JP2804136B2 - Hot-dip plating method and apparatus - Google Patents

Description

The present invention relates to a hot-dip galvanizing method and apparatus for steel strip,
In particular, the present invention relates to a hot-dip plating method and apparatus using both roll drawing and gas drawing.

[Conventional technology]

2. Description of the Related Art As shown in FIG. 1 of Japanese Patent Publication No. 49-25816, for example, a conventional hot dip coating apparatus has two draw rolls arranged at an outlet of a plating bath, and these rolls are used to squeeze a hot-dip plated material. As shown in FIGS. 2 and 3 and “Hitachi Honron” vol-65, No. 2 of the drawing method, a nozzle for injecting gas at the outlet of the plating bath is arranged,
There is a gas squeezing method in which a hot-dip plating material is squeezed into the gas.

[Problems to be solved by the invention]

However, in the roll drawing method, the metal drawing roll surface is exposed to high-temperature molten metal, so it is necessary to manage the roll surface in order to maintain the quality of the plated surface,
There was a problem that the frequency of maintenance was high. For this reason, in recent years, the gas throttle system has been frequently used.

However, the gas squeezing method also has a problem in that there is a limit in thinning, and the plating thickness unevenness occurs due to the strip warpage (C warp) due to the vibration of the strip due to the injection pressure of the gas or the bending by the sink roll. Yes, not always satisfied.

On the other hand, the needs of hot-dip products in recent years have been diversified, and for example, thinning of 20 g / m ² or less on one side, which is similar to electroplating, is required. Along with that, the thickness unevenness of plating is required to be ± 10 g / m ² to ± 5 g / m ² and a level of 1/2 or less. The conventional gas throttle system cannot meet this requirement.

In particular, there is a strong demand for a plated steel sheet for automobiles, which has a difference in plating thickness, that is, a difference in plating thickness on both sides of the strip. For example, one side 30 g / m ^2, a large different thickness ratio of the other surface as thin as possible 10 g / m ² is required. However, none of the conventional techniques can meet this demand.

SUMMARY OF THE INVENTION An object of the present invention is to provide a hot-dip plating method and apparatus capable of reducing the amount of maintenance, enabling thin coating, and further reducing unevenness in plating thickness.

Another object of the present invention is to provide a hot-dip plating method and apparatus suitable for differential pressure plating in which the plating thickness on both sides of the strip is different.

[Means for solving the problem]

In order to achieve the above object, the present invention introduces a steel strip into a hot-dip plating bath, changes the direction by a sink roll in the plating bath, pulls up in the vertical direction, and a hot-dip plating apparatus that performs a plating process on the steel strip. At the outlet of the plating bath in which the steel strip is pulled up in the vertical direction, the lower part is immersed in the plating bath and is in contact with one surface of the steel strip. And a nozzle for injecting a gas on the surface of the nozzle.

Further, the present invention provides a hot-dip plating method in which a steel strip is introduced into a hot-dip plating bath, the direction is changed by a sink roll in the plating bath and pulled up in the vertical direction, and the strip is plated. While supporting one surface of the steel strip pulled up in the direction with the squeezing roll, a gas is jetted from the nozzle arranged opposite to the squeezing roll to the other surface, and one surface of the steel strip is roll-squeezed, The other surface is a gas restrictor, and one surface of the steel strip adjusts the plating thickness by changing the roll peripheral speed of the drawing roll, and the other surface is a gas pressure of the gas to be injected or a nozzle for injecting the gas. The plating thickness is adjusted by changing the distance between the steel strip and the steel strip.

[Action]

By supporting one side of the strip, that is, the strip, with the squeezing roll, the stop vibration is stopped and the width warpage (C warpage) of the strip is also eliminated. By injecting the gas onto the other surface, the gas is throttled without vibration and C warpage, and uneven plating thickness of the gas throttle due to these is significantly reduced.

In addition, since the position of the strip supported by the squeezing roll is constant, the nozzle can be brought as close as possible to the strip surface, and thinning by gas squeezing is possible due to the close arrangement of the nozzle and the reduction in the plating thickness unevenness described above. Becomes Naturally, thick coating with less plating thickness unevenness is also possible.

On the other hand, the surface of the strip supported by the drawing roll is plated by roll drawing. The roll drawing is originally suitable for thinning, and a relatively beautiful plated surface can be obtained.

As described above, first, since only one side of the strip is roll-drawn in the present invention, the maintenance amount of the drawing roll is reduced by half as compared with the conventional double-sided roll drawing method. Also,
Since thinning can be performed with a gas throttle, thinning with an equal thickness on both sides, which is impossible with a conventional double-sided gas throttle system, can be performed. Further, since the plating thickness unevenness can be reduced, the plating thickness can be reduced accordingly, and the amount of the hot-dip plated material can be reduced, and a beautiful plated surface can be obtained.

Further, since the roll drawing can be originally thinned on one side of the steel strip and the thinning by gas drawing can be made thicker on the other side as described above, the plating thickness ratio (difference thickness ratio) is large. Differential pressure plating is possible.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

1 and 2, which show a hot-dip coating apparatus according to one embodiment of the present invention, a strip steel heated by degreasing, that is, a strip 1, is provided with a plating bath 4 in a plating tank 3 in which a hot-dip plating material 2 is heated and melted. And the direction is changed by the sink roll 5 in the plating bath 4, and proceeds upward while being supported by the support roll 6 in the plating bath 4. At the outlet of the plating bath 4, a squeezing roll 7 having a lower part immersed in the plating bath and a nozzle 8 opposed to the squeezing roll 7 are arranged. It comes into contact with the squeezing roll 7, and the hot-dip plated material on the surface is squeezed by the squeezing roll 7. On the other hand, a pressurized gas 9 is ejected from the nozzle 8 toward the other surface of the strip 1,
While the strip 1 is supported by the squeezing roll 7, the hot-dip plated material on the other surface is squeezed by the pressurized gas 9.

The support roll 6 is movable and adjustable in the horizontal direction. By adjusting the horizontal position of the support roll 6, the strip 1 is brought into firm contact with the squeezing roll 7. On the roll surface of the squeezing roll 7, a large number of circumferential grooves 7A are formed as shown in FIG.

The process of forming the plating surface in the present embodiment configured as described above will be described with reference to FIG. The strip 1 is a support roll 6 that can be moved horizontally with a stroke δ.
And is in contact with the squeezing roll 7 with the force of F. The hot-dip plated material 2 of the plating bath 4 is carried upward by the groove 7A of the squeezing roll 7 as shown by reference numeral 11 in FIG.
Between the first strip and the first strip;
The plating material is separated upward as described above, and the plating material is separated as indicated by reference numerals 12 and 13 on the squeezing roll 7 in the rotation direction. The plating material 12 on the strip 1 is cooled upward and solidifies to form a plating surface. On the other hand, on the other surface of the strip 1, the plating material 14 attached to the strip 1 from the plating bath 4 is squeezed by the gas 9 continuously jetted from the nozzle 8, and the upper surface thereof, like the plating material 15 on the strip 1. And then cooled and solidified to form a plating surface.

In the above process, the plating thickness by roll drawing is determined as follows. First, the total amount of the plating material 11 carried upward by the groove 7A of the drawing roll 7 is determined by the product of the size of the groove 7A and the roll peripheral speed VR. The size of the groove 7A is the fourth
Assuming that the width of the groove 7A in the drawing is b and the height is h, it can be represented by an area S of b × h = S. The total amount of the plating material 11 is separated as indicated by 12 and 13, and the separation ratio is determined by the ratio of the strip speed VS to the roll peripheral speed VR. At this time, if the wettability between the roll surface and the plating material is small, more plating material is distributed to the strip 1. When the above is expressed by a mathematical formula,
The thickness ΔR of the plating material 12 is Here, K is a correction coefficient based on the wettability between the squeezing roll 7 and the plating material. If the wettability of the strip 1 and the squeezing roll 7 is the same, K = 1. Z is the roll peripheral speed VR
And the strip speed VS (VR / VS). A is the pitch of the grooves 7A shown in FIG.

As described above, in order to change the plating thickness, the size of the groove 7A may be changed or the speed ratio Z, that is, the roll peripheral speed VR may be changed. Further, in order to reduce the thickness, the groove 7A may be reduced or the roll peripheral speed VR may be reduced. In this way, a thin plating thickness of 10 g / m ² (one side) can be easily obtained by the roll drawing method. In order to reduce the size of the groove 7A, a large number of fine concave portions such as a surface of shot blasting may be formed.

On the other hand, the plating thickness by the gas throttle can be adjusted by changing the pressure P of the jet gas or the distance 1 between the strip 1 and the nozzle 8. That is, the plating thickness can be reduced by increasing the pressure P or decreasing the distance l.

By the way, in the conventional double-sided gas throttle method, vibration of the strip 1 is unavoidable, and the strip 1 is bent by the sink roll 5 in the plating bath 4 to generate a width warp (C warp). In addition, the distance 1 between the strip 1 and the nozzle 8 fluctuated in both the longitudinal direction and the width direction of the strip, resulting in uneven plating thickness.

In order to make a thinner coating, the gas pressure P may be increased or the distance 1 between the strip 1 and the nozzle 8 may be reduced. However, when the pressure P is increased, the scatter of the plating material is increased. There is a limit, and there is a limit in approaching the nozzle 8 due to the above-described vibration and the warpage of the strip 1, and in any case, there is a limit in thinning. Specifically, about 30 g / m ² (one side) was the limit of thinning the plating thickness.

On the other hand, in this embodiment, the strip 1 is stably supported by the squeezing roll 7, so that the vibration of the strip 1 at this portion is very small, and at the same time, it is generated by the sink roll 5 in the plating bath 4. The warpage of the strip is also eliminated. For this reason, plating thickness unevenness can be significantly reduced. When the plating thickness unevenness decreases,
The plating thickness can be reduced accordingly. That is, for example, a plating thickness unevenness is a ± 10g / m ² (one side), in order to ensure a minimum plating thickness 20 g / m ² (one side) is
A basis weight of 30 g / m ² (30 = 20 + 10) is required. this,
If the plating thickness unevenness can be made ± 5 g / m ² (one side), 25 g / m ²
It is only necessary to provide a basis weight (one side), and the plating thickness can be reduced by 5 g / m ² without impairing the performance of the plated product, and the economic effect is large.

Further, since the position of the strip 1 supported by the squeezing roll 7 is constant, the nozzle 8 can be brought as close to the strip 1 as possible. Due to the close arrangement of the nozzles 8 and the above-mentioned reduction in plating thickness unevenness, thinning of 20 g / m ² (one side) or less, which was impossible with a conventional gas throttle, becomes possible. It is to be noted that it is naturally possible to apply a thick coating with less plating thickness unevenness.

Therefore, according to the present embodiment, since thinning can be performed with a gas throttle, thinning with the same thickness on both sides can be performed, which is impossible with the conventional double-sided gas throttle method. Also, on one side of the strip, it is possible to roll the original thinning of the roll,
On the other side, as described above, thinning to thickening by the gas throttle is possible, so that differential pressure plating with a large plating thickness ratio (differential thickness ratio) can be easily performed.

FIG. 5 shows the minimum plating thickness and the differential pressure ratio that can be plated by the drawing method of the present invention in comparison with the conventional method.

For double-sided such thick plating, whereas the a diaphragm conventional gas is the minimum thickness of 30 g / m ^2, a minimum thickness of 20 g / m ² next to a decrease in plating thickness unevenness described above in the manner of the present invention,
Only thinly diluted with 10g / m ² is possible.

In addition, in the case of differential thickness plating, the minimum thickness is as large as 40 g / m ² in the conventional gas squeezing method, and the plating thickness ratio, that is, the differential thickness ratio is limited to twice, and a differential pressure ratio higher than that is obtained. I can't. On the other hand, with the conventional roll drawing method, a thinning of 10 g / m ² is possible, but the difference in thickness ratio is limited to about 1.5 times, and the range is extremely narrow, so that it is difficult to put to practical use. In the present invention method, on the other hand, the minimum plating thickness is as small as 10 g / m ^2,
In addition, the thickness difference ratio can be very large, for example, six.

In normal differential thickness plating, one side is a service coating, and it is desired that the surface is as thin as possible, and the other side is relatively thick, that is, a large differential thickness ratio is required. You can see that it is very suitable for In recent years, the demand for single-sided plating, which is plated only on one side, has been reduced, and the use of thinner-differential plating on one side is about to replace it.However, the conventional drawing method could not meet this requirement, but the present invention does not meet this requirement. To 100%
It can be handled.

Further, according to the present embodiment, since only one side of the strip is used as the roll drawing, the maintenance amount of the drawing roll can be reduced to half as compared with the conventional double-sided roll drawing method. Also,
Since the plating thickness non-uniformity can be reduced, the plating thickness can be reduced accordingly, the amount of hot-dip plated material can be reduced, and a beautiful plated surface can be obtained.

The effect of the present embodiment described above is compared with the conventional method, and
This is summarized in the figure. From this figure, it can be seen that the method of the present invention is superior to any of the conventional methods in performing differential pressure plating, and that thinning and plating unevenness are superior to the conventional gas restriction method in terms of unevenness. It can be easily understood that it is more advantageous than the squeezing roll method.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to this invention, the differential pressure plating with a large differential pressure ratio is possible, and the application range of a differential pressure plating can be expanded.

In addition, thinning of about 20 g / m ² is possible with the same thickness plating on both sides, which was impossible with the conventional gas drawing method, and it can be replaced with electroplating, and the plating thickness unevenness is significantly reduced compared to the conventional gas drawing method. Thus, it is possible to save the hot-dip plating material and obtain a beautiful plated surface.

Further, the maintenance amount of the squeezing roll can be reduced by half compared to the conventional double-sided roll squeezing method, and the workability is improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a hot-dip coating apparatus according to one embodiment of the present invention, FIG. 2 is a top view of the hot-dip coating apparatus, and FIG. 3 (A) is a plan view of a drawing roll. FIG. 3 (B) is an enlarged view of a drawing roll, FIG. 4 is a view for explaining a plating forming process by the hot-dip coating apparatus of FIG. 1, and FIG. FIG. 6 is a diagram showing the thickness and the differential pressure ratio in comparison with the conventional system, and FIG. 6 is a diagram showing the effect of the present invention in comparison with the conventional system. DESCRIPTION OF SYMBOLS 1 ... Strip (strip) 2 ... Hot-dip coating material 4 ... Hot-dip coating 7 ... Squeezing roll 8 ... Nozzle 9 ... Gas

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 2/00-2/40

Claims (2)

(57) [Claims] 1. A hot-dip galvanizing apparatus for introducing a steel strip into a hot-dip plating bath, changing the direction by a sink roll in the hot-dip bath, and pulling up the steel strip in a vertical direction, thereby plating the steel strip. At the exit of the plating bath to be pulled up, the lower part is immersed in the plating bath and is in contact with one side of the strip, and is positioned opposite to the reduction roll, and injects gas to the other side of the strip. A hot-dip plating apparatus, wherein a hot-dip nozzle is arranged. 2. A hot-dip coating method for introducing a steel strip into a hot-dip plating bath, changing the direction by a sink roll in the hot-dip bath, and pulling up the steel strip in a vertical direction, thereby plating the steel strip. While supporting one surface of the steel strip pulled up by the squeezing roll, a gas is injected from the nozzle arranged opposite the squeezing roll to the other surface, and one surface of the steel strip is used as a roll squeezed, and the other Is a gas throttle,
Furthermore, one side of the strip changes the plating thickness by changing the roll peripheral speed of the squeezing roll, and the other side changes the gas pressure of the gas to be injected or the distance between the gas injection nozzle and the strip. A hot-dip plating method characterized in that the plating thickness is adjusted by causing the plating.