two-end-opposite-vertex manner, and performing point position teaching on the to-be-repaired part on the crankshaft crank web through a robot linkage coordination program to complete program logic editing; S3, running a track according to the point position teaching program, and first laser cladding a primer layer on the to-be-repaired part, and then laser cladding a high-hardness layer on the surface of the primer layer; and S4, finishing the high-hardness layer. The present application has the advantages that the repair operation of the damaged part on the crankshaft crank web is simple, no additional eccentric clamp and other customized tooling is needed, and the repaired damaged part has high hardness, thereby improving the service life of the crankshaft.

Description

Technical Field

[0001] This invention relates to the field of laser cladding technology, specifically to a laser cladding repair process for crankshaft cranks. Background Technology

[0002] The crankshaft is the most important component in an engine. It bears the force transmitted from the connecting rod and converts it into torque, which is then output through the crankshaft to drive other accessories on the engine. The crankshaft is subjected to the combined effects of centrifugal force from the rotating mass, periodically changing gas inertial force, and reciprocating inertial force, resulting in bending and torsional loads. Therefore, the crankshaft is required to have sufficient strength and rigidity, and the journal surfaces must be wear-resistant, operate evenly, and have good balance.

[0003] After a period of service, engine crankshafts will experience wear on the crankshaft cranks, and cracks will appear at the transition fillets between the crankshaft cranks and crank arms, as well as at the edges of the oil holes. If the wear is minor and the cracks are shallow, a grinding process can be used for repair. If the wear and cracks exceed the dimensions for grinding, surface repair techniques can be chosen. While thermal spraying can be used to repair damaged areas of the crankshaft, a single coating will peel off from the surface after a period of use, and the coating adhesion strength is low.

[0004] Laser cladding technology simultaneously melts the surface of the part and the powder, then rapidly cools and solidifies, forming a metallurgical bond between the cladding layer and the part surface, thus improving the bonding strength. Damaged areas at the crankshaft crank joint can be repaired using laser cladding. For example, CN110747458A discloses a method for repairing a crankshaft from a hot-rolled fixed-width press. This method uses laser cladding to prepare a base layer and a cover layer on the crankshaft surface. The base layer is made of nickel-based alloy powder, and the cover layer is made of cobalt-based alloy powder. A laser cladding machine is used, with the crankshaft placed on a worktable. The crankshaft rotates, and a powder feeding device delivers the alloy powder to the laser melting pool. The powder feeding amount is adjusted to achieve the desired coating thickness. The laser beam and powder feeding head are fed axially along the crankshaft, rotating at a set speed, resulting in a uniform and dense laser cladding layer on the machined surface. The drawbacks of this patent are twofold: first, the use of laser cladding technology to prepare a self-lubricating wear-resistant layer to restore the crankshaft dimensions results in a low hardness of the obtained wear-resistant layer; second, the patent requires a worktable fixture for the laser cladding operation. Summary of the Invention

[0005] To address the technical problems of low hardness and the need for tooling in laser cladding repair, this invention provides a laser cladding repair process for crankshafts and crankpins. The repair operation is simple, and the repaired damaged parts have high hardness, thus improving the service life of the crankshaft.

[0006] This invention provides a laser cladding repair process for crankshaft cranks, comprising the following steps:

[0007] S1. Pre-treatment of the crankshaft crank section to be repaired;

[0008] S2. The crankshaft is clamped at both ends, and the robot linkage coordination program teaches the points to be repaired at the crankshaft crank to complete the program logic editing.

[0009] S3. Following the point-to-point teaching procedure, first, a layer of base coat is laser-fused onto the crankshaft crank section to be repaired, and then a high-hardness layer is laser-fused onto the surface of the base coat.

[0010] S4. Final processing of high-hardness layers.

[0011] Furthermore, in step S1, the pretreatment method for the crankshaft crank section to be repaired is as follows:

[0012] S11. Grind away the nitriding layer at the crankshaft crank section to be repaired;

[0013] S12. Test the surface hardness of the crankshaft crank after grinding, and make the surface hardness meet 35-40HRC. The reason for pre-treating the crank part to be repaired is that the surface of the crank has been nitrided and the hardness is generally above 60HRC. Direct laser cladding will definitely crack. Therefore, the nitrided layer on the surface of the crank is ground off to a hardness of 35-40HRC.

[0014] Furthermore, in step S2, the crankshaft is clamped in a clamping-on-top manner, and the crankshaft to be repaired is divided into 1cm points around one revolution. Through the robot's linkage and coordination function, when the crankshaft reaches its highest point, the points are taught one by one. When teaching the points, it is ensured that the light spot size of each equal part is consistent and uniform, and the program logic is edited.

[0015] Furthermore, in step S3, the method for laser cladding a base layer on the part to be repaired is to laser clad the first iron-based alloy powder onto the part to be repaired to form a base layer. The laser cladding process parameters are as follows: laser power is 1800W, spot size is 3mm, robot running fitting speed is 80cm / min, protective gas is Ar, gas flow rate is 9L / min, program running trajectory is clockwise linkage rotation along the circumference of the crank, laser head is at a 90° angle with end face, off-axis powder feeding nozzle is at a 70° angle with end face, and powder feeding rate is 2.5r / min.

[0016] Furthermore, the first iron-based alloy powder comprises the following chemical composition by weight percentage: Cr 19.5%, Ni 12.51%, Nb 1.23%, Mo 2.02%, with the balance being Fe and unavoidable impurities; the first iron-based alloy powder has a particle size of 270–400 mesh and an average hardness of 35–40 HRC.

[0017] Furthermore, in step S3, the method for laser cladding a high-hardness layer onto the surface of the substrate is as follows: the second iron-based alloy powder is laser clad onto the surface of the substrate to form a high-hardness layer. The laser cladding process parameters are: laser power of 2200W, spot size of 3mm, robot running fitting speed of 80cm / min, protective gas of Ar, gas flow rate of 8L / min, program running trajectory of clockwise linkage rotation along the circumference of the crank, laser head at a 90° angle to the end face, off-axis powder feeding nozzle at a 70° angle to the end face, and powder feeding rate of 4.0r / min.

[0018] Furthermore, the second iron-based alloy powder comprises the following chemical composition by weight percentage: Cr 17.09%, Ni 2.13%, Mo 0.031%, Mn 0.42%, Nb 0.14%, with the balance being Fe and unavoidable impurities; the second iron-based alloy powder has a particle size of 270–400 mesh and an average hardness of 55–60 HRC.

[0019] Furthermore, in step S3, after laser cladding a base layer onto the area to be repaired, the base layer is ground and inspected for flaws. The thickness of the ground layer is half the thickness of the base layer. This ensures that the base layer has sufficient thickness to cover dimensional defects while also separating the high-hardness surface layer from the curved substrate, reducing or avoiding the risk of cracking during laser cladding of the high-hardness layer.

[0020] Furthermore, in step S4, the final processing method for the high-hardness layer is to perform final grinding processing according to the dimensions of the finished crankshaft to ensure dimensional accuracy and surface finish.

[0021] Furthermore, in step S4, after the high-hardness layer is finally processed, hardness testing and surface flaw detection are performed to ensure that the surface hardness is ≥58HRC and the end face is free of cracks and pores.

[0022] The beneficial effects of this invention are as follows:

[0023] (1) In this invention, the crankshaft crank section to be repaired is laser-clad with a base layer and a high-strength layer in sequence. The base layer material is selected from powders with low hardness and easy fusion to achieve the purpose of dimensional repair and spacing of the high-hardness surface layer. The high-hardness surface layer is mainly composed of chemical components with high hardness and wear resistance, providing a stable working environment for the crankshaft. After repair, it has strong hardness and improves the service life of the crankshaft.

[0024] (2) In the method of crankshaft and crankpin repair, the present invention does not use the traditional custom eccentric tooling. Instead, it directly clamps both ends of the crankshaft and coordinates the crankpin to complete the linkage and following through the robot. This method is not limited by the size of the crankshaft and does not rely on custom tooling. At the same time, the present invention divides the crankshaft and crankpin into uniform points and realizes the following action at the crankshaft and crankpin through program logic, saving the design and assembly of eccentric tooling and making it more flexible. Attached Figure Description

[0025] 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, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 This is a process flow diagram of a specific embodiment of the present invention.

[0027] Figure 2 These are actual photos of the damaged crankshaft crank section to be repaired before and after pretreatment, according to a specific embodiment of the present invention.

[0028] Figure 3 This is a physical diagram of the evenly distributed points of the damaged crankshaft crankpin according to a specific embodiment of the present invention.

[0029] Figure 4 This is a physical image of the damaged crankshaft offshaft powder feeding device according to a specific embodiment of the present invention.

[0030] Figure 5 This is a photograph of the damaged crankshaft and crankpin after laser cladding of the bottom layer, according to a specific embodiment of the present invention.

[0031] Figure 6 This is a photograph of the high-hardness layer on the surface of the crankshaft crankpin after repair according to a specific embodiment of the present invention.

[0032] Figure 7 This is a photograph of the damaged crankshaft and crankpin after flaw detection, according to a specific embodiment of the present invention. Detailed Implementation

[0033] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0034] Example 1

[0035] like Figure 1 As shown, this invention provides a laser cladding repair process for crankshaft crankpins, and the specific process steps are as follows:

[0036] Step 1: Removal of the nitrided layer: Grind the crank surface to a hardness of 35-40 HRC using a grinding machine, and determine the dimensional difference between the surface before and after grinding; for example... Figure 2 This embodiment shows actual images of the damaged crankshaft crank section to be repaired before and after pretreatment.

[0037] Step 2: Without using custom-made eccentric fixtures, using a clamping and aligning method, divide the crankshaft crank section to be repaired into 1cm points, such as... Figure 3 A physical diagram shows the evenly distributed points on the damaged crankshaft crank. Through the robot's linkage and coordination function, each time the crankshaft crank rotates to its highest point, point teaching is performed sequentially. After one revolution of the crankshaft crank, the point teaching is complete. The trajectory is then shifted a certain distance (cladding overlap), and the entire system rotates 360° to enter the second revolution of the crankshaft, completing the program logic editing and achieving continuous looping; as shown... Figure 4 A physical diagram of the damaged crankshaft offshaft powder feeding device of this embodiment is shown.

[0038] Step 3: Clamping and Cladding: The crankshaft is clamped tightly at both ends. Parameters such as crank length, fitting speed, powder feed amount, and laser power are calculated. A base layer is applied to fill the crankshaft crank area, with a thickness of 1 / 3 to 1 / 2 of the grinding dimension in Step 1. Specifically, the first iron-based alloy powder is laser-clad onto the crankshaft area to be repaired to form a base layer. The base layer iron-based alloy powder has the following chemical composition by weight percentage: Cr 19.5%, Ni 12.51%, Nb 1.23%, Mo 2.02%, with the balance being Fe and unavoidable impurities. The particle size of the base layer iron-based alloy powder is 270-400 mesh, and the average hardness is 35-40 HRC. The laser cladding process parameters for the bottom layer are as follows: laser power 1800W, spot size 3mm, robot running fitting speed 80cm / min, protective gas Ar, gas flow rate 9L / min, programmed running trajectory clockwise rotation along the circumference of the crank, laser head at a 90° angle to the end face, off-axis powder feeding nozzle at a 70° angle to the end face, and powder feeding rate 2.5r / min. Figure 5 The image shows a physical photograph of the damaged crankshaft after laser cladding was applied to the crankshaft.

[0039] Step 4: Preliminary machining of crankshaft crank joint: Grind the end face of the bottom layer of the crankshaft flat using a grinding machine. The grinding thickness is half the thickness of the bottom layer. Perform flaw detection and measure the dimensions.

[0040] Step 5: Clamping and Cladding: Based on the finished product dimensions in the drawings, confirm the relevant laser cladding process parameters and complete the processing of the high-hardness layer on the surface of the crankshaft crank. The thickness of the high-hardness layer is the grinding dimension in Step 1. The second iron-based alloy powder of the high-hardness layer includes the following weight percentage composition: Cr 17.09%, Ni 2.13%, Mo 0.031%, Mn 0.42%, Nb 0.14%, with the balance being Fe and unavoidable impurities. The particle size of the second iron-based alloy powder is 270-400 mesh, and the average hardness is 55-60 HRC. The process parameters for laser cladding of the high-hardness layer are: laser power 2200W, spot size 3mm, robot running fitting speed 80cm / min, protective gas Ar, gas flow rate 8L / min, program running trajectory clockwise linkage rotation along the crank circumference, laser head at a 90° angle to the end face, off-axis powder feeding nozzle at a 70° angle to the end face, and powder feeding rate 4.0r / min. like Figure 6 The image shows a physical photograph of the high-hardness layer on the surface of the crankshaft crankpin after repair.

[0041] Step 6: Crankshaft and crankpin final machining: Grind the high-hardness layer on the end face of the crankshaft and crankpin to make it smooth, ensuring the dimensions and surface finish, and measure the finished product dimensions according to the drawings.

[0042] Step 7: Inspection: Measure the hardness, dimensions, and flaw detection effect of the crankshaft crank face. The tested hardness of the repaired area's end face ranged from a maximum of 60 HRC to a minimum of 58 HRC, with an average hardness of 59 HRC. No cracks or porosity were found on the end face. Figure 7 The image shows a physical photograph of the damaged crankshaft after repair and flaw detection.

[0043] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A laser cladding repair process for crankshaft cranks, characterized in that, Includes the following steps: S1. Pre-treatment of the crankshaft crank section to be repaired; S2. The crankshaft is clamped at both ends, and the robot linkage coordination program teaches the points to be repaired at the crankshaft crank to complete the program logic editing. S3. Following the point-to-point teaching procedure, first, a layer of base coat is laser-fused onto the crankshaft crank section to be repaired, and then a high-hardness layer is laser-fused onto the surface of the base coat. S4. Final processing of high-hardness layers; In step S3, the method for laser cladding a base layer on the part to be repaired is to laser clad the first iron-based alloy powder onto the part to be repaired to form a base layer. The laser cladding process parameters are as follows: laser power is 1800W, spot size is 3mm, robot running fitting speed is 80cm / min, protective gas is Ar, gas flow rate is 9L / min, program running trajectory is clockwise linkage rotation along the circumference of the crank, laser head is at a 90° angle with end face, off-axis powder feeding nozzle is at a 70° angle with end face, and powder feeding rate is 2.5r / min. The first iron-based alloy powder comprises the following chemical composition by weight percentage: Cr 19.5%, Ni 12.51%, Nb 1.23%, Mo 2.02%, with the balance being Fe and unavoidable impurities; the first iron-based alloy powder has a particle size of 270~400 mesh and an average hardness of 35~40 HRC.

2. The laser cladding repair process for crankshaft cranks as described in claim 1, characterized in that, In step S1, the pretreatment method for the crankshaft crank section to be repaired is as follows: S11. Grind away the nitriding layer at the crankshaft crank section to be repaired; S12. Detect the surface hardness of the crankshaft crankpin after grinding, and make the surface hardness meet 35~40HRC.

3. The laser cladding repair process for crankshaft cranks as described in claim 1, characterized in that, In step S2, the crankshaft is clamped using a clamping-on-top method, and the crankshaft crank to be repaired is divided into 1cm points. Through the robot's linkage and coordination function, when the crankshaft crank rotates to the highest point, the points are taught in sequence to complete the program logic editing.

4. The laser cladding repair process for crankshaft cranks as described in claim 1, characterized in that, In step S3, the method for laser cladding a high-hardness layer onto the surface of the base layer is as follows: the second iron-based alloy powder is laser clad onto the surface of the base layer to form a high-hardness layer. The laser cladding process parameters are: laser power of 2200W, spot size of 3mm, robot running fitting speed of 80cm / min, protective gas of Ar, gas flow rate of 8L / min, program running trajectory of clockwise linkage rotation along the circumference of the crank, laser head at a 90° angle to the end face, off-axis powder feeding nozzle at a 70° angle to the end face, and powder feeding rate of 4.0r / min.

5. The laser cladding repair process for crankshaft cranks as described in claim 4, characterized in that, The second iron-based alloy powder comprises the following chemical composition by weight percentage: Cr 17.09%, Ni 2.13%, Mo 0.031%, Mn 0.42%, Nb 0.14%, with the balance being Fe and unavoidable impurities; the particle size of the second iron-based alloy powder is 270~400 mesh, and the average hardness is 55~60 HRC.

6. The laser cladding repair process for crankshaft cranks as described in claim 1, characterized in that, In step S3, after the area to be repaired is laser-clad with a base layer, the base layer is ground and inspected for defects. The thickness of the ground layer is half the thickness of the base layer.

7. The laser cladding repair process for crankshaft cranks as described in claim 1, characterized in that, In step S4, the final processing method for the high-hardness layer is to perform final grinding based on the dimensions of the finished crankshaft.

8. The laser cladding repair process for crankshaft cranks as described in claim 1, characterized in that, In step S4, after the high-hardness layer is finally processed, hardness testing and surface flaw detection are performed to ensure that the surface hardness is ≥58HRC and the end face is free of cracks and pores.

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