KR20060023076A - Apparatus and method for controlling temparature in an horizontal type induction heating apparatus - Google Patents

Abstract

The present invention relates to a temperature control apparatus and a temperature control method of a horizontal induction furnace for controlling the temperature of the material conveyed to improve the quality and temperature control of the steel pipe material in the billet (induction) furnace, In detail, the material temperature prediction model is introduced by evaluating the temperature control by a manual operation or an indirect measuring device such as a pyrometer, and by using a real-time material temperature calculation and a temperature control algorithm, The present invention relates to a temperature control apparatus and a method for a horizontal induction furnace designed to enable improved quality of a final product and planned production of materials.

According to the present invention, the variation in material temperature caused by temperature control, which is performed only by a skilled worker in the related art, is reduced, and the quality defect rate generated during steel pipe manufacturing can be significantly lowered, as well as the degree of consistency with the post-process. It is possible to increase the treatment capacity of the furnace by increasing the temperature, and to easily manage the target temperature of the material, thereby reducing the temperature rising energy of the induction furnace.

Induction furnace, radiant thermometer, temperature control

Description

Temperature control device of horizontal induction furnace and its method {APPARATUS AND METHOD FOR CONTROLLING TEMPARATURE IN AN HORIZONTAL TYPE INDUCTION HEATING APPARATUS}

1 is a conceptual view schematically showing the configuration of a conventional induction heating furnace.

2 is a conceptual diagram showing the principle of induction heating.

3 is a conceptual diagram for showing a preferred temperature control device according to the present invention.

Figure 4 is a flow chart for showing a preferred temperature control method according to the present invention.

5 is a graph showing the temperature rise history of the raw material according to the conventional operation method.

Figure 6 is a graph for showing the temperature rise history when applying the temperature prediction model of the material according to the present invention.

* Description of the symbols for the main parts of the drawings *

    1: heating material 2: first heating table

    3: second heating table 4: third heating table

    5: Pusher 6: Trolley jaw

    7: Pyromter 8: Holding chamber

    9: Rejector 10: Controller

    11: input signal line 12: output signal line

    14: magnetic field 15: induction current of the material

    16: induction coil 17: coil induction current

The present invention relates to a temperature control apparatus and a temperature control method of a horizontal induction furnace for controlling the temperature of the material conveyed to improve the quality and temperature control of the steel pipe material in the billet (induction) furnace, In detail, the material temperature prediction model is introduced by evaluating the temperature control by a manual operation or an indirect measuring device such as a pyrometer, and by using a real-time material temperature calculation and a temperature control algorithm, The present invention relates to a temperature control apparatus and a method for a horizontal induction furnace designed to enable improved quality of a final product and planned production of materials.

Generally, an induction heating furnace includes a heating stand portion including a first heating stand 2, a second heating stand 3, and a third heating stand 4 in accordance with the order of starting heating from the time of charging as shown in FIG. 1, and a billet. While maintaining the material pusher (5) for pushing the material (1) and charging the material (1) passing through the third heating table (4) at a constant temperature, a kind of buffer ( Extrusion process of holding chamber (8) serving as a buffer, a material extractor (Trolley jaw) (6) for mounting and extracting material (1) from holding chamber (8), and material (1) Rejector (9) for pushing to send, and a radiation thermometer (Pyrometer) (7) for detecting and generating a temperature signal of the material (1) to control to maintain a constant set temperature for each steel grade.

Material 1 is a circular billet (Circular Billet), the size depends on the size of the tube (Tube) to be produced by extrusion, and usually has a length of 25 ~ 165 mm, length 350 ~ 450 mm.

Looking at the transport mechanism (Mechanism) that the material (1) is conveyed, as shown in Figure 1, each time the timer (Timer) set on the control panel (Control Panel) signals the material pusher (Pusher) 5 round billet ( The circular billet is charged into the furnace one by one while maintaining a stroke of about 37 mm, and inside the furnace, materials (1) are continuously transported from left to right while maintaining continuous contact. have.

2 shows an induction heating principle in which heating is performed in such an induction heating furnace.

First, when an induction coil 16 passes an alternating current 17, a magnetic field 14 is generated by an alternating current around the induction coil 16, and a conductive material 1 placed in the magnetic field 14 is formed. Induced current 15 is generated.

This current is called Eddy Current and Joule heat is generated by the resistivity and Eddy Current of the material 1 to be heated. This is called Eddy Current loss. Used as a heating source.

Advantages of such induction heating include rapid heating and local or surface selective heating, as well as uniform temperature distribution of the material to be heated. However, the transport beam guiding the material 1 and the area exposed to the atmosphere In addition, there is a problem that a temperature non-uniformity of the material 1 is caused due to a failure of a post-process that is an extrusion process and a charging process of the material 1, resulting in a temperature deviation up to 85 ° C. As a result, defects may occur on the surface of the steel pipe during extrusion, or may not be able to normally perform the extrusion process.

In addition, since the inside of the induction furnace is very hot at about 1,250 ° C., a skid (sleeper) is installed at the bottom of the furnace to induce protection of the facility and induce stable transport of the material (1). As it encourages cooling, a higher accuracy of temperature measurement is required.

However, the radiation thermometer 7 used in the related art has a very inaccurate temperature measured according to the oxide film or the local surface state of the material 1, and the material 1 is discontinuously charged, transported and extracted. While repeating the process, accurate temperature collection is difficult with the temperature sensor alone, and thus high temperature control is impossible.

In addition, it is possible to predict the temperature of the material by implanting a predictive model for calculating the temperature value of the material 1 by numerically simulating the following Equations 1 to 5 to the controller 1, but the calculation capacity and calculation Due to time issues, temperature control in real time is virtually impossible.

..........................................(수학식 1)

..... (Equation 1)

..........................................(수학식 2)

..... (Equation 2)

..........................................(수학식 3)

Equation 3

..........................................(수학식 4)

Equation 4

는 전류의 각속도, 그리고 j 는 복소수 (

)이다.)Where H is magnetic field strength, J is current density, B is magnetic flux density, and Is the electric field density, D is the electric field displacement,

Is the angular velocity of current, and j is the complex number (

)to be.)

..............(수학식 5)

............. (Equation 5)

Where T is the temperature of the material, t is the time, ρ is the density of the material, Cp is the specific heat of the material, K is the thermal conductivity of the material, and r is the radial position from the material center along the cylindrical coordinate system, q ^'''eddy is a Joule heat by the eddy currents (eddy Current) generated in the material.)

Therefore, the present invention has been made to solve the above-described problems of the prior art, and reads to the radiation thermometer (7), which is provided in the existing, that the temperature deviation of the material (1) occurs in the furnace, and charges according to the prior operation plan. Compensation for this temperature difference when loading the material (1) by comparing with the temperature of the material (1) obtained by the temperature prediction model taking into account the type of material, the final target temperature, the size of the material, etc. The purpose of the present invention is to provide an apparatus and a control method thereof which can improve the quality of steel pipe and the actual yield of the product during extrusion by improving the accuracy of conveying and conveying judgment as well as controlling it accurately.

Another object of the present invention is to facilitate the target temperature management of the material to prevent the waste of energy required to increase the temperature of the induction heating furnace to improve the temperature saving energy saving effect.

Another object of the present invention will be described in more detail in the configuration and operation to be described later.

The temperature control device of the horizontal induction furnace according to the present invention for achieving the above object,

Heating table for induction heating the material charged from the material charging machine;

A radiation thermometer disposed at a plurality of portions of the heating table to detect and output a temperature signal for each portion of the material; And

 Operation planning data on the type, final target temperature, size, etc. for the material to be charged is input in advance, and the temperature signal for each predetermined portion of the material output from the radiation thermometer is applied to compare the data with the final target temperature. And calculating a temperature deviation data and then applying a corrected induction current to the heating zone to control an error between the detected part temperature and the final target temperature to be reduced.

The method of controlling the temperature in the temperature control device of the horizontal induction furnace,

In the horizontal induction furnace in which a billet material is pushed into a material charging device, charged, induction heated, extracted, and applied in an extrusion process, a first operation condition for granting predetermined operating conditions and boundary conditions for the type, size, and condition of the material is provided. step;

A second step of calculating a prediction temperature for each location of the inside of the furnace and the material;

A third step of measuring and collecting a surface temperature of a predetermined position of the material by using a plurality of radiation thermometers;

A fourth step of calculating an objective function value and an objective function gradient value using a formula including design variables to be constrained in the design;

A fifth step of calculating a charging speed of a power source and a material for each heating zone, which is a change value of a design variable in a direction of minimizing the objective function calculated in the fourth step;

A sixth step of obtaining a new objective function value in the case of advancing in the defined direction of the objective function gradient value calculated in the fourth stage;

A seventh step of repeating the fourth to sixth steps until the defined objective function becomes minimum;

If the minimization condition of the seventh step is satisfied, the power and charging speed for each heating zone are output and the optimized value is calculated in real time and applied to the controller. If the minimization condition is not satisfied, the minimization direction is returned to the fourth step. It is characterized by consisting of; the eighth step of proceeding to the steps after the fourth step again by changing the.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, and in the following description of the present invention, specific descriptions of related well-known functions or configurations may unnecessarily obscure the subject matter of the present invention. If so, the detailed description thereof will be omitted.

The following terms are terms set in consideration of functions in the present invention, which may vary depending on the intention or custom of the producer, and their definitions should be made based on the contents throughout the specification.

3 is a conceptual diagram illustrating a preferred temperature control device according to the present invention. According to FIG. 3, the first heating table 2, the second heating table 3, and the third heating table ( While maintaining the portion of the heating table made of 4), the material pusher 5 for pushing and charging the billet material 1, and the material 1 passing through the third heating table 4 at a constant temperature, In order to match the process with the post process, the holding chamber 8, which serves as a buffer, and the material extractor 6 and the material 1 for mounting and extracting the material 1 from the holding chamber 8 are extruded. It is composed of a ejector 9 for pushing, and a radiation thermometer 7 for detecting and generating a temperature signal of the raw material 1 for controlling to maintain a constant set temperature for each steel grade.

The controller 10 is previously inputted with operation plan data on the type, the final target temperature, the size, and the like of the material 1 to be charged, and applies a temperature signal for a predetermined part of the material 1 output from the radiation thermometer 7. The temperature deviation data is calculated by comparing the data with the final target temperature, and then the corrected induction current is applied to the heating table 2, 3, and 4 so that And to control the error to be reduced.

As described above, a method of controlling the temperature of the horizontal induction furnace in the controller 10 to which the numerical optimization technique of the present invention is applied in connection with FIG. 3 will be described below.

In the present invention, predetermined operating conditions and equipment conditions, such as steel grade and the size of the material 1 by the initial plan production, are given (step S1).

Subsequently, a predicted temperature for each position of the inside of the heating furnace and the inside of the material is calculated by an equation based on an analytical method that can be simplified and real-time calculated as in Equation 6 below (step S2).

...(수학식 6)

... (Equation 6)

Where T is the temperature, t is the time, r is the radial position of the material (1), ρ is the density of the material, C is the specific heat of the material (1), and λ is the thermal conductivity of the material, and T _O is t The temperature at = 0 sec, PA is the heat flux applied to the material 1, R is the radius of the material 1, alpha is the correction factor, and n is the calculated node number.

Next, as shown in FIG. 3, the surface temperature of the raw material 1 for each position of the heating table showing TM1, TM2, and THC is measured and collected (step S3).

Subsequently, an objective function value of Equation 7 and an objective function gradient value of Equation 8 are calculated using a formula including design variables to be constrained in the design (step S4).

....................(수학식 7)

(Equation 7)

Here, T (t, R) is the surface temperature of the other material at time t calculated by Equation 6, Ti is the temperature collected by the position of the heating table indicating TM1, TM2, THC as shown in Figure 3, P1 , P2, P3 represents the size of power for each heating zone.

i=1에서 n...............................(수학식 8)

i = 1 to n ..................... (Equation 8)

Here, Xi represents the value of the design variables related to the current amount per heating zone, charging speed, etc., F represents the objective function value as shown in equation (7), di is by the steep descent method (optimization method) Indicates the direction vector to be obtained.

Then, the change value of the design variable in the direction of minimizing the objective function in Equation 8 above, that is, the power supply for each heating station, the charging speed of the material (1), etc. are calculated (step S5), and is defined by Equation 8 The new objective function value is obtained in the case of advancing in the direction (step S6), and the process is repeated until the defined objective function is minimized.

That is, it is determined whether the objective function value obtained in step S6 satisfies the minimization condition (step S7). If the objective function value of the seventh step satisfies the minimization condition, the controller 10 outputs an optimum power supply for each heating zone, charging speed, and the like. By applying to the optimum heating zone induction current and charging speed by controlling the optimized values of the operating factors to the process in real time (step S8), if the objective function value of the seventh step is not satisfied the minimum conditions, return to step S4 By changing the minimization direction, the steps after step S4 are performed again (step S9).

By using the temperature control device 11 of the material, it is possible to stably limit the material temperature to a certain range even when the operating conditions are changed, thereby enabling quality defects and productivity increase of the material 1.

As described above, in order to confirm the usefulness of the temperature control apparatus and the temperature control method of the horizontal induction furnace according to the present invention, after applying arbitrary casting conditions to the horizontal induction furnace, the optimal algorithm derived from the present invention and The optimum operating pattern and temperature value of the material were calculated using the material temperature prediction model by the analytical method, and the results are shown in FIGS. 5 and 6. Figure 5 is the temperature rise history of the material when adopting the existing operation method, Figure 6 is the temperature rise history when the material temperature prediction model according to the present invention.

As can be seen in Figures 5 and 6, by introducing a temperature prediction model to the actual operation temperature control, which is controlled only depending on the actual skill of the operator, it is possible to set a more accurate operation pattern, the temperature can also directly The results were better than those obtained from the calculations, and compared with the other operating conditions, the model was physically very valid.

According to the present invention as described above, the variation in the material temperature generated by the temperature control made only by the conventional skilled workers is reduced, and the quality defect rate generated during steel pipe manufacturing can be significantly reduced, as well as the post-process. It is possible to improve the heat treatment capacity by increasing the degree of concordance with the material, and it is possible to easily manage the target temperature of the material, thereby achieving the effect of reducing the temperature energy of the induction furnace.

Claims (2)

In the temperature control device of a horizontal induction heating furnace configured to push the billet material into the material charging charge, induction heating, extraction and pushing the billet material in the extrusion process, Heating table for induction heating the material charged from the material charging machine; A radiation thermometer disposed at a plurality of portions of the heating table to detect and output a temperature signal for each portion of the material; And  Operation planning data on the type, final target temperature, size, etc. for the material to be charged is input in advance, and the temperature signal for each predetermined portion of the material output from the radiation thermometer is applied to compare the data with the final target temperature. A controller configured to control the error between the detected target temperature and the final target temperature by applying a corrected induction current to the heating table after calculating temperature deviation data. Temperature control device. In the method of controlling the temperature of a horizontal induction furnace in which a billet material is pushed into a material charging device, charged, induction heated, extracted, and applied in an extrusion process, In the horizontal induction furnace in which a billet material is pushed into a material charging device, charged, induction heated, extracted, and applied in an extrusion process, a first operation condition for granting predetermined operating conditions and boundary conditions for the type, size, and condition of the material is provided. step; A second step of calculating a prediction temperature for each location of the inside of the furnace and the material; A third step of measuring and collecting a surface temperature of a predetermined position of the material by using a plurality of radiation thermometers; A fourth step of calculating an objective function value and an objective function gradient value using a formula including design variables to be constrained in the design; A fifth step of calculating a charging speed of a power source and a material for each heating zone, which is a change value of a design variable in a direction of minimizing the objective function calculated in the fourth step; A sixth step of obtaining a new objective function value in the case of advancing in the defined direction of the objective function gradient value calculated in the fourth stage; A seventh step of determining whether the objective function value of the sixth step satisfies a minimization condition; An eighth step of outputting power and charging speed for each optimum heating zone and calculating the optimized value in real time and applying the result to the controller when the result of the seventh step is satisfied; A ninth step of returning to the fourth step to change the minimization direction to proceed to the steps after the fourth step if the result of the seventh step is not satisfied with the minimization condition; Temperature control method.

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