JPH079096A - Method for pouring molten metal at the end stage of ladle - Google Patents

Abstract

PURPOSE:To reduce the mixed quantity of ladle slag into a tundish as little as possible and to reduce the remained molten steel. CONSTITUTION:In the molten steel pouring method at the end stage of the ladle, relation between the remained molten steel quantity in the ladle and the pouring quantity in an eddy developing limit is obtd. beforehand, and the remained molten steel quantity from a load cell 9 in the ladle 1 is grasped, and also, the pouring quantity at this time from the variation of the load cell per unit time is grasped, and the molten steel is poured into the tundish 5 at the pouring flow rate in the range which does not develop the eddy. Further, by using the tundish enabling receive of the molten steel at the same time from plural ladies, the operation can be executed without dropping the casting speed. As the flowing-out slag into the tundish can be almost zero, the quantity of a cast slag is remarkably improved, and as the remained molten steel at the last stage can be almost zero, the yield of the molten steel is remarkably improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pouring method at the final stage of ladle injection, and more particularly to a pouring method capable of reducing slag flowing from a ladle to a tundish and minimizing the amount of residual hot water. .

[0002]

2. Description of the Related Art As is well known, when continuously casting slag, for example, molten steel is first poured from a ladle into a tundish and then supplied from a tundish to a mold, but the slag inside the ladle flows into the tundish. If this is cast as it is, slag may be mixed as inclusions in the obtained slab, and the quality of the slab may be significantly impaired. However, as a technique for preventing the mixing of slag, JP-A-61-119358 and JP-A-2-4174 are disclosed.
No. 4 publication is proposed.

The former uses a tundish having a structure in which the tundish is divided into two parts in the width direction and the function is divided into a hot water receiving room and a hot water discharging room. This is a casting method in which ladles are placed at both ends of the hot water receiving chamber and molten steel is poured alternately, but as a countermeasure for the slag outflow at the end of injection of the previous ladle, it is a method of inserting a slag stopper, which leads to an increase in cost and , It is difficult to surely engage the slag stopper with the ladle upper nozzle, and the slag outflow cannot be completely stopped.

In the latter case, in order to prevent slag from being mixed into the tundish, the molten metal is left in the ladle before the molten steel vortex is generated, the pouring is stopped, and the residual steel and slag in the ladle are refined while still hot. This is a method of reloading into the furnace (converter), but usually the existing steelworks do not have a logistics structure that allows the residual steel to be reloaded into the refining furnace while it is still hot. In order to do so, a large amount of equipment remodeling cost is required. Also, the yield of molten steel per charge is low.

[0005]

DISCLOSURE OF THE INVENTION It is an object of the present invention to provide an inexpensive pouring method capable of reliably preventing the mixing of slabs when pouring from a ladle into a tundish and dramatically improving the molten steel yield. And

[0006]

The present invention has been made in order to advantageously solve the above-mentioned object, and its gist is to: (1) The relationship between the ladle residual hot water amount and the vortex generation limit injection amount. It is characterized in that the amount of remaining hot water is grasped from the load cell of the ladle, the amount of pouring at that time is grasped from the change of the load cell value per unit time, and the tundish is poured at the pouring flow rate in the region where no vortex is generated. The pouring method at the end of ladle injection. (2) The method according to (1) above, wherein a tundish that can simultaneously receive hot water from a plurality of ladles is used.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained based on the embodiment apparatus shown in FIG. 1a is a front ladle and supplies molten steel 2a to a tundish 5 via a long nozzle 3 and an SN plate 4 provided on the long nozzle 3. An immersion nozzle 6 is provided in the tundish 5 to inject the molten steel 2a into the mold 7. Reference numeral 8 indicates a slab.

A load cell 9 detects the amount of remaining hot water in the ladle 1a. Numeral 10 is a molten steel reduction amount calculator per unit time from the signal of the load cell 9 to grasp the molten steel injection amount from the long nozzle 3. Reference numeral 11 denotes a computer, and the computer stores in advance the relationship between the residual ladle amount and the vortex generation limit injection amount shown in FIG.

However, the current residual hot water amount from the load cell 9 and the molten steel injection amount data from the molten steel reduction amount calculator 10 are input to the computer 11 one by one, and the computer 11 calculates the vortex generation limit injection amount from the residual molten steel amount. Is calculated (FIG. 1) and compared with the current injection amount, and an SN plate opening / closing signal is output so that the injection amount becomes high in the operating region. The open / close signal is converted through the signal converter 12, and the SN of 13 is converted.
The opening of the SN plate 4 is changed by being input to the hydraulic unit. This control is repeatedly executed to control the injection amount according to the molten steel residual molten metal amount.

FIG. 2 shows a state in which two ladles are arranged in the tundish 5, but in the case of arranging only the ladle 1a, the molten steel pouring amount at the final stage of pouring the ladle 1a is shown in FIG. Set in the operating area of. At this time, the weight of molten steel in the tundish 5 decreases and the level of the molten metal decreases. However, when it is desired to reduce the amount of decrease in the molten metal level, the change in the molten metal level can be reduced by setting the drawing speed of the slab 8 low.

On the other hand, the ladle 1a, 1 which is the embodiment of FIG.
When two ladle b of b are operated, the molten steel pouring amount of the front ladle 1a at the end of pouring is performed in the operating region of FIG. 1, and the pouring amount is reduced according to the residual hot water amount. At this time, the weight of the molten steel in the tundish 5 decreases, but by supplying this amount from the rear ladle 1b, the molten steel level in the tundish 5 does not decrease, and therefore, the slab drawing speed is not reduced and continuous It becomes possible to operate.

Although the load cell 9 to the SN hydraulic unit 13 are arranged only on the front ladle 1a side in FIG. 2, the same operation is also arranged on the rear ladle 1b side (see the figure). Omitted).

Next, a concrete operation example will be given. (Invention) In FIG. 2, a low carbon aluminum killed steel 250t is charged into the ladle 1a (without the ladle 1b) and the capacity is 6
Using 0 t of tundish 5, a slab 8 of 245 mm × 1400 mm was cast. Based on the relationship of FIG.
It is injected at a rate of 10 t / min until it reaches the limit, and the amount of remaining hot water is 7 after that.
The injection rate was 5 ton / min until ton, and then the injection rate was set to 2 ton / min. The operation status at this time is shown in FIG.

(Comparative Example) In FIG. 2, 250 tons of low carbon aluminum killed steel was charged into the ladle 1a (without the ladle 1b) and a tundish 5 having a capacity of 60 tons was used to prepare 245 mm × 1.
400 mm slab 8 was cast. The amount of molten steel remaining was measured by the load cell 9, and the amount of the molten steel was injected at the rate of 10 t / min until the end.
The operation status at this time is shown in FIG.

As a result of the above-described operation, the residual hot water amount and the quality results are shown in FIGS. 4 (a) and 4 (b). According to the present invention, the outflow amount of the slag 2b into the tundish at the final stage of ladle injection can be made almost zero, and the quality of the cast slab is greatly improved. Further, the amount of residual hot water can be reduced to almost 0, so that the molten steel yield can be greatly improved.

[0016]

As described above, according to the method of the present invention in which the pouring amount at the final stage of ladle pouring is made equal to or lower than the vortex generation limit pouring amount, the outflow slag can be made almost zero and the final molten steel residual hot water amount can be made almost zero. The molten steel yield can be improved. In addition, there is no need to use a slag stopper, and there is no need to improve the physical distribution structure within the factory, which is economically advantageous.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a relationship between a ladle remaining hot water amount and a vortex generation limit injection amount.

FIG. 2 is a device layout diagram showing an example of a device for carrying out the present invention.

FIG. 3 is an explanatory diagram showing an operation example and a comparative operation example according to the present invention.

FIG. 4 is an explanatory diagram showing operation results in an operation example of the present invention and a comparative example.

[Explanation of symbols]

1 Ladle 2a Molten Steel 2b Slag 3 Long Nozzle 4 Sliding Nozzle Plate 5 Tundish 6 Immersion Nozzle 7 Mold 8 Slab 9 Load Cell 10 Molten Steel Reduction Calculator 11 Computer 12 Signal Converter 13 SN Hydraulic Unit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hidemi Watanabe 5-3 Tokai-cho, Tokai-shi, Aichi Nippon Steel Co., Ltd. Inside the Nagoya Works

Claims (2)

[Claims] 1. A relationship between the ladle residual hot water amount and the vortex generation limit injection amount is obtained, and the residual hot water amount is grasped from the load cell of the ladle, and the pouring amount at that time is grasped from the change in the load cell value per unit time to generate the vortex. A pouring method at the final stage of ladle injection, which is characterized by pouring in a tundish at an injection flow rate in a non-filling region. 2. The method according to claim 1, wherein a tundish that can simultaneously receive hot water from a plurality of ladles is used.