JPS5916653A - Pressure type continuous casting method - Google Patents

Abstract

PURPOSE:To control stably the melt level in a mold and to perform titled continuous casting by regulating the flow rate in the initial period when charging is started with a steel orifice mounted to the tip of an immersion nozzle made of refractories, melting the orifice by molten steel with time and expelling the air in the immersion nozzle in a short time right after starting of charging. CONSTITUTION:A tundish stopper 6 is opened to start charging molten metal into a mold in order to start casting by using an immersion nozzle 5 made of refractories. The molten steel in the tundish 1 is charged into the mold 2 at the low flow rate throttled with a steel orifice block 9 having a small diameter. There is therefore no possibility of charging the molten steel at one time into the mold 2 in the stage of starting the casting, so that a good connection between a dummy bar head and a billet is obtd. The air in the nozzle 5 is substd. with the molten steel and the equil. state between the total head of the molten steel and the gaseous pressure is obtained in an extremely short time in order to maintain a stopper 6 in the intermediate casting state. The block 9 is melted by the molten steel flowing downward so that the bore thereof is gradually expanded until finally the block is thoroughly melted and the stable operation is started.

Description

[Detailed description of the invention] The present invention relates to a novel method for operating pressurized continuous casting equipment.

The tundish and the mold are surrounded by a sealed chamber, an inert gas is supplied into the sealed chamber, and the slab is pulled out while keeping the gas pressure and the total water head of the molten steel roughly balanced. In the pressure continuous casting method, after opening the tundish stopper and starting pouring, the liquid level in the mold rises and when it reaches a certain level, inert gas is supplied into the sealed chamber to raise the liquid level. In this case, the immersion nozzle is attached to the tundish and the inside diameter of the nozzle is sufficiently large, so when the slab is pulled out at a constant speed, the flow velocity of the molten steel is small. This has the advantage that the stirring zone within the mold can be made shallow and nozzle clogging is less likely to occur. However, on the other hand, when starting pouring into the mold 9, the large diameter immersion nozzle poses a problem. That is, when the tundish stop is opened, a large amount of molten steel is injected into the mold at once, resulting in insufficient connection between the damino 2-head and the slab, and when the slab is pulled out through the dummy bar. There is a risk that the dummy bar and slab may separate. Conventionally, in order to prevent this accident, a method has been adopted in which a tundish stopper is intermittently opened and closed when pouring into the mold begins, thereby preventing a large amount of molten steel from being poured into the mold all at once. However, this intermittent opening/closing operation of the tundish stopper takes time for the air accumulated in the submerged nozzle to escape, and also causes a type of bubbling phenomenon as the air in the nozzle rises to the surface. Meanwhile, there was a drawback that it became difficult to control the level of the mold inside the mold using gas pressure.

The present invention solves the drawbacks of the conventional intermittent opening/closing operation method of the tundish stopper, eliminates the air in the immersion nozzle within a very short time immediately after starting pouring, and stabilizes the molten metal level in the mold. This was proposed for the purpose of proposing a method of operating a pressurized continuous casting facility that can be controlled.The tundish and mold 9 are surrounded by a sealed chamber, and the pouring from the tundish into the mold is controlled by a refractory immersion method. In the pressurized continuous casting method, in which continuous casting is carried out using a nozzle, inert gas is supplied into the sealed chamber, and the gas pressure and the total water head of the molten steel are approximately balanced, the tip of a refractory immersion nozzle is used. At the same time, the flow rate at the initial stage of pouring is regulated by a steel orifice, and the steel orifice is melted by molten steel over time, until it is completely melted and the steel can be poured using only a refractory immersion nozzle. This relates to a characteristic pressure continuous casting method.

The present invention will be specifically explained below with reference to FIG. In the figure, 1 is a tongue tissue, 2 is a mold, and 3 is a vertically expandable cylindrical tube attached to form a sealed chamber 10 between the bottom surface of the tongue tissue 1 and the upper end surface of the mold 2. The members include 4 a dummy par, 5 a refractory immersion nozzle, 6 a dummy burst collar, 7 an inert gas inlet pipe with an air supply valve 7a interposed therein, and 8 an inert gas inlet pipe with an exhaust valve 8a interposed therein. Each shows an active gas discharge pipe,
The structure, operation, and mutual relationship of these members are substantially the same as those of conventional pressurized continuous casting equipment.

Reference numeral 9 denotes a small-diameter steel orifice block fitted into the tip opening of the refractory immersion nozzle 5. The inner diameter of the steel orifice block 9 is the same as that of the tundish 1 to the immersion nozzle 5 at the start of casting. The flow rate of molten steel into the mold 2 through is determined.

An example of the immersion nozzle for implementing the present invention is configured as described above, and in order to start casting using the immersion nozzle 5, the tundish stopper 6 is opened and pouring into the mold 2 is started. The molten steel in the tundish 1 is constricted by a small-diameter steel orifice block 9 and injected into the mold 2 at a low flow rate. Therefore, compared to the case of using only a conventional immersion nozzle, there is no risk of molten steel being injected into the mold at once at the start of pouring, and there is no risk of an accident occurring due to insufficient connection between the dummy bar head 9 and the slab. Also, since the tundish stopper 6 is held in the open state, the air in the immersion nozzle 5 is replaced with molten steel, and in a very short period of time, the tundish stopper 6 is kept in the open state. It escapes upward through the nozzle 5, and in a short period of time, an equilibrium state between the total water head of the molten steel and the gas pressure is achieved, eliminating the drawbacks of the conventional method and stably controlling the molten metal level in the mold 2. will be carried out. 1.
In addition, since the steel orifice lock 9 is made of steel,
It is melted by the flowing molten steel, the inner diameter gradually expands, and the amount of molten metal poured into the mold 2 changes over time.
Eventually, it melts completely, and the molten steel reaches a flow rate determined by the inner diameter of the refractory immersion nozzle 5, resulting in a normal casting flow rate, and stable operation begins.

In the example shown in FIG. 1, a nozzle is used in which a small-diameter steel orifice block 9 is fitted into the tip opening of the refractory immersion nozzle 5, but as shown in FIG. ,
A nozzle may be used in which a steel cap 9/ (steel orifice) having a small diameter hole 9/a is screwed into the tip of the refractory immersion nozzle 5.

In summary, the present invention surrounds the tundish and the mold with a sealed chamber, pours molten metal from the tundish into the mold 9 using a refractory immersion nozzle, supplies an inert gas into the sealed chamber, and In the pressurized continuous casting method, in which continuous casting is performed with the gas pressure and the total water head of molten steel approximately balanced, a steel orifice is attached to the tip of the refractory immersion nozzle, and the steel orifice controls the flow rate at the initial stage of casting. The gist is a pressurized continuous casting method that is characterized by regulating the steel orifice and melting the steel orifice with molten steel over time until it is completely melted and pouring the metal only with a refractory immersion nozzle. Because it is something that
According to the present invention, it is possible to eliminate the drawbacks of the conventional pressurized continuous equipment operating system, and to ensure the connection between the dummy bar head 9 and the slab by regulating the flow rate to the mold immediately after the start of casting. In addition to this, it also has the practical effect of maintaining stable operating conditions.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view of an example of a main part of equipment for implementing the present invention, and FIG. 2 is a vertical cross-sectional view of a main part of a modified example of a small diameter steel nozzle. 1: Tundish, 2: Mold, 3: Cylindrical member, 4: Dummy bar heater), 5: Immersion nozzle made of large-sized material, 6: Tundish stock 7ξ. 7: Air supply pipe interposed with air supply valve 7a , 8: Exhaust valve 8
Exhaust pipe with a inserted +979': steel orifice,
10: Closed room. Sub-agent Patent Attorney Teru Ito (2 others)

Claims (1)

[Claims] A sealed chamber surrounds the space between the tundish and the mold. Molten metal is poured from the tundish into the mold 8 using a refractory immersion nozzle, and an inert gas is supplied into the sealed chamber to reduce the gas pressure and the total amount of molten steel. In the pressurized continuous casting method, in which continuous casting is performed with the water head approximately balanced, a steel orifice is attached to the tip of the refractory immersion nozzle, and the steel orifice regulates the flow rate at the initial stage of casting. A pressurized continuous casting method characterized by melting a steel orifice with molten steel over time until it is completely melted and pouring the steel only through a refractory immersion nozzle.