JP3134757B2 - Vibration prevention method for hot-dip galvanized steel strip - 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 vibration of a hot-dip galvanized steel strip when heating the hot-dip galvanized steel strip to produce an alloyed hot-dip galvanized steel strip.

[0002]

2. Description of the Related Art A hot-dip galvanized steel strip is used as a rust-proof steel sheet for a wide range of applications such as electric appliances for home appliances, building materials, and automobiles because of its excellent corrosion resistance. Among these hot-dip galvanized steel strips, alloyed hot-dip galvanized steel strips are particularly excellent in paintability, corrosion resistance, weldability and workability, so they have high corrosion resistance, welding workability, workability and beautiful after painting. It is often used for automobile steel plates and the like that require The alloyed hot-dip galvanized steel strip described above is manufactured by the process shown in FIG.

In FIG. 6, a steel strip 3 immersed in a hot-dip galvanizing tank 2 filled with hot-dip zinc 1 has its traveling direction changed by a sink roll 4 and is pulled up vertically. Since the amount of zinc adhering to the front and back surfaces of the steel strip 3 increases substantially in proportion to the pulling speed (= line speed) from the hot-dip galvanizing tank 2, excess zinc generally adheres.

The excess zinc is blown out by blowing a high-pressure gas such as air, nitrogen or the like with a wipe pink nozzle 5 provided above the hot-dip galvanizing tank 2.

[0005] In this way, the hot-dip galvanized steel strip 6 to which a predetermined amount of zinc has adhered passes through the touch roll 7,
It is guided vertically into the alloying furnace 8 and heated to about 460 to 600 ° C.

[0006] Further, after being maintained at a constant temperature for a certain time in a tropic 9 provided above the outlet of the alloying furnace 8, the tropic 9 is maintained.
The steel sheet 11 is cooled by a cooling zone 10 provided above to become an alloyed hot-dip galvanized steel strip 11, and the traveling direction is changed from a vertical direction to a horizontal direction by a top roll 12 disposed above the cooling zone 10. Go in.

[0007] Preservation zone 9 provided above the exit of the alloying furnace 8
Alternatively, a cooling zone can be provided to start cooling immediately after the alloying furnace 8.

In the above-described manufacturing process of the alloyed hot-dip galvanized steel strip, although tension is applied to the hot-dip galvanized steel strip 6 between the sink roll 4 and the top roll 12, in a recent high-speed line, Since the distance between the sink roll 4 and the top roll 12 is 40 m or more, a phenomenon occurs in which the hot-dip galvanized steel strip 6 vibrates or twists in the thickness direction.

The following problems occur due to the occurrence of vibration or torsion of the galvanized steel strip 6. Variations in plating adhesion. The steel strip comes into contact with the alloying furnace, causing flaws in the product, and there is a high risk of equipment damage. When the induction heating method is adopted in the alloying furnace, a steel strip comes into contact with the heating coil, sparks are generated, and flaws are generated in the product.

Various measures have been taken as a technique for preventing such vibration or torsion.

Japanese Patent Application Laid-Open No. 5-78806 discloses that when compressed air is blown by a slit nozzle to both surfaces of a hot-dip galvanized steel strip passing between a sink roll and a top roll, a pressure difference is provided between the compressed air blown to both surfaces. A method for preventing vibration of a hot-dip galvanized steel strip when manufacturing an alloyed hot-dip galvanized steel strip is disclosed.

Here, as shown in FIG. 7, between the cooling nozzles 13 of the cooling zone 10, a pair of static nozzles having two upper and lower slit nozzles provided on both sides such that the spraying direction is directed to the center in the vertical direction. Two sets of pressure pads 14a, 14b and static pressure pads 15a, 15b are provided. This static pressure pad is provided with a pair of compressed air blowing devices 21 provided on both sides of the galvanized steel strip 6 in the cooling zone as shown in FIG.
Compressed air is blown onto both surfaces of the hot-dip galvanized steel strip 6 through the slit nozzle 27 to a and 21b to generate a static pressure region on the surface of the hot-dip galvanized steel strip 6.

[0013]

Problems to be Solved by the Invention Japanese Patent Laid-Open No. 5-78806
The method of preventing vibration of hot-dip coated steel sheet as disclosed in Japanese Patent Application Publication No. 2005-214,979 is based on applying a pressure difference exceeding this pressure fluctuation to the compressed air on both sides even if the blower that sends compressed air has pressure fluctuations. An effect that does not generate vibration is expected.

However, the above-described method for preventing vibration of a hot-dip coated steel strip has the following problems.

The distance between the sink roll 4 and the top roll 12 is 4
In a hot-dip galvanized steel strip running at a high speed on a line having a distance of 0 m or more, the static pressure pad 1 in the cooling zone 10
4a, 14b, and static pressure pads 15a, 15b, even if a pressure difference is provided on both sides and compressed air is blown, there may be cases where vibration of the hot-dip coated steel sheet cannot be prevented, and the above-mentioned problems (1) to (4) are solved. Has not been reached. In addition, the use of the touch roll 7 is intended to reduce the above-mentioned problems. However, since the distance from the touch roll 7 to the anti-vibration device installed in the cooling zone is long, not only sufficient effects are not obtained, but also the touch The use of the roll 7 causes the following problem.

[0016] The vibration control effect of the touch roll is not sufficient,
Since the rolls are offset and pressed into each other for use, a roll pattern (generally referred to as a roll mark) is generated in the width direction of the product surface, and the product value is reduced.

Since the semi-molten zinc comes into contact with the touch roll, zinc dust is generated and the working environment deteriorates.
The zinc dust accumulates over time and adheres to the product, resulting in surface defects.

The present inventors have conducted intensive studies on a method for preventing the galvanized steel strip from vibrating by blowing compressed air by providing the above-mentioned pressure difference. From the lower side to about 1/2, that is, the position where the alloying process is performed.

The present invention has been made based on the above findings. The present invention is an improvement of the method for preventing vibration of the hot-dip galvanized steel strip, even if the line between the sink roll and the top roll has a long distance, the hot-dip galvanized steel strip passing therethrough in the thickness direction. An object of the present invention is to provide a method for preventing vibration of an alloyed hot-dip galvanized steel strip which does not generate vibration or twist.

[0020]

According to the present invention, when performing galvannealing using a hot-dip galvanizing tank, an induction heating furnace for alloying, a heat-holding furnace, and a cooling zone, A method for preventing vibration of a hot-dip galvanized steel strip, characterized in that one or more pairs of blowing nozzles are provided on both sides of a steel strip in an induction heating furnace, and gases having different pressures are blown from the blowing nozzles to the steel strip. It is.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a view showing the whole of a static pressure pad used in the method of the present invention incorporated in an induction heating furnace, and FIG. 2 is a view showing a state where the static pressure pad is incorporated in an induction heating type alloying furnace. FIG. 3 is a side sectional view of a static pressure pad used in the present invention, and FIG. 4 is a view taken along line AA of FIG.

In FIGS. 1 to 4, the same reference numerals as those in FIG. 6 are used for the same parts. In FIG. 1, a pair of static pressure pads 21a, 21b and static pressure pads 22a, 22b are incorporated in an induction heating type alloying furnace 20.

The pair of static pressure pads 21a and 21b and the static pressure pads 22a and 22b are installed on both sides of the hot-dip galvanized steel strip 6 at a predetermined distance from each other.

As shown in FIGS. 3 and 4, two static pressure pads 21a and 21b are provided on both sides of the ascending hot-dip galvanized steel strip 6 so that the spray direction is directed to the center in the vertical direction. It has a slit nozzle 27. Static pressure pad 2
A supply port 28 for compressed air is provided in each of 1a and 21b.

G indicates a slit gap, W indicates a slit width, and L indicates a slit interval.

The structure of the static pressure pads 22a and 22b is the same. Here, a pair of the same static pressure pads 23 as described above is used.
a, 23b, static pressure pads 24a, 24b, static pressure pad 2
5a, 25b and static pressure pads 26a, 26b
It is incorporated in the cooling zone 10 above zero.

The reason why the alloying furnace 20 is of the induction heating type is as follows.
The static pressure pads 21a and 21b and the static pressure pad 22a,
This is to eliminate the interference of the alloying heating gas with the 22b.

Since there is no interference of the alloying heating gas in the alloying furnace 20, the compressed air on both sides of the hot-dip galvanized steel strip 6 by the static pressure pads 21a, 21b and the static pressure pads 22a, 22b is accurately differentiated. Can be pressed and sprayed.

As shown in FIG. 2, a galvanized steel strip 6 rising vertically is provided inside an induction heating type alloying furnace 20.
And a pair of static pressure pads 21a, 21b and static pressure pads 22a, 22b having the above-mentioned two upper and lower slit nozzles are provided between the heating coils 29.
The alternate long and short dash line indicates the alloying furnace 20.

In this case, the hot-dip galvanized steel strip 6 rising in the alloying furnace 20 is sprayed on both surfaces by applying a differential pressure of compressed air from the static pressure pads 21a and 21b and the static pressure pads 22a and 22b to prevent vibration. You.

Therefore, the hot-dip galvanized steel strip 6 is uniformly heated by the heating coil 29, and an appropriate alloying treatment can be performed.

FIG. 5 is a piping diagram for supplying air for blowing to a pair of static pressure pads provided on both sides of a hot-dip galvanized steel strip.

In FIG. 5, the dashed line indicates the alloying furnace 20. Static pressure pads 21a and 21b and static pressure pads 22a and 22b installed in the induction heating type alloying furnace 20;
Can be set independently of the hot-dip galvanized steel strip 6 rising in the alloying furnace 20 by moving the distance in the direction of the arrow.

The compressed air sent out by the compressed air supply device 32 has passed through the damper 30, and is supplied to the static pressure pad 21 a and the static pressure pad 22 a on the front side of the hot-dip galvanized steel strip and passed through the damper 31. The material is supplied to the hydrostatic pad 21b and the hydrostatic pad 22b on the back side of the galvanized steel strip.

Here, the compressed air having various pressure differences is supplied to the front and back sides of the hot-dip galvanized steel strip by changing the opening degree of the dampers 30 and 31.

In the present invention, the traveling direction of the steel strip 3 immersed in the hot-dip galvanizing bath 2 filled with the hot-dip zinc 1 is changed by the sink roll 4 and pulled up in the vertical direction.

Excess zinc adhering to the front and back surfaces of the steel strip 3 is squeezed out by blowing a high-pressure gas such as air, nitrogen or the like by a wipe pink nozzle 5 provided above the hot-dip galvanizing tank 2.

In this manner, the hot-dip galvanized steel strip 6 to which a predetermined amount of zinc has adhered passes through the touch roll 7 and
It is guided vertically into the induction heating type alloying furnace 20 and is heated to about 460 to 600 ° C. by the heating coil 29.

In the alloying furnace 20, the opening degree of the dampers 30, 31 is changed to apply a pressure difference between the pair of static pressure pads 21a, 21b and the static pressure pads 22a, 22b to the front and back sides of the galvanized steel strip. Compressed air is supplied to prevent vibration of the hot-dip galvanized steel strip 6 and the like.

Further, after being kept at a constant temperature for a certain period of time in a preservation zone 9 provided above the outlet of the alloying furnace 8, the preservation zone 9 is maintained.
It is cooled in a cooling zone 10 provided above, and becomes an alloyed hot-dip galvanized steel strip 11.

In the cooling zone 10, a pair of static pressure pads 23
a, 23b, static pressure pads 24a, 24b, static pressure pad 2
5a, 25b, static pressure pads 26a, 26b are installed,
Compressed air having a pressure difference is supplied to the front and back sides of the galvannealed steel strip 6 that has been subjected to the alloying treatment, and the vibration of the galvanized steel strip 6 is further prevented.

The traveling direction of the alloyed hot-dip galvanized steel strip 11 leaving the cooling zone 10 is changed from the vertical direction to the horizontal direction by the top roll 12 disposed above, and the process proceeds to the next step.

In the above, the vibration measuring position 33 is set at a position 500 mm above the wiping nozzle 5 and at the center in the height direction in the induction heating type alloying furnace 20, and the vibration of the hot-dip galvanized steel strip 6 is continuous. Is detected.

[0045]

Next, the magnitude of the vibration amplitude, the center of the vibration and the original pass line of the hot-dip galvanized steel strip 6 when the method according to the present invention is used and when the hydrostatic pad is used only in the conventional cooling zone. The following describes the test results for evaluating the amount of deviation from the center of the roll, the state of the roll pattern generated on the product surface by the touch roll, and the amount of zinc dust generated from the touch roll.

The operating conditions and measurement conditions at this time are as follows. However, the amount of zinc dust generated from the touch roll does not correspond to the following item (6) since the amount of deposition in 14 days of the average continuous operation was measured and evaluated in each case.

(1) Blower capacity Air volume 30000 Nm ³ / Hr Discharge pressure 400 mmH ₂ O

(2) Static pressure pad shape Slit gap (G) 25 mm, slit width (W) 2
000mm, 2 slits, slit interval 200
mm

(3) Distance between static pressure pads Between static pressure pads 21a (21b) and 22a (22b): 5.3m Static pressure pads 23a (23b), 24a (24b),
Between 25a (25b) and 26a (26b): 5m each

(4) Vibration measurement position 500 above the wiping nozzle above the hot-dip galvanizing tank
mm Induction heating type alloying furnace height center

(5) Measurement method Laser type distance sensor

(6) Coil used, operating conditions Plate thickness 0.75 mm Plate width 1250 mm Line speed 90 mpm Target coating weight 60 g / m ² (per side)

Tables 2 and 3 show the relationship between the used static pressure pad and damper opening, the magnitude of the amplitude, and the deviation between the center of the amplitude and the center of the original pass line. evaluated. In the evaluation section in the table, x indicates poor, Δ indicates slightly defective, ○ indicates acceptable, and ◎ indicates good.

The + sign of the displacement indicates the displacement to the front side, and the-sign indicates the displacement to the back side. In addition, the evaluation of the state of the roll pattern generated on the product surface by the touch roll was performed using the results of the sensitivity inspection of the operator who regularly conducts inspection work on the product surface in the final process of the hot-dip galvanizing equipment. .

Here, the used static pressure pads are 21a and 21b.
26a and 26b, 21a to 26a are installed on the front side (abbreviated as table) of the hot-dip galvanized steel strip 6, and 2
1b to 26b are installed on the back side (abbreviated as back) of the hot-dip galvanized steel strip 6.

[0056]

[Table 1]

[0057]

[Table 2]

[0058]

[Table 3]

As is clear from Tables 2 and 3, the test Nos. 1, No. 2, No. 3, No. 4 was evaluated as ○ or ◎.

Test No. according to the comparative example. 5, no. 6, N
o. 7, no. 8, no. 9 was evaluated as x mark or Δ mark.

From these facts, when the compressed air is blown by the differential pressure using the static pressure pad in the induction heating type alloying furnace, in addition, when the compressed air is blown by the static pressure pad in the cooling zone, the molten zinc is blown. Vibration of the plated steel strip can be suppressed to a small level.

In this case, the blowing of the compressed air by the static pressure pad in the cooling zone may be either the differential pressure or the same pressure.

Next, the hot-dip galvanized steel strip at a position 500 mm above the wiping nozzle at the top of the hot-dip galvanizing tank was adjusted so that the amplitude was within 4 mm and the deviation between the center of the amplitude and the center of the original pass line was within 4 mm. The use condition of the touch roll to perform the test and the state of occurrence of the roll pattern generated on the product surface by the touch roll in that case were tested. The results are shown in Tables 4 and 5.

[0064]

[Table 4]

[0065]

[Table 5]

As is clear from Tables 4 and 5, the test Nos. 10, No. 11, No. 12, No.
13 was evaluated as 評 価 or ◎.

Test No. according to the comparative example. 14, No. 1
5, no. 16, No. 17, No. The sample No. 18 was evaluated as x mark or Δ mark.

From these facts, when the compressed air is blown with the differential pressure by the static pressure pad in the induction heating type alloying furnace, and when the compressed air is blown with the static pressure pad in the cooling zone, the touch roll It can be seen that the conditions for pushing in are loosened, or that the touch roll reduces the roll pattern generated on the product surface.

Table 6 shows the test results for evaluating the amount of zinc dust generated from the touch roll.

[0070]

[Table 6]

As is clear from Table 6, the test Nos. 19, no. 20, no. 21 was evaluated as ○ or ◎.

Test No. by Comparative Example In No. 22, the evaluation was x. From these facts, when the compressed air is blown by the differential pressure by the static pressure pad in the induction heating alloying furnace, and in addition, when the compressed air is blown by the static pressure pad in the cooling zone, the touch roll is generated. It can be seen that zinc dust is drastically reduced.

In the above embodiment, a static pressure pad is provided between the heating coils in the alloying furnace, and the static pressure pad is provided on both sides of the hot-dip galvanized steel strip while preventing the heating gas for alloying from interfering with the static pressure pad. The case where the compressed air by the pad is blown with a differential pressure has been described. However, the present invention is not limited to this. It is sufficient that the compressed air by the pressure pad can be blown with a differential pressure.

As means for eliminating interference of other gases with the static pressure pad, an auxiliary pad is provided at a position immediately before and / or immediately after the static pressure pad, and the same compressed air as the static pressure pad is used as compared with the static pressure pad. Spraying on both sides of the hot-dip galvanized steel strip at a low pressure.

[0075]

According to the present invention, even when the line between the sink roll and the top roll has a long distance, compressed air can be accurately differentiated by the static pressure pad at least between the molten metal surface and the alloying position. Since it can be pressed and sprayed on both sides of the hot-dip galvanized steel strip, the alloyed hot-dip galvanized steel strip passing therethrough does not generate vibration or twist in the thickness direction.

[Brief description of the drawings]

FIG. 1 is a view showing an entirety of a static pressure pad used in a method of the present invention, which is incorporated between a surface of a molten metal and an alloying process.

FIG. 2 is a view showing a state in which a static pressure pad is incorporated in the induction heating type alloying furnace of the present invention.

FIG. 3 is a side sectional view of a static pressure pad used in the present invention.

FIG. 4 is a view taken in the direction of arrows AA in FIG. 3;

FIG. 5 is a piping system diagram for supplying blowing air to the static pressure pad portion of the present invention.

FIG. 6 is a view showing a manufacturing process of a general alloyed hot-dip galvanized steel strip.

FIG. 7 is a view showing an example of conventional vibration prevention in a manufacturing process of a galvannealed steel strip.

[Explanation of symbols]

Reference Signs List 20 alloying furnace 21a, 21b, 22a, 22b static pressure pad (installed in alloying furnace) 27 slit nozzle 28 compressed air supply port 29 heating coil 30, 31 damper 32 compressed air supply device 33 vibration measurement position

Continuation of the front page (72) Inventor Keishi Yamashita 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Kokan Co., Ltd. (56) References JP-A-5-78806 (JP, A) JP-A-3-10055 ( JP, A) JP-A-5-320852 (JP, A) JP-A-5-320847 (JP, A) JP-A-1-161256 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , (DB name) C23C 2/00-2/40

Claims (1)

(57) [Claims] When performing galvannealing using a hot-dip galvanizing tank, an induction heating furnace for alloying, a heat-holding furnace, and a cooling zone, a pair of steel strips are placed in both sides of the steel strip in the induction heating furnace. A method for preventing vibration of a hot-dip galvanized steel strip, comprising: providing at least one pair of blow-off nozzles, and blowing gas having different pressures from the blow-out nozzles to the steel strip.