JPH0270360A - Continuous casting method - Google Patents

Abstract

PURPOSE:To separately produce plural steel slabs having different compositions from molten steel in one heat ladle by interrupting pouring of molten steel into a tundish at the time of changing cast steel kind, inserting metal fitting for preventing the mixture in a mold, restarting the pouring of molten steel and changing the kind and quantity of additive. CONSTITUTION:The additive 11 is added into the molten steel 8 in the tundish 7 to continuously cast two or more kinds of the steel slab from the molten steel 2 in the one heat label 1. Then, at the time of changing the cast steel kind, the pouring of molten steel into the tundish 7 from the ladle 1 is interrupted. At this time, the inert gas bubbling is executed at the ladle nozzle 3 part and also the metal fitting 20 for preventing the mixture of the molten steel having different compositions into the mold 4 is inserted. Successively, the pouring of molten steel into the tundish 7 from the ladle 1 is restarted and the kind and quantity of the additive are changed. By this method, the plural number of the steel slabs having different compositions can be separately produced from the molten steel in the one heat ladle.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a continuous casting method for producing two or more types of steel slabs having different compositions from one heat of ladle molten steel.

[Conventional technology]

In the conventional continuous casting method, basically only slabs with the same composition as the bay steel in the ladle can be produced, so even if the ordered lofts are concentrated and it is less than 1 heat, at present it is possible to produce only 1 heat. We are producing more than the necessary amount. Therefore, the excess amount needed to be kept in stock until an order for the same steel type was received as a slab, and this inventory period could last from several months to several years, which was a major problem in the process.

Therefore, a method for continuously producing slabs of different steel types having different compositions from one heat of ladle molten steel has been desired. Therefore, as a means to solve this problem, a technique as disclosed in Japanese Patent Laid-Open No. 56-9049 has been proposed. That is, as an example of this technique, a method is disclosed in which the addition of alloying elements to the tundish and the splicing of slabs by the sequence block method are combined.

[Problem to be solved by the invention]

However, in the above technology, when continuously casting different components, the sequential block method, which is a joint operation, is carried out while continuously pouring the metal from the ladle into the tundish.

By the way, in the successive casting method of different steel types that aims to prevent the mixing of different types of molten steel as shown in Japanese Patent Application Laid-open No. 1945-1945, which is cited as an i-type sequence block method, from the viewpoint of workability, the tundish is placed at the casting position. They have no choice but to ascend or evacuate. Therefore, at this time, in order to continue pouring from the ladle into the tundish, it is necessary to raise or retreat the ladle by synchronizing the raising or retracting operation of the tandish. This requires major modification and renewal, which is not practical either from an equipment standpoint or an economic standpoint.

Therefore, in order to carry out the sequence block method, it is necessary to temporarily stop pouring metal from the ladle into the tundish, and to raise or retreat the tundish from the casting position.

In this case, the molten steel in the ladle nozzle solidifies, so even if the nozzle is opened, the molten steel does not come out. Therefore, the worker must clean the solidified material in the nozzle with oxygen, etc., which is not desirable from the standpoint of safety and quality. There is no way.

This invention was made in view of such conventional problems, and involves adding additives to the tundish while pouring the required amount of molten steel from the beginning, and stopping the pouring when the pouring is completed. The purpose of the present invention is to solve the above problems by performing gas bubbling at the ladle nozzle, inserting a metal fitting to prevent ingredient contamination in the mold, and then restarting the pouring process after canceling.

[Means to solve the problem]

This invention adds additives to tanditush molten steel, and
In the continuous casting method that produces two or more types of steel slabs with different compositions from molten steel in a heat ladle, the required amount of molten steel is poured from the ladle and additives are put into the tundish, and when changing the type of steel to be cast. , the pouring of metal from the ladle into the tundish was interrupted, and at this time, inert gas bubbling was carried out at the cancel nozzle part, and a contamination prevention fitting was inserted to prevent molten steel of different composition from entering the mold, and then This is a continuous casting method in which continuous casting is continued by restarting pouring from the ladle into the tundish and changing the type or amount of additive material added into the tundish.

[Effect]

Since the present invention has the above-described configuration, when the required amount of the first steel type is poured into the tundish, the pouring from the ladle to the tundish is interrupted by, for example, a sliding bubble, and the molten steel in the tundish is poured. When pouring into the mold, insert the anti-contamination fitting into the mold. Then, by opening the sliding pulp again and restarting pouring from the ladle to the tundish, changing the type or amount of additives and casting a different steel type, the first steel type and the later different copper type will be prevented from mixing. Continuously cast, separated by metal fittings. In addition, since inert gas huffing is performed at the ladle nozzle part during the interruption for changing the steel type, the molten steel is stirred and the nozzle part is not clogged. Similarly, in the tundish, the molten steel inside is heated and gas buffing is performed from the bottom. As a result, the nozzle does not become clogged even when the anti-contamination fitting is inserted, and continuous casting can be carried out smoothly.

〔Example〕

Hereinafter, the present invention will be explained based on the drawings. Figures 1 to 3
The figure shows an embodiment of the present invention.

FIG. 1 is a schematic diagram of the entire invention, in which molten steel 2 filled in a ladle I is poured into a tundish 7 via a ladle nozzle 16 and a sliding nozzle 3. At this time, the molten steel is poured into the heat insulating sealing material 4° injection tube 5. The molten metal is poured into the tundish 7 while being isolated from the outside air by the immersion pipe 6 or the like.

1) is an additive, which is added from the hopper 10 to the molten steel 8 in the tundish 7 from the charging chute 13 while adjusting its addition amount via the charging speed control device 9, and is different from the molten steel 2 in the ladle 1. The result is molten steel with a composition of Furthermore, when using two or more brands of additive 1), two or more types of addition means as described above may be installed.

The temperature of the molten steel 8 in the tundish 7 decreases due to the addition of additives 1), etc., so to prevent this, the molten steel pouring temperature is maintained constant by adjusting the heating with a heating device (for example, induction heating) not shown. . Furthermore, inert gas is injected and bubbled from below inside the tundish 7 at the lower part of the charging end of the charging chute 13 or downstream thereof so that the additive 1) is uniformly dispersed in the molten steel 8.

Next, when changing the amount or brand of additives within one heat, it is necessary to prevent molten steel with different components from mixing in the mold 14. As a method, first, the casting speed is reduced or zero, the injection from the tundish into the mold 14 is interrupted by closing the tundish nozzle 22 with the stopper 21, the tundish 7 is retracted from directly above the mold 14, and the mixing prevention fitting 20 is inserted into the mold. Insert into 14. Note that if the metal fitting 20 can be inserted simply by raising the tundish 7 from the steady casting position, it is of course not necessary to evacuate the tundish 7 from directly above the mold 14.

Further, when inserting the anti-contamination fitting 20, it is necessary to temporarily interrupt pouring the hot water from the ladle into the tundish 7 (for about a few minutes to 10 minutes in the embodiment). Generally, a sliding nozzle 3 is used to control the injection amount from the ladle 1 to the tundish 7, as shown in detail in Fig. 2. However, when the nozzle 3 is fully closed, the molten steel in the ladle nozzle 16 solidifies. , making re-injection difficult. Therefore, in this embodiment, argon and nitrogen are supplied from the lower plate 18 of the sliding nozzle 3.

A so-called bubbling process is performed in which an inert gas such as helium is blown into the ladle 2 to stir the molten steel 2 in the ladle 2, thereby making the temperature of the molten steel uniform and preventing solidification in the nozzle 16. In addition,
This bubbling process also helps to clean the solution m2. Note that similar bubbling may be performed even when using a low-flow nozzle. In FIG. 2, 17 is the upper plate;
It is designed to slide on the lower plate 18, and by the sliding of both plates, the ladle nozzle hole 16a and the lower plate nozzle hole taa are brought into alignment, thereby pouring the molten metal from the ladle 1 into the tundish 7. It will be done.

Next, an example will be described in which two types of steel slabs with different components were manufactured from one heat using the apparatus shown in FIG. 1. Figures 3 fl) to (5) show the flow of work at that time. At this time, the molten steel A in the drawer 5FJIl has a composition equivalent to 320C. (In this example, 520C: 40Ton is produced from 80Ton of molten steel in one heat.

This is an example in which 530C:40Ton was manufactured. The slab size is 200mm x 1000mm).

First, from ladle 1 to tandish 7 1.0 Ton/
and cast at a casting speed of 0.64 m/min. Therefore, the molten steel in the tundish 7 has a component A equivalent to 5200C, and is poured into the mold 14 to form a 520C slab A1.
is obtained ((1) in the same figure). After injecting a total of 40 tons from the ladle 1 into the tundish 7, the sliding nozzle 3 of the ladle is fully closed and Ar bubbling is performed within the nozzle ((2) in the same figure).

(The flow rate of Ar bubbling is preferably in the range of 50 to 300 It/min; if it falls below this, the molten steel in the nozzle will solidify. If it exceeds this, the molten steel will scatter from the top of the ladle, which is dangerous.) Next Then, the remaining molten steel in the kundish 7 is continuously poured into the mold 14. As shown in FIG. 31, when the weight of the molten steel in the kundish reaches I Ton, the stopper 21 is lowered to interrupt the injection from the kundish into the mold 14. Next, the tundish 7 was evacuated from directly above the mold, and the anti-contamination fitting Z was inserted into the mold ((4) in the same figure). (At this time, the drawing speed of the steel piece was 0 or 0.1 m/min).

In order to improve quality, the remaining steel and residue in the tundish were discharged into pot Y ((3) in the same figure). However, if the steel type has no quality problems, it is not necessary to carry out this work.

Next, after the above work is completed, the tundish 7 is returned to the casting position, and the pouring from the ladle into the tundish is started.
After the weight of the tundish reached a predetermined level, the stopper 21 shown in FIG. Figure (5)). Therefore, the molten steel in the tundish had a component B equivalent to 330C, and a slab B1 of 530C was obtained.

Here, the speed of adding the additive to the tundish may be determined by calculating from the speed of pouring the molten metal into the tundish from the time of cancellation. Therefore, in the case of steady state, it is sufficient to calculate from the throughput determined from the size of the slab and the casting speed.
In the case of an unsteady state, it is determined from the rate of change in the weight of molten steel in the tandice, the rate of change in the level of molten steel in the tundish, etc.

Further, in the case of manufacturing a slab having three or more types of components from one heat, the above operation may be performed two or more times.

FIG. 4 shows the results of the above example. That is, 40 tons of slabs with different components were obtained from 3Q tons of molten steel per heat. Furthermore, there was no contamination of foreign components, and a good product was obtained by simply discarding several fins on the front and back of the inserted contamination prevention fitting. Furthermore, by performing gas bubbling inside the cancellation nozzle, it was possible to reopen the nozzle without oxygen cleaning even if the nozzle was fully closed for a maximum of 15 minutes.

[Effects of the Invention] As explained above, according to the present invention, it is possible to separately produce two or more types of steel slabs with different compositions from one-heat ladle molten steel according to the demand, and it is possible to separately produce two or more types of steel slabs with different components as required. The situation of long-term inventory of the same type of steel waiting for orders has been eliminated, and inventory management can now be carried out rationally and economically.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the entire embodiment according to the present invention, and FIG.
The figures are an enlarged detailed view of the ladle nozzle in FIG. 1, FIG. 3 is a schematic diagram showing the process flow according to the example, and FIG. 4 is a diagram showing the implementation results of the example. 1... Ladle, 2,8... Molten steel, 3...
...Ladle nozzle, 7...Tandish,
1)...additive material, 14...mold, 20
・・・・・・Contamination prevention metal fittings. A...52OC equivalent molten steel, AI...5
20C slab, B...530C equivalent molten steel, B...
... 530C slab, Y ... discharged residual steel, Xl ... added carbon. Z... Contamination prevention fitting 20, Fig. 2 +60

Claims (3)

[Claims] (1) In a continuous casting method in which additives are added to tundish molten steel and two or more types of steel slabs with different compositions are produced from one heat of ladle molten steel, the required amount of molten steel is poured from the ladle. When adding additives to the tundish and changing the cast steel type, stop pouring from the ladle into the tundish.
At this time, inert gas bubbling is performed at the ladle nozzle, and a contamination prevention fitting is inserted to prevent molten steel of different composition from entering the mold, and then pouring from the ladle into the tundish is resumed. At the same time, the continuous casting method is characterized in that continuous casting is carried out by changing the type or amount of additive material added into the tundish. (2) The continuous casting method according to claim (1), wherein the inert gas is injected from the lower part of the tundish downstream of the additive material input part in the tundish to perform bubbling. (3) The continuous casting method according to claim (1) or (2), wherein the molten steel poured into the tundish is heated.