CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit under 35 U.S.C. § 371 to international application No. PCT/EP2018/081292, filed on Nov. 15, 2018, which claims priority to German application No. DE 102017220891.0, filed on Nov. 22, 2017, the contents of which are incorporated by reference in their entireties.

FIELD OF INVENTION

The invention relates to a method for cooling a metallic item by discharging a cooling medium from a cooling bar onto the item, wherein the cooling medium is discharged through a slot in the cooling bar. The invention further relates to a cooling bar for discharging a cooling medium onto an item to be cooled.

BACKGROUND OF INVENTION

A cooling bar according to the preamble and a method for cooling a metallic item thereby are known from CN 101020196 A for example. A cooling medium (usually water) which is under pressure is guided here through the cooling bar and exits from the cooling bar through a slot (nozzle slot) to reach the item to be cooled. Here, by means of a straight component which can be screwed down on the cooling bar, the desired slot width can be set. However, the slot width then remains fixed during the ongoing process. Variations in the cooling power are then only possible by changing the pressure of the cooling medium. EP 1 420 912 B1 shows a similar solution.

When cooling sheet metal, water is generally applied onto the surface of the metal sheet. In the case of a long metal sheet, the cooling water can simply run off over the edges of the metal sheet. In the case of a uniform application over the width of the metal sheet, this leads to an increase of the volumetric flow rate of the cooling water on the surface of the metal sheet toward the edges of the metal sheet. This leads to a nonuniform cooling action or cooling down. Moreover, a process-caused inhomogeneity in the temperature profile can occur. Both lead to nonuniform mechanical properties and unevenness of the metal sheet.

Although in the previously above disclosed solutions the nozzle geometry can in fact be adjusted, this setting cannot be altered during ongoing operation. It is therefore impossible to react to changing process parameters.

Thus, a drawback in the known solution is that no possibility exists for varying the cooling power beyond the above-disclosed extent during the process. This applies particularly also in reference to the setting of the volume flow of the cooling medium in a direction transverse to the conveying direction of the metallic item (or of the cooling bar, if said cooling bar is moved relative to the item to be cooled).

Therefore, the aim underlying the invention is to provide a method of the type mentioned at the start as well as a cooling bar which makes it possible to allow an optimal setting of the cooling power at desired or required boundary conditions, wherein it should be possible to carry out said setting rapidly and during the process. To that extent, the cooling should be improved.

SUMMARY OF INVENTION

The achievement of this aim by the invention is characterized in terms of method in that during the cooling process the width of the slot in conveying direction of the item or of the cooling bar (if said cooling bar is moved relative to the item) is altered in order to bring the cooling power of the control medium to a desired or predefined level by open-loop or closed-loop control.

In particular, it is provided here that the slot is delimited by at least two sections of the cooling bar, wherein the at least two sections can be moved relative to one another in a feed direction.

The width of the slot in a direction transverse to the conveying direction and perpendicular to the outlet direction of the cooling medium can here also be altered differently in sections according to a development of the invention.

When viewed perpendicularly to the outlet direction of the cooling medium, the two sections of the cooling bar can have a nonlinear course here. Here, it is provided in particular that, when viewed perpendicularly to the outlet direction of the cooling medium, the two sections of the cooling bar in each case have a concave portion and adjoiningly thereto a convex portion. In this case, it is preferably provided that, for the purpose of setting the nozzle gap, the at least two sections of the cooling bar can be shifted in a direction perpendicular to the outlet direction of the cooling medium and perpendicular to the conveying direction (that is to say in a direction transverse to the conveying direction) in order to alter the width of the slot.

In the process, the width of the slot can be set so that the width is greater in a central area of the item to be cooled than in the lateral end areas of the item to be cooled.

The proposed cooling bar for discharging a cooling medium onto an item to be cooled is characterized according to the invention in that electrical, pneumatic or hydraulic adjustment means are present, by means of which the width of the slot in the conveying direction (of the item or of the cooling bar) can be altered.

The adjustment means can here be in connection with an open-loop control, wherein at least one sensor in connection with the open-loop control is arranged, by means of which a physical property of the item can be determined.

The slot is preferably delimited by at least two sections of the cooling bar, wherein the at least two sections of the cooling bar, when viewed perpendicularly to the outlet direction of the cooling medium, have a nonlinear course, preferably an S-shaped course.

The proposed design or the proposed cooling bar is suitable for plate mills, in hot strip mills and in heat treatment lines in particular for steel materials. However, a use for nonferrous metals is likewise possible. In particular, a use in quenching lines with slotted-nozzle cooling bars for cooling water application is also possible.

Thus, a cooling bar with a slotted nozzle and a nozzle geometry which can be altered over the width is provided. Thereby, using defined specifications, the nozzle geometry can be influenced in a targeted manner, in particular during the cooling process itself.

Thus, the present invention provides cooling bars with slotted nozzles, wherein the nozzle geometry and thus the volume flow over the width of the item to be cooled can be altered during ongoing operation. Thus, a closed-loop control system can be implemented, which provides specifications for a designated actuator.

Preferably, the slotted nozzle of the proposed cooling bar consists of at least two portions, wherein at least one portion of the nozzle is designed to be movable. The alteration of the slot geometry can occur, for example, via a closing off of one nozzle portion in the direction of the other nozzle portion. This closing off can occur nonuniformly over the nozzle width. Thus, for example, less cooling water can be applied toward the edges. This helps eliminate the aforementioned drawback.

Another possibility consists in providing the nozzle portions with a special contour, in particular an S-shaped geometry, and then altering the nozzle slot via an axial shifting of the portions with respect to one another.

The adjustment of the slot can here occur manually or automatically. An actuator is provided for an automatic slot adjustment and the resulting possible variable water application over the width of the metal sheet. This actuator preferably receives the specific adjustment values from an automation system (closed-loop control system). The automation system receives information on the dimensions of the metal sheet and the material characteristic (primary data), target properties (hardness, strength, etc.), data from process sensors (material temperatures, actual evenness, etc.), before, in and after the cooling device, and achieved actual properties after the process. With this information, the system is able to transmit adjustment values to the actuator. By means of this continuous backflow of the actual properties, it is possible to select the values so that a homogeneous distribution of the properties of the metal sheet in particular over the width is set. However, it is also possible to set different properties in a targeted manner over the width of the metal sheet.

It is possible (in spite of filters in the intakes of the cooling bars) that blockages or deposits on cooling water nozzles repeatedly occur. By means of the adjustment of the nozzle gap of the slotted nozzle, the nozzle gap can be opened, whereby dirt particles, for example, in the form of clumps or small plates can be rinsed out of the slot.

The proposed solution makes it possible to variably set or adjust the geometry of a slotted nozzle. This adjustment can also occur during ongoing operation during the cooling of an item (metal sheet). Thereby, it is possible to deliver a different water application to the metal sheet head or metal sheet foot.

Moreover, a closed-loop control can be provided, which, depending on different process and specification values, specifies target values for the open-loop control of the nozzle geometry.

By these measures, a better evenness and optimized material properties can be achieved during the cooling process.

By means of the proposed solution, it is possible to control the cooling medium which is running off laterally in a targeted manner so that a desired cooling over the width of a strip occurs. Thus, in particular, a uniform cooling over the strip width can be achieved.

