JPH0448058A - Spangle control method for galvanized steel sheet - Google Patents

Abstract

PURPOSE:To assure rapid spangle control even if the temp. change of a steel sheet is large by executing the temp. control of the Zn layers of the steel sheet and the feed forward control of the position control of a treating device for fining spangles in accordance with the temp. of the steel sheet before immersion into a molten Zn bath and material information. CONSTITUTION:IR radiation thermometers 11, 12 are disposed on the respective upper sides of an oxygen free furnace 2 and the above-mentioned treating device 10. The respective temps. of the Zn layers of the above-mentioned steel sheet 1 and the plated steel sheet 6 are inputted via image processors 14, 13 to an arithmetic control unit 21. The position of the treating device 10 having a liquid chemical spraying nozzle 9 moved vertically by a motor M is inputted by the pulse of a pulse generator PG installed to the motor M to the above-mentioned control unit 21. The unit 21 controls the heating quantity with a burner box 7, the cooling quantity with a cooler box 8, the lifting position of the above- mentioned treating device 10, and the liquid chemical spraying rate in this position, thereby controlling the spangles.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a spangle control method for reducing the so-called spangle spots that appear on the surface of hot-dip galvanized products, particularly hot-dip galvanized steel sheets.

[Conventional technology]

Spangles have a pattern based on zinc crystals, but if these become coarse, the luster of the product deteriorates, and if stored for a long time, the surface changes and loses its commercial value, so in recent years zero spangles, In addition, there is a strong demand for products with finer crystal patterns called minimum spangles.

It is known that the state of spangle formation is closely related to the cooling rate of the molten zinc layer after molten galvanizing, and in order to obtain a product with fine spangles and gloss, the cooling rate of the molten zinc layer must be adjusted. Must be precisely controlled.

The molten zinc layer on the surface of the steel sheet immediately after plating is cooled by injecting a cooling medium such as air, water, or an aqueous solution for promoting solidification onto the molten zinc layer. However, the temperature of the molten zinc layer on the surface of the steel sheet being pulled out of the molten zinc bath changes in the width direction of the steel sheet, and accurate cooling cannot be achieved by simply spraying the cooling medium uniformly from nozzles arranged in a row in the width direction of the steel sheet. Speed control is not possible.

As a countermeasure to this problem, in order to eliminate the deviation in temperature distribution in the width direction of the molten zinc layer attached to the steel plate, for example, there is a method of reheating both ends of the steel plate (Japanese Patent Application Laid-Open No. 4884038).
, or a method of changing the arrangement of refrigerant injection nozzles according to the temperature distribution of the molten zinc layer (Japanese Patent Laid-Open No. 15885-1985)
Publication No. 9) etc. have been proposed.

However, the method of simply reheating not only increases the energy cost, but also leads to abnormal development of the alloy layer and the risk of poor adhesion of the galvanized layer.Also, the method of changing the nozzle arrangement does not change the nozzle position. Due to the difference in height, the water head pressure between the nozzles fluctuates, posing the problem that the water head pressure must be adjusted as well as the amount of water.

Therefore, the present inventors invented the apparatus shown in FIG. 3 (Japanese Patent Application No. 1-120066). In the figure, reference numeral 1 denotes a strip of, for example, a cold-rolled steel plate, and the strip L is conveyed in the direction of the arrow, immersed in a molten zinc bath 3, turned over by a zinc roll 4, and left as a plating strip 6 from the molten zinc bath 3. It is pulled up in the vertical direction, and gas is injected by a wiping nozzle 5 placed facing the pulling path to adjust the plating thickness. The temperature of the molten zinc layer on the surface of the plating strip 6 is controlled by a burner box 7 and a cooler box 8, and a chemical solution is sprayed from a chemical spray nozzle 9 disposed in the atomization processing apparatus IO in a spangle atomization processing bag N10. , coagulated.

In burner box 7, flow from LPG tank 18fflf
LPG is supplied to the burner via the fl control valve 17. In the cooler box 8, the flow rate control valve 16 is connected to the air tank 19.
Air is supplied to the air nozzle via. In the atomization processing apparatus 10 , a chemical liquid is supplied from a chemical liquid tank 20 to a chemical liquid spray nozzle 9 via a flow rate control valve 15 .

The opening degrees of the flow control valves 15, 16 and 17 described above are controlled by the arithmetic and control unit 21.

The refining treatment device 10 is configured to be able to move up and down along the conveyance direction of the steel plate by a motor M, and a pulse generator PG attached to the motor M generates pulses while the refining treatment device IO moves. The arithmetic and control device 21 controls the rotation amount of the motor M to control the position of the micronization processing device 10.

Infrared radiation thermometers 12 and 32 are arranged on the upper and lower sides of the miniaturization processing apparatus 10, respectively. Infrared radiation thermometer 1
2.32 is configured to detect the two-dimensional temperature distribution by capturing the zinc layer of the Menki strip 6 within its field of view over its entire width and a predetermined length in the conveying direction, and converts the temperature of each part of the zinc layer into an electrical signal. They are converted and output to image processing devices 13 and 33, respectively.

The image processing device 13.33 performs image processing on the input signal and outputs it to the arithmetic and control device 21.

In the conventional device configured as described above, the infrared radiation thermometer 1
2 and 32 measure the temperature of the zinc layer of the plated strip 6, adjust the LPG flow rate in the burner box 7 so that the temperature of the zinc layer of the plated strip 6 is uniform in the width direction, and adjust the air flow rate in the cooler box 8. At the same time as adjusting the flow rate, the solidification position of the zinc layer of the Menki strip 6 is determined, and the atomization processing device 10 is controlled to be located upstream of the solidification position, and the zinc layer is cooled at that position to generate spangles. is suppressed.

In addition, as another spangle control method, JP-A-1-3065
There is an invention disclosed in Publication No. 47. This is a method to suppress spangles by spraying zinc powder on the surface of the galvanized steel strip immediately after plating.The temperature distribution in the width direction of the steel strip before and after the zinc powder spraying device is measured, and from this This method involves calculating the position where the temperature is slightly higher than the solidification temperature of zinc over the entire width, and moving the zinc powder spraying device to this position.

[Problem to be solved by the invention]

However, when the temperature change in the longitudinal direction of the steel plates is large, such as when different steel plates are connected by a seam, the invention of Japanese Patent Application No. 1-120066 also
The invention disclosed in Japanese Patent No. 306547 also had a problem in that the response to the position control of the atomization treatment device or the zinc powder spraying device was delayed.

The present invention has been made in view of the above circumstances, and its purpose is to ensure control of spangles in the longitudinal direction of the steel plate even when the temperature change of the steel plate is large by performing feedforward control on galvanized steel sheets. To provide a spangle control method.

[Failure to solve the problem]

A first aspect of the spangle control method for a galvanized steel sheet according to the present invention is to control the temperature of a zinc layer formed on the surface of a steel sheet immersed in a molten zinc bath and pulled up, and to control the temperature of a zinc layer formed on the surface of a steel sheet immersed in a molten zinc bath and pulled up. In the method of controlling the spangles of a galvanized steel sheet by controlling the position of a refining treatment device which is movably installed in the zinc layer and refines the spangles by cooling the zinc layer, the steel sheet before being immersed in a molten zinc bath. Feedforward control of the temperature control of the zinc layer and the position control of the refinement processing device is performed based on the temperature and material information of the steel plate.

The second invention of the spangle control method for galvanized steel sheets according to the present invention is based on the feedforward control of the first invention and the temperature on the downstream side of the steel sheet transport direction of the refining processing equipment, so that the zinc layer on the upstream side of the refining processing equipment is It is characterized by a combination of temperature control and feed-hack control that controls the position of the miniaturization processing device.

[Effect]

In the first aspect of the present invention, when controlling the spangle of a galvanized steel sheet in a refining treatment device, the position at which the solidification of the zinc layer is completed is predicted and calculated based on empirical rules based on the temperature and material information of the steel sheet before immersion in a molten zinc bath. Since the temperature control of the zinc layer on the upstream side of the refinement treatment device and the feedforward control of the position control of the refinement treatment device are carried out, it is possible to respond quickly even when the temperature of the steel plate changes rapidly.

In addition, in the second aspect of the present invention, when controlling the spangles of the galvanized steel sheet in the spangle refinement processing device, both feedforward control and feedback control are performed, so the control of the spangles in the longitudinal direction of the steel sheet is more ensured. be done.

〔Example〕

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The spangle control method for galvanized steel sheets according to the present invention will be specifically described below with reference to the drawings.

In the figure, 1 is a strip of cold-rolled steel plate, for example, and the strip 1 is conveyed in the direction of the arrow in the non-oxidizing furnace 2, immersed in a molten zinc bath 3, and placed in a zinc roll provided in the molten zinc bath 3. 4, and is vertically pulled up from the molten zinc bath 3 as a coating strip 6, and gas is injected by a wiping nozzle 5 arranged facing the pulling path to adjust the plating thickness. The temperature of the molten zinc layer on the surface of the plating strip 6 is controlled by a burner box 7 and a tara box 8, and a chemical solution is sprayed from a chemical spray nozzle 9 disposed in the spangle refinement processing device 10. , coagulated.

In the burner box 7 , LPG is supplied from the LPG tank 18 to the burner via the flow control valve 17 . In the Tarabonox 8, air is supplied from the air tank 19 to the air nozzle via the flow ff18m control valve 16. In the atomization processing apparatus 10 , a chemical liquid is supplied from a chemical liquid tank 20 to a chemical liquid spray nozzle 9 via a flow rate control valve 15 .

The opening degrees of the flow control valves 15, 16 and 17 described above are controlled by the arithmetic and control unit 21.

The refining processing device 10 is configured to be able to move up and down along the conveyance direction of the steel plate by a motor M, and a pulse generator PG attached to the motor M outputs pulses to the arithmetic and control device 21. The arithmetic and control unit 21 is a motor M.
The position of the micronization processing apparatus 10 is controlled by controlling the amount of rotation of the micronization processing apparatus 10 .

On the upper side of the non-oxidation furnace 2 and on the upper side of the refining treatment equipment 10,
Infrared radiation thermometers 11 and 12 are respectively arranged. Infrared radiation thermometer 11.12 is Metsu;)-su] Lip 6
The image processing device 14. is configured to detect the two-dimensional temperature distribution by capturing the zinc layer over its entire width and a predetermined length in the conveying direction within the field of view, converting the temperature of each part of the zinc layer into an electrical signal and transmitting it to the image processing device 14. 13 respectively. Image processing device 14
．． 13 performs image processing on the input signal and outputs it to the arithmetic and control unit 21 .

In the embodiment of the present invention, as will be described later, in accordance with the results of measuring the surface temperature of the strip 1 using an infrared radiation thermometer 11 and measuring the temperature of the solidified zinc layer of the Menki strip 6 using an infrared radiation thermometer 12, Spangles are controlled by controlling the amount of heating, the amount of cooling in the cooler box 8, the position of the spangle atomization processing device 10, and the amount of chemical liquid sprayed at that position.

Normally, steel plates have a mountain-shaped temperature distribution where the temperature is high in the center of the copper plate and decreases towards both sides due to the difference in cooling efficiency between the widthwise central part and the edge parts at both ends. Temperature measurement by the radiation thermometer 11 and infrared radiation thermometer 12, and control of the amount of heating in the Harnabosox 7, the amount of cooling in the cooler box 8, and the amount of chemical spray in the spangle refinement processing device 10 are performed in zones divided into three in the width direction of the steel plate. I'm doing it separately.

FIG. 2 is a flowchart showing the process of controlling spangles appearing on the surface of a galvanized copper plate.

First, the non-oxidation furnace 2 is measured using an infrared radiation thermometer 11.
It is determined whether the temperature change on the surface of the strip 1 within is equal to or greater than a threshold value (step Sl). If the temperature change on the surface of the strip 1 is equal to or higher than the threshold value, the strip l measured by the infrared radiation thermometer 11 as current control data.
surface temperature T5, LPG flow 1tFL in Harnabo Sox 7, air flow in cooler box 8! ! F.A.
, the position H of the atomization treatment device 10, the amount of chemical spray Fl in the atomization treatment device 10, the temperature T2 of the solidified zinc layer of the plating strip 6 measured by the infrared radiation thermometer 12, the conveyance speed S of the strip, and the molten zinc bath 3. temperature T3 is taken in (step S2).

Next, the material, plate thickness, plate width, area weight, and target spangle diameter are imported as material information from the process computer 25 (
Step S3). Then, calculations regarding feedforward (FF) control and feedback (FB) control are performed using the information acquired in steps S2 and S3 (step S4). Feedforward system'41■
For feedback control, in order to make the temperature on the downstream side of the atomization processing device 10 a required temperature, and for feedback control, in order to make the temperature on the upstream side of the atomization processing device 10 a required temperature, the flow rate FL of LPG in the Harnabosox 7, Air flow rate FA in cooler box 8, atomization processing device 1
0 position H and the chemical spray amount FC in the atomization processing apparatus 10 are calculated.

Furthermore, the combination ratio of the above-mentioned feedforward control and feedback control is calculated according to the amount of temperature change on the surface of the slip 1 in the non-oxidizing furnace 2 measured by the infrared radiation thermometer 11 (step S5). Then, according to the calculation result in step S5, feedforward control and feedback control are combined to perform spangle control (step S6), and the process returns to step S1.

If the temperature change on the surface of the strip 1 in the non-oxidizing furnace 2 measured by the infrared radiation thermometer 11 in step S1 is less than the threshold value, the LPG flow ffi p L in the Harnavosox 7 and the cooler box 8 are determined as current control data. Air flow IFA, m-fine processing device 10
Chemical spray amount FC, position 1 of the atomization processing device IO at
■ and Menkis measured by infrared radiation thermometer 12)
- Take in the temperature T2 of the solidified zinc layer of Rinpro (step S7).

Then, calculations regarding feedback control are performed (step S8). In order to bring the upstream temperature of the atomization processing device 10 to a required temperature, the flow rate FL of LPG in the Harnabosox 7, the flow rate FA of air in the cooler box 8,
Position I of the microfabrication processing device 10 (and the microfabrication processing device 10
Calculate the chemical spray amount FC in .

Then, according to the calculation result in step S8, the spangle is controlled by performing feedback control (step S8).
9), return to step S1.

In the embodiment according to the present invention configured as above, the temperature of the steel plate in the non-oxidation furnace 2 is measured, so the temperature change of the steel plate is large as when different steel plates are connected at a joint. Even if the flow rate of LPG in the burner box 7 is tH; "L, the flow rate of air in the cooler box 8 is F.
The position I of the A% refinement treatment apparatus 10] and the chemical spray amount Fc in the refinement treatment apparatus IO can be controlled in advance, and control of the spangle in the longitudinal direction of the steel plate is ensured.

In addition, in the embodiment according to the present invention, as described above, the temperature is measured by the infrared radiation thermometers 11 and 12, and the amount of heating in the burner box 7, the amount of cooling in the cooler box 8, and the amount of chemical spray in the atomization processing device 10 are measured. Although the control is performed for each zone divided into three in the width direction of the steel plate, the method of dividing the zones is not limited to this and can be freely selected.

〔effect〕

As described above, in the present invention, the temperature of the steel plate in the non-oxidation furnace is measured, and even when the temperature change of the copper plate is large, such as when different steel plates are connected by a seam, the spangle fineness is measured by feedforward control. The amount of heating in the burner box, the amount of cooling in the cooler box, the amount of cooling in the spangle refining device and the device can be controlled in advance so that the temperature distribution on the downstream side of the chemical processing device becomes the required temperature distribution. The present invention has excellent effects such as being able to quickly control the spangle and ensuring control of the spangle in the longitudinal direction of the steel plate.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an apparatus to which an embodiment of the present invention is applied;
FIG. 2 is a flowchart 1 showing the spangle control process according to the present invention, and FIG. 3 is a schematic diagram of a conventional device. 1...Strip 2...Non-oxidation furnace 3...)8
Zinc bath 5... Wiping nozzle 6... Plating strip 7... Burner box 8... Cooler box 10... Spangle refinement processing device 11.
12... Infrared radiation thermometer 13.14... Image processing device 21... Calculation ηill? ff1l 'tM
'l 25... Process computer patent Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Kawa
No Noboo Diagram / Diagram

Claims (2)

[Claims] 1. It controls the temperature of a zinc layer formed on the surface of a steel plate immersed in a molten zinc bath and pulled up, and is movable downstream from this control area in the steel plate transport direction. A method for controlling the spangles of a galvanized steel sheet by controlling the position of a refining treatment device for refining the spangles, which comprises: controlling the temperature of the zinc layer and controlling the spangles according to the temperature of the steel sheet before immersion in a molten zinc bath and the material information of the steel sheet; 1. A spangle control method for a galvanized steel sheet, characterized by performing feedforward control of position control of a chemical treatment device. 2. Controlling the temperature of the zinc layer on the upstream side of the refinement treatment device by the temperature downstream of the steel plate transfer direction of the refinement treatment device,
2. The spangle control method for a galvanized steel sheet according to claim 1, further comprising performing feedback control to control the position of the refining treatment device.