JP2725512B2 - Method of preventing electric spark generated when steel sheet is heated by edge heater - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing electric spark generated when a steel sheet is heated by an edge heater.

[0002]

2. Description of the Related Art When a steel sheet is hot-rolled, the temperature of the steel sheet needs to be uniform over its width direction. Is larger at the end in the width direction of the steel sheet than at the center of the steel sheet. Therefore, conventionally, in order to equalize the temperature in the sheet width direction of the steel sheet after the rough rolling and before the finish rolling,
As shown in FIG. 3, both ends of the steel sheet 2 in the width direction are locally heated by about 100 mm by induction heating type edge heaters 3 arranged on both sides in the width direction of the steel sheet 2 moving on the conveying roller 1. Was.

[0003]

However, in the case where the both ends in the width direction of the steel plate 2 are locally heated by the induction heating type edge heater 3, there are the following problems. Principle of heating steel sheet by induction heating type edge heater 3
Is as follows. That is, generated by the edge heater 3
When the moving magnetic flux is interrupted by the moving steel plate 2,
An eddy current is generated inside the steel plate 2, and the steel plate 2
The steel plate 2 is heated to have air resistance. Like this
The steel plate 2 is heated, but the eddy current is generated.
In a limited area of the plate, the conveying roller 1 and the steel plate 2
If a potential difference occurs between them and they are in contact,
Happens. Under such circumstances, the concave portion 5 due to local wear is formed on the transport roller 1 (the hatched transport roller in FIG. 3) of the induction heating type edge heater 3 as shown in FIG. When the steel sheet 2 is separated from the conveyance roller 1, a spark is generated between the steel sheet 2 and the conveyance roller 1 due to a leakage current 4 flowing between the steel sheet 2 and the conveyance roller 1 at the moment when the steel sheet 2 is separated from the conveyance roller 1, and a crater-like surface is formed on the surface of the steel sheet 2. There is a possibility that scratches may occur. The flaws formed on the surface of the steel sheet 2 in this way remain even after finish rolling, and significantly impair the commercial value of the rolled coil. Note that the eddy current described above is
Occurs only in the steel plate in a specific area near the
Far enough away, for example, the entry and exit transport rollers 1
In the part, for example, the steel plate 2 and the entrance and exit conveyance rollers 1
Are in electrical contact with each other and no current is generated anymore.
Therefore, no spark phenomenon occurs.

[0004] Therefore, the present invention provides an electric heater which heats a steel sheet when the steel sheet is heated by the edge heater when the widthwise both ends of the steel sheet are locally heated by the induction heating type edge heater and the surface of the steel sheet is free from flaws due to electric spark. It is to provide a spark prevention method.

[0005]

SUMMARY OF THE INVENTION According to the present invention, when a widthwise end portion of a steel sheet moving on a conveyance roller is locally heated by an induction heating type edge heater, the conveyance roller at the edge heater portion and the steel sheet are connected to each other. In a method for preventing electric spark generated between the transport roller of the edge heater portion and the steel plate by a leakage current flowing between the edge heater portion, an entrance-side transport roller capable of ascending and descending is provided on an entrance side of the edge heater, An exit-side transport roller that can move up and down is provided on the exit side of the edge heater, and when the leading end of the steel sheet passes through the exit-side transport roller, the entrance- side transport roller and the exit-side transport roller are raised, and the steel sheet is raised. Lower surface and the edge heater
Part of the conveying roller, and at the time when the rear end of the steel sheet passes through the output side conveying roller, lowers the input side conveying roller and the output side conveying roller, thus,
While heating both ends of the steel sheet in the width direction by the edge heater, the steel sheet and the transport roller of the edge heater are maintained in an electrically non-contact state.

Next, an embodiment of a method for preventing electric spark generated at the time of heating a steel plate by an edge heater according to the present invention will be described with reference to the drawings. FIG. 1 is a side view showing the position of the transport roller when heating the steel sheet by the edge heater in the present invention, and FIG. 2 is a side view showing the position of the transport roller when the heating of the steel sheet by the edge heater is completed in the present invention. It is.

1 and 2, reference numeral 1 denotes a conveying roller for the steel plate 2, 1A denotes an input side conveying roller provided on the input side of an induction heating type edge heater described later, and 1B denotes an output of the edge heater. Delivery rollers provided on the side, 1C to 1E
Denotes a transport roller at the edge heater portion. Both the entrance-side transport roller 1A and the exit-side transport roller 1B are capable of moving up and down. 3 is between the transport rollers 1C and 1D and the transport rollers
An induction heating type edge heater is provided between 1D and 1E on both sides in the width direction of the steel plate 2.

According to the present invention, the electric spark generated between the steel plate and the conveying roller can be prevented as follows. That is, as shown in FIG. 1, at the time when the tip 2A of the steel plate 2 passes through the entrance-side transport roller 1A and passes through the exit-side transport roller 1B , the entrance-side transport roller 1A and the exit-side transport roller 1B are simultaneously raised. . Thereby, the lower surface of the steel plate 2
And the transfer between the input side transfer roller 1A and the output side transfer roller 1B.
Rollers 1C, 1D, and 1E, that is, transport rollers for the edge heater 3
Rollers 1C, 1D, and 1E, and keep them away from each other. Then, as shown in FIG. 2, when the rear end portion 2B of the steel sheet 2 passes through the output side conveyance roller 1B, the input side conveyance roller 1A and the output side conveyance roller 1B are simultaneously lowered, and the lower surface of the steel sheet 2 is inserted. Side transport
Feed roller 1A, outgoing transport roller 1B, and incoming transport roller 1A
Contact the transport rollers 1C, 1D, and 1E between
Touch. As a result, while both ends in the width direction of the steel plate 2 are heated by the edge heater 3, the steel plate 2 and the transport rollers 1C to 1E of the edge heater 3 are maintained in a non-contact state. Therefore, during the heating of the steel sheet 2 at both ends in the width direction by the edge heater 3, no electric spark is generated between the conveying rollers 1C to 1E of the edge heater 3 and the steel sheet 2 due to the leakage current. The tip 2A of the steel plate 2
Passing through the entrance conveyance roller 1A and reaching the exit conveyance roller 1B
Until then, the problems caused by the electric spark phenomenon described above are inevitable.
However, this is negligible when viewed from the overall length of the steel plate 2.
It is. In addition, the rear end 2B of the steel plate 2
After passing through, the rear end 2B of the steel plate 2 hangs down due to its own weight.
Do not come down and contact the transport rollers 1C, 1D, 1E.
No. The reason is that the incoming transport roller 1A and the outgoing transport roller 1B
Is relatively short, and the steel plate 2 is rigid.
Because.

[0009]

As described above, according to the present invention, when the both ends in the width direction of the steel sheet are locally heated by the induction heating type edge heater, the transport rollers on the entrance side and the exit side of the edge heater are used. Has a useful effect of preventing electric spark due to leakage current, which is generated between the steel plate and the conveying roller at the edge heater.

[Brief description of the drawings]

FIG. 1 is a side view showing a position of a transport roller when a steel sheet is heated by an edge heater in the method of the present invention.

FIG. 2 is a side view showing a position of a conveying roller when heating of a steel sheet by an edge heater is completed in the present invention.

FIG. 3 is a plan view showing a transport roller provided with an induction heating type edge heater.

FIG. 4 is a schematic front view showing a flow of a leakage current.

[Explanation of symbols]

 1: Conveying roller, 1A: Incoming side conveying roller, 1B: Outgoing side conveying roller, 1C-1E: Conveying roller of edge heater part, 2: Steel plate, 2A: Front end of steel plate, 2B: Rear end of steel plate, 3 : Edge heater, 4: leakage current, 5: recess.

Claims (1)

(57) [Claims] When a widthwise end of a steel sheet moving on a conveyance roller is locally heated by an induction heating type edge heater, a leakage current flowing between the conveyance roller of the edge heater portion and the steel sheet is used. a method of preventing electrical sparks generated between the conveying roller and the steel sheet of the edge heater portion, the temperature on the entry side of the edge heater
Provide an entrance-side transport roller that can be lowered, and provide an exit-side transport roller that can move up and down on the exit side of the edge heater.When the leading end of the steel plate passes through the exit-side transport roller, the entrance-side transport roller and the Raise the delivery roller and move the steel
Separate the lower surface of the plate and the transport roller of the edge heater.
And, then, lowers the entering-side transport roller and the outlet side conveyance roller when the rear end portion of the steel sheet has passed the exit-side transport roller, thus, the both edges in the width direction of the steel sheet the edge heater A method for preventing an electric spark generated when a steel sheet is heated by an edge heater, wherein the steel sheet and a transport roller of the edge heater portion are kept in non-contact during heating.