JPS59101260A - Construction of tundish nozzle part for horizontal continuous casting - Google Patents

Abstract

PURPOSE:To prevent the damage and breakage of a nozzle owing to a solidified shell by impregnating a high melting pulverous material in the part of a tundish nozzle connecting, via annular refractories for connection, to a casting mold, where the solidified shell is liable to be formed. CONSTITUTION:A tundish nozzle 7 consisting of porous oxide refractories is connected, via annular refractories 2 for connection, to a casting mold 3, thereby constituting a tundish nozzle part. An area 5 impregnated with a high melting pulverous material (MgO, alumina, SiO2, etc.) is formed in the part of such nozzle 1 where a solidified shell is liable to be produced by receiving the cooling effect of the mold 3 in the initial period of casting or when drawing is stopped for a long time. The impregnated layer is further preferably subjected to a heat treatment. The nozzle 1 is thus prevented from the mechanical damage or breakage that may arise owing to the formation of the permeable solidified shell.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a horizontal continuous casting nozzle part in which an annular connecting refractory is interposed between a tundish nozzle and a mold. Regarding the structure of a tundish nozzle part for horizontal continuous casting, which allows casting slabs with good surface properties without damaging or destroying the nozzle part even during operation after drawing has been stopped for a long time. It is.

The horizontal continuous casting method is a method in which the entire process, from pouring molten steel into the mold and solidifying it to drawing and cutting the slab, is performed in a nearly horizontal straight line, and it is different from the currently mainstream vertical or curved casting method. Compared to the continuous casting method ■The machine height is low, so operation and maintenance are easy, and the weight of the machine is small and the construction cost is low. ■The tundish and mold are connected via the tundish nozzle and connecting refractories. It has recently attracted particular attention because of its advantages such as the high static pressure of the molten steel in the mold and the high accuracy of the slab shape, and the prevention of secondary oxidation due to the large sword of molten steel, which improves the cleanliness of the VJ slab. , efforts are being actively made to industrialize it.

However, although it has the above-mentioned advantages, it also has some peculiar disadvantages. One of these disadvantages is that the conditions required for the nozzle structure are extremely difficult. can.

That is, Tandates V unit nozzle is required to have properties such as 11) thermal shock resistance against large temperature changes that occur during injection of molten steel, and (2) resistance to melting damage that is suitable for long-term casting of various types of molten steel. In addition, since the cooling effect from type #1 is relatively small, a solidified shell is generated, and since it is a relatively large component, it is desirable to use an inexpensive material. Type + rut big game is used.

On the other hand, the connecting refractory has good workability that enables high dimensional accuracy for accurate joining with the 11+ mold, (2) thermal shock resistance against large temperature changes during injection of molten steel,
(3) Erosion resistance and abrasion resistance that can withstand long-time casting of each Azusa molten steel; (4) A solidified shell is generated on the surface of this refractory, but it is dense and smooth to reduce the frictional resistance of the DA hard shell. surface properties, low wettability and low porosity to prevent molten steel from entering the pores, etc., and expensive ceramics such as BN thread materials or Si3N4-based materials are used as materials that satisfy these requirements. .

Fig. 1 is an explanatory cross-sectional view showing the structure of a tundish nozzle for horizontal continuous casting made of such materials, where l is the tundish nozzle, 2 is the connecting refractory, 8 is the mold, and molten steel is indicated by the arrow. It is sent in the input direction, reaches the position of the connecting refractory 2 or the mold 8, forms a solidified shell, and is drawn out as a slab. By the way, in the above-mentioned nozzle part structure, if the drawing stop time becomes long during the initial stage of casting or due to some abnormality in operation, the inner surface of the terminal end of the tundish nozzle l made of porous material (tltll on the right side of the drawing) The molten steel that has permeated therein may be cooled and solidified to form a solidified V-ell (hereinafter referred to as a permeable solidified shell). When the permeable solidified shell at the end of the tundish nozzle and the solidified shell formed in the runner are integrated, tensile force is applied to the permeable solidified shell in the casting direction as casting is restarted.
, the surface layer of Tandates V unit nozzle suffers damage such as peeling.

However, in order to prevent damage to the nozzle structure, (l
) It is thought that it would be better to make the refractory finer in order to prevent the penetration of molten steel into areas where permeable solidified shells are likely to occur. Specifically, for example, a material with a small porosity (such as BN ceramics) should be used. It is possible to form a tundish nozzle, but this method does not satisfy the mechanical properties required for a tundish nozzle, especially thermal shock resistance (thermal spalling) and resistance, and is not a good solution. I don't get it. Therefore, the next method was to coat only the surface of the tanditshu nozzle with a dense refractory material (1984-484).
41), the mere coating method results in insufficient bonding between the coating layer and the base material), and the problem remains that the coating layer easily peels off from the base material.

On the other hand, depending on the cast M type (particularly stainless steel), the connecting refractory may react with molten steel and be damaged by erosion, and the connecting refractory may not only prevent the formation of a permeable solidified shell but also be resistant to erosion. This is an important item. Generally used BN-based ceramics, etc., almost satisfy both requirements, but these materials are expensive, have problems with erosion resistance, and are not compatible with dense materials other than BN-based materials. Ceramics, such as dense ceramics made of Si3N4 threads, have high strength and are difficult to work with (and are not cheap. Therefore, porous Si prepared using the reaction sintering method is
3N4 thread ceramics are used but are subject to mechanical damage due to the development of a permeable solidified shell. Therefore, it would be desirable to develop a material that is as inexpensive as possible and is resistant to ff1It erosion and penetration into molten steel, but this has not yet been completed.

The present invention has been made in view of these circumstances, and enables continuous casting without damaging the nozzle portion even during the initial stage of casting or after the bend drawing has been stopped for a long time due to an operational abnormality. The purpose of this is to provide a similar structure to the continuous insulating nozzle.

However, the unexploded Mh') nozzle part 4i achieved the above purpose.
1 is a tundish nozzle structure for horizontal continuous casting in which an annular connecting refractory is interposed between the tundish nozzle and the mold, and it is used in areas where solidification V-wells are likely to occur. Existing non-M1. The purpose is to impregnate a high-melting-point particulate material into a sealed body, and the above object can be achieved more effectively if the material is further heat-treated if necessary.

In other words, the non-dense refractory existing in the area where solidified shells are likely to occur as referred to in fmrM above refers to the refractory in the area that is easily affected by the cooling action of the mold, such as the tundish shown in Figure 1. The part of the nozzle that is close to the connecting refractory 2 is one example, and even if the connecting refractory 2 is subjected to the cooling effect by the mold 8, if it is made of a dense refractory. The above conditions are not met. In short, it is made of refractory material with a certain degree of porosity (usually 5 mm or more), and is used in areas where there is a risk of a permeable solidified shell forming due to the cooling effect from the mold, such as when drawing is stopped for a long time. Refers to non-dense refractories present. Therefore, of course, there are cases in which the conditions of the present invention are met even when there are cases other than tundish nozzles (see Example 2.8).

In addition, the above-mentioned high melting point fine particles include MgO, alumina,
5102, Z r 02, BN, C, zircon, 81
Examples include fine particles such as 3N4, spinel ([0-Al2O2, etc.), and mullite. When forming an impregnated layer by suspending the above-mentioned high melting point fine particulate material in water or an organic solvent, a solidified shell is generated by press injection or vacuum treatment, and it is applied to the surface of the non-dense refractory existing in the rough areas. After infiltration, the water or organic solvent may be evaporated. However, at this stage, the high melting point fine particulate material has only penetrated into the small pores in the refractory, and no bond is formed between the i-melting point fine particulate material and the refractory. However, when casting is carried out using a nozzle impregnated with high melting point fine particulate material, the temperature of the impregnated layer rises and a bonding reaction occurs between the impregnated material and the refractory, resulting in stabilization and closing the small pores of the refractory. A dense impregnated layer is formed that can prevent the penetration of molten steel. Since the reaction between the impregnated material and the refractory does not proceed instantaneously, care must be taken in the early stages of casting to avoid accidents such as interruptions in casting.

Therefore, without relying on heat treatment during use during casting, it is possible to infiltrate high-melting point fine particles into refractories and then perform active heat treatment to create an impregnated layer that improves bonding with the refractories from the beginning. Forming is also recommended. There are no particular restrictions on the heat treatment conditions, but for example, if the impregnating material is alumina and the base material is 813 Na, it is sufficient to maintain the temperature in an atmosphere of 1600°C or higher for several hours; Not only can a well-bonded structure be obtained, but also the erosion resistance is extremely high from the beginning. This heat treatment mound temperature should be determined in consideration of the humidity necessary for the reaction between the impregnated material and the refractory to proceed sufficiently, and will vary depending on the combination of the impregnated material and the refractory. Needless to say. If a high melting point granular material is infiltrated into the refractory of the above-mentioned component and then heat treated, a strong impregnated layer with high bonding properties with the refractory can be formed from the beginning.

Even if a trouble such as a temporary interruption occurs at the start of casting, the generation of a permeable solidified shell can be avoided.

The impregnated layer of high-melting point fine grain material formed as described above, especially the layer combined with the matrix, has strong bonding properties with the refractory base, and most of the pores that originally existed are sealed, so the molten steel is It also shows excellent corrosion resistance against highly reactive molten steel such as SUS. Further BN
Alternatively, in the case of 7IC, the entire refractory is impregnated with an impregnating agent with high thermal conductivity, such as C, which increases the density of the refractory and increases the thermal conductivity of the refractory (also has the effect of improving spalling resistance. can get.

The present invention is roughly constructed as described above, and does not require a long period of suspension of extraction due to the initial stage of assembly or abnormal operation.
It has been possible to provide a nozzle part structure for horizontal continuous sowing that allows casting of slabs with good surface properties without damaging or damaging the nozzle part even after the nozzle part has been washed.

The configuration and effects of the present invention will be further clarified by the following examples.

FIG. 2 is an explanatory cross-sectional view showing the nozzle part 19 of the present invention (embodiment), and the shapes of the tundish nozzle A/1, the connecting refractory 2, and the mold 8 are shown in accordance with FIG. The tundish nozzle 1 in this example is made of a zircon refractory, and the connecting refractory 2 is made of a windowed boron claw. Alumina is impregnated in the range of tongue ff1ff (diagram line area).

In the nozzle structure as described above, the casting temperature is 1570℃.
When we cast 4.5 tons of stainless steel (5US804) under the conditions of a slab diameter of 110 m + φ and a drawing speed of 1.7 m/min, we were able to successfully complete a cast slab of about 64 m (casting time: 88 minutes). Further, when the inner surface of the nozzle part after casting was investigated, the impregnated part remained in a substantially healthy state, and no damage was observed in the tundish nozzle 1. In a casting experiment using the same conventional nozzle part Q, the drawing resistance increased during casting and casting was interrupted at a length of 18 m, and large damage was observed on the inner surface of the tundish nozzle L after WJKi. Molten steel was inserted into the boundary between the tundish nozzle 1 and the connecting refractory 2, causing cracks in the connecting refractory 2.

FIG. 8 is a cross-sectional explanatory view showing another nozzle part structure (Embodiment 2) of the present invention. In the nozzle part 5 having the same shape as the example in FIG. 2, the tundish nozzle 1 is formed of a zircon refractory, In addition, the connecting refractory 2 is 5i3hr4 (90 volume%
) and BN (10ffi square). The inner surface of the tundish nozzle 1 is impregnated with alumina to a depth of about 10 degrees from the surface. Further, the entire connecting refractory 2 is impregnated with tar and heat-treated at 1000°C.

In the nozzle structure as described above, the casting humidity is 1570℃.
, Stainless steel x, 'M (5US804) 4.5) was cast under the conditions of a slab diameter of 110 mm and a drawing speed of 1.7 m/min, and a slab of approximately 64 m was successfully cast. I was able to do that. (During casting (88 minutes).

In a weight-bearing test using the same conventional nozzle part 171 structure, the Xf structure was interrupted at a length of 151n due to increased pull-out resistance during casting. Further, after casting, the connecting refractory was eroded and damaged, molten steel was inserted into the boundary between the tundish nozzle l and the connecting refractory, and scratches were generated on the inner surface of the mold.

FIG. 4 is a cross-sectional explanatory view showing another nozzle part structure (Embodiment 8) of the present invention, in which an intermediate ring 4 is placed between a tundish nozzle 1 made of a zircon refractory and a connecting refractory 2 made of a BN car body. By interposing the
The structure is designed to prevent the formation of coagulated shells as much as possible. In Okamoto's example, the intermediate ring 4 is made of zircon refractory, but is made of 5t3N4, B
N, Al203-C11mgm V! It can also be made of refractories such as J:ty, zircon, and S/y conquerite. The intermediate ring 4 (thick line portion) is impregnated with alumina. In the nozzle structure as described above, stainless steel (SUS804
) When 4.6 tons were cast, approximately 84 m was able to be completely cast (casting time 28 minutes).

After construction, no damage was found on the inner surface of the intermediate ring or the tundish nozzle.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a conventional horizontal continuous casting nozzle structure, and FIG. 2.8.4 is a sectional view showing a horizontal continuous casting nozzle structure according to the present invention. l... Tundish nozzle 2... Connection refractory 8... Mold 4... Intermediate ring 6... Impregnated area Applicant Kobe Steel, Ltd. Figure 1 Figure 3 Figure 2 Figure 4

Claims (1)

[Scope of Claims] A tundish nozzle structure for horizontal continuous casting in which an annular connecting refractory is interposed between the tundish nozzle and the mold, which exists at least in a portion where a solidified shell is likely to occur. A structure of a tundish nozzle for horizontal continuous casting, which is characterized by forming an impregnated layer of high point fine grain material on a non-dense refractory. f2! / :/ A tundish nozzle structure for horizontal continuous casting in which an annular connecting refractory is interposed between a tissue nozzle and a mold. A horizontal continuous kh tundish nozzle structure, characterized in that an impregnated layer of high-melting point fine grain material is formed on a dense refractory material, and then heat-treated.