KR100935915B1 - Automatic control method of drying operation by near infrared ray at continuous coil coating line - Google Patents

Abstract

In the method of automatic control of drying operation in the production line of continuous color steel sheet, the information of steel plate material is collected from the production management system, and in the drying operation data setting system, the indication values for steel grade, thickness of steel sheet and color of steel sheet are used. Calculate the painting work data about power ratio and line speed, and display the calculated result on HMI (Human Machine Interface) terminal so that the operator can confirm and the calculated result is controlled by the network hub. And automatic control of drying operation using near infrared rays in a continuous color steel sheet production line which is automatically set in a PLC for data processing.

Near Infrared (NIR), Maximum Drying Temperature (PMT), Coating Work Data

Description

Automatic control method of drying operation by near infrared ray at continuous coil coating line}

The present invention relates to an automatic control method for painting and drying work using near infrared rays in a continuous color steel sheet production line.

In particular, the present invention simulates the drying conditions according to the material conditions, in particular, the dry conditions of the wet paint using an oven using near infrared rays (NIR), to derive the results and to automatically set them in the PLC for data processing to automatically control the drying operation. The present invention relates to a method for automatic control of a painting and drying operation, which makes it possible to use the present invention.

 In general, the continuous color steel sheet production line uses hot air oven to dry the wet paint after coating the paint, which is generated by burning LNG gas on the wet coated steel sheet passing through the box-type oven. In the heat transfer mechanism, the air is heated by a fan and blows to the surface of the steel sheet by blowing a fan. Convective heat transfer occupies most of the heat transfer mechanism, and conductive heat transfer and radiant heat transfer take up the rest. . Therefore, the conventional hot air drying oven requires a long time to increase the temperature to the maximum temperature (PMT: Peak Metal Temperature) for the steel sheet is heated up by the convection heat transfer and the paint is dried, and the length of the oven becomes that long.

The present invention is an oven equipment using near infrared rays (NIR, Near Infrared Ray, hereinafter "NIR") to the coating steel sheet production line to dry the paint by radiant heat transfer using the light of the near infrared oven to enable rapid heating Shorten the length of.

Herein, NIR is a term referring to the infrared range of the wavelength range of 0.7 to 1.5 µm among infrared rays having a wavelength range of 0.7 to 1,000 µm, and is called near infrared ray. Near-infrared heat transfer uses radiant heat energy, and due to instantaneous and direct heat transfer, the reaction rate is much faster than conduction or convective heat transfer. In addition, NIR is harmless to the human body and varies in the degree of transmission, reflection and absorption depending on the material.

The present invention is intended to dry the wet paint in place of the existing hot air drying oven by using the NIR oven equipment, NIR oven equipment according to the present invention in the line that produced the product mainly on the existing steel plate for building materials By introducing the will be able to produce color steel sheet for home appliances and high quality building materials.

Therefore, the present invention grasps the NIR curing phenomenon of the paint through pre-simulation before installing the above-described NIR oven equipment on the coated steel sheet line, such as the coil coating line (CCL) and the multi-purpose coil coating line (MCCL), and the drying quality is improved. It aims to standardize the simulation conditions that appear to be good and achieve early normalization during plant operation. In addition, by modeling the working conditions tuned during the test run, the operating conditions of the oven are standardized and automatically set to minimize the quality deviation of each worker. In order to achieve the object of this invention, the NIR drying technology of the continuous color long line is stably secured, the temperature control ability of the NIR oven can be achieved more than 90%, and the automatic setting, the control technology development, and the field application are possible. As a result, it is possible to homogenize paint quality between workers and to secure excellent paint quality. In addition, it is possible to secure the steel sheet temperature control ability to achieve the late adhesion of the heat-sealed protective film steel sheet.

In order to achieve the above object of the present invention, the present invention mainly introduces the NIR oven equipment in the steel sheet manufacturing process for building materials, it is possible to collect the work order data as an automatic setting method of the NIR oven, production schedule formation function, automatic NIR oven drying model It is the development of automatic setting technology consisting of setting function, monitoring function and quality data collection / storage / analysis function.

FIG. 1 shows the process of the CCL line as an example, of which a schematic diagram of ovens 16 and 18 is shown in FIG. 2. The oven is a device for drying the wet paint on the surface of the steel sheet when the electric power is applied to irradiate infrared light from the NIR lamp inside the oven.

Figure 3 schematically shows a hardware device of the present invention for the automatic treatment of the drying operating conditions of the NIR oven.

4 is a conceptual diagram of a NIR radiant heat transfer method.

FIG. 5 illustrates a screen displaying a calculation result of a drying operation of an NIR oven displayed on the HMI terminal screen of FIG. 3.

The drying of the coating material using NIR is demonstrated below.

Until now, the drying technology used for drying the paint includes hot air drying technology, UV drying technology using ultraviolet rays, EB drying technology using an electron beam beam, and induction drying technology using induction heating. Finally, we developed EB drying technology for the drying of top clear paints, such as NIR drying technology for drying aftertreatment of # 2CGL, and Induction drying technology for drying aftertreatment of # 4CGL, for example. The invention came to the following.

Infrared radiation is a kind of electromagnetic wave having a wavelength larger than visible light. When an object is at an absolute temperature (-273 ° C.) or higher, molecules or atoms vibrate or diffract. At this time, the electromagnetic wave that vibrates and emits is called infrared rays. Infrared rays are classified into near infrared rays, mid infrared rays, far infrared rays, and extreme infrared rays. 6 shows the wavelength range of infrared rays.

Among these, the near infrared (NIR) refers to the infrared range of the wavelength range of 0.7 ~ 1.5㎛ in the infrared having a wavelength range of 0.7 ~ 1,000㎛ as described above. Near-infrared uses radiant heat energy, so the reaction rate is much faster than conduction or convective heat transfer due to instantaneous and direct heat transfer. 4 shows a conceptual diagram of radiant heat transfer. The present invention adopts a near-infrared (NIR) oven drying method having a very high heat transfer rate instead of the conventional hot air drying oven.

In general, when energy enters a workpiece, some will absorb it, some will reflect, and some will penetrate the workpiece. As can be seen in Figure 7 the incident energy is equal to the sum of the absorbance, reflectance and transmittance. The degree to which the incident energy is converted into thermal energy that raises the workpiece depends on the magnitude of the absorption rate. This absorption rate ε is also called the emissivity and emissivity. In the present invention, it is referred to as emissivity. This emissivity varies depending on the type of material, temperature, wavelength band and the like and is shown in FIG. 8.

In addition, the emissivity values according to the types of materials are shown in Table 1.

As can be seen in Table 1 above, the emissivity depends not only on the type of material but also on the surface roughness, glossiness and oxidation degree.

The rate of energy released per unit area (Q / A) is the surface radiance (E), Ts is the absolute temperature of the surface, σ is the Stefan-Boltzmann constant (5.67108 W / m2K4), and ε is the emissivity .

In the above equation, an object with an emissivity of ε = 1 is called a black body. A black body is an object that radiates energy according to the T ⁴ law. We call such an object a black body because a black surface, such as a piece of metal covered with black carbon, is close to the T ⁴ law. Other types of surfaces, such as polished or polished metal plates, do not radiate energy as much as the black body, but the total radiation emitted to these objects is in accordance with the T ⁴ proportional law. The factor that considers such gray properties of the surface is the emissivity ε. The emissivity ε is the factor that correlates the radiation of the gray surface with that of the ideal blackbody surface.

Figure 9 shows the change in emissivity according to the material state of the epoxy (epoxy) paint in the near infrared wavelength range.

There are three ways to find out the emissivity. First, measure the temperature of the workpiece using a thermocouple, and measure the temperature using an infrared thermometer that can adjust the emissivity. To adjust the emissivity of the infrared thermometer so that the display temperature is the same, the second method is to obtain the emissivity value by attaching a masking tape which knows the emissivity value to the object and measuring the exposure with an infrared thermometer. The third way is to use known reference values. The first and second methods mentioned above are shown in FIG.

In Figure 10 (a) is the emissivity determination method, (b) shows the masking tape using method, respectively, Table 2 shows the difference between the drying method of the paint in the color line.

[Table 2] Comparison of characteristics of hot air drying and NIR drying method

As can be seen from Table 2, the NIR drying method has the advantage that the drying time is very fast, and as mentioned above, the temperature rise degree of the coating material varies depending on the emissivity of the material. When the NIR energy is incident on the metal, part of the incident energy is absorbed by the paint, and some of the energy penetrates the paint to reach the steel sheet substrate. At this time, the NIR incident energy transmitted through the paint will vary depending on the radiation rate of the base material.

In addition to the advantage that the oven length is shorter than the hot air oven, the NIR drying oven of the present invention has an advantage that productivity is extremely low. Therefore, it is possible to produce color steel sheets of excellent quality without surface defects.

On the other hand, the NIR oven equipment of the present invention at the time of introduction into the MCCL is primarily intended for heating the steel sheet for the development of a steel sheet with a heat-sealing protective film. This heat-sealed protective film-coated steel sheet is a product of superior quality that does not cause poor transfer of adhesives compared to the conventional adhesive-bonded protective film-coated steel sheet, and can replace existing general adhesive protective film-coated steel products including ship interior materials. .

In order to develop the above-described setting and control technology of the MCCL NIR oven, the emissivity for each coating condition was derived. Applicable steel grades were applied to GI, GA, ALCOT, EGI, BP, CR, GALVALµmE, TP, aluminum alloy plated steel sheet and stainless steel sheet. In addition, steel sheet thickness of 0.45 to 0.8 mm was mainly selected.

Emissivity for top coat can be combined with the measurement method of # 1CCL described above.

Hereinafter, the present invention will be described in more detail with reference to one embodiment.

(Example)

The key potential factors affecting PMT to derive the drying conditions of paint are power ratio, line speed, steel grade, steel sheet thickness, resin type, color, glossiness, and film thickness. In order to derive the phosphorus relation, the experimental plan was established by the partial placement method of 7 factor 2 level as shown in Table 4.

Table 3 shows the results of the steel type constant, coefficient (ai) power ratio, (pelec) line speed, and steel sheet thickness to derive the maximum temperature (PMT) heating condition.

In the continuous color steel sheet production line which derives the value of the power ratio calculated by the following relationship for the steel sheet material condition of beige, orange, blue, white, red, green, brown, yellow, metallic (silver) and black. In order to automatically control the drying operation in the NIR oven, the maximum steel plate temperature (PMT) was set as follows.

PMT _n = Constant ( const ) + a _One P _elec + a ₂ v _line + a ₃ t _sub + a ₁₂ P _elec v _line + a ₁₃ P _elec t _sub + a ₂₃ v _line t _sub

(*) PMT: Peak Metal Temperature

n: steel grade (steel, AL, STS)

const: constant determined by steel plate color

ai: coefficient determined by the color of the steel sheet as EK

pelec: power ratio

vline: line speed

tsub: steel plate thickness

[Table 3] Values of Constants and Coefficients when the Steel Grade of the Steel Sheet is Steel

[Table 4] Experimental plan for deriving PMT heating condition

For each condition, experiments were performed for each color of the paint. The experiment used seven colors of beige, orange, yellow, blue, white, metallic (silver) and black. As a result of the experiment, key factors were selected by color and the quantitative relationship between them was derived as follows.

PMT_Group1 = 170.46 + 0.56 * Power Ratio -1.98 * Line Speed -91.43 * Steel Thickness

        + 1.14 * line speed * steel plate thickness

PMT_Yellow = 152.11 + 0.57 * Power Ratio -1.76 * Line Speed -64.82 * Steel Thickness

        + 0.75 * line speed * steel plate thickness

PMT_Silver = 139.27 + 1.19 * Power Ratio -1.05 * Line Speed -108.93 * Steel Thickness

                   -0.01 * power ratio * line speed + 1.5 * line speed * steel plate thickness

PMT_Black = 35.66 + 2.40 * Power Ratio -0.51 * Line Speed + 25.6 * Steel Grade -14.47 * Steel Thickness

       -0.02 * Power Ratio * Line Speed -1.03 * Power Ratio * Steel Thickness +

       1.53 * line speed * steel thickness -32.28 * steel grade * steel thickness

(Note) Group 1: Beige, Orange, Blue, White, Red, Green, Auburn, Yellow, Silver, Black

In order to develop the automatic setting technology of the NIR oven, as described above, PMT core factors were selected and quantified according to the material conditions, and the automatic setting technology was developed. MCCL has already built the Levle 2 feature, which has developed the NIR oven model, automatic setup and monitoring. Process definition was made through process mapping, ideas were collected, and design items were selected as shown in the following Table 5. Detailed design was carried out for each design item.

TABLE 5

There are three ways to set the working conditions of the NIR oven: automatic setting method, manual setting method and simulation method. The automatic setting method automatically calculates the setting value according to the material condition when receiving the work instruction data from the table model, and the manual setting method provides the work table format of the pattern table that the operator can input / modify / edit. In addition, the simulation method is a function that allows the operator to simulate the PMT value while changing the material conditions in the user interface (HMI). The operator can utilize the setpoint using the three methods described above for the NIR task. 11 shows a setting method.

Next, in order to develop the automatic setting technology of the NIR oven, we developed a technique for simulating the drying conditions according to the material conditions to derive the results and automatically setting them. First, the functions of this automatic setting technology include work order data collection function, production schedule formation function, NIR oven drying model, automatic setting function, monitoring function, and quality data collection / storage / analysis function. A flowchart of these six functions is shown in FIG.

Process mapping was performed as shown in FIG. 13 to calculate design elements for the six functions.

Core ideas were collected and grouped for this process mapping to derive design items as shown in FIG.

Detailed design was carried out according to the design items derived above. First, as shown in FIG. 15, the automatic setting model of the NIR oven is designed to process four cases of PMT automatic calculation processing, PMT screen calculation processing, pattern call processing, and pattern storage processing.

The automatic setting items of the NIR oven are line speed, power ratio and steel plate temperature, which are automatically set according to the material conditions such as steel grade, steel plate thickness, paint maker and paint type. In addition, user interface screens can be created to simulate NIR working conditions.

After applying the above-described development to the site, fine adjustments were made during commissioning. First, the optimum PMT value for each material condition was derived to secure the temperature control capability in the normal speed section. This is a field adjustment of the values derived through the simulation, and the power ratio was adjusted to achieve the target steel plate temperature. The temperature control capability in the acceleration / deceleration section was secured. By adjusting the line speed compensation value, a line speed variation control factor, the temperature deviation during acceleration and deceleration is reduced to within 5 ° C. It secured the ability to respond to temporary unpainting. By tuning the standby power mode switching factor to 60 sec, the target temperature of the steel sheet was accurately matched by eliminating the power reduction phenomenon when the coating roll was turned off instantaneously. In addition, in order to secure the accuracy of the non-contact infrared thermometer, the temperature of the steel sheet was corrected using a contact thermocouple.

On the other hand, with the introduction of NIR oven equipment for the development of heat-sealing protective film in multi-purpose coil coating line (MCCL), the NIR oven was developed and applied to the field. The control conditions of the oven were simulated and modeled on the basis of the proper adhesion temperature of the protective film selected by simulation, and the setting function was established by automatic setting, manual setting and simulation method. The results prepared thoroughly before the installation of this facility were finely adjusted through the trial run, and rapid normalization was achieved. Table 6 summarizes the tuning performed during commissioning.

[Table 6] Tuning details for securing the accuracy of MCCL NIR oven

NIR ovens are installed on the line exit side, and the line speed changes greatly during product shearing or quality inspection. Therefore, it is necessary to control the NIR oven in response to such a large line speed. The line speed compensation item, a control factor of NIR ovens for line speed changes, was adjusted to respond quickly to speed changes. FIG. 16 shows that the actual steel plate temperature accurately tunes to the target steel plate temperature when the line speed changes rapidly between 20mpm and 70mpm.

In addition, the short term capability of temperature control to determine the accuracy of the measured PMT relative to the target PMT represents about 3.3σ. Figure 17 shows the PMT capability analysis results. According to the analysis result, it is possible to confirm the accuracy of the application of the present invention and to obtain a result that can be substantially matched with the actual situation through supplementation of various conditions.

1 is a schematic diagram illustrating a continuous color painting line.

2 is a schematic diagram illustrating a continuous drying oven.

3 is a block diagram showing the structure of the hardware of the present invention.

4 is a conceptual diagram of radiant heat transfer method.

5 is an example of use of drying operation data setting.

6 is an infrared wavelength range classification diagram.

7 is a conceptual diagram of radiant energy of an object.

8 is a temperature and wavelength band influencing emissivity.

9 is a change in emissivity of the near infrared epoxy paint

      (a) chipping state, (b) liquid state

10 is a conceptual diagram of the method of determining emissivity

      (a) Thermocouple method (b) Masking tape method

11 is a flowchart of a setting method of an NIR oven.

12 is a drying operation automatic setting flow chart.

13 is a process map drawing for design element calculation.

14 is a process of deriving design items and design elements.

15 is a flowchart of setting processing of the NIR oven (four examples).

16 is a diagram showing an example of temperature control according to a change in line speed.

17 shows an example of a temperature control capability analysis diagram.

Major code

10. Winding frame 11. Unwinding frame

12. Entrance storage frame 13. Cleaning equipment

14. Pretreatment Equipment 15. Undercoat Sprayer

16. Top oven 17. Top coater

18. Top coat oven 19. Exit storage box

Claims (3)

In the automatic control method of drying operation in the production line of continuous color steel sheet, Collect the steel sheet material information from the production management system, and in the drying operation data setting system, the steel grade of the steel sheet, the thickness of the steel sheet, the indication values for the color of the steel sheet and the paint of the steel sheet are required to dry. The paint job data for power ratio and line speed are calculated on the basis of the highest temperature (PMT), and the calculation result is displayed on the HMI (Hμman Machine Interface) terminal for the operator to check and at the same time. The result value is automatically set in the PLC for unit control and data processing through the network hub, and the PLC automatically controls the near-infrared drying operation of the continuous color steel sheet production line according to the power ratio and line speed included in the calculated result value. Automatic control method of drying operation using near infrared ray in continuous color steel plate production line. In the automatic control method of drying operation in the production line of continuous color steel sheet, Drying in an oven using near-infrared (NIR), but in particular, the drying conditions of wet paints are simulated to derive the results, and based on this, the operating conditions of the NIR oven are set as the automatic setting method, manual setting method and simulation method. The automatic setting method automatically calculates the setting value from the table model according to the line speed, power ratio, steel plate temperature, steel grade, steel plate thickness, paint maker and paint type that meet the material conditions when receiving the work instruction data. And manual setting method provides working standard in the form of pattern table that can be input / modified / edited by the operator, and simulation method can simulate PMT value by changing the material condition by the operator on the user interface screen (HMI). Function allows the operator to utilize the setpoint using the three methods described above for NIR work, Near-infrared in continuous color steel production, characterized in that the drying operation using near-infrared in continuous color steel sheet production by controlling the power ratio and line speed of the operating conditions of the oven using the near infrared ray (NIR) according to the set value. Drying operation automatic control method using. The method of claim 1, wherein when the steel grade of the steel sheet is steel, the PMT value is controlled automatically by using a near infrared ray in a continuous color steel sheet production line derived from the following equation. PMT_Group1 = 170.46 + 0.56 * Power Ratio -1.98 * Line Speed -91.43 * Steel Thickness         + 1.14 * line speed * steel plate thickness PMT_Yellow = 152.11 + 0.57 * Power Ratio -1.76 * Line Speed -64.82 * Steel Thickness         + 0.75 * line speed * steel plate thickness PMT_Silver = 139.27 + 1.19 * Power Ratio -1.05 * Line Speed -108.93 * Steel Thickness                    -0.01 * power ratio * line speed + 1.5 * line speed * steel plate thickness PMT_Black = 35.66 + 2.40 * Power Ratio -0.51 * Line Speed + 25.6 * Steel Grade -14.47 * Steel Thickness        -0.02 * Power Ratio * Line Speed -1.03 * Power Ratio * Steel Thickness +        1.53 * line speed * steel thickness -32.28 * steel grade * steel thickness [Here, (*) PMT: The highest temperature (PMT) required for drying the paint of the steel sheet, that is, the highest metal drying temperature (Peak Metal Temperature), Group 1: Beige, Orange, Blue, White, Red, Green, Auburn, Yellow, Silver, Black, Beige, orange, blue, white, red, green, maroon, yellow, silver and black are the colors of the steel sheet.]

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