KR100260598B1 - Descaling device - Google Patents

Abstract

In order to optimally adjust the impact pressure of the water on the slab of the descaling device, at least two seized piston pumps are provided, which are connected in parallel, so that each said pump can be operated or shielded separately. Is suggested.

Description

Descaling device

1 is a plot of the P / Q ratio of a piston pump.

2 is a diagram showing an example of a resistance characteristic curve of a nozzle.

3 illustrates pressure adjustment of a system by one or more piston pumps.

4 is a schematic diagram of a descaling device according to the present invention.

5 is a schematic diagram of a descaling device of the present invention having two nozzle rows.

* Explanation of symbols for main parts of the drawings

1: slab 2: driving part

3: stand 4,11: nozzle

5: descaling device 6,7: piston pump

8: filter 9: tank

10: controller

The present invention relates to a descaling apparatus for removing scales attached to the surface of slabs or scrips in a hot rolling mill by using nozzles fed by a seizure piston pump.

When descaling slabs and strips prior to hot rolling, there is a distinction between the primary and secondary scales. The secondary scale is what happens to the material when the material already pressed is heated to or maintained at the rolling temperature. However, primary scale refers to the scale that occurs on the material after the perimeter of the slab or strip. The primary scale is much more adherent to the material than the secondary scale. If the temperature of the cast material is maintained for a long time, more highly adherent scales are formed. Sticking of the scale also depends heavily on the material used.

Descaling of the slab or strip to which the secondary scale is fixed is carried out using seizure sprayed onto the surface of the slab or strip by a nozzle. Seizure is usually conveyed by centrifugal pumps operating at up to 300 bar. In this case, the specific impact generated and the amount of water determine the descaling effect. By such a structure, satisfactory results are obtained in the case of the secondary scale.

However, the slabs and strips continue to be cast and optionally hot rolled by the heat of casting through a compensation furnace. Because of this, the stuck primary scale must be removed. The descaling effect depends on the amount of water and on the pressures that generate impact in particular.

In the case of continuous casting and subsequent hot rolling by casting heat, the pulling speed in the first hot rolling stand is approximately 1/3 of the pulling speed of the already rolled material. Due to this difference in drawing speed, the cast material is overcooled compared to the pre-rolled material even though the amount of water per unit time is the same, so that the minimum temperature for hot rolling operation is not reached. On the other hand, even if the amount of water per unit time is converted to a slower inlet speed, it is almost impossible to increase the amount of water in the cast material, because the material is already overcooled with only a slower inlet speed so that the amount of water This is because increasing the material causes the material to cool too much.

Therefore, the only way to increase the impact of water is to increase the pressure. In this case, a pressure of 600 bar or less is required, so the centrifugal pump must be replaced by a piston pump. However, at such high pressures, the descaling device proved to be badly worn.

Therefore, an object of the present invention is to improve the descaling device to the primary scale to reduce the wear and the cost of descaling by fitting pressure to the requirements.

It is possible to partially solve the object of the present invention by configuring the piston pump to be adjustable in terms of its rotational speed and in relation to the amount of conveying according to this rotational speed. However, the return pump, which must be adjustable over the range of 0 to approximately 600 bar, is very bulky and expensive, so wear can be reduced but cost cannot be reduced.

The problem is solved according to the invention by providing at least one other seized piston pump, which piston pumps are connected in parallel, and each pump can be switched on or off alone.

Unlike centrifugal pumps, piston pumps are capable of carrying almost constant volume flow regardless of pressure (see FIG. 1, which shows the P / Q ratio of a piston pump). On the other hand, the resistance of the nozzle and pipe of the descaling facility allows the volume flow to be confirmed as a quadratic function depending on the pressure (see FIG. 2 nozzle, resistance characteristics).

Therefore, the resistance characteristic of the descaling device corresponds to a specific quadratic function without changing the number of nozzles or the size of the nozzle opening. Thus, the increase in pressure at the nozzle can only be made on line of the quadratic function. In addition, the increase in pressure should also be considered for the increase in pressure. Therefore, the pressure can be increased or decreased by turning the piston on and off, thereby making it possible to match the effective impact force of the water to the slab or the strip (see FIG. 3).

It is an advantage that at least one piston pump is adjustable with respect to the volumetric flow of the piston pump. Through this volume flow adjustment, it is possible to set any correction on the resistance characteristic curve so that an optimum pressure / volume flow characteristic can be realized.

If nearly identical piston pumps are provided as described in claim 3, the manufacture, placement and maintenance of the piston pumps is economically viable.

By changing the resistance characteristic curve by changing the number of nozzles or the cross sectional area of the opening of the nozzle, the linkage with the piston pump allows the pressure / volume characteristics to be adjusted. In this case, if the resistance characteristic curve is steeply inclined, a large pressure change can be made only by slightly changing the volume flow. On the other hand, if the resistance characteristic curve is flat, a large pressure change cannot be obtained unless the volume flow is largely changed.

The descaling of the descaling device and thus the descaling effect can be better adapted to the corresponding requirements if the second nozzle row is provided. In this case, the first nozzle row preliminarily removes the scale and the second nozzle row completely removes the scale. In this case, each of the two nozzle rows may operate at a pressure lower than that of the descaling device having only one nozzle row. The first nozzle row may be supplied with a centrifugal pump, and only the second nozzle row may be supplied with the piston pump. In this case both nozzles must be separated by, for example, mechanical or pneumatic shields, or simply placed with a suitable gap in order to prevent the seizure and the water remaining in the material to be descaled. . The invention is next described using the accompanying drawings.

4 shows a process for rolling the cast material, for example the slab 1. In the area of the slab 1, nozzles 4, 4 'of the descaling device 5 are located between the drive unit 2 and the first stand 3 of the hot rolling furnace. The nozzles 4 and 4 'are connected to two piston pumps 6 and 7 which take out water from the tank 9 via the filter 8 and return it to the nozzles 4 and 4'. Each piston pump 6, 7 can be individually controlled by the control device 10 shown schematically.

FIG. 5 shows an embodiment in which another nozzle 11, 11 'is connected to the filter 8 via two piston pumps 6', 7 'in addition to the descaling device shown in FIG. Shows. Each piston pump 6 ', 7' can be individually controlled by a control device 10 'schematically shown.

Claims (5)

In the descaling device for removing the scale attached to the surface of the slab 1 or strip of the hot rolling mill by using the nozzles 4, 4 'supplied by the seizure piston pump 6, at least one other A seizure piston pump 7 is provided, characterized in that the seizure piston pumps 6, 7 are connected in parallel, and each seizure piston pump 6, 7 can be operated or shut off individually. Descaling device. 2. A descaler as claimed in claim 1, characterized in that the at least one seized piston pump (6,7) is adjustable with respect to its volumetric flow. 3. The scale removing device according to claim 1, wherein the same seizure piston pump (6, 7) is provided. 2. The second nozzle row 11 according to claim 1, wherein the second nozzle row 11, 11 ′ is positioned in front of the nozzles 4, 4 ′, so that the seizure does not affect each other. And 11 'are separated from the nozzles 4 and 4', and the seizure piston pumps 6 'and 7' connected in parallel receive a seizure with a lower pressure than the seizure piston pumps 6 and 7. 11 '), the descaling apparatus characterized in that the supply. 4. The second nozzle row (11, 11 ') according to claim 3, wherein the second nozzle rows (11, 11') are positioned in front of the nozzles (4, 4 '), so that the seizure does not affect each other. Is separated from the nozzles 4 and 4 ', and the seizure piston pumps 6' and 7 'connected in parallel to the nozzle rows 11 and 11' receive a seizure of lower pressure than the seizure piston pumps 6 and 7. Descaler, characterized in that for supplying.