JPH0711413A - Method and device for controlling degree of alloying by emissivity - Google Patents

Abstract

PURPOSE:To provide the method and device for controlling alloying by emissivity capable of inexpensively controlling the degree of alloting of a metallic strip with relatively simple constitution by measuring the emissivity by utilizing a correlative relation between the degree of alloying, emissivity and surface temp. of the metallic strip. CONSTITUTION:The emissivity and temp. of the metallic strip 10 on the outlet side of a heating zone 15 are measured by a radiation thermometer 30 and are inputted to an emissivity controller 36 and a strip temp. controller 38 respectively. The outputs thereof are inputted to an override table 39 and are converted to such control target values at which a control system converges rapidly and safely. These values are thereafter passed through load distribution tables 40a to 40d and are made into the control target values of a fuel controller 54a and an air controller 57a so that fuel and air are supplied at prescribed flow rates to a burner 60a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloying degree control method and apparatus for controlling the degree of alloying of a metal strip surface in an alloying furnace for alloying the surface of a metal strip plating.

[0002]

2. Description of the Related Art Conventionally, as a plating state measuring method for determining the product quality of a coil such as a galvanized steel sheet, (a) the amount of a plated layer peeled off by a bending / bending back test of a sampled sample is visually determined. A so-called powdering test, (b) a chemical analysis method for measuring the average Fe concentration in the plating layer of the sample sampled,
(C) Cross-section polishing of the sampled sample is observed using an optical microscope or a scanning electron microscope, and
Method for measuring thickness of δ ₁ phase and Γ phase, (d) X-ray diffraction profile of sampled sample is measured using X-ray diffractometer for analysis, and X of ζ phase, δ ₁ phase and Γ phase is measured.
A method for measuring the line diffraction intensity, (e) a method for measuring the radiant energy and the reflected light intensity of the plating layer after the alloying treatment,
(F) A method of measuring the X-ray diffraction intensity of the η-Zn phase, the X-ray diffraction intensity ratio of the η-Zn phase and the δ ₁ phase, and the X-ray diffraction intensity ratio of the Γ phase and the α phase.

[0003]

However, the above-mentioned measuring methods (a), (b), and (c) cannot be applied to real-time control because they are offline measurements using test pieces sampled from the product. . Also, (d)
Although the measuring method of (1) can arrange a measuring device in the line, it requires time for X-ray diffraction profile measurement and signal processing, and cannot be used for feedback control.
Further, the methods (e) and (f) allow online measurement and have real-time characteristics, but the overall system configuration tends to be complicated and expensive.

As described above, there is no method for measuring the plating state of the metal strip with a simple structure, and conventionally, the alloying degree is estimated by detecting the outlet plate temperature of the heating zone to control the heating amount. ing.

In order to solve the above-mentioned problems, an object of the present invention is to measure and control the emissivity by utilizing the correlation between the alloying degree of the metal band, the emissivity and the surface temperature. It is an object of the present invention to provide a method and a device for controlling the degree of alloying by emissivity, which can control the degree of alloying of the alloy with a relatively simple structure and at low cost.

[0006]

DISCLOSURE OF THE INVENTION The present invention provides a method for controlling the degree of alloying by heating a metal strip having molten metal adhered to its surface to control the degree of alloying. Using the correlation between the surface temperatures, the step of measuring the emissivity and the step of comparing the emissivity with a predetermined target emissivity to obtain an emissivity deviation and outputting this as a target heating amount. And a step of controlling the heating amount to the metal band based on the target heating amount, the method for controlling the degree of alloying by emissivity.

The present invention also includes a step of measuring the plate temperature of the metal strip, a step of comparing the plate temperature with a predetermined target plate temperature to obtain a plate temperature deviation, and the plate temperature deviation and the radiation. And a step of switching the rate deviation for each predetermined condition and outputting the target heating amount.

Further, the present invention corresponds to the plate temperature of the metal strip,
It is characterized by including the step of switching the measurement wavelength of the emissivity.

Further, according to the present invention, in the alloying degree control device for controlling the degree of alloying by heating the metal zone having the molten metal adhered to the surface, the correlation between the alloying degree of the metal zone, the emissivity and the surface temperature is obtained. Using the relationship, the emissivity measuring means for measuring the emissivity and the emissivity are compared with a predetermined target emissivity to obtain an emissivity deviation, which is output as a target heating amount. An emissivity alloying degree control device comprising: means and a heating amount control means for controlling the heating amount to the metal strip based on the target heating amount.

The present invention further includes a plate temperature measuring means for measuring the plate temperature of the metal strip, and a plate temperature adjusting means for comparing the plate temperature with a predetermined target plate temperature to obtain a plate temperature deviation. A target heating amount output means for switching the plate temperature deviation and the emissivity deviation for each predetermined condition to output a target heating amount is provided.

Further, the present invention corresponds to the plate temperature of the metal strip,
It is characterized by comprising a measurement wavelength switching means for switching the measurement wavelength of the emissivity.

[0012]

According to the present invention, the emissivity is measured by utilizing the correlation between the alloying degree of the metal strip, the emissivity, and the surface temperature, thereby accurately capturing the alloying degree of the metal strip. You can In detail, the conditions for measuring the spectral radiance of an object, that is, when the measurement wavelength and the optical system are fixed, the emissivity is a physical property such as the composition and surface roughness of the object surface, that is, the surface condition. I can catch it. If this is expressed by an equation, 1- (reflectance) = (emissivity).

FIG. 3 is a graph showing changes in plate temperature and emissivity of the metal strip with respect to heating time of the metal strip. In this graph, immediately after the plated metal adheres to the surface of the metal strip, the plated metal on the surface remains in a molten state even though the plate temperature T shows around 500 ° C. It has a luster. Therefore, the wavelength λ1 = 1.5
Emissivity ελ1 measured at 5 μm and wavelength λ2 = 2.
The emissivity ελ2 measured at 2 μm has a value of about 0.1 to 0.2. Thereafter, as the alloying progresses over time, the metallic luster of the surface is gradually lost, and the emissivity ελ1 and ελ2 gradually and monotonically increase, although the plate temperature T hardly changes. After that, when the state is overheated, that is, a so-called hard bake state, the alloying degree is saturated and the plate temperature T does not change much, but the emissivities ελ1 and ελ2 are values of about 0.5 to 0.6. As described above, the degree of alloying can be controlled by utilizing the correlation that the emissivity ελ1 and ελ2 monotonically increase as the alloying progresses.

Further, the measured emissivity is compared with a predetermined target emissivity to obtain an emissivity deviation, and this is used as a target heating amount to control the heating amount to the metal band, thereby controlling the metal band. The degree of alloying can be controlled with high precision.

Further, the plate temperature of the metal strip is measured, the plate temperature is compared with a predetermined target plate temperature to obtain a plate temperature deviation, and the plate temperature deviation and the emissivity deviation described above are predetermined. By switching each condition and outputting the target heating amount, these 2
It is possible to switch which of the plate temperature control and the emissivity control is preferentially operated according to one deviation state. Therefore, for example, if it deviates significantly from a certain target value, the plate temperature control is used to prioritize temperature stabilization,
If it converges near the target value, use emissivity control,
By prioritizing the stabilization of the alloying degree, cooperative control of the plate temperature control and the emissivity control becomes possible, so that the stability and safety of the control can be improved.

Further, since the emissivity measurement can be performed with higher accuracy by switching the emissivity measurement wavelength according to the plate temperature of the metal strip, the target accuracy of the alloying degree control can be improved. You can

According to the invention, the degree of alloying of the metal strip,
By providing the emissivity measuring means for measuring the emissivity by utilizing the correlation between the emissivity and the surface temperature, as described above, the alloyed layer of the metal band can be accurately captured. Further, the measured emissivity is compared with a predetermined target emissivity to obtain an emissivity deviation, and the emissivity adjusting means for outputting the deviation as a target heating amount, and the metal band to the metal band based on the target heating amount. By providing the heating amount control means for controlling the heating amount of, the degree of alloying of the metal strip can be accurately controlled.

Also, a plate temperature control means for measuring the plate temperature of the metal strip, a plate temperature adjusting means for comparing the plate temperature with a predetermined target plate temperature to obtain a plate temperature deviation, and a plate temperature deviation And a target heating amount output means for outputting a target heating amount by switching between the emissivity deviation and the emissivity deviation for each predetermined condition, thereby giving priority to either the plate temperature control or the emissivity control depending on these two deviation states. It is possible to switch between automatic operation and the stability and safety of the control system can be improved by the cooperative control of the plate temperature control and the emissivity control.

Since the emissivity measurement can be performed with higher accuracy by switching the emissivity measurement wavelength in accordance with the plate temperature of the metal strip, the target accuracy of alloying degree control can be improved. You can

[0020]

1 is a block diagram showing the configuration of an embodiment of the present invention. A metal strip 10 such as a steel plate is conveyed at a predetermined speed, is immersed in a plating bath 11 that stores a molten metal 12 such as molten zinc, and a sink roll 13 changes the conveying direction vertically upward, and a wiping device such as a high pressure nozzle. After adjusting to a predetermined amount of plating by 14
Enter the heating zone 15. In the heating zone 15, the metal zone 10 is heated to a temperature required for the alloying treatment by burners 60a, 60b, 60c, 60d such as a direct flame burner, and the alloying proceeds to a certain depth from the surface.

A radiation thermometer 30 is installed at a predetermined distance from the outlet side of the heating zone 15, and the emissivity ελ1 and ελ2 of the metal zone 10 from a converter 31 connected to this radiation thermometer 30.
And the plate temperature T is output. The radiation thermometer 30 collects the radiated wave from the heated metal surface with a lens, disperses it with a mirror or an interference filter, and G
The light is received by a plurality of photodetectors such as e and PbS, and the spectral luminance at each wavelength is measured. The emissivity εx at each wavelength λx and the plate temperature T is εx = Lx / Lb (λx,
It is given by the formula T). Note that Lx is the spectral radiance and Lb is the blackbody spectral radiance.

Thus, the converter 31 has, for example, a wavelength λ.
1 = emissivity ελ1 measured at 1.55 μm, wavelength λ2 =
The emissivity ελ2 and the plate temperature T measured at 2.2 μm are output. These two emissivities ελ1 and ελ2 are input to the switch 32, one of the emissivities is selected based on the command from the measurement wavelength selector 20, and the emissivity controller 3
6 is input.

On the other hand, in order to set the target emissivity as the control reference value, the λ1 emissivity setting section 33 and λ2 are set for each wavelength.
An emissivity setting unit 34 is provided, and each output is input to the switch 35. The switch 35 selects one output based on a command from the measurement wavelength selector 20 and outputs it to the emissivity controller 36. The switching of the emissivity measurement wavelength in the measurement wavelength selector 20 can be performed manually by an operator, but the plate temperature T output from the converter 31 is judged and the emissivity measurement wavelength is determined by the measurement wavelength selector 20. By providing the automatic determination unit 21 that issues a command, it becomes possible to perform emissivity measurement with higher accuracy.

In the emissivity controller 36, the switch 32
The emissivity deviation between the emissivity selected in step 1 and the target emissivity selected by the switch 35 is calculated, and PID control is performed, for example, and the result is input to the override table 39 described later.

On the other hand, the plate temperature T output from the converter 31 is input to the plate temperature controller 38, and the plate temperature deviation from the target plate temperature set by the plate temperature setting unit 37 is calculated.
The control is performed and the data is similarly input to the override table 39.

FIG. 2 shows the override table 39 shown in FIG.
It is a graph which shows an example. Override table 39
Is divided into five regions R1 to R5 with the plate temperature T on the X axis and the emissivity ε on the Y axis, and the plate temperatures TL and TH that can be set and the emissivity εL and εH being boundaries. The output value of the override table 39 changes depending on which region the plate temperature T and the emissivity ε output from the converter 31 correspond to. In the following, (1) when the measured value (T, ε) is located in the region R1 (T <TL and ε> εH), the measured plate temperature T is given priority over the emissivity control and the measured plate temperature T is set to the plate temperature TL and TH. Therefore, the difference between the actually measured plate temperature T and the plate temperature TL is output as the target control value for the next stage. Therefore, when the whole control loop works,
The measured value (T, ε) is controlled so as to approach the plate temperature TL.

(2) Region R2 (T <TL and ε ≦ εH)
When the measured value (T, ε) is located at, the measured plate temperature T is set in order to quickly converge the larger emissivity deviation and plate temperature deviation.
And the plate temperature TL, the measured emissivity ε and the target emissivity ε
The difference from S is obtained, and the one with the larger absolute value is output as the target control value for the next stage. Therefore, when the entire control loop operates, the measured value (T, ε) becomes the point E (TL, ε).
It is controlled so that it approaches stepwise toward S).

(3) When the measured value (T, ε) is located in the region R3 (TL≤T≤TH), the measured emissivity ε is promptly brought close to the target emissivity εS in preference to the plate temperature control. , The difference between the measured emissivity ε and the target emissivity εS is output as the target control value for the next stage. Therefore, when the entire control loop operates, the measured value (T, ε) is controlled so as to approach the target emissivity εS.

(4) Region R4 (T> TH and ε ≧ εL)
When the measured value (T, ε) is located at, the measured plate temperature T is set in order to quickly converge the larger emissivity deviation and plate temperature deviation.
And plate temperature TH, and measured emissivity ε and target emissivity ε
The difference from S is obtained, and the one with the larger absolute value is output as the target control value for the next stage. Therefore, when the entire control loop operates, the measured value (T, ε) becomes the point G (TH, ε).
It is controlled so that it approaches stepwise toward S).

(5) Region R5 (T> TH and ε <εL)
When the measured value (T, ε) is located at, the measured plate temperature T and the plate temperature TH are set in order to quickly set the measured plate temperature T within the range between the plate temperatures TL and TH in preference to the emissivity control. Is output as the target control value for the next stage. Therefore, when the entire control loop operates, the measured value (T, ε) is controlled so as to approach the plate temperature TH.

This operation will be described in detail. First, when the measured value (T, ε) output from the converter 31 is the point U1, the area moves toward the region R3 in parallel with the X axis,
Point U2 is reached due to overshoot or the like. Then,
At the point U2, the line segment EG moves in parallel with the Y axis. In this way, the measured values belonging to the region R1 converge near the line segment EG.

Next, when the measured value (T, ε) is the point P1, the deviation from the target emissivity εS is larger than the deviation from the plate temperature TL. , P2 is reached due to overshoot or the like. Then, at the point U2, since the deviation from the plate temperature T is larger than the deviation from the target emissivity εS, the point E2 moves parallel to the X axis and reaches the point P3. Then, at the point P3, since the deviation from the target emissivity εS is larger than the deviation from the plate temperature, the point P3 moves parallel to the Y axis. In this way, it converges stepwise in the vicinity of point E so as to straddle a straight line (shown by a broken line) in which the deviation from the plate temperature TL and the deviation from the target emissivity εS are equal.

Next, when the measured value (T, ε) is the point Q1, as in the region R2, a straight line (shown by a broken line) in which the deviation from the plate temperature TH and the deviation from the target emissivity εS are equal to each other. It crosses points Q2 and Q3 and moves in a stepwise manner to converge near point G.

Next, when the measured value (T, ε) is the point V1, like the region R1, it first moves to the point V2 and then converges toward the line segment EG.

In this way, the measured values (T, ε) located in each of the regions R1 to R5 are controlled so as to finally converge near the line segment EG. The number and arrangement of the divided areas of the override table 39 are not limited to those shown in FIG. 2, and can be changed as appropriate according to the operating conditions.

Returning to FIG. 1, the override table 39
Is input to the four load distribution tables 40a to 40d and converted into target combustion amounts corresponding to the burners 60a to 60d. The output of the load distribution table 40a is switched based on the command from the control mode switch 22 to the switch 5.
It is input to one of 2a. On the other hand, the output from the plate temperature controller 38 is input to the four load distribution tables 41a to 41d and converted into target combustion amounts corresponding to the burners 60a to 60d. Then, the output of the load distribution table 41a is input to the other of the switches 52a. The control mode switch 22 is provided to select a cooperative control mode of emissivity control and plate temperature control or a plate temperature control mode. The output of the switch 52a is input to the row select unit 53a.

On the other hand, the output from the furnace thermometer 61a such as a thermocouple arranged near the burner 60a is the furnace temperature controller 51.
is input to a, the furnace temperature deviation from the target furnace temperature set by the furnace temperature setting unit 37 is obtained, for example, PID control is performed, and similarly input to the row select unit 53a.

In the row select section 53a, the switch 52
The target combustion amount output from a is compared with the target combustion amount output from the furnace temperature controller 51a, and the smaller one is selected and output. Therefore, when the target combustion amount output by the emissivity control or the plate temperature control becomes abnormally high, the furnace temperature control is prioritized and the safety of the control system is ensured.

The target combustion amount selected by the low select section 53a is input to the fuel controller 54a and the air controller 57a, and cascade control is performed. Fuel sent from a fuel supply device (not shown) such as a fuel tank is supplied to the burner 60a through the flow meter 55a and the flow control valve 56a. The fuel flow rate measured by the flow meter 55a is input to the fuel controller 54a, compared with the target combustion amount, for example, PID controlled, and the opening degree of the flow control valve 56a is adjusted.

Air sent from an air supply device (not shown) such as an air tank is supplied to the burner 60a through the flow meter 58a and the flow control valve 59a. Similarly, the air flow rate measured by the flow meter 58a is input to the air controller 50, is compared with the target combustion amount, and is PID-controlled, for example, and the opening degree of the flow control valve 59a is adjusted.

The burner control system A for controlling the amount of combustion in the burner 60a has been described above in detail, but other burner control systems B, C, D are provided, and commands from the control mode switching unit 22 and load. Distribution tables 40b-40d, 41b-
The output from 41d and the outputs from the furnace thermometers 61b to 61d are input to the burner control systems B, C and D, respectively, and the flow rates of combustion and air supplied to the burners 60b to 60d are controlled.

The operation of the alloying control device thus configured and the alloying degree control method according to the present invention will be described. The metal strip 10 is conveyed at a predetermined speed, and the plating bath 12
And the amount of plating adhered is adjusted by the wiping device 14 and then enters the heating zone 15 to burner 60a ...
It is heated by 60d. The furnace temperature of the heating zone 15 is measured by the furnace thermometers 61a to 61d.

The radiation thermometer 30 provided on the outlet side of the heating zone 15 measures the emissivity and the plate temperature of the metal zone 10. For example, the emissivity ελ1 at the wavelength λ1 is input to the emissivity controller 36. , The emissivity deviation is obtained and input to the override table 39. On the other hand, the plate temperature measured by the radiation thermometer 30 is input to the plate temperature controller 35, the plate temperature deviation is obtained, and the plate temperature is input to the override table 39.

The override table 39 calculates a predetermined target combustion amount according to the values of the plate temperature deviation and the emissivity deviation and outputs it to the four load distribution tables 40a-40d. In the burner control system A, the load distribution table 40a
Output of the fuel controller 51a is lower than the output of the fuel controller 51a, the low selector 53a outputs the fuel controller 54a and the air controller 57a as control target values to control the fuel flow rate and the air flow rate. 6
0a. In this way, the emissivity of the metal strip and the plate temperature are used as the control parameters to perform the coordinated control of the emissivity control and the plate temperature control, whereby the alloying process of the metal strip progresses and the surface state changes. However, it becomes possible to control to an appropriate degree of alloying.

In such coordinated control, the alloying degree of the metal band can be more accurately captured by switching the emissivity measurement wavelength according to the plate temperature T measured by the radiation thermometer 30. As a control parameter,
The plate temperature control using only the plate temperature is realized by switching the switch 52a to the right in FIG.

Although the burners 60a to 60d are used as means for heating the metal strip 10 in the above embodiments, an induction heater for applying an alternating magnetic field to the metal strip 10 for induction heating is used. It doesn't matter.

[0047]

As described in detail above, according to the present invention, the emissivity can be controlled by simply and inexpensively changing the alloying degree control device used in the conventional plate temperature control. As a result, the degree of alloying of the metal strip can be captured with higher accuracy, and a stable alloying treatment can be performed.
Further, the coordinated control of the plate temperature control and the emissivity control prevents the control system from running out of control even when the emissivity suddenly changes, so that a safer alloying process can be performed. Therefore, product quality and manufacturing yield are improved, and
The operating conditions according to the product type can be changed with good reproducibility, and the productivity can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention.

FIG. 2 is a graph showing an example of an override table 39 in FIG.

FIG. 3 is a graph showing changes in plate temperature and emissivity of a metal strip with respect to heating time of the metal strip.

[Explanation of symbols]

 10 Metal Band 11 Plating Bath 12 Molten Metal 13 Sink Roll 14 Wiping Device 15 Heating Zone 20 Measurement Wavelength Switch 21 Automatic Judgment Unit 22 Control Mode Switch 30 Radiation Thermometer 31 Converter 32, 35, 52a Switch 33 λ1 Emissivity Setting Part 34 λ2 emissivity setting part 36 emissivity controller 37 plate temperature setting part 38 plate temperature controller 39 override table 40a-40d, 41a-41d load distribution table 50a furnace temperature setting part 51a furnace temperature controller 53a low select part 54a Fuel controller 55a Flow meter 56a Flow control valve 57a Air controller 58a Flow meter 59a Flow control valve 60a-60d Burner 61a-61d Furnace thermometer

Front page continuation (72) Inventor Katsuyuki Takezaki 5 Ishizu Nishimachi, Sakai City, Osaka Prefecture Sakai Works, Nisshin Steel Co., Ltd. (72) Inventor, Kazuhiro Majima 5 Ishizu Nishimachi, Sakai City, Osaka Nisshin Steel Co. In-house (72) Hozumi Akita 1-1-30 Oyodochu, Kita-ku, Osaka-shi, Osaka In-house Toshiba Kansai Branch (72) Inventor Hiroyuki Suzuki 1-1-30 Oyodo-naka, Kita-ku, Osaka, Osaka Toshiba Corporation Kansai branch office

Claims (6)

[Claims] 1. A method of controlling the degree of alloying by heating a metal band having a molten metal adhered to its surface to control the degree of alloying, utilizing the correlation between the alloying degree of the metal band, the emissivity and the surface temperature. Then, a step of measuring the emissivity and a step of comparing the emissivity with a predetermined target emissivity to obtain an emissivity deviation and outputting the deviation as a target heating amount, based on the target heating amount. And a step of controlling the amount of heat applied to the metal band by means of emissivity. 2. A step of measuring a plate temperature of a metal strip, a step of obtaining a plate temperature deviation by comparing the plate temperature with a predetermined target plate temperature, and the plate temperature deviation and the emissivity deviation. The method of controlling the degree of alloying by emissivity according to claim 1, further comprising: 3. The method for controlling the degree of alloying by the emissivity according to claim 1 or 2, further comprising the step of switching the measurement wavelength of the emissivity according to the plate temperature of the metal strip. 4. An alloying degree control device for controlling a degree of alloying by heating a metal zone having a molten metal adhered to a surface thereof, utilizing a correlation between the degree of alloying, emissivity and surface temperature of the metal zone. Then, the emissivity measuring means for measuring the emissivity, the emissivity adjusting means for comparing the emissivity with a predetermined target emissivity to obtain an emissivity deviation, and outputting the deviation as a target heating amount, An emissivity alloying degree control device, comprising: a heating amount control means for controlling the heating amount to the metal strip based on the target heating amount. 5. A plate temperature measuring means for measuring a plate temperature of a metal strip, a plate temperature adjusting means for comparing the plate temperature with a predetermined target plate temperature to obtain a plate temperature deviation, and the plate temperature deviation. The emissivity-based alloying degree control device according to claim 4, further comprising: a target heating amount output means that switches the emissivity deviation for each predetermined condition to output a target heating amount. 6. The emissivity alloying degree control device according to claim 4, further comprising a measurement wavelength switching means for switching the measurement wavelength of the emissivity in accordance with the plate temperature of the metal strip. .