METHOD FOR ORIENTING STEEL SHEET GRAINS, CORRESPONDING DEVICE, AND FACILITY IMPLEMENTING SAID METHOD OR DEVICE

Abstract

The invention concerns a method for accentuating the orientation of the grains of a continuous steel sheet (1), in particular for producing electrical sheet steel, said method involving, during the movement of the steel sheet (1) in the longitudinal direction of same, a longitudinal stretching of the steel sheet (1) in a stretch region (1d) in which the steel sheet (1) moves at a temperature of between approximately 750° C. and approximately 900° C. The invention also concerns a device for implementing said method in which the stretching is carried out by two tensioning blocks (41, 42) comprising traction rollers arranged to move and guide the steel sheet (1). The invention further concerns a facility for producing electrical sheet steel comprising a line comprising a rolling mill and on which said method and said device are implemented downstream from the rolling mill.

Claims

1. A method for accentuating the orientation of the grains of a sheet of grain oriented steel during an operation of annealing the steel sheet in a continuous heat treatment furnace, this operation being used in particular for the manufacture of magnetic steel sheet, wherein the method comprises: a step of moving the steel sheet in its longitudinal direction, during which the steel sheet is moved in the furnace, a step of soaking of maintaining a stretch region of the steel sheet at a set temperature of between 750° C. and 900° C., a step of stretching the steel sheet longitudinally in the stretch region.

2. The method as claimed in claim 1, wherein in order to stretch the steel sheet it is brought into driving engagement with two motorized tensioning blocks situated in the furnace, the tensioning blocks being situated one on each side of the stretch region and defining two different speeds of travel for the steel sheet, respectively upstream and downstream of the stretch region.

3. The method as claimed in claim 1, wherein after the stretching step, the steel sheet passes continuously to a nitriding step.

4. The method as claimed in claim 1, wherein the degree of elongation applied to the steel sheet during the stretching step is less than or equal to 10 percent.

5. A device for implementing the method as claimed in claim 1, the device comprising traction apparatus, said traction apparatus comprising at least one upstream tensioning block and one downstream tensioning block, the upstream tensioning block comprising a first group of traction rolls, the downstream tensioning block comprising a second group of traction rolls, the traction rolls of the upstream tensioning block and of the downstream tensioning block being arranged in such a way as to apply traction to the stretch region of the steel sheet, the furnace comprising heating means able to heat the stretch region of the said sheet to the set temperature and hold it at that temperature.

6. The device as claimed in claim 5, further comprising a leveler adjacent to a tensioning block of the traction apparatus.

7. A facility for producing magnetic sheet, comprising a line comprising a rolling mill and implementing the device of claim 5 downstream of the rolling mill.

8. The facility as claimed in claim 7, wherein the line further comprises a leveler comprising leveling rolls.

9. The facility as claimed in claim 7, wherein the line further comprises a decarburizing device upstream of said method or device.

10. The facility as claimed in claim 7, wherein the line further comprises a nitriding device downstream of said method or device.

Description

DESCRIPTION OF THE FIGURES AND EMBODIMENTS

[0073] Further advantages and specifics of the invention will become apparent from reading the detailed description of non-limiting embodiments and implementations, and from studying the following attached figures:

[0074] FIG. 1 depicts a specimen of non-grain-oriented steel sheet,

[0075] FIG. 2 depicts a specimen of grain oriented steel sheet,

[0076] FIG. 3 illustrates the crystal structure of a specimen of steel sheet on a plane parallel to a main face of the sheet,

[0077] FIG. 4 depicts a steel sheet deformed by three leveling rolls,

[0078] FIG. 5 depicts a steel sheet passing over transport rolls and traction rolls of a traction system according to a first embodiment,

[0079] FIG. 6 depicts a steel sheet passing over transport rolls and traction rolls of the traction system according to a second embodiment,

[0080] FIG. 7 depicts the device of FIG. 5 in which the steel sheet is not inserted through the traction system,

[0081] FIG. 8 depicts the device of FIG. 5 comprising a leveler installed upstream of the traction system,

[0082] FIG. 9 depicts two grains respectively before and after implementation of the method according to the invention.

[0083] Because the embodiments described in this text are entirely nonlimiting, alternative forms of the invention comprising only a selection of the features described, in isolation from the other features described may notably be considered (even if this selection is isolated from within a sentence containing these other features) if this selection of features is enough to confer a technical advantage or to differentiate the invention from the prior art. This selection comprises at least one feature which is preferably functional without structural details or with just some of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art.

[0084] With reference to FIGS. 5 to 8, the traction apparatus 4 according to the invention preferably comprises two tensioning blocks 41, 42.

[0085] Each tensioning block, or S-block, comprises at least one traction roll, for example as in FIGS. 5 to 8, where there are four.

[0086] These traction rolls may have mutually identical diameters (FIGS. 5, 7 to 9), or different diameters from one another (FIG. 6).

[0087] In the example depicted in FIG. 7, a steel sheet 1 is passing through a furnace 9, for example an annealing furnace on support rolls 911, 912, 913, from an inlet (to the left in the figure) to an outlet (to the right in the figure) of this furnace 9. In this example, the steel sheet 1 is not inserted through the traction rolls of the traction apparatus 4 and this traction apparatus 4 therefore does not perform its function of stretching the steel sheet 1. This configuration, for example, makes it possible to perform a heat treatment on the steel sheet 1 in the furnace 9 without applying any stretching force to the steel sheet 1. Alternatively, the traction apparatus 4 may be installed in the furnace 9 so that no traction roll at all is brought into contact with the steel sheet 1 when the sheet is being moved according to what has just been described.

[0088] With reference to FIG. 5, the steel sheet 1 also rests on the support rolls 911, 912, 913. In the traction zone 4, the sheet is wrapped around the rolls of the S-blocks in such a way that sufficient adhesion can be obtained between these rolls and the sheet to obtain the desired level of traction in a region 1d of stretching of the sheet 1. The stretching force on the sheet in the stretching region 1d may be obtained and controlled by a differential between the speeds or torques of various traction rolls.

[0089] The same comments apply to the example depicted in FIG. 6, in which the actuated rolls are, for example, the traction rolls 418, 425. It may be seen that the arrangement of the traction rolls in FIG. 6 results in the region of stretching 1e of the steel sheet 1 having a dimension which is greater (in the direction of travel of the sheet, namely from left to right in the figure) than that of the region of stretching 1d of FIG. 5.

[0090] The layout of the traction rolls in the tensioning blocks 41, 42 or even the relative positioning of the tensioning blocks 41, 42 in the traction apparatus allows control over the dimension of the region of stretching 1d, 1e of the steel sheet 1 in the direction of travel of this sheet, making it possible to optimize the stretching force applied as a function, for example, of the mechanical properties of the steel sheet 1 or of the thermal conditions of the furnace 9. It is known, for example, that a larger region of stretching 1e allows the sheet to be kept under tension in this region of stretching for longer in order to obtain given mechanical properties at the end of this treatment.

[0091] The optimization of this stretching force, or the conditions of friction of the steel sheet 1 against the traction rolls, can also be controlled through the diameter of the traction rolls (for example multiple diameters of roll in the example of FIG. 6) and through the choice of material from which these rolls are made or of the surface finish of the table of the rolls.

[0092] More generally, the layout of the traction rolls may thus be chosen according to the type of treatment to be performed or the type of material to be treated.

[0093] FIG. 8 depicts the device of FIG. 5 with a leveler 7 installed upstream of the traction apparatus 4. This leveler 7 comprises leveling rolls 793, 794, 795 brought alternately into contact with the upper 11 and lower 12 surfaces of the steel sheet 1.

[0094] FIG. 4 depicts three leveling rolls 791, 792, 793 and a steel sheet comprising four parts 1a, 1b, 1c, 1f situated respectively upstream of the leveling roll 791, between the two leveling rolls 791, 792, between the two leveling rolls 792, 793, and downstream of the leveling roll 793. The distance 79a separating the leveling rolls 791, 792, 793 is preferentially substantially equal to 70% of the diameter of these leveling rolls 791, 792, 793. When several leveling rolls are installed in the leveler 7, this separation 79a may vary so as to avoid, for example, any residual curl in the steel sheet 1 leaving the leveler 7.

[0095] According to FIG. 8, the leveler 7 is arranged in such a way as to reduce defects in the shape of the sheet entering the traction system 4 so as to allow the sheet to be tensioned uniformly across its width.

[0096] Alternatively, the leveler may be mounted downstream of the traction apparatus 4 so as to obtain, for example, flatness characteristics suited to treatment steps performed on the steel sheet 1 after the stretching method according to the invention.

[0097] Of course, the invention is not limited to the examples that have just been described and numerous variations may be made to these examples without departing from the scope of the invention. In addition, the various features, forms, alternatives and embodiments of the invention may be combined with one another in various combinations insofar as they are not mutually incompatible or mutually exclusive.