JPS6051659A - Porous nozzle - 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 is directed to a casting nozzle that is attached to a molten steel container such as a ladle or tundish. This relates to a porous nozzle designed to prevent blowing.

In recent years, the proportion of various types of steel products being directly obtained through continuous production has increased in the production of steel presses, and with the adoption of sliding nozzles, large amounts of molten steel can be processed quickly. Precipitates inside, especially alumina particles, adhere to the inner circumferential surface of the nozzle refractory hole, resulting in the nozzle being pinched and eventually clogging, leading to a decrease in productivity and steel quality. . Therefore, in order to prevent such a situation, an inert gas such as argon gas is injected through the structural gaps of the nozzle refractory to form a gas film at the interface between the inner peripheral surface of the nozzle hole and the molten steel flow, or By stirring the molten steel flow with gas and making the molten steel temperature uniform, m
This prevents deposits from adhering to the nozzle and prevents the nozzle from becoming pinched or blocked.

Porous nozzles for gas blowing are used in such applications, and the characteristics required for these porous nozzles include, of course, high corrosion resistance and thermal shock resistance.
It has sufficient air permeability to fulfill its purpose, and gas is ejected uniformly from each part of the required area of the nozzle refractory.
= t is a requirement. Furthermore, as special steels with high oxygen concentrations have been increasingly processed in recent years, the corrosion resistance of conventional alumina porous nozzles has become a problem.

It is well known that basic materials such as magnesia refractories exhibit excellent corrosion resistance against this type of molten steel, but on the other hand, basic materials have poor thermal shock resistance due to their high expansion coefficients. The drawbacks are that basic materials are easily used for porous nozzles based on these properties, and that structural spalls are likely to occur at the boundary between the permeable layer and the protogenous layer due to the penetration of steel. It has excellent corrosion resistance and thermal shock resistance even against special steel types such as those listed above.
Moreover, a porous nozzle with uniform air permeability was long-awaited.

The present invention was made in view of the current situation, with the aim of proposing a porous nozzle that achieves the desired air permeability and uniformity of each part of the structure, and also has excellent durability against molten steel with a high oxygen content. The object of the present invention is to provide a porous nozzle that is rich in corrosion resistance and has high thermal shock resistance by using alumina-magnesia spherical particles and magnesia spherical particles that have excellent corrosion resistance.

Hereinafter, one embodiment of the present invention will be described. The refractory material used in the present invention is a magnesia-alumina spherical refractory material and a magnesia-based spherical refractory material, and its chemical composition is composed of 10% or more (wt%) of amagnetic θ content, and if MgO If it is less than 10, it is equivalent to alumina in terms of corrosion resistance.

The reasons for using so-called spherical particles, which are spherical or nearly spherical, are: (1) improved filling properties, (2) easier to obtain a structure with a uniform structure, and (3) easier control of the physical properties required for refractories. This is because it has advantages such as being easy.

Moreover, good results can be obtained by limiting the maximum particle diameter of the spherical refractory material used here to 2 mm.

In other words, when the maximum particle size is 2111 or more, the pore size formed between particles is extremely large for a porous nozzle, and a large amount of fine powder must be added to adjust it. This is because the effect of forming spherical particles in order to obtain a uniform structure is weakened, and the maximum particle diameter desirable for achieving the original purpose of spherical particles is 1.0 to 1,211.
It is 11.

Furthermore, in order to improve thermal shock resistance and corrosion resistance,
In addition, in order to prevent structural spalling and to control the physical properties of refractories, per 100 parts by weight of spherical particles, within a range that does not reduce the effect of forming spherical refractory particles,
Fine powder with an average particle diameter of 100μ or less, Zr5iO: 1 to 10 parts by weight 5in2: l to 5 Zr01: 2 to 20 # Cr2O: 0.2 to 0.3' MgO: 25 parts by weight or less'hos: 25 The composition is one in which one or two or more of these are added.

ZrSiO4 or 8302 is added mainly to improve thermal shock resistance, ZrO2 or 20g of Cr is added mainly to prevent v-transmission and improve corrosion resistance, and MgO or M2O3 is added to control microscopic physical properties.

Next, the specific structure of the porous nozzle of the present invention will be described.

First, the spherical aggregate refractory material in the present invention is prepared by mixing commercially available or pulverized magnesia and alumina refractory materials with an average particle diameter of 100 μm or less in a preset ratio, and then using a rotating plate granulator, a spray dryer, and a rotating plate. It is obtained by granulating it using a type mixer or the like and heat-treating it at 1,700 to 2,000°C. The thus obtained spherical refractory material is sieved and the particle size is adjusted so as to obtain predetermined physical properties.

From the viewpoint of thermal shock resistance, it is preferable to have a discontinuous particle size distribution or a continuous particle size distribution rather than a regular particle size distribution.

A matrix fine powder is further added to the spherical aggregate particles whose particle size has been adjusted, and the mixture is kneaded with a binder such as a phenol resin, and then molded and fired.

Examples of the present invention will now be described. First, the differences in the effects obtained when using alumina spherical particles, as an example of which is currently used as a porous nozzle, and when using alumina-magnesia spherical particles were examined using each example. It is something.

Example 1 Commercially available fine powder alumina with an average particle size of 22 μm and fine powder magnesia, which was obtained by crushing commercially available sintered magnesia to have an average particle size of 35 μm, were mixed into the spherical aggregate refractory materials shown in Table 1. They were mixed in proportions according to their chemical compositions and granulated by rolling using pulp waste liquid. The spherical particles obtained by granulation are fired through a 1soo"c tunnel kiln,
The spherical particles used in the present invention were made to have the necessary strength.

The spherical particles obtained in this way were adjusted to the particle size distribution shown in Table 1, and then a fine powder with an average particle diameter of 35μ obtained by crushing the above-mentioned sintered magnesia was added as a matrix fine powder (in parentheses in each table). After adding a phenol resin and kneading it in a fret mill, it was molded in a 7-rection press. The molded body is 150
After drying at 'C', it was fired at 1730'C, and the physical properties and corrosion resistance of this fired body were measured.

The corrosion resistance was evaluated based on the rotary erosion method under the following conditions: Temperature: 1650℃ Duration: 30 minutes Number of immersions: 5 repetitions Steel type: Iron is taken as a comparative example, and the amount of erosion of this comparative example Nal is 1
00, the volume of each Example was expressed as an index and is also shown in Table 1. As is clear from these values, those using Al208-MgO spinel or MgO spherical particles as the aggregate refractory material have a lower erosion index and extremely high corrosion resistance than those using alumina spherical particles. It is clearly shown that this shows that.

On the contrary, the amount of penetration is larger than that using alumina spherical particles, but the reason for this is that the melting point of MgO is 2.
It is presumed that as MgO increases, sintering tends to be insufficient at the same sintering temperature, resulting in a larger apparent porosity and pore diameter, resulting in a larger amount of permeation.

Thermal shock resistance was determined by making a test piece of 50 x 50 x 50 MN from the fired body and placing it in an electric furnace at 1500°C for 30 minutes.
After holding for 0 minutes, take it out and cool it in the air. This operation was repeated, and the results were shown as ◎ ~ No crack after 2 repetitions O ~ No crack after 1 repetition Δ ~ Slight crack after 1 repetition X ~ Large crack after 1 repetition , Thermal shock resistance Since the expansion coefficient increases with the addition of MgO, it tends to be inferior to those using alumina spherical particles.

Practical row 2 When the chemical composition of spherical aggregate refractory materials is the same, this study clearly shows how the physical properties and corrosion resistance of the molded product obtained by firing are affected by the maximum particle size of the material. In Example 1, the chemical composition shown in Table 2 was used. Spherical particles were prepared in the same manner as above and fired in the same manner to obtain a molded body.

Corrosion resistance was based on Comparative Example No. 1 shown in Table 1. The test results shown in Table 2 show that by increasing the maximum particle diameter, the porosity of the molded product becomes smaller and more dense. It can also be seen that the corrosion resistance improves accordingly, and at the same time the amount of penetration decreases.

Although the thermal shock properties were slightly improved compared to the Examples shown in Table 1, it was recognized that there was room for further improvement.

Also, in terms of the finished appearance of the product, a maximum particle size of 2 mm for the spherical aggregate refractory material is excessive and the product looks inferior, so the maximum particle size should be around 1.5 mm. is desirable because it yields good results in all aspects.

The methods for measuring corrosion resistance and thermal shock resistance are the same as in Example 1.

Example 3, Example 1. and 2. Tables 1 and 2 showing the results show that the porous nozzle refractory obtained using the spherical particles of the present invention has better corrosion resistance than alumina, but has poor thermal shock resistance. However, there is still room for further improvement, and this example uses magnesia spherical particles to improve thermal shock resistance.

The preparation of the spherical aggregate refractory material, the manufacturing method of the molded body, and the evaluation method are as described in Example 1. and 2. It is exactly the same.

Magnesia-alumina spherical particles and magnesia spherical particles have a particle size distribution shown in Table 3, and furthermore, in addition to magnesia fine powder, alumina, silica, zircon, zirconia, or chromium oxide is added as an additional matrix fine powder to improve thermal shock resistance. Improved sex.

No. 1411: Comparative example using alumina spherical particles.

Nos. 15 to 19 show the effect of the amount of alumina fine powder while keeping the amount of magnesia added constant. As the amount of added magnesia increases, the strength improves due to the formation of magnesia-alumina spinel bonds. Further, although the thermal shock resistance was improved by adding fine alumina powder, it was inferior to Comparative Example r4α14.

Figures 20-23 examined the effect of adding 5i02 using ball clay, and found that thermal shock resistance improved when Si02 was 3-7%, and this was due to forsterite, a low melting point substance. It is thought that then. Therefore, corrosion resistance deteriorates as the amount of addition increases, but Sin is approximately 5%.
It shows high corrosion resistance when added in an amount within 1. That is,
If the amount of Sin added is in the range of 1 to 5 inches, excellent physical properties are exhibited in both corrosion resistance and thermal shock resistance.

Similar results are also observed for the addition of zircon seen in lines 24-27. The improvement in thermal shock resistance due to the addition of zircon is due to the increase in the amount of zircon produced by the thermal dissociation of zircon
This is due to the effect of .

Zr5i04-e ZrO2+ Sing style 28~32
Although this was used to confirm the effect of adding chromium oxide, no effect was obtained in either corrosion resistance or thermal shock resistance. One reason why no effect on corrosion resistance was obtained is thought to be that the porosity was high due to insufficient sintering.

This is because, as shown in N1139 or Taka41, even chromium oxide has high corrosion resistance and high thermal shock resistance when used in combination with zircon.

By using chromium oxide, which has poor wettability with molten steel, and in combination with zircon, which promotes sintering, it is possible to obtain physical properties with excellent corrosion resistance and thermal shock resistance.

Fish Nos. 33 to 37 were tested for the effect of adding unstabilized zirconia, and it can be seen that the strength increases with the amount added. This is thought to be because magnesia and zirconia form a solid solution, and zirconia becomes stabilized.

If the amount added is as large as 30, the porosity will be significantly lower and it will be difficult to obtain favorable results from the standpoint of thermal shock resistance.From these points of view, the desirable amount of unstabilized zirconia added is 2 to 2. It is 20 inches.

Kite No. 38 was investigated for the effect of adding stabilized zirconia, and it was found that the effect of adding unstabilized zirconia contributed to improvements in corrosion resistance and thermal shock resistance to the same extent as the effect of adding unstabilized zirconia.

Those with Na42 to Na44 are obtained when the chemical composition of the spherical aggregate refractory material is changed to magnesia-alumina particles, but from the results in Table 3, the physical properties are almost the same as those obtained with magnesia particles.

As is clear from the above explanation, the technical matter of the present invention is a porous nozzle refractory using basic spherical particles with excellent corrosion resistance.
, AltOB , 5i02 , Zr3i01 , Zr
It has a structure consisting of one or more types of IJ Lux fine powder of O2 and 20g of Cr.

The porous nozzle of the present invention, when attached to a ladle or tundish, achieves a remarkable effect in preventing troubles such as alumina adhesion or base metal adhesion, and its technical idea is limited to the above-mentioned embodiments. Needless to say, the invention is not limited to the above, and any applications, diversions, or modifications derived therefrom are also included within the technical scope of the present invention.

Indication of procedural amendment case Title of invention of patent application No. 1982-J Geotsu No. 2B Relationship with the case of the person making the porous nozzle amendment Attorney for the patent applicant and one other person with 1 Y/o 1979 Year/Month/Date (self-motivated) Amendment Target Specification, Claims, Detailed Description of the Invention.

l　The scope of the patent claims will be amended as follows.

[A spherical aggregate refractory material with a chemical composition mainly composed of MgO or MgO and Al2O8 that contains 10 wt% or more of MgO as a chemical component and whose particle size is 2M or less, with an average particle size of 100μ The following MgO, Ad20H
, 5i02, ZrSiO4, ZrO2, and Cr2O3. ” n Specification v, page 19, line 4, “Zr5i02J”, [Zr5iO4
Correct it with J.

Procedural amendment person who makes corrections Relationship with matter 1'1 Patent applicant 1 other person Showa year, month, day (voluntary) with 1 piece The scope of patent claims will be amended as follows.

Claims (1)

[Claims] It has a chemical composition mainly composed of MgO or MgO and Al2O8, with a particle size of 2ffIl, containing 10 wt% or more of MgO as a chemical component! The following spherical aggregate refractory materials include MgO and Al with an average particle size of 100μ or less.
*Os %5i02, Zr5iO,, Zr01, C
A porous nozzle characterized by using a material to which 91 types or 2 g of rzOB can be added.