JPH04214851A - Method for hot dip metal coating and device therefor - Google Patents

Abstract

PURPOSE:To easily obtain a coated sheet of high quality with uniform coating weight and to offer a method for hot dip metal coating and an apparatus therefor with inexpensive production cost and maintenance cost. CONSTITUTION:This apparatus is provided with a seal box 11 in which the inside is heated to a temp. in the vicinity of the melting temp. of metal and the atmosphere is kept to a nonoxidizing one, a high pressure molten metal feeding apparatus 13 for pressurizing molten metal to the high pressure of at least >=50kg/cm<2> and a molten metal injection nozzle 12 for dispersing the molten metal into fine grains against the surface of the steel sheet S to be coated and injecting them into a flat spray pattern shape in the above seal box 11.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molten metal plating method and apparatus for plating a steel plate by spraying molten metal under high pressure onto a steel plate.

0002

[Prior Art] Conventionally, as a method for continuously applying zinc plating to a strip-shaped thin steel sheet (hereinafter referred to as a steel sheet to be plated), either electrogalvanizing or hot-dip galvanizing has been commonly used. applied to.

[0003] Electrogalvanizing is suitable for cases where the area weight is relatively small (approximately 25 g/m2 or less), but
If the basis weight is large, a large amount of electricity is required and the manufacturing cost is extremely high, which is a drawback.However, hot-dip zinc immersion plating has its limitations in the range of small basis weights. Since it has the advantage of being able to be manufactured at a low cost when the basis weight is relatively large,
In recent years, the demand for galvanized steel sheets produced by this method has increased significantly.

In this hot-dip galvanizing method, galvanized steel sheets are manufactured using basic equipment as shown in FIG.

[0005] This equipment includes rolls 2 in the bath for vertically changing the direction of a steel plate S to be plated, which is transferred in the direction of the arrow, after being drawn into a molten zinc bath 1, and a roll 2 that follows the steel plate S to be plated. It consists of main parts such as a wiping nozzle 3 for blowing off (wiping) excess molten zinc and finishing it to the required basis weight.

Although such equipment has been widely used, it has a number of disadvantages in actual operation, as described below. 1. Since the roll 2 in the bath is immersed in the molten zinc bath 1, erosion of the roll surface and foreign matter adhesion to the roll surface occur, and the roll 2 must be replaced frequently. 2. Since the bearings for supporting the rolls 2 in the bath are placed in molten zinc, their lifespan is extremely short. 3. It is necessary to hold a large amount of molten zinc, which not only causes a large amount of heat loss due to cooling, but also has extremely poor responsiveness when changing components. 4. If wiping is carried out at a high threading speed of approximately 150 m/min or higher, a large amount of molten zinc will be scattered, and there is a risk that the operation will be impossible. There is a limit to the light weight of about 5.25 g/m2 or less. 6. The wiping force fluctuates due to vibration or poor shape of the steel sheet S to be plated, which tends to result in uneven basis weight. 7. In order to improve the contact conditions between the steel sheet S to be plated and the roll in the bath 2, it is necessary to provide a groove on the circumference of the roll in the bath 2 to facilitate the discharge of molten zinc.
These grooves often form a pattern that is transferred to the plated surface, resulting in quality deterioration. 8. The gas injected from the wiping nozzle 3 generates a large amount of noise, which harms the working environment. 9. Oxidation loss of molten zinc is large. 10. The iron content of the steel sheet S to be plated dissolves into the molten zinc bath 1, and this may become a solid compound (dross) and adhere to the plated surface, causing quality deterioration. 11. A large amount of wiping gas is required, and the cost required to pressurize it is high.

[0007] As a hot-dip galvanizing method that replaces the hot-dip galvanizing method, which has many drawbacks, there is a method of coating or sprinkling molten metal on the steel plate to be plated.
Furthermore, methods have been devised that involve spraying with extremely low pressure.

[0008] As such a method, for example, Japanese Patent Application Laid-open No. 1983
-274749, JP 60-136664, JP 64-15351, JP 1-201456,
Japanese Patent Laid-Open Nos. 63-14848 and 2-111004 have been proposed so far.

[0009]

[Problems to be Solved by the Invention] Among these methods, the method of plating by applying molten zinc has the disadvantage that the application scratches the steel plate to be plated, and also the method of plating by applying molten zinc. The method of plating is
Since uniform zinc cannot be obtained just by sprinkling, it has the disadvantage that wiping or smudging must be performed after sprinkling, and both methods have many problems in practical use.

[0010] Also, regarding the spraying method, the method disclosed in JP-A-1-201456, in which molten metal is acceleratedly injected onto the steel plate to be plated using the force of a jet stream of pressurized gas, Not only does this prevent the metal from reaching the surface to be plated, increasing the amount of molten metal that is wasted, but it also makes it difficult to disperse the molten metal uniformly due to the large difference in specific gravity between the molten metal and the gas. However, it has the disadvantage that it is extremely difficult to obtain a uniform zinc coating.

Furthermore, a method for spraying molten metal without using the force of gas flow is disclosed in Japanese Patent Application Laid-Open No. 63-274749.
0.4 kg of molten metal is ejected through a slit-shaped injection port that extends across the entire width of the steel plate to be plated.
In the method of injection at a low pressure of about /cm2, the minimum amount of molten metal that can be passed through the opening reliably is relatively large due to problems such as the processing accuracy of the opening and the occurrence of non-uniformity due to backflow of the discharge flow. Moreover, it has the disadvantage that it is practically impossible to obtain a stable and uniform zinc coating due to thermal distortion of the opening.

The present invention has been made in order to eliminate the drawbacks of the various methods described above, and is a method of hot-dip metal plating that can easily obtain a high-quality plated plate with a uniform basis weight and has low production and maintenance costs. An object of the present invention is to provide a method and apparatus.

[0013]

[Means for Solving the Problems] In order to achieve the above object, the hot-dip metal plating method of the present invention is a hot-dip metal plating method in which molten metal is injected onto a steel sheet to be plated. , at least 50 kg/c
Plating is performed by dispersing and spraying molten metal pressurized to a high pressure of m2 or higher into fine particles from a nozzle with a flat spray pattern.

[0014] In addition, a hot-dip metal plating device is a hot-dip metal plating device that sprays molten metal onto a steel plate to plate it, and the inside is heated to a temperature close to the melting temperature of the metal and is kept in a non-oxidizing atmosphere. a high-pressure molten metal supply device for pressurizing molten metal to a high pressure of at least 50 kg/cm2; and a high-pressure molten metal supply device for pressurizing molten metal to a high pressure of at least 50 kg/cm2; The present invention is characterized by comprising a molten metal injection nozzle for dispersing the molten metal into fine particles and spraying it in a flat spray pattern.

The high-pressure molten metal supply device has a container for storing molten metal, and an opening opening at the top of the container and provided with seals arranged in at least two stages on the inner circumference, A high pressure is generated by continuously pushing rod-shaped plating metal material with a length shorter than the distance between the molten metal surface and the lower end of the seal from the opening, and the pushed metal A pressurized molten metal is obtained by melting the metal in the container.

Furthermore, the rod-shaped metal material for plating is characterized in that a convex portion and a concave portion that fit into each other are coaxially provided on both end faces.

[0017]

[Operation] Molten metal supplied to the injection nozzle is 50 kg/
Since it is pressurized to a high pressure of cm2 or more, the jet stream becomes uniform and fine particles, and therefore a high-quality plated surface with a uniform and beautiful basis weight can be obtained.

[0018]

[Embodiment] An embodiment of the present invention will be described below using hot-dip galvanizing as an example. When obtaining the desired plating by spraying molten metal onto a steel plate to be plated, the most important thing to consider is how to pressurize the molten metal to a high level and spray it uniformly. The type of nozzle used to inject the metal, the durability of the nozzle, and the method for recovering the ineffective components of the injected molten metal must be considered.

In FIG. 1, reference numeral 10 indicates a hot-dip galvanizing apparatus, which is composed of main parts such as a seal box 11, a molten zinc injection nozzle 12, and a high-pressure molten zinc supply device 13.

The purpose of the seal box 11 is to prevent the surface of the pre-cleaned steel plate S to be plated from being oxidized during the plating process, but it is equally important to The purpose is to prevent the plated steel sheet S, which has been pressurized to the optimum temperature for plating in advance, from being allowed to cool, and to prevent the injected molten metal from solidifying. have.

In order to maintain the inside of this seal box 11 in a non-oxidizing atmosphere, the gas injection pipe 11a is installed in the embodiment.
By injecting nitrogen gas N2 from the tank, the internal pressure is raised slightly above atmospheric pressure and the tank is filled with nitrogen.

[0022] Maintaining the inside of the seal box 11 in a non-oxidizing atmosphere can also be achieved by injecting an inert gas or reducing gas other than nitrogen gas into the inside, or by making the inside a vacuum state. The simplest method is to use nitrogen gas.

The inside of the seal box 11 prevents the molten zinc injected therein from being cooled and solidified before reaching the steel plate S to be plated, and
The temperature is kept close to the melting temperature of zinc to prevent the ineffective components that did not adhere to the inner wall surface from solidifying and adhering to the inner wall surface. is lined with superior ceramics.

The heater 11b is used to heat the outer wall surface of the seal box 11 to maintain the inside of the seal box 11 at a temperature close to the melting temperature of zinc.

This seal box 11 is designed to prevent scattered molten zinc from adhering to or depositing on its inner surface, and to have a shape that eliminates horizontal surfaces as much as possible.

The discharge pipe 11c provided on the lower surface of the seal box 11 is for quickly discharging and recovering the molten zinc that was not directly injected onto the steel plate S to be plated, that is, the ineffective molten zinc. The outer periphery of this is kept warm or heated to prevent the zinc from solidifying inside.

The molten zinc injection nozzle 12 is a so-called flat spray pattern nozzle, and has a relatively small and elongated injection port, from which the molten zinc is turned into fine particles and spread in a wide straight line so as to have a uniform density. It spreads out and sprays it.

The molten zinc supplied to the molten zinc injection nozzle 12 is required to be pressurized to a high pressure in order to make the jet stream uniform and fine particles. Ceramic, which is a material with excellent resistance to molten zinc and wear, is used for the injection nozzle.

The pressure of the molten zinc supplied to the molten zinc injection nozzle 12 must be at least 50 kg/cm2 or higher, and if this pressure is low, the molten zinc will have good fine particles. Therefore, a plated surface with a uniform and beautiful basis weight cannot be obtained. The molten zinc injection nozzle 12 is arranged in such a direction that the jet stream spreads in a direction perpendicular to the traveling direction of the steel plate S to be plated. Multiple pieces are placed side by side in the direction.

Furthermore, when a thick coating weight is required or a more uniform coating weight is required, the molten zinc injection nozzles 12 can be arranged in multiple rows in the advancing direction of the steel sheet S to be plated. It becomes possible.

The high-pressure molten zinc supply device 13 is for supplying molten zinc pressurized to a high pressure to the molten zinc injection nozzle 12, and is used to melt solid zinc material and to inject molten zinc into the molten zinc. It plays an important role in applying pressure.

This high-pressure molten zinc supply device 13 is made of a strong container 13a with excellent molten zinc resistance and pressure resistance, and a heater with sufficient capacity to melt the zinc is installed on the outer periphery of the lower part of the container 13a. 13b is placed.

In the upper part of this container 13a, there is an opening 13 for pushing and supplying rod-shaped zinc materials M1, M2, M3, etc., which have high diameter dimensional accuracy and whose surfaces have been cleaned in advance.
A seal 13d is provided on the inner periphery of the opening 13c to maintain airtightness with the zinc M2 passing through the opening 13c.

It is a necessary condition that these seals 13d are arranged in at least two stages, and even when the joints of zinc materials M1, M2, M3, etc. Care has been taken to ensure that it is effective and that the airtightness in this area is not broken.

The opening 13c is provided at a sufficient distance above the heater 13b so as not to be affected by heat from below, and at the same time, the outer periphery of the opening 13c is forcibly closed by a radiator 13e through which the cooling water W flows. It is cooled to prevent the temperature from rising.

A space is maintained between the upper surface of the molten zinc Z inside this container 13a and the lower end of the seal 13d by being filled with a gas inert to the molten zinc. The necessary gas G is supplied from the gas supply pipe 13
It is supplied from f.

This gas G is maintained at a pressure corresponding to the pressure required to inject molten zinc from the molten zinc injection nozzle 12, and the zinc materials M2, M3, etc. are continuously pushed in at an appropriate speed. When the zinc material M2
, M3, etc., or when the pushing speed becomes slow, this gas G flows in the direction in which it is supplied in order to prevent the pressure inside the container 13a from decreasing.

However, this gas G is substantially sealed 13d.
Since there is no loss other than leakage from the pump, almost no power is required to pressurize it, and it can also be supplied from an accumulator or cylinder (not shown).

A calibration measurement probe 13g for detecting the amount of molten zinc Z inside is inserted into this container 13a, and based on the measurement results, the zinc materials M1 and M
2. Controls the pushing speed of M3, etc.

Furthermore, a temperature measuring probe 13h for detecting the temperature of the molten zinc Z inside the container 13a is installed, and based on the measurement results, the heater 13b is
The temperature of the molten zinc Z is controlled to be constant by adjusting the heating capacity of the molten zinc Z.

Zinc material M1 pushed into container 13a
, M2, M3, etc., are shorter than the distance between the upper surface of the molten zinc Z and the lower end of the seal 13d. Therefore, the zinc M1 that has passed through the seal 13d is The influence of the pressure inside the container 13a acting on this disappears, and the lower end of the molten zinc Z
Before reaching the top surface of the zinc M2, it always leaves the zinc M2 passing through the seal 13d and falls into the molten zinc Z.

[0042] Therefore, molten zinc Z
This completely prevents the heat from being transmitted to the seal 13d and causing it to burn out.

Furthermore, in order to further actively reduce the thermal influence on the seal 13d, it is also effective to circulate the gas filled above the molten zinc Z to cool it.

A pipe 13i connected to the molten zinc injection nozzle 12 is provided on the lower surface of the container 13a, and is insulated or heated to prevent the molten zinc inside from solidifying. Zinc Z is pumped to the molten zinc injection nozzle 12.

Zinc material M pushed into container 13a
1, M2, M3, etc., are coaxially arranged, for example, with a protrusion 14a on one end surface and a recess 14b on the other end surface, so that problems will not occur when passing through the seal 13d due to misalignment of their axes. and their respective ends are fitted into each other and aligned in a straight line.

Next, a specific example of galvanizing by such a hot-dip galvanizing apparatus 10 will be described.
If the diameter of the molten zinc Z is 100 mm and the force to push it is 40 tons, the pressure applied to the molten zinc Z is approximately
500kg/cm2, spray pattern approximately 50mm
x 1000mm and a discharge rate of 3.6kg/min, when injected onto the surface of a steel plate S to be coated with a width of 1m running at a speed of 180m/min at a distance of 500mm, the amount of molten zinc was sprayed onto the surface of the steel plate S to be plated in the form of extremely fine particles, and this surface was plated with a basis weight of 20 g/m2.

In this case, the basis weight can be changed by changing the size of the injection port of the molten zinc injection nozzle 12 or by changing the transfer speed of the steel sheet S to be plated. It was also possible to some extent by changing the pressure of the molten zinc Z.

Needless to mention, when using this hot-dip galvanizing apparatus 10 to vary the coating weight on both sides of the steel sheet S to be plated, it is easy to do so by varying the amount of hot-dip zinc injected onto both sides. Also, if you stop spraying on one side, you can easily perform single-sided plating.

In order to continuously push the rod-shaped zinc material into the high-pressure molten zinc supply device 13, although not shown, it can be easily automated using conventional techniques by combining a pusher, a manipulator, etc.

As a result of galvanizing using the hot-dip galvanizing apparatus according to the present invention as described above,
15-200g/m2 over a wide range of speeds up to 200m
Not only was it possible to easily obtain a coating weight within the range of , we were able to obtain significant benefits in terms of quality, production capacity, cost, and maintenance.

[0051] In the above embodiments, zinc plating has been described, but it goes without saying that similar advantages can be obtained when the present invention is applied to plating other metals such as tin and aluminum.

Furthermore, by arranging a plurality of such molten metal plating apparatuses side by side in the direction of movement of the steel sheet S to be plated and spraying the same type of molten metal from each, it is possible to obtain a thicker coating weight. Alternatively, multilayer plating can be performed by injecting different types of molten metal from each layer.

In this case, it goes without saying that even if different metals are injected from different nozzle rows within the same seal box, the same multilayer plated steel sheet can be obtained.

[0054]

As described above, in the present invention, the molten metal supplied to the injection nozzle is pressurized to a high pressure of 50 kg/cm2 or more, so the injection flow becomes uniform and fine particles. A high quality plating surface with a beautiful basis weight can be easily obtained. In addition, production costs and maintenance costs are low, repairs are not complicated, and different thickness plating is used.
It has a wide range of applications such as single-sided plating and multilayer plating, and its industrial value is great.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the device of the present invention.

FIG. 2 is a perspective view showing an immersion plating method as a conventional example.

[Explanation of symbols]

10 Hot dip galvanizing equipment 11 Seal box 12 Molten metal injection nozzle 13 High pressure molten zinc supply equipment 13a Container 13c Opening 13d Seal 14a Convex part 14b Recessed part S　Plated steel plate Z Molten zinc

Claims (4)

[Claims] Claim 1: In a hot-dip metal plating method in which molten metal is sprayed onto a steel plate to be plated, the molten metal pressurized to a high pressure of at least 50 kg/cm2 is applied to the plated steel plate in a flat spray pattern. A molten metal plating method characterized by applying plating by dispersing and spraying fine particles from a nozzle. 2. In a hot-dip metal plating apparatus that injects molten metal onto a steel plate to be plated, the inside thereof is heated to a temperature close to the melting temperature of the metal and is maintained in a non-oxidizing atmosphere. , a high-pressure molten metal supply device for pressurizing molten metal to a high pressure of at least 50 kg/cm2; and a pressurized molten metal is dispersed in the form of fine particles on the surface of the steel plate to be plated in the seal box and flattened. A molten metal plating apparatus comprising: a molten metal injection nozzle for spraying in a spray pattern. 3. The high-pressure molten metal supply device according to claim 2, comprising: a container for storing the molten metal; and seals opened at the top of the container and arranged in at least two stages on the inner periphery. High pressure is generated by continuously pushing rod-shaped plating metal material whose length is shorter than the distance between the molten metal surface and the lower end of the seal through the opening. A high-pressure molten metal supply device characterized in that pressurized molten metal is obtained by melting the pushed metal in the container. 4. The rod-shaped metal material for plating according to claim 3, wherein the rod-shaped metal material for plating is provided with convex portions and concave portions that fit into each other on both end faces, respectively, coaxially.