JPH0636962B2 - Breaking ring tightening method in horizontal continuous casting - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of tightening a break ring in horizontal continuous casting.

[Prior art] With the horizontal continuous casting method, the connection between the tundish and the mold is
Generally, this is done as shown in FIG. A front nozzle 2 is horizontally attached to a lower portion of a steel shell 1a of a tundish 1, while a break ring 5 for facilitating the formation of a solidified shell of a slab in the mold is fitted to an end of a mold 4. Has been done. Then, the mold is connected to the tundish via the feed tube 3.

By the way, in the break ring 5, the joint surface side with the mold 4 is kept at a low temperature by cooling the mold 4, while the molten steel inflow side has a temperature close to the melting point of the molten steel. growing. As a result, a large tensile stress acts in the circumferential direction of the break ring 5, and the break ring weak in tensile strength may be broken.

Therefore, as a countermeasure against this, Japanese Patent Laid-Open No. 56-11164 discloses that a compressive stress that reduces the tensile stress is applied to the break ring in advance to prevent breakage of the break ring. That is, as shown in FIG. 7, the pressing metal fitting 6 is brought into contact with the outer circumference of the feed tube 3, and the bolt 7 penetrating the pressing metal fitting is tightened to the mold 4,
The break ring 5 is pressed via the feed tube 3. In this way, compressive stress is applied to the outer circumference of the break ring 5 in advance.

[Problems to be Solved by the Invention] Good results have been obtained in the case of casting a slab having a small cross-sectional angular size and a round cross-section by the above method.

However, when casting a large-angled cross section, there is a problem that the break ring is likely to be broken at the beginning of casting.

It is an object of the present invention to provide a method of tightening a break ring that can solve the above problems.

[Means and Actions for Solving Problems] In order to clarify the above problems, FIG. 3 shows the results of investigating the axial movement of the break ring 5 with respect to the mold 4 in the initial stage of casting. In the figure, + indicates the movement of the break ring 5 to the left side in FIG. 4, and − indicates the movement to the right side. The solid line shows the combination of the round mold and the round break ring, which is pushed into the-side by the pressing force during preheating, but the break ring thermally expands simultaneously with the injection of molten steel and moves to the + side against the pressing force. ing. Then, in this state, the tensile stress acting on the outer circumference of the break ring due to thermal expansion is reduced by the compressive stress due to the pressing force.

On the other hand, the broken line shows the combination of the square mold and the square break ring, and the movement of the break ring is small. This is because in the case of corners, when the break ring thermally expands, the outer surface of the break ring is not pressed against the taper part of the mold in a negative manner, but the corner part 5a (Fig. 5) having high rigidity is mainly pressed, and in the case of a circle. It is difficult to move smoothly in the axial direction as described above, and it is considered that the break ring is pressed in the axial direction from the beginning. The axial movement of the break ring is restricted in this way, and as a result,
Excessive compressive stress acts on the outer surface of the break ring, causing the side 5b of the break ring to buckle, as shown in FIG.
It is likely to lead to breakage.

Therefore, in the present invention, considering the thermal expansion of the break ring at the time of pouring the molten steel, the break ring is made to move easily in the axial direction without being pressed from the beginning, and the molten steel is injected into the tundish to allow the initial expansion. From, press the break ring.

That is, the method of tightening the break ring in the continuous casting of the present invention includes a tundish equipped with a front nozzle, a mold having a break ring fitted to the end thereof, and a treadish when the horizontal continuous casting is performed through a feed tube. By injecting molten steel into the break ring to allow axial movement due to the initial thermal expansion of the break ring, a pressing force is applied to apply compressive stress that acts to reduce the tensile pressure that acts on the outer peripheral surface of the break ring during casting. It tightens the break ring.

This makes it possible to prevent breakage of the break ring in the initial stage of casting and breakage during casting.

[Example] An example of an apparatus for carrying out the method of the present invention will be described with reference to FIGS. 1 and 2. The same parts as those in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted.
A plurality of brackets 11 are welded to the outer surface of the feed tube 3. A pulling cylinder 12 having a piston rod end connected to the mold 4 is provided on these brackets 11. Hydraulic oil is supplied to these cylinders 12 by the hydraulic circuit shown in FIG. The hydraulic circuit is provided with a pressure reducing valve 13 for setting the pressure of hydraulic oil, a main switching valve 14 and an opening / closing valve 15, and an accumulator 16.

Before the start of casting, as shown in FIG.
4 is closed, the on-off valve 15 is opened, and the cylinder 12 is left unloaded. Even if casting is started in this state, since the cylinder is unloaded, the break ring 5 can move in the axial direction, and breakage of the break ring due to thermal expansion at the initial stage of casting can be prevented. When the initial expansion of the break ring 5 is completed, the on-off valve 15 is closed and the main switching valve 14 is switched to feed the working oil to the cylinder 12 to press the break ring 5 via the feed tube 3.
In this case, since the hydraulic circuit is provided with the accumulator 16, it is possible to reduce the impact when the cylinder is operating. Thus, compressive stress is applied to the outer surface of the break ring to reduce tensile stress due to thermal expansion during casting and prevent breakage of the break ring.

The method of the present invention is particularly effective in the case of a break ring for a large-section square mold, but it can also be applied to a small-angle section with a small movement of the break ring and a round mold with a large movement.

[Advantages of the Invention] The present invention is as described above, and can prevent breakage of the break ring during the initial stage of casting and during casting.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an embodiment of an apparatus for carrying out the method of the present invention, FIG. 2 is an explanatory view of a hydraulic circuit, and FIG. 3 shows the movement of the break ring in the axial direction at the initial stage of casting. Explanatory drawing, FIG. 4 is a longitudinal sectional view showing a state where the square break ring is fitted in the mold, FIG. 5 is an explanatory diagram showing a deformed state of the square break ring, and FIG. 6 shows a connection state of the tundish and the mold. FIG. 7 is a longitudinal sectional view showing the conventional break ring tightening device. 1 ... Tundish, 2 ... Front nozzle, 3 ... Feed tube, 4 ... Mold, 5 ... Break ring, 12 ... Tension cylinder

Claims (1)

[Claims] 1. A tundish having a front nozzle,
When performing horizontal continuous casting by connecting via a feed tube with a mold fitted with a break ring at the end,
Molten steel is poured into the tundish to allow axial movement due to the initial thermal expansion of the break ring, and then a pressing force is applied to apply compressive stress that acts to reduce the tensile stress that acts on the outer peripheral surface of the break ring during casting. A method for tightening a break ring in horizontal continuous casting, which comprises: