WO1998032899A1

WO1998032899A1 - Continuous chemical metal strip descaling process and device

Info

Publication number: WO1998032899A1
Application number: PCT/EP1998/000323
Authority: WO
Inventors: Bernd Berger; Jörg WITTE
Original assignee: Sundwig Gmbh
Priority date: 1997-01-25
Filing date: 1998-01-22
Publication date: 1998-07-30
Also published as: ATE226984T1; JP2001508833A; ES2186125T3; DE19702639C1; EP0961842B1; EP0961842A1; DE59806113D1

Abstract

A process and device are disclosed for the continuous chemical descaling of metal strips in a pickling bath. A number of pickling jets (4) is perpendicularly applied to the surface to be descaled of the strip (1) and form a gushing stream SS around their point of impact in the pickling tank (2).

Description

Device and method for the continuous chemical descaling of metal strip

The invention relates to an apparatus and a method for the continuous chemical descaling of metal strip in a pickling tank through which the metal strip runs.

There are several ways to increase the pickling speed when pickling a metal strip as it passes through a pickle. So can on the

Pickling speed can be influenced both via the composition of the pickling agent and via its temperature. It is also known that

To intensify the surface flow of the stain on the belt, which results from the movement of the belt, by pickling agent being drawn off on the inlet and outlet sides of the pickling tank and in the middle of the tank. In order to obtain a uniform pickling intensity over the entire surface, it is necessary to give the entire pickling bath a uniform flow rate, which is only possible with a correspondingly large pump output.

A pickling device is known from DD 266 813 A5, in which the strip runs in the longitudinal direction through a horizontally arranged closed treatment channel, which is arranged inside a container which encloses the treatment channel and is closed by a lid, into which the treatment channel is supplied on the inlet or outlet side Treatment medium can be derived. To improve pickling quality and minimize pickling times is within of the closed container, a separate treatment channel is arranged, to which the treatment medium is supplied via nozzle bars arranged on the inlet and outlet sides and associated pumps. However, the pump output required for the pickling intensity that can be achieved is also relatively high here.

From DE 40 31 234 AI a method and an apparatus for pickling a metal strip is known, the metal strip being replaced by a

Treated treatment liquid filled treatment container and the treatment liquid is conveyed via pipes and at least one pump-around container in the circuit. To shorten the pickling times and to improve the quality of the metal strip, the treatment liquid is conveyed below the liquid level in the treatment tank by means of jet nozzles above and below the metal strip, directed in opposite directions from both longitudinal sides at an acute angle against the metal strip. Here too, increasing the pickling intensity requires a relatively high pump output.

DE 29 11 701 AI discloses a method and an apparatus for the treatment of material webs in a treatment chamber. In the interior of the treatment chamber, successive, turbulent flows of a gaseous or liquid treatment medium are directed onto the two material web surfaces under pressure at an acute angle and in the opposite direction to the path of the web, in such a way that the web is treated and at the same time through the medium bed that is formed in an approximately horizontal path the treatment chamber is guided. For this purpose, the known device has at least one upper and one lower row of treatment nozzles, which are elongated in a direction perpendicular to the direction of travel of the material web are trained. Each of the nozzles has a longitudinal slot pointing to the continuous material web, the length of which is at least equal to the width of the material web, the nozzles being designed to move a turbulent medium stream from the slots onto the material web at an acute angle and in a direction opposite to the direction of flow Steer material web.

Finally, from AT 399 517 B a method for pickling metal strip is known, in which the metal strip is passed through a treatment room with at least one inlet and outlet for the treatment medium circulated through the treatment room, the treatment medium under pressure in the form of a directed and Treatment room filling flow and thereby the pressure and speed of the treatment medium are changed. In order to improve the pickling effect and to shorten the pickling time, the pressure at the inlet point or inlet points is set between 2 and 10 bar and the flow velocity at the outlet point is kept between 10 and 30 m / s. Furthermore, in AT 399 517 B a device for carrying out the method is described, which is characterized in that its outlet opening is provided in the form of a circumferential gap provided in the side walls of the treatment room at the level of the metal strip, which also serves as an introduction and discharge opening for the metal band serves.

The object of the invention is to develop a device and a method with which the pickling intensity can be increased with comparatively low pumping powers.

The object is achieved in that the pool has a lower and an upper group of full jet nozzles trained, perpendicular to the belt liquid nozzles for the stain, the pressure and nozzle diameter are so matched to their distance from the surface of the loaded metal strip that around the point of impact of the respective impact jet of the individual liquid nozzles, an area with shooting flow is created.

With this solution, the impingement jets on the metal strip surface to be pickled produce an unusually high flow rate and thus an increased mass transfer, which results in a high pickling intensity. The pump output required for this is comparatively low, since only a relatively small volume of pickling is required for the shooting flow. The peculiarity of the "shooting current" is that its speed is greater than the speed of the gush (introduction to technical fluid dynamics by Prof. Wolfgang Kalide, Carl Hanser Verlag, Munich, Vienna, 6th edition 1984, pages 97/98 ).

In the invention, the pickling tank can be filled with pickling liquid so that the strip to be pickled is drawn through the pickling liquid. In this case, the impact jets penetrate the liquid surrounding the belt. The shooting flow is formed ^'on the tape then in each case under the covering them liquid layer of the stain.

The liquid nozzles are preferably formed in the bottom and lid of the pickling tank.

In the case of a pickling tank with tubular electrodes for an electrolytic strip treatment, which run transversely to the strip running direction, the liquid nozzles can be formed in the electrodes, the tubular electrodes serve as a lead for the pickle to the liquid nozzles. Alternatively, in the case of a pickling tank with electrodes spaced apart from one another in the strip running direction and extending transversely to the strip running direction, the liquid nozzles can be formed in tubular strips arranged in the spaces between the electrodes, via which the pickling can be fed to the liquid nozzles.

The liquid nozzles are preferably arranged regularly, in particular in a plurality of rows lying one behind the other and running transversely from row to row to the tape running direction, the liquid nozzles of successive rows being offset transversely to the tape running direction. The transverse displacement of the liquid nozzles in rows one behind the other is in particular half a pitch of adjacent impact jets. In this way, with sufficient mutual spacing of the nozzles to form the shooting flow of the impingement jets, the strip can be applied uniformly over its entire width with pickling.

In order to discharge the pickling supplied via the impact jets, the rows lying one behind the other in the strip running direction should form outflow channels leading to the strip edges. According to a further embodiment, the outflow of the stain in these channels can be favored in that a supporting flow is generated from the belt edges by means of nozzles assigned to the outflow channels.

In order to achieve different pickling intensities on the top and bottom, but also across the width, the liquid nozzles can be switched on and off individually or in groups. The invention is explained in more detail below with the aid of a drawing showing exemplary embodiments. Show in detail

1 is a pickling tank in cross section perpendicular to the direction of strip travel,

2 shows a liquid nozzle with an impact jet and shooting flow on a belt as a basic illustration,

3 to 6 different nozzle arrangements,

7 shows a partial section of a pickling basin in a different embodiment from FIG. 1 in vertical section in the strip running direction with tubular electrodes arranged on the top and bottom.

8 shows a pair of electrodes in section X of FIG. 7 in cross section transverse to the direction of tape travel,

9 shows an electrode according to FIGS. 7 and 8 in an enlarged view, and

Fig. 10 shows a partial section of a pickling basin in a different embodiment to Fig. 1 and 7 in vertical section in the tape running direction with plate-shaped electrodes.

In the exemplary embodiment in FIG. 1, a belt 1 runs through a pickling tank 2 with a bottom 2a and a lid 2b. Both in the bottom 2a and in the lid 2b there are liquid nozzles 3a, 3b which are directed towards the band 1 Beam direction formed. The nozzles 3a, 3b are fed with pickling via feed lines 3c, 3d. The pickling tank 2 is not necessarily but preferably filled with pickling liquid to such an extent that the strip 1 is immersed therein. By immersing the strip 1 in the pickling liquid, the pickling effect on the top and bottom of the strip 1 is evened out.

Each of the nozzles 3a, 3b is designed as a full jet nozzle according to FIG. 2. A from the nozzle 3a, 3b under high pressure, e.g. B. from 2 to 10 bar emerging full jet 4 impinges on the belt 1 as an impact jet. At the point of impact, a stagnation zone SZ is formed, from which a shooting flow SS radially emerges, for which it is characteristic that a wave W forms at the end. The pressure with which the nozzle 3a, 3b is acted upon, its outlet diameter, its distance from the surface of the strip 1 and the thickness of the pressure which is established on the surface are essential for the formation of the shooting flow SS

Liquid layer. The thicker the liquid layer, the greater the pressure and / or the nozzle cross section and / or the smaller the distance.

The exemplary embodiments in FIGS. 3 to 5 show different geometrical arrangements of the individual liquid nozzles. All versions have in common that the nozzles are arranged in rows one behind the other, the areas of the flowing flow SS of the nozzles of each row overlapping one another.

While in the exemplary embodiment in FIG. 3 the center points of the nozzles of each row lie on a line perpendicular to the tape running direction R and are offset from row to row by half a pitch of adjacent nozzles, in the exemplary embodiment in the figure 4 the centers of successive nozzles on a line slightly inclined to the direction of strip travel R. In addition, the centers of the juxtaposed nozzles are also on a line that is inclined to the tape running direction. In particular, the inclination of the center line of successive nozzles to the tape running direction results in a geometrical displacement of the nozzles from row to row in the tape running direction and thus a more uniform distribution of the impact jets of the tape surface. In the exemplary embodiment in FIG. 5, it is also provided that the centers of the nozzles of rows lying one behind the other are offset by half a pitch of adjacent rows. In this case, too, the lines on which the center points of the nozzles of every second row lying one behind the other can be slightly inclined to the tape running direction R.

In all of the exemplary embodiments, an outflow channel A is left between the individual rows of nozzles for the pickling agent drain to the strip edges, as is indicated by the arrows between the rows of nozzles.

In the exemplary embodiment in FIG. 6, the outflow channels A are provided on the side next to the belt 1, and nozzles which promote the outflow of pickling agent and drive pickling agent into the outflow channels A.

In the exemplary embodiment of FIGS. 7 to 9, above and below the belt 1, transverse to the belt running direction and at a distance from one of the tubular electrodes EL in the belt running direction, in which nozzle openings 3a are indicated by arrows (FIG. 8) or specifically (FIG. 9) , 3b are formed. The pickling is fed to the nozzle openings 3a, 3b via the tubular electrodes EL. In the exemplary embodiment in FIG. 10, electrodes E are arranged in the pickling tank 2 above and below the strip 1 at a distance from one another in the strip running direction. In the spaces between electrodes E, tubular strips L are arranged, in which nozzle openings 3a, 3b are indicated by arrows, to which the stain is fed via the tubular strips L.

In both exemplary embodiments of FIGS. 7 to 10, the nozzle openings 3a, 3b, via which the impact jets act on the belt 1, can be accommodated in a space-saving manner.

Claims

PATENTA SPEECH

1. Device for the continuous chemical descaling of metal strip (1) in a pickling tank (2) through which the metal strip (1) runs, characterized in that the tank (2) has a lower and an upper group of full jet nozzles, perpendicular to the Band (1) directed liquid nozzles (3a, 3b) for the pickle, the pressure and nozzle diameter of which are matched to their distance from the surface of the loaded band (1) such that around the point of impact of the impact jet of the individual liquid nozzles (3a, 3b) an area with shooting current (SS) is created.

2. Device according to claim 1, so that the liquid nozzles (3a, 3b) in the bottom (2a) and in the lid (2b) of the pickling tank (2) are formed.

3. Apparatus according to claim 1 or 3, characterized in that the liquid nozzles (3a, 3b) are arranged in a plurality of rows arranged one behind the other, extending transversely to the tape running direction (R), the liquid nozzles (3a, 3b) of successive rows from row to row transverse are mutually offset to the tape running direction (R).

4. The device according to claim 3, characterized in that the transverse displacement of the liquid nozzles (3a, 3b) consecutive rows up to half a pitch of adjacent liquid nozzles (3a, 3b).

5. Device according to one of claims 1 to 4, characterized in that in a pickling tank (2) with transverse to the strip running direction (R) extending tubular electrodes (EL) for electrolytic strip treatment in the electrodes (EL), the liquid nozzles (3a, 3b ) are formed and the tubular electrodes (EL) serve as feed lines for the pickling to the liquid nozzles.

6. Device according to one of claims 1 to 4, characterized in that in a pickling tank (2) with in the strip running direction (R) spaced apart and transverse to the strip running direction (R) extending electrodes (E) for an electrolytic strip treatment, the liquid nozzles in tubular strips (L) which are arranged in the spaces between the electrodes (E) and through which the pickle is fed.

7. Device according to one of claims 1 to 6, so that the rows of liquid nozzles (3a, 3b) lying one behind the other in the tape running direction (R) form outflow channels (A) leading to the tape edges for the stain.

8. The device according to claim 7, characterized in that the outflow channels (A) are associated with the outflow of the pickling support nozzles (D).

9. Device according to one of claims 1 to 8, so that the liquid nozzles (3a, 3b) can be switched on and off individually or in groups.

10. A method for the continuous chemical descaling of metal strip in a pickle which passes through the metal strip, characterized in that the strip surface is acted upon by a plurality of such impact beams directed perpendicularly against the strip surface and distributed over it, that around the point of impact of the respective impact beam create an area with a flowing current.