MXPA98010013A - Process and apparatus to guide better a ba - Google Patents

Abstract

The present invention relates to a process for contacting a web material with a liquid bath, comprising the steps of: feeding a web material towards a receiving end of a trough and directing the web material to a discharge end of the tundish, the tundish includes a bottom wall which extends from the receiving end to the discharge end and which has opposite side walls to define a contact zone of the tundish material in a lower section of the tundish, the tundish contains the tundish. liquid bath in the contact zone, a plurality of liquid spray nozzles separated by a space in a direction between the receiving end and the discharge end, transporting the web material through the contact zone and creating a liquid stream through the contact area from the receiving end and to the discharge end of the tundish, spraying a supply of the liquid through each of the nozzles in a di substantially upward in the contact area towards the web material with sufficient force to avoid contact of the web with the bottom wall and without raising the web from the liquid bath regardless of the web material advance speed, The liquid is sprayed from the nozzles into the contact zone at a pressure to produce a plurality of alternating high and low pressure zones between the web material and the bottom wall, and discharges the web of material from the discharge end of the art.

Description

PROCESS AND APPARATUS TO GUIDE BETTER A BAND FIELD OF THE INVENTION The invention relates to a process for better guiding a strip in the treatment bath of strip treatment plants, wherein the strip of metal to be treated is guided horizontally through superficial liquid baths. BACKGROUND OF THE INVENTION In accordance with the state of the art, these strip treatment baths, for example deoxidants, are constructed with a depth of approximately 100 to 500 millimeters, and each individual liquid bath is normally from 10 to approximately 40 meters of long. The reaction rate of the treatment medium on the surface of the web material to be treated is positively influenced by the bath which is as superficial as possible, because the higher Reynolds number causes greater turbulence in the bath, and reduces the liquid boundary layer on the band as a result of increased shear stress. As a result, there is a tendency towards more shallow baths, which lead to less sinking of the band in the treatment bath. An additional reason for a very small band sag, or for the band to run without sinking, can be found in the sections of the plant before and after a strip treatment plant. The band voltages frequently required in these sections of the plant differ from those required for the sinking of the band in the treatment basin. In order to save on the band tension control equipment necessary for this purpose, the strip treatment plants are built with little or no sinking. Here, the bath can be sealed using known processes, for example, European Patent Number EP 0,655,519 Al, in such a way that the level of treatment medium in the treatment bath is higher than that of the entrance and exit of the band. In addition to an optimum treatment effect, the surface quality of the strip to be treated should not be impaired by scratching, scratching, or polishing, as a result of coming into contact with the bottom of the treatment bath. Although the band that is going to be treated can be passed in a catenary curve through deeper treatment baths without touching the bottom, the baths with a slight sinking of the band can only use a catenary curve with the band touching the bottom, because the relationship between the sinking and the length of the band is not adequate for a reliable control of the sinking of the band. In this case, the contact with the bottom of the bath is merely alleviated as a result of the tension of the band, but this does not raise the band from the bottom. In many cases, sliding wedges are mounted on the bottom of the bath to limit contact of the band with these wedges only. A distinction must be made between two different speed conditions in the case of a contact with the bottom of the bath. At higher speeds of the belt, a hydrodynamic sliding film is formed between the belt and the bottom of the tank or the sliding wedges in the treatment bath, preventing scratches or polishing on the belt. However, at low band speeds, the strip is scraped along the bottom or on the sliding wedges of the treatment bath, in such a way that the surface quality of the strip, and the bottom of the bath or the surfaces thereof, may be impaired. Sliding wedges suffer wear. The continuous strip treatment plants have known equipment for welding the individual bands to be treated together, and consequently, they are allowed to be pulled through the treatment baths without breaking. In a particular type of band treatment plant, for example, push-type deoxidants according to European Patent Number EP 0,302,057 Bl, suitable equipment pushes the bands through the treatment baths starting individually with the part front of the band, then the front part of the band is clamped, and the entire band is pulled through the treatment bath. After the insert procedure, these plants are subject to the same conditions for the treatment bath as described above for the web treatment plants. However, unlike continuous band plants, there is no means to alleviate the contact forces between the band and the bottom of the bath by using the band tension, while the band is being pushed inward, and it is pulling out, because the front and rear parts of the band are not secured, and therefore, it is not possible to apply sufficient tension of the band. What's more, even turns can be formed when the band is inserted. These turns are caused by the friction between the band and the bottom of the bath, or by a failed guide of the front part of the band, with the result that the operations of the plant have to be stopped, and it has to be returned to insert the band in the treatment bath. OBJECT OF THE INVENTION The purpose of the present invention is to improve the guidance of the band in the treatment plants described above, with long shallow treatment baths, in such a way that contact with the bottom of the bath at low speeds is avoided, and the operation inconsfiability caused by the turns that are formed in the push type plants is reduced.

PREFERRED MODALITIES OF THE INVENTION The invention, therefore, is characterized in that the treatment medium is sprayed through nozzles between the bottom of the bath and the band to be treated, causing a bearer and pull effect, which relieves contact of the band with the bottom of the bathroom, and prevents the band from being lifted straight up. As a result, the stationary band, which runs slowly, and also at high speed, is retained near the bottom of the treatment bath. The factor that determines the forces acting on the band is the relationship between the flow velocity and the friction of the fluid film between the band and the bottom of the treatment bath in the vicinity of a support source. The high flow velocities below the belt cause low pressure areas to form, and the resultant force component generated by the dead weight of the belt and the suction effect of the source stream pulls the belt to the bottom. The smaller the tolerance between the band and the bottom, the greater the resistance to flow, and therefore, the higher the pressure under the band, creating a support effect, as from a particular hollow height, which it prevents the band from coming into contact with the bottom of the tank. The tolerance between the band to be treated and the bottom of the bath is thus held in a continuous position by the negative pressure, the excessive pressure, and the external forces acting on the band. When the speed of the band is increased, a current generated by the drag effect of the band on top of the source current is superimposed, which causes the hydrodynamic effect of securing the band in place, to extend over a large area. The advantages of the described equipment are that, even a slightly excessive pressure of a few mbar, is sufficient to compensate the weight of the band, because all the lower side of the band is available as reaction surface, and because it is also reached a support effect when the band is stationary. A favorable additional development of the invention is characterized by at least two input flows that are provided, between which a support cushion is formed, due to the barrier effect of the influx. In the push type strip treatment plants, in particular, the length of the free loop of the strip is greatly reduced, since it is hydrodynamically retained at several points in the direction in which the band runs, thus reducing the risk of let there be turns. A convenient configuration of the invention is characterized by a curve that is formed through the web, particularly with the thin web, due to the suction effect of the hydrodynamic retention, combined with the bottom of the treatment bath that is made slightly in trough . This curve increases the resistance to the formation of loops. A further favorable development of the invention is characterized by at least two connected sources, which allow the treatment liquid to flow freely inwards, by being provided below the band,. The suction effect of the sources combined with the mechanical link through the band, alternately shifts the output flow again and again from one source to the other connected source, thereby forming a system that can oscillate. The violent oscillation resulting from the band has a convenient effect, because it reduces the barrier layer immediately after the band. It has been proven to be favorable for the oscillatory movement of the band, to arrange the sources at right angles to the direction in which the band runs, one immediately after the other, and with a spacing smaller than the width of the band. A further favorable development of the invention is characterized by at least two connected sources, which allow the treatment liquid to flow freely inwards, by being provided below the band., and forming the mechanical link through the band, a system that can oscillate. As an alternative, however, the connected sources can also be configured above the band. The invention also relates to a device for the surface treatment of strips using liquids in a surface deoxidizing bath, particularly for deoxidizing metal strip rolled in a tank of deoxidizer in the form of a trough, covered. It is characterized in that the base of the deoxidizer tank has one or more inlet orifices in the vicinity of the strip to be deoxidized, and through which the treatment liquid is directed towards the underside of the strip. A further preferred development of the invention is characterized in that there are at least two entry holes in the base of the deoxidizer tank, and because this causes a support cushion to be formed between these openings, as a result of the barrier effect of the influx. A convenient configuration of the invention is characterized in that there are one or more entry holes above the band, in order to guide it and to balance any irregularities in the deoxidizing effect between the upper part and the lower side of the band. A further favorable development of the invention is characterized in that the inlet holes are directed diagonally against the direction in which the band runs, to counteract the drag effect generated by the moving band. A further advantageous development of the invention is characterized in that the bottom of the treatment tank is slightly formed in a tundish. A further convenient development of the invention is characterized by at least two connected sources, which allow the treatment liquid to flow freely inwards, by being provided under the band, and forming the mechanical link through the band, a system which can range. As an alternative, however, the connected sources can also be configured above the band.

BRIEF DESCRIPTION OF THE DRAWINGS Now the invention will be explained in the examples based on the drawings, in which Figure 1 shows the distribution of the compression if there is a large gap between the band and the source; Figure 2 shows the distribution of the compression if there is a small gap between the band and the source; Figure 3 shows a deoxidation section according to the invention; Figure 4 is a horizontal view of Figure 3; and Figure 5 is a section through line V-V of Figure 3.

DETAILED DESCRIPTION OF THE INVENTION Figure 1 illustrates the distribution of compression around a support source if there is a large gap between the metal band and the source. The band 1 is guided along the bottom 2 of a treatment tank at a certain distance 5. The treatment liquid 4 is sprayed through a connection nozzle 3. The high flow velocities below the band cause them to form low pressure areas. The force component resulting from the dead weight of the band and the suction effect of the source current pulls the band down towards the bottom of the tank. Figure 2 shows an analogous distribution of compression, when there is a small gap between the band and the source. Here also, the illustration shows the metal band 1, the bottom of the tank 2, the inlet 3, and the tolerance 5 between the band 1 and the bottom of the tank 2. The smaller the tolerance between band 1 and the bottom of tank 2, the greater the resistance to flow, and therefore, the pressure below the band, causing a support effect from a certain height of the gap, which prevents the surface contact between the band and the bottom of the tank. This figure shows this situation. Figure 3 shows a strip treatment plant, particularly a deoxidation section, wherein the strip 1 is guided in the direction 13 through the tank 12 containing the deoxidizing liquor 6. In addition, the tank has a cover 7. The band 1 is inserted into the tank 12 in an inlet box 8. Here, the deoxidizing liquor 6 runs on an overflow into the tank 10. At the outlet, the band 1 is conducted through an outlet box 9. Also here, the deoxidizing liquor 6 runs on an overflow into the tank 10. From there, it is sprayed back through the inlet holes 3, towards the deoxidizing liquor 6, by means of a pump 11, and by means of an exchanger of heat 14 if required. If necessary, the deoxidizing liquor can also undergo the appropriate treatment in the tank 10, that is, it can be reactivated, for example by adding fresh deoxidizing acid. Figure 4 shows a horizontal view of the plant according to Figure 3. The band 1 and the inlet holes 3 are clearly shown in this illustration. Figure 5 shows a section through the line marked with VV in Figure 3. In addition to the location of the entrance orifice, this figure also clearly shows the trough-like bottom 2 that makes an additional contribution to stabilize the band 1. Figure 6 shows a variant of the invention, wherein the inlet orifices are directed against the direction in which the band runs. Otherwise, Figure 6 is identical to Figure 3.

Claims (12)

NOVELTY OF THE INVENTION Having described the above invention, it is considered as a novelty, and therefore, the content of the following is claimed as property: CLAIMS

1. A process for the surface treatment of bands using liquids, particularly to deoxidize a strip of rolled metal, to guide the strip through the treatment bath, where the metal strip to be treated is guided through liquid baths superficial, characterized in that the treatment medium is sprayed through nozzles between the bottom of the bath and the band to be treated, causing a bearer and pull effect that relieves the contact of the band with the bottom of the bath, and prevents that the band is lifted straight up.

2. The process according to claim 1, characterized in that at least two inflows are provided, between which a support cushion is formed due to the barrier effect of the influx.

3. The process according to claim 1 or 2, characterized by a curve that is formed through the band to increase the resistance to the formation of loops, particularly with a thin band, due to the suction effect of the hydrodynamic retention combined with the bottom of the treatment bath that has a light trough shape.

The process according to claim 1 of claim 1, characterized by at least two connected sources, which allow the treatment liquid to flow freely inward, which are provided below the band, and forming the bond mechanical through the band, a system that can oscillate.

5. The process according to claim 1 of claim 1, characterized by at least two connected sources, which allow the treatment liquid to flow freely inward, which are provided above the band, and forming the bond mechanical through the band, a system that can oscillate.

6. A device for the surface treatment of bands using liquids in a surface deoxidizing bath, particularly for deoxidizing metal strip rolled in a deoxidation tank in the form of a trough, covered, characterized in that the base of the deoxidation tank has one or more holes of entry into the vicinity of the band to be deoxidized, and through which the treatment liquid is directed towards the underside of the band.

7. The device according to claim 6, characterized in that at least two inflows are provided, between which a support cushion is formed, due to the barrier effect of the inflow.

The device according to claim one of claims 6 or 7, characterized in that the entry holes are directed diagonally against the direction in which the band runs.

The device according to claim one of claims 6 to 8, characterized in that there are one or more entry holes above the band, in order to guide and balance any irregularity in the deoxidation effect between the upper part and the lower side of the band.

The device as claimed in one of claims 6 to 9, characterized in that the bottom of the treatment tank is made slightly in the form of a tundish.

The device according to claim one of claims 6 to 10, characterized by at least two connected sources, which allow the treatment liquid to flow freely inward, which are provided below the band, and forming the bond mechanical through the band, a system that can oscillate.

12. The device as claimed in one of claims 6 to 10, characterized by at least two connected sources, which allow the treatment liquid to flow freely inward, to be provided above the band, and forming the mechanical link through the band, a system that can oscillate.