JPS62188786A - Pickling tank for continuous pickling device - Google Patents

Abstract

PURPOSE:To prevent the deterioration in pickling performance/and to improve said performance by forming the bottom plate of a pickling tank to the shape coinciding with the shape of a steel strip to be passed therethrough, disposing said plate in proximity to the steel strip and increasing the size of the spaces between both ends in the transverse direction of the steel strip and both side walls of the pickling tank. CONSTITUTION:The bottom plate 16 of the pickling tank or the curved plate to be installed in the lower part of the pickling tank is formed to the shape coinciding with the catenary curve formed by the steel strip 5 to be passed through the pickling tank and the above- mentioned bottom plate 15 or curved plate is disposed in extreme proximity to the steel strip 5 passing in the tank. The spaces between the ends 13 in the transverse direction of the steel strip 5 and the side walls 14 of the pickling tank are provided to the larger sizes. The thickness in the boundary layer of an acid soln. 4 around the steel strip 5 is thereby decreased and the level difference of the acid soln. between the inlet and outlet of the tank is decreased. The exposing length of the steel strip 5 in the inlet of the tank is thereby decreased, by which the deterioration in pickling performance is prevented and the pickling performance is improved. The overflow of the acid soln. 4 beyond the partition is obviated and the adequate concn. difference between the tanks is maintained. The cost of the operation is thus reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a pickling tank in a continuous pickling device applied to process equipment of iron-making machinery.

[Conventional technology]

A conventional general pickling tank will be explained with reference to FIGS. 6 and 7. Figure 6 is an overall view of a conventional pickling tank, and the 7'
The figure is a partially enlarged detailed view of the pickling tank shown in FIG. 6.

In Fig. 6, 1 is the pickling tank main body, 2 is the partition, 3 is the cover, 4 is the acid solution, 5 is the steel strip, 6 is the inlet side support roll, 7
8 is a squeezing roll for removing the acid solution adhering to the surface of the steel strip, and 8 is a washing tank for washing the steel strip after pickling. Further, in FIG. 7, numeral 9 is a case of welded steel plate structure, numeral 10 is made of acid-resistant porcelain bricks, and numeral 11 is a skid for supporting the steel strip installed on the upper part of the partition 2.

As shown by the arrow, the steel strip 5 enters the first tank of the pickling tank from the inlet side support roll 6, moves in a catenary curve through the acid solution 4 stored in the tank, and passes through the partition screen 2. and enters the second divided tank. In this divided tank, the acid solution moves in a catenary curve in the same way as in the first tank, and passes through the third and fourth divided tanks, and thus the strip steel 5 is exposed to acid. liquid 4
While passing through the inside, the oxide film on the surface is removed one by one,
After that, it passes through the water in the washing tank 8, is washed with water, and is sent to the next process.

[Problem that the invention seeks to solve]

Recently, pickling lines have been made faster in order to make them more continuous with rolling lines and to improve productivity. As pickling lines become faster, the following problems have arisen.

(aJ As shown in Figure 8, liquid level difference Δh =:
Since h2-h, (h2: tank outlet liquid level, hl: tank inlet liquid level) becomes large, the exposed length l of the steel strip 5 at the inlet becomes long, which deteriorates the pickling performance.

(b) As shown in Figure 8, when the difference in the level of the liquid is large, when the acid solution 4 exceeds the partition 2 (part A), there is no difference in the concentration of hydrochloric acid between the species, and it is relatively If the concentration of waste acid is high, the operating costs will be high.

〔the purpose〕

An object of the present invention is to provide a pickling tank in a continuous pickling apparatus that solves the problems (al, (bJ) of the conventional pickling tank described above).

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention has the following features:
It has a shape that matches the catenary curve formed by the steel strip passing through the pickling tank, and is installed very close to the steel strip that passes through the entire bottom plate or curved plate, and in such a way that both ends of the steel strip in the width direction are connected to the acid pickling tank. This invention provides a pickling tank in a continuous pickling device, characterized in that the gap between both side walls of the washing tank is large.

〔Example〕

Hereinafter, the present invention will be described in detail based on the drawings.

FIG. 1(a) shows a pickling tank showing one embodiment of the present invention, in which the shape of the bottom plate of the pickling tank matches the catenary curve formed by the steel strip passing through the tank, and the bottom plate The structure is such that it comes very close to the steel strip, and Fig. 1(b) is similar to Fig. 1(a).
) is a cross-sectional view taken along the line C-σ.

That is, in FIGS. 1(a) and 1(b), the steel strip 5 and the bottom plate 16 of the pickling tank are brought close to each other in the longitudinal direction of the tank along a catenary curve, and The gap between the end portion 13 and the side wall 14 of the pickling tank is increased. Note that other symbols in FIG. 1 (aJ, (b)) have the same meanings as those in FIGS. 4 to 6.

FIG. 2(a) shows a pickling tank showing another embodiment of the present invention, in which there is a curved line below the pickling tank that matches the catenary curve formed by the steel strip passing through the tank. It has a structure in which all plates are provided very close to the steel strip, and FIG. 2 (1)) is a sectional view taken along the line c-c' of FIG. 2 (al).

That is, in FIG. 2 (1, (1)), the steel strip 5 and the curved plate 17 are brought very close to each other along the catenary curve in the longitudinal direction of the tank, and the ends of the steel strip 5 in the width direction are 13 and the side wall 14 of the pickling tank. The other symbols in FIGS. 2(a) and 2(b) have the same meanings as those in FIGS. 4-6.

[Effect]

FIG. 3 (a) is a diagram for explaining the flow of the acid solution 4 in the pickling tank shown in FIGS. 1 (aJ, (b)).

As shown in Fig. 3 j &), by separating the flow area in the moving direction of the steel strip 5 (■ mark) and the flow area in the return direction (■ mark), interference in the flow of the acid solution 4 is prevented. As a result, the level difference of the acid solution 4 becomes smaller.

FIG. 3 (bJ is a diagram for explaining the flow of pickling 4 in the pickling tank shown in FIG. 2 (aj, (bJ).

As shown in FIG. 3 (1: IK), by separating the flow area (0 mark) in the moving direction of the steel strip 5 and the flow area (■ mark) in the return direction (section B), the acid solution 4 There is no flow interference, and as a result, the difference in the level of the acid solution 4 is reduced.

Note that FIG. 4 is a diagram for explaining the boundary Irk of the acid solution 4 caused by the movement of the steel strip 5. Generally, a boundary layer develops due to the movement of the steel strip 5, and within this boundary layer thickness 15,
The acid solution 4 is affected by the moving speed of the band $5. Therefore, the flow direction of the acid solution 4 within the boundary layer thickness 15 coincides with the moving direction of the steel strip 5, as shown in FIGS. 3(a) and 3(b) described above. In addition, within the boundary layer thickness 15, the supply flow shown by the arrow in FIG. (i.e., bottom plate 16, curved plate 17),
Figure 3 (a), (b) [Figure 1 (bl, Figure 2 (b)]
As shown by the arrow, a flow is formed in the width direction of the steel strip 5, and the development of a boundary layer is suppressed due to this width direction flow.

In addition, the relationship between the immersion length of the steel strip and the boundary layer thickness in the conventional pickling tank as shown in FIGS. 6 to 8 and the pickling tank of the present invention is shown in the fifth column in comparison.

The symbols in FIG. 5 are as follows.

δ. Boundary layer thickness at the position of length Xo from the input side of the two-band steel band δt: Boundary layer thickness at the position of length X from the input side of the steel band Xo: From the input side to the exit side of the steel band Length The layer does not develop and the vinegar cleaning process can be continued in good condition.

In addition, the difference in liquid level is generally expressed by the following formula.

4m2g 4m2gA [λ: coefficient of friction, L: tank length (steel immersion length), 4m: hydraulic average diameter, Q: return flow rate, A: return cross-sectional area] Therefore, the end portion 13 of the steel strip 5 in the width direction Gap between side wall 14 of pickling tank? If it is made larger, the return cross-sectional area A and the average hydraulic diameter of 4 m will become larger, and accordingly, the difference in liquid level will become smaller.

Next, FIG. 1 (aJ, (
b) To explain the specific design method of the pickling tank shown in K, the curvature of the bottom surface of the bottom plate 16 of the thorough cleaning tank is designed using the following method.

Song "4" of band #5 is expressed by equation (1).

γ σT [γ: Specific weight (kg/m), X: Distance from the steel strip length center (m), σT: Tension (kg/m2), h: Distance from the strip steel length center at the position of X Suspension amount (1rL)] Therefore, the curvature of the bottom surface of the steel strip 5 is adjusted to the curvature of the steel strip 5 so that the steel strip 5 does not come into contact with the bottom surface of the bottom plate 16 of the Japanese cypress, and when the set tension is σa, X and h Design the shape so that it has a relationship with

Moreover, the clearance between the steel strip 5 and the bottom plate 16 is set by the following method. The boundary layer thickness is expressed by equation (2).

δ = 0.38(-)-%・z15 ・・・・・・(2
) ν [δ,: Boundary layer thickness, V: Steel strip speed (m/s), C: Kinematic viscosity (m/s), 2: Length T from the end of the strip
rL)) Therefore, the clearance between the steel strip 5 and the bottom plate 16 is δ1
If they are brought very close to each other so that the width is small, the flow of the acid solution 4 in the width direction of the steel strip 5 will increase, and the development of a boundary layer can be suppressed.

〔effect〕

As described in detail above, the present invention has a small level difference between the two liquids, so the exposed length l of the steel strip at the tank inlet is small, which prevents deterioration in pickling performance, and also reduces the amount of stress on the steel strip. By bringing the surfaces very close together, the thickness of the boundary layer becomes thinner, which has the effect of improving pickling performance.

Furthermore, in the present invention, since the difference in the level of the liquid is small, the acid liquid does not exceed the partition, so an appropriate concentration difference is obtained in the calibration, and the remarkable effect of reducing the concentration of waste acid and reducing operating costs is produced.

[Brief explanation of drawings]

Figure 1 (aJ is a diagram showing one embodiment of the present invention, Figure 1 (1
)J is a cross-sectional view taken along the line C-C' in FIG. 1(a).
J is a diagram showing another embodiment of the present invention, FIG.
Figure 3 is a cross-sectional view taken along line c-c' in Figure (a) (aJ is the first
Figures (a) and (b) are diagrams for explaining the flow of acid solution in the pickling tank shown in K, and Figure 3 (b) is a diagram for explaining the flow of acid solution in the pickling tank shown in Figures 2 (al and (b)). Figure 4 is a diagram to explain the flow. Figure 5 is a diagram to explain the boundary layer thickness. Figure 5 is the immersion length and boundary layer thickness of the steel strip in the conventional pickling tank and that of the present invention. Fig. 6 is an overall view of a conventional pickling tank, Fig. 7 is a partially enlarged detailed view of the same tank, and Fig. 8 is a diagram for explaining similar problems. 1; Pickling tank body 9; Housing 2; Partition p 10; Acid-resistant porcelain bricks 3; Cover 11; Band-support skid 4
;Acid liquid 13;End portion 5 in the width direction of the steel strip
;Strip steel 14;Side wall of pickling tank 6;Inlet side support roll 15;Boundary layer thickness 7;Squeezing crawl 1
6; Bottom of the pickling tank 8; Washing tank 17; Curved board sub-agent 1) Akihiro agent Ryo Hagihara - sub-agent Atsuo Anzai Figure 3 (αρ Figure 3 (b)

Claims (1)

[Claims] The bottom plate of the pickling tank or the curved plate installed below the pickling tank has a shape that matches the catenary curve formed by the steel strip passing through the pickling tank, and the strip passing through the bottom plate or curved plate A pickling tank in a continuous pickling device, characterized in that it is installed very close to the steel and leaves a large gap between both ends of the steel strip in the width direction and both side walls of the pickling tank.