High-quality metal mold repairing method based on small light spots and low-power pulse laser

Abstract

The invention provides a high-quality metal mold repairing method based on small light spots and low-power pulse laser. According to the method, a laser beam with specific parameters is output through a small-light-spot and low-power pulse laser, in combination with a preset scanning path and a layer-by-layer deposition repairing strategy, fine defects such as scratches, abrasion and microcracks of the metal mold can be repaired in time and effectively at high quality, and the defect that the repairing range is excessively expanded in a traditional repairing technology is effectively overcome. A low-heat input repair system is constructed by relying on the core characteristics of small light spots and low power, near-heat-affected-zone repair is achieved, and the problem that fine repair, performance matching and matrix protection are difficult to meet at the same time in a traditional repair technology is solved.

Description

Technical Field

[0001] This invention belongs to the field of mold manufacturing and repair technology, specifically involving a high-quality repair method for metal molds based on small spot and low-power pulsed laser. It is applicable to the repair and remanufacturing of minute defects on the surface of high-precision and high-hardness metal molds (such as cold working molds and hot working molds). Background Technology

[0002] As a core support of industry, molds are widely used in automotive, electronics, and machinery industries. Their surface integrity and mechanical properties directly determine their precision and service life. During service, metal mold surfaces are prone to micro-scale defects (also known as minute defects, width < 0.5mm, depth < 0.3mm) such as micro-scratches, micro-cracks, and localized minor wear due to wear, impact, and thermal fatigue. Although these defects are initially small, they directly affect the sealing performance and forming accuracy of the metal mold, and may exacerbate damage evolution during subsequent service, leading to premature mold failure, resource waste, and increased production costs for enterprises. Therefore, achieving high-quality defect repair is crucial to ensuring the long-term service life of high-precision metal molds.

[0003] However, existing metal mold repair technologies, limited by their own principles and process characteristics, struggle to simultaneously meet the stringent requirements of high-precision molds for fine repair (the core of fine repair is "fineness," specifically referring to the repair of micro-scale defects, emphasizing the ability to target and process "small defects," i.e., accurately covering micro-scale defects and avoiding over-repair), preservation of substrate properties, and matching of the mechanical properties of the repair layer with the substrate. These technologies suffer from several core shortcomings. Traditional repair methods such as arc welding, argon arc welding, or high-power laser repair all suffer from poor repair precision, inability to accurately fill micro-defects, large heat-affected zones (causing substrate softening and substandard performance), the need for extensive post-repair processing, and poor repair quality. They cannot guarantee the original properties of the substrate while achieving fine repair. Specifically, while high-power laser repair can improve the bonding strength and repair efficiency of the repair layer, its wide heat-affected zone still makes it difficult to avoid substrate degradation, and its high energy consumption, coupled with the fact that the laser spot size is typically larger than 2 mm, makes it impossible to accurately cover micro-scale defects, and it also suffers from heat-affected zones ≥0.3 mm and excessively rapid attenuation of substrate hardness. Chinese patent CN105252203B discloses a method for repairing mold cracks. This method involves manually applying TIG (Tungsten Inert Gas) filler wire to the repair area. While it can repair macroscopic cracks, the high heat input can easily lead to significant thermal deformation and internal stress in the repaired area. This is especially true for high-hardness mold steels such as Cr12MoV and H13, which can easily cause cracking after repair. Furthermore, the thickness of the heat-affected zone of the weld after repair can reach up to 2 mm, severely affecting the performance of the base material. Additionally, the repair precision is insufficient, and the filler wire amount is difficult to control precisely, easily resulting in overmelting or incomplete filling.

[0004] In summary, the industry urgently needs a new metal mold repair technology that can achieve fine repair, precise control of the heat effect range, and ensure that the mechanical properties of the repair layer are highly matched with the substrate. It also has advantages such as low heat input, small heat-affected zone, strong bonding, and low energy consumption, in order to solve the pain points of existing technologies and promote the upgrading of fine mold remanufacturing technology. Summary of the Invention

[0005] The purpose of this invention is to solve the problem that existing metal mold repair technologies cannot simultaneously meet the stringent requirements of fine repair, preservation of substrate properties, and high matching of the mechanical properties of the repair layer with the substrate, and to provide a high-quality metal mold repair method based on small spot and low-power pulsed laser.

[0006] The concept of this invention:

[0007] Addressing the core pain points of existing laser repair technologies, such as "insufficient precision repair, large heat-affected zone, and poor performance matching," this invention follows the logic of "targeting pain points - supporting mechanisms - synergistic solutions - verifying effects" to form a closed-loop design system.

[0008] First, based on the needs of repairing minute defects in high-precision metal molds and the high alloy and low thermal conductivity characteristics of mold steel, the core design objective is to simultaneously achieve the synergistic effect of "precise coverage of minute defects, matching of mechanical properties of the repair layer with the substrate, near-zero thermal damage to the substrate, and low-energy-consumption and high-efficiency repair", thus responding to the industry's technical demands in a targeted manner.

[0009] Secondly, based on thermodynamic principles and laser processing mechanisms, the technical implementation path is determined as follows: using "small spot + low-power pulsed laser" as the core energy carrier, the energy range is locked in the spatial dimension by precisely matching the spot size with the spatial characteristics of the defect, thus avoiding "over-repair"; utilizing the "instantaneous power supply" characteristic of pulsed laser, a parameter combination of "low pulse width + high frequency" is designed, along with an appropriate scanning speed, to construct a "instantaneous power supply - rapid power cut-off - intermittent heat dissipation" mechanism, blocking heat conduction to the substrate and reducing the heat accumulation effect; simultaneously integrating material adaptation (customizing repair powder with the same composition as the substrate), process synergy, and other factors to ensure the density and mechanical properties of the repair layer are matched.

[0010] Finally, a design closed loop is formed through "example verification + multi-dimensional comparison": examples are constructed with exclusive parameter ranges and collaborative solutions to verify the effects of "fine repair, near-zero thermal impact, and high-performance matching"; through comparisons that deviate from design parameters and use high-power lasers, the uniqueness and necessity of the design scheme are verified in reverse, ensuring that the technical solution has both mechanistic rationality and practical application feasibility, and systematically breaks through existing technical bottlenecks.

[0011] Based on the above inventive concept, and to achieve the above objectives, the technical solution provided by this invention is as follows:

[0012] A high-quality repair method for metal molds based on small-spot, low-power pulsed lasers is characterized by the following steps:

[0013] 1) Preparations before repair

[0014] The surface of the metal mold to be repaired (the part to be repaired has micro-scale defects such as micro-scratches, micro-cracks, and localized minor wear) is cleaned, and the size and material of the area to be repaired are determined.

[0015] Among them, determining the size of the area to be repaired is to determine the scope to be repaired, such as width, length and thickness, which can be obtained through conventional measurement methods; the material of the area to be repaired is the material of the metal mold.

[0016] 2) Develop repair techniques

[0017] Based on the size and material of the area to be repaired determined in step 1), select the repair powder, determine the repair path and repair process parameters;

[0018] The repair powder is a powder with the same material composition as the area to be repaired, and the particle size is 50-200 μm.

[0019] 3) Laser repair

[0020] Fix the metal mold on the worktable with the part to be repaired facing upwards, ensuring that the repair surface is perpendicular to the laser beam direction; according to the repair path and repair process parameters, use a laser generator to deposit repair powder layer by layer (i.e., multi-layer deposition, forming the next layer on top of each layer) on the part to be repaired, and the area and thickness of the deposited area are greater than the part to be repaired.

[0021] The laser generator uses a pulsed Nd:YAG laser light source with a laser wavelength of 1064 nm;

[0022] The repair process parameters are as follows:

[0023] Pulse width: 3-5 ms, frequency: 16-20 Hz, repair speed: 3-5 mm / s, power: 100-200 W, powder feed rate: 3-5 g / min, spot size: 0.4-0.6 mm, single layer height: 50-150 μm, overlap rate: 30%-50%. Argon gas protection is used during the repair process, with a protective gas flow rate of 8-12 L / min to prevent oxidation of the repaired area.

[0024] 4) Post-processing

[0025] The repaired area is subjected to flaw detection to observe whether there are any defects inside (such as porosity, cracks, lack of fusion, etc.), and is machined according to the original dimensions of the metal mold drawings to ensure that the dimensions and surface accuracy of the machined part fully meet the requirements of the original drawings.

[0026] Furthermore, in step 3), the size of the deposited area is 2-3 mm larger than the periphery of the area to be repaired after cleaning (i.e., the deposited area is 2-3 mm larger than the area to be repaired after cleaning in all directions), and the thickness is 0.5-1 mm higher than the original surface of the area to be repaired.

[0027] Furthermore, in step 1), the surface cleaning of the metal mold part to be repaired specifically involves:

[0028] The area to be repaired is then ground using a grinder and sandpaper, and then cleaned to remove the oxide layer, oil, and other impurities.

[0029] Furthermore, in step 1), the grinding wheel is a white corundum grinding wheel;

[0030] The sandpaper used is 80-grit metallographic sandpaper;

[0031] Use alcohol, such as 75 vol.%, for cleaning.

[0032] Furthermore, in step 2), the repair powder material is H13 or Dievar, depending on the material of the metal mold.

[0033] Furthermore, in step 2), the repair path adopts a serpentine scanning strategy.

[0034] In addition, the present invention also provides a metal mold repaired using the above-described repair method, wherein the hardness of the repair layer is significantly improved relative to the substrate.

[0035] The core of this invention's high-quality repair lies in:

[0036] Firstly, the innovative scenario-based repair system breaks through the existing "general repair" logic and constructs a "targeted repair system" for typical minor defects (width < 0.5mm, depth < 0.3mm) and high alloy characteristics of mold steel, rather than simply relying on the inherent properties of pulsed lasers, to achieve a triple synergy of "precise repair - substrate protection - performance matching".

[0037] Secondly, based on the characteristics of pulsed lasers, this invention designs a closed loop of "small spot + low power + coordinated parameters", adjusts process parameters, and adopts a combination of low pulse width and high frequency parameters to form a core mechanism of "instantaneous power supply - rapid power cut-intermittent heat dissipation", which solves the thermal impact from the root.

[0038] Thirdly, the repair quality is improved. By using the repair method of this invention, the repair layer and the substrate form a stable metallurgical bond. Its mechanical properties, such as hardness and tensile strength, are superior, ensuring the overall service reliability of the metal mold after repair. Moreover, the method of this invention has low energy consumption and strong repair stability, and is suitable for the repair and remanufacturing of various high-precision metal molds. It can meet the stringent requirements of molds for the dimensional accuracy and mechanical properties of the repaired parts.

[0039] The beneficial effects of this invention are:

[0040] 1. Precise repair of minute defects: Utilizing an ultra-small 0.4-0.6mm spot size, it can accurately target and cover minute defects such as microcracks with a width of <0.5mm and microscratches with a depth of <0.3mm. Unlike traditional repair methods, it does not require expanding the repair area, thus avoiding the waste of substrate and dimensional accuracy deviations caused by the repair area being much larger than the defect area. After repair, only minimal machining is required (the deposition thickness is only 0.5-1mm higher than the original surface) to meet the requirements of the original drawings. Compared with the problems of traditional repair methods, such as the inability to perform precise repairs and the need for complex processing procedures after repair, it significantly improves the precision of repairs and is particularly suitable for the stringent requirements of high-precision molds for "millimeter-level defects and micron-level repairs".

[0041] 2. The high-energy-density pulsed output of the pulsed laser can create high-frequency disturbances in the molten pool during the repair process, effectively breaking down the initially formed coarse grains and forcibly refining them. At the same time, the pulsed laser can achieve rapid metallurgical bonding between the repair material and the substrate material, reducing the microstructural degradation caused by the continuous high temperature of the molten pool. This results in a uniform and fine microstructure in the repair layer, free from common defects such as cracks and pores. It can also significantly improve the hardness, wear resistance, and fatigue resistance of the repaired area. The mechanical properties of the repaired area are highly matched with the substrate and even locally optimized, effectively ensuring the long-term service performance of the mold after repair.

[0042] 3. During the repair process, the local energy concentration characteristics of pulsed lasers, through specific heat input control (i.e., pulse frequency and pulse width), employ a combination of low pulse width and high frequency parameters to form a core mechanism of "instantaneous power supply - rapid power cut-off - intermittent heat dissipation." This ensures that the heat generated during each repair layer is dissipated immediately, terminating power supply before heat transfer to deeper layers of the substrate. Simultaneously, the pulse frequency and repair speed work together to achieve intermittent power supply and sufficient heat dissipation, preventing heat accumulation caused by continuous energy input and addressing the core pain points of existing technologies, such as additional substrate heating and large heat-affected zones. Only by using the repair process parameters of this invention can a near-zero heat-affected zone be achieved; other parameter combinations cannot simultaneously achieve the effects of dense formation and a near-zero heat-affected zone.

[0043] 4. The core innovation of this invention lies in the "scenario-based application system and process parameter design of lasers", rather than the laser instrument itself; the pulsed laser instrument used is a commercially available conventional device, obtained through standardized procurement. The creativity of this invention does not rely on the originality of the instrument, but rather on the application innovation and parameter reconstruction of commercially available instruments to achieve mold steel repair effects that existing equipment cannot achieve. Attached Figure Description

[0044] Figure 1 The images shown are metallographic images, scanning morphology images, and hardness distribution diagrams of the repaired area in Embodiment 1 of the present invention; (a) is a metallographic image, (b) is a scanning morphology image, and (c) is a hardness distribution diagram from the substrate to the repair layer.

[0045] Figure 2 These are morphological images of the actual object after repair in Embodiment 2 of the present invention; (a) is before repair, and (b) is after repair.

[0046] Figure 3 The images shown are metallographic images, scanning morphology images, and hardness distribution diagrams of the repaired area in Comparative Example 1 of the present invention; (a) is a metallographic image, (b) is a scanning morphology image, and (c) is a hardness distribution diagram from the substrate to the repair layer.

[0047] Figure 4 The image shows the metallographic structure of the repaired area in Comparative Example 2.

[0048] Figure 5 The images show the microstructure, hardness distribution, and surface morphology of the repaired area after continuous laser repair in Comparative Example 3; (a) is a metallographic image, (b) is a hardness distribution image from the substrate to the repair layer, and (c) is a surface morphology image.

[0049] Figure 6 This is a hardness distribution diagram of the repaired area after repair using a large-spot pulsed laser in Comparative Example 4. Detailed Implementation

[0050] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0051] The repair method of this invention achieves precise and efficient repair of mold defects by using small spot and low power pulsed laser, optimizing process parameters and repair process, while reducing heat input and energy consumption, and improving the mechanical properties and service life of the repaired mold. It is a repair method with high repair accuracy, good performance of the repaired area, strong bonding ability between the repaired area and the substrate, and minimal impact on the substrate.

[0052] Example 1

[0053] A high-quality repair method for metal molds based on small-spot, low-power pulsed lasers includes the following steps:

[0054] (1) Clean the surface of the damaged parts of the metal mold, use a white corundum grinding wheel and 80-grit metallographic sandpaper to grind the parts to be repaired, and wipe the parts to be repaired with 75 vol.% alcohol to remove the oxide layer, oil and other impurities.

[0055] (2) Measure the area to be repaired. The size of the area to be repaired is 10 mm × 10 mm × 2 mm;

[0056] (3) The base material has been confirmed to be H13 mold steel;

[0057] (4) Formulate the repair process: H13 spherical powder with a particle size of 50-200 μm is selected as the repair material. The repair path adopts a serpentine scanning strategy. After each layer is formed, the next layer is deposited according to the program settings until the area to be repaired is completed.

[0058] (5) Laser repair: Fix the metal mold on the worktable with the part to be repaired facing upwards, and ensure that the repair surface is perpendicular to the laser beam direction. The laser generator used for repair is a pulsed Nd:YAG laser source with a laser wavelength of 1064 nm. The repair process parameters are: pulse width: 3 ms, frequency: 16 Hz, repair speed: 3 mm / s, power: 120 W, powder feed: 3 g / min, spot size: 0.5 mm, single layer height: 50-150 μm, overlap rate: 30%-50%. Argon gas protection is used during the repair process, and the protective gas flow rate is 8-12 L / min to prevent the repair part from being oxidized.

[0059] (6) Post-processing: The repaired part is subjected to flaw detection to observe whether there are defects such as air holes and cracks inside the repaired part, and is machined according to the original drawing size of the mold to ensure that the dimensions and surface accuracy after processing fully meet the requirements of the original drawing.

[0060] After repair, as shown Figure 1 As shown in the figures, (a) is a metallographic image, (b) is a scanning morphology image, and (c) is a hardness distribution diagram from the substrate to the repair layer. It can be seen from the figures that the forming quality after repair using the method of Example 1 is good. From the hardness distribution, no obvious hardness decay was observed on the substrate; the overall hardness of the substrate remained at approximately 490 HV, effectively protecting the substrate's properties and achieving a near-zero heat-affected zone. Furthermore, regarding the hardness, strength, and elongation at break of the repair layer, its hardness is approximately 580 HV, yield strength is 1436 MPa, tensile strength is 1982 MPa, and elongation at break is 7% (related tensile properties are shown in Table 1), achieving a high-quality repair with high mechanical properties.

[0061] Example 2

[0062] A high-quality repair method for metal molds based on small-spot, low-power pulsed lasers includes the following steps:

[0063] (1) Clean the surface of the damaged parts of the metal mold, use a white corundum grinding wheel and 80-grit metallographic sandpaper to grind the parts to be repaired, and wipe the parts to be repaired with 75 vol.% alcohol to remove the oxide layer, oil and other impurities.

[0064] (2) Measure the area to be repaired. The area to be repaired is a circular area with a diameter of 100 mm;

[0065] (3) The base material has been confirmed to be H13 mold steel;

[0066] (4) Formulate the repair process: H13 spherical powder with a particle size of 50-200 μm is selected as the repair material. The repair path adopts a serpentine scanning strategy. After each layer is formed, the next layer is deposited according to the program settings until the area to be repaired is completed.

[0067] (5) Laser repair: Fix the metal mold on the worktable with the part to be repaired facing upwards, and ensure that the repair surface is perpendicular to the laser beam direction. The laser generator used for repair is a pulsed Nd:YAG laser source with a laser wavelength of 1064 nm. The repair process parameters are: pulse width: 3 ms, frequency: 16 Hz, repair speed: 3 mm / s, power: 120 W, powder feed: 3 g / min, spot size: 0.5 mm, single layer height: 50-150 μm, overlap rate: 30%-50%. Argon gas protection is used during the repair process, and the protective gas flow rate is 8-12 L / min to prevent the repair part from being oxidized.

[0068] (6) Post-processing: The repaired part is subjected to flaw detection to observe whether there are defects such as air holes and cracks inside the repaired part, and is machined according to the original drawing size of the mold to ensure that the dimensions and surface accuracy after processing fully meet the requirements of the original drawing.

[0069] like Figure 2 The morphology of the repaired object is shown in the figure. (a) is before repair and (b) is after repair without processing. As can be seen from the figure, the repaired object using the method of this embodiment has a relatively fine repair quality. The repaired area strictly follows the pre-set path. There is no phenomenon of increased roughness caused by powder adhesion on the repaired surface. The overall surface morphology is better and has a metallic luster.

[0070] Example 3

[0071] The difference from Example 1 is as follows:

[0072] (5) The repair process parameters are: pulse width: 5 ms, frequency: 20 Hz, repair speed: 5 mm / s, power: 180 W, powder feeding amount: 5 g / min, spot size: 0.6 mm, single layer height: 50-150 μm, overlap rate: 30%-50%, argon gas protection is used during the repair process, and the protective gas flow rate is 8-12 L / min.

[0073] After repair using the parameters of Example 3, the repair layer showed good forming quality with no obvious pores on the surface, achieving a good densification effect. The matrix hardness did not show significant attenuation, remaining at approximately 490 HV. The repair layer hardness reached approximately 580 HV. Tensile mechanical properties showed a yield strength of 1412 MPa, a tensile strength of 1957 MPa, and an elongation at break of 7% (related tensile properties are shown in Table 1).

[0074] Example 4

[0075] The difference from Example 1 is as follows:

[0076] (5) The repair process parameters are: pulse width: 4 ms, frequency: 17 Hz, repair speed: 4 mm / s, power: 150 W, powder feeding amount: 4 g / min, spot size: 0.4 mm, single layer height: 50-150 μm, overlap rate: 30%-50%, argon gas protection is used during the repair process, and the protective gas flow rate is 8-12 L / min.

[0077] After repair using the parameters of Example 4, the repair layer showed good forming quality with no obvious pores on the surface, achieving a good densification effect. The matrix hardness did not show significant attenuation, remaining at approximately 490 HV. The repair layer hardness reached approximately 580 HV. Tensile mechanical properties showed a yield strength of 1451 MPa, a tensile strength of 1969 MPa, and an elongation at break of 8% (related tensile properties are shown in Table 1).

[0078] Comparative Example 1

[0079] The difference from Example 1 is as follows:

[0080] (5) The repair process parameters are: pulse width: 10 ms, frequency: 12 Hz, repair speed: 6 mm / s, power: 180 W, powder feeding amount: 5 g / min, spot size: 0.5 mm, single layer height: 50-150 μm, overlap rate: 30%-50%, argon gas protection is used during the repair process, and the protective gas flow rate is 8-12 L / min.

[0081] After repair, as shown Figure 3 As shown, (a) is a metallographic image, (b) is a scanning morphology image, and (c) is a hardness distribution map from the substrate to the repair layer. Comparative Example 1 and Example 1 have the same spot size, and although the power is different, it is quite similar, resulting in good final repair quality. However, the hardness distribution map shows a significant hardness decrease in the substrate, ranging from approximately 0.3 mm, with the lowest hardness reaching 430 HV, a significant decrease compared to the substrate. Therefore, it is believed that a heat-affected zone has appeared, leading to a degradation of the substrate properties.

[0082] Comparative Example 2

[0083] The difference from Example 1 is as follows:

[0084] (5) The repair process parameters are: pulse width: 10 ms, frequency: 15 Hz, repair speed: 8 mm / s, power: 220 W, powder feeding amount: 7 g / min, spot size: 0.5 mm, single layer height: 50-150 μm, overlap rate: 30%-50%, argon gas protection is used during the repair process, and the protective gas flow rate is 8-12 L / min.

[0085] After repair, as shown Figure 4 As shown, although this comparative example uses a small light spot just like Example 1, the other repair process parameters are outside the repair process parameters of this invention, and the repair result is not ideal, showing poor forming quality.

[0086] Comparative Example 3

[0087] The difference from Example 1 is as follows:

[0088] (2) Measure the area to be repaired. The dimensions of the area to be repaired are 70 mm × 50 mm × 5 mm.

[0089] (5) Laser repair: Fix the metal mold on the worktable with the part to be repaired facing upwards, and ensure that the repair surface is perpendicular to the laser beam direction. The laser generator used for repair is a continuous laser source with a laser wavelength of 1080 nm. The repair process parameters are: repair speed: 5 mm / s, power: 1800 W, powder feed: 6 g / min, spot size: 3 mm, single layer height: 0.8 mm, overlap rate: 30%-50%. Argon gas protection is used during the repair process, and the protective gas flow rate is 8~12 L / min to prevent the repaired part from being oxidized.

[0090] After repair, as shown Figure 5 As shown, (a) is a microstructure diagram, (b) is a hardness distribution diagram from the substrate to the repair layer, and (c) is a surface morphology diagram after forming. Compared with Example 1, this repair result exhibits a coarser microstructure, a larger heat-affected zone, and a significant decrease in substrate hardness within the heat-affected zone. The hardness decrease range can reach 1 mm, with the lowest substrate hardness reaching approximately 350 HV, indicating severe degradation of substrate properties. The repaired surface exhibits significant roughness, with a small amount of powder particles adhering to the edges, failing to achieve a satisfactory fine repair. Furthermore, in terms of the hardness, strength, and elongation at break of the repair layer, its hardness is approximately 520 HV, yield strength is 1162 MPa, tensile strength is 1671 MPa, and elongation at break is 6% (related tensile properties are shown in Table 1), which are lower than the mechanical properties of the repair layer from the low-power pulsed laser.

[0091] Comparative Example 4

[0092] The difference from Example 1 is as follows:

[0093] (2) Measure the area to be repaired according to the drawings. The dimensions of the area to be repaired are 50 mm × 50 mm × 4 mm.

[0094] (5) Laser repair: Fix the metal mold on the worktable with the repair surface facing upwards, and ensure that the repair surface is perpendicular to the laser beam direction. The laser generator used for repair is a pulsed laser source with a laser wavelength of 1080 nm. The repair process parameters are: pulse width: 25 ms, frequency: 8 Hz, repair speed: 5 mm / s, power: 1500 W, powder feed: 6 g / min, spot size: 3 mm, single layer height: 0.8 mm, overlap rate: 30%-50%. Argon gas protection is used during the repair process, and the protective gas flow rate is 8-12 L / min to prevent the repaired part from being oxidized.

[0095] The hardness distribution diagram after repair is as follows Figure 6 As shown, compared to Example 1, the repair result exhibits a larger heat-affected zone and a significant decrease in the hardness of the matrix within the heat-affected zone, ranging from 0.8 mm to approximately 370 HV. The relevant tensile properties are shown in Table 1.

[0096] Table 1 Comparison of relevant strength and elongation at break in some embodiments and comparative examples

[0097]

[0098] Through the synergistic design of "ultra-small spot targeted repair + precise pulse energy control + low heat input heat dissipation closed loop", this invention systematically achieves core advantages and excellent repair results, and this effect can only be achieved within the repair process of this invention: Example verification shows that relying on the 0.4-0.6mm ultra-small spot, precise coverage of minute defects is achieved without expanding the repair area. Only a small amount of post-processing is needed to meet high precision requirements, perfectly adapting to the demand for "millimeter-level defects and micron-level repair"; utilizing the high energy density characteristics of pulsed lasers and parameter control synergistically, the repair layer structure is dense and defect-free, with mechanical properties highly matched with the substrate and even locally optimized, ensuring long-term mold service; fully utilizing the characteristics of pulsed laser parameters, a precise match between low pulse width, high frequency and repair speed is designed to construct an "instantaneous energy supply - rapid energy cut-off - intermittent heat dissipation" mechanism, completely avoiding thermal damage to the substrate, achieving near-heat-affected zone repair, and producing good formed structure properties. The hardness of the repaired material is also significantly improved compared to the substrate.

[0099] The comparative examples also fully demonstrate that no other technical solution can simultaneously achieve the aforementioned advantages: improper light spot or energy control may fail to accurately cover minute defects, leading to dimensional accuracy deviations; or a mismatch between energy input and heat dissipation mechanisms may result in coarse tissue, an expanded heat-affected zone, or deterioration of forming quality. In summary, this invention, through the deep integration of advantages and technical solutions, overcomes the core bottleneck of existing technologies that struggle to simultaneously achieve "precise repair, performance improvement, and substrate protection." It realizes a metal mold repair technology that achieves precise repair, accurate control of the heat-affected zone, and ensures a high degree of matching between repair performance and the original substrate, while also possessing the advantages of low heat input, small heat-affected zone, high precision repair, and low energy consumption.

[0100] In summary, the high-quality metal mold repair method based on small-spot, low-power pulsed laser proposed in this invention successfully solves the key pain points of traditional repair technologies (such as fusion welding and conventional laser repair) in repairing micron-level defects: First, the use of an ultra-small spot system of 0.4-0.6 mm precisely limits the repair area to the defect body, avoiding the waste of substrate caused by the need to expand the repair area (usually 3-5 times the size of the defect area) in existing technologies; Second, by developing a closed-loop parameter of "low pulse width (3-5ms) + high frequency (16-20 Hz)," a thermal management mechanism of "instantaneous power supply - rapid power cut-off - intermittent heat dissipation" is constructed to effectively control the thickness of the heat-affected zone of the substrate. At the same time, the multi-level particle size technology of homogeneous alloy powder is used to achieve a stable improvement in the density and hardness matching of the repair layer; In addition, the method has high adaptability, with adjustable spot size, controllable repair layer height, and adaptive tilt repair angle, enabling it to establish a dynamic adaptation system for mold repair needs of different materials and geometric features, and has significant engineering application value.

[0101] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the scope of the technology disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A high-quality repair method for metal molds based on small-spot, low-power pulsed laser, characterized in that, Includes the following steps: 1) Preparations before repair The surface of the metal mold to be repaired is cleaned, and the size and material of the area to be repaired are determined. 2) Develop repair techniques Based on the size and material of the area to be repaired determined in step 1), select the repair powder, determine the repair path and repair process parameters; The repair powder is a powder with the same material composition as the area to be repaired, and the particle size is 50-200 μm. 3) Laser repair Fix the metal mold on the worktable with the part to be repaired facing upwards, ensuring that the repair surface is perpendicular to the laser beam direction; according to the repair path and repair process parameters, use a laser generator to deposit repair powder layer by layer on the part to be repaired, and the area and thickness of the deposited area are larger than the part to be repaired; The laser generator uses a pulsed Nd:YAG laser light source with a laser wavelength of 1064 nm; The repair process parameters are as follows: Pulse width: 3-5 ms, frequency: 16-20 Hz, repair speed: 3-5 mm / s, power: 100-200 W, powder feed rate: 3-5 g / min, spot size: 0.4-0.6 mm, single layer height: 50-150 μm, overlap rate: 30%-50%, argon gas protection is used during the repair process, and the protective gas flow rate is 8-12 L / min; 4) Post-processing The repaired area is subjected to flaw detection to observe whether there are any defects inside. It is then machined according to the original dimensions of the metal mold drawings to ensure that the dimensions and surface accuracy of the machined part fully meet the requirements of the original drawings.

2. The high-quality repair method for metal molds based on small spot, low-power pulsed laser according to claim 1, characterized in that: In step 3), the size of the deposited area is 2-3 mm larger than the outer perimeter of the area to be repaired after cleaning, and the thickness is 0.5-1 mm higher than the original surface of the area to be repaired.

3. The high-quality repair method for metal molds based on small spot, low-power pulsed laser according to claim 1 or 2, characterized in that: In step 1), the surface cleaning of the part of the metal mold to be repaired specifically involves: The area to be repaired is then ground using a grinder and sandpaper, and then cleaned to remove the oxide layer, oil, and other impurities.

4. A high-quality repair method for metal molds based on small spot, low-power pulsed laser as described in claim 3, characterized in that: In step 1), the grinding wheel is a white corundum grinding wheel; The sandpaper used is 80-grit metallographic sandpaper; Use alcohol to wipe it during cleaning.

5. The high-quality repair method for metal molds based on small spot size and low power pulsed laser according to claim 4, characterized in that: In step 2), the repair powder material is H13 or Dievar.

6. The high-quality repair method for metal molds based on small spot, low-power pulsed laser according to claim 5, characterized in that: In step 2), the repair path adopts a serpentine scanning strategy.

7. A metal mold repaired using the high-quality repair method for metal molds based on small spot, low-power pulsed laser as described in any one of claims 1-6.

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