CONTINUOUS PROCESSING LINE FOR PROCESSING A NON-MAGNETIC METAL STRIP INCLUDING A GALVANNEALING SECTION AND METHOD FOR INDUCTION HEATING OF SAID STRIP IN SAID GALVANNEALING SECTION

Abstract

Disclosed is a continuous processing line for processing a non-magnetic metal strip 1 and specifically to an induction heating apparatus 14 and method intended for heating the non-magnetic metal strip travelling through the continuous processing line, including a coating section 20, the apparatus being installed downstream from the coating section in the direction of travel of the strip, the apparatus making it possible to raise the temperature of the strip across the entire width thereof to the level required to obtain the sought development of the coating thereof, the heating apparatus including at least one cross-flow inductor 15.

Claims

1. A continuous processing line for processing a nonmagnetic metal strip (1), the processing line comprising a coating section (20) and a galvannealing section placed downstream of the coating section (20) and comprising an induction heating apparatus (14) intended to heat said nonmagnetic metal strip, characterized in that the heating apparatus comprises at least one transverse flux inductor (15).

2. The processing line as claimed in claim 1, comprising screens (18) which can be moved laterally over the strip width so as to influence the transverse temperature profile of the strip, characterized in that adjustment of the position of the screens makes it possible to regulate overheating of the edges (19) of the strip.

3. The processing line as claimed in claim 2, characterized in that the screens (18) can be moved transversely in order to adjust their spacing with respect to the strip.

4. The processing line as claimed in claim 1, characterized in that the transverse flux inductor (15) comprises at least two pairs of coils (16).

5. A method for induction heating of a nonmagnetic metal strip (1) in a galvannealing section of a continuous processing line for processing said nonmagnetic metal strip, said processing line comprising a coating section (20), the galvannealing section being placed downstream of the coating section, characterized in that the heating of the strip is carried out by means of a transverse flux inductor (15).

6. The method as claimed in claim 5, characterized in that the position of movable screens (18) is adjusted so as to regulate overheating of the edges of the nonmagnetic metal strip (1) by the transverse flux inductor (15) and to obtain a substantially homogeneous temperature of the strip at the exit of the inductor.

Description

[0019] The characteristics and advantages of the invention will become apparent on reading the following description, which is given by way of nonlimiting example and with reference to the following appended figures:

[0020] FIG. 1: schematically represents a coating section of a galvanization line for processing magnetic steels, comprising galvannealing with longitudinal flux induction heating according to the prior art,

[0021] FIG. 2: schematically illustrates the magnetic flux which results from a longitudinal flux inductor,

[0022] FIG. 3: schematically illustrates the magnetic flux which results from a transverse flux inductor,

[0023] FIG. 4: schematically represents an exemplary embodiment of an induction heating apparatus according to the invention, and

[0024] FIG. 5: schematically represents a sectional view of an exemplary embodiment of an induction heating apparatus according to the invention, showing in particular the use of movable screens.

[0025] FIG. 1 schematically represents a galvanization tower 21 of a galvanization line. A galvannealing section is placed downstream of the coating section 20. The strip 1 coming from the annealing furnace is immersed in the zinc bath 2. The direction of advance of the strip is indicated by the arrow 13. At the exit of the zinc bath, the strip rises vertically in the galvanization tower. It passes through a dryer 3 which makes it possible to keep on the strip only the required coating thickness before entering the galvannealing section.

[0026] The strip passes first through the heating apparatus 4 equipped with a longitudinal flux inductor 5, which makes it possible to bring the strip to the temperature required for the galvannealing. It then passes through the holding unit 6 equipped with electrical resistors 7. The strip is then cooled with air by successive cooling sleeves 8 then with water in a water tank 9.

[0027] FIG. 2 schematically illustrates the magnetic flux 10 which results from a longitudinal flux inductor 5. This flux is tangent to the surface of the strip 1.

[0028] FIG. 3 schematically illustrates the magnetic flux 11 which results from a transverse flux inductor 12. This inductor consists of a pair of coils 12a, 12b. The flux is directed perpendicularly to the surface of the strip 1.

[0029] FIG. 4 schematically represents an exemplary embodiment of an induction heating apparatus 14 according to the invention. This apparatus comprises a transverse flux inductor 15 comprising two pairs of coils 16a, 16b, which follow one another in the direction of advance of the strip. One pair consists of coils placed on each side of the strip 1. The coils are held by supports 17.

[0030] The apparatus also comprises screens 18 placed on either side of the edges 19 of the strip. FIG. 5 illustrates in more detail the positioning of these movable screens 18a, 18b with respect to the strip 1, to the coils 16 and to the support plates 17.

[0031] These screens can be removed laterally over the width of the strip so as to influence the transverse temperature profile of the strip. Lateral adjustment is intended to mean that 2 screens 18a, 18b placed on the two opposite edges 19 of the strip are moved closer together or further away. Adjustment of the position of the screens makes it possible to regulate overheating of the edges in order to compensate for the side effects which have led to greater cooling of the edges and thus to obtain a substantially homogeneous temperature of the strip at the exit of the inductor.

[0032] According to one alternative embodiment of the invention, the screens 18 can also be moved transversely in order to adjust their spacing with respect to the strip. This complementary adjustment allows a further possibility of regulating the heating apparatus.

[0033] Controlling the screens thus makes it possible to correct an insufficient temperature of the edges existing before the galvannealing section, and to do so for sheet metal of different widths, in which the position and the width of the underheating can vary along the width and thickness of the steel strips to be treated.

[0034] According to one exemplary embodiment of the invention, which is represented in FIG. 4, the control of the transverse flux inductor is carried out on the basis of a temperature measurement of the strip by a contactless temperature measurement system 22 with a panoramic view, covering the entire width of the strip, or one composed of several contactless measurement systems over the width of the strip, for example one system 22a located on the center of the strip and two systems 22b located on its edges.

[0035] Advantageously according to the invention, the position of the strip with respect to the theoretical axis of the line, and its possible drift with respect to the center of the line, is monitored by the system/systems for measuring the temperature at the edges, by carrying out actual detection of the position of the edges, which is obtained by the difference between the temperature of said edges and of the bottom of the furnace. If necessary, the position of the inductor is adjusted in order to maintain optimum heating of the strip even in the event of a drift thereof with respect to the center of the line.

[0036] Furthermore, the overall temperature level of the strip at the exit of the inductor is adjusted with a minimum difference from the average temperature imposed by the method by using the system 22 for measuring the temperature of the strip, while considering only the central part of the strip, or an average temperature after excluding the temperature of the edges.