Method for cleaning and / or descaling a slab or strip using a descaling washer and descaling scrubber

Abstract

The invention relates to a method for cleaning and / or descaling a slab or strip (1) by means of a descaling washer (2), wherein the descaling washer (2) has at least one nozzle (3) through which water under pressure (p) is applied to the surface of the slab or strip (1).In order to achieve a good descaling result in an energy-saving manner, the invention provides that the outlet (4) of the nozzle (3) is rectangular or slot-shaped in the direction normal (N) to the surface of the slab or pre-strip (1) with at least a partially arc-shaped profile, so that the water is applied as a continuous strip-shaped jet (5) over the entire width (B) of the slab or pre-strip (1), wherein the width (b) of the outlet (4) of the nozzle (3) in the conveying direction (F) of the slab or pre-strip (1) is selected between 0.2 mm and 1.5 mm, wherein the water is supplied to the nozzle (3) at a pressure between 5 bar and 50 bar, and wherein the distance (a) between the outlet (4) of the nozzle (3) and the surface of the slab or pre-strip (1) is selected between 8 mm and 35 mm. Furthermore, the invention relates to a tinder scrubber.

Description

[0001] The invention relates to a method for cleaning and / or descaling a slab or a pre-strip using a scale washer, wherein the scale washer has at least one nozzle through which pressurized water is applied to the surface of the slab or pre-strip. Furthermore, the invention relates to a scale washer.

[0002] Scale washers are required for the clean removal of primary or secondary scale, whereby in a scale washer of this type, water is applied to the slab to be cleaned at a sufficiently high water pressure.

[0003] The energy consumption of a descaler, such as a descaler for a finishing mill, is considerable. Depending on the set pressure level and the water volume per unit time, energy consumption can be up to 4.5 MW. A maximum water pressure of 380 bar, for example, is used. Reducing energy consumption is directly associated with a decrease in water pressure, which in turn reduces the quality of the descaling or cleaning results.

[0004] Scale washers in various designs are known from DE 693 14 275 T2, from WO 2009 / 056712 A2, from JP 59 076 615 A ​​and from JP 2010 247 228 A.

[0005] The water is sprayed onto the surface of the slab or rolled stock through a number of adjacent nozzles. Such systems, for example, have approximately 50 adjacent nozzles per beam.

[0006] According to previously known solutions, a sufficiently large distance is provided between the nozzle outlet and the slab to be descaled. This results from the fact that the sensitivity with regard to clean coverage of the individual nozzles increases, particularly with a longitudinal or transverse curvature of the slab. Furthermore, the nozzles cannot be mounted or arranged as closely as desired next to one another, so that neighboring nozzles are offset from one another. This means that the jets of the individual nozzles interfere with each other due to running off water. If the distance between the nozzle outlet and the slab surface is small, measures may also be required to ensure the slab tip is securely threaded into the scale washer. Furthermore, there is a limit to the arbitrary increase in the number of nozzles for cost reasons.

[0007] A device for applying a pressurised water jet across the width of the strip to metal strips is known from US 2 921 748 A, in particular Fig. 1 to 5 and from the description column 1, lines 15 to 26, column 2, line 20 to column 3, line 34, as well as from US 4 617 815 A, in particular Fig. 2 and Fig. 3, as well as the description column 4, lines 22 to 24, 54 to 66, column 5, lines 40 to 47 and from US 4 210 288 A, in particular Fig. 1 to 5 with description column 3, line 18 to column 4, line 53.

[0008] The invention is therefore based on the object of proposing a method of the type mentioned above and a scale washer with which good descaling and cleaning results can be achieved while simultaneously requiring significantly less energy. Furthermore, the temperature losses of the slab or the transfer strip are to be reduced.

[0009] The solution to this problem by the invention is characterized in that the nozzle outlet is rectangular (rectangular nozzle) or slot-shaped with an arcuate course at least in sections, viewed in the direction normal to the surface of the slab or the preliminary strip, so that the water is applied as a continuous strip-shaped jet over the entire width of the slab or the preliminary strip, the width of the nozzle outlet in the conveying direction of the slab or the preliminary strip being selected between 0.2 mm and 1.5 mm, the water being supplied to the nozzle at a pressure between 5 bar and 50 bar, and the distance between the nozzle outlet and the surface of the slab or the preliminary strip being selected between 8 mm and 35 mm.

[0010] Preferably, the width of the nozzle outlet in the conveying direction of the slab or the pre-strip is selected between 0.3 mm and 0.8 mm, particularly preferably between 0.4 mm and 0.6 mm.

[0011] The water is preferably supplied to the nozzle at a pressure between 10 bar and 40 bar, in particular between 15 bar and 35 bar.

[0012] The distance between the nozzle outlet and the surface of the slab or pre-strip is preferably chosen between 10 mm and 30 mm, in particular between 15 mm and 20 mm.

[0013] The combination of the above data has surprisingly led to very good cleaning and descaling results, with energy consumption being significantly reduced.

[0014] The strip-shaped jet is preferably directed at an angle of between 10° and 30°, preferably between 15° and 25°, to the direction normal to the surface of the slab or the transfer strip against the conveying direction of the slab or transfer strip.

[0015] A further development provides that boundary edges of nozzle plates, which define the nozzle outlet, are adjusted to different distances from the surface of the slab or the pre-strip.

[0016] The proposed scale washer for cleaning and / or descaling a slab or a pre-strip is characterized according to the invention in that the outlet of the nozzle is rectangular or slit-shaped in the direction normal to the slab or pre-strip surface with an arcuate course at least in sections, wherein the width of the outlet of the nozzle in the conveying direction of the slab or pre-strip is between 0.2 mm and 1.5 mm and wherein the movement means are provided with which the distance between the outlet of the nozzle and the surface of the slab or pre-strip can be adjusted.

[0017] According to a preferred embodiment of the invention, the nozzle is housed in a housing that can be pivoted about an axis arranged horizontally and transversely to the conveying direction of the slab or pre-strip. A section or projection can be arranged on the housing, which, when the scale washer is used as intended, is located closer to the surface of the slab or pre-strip than the nozzle outlet. This allows for efficient protection of the nozzle.

[0018] The outlet of the nozzle can be formed by two nozzle plates arranged adjacent to one another - and preferably linearly shaped - wherein at least one of the nozzle plates is arranged adjustable in the conveying direction of the slab or the preliminary strip and / or in the direction normal to the surface of the slab or the preliminary strip and / or transversely to the conveying direction of the slab or the preliminary strip.

[0019] A further embodiment of the invention provides that the nozzle outlet is formed by two linear nozzle plates arranged adjacent to one another. The two nozzle plates have boundary edges for the water passage, which extend at a wedge angle, preferably between 1° and 5°, to the horizontal direction transverse to the conveying direction of the slab or the pre-strip, viewed in the direction normal to the surface of the slab or the pre-strip, and the two nozzle plates are adjustable relative to one another in the horizontal direction transverse to the conveying direction of the slab or the pre-strip. This allows the size of the nozzle gap to be easily changed.

[0020] Instead of straight nozzle plate edges, the edges can also be contoured as desired, in particular with a contour according to an nth-order polynomial, so that – similar to CVC technology – a parabolic gap variation, for example, is achieved across the width. Accordingly, a further development provides for the nozzle outlet to be formed by two nozzle plates with any desired contour, whereby the two nozzle plates can be adjusted relative to each other so that the gap width changes unevenly across the width of the slab or pre-strip.

[0021] The nozzle gap width can also be made adjustable in sections over the width of the slab or pre-strip to be descaled; accordingly, it is provided that the width of the nozzle outlet in the conveying direction can be adjusted in sections over the width of the slab or pre-strip.

[0022] Preferably, a filter is arranged in the water supply line, the mesh size of which is smaller than the slot width of the nozzle.

[0023] A further advantageous development provides that the outlet of the nozzle is formed by two correspondingly contoured plates which, when displaced relative to one another, change the gap across the width of the slab or the pre-strip.

[0024] It can be planned to use only one spraying row – preferably with a lower water quantity. The furnace temperature can be reduced to compensate for the temperature difference that occurs during descaling due to the resulting reduced cooling effect.

[0025] The rectangular nozzle unit can consist of the components water inlet area, if necessary a filter plate, a jet straightener, a nozzle compensation section, a jet bundling in front of the nozzle gap and the nozzle gap.

[0026] The boundary edges of the two nozzle plates can also be arranged at a different distance from the slab or the pre-strip or can be set to such a different distance.

[0027] The rectangular gap can also be curved. The nozzle gap width can also be adjusted in sections across the nozzle width.

[0028] Thus, the invention proposes a combination of different measures to achieve a good descaling result with significantly reduced energy consumption.

[0029] The distance between the outlet of the rectangular nozzle and the surface of the slab or rolled stock is preferably 20 mm, although a range between 10 mm and 30 mm also produces very good results. A particular advantage is that a rectangular nozzle allows for small distances to the slab or pre-strip without the nozzle overlap being relevant across the width, since it is a rectangular nozzle.

[0030] Since a rectangular nozzle can already achieve a uniform descaling effect across the width, one descaling bar per side is usually sufficient.

[0031] The pressure level is preferably maintained at 25 bar, although values ​​between 10 and 40 bar also produce good results. This results in significant energy savings.

[0032] The slot width of the rectangular nozzle is preferably set to 0.5 mm; the preferred value range is between 0.3 and 0.8 mm.

[0033] At the relatively low pressure and suitable gap width, a low descaling water quantity can be set, which reduces the cooling effect of the slab or pre-strip.

[0034] The nozzle plates can be designed to be replaceable. They are preferably made of heat-resistant stainless steel, hardened steel, carbide, or ceramic.

[0035] The angle of the nozzle jet is preferably set so steeply that all the water runs against the direction of belt travel; an angle between 10° and 25° is preferred.

[0036] The scale washer is preferably located in front of the finishing train or behind the slab furnace.

[0037] The adjustable distance between the nozzle outlet and the slab surface not only optimizes the descaling process but also protects the nozzle when the slab thickness changes. During transport of the transfer strip or slab head through the descaler and its nozzle area, the nozzle can be raised slightly or deflected on its pivoting housing in response to an external force, thus preventing damage. Accordingly, the descaler beam with the rectangular nozzle is preferably mounted on a rocker arm.

[0038] As an additional measure to protect the nozzle and increase transport safety, a pre-strip or slab head shape detection (ski) can also be provided in front of the scale washer (optical or mechanical system) and this can be used to control the nozzle position at the head of the slab or strip.

[0039] The slot width of the rectangular nozzle can be changed by replacing the nozzle plates. It is also possible to vary the slot width using an adjustment mechanism (e.g., an eccentric or a wedge); for this purpose, a nozzle plate can be arranged so that it can be moved. This makes it possible to compensate for nozzle plate wear. Furthermore, it makes it possible to open the gap, for example, for possible nozzle cleaning.

[0040] As a further development, the nozzle gap can be adjusted only in sections across the width of the rectangular nozzle (perpendicular to the slab conveying direction). This allows the nozzle gap to be closed in sections, allowing the width to be adjusted to different slab widths.

[0041] According to the invention, the descaling pressure is thus significantly reduced compared to the prior art, while the proposed combination of features nevertheless achieves a largely consistent descaling result.

[0042] As the distance between the nozzle and the rolling stock to be descaled decreases, the impact pressure of the water jet on the slab surface increases, and thus the cleaning effect increases. The invention therefore works by reducing the distance and water pressure while maintaining the same descaling quality.

[0043] The distance between the nozzle outlet and the slab surface can be adjusted using a suitable actuator. To achieve a small distance between the nozzle outlet and the slab, it may be necessary to adjust the distance between the nozzle and the rolling stock at the head. The use of the provided rectangular nozzle is advantageous here, as it achieves a uniform descaling or cooling effect across the width of the slab, regardless of the distance. This also applies to a curved rolling stock surface.

[0044] By reducing the distance between the nozzle outlet and the slab surface as described above, the amount of water required per unit time can be significantly reduced. This reduces the cooling effect of the slab or transfer strip. The reduced cooling effect can then be used to save energy, for example, by reducing the furnace temperature (heating effect).

[0045] Instead of using conventional nozzles, the invention provides a rectangular nozzle with which a water curtain can be generated and directed onto the slab to be descaled.

[0046] If a large number of nozzles were conventionally arranged side by side, significantly more nozzles would be required to ensure sufficient coverage at the same spray angle, given the reduced distance between the nozzle outlet and the slab according to the invention. Alternatively, the spray angle could be increased while maintaining the same number of nozzles; however, this would have the disadvantage of reducing the impact pressure and thus negatively impacting the descaling result.

[0047] The proposed design is characterized by a cost-effective concept. This is due, on the one hand, to the possibility of using low-pressure pumps; on the other hand, cheaper pipelines and spray booms with thinner walls can be used. Shielding against the high pressure applied is also less complex. Furthermore, wear on the rectangular nozzle is reduced due to the low pressure. This also requires less maintenance.

[0048] The scale washer also advantageously takes up less space, since only one row of nozzles per side needs to be provided for the scale washer.

[0049] This also advantageously results in reduced cooling of the slab due to a smaller wetted area or due to the lower volume flow of water required for descaling.

[0050] The rectangular nozzle used also results in optimal coverage of the slab across the width, even with different distances between the nozzle outlet and the slab surface.

[0051] By using the proposed rectangular nozzle with the specified operating parameters, the impact pressure is kept at least the same as with previously known high-pressure nozzles.

[0052] Where reference is made here to a slab or a pre-strip, this generally means any type of slab (thin slab, thick slab) or pre-strip, as well as generally any material to be descaled, preferably with a square cross-section.

[0053] The drawings illustrate exemplary embodiments of the invention. They show: Fig. 1 schematically shows the side view of a scale washer with a nozzle arranged above a slab and a nozzle arranged below the slab, Fig. 2 schematically shows the side view of a nozzle of the scale washer according to a first embodiment of the invention, Fig. 3 schematically shows the side view of a nozzle of the scale washer according to a second embodiment of the invention, Fig. 4 schematically shows the side view of a nozzle of the scale washer according to a third embodiment of the invention, Fig. 5 the view of an outlet of a curved nozzle of the scale washer in a view normal to the surface of the slab and Fig. 6 the nozzle Fig. 5, seen in the conveying direction of the slab.

[0054] In Fig. 1 shows a descaler 2, which is used to descale a slab 1 on its top and bottom sides. Accordingly, a nozzle 3 is arranged above and below the slab 1. The slab 1 moves past the descaler 2 in the conveying direction F.

[0055] As can be seen in the overview of the Fig. As can be seen from Figures 2 to 4, each nozzle 3 has an outlet 4 from which water is discharged under pressure. The nozzle 3 is one that extends across the width B of the slab 1 (see Fig. 5) emits a jet 5 in the form of a water curtain, i.e. the nozzle gap at the outlet 4 is a rectangular gap (rectangular nozzle cross-section) which extends over the entire width B of the slab 1 horizontally and transversely to the conveying direction F.

[0056] The nozzle 3 is arranged in a housing 7. The housing 7 is pivotally mounted on an axis A, which is aligned horizontally and transversely to the conveying direction F. A movement means 6 allows the movement of the housing 7 and thus the up and down movement of the nozzle 3 and thus of the nozzle outlet 4. The nozzle outlet 4 can thus be moved in the direction N perpendicular to the slab surface. This allows the distance a between the outlet 4 of the nozzle 3 and the surface of the slab 1 to be adjusted.

[0057] In Fig. 1 further shows that a section or projection 8 is arranged on the housing 7. This section projects beyond the nozzle outlet 4 and thus provides protection for the nozzle 3. Accordingly, a distance a' between the lower edge of the section or projection 8 and the surface of the slab 1 is smaller than the distance a between the outlet 4 of the nozzle 3 and the slab surface.

[0058] Furthermore, it can be seen that the jet 5 emerging from the nozzle 3 is directed against the direction N normal to the slab 1 at an angle α (see Fig. 1, bottom). The orientation is opposite to the conveying direction F.

[0059] The water is fed to the nozzle 3 at a pressure p via a supply line 12. Behind a filter plate 13, the water enters a jet straightener 14, which consists of grid plates. From here, the water flows into a nozzle straightening section 15.

[0060] The rectangular nozzle unit consists of the main components water inlet area 12, optionally a filter plate 13, a jet straightener 14, a nozzle compensation section, a jet bundling in front of the nozzle gap and finally the nozzle gap.

[0061] The nozzle gap itself is formed by two nozzle plates 9 and 10, which have respective boundary edges 11 (see Fig. 4). The boundary edges 11 of the two sides can be arranged at different levels (distance a from the slab 1) in an adjustable or fixed manner. The nozzle plates can be designed to be interchangeable.

[0062] The rectangular nozzle outlet 4 has an outlet area which is the product of the width b of the outlet 4 of the nozzle 3 in the conveying direction F (see Fig. 3) and the width of the nozzle gap horizontally and transversely to the conveying direction F.

[0063] Shown in Fig. 1 also transport rollers (roller table rollers) 16. Squeeze rollers can also be arranged on the top side - above the transport roller - so that the pair of rollers can act as a driver. Indicated in Fig. 1 also a deflector rib 17.

[0064] In Fig. Figure 2 shows a nozzle 3 in more detail. Here, the nozzle is screwed to or inside the housing 7 using screws 18. The water exits the nozzle in the direction of the arrow. The screws are located on the side facing away from the slab—thus protecting it from radiant heat.

[0065] A seal 19 creates a tight connection between the nozzle body and the nozzle plates 9 and 10.

[0066] Also worth mentioning is a toothing or profiling 20 which is provided between the nozzle body and the nozzle plates 9, 10 in order to hold the nozzle plates 9, 10 in a form-fitting manner and thus with a defined and reproducible fit in the nozzle body.

[0067] In Fig. 3 shows that the outlet 4 of the nozzle 3 is adjustable in width b. For this purpose, one nozzle plate 10 is arranged to be displaceable in the direction of the double arrow (the displacement means are not shown; these can be mechanical, hydraulic, pneumatic, or electrical actuators).

[0068] In Fig. 4 is alternative to Fig. 3, one nozzle plate 10 is movable in the direction N perpendicular to the slab surface. This also allows the gap size of the rectangular gap of the nozzle 3 to be changed.

[0069] Alternatively, it can also be provided, although this is not illustrated, that a displacement of one nozzle plate 10 relative to the other nozzle plate 9 takes place in a direction transverse to the conveying direction F, i.e. in the direction of the slab width, in order to effect a change in the gap width, for example in the case of a conical cut of the boundary edge 11 of the nozzle plate, up to the complete closure of the nozzle 3.

[0070] In the Fig. 5 and Fig. 6 shows that the outlet 4 of the nozzle 3 does not necessarily have to be linear (straight), but can also be curved. The outlet 4 of the nozzle 3 slightly protrudes laterally beyond the width B of the slab 1. The arrows in Fig. 5 indicate the direction of water flow. List of reference symbols: 1 slab / support strip 2 scale washers 3 nozzles 4 Nozzle outlet 5 beam 6 Means of movement 7 housings 8 Section / Projection 9 Nozzle plate 10 nozzle plate 11 Boundary edge 12 Inlet line 13 Filter plate 14 jet directors 15 nozzle rectifier section 16 transport roller (roller table roller) 17 Deflector rib 18 Screw 19 Seal 20 Gearing / Profiling A axis of pivoting B Width of the slab or transfer strip F Conveying direction N direction normal to the surface of the slab or transfer strip a Distance between nozzle outlet and surface of the slab or pre-strip a' Distance between the lower edge of the section / projection and the surface of the slab or the transfer strip b Width of the nozzle outlet in the conveying direction p pressure α angle

Claims

[1] Method for cleaning and / or descaling a slab or a preliminary strip (1) by means of a scale washer (2), wherein the scale washer (2) has at least one nozzle (3) through which water under pressure (p) is applied to the surface of the slab or the preliminary strip (1), characterized bythat the outlet (4) of the nozzle (3) is rectangular or slit-shaped, viewed in the direction normal (N) to the surface of the slab or the preliminary strip (1), with an arcuate course at least in sections, so that the water is discharged as a continuous strip-shaped jet (5) over the entire width (B) of the slab or the preliminary strip (1), the width (b) of the outlet (4) of the nozzle (3) in the conveying direction (F) of the slab or the preliminary strip (1) being selected between 0.2 mm and 1.5 mm, the water being supplied to the nozzle (3) at a pressure (p) of between 5 bar and 50 bar, and the distance (a) between the outlet (4) of the nozzle (3) and the surface of the slab or the preliminary strip (1) being selected between 8 mm and 35 mm. [2] Method according to claim 1, characterized by that the width of the outlet (4) of the nozzle (3) in the conveying direction (F) of the slab or the pre-strip (1) is selected between 0.3 mm and 0.8 mm, preferably between 0.4 mm and 0.6 mm. [3] Method according to claim 1 or 2, characterized by that the water is supplied to the nozzle (3) at a pressure (p) between 10 bar and 40 bar, preferably between 15 bar and 35 bar. [4] Method according to one of claims 1 to 3, characterized by that the distance (a) between the outlet (4) of the nozzle (3) and the surface of the slab or the pre-strip (1) is selected between 10 mm and 30 mm, preferably between 15 mm and 20 mm. [5] Method according to one of claims 1 to 4, characterized by that the strip-shaped jet (5) is directed at an angle (α) of between 10° and 30°, preferably between 15° and 25°, to the direction normal (N) to the surface of the slab or the preliminary strip (1) against the conveying direction (F) of the slab or the preliminary strip (1). [6] Method according to one of claims 1 to 5, characterized bythat boundary edges (11) of the nozzle plates (9, 10) defining the outlet (4) of the nozzle (3) are set to different distances from the surface of the slab or the pre-strip (1). [7] Scale washer (2) for cleaning and / or descaling a slab or a pre-strip (1), which has at least one nozzle (3) through which water under pressure (p) can be applied to the surface of the slab or the pre-strip (1), in particular for carrying out the method according to one of claims 1 to 6, characterized bythat the outlet (4) of the nozzle (3) is rectangular or slit-shaped in the direction normal (N) to the slab or pre-strip surface with an arcuate course at least in sections, wherein the width (b) of the outlet (4) of the nozzle (3) in the conveying direction (F) of the slab or pre-strip (1) is between 0.2 mm and 1.5 mm and wherein the movement means (6) are present with which the distance (a) between the outlet (4) of the nozzle (3) and the surface of the slab or pre-strip (1) can be adjusted. [8] Scale washer according to claim 7, characterized by that the nozzle (3) is accommodated in a housing (7) which is pivotable about an axis (A) which is arranged horizontally and transversely to the conveying direction (F) of the slab or the preliminary strip (1). [9] Scale washer according to claim 8, characterized bythat at least one section (8) or projection is arranged on the housing (7) which, when the scale washer is used as intended, is arranged closer (a') to the surface of the slab or the pre-strip (1) than the outlet (4) of the nozzle (3). [10] Scale washer according to one of claims 7 to 9, characterized by in that the outlet (4) of the nozzle (3) is formed by two nozzle plates (9, 10) arranged adjacent to one another, wherein at least one of the nozzle plates (9, 10) is arranged to be adjustable in the conveying direction (F) of the slab or the preliminary strip (1) and / or in the direction normal (N) to the surface of the slab or the preliminary strip (1) and / or transversely to the conveying direction (F) of the slab or the preliminary strip (1). [11] Scale washer according to one of claims 7 to 9, characterized byin that the outlet (4) of the nozzle (3) is formed by two ruler-shaped nozzle plates (9, 10) arranged adjacent to one another, the two nozzle plates (9, 10) having boundary edges (11) for the passage of water, which, viewed in the direction normal (N) to the surface of the slab or the preliminary strip (1), run at a wedge angle, preferably between 1° and 5°, to the horizontal direction transverse to the conveying direction (F) of the slab or the preliminary strip (1), and the two nozzle plates (9, 10) are designed to be adjustable relative to one another in the horizontal direction transverse to the conveying direction (F) of the slab or the preliminary strip (1). [12] Scale washer according to one of claims 7 to 9, characterized bythat the outlet (4) of the nozzle (3) is formed by two nozzle plates (9, 10) of any desired contour, wherein the two nozzle plates (9, 10) can be adjusted relative to one another in such a way that the gap width changes unevenly over the width of the slab or the preliminary strip (1). [13] Scale washer according to one of claims 7 to 12, characterized by that the nozzle plates (9, 10) are made of heat-resistant stainless steel, hardened steel, hard metal or ceramic. [14] Scale washer according to one of claims 7 to 13, characterized by that it has a nozzle unit with the components water inlet area, preferably filter plate, jet straightener, nozzle compensation section, jet bundling in front of the nozzle gap and nozzle gap. [15] Scale washer according to one of claims 7 to 14, characterized bythat the width (b) of the outlet (4) of the nozzle (3) in the conveying direction (F) can be adjusted in sections over the width of the slab or the pre-strip (1).

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