JPS59182903A - Method for adding powder and granule to molten metal - Google Patents

Abstract

PURPOSE:To add powder and granules to a molten metal in a tundish nozzle without interfering with the operating surface in the stage of adding the powder and granules from the hollow part of a stopper to the molten metal by providing an extension part having a specified length to the top end of the stopper. CONSTITUTION:Steel particles 8 are added via a hollow part 5 of a stopper 11 into a molten steel 2 in the stage of supplying the molten steel 2 via a nozzle 4 from a tundish 3 into a casting mold 9. The inside diameter in the hollow part 5 of the stopper 11 is set at about 10mm. and an extension part 6 is provided to the top end thereof. The top end of the part 6 is set at the position in the depth exceeding 0.7lR(lR is the length in the curved part at the top end of the nozzle 4) downward from the top end of the nozzle 4. The outside diameter in the part 6 is so selected that the steel 2 flows at a required speed between the curved part of the nozzle 4 and the part 6.

Description

[Detailed description of the invention] The present invention relates to a method for adding powder to molten metal.

It is well known that adding a coolant externally during the solidification process of molten steel promotes equiaxed crystallization, which improves the internal quality of steel ingots and slabs. It is effective to use wood.

Therefore, when cooling and solidifying molten steel using the continuous casting method, a granular coolant is used and added to the molten steel. It is clear that the most stable and reliable method is to drop the granular coolant into the center and wind it up.

One such method is JP-A No. 54-94437, in which a hollow hole 5 is provided in the stopper 1 directly above the tundish nozzle 4, as shown in FIG. At the same time, by the suction action of the molten steel flow at the upper end of the nozzle 4, the steel grains 8 are completely included and mixed in the molten steel flow.

However, in order to create a suction effect by the molten steel flow with this method, the tip of the stopper 1 and the tundish nozzle 4 must be
It is necessary to make the distance from the upper end, that is, the stopper opening, very narrow, but at that stopper opening, the amount of molten steel 2 flowing out is small. Therefore, if it is necessary to flow out the molten steel 2 in excess of this flow rate, the stopper opening degree is increased so that no suction action is produced and the steel grains 8 are not ejected.

Additionally, JP-A No. 53-130234 basically has a stopper hollow hole 5 similar to the above-mentioned JP-A No. 54-94437.
The steel grains 8 are added to the molten steel 2, but the steel grains 8
The purpose is to compensate for the lack of suction effect caused by the molten steel flow by pneumatically transporting the molten steel with a carrier gas such as Ar. A considerable amount of gas is required to make up for this deficiency, and this gas gets caught up in the molten steel flow and forms bubbles, which not only impairs the internal quality of the slab, but also induces surface vibration in the mold, causing operational problems. There is a risk of causing

The present invention has been made in order to solve the problems of the prior art.It is an object of the present invention to provide a method for adding powder and granules that does not deteriorate the internal quality of the cast slab or cause any problems in terms of operation. With the goal.

The method of adding powder and granules into molten metal according to the present invention is a method of adding powder and granules into molten metal through a hollow part provided in a stopper located above a tundish nozzle. The stopper is characterized by the use of a stopper having one tip extended so that it can be set at a depth exceeding 0.71RC (where lR is the length of the curved surface portion of the upper end of the nozzle).

The present invention will be specifically explained below. In Fig. 1(a), the length f consists of a straight part of length 18 whose inner diameter is constant and a long curved part whose inner diameter is expanded upward.
(=-/8-1/R) When the molten steel 2 flows out into the steel bath from the tundish nozzle 4, the flow velocity V of the molten steel in the straight section can be calculated using the following formula il1.

However, g: Gravitational acceleration ζ: Loss coefficient λ: Friction coefficient d Nozzle inner diameter of Nistrade part H: Steel bath depth in the tundish I! D: Immersion depth of the nozzle tip in the steel bath inside the mold (not shown) Next, the pressure P2 at a height of 2 from the mold surface (atmospheric pressure) is calculated from the following equation (2) based on Berthail's theorem. .

However, γ: Specific weight of molten steel Pot V(++ (L): Pressure at the molten metal surface, flow velocity, and nozzle inner diameter PZI VZ: Pressure and flow velocity at height 2 Note that the molten steel flow velocity v2 is constant regardless of the height Z in the straight part However, since the inner diameter is different in the curved part, it changes according to the following equation (3).The cross section of the curved part is assumed to be 1/4 circle.

V2* 1/4id" = K - f31 However, K: constant Substitute the following numerical value into the above formula (3).

That is, H=600mm, 1=1000st+++
1 = 100m, ! ,=70m+! =9
30m, d=60Wmγ=7.2g/country 3.
ζ=0.01λ=0.02, g=
The results of calculating the nozzle internal pressure distribution by substituting 980 am/sec 1 are shown in FIG. 1(b). As seen in this figure, in the straight part, the pressure decreases upward from the lower end of the nozzle 4, and when it enters the curved part, the pressure decreases from the lower end of the nozzle 4.
The pressure is lowest at about 0 coefficient, and rises rapidly as it goes above that level. In order for the steel grains 8 added to the stopper hollow part 5 to be drawn into the molten steel by the suction effect of the molten steel flow, that is, by the pressure difference, the stopper hollow part 5 is at atmospheric pressure, so the pressure at the tip of the stopper 1 is set to atmospheric pressure. need to be lower.

According to calculations, the position where the internal pressure of the nozzle 4 becomes equal to the atmospheric pressure is a point 0.7 degrees from the top of the nozzle, and this is almost the same regardless of the length of the nozzle, the shape of the curved surface, and the immersion depth of the nozzle tip in the steel bath. is uniquely determined by equation (3). Therefore, if the tip opening of the stopper 1 is located at a position deeper than 0.7 fR from the upper end of the nozzle, the steel grains 8 will be sucked into the molten steel flow in the nozzle 4 and become involved. Increasing the pressure in the hollow part 5 of the stopper 1 using a gas such as Ar increases the pressure difference between this pressure and the pressure at the opening at the tip of the stopper 1, and is therefore effective in increasing the amount of steel grains added. Conceivable. The above-mentioned Japanese Patent Application Publication No. 53-1302
No. 34 is based on this idea.

Now, when the flow rate of molten steel in the nozzle 4 is Q and the flow rate of molten steel in the nozzle 4 is V, the pressure P in the nozzle 4 is expressed by the following equation (4).

γ P-1・QIIv (4) However, from the viewpoint of internal quality of slab and operation, the amount of gas that can be blown into the tundish nozzle varies depending on the operating conditions, but is generally 100
It is around 1 minute. When this flows into a hollow part of 110ff1φ, the pressure P (relative pressure) is 0.006 kg/am
It is about 2. Even if there is this pressure increase, the position of the end opening of the stopper that can be raised is the first.
As can be seen from the figure (Figure 1), there are only a few bubbles, which form bubbles in the steel as described above, impairing the internal quality of the slab, and can be said to be a drawback of JP-A-53-130234. In other words, even when blowing a gas such as Ar, it is necessary to set the end opening position of the stopper to a position deeper than 0.7 fR.

Accordingly, in the present invention, the granular material is added using a stopper that can realize this. FIG. 2 is a schematic diagram showing the implementation state of the method of the present invention, and FIG. 3 is an enlarged view of the vicinity of the stopper tip. In the figure, numeral 3 denotes a tundish for continuous casting, and molten steel 2 supplied from a ladle (not shown) is stored inside the tundish. The flow rate of the molten steel 2 is adjusted by a stopper 11, and the molten steel 2 is charged into a mold 9 through a nozzle 4. The stopper 11 is the first
Unlike the conventional one shown in Figure (a), this tip has a thin extension 6 with a length of about 150 mm, and the inner diameter of the hollow part 5 through which the steel rod β is to flow is 10 mm. Exit 6
The outer diameter of the nozzle 4 is selected to be such that there is no problem in inserting the nozzle 4 into the nozzle 4, and the molten steel can flow between the curved surface of the nozzle 4 and the extension 6 at the required speed. Its shape may also be determined in accordance with the shape of the curved surface portion of the nozzle 4.

The extending portion 6 may be integrated with the stopper 11, or may be a split type that is screwed onto the stopper 11. Further, the stopper 11 is supported by a support device (not shown) via the steel grain supply pipe 7, and is connected to a steel grain storage tank (not shown) that stores the steel grains 8.
Steel grains 8 are sent from the steel grain supply pipe 7 to the stopper 1.

The nozzle 4 is a heavy-duty piece with a total length of 1000 mm with l = 76 mm and 18 = 924 nm, and its lower part is immersed in the molten steel 2 in the mold 9 for 100 hours.

0.7 below the upper end of nozzle 4 under the operating conditions described above.
The stopper opening degree is limited so that the lower end of the extension part 6 at the bottom of the stopper 1 is located at a depth exceeding 1R (=53M). Thereby, the object of the present invention can be achieved.

Next, examples of the method of the present invention will be described. First, by the above-described method of the present invention, a distance of 100 mm (>0.
It was confirmed that when the lower end of the extension part 6 was located at a depth of 71R), the steel grains 8 decreased by a predetermined amount over time and were normally added to the molten steel.

Therefore, if the stopper 1 is slightly raised and the lower end of the extension part 6 is positioned at a depth of about 53 tyt' (-71R) below the upper end of the nozzle 4, the steel grains 8 will no longer decrease and the supply will stop. . Then, leaving the stopper 1 in the same position, the extension part 6 was observed after the casting was completed.
It was discovered that the tip was blocked by metal. This confirmed the significance of the present invention.

The length of the extending portion 6 is such that its tip is 0.00 m from the upper end of the nozzle 4.
．． The shortest length is determined by the need to locate at a depth exceeding 71R, but on the other hand, the shortest length is determined from the viewpoint of both durability and strength.
It is preferable to make it 00 fights or less. In the above explanation, continuous casting of steel was taken as an example, but the present invention can also be applied to continuous casting of other metals or casting by an ingot method, and copper powder is still used as the powder. Of course, in addition to the coolant such as grains or iron powder, ferroalloy or a deoxidizing agent may also be used. Furthermore, the method of the present invention does not preclude the use of gas blowing such as Ar.

As explained above, when using the method of the present invention, the powder or granules are forcibly drawn into the molten metal flow due to the pressure difference between atmospheric pressure and the internal pressure of the nozzle 4, thereby stably and reliably adding the powder or granules into the molten metal. It is possible to obtain high-quality slabs. In addition, since the molten metal flows between the narrow extension 6 of the stopper 11 and the curved surface of the nozzle 4, the present invention does not require a long time to introduce the molten metal into the mold, which does not affect the operation. has excellent effects.

[Brief explanation of the drawing]

Fig. 1(a) is a schematic diagram showing the implementation state of the conventional method, Fig. 1(b) is a diagram of the pressure inside the nozzle, Fig. 2 is a schematic diagram showing the implementation state of the present invention, and Fig. 3 is the part thereof. This is an enlarged view. 1.11... Stopper 2... Molten steel 3... Tundish 4... Nozzle 5... Hollow part 6...
Extended portion 8...Steel grain patent applicant Noboru Kono, patent attorney representing Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] 1. In the method of adding powder to molten metal through a hollow part provided in a stopper located above a tundish nozzle, the tip thereof is 0.71R below the upper end of the nozzle (where 1R is the length of the curved part of the upper end of the nozzle). A method for adding powder to molten metal, characterized by using a stopper with an extended tip so that the stopper can be set at a depth exceeding .