JPH06218509A - Method of large rolling reduction of cast slab strand in continuous casting - Google Patents

Abstract

PURPOSE:To improve the quality of the inside of the cast slab strand with a relatively small rolling force (simplification of the facility and downsizing is possible). CONSTITUTION:In executing the large rolling reduction of the ingot strand which is drawn from a continuous casting mold in the vicinity of the solidification completion point, a planetary mill 3 which is combined with a pair of back-up rolls 3b, 3c to hold the cast slab strand from both sides and a plurality of rotating work rolls w while turning around these back-up rolls 3b, 3c respectively is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for large reduction of slab strands (strict center segregation strict materials such as high-grade thick plate materials and high-grade wire rod materials) in continuous casting, which is effective for reducing the required reduction force. It is intended to give.

[0002]

2. Description of the Related Art In a slab obtained by continuous casting, it is inevitable that center segregation or scratch marks, which cause quality deterioration, occur.
In order to reduce such center segregation, it has been clarified that it is extremely effective to reduce the area near the completion of solidification in the drawing process of the cast slab. 61-189850, JP-A-61
A number of proposals have already been made, such as the -238448 publication or the JP-A-62-86951 publication.

[0003]

Specific methods for reducing center segregation and the like are roughly classified into two types: a roll reduction method in which a roll is used for reduction and a press reduction method in which a die is used for reduction. However, although any type of improvement effect was recognized, a problem as described below still remains, and its solution is desired.

Roll reduction system: Suitable for light reduction, but when large reduction is performed such that the solidified shell is crimped near the solidification completion point of the cast strand, it is necessary to increase the strength and drive torque of the roll. There is also a need to increase the roll diameter from the viewpoint of preventing internal cracking of the strands, and even if the same amount of reduction is used, the reduction force must be increased, and the size of the device increases. It is difficult to apply to existing continuous casting machines.

Press-pressing method using a die: A large press-down can be performed without causing internal cracks, but there is a limit to downsizing due to the press structure, and existing continuous casting machines with severe installation space restrictions It is difficult to apply, especially when processing a relatively large bloom or slab, the required rolling force becomes large, so it was difficult to apply the device unless there was a considerable amount of installation space.

[0006] It is an object of the present invention to propose a large reduction method capable of ensuring a reduction force required for performing reduction in the vicinity of a solidification completion point of a cast strand in a minimum space.

[0007]

The present invention provides a pair of backup rolls for sandwiching the slab strands from both sides when the slab strands pulled out from the continuous casting mold are largely rolled down in the vicinity of their solidification completion points. It is a large reduction method of a cast strand in continuous casting, characterized by using a planetary mill that is a combination of a plurality of work rolls that revolve around each of the backup rolls while rotating, and in the present invention, a cast strand The strand may be pushed into the planetary mill by using a device for pulling out.

[0008]

[Function] The planetary mill attaches a large number of small-diameter work rolls around a large backup roll, and drives the backup rolls to revolve and rotate the work rolls around the backup rolls. 1 is added as a whole.
It is possible to obtain a large amount of reduction in one pass, and if this is applied to the reduction in the vicinity of the solidification completion point of the slab strand, 1) crimp the solidified shell of slab Stunrad without causing internal cracking. can do. 2) The curvature of the pressing surface is almost equal to the curvature of the circumscribed circle of the work roll, and even if the work roll has a small roll diameter, it can be regarded as a reduction by the large diameter roll as a whole, which is extremely advantageous for internal cracking and surface cracking. Is. 3) By reducing the rolling force, equipment specifications can be simplified and made compact. It has advantages such as the above, and can be applied to an existing continuous casting machine very easily.

FIG. 1 shows a configuration of equipment suitable for carrying out the present invention, with respect to a planetary mill arranged downstream of a continuous casting mold (in the vicinity of a solidification point completion region of a cast strand). In the figure, 1 is a cast strand drawn from a continuous casting mold, 2 is a guide roller for supporting the cast strand 1, 3 is a planetary mill, and this mill 3 is a pair of backups in a frame 3a. The rolls 3b and 3c, and a plurality of work rolls W that revolve around these backup rolls while rotating around them, and a strand pushing roll 3d having reduction cylinders Sa and Sb are incorporated.

FIG. 2 shows the situation in which the planetary mill having the above-mentioned structure is used to reduce the area around the solidification completion point of the slab strand 1. The planetary mill has a structure such that the slab strands 1 are directly pressed down by the work roll W having a small diameter and the reaction force at that time is received by the backup rolls 3b, 3c having a large diameter, whereby the required strength can be secured. Has become.

The rolling force P and rolling torque T of the mill required for rolling down the cast strand 1 are shown below in the case of normal roll rolling as shown in FIG.

## EQU1 ## P = Qσb (Dδ / 2) ^1/2 (1) T = P (Dδ / 2) ^1/2 = QσbDδ / 2 (2) where, Q: rolling force coefficient σ: deformation resistance b:
Slab width D: Roll diameter δ: Reduction amount

That is, according to the usual roll reduction method, when the reduction amount δ is constant, the reduction force is P∝ (D) ^{1/2 and the} torque is T∝D.

In the case of a planetary mill, FIG.
As shown in, the diameter D of the work roll W _WIs the diameter D of the circumscribed circle₀
Can be a fraction of 10 to a fraction of 10, where D
_W= D₀/ 10 = D / 10 and pressure by planetary mill
The subscript (w) is applied for normal roll pressure.
Add a subscript (r) to the product to compare the rolling force with the torque.
The comparison is as follows.

[Formula 2] P _W = (D _W / D) ^1/2 _Pr = (1/10) ^1/2 _Pr =
_{0.316 P r T W = (D} W / D) T r = (1/10) T r = 0.10T r

In the reduction by the planetary mill,
Although the number of working whirl rolls W at the time of reduction varies depending on the amount of reduction, it is about 2 to 2.5 in the case of normal large reduction, so the reduction force P and torque T by the planetary mill are given the subscript p. And compared with the reduction by the normal roll,

[Formula 3] P _p = (2-2.5) P _W = (2-2.5) × 0.316 P
_{r = (0.63~0.79) P r T} p = (2~2.5) T W = (2~2.5) × 0.1 T r = (0.2
~ 0.25) T _r

According to the reduction by the planetary mill, the reduction force can be reduced by about 20 to 40% and the rolling torque can be reduced by about 75 to 80% as compared with the normal roll reduction.

In a planetary mill, since it is difficult to apply a driving torque to the work roll W, a roll for applying a driving torque is provided on the entrance side of the mill, and the slab strand 1 is fed into the mill by the roll. It is better to push it in. If the pull-out force of the pinch roll used for pulling out the slab strand 1 has a margin, it can be used instead, but in this case, tensile strain acts on the solidification interface of the slab strand 1, so that FIG. As shown, it is preferable to provide the pushing roll 3d in the frame constituting the mill so that the slab strand 1 is pushed into the mill. Although this roll 3d is shown in the case where one set is installed, two or three sets can be arranged as required.

As described above, in the conventional roll reduction method, as the size of the roll for reducing the cast strand becomes larger, the reduction force and the reduction torque become excessive, and the equipment itself becomes correspondingly large. Although it was difficult to be suitable, in the present invention, since the planetary mill is used, the necessary and sufficient rolling force can be secured without increasing the size of the equipment.

[0018]

[Example] A slab strand with a thickness of 300 mm and a width of 400 mm
In the continuous casting of (S55C), the planetary mill having the structure shown in Fig. 1 in the vicinity of the solidification completion point.
(Mill specifications: D ₀ = 1500 mm, D _W = 150 mm, P _p = 400
_{t, t p = 33t-m} ) large pressure by the (casting speed: 0.9m / mi
n, Reduction: 90mm, Surface temperature of cast strand: 950 ℃)
Then, the internal quality of the obtained slab was investigated. As a result, it was confirmed that the segregation was very small and the internal quality was good. In addition, here, when using a die for rolling down
(Mold reduction: 400 mm, reduction cycle: 8 seconds, P _f = 600t,
T _f = 10 tm) and rolled down by a normal roll
The results of (D = 1500 mm, P _r = 700 t, T _r = 160 t-m) were also examined, but no great difference in quality was observed. However, the reduction force P required to reduce the slab strand is 400t when using a planetary mill.
It was confirmed that the required rolling force can be reduced with a certain degree,
In addition, a comparison of the installation space of the equipment for pressing down the cast strands (the size of the continuous casting machine, excluding the driving device) shows a width of 2 m in the case of the press pressing method using a die.
A space with a length of 3 m and a height of 8 m needed a width of 2 m, a length of 3 m, and a height of 7 m in the case of the normal roll rolling method, whereas the space with a planetary mill uses a width of 3 m. It is 2m long, 2.5m long and 5m high, and the installation space is smaller than the former two. When the equipment cost (index) is 100 when the planetary mill is used, the result is 150 for the press reduction method using a die and 180 for the roll reduction method.

[0019]

[Effects of the Invention] When attempting to improve the internal quality by applying a large reduction in the area near the solidification completion point of the slab of strands during continuous casting, a large reduction force is required under the conventional method. However, according to the present invention, it is possible to improve the internal quality of the slab of strands with a relatively small rolling force (the equipment can be simplified and made compact).

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of equipment suitable for carrying out the present invention.

FIG. 2 is a diagram showing a state of rolling down a cast strand.

FIG. 3 is a diagram showing a rolling situation according to a conventional roll rolling system.

[Explanation of Codes] 1 slab strand 2 guide roller 3 planetary mill 3a frame 3b, 3c backup roll 3d slab strand pushing roll W work roll

Claims (2)

[Claims] 1. When a slab strand drawn out from a continuous casting mold is subjected to large reduction in a region near its solidification completion point, a pair of backup rolls sandwiching the slab strand from both sides and revolutions around the respective backup rolls. A method for large reduction of strand strands in continuous casting, characterized by using a planetary mill that is combined with a plurality of work rolls that rotate while rotating. 2. The method according to claim 1, wherein the slab strand is pulled into a planetary mill by using a device for pulling the slab strand.