JPS6159829B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to containers such as ladles and tundishes for transporting or temporarily retaining molten metal, in which the molten metal is poured out using a sliding nozzle type (not a stopper nozzle type) opening/closing device. The present invention relates to a method for opening a spouting channel in a case where the spouting channel is opened.

As is well known, the opening/closing device for a molten metal container uses hydraulic or electric power to slide or rotate a plurality of refractory plates attached under the upper nozzle brick for dispensing provided at the bottom of the container. , is a device that controls the flow rate of molten metal by adjusting the opening degree of the hole drilled in the plate, but when molten steel is first received into the container, a long and slender cylindrical upper nozzle brick attached to the bottom of the container First, molten steel falls into the nozzle hole of the pouring nozzle and is filled, but the molten steel in the nozzle hole cools and solidifies until the container is filled with a predetermined amount and the pouring operation begins. The nozzle hole is often blocked, which makes pouring out molten steel, that is, casting work, difficult.

In order to prevent this, it is common practice to fill the nozzle hole of the upper nozzle brick with powder refractory in advance and perform the first steel receiving. To explain this with drawings, Figure 1 is a partial longitudinal side view of the bottom of the molten metal container, where 1 is the bottom refractory of the container, 2 is the outer shell, 3 is the upper nozzle brick, 4 is the nozzle hole, 5
6 is a sliding opening/closing device (flow control device) with a fixed plate brick on the top and a sliding plate brick on the bottom, and 6 is a collector nozzle for consolidating the falling direction of the poured steel. 7 is the molten steel contained in the container, and 8 is the powder refractory filled in the nozzle hole. That is, when the flow rate control device 5 is set to "fully open" after receiving the molten steel 7 , the powder refractory 8 first falls through the collector nozzle 6, and then the molten steel 7 in the uncooled container flows naturally without any artificial means. Although the nozzle hole 4 is sometimes blocked and does not open even in this method, the natural opening ratio remains at 70 to 90%.

To explain the reason why it does not open using a schematic diagram, FIG. 2 is a vertical cross-sectional view showing the upper part of the powder refractory 8 packed in the nozzle hole 4 of the upper nozzle brick 3 in FIG. Figure b shows the state before receiving the steel, and the state shown several minutes after receiving the steel.
~165℃) penetrates into the surface layer of the powder refractory 8 , and the powder refractory 8 , whose main component is silicic acid (SiO ₂ ), is sintered by the heat of the molten steel and becomes a hard wall. The molten steel is cooled down.

Eventually, a portion of the surface layer becomes vitrified as shown at 9 in Fig. c. As the molten steel residence time increases, the molten steel above the powder refractory is further cooled and solidified, and the sintered layer 9 becomes thicker and stronger, so even if the powder refractory is dropped, it remains strong as shown in Figure d. The sintered solidified bridge 10 is suspended in the air and is difficult to break due to the static pressure of the molten steel 7 alone.

The formation of such a solidification bridge 10 depends on factors such as the temperature of the molten steel, the residence time of the molten steel in the container, the stirring condition of the molten steel, the refractory degree and packing area of the powder refractory, and the thickness, strength, and shape of the bridge. The bridge may or may not be destroyed due to the influence of complex factors such as the static pressure of molten steel (approximately 100 to 200 kg/ ^cm2 ) which varies depending on the size and type of container, so the nozzle hole The natural aperture ratio will fluctuate.

If the bridge 10 does not open naturally as planned, the bridge 10 must be destroyed manually. Normally, this work is carried out by inserting an iron pipe from the bottom of the switchgear and blowing oxygen onto the suspended bridge to generate high temperature and melt it. A collector nozzle is installed, and recently a longer nozzle has been installed below it to prevent air oxidation during pouring and casting of molten steel, making it extremely difficult to open the hole manually. Not only is this dangerous, but it is also dangerous and may damage the refractory material in the nozzle hole. In addition, if such opening work takes time, the casting work will not proceed smoothly, and especially in continuous casting operations using the continuous casting method, the supply of molten steel will be interrupted between the front ladle and the rear ladle, making it difficult to operate the entire continuous casting machine. This causes the inconvenience of having to restart the operation by resetting the steel receiving system from the beginning.

Therefore, each company uses the natural aperture ratio of the nozzle hole mentioned above.
In order to get close to 100%, the following methods are used as appropriate.

In order to minimize the penetration of molten steel into the refractory particles, the grain size of the sand is made as small as possible and the filling surface is made as flat as possible by eliminating unevenness.

In order to suppress the floating of refractory particles and their sintering and vitrification, silicic acid (SiO ₂ ) particles are switched to zirconia (ZrO ₂ ) particles, which have a large specific gravity and high fire resistance.

By increasing the amount of refractory particles to be filled and widening the upper surface, the area of the bridge is increased, thereby weakening the support strength and making it easier to break under loads from above.

Even with the methods described above, the natural aperture rate remains at around 90%, and a complete solution has not yet been reached.

Next, as mentioned above, it was found through experiments that another factor causing the natural aperture ratio to fluctuate and decrease is the shape of the nozzle hole in the upper nozzle brick. That is, as shown in FIG. 1, the conventional nozzle hole 4 has a cylindrical hole that is wider at the top and narrower at the bottom.
When the solidification bridge 10 is pushed down by the load of the molten steel 7 at the time shown in FIG. d, the bridge, which is a solid solution, is compressed because of its narrow shape at the bottom. Therefore, even if the bridge is pushed down by the falling powder refractories (in most cases the center part is pulled first) and the molten steel flows down through the gap created in the bridge, the above-mentioned compressed Since the molten steel is blocked by the bridge and stagnates there, the molten steel further solidifies, thereby preventing the molten steel from falling roughly.

Furthermore, since the shape of the nozzle hole is wide and narrow at the top and bottom, the falling powder refractory has an extremely slow flow rate due to the resistance of the peripheral wall and the collision phenomenon at the bottom. In addition, the shrinkage of the powder refractory flows into the center of the hole like a hell of ants, so even if new molten steel flows down into the narrow area created here, it is blocked by the powder refractory and solidifies. It turned out that I would.

Therefore, the inventors prototyped an upper nozzle brick in which the nozzle hole was narrower at the top and wider at the bottom, and conducted a molten steel pouring experiment. As a result, the opening of the nozzle hole was extremely smooth. That is, FIG. 3 is a vertical cross section for explaining this experiment as a schematic diagram, and the irregularly shaped upper nozzle brick 11 is
In a, the nozzle hole is narrow at the top and wide at the bottom. As a result of experimenting with this irregularly shaped upper nozzle brick under the same conditions as the conventional upper nozzle brick with a standard shape with a wide top and a narrow bottom shape,
The conditions before the receiving steel in Fig. 3a and immediately after the receiving steel in Fig. 3 are not much different from the states in Fig. 2 a and b of the conventional method in Fig. 2, but when the powder refractory 8 starts falling, its falling speed increases. Since the nozzle hole is large and wide at the bottom, the bridge 10 is pushed down as shown in Figure c.
expands and disperses to the surrounding area and collapses. Next, the molten steel 7 flowing down the gap does not have enough time to solidify even if it comes into contact with the powder refractories because the powder refractories fall rapidly and relatively flatly in about 2 seconds.
As shown in Figure d, the bridge and molten steel were dispersed in the surrounding area and easily fell, resulting in an opening. That is, we have obtained the knowledge that the most important point in making the opening easier during tapping is to rapidly drop the powder refractory inside the nozzle hole.

However, it turned out that the upper nozzle bricks with narrow top and wide bottom that were used in the experiment had various manufacturing difficulties.
This invention is based on the findings from the above-mentioned experiments, and even when using a conventionally shaped top nozzle brick with a narrow top and bottom, it is possible to ensure rapid fall of powder refractories and to improve the natural aperture ratio of the nozzle hole in a molten metal container. The purpose is to provide an aperture method that increases the number of holes to nearly 100%, and its characteristics are as follows:
A hollow right cylindrical cylinder or a hollow crested right conical cylinder made of thin iron plate is inserted, a heating element is installed on the molten steel side of this hollow insertion cylinder, and a powder refractory is installed inside this insertion cylinder and the nozzle hole around it. This is an opening method in which a container is filled with a substance, receives molten metal such as molten steel, and the sliding opening/closing device is fully opened to allow the nozzle hole to open naturally, allowing the molten steel etc. to flow down smoothly.

That is, most of the powder refractory in the nozzle hole is allowed to fall rapidly through the hollow insertion tube without any resistance, and at the same time, the molten steel is passed through the nozzle hole and opened without being cooled.

To explain this invention based on the drawings, the fourth
The figure shows the ladle and sliding opening/closing device turned over for inspection, repair, etc. 12 is made of iron plate or galvanized iron plate with a thickness of 0.2 to 0.5 mm and is inserted into the nozzle hole 4. It is a hollow insertion tube in the shape of an open right cylinder or a truncated right cone. In the former case, its outer diameter is approximately the same as the diameter of the discharge port 13 of the upper nozzle brick 3, and is usually 30 to 100 mm; in the latter case, one end that fits into the discharge port is approximately the same as the diameter of the discharge port, and the other end is smaller than that. It is desirable that the length of these insertion tubes be slightly longer than the length of the upper nozzle brick.

An example of an insertion tube is shown in FIG. 7, which is made by rounding a thin iron plate so that the lower end shown in the figure can fit almost tightly into the discharge port of the upper nozzle brick to be inserted, and the upper end is spot welded 14. The structure is such that the outer diameter of the lower end can be expanded and contracted to a certain extent by adjusting. 15 is a heat-generating material attached to the inner surface of the molten steel side (upper end) of the insertion tube, and the material is made of a material that generates high-temperature gas when heated, such as pulp material, with a height of 10 to 50 mm and a thickness of 10 to 50 mm. Form into a cylindrical shape with an outer diameter of about 5 mm to match the inner diameter of the insertion tube, fit into the upper end of the insertion tube, and fix with heat-resistant adhesive or the like. Note that it is desirable that the insertion tube be provided with an appropriate ejection hole 16 so that the high temperature gas is ejected outwardly as well.

When the ladle is overturned, the entire length of the insertion cylinder is inserted into the nozzle hole 4 from the discharge port side 13, as shown in FIG. 4, and one end is fitted into the discharge port 13. At this time, the heat generating material 15 is located on the molten steel receiving side. Next, a collector nozzle 6 is attached to the discharge port side, the ladle is made to stand upright, the sliding opening/closing device 5 is closed, and powder refractories are introduced from above. The powder refractory 8 is filled up to the upper end of the insertion tube, and is also filled into the surrounding nozzle holes to almost the same height. In this case, it is best to adjust the filling height of the powder refractory so that it is approximately halfway between the upper end of the upper nozzle brick 3 and the bottom of the container. A sintered layer is formed that obstructs natural opening, and if the temperature is too low, the insertion tube and heat generating material will melt at an early stage, which is not preferable.

Next, when the molten steel is received into the ladle, the situation shown in Figure 5 will occur in about 10 minutes, but the heat generating material 15 generates high temperature gas by receiving heat and heats the surrounding powder refractories, so the molten steel Even if it penetrates into the powder refractory, cooling and solidification is suppressed, and no solidification bridges are formed on the surface layer of the powder refractory. Next, when the opening/closing device is opened, the hollow insertion tube 12 is vertical or wide at the bottom as described above, so the powder refractory inside is removed in 1 to 2 seconds (in the conventional method with a wide top and a narrow bottom, the hollow insertion tube 12 is vertical or wide at the bottom).
As shown in Figure 6, the molten steel flows down inside the cylinder and at the same time melts the metal insertion tube, and then the surrounding powder refractories are washed away by the falling molten steel. In 3 to 4 seconds after opening the nozzle hole, the nozzle hole is completely opened and ready for pouring molten steel.

Conventionally, even in the case of natural opening, it took 5 to 10 seconds to completely discharge the powdered refractories and broken sintered materials.

Furthermore, since water vapor is generated in the nozzle hole from the moisture contained in the mortar and refractories around it, it moistens the filled powder refractories and solidifies slightly due to the pressure received from above, which conventionally prevents them from falling. However, in this invention, the powder refractories that fall first are isolated by a metal insertion tube, so they do not get wet, making rapid falling even easier.

As explained above, in this invention method, a hollow insertion tube made of iron plate and generating high-temperature gas is provided in the center of the powder refractory in the nozzle hole, so the molten steel cools in the upper part of the insertion tube and its surroundings. The molten steel falls simultaneously with the rapid fall of the powder refractories in the insertion tube, followed by the melted insertion tube and the remaining powder refractories falling almost simultaneously. Therefore, it is possible to achieve a natural aperture ratio of almost 100% even with a conventionally shaped nozzle hole with a wide top and a narrow bottom, and it has a great effect on smoothing the casting work of molten steel without the need for manual opening work.

Although the above description has mainly been given to the case of a molten steel ladle, it can be applied to pouring operations for all other molten metal containers including non-ferrous metals that are equipped with a sliding opening/closing device.

[Brief explanation of the drawing]

Figure 1 is a partial vertical sectional view of the bottom of the molten steel container showing the state in which the nozzle hole is filled with powder refractory;
The figure is a vertical cross-sectional view of the upper part of the nozzle hole showing the conventional situation where the nozzle hole does not open. 6 are longitudinal cross-sectional views showing embodiments of the present invention, and FIG. 7 is a perspective view (a) and b' (longitudinal cross-sectional view) showing an example of a metal hollow insertion tube used in the present invention. In each figure, 1...bottom refractory of molten metal container, 3...upper nozzle brick, 4...nozzle hole, 5...
...Sliding type switchgear, 7 ... Molten steel (molten metal), 8
... Powder refractory, 12 ... Metal hollow insertion tube, 1
5... Heating element.

Claims (1)

[Claims] 1 Insertion into the nozzle hole of the upper nozzle brick in a molten metal container equipped with a sliding opening/closing device, the lower end of which is made of a thin iron plate is a hollow rectangular shape or a hollow truncated conical shape and has an ejection hole at the upper part. A cylinder, and the insertion cylinder has an inner cylinder with a heat-generating material such as pulp material molded into a cylindrical shape according to the inner diameter of the insertion cylinder, fitted into the upper end of the insertion cylinder and fixed with heat-resistant adhesive, and the insertion cylinder is inserted through the nozzle hole, powder refractory is filled in the hollow insertion cylinder and the nozzle hole around it, the molten metal is received in the molten metal container, and the opening/closing device is fully opened. A method for opening a nozzle hole in a molten metal container, which comprises opening the nozzle hole.