JPH0563546B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a continuous melt plating device. [Prior Art] When producing plated steel sheets using a continuous hot-dip plating device, the advancing direction of the steel strip is turned by sink rolls in the plating bath, and the steel strip after turning has a widthwise warpage called width warpage. It is known that warpage occurs in When this width warpage becomes noticeable, the control of the amount of plating deposited in the gas wiping device becomes uneven in the width direction, leading to a deterioration in the quality of the plated steel sheet. Conventionally, no countermeasures have been taken to prevent width warping, and it is usually accompanied by tatsuchi rolls or pads to prevent vibration of the steel strip, which is the cause of uneven plating coverage. Generally speaking, efforts have been made to suppress this width warping. [Problem to be Solved by the Invention] However, it is impossible to completely eliminate width warpage with the additional measures to prevent width warpage using tatsuchi rolls or pads. However, it is true that even with such measures, width warping can be considerably improved, and when the steel strip progresses at low speed, even with this measure there was no particular problem. However, as the recent trend toward thinner coatings and higher speeds progresses, the gas wiping nozzle approaches the steel strip, and unevenness in the amount of plating deposited due to small width warping, which was not a problem in the past, becomes noticeable. , this has become a problem as a factor that hinders thinning and speeding up. The present invention was made in view of this situation, and an object of the present invention is to provide a melt plating device that can almost completely eliminate width warping. [Means for Solving the Problems] In order to achieve this objective, the present inventors have grasped the basic characteristics of roll width warping in a plating bath through model experiments, and based on this, have conducted various analyzes and experiments using actual machines. The experiment was repeated. the result,
The following findings were obtained. Regarding the roll arrangement in the plating bath, there are two types shown in FIGS. 4a and 4b. In the roll arrangement shown in FIG. 4a, among a pair of snap rolls 3a and 3b that contact both sides of the steel strip 1 in the plating bath,
The inner snack roll 3a that is in contact with the surface that the sink roll 4 contacts is the outer snack roll 3.
In the roll arrangement shown in FIG. 4b, the inner snack roll 3a is located above the outer snack roll 3b. In general,
The former roll arrangement is often used for the purpose of suppressing the adhesion of dross in the bath to the steel strip 1. The former is referred to as type A, and the latter is referred to as type B. When these two types of roll arrangement are compared from the viewpoint of width warpage, no matter which roll arrangement is adopted, the steel strip 1 of the outer snout roll 3b is The amount of indentation affects the width warpage. However, the degree of influence is greater in the former type A roll arrangement in which the outer snack roll 3b is located on the upper side. In other words, although the former type A roll arrangement can suppress width warping of the steel strip depending on the conditions, it reacts too sensitively to changes in conditions such as sheet thickness and tension, and has a stable width warpage prevention effect in actual operation. cannot be obtained. On the other hand, in the latter type B roll arrangement, the amount of pushing of the outer snap roll 3b has a small influence on width warping. This means that it is insensitive to width warping, but on the other hand, once the width warpage suppressing effect is obtained, it means that the effect is stable. In other words, in the case of B type roll arrangement, the pushing amount of the lower snout roll located on the outside,
When the diameter of each roll and the distance from the bath surface to the center of each roll are within specific ranges, warping of the width of the steel strip is suppressed, and the suppressing effect is extremely stable. To be more specific, the effect of suppressing width warping changes depending on the pushing amount of the lower snout roll, etc., but the control range of the pushing amount that can suppress width warping is wide, and it is extremely easy to prevent width warping even in actual operation. can be suppressed. Further, the amount of pushing that can suppress width warping is generally smaller than that of the A-type roll arrangement, and there are almost no adverse effects associated with pushing. The present invention was made based on this knowledge, and among the pair of snout rolls that contact both sides of the steel strip in the plating bath after passing through the sink roll, the snout roll that comes into contact with the sink roll contact surface of the steel strip is In order to make variable the pushing amount L ₃ of the snack roll located above and below the side snack roll against the steel strip, the snack roll is movably supported in a direction substantially perpendicular to the steel strip, and these If the roll is D ₃ > D ₁ > D ₂ L ₁ 1/2D ₁ 0.45 (L ₄ - D ₃ /2 + 2L ₁ ) < L ₂ < 0.55 (L ₄ - D ₃ /2 + 2L ₁ ) 1.05D ₃ < L ₄ < 1.5 D ₃ However, D ₁ : Diameter of the upper snack roll D ₂ : Diameter of the lower snack roll D ₃ : Diameter of the sink roll L ₁ : Distance between the bath surface and the center of the upper snack roll L ₂ : Distance between the bath surface and the center of the lower snack roll L ₃ : The gist of this invention is a melt plating device characterized by satisfying the condition of the distance between the bath surface and the center of the sink roll. FIGS. 5a and 5b are graphs showing the relationship between the amount of width warpage and the amount of push-in of the snap roll obtained in the model test for A type and B type roll arrangements. In either roll arrangement, pushing is performed by the outer snap rolls, and the sink rolls are slightly offset to the outside with respect to the set of snap rolls. In the A type roll arrangement, as shown in Figure 5a, the relationship between the amount of push and the amount of width warpage is almost a linear function, and when the amount of push is 0, positive width warpage occurs, and when the amount of push is negative, The width warpage decreases as it increases toward , and disappears when the pushing amount is close to -10 mm. However, if the pushing amount increases even slightly to the negative side, negative width warping begins to occur. In other words, in the A-type roll arrangement, as mentioned above, the width warping is resolved by pushing the snout roll, but it is only resolved by a certain pushing amount, and the influence of tension is relatively large, and the plating conditions In actual operation, where the width changes in various ways, a stable width warpage suppression effect cannot be obtained. On the other hand, in the B type roll arrangement, the fifth
As shown in Figure b. ± centering on push amount 0
The width warpage is eliminated at two points within a 5 mm range, and the width warpage is almost completely eliminated not only in the vicinity of the two points but also between the two points. In this way, in the case of the B type roll arrangement, the pushing amount has a wide range for suppressing width warping, and the pushing amount required to prevent width warping is small overall, which shows the influence of tension on the width warping prevention effect. There are also few. Therefore, a stable width warping suppressing effect can be obtained even in actual operation. [Operation] In the plating device of the present invention, D ₁ , D ₂ , D ₃ ,
By limiting L ₁ , L ₂ , and L ₄ as described above and adjusting the pushing amount L ₃ of the lower snout roll, width warping can be almost completely eliminated under normal plating operating conditions. In addition, width warpage control by pushing the lower snap roll has the advantage that flow of the plating bath in the vicinity of the plating bath surface, which causes surface flaws, hardly occurs. The reasons for limiting D ₁ , D ₂ , D ₃ , L ₁ , L ₂ , and L ₄ are as follows. When D ₂ ≧D ₁ , it is difficult to correct the width warpage of a relatively thick material, and depending on the conditions, the width warp correction may not be possible. When D ₃ ≦D ₁ , D ₂ , warpage is large in thick materials;
It becomes difficult to straighten the warpage using the snout roll, and the surface of the sink roll wears out quickly, shortening the replacement cycle. When L ₁ >D ₁ /2, non-uniform plating bath flow occurs directly above the upper snout roll, which tends to cause surface defects. When L ₁ <D ₁ /2, a part of the upper snout roll is in the air, so the flow of the plating bath on the bath surface becomes uneven, especially at high speeds, and surface defects are likely to occur.
Therefore, it is set as L ₁ /1/2D ₁ . When L ₂ ≦0.45 (L ₄ - D ₃ /2 + 2L ₁ ), D ₁ and D ₂ are too close together, and the width warpage correction sensitivity becomes too high, and the influence of the upper snout roll becomes too large, making it difficult to correct the width warpage. Occurs when it is difficult to When L ₂ ≦0.55 (L ₄ - D ₃ /2 + 2L ₁ ), the upper snack roll and the lower snack roll are too far apart,
The influence of the lower snap roll becomes excessive, and correction may become difficult depending on the conditions. Moreover, the correction sensitivity is extremely deteriorated. When L ₄ ≧1.5D ₃ , the bathtub size becomes large. Therefore, a smaller diameter is preferable, but when L ₄ ≦1.05D ₃ , the rolls are too close together, which is unfavorable in terms of engineering and maintenance. [Example] The present invention will be described below with reference to Examples. As shown in FIG. 1, the plating device of the present invention has the following features:
A welding tank 11 containing a plating bath 10 is provided.
A sink roll 12 is disposed in the melt tank 11, and snack rolls 13a and 13b are disposed above it. Steel strip 15 sent out from the annealing furnace 14
enters the plating bath 10 in the melt tank 11 through the snout 16, is turned around by the sink roll 12, and is pulled up almost directly above. The steel strip 15 is coated with snout rolls 13a, 1 in the plating bath 10 during its pulling.
3b and passes through the gas wiping device 17 after leaving the plating bath 10. Among the snap rolls 13a and 13b that contact the steel strip 15 in the plating bath 10, the sink roll 12
The inner snap roll 13a in contact with the surface of the steel strip 15 that is in contact with is located above the opposite outer snap roll 13b. And the diameter D ₁ of the upper snack roll 13a,
The diameter D ₂ of the lower snack roll 13b and the diameter D ₃ of the sink roll 12 are set to satisfy D ₃ >D ₁ >D ₂ . Further, the distance L ₁ from the bath surface to the center of the upper snack roll 13a, the distance L ₂ from the bath surface to the center of the lower snack roll 13b, and the distance L ₄ from the bath surface to the center of the sink roll 12 are L ₁ 1 / _2D1 0.45( _{L4- D3 /} 2+ _2L1 )< _L2 <0.55(L4- _D3 /2+ _2L1 ) _1.05D3 < _L4 < _1.5D3 , respectively. Further, the lower snap roll 13b that pushes the steel strip 15 is movably supported in a direction perpendicular to the steel strip 15 by a drive mechanism 20 so that the pushing amount _L3 can be adjusted. Note that the sink roll 12 has a lower snack roll 1 with respect to a pair of snack rolls 13a and 13b.
3b, and the amount L ₀ is commonly called offset. The drive mechanism 20 of the lower snack roll 13b is
As shown in FIGS. 2a and 2b, a pair of left and right supports 21a and 2 are disposed on the stand 21 outside the melt tank 11.
1b. The supports 21a and 21b respectively support slide blocks 22a and 22b with guide rods 23 and the like so that they can move back and forth. The slide blocks 22a and 22b have a J-shaped arm 2 at the tip.
3a and 23b, and rotatably supports a lower snout roll 13b at the tip thereof. The rotation of the motor 24 disposed on the side of one of the supports 21a is carried out via the horizontal shaft 25 of each support 21a.
It is transmitted to the vertical shaft 26 provided at 1a and 21b. The rotation of the vertical axis 26 further rotates each support 21a,
21b horizontal screw rod 27
is transmitted to. The screw rod 27 is screwed into the slide blocks 22a, 22b, and rotates as the motor 24 rotates to move the slide blocks 22a, 22b forward and backward. In this way, the lower snap roll 13b supported by the slide blocks 22a and 22b reciprocates in the horizontal plane in a direction perpendicular to its rotation axis, and by controlling the amount of movement, the steel strip 1 of the lower snap roll 13b
The pushing amount L ₃ with respect to 5 is adjusted. The results of an actual machine test using the above-mentioned plating device will be explained next.

〔Effect of the invention〕

The hot-dip plating device of the present invention eliminates width warping due to its roll configuration, and as a result, even when the gas wiping nozzle is brought close to the steel strip, a uniform basis weight is guaranteed in the strip width direction, and the plating operation is improved. Contributes to higher speed and lighter weight. In addition, by adjusting the amount of push by moving the lower snout roll, the width warpage can be controlled with high precision.
Optimal width warping prevention effects can be obtained even under various conditions such as plate thickness, plate width, and tension.

[Brief explanation of the drawing]

FIG. 1 is a side view showing the overall structure of a melt plating device embodying the present invention, FIGS. 2a and 2b are a side view and a plan view of the drive mechanism of the lower snout roll,
FIGS. 3a to 3c are graphs showing the relationship between the pushing amount and the width warping amount for the present invention example and the comparative example, and FIGS. 4a and 4b are schematic diagrams showing two types of roll arrangement.
FIGS. 5a and 5b are graphs showing the relationship between the amount of pushing and the amount of width warpage for two types of roll arrangements. In the figure, 12: sink roll, 13a, 13b:
Snut Prowl, 15: Steel strip, 20: Drive mechanism.

Claims (1)

[Scope of Claims] 1 Among a pair of snout rolls that contact both sides of the steel strip after passing through a sink roll in a plating bath, the snout roll that comes into contact with the sink roll contact surface of the steel strip is located above the opposite side of the snout roll. In order to make the pushing amount L ₃ of the lower Snut roll into the steel strip variable, the Snut roll is movably supported in a direction substantially perpendicular to the steel strip, and these rolls are arranged so that D ₃ > D ₁ >D ₂ L ₁ 1/2D ₁ 0.45 (L ₄ - D ₃ /2 + 2L ₁ ) < L ₂ < 0.55 (L ₄ - D ₃ /2 + 2L ₁ ) 1.05D ₃ < L ₄ < 1.5D ₃ However, D ₁ : Upper side Diameter of the snack roll D ₂ : Diameter of the lower snack roll D ₃ : Diameter of the sink roll L ₁ : Distance between the bath surface and the center of the upper snack roll L ₂ : Distance between the bath surface and the center of the bottom snack roll L ₃ : Between the bath surface and the center of the sink roll A melt plating device characterized by satisfying the condition of distance.