JPH0559511A - Galvanizing equipment for steel strip - Google Patents

Abstract

PURPOSE:To change the direction of a plated steel strip of high temp. in noncontact by arranging plural electromagnets in such a manner that the shape of the sucking face against the steel strip is formed into a circular-arc one, controlling an exciting current and floating the steel strip up to a certain place by a magnetic force. CONSTITUTION:Electromagnets 11a to 11c are arranged in a curcular-arc state against a steel strip 1. Sensors 12a to 12c measure the distance between the electromagnets 11a to 11c and the steel strip 1 to control an exciting current and to float the steel strip 1 up to a certain place by a magnetic force. An auxiliary roll 13 is needless in the process of ordinary operation, but it is used in the case of sheet passing in the initial stage or in the case of an accident at the time of power failure. The progressing direction of the plated steel strip 1 of high temp. can be changed in noncontact.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous galvanizing equipment for steel strip.

[0002]

2. Description of the Related Art FIG. 8 shows a typical hot dip galvanizing facility. The steel strip 1 is plated with a molten zinc pot 2, the plating layer is alloyed at a temperature of about 500 ° C. in an alloying furnace 3, cooled to 300 to 350 ° C. in a cooler 4, and then the direction of travel is changed by a top roll 6, Cooler 5 and water cooling tank 7
It is cooled down to room temperature.

[0003]

The height H of the plating equipment having such an equipment structure is 60 m or more in a line with a speed of 150 mpm, which makes the equipment cost including the building extremely expensive, and the construction of a high-rise building. The construction process with approval is lengthened.

[0004] When the steel strip after plating is in a high temperature state, it is impossible to change the traveling direction by touching the roll due to the quality of the product, and thus such a problem occurs. Needless to say, it is desirable to change the traveling direction of the steel strip without contacting the steel plate.
And ACB (air cushion bearing) shown in FIG.
There are 20. This ejects air from the slit 21,
The steel strip 1 is supported by the static pressure generated inside the rectangular slit path. However, as the thickness of the steel strip becomes thicker, the power of the blower 22 required to levitate and support the steel strip by the ACB 20 sharply increases, making it difficult to make a realistic design. For example, a blower power of 500 kW or more is required to support a steel strip having a thickness of 1 mm and a width of 1000 mm.

The present invention has been devised in various ways to solve the problems of the prior art. It enables efficient non-contact support with low energy consumption and does not require a high-rise building even if the line speed is increased. It is an object to provide a hot-dip galvanizing equipment for steel strip.

[0006]

According to the present invention, a plurality of electromagnets are arranged above a plating pot of a hot-dip galvanizing line so that the suction surface for a steel strip has a circular arc shape or a shape close to a circular arc. A melting point characterized by providing a sensor for measuring the distance between the surface of the steel strip and the surface of the steel strip, and controlling the exciting current of the electromagnet based on the distance by the sensor to magnetically levitate the steel strip to a certain position while changing its traveling direction. The main point is galvanizing equipment.

[0007]

EXAMPLE FIG. 1 shows hot dip galvanizing equipment using the magnetic levitation method of the present invention. The steel strip 1 plated with the zinc pot 2 and pulled up passes through the alloying furnace 3a and is maintained at a temperature of about 500 ° C., and the traveling direction is changed downward through the magnetic levitation device 10 and further alloyed in the alloying furnace 3b. After that, the process of cooling to normal temperature is started. In FIG. 1, in order to prevent the flatness of the steel strip from deteriorating, primary cooling is performed in a water cooling tank 8 filled with water close to the boiling point at a relatively low cooling rate, and then cooled to room temperature in a water cooling tank 7 filled with room temperature water. Note that these cooling facilities are not the gist of the present invention, and any means such as an air jet cooler may be used. However, when a means with a low cooling rate such as an air jet cooler is used, the traveling direction of the steel strip is changed again at a high temperature, so as shown in FIG. Direction bending devices 10a, 10b are required.

FIG. 3 shows the details of the apparatus 10 for bending the traveling direction of the steel strip by the magnetic levitation method according to the present invention. 11a ~
Reference numeral 11c is an electromagnet, and 12a to 12c are sensors for detecting the position of the steel strip, which are known laser type displacement gauges, ultrasonic type displacement gauges or the like. Reference numeral 13 is an auxiliary roll, which is not necessary during normal operation, but is used for the initial passage. In addition, it is necessary to prevent the steel strip from falling if an accident such as a power failure occurs during normal operation.

Next, a specific design method of the electromagnet will be described. In FIG. 3, where the thickness of the steel strip 1 is t, the unit tension acting on the steel strip is σ, and the bending diameter of the steel strip is D, the attraction force required to hold the steel strip (per unit area of the magnet attraction surface) ) F is f = 2tσ / D (1) On the other hand, in the magnetic circuit shown in FIG. 4, the attraction force by the electromagnet 11 is A: the area of the electromagnet attraction surface, B: the magnetic flux passes in the steel strip. Cross-sectional area of the portion to be applied, l _A : length of electromagnet core, l _B : length of magnetic flux passing through the steel strip, μ
_O : vacuum permeability, μ _A : relative permeability of electromagnet core, μ _B :
Relative permeability of steel strip, δ: distance between electromagnet attraction surface and steel strip,
Assuming that N is the number of turns of the coil and I is the current of the coil, the total magnetic resistance of the magnetic circuit is R = (l _A / (μ _A · A) + 2δ / A + l _B / (μ _B · B)) / μ _O .... … (2) Total magnetic flux Φ = N · I / R ……… (3) Attraction force (per electromagnet) F = Φ ² / (μ _O · A) ……… (4) (1) to (4) ) A specific design example based on the equation will be described. Although three electromagnets are shown in FIG. 3, in practice, it is preferable to arrange more small magnets in the circumferential direction and in the width direction of the steel strip.

Steel strip thickness: 2 mm, steel strip width: 1000 mm, tension σ: 1 kg / mm ² , bending diameter D: 3000 mm, number of magnets: 9
(Circumferential direction) × 4 (Width direction) = 36, Permeability μ _A : 10
When 00, μ _B : 1000 and air gap σ: 10 mm, the magnetomotive force required per magnet is 7500 ampere-turns. The number of coil turns N and the current I can be freely combined. If N is increased, I is decreased and power consumption is reduced. However, if N is made large, the self-inductance of the electromagnet becomes large and controllability deteriorates. As a result of the study by the present inventor, it is desirable that this inductance be 1 henry or less. If N = 100, the inductance will be 0.2 henry, and if a copper wire with a wire diameter of 2 mm is used for the coil, the total power consumption of the 36 magnets will be 45 kW.
Compared with the conventional technology (ACB) of 500 kW, the power consumption is 1/10 or less.

FIG. 5 shows a method of controlling the floating of the steel strip according to the present invention. Exciting current of the electromagnet is controlled in accordance with the deviation between the steel plate position [delta] and the command value [delta] _{re f.} S is the Laplace variable, K
_I , K _P , and K _D are integral, proportional, and derivative control gains of the position control system that converts the position deviation into an exciting current command, respectively.
K _ID and K _IP are differential and proportional control gains of the current control system that controls the voltage applied to the electromagnet according to the deviation between the current command value and the actual current.

FIG. 6 shows an example of the control result. The above graph shows the position of the steel strip, the +20 mm position is the magnet's attraction surface,
The position of 20 mm is the surface of the auxiliary roll 13, and the target control position is +10 mm. Control gain is K _I = 5A / mm ・
sec, K _P = 30 A / mm, K _D = 5 A · sec / mm, K _IP
= 5V / A and K _ID = 0.005V · sec / A. One scale on the horizontal axis is 1 second, and as is clear from FIG. 6, the steel strip that was initially on the auxiliary roll reached the target position within 1 second after starting the control, and thereafter maintained the target position in a stable state. ing.

FIG. 7 shows a case where the differential control gain K _D = 0. The steel strip position reciprocates between the magnet and the auxiliary roll,
Stable control is not possible. The unstable state shown in FIG. 7 occurs regardless of how other gains are adjusted when the differential control is not performed. That is, it is noteworthy that the differential control of the position control system is essential in this magnetic levitation control.

A current control system (a system including K _ID and K _IP ) is not essential, but it is desirable to provide it for stabilizing the control. It should be noted that the respective control gains may be selected according to the specifications of the equipment (the thickness of the steel strip, the tension, etc.) while observing the movement of the steel strip in the actual machine, and it is not necessary to stick to the above values.

[0015]

EFFECTS OF THE INVENTION By using the technique of the present invention, it is possible to change the traveling direction of a high temperature plated steel strip in a non-contact manner, and it is not necessary to make a huge high-rise building as in the conventional case even if the line specifications are speeded up. The equipment cost will be significantly reduced.
Further, it has an advantage that power consumption is 1/10 or less as compared with ACB (air cushion bearing) which is an existing technology for non-contact traveling direction change. Further, since it does not have a forced cooling effect like ACB, it becomes possible to change the traveling direction in the middle of a high temperature alloying furnace, and it is possible to provide a technology indispensable for realizing a future high-speed hot dip galvanizing line. ..

The technique of the present invention can be used not only for hot-dip galvanizing equipment for steel strips but also for drying furnaces in steel strip coating lines for the purpose of non-contact supporting the steel strips after coating and drying. You can

[Brief description of drawings]

FIG. 1 shows an example of hot dip galvanizing equipment using a magnetic levitation type steel strip traveling direction changing device of the present invention.

FIG. 2 is another example of hot dip galvanizing equipment using the magnetic levitation type steel strip traveling direction changing device of the present invention.

FIG. 3 is a detailed structure of a magnetic levitation type steel strip traveling direction changing device of the present invention.

FIG. 4 is a diagram for explaining an equation for obtaining magnetic attraction.

FIG. 5 is a control system for levitating the steel strip to a target position by magnetic attraction.

FIG. 6 shows an example of magnetic levitation control results.

FIG. 7 shows an example of magnetic levitation control results.

FIG. 8 shows an outline of conventional galvanizing equipment.

FIG. 9 shows an air cushion bearing which is a conventional non-contact support system.

FIG. 10 is a development view of an arc portion of FIG.

[Explanation of symbols]

 1 Steel strip 2 Zinc pot 3 Alloying furnace 7,8 Water cooling tank 10 Magnetic levitation device 11 Electromagnet 12 Position detection sensor 13 Auxiliary roll

Claims (1)

[Claims] 1. A plurality of electromagnets are arranged above a galvanizing pot of a hot dip galvanizing line so that a suction surface for a steel strip is a circular arc or a shape close to a circular arc, and a distance between the suction surface of the electromagnet and the steel strip surface. A hot dip galvanizing facility characterized in that a sensor for measuring the temperature is provided, and the exciting current of the electromagnet is controlled based on the distance by the sensor to magnetically levitate the steel strip to a fixed position while changing its traveling direction.