JP5697193B2 - Nozzle for gas injection - Google Patents

Description

  The present invention relates to a gas blowing nozzle having a function of blowing gas into a nozzle inner hole from the surface of the nozzle inner hole through which molten metal passes.

  The nozzle for transferring the molten steel to the next process from the molten steel container such as a ladle or tundish has a nozzle inner hole through which the molten steel passes, but the surface of the nozzle inner hole adheres with alumina or the like precipitated from the molten steel, There is a problem that nozzle clogging occurs. As a measure to prevent this nozzle clogging, a gas blowing nozzle has been conventionally used which has a nozzle body made of a breathable refractory and has a function of blowing an inert gas such as nitrogen or argon from the surface of the nozzle inner hole into the nozzle inner hole. Is used (for example, Patent Document 1).

  FIG. 3 is a sectional view showing the bottom of a tundish to which a conventional gas blowing nozzle is applied. An upper nozzle 2 is fitted as a gas blowing nozzle into a tuyere 1 a provided at the bottom of the tundish 1, and a sliding nozzle device 3 for controlling the flow rate of molten steel is installed on the lower surface side of the upper nozzle 2.

  The nozzle body 2a of the upper nozzle 2 is made of a breathable refractory and has a nozzle inner hole 2b through which molten steel passes at the center. The outer peripheral surface of the nozzle body 2a is surrounded by a metal case 2c with a gap, and the space between the outer peripheral surface of the nozzle body 2a, the inner peripheral surface of the metal case 2c, and a sealing material 2e such as mortar is a gas pool. 2d. A gas supply pipe 4 is connected to the gas pool 2b via a metal case 2c. The gas supplied from the gas supply pipe 4 fills the gas pool 2b, passes through the nozzle body 2a, and is blown into the nozzle inner hole 2b from the surface of the nozzle inner hole 2b.

  In such an upper nozzle 2 (gas blowing nozzle), a blowing back pressure of about 0.1 to 0.2 MPa is normally applied to the gas pool 2d. On the other hand, during casting, the metal case 2c becomes a high temperature of 800 ° C. or higher, and when subjected to back pressure in the high temperature region, the metal case 2 is easily deformed and gas leaks. This reduction in back pressure due to gas leakage causes a reduction in gas blowing function or a reduction in gas blowing uniformity, which is one of the problems that the gas blowing nozzle has.

  In order to prevent gas leakage due to the above-described deformation of the metal case in the gas blowing nozzle, it is conceivable that the gas pool is formed in a slit shape inside the nozzle body, not between the metal case and the nozzle body. .

  However, when forming a slit to be a gas pool by a common uniaxial molding method as a method for manufacturing a gas blowing nozzle, there is a limit to securing the length in the height direction. That is, in the uniaxial molding method, a molding pressure is applied in the height direction of the gas blowing nozzle, so that it is difficult to form a long slit in the height direction. When the length in the height direction of the slit is limited, it is impossible to meet the requirement of blowing gas uniformly from the whole in the height direction of the nozzle inner hole.

  Note that FIG. 1 of Patent Document 1 shows an example in which a slit-like gas pool that is relatively long in the height direction is formed inside the nozzle body, which employs a special manufacturing method. In addition, even in this example, the gas pool cannot be formed over the entire height direction of the nozzle inner hole, so that it is sufficient to meet the requirement of blowing gas uniformly from the whole in the height direction of the nozzle inner hole. Can not. Further, since a special manufacturing method is adopted, the cost is increased.

Japanese Utility Model Publication No. 6-19966

  The problem to be solved by the present invention is to provide a gas blowing nozzle that is less likely to cause gas leakage and that can blow gas uniformly from the whole in the height direction of the nozzle inner hole.

The present invention has a nozzle inner hole through which molten metal passes, and in a gas blowing nozzle for blowing gas from the surface of the nozzle inner hole, a second is provided on the outer peripheral side of the first breathable refractory having the nozzle inner hole. A breathable refractory is disposed, the first breathable refractory and the second breathable refractory are in direct contact, and a metal case is disposed on the outer peripheral side surface of the second breathable refractory and, wherein between the second outer circumferential side surface and the metal case of the gas-permeable fireproof material and sealing material filled, connects the gas supply pipe to the second gas-permeable fireproof material, said second The average pore diameter of the breathable refractory is larger than the average pore diameter of the first breathable refractory.

  Here, the “average pore diameter” means an average pore diameter (average pore diameter) measured with a mercury porosimeter.

  In the gas blowing nozzle according to the present invention, the average pore diameter of the second breathable refractory disposed on the outer peripheral side of the first breathable refractory is larger than that of the first breathable refractory, and the airflow resistance is small. The second breathable refractory works as a gas pool for supplying gas to the first breathable refractory. This makes it possible to fill the entire mortar between the metal case and the refractory (no need to provide a gas pool), so that the gas blowing pressure that deforms the metal case is not applied to the metal case. Gas leakage is suppressed.

  In addition, by disposing the second breathable refractory serving as a gas pool almost entirely on the outer peripheral side of the first breathable refractory, the height of the nozzle bore formed in the first breathable refractory is increased. It becomes possible to blow gas uniformly from the whole in the direction.

It is sectional drawing which shows an example of the nozzle for gas blowing of this invention. It is sectional drawing which shows the other example of the nozzle for gas blowing of this invention. It is sectional drawing which shows the bottom part of the tundish to which the nozzle for conventional gas blowing is applied.

  Embodiments of the present invention will be described below based on examples shown in the drawings.

  FIG. 1 is a cross-sectional view showing an example of a gas blowing nozzle according to the present invention. A gas blowing nozzle 2 shown in FIG. 1 is used by being fitted into a tuyere provided at the bottom of a tundish as an upper nozzle, similarly to the conventional gas blowing nozzle shown in FIG.

  The nozzle body 2a of the gas blowing nozzle 2 shown in FIG. 1 includes a first breathable refractory 2a-1 having a nozzle inner hole 2b through which molten steel passes in the center, and a first breathable refractory 2a-1. It consists of the 2nd breathable refractory 2a-2 arrange | positioned without leaving a space | interval in the outer peripheral side.

  The outer periphery of the second breathable refractory 2a-2 is covered with a metal case 2c through a sealing material 2e. That is, the sealing material 2e is filled between the outer peripheral surface of the second breathable refractory 2a-2 and the inner peripheral surface of the metal case 2c, and there is no gas pool here. On the other hand, the gas supply pipe 4 penetrates the metal case 2d and the sealing material 2e and is connected to the second breathable refractory 2a-2. As described later, the second breathable refractory 2a-2 is Has the effect of a gas pool.

  In the present invention, since the second breathable refractory 2a-2 has a gas pool action, the average pore diameter of the second breathable refractory 2a-2 is the first breathable refractory 2a-1. Larger than the average pore diameter. Preferably, the average pore diameter of the first breathable refractory 2a-1 is less than 50 μm, and the average pore diameter of the second breathable refractory 2a-2 is 70 μm or more. When the average pore diameter of the first breathable refractory 2a-1 is 50 μm or more, the bubble diameter of the gas blown into the molten steel becomes large, so a large gas flow rate is required when trying to discharge the gas from the entire nozzle. It becomes. When the flow rate of the blown gas increases, the molten metal surface in the mold may boil and the operation may become unstable. Furthermore, the surface area with respect to the flow rate of the blown gas is reduced, and the chance of capturing fine alumina particles suspended in the molten steel with gas bubbles is reduced. On the other hand, if the average pore diameter of the second breathable refractory 2a-2 is less than 70 μm, the difference in breathing resistance with the first breathable refractory 2a-1 becomes small, and the second breathable refractory 2a- 2 may not sufficiently function as a gas pool for diffusing the gas from the supply position to the whole. More preferably, the average pore diameter of the first breathable refractory 2a-1 is 10 μm or more and less than 50 μm, and the average pore diameter of the second breathable refractory 2a-2 is 70 μm or more and 200 μm or less.

  As described above, since the second breathable refractory 2a-2 has a smaller airflow resistance than the first breathable refractory 2a-1, the second breathable refractory 2a-2 is connected to the second breathable refractory 2a-2 from the gas supply pipe 4. By supplying the gas directly, the second breathable refractory 2a-2 has the same effect as the conventional gas pool. That is, the gas supplied from the gas supply pipe 4 is once filled in the second breathable refractory 2a-2 and then supplied to the first breathable refractory 2a-1, and the surface of the nozzle inner hole 2b. To the nozzle inner hole 2a.

  In the present embodiment, as shown in FIG. 1, the nozzle body 2a is arranged by arranging the second breathable refractory 2a-2 on the outer peripheral side of the first breathable refractory 2a-1 without a gap. In such a nozzle body 2a, a cylindrical partitioning jig is attached to a molding die, and the composition of particle size is adjusted (adjusted average pore diameter is adjusted). Can be manufactured by applying pressure to the inside and outside of the partitioning jig, removing the partitioning jig, and pressurizing.

  The average pore diameter of the first and second breathable refractories can be adjusted by changing the particle size constitution of the blend (kneaded product). That is, if the particle size composition of the blend is coarsened, the average pore diameter is large, and if the particle size composition is fine, the average pore diameter is small. The first and second breathable refractories are generally breathable refractories containing one or more of alumina, silica, mullite, magnesia, spinel, etc. as a main component and containing zirconia-containing raw materials, chromia, etc. Any material can be used.

  Further, in this embodiment, the upper end portion of the nozzle body 2a exposed without being covered with the metal case 2c to be in contact with the molten steel during use is formed of the first breathable refractory 2a-1. This is because if this portion is formed of the second breathable refractory 2a-2, the gas escapes from the upper end of the nozzle body 2a. However, since the second breathable refractory 2a-2 serving as a gas pool is arranged on the entire outer peripheral side of the first breathable refractory 2a-1 except for the upper end portion of the nozzle body 2a, the nozzle Gas can be uniformly blown from the whole in the height direction of the inner hole 2b.

  FIG. 2 is a sectional view showing another example of the gas blowing nozzle of the present invention. In this embodiment, the first breathable refractory 2a-1 is thickened so that the second breathable refractory 2a-2 is not exposed at the upper end of the nozzle body 2a. Thereby, gas can be blown uniformly from the whole in the height direction of the nozzle inner hole 2b while preventing the gas from escaping from the upper end of the nozzle body 2a.

  The gas blowing nozzle of the present invention can be used not only as an upper nozzle used at the bottom of a tundish but also as an upper nozzle used at the bottom of a ladle.

1 Tundish 1a Tuyere 2 Gas blowing nozzle (upper nozzle)
2a Nozzle body 2a-1 1st breathable refractory 2a-2 2nd breathable refractory 2b Nozzle hole 2c Metal case 2d Gas pool 2e Sealing material 3 Sliding nozzle device 4 Gas supply pipe

Claims (2)

In the nozzle for gas blowing, which has a nozzle inner hole through which the molten metal passes, and blows gas from the surface of the nozzle inner hole,
Disposing a second breathable refractory on the outer peripheral side of the first breathable refractory having a nozzle inner hole;
The first breathable refractory and the second breathable refractory are in direct contact;
A metal case is disposed on the outer peripheral side surface of the second breathable refractory, and a sealant is filled between the outer peripheral side surface of the second breathable refractory and the metal case,
A gas supply pipe is connected to the second breathable refractory;
A gas blowing nozzle, wherein an average pore diameter of the second breathable refractory is larger than an average pore diameter of the first breathable refractory.   2. The gas blowing nozzle according to claim 1, wherein an average pore diameter of the first breathable refractory is less than 50 μm and an average pore diameter of the second breathable refractory is 70 μm or more.

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