JPS63188454A - Method for pouring in metal foil continuous casting apparatus - Google Patents

Abstract

PURPOSE:To prevent variation of thickness of metal foil and development of crack by using a pouring nozzle having double structure and also setting so as to satisfying each the specific condition of thickness of a porous refractory and height position of an inner nozzle tip. CONSTITUTION:The pouring nozzle having double structure is constituted by the inner nozzle 1 and an outer nozzle 2 and molten steel is poured into molten basin part 7 formed by cooling drums 5a, 5b. Then, the inside width L of the outer nozzle 2 and the interval distance (h) between the tip of the inner nozzle 1 and the porous refractory 4 are set, so as to satisfy the inequality I. Further, the thickness (t) of the refractory 4 is decided, so as to satisfy the inequality II related to the inside width L and length W of the outer nozzle 2, cell size S of the refractory and flow rate Q of the molten metal. In this way, the solidified shell, which is uniform toward length direction of the cooling drums 5a, 5b, is developed. Therefore, the variation of thickness of the metal strip 8 and the development of crack are prevented.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a method in which, for example, in a twin drum method, a uniform flow is formed in a pool formed on the surface of a cooling drum in the longitudinal direction of the cooling drum. This invention relates to a method for pouring molten metal.

[Traditional techniques]

Recently, a method of directly producing a thin ribbon having a thickness close to the final shape from molten metal such as molten steel has been attracting attention. When using this continuous casting method, there is no need for a hot rolling process, and only a light rolling process is required to form the final shape, so that the process and equipment can be simplified.

One such continuous casting method is the twin drum method. In this method, a pair of cooling drums that rotate in opposite directions are arranged horizontally, and a pool is formed in a recess defined by the pair of cooling drums and, in some cases, a side weir.

The molten metal accommodated in the molten metal pool is cooled and solidified at the portion in contact with the cooling drum to become a solidified shell. As the cooling drums rotate, this solidified shell moves to a so-called roll gap area where a pair of cooling drums face each other at the closest position. At this roll gap part,
The solidified shells formed on the surfaces of each cooling drum are pressed together and integrated to form the desired metal ribbon.

In addition to this twin drum method, one cooling drum is used and a pool is formed on the circumference of the cooling drum.
Similarly, a single roll method for producing metal ribbon by rapid solidification is also known.

In this manner, when molten metal is rapidly cooled and solidified on the surface of the cooling drum to form a solidified shell, the molten metal supplied from a container such as a tundish tends to fluctuate along the longitudinal direction of the cooling drum. When the flow of the supplied molten metal is non-uniform, the thickness of the metal ribbon produced when the molten metal is cooled and solidified by the cooling drum will vary in the width direction. Furthermore, if the fluctuation is significant, fractures occur along the longitudinal direction of the obtained metal ribbon, making it unsuitable as a product.

Further, since the heat capacity of the molten metal in the tundish portion is not uniform along the longitudinal direction of the cooling drum, stress tends to be locally concentrated, which causes a defective shape in the obtained metal ribbon.

Therefore, the inventors of the present invention developed a double-structured pouring nozzle as shown in Fig.
The application was filed as No. This pouring nozzle has a dual structure of a hollow cylindrical inner nozzle 1 and an outer nozzle 2 surrounding it. Two openings 3 are provided on the circumferential surface near the tip of the inner nozzle 1 at symmetrical positions in the circumferential direction. other.

On the other hand, the outer nozzle 2 has a flat interior space that widens toward the bottom, and a porous refractory 4 is attached to the lower part of the interior space.

When such a pouring nozzle is used to send molten metal to the sump on the surface of the cooling drum, the molten metal flowing out from the inner nozzle 1 spreads along the longitudinal direction of the porous refractory 4, and then The porous refractory material 4 provides a rectifying effect. As a result, fluctuations in the flow of the molten metal flow passing through the porous refractory 4 along the longitudinal direction of the porous refractory 4 are suppressed.

[Problem that the invention seeks to solve]

However, even when the pouring nozzle shown in FIG. 4 is used, if the pouring conditions change, molten metal flows out from the porous refractory 4 as shown in FIGS. 5(a) and 5). The flow may not be uniform.

That is, in FIG. 3(a), the molten metal flow a flowing out from the opening 3 of the inner nozzle l spreads laterally in the inner space of the outer nozzle 2, and moreover, the molten metal flow a flows out from the opening 3 of the inner nozzle l, and the melt accumulated on the porous refractory 4 This shows a case where the amount of metal oxide is small or the position of the tip of the inner nozzle 1 is too high relative to the porous refractory 4. In such a case, the kinetic energy of the molten metal flow a is applied to a part of the porous refractory 4, and the porous refractory 4 is heated at that part.
The amount of molten metal passing through increases. Therefore, the molten metal flow C that has passed through the porous refractory 4 fluctuates as shown in the figure.

On the other hand, the same figure (b) shows the tip of the inner nozzle 1 and the porous refractory material 4.
This shows a case in which the distance from At this time, the kinetic energy of the molten metal flow a flowing out from the opening 3 of the inner nozzle 1 does not spread over the entire length of the porous refractory 4, but instead reaches the central portion of the porous refractory 4 centered on the inner nozzle 1. Limited. Therefore, the molten metal flow C passing through the porous refractory 4 has a larger flow rate in the center.

Therefore, when pouring molten metal using this dual structure pouring nozzle, the present invention makes the molten metal flow flowing out of the porous refractory into a more uniform flow. The objective is to make the flow rate of molten metal uniform in the longitudinal direction of the cooling drum and to form a molten metal boule necessary for producing defect-free metal ribbon.

[Means for solving problems]

In order to achieve the object, the pouring method of the present invention has an internal structure in which openings are formed at opposite positions of the curved surface near the tip of the pipe part along the longitudinal direction of the cooling drum of the continuous metal ribbon casting apparatus. The cooling drum is heated using a double structure pouring nozzle consisting of a nozzle and an outer nozzle, which has a bottom surface along the longitudinal direction of the cooling drum and a vertical cross-sectional shape that widens toward the end, and a porous refractory is attached to the bottom. When pouring molten metal into the pool formed on the surface of (Cm), maintain 1/12L<h<115L, and set the thickness t (cm) of the porous refractory to the inner width L (cm) and length W of the outlet of the outer nozzle. (cm), the cell size S of the porous refractory and the flow rate Q of the molten metal (c
d/sec) is maintained at t>α·L×W×S/Q (where α is a coefficient of 1 to 3 determined depending on the casting temperature and the type of molten metal). Here, the cell size S is the number of cells of the porous refractory within a length of 24.5 au++.

[Effect]

FIG. 1 is a diagram conceptually showing the state when pouring hot water while maintaining the conditions specified in the present invention.

The tip of the inner nozzle 1 is maintained at a height h (cm) from the surface of the porous refractory 4. This height h is
1/with respect to the inner width L (, cm) of the outlet of the outer nozzle 2.
The relationship is 12L<h<115L. This value of h is a value determined empirically by the inventor from the results of measurements using a water model device and molten steel. As shown in Fig. 5(a), when the height of the tip of the inner nozzle 1 is greater than 115 L with respect to the upper surface of the porous refractory, the discharge flow distribution C has a bias in which the flow rate is large from both ends of the nozzle. . In addition, when the height of the inner nozzle is smaller than 1/12L,
), the discharge flow distribution C is biased toward the center in the nozzle width direction, so in order to make the discharge flow distribution C uniform, l/12L is required.
< h < 115L was found to be appropriate.

Further, the thickness t (cm) of the porous refractory 4 is maintained in the following relationship.

t>α-LXWXS/Q However, W is the inner length of the outer nozzle 2 (cm), S is the cell size of the porous refractory 4 (inch-'), Q is the flow rate of the molten metal (cat/sec), α is a coefficient of 1 to 3 determined depending on the casting temperature and the temperature and type of molten metal.

The above relational expression was determined from the results of an experiment on the outflow characteristics of a porous refractory using molten metal, a water model, and the results of the outflow characteristics of a nozzle using molten steel.

That is, even if the height h of the inner nozzle is specified, a uniform discharge flow distribution C may not be obtained unless the thickness of the porous refractory 4 is equal to or greater than the value determined by the relational expression.

To explain this based on the experimental results of the water model, the inner nozzle 1
This is believed to be because a uniform discharge flow cannot be obtained unless the opening 3 is immersed in the pool of molten steel that accumulates on the upper surface of the porous refractory 4. Furthermore, since the passage resistance of the porous refractory 4 varies depending on the temperature and type of molten metal, the value of α changes from 1 to 3.

FIG. 2 is a graph specifically expressing the relationship t>α·L×W×S/Q. The shaded area in this figure indicates the range in which the flow rate distribution of the molten metal flow C along the width direction is suppressed to within ±7%.

In this way, when determining the height of the inner nozzle 1, the size of the outer nozzle 2, etc., the molten metal flow a flowing out from the inner nozzle 1 is
The kinetic energy is uniformly transmitted to the front surface of the porous refractory 4 without being concentrated in one part. Therefore, the molten metal accumulated on the porous refractory 4 passes through the porous refractory 4 with uniform pressure, and the flow change in the width direction of the molten metal flow C is reduced.

〔Example〕

FIG. 3 shows the pouring nozzle shown in FIG. 1 installed in a continuous metal ribbon casting apparatus.

This continuous casting apparatus includes a pair of cooling drums 5a and 5b. Side weirs 6a are arranged on the surfaces of these cooling drums 5a, 5b and on the sides of the cooling drums 5a, 5b.

A hot water reservoir 7 is defined by the water reservoir 6b.

The pouring nozzle shown in FIG. 1 is arranged along the longitudinal direction of this pool l1lS7. As a result, the molten metal flow C that has passed through the porous refractory 4 is poured with a uniform flow distribution over the entire length of the sump 7.

The molten metal pool thus generated in the molten metal pool 7 has a portion that contacts the cooling drums 5a, 5b.
It cools and solidifies by removing heat through the surface of 5b, and becomes a solidified shell. This solidified shell is formed on cooling drums 5a, 5b.
It moves while growing as the rotation of the

The solidified shells generated on the surfaces of the respective cooling drums 5a and 5b are pressed together and integrated at the roll gap portion where the gap between the cooling drums 5a and 5b is the narrowest, and is discharged as a metal ribbon 8. Ru.

In the process of producing the metal ribbon 8 from this molten metal, the amount of molten metal supplied to the sump 7 is changed to the cooling drum 5a,
Since the molten metal is uniform along the longitudinal direction of the molten metal, there will be no local oversupply or undersupply of molten metal. Therefore, the solidified shell is generated and grown uniformly in the longitudinal direction of the cooling drums 5a, 5b. Therefore, the variation in thickness of the metal ribbon 8 in the width direction is also small.

Here, h = 3cm, L = 75cm, W = 5cm
, t = 5'cm and 5 = 13, temperature 152
The flow rate of molten steel (α=1.2) at 0℃ is Q-1000.
Pouring at a rate of ctl/sec to a thickness of 2.5fflI11
A thin metal ribbon 8 was cast. The thickness variation along the width direction of the obtained metal ribbon 8 was ±2%.

In the pouring nozzle shown in FIG. 1, the opening 3 provided on the circumferential surface of the inner nozzle l is circular, but without being restricted by this, for example, a slit along the longitudinal direction of the inner nozzle 1 can be formed. The opening 3 can also be formed as a. In this case, the molten metal flow a flowing out from the inner nozzle l is
It is more effective because it spreads more easily into the inner space of the outer nozzle 2.

〔Effect of the invention〕

As explained above, when using the pouring method of the present invention,
Molten metal can be delivered to the sump in a uniform flow along the length of the cooling drum. Therefore, the contact state between the molten metal pool and the surface of the cooling drum becomes uniform along the longitudinal direction of the cooling drum, a solidified shell that is uniform in the longitudinal direction is generated and grows, and a metal ribbon with little thickness variation in the width direction is obtained. It will be done. Further, since there is no local oversupply or shortage of molten metal, the occurrence of vertical cracks in the metal ribbon can be reliably suppressed. In this way, according to the invention, it is possible to produce metal ribbons of excellent quality.

[Brief explanation of the drawing]

Figure 1 shows the flow state of molten metal when pouring according to the present invention, and Figure 2 shows the relationship between the thickness of the porous refractory and the size of the outer nozzle, etc., which has little variation in flow rate distribution. This is a graph, and FIG. 3 shows a state in which a metal ribbon is continuously cast. Further, FIG. 4 shows a double-structured pouring nozzle that the present inventors previously applied for, and FIG. 5 is a diagram illustrating the occurrence of a molten metal flow with large fluctuations in flow rate distribution. Patent Applicant Nippon Steel Corporation Representative Masu Kobori (and 2 others) Figure 5 (a) (b) Figure 1 C Figure 2 XWXS Figure 3 Lightning Figure 4

Claims (1)

[Scope of Claims] 1. An inner nozzle having openings formed at opposing positions on the circumferential surface near the tip of the tube along the longitudinal direction of the cooling drum of the continuous metal ribbon casting apparatus; It is formed on the surface of the cooling drum using a double-structured pouring nozzle consisting of an outer nozzle with a longitudinal cross-sectional shape and a vertical cross-sectional shape that widens toward the end, and a porous refractory is attached to the bottom. When pouring molten metal into the pool, the distance h (cm) from the center of the tip of the inner nozzle to the upper surface of the porous refractory is the inner width L of the outlet of the outer nozzle.
(cm), 1/12L<h<1/5L
and maintain the thickness t (cm) of the porous refractory to the inner width L (cm) and length W (cm) of the discharge port of the outer nozzle, the cell size S of the porous refractory, and the molten metal. The flow rate Q(
cm^2/sec), t>α・L×W×S/
A pouring method in a continuous metal ribbon casting apparatus, characterized in that the pouring method is maintained at Q (where α is a coefficient of 1 to 3 determined depending on the casting temperature and the type of molten metal).