JPH05263209A - Operation method of vertical furnace for galvanizing and its furnace - Google Patents

Abstract

(57) [Summary] [Purpose] Even if the plate width is changed during operation, the furnace opening is kept to the necessary minimum to prevent excess outside air from entering the furnace, and keep the furnace temperature at a specified value. Stabilize product quality. [Structure] A split door 10 is provided integrally with the vertical furnace 6 at the entrance of the steel plate 5 of the vertical furnace 6, and a plate thermometer 12 detects that the plate width of the steel plate 5 has been changed, and a control device By 11, the split door 10 is changed according to the plate width, and the plate temperature is constantly controlled to be a predetermined value. The split door 10 is divided into a plurality in the plate width direction, and the opening area thereof is adjustable in the plate width direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical furnace seal for galvanized steel sheets, and more particularly to a method of operating a vertical furnace for maintaining the plate temperature at a predetermined value even when the width of the plate to be penetrated is changed. And the furnace.

[0002]

2. Description of the Related Art Conventionally, as a galvanized steel sheet, an alloyed hot-dip galvanized steel sheet is known in which a part or the whole of the galvanized layer is an Fe—Zn alloy layer. As shown in FIG. 4, the galvanizing bath 1 is used for such alloying treatment.
A vertical furnace 6 is arranged immediately above the plate, and the zinc on the surface of the steel plate 5 pulled up from the plating tank 1 is drawn by a zinc drawing device 4,
Adjust the zinc adhesion amount. Immediately thereafter, the steel plate 5 is heated in the vertical furnace 6 to diffuse iron into the zinc layer.

[0003]

A long chimney-shaped heating furnace has been used as a vertical furnace for alloying a galvanized steel sheet, but conventional furnaces have problems in terms of energy saving and quality stability. was there. For example, (1) In the conventional furnace, because the furnace inlet and outlet were not sufficiently sealed, a large amount of outside air entered due to the draft of the high temperature gas in the furnace, and the amount of heat required to heat this outside air to the required furnace temperature was It corresponds to about 20% of the heat output (results of actual furnace measurement). In addition, the increase of the furnace temperature is hindered by the invading outside air, which greatly hinders the productivity improvement of the vertical furnace.

(2) In the vertical furnace heating method, the furnace wall is heated by gas heating and the plate is heated by radiation from the furnace wall, and the plate temperature is controlled according to load fluctuation. However, there was a problem that the plate temperature responsiveness was poor. In order to solve such a problem, as to (1), there is a "galvanile furnace" (Japanese Patent Laid-Open No. 60-149759) in which a partition wall is provided in the furnace as a means for reducing the draft of the atmosphere in the furnace. It is disclosed. In this furnace, a) The distance between the steel plate and the partition wall cannot be made very small in consideration of the flapping of the steel plate passing through the furnace, so the draft reduction effect is small.

(A) Once the partition wall is installed, the draft reduction amount is uniquely determined by the combustion amount, so that it is difficult to perform, for example, furnace pressure control and furnace atmosphere O ₂ control. There is such a problem. Regarding (2), it is possible to improve the plate temperature response by changing the heating method to an induction heating method, but there is a problem in terms of cost and the like.

In addition to the methods (1) and (2), there is a method for improving the plate temperature response by applying a static pressure pad near the steel plate discharge port at the upper end of the vertical furnace to control the amount of intruding air. However, this method has a problem in terms of cost because the control method is difficult. In addition, with respect to (2), in order to prevent air from entering the furnace and prevent lowering of the furnace temperature, shutters are arranged on the vertical furnace inlet side and outlet side of the "plated steel strip alloying furnace". There is a problem of poor response in plate temperature control according to load variation, as described later.

The present invention has been proposed to solve the above problems.

[0008]

Means for Solving the Problems The present invention is intended to solve the above-mentioned problems. A Method invention The present invention is a furnace in which a steel sheet is immersed in a galvanizing bath and the galvanized steel sheet is placed directly above the plating bath. It is applied to the operation method of a vertical furnace for zinc plating in which it enters from the lower end, is heated and then discharged from the upper end, and the following method was adopted. That is, it is a method of operating a vertical furnace for zinc plating, characterized in that the opening area of the furnace inlet is changed according to the plate width of the steel sheet to maintain the furnace temperature at a predetermined value.

B Device Invention The present invention relates to a vertical galvanizing furnace in which a steel sheet is dipped in a galvanizing bath, the galvanized steel sheet is introduced from the lower end of a furnace disposed immediately above the galvanizing bath, heated and then discharged from the upper end. And adopted the following technical means. That is, an opening / closing door provided on both sides in the steel plate thickness direction on the lower end side of the furnace and divided into a plurality of parts in the steel plate width direction and having an opening area variable in the width direction, a furnace exit side plate thermometer, and the plate thermometer A vertical furnace for galvanizing, comprising a control device that detects a change in plate width due to a change and opens and closes the opening / closing door according to the plate width.

[0010]

In the present invention, since the opening area of the opening / closing door is changed according to the plate width, useless outside air can be prevented from entering and the temperature inside the furnace can be maintained at a predetermined value.

[0011]

EXAMPLES The constitution of the vertical furnace of the present invention will be explained based on the example shown in FIG. Galvanized steel sheet 5 is galvanized tank 1
Then, the amount of zinc adhered is adjusted to a target value through the sink roll 3 and the zinc squeezing device 4, and then enters the vertical furnace 6. In the vertical furnace 6, the galvanized steel sheet is heated and soaked by the direct flame burner 7 to perform a predetermined alloying treatment. Split type door 10
Is installed at the steel plate entrance at the lower end of the vertical furnace in an integrated structure with the alloying furnace, and adjusts the opening degree of the divided box-shaped heat insulating material according to the width of the steel plate. By appropriately adjusting the opening area of the vertical furnace inlet, it is possible to suppress the inflow of invading outside air from the lower part of the furnace and the draft in the furnace. In addition, 8 is a heating zone and 9 is a soaking zone.

FIG. 2 shows an explanatory view of the operation of the present invention. Figure 2
(A) is explanatory drawing of the cross section of the split door 10, and FIG.2 (b) is a sectional view on the AA arrow of FIG.2 (a). Reference numeral 5 denotes a vertically running steel plate, 10 denotes a split door which is close to the steel plate 5 and is integrally formed with the alloying furnace, and 13 denotes a flow of outside air rising from the lower part of the furnace. This flow of outside air is blocked by the split door 10 from entering, thus strengthening the furnace seal and controlling the amount of entering outside air.

During operation of the vertical furnace, the inflowing outside air amount is adjusted in order to control the vertical furnace outlet side plate temperature to a target value by the vertical furnace outlet side plate thermometer 12 and the plate temperature control device 11 installed on the furnace outlet side. It is possible to control the temperature of the vertical furnace outlet plate with good responsiveness. Fig. 5 shows the effect when used in actual operation. In this embodiment, the line speed is 80 m / min and the plate width is 12
When the plate width was changed to 1000 mm during the operation under the condition of 00 mm, the plate temperature deviation in the prior art was 122 seconds, but according to the present invention, the split door at the lower part of the vertical furnace is changed to the plate width. By closing according to (1200 mm → 1000 mm), the plate temperature deviation was shortened to 27 seconds.

[0014]

According to the present invention, since the plate temperature can be quickly controlled in response to load fluctuation, it is possible to achieve excellent effects of energy saving and stable product quality.

[Brief description of drawings]

FIG. 1 is a structural explanatory view of a vertical furnace according to the present invention.

2A and 2B are explanatory views of an opening / closing door, FIG. 2A is a vertical sectional view, and FIG. 2B is a sectional view taken along the line AA of FIG. 2A.

FIG. 3 is a graph showing the effect of the present invention.

FIG. 4 is an explanatory diagram of a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Galvanizing tank 2 Hot-dip zinc 3 Sink roll 4 Zinc squeezing device 5 Galvanizing steel plate 6 Vertical furnace 7 Direct-fired burner 8 Alloying furnace heating zone 9 Alloying furnace soaking 10 Split door 11 Plate temperature control device 12 Vertical Type furnace exit side plate thermometer 13 Flow of outside air

Front page continued (72) Inventor Hiroshi Tsunekawa 1 Kawasaki-cho, Chiba City Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Inventor Katsunori Akiyoshi 1 Kawasaki-machi Chiba City Kawasaki Steel Co., Ltd. Chiba Steel Works (72) Invention Nobu Arai No. 1 Kawasaki-cho, Chiba City Chiba Steel Works, Kawasaki Steel Corporation

Claims (2)

[Claims] 1. A steel plate is dipped in a galvanizing bath, and the plated steel plate is introduced from the lower end of a furnace arranged directly above the plating bath,
A method of operating a vertical furnace for zinc plating that is heated and then discharged from the upper end, characterized in that the opening area of the furnace inlet is changed according to the plate width of the steel plate to maintain the furnace temperature at a predetermined value. Vertical furnace operation method. 2. A steel sheet is dipped in a galvanizing bath, the plated steel sheet is introduced from the lower end of a furnace arranged directly above the plating bath,
In a vertical galvanizing furnace that is heated and then discharged from the upper end, an opening and closing door that is provided on both sides of the lower end of the furnace in the thickness direction of the steel plate, is divided into multiple parts in the width direction of the steel plate, and the opening area is variable in the width direction A vertical furnace for zinc plating, comprising: a furnace exit side plate thermometer; and a control device for detecting a change in the plate width by a change in the plate thermometer and opening / closing the opening / closing door according to the plate width. ..