Patent Publication Number: US-11655532-B2

Title: Gas wiping nozzle and method of manufacturing hot-dip metal coated metal strip

Description:
TECHNICAL FIELD 
     This disclosure relates to a gas wiping nozzle that blows gas onto a metal strip pulled up from a molten metal bath and adjusts the amount of a molten metal coated to a surface of the metal strip and a method of manufacturing a hot-dip metal coated metal strip using the gas wiping nozzle. 
     BACKGROUND 
     A hot-dip galvanized steel sheet, which is a type of hot-dip metal coated steel sheets, is widely used in fields such as building materials, automobiles, and home appliances. In those applications, an excellent appearance is required for the hot-dip galvanized steel sheet. Since the appearance after painting is strongly affected by surface defects such as uneven coating thickness, flaws, and adhesion of foreign matter, it is important that the hot-dip galvanized steel sheet has no surface defects. 
     In a continuous hot-dip metal coating line, normally, a steel strip as a metal strip annealed in a continuous annealing furnace in a reducing atmosphere passes through a snout and is introduced into a molten metal bath in a coating tank. The steel strip is pulled up above the molten metal bath via a sink roll and a support roll in the molten metal bath. Thereafter, the amount (also referred to as a basic weight amount) of molten metal coated is adjusted by blowing wiping gas from gas wiping nozzles located on both sides of the steel strip onto the surface of the steel strip and scraping off the excess molten metal coated to the surface of the steel strip and pulled up. To correspond to various steel strip widths and also cope with displacement in the width direction when the steel strip is pulled up, the gas wiping nozzle is normally configured to be wider than the width of the steel strip and extends outward from an end portion in the width direction of the steel strip. 
     In such a gas wiping method, hot metal wrinkles (also referred to as hot metal sagging) with corrugated flow pattern are often generated on the coated surface due to minute vibration of the steel strip or irregular hot metal flow on the coating layer due to the blowing of wiping gas. When the coated surface of a coated steel sheet with such hot metal wrinkles is used as a coating base surface in an outer coating application, a surface texture of a coating film, particularly smoothness, is impaired, and thus the coated steel sheet cannot be used for an exterior sheet to be suitable for a coating treatment having an excellent appearance, which significantly affects the yield of the coated steel sheet. 
     To solve this problem, for example, those described in Japanese Patent No. 6011740 are known. 
     A continuous hot-dip metal coating method described in JP &#39;740 is a method in which a steel strip is continuously immersed in a molten metal coating bath, and gas is blown from a gas wiping nozzle onto the steel strip immediately after being drawn out from the molten metal coating bath to control the amount of coating. The temperature T of the wiping gas blown from the gas wiping nozzle is controlled according to a DB value represented by a ratio of the distance D between a tip end of the gas wiping nozzle and the steel strip, and a gas wiping nozzle gap B. 
     In addition, in the known gas wiping method, a phenomenon that the edge portion of the steel strip may be supercooled from a central portion occurs during wiping, the steel strip may be warped, the amount of coating in the width direction may be uneven, and there may also be a problem of wasting a large amount of zinc in vain to guarantee the lower limit of the amount of zinc coated. 
     To solve this problem, for example, a method described in JP H08-176776 A is known. 
     A wiping method in continuous hot-dip galvanizing described in JP &#39;776 is a method of heating wiping gas such that the temperature T G  (° C.) of the wiping gas and the sheet thickness D (mm) of a steel strip to be coated satisfy equation (1), in the continuous hot-dip galvanizing, when the wiping gas is blown from a gas wiping nozzle to wipe the hot-dip zinc coating to the front and rear of the steel strip to be coated:
 
Wiping gas temperature  T   G  (° C.)≥−400 D+ 400  (1).
 
     In addition, as the gas wiping nozzle, for example, a nozzle described in JP 2018-178159 A is also known. 
     The gas wiping nozzle described in JP &#39;159 is a nozzle that blows gas onto a steel strip pulled up above a molten metal coating bath and adjusts a film thickness of a molten metal film coated to the surface of the steel strip. The gas wiping nozzle includes a first lip portion and a second lip portion that are provided to face each other and form a nozzle chamber into which gas is introduced, a slit formed between the end portions of the first lip portion and the second lip portion on the steel strip side, as a blowing port for gas blown from the nozzle chamber, and a fixing member provided on the slit side in the nozzle chamber and fixing the first lip portion and the second lip portion. In the fixing member, a plurality of first communication holes that communicate the slit side and the opposite side of the slit with respect to the fixing member is disposed side by side along the width direction of the steel strip. 
     According to the gas wiping nozzle described in JP &#39;159, even when each part is reassembled to replace a part or all of the parts constituting the gas wiping nozzle, it is possible to suppress variations in a gap of the slit (also referred to as a slit gap) after assembly for each assembly. 
     However, the continuous hot-dip metal coating method described in JP &#39;740, the wiping method in the continuous hot-dip galvanizing described in JP &#39;776, and the gas wiping nozzle described in JP &#39;159 in the related art have the following problems. 
     That is, in the continuous hot-dip metal coating method described in JP &#39;740 and the wiping method in continuous hot-dip galvanizing described in JP &#39;776, the wiping gas is heated to create a high temperature atmosphere around the gas wiping nozzle, and the gas wiping nozzle itself is also heated as the wiping gas is heated. The material of the gas wiping nozzle is not described in JP &#39;740 and JP &#39;776, and when the gas wiping nozzle is made of metal according to a normal method, the nozzle is significantly deformed due to the property of being easily plastically deformed or the property of having a high coefficient of linear expansion. As a result, there is a problem that a gap of a slit as a gas blowing port provided at the end portion of the gas wiping nozzle on the steel strip side, that is, the gap in the width direction orthogonal to the length direction of the slit cannot be uniformly held along the length direction of the slit, and the amount of coating to the steel strip along the width direction of the steel strip is non-uniform. 
     On the other hand, in the gas wiping nozzle described in JP &#39;159, since the first lip portion and the second lip portion are fixed on the slit side in the nozzle chamber by the fixing member, it is possible to suppress variations in the slit gap after assembly for each assembly when replacing a part or all of the parts constituting the gas wiping nozzle. 
     However, since the fixing member in the gas wiping nozzle described in JP &#39;159 and the bolt used to fix the fixing member are made of metal, there is a problem that the fixing member, the bolt or the like extends in a high temperature atmosphere, which changes the slit gap, and the gap of the slit cannot be uniformly held along the length direction of the slit. 
     Therefore, it could be helpful to provide a gas wiping nozzle capable of uniformly holding a gap in the width direction orthogonal to the length direction of a slit as a gas blowing port along the length direction of the slit even in a high temperature atmosphere, and a method of manufacturing a hot-dip metal coated metal strip using the gas wiping nozzle. 
     SUMMARY 
     We thus provide a gas wiping nozzle configured to blow wiping gas onto a metal strip pulled up from a molten metal bath and adjust an amount of a molten metal coated to a surface of the metal strip, the gas wiping nozzle including: a first nozzle member and a second nozzle member provided to face each other, in which a slit as a gas blowing port is formed to extend in a length direction between end portions of the first nozzle member and the second nozzle member on the metal strip side; and a shim member configured to adjust a gap of the slit in a width direction orthogonal to the length direction, in which the shim member is made of a ceramic material or a carbon material, each of the first nozzle member and the second nozzle member has a groove portion, and the shim member is fitted into both of the groove portions of the first nozzle member and the second nozzle member and fixes the first nozzle member and the second nozzle member. 
     We also provide a method of manufacturing a hot-dip metal coated metal strip, the method including: disposing a pair of the gas wiping nozzles described above on both surface sides of a metal strip pulled up from a molten metal bath; blowing wiping gas from each slit of the pair of gas wiping nozzles to each surface of the metal strip to adjust an amount of molten metal coated to both surfaces of the metal strip; and continuously manufacturing a hot-dip metal coated metal strip. 
     According to our gas wiping nozzle and the method of manufacturing the hot-dip metal coated metal strip, it is possible to provide the gas wiping nozzle capable of uniformly holding the gap in the width direction orthogonal to the length direction of the slit as the gas blowing port along the length direction of the slit even in a high temperature atmosphere, and the method of manufacturing the hot-dip metal coated metal strip using the gas wiping nozzle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic view illustrating a schematic configuration of continuous hot-dip metal coating equipment provided with a gas wiping nozzle according to an example. 
         FIG.  2    is a perspective view illustrating a schematic configuration of the gas wiping nozzle used in the continuous hot-dip metal coating equipment illustrated in  FIG.  1   . 
         FIG.  3    is a cross-sectional view taken along line A-A in  FIG.  2   . 
         FIG.  4    is a cross-sectional view taken along line B-B in  FIG.  3   . 
         FIG.  5    is an enlarged view illustrating a vicinity of a groove portion of a first nozzle member, a groove portion of a second nozzle member, and a shim member in  FIG.  4   . 
         FIG.  6    is a view similar to  FIG.  4    that shows a modification example of a groove portion of a first nozzle member, a groove portion of a second nozzle member, and a shim member. 
         FIG.  7    is an enlarged view illustrating a vicinity of the groove portion of the first nozzle member, the groove portion of the second nozzle member, and the shim member in  FIG.  6   . 
         FIG.  8    is a view similar to  FIG.  4    that shows an example in which a pin is used to connect the groove portion of the first nozzle member and the shim member and connecting the groove portion of the second nozzle member and the shim member. 
         FIG.  9    is an enlarged view illustrating a vicinity of the groove portion of the first nozzle member, the groove portion of the second nozzle member, the shim member, and the pin in  FIG.  8   . 
         FIG.  10    is a view similar to  FIG.  4    that shows a Comparative Example. 
     
    
    
     REFERENCE SIGNS LIST 
     
         
           1  continuous hot-dip metal coating equipment 
           2  snout 
           3  coating tank 
           4  molten metal bath 
           5  sink roll 
           6  support roll 
           10  gas wiping nozzle 
           11  first nozzle member 
           11   a  front end surface 
           11   b  rear end surface 
           11   c  end portion 
           11   d  side surface 
           12  second nozzle member 
           12   a  front end surface 
           12   b  rear end surface 
           12   c  end portion 
           12   d  side surface 
           13  hollow portion 
           13   a  hollow portion forming space 
           13   b  hollow portion forming space 
           13   c  hollow portion forming space 
           14  slit 
           15  nozzle header 
           16  gas supply path 
           17  gas supply pipe 
           21  groove portion of first nozzle member 
           21   a  linear portion 
           21   b  dovetail-shaped portion 
           21   c  corner portion 
           22  groove portion of second nozzle member 
           22   a  linear portion 
           22   b  dovetail-shaped portion 
           22   c  corner portion 
           23  mating surface 
           30  shim member 
           31  first fitting portion 
           31   a  inclined surface 
           32  second fitting portion 
           32   a  inclined surface 
           41  groove portion of first nozzle member 
           41   a  first linear portion 
           41   b  second linear portion 
           41   c  corner portion 
           42  groove portion of second nozzle member 
           42   a  first linear portion 
           42   b  second linear portion 
           42   c  corner portion 
           50  shim member 
           51  first fitting portion 
           51   a  lower surface 
           52  second fitting portion 
           52   a  upper surface 
           61  groove portion of first nozzle member 
           61   a  corner portion 
           62  groove portion of second nozzle member 
           62   a  corner portion 
           70  shim member 
           71  pin 
           81  groove portion of first nozzle member 
           82  groove portion of second nozzle member 
           90  shim member 
           91  metal bolt 
         L 1  slit length 
         L 2  slit depth 
         L 3  slit width (gap of slit) 
         S steel strip (metal strip) 
         X length direction of slit (width direction of steel strip) 
         Y depth direction of slit (sheet thickness direction of steel strip) 
         Z width direction of slit (sheet length direction of steel strip) 
       
    
     DETAILED DESCRIPTION 
     Hereinafter, examples of our nozzles and methods will be now described with reference to the drawings. The examples illustrated below represent devices and methods embodying our technical ideas, and the technical ideas do not specify the material, shape, structure, arrangement, and the like of the component parts in the following examples. 
     In addition, the drawings are schematic. Therefore, a relationship, ratio and the like between a thickness and a plane dimension are different from the actual ones, and there are parts where the relationship and ratio of the dimensions are different between the drawings. 
       FIG.  1    illustrates a schematic configuration of continuous hot-dip metal coating equipment provided with a gas wiping nozzle according to an example. 
     The continuous hot-dip metal coating equipment  1  illustrated in  FIG.  1    is equipment that continuously coats molten metal to the surface of a steel strip S as a metal strip by immersing the steel strip S in a molten metal bath  4  made of the molten metal, and then bringing the molten metal into a predetermined amount of coating. 
     The continuous hot-dip metal coating equipment  1  includes a snout  2 , a coating tank  3 , a sink roll  5 , and a support roll  6 . 
     The snout  2  is a member having a rectangular cross section perpendicular to the traveling direction of the steel strip S, which partitions a space through which the steel strip S passes. The upper end of the snout  2  is connected to, for example, the outlet side of a continuous annealing furnace, and the lower end is immersed in the molten metal bath  4  stored in the coating tank  3 . The steel strip S annealed in the continuous annealing furnace in a reducing atmosphere passes through the snout  2  and is continuously introduced into the molten metal bath  4  in the coating tank  3 . Thereafter, the steel strip S is pulled upward from the molten metal bath  4  via the sink roll  5  and the support roll  6  in the molten metal bath  4 . 
     Wiping gas is blown onto both surfaces of the steel strip S pulled upward from the molten metal bath  4  from a pair of gas wiping nozzles  10  (slits  14  described later) disposed on both surface sides of the steel strip S and the amount of molten metal coated to both surfaces of the steel strip S is adjusted. Thereafter, the steel strip S is cooled by cooling equipment (not illustrated) and guided to a subsequent step, and the hot-dip metal coated steel strip S is continuously manufactured. 
     Each of the pair of gas wiping nozzles  10  disposed on both surface sides of the steel strip S includes a nozzle header  15  and a first nozzle member  11  disposed on the upper side and a second nozzle member  12  disposed on the lower side that are connected to the nozzle header  15  as illustrated in  FIG.  2   . The first nozzle member  11  and the second nozzle member  12  are provided to face each other, and the slit  14  as a gas blowing port is formed to extend elongated in the length direction X between the end portions  11   c  and  12   c , on the steel strip S side, of the first nozzle member  11  and the second nozzle member  12 . Each gas wiping nozzle  10  is disposed on each surface side of the steel strip S so that the length direction X of the slit  14  is along the sheet width direction of the steel strip S, the width direction Z orthogonal to the length direction X of the slit  14  is along the sheet length direction of the steel strip S, and the depth direction Y of the slit  14  is along the sheet thickness direction of the steel strip S. The width direction Z of the slit is the same as the vertical direction of the gas wiping nozzle  10 . The wiping gas is blown from the slit  14  toward one surface of the steel strip S from one of the gas wiping nozzles  10 . In addition, the wiping gas is blown from the slit  14  toward the other surface of the steel strip S from the other gas wiping nozzle  10 . As a result, excess molten metal is scraped off on both surfaces of the steel strip S, the amount of coating (molten metal) is adjusted, and the amount of coating is made uniform in the sheet width direction and the sheet length direction of the steel strip S. To correspond to various sheet widths of steel strip S and cope with displacement in the width direction when the steel strip S is pulled up, each gas wiping nozzle  10  is configured to be longer than the sheet width of steel strip S so that the length of the slit  14  is longer than the sheet width of steel strip S, and extends outward from an end portion of the steel strip S in the width direction. 
     The nozzle header  15  of each gas wiping nozzle  10  is formed in a substantially rectangular shape extending in the length direction X, the depth direction Y, and the width direction Z, and the material thereof is a metal such as chrome molybdenum steel, for example. As illustrated in  FIG.  3   , the nozzle header  15  is formed so that a hollow portion forming space  13   c  constituting a hollow portion  13  described later opens on the front surface thereof (left surface in  FIG.  3   ). A gas supply pipe  17  is connected to the base end portion (rear end portion) of the nozzle header  15 , and a gas supply path  16  that connects the gas supply pipe  17  and the hollow portion forming space  13   c  is formed in the base end portion of the nozzle header  15 . 
     In addition, as illustrated in  FIGS.  2  and  3   , the sheet thickness of the first nozzle member  11  disposed on the upper side gradually decreases from a rear end surface  11   b  toward a front end surface  11   a , and the first nozzle member  11  is formed in a rectangular shape extending in the length direction X and the depth direction Y when viewed from above (upper side in  FIG.  3   ). On the lower surface of the first nozzle member  11 , a hollow portion forming space  13   a  constituting the hollow portion  13  described later is formed to taper from the rear side to the front side. 
     In addition, as illustrated in  FIGS.  2  and  3   , the sheet thickness of the second nozzle member  12  disposed on the lower side gradually decreases from a rear end surface  12   b  toward a front end surface  12   a , and the second nozzle member  12  is formed in a rectangular shape extending in the length direction X and the depth direction Y when viewed from below (lower side in  FIG.  3   ). On the upper surface of the second nozzle member  12 , a hollow portion forming space  13   b  constituting the hollow portion  13  described later is formed to taper from the rear side to the front side. 
     The first nozzle member  11  and the second nozzle member  12  are vertically aligned and fixed, and each of the rear end surface  11   b  of the first nozzle member  11  and the rear end surface  12   b  of the second nozzle member  12  is connected to the front surface of the nozzle header  15 . As a result, the hollow portion  13  is formed to include the hollow portion forming space  13   c  formed in the nozzle header  15 , the hollow portion forming space  13   a  formed in the first nozzle member  11 , and the hollow portion forming space  13   b  formed in the second nozzle member  12 . The lower surface of the end portion  11   c  of the first nozzle member  11  on the steel strip S side and the upper surface of the end portion  12   c  of the second nozzle member  12  on the steel strip S side are opposite planes, and the space between these planes is the slit  14  as the gas blowing port described above. As described above, the slit  14  is elongated in the length direction X, the length of the length direction X is L 1  as shown in  FIG.  2   , the width in the width direction Z orthogonal to the length direction X, that is, the gap is L 3  as shown in  FIG.  3   , and the depth of the depth direction Y orthogonal to the length direction X is L 2  as shown in  FIG.  3   . Although the size of the slit  14  is not particularly limited, the length L 1  of the slit  14  is set with a margin according to the width of the steel strip S, and can be set to, for example, approximately 1500 to 2500 mm. In addition, the gap L 3  of the slit  14  can be set to, for example, approximately 0.5 to 3.0 mm. Furthermore, the depth L 2  of the slit  14  can be set to, for example, approximately 5 to 30 mm. 
     The slit  14  communicates with the hollow portion  13  in the depth direction Y. The hollow portion  13  functions as a pressure equalizing portion, and the wiping gas introduced into the hollow portion  13  from the gas supply pipe  17  via the gas supply path  16  is blown at a uniform pressure over the entire length direction X of the slit  14 . 
     In addition, as illustrated in  FIGS.  4  and  5   , each gas wiping nozzle  10  includes a pair of shim members  30  for adjusting the gap L 3  in the width direction Z orthogonal to the length direction X of the slit  14 . 
     These shim members  30  also have a function of fixing the first nozzle member  11  and the second nozzle member  12 . To fix the first nozzle member  11  and the second nozzle member  12  by the shim members  30 , the first nozzle member  11  and the second nozzle member  12  respectively have groove portions  21  and  22  into which these shim members  30  are fitted. 
     As illustrated in  FIGS.  3  and  4   , a pair of groove portions  21  of the first nozzle member  11  are formed on both sides of the hollow portion forming space  13   a  in the length direction X. Each groove portion  21  extends forward over a length  1  from the rear end surface  11   b  of the first nozzle member  11  to open on the lower surface of the first nozzle member  11 , that is, a mating surface  23  with the second nozzle member  12 . 
     In addition, as illustrated in  FIGS.  3  and  4   , a pair of groove portions  22  of the second nozzle member  12  are also formed on both sides of the hollow portion forming space  13   b  in the length direction X. Each groove portion  22  extends forward over the length  1  from the rear end surface  12   b  of the second nozzle member  12  to open on the upper surface of the second nozzle member  12 , that is, the mating surface  23  with the first nozzle member  11 . The length  1  of the groove portions  21  and  22  is approximately 5 mm, and the length  1  is not limited thereto. 
     As illustrated in  FIG.  5   , the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  communicate with each other on the mating surface  23  of the first nozzle member  11  and the second nozzle member  12 , and are plane-symmetrical with the mating surface  23  as a plane of symmetry. 
     The cross-sectional shape of each of the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  is a dovetail groove shape as illustrated in  FIG.  5   . Specifically, the groove portion  21  of the first nozzle member  11  includes a linear portion  21   a  that opens on the mating surface  23  and extends linearly upward from the mating surface  23 , and an inverted trapezoidal shaped dovetail-shaped portion  21   b  extending upward from the upper end of the linear portion  21   a  to gradually widen. In addition, the groove portion  22  of the second nozzle member  12  includes a linear portion  22   a  that opens on the mating surface  23  and extends linearly downward from the mating surface  23 , and a trapezoidal shaped dovetail-shaped portion  22   b  extending downward from the lower end of the linear portion  22   a  to gradually widen. A corner portion  21   c  in the groove portion  21  and a corner portion  22   c  in the groove portion  22  may be formed in a rounded shape. As a result, stress concentration can be prevented and damage to the shim member  30  can be suppressed. 
     In addition, as illustrated in  FIG.  3   , each of the pair of shim members  30  is fitted into a pair of groove portions  21  and  22  formed on both sides of the hollow portion  13 , and fixes the first nozzle member  11  and the second nozzle member  12 . As illustrated in  FIG.  5   , the cross-sectional shape of each shim member  30  is complementary to a shape obtained by combining the dovetail groove shape of the groove portion  21  of the first nozzle member  11  and the dovetail groove shape of the groove portion  22  of the second nozzle member  12 , which are plane-symmetrical with each other. Each shim member  30  includes a first fitting portion  31  fitted into the groove portion  21  of the first nozzle member  11 , and a second fitting portion  32  fitted into the groove portion  22  of the second nozzle member  12 , and the first fitting portion  31  and the second fitting portion  32  are integrally formed. 
     As illustrated in  FIG.  5   , the width A 1  of a narrowest portion (joint portion of the first fitting portion  31  and the second fitting portion  32 ) of each shim member  30  corresponding to the width of the linear portions  21   a  and  22   a  of the groove portions  21  and  22  is approximately 3 to 20 mm. In addition, the width A 2  of the widest portion (upper side of the first fitting portion  31  and lower piece of the second fitting portion  32 ) of each shim member  30  corresponding to the width of the widest portion of the dovetail-shaped portions  21   b  and  22   b  of the groove portions  21  and  22  is approximately 5 to 30 mm. In addition, the length A 3  of the linear portion of each shim member  30  corresponding to the vertically combined length of the linear portions  21   a  and  22   a  of the groove portions  21  and  22  is approximately 0 to 15 mm, and the height A 4  of each shim member  30  corresponding to the total vertical length of the groove portions  21  and  22  is approximately 10 to 40 mm. However, A 1 &lt;A 2  and A 3 &lt;A 4  are set. The length of each shim member  30  in the front-rear direction corresponding to the length  1  of the groove portions  21  and  22  in the front-rear direction is approximately 5 mm. 
     The shim member  30  is attachable to and detachable from each of the groove portions  21  and  22  in a direction parallel to the extending direction (front-rear direction) of each of the groove portions  21  and  22  of the first nozzle member  11  and the second nozzle member  12  from the rear end surface  11   b  of the first nozzle member  11  and the rear end surface  12   b  of the second nozzle member  12 . 
     The first nozzle member  11 , the second nozzle member  12 , and each shim member  30  are made of a ceramic material or carbon material having low wettability with respect to molten metal such as hot-dip zinc, being hard to be plastically deformed, and having a low coefficient of linear expansion. Specifically, examples of the ceramic material include alumina, sialon, silicon nitride, zirconia, barium titanate, hydroxyapatite, silicon carbide (SiC), and fluorite, examples of the carbon material includes graphite, and the material is not limited thereto. In addition, since graphite oxidizes and volatilizes in a highly oxidizing atmosphere, it is preferable to coat the surface layer with silica or the like. 
     Since invar or tungsten has a low coefficient of linear expansion, but are plastically deformed, invar or tungsten is not suitable as a material for the first nozzle member  11 , the second nozzle member  12 , and each shim member  30 , in particular, as a material for each shim member  30 . 
     As the ceramic material or carbon material, those having a bending strength of 600 MPa or more are preferable, and those having a bending strength of 800 MPa or more are more preferable. Therefore, it is preferable to use zirconia, silicon nitride, sialon or the like as the ceramic material. When these materials are used, it is hard to be plastically deformed, and when an applied strength is equal to or lower than fracture strengths of these materials, substantial deformation can be suppressed. 
     When zinc adheres to the first nozzle member  11  and/or the second nozzle member  12  and closes the slit  14  during the operation of the actual machine, the amount of the coating to the steel strip S partially increases at that location, and linear defects occur in the same direction as the traveling direction of the steel strip S. Therefore, the zinc adhered to the first nozzle member  11  and/or the second nozzle member  12  is removed by a dedicated jig. At this time, when the hardness of the surfaces of the first nozzle member  11  and the second nozzle member  12  is low, cracks or chips may occur. To avoid such cracks and chips, the ceramic material and carbon material used for the first nozzle member  11 , the second nozzle member  12 , and each shim member  30  preferably have a Vickers hardness of 800 HV or more, and more preferably 1000 HV or more. For the same reason, a fracture toughness of the ceramic material or carbon material is preferably 5 MPa·m 1/2  or more, and more preferably 7 MPa·m 1/2  or more. 
     When a high-temperature gas is used as the wiping gas, cracks may occur when a thermal shock resistance of each of the first nozzle member  11  and the second nozzle member  12  is the high-temperature gas or less. Therefore, the thermal shock resistance of the ceramic material or carbon material is preferably the temperature or higher used as the wiping gas, the thermal shock resistance is preferably 430° C. or higher, and more preferably 600° C. or higher. 
     From the viewpoint of suppressing nozzle deformation due to thermal influence, the coefficient of linear expansion of the first nozzle member  11  and the second nozzle member  12  is preferably ½ or less, and more preferably ⅓ or less, with respect to the coefficient of linear expansion of the nozzle header  15  to which the first nozzle member  11  and the second nozzle member  12  are fixed. 
     Next, when a method of fixing the first nozzle member  11  and the second nozzle member  12  is described, first, the members are combined vertically with the first nozzle member  11  on the upper side and the second nozzle member  12  on the lower side. 
     Next, the first nozzle member  11  and the second nozzle member  12  are each subjected to dovetail groove processing from the rear end surfaces  11   b  and  12   b  to form the groove portions  21  and  22 . 
     Thereafter, the shim member  30  is fitted into both of the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  in a direction parallel to the direction where the groove portions  21  and  22  extend from the rear end surfaces  11   b  and  12   b  of the first nozzle member  11  and the second nozzle member  12 . 
     As a result, the first nozzle member  11  and the second nozzle member  12  are fixed. In a state where the shim member  30  is fitted into both of the groove portion  21  and the groove portion  22  as illustrated in  FIG.  5   , the first fitting portion  31  of the shim member  30  is fitted into the groove portion  21 , and the second fitting portion  32  is fitted into the groove portion  22 . In this state, when the first nozzle member  11  and the second nozzle member  12  tend to separate vertically, the first nozzle member  11  is caught on an inclined surface  31   a  of the first fitting portion  31  having a shape complementary to the inclined surface of the dovetail-shaped portion  21   b  of the groove portion  21 . On the other hand, the second nozzle member  12  is caught on an inclined surface  32   a  of the second fitting portion  32  having a shape complementary to the inclined surface of the dovetail-shaped portion  22   b  of the groove portion  22 . Since the shim member  30  is made of a material that is not easily plastically deformed, the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically. Since the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically, the gap L 3  of the slit  14  formed between the end portions  11   c  and  12   c  of the first nozzle member  11  and the second nozzle member  12  on the steel strip S side is held. 
     The rear end surface  11   b  of the fixed first nozzle member  11  and the rear end surface  12   b  of the fixed second nozzle member  12  may be connected to the front end surface of the nozzle header  15  by a fixing member such as a screw (not illustrated). 
     The step of forming the groove portions  21  and  22  by performing dovetail groove processing on the first nozzle member  11  and the second nozzle member  12  may be performed before combining the first nozzle member  11  on the upper side and the second nozzle member  12  on the lower side vertically. The first nozzle member  11  in which the groove portion  21  is formed and the second nozzle member  12  in which the groove portion  22  is formed are vertically combined so that the groove portion  21  and the groove portion  22  are plane-symmetrical. Thereafter, the shim member  30  is fitted in the direction parallel to the direction where the groove portions  21  and  22  extend from the rear end surfaces  11   b  and  12   b  of the first nozzle member  11  and the second nozzle member  12 . When the first nozzle member  11  in which the groove portion  21  is formed and the second nozzle member  12  in which the groove portion  22  is formed are vertically combined so that the groove portion  21  and the groove portion  22  are plane-symmetrical, the accuracy of the groove portions  21  and  22  may be confirmed, and then the first nozzle member  11  and the second nozzle member  12  may be disassembled to be combined after the groove portions  21  and  22  are reprocessed. Alternatively, after combining the first nozzle member  11  in which the groove portion  21  is formed and the second nozzle member  12  in which the groove portion  22  is formed vertically so that the groove portion  21  and the groove portion  22  are plane-symmetrical, the groove portions  21  and  22  may be subjected to processing such as polishing to finish to a predetermined size. 
     When the gas wiping nozzle  10  is placed in a high temperature atmosphere, for example, when the wiping gas is heated and the gas wiping nozzle  10  itself is also heated with the heating of the wiping gas, the metal nozzle header  15  tends to extend in the vertical direction, that is, in the width direction Z of the slit  14  due to thermal expansion. As a result, the rear end surface  11   b  of the first nozzle member  11  and the second nozzle member  12  are also pulled by the metal nozzle header  15  and tend to separate from each other vertically. However, the first nozzle member  11  is caught on the inclined surface  31   a  of the first fitting portion  31  having a shape complementary to the inclined surface of the dovetail-shaped portion  21   b  of the groove portion  21 . On the other hand, the second nozzle member  12  is caught on the inclined surface  32   a  of the second fitting portion  32  having a shape complementary to the inclined surface of the dovetail-shaped portion  22   b  of the groove portion  22 . Since the shim member  30  is made of a material that is not easily plastically deformed, the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically. Since the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically, the gap L 3  of the slit  14  formed between the end portions  11   c  and  12   c  of the first nozzle member  11  and the second nozzle member  12  on the steel strip S side is held. 
     In addition, in the gas wiping nozzle  10  according to this example, since the first nozzle member  11 , the second nozzle member  12 , and the shim member  30  are all made of ceramic materials or carbon materials, the coefficient of linear expansion is small and there is no difference in the coefficient of linear expansion between these members. Therefore, even in a high temperature atmosphere, the gap L 3  in the width direction orthogonal to the length direction X of the slit  14  as the gas blowing port can be uniformly held along the length direction X of the slit. In particular, since the sheet thickness of each of the first nozzle member  11  and the second nozzle member  12  decreases from the rear side to the front side and there is a difference in sheet thickness, even when the same amount of heat is applied, the amount of temperature rise differs. Therefore, it is effective to use a ceramic material or carbon material with a small coefficient of linear expansion. 
     When the nozzle header  15  is also made of a ceramic material or a carbon material, it is more effective to uniformly hold the gap L 3  of the slit  14 , but since it is difficult to use a ceramic material or carbon material that can withstand high-pressure wiping gas (can withstand at least 60 kPa), the nozzle header  15  is not made of a ceramic material or carbon material. 
     In addition, in the gas wiping nozzle described in JP &#39;159, since the first lip portion and the second lip portion are fixed on the slit side in the nozzle chamber by the fixing member, it is possible to suppress variations in the slit gap after assembly for each assembly when replacing a part or all of the parts constituting the gas wiping nozzle. 
     However, since the fixing member for fixing the upper and lower nozzle members in the gas wiping nozzle described in JP &#39;159 and the bolt used to fix the fixing member are made of metal, there is a problem that the fixing member, the bolt or the like extends in a high temperature atmosphere, which changes the slit gap, and the gap of the slit cannot be uniformly held along the length direction of the slit. 
     On the other hand, in our gas wiping nozzle  10 , not only the first nozzle member  11  and the second nozzle member  12  are made of a ceramic material or a carbon material, but also the shim member  30  is made of a ceramic material or a carbon material and, furthermore, the shim member  30  also has a function of fixing the first nozzle member  11  and the second nozzle member  12 . Therefore, there is no member that fixes the first nozzle member  11  and the second nozzle member  12  that acts to widen the gap L 3  of the slit  14  in a high temperature atmosphere. Since the shim member  30  is made of a material that is not easily plastically deformed, the gap L 3  of the slit  14  as the gas blowing port can be uniformly held along the length direction X of the slit even in a high temperature atmosphere. 
     In a configuration assuming that the shim member  30  does not have the function of fixing the first nozzle member  11  and the second nozzle member  12 , and the first nozzle member  11  and the second nozzle member  12  that are made of ceramic materials are fixed by metal bolts, it is necessary to make bolt holes in the first nozzle member  11  and the second nozzle member  12  made of the ceramic materials and close the metal bolts in the bolt holes. Thus, the first nozzle member  11  and the second nozzle member  12 , which are made of ceramic materials, may be damaged by the torque when the metal bolt is tightened or thermal expansion of the metal bolt. 
     On the other hand, in our gas wiping nozzle  10 , not only the first nozzle member  11  and the second nozzle member  12  are made of a ceramic material or a carbon material, but also the shim member  30  is made of a ceramic material or a carbon material and, furthermore, the shim member  30  also has a function of fixing the first nozzle member  11  and the second nozzle member  12 . Therefore, the first nozzle member  11  and the second nozzle member  12  are not damaged by the torque when the metal bolt is tightened or thermal expansion of the metal bolt. 
     Next, a modification example of the groove portion of the first nozzle member, the groove portion of the second nozzle member, and the shim member will be described with reference to  FIGS.  6  and  7   . 
     The basic configuration of a groove portion  41  of the first nozzle member  11  and a groove portion  42  of the second nozzle member  12  illustrated in  FIGS.  6  and  7    is the same as that of the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  illustrated in  FIGS.  3  to  5   . However, the cross-sectional shapes of the groove portion  41  of the first nozzle member  11  and the groove portion  42  of the second nozzle member  12  are different from the cross-sectional shapes of the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  illustrated in  FIGS.  3  to  5   . With this difference in cross-sectional shape, the cross-sectional shape of a shim member  50  illustrated in  FIGS.  6  and  7    is also different from the cross-sectional shape of the shim member  30  illustrated in  FIGS.  3  to  5   . 
     That is, the cross-sectional shape of each of the groove portion  41  of the first nozzle member  11  and the groove portion  42  of the second nozzle member  12  illustrated in  FIGS.  6  and  7    is T-shaped groove shape. Specifically, the groove portion  41  of the first nozzle member  11  includes a first linear portion  41   a  that opens on the mating surface  23  and extends linearly upward from the mating surface  23 , and a second linear portion  41   b  that extends symmetrically from the upper end of the first linear portion  41   a  with the first linear portion  41   a  interposed in parallel with the mating surface  23 . In addition, the groove portion  42  of the second nozzle member  12  includes a first linear portion  42   a  that opens on the mating surface  23  and extends linearly downward from the mating surface  23 , and a second linear portion  42   b  that extends symmetrically from the lower end of the first linear portion  42   a  with the first linear portion  42   a  interposed in parallel with the mating surface  23 . A corner portion  41   c  in the groove portion  41  and a corner portion  42   c  in the groove portion  42  may be formed in a rounded shape. As a result, stress concentration can be prevented and damage to the shim member  50  can be suppressed. 
     The groove portion  41  of the first nozzle member  11  extends forward from the rear end surface  11   b  as shown in FIGS. 1 and 2 of the first nozzle member  11  over the length  1 . In addition, the groove portion  42  of the second nozzle member  12  also extends forward from the rear end surface  12   b  as shown in FIGS. 1 and 2 of the second nozzle member  12  over the length  1 . In this example, the length  1  of the groove portions  41  and  42  in the front-rear direction is approximately 5 mm. 
     In addition, as illustrated in  FIG.  6   , the cross-sectional shape of the shim member  50  is complementary to an I-shaped groove shape obtained by combining the T-shaped groove shape of the groove portion  41  of the first nozzle member  11  and the T-shaped groove shape of the groove portion  42  of the second nozzle member  12 , which are plane-symmetrical with each other. As illustrated in  FIG.  7   , the shim member  50  includes a first fitting portion  51  fitted into the groove portion  41  of the first nozzle member  11  and a second fitting portion  52  fitted into the groove portion  42  of the second nozzle member  12 , and the first fitting portion  51  and the second fitting portion  52  are integrally formed. 
     As illustrated in  FIG.  7   , the width B 1  of a narrowest portion of the shim member  50  corresponding to the width of the first linear portions  41   a  and  42   a  of the groove portions  41  and  42  is approximately 3 to 20 mm, and the width B 2  of a widest portion of the shim member  50  (upper side of the first fitting portion  51  and lower piece of the second fitting portion  52 ) corresponding to the width of a widest portion of the second linear portions  41   b  and  42   b  of the groove portions  41  and  42  is approximately 5 to 30 mm. In addition, the length B 3  of the linear portion of the shim member  50  corresponding to the vertically combined length of the first linear portions  41   a  and  42   a  of the groove portions  41  and  42  is approximately 5 to 50 mm, and the height B 4  of the shim member  50  corresponding to the total vertical length of the groove portions  41  and  42  is approximately 10 to 40 mm. However, B 1 &lt;B 2  and B 3 &lt;B 4  are set. The length of the shim member  50  in the front-rear direction corresponding to the length  1  of the groove portions  41  and  42  in the front-rear direction is approximately 5 mm. 
     In a state where the shim member  50  is fitted into both of the groove portion  41  and the groove portion  42  as illustrated in  FIG.  7   , the first fitting portion  51  of the shim member  50  is fitted into the groove portion  41 , and the second fitting portion  52  is fitted into the groove portion  42 . In this state, when the first nozzle member  11  and the second nozzle member  12  tend to separate vertically, the first nozzle member  11  is caught on a lower surface  51   a  of a wide portion of the first fitting portion  51  having a shape complementary to the second linear portion  41   b  of the groove portion  41 . On the other hand, the second nozzle member  12  is caught on an upper surface  52   a  of a wide portion of the second fitting portion  52  having a shape complementary to the second linear portion  42   b  of the groove portion  42 . Since the shim member  50  is made of a material that is not easily plastically deformed, the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically. Since the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically, the gap L 3  of the slit  14  formed between the end portions  11   c  and  12   c  of the first nozzle member  11  and the second nozzle member  12  on the steel strip S side is held. 
     When the gas wiping nozzle  10  illustrated in  FIGS.  6  and  7    is placed in a high temperature atmosphere, for example, when the wiping gas is heated and the gas wiping nozzle  10  itself is also heated with the heating of the wiping gas, the metal nozzle header  15  as shown in  FIGS.  1  and  2    tends to extend in the vertical direction, that is, in the width direction Z of the slit  14  due to thermal expansion. As a result, the rear end surface  11   b  of the first nozzle member  11  and the second nozzle member  12  are also pulled by the metal nozzle header  15  and tend to separate from each other vertically. However, the first nozzle member  11  is caught on the lower surface  51   a  of the wide portion of the first fitting portion  51  having a shape complementary to the second linear portion  41   b  of the groove portion  41 . On the other hand, the second nozzle member  12  is caught on the upper surface  52   a  of a wide portion of the second fitting portion  52  having a shape complementary to the second linear portion  42   b  of the groove portion  42 . Since the shim member  50  is made of a material that is not easily plastically deformed, the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically. Since the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically, the gap L 3  of the slit  14  formed between the end portions  11   c  and  12   c  of the first nozzle member  11  and the second nozzle member  12  on the steel strip S side is held. 
     Since the shim member  50  is made of a ceramic material or a carbon material as well as the first nozzle member  11  and the second nozzle member  12 , and also has a function of fixing the first nozzle member  11  and the second nozzle member  12 , the shim member  50  exhibits the same effect as when the groove portions  21  and  22  and the shim member  30  illustrated in  FIGS.  3  to  5    are used. 
     Next, an example in which a pin is used to connect the groove portion of the first nozzle member and the shim member and connect the groove portion of the second nozzle member and the shim member will be described with reference to  FIGS.  8  and  9   . 
     First, the basic configuration of a groove portion  61  of the first nozzle member  11  and a groove portion  62  of the second nozzle member  12  illustrated in  FIGS.  8  and  9    is the same as that of the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  illustrated in  FIGS.  3  to  5   . However, the cross-sectional shapes of the groove portion  61  of the first nozzle member  11  and the groove portion  62  of the second nozzle member  12  are different from the cross-sectional shapes of the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  illustrated in  FIGS.  3  to  5   . With this difference in cross-sectional shape, the cross-sectional shape of a shim member  70  illustrated in  FIGS.  8  and  9    is also different from the cross-sectional shape of the shim member  30  illustrated in  FIGS.  3  to  5   . 
     The cross-sectional shape of each of the groove portion  61  of the first nozzle member  11  and the groove portion  62  of the second nozzle member  12  illustrated in  FIGS.  8  and  9    is a rectangular shape. The groove portion  61  of the first nozzle member  11  extends forward from the rear end surface  11   b  as shown in FIGS. 1 and 2 of the first nozzle member  11  over the length  1 . In addition, the groove portion  62  of the second nozzle member  12  also extends forward from the rear end surface  12   b  as shown in FIGS. 1 and 2 of the second nozzle member  12  over the length  1 . In this example, the length  1  of the groove portions  41  and  42  in the front-rear direction is approximately 5 mm. In addition, a corner portion  61   c  in the groove portion  61  and a corner portion  62   c  in the groove portion  62  may be formed in a rounded shape. As a result, stress concentration can be prevented and damage to the shim member  70  can be suppressed. 
     In addition, the shim member  70  has a rectangular parallelepiped shape and, as illustrated in  FIG.  9   , the cross-sectional shape thereof is complementary to a rectangular shape obtained by combining the rectangular shape of the groove portion  61  of the first nozzle member  11  and the rectangular shape of the groove portion  62  of the second nozzle member  12 , which are plane-symmetrical with each other. As illustrated in  FIG.  9   , the width C 1  of the shim member  70  corresponding to the width of the groove portions  61  and  62  is approximately 5 to 20 mm, the height C 2  of the shim member  70  corresponding to the vertically combined length of the groove portions  61  and  62  is approximately 5 to 40 mm, and the length of the shim member  70  in the front-rear direction corresponding to the length  1  of the groove portions  61  and  62  in the front-rear direction as shown in  FIG.  3    is approximately 5 mm. 
     When fixing the first nozzle member  11  and the second nozzle member  12 , the shim member  70  is fitted into both of the groove portion  61  of the first nozzle member  11  and the groove portion  62  of the second nozzle member  12 . Furthermore, a plurality of pins  71  are used to connect the groove portion  61  of the first nozzle member  11  to the shim member  70 , and to connect the groove portion  62  of the second nozzle member  12  to the shim member  70 . As described above, in this example, the shim member  70  can be fitted before the first nozzle member  11  and the second nozzle member  12  are combined so that assembling is possible without inserting the shim member  70  into the groove portions  61  and  62  from the rear end surfaces  11   b  and  12   b  of the first nozzle member  11  and the second nozzle member  12 . Therefore, the shim member  70  may be provided at a plurality of locations in the depth direction Y of the first nozzle member  11  and the second nozzle member  12 . As a result, the gap L 3  of the slit  14  can be held with higher accuracy. 
     As illustrated in  FIG.  8   , as the pin  71 ,  a  total of four pins  71  are used, two pins used to connect the groove portion  61  of the first nozzle member  11  and the shim member  70 , and two pins used to connect the groove portion  62  of the second nozzle member  12  and the shim member  70 . When the shim member  70  is provided at a plurality of locations in the depth direction Y of the first nozzle member  11  and the second nozzle member  12 , the number of pins used may be increased according to the number of shim members  70 . 
     When connecting the groove portion  61  of the first nozzle member  11  and the shim member  70 , as illustrated in  FIGS.  8  and  9   , the pin  71  is inserted into the shim member  70  from the side surface  11   d  of the first nozzle member  11  to a predetermined depth C 3  after the shim member  70  is fitted into the groove portions  61  and  62 . Similarly, when connecting the groove portion  62  of the second nozzle member  12  to the shim member  70 , as illustrated in  FIGS.  8  and  9   , the pin  71  is inserted into the shim member  70  from the side surface  12   d  of the second nozzle member  12  to a predetermined depth C 3  after the shim member  70  is fitted into the groove portions  61  and  62 . 
     Each pin  71  is formed of a cylinder, and the diameter C 4  thereof is approximately Φ1 to 10 mm, and the insertion depth C 3  of the pin  71  is approximately 1 to 15 mm. However, the insertion depth C 3  of the pin  71 &lt;the width C 1  of the shim member  70 , and the diameter C 4  of the pin  71 &lt;the height C 2  of the shim member  70  are set. Similarly, as the material of each pin  71 , a ceramic material or a carbon material is preferable. In addition, the bending strength of each pin  71  is preferably 600 MPa or more, and more preferably 800 MPa or more. Therefore, it is preferable to use zirconia, silicon nitride, sialon or the like as the ceramic material. 
     When the gas wiping nozzle  10  illustrated in  FIGS.  8  and  9    is placed in a high temperature atmosphere, for example, when the wiping gas is heated and the gas wiping nozzle  10  itself is also heated with the heating of the wiping gas, the metal nozzle header  15  as shown in  FIGS.  1  and  2    tends to extend in the vertical direction, that is, in the width direction Z of the slit  14  due to thermal expansion. As a result, the rear end surface  11   b  of the first nozzle member  11  and the second nozzle member  12  are also pulled by the metal nozzle header  15  and tend to separate from each other vertically. However, since the first nozzle member  11  and the second nozzle member  12  are connected to the shim member  70  by the pin  71  and the shim member  70  is made of a material that is not easily plastically deformed, the first nozzle member  11  and the second nozzle member  12  do not separate vertically. Since the first nozzle member  11  and the second nozzle member  12  are not separated from each other vertically, the gap L 3  of the slit  14  formed between the end portions  11   c  and  12   c  of the first nozzle member  11  and the second nozzle member  12  on the steel strip S side is held. 
     Next, in the manufacturing of the steel strip S, it is preferable to control the temperature of the wiping gas so that the temperature T (° C.) of the wiping gas immediately after being blown from the slit  14  of the gas wiping nozzle  10  satisfies T M −150≤T≤T M +250 in relation to the melting point T M  (° C.) of the molten metal. When the temperature T (° C.) of the wiping gas is controlled in this range, cooling and solidification of the molten metal can be suppressed so that uneven viscosity is unlikely to occur and the occurrence of hot metal wrinkles can be suppressed. On the other hand, when the temperature T (° C.) of the wiping gas is less than T M −150° C. and is too low, the temperature T does not affect the fluidity of the molten metal and is not effective in suppressing the occurrence of hot metal wrinkles. In addition, when the temperature T (° C.) of the wiping gas is higher than T M +250° C., alloying is promoted and the appearance of the steel sheet is deteriorated. 
     In addition, a method of raising the temperature of the wiping gas supplied to the gas wiping nozzle  10  is not particularly limited. Examples thereof include a method of heating with a heat exchanger and raising the temperature to supply, and a method of mixing the combustion exhaust gas of the annealing furnace with air. 
     In addition, examples of the hot-dip metal coated metal strip manufactured by applying the gas wiping nozzle and the method of manufacturing the hot-dip metal coated metal strip include a hot-dip galvanized steel strip. The hot-dip galvanized steel strip includes both a coated steel sheet (GI) that is not subjected to an alloying treatment after the hot-dip galvanized treatment and a coated steel sheet (GA) that is subjected to the alloying treatment. However, the hot-dip metal coated metal strip manufactured by applying the gas wiping nozzle and the method of manufacturing the hot-dip metal coated metal strip is not limited thereto, and includes all hot-dip metal coated steel strips containing other molten metals such as aluminum and tin other than zinc. 
     Although examples of our nozzles and methods are described above, this disclosure is not limited thereto, and various modifications and improvements can be made. 
     For example, only the shim member may be made of a ceramic material or a carbon material, and it is not always necessary that the first nozzle member  11  and the second nozzle member  12  are made of a ceramic material or a carbon material. 
     In addition, although the first nozzle member  11 , the second nozzle member  12 , and the shim member are all made of a ceramic material or a carbon material, this is a concept that the first nozzle member  11 , the second nozzle member  12 , and the shim member may not all be made of the same material. However, it is preferable that the first nozzle member  11 , the second nozzle member  12 , and the shim member are all made of the same material. As a result, the difference in the coefficient of linear expansion between the first nozzle member  11 , the second nozzle member  12 , and the shim member can be surely eliminated. 
     In addition, as long as a shim member is fitted into each of the groove portions  21  and  41  of the first nozzle member  11  and the groove portions  22  and  42  of the second nozzle member  12 , and the first nozzle member  11  and the second nozzle member  12  can be fixed, the groove portions do not necessarily need to be plane-symmetrical with the mating surface  23  of the first nozzle member  11  and the second nozzle member  12  as a plane of symmetry. 
     In addition, as long as a shim member is fitted into each of the groove portions  21  and  41  of the first nozzle member  11  and the groove portions  22  and  42  of the second nozzle member  12 , and the first nozzle member  11  and the second nozzle member  12  can be fixed, the cross-sectional shape of the groove portions  21  and  41  of the first nozzle member  11  and the groove portions  22  and  42  of the second nozzle member  12  need not be a dovetail groove shape or a T-shaped groove shape. 
     In addition, as long as the shim member is fitted into each of the groove portions  21  and  41  of the first nozzle member  11  and the groove portions  22  and  42  of the second nozzle member  12 , and the first nozzle member  11  and the second nozzle member  12  can be fixed, the cross-sectional shape of the shim member need not be complementary to a shape obtained by combining the dovetail groove shape and T-shaped groove shape of the groove portions  21  and  41  of the first nozzle member  11 , and the dovetail groove shape and T-shaped groove shape of the groove portions  22  and  42  of the second nozzle member  12 , which are plane-symmetrical with each other. 
     In addition, the shim member is not limited to an aspect in which two shim members are provided as independent members in the length direction X. For example, as long as portions of the shim member are fitted into the groove portions of the first nozzle member  11  and the groove portion of the second nozzle member  12 , the shim member may be an integral member by providing a connecting portion for connecting the portions to be fitted into the groove portions of the nozzle members. 
     In addition, when the groove portion  61  of the first nozzle member  11  is connected to the shim member  70  and the groove portion  62  of the second nozzle member  12  is connected to the shim member  70  by using the pin  71 , the cross-sectional shape of the groove portions  61  and  62  is not limited to a rectangular shape, and may be a dovetail groove shape, a T-shaped groove shape, or another shape. In addition, the cross-sectional shape of the shim member  70  may be changed according to the cross-sectional shape of the groove portions  61  and  62 . In addition, the shape of the pin  71  does not need to be a cylinder, and may be a rectangular parallelepiped or another shape. 
     When a distance between the mating surfaces  23  of the first nozzle member  11  and the second nozzle member  12  changes, the wiping gas may leak from the mating surfaces  23 . Therefore, groove portions extending in the depth direction Y, which are separate from the groove portions  21  and  22 , may be formed in the first nozzle member  11  and the second nozzle member  12 , and a side wall (not illustrated) having a height of 5 to 10 mm and a length matching the mating surfaces  23  may be inserted into each of the groove portions to prevent gas leakage from the mating surfaces  23 . 
     The side wall that prevents leakage of the wiping gas from the mating surfaces  23  and the shim member may be the same member. In this example, the shim member is preferably set to a height of approximately 5 to 10 mm so that the height in the slit width direction Z is smaller toward the slit  14  side in the depth direction Y. In addition, in this example, it is preferable to match the length of the shim member in the front-rear direction with the length of the mating surfaces  23  in the depth direction Y to prevent gas leakage from the mating surfaces  23 . When the shim member also serves as a side wall, and the cross-sectional shape is rectangular, it is necessary to fix the shim member to the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  by using the pin  71 . 
     EXAMPLE 
     Using the continuous hot-dip metal coating equipment  1  having the basic configuration illustrated in  FIG.  1   , a hot-dip galvanized steel strip was manufactured by passing a steel strip S having a sheet thickness of 1.0 mm and a sheet width of 1200 mm into a hot-dip zinc bath at a sheet speed of 2.0 m/s. The dimensions of the slit  14  of the wiping nozzle  10  are 1800 mm for the length L 1 , 20 mm for the depth L 2 , and 1.2 mm for the width (gap) L 3 . In addition, the hot-dip galvanizing bath temperature at the time of the experiment was 460° C., and the gas temperature T at the tip end of the wiping nozzle was 500° C. As the wiping gas, a gas prepared by mixing the exhaust gas of the combustor and air was used. In addition, the melting point T M  of the hot-dip galvanizing bath is 420° C. 
     The bending strength of sialon described in the following Examples and Comparative Examples is 980 MPa, the Vickers hardness is 1620 HV, the fracture toughness is 6 MPa·m 1/2 , the thermal shock resistance is 650° C., and the coefficient of linear expansion is 3.2×10 −6 /K. In addition, the yield stress of chrome molybdenum steel is 400 MPa, the Vickers hardness is 300 HV, the fracture toughness is 236 MPa·m 1/2 , and the coefficient of linear expansion is 11.2×10 −6 /K. 
     Hereinafter, the materials and structures of the gas wiping nozzles of Examples 1 to 3 and Comparative Examples 1 and 2 will be described. 
     Example 1 
     In Example 1, the materials of the first nozzle member  11 , the second nozzle member  12 , and the shim member  30  were all sialon, and the material of the nozzle header  15  was chrome molybdenum steel. In addition, as illustrated in  FIGS.  4  and  5   , the cross-sectional shape of each of the groove portion  21  of the first nozzle member  11  and the groove portion  22  of the second nozzle member  12  was a dovetail groove shape, and the cross-sectional shape of the shim member  30  was complementary to a shape obtained by combining the dovetail groove shape of the groove portion  21  of the first nozzle member  11  and the dovetail groove shape of the groove portion  22  of the second nozzle member  12 , which were plane-symmetrical with each other. The width A 1  of the narrowest portion of the shim member  30  was 5 mm, the width A 2  of the widest portion of the shim member  30  was 15 mm, the length A 3  of the linear portion of the shim member  30  was 5 mm, the height A 4  of the shim member  30  was 20 mm, and the length of the shim member  30  in the front-rear direction was 5 mm. 
     Example 2 
     In Example 2, the materials of the first nozzle member  11 , the second nozzle member  12 , and the shim member  30  were all sialon, and the material of the nozzle header  15  was chrome molybdenum steel. In addition, as illustrated in  FIGS.  6  and  7   , the cross-sectional shape of each of the groove portion  41  of the first nozzle member  11  and the groove portion  42  of the second nozzle member  12  was a T-shaped groove shape, and the cross-sectional shape of the shim member  50  was complementary to an I-shaped groove shape obtained by combining the T-shaped groove shape of the groove portion  41  of the first nozzle member  11  and the T-shaped groove shape of the groove portion  42  of the second nozzle member  12 , which were plane-symmetrical with each other. The width B 1  of the narrowest portion of the shim member  50  was 5 mm, the width B 2  of the widest portion of the shim member  50  was 15 mm, the length B 3  of the linear portion of the shim member  50  was 10 mm, the height B 4  of the shim member  50  was 20 mm, and the length of the shim member  50  in the front-rear direction was 5 mm. 
     Example 3 
     In Example 3, the materials of the first nozzle member  11 , the second nozzle member  12 , and the shim member  30  were all sialon, and the material of the nozzle header  15  was chrome molybdenum steel. In addition, as illustrated in  FIGS.  8  and  9   , the cross-sectional shape of each of the groove portion  61  of the first nozzle member  11  and the groove portion  62  of the second nozzle member  12  was rectangular, and the shim member  70  had a rectangular parallelepiped shape. The width C 1  of the shim member  70  was 15 mm, the height C 2  of the shim member  50  was 20 mm, and the length of the shim member  70  in the front-rear direction was 5 mm. 
     In addition, the pin  71  was used to connect the groove portion  61  of the first nozzle member  11  to the shim member  70 , and to connect the groove portion  62  of the second nozzle member  12  to the shim member  70 . The insertion depth C 3  of the pin  71  was 10 mm, and the diameter C 4  of the pin  71  was Φ3 mm. 
     Comparative Example 1 
       FIG.  10    illustrates a cross section that shows a structure of a gas wiping nozzle of Comparative Example 1 
     In the gas wiping nozzle  10  illustrated in  FIG.  10   , a pair of groove portions  81  of the first nozzle member  11  are formed on both sides of the hollow portion forming space  13   a  in the length direction X, and a pair of groove portions  82  of the second nozzle member  12  are formed on both sides of the hollow portion forming space  13   b  in the length direction X. Each of the groove portions  81  and  82  is formed to open on the mating surface  23  of the first nozzle member  11  and the second nozzle member  12 , and extends forward from the rear end surface of the first nozzle member  11  or the rear end surface of the second nozzle member  12  over a predetermined length. 
     The groove portion  81  of the first nozzle member  11  and the groove portion  82  of the second nozzle member  12  communicate with each other on the mating surface  23  of the first nozzle member  11  and the second nozzle member  12 , and are plane-symmetrical with the mating surface  23  as a plane of symmetry. 
     The cross-sectional shape of each of the groove portion  81  of the first nozzle member  11  and the groove portion  82  of the second nozzle member  12  is rectangular, and a shim member  90  fitted into a pair of groove portions  81  and  82  has a rectangular parallelepiped shape. 
     Furthermore, to fix the shim member  90  fitted into the pair of groove portions  81  and  82  to the first nozzle member  11  and the second nozzle member  12 , the shim member  90  is interposed between two metal bolts  91  from above and below the first nozzle member  11  and the second nozzle member  12 . As a result, the shim member  90  is fixed to the first nozzle member  11  and the second nozzle member  12 , and the first nozzle member  11  and the second nozzle member  12  are fixed. 
     That is, in Examples 1 to 3, by devising the shape of each of the groove portions of the first nozzle member  11  and the second nozzle member  12  and the shape of the shim member fitted therein, the first nozzle member  11  and the second nozzle member  12  are fixed without using bolts. However, in Comparative Example 1, the first nozzle member  11  and the second nozzle member  12  are fixed by using the metal bolts  91 . 
     In addition, in Comparative Example 1, in the gas wiping nozzle  10  having such a structure, the materials of the first nozzle member  11 , the second nozzle member  12 , the shim member  90 , and the nozzle header  15  were all chrome molybdenum steel. 
     Comparative Example 2 
     In Comparative Example 2, a structure of the gas wiping nozzle is the same as that illustrated in  FIG.  10   . That is, in Comparative Example 2, in the gas wiping nozzle  10 , the first nozzle member  11  and the second nozzle member  12  are fixed by using the metal bolts  91  as in Comparative Example 1. 
     In addition, in Comparative Example 2, in the gas wiping nozzle  10  having such a structure, the materials of the first nozzle member  11 , the second nozzle member  12 , and the shim member  90  were all sialon, and the material of the nozzle header  15  was chrome molybdenum steel. 
     In Examples 1 to 3 and Comparative Examples 1 and 2, a nozzle damage state, a change rate in the slit gap, a deviation of the amount of coating in the width direction, and a generation rate of linear marks were evaluated. The change rate in the slit gap (%) is a value indicated by the amount of the maximum slit gap (size of gap L 3  in width direction Z orthogonal to length direction X of slit  14 ) in the width direction (length direction X of slit  14 ) of the wiping nozzle  10 /the amount of the minimum slit gap×100. In addition, the deviation of the amount of coating in the width direction (%) is a value indicated by the amount of the maximum coating in the width direction of the steel strip S/the amount of the minimum coating×100. Furthermore, the generation rate of linear marks (%) is a ratio of a length of the steel strip S visually determined to have a linear mark defect in an inspection step to a length of the steel strip S passed under each manufacturing condition. 
     The evaluation results are illustrated in Table 1. 
     
       
         
           
               
               
               
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                   
                   
                   
                 Change  
                 Deviation of  
                 Generation  
                   
               
               
                   
                   
                 Nozzle 
                 rate 
                 amount of  
                 rate 
                   
               
               
                   
                   
                 damage  
                 in gap  
                 coating in width  
                 of linear 
                   
               
               
                   
                 Classification 
                 [-] 
                 [%] 
                 direction [%]  
                 marks [%]  
               
               
                   
               
             
            
               
                   
                 Example 1 
                 Absent 
                 101 
                 108 
                 0.28 
                   
               
               
                   
                 Example 2 
                 Absent 
                 101 
                 110 
                 0.29 
                   
               
               
                   
                 Example 3 
                 Absent 
                 103 
                 112 
                 0.24 
                   
               
               
                   
                 Comparative 
                 Absent 
                 175 
                 217 
                 1.61 
                   
               
               
                   
                 Example 1 
                   
                   
                   
                   
                   
               
               
                   
                 Comparative 
                 Present 
                 138 
                 163 
                 0.94 
                   
               
               
                   
                 Example 2 
               
               
                   
               
            
           
         
       
     
     As is clear from Table 1, in Examples 1 to 3, the change rate in the slit gap, the deviation of the amount of coating in the width direction, and the generation rate of linear marks could be significantly reduced compared to Comparative Examples 1 and 2. 
     In addition, after manufacturing was completed, although the first nozzle member  11  and the second nozzle member  12  were disassembled and visually inspected, no nozzle damage was observed under any of the conditions of Examples 1 to 3 and Comparative Example 1. On the other hand, in Comparative Example 2, the nozzle damage was observed. We believe that this is because the ceramics (sialon) having a toughness lower than that of the metal were damaged due to the thermal expansion of the metal bolt  91 . 
     In any of Examples 1 to 3 and Comparative Examples 1 and 2, the temperature of the wiping gas is controlled so that the temperature T (° C.) of the wiping gas immediately after being blown from the slit  14  of the gas wiping nozzle  10  satisfies T M −150≤T≤T M +250 in relation to the melting point T M  (° C.) of the molten metal. Therefore, no hot metal wrinkle defect occurred in any of the Examples 1 to 3 and Comparative Examples 1 and 2. 
     Therefore, we confirmed that, with our gas wiping nozzle and our method of manufacturing the hot-dip metal coated metal strip, the gap L 3  in the width direction Z orthogonal to the length direction X of the slit  14  as the gas blowing port can be uniformly held along the length direction X of the slit  14  even in a high temperature atmosphere.