JPS6046312A - Multiple layer type porous plug - Google Patents

Abstract

PURPOSE:To heighten stirring effect of molten metals in a vessel by forming inner-most part, intermediate parts, and circumferencial part for a porous plug with porous bodies the air permeability of which is different to each other. CONSTITUTION:The porous plug 3 is formed to a multi-layer type by laminating low air-permeable porous part 13, medium air-permeable porous part 12 and high permeable one 11, which extend from the center to the circumferencial part to form co-axial annual rings. The plug 3 is mounted on the bottom wall 2 of the vessel 1, through which blowing gas 6 is forced into the vessel 1. The blowing-in gas 6 passing through each porous part is injected into molten steel in various energized conditions according to the respective air permeability of the porous parts. Thus the stirring effect is improved with the increased number of circulation flows 5 of the molten steel and by differences in relative speed generated between each of circulation flow of the melt.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method for promoting stirring of molten steel, equalizing the temperature of molten steel, and This invention relates to a porous plug that allows gas to be blown in such a way as to effectively promote the separation and flotation of inclusions or the homogenization of components.

Conventional porous plugs used for the above purposes are made integrally as porous refractories with a single material composition, although there may be slight local deviations in composition or variations in air permeability. Therefore, when gas is blown with the porous plug installed, the flow of gas (bubbles) is dominant in the gas blowing direction and becomes the mainstream, and the flow of molten steel rises in the center and flows along the side walls. It becomes a descending streamline,
Macroscopically, it becomes a circulating flow (5) as shown in FIG.

In other words, when the blowing gas (6) is injected into the charged molten steel using a conventional porous plug (3γ) attached to the bottom wall (2) of the container (1), gas bubble streamlines (4) are formed.
flows along the side wall, and the molten steel @ stirred flow becomes a circulating flow (5). Therefore, the temperature of the molten steel is equalized and the components are homogenized by gas diffusion within each circulating flow or by each circulating flow. This was done only by interacting with the gas only in the central area where the gases were in contact with each other, and the effect of gas injection was extremely poor.

The present invention has been developed in view of the current situation, by complicating the molten steel circulating flow and increasing the number of them, and at the same time varying the flow speed of the circulating flow! It is an object of the present invention to provide a porous plug that can provide a wide variety of stirring conditions brought about by blown gas to molten steel so as to exert an excellent stirring effect on molten steel.

The porous plug of the present invention will be explained below. Main departure,
As a result of observing the behavior of the circulating flow of molten metal caused by blown gas, they found that the number of macroscopic circulating flows and the speed of the circulating flow change depending on the state of the gas bubble flow, and that these are effective in stirring the molten steel. We have confirmed that it makes an effective contribution and have repeatedly studied the possibility of creating a porous plug that can provide a wide variety of gas injection conditions. We have completed various types of porous plugs that enable gas injection with high stirring effects.

That is, one practical example of the porous plug of the present invention is the second example.
As shown in the figure or Fig. 3, porous bodies with different air permeability are
It has a multi-layered annual ring-like structure that shares a common central axis, and its cross section is circular or polygonal.

As shown in Figure 2, from the center toward the outer periphery, the small permeability porous part α, the medium permeability porous negative part (6), and the large permeability porous part (b) are arranged in a coaxial tree ring shape. The porous plug (3) of the present invention is thus formed. The porous plug (3) of the present invention configured as described above is attached to the bottom wall (2) of the container (1).
As shown in Figure 3, the gas (6) passing through the multi-layered porous parts will change the air permeability to small, medium, and small. As a result, the number of circulating flows (5) of the molten steel can be increased, and the stirring effect of the molten steel can be improved due to the relative velocity difference between each circulating flow. It is.

The molten steel stirring flow in this case macroscopically has three circulating flow elements, but in the area a The stirring effect is improved because three types of circulating flows with different temperatures and components are combined.

In addition, in regions b or C, there are circulating flows with different velocities of molten steel outside each region, and these act to reduce the relative velocity between the circulating flows due to the viscosity effect of molten steel. Each circulation flow becomes homogeneous and the entire body moves in circulation, and the bχ stirring function is uniformly applied to each part of the molten steel, further improving the stirring effect.

In order to obtain the multi-layer type porous plug of the present invention, the following manufacturing method can be used. Kneaded clay consisting of the same ingredients and having different particle size distribution or amount of fine powder added in accordance with the desired air permeability is mixed into a circular shape. The product is placed in a mold with a partition plate, and then the partition plate is removed and molded in the same way as a normal porous plug. In this case, as long as the partition plate is combustible and thin, it may be molded using the remaining material without removing it. Furthermore, in order to compose layers having different air permeability, it goes without saying that the porous portions may be made of different materials.

Next, an experimental example will be shown to confirm the effects of the present invention.

Three types of fine powder alumina are added to the basic formulation for porous plugs, which is mainly composed of alumina, and the air permeability is 0.7, 1.0 and 1.5 (cc-cyg/d).
A three-layer type porous plug consisting of porous portions of -5ec-cmH20) and a conventional type porous plug consisting of porous portions of various air permeabilities were manufactured, respectively.

A cylindrical container made of transparent acrylic resin with an inner diameter of 60cw and a height of 1000m was filled with CCZ, which has flow characteristics very similar to molten steel.
Each of the above-mentioned porous plugs was sequentially attached to the bottom wall of the container containing No. 4, and the colorant was dripped into the container while the gas (
In this case, air sound was used) at 3 atm and 2004 per minute.
The amount of time it takes for the coloring agent to be uniformly dispersed was measured by stirring. The results are shown in the graph of FIG. The vertical axis of the graph is the time (seconds) required for sufficient circulation and stirring to reach a uniform state, and the horizontal axis is A, B, and C.
is a conventional type porous plug, A has an air permeability of 0.7,
B has an air permeability of 1.0, C has an air permeability of 1.5, and D
is a multilayer type porous plug (three layers in this experimental example) of the present invention. The required stirring time for each porous plug to be tested is indicated by a black circle if gas is continuously injected at a constant pressure, and by a white circle if gas is intermittently injected at a cycle of 1 second. . In addition, for the multilayer type porous gellag of the present invention, the time required when a fire is used and gas is continuously blown at a constant pressure, contrary to D, is also shown with an X mark.

From this result, the multilayered porous plug of the present invention has a much better stirring effect than the conventional porous plug, and it can be inferred from this tendency that the multilayered porous plug of the present invention has a much better stirring effect than the conventional porous plug with a high air permeability. It is clear that this also contributes to improving operational efficiency.

The graph shown in Figure 4 also shows a three-layer porous plug in which the high permeability porous part and the low permeability porous part are exchanged between the center and the outer layer. The stirring effect is slightly inferior when using a dog. The reason for this is that the gas (bubbles) flow in the center is dominated by upward flow.
It is presumed that this type of atrium is caused by a phenomenon.

In addition, as another example, the innermost part of the small permeability porous part, the medium permeability porous negative part, and the large permeability porous part, each intermediate layer part, and the outer peripheral layer are arranged in concentric circles that share the same axis. Instead of a multilayer body, it is also possible to form a multilayer body with uneven thickness in which the axes of each layer are eccentric from each other. In this type of porous plug, the strength of the blown gas is naturally unevenly distributed, and the circulating flow of molten steel also exhibits various behaviors. Especially when the porous plug is attached to the molten steel container away from the center, An effective stirring function can be achieved by appropriately setting the angle of rotation of the uneven thickness that composes the multi-layer type, and in this example as well, intermittent blowing operation is adopted for the injection of blowing gas. As in the previous embodiment, the stirring effect can be further improved by this method.

As explained above, the multilayer type porous plug of the present invention transforms the monotonous circulating flow with few changing elements seen in conventional porous plugs into a complex and interrelated circulating flow, and further This leads to a state in which the relative speed difference between the circulating flows also contributes, and the stirring effect is greatly improved. It should be noted that the porous plug of the present invention is not limited to the three-layer type mentioned in the embodiment, but can have a multi-layer structure including two layers, and the circulation flow increases in proportion to the number of layers. It is possible to diversify and increase the effect of stirring, and it is also possible to individually select different materials for each layer, and any of these applications or modifications are not included within the technical scope of the present invention. Needless to say.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram when a conventional porous plug is used, and Fig. 2 shows an embodiment of the present invention.
[) is a cut portion, (g) is a longitudinal sectional view, Fig. 3 is an explanatory diagram schematically showing the usage situation when the porous plug of the present invention is installed, Fig. 4 is each porous plug of the present invention and the conventional porous plug. It is a figure showing the experimental result of the usage effect. (1)...Melzer (2)...Bottom wall (3) (3γ...Porous plug (4)...Gas bubble streamline (5)...Circulating flow (6)... Blow-in gas Φ Porous negative part (2) Medium permeability porous negative part 04 Low permeability porous part Fig. 1 CII) Fig. 3 Fig. 4, main part Rough゛≧Kawabetsu

Claims (1)

[Claims] A multilayer porous plug for blowing gas into molten metal, in which the innermost layer, each intermediate layer, and the outer circumference are made of porous materials with different air permeability.