JP5483360B2 - Deterioration state diagnosis method and apparatus for plating - Google Patents

Description

  The present invention relates to a method and apparatus for diagnosing the corrosion status of plated metal, that is, the degradation status of plating. More specifically, the present invention is suitable for use in evaluating plating depletion conditions for long-term operation and maintenance of hot-dip galvanized steel used in, for example, power transmission towers and distribution members. The present invention relates to a diagnostic method and an apparatus thereof. In the present specification, the deterioration of the plating is also referred to as plating depletion, thinning or corrosion, and is mainly used to mean a reduction in plating thickness.

  Hot dip galvanized steel is used in many facilities such as power transmission towers and power distribution facilities from the viewpoint of durability and corrosion resistance. However, since the plating wears down over time, rusting occurs if proper grasping and maintenance of the state of plating is neglected. Therefore, it is important to grasp the deterioration state of the plating by periodic inspection. Of course, it is important to grasp the deterioration state not only in hot dip galvanized steel but also in other plating.

  Here, as a method for diagnosing the deterioration state of the plating applied to the metal object, conventionally, visual observation or visual observation with a camera image, film thickness measurement using an electromagnetic film thickness meter, an ultrasonic generator or the like And an inspection apparatus such as an EPMA (Electron Probe Micro Analyzer). In particular, visual inspection is generally used for on-site deterioration diagnosis of hot-dip galvanized steel used in power transmission towers and the like. In this visual inspection, a photograph sample is prepared in advance, and the degree of deterioration is evaluated in five stages by comparing with a sample. In recent years, deterioration due to image processing has also been evaluated. In the method by image processing, the color information of the photographed image is used to judge the deterioration that the inspector subjectively performed in the visual inspection by mechanically processing the image processing (Patent Document 1). ). Moreover, in the deterioration diagnosis of plating by film thickness measurement, an instrument such as an electromagnetic film thickness meter or an ultrasonic generator is brought into contact with the plating surface, and the deterioration is determined by measuring the film thickness of the plating.

JP 11-37950 A

  However, it is difficult to diagnose a corrosion situation that hardly changes in appearance such as zinc corrosion products by visual observation or camera photography. In addition, in the case of the invention described in Patent Document 1, since the way the inspection object is reflected changes due to changes in weather conditions such as in fine weather or rainy weather or shadows of the subject, the determination result of deterioration by image processing is based on the imaging conditions. It is greatly influenced by and changes. In addition, when the appearance changes due to dirt or the adhesion status of adhered products, even if it is judged from the image that the deterioration has not progressed, the wear of the plating that is actually hidden by the dirt may be large. is there. Furthermore, it is difficult to apply an image processing method to a place where photographing with a camera is difficult, such as a hollow steel pipe.

  On the other hand, the electromagnetic film thickness meter and the ultrasonic generator can measure the film thickness, but if the plating surface is contaminated or the corrosion product is thick, the film thickness is evaluated to be larger. Therefore, it is not possible to accurately grasp the wear of the plating. Moreover, although an analyzer such as EPMA can accurately measure the film thickness and analyze the corrosion state, it is necessary to cut the material to be analyzed, and the measurement cannot be performed on site. Therefore, in the case of hot-dip galvanized steel used in many facilities such as transmission towers and distribution facilities, it is impossible to measure on-site. It was not possible to apply because it was a destructive inspection.

  The present invention provides a method and an apparatus for diagnosing a deterioration state of a plated steel material that can be objectively inspected without being affected by the appearance of measurement conditions and dirt, etc. while having the convenience of visual observation. Objective. It is another object of the present invention to provide an apparatus that enables inspection of a location where it is difficult for an inspector and inspection equipment such as an inner surface of a steel pipe to approach.

  As a result of various experiments and researches by the present inventors in order to achieve such an object, the plating layer is not formed of only the plating component, but forms an alloy of the plating component and the metal base so that it approaches the metal base. Focusing on the fact that the content of the metal substrate changes in the direction of decreasing the components and elements of the metal substrate as the component / element of the metal substrate increases and toward the plating surface, plating is performed by ablating the plating surface with laser light. To know that it is possible to judge the progress of plating depletion (that is, deterioration of plating) by making the components contained in the layer emit plasma and taking the emission intensity ratio between the metal base component and the plating component It came.

  The present invention has been made on the basis of such knowledge, and the plating deterioration diagnosis method according to claim 1 comprises ablating the surface of the plating by irradiating the plating surface to be inspected with a pulsed laser beam. The emission intensity of the element constituting the metal substrate and the emission intensity of the plating component element are obtained by measuring and spectrally measuring the emission of the plasma generated by the above, and the emission intensity of the element constituting the metal substrate and the emission intensity of the plating component element The deterioration state of the plating applied to the metal object is diagnosed from the change in the strength ratio of the metal.

  In the plating deterioration diagnosis method of the present invention, a correlation between the intensity ratio between the light emission intensity of the element constituting the metal substrate and the light emission intensity of the plating component and the plating thickness is obtained in advance using the sample to be inspected. The deterioration state of the plating layer is preferably quantified from the emission intensity ratio based on the measured value and the correlation.

  Further, in the plating deterioration diagnosis method of the present invention, the object to be inspected is a hot dip galvanized steel material, and any one of 328.23, 330.21, 334.57, 468.01, 472.21, 481.05 nm zinc emission line, and 338.01, 339.26, 340.74. , 342.71, 344.09, 346.58, 347.54, 349.05, 349.78, 351.38, 352.60, 354.20, 355.49 nm, the intensity ratio of zinc and iron luminescent lines was determined, and the plating thickness was determined. It is preferable to evaluate.

  In addition, the plating deterioration diagnosis apparatus according to the present invention includes a laser apparatus for ablating a plating surface by irradiating the plating surface to be inspected with a pulsed laser beam, and measuring and emitting a plasma emission generated by the ablation. Measuring the emission intensity of the element of the metal base and the emission intensity of the element of the plating component, and evaluating the deterioration state of the plating layer from the change in the intensity ratio between the emission intensity of the metal base element and the emission intensity of the plating component And an analyzing device to be provided.

  Furthermore, in the plating deterioration diagnosis apparatus according to the present invention, data obtained by using the sample to be inspected in advance to obtain the correlation between the plating ratio and the intensity ratio between the emission intensity of the metal base element and the emission intensity of the plating component is stored. It is preferable to quantify the deterioration state of the plating layer from the correlation between the emission intensity ratio based on the measured value, the emission intensity ratio determined in advance, and the plating thickness.

  Furthermore, in the plating deterioration diagnosis apparatus according to the present invention, the inspection object is a hot dip galvanized steel material, and any one of 328.23, 330.21, 334.57, 468.01, 472.21, 481.05 nm zinc emission line, and 338.01, 339.26, Deterioration of plating by using one of 340.74, 342.71, 344.09, 346.58, 347.54, 349.05, 349.78, 351.38, 352.60, 354.20, and 355.49 nm of the iron emission line to determine the intensity ratio of zinc and iron emission line It is preferable to evaluate the situation.

  Furthermore, in the plating degradation diagnosis apparatus according to the present invention, a light receiving element having a gate function for receiving light emitted from a plasma substance dispersed through a spectroscopic device and obtaining an emission spectrum, and a gate of the laser and the light receiving element It is preferable to provide a controller that controls a time difference from the opening start time.

  According to the plating deterioration diagnosis method and apparatus according to the present invention, the surface of the plating to be inspected is ablated with a laser beam, and the generated plasma emission is measured to determine the emission intensity ratio between the metal substrate and the plating element. Thus, the deterioration state of the plating layer can be evaluated, so that the deterioration state of the plating can be directly diagnosed in a non-destructive manner in a short measurement time based on on-site measurement. Moreover, since it is possible to measure remotely as long as it is within the reach of the laser beam, it can be applied to the measurement where the measurer cannot easily reach such as measurement near the live line or measurement inside the steel pipe. Is possible. Accordingly, it is possible to realize on-site plating deterioration diagnosis of hot dip galvanized steel used in many facilities such as power transmission towers and power distribution facilities. Furthermore, even in places where photographing with a camera such as a hollow steel pipe is difficult, the corrosion situation can be easily diagnosed if the optical path of the laser beam is secured. That is, the plating deterioration diagnosis method and apparatus according to the present invention enables inspection of places where it is difficult for an inspector and inspection equipment such as the inner surface of a steel pipe to approach.

  On the other hand, even when dirt adheres to the plating surface or a thick corrosion product is formed, dirt on the plating surface is evaporated or peeled off by ablation with a laser beam, and an emission intensity ratio corresponding to the film thickness is obtained. Therefore, it is possible to accurately grasp plating depletion. In other words, even if dirt or corrosion products on the plating surface are emitted by plasma due to laser ablation, it only affects the light emission of the elements of the metal base and plating components, and this affects the diagnosis of plating deterioration. There is no.

  In other words, the plating deterioration diagnosis method and apparatus according to the present invention can be objectively inspected without being affected by the appearance of measurement conditions and dirt, while having the convenience of visual observation. In addition, the destruction of the plating layer due to ablation is about several hundreds of nanometers per ablation, whereas the plating thickness is 200 μm or more, so it may only correspond to about 1/1000 to 1/5000. This was confirmed by the inventors' experiments. In addition, since the surface of the actual plating has irregularities of 1 to 2 μm (that is, corrodes), there is no concern that corrosion is promoted by ablation by laser light.

  Further, in the plating deterioration diagnosis method and apparatus of the present invention, the correlation between the intensity ratio between the emission intensity of the element constituting the metal substrate and the emission intensity of the plating component and the plating thickness is obtained in advance using the sample to be inspected. In this case, the deterioration state of the plating layer can be quantified from the emission intensity ratio based on the measured value and the correlation.

  Furthermore, in the plating deterioration diagnosis apparatus according to the present invention, when a light-receiving element having a gate function and a controller for controlling a time difference between the laser and the gate opening start time of the light-receiving element are provided, light emission called white light is emitted. It is possible to increase the measurement sensitivity because it is possible to obtain an emission spectrum by eliminating the influence of high intensity light (background noise) and receiving light by the light receiving element at the timing when the emission peak becomes remarkable.

It is a conceptual diagram which shows the structure of a hot dip galvanization layer. It is a conceptual diagram of the deterioration diagnostic device for remote measurement. It is a conceptual diagram which shows the deterioration diagnostic apparatus of the location where proximity | contact is difficult using an optical fiber. It is a conceptual diagram which shows the deterioration diagnostic apparatus of the location where proximity | contact is difficult using an optical transmission tube. It is a layout of an experimental device. In the graph which shows the emission spectrum of the plasma emission spectrum in the hot dip galvanized layer, the solid line shows the emission spectrum on the plating surface before deterioration, and the broken line shows the emission spectrum when reaching the bare metal after deterioration. It is a graph which shows the emission spectrum of the emission spectrum of zinc in a hot dip galvanization layer. It is a graph which shows the continuous measurement result of the emission spectrum of the plasma in a hot dip galvanization layer. It is a graph which shows the intensity | strength of the emission line of iron and zinc. It is a graph which shows the relationship between the luminous intensity ratio of zinc and iron, and the structure of the plating layer of hot dip zinc. It is an image which shows the condition of the hollow of the irradiation trace after irradiating a laser beam 4000 times. It is an image which shows the condition of the hollow of the irradiation trace after irradiating a laser beam 1000 times. It shows the surface roughness of the trace irradiated with the laser light 4000 times, and (A) shows a photograph of the irradiation trace and the roughness measurement position (red line portion). (B) is a graph showing surface roughness. It is a graph which shows the relationship of the depth of the hollow with respect to the frequency | count of laser irradiation. It is a graph which shows the luminous intensity change of zinc and iron, (A) shows the luminous intensity change of zinc, (B) shows the luminous intensity change of iron. It is a graph which shows the luminescence intensity change of zinc and iron, (A) is what normalized the luminescence intensity change of zinc, (B) is what normalized the luminescence intensity change of iron.

  Hereinafter, the configuration of the present invention will be described in detail based on embodiments shown in the drawings. In the present embodiment, a hot dip galvanized steel sheet is taken as an example for inspection.

  FIG. 1 shows the configuration of the hot dip galvanized layer. An alloy layer of zinc and iron is formed inside the plating layer, and the iron content becomes higher as it is closer to the iron base material to be plated. As the galvanized layer deteriorates, it is depleted from the η layer, and the alloy layer is exposed. Further deterioration causes rusting and leads to corrosion of the base material. That is, the ratio of elements contained in the plating surface is changed by changing the plating thickness due to the wear of the plating. From this, if the plating surface is ablated with laser light, plasma emission corresponding to the elements contained in the plating surface can be obtained. As the plating progresses, the emission intensity ratio between the metal base component and the plating component changes. Here, the emission continuous spectrum and the emission intensity do not represent the content ratio (component ratio) of the plating itself. Further, the emission intensity does not represent the content of the plating component itself. However, the component ratio can be specified by taking the emission intensity ratio between a plurality of elements. That is, the progress of the deterioration (corrosion) of the plating is judged by taking the emission intensity ratio between the metal base component (Fe) and the plating component (Zn), that is, by measuring the iron content in the plating layer. Is possible. In addition, in the case of hot dip galvanization to be inspected in the present embodiment, since it is single phase plating, the substrate and the base are the same.

  Therefore, as shown in FIG. 2, the plating surface of the hot dip galvanized steel sheet 1 to be inspected is irradiated with pulsed laser light 8 to ablate the plating surface, and then the light emitted from the plasma 2 generated by the ablation is spectroscopic apparatus. Degradation of plating by measuring and spectrally measuring at 4 and measuring the light emission intensity of the metal base component (Fe) and the plating component (Zn), and further obtaining the light emission intensity ratio between the metal base component and the plating component by the measuring device 5 Determine the situation. Note that the deterioration diagnosis apparatus of the embodiment shown in FIG. 2 is for diagnosing deterioration of an inspection object existing at a remote place, and is provided with a telescope 3 in the light receiving unit to improve the light receiving sensitivity. In the figure, reference numeral 4 is a spectroscopic device, 5 is a measuring device, 6 is a timing controller, and 7 is a laser device.

Regarding the laser device 7 to be used, a laser having a peak power sufficient to ablate and turn into plasma, for example, a pulse laser such as Nd: YAG laser, fiber laser, titanium sapphire laser, glass laser, CO ₂ laser, excimer laser, etc. Is used. That is, if it is a pulse laser, a nanosecond laser or an ultrashort pulse laser can be used.

  The spectroscopic device 4 measures the light emission lines of the component elements of the metal base and plating by dispersing the received plasma emission. In the case of diagnosing deterioration of a hot dip galvanized steel sheet, zinc and iron emission lines are measured by spectroscopy. At this time, the intensity of the emission line of each element is proportional to the content of the element in the ablated portion. Furthermore, the ratio of the emission intensity between different elements is proportional to the content of each element.

  Since the zinc and iron content of the plating layer changes as it approaches the iron substrate, for example, changes in the emission intensity as shown in FIGS. 6 and 7 are measured. Therefore, one of the 328.23, 330.21, and 334.57 nm zinc emission lines and the 338.01, 339.26, 340.74, 342.71, 344.09, 346.58, 347.54, 349.05, 349.78, 351.38, 352.60, 354.20, and 355.49 nm iron emission lines. By using any one of the above and taking the intensity ratio between zinc and iron emission lines as shown in FIG. 10, the iron content can be determined. Even if the element content is the same, the intensity of the emission line of each element varies depending on the laser irradiation conditions. However, by taking the ratio of the emission intensity of each element acquired at once by measurement, the contribution of the measurement conditions is canceled out, and a value that depends only on the content of the measurement location is obtained. Even if the deterioration state is the same and the appearance is different due to dirt or the like, the method is not affected by substances other than iron and zinc, and therefore does not affect the measurement results. Here, the light emission lines for obtaining the light emission intensity ratio between the metal base component and the plating component are not established only between specific light emission lines, but are established between all light emission lines. For example, taking a hot dip galvanized steel sheet as an example, as shown in FIGS. 15 (A) and 15 (B), there are a number of light emission lines indicating zinc and iron, respectively, depending on the plating depletion situation. As shown in FIGS. 16 (A) and 16 (B), it is clear that the same change in the emission intensity is shown. Therefore, it can be seen that the same change in the emission intensity ratio can be obtained with respect to the progress of the depletion of plating, regardless of which of the emission lines of zinc and iron is used.

  Incorporation of emission spectrum from plasma 2 obtained by ablation of plating surface, extraction of emission intensity of arbitrary emission lines of zinc and iron, calculation of emission intensity ratio of zinc and iron, and plating based on the obtained emission intensity ratio The evaluation of the deterioration state of is performed in the measuring device 5. Although not shown, the measuring device 5 is a central processing unit that is mounted with a light receiving element having a gate function that takes in an output from the spectroscopic device 4 according to an instruction from the timing controller 6, and various analysis programs for analyzing the spectral intensity distribution. In addition, a storage unit is provided to input information on the emission intensity for each emission line, save this data, and extract the emission intensity of any emission line of zinc and iron to calculate their emission intensity ratio. The change in the ratio of elements contained in the plating surface, that is, the deterioration state of the plating is obtained from the emission intensity ratio and output to a display or the like. The timing controller 6 controls the time difference between the time of irradiation of the laser beam 8 by the laser device 7 and the gate opening start time of the light receiving element of the measuring device 5. The measuring device 5 includes a storage device (not shown), and uses the sample to be inspected to correlate the intensity ratio between the emission intensity of the element constituting the metal substrate and the emission intensity of the plating component and the plating thickness. A calibration curve or a table obtained in advance may be stored in a storage device, and this correlation may be read from the storage device to quantify the deterioration state of the plating layer from the relationship with the emission intensity ratio based on the measured value. .

  According to the plating deterioration diagnosis apparatus configured as described above, the timing controller 6 irradiates the plating surface of the hot dip galvanized steel sheet 1 to be inspected from the laser device 7 by irradiating the surface of the plating with the pulse laser beam 8. Then, the light emission 9 of the plasma 2 generated by ablation is measured through the telescope 3 and the spectroscopic device 4, and the light emission intensity of the element constituting the metal substrate and the light emission intensity of the plating component element are obtained by spectroscopic measurement. The deterioration state of the plating layer can be evaluated from the change in the intensity ratio between the light emission intensity of the element constituting the metal substrate and the light emission intensity of the plating component element.

  Next, FIG. 3 shows a conceptual diagram of an apparatus for diagnosing plating deterioration at locations where it is difficult for an inspector and inspection equipment such as the inner surface of a steel pipe to approach. FIG. 3 is a conceptual diagram of an apparatus for transmitting laser light 8 and receiving plasma light emission 9 using an optical fiber. The apparatus consists of a fiber 11 for transmitting laser light and a fiber 12 for receiving plasma, which are bundled by a hollow tube 13 and used. At the laser irradiation end, the laser light 8 is condensed by the convex lens 14 and ablation is performed. Since the optical fibers 11 and 12 themselves have a certain degree of flexibility, it is possible to perform measurement along the shape. Of course, instead of using the hollow tube 13, it may be configured only by the exposed optical fiber 11 for laser light transmission and the optical fiber 12 for light emission measurement. In this case, each of the optical fibers 11 and 12 is wound around a winding drum (not shown) and suspended in a narrow space such as in a steel pipe, and the end of the cable is bent so as to face the plating surface. It is provided so that it can be moved up and down. It is possible to diagnose the deterioration state of the plating on the surface of the inner peripheral surface 1 ′ of the steel pipe to be inspected.

  FIG. 4 is a conceptual diagram of another embodiment using an optical transmission tube. This optical transmission tube has a hollow tube 19 in which an optical system for laser light transmission and an optical system for light emission measurement are incorporated, and the plating surface to be inspected is transparent at the tip of the hollow tube 19. The tip opening provided with the glass window 18 is used so as to be opposed to each other. Here, the optical system for laser beam transmission includes a condensing lens 17 and a wavelength selective mirror 15 that reflects only the wavelength of the laser beam 8 and irradiates the plating surface with the laser beam 8. The optical system for light emission measurement is a reflection mirror 16 that does not depend on the wavelength for reflecting the plasma light emission 9 that is disposed behind the wavelength selective mirror 15 and transmits the plasma light emission 9 transmitted through the wavelength selective mirror 15 by ablation of the plating surface. including. Therefore, the laser beam 8 propagates through the hollow tube 19 and is irradiated to the inspection target portion through the wavelength selective mirror 15 and the window glass 18 at the irradiation end. The light emission 9 propagates through the hollow tube 19 through the window glass 18 and using the mirror 16 in the hollow tube 19. In the present apparatus, it is possible to measure a vertically long portion over a wide range by making the hollow tube 19 into an expandable structure.

  The above-described embodiment is an example of a preferred embodiment of the present invention, but is not limited thereto, and various modifications can be made without departing from the scope of the present invention. For example, in the present embodiment, the diagnosis of the deterioration of the hot dip galvanized steel sheet is mainly described as an example, but the plating to be diagnosed is not particularly limited to this, and other platings are also to be measured. It is possible to diagnose the deterioration state only with different elements. An object of the present invention is to estimate a depletion state of plating by examining an element ratio between a metal base and a plating material. Therefore, for example, in the case of tin plating in which the metal base is iron and the plating material is tin, it is possible to estimate the tin depletion state by examining the element ratio of iron and tin from the emission intensity ratio. In addition, the components and types of plating to be inspected need not be known in advance. Since the abundance ratio of the plating composition components is determined from the emission intensity ratio, the plating composition component elements can be specified by the shape of the emission spectrum and the peak wavelength. Therefore, even if the composition of the plating or the metal base is unknown, the deterioration diagnosis of the plating can be performed without questioning the type of plating.

  In addition, the type of laser, irradiation time, irradiation method, and the like given as preferable examples in the above-described embodiment are not particularly limited. Although it is conceivable that the emission intensity itself of each element varies depending on the type of laser, how to apply laser light, irradiation time, etc., it is estimated that the emission intensity ratio between arbitrary elements is constant. Therefore, it is not particularly limited to a specific type of laser, a method of applying laser light, an irradiation time, or the like as long as it does not adversely affect the plating layer.

  Further, in the present embodiment, since the measurement sensitivity is not so much required, plasma emission is obtained with a single pulse, but in some cases, plasma emission may be obtained with a double pulse. In this case, since the light emission of the ablated element can be measured without omission, the measurement sensitivity can be improved. In other words, the particles excited by the first ablation are effectively reheated or re-excited by the second laser beam to extend the emission lifetime of the excited atoms and are plated without being converted to plasma by the first ablation. Since particles ejected from the surface are also excited, it is possible to increase the ablation efficiency and improve the measurement sensitivity while suppressing damage to the material with lower power. In addition, since the energy of the first laser pulse can be reduced, damage caused by laser light on the plating surface can be reduced. In particular, the first step of ablating the plating surface by irradiating the pulsed laser light toward the plating surface, and the first step of irradiating the plasma formed by ablation in parallel with the plating surface. This is more effective when performed in the second step of reheating or reexcitation including particles that have not been excited. In this case, by giving a time difference of 0.5 μs to 5 μs between the laser beam irradiated in the first step and the laser beam irradiated in the second step, the effect of additional heating is obtained and the excited particles Sufficient additional heating can be applied before the splashes. Furthermore, the laser beam irradiated in the first step is weaker than the laser beam irradiated in the second step, and is sufficient to eject at least the plating component to be measured from the plating surface. If the laser light to be irradiated is sufficient to excite and emit the components ejected in the first step, the measurement sensitivity can be increased while minimizing damage by the laser light on the plating surface. it can.

  In addition, measurement of ablation by laser light irradiation and light emission from the ablation plume is performed by an optical system using an optical lens, a mirror, or the like. Or may be taken into a spectroscope. An optical fiber normally does not pass light in the ultraviolet region (wavelength of 200 nm or less), and is therefore effective in measuring such light emission. Of course, it is also preferable to improve the measurement sensitivity by increasing the intensity of the separated light by condensing on the optical fiber using a lens. Alternatively, a bundle fiber may be used as the optical fiber, and the coupling efficiency between the optical fiber and the spectroscope may be improved by matching the output shape of the optical fiber to a line shape and the slit shape of the spectroscope. It is also possible to set the condensing of the laser light and the condensing of the emitted light coaxially. Thereby, the system can be simplified.

  An experiment was conducted to confirm that the present invention can diagnose the deterioration of the plating. As shown in FIG. 5, the experimental apparatus inspects the laser light 8 from the laser apparatus 7 whose irradiation with the laser light 8 is controlled by the timing controller 6 via the reflection mirror 21 and the convex lens 22 (hot dip galvanized steel sheet). 1 and the emission spectrum of plasma 2 obtained by ablation is captured by a spectroscope 26 and an ICCD camera (industrial camera) 27 via a plano-convex lens 23, a sharp cut filter 24 and an optical fiber 25, and analyzed by a personal computer 28. The corrosion situation is evaluated. In addition, the timing controller 6 outputs a trigger for issuing an instruction for the personal computer 28 to release the shutter of the ICCD camera 27 and keep it open for a predetermined time with a predetermined delay after the laser beam is emitted from the laser device 7. The personal computer 28 captures the image signal from the ICCD camera 27, saves the emission spectrum as necessary, calculates, and analyzes the emission intensity of the elements constituting the metal substrate and the emission of the plating component elements. The strength is obtained, and the deterioration state of the plating layer is evaluated from the change in the intensity ratio between the light emission intensity of the element constituting the metal substrate and the light emission intensity of the plating component element. It is also possible to use a spectroscope 26 and a photomultiplier tube (not shown) as the light receiving system, or to use a linear light receiving element such as a normal CCD camera or a linear photodiode as the light receiving element having a gate function. In some cases, a single light receiving element such as a photomultiplier tube or a photodiode may be used as the light receiving element.

  In the experiment, the second harmonic (532 nm) was oscillated from the Nd: YAG laser device 7 and the laser beam 8 was made to enter the hot dip galvanized steel sheet 1 perpendicularly. The laser beam 8 was condensed by the convex lens 22 for ablation. In order to measure light emission 9 of plasma 2 generated by ablation, light was received using a plano-convex lens 23, a sharp cut filter 24, and an optical fiber 25, and received by an ICCD camera 27 via a spectroscope 26. In the measurement, the same spot was continuously irradiated and the emission spectrum was continuously measured in the process while ablating the galvanized layer little by little. By measuring in this way, the emission spectrum in the region from the plating layer surface to the iron substrate was measured under the same experimental conditions. The energy of the laser was 30 mJ, and the light emission was measured by opening the shutter of the ICCD camera 27 for 500 nsec 1.7 μsec after the laser irradiation. The emission spectrum was averaged 20 times. The hot dip galvanized sample used in the measurement was one with a degradation degree of about 2 (zinc layer disappeared and alloy layer exposed).

  FIG. 6 shows the emission spectrum of plasma in the hot dip galvanized layer. Zinc emission lines were confirmed at 325 to 335 nm, and iron emission lines were confirmed at 335 to 355 nm.

  The result of measuring the spectrum while irradiating the laser is shown in FIG. Immediately after the laser irradiation, it corresponds to the surface of the plating layer in the figure. When the irradiation is continued, the plating is gradually removed by ablation and approaches the iron substrate. The closer to the iron substrate, the lower the emission intensity of zinc and the higher the emission intensity of iron. As shown in FIG. 1, this is considered to be because the iron content in the plating layer increases as it is closer to the iron substrate. That is, it is considered to reflect the characteristics of the alloy layer (the closer to the bare metal, the more Fe).

  FIG. 9 shows changes in the intensity of the zinc and iron emission lines. On the plated surface, the emission intensity of Zn was strong, but the emission intensity of Fe was relatively higher as it was closer to the metal. Moreover, both emission intensity became small, so that it approached an iron substrate. This is considered to be due to the fact that the ease of ablation changes, that is, the ablation is easier to ablate as the plating surface is closer to the metal substrate. That is, it can be considered that the measurement condition has changed due to the gradual change of the position of the laser light irradiation point due to ablation. As described above, since the emission intensity is affected by the measurement conditions, it is difficult to directly estimate the content of each element from the emission intensity.

  Therefore, by taking the ratio of the emission intensity of zinc and iron as shown in FIG. 10, it is possible to cancel the influence of the emission intensity due to the measurement conditions and estimate the iron content to zinc. Ideally, the zinc emission should disappear in the iron base region, but the emission intensity ratio does not actually become zero due to background light noise. In practice, it is necessary to evaluate the degree of degradation III (overall exposure of the ζ layer), which is said to be a replacement standard for replating. In this experiment, a sample having a degree of degradation of about II is used, and each layer can be evaluated from the change in the slope of the emission intensity ratio as shown in FIG. For this reason, the degree of deterioration III is determined when the emission intensity ratio is 0.7 or more. That is, based on the result of this experiment, a threshold value may be set to a light emission intensity ratio of 0.7 or more to determine whether or not there is a necessity for diagnosing plating deterioration, for example, re-plating.

  In the plating diagnostic method according to the present invention, if the intensity of the laser beam is too high, the plating may be excessively removed. Therefore, it was clarified by optical microscope observation how much plating was removed when measurement was performed under the present experimental conditions. FIG. 11 is a three-dimensional representation of the roughness in the vicinity of an irradiation mark of a mark irradiated with the same portion 4000 times under the present experimental conditions. From the figure, it can be seen that the plating mark is hardly removed around the irradiation mark, and only a small area is removed.

  FIG. 12 is a three-dimensional representation of the roughness near the irradiation mark of the mark irradiated with the same spot 4000 times under the present experimental conditions.

  FIG. 13 shows the surface roughness of the irradiation mark measured in FIG. An area of 400 to 600 μm in the figure shows an unirradiated surface. The surface of the unirradiated area has a variation of about 10 μm. Although there is a variation in roughness on both the irradiated surface and the unirradiated surface, it can be seen that the depth is about 90 μm.

  FIG. 14 shows the depth of the depression with respect to the number of times of laser irradiation. Assuming that the amount of plating to be removed by one irradiation is constant, the calculation is to remove the plating having a thickness of about 20 nm by one irradiation. This is about 1/2000 of the plating surface roughness (-10 μm) before irradiation. Further, the thickness of the plating is about 200 μm immediately after the plating treatment, and if the number of times of irradiation in one measurement is 20 times as in the example, about one half of the thickness of the plating is obtained by one measurement. It will be a calculation to remove.

This time, the surface of the plating was irradiated with a laser with an energy fluence equivalent to 15 W / cm ^2. However, if the fluence is high, the removal amount of the plating is large. However, if the fluence is too low, ablation does not occur and plasma emission cannot be measured. From the results of this experiment, it was confirmed that the lower limit of the fluence at which plasma was generated was 15 W / cm ² , the same as the experimental conditions. In addition, the shutter of the ICCD camera 7 was opened 1.7 μsec after the laser irradiation, but if the timing of opening the shutter is too early, light of high emission intensity called white light is received simultaneously with the light emission of each element. It becomes impossible to measure. On the other hand, if the timing is late, the intensity of the emission line of each element is lowered and the sensitivity is lowered. Therefore, the timing for opening the shutter is about 1 to 20 μsec, more preferably about 1 to 2 μsec.

DESCRIPTION OF SYMBOLS 1 Hot-dip galvanized steel plate 2 Plasma 3 Telescope 4 Spectrometer 5 Spectrometer 5 Measuring device 6 Timing controller 7 Laser device 8 Laser light 9 Plasma emission 25 Optical fiber 26 Spectrometer 27 ICCD camera 28 Personal computer

Claims (7)

In a method for diagnosing the deterioration of plating applied to a metal object, the surface of the plating is ablated by irradiating the plating surface to be inspected with a pulsed laser beam, and the emission of plasma generated by the ablation is measured. The emission intensity of the element constituting the metal substrate and the emission intensity of the plating component element are obtained by spectroscopy, and the intensity ratio between the emission intensity of the element constituting the metal substrate and the emission intensity of the plating component element is calculated. A plating deterioration diagnosis method that evaluates the deterioration state of a plating layer from changes. Using the sample to be inspected, the correlation between the emission ratio of the element constituting the metal substrate and the emission intensity of the plating component and the plating thickness is obtained in advance, and the emission intensity ratio based on the measured value and The plating deterioration diagnosis method according to claim 1, wherein the deterioration state of the plating layer is quantified from the correlation. The inspection object is a hot dip galvanized steel material, any one of 328.23, 330.21, 334.57, 468.01, 472.21, 481.05 nm zinc emission line, 338.01, 339.26, 340.74, 342.71, 344.09, 346.58, 347.54, 349.05, 349.78, 351.38, 352.60, 354.20, 355.49 nm, using one of the iron emission lines, obtaining the intensity ratio of the zinc and iron emission lines, and evaluating the plating film thickness. The plating deterioration diagnosis method according to 1 or 2. An apparatus for diagnosing the deterioration state of plating applied to a metal object, a laser device for ablating the plating surface by irradiating the plating surface to be inspected with a pulsed laser beam, and the ablation A spectroscopic device that measures and divides the emission of plasma, obtains the light emission intensity of the element of the metal base and the light emission intensity of the element of the plating component, and calculates the light emission intensity of the metal base element and the light emission intensity of the plating component. An apparatus for diagnosing deterioration of plating, comprising: an analyzer for evaluating a deterioration state of a plating layer from a change in intensity ratio. Using a sample to be inspected, a storage device that stores data obtained by calculating a correlation between an intensity ratio between the emission intensity of the metal base element and the emission intensity of the plating component and a plating thickness in advance, and based on the measurement value 5. The plating deterioration diagnosis apparatus according to claim 4, wherein the deterioration state of the plating layer is quantified from the correlation between the emission intensity ratio, the emission intensity ratio, and the plating thickness. The inspection object is a hot dip galvanized steel material, any one of 328.23, 330.21, 334.57, 468.01, 472.21, 481.05 nm zinc emission line, 338.01, 339.26, 340.74, 342.71, 344.09, 346.58, 347.54, 349.05, 349.78, 351.38, 352.60, 354.20, 355.49 nm, using one of the iron emission lines, obtaining the intensity ratio between the zinc and iron emission lines, and evaluating the deterioration of the plating. Item 6. The plating deterioration diagnosis apparatus according to Item 4 or 5. Controls a time difference between a light receiving element having a gate function for receiving light emitted from the plasma substance dispersed through the spectroscopic device and obtaining a light emission spectrum, and a gate opening start time of the laser and the light receiving element. A plating deterioration diagnosis apparatus according to claim 4, further comprising a controller for performing the plating.