JPS5831073A - Metal sheet continuous zinc electroplating process - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous galvanizing method for metal sheets, and more particularly to a method for galvanizing only one side of a thin steel sheet.

The method of continuous galvanizing of thin steel sheets has been well known for many decades and is now successfully used to produce high-quality products using equipment that is technically well suited to the task in question. .

By the way, 1. Irrespective of their various inherent characteristics, these methods generally all involve galvanizing on both sides, and most involve passing the steel strip continuously through a bath of molten zinc.

However, there are cases in which it is necessary to galvanize only one side of the sheet and not deposit any zinc on the other side.

For example, a thin steel plate used as a material for an automobile body belongs to this example. In this case, as a general rule, paint is applied to the side that will not be galvanized.

The characteristics of the currently known single-sided continuous galvanizing method are:
The advantage is that the surface to be galvanized is partially immersed in the hot-dip galvanizing bath and is brought into contact with the immersed portion of a horizontally mounted rotating roller. However, in this case, at least on the introduction side where the thin steel plate is guided to come into contact with the large-diameter guide roller, a small-diameter contact roller is arranged to prevent molten zinc from penetrating and adhering to the back side of the thin steel plate. ing.

However, in conventionally known devices of this type, one or several contact rollers are arranged on the immersion side circumferential surface of the guide roller, which does not make the initial drawing of the metal sheet difficult. However, there is a drawback that zinc particles adhere and accumulate on the contact roller, making it impossible to achieve a beautiful finish on the galvanized layer.

In addition, if the surface of the guide roller is not provided with protection that does not mix with zinc, as in the present invention, zinc particles will adhere and accumulate on the surface of the roller, causing the metal sheet to be evenly distributed. This may cause problems such as hindering the sheet feeding, or causing the particulate matter to migrate to the back surface of the metal sheet on the non-plated side, deteriorating the finish of the metal sheet.

Precise galvanizing also prevents the formation of zinc particles that adhere to and accumulate in the edges of the guide rollers that protrude beyond contact with the metal sheet, unless fluid or solid wiping means are provided. effect cannot be achieved. That is, the edge portion becomes uneven, creating an opportunity for molten zinc to enter the back surface of the metal sheet from the edge portion.

The present invention makes it possible to continuously galvanize a steel plate sheet, such as a thin steel plate, without causing the above-mentioned disadvantages, and also by any conventionally known method (pickling, heating, oxidation or reduction). The subject matter is a method that can also be applied to thin plates processed by

The basic concept of the method covered by this invention is that, before the thin sheet is introduced into the molten zinc bath, it is rotated about a (more or less horizontal) longitudinal axis and partially immersed in the molten zinc bath. The thin plate is brought into contact with a roller, the thin plate sheet wrapped in its entire width around a part of the outer circumference of the roller without protruding from the edge of the roller is introduced into a zinc bath, and only after the thin plate sheet has left the zinc bath is the thin plate This is designed to release the contact between the sheet and the roller.

The gist of the present invention based thereon is set forth in the claims set forth in the header.

In the method according to the invention, sufficient tension is applied to the zinc bath entry side and the zinc bath exit side of the thin plate sheet to completely bring the thin plate sheet and the roller into close contact over the entire length of the thin plate sheet located in the zinc bath. do.

In particular, in the galvanizing method described above, the rollers around which the metal sheet to be galvanized is wound are kept sufficiently clean so that zinc particles can be deposited on the unplated side of the metal sheet. It is extremely important to avoid any adhesion. The protective coating for this purpose can be used together with other metal coatings, in this case aluminum or tin, and such metal protection also forms part of the invention.

The first possibility is that such a result is achieved by removing the molten zinc that tends to adhere to the ends of the rollers, which are periodically dipped into the zinc bath slightly beyond the width of the metal sheet in the axial direction. can be obtained. If we recall that during the galvanizing operation the metal sheet may move axially along the guide rollers, it will be appreciated that the zinc on both ends of the guide rollers must be removed all the more.

There are several advantageous ways to remove zinc deposited on rollers. For example, solid means such as brushes, star blades, etc. can be used to move the zinc towards the edge of the roller or down the ends, preferably with the movement of the zinc being independent of the direction of rotation of the roller. It is desirable to include a motion component in the opposite direction.

It is also advantageous to blow the zinc back down the roller edge or ends with gas. In the case of such a method, the conditions for zinc spraying can also be reliably adjusted.

The second possibility is that at least the outer circumferential portion is made of a material that does not "receptive to galvanizing," in other words, it does not chemically or physically react with zinc at least at the melting point of zinc and cannot be wetted by zinc. Similar results can be obtained using guide rollers with a covering layer made of non-containing material.

For example, coating materials that meet this requirement include certain silicones, silicate-aluminates, and plasma coatings.

FIG. 1 of the drawings shows the basic aspect of the apparatus for carrying out the method of the invention, in which 1 is a guide roller, 2 is a metal sheet, 3 is a molten zinc bath, 4 is a bath thereof, and 5 is a heater for heating the zinc bath. The electric heating coil, 6 is a heat insulating material layer in which the electric heating coil 5 is embedded, 7 is a gas spray nozzle, and the guide roller 1 is located at both empty edges IA and 1B (not covered by the metal sheet 2). In order to prevent zinc particles from adhering to the surface (see Figure 3), one or more zinc particles are appropriately placed on the surface.

What is shown in Figure 1 is an explanatory diagram of the operating principle, so
Although the guide roller 1 is shown as if it is constantly immersed in the molten zinc bath 3, before the metal sheet 2 is passed through the roller, it must be pulled out of the molten zinc bath 3 and undergo such preparatory work. Of course, it is desirable to do so.

In FIG. 2, the guide roller 1 is the same as in FIG.

Similarly, the state in which the metal sheet 2 is slightly dipped in the molten zinc bath 3 at the working position is shown, but the reference numeral 1a indicates that the metal sheet 2 is pulled diagonally upward slightly from the liquid level 3a of the bath 3 during the preparatory work for passing the metal sheet 2 through the rollers. It shows a fried condition.

The metal sheet 2 enters through the inlet 11 provided in the sink 10, passes through the first tension roller 8 and the second tension roller 9 in a cross-legged manner, and then reaches a position just above the liquid level 3a. is in contact with the outer peripheral surface of the guide roller 1 at
It moves clockwise along the guide roller 1 at the same circumferential speed along with the guide roller 1 for a length slightly less than half a revolution, and then rises almost straight up and is mounted on the top of the casing 10. The material is then removed through the outlet 12 and wound into a coil on winder rollers (not shown).

In order to perform the above-mentioned vertical operation of the guide roller 1, an operating cylinder 12' using pressure oil or compressed air as a working medium is fixedly provided on the outer surface of the casing 10, and when the working medium is introduced into it ( Its supply source, supply conduit, supply port, discharge port, discharge conduit are well known and not shown), and an internal piston (not shown) is located on the right in FIG. The link rod 14, the upper end of which is pivotally connected, comes to a position 14a shown in phantom in FIG. The lower end of the link rod 14 is pivotally supported on the shaft 9a of the second tension roller 9, and is rigidly integrated with the base end of the support arm 150.
is rotatably supported at the tip of the support arm 15 via a bearing 16, so that the guide roller 1 is connected to the bath 3.
It is then pulled up and brought to the upper play position shown at 1a.

After the metal sheet 2 is put on the roller, the operation cylinder 12'
When the pressure medium is discharged further, the guiding roller 1 is automatically brought by its own weight from the idle position 1a into the active position immersed in the bath 3. The second link rod 17 and the link device linked thereto form a pre-stopping mechanism for preventing the guide roller 1 from wobbling during the above-mentioned vertical operation.

FIG. 3 shows blank edges IA where the metal sheet 2 on the guide roller 1 does not come into contact with each other by mechanical means.

FIG. 2 is an enlarged plan view of an apparatus that cleans and removes zinc that rarely adheres to IB by immersing it in a molten zinc bath 3.

In this Fig. 3, 19.20 is a wire brush made by implanting or gathering a large number of steel wires and then bundling them together. The guide roller 1 is slid in a preferably synchronous and symmetrical manner in the X and Y directions to remove deposited zinc on both side blank edges IA and IB of the guide roller 1.

When such adhesion of zinc occurs, a gap is created between the surface of the guide roller 1 and the metal sheet 2, resulting in the disadvantage that zinc adheres and is plated on the back side of the metal sheet, which should not be plated. However, according to the device of the present invention, there is no such fear.

Note that the wire brushes 19 and 20 may be rotated while contacting the roller surface, as shown by reference numerals 19'(20') in FIG. Alternatively, reciprocating motion and rotational motion may be applied simultaneously.

Numerical Examples Before proceeding to implementation of full-scale factory equipment, the present inventor built a test plant and conducted experiments.

As the metal sheet, a metal sheet made of cold-rolled rimmed steel was used. The thickness of the sheet can be 0.12 to 1.25 m, but in experiments, the thickness was 0.8 mm and the width was 50 to 150 mm.
■It can be done as 1,504 in the experiment. Further, the metal sheet feeding speed may be 0.5 to 30 m/min, but in the experiment, it was selected to be about 10 doors/min.

The temperature of the galvanizing bath was maintained at 450°C, and the temperature of the metal sheet introduced into the plating bath was maintained at the same temperature as the plating bath, that is, approximately 4'50°C. The metal sheet used as the experimental material weighs 450 kg (maximum 1 ton) and is placed on a very well-known decoiler (not shown) installed at the starting point in two turns, one turn at a time. For example, it was confirmed that the method of the present invention is capable of continuous operation by quickly welding the IJ tube by hand in the immediate vicinity of the decoiler.

Tension was applied to the metal sheet 2 by a pair of tension rollers 8.9 (at least one of which is preferably adjustable in position, the means for this being not shown). The section from the tension roller to the decoiler is the so-called sheet introduction side (or unwinding side), and the tension therein can be 3 to 20 kf71-dl, and the tension was measured immediately near the decoiler outlet. 10 in the experiment
1F', 11. The tension between the guide roller 1 and the shrivel roller (also called a coin) is the so-called winding side, and the tension thereon can be 10 to 50 kVcr/l, but in experiments it was as high as 25 kVcr/l.

The thickness of the galvanized layer applied to one side of the metal sheet is 0
．． It can be set to 0.03 to 0.2 m, but in the experiment it was set to 0.1 m.

In addition, immediately after the metal sheet is fed out from the decoiler,
It was passed through a soaking furnace or soaking channel (neither shown) and tempered under the protection of a non-oxidizing atmospheric gas. The temperature when exiting this furnace or channel is 5
Although the temperature can be set at 00 to 800°C, the temperature was set at 800°C in the experiment.

The metal sheet thus heated to 800°C is passed through the first cooling zone where a jet of cold water is sprayed onto the metal sheet to cool the sheet at 500°C.
The process was also carried out in the presence of a non-oxidizing protective gas.

The metal sheet leaves this first cooling zone and is similarly sprayed with cold water spray in a second cooling zone to bring the temperature to 400%.
℃ and sent to the inlet 11 and into the casing 10. Although the introduction temperature can be 300 to 500°C, it was set to 400°C in the experiment.

Note that this treatment was also carried out in an atmosphere of non-oxidizing protective gas inside the casing 10. This is especially
This is to protect the non-plated surface of the metal sheet from oxidation.

The electric heating coil 5 has a current capacity of 401#, and the plating tank 4
The capacity was 7 tons of zinc.

Note that as the above-mentioned protective gas, N2, N2, or a mixed gas of both was used. The mixing ratio of N2 can be 0 to 100%.

The metal sheet exiting from the outlet 12 is passed through a third cooling zone (not shown) in an atmosphere of protective gas, the temperature is cooled from 400°C to 200-250°C by spraying water, and then It was wound on a winder roll and made into a coil.

When the galvanized surface was examined, the adhesion of zinc was good, the adhesion was good, and a high-quality single-sided plated product was obtained. .

[Brief explanation of the drawing]

Fig. 1 is a schematic longitudinal cross-sectional view of a galvanizing apparatus showing the principle of implementing the method of the present invention, Fig. 2 is a longitudinal cross-sectional view of a concrete implementation apparatus, and Fig. 3 shows a part of a metal sheet, a guide roller, and a It is an enlarged plan view showing a combination with a pair of wipers. In these figures, 1... guide roller. 2...Metal sheet. 3... Molten zinc bath. 4... Bathtub. 5... Electric heating coil. 6...
・Heat insulation material layer. 7... Gas spray nozzle. 8.9...Tension roller.

Claims (1)

[Claims] Before the metal sheet is introduced into the molten zinc bath, a horizontally arranged guide roller with a movable axis, which rotates about a vertical axis and is partly immersed in the molten zinc bath, is kept clean. A metal sheet is brought into contact under tension with the surface of the guide roller, which has a protective layer that is immiscible with zinc so that the
A series of metal sheets in which only one side of the metal sheet is plated, characterized in that both edges protruding from the metal sheet are kept clean by blowing compressed air or by mechanical cleaning means. Plating method.