JPH06277825A - Lower nozzle brick for sliding gate - Google Patents

Abstract

PURPOSE:To solve the problem of the generation of cracks by rapid thermal impact and the corrosion resistance at the time of many times of use and to improve spalling resistance. CONSTITUTION:Refractory raw materials having a chemical compsn. consisting of 30 to 80wt.% Al2O3, 10 to 65wt.% ZrO2 and 5 to 25wt.% SiO2 are used at 10 to 45wt.% in the lower nozzle brick for a sliding gate consisting of 60 to 90wt.% aluminous refractory material. The lower nozzle brick for the high aluminous SN formed by using the refractory raw materials having the chemical compsn. consisting of 30 to 80wt.% Al2O3, 10 to 65wt.% ZrO2 and 5 to 25wt.% SiO2 is greatly improved in the spalling resistance. A service life of 1.6 to 2.0 times the service life of the conventional lower nozzle brick for the high aluminous SN is obtd. even in actual use.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lower nozzle brick for a slide gate used in a slide gate for controlling the flow rate of molten metal.

[0002]

2. Description of the Related Art Generally, a slide gate method (hereinafter referred to as SN
Method) is used as a useful control means of the molten metal flow rate, and is widely used especially in the steel industry where the usage conditions are severe. As is well known, this SN system is composed of an upper nozzle, a plate brick (fixing plate and slide plate), and a lower nozzle,
The durability of each refractory material is limited by factors such as chemical erosion due to contact with high-temperature molten steel, thermal spall, and mechanical wear due to molten steel flow.

Among them, the lower nozzle is located at the lowest stage of the brick for the slide gate nozzle due to the structure of the slide gate nozzle device, and part of it is outside the slide gate nozzle device. Therefore, there is no pressing from the outside, and improving the spall resistance is an important issue for stable use.

[0004]

Generally, high-alumina SN lower nozzle bricks for SN are widely used. However, in this high-alumina SN lower nozzle brick for SN, crevices caused by a sudden thermal shock are generated. Occurrence is seen,
The current situation is that sufficient effects have not been obtained.

[0005]

In order to improve the spalling resistance of the lower nozzle brick for high alumina SN, the present invention uses 30-80% by weight of Al ₂ O ₃ and Zr.
It is characterized by using 10 to 45% by weight of a low expansion refractory raw material having a chemical composition of 10 to 65% by weight of O _{2 and} 5 to 25% by weight of SiO ₂ .

The chemical composition of this refractory raw material is Al ₂
O ₃ 30 to 80 wt%, ZrO ₂ 10 to 65 wt%, Si
A suitable amount is 5 to 25% by weight of O ₂ . When the amount of ZrO ₂ is less than 10% by weight, the amount of zirconia precipitated in or around the mullite or corundum crystal is small, which not only impairs the low expansion property but also causes a problem in corrosion resistance. If the amount of ZrO ₂ exceeds 65% by weight, abnormal expansion occurs due to the presence of ZrO ₂ in a monoclinic type crystal, resulting in poor spall resistance. In order to make the remaining mineral phase coexist in mullite and corundum, Al ₂ O ₃ 30 to 80% by weight, S
iO ₂ is limited to 5 to 25% by weight, respectively.

A suitable amount of the refractory raw material having these chemical compositions is 10 to 45% by weight. This is because if it is less than 10% by weight, the effect of improving the spalling resistance is small, and if it is more than 45% by weight, a problem arises in the corrosion resistance. It may be used in any of coarse particles, medium particles, and bifunous parts, but in consideration of corrosion resistance, it is preferable to use in coarse particles and medium particles.

Lower nozzle bricks for high-alumina SN using refractory raw materials having these chemical components are manufactured by kneading, molding and then firing. Also after that tar. It may be impregnated with pitch or the like.

Next, the effects of the present invention will be described with reference to examples.

[0010]

EXAMPLES The physical properties of the lower nozzle for high-alumina SN using the refractory raw material having the chemical composition according to the present invention, the actual use results in the actual furnace and the comparison with the conventional products are shown in Tables 1 and 2 below.
Shown in.

[0011]

[Table 1]

[0012]

[Table 2]

[0013]

As described above, Al ₂ O _{3 is} 30 to 80% by weight, ZrO _{2 is} 10 to 65% by weight, and SiO _{2 is} 5 to 25% by weight.
In the lower nozzle brick for high-alumina SN using the refractory raw material having the chemical composition of, the spalling resistance is greatly improved, and in actual use, it is compared with the conventional lower-aluminum SN lower nozzle brick. 1.6 ~
It was possible to obtain a durability of 2.0 times.

Claims (1)

[Claims] In a lower nozzle brick for a slide gate, which is composed of 60 to 90% by weight of an alumina refractory material, Al ₂ O ₃ 30 to 8
0 wt%, ZrO ₂ 10-65 wt%, SiO ₂ 5-25
A lower nozzle brick for a slide gate, characterized in that 10 to 45% by weight of a refractory raw material having a chemical composition of 10% by weight is used.