JP2013221212A - Snout of continuous hot dip galvanizing device, and control method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a snout of a continuous hot dip galvanizing device capable of eliminating deposition and separation of top dross on the inner surface of a fore end part of a snout body, and a control method thereof.SOLUTION: The snout 1 of a continuous hot dip plating device with its fore end immersed in a plating bath, includes an ultrasonic sensor 15 for detecting the bath surface level of the plating bath 3, an elevating/lowering motor cylinder 12 for elevating/lowering the fore end position of the snout body 1, and a level control device 16 which elevates/lowers the fore end position of the snout body 1 by the elevating/lowering motor cylinder 12 according to the bath surface level detected by the ultrasonic sensor 15, and keeps the relative position between the bath surface level and the fore end position of the snout body 1 at a fixed value.

Description

  The present invention relates to a snout of a continuous hot dipping apparatus, and more particularly to a snout capable of preventing the top dross from adhering to and peeling from the inner surface of the tip of a snout body immersed in a plating bath and a control method therefor. .

  As shown in FIG. 7, in the conventional continuous hot dipping apparatus, after the steel strip P is reduced by the reduction furnace 2, it is immersed in the plating bath 3 while preventing the steel strip P from being oxidized by the duct-shaped snout 100. Then, the direction of the steel strip P is changed vertically by the roll 4, and the plating adhesion amount is adjusted by the wiping device 5 disposed immediately above the plating bath 3. The base of the snout 100 is connected to the reduction furnace 2, and the tip is immersed in the plating bath 3 and sealed, thereby preventing air from entering the inside (see, for example, Patent Document 1).

  About the immersion depth of the front-end | tip part of this snout 100, considering the erosion of the snout 100 by zinc, it is normally set and fixed about 350 mm. During the continuous hot dipping operation, as the plating progresses, the bath surface of the plating bath 3 is lowered, so that zinc ingot is added and replenished as needed. As a result, the bath surface of the plating bath 3 fluctuates up and down. The immersion depth 350 mm is determined from the bath surface fluctuation width of 100 mm and the erosion allowance (margin allowance) of 250 mm, and the snout 100 is replaced when eroded by about 200 mm.

JP 2004-99953 A

  However, as described above, the conventional snout 100 has the tip portion immersed at a constant depth during the continuous hot dipping operation, which causes defects in sheet metal and plating quality. FIG. 8 shows the mechanism of occurrence of poor plating quality. As shown in FIG. 8A, when the bath surface of the plating bath 3 is raised, as shown in FIG. 8B, the top dross adheres to the inner surface of the tip portion of the snout 100. When the rise and fall of the bath surface are repeated, the top dross attached to the snout 100 grows. When the bath surface rises again after a certain amount of growth, as shown in FIG. The top dross on the inner surface of the tip part peels off and floats on the bath surface as shown in FIG. When the top dross floating on the bath surface comes into contact with the steel strip P, defects in the sheet metal and plating quality occur.

  Therefore, an object of the present invention is to provide a snout for a continuous hot dipping apparatus capable of eliminating the adhesion and peeling of the top dross to the inner surface of the tip portion of the snout body and a control method therefor.

  The snout of the continuous hot dipping apparatus of the present invention is a snout of a continuous hot dipping apparatus in which the tip is immersed in a plating bath, and includes a bath surface level detecting means for detecting the bath surface level of the plating bath, and the tip of the snout body. Lifting means for raising and lowering the position, and control for raising and lowering the snout body tip position by the raising and lowering means according to the bath surface level detected by the bath surface level detecting means, and keeping the relative position between the bath surface level and the snout body tip position constant. Means.

  Further, the method of controlling the snout of the continuous hot dipping apparatus of the present invention is a method of controlling the snout of the continuous hot dipping apparatus in which the tip is immersed in the plating bath, and detecting the bath surface level of the plating bath. It includes raising and lowering the tip position of the snout body according to the bath surface level, and keeping the relative position between the bath surface level and the tip position of the snout body constant.

  According to these inventions, the tip position of the snout body moves up and down according to the change in the bath surface level of the plating bath, the relative position between the bath surface level and the tip position of the snout body is kept constant, and the plating of the tip portion of the snout body Since the immersion position in the bath is always constant, there is no adhesion or peeling of the top dross to the inner surface of the tip of the snout body.

  Here, the snout of the continuous hot dipping apparatus of the present invention comprises temperature detecting means for detecting the snout body surface temperature, and tip position calculating means for calculating the snout body tip position from the snout body surface temperature detected by the temperature detecting means. It is desirable to have. As a result, the more accurate snout body tip position including the amount of thermal expansion of the operating snout body is calculated, so the relative position between the bath surface level and the snout body tip position is more accurately and constantly maintained. .

  Moreover, as for the immersion depth in a plating bath, it is desirable that it is 10-100 mm. As a result, the internal stress of the snout body can be reduced when the snout body tip is immersed in the plating bath, and cracks and the like are less likely to occur in the snout body. If the immersion depth is less than 10 mm, the sealing performance may not be ensured when the furnace pressure of the reduction furnace varies. On the other hand, if it exceeds 100 mm, the internal stress of the snout body increases when the tip of the snout body is immersed in the plating bath, and cracks and the like are likely to occur in the snout body.

  Moreover, in the snout of the continuous hot dipping apparatus of the present invention, it is desirable to further lower the tip position of the snout body by the amount of wear due to the erosion of the snout body. The tip of the snout body immersed in the plating bath is eroded by the zinc in the plating bath, but the snout body can be used for a long period of time by lowering the position of the tip of the snout body by the amount of wear caused by this erosion. It becomes possible to do.

(1) By detecting the bath surface level of the plating bath, raising and lowering the snout body tip position according to the bath surface level, and keeping the relative position between the bath surface level and the snout body tip position constant, the snout body tip Since the dipping position in the plating bath is always constant, there is no adhesion or peeling of the top dross to the inner surface of the tip portion of the snout body, and it is possible to eliminate plate defects and poor plating quality.

(2) When the immersion depth in the plating bath is 10 to 100 mm, the internal stress of the snout body can be reduced when the tip of the snout body is immersed in the plating bath, and there are cracks in the snout body. Since it becomes difficult to generate | occur | produce, the lifetime of a snout main body is extended.

(3) The life of the snout body can be further extended by lowering the tip position of the snout body by the amount of wear due to the erosion of the snout body.

It is a schematic block diagram of the snout of the continuous hot dipping apparatus in embodiment of this invention. It is explanatory drawing which shows the control condition of a snout main body front-end | tip position. It is explanatory drawing which shows the eddy current generation | occurrence | production state by rushing into the bath surface of the plating bath of a steel strip. It is a figure which shows the bath surface fluctuation | variation in the plating bath of a continuous hot dipping apparatus. It is the A section enlarged view of FIG. It is a figure which shows the stress log | history of the moment which immersed the snout front-end | tip in the bath surface by FEM analysis. It is a schematic block diagram of the snout of the conventional continuous hot dipping apparatus. It is explanatory drawing which shows the mechanism of plating quality defect generation | occurrence | production.

  FIG. 1 is a schematic configuration diagram of a snout of a continuous hot dipping apparatus in an embodiment of the present invention. In FIG. 1, the continuous hot dipping apparatus in the embodiment of the present invention reduces the steel strip P in the reduction furnace 2, and then prevents the steel strip P from being oxidized in the duct-shaped snout body 1. It is immersed in the plating bath 3, the direction of the steel strip P is changed vertically by the roll 4, and the plating adhesion amount is adjusted by the wiping device 5 disposed immediately above the plating bath 3.

  The snout main body 1 includes a base side main body 10 a connected to the reduction furnace 2 and a front end side main body 10 b whose front end is immersed in the plating bath 3. In addition, a bellows 11 is provided between the base side main body 10a and the tip end side main body 10b so that the inside of the snout main body 1 is airtight and the snout main body 1 is extendable. The tip side main body 10b is provided with a lifting motor cylinder 12 as lifting means for lifting and lowering the tip position of the snout body 1.

  The elevating motor cylinder 12 is provided with a movement amount sensor 13 such as a PLG (Pulse Logic Generator; speed detector) or an analog position sensor as detection means for detecting the movement amount of the cylinder rod 12a. A temperature sensor 14 is provided on the surface of the tip end side main body 10b of the snout main body 1 as temperature detecting means for detecting the surface temperature. Further, an ultrasonic sensor 15 as a bath surface detection level detecting means for detecting the bath surface level of the plating bath 3 is provided on the upper part of the plating bath 3.

  In addition, the snout in this embodiment includes a level control device 16 as a control means for controlling the lifting motor cylinder 12. The movement amount sensor 13, the temperature sensor 14, and the ultrasonic sensor 15 are connected to the level control device 16. The ultrasonic sensor 15 is connected to the level control device 16 via the level transducer 17. The level control device 16 controls the lifting motor cylinder 12 based on input signals from the movement amount sensor 13, the temperature sensor 14, and the ultrasonic sensor 15.

  Specifically, the level control device 16 determines the reference of the snout body 1 obtained from the following equation (1) based on the preset immersion depth (L2) of the distal end portion of the distal end body 10b of the snout body 1. The moving amount of the elevating motor cylinder 12 is controlled so that the moving distance (Lset) from the position X is constant.

Lset = (L1 + L2) / sin θ− (L3 + L3 · E · Ts) (1)
In addition,
Lset: movement distance from the reference position X of the snout body 1 L1: distance from the bath surface to the reference position X of the snout body 1 L2: distance from the bath surface to the tip position Y of the snout body 1 (immersion depth: control setting) value)
L3: Physical distance from the reference position X to the tip position Y of the snout body 1 (L4) −Lset
E: Linear thermal expansion coefficient [/ ° C.] of the snout body 1
Ts: surface temperature of the snout body 1 [° C.]
It is.

  Here, the distance L1 from the bath surface to the reference position X of the snout body 1 is calculated from the bath surface level detected by the ultrasonic sensor 15 and the movement amount of the cylinder rod 12a detected by the movement amount sensor 13. Although immersion depth L2 can be set freely, it is desirable to set in the range of 10-100 mm. The physical distance L4 from the reference position X to the tip position Y of the snout body 1 is a distance obtained by measuring the amount of wear during periodic inspection of the equipment and taking this amount of wear into account.

  Next, a snout control method having the above-described configuration will be described with reference to FIG. FIG. 2 is an explanatory diagram showing the control status of the tip position of the snout body.

  In the snout in the present embodiment, the level control device 16 uses the lifting motor cylinder 12 in accordance with the bath surface level detected by the ultrasonic sensor 15, that is, the tip position Y of the snout body 1, that is, the tip side main body 10 b of the snout body 1. And the relative position between the bath surface level and the tip position Y of the snout body 1 is kept constant.

  2A, when the bath surface of the plating bath 3 rises as shown in FIG. 2B, the tip of the snout body 1 is moved to the lowering of the bath surface. The part-side main body 10b is lowered, and the immersion depth L2 is kept constant. Moreover, when the bath surface rises again as shown in FIG. 5C, the tip side body 10b of the snout body 1 rises with the rise of the bath surface, and the immersion depth L2 is kept constant. That is, since the immersion position of the tip portion of the snout body 1 in the plating bath 3 is always constant, the adhesion and peeling of the top dross to the inner surface of the tip portion of the snout body 1 is prevented, and the sheet metal and plating quality are poor. Is prevented.

  In addition, the snout in this embodiment includes a temperature sensor 14 that detects the surface temperature of the snout body 1, and the level controller 16 detects the surface temperature of the snout body 1 detected by the temperature sensor 14 as described above. It functions as a tip position calculating means for calculating the tip position of the snout body 1, and a more accurate tip position of the snout body 1 is calculated by the equation (1) including the amount of thermal expansion of the operating snout body 1, The relative position between the bath surface level and the tip position of the snout body 1 is kept more accurately and constant.

  Moreover, in the snout in this embodiment, since the immersion depth L2 in the plating bath 3 can be kept constant within a range of 10 to 100 mm, the tip portion of the snout body 1 is immersed in the plating bath 3. The internal stress of the snout body 1 can be reduced, and cracks and the like are less likely to occur in the snout body 1. Moreover, since the immersion depth L2 is small, as shown in FIG. 3, the top dross scraping effect by an ash etc. is also acquired by the eddy current by the penetration of the steel strip P into the bath surface of the plating bath 3.

  Further, in the snout in the present embodiment, the physical distance L3 from the reference position X to the tip position Y of the snout body 1 is set to a distance including the amount of wear of the snout, so that only the wear due to the erosion of the snout body 1 is obtained. Since the tip position of the snout body 1 is lowered, the snout body can be used over a long period of time.

  It verified about the quality improvement effect of the steel strip P by the snout in the said embodiment. Table 1 shows the results of operation of the continuous hot dipping apparatus for 3 months at a plate thickness of 0.4 to 3.0 mm, a plate width of 750 to 1850 mm, and a line speed of 60 to 135 mpm. As can be seen from Table 1, in the conventional snout, the bath surface in the snout fluctuates up to 100 mm, whereas in the snout of this embodiment, only up to 5 mm fluctuates, and there is no plating quality defect. It is.

  Next, the following speed with respect to the bath surface fluctuation was verified. FIG. 4 is a diagram showing the bath surface fluctuation in the plating bath of the continuous hot dipping apparatus, and FIG. In FIG. 4, the bath surface level of the plating bath has a fluctuation range of 50 mm from a minimum of 30 mm to a maximum of 80 mm, but a fluctuation range of a maximum of 100 mm is confirmed in actual operation. And as shown in FIG. 5, since the bath surface fluctuation | variation speed | rate at this time is 30 mm / 1.5min = 20mm / min at the maximum, it turns out that the raising / lowering motor cylinder 12 should just be controlled more than this speed | rate. .

  Next, the internal stress when the tip of the snout was immersed in the plating bath was verified. FIG. 6 shows the stress history at the moment when the snout tip is immersed in the bath surface by FEM analysis. As can be seen from FIG. 6, in the snout of this example, the immersion amount at the tip of the snout is as shallow as 100 mm, and the maximum stress of the new support can be reduced.

  INDUSTRIAL APPLICABILITY The present invention is useful as a snout for a continuous hot dipping apparatus that prevents the steel strip after being reduced in a reduction furnace from being oxidized and leads it to a plating bath and a control method therefor.

P Steel strip 1 Snout body 2 Reduction furnace 3 Plating bath 4 Roll 5 Wiping device 10a Base side body 10b Tip side body 11 Bellows 12 Lifting motor cylinder 12a Cylinder rod 13 Movement sensor 14 Temperature sensor 15 Ultrasonic sensor 16 Level control Equipment 17 Level transducer

Claims (5)

Snout of a continuous hot dipping apparatus in which the tip is immersed in a plating bath,
Bath surface level detecting means for detecting the bath surface level of the plating bath;
Elevating means for elevating and lowering the snout body tip position;
Control means for raising and lowering the snout body tip position by the elevating means according to the bath surface level detected by the bath surface level detecting means, and maintaining the relative position between the bath surface level and the snout body tip position constant. Snout of continuous hot dipping equipment. Temperature detecting means for detecting the surface temperature of the snout body,
The snout of the continuous hot dipping apparatus according to claim 1, further comprising a tip position calculating means for calculating the tip position of the snout body from the surface temperature of the snout body detected by the temperature detecting means.   The snout of the continuous hot dipping apparatus according to claim 1 or 2, wherein the immersion depth in the plating bath is 10 to 100 mm. A method for controlling the snout of a continuous hot dipping apparatus in which the tip is immersed in a plating bath,
Detecting the bath level of the plating bath,
A method for controlling the snout of a continuous hot dipping apparatus, comprising raising and lowering the tip position of the snout body in accordance with the bath surface level and keeping the relative position between the bath surface level and the tip position of the snout body constant.   The snout control method for a continuous hot dipping apparatus according to claim 4, wherein the tip position of the snout body is lowered by an amount of wear due to erosion of the snout body.