JP2547771Y2 - Immersion nozzle for continuous casting - Google Patents

Description

The present invention relates to a submerged nozzle for continuous casting.

2. Description of the Related Art Continuous casting in a steel mill uses an immersion nozzle to inject molten steel from a tundish into a mold. In order to prevent reoxidation of the molten steel surface and seizure to the mold, a flux powder is floated on the molten steel surface in the mold.

The problem to be solved by the invention Flux powder melts by receiving heat from molten steel, which flows into the gap between the mold wall and the solidified shell on the steel surface, preventing seizure of the mold and causing cracks on the surface of the cast steel slab Is prevented.

For this reason, if the amount of the flux powder is too large or too small, cracks occur on the surface of the cast slab.

FIG. 3 is a perspective view of casting by a conventional immersion nozzle.

The conventional continuous casting immersion nozzle 1 generally has discharge ports 3 on both sides of a lower end portion thereof. Therefore, although the molten steel circulates upward and downward between the wall surface of the mold 4 and the immersion nozzle 1 as shown in FIG. 3, stagnation occurs on the side surface of the immersion nozzle 1 near the center of the molten metal surface. The heat in the stagnation portion lowers the temperature of this portion, making the flux powder 6 difficult to melt, and the amount of the flux powder 6 flowing into the molten steel is not stable.

In Japanese Utility Model Laid-Open Publication No. 52-165113 and the like, an opening is provided on the side of the discharge port, but these are opened at the same height as the discharge port. Not a solution.

Means for Solving the Problems The present invention has been made in view of the above points, and in order to solve the above problems, in a continuous casting immersion nozzle having discharge ports opened on both sides of a lower end portion, a discharge nozzle on both sides is provided. Between the outlets, above the discharge ports on both sides, below the molten steel surface, open a sub-discharge port on the side of the immersion nozzle so as to eliminate stagnation of the molten steel surface, and Of the above outlet
It is an object of the present invention to provide an immersion nozzle for continuous casting, characterized in that it has a size of 1/100 to 1/5 and is opened in a slit shape along the axial direction of the immersion nozzle.

In the present invention, when molten steel is injected from the immersion nozzle into the mold, the sub-discharge port opened slightly above the side of the discharge port is located slightly below the surface of the molten steel and slightly melts the molten steel. It is possible to prevent the flux powder from flowing out and stagnating on the side surface of the immersion nozzle.

And the size of the sub-discharge port is 1/100 of the discharge port.
Because it is as small as one-fifth, it does not discharge new molten steel, but eliminates the formation of stagnation on the side of the immersion nozzle, prevents the temperature from dropping in this part, and melts the flux powder to stabilize And poured into molten steel. Without lowering the strength of the immersion nozzle, the molten steel can slightly flow out of the sub-discharge port in a slit shape, stabilizing the flow direction of the molten steel, eliminating the stagnation of the molten steel surface on the side of the immersion nozzle. Thus, it is possible to effectively prevent the temperature of the molten steel at this portion from decreasing.

Embodiment Hereinafter, the present invention will be described based on an embodiment.

1 and 2 show an embodiment of the present invention. As shown in FIG. 1, the immersion nozzle 1 opens a flow hole 2 for injecting into molten steel at the center, and discharge ports 3 of a predetermined size on both sides of a lower end thereof, respectively. Molten steel can be injected into the mold 4. Sub-discharge ports 5 are respectively opened slightly above the discharge ports 3 between the discharge ports 3 on both sides of the lower end of the immersion nozzle 1 and when molten steel is poured into the mold 4 as shown in FIG. The sub-discharge port 5 is located slightly below the molten metal surface.

The sub-discharge port 5 is opened in a slit shape along the axial direction of the immersion nozzle 1 as shown in FIG. 2, and the molten steel can be discharged from the discharge port 3 in a direction perpendicular to the molten steel outflow direction or obliquely. Like that. The cross-section of the sub-discharge port 5 is 1/100 to 1/5 of the size of the discharge port 3, preferably 1/100.
During the injection of molten steel from the tundish into the mold 4, the molten steel slightly flows out of the side of the immersion nozzle 1 (in some cases, it may flow in), and the molten steel flows into the immersion nozzle 1. It is designed to prevent stagnation on the side of the hot water surface. If the secondary discharge port 5 is large,
The outflow speed of the molten steel from the sub-discharge port 5 increases, and the discharge port 3
A new stagnation portion of molten steel is generated between the discharge port and the sub-discharge port 5, which is not preferable, and can be appropriately adjusted within the above range to achieve the object in accordance with the molten steel injection amount. Also,
Since the opening direction of the sub-discharge port 5 is less effective in the same direction as the discharge port 3, it is desirable that the auxiliary discharge port 5 be in a state orthogonal to the direction of the discharge port 3 or in an oblique state. In particular, the opening in the slit along the axial direction of the immersion nozzle 1 as in the embodiment makes it possible to stabilize the flow direction of the molten steel from the sub-discharge port 5 without reducing the strength. It is preferable because the stagnation of the molten steel surface on the side surface of the immersion nozzle 1 which is the object of the invention can be prevented, and the temperature of the molten steel at this portion can be effectively prevented from lowering.

Water Model Experiment and Actual Machine Test An immersion nozzle having the above configuration was subjected to an experiment using an electrolyte solution as a tracer using a water model experiment device having the same dimensions as the actual machine.

As a result of the experiment, the tracer could be detected near the immersion nozzle immediately after adding the tracer. However, in the conventional immersion nozzle having no sub-discharge port, the tracer could be detected in the vicinity of the immersion nozzle only three times after 20 tests.

From this result, it was confirmed that when the sub-discharge port was provided in the immersion nozzle, the molten steel on the side surface of the immersion nozzle was stirred.

Then, as a result of using the above-described immersion nozzle 1 of the present invention in an actual machine, the flux powder 6 can be stably melted, and the rate of occurrence of small cracks in a slab manufactured by continuous casting is reduced from 0.3% to 0.01 in the conventional slab. % And improved quality.

Effect of the Invention As described above, in the present invention, when molten steel is injected from the immersion nozzle into the mold, the sub-discharge port opened slightly above the side of the discharge port is located slightly below the molten steel surface. As a result, the molten steel flows out slightly in the form of a slit, and the flux powder can be prevented from stagnating on the side surface of the immersion nozzle. Further, the sub-discharge port is set to 1/100 to 1/5 of the above-mentioned discharge port.
The size of the opening is slit-shaped along the axial direction of the immersion nozzle, so that the molten steel can flow out of the sub-discharge port slightly in a slit shape without reducing the strength of the immersion nozzle, stabilizing the flow direction of the molten steel. Thus, stagnation of the molten steel surface on the side surface of the immersion nozzle can be eliminated, and the temperature of the molten steel at this portion can be effectively prevented from lowering. Therefore, a predetermined surface temperature can be ensured, and the flux powder in a portion where stagnation is likely to occur can be melted and stably poured into the molten steel to prevent cracks on the surface of the cast steel slab.

In addition, as a result, flux powder is not entangled in the molten steel, and quality defects due to the flux powder can be reduced, and the injection speed of the molten steel can be increased, thereby improving the productivity of continuous casting of high-quality steel. Can be.

[Brief description of the drawings]

FIG. 1 is a perspective view of a main part of the immersion nozzle of the present invention, FIG. 2 is a side sectional view for explaining the operation and effects of the same, and FIG. 3 is a perspective sectional view for explaining a conventional example. 1 ... Immersion nozzle, 3 ... Discharge port, 5 ... Sub discharge port.

Claims (1)

(57) [Scope of request for utility model registration] An immersion nozzle for continuous casting having discharge ports opened on both sides of a lower end portion, wherein the molten steel surface portion is located between the discharge ports on both sides, above the discharge ports on both sides, and below the molten steel surface. A sub-discharge port is opened on the side of the immersion nozzle to eliminate stagnation,
An immersion nozzle for continuous casting, wherein the sub-discharge port has a size of 1/100 to 1/5 of the discharge port and is opened in a slit shape along the axial direction of the immersion nozzle.