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(11) | EP 0 150 549 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Nozzle for continuous casting |
| (57) The present invention relates to a nozzle for continuous casting, and more particularly
to a nozzle which is capable of uniformly supplying a required amount of gas to the
inner wall surface thereof by providing a plurality of communication holes (14) inside
the nozzle body (10) between the inner surface thereof and a gas pressure balance
chamber (11) disposed inside the nozzle body (10) so as to communicate said chamber
with said inner surface, said communication hole having a square measure corresponding
to that of a circular hole having a diameter of 1.0 mm or less. |
[0002] So far, the gas blow-in type nozzle for continuous casting has been known wherein an inert gas is blown in to an inner surface of the nozzle through the nozzle body so as to form a gas seal on the inner wall surface and prevent the nozzle from clogging. As shown in . Figures 1 and 2, this kind of nozzle has a gap which is made by using such solid material as will disappear during the burning process for manufacturing a nozzle, for example, paper, polypropyrene, nylon, paraffin, etc. Namely the gap is made by providing said material in an appropriate place inside the nozzle body at the time of molding and thereafter burning it down. The gap or gas pressure balance chamber 2 is connected via a gas inlet hole 3 to an inert gas supply source disposed outside the nozzle body 1 while being communicated to the inner surface of the nozzle body via open pores existing therein, whereby the inert gas is made to blow into the space between the inner wall surface and the molten steel. The open pores which communicate the gas pressure balance chamber 2 with the inner surface of the nozzle are naturally formed during the nozzle manufacturing process so that the existence of the open pores is not always uniform and varies according to the manufacturing conditions. Therefore there has arisen a problem that the amount of gas supplied to the inner surface is not constant or uniform. Especially in case that the open pores of less than 5 um in diameter exist more than 50%, it is practically difficult to blow in the gas and impossible to form a perfect gas seal.
Summary of the Invention
[0003] It is an object of the present invention to eliminate the foregoing disadvantages as seen in the conventional gas blow-in type nozzle for continuous casting and to provide a new and useful nozzle capable of uniformly supplying a required amount of gas to the inner wall surface of the nozzle and also capable of continuous casting without clogging the nozzle, by providing a plurality of communication holes in the nozzle body between the gas pressure balance chamber and the inner surface of the nozzle so as to communicate said chamber with said inner surface, said communication hole having a square measure corresponding to that of a circular hole having a diameter of 1.0 mm or less.
Brief Description of the Drawings
[0004]
Figs. 1 and 2 are vertical sectional views showing conventional nozzles;
Figs. 3 and 4 are vertical sectional views showing nozzles according to the present invention.
Detailed Description of the Embodiments
[0005] Referring to Figs. 3 and 4, a nozzle body 10 has a slit-form gap or gas pressure balance chamber 11 which is disposed in an appropriate place inside the nozzle body 10. A gas inlet hole 12 is formed inside the nozzle body 10 so as to connect the gas pressure balance chamber 11 to an inert gas supply source disposed outside the nozzle. Numeral 13 indicates a slag line portion. A plurality of communication holes 14 are formed in the longitudinal and diametrical directions of the nozzle body 10 at appropriate intervals so as to communicate the gas pressure balance chamber to the inner wall surface of the nozzle body 10. The communication hole is 1.0 mm or less in diameter, or preferably the best-suited diameter is 0.03 to 0.5 mm considering the penetration of the molten steel to the communication hole 14 when the inert gas is not blown in. The best-suited sectional shape of the communication hole is a circular one for the purpose of preventing the occurrence of the structural defects of the nozzle, but of course it is to be noted that the sectional shape of the communication hole 14 must not be limited thereto and may be in any shape whatever as long as the square measure of the hole corresponds to that of a circular hole within the scope of the aforementioned size. The present invention is most effective when the nozzle body is mainly made of generally known natural graphite and various kinds of alumina, for example, sintered alumina, d -alumina,/3-alumina, high-alumina materials (mullite, sillimanite, etc.) and chemically composed of 10% to 40% carbon, 40% to 80% alumina and 20% or less silica, etc., with the use of synthetic resin bond as a bonding agent.
[0006] The present invention will be explained hereinbelow with reference to the preferable examples.
Example 1
[0007] When simultaneously using the two immersion nozzles shown in Table 1 for pouring Al-killed steel of Sol-Al 0.070% with ladle having a capacity of 250 ton, the present nozzle was capable of perfectly pouring eight ladles without any adhesion of A1203 while the conventional nozzle was adhered with A1203 when it poured five ladles and incapable of further casting. Thus the remarkable effects of the present nozzle have been confirmed.
Example 2
[0008] When simultaneously using the two immersion nozzles shown in Table 2 for pouring Al-killed steel of Sol-Al 0.05% with ladle having a capacity of 300 ton, the present nozzle was capable of perfectly pouring seven ladles without any adhesion of A1203 while the conventional nozzle was adhered with Al203 when it poured four ladles and incapable of further casting. Thus the remarkable effects of the present nozzle have been confirmed.
1. A nozzle for continuous casting characterised by a gas pressure balance chamber
(11) which is formed annularly inside the nozzle body (10) and connected to the outside
thereof, said gas pressure balance chamber (11) being communicated to the inner wall
surface of the nozzle by means of a plurality of communication holes (14) each having
a square measure corresponding to a circular hole having a diameter of 1.0 mm or less.
2. A nozzle for continuous casting as claimed in Claim 1 characterised in that said
nozzle body (10) has 20% or less porosity and contains 50% or more open pores each
having a diameter of 5 um or less.
3. A nozzle for continuous casting as claimed in Claim 1 or 2 characterised in that
said communication hole (14) has a square measure corresponding to a circular hole
having a diameter of 0.03 to 0.5 mm.