JPS6027448A - Continuous casting method of steel plate - Google Patents

Abstract

PURPOSE:To suppress effectively the growth of a solidified shell generated at the terminal of a pouring inlet in the stage of casting continuously a molten steel into the space between cooled casting molds which face each other at a suitable space and move circumferentially in the same direction by bringing the molten steel into contact with a specific part. CONSTITUTION:For example, cooling rolls 1, 1 are rotated in an arrow direction and a molten steel 2 is supplied to frame bodies 3 of both rolls. A solidified layer 5 formed by said rolls is cast continuously to a steel plate 6. A solidified shell 12 is formed to grow on the inside surface of the bottom end part 3a of the frame body 3 and the shell 12 solidifies to connect the boundary 4 between the roll 1 and the body 3 in some case. If such sheel is left intact, shearing force is acted in the solidified and connected part by the revolution of the rolls 1 and in a worse case the body 3 is broken by the resultant flaw and crack therefrom. The flow of the molten steel is thereupon divided by the peak part of a guide body 20 in the state of supplying the molten metal from above into the body 3 so as to flow downward along the slope of said body to collide vigorously against the boundary 4. The shell 12 under growth is then quickly melted by a large amt. of continuous heating received to the high-velocity flow of the molten steel and the formation thereof is suppressed.

Description

[Detailed description of the invention] The present invention relates to a continuous casting method for steel plates using a moving mold,
In particular, the flow rate of molten steel is increased to reduce the heat of the undesirable solidified shell of 0-molten steel that forms and grows as a result of heat dissipation or cold heat from the mold at the end of the dip pouring spout facing close to the cooling mold. It acts effectively to suppress the growth of the solidified shell,
The present invention relates to a continuous casting method for steel sheets that can eliminate as much as possible the problems caused by the solidified shell growing and connecting with the solidified layer of the original molten steel that is formed on the cooling mold and grows.

In general, continuous casting methods include two methods: one method is to continuously cast molten metal into a fixed mold and continuously draw out the solidified ingot, and the other is to continuously pour molten metal into a moving mold and solidify the ingot as the mold moves. There is a method of sending out chunks continuously. The former is mainly used to produce slabs, and the latter is used to produce thin steel sheets. In the case of casting slabs, a rolling process is added later and the casting process is significantly extended, so the casting speed is not required as high. However, in the case of casting steel plates, the cast steel plate becomes the product as it is, so in order to increase productivity, the casting speed is particularly high. It is necessary to increase In order to increase this casting speed, the continuous casting method for steel plates uses a moving mold instead of a fixed mold as described above.

There are two types of continuous casting methods for steel plates using this moving mold: a roll type with a relatively short cooling length and a block type with a relatively long cooling length.

First, regarding the roll type casting method, the method shown in FIG. 1 is known as a conventional roll type continuous casting method. That is, a molten metal 2 is supplied onto two cooling rolls 1, 1 which are arranged parallel to each other so as to be freely rotatable in the horizontal direction, and while the molten metal 2 is cooled and solidified, a plate-shaped metal is placed between the rolls 1, 1 downwardly. This is a method of continuously casting castings. In this method, as shown in the figure, a refractory frame 3 is provided which serves as a warm inlet for storing molten metal on a cooling roll 1 and continuously supplying the molten metal between the rolls 1.1. The lower end of the frame 3 is formed along the curved surface of the cooling roll 1.1 to reduce leakage of molten metal, and there is a slight gap or is not pressed at the boundary 4 with the opposite part of the roll 1. There are no gaps. The molten metal 2 is cooled and solidified by coming into contact with the cooling roll 1, and a solidified layer 5 is formed on the surface of the cooling roll 1.

This solidified layer 5 is extruded from between the rolls 1.degree. by the rotation of the rolls 1 and becomes a steel plate 6.

Next, the block type casting method will be explained. As a conventional block type continuous casting method, the method shown in FIG. 2 is known. That is, the block-shaped cooling molds 7.7 are connected on endless tracks that face each other and move in the same direction.
This is a method in which molten metal is supplied to the cavities 8 and is cooled and solidified while continuously casting plate-shaped castings in front of the cavities 8. In this method, as shown in the figure, a refractory nozzle 10, which serves as a warm inlet for continuously supplying the molten metal stored in the sump 9, is installed between the molds 7 and 7 where the opposing cooling molds 7 begin to engage with each other. It has been extended. The tip of the nozzle 10 is dimensioned so as to be almost in contact with the mold 7 so as to reduce sagging. Cavity 8
The 7Cr8 hot water is injected into the cooling mold 7 and solidifies sequentially while moving together with the cooling mold 7 to form a continuous steel plate 11 which is extruded from the end of the mold 7.

In this way, both methods are basically the same in that molten steel is continuously injected from the warm inlet between cooling molds that face each other and move circumferentially in the same direction while being appropriately spaced apart, and because they are the same, they are common. In addition to the above-mentioned roll type and block type, which have problems, there are also systems such as twin belts and combinations of belts and grooved wheels, but the situation is similar. .

Looking at this problem in the roll-type continuous casting method, as shown in Fig. 3, the solidified layer 5 formed on one surface of the cooling roll has
There is a problem in that the solidified shell 12 formed and grown on the lower end 3a of the frame 3 connects and causes streak-like scratches or plate breaks 13 on the surface of the cast steel plate 5.

That is, since the frame body 3 stores high-temperature hot water, its temperature is high overall, but since its lower end portion 3a faces the cooling roll 1 in close proximity, it receives more cold heat A than the cooling roll 1.
In addition, due to the heat radiation B from the outer surface of the frame 3, it tends to be cooled significantly compared to other parts. Therefore, a solidified shell 12 is gradually formed on the inner surface of the lower end portion 3a of the frame from the portion in contact with the cooling roll 1, and grows larger with the passage of time. The solidified shell 12 formed on the lower end 3a reaches the boundary 4 with the cooling roll 1, and is finally connected and fixed to the solidified layer 5 formed on the surface of the cooling roll 1. As a result, a large shearing nozzle J is applied to this connected and fixed portion by the rotation of the cooling hole 1, and cracks are formed in the solidified layer 5 formed on the surface of the cooling roll 1. These cracks may disappear when the steel plate is repeatedly rolled, as in the case of a slab, but in the case of a steel plate, they remain as streak-like scratches on the surface or cause the plate to break. In addition, if the solidified shell 12 grows quickly and the fixing force of the connecting fixing portion is strong, the solidified layer 5 is attached to the frame 3.
A large shearing force is applied by the rotation of the cooling roll 1 through the cooling roll 1, and the tip portion 3a of the frame body 3 may be damaged and the portion may be torn off, resulting in a defective portion. In such a case, the situation becomes so serious that the operation has no choice but to be stopped.

In the case of a roll type like this, the end portion 3a of the frame 3
During this process, an undesirable solidified shell 12 is formed and grows, which adversely affects the steel plate to be cast, and in extreme cases, there is a problem in that the operation is stopped.

The above situation is exactly the same for the block type. That is, as shown in FIG. 4, the nozzle tip 10a is cooled by the cold heat from the cooling mold 7, and a similar solidified shell 16 is formed and grown on its surface, and is formed on the surface of the cooling mold 7. This has the same name as solidification M17, which has the disadvantage of forming scratches on the surface of the steel plate or damaging the nozzle tip 10a.

The present invention has been made in view of the above circumstances, and an object of the present invention is to effectively prevent the formation and growth of a solidified shell at the end of the warm inlet that faces the cooling mold, and to To provide a continuous casting method for steel plates, which effectively prevents the occurrence of scratches on the steel plate surface or breakage of the steel plate, or damage to the thermal inlet, and enables efficient casting of high-quality steel plates.

According to the present invention, the above object is achieved as follows. That is, when molten steel is continuously injected between cooling molds that face each other and move circumferentially in the same direction while being appropriately spaced apart,
Pour the molten steel so as to hit the boundary between the end of the cavernous inlet into which the molten steel is to be poured and the facing part of the cooling mold, and pour the molten steel so as to hit the boundary between the end of the cavity inlet where the molten steel is to be poured and the facing part of the cooling mold. In this method, a steel plate is continuously cast by forming a flow of molten steel that flows between the molds at a high velocity along the flow direction.

A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 5 is a continuous roll type v for explaining the method of the present invention.
FIG. 2 is a schematic explanatory diagram showing an example of an ifi device.

An example of the roll-type continuous casting apparatus according to the method of the present invention has the same basic configuration as the conventional example.

As shown in the figure, molten steel 2 is supplied into the frame 3.
The boundary 4 between the lower end 3a of the frame body and the cooling roll 1 is separated.
, More specifically, in order to guide the apex to the junction point consisting of the three boundaries of the solidified shell 12 to be formed on the inner surface of the lower end portion 3a of the frame, the solidified layer 5 formed on the surface of the cooling roll, and the molten steel 2. A guide body 20 having a substantially triangular cross section with the bottom facing upward and the bottom facing downward is placed on the center line between the rolls 1.1. The top of the guide body 20 is preferably made to protrude from the surface of the molten metal, and it is preferable that the molten steel supplied not only within the plant but also outside the molten steel be diverted in advance. This is because the static pressure of molten steel is large.
If the flow rate is high, the adhesion to the cooling roll 1 will be higher and the surface of the steel plate will be more beautiful, so there is a need to improve the flow rate.If the flow rate is high, there is a possibility that a sufficiently high flow velocity may not be obtained by guiding only within the site. This is because there is a

The guide body 20 is made of a refractory material like the frame body 3, and although the illustrated example shows the simplest shape, the guide body 20 is not limited to this shape. The most important thing about the guide body 20 is that due to the presence of the guide body 20, the molten steel supplied to the boundary 4 collides with force, and a high-speed flow toward the boundary 4 is formed so that a stagnation area is not formed. Therefore, boundary 4 (=l
As long as a high-speed flow is formed nearby, it may be one that generates a vortex flow, or it may be a submerged nozzle that spouts molten steel directly toward the boundary 4. In addition, the guide body 2 of the illustrated embodiment
0, as a result, a restriction is formed on both sides of the bottom, that is, in the vicinity of the boundary 4, and an increase in the flow velocity due to this restriction is also taken into account.

Next, the operation of the roll type continuous casting apparatus having the above configuration will be explained.

The cooling rolls 1, 1 are driven to rotate in the same direction by a motor (not shown), and molten steel is supplied to the frame bodies 3 of the cooling rolls 1, 1. The cooling roll 1 is constantly cooled by cooling water flowing through cooling grooves (not shown) provided inside the roll 1, and the molten steel 2 supplied to the frame 3 comes into contact with the cooling roll 1, is cooled and solidified, and is cooled by the cooling roll 1. A coagulated layer 5 is formed on one surface. The cooling speed by the cooling roll 1 is fast and the solidification layer 5
grows in a short time and is slightly rolled between the rolls 1.1 to continuously cast the steel plate 6.

The molten steel 2 in the frame 3 is at a high temperature, and therefore the frame itself is also quite high temperature, so unlike the cooling roll 1, a solidified shell is not easily formed on the inner surface of the frame due to cooling. However, since the lower end 3a of the frame 3 is close to the cooling roll 1, a solidified shell 12 is formed and grows on its inner surface, and the solidified shell 12 solidifies the boundary 4 between the roll 1 and the frame 3. May be connected. If this is left as it is, shearing force will be applied to the assimilation connection part due to the rotation of the roll 1, causing scratches and cracks in the coagulated layer 5 on the roll 1 surface, and in severe cases, the frame body 3 will be damaged.

However, in this embodiment, damage to the steel plate 6 or damage to the frame 3 can be avoided in the following manner. In other words, when molten steel is supplied into the frame 3 from above the frame 3, the molten steel 2 is separated at the top of the guide 20 and flows down along the slope of the guide 20, reaching the lower end 3a of the frame. It is accelerated toward the boundary 4 of the opposing portion of the cooling roller 1 facing this. Therefore, this accelerated molten steel is poured so as to hit the boundary 4, collides with the boundary 4 with force, and the lower end 3a of the frame body
A high-velocity flow is formed along the opposing portion of the roll 1. The solidified shell 12 that was forming or growing on the lower end 3a of the frame body is rapidly melted by the continuous and large amount of heat 11 caused by the high-speed flow, and its formation is prevented, and the roll 1
It does not connect and stick to the coagulated layer 5 formed on the surface.

Further, since a restriction is formed at the boundary 4 by the guide body 20, the flow velocity at the boundary 4 is higher than at other parts. Therefore, compared to the case where the guide body 20 is not present, the formation speed of the solidified shell at the lower end portion 3a of the frame body is reduced, and the growth in the direction of the roller 1 is suppressed as much as possible, and the above-mentioned connection sticking occurs. Never.

As described above, in this embodiment, the molten steel is actively poured toward the boundary between the lower end 3a of the frame body where the solidified shell 12 is to be formed and the roll facing portion, or the flow velocity of the molten steel at the boundary is increased. Therefore, the formation of the solidified shell 12 at the lower end 3a of the frame body is effectively prevented, and the generation of streak-like scratches on the steel plate surface, plate breakage, or damage to the frame body 3 due to the growth of this solidified shell is effectively prevented. can do.

Incidentally, by pouring the molten steel 2 into the boundary 4 in a mtii manner, there is a problem with the effect it has on the solidified layer 5 that is originally required to be formed on the surface of the roll 1, but it is true that pouring the molten steel 2 into the boundary 4 will affect the area in question. Although it is recognized that the formation of the coagulated layer 5 is somewhat inhibited, this is a problem because the gain gained (no scratches, etc., and prevention of damage to the frame 3) is far greater than what is lost due to this inhibition. It is not. In addition, sometimes the coagulated layer 5 on the roll 1 side grows rapidly and its layer thickness becomes thinner, resulting in connection sticking from the O-ru 1 side as well, but this cannot be effectively prevented. There are advantages that can be achieved.

Next, the method of the present invention will be explained using an example of a block type continuous casting apparatus. Even in an example of a block type continuous casting apparatus, the basic configuration is the same as that of the conventional example.

As shown in FIG. 6, the molten steel flow 22 ejected from the tip 10a of the nozzle 10 is prevented from proceeding straight in the axial direction, and the nozzle tip 10a located radially outward of the nozzle 10 and the cooling mold 7 A guide body 30 having a substantially triangular cross section with its base facing upstream and its top facing downstream is provided with a mounting number in front of the tip 10a so that the guide body 30 will go straight after being guided around the boundary 40 of the tip 10a. There is. The guide body 30 is made of a refractory material like the nozzle 10, and the attachment means 31 to the tip is shown as the simplest connecting body in which the guide body 30 and the nozzle 10 are integrally constructed in the illustrated example. Other monetary instruments may also be used. Further, the nozzle tip 10a is provided with a taper 32 to guide the molten steel flow toward the boundary 40 (as shown in the illustrated example).

Note that the guide body 30 has the same function as the guide body 30 in the roll type described above, which has the function of forcefully applying molten steel to the boundary, so it is not limited to the shape shown in the example shown. A helical groove may be provided on the inner circumferential surface of the molten steel passage of the nozzle 10 by disposing the body 30 so that the vortex generated by the groove is diffused during ejection and collides with the boundary 40 located radially outward.

According to the block type continuous casting apparatus, the jetted molten steel flow hits the boundary 40 with force due to the guide body 30 and the taper 32 formed at the tip 10a, and the temperature of the boundary 40 is increased as much as possible, so that the nozzle tip Formation of solidified shell 16 in portion 10a is effectively suppressed. Therefore, the connection and fixation of the solidified shell 16 does not occur, and damage to the steel plate or damage to the nozzle 10 caused by this can be prevented.

In this way, regardless of whether it is a roll type or a block type, the boundary between the frame 3 or the tip of the nozzle 10, which serves as the pouring opening, and the opposing roll 1 or cooling mold 7 is always kept away from the hot molten steel. By washing with water, it is possible to effectively suppress the formation of an undesirable solidified shell at the tip of the warm inlet. It goes without saying that the method is not limited to the above method, but can also be applied to a belt type method, and the same effect can be obtained.

In short, according to the present invention, the following excellent effects ψ are produced.

('1) The growth of the solidified shell that occurs at the end of '12I:' during warming is effectively suppressed, and the occurrence of streak-like scratches and plate breaks on the steel plate surface caused by the growth of this solidified shell is effectively suppressed. can be prevented from
We can cast beautiful steel plates.

(2) It is possible to prevent damage to the end portion of the heat exchanger 1 due to the growth of the solidified shell, thereby dramatically increasing work efficiency.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view showing a conventional O-roll type continuous casting machine, Fig. 2 is a schematic sectional view showing a conventional block type continuous casting machine, and Figs. 3 and 4 are respectively a conventional roll type continuous casting machine. FIG. 5 is a schematic sectional view showing a preferred embodiment of a roll-type continuous casting apparatus that implements the method of the present invention, and FIG. 6 is the same. 1 is an enlarged schematic sectional view of a main part showing a preferred embodiment of a block type continuous casting apparatus. In addition, 1 and 7 in the figure are cold F! exemplifying cooling molds. 10-
2 and 22 are molten steel or molten steel flow; 3 and 10 are frames and nozzles that are examples of warm inlets; 3a and 10a are frames that are examples of end portions of stud inlets; The nozzle tips 4 and 40 are the boundaries between the end of the warm inlet and the facing part of the cold NJ mold, and 6 and 11 are cast steel plates. Patent applicant: Patent attorney representing Ishikawajima-Harima Heavy Industries Co., Ltd.
Nobuo KinutaniFigure 3Figure 4Figure 5Figure 6

Claims (1)

[Claims] When molten steel is continuously injected between cooling molds that move circumferentially in the same direction while facing each other while being appropriately spaced apart from each other, it is necessary to The molten steel is poured so as to hit the boundary, and a molten steel flow is formed at the boundary from the end of the warm inlet to the opposite part of the cooling mold, increasing the flow rate between the molds to form a steel plate. A continuous casting method for steel sheets.