JP2002309357A - Device for removing deposit from roll in hot-dip metal coating bath - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device for removing deposits from a roll in a hot-dip metal coating bath of which the cost can be reduced owing to its simplified structure, which can minimizing troubles, has excellent maintainability and enables stable plating quality. SOLUTION: This device has a guide which is attached to a screw shaft in a manner to be freely movable and with which a rod is engaged in such a way that it can freely move up and down. A pontoon is provided to the rod in a manner to be immersed in the hot-dip metal coating bath and generates buoyancy. By regulating the buoyancy of the pontoon, a doctor blade can be brought into stable contact with the roll in the bath.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous hot-dip metal plating line for removing deposits such as dross from the surface of a roll in a bath such as a sink roll provided by dipping in a hot-dip metal plating bath. The present invention relates to a technique for preventing a flaw generated on the surface of a metal strip. In the following, an example will be described in which the molten metal in the molten metal plating bath is molten zinc, and the metal strip to be immersed is a steel strip (sometimes referred to as a steel sheet). is there.

[0002]

2. Description of the Related Art First, a continuous hot-dip galvanizing line will be described with reference to FIG. The steel strip S guided from the annealing furnace (not shown) into the hot-dip galvanizing bath 2 through the snout 1 is turned upward by the sink roll 3 in the bath, and its pass line position is set by the support rolls 4a and 4b in the bath. After being lifted out of the bath, the gas is adjusted to a predetermined plating amount by the gas wiping nozzle 5. Furthermore,
In some cases, heat treatment is performed in the alloying furnace 7 as necessary, and alloying hot-dip galvanizing in which iron is diffused in the galvanized layer may be performed.

Meanwhile, in a plating bath, in addition to zinc (Zn), about 0.1 to 0.2% by mass of aluminum (A) added for improving the adhesion and powdering properties of a plating layer.
l) and iron (Fe) eluted from the steel strip. These components of Zn, Fe, and Al form an intermetallic compound called dross, and there are differences depending on the conditions of Al concentration and bath temperature, but FeZn ₇ in which Fe and Zn are combined, FeZn ₇ in which Fe and Al are combined ₂ Al ₅

When continuous plating is performed for a long time, a phenomenon occurs in which these dross adhere to the surface of a sink roll in a bath or a support roll in a bath (hereinafter, these are collectively referred to as rolls in a bath). There is a problem that the adhered material becomes a press flaw defect to damage the steel strip or cause local elongation of the steel strip, thereby deteriorating the quality. Since the hot-dip galvanized steel sheet is relatively inexpensive and has excellent rust prevention ability, it has been widely used as a steel sheet for automobiles and a steel sheet for home electric appliances.

In particular, in recent years, galvannealed steel sheets have been frequently used as steel sheets for automobiles, and the quality requirements of automobile manufacturers have become more severe than in the past, and the surface of the plated steel sheets is very small. The situation is becoming unacceptable even for the most flaws. Therefore, for the supplier of the steel sheet, the above-mentioned pressing defect caused by the adhesion of dross to the surface of the roll in the bath has become a more serious problem.

[0006] As a countermeasure for this, researches have been conducted in the past, and for example, a technique of spraying ceramics to which dross hardly adheres to the surface of a sink roll as a roll in a bath has been proposed. However, this technique cannot completely prevent dross from adhering to the sink roll surface. Therefore, a method for mechanically removing foreign substances on the roll surface in a bath has been developed and has already been put to practical use. Specifically, this is a technique in which a blade (referred to as a doctor blade) having a length extending over the entire length in the axial direction is pressed against the surface of a roll in a bath, and foreign matter is scraped off. In the prior art, it was necessary to make the doctor blade uniformly contact the entire surface of the sink roll surface in the axial direction.However, this uniform contact is extremely difficult, and it is still necessary to make the surface of the sink roll completely satisfactory. Is not yet reached.

[0007] In particular, doctor blades have the disadvantage that they wear out during use and make uniform contact more difficult.
Further, when a part of the doctor blade is unevenly worn, it is necessary to replace the entire doctor blade for uniform contact, and there is a problem that the doctor blade cost is increased. For this reason, a method has been already developed in which the doctor blade is made narrower than the roll width and the narrowed doctor blade is moved in the axial direction of the roll to remove foreign matter.

[0008] Some specific examples are shown below. Japanese Utility Model Application Laid-Open No. 61-16428, Japanese Utility Model Application No. 2-51253, a wiper blade narrower than the width of the roll in the bath, or
A scraper blade (that is, a doctor blade referred to in the present application) is provided with a pressing device such as a cylinder that presses the scraper blade against a roll in a bath, and is moved in the roll axis direction. The pressing force of the doctor blade against the roll in the bath is detected by a torque sensor, and the pressing force is adjusted to an appropriate value by controlling the forward / backward driving means of the doctor blade based on the detected value.

The roll in the bath is generally not rotated by an electric motor, but is rotated by a steel strip running in contact with the roll. Therefore, if the pressing force is too large, the roll stops and becomes non-rotating, and the operation is stopped. You can't do it smoothly.

[0010]

In the technology disclosed above, an air cylinder is generally applied as a rolling-down device. However, in order to remove the deposits while preventing the roll from rotating in the bath and preventing the roll surface from being damaged by the blade, it is necessary to finely adjust the rolling force of the air cylinder. However, since the air cylinder has a sliding resistance between the cylinder and the piston, only the adjustment of the air pressure causes a large variation in the actually applied pressing force. For this reason, there is a problem that a great variation occurs in the attached matter removing effect, and the plating quality is not stable.

Further, in the technology disclosed above, feedback control based on the detected value of the torque sensor is required, and not only the mechanical device but also the control device is required, which increases the equipment cost. Further, since the torque sensor is installed in the middle of the pressing mechanism, the rigidity of the equipment is weakened, so that there is a problem that it is not possible to remove the adhered substances stably. Further, there is a problem in that the above-mentioned control means must be installed immediately above the hot-dip galvanizing bath. That is, in order to adjust the amount of hot-dip galvanized coating, the above-mentioned gas wiping nozzle or the like is installed in the immediate vicinity of the control means, but the molten metal adhered to the steel strip with the gas used for the wiping is provided. Some of the plating will be scattered and will be placed in a very poor environment. Therefore, it is also a problem that adjustment of the control means and maintenance and inspection become difficult.

The present invention provides a technique for solving the above problems in a doctor blade type foreign matter removing apparatus. That is, the present invention has a simple structure, is low in equipment cost, has few failures, is excellent in maintainability, and is capable of stabilizing plating quality. A removal device is provided.

[0013]

According to the present invention, there is provided a doctor blade which is pressed against the surface of a roll in a bath which is immersed and arranged in a hot-dip metal plating bath in which a metal strip runs, and which scrapes off deposits on the roll surface. A rod for supporting a doctor blade, and a screw shaft provided above and traversing the plating bath so as to be movable along the axis of the roll in the bath. In the attached matter removing apparatus, a guide movably engaged with the screw shaft, and the rod is movably engaged with the rod vertically, and the rod is immersed in the molten metal plating bath and provided. Wherein the doctor blade is stably brought into contact with the roll in the bath by adjusting the buoyancy of the float box. It solves the above problems by deposit removing device of Kki the bath roll.

Further, the present invention provides the floating box, wherein the buoyancy is adjusted so that the doctor blade and the roll in the bath come into contact with almost no load, and thereafter, the desired weight is applied to the rod. It has been found that it is preferable that the contact weight of the doctor blade to the roll in the bath can be freely adjusted by providing a weight. Further, the present invention is such that in the above invention, the guide is preferably a ball spline.

[0015]

FIG. 1 shows a preferred embodiment of the present invention.
It will be described based on. The same members as those in the conventional continuous hot-dip galvanizing line already described with reference to FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted. In the following, an example in which the applied in-bath roll is a sink roll will be described, but it goes without saying that the present invention can be similarly applied to a in-bath support roll.

The doctor blade 11 has a rod
13 is attached to the leading end of the roll, receives a pressing load, and comes into contact with the rotating sink roll 3 as the steel strip S is conveyed to remove foreign substances on the roll surface. Here, one feature of the present invention is that the rod 13 is engaged with the guide 14 so as to be vertically movable.

The guide 14 is preferably designed to minimize the sliding resistance with the rod 13, and is preferably a guide having a built-in bearing or the like. In particular, it is preferable to apply a ball spline which has almost no sliding resistance and can be moved up and down. Guide 14
Are mounted on the traversing frame 15. Further, the traversing frame 15 is fixed to the screw shaft 18 and the screw shaft 18
Is attached to a bath equipment frame 19 disposed in parallel with the axial direction of the sink roll 3, and freely moves in the axial direction of the sink roll 3. Then, it is possible to remove the deposits over the entire surface of the sink roll 3.

Here, the traversing frame 15 is provided with retreating means 17 typified by an air cylinder, and the retreating means 17 is provided with a bracket 16 engaged with the rod 13. By doing so, it becomes possible to operate the retreating means 17 and retreat the doctor blade 11 out of the bath 2 freely. Also, in the present invention, one of the features is that the floating box 12 is provided on the rod 13.

The floating box 12 receives buoyancy from the hot-dip galvanizing bath 2 and acts in a direction to retract the doctor blade 11 from the sink roll 3. Floating box 12 is SUS3
It may be made of a material having corrosion resistance to Zn, such as 16L, and welded to form a box. On the other hand, the doctor blade 11 includes the doctor blade 11 itself,
The total weight of the bracket 16 and the floating box 12 attached to the bracket 13 is applied as its own weight. The weight of the present inventors who presses the doctor blade 11 against the sink roll 3 with a relatively small value is sufficient, and this weight alone is sufficiently heavy. The present invention has been made by paying attention to the point that the optimum value is exceeded.

In the present invention, the buoyancy of the floating box 12 is adjusted to offset the difference from the own weight, thereby making the doctor blade 11 adjustable.
Are those in which the pressing load abutting on the sink roll 3 is optimized. When adjusting the buoyancy, it is naturally necessary to consider the buoyancy applied to the doctor blade 11 and the rod 13 immersed in the bath. Here, the present invention largely depends on the fact that the provision of the guide 14 makes it possible to suppress the sliding resistance of the rod 13 connected to the screw shaft 18 to a negligible level.

As another embodiment of the present invention, FIG.
It is preferable to apply a weight 20 having a desired weight to the rod 13 as shown in FIG. In the case of this embodiment, first, at the time of adjusting the buoyancy in the floating box 12, the pressing load applied to the doctor blade 11 is adjusted to be zero without the weight 20, and then the weight is adjusted. With the addition of 20, the pressing load can be adjusted.

By doing so, the pressing load applied to the doctor blade can be freely adjusted from outside the bath, and the on-site adjustment during operation becomes extremely easy. As is clear from the above, in the present invention, the pressing load applied to the doctor blade does not fluctuate, and the pressing force of the doctor blade against the roll in the bath can be stabilized, so that the doctor blade can be stably and reliably provided. Deposits can be removed.

[0023]

EXAMPLE The apparatus for removing deposits on a roll in a hot-dip metal plating bath according to the present invention shown in FIG. 1 was disposed in a hot-dip galvanizing bath for steel strip, and a continuous hot-dip galvanizing operation was actually performed. The steel strip is obtained by cold rolling a continuous cast piece of ultra-low carbon steel.
0.5 to 1.6 mm, 800 to 1600 mm in width. The line speed was in the range of 80 to 120 mpm. The temperature of the hot dip galvanizing bath was 465 ° C.

On the other hand, the width of the sink roll was 2000 mm, while the width of the doctor blade was 300 mm. The traversing speed of the doctor blade is 30 mm / sec. The total load of the doctor blade etc. was 200 kg, the total buoyancy of the floating box etc. was adjusted to 170 kg, and the pressing force was equivalent to 30 kg. As described above, as a result of performing the operation using the apparatus for removing deposits on the roll in the molten metal plating bath of the present invention, the average
It was confirmed that operation was possible without any problems caused by the roll surface during the bath for 15 days. On the other hand, conventionally, quality problems such as surface roughness have occurred on and after the sixth day on average, and the effects of the present invention are clear.

[0025]

According to the present invention, the pressing force of the doctor blade against the roll in the bath can be stabilized, and the prevention of the rotation of the roll in the bath and the removal of deposits can be achieved at the same time. Quality could be stabilized.

[Brief description of the drawings]

FIG. 1 is a schematic view of an apparatus for removing deposits on a roll in a hot-dip metal plating bath according to the present invention.

FIG. 2 is a schematic view showing another embodiment of the present invention.

FIG. 3 is a schematic diagram illustrating continuous plating in a conventional hot-dip metal plating bath.

[Explanation of symbols]

 Reference Signs List 1 Snout 2 Molten metal plating bath (Molten metal solution) 3 Sink roll (roll in bath) 4a, 4b Support roll in bath (roll in bath) 5 Gas wiping nozzle 6 Support roll on bath 7 Alloying furnace 11 Doctor blade 12 Floating Box 13 Rod 14 Guide (ball spline) 15 Traversing frame 16 Bracket 17 Evacuation means (air cylinder) 18 Screw shaft 19 Bath frame 20 Weight

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4K027 AA02 AA22 AB42 AD08 AD17 AE04

Claims (3)

[Claims] 1. A doctor blade which is pressed against the surface of a roll in a bath immersed and arranged in a hot-dip metal plating bath in which a metal strip runs, and scrapes off deposits on the roll surface; and a rod for supporting the doctor blade; A screw shaft that is provided above the plating bath and traverses the plating bath and that enables a doctor blade to move along the axis of the roll in the bath; and A guide that is movably engaged with a shaft and that engages the rod movably up and down;
A floating box that is immersed and provided in the molten metal plating bath to generate buoyancy, and the buoyancy of the floating box is adjusted so that the doctor blade stably contacts the roll in the bath. An apparatus for removing deposits on a roll in a hot-dip metal plating bath. 2. The floating box is a floating box whose buoyancy is adjusted such that the doctor blade and the roll in the bath come into contact with almost no load, and then a weight having a desired weight is attached to the rod. 2. The apparatus for removing deposits on a roll in a molten metal plating bath according to claim 1, wherein the contact load of the doctor blade on the roll in the bath can be freely adjusted by the application. 3. 3. The apparatus for removing deposits on a roll in a hot-dip metal plating bath according to claim 1, wherein the guide is a ball spline.