Hot dip coating apparatus and method of operating same

Abstract

The present invention relates to a method for operating a hot dip galvanizing apparatus, the hot dip galvanizing apparatus comprising a snout, an air knife, and a vessel containing a liquid metal bath. The method includes disposing a first groove including a first edge inside the snout. The method further includes disposing a second groove including a second edge facing the air knife outside the snout; the second groove is disposed between the snout and the air knife such that the second edge of the second groove and the first edge of the first groove are aligned in the same horizontal plane, for removing surface dross between the snout and the air knife using the second groove.

Description

[Technical Field]

[0001] The present invention relates to a method of operating a hot dip galvanizing apparatus. In a further aspect, the present invention relates to a hot dip galvanizing apparatus comprising a snout, an air knife, and a vessel containing a liquid metal bath. The present invention also relates to a method of coating steel strip using the hot dip galvanizing apparatus. [Background technology]

[0002] Hot dip coating is a well-known process for protecting steel products against corrosion. Hot dip coating equipment is used to apply a metallic coating, such as zinc or aluminum, onto a moving metal sheet. In the context of this invention, the metal sheet is also referred to as metal strip. Hot dip coating equipment typically includes a vessel for a liquid metal bath containing the coating material in use. The ingot is placed partially immersed in the liquid metal bath in the vessel. At the operating temperature of the liquid metal bath, dissolution of iron from the steel strip into the metal bath can occur, forming intermetallic particles. Apart from the intermetallic particles, the liquid metal is oxidized by oxygen in the ambient air and forms oxide particles. These oxide particles remain in the upper layer of the liquid metal. These intermetallic particles, as well as the oxide particles, are known as dross.

[0003] An example of a hot-dip coating apparatus is a hot-dip galvanizing apparatus. It is known that in a continuous galvanizing line, the molten zinc bath is primarily saturated with iron dissolved from the steel strip continuously passing through the bath. Iron in an amount exceeding its solubility at the prevailing bath temperature is present in the form of dross. Dross present on the surface of the liquid metal bath is known as surface dross. Surface dross is also called floating dross or top dross. Surface dross, derived from oxidized liquid metal, is present in and around the air knife, where fresh liquid metal comes into contact with ambient air containing oxygen. This surface dross is continuously generated and accumulates in the area between the snout and the air knife. Dross that remains within the liquid metal bath or is submerged in the liquid metal bath is known as bottom dross. Both surface and bottom dross have detrimental effects on the final product manufactured from the steel strip. For example, small dross particles can be incorporated into the coated alloy layer and affect the appearance of the coated steel part. This is particularly detrimental to steel strip that is pressed to form exterior automotive parts. The included particles can cause inhomogeneous deformation and result in surface defects and irregularities, such as minute protrusions and bumps, even when present on the non-exposed side of the automotive part. The surface irregularities of the steel part produce undesirable reflections that unacceptably affect the appearance. Because the metal coating is applied after the hot-dip galvanizing step, the applied coating should meet requirements such as the metal layer being free of dross or debris. This is important not only to enable the coated steel strip to undergo forming operations, but also for the final appearance of the final steel product formed from the coated steel strip. Removal of dross from the liquid metal bath of the hot-dip galvanizing equipment is therefore desirable.

[0004] Various methods are used to remove dross from the metal bath of a hot dip coating equipment. Methods used to remove bottom dross may not be effective for removing surface dross. An existing solution for removing surface dross or surface debris involves manually moving it to the side of the liquid metal bath using a rake and then scooping it out. This is typically performed by humans or robots. This is not a continuous process, and therefore, surface dross accumulates between removals. Furthermore, it is a time-consuming process. Furthermore, these processes cannot be used to access areas in the liquid metal bath that are difficult to reach manually. Korean Patent Application KR20140081453A describes a dross removal device that removes dross by suction using a suction unit attached to the end of the coating bath snout. The suction unit first bends outward horizontally at the end of the snout and then bends upward again to form a suction space. From the suction unit, the molten zinc and dross are sucked by a transfer pipe and transferred to a bucket. Other methods include moving the surface dross with electromagnetic devices. Electromagnetic devices require increased power, which can make moving the dross layer difficult because the dross layer can have significant mechanical strength. This also moves a substantial portion of the liquid metal along with the dross, which is undesirable. These existing solutions also easily disturb the surface layer of dross and the liquid metal bath. This can lead to the surface dross sinking into the liquid metal bath, making further removal of the surface dross from the liquid metal bath difficult.

[0005] Another problem with most existing solutions for dross removal is that they do not operate continuously. This is disadvantageous because it results in more surface dross accumulation in the metal bath, which is difficult to remove in large quantities at later stages. On an industrial scale in the steelmaking industry, for example, for hot-dip galvanizing lines, a single galvanizing bath is operated continuously for periods ranging from several weeks to several months before any shutdown occurs in terms of necessary maintenance and replacement. In practice, such galvanizing lines are used to produce galvanized steel strip of different qualities in successive runs. In particular, switching from producing steel strip meeting less strict quality requirements to producing steel strip for highly demanding end uses is complex and critical. After such a switch in production, the newly produced steel strip is likely to be rejected if it does not meet the required higher standard. Therefore, there is a need for continuous removal of surface dross from the liquid metal bath of a hot-dip galvanizing apparatus that does not affect the quality of steel production when a switch in production occurs. Furthermore, existing methods have problems removing surface dross from difficult-to-access locations in the liquid metal bath. In particular, the above-mentioned existing methods cannot be operated without shutting down the system to remove surface dross from inaccessible locations. Therefore, there is a need to find a reliable solution for effectively removing dross, especially surface dross, from a liquid metal bath in a hot dip galvanizing apparatus. Summary of the Invention [Problem to be solved by the invention]

[0006] SUMMARY OF THE INVENTION It is an object of the present invention to provide an effective method for removing surface dross in hot dip galvanizing equipment from difficult to access locations within the liquid metal bath of the equipment.

[0007] SUMMARY OF THE INVENTION It is an object of the present invention to provide a continuous method for removing surface dross in hot dip galvanizing equipment.

[0008] It is also an object of the present invention to provide a method for removing surface dross that can be used in industrial galvanizing lines.

[0009] It is also an object of the present invention to provide a hot dip galvanizing apparatus in which surface dross is removed from difficult to access locations within the liquid metal bath of the hot dip galvanizing apparatus.

[0010] It is also an object of the present invention to provide a hot dip galvanizing apparatus in which surface dross is continuously removed from difficult to access locations within the liquid metal bath of the hot dip galvanizing apparatus.

[0011] Another object of the present invention is to provide a method for coating steel strip using a hot dip galvanizer in which surface dross is removed from difficult to access locations within the liquid metal bath of the hot dip galvanizer. [Means for solving the problem]

[0012] One or more of these objectives may be - Snout; - air knife; - a vessel containing a liquid metal bath; A method of operating a hot dip coating apparatus comprising: The method includes disposing a first groove including a first edge inside the snout; The method further includes disposing a second groove on an exterior side of the snout, the second groove including a second edge facing the air knife; This is achieved by the method in which the second groove is disposed between the snout and the air knife such that the second edge of the second groove and the first edge of the first groove are arranged in the same horizontal plane, in order to use the second groove to remove surface dross between the snout and the air knife.

[0013] Hot dip galvanizing equipment delivers a metal coating onto a moving metal sheet and includes a liquid bath of metal coating material during use, which is applied to the moving metal sheet during use. During the hot dip galvanizing process, surface dross accumulates on the surface of the liquid metal bath in the hot dip galvanizing equipment. The metal strip leaves the liquid metal bath in a near-vertical direction, after which the excess applied metal coating is blown off with a high-pressure air / gas wiping device known as an air knife or gas knife. Air knives or gas knives use air or gas, such as nitrogen, to blow off the excess metal coating. In the context of the present invention, the terms air knife and gas knife can be used interchangeably. One of the key areas where surface dross accumulates in the liquid metal bath is the area between the air knife and the snout, or the area between where the strip exits the bath and the outer wall of the snout. Dross formed in the backflow from the air knife accumulates toward the snout wall because that is the direction of the surface flow. At some point, the surface dross is forced into the bulk of the metal bath, resulting in dross contamination. This location is also difficult to reach and clean because the clearance between the snout and the air knife is relatively small. Therefore, this location is a critical area to clean to prevent significant accumulation of surface dross therein. The present invention provides a solution to this problem. In a first aspect of the present invention, a method of operating a hot dip galvanizing apparatus is provided. The hot dip galvanizing apparatus includes a snout, an air knife, and a vessel containing a liquid metal bath. The method includes disposing a first groove having a first edge on the inside of the snout. The method further includes disposing a second groove having a second edge facing the air knife on the outside of the snout. The second groove is disposed between the snout and the air knife such that the second edge of the second groove and the first edge of the first groove are aligned in the same horizontal plane, so that the second groove can be used to remove surface dross between the snout and the air knife. The groove can be made from the same material as the snout or from a different material. The groove typically includes a bottom and a front portion that are connected to each other to form a "└" shape.The bottom of the groove can be attached to the outside or inside wall of the snout. The first groove is located on the inner wall of the snout during use. The second groove is located on the outer wall of the snout during use. The front of the groove includes an edge portion known as a rim at its open end. The front of the first groove includes an edge portion known as a first rim at its open end, and the front of the second groove includes an edge portion known as a second rim at its open end. The second groove is located between the snout and the air knife of the hot dip coating apparatus, allowing the second groove to collect surface dross from that area. The bottom of the second groove is attached to the outer wall of the snout with the second edge facing the air knife. The area between the front and bottom of the second groove is a collection area used to collect surface dross, from which it can be removed. The second edge of the second groove and the first edge of the first groove are aligned in the same horizontal plane, which is the same plane as the surface bath level of the liquid metal bath. Therefore, the second edge, the first edge, and the surface bath level of the liquid metal bath are aligned in the same horizontal plane.

[0014] The dross removal device described in Korean Patent Application KR20140081453A requires the end of the snout to be bent horizontally outward, and then bent upward again to form a "└┘" shape, where the top is open to form a space inside. The dross removal device in KR20140081453A can only be attached to the end of the snout. According to this prior art document, the end of the snout can only be bent either inward or outward, but it cannot be bent both inward and outward. This prior art is silent about removing dross from the inside of a snout when the snout has a bend formed on its outside.

[0015] The recovery area of ​​the second groove of the present invention recovers surface dross from where it can be removed by a removal device, such as a pump, connected to the second groove. Typically, a certain amount of liquid metal also flows into the second groove along with the surface dross. To prevent excessive liquid metal from flowing into the second groove, the second groove is installed just below the surface bath level of the hot dip galvanizing equipment. To allow the surface dross to flow freely from the liquid bath into the second groove, the second edge of the second groove is positioned just below the surface bath level of the hot dip galvanizing equipment. If the second edge of the second groove is installed above the surface bath level, the surface dross and / or liquid metal will not flow into the second groove. If the second edge of the second groove is positioned too deep below the surface bath level, too much liquid metal will flow in, and at a certain depth, the surface dross will remain in the liquid metal bath. Furthermore, if this distance is too large or the second edge is held at a position too deep, the pumping effort required to remove the surface dross from the second groove increases when a pump is connected to the second groove. Therefore, an optimal distance between the second edge of the second groove and the surface bath level of the liquid metal bath is preferred. In one embodiment of the present invention, the method includes placing the second edge of the second groove below the surface bath level of the liquid metal bath. This allows for natural, free flow of surface dross from the liquid metal bath into the second groove by gravity. Typically, the second edge of the second groove is placed at least 5 mm below the surface bath level of the liquid metal bath of the hot dip galvanizing apparatus. In one embodiment of the present invention, the method includes placing the second edge of the second groove at a distance of 5 to 20 mm below the surface bath level of the liquid metal bath, preferably at a distance of 5 to 15 mm below the surface bath level of the liquid metal bath, and more preferably at a distance of 5 to 10 mm below the surface bath level of the liquid metal bath. This ensures that the second edge of the second groove is at an optimum depth to allow free flow of surface dross from the liquid metal bath into the second groove.

[0016] The modular design of the second groove according to the present invention results in an apparatus that can be easily assembled and disassembled to the snout outer wall and used in industrial hot-dip galvanizing lines, such as hot-dip galvanizing lines. One embodiment of the present invention includes a method for attaching a second groove to the snout of a hot-dip galvanizing apparatus. Preferably, the second groove is made in one piece for ease of manufacture. This also allows for easy assembly of the second groove to the snout. The second groove can be removably connected to the snout outer wall, for example, with fasteners via a support. This allows the second groove to be removed from the snout for any purpose, such as for repair, intermediate cleaning, or emptying. The present invention can be used for all types of plating using hot-dip techniques and is particularly useful for coating metal sheets with zinc or a zinc alloy, preferably a zinc-aluminum alloy, a zinc-magnesium alloy, or a zinc-aluminum-magnesium alloy, or with aluminum or an aluminum alloy, preferably an aluminum-silicon alloy.

[0017] In one embodiment, the second groove is detachably attached to the snout. This allows for detachable connection of the second groove to the snout. In another embodiment of the snout, the vertical position of the second groove can be adjusted relative to the surface bath level of the liquid metal bath. This further allows for easy adjustment of the second groove from the snout, which has the advantage that the vertical distance between the surface bath level outside the second groove and the liquid level of the fluid within the second groove can be easily adjusted according to required specifications. In a possible embodiment, the method includes maintaining the liquid level in the second groove lower than the surface bath level of the liquid metal bath. Typically, the surface bath level of the liquid metal bath in the vessel can be adjusted by controlling the depth of the ingot in the liquid metal bath. The liquid level in the second groove can be lowered by pumping liquid out of the second groove. This ensures that the amount of liquid metal recovered together with the surface dross in the second groove can be minimized. Another embodiment of the present invention includes controlling the distance between the second edge and the first edge so that the second edge and the first edge are aligned in the same horizontal plane. The distance can be controlled using a controller attached to the second groove and / or the first groove. The controller can vary the distance between the surface bath level and the second edge of the second groove and / or the surface bath level and the first edge of the first groove to ensure that the second edge, the first edge, and the surface bath level of the liquid metal bath are aligned in the same horizontal plane.

[0018] As mentioned above, the area between the air knife and the outer wall of the snout is difficult to reach and clean, and this critical area needs to be cleaned regularly and continuously. This ensures that surface dross does not accumulate in large quantities and interfere with the operation of the hot dip galvanizing line. In a possible embodiment, the method includes continuously removing surface dross from the surface bath level of the hot dip galvanizing equipment. For continuous removal, the second groove can be connected to a pump that can continuously remove surface dross from the second groove. Continuous operation also prevents any requirement for system shutdown for a specific period of time. The pumping system can remove the surface dross via a transfer tube to a separate dross collection container. The first groove can also be connected to a pump that can continuously remove surface dross from the first groove. Thus, separate pumps can be connected to the second groove and the first groove. In one embodiment of the present invention, the method includes pumping the surface dross from the second groove and / or the first groove. The pumping can be continuous, so that the collected surface dross is continuously removed from the second groove. This also allows the surface bath level outside the second groove to be maintained above the liquid level of the fluid within the second groove. In possible embodiments, the flow rate of the surface dross to the second groove and / or the first groove is in the range of 0.03 to 0.24 kg / cm s. The flow rate of the surface dross is expressed as dross per cm of groove length per second.

[0019] In a further aspect, the present invention relates to a hot dip galvanizing apparatus. The hot dip galvanizing apparatus includes a snout, an air knife, a vessel containing a liquid metal bath, and a first groove including a first edge inside the snout. The hot dip galvanizing apparatus further includes a second groove including a second edge facing the air knife outside the snout. The second groove is positioned between the snout and the air knife so that the second edge of the second groove and the first edge of the first groove are aligned in the same horizontal plane, so that the second groove can be used to remove surface dross between the snout and the air knife. The first groove is positioned on the inner wall of the snout. The second groove is positioned on the outer wall of the snout. The second groove is positioned between the snout and the air knife in the hot dip galvanizing apparatus. As mentioned above, this position is important because much of the surface dross is generated by the air knife in this region and flows toward the snout. When installed, the second edge of the second groove is configured to be aligned with the surface bath level of the hot dip galvanizing equipment. The second edge of the second groove and the first edge of the first groove are arranged in the same horizontal plane. This also ensures that the second edge and the first edge are configured to be aligned with the surface bath level of the hot dip galvanizing equipment in the same horizontal plane. However, the liquid level inside the second groove and the liquid level inside the first groove may not be on the same horizontal plane. The second edge of the second groove is installed below the surface bath level of the liquid metal bath. This position of the second groove ensures that surface dross present in the area between the snout and the air knife can easily flow into the second groove. In another embodiment of the present invention, the second edge of the second groove is positioned 5 to 20 mm below the surface bath level of the liquid metal bath during use, preferably 5 to 15 mm below the surface bath level of the liquid metal bath during use, and more preferably 5 to 10 mm below the surface bath level of the liquid metal bath during use. Because the second edge of the second groove and the first edge of the first groove are arranged in the same horizontal plane, this also results in the first edge of the first groove being positioned, during use, at a distance of 5 to 20 mm below the surface bath level of the liquid metal bath, preferably, during use, at a distance of 5 to 15 mm below the surface bath level of the liquid metal bath, and more preferably, during use, at a distance of 5 to 10 mm below the surface bath level of the liquid metal bath.The present invention provides a very simple device that can be easily implemented in industrial hot dip coating equipment. In one embodiment, the second groove is attached to the snout of the hot dip coating equipment. The second groove is detachably attached to the snout. In such a case, the bottom of the second groove is detachably attached to the outer wall of the snout. If it is detachably attached, it can be removed from the system according to requirements. In such a case, the hot dip coating equipment can still function as a normal hot dip coating equipment without the second groove. The second groove can also be permanently integrated into the outer wall of the snout. In one embodiment, the second groove is part of the snout. In one embodiment of the present invention, a control device for controlling the distance between the second edge and the first edge is attached to the second groove. Therefore, during use, the second edge and the first edge are aligned in the same horizontal plane. This ensures proper alignment of the second groove vertically with the surface bath level of the liquid metal bath; the second groove is attached to the snout. The controller ensures that the liquid level of the fluid in the second groove is always lower than the surface bath level of the liquid metal bath. An alignment control means is used for this purpose. When the second groove is full, no more surface dross flows into the second groove. This causes the surface dross to begin to accumulate on the upper surface of the liquid metal. A removal system, such as a pump, can optionally be installed to remove recovered surface dross and / or liquid metal from the second groove. This ensures that the second groove does not fill up during operation. The removal system connected to the second groove to remove recovered surface dross ensures that the hot dip coating apparatus can operate continuously if needed. Typically, a small amount of liquid metal can also be removed along with the surface dross. In one embodiment, the hot dip coating apparatus includes a pump for removing surface dross and / or liquid metal from the second groove. This ensures that the level of surface dross in the second groove is lower than the level of surface dross in the liquid metal bath, allowing newly formed surface dross to easily flow into the second groove in a continuous manner.The pump may also be operated at specific time intervals to pump out surface dross.

[0020] In one embodiment, the hot-dip coating apparatus is a hot-dip galvanizing apparatus. In a hot-dip galvanizing apparatus, a steel strip passes through a molten zinc bath containing zinc, aluminum, iron, and unavoidable impurities, and optionally, a small amount of one or more alloying elements. For coating steel metal sheets, it is often preferred that the liquid metal bath be a zinc or zinc alloy, preferably a zinc-aluminum alloy, zinc-magnesium alloy, or zinc-aluminum-magnesium alloy, or that the liquid metal bath be an aluminum or aluminum alloy, preferably an aluminum-silicon alloy. In the context of the present invention, the metal sheet or strip typically has a length of at least several hundred meters, a width of up to approximately two meters, and a thickness of at most several millimeters. The second groove in the hot-dip galvanizing apparatus is installed on the outer wall of the snout so that it is located between the snout and the air knife. The second edge of the second groove is configured to be aligned below the zinc bath level of the hot-dip galvanizing apparatus. In the hot-dip galvanizing apparatus, the second groove collects surface dross or surface debris and removes it, for example, by pumping it outward from the second groove.

[0021] One or more of the objects of the present invention are achieved by providing a method for coating a metal sheet using the above-described hot-dip galvanizing apparatus, the method comprising: passing a steel strip through a snout into a vessel containing a liquid metal bath; passing the steel strip out of the liquid metal bath with a sink roll after the steel strip leaves the liquid metal bath; adjusting the coating weight of the molten metal on the steel strip with an air knife; using a first groove to remove surface dross from the liquid metal bath and recovering the surface dross inside the snout; and using a second groove to remove surface dross from the liquid metal bath and recovering the surface dross between the snout and the air knife. The sink roll is provided in the vessel below the surface level of the liquid metal bath. The coating weight of the molten metal on the steel strip is adjusted by blowing off excess applied metal coating with an air knife. As described above, the hot-dip galvanizing apparatus includes a first groove including a first edge inside the snout. The hot-dip galvanizing apparatus includes a second groove including a second edge outside the snout and facing the air knife. In a possible embodiment of the present invention, the second edge of the second groove and the first edge of the first groove are arranged on the same horizontal plane. In a possible embodiment of the present invention, the second groove is arranged between the snout and the air knife so that the second edge of the second groove and the first edge of the first groove are arranged on the same horizontal plane, so that the second groove is used to remove surface dross between the snout and the air knife. In a possible embodiment of the present invention, the second edge of the second groove is located below the surface bath level of the liquid metal bath. In this embodiment, since the second edge of the second groove and the first edge of the first groove are arranged on the same horizontal plane, the first edge of the first groove is also located below the surface bath level of the liquid metal bath. In a possible embodiment of the present invention, the second edge of the second groove is located 5 to 20 mm below the surface bath level of the liquid metal bath, preferably 5 to 15 mm below the surface bath level of the liquid metal bath, and more preferably 5 to 10 mm below the surface bath level of the liquid metal bath. In one possible embodiment, the second groove is attached to the snout of the hot dip galvanizing device. In another possible embodiment, the second groove is part of the snout.In a possible embodiment of the invention, the second groove is attached to the outer wall of the snout and the first groove is attached to the inner wall of the snout.

[0022] The invention is further illustrated by the following figures. [Brief explanation of the drawings]

[0023] [Figure 1] FIG. 1 is a diagram showing a schematic diagram of a production line including an annealing section and a hot dip galvanizing unit according to the present invention. [Figure 2] FIG. 2 shows an embodiment of the present invention including a snout and hot dip galvanizing apparatus. [Figure 3] FIG. 3 shows another embodiment of the present invention including a snout and hot dip galvanizing apparatus. [Figure 4] FIG. 4 is a diagram showing a schematic diagram of gas flow in the snout in accordance with the present invention. [Figure 5] FIG. 5 shows a schematic diagram of a second groove and a first groove attached to a snout in accordance with the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] Coated steel strip is used, for example, to manufacture parts in the automotive industry, where the applied coating needs to meet requirements such as that the metal layer should be free of dross that could contaminate subsequently applied coatings. Embodiments of the present invention reduce the possibility of any contamination of the coating by removing surface dross from the liquid metal bath of the hot dip galvanizing apparatus.

[0025] FIG. 1 shows a schematic diagram of a production line including an annealing section 1 and a hot-dip galvanizing apparatus 19. The annealing section 1 for a steel strip 2 is well known to those skilled in the art. The annealing section 1 includes a first heating section 3, such as a direct flame furnace, a connecting chamber 4 connecting the first heating section 3, and a second heating section 5, such as a radiant tube furnace. In the connecting chamber 4, one or more devices 6 are arranged on one or both sides of the steel strip 2 for oxidizing the steel strip 2 using an oxidizing gas mixture. The steel strip 2 is worked or annealed in direction (A). Optionally, the annealing section includes a cooling section 22. The production line further includes a hot-dip galvanizing apparatus 19, which may be, for example, a hot-dip galvanizing apparatus. The metal coating is applied by hot-dip galvanizing, in which, in a continuous or semi-continuous process, the metallic steel strip 2 passes through a bath of molten metal, such as Zn, a Zn+Fe alloy, Zn+Al, or Zn+Mg+Al. Removal of excess metal coating from the moving metal strip 2 controls the thickness of the applied metal coating. The steel strip 2 passes from the annealing section 1 into the hot dip galvanizer 19 via introduction point 31 using a hot bridle 16. The hot dip galvanizer 19 further includes a sink roll 28 for passing the steel strip 2 out of the metal bath 18.

[0026] 2 shows a schematic of a snout 50, in which a steel strip 2 is passed from the annealing section 1 into a hot dip galvanizer 19 via an inlet point 31. The steel strip 2 is passed from the annealing section 1 into the hot dip galvanizer 19 using a hot bridle 16. The hot dip galvanizer 19 includes a liquid metal bath 18 having a surface bath level 20. An ingot 15 is placed partially immersed in the liquid metal bath 18. The hot dip galvanizer 19 also includes a sink roll 28 for passing the steel strip 2 out of the liquid metal bath 18. The steel strip 2 passes through the sink roll 28 into an air knife 14. The air knife 14 is used to adjust the coating weight of the molten metal on the steel sheet.

[0027] FIG. 3 shows a schematic of the snout 50. The second groove 60 is attached to the outer wall of the snout, and the first groove 160 is attached to the inner wall of the snout. The second edge of the second groove is located below the surface bath level 20 of the liquid metal bath 18. The second edge of the second groove and the first edge of the first groove are arranged in the same horizontal plane. Therefore, the first edge of the first groove is also located below the surface bath level 20 of the liquid metal bath 18. FIG. 3 shows the first groove attached to the inner wall of the snout. The steel strip 2 is passed through the snout 50 into the liquid metal bath 18 of the hot dip galvanizing apparatus 19 and leaves the liquid metal bath 18 in a near-vertical direction into the air knife 14. Surface dross 80 present between the snout 50 and the air knife 14 flows into the second groove 60, where it is collected and removed, for example, using a pump.

[0028] FIG. 4 shows a schematic diagram of a snout 50. Arrows 11 and 12 indicate the flow of various gases within the snout 50. Gas, comprising gas flow 11, is passed into the snout 50 from the hot bridle 16. At one end of the snout 50, the snout 50 includes a first opening through which the steel strip is introduced from the preceding annealing section 1. At the other end of the snout 50, the snout 50 includes a second opening, which is immersed in a liquid metal bath. Optionally, different gases, comprising gas flow 12, can be introduced into the snout 50 through multiple injection points or inlets 9. FIG. 4 shows two of these injection points or inlets located in opposite directions on the wall of the snout 50. A second groove 60 is attached to the outer wall of the snout 50. A first groove 160 is attached to the inner wall of the snout 50. The second groove 60 includes an edge portion at its open end known as the second edge 63. The second edge 63 of the second groove 60 is aligned and positioned directly below the surface bath level 18 of the liquid metal bath 20 so that surface dross 80 from the outside of the snout can easily flow into the second groove 60. Similarly, the first edge 163 of the first groove 160 is aligned and positioned directly below the surface bath level 18 of the liquid metal bath 20 so that surface dross 80 from the inside of the snout can easily flow into the first groove 160. The second edge of the second groove and the first edge of the first groove are aligned on the same horizontal plane. The levels of surface dross in the second groove and the first groove may not be on the same level. By maintaining the second edge of the second groove 60 lower than the level of the surface dross in the liquid metal bath, the surface dross 80 can freely flow into the second groove 60 with the aid of gravity.

[0029] FIG. 5 shows an enlarged view of an embodiment of the present invention. During use, the second groove 60 is installed on the outer wall of the snout 50. The second groove 60 includes a bottom portion 61 and a front portion 62 that are connected to each other to form a collection area therebetween. The bottom portion 61 of the second groove is attached to the outer wall of the snout 50. The second edge 63 of the second groove is aligned and installed directly below the surface bath level 20 of the liquid metal bath so that the surface dross 80 can easily flow into the second groove 60. The second edge of the second groove is installed, for example, 7 mm below the surface bath level of the liquid metal bath. The second groove 60 is installed on the outer wall of the snout 50 so that the second edge 63 of the second groove faces the air knife 14. By maintaining the liquid level 66 of the second groove 60 lower than the surface level of the liquid metal bath, the surface dross 80 can freely flow into the second groove 60, assisted by gravity. The surface dross 80 collected in the collection area between the front and bottom of the second groove can be removed, for example, by pumping. The first groove 160 is installed on the inner wall of the snout 50. The bottom of the first groove is attached to the inner wall of the snout 50. The second edge 63 of the second groove 60 and the first edge 163 of the first groove 160 are aligned on the same horizontal plane. The first edge 163 of the first groove is aligned and installed directly below the surface bath level 20 of the liquid metal bath so that the surface dross 80 from inside the snout can easily flow into the first groove 160. By maintaining the liquid level of the first groove lower than the surface level in the liquid metal bath, the surface dross 80 can flow freely into the first groove 160.

[0030] Although the present invention has been discussed above with reference to exemplary embodiments of the hot dip coating apparatus of the present invention, the present invention is not limited to these specific embodiments, which may vary in many ways without departing from the present invention. The discussed exemplary embodiments should therefore not be used to strictly interpret the appended claims accordingly. On the contrary, the embodiments are intended merely to explain the terms of the appended claims, without intending to limit the claims to these exemplary embodiments. The scope of protection of the present invention should therefore be interpreted solely in accordance with the appended claims, whereby possible ambiguities in the terms of the claims should be resolved using these exemplary embodiments.

Claims

1. - Snout (50); - air knife (14); a vessel (22) containing a liquid metal bath (18); - a first groove (160) including a first edge (163) inside the snout (50); A hot dip coating apparatus (19) comprising: The hot dip coating apparatus (19) further includes a second groove (60) on the outside of the snout (50) including a second edge (63) facing the air knife (14); A hot dip coating apparatus (19) in which the second groove (60) is disposed between the snout (50) and the air knife (14) such that the second edge (63) of the second groove (60) and the first edge (163) of the first groove (160) are arranged in the same horizontal plane in order to remove surface dross (80) between the snout (50) and the air knife using the second groove (60).

2. 2. The hot dip coating apparatus (19) according to claim 1, wherein the second edge (63) of the second groove is located, during use, at a distance of 5 to 20 mm below the surface bath level (20) of the liquid metal bath (18), preferably at a distance of 5 to 15 mm below the surface bath level (20) of the liquid metal bath (18), more preferably at a distance of 5 to 10 mm below the surface bath level (20) of the liquid metal bath (18).

3. The hot dip galvanizing apparatus (19) according to any one of claims 1 to 2, wherein the second groove (60) is attached to a snout (50) of the hot dip galvanizing apparatus (19).

4. The hot dip coating apparatus (19) according to any one of claims 1 to 2, wherein the second groove (60) is part of the snout (50).

5. The hot dip coating apparatus (19) according to any one of claims 1 to 4, wherein a control device for controlling the distance between the second edge (63) and the first edge (163) is attached to the second groove (60).

6. The hot dip coating apparatus (19) according to any one of claims 1 to 5, wherein the hot dip coating apparatus (19) comprises a pump (15) for removing surface dross (80) and / or liquid metal from the second groove (60).

7. The hot dip coating apparatus (19) according to any one of claims 1 to 6, wherein the hot dip coating apparatus (19) is a hot dip galvanizing apparatus.

8. A method for coating a steel strip (2) using a hot dip coating apparatus (19) according to any one of claims 1 to 7, comprising the steps of: passing the steel strip (2) through the snout (50) into a vessel (22) containing a liquid metal bath (18); passing the steel strip (2) out of the liquid metal bath (18) through a sink roll (28); adjusting the coating weight of the molten metal on the steel strip (2) with an air knife (14) after the steel strip (2) leaves the liquid metal bath (18); recovering surface dross inside the snout (50) by removing the surface dross from the liquid metal bath (18) using the first groove (160); Recovering surface dross between the snout (50) and the air knife (14) by using a second groove (60) to remove surface dross from the liquid metal bath (18). A method comprising:

9. 9. The method according to claim 8, wherein the second edge (63) of the second groove (60) is located at a distance of 5 to 20 mm below the surface bath level (20) of the liquid metal bath (18), preferably at a distance of 5 to 15 mm below the surface bath level (20) of the liquid metal bath (18), more preferably at a distance of 5 to 10 mm below the surface bath level (20) of the liquid metal bath (18).

10. The method of any one of claims 8 to 9, comprising maintaining a liquid level (66) in the second groove (60) below a surface bath level (20) of the liquid metal bath (18).

11. 11. The method according to any one of claims 8 to 10, comprising controlling the distance between the second edge (63) and the first edge (163) such that the second edge (63) and the first edge (163) are aligned in the same horizontal plane.

12. The method of any one of claims 8 to 11, comprising continuously removing surface dross (80) from a surface bath level (20) of a hot dip galvanizing apparatus (19).

13. The method of any one of claims 8 to 12, comprising pumping out the surface dross (80) from the second groove (60) and / or the first groove (160).

14. The method according to any one of claims 8 to 13, wherein the flow rate of the surface dross into the second groove (60) and / or the first groove (160) is in the range of 0.03 to 0.24 kg / cm s.

15. Use of a hot dip coating apparatus (19) according to any one of claims 1 to 7 in a hot dip coating process for producing coated steel strip.

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