JP4858015B2 - Foreign matter removal device in the snout of continuous molten metal plating equipment - Google Patents

Description

  The present invention relates to a device for removing foreign matter in a snout of a continuous molten metal plating facility.

  In continuous hot dip galvanizing, generally, a steel strip led from an annealing furnace through a cooling zone to a plating bath via a snout is turned upward by a sink roll in the bath and warped by a support roll in the bath. After being corrected, it is pulled out of the bath and the amount of plating adhesion is adjusted by the gas wiping nozzle. In such continuous hot dip galvanization, foreign matter adheres to the surface of the steel strip in the plating bath, resulting in quality defects. The foreign matter generated in the plating tank includes foreign matter called dross, ash solidified with zinc fume, and the like.

Dross is commonly referred to as top dross, which is Fe ₂ Al ₅ produced by the reaction of Fe eluted from the steel strip into the zinc bath and Al that is added to the zinc bath and improves plating adhesion. When it adheres to the steel strip and the attached steel plate is processed, it will damage the mold or generate push.

  Ash is a solid of zinc fume and is hot dip galvanized while adhering to the surface of the steel sheet. Therefore, after hot dip galvanization, if blown off by gas wiping, an unplated part will occur.

  In the plating bath, in addition to the dross and ash described above, there is also an oxidized dross that is generated when the zinc bath comes into contact with air, and these foreign substances often adhere to the steel strip on the bath surface inside the snout, and are particularly oxidized. The dross is drawn into the snout by the flow as the steel strip is drawn into the zinc bath.

  For this reason, various methods and apparatuses for removing foreign substances such as dross from the bath surface in the snout have been proposed, and Patent Document 1 describes a method for sucking foreign substances such as dross together with molten zinc by a motor pump and discharging it outside the snout. ing.

  In Patent Document 2, a U-shaped communication pipe is set in the plating tank, and one end of the U-shaped communication pipe is opened at the bath surface position in the snout by a suction side pipe to suck in foreign matters such as dross, and the other end is a discharge side pipe. Describes a foreign matter removing device in the snout using a gas lift pump which is opened under the bath surface outside the snout and discharges foreign matters such as dross in the snout from the opening.

  The suction of foreign matter from the inside of the snout is caused by the rise of molten zinc caused by the rise of the inert gas discharged from the gas supply pipe inserted along the pipe axis from above the opening in the discharge side pipe. By flow.

  In the case of the method described in Patent Document 2, the concentric distance between the discharge-side pipe and the gas supply pipe inserted therein is narrow, and when the U-shaped communication pipe is temporarily lifted from the bath, dross in the pipe is solidified. In many cases, it cannot be reused.

  For this reason, in Patent Document 3, a hole is provided in the center of the bottom of the U-shaped tube, and a gas supply pipe is inserted into the discharge side pipe from its side wall to secure a foreign matter discharge route. Suggests that the U-tube be completely kept out of the bath. In any case, in Patent Documents 2 and 3, it is not sufficient to uniformly disperse bubbles that undergo gas lift, and there remains a problem that foreign matters are efficiently discharged out of the snout.

In Patent Document 4, a nozzle that blows nitrogen gas downward on a steel sheet that passes through the plating bath surface in the snout is provided, and the scum that floats on the bath surface in the snout using the reflectivity of the nitrogen gas is removed from the steel plate. A device for preventing scum adhesion in a snout that uses a gas lift pump in combination with peeling is described.
JP-A-3-140448 JP 2000-265254 A JP 2005-264224 A JP-A-7-150323

By the way, recently, quality requirements regarding the surface properties of surface-treated steel sheets have become stricter in the automobile industry and the home appliance industry, and it is necessary to improve the performance of gas lift pumps in order to further reduce surface defects due to foreign matters floating on the bath surface in the snout. It has become.

  In the case of a gas lift pump, the influence of the flow rate of the upward flow of molten zinc in the discharge pipe and the distribution of the upward flow in the discharge pipe is predicted, but there is no description in any of Patent Documents 2 to 4, and in hot dip galvanization A method for improving the performance of the gas lift pump has not been clarified.

  Then, an object of this invention is to provide the foreign material removal apparatus in the snout of the continuous molten metal plating equipment provided with the gas lift pump which is excellent in the discharge | emission performance of the foreign material etc. which floats on the bath surface in a snout outside the snout.

The object of the present invention can be achieved by the following means.
1. A device for removing foreign matter in a snout that discharges foreign matter generated on the bath surface inside the snout using a gas lift pump, wherein the gas lift pump is a suction whose one straight pipe has a suction port on the plating bath surface in the snout. A substantially U-shaped communication pipe that forms a pipe and the other straight pipe part forms a discharge pipe having a discharge port on the plating bath surface outside the snout, and a gas supply that is inserted into the discharge pipe and releases gas for gas lift The gas supply pipe includes a straight pipe portion to which a gas lift gas is supplied and a tip member that is coaxially attached to a tip of the straight pipe portion and that discharges the gas lift gas. Continuous molten metal plating characterized in that it is a cylindrical member having a diameter larger than that of the straight pipe part, and has a plurality of openings arranged along the outer periphery of the straight pipe part on the end surface on the discharge port side. Equipment snau Internal foreign matter removing apparatus.
2. 2. The apparatus for removing foreign matter in a snout of a continuous molten metal plating facility according to claim 1, wherein the tip of the tip member is a cone.

  According to the present invention, since uniform gas-liquid mixing can be obtained in the discharge pipe, the foreign matter in the snout can be efficiently discharged with a small amount of gas, which is extremely useful industrially.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic diagram for explaining the configuration of a foreign matter removing device in a snout of a continuous molten metal plating facility according to an embodiment of the present invention, in which 1 is a plating bath, 2 is a sink roll, 3 is a snout, and 4 is a support. Roll, 5 is a gas wiping nozzle, 6 is a U-shaped communication pipe, 6a is a suction pipe for the U-shaped communication pipe 6, 6b is a discharge pipe for the U-shaped communication pipe, 7 is a gas supply pipe, 71 is the tip of the gas supply pipe 7 Part, a is a steel strip, b is a foreign substance, and c is a bubble of N ₂ gas.

  The illustrated device for removing foreign matter in the snout floats on the bath surface inside the snout by a gas lift pump system that raises the molten metal in association with bubbles rising from the gas supply pipe inserted into the molten metal of the U-shaped communication pipe. To discharge foreign matter to the outside of the snout.

  The U-shaped communication pipe 6 has a suction pipe 6a at one straight pipe portion, and has a height at which the plating bath surface serves as a suction port so that foreign matters floating on the plating bath surface inside the snout 3 can be sucked.

  The other straight pipe portion of the U-shaped communication pipe 6 forms a discharge pipe 6 b, and the gas supply pipe 7 is inserted so that the tip end portion is near the bottom of the discharge pipe 6. An inert gas such as N 2 gas is supplied to the gas supply pipe 7 from a gas supply device (not shown), and is discharged into the discharge pipe 6 b from the tip near the bottom of the discharge pipe 6.

  In the in-snout foreign matter removing apparatus according to the present invention, the gas supply pipe 7 includes a straight pipe portion to which a gas for lift gas is supplied and a tip member 71 having an opening which is coaxially attached to the tip thereof and discharges gas.

  FIG. 2 schematically shows the shape of the tip member 71 and how the molten zinc is gas-lifted. The distal end member 71 has a cylindrical portion having a diameter larger than that of the straight pipe portion of the gas supply pipe 7, and a plurality of openings 71 b are formed along the outer periphery of the straight pipe portion on the end surface on the discharge port side of the discharge pipe 6 b. Is provided.

  The N2 gas supplied to the gas supply pipe 7 passes through the straight pipe portion, and is evenly released around the gas supply pipe from the opening 71b of the tip end portion 71 toward the upper liquid surface of the molten zinc. Bubbles 7 are generated, and an upward flow d of molten zinc is generated in the discharge pipe 6.

  Since the tip member 71 has the above-described structure, the bubbles c are dispersed and the gas-liquid mixing is made uniform as compared with the case of being directly discharged from the straight pipe portion of the gas supply pipe 7, and with a smaller amount of nitrogen, The dross in the snout can be discharged. Further, since the N2 gas is released upward, the bubbles c rise smoothly, and the upward flow d of molten zinc also becomes smooth.

  As a result, the stirring of the hot water surface at the discharge port of the discharge pipe 6b is suppressed, oxidation of molten zinc at the discharge port is suppressed, dross generation is reduced inside the plating bath 1, and quality defects can be avoided. In addition, it is preferable that the plurality of openings 71b be evenly arranged to further equalize the dispersion of bubbles.

  If the tip 71a of the tip member 71 is a cone, the resistance to molten zinc that causes gas lift is further reduced, and the discharge amount can be increased, which is preferable.

  In the present invention, the U-shaped communication pipe 6 includes a substantially U-shaped communication pipe having straight pipe portions that are parallel on the left and right. Further, the diameters of the discharge pipe 6, the straight pipe part of the gas supply pipe 7, and the cylindrical part of the tip member are not particularly defined. Appropriate selection is made according to the desired dross discharge capacity.

The present invention was carried out using the snout foreign matter removing apparatus shown in FIGS. 1 and 2 in a plating bath for continuous hot dip galvanization. The steel plate a has a maximum plate width of 1880 mm, the communication pipe 6 b constituting the gas lift pump uses an inner diameter of 74 mmφ, the gas supply pipe 7 uses an inner diameter of 11 mmφ, and the tip of the nitrogen gas discharge opening is 3 mmφ × 8 pieces below the bath surface. It was inserted up to about 650 mm, and the flow rate of nitrogen gas was 20 m ³ / hour. Under the above conditions, the operation was continued for about 2 weeks, but the foreign matter defects related to dross and ash in the snout were greatly reduced.

The figure explaining the structure of the foreign material removal apparatus in a snout of the continuous molten metal plating equipment which concerns on one Example of this invention. The figure which expands a part of snout foreign substance removal apparatus shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Plating bath 2 Sink roll 3 Snout 4 Support roll 5 Gas wiping nozzle 6 U-shaped communication pipe 6a Suction pipe 6b Exhaust pipe 7 Gas supply pipe 71 Tip member 71a Tip part 71b Opening a Steel strip b Foreign object c Bubble d Upflow

Claims (2)

  A device for removing foreign matter in a snout that discharges foreign matter generated on the bath surface in the snout using a gas lift pump, wherein the straight pipe portion has a suction port on the plating bath surface in the snout. A substantially U-shaped communication pipe that forms a pipe and the other straight pipe part forms a discharge pipe having a discharge port on the plating bath surface outside the snout, and a gas supply that is inserted into the discharge pipe and releases gas for gas lift The gas supply pipe includes a straight pipe portion to which a gas lift gas is supplied and a tip member that is coaxially attached to a tip of the straight pipe portion and that discharges the gas lift gas. Continuous molten metal plating characterized in that it is a cylindrical member having a diameter larger than that of the straight pipe part, and has a plurality of openings arranged along the outer periphery of the straight pipe part on the end surface on the discharge port side. Equipment snau Internal foreign matter removing apparatus. The apparatus for removing foreign matter in a snout of a continuous molten metal plating facility according to claim 1, wherein the tip of the tip member is a cone.

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