Device and method for removal of scale from a metal product

Abstract

Device for the removal of scale from the surface of a metal product (11) by delivering water under pressure, said device comprising a box-like structure (20) defining an internal space (22) for the passage of the water under pressure, connected to an exit fissure having a gap (23) with a gap value of less than a millimeter, the gap extending continuously for at least the entire width of the metal product (11).

Claims

1. A device for removal of scale from a surface of a metal product by delivering water under pressure, the device comprising: a box-shaped structure defining an internal space for passage of the water under pressure, and having an exit fissure, the exit fissure having a length, a width, and a gap, the gap having a gap value being less than one millimeter, so that water exiting the gap forms a blade of water extending across a width of the metal product, wherein the exit fissure is defined by adjacent surfaces of two adjacent tiles, the surfaces having a rounded shape, and wherein the device further comprises an adjustment means to adjust the gap value, the adjustment means comprising a plurality of connection and stiffening tie-rods disposed substantially transverse to the gap, each of the tie-rods being connected to a corresponding position transducer and to a corresponding actuator to act on the corresponding tie-rod to restore a correct gap value if the position transducer detects that at least one of the following conditions exists: (a) the gap value is modified with respect to a pre-set value, or (b) the gap value does not correspond to a programmed variable value.

2. The device according to claim 1, wherein the water forms a stream passing through the exit fissure, and the adjacent tiles define a configuration of the exit fissure having a first region where the stream is accelerated, the first region being defined by segments of reciprocally converging walls and a terminal region where the stream is stabilized, the terminal region being defined by segments of reciprocally parallel walls.

3. The device according to claim 1, wherein the gap value between 1 and 10 hundredths of a millimeter.

4. A method to remove scale from a surface of a metal product by delivering water under pressure, the method comprising the following steps: supplying a device to deliver water under pressure comprising a box-shaped structure defining an internal space for passage of the water under pressure, and having an exit fissure, the exit fissure having a length, a width, and a gap, the gap having a gap value so that water exiting the gap forms a blade of water extending across a width of the metal product; adjusting the gap value of the exit fissure to a gap value of less than one millimeter by an adjustment means comprising a plurality of tie-rods disposed substantially along the width of the exit fissure, each of the tie-rods being connected to a corresponding actuator and to a position transducer; positioning the exit fissure at a distance between about 10 and 30 mm from the surface of the product; feeding water to the internal space of the box-shaped structure at a pressure higher than at least 75 bar, in order to generate an exit speed of the water on an order of 100-150 m/s, the water exiting the gap so that the water forms a blade of water extending across the width of the metal product; contacting the blade of water with the surface of the metal product to remove scale from the surface; detecting, via at least one of the position transducers, that at least one of the following conditions exists: (a) a gap value of the exit fissure is modified with respect to a pre-set value, or (b) a gap value of the exit fissure does not correspond to a programmed variable gap value; and restoring a correct gap value with a corresponding actuator on at least one of the tie rods.

5. The method according to claim 4, further comprising a step of setting a position of the transducers, wherein the setting step includes the following steps: activating the transducers by an equal force completely closing the gap; introducing a pressure inside the box-shaped structure equal to a working pressure of the water; and zeroing all the transducers to obtain a common reference.

6. The method according to claim 4, further comprising carrying out at least a step of cleaning the exit fissure by widening the exit fissure to have a higher gap value than the gap value used for removal of the scale, and then delivering water through the widened exit fissure.

7. The method according to claim 4, further comprising, during use, adjusting and setting the position of the tie-rods, so as to progressively reduce, at predetermined intervals of time, the gap value of the exit fissure to compensate for wear on the exit fissure.

8. A method to remove scale from a surface of a metal product by delivering water under pressure, the method comprising: providing a first and a second device, each of the first and second devices comprising: a box-shaped structure defining an internal space for passage of the water under pressure, and having an exit fissure, the exit fissure having a length, a width, and a gap, the gap having a gap value being less than one millimeter, so that the water exiting the gap forms a blade of water extending across a width of the metal product, wherein the exit fissure is defined by adjacent surfaces of two adjacent tiles, the surfaces having a rounded shape, and wherein the device further comprises an adjustment means to adjust the gap value, the adjustment means comprising a plurality of connection and stiffening tie-rods disposed substantially transverse to the gap, each of the tie-rods being connected to a corresponding position transducer and to a corresponding actuator to act on the corresponding tie-rod to restore a correct gap value if the position transducer detects that at least one of the following conditions exists: (a) the gap value is modified with respect to a pre-set value, or (b) the gap value does not correspond to a programmed variable value; configuring the first device so that the blade of water is directed towards an upper surface of the metal product; configuring the second device so that the blade of water is directed towards a lower surface of the metal product, wherein a delivery pressure of the water of the first device is greater than a delivery pressure of the water of the second device; and removing scale from at least one of the upper surface and the lower surface of the metal product by contacting the metal product and the blades of water of the first and second devices.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example with reference to the attached drawings wherein:

(2) FIG. 1 shows a possible application of the present invention to a rolling line with a Steckel reversing rolling mill;

(3) FIG. 2 is a variant of FIG. 1;

(4) FIG. 3 is a front view of the scale-removal device according to the present invention;

(5) FIG. 4 is a section from A to A of FIG. 3;

(6) FIG. 4a shows an enlarged detail of FIG. 4;

(7) FIG. 5 is a lateral view of the scale-removal device according to the present invention;

(8) FIG. 6 is the section from B to B of FIG. 5.

DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT

(9) With reference to the attached drawings, FIG. 1 shows one form of embodiment of a Steckel reversing rolling mill 50 for flat rolled products 11 where the scale-removal device 10 according to the present invention is preferably applied.

(10) The rolling mill 50 comprises, in a known manner, a reversing rolling stand 51, a winding/unwinding furnace 52a located upstream and a winding/unwinding furnace 52b located downstream of the reversing stand 51.

(11) Between the furnaces 52a, 52b and the stand 51 there are scale-removal devices 10 according to the present invention, in this case one for each face of the product 11.

(12) In the solution shown in FIG. 1, the devices 10 are facing each other, while in the solution shown in FIG. 2 they are longitudinally offset and cooperate on the opposite side of the rolled product 11 with a respective contrasting roll 12. In the case of FIG. 1, laterally to the device 10 there are support rolls 12 in which the strip can be stabilized, in particular if the delivery pressures of the devices are different from each other.

(13) The device 10 comprises a box-like containing structure 20 which, in this case, has a substantially cylindrical section shape. It comes within the field of the present invention that the structure may have a polygonal shape, for example square, rectangular, hexagonal etc., or also oval, or any other suitable shape.

(14) On the heads of the box-like structure 20 there are flanges 21 by means of which a device to feed the water can be connected with the desired parameters of pressure and flow rate.

(15) The water, fed through the heads 25, in the directions indicated by the arrows, passes through the internal space 22 of the box-like structure 20 to be made to exit through an exit fissure and a gap 23 defined by the adjacent surfaces of two tiles 24, appropriately shaped.

(16) The tiles 24 have a suitably rounded shape so as to accompany and facilitate the exit of the water from the exit fissure and the gap 23, without creating slowdowns or obstacles in the path.

(17) In particular, the shape of the two tiles 24, as shown in the enlarged detail in FIG. 4a, has an asymptotic converging development determined by the respective converging surfaces 124, which determines a progressive acceleration of the stream of water, and a last segment with a parallel development, determined by the respective parallel surfaces 224, which determines a stabilization of the stream of water. The stabilization part, defined by the parallel walls 224, advantageously has an extension comprised between 5 and 20 times the value of the gap 23 and allows to direct the stream of water in a precise and point-by-point manner in the desired direction, and to prevent the detachment of fluid threads with consequent loss of efficiency and effectiveness of the jet toward the strip 11.

(18) Furthermore, the rounded surfaces of the tiles 24 are advantageously chromed and/or polished on the surface, in order to reduce to a minimum value the sliding friction with respect to the stream of water.

(19) Advantageously, moreover, the tiles 24 are mounted in replaceable manner on the box-like structure 20, so as to allow them to be easily controlled, maintained and/or replaced.

(20) With the above device 10 a blade of water is thus created with a uniform thickness, which hits the surface of the metal product 11 below, for example a strip to be sent for rolling, at high speed and high pressure.

(21) The distance h at which the gap 23 is located from the surface of the strip 11 is selected according to requirements but it is assumed to be comprised between 10 and 30 millimeters approximately.

(22) An automatic adjustment mechanism of said distance h may be provided, which keeps it at a pre-set optimal value, adjusting the position of the device 10 as the thickness of the strip 11 varies as the rolling passes continue.

(23) The distance h can instead be varied according to a table of predefined values as the thickness of the strip 11 varies, in order to maintain at high level the efficiency of the removal of the scale exerted by the blade of water without creating defects in the strip 11 when it assumes a thickness in the range of 2 or 3 millimeters.

(24) The value of the gap 23, which defines the thickness of the blade of water emerging, according to the present invention is less than a millimeter, advantageously in the range of tenths of a millimeter, more advantageously in the range of hundredths of a millimeter.

(25) The exit pressure of the water is at least more than 75 bar, advantageously comprised between 100 and 150 bar which, combined with the limited width of the gap 23 and the speed of feed of the strip 11, which can be comprised between 4 and 10 m/s, determines the emission of a blade of water with an extremely high kinetic energy which removes the scale from the surface of the strip 11 with the water remaining in contact with the surface for a minimum contact time.

(26) This reduced contact time considerably reduces the removal of temperature from the strip 11, so that the treatment does not prejudice the subsequent sending of the strip 11 for rolling.

(27) Applicant has calculated that, using the device according to the present invention, with a speed of feed of the strip in the range of 10 m/s, the water remains on the surface of the strip 11 in the range of about one ten thousandth of a second (according to the measurements made by Applicant), so that the reduction in temperature of the surface of the strip is limited to no more than 1.0-1.5 C., which is an acceptable value for the rolling operations carried out at exit from the scale-removal treatment.

(28) In order to guarantee that the definitive gap value of the gap 23 is maintained, the box-like structure has a plurality of connection and stiffening tie-rods 26, which are disposed transverse to the longitudinal development of the box-like structure 22.

(29) The tie-rods 26 are positioned upstream of the exit zone of the water, that is, upstream of the gap 23, in particular in a low-speed zone of the water, so as not to disturb the stream and to reduce its speed.

(30) Furthermore, the tie-rods 26 have a preferably circular geometry, in this case too to determine as little disturbance as possible to the water.

(31) Each of the tie-rods 26, disposed so as to cover a substantial part but not all of the width of the device 10 (that is, the part of the width that substantially corresponds to the width of the strip 11), is associated with a corresponding position transducer 27 connected to a control unit, not shown.

(32) A desired value of the gap 23 may be set, at start of process, in the control unit, or a table of values corresponding for example to each pass of the strip 11 through the rolling stand 50.

(33) A corresponding actuator 28 is also associated with each tie-rod 26, for example hydraulic or oil-dynamic.

(34) If, through the control unit, the position transducer 27 detects that the gap value of the gap 23 has been modified with respect to the pre-set value, or does not correspond to the programmed variable value (for example because of the pressure exerted by the water on the facing internal walls of the tiles 24, which pressure can be different between the center and lateral ends, or caused by a different abrasion effect of the particles transported by the water), then a command is sent to the actuator 28 corresponding to the tie-rod 26, to restore the correct value.

(35) Since this control is advantageously applied to all the tie-rods 26 distributed on the width that defines the blade of water delivered against the surface of the strip 11, in this way the maintenance of the desired gap value of the gap 23 is ensured even after repeated delivery cycles at high water speed and high water pressure.

(36) The presence of the actuators 28 associated with the tie-rods 26 allows to increase the gap 23 of the exit fissure in order to perform, for example, periodic cycles of water delivery with a larger gap without the strip 11 below, in order to clean the exit fissure of possible impurities and residues.

(37) Furthermore, the actuators 28 can be used to perform an initial setting, in which all the tie-rods 26 are subjected to equal force, after the gap 23 has been closed, a pressure is introduced inside the box-like structure 20 equal to the working pressure of the water, and all the transducers 27 are zeroed, so that they have a common reference and so that the precision and constancy of the 23 are guaranteed over the whole of its width.

(38) The tie-rods 26 can also have an oval section or other suitable for the purpose, advantageously at least partly rounded for the purpose given above.

(39) On the lateral parts of the box-like structure 20 there are two fixed connection and stiffening tie-rods 29, to connect with the head flanges 21.

(40) The orientation of the device 10 with respect to the strip 11 can be such as to dispose the blade of water substantially vertical to the surface of the strip 11 (as can be seen in FIG. 4), or the blade of water can form an angle with respect to the vertical comprised between 5 and 15, advantageously oriented in counter-flow with respect to the direction of feed of the strip 11.

(41) An automated positioning device (not shown) may be provided for the device 10, which adjusts the distance h with respect to the surface of the strip 11, and/or the inclination, in order to vary the angle at which the blade of water hits, in an automated manner and/or according to a predefined table which follows the variation in thickness of the strip 11 as the rolling passes proceed.

(42) Modifications and variants may be made to the present invention, all of which shall come within the field of protection as defined by the following claims.