JPS5921697B2 - Continuous casting tandesh - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides continuous casting of molten metal. An upper weir is installed higher than the surface of the molten metal in the tumbler, and an upper weir is installed inside the upper weir to make the molten metal injected from the ladle long nozzle flow upward in the tumbler. This relates to a continuous casting tumble pusher that floats and separates non-metallic inclusions.

Generally, in the method of injecting molten metal from a ladle into a tumbler through a long nozzle, a portion of the molten metal may flow along the bottom of the tumbler and be immediately injected into the mold.

When such a direct flow into the mold occurs, the residence time of the molten metal in the tamp push is short, and the floating separation of non-metallic inclusions (especially Al2O3 type) in the molten metal is insufficient.
The amount of inclusions in slabs and finished products increases, deteriorating the quality of slabs.

Conventionally, various methods are known for the purpose of reducing non-metallic inclusions within a tongue pusher.

FIG. 1 shows various conventional methods.

The method shown in FIG. 1a uses two weirs 1 and 2 to strengthen mixing and agitation.

In this method, Al2O3 particles collide with each other to cause agglomeration and enlargement to promote flotation and separation, but the flow rate of molten metal in a normal tump push (1 m3/min or less) does not provide sufficient stirring energy, resulting in very small particles. There is a limit to the enlargement of Al2O3 particles, and therefore there is also a limit to the degree of flotation separation.

In the method shown in Figure 1, a pool weir 3 is provided directly below the ladle long nozzle to orient the injected flow upward to achieve flotation and separation. Since it is exposed to water, it is reoxidized and non-metallic inclusions are generated, which have the disadvantage of being re-engulfed in the metal bath.

The method shown in FIG. 1C promotes flotation and separation using a tundish with a single weir.

In this case, the molten metal is aligned upward between the two weirs 4, 4, and thereafter a rectified flow is formed along the bath surface to provide conditions suitable for floating and separating particles.

A disadvantage of this method is that the stirring energy is greater than that of the method shown in a + b above.

Therefore, there is a limit to the size of particles due to collisions and agglomeration, and in order to promote flotation separation of particles, it is necessary to lengthen the time required for flotation separation (i.e., increase the size of the tongue push).
Is required.

As mentioned above, in the various conventional methods, various types of weirs are installed in the tumble push to increase the flotation separation rate of inclusions, and compared to the previous tump push without a weir, all of them are Although these methods are known to be effective, as mentioned above, there are two methods: simply promoting agglomeration and separation of particles by strengthening agitation, or simply rectifying the injected flow in an upward direction or along the bath surface to prevent particles from flowing. There was a problem because it was too difficult to provide conditions that would facilitate flotation and separation.

In order to eliminate this drawback, the present invention provides an upper weir on the surface of the molten metal in the tambutsu, accumulates a flux with high inclusion absorbing ability inside the weir, and deposits the flux inside the upper weir and directly below the ladle long nozzle. An upper weir is installed nearby, and the upper weir directs the flow injected from the ladle long nozzle into an upward flow, strengthens the contact between the flux accumulated inside the upper weir and the molten metal, and removes inclusions caused by the flux. This method promotes absorption and removal.

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIGS. 2a and 2b are a front sectional view and a plan view showing an example of the present invention in a mother tongue pusher.

The injected flow from the ladle long nozzle 6 provided at the bottom of the ladle 5 is directed into an upward flow 12 by the upper weir 10, and comes into contact with the flux 11 accumulated inside the upper weir 9, and then flows into the tump push nozzle 8. pass through and enter the mold.

FIGS. 3a and 3b are a front sectional view and a plan view showing another example of the present invention in a box-type tongue pusher.

In this case, the upper weir 9 is arranged to divide the tongue pusher into two parts in the width direction, and is installed over the entire vertical section of the tongue pusher in the height direction except for the molten metal flow hole 9'.

In addition, the upper weir 10 has a ladle long nozzle 6 in the portion divided by the upper weir 9 on the tongue push plane as shown in Figure 3.
Install it on the immersion side of the

After the molten metal injected flow exits the ladle long nozzle 6, it is directed into an upward flow 12 by the upper weir 10, and flows into the opposite divided side through the molten metal flow hole 9' provided in the upper weir 9. do.

During this time, it comes into contact with the flux 11 and captures nonmetallic inclusions.

FIGS. 4a and 4l) are a front sectional view and a plan view showing still another example of the present invention in a T-type tongue pusher.

In this way, the present invention promotes the contact reaction between the upward flow from the upper weir and the flux accumulated inside the upper weir by the shape of the tongue push, regardless of whether it is symmetrical or asymmetrical with the ladle long nozzle as an axis. It is a characteristic of

In the present invention, there are appropriate positions for installing the upper weir and the installation position of the upper weir.

That is, by varying the ratio S2/S1 of the inner area S2 of the upper weir to the inner area S1 of the upper weir and the inner area S1 of the upper weir in Fig. 2.3.4, the Al2O3 in the flux in the upper weir was changed. The concentration change was investigated and the Al2O3 absorption ability was evaluated.

In addition, the flux is the component before use: Cab: 51, Sin: 4
Part 4, Al2O3: : Part 3, and the rest: 9/T were used at a ratio of 0.3 to the amount of molten steel injected.

Figure 5 shows Al2 in the flux measured as above.
FIG. 3 is a diagram illustrating organized data on O3 concentration increase (difference between during casting and before use).

As is clear from Fig. 5, when the 81 value is less than 175 of the molten steel surface area S in the tank push, the Al2O3 concentration in the flux increases as the 527S1 ratio increases;
It tends to be saturated at 0 or more.

On the other hand, when the S1 value exceeds 115 of the surface area of the molten steel in the tamp push, the increase in the Al2O3 concentration is small.

Based on the above measurement results, inclusions (A1203) can be effectively absorbed and removed by setting the S1 value to 115 or less of the surface area of molten steel in the tambutsu and setting the S2/S1 ratio to 2.0 or more. .

Using the tongue push of the present invention, bloom slabs (size 2)
47X300, steel type 545C), and the slab was
As a result of ground flaw inspection (JIS method) for φ steel bars,
As shown in Table 1, an improvement effect on ground defect results was observed.

[Brief explanation of drawings]

FIGS. 1A, 1B, and 1E are front sectional views showing a conventional tongue pusher equipped with a weir. 2 to 4 show embodiments of the present invention, each a is a front sectional view, b is a plan view, FIG. 2 is an example of a flying tongue pusher, and FIG. 3 is a box This is an example of a T-type tongue push, and FIG. 4 is an example of a T-type tongue push. FIG. 5 is a diagram showing the relationship between the upper weir and the area of the upper weir and the state of inclusion collection. 1.2: Weir, 3: Weir, 4: Weir, 5: Ladle, 6: Ladle long nozzle, 7: Tongue push, 8: Tongue push nozzle, 9. Top weir, 9': Molten metal Flow hole, 10: Upper weir, 11: Flux, 12: Upward flow.

Claims (1)

[Claims] 1. In a continuous casting tunpush, an upper weir is provided whose upper part is higher than the molten metal level in the tumbler, and an upper weir is installed at the bottom of the tungpush inside the upper weir, and the inner area of the upper weir is set to S.
1. A continuous casting tumble pusher characterized in that, where S2 is the inner area of the upper weir and S is the total surface area of molten steel in the tumbler, S2/S1≦2.0 and Sl is 15S.