JP6813471B2 - Refractory nozzle - Google Patents

Description

The present invention relates to refractory nozzles used in continuous steel casting.

In continuous steel casting equipment, when transferring molten steel from a ladle to a tundish, which is an intermediate container, a dedicated refractory nozzle (also called a "long nozzle") is used to prevent oxidation of the molten steel. There is. The refractory nozzle is formed of a refractory material of a different material depending on the place of use, such as an inner hole portion, a dipping portion immersed in molten steel, and a main body portion not immersed in molten steel. Further, an iron skin covering the outer circumference of the main body may be attached to the upper part of the main body formed of refractories made of different materials for reinforcement.

For such a refractory nozzle, it is important to prevent the adhesion of alumina to the inner hole side and the cracking and breakage due to thermal stress. For example, in Patent Document 1, a swivel vane is installed in the inner hole of the dipping nozzle as a method of preventing the adhesion of alumina to the dipping nozzle used when transferring molten steel from a tundish of a continuous casting facility to a mold. The method of doing so is disclosed. Further, Patent Documents 2 and 3 disclose a method of optimizing the shape of a main body made of a refractory as a method of improving the durability of a refractory nozzle.

International Publication No. 2005/018851 Japanese Unexamined Patent Publication No. 2012-91235 JP-A-2015-123473

By the way, in the refractory nozzle used in continuous steel casting, from the viewpoint of durability, it is necessary to prevent breakage due to stress concentration caused by parts attached to the main body such as iron skin for reinforcement. .. In particular, when the refractory nozzle is provided with a reinforcing iron skin, stress is concentrated on the lower end of the iron skin, and the refractory nozzle may be broken. On the other hand, in the methods of Patent Documents 2 and 3, the stress at the lower end of the iron skin could not be relaxed, and the breakage could not be prevented. It is also possible to analyze the stress generated at the lower end of the iron skin and change it to a shape that relieves the stress, but the shape of the refractory nozzle has a large effect on operations and the quality of molten steel (products). It was not easy to achieve both shape and durability in consideration of these effects. Further, it is conceivable to reduce the weight of the refractory nozzle as a method of relieving the stress, but the problem is that the service life is reduced.

Therefore, the present invention has been made by paying attention to the above-mentioned problems, and prevents breakage due to stress concentration at the lower end of the iron skin without changing the shape of the refractory body of the refractory nozzle. It is intended to provide a refractory nozzle capable of providing.

According to one aspect of the present invention, it is a refractory nozzle used for continuous casting of steel, which is provided on a cylindrical main body made of refractory and an upper part in the vertical direction which is the extending direction of the main body. The refractory nozzle is provided with an iron skin covering the outer periphery of the main body, and the iron skin is characterized in that a plurality of notches including a curved portion are formed at the lower end in the vertical direction.

According to one aspect of the present invention, there is provided a refractory nozzle capable of preventing breakage due to stress concentration at the lower end of the iron skin without changing the shape of the refractory main body of the refractory nozzle. ..

It is a front view which shows the refractory nozzle which concerns on one Embodiment of this invention. It is sectional drawing which shows the refractory nozzle which concerns on one Embodiment of this invention. It is a development view which shows the iron skin. It is a schematic diagram which shows the continuous casting equipment. It is a developed view which shows the iron skin in the modification. It is a graph which shows the stress index in an Example and a comparative example. It is explanatory drawing which shows the test method in an Example. It is a graph which shows the breakage limit pressure index in an Example.

The following detailed description describes many specific details to provide a complete understanding of embodiments of the present invention. However, it will be clear that one or more embodiments can be implemented without such specific details. In addition, well-known structures and devices are shown in schematics to simplify the drawings.

<Refractory nozzle>
First, the refractory nozzle 1 according to the embodiment of the present invention will be described with reference to FIGS. 1 to 4. As shown in FIGS. 1 and 2, the refractory nozzle 1 includes a main body 2 and an iron skin 3.
The main body 2 is a cylindrical fireproof material, and the lower end side in the vertical direction (vertical direction in FIGS. 1 and 2), which is the extending direction, has an outer diameter and an outer diameter as compared with the center in the vertical direction (also referred to as "neck"). It is formed so that the inner diameter is large. Further, as will be described later, the upper end side of the main body 2 is formed in a flange shape so that the outer diameter is larger than that of the neck portion so that it can be held by a fixing device that holds the refractory nozzle 1 during use. Further, the upper end side of the main body 2 is formed so that the inner diameter is larger than the inner diameter of the neck portion so that it can be fitted with the sliding plate of the ladle, as will be described later. The main body 2 is normally used in continuous casting equipment, and has a refractory on the inner hole side, a refractory on the lower surface to be immersed in molten steel during use, and a refractory on the upper end side that fits into a ladle. The object and the refractory on the central surface are composed of refractories having different compositions and properties depending on the required characteristics.

The iron skin 3 is an iron cylindrical member formed on the upper portion of the main body 2 so as to cover the outer circumference of the upper portion of the main body 2. The length at which the iron skin 3 is provided is such that it is not affected by heat from the molten steel in the tundish during use and that deformation of the upper side of the neck of the main body 2 due to vibration during use is suppressed. As shown in FIGS. 1 and 3, the iron skin 3 is provided with six arc-shaped notches 31 at equal intervals at the lower end.

Such a refractory nozzle 1 is used in the continuous casting facility shown in FIG. As shown in FIG. 4, in the continuous casting facility, slabs and blooms are produced by casting the molten steel 5 that has been refined and housed in the ladle 4. At this time, the molten steel 5 housed in the ladle 4 is transferred to the tundish 6 through the tuyere 41 provided at the bottom of the ladle 4, the sliding plate 42 for adjusting the injection amount, and the refractory nozzle 1. To. The molten steel 5 transferred to the tundish 6 is then transferred from the tundish 6 to a mold (not shown) and solidified into a predetermined shape to form a slab.
In such a continuous casting facility, the refractory nozzle 1 is held in a state where the upper end is fitted to the sliding plate 42 of the ladle 4 and pressed upward by a fixing device (not shown).

<Modification example>
Although the present invention has been described above with reference to specific embodiments, it is not intended to limit the invention by these descriptions. By referring to the description of the present invention, other embodiments of the present invention will be apparent to those skilled in the art as well as various variations of the disclosed embodiments. Therefore, it should be understood that the scope of claims also covers these modifications or embodiments included in the scope and gist of the present invention.

For example, in the above embodiment, the notch 31 of the iron skin 3 has an arc shape, but the present invention is not limited to such an example. The notch 31 of the iron skin 3 includes a curved portion, and may have another shape as long as a plurality of notches 31 are provided. For example, as shown in FIG. 5, the notch 31 of the iron skin 3 may be notched in a wavy shape in which adjacent notches 31 are connected by a curve. As will be described later, in the refractory nozzle 1, the lower end of the iron skin 3 is notched in a curved shape, so that the stress applied to the lower end of the iron skin 3 can be relaxed. Therefore, the shape and dimensions of the notch 31 are appropriately selected according to the force applied to the refractory nozzle 1 during use, the workability of the iron skin 3, and the like.
Further, the shape and material of the main body 2 are not limited to the above-described embodiment, and other shapes and materials may be used as long as they are generally used in a continuous casting machine.

<Effect of embodiment>
(1) The refractory nozzle 1 according to one aspect of the present invention is a refractory nozzle 1 used in continuous casting of steel, and is a refractory cylindrical main body 2 and a extending direction of the main body 2. The iron skin 3 is provided on the upper part in the vertical direction and covers the outer periphery of the main body 2, and the iron skin 3 is formed with a plurality of notches 31 including a curved portion at the lower end in the vertical direction.

Here, the refractory nozzle 1 is used in a state where the upper end of the main body 2 is pressed against the sliding plate 42 of the ladle 4 at the time of casting the molten steel 5 to be used, as shown in FIG. At this time, since the molten steel 5 passes through the refractory nozzle 1 in the vertical direction (vertical direction in FIG. 4), the main body 2 receives a force from the horizontal direction orthogonal to the vertical direction with the upper end fixed and vibrates. .. Therefore, when the refractory nozzle 1 is only the main body 2, the upper end side of the neck portion held by the fixing device is the portion where the stress is greatest. However, when the refractory nozzle 1 is provided with the iron skin 3, the iron skin 3 suppresses the deformation of the upper end side of the neck portion, so that the lower end of the iron skin 3 is the place where the stress is greatest.

On the other hand, according to the configuration of (1) above, the curved notch 31 is formed at the lower end of the iron skin 3, so that even if the main body 2 is elastically deformed due to vibration during casting, the main body 2 The iron skin 3 is easily elastically deformed according to the deformation. Therefore, for example, as compared with the case where the lower end of the iron skin 3 is straight as in the conventional case, the stress of the neck portion of the main body 2 in contact with the lower end of the iron skin 3 is relaxed, so that the neck portion of the main body 2 is broken. Can be prevented. Further, according to the configuration of (1) above, since it is not necessary to change the shape of the main body 2, there is no influence on the operation and the quality of the molten steel (product).
(2) In the configuration of (1) above, the notch 31 has an arc shape.
According to the configuration of (2) above, the notch 31 of the iron skin 3 can be easily processed.

Next, the examples carried out by the present inventors will be described. In the examples, with respect to the refractory nozzle 1 shown in FIGS. 1 to 3, when a load was applied in the horizontal direction, the stress generated at the portion of the main body 2 in contact with the lower end of the iron skin 3 was numerically analyzed. Further, as a comparative example, the refractory nozzle 1 having a linear lower end without providing the notch 31 was also subjected to numerical analysis under the same conditions, and the generated stress was compared.

FIG. 6 shows the analysis results of the examples. The vertical axis of FIG. 6 is an index of the maximum stress on the surface of the main body 2 in contact with the lower end of the iron skin 3. In the examples, the stress value of the comparative example was set to 1 for indexing. As shown in FIG. 6, it was confirmed that the stress was relaxed by about 1.4% in the examples as compared with the comparative examples. From this, by providing a notch 31 having a curved portion at the lower end of the iron skin 3, the stress at the lower end of the iron skin 3 is relaxed, and breakage due to stress concentration at the lower end of the iron skin 3 can be prevented. It was confirmed that it could be done.

Further, as an example, the inventors have heated the refractory nozzle 1 and then applied a load to the refractory nozzle 1 to investigate the force leading to breakage and the breakage position. In the embodiment, first, the refractory nozzle 1 was heated by using the heating device 7 shown in FIG. 7. The heating device 7 has a heating furnace 70 for heating the inside and a holder 71 for supporting the refractory nozzle 1. In heating the refractory nozzle 1, the holder 71 supports the upper end of the refractory nozzle 1, the lower end side of the refractory nozzle 1 is installed in the heating furnace 70, and the heating furnace 70 heats the refractory nozzle 1. Heating was performed until the refractory nozzle 1 inside was about 1000 ° C. After that, the heated refractory nozzle 1 was taken out from the heating furnace 70, and a load was applied horizontally to the lower end of the taken out refractory nozzle 1 using a hydraulic piston to break the refractory nozzle 1. At this time, the force at which the refractory nozzle 1 leads to breakage and the breakage position were evaluated. Further, as a comparative example, a refractory nozzle having a linear lower end without providing a notch 31 at the lower end of the iron skin 3 was also tested under the same conditions as in the embodiment, and the force leading to breakage and the breakage position were determined. Compared.

FIG. 8 shows the test results in Examples and Comparative Examples. The vertical axis of FIG. 8 shows a value (breakage limit pressure index) obtained by indexing the stress of the comparative example as 100 as the pressure at which the main body 2 has broken. Similar to the result of the numerical analysis of FIG. 6, it was confirmed that the example can withstand a stress 12% higher than that of the comparative example. That is, according to the present invention, it was confirmed that the breakage of the refractory nozzle 1 can be suppressed without changing the shape, material, or the like of the main body 2.

Further, in the comparative example, it was confirmed that the broken position of the refractory nozzle is 30 from the upper end when the total length of the refractory nozzle is quantified as 100. On the other hand, in the embodiment, it was confirmed that the broken position of the refractory nozzle is 40 from the upper end when the total length of the refractory nozzle is quantified as 100. That is, it was confirmed that the broken position was changed by providing the notch 31 at the lower end of the iron skin 3 and changing the shape. Since the breakage position differs depending on the shape of the lower end of the iron skin 3, it was assumed that the breakage of the refractory nozzle could be further prevented by grasping the breakage position in advance and further changing the shape of the main body 2.

1 Refractory Nozzle 2 Main Body 3 Iron Skin 31 Notch 4 Ladle 41 Tue 42 Sliding Plate 5 Molten Steel 6 Tundish 7 Heating Device 70 Heating Furnace 71 Holder

Claims (1)

A refractory nozzle used in continuous steel casting
A cylindrical body made of refractory and
It is provided on the upper part in the vertical direction, which is the extending direction of the main body, and is provided with an iron skin that covers the outer periphery of the main body.
The iron skin is a refractory nozzle characterized in that a plurality of arc-shaped notches are formed at the lower ends in the vertical direction .

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