JPH0299250A - Method for removing slag in tundish - Google Patents

Abstract

PURPOSE:To obtain the long service life of tundish lining by advancing local heating burners as freely possible to advance/retreat to near a pouring nozzle and discharging hole and heating to prevent solidification in inner face thereof after discharging molten slag by heating with a burner. CONSTITUTION:After completing the casting, the burners 6, 7 are executed to burn in the tundish 1 to melt the slag 11 and both of the remaining molten steel 12 and slag 13 are discharged. The local heating burners 22, 23 are advanced to near the insert nozzle 21 and discharging hole 16 and burnt to discharge the dripped slag without solidifying. As the slag stuck to inner face is heated and melted while the tundish 1 is yet under high temp. condition after completing the casting, the contamination of the molten steel caused by the remaining slag at the initial stage in the next heat casting is only a little. As the slag is discharged together with the remaining molten steel 12 having good fluidity, this is smoothly discharged. The long service life of the refractory in the tundish 1 is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for removing slag from a tundish used in continuous casting of sandstone.

[Prior Art] Conventionally, maintenance work for a tundish involves mechanically peeling off and removing residual molten steel and slag within the tundish after the tundish has cooled down to a certain level after casting. For this reason, the refractories are easily damaged, and the durability of the refractories is likely to deteriorate due to the forced cooling of the tundish. Each time, I had to reinstall it.

In addition to such maintenance conditions, in recent years, in continuous casting of molten steel, the number of maintenance times for tundishes has increased due to the diversification of the product mix of steel products, and the lifespan of the refractories in tundishes has become shorter and shorter. , the basic unit of refractories in tanditshu is increasing.

In recent years, various techniques have been proposed for servicing tundishes in a hot state in order to prevent damage to refractories and deterioration of durability during tundish maintenance after casting.

For example, Japanese Patent Application Laid-Open No. 60-261653 discloses cleaning of the lining of tanditshu in which the denatured layer is removed with a solvent using a burner flame that is higher than the melting point of the altered layer formed in the CaO-based lining material of tanditshu, and the lining material is reused. The method is described.

Furthermore, in Japanese Patent Application Laid-Open No. 103653/1984, the tundish is turned upside down and placed on a support stand that closes the entire open part of the tundish, and the inside of the tundish is heated from this support stand with a burner. A tanditshu slag removal method is described in which slag that has adhered to and permeated a refractory is removed by melting and flowing down.

In addition, Japanese Patent Application Laid-Open No. 61-137656 describes slag,
Alternatively, the altered layer of the lining material of the tanditshu due to adhesion and fusion of molten steel is melted using a solvent burner with a flame temperature higher than the melting point of this altered layer, and this molten layer is cut or blown away with a secondary gas fluid. A method for cleaning tundish linings is described.

[Problem to be solved by the invention]

By the way, as mentioned above, the refractories for tanditshu include the lining material, the weir, the insert nozzle, the molten steel injection valve, and the immersion nozzle attached to the tanditshu, but the refractories for the tanditshu inner lining described in the above-mentioned publication are as follows: The cleaning method or the slag removal method for the tundish is a technology that reduces damage to the lining material of the tundish and deterioration of its durability, and it is used to remove slag from the weir, insert nozzle, etc. attached to the tundish. The gtA injection valve, immersion nozzle, etc. have to be reinstalled each time, and therefore, the effect of reducing the basic unit of refractories for tanditshu cannot be said to be sufficient.

Therefore, in view of the above-mentioned problems, the present invention removes not only the refractory lining material of the tundish but also the weir, insert nozzle, molten steel injection valve, and immersion nozzle attached to the tundish from the tundish. To provide a method for removing slag from a tundish, which can prevent damage and maintain the durability of the refractory by maintaining it in a hot state without any damage, thereby extending the life of the refractory in the tundish. The purpose is to

[Means to solve the problem]

In order to achieve the above object, the method for removing slag from a tundish of the present invention heats the inside of the tundish in a high temperature state after casting with a burner to melt and flow down the slag that is solidifying on the inner peripheral surface of the tundish. After that, drill the pouring nozzle and discharge hole on the bottom of the tanditshu, and remove the remaining
The molten slag floating on the I'8 steel is discharged together with the remaining molten steel, and after a predetermined period of time the heating burner is controlled to lower the temperature inside the tundish to a predetermined temperature. The molten metal enters through the tundish lid to the vicinity of the openings of the pouring nozzle and discharge hole on the bottom of the tundish and burns, heating the inner surface of the pouring nozzle and the discharge hole, and the slag flowing down to these inner surfaces is heated. It prevents solidification and discharges >8 melt.

[For production]

After casting, the inside of the tundish has a temperature of around 1000°C. At this temperature, molten steel with floating slag remains at the bottom of the tundish as a pool of molten steel, and there is no adhesion on the inner wall surface. The slag is stuck in a solidified state.

The inside of Tanditsu in such a state was heated to 150 degrees with a burner.
When heated to a temperature of 0'C or higher (preferably 1600C or higher), the slag stuck to the inner wall surface in an assimilated state melts and flows down to float on the remaining molten steel.

After this, by opening the pouring nozzle and discharge hole on the bottom of the tundish, the slag floating on the remaining molten steel can flow out from the opening together with the remaining molten steel, which has good fluidity. Can be drained well.

After a predetermined period of time has elapsed to almost complete the discharge of the remaining molten steel, the heating burner is controlled to lower the temperature inside the tundish to less than 1500'C (preferably 1400°C or less), and the pouring nozzle and discharge By injecting a local heating burner into the vicinity of the opening of the hole and burning it, the slag slightly dripping on the inner wall is solidified and stopped flowing to the opening of the pouring nozzle and discharge hole on the bottom of Kundi Soche, and at the same time, The slag already dripping and flowing on the opening surfaces of the pouring nozzle and the discharge hole and on their inner peripheral surfaces can be almost completely discharged.

In this way, the slag is removed and reused without removing the tanditshu's accessory refractories, such as the weir, insert nozzle, molten steel injection valve, and immersion nozzle, so the lifespan of these accessory refractories can be effectively extended. .

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIGS. 1 and 2 are diagrams illustrating the process of removing slag from a tundish.

At the same time as casting is completed, the molten steel injection valve 3 of the immersion nozzle 2 provided on the underside of the tundish I is closed, the turntable-type lifting platform 4 on which the tundish 1 is placed is raised, and the mold (not shown) is removed. At the same time, the immersion nozzle 2 is evacuated from the tundish 1 by moving the turntable-type lifting platform 4 to adjust the tundish 1 to the fA field (see Figure 1).
Next, during casting, a three-way valve installed in the pipe midway through the burner was switched to the burner 67 installed on the top surface of the tundish M5, which was supplying argon gas to prevent oxidation of the molten steel in the tundish 1. By supplying fuel and a combustion improver enriched with oxygen and burning it in the tundish 1, the steel receiving chamber 8 and the molten steel injection chamber 9 of the tundish 1 are
The slag 11 at a temperature of 1200°C to 1300°C adhering to the sidewall of the weir 10 provided at the boundary between the two chambers 8.9 and 8.9 is heated to about 1600°C. 8
The slag 13 is melted and floated down on the slag 13 floating on the molten E12 on the bottom of the tundish 1.

Next, the molten steel injection valve 3 is opened, and the slag 13 and residual molten steel 12 accumulated on the bottom surface of the molten steel injection chamber 9 are removed from the slag drainage gutter 14 previously installed below the molten steel injection chamber 9 and below the immersion nozzle 2. While supplying oxygen, an oxygen lance 17 for opening a nozzle, which can be raised and lowered through the tandish M5, is inserted into a discharge hole 16 provided at the bottom of the steel receiving chamber 8 while supplying oxygen. And the rest? The plug 18 of the discharge hole 16 filled with 8 steel 12 is melted and opened by the heat of reaction with oxygen, and the slag 13 and the remaining 18F 112 are placed in advance on the lower surface of the steel receiving chamber 8 and below the discharge hole 16. The sludge is discharged to the sludge hanger 20 via the slag drain trough 19. On the other hand, after the discharge hole 16 is opened, the nozzle opening oxygen lance 17 stops supplying oxygen and retreats to a predetermined position.

After about 5 minutes have elapsed after the above opening, the combustion amount of burner 6.7 is controlled to bring the temperature inside tundish 1 to about 1450°C.
At the same time, the inner nozzle 21 and the discharge hole 16 buried in the bottom of the tundish 1 communicating with the immersion nozzle 2 are The local heating burners 22 and 23 provided on the top surface of the tundish lid 5 are introduced into the vicinity of the opening of the tundish lid.
．． 23 is supplied with fuel and a combustion improver enriched with oxygen, and is combusted. To discharge dripping slag without solidifying it.

When the discharge of the slag and residual molten steel is completed as described above, combustion of the local heating burner 23 above the opening of the discharge hole 16 is stopped and the tundish lid 5 is raised to the upper surface. On the other hand, the local heating burner 2 above the opening of the insert nozzle 21
2 and burner 6.7 continue to burn as they are to burn the inner peripheral surface of the tundish 1, the weir 10, and the insert nozzle 2.
1. Keep the molten steel injection valve 3 and the immersion nozzle 2 warm, wait in this state until the tundish 1 is used for the next casting operation, and turn on the local heating burner 22 and burner 6.7 at the appropriate timing before starting use. The combustion is stopped, the local heating burner 22 is pulled up to the upper surface of the tundish lid 5, the molten steel injection valve 3 is closed, the discharge hole 16 is plugged with a plug 18, and the molten steel is reused for casting.

As mentioned above, when the tundish 1 is still in a high temperature state after the completion of casting, the slag attached to the inner surface of the tundish 1 can be heated and melted until it reaches a slightly 'a flow state. In addition to reducing the initial contamination of molten steel, the molten slag is discharged together with the remaining 7 volumes of steel, which has good fluidity, so the slag can be discharged extremely smoothly.

In addition, not only during this slag removal, but also after removal until the tundish 1 is reused, the inner peripheral surface of the tundish i, the weir 10, the insert nozzle 21,
Since the refractories of the molten steel injection valve 3 and the immersion nozzle 2 are kept warm, they can withstand reuse sufficiently, and the life of the refractories of the tundish 1 can be extended.

In addition, in FIG. 1 and FIG. 2 shown in the above embodiment, 24.
25 is a pipe for discharging gas from inside the tandish 1;
6.27 is a cylinder for moving the local heating burner 22.23 forward and backward, and 28 is a cover that is provided so as to be able to move forward and backward with respect to the immersion nozzle 2 and surrounds the immersion nozzle 2 to keep it warm.

〔Effect of the invention〕

As described above, according to the present invention, the slag adhering to the inner circumferential surface of the tundish after casting is reheated in a hot state without removing the incidental refractories, such as the weir, insert nozzle, molten steel injection valve, and immersion nozzle. Therefore, the life of the tundish including these accessory refractories can be effectively extended.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the process of removing slag from a tundish according to the present invention, and FIG. 2 is a sectional view taken along the line AA in FIG. 1. 1 Tundish 2 Immersion nozzle 3 Molten steel injection valve 4 Lifting platform 5 Tundish lid 6,7 Burner 8 Steel receiving chamber
9 Molten steel injection chamber 10 Weir
11.13 Slag 2 Residual Molten Steel 16
Discharge hole 17 Oxygen lance 18 Plug 21
Insert nozzle 22.23 Local heating burner patent applicant Kobe Steel Corporation agent Patent attorney Akira Kanemaru - Figure 1 10 Figure 2 - 0

Claims (1)

[Claims] (1) After the completion of casting, the inside of the tundish, which is in a high temperature state, is heated with a burner to melt and flow down the slag that is solidifying on the inner circumferential surface of the tundish, and then the slag is poured into the pouring nozzle and discharge hole on the bottom of the tundish. A hole is opened, the molten slag floating on the remaining molten steel is discharged together with the remaining molten steel, and after a predetermined period of time, the heating burner is controlled to lower the temperature inside the tundish to a predetermined temperature. A local heating burner is introduced through the tundish lid to the vicinity of the openings of the pouring nozzle and discharge hole on the bottom of the tundish and burns, heating the inner surface of the pouring nozzle and the discharge hole.
A method for removing slag from a tundish, characterized in that the slag flowing down onto these inner surfaces is melted and discharged while being prevented from solidifying on these inner surfaces.