Patent Application
20200047231
The invention relates to a descaling device for the chemical descaling of a metal strip and to a method for chemical descaling of a metal strip.
During hot rolling of a metal strip, a scale layer forms on its surface. Prior to any subsequent cold rolling of the metal strip, the scale layer must be removed. Especially for this reason, after hot rolling, a metal strip is usually subjected to a descaling, during which the scale layer is removed.
In the field of chemical descaling of a metal strip, where an acid-containing pickling agent is usually used, one distinguishes between so-called dip pickling and so-called spray pickling. In dip pickling, the metal strip being treated is dipped into a dip tank filled with the pickling agent, whereas in spray pickling the pickling agent is sprayed onto the metal strip being treated. The spray pickling technology is characterized by a shorter treatment time as compared to dip pickling.
The problem which the invention proposes to solve is to enable a high pickling effectiveness to be achieved in a pickling spray treatment of a metal strip.
This problem is solved according to the invention by a descaling device and by a method according to the invention.
The descaling device according to the invention for the chemical descaling of a metal strip comprises at least one first spraying device and at least one further spraying device for respectively spraying a pickling agent onto a top side or bottom side of the metal strip. The first spraying device and the further spraying device comprise a first outer spraying unit for spraying the pickling agent onto a first edge region of the top side/bottom side of the metal strip and a second outer spraying unit for spraying the pickling agent onto a second edge region of the top side/bottom side of the metal strip situated opposite the first edge region. Furthermore, the first spraying device further comprises a middle spraying unit for spraying the pickling agent onto a middle region of the top side/bottom side of the metal strip situated between the edge regions.
At least one of the two outer or the middle spraying units of the first spraying device comprises multiple rows of solid stream nozzles and each of the spraying units of the first spraying device comprises its own pickling agent distribution chamber.
At least one of the two outer spraying units of the further spraying device comprises one or more slotted nozzles and each of the two outer spraying units has its own pickling agent distribution chamber.
The nozzles of the respective spraying units are advantageously connected to their pickling agent distribution chamber. Such an embodiment of the spraying device enables an easily manufactured construction of the spraying device as well as slight control expense for the spraying device.
Solid stream nozzles are relatively robust and easy to manufacture on account of their simple geometry.
Whereas nozzles used heretofore in descaling devices, such as flat stream nozzles, tongue nozzles, or conical jet nozzles, each produce a jet which expands and therefore has an inhomogeneous momentum distribution, with the aid of a solid-stream nozzle one can create a closed, stable and high-energy solid stream, having a homogeneous momentum distribution across its jet diameter and expanding little if at all over a long distance. With such a high-energy solid stream, the laminar boundary layer of the pickling agent formed or forming on the metal strip can be kept as thin as possible, having a positive impact on the material exchange and thus enhancing the pickling effectiveness. Furthermore, such a high-energy solid stream makes it possible to “wash away” clinging scale.
Due to the higher pickling effectiveness, the necessary treatment time for complete descaling of the metal strip can be shortened. This makes possible a shorter treatment lane (shorter structural length) or, for the same treatment lane, a higher delivery speed of the metal strip.
Furthermore, when using one or more solid stream nozzles for the spraying device, a lower pickling agent supply pressure is required than when using flat stream nozzles, tongue nozzles, or conical jet nozzles in order to achieve the same effect, because the jet of a solid-stream nozzle expands little if at all over a long distance and thus makes a high impact action on the metal strip surface possible. This, in turn, makes lower operating costs possible, e.g., because more favorable pumps can be used. For example, the spraying devices can be operated with a pickling agent supply pressure of 4 bar.
Moreover, the jet produced by a solid-stream nozzle advantageously contains no admixture of surrounding air. In other words, the jet which is produced by a solid-stream nozzle advantageously does not mix with the surrounding air.
The solid stream nozzles of the spraying device preferably each have a pickling agent outlet bore with nonconstant cross section. Thus, for example, the cross section area of the pickling agent outlet bore of the respective solid-stream nozzle may decrease toward the outlet-side nozzle end of the solid-stream nozzle. By the outlet-side nozzle end of a nozzle is meant its end facing the metal strip. Accordingly, by the inlet-side nozzle end of a nozzle is meant its end facing away from the metal strip.
Preferably, the narrowest point of the pickling agent outlet bore of the respective solid-stream nozzle is located at its outlet-side nozzle end. The pickling agent outlet bore of the respective solid-stream nozzle may be configured as a funnel, in particular.
Moreover, preferably the pickling agent outlet bore of the respective solid stream nozzle has at its narrowest place an inner diameter of at least 2 mm and at most 6 mm. Especially preferably, the pickling agent outlet bore of the respective solid stream nozzle has at its narrowest place an inner diameter of 4 mm.
One modification of the descaling device according to the invention calls for the further spraying device to comprise in addition a middle spraying unit with one or more slotted nozzles for spraying the pickling agent onto a middle region of the top side/bottom side of the metal strip situated between the edge regions, as well as its own pickling agent distribution chamber.
While a pickling agent jet produced by a solid-stream nozzle typically results in a pointlike application of pickling agent to the metal strip surface, a pickling agent jet produced by a slotted nozzle usually results in a linear application of pickling agent to the metal strip surface. With the aid of a slotted nozzle, a closed, stable and high-energy jet can be created, having a homogeneous momentum distribution and expanding little if at all over a long distance. Thanks to the use of one or more slotted nozzles, similar results can be achieved as in the use of one or more solid stream nozzles.
Advantageously, the descaling device comprises a strip conveying device for transporting the metal strip along a horizontal conveying direction. The strip conveying device may be designed, e.g., as a roller conveyor. Preferably, the conveying direction corresponds to the length direction of the metal strip being treated. In other words, the metal strip is preferably transported by the strip conveying device along its length direction.
Preferably, the two outer spraying units are outfitted with nozzles of the same type. If the first outer spraying unit for example has one or more solid stream nozzles, then the second outer spraying unit will preferably likewise have one or more solid stream nozzles. If the first outer spraying unit has one or more slotted nozzles, then the second outer spraying unit will preferably likewise have one or more slotted nozzles.
Moreover, it is advantageous for the spraying device to have a middle spraying unit for spraying the pickling agent onto a middle region of the top side/bottom side of the metal strip situated between the edge regions. It is especially preferable for the middle spraying unit to comprise one or more solid stream nozzles, especially multiple rows of solid stream nozzles, and/or one or more slotted nozzles, especially for the aforementioned reasons.
Each of the aforementioned spraying units advantageously comprises a group of nozzles for spraying the pickling agent onto the top side/bottom side of the metal strip.
Advantageously, the spraying device is designed as a spray bar. In this case, the aforementioned pickling agent distribution chambers may be formed for example with the aid of partition walls arranged inside the spray bar, especially metal dividers. In other words, in the case of an embodiment of the spraying device as a spray bar, the individual pickling agent distribution chambers may be separated from each other by multiple partition walls, especially metal dividers. The partition walls advantageously cause only a slight decrease in the internal volume of the spray bar, so that friction losses inside the spray bar can be kept low.
In another variant of the invention, the spraying device may comprise for example separate spray bars, forming the aforementioned spraying units. In such a case it is advisable for these separate spray bars to be arranged with an offset from each other perpendicular to the conveying direction. They may likewise be arranged with an offset from each other in the conveying direction. Alternatively, the separate spray bars may be arranged in the same position relative to the conveying direction.
Moreover, the spraying device may comprise a device in each of its pickling agent distribution chambers ensuring that the pickling agent is applied homogeneously to the nozzles of the respective spraying unit.
Preferably, the spraying device has an interior height of at least 10 cm. This makes it possible to avoid high pressure gradients inside the spraying device. By the interior height of the spraying device is meant its inner dimension perpendicular to the top side/bottom side of the metal strip.
The descaling device may have a pickling agent supply line for each of the three spraying units. Advantageously, the descaling device comprises a first pickling agent supply line, which is connected at the outlet side to the first outer spraying unit, a second pickling agent supply line which is connected at the outlet side to the second outer spraying unit, and a third pickling agent supply line which is connected at the outlet side to the middle spraying unit.
Advantageously, each of the three pickling agent supply lines empties into the respective spraying unit perpendicular to its spraying direction. That is, advantageously the first pickling agent supply line empties perpendicular to the spraying direction of the first outer spraying unit into the first outer spraying unit, while the second pickling agent supply line empties perpendicular to the spraying direction of the second outer spraying unit into the second outer spraying unit and the third pickling agent supply line empties perpendicular to the spraying direction of the middle spraying unit into the middle spraying unit. In this way, a uniform pressure distribution can be achieved in the individual spraying units and thus a uniform pressure distribution at their nozzles.
Each of the spraying units is advantageously adapted to spraying the pickling agent in perpendicular or substantially perpendicular manner onto the top side/bottom side of the metal strip. This is accomplished, e.g., if the nozzles of the spraying units are oriented such that the spraying units each time have a spraying direction which is oriented perpendicular or substantially perpendicular to the top side/bottom side of the metal strip, i.e., vertically or substantially vertically upward or vertically or substantially vertically downward.
By the spraying direction of the respective spraying unit is meant the direction in which the spraying unit sprays out the pickling agent. The phrasing “substantially perpendicular to the top side/bottom side of the metal strip” may be understood as having a deviation of up to +/−20°, preferably up to +/−10°, from the right angle to the top side/bottom side of the metal strip.
Furthermore, at least one of the spraying units of the spraying device may be tilt or swivel-mounted, preferably about a horizontal axis, parallel to the conveying direction.
In one advantageous embodiment of the invention, the descaling device comprises a control device by means of which a pickling agent dispersing rate of the respective spraying unit of the spraying device is adjustable, especially continuously or in several discrete steps.
The pickling agent dispersing rate of the respective spraying unit is understood to be the quantity of pickling agent emerging from the respective spraying unit per unit of time, in other words the volume flow of the pickling agent emerging from the respective spraying unit.
In the sense of the invention, controlling a quantity may include regulating that quantity, i.e., a control with a measured value feedback. The aforementioned control device may thus be in particular a regulating device.
Moreover, in the sense of the invention a quantity is “adjustable in several discrete steps” if that quantity can also be set at another value between a value other than zero and a maximum value of the quantity (which can be achieved in the descaling device). In other words, in the sense of the invention, a quantity is “adjustable in several discrete steps” if that quantity can be set at least at two values other than zero.
By means of the control device, the pickling agent dispersing rate of the middle spraying unit is preferably adjustable independently of the pickling agent dispersing rate of the first outer spraying unit and independently of the pickling agent dispersing rate of the second outer spraying unit. This makes it possible to adjust the pickling agent application to the metal strip in the width direction according to the nature of the width profile of the thickness of the scale layer on the top side/bottom side of the metal strip.
Typically, the thickness of the scale layer at the strip edges is greater than in the strip middle region. If the metal strip is applied with pickling agent homogeneously over its width, this will have the effect of “overwetting” the strip middle region in the event of a heavy pickling agent application, i.e., not only the scale layer but also base material lying underneath will also be removed by the pickling agent, whereas in the event of a slight pickling agent application the scale layer will not be entirely removed, especially at the strip edges.
If the metal strip has a greater thickness of the scale layer at the edge regions of its top side/bottom side than in the middle region of the top side/bottom side situated in between them, the pickling agent dispersing rate of the middle spraying unit can be set at a lower value than the pickling agent dispersing rate of the outer spraying units. In this way, it is possible to achieve a homogeneous descaling result. Since an overpickling of the metal strip can be avoided in this way, it is furthermore possible to reduce the need for pickling agent, which in turn makes possible a decrease in the cost of regeneration of the pickling solution.
Preferably, the pickling agent dispersing rate of the first outer spraying unit is adjustable by means of the control device independently of the pickling agent dispersing rate of the second outer spraying unit. In this way, it is possible to apply a different amount of pickling agent to the first edge region of the top side/bottom side of the metal strip than to the second edge region of the top side/bottom side of the metal strip.
Further, the control device may comprise multiple pickling agent delivery pumps connected at the exit side to the spraying device. With the aid of the pickling agent delivery pumps, the pickling agent can be delivered to the spraying device. The pickling agent delivery pumps can be used to adjust the pickling agent dispersing rates of the spraying units. In particular, the pickling agent delivery pumps may be frequency-regulated pumps.
One of the pickling agent delivery pumps may be connected to the two outer spraying units, while another of the pickling agent delivery pumps can be connected to the middle spraying unit. Alternatively, a first pickling agent delivery pump can be connected to the first outer spraying unit, a second pickling agent delivery pump to the second outer spraying unit and a third pickling agent delivery pump to the middle spraying unit.
The pickling agent delivery pumps are preferably connected to a control unit of the control device. The control unit is advantageously designed to adjust the delivery performance of the respective pickling agent delivery pump, especially continuously or in several discrete steps. Further, it is advantageous for the delivery performance of the respective pumps to be adjustable independently of the delivery performances of the other pickling agent delivery pumps. By altering the respective delivery performance, the pickling agent dispersing rate of the respective spraying unit can be altered.
Furthermore, the control device may comprise multiple valves. These may be used alternatively or additionally to the pickling agent delivery pumps for adjusting the pickling agent dispersing rates of the spraying units. Advantageously, the spraying device is connected at the entry side to the valves, especially across the aforementioned pickling agent supply lines.
For the two outer spraying units, a common valve or a respective separate valve each may be provided. The middle spraying unit is preferably provided with its own valve. Further, it is advantageous for the valves to be connected to the control unit of the control device.
The control unit is preferably designed to adjust the valve position of the respective valve, especially continuously or in several discrete steps. By altering the respective valve position, the pickling agent dispersing rate of the respective spraying unit can be altered.
Moreover, the aforementioned pickling agent supply lines may be respectively outfitted with a pressure and/or flow rate sensor for monitoring the pickling agent pressure or the pickling agent flow rate in the respective pickling agent supply line. These sensors are preferably connected to the control unit of the control device. The control device, especially its control unit, may be designed to control the aforementioned pickling agent delivery pumps and/or the valves in dependence on the sensor signals of these sensors.
In addition to the aforementioned spraying units, the spraying device may comprise further spraying units for spraying the pickling agent onto the top side/bottom side of the metal strip. For example, the spraying device may comprise between the middle and the first outer spraying unit a first further spraying unit and between the middle and the second outer spraying unit a second further spraying unit. The pickling agent dispersing rate of the respective further spraying unit is preferably adjustable by means of the control device independently of the pickling agent dispersing rates of the other spraying units of the spraying device.
Furthermore, the control device may comprise a sensor unit having one or more sensors for detecting a surface parameter of the metal strip, especially a surface parameter dependent on a thickness of the scale layer of the metal strip.
The surface parameter can be, for example, the thickness of the scale layer itself or another surface parameter dependent on the thickness of the scale layer. In particular, the sensor unit may comprise one or more noncontact measuring sensors for detecting the surface parameter.
Moreover, the sensor unit may be designed in particular to measure said surface parameter with position resolution across the width of the metal strip, in other words a width profile of the surface parameter. The sensor unit may be arranged before or after the spraying device in terms of the conveying direction.
Furthermore, it is advantageous for the sensor unit to be connected to the control unit of the control device. The control device, especially its control unit, is designed to adjust the pickling agent dispersing rate of the respective spraying unit in dependence on an output signal of the sensor unit.
Furthermore, the pickling agent dispersing rate of the respective spraying unit can be controlled in dependence on one or more known production parameters, such as the so-called coiling temperature of the metal strip and/or its material grade. Such a parameter is advantageously relayed to the control device, especially to its control unit. Preferably, the control unit is designed to calculate the pickling agent dispersing rate to be set for the respective spraying unit with the aid of the sensor signals and/or production parameters relayed to the control unit.
Furthermore, the descaling device may comprise at least one further or second spraying device, especially at least one further spray bar, for spraying the pickling agent on the same side of the metal strip as the first mentioned spraying device. The first mentioned and the further spraying device(s) are preferably arranged in succession in the conveying direction.
Just like the first mentioned spraying device, such a further spraying device may comprise a first outer spraying unit for spraying the pickling agent onto the first edge region of the top side/bottom side of the metal strip and a second spraying unit for spraying the pickling agent onto a second edge region of the top side/bottom side of the metal strip. Optionally, such a further spraying device may comprise a middle spraying unit for spraying the pickling agent onto the middle region of the top side/bottom side of the metal strip. Preferably, in such a further spraying device the pickling agent dispersing rates of its spraying units can be controlled by means of the control device in the same way as the pickling agent dispersing rates of the spraying units of the first mentioned spraying device.
Moreover, the first mentioned and the further spraying device(s) may have different kinds of nozzles. One of the spraying devices may have, e.g., solid stream nozzles (exclusively), another of the spraying devices may in turn have, e.g., slotted nozzles (exclusively).
Furthermore, the descaling device may comprise at least one additional spraying device for spraying the pickling agent on the other side of the metal strip. The phrasing “other side” of the metal strip should be understood here as meaning that if the first mentioned spraying device sprays the pickling agent onto the top side of the metal strip, then the other side is the bottom side of the metal strip. Conversely, if the first mentioned spraying device sprays the pickling agent onto the bottom side of the metal strip, then the other side is the top side of the metal strip. The features mentioned in connection with the first mentioned spraying device may pertain in analogous manner to such an additional spraying device.
Those elements of the descaling device which come into contact with the pickling agent advantageously consist of an acidresistant material, especially a plastic and/or a ceramic. The aforementioned nozzles may for example consist of polyvinylidene fluoride (PVDF) and/or polypropylene (PP), or contain these materials.
Furthermore, the descaling device may comprise a dip tank for a dip pickling treatment of the metal strip. This is preferably arranged after the spraying device in terms of the conveying direction. The dip pickling treatment in the dip tank may serve to even out the pickling effect and/or to remove scale residue not removed during the spray treatment.
Moreover, the descaling device may comprise a further dip tank for a dip pickling treatment of the metal strip, the spraying device being arranged between the two dip tanks in terms of the conveying direction, for example.
In the method according to the invention for the chemical descaling of a metal strip, a pickling agent is sprayed onto a top side or bottom side of the metal strip by means of at least one first spraying device and at least one further or second spraying device. In this process, the pickling agent is sprayed by a first outer spraying unit of the first and the further spraying device onto a first edge region of the top side/bottom side of the metal strip and by a second outer spraying unit of the first and the further spraying device onto a second edge region of the top side/bottom side of the metal strip situated opposite the first edge region. In addition, a pickling agent is sprayed by a middle spraying unit of the first spraying device onto a middle region of the top side/bottom side of the metal strip situated between the edge regions. In the method according to the invention it is provided that the pickling agent is sprayed onto the top side/bottom side of the metal strip by at least one of the two outer spraying units or the middle spraying unit of the first spraying device through multiple rows of solid stream nozzles and by at least one of the two outer spraying units of the further spraying device through one or more slotted nozzles.
It is especially preferable when the pickling agent is sprayed onto a middle region of the top side/bottom side of the metal strip situated between the two edge regions through one or more slotted nozzles of a middle spraying unit of the at least one further spraying device.
The descaling device according to the invention may be used to carry out the method according to the invention. That is, the devices mentioned in connection with the method may be in particular elements of the descaling device.
The spraying of the pickling agent onto the metal strip preferably brings about not only a chemical descaling of the metal strip, but also a mechanical ablation of the scale layer.
In the method, the metal strip is preferably transported parallel to its length direction by a strip conveying device, especially by the aforementioned strip conveying device of the descaling device.
Preferably, the pickling agent which is sprayed onto the metal strip is or contains an acid, such as hydrochloric acid. The metal strip may be in particular a steel strip. Moreover, the metal strip is preferably a hot rolled metal strip.
In one advantageous embodiment of the invention, a pickling agent dispersing rate of the first outer spraying unit and a pickling agent dispersing rate of the second outer spraying unit of the at least one first spraying device and/or the at least one further spraying device is set by means of a control device each time at a value which is different from a pickling agent dispersing rate of the respective middle spraying unit of the first spraying device and the further spraying device. In this way, a homogeneous descaling result can be achieved especially in the case when the scale has a different thickness at the edge regions than in the middle region.
For example, the pickling agent dispersing rate of the first outer spraying unit and the pickling agent dispersing rate of the second outer spraying unit may be set by means of the control device at a value which is larger than the pickling agent dispersing rate of the middle spraying unit, especially in the case of a larger thickness of the scale layer at the two edge regions.
Basically, it is possible for the pickling agent dispersing rate of the first outer spraying unit and the pickling agent dispersing rate of the second outer spraying unit to be set by means of the control device at different values. Thus, e.g., it is possible to set only the pickling agent dispersing rate of one of the two outer spraying units by means of the control device at a value which is different from the pickling agent dispersing rate of the middle spraying unit.
Advantageously, the pickling agent dispersing rate of the respective spraying unit of the at least one first spraying device and/or the at least one further spraying device is set with the aid of the control device such that the metal strip is acted upon in its width direction by the first and/or the further spraying device with a given pickling agent spray profile. By the pickling agent spray profile is meant the profile of the pickling agent quantity applied by the spraying device to the metal strip along a given direction (here: the width direction of the metal strip).
The pickling agent spray profile may increase or decrease to the outside in the first and/or in the second edge region, especially increase or decrease in linear manner. Moreover, the spray profile may be symmetrical with respect to the strip center plane. By the strip center plane is meant here a vertical plane relative to which the metal strip has a mirror symmetry.
Furthermore, the pickling agent spray profile with which the metal strip is acted upon may have no plateau. Alternatively, the pickling agent spray profile may have a plateau, especially between said two edge regions.
A pickling agent spray profile of the aforementioned kind can be realized, e.g., in that the nozzles of the first outer spraying unit are arranged alongside each other in a triangle, the nozzles of the second outer spraying unit are arranged alongside each other in a triangle and the nozzles of the middle spraying unit are arranged alongside each other in a trapezoid, especially in the form of an equilateral trapezium, or likewise in a triangle.
The description given thus far of advantageous embodiments of the invention contains numerous features which have been presented in the individual dependent patent claims, sometimes assembled with several of them. However, these features may also be considered individually and be assembled into further meaningful combinations. In particular, these features may be combined individually and in any suitable combination with the descaling device according to the invention and the method according to the invention. Moreover, method features may also be viewed as an attribute of the corresponding device unit.
Even if certain terms in the specification or in the patent claims are used in the singular or in connection with a numeral, the scope of the invention shall not be limited for these terms to the singular or the particular numeral.
The above described attributes, features and benefits of the invention, as well as the manner in which they are achieved, shall become more clear and distinctly understandable in connection with the following description of the exemplary embodiments of the invention, which shall be discussed more closely in connection with the figures. The exemplary embodiments serve for the explaining of the invention and do not limit the invention to the combinations of features indicated therein, or in regard to functional features.
Moreover, suitable features of each exemplary embodiment may also be considered explicitly in isolation, removed from an exemplary embodiment, introduced into another exemplary embodiment in order to supplement it, and combined with any one of the claims.
If the same reference numbers are used in different figures, they denote substantially the same or equivalent elements. For reasons of expedience, however, substantially identical or equivalent elements may also be denoted with different reference numbers.
In the specification and claims “/” between two words or sets of words indicates one or the other is being named; “and/or” between two words or sets of words means either one or both.
The descaling device 2 is outfitted with a strip conveying device 6 for transporting the metal strip 4 along a conveying direction 8. In the present exemplary embodiment, the strip conveying device 6 is designed as a roller conveyor with multiple rollers 10.
Moreover, the descaling device 2 comprises multiple first or upper spraying devices 12 for spraying a pickling agent 14 containing hydrochloric acid onto a top side 16 of the metal strip 4 and multiple second or lower spraying devices 12 for spraying the pickling agent 14 onto a bottom side 18 of the metal strip 4. In
The upper spraying devices 12 are arranged in succession in the conveying direction 8 of the strip conveying device 6. Likewise, the lower spraying devices 12 are arranged in succession in the conveying direction 8 of the strip conveying device 6. Moreover, the spraying devices 12 are each configured as a spray bar.
In the present exemplary embodiment, all the upper spraying devices 12 of the descaling device 2 are arranged at the same height. All the upper spraying devices 12 of the descaling device 2 have the same distance to the top side 16 of the metal strip 4. Moreover, all the lower spraying devices 12 of the descaling device 2 are arranged at the same height. All the lower spraying devices 12 of the descaling device 2 have the same distance to the bottom side 18 of the metal strip 4.
The distance of the upper spraying devices 12 from the top side 16 of the metal strip 4 may be less than or greater than the distance of the lower spraying devices 12 from the bottom side 18 of the metal strip 4. Alternatively, these two distances may be equal. It is especially preferable when the distance of the lower spraying devices 12 from the bottom side 18 of the metal strip 4 is smaller than the distance of the upper spraying devices 12 from the top side 16 of the metal strip 4.
Some of the upper and lower spraying devices 12 may be spraying devices 12a of a first type. Some others of the upper and lower spraying devices 12 may be spraying devices 12b of a second type. The spraying devices 12a of the first type comprise a multitude of solid stream nozzles 20, whereas the spraying devices 12b of the second type comprise a multitude of slotted nozzles 22 (see
In the present exemplary embodiment, the spraying devices 12a of the first type and the spraying devices 12b of the second type are arranged alternating in the conveying direction 8 of the strip conveying device 6. That is, a spraying device 12a of the first type is followed in the conveying direction 6 by a spraying device 12b of the second type, which in turn is followed in the conveying direction 8 by a spraying device 12a of the first type, and so forth. But, such alternation of two spraying devices next to each other is not required.
The spraying devices 12b of the second type, i.e., the spraying devices 12b with slotted nozzles 22, are utilized in this embodiment in particular to homogenize the descaling result.
However, the arrangement of the spraying devices 12 need not be such an alternating one. Moreover, the same number of spraying devices 12a of the first type and spraying devices 12b of the second type need not be present. Furthermore, it is basically possible to use only spraying devices 12 of the same type in the descaling device 2.
Moreover, the descaling device 2 comprises a pickling chamber 24, in which said spraying devices 12 are arranged. The pickling chamber 24 comprises a lower chamber portion 26 to receive the pickling agent 14 draining from the metal strip 4 and an upper chamber portion 28 arranged above the lower chamber portion 26.
Furthermore, the descaling device 2 comprises a first squeezing roller pair 30 and a second squeezing roller pair 32 each having an upper squeezing roller 34 and a lower squeezing roller 36. The first squeezing roller pair 30 is arranged in front of the pickling chamber 24 in terms of the conveying direction 8, while the second squeezing roller pair 32 is arranged in the pickling chamber 24. The squeezing rollers 34, 36 support and guide the metal strip 4. In moving through a squeezing roller pair 30, 32, a liquid present on the metal strip surface is expelled by the squeezing rollers 34, 36.
Furthermore, the descaling device 2 comprises a control device 38, of which
Said sensor units 42a, 42b are connected to the control unit 40 and each comprise an upper sensor row 44 and a lower sensor row 46. The sensor rows 44, 46 of the first sensor unit 42a are arranged in front of or preceding the spraying devices 12 in regard to the conveying direction 8 of the strip conveying device 6. The sensor rows 44, 46 of the second sensor unit 42b are arranged behind or following the spraying devices 12 in regard to the conveying direction 8 of the strip conveying device 6. Preferably, the sensor rows 44, 46 of the respective sensor unit 42a, 42b—as shown in
The metal strip 4 is transported by the strip conveying device 6 parallel to its length direction 48 through the descaling device 2. In the pickling chamber 24, the metal strip 4 has the pickling agent 14 applied to it by the spraying devices 12 in order to chemically descale the metal strip 4, in other words, to remove a scale layer located on the metal strip 4.
The upper sensor row 44 of the first sensor unit 42a detects, in front of or preceding the spraying devices 12 and resolved in location across the width of the metal strip 4, a surface parameter of the metal strip 4 which is dependent on the thickness of the scale layer on the top side 16 of the metal strip 4. Accordingly, the lower sensor row 46 of the first sensor unit 42a detects, preceding or in front of the spraying devices 12 and resolved in location across the width of the metal strip 4, a surface parameter of the metal strip 4 which is dependent on the thickness of the scale layer on the bottom side 18 of the metal strip 4.
The upper sensor row 44 of the second sensor unit 42b likewise detects, after or following behind the spraying devices 12 and resolved in location across the width of the metal strip 4, a surface parameter of the metal strip 4 which is dependent on the thickness of the scale layer on the top side 16 of the metal strip 4. Accordingly, the lower sensor row 46 of the second sensor unit 42b detects, after or following behind the spraying devices 12 and resolved in location across the width of the metal strip 4, a surface parameter of the metal strip 4 which is dependent on the thickness of the scale layer on the bottom side 18 of the metal strip 4. The sensor rows 44, 46 of the second sensor unit 42b may in particular detect each time the same surface parameter as the sensor rows 44, 46 of the first sensor unit 42a.
The sensor signals generated by the sensor rows 44, 46 of the sensor units 42a, 42b are relayed to the control unit 40.
With the help of the control unit 40, the pickling agent application on the metal strip 4 is controlled in dependence on the aforementioned sensor signals so that the most homogeneous possible descaling result is achieved, preferably with complete removal of the scale layer.
Basically, it is possible for the descaling device 2 to have only one of the two sensor units 42a, 42b, instead of both sensor units 42a, 42b, and to control accordingly the pickling agent application on the metal strip 4 in dependence on the sensor signals of only one of the sensor units 42a, 42b.
The descaling device 2 can moreover have one or more dip tanks (not shown) for a dip pickling treatment of the metal strip 4. For example, the descaling device 2 may have one dip tank before the pickling chamber 24 and a further dip tank after the pickling chamber 24. In the respective dip tank, the same pickling agent may be used as is sprayed by the spraying devices 12 onto the metal strip 4, or a different pickling agent may be used.
Referring to
As already mentioned, the spraying devices 12 are each configured as a spray bar.
The upper spraying devices 12 each comprise a first outer spraying unit 50 for spraying the pickling agent 14 onto a first edge region 52 of the top side 16 of the metal strip 4, a second outer spraying unit 54 for spraying the pickling agent 14 onto a second edge region 56 of the top side 16 of the metal strip 4, situated opposite the first edge region 52, and a middle spraying unit 58, arranged between the two outer spraying units 50, 54, for spraying the pickling agent 14 onto a middle region 60 of the top side 16 of the metal strip 4 situated between the edge regions 52, 56.
Accordingly, the lower spraying devices 12 each comprise a first outer spraying unit 50 for spraying the pickling agent 14 onto a first edge region 52 of the bottom side 18 of the metal strip 4, a second outer spraying unit 54 for spraying the pickling agent 14 onto a second edge region 56 of the bottom side 18 of the metal strip 4, situated opposite the first edge region 52, and a middle spraying unit 58, arranged between the two outer spraying units 50, 54, for spraying the pickling agent 14 onto a middle region 60 of the bottom side 18 of the metal strip 4 situated between the edge regions 52, 56.
Said spraying units 50, 54, 58 of the respective spraying device 12 are arranged in succession in the width direction 62 of the metal strip 4. Moreover, each of the spraying units 50, 54, 58 comprises multiple nozzles 20, 22 (see
Furthermore, the spraying units 50, 54, 58 are designed to spray the pickling agent 14 perpendicularly onto the top side 16 or bottom side 18 of the metal strip 4. The nozzles 20, 22 of the spraying units 50, 54, 58 are oriented such that the spraying units 50, 54, 58 each have a spraying direction 64 which is directed perpendicular to the top side 16 or bottom side 18 of the metal strip 4, i.e., vertically upward or vertically downward.
The distance of the spraying devices 12 from the strip surface, or more properly the distance of their nozzles 20, 22 from the strip surface, may be as much as 500 mm in the present example.
Furthermore, each of the spraying units 50, 54, 58 has its own pickling agent distribution chamber 66, to which the nozzles 20, 22 of the respective spraying units 50, 54, 58 are each connected by their inlet-side nozzle end.
Moreover, the descaling device 2 comprises a pickling agent supply line 68 for each of the spraying units 50, 54, 58. The respective pickling agent supply line 68 empties into the respective spraying unit 50, 54, 58 perpendicular to its spraying direction 64, so that a uniform pressure distribution is achieved in the individual spraying units 50, 54, 58.
Furthermore, the aforementioned control device 38 comprises multiple pickling agent delivery pumps 70, in the present exemplary embodiment there being provided a separate pickling agent delivery pump 70 for each of the spraying units 50, 54, 58 (see
Said pickling agent delivery pumps 70 are moreover each connected to the aforementioned control unit 40 of the control device 38, which is designed to use a given control algorithm to control the pickling agent volume flow of the pickling agent delivery pumps 70.
The control device 38 is designed to set the pickling agent dispersing rate of the respective spraying units 50, 54, 58, and this independently of the pickling agent dispersing rates of the other spraying units 50, 54, 58. By a change in the pickling agent volume flow of one of the pickling agent delivery pumps 70, the control unit 40 can change the pickling agent dispersing rate of the corresponding spraying unit 50, 54, 58.
Preferably, the sum of the pickling agent dispersing rates of the three spraying units 50, 54, 58 of the respective spraying device 12 lies in the range of 100 to 150 m3/h.
As mentioned above, the pickling agent application on the metal strip 4 is controlled in dependence on the previously mentioned sensor signals of the sensor units 42a, 42b such that the most homogeneous possible descaling result is achieved.
If the thickness of the scale layer in the middle region 60 of the metal strip 4 is less than that on the edge regions 52, 56 of the metal strip 4, the pickling agent dispersing rate of its first outer spraying unit 50 and the pickling agent dispersing rate of its second outer spraying unit 54 in the respective spraying device 12 will be set by the control device 38 respectively at a value which is greater than the pickling agent dispersing rate of its middle spraying unit 58. On the other hand, if the thickness of the scale layer in the middle region 60 of the metal strip 4 is greater than that on the edge regions 52, 56 of the metal strip 4, the pickling agent dispersing rate of its first outer spraying unit 50 and the pickling agent dispersing rate of its second outer spraying unit 54 in the respective spraying device 12 will be set by the control device 38 respectively at a value which is smaller than the pickling agent dispersing rate of its middle spraying unit 58.
If the thickness of the scale layer is symmetrical with respect to a vertical strip center plane, the pickling agent dispersing rate of its first outer spraying unit 50 and the pickling agent dispersing rate of its second outer spraying unit 54 in the respective spraying device 12 will be set by the control device 38 at the same value.
In the event of a production-related decrease in the delivery speed of the metal strip 4, one or more spraying units 50, 54, 58 of the spraying devices 12 can be switched off to avoid an overpickling of the metal strip 4.
In
Moreover, the already mentioned pickling agent delivery pumps 70 and the pickling agent supply lines 68 connected to the spraying units 50, 54, 58 are represented in
In the spraying device 12a of the first type in
The distance between adjacent solid stream nozzles 20 from the same nozzle row may correspond in particular to the distance between adjacent nozzle rows. This distance may amount to 25 mm, for example. At their exit opening, the solid stream nozzles 20 preferably have an inner diameter of 4 mm.
Moreover, the solid stream nozzles 20 of one nozzle row are arranged with an offset with respect to the row length direction from the solid stream nozzles 20 of the adjacent nozzle row, in order to avoid the formation of a striped spray pattern on the metal strip 4.
In the spraying device 12b of the second type in
In both the spraying device 12a of the first type in
In both the spraying device 12a of the first type and in the spraying device 12b of the second type, the pickling agent distribution chambers 66 are separated from each other by partition walls, which are indicated in
Alternatively or additionally, for one or more of the spraying devices 12a, 12b of the first or second type the descaling device 2 may have a spraying device not divided into three spraying units whose pickling agent dispersing rates are adjustable independently of each other, but instead has only a single spraying unit. Such a spraying device may have slotted nozzles, for example, which extend substantially across the entire width of the spraying device.
In the diagram, the quantity of pickling agent V sprayed by the spraying device 12a, 12b onto the metal strip 4 is represented as a solid line as a function of a length coordinate x in the width direction 62 of the metal strip 4. The value b of the abscissa length coordinate x corresponds to the width of the metal strip 4.
The contribution of the two outer spraying units 50, 54 to the pickling agent spray profile is represented in the diagram respectively by means of a dashed line, whereas the contribution of the middle spraying unit 58 is represented by a dotted line.
The pickling agent spray profile shown has a mirror symmetry. In the middle region 60 of the metal strip 4, the pickling agent spray profile has a plateau 72. In the middle region 60 the pickling agent spray profile does not change with the length coordinate x. In the first and in the second edge region 52, 56 of the metal strip 4, however, the pickling agent spray profile increases toward the outside (starting from the plateau 72).
These two spraying devices 12c, 12d may be used in the descaling device 2 of
The spraying device 12c of the third type, like the spraying device 12a of the first type, comprises a multitude of solid stream nozzles 20, whereas the spraying device 12d of the fourth type, like the spraying device 12b of the second type, comprises a multitude of slotted nozzles 22.
The spraying devices 12c, 12d of the third and fourth type in
Moreover, in the embodiments of
This pickling agent spray profile differs from the pickling agent spray profile of
The pickling agent spray profiles represented in the diagrams of
Although the invention has been illustrated and described more closely in detail by the preferred exemplary embodiments, the invention is not limited by the examples disclosed and other variations may be derived from it, without leaving the scope of protection of the invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17164759.7 | Apr 2017 | EP | regional |
The present application is a 35 U.S.C. §§ 371 national phase conversion of PCT/EP2018/058305, filed Mar. 30, 2018, the contents of which are incorporated herein by reference which claims priority of European Patent Application No. 17164759.7, filed Apr. 4, 2017, the contents of which are incorporated by reference herein. The PCT International Application was published in the German language.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/058305 | 3/30/2018 | WO | 00 |
