Method and device for rapidly measuring thickness of galvanized layer of steel plate

Abstract

The invention discloses a method and a device for rapidly measuring the thickness of a galvanized layer of a steel plate. The method comprises the following steps: 1) coating a to-be-detected part on a galvanized plate sample with a color as a mark; (2) drilling a blind hole in the surface of the marked part of the galvanized sheet sample until the blind hole is exposed out of the base body; (3) hydrochloric acid is dropped into the blind holes through a dropper, so that the zinc layer and the substrate are corroded; (4) after the color change in the blind hole is seen, the surface of the galvanized sheet and the interior of the blind hole are cleaned and dried; 5) observing the position of the blind hole under a microscope, performing microscopic infrared analysis on the corroded blind hole according to different forms of the zinc layer in the blind hole and the substrate corroded by hydrochloric acid, and observing an inner circle-shaped boundary line and an outer circle-shaped boundary line at three junctions with different colors; 6, a plurality of points are selected on each of the two boundary lines, the average distance between the two boundary lines is determined according to the selected points, and the average distance is the thickness of the zinc layer. The method is few in operation step, short in analysis period and high in accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgical material detection, and in particular to a method and a device for quickly measuring the thickness of a galvanized layer of a steel plate. Background Art

[0002] The zinc coating on steel effectively protects the substrate from corrosion. Galvanized steel is a crucial component of corrosion protection for automotive, appliance, and construction applications. The thickness of the zinc coating is a crucial factor in determining the corrosion resistance of the steel. A zinc coating that is disproportionate to the thickness of the steel will compromise its adhesion to the substrate, while an excessively thick coating can result in a rough appearance and susceptibility to flaking. The thickness of the zinc coating determines the corrosion resistance of the coated component, making accurate measurement crucial.

[0003] Currently, the common methods for measuring the thickness of zinc coatings include magnetic measurement, weighing method, glow spectroscopy, anodic dissolution coulometric method, and cross-sectional microscopy.

[0004] Magnetic measurement is a nondestructive testing method based on the Edwin Hall effect. The instrument records the voltage and converts it into a thickness value using one of the probe's characteristic curves, which maps the measured signal to the coating thickness. This method is suitable for on-site quality control, but factors such as the substrate's magnetic properties, sample shape, and surface roughness can significantly affect the measurement results.

[0005] The weighing method uses an acidic solution to dissolve the zinc on the surface of the stripping solution, then weighs the sample before and after stripping, and calculates the thickness of the coating based on the density of the zinc layer. This method is relatively complicated to operate.

[0006] Glow spectroscopy, based on the principle of inert gas discharge at low pressure, peels off the sample surface layer by layer to obtain elemental data at different depths. However, this method requires a lot of preparatory work, such as working curves and standard samples, which is time-consuming and costly.

[0007] The anodic dissolution coulometric method uses an appropriate electrolyte to dissolve a precisely defined area of coating at the anode. The change in cell voltage indicates complete dissolution of the coating. The coating thickness is calculated from the amount of electricity consumed (in coulombs) during electrolysis. The time it takes to dissolve the coating and the amount of electricity consumed are then used to calculate the coating thickness. This method generally requires specialized equipment and is relatively complex to operate.

[0008] The principle of cross-sectional microscopy is to cut a specimen from the workpiece to be tested, mount it, and then grind, polish, and etch the cross section using appropriate techniques. The thickness of the coating cross section is measured using a calibrated ruler. The preparation of the cross-sectional specimen in this method is relatively difficult and the operation is relatively complex.

[0009] In summary, the above methods have their own applicability, but also have certain shortcomings. Therefore, it is necessary to invent a method for convenient, reliable and rapid detection of the thickness of the galvanized layer of steel plates. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a convenient and reliable method for quickly measuring the thickness of the galvanized layer of a steel plate; the present invention also provides a device for quickly measuring the thickness of the galvanized layer of a steel plate.

[0011] In order to solve the above technical problems, the technical solution adopted by the present invention includes the following steps: 1) Paint the part to be tested on the galvanized sheet sample with color as a mark; 2) Drill blind holes on the surface of the galvanized sheet where the marking is applied, the blind holes being deep enough to expose the substrate; 3) Use a dropper to drip hydrochloric acid into the blind hole to corrode the zinc layer and the substrate; 4) When the color change in the blind hole is observed, clean the galvanized sheet surface and the blind hole and dry them; 5) Place the blind hole under a microscope for observation. Based on the different morphologies of the zinc layer inside the blind hole and the substrate after being corroded by hydrochloric acid, perform microscopic infrared analysis on the corroded blind hole. Two inner and outer circular dividing lines can be observed at the intersection of three different colors. 6) Select several points on each of the two boundary lines and determine the average distance between the two boundary lines based on the selected points. The average distance is the thickness of the zinc layer.

[0012] Furthermore, in step 6), circles can be fitted based on the points selected from each boundary line, and the difference between the radii of the two fitted circles is the average distance between the two boundary lines.

[0013] Furthermore, in step 5), the magnification range of the blind hole observation under a microscope is 0.7X to 3X.

[0014] Furthermore, in step 6), at least 8 points are selected on each boundary line.

[0015] The device of the present invention includes an infrared microscope; the infrared microscope includes a base, a stage, a lens horizontal angle adjuster and a lens; the lens horizontal angle adjuster is connected to the lens and can adjust the position of the lens above the stage; the lens includes a lens barrel, an objective lens and a lens wall, an infrared recognition system module is provided in the objective lens, and a focusing screw is provided on the lens barrel.

[0016] Furthermore, it also includes a display analysis device, and the lens signal is connected to the display analysis device.

[0017] The beneficial effect of adopting the above technical solution is that: the present invention uses microscopic infrared analysis to identify the boundaries of the zinc layer and the different morphological layers of the substrate after being corroded by hydrochloric acid, automatically magnifies to an appropriate multiple, and then uses the photo-taking and point-selection functions of the computer software to quickly measure the thickness of the galvanized layer, thereby achieving fast and convenient detection.

[0018] The method drills a hole from the colored portion of the steel plate surface to the substrate, which is simple to operate and eliminates the need for complex processes such as inlaying and grinding. Hydrochloric acid is dripped into the hole to cause corrosion, and the infrared intelligent recognition module of an infrared microscope quickly and easily reveals the morphological differences between the zinc layer and the substrate. The thickness of the zinc coating can then be observed and measured through a microscope using the computer software's photography and point selection functions. This method clearly demonstrates the zinc coating thickness with a minimal number of steps, a short analysis cycle, and high accuracy. This method addresses the significant sample loss associated with traditional cross-section microscopy methods, providing a convenient and reliable technical solution for zinc coating thickness testing on steel plates. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 It is a schematic structural diagram of the sample of the present invention when corroded; Figure 2 is a main diagram of the measuring device of the present invention; Figure 3 is a side view of the measuring device of the present invention; Figure 4 This is the image after corrosion according to the embodiment of the present invention.

[0021] In the figure: 1. Sample; 2. Dropper; 3. Blind hole; 4. Lens horizontal angle adjuster; 5. Lens barrel; 6. Display and analysis device; 7. Focusing screw; 8. Infrared recognition system module; 9. Objective lens; 10. Mirror wall; 11. Stage; 12. Sample left and right position adjustment knob; 13. Sample up and down position adjustment knob; 14. Base; 15. Wires. DETAILED DESCRIPTION

[0022] Figure 2 、 Figure 3As shown, the device for rapidly measuring the thickness of the zinc coating on steel plates comprises an infrared microscope. The infrared microscope includes a base 14, a stage 11, a lens horizontal angle adjuster 4, and a lens. The lens horizontal angle adjuster 4 is connected to the lens and can adjust the lens' position above the stage 11. The lens comprises a lens barrel 5, an objective lens 9, and a lens wall 10. An infrared recognition system module 8 is located within the objective lens 9, and a focusing screw 7 is located on the lens barrel 5. The device also includes a base 14, and a sample left-right orientation adjustment knob 12 and a sample up-down orientation adjustment knob 13 located on the base 14. The left-right orientation adjustment knob 12 is used to adjust the left-right orientation of the sample, and the up-down orientation adjustment knob 13 is used to adjust the up-down orientation of the sample. The two knobs 12 and 13 cooperate to provide a clearer observation of the sample. The device also includes a display and analysis device 6, to which lens signals are connected. The display and analysis device is preferably a computer with relevant software installed. An electrical wire 15 is also provided for connecting to a power source.

[0023] This method for quickly measuring the thickness of the zinc coating on steel plates uses the following steps: 1) For the galvanized sheet sample to be tested, wipe the sample surface with absorbent cotton dipped in anhydrous ethanol solution and blow dry. Use a colored marker to mark a spot near the center of the sample to distinguish the hole from the sample surface. The colored marker includes, but is not limited to, a water-based pen or paint.

[0024] 2) At the colored mark on the surface of the sample in step 1), a blind hole is drilled on the surface of the sample using a fixed-angle drill punch, the blind hole being deep enough to expose the base of the galvanized sheet.

[0025] 3) Figure 1 As shown, hydrochloric acid is dripped into the blind hole 3 of the sample 1 using a dropper 2 to corrode the zinc layer and the substrate; the hydrochloric acid is highly corrosive hydrochloric acid, including chemically pure, analytically pure, and high-grade pure hydrochloric acid, but not limited to these.

[0026] 4) When the color change in the blind hole is observed, clean the sample surface and the blind hole and dry them.

[0027] 5) Figure 2 、 Figure 3 As shown, the blind hole position after cleaning and drying in step (4) is placed under an infrared microscope for observation. The zinc layer and the substrate will show different depths of color under infrared light. The infrared intelligent recognition module of the infrared microscope is used to automatically magnify the different morphological boundaries of the zinc layer and the substrate after being corroded by hydrochloric acid in the blind hole to a suitable magnification. Then, the microscope is manually fine-tuned to adjust the magnification range to 0.7X~3X, and the focal length is adjusted to make the image of the small hole clear.

[0028] 6) Based on the different forms of the zinc layer and substrate in the blind hole after being corroded by hydrochloric acid, use the photo and point selection function of the computer software. The photo will show two inner and outer circle-shaped boundary lines between the three different colors of the zinc layer, substrate and mark, namely the inner boundary line between the zinc layer and the substrate, and the outer boundary line between the zinc layer and the mark.

[0029] (7) Select several points on each boundary line. The points on each line should be evenly distributed. It is best to select at least 8 points on each boundary line. Determine the average distance between the two boundary lines based on the selected points. The average distance is the thickness of the zinc layer.

[0030] The average distance between two boundary lines can be determined in any of the following ways: ① The points selected by the two boundary lines are fitted with circles respectively, and the difference between the radii of the two fitted circles is the average distance between the two boundary lines.

[0031] ②Measure the distance from each selected point to the center of the blind hole, calculate the average distance from the inner and outer boundary lines to the center of the blind hole, and the difference between the two average values is the average distance between the two boundary lines.

[0032] ③ With the center of the blind hole as the center point, that is, with the center point of the two boundary lines as the center point, draw several straight lines in a radial shape. Each straight line has four intersections with the two boundary lines. These intersections are used as selected points; measure the distance between the two intersection points on each straight line, and calculate the average value of the distance, which is the average distance between the two boundary lines.

[0033] There are other ways to calculate the average distance between two boundary lines.

[0034] Example: The method for quickly measuring the thickness of the galvanized layer of a steel plate is specifically described as follows.

[0035] 1) The size of the galvanized sheet sample is 20×80mm. Use absorbent cotton dipped in anhydrous ethanol solution to wipe the surface of the sample and blow it dry. Use a colored marker to color a spot near the center of the sample to distinguish the hole from the sample surface. 2) At the color of the sample surface in step (1), use a fixed angle drill to drill a blind hole from the color surface to the substrate; 3) Use a dropper to drip analytical pure hydrochloric acid into the blind hole to corrode both the zinc layer and the substrate; 4) When the color change is observed, clean the sample surface and blind hole with pure water and blow dry; 5) Place the clean blind hole described in step (4) under an infrared microscope for observation, adjust the magnification range to 2X, and adjust the focus so that the image of the small hole is clearly presented; 6) Based on the different morphologies of the zinc layer in the blind hole and the substrate after being corroded by hydrochloric acid, the boundary lines of the inner and outer circles were observed using the camera in the analysis software; 7) Using the point selection function in the analysis software, draw 4 straight lines in a radial pattern with the center of the blind hole as the center point. Each straight line has four intersections with the two boundary lines, that is, select 8 symmetrical points evenly on each boundary line, such as Figure 4 As shown; the selected 16 points are precisely adjusted, the distance from the center of the blind hole to 8 points on the inner boundary line is measured, the distance between two adjacent points on the two boundary lines on the same straight line is measured, and the average value is calculated. The obtained position data is recorded in Table 1; Table 1: Data record 1 of the positions of the two boundary lines of the galvanized sheet in the embodiment

[0036] In Table 1, the first layer is the distance from 8 points on the inner boundary line to the center of the blind hole; the second layer is the distance between two adjacent points on the two boundary lines on the same straight line.

[0037] 8) Use the above steps 1) to 7) to re-measure the same galvanized sheet sample, and the measured position data are recorded in Table 2; Table 2: Data record 2 of the positions of the two boundary lines of the galvanized sheet in the embodiment

[0038] In Table 2, the first layer is the distance from 8 points on the inner boundary line to the center of the blind hole; the second layer is the distance between two adjacent points on the two boundary lines on the same straight line.

[0039] 9) Verification: Use a standard sample of known thickness (such as calibration foil or standard block) to perform multiple measurements and calculate the deviation, which should be less than ±5%.

[0040] It can be seen from Table 1 that the thickness of the zinc layer measured for the first time is 7.61 μm, and from Table 2 that the thickness of the zinc layer measured for the second time is 7.25 μm, with a deviation of 4.8%. The deviation value is within the data error range, thus proving that this method is accurate and reliable.

[0041] Statistical case: This method was used to measure the galvanized layer of steel plates 20 times in total. The deviation between the measured zinc layer thickness and the original marked thickness was within the range of ≤5%. It can be seen that this method has high measurement accuracy.

Claims

1. A method for quickly measuring the thickness of the galvanized layer of a steel plate, characterized in that: The method comprises the following steps: 1) painting a color on the part to be tested on the galvanized sheet sample as a mark; 2) Drill blind holes on the surface of the galvanized sheet where the marking is applied, the blind holes being deep enough to expose the substrate; 3) Use a dropper to drip hydrochloric acid into the blind hole to corrode the zinc layer and the substrate; 4) When the color change in the blind hole is observed, clean the galvanized sheet surface and the blind hole and dry them; 5) Place the blind hole under a microscope for observation. Based on the different morphologies of the zinc layer inside the blind hole and the substrate after being corroded by hydrochloric acid, perform microscopic infrared analysis on the corroded blind hole. Two inner and outer circular dividing lines can be observed at the intersection of three different colors. 6) Select several points on each of the two boundary lines and determine the average distance between the two boundary lines based on the selected points. The average distance is the thickness of the zinc layer.

2. The method for quickly measuring the thickness of the zinc coating on a steel plate according to claim 1, wherein: In step 6), circles can be fitted based on the points selected from each boundary line, and the difference between the radii of the two fitted circles is the average distance between the two boundary lines.

3. The method for quickly measuring the thickness of the zinc coating on a steel plate according to claim 1, wherein: In step 5), the magnification range of the blind hole observation microscope is 0.7X to 3X.

4. A method for rapidly measuring the thickness of a galvanized layer on a steel plate according to claim 1, 2 or 3, characterized in that: In step 6), at least 8 points are selected on each boundary line.

5. A device for quickly measuring the thickness of the zinc coating on a steel plate, characterized by: The invention comprises an infrared microscope; the infrared microscope comprises a base (14), a stage (11), a lens horizontal angle adjuster (4) and a lens; the lens horizontal angle adjuster (4) is connected to the lens and can adjust the position of the lens above the stage (11); the lens comprises a lens barrel (5), an objective lens (9) and a lens wall (10); an infrared recognition system module (8) is provided in the objective lens (9), and a focusing screw (7) is provided on the lens barrel (5).

6. The device for rapidly measuring the thickness of the zinc coating on a steel plate according to claim 5, characterized in that: It also includes a display analysis device (6), and the lens signal is connected to the display analysis device (6).

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