The present invention relates to a device for transforming metal slab from coil configuration into sheet configuration, subsequently comprising: a rotatable coil holder; at least one align unit; a separator; and a stacking unit; wherein the rotatable coil holder, the at least one align unit, the separator and the stacking unit are placed in line. The present invention also relates to a method for transforming a metal slab from coil configuration into sheet configuration, comprising the method steps: A) placing a metal slab coil on a rotatable coil holder; B) rotating the metal slab coil and unwinding the coil; C) feeding the unwound metal slab through at least one at align unit; and D) separating individual metal slab sheets.

In the metal production industry use is made of flat metal sheet material. Typically the sheet metal material is manufactured, shipped and stored in large diameter slab coils (rolls) with weights up to tens of tons to optimise production. Before further use of the material the coiled slab may be transformed into flat sheet configuration. Such processing of a coiled slab is also referred to as "decoiling" and involves unwinding the coiled slab and subsequently feeding the unwound metal slab through one or more roll- forming units after the passage of which usually the unwound flat slab is split up in individual metal sheets of adjustable length. The decoiling takes place in a production line of considerable length wherein also other operations may be performed such as for instance edge trimming, stress relieving operations, slitting and stacking. A typical - but not limitative - decoil-line involves the subsequent processing steps of: unwinding; pre- aligning; first aligning; second aligning and cutting. The decoiling of metals slab thus results in the transformation of a coiled slab into flat sheets of adjustable size and is suited for the transformation of various types of coils, like for instance process hot rolled coils, pickled and oiled coils and tear drop steel coils. A problem that may arise in the transformation of coiled slab into flat sheet

configuration is that the resulting surface quality of the flat sheets is negatively influenced by the transformation process. The object of the present invention is to provide an improved method and an improved device for transforming a metal slab from coil configuration into sheet configuration wherein the surface quality is more positively influenced than it is influenced by the transformation process according the prior art.

The invention provides for this purpose a device for transforming metal slab from coil configuration into sheet configuration, subsequently comprising: a rotatable coil holder; at least one align unit and a separator; wherein the rotatable coil holder, the at least one align unit, the separator and the stacking unit are placed in line, and wherein the rotatable coil holder is provided with at least one air knife that directs an air flow onto the width of the metal slab. Due to the air knife acting onto the metal slab before the first aligning of the slab takes place the metal slab will at least partly be stripped of pollutants like for instance pollutants shaped as powder, loose or more or less attached parts and/or plates, stains, inorganic contaminants, rust or scale. These pollutants may for instance be liquid (water) and/or other non-metal pollutants as well as pollutants originating from the metal slab or oxides of the metal slab. The removal of the pollutants using the air knife makes that the pollutants are not influencing the surface quality of the metal slab in an alignment unit which results in a higher surface quality grade of the sheet configuration metal slab after transformation process than the surface quality of the transformed metal slab according the prior art. The higher surface quality grade may be realised due to the fact that less pollutants are present during the first aligning, during which aligning process at least local pressure is exerted on the metal slab. The air knife may be directed to the metal slab at a location where the metal slab is still on the coil or may be directed onto the metal slab shortly after the slab has been fed away (thus being unwound) from the coil. The device according the present invention may also be provided with one or more brushes for further cleaning of the metal slab, which brushes may cooperate with the air knife to further enhance the combined cleaning effect. In an embodiment the device may also comprise a stacking unit placed in line with the rotatable coil holder, the at least one align unit and the separator. After the metal slab from coil configuration is configured in separated flat sheets of metal slab the sheets have to be processed further. As normally the transforming device is not coupled with a subsequent sheet processing unit, the metal sheets have to be transported from the transforming device to another location where a subsequent sheet processing takes place. Stacking of the metals sheets may enable economic transportation of the sheets.

In a further embodiment of the device according the present invention the air knife may comprise an air feed and a nozzle with a width of at least the width of the metal slab coil to be transformed. Such a nozzle enables the removal of pollutants over the complete width of the metal slab. To provide the air flow the air knife may also be provided with one or more fans, for instance a blower. A typical seize of the nozzle aperture is 2000 * 1 mm, or more than 1500 mm, and a typical air speed of the air knife may be 100 - 200 m/s, for instance 150 m/s. In case the air knife is provided with at least one heater the air blown to the metal slab may be heated, which may for instance be helpful in case the metal slab contains liquid residue. Such an air heater may for instance be embodied as an electric heating coil. To enable control of the intensity of the air flow contacting the metal slab the nozzle of the air knife may be mounted on a nozzle carrier that is moveable relative to the rotatable coil holder. Such moveable holder enables to control the distance of the nozzle to the metal slab and thus also the intensity of the air flow contacting the metal slab. The nozzle carrier may be provided with bias means and at least one stop directed towards the rotatable coil holder to contact the outside of the metal slab coil. In such configuration the distance of the nozzle of the air knife to the outside of the coil is constant as the nozzle is urged to the metal slab and the stop makes that the nozzle is always as close as possible to the metal slab independent on the diameter change of the metal slab coil dependent on the status of unwinding of the remaining part of the metal slab coil. The stop may be embodied as one or more wheels or rollers. With for instance the use of a balance weight the nozzle carrier may be urged against the outside of the metal slab coil with a constant pressure. Furthermore it is an option to connect the nozzle carrier pivotable (swivelling) to the rotatable coil holder so that the distance of the nozzle to the metal slab is to control with a simple construction that may utilize gravitation to at least partially drive the displacement of the nozzle carrier. However also alternative bias means may be used, like for instance various types of springs or cylinders that may urge the nozzle carrier with a constant pressure against the outside of the metal slab coil. It is also possible to drive the movement of the nozzle carrier in different direction with different means; for instance to make the nozzle carrier to follow the decreasing diameter from the outside of the remaining metal coil by gravity and to make the return movement (away from the coil) by a (hydraulic of pneumatic) cylinder. To further enhance the control of the distance of the nozzle to the metal slab also an electronic control system may be provided.

In yet a further embodiment of the device according the present invention parallel to the air knife a subsidiary air blower may be situated. Such subsidiary air blower may for instance comprise at least one air blower fan, an air blower feed and an air blower nozzle with a wide of at least the width of the metal slab coil to be transformed.

Also the air knife may be provided with at least one inlet for the extraction of air. Loose pollutants due to the activity of the air knife acting on the metal slab may be removed (sucked away) from the transforming device preventing precipitation of the pollutants at locations where it may have a negative effect for the equipment and/or the processing quality.

The present invention also provides a method for transforming a metal slab from coil configuration into sheet configuration, comprising the method steps: A) placing a metal slab coil on a rotatable coil holder; B) rotating the metal slab coil and unwinding the coil; C) feeding the unwound metal slab through at least one at align unit; and D) separating individual metal slab sheets; wherein an air knife is directs an air flow onto the width of the metal slab before the unwound metal slab is fed through an align unit. The location of the air knife acting on the metal slab may be there where the metal slab is still on the metal slab coil (and thus forms a part of the exterior of the metal slab coil) or, as an alternative, there where the metal slab is already unwound of the metal slab coil but at a location before the unwound metal slab coil is fed to a first align unit. The present transformation method of metal slab form coil figuration to sheet configuration enables to realise a higher surface quality grade metal sheets. For further explanation and additional advantages reference is made to the above clarification in relation to the device according the present invention, which is incorporated here by reference in relation to the present transformation method as well.

The method may also comprise a method step E) stacking the individualised metal slab sheets on at least one stack and/or the air flow may be directed onto the width of the metal slab. Furthermore a nozzle directing the air knife onto the metal slab may be moved relative to the rotatable coil holder to maintain a substantial constant distance between the nozzle and the metal slab before feeding it through an align unit. To enhance the cleaning effect the air knife may be directed onto the metal slab with a pulsating variable air speed. The air knife may also heat the air directed onto the metal slab and/or an additional blow-drier may be used, for instance with an air temperature of 60 - 90°C.

The invention will be further elucidated herein below on the basis of the non-limitative exemplary embodiments shown in the following figures. Herein: figure 1 shows a schematic side view on a device for transforming a metal slab from coil configuration into sheet configuration according the prior art;

figures 2A and 2B show schematic two embodiments of a rotatable coil holder that is provided with an air knife according the present invention; and figures 3A and 3B show a third embodiments of a rotatable coil holder that is provided with an air knife according the present invention in two different positions. In a metal slab transforming device 1 a metal slab in coil configuration 2 is converted into metal slab sheets 3. A coil holder 4 that is rotatable according arrow Pi holds the metal slab coil 2 from which the metal slab 5 is unwound according arrow P ₂ . After being unwound of the metal slab coil 2 the metal slab 5 is fed through a first align unit 6. After being aligned for a first time brushes 7 clean the metal slab 5 after which brushes 7 a second align unit 8 acts on the unwound metal slab 5. The straightened metal slab is then cut into individual sheets by a separator 9 to be stacked in a stacking unit 10. The rotatable coil holder 4, the align units 6, 8, the brushes 7, the separator 9 and the stacking unit 10 are placed in line. Some typical dimensions of a metal slab transforming device 1 are: thickness of the metal slab (gauge) 3 - 20 mm, maximal width of the metal slab 2100 mm, maximum length of the metal slab 16 metres, maximum coil weight 36 tons, optional provision in the line of side trimmers, and metal slab yield strengths for example 1000 MPa at 2000 mm width and 10 mm thickness. Figure 2A shows an embodiments of a rotatable coil holder 20, holding a metal slab coil 21 on the outside of which coil 21 an air knife 22 is acting. The air knife 22 is moveable in a radial direction (see P ₃ ) to the coil 21 and comprises two stops 23 that contact the outside of the coil 21. A cylinder 24 urges a nozzle 25 towards the coil 21 so that the stops 23 a pressed against the coil 21. The nozzle 25 is connecting to a gas feed 26. In figure 2B an air knife 27 is shown with a nozzle 28 that is urged by springs 29 to metal slab 30 at a location where the metal slab 30 is already unwound of coil 31.

Figures 3 A and 3B show an air knife 40 that is carried by a rotatable arm 41. In figure 3A a coil 42 is relatively large while in figure 3B the coil 42 is unwound for a substantial part so that the remaining coil part 43 has a substantial smaller diameter than the coil 42 as depicted in figure 3 A. The arm 41 is connected to a weight 43 That urges the air knife 40 against the coil 42. Furthermore is shown that the air knife 40 connects via a hose 44 and a pipe 45 to a fan assembly 46. Above the air knife 40 also a blow- drier 47 is attached to the arm 41 to further enhanced cleaning.