JPH04358052A - Method for finding cause of uneven sticking in galvanizing - Google Patents

Abstract

PURPOSE:To obtain uniform sticking of a galvanized film by finding the cause of uneven sticking of plating on a steel sheet applying galvanizing. CONSTITUTION:The uneven sticking of plating on the steel sheet 4 to be plated is measured and outputted at the outlet side part of a zinc pot 1. This output signal is converted in frequency and by comparing the waving form of this frequency with the frequency in the other plating attached device, the cause of uneven sticking in galvanizing is specified and where the cause of uneven sticking in galvanizing is present is found and the cause is fed-back to realize the uniform sticking of plating film at all times.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for determining the cause of uneven zinc adhesion, which is mainly observed when the hot-dip galvanizing process progresses irregularly, especially during the production of hot-dip galvanized steel sheets used as steel sheets for automobiles. In order to eliminate uneven plating adhesion, we will propose a method to find out the cause of its occurrence.

0002

BACKGROUND OF THE INVENTION In hot-dip galvanizing, it is important to ensure uniform adhesion of the plating film. For this reason, the occurrence of uneven zinc adhesion is generally observed on this plating line in order to achieve uniform adhesion. This observation can be made by the operator by looking at the display on a zinc coating meter, by measuring the fluttering of the plate in the gas wiping section with a non-contact displacement meter, and by looking at the display. The occurrence of uneven adhesion is detected by directly visually observing the vibrations, or so-called flapping, of the threaded material using a camera installed nearby.

[0003] Conventional techniques for preventing uneven zinc adhesion are as follows:
This is a control method based on the observation results described above. for example,
JP-A-58-3959 and JP-A-2-62355
This is the method disclosed in the publication No. These conventional technologies use a displacement meter or a distance sensor to detect the vibration (flapping) of the threaded material at the gas wiping part of the strip, and directly control the wiping pressure from the output signal, or directly control the wiping pressure using a magnet. It is known as a method for controlling flapping.

[0004] Also, Japanese Patent Publication No. 58-27343, Japanese Patent Application Laid-Open No. 57-5853, and Japanese Patent Application Laid-Open No. 61-14357
As disclosed in Publication No. 3 and Japanese Unexamined Patent Publication No. 1-92349, a plating coating weight meter is used, the signal is directly fed back as a control signal, and the tension is applied by a magnet in the width direction of the strip. There are also known methods of controlling wiping pressure, flow rate, nozzle position, etc.

[0005]

[Problems to be Solved by the Invention] However, each of the above-mentioned prior art methods detects the "flapping" of the threaded material using a displacement meter and directly controls it using the signal. Since these methods directly control the output obtained using a plating coating weight meter, the degree of flapping and uneven adhesion can be determined by these methods, but it is difficult to determine the cause of the flapping and uneven adhesion. The problem was that it could not be done. Therefore, there was a problem in that it was not possible to formulate important measures to specifically control and prevent flapping and uneven plating adhesion.

An object of the present invention is to solve the above-mentioned problems of the prior art, to accurately identify the cause of uneven plating adhesion, and to promptly apply effective means for preventing it to achieve uniform plating. There is a particular thing.

[0007]

[Means for Solving the Problems] As a result of intensive research into means for achieving the above object, the present invention measures the amount of zinc plating deposited on the steel sheet to be plated at the outlet side of the zinc pot, and provides an analog By converting the output into a frequency, analyzing the waveform, and searching for plating equipment that has the same waveform, the cause of the uneven zinc adhesion was determined.

[0008] According to such a method, the cause of the uneven adhesion can be clearly identified, so that the cause can be immediately removed. Therefore, uneven adhesion of zinc plating can be fundamentally eliminated, and uniform adhesion of the zinc plating film can be achieved.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the method of the present invention, and is a system configuration diagram incorporating a logic for determining adhesion unevenness. FIG. 2 is a diagram showing the equipment configuration around the molten zinc pot and the installation method of the displacement sensor. The illustrated reference numeral 1 is a zinc pot, and molten zinc 2 is stored in this pot. In the figure, numeral 3 indicates a sink roll, and numeral 4 indicates a steel plate to be plated, and the steel plate to be plated is passed through a heat treatment furnace, etc., and passed through a snout 5 to be introduced into the bath. The steel plate to be plated passes through a sink roll 3, a pair of front and rear bath support rolls 6 and 7, and is wiped on the bath surface by a pair of front and rear gas wipers 8a and 8b. Thereafter, it passes through a pair of front and rear support rolls 10 and 11 on the bath to reach an alloying furnace 12, where it is subjected to alloying treatment, and then transported out via rollers 13 and 14.

[0010] Furthermore, this plating apparatus is provided with a zinc adhesion meter 9 facing the steel plate to be plated downstream of the rollers 13 and 14, so that the amount of molten zinc adhering to the steel plate can be measured online. can be measured at any time.

The measurement output signal from the zinc coating amount meter 9 is transmitted to an amplifier 1 for the zinc coating amount meter, as shown in FIG.
5 and outputs it as an analog signal, and the analog signal is frequency-converted via a fast Fourier transformer 16 and subjected to a determination described later. That is, after the measurement output is converted into a frequency, the result is sent to the CPU 17.
The CPU 17 analyzes the waveform to determine the cause of uneven adhesion. Moreover, this analysis result is output to the alarm device 18, CRT 19, printer 20, etc. connected to the CPU 17.

3 and 5, the thickness is 0.9 mm,
This shows the uneven coating on the steel plate to be plated when an automotive steel plate with a width of 1800 mm is passed through a hot-dip galvanizing line at a line speed of 150 mpm. This is the output waveform. Note that the waveform shown in FIG. 3 is the waveform when uneven adhesion occurs, and the waveform shown in FIG. 5 is the waveform when normal. 4 and 6 show the results of frequency analysis of the above two waveforms, respectively. From Fig. 4, it was found that the plated steel sheet had a frequency of 3.5Hz.

[0013] Therefore, when we investigated the frequency of each of the incidental equipment around the zinc pot 1, we found that the frequency of the sink roll 3 was 1.
3Hz, the frequency of the bath support roll (front) 6 is 3
．． 5Hz, the frequency of the bath support roll (rear surface) is 4
．． It was found that the bath support roll (front) rotated at a frequency of 2 Hz, the bath support roll (front) 10 rotated at a frequency of 5.1 Hz, and the bath support roll (rear) 11 rotated at a frequency of 5.1 Hz.

From this, the CPU 17 compares the waveform conversion output due to uneven zinc adhesion on the steel sheet to be plated and the frequencies of each of the incidental equipment, and in this example, the in-bath support roll (front) 6 It was found that uneven zinc adhesion was caused by rotational vibration.

Therefore, on the day when the plating line was stopped, the bath support roll (front) 6 was removed from the zinc pot 1 and examined, and it was found that the bath support roll 6 was slightly eccentric, so this roll was replaced. When zinc plating was subsequently performed, the state returned to normal as shown in FIG.

[0016] Although this example has been explained as an example of galvanizing a steel plate, it can also be applied to various plating lines such as aluminum plating and tin plating.

[0017]

[Effects of the Invention] As explained above, according to the present invention, the amount of zinc deposited on the steel sheet to be plated is measured at the outlet side of the zinc pot, and the measurement output is subjected to frequency analysis. Therefore, the cause of uneven zinc plating adhesion can be clearly determined. Therefore, the cause of uneven plating adhesion can be fundamentally removed.
Uniform adhesion of the plating film can be achieved at all times.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a system for determining the cause of uneven zinc adhesion according to the present invention.

FIG. 2 is a plating line configuration diagram showing the installation status of a zinc coating meter.

FIG. 3 is a graph when the unevenness of plating adhesion to the steel plate to be plated is large.

FIG. 4 is a frequency analysis diagram of the waveform of FIG. 3;

FIG. 5 is a graph when there is little unevenness in adhesion to the steel plate to be plated.

FIG. 6 is a frequency analysis diagram of the waveform of FIG. 5;

[Explanation of symbols]

1 Zinc pot
16 Fourier transformer 2 Molten zinc
17 CPU 3 Synchronization
18 Alarm 4 Steel plate
19 CRT 5 Snout
20 Printer 6 Bath support roll (front) 7 Bath support roll (rear) 8a Gas wiper (front) 8b Gas wiper (rear) 9 Zinc coating meter 10 Bath support roll (front) 11 Bath support roll (rear) ) 12 Alloying furnace 15 Zinc deposition meter amplifier

Claims (1)

[Claims] [Claim 1] By measuring the amount of zinc plating on the steel plate to be plated at the outlet side of the zinc pot in the hot-dip galvanizing line, converting the output of the measured value into a frequency and analyzing the waveform, A method for determining the cause of uneven zinc plating adhesion, characterized by determining the cause of uneven zinc adhesion.