JP7140706B2 - snout equipment - Google Patents

Description

The present invention relates to a snout installation for a hot dip galvanizing line.

Snout equipment is known as line equipment for hot-dip galvanizing lines, in which steel strips annealed in an annealing furnace enter a molten metal bath via hot bridle rolls and snouts (see, for example, Patent Document 1). The snout extends into a plating pot containing molten metal, and in the case of Galvalume Steel Sheets (registered trademark), a 55% Al—Zn alloy is used as the molten metal.

In the line equipment described above, since the bath temperature is high (600° C. or higher), Zn gas is generated from the plating pot. After flowing into the annealing furnace through the snout, the generated Zn gas is cooled and solidified. It may adhere to the steel strip as a substance. In order to solve this problem, a technique of installing a heater at the end of the annealing furnace is known. By operating the heater to prevent the temperature of the Zn gas from lowering, solid matter derived from the Zn gas is prevented from adhering to the steel strip.

JP-A-11-293436

The inventors of the present invention have discovered a problem that a hot bridle roll heated by a heater is thermally deformed into a drawing shape, and the steel strip meanders.

In order to solve the above problems, the snout equipment according to the present invention includes (1) a hot bridle roll disposed at the terminal end of an annealing furnace, and a hot bridle roll extending from the terminal end toward a plating pot in which molten metal is stored. A snout facility for a hot-dip galvanizing line, comprising: a heater for increasing the ambient temperature of the terminal end; and temperature control means for reducing the temperature difference with the non-contact portion of the steel strip.

(2) The snout equipment according to (1) above, wherein the temperature control means is cooling means for cooling the steel strip non-contact portion of the hot bridle roll.

(3) The snout equipment according to (2) above, wherein the cooling means is a blowing device for blowing an inert gas for cooling against the steel strip non-contact portion.

(4) The snout equipment according to (3) above, wherein the inert gas is sprayed at a position within 125 mm from the axial end of the roll body of the hot bridle roll.

(5) Any one of (1) to (4) above, wherein the molten metal contains 55% by mass of Al, 1.6% by mass of Si, and the balance is Zn. One snout device.

(6) Any one of the above (1) to (5), wherein the ambient temperature of the end portion heated by the heater is higher than the plate temperature of the steel strip entering the end portion. Snout equipment as described in Section 1.

According to the present invention, by installing a heater for increasing the atmospheric temperature at the terminal end of the annealing furnace, it is possible to prevent solid matter derived from Zn gas generated from the plating pot from adhering to the steel strip. In addition, by providing a temperature control means for reducing the temperature difference between the steel strip contact portion with which the steel strip in the hot bridle roll contacts and the steel strip non-contact portion with which the steel strip does not contact, the hot bridle roll can be formed into a drawing shape. It can prevent the steel strip from meandering due to thermal deformation.

1 is a schematic view of part of a hot dip galvanizing line; FIG. It is an enlarged view which expanded the terminal part of an annealing furnace. It is an installation drawing of a spraying device. It is an installation drawing of a heat insulating board.

FIG. 1 is a schematic view of part of a hot-dip galvanizing line, with arrows indicating the conveying direction of a steel strip S. As shown in FIG. FIG. 2 is an enlarged view of 15A indicated by the dotted line in FIG. 1, in other words an enlarged view of the end of the annealing furnace. In the hot-dip galvanizing line 1 , the steel strip S is transported to an annealing furnace 15 via a pair of upper and lower entry side bridle rolls 11 . The annealing furnace 15 continuously anneals the steel strip S by applying a temperature pattern such as heating, temperature retention, and cooling. A pair of hot bridle rolls 12 are installed at the end portion 15A of the annealing furnace 15 . The hot bridle roll 12 located upstream in the conveying direction of the steel strip S is defined as an upstream hot bridle roll 12a, and the hot bridle roll 12 located downstream in the conveying direction of the steel strip S is particularly a downstream hot bridle roll. shall be defined as roll 12b. However, when there is no particular need to distinguish between the upstream hot bridle roll 12a and the downstream hot bridle roll 12b, they are collectively referred to as the hot bridle roll 12.

A duct-shaped snout 17 extending toward the plating pot 14 is further provided at the end portion 15A of the annealing furnace 15 . The hot bridle rolls 12 change the conveying direction of the steel strip S that has reached the terminal end portion 15A of the annealing furnace 15 from the horizontal direction to the downward oblique direction, and advance the steel strip S toward the snout 17 . The snout 17 prevents the steel strip S from being exposed to the outside air when the steel strip S is conveyed from the annealing furnace 15 to the plating pot 14 . Thereby, the steel strip S can be prevented from being oxidized on the way to the plating pot 14 .

A molten metal containing aluminum and zinc is stored in the plating pot 14 . In other words, the plating pot 14 stores molten metal containing a large amount of Al component for manufacturing the Galvalume steel sheet (registered trademark) defined in JIS G3321. More specifically, molten metal containing 55% by mass of Al, 1.6% by mass of silicon and the balance of Zn is stored in the plating pot 14 . Here, since the bath temperature of the molten metal is high (approximately 600° C.), Zn stored in the plating pot 14 is partly gasified and enters the snout 17 .

A sink roll 13 is immersed in the plating pot 14 . The sink roll 13 changes the conveying direction of the steel strip S that has entered the molten metal from the oblique downward direction to the upward direction. The surface of the sink roll 13 is desirably surface-treated with a thermal spray coating having molten metal corrosion resistance.

Here, the Zn gas entering the snout 17 rises inside the snout 17 and flows into the terminal end portion 15A of the annealing furnace 15 . If the Zn gas is cooled at the end portion 15A of the annealing furnace 15, Zn may adhere to the steel strip S and cause product defects. Therefore, a heater is provided at the end portion 15A of the annealing furnace 15 . The heater of this embodiment is composed of a tube heater 16 and a steel shell heater 18 . The shell heater 18 is installed on the shell that forms the outer wall of the terminal portion 15</b>A of the annealing furnace 15 . However, in order to protect the outer wall of the terminal portion 15A, a heat insulating plate (not shown) may be interposed between the shell heater 18 and the shell. By operating the iron shell heater 18, the ambient temperature of the terminal end portion 15A can be raised to a predetermined temperature or higher. However, the steel shell heater 18 alone may not be able to control the ambient temperature of the end portion 15A to a temperature higher than the temperature at which the Zn gas solidifies. Therefore, in this embodiment, the tube heater 16 is installed in order to control the ambient temperature of the end portion 15A to a temperature higher than the solidifying temperature.

The tube heater 16 is installed in the furnace of the annealing furnace 15 (in other words, in the furnace of the terminal portion 15A). Here, since it is necessary to arrange the hot bridle rolls 12 and form the conveying path of the steel strip S at the end portion 15A, the space for arranging other members is limited. In the present embodiment, the tube heater 16 is installed in an installation space formed on the side of the downstream hot bridle roll 12b (in other words, upstream of the downstream hot bridle roll 12b in the conveying direction of the steel strip S in the annealing furnace 15). is installed. For the tube heater 16, for example, a steel pipe in which a heater is inserted can be used.

Here, if the distance between the tube heater 16 and the downstream hot bridle roll 12b becomes excessively long, the temperature of the Zn gas flowing into the furnace will drop, and the steel strip S will adhere to solid Zn. Therefore, the tube heater 16 is desirably installed within L mm from the roll center of the downstream hot bridle roll 12b toward the upstream in the conveying direction of the steel strip S. Lmm can be set to 1000 mm, for example. By installing the tube heater 16 within 1000 mm toward the upstream in the conveying direction of the steel strip S from the roll center of the downstream hot bridle roll 12b, the ambient temperature of the end portion 15A is controlled to a target temperature of about 570 ° C. be able to. As a result, the Zn gas whose temperature has been lowered can be prevented from adhering to the steel strip S as a solid matter. Note that the end point of Lmm corresponds to the start position of the terminal end portion 15A. That is, the region of the annealing furnace 15 on the right side of the dotted line X1 (see FIG. 2) corresponds to the terminal end portion 15A. The tube heater 16 is set to have a larger axial length than the hot bridle roll 12 .

Although two tube heaters 16 are installed in this embodiment, the number of tube heaters 16 is not particularly limited as long as the ambient temperature of the end portion 15A can be controlled to about 570°C. For example, the number of tube heaters 16 may be one, or three or more.

Next, problems caused by installing the tube heater 16 will be described. Since the conveying path of the steel strip S is formed just above the tube heater 16, the radiant heat directed to the steel strip S is reflected by the steel strip S. As a result, the downstream hot bridle roll 12b is heated by the reflected radiant heat (hereinafter sometimes referred to as reflected radiant heat). As the width of the steel strip S increases, the axial length (area) of the downstream hot bridle roll 12b heated by reflected radiant heat increases.

Here, the temperature of the steel strip S entering the hot bridle roll 12 is set to approximately 520°C. Therefore, the downstream hot bridle roll 12b is exposed to a temperature atmosphere of about 570 ° C. due to reflected radiant heat, while the portion in contact with the steel strip S (hereinafter sometimes referred to as the steel strip contact portion) has a lower temperature. It is cooled by contact with the steel strip S. Therefore, a temperature difference occurs between the portion of the downstream hot bridle roll 12b that contacts the steel strip and the portion that does not come into contact with the steel strip S (hereinafter sometimes referred to as the non-contact portion of the steel strip). As a result, the downstream hot bridle roll 12b is thermally deformed into a constricted shape with a small diameter at the center in the axial direction and a large diameter at the end portions in the axial direction, and the steel strip S may meander.

Here, by bringing the temperature of the steel strip S close to the atmospheric temperature of the terminal end portion 15A of the annealing furnace 15, it is possible to suppress the thermal deformation of the downstream hot bridle roll 12b into a drawing shape. However, if the temperature of the steel strip S is raised to a temperature higher than 520°C (for example, 570°C), the iron component eluted from the steel strip S that has entered the plating pot 14 increases, and bottom dross adversely affects the appearance of the plating surface. may progress in the plating pot 14 .

As a method of solving the above-mentioned problem (meandering of the steel strip S due to the thermal deformation of the downstream hot bridle roll 12b into a drawn shape), a cooling means for cooling the steel strip non-contact portion of the downstream hot bridle roll 12b is provided. can be considered. FIG. 3 is an installation diagram (perspective view) of a blowing device, which is an example of the cooling means. The downstream hot bridle roll 12b has a roll main body 12b1 and a roll shaft portion 12b2. The roll shaft portion 12b2 is supported by a bearing portion (not shown) and rotates in a direction corresponding to the direction in which the steel strip S is conveyed. The roll main body 12b1 is formed in a cylindrical shape with a constant outer diameter at room temperature (that is, when the tube heater 16 is stopped).

For convenience of explanation, the steel strip contact portion R1 of the roll body 12b1 is hatched, and the steel strip non-contact portion R2 of the roll body 12b1 is not hatched. A blowing device 19 is arranged at a position facing the steel strip non-contact portion R2 in the radial direction. The blowing device 19 blows N ₂ gas as an inert gas supplied through the introduction pipe 19a toward the steel strip non-contact portion R2. Oxidation of the steel strip S can be suppressed by using an inert gas as the cooling gas.

Here, the axial length of the roll body 12b1 is generally about 1500 mm, and the width of the steel strip S is generally 610 mm to 1219 mm. When the inert gas is directly blown onto the steel strip S, the temperature of the steel strip S decreases, while the width of the steel strip S is not constant, and the area ratio of the steel strip contact portion R1 and the steel strip non-contact portion R2 changes. Therefore, even when the width of the steel strip S is the maximum (1219 mm), the inert gas should be sprayed within 125 mm from the axial end of the roll body 12b1 so that the inert gas does not hit the steel strip S. Position should be set.

As described above, by cooling the steel strip non-contact portion R2 of the roll body 12b1, the temperature difference between the steel strip contact portion R1 and the steel strip non-contact portion R2 is reduced. Thereby, it is possible to suppress the outer diameter of the lower hot bridle roll 12b from fluctuating according to the position in the axial direction. That is, since the roll main body 12b1 can be maintained in a substantially cylindrical shape, meandering of the steel strip S can be suppressed.

Here, it is conceivable to form the roll body 12b1 in advance in a crown shape in consideration of thermal deformation without providing a cooling means. However, since the plate temperature of the steel strip S fluctuates within a predetermined range (470° C. to 520° C.), when the plate temperature of the steel strip S changes, the line is stopped and another lower side with a different crown The hot bridle roll 12 must be replaced. Therefore, the method of solving the meandering of the steel strip S by the crown shape causes a decrease in productivity. In contrast, in the present embodiment, when the steel strip S is changed, the temperature variation in the axial direction of the lower hot bridle roll 12 can be suppressed simply by changing the amount of inert gas blown. For example, when the plate temperature of the steel strip S is lowered from 520° _C to 470°C, the temperature of the steel strip contact portion R1 is further lowered. Temperature variations in the contact portion R1 and the steel strip non-contact portion R2 can be effectively suppressed.

(Modification 1)
In the above-described embodiment, meandering of the steel strip S is prevented by blowing _N2 gas onto the steel strip non-contact portion R2, but along with this, a steering function may be implemented in the line. Thereby, meandering of the steel strip S can be prevented more effectively. For example, as shown in Patent Document 1, by installing a turndown roll having a steering function between the lower hot bridle roll 12 and the sink roll 13, or by mounting the steering function on the sink roll 13, the steel strip Meandering of S can be prevented more effectively.

(Modification 2)
In the above-described embodiment, meandering of the steel strip S is prevented by blowing _N2 gas onto the steel strip non-contact portion R2, but the present invention is not limited to this. A refrigerant pipe (corresponding to a cooling means) for passing a refrigerant is formed in a region corresponding to the contact portion R2, and cooling water or cooling gas is caused to flow through the refrigerant pipe, thereby removing the steel strip non-contact portion R2. Allow to cool. Further, as shown in FIG. 4, a heat insulating plate 30 (corresponding to a temperature control means) may be installed between the roll body 12b1 and the steel strip S to make it difficult for the reflected radiant heat to reach the roll body 12b1. .

1 hot-dip galvanizing line 1
11 entry side bridle roll 12 hot bridle roll 12a upstream hot bridle roll 12b downstream hot bridle roll 13 sink roll 14 plating pot 15 annealing furnace 15A termination of annealing furnace 16 tube heater 17 snout 18 steel skin heater 19 blowing device

Claims (6)

A snout facility for a hot-dip galvanizing line having a hot bridle roll disposed at the terminal end of an annealing furnace and a snout extending from the terminal end toward a plating pot in which molten metal is stored,
a heater for increasing the ambient temperature of the terminal end;
temperature control means for reducing a temperature difference between a steel strip contact portion with which the steel strip contacts and a steel strip non-contact portion with which the steel strip does not contact in the hot bridle roll;
A snout facility comprising: 2. The snout equipment according to claim 1, wherein said temperature control means is cooling means for cooling said steel strip non-contact portion of said hot bridle roll. 3. The snout equipment according to claim 2, wherein the cooling means is a blowing device for blowing inert gas for cooling against the steel strip non-contact portion. 4. The snout equipment according to claim 3, wherein the inert gas is sprayed at a position within 125 mm from the axial end of the roll body of the hot bridle roll. 5. The snout equipment according to any one of claims 1 to 4, wherein the molten metal contains 55% by mass of Al, 1.6% by mass of Si and the balance of Zn. 6. The snout equipment according to any one of claims 1 to 5, wherein the ambient temperature of the end portion heated by the heater is higher than the plate temperature of the steel strip entering the end portion. .

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