EP1205572A1 - Process and apparatus for hot dip coating of metallic strip, especially steel strip - Google Patents

Abstract

Process for hot dip coating of steel strands (1) comprises: (i) feeding the strands vertically through a melting vessel containing a molten coating metal (2) and a connected guiding channel (5); (ii) producing induction currents in the coating metal using an electromagnetic field; and (iii) applying an electromotive force to interact with the electromagnetic field to retain the coating metal. To guide the metal strand in the guiding channel without contact, a force equilibrium is adjusted between the electromagnetic field in the metal strands and in the guiding channel by rotating an inductor (4) about its longitudinal axis. An Independent claim is also included for a device for hot dip coating of steel strands. Preferred Features: The induction forces affecting the deformation of the steel strands and/or the induction forces affecting the guiding channel are measured and the measured values are processed in a control system to an adjusting signal for rotating the inductor.

Description

The invention relates to a method and a device for hot dip coating of metal strands, in particular of steel strip, in which the metal strand vertically through one that receives the molten coating metal Melting vessel and passed through an upstream guide channel is caused by an electromagnetic field in the coating metal induction currents be induced to interact with the electromagnetic Field an electromotive force to retain the coating metal cause.

The hot-dip coating of strips made of soft, unalloyed steels is known as vertical hot dip galvanizing and is used in various publications described. In this process, a metal strip runs through with molten metal filled with zinc and / or aluminum alloys from bottom to top, with the metal strip first undergoing a temperature treatment has experienced and the entry of the metal strip into the melt with the exclusion of air he follows.

Such a method is e.g. known from EP 0 673 444 B1. However, there is solved the task of creating a process to calm the To achieve melt in the guide channel and also in the container because of the magnetic Forces are distributed unevenly and vortices arise. The well-known solution consists of a hiking field in the upper area, in Near the melting vessel, the guide channel, a constant direct or alternating current field is directed in the opposite direction, which causes a swirl in the coating metal dampens in this area.

Another method provides (WO 96/03533) by means of the guide channel arranged field generators to generate an oscillating field. The induced Forces, however, only have the electromagnetic lock of the To close the guide channel and do no other tasks.

A controllable magnetic field is used in the area of the feed-through channel for band stabilization (DE 195 35 854 A1).

The procedures described above are mainly used for hydrodynamic Sealing the coating metal down from the container, that is, the basic physical quantities required by the process make it possible as such.

The use of electromagnetic forces induces eddy currents in the melt, the vertical, resulting forces in the melt produce. The magnetic fields generate forces perpendicular to the metal strand surface that just cancel each other out for the symmetrical case, which, however, with decreasing distance from the metal strand surface to Rising inductor surface. The symmetrical position of the fields to the surfaces of the metal strand, however, is in practice an exceptional case that can rarely be achieved. For the normal case that the metal strand is the Leaves the center position in the inductor, the attractive forces towards the inductor, to which the starting movement was initially approached, larger and additionally reinforcing the attractive forces become smaller towards the inductor, from which the starting movement first went away.

Provided that the position of the metal strand in the guide channel for the magnetohydrodynamic Closure is unstable, only the mechanical longitudinal pull remains, which rests on the metal strand during the process, but which is not sufficient, to keep the metal strand in a stable central position.

This positional instability affects the central position of the metal strand on the one hand and others, however, also the shape of the metal strand parallel to the direction of the strand in Guide channel. A slight flatness disorder located in a steel strip becomes also reinforced, i.e. a cross bow in the band is enlarged. First try have shown that in the magneto-hydrodynamic closure of the guide channel Forces act which, in combination with the coating temperature, become plastic Change the shape of the tape. In addition to the cross bow errors S-shaped tape shape errors parallel to the tape running direction also found. The observed waveforms of the deformation are greater than or equal to the 2nd Order.

The invention has for its object the metal strand, which is under a operational tension of the pulley arrangement is located in Guide channel deformed into an approximately central, straight, stretched position in the guide channel bring to.

The object is achieved according to the invention in that the contactless Guiding the metal strand in the guide channel or in the induction channel a balance of forces between the electromagnetic field in the metal strand and in the guide channel by rotating at least the inductor about its longitudinal axis is set. This prevents and prevents an S-shape of the metal strand the metal strand does not touch the channel walls of the guide channel either.

This ensures a stable belt run. Such a system doesn't do that Attempt to stabilize the strand run, but the metal strand is set via the inner cross section of the inductor.

This can be assisted by the fact that they bring about the deformation of the metal strand Induction forces and / or the induction forces acting on the guide channel measured and the measured values in a control loop to one Control signal for a rotary drive of the inductor are processed.

Other features are that the metal strand is under an elevated specific tractive force is maintained. This procedure is possible because the Metal strand mechanically via a pair of rollers before entering the guide channel is managed and stabilized.

A device for hot-dip coating of metal strands, in particular of steel strip in which the metal strand passes vertically through the molten coating metal receiving melting vessel and by an upstream Guide channel is movable through, in which by an electromagnetic field Induction currents can be induced in the coating metal, which interact with the electromagnetic field an electromagnetic force to hold back of the coating metal, solves the task set at the outset by that at least the inductor for the metal strand by means of a controllable Twist drive to the continuous metal strand in the cross section of the guide channel It can be aligned that the metal strand is non-contact and approximately in the middle runs within the cross section of the guide channel. This is a touch the inner channel wall of the guide channel avoided and the metal strand can be largely smooth and centered. The magnetic force effect stands within the guide channel at a certain angle of rotation of the guide channel in balance with the forces caused by the roller arrangement be exerted together with the specific tensile force in the metal strand.

This makes the belt run stable and the metal strand can have the aforementioned S shape no longer accept.

The regulated setting can be designed such that the outside of the inductor an adjusting cylinder with lever distance to a vertical axis of rotation of the

Guide channel is articulated. This can also be used for the guide channel can be adjusted to the position of the metal strand cross-section to ensure the desired contact-free, largely central belt run.

According to further features, it is provided that the inductor together with the Melting vessel is rotatable about the vertical axis of rotation. You can Form the guide channel and the melting vessel.

A further development provides that a control loop with measuring devices for the determination the metal strand cross-sectional layer is formed in the guide channel. This allows receive the necessary measured values for the actuating signals of the rotary actuator become.

Another embodiment is that the induction force within the Guide channel depending on the angle of rotation of the metal strand in one horizontal level is measurable. This creates an additional type of measurement.

The device is also designed such that the induction force within of the inductor as a function of the angle of rotation of the metal strand in equilibrium is measurable and adjustable with the forces, which by an arrangement of Deflection rollers arise within a preheating furnace housing by means of which Metal strand can be transported under a pulling force. This can reduce accuracy the measurement can be increased.

The device can also advantageously be accommodated such that the Furnace housing accommodating deflection roller arrangement on an upper cover surface the melting vessel with the guide channel for one from bottom to top moving metal strand and that on the furnace housing next to the Melting vessel and the guide channel of the rotary drive is arranged, the by means of a handlebar with the melting vessel and / or with the guide channel housing connected is.

In the drawing, an embodiment of the invention is shown and will be explained in more detail below.

Fig. 1

eine Seitenansicht des Ofens mit Ofengehäuse, Schmelzgefäß und Führungskanal bzw. Induktionskanal,

Fig. 2

dieselbe Seiten-Ansicht wie Fig. 1 mit dem Verdrehantrieb,

Fig. 2A

eine Draufsicht auf dass Schmelzgefäß und den Führungskanal,

Fig. 3A

eine Draufsicht auf den Querschnitt des Induktors mit dem Führungskanal ohne die Wirkung der Induktionskraft,

Fig. 3B

den Querschnitt des Induktors mit dem Führungskanal mit wirkender Induktionskraft, aber ohne Einschalten des Verdreh-Antriebs und

Fig. 3C

den Querschnitt des Führungskanals bei wirkender Induktionskraft und eingeschaltetem Verdreh-Antrieb für den Führungskanal.

Show it:

Fig. 1

a side view of the furnace with furnace housing, melting vessel and guide channel or induction channel,

Fig. 2

the same side view as Fig. 1 with the rotary drive,

Figure 2A

a plan view of the melting vessel and the guide channel,

Figure 3A

a plan view of the cross section of the inductor with the guide channel without the effect of the induction force,

Figure 3B

the cross section of the inductor with the guide channel with effective induction force, but without switching on the rotary drive and

Figure 3C

the cross section of the guide channel when the induction force is active and the rotary drive for the guide channel is switched on.

The method for hot dip coating of metal strands 1, in particular of steel strip 1a, presupposes that the metal strand 1 is vertical (from below upwards) by a receiving the molten coating metal 2 Melting vessel 3 and passed through an upstream guide channel 5 becomes. In the guide channel 5 by an electromagnetic field in the Coating metal generates 2 induction currents that interact with the electromagnetic field of the inductor 4 an electromotive force for restraint of the coating metal 2 against downward leakage.

The metal strand 1 now becomes contactless with the inner guide channel wall guided in the center of the guide channel 5 by a balance of forces between the electromagnetic field of the induction channel in the metal strand 1 and in the guide channel 5 by rotating the guide channel 5 about its longitudinal axis 4a takes place (first alternative).

For this purpose, the inductive forces causing the metal strand 1 to deform measured and the measured values in a control loop for a control signal for processed a rotary drive 6 of the inductor 4. The metal strand 1 can also be kept under an increased specific tensile force.

1, hot-dip coating of metal strands 1 takes place, in particular of steel strip 1a, which is melted vertically from the bottom up through that Coating metal 2 receiving melting vessel 3 and through the upstream guide channel 5 is pulled instead. The metal strand 1 is in preheated an oven 7 and via a roller arrangement 8 with a deflecting roller 8a into the guide channel 5 or the inductor 4. The guide channel 5 has process-related e.g. an opening width of approx. 20 mm and a Height (= length) of e.g. 500 mm. The coating is found in the melting vessel 3 instead of. The coating metal 2 can e.g. made of a zinc or aluminum alloy consist. The inductor 4 is by means of an adjustable adjusting cylinder 9 with its cross section 4b in such a way that the metal strand 1 non-contact and largely centered within the cross section 4b of the guide channel 5 runs (see FIG. 2A).

On the inductor 4 is the adjusting cylinder 9 with a lever distance 10 (e.g. via a piston rod) articulated to the vertical longitudinal axis 4a of the inductor 4.

The guide channel 5 can also together with the melting vessel 3 as a unit be rotatable.

The control circuit (not shown in detail) has measuring devices for determining the Metal strand cross-sectional position in the guide channel 5. The induction force in the inductor 4 depending on the angle of rotation of the metal strand 1 in one horizontal plane can be measured. The induction force is within the Inductor 4 as a function of the angle of rotation of the metal strand 1 in equilibrium measurable and adjustable with the forces. These readings are through co-determines an arrangement 8 of deflection rollers 8a within a furnace vessel 7a, because the metal strand 1 is transported under an increased tensile force.

The furnace housing 7a receiving the roller arrangement 8 is on an upper one Cover surface 11 with the involvement of a compensator 12 with the guide channel 5 or the inductor 4. The metal strand 1 is through the guide channel 5 moved from bottom to top. On the furnace housing 7a is next to the melting vessel 3 and the induction channel of the rotary drive 6, the an adjustable hydraulic adjusting cylinder 9 can exist.

According to FIG. 3A (second alternative) the cross section 4b is without the belt run Effect of induction force shown. In Fig. 3B the tape run takes place under the Effect of the induction force instead, so that the disadvantageous S shape of the steel strip results. 3B, the rotary drive 6 is not switched on. The best possible The solution is therefore shown in FIG. 3C, in which the tape run with induction switched on and switched-on rotary drive 6 is shown, so that there is a complete central position of the cross section 4b in the guide channel 5 results.

LIST OF REFERENCE NUMBERS

1

metal strand

1 a

steel strip

2

molten coating metal

3

melting vessel

4

inductor

4a

rotary axis

4b

cross-section

5

guide channel

6

turning drive

7

oven

7a

furnace housing

8th

Roller arrangement

8a

guide rollers

9

adjusting cylinder

10

lever distance

11

upper surface

12

compensator

Claims (10)

Process for hot-dip coating of metal strands, in particular steel strip, in which the metal strand is passed vertically through a melting vessel which holds the molten coating metal and through an upstream guide channel in which induction currents are induced by an electromagnetic field in the coating metal which interact with the electromagnetic field cause electromotive force to retain the coating metal,
characterized in that for the contactless guidance of the metal strand in the guide channel or in the induction channel, a balance of forces between the electromagnetic field in the metal strand and in the guide channel is set by rotating at least the inductor about its longitudinal axis. Method according to claim 1,
characterized in that the induction forces causing the deformation of the metal strand and / or the induction forces acting on the guide channel are measured and the measured values are each processed in a control loop to form a control signal for a rotary drive of the inductor. Method according to one of claims 1 or 2,
characterized in that the metal strand is held under an increased specific tensile force. Device for hot-dip coating of metal strands, in particular steel strip, in which the metal strand can be moved vertically through a melting vessel which holds the molten coating metal and through an upstream guide channel in which induction currents can be induced by an electromagnetic field in the coating metal, which interact with the electromagnetic field exert electromagnetic force to retain the coating metal,
characterized in that at least the inductor (4) for the metal strand (1) can be aligned in cross-section (4b) of the guide channel (5) by means of a controllable rotary drive (6) to the metal strand (1) that passes through it, such that the metal strand (1 ) runs without contact and approximately centrally within the cross section (4c) of the guide channel (5). Device according to claim 4,
characterized in that on the outside of the inductor (4) an adjusting cylinder (9) is articulated with a lever distance (10) to a vertical axis of rotation (4b) of the guide channel (4). Device according to claim 4,
characterized in that the inductor (4) can be rotated together with the melting vessel (3) about the vertical axis of rotation (4b). Device according to one of claims 4 to 6,
characterized in that a control loop is formed with measuring devices for determining the metal strand cross-sectional position in the guide channel (5). Device according to one of claims 4 to 7,
characterized in that the induction force within the guide channel (5) can be measured in a horizontal plane as a function of the angle of rotation of the metal strand (1). Device according to one of claims 4 to 8,
characterized in that the induction force within the inductor (4) is measurable and adjustable in dependence on the angle of rotation of the metal strand (1) in equilibrium with the forces generated by an arrangement (8) of deflection rollers (8a) within a preheating furnace housing (7a ) arise, by means of which the metal strand (1) can be transported under a tensile force. Device according to one of claims 4 to 9,
characterized in that the furnace housing (7a) accommodating the deflecting roller arrangement (8) carries the melting vessel (3) with the guide channel (5) for a metal strand (1) moving from bottom to top on an upper cover surface (11) and in that The rotary drive (6) is arranged on the furnace housing (7a) next to the melting vessel (3) and the guide channel (5) and is connected to the melting vessel (3) and / or to the inductor (4) by means of a handlebar.

Images