JPS6349584B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secondary cooling device for a continuous casting apparatus, and an object thereof is to provide a device that allows precise cooling control.

Now, as is well known, in continuous casting equipment, 1
Following the next cooling, a method is adopted to promote the solidification of the slab through secondary cooling such as spray cooling or air/water cooling, and in addition, to ensure that the slab that has been cut into specified dimensions maintains a specified temperature. Cooling is controlled. By the way, in recent years, with the aim of energy saving, high productivity, and high quality, so-called direct rolling has been put into practice, in which continuously cast slabs are sent directly to a hot rolling process without passing through cold treatment or heating furnaces. The inventors of the present invention, who have been engaged in implementing this method on an industrial scale, have found that various technical problems remain in the secondary cooling of slabs.

One of these problems is that it is difficult to properly roll the slab unless it is cut at a high temperature (for example, 1150°C) and sent to the hot rolling process as soon as possible. Attempts to avoid supercooling tend to cause the solidified shell to break, causing breakouts, which is a trade-off. Uniformly cooling each part of the strand requires extremely difficult operations due to physical constraints such as cooling nozzle arrangement, roll arrangement, and various guide arrangements, as well as variable factors such as nozzle clogging and casting trouble. This problem becomes an important control factor, especially in cooling control, such as changing the casting speed.

In addition, steel ingots have a property called hot brittleness, and there is a problem in that direct rolling becomes impossible if excessive cooling or temperature changes are applied.

Therefore, the present inventors have developed the present invention as a result of research into a secondary cooling device that can always maintain the desired temperature of the strand during casting. The secondary cooling device consists of a spray cooling device followed by an air/water cooling device and an external roll cooling device, or a device in which an air/water cooling device and a roll external cooling device are arranged in sequence, and further the water cooling device is , an arithmetic cooling control device that instructs cooling of the entire strand and selective cooling of the strand in the width direction according to the difference between the actual measurement value from the strand temperature measurement device and the set temperature; This is a secondary cooling device for a continuous casting apparatus characterized by having a group of nozzles that can be freely switched and controlled in three modes of water and gas ejection, or in addition, four modes of no ejection.

Next, referring to the drawings, an example apparatus in which the present invention is applied to a curved continuous casting apparatus will be described in detail below.

FIG. 1 is a schematic block diagram of a secondary cooling device according to the present invention, in which molten steel is injected into a mold 1 from a tundish (not shown), is primarily cooled, becomes a strand 2, and is pulled out from the casting. (The oscillation device, mount, rolls, etc. are omitted for convenience of explanation.) 3 is a spray cooling device, which is composed of a large number of cooling water nozzles and a group of supply water pipes installed between apron rolls (not shown), and the strand 2 is solidified while passing through the spray cooling device 3. Has Ciel. Next, 4 is an air/water cooling device, which includes guide rolls, pinch rolls,
It consists of a large number of air/water nozzles that face between groups of rolls such as bending rolls, and a group of supply pipes that supply water and gas (for example, air or gases such as N ₂ and CO ₂ ) to these nozzles. While passing through the air-water cooling device 4, the sland 2 is cooled to a desired surface temperature (or average temperature). 5
The roll external cooling device is composed of a group of air/water cooling nozzles, spray nozzles, or cooling gas nozzles provided opposite to the outer surface of a horizontal guide roll, and a group of supply pipes for supplying a cooling medium thereto. 6 is a surface temperature measuring device (non-contact type or contact type) of the strand 2 installed between the spray cooling device 3 and the air/water cooling device 4; A surface temperature measurement device 8 is provided between the strands 2 and 2, and 8 is a surface temperature measurement device that measures the surface temperature of the strand 2 that has passed through the roll external cooling device 5 and reached the front of the cutting device (for example, a gas cutting device) 9. be. 10 is a unit slab having predetermined dimensions after cutting; 11 is an induction heating device that heats a locally low-temperature portion of the unit slab 10; and 12 is installed at the front of a hot rolling mill (not shown). It's a scale breaker.

Next, 13 is a comprehensive process control device that controls the target surface temperature of the strand 2 to be cast.
A command is given to the calculation cooling control unit 14. The arithmetic cooling control device 14 receives command signals from the overall process control device, measured values of the surface temperature measuring devices 6 to 8, and other parameters related to cooling control (molten steel temperature,
refrigerant supply opening/closing valve device 15 of the spray cooling device 3 according to calculation results based on cooling capacity, casting speed, etc.);
Refrigerant supply on-off valve device 16 of the air-water cooling device 4 and refrigerant supply on-off valve device 17 of the roll external cooling device 5
sends a control signal to the

The strand 2 needs to have a desired average temperature represented by a predetermined surface temperature (temperature that allows direct hot rolling) immediately before the cutting device 9, so that the measured value of the surface temperature measuring device 8 is used for cooling calculation. Used as the main factor. A unit slab 10 (hereinafter simply referred to as slab 1) cut into a predetermined size by a cutting device 9
0) is sent to the rolling process as it is, or in the induction heating device 11 shown in the figure, the temperature drops locally in the area where the temperature has dropped (particularly the front and both sides of the slab, where the temperature tends to drop due to heat radiation). (It may be necessary to raise the temperature because cracks, shape defects, and quality defects are likely to occur during the rolling process) and the material is heated and sent to the rolling process.

FIG. 2a is a schematic explanatory diagram of a device according to an embodiment of the present invention different from that described above. In this embodiment, there is no spray device, and the secondary cooling device is composed of an air/water cooling device 4 and an external roll cooling device 5. has been done. In the figure, 18 indicates a tundish. FIG. 2b is a partially enlarged view of the air/water cooling device 4, showing the guide roll 19.
A nozzle 20 faces between the strands 2 and 2.
is cooled by air, water, or gas (usually air is used) ejected from the nozzle 20, and in some cases, the ejection of air, water, or gas from the nozzle 20 is selectively stopped. (Details will be explained later). FIG. 2c is a partially enlarged view of the roll external cooling device 5, in which air water or cooling gas is blown from the nozzle 21 onto the outer surface of the horizontal guide roll 22. Also, in this roll external cooling cooling device 5, the jetting of the air water and cooling gas from the nozzle 21 can be freely controlled by controlling the opening/closing device 17 described above.
Depending on the case, it is also possible to stop it selectively. Therefore, the refrigerant is not directly blown onto the strand 2 in this portion.

FIG. 3 is a partial detailed view of the spray cooling device 3.
A large number of spray nozzles 24 are provided between the apron rolls 23 and are controlled by a control valve 25 to spray refrigerant (usually cooling water) onto the strands 2. If necessary, the nozzles 24 may be controlled simultaneously by providing one control valve for each of the nozzles 24.

Next, FIG. 4 is a partial detailed diagram of the air/water cooling device 4.
26 is an air control valve, 27 is a cooling water control valve,
Air and water are ejected from the nozzle 20. If the air control valve 26 is closed in this state, only water will be ejected from the nozzle 20, and conversely, if the cooling water control valve 27 is closed and the air control valve 26 is opened, only air will be ejected from the nozzle 20.
Further, when the air control valve 26 is closed, cooling is no longer performed. The above-mentioned three embodiments or in addition to the four non-ejection modes are implemented for each nozzle or for each nozzle group, as will be described in more detail later.

FIG. 5 is a schematic block diagram of different embodiments showing cooling control procedures according to the present invention.
is a compressed air supply pipe, 29 is a pressure gauge, 30 is a flow meter, 31 is a flow rate control valve, 32 is a pressure indicator controller,
33 is a flow rate indicator controller, 34 is a pressure and flow rate selection controller, 35 is a cooling water supply pipe, 36 is an electromagnetic flow meter, 37 is a flow rate control valve, 38 is a flow rate indicator controller, and 39 is a control mode selection controller. The indicator 40 is a temperature indicator controller, and 41 is a control change command device.

In this device, the surface temperature of the strand 2 is measured by a surface temperature measuring device 8, and the measurement signal is input to a temperature indicator controller 40. The temperature indicator controller 40 compares the command signal from the control change command device 41 with the measurement signal, and if there is a difference, inputs the difference signal to the control mode selection indicator 39. The control mode selection indicator 39 selects the most appropriate control mode to eliminate the difference, and sends a control signal to the cooling water flow rate indicator 38, pressure indicator 32, and air flow rate indicator 33. give. The pressure and flow rate selection controller 34 selects either the pressure or the flow rate, or both, based on the instructions, and the flow rate regulating valve 31 operates. On the other hand, the flow control valve 37 is
is activated. Through the above control operations, the nozzle 20
takes the following three modes (1) to (3) or four modes (1) to (4) in which no ejection is added.

(1) Spout air and water.

(2) Spout water.

(3) Blow out air.

(4) No eruption.

Therefore, the above (1) to (3) also include quantitative changes. The control change command device 41 operates in response to commands from the arithmetic cooling control device 14 (not shown), and performs not only the aforementioned feedback control but also feedback control. Further, although only one nozzle 20 is shown, as mentioned above, a plurality of nozzles may be grouped together, or the operating mode may be controlled to differ in the strand width direction.
The details will be explained using the cooling patterns shown in FIGS. 6a, b, and c. The strands 2a to 2c shown in the front partial view in the width direction are pulled out in the direction of the arrow 45, the block 42 shown with diagonal lines is strongly cooled with air and water, and the block 43 shown with dotted lines is cooled with a small amount of water. The white block 44 shows the part cooled by air. Cooling pattern a~ as needed
c and other arbitrary cooling patterns to control the temperature in the length and width directions of the strands, resulting in an optimal temperature distribution that guarantees high quality and energy savings.

FIG. 7 is a schematic diagram for explaining specific examples of the above-mentioned three aspects (1) to (3) of the nozzle 20, and there are four or more nozzles 20 in each row in the vertical direction of the strand 2 showing the front part in the width direction. Five of them are arranged in parallel and in the shape of a dried bird. ◎ indicates that air and water are being ejected, ○ indicates that a small amount of water is being ejected, and * indicates that only air is being ejected.
The temperature at the center in the width direction of the strand 2 is high and requires relatively strong cooling, but since the temperature tends to drop more easily at both ends, good results can usually be expected by using weak cooling.

FIG. 8 shows an example of a group configuration of the supply pipe system for the nozzle 20, and in this way, the unit nozzle 20
Good results can sometimes be obtained by using a supply pipe system configuration in which each unit can be individually controlled, or a group configuration in which a suitable plurality of units are controlled simultaneously.

As a specific implementation of the present invention, the thickness is 250 mm.
Casting speed 0.5~1.8 mm, width 1200mm strand
m/min, the device according to the invention lowers the surface temperature of the strand by 50 m/min in front of the cutting device 9, compared to conventional single air/water cooling.
The temperature was increased by ~100℃, and we succeeded in obtaining a high-temperature product of 1,100 to 1,190℃ as an example. In terms of quality, we achieved high results with yields increasing by 5 to 10%, and energy-saving effects improved by approximately 5%.

[Brief explanation of the drawing]

The figures show embodiments of the present invention; FIG. 1 is a schematic block diagram of a device according to the present invention, and FIGS. 2 a, b, and c are schematic block diagrams of other embodiments of the device according to the present invention. and partially enlarged views, Figures 3 and 4.
The figure is a schematic diagram of a nozzle and a refrigerant supply pipe, FIG. 5 is a schematic diagram of a device showing the cooling control procedure of the present invention, FIGS. 6 a, b, and c are schematic diagrams of cooling patterns, and FIG. FIG. 8 is a schematic explanatory diagram of the refrigerant supply pipe configuration. 1 is a mold, 2 is a strand, 3 is a spray cooling device, 4 is an air/water cooling device, 5 is a roll external cooling device, 6 is a surface temperature measuring device, 7 is a surface temperature measuring device, 8 is a surface temperature measuring device, 9 is a cutting device, 10
1 is a unit slab, 11 is an induction heating device, 12 is a scale breaker, 13 is a comprehensive process control device, 14 is a calculation cooling control device, 15 is a refrigerant supply opening/closing valve device,
16 is a refrigerant supply on-off valve device, 17 is a refrigerant supply on-off valve device, 18 is a tundish, 19 is a guide roll, 20 is a nozzle, 21 is a nozzle, 22 is a horizontal guide roll, 23 is an apron roll, 24 is a spray nozzle, 25 is a control valve, 26 is an air control valve, 27 is a cooling water control valve, 28 is a compressed air supply pipe, 29 is a pressure gauge, 30 is a flow meter, 31 is a flow rate adjustment valve, 32 is a pressure indicator controller, 33 is a flow rate 34 is a pressure and flow rate selection controller, 35 is a cooling water supply pipe, 36 is an electromagnetic flowmeter, 37 is a flow rate adjustment valve, 38 is a flow rate indicator and controller, 39 is a control mode selection indicator, 40 is a temperature The indicator controller 41 is a control change command device.

Claims (1)

[Claims] 1. In the secondary cooling device of continuous casting equipment, said 2
The secondary cooling device consists of a spray cooling device followed by an air/water cooling device and a roll external cooling device, or a device in which an air/water cooling device and a roll external cooling device are arranged in sequence, and the air/water cooling device further comprises: A calculation cooling control device that commands cooling of the entire strand and selective cooling of the strand in the width direction according to the difference between the actual measurement value from the strand temperature measurement device and the set temperature;
A secondary cooling device for a continuous casting apparatus, characterized in that it is equipped with a nozzle group that can be freely switched and controlled in three modes of ejecting water and gas, or in addition, four modes of no ejection.