JPS6077162A - Sliding nozzle plate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention particularly relates to a sliding nozzle plate (hereinafter referred to as 8N plate) that has excellent corrosion resistance against steel types with high oxygen concentration such as non-deoxidized steel.

A sliding nozzle device attached to a ladle, tundish, etc. consists of multiple S.
The flow rate of molten steel is controlled by sliding the N plate and opening and closing the flow holes.

The sliding surfaces and outflow holes of the SN plate are exposed to the flow of molten steel and are severely damaged by wear or chemical erosion. To provide resistance to this damage, the material must be chemically stable and have high high temperature strength.

Further, in the SN plate, since molten steel flows through the flow holes drilled in the flat plate shape, there is a temperature difference of 1000° C. or more between the periphery of the plate and the vicinity of the flow holes. Therefore, although it is undeniable that some cracks will occur, it is necessary that even if cracks occur, the cracks do not lead to leakage of molten steel. In other words, even if cracks form at high temperatures during use, it is important that the residual expansion after cooling causes the cracks to stick together so that when the ladle or tundish receives molten steel again, molten steel does not leak through the cracks. be.

As described above, the usage conditions of SN plates are significantly different from those of other refractories, and special characteristics are required.

Conventional general SN plate materials are made by adding carbon, metallic silicon, etc. to refractory raw materials such as sintered alumina, fused alumina, mullite, and sillimanite, cross-wired with pitch or phenol resin, then molded and fired. It is something.

This material is widely used because it has a relatively well-balanced combination of high-temperature strength, thermal shock resistance, residual expansibility, etc. required for SN plates. However, although it is good for molten steel with a relatively low oxygen level of 100 ppm or less, its corrosion resistance is extremely poor for steel types that have an oxygen concentration of 100 ppm or more, which is called non-deoxidized steel. There was a drawback that it deteriorated.

The present invention aims to solve the above-mentioned drawbacks of conventional materials, and is characterized in that the main crystal phase is monoclinic zirconia, and particles with a grain size of 0.1 ms or more are mixed into 5Qwt. Zirconia raw material containing 1 to 40 Wt
H. It is a sliding nozzle plate made by mixing, molding, and firing a blend consisting of the remaining magnesia raw materials.

A zirconia raw material whose main crystal phase is diagonal zirconia undergoes the following phase transformation depending on the temperature, resulting in a large volume change. Especially between monoclinic and tetragonal crystals,
The volume change can be up to 9 inches.

In the present invention, by adding this zirconia raw material, fine racks are introduced into the magnesia structure of the base material during firing. The SN plate generates radial cracks starting from the communication holes due to thermal shock during use, but the action of the above-described microscopic racks branches the tips of the radial cracks and suppresses the progress of the cracks. As a result, the thermal shock resistance of the SN plate is significantly improved.

This volume change of the zirconia raw material also occurs during heating and cooling when the SN plate is used, and serves to close cracks generated by heating during cooling.

Therefore, after the SN plate has paused and cooled down,
Even if it is used again, the radial cracks are closed, so molten steel will not enter or leak from them.

Moreover, zirconia forms a solid solution with magnesia, and a bond is generated between magnesia and zirconia. Therefore, even if fine racks are formed in the structure due to volume expansion due to zirconia transformation, if the amount of zirconia added is limited to a certain amount, the strength at temperatures above 14,000 C tends to improve, and wear due to molten steel increases. Melting loss is reduced.

The zirconia raw material has 6 particles with a particle size of 0.1 wn or more.
It is necessary that the content is 0 wt% or more. 0.1 trt
When the particle size of n or more is less than 60 wt% and most of the zirconia raw material is occupied by fine particles, the solid solution formation reaction between magnesia and zirconia described above is almost completed when the SN plate is fired, and free The proportion of zirconia decreases.

Therefore, in the SN plate, fine cracks due to changes in the volume of the zirconia raw material do not occur, and the effect of imparting thermal shock resistance cannot be obtained. Most preferably, 0.1 ttm or more is 9 Qwt% or more.

The ratio of zirconia raw material to the entire compound is 1wt%
If it is less than that, there will be no effect on thermal shock resistance.

If it exceeds 4Qwt%, there will be too many microscopic raw spheres of rack, resulting in insufficient strength. More preferably 5 to 20wt
It is Chi.

Specific examples of the zirconia raw material include batchlite raw materials that meet the above conditions, or electrofused zirconia raw materials obtained by electromelting and refining batchlite or zircon.

The magnesia raw material that occupies the remainder is fused magnesia or sintered magnesia with a total of Mg090 of 4 or more, and is made into an acrylic resin. The particle size is appropriately adjusted to coarse, medium, or fine, taking into consideration the particle size of the zirconia raw material.

By the way, it has been found that when 20 wt % or less of the chromium oxide raw material is added to the SN plate of the present invention, it is even better in preventing penetration of molten steel and slag into the SN plate structure. This is thought to be due to the fact that chromium oxide is difficult to leak into molten steel and slag. The chromium oxide raw material preferably has a purity of 9Qwt% or more and a particle size of 10 μm or less.

When the addition ratio exceeds 20 wt%, the structure becomes dense and the thermal shock resistance becomes poor. The most effective ratio is 1-15virt
It is Chi.

The SN plate of the present invention comprises the above raw materials in a predetermined ratio.
After blending, the rest is manufactured by conventional methods.

That is, about 1 to 1Qwt% of a binder commonly used for molding refractories, such as bittern, molasses, water, resin, and wax, is added to the mixture, and the resulting green body is sufficiently dried. It may be impregnated with a 1100°C nord resin, furan resin, etc. in which at least zirconia transitions from monoclinic to tetragonal.

The SN plate of the present invention thus obtained has excellent high-temperature strength, thermal shock resistance, corrosion resistance, etc., as described above. Further, since the residual expansion is large, there is no problem of molten steel leaking through cracks when the SN plate is cooled and is ready for reuse.

Furthermore, it exhibits excellent corrosion resistance even against undeoxidized steel with a high oxygen concentration. This is due to the fact that the blended raw materials do not contain carbon, which is subject to oxidation, unlike conventional SN plates, and the magnesia raw materials have significantly greater erosion resistance against FeO, which is produced in steel with a high oxygen concentration. This is probably because it has a sexual nature.

The effects of the present invention will be explained with reference to examples.

Table 1 shows the grain size and crystalline phase of the zirconia raw material used on each side. Table 2 shows the compounding compositions of the inventive examples and comparative examples, and the obtained SN plate sintered magnesia clinker.
1 Electrofused magnesia both have an MgO component of 98 wt%.
I used the above.

The formulations of Comparative Examples and Examples were both kneaded using a fret, formed into a predetermined SN plate shape using a friction press, dried at 80 to 150°C for 48 hours, and then fired at 1600°C for 5 hours in a tunnel kiln. did.

In Example 6.9 and Comparative Example 1.5, impregnation treatment was performed after firing.

The test method is as follows.

A 40 x 40 x 40 cube was cut out from the Qin compressive strength SN plate and measured using an Amsler testing machine.

*Hot bending strength at 1500℃ From SN plate Width 30mm, Thickness 15mm, Length 120M
A test piece was cut out, heated for 1 hour in an electric furnace kept at 1500°C, and then subjected to a three-point bending test.

*The outflow hole of the thermal shock resistant SN plate was heated with a propane gas burner, and the spacing until cracks appeared around the outflow hole was measured.

The larger the number, the greater the thermal shock resistance.

*Erosion resistance A rotating drum type erosion test device was used.

1 with a 100% steel corrosive agent with an oxygen concentration of about 300 ppm
Heated with a propane gas burner at 650℃ for 3 hours and measured the dimensions of erosion.

Among the respective erosion dimensions, the erosion dimension of Example 2 was set as 100.
The erosion dimensions of other examples are expressed as relative values.

The smaller the number, the better the erosion resistance.

Residual line change rate after heating → cooling A sample of 25 x 25 x 120 cm was cut out from the SN plate and heated in an electric furnace at 1500°C for 1 hour, then cooled to room temperature and the dimensional change rate before and after the test was measured.

If it is positive, it means residual expansion, and if it is negative, it means residual shrinkage.

As can be seen from Table 2, the examples of the present invention show well-balanced results in each test, but the comparative examples 1.2.
3.5.6 has poor thermal shock resistance. Comparative Example 4 did not have sufficient strength as an SN plate, and required surface accuracy could not be obtained by polishing the sliding surface. Comparative Example 1.2, which is a single magnesia raw material, had residual shrinkage and the crack opening after the thermal shock test was large. Furthermore, when a conventionally used alumina/carbon SN plate was tested under the same conditions, its erosion resistance was more than three times higher than that of the present invention.

Furthermore, in order to confirm the effects of the present invention, Examples 3 and Nα7 of the present invention were attached to a ladle sliding device manufactured by A company 250, and used on steel with a high oxygen concentration of 100 to 300 ppm. In the alumina/carbon SN plate used conventionally, the outflow hole and sliding surface were eroded after one or two ladle turns, making it unusable.

On the other hand, Example 3 of the present invention has 3 to 5 charges,
The one with No. 7 exhibited high durability with 4 to 7 charges, confirming the effect of the present invention.

1 Patent Applicant: Harima Refractory Brick Co., Ltd. Procedural Amendment (Voluntary) October 31, 1945 Director-General of the Patent Office Kazuo Wakasugi 1. Indication of the Case: Japanese Patent Application No. 1880-634 2. Name of the Invention: Sliding Nozzle Plate 3. Relationship with the case of the person making the amendment Applicant: Harima Refractory Brick Co., Ltd. 4, Agent: Toranomon-1-18-5, Minato-ku, Tokyo
, Subject of amendment Detailed description of the invention in the specification.

6. Contents of correction As per attached sheet.

Claims (2)

[Claims] (1) Mixing a mixture of 1 to 40 wt% of a zirconia raw material in which the main crystal phase is monoclinic zirconia and contains 5 Qwt% or more of particles with a grain size of 0.1 scale or more, and the balance is a magnesia raw material, A sliding nozzle plate made by molding and firing. (2) Zirconia raw material 1 to 40 Wt96 whose main crystal phase is monoclinic zirconia and contains 60 wt% or more of particles with a particle size of 0.1 van or more, chromium oxide raw material 2
A sliding nozzle plate made by mixing, molding, and firing a compound containing 0 wt% or less of the balance magnesia raw material.