DE10332693A1 - Method for de-scaling and/or cleaning of esp. warm-rolled steel band uses sensor to measure metal surface structure at a defined point, and pickling fluid spray intensity control devices - Google Patents

Abstract

A cleaning and/or de-scaling device (2) has a first section (3), where a pickling fluid is sprayed on the steel band (1), and a second section (4), where the band is dipped in such a fluid. A parameter characteristic of the steel band surface structure is measured at a defined point (5) of the device, behind the two sections as seen in direction of transport (R). Intensity of the fluid spray in the first section is controlled or regulated dependent upon the measured parameter. The de-scaling device has a sensor (7) located at the defined point, spray intensity control devices (8), and a flat jet nozzle (6) etc.

Description

The The invention relates to a method for descaling and / or cleaning a metal strand, in particular a hot rolled strip of mild steel or stainless steel, in which the metal strand in a conveying direction passed through a device in which it undergoes descaling and / or cleaning is, wherein the metal strand in at least a first portion of the Device is subjected to a process in which the surface of the Metallstranges a pickling liquid is sprayed, and wherein the metal strand in at least one second section of the device is subjected to a process in which the metal strand is immersed in pickling liquid. Of Furthermore, the invention relates to a device, in particular for execution of the procedure.

For further processing - eg. For example, by cold rolling, for a metallic coating or the direct processing into a final product - hot rolled steel strip must have a scale-free surface. Therefore, the scale formed during hot rolling and subsequent cooling must be removed completely. This is done in prior art solutions usually by a pickling process, wherein the from the various iron oxides (FeO, Fe ₃ O ₄ , Fe ₂ O ₃ ) or stainless steels also chromium-rich iron oxides existing scale depending on steel quality by means of various acids (eg. As hydrochloric acid, sulfuric acid, nitric acid or mixed acid) is dissolved at elevated temperatures by chemical reaction with the acid.

In front Pickling is another additional mechanical treatment for mild steel by stretching bends required to break up the scale and thus a faster penetration of the acid into the scale layer enable. In the much more difficult to pickle stainless, austenitic and ferritic steels and a mechanical descaling of the strip during the pickling process upstream to one as possible good heatable tape surface to achieve. After pickling, the steel strip must be rinsed, dried and oiled as needed to prevent oxidation.

From the DE 42 28 808 A1 a method and an associated apparatus for the surface treatment of band-shaped material to be treated is described, wherein in particular is intended to rolling stock. The material to be treated is continuously passed through a treatment tank, in which the treatment liquid is kept. In order to achieve that the removal of the resulting precipitation during immersion pickling during the treatment process or during the dissolution of the scale layer is made possible without special investment, the material to be treated is additionally subjected to a spray treatment with the treatment liquid after an immersion treatment. In this case, the material to be treated can be subjected to the spray treatment between two immersion treatments. It is also stated that the injection pressure and / or the spray quantity of the treatment liquid can be set as a function of the item to be treated. The device described for the spray treatment of the material to be treated has a plurality of above and below the strip-like material to be treated arranged spray tubes.

From the DE 42 40 572 A1 It is known to operate a pickling plant for metal strands so that a flexible adaptation to the respective pickling task is possible. For this purpose, it is provided that lateral injections of the pickling are controlled variably, wherein the injection takes place above and below the strip running plane. The injection can be controlled variably and in particular an arbitrarily preselectable amount of pickling medium can be injected. Similarly, the nozzle exit velocity of the pickling medium can be preselected.

Out WO 98/32899 it is known to produce a scale-free surface to provide a metal strand that in a pickling tank to descaling surface of the band with a variety of impinging vertically on it Impingement is applied to the impact point around a shooting one flow form.

Similarly, the EP 0 814 180 A1 a method for surface treatment of existing stainless steel, in particular band-shaped items to be treated. To remove the scale by means of a pickling solution, a spray treatment with hydrochloric acid is also provided here. The material to be treated can be subjected to a dip treatment before and / or after the spray treatment.

The DE 198 42 971 A1 Finally, discloses a method for pickling band-shaped material to be treated, wherein it is provided that the pickling solution is injected over a plurality of successively arranged in the direction of movement of the material to be treated nozzles from both sides at an angle from below and above against the material to be treated.

It is common to all previously known solutions that the pickling result is mainly dependent on the pickling time, ie on the time during which the acid acts on the metal strand and, in particular, on the scale layer present on it can. The aggressiveness of the pickling solution is influenced by the temperature of the acid, its concentration and the turbulence of the flow.

adversely is in all previously known embodiments that over the Length of pickling the pickling line is specified. Adjustments of the pickling bath length to different ones Operating conditions can so not done become. The result will be over the temperature of the pickling medium influenced, but when required changes because of the big one Amounts of acid, which are in circulation, represents a very slow manipulated variable.

at Flachbettbeizanlagen with injections are at each end of the container nozzle tubes attached as well as lateral injections and special lid designs available. This can be the picking result at given material speed over the injected quantity and the changed flow (turbulence) However, only very limited influences become.

to Influencing the quality the descaling or cleaning, it is therefore common, the conveying speed adapt, with which the metal strand transported through the device becomes. This allows the surface the metal strand of the needed Exposure time of the stain, causing the descaling or cleaning result improved. The disadvantage here is that a Reducing the conveying speed the metal strand through the device economically negative effect.

Of the The invention is therefore based on the object, a method for descaling and / or to clean a metal strand with which it is made possible is to avoid the disadvantages mentioned and in particular one to make possible improved descaling and / or cleaning of the metal strand, being both economic as well as ecological Benefits should be achieved.

The solution this object by the invention is characterized in that at a defined position of the device in the conveying direction look at the surface of the metal strand characterizing parameter is measured and the intensity the spraying of the pickling liquid on the metal strand in the at least one first section of the Device in which the spray treatment takes place, depending the measured parameter is controlled or controlled.

In order to will it be possible targeted to the quality the descaling or cleaning of the metal strand to influence without economic disadvantages due to a reduced conveying speed of the strand through the device in purchase.

According to one preferred embodiment, the measurement of the surface of the Metallstranges characterizing parameter in the conveying direction behind the first and second sections.

Of the the surface of the metal strand characterizing parameters, the surface structure be the metal strand. Particularly preferred is the proportion of still on the surface of the Metallstranges Zunders or the achieved roughness of Surface.

A Particularly advantageous embodiment provides that a first Section for considered the spray treatment of the metal strand in the conveying direction at least a second section for dipping. After that would start the descaling or cleaning with a spray treatment, what followed the dipping treatment.

It but has also proven itself that is a first section for spray treatment in the conveying direction considered between two second sections for immersion treatment located.

For influencing the intensity of the spraying of the pickling liquid, various options are alternatively or additionally available:
A first possibility is to adjust the intensity of the spraying of the pickling liquid in the at least one first section by changing the volume flow of the pickling liquid sprayed onto the metal strand. It is also possible that the adjustment of the intensity of the injection takes place by changing the pressure with which the pickling liquid is sprayed onto the metal strand. Furthermore, the intensity can be influenced by adjusting the distance of at least one of the spray nozzles provided for spraying from the surface of the metal strand. It has also proved useful to adjust the intensity by changing the number of activated spray nozzles.

Finally sees another embodiment, that the spraying of the pickling liquid on the metal strand in the at least one first section with individual injection pulses and that the adjustment of the intensity of the spray the pickling liquid by change the frequency of the injection pulses takes place.

In all embodiments, it is preferably provided that the metal strand continuously through the device is guided.

The Device for descaling and / or cleaning the metal strand has at least a first section, in which on the surface of the Metallstranges a pickling liquid is sprayed on, and at least a second section in which the metal strand in pickling liquid is immersed.

The Device is characterized according to the invention by a sensor, in the conveying direction considered arranged at a defined position of the device and one the surface of the Metal strand characterizing parameter can measure, as well as by means for controlling or controlling the intensity of the spray the pickling liquid on the metal strand in the at least one first section in FIG dependence the measured parameter.

With Advantage is the spraying of the pickling liquid on the metal strand by means of at least one nozzle, this being a flat jet nozzle, a full cone nozzle or a tongue nozzle can be.

By the proposal according to the invention will it is possible an optimal pickling result by controlling the intensity of the spray to reach the pickling medium, with different easily accessible Materials without changing the conveyor speed of the metal strand processed by the device, d. H. pickled can be.

As so far can additionally to the proposed method or to the proposed device be provided that the temperature of the pickling medium in a known Chosen way and is adjusted, thereby further optimizing the pickling efficiency can be. However, it comes in an advantageous manner by the Invention proposal no longer solely on the temperature of the pickling medium, as far as the effectiveness of descaling or cleaning is concerned.

All in all increases the cost-effectiveness of the procedure, since no reduction the conveying speed of the metal strand must be accepted.

Consequently results in a highly productive process for processing a Metal strands, preferably for hot-rolled strip of mild steel or stainless steel, the one economic and ecological Ensures descaling and / or cleaning of the metal strand and especially in combination with downstream treatment facilities proven Has.

In the drawing are embodiments of Invention shown. Show it:

1 schematically a device for descaling and / or cleaning a metal strand in the side view and

2 one too 1 analogous representation of an alternative embodiment.

In 1 is schematically a device 2 for descaling and / or cleaning a metal strand 1 to see. The metal strand 1 Moves through the device at a fixed, constant speed v in the conveying direction R. 2 ,

When entering the device 2 indicates the metal strand 1 on its surfaces - on the top and bottom of the strand - a scale layer on. It can come from one directly on the metal strand 1 consist of adhesive lower scale layer, which consists of magnetite and / or wustite. On this lower scale layer, an upper scale layer consisting of brittle hematite can be arranged.

The scale layer or the scale layers are in the device 2 away. At the exit of the device 2 is the metal strand 1 scale-free.

As 1 can be removed at the beginning of the descaling or cleaning of the metal strand 1 in the device 2 first a spray treatment in a first section 3 the device 2 instead of. As indicated only schematically, are in the first section 3 formed as a chamber, a number of nozzles 6 , about the pickling liquid on the surface of the metal strand 1 is sprayed.

The intensity of the pickling effect in the first section 3 depends on the volume flow Q, with which the pickling liquid on the metal strand 1 passes, front pressure p, with the pickling liquid on the metal strand 1 is sprayed on, as well as the temperature T of the pickling liquid. A further relevant variable that significantly influences the picking result is the distance a between the individual nozzles 6 and the surface of the metal strand 1 ,

Following the first section 3 - viewed in the direction R - close two dip tanks 9 and 10 which are filled with pickling liquid and through which the metal strand 1 to be led. Both immersion tanks 9 . 10 each extend over a second section 4 ,

Behind the device 2 , so at the exit de of the metal strand 1 from the device 2 , is in a position 5 a sensor 7 , This is able to measure a parameter of the surface of the metal strand 1 characterized. This is in particular to such a sensor 7 thought that still on the metal strand 1 adhesive scale layer measures and the measurement result of a control or regulatory means 8th feeds. On the basis of the control means 8th deposited control or regulating algorithm is in dependence on the measured value of said parameter influence on at least one of the process variables volume flow Q, pressure p and distance a, while it should be noted that the speed v of the metal strand 1 remains unchanged.

As 1 can be further removed, are above and below the metal strand 1 in the first section 3 three nozzles each 6 arranged in the conveying direction R following. To influence the intensity of the action of the pickling liquid can be provided that not all nozzles 6 Beizflüssigkeit be acted upon, but that individual nozzles depending on the sensor 7 be switched on or off to measure the intensity of the pickling of the metal strand 1 to influence.

As 2 can also be provided that the spray treatment in the first section 3 between two dipping treatments in the two second sections 4 he follows. The same applies to the design of this alternative, which is already in connection with 1 was executed.

Experiments have shown that the use of flat jet nozzles advantageous for the respective renewal of the acid film on the metal strand 1 is. However, other types of nozzles, such as. B. full cone nozzles.

The arrangement of the nozzle bars and the nozzles located thereon 6 can be equidistant to each other; but it is also possible, especially for optimal processing of the surface of the metal strand 1 to make a choice. In addition to nozzle bars with over the entire strand width equidistantly arranged nozzles 6 are also nozzle bars possible, which are effective especially in the edge region of the metal strand and accordingly switched on or off.

The supply of the first section 3 with pickling liquid can in the acid cascade control of the dip tank 9 . 10 to be involved.

In the figures, the arrangement of the nozzles 6 shown only very schematically. The distribution of the nozzles 6 both in the conveying direction R and transversely to this is possible in manifold ways. There may be a covering of the metal strand 1 be provided with short nozzle bars, which are only over a range of z. B. 20% to 40%. These can be combined with nozzle bars that span the entire width of the metal strand 1 extend. The individual nozzle bars can also be arranged offset in succession.

1

metal strand

2

contraption

3

first section

4

second section

5

position of the sensor

6

jet

7

sensor

8th

control or regulatory means

9

dip tank

10

dip tank

R

conveying direction

Q

flow

p

print

a

distance

T

temperature

V

speed

Claims (10)

Method for descaling and / or cleaning a metal strand ( 1 ), in particular a hot-rolled strip of mild steel or of stainless steel, in which the metal strand ( 1 ) in a conveying direction (R) through a device ( 2 ) in which it is subjected to descaling and / or purification, the metal strand ( 1 ) in at least a first section ( 3 ) of the device ( 2 ) is subjected to a process in which on the surface of the metal strand ( 1 ) is sprayed on a pickling liquid, and wherein the metal strand ( 1 ) in at least a second section ( 4 ) of the device ( 2 ) is subjected to a process in which the metal strand ( 1 immersed in pickling liquor, characterized in that at a detined position ( 5 ) of the device ( 2 ) in the conveying direction (R), the surface of the metal strand ( 1 ) Characterizing parameter is measured and the intensity of the spraying of the pickling liquid on the metal strand ( 1 ) in the at least one first section ( 3 ) is controlled or controlled as a function of the measured parameter. A method according to claim 1, characterized in that the measurement of the surface of the metal strand ( 1 ) characterizing parameter in the conveying direction (R) behind the first and second sections ( 3 . 4 ) he follows. Method according to claim 1 or 2, characterized in that the surface of the metal strand ( 1 ) characterizing parameters the surface structure of the metal strand ( 1 ). Method according to claim 1 or 2, characterized in that the surface of the metal strand ( 1 ) characterizing parameter is the proportion of itself still on the surface of the metal strand ( 1 ) Zunders is. Method according to one of claims 1 to 4, characterized in that the adjustment of the intensity of the spraying of the pickling liquid in the at least one first portion ( 3 ) by changing the volume flow (Q) of the metal strand ( 1 ) sprayed pickling liquid takes place. Method according to one of claims 1 to 5, characterized in that the adjustment of the intensity of the spraying of the pickling liquid in the at least one first section ( 3 ) by changing the pressure (p), with the pickling liquid on the metal strand ( 1 ) is sprayed on. Method according to one of claims 1 to 6, characterized in that the adjustment of the intensity of the spraying of the pickling liquid in the at least one first section ( 3 ) by changing the distance (a) of at least one nozzle ( 6 ) from the surface of the metal strand ( 1 ) takes place, with the pickling liquid on the metal strand ( 1 ) is sprayed on. Method according to one of claims 1 to 7, characterized in that the adjustment of the intensity of the spraying of the pickling liquid in the at least one first section ( 3 ) by changing the number of activated nozzles ( 6 ) takes place, with which the pickling liquid on the metal strand ( 1 ) is sprayed on. Contraption ( 2 ) for descaling and / or cleaning a metal strand ( 1 ), in particular a hot-rolled strip of mild steel or of stainless steel, through which the metal strand ( 1 ) is passed in a conveying direction (R) for descaling and / or cleaning, wherein the device ( 2 ) at least a first section ( 3 ), in which on the surface of the metal strand ( 1 ) is sprayed on a pickling liquid, and wherein the device ( 2 ) at least a second section ( 4 ), in which the metal strand ( 1 ) is immersed in pickling liquid, in particular for carrying out the method according to one of claims 1 to 8, characterized by a sensor ( 7 ), viewed in the conveying direction (R) at a defined position ( 5 ) of the device ( 2 ) is arranged and one of the surface of the metal strand ( 1 ) characterizing parameters, and by means ( 8th ) for controlling or regulating the intensity of the spraying of the pickling liquid onto the metal strand ( 1 ) in the at least one first section ( 3 ) depending on the measured parameter. Apparatus according to claim 9, characterized in that the spraying of the pickling liquid on the metal strand ( 1 ) by means of at least one nozzle ( 6 ), which is a flat jet nozzle, a full cone nozzle or a tongue nozzle.