JPS6183670A - Refractories for slide gate - 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 Technical Field of the Invention The present invention is used in sliding gates. Concerning the improvement of refractories.

[Technical background of the invention and its problems] Various refractories such as high alumina and alumina-carbon refractories have been studied as refractories for slide gates.
'rT1. Since it is essential, satisfactory results have not been obtained with any refractory materials.Q~.

In addition, magnesia refractories have excellent corrosion resistance against molten metal or basic slag, so they are used as furnace materials for various types of steelmaking, including converters, but they have poor spalling resistance. Therefore, it is not used as a refractory for slide gates (1).

Attempts to improve the spalling resistance of magnesia-based refractories are known, for example, in Japanese Patent Publications 13643-1983, 11669-1980, 107749-1980, 26073-1980, etc. .

Japanese Patent Publication No. 53-13643 uses a mixture of magnesia raw material and vericleyse-spinel raw material,
Although considerable respect is expected regarding spalling resistance, satisfactory results have not been obtained with refractories for slide gates, which are used under much harsher conditions than ordinary steelmaking furnace vessels.

Furthermore, JP-A-55-11669 attempts to improve the spalling resistance by adding a carbon raw material to a magnesia raw material. However, when a carbon raw material is added to a magnesia raw material, although spalling resistance is improved, the necessary strength cannot be obtained.

Furthermore, JP-A-55-107749. Japanese Patent Publication No. 58-260
No. 73 etc. improve the spalling resistance by adding a carbon material to the magnesia material, and at the same time, Si, 5iC-A1.
Fe-3i and the like are added and fired in a non-oxidizing atmosphere. However, such magnesia-based refractories require heat treatment in a non-oxidizing atmosphere, resulting in high costs, and also have the problem of structural deterioration due to oxidation of carbonaceous raw materials during use. In addition, various attempts have been made in recent years to
When used for casting steels that are highly corrosive to refractories, such as a-added steel or various free-cutting steels, satisfactory results cannot be obtained as with conventional high alumina or alumina-carbon materials.

[Object of the invention] The present invention has been made in view of the above circumstances, and has improved beer resistance without using any special manufacturing method, and has excellent corrosion resistance against molten metal and basic slabs. The purpose is to provide a refractory for slide gates.

[Summary of the invention] The refractory for sliding gates of the present invention is A L 20340.
Alumina-magnesia spinel raw material 1 consisting of ~70% by weight, MgO 25-60% by weight, and the balance 10% by weight or less
0 to 30 parts by weight, and 90 to 70 parts by weight of magnesia raw material containing 90% by weight or more of MgO, and Al20310 to
It is characterized by containing 25% by weight and 90 to 75% by weight of MgO.

The composition and blending ratio of raw materials in the present invention are interrelated.

The alumina-magnesia spinel raw material used in the present invention has a theoretical composition value (At□0371.7% by weight,
Although the composition is approximately equal to MgO (28.3%) or is rich in magnesia, the reason why the composition is limited as described above is as follows. First, Al2
If O, is less than 40% by weight, or if MgO is more than 60% by weight, the spinel crystal phase consisting of alumina periclase will decrease, and the effect of improving the beer resistance will be reduced. On the other hand, if A12Off is more than 75% by weight or MgO is less than 25% by weight, excessive frundum crystals exist around the spinel grains, resulting in poor corrosion resistance.

Furthermore, the reason why the composition of the magnesia raw material used in the present invention is set to 90% by weight or more of MgO is because if the content of MgO is less than 90% by weight, corrosion resistance is poor.

In addition, the mixing ratio of the alumina-magnesia spinel raw material is 10 to 30 parts by weight, and the mixing ratio of the magnesia raw material is 90 to 70 parts by weight, because the alumina-magnesia spinel raw material is less than 10 parts by weight, or If the magnesia raw material exceeds 90 parts by weight, there is no effect of improving the beer resistance, while if the alumina magnesia asvinel raw material exceeds 3Qi parts, or if the magnesia raw material exceeds 70 parts by weight,
This is because if the amount is less than 1 part by weight, the melting resistance and the peeling resistance will be poor.

This is because the alumina-magnesia spinel raw material and the magnesia raw material have different coefficients of thermal expansion, but if the raw materials are blended within the above range, thermal strain due to the difference in coefficient of thermal expansion can be absorbed. it is conceivable that.

To obtain a refractory for a slide gate using the raw materials as described above, a method similar to that used for obtaining a general magnesia refractory may be used. That is, an organic binder, an inorganic binder, or both are added to alumina-magnesia spinel raw material and magnesia raw material in a predetermined mixing ratio, and the mixture is kneaded using a kneading machine such as a mixer or a wet pan, and then kneaded using a friction press. After molding and drying with an oil press or rubber press, etc., it is heated in a single kiln or tunnel kiln in a normal oxidizing atmosphere for 15 minutes.
It may be fired at 00°C or higher.

The particle size of the raw material used is not particularly limited, but the alumina-magnesia spinel raw material is coarse to coarse.
It is more preferable to use medium-grain powder, since alumina has poorer corrosion resistance than magnesia, so the amount of fine powder alumina should be reduced. In addition, the firing temperature is desirably 1500°C or higher in order to obtain the desired strength, and more preferably 1500°C or higher in terms of quality and cost.
The temperature is preferably 650 to 1750°C.

The chemical composition of the refractory obtained as above is A l
The reason why the content is limited to 20310 to 25% by weight and MgO 90 to 75% by weight is related to peeling resistance and corrosion resistance as well as the blending ratio of raw materials. More preferably, the chemical composition is At20312-20% by weight, MgO88-80% by weight.
Weight% Kayoi.

[Embodiments of the invention] The present invention will be explained in detail below.

First, the raw materials shown in Table 1 below were prepared and kneaded using a wet pan in the proportions shown in Table 2 below. Next, it was molded into dimensions of approximately 400 x 200 x 50 mm using an oil press at a pressure of 1000 kg/cm2, and heated to 100°C.
After drying at 1,700° C. in a tunnel kiln in a normal oxidizing atmosphere, a refractory for a slide gate was obtained.

The physical properties of the obtained refractory are also listed in Table 2 below. In addition,
Apparent porosity, bulk specific gravity, and compressive strength were measured according to JIS. Corrosion resistance is 20X20X15 from the obtained refractory
A test sample of 0+sm was cut out and immersed for 2 hours in 1600° C. molten steel melted in a 100 kg high-frequency induction furnace, and then its erosion damage size was measured. The bealling resistance was determined by polishing the 200x400 surface of the obtained refractory to 5/L.
After achieving a smoothness of OOmm or less, the surface was rapidly heated with an oxygen-acetylene burner, held for 1 minute, and judged by whether or not the surface peeled off in a shell-like manner.

As is clear from Table 2, Examples 1 to 4 and Comparative Example 1
There is nothing particularly noteworthy about the apparent porosity, bulk specific gravity, and compressive strength of the refractories No. 4 to 4.

In addition, regarding corrosion resistance, Al 20. The higher the content, the more likely it is to be eroded.

However, regarding peeling resistance, the refractories of Comparative Examples 1 to 4 have a large to moderate peeling phenomenon, whereas the refractories of Examples 1 to 4 have no to small peeling phenomenon, which is obvious. Differences were observed.

Table 1 further shows a sliding plate made of one refractory for a sliding gate according to the present invention (Example 5), a sliding plate made of a conventional high alumina refractory impregnated with tar or pitch (Comparative Example 5), and alumina - Sliding plate made of carbon refractory (Comparative Example 6)
) under the following conditions.

Practical test 1 Ladle capacity 250 tons Steel type Low carbon aluminum killed steel and Ca-added steel Casting temperature Ladle temperature 1580-1600℃ Casting time 50-60 minutes Sliding plate hole diameter 75-80 mm Practical test 2 Ladle capacity 70 tons Steel type: Low carbon (GO, 05%) ordinary steel Casting temperature: Temperature inside the ladle: 1650°C Casting time: 90 to 100 minutes Sliding plate hole diameter: 35 mm Note that low carbon aluminum killed steel has a #element content of 50 Pp in the steel.
o or less, Ca-added steel is used as a representative of a steel type with relatively high reactivity with refractories, and low-carbon ordinary steel is used as a representative of a steel type with an oxygen content of 100 to 2501) PH1. ing.

Table 3 below shows the average number of times each set was used when 100 of each of the above-mentioned IH printing plates were injected with steel.

Table 3 As is clear from Table 3, in the case of low carbon aluminum killed steel with a low oxygen level in the steel, there is no difference in the number of uses depending on the three types of materials that make up the sliding plate. However, low carbon ordinary steel with a relatively high oxygen level or carbon steel with a strong reducing power
In the case of a-added steel, the number of times of use was increased by 1 to 2 times compared to conventional materials, and the service life could be extended. The main reason for this is thought to be that the reaction of orphans to the high temperature molten steel of 5i02 contained in the refractory is related to melting loss. That is, compared to conventional high alumina refractories impregnated with tar or pitch and alumina-carbon refractories, the alumina-magnesia refractories of the present invention contain less Si.
Since the value of O□ is low, there is little reaction to strong reducing forces such as Ca and Mn01FeO contained in steel, and the structure is strong, which can be said to lead to an extended life.

Note that the raw material used in the present invention may be obtained by sintering or thermal melting, and is not limited in any way by the method of producing the raw material.

In addition, in the present invention, refractory raw materials other than alumina-magnesia spinel raw materials and magnesia raw materials, such as chromite, chromium oxide, zirconia, etc., or 3i,
It is also possible to add metals such as Al, Fe-3T, Mg, etc.) As mentioned above, when metals such as Si and AI are added, it is fired in a nitrogen atmosphere and 5izN
+bond I/'1ζ±AIN bond may be generated1゜Furthermore, tar, pitch, resin, or components that become silica, alumina, magnesia, zirconia, chromium oxide, etc. by heat treatment may be added to the refractory according to the present invention. The service life can be further improved by impregnating it with the liquid substance it contains and then treating the remaining 1% to remove volatile components to make it into a refractory for a slide gate.

[Effects of the Invention] As detailed below, according to the slide refractory for gates of the present invention, the bealling resistance is improved without using any special manufacturing method, and moreover, it can be made of metals and bases that can be melted. It has excellent corrosion resistance against steel slag, and has remarkable effects such as improving lifespan.

Applicant's agent, patent attorney, Takehiko Hand-painted by Masaguchi Neichi] March 77, 1985

Claims (1)

[Claims] Al_2O_310 consists of 10 to 30 parts by weight of an alumina-magnesia spinel raw material consisting of 340 to 70% by weight of Al_2O_3, 25 to 60% by weight of MgO, and a balance of 10% by weight or less, and 90 to 70 parts by weight of a magnesia raw material of 90% by weight or more of MgO. ~25% by weight, MgO90~75
% by weight.