JPH0620625B2 - Temperature control method of steel slab in continuous casting process - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for adjusting the temperature of a steel slab in a continuous casting process, and more particularly to a continuous casting machine end of each steel slab continuously cast at various drawing speeds in a wide range. The present invention relates to a method for adjusting the temperature of a steel slab in which the desired temperature is set to a temperature at which desired direct rolling and direct heating furnace charging can be performed.

(Prior Art) In recent years, from the viewpoint of energy saving or metallurgical reasons, a method of directly rolling a continuously cast (hereinafter referred to as CC) high temperature steel slab with a hot rolling mill (CC-DR). Method) or a method of charging directly into a heating furnace (called CC-DHC method) has been proposed and partially implemented.

Whether or not the CC-DR method and the CC-DHC method can be carried out is determined by C.I. C. C at the cross section of the slab at the machine end
The question is whether or not the high temperature necessary for carrying out the C-DR method and CC-DHC method can be secured. In order to obtain a high-temperature steel slab, unsolidified recuperation is basically used as disclosed in Japanese Patent Publication No. 49-6974.

And, in the case of performing the non-solidification recuperation and obtaining the high temperature steel slab, it is important that the crater end (complete solidification end) is as close as possible to the end of the CC apparatus.

The position of this crater end varies in the machine length direction depending on the drawing speed of the C.C. device. When the drawing speed is fast, it becomes far from the meniscus, and when the drawing speed is slow, it approaches the meniscus. , It depends on the drawing speed.

Therefore, the captain of the CC equipment for obtaining the high temperature steel slab by the non-solidification recuperation is at a position almost equal to the position of the crater end when casting at the maximum drawing speed in the CC equipment. It is designed so that the end of the CC device is located. That is, generally, a slab cutter is provided immediately after the machine end,
This is because the steel slab is cut into a predetermined length, and if the crater end is located outside the machine end at that time, molten steel will flow out, which is extremely dangerous.

(Problems to be Solved by the Invention) C. C. In the equipment, the optimum drawing speed (casting speed) is given depending on the steel type, and the drawing speed may inevitably change depending on the circumstances of the previous process.

It is not uncommon that the drawing speed fluctuates considerably due to such factors as, for example, about 1.3 m / min to about 2.2 m / min.

Since the drawing speed fluctuates as described above, the CC with the machine length designed according to the highest drawing speed as described above.
In the case of the equipment, at the slower drawing speed, the crater end after the unsolidified recuperation is located inside the machine, and therefore the temperature of the steel slab at the machine end is higher than the temperature of the crater end. It decreases in proportion to the decrease in speed.

For example, in the case of the CC device having the maximum drawing speed of about 2.2 m / min and the machine length designed according to this, when the drawing speed is the slowest of about 1.3 m / min, from the machine end There is a crater end at a position about 23 m before, and the temperature of the steel slab at the machine end is about 180 ° C lower than the temperature at the crater end. CC-DR method, CC-DH
It was impossible to secure the high temperature necessary for carrying out the method C.

Therefore, the object of the present invention is to determine the temperature at the machine end of the CC apparatus of each steel slab cast at a wide range of various drawing speeds so that the CC-DR method and the CC-DHC method can be performed at high temperatures. It is to provide a method for adjusting the temperature of a steel slab.

Another object of the present invention is to provide a method for adjusting the temperature of a steel slab capable of finely adjusting and controlling the temperature of the steel slab at the machine end, whereby a metallurgical effect can be appropriately obtained according to the type of steel.

Furthermore, it is an object of the present invention to provide a method for adjusting the temperature of a steel slab using a compact and economical CC apparatus that shortens the length of the CC apparatus.

(Means for Solving Problems) In order to achieve the above-mentioned object, the temperature adjusting method of the present invention cools a steel slab directly by a refrigerant in an unsolidified reheat step of a horizontal portion of a continuous casting device. In addition to providing an adjusting cooling device for the steel slab, cast the captain of the continuous casting device at the maximum drawing speed in the continuous casting device to reheat the unsolidified recuperation process and adjust the steel slab. If the length of the steel slab is almost equal to the crater end position at the time when the steel slab reaches the desired temperature, and the crater end position after unsolidified recuperation is at the drawing speed within the machine of the continuous casting device, the unsolidified Perform only recuperation or use adjustment cooling together with this, and if the crater end position after unsolidified recuperation is at a drawing speed outside the machine end of the continuous casting machine, use it in unsolidified recuperation as well. Adjust the cooling to The data end is located at substantially the same position as the machine end or inside the machine.

(Operation) The following is a low C.I. for carrying out the method of the present invention. C. The operation of the method of the present invention will be described with reference to FIG. 1 showing an example of the apparatus.

In the figure, 1 is a mold, 2 is a first cooling zone consisting of primary and secondary cooling zones (a cooling device is not shown).
In the secondary cooling zone of the cooling zone 2, gentle cooling is performed to prevent cracking of the slab. 3 is a horizontal part and is also a non-solidification recuperation zone. Reference numeral 4 denotes an adjustment cooling zone provided near the first cooling zone 2 in the unsolidified recuperation zone 3 for carrying out the method of the present invention. Cooling that allows steam cooling above and below the steel slab S as a cooling device. A device 5 was provided. When not cooled by the cooling device 5, the adjusted cooling zone 4 acts as the unsolidified recuperation zone 3.

By providing the adjustment cooling zone 4 in the horizontal portion, it is possible to uniformly cool the slab in the longitudinal direction and the width direction. Incidentally, E in the drawing indicates a crater end.

6 is an unsolidified recuperation zone 3 in which the cooling device 5 is not provided.
Is the rest of. A hydraulic shear 7 and an end heat compensation device 8 are provided outside the machine, and a hot rolling device 9 is provided in another line which is directly connected or is close to it.

A captain 10 of a CC apparatus for carrying out the method of the present invention was cast at a maximum drawing speed as described in the claims,
Then, the maximum unsolidified recuperation zone 3 is used for recuperation, and the cooling zone 4 is conditioned and cooled so as to obtain a desired temperature for CC-DR or CC-DHC. Thus, the crater end formed on the steel slab S is obtained. The length to the position of E is almost the same as the position of E. Therefore, the captain 10 of the above CC device,
The length is greatly shortened compared to the length of a conventional CC apparatus that does not have an adjustment cooling zone.

When the CC device of the captain 10 is used, the drawing speed is low, and when cooling is not performed in the adjustment cooling zone 4, the position of the crater end E'even if the heat treatment is performed again in the unsolidified recuperation zone 3 in the horizontal portion. May be upstream from the machine end 11, but since the captain of the CC apparatus for carrying out the method of the present invention is shorter than that of the conventional CC apparatus as described above, the crater concerned. The distance from the position of the end E ′ to the machine end 11 is short, the temperature drop is small accordingly, and the temperature of the steel slab at the machine end is high.

On the other hand, if cooling is not performed in the adjustment cooling zone 4, the adjustment cooling zone 4 controls the crater end so that the position of the crater end is almost at the end 11 when the crater end is at the extraction speed outside the machine. It can be cooled, which allows the temperature of the steel slab at the end 11 to reach the desired high temperature. In this case, the temperature of the steel slab at the machine end 11 can be made a delicately controlled temperature by finely controlling the cooling in the adjustment cooling zone 4.

(Example) (1) Type of C.C. device ... Bending type of bending portion 3mR (2) Range of drawing speed ... 1.3 to 2.2m / min. (3) Slab size ... 250mm thickness x 1700mm width ( 4) Test steel type: Low carbon aluminum killed steel Under the above conditions, the conventional captain's CC device (conventional example),
With the CC device of the captain of the method of the present invention (example of the present invention),
The drawing speed was changed by 0.1 m, and the drawing was performed, and the average temperature of the cross section of the steel slab at the machine end at each speed was measured. The results are shown in the table below. In the example of the present invention, when the drawing speed was 1.8 m / min or more, cooling was performed in the adjustment cooling zone to recover the unsolidified heat. Further, when the drawing speed is 1.7 m / min or less, the unsolidified recuperation is performed without cooling in the adjustment cooling zone, and in the conventional example, the unsolidified recuperation is performed in the horizontal portion at all drawing speeds. It was

The conventional captain 53m in the above table is a conventional captain designed so that the end of the crater end is approximately the same as the crater end position after the unsolidified recuperation when pulled out at 2.2m.
1 m is approximately the same as the crater end position when unsolidified recuperation and adjusted cooling are performed so that the temperature can be extracted at 2.2 m and the CC-DR method can be performed at a temperature (for example, about 1190 ° C. or higher). 1 shows a captain of the present invention designed so that the position is at the machine end. The following facts are found from the above table.

(1) The captain of the present invention is shortened by 12 m as compared with the conventional example.

(2) In the case of the above low carbon aluminum killed steel, CC-
The minimum temperature at which the DR method can be carried out is about 1190 ° C. or higher in machine temperature, but in the conventional example, the drawing speed is 1.6 m /
If it is less than a minute, the temperature is not secured. On the other hand, in the example of the present invention, the CC-DR method possible temperature is secured at all the drawing speeds.

(3) In the present invention example, when the drawing speed was 1.7 m / min or less, the temperature was controlled within the same range as when heating the steel slab in the heating furnace by performing fine adjustment cooling in the adjustment cooling zone. A steel slab can be obtained.

The proposals for improving the material properties by the metallurgical effect by the CC-DR method and the CC-DHC method include JP-B-56-21330, JP-B-56-24018, and JP-B-58-9812. JP-B-57-43130, JP-B-59-37330, JP-A-59-19412, and the like. According to the present invention, a slab having a temperature suitable for implementing these proposals can be provided.

(Effects of the Invention) As described in detail above, according to the present invention, a captain designed under the conditions specified by the present invention, which has a C.C. With the device
At the low drawing speed side drawing speed, the crater end is located upstream of the machine end but the distance between the crater end and the machine end is the same as the conventional C.C. It has the effect that it is shorter than in the equipment and the steel slab at the end of the machine is still maintained at high temperature. Further, in the drawing at the high drawing speed side, there is an effect that the steel slab temperature at the machine end can be set to a desired high temperature by finely controlling and using the adjusted cooling. Therefore, this invention is CC-
This greatly contributes to the implementation of the DR method and CC-DHC method.

[Brief description of drawings]

The drawing is an illustration of an example of a CC apparatus for carrying out the method of the present invention. 3 ... Unsolidified recuperation process, 4 ... Adjusting cooling zone, 5 ...
Cooling device, 10 ... Captain, 11 ... End, S ... Steel slab, E ... Crater end.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Asaaki Yamazaki 1 Fuji-machi, Hirohata-ku, Himeji-shi, Hyogo Nippon Steel Corporation Hirohata Works (72) Inventor Takashiro Nonaka 2-chome, Otemachi, Chiyoda-ku, Tokyo No. 6-3 Shin Nippon Steel Co., Ltd. (56) Reference JP-A-58-168466 (JP, A) JP-A-60-54257 (JP, A) JP-A-57-139458 (JP, A)

Claims (1)

[Claims] 1. A steel slab adjustment cooling device for directly cooling a steel slab with a refrigerant is provided in the unsolidified recuperating process of a horizontal portion of the continuous casting device, and the cap length of the continuous casting device is set in the continuous casting device. Casting at the maximum drawing speed, reheating in the unsolidified recuperation process and adjusting cooling of the steel slab to make the length almost equal to the crater end position when the steel slab reaches the desired temperature. , If the crater end position after the unsolidified recuperation is the drawing speed so that it is within the machine of the continuous casting device, only the unsolidified reheat is performed or this is used together with the adjustment cooling, while the crater end after the unsolidified reheat is performed. When the position is a drawing speed that is outside the machine end of the continuous casting device, adjustment cooling is performed in combination with unsolidified recuperation heat, and the crater end is at substantially the same position as the machine end or inside the machine. , Continuous casting process Temperature adjustment method of in steel slab.