Method for evaluating quality of metal parts

Abstract

The invention discloses a method for evaluating the quality of a metal part, which comprises the following steps of: determining the laser type according to the characteristics of the metal part, obtaining various laser parameters for evaluating the quality of the metal part through an experimental method, and performing laser irradiation by adopting the accurately controlled laser parameters. In combination with real-time monitoring and regulation of instruments such as a power meter, a spectrograph, a roughmeter and an optical microscope, a laser parameter-grain boundary definition data set is formed, and finally a quality evaluation model is established to realize accurate evaluation of the quality of the metal parts. According to the method, the quality of the metal parts can be evaluated quickly and economically.

Description

Technical Field

[0001] The invention relates to the technical field of laser processing, in particular to a method for evaluating the quality of metal parts. Background Art

[0002] Laser processing technology is an advanced manufacturing technology that uses the interaction between high-energy laser beams and materials to achieve material cutting, marking, surface treatment and other processing processes. By precisely controlling the power, focus and scanning path of the laser beam, it can achieve fine, fast and efficient processing on various materials. Laser etching technology has gradually been applied to the field of precision processing, especially for micro-nano-level surface treatment. However, the energy control, scanning speed and spacing adjustment in the laser etching process directly affect the depth and uniformity of etching, which poses a challenge to the microstructure processing of materials (such as grain boundary exposure). Existing laser etching processes usually focus on the optimization of material removal rate and surface roughness, but pay less attention to the clarity and uniformity of grain boundaries during etching. In addition, excessive energy during laser etching may cause surface melting or oxide layer formation, which will affect the performance of metal parts.

[0003] Laser irradiation of different wavelengths has different effects on metal parts. Usually, 1064nm laser, as an infrared laser, has a longer wavelength and has a significant melting effect on metal materials; 355nm laser, as an ultraviolet laser, has the characteristics of a short wavelength and a significant photochemical etching effect. In particular, lead brass alloy, as a high reflectivity material, has a high absorption rate for this laser, which makes 355nm laser have a significant effect on the surface of lead brass. Lead brass is often used as an electrode for photolithography machines due to its excellent conductivity and corrosion resistance. The mechanism of action of ultraviolet laser and lead brass materials includes the polishing mechanism of photothermal effect and the etching mechanism of photochemical effect. In electrode materials, high impurity areas such as grain boundaries will more easily absorb laser energy due to differences in elemental properties, resulting in selective etching of these areas. After local laser irradiation treatment, high impurity areas such as grain boundaries will appear due to the absorption of more laser energy. The accumulation of laser energy in these areas leads to a faster material removal rate, making microstructural features such as grain boundaries more obvious. In this way, when processing materials, the 355nm UV laser can produce two different effects: etching grain boundaries and melt polishing through high absorption rate and thermal effect, which depends on the laser parameters and the impurity content.

[0004] High reflectivity materials are often widely used in metal parts. For example, lead brass is used as a high reflective material as an electrode in a photolithography machine. The role of the electrode in the photolithography machine is mainly reflected in the photolithography process. It works with components such as light sources, lenses, and control systems to achieve high-precision pattern transfer. The electrode in the photolithography machine involves the power supply and current control of the photolithography machine, ensuring that the light source can stably emit light of the required wavelength for exposure. During the photolithography process, the electrode can be used to control the electric field inside the photolithography machine to optimize the exposure effect of the photoresist, thereby forming a precise circuit pattern on the silicon wafer. Therefore, the electrode in the photolithography machine is crucial to maintaining the stable operation of the photolithography machine and achieving high-precision photolithography. Before the lead brass material is used as a photolithography machine electrode, its quality needs to be evaluated, such as surface quality characteristic parameters such as purity and grain size. At present, the detection of electrode surface quality mainly relies on microscopic observation, roughness measurement, and electrical performance detection. However, these methods often cannot fully reflect the microstructural characteristics of the electrode surface, such as the uniformity of grain boundaries and the distribution of surface components. In the existing technology, the etched surface is mainly observed by scanning electron microscope (SEM), atomic force microscope (AFM) and optical microscope, but these methods are inefficient in terms of rapid and high-precision quality assessment. In addition, there is a lack of rapid detection methods for grain boundary clarity and oxide layer distribution, making it difficult to achieve real-time evaluation of electrode surface processing quality.

[0005] The above problems show that the characterization of metal parts quality is a tedious, time-consuming and laborious process. In actual operation, there is a lack of correlation model between laser parameters (such as power, scanning speed, spacing, etc.) and metal parts quality, which leads to low experimental efficiency and difficulty in achieving precise control. The current evaluation of metal parts lacks a fast, simple, direct and economical quality evaluation method. Summary of the invention

[0006] In order to solve the problem that the current method of characterizing the quality parameters of metal parts requires the intervention of large instruments, is time-consuming and labor-intensive, and is difficult to quickly provide qualified indicators of materials, the purpose of the present invention is to provide a method for evaluating the quality of metal parts. The present invention is aimed at the problem of rapid quality evaluation required for metal parts. The type of laser is selected by distinguishing the material properties of metal parts, and the impurity distribution on the surface is distinguished by local irradiation of ultraviolet laser. Combined with roughness meter measurement, absorption spectrum verification and online analysis of optical microscope images, a laser parameter-etching depth-grain boundary clarity model is established to achieve rapid and economical quality evaluation of metal parts.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A method for evaluating the quality of metal parts comprises the following steps:

[0009] Step (1): The reflectance and absorption ratio of the opaque material to the laser is given by formula 1 = ρ R +α A Given, where ρ R is the reflectance, α A is the absorption ratio. The absorption rate A of the material to the laser depends on the type of material and the wavelength of the laser. The complex refractive index of the material is n=n1+in2, where n1 is the refractive index, n2 is the extinction coefficient, and i is the imaginary unit. When the laser is incident vertically on the flat material, the reflectance ratio ρ of the laser is R for Get the absorption ratio Therefore, the absorption rate λ is the laser wavelength;

[0010] Step (2): Selecting the laser wavelength λ according to the difference in absorption rate between the base material and impurities in the metal parts to be evaluated;

[0011] Step (3): According to the selected laser power characteristics, the laser frequency Q frequency that can produce the maximum power change is selected by measuring the laser marker working condition through a power meter;

[0012] Step (4): Project the light spot onto the CMOS photosensor, record the real-time image of the light spot, and adjust the shape and size of the light spot by analyzing the image through software; Project the light spot onto dimming paper to ensure good focusing characteristics of the laser spot and avoid the light spot shape and light intensity distribution affecting the etching effect of the laser marker;

[0013] Step (5): using a water and oxygen sensor to monitor the water and oxygen content in the laser processing environment in real time and adjust them; using a nozzle to blow argon gas to provide atmosphere protection for the pre-treated surface of the metal parts;

[0014] Step (6): Ensure that the humidity is less than 10 ppm and the oxygen content is less than 0.1%, otherwise start the purification system to adjust the environment;

[0015] Step (7): clean the surface of the metal parts to remove surface impurities; irradiate the surfaces of the metal parts with different roughness Ra with a fixed power, and use a temperature sensor to monitor the temperature change over time in real time and record the data;

[0016] Step (8): Plot the data recorded by the temperature sensor into a temperature rise-temperature drop curve under different roughness conditions, and use the sample temperature change formula during laser irradiation: Where T(t) is the sample temperature, T(c) is the measurement environment temperature, A is the sample absorption rate, P is the laser power, m is the sample mass, c is the sample specific heat capacity, γ is the sample heat loss coefficient, t is the laser irradiation time, t1 is the laser irradiation start time, t2 is the laser irradiation end time, and the absorption rate A of different roughness to the laser with a wavelength of λ is calculated by fitting;

[0017] Step (9) Use a mechanical polishing device to treat the surface of the metal parts to a maximum absorption rate A max Corresponding surface roughness Ra;

[0018] Step (10): Use the selected laser frequency Q frequency, surface roughness Ra, and the to-be-determined scanning speed V mn , Power W m0 , scanning distance L m0 Under the laser parameter conditions, single-path laser scanning is performed, and the light spot and path morphology are observed using an optical microscope to form an optical microscope image;

[0019] Step (11): import the optical microscope image into the image analysis software, measure the spot diameter d and calculate the spot overlap ratio R;

[0020] Step (12): If the spot overlap ratio is between 50% and 70%, select the scanning speed V corresponding to Ri that meets the spot overlap ratio range requirement. m Continue scanning to proceed to the next step, otherwise the gradient increases the scanning speed and proceeds to step (10);

[0021] Step (13): Use the selected laser frequency Q frequency, surface roughness Ra, scanning speed V m , the laser power to be determined W mn , perform laser single-channel scanning, and use spectral equipment to monitor the absorption peak position and peak value of its laser-induced absorption spectrum in real time;

[0022] Step (14): When the absorption peak position and peak value of the monitored laser induced absorption spectrum remain stable, there is no absorption peak shift and no new absorption peak is generated, and the mechanism of action between the laser and the metal component material is mainly an etching effect, the corresponding laser power W is used. m Go to the next step; when the absorption peak shifts, the intensity changes, and the melting effect of the laser on the metal component material is significant, the laser power is increased gradually to enter step (13);

[0023] Step (15): Use the selected laser frequency Q frequency, surface roughness Ra, scanning speed V m , Laser power W m , the scanning distance L to be determined mn, perform laser plane scanning, and use spectral equipment to monitor the absorption peak position and peak value of its laser induced absorption spectrum in real time;

[0024] Step (16): When the absorption peak of the absorption spectrum of the monitoring spectral equipment changes within 10% of the peak intensity and the absorption peak broadening remains relatively intact, use an optical microscope to observe the uniformity of the etching effect on the scanning plane; if the absorption peak of the absorption spectrum changes by 10% or more from the peak value and broadening, use the scanning spacing L m =L mn +0.002mm enter step (15);

[0025] Step (17): When the morphology of the etched area in the scanning plane under the optical microscope is consistent, the surface texture is consistent, and the etching depth in the spot overlap area is close to that in the laser single-track scanning area, proceed to the next step, otherwise the scanning interval L is used. m =L mn -0.002mm enter step (15);

[0026] Step (18): Use the selected laser frequency Q frequency, surface roughness Ra, scanning speed V m , Laser power W m , scanning distance L m , perform laser local plane irradiation scanning, and use spectral equipment to monitor the absorption peak position and peak value of its laser induced absorption spectrum in real time;

[0027] Step (19): When the absorption peak of the absorption spectrum changes, a targeted change occurs to the impurities, and the absorption peak intensity increases, a roughness meter is used to measure the change in the surface roughness of the material; otherwise, the absorption rate of the metal component material is low and the grain boundary cannot be etched. The mechanism of action of the laser and the metal component material is mainly a melting effect. The number of scans is increased once but not more than five times, and then step (18) is entered;

[0028] Step (20): After measuring the surface roughness with a roughness meter, if the roughness Ra increases by more than 10%, observe the surface structure changes in the scanned area under an optical microscope to see whether grain boundary features appear; otherwise, the grain boundary is not etched, the surface melting effect accounts for more than the etching effect, increase the number of scans by one but not more than five times, and proceed to step (18);

[0029] Step (21): observe the morphological characteristics of the etched area under an optical microscope. If the grain boundary is etched, obvious linear boundaries and mesh grain boundary structures will be observed. The grain boundary structure is rougher and darker than the non-irradiated area. Otherwise, the grain boundary is not etched. The absorption rate of the metal component material is low and the grain boundary cannot be etched. The mechanism of action between the laser and the metal component material is mainly the melting effect. Increase the number of scans once but not more than five times, and proceed to step (18).

[0030] Step (22): When the number of scans reaches the upper limit of five times, the laser has a deep enough action depth on the metal component material but still fails to characterize the grain boundary. In this case, the melting effect in the action mechanism of the laser on the metal component material is significantly stronger than the etching effect, and the grain boundary cannot be etched;

[0031] Step (23): After the grain boundary region is etched, the etched grain boundary region and the unetched region are observed under an optical microscope and a ratio K of the planar areas of the two regions is calculated;

[0032] Step (24): If K≥1, it means that the metal component has a significant etching effect on the surface, and the grain boundary is etched out under an optical microscope, and it is evaluated that the surface quality of the metal component is good and can be used for subsequent processing; if K<1, the surface melting effect is significant, and the surface is melted and stacked under an optical microscope, and it is evaluated that the surface quality of the metal component is poor and cannot be used for subsequent processing;

[0033] Step (25): accurately measuring the etching depth at different scanning times by means of a laser confocal microscope system, and recording the etching amount after each scanning to obtain a depth versus scanning time curve; correlating the scanning times with the etching depth and grain boundary clarity data to establish a scanning times-etching depth-grain boundary clarity relationship model; determining the optimal scanning times through the model so that the etching depth can both reveal the grain boundary and avoid material damage to metal parts or increased surface roughness caused by excessive etching;

[0034] Step (26): construct a data set of the relationship between laser characteristics, laser scanning parameters, etching depth and grain boundary clarity, and comprehensively record and analyze the processing effects under different laser scanning parameter combinations to form an evaluation standard for the quality of metal parts; based on the data set standard, grade the etching effect and divide the quality of metal parts into different grades. The graded evaluation of metal parts is used as a rating indicator for subsequent processing; wherein the laser scanning parameters include Q frequency, roughness Ra, scanning speed V m , Laser power W m , scanning distance L m .

[0035] Preferably, cleaning the surface of metal parts includes solvent wiping and ultrasonic cleaning steps. The advantage of this step is that it lays a foundation for the subsequent regulation of laser parameters and accurate quality evaluation, ensures the accuracy of the experiment and the consistency of results, and improves process reliability and efficiency.

[0036] Compared with the prior art, the present invention has the following advantages:

[0037] (1) The choice of laser wavelength is determined by the difference in absorption between the base material and impurities in metal parts. Laser irradiation with the same wavelength will produce significant differences between impurities and the base. Judging the change in absorption rate by laser irradiation is a sensitive method. At the same time, lasers of different wavelengths will produce easily distinguishable photothermal and photochemical effects when acting on metal parts, making it easier to analyze the quality.

[0038] (2) The previous technology for evaluating surface quality requires the help of a large microscope and requires tedious operations such as sample grinding, sample preparation, and mounting. The technical solution proposed in the present invention is easy to operate, has rapid judgment results, low economic cost, and high efficiency.

[0039] (3) Through the combination of optical microscope detection, spectral analysis and other monitoring methods, the etching effect of the metal parts surface under different laser parameters can be monitored in real time, including grain boundary exposure and surface flatness. This makes the evaluation of surface quality more comprehensive and reliable.

[0040] (4) By selecting a suitable combination of multiple parameters such as laser frequency, scanning speed, power and scanning spacing, the laser action process can be precisely controlled. This fine adjustment can effectively optimize the etching effect and improve the uniformity and stability of the surface treatment of metal parts. By measuring specific values ​​such as absorption peaks, surface roughness, and grain boundary clarity, the quality of the surface of metal parts can be evaluated in a quantitative manner. This method does not rely solely on subjective observation, but has a more scientific and objective evaluation standard.

[0041] (5) Laser irradiation causes little damage to the surface of metal parts and affects a small area, which can ensure the integrity of metal parts and meet subsequent use requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 The figure is a flow chart of the method of the present invention.

[0043] Figure 2 The grain boundaries appear after local irradiation etching with 355nm laser, where (a) is scanned once, (b) is scanned twice, and (c) is scanned three times. DETAILED DESCRIPTION

[0044] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the preferred implementation examples described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0045] like Figure 1 As shown, the present invention provides a method for evaluating the quality of metal parts, taking a lead brass part used as an electrode of a photolithography machine as an example, comprising the following steps:

[0046] (1) Through calculation, it is found that under the irradiation condition of 355nm laser, the base and impurities of the selected lead brass will produce the most significant absorption difference, and the laser wavelength is determined to be 355nm.

[0047] (2) The Q frequency is determined according to the power variation range of the 355 nm laser. It is required that the laser marker has the largest power range under this Q frequency. The laser has the maximum power amplitude under the condition of Q frequency = 30 kHz.

[0048] (3) The light spot is imaged by a CMOS camera, adjusted to a circular shape, and the light intensity of the light spot is evenly distributed, and the focusing of the laser spot is ensured by dimming paper.

[0049] (4) Adjust the laser working environment to an atmosphere with a humidity of less than 10 ppm and an oxygen content of less than 0.1%, and blow argon gas for protection.

[0050] (5) Clean the surface of the electrode material, process the surface of the material to different roughness, use 5W power for continuous irradiation, draw the temperature change curve, and calculate the absorption rate A by fitting the temperature change of the sample during laser irradiation. The fitting calculation results are shown in the following table. The roughness of 1.4μm is selected as the subsequent condition.

[0051]

[0052] (6) The Q frequency of the 355nm laser is set to 30kHz, the surface roughness of the material is set to 1.4μm, and the scanning speed V is set to mn Make gradient changes, such as 50mm / s, 100mm / s, 150mm / s, 200mm / s, 250mm / s... The lead brass material is placed at the focus and a single-channel laser scan is performed.

[0053] (7) Observe the laser single-track scanning path under an optical microscope and calculate the spot overlap ratio R on the path i , record the spot overlap ratio R1, R2, R3, R4, R5 corresponding to the change of gradient scanning speed...

[0054] (8) Comparison R i (i=1,2,3...) is between 50%-70%, select the R that meets the range requirement i The corresponding V m , and the laser scanning speed is obtained to be 100 mm / s.

[0055] (9) The Q frequency of the 355nm laser is set to 30kHz, the scanning speed is 100mm / s, and the laser power percentage W is mn Make gradient changes, such as 5%, 10%, 15%, 20%, 25%... The lead brass material is placed at the focus, and laser single-channel scanning is performed, and the spectral equipment is monitored in real time.

[0056] (10) When the laser power is 12%, the absorption peak of the absorption spectrum remains stable, the intensity does not change, and no new absorption peak is generated.

[0057] (11) The Q frequency of the 355nm laser is set to 30kHz, the scanning speed is 100mm / s, the power percentage is 12%, and the scanning interval L is mn Make gradient changes, for example 0.006mm, 0.008mm, 0.01mm, 0.012mm, 0.014mm... The lead brass material is placed at the focus, and laser plane scanning is performed, and the spectral equipment is monitored in real time.

[0058] (12) When the scanning interval is 0.008 mm, the absorption peak shift and intensity change are within 10%, and the broadening remains relatively complete compared to other scanning interval results. When the scanning plane is observed under an optical microscope, the scanning area is etched evenly and the melt stack is smaller than other scanning interval results, indicating that the spacing is appropriate.

[0059] (13) The laser parameters were determined as Q frequency 30 kHz, scanning speed 100 mm / s, power percentage 12%, and scanning spacing 0.008 mm. A local area was scanned once, and the results of optical microscopy monitoring were as follows: Figure 2 As shown in (a), the grain boundary area is not completely scanned; a second scan is performed, and the optical microscope monitoring results are as follows Figure 2 As shown in (b), the scanning area is observed and the grain boundary area is partially scanned out; the third scan is performed and the optical microscope monitoring results are as follows Figure 2 As shown in (c), the grain boundaries are completely scanned out. The spectral equipment monitors in real time, and the absorption peak of the absorption spectrum changes, which produces targeted changes for impurities. The surface roughness is measured using a roughness meter, and it is found that the irradiated area is rougher than the unirradiated area. The changes in the structure of the scanned area are observed under an optical microscope, and linear and mesh structures are found, and the grain boundaries are etched out in the scanned area.

[0060] (14) The irradiated plane is observed under an optical microscope. The grain boundary clarity K is defined as the ratio of the plane area of ​​the grain boundary region to the plane area of ​​the non-grain boundary region. When K is equal to 9, the etching effect is significant. The material can be used as an electrode material for a photolithography machine.

[0061] (15) The relationship between etching depth and grain boundary clarity at different scanning times was detected under a laser confocal system, and a quality evaluation data set of laser wavelength-scanning parameters-etching depth-grain boundary clarity was established to evaluate the quality level of electrode materials.

Claims

1. A method for evaluating the quality of metal parts, characterized in that: The steps include: Step (1): The reflectance and absorption ratio of the opaque material to the laser is given by formula 1 = ρ R +α A Given, where ρ R is the reflectance, α A is the absorption ratio. The absorption rate A of the material to the laser depends on the type of material and the wavelength of the laser. The complex refractive index of the material is n=n1+in2, where n1 is the refractive index, n2 is the extinction coefficient, and i is the imaginary unit. When the laser is incident vertically on the flat material, the reflectance ratio ρ of the laser is R for Get the absorption ratio Therefore, the absorption rate λ is the laser wavelength; Step (2): Selecting the laser wavelength λ according to the difference in absorption rate between the base material and impurities in the metal parts to be evaluated; Step (3): According to the selected laser power characteristics, the laser frequency Q frequency that can produce the maximum power change is selected by measuring the laser marker working condition through a power meter; Step (4): Project the light spot onto the CMOS photosensor, record the real-time image of the light spot, and adjust the shape and size of the light spot by analyzing the image through software; Project the light spot onto dimming paper to ensure good focusing characteristics of the laser spot and avoid the light spot shape and light intensity distribution affecting the etching effect of the laser marker; Step (5): using a water and oxygen sensor to monitor the water and oxygen content in the laser processing environment in real time and adjust them; using a nozzle to blow argon gas to provide atmosphere protection for the pre-treated surface of the metal parts; Step (6): Ensure that the humidity is less than 10 ppm and the oxygen content is less than 0.1%, otherwise start the purification system to adjust the environment; Step (7): clean the surface of the metal parts to remove surface impurities; irradiate the surfaces of the metal parts with different roughness Ra with a fixed power, and use a temperature sensor to monitor the temperature change over time in real time and record the data; Step (8): Plot the data recorded by the temperature sensor into a temperature rise-temperature drop curve under different roughness conditions, and use the sample temperature change formula during laser irradiation: Where T(t) is the sample temperature, T(c) is the measurement environment temperature, A is the sample absorption rate, P is the laser power, m is the sample mass, c is the sample specific heat capacity, γ is the sample heat loss coefficient, t is the laser irradiation time, t1 is the laser irradiation start time, t2 is the laser irradiation end time, and the absorption rate A of different roughness to the laser with a wavelength of λ is calculated by fitting; Step (9) Use a mechanical polishing device to treat the surface of the metal parts to a maximum absorption rate A max Corresponding surface roughness Ra; Step (10): Use the selected laser frequency Q frequency, surface roughness Ra, and the to-be-determined scanning speed V mn , Power W m0 , scanning distance L m0 Under the laser parameter conditions, single-path laser scanning is performed, and the light spot and path morphology are observed using an optical microscope to form an optical microscope image; Step (11): import the optical microscope image into the image analysis software, measure the spot diameter d and calculate the spot overlap ratio R; Step (12): If the spot overlap ratio is between 50% and 70%, select the scanning speed V corresponding to Ri that meets the spot overlap ratio range requirement. m Continue scanning to proceed to the next step, otherwise the gradient increases the scanning speed and proceeds to step (10); Step (13): Use the selected laser frequency Q frequency, surface roughness Ra, scanning speed V m , the laser power to be determined W mn , perform laser single-channel scanning, and use spectral equipment to monitor the absorption peak position and peak value of its laser-induced absorption spectrum in real time; Step (14): When the absorption peak position and peak value of the monitored laser induced absorption spectrum remain stable, there is no absorption peak shift and no new absorption peak is generated, and the mechanism of action between the laser and the metal component material is mainly an etching effect, the corresponding laser power W is used. m Go to the next step; when the absorption peak shifts, the intensity changes, and the melting effect of the laser on the metal component material is significant, the laser power is increased gradually to enter step (13); Step (15): Use the selected laser frequency Q frequency, surface roughness Ra, scanning speed V m , Laser power W m , the scanning distance L to be determined mn , perform laser plane scanning, and use spectral equipment to monitor the absorption peak position and peak value of its laser induced absorption spectrum in real time; Step (16): When the absorption peak of the absorption spectrum of the monitoring spectral equipment changes within 10% of the peak intensity and the absorption peak broadening remains relatively intact, use an optical microscope to observe the uniformity of the etching effect on the scanning plane; if the absorption peak of the absorption spectrum changes by 10% or more from the peak value and broadening, use the scanning spacing L m =L mn +0.002mm enter step (15); Step (17): When the morphology of the etched area in the scanning plane under the optical microscope is consistent, the surface texture is consistent, and the etching depth in the spot overlap area is close to that in the laser single-track scanning area, proceed to the next step, otherwise the scanning interval L is used. m =L mn -0.002mm enter step (15); Step (18): Use the selected laser frequency Q frequency, surface roughness Ra, scanning speed V m , Laser power W m , scanning distance L m , perform laser local plane irradiation scanning, and use spectral equipment to monitor the absorption peak position and peak value of its laser induced absorption spectrum in real time; Step (19): When the absorption peak of the absorption spectrum changes, a targeted change occurs to the impurities, and the absorption peak intensity increases, a roughness meter is used to measure the change in the surface roughness of the material; otherwise, the absorption rate of the metal component material is low and the grain boundary cannot be etched. The mechanism of action of the laser and the metal component material is mainly a melting effect. The number of scans is increased once but not more than five times, and then step (18) is entered; Step (20): After measuring the surface roughness with a roughness meter, if the roughness Ra increases by more than 10%, observe the surface structure changes in the scanned area under an optical microscope to see whether grain boundary features appear; otherwise, the grain boundary is not etched, the surface melting effect accounts for more than the etching effect, increase the number of scans by one but not more than five times, and proceed to step (18); Step (21): observe the morphological characteristics of the etched area under an optical microscope. If the grain boundary is etched, obvious linear boundaries and mesh grain boundary structures will be observed. The grain boundary structure is rougher and darker than the non-irradiated area. Otherwise, the grain boundary is not etched. The absorption rate of the metal component material is low and the grain boundary cannot be etched. The mechanism of action between the laser and the metal component material is mainly the melting effect. Increase the number of scans once but not more than five times, and proceed to step (18). Step (22): When the number of scans reaches the upper limit of five times, the laser has a deep enough action depth on the metal component material but still fails to characterize the grain boundary. In this case, the melting effect in the action mechanism of the laser on the metal component material is significantly stronger than the etching effect, and the grain boundary cannot be etched; Step (23): After the grain boundary region is etched, the etched grain boundary region and the unetched region are observed under an optical microscope and a ratio K of the planar areas of the two regions is calculated; Step (24): If K≥1, it means that the metal component has a significant etching effect on the surface, and the grain boundary is etched out under an optical microscope, and it is evaluated that the surface quality of the metal component is good and can be used for subsequent processing; if K<1, the surface melting effect is significant, and the surface is melted and stacked under an optical microscope, and it is evaluated that the surface quality of the metal component is poor and cannot be used for subsequent processing; Step (25): accurately measuring the etching depth at different scanning times by means of a laser confocal microscope system, and recording the etching amount after each scanning to obtain a depth versus scanning time curve; correlating the scanning times with the etching depth and grain boundary clarity data to establish a scanning times-etching depth-grain boundary clarity relationship model; determining the optimal scanning times through the model so that the etching depth can both reveal the grain boundary and avoid material damage to metal parts or increased surface roughness caused by excessive etching; Step (26): construct a data set of the relationship between laser characteristics, laser scanning parameters () and etching depth and grain boundary clarity, and comprehensively record and analyze the processing effects under different laser scanning parameter combinations to form an evaluation standard for the quality of metal parts; according to the data set standard, grade the etching effect and divide the quality of metal parts into different grades, and grade the metal parts for subsequent processing. The laser scanning parameters include Q frequency, roughness Ra, scanning speed V m , Laser power W m , scanning distance L m .

2. A method for evaluating the quality of metal parts according to claim 1, characterized in that: In step (7), cleaning the surface of the metal parts includes solvent wiping and ultrasonic cleaning steps.

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