JP3456816B2 - High-speed hot-dip plating method and apparatus - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to high-speed hot-dip galvanizing, and in particular, a steel plate is sandwiched by blades, and a coating amount (molten metal) of a required amount is supplied between the blade and the steel plate to adjust the coating weight. The present invention relates to a high-speed hot dip plating method and apparatus.

[0002]

2. Description of the Related Art In continuous hot dip galvanizing equipment,
When trying to speed up plating, as a factor that inhibits this, splashing occurs at high speed (at about 180 rpm or more), the time required to change and adjust the bath, the steel plate to pass through, the immersed rolls, etc. The problem is that dross is generated due to the elution of iron from the steel.

In order to avoid these obstructing factors, if the molten metal (alloy) can be applied to the steel sheet at a high speed and as much as necessary, the problems will be solved all at once. For that purpose, the conventional continuous hot-dip galvanizing equipment with bath and wiping, etc. is replaced with a plating equipment without bath and wiping, which realizes the plating equipment in the high-speed range which has been impossible until now. Will be needed. Usually, the amount of zinc adhered is proportional to the pulling rate of the steel sheet from the bath, so that excess zinc is removed. As this method, there are a roll squeezing method using a grooved roll and a gas squeezing method in which high-pressure gas is blown and a gas jet knife is used to squeeze. Air, steam, nitrogen gas, combustion waste gas, or the like is used as the gas for gas reduction. These are automatically controlled by linking them with a continuous deposition meter. In addition, this method causes a large amount of noise due to the use of high-pressure gas, which causes a problem in working environment.

On the other hand, in the field of coated paper for printing, a technique for improving productivity by a blade coater having a blade blade is
For example, JP-A-2-6695 and JP-A-3-106470.
Japanese Patent Application Laid-Open No. 3-38276, Japanese Patent Application Laid-Open No. 4-316698.
It is disclosed in Japanese Patent Publication No. These are techniques for improving non-uniformity of the coating amount in the width direction, preventing streak, excellent coating amount profile, and improving smoothness and surface condition. As shown in FIG. 9, these representative techniques supply the paint from the fan ten lip 14 while sending the base paper sent by the backing roll 13 to the blade 12 when applying the paint to the base paper 11. is there. That is, the coated surface is finished by scraping off the sprayed coating surface with a blade.

[0005] In hot dip metal plating, the plating is required to have a high basis weight in a high temperature state, and its base is a steel plate or the like, which is different from the above-mentioned papermaking technique in basic conditions. However, on the premise of high-speed processing, application of the blade coater technique to metal hot dip plating is desired, aiming at obtaining a stable and smooth plating layer on the surface of metal.

[0006]

In view of the above-mentioned conventional problems, an object of the present invention is to prevent the occurrence of splash and to eliminate dross defects as an inhibiting factor for increasing the speed of hot dip plating. A bathless hot dip plating method and apparatus. Further, another object of the present invention is to provide a bathless plating method having a device configuration capable of rapid product type change and control of the coating weight, assuming high productivity in the case of bathless plating. And a device.

Another object of the present invention is to study the application of the blade coater in the papermaking equipment to a hot dipping hot-dip galvanizing line, and to analyze the flow due to the viscosity of the molten metal during high-speed passage of a steel sheet. Provided is a hot-dip plating method and apparatus capable of optimizing the plating conditions.

[0008]

The above objects can be achieved by the present invention having the following points. (1) In a hot dip plating method for continuously plating a steel sheet moving at a high speed, there is an interplanar distance that gradually decreases in the moving direction of the steel sheet due to planes that sandwich the entire widthwise opposing surface of the steel sheet. Forming a tapered gap, carrying the steel sheet while supplying molten metal from the upper part to the tapered gap part, and performing plating, and adjusting the amount of plating deposition by the distance of the closest proximity of the tapered gap to the steel plate. A high-speed hot dip plating method.

(2) In the above (1), the stress caused by the molten metal is canceled and a predetermined stress for adjusting the distance of the tapered gap portion is applied to the plane forming the tapered gap. High-speed hot dip plating method.

(3) A high-speed hot-dip plating method according to the above (1), wherein the amount of the coating liquid is adjusted by moving a plane forming a gap.

(4) In a hot dip coating apparatus for continuously plating a steel plate moving at high speed, blades extending in the width direction of the steel plate are arranged at positions facing each other across the steel plate moving at high speed, The blade has a gap that gradually expands toward the rear of the steel plate traveling direction, and has a mechanism for adjusting to a predetermined gap with the steel plate in the front of the steel plate traveling direction, and in the gap between the blade and the moving steel plate. A hot-dip galvanizing apparatus comprising a die for supplying a predetermined amount of molten metal.

(5) The hot dipping apparatus according to the above (4), wherein at least one of the blades is a flat plate material. (6) In the hot dip galvanizing apparatus according to the above (4), the blade is movable back and forth in the traveling direction of the steel sheet.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a steel plate moving at high speed is sandwiched by blades (elastically deformable), and a necessary amount of coating liquid (molten metal) is supplied between the blade and the steel plate by a die. Further, in the present invention, a force corresponding to the pressure and shearing force generated by the wedge effect between the blade and the steel plate is applied from the outside of the blade. This makes it possible to adjust the coating weight on the surface of the steel plate by controlling the gap with the steel plate on the blade exit side.

The case where the present invention is applied to the conventional hot-dip galvanizing shown in FIG. 8 will be described. In the conventional plating apparatus, as shown in FIG. 8, the steel plate 1 is dipped in a molten zinc bath 6 through a sink roll 10 to be plated. After that, the coating weight is adjusted by the injection nozzle 9,
The alloying furnace 9 and the cooling zone 5 condition the plating layer. On the other hand, the present invention is shown in FIG. As shown in this figure,
In the present invention, the conventional process is inverted.
This is because the present invention achieves higher speed and stabilization of plating.

That is, in the present invention, the steel plate 1 is supplied from the upper part to the plating apparatus via the upper hearth roll 2 and is conveyed downward. The plating apparatus comprises a special molten metal supply die 3 and a blade 4 in order to control the molten metal (molten zinc) so that it can be applied to the steel sheet 1 at a constant rate. As shown in FIG. 2, an atmosphere of an inert gas, for example, N ₂ gas 8 is formed in the internal space of the molten metal supply die 3, and means for preventing the oxidation of the molten metal is taken. The molten metal supply die 3 can temporarily retain the molten metal (molten zinc 6) and can supply a fixed ratio between the blade 4 and the steel plate 1. Further, the blades 4 are coated with plated metal on both surfaces of the steel plate 1 so as to form a plated layer 7 having a constant film thickness. For this reason, two planes that are inclined downward are arranged to face the steel plate 1. In the present invention, the blade is not particularly limited, but any blade having a plane inclined portion and capable of withstanding molten metal for a considerable period of time is desirable. The die is also not particularly limited as long as it can withstand the molten metal for a considerable time.

FIG. 3 shows the stress condition during the plating treatment of the present invention.
5 is shown as a schematic diagram in FIG. FIG. 3 is a diagram showing only the stress relationship with the steel plate 1 on one side of the blade 4, in which the vertical direction is replaced by the horizontal direction. From the molten metal 6, two stresses, that is, a stress that is in equilibrium with the blade 4 and a stress that is perpendicular to the blade 4 are generated. This corresponds to the pressure and shearing force generated by the wedge effect between the blade and the steel plate, and these have a considerable influence on the stability of the plating. Therefore, in order to cancel this, it is necessary to apply an evenly distributed stress from the back surface of the blade 4 to adjust the gap between the blade 4 and the steel plate 1. In the case of this figure, the movable axial point (pivot) is made to exist in the portion indicated by the black circle, and the blade surface is made movable.

FIG. 4 shows stress evaluation using the blade 4 of the present invention as a rigid body. With the gap between the blade 4 and the steel plate 1 being h, the stress P is given by the following equation according to the Reynolds equation as a macroscopic treatment. dP / dx = 6 μ (U / h ² −2q / h ³ ), where U is the line speed, h is the gap, q is the flux, and μ is the viscosity coefficient. In this case, the film thickness hd becomes equal to the exit side gap, and can be controlled by controlling the blade pressing force as the blade pressing force, that is, by pressing the blade back surface with the total force of the lift force and the drag force.

[0018]

EXAMPLE As an example of the present invention, FIG. 6 shows the relationship between the stress acting on the blade and the distance x based on the above stress analysis. This figure shows a line speed LS of 1000
mpm, the viscosity coefficient is 5 cp (molten Zn),
This is for the case where the output side gap is 5 μm. It can be seen that the distribution has a sharp rise in pressure near the outlet side of the blade. For this reason, if local abrasion of the blade occurs, the bending moment increases, and the jet flow on the outlet side becomes unrectified, which may affect the plating thickness.

FIG. 7 is a diagram showing the relationship between the pressing force of the first term blade and the plating film thickness in the present invention. In the case of the molten zinc of the present invention, the viscosity of the plating solution is 3 to 5 cp, and at such a low viscosity, as shown in this figure,
When the line speed is 100 mpm or 500 mpm, the blade pressing force changes little with respect to the film thickness, and it is difficult to control the film thickness by the pressing force. On the other hand, it can be seen that when the line speed is as high as 1000 mpm, this change becomes large and control becomes possible.

Further, as a method of controlling the film thickness in the case of the laminar flow in the present invention, there is a method shown in FIG. In this method, the relationship of t = G / 2 is utilized between the gap G between the blade 4 and the steel plate 1 and the plating film thickness t. In this method, a method of controlling the blade position by detecting the film thickness at the time of wet and feeding it back, and a method of directly detecting the gap between the blade and the steel plate and feeding it back to control the blade position are possible. The former is
This is the most direct and efficient control method when the film thickness can be measured at high speed and with high accuracy even in the wet state (when it is difficult to fix the steel plate).

On the other hand, the latter method is an indirect control method on the condition that the relationship between the film thickness and the gap between the blades forming the both surfaces and the steel sheet is accurately known. Next, the results of performing cooling after plating by the apparatus of the present invention as a comparative test with cooling in the current hot dip galvanizing will be described. The measurement results of each example are summarized as follows.

[Inventive Example] Maximum speed with blade coater: 1000 mpm, Blade coater outlet side temperature: 450 ° C. Steel sheet temperature during roll contact: 300 ° C. [Conventional method example] Velocity of plating bath type molten zinc: 180 mpm AS furnace outlet Side: 500 ° C. Top roll ingress restriction: 300 ° C. As described above, in the plating line of the present invention, the cooling after galvanizing is sufficiently the same in the ultra-high speed state as compared with the cooling conditions at the conventional temperature. Realization of temperature conditions is possible. From this, it can be seen that the quality of the plating material of the present invention can be achieved at substantially the same level as the conventional level.

[0023]

According to the present invention, the productivity per hour of hot dip plating is extremely improved, the efficiency of the plating line is improved and the labor is saved, and the drossless operation is realized, resulting in a large working time. Achieve a shortening. Further, the present invention makes it possible to improve the yield of plating, thereby significantly reducing the total cost of plating.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a plating line according to the present invention.

FIG. 2 is a schematic diagram of a main part showing a configuration of a plating apparatus according to the present invention.

FIG. 3 is a schematic view showing a stress state acting on a blade surface according to the present invention.

FIG. 4 is a schematic diagram of stress analysis when the blade according to the present invention is a rigid body.

FIG. 5 is an analysis diagram of a relationship between a gap and a film thickness when the plating solution flow according to the present invention is rectified.

FIG. 6 is a diagram showing the relationship between the pressure acting on the blade and the length in the x-axis direction according to the embodiment of the present invention.

FIG. 7 is a diagram showing a relationship between a blade pressing force and a film thickness according to an example of the present invention.

FIG. 8 is an explanatory view of a conventional hot-dip galvanizing line.

FIG. 9 is a diagram showing an outline of a conventional paper manufacturing process.

[Explanation of symbols]

1 ... steel plate 2 ... hearth rolls 3 ... die 4 ... blade 5 ... cooling zone 6 ... molten zinc 7 ... plating layer 8 ... N ₂ atmosphere 9 ... alloying furnace 10 ... injection nozzle 11 ... sink roll 12 ... fiberboard 13 ... blade 14 … Backing roll 15… Fan ten lip

─────────────────────────────────────────────────── --- Continuation of front page (56) References JP-A-1-139745 (JP, A) JP-A-4-48056 (JP, A) JP-A-53-118230 (JP, A) JP-A-54- 141342 (JP, A) JP 53-134736 (JP, A) Actual development 56-146767 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) C23C 2/00-2 / 40

Claims (6)

(57) [Claims] 1. A hot dip coating method for continuously plating a steel sheet moving at a high speed, wherein the planes sandwiching the widthwise entire surface of the steel sheet facing each other are used to reduce the distance between the planes gradually decreasing in the moving direction of the steel sheet. A tapered gap is formed, the molten steel is fed from above into the tapered gap to convey the steel sheet, and plating is performed, and the amount of plating adhered is adjusted by the distance of the taper gap closest to the steel sheet. A high-speed hot-dip plating method characterized by the above. 2. The method according to claim 1, wherein the stress generated by the molten metal is canceled out, and a predetermined stress for adjusting the distance of the tapered gap portion is applied to the plane forming the tapered gap. High-speed hot dip plating method. 3. The high-speed hot-dip plating method according to claim 1, wherein the amount of the coating liquid is adjusted by moving a plane forming a gap. 4. A hot dip galvanizing apparatus for continuously plating a steel plate moving at high speed, wherein blades extending in the width direction of the steel plate are arranged at positions facing each other with the steel plate moving at high speed interposed therebetween. The blade has a gap that gradually expands toward the rear of the steel plate traveling direction, and has a mechanism for adjusting to a predetermined gap with the steel plate in the front of the steel plate traveling direction, and a position in the gap between the blade and the moving steel plate. A hot dip plating apparatus, which is provided with a die for supplying a fixed amount of molten metal. 5. The hot dip plating apparatus according to claim 4, wherein at least one of the blades is a flat plate material. 6. The hot dip galvanizing apparatus according to claim 4, wherein the blade is movable back and forth in the traveling direction of the steel sheet.