Additive repairing method suitable for defects of vehicle crankshaft pre-forging die

Abstract

The invention discloses an additive repairing method suitable for vehicle crankshaft pre-forging die defects, and belongs to the field of pre-forging die repairing. Through the gradient design of the bionic layered structure, layer-by-layer additive repair is carried out in the stress concentration and vulnerable area of the mold, so that gradient transition is formed between hardness and toughness of the repaired area, the wear resistance, fatigue resistance and heat resistance of the mold are improved, the service life of the mold can be prolonged, and production stagnation caused by frequent replacement and maintenance is reduced. And in addition, the pre-forging die is repaired in the mode that the cold metal transition welding technology is adopted for fuse wire additive manufacturing, the maintenance cost is reduced, and the repair efficiency and the repair quality of the pre-forging die are improved.

Description

Technical Field

[0001] The present invention belongs to the field of pre-forging die repair, and in particular relates to an additive repair method suitable for defects in a pre-forging die of a vehicle crankshaft. Background Art

[0002] The crankshaft pre-forging mold of the vehicle is subjected to complex mechanical loads and high temperature environment during production. The mold is usually made of materials such as H13 steel. This type of material meets the requirements of high temperature resistance, high wear resistance and high impact resistance required by the pre-forging mold.

[0003] However, crankshaft pre-forging dies often suffer from wear and cracks during use, which can reduce the die's service life and production efficiency. Traditional repair methods often rely on welding and machining, but these methods have limitations when repairing large and complex dies, making it difficult to ensure that the repaired dies retain their high wear and impact resistance.

[0004] To address these performance issues, a biomimetic layered structure can be introduced during the mold repair process. The design of this biomimetic layered structure is inspired by nature, such as the gradient layer structure of shells and bones. This structural design achieves a balance between hardness, strength, and toughness through gradient changes in the material. However, the main challenges faced in practical applications are complex processes, difficulty in material selection and layered design, high costs, and a lack of standardization, which have limited mass adoption.

[0005] Therefore, an economical and efficient way is needed to perform bionic structural repair on pre-forging dies. Summary of the Invention

[0006] In view of the above-mentioned problems existing in the prior art, the object of the present invention is to provide an additive repair method suitable for defects in vehicle crankshaft pre-forging dies.

[0007] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0008] An additive repair method for defects in a vehicle crankshaft pre-forging die comprises the following steps:

[0009] Step 1: Clean the crankshaft pre-forging die for defects;

[0010] Step 2: After the defects are cleaned, the pre-forging die is repaired by CMT welding of the bionic layered structure;

[0011] Step 3: Finish the repaired surface to restore the mold repair area to normal dimensional accuracy.

[0012] Furthermore, the step 1 includes the following steps:

[0013] Step 101, using a non-destructive testing method to accurately locate the damaged areas of the mold surface and internal defects;

[0014] Step 102: Determine the depth of the groove to be ground based on the deepest defect position from the mold surface in the detected defect area.

[0015] Step 103, removing the damaged surface material in the defective area and processing the groove to form a flat-bottomed groove with sloped sides;

[0016] Step 104: Grind the groove until the surface is bright and clean the surface.

[0017] Furthermore, the step 2 includes the following steps:

[0018] Step 201: heating the defective portion of the crankshaft pre-forging die after the defect is cleaned using a heating platform;

[0019] Step 202: After the crankshaft pre-forging die is heated to a set temperature, the CMT welding machine is turned on, the welding gun is perpendicular to the bottom plane of the groove, the welding gun travel speed and travel path are set, and the distance between the welding wire and the bottom end of the groove is adjusted;

[0020] Step 203, controlling the welding gun to perform the first layer repair on the bottom of the groove;

[0021] Step 204: After the first layer repair is completed, the welding gun is raised and the second welding wire is replaced, and the second layer repair is performed based on the plane of the first layer repair;

[0022] Step 205: After completing the second layer repair, raise the welding gun and replace the third welding wire. Perform the third layer repair based on the plane of the second layer repair. Stop the welding repair after the repair position is a certain distance higher than the surface of the crankshaft pre-forging die, and turn off the heating of the crankshaft pre-forging die.

[0023] Furthermore, the finishing in step 3 includes the following steps:

[0024] Step 301, check whether the repaired area is flat;

[0025] Step 302: Use machining equipment to finish-process the repair area and remove excess repair material.

[0026] Step 303: polish and correct the surface of the repaired area so that the surface finish of the repaired area meets the precision size requirements of the mold.

[0027] Furthermore, the cleaning liquid used to clean the groove in step 104 is anhydrous ethanol.

[0028] Furthermore, the travel route of the welding gun set in step 2 is planned based on the contour edge of the bottom plane of the groove, and the overall shape of the travel route is multiple S-shaped lines connected end to end, and the travel routes of the three different planes to be repaired are staggered with each other.

[0029] Furthermore, argon gas is used for protection during the welding repair process in step 2.

[0030] Furthermore, after completing each layer of repair in step 2, the oxide on the surface of the repaired layer needs to be quickly cleaned off before proceeding to the next layer of repair.

[0031] Furthermore, different welding wires are used for the three-layer welding repair in step 2. The first layer of the repaired plane is selected with a welding wire that has good bonding with the substrate, the second layer of the repaired plane is selected with a welding wire with good strength and toughness, and the third layer of the repaired plane is selected with a welding wire with good thermal stability and impact resistance.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The present invention uses a gradient design of a bionic layered structure to perform layer-by-layer additive repair in stress-concentrated and vulnerable areas of the mold, forming a gradient transition between hardness and toughness in the repaired area, thereby improving the mold's wear resistance, fatigue resistance, and heat resistance, extending the mold's service life, and reducing production stagnation caused by frequent replacement and maintenance.

[0034] Furthermore, the present invention uses cold metal transfer welding technology (CMT) to perform fused wire additive manufacturing to repair the pre-forging die, thereby reducing maintenance costs and improving repair efficiency and repair quality of the pre-forging die. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the overall flow chart of this method;

[0036] Figure 2 Schematic diagram of the process for determining the groove depth and shape;

[0037] Figure 3 A roadmap for a three-level flat repair of a welding gun. DETAILED DESCRIPTION

[0038] The present invention will be further described below with reference to specific embodiments.

[0039] The overall repair process of the present invention comprises the following steps:

[0040] Step 1: Clean the crankshaft pre-forging die for defects;

[0041] Step 101, using a non-destructive testing method to accurately locate the damaged areas of the mold surface and internal defects;

[0042] Step 102: Determine the depth of the groove to be ground based on the deepest defect position from the mold surface in the detected defect area.

[0043] Step 103, removing the damaged surface material in the defective area and processing the groove to form a flat-bottomed groove with sloped sides;

[0044] Step 104: polishing the groove to a bright surface and cleaning the surface;

[0045] Step 2: After the defects are cleaned, the pre-forging die is repaired by CMT welding of the bionic layered structure;

[0046] Step 201: heating the defective portion of the crankshaft pre-forging die after the defect is cleaned using a heating platform;

[0047] Step 202: After the crankshaft pre-forging die is heated to a set temperature, the CMT welding machine is turned on, the welding gun is perpendicular to the bottom plane of the groove, the welding gun travel speed and travel path are set, and the distance between the welding wire and the bottom end of the groove is adjusted;

[0048] Step 203, controlling the welding gun to perform the first layer repair on the bottom of the groove;

[0049] Step 204: After the first layer repair is completed, the welding gun is raised and the second welding wire is replaced, and the second layer repair is performed based on the plane of the first layer repair;

[0050] Step 205: After the second layer repair is completed, the welding gun is raised and the third welding wire is replaced. The third layer repair is performed based on the plane of the second layer repair. The welding repair is stopped after the repair position is a certain distance above the surface of the crankshaft pre-forging die. At the same time, the heating of the crankshaft pre-forging die is turned off.

[0051] Step 3: Finish the repaired surface to restore the mold repair area to normal dimensional accuracy;

[0052] Step 301, check whether the repaired area is flat;

[0053] Step 302: Use machining equipment to finish-process the repair area and remove excess repair material.

[0054] Step 303: polish and correct the surface of the repaired area so that the surface finish of the repaired area meets the precision size requirements of the mold.

[0055] It should be noted that in step 2, different welding wires are used for the three-layer welding repair. The first layer of the repair plane uses a welding wire with good bonding with the substrate, the second layer of the repair plane uses a welding wire with good strength and toughness, and the third layer of the repair plane uses a welding wire with good thermal stability and impact resistance. After completing each layer of repair, the oxide on the surface of the repair layer needs to be quickly cleaned before proceeding to the next layer of repair. Argon gas is used for protection during the entire welding repair process.

[0056] In order to better understand the actual implementation process of this program, please refer to Figure 1-3 , demonstrated by taking the crankshaft pre-forging die whose repair material is H13 die steel as an example.

[0057] Step 1: Clean the defects of the crankshaft pre-forging die;

[0058] The steps for defect cleanup in step 1 include:

[0059] Step 101: Use non-destructive testing methods to accurately locate the damaged areas on the mold surface and internal defects;

[0060] Step 102: In the detected defect area, determine the groove depth H based on the deepest defect position h from the mold surface; in this embodiment, the groove depth H is 5 mm greater than h;

[0061] Step 103: Figure 2 As shown, machining is used to remove the damaged surface material and prepare the groove. The overall shape of the groove is a flat-bottomed groove with slopes on both sides. The angle θ of the slopes on both sides of the groove prepared in this embodiment is 130°.

[0062] Step 104: Grind the groove until the surface is bright and clean it with anhydrous ethanol to complete the cleaning of defects of the crankshaft pre-forging die. The concentration of anhydrous ethanol used in this embodiment is 99.7%.

[0063] After the cleaning is completed, the defects are repaired by the CMT welder. In this embodiment, the CMT welder selected is a CMT welder with a unified expert library. The welding machine parameters include the expert library of H13 mold steel and other alloy welding wires. The arc length correction is adjusted to 0%. After the selection is completed, step 2 is implemented.

[0064] Step 2: After the defects are cleaned, the pre-forging die is repaired by CMT welding of the bionic layered structure;

[0065] Step 201: heating the defective portion of the commercial vehicle crankshaft pre-forging die after defect cleaning using a heating platform. In this embodiment, the heating temperature is 450° C.

[0066] Step 202: When the temperature of the crankshaft pre-forging die reaches 450°C, the CMT welding machine is turned on after setting the parameters. The welding gun is perpendicular to the bottom plane of the groove. H13 steel welding wire is installed. The welding gun travel speed and travel path are set. The welding wire extension range and the distance between the welding wire and the bottom end of the groove are adjusted. In this embodiment, the distance between the front end of the welding wire and the bottom end of the groove is 1-2 mm. The welding gun travel speed is 3 mm / s, and the welding wire extension range is 13-15 mm.

[0067] like Figure 3 As shown, the path planning is based on the contour edge. The overall shape of the path is a plurality of S-shaped paths connected end to end, and the paths of the three different planes to be repaired are staggered. In this embodiment, each straight path in the S-shaped path is 6 mm apart.

[0068] Step 203: Control the welding gun to start arcing at the bottom of the groove, with an arcing time of 0.1s, to complete the first layer repair of the bottom of the groove;

[0069] Step 204: After completing the first layer of alloy repair, control the welding gun to raise 3-4 mm, replace the nickel-based alloy welding wire, and complete the second layer of repair by welding the gun according to the plane path;

[0070] Step 2.5: After completing the second layer of alloy repair, control the welding gun to raise 3-4mm, replace the cobalt-based alloy welding wire, and complete the third layer of repair according to the plane path. After the repair position is 2-3mm higher than the surface of the crankshaft pre-forging die, stop welding and stop heating the crankshaft pre-forging die at the same time.

[0071] During the entire process of repairing welding defects of the crankshaft pre-forging mold, dry argon gas with a purity of more than 99.99% is used for protection. The gas flow rate of argon gas in this embodiment is 15-20L / min. After completing each layer of repair, the alloy oxide on the surface of the repair layer is quickly cleaned before the next layer of repair is carried out.

[0072] Step 3: Finish the repaired surface to ensure that the repaired area reaches the dimensional accuracy required by the mold.

[0073] The steps for finishing the surface in step 3 include:

[0074] Step 301: Check whether the repair area is flat, confirm whether there are surface defects or unevenness, and perform preliminary assessment if necessary.

[0075] Step 302: Use machining equipment to perform fine processing on the repair area to remove excess repair material.

[0076] Step 303: Grind and correct the surface of the repaired area to ensure that the surface finish of the repaired area meets the precision dimensional requirements of the mold.

[0077] This bionic layered additive repair method for vehicle crankshaft preforging dies achieves high-quality, pore-free, crack-free repairs. Layer-by-layer additive repairs target stress-concentrated and vulnerable areas of the die, creating a gradient transition between hardness and toughness. This improves the die's wear, fatigue, and heat resistance, extending its service life and reducing production downtime caused by frequent replacement and repairs.

[0078] In addition, the method uses a CMT welding machine to perform fused wire additive manufacturing to repair the pre-forging die, which reduces the maintenance cost and effectively improves the repair efficiency.

[0079] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical content disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent replacement and improvement of the above embodiments made according to the technical essence of the present invention, within the spirit and principles of the present invention, without departing from the content of the technical solution of the present invention, shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for repairing defects in a crankshaft pre-forging die of a vehicle, characterized in that: The following steps are involved: Step 1: Clean the crankshaft pre-forging die for defects; Step 2: After the defects are cleaned, the pre-forging die is repaired by CMT welding of the bionic layered structure; Step 3: Finish the repaired surface to restore the mold repair area to normal dimensional accuracy.

2. The additive repair method for defects in a vehicle crankshaft pre-forging die according to claim 1, characterized in that: The step 1 comprises the following steps: Step 101, using a non-destructive testing method to accurately locate the damaged areas of the mold surface and internal defects; Step 102: Determine the depth of the groove to be ground based on the deepest defect position from the mold surface in the detected defect area. Step 103, removing the damaged surface material in the defective area and processing the groove to form a flat-bottomed groove with sloped sides; Step 104: Grind the groove until the surface is bright and clean the surface.

3. The additive repair method for defects in a vehicle crankshaft pre-forging die according to claim 2, characterized in that: The step 2 comprises the following steps: Step 201: heating the defective portion of the crankshaft pre-forging die after the defect is cleaned using a heating platform; Step 202: After the crankshaft pre-forging die is heated to a set temperature, the CMT welding machine is turned on, the welding gun is perpendicular to the bottom plane of the groove, the welding gun travel speed and travel path are set, and the distance between the welding wire and the bottom end of the groove is adjusted; Step 203, controlling the welding gun to perform the first layer repair on the bottom of the groove; Step 204: After the first layer repair is completed, the welding gun is raised and the second welding wire is replaced, and the second layer repair is performed based on the plane of the first layer repair; Step 205: After completing the second layer repair, raise the welding gun and replace the third welding wire. Perform the third layer repair based on the plane of the second layer repair. Stop the welding repair after the repair position is a certain distance higher than the surface of the crankshaft pre-forging die, and turn off the heating of the crankshaft pre-forging die.

4. The additive repair method for defects in a vehicle crankshaft pre-forging die according to claim 3, characterized in that: The finishing process in step 3 includes the following steps: Step 301, check whether the repaired area is flat; Step 302: Use machining equipment to finish-process the repair area and remove excess repair material. Step 303: polish and correct the surface of the repaired area so that the surface finish of the repaired area meets the precision size requirements of the mold.

5. The additive repair method for defects in a vehicle crankshaft pre-forging die according to claim 2, characterized in that: The cleaning liquid used to clean the groove in step 104 is anhydrous ethanol.

6. The additive repair method for defects in a vehicle crankshaft pre-forging die according to claim 3, characterized in that: The travel route of the welding gun set in step 2 is planned based on the contour edge of the bottom plane of the groove. The overall shape of the travel route is multiple S-shaped lines connected end to end, and the travel routes of the three different planes to be repaired are staggered with each other.

7. The additive repair method for defects in a vehicle crankshaft pre-forging die according to claim 3, characterized in that: In the step 2, argon gas is used for protection during the welding repair process.

8. The additive repair method for defects in a vehicle crankshaft pre-forging die according to claim 3, characterized in that: After completing each layer of repair in step 2, the oxide on the surface of the repaired layer needs to be quickly cleaned off before proceeding to the next layer of repair.

9. The additive repair method for defects in a vehicle crankshaft pre-forging die according to claim 1, characterized in that: Different welding wires are used for the three-layer welding repair in step 2. The first layer of the repaired plane is selected with a welding wire that has good bonding with the substrate, the second layer of the repaired plane is selected with a welding wire with good strength and toughness, and the third layer of the repaired plane is selected with a welding wire with good thermal stability and impact resistance.

Images