JPH0455041A - Multi-nozzle for producing rapidly cooled thin strip - Google Patents

Abstract

PURPOSE:To decrease the transverse deviation of the thickness of a metallic thin strip by determining the number of the nozzle holes according to the nozzle hole diameter of the multi-nozzle for continuously supplying a molten metal at the time of producing the metallic thin strip by continuously supplying the molten metal and rapidly solidifying the molten metal. CONSTITUTION:If the multi-nozzle is eroded and the hole diameter of a part of the nozzles begins to expand, the nozzle hole of the nozzle of the part corresponding thereto is closed. Further, the height of a molten steel head on this nozzle hole decreases and the surface tension of the molten steel in the outlet of the nozzle hole exceeds the static pressure of the molten steel to close the nozzle hole when the flow rate of the molten metal from the nozzle hole expanded by the erosion increases. Such an initial diameter of the nozzle hole and number of holes as to maintain the head height at which the static pressure of the molten steel exceeding the surface tension is obtd. in the outlet of the nozzle holes are provided. The uniform and stable pouring in the transverse direction is executed in this way and the deviation of the thickness in the transverse direction is decreased.

Description

[Detailed Description of the Invention] <Industrial Field of Application> The present invention is directed to an elephant cooling Fill'! The present invention relates to a porous nozzle for pouring molten metal between twin rolls in an F manufacturing apparatus, and particularly to a porous nozzle that causes fewer troubles due to erosion of the nozzle hole by the molten metal.

<Prior art> In a twin-roll quenched ribbon manufacturing device, in order to uniformly pour molten metal in the width direction of the rolls, a method has traditionally been adopted in which molten metal is poured between the twin rolls from a wide porous nozzle ( (See Fig. 3) Wide slit nozzles have also been proposed, but they tend to deform due to heat and are difficult to manufacture.
Multi-hole nozzles are advantageous.

Thickness deviations occur in the cast ribbon due to the pouring amount distribution in the width direction of the roll. A technique has been proposed to reduce plate thickness deviation by adjusting the . However, a large amount of hot water (
IL/charge or higher), f' of the refractory nozzle
8 tM causes variations in the nozzle diameter and the pouring flow rate becomes non-uniform. Furthermore, there is a problem in that nozzle holes whose flow rate is reduced compared to other nozzle holes are clogged, which increases the non-uniformity of the pouring flow rate.

<Problems to be Solved by the Invention> The present invention aims at increasing the flow rate of molten metal from the nozzle hole with large melting loss in a multi-hole nozzle when casting a large quantity of quenched ribbon, and reducing the flow rate of molten metal from the nozzle hole with small melting loss. This was done in order to provide a multi-hole nozzle for producing cold ribbon to solve the problem of reduced flow rate, nozzle clogging, plate thickness deviation or sudden holes in the cold ribbon. be.

<Means for Solving the Problems> The present invention consists of: (i) continuous supply of molten metal to a casting space formed by a pair of cooling rolls and an end face pressing member disposed in contact with the end faces of the rolls; A porous nozzle for producing quenched ribbon, characterized in that the number of nozzle holes is determined according to the nozzle hole diameter of the porous nozzle, in which the molten metal is continuously supplied when manufacturing a metal ribbon. and ■ In the multi-hole nozzle described in the previous section ■, nozzle erosion rate: U (m/s), nozzle flow coefficient: C, and number of nozzle holes:
N (pieces), nozzle hole diameter: D (m), pouring time: T
(s), pouring speed: Q (kg/s), N (D
+ 2 UT)"" 〈4Q/πC(8ρσ)-1/! −・・−−−
-fil This is a multi-hole nozzle for producing a 2-cold ribbon, characterized in that the nozzle diameter and the number N of nozzle holes are determined to satisfy the fl1 formula above.

However, ρ: Molten steel density (kg/bo), σ: Molten steel surface tension (N/m).

<Function> It has been confirmed through experiments that when the multi-hole nozzles are eroded and the pore diameter of some nozzles begins to expand, the nozzle holes of other nozzles become clogged in response.

On the other hand, deeper observation shows that when the flow rate of molten metal increases from the nozzle hole enlarged due to melting damage, the height of the molten steel head above the nozzle hole decreases, and the surface tension of the molten steel at the nozzle hole exit decreases. It was discovered that the pressure exceeds the limit and the nozzle hole becomes clogged.

Therefore, in order to prevent the nozzle hole from clogging, even if the nozzle hole melts during the pouring time, the initial height of the head can be maintained so that the static pressure of molten steel that exceeds the surface tension at the nozzle hole exit can be maintained. It is essential to provide the nozzle hole diameter and number of holes.

Here, the erosion rate of the nozzle hole is U (m/S), the initial nozzle hole diameter is D' (m), the number of nozzle holes is N (pieces), the pouring speed is Q (kg/s), and the molten steel flow rate is V (m/S), the molten steel density is ρ (kg/m3), and the pouring time is T (s), then ρ・N・(D+2UT)”・−・V−Q (constant)(
1).

Also, from Bernoulli's theorem, if the flow coefficient is C, V = CJT ``---・(2).

Here, H is the height of the molten steel head above the nozzle hole (m), and g is the gravitational acceleration (m/s'').

On the other hand, since it is necessary for the static pressure of the molten steel to exceed the surface tension of the molten steel at the exit of the nozzle hole in order to prevent blockage, the following inequality holds true.

Here, σ is the surface tension of molten steel (N/m), (1), (2
), From equation (3), the following equation holds true, assuming that the total pouring time is Tt(s).

N (D+2UT! )”' π C Nozzle diameter and number of nozzle holes N that satisfy this fl1 formula
By using a multi-hole nozzle, stable and uniform pouring can be performed and the nozzle holes can be prevented from clogging.

<Example> In order to confirm the effect of the porous nozzle according to the present invention, a quenched ribbon was produced using a porous nozzle made of fused silica under the following conditions.

Pouring speed: 4kg/s, Pouring time: 10 minutes, Note: Hot water material: 5US304, Note: Hot water width: 400a.

As a result of the experiment, the erosion rate was 0.25 m/min, and the experimental results are shown in Figure 1. Here, the exit porosity refers to the nozzle hole that exited without being blocked during 10 minutes of pouring. It is the ratio of the number of holes to the initial number of holes.

As is clear from the figure, it has become clear that clogging of the nozzle holes can be reduced by setting the nozzle hole diameter and number of nozzle holes such that the relational expression according to the present invention is satisfied.

Fig. 2 shows the thickness deviation of a quenched ribbon with an average thickness of 5001 mm, which was cast using twin rolls with a roll diameter of 550 mφ and a peripheral speed of 2.1 m/s, after pouring with multi-hole nozzles with different nozzle hole diameters and numbers of holes. 6mφ that satisfies the relational expression according to the present invention shown in FIG.
- It was revealed that plate thickness deviation was reduced by using a multi-hole nozzle with 16 holes.

<Effects of the Invention> Uniform pouring in the width direction can be stably performed by the multi-hole nozzle for producing a quenched ribbon according to the present invention, which has an initial nozzle hole diameter and number of holes that can maintain the head height of the molten metal in the nozzle. As a result, the deviation of the plate thickness in the plate width direction is reduced.

[Brief explanation of drawings]

Figure 1 is a characteristic diagram showing the relationship between porous nozzle shape and tapping porosity, Figure 2 is a characteristic diagram showing the relationship between porous nozzle shape and sheet thickness deviation, and Figure 3 is a characteristic diagram showing the relationship between porous nozzle shape and plate thickness deviation. FIG. 3 is a perspective view showing the casting situation. 1... Porous nozzle, 2... Molten steel pool on the nozzle, 3... Nozzle hole, 4... Molten pouring flow, 5...
- Nozzle clogging, 6...Cooling roll, 7...Quiet-quenched ribbon, 8...End face pressing member.

Claims (1)

[Claims] 1. Manufacturing a metal ribbon by continuously supplying molten metal to a casting space formed by a pair of cooling rolls and an end face pressing member disposed in contact with the end faces of the rolls and rapidly solidifying the metal. 1. A porous nozzle for producing quenched ribbon, characterized in that the number of nozzle holes is determined according to the nozzle diameter of the porous nozzle, in a porous nozzle for continuously supplying molten metal. 2. In the multi-hole nozzle according to claim 1, nozzle erosion rate: U (m/s), nozzle flow coefficient: C, number of nozzle holes: N (pieces), nozzle hole diameter: D (m), pouring time: T(s
), pouring speed: Q (kg/s), N(D+2UT)^3^/^2 <4Q/πC(8ρσ)^-^1^/^2...
(I) A multi-hole nozzle for producing a quenched ribbon, characterized in that the nozzle diameter D and the number N of nozzle holes are determined to satisfy the above formula (I). However, ρ: Molten steel density (kg/m^3), σ: Molten steel surface tension (N/m).