KR20080027816A - A device and a method for coating an elongated metallic element with a layer of metal - Google Patents

Abstract

A device and a method for controlling the thickness of a metallic coating on an elongated metallic element (1), wherein the coating is adapted to be applied by continuously transporting the element through a bath (2) of molten metal, and the element is transported from the bath in a transport direction (3) along a predetermined transport path (x). The device comprises at least one pair of electromagnetic wiping members, comprising one wiping member on each side of the element (1) for wiping off excessive molten metal from the element by applying a travelling magnetic field, and wherein each wiping member comprises a wiping pole (5). The device comprises at least one pair of electromagnetic stabilizing members, comprising one stabilizing member on each side of the element (1) for stabilizing the position of the element with respect to the predetermined transport path (x), the stabilizing member comprising a stabilizing pole (5). The wiping member and the stabilizing member on the same side of the element (1) are arranged such that the wiping pole (5) and the stabilizing pole (5) coincide. ® KIPO & WIPO 2008

Description

A DEVICE AND A METHOD FOR COATING AN ELONGATED METALLIC ELEMENT WITH A LAYER OF METAL}

The present invention is a device for controlling the thickness of a metal coating of an elongated metal element, wherein the coating is formed when the elongated metal element passes continuously through the molten metal bath, the element being conveyed from the bath in a conveying direction along a predetermined conveying path. do.

The invention also relates to a method of controlling the metal coating thickness of an elongated metal element. The coating is formed when the elements pass continuously through the molten metal bath.

Such an apparatus and method is particularly advantageous when galvanizing a metal strip continuously. The invention is described below in connection with such an application. However, the present invention may also apply galvanization to other metal objects such as wires, rods, tubes or other elongated elements. The invention is also applicable to coating elongated metal elements with other coatings besides zinc, such as tin or aluminum or mixtures thereof or other metals.

When continuously galvanizing metal strips, for example in steel strips, this steel strip generally passes continuously through a bath comprising zinc molten metal. In the bath, the strip generally moves upward through the stabilization and correction rollers after passing under the immersion rollers. The strip exits the bath and is transported through a wiper device, for example a gas knife or an electromagnetic wiper. Electromagnetic wipers generate a variable magnetic field which is used to control the coating thickness and to remove any excess zinc from the metal bath. The excess zinc may be returned to the bath and reused. The strip is then conveyed without support until the coating cools and solidifies. The coated strip is then directed or directed through the upper roller to the arrangement for cutting the strip into individual strip elements or winding the strip onto the rollers. In general, the strip moves vertically from the immersion roller and gas knife to the upper roller via a calibration and stabilization roller and wiper device.

When the steel strip is galvanized, it is intended for flat and thin coating thicknesses. A common way to control the coating thickness is to measure the amount of coating after excess molten metal is removed from the band and the coating solidifies, for example after the strip passes through the upper roller. This recording is used to control the gas knife, thus adjusting the coating thickness. However, due to the shape of the steel strip, unsupported strip distance, the speed of the strip and the electromagnetic wiper, the metal strip essentially moves or vibrates perpendicular to the conveying direction. Specific measures used to calibrate or stabilize the rollers and controlling the steel strip speed and / or adjusting the distance that the strip is not supported are performed to reduce the transverse movement. If the transverse movement is not diminished, this transverse movement significantly disturbs the removal correctly, resulting in a rugged coating thickness. Furthermore, the disturbing force of the strip can be generated by the wiper device. WO 02/14574 known a device for controlling the coating thickness of metal strips. The apparatus includes an electromagnetic wiping member disposed on each side of the strip, and the electromagnetic wiping member includes two wiping poles arranged in turn in the direction of movement of the strip. The excess molten metal is removed from the strip by the wiping member by applying magnetic force to the coating. The device also includes an electromagnetic stabilization device, which is arranged on each side of the strip and comprises three stabilizing poles. In order to damp the vibrations of the strip generated by the free length of the strip and the disturbing forces generated in the wiping member, each electromagnetic wiping pawl is arranged between two stabilizing pawls in the conveying direction of the strip.

The present invention aims at improving an apparatus for controlling the thickness of a metal coating when coating the metal strip, so that the quality of the coated strip is improved.

According to a first aspect, the invention relates to an apparatus for controlling the thickness of a metal coating on an elongated metal element according to claim 1. The elongated metal element is preferably a metal strip.

In an apparatus for controlling the metal coating thickness of a metal strip, the coating is formed when the strip continuously passes through the molten metal bath. The strip is conveyed from the bath in a conveying direction, along a predetermined conveying path, the apparatus comprising one or more pairs of electromagnetic wiping members, for removing excess molten metal from the strip by applying a moving magnetic field to the strip. One wiping member is disposed on each side of the wiping member and each wiping member includes a wiping pawl. The apparatus includes one or more pairs of electromagnetic stabilizing members, including one stabilizing member on each side of the strip to stabilize the position of the strip with respect to a predetermined movement path, each stabilizing member comprising a stabilizing pawl. The wiping member and the stabilizing member allow the wiping pawl and the stabilizing pawl on the same side of the strip to coincide. Thus, the stabilizing magnetic force from the stabilizing member is generated in the same region as the disturbing force from the wiping member. Since the stabilizing force acts on areas such as disturbances to the strip generated from the wiping member, the bending and vibration of the sheet are reduced. Another advantage is that the device provides a more compact configuration than the prior art devices. The wiping member and the stabilizing member preferably have a common magnetic core. The common magnetic core includes a rear and front magnetic core portion.

According to one embodiment, the wiping member and the stabilizing member form an integrated device, which makes the configuration of the device compact.

According to one embodiment, the wiping member has two phase windings. By having only two phase windings rather than three phase windings as conventionally to remove excess metal, only one peak of the removal force of the coating sufficient to satisfactorily remove the excess coating is obtained. This also means that disturbances generated in the wiping device occur only in the region of the strip across the conveying direction of the strip.

According to one embodiment, the stabilizing member comprises a stabilizing winding. The stabilization winding is arranged between the strip and the phase winding. By arranging the stabilizing windings between the strip and the phase windings, the stabilizing member can act in the same area as the wiping member.

According to one embodiment, the magnetic core has an essentially T-shaped cross section and comprises a base and a loop. The base consists essentially of a front magnetic core portion, the magnetic core portion comprising a wiping pole and a stabilizing pawl and the loop substantially comprising a rear magnetic core portion. The loops are arranged essentially in a direction parallel to the conveying direction and the base extends from the roof in the direction towards the strip.

According to one embodiment, the stabilizing winding is arranged around the base and the phase winding is disposed around the loop on each side of the base. Thus, a compact configuration is obtained, and as a result, the stabilizing magnetic force generated in the stabilizing member acts on the same region as that in which disturbance generated from the wiping member occurs. Since the stabilizing force acts in the same area as the disturbance generated from the wiping member, the warpage and vibration of the sheet will be reduced and at the same time the quality of the coating is maintained or improved.

According to another embodiment, the apparatus has a second pair of wiping members, which are disposed away from the first pair of wiping members in a direction transverse to the conveying direction. Furthermore, as a result, adjusting the thickness across the width of the strip is improved, and the quality of the coated strip is improved.

According to one embodiment, the apparatus comprises a third pair of wiping members, which are away from the first and second pair of wiping members in a direction transverse to the conveying direction. By arranging three wiping members across the conveying direction and along the width of the strip, it is possible to control the removal and stabilizing forces in accordance with the current needs in the very area covered by each wiping member. For example, one wiping member is located across the centerline of the strip and the other two wiping members are located on both sides of the wiping member disposed across the centerline. As a result, in addition, the adjustment of the width thickness of the strip is improved, which improves the quality of the coated strip.

According to one embodiment, one or more sensors for sensing the position of the strip with respect to the predetermined transport path are arranged in the vicinity of the one or more wiping members. By placing one or more sensors close to the point where disturbances are generated, for example near the wiping member, sensing the position of the strip is enhanced. In other words, the control of stabilizing the strip is improved and therefore the quality of the coated strip is improved.

According to one embodiment, the device comprises a stabilizing element that controls the permeability of the portion of the stabilizing pawl closest to the strip. The stabilizing element comprises, for example, an outer coil disposed outside of the stabilizing winding. The permeability of this portion of the stabilization pole is determined based on the strip distance to each stabilization pole. By adjusting the permeability of this part of the stabilizing pawl, the position of the strip between the stabilizing pawls is adjusted.

According to one embodiment, the device comprises an electrical circuit, which supplies current to one edge of the strip to generate a supplemental removal force. The current applied at one edge of the strip emerges at the other edge of the strip, for example through a closed circuit or by short-circuiting. The supplementary removal force is formed by the combination of the applied current and the magnetic field generated in the wiping pole, and also forms a supplemental removal force directed downward toward the bath. The circuit allows at least a current applied to one edge of the strip to be adjusted based on the actual thickness of the coating along the width of the strip compared to the requested value of the coating thickness along the width of the strip. The actual thickness of the coating is measured, for example, in a control device arranged behind the wiping member. The replenishment removal force is generally the largest at the edge of the strip and allows more uniform wiping across the strip if necessary.

According to a second aspect, the invention relates to a method for controlling the metal coating thickness of an elongated metal element according to claim 17. According to one embodiment, the elongated metal element is a metal strip.

When adjusting the thickness of the metal coating of the metal strip, the coating is formed while the strip continuously passes through the molten metal bath. The strip is conveyed in a conveying direction along a predetermined conveying path, and excess molten metal of the strip is removed by applying a moving magnetic field to the yet uncoagulated coating on the strip. Moreover, the position of the strip is stabilized with respect to the predetermined conveying path by applying a stabilizing magnetic force to the strip in the same region where the moving magnetic field acts on the strip. In this way, the strip is stabilized in the same area as the disturbance occurs, thereby reducing the deflection or vibration of the strip and thus allowing a greater force density of the wiper, thus increasing the strip speed and improving the quality of the strip. Maintain or improve to allow faster processing.

The thickness of the coating is measured after the excess molten metal is removed, and the measured thickness and the requested thickness value control the current flowing in the two phase windings that generate a moving magnetic field.

According to one embodiment, the position of the strip with respect to the conveying path is determined by one or more sensors which generate a parameter value, said parameter value being, for example, the distance between the actual position of the strip and the predetermined conveying path and stabilizing magnetic force. Adjust the size of the. The stabilizing magnetic force is then applied to the strip in response to the position of the strip.

According to one embodiment, the strip is stabilized by controlling the permeability of at least a portion of the stabilizing pole closest to the strip. The permeability of this part of the stabilizing pawl is controlled by the stabilizing element, which for example comprises an external coil. By controlling the permeability based on the point where the metal strip is located between the wiping poles, the metal strip is prevented from moving toward one pole due to the magnetic force, but instead the strip is located in the center between the wiping poles.

According to one embodiment of the invention, current is provided at one or more edges of the metal strip. By providing a current combined with the magnetic field generated in the wiping pole, a downward force is obtained which contributes to obtaining a uniform wiping action. The downward force is greatest at the edge of the strip.

The invention is explained in more detail with examples by reference to the accompanying drawings.

1 schematically shows a cross section taken in one embodiment of an apparatus for controlling the metal coating thickness of a metal strip viewed from the side.

FIG. 2 schematically shows a first embodiment of the apparatus of FIG. 1 seen from the front.

3 shows schematically a second embodiment of the device of FIG. 1 seen from the front.

4 schematically shows a third embodiment of the device of FIG. 1 seen from the front.

5 shows the saturation of the end of the wiping pole disposed closest to the strip.

The following description relates to apparatus and methods. 1 shows an apparatus for adjusting the thickness of the metal coating of the metal strip 1. The strip 1 is coated with a molten metal layer while continuously passing through the bath 2. The strip is conveyed from the bath in the conveying direction 3 along the predetermined path x. The predetermined conveying path x substantially extends between the roll immersed in the bath 2 and the upper rollers disposed after the wiping and stabilizing devices 4a, 4b. The wiping and stabilizing devices 4a and 4b allow to remove excess metal from the strip 1 and to stabilize the strip 1. The wiping and stabilizing device 4a, 4b comprises a wiping member, a stabilizing member and a common magnetic core 12a, 12b, which wiping the first phase winding for the first phase ( 6a, 6b and second phase windings 7a, 7b for the second phase, said stabilizing member comprising stabilizing windings 8a, 8b, said common magnetic core being a wiping and stabilizing pole 5a. , 5b). The wiping and stabilizing devices 4a, 4b are located at essentially the same height on both sides of the strip.

The magnetic cores 12a, 12b comprise rear magnetic core portions 9a, 9b and front magnetic core portions, and have a substantially T-shaped cross section, wherein the cross section comprises a base and a loop. The base consists essentially of the front magnetic core portion, which comprises the wiping and stabilizing pawls 5a, 5b and the loop consists essentially of the rear magnetic core portions 9a, 9b. The loops are arranged essentially in a direction parallel to the conveying direction 3 and the base extends from the loop in the direction towards the strip 1. The stabilizing windings 8a, 8b are arranged around the base and the phase windings 6a, 6b, 7a, 7b are arranged around the loop on each side of the base.

The phase windings 6a, 6b, 7a, 7b are supplied with alternating current (not shown), and an alternating magnetic field, also called a moving magnetic field, is generated in the strip 1. This magnetic field generates a current path (I) in the coating (not shown) and forces act on the coating in the direction opposite to the transport direction of the strip. The wiping member acts according to the principle of an electromagnetic stirrer or linear motor to generate an electromagnetic field. In this way, excess coating material is removed in the longitudinal direction of the strip.

Direct current is supplied to the stabilization windings 8a and 8b so that the stabilizing force acts perpendicular to the strip 1. Since the stabilizing pawls 5a, 5b are adapted to coincide with the wiping pawls 5a, 5b, the stabilizing force can act on the strip in the same area as the disturbance caused by the wiping pawl. Disturbance or vibration can of course also be caused by other causes besides the wiping member, for example due to the free length of the strip 1 (the length at which the strip 1 is not supported). This disturbance or vibration can also be stabilized with the wiping member. The wiping and stabilizing pawls 5a, 5b are arranged at a certain distance in the predetermined transport path x. The distance varies, of course, depending on the current thickness of the strip 1 and the thickness of the coating.

As shown in FIG. 1, sensors 10a, 10b for sensing the position of the strip 1 with respect to the predetermined transport path x are arranged on each side of the strip 1. The sensors 10a, 10b are arranged in close proximity to the wiping and stabilizing devices 4a, 4b. The sensors 10a, 10b detect the value of the parameter depending on the position of the strip with respect to the predetermined feed path x, whereby the stabilizing member exerts a force on the strip 1 corresponding to the detected value. do. The signal generated by the sensors 10a, 10b is processed in a signal processing device (not shown), and a control program (not shown) of the converter receives current flowing through the stabilization windings 8a, 8b to stabilize the strip 1. To control.

Control devices 11a and 11b for measuring the layer thickness are arranged behind the wiping and stabilizing devices 4a and 4b.

FIG. 2 schematically shows how the first wiping and stabilizing devices 4a, 4b of the first pair of wiping and stabilizing devices according to FIG. 1 are arranged along the width of the strip.

FIG. 3 schematically shows how the second wiping and stabilizing devices 17a, 17b of the second pair of wiping and stabilizing devices are arranged away from the first pair in a direction crossing the conveying direction 3.

4 schematically shows how the third wiping and stabilizing devices 18a, 18b of the third pair of wiping and stabilizing devices are arranged away from the second pair in the direction crossing the conveying direction 3. 4 also shows how the circuit 16 is arranged to apply a current I to one edge 13a of the strip 1 to create another removal force on the coating. The removal force is generated by the current I in combination with the electromagnetic force generated in the wiping members 4a, 4b, 4c. The current I comes from the other edge of the strip 13b.

FIG. 5 shows that at least the permeability of the portions 15a, 15b of the stabilizing poles 5a, 5b (the portion disposed closest to the strip) is controlled by a stabilizing element comprising, for example, an outer coil. The permeability of each part 15a, 15b is controlled based on the point where the metal strip is located between the wiping pawls 5a, 5b of the pair of wiping and stabilizing devices. By controlling the permeability, the metal strip is suppressed from moving toward one pole due to the magnetic force, but instead the strip is located in the center between the wiping poles 5a, 5b.

The invention is not limited to the embodiments shown above, but one of ordinary skill in the art can, of course, vary in many ways within the scope of the invention as defined in the claims. For example, if three pairs of wiping and stabilizing devices 4a, 4b, 17a, 17b, 18a, 18b are arranged across the conveying direction 3, the two outermost wiping and stabilizing devices ( 4a, 4b, 18a, 18b can be arranged along the same line along the strip across the conveying direction, with the middle wiping and stabilizing device 17a, 17b of the two outermost wiping and stabilizing devices. It can be placed before or after.

Claims (21)

A device for controlling the metal coating thickness of an elongated metal element (1), wherein the coating is formed when the elongated metal element (1) continuously passes through the molten metal bath (2), the element being a predetermined feed path (x). Conveyed from the bath (2) in the conveying direction (3) along the direction, the apparatus comprising one or more pairs of electromagnetic wiping members, each of the elements being removed to remove excess molten metal from the element by applying a moving magnetic field to the element. One wiping member is arranged on the side, each wiping member comprises wiping pawls 5a, 5b, and the device also comprises one or more pairs of electromagnetic stabilizing members, in a predetermined conveying path (x). In the apparatus, in which one stabilizing member is disposed on each side of the element to stabilize the position of the element relative to the element, The wiping member has first and second phase windings 6a, 6b, 7a, 7b and the wiping member and the stabilizing member on the same side of the element are the wiping pawls 5a, 5b and the stabilizing pawls 5a, 5b) is arranged to coincide, characterized in that the device for controlling the thickness of the metal coating of the elongated metal element (1). 2. Device according to claim 1, characterized in that the elongated metal element is a metal strip (1). Apparatus according to claim 1 or 2, characterized in that the wiping member and the stabilizing member have a common magnetic core (12a, 12b). Apparatus according to any one of the preceding claims, characterized in that the wiping member and the stabilizing member form an integrated device. 5. The device as claimed in claim 1, wherein the stabilizing member comprises stabilizing windings (8a, 8b). 6. The elongated metal element according to claim 2, wherein the stabilizing windings 8a, 8b are arranged between the strip 1 and the phase windings 6a, 6b, 7a, 7b. 1) Device to control the metal coating thickness. 7. The magnetic core 12 according to any one of claims 2 to 6, wherein the magnetic core 12 has a substantially T-shaped cross section and has a base and a loop, the loops being arranged in a direction substantially parallel to the conveying direction 3 and the base Device for controlling the thickness of the metal coating of the elongated metal element (1), characterized in that it extends from the loop in the direction towards the strip (1). Elongated metal element (1) according to claim 7, characterized in that the stabilizing winding (8) is arranged around the base, and the phase windings (6a, 6b, 7a, 7b) are arranged around the loop on each side of the base. Device to control the metal coating thickness of the. The device according to any one of the preceding claims, wherein the device has a second pair of wiping members, which are separated from the first pair of wiping members in a direction transverse to the conveying direction (3). Apparatus for controlling the metal coating thickness of the elongated metal element (1), which is arranged. 10. The device according to claim 9, wherein the device comprises a third pair of wiping members, which are disposed away from the first and second pair of wiping members in a direction transverse to the conveying direction (3). Device for controlling the metal coating thickness of the elongated metal element (1). The apparatus according to any one of claims 2 to 10, wherein at least one sensor (10a, 10b) for sensing the position of the strip (1) relative to the predetermined conveying path (x) is arranged in the vicinity of at least one wiping member. Device for controlling the thickness of the metal coating of the elongated metal element (1). 12. A stapling element according to any one of claims 3 to 11, characterized in that it comprises a stabilizing element that controls the permeability of the portions 15a, 15b of the stabilizing poles 5a, 5b closest to the strip 1. Device for controlling the metal coating thickness of the elongated metal element 1. 13. Apparatus according to claim 12, characterized in that the stabilizing element comprises an outer coil (14a, 14b) disposed outside of the stabilizing winding (8a, 8b). 14. A circuit as claimed in any one of claims 2 to 13, characterized in that it comprises a circuit (16) for providing a current to at least one edge (13a, 13b) of the strip (1) to generate an additional removal force. Device for controlling the metal coating thickness of the elongated metal element 1. 15. The apparatus of claim 14, wherein the circuit (16) is adapted to adjust the current (I) based on the coating thickness measured after removal. In the method of controlling the metal coating thickness of the elongated metal element 1, the coating is formed when the elongated metal element passes continuously through the molten metal bath 2, which method The element 1 is conveyed in a conveying direction 3 along a predetermined conveying path x, Applying a moving magnetic field to the element 1 with the metal coating not yet solidified to remove excess molten metal from the elongated metal element 1, Measuring the coating thickness after removing excess molten metal and controlling the current flowing in the phase windings 6a, 6b, 7a, 7b to generate a moving magnetic field according to the difference between the measured thickness and the desired thickness value, Of the elongated metal element 1, characterized in that it is applied to the elongated metal element 1 in the same region as the moving magnetic field acts on the element to stabilize the position of the object with respect to the predetermined transport path x. How to control metal coating thickness. 17. The method according to claim 16, wherein the elongated metal is a metal strip (1). The method of claim 17, Determine the position of the strip 1 with respect to the predetermined conveying path x by means of one or more sensors 10a, 10b that produce parameter values that control the magnitude of the stabilizing magnetic force, A method for controlling the thickness of the metal coating of the elongated metal element (1), characterized in that the stabilizing magnetic force is applied to the strip according to the position of the strip (1). 19. Elongated metal element according to claim 17 and 18, characterized in that the strip (1) is stabilized by adjusting the permeability of the portions (15a, 15b) of the stabilizing pole (5) at least closest to the strip (1). 1) to control the metal coating thickness. 20. Elongated metal element (1) according to claim 19, characterized in that the magnetic permeability of the portions (15a, 15b) of at least the stabilizing pole (5) closest to the strip (1) is controlled by the outer coils (14a, 14b). To control the metal coating thickness. 21. The method according to any one of claims 17 to 20, characterized in that a current is applied to at least one edge (13a, 13b) of the strip (1) such that a removal force towards the bath (2) with a moving magnetic field is produced. A method of controlling the metal coating thickness of an elongated metal element 1.

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