KR100605696B1 - A Submerged Nozzle For Continuous Casting - Google Patents

Abstract

The present invention relates to an immersion nozzle for supplying molten steel from a tundish to a mold when continuous casting of molten steel, by not causing mold level hunting during casting, so that it can appropriately cope with the soft casting method and prevent mold breakage as well. An object of the present invention is to provide a continuous casting immersion nozzle capable of stabilizing the water surface.

The present invention comprises a pipe portion to which the insert is coupled to the upper portion and a transmission portion connected to the lower portion of the pipe portion, wherein the pipe portion and the transmission portion are each formed with an internal passage for communicating the melt flowing through the insert is formed Immersion nozzle for continuous casting,

It is to provide a continuous casting immersion nozzle, characterized in that the length of the pipe portion (L1) from the lower part of the insert to the transmission portion is equal to or greater than the length to complete the flow separation of molten steel generated during casting.

Combustion casting, Immersion nozzle, Insert, Pipe part, Transmission part, Mold level hunting

Description

Immersion Nozzle for Continuous Casting {A Submerged Nozzle For Continuous Casting}

1 is a schematic diagram showing a conventional immersion nozzle

(a) shows a front view and (b) shows a side view.

Figure 2 is a schematic diagram showing another conventional immersion nozzle

(a) shows a front view and (b) shows a side view.

3 is a pressure change diagram according to the distance of the conventional immersion nozzle of FIG.

4 is a pressure change diagram according to the distance of the conventional immersion nozzle of FIG.

5 is a schematic view when the flow separation of the upper immersion nozzle occurs

(a) shows the case where the flow separation is completed in the pipe section,

(b) shows the case where flow separation is completed at the transmission.

6 is a detailed view of the upper part of the immersion nozzle;

(a) shows the case where the insert inner diameter in contact with the pipe portion is smaller than the inner diameter of the pipe portion,

(b) shows the case where the inner diameter of the insert in contact with the pipe portion is the same as the inner diameter of the pipe portion.

7 is a graph showing the flow separation completion length according to the ratio of the insert inner diameter D0 / pipe portion inner diameter D1.

      * Description of the symbols for the main parts of the drawings *

One . . . Stopper 13,25,33,43,53,63. . . Insert 10,20,30,40,50,60. . . Immersion nozzles 11,21,31,41,51,61. . . Pipe section 12,22,23,32,42,52,62. . . Transmission 14,24. . . Divider

The present invention relates to an immersion nozzle for supplying molten steel from a tundish to a mold when continuously casting molten steel, and more particularly, to an immersion nozzle for continuous casting in which mold level hunting does not occur during casting.

The immersion nozzle for continuous casting has a purpose to stably supply molten steel from the tundish to the mold, and it is necessary to design it to stably maintain the molten surface of the mold.

Surface stability in the mold is extremely important to induce uniform mixing of the mold powder and uniform formation of the solidification shell to ensure the quality of the cast slab.

Therefore, the prior art stipulates the shape of the immersion nozzle to induce a stable molten steel flow at the nozzle outlet.

Representative forms of such immersion nozzles are shown in FIGS. 1 and 2.

The immersion nozzle of FIG. 1 is shown in US Pat. No. 5,785,880, and the immersion nozzle of FIG. 2 is shown in US Pat. No. 6,152,336.

The immersion nozzle 10 shown in FIG. 1 gradually decelerates the molten steel from the tundish to the pipe portion (length: L11) 11 by using a transmission portion (length: L12 and L13) 12. In order to induce a stable flow at the outlet, the convergence angle of the front and rear nozzle walls is changed to 2-8.6 degrees and the divergence angle of the left and right walls is 6-16.6 degrees so that the flow is not separated from the nozzle walls.

In FIG. 1, reference numeral 1 denotes a stopper, reference numeral 13 denotes an insert, and reference numeral 14 denotes a divider.

On the other hand, the immersion nozzle 20 shown in Figure 2 increases the flow rate while reducing the cross-sectional area of the molten steel flowing into the pipe portion (length: L21) (21) at the first transmission portion (length: L22) (22) In the second transmission portion (length: L23) 23, the cross-sectional area is further increased to decrease the flow rate to supply molten steel into the mold.

In FIG. 2, reference numeral 1 denotes a stopper, reference numeral 24 denotes a divider, and 25 denotes an insert.

In order to prevent separation of the flow in the nozzle, they also define the angle of the left and right wall surface of the outlet at 7.5 degrees or less and the middle divider wall surface at the angle of 7.5 degrees or less to induce a stable flow at the outlet.

However, in the case of casting using the immersion nozzles manufactured based on these patents, the flow rate is controlled by the stopper while the so-called mold level hunting occurs in which the hot water of the mold moves abnormally over a certain casting time. This becomes impossible and eventually stops casting, there is a problem that often occurs.

 The present inventors have conducted research and experiments to improve the above-mentioned problems of the prior art, and based on the results, the present invention proposes the present invention, and the present invention does not cause mold level hunting during casting so that it can cope with the soft casting method properly. It can be, and to provide a continuous casting immersion nozzle that can prevent the casting stop as well as the stabilization of the mold surface, the object is to.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated.

The present invention comprises a pipe portion to which the insert is coupled to the upper portion and a transmission portion connected to the lower portion of the pipe portion, wherein the pipe portion and the transmission portion are each formed with an internal passage for communicating the melt flowing through the insert is formed Immersion nozzle for continuous casting,

It relates to a continuous casting immersion nozzle having a pipe length (L1) from the lower part of the insert to the shifting portion is equal to or greater than the length to complete the flow separation of molten steel generated during casting.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail.

First, mold level hunting generated during continuous casting will be described.

Figure 3 shows the pressure change according to the distance change from the insert during casting using the conventional immersion nozzle shown in FIG.

The immersion nozzle is actually arranged vertically, but in FIG. 3, the immersion nozzle is arranged horizontally for convenience.

As shown in Fig. 3, the inner diameter of the insert 13 attached for flow control is smaller than the inner diameter of the pipe portion 11, so that the drawn molten steel increases speed directly under the insert 13 and is separated from the nozzle wall. Generate a flow.

This flow separation occurs even under the stopper 1 provided for controlling the flow rate even when the inner diameter of the insert 13 is equal to the inner diameter of the pipe portion 11.

As shown in FIG. 3, the static pressure distribution of the molten steel by the flow separation is significantly lowered directly below the insert 13, and the pressure is gradually lowered toward the downstream of the flow, thereby gradually recovering the pressure and eliminating the flow separation.

In FIG. 3, (3-a) is a curve when the pressure is normally restored during casting, and after the distance L11, the pressure gradually rises as the flow velocity decreases without flow separation from the wall.

However, if the molten steel enters the section where the cross-sectional area under the distance L11 is changed while the flow is not lost and the pressure is low, that is, the transmission part 12, rapid pressure recovery occurs as shown in (3-b).

This pressure recovery requires the molten steel to decelerate rapidly, resulting in a strong flow on the wall as opposed to the molten steel flow.

On the other hand, Figure 4 shows the pressure change according to the change in distance from the insert when casting using the conventional immersion nozzle shown in FIG.

In FIG. 4, the immersion nozzle is horizontally disposed as in FIG. 3 for convenience.

The flow separation phenomenon can be described in the same manner as in the immersion nozzle of FIG. 3 with respect to the immersion nozzle shown in FIG. 4.

In FIG. 4, (4-a) shows the pressure change according to the distance in the case of the normal flow, and (4-b) is for the abnormal flow.

In FIG. 4, L21 represents the length of the pipe part.

Figure 5 schematically shows the flow of the actual molten steel, Figure 5 (a) shows the normal molten steel flow in which the molten steel flow separation is terminated in the pipe portion.

In (a) of FIG. 5, the velocity of the molten steel introduced into the pipe part 31 from the insert 33 is significantly increased under the insert 43 to generate a separate flow from the wall of the immersion nozzle 30 while causing small swirls on the wall. There is a zone 5 in which is generated.

This zone serves to slow down the molten steel and is the opposite of the molten steel flow.

When the molten steel recovers the pressure within the length of the pipe portion, L51, the molten steel flows into the transmission part 32 after the flow separation is eliminated and becomes a stable flow.

However, if the molten steel does not recover the pressure within the length of the pipe portion 41, L52, as shown in FIG. 5 (b), flow separation does not disappear and the molten steel has to recover pressure rapidly. The mammary gland of is bent rapidly. After that, the flow is separated and flows in a stable flow as in the normal flow.

In FIG. 5B, reference numeral 43 denotes an insert.

When the wire of the molten steel is rapidly changed direction, the molten steel flow is applied to the relatively slow zone (5). This transmitted force causes the molten steel to vibrate in the zone 5 in which the molten steel flows slowly. This vibration is transmitted upwards, blocked at the inserts and damped while inducing molten steel flow directly under the inserts. The vibration reflected from the insert is also transmitted to the lower molten steel so that the size of the region where the flow separation occurs is periodically changed, and the pressure of the molten steel immediately below the insert changes periodically.

Accordingly, the velocity of the molten steel discharged from the insert is periodically changed, causing a pulsating flow in which the amount of molten steel supplied to the mold is periodically changed.

When a pulsation flow is generated in this way, the molten steel of the molten steel in the mold becomes unstable and eventually causes mold level hunting. In addition, the molten steel flow in the lower part of the insert is increased, thereby increasing the melting loss of the insert.

In order to prevent this phenomenon, the molten steel introduced from the insert should be sufficiently restored to the pressure in the pipe to be introduced into the shift section after the flow separation is eliminated. That is, it is understood that sufficient pipe length must be secured.

The present invention is based on the above findings and is characterized by an immersion nozzle for continuous casting in which the length of a pipe portion is properly set in connection with flow separation of molten steel in order to prevent mold level hunting.

That is, the present invention provides a continuous casting immersion nozzle having a length equal to or longer than the length of the pipe portion from the insert lower portion to the transmission portion to complete the flow separation of molten steel generated during casting.

The idea of the present invention includes a pipe portion 51 to which the insert 53 is coupled to the upper portion thereof and a transmission portion 52 connected to the lower portion of the pipe portion 51, as shown in FIG. In addition, the pipe part 51 and the transmission part 52 are applied to the continuous casting immersion nozzle 50 each having an internal passage for communicating the melt flowing through the insert 53,

In addition, the idea of the present invention is that the pipe portion of the continuous casting immersion nozzle for the continuous casting immersion nozzle having the same maximum internal diameter and the minimum internal diameter or the upper inner diameter (D1) of the pipe portion located in the lower portion of the insert on the top of the transmission portion. The lower inner diameter to be positioned, that is, the inner diameter D2 greater than the inner diameter D2 of the pipe portion at the position where the shift is started, and the reduction in the inner diameter from the upper portion to the lower portion is applied to the constant casting immersion nozzle.

The inner diameter D2 of the pipe portion at the position where the shift is started is usually the same as or slightly smaller than the inner diameter D1 of the pipe portion under the insert in the case of a nozzle.

This is to facilitate demolding of the mold for molding when producing the nozzle.

Therefore, the angle of the wall of the pipe part is vertical or the shape of the inner diameter is reduced while going downward.

In the present invention, when the ratio of the inner diameter DO of the insert / the inner diameter D1 of the upper portion of the pipe portion is 0.4 or more and less than 1.0, it is preferable to set the length of the pipe portion to be about 6-8 times or more of the average diameter of the pipe portion.

In addition, according to the present invention, as shown in FIG. 6 (b), the immersion nozzle 60 for continuous casting includes a portion in which the insert 63 has the same inner diameter D0 as the upper inner diameter D1 of the pipe portion 61. Also applies to

When the present invention is applied to such an immersion nozzle, the length L1 of the pipe portion 61 includes an insert portion having the same inner diameter as the upper inner diameter of the pipe portion 61, and accordingly, in the present invention, the upper portion of the pipe portion The length of the pipe portion including the insert portion having the same inner diameter as the inner diameter may be equal to or greater than the length to complete the flow separation of molten steel generated during casting.

In FIG. 6B, reference numeral 62 denotes a transmission part.

As such, when the present invention is applied to a continuous casting immersion nozzle including a portion having an inner diameter equal to the upper inner diameter of the pipe portion, the length of the pipe portion including up to an insert portion having the same inner diameter as the upper inner diameter of the pipe portion is equal to that of the pipe. It is desirable to be 6-8 times or more of the average diameter of negative.

Hereinafter, the present invention will be described in more detail with reference to Examples.

Example 1

In order to determine the length that no flow separation occurs in the pipe part, a nozzle having a pipe part length L1 as shown in FIG. At this time, the insert inner diameter (Do) was 60 mm and the inner diameter (D1) and the inner diameter (D2) of the transmission portion of the pipe portion of the lower portion of the insert were changed as shown in Table 1 below, and the length of the pipe portion was sufficiently long to be 1000 mm. As the discharge amount increases, the length of the flow separation elimination will increase, so the discharge amount in the normal continuous casting operation is 2.5 to 3.5 ton / min, so the upper stopper opening degree is adjusted to correspond to the condition of the highest discharge amount to 3.5 ton / min. It was.

In the position where the molten steel discharged from the insert is completed, the streamline is formed to be in close contact with the wall of the nozzle, and thus the length of the streamline is measured to the point where the streamline is in close contact with the molten steel, and the results are shown in Table 1 below.

At this time, when the inner diameter of the insert is smaller than the inner diameter of the pipe part as shown in FIG. 6 (a), the length is directly below the insert. As shown in FIG. 6 (b), the curvature of the insert part is the same as the inner diameter of the insert and the pipe part. This is the distance from the ending site.

On the other hand, the flow separation completion length according to the change of the ratio of the inner diameter D0 of the insert / the upper inner diameter D1 of the pipe portion to the four nozzles of the nozzles of Table 1 is the average inner diameter of the pipe portion [{the upper inner diameter D1 of the pipe portion. ) And the lower inner diameter (D2)} / 2] of the pipe part are shown in FIG. 7.

Discharge rate (ton / min) Do (mm) D1 (mm) D2 (mm) Flow separation completion length (mm) 3.5 60 150 150 900 3.5 60 100 100 750 3.5 60 75 75 600 3.5 60 60 60 480 3.5 60 150 140 870 3.5 60 100 80 675 3.5 60 75 70 580

As shown in Table 1, it can be seen that the longer the flow separation is completed, the longer the inner diameter of the insert is compared to the inner diameter of the pipe part, because the molten steel introduced into the pipe part is affected by friction with the surrounding molten steel. . Therefore, their flow separation completion length is influenced by the ratio of the inner diameter of the insert to the inner diameter of the pipe part.

In addition, as shown in Figure 7, when the ratio of the inner diameter (DO) of the insert / the inner diameter (D1) of the upper portion of the pipe portion is 0.4 to 1.0, the flow separation completion length of the molten steel is about 6-8 times the average diameter of the pipe portion Able to know.

On the basis of the flow separation completion length of the molten steel obtained as described above, it is possible to obtain the length of the pipe portion required to complete the flow separation before being introduced into the shift section, that is, the cross-sectional change section.

Example 2

To measure the time when the mold level hunting occurs when actually casting using the conventional nozzle of the following Table 2 and the immersion nozzle of the present invention, the results are shown in Table 2 below.

Conventional nozzles 1-6 in Table 2 represent immersion nozzles shown in U.S. Patent No. 5,785,880, and conventional nozzles 7-8 represent immersion nozzles shown in U.S. Patent No. 6,152,336.

In addition, in Table 2, Do is the inner diameter of the insert, D1 is the upper inner diameter of the pipe portion, D2 is the lower inner diameter of the pipe portion, L1 is the length of the pipe portion, and the mold level hunting generation time is the mold level hunting after the start of casting It represents the time when it occurred.

Nozzle Classification Average discharge amount (ton / min) Do (mm) D1 (mm) D2 (mm) Flow separation completion length (mm) L1 (mm) Mold level hunting occurrence time (min) Conventional Nozzle 1 2.55 60 72 71 572 230 204 Conventional Nozzle 2 2.69 60 72 71 572 230 224 Conventional Nozzle 3 2.70 60 72 71 572 230 199 Conventional Nozzles 4 2.91 60 72 71 572 230 170 Conventional nozzles 5 2.75 60 72 71 572 240 211 Conventional Nozzle 6 2.15 72 72 71 572 230 130 Conventional nozzles 7 2.64 60 97 95 768 697 345 Conventional nozzles 8 2.61 60 97 95 768 697 388 Invention Nozzle 1 2.90 60 60 59 476 535 None (403 min cast) Invention Nozzle 2 2.05 60 60 59 476 535 None (total 473 min castings)

As shown in Table 2, in the case of the conventional nozzle it can be seen that the mold level hunting is generated, the closer the length (L1) of the pipe portion to the flow separation completion length, the longer the time for the mold level hunting is generated, the more stable flow You can also see indirectly that

On the other hand, in the case of the nozzle of the present invention it can be seen that the mold level hunting does not occur even if cast for more than 400 minutes.

As described above, the present invention provides an immersion nozzle for continuous casting in which mold level hunting does not occur, thereby reducing costs due to increase in annual cast, productivity through prevention of casting stop, and securing cast quality by stabilizing mold surface. There is.

Claims (6)

A continuous column including a pipe part to which the insert is coupled to the upper part and a transmission part connected to the lower part of the pipe part, wherein the pipe part and the transmission part are each formed with internal passages for communicating the melt flowing through the insert. In the quiet immersion nozzle, The length of the pipe portion L1 from the lower part of the insert to the speed change portion is equal to or greater than the length for completing the flow separation of molten steel generated during casting. In this case, the ratio (D0 / D1) of the inner diameter D0 of the insert to the inner diameter D1 of the upper portion of the pipe portion is 0.4 or more and less than 1.0, The length of the pipe is a continuous casting immersion nozzle, characterized in that more than a value set within the range of 6-8 times the average diameter of the pipe portion. The immersion nozzle for continuous casting according to claim 1, wherein the pipe part has the same maximum internal diameter and the minimum internal diameter. According to claim 1, wherein the pipe portion of the upper inner diameter (D1) located in the lower portion of the insert is larger than the lower inner diameter (D2) located in the upper portion of the shifting portion and the degree of reduction of the inner diameter is constant while going from top to bottom Continuous casting immersion nozzle The method according to any one of claims 1 to 3, wherein The insert comprises a portion having an internal diameter equal to the upper internal diameter of the pipe portion, and The pipe part has a length of the continuous casting immersion nozzle, characterized in that it comprises an insert portion having the same inner diameter as the upper inner diameter of the pipe portion delete delete

Images