JPH0569912B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a continuous hot-melt plating device in which the entrance path of a steel strip entering a plating bath is blocked from the outside air by a duct called a snout. .

[Conventional technology]

When producing plated steel sheets using continuous hot-dip plating equipment, the work hardening of the cold-rolled steel sheets, which are the raw material, is removed.
In addition, in order to reduce and purify the surface, it has become customary to treat the raw steel sheet in an annealing furnace in a reducing atmosphere before plating.

In such a continuous melt plating device, as shown in FIG. 4. The steel strip 2 is drawn out of the plating bath 7 through the Snap roll 5, and the plating layer adhering to the surface in excess is blown away by a nozzle 8 outside the bath, so that the surface of the steel strip 2 is plated to a predetermined thickness. The snout 3 has an upper end connected to the outlet of the annealing furnace 1 and a lower end immersed in the plating bath 7 to block the entrance path of the steel strip 2 entering the plating bath 7 from the outside air, and to prevent the inside of the annealing furnace 1 from entering. The steel strip 2 is maintained in a similar reducing atmosphere to prevent surface oxidation of the steel strip 2.

By the way, conventionally, in hot-dip galvanizing, a small amount of Al has been added to the plating bath for the purpose of improving the adhesion of zinc to the steel strip. This Al reacts with Fe precipitated from the steel strip to form Fe ₂ Al ₅
It forms and floats on the bath surface as so-called topdross. Furthermore, foreign matter carried from the furnace by the steel strip and zinc vapor in the snout also exist as floating foreign matter on the bath surface.

In the absence of a snout, these contaminants would spread over the bath surface and, even if concentrated near the point where the steel strip enters the plating bath, would be easily removed. However, if a snout exists, all of these foreign substances will be concentrated near the position where the steel strip enters the plating bath, and may adhere to the steel strip just before plating, or may be deposited in the bath as the steel strip enters the bath. It becomes entangled and adheres to the steel strip moving through the bath. As a result, plating defects such as incomplete plating and indentation scratches due to dross adhesion occur. Further, even if these foreign substances are removed from within the snout, the conventional technology cannot avoid operation interruption and gas replacement within the snout.

[Problem to be solved by the invention]

For example, in Japanese Patent Publication No. 63-49743, there is a method in which the snout is slightly raised above the bath surface, and while inert gas is flowing through the snout, foreign matter accumulated on the bath surface inside the snout is removed to the outside. A foreign material removal method is disclosed. According to this, there is no need to replace the inside of the snout with outside air conditions, no oxygen is sucked into the annealing furnace, and the removal work becomes easier, so the working time is certainly shortened. However, it is still necessary to stop the line when removing foreign matter, and the use of inert gas inevitably increases costs. Lines have to be stopped twice a week in most cases to remove foreign matter, and this is a major factor hindering productivity.

The present invention was made in view of this situation,
It is an object of the present invention to provide a continuous melt plating device that does not require stopping a line or using an inert gas when removing foreign matter.

[Means to solve the problem]

The plating device of the present invention is a continuous melt plating device in which the entrance path of the steel strip entering the plating bath is shielded from the outside air by a snout, and the main snout is configured such that its tip can be lifted out of the plating bath. is disposed inside the main snout with a space between it and the inner surface thereof, the upper end is airtightly sealed against the inner surface, and the lower end is raised from the plating bath independently of the main snout. and a secondary snout configured to allow

[Effect]

In the plating device of the present invention, when the plating operation is performed with the main snout tip immersed in the plating bath and the sub snout tip lifted from the plating bath surface,
Foreign matter accumulates on the plating bath surface in the main snout. By immersing the tip of the secondary snout in the plating bath at the right time, and then lifting the tip of the main snout from the surface of the plating bath, the main snout and the sub snout can be immersed in the plating bath while the steel strip entry path to the plating bath is blocked from the outside air. Foreign matter that had accumulated on the plating bath surface between the two is exposed to the outside. After removing the foreign matter exposed to the outside, the tip of the main snout is immersed in the plating bath, and after replacing the space between the main snout and the sub-snout with the furnace atmosphere gas, the tip of the sub-snout is lifted from the surface of the plating bath. By repeating this operation as necessary, the foreign matter in the snout is discharged to the outside while the steel strip approach path remains isolated from the outside air and without using inert gas.

〔Example〕

The present invention will be described below with reference to Examples.

FIGS. 1 and 2 are a side view and a front view showing the structure of a main part (snout) of an example of a plating device embodying the present invention.

The snout used in the plating device of the present invention is
It is composed of a main snout 10 and a sub snout 20 provided inside the main snout 10.

The main snout 10 has its upper end connected to the outlet of the annealing furnace and is inclined at a predetermined angle. The main snout 10 has a fixedly provided upper snout 11 and a lower snout 13 connected to the lower end of the upper snout 11 by a heat-resistant and airtight bellows 12.

A guide rod 14 whose lower ends are fixed to both sides of the lower snout 13 is slidably inserted into a rod guide 15 provided in two stages at the lower end of the upper snout 11. By this guide mechanism, the lower snout 13 reciprocates in the vertical direction while maintaining a predetermined inclination angle, and due to this reciprocating movement, the lower end of the lower snout 13 is immersed in the plating bath, and lifted from the surface.

As a drive mechanism for moving the lower snout 13 in this manner, the lower end of a screw 16 is fixed to both sides of the upper surface of the lower snout 13, and the upper end of the screw 16 is fixed to both sides of the upper surface of the upper snout 11. It is engaged with Yujiyatsuki 17.
A motor 18 provided on the side of one of the screw jacks 17 simultaneously drives both screw jacks 17 through a rod 180 to reciprocate the lower snout 13 in the vertical direction.

Note that 19 is a gas replacement valve provided in the upper snout 11.

The sub-snout 20 provided inside the main snout 10 has the same inclination angle as the main snout 10,
A space is formed around the entire circumference between the snout and the inner surface of the main snout 10. Like the main snout 10, this sub-snout 20 also has an upper snout 21, a bellows 22, and a lower snout 23, and the upper end of the upper snout 21 is hermetically joined to the inner surface of the upper snout 11 of the main snout 20. .

The lower snout 23 is located between the main snout 10 and the secondary snout 20 so that it can move up and down within the main snout 10 independently of the upper snout 11.
The section has a dedicated guide mechanism and drive mechanism. These mechanisms themselves are the same as those provided in the main snout 10.

That is, the guide rod 2 is used as a guide mechanism.
4. It has a rod guide 25, and has a screw 26, a screw jack 27, a motor 28, and a rod as a drive mechanism, and these mechanisms allow the lower snout 23 to maintain the same inclination angle as the main snout 10. , the main snout 10 reciprocates in the vertical direction independently of the lower snout 13, and as a result of this reciprocating movement, the lower end of the lower snout 13 is immersed in the plating bath and also lifted from the plating bath surface.

The cross-sectional shape of the main snout 10 and the sub-snout 20 is such that the sub-snout 20 needs to be wide enough not to obstruct the movement of the steel strip passing through the inside, and the main snout should be as wide as possible, and the space between the main snout 10 and the sub-snout 20 should be as wide as possible. It is desirable to form a sky large enough for

In the plating apparatus of the present invention having the snout as described above, the plating operation is carried out in the steps shown in FIGS. 3a to 3c.

During normal operation, as shown in Figure 3a, the lower snout 13 of the main snout 10 is lowered and its lower end is immersed in the plating bath, while the lower snout 23 of the secondary snout 20 is raised and its lower end is immersed in the plating bath. Leave it on standby with the bottom end lifted out of the plating bath.

The steel strip 2 sent from the annealing furnace 1 passes through the upper snout 11 of the main snout 10, enters the sub snout 20, passes through this, and enters the plating bath. Inside the main snout 10 is its lower snout 13.
Since the lower end is immersed in the plating bath and sealed, the entire area including the inside of the sub snout 20 is maintained in the same reducing atmosphere as the inside of the annealing furnace 1, and as a result, the steel strip 2 is heated until it enters the plating bath. Prevents oxidation from occurring on the surface. The steel strip 2 which has passed through the sink roll 4 and the snap roll 5 and has come out of the plating bath has an excess plating layer blown off by a nozzle 8 to form a plated steel plate with a predetermined plating thickness.

As the Metsuki operation progresses, the main snout 1
Top dross is generated on the plating bath surface in the main snout 10, and foreign matter carried from the furnace or generated from metal vapor in the snout also floats on the plating bath surface in the main snout 10.

When these foreign substances are generated to the extent that they affect the plating quality, as shown in FIG. 23 is lowered and its lower end is immersed in the plating bath. As a result, the inside of the secondary snout 20 and the area above the connecting portion of the secondary snout 20 in the main snout 10 are cut off from the outside. In this way, as shown in FIG. 3c, the lower snout 1 of the main snout 10
3 and lift its lower end above the surface of the plating bath. By this lifting, foreign matter floating on the plating bath surface between the main snout 10 and the sub snout 20 is exposed to the outside. Even if foreign matter is exposed to the outside, the inside of the sub snout 20 remains isolated from the outside.

After removing the foreign matter exposed to the outside, first remove the lower snout 1 of the main snout 10 by reversing the above steps.
3 is lowered and its lower end is immersed in the plating bath (see Figure 3b). As a result, the inside of the main snout 10 is again cut off from the outside. In this way, the valve 19 is placed between the main snout 10 and the sub snout 20.
After blowing in more furnace atmosphere gas and replacing this space with furnace atmosphere gas, the lower snout 23 of the sub snout 20 is raised, its lower end is lifted above the plating bath surface, and the normal operating state is returned (Fig. 3a). reference). The inside of the main snout 10 is cut off from the outside in advance,
In addition, since the furnace atmosphere exists between the main snout 10 and the sub-snout 20, even if the lower end of the sub-snout 20 is lifted above the plating bath surface, the steel strip path in the snout remains in the furnace atmosphere. becomes.

By raising the lower snout 23 of the sub-snout 20, the foreign matter floating on the plating bath surface inside it is diffused throughout the main snout 10, reducing the dispersion density and affecting the plating quality. I won't give it anymore.

By appropriately carrying out the above operations during plating operation, the dispersion density of foreign matter floating on the plating bath surface in the snout can be maintained at a level that does not affect the plating quality.

Further, since the steel strip advancing path within the snout continues to be blocked from the outside, there is no need to interrupt the plating operation when removing foreign matter, and there is no need to use inert gas. The surface of the steel strip will not be oxidized even if the plating operation is not interrupted or an inert gas is not used.

FIG. 4 is a sectional view showing another embodiment of the present invention.

In this embodiment, a plurality of nozzles 30 are provided in the width direction of the steel strip on the surface of the lower end of the lower snout 13 of the sub-snout 20 facing the steel strip.
Atmosphere gas in the annealing furnace 1 is discharged from zero to collect foreign matter floating on the plating bath surface in the main snout 10 near the inner surface of the main snout 10.

By doing this, when lowering the lower snout 23 of the sub snout 20 when removing foreign objects (the third
(see Figure b), no foreign matter enters therein, and most of the foreign matter that accumulates in the main snout 10 during normal operation is removed by the above-mentioned foreign matter removal.

Further, the gas discharged from the nozzle 30 is the atmospheric gas inside the annealing furnace 1, and the gas discharged from the main snout 10
Since the gas is not discharged outside, there is no need for gas costs.

In the embodiment shown in FIGS. 1 and 2, a mechanism using screw jacks 17 and 27 is adopted as the drive mechanism for the lower snouts 13 and 23, but the mechanism is not limited to this. For example, a rack and pinion type or a cylinder type may be used, and the guide mechanism is not limited to the above embodiment.

〔Effect of the invention〕

The continuous melt plating device of the present invention does not require stopping the line or using inert gas when removing foreign substances, and does not cause any quality problems even without stopping the line or using inert gas. Never. Therefore, the efficiency of Metsuki operation is significantly improved,
Yield losses due to line stoppages are eliminated, and the expense required to remove foreign matter is also drastically reduced, making it possible to significantly reduce plating costs from these aspects. Furthermore, removing foreign matter does not involve stopping the line.
Since the cost is low, foreign matter can be removed frequently and the plating quality can be improved.

[Brief explanation of drawings]

1 and 2 are a side view and a plan view showing the main part (snout) of the plating device according to the present invention, and FIGS. 3 a, b, and c are side views showing the procedure for removing foreign matter in the plating device of the present invention. FIG. 4 is a side view of a plating device showing another embodiment of the present invention, and FIG. 5 is a side view showing a conventional example of the plating device. In the figure, 2: steel strip, 10: main snout, 20: secondary snout.

Claims (1)

[Claims] 1. A continuous melt plating device in which the entrance path of the steel strip entering the plating bath is shielded from the outside air by a snout, and the main snout is configured such that its tip can be lifted out of the plating bath, and the main snout The snout is disposed on the inside at a distance from the inner surface thereof, and the upper end is airtightly sealed to the inner surface, and the lower end is configured to be raised from the plating bath independently of the main snout. A continuous melt plating device characterized in that it is equipped with a sub-snout.