JPH05156415A - Hot dip coating equipment - Google Patents

Abstract

(57) [Summary] [Purpose] To minimize the widthwise warpage of the steel strip during hot dipping. [Structure] A fluid-supporting roll is brought into contact with a steel strip inverted by a sink roll, and the contact surface is an involute curved surface. The pushing amount by this roll is adjustable and rotatable. [Effect] Since the widthwise warp of the steel strip is reduced,
High-speed thin weighting is possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a continuous hot dip coating apparatus,
Particularly, the present invention relates to a continuous hot dip galvanizing apparatus for steel strips in which warpage in the widthwise direction of the steel strips during plating operation is minimized.

[0002]

2. Description of the Related Art When a plated steel sheet is manufactured by a continuous hot dip galvanizing machine, a sink roll in a plating bath reverses the traveling direction of a steel strip. It is known that the steel strip is warped in the width direction depending on the shape of the base material. In hot dip plating, a gas wiping device is used to control the amount of plating adhered, but if warpage occurs in the width direction, the uniformity of the plating thickness in the width direction is hindered, which leads to deterioration of the quality of the plated steel sheet.

The cause of the warp in the width direction of the steel strip is that the stress remains unevenly in the thickness direction of the steel strip due to the bending process at the time of reversal. However, such residual stress can be suppressed in that portion by the mechanical restraining force. Therefore, a method of preventing vibration of the steel sheet by using a touch roll or a pad and additionally suppressing the warp in the width direction by the restraining force is generally performed.

An apparatus for bending a steel strip with a snap roll in a bath to correct the warp is disclosed in Japanese Patent Laid-Open No. 2-20.
It is proposed in Japanese Patent No. 0759. Furthermore, Japanese Examined Sho 63-5041
As disclosed in Japanese Patent No. 8 and Japanese Patent Laid-Open No. 3-31464,
An apparatus and method for supporting a steel strip in a non-contact form while ejecting molten metal and bending it into an S shape have been proposed.

[0005]

However, it is difficult to completely eliminate the width warp by an incidental deterrent measure by a touch roll or a pad. Therefore, when the line runs at a low speed, although it was not a big problem,
When increasing the speed, a small warp, which has not been a problem in the past because the gas wiping nozzle needs to be close to the steel strip, has come to affect the uniform coating amount.

Therefore, a snap roll is arranged in the bath,
A method has been proposed in which the widthwise warp on the bathing side is eliminated by correcting the warp and eliminating the residual stress. In this method, the processing curvature is changed depending on the amount of pressing of the straightening roll with respect to the steel strip, but if the roll diameter and roll arrangement are proper, the accuracy of straightening the warp is relatively good.

However, the roll diameter is not necessarily optimally selected at the maximum and minimum plate thicknesses among the threading materials, but is selected so as to be optimized with respect to the representative plate thickness. The roll diameter may be changed appropriately, but since the roll is provided in the bath, replacement is not easy, and the straightening width is limited depending on the plate thickness or thin plate. Further, since the roller in the bath also has a bearing in the bath, corrosion and wear due to the molten metal occur after long-term use, causing rattling and whirling of the roll shaft, which induces vibration of the steel strip. This also makes the plating thickness non-uniform.

On the other hand, the method of supporting the steel strip in a non-contact manner by the jet flow of the molten metal has the advantage of suppressing the occurrence of flaws because it is non-contact. However, the method of bending the steel strip into an S shape and flattening it on the bathing side is not as accurate as the method of bending the steel strip by rolling to eliminate warpage, and the pass line is stable. It is hard to say that

Here, the present invention provides a hot dip coating apparatus capable of suppressing the occurrence of vibrations and flaws, accurately correcting warpage, and greatly changing the plate thickness range that can be corrected, and performing high-speed plating. Also aims to improve the accuracy of the plating thickness regardless of the plate thickness.

[0010]

[Means for Solving the Problems] The inventors of the present invention have made various investigations to solve the problems, and at that time, pay attention to the following points.

As already known, it is possible to apply a plastic deformation by winding a steel strip around a roll and give an appropriate working curvature to straighten and eliminate the warp. Conventionally, such a plastic deformation is applied by a snap roll dipped in a plating bath to correct the warp. However, if the processing curvature given to the steel strip is the same, it is not necessary to use a roll, and if an external force is applied to the steel strip via a fluid to give a predetermined processing curvature, it should be similarly corrected. With such a configuration, vibration should be greatly suppressed because there is no rotating part by the roll. Here, the inventors have obtained the following findings through such studies.

When the steel strip is bent by colliding the jet flow with the steel strip, a smooth working curvature cannot be obtained as in the case of using a roll, but the portion contacting the steel strip is an arc in the longitudinal direction of the steel strip. Bending using a supporting member having a shape enables accurate correction.

If the radius of the arc shape is continuously changed with respect to the longitudinal direction of the steel strip, rotating the support member to change the contact surface with the steel strip changes the roll diameter. That would be the case.

Moreover, the arcuate support member supplies the liquid to form a thin fluid layer at the interface with the facing steel strip, so that the contact with the steel strip can be eliminated and the occurrence of flaws can be suppressed. ..

Therefore, the gist of the present invention is to provide a plating bath, a sink roll held at a position immersed in the plating bath accommodated in the plating bath, and a sink roll provided downstream of the sink roll. What is claimed is: 1. A hot dip plating apparatus comprising: a steel strip supporting member that abuts on both sides or one side of a steel strip via a fluid in a plating bath, wherein a surface of the supporting member facing the steel strip is a traveling direction of the steel strip. On the other hand, the radius is a continuously changing arc shape, and a mechanism for changing the pushing amount of the support member with respect to the steel strip is provided, and the radius of the arc on the surface of the support member facing the steel strip is changed. The hot dip plating apparatus is provided with a rotating mechanism for

According to a preferred embodiment of the present invention, the sink roll has symmetrically two or more fluid outlets on the roll surface over the entire circumference of the roll, and two or more fluid outlets are provided in the outlet in the radial direction of the roll. You may comprise from the fluid support roll which provided the partition plate. The chance of contact between the steel strip and the roll is reduced, and thus the occurrence of flaws is effectively prevented.

According to another aspect, in the fluid support roll, a fluid chamber is arranged on the opposite side of the steel strip winding surface of the roll, and an interface between the roll and the steel strip is formed from a boundary between the fluid chamber and the roll. It may have a structure in which a fluid is jetted out.

[0018]

The operation and mechanism of the present invention will be described more specifically with reference to the accompanying drawings.

(1) Straightening Method FIG. 1 shows an example of a hot dip plating apparatus provided with a fluid support member. In the figure, a hot dip plating apparatus 10 according to the present invention is composed of a plating tank 12, a sink roll 14 partially shown in a schematic form, and support members 16 and 18 provided in pairs downstream thereof.
Each of these elements is immersed in a plating bath (not shown).
The steel strip 22 is bent by a large number of rolls before reaching the plating bath, and as a result, warpage occurs. Considering the effect of the latest roll, the sink roll 14 of C forms a positive widthwise warp. In the figures, A and B are provided with fluid support members 16 and 18 for straightening warpage, and heretofore, snap rolls (also called straightening rolls or stabilizing rolls) have been arranged. Here, by changing the pushing amount of the B support member 16, the bending curvature of the steel strip 22 changes, and the warpage amount is controlled and corrected.

In FIG. 2, the radius of the surface of the upper support member facing the roll is Ru (= 150 mm), and that of the lower support member is R _L (= 125 m).
As m), the relationship between the pushing amount of the fluid support member 16 of B and the amount of warp at that time when a 0.4 to 2.0 mm steel strip is straightened with each fixed. Focusing on a steel strip having a thickness of 0.8 t (mm), it is possible to make a warp from negative to positive by pushing the support member 16 of B. In other words, the warp can be corrected. If the plate thickness is 0.8t (mm), the warpage can be reduced to zero by changing the pushing amount to around 20mm. However, when the plate thickness changes, the warp behavior with respect to indentation changes. Although there is a pushing amount that makes the warp zero, it is desirable to balance the positive and negative in terms of ease of control. In the illustrated example, the supporting members 16 and 18 have a semicircular arc shape, and the radius of curvature of the surface is continuously changed.

Next, FIGS. 3 and 4 show the results of rotating the fluid support members 16 and 18 of A and B to change the radii Ru and _RL of the surface facing the steel strip. The fluid support members 16 and 18
Although the support and rotation mechanism of No. 1 is not particularly described, it will be apparent to those skilled in the art from the above description.

FIG. 3 shows the relationship between indentation and warpage with respect to a 0.4 t steel strip, and shows that the positive / negative balance is improved by making Ru small as indicated by a triangle mark. In other words, it became easier to correct by changing the pushing amount near 15 mm.

Further, FIG. 4 shows that the positive and negative balance is improved as shown by the cross mark by increasing Ru in relation to the indentation and warpage with respect to the 2.0 t steel strip. In other words, it became easier to correct by changing the pushing amount near 15 mm.

As described above, it is understood that not only the pushing amount is changed, but also the radius of curvature of the fluid supporting member with respect to the steel strip is changed, so that various plate thicknesses can be accurately corrected.

(2) Vibration Suppression Effect The snap roll and sink roll have a bearing portion for rotation, and this portion is easily corroded in the plating bath, and rattling and uneven rotation are likely to occur. In particular, since the snap roll has a small winding angle, it is necessary to drive the shaft in an auxiliary manner, which causes vibration and the like to cause uneven plating thickness. However, according to the present invention, by fluidly supporting the steel strip using fluid support members 16, 18 instead of them,
The rotation of the roll is eliminated and vibration is suppressed. Also,
The occurrence of flaws due to contact with the roll is also prevented.

(3) Effect of floating support of sink rolls FIG. 5 shows a structure in which the sink rolls 14 are fluid-supporting rolls 24. FIG. 6 shows an example of the fluid support roll 24.
FIG. 7 shows an exploded view thereof, and FIG. 8 shows an example of a combination of the fluid support roll 24 and the fluid chamber. In FIG. 6, there are two or more fluid outlets 52 extending symmetrically on the surface of the roll at intervals W _O, and the outlets 52 are provided.
At 52, two or more partition plates are provided in the roll radial direction.

In the structure of the illustrated example, the roll main body 50 has an inner roll 60 and an outer roll 62 incorporated therein. The outlet 52 is formed by inner and outer rolls 60 and 62, and the outlet angle (θ) of the fluid outlet 52 is adjusted to, for example, 30 ° ≦ θ ≦ 90 ° with respect to the roll center axis as shown in the figure. .. 70 is a fluid supply port from the fluid reservoir 63 to the outlet 52.

FIG. 7 is an exploded view of the fluid support roll of FIG. 6, showing a plurality of partition plates 14 at the outlet 52 in the roll radial direction.
0 is provided. Performs a kind of rectifying action and blows out
A fluid having a uniform pressure can be supplied in either direction of 52.

FIG. 8 shows an example in which the fluid support roll has a fluid chamber arranged on the side opposite to the steel strip winding surface of the roll. A fluid chamber 56 is provided facing the surface.
The slit portion formed at the boundary between the fluid chamber 56 and the fluid support roll is provided with two fluid ejection nozzles on both sides for supplying a fluid to the interface between the fluid support roll and the strip. Reference numeral 59 indicates a fluid supply pipe to the fluid chamber 56.

To start the operation, first, the fluid is introduced into the fluid support device from the outside through the fluid supply pipes 54 and 59.
The fluid introduced at that time is supplied to the roll main body 50 and the fluid chamber 56, respectively. The fluid sent to the roll main body 50 is stored in the hollow portion at the center of the roll, and then the fluid flows in the direction of the arrow shown in FIG. (See FIG. 6) and is radially ejected from a nozzle 52 provided on the roll surface.

At this time, the ejection of the fluid from the nozzle 52 on the lower surface of the roll 50 is suppressed by the arc portion 86 of the fluid chamber 56 facing the roll, as shown in FIG. On the other hand, the fluid supplied to the fluid chamber 56 installed on the lower surface of the roll is jetted to the interface between the roll and the steel strip from the boundary with the roll surface, that is, the slit 58.

As described above, when the steel strip is floated and supported as an alternative to the sink roll, indentation flaws caused by the inclusion of dross and other foreign matter between the roll and the steel strip are suppressed. In other words, product quality is improved by synergistic effects of vibration and slip prevention using the fluid support member.

(4) Fluid Support Member FIGS. 9 and 10 show examples of the fluid support members 16 and 18, but a fluid blowout nozzle 80 extending in the width direction may be formed, or a large number of ejection ports 82 are provided. The format is also acceptable and is not particularly limited.

Next, the cross-sectional shape of the fluid support members 16 and 18, that is, the radius of curvature of the arc with respect to the longitudinal direction of the steel strip will be described. The shape is not particularly limited as long as the small radius continuously exists up to the large diameter. Since it is desirable to change continuously, it is good to design using an involute curve as an example. The involute curve is displayed in the following coordinate system. Each symbol in the formula is as shown in FIG.

[0035]

[Equation 1]

The radius of curvature is changed according to the plate thickness, but 100
If the radius is set to about 200, the correction ability will be sufficiently large. So, for example, if l ₁ = 250 mm and R = 57 mm,

[0037]

[Equation 2]

Since the radius changes from 250 to 100 mm, an appropriate curve can be obtained.

However, the present invention is not limited to this, and l ₁ , R, and θ may be appropriately combined according to the plate thickness.

(5) Floating height of steel strip Although the steel strip is floated and supported via fluid (molten metal), it is important to follow the arc shape in order to correct the steel strip accurately. .. A concrete floating support mechanism for the steel strip is the fluid ejection nozzle 80 and the ejection port 82 described in FIGS. 9 and 10 described above.

Then, the fluid is supplied from the surface facing the steel strip,
Form a fluid layer. The levitation height is required to be within a few mm in order to improve the accuracy of the machining curvature, and it is desirable that the levitation height is within 1 mm. In terms of running cost, it is not necessary to float it more than necessary.

[0042]

EXAMPLE A hot dipping apparatus according to the present invention shown in FIG. 11 was prepared. The specific configuration was similar to that shown in FIGS. Figure
12 shows only the arrangement of the support members 16 and 18. In the plating bath, a sink roll 14 which is a fluid support roll of C and a fluid chamber 56 of D combined with the sink roll 14 are also provided, and support members 16 and 18 which are correction members of A and B are arranged. The molten zinc in the bath was circulated by a pump and supplied to the fluid support member, the roll, and the fluid chamber. After the steel strip 22 passes through the snout from the annealing furnace,
The sink roll 14 of the fluid support roll reverses the direction and is pulled upward.

Then, the steel strip 22 is formed by the fluid supporting members 16 and 18.
Was corrected. Here, the support member 16 has a radius of curvature of 100 to 230.
The shape of the support member 18 varies continuously from 120 to 120 mm.
The shape changed between 200 mm. In both cases, the minimum radius of curvature of the surface facing the steel strip can be arbitrarily set within the above numerical range by changing the angle of the rotary support.
It also has a mechanism for changing the amount of pushing into the steel strip.

The diameter of the sink roll 14 was 700 mm. With this arrangement, 0.3 to 3.2 mm thick × 1800 width steel plate was hot-dipped, but as a result of the steel strip being supported by the fluid, the occurrence of flaws due to slip between rolls and strips and indentation flaws due to dross was greatly reduced did. Variations in plating thickness were prevented because vibrations caused by rattling due to roll rotation and vibrations generated by the drive system of the snap rolls were eliminated.

Next, using the above-mentioned apparatus, the amount of coating applied when hot-dip galvanizing was performed at a high speed of 180 m / min for the steel strip, and
FIG. 15 shows the results of examining the amount of plating adhered when hot dip galvanizing was performed at a steel strip speed of 100 m / min by a conventional method in which the supporting members 16 and 18 were not operated in the above apparatus. As is clear from the figure, the present invention enables the weighting even at high speed.

The straightening effect of the steel strip is similar to that of the case of using a roll, and if the roll is a roll, the straightening area changes depending on the plate thickness. Since the radius of curvature that changes with time can be selected arbitrarily, the correction area is also sufficiently wide corresponding to the plate thickness. That is, since the wiping nozzle can be brought closer to the steel strip by improving the accuracy of vibration suppression and warp correction, the uniformity of the plating thickness is improved and the deviation can be suppressed to 2% or less of the reference thickness. It was also possible to prevent slippage between the snap roll and the steel plate due to speeding up and increase in vibration from the drive system.

Further, an experiment was conducted with the arrangement shown in FIG. 13 in addition to the arrangement shown in FIG. 12, and it was confirmed that the warp of the steel strip could be corrected. That is, the arrangement is not limited to the above-described arrangement, and various arrangements are possible.

[0048]

The hot dipping apparatus of the present invention can manufacture a plated steel sheet having a uniform basis weight in the width direction by correcting the width warp with high accuracy and bringing the wiping nozzles close to each other.
Moreover, since vibrations and the like are suppressed, it is highly effective in speeding up and weight reduction, and the occurrence of flaws on the surface of the steel sheet can be greatly reduced.

Also for the lateral warp correction, it is possible to provide a device in which the amount of warp can be easily controlled and handled easily. Moreover, since the rotating portion can be reduced or eliminated, deterioration of accuracy with time is also reduced.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a plating apparatus according to the present invention.

FIG. 2 is a diagram showing a relationship between a pushing amount and a warping amount of a fluid support member (when the radius of curvature is fixed) in the present invention.

FIG. 3 is a graph showing the effect on warp correction according to the present invention.

FIG. 4 is a graph showing the effect on warp correction according to the present invention.

FIG. 5 is another schematic view of the plating apparatus according to the present invention.

FIG. 6 is a cross-sectional view of an example of a fluid support roll.

FIG. 7 is an exploded view of the fluid support roll of FIG.

FIG. 8 is a perspective view of an example of a combination of a fluid support roll and a fluid chamber.

FIG. 9 is an explanatory diagram of a nozzle shape of a fluid support member.

FIG. 10 is an explanatory diagram of another nozzle shape of the fluid support member.

FIG. 11 is a schematic view of a fluid supply path according to the present invention.

FIG. 12 shows an arrangement example of a fluid support member.

FIG. 13 shows another exemplary arrangement of fluid support members.

FIG. 14 is an explanatory diagram of an involute curve.

FIG. 15 is a graph showing the results of the examples of the present invention.

[Explanation of symbols]

 10: Hot dip coating device 12: Plating tank 14: Sink roll 16: Fluid support member 18: 〃 20: Top roll 22: Steel strip

Claims (3)

[Claims] 1. A plating bath, a sink roll held at a position to be immersed in a plating bath housed in the plating bath, and a plating bath on both sides or one side of a steel strip provided on the downstream side of the sink roll. A hot dip plating apparatus comprising a support member of a steel strip that abuts via a fluid, wherein a surface of the support member facing the steel strip is in a traveling direction of the steel strip,
It has an arc shape whose radius changes continuously, and is provided with a mechanism for changing the pushing amount of the support member with respect to the steel strip, and a rotation mechanism for changing the radius of the arc on the surface of the support member facing the steel strip. The hot dip plating apparatus is provided with. 2. The sink roll has, on the roll surface, symmetrically two or more fluid outlets extending over the entire circumference of the roll, and at the outlets, two or more partition plates are provided in the roll radial direction. The hot dip coating apparatus according to claim 1, which is a fluid-supporting roll. 3. The fluid-supporting roll has a fluid chamber arranged on the opposite side of the steel strip winding surface of the roll, and jets a fluid from the boundary between the fluid chamber and the roll to the interface between the roll and the steel strip. The hot dip plating apparatus according to claim 2, which has the above structure.