Detection method for surface coating of hot-rolled steel plate

Abstract

The invention discloses a method for detecting a coating on the surface of a hot-rolled steel plate, which is characterized by comprising the following steps: adding a fluorescent agent into a coating for forming the coating on the surface of the hot-rolled steel plate, and coating the coating on the surface of the hot-rolled steel plate to form the coating, during detection, the hot-rolled steel plate is placed in a dark field environment, and ultraviolet rays are adopted to irradiate the surface of the hot-rolled steel plate so as to excite the fluorescent effect of a surface coating; and the actually-measured fluorescence intensity of the surface coating is collected, and whether the thickness of the surface coating meets a set threshold value or not is judged according to comparison between the actually-measured fluorescence intensity and the hot-rolled steel plate standard sample database. The method can be used for on-line detection of a transparent coating on the surface of a hot rolled plate and can also be used for on-line detection of other steel coatings.

Description

Technical Field

[0001] The invention relates to a detection method, in particular to a detection method for coatings. Background Art

[0002] In order to solve the problem that the oxide scale of hot-rolled plates is loose and easy to fall off to form black ash and is porous and prone to rust, the original loose and porous structure of the oxide scale can be changed by allowing small-particle resin molecules to penetrate into the oxide scale and cross-link and solidify in the hot rolling production line, thereby avoiding black ash and delaying rust.

[0003] This technology can significantly improve the original properties of the oxide scale, forming a transparent coating mainly composed of modified oxide scale on its surface. The thickness of the coating is only 0.1 to 3 microns thicker than the oxide scale and has a similar appearance to the surface of the oxide scale, making it difficult to distinguish with the naked eye, and thus impossible to achieve product inspection and quality control.

[0004] The existing coating online detection technologies mainly include image detection, electrical signal detection, and online thickness detection. Among them:

[0005] Image detection is the most commonly used online detection method. Conventional coatings can mostly be filled with pigments to make the coating and the steel plate have different color appearances, and the coating and its quality can be detected by visual or online video detection. However, since the oxide scale itself is black, a certain coating thickness is required for the color to appear. Too thick a coating will affect the weldability of subsequent products, so it is difficult to implement effectively. Moreover, the addition of pigments will affect the surface detection of the hot-rolled product itself, making it impossible to detect the internal oxide scale defects, which will bury hidden dangers for product quality.

[0006] The electrical signal detection method is another common coating online detection technology. Its principle is that when a charged brush is swept across the surface of the steel plate, there is a certain potential difference between the steel plate and the brush. However, when the surface of the steel plate is covered with a coating, there is no electrical signal between the brush and the steel plate due to the insulation of the coating. Once the coating is damaged and penetrates the substrate, the circuit connection between the steel plate and the brush causes a change in the current or resistance signal, or an electric spark occurs, indicating the damaged area and issuing an early warning. However, this technology is difficult to work for hot-rolled plates. Because the coating is composed of oxide scale and cured film-forming resin, the coating itself is also electrically conductive. This makes it difficult to detect effectively.

[0007] Similarly, online thickness detection methods are difficult to be effective because the coating is mainly composed of oxide scale, and it is impossible to distinguish whether the oxide scale has been treated.

[0008] Therefore, a method is needed to conveniently detect the transparent coating on the surface of the hot-rolled plate, which method can facilitate the inspection of the coating without affecting the surface quality of the hot-rolled strip itself. Summary of the invention

[0009] The purpose of the present invention is to provide a method for detecting the surface coating of a hot-rolled steel plate. After being processed by the method, the original characteristics of the coating are not changed, but it becomes visible under specific conditions, thereby realizing online detection of the coating. Under other circumstances, it is still colorless and transparent, thus not affecting the original online detection of the surface of the hot-rolled steel plate.

[0010] In order to achieve the above object, the present invention provides a method for detecting a surface coating of a hot-rolled steel plate, which comprises the steps of:

[0011] Adding a fluorescent agent to a coating for forming a surface coating of a hot-rolled steel plate, and applying the coating to the surface of the hot-rolled steel plate to form a coating;

[0012] During testing:

[0013] The hot-rolled steel plate is placed in a dark field environment, and ultraviolet rays are used to irradiate the surface of the hot-rolled steel plate to stimulate the fluorescence effect of the surface coating;

[0014] The measured fluorescence intensity of the surface coating is collected, and based on the comparison between the measured fluorescence intensity and the hot-rolled steel plate standard sample database, it is determined whether the surface coating thickness meets the set threshold.

[0015] Furthermore, in the method for detecting the surface coating of a hot-rolled steel plate described in the present invention, when the coating is a water-based coating, a water-based fluorescent agent is added thereto; when the coating is an oil-based coating, an oil-based fluorescent agent is added thereto.

[0016] Furthermore, in the method for detecting the surface coating of the hot-rolled steel plate described in the present invention, the mass ratio of the added fluorescent agent to the coating is 1:(1000-1000000).

[0017] Furthermore, in the method for detecting the surface coating of the hot-rolled steel plate described in the present invention, the mass ratio of the added fluorescent agent to the coating is 1:(10000-200000).

[0018] Furthermore, in the method for detecting the surface coating of the hot-rolled steel plate described in the present invention, the mass ratio of the added fluorescent agent to the coating is 1:(80000-120000).

[0019] Furthermore, in the method for detecting the surface coating of the hot-rolled steel plate described in the present invention, the illumination value of the dark field environment is lower than 10 lux.

[0020] Furthermore, in the method for detecting the surface coating of a hot-rolled steel plate described in the present invention, the illumination value of the dark field environment is lower than 1 lux.

[0021] Furthermore, in the method for detecting the surface coating of a hot-rolled steel plate described in the present invention, the illumination value of the dark field environment is lower than 0.02 lux.

[0022] Furthermore, in the method for detecting the surface coating of a hot-rolled steel plate described in the present invention, the wavelength of the ultraviolet light source is 300-400nm.

[0023] Furthermore, in the method for detecting the surface coating of a hot-rolled steel plate described in the present invention, the wavelength of the ultraviolet light source is 320-390 nm.

[0024] Furthermore, in the method for detecting the surface coating of a hot-rolled steel plate described in the present invention, the wavelength of the ultraviolet light source is 340-390 nm.

[0025] Furthermore, in the method for detecting the surface coating of a hot-rolled steel plate of the present invention, the hot-rolled steel plate standard sample database is obtained based on the following steps:

[0026] preparing a hot-rolled steel plate standard sample, placing the hot-rolled steel plate standard sample in a dark field environment, irradiating the surface of the hot-rolled steel plate standard sample with ultraviolet light, and collecting the fluorescence intensity of the coating on the surface of the hot-rolled steel plate standard sample;

[0027] Construct the corresponding relationship between the coating thickness of the hot-rolled steel plate standard sample and the corresponding fluorescence intensity.

[0028] Compared with the prior art, the method for detecting the surface coating of the hot-rolled steel plate of the present invention has the following beneficial effects:

[0029] The present invention provides an online detection technology for transparent coatings on the surface of steel plates, especially hot-rolled plates. The technology adds a very small amount of fluorescent agent to the coating to give the coating fluorescent properties under ultraviolet light without almost changing the original properties of the coating. Then, by irradiating with ultraviolet light, an online high-speed video camera is used to capture the fluorescence emitted by the coating in a dark field environment and realize online detection of the coating condition of the transparent coating according to the image brightness. The technology can be used for online detection of transparent coatings on the surface of hot-rolled plates, and can also be used for online detection of coatings on other steel materials, and has good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The schematic diagram of the principle of the method for detecting the surface coating of the hot-rolled steel plate according to the present invention is exemplarily shown. DETAILED DESCRIPTION

[0031] The following will further explain and illustrate the detection method for the surface coating of a hot-rolled steel plate described in the present invention in combination with specific embodiments and the drawings in the specification. However, such explanation and illustration do not constitute an improper limitation on the technical solution of the present invention.

[0032] In some embodiments, the method for detecting the surface coating of a hot-rolled steel plate according to the present invention comprises the steps of:

[0033] Adding a fluorescent agent to a coating for forming a surface coating of a hot-rolled steel plate, and applying the coating to the surface of the hot-rolled steel plate to form a coating;

[0034] During testing:

[0035] The hot-rolled steel plate is placed in a dark field environment, and ultraviolet rays are used to irradiate the surface of the hot-rolled steel plate to stimulate the fluorescence effect of the surface coating;

[0036] The measured fluorescence intensity of the surface coating is collected, and based on the comparison between the measured fluorescence intensity and the hot-rolled steel plate standard sample database, it is determined whether the surface coating thickness meets the set threshold.

[0037] In some embodiments, the hot-rolled steel plate standard sample database can be obtained based on the following steps:

[0038] Prepare hot-rolled steel plate standard samples, the surface condition and coating used in the standard samples are consistent with those of the object to be tested;

[0039] The hot-rolled steel plate standard sample is placed in a dark field environment, irradiated with ultraviolet light, and the morphology photos of the hot-rolled steel plate standard sample are recorded by a high-speed motion camera;

[0040] The coating thickness of several areas of the hot-rolled steel plate standard sample and the corresponding brightness value of the hot-rolled steel plate standard sample morphology photograph are measured, and the corresponding relationship between the brightness of the hot-rolled steel plate standard sample morphology photograph image and the coating thickness is established to construct a hot-rolled steel plate standard sample database.

[0041] In some implementations, a brightness threshold of an image that satisfies a specified thickness may also be set.

[0042] During actual detection, a high-speed motion camera is used to record continuous fluorescent image information on the strip surface. Based on the fluorescence intensity in the image, that is, the brightness of the photo, and by comparing the measured fluorescence intensity with the hot-rolled steel plate standard sample database, the coating thickness at each point on the continuous strip surface can be monitored.

[0043] In some embodiments, when the fluorescence intensity of an image is found to be lower than a set threshold, an alarm may be issued and the location may be marked.

[0044] It should be noted that the dark field environment of the hot-rolled steel plate standard sample, the selected ultraviolet light source, the high-speed motion camera and parameters, and the relative positions of the light source and the high-speed motion camera are exactly the same as those of the object being tested.

[0045] Figure 1 The schematic diagram of the principle of the method for detecting the surface coating of the hot-rolled steel plate according to the present invention is exemplarily shown.

[0046] like Figure 1 As shown, a light shield 2 covering the entire width of the steel strip is suspended near the upper and lower surfaces of the steel strip 1, and is positioned as close to the surface of the steel strip as possible while ensuring that the device does not contact the steel strip, so as to block as much light as possible outside the light shield 2, so as to construct a dark field environment on the upper and lower surfaces of the steel strip, and the dark field area covers the entire field of view of the high-speed motion camera 4.

[0047] In some embodiments, a violet light source 3 (e.g., a violet light tube) may be provided in the light shield 2 to emit ultraviolet light 6 with a wavelength of 300 to 400 nm to the upper and lower surfaces of the steel strip 1, and the ultraviolet light 6 covers the entire width of the plate. Another function of the light shield 2 is to prevent the ultraviolet light 6 from spilling out and affecting the environment and surrounding human bodies. A high-speed motion camera 4 is provided in the light shield 2, the purpose of which is to continuously capture image information on the surface of the steel strip, the camera field of view covers the entire bandwidth, and all image information on the surface of the steel strip 1 is recorded by high-speed photography.

[0048] The transparent coating 5 on the surface of the steel strip 1 contains a fluorescent agent, which emits fluorescence 7 after being irradiated by the ultraviolet light 6 emitted by the violet light source 3, and the fluorescence 7 is recorded by the high-speed motion camera. The light 8 in the external environment is blocked by the light shield to avoid interference, so that the brightness of the image obtained by the high-speed motion camera 4 is only related to the fluorescence intensity.

[0049] The thicker the coating 5 is, the more fluorescence 7 there is per unit area, and the brighter the image is. Vice versa. Therefore, according to the brightness of the image obtained by the high-speed motion camera 4, the thickness of the coating 5 can be known accordingly, and online detection of the coating can be achieved.

[0050] In some specific implementations, the high-speed motion camera 4 can continuously record continuous images within the width of the steel strip in the dark field area.

[0051] In some more specific implementations, the high-speed motion camera 4 selects different camera parameters according to different strip speeds to ensure that a clear and continuous fluorescent morphology of the strip surface can be obtained.

[0052] The following examples 1-6 will be used to verify the implementation effect of the present invention:

[0053] Examples 1-6 all use BS700 hot-rolled high-strength steel plates with a width of 1.5 meters as the strip steel substrates, and different transparent paints or water-based paints are coated on the surfaces thereof, to which different concentrations of oil-based or water-based soluble fluorescent agents are added. The coating is intentionally applied unevenly during the coating process, and then the strip steel surface coating condition is online detected using the steps described above.

[0054] Table 1 lists the specific parameters and test results of the detection methods of Examples 1-6.

[0055] Table 1.

[0056]

[0057]

[0058] As can be seen from the table, this method can better detect the thickness of the transparent coating on the surface of the steel plate. It can automatically determine the coating thickness by the brightness of the fluorescent image and display the area where the thickness exceeds the control range.

[0059] It should be noted that the above-listed embodiments are only specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made therewith can be directly derived or easily associated with by those skilled in the art from the contents disclosed in the present invention, and all should belong to the protection scope of the present invention.

Claims

1. A method for detecting a surface coating of a hot-rolled steel plate, characterized in that: Includes steps: Adding a fluorescent agent to a coating for forming a surface coating of a hot-rolled steel plate, and applying the coating to the surface of the hot-rolled steel plate to form a coating; During testing: The hot-rolled steel plate is placed in a dark field environment and ultraviolet rays are used to irradiate the surface of the hot-rolled steel plate to stimulate the fluorescence effect of the surface coating; The measured fluorescence intensity of the surface coating is collected, and based on the comparison between the measured fluorescence intensity and the hot-rolled steel plate standard sample database, it is determined whether the surface coating thickness meets the set threshold.

2. The method for detecting the surface coating of a hot-rolled steel plate according to claim 1, characterized in that: When the coating is a water-based coating, a water-based fluorescent agent is added thereto; when the coating is an oil-based coating, an oil-based fluorescent agent is added thereto.

3. The method for detecting the surface coating of a hot-rolled steel plate according to claim 1, characterized in that: The mass ratio of the added fluorescent agent to the coating is 1:(1000-1000000).

4. The method for detecting the surface coating of a hot-rolled steel plate according to claim 3, characterized in that: The mass ratio of the added fluorescent agent to the coating is 1:(10000-200000).

5. The method for detecting the surface coating of a hot-rolled steel plate according to claim 4, characterized in that: The mass ratio of the added fluorescent agent to the coating is 1:(80000-120000).

6. The method for detecting the surface coating of a hot-rolled steel plate according to claim 1, characterized in that: The illumination value of the dark field environment is lower than 10 lux.

7. The method for detecting the surface coating of a hot-rolled steel plate according to claim 6, characterized in that: The illumination value of the dark field environment is lower than 1 lux.

8. The method for detecting the surface coating of a hot-rolled steel plate according to claim 1, characterized in that: The illumination value of the dark field environment is lower than 0.02 lux.

9. The method for detecting the surface coating of a hot-rolled steel plate according to claim 1, characterized in that: The wavelength of the ultraviolet light source is 300-400nm.

10. The method for detecting the surface coating of a hot-rolled steel plate according to claim 9, characterized in that: The wavelength of the ultraviolet light source is 320-390nm.

11. The method for detecting the surface coating of a hot-rolled steel plate according to claim 10, characterized in that: The wavelength of the ultraviolet light source is 340-390nm.

12. The method for detecting the surface coating of a hot-rolled steel plate according to claim 1, characterized in that: The hot-rolled steel plate standard sample database is obtained based on the following steps: preparing a hot-rolled steel plate standard sample, placing the hot-rolled steel plate standard sample in a dark field environment, irradiating the surface of the hot-rolled steel plate standard sample with ultraviolet light, and collecting the fluorescence intensity of the coating on the surface of the hot-rolled steel plate standard sample; Construct the corresponding relationship between the coating thickness of the hot-rolled steel plate standard sample and the corresponding fluorescence intensity.

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