JPH1143752A - Cleaning nozzle arrangement structure for hot dip metal coating line - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of providing a remedy against corrective action dent flaws caused by ash at a small running cost without the disturbance in the liquid level of a plating liquid. SOLUTION: A cleaning nozzle 10 which blows inert gas atop a steel strip 7 just before the change in direction by a first outlet roll 3 and directs the blowing direction to the upstream side of the steel strip 7 is disposed in a cooling zone outlet 2 in a hot dip metal coating line of a type to change the steel strip 7 subjected to a heat treatment in a continuous furnace diagonally downward from horizontal while guiding the steel strip to an S shape by the first outlet roll 3 and a second outlet roll 4, then to immerse the steel strip into the plating liquid 6. Only the supersatd. component of the ash sticking to walls falls to the cooling zone and, therefore the amt. of the ash placed on the steel strip is not so much. Since just a small amt. of the ash is splashed, the smaller amt. of the inert gas is necessitated and there is no worry about the disturbance of the plating liquid level by blowing in. The execution of the stable plating is thus ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for preventing ash in a molten metal plating line.

[0002]

2. Description of the Related Art FIG. 8 is a diagram showing the principle of a conventional hot-dip metal plating line.
02 and a cooling zone 103, a downwardly extending cylindrical snout 105 is extended from the cooling zone outlet 104 of the continuous furnace 101,
This is a continuous processing facility in which the lower end of the snout 105 is inserted into the plating solution 107 of the molten metal plating tank 106.
1, heated to a predetermined temperature in a heating zone 102, held and cooled in a cooling zone 103, and then annealed, and a first outlet roll 109 and a second outlet roll provided at a cooling zone outlet 104. By guiding in an S-shape at 110, the plating liquid 107 is turned obliquely from horizontal to oblique as shown by the arrow.
In this way, a large amount of metal-plated steel sheet is produced by immersion in a steel sheet.

In recent years, an operation method has been adopted in which the plating solution 107 is heated and a steel strip having a relatively high temperature is immersed to improve the adhesion of plating. As a result, metal vapor or smoke (hereinafter, referred to as “fume”) rises from the upper surface of the plating solution 107, and a part thereof enters the continuous furnace 101 through the snout 105, and the cold wall (the cold wall) of the cooling zone 105. The phenomenon of solidification, solidification, and deposition in contact with the ceiling and side walls) has become remarkable. This deposit is called ash.

There is no problem if this ash is a small amount,
When the deposits exceed a certain level, they are separated from the surface by the vibration action of the continuous furnace, and the separated ash is placed on the steel strip. On the other hand, the ash placed on the steel strip does not contact the first exit roll 109, but directly contacts the next second exit roll 110. Therefore, there arises a problem that ash adheres to the second exit roll 110, and a pressing flaw of the ash is generated on the steel strip 111 by the pressing force of the second exit roll 110.

Therefore, as a countermeasure, for example, Japanese Unexamined Patent Publication No.
No. 57854, "Method and apparatus for cleaning hot-dip metal plating in a snout" was tried. FIG. 1 of this publication will be described with reference to the following figure. However, the signs have been re-assigned. FIG. 9 is a principle view of a main part of a conventional apparatus for cleaning a molten metal plating in a snout.
The fume rising into the snout 105 as indicated by an arrow is forcibly discharged as indicated by an arrow by a kind of gas curtain formed between the reflux pipe 113 and the suction pipe 114.

[0006]

However, the reflux pipe 1
It has been found that the fume blocking effect cannot be sufficiently obtained unless the flow of gas from 13 to the suction pipe 114 is made strong. When the flow rate and the gas flow rate of the gas are increased in order to increase the gas flow, the upper surface of the plating solution 107 is wavy, causing a problem that the adhesion of the plating varies. In addition, a large-capacity blower is required to flow a large amount of gas, which not only increases the cost of the equipment but also increases the running cost such as the power cost, which requires a review. Accordingly, an object of the present invention is to provide a technique capable of taking measures against ash pressing flaws without disturbing the level of a plating solution and at a small running cost.

[0007]

According to a first aspect of the present invention, there is provided a horizontal continuous furnace having a heating zone and a cooling zone. Then, a downward cylindrical snout is extended from the cooling zone outlet, the lower end of the snout is inserted into the plating solution of the molten metal plating tank, and the steel strip heat-treated in the continuous furnace is S-shaped by the first outlet roll and the second outlet roll. In a molten metal plating line of a type in which the direction is changed from horizontal to diagonally downward and then immersed in the plating solution, an inert gas is blown onto the upper surface of the steel strip immediately before the direction is changed by the first exit roll. A cleaning nozzle is provided at the outlet of the cooling zone so that the spraying direction is directed to the upstream side of the steel strip.

[0008] The ash separated from the wall of the cooling zone and placed on the steel strip is blown off with an inert gas jetted from a cleaning nozzle, and is removed at least from the upper surface of the steel strip. Since the steel strip without ash is wound around the first and second exit rolls, there is no fear that the steel strip is scratched. The amount of ash on the steel strip is not so large because it falls by the supersaturated amount of the ash attached to the wall in the cooling zone. Since only a small amount of ash is blown off, the required amount of inert gas is small, and there is no risk of disturbing the plating liquid surface due to blowing, and stable plating can be performed.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a side cross-sectional view of a cooling zone outlet provided with a cleaning nozzle according to the present invention, in which a first outlet roll 3 and a second outlet roll 4 are arranged vertically in a cooling zone outlet 2 of a horizontal continuous furnace 1, A downwardly extending cylindrical snout 5 is extended from the cooling zone outlet 2, the lower end of the snout 5 is inserted into the plating solution 6 of the molten metal plating tank, and the steel strip 7 heat-treated in the continuous furnace is subjected to the first outlet roll 3 and the second outlet roll. 4
This is a molten metal plating line in which the direction is changed from horizontal to diagonally downward while being guided in an S-shape, and then immersed in the plating solution 6. Cleaning nozzle 1 which blows an inert gas onto the upper surface and the blowing direction is directed to the upstream side of steel strip 7
0 is provided at the cooling zone outlet 2.

The cleaning nozzle 10 is supplied with an inert gas in an inert gas container 11 whose pressure is regulated by a pressure reducing valve 12, whose flow rate is measured by an orifice 13, and whose flow rate is controlled by a flow control valve 14. As the inert gas, a nitrogen gas or a nitrogen-hydrogen mixed gas is appropriate. A controller 15 determines the flow rate based on an external signal or a built-in control logic and controls the opening of the flow control valve 14. The feedback of the flow control is performed by the orifice 13.

FIG. 2 is a plan sectional view of a cooling zone outlet provided with a cleaning nozzle according to the present invention. One or more cleaning nozzles 10 are provided according to the width of the steel strip 7. Reference numeral 16 denotes a header, and reference numerals 17 and 17 denote manual valves. The ash 19... (... Indicates a plurality of ashes) placed on the steel plate 7 is blown off by the inert gas injected from the cleaning nozzles 10 and 10.

Assuming that the ash is not blown off, the ash 19 is placed on the upper surface of the steel strip 7.
There is no need to worry about contact with the first exit roll 3. However, FIG.
At contact with the second outlet roll 4, causing various problems. Therefore, if cleaning is performed with an inert gas, the ash does not need to reach the second outlet roll 4.

As shown in the drawing, the steel strip 7 is blown in the direction opposite to the moving direction of the steel strip 7 aiming at the point A just above the first outlet roll 3 for the following reason. The ash 19 attached to the wall of the cooling zone 2, especially the ceiling 2a becomes a problem. For example, if blowing is performed at the point B in FIG. 1, there is a possibility that a new ash 19 will be placed on the cleaned steel strip 7 from the point B to the point A. Further, if the blow is performed at the point C, which is an intermediate point between the first exit roller 3 and the second exit roller 4, it seems that the steel strip 7 is almost vertical and can be effectively cleaned with a small amount of inert gas. However, the removed ash 19 may fall and enter between the second exit roller 4 and the steel strip 7. Therefore, not point B and point C, but point A (or its vicinity) immediately above the first exit roller 3
Must be.

Next, the type, temperature, injection pressure and injection angle of the cleaning gas will be described. (1) Type of cleaning gas FIG. 3 is a comparison graph of gas for cleaning,
The vertical axis represents the amount (g) of iron oxide per unit area (m ² ) generated in the treated steel strip. In the case of nitrogen gas, the amount of iron oxide is almost zero, and the nitrogen-hydrogen mixed gas is almost zero. Was
When compressed air was used, as much as 25 g / m ^{2 of} iron oxide was generated, which was a cause of plating failure. Therefore, it is necessary to use an inert gas as the cleaning gas, and a readily available nitrogen gas or a mixed gas of nitrogen and hydrogen is preferable.

(2) Temperature of cleaning gas The temperature of the steel strip at the cooling zone outlet is 300 to 600 ° C.
As a result of the investigation, the temperature of the cleaning gas was (temperature of steel strip +
If the temperature exceeds 250 ° C., the temperature balance on the surface of the steel strip is lost, and poor plating is observed.
° C), poor plating was observed. Therefore, it is necessary to keep the temperature of the cleaning gas in the range of (steel strip temperature ± 250 ° C.).

(3) Cleaning Gas Injection Pressure FIG. 4 is a graph showing the relationship between the gas injection pressure and the cooling zone outlet pressure in the continuous annealing furnace. The horizontal axis indicates the cleaning nozzle injection pressure, and the vertical axis indicates the cooling zone. Indicates the outlet pressure. When the nozzle diameter is 40 mm and an inert gas is injected at 0.5 to ⁴ kg / cm ² (nozzle pressure), the pressure at the outlet of the cooling zone is 5.0 kg / cm ² , and there is no defective plating. Did not. When the inert gas was injected at 5 to 6 kg / cm ² (nozzle pressure), the pressure at the outlet of the cooling zone was 5.0 kg.
/ Cm ² , and there was no failure in plating. Therefore,
It was found that the injection pressure of the nozzle did not affect the plating quality.

(4) Nozzle Angle FIG. 5 is a graph showing the relationship between the nozzle angle and the remaining amount of ash. As shown in FIG. Cleaning was performed with the cleaning nozzles 10 and 10 at an angle θ with respect to L. (B)
The horizontal axis indicates the nozzle angle θ, and the vertical axis indicates the amount of ash remaining on the steel strip. When θ = 0, that is, when the nozzle was in parallel with the line, only 10 g / m ^{2 of} ash remained because only the ash on the steel strip was blocked and the effect of dropping from the edge was poor. Assuming that the nozzle angle θ is 10 ° or 30 °, the remaining ash decreased to 4 g / m ² or 2 g / m ² .

Further, the nozzle angle θ is set to 40 °, 60 °, 80
Then, the ash residue was reduced to 1 g / m ² . When the nozzle angle θ was 85 ° or 90 °, the ash residue increased to 3 g / m ² or 8 g / m ² . Since θ = 90 ° blows at right angles to the steel strip, falling from the edge is good. However, since the blow area becomes narrow, the steel strip passes before the ash is sufficiently dropped. Assuming that the allowable remaining amount of the ash is 4 g / m ² , the nozzle angle θ may be in the range of 10 to 85 °, preferably the nozzle angle θ is in the range of 40 to 80 °.

[0019]

Embodiments of the present invention will be described below. Common conditions: Steel strip thickness 1.2 mm Steel strip width 1150 mm Steel strip feed rate 84 m / min Steel strip temperature 470 ° C (cooling zone outlet)

Conditions of the embodiment: Cleaning nozzle Yes Gas type Nitrogen gas Nozzle pressure 2.0 kg / cm ² Nozzle diameter 40 mm Nozzle angle θ 45 ° Gas temperature 250 ° C.

Conditions of Comparative Example: No cleaning nozzle

FIG. 6 is a comparative graph regarding the remaining amount of ash. In the comparative example, as much as 15 g / m ^{2 of} ash remained. On the other hand, in the example, 1-2 g / m ² of ash remained.

FIG. 7 is a comparison graph regarding the amount of indentation flaws generated in the steel strip. In the comparative example, a defect of about 50 tons / month was generated. In contrast, in the example, the defect was about 2 ton / month. Therefore, the cleaning nozzle of the present invention is extremely useful.

In FIG. 1, the cleaning nozzle 10 is provided slightly above the upper surface of the steel strip. However, the mounting position may be made slightly higher so that the nozzle is jetted slightly downward from the horizontal. If the mounting position is too high, the horizontal moment decreases, so that the mounting position is set to, for example, a size not exceeding 1.0 times the diameter of the first outlet roll 3. Further, the cleaning nozzle 10 may be a flat nozzle or a perforated pipe,
In short, it is only necessary that the inert gas for blowing off the ash be jetted in a directional manner. Further, hot-dip metal plating to which the present invention can be applied is hot-dip galvanizing, hot-dip aluminum plating, and hot-dip tin plating.

[0025]

According to the present invention, the following effects are exhibited by the above configuration. A first outlet roll and a second outlet roll are sequentially disposed at a cooling zone outlet of a horizontal continuous furnace having a heating zone and a cooling zone, and a downward cylindrical snout is extended from the cooling zone outlet. Was inserted into the plating solution of the molten metal plating tank, and the steel strip heat-treated in the continuous furnace was turned obliquely downward from horizontal while being guided in an S-shape by the first and second exit rolls. In a molten metal plating line of a type that is immersed in a plating solution later, an inert gas is blown on the upper surface of the steel strip immediately before changing the direction by the first outlet roll, and the blowing direction is directed to the upstream side of the steel strip. The nozzle is provided at a cooling zone outlet.

The ash separated from the wall of the cooling zone and resting on the steel strip is blown off with an inert gas injected from a cleaning nozzle, and is removed at least from the upper surface of the steel strip. Since the steel strip without ash is wound around the first and second exit rolls, there is no fear that the steel strip is scratched. Therefore, while being able to produce a high quality plated steel strip,
The life of the second exit roll can be greatly extended.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a cooling zone outlet provided with a cleaning nozzle according to the present invention.

FIG. 2 is a plan sectional view of a cooling zone outlet provided with a cleaning nozzle according to the present invention.

FIG. 3 is a comparison graph of gas for cleaning.

FIG. 4 is a graph showing the relationship between gas injection pressure and cooling zone outlet pressure in a continuous annealing furnace.

FIG. 5 is a graph showing the relationship between the nozzle angle and the remaining amount of ash.

FIG. 6 is a comparison graph regarding ash remaining amount.

FIG. 7 is a comparison graph regarding the amount of indentation flaws generated in a steel strip.

FIG. 8 is a principle diagram of a conventional hot-dip metal plating line.

FIG. 9 is a principle view of a main part of a conventional apparatus for cleaning a molten metal plating in a snout.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Horizontal continuous furnace, 2 ... Cooling zone outlet, 3 ... First outlet roll, 4 ... Second outlet roll, 5 ... Snout, 6 ... Plating solution, 7 ... Steel strip, 10 ... Cleaning nozzle, 11 ... Inert gas Container, 19: Ash, 102: Heating zone, 103
... cooling zone.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akira Miyazaki 3 Oaza Hikari, Kashima City, Ibaraki Prefecture Sumitomo Metal Industries, Ltd. Inside Kashima Works (72) Inventor Masato Obata 3 Oaza Hikari, Kashima City, Ibaraki Prefecture Sumitomo Metal Industries, Ltd. Inside Kashima Works

Claims (1)

[Claims] A first outlet roll and a second outlet roll are sequentially disposed at a cooling zone outlet of a horizontal continuous furnace provided with a heating zone and a cooling zone, and a downward cylindrical snout is extended from the cooling zone outlet. Into the plating solution of the molten metal plating tank, and while the steel strip heat-treated in the continuous furnace is guided in an S-shape by the first exit roll and the second exit roll, the steel strip is turned obliquely downward from horizontal. In a hot-dip metal plating line of the type of dipping in a plating solution afterwards, an inert gas is blown on the upper surface of the steel strip immediately before changing the direction by the first outlet roll, and this blowing direction is directed to the upstream side of the steel strip. A cleaning nozzle arrangement structure for a molten metal plating line, wherein a cleaning nozzle is provided at an outlet of the cooling zone.