JPS62144856A - Continuous casting method - Google Patents

Abstract

PURPOSE:To obtain a casting slab having excellent surface characteristics and internal quality with high speed and stability by arranging a heating zone and a cooling zone successively toward advancing direction of the casting slab at an inner side of a mold and drawing the casting slab as controlling a solidified starting point by heating and cooling rate. CONSTITUTION:The heating zone 5 and the cooling zone 6 are arranged successively under the upper vessel 4 and at an inner surface of the heating zone 5, steel is controlled to supply quantity of heat to the heating zone 5, so as to keep it therein to molten state. Further, in an inner surface of the cooling zone 6, coolant is controlled to begin to solidify surely for molten steel and it is controlled to come to near a boundary between the heating zone 5 and the cooling zone 6 for a starting point of the solidification without using of a brake ring. In this way, the starting point of the solidification is controlled at almost a fixed position, and the casting slab having excellent surface characteristics and internal quality is obtd.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a continuous casting method for producing defect-free clean gA slabs with few inclusions and good surface properties. .

(Prior art) In the commonly practiced continuous steel casting method, molten steel produced in a furnace or the like is received in a tundish. : The molten steel is injected into a mold through a submerged nozzle, and the injected molten steel forms a solidified shell from the mold wall side, and this vertical S shell is drawn out from directly below the mold while being cooled by spray. In this case, in order to prevent seizing between the slab and the mold and to reduce friction resistance, the mold performs an off-shielding operation as shown by the arrow in Figure 2, and powder is introduced into the meniscus. It is well known that lubrication is performed.

However, the vibration means for the mold uses an electric motor or a fluid cylinder as a driving source, and uses a link mechanism or a cam fi 61 to mechanically move the mold, and the vibration frequency is usually about several Hz, and the vibration I The fortune is around a few Ifim. In the conventional mold vibration force type, the vibration frequency is low, so the flow of molten powder between the mold inner wall and the solidified slab shell is not uniform, and the original purpose cannot be completely achieved. A striped pattern with a depth of about 0.1 to 0.511II11 called an oscillation mark is formed on the surface of the slab due to mold vibration, and this oscillation mark is a cause of surface flaws. In addition, the powder added as a lubricant melts at the meniscus, and when the casting speed is high, the molten powder is drawn into the molten steel by the molten steel flow near the meniscus in the mold, causing deterioration of the internal quality of the slab. .

In order to solve these problems, Japanese Patent Application Laid-Open No. 57-4184
11 types of horizontal casting systems disclosed in Japanese Patent Laid-open No. 9 and Japanese Patent Application Laid-Open No. 58-65547 are used in small-scale facilities. In this method 1, although the conditions of no oscillation and no powder are satisfied, a refractory material called a break ring as shown in JP-A-59-107977 is inserted between the tundish and the mold. Since the slab is drawn out intermittently (i.e., the slab is pulled out and the slab is stopped repeatedly), the surface condition of the slab has the same defects as in the mold vibration method described above.

Examples of applying the same retaining force as that of Mizuko continuous casting to rigid continuous casting equipment are shown in Japanese Patent Application Laid-Open No. 59-225861 and Japanese Patent Application Laid-Open No. 59-127953, etc. In all of these methods, vibrations are applied to the mold itself and the slab is pulled out intermittently, so it is currently not possible to obtain a sufficiently sound and uniform surface texture of the slab. Problems to be Solved) The present invention eliminates the 5-mark mark on the driver, and
By not using powder, bag entrainment can be completely avoided and slabs with excellent surface and internal quality can be produced quickly! I
) The purpose of the present invention is to provide a continuous casting method that allows stable production.

(Means for Solving the Problems) The present invention provides a heating zone and a cooling zone inside the mold in the direction of progress of the slab when continuously casting molten steel through a device in which a mold is integrally fixed at the bottom of an upper container. Continuous g is characterized by continuously pulling out the slab while controlling the starting point of solidification of the slab by controlling the amount of heating and cooling.
This is the J construction method.

(Operation) A detailed explanation will be given below using examples of the present invention and conventional examples.

FIG. 1 is an explanatory diagram showing an example of an apparatus for carrying out the present invention;
FIG. 2, FIG. 3, and FIG. 4 are explanatory diagrams showing conventional examples.

1 is a ladle, 2 is an injection nozzle, 3 is molten steel, 4 is an upper container,
5 is a heating zone, 6 is a cooling amount, 7 is a solidified shell, 8 is a tundish, 9 is an immersion nozzle, 10 is a powder, 11 is a break ring, and 12 is a stopper.

In the conventional continuous casting process, as shown in FIG.
At this time, powder 10 is poured onto the surface of the molten steel in order to prevent the inner wall of the cooling unit 6 from seizing on the solidification shelf, and the slab is driven while the cooling unit 6 is vibrated up and down. Generally, it is pulled out in the opposite direction. However, due to this mold vibration, the surface of the slab is exposed to a
Surface defects called "marks" are formed, which impedes the use of no-maintenance slabs and direct conveyance to the rolling process, and the powder 10 thrown onto the surface of the molten steel is ejected from the discharge port of the immersion nozzle 9. In this way, the powder becomes involved in the molten steel flow and becomes an inclusion-based defect, which causes deterioration of the internal quality of the slab.

η#,,-r,,h, or 7,4++ [4r
JL: lii gourd 11 已・ha J
In order to stably produce products that are excellent in both FIFi f'l ψ) and internal quality, it is considered essential to have a means to make it possible to eliminate balagure and the mold.

From this point of view, the horizontal continuous casting method shown in FIG. 3 and the continuous casting method shown in FIG. 4, which is an application of the horizontal continuous casting method to a vertical mold, are known as manufacturing methods aimed at padderless and off-sill a-less manufacturing methods. In these processes, a break ring 11 is installed between the upper vessel 4 and the cooling amount 6 in order to control the solidification point at a constant level, and the slab is pulled out intermittently, so the solidification form is not uniform. The reality is that they have a defect called a cold shaft mark.

From the above, in addition to the above-mentioned barrier-free and oscillation-less methods, continuous drawing is necessary to stably produce high-quality slabs.

In contrast, in the present invention, as shown in fjSll, ¥J, a heating zone 5 and a cooling amount 6 are successively installed under the upper container 4, and the steel is heated on the inner wall of the heating zone 5 so that it is always in a molten state. By controlling the amount of heat supplied to the tropical zone 5 and controlling the cooling flow so that the molten steel always begins to solidify on the inner wall of the cooling zone 6, the solidification start point can be set to the heating zone 5 without using a break ring. It becomes possible to perform control so that the cooling amount exists near the boundary between the cooling amount and the cooling amount 6.

In addition, when using the break ring shown in Figures 3 and 4, when the slab is continuously pulled out, the solidification origin separates from the break ring, gradually moves in the pulling direction as the slab is pulled out, and finally When the solidification starting point reaches the rear end of the mold, a breakout occurs and casting has to be interrupted. Therefore, it is well known that when using conventional break rings, it is common to have to pull them out intermittently (Reference Tetsu to Hagane (1981), 1377).

In contrast, in the case of the present invention, by controlling the heating amount and cooling amount in the heating zone to appropriate values, it is possible to control the solidification origin so that it is constantly located at a specific position. Therefore, it is possible to draw the slab continuously.9 The method of supplying heat to the heating zone is basically not limited as long as a certain amount of heat can be supplied, and direct energization and induction can be used. Even with electric heating such as heating,
Although a certain effect can be obtained using space heating, electric heating is more suitable in order to enable highly accurate control and to enjoy the effects of the present invention to a greater extent.

Conventional bag-based lubricants are not used to prevent 7I ■ slippage inside the mold, but various solid lubricants are applied to the inner walls of the mold to reduce the frictional resistance between the mold and the solidified slab shell. In order to further improve the effects of the present invention, applying graphite or forming part or all of the mold from graphite can be carried out as necessary. Furthermore, in order to further reduce the frictional resistance force, it is also possible to apply high-cycle m-vibration such as ultra-A waves to the mold, if necessary.

(Example) Low carbon aluminum killed steel slab for thin plate with slab width 1600mm and slab thickness 245m+n # speed 1.85+n/vl
The length is 200+ on top of the cooling amount of the continuous casting machine that casts in.
A 2-t capacity upper container was placed above the heating cylinder. Molybdenum disulfide is applied as a solid lubricant to the inner surface of the mold, and a heating coil capable of supplying 0.5 MW of electrical energy to the heating zone is buried, ensuring that the solidification start point is near the joint between the heating zone and the cold J zone. (f exists here + here,
Casting was carried out for about 5 hours while controlling the amount of water supplied to the heating zone and the amount of water supplied to the cooling zone (IT) and continuously drawing out the slab without powder and without off-sillage. As a result, slabs with no oscillation marks observed on the outside and good internal quality can be produced stably using WJI without any operational problems such as breakouts or burnout.

(Effects of the Invention) As described in detail above, by applying the present invention, the fixation starting point can be controlled to approximately a predetermined position ifi, and the tip of the solidified shell can also maintain a sharp shape. The sections produced in this way can be transferred to the next rolling process without any manual work. In other words, according to the present invention, slabs with excellent surface texture and internal quality can be produced +l'
It becomes possible to cast fi-speed and stably6

[Brief explanation of drawings]

tjS1 is an explanatory diagram showing an example of an apparatus for implementing the present invention, and FIGS. 2, f:tS3, and 4 are explanatory diagrams showing a conventional example. 1... Ladle, 2... Injection nozzle, 3... Molten steel, 4
... Upper container, 5 ... Heating zone, 6 ... Cooling amount, 7
... solidified shell, 8... tandish, 9...
Immersion nozzle, 10...powder, 11...break ring, 12...stopper.

Claims (1)

[Claims] (1) When continuously casting molten steel through a device in which a mold is integrally fixed at the bottom of an upper container, a heating zone and a cooling amount are connected in the direction of progress of the slab inside the mold, and the amount of heating and cooling is controlled. A continuous casting method characterized by continuously drawing out slabs while controlling the solidification start point of slabs.