WO2011004302A1 - Device for separating atmospheres - Google Patents

Abstract

The invention relates to a device for separating atmospheres installed between two chambers (Ca, Cb) of a continuous line for treating metal strips, said chambers having different types of atmospheres, in order to prevent the atmosphere of a first upstream chamber (Ca) from entering into a second downstream chamber (Cb), and vice versa, said device including: a first pair of motor-driven rollers (R1a, R1b), between which the strip (1) travels at the inlet of the device; and a second pair of motor-driven rollers (R2a, R2b), between which the strip travels at the outlet of the device. The pairs of rollers (R1a, R1b, R2a, R2b) are placed so as to cause a change in the plane of movement (Pa, Pb) of the strip between the inlet and outlet of the device, and the spacing between the rollers is adjusted such that, when the strip has defects in the shape thereof, the rollers reduce the defects in the strip on the width thereof, in order to limit the gas flows (Fa, Fb).

Description

 DEVICE FOR SEPARATING ATMOSPHERES.

The invention relates to an atmospheric separation device implanted between two chambers of an oven of a line of continuous heat treatment of metal strips, the chambers having atmospheres of different natures.

 The treatment line may be, for example, an annealing line or a galvanizing line.

 The heat treatment band circulates continuously in successive chambers, including heating, holding and cooling to follow the thermal path adapted to the mechanical properties.

The thermal cycle may, for example, include heating at a temperature of 800 ^° C., holding for 10 seconds at this temperature, followed by rapid cooling. To prevent oxidation of the band, the furnace is generally maintained under a reducing atmosphere composed of a mixture of nitrogen and hydrogen.

 The hydrogen content in the heating and slow cooling chambers is generally between 5 and 15%. In convective cooling chambers, it is advantageous to have a higher hydrogen content in order to increase the cooling performance, for example 20 to 80% hydrogen.

Continuous annealing furnaces of metal strips generally have large volume chambers. The flow rate of the atmosphere injected continuously to keep the chambers under slight pressure is high, for example 100 to 300 m ³ / h. Since hydrogen is much more expensive than nitrogen, it is advantageous to keep the heating and holding chambers under a low hydrogen content so as to limit the cost of the injected atmosphere. The atmospheres of two successive chambers of a continuous treatment furnace of metal strips can thus be of different natures, in particular in their concentration of hydrogen.

 In the absence of a barrier between the different chambers of the furnace, a migration of the atmospheres will take place from one chamber to another causing a change in the content of each component that may influence the result of the heat treatment or the surface quality of the the band.

In addition, the implementation of hydrogen-rich atmospheres requires special precautions for the safety of the installation. Increasing the hydrogen content that would result from a large migration from a high hydrogen content chamber to a low grade chamber may require additional shielding also in the low grade chamber.

 To maintain the composition of the atmosphere of each section, it is necessary to inject into them additional gas which has an impact on the economic balance of the equipment.

 The technical problem is therefore to create a barrier between the different sections of the equipment so as to maintain good control of these atmospheres, while allowing the band to pass without physical damage to it. This barrier must also make it possible to limit the migration of atmospheres between the two chambers.

 According to the state of the art, the separation of the controlled atmospheres of the different sections of the equipment is obtained by interposing a separating device comprising two necking zones between which either a gas is injected to create a buffer zone, or they are sucked in. gas passing between the zones of narrowing.

 These necking are for example in the form of flaps positioned on either side of the strip and creating a product passage window. They condition the relative tightness of the device by the adjustment distance of the window.

 The metal strip may have different geometric defects such as uneven flatness with a tile shape, or creases on the strip.

These defects require an adjustment of the necking devices with an enlarged passage window to allow the passage of the band without damage but this increases the leakage section and thus reduces the efficiency of the device.

 JP 05 214450 shows an atmosphere separation device placed at the inlet and outlet of a bright stainless steel annealing furnace, maintained under a high hydrogen content. The scroll plane of the strip at the output of the device is the same as that at the input.

To limit the leakage section, modifications of the sealing devices are sometimes made by fitting flexible metal elements holding at high temperature. These elements can reduce the leakage section but they can cause scratches on the tape in case of contact with it. This contact between the flexible elements and the band can occur in the event of a misalignment of the flexible elements or defects of geometry of the band. The holding in time of the elements flexible is also limited when the strip is at a high temperature, for example 700 ⁰ C.

 The invention thus relates to an atmospheric separation device implanted between two chambers of a line of continuous treatment of metal strips having atmospheres of different natures, making it possible to avoid the entry of the atmosphere of the chamber. located upstream of the device in the downstream chamber, and vice versa.

 An atmospheric separation device according to the invention comprises:

 a first pair of motorized rollers between which the strip travels, this first pair of rollers ensuring the essential of the seal between the first chamber and the inside of the device,

 a second pair of motorized rollers between which the strip travels, this second pair of rollers ensuring the essential of the seal between the second chamber and the inside of the device,

 and is characterized in that the pairs of rollers are arranged to cause a change in the running plane of the web between the input and the output of the device, and in that the spacing between the rollers of each pair is adjusted so that when the band has geometric defects, including a transverse tile profile, the rollers reduce the defects of the band over its width, so as to limit the gas flow.

 The band does not undergo plastic deformation during its passage between the rollers of the device according to the invention. Thus, the band resumes its initial profile, for example in tile, after passing through the device.

 In another aspect, the atmosphere separation device comprises:

 a box in which opens the outlet of the upstream chamber and the inlet of the downstream chamber,

 a first pair of motorized rollers at the inlet of the box, between which the strip circulates and ensuring the essential of the seal between the upstream chamber and the inside of the box,

 a second pair of motorized rollers, at the outlet of the box, between which the strip circulates and ensuring the essential of the seal between the downstream chamber and the inside of the box,

 and is characterized in that:

the pairs of input and output rollers of the box are shifted transversely with respect to the running direction of the strip, so as to cause a change in the strip's traveling plane between the inlet and the outlet of the casing, a roller of the input pair bearing against a concave portion of the band, and a roller of the output pair bearing against another concave portion of the band located from opposite side to the first roll,

 and the spacing between the rolls of at least one pair is adjusted so that, when the band has geometric defects, in particular a transverse tile profile, the rollers of this pair reduce the geometric defects of the band on its width, so limit the gaseous flow.

 Preferably, the distance between the strip travel planes between the input and the output of the device is between 30 and 100 mm.

 The device may comprise means for withdrawing the atmosphere present inside the volume between the pairs of rollers, leading to gaseous flows of the chambers towards the inside of the device.

 Alternatively, the device may include means for injecting a gas within the volume between the pairs of rollers, leading to gaseous flows from the interior of the device to the chambers.

 Advantageously, at least the rollers opposed to those which bear against the web as a result of the change of plane of movement are movable in translation for adjustment of the spacing between rollers, and the distances between the rollers of each pair are adjusted according to the importance of the geometrical defects of the band.

 Preferably, the rollers are carried by rotatably mounted shafts in bearings fixed on carriages slidable on slides, the translational movement of the carriages being obtained by a motor member. A flexible sealing device is provided to establish a tight connection between the walls of a box surrounding the rollers and the fixed housings of the bearings. The operating position of the rollers can be achieved via adjustable stops.

 Preferably, the peripheral speed of the rollers is synchronous with the running speed of the band. The leakage section can thus be minimized because the strip is forced to pass between the rollers by "rolling" effect without damage to it because the circumferential speed of the rollers is synchronous with the speed of travel of the strip. Moreover, the surface state of each roll is determined so as to avoid any marking of the band.

With a configuration according to the invention, the adjustment of the leakage section is more accurate because the strip bears on one of the two rollers component each pair which allows to have a geometric reference position.

 The support of the band on one of the two rollers composing each pair, caused by the change of plane of travel of the band according to the invention, prevents any floating of the band between the pairs of rollers. On the other hand, a device without deflection of the band between the two pairs of rollers would lead to a floating of the band likely to mark the surface of the strip or to generate band flaps upstream or downstream of the atmosphere separation device. .

 With the characteristics of the device according to the invention, the geometrical defects of the strip are no longer a limit to the efficiency of the separation of atmospheres.

 Profiled sealing blocks may be provided on either side of the outlet of the upstream chamber, and the inlet of the downstream chamber to close as far as possible, without hindering the rotation of the rollers, the gap between the periphery rollers and the wall of the chamber.

The device according to the invention is designed to operate with a product that may be at a high temperature, for example 800 ^° C., and atmospheres that may be hot, for example at 500 ^° C. The device is also designed to operate with a difference significant temperature between the atmospheres located upstream and downstream of the device.

 The device according to the invention can advantageously be used to effect the separation of atmospheres of very different types, for example between an oxidizing atmosphere for the strip and a reducing atmosphere or between a humid atmosphere and a dry atmosphere.

 The invention can be implemented on a vertical or horizontal furnace, with a band flowing at the device on a horizontal plane or on a vertical plane.

 The invention consists, apart from the provisions set out above, in a number of other provisions which will be more explicitly discussed below with regard to exemplary embodiments, but which are in no way limiting. On these drawings:

- Fig. 1 is a schematic vertical section of a device according to the invention, the strip moving in a vertical plane. To facilitate the understanding of the invention, certain dimensions are deliberately disproportionate. - Fig. 2 is a cross section on a larger scale, along the line M-II of Fig.1, showing an example of profile of the strip before entering the device.

 - Fig. 3 is a partial cross-section along the line Ml-Ml of FIG. 1, showing an example of a profile of the strip during its passage between a pair of rollers of the device according to the invention.

 - Fig.4 is an end view, on a larger scale, of two rollers, without the box that surrounds them normally.

 FIG. 5 is a view from above of the rollers of FIG. 4, on a smaller scale, along the arrow V of FIG.

 - Fig.6 is a section similar to that of Fig.1 of a device according to the invention with gas injection into the box.

 Fig.1 shows a band 1 traveling vertically from an upstream chamber Ca to a downstream chamber Cb, according to the running direction of the band represented by an arrow Δ. According to the example of Fig.1 the tape scrolls from top to bottom, but the opposite is possible, as well as a scroll in a direction inclined relative to the vertical. The band could also scroll horizontally.

 A device A for separating atmospheres is placed between chambers Ca and Cb. The device A comprises a thermally insulated casing 2 providing a tight connection between the upstream Ca and downstream Cb chambers. In the box 2 two pairs of motorized rollers R1 a / R1 b and R2a / R2b are respectively located at the inlet and the outlet of the box. The band 1 circulates between the rollers of each pair.

 The pairs of rollers R1 a / R1b input, and R2a / R2b output, are shifted transversely, a distance D, relative to the running direction of the strip so as to cause a change of the scroll plane between the inlet and the outlet of the caisson 2. The scroll plane is designated Pa upstream, and Pb downstream of the caisson. The pairs of rollers are positioned so as to ensure a straight support of the band on one of the two rollers making up each pair. According to FIG. 1, the strip 1 is in a straight bearing on the rollers R1a and R2a, or deflection rollers. The deviating roller R1 of the input pair bears against a concave portion of the belt, and the deflection roller R2a of the output pair also bears against a concave portion on the side of the opposite web to the first roller R1a.

The two planes Pa and Pb may be parallel or inclined relative to each other. The distance D between the planes Pa and Pb is such that it allows a sufficient deflection α of the band thus ensuring the support thereof on the deviating rollers R1a and R2a. This distance D is preferably between 30 and 100 mm.

 Elements 3a, 3b, 3c and 3d, or profiled sealing blocks, make it possible to reduce the leakage section between the generatrices of the rollers and the chambers Ca and Cb so as to limit the consumption in atmosphere. The elements 3a, 3b, 3c and 3d are formed by shaped parts, fixed on a chamber wall or box, which have a concave surface conforming to the contour of the rollers to limit lateral leakage at the rollers. The elements 3a, 3b, 3c and 3d are provided on either side of the inlet and the outlet of the box.

 The rollers of a pair rotate in opposite directions relative to each other and are driven, by motor means not shown, at a speed synchronous with the speed of travel of the band. This makes it possible to obtain a zero relative speed between the faces of the strip and the outer generatrices of the rollers so as not to mark the strip.

 Fig.4 and 5 show, on a larger scale than Fig.1, the mounting of the rollers R2a, R2b. Rollers R1a, R1b are mounted in a similar manner and the description of the arrangement will therefore be limited to R2a, R2b.

 The rollers R2a, R2b are carried by shafts 4a, 4b (Fig.5) rotatably mounted in bearings 5a, 5b placed and fixed on carriages 6a, 6b. These carriages 6a, 6b slide on horizontal slideways 7a, 7b, orthogonal to the geometric axis of the rollers R2a, R2b. The translational movement of the carriages 6a, 6b and the rollers R2a, R2b is obtained by a pneumatic, hydraulic, mechanical or electrical motor element 8a, 8b. According to the embodiment of Fig.4 and 5, the drive member 8a, 8b is formed by a cylinder 9a, 9b, double effect, hydraulic or pneumatic whose axis is oriented parallel to the slideways 7a, 7b. The cylinder of each cylinder is fixed relative to the slides 7a, 7b, while the outer end of the rod of each cylinder is coupled to a respective carriage 6a, 6b.

 A flexible sealing device 10a, 10b, in particular constituted by an elastomer bellows, in the form of an accordion, is provided to establish a tight connection between the walls 11 of the box 2, having openings 12 traversed by the shafts 4a, 4b , and the fixed housings of the bearings 5a, 5b.

 The possible displacements in translation of the carriages 6a, 6b are illustrated by the double arrows 13a, 13b.

The operating position of the rollers R2a, R2b is obtained through adjustable stops 14a, 15a and 14b, 15b. The position of each stop can be controlled by a screw / nut system, with an electric motor drive in rotation of the screw. The electric motor receives instructions from a remote control station. The support of a carriage against a stop acts in general on an electrical contact which controls the stopping of the drive member 8a, 8b in the position reached. The adjustable stops make it possible to adjust the spacing of the rollers, that is to say the width of the passage window of the strip, according to its geometric characteristics upstream of the device.

 According to an exemplary embodiment of the invention, a member (not shown) continuously measures the geometrical characteristics of the strip at the inlet of the atmosphere separation device and sends a signal to a control system of the line. This signal is taken into account to automatically adjust the positioning of the rollers of the atmospheres separation device.

 According to the embodiment of Fig.1, the support rollers R1a and R2a are fixed in translation, only the rollers R1b and R2b are movable in translation in a direction orthogonal to the parallel geometric axes of the rollers. According to another embodiment, the four rollers are movable in translation along the said direction.

 The device, according to the embodiment of FIG. 1, comprises a means for withdrawing K from the atmosphere present inside the volume between the pairs of rollers, leading to gaseous flows of the chambers towards the inside of the device.

 The atmosphere present inside the box 2 is sucked and rejected out of it by a conduit E placed between the two pairs of rollers and connected to the withdrawal or suction means K. This suction leads to a flow flow of the atmospheres present in the chambers Ca and Cb towards the interior of the box. The flow rate F rejected outside the device is thus the sum of the flow Fa from the chamber Ca and the flow Fb from the chamber Fb. The flow direction of the chamber atmospheres towards the inside of the device A makes it possible to prevent the atmosphere of the chamber Ca entering the chamber Cb and vice versa. The device according to the invention makes it possible to obtain a good separation of the atmospheres between the two chambers Ca and Cb.

According to another possibility, illustrated in FIG. 6, the device comprises means for injecting a gas G into the volume between the pairs of rollers, that is to say in the box 2, leading to to gaseous flows from the inside of the device to the chambers Ca, Cb as illustrated by the arrows Ga, Gb inverted with respect to FIG. Fig.2 shows a strip 1 having a profile in tile, that is to say in curve arc, at the input of the device. The importance of the geometric deformation in tile is represented by the distance X corresponding to the arrow of the curve arc. Fig. 3 shows that the geometric deformation of the web is greatly reduced to an arrow value Y, as the web passes between the pairs of rollers. The arrow Y can be reduced to the thickness of the strip when it is slightly deformed, or thin.

 At the exit of the atmospheres separation device according to the invention, the band can take a shape similar to that which it had before entering the device.

To clarify the description, and without any limiting character, an example of dimensions of the device according to the invention is given below, for a strip of 1500 mm wide and 2 mm thick:

. Internal length of the box: 2000 mm

 (dimension following the direction of travel of the band). Section of passage of the band: 1700 x 290 mm

 (useful section indoor fumistery)

 . Roll diameter: 300 mm

 . Z-spacing between the two pairs of rollers: 1100 mm

 . Distance D: 50 mm

Claims

1. Apparatus for separating atmospheres implanted between two chambers (Ca, Cb) of a line of continuous treatment of metal strips, having atmospheres of different natures, to prevent the entry of the atmosphere of a first chamber (Ca) located upstream of the device in a second chamber (Cb) located downstream, and vice versa, comprising:  a first pair of motorized rollers (R1a, R1b) between which the strip travels, this first pair of rollers ensuring the essential of the seal between the first chamber (Ca) and the inside of the device,  and a second pair of motorized rollers (R2a, R2b) between which the strip travels, this second pair of rollers ensuring the essential of the seal between the second chamber (Cb) and the inside of the device, characterized in that the pairs of rollers (R1a, R1b; R2a, R2b) are arranged to cause a change of the scroll plane (Pa, Pb) of the strip between the inlet and the outlet of the device, and in that the spacing between the rollers of each pair is adjusted so that when the strip has geometric defects, in particular a transverse tile profile, the rollers reduce the defects of the band over its width, so as to limit the gas flow (Fa ₁ Fb). 2. Apparatus for separating atmospheres implanted between two chambers (Ca, Cb) of a line of continuous treatment of metal strips having atmospheres of different natures, to prevent the entry of the atmosphere of a first chamber ( Ca) located upstream of the device in a second chamber (Cb) located downstream and vice versa, comprising:  a caisson (2) in which the outlet of the upstream chamber (Ca) and the inlet of the downstream chamber (Cb) open,  a first pair of motorized rollers (R1a, R1b) at the inlet of the box, between which the strip circulates and ensuring the essential of the seal between the upstream chamber (Ca) and the interior of the box,  and a second pair of motorized rollers (R2a and R2b), at the outlet of the box, between which the strip circulates and ensuring the essential of the seal between the downstream chamber (Cb) and the inside of the box, characterized in that the pairs of input and output rollers (R1a, R1b, R2a, R2b) are shifted transversely relative to the running direction (Δ) of the strip, so as to cause a change in the scroll plane (Pa , Pb) the strip between the inlet and the outlet of the casing, a roller (R1 a) of the input pair bearing against a concave portion of the strip, and a roller (R2a) of the bearing pair bearing against another concave part of the strip situated on the opposite side to the first roll (R1 a), and the spacing between the rolls of at least one pair is adjusted so that, when the band has geometric defects, in particular a transverse tile profile, the rollers of this pair reduce the geometric defects of the band on its width, so to limit the gas flow (Fa ₁ Fb). 3. Device according to claim 1 or 2, characterized in that the distance (D) between the planes (Pa ₁ Pb) of travel of the strip between the inlet and the outlet of the device is between 30 and 100 mm. 4. Device according to any one of claims 1 to 3, characterized in that it comprises a means for withdrawing the atmosphere present within the volume between the pairs of rollers, leading to gas flows from the chambers to inside the device. 5. Device according to any one of claims 1 to 3, characterized in that it comprises a means for injecting a gas within the volume between the pairs of rollers, leading to gas flows of the inside the device to the rooms. 6. Device according to any one of the preceding claims, characterized in that at least the rollers (R1 b, R2b) opposite to those (R1a, R2a) which bear against the strip as a result of the change of scroll plane, are movable in translation for adjusting the spacing between rollers, and in that the distances between the rollers of each pair (R1a, R1b, R2a, R2b) are adjusted according to the importance of the geometric defects of the web . 7. Device according to any one of the preceding claims, characterized in that the rollers (R1a, R1b, R2a, R2b) are carried by shafts (4a, 4b) rotatably mounted in bearings (5a, 5b) fixed on carriages (6a, 6b) slidable on slides (7a, 7b), the translational movement of the carriages (6a, 6b) being obtained by a motor member (8a, 8b). 8. Device according to claim 7, characterized in that a flexible sealing device (10a, 10b) is provided to establish a tight connection between the walls (11) of a box (2) surrounding the rollers and housings fixed bearings (5a, 5b). 9. Device according to claim 7 or 8, characterized in that the operating position of the rollers (R1a, R1b, R2a, R2b) is obtained by means of adjustable stops (14a, 15a, 14b, 15b). 10. Device according to any one of the preceding claims, characterized in that the peripheral speed of the rollers is synchronous with the running speed of the band. 11. Device according to any one of the preceding claims, characterized in that profiled sealing blocks (3a, 3b, 3c, 3d) are provided on either side of the outlet of the upstream chamber (Ca), and the inlet of the downstream chamber (Cb) for closing the interstice between the periphery of the rollers and the wall of the chamber to a maximum, without hindering the rotation of the rollers. 12. Device according to claim 2, characterized in that the box (2) is thermally insulated.