RU2208657C2 - System of coating application to steel strip by dipping - Google Patents

Abstract

FIELD: processes of application of molten coating to steel strip by its dipping into coating material melt, for instance, zinc or aluminum. SUBSTANCE: system has bath of coating molten metal in container having opening for strip passage found under upper surface of bath molten metal. Metal strip is directed along line running through opening for strip passage and through bath of coating molten metal for application of coating to strip. Used in system is electromagnet for prevention of exit of molten metal mass through opening for strip passage with simultaneous passage of strip through bath. System is also provided with means reducing loss of coating molten metal through opening for strip passage. EFFECT: provided keeping of mass of coating molten metal and reduced leakage or soaking of coating molten metal through opening for strip passage. 32 cl, 25 dwg

Description

 This application is a partial continuation of application 08/964428 "Hot Dip Coating Employing A Plug of Chilled Coating Metal", the publication of which is incorporated herein by reference.

 The present invention relates generally to methods for applying a molten coating to a metal strip, for example a steel strip, with a coating metal such as zinc or aluminum, and more particularly, the invention relates to a coating process by immersion in molten material without the need for one or more rolls (rollers) located under the mirror (surface) of the bath of molten coating metal.

 The coating material (metal), such as zinc or aluminum, is applied to a steel strip to increase resistance to corrosion or oxidation. One way to coat a steel strip is to dip the steel strip into a bath of molten coating metal. Existing coating processes by immersion in a molten bath are continuous, and they usually require, as a preparatory step, pretreatment of the steel strip before coating. The pre-treatment improves the adhesion of the surface of the steel strip to the coating, and at the pre-treatment step, either (a) a pre-heating operation in a controlled environment or (b) a fluxing operation in which the surface of the tape is pre-treated with an inorganic flux can be performed.

 Regardless of the pre-treatment method in the traditional coating process by immersion in molten material, a coating step is used, performed in a bath of molten coating material (metal), in which there are one or more guide rolls (rollers) that change the direction of movement of the steel strip or otherwise guide steel tape at the stage of applying the molten coating. More specifically, the steel tape usually enters the bath of molten coating material from above and moves in the downward direction, then passes through one or more guide rolls immersed in the melt, which change the direction of movement of the steel tape from downward to upward, after which the tape is removed from the molten metal bath coverings.

 When using guide rolls immersed in a bath with molten coating metal, a number of problems arise. These problems are described in detail in the application 08/822782 "Hot Dip Coating Method And Apparatus", and this description is incorporated herein by reference.

 Certain methods have been proposed for avoiding the use of rolls immersed in the melt during the application of the molten coating. In these methods, a steel strip is introduced into the molten coating metal through an elongated passage opening (passage channel) in a container containing a bath; this hole is usually located under the mirror (surface) of the bath, and the tape is guided through this hole and through the bath up in a straight line. Pulling the steel strip through the bath in a straight line upwards eliminates the use of guide rolls immersed in the melt, which are required if necessary to change the direction of the tape as it passes through the bath.

 An elongated ribbon bore (a ribbon bore) is typically located at the bottom of the container containing the bath, and various methods are used to prevent molten metal from the bath from escaping from this bore.

 In some cases, sealing openings are used. These sealing seals come into contact with the side surfaces and edges of the tape when the tape passes up through the hole, which leads to wear or seal failure, and this, in turn, leads to leakage of molten metal through the hole. Other problems associated with sealing seals include solidification and large temperature gradients in the bath of molten coating metal, as well as problems with the quality of the coating of the tape, including uneven thickness of the coating of the tape.

 In other cases, electromagnetic devices are used that are located next to the passage opening and create magnetic forces that allow the molten metal of the bath to be held at a certain distance from the passage hole. These devices can prevent the molten metal bulk from leaving the bath (mass retention), but they still allow some leakage or seepage of molten bath metal through the duct passage, especially on the side surfaces and ends of the elongated container opening. A leak of this kind can be a serious problem.

 The present invention is intended for a system for coating by immersion in the melt, which provides all the advantages associated with the rejection of the use of immersed in the melt rolls (rollers); in addition, this invention not only provides retention of the mass of molten metal coating, but also significantly reduces the leakage or seepage of molten metal coating through the hole for the passage of the tape. By leakage reduced by the system of the present invention is meant leakage that is allowed by the electromagnetic devices described in the previous paragraph. The system according to the present invention includes one or more additional means, which are described below.

 The container containing the molten metal bath of the coating has the form of a chute with side walls that converge down to the opening for the passage of the tape located in the base (bottom) of this container. The corresponding electromagnet has two pole surfaces facing each other, each of which is located next to the corresponding adjacent side wall of the container and has almost the same contours (profile) as the adjacent wall. This increases the density of the electromagnetic flux generated by the electromagnet at the bottom of the container, which in turn increases the upward magnetic force, which “repels” the lower part of the molten metal bath coating from the passage opening of the bottom of the container.

 The action of the electromagnet drives (excites) the bath material, and this creates a leakage problem. According to the present invention, there is provided a device for mechanically damping ("calming") the movement of bath material caused by the action of an electromagnet. This damping device is made in the form of several horizontally arranged and vertically spaced pairs of flat elements, between which there is a gap through which the steel strip passes.

 The flat elements defined in the previous paragraph are made of ferromagnetic material, and they define a path (contour) with low magnetic resistance for the magnetic flux in the gap between the pole surfaces facing each other. These flat elements reduce the effective gap between the facing surfaces of the poles of the electromagnet, thereby increasing the magnetic flux density in the gap, which, in turn, increases the upward magnetic force in the passage opening of the bottom of the container. The effective clearance-reducing planar ferromagnetic elements can be used independently of the damping device described in the previous paragraph.

 There are guide elements that hold the steel strip centered inside the container. These guiding elements prevent the tape from being attracted to one of the surfaces of the poles of the electromagnet facing each other, and prevent unwanted side-to-side vibrations (lateral displacements) of the steel tape to which this tape would otherwise be subjected.

 There is an electric current conductor having two ends (leads), each of which is in direct contact with the molten bath at the bottom of this bath, and each lead is in a collector (recess) on the corresponding end side of the channel for the passage of the tape. Through the conductor, either (a) direct current from an external source (when power is supplied to the electromagnet from a direct current source) or (b) eddy currents that are induced by magnetic flux from an electromagnet (when power is supplied to the electromagnet from a time-varying current source) . The electric current described above passes between the ends of the current conductor at the bottom of the molten bath metal coating. This electric current interacts with the magnetic flux from the electromagnet at the bottom of the bath, creating a magnetic force that repels the lower part of the bath melt from the hole at the bottom of the container. The use of an electric conductor concentrates the passage of electric current in the right places at the bottom of the bath and significantly increases the efficiency of the top-directed magnetic force compared with the magnetic force that occurs in the absence of an electric conductor.

 In one example embodiment of the invention, the windings for an electromagnet are part of the so-called LCR type electrical circuit (L is the inductance, C is the capacitance, R is the resistance). This circuit is controlled in such a way that when lowering the level of the lower part of the bath of molten metal located above the passage opening of the bottom of the container, the current increases automatically. This increases the value of the magnetic force acting in the vertical direction on the lower part of the molten bath.

 Other possibilities and advantages are determined by the claimed and described method and device or become apparent to specialists in this field from the following detailed description in combination with the accompanying schematic drawings.

 In FIG. 1 shows schematically (partially in cross section) a system for coating by immersion in a melt according to one embodiment of the present invention.

 Figure 2 shows a perspective view of the container and the electromagnet used in this system.

 Figure 3 shows an enlarged vertical section of part of this system.

 In FIG. 4 shows, in perspective, one embodiment of a container used in the system.

 In FIG. 5 shows a perspective view of the container of FIG. 4 in an inverted position.

 In FIG. 6 shows a side view in vertical section of a detachable half of the container shown in FIGS. 4 and 5, when viewed from the inside of the container.

 FIG. 7 is a vertical sectional view of a portion of the container along line 7-7 of FIG. 6, but showing both halves of the container connected together.

 In FIG. 8 is a vertical sectional view similar to FIG. 7 along line 8-8 of FIG. 6.

 In FIG. 9 is a vertical sectional view similar to FIG. 8 along line 9-9 of FIG. 6.

 In FIG. 10 is a perspective view of one embodiment of an electromagnet used in a given system.

 In Fig.11 shows an end view, partially in cross section, of a part of the electromagnet shown in Fig.10.

 12 is a horizontal sectional view taken along line 12--12 of FIG. 10.

 On Fig shows an inside view of half of the container, which shows examples of the implementation of certain internal components used in this system to reduce leakage.

 In FIG. 14 shows an enlarged vertical section of the inside of the container and an example embodiment of a device for damping the movements of molten metal in a container.

 On Fig shows a perspective view of this damping device.

 On Fig shows a perspective view of the container and one of the embodiments of the electrical conductor used in the system.

 In FIG. 17 is an enlarged sectional view of a fragment of an end portion of an electrical conductor.

 In FIG. 18 is an enlarged cross-sectional view of the cross section relative to that shown in FIG. 17, which shows other parts of the electrical conductor.

 In FIG. 19 is a partial internal view of a half of a container, showing another embodiment of an electrical conductor.

 In FIG. 20 shows a circuit diagram with a current conductor through which direct current passes.

 In FIG. 21 shows a vertical section with components inside the container, designed to reduce the effective gap between the facing surfaces of the poles of the electromagnet located outside the container.

 On Fig shows a bottom view of one of the two guiding tape elements (grooves) located on opposite ends at the bottom of the container.

 In FIG. 23 is a circuit diagram of a series circuit for an electromagnet.

 On Fig shows a schematic diagram of a parallel electrical circuit for an electromagnet.

 FIG. 25 shows a graph of current (I) versus inductance (L) for the series circuit of FIG. 23.

 Figure 1 under the general designation 30 shows one example of the implementation of the system according to the present invention for coating by immersion in the melt. The system 30 of FIG. 1 is intended for coating a continuously flowing metal strip, for example a steel strip, using a metal coating containing zinc or a zinc alloy. In other exemplary embodiments of the melt dip coating system of the present invention, other metals such as aluminum, aluminum alloys, and the like can be used to coat the continuous metal strip. Tin, lead and alloys of these metals are examples of other coating metals that can be used in melt coating systems according to other embodiments of the present invention.

 Consider FIG. 1 and 3. A continuous steel strip 32 is unwound from a roll (not shown) and subjected to traditional pre-treatment (also not shown). After pre-processing, the tape 32 passes through the rollers 36, 37 and enters through the elongated slotted hole 43 into the lower part of the elongated container 38 in the form of a trough containing a bath 40 of molten coating metal, in this case zinc. The bath 40 has a mirror (upper surface) 41, and the hole 43 at the bottom of the container is below the mirror 41 of the bath 40. The hole 43 facilitates the entry of the tape 32 into the bath 40, after which the tape moves in a straight line through the bath 40. While moving the tape 32 through the bath 40, a layer of coating metal is applied to the tape 32, which contains the bath 40, after which the coated tape exits the bath 40.

 The container 38 has an open upper edge 42 through which the coated metal tape 31 extends upward after the bath 40 passes. Above the container 38 are a pair of so-called air scrapers 44, 44 (FIG. 1), which are commonly used to control the thickness of the coating on the tape 31 for example, by directing a stream of heated or unheated air or nitrogen onto the belt 31. After the air scrapers 44, 44 there is a take-up reel (not shown) onto which the tape 31 is wound in the form of a roll, which can then be removed from the take-up reel.

 We will now give a more detailed description of the container 38 with reference to FIG. 3-8.

 As shown in FIG. 3, the container 38 has a vertical cross-sectional shape of a bell (funnel) in a vertical plane perpendicular to the plane of the tape 32. In addition, as shown in FIG. 3, the container 38 has (i) a relatively narrow lower part 58 starting from the opening 43, and (ii) a relatively wide part 59 located above the narrow part.

 In FIG. 4-8 it is shown that the container 38 consists of two halves 52, 52 connected together at opposite edges along the vertical flanges 53, 53. The halves of the container joined together form an elongated container 38 in the form of a gutter.

 The container 38 has a pair of longitudinal side walls 55, 55 and a pair of end walls 56, 56 located between the edges of the side walls 55, 55. The side walls 55, 55 form a vertical funnel-shaped cross section as shown in FIG. 3 and 8-9. The container 38 and its funnel-shaped cross section contain the aforementioned relatively narrow lower part 58 and the relatively wide upper part 59. The intermediate part 60 of the container is between the wide upper part 59 and the narrow lower part 58 and contains two side walls 61, 61 converging (converging) in the direction from the wide upper part 59 to the narrow lower part 58.

 The materials from which the container 38 can be made include non-magnetic stainless steel and heat-resistant (refractory) materials.

 In FIG. 6 shows an inside view of the container 38, where the narrow portion of the container 58 comprises a passage channel 62 starting from the opening 43 of the bottom of the container. Channel 62 is formed by two opposite longitudinal sides 63, 63 (only one of which is shown in Fig.6) and two opposite end sides 64, 64, each of which is located between the walls of channel 63, 63.

 Now we give a more detailed description of the electromagnet 50 with reference to figures 2 and 10-12.

 The electromagnet 50 consists of a rectangular outer part 100 made of non-magnetic material and consisting of two longitudinal side walls 101, 101 and two end walls 102, 102, each of which is located between the respective edges of the side walls 101, 101. The side walls 101, 101 together with end walls 102, 102 form an inner space 104 having respective open upper and lower ends 105 and 106.

 The electromagnet 50 also contains two poles 108, 108, each of which is made of magnetic material and is mounted on the corresponding side wall 101 of the outer part 100 inside the vertically located space 104. Each pole 108 expands inside the space 104 towards the other pole and ends with the surface of the pole 109 which faces the surface 109 of the other pole 108 (see FIGS. 10 and 12). The surfaces of the poles 109, 109 define the gap (gap) between them, in which the container 38 is placed.

 As shown in FIG. 11, each pole 108 is surrounded by a winding 112 through which electric current flows. According to one embodiment of the present invention, a time-varying current from a current source 113 passes through each winding 112, inducing a magnetic field inside a pole 108 surrounded by a winding 112. The current source 113 is typically adjustable to change the amount of time-varying current supplied to the winding 112 that allows you to control the intensity of the magnetic field, which is created by the electromagnet 50.

 In another embodiment, to generate a magnetic field, a direct current is passed through the winding 112. An adjustable current source may also be used in this embodiment.

 The winding 112 consists of turns 115 of the winding, each of which passes around the pole 108, and the turns are made of a corresponding conductive material, such as copper. The turns of the winding 115 are isolated from each other, as well as from the pole, by electrical insulation (not shown). In the example embodiment of FIG. 11, the winding 112 consists of a solid wire (conductor); in other examples, the winding may consist, for example, of copper tubes in which coolant can circulate.

 The poles 108, 108 and the outer part 100 form a magnetic flux circuit 116 (magnetic field circuit), which is created as a result of the passage of current through the winding 112. The circuit 116 is shown in FIG. 12 by dashed lines with arrows. More specifically, the magnetic flux leaves the surface 109 of one of the poles 108 and passes through the gap 110 to the surface 109 of the second pole 108. This magnetic flux then passes sequentially through the second pole 108, then in opposite directions through the longitudinal side wall 101 on which it is mounted this pole, then through both end walls 102, 102 on the outer part 100, then through the longitudinal side wall 101 on which the first pole is mounted, and then through the first pole 108 again to the surface 109 of this pole.

 The direction of the current through each of the windings 112 at each of the poles 108 is determined so that the magnetic flux generated by each of the windings passes through the gap 110 in the same direction. The electromagnet 50 is made of any conventional magnetic material, such as ferrite or electrical steel plates.

 As shown in FIGS. 10 and 12, the electromagnet 50 consists of two “semi-magnets” 114, 114, each of which is E-shaped in a horizontal cross section.

 In accordance with figure 3, each surface 109 of the pole 108 is located next to the corresponding side wall 55 of the container 38, almost adjacent to this side wall in the lower narrow part 58 and in the region of the tapering part 61. The surface 109 of each pole has an outline (profile), repeating in this embodiment, the contours of the adjacent side wall 55, in particular along the side walls of the tapering portion 61 and along the bottom of the container 58.

 The distance between the surfaces of the poles 109, 109 facing each other (gap 110) is minimal in the narrow part of the container 58 near the passage opening 43 of the bottom of the container. Since the width of the gap 110 between the surfaces of the poles is minimal at this point, the magnetic field strength (magnetic flux density) is maximum in this area compared to the regions of the narrow portion 58 of the container located above, where the gap 110 becomes wider. In addition, since the resistance to the passage of magnetic flux (i.e., magnetic resistance) is less in free space than in the molten metal of the bath 40, the magnetic flux passing between the poles 109, 109 is concentrated directly below the bath 40 in the passage channel 62 - next with a passage opening 43 of the bottom of the container. Accordingly, for a given time-varying current passing through the windings 112, 112, the magnetic force that is applied to the bath 40 by the electromagnet 50 is greater in the lower part of the container 58 near the passage opening of the bottom of the container than in any other place in the bath 40 molten metal. Typically, the magnetic power (and magnetic flux) can be controlled by varying the time-varying current that is used to power the magnet. The magnetic flux generated by the time-varying current passes through the gap 110 (see FIG. 3) and induces eddy currents inside the bath 40. According to FIG. 6, the eddy current circuit 45 contains a portion 46 that extends horizontally along the bottom of the bath 40 horizontally in the longitudinal direction. the direction of the container 38 next to the passage opening 43. The direction of the eddy currents in this area is perpendicular to the direction of the magnetic flux at this point. As a result, this flow and eddy currents intersect in a horizontal plane, creating upward magnetic forces, as shown in Figs. 3 and 6. These magnetic forces “push up” that part of the bath 40 that is adjacent to the passage opening 43 of the bottom of the container ( i.e. the lower part of the bath 40), an effect known as magnetic levitation.

 Magnetic levitation resulting from the action of a vertical magnetic force repelling a portion of the molten metal bath that is adjacent to the passage opening 43 of the bottom of the container is an important factor in retaining the bulk of the molten metal bath. The magnetic levitation described above can contribute to the retention of up to 98% or more of the mass of the material of the bath 40, if the effect of the magnet 50 is enhanced by other means, which are described below. The mass retention due to this type of magnetic levitation can be successful in preventing the majority of the molten metal from the bath 40 from escaping through the belt passage 43, and this can reduce to some extent possible leakage or leakage along the sides 63, 63 and the ends 64, 64 of the passage channel 62 (Fig.6).

 The action of the electromagnet 50 sets in motion (excites) the material of the bath 40, creating flows in the form of circulation (eddies) or in an oscillatory form having a vertical component; this movement facilitates leakage or leakage through the passage opening 43 of the container 38. The damping device for the movements of the bath material is shown under the general designation 70 in FIGS. 13-15. The device 70 consists of several pairs of parallel flat elements 71, 72. Preferably, each flat element 71, 72 is made of a material, such as stainless steel, which is resistant to the temperature conditions of the molten bath metal 40. Alternatively, the flat elements 71, 72 may be coated with heat insulation material (not shown).

 Pairs of flat elements 71, 72 are spaced vertically relative to other pairs along the line of movement of the tape 32, and each pair of flat elements 71, 72 is located across the bath 40 in a direction perpendicular to the line of movement of the tape. Between each pair of flat elements 71, 72 there is a gap (gap) 73. Each gap 73 is aligned with the slots of the other pairs of flat elements 71, 72 so that the tape 32 can pass through these slots as it moves. The flat elements 71, 72 intersect the flows in the bath material created by the electromagnet 50, and thereby contribute to the damping of these flows.

 As shown in FIG. 14, some of the planar elements 71, 72 are located in the container 38 between the downwardly converging portions 61, 61 of the side walls. These flat elements have corresponding lateral dimensions in the direction between the portions 61, 61 of the side walls, and these dimensions gradually decrease downward. Vertically aligned flat elements 71, 71 and vertically aligned flat elements 72, 72 are supported at certain vertical distances using spacers 75, 75, each of which is between adjacent flat elements 71, 71 and adjacent flat elements 72, 72.

 In one embodiment of the invention, all flat elements 71, 71 of the damping device 70 are held together in a block by their spacers 75, each of which is rigidly connected to the flat elements located above and below it; all flat elements 72, 72 of the damping device 70 are also held together in block form by their struts 75. In another embodiment, all flat elements of the block are held together by vertical rods (not shown) that pass through aligned holes in the flat elements and struts. A group of horizontally spaced and vertically spaced transverse elements 76, 77, 78, 79 located at each end of the damping device 70 connects a block of vertically spaced flat elements 71, 71 with a block of vertically spaced flat elements 72, 72, forming pairs of horizontally aligned elements 71, 72.

 The damping device 70 has a vertical size, preferably corresponding to the depth of the molten metal bath 40, which is located in the container 38.

 In the embodiment of FIGS. 13-15, the damping device 70 is suspended from above on end brackets 80, 80 located at opposite ends of the damping device 70 and extending vertically upward from this device. Each end bracket 80 has an opening 82 for a threaded element 81 used to attach the bracket 80 to the link 84 of the device 83, which, among other functions, is used as a frame for attaching the damping device 70 in the embodiment shown in FIG. 13. The device 83 also performs other functions, which will be described in detail below.

 The means described above used to connect the flat members of the damping device 70 and to mount the damping device 70 inside the container 38 are shown for illustrative purposes only; other means may be used for the same purpose. In some embodiments, instead of each pair of flat elements 71, 72, one flat element can be used having a transverse dimension corresponding to the sum of the transverse dimensions of the flat elements 71, 72, and containing a single elongated gap located in the middle instead of the gap 73.

 As noted previously with reference to FIG. 3, there is a gap 110 between the facing surfaces of the poles 109, 109 of the magnet 50. As can be seen from FIG. 3 and 14, pairs of flat elements 71, 72 are located horizontally between the facing surfaces of the poles 109, 109 in that part of the gap 110 that is above the narrow lower part 58 of the container 38. This part of the gap 110 is wider than that part of the gap that is in the narrow lower part 58. The greater the width of the gap between the surfaces of the poles 109, 109, the lower the density of the magnetic flux passing through this part of the gap. But since a high magnetic flux density is required, it can be increased by decreasing the effective gap between the surfaces of the poles 109, 109. The following paragraph describes the means intended for this purpose.

 In a preferred embodiment of the invention, the flat members 71, 72 are made of a ferromagnetic material, for example carbon steel or magnetic stainless steel. Compared to the metal of the molten bath 40 (for example, zinc), both of the materials described in the previous proposal have a higher magnetic permeability and relatively lower magnetic resistance for the passage of magnetic flux between the surfaces of the poles 109, 109. When using these materials for flat elements 71, 72, the effective gap between the pole surfaces 109, 109 decreases. More precisely, the effective gap decreases to (a) the gap width 73 plus (b) the distance between the outer edge 74a p oskogo element 71 and the adjacent surface of the pole 109 plus (c) the distance between the outer edge 74b of the flat element 72 and the adjacent surface of the pole 109.

 In FIG. 21 shows an alternative embodiment of a means for reducing the effective gap between the surfaces of the poles 109, 109. In this embodiment, a space 173 is formed between vertically aligned pairs of horizontally arranged flat elements 171, 172 through which the path of the belt 32 passes. Each pair flat elements 171, 172 is located in the gap 110 between the surfaces of the poles 109, 109 in that part of the gap 110, which is located above the narrow lower part 58 of the container 38 (compare figures 3 and 2 1). Both flat elements of the pair lie in the same horizontal plane. Each flat element starts from the surface 174, 175 corresponding to the downwardly converging portion 61, 61 of the inner side wall and passes through the bath 40 towards the paired flat element, i.e. in the direction perpendicular to the line of movement of the tape. The flat elements 171, 172 are made of ferromagnetic material, for example, magnetic stainless steel, which allows reducing the effective gap between the surfaces of the poles 109, 109 facing each other in the same way as in the case of flat elements 71, 72 (see the previous paragraph )

 In the example shown in FIG. 21, the flat members 171, 172 are partially embedded in the side walls 61, 61 of the container 38. Other methods of attaching the flat members 171, 172 to the side walls may be used.

 Referring now to Figs. 6-8 and 13. As noted above, the channel 62 has two opposite ends 64, 64, and each of them is separated from the adjacent end wall 56 of the container 38. There is an end gap 67 between the end wall 56 of the container and the end 64 channel. The jumper 65 is located at the top of each end face 64 of the channel and is located across the inner part of the container between the opposite converging parts 61, 61 of the side walls of the intermediate part 60 of the container (Fig.7-8). Each jumper 65 occupies a portion of the space between the end wall 56 of the container and the end face 64 of the channel. At each end of the container 38 between the end wall 56 of the container and the jumper 65 there is a collector (recess) 66. Each collector 66 forms a structure to limit the bath of molten metal. The collection 66 is located above the lower part 68 of the container wall between the end face 64 of the passage channel 62 and the adjacent end wall 56 of the container 38.

 In the example of the invention shown in figures 3 and 13, each pole 108 (and its surface 109) is located (a) towards the bottom of the passage channel 62 (corresponding to the opening of the bottom of the container 43) and (b) in the longitudinal direction to a position adjacent to with each end gap 67 of the container 38. Accordingly, when the magnetic flux passes between the surfaces of the poles 109, 109, part of this flux passes at the bottom of the channel 62 and the end gaps 67, 67.

 13 and 16-18 show another component designed to reduce leakage or seepage of molten metal through the passage opening 43 of the bottom of the container. This component is in the form of an electrical conductor, one example of which is represented by the general designation 83 in FIG. 13.

 It was previously noted that when the electromagnet 50 acts in conjunction with a time-varying electric current (alternating current or direct current ripple), the magnetic flux generated by this electromagnet induces eddy currents in the molten metal bath 40. These eddy currents usually circulate along a contour that is represented by dashed line 45 in FIG. 6 and which comprises a portion 46 extending along the bottom of the bath 40.

 In accordance with FIG. 13, the electrical conductor 83 is typically represented by a U-shaped member made of an electrically conductive material such as copper. The conductor 83 comprises (i) two vertical links 84, 84, each of which is adjacent to the corresponding end wall 56 of the container 38, and (ii) of the transverse element 86. Each link 84 has an upper end portion 85 connected by a transverse element 86 to the upper end part 85 of the second link. The electrical conductor 83 also has lower end parts 87, 87, each of which is connected to a corresponding link 84, is located inside the corresponding end gap 56 of the container 38 above the lower part 68 of the container wall and is in electrical contact with the part of the bath 40 located in the collector 66. Although not shown in FIG. 13, conductor 83 is electrically isolated from contact with damping device 70 and bath 40 (except for part of bath 40 in collector 66).

 In the example of FIG. 13, eddy currents pass through an electrical conductor 83 rather than circulating through a bath 40 along a circuit 45 (FIG. 6), and they are guided by an electrical conductor 83 to the end gap 67 of the container 38, i.e., to that part of the molten metal bath 40, which is in collection 66.

 As noted above, the magnetic force created by the interaction of the electromagnet 50 and the eddy currents that are induced in the bath 40 “repels” the molten metal of the bath 40 from the passage opening 43 of the bottom of the container and helps to hold the bottom of the bath 40 above the passage opening 43 of the bottom of the container .

 The upward magnetic force acting on the lower part of the bath 40 at any point along the length of the container 38 depends on (a) the magnitude of the magnetic flux at this point and (b) the magnitude of the eddy current at this point. The surfaces of the poles 109, 109 face each other through the end gaps 67, 67, thereby creating a magnetic flux in these areas. As noted above, the electric conductor 83 directs the eddy current induced by the electromagnet 50 to the end gaps 67, 67 located near the bottom of the container 38. In the absence of the electric conductor 83, at least some of the eddy currents can pass along the circuit 45, which passes by the end gaps 67, 67 (see Fig.6). When using an electrical conductor 83 having non-insulated end parts 87, 87 located in the region of end gaps 67, 67 inside collectors 66, 66, eddy current is more concentrated in end gaps 67, 67 than in the absence of electric conductor 83. This helps to increase the upward magnetic force in the end gaps 67, 67, which, in turn, helps to reduce leakage or seepage through the passage opening 43 of the bottom of the container, especially along the ends 64, 64 of the passage channel 63.

 An electrical conductor 83 is also used to substantially reduce the flux density of the circulating eddy currents along the upper part of the bath 40. This is preferable because the eddy currents circulating along the upper part of the bath 40 interact with the magnetic field that is generated by the electromagnet 50, creating a magnetic force that acts down to bath 40 in this area. Since the electric conductor 83 significantly reduces the density of the eddy current circulating along the upper part of the bath, this also contributes to a significant decrease in the magnitude of the magnetic force acting on the bath in this area in the downward direction. This, in turn, increases the efficiency of the magnetic force acting on the bath upward in the lower part of the bath, which in turn helps to reduce leakage or seepage from the bath through the passage opening 43 of the bottom of the container.

 As noted above, the density of the magnetic flux generated by the electromagnet 50 is maximum in those places where the gap 110 between the facing surfaces of the poles 109, 109 of the electromagnet 50 is minimal. Similarly, the eddy currents that are induced in the bath 40 are relatively high in areas of relatively small gaps, i.e. adjacent to the bottom of the bath 40. In addition, the electrical conductor 83 concentrates the eddy current along the bottom of the bath 40 adjacent to the top of the passage opening 63.

 As noted above, the electrical conductor 83 has vertically arranged links 84, 84, a significant portion of which are within the bath 40. In the alternative embodiment of the invention shown in FIG. 16, a U-shaped electrical conductor is used under the general designation 183, containing vertically arranged links 184, 184 located entirely outside the bath 40, and a transverse element 186 connecting the links 184, 184. Only the end parts 187, 187 of the electrical conductor 183 are within 40 baths (in end gaps 67, 67 inside collectors 66, 66). Between each end part 187 and the corresponding link 184 is a connecting element 188 passing through the longitudinal side wall 55 of the container 38.

 All the previous discussion concerned the electromagnet 50, which receives a time-varying current, i.e. alternating current or pulsating direct current. In such cases, the resulting magnetic flux induces eddy currents in the bath 40 passing through the low resistance circuit formed by the electrical conductor 83 or 183.

 In another embodiment of the present invention, the electromagnet 50 can operate with a current that does not change over time, for example with a non-pulsating direct current. In this case, each winding 112 of the pole 108 of the magnet 50 (Fig. 11) is connected to a direct current source, which passes without interruption through the winding 112, as a result of which a magnetic field is created with a stream passing through the bath 40 between the pole surfaces 109 facing each other 109 (Fig. 3). The magnetic field created in this way does not induce eddy currents in the bath 40. Instead, an external source is used to supply direct current to the bath 40 in the region between the surfaces of the poles 109, 109. One example of this kind of implementation is shown in Fig. 20 (last sheet drawings).

 In the example shown in FIG. 20, the direct current source 119 is connected via a line 117 to the end parts 118, 118, each of which is located in the corresponding end gap 67 of the container 38 above the lower part of the walls 68 and is in electrical contact with the bath in the collector 66 (see Fig.6). A direct current flows from the end portion 118 and runs along the bottom of the bath 40 in the longitudinal direction of the container 38. This direct current interacts with the magnetic field, which is created by passing a direct current through the windings 112 at the poles of the electromagnet 50 (Fig. 11). As a result of this interaction, a magnetic force is created that “repels” the molten metal of the bath 40 upward from the passage opening 43 of the bottom of the container 38.

 In all embodiments of the present invention, the end parts of the conductor (87, 187 or 118) are made of a material having a lower electrical resistance than the molten metal of the bath 40. Typically, the end parts are made of copper, while the bath of the molten coating metal contains zinc. The copper of the end part is metallurgically combined with zinc in the bath, forming an alloy of copper and zinc (brass), which is absorbed in the bath. The end result is erosion of the end portion of the conductor. In the light of the present invention, the phenomenon described above is undesirable; in accordance with this, the invention provides a means of preventing erosion of the copper ends located in the molten zinc bath 40.

 As shown in FIGS. 17 and 18, each end portion 187 is provided with an internal channel 189 connected to the internal channel 190 in the connecting part 188. The internal channel 190 is connected to an inlet pipe 191 connected to a source of coolant 192, such as chilled water. Coolant enters from source 192 through inlet tube 191 and channel 190 into channel 189 to cool the lower end portion 187, helping to solidify some portion of the coating metal (zinc) in the collector 66 as a “crust” or layer 194 around the end portion 187 (FIG. .17). Layer 194 protects the copper end portion 187 from erosion in the molten zinc of the bath 40. The used coolant is discharged from the channel 189 through the exhaust pipe 193 (Fig. 18).

(In FIG. 17, the jumper 65 and the lower part 68 of the walls of the container have a thickness that is less than the thickness of the corresponding elements in FIGS. 6 and 13. Any deviations may be used.)
In the embodiment shown in FIG. 20, a non-pulsating direct current is used, the end portion 118 has an internal channel 289 connected to the inlet pipe 291, and an exhaust pipe 293. The inlet pipe 291 is connected through a channel 294 to a coolant source (not shown). An exhaust pipe 293 is connected through a channel 295 to a drain for used chilled fluid. The circulation of the cooled liquid through the channel 289 helps to create a protective layer ("crust") of solidified zinc around the copper end portion 118 to prevent erosion in the molten zinc of the bath 40.

 As noted above, the electrical conductor 183 has links 184, 184 and a transverse element 186, which are located outside the bath 40 of the molten metal coating (Fig.16). A variation of the embodiment described above is shown in FIG. 19, where at least a portion of each link 184 is placed in the molten metal of the bath 40. To protect part of the link 184 placed in the bath 40, an insulating layer 196 is used to create electrical and thermal isolating this part of the link from the molten metal of the coating of the bath 40. The part of the link 184 adjacent to the junction of the link 184 with the lower end part 187 is protected from the bath of the molten coating by the frozen coating metal crust 194 (described above in connection with and 17).

 An electrical and thermal insulation layer similar to layer 196 of FIG. 19 is used in the example shown in FIG. 13 to protect this part of each link 84 immersed in the bath 40. The end portion 87 of the electrical conductor 83 is not cooled in the example of the invention shown in FIG. 13, and is exposed to a bath of molten coating metal. The unprotected end portion 87 may be used in situations where the molten coating metal does not form an alloy with the metal of which the end portion 87 (e.g., copper) is made. As a less preferred alternative, end portion 87 may be protected by an insulation layer (e.g., layer 196 shown in FIG. 19), with the exception of pin 89 of end portion 87.

 As shown in Fig.21-22, there is a guide element 120 located on each end 64 of the passage channel 62, which, as noted above, is located in the narrow lower part 58 of the container 38 (see Fig.6 and 13). Each guide element 120 has a horizontally located recess (groove) 121 having an open end 123 opposite the corresponding open end of the corresponding recess of the guide element 120 at the other end 64 of the passage channel 62. Each recess 121 has a corresponding structure for engaging the corresponding edge of the steel strip 32 when the tape is pulled through the passage channel 62. The recesses 121, 121 allow the tape to pass almost in the middle between the facing surfaces of the poles 109, 109 m the sockets 50 and restrict the movement of the steel strip 32 from side to side as it passes through the container 38. This allows you to counteract the property of the electromagnet 50 to attract the tape 32 to one of the surfaces of the poles of the electromagnet facing each other, which, in turn, can cause unwanted displacements tapes from side to side as it passes through the container.

Consider Figs. 23-24. On Fig shows a series circuit type LCR (L - inductance, C - capacitance, R - resistance) for the electromagnet 50, and Fig.24 shows a parallel circuit type LCR for the electromagnet 50. Each LCR circuit contains a source that varies 113 of current time, capacitor 125, winding 112 for each pole 108 of magnet 50 and resistance 127. In both schemes, designation C represents the electric capacitance of the circuit, L is the inductance of the circuit (which includes one winding 112 for each pole 108), and R _L is the resistance of these windings. Inductance is proportional to the magnetic flux generated by the winding and the number of turns of the winding and inversely proportional to the current level (current strength in amperes). Inductance gives a lag in frequency (phase) in comparison with the frequency of the power source; the capacitance gives an advance in frequency (phase).

 The control in the LCR type series circuit shown in FIG. 23 is such that when lowering the level of molten metal in the lower part of the bath 40, the current increases automatically; thereby increasing the value of the magnetic force acting in the vertical direction up on the lower part of the bath. This property is discussed in the following four paragraphs.

 In FIG. 25 shows a graph of current as a function of inductance for a system using the LCR type series circuit shown in FIG. The inscription on the vertical line "Resonance" of Fig. 25 means the state of the LCR type serial circuit, in which the frequency advance due to the circuit capacitance coincides (equalizes) the frequency lag due to the circuit inductance, that is, the natural frequency of the circuit is equal to the frequency of the power source . With a given power source, the resonance state provides more energy for the magnet to which current is supplied through this circuit than in the non-resonant state. When the LCR type series circuit shown in FIG. 25 is in a state close to resonance, the current level in this circuit depends on how close the circuit is to the resonance state. With fixed capacitance (C) and resistance (R), current (I) is a function of inductance (L) (see Fig. 25); this graph shows how changes in inductance (L) affect current (I).

 The system 30 and magnet 50 typically operate in such a way that the bottom of the bath 40 is held above the passage opening 43 of the container 38 (see FIG. 3). Anywhere between the surfaces of the poles 109, 109, the density of the magnetic flux passing through the free space (air) is greater than the density of the magnetic flux that would pass in the same place through the molten metal of the bath 40. When the mass of the bath 40 increases, for example, by adding into the molten metal bath of the coating, the increased mass initially lowers the lower part of the bath towards the passage opening 43. If this occurs, part of the gap 110 previously occupied by air (free space) is filled molten metal coating; thereby reducing the inductance of the system (L), since the descending molten metal acts as a magnetic shield, which reduces the magnetic flux density in that part of the gap 110, where the lower level of the bath. A magnetic screen reduces the magnetic flux density in this region, and a decrease in the total magnetic flux density leads to a decrease in inductance.

 The LCR type series circuit shown in FIG. 23 operates in such a way that the inductance value (L) in the graph of FIG. 25 is located to the right of the vertical line labeled “Resonance”, and the decrease in inductance (L) increases current (I). This, in turn, causes an increase in the total density of the magnetic flux passing through the gap 110, thereby increasing the magnetic force repelling the lower part of the bath 40. As a result, a system using the LCR type serial circuit shown in FIG. 23 and operating as described above thus, it is self-regulating in the sense that it compensates for the fall of the lower level of the bath 40.

Continuous tape 32 is usually a flat thin element, for example, in the form of a steel sheet (strip). However, the tape having the configuration described in the previous sentence merely illustrates one type of continuous tape for which the present invention can be used,
Other forms of tape may also be used, such as a bar, strip, wire, pipe or shaped article, provided that it is possible to minimize leakage of the molten coating method from the molten metal bath of the present invention.

 The present invention is illustrated in the context of a passage opening for a tape under a container containing a bath of molten coating metal. However, the present invention can also be used in a system where (i) the ribbon bore is located in the side wall of the container, and (ii) the container contains a molten coating metal bath having an upper surface (mirror) above the level of the ribbon bore.

 The foregoing detailed description is provided only for clarity of understanding of the invention, and no limitation follows from this description, since any modifications are obvious to those skilled in the art.

Claims (32)

 1. System for coating a steel strip by immersion in a melt, comprising an elongated gutter-shaped container containing a bath of molten coating metal having two opposite side walls located in the longitudinal direction of the container, two opposite end walls and an elongated passage opening in the bottom of the container, means for moving the steel strip along the line passing up through the passage in the bottom of the container and the bath, and an electromagnet containing elements to prevent an outlet through the passageway of the molten bath metal mass, characterized in that the container has a relatively wide upper and relatively narrow lower parts, said side walls converging downward toward said narrow part, wherein the electromagnet is located along said container and has two opposite poles made of magnetic material, and each pole is located along the corresponding side wall of the specified container, and these poles are facing to each other the surfaces of the poles, each of which is located next to the corresponding side wall of the container, practically adjacent to it in the lower part and in the part of the side wall, converging towards the opposite wall, each of these surfaces of the poles having contours that almost repeat the contours of the adjacent a side wall along a portion converging toward another side wall, and also along the bottom of the container.  2. The system according to claim 1, characterized in that said electromagnet is configured to hold a mass of molten metal while allowing some leakage of molten metal from said bath through said hole in the bottom of the container, the system further comprising means for reducing leakage of molten metal, allowed by the specified electromagnet.  3. The system according to claim 1, characterized in that said electromagnet comprises means configured to drive said bath, the system comprising means for damping the movement of molten bath material caused by said electromagnet.  4. The system according to claim 3, characterized in that said damping means consists of several practically parallel pairs of flat elements spaced vertically along the line of movement of the specified tape and located across the specified bath in the direction perpendicular to the direction of movement of the tape between the flat elements of each pair a slit is formed, vertically aligned with the slots of all other pairs of flat elements, to ensure the passage of the specified tape through the slots during its movement.  5. The system according to claim 4, characterized in that at least some flat elements are placed inside said container between its side walls converging downward and have transverse dimensions in a horizontal plane between said side walls, gradually decreasing downward.  6. The system according to claim 4, characterized in that it has a gap between the surfaces of the poles facing each other, wherein said pairs of flat elements are placed in this gap and between the side walls converging downwards of said container and at least one pair of said flat elements made of ferromagnetic material to reduce the effective gap between the indicated surfaces of the poles.  7. The system according to claim 6, characterized in that the said one pair of ferromagnetic flat elements is located next to the specified narrow lower part of the container.  8. The system according to claim 1, characterized in that a gap is made between the pole surfaces facing each other, the system comprising means for reducing the effective gap between the pole surfaces facing each other.  9. The system of claim 8, characterized in that the said means of reducing the gap include a pair of horizontally located and separated from each other flat elements lying in the same plane and located across the container between the respective inner surfaces of the side walls in a direction perpendicular to the line of movement tape, while these flat elements are installed with a gap for the tape to pass along the line of movement through the specified gap between these flat elements, and the specified pair of flat ele ENTOV placed in the gap between said downwardly converging side walls of the container, said flat elements made of ferromagnetic material.  10. The system according to claim 1, characterized in that said narrow lower part of the container has a passage channel upward from said passage hole in the bottom of the container, formed by two opposite longitudinal sides and two opposite end sides located between said longitudinal sides of the passage channel, and each end side of the passage channel is separated from the adjacent end wall of the container containing a jumper on each end side of the passage channel, directed upward at tvetstvuyuschey end side of the through passage and extending transversely of the inner container between the opposite sidewalls.  11. The system of claim 10, characterized in that said container contains a collector at each of its ends located between the end wall of the container and an adjacent jumper.  12. The system according to claim 11, characterized in that each of these collections contains means for limiting the bath of molten metal.  13. The system according to claim 1, characterized in that said electromagnet comprises means for creating a magnetic field between said pole surfaces facing each other, and said system comprises means for creating an electric current loop for passing one part of the current along the lower part of said bath in the longitudinal direction of the specified container, the interaction with the specified magnetic field generated by the specified electromagnet, and obtaining a magnetic force repelling the specified bath of molten metal about said passage opening in the bottom of the container, wherein said system comprises a conductor of electric current forming circuit with low resistance to the passage thereon another part of said electrical current other than the portion extending along said bottom of the tub.  14. The system according to item 13, wherein said narrow lower part of the container has a passage channel upward from said passage hole in the bottom of the container, formed by two opposite longitudinal sides and two opposite end sides located between these longitudinal sides of the passage channel, and each end side of the passage channel is separated from the adjacent end wall of the container containing a portion of the lower wall located between the end side of the passage channel and the adjacent end wall of the container, wherein said electrical conductor further comprises means for directing electric current into the end gap between the end side of the passage channel and the adjacent end wall of the container.  15. The system of claim 14, wherein said electromagnet comprises windings, and said system comprises means for passing a time-varying electric current through said windings to create a magnetic field, wherein said electromagnet comprises means for passing a time-varying current through these windings and creating a magnetic field with a magnetic flux passing through the specified bath of molten metal between the indicated facing each other surfaces of the poles and, in turn ed inducing eddy currents in said bath comprising a portion of the current flowing along the bottom of said bath.  16. The system of claim 15, wherein said electrical conductor comprises means for substantially reducing eddy current density along the top of said bath.  17. The system of claim 15, wherein said electrical conductor is made of electrically conductive material and contains two links, each of which is located next to the corresponding end wall of said container and is connected by an electrically conductive part to another link, wherein said electrical conductor contains two end parts, each of which is connected to the corresponding link and located inside the corresponding end gap of the specified container in electrical contact with the mat bath series.  18. The system according to 17, characterized in that each of these links contains a part located inside the specified container, while this system contains elements of electrical and thermal insulation of the specified part of the link from the molten metal bath.  19. The system according to 17, characterized in that both of these links are located outside the specified container, and the specified electrical conductor contains a connecting part extending from each end part of the conductor through the wall of the specified container to the specified link.  20. The system according to 17, characterized in that said end part is made of copper, said coating metal is zinc, and the system comprises means that prevent the formation of a copper alloy of said end part of the conductor and zinc of said bath of molten coating metal.  21. The system according to claim 20, characterized in that said obstructing means include means for cooling said end parts of the conductor for solidifying the coating metal around the end part and protecting it from erosion caused by the molten coating metal of said bath.  22. The system according to item 21, wherein said cooling means include an inner channel inside said end portion of the conductor and means for supplying coolant through said inner channel.  23. The system of claim 14, wherein said electromagnet comprises windings, and the system comprises means for passing a constant continuous current through said windings to create a magnetic field with a magnetic flux passing through said bath between said pole surfaces facing each other , the specified electrical conductor contains two end parts, each of which is located inside the corresponding end gap of the specified container above the specified part of the lower wall of the container and in electrical contact with the bath material there, and the system comprises means for connecting each of said end parts to a direct current source.  24. The system according to 14, characterized in that the container contains a jumper on each of the end sides of the specified passage channel, directed upward on the corresponding end side of the passage channel and located across the inner part of the container between its opposite side walls, wherein said container contains a collector at each of its ends between the end wall of the container and the adjacent jumper containing means for limiting the bath of molten metal, and the specified electrical conductor with will contain two end parts located inside the corresponding collector of the specified container above the specified part of the lower wall of the container in electrical contact with the molten metal bath in the specified collection.  25. The system according to claim 1, characterized in that said system comprises means for holding said steel strip during its movement almost in the middle between said facing surfaces of the poles and limiting lateral displacements of the steel strip from said facing surfaces of the poles in time of its passage along the line of movement through the container.  26. The system of claim 25, wherein said steel strip has two opposite edges, said narrow lower part of the container having a passage channel upward from said passage hole in the bottom of the container, formed by two opposite longitudinal sides and two opposite end faces parties located between the specified longitudinal sides of the passage channel, and each end side of the passage channel is separated from the adjacent end wall of the container, and these means for The holding of the steel strip almost in the middle are two horizontally located recesses located opposite each other on the corresponding end sides of the passage channel, and each recess contains elements for engaging the corresponding edge of the steel strip when it moves along the specified line.  27. The system according to claim 1, characterized in that it contains means including said electromagnet to create an upward magnetic force repelling the lower part of said bath, a winding for each of the indicated poles of this electromagnet, a series electric circuit including said windings and comprising an electric current source and a capacitor connected in series with said windings, said circuit having a fixed capacitance, a fixed resistance and a variable, and inductance and includes means configured to ensure its operation is close to its resonance, and means configured to maintain inductance values slightly higher than the inductance corresponding to resonance in this circuit to increase the current supplied to said windings each time a decrease occurs level of the lower part of the specified bath of molten metal, and an increase in the magnetic force acting upward on the lower part of the specified bath.  28. The system according to claim 1, characterized in that said electromagnet is located around said container and comprises an external part made of ferromagnetic material and containing two opposite longitudinal side walls, each of which has two opposite ends, and two end walls, each of which is located between the respective ends of the specified side walls, while the side and end walls form a vertically located space having open upper and lower sides for placing the decree of the container, and each of the poles of the electromagnet is located on the corresponding side wall of the specified outer part inside the specified vertically located space, is extended downward towards the other pole and has one of the corresponding indicated facing surfaces of the poles, and a gap is formed between the indicated surfaces of the poles, in which the specified container is placed, and two windings for the passage of electric current, each of which is placed around the corresponding specified field a and comprises elements for supplying electric current to said coil and generate a magnetic field at the pole, which extends around said winding.  29. The system of claim 28, wherein said electromagnet comprises elements, including said poles and an outer part, for creating a contour for a magnetic flux from a surface of one of the poles to pass through said gap to the surface of another pole, then sequentially through the other pole, through the longitudinal side wall on which the specified other pole is located, through the specified end walls of the outer part, through the specified longitudinal side wall on which the specified first pole is located, and then through the decree the first pole to the indicated surface of the first pole.  30. The system according to p. 28, characterized in that said electromagnet consists of two halves, each of which is elongated in the longitudinal direction of said container and has an E-shaped horizontal cross section.  31. The system according to claim 1, characterized in that said container is made of heat-resistant material.  32. The system according to claim 1, characterized in that said container is made of non-magnetic stainless steel.

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