JPH07150398A - Spark flaw detector - Google Patents

Abstract

PURPOSE:To suppress erroneous detection to a lower level than heretofore and to improve the accuracy of spark flaw detection. CONSTITUTION:This spark flaw detector is composed of a current detector 6 constituting a current detecting means, a voltage detector 7 constituting a voltage detecting means and a controller 8. The changes in current values and voltage values are continuously determined by each of prescribed time interval units. The presence or absence of the generation of spark flaws is detected by making judgment that the current values change to a positive value and that the voltage values change to a negative value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark flaw detection device for detecting spark flaws generated in a steel plate, equipment or the like due to short-circuiting of both electrodes during electroplating.
In particular, the present invention relates to a spark flaw detection device suitable for an electroplating line that continuously performs electroplating such as galvanizing or alloy plating on a steel sheet surface.

[0002]

2. Description of the Related Art An electroplating line is disclosed, for example, in Japanese Unexamined Patent Publication No.
As described in Japanese Patent Publication No. 191400 and the like, a steel sheet continuously conveyed from the left side to the right side is sandwiched between a pair of upper and lower energizing rolls and a backup roll, and on both upper and lower surfaces of the steel sheet, respectively. A plate-shaped upper electrode and a lower electrode are arranged to face each other with a predetermined interval.

Further, one end of the AC power supply is connected to each energizing roll, and the other end is connected to the upper and lower electrodes via a rectifying circuit. In the vicinity of the upper and lower electrodes, a plurality of nozzles capable of ejecting the plating solution toward the surface of the steel plate are arranged, and a plating solution tank for collecting the plating solution is arranged below the steel plate. ing.

By energizing between the energizing roll and the upper and lower electrodes, a plating layer deposited on the upper and lower surfaces of the steel sheet which is continuously conveyed is formed, and the thickness of the plating layer is successively increased with the conveyance. . The electric power consumed in the electroplating line is, in addition to the electric power consumed in the plating reaction itself, a considerable proportion of the electric power consumed as Joule heat due to the electric resistance between the electrode and the steel plate.

For this reason, in recent years, there has been a tendency to set a small gap between the electrode and the steel sheet as an energy saving measure in the electroplating line, and a spark flaw caused by a short circuit between the electrode and the steel sheet has become a problem. As a conventional device for detecting the occurrence of such a spark flaw, for example, there is one described in JP-A-4-191400.

This utilizes the fact that when the electrode and the steel plate are short-circuited, a large amount of current temporarily flows and spark flaws occur, and the amount of current flowing between the electrode and the energizing roll is detected by the current detecting means. , While converting the detected current value into a digital value in a predetermined interval unit, while obtaining the difference between the previous value and the current value in the digital value, when the absolute value of the difference value exceeds a predetermined threshold value, We have determined that spark defects have occurred.

[0007]

However, in the above-described spark flaw detection device, when noise is input due to changes in the width of the steel plate, the weight per unit area, etc., or changes in the transport speed of the steel plate, the electrodes and the power supply are turned on. The amount of current flowing between the rolls may change, and it may be erroneously detected as the occurrence of spark defects. Also,
The plating voltage temporarily rises due to the vibration of the steel plate,
It may be erroneously detected as a spark defect.

In order to avoid the erroneous detection, there is no choice but to raise the threshold value. However, if the threshold value is raised, there is a possibility that the spark flaw may not be detected in many cases.
The present invention has been made in view of the above problems, and an object thereof is to suppress erroneous detection more than before and improve the accuracy of spark flaw detection.

[0009]

In order to achieve the above-mentioned object, a spark flaw detecting device is provided with an electrode connected to one pole of a power source and arranged opposite to a steel plate surface with a predetermined gap, and to the other pole. Equipped with an electroplating line having an energizing roll in contact with the steel plate, in a spark flaw detection device for detecting the occurrence of spark flaws, a current detecting means for detecting a current value between the electrode and the energizing roll, It is connected to the voltage detecting means for detecting the voltage value between the electrode and the energizing roll, the current detecting means and the voltage detecting means, and is detected based on the signals from the current detecting means and the voltage detecting means. When the current value changes in the positive direction to a predetermined threshold value or more and at the same time the detected voltage value changes in the negative direction to a predetermined threshold value or more, the controller determines that a spark defect has occurred. There.

[0010]

[Function] As a result of investigating the current value and the voltage value between the electrode and the energizing roll when the spark flaw occurs, only when the current value changes in the positive direction and the voltage value changes in the negative direction at the same time, It was confirmed that Based on this result, while detecting the current value and the voltage value between the electrode and the energizing roll, the detected current value changes in the positive direction to the predetermined threshold value or more, and at the same time, the voltage value in the negative direction becomes the predetermined threshold value or more. When it changed, it was judged that spark flaw had occurred.

[0011]

Embodiments of the present invention will be described with reference to the drawings.
First, the structure of the electroplating line will be described. As shown in FIG. 1, a steel plate 1 continuously supplied from the left side to the right side in the drawing is provided with a pair of upper and lower energizing rolls 2 and a backup roll 3 from above and below. It is sandwiched. Further, plate-shaped upper electrodes 4 and lower electrodes 4 are arranged to face each other on the upper and lower surfaces of the steel plate 1 at predetermined intervals in the vertical direction.

Further, one end 5a of the power source 5 is connected to each energizing roll 2
And the other end 5b is connected to the upper and lower electrodes 4. In FIG. 1, only one set of the spark flaw detection device and the electroplating device portion is shown. In addition, a plurality of nozzles (not shown) for ejecting the plating solution from the vicinity of the upper and lower electrodes 4 toward the surface of the steel plate 1 are arranged, and below the steel plate 1, a solution tank (not shown) for collecting the plating solution. Is provided.

A plurality of the electroplating devices as described above are arranged along the line, and by energizing between the respective energizing rolls 2 and the upper and lower electrodes 4, the upper and lower surfaces of the steel sheet 1 continuously supplied. The deposited plating layer is formed, and the thickness of the plating layer increases as it moves to the right. A spark flaw detection device is installed for each of the electroplating devices.

The spark flaw detecting device is composed of a current detector 6 constituting a current detecting means, a voltage detector 7 constituting a voltage detector 7, and a controller 8. The current detector 6 is interposed between the other terminal of the power supply 5 and the electrode 4, and can supply the detected current value to the controller 8. The voltage detector 7 is also capable of detecting the voltage value between the energizing roll 2 and the electrode 4 and supplying the detected voltage value to the controller 8.

As shown in FIG. 2, the controller 8 inputs a current value from the current detector 6 and temporarily stores the current value, and at the same time, stores the difference value ΔI from the previously stored current value. Ask for. At the same time, the voltage value is input from the voltage detector 7, the voltage value is temporarily stored, and the difference value ΔV from the previously stored voltage value is obtained (steps 1 and 2).

Next, the difference value ΔI of the calculated current value
Is compared with a preset positive threshold I _0, and the threshold I
_{If 0} or less, it is determined to be normal, and the process returns to the difference value calculation process (step 3). If the difference value ΔI of the current value is larger than the threshold value I ₀ , the difference value Δ of the calculated voltage value Δ
V is compared with a preset positive threshold value V _0, and if it is less than or equal to the threshold value V ₀ , it is determined to be normal, and the process returns to the difference value calculation process (step 4).

If the difference value ΔV of the voltage values is larger than the threshold value V ₀ , it is judged that a spark flaw has occurred, and the controller 8
Outputs a spark flaw detection signal (step 5). In such a spark flaw detecting device, for the steel sheet 1 which is continuously conveyed, the change of the current value and the voltage value is continuously obtained for each predetermined time interval unit, and the current value changes positively and the voltage value changes. The presence or absence of spark flaws is detected by determining that has changed to a negative value.

When it is determined that the spark flaw has occurred, the controller 8 supplies a spark flaw detection signal to the controller of the electroplating line (not shown) and the abnormality display device. For example, as shown in FIG. 3, each time T1 to T
Even if the current value and the voltage value fluctuate up to 5, the spark flaws are not generated at the time of T1 or T2, which was conventionally erroneously detected, only at the time T5 when the spark flaws are actually generated. To judge.

As described above, in the spark flaw detecting apparatus of the present embodiment, not only the change in the current value in the positive direction but also the change in the voltage value in the negative direction are detected and judged. Therefore, the accuracy of the spark flaw detection is high. It becomes higher, and defects in the steel plate and damage to the electrodes can be suppressed more than before.

[0020]

As described above, the spark flaw detection device of the present invention has the effect of improving the accuracy of spark flaw detection as compared with the prior art.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an electroplating line and a spark flaw detection device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a processing procedure of a controller according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of changes in current value and voltage value according to the embodiment of the present invention.

[Explanation of symbols]

 1 Steel Plate 2 Energizing Roll 4 Electrode 5 Power Supply 6 Current Detector 7 Voltage Detector 8 Controller

Claims (1)

[Claims] 1. An electroplating line equipped with an electrode connected to one pole of a power source and opposed to the surface of a steel sheet with a predetermined gap, and an energizing roll connected to the other pole and in contact with the steel sheet. In the spark flaw detection device for detecting the occurrence of spark flaws, current detection means for detecting a current value between the electrode and the energizing roll, voltage detection means for detecting a voltage value between the electrode and the energizing roll, and A voltage value which is connected to the current detecting means and the voltage detecting means, and at the same time the detected current value changes in the positive direction by a predetermined threshold value or more based on the signals from the current detecting means and the voltage detecting means. A spark flaw detection device comprising: a controller that determines that spark flaws have occurred when changes in a negative direction to a predetermined threshold value or more.