JP3132108B2 - Hot-dip plating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a continuous hot-dip plating apparatus,
Particularly, the present invention relates to a continuous hot-dip galvanizing apparatus for a steel strip in which warpage in a steel strip width direction during a plating operation is reduced as much as possible.

[0002]

2. Description of the Related Art When a plated steel sheet is manufactured by a continuous hot-dip coating apparatus, the traveling direction of a steel strip is reversed by a sink roll in a plating bath. 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 applied. However, if warpage occurs in the width direction, the uniformity of the plating thickness in the width direction is impaired, which leads to deterioration in the quality of the plated steel sheet.

[0003] The cause of the warp in the width direction of the steel strip is caused by non-uniform stress remaining in the thickness direction of the steel strip due to bending at the time of reversal. However, such residual stress can be suppressed in that part by a mechanical restraining force. Therefore, a method of using a touch roll or a pad to prevent the vibration of the steel plate and to suppress the warp in the width direction by the restraining force is generally performed.

Japanese Patent Laid-Open No. 2-20 discloses a device for bending a steel strip by bending it with a snap roll in a bath.
It has been proposed in Japanese Patent Publication No. 0759 and the like. Furthermore, Japanese Patent Publication No. 63-5041
No. 8 and JP-A-3-31464,
There has been proposed an apparatus and a method for supporting a steel strip in a non-contact manner while ejecting a molten metal and bending the steel strip into an S-shape.

[0005]

However, it is difficult to completely eliminate the warpage by the additional restraint measures using touch rolls or pads. Therefore, when the line progressed at low speed, although it was not a problem,
When increasing the speed, small warpage, which has not been a problem in the past because the gas wiping nozzle needs to be close to the steel strip, has affected uniforming the coating weight.

[0006] So, in the bath, arrange a snap roll,
A method has been proposed in which the warpage is corrected to eliminate the residual stress, thereby eliminating the warpage in the width direction on the bathing side. In this method, the processing curvature is changed according to the amount of the straightening roll pressed into the steel strip. However, if the roll diameter and the arrangement of the rolls are properly set, the accuracy of the warp straightening is relatively good.

However, the roll diameter is not always optimally selected at the maximum and minimum sheet thicknesses of the passing sheet material, but is selected so as to optimize the representative sheet thickness. The roll diameter may be changed appropriately, but the roll is provided in the bath, so it is not easy to replace it and it becomes a reference
The range that can be corrected for thick or thin plates that differ greatly
The enclosure is restricted. In addition, since the roller in the bath also has a bearing in the bath, corrosion and abrasion due to the molten metal occur over a long period of use, and the roll shaft rattles and whirls, causing the steel strip to vibrate. This results in a non-uniform plating thickness.

On the other hand, the method in which the steel strip is supported in a non-contact manner by the molten metal jet has the advantage of suppressing the generation of flaws since it is non-contact. However, the method of bending the steel strip into an S-shape and flattening it on the bath side is not as accurate as the method in which the steel strip is bent by pressing the roll to eliminate the warpage, and the pass line is stable. It is hard to say that.

[0009] Here, the present invention provides a hot-dip coating apparatus capable of suppressing vibration and flaw generation, accurately correcting warpage, and capable of greatly changing the range of plate thickness that can be corrected, and performing high-speed plating. It is also intended 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 studies to solve such problems, and focused on the following points.

As is 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 correct and eliminate the warpage. Conventionally, such plastic deformation has been applied by a snap roll immersed in a plating bath to correct the warpage. However, if the processing curvature applied to the steel strip is equal, it is not necessary to use a roll. If an external force is applied to the steel strip through a fluid to give a predetermined processing curvature, the steel strip should be similarly corrected. With such a configuration, the vibration should be greatly suppressed because there is no rotating portion by the roll. Here, the present inventors have obtained the following findings through such studies.

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

If the radius of the arc is continuously changed in the longitudinal direction of the steel strip, changing the contact surface with the steel strip by rotating the supporting member changes the roll diameter. This is equivalent to:

Moreover, the arc-shaped support member supplies the liquid and forms a thin fluid layer at the interface with the opposed steel strip, so that the contact with the steel strip can be eliminated and the generation of flaws can be suppressed. .

Therefore, the gist of the present invention is to provide a plating tank, a sink roll held at a position immersed in a plating bath housed in the plating tank, and a sink roll provided downstream of the sink roll. A hot-dip galvanizing apparatus comprising: a steel strip supporting member that abuts both sides or one side of the steel strip via a fluid in a plating bath, wherein a surface of the supporting member facing the steel strip is in a traveling direction of the steel strip. Has a mechanism that changes the pushing amount of the support member against the steel strip, and changes the radius of the arc on the surface of the support member facing the steel strip. Hot-dip coating apparatus provided with a rotating mechanism for the hot-dip plating.

According to a preferred aspect of the present invention, the sink roll has a fluid outlet on the roll surface extending over the entire circumference of two or more rolls symmetrically on the roll surface, and the outlet has two or more fluid outlets in the roll radial direction. May be constituted by a fluid supporting roll provided with a partition plate. The chance of contact between the steel strip and the roll is reduced, and the occurrence of flaws is effectively prevented accordingly.

According to another aspect of the present invention, in the fluid supporting roll, a fluid chamber is disposed on a side of the roll opposite to a surface on which the steel strip is wound, and an interface between the roll and the steel strip is defined by a boundary between the fluid chamber and the roll. The structure may be such that a fluid is ejected to the surface.

[0018]

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

(1) Correction Method FIG. 1 shows an example of a hot-dip plating apparatus provided with a fluid supporting member. In the figure, a hot-dip plating apparatus 10 according to the present invention includes a plating tank 12, a sink roll 14, and supporting members 16, 18 provided in pairs downstream thereof, which are schematically indicated.
Each of these elements is immersed in a plating bath (not shown).
The steel strip 22 has been bent by a number of rolls before reaching the plating bath, resulting in warpage. Considering the influence of the nearest roll, the C sink roll 14 forms a positive warpage in the width direction. In FIGS. 1A and 1B, warp correcting fluid support members 16 and 18 are disposed, and a snap roll (also referred to as a correcting roll or a stabilizing roll) is conventionally disposed at this position. Here, by changing the pushing amount of the support member 16 of B, the bending curvature of the steel strip 22 is changed, and the warpage 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).
m) shows the relationship between the pushing amount of the fluid supporting member 16 of B and the amount of warping at that time when a steel strip of 0.4 to 2.0 mm is straightened with each fixed. Focusing on a steel strip having a thickness of 0.8 t (mm), the warp can be made from negative to positive by pushing the support member 16 of B. In other words, warpage can be corrected. In the case of a plate thickness of 0.8 t (mm), the warpage can be reduced to zero by changing the pushing amount around 15 mm . However, when the plate thickness changes, the warping behavior against the indentation changes. Although there is a pushing amount that makes the warp zero, it is desirable to improve the positive / negative balance in terms of ease of control. In the illustrated example, the arc shapes of the support members 16 and 18 are semicircular, and the radii of curvature of the surfaces are 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 surfaces facing the steel strip. The fluid support members 16, 18
The supporting and rotating mechanism is not particularly described, but it will be obvious to those skilled in the art from the above description.

FIG. 3 shows the relationship between the indentation and the warpage of the steel strip of 0.4 t, and shows that the balance between positive and negative was improved by reducing Ru as indicated by the symbol △. In other words, the straightening can be easily performed by changing the pushing amount near 15 mm.

FIG. 4 shows that the positive / negative balance was improved by increasing Ru in relation to the indentation and warpage of the 2.0 t steel strip, as indicated by the crosses. In other words, the straightening can be easily performed by changing the pushing amount near 15 mm.

It can be seen that not only the pushing amount is changed but also the curvature radius of the fluid supporting member with respect to the steel strip is changed, so that it is possible to accurately correct various plate thicknesses.

(2) Vibration Suppression Effect Snap rolls and sink rolls have bearings for rotation, and these parts are easily corroded in the plating bath and tend to cause looseness and uneven rotation. In particular, since the winding angle of the snap roll is small, it is necessary to drive the shaft in an auxiliary manner, and vibration and the like are generated, which causes uneven plating thickness. However, according to the invention, instead of using them, the steel strips are fluid supported using the fluid support members 16, 18,
The rotation of the roll is eliminated, and the occurrence of vibration is suppressed. Also,
The generation of flaws due to contact with the roll is also prevented.

(3) Effect of Floating Support of Sink Roll FIG. 5 shows a configuration in which the sink roll 14 is a fluid-supporting roll 24. FIG. 6 shows an example of the fluid support roll 24,
7 shows an exploded view thereof, and FIG. 8 shows an example of a combination of the fluid supporting roll 24 and the fluid chamber. In FIG. 6, the roll surface has a fluid outlet 52 over the entire circumference of two or more rolls with a spacing W _O symmetrically on the roll surface.
At 52, two or more partition plates are provided in the roll radial direction.

In the structure of the illustrated example, the roll body 50 has a configuration in which an outer roll 62 is incorporated into an inner roll 60. 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 illustrated. . Reference numeral 70 denotes a fluid supply port from the fluid reservoir 63 to the outlet 52.

FIG. 7 is an exploded view of the fluid supporting roll of FIG.
0 is provided. Performs a kind of rectification, and the outlet
A fluid having a uniform pressure can be supplied in any of the directions 52.

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

In order to start the operation, first, a fluid is introduced into the fluid supporting device from the outside via the fluid supply pipes 54 and 59.
The fluid introduced at that time is supplied to the roll body 50 and the fluid chamber 56, respectively. Here, the fluid sent to the roll body 50 is stored in a hollow portion at the center of the roll, and then flows in the direction of the arrow shown in FIG. (See FIG. 6), and is ejected radially 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 facing the roll in the fluid chamber 56 as shown in FIG. On the other hand, the fluid supplied to the fluid chamber 56 provided on the lower surface of the roll is jetted from the boundary with the roll surface, that is, from the slit 58 to the interface between the roll and the steel strip.

As described above, when the steel strip is levitated and supported as an alternative to the sink roll, the indentation flaw generated by entrapping dross and other foreign matter between the roll and the steel strip is suppressed. In other words, the product quality is improved in synergy with the vibration using the fluid supporting member and the slip suppressing effect.

(4) Fluid Support Member FIGS. 9 and 10 show examples of the fluid support members 16 and 18. A fluid discharge nozzle 80 extending in the width direction may be formed, and a plurality of jet ports 82 are provided. It may be in a format and is not particularly limited.

Next, the cross-sectional shape of the fluid supporting members 16, 18, that is, the radius of curvature of the circular arc in the longitudinal direction of the steel strip will be described. The shape is not particularly limited as long as the small radius continues to the large diameter. Since it is desirable that the change is continuous, it is preferable 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 sheet thickness.
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 in the range of 250 to 100 mm, an appropriate curve can be obtained.

However, without being limited to this, l ₁ , R, and θ may be appropriately combined according to the plate thickness.

(5) Floating height of steel strip The steel strip is levitated and supported via a fluid (molten metal). In order to correct the steel strip accurately, it is important to follow the arc shape. . The concrete floating support mechanism of the steel strip is the fluid blowing nozzle 80 and the jet port 82 described with reference to FIGS.

Then, a fluid is supplied from the surface facing the steel strip,
A fluid layer is formed. It is necessary for the floating height to be within a few mm in order to improve the accuracy of the processing curvature, and it is desirable that the floating height be within about 1 mm. In addition, it is not necessary to raise the running cost more than necessary.

[0042]

EXAMPLE A hot-dip plating apparatus according to the present invention shown in FIG. 11 was prepared. The specific configuration was the same as in FIGS. Figure
FIG. 12 shows only the arrangement of the support members 16 and 18. The plating bath also had a sink roll 14 as a fluid support roll for C and a fluid chamber 56 for D combined with the sink roll, and support members 16 and 18 as correction members for A and B were arranged. The molten zinc in the bath was circulated by a pump and supplied to a fluid support member, a roll, and a fluid chamber. After passing through the snout from inside the annealing furnace,
The direction is reversed by the sink roll 14 of the fluid support roll, and the fluid support roll is pulled upward.

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.
mm, and the supporting member 18 is 120 to
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 range by changing the angle of the rotary support.
In addition, it has a mechanism for changing the amount of pushing into the steel strip.

The diameter of the sink roll 14 was 700 mm. In this arrangement, hot-dip plating of 0.3 to 3.2 mm thick x 1800 wide steel plate was performed, but as a result of the steel strip being supported by the fluid, the occurrence of scratches due to slippage between rolls and steel strip and indentation scratches due to dross was significantly reduced. did. Vibration caused by rattling due to rotation of the roll and vibration generated by the drive system of the snap roll are eliminated, thereby preventing the plating thickness from fluctuating.

Next, the amount of coating when hot-dip galvanizing was performed at a steel strip speed of 180 m / min using the above apparatus,
Conventional method not using the supporting support member 16, 18 in the equipment (B
And the amount of coating when hot-dip galvanizing was performed at a steel strip speed of 100 m / min .

In the conventional method, the roll vibrates due to rattling or the like.
And the speeding up is restricted, and the width
The distance of the wiping nozzle was also limited. In the present invention
According to the straightening effect of the steel strip is the same as the case of the roll, moreover, if the roll, the straightening area changes depending on the thickness of the plate, according to the apparatus of the present invention, the continuous support member corresponding to the roll diameter Since the changing radius of curvature can be arbitrarily selected, the correction area is also sufficiently widened according to the sheet thickness.
In other words, the wiping nozzle could be brought closer to the steel strip by the improvement of the accuracy of vibration suppression and warpage correction, so that the plating thickness uniformity was improved and the deviation could be suppressed to 2% or less of the reference thickness. In addition, the slip between the snap roll and the steel plate due to the high speed and the increase in vibration from the drive system were also prevented. As a result, as shown in FIG.
It was clear that thinning was possible even at higher speeds.

Further, experiments were 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 particularly limited to the above-described arrangement, and various arrangements are possible.

[0048]

The hot dip coating apparatus of the present invention can manufacture a coated steel sheet having a uniform basis weight in the width direction by correcting the width warpage with high accuracy and bringing the wiping nozzle close to the wiping nozzle.
In addition, since vibrations and the like are suppressed, the effect of increasing the speed and thinning is great, and the occurrence of flaws on the steel sheet surface can be greatly reduced.

Also for the width warpage correction, it is possible to provide an apparatus which can easily control the amount of warpage and is easy to handle. In addition, since the number of rotating parts can be reduced or eliminated, the deterioration of accuracy over time is reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view 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 supporting member (when a radius of curvature is fixed) in the present invention.

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

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

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

FIG. 6 is a sectional view of an example of a fluid supporting roll.

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

FIG. 8 is a perspective view of an example of a combination of a fluid supporting 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 example of the arrangement of the fluid support members.

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

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

[Explanation of symbols]

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

Claims (4)

(57) [Claims] 1. A plating tank, a sink roll held at a position immersed in a plating bath accommodated in the plating tank, and a plating bath provided on both sides or one side of a steel strip provided downstream of the sink roll. A hot-dip plating apparatus comprising a steel strip supporting member abutting through a fluid therein, wherein a surface of the supporting member facing the steel strip is in a traveling direction of the steel strip,
A hot-dip plating apparatus having a circular arc shape in which a radius continuously changes, and having a mechanism for changing a pushing amount of the support member into a steel strip. 2. A rotating mechanism for changing a radius of an arc on a surface of the support member facing a steel strip.
The hot-dip plating apparatus according to claim 1. 3. The sink roll has, on the roll surface, two or more rolls of fluid outlets over the entire circumference of the roll in a symmetrical manner, and at the outlets, two or more partition plates are provided in the roll radial direction. The hot-dip plating apparatus according to claim 1, wherein the hot-dip plating apparatus is a fluid supporting roll. 4. The fluid supporting roll has a fluid chamber disposed on a side of the roll opposite to a surface on which the steel strip is wound, and ejects a fluid from a boundary between the fluid chamber and the roll to an interface between the roll and the steel strip. 4. The hot-dip plating apparatus according to claim 3, which has a structure as described above.