JPH0299252A - Nozzle for continuous casting - Google Patents

Abstract

PURPOSE:To enhance corrosion resistance and thermal impact resistance by specifying the contents of ZrO2, 3Al2O3.2SiO2, and Al2O3 as the material of a sleeve for preventing erosion to be mounted to the powder line of the nozzle. CONSTITUTION:The sleeve is made of the ceramics consisting, by wt.%, of >=10 ZrO2, 10 to 40 3Al2O3.2SiO2, and the balance Al2O3. The 3Al2O3.2SiO2 have a small coefft. of thermal expansion and forms the liquid phase having plasticity at a high temp. of >=1200 deg.C and, therefore, there is an effect of relieving thermal stress. However, the corrosion resistance thereof is low and, therefore, the corrosion resistance is improved by adopting the Al2O3-ZrO2-3Al2O3.2 SiO2 system. This ceramics sleeve is mounted to the outside surface of the immersion nozzle, by which the immersion nozzle for continuous casting having the high corrosion resistance and the high thermal impact resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a submerged nozzle used for injecting molten steel from a tundish into a mold during continuous casting of T8 m.

(Prior Art) In continuous casting of molten metal, a long nozzle 2 and an immersion nozzle 4 as shown in FIG. 1 are used between the ladle and the tundish and from the tundish to the mold. In this case, mold powder, which is mainly composed of calcium oxide, silicon oxide, aluminum oxide, iron oxide, alkali, etc., is used to prevent oxidation of the molten metal and to lubricate between the mold and the shell.

In the current immersion nozzle, the nozzle body 4 is made of Al2O, -C, and the part 5 in contact with powder (powder line part) is made of ZrO, -C. This powder damages the submerged nozzle very severely, causing localized damage. Due to this local damage, even though other parts of the immersion nozzle can be used, the lifespan of the powder line section becomes a bottleneck, and this determines the limit of the use of the immersion nozzle.

Therefore, it is desired that the corrosion resistance of current nozzles be improved.

However, the current nozzle has no problems with thermal shock resistance.

Conventionally, as a measure to improve the durability of the powder line portion of the immersion nozzle, (1) a highly corrosion-resistant material such as zirconia graphite is used for the nozzle itself.

(2) Attach a sleeve to the outer surface of the powder line to prevent erosion. (Jitko No. 4.6-26241.

Utility Model Publication No. 53-42568) (3) Spraying a highly durable material onto the powder line area, etc. However, measures (1) and (3) are not sufficient for corrosion resistance.

When method (2) is adopted, the sleeve material must be made of high-purity, high-density fine ceramics equivalent (A Q 20
3 HZ r○2 etc.) (corrosion resistance 2 to 3 times that of current nozzles) has the advantage of practical use. However, since such a material is dense, when the sleeve is immersed in molten steel, it is damaged or cracked due to thermal shock, making it impractical for practical use. Therefore, the development of a sleeve material that has corrosion resistance comparable to that of fine ceramics and can sufficiently withstand thermal shock is a major challenge in improving the durability of the immersion nozzle powder line section.

By the way, for materials such as fine ceramics that crack due to brittle fracture when subjected to thermal shock, the thermal shock resistance can be evaluated using the following index.

E α Therefore, the larger the value of “R4”, the better the thermal shock resistance.

In the conventional technology, as a measure to improve thermal shock resistance, the above-mentioned
As shown in Japanese Patent No. 3-42568, a metal wire made of a highly thermally conductive material is enclosed in a sleeve, and the thermal conductivity of the sleeve is
The aim is to increase thermal shock resistance by increasing R4 by increasing R4, but the above measures cause the metal wire to melt due to the high temperature of the molten steel immersion part of the sleeve, resulting in problems with corrosion resistance. was there.

Therefore, at present, a sleeve material that satisfies both corrosion resistance and thermal shock resistance has not been put into practical use.

(No problem to be solved by the invention) As mentioned above, in the method of attaching a sleeve to the outer surface of the powder line part to prevent erosion damage as a measure to improve the durability of the nozzle, it is necessary to select a sleeve material that satisfies both corrosion resistance and thermal shock resistance. I have not been able to find it until now.

Accordingly, an object of the present invention is to provide a material for a protection sleeve for the powder line portion of an immersion nozzle that solves these problems and has both corrosion resistance and thermal shock resistance.

(Means for Solving the Problems) The present invention aims to solve the above-mentioned problems by providing a powder that has corrosion resistance and thermal shock resistance that can be used in actual equipment, and is made of Al2O.

ZrO, -3Al2O.・Constructed from 2Sin2 series ZrO
2: 10 wt% or more, (ZrO2 is CaO, MgO,
Either a material stabilized with Y2O, etc. or an unstabilized material may be used. )3Al2O3-2SiO2:10-4
This is a ceramic sleeve molded and fired with 0wt2 and the rest with AQ, ○□.

Traditionally, fine ceramics such as ZrO2 and Al2O have been highly corrosion-resistant materials, and ZrO in particular has excellent corrosion resistance and has attracted attention as a protective sleeve for the powder line of immersion nozzles, but due to its low thermal shock resistance, it has not been applied to actual equipment. It was difficult.

Therefore, in order to improve the thermal shock resistance of the sleeve, the present inventors selected AQ, 03. We considered that 3Al2O.・We focused on 2SiO. 3
/120. -2SiO is a material that has a certain degree of corrosion resistance at high temperatures and has a small coefficient of thermal expansion as shown in Table 1.

Table 1 The thermal expansion coefficient of each material and 3AQz03・2SiO, ceramics is 120
At high temperatures of 0° C. or higher, a plastic liquid phase is generated, which is effective in alleviating thermal stress.

However, since 3AQ, 03"2Sin, has inferior corrosion resistance compared to ZrO2, the actual sleeve material should be

A QzO, -ZrO, -3A Q, O," 2 Si
n, system. Table 2 shows the materials prototyped this time and ZrO2
゜The physical property values of Al2O3 ceramic materials and the results of a thermal shock resistance evaluation test conducted by immersion test in molten steel are shown. The molten steel immersion test was conducted after the sleeve was preheated to 900°C, which is the same as in actual machine operation.

Soaked. The nozzle material to which the sleeve material was attached was Al2O3: 48wt%, C: 28wt%, and the remainder S.
iC+SiO2.

Table 2 Thermal shock resistance comparison test results As shown in Table 2, AQ 20. -ZrO,-
3AQ, O, ceramics (sample 1) has Z r O, although its thermal shock resistance is slightly higher than that of the current nozzle.

-It was several steps more expensive than AQ, 03. Note that the current nozzle material has poor corrosion resistance, so it cannot be used as a sleeve. Therefore, sample 1 is considered to be a sleeve material that has no problems in thermal shock resistance and has excellent corrosion resistance when used in actual equipment.

Next, AQzozpZrchp focusing on the composition of sample 1
3AQ□03・2Sin, sleeves with different mixing ratios were created, and as a basic experiment, a powder immersion test was conducted using a 300) cg induction furnace. The soak test was for 2 hours. The powder was a low viscosity powder with a large amount of erosion loss. The powder composition is shown in Table 3. The test results are shown in Table 4.

Melting point: 1108°C, viscosity (1300°C): 1. lpoi
sA Q 203- Z r O2-3A n 20
The corrosion resistance of the l' 2 S 102 ceramic sleeve is required to be at least twice that of the current nozzle. Therefore, our goal was to develop a sleeve that has twice the corrosion resistance of current nozzles and has excellent thermal shock resistance.

3 A Q Due to the influence of the addition of 203.2SiO□, the corrosion resistance was 50wt'! : The above sample 3 has poor corrosion resistance, and below that, the corrosion resistance is good. On the other hand, 3An20. -28in2 is 10
If wt is less than 1 (sample 5), there is a problem in thermal shock resistance.

Therefore, 3AI220, 2Si○2 addition amount 10i+t%~
40 wt% (samples 1, 2, 4.6) is good.

Regarding the effect of ZrO2 addition, when ZrO2 is less than 10 tit% (Samples 8 and 9), corrosion resistance deteriorates. Therefore, ZrO.

The amount of addition must be 10 tzt% or more (Samples 1 and 7).

From this, the ceramic sleeve material with high corrosion resistance and excellent thermal shock resistance is AQz○, -ZrO2-3A.
Q20.・2Sio, ZrO2: 10wt% or more in the system, 3A (120, -2Sin, : 10w
It is a t% to 40Ilt% type material. Also, ZrO, is C
ab,Y2O,.

Even when ZrO2 stabilized with MgO or the like is applied, it has become possible to obtain a ceramic sleeve with equivalent corrosion resistance and thermal shock resistance.

Next, when we conducted a confirmation test on an actual machine using Sample 1, we confirmed that the product's lifespan was 2.5 times longer than that of conventional materials.

(Effect of the invention) In this way, A"z O3-Z r○2-3Al2O.・
By attaching a 2Si02 ceramic sleeve to the outer surface of the immersion nozzle, a continuous casting immersion nozzle with high corrosion resistance against powder and high thermal shock resistance can be expected.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a long nozzle and a submerged nozzle being used in a continuous casting tandy cloth, and FIG. 2 is a cross-sectional view showing a sleeve installed on the outer surface of a powder line portion according to the present invention. 1... Tandite shu 2... Long nozzle 3.
・Stopper 4... Continuous casting nozzle 5...
・Mold 6... Ceramic sleeve of the present invention No. 11! Atsushi 2 figure

Claims (1)

[Claims] In a continuous casting nozzle for molten metal, which is located in the powder line of the continuous casting nozzle and has a sleeve for preventing erosion damage attached to the outer surface, ZrO_2 is used as the sleeve.
10wt% or more, 3Al_2O_3・2SiO_210
A continuous casting nozzle characterized in that it uses a sleeve consisting of Al_2O_3 in wt% to 40wt%, the balance being Al_2O_3.