KR100830113B1 - Corona control apparatus and method in pure N2 environment for powder zinc galvanizing process - Google Patents

Abstract

The present invention is to provide a method for controlling corona by DC overlapping pulse high voltage for use in powder zinc plating. According to the corona generation control in the nitrogen atmosphere according to the present invention, an electrode in which a pulse power source is superposed on a direct current power source is formed in the configuration of the power source. The pulse power supply is a method of controlling a high voltage corona that does not transition to arc discharge by providing an electrostatic discharge electrode using a direct current superimposed pulse static electricity having a variable type electrode capable of varying a pulse width and a pulse generation period. To prevent arc discharge by applying a DC voltage of 73% of the discharge start voltage and superimposed thereon, a pulse high voltage of 200% higher than a DC voltage is applied, but the electric sound It provides a control method that can generate stable corona even in low nitrogen atmosphere. By having a contact voltage and current of 200% or more, adhesion of the powder zinc to the steel sheet can be effectively increased.

      Corona, pulse width, static electricity

Description

 Corona control apparatus and method in pure N2 environment for powder zinc galvanizing process)

Figure 1 is a schematic perspective view showing the configuration of a conventional powder zinc plating system

2 is a conceptual diagram of a device used to implement a corona control electrode device and a control method according to an embodiment of the present invention;

3. Diagram of control logic performed using the control circuit shown in FIG.

4. Experimental Comparison Table of Discharge Characteristics in Conventional Oxygen and Nitrogen Atmosphere

5. Corona current test result table according to the frequency change when the pulse width 10sec according to an embodiment of the present invention

6. Corona current test result table according to the frequency change when the pulse width 100sec according to an embodiment of the present invention

********** Symbol description of the main parts of the drawing **********

       10: chamber 11: molten zinc

12: zinc bath 13: flow control valve

14: Horn 15: ultrasonic generator

16: high voltage electrode 17: high voltage generator

18: zinc particles 19: plated steel sheet                 

20: drain pump 30: power supply

31: variable DC power supply 32: charging output unit

33: variable pulse power supply 34: resistance output unit

35: high voltage cable 40: power control unit

41: pulse waveform measuring instrument 42: DC voltage measuring instrument

43: current sensor 44: hysteresis comparator

45: numerical controller 50: pulse and DC control unit

     51: pulse width, frequency controller 52: pulse switching circuit

     53: DC voltage controller 54: voltage switching circuit

The present invention relates to a method of making a galvanized steel sheet by attaching the finely divided zinc particles to the steel sheet by the electrostatic force generated by the high voltage electrode, and more particularly, to a method of controlling the electrostatic voltage generating high voltage corona in a nitrogen atmosphere.

The prior art related to a method of making a plated steel sheet using zinc particles is as follows. As shown in FIG. 1, a zinc bath 12 storing molten zinc 11 melted by a heater supplying a heat source necessary for melting zinc, a valve 13 regulating a flow rate of molten zinc, and molten zinc A horn 14 in direct contact with the ultrasonic generator 15 to atomize the particles, a steel plate 19 to be plated with the zinc particles 18 atomized by the horn, a high voltage generator for applying electrostatic force to the zinc particles ( 17 and the high voltage electrode 16. Also included is a drain pump 20 for discharging residual zinc. And a chamber 10 for sealing the plating section is required.

In such a method of plating zinc, it is essential to use the electrostatic force formed between the charging of the zinc particles and the steel sheet and the electrode in order to attach the zinc particles to the steel sheet. The use of static electricity is a dust collector as a representative example. According to the patent of 1999-18620, the method of plating the steel sheet and the device (Kim Sangheon, Jung Won Cheol) used therein, a high voltage device capable of generating static electricity is applied. It does not describe how to control corona in nitrogen atmosphere.

Application number 2001-14502, according to the method of manufacturing a hot-dip galvanized steel sheet (Kim Sang-heon) is using a high voltage superimposed on a pulse instead of a direct current high voltage to increase the plating efficiency. The use of pulses can improve the adhesion efficiency rather than direct current.However, the calculation of the capacitance and the method of setting the discharge start voltage according to the composition of the electrode are not described, and due to some fundamental problems described below, There is no fundamental solution to corona outbreaks.

The fundamental reason that corona is difficult to generate in a nitrogen atmosphere is because nitrogen is an inert gas with low electronegativity. Corona generation is possible in a high-negative gas atmosphere containing oxygen atoms such as oxygen, carbon dioxide, H ₂ O. On the other hand, the corona phenomenon is a phenomenon in which a partial spark discharge occurs because a gas near the surface is ionized when a high voltage is applied to a surface of a metal having a small radius of curvature. The ionized gas is attached to the zinc particles and moves to the steel sheet, thereby contributing to the plating. When using a DC voltage, the ionized electrons continue to be forced toward the sieve steel sheet, which is not attached to a gas with low electronegativity, causing excessive current flow to cause arc discharge.

4 is a table showing the phenomenon that occurs when the DC high voltage is increased from 0 to 50 kV in both the air (79% oxygen, 21% nitrogen) and nitrogen atmosphere (99.9% nitrogen). In case of oxygen, corona starts at about 32kV and it occurs stably even if it takes about 50kV, but in the nitrogen atmosphere, corona is started near 27.5kV, and arc discharge occurred at 28kV almost instantaneously, making it impossible to form corona. .

The present invention has been made to solve the problems of the prior art, in the method for continuing the corona generation even in a nitrogen atmosphere to provide an electrode capable of applying a pulsed high voltage superimposed on the direct current, the DC voltage below the discharge voltage It prevents arc discharge by applying instantaneous pulsed high voltage to nitrogen gas with low electronegativity and forms corona to control the repulsive force and attraction force of zinc particles through stable corona generation. It is an object of the present invention to provide an electrode device and a control method for increasing the amount of plating by moving.

The construction of the present invention for achieving the above object, the steel plate to be plated 19 and the electrode 16 formed in a plurality of lines located at a predetermined distance opposite thereto, the power supply unit 30 for applying an electrostatic force to the electrode And a power control unit 40. First, in the configuration of the power supply unit, the variable pulse power supply 33 having the variable DC power supply 31 having the charge output unit 32 and the resistance output unit 34 connected in series with the charge output unit 32 to superimpose a pulse voltage is provided. ). The resistance output section 34 of the power supply unit is connected to the electrode by the high voltage cable 35.

The power supply control unit 40 requires the feedback of voltage and current for corona control. For this purpose, the measurement is possible by installing the current sensor 43 in the pulse waveform measuring device 41, the DC voltage measuring device 42, and the high voltage cable 35. Let's do it. The corona current measured by the current sensor 43 is compared by the hysteresis comparator 44 in the range of 8-20 [mA].

 In this way, the value fed back by the pulse waveform measuring unit 41, the DC voltage measuring unit 42 and the hysteresis comparator 44 is input to the numerical controller 45 into which the program for setting the output voltage is input by the equation and the numerical controller 45 outputs control amounts of pulses and direct current, respectively, according to the equation. The control amount output in this way is input to the pulse and DC controller 50, that is, the pulse width, the frequency generating controller 51 and the DC voltage controller 53, respectively, by the pulse switching circuit 52 and the voltage switching circuit 54, respectively. The pulse power supply 33 and the DC power supply 31 of 30 are driven. In addition, the method for implementing the present invention according to the described apparatus is made according to the following steps. In other words, for the corona control method in the nitrogen atmosphere, an insulated high voltage electrode capable of variable adjustment of the pulse width and pulse generation period is installed corresponding to the steel plate, and the field generating unit and the direct current high voltage generator of the ship plate structure are provided for the capacitance. Calculating, setting and controlling the voltage and current to detect the strength of the voltage of the high voltage electrode and the amount of current that charges the powder zinc at the electrode, and the width and period of the pulse from the measured intensity and current amount and voltage. It can be carried out by a method including an output step of determining and outputting from the voltage generator.

On the other hand, in the present invention, it is possible to control the static electricity of the powder galvanized by using a pulsed high voltage superimposed on the direct current, and by controlling the pulse width and pulse generation period of the pulse superimposed on the direct current in the corona even in a low nitrogen atmosphere atmosphere corona It was possible to generate. A pulse is a power supply capable of applying high voltage static electricity in a short time and is defined as a pulse width, a pulse generating period, and a pulse rising time. By applying a pulse, a strong electrostatic force can be applied in a short time, and at the same time, a rise in current can be prevented, thereby suppressing the transition from a direct current to an arc discharge. In the present invention, by controlling the pulse width and pulse generation period of the pulse superimposed on the direct current, it is possible to generate corona even in a nitrogen atmosphere with low electronegativity.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. 2 illustrates a corona control electrode device and a device used to implement the control method. The electrostatic electrode in FIG. 2 can be designed in the form of a shipboard flat plate or a plateboard plate. The electrode for powder plating adopted the structure of a ship plate. In order to create an electrostatic phenomenon, a structure in which a high voltage is applied to the discharge electrode and the plate is grounded is required.                     

For the circuit design of the power supply, the values of inductance, resistance, and discharge start voltage of the corona reactor structure as the load must be estimated. The inductance of the structure of the corona reactor is estimated to be about 1 H, and other values can be obtained by the estimation equation. The load of a high voltage power supply is an electrode and, in electrical circuits, becomes a capacitor. The capacitor C for the electrode structure of FIG. 2 is represented by Equation 1.

Where L is the total length of all discharge electrodes operated by one and the same voltage source. F is a constituent of the electrode system that varies with the radius of the discharge electrode and various relative distances of the discharge electrode. ε ₀ is the dielectric constant of the vacuum and ε ₁ is the dielectric constant of the gas. R is the radius of the corona generated at the discharge electrode, and r is the radius of the discharge electrode.

The capacitance and the corona resistance of the reactor according to the distance between the discharge electrode and the dust collecting electrode implemented by Equations 1 and 2 are shown. When L = 100cm, D = 10cm, S = 13cm and d = 2mm, the calculated capacitance value was 12.52 pF / m. The corona resistance is inversely proportional to the applied voltage and the length of the discharge electrode as a function of the distance between the discharge electrode and the ground plate, the applied voltage and the length of the discharge electrode, and is proportional to the square of the distance between the discharge electrode and the ground plate. In this case, the proportional constant of the resistance has a value of approximately 7031. Therefore, the value according to the structure of a given reactor is calculated and the range of resistance is shown in FIG. 4. The resistance value of the corona discharge is 17.57.

The discharge start voltage is expressed by Equation 3 with respect to the line-to-plate electrode structure having an infinite number of regularly arranged.

Where V ₀ is the discharge start voltage, E ₀ is the strength of the electric field, R ₀ is the radius of the discharge electrode, S is the distance between the discharge electrodes, D is the distance between the steel plate and the discharge electrodes, and sinh is a hyperbolic sine. A and B are uncertain, but in nitrogen, A and B are 32.2 * 10 ⁵ and 0.846 * 10 ⁵ . δ is the relative gas density of the gas density around the electrode. When a high voltage is applied with a variable distance between electrodes, the point where the corona is generated should be found. When the thickness of the discharge electrode is 2 mm, the discharge start voltage is approximately 34.8 kV.

The magnitude of the voltage generated by the corona should be about 24 kV / cm or more in the atmosphere at 1 atm. If the discharge start voltage according to the reactor structure is 34.8 kV, the distance between the poles of the discharge electrode is 13 cm, the distance between the dust collecting electrode and the steel plate is 15 cm, and the thickness of the discharge electrode is 2 mm.                     

FIG. 5 is an experiment content applied while varying the voltage of a pulse while superimposing on a direct current voltage of 15.6 kV. The pulse width of the pulse used here is 10 [sec] and the experiment was performed while varying the frequency from 10 to 1000 [hz]. It can be seen that the output current increases with increasing frequency, and stable corona can be generated without discharging even if the applied voltage is 39.6kV.

FIG. 6 is an experiment content applied while varying the voltage of a pulse while superimposing on a DC voltage of 15.6 kV. The pulse width of the pulse used here is 100 [sec] and the experiment was performed while varying the frequency from 10 to 100 [hz]. It can be seen that the output current increases with increasing frequency, and stable corona can be generated without discharging even if the applied voltage is 39.6kV.

Comparing FIG. 5 and FIG. 6, the pulse width is increased by 10 times, and accordingly, the magnitude of the output current increases by about 117%. In practice, the conditions under which the corona current is formed are DC bias voltage of 15.6kV, pulse applied voltage of 20 to 24 kV, pulse width of 10 to 100 sec, and pulse repetition frequency of 10 to 1000Hz. At this time, the range of the current value can secure a control range of 8 ~ 20.8 mA.

 FIG. 2 is a conceptual diagram of an apparatus used to implement a corona control method in a nitrogen atmosphere according to an embodiment of the present invention, and FIG. 3 is a flowchart of control logic performed using the apparatus shown in FIG. The zinc powder partial flow apparatus using the bipolar high voltage shown in FIG. 2 forms an electrode in which a pulse power source is superimposed on a direct current power source due to the configuration of the power source. The pulsed power supply includes an electrostatic discharge electrode using a DC superimposed pulse static electricity, characterized by a variable type electrode capable of varying a pulse width and a pulse generation period. Meanwhile, a high voltage generator and a high voltage cable are required to generate and control the high voltage. Based on the above equations, a method of controlling static electricity according to zinc injection amount will be described in detail for each step shown in FIG. 3. In S1 shown in FIG. 3, the inter-pole distance between the high voltage electrode and the discharge electrode is set, and in S2, the distance between the discharge electrode and the diameter of the electrode is set. In S3, the reactor capacitance is calculated as in Equation 1, and in S4, the discharge start voltage is calculated as in Equation 3. In S5, the DC bias voltage is set with a margin of 70% from the calculated discharge start voltage.

In S6, the pulse voltage is set between 20 and 24 kV. In S7, the pulse width is set between 10 and 100 µsec. In S8, the pulse generation period is set between 10 and 1000 Hz. After the setting is completed, in S9, the corona current is measured. In S10, compare whether the corona current measured in S9 is the proper range of 8 ~ 20.8 mA. If out of range, it will return to S6, S7 and S8 to reset the proper range. If it is within the range, the current is output to the electrostatic electrode in S11 and the corona current control is completed.

Although the invention has been particularly shown and described with reference to the preferred embodiments, those skilled in the art will appreciate that various modifications are possible without departing from the spirit and scope of the invention. Accordingly, the invention is limited only by the claims.

As described above, the present invention, in the method for controlling the high voltage corona in the nitrogen atmosphere, by applying a direct current voltage of 73% of the discharge start voltage to prevent arc discharge and superimposed thereon pulse high voltage 200% higher than the direct current voltage By controlling the width of the pulse and the generation period of the pulse to provide a control method that can generate a stable corona even in a low nitrogen atmosphere atmosphere. By having a contact voltage and current of 200% or more, there is an effect that the adhesion of the powder zinc to the steel sheet can be effectively increased.

Claims (2)

In a corona electrostatic control device in a metal powder plating system for plating a steel sheet in a nitrogen atmosphere, A plurality of electrodes formed to face the steel sheet; A power supply unit connected to the electrode to apply an electrostatic force; A power control unit connected to the power supply unit for measuring values for corona control; A hysteresis comparator connected to the power controller to determine whether a corona current value measured by the power controller is within a predetermined range; A numerical controller connected to the power control unit for outputting a control amount of pulse and direct current according to the measured value of the power control unit and the value of the hysteresis comparator; Pulse and DC control unit for driving the power supply according to the output value of the numerical controller; High voltage control device capable of controlling the pulse width and the frequency of pulse generation, characterized in that for applying a DC overlapping pulse high voltage to the metal powder. A method of controlling corona static electricity in a metal powder plating system for plating a steel sheet in a nitrogen atmosphere, Setting a distance between the high voltage electrode and the discharge electrode; Calculating a reactor capacitance from the interelectrode distance of the discharge electrode and the diameter of the electrode; Calculating a discharge start voltage from the capacitance; Setting a DC bias voltage with a margin of 70% from the discharge start voltage; Setting a pulse value from the DC bias voltage; Measuring the corona current according to the pulse value and repeating the pulse value setting depending on whether the corona current is within a predetermined range; High voltage control method capable of controlling the pulse width and the frequency of pulse generation, characterized in that for applying a DC overlapping pulse high voltage to the metal powder.

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