Cooling bar and cooling process with variable cooling rate for steel sheets

Abstract

A cooling device with variable cooling rate for treating metal materials, in particular for cooling steel sheets in plate mills, hot strip mills or thermal treatment lines, by means of a spray nozzle cooling system. The cooling device consists of at least two cooling bars one of each two cooling bars being situated on the lower side and the other on the upper side transversely to the sheet travel direction of the sheet and centrally between two roller table rollers and includes a spray nozzle cooling system with which a plurality of full jet nozzles and a plurality of full cone nozzles are associated, the full jet nozzles being arranged symmetrically to the full cone nozzles. A method for operating the cooling device according to the disclosure.

Claims

1. A cooling device with variable cooling rate for treating steel materials, comprising: at least one pair of cooling bars, a first cooling bar of each pair of cooling bars arranged below a sheet to be cooled and a second cooling bar of each pair of cooling bars arranged above the sheet to be cooled, opposite the first cooling bar, wherein each pair of cooling bars is arranged between two roller table rollers, wherein the first and second cooling bars each comprise a spray nozzle cooling system which extends transversely to a travel direction of the sheet to be cooled, wherein the spray nozzle cooling system comprises a row of full cone nozzles extending transversely to the travel direction and a row of full jet nozzles provided on each side of the row of full cone nozzles, and wherein each nozzle of the rows of full cone nozzles and rows of full jet nozzles are individually controllable.

2. The cooling device according to claim 1, wherein a ratio of coolant flow through the rows of full cone nozzles and the rows of full jet nozzles is adjustable to cool the sheet at a rate of 5 to 150 K/s.

3. The cooling device according to claim 1, wherein a ratio of coolant flow through the rows of full cone nozzles and the rows of full jet nozzles is adjustable to cool the sheet at a rate of 1 to 19 K/s.

4. The cooling device according to claim 1, wherein a ratio of coolant flow through the rows of full cone nozzles and the rows of full jet nozzles is adjustable while the cooling device is cooling the sheet.

5. The cooling device according to claim 1, wherein the rows of full jet nozzles are arranged symmetrically about the row of full cone nozzles.

6. The cooling device according to claim 1, wherein flatness sensors and temperature sensors are arranged upstream of the cooling device, and wherein a controller individually controls the nozzles of the rows of full cone nozzles and the rows of full jet nozzles according to a cooling model based on values provided by the flatness sensors and the temperature sensors.

7. The cooling device according to claim 6, wherein a coolant flow rate and a coolant surge pressure are controllable for each nozzle of the rows of full cone nozzles and rows of full jet nozzles.

8. The cooling device according to claim 6, wherein the controller individually controls the nozzles of the rows of full cone nozzles and rows of full jet nozzles to achieve a target hardness of the sheet.

9. A method for operating the cooling device according to claim 1, comprising: controlling the nozzles according to a cooling model in order to achieve a desired grade in the sheet, and passing the sheet between the at least one pair of cooling bars while flowing a coolant through one or more of the at least one pair of cooling bars to cool the sheet.

10. The method according to claim 9, further comprising: switching between a high cooling rate and a low cooling rate according to the cooling model, wherein the high cooling rate activates the rows of rows of full jet nozzles and the low cooling rate activates only the rows of full cone nozzles.

11. The method according to claim 10, wherein a coolant quantity and a coolant surge pressure are adjusted for each nozzle of the rows of full cone nozzles and rows of full jet nozzles.

12. The method according to claim 11, wherein at least one control parameter is measured for controlling the cooling rate, and wherein the control parameter is a mechanical property of the sheet comprising at least one of hardness, phase distribution, and grain size.

13. The method according to claim 12, wherein the control parameter is considered with at least one of a dimension, a material grade, and a target property of the sheet.

14. The method according to claim 13, wherein flatness sensors and temperature sensors are arranged both upstream and downstream of the cooling device, and wherein the cooling model compares target output properties with actual output properties of the sheet measured at the sensors arranged downstream of the cooling device, wherein control of the cooling device is adjusted in response to differences between the target output properties and the actual output properties in order to achieve the desired grade.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The disclosure will be explained in more detail below by way of an exemplary embodiment with reference to the accompanying drawings. In the figures:

(2) FIG. 1 shows the side view of the cooling device according to the invention in a schematic sectional representation, wherein the cooling device is arranged between two roller tables of a rolling line;

(3) FIG. 2 shows the schematic side view of a cooling bar forming the cooling device in cross-section;

(4) FIG. 3 shows the graphic representation of a cooling device on which the performance of the method according to the invention is to be based;

(5) FIG. 4 shows a graphic detail view of the interaction between the computerized cooling model and the cooling device of FIG. 3 according to the invention.

DETAILED DESCRIPTION

(6) As shown in FIG. 1, apparatus 10 essentially consists of two opposing cooling bars 16, 16a and 17, 17a arranged between two roller table rollers 12, 13, 14. Cooling bars 16, 16a and 17, 17a are implemented with a very compact design. To this end, two cooling systems 16 and 17 as well as 16a and 17a have basically been combined to form a cooling unit 18 and 18a.

(7) It is intended for cooling units 18, 18a to be operated in an interlinked and synchronized manner. Cooling bars 16, 16a are associated with the upper side of the sheet and cooling bars 17, 17a with the lower side of the sheet.

(8) FIG. 2 shows an enlarged representation of lower cooling bar 17 of FIG. 1, cooling bars 16, 16a and 17a being constructed in the same way.

(9) As further shown in FIGS. 1 and 2, the compact design is based on there being at least two types of nozzles, in this case full jet nozzles 19 and full cone nozzles 20, arranged and integrated in cooling bar 16, 16a and 17, 17a in a special manner. A nozzle cooling system preferably having full jet nozzles 19, 19a for a high cooling rate, and a nozzle cooling system preferably having full cone nozzles 20 for low cooling rates (gentle cooling) are installed, by which a cooling medium 29 can be selectively directed at sheet 22.

(10) Full cone nozzles 20 are arranged centrally and full jet nozzles 19, 19a are spaced therefrom and arranged in parallel next to full cone nozzles 20 in cooling bar 16, 16a and 17, 17a. Preferably, the nozzle cooling system is arranged in cooling bar 16, 16a and 17, 17a transversely to sheet travel direction 20 and over the entire width of a sheet 22 to be rolled.

(11) FIG. 3 is a graphic representation showing the control of sheet cooling using cooling system 16, 16a and 17, 17a of FIG. 2, according to the invention. In principle, preliminary information such as primary sheet data 23, target sheet properties 24 and actual sheet properties 25 can be provided to a cooling model 26 for cooling control. This basic data serves to control cooling device 28. Cooling model 26 is controlled by the values sensed by sensors 27, 27a. As such, the actual properties of sheet 22 before cooling can be compared with the target properties after cooling of sheet 22. If the target properties are not reached, this information is transmitted to the cooling model and the cooling device is readjusted accordingly, as shown in FIG. 4.

(12) This ensures a safe and reliable process. The cooling device can be used with maximum flexibility. Manual interventions by operating personnel are minimized by means of automatic control through the model computer.

(13) As such, cooling model 26 interacts perpetually and virtually online with cooling device 28. Thus, a cooling model is possible for each section of the machine. Volumetric flow rates and the actual data are also constantly compared and readjusted if necessary.

(14) This makes it possible to produce maximum uniformity of cooling transversely and longitudinally to the strip travel direction, wherein cooling rates of lowest to very high values can be achieved.

(15) The control concept can be used to operate a plate mill, a hot strip mill or a thermal treatment line, for example, with maximum flexibility. This means that the desired cooling rate can be freely set at any time and over the entire length of the machine. The model computer (not shown) that controls cooling model 26 autonomously decides which cooling application (cooling rate) is necessary and most economical for the material properties to be achieved.