JPH059696A - Method and apparatus for manufacturing alloyed molten zinc plated steel sheet - Google Patents

Abstract

(57) [Summary] [Structure] After passing the steel sheet through the molten zinc bath and adjusting the zinc deposition amount, before the entrance of the alloying furnace, the edge roll overcoated part of the steel sheet edge where alloying is insufficient After roughening the surface and increasing the plate surface emissivity of the overcoat portion, alloying treatment is performed in an alloying furnace. [Effect] According to the present invention, alloying of the edge portion of the steel sheet can be effectively promoted, and the alloy can be uniformly alloyed in the sheet width direction. In addition, it is possible to eliminate the drawbacks of the conventional products in which the powdering resistance is deteriorated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an alloyed hot dip galvanized steel sheet by heating and heat-retaining a hot-dip galvanized steel sheet mainly by radiant heat transfer.

[0002]

2. Description of the Related Art Conventionally, when a steel sheet immediately after hot dip galvanizing is heated and retained mainly by radiant heat to produce an alloyed hot dip galvanized steel sheet, the edge portion of the steel sheet tends to be overcoated, There is a problem that alloying of the edge portion does not proceed sufficiently. As a countermeasure against this, conventionally, the operation has been carried out so that the edge portion where the alloying has not progressed the most is within the lower limit of alloying, so that there is a problem that the alloying progresses too much and the powdering resistance is poor.

Therefore, for example, as disclosed in Japanese Patent Laid-Open No. 59-31858, a method has been developed in which a burner dedicated to the edge portion is installed and only the edge portion is heated. However, this method has a drawback that actual control is not easy. Further, although measures have been taken to prevent overcoating of the edge portion, it is difficult to completely flatten it.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing an alloyed hot-dip galvanized steel sheet which solves the above problems.

[0005]

SUMMARY OF THE INVENTION According to the present invention, a steel sheet is passed through a molten zinc bath to adjust the zinc deposition amount, and before an alloying furnace inlet, an overcoat portion of a steel sheet edge where alloying is insufficient. Is a method for producing a galvannealed steel sheet, characterized by performing a roughening process on the surface of, and increasing the plate surface emissivity of the overcoat portion, and then performing an alloying treatment in an alloying furnace. In the middle of the alloying treatment or after the alloying treatment, the alloying distribution in the plate width direction is detected by an alloying degree meter, and roughening is performed based on the detected alloying distribution. is there.

According to the present invention, the steel sheet is passed through a molten zinc bath, the zinc adhesion amount is adjusted by a zinc adhesion amount adjusting device such as gas wiping, and then alloying treatment is performed in an alloying furnace. In an apparatus for producing a coated steel sheet, between the zinc adhesion adjusting device and the alloying furnace, the surface of the overcoat portion of the edge of the steel sheet is roughened to increase the emissivity of the sheet surface. A device for manufacturing an alloyed hot-dip galvanized steel sheet, characterized in that a processed edge roll is disposed, and a device for adjusting a gap and a plate width direction position of the edge roll, and controlling the adjusting device. An alloying degree meter for sending a command and detecting an alloying distribution in the plate width direction is provided.

[0007]

[Operation] The temperature rise of the hot-dip galvanized steel sheet in the alloying furnace is
Radiation-based heating is the main rather than convection of furnace gas. On the other hand, the surface of the hot-dip galvanized steel sheet after the gas wiping exhibits luster, so that the radiant heat is not efficiently absorbed. This is because the higher the plate surface emissivity, the better the heat absorption in the alloying furnace.

Here, the inventors have come to the conclusion that it is possible to improve the absorption of radiant heat by increasing the plate emissivity of the hot-dip galvanized steel sheet after gas wiping, and have made earnest studies. As a result, the following findings were obtained. That is, when a solid such as a roll is brought into contact with the surface of a hot-dip galvanized steel sheet that has not been alloyed after being immersed in a hot-dip zinc bath and the amount of adhesion is adjusted by gas wiping, (roll pushing amount / roll reference It has been found that there is a relationship as shown in FIG. 5 between the amount of indentation) and the (plate surface emissivity after roll reduction / plate surface emissivity before roll reduction).

[0009] Based on this knowledge, if the edge portion of insufficient alloying is rolled down by a solid such as a roll to roughen the surface of the plated steel sheet and raise the plate surface emissivity in advance, the plated steel sheet in an alloying furnace It is possible to raise the temperature of the edge part faster than the other parts, and it is possible to eliminate the insufficient alloying of the edge part.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is an overall configuration diagram of an embodiment of the present invention. Figure 2
3 is a perspective view of a main part of an embodiment of the present invention, FIG. 3 is a side view thereof, and FIG. 4 is a plan view thereof. However, in FIG. 2, the device on the back side is omitted.

1 to 4, 1 is a plated steel plate, 2 is a normal bath support roll, 3 is a normal wiping nozzle, and 4 is a zinc bath. 5 is an alloying furnace, 6 is a heating zone, and 7 is a heat retaining zone. Reference numeral 8 denotes an edge roll, and the roll surface is roughened by shot blasting, electrolytic method or the like.

Only the portion (edge portion) of the plated steel sheet 1 that the edge roll 8 has rolled down has its surface changed to a rough surface and the heat absorption rate is improved. As a result, the amount of temperature rise in the heating zone becomes large, and alloying easily proceeds. In addition, edge roll 8
The shafts 8a and 8b of the edge roll 8 are preferably internally cooled. Further, in this embodiment, the left and right edge rolls 8, 8 are connected by the shaft 8b, but not by the shaft 8b,
It may be cantilevered. Further, in this embodiment, the edge roll 8
Is driven without being driven, but may be driven in synchronization with the plated steel plate 1.

Reference numeral 9 denotes a device for adjusting the gap between the edge rolls 2 and the position in the plate width direction. Reference numeral 11 is an edge detection device for the plated steel sheet 1. What is important here is that the gap between the edge rolls 8 is determined from the viewpoint of the necessary amount of reduction for roughening the plated steel sheet 1. That is, it is not decided from the viewpoint of the plate thickness of rolling down so as to be equal to the thickness of.

By adjusting the position of the edge roll 8 in the plate width direction, the edge portion of the plated steel plate 1 and the edge roll 8 can be formed in accordance with the plate width of the plated steel plate 1 and the distribution of the alloying degree in the width direction. The contact length can be adjusted, and uniform alloying control becomes possible. Reference numeral 10 denotes an alloying degree meter that detects the distribution of the alloying degree of the plated steel sheet in the plate width direction. For example, the methods disclosed in JP-A-55-90846 and JP-A-2-88954 may be used.

Feedback information on the gap between the edge rolls 8 and the contact length between the edge portion of the plated steel sheet 1 and the edge roll 8 can be feedback-controlled by the distribution information of the alloying degree of the plated steel sheet 1 of the alloying degree meter 10 in the plate width direction. It will be possible. In addition, when carrying out the present technology, if sufficient operation data is obtained, it is possible to perform a steady operation without using an alloying degree meter.

Next, specific examples of the present invention will be described. Plate thickness 1.0mm, plate width 1200m using the device of Figures 1-4
m, line speed 60 m / min, bath temperature 460 ° C, deposition amount 45/45 g / m,
Fig. 6 shows the alloying degree (wt%) distribution results in the sheet width direction (table) when operated at a heat retention temperature of 500 ° C and a holding time of 10 seconds.
The results when the edge roll of the present invention is not used are also shown in FIG.

It can be seen from FIG. 6 that in the case of the present invention, alloying at the edge portion is promoted and the insufficient alloying is eliminated. FIG. 7 shows the results of controlling by the distribution of the plate width and the degree of alloying in the width direction. The results when the edge roll of the present invention is not used are also shown in FIG. It can be seen that by changing the position of the edge roll of the present invention, it is possible to sufficiently respond to the fluctuation in the range where the alloying has not progressed from the edge.

[0018]

As described above, according to the present invention, the alloying of the edge portion of the steel sheet can be effectively promoted and the alloy can be uniformly alloyed in the sheet width direction. In addition, it is possible to eliminate the drawbacks of the conventional products in which the powdering resistance is deteriorated.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of an embodiment of the present invention.

FIG. 2 is a perspective view of a main part of an embodiment of the present invention.

FIG. 3 is a side view of an essential part of an embodiment of the present invention.

FIG. 4 is a plan view of an essential part of an embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the roll pushing amount and the plate surface emissivity.

FIG. 6 is a diagram showing an effect of one embodiment of the present invention.

FIG. 7 is a diagram showing the effect of the width direction control of the edge roll of the present invention.

[Explanation of symbols]

1 plated steel sheet 2 Bath support roll 3 Wiping nozzle 4 zinc bath 5 alloying furnace 6 heating zone 7 tropical zone 8 edge rolls 8a axis 8b axis 9 Edge roll gap and board width direction adjustment device 10 Alloying degree meter 11 Edge detector

Claims (4)

[Claims] 1. A steel sheet is passed through a molten zinc bath to adjust the zinc deposition amount, and then the surface of the overcoat portion of the steel sheet edge where alloying is insufficient is roughened before the alloying furnace inlet. A method for manufacturing a galvannealed steel sheet, comprising performing an alloying treatment in an alloying furnace after increasing the plate surface emissivity of the overcoat portion. 2. During the alloying treatment or after the alloying treatment,
The method for producing a galvannealed steel sheet according to claim 1, wherein the alloying distribution in the plate width direction is detected by an alloying degree meter, and roughening is performed based on the detected alloying distribution. . 3. Production of an alloyed hot dip galvanized steel sheet in which a steel sheet is passed through a hot dip zinc bath, the zinc adhesion amount is adjusted by a zinc adhesion amount adjusting device such as gas wiping, and then an alloying treatment is performed in an alloying furnace. In the device, between the zinc adhesion adjusting device and the alloying furnace, the peripheral surface is roughened for roughening the surface of the overcoat portion of the steel plate edge to increase the plate surface emissivity. An apparatus for producing an alloyed hot-dip galvanized steel sheet, which is provided with an edge roll. 4. An edge roll gap and a plate width direction position adjusting device, and an alloying degree meter for sending a command for controlling the adjusting device and for detecting an alloying distribution in the plate width direction. The apparatus for manufacturing an alloyed hot-dip galvanized steel sheet according to claim 3.