A hot dip coating device and a method of coating a metal strip in a hot dip coating device

Abstract

The invention relates to a hot dip coating device for providing a metal coating on a metal strip. The hot dip coating device comprises a container containing a liquid metal bath in use, a snout for guiding the metal strip into the liquid metal bath in use, wherein the snout comprises a lower opening immersed in the liquid metal bath in use, a sink roll for guiding the metal strip through the liquid metal bath in use, wherein the sink roll is provided in the container, below the surface level of the liquid metal bath in use, and at least two stabilisers of which at least one stabiliser is arranged on each side of the metal strip in use, for stabilising the metal strip. The invention also relates to a method of coating a metal strip.

Description

[0001] A hot dip coating device and a method of coating a metal strip in a hot dip coating device

[0002] Field of the invention

[0003] The present invention relates to a hot dip coating device for providing a metal coating on a metal strip. In a further aspect the present invention relates to a method of coating a metal strip in a hot dip coating device.

[0004] Background of the invention

[0005] Hot dip coating is a well-known process for protecting a metal strip against corrosion. An example of a hot dip coating device is a hot dip galvanizing device. A hot dip coating device is typically used to provide a metal coating such as zinc or aluminium on a moving metal strip. The moving metal strip in this context can also be called a metal strip. The hot dip coating device typically comprises a container for a liquid metal bath of a coating material in use. For some applications, the coating material may consist almost entirely of zinc (>99%) known as Gl coatings or almost entirely of aluminium (>99%). For other applications, the zinc coatings or aluminium coatings are alloyed with other metals such as magnesium or silicon, which is advantageous owing to their improved corrosion resisting performance and improved pressing performance. In the context of the present invention, the metal strip is also called a metal sheet.

[0006] The metal strip is passed from a previous annealing section of an annealing furnace into the hot dip coating device. To guide the metal strip from the previous furnace into and out of the container, a snout and several rolls can be present in the hot dip coating device. A snout is a duct that shields the annealed steel strip from an open atmosphere, which is necessary to avoid oxidation and to maintain the strip temperature. Generally, the snout guides a steel strip into a liquid metal bath. The snout is typically rectangular in cross section, but it is also possible for a snout to have a cross section other than rectangular. The lower part of the snout has an opening that is immersed in the liquid metal bath during use. The metal strip or the metal sheet can be passed through this opening into the liquid metal bath. The last roll or rolls in the annealing section to guide the metal strip into the snout is known as a bridle or a hot bridle. The snout is placed between the hot bridle and the container, as part of a hot dip coating device. A sink roll is used inside the container to guide the metal strip from the liquid metal bath to out of the liquid metal bath. Typically at least one supporting roll is also provided in the liquid metal bath between the sink roll and the surface level of the liquid bath at the side of a gas knife, which is used to control the thickness of the coating on the metal strip. This at least one supporting roll is used to influence the shape of the metal sheet in its width direction at the location of the gas knife.

[0007] The atmosphere in the snout is generally dry and this dry atmosphere is known to lead to metal evaporation from the liquid metal bath. For a hot dip galvanizing device that is used to coat a steel strip with zinc or zinc alloy, this dry atmosphere leads to zinc evaporation. The zinc evaporation leads to condensation of zinc against the snout walls which, in turn, leads to formation of zinc dust against the walls that can fall on the steel strip or on the zinc bath surface, leading to coating defects. The evaporation of zinc is limited by moistening the atmosphere inside the snout directly above the liquid zinc surface. This creates an oxide layer on the liquid zinc surface that limits the zinc evaporation. It is known that in a continuous galvanizing line, the molten zinc bath is usually saturated with iron, which dissolves from the steel strip that is continuously passed through the bath. The molten zinc bath may also contain unwanted particles such as oxide particles that are formed when oxygen in the surrounding air oxidises the liquid zinc. Such oxide particles typically stay in the top layer of the liquid zinc. Further, at the operating temperature of the liquid zinc bath, dissolution of iron from the steel strip into the metal bath can occur that forms intermetallic particles. These intermetallic particles as well as the oxide particles are known as dross. Dross present on the surface of the liquid metal bath or dross that rises to the surface if present underneath the surface is known as surface dross or floating dross or top dross. Since the lower part of the snout is immersed in the liquid zinc bath, the liquid zinc bath that is present within the snout also contains dross such as surface dross. If not properly controlled, the surface dross within the snout will be collected by the moving steel strip, which will have detrimental effects on the final products that are manufactured from the steel strip. For example, small dross particles may be incorporated in the coated alloy layer and affect the appearance of the coated steel parts. This is particularly disadvantageous for steel strips from which exterior automotive parts are shaped by pressing. The included particles may cause inhomogeneous deformation resulting in surface defects and irregularities such as tiny projections and bulges, even when present at the non-exposed side of the automotive parts. The unevenness in the surface of the steel parts results in undesired reflections that affect the appearance in an unacceptable way. Such a situation could also result from using a coating metal not being zinc and a metal strip not being a steel strip.

[0008] In view of the use of the coated metal strip, the applied metallic coating in the hot dip coating step should fulfil requirements such as that the metal layer has to be without any dross or debris. This is important not only to be able to subject the coated steel strip to forming operations but also for the final appearance of the final metal product formed from the coated metal strip. Surface defects are also related to a dynamic wetting process when the metal strip moves into the zinc bath in the snout. A vibration of the moving metal strip will make wetting more difficult and has an effect on the entrainment of surface debris. The surface debris or surface dross that floats on the metal bath surface in the snout is similar to a floating fleece. This surface dross has a mechanical strength. By getting exposed to mechanical disturbances, the surface dross will get loose from this fleece and will be picked up by the moving metal strip. Typically these mechanical disturbances are enhanced by vibrations or instability of the moving metal strip, especially when the vibrations are perpendicular to the travel direction of the moving metal strip. If the strip is unstable in the snout due to its vibrations, these vibrations trigger the surface dross to be detached from the floating fleece. The detached surface dross will be easily picked up by the moving metal strip, which will contaminate the subsequent coated metal strip. Also, a stable strip will generate a smaller free zinc surface that can evaporate or oxidise, thus reducing the formation of further oxidic dross. Hence, there is a desire to reduce the vibrations of a moving metal strip so that it is stable within the snout.

[0009] Prior art documents mainly describe methods to remove surface dross from the liquid metal bath within the snout. However, it is also required that the surface dross that is already present in the snout, especially the surface dross that is present close to the moving metal strip entering the zinc bath, does not have exposure to mechanical disturbances and that it stays as still as possible. If there is exposure to mechanical disturbances it can lead to a breakup of the dross fleece near the moving strip which will result in a subsequent dross pickup by the moving strip. The force that will drive the surface dross to the metal strip induced by the flow of the molten metal in the snout is larger than any other force acting on the surface dross that is close to the strip. As the vibration of the moving metal strip in the snout enhances the mechanical disturbance of surface dross, there is a desire to reduce the vibration of the moving metal strip in the snout. This will reduce coating contamination and defects and will eventually lead to a homogenous coating of the steel strip.

[0010] Objectives of the invention

[0011] It is therefore an object of the invention to provide a hot dip coating device with which the vibration of the moving metal strip before it enters the liquid metal bath in a snout can be reduced.

[0012] It is a further object of the invention to provide a method of coating a metal strip in a hot dip coating device by which the vibration of the moving metal strip before it enters the liquid metal bath in a snout can be reduced. It is also an object of the invention to provide a hot dip coating device and a method to use it with which to avoid picking up of surface dross by a moving metal strip in a snout.

[0013] It is also an object of the invention to provide a hot dip coating device and a method to use it with which to improve the wettability of a moving metal strip in a snout of a hot dip coating device.

[0014] Description of the invention

[0015] According to a first aspect of the invention one or more of these objects are reached with a hot dip coating device for providing a metal coating on a moving metal strip, comprising: a container containing a liquid metal bath in use; a snout for guiding the metal strip into the liquid metal bath in use, wherein the snout comprises a lower opening immersed in the liquid metal bath in use; a sink roll for guiding the metal strip through the liquid metal bath in use, wherein the sink roll is provided in the container, below the surface level of the liquid metal bath in use, and at least two stabilisers of which at least one stabiliser is arranged on each side of the metal strip in use, for stabilising the metal strip; wherein each of the at least two stabilisers has a surface facing the metal strip in use, arranged such that in use the surface of each of the at least two stabilisers remains constantly positioned on each side of the metal strip and wherein the at least two stabilisers are positioned before the sink roll, in the travelling direction of the metal strip in use.

[0016] The present invention reduces the vibration of the moving metal strip before the metal strip enters the liquid metal bath by using at least two stabilisers. The at least two stabilisers stabilise the moving metal strip, during its use. It can be a pair of stabilisers. The stabilisers generate electromagnetic or hydrodynamic force to provide stabilisation without contact with the strip. Of the at least two stabilisers at least one stabiliser is positioned on each side of the moving metal strip, and the stabilisers are arranged such that the facing surface of each of the stabilisers faces the metal strip. Thus, the stabilisers do not rotate around their axis. In use, the stabilisers are immobile. As the stabilisers do not have any moving parts and their facing surface is placed on each side of the moving metal strip during use, this will substantially reduce vibrations. Any moving part, if present, will create extra flows in the bath or when installed above the metal bath will attract zinc dust coming from the condensed zinc vapour that is present in the snout above the bath level. Rotating parts of a stabiliser are additionally costly as they require regular maintenance due to replacement of parts such as bearings. The at least two stabilisers are placed as opposing stabilisers on both sides of the metal strip. The stabilisers reduce the vibration of the moving metal strip, thus reducing picking up of surface dross from within the snout.

[0017] Preferred embodiments of the hot dip coating device are provided in the subclaims.

[0018] In an embodiment of the present invention, the at least two stabilisers are at least partially immersed in the liquid metal bath in use. The at least two stabilisers can be partially or fully immersed in the liquid metal bath. These stabilisers enable hydrodynamic pressure to increase. In other words, when the strip moves to the one side, the channel between the stabiliser and the strip is narrowed so it creates increased hydrodynamic pressure that stabilises the strip by pushing the strip back to the center. In addition, the stabilisers can be present at the spot where the metal strip enters the liquid metal bath, to ensure better stabilisation. In an embodiment of the invention, at least one of the stabilisers is positioned so as to narrow the horizontal distance between the stabiliser and the strip in the travelling direction of the metal strip. Thus, the converging channel between the stabiliser and the strip increases the hydrodynamic pressure and provides better stabilisation.

[0019] In an embodiment of the present invention the at least two stabilisers are pads. The pads are rigid structures. The pads are made of a non-corrosive material in order to withstand any corrosion from the compositions of metal bath. Preferably the at least two stabilisers are stainless steel pads or tungsten pads. The thickness of the pads can be in the range of 5 mm to 10 mm. Pads advantageously allow to avoid trapping debris or dross located at the surface of the bath primarily upon starting up the line, while pads favour stabilisation.

[0020] As such, pads are known to the skilled person. US patent application US2019032188 A1 describes a dissipating hydrodynamic device allowing to stabilise a metal strip in continuous motion passing through dryers at the end of a dip-coating operation. It comprises a plurality of hydrodynamic pads configured to apply a load to at least one side of the metal strip and mounted so as to pivot around hinges so as to self-align the pads, the plurality of hydrodynamic pads extending transversely across a width of the strip, and positioned such that, when in use, the liquid-metal return stream of the drying wave flows at least in part over backs of the pads. Pads refer to rigid planar devices such as plates. They may either have a partially immersed part, or even be completely immersed. The loading of the pads aims to balance the hydrodynamic lift generated within the film of liquid metal at the strip-pad interface, and also to flatten the strip upon its exit from the bath. Foils are also known as such to the skilled person.

[0021] In another embodiment of the present invention the at least two stabilisers are foils. The foils are also made of a non-corrosive material in order to withstand any corrosion from the compositions of both the metal bath. Preferably the at least two stabilisers are stainless steel foils or tungsten foils. The thickness of the foils are lower than the thickness of the pads. The thickness of the foils can be in the range of 0.01 mm to 2 mm. Preferably, the thickness of the foils can be in the range of 0.03 mm to 1 mm or in the range of 0.05 mm to 0.5 mm. The foils are comparatively more flexible than the pads. Foils are known as such to the person skilled in the art.

[0022] According to a preferred embodiment, a pressure apparatus is provided that is connected with the at least two stabilisers to press the at least two stabilisers towards the metal strip in use. By pressing the pads or foils towards the metal strip, the immobilization of the stabilisers are provided and the vibration of the metal strip is minimised.

[0023] In another embodiment of the present invention, the lower opening of the snout surrounds an upper portion of the at least two stabilisers. The upper portion of the at least two stabilisers forms an opening through which the moving steel strip is transferred into the metal bath.

[0024] According to a further preferred embodiment of the invention, the at least two stabilisers are placed within the snout. The stabilisers are thus present between the hot bridle and the lower opening of the snout.

[0025] In an embodiment, the at least two stabilisers are placed above the surface level of the liquid metal bath in use. In this case, the stabilisers are not in contact with the liquid metal bath. This is advantageous when the liquid metal is liquid zinc, because liquid zinc is quite corrosive.

[0026] In a preferred embodiment of the present invention, the at least two stabilisers are electromagnetic stabilisers. Prior art documents disclose electromagnetic stabilisers that are used for reducing vibrations of a steel strip after exiting the liquid metal bath of a hot dip coating device. Typically an electromagnetic stabiliser consists of an electromagnet, an eddy-current type displacement sensor, a control unit, and a power unit. The electromagnet of the electromagnetic stabiliser is placed near the surface of the steel strip. Vibrations are detected by the sensor, which activates the magnet to keep the steel strip flat and vibration-free. Electromagnets with dynamically controlled power amplifiers are used to correct and stabilise the position of the moving metal strip and to limit strip vibrations. In this manner the majority of frequencies are damped to a level that is close to a noise spectrum. The at least two electromagnetic stabilisers can be a pair of electromagnets. The pair of electromagnetic stabilisers are not in fluidic contact with the liquid metal bath.

[0027] For industrial applications, it is often required that the at least two stabilisers stabilise the moving metal strip continuously during a continuous hot dip coating process. On a commercial scale in the steel industry, for example for a hot dip galvanizing line, a single galvanizing bath is continuously operated for time periods of some weeks up to several months, before any shut down occurs in view of a necessary maintenance and replacement. In practice such a galvanizing line is used to produce galvanized steel strips of different qualities in consecutive runs. In particular a switch from producing steel strips that meet less stringent quality requirements to steel strips for high demanding end purposes is complicated and critical. After such a switch of production, if the freshly produced steel strip does not meet the required higher standards, it will likely be rejected. Hence, there is also a requirement for a continuous stabilisation of the moving metal strip before entering the liquid metal bath so that it will not affect the quality of steel production if a switch of production occurs. If the stabiliser is not able to continuously stabilise the moving metal strip, the moving metal strip will pick up surface dross. Thus, the stabilisers have to continuously stabilise the moving metal strip or sheet. Occasionally, it may be needed to remove the stabilisers for various purposes such as maintenance, cleaning or for replacement. Therefore, in another embodiment of the invention, the at least two stabilisers are removably mounted to the hot dip coating device.

[0028] According to a second aspect, the present invention relates to a method of coating a metal strip in a hot dip coating device according to the first aspect of the invention. According to the method the metal strip passes between at least two stabilisers for stabilising the metal strip, and the metal strip is coated with a metal coating material that is contained in a container of the hot dip coating device. Using this method of coating with the hot dip coating device as elucidated above, picking up of surface dross from within the snout is reduced and less zinc dust will be generated, so less contamination of the moving metal strip will take place. Also the wettability of the moving metal strip will be improved.

[0029] According to preferred embodiments of the method the at least two stabilisers are pads or foils that are pressed towards the metal strip by a pressure apparatus, or the at least two stabilisers are electromagnetic stabilisers wherein an electric field is applied between the stabilisers. This has been elucidated above.

[0030] As described previously, the liquid metal bath is used to coat a metal coating material on the moving metal strip. In an embodiment of the present invention, the metal strip is coated with a metal coating material which is a zinc or zinc alloy, preferably a zinc aluminium alloy or zinc magnesium alloy or zinc aluminium magnesium alloy, or an aluminium or aluminium alloy, preferably an aluminium silicon alloy or an aluminium silicon magnesium alloy. These types of metal coating material are as such known to the person skilled in the art, and are especially used to coat a steel strip.

[0031] In another embodiment of the present invention, the metal strip is coated with a zinc alloy coating comprising 0.3 - 4.0% magnesium and 0.3 - 6.0% aluminium; optionally at most 0.2% of one or more additional elements; unavoidable impurities; the remainder being zinc. Preferably the alloying element contents in the coating shall be 1.0 - 2.0 % magnesium and 1.0 - 3.0 % aluminium, optionally at most 0.2% of one or more additional elements, unavoidable impurities and the remainder being zinc. In a more preferred embodiment, the zinc alloy coating comprises at most 1.6% magnesium and between 1.6 and 2.5% aluminium, optionally at most 0.2% of one or more additional elements, unavoidable impurities and the remainder being zinc. In another embodiment, the metal coating material in use comprises a liquid bath of aluminium or aluminium alloy, preferably an aluminium silicon alloy, an aluminium silicon magnesium alloy. In an embodiment, the metal coating material can also contain zinc - aluminium or zinc - aluminium - magnesium alloys but having a higher content of aluminium.

[0032] The additional elements elements that could be added in a small amount, less than 0.2 weight %, could be Pb or Sb, Ti, Ca, Mn, Sn, La, Ce, Cr, Ni, Zr or Bi. Pb, Sn, Bi and Sb are usually added to form spangles. These small amounts of an additional element do not alter the properties of the coating nor the bath to any significant extent. Preferably, less than 0.1 weight % of such an additional element is added, more preferably less than 0.05 weight %.

[0033] Brief description of the drawings

[0034] The invention is further explained by the following figures.

[0035] FIG. 1 shows a schematic representation of a usual hot dip coating device.

[0036] FIG. 2 shows a schematic representation of an embodiment of a hot dip coating device with at least two stabilisers.

[0037] FIG. 3 shows a schematic representation of another embodiment of a hot dip coating device with at least two stabilisers.

[0038] FIG. 4 shows a schematic representation of an even further embodiment of a hot dip coating device with at least two stabilisers.

[0039] Detailed description of the drawings

[0040] Coated steel strips are used in many applications such as for manufacturing parts in the automotive industry, where the applied coating is required to fulfil requirements such as that the metal coating should not be with any dross. The present invention embodiments reduce the chances of occurring contamination in a coating layer by stabilising the steel strip before or during the coating process. The present invention embodiments result in stabilising a steel strip before entering the liquid metal bath or while in the liquid metal bath. This reduces the chances of adhering surface dross that is present in the snout on the moving metal strip.

[0041] FIG. 1 shows a schematic representation of a usual hot dip coating device 19. A steel strip 2 is passed from a previous annealing section through an introduction point 31 into a snout 50 using hot bridles 16. The hot dip coating device 19 comprises a liquid metal bath 18 having the surface bath level 20. An ingot 15 is placed in the liquid metal bath 18 to replenish the liquid metal bath 18. The hot dip coating device 19 also comprises a sink roll 28 that is used to pass the steel strip 2 out of the liquid metal bath 18 to air knives 14. Air knives 14 are used for adjusting the coating amount of molten metal on the steel strip or steel sheet. The hot dip coating device 19 may additionally comprise supporting rolls 33, 34 that are used for acquiring a desired shape to the steel strip. In figure 1 , the supporting rolls 33, 34 are placed in the liquid metal bath 18 and in between the sink roll 28 and the air knives 14.

[0042] FIG. 2 shows a schematic representation of an inventive embodiment of a hot dip coating device 19 with at least two stabilisers 100 placed within the snout 50. The moving steel strip 2 is passed from a previous annealing section into a container 22 comprising a liquid metal bath 18 of a metal coating material in use such as molten zinc. The arrow denotes the travelling direction of the steel strip 2. An ingot 15 is placed in the liquid metal bath 18 to replenish the liquid metal bath. The snout 50 has a lower opening 39 that is immersed in the liquid metal bath 18. Of the at least two stabilisers 100 one stabiliser is placed on each side of the moving metal strip 2 such that the at least two stabilisers 100 are partially immersed within the liquid metal bath 18. The at least two stabilisers of Fig. 2 are a pair of stabilisers. They are pads made of, for example, stainless steel material. The pads are rigid structures and are made of non-corrosive material. The pads 100 are placed as a pair of stabilisers with one face of each stabiliser facing the metal strip. They are placed as opposing stabilisers on both sides of the moving metal strip 2 so that they rely on the pressure build-up by the flow induced by the moving metal strip 2. As the molten zinc has a much higher density than air, the pressure that is build up in the molten zinc bath 18 dampens the vibrations of the metal strip 2 effectively and flattens the metal strip 2 since crossbow will be reduced. This reduces the strip vibration thereby reducing the possibilities of picking up of any surface dross that is floating in the liquid metal bath within the snout. The pads 100 have an upper portion and a lower portion. The lower opening 39 of the snout 50 encloses the upper portion of the pads 100. The lower portion of the pads 100 opens to the liquid metal bath 18 of the container 22. The lower portion of the pads forms an opening that is in the range of 20 mm to 80mm. The upper portion of the pads are above the surface bath level 20 of the liquid metal bath 18. The hot dip coating device 19 also comprises a sink roll 28 for guiding the steel strip 2 out of the liquid metal bath 18. From the snout, the steel strip 2 moves downwards through the stabilisers, around the sink roll 28 and then moves upwards out of the liquid metal bath 18 to the air knives 14. Air knives 14 are used for adjusting the coating amount of molten metal on the steel strip.

[0043] Figure 3 shows a schematic representation of another inventive embodiment of a hot dip coating device 19. The steel strip 2 is passed from a previous annealing section into a container 22 comprising a liquid metal bath 18 of a metal coating material in use such as molten zinc. An ingot 15 is placed in the a liquid metal bath 18. At least two stabilisers 110 are placed in the snout 50. The snout 50 has a lower opening 39 that is immersed in the liquid metal bath 18. The at least two stabilisers 110 are a pair of foils that are placed on each side of the moving metal strip 2. The foils 110 are flexible structures and are made of noncorrosive material such as stainless steel. The foils 110 have an upper portion and a lower portion. The upper portion is placed above the surface bath level 20 of the liquid metal bath 18. The lower opening 39 of the snout 50 encloses the upper portion of the foils 110. The lower portion of the foils 110 opens to the liquid metal bath 18. The lower portion of the foils forms an opening that is in the range of 20 mm to 80 mm. The metal strip 2 passes through the pair of foils 110 into the liquid metal bath 18. The hot dip coating device 19 also comprises a sink roll 28 that is used to guide the moving steel strip 2 out of the liquid metal bath 18 into the air knives 14. The air knives 14 are used for adjusting the coating amount of the molten zinc. The foils 110 are placed as opposing stabilisers on both sides of the metal strip 2 so that they rely on the pressure built up by the flow induced by the moving metal strip 2. As the molten zinc has a much higher density than air, the pressure that is build up in the molten zinc bath 18 dampens the vibrations of the metal strip 2 effectively and flattens the metal strip 2. This reduces the strip vibration thereby reduces the possibilities of picking up of any surface dross that is floating in the liquid metal bath within the snout.

[0044] FIG. 4 shows a schematic representation of a further inventive embodiment of a hot dip coating device 19. The moving steel strip 2 is passed from a previous annealing section into the container 22. At least two electromagnetic stabilisers 120 are placed in the snout 50 of the hot dip coating device. The at least two electromagnetic stabilisers are placed as a pair of stabilisers 120 above the container 22, within the snout. An ingot 15 is placed in the a liquid metal bath 18. The snout 50 has a lower opening 39 that is immersed in the liquid metal bath. The hot dip coating device 19 also comprises a sink roll 28 that is used to guide the steel strip 2 out of the liquid metal bath 18 into the air knives 14. The air knives 14 are used for adjusting the coating amount of the molten zinc. Typically an electromagnetic stabiliser 120 consists of an electromagnet, an eddy- current type displacement sensor, a control unit, and a power unit (not shown). The electromagnet of the electromagnetic stabiliser is placed near the surface of the steel strip, in the range of 10 to 80 mm from the surface of the moving steel strip. Vibrations are detected by the sensor, which activates the magnet of the stabiliser to keep the steel strip flat and vibration-free. Electromagnets with dynamically controlled power amplifiers are used to correct and stabilise the position of the moving metal strip and to limit strip vibrations. In this manner the majority of frequencies are damped to a level that is close to a noise spectrum. The pair of electromagnetic stabilisers are not in fluidic contact with the liquid metal bath.

[0045] Although the invention has been discussed in the foregoing with reference to an exemplary embodiment of the hot dip coating device of the invention, the invention is not restricted to these particular embodiments, which can be varied in many ways without departing from the invention.

[0046] The discussed exemplary embodiments shall therefore not be used to construe the appended claims strictly in accordance therewith. On the contrary the embodiments are merely intended to explain the wording of the appended claims without intent to limit the claims to these exemplary embodiments. The scope of protection of the invention shall therefore be construed in accordance with the appended claims only, wherein a possible ambiguity in the wording of the claims shall be resolved using these exemplary embodiments.

Claims

CLAIMS1. A hot dip coating device (19) for providing a metal coating on a metal strip (2), comprising: a container (22) containing a liquid metal bath in use; a snout (50) for guiding the metal strip (2) into the liquid metal bath (18) in use, wherein the snout (50) comprises a lower opening (39) immersed in the liquid metal bath (18) in use; a sink roll (28) for guiding the metal strip (2) through the liquid metal bath (18) in use, wherein the sink roll (28) is provided in the container (22), below the surface level (20) of the liquid metal bath (18) in use, and at least two stabilisers (100, 110, 120) of which at least one stabiliser is arranged on each side of the metal strip (2) in use, for stabilising the metal strip (2); wherein each of the at least two stabilisers has a surface facing the metal strip (2) in use, arranged such that in use the surface of each of the at least two stabilisers remains constantly positioned on each side of the metal strip (2) and wherein the at least two stabilisers (100, 110, 120) are positioned before the sink roll (28) in the travelling direction of the metal strip (2) in use.

2. The hot dip coating device (19) according to claim 1 , wherein the at least two stabilisers (100, 110) are at least partially immersed in the liquid metal bath (18) in use.

3. The hot dip coating device according to claim 2, wherein the at least two stabilisers (100, 110) are pads.

4. The hot dip coating device according to claim 2, wherein the at least two stabilisers (100, 110) are foils.

5. The hot dip coating device (19) according to any one of claims 2-4, wherein a pressure apparatus is provided that is connected with the at least two stabilisers (100, 110) to press the at least two stabilisers towards the metal strip (2) in use.

6. The hot dip coating device (19) according to any one of claims 2-5, wherein the lower opening (39) of the snout surrounds an upper portion of the at least two stabilisers (100, 110).

7. The hot dip coating device (19) according to claim 1 , wherein the at least two stabilisers (100, 110, 120) are placed within the snout (50).

8. The hot dip coating device (19) according to claim 7, wherein the at least two stabilisers (120) are placed above the surface level (20) of the liquid metal bath in use (18).

9. The hot dip coating device (19) according to claim 7 or 8, wherein the at least two stabilisers are electromagnetic stabilisers (120).

10. The hot dip coating device (19) according to any one of the previous claims, wherein the at least two stabilisers (100, 110, 120) are removably mounted to the hot dip coating device.

11. A method of coating a metal strip (2) in a hot dip coating device (19) according to any one of claims 1-10, wherein the metal strip (2) passes between at least two stabilisers (100, 110, 120) for stabilising the metal strip (2); and wherein the metal strip (2) is coated with a metal coating material that is contained in a container (22) of the hot dip coating device (19).

12. The method of coating a metal strip (2) in a hot dip coating device (19) according to claim 11 , wherein the at least two stabilisers are pads (100) or foils (110), and wherein the at least two stabilisers (100, 110) are pressed towards the metal strip (2) by a pressure apparatus.

13. The method of coating a metal strip (2) in a hot dip coating device (19) according to claim 11 , wherein the at least two stabilisers are electromagnetic stabilisers (120), and wherein an electric field is applied between the at least two stabilisers.

14. The method of coating a metal strip (2) in a hot dip coating device (19) according to any one of claims 11-13, wherein the metal strip (2) is coated with a metal coating material, wherein the metal coating material is a zinc or zinc alloy, preferably a zinc aluminium alloy or zinc magnesium alloy or zinc aluminium magnesium alloy, or wherein the metal coating material is an aluminium or aluminium alloy, preferably an aluminium silicon alloy or an aluminium silicon magnesium alloy.

15. The method of coating a metal strip (2) in a hot dip coating device (19) according to claim 14, wherein the metal strip (2) is coated with a zinc alloy coating comprising 0.3 - 4.0% Mg and 0.3 - 6.0% Al; optionally at most 0.2% of one or more additional elements; unavoidable impurities; the remainder being zinc.

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