JP2826953B2 - Casting method for tundish upper nozzle - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for casting a tundish upper nozzle used in a tundish for continuous casting of steel. 2. Description of the Related Art At the present time, when a molten metal is poured into a mold from a tundish, gas bubbling by an upper nozzle is widely practiced as a measure for preventing nozzle clogging due to precipitation of inclusions such as Al ₂ O _3. Further, gas bubbling can be performed very effectively by a two-stage type upper nozzle in which the gas blowing amount is independently adjusted vertically. [0003] However, even in the upper nozzle having the above-mentioned structure, unless gas leakage is completely prevented, effective blowing of gas cannot be performed, and there is a limit in preventing nozzle blockage. In addition, in the case of a conventional porous body or non-porous body, it is not possible to directly connect a gas introduction pipe to the upper porous portion, and at present, a gas pool is formed on the nozzle side surface to communicate with the upper porous refractory. And a gas introduction pipe is arranged. As shown in FIG. 1, after the porous refractory 1 and the non-porous refractory 2 are integrally formed, a small gap between the outer periphery of the main body and the metal case 3 is provided in a small gap as shown in FIG. It is performed by filling the adhesive mortar 4 and setting it integrally. However, the mortar 4 shrinks and deforms due to heat history during actual use, and a gap is formed between the metal case 3 and the main body, which causes gas leakage. [0005] As a problem to be solved by the present invention, a method for preventing gas leakage as in the prior art and performing effective gas bubbling is studied, and a method for forming the refractory is described. It also seeks to provide an example of. SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the gist of the present invention is to provide a tundish upper nozzle having a gas blowing function, in which an outer peripheral portion of a main body is provided. The outer peripheral surface of both upper and lower porous refractories, which are surrounded by a metal case and installed on the inner surface of the nozzle, are covered with steel shell via a gas pool that passes directly through the gas introduction pipe, Between the cases,
A casting method for a tundish upper nozzle, characterized by being filled with a castable dense refractory material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The following method is conceivable as a method of casting the upper nozzle. First, as shown in FIG. 2, the outer peripheral surfaces of the porous refractories 1 a and 1 b are previously covered with steel shells 2 a and 2 b via a gas pool 5, and are installed at the gas blowing locations inside the metal case 3. Thereafter, the gas introduction pipe 6 is also set in advance. Next, as shown in FIG. 3, the porous refractory main body surrounded by the metal case 3 is fixed to the casting jig 7 upside down. At this time, it is desirable to seal the lower end 9 in order to prevent the castable dense refractory material 8 from flowing out from the lower end of the main body during the casting. Then, the castable jig is set on a vibrating table 10 and the castable dense refractory material 8 which has been previously kneaded by a mixer is applied to the metal case 3 at the bottom of the nozzle body and the porous body while giving an appropriate vibration. It is thrown in from the gap between the high quality refractory 1b. Since the porous refractories 1a and 1b arranged facing the inner surface of the gas blowing hole are partially arranged, the boundary with the castable dense refractory material 8 is in direct contact with the molten metal. Therefore, in order to prevent gas leak from that portion, it is desirable that the castable refractory material 8 slightly penetrates into the boundary between the porous refractories 1a and 1b. Therefore, sufficient consideration must be given to the casting time. For example, if the water content is excessive, the casting time is certainly shortened, but the effective gas injection cannot be performed due to excessive penetration into the porous refractory. On the other hand, if the amount is too small, there is a problem in proper penetration into porous refractories and workability. Paying attention to the above items, castable dense refractory material 8
Is charged to a predetermined position, and the process is completed through steps such as natural drying, demolding, and forced drying. The method for filling the castable dense refractory material is not limited to the above-mentioned casting method. As described above, in this embodiment, the castable dense refractory material 8 is filled between the porous refractory material 1a, 1b and the metal case 3 by the casting method. Since the dense refractory material 8 has a small heat shrinkage and a high strength, it can effectively prevent gas leakage. Next, a test example of the present embodiment having the above configuration will be described. In the present embodiment, the gas introduction pipe 6 is directly connected to the porous refractories 1a and 1b at both the upper and lower portions of the nozzle body via the gas pool 5 by the covered steel shells 2a and 2b. For this reason, the gas is effectively discharged from the porous refractories 1a and 1b.
The upper nozzle having such a configuration was compared with a conventional example having a structure in which mortar was filled between a porous refractory and a steel shell. The test method investigated the change of back pressure due to heating of the upper nozzle. In this case, heating was carried out with a gas burner and 3.0.
While flowing the air pressure of 1 / min, the temperature inside the nozzle hole was raised to 1600 ° C. and maintained for 3 hours. Table 1
This shows the change with time of the back pressure of the upper nozzle, and as is apparent from this, it can be seen that according to the present embodiment, the back pressure of the upper nozzle does not decrease and gas leak can be effectively prevented. [Table 1] It goes without saying that the tundish upper nozzle according to the present invention can be applied to either an extrapolation type or an interpolation type. As described above, the porous refractory can be freely installed at an arbitrary gas blowing position by the tundish upper nozzle according to the present invention, and each gas pool is surely made independent. Can prevent the inclusion of inclusions. In addition, gas lean from the castable-metal case boundary and the porous-castable boundary can be effectively prevented, and as a result of effective gas injection,
The back pressure of the upper nozzle during use is not reduced, inclusions can be effectively removed, and nozzle blockage can be effectively prevented.
Industrial applicability is great.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing a tundish upper nozzle of a conventional porous body and a non-porous body integrally molded product. FIG. 2 is a longitudinal sectional view showing one embodiment of a forming process of a tundish upper nozzle according to the present invention. FIG. 3 is an explanatory diagram showing an example of a step of filling a castable dense refractory material between a main body porous refractory and an outer peripheral metal case. FIG. 4 is a longitudinal sectional view showing one embodiment of a tundish upper nozzle according to the present invention. [Description of Signs] 1 Porous refractory 2 Non-porous refractory 1a, 1b Porous refractory 2a, 2b Inner skin 3 Outer metal case 4 Mortar 5 Gas pool 6 Gas inlet pipe 7 Casting jig 8 Castable Dense fireproof material 9 Metal case lower end 10 Shaking table

Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) B28B 1/26 101 B22D 11/10 320 B22D 11/10 360 B22D 41/52 B22D 41/58

Claims (1)

(57) [Claims] In a tundish upper nozzle having a gas blowing function, the outer periphery of the main body is surrounded by a metal case, and both upper and lower porous refractories are freely installed on the inner surface of the nozzle. Then, the outer peripheral surfaces are covered with steel skin via gas pools that pass directly to the gas introduction pipes independently, and the castable dense refractory material is filled between the outer peripheral part of the main body and the metal case. Casting method for a tundish upper nozzle.