Patent Application
20240247358
The present invention pertains to manipulation of dross in molten metal coating operations such as galvanizing or galvannealing. Dross may form, for example, in hot dip galvanizing, galvannealing, or aluminizing lines when the molten coating material is incidentally exposed to contaminants such as oxygen, and/or etc. In the presence of such contaminants, the coating material may react and form certain undesirable constituents. Some such constituents may settle to the bottom of the bath due to relatively high density, while others may remain in suspension or float on the surface of the bath as dross.
When dross accumulates near the material being coated, the dross may adhere to the material being coated along with the coating material. Some constituents of dross may be excessively hard, brittle, and/or large. Thus, excessive dross may be undesirable as it may lead to a defective coating due to the presence of large, brittle, and/or excessively large particles.
In some circumstances, certain weirs and/or molten metal pumps may be used for the management of dross. Such weirs and/or molten metal pumps may manipulate the dross to segregate the dross to certain predetermined areas within the molten metal bath. However, the use of weirs may be undesirable in some circumstances due to complexity and/or limited campaign life. Similarly, some molten metal pumps may exhibit unpredictable campaign life due to molten metal solidification in one or more portions of the pump or the incidental breakdown of internal moving parts. Therefore, it may be desirable to manage dross by other mechanisms either in addition to, or in lieu of more conventional weirs and/or molten metal pumps.
The need to move molten metal from one location to another may exist in a variety of material handling applications. Although examples are described herein in the context of moving molten metal in hot-dip coating of steel sheet, the teachings herein may be used in a variety of other alternative contexts. Indeed, the methods and apparatuses described herein may be readily applied in any context where movement or manipulation of molten metal is desired. For instance, examples described herein may be applied in contexts where molten metal circulation or transport is desired such as in casting furnaces, smelting furnaces, nuclear reactors, and/or etc. In addition, or in the alternative, while molten metal is described herein as the principal agent being moved, it should be understood that the teachings herein may be readily applied to the movement of other materials such as polymers, molten salts, and/or etc.
As can be seen, coating portion (10) includes a dip tank (20) (also referred to as a molten metal pot or bath), an introducer sheath (30) (also referred to as a snout), one or more stabilizing rolls (40) (also referred to as correcting rolls, or support rolls), and a sink roll (50). As will be understood, coating portion (10) is generally configured to receive, flatten, and stabilize an elongate steel sheet (60) for coating of steel sheet (60). Dip tank (20) is defined by a solid wall configured to receive molten metal (22) (e.g., zinc, aluminum, zinc-aluminum alloys, etc.). In some versions, dip tank (20) may be lined with certain ceramic refractory materials that are particularly suited to contain molten metal (22).
The surface of molten metal (22) contained within dip tank (20) may include a dross layer (24). Dross layer (24) may form due to chemical reactions occurring between steel strip (60) and molten metal (22), between molten metal (22) and atmosphere, and between various combinations of steel strip (60), molten metal (22), and atmosphere. Although some amount of dross layer (24) may be permitted, an excessive amount of dross layer (24) is generally undesirable. For instance, dross layer (24) may accumulate within introducer sheath (30) adjacent to steel sheet (60). Such accumulation may result in the coating formed on steel sheet (60) being contaminated with undesirable constituents of dross layer (24) such as oxides. Thus, it may be desirable to control the amount of dross layer (24). In some versions, dross layer (24) may be controlled using one or more gas displacement assemblies (100, 200, 300, 400) described in greater detail below.
Introducer sheath (30) is configured to be partially submerged within molten metal (22) contained within dip tank (20). Accordingly, it should be understood that introducer sheath (30) generally provides an airtight seal around steel sheet (60) during entry into molten metal (22). Introducer sheath (30) includes a hollow interior (32) (see
One or more stabilizing rolls or correcting rolls (40) may be positioned relative to dip tank (20) to stabilize, tension, and/or flatten steel sheet (60) before steel sheet (60) exits molten metal (22). Thus, it should be understood that stabilizing rolls (40) are generally configured to promote stability and flatness of steel sheet (60) at various stages during the coating procedure such as when steel sheet (60) exits dip tank (20) and passes through one or more other features such as air knives. Although coating portion (10) of the present example is shown as including one group of two stabilizing rolls (40), it should be understood that any suitable number and any suitable grouping of stabilizing rolls (40) may be used. For instance, in some versions, coating portion (10) may be equipped with a group of one or more stabilizing rolls (40) as steel sheet (60) both exits and enters molten metal (22). In other versions, stabilizing rolls (40) or other similar rolls, may be included to change or alter the direction of steel sheet (60) as steel sheet (60) progresses through, and out of, molten metal (22). In still other versions, stabilizing rolls (40) may include a combination of a stabilizer roll and a correcting roll. In such versions, the stabilizer roll may be fixed on an axis on the sink roll (50) side of steel sheet (60), while the correcting roll may be movable relative to a pass line to adjust the flatness of steel sheet (60). Additionally, the stabilizer roll and correcting roll may be of varying diameters relative to each other. In yet other versions, stabilizing rolls (40) may be omitted entirely. Of course, various alternative configurations for stabilizing rolls (40) will be apparent to those of ordinary skill in the art in view of the teachings herein.
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Additionally, each gas distributor (110) is generally positioned above dross layer (24) and molten metal (22). The particular height of each gas distributor (110) within introducer sheath (30) is about 10 to 200 centimeters above the meniscus defined by the interface between molten metal (22) and/or dross layer (24) and steel sheet (60). As will be described in greater detail below, the particular height used may be a factor of the desired angle for the flow of gas extending from each gas distributor (110) to steel sheet (60).
Each gas distributor (110) is tilted or oriented at an angle to direct gas towards a portion of steel sheet (60). Specifically, each gas distributor (110) may be configured to generate a flow of gas along a vector shown in
Each gas distributor (110) may be configured to generate a variety of flow patterns with the gas. Generally, the flow pattern of the gas may be in the form of a low-pressure wave configured to move at least a portion of dross layer (24) without turbulence or splashing. Additionally, the flow pattern may be generally planar, although other flow patterns may be present.
A variety of gases may be emitted by each gas distributor (110). Generally, suitable gases may include gasses that are non-oxidizing to steel or other materials. Examples of non-oxidizing gasses may include nitrogen, hydrogen, argon, nitrogen-hydrogen (HNx), and/or etc. Such gases may be at a predetermined pressure. In some versions, the predetermined pressure is metered or regulated at 100 pounds per square inch (PSI) or less. Of course, other suitable gasses may be used as will be apparent to those of ordinary skill in the art in view of the teachings herein.
The gas emitted by each gas distributor (110) may also be preheated in some versions. The gas may be preheated to a variety of temperatures. For instance, in some versions, the gas may be preheated to a temperature near the temperature of molten metal (22) (e.g., about 790° F. or 420° C.). In other versions, the gas may be preheated to between about 500° F. (269° C.) and about 350° F. (176.7° C.). In yet other versions, the gas may be preheated to a temperature greater than or equal to 500° F. In yet other versions, the temperature of the gas composition may be a function of the temperature of molten metal (22). For instance, in some versions, the temperature of the gas may be 470° F.+100° F. (e.g., between 370° and 570° F.) less than the temperature of molten metal (22). In other words, if the molten metal is approximately 870° F., the gas composition may be approximately 400° F. or between 300° and 500° F. Of course, various suitable alternative temperatures may be used depending on the particular molten metal being used with coating portion (10).
Although a single gas distributor (210) is shown, it should be understood that multiple gas distributors (210) may be used in a variety of configuration. For instance, in some versions, there may be a single gas distributor (210) on each side of introducer sheath (30). In other versions, multiple gas distributors (210) may be used on each side of introducer sheath (30) with each gas distributor (210) aligned along a single axis or multiple axes.
As similarly described above, gas distributor (210) may be oriented within introducer sheath (30) on a sidewall of introducer sheath (30) along the longitudinal axis of introducer sheath (30). Additionally, gas distributor (210) may be generally positioned above dross layer (24) and molten metal (22). The particular height of gas distributor (210) within introducer sheath (30) may be about 10 to 200 centimeters above the meniscus defined by the interface between molten metal (22) and/or dross layer (24) and steel sheet (60).
Gas distributor (210) may similarly be titled or oriented at an angle within introducer sheath (30) to direct gas towards a portion of steel sheet (60) along a flow vector (see
Gas distributor (210) in the present version may be configured as an elongate tube (212) having a plurality of gas outlets (214) in communication with tube (212). Tube (212) of the present version is configured as a circular or cylindrical tube or header. In other versions, tube (212) may take on a variety of elongate shapes. For instance, tube (212) may have a square, rectangular, or oval-shaped cross-section. Rectangular or oval-shaped cross-sections may be desirable in some versions to provide a low profile suitable for the confined space within introducer sheath (30).
Each gas outlet (214) in the present version is integral with tube (212) in the present version. The integral configuration of each gas outlet (214) may be desirable to promote an overall low profile of gas distributor (210). In other versions, gas outlets (214) may be attached separately to tube (212). Such versions may be desirable to permit adjustability of gas outlets (214).
In the present version, gas outlets (214) are spaced evenly along the length of tube (212). In other versions, gas outlets (214) may be clustered or spaced unevenly. In addition, gas outlets (214) may be all positioned along a common axis in some versions, or oriented along two or more axes in other versions.
Each gas outlet (214) may be configured to generate a variety of flow patterns with the gas. Thus, each gas outlet (214) may be configured as a nozzle suitable to project gas in a predetermined flow pattern. Generally, the flow pattern of the gas may be in the form of a low-pressure wave configured to move at least a portion of dross layer (24) without turbulence or splashing. Additionally, the flow pattern may be generally planar, although other flow patterns may be present.
Gas distributor (210) may further include one or more fasteners (216) oriented along the length of tube (212). Fasteners (216) may be configured to couple gas distributor (210) to structures such as introducer sheath (30). In the present version, fasteners (216) may be configured as magnetic fasteners to facilitate removable coupling to introducer sheath (30) with a low profile. In other versions, fasteners may include various alternative removable and non-removable configurations such as screws, clips, adhesive or welded bonds, and/or etc. Gas source (230) is generally configured to communicate a gas to gas distributor (210). To facilitate such communication, gas source (230) may include a gas line (232) extending from gas source (230) to gas distributor (210) and/or gas preheater (240). In some versions, gas line (232) may be flexible, yet durable to promote ease of raising and lowering introducer sheath (30) relative to dip tank (20).
Gas source (230) may be configured to communicate a variety of gases to gas distributor (210). As described above, suitable gases may include gasses that are non-oxidizing to steel or other materials. Examples of non-oxidizing gasses may include nitrogen, hydrogen, argon, nitrogen-hydrogen (HNx), and/or etc. Of course, other suitable gasses may be used as will be apparent to those of ordinary skill in the art in view of the teachings herein.
The gas emitted by gas distributor (210) may also be preheated in some versions via gas preheater (240). Preheating the gas emitted by gas distributor (210) may be desirable to minimize or eliminate condensation of metallic vapors such as vaporized zinc onto the surface of gas distributor (210) and/or introducer sheath (30). Optionally, in some examples, the preheated gas can be used to preheat one or more components associated with the gas such as portions of gas distributor (210) (e.g., conduits, nozzels, etc.) or one or more portions of introducer sheath (30). Such preheating of components may also be desirable to minimize or eliminate condensation of metallic vapors. Gas preheater (240) may be configured to preheat gas flowing from gas source (230) to gas distributor (210) to a variety of temperatures. For instance, in some versions, the gas may be preheated using gas preheater (240) to a temperature near the temperature of molten metal (22) (e.g., about 865° F. or 463° C. for zinc-based coatings, and about 1250° F. or 677° C. for aluminum-based coatings). In other versions, the gas may be preheated using gas preheater (240) to between about 500° F. (269° C.) and about 350° F. (176.7° C.). In yet other versions, the gas may be preheated using gas preheater (240) to a temperature greater than or equal to 500° F. In yet other versions, the temperature of the gas heated by preheater (240) may be a function of the temperature of molten metal (22). For instance, in versions where a zinc-based coating is used, the temperature of molten metal (22) may be about 865° F. or 463° C., while the gas heated by preheater (240) may be 865° F.+100° F. (e.g., between 765° and 965° F.) or 463° C.±60° C. (e.g., between 403° C. and 523° C.). Similarly, in versions where an aluminum-based coating is used, the temperature of molten metal (22) may be about 1250° F. or 677° C., while the gas heated by preheater (240) may be 1250° F.±100° F. (e.g., between 1150° F. and 1350° F.) or 677° C.±60° C. (e.g., between 617° C. and 737° C.). Of course, various suitable alternative temperatures may be used depending on the particular molten metal being used with coating portion (10).
As with gas distributor (210) described above, gas distributor (310) of the present version may generally be used in combination with introducer sheath (30). For instance, as similarly described above, gas displacement assembly (300) may include two gas distributors (310) disposed on opposite sides of introducer sheath (30) to communicate gas within hollow interior (32) of introducer sheath (30) toward the pass line of steel sheet (60).
Although a single gas distributor (310) is shown, multiple gas distributors (310) may be used in a variety of configurations. For instance, in some versions, there may be a single gas distributor (310) on each side of introducer sheath (30). In other versions, multiple gas distributors (310) may be used on each side of introducer sheath (30) with each gas distributor (310) aligned along a single axis or multiple axes.
As similarly described above, gas distributor (310) may be oriented within introducer sheath (30) on a sidewall of introducer sheath (30) along the longitudinal axis of introducer sheath (30). Additionally, gas distributor (310) may be generally positioned above dross layer (24) and molten metal (22). The particular height of gas distributor (310) within introducer sheath (30) may be about 10 to 200 centimeters above the meniscus defined by the interface between molten metal (22) and/or dross layer (24) and steel sheet (60).
Gas distributor (310) may similarly be titled or oriented at an angle within introducer sheath (30) to direct gas towards a portion of steel sheet (60) along a flow vector (see
As with gas distributor (210) described above, gas distributor (310) in the present version may be configured as an elongate tube (312). However, unlike gas distributor (210) described above, gas distributor (310) of the present version includes a single elongate outlet (314) in communication with tube (312). Tube (312) may be configured similarly as tube (212) described above. For instance, tube (312) of the present version is configured as a circular or cylindrical tube or header. In other versions, tube (312) may take on a variety of elongate shapes. For instance, tube (312) may have a square, rectangular, or oval-shaped cross-section. Rectangular or oval-shaped cross-sections may be desirable in some versions to provide a low profile suitable for the confined space within introducer sheath (30).
In the present version, gas outlet (314) is shaped as a single elongate slot. Although a single gas outlet (314) is used in the present version, in other versions, tube (312) may include multiple elongate slot structures. In such versions, the multiple slots may be spaced evenly or unevenly. In addition, such elongate slots may be all positioned along a common axis in some versions, or oriented along two or more axes in other versions.
Gas outlet (314) may be configured to generate a variety of flow patterns with the gas. Thus, gas outlet (314) may be configured as an elongate nozzle suitable to project gas in a predetermined flow pattern. Generally, the flow pattern of the gas may be in the form of a low-pressure wave configured to move at least a portion of dross layer (24) without turbulence or splashing. Additionally, the flow pattern may be generally planar, although other flow patterns may be present.
Gas distributor (310) may further include one or more fasteners (316) substantially similar to fasteners (216) described above. As similarly described above, fasteners (316) may be oriented along the length of tube (312). Fasteners (316) may be configured to couple gas distributor (310) to structures such as introducer sheath (30). In the present version, fasteners (316) may be configured as magnetic fasteners to facilitate removable coupling to introducer sheath (30) with a low profile. In other versions, fasteners may include various alternative removable and non-removable configurations such as screws, clips, adhesive or welded bonds, and/or etc.
As with gas distributors (210, 310) described above, gas distributor (410) of the present version may generally be used in combination with introducer sheath (30). For instance, as similarly described above, gas displacement assembly (400) may include a plurality of gas distributors (410) disposed on opposite sides of introducer sheath (30) to communicate gas within hollow interior (32) of introducer sheath (30) toward the pass line of steel sheet (60).
Although a single gas distributor (410) is shown, multiple gas distributors (410) may be used in a variety of configurations. For instance, in the present version, gas distributor (410) is configured in a relatively short configuration such that multiple gas distributors (410) may be used along the length of a given side of introducer sheath (30). In such multi-gas distributor (410) configurations, gas distributors (410) may be used on each side of introducer sheath (30) with each gas distributor (410) aligned along a single axis or multiple axes.
As similarly described above, gas distributor (410) may be oriented within introducer sheath (30) on a sidewall of introducer sheath (30) along the longitudinal axis of introducer sheath (30). Additionally, gas distributor (410) may be generally positioned above dross layer (24) and molten metal (22). The particular height of gas distributor (410) within introducer sheath (30) may be about 10 to 200 centimeters above the meniscus defined by the interface between molten metal (22) and/or dross layer (24) and steel sheet (60).
Gas distributor (410) may similarly be titled or oriented at an angle within introducer sheath (30) to direct gas towards a portion of steel sheet (60) along a flow vector (see
Unlike gas distributors (210, 310) described above, gas distributor (410) of the present example omits structures similar to elongate tube (212, 312). Instead, gas distributor (410) of the present version includes a base (412) with a gas emitter (414) projecting outwardly from base (412). Base (412) is generally configured as a low profile cylindrical structure. In some versions, base (412) may be configured for mounting directly onto a surface of intruder sheath (30) either by structures similar to fasteners (216, 316) or other coupling mechanisms.
Gas emitter (414) defines a generally triangular structure, narrow in thickness, fanning outwardly away from base (412). At the outer end of gas emitter (414), gas emitter (414) defines an elongate outlet (416) similar in configuration to elongate outlet (314) described above.
In the present version, elongate outlet (416) is shaped as a single elongate slot. Although a single elongate outlet (416) is used in the present version, in other versions, multiple elongate outlets (416) may be used. In such configurations, multiple elongate outlets (416) may be defined by a single gas emitter (414) or by multiple gas emitters (414) coupled together. Where multiple elongate outlets (416) are used, such elongate outlets (416) may be all positioned along a common axis in some versions, or oriented along two or more axes in other versions.
Elongate outlet (416) may be configured to generate a variety of flow patterns with the gas. Thus, elongate outlet (416) may be configured as an elongate nozzle suitable to project gas in a predetermined flow pattern. Generally, the flow pattern of the gas may be in the form of a low-pressure wave configured to move at least a portion of dross layer (24) without turbulence or splashing. Additionally, due to the narrow thickness of gas emitter (414), the flow pattern may be generally planar, although other flow patterns may be present.
An apparatus for displacing a portion of a dross layer enclosed within an introducer sheath of a dip tank, the apparatus comprising: a gas source; and a gas distributor in communication with the gas source via a gas line, the gas distributor including one or more gas outlets or a gas emitter, the gas distributor being configured to direct a flow of gas towards the dross layer at an angle to move the portion of the dross layer away from a predetermined point.
The apparatus of Example 1, the gas distributor including an elongate tube with one or more gas outlets disposed along the length of the elongate tube.
The apparatus of Example 2, the one or more gas outlets including a plurality of gas outlets, each gas outlet of the plurality of gas outlets being oriented along a common longitudinal axis defined by the elongate tube.
The apparatus of any of Examples 1 through 3, the one or more gas outlets including a nozzle configured to emit a planar flow of gas along a predetermined flow vector.
The apparatus of Example 1, the gas distributor including a base and the gas emitter extending from the base, the gas emitter having a triangular configuration fanning outwardly from the base.
The apparatus of Example 5, the gas emitter defining an elongate outlet, the elongate outlet being an elongate narrow slot configured to emit a planar flow of gas along a predetermined flow vector.
The apparatus of any of Examples 1 through 6, the gas source being configured to communicate a non-oxidizing gas to the gas distributor.
The apparatus of Example 7, the non-oxidizing gas including any one or more of nitrogen, hydrogen, argon, and nitrogen-hydrogen (HNx).
The apparatus of any of Examples 1 through 8, further comprising a gas preheater in communication with the gas source and the gas distributor via the gas line, the gas preheater being configured to heat gas communicated from the gas source to the gas distributor to a predetermined temperature.
The apparatus of any of Examples 1 through 9, the gas distributor being configured to communicate a non-turbulent flow of gas along a gas flow vector.
The apparatus of any of Examples 1 through 9, the gas distributor being configured to communicate a non-turbulent flow of gas along a gas flow vector, the gas flow vector being oriented at an angle relative to a pass line defined within the introducer sheath.
The apparatus of any of Examples 1 through 11, the gas line being configured to deform in response to movement of the introducer sheath.
The apparatus of any of Examples 1 through 12, the gas distributor including one or more fasteners, the one or more fasteners being configured to removably fasten the gas distributor to a portion of the introducer sheath.
The apparatus of any of Examples 1 through 13, the gas distributor including a pair of gas distributors configured to be positioned on opposite sides of the introducer sheath.
The apparatus of Example 14, each gas distributor of the pair of gas distributors being of a substantially similar configuration.
A system for coating steel, the system comprising: a dip tank configured to contain molten metal; an introducer sheath, a portion of the introducer sheath extending into the molten metal contained within the dip tank, the introducer sheath defining a hollow interior; and a gas displacement assembly, the gas displacement assembly including a gas source, a first gas distributor and a second gas distributor, the first gas distributor and the second gas distributor being in communication with the gas source via a gas line, the first gas distributor and the second gas distributor disposed on opposing sides of the introducer sheath, the first gas distributor and the second gas distributor being configured to direct a flow of gas toward the molten metal within the hollow interior of the introducer sheath.
The system of Example 16, the first gas distributor and the second gas distributor being disposed within the introducer sheath at a height of 10 to 200 centimeters above a meniscus of the molten metal.
The system of any of Examples 16 or 17, the first gas distributor and the second gas distributor each including a tube and a plurality of gas outlets, the gas outlets including a plurality of nozzles being evenly spaced along the length of the tube.
The system of any of Examples 16 or 17, the first gas distributor and the second gas distributor each including a tube and an elongate gas outlet, the elongate gas outlet including an elongate slot extending along a longitudinal axis defined by the tube.
The method for communicating dross on a surface of molten metal from a first portion of a molten metal bath to a second portion of the molten metal bath, the method comprising: positioning a gas distributor at an angle relative to the surface of the molten metal bath and 10 to 200 centimeters above the molten metal bath; communicating a gas from the gas distributor to the surface of the molten metal bath to generate a low pressure wave; and continuing to communicate the gas from the gas distributor to move at least a portion of the dross from the first portion of the molten metal bath to the second portion of the molten metal bath.
The method of Example 20, further comprising preheating the gas to a predetermined temperature prior to the step of communicating the gas from the gas distributor to the surface of the molten metal bath.
The method of Examples 20 or 21, further comprising moving an introducer sheath into and out of the molten metal bath, the gas distributor moving in combination with the introducer sheath as the introducer sheath is moved into and out of the molten metal bath.
This application claims priority to U.S. Provisional Patent App. No. 63/440,156, entitled “Gas Assisted Snout Interface Removal,” filed on Jan. 20, 2023, the disclosure of which is hereby incorporated by reference herein.
| Number | Date | Country | |
|---|---|---|---|
| 63440156 | Jan 2023 | US |
