JPH0734978B2 - Immersion nozzle for continuous casting and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a continuous casting immersion nozzle, and more specifically, to prevent alumina from adhering to the inner wall of the nozzle and the wall surface of the discharge port to prevent clogging of the inner hole. And a method for manufacturing the same.

[Conventional technology]

Immersion nozzles, which are indispensable for continuous steel casting operations, are required to have high properties such as spall resistance, wear resistance, and corrosion resistance. A refractory material that meets these requirements is Al ₂ O ₃ -C
The quality is widely used, and ZrO ₂ -C quality with high corrosion resistance is often used in the powder line part around the nozzle.

One of the problems with the continuous casting immersion nozzle is the clogging of the nozzle bore due to the adhesion of alumina. Especially during continuous casting of aluminum-killed steel and aluminum-silicon-killed steel, non-metallic inclusions such as alumina, which is a deoxidation product in molten steel, adhere to the inner hole of the immersion nozzle, the wall surfaces of the discharge hole, etc.
In many cases, it gradually grows and thickens, and eventually nozzle clogging occurs.
Furthermore, if these deposits are captured by molten steel, product deterioration cannot be avoided.

In order to prevent nozzle clogging, a method has also been adopted in which an inert gas such as argon is blown into the wall surface of the nozzle inner hole to prevent adhesion of Al ₂ O ₃ or the like. However, even with this method, non-metallic inclusions such as alumina adhere and grow as the continuous casting overlaps, and the nozzle holes are clogged. Therefore, the clogging prevention measures, including the running cost, are insufficient. Depending on the steel type, gas injection itself may not be desirable for the product.

Attempts have also been made to prevent the adhesion of alumina and the like by selecting the material of the nozzle refractory. As a material that meets this purpose, ZrO ₂ -C a _O-C based material has attracted attention. For example, Japanese Unexamined Patent Publication (Kokai) No. 56-37275 proposes an immersion nozzle for continuous casting using a raw material in which a calcium zirconate clinker and carbon are combined. This product is calcium zirconia clinker 40-93wt%, graphite 5-50wt% and metallic silicon 2 which is obtained by mixing zirconia with 3-35wt% calcia and firing at 1600 ℃ or higher.
It has a composition of 13 wt%. The nozzle having this composition is intended to improve the corrosion resistance in the powder line portion. The proposal in Japanese Unexamined Patent Publication (Kokai) No. 62-288161 has a raw material composition of 20 to 95 wt% calcium zirconate clinker, 5 to 50 wt% graphite, and 0 to 1 wt% metallic silicon. Calcium zirconate-based clinker of the nozzle is a C a _O
16 to 35 wt%, 0.5 to 5 wt% of one or more oxides of group III and group IV elements, and Ca Zr as _a mineral composition
It is mainly composed of O ₃ . Further, in JP-A-64-40154, a composition comprising 60-90 wt% of calcium zirconate containing 40-55% of CaO in _a molar ratio and 10-40 wt% of graphite has an effect of preventing adhesion of alumina. There is a nozzle disclosed.

The present inventors also in JP 63-333981, and fused the ZrO ₂ was added C _{a O} of from 15 to 31% by weight, electrostatic its generation mineral consisting cubic ZrO ₂ and C _a ZrO ³ As a melting raw material, this is crushed to a particle size of 0.2 mm or less and the particle size is adjusted, and 50 to 90 wt% and 10 to 50 wt% of graphite are mixed. ~
A dipping nozzle for continuous casting, which is obtained by adding 6 wt% phenol resin, kneading, press-molding, drying, and firing in a non-oxidizing atmosphere, is proposed.

[Problems to be Solved by the Invention]

ZrO ₂ -C a _O-C refractories when theoretically in contact with alumina inclusions in steel, moderate melting by flushing the TeiTorubutsu that reaction product at its operating surface molten steel flow It is expected that the result will be that the operating surface is constantly updated and that the adhesion or growth of alumina is prevented. However, in practice and try to use by providing the ZrO ₂ -C a _O-C refractories in the immersion nozzle, the steel type and use conditions, the above-mentioned progress soluble in or or vice a excessive erosion There is a problem that a stable state of use cannot always be obtained, such as a loss being small and alumina adhered when used for a long time. The present invention provides _a dipping nozzle for continuous casting and a method for producing the same in _a ZrO ₂ —Ca O—C refractory material, which solves the above-mentioned problems by causing melting loss corresponding to constantly updating the operating surface by molten steel. To do.

[Means for Solving the Problems]

The present inventors have, ZrO ₂ -C a _O-C protein alumina adhesion prevention mechanism of the immersion nozzle a result of various studied, ZrO ₂ · C
involved in the reaction in _{a O} material, by controlling the S _i O ₂ amount including so-called active S _i O ₂ content and activity S _i O ₂ of the bricks in the composition, also stable during extended operation Therefore, it was found that alumina did not adhere. The active _{S i} O ₂ as referred to herein, C of fused ZrO ₂ · _{C a} O in the starting material
In _{S i} O ₂ involved in the reaction with _a ZrO _3, fused ZrO ₂ · _C a O
Shows the total amount of S _i O ₂ added hitting the producing S _i O ₂ and the product of the present invention is contained in the raw material, S contained as part of the ash between layers of scaly graphite S _i O ₂ which is not involved in the reaction _{for i} O ₂ as described is not in contact with the contact C _a ZrO ₃ is defined as excluding.

The present invention based on this finding, a least refractory of the portion in contact with the molten steel, ZrO _2, C _a
ZrO ₂ —C _a O—C refractory containing O and C as main components,
The refractory active S _i O ₂ content immersion nozzle, characterized in that less 0.3 wt% to in the composition, and the gist. Furthermore, 2 mineral composition has a _{C a} ZrO ₃ and cubic ZrO ₂ and _{S i} the O ₂ containing less 0.4 wt% fused ZrO ₂ · _C a O
Provided is a method for producing a continuous casting immersion nozzle, which comprises a step of mixing 50 to 95 wt% of a raw material and 5 to 50 wt% of graphite, and a step of adding a binder to this mixture, kneading the mixture, and firing after molding.

[Work]

When Al ₂ O ₃ in the molten steel is in contact with the working surface of the ZrO ₂ -C a _O-C bricks _{is, Al 2 O 3 C a ZrO} 3 is a main component of the ZrO ₂ -C a _O fused material It has been confirmed by the study of the present inventors that it directly reacts with the following reaction formula.

xC _a ZrO ₃ + yAl ₂ O ₃ → xC _a O ・ yAl ₂ O ₃ + xZrO ₂ (SS) (1) This reaction mode causes the precipitation of C _a O after the previously considered decomposition of C _a ZrO _3. and, it is not equal to what its C _{a O} and Al ₂ O ₃ reacts. That is, (1) a reaction form of expression is C _a ZrO ₃ has arisen reaction by contact -system and Al ₂ O _3. C _a ZrO ₃ in other words is stable unless contact -system and Al ₂ O _3, also means that the reaction proceeds of (1) depending on the amount of Al ₂ O ₃ in the steel.

_{(1) xC a O · yAl} 2 O 3 produced by the formula (calcium aluminate) produces a _{ZrO 2 -C a O-Al 2} O 3 based low Torubutsu as a liquid phase at operating temperature range of the nozzle. Figure 1 shows Zr
_{O 2 -C a O-Al 2} O 3 system is a distribution diagram of a three-component analysis after operation in the first drawing the reaction layer of the nozzle (after molten steel immersion) (will be described later this part) Although the existence range of the value is shown, the whole amount does not become the liquid phase in the operating temperature range such as 1550 to 1600 ° C, but a part of it becomes the liquid phase and an appropriate liquid phase amount is generated. . Therefore, appropriate melting loss occurs, the working surface of the nozzle is constantly renewed, and alumina adhesion is effectively prevented.

In terms of this reaction mechanism, the reaction and melting loss should proceed and continue depending on the amount of Al ₂ O ₃ that enters from the molten steel during operation, but in reality this adhesion prevention function Was not maintained, and there were cases where alumina adhesion occurred. We further study results, the formation behavior of TeiTorubutsu which are the basis of the anti-adhesion of alumina, it was confirmed that a large effect of active S _i O ₂ involved in the formation reaction. That, although fused by mixing and baddeleyite (ZrO ₂₎ and limestone (C _a CO ₃₎ to make C _a ZrO ₃ raw material, the active S _i O ₂ of about 0.5% to 1% due to the starting material It was generally inevitable. The _{C a} O and Zr
All When the O was fused is C _a ZrO ₃ and cubic ZrO ₂
However, free _{Ca 2} O may remain in a slight amount, and the brick structure may be destroyed by hydration with moisture in the air during storage of raw materials or during production. To avoid this, the free C _a O
The case of fused there were many by adding S _i O ₂ of about 1-3% to secure as calcium silicate.

Even if inevitable, even in the operating manner is active S _i O ₂ involved in the reaction are coexist in ZrO ₂ -C a _O raw material or ZrO ₂ -C
When in contact with the _{a O} material, if brick is heated, it immediately reacts with C _a ZrO ₃ and S _i O ₂ decomposes C _a ZrO _3, to form calcium silicate as: become.

_{xC a ZrO 3 + yS i O} 2 → xC a O · yS i O 2 + xZrO 2 ...... (2) for this reaction which occurs in unaffected zone layer is Al ₂ O ₃ in the steel does not contact _{C a} ZrO ₃ and Kai C _a ZrO ₃ is taken, Al ₂ O ₃ that follow in steel
There will be (1) the reaction of equation does not occur sufficiently between Al ₂ O ₃ and C _a ZrO ₃ be in contact Kai, eventually will elicit alumina deposition.

The present inventors have found that (1) a result of repeated correlations per experiment with the generation of calcium silicate by the generation and (2) calcium aluminate according to formula, ZrO · C _a
The O Fused S _i O ₂ content in the raw material and less 0.4 wt%, by limiting the content of active S _i O ₂ involved in the reaction, long alumina adhesion preventing function at the nozzle refractory It was possible to maintain it throughout operation. The presence of this excess active S _i O ₂ generates a _{C a O-Al 2 O 3} -S i O 2 system very low melting point of the reactants when reacted with Al ₂ O _3, the alumina deposition It was also confirmed that the melting loss of the nozzle for preventing it was significantly increased and the nozzle life was shortened.

The present invention is a ZrO ₂ -C _a O-C refractories, ZrO _2, C
_a Active S mainly containing O and C and participating in the reaction
_{The i} O ₂ content is 0.3 wt% or less of the total refractory composition. S _i
The O source is by ZrO ₂ · C a _O fused material others contained in those contained in the scaly graphite is used as carbon source and added the S _i compound. Scaly graphite S _i O ₂ or less generally several percent during is included as part of the ash. However, S _i O ₂ in phosphate-like graphite is distributed between layers of the graphite, since it is not possible to produce reaction between the C _a ZrO ₃ because it does not directly contact the C _a ZrO _3, the reaction of this embodiment often less of inert S _i O ₂ which is not involved in the not affect the low melting product generation reaction during refractory operation.
Accordingly, ZrO ₃ -C a _O-C protein as S _i O ₂ of the refractories was much, including those contained in the scaly graphite of which reaction not involving inert S _i O ₂ Except C
book amount of active S _i O ₂ to react directly with _a ZrO ₃ is when the material adjusted to be less than 0.3 wt% with respect to the entire brick composition, thereby rise to optimum erosion for wall updated by the molten steel stream The object of the invention will be achieved. for that purpose,
SiO ₂ component of ZrO ₂ · C a _O fused in the raw material is of preferably at most 0.4 wt%.

On the other hand, many examples in the carbon-containing refractory of adding metallic silicon and S _{i C,.} 2 to the metal silicon in the technique described in JP-A-56-37275 mentioned above as antioxidant and sintered material of graphite 13% is added. In addition, JP-A-62-28
In the technology described in 8161 JP added 1% for antioxidant and enhancing strength of the metal silicon, and further corrosion resistance, even the addition of S _{i C} for spalling resistance improvement can with.
However, according to the research conducted by the present inventors, the addition of these causes the reactions shown in the following formulas (3) and (4) during operation of the refractory, and finally becomes S _i O ₂ as described above. C _a ZrO ₃
Will be disassembled.

S _i + C → S _i C (3) Accordingly, the present invention while limiting the active S _i O ₂ content in the raw material, S _i O _2, metallic silicon, it is not added any S _i or S _i based compounds such as S i _C is a requirement. That, including those contained in the scaly graphite, active S _i O ₂ amount excluding inactive S _i O ₂ which is not involved in the reaction, is not more than 0.3 wt% with respect to the entire brick composition. Also,
Since the metal S _i, which is useful for improving strength, is not used as a sintered material, strength is improved by using pitch and resin together as a binder to form a strong carbon bond.

Of the present invention [Effect of the Invention, and the content of active S _i O ₂ and less 0.4 wt% ZrO
Immersion nozzle for a ₂ · C a _O fused material as a main material lasts alumina prevention function for a long time during its operation, stable operation state can be obtained.

〔Example〕

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

Immersion nozzle of the first invention, a manufacturing method is the second invention, i.e., 15～31Wt% of C a _O, a S _i O ₂ 0.4 w
The graphite was mixed 5-50 wt% to the fused ZrO ₂ · C a _O material mainly composed of the C _a ZrO ₃ and cubic ZrO ₂ containing t% or less,
An organic binder such as pitch or resin is added to this mixture, which is kneaded, pressure-molded, dried, and fired in a non-oxidizing atmosphere.

Here the amount of C _{a O} components in fused material was 15～31Wt%, when C _{a O} amount is small is less than 15 wt%, calcium aluminate amount reacts with alumina in molten steel It is too small to sufficiently prevent the adhesion of alumina. Reacts with C _{a O} all ZrO ₂ upon fused when more than 31 wt% and C _a Zr
O ₃ and not the free C _{a O} is the remaining digestion resistant poor.

Fused ZrO ₂ · C a _O material was purified active S _i O ₂ content 0.
It was not more than 4 wt% is for the adverse effects mentioned above the active S _i O ₂ content is high occurs, the active S _i O ₂ content is of course better less as possible .

Phosphorous graphite is usually used as the graphite to be combined with the electromelting raw material, and 5 to 50 wt% is added to impart spall resistance.
If the amount of graphite added is less than 5 wt%, spall resistance becomes difficult, and if it exceeds 50 wt%, corrosion resistance deteriorates, so the above range is preferred. The purity of the scaly graphite because some S _i O ₂ in phosphate-like shaped graphite is contained as ash content is preferably higher. But not affect the properties of the product because in the case of a scaly graphite does not contact directly with C _a ZrO ₃ distributed between layers of the graphite, as described above.

In addition, the pitch is 5 to 15 wt% when applied outside the refractory composition.
(Preferably 8 to 13 wt%), phenol resin 2 to 10
A nozzle refractory with high corrosion resistance can be obtained by adding wt% (preferably 4 to 6 wt%). The pitch used here may be either coal-based or petroleum-based, and the softening point is 70 to 45.
Although various substances can be used over the range of 0 ° C., the volatile content is preferably 5% or less with respect to the entire refractory material. The reason for this is that if the volatile content exceeds 5%, there is a risk that the molded body will swell due to the large amount during volatilization decomposition during firing, and the structure will become weakened. The amount of phenolic resin added is 2 to 10 wt%, but if it is less than 2 wt%, the pore size after firing is as large as about 1 μm, and if it exceeds 10 wt%, the volatile content is large, so that cracks or blistering may occur during firing. There are many. Therefore, the amount of phenolic resin added is 4
The range of 6 to 6 wt% is preferable because the size of the pore diameter can be set to about 0.5 μm.

In these additives, may be added phenol resin were mixed pitch was finely divided state but, ZrO ₂ · C _a O
A step of adding pitch to the electromelt and kneading while melting the pitch at a temperature equal to or higher than the softening point to form a granule in which the periphery of the aggregate is covered with the pitch and adding a phenol resin after cooling is preferable. By this means, the periphery of the individual oxide particles is covered with carbon, and the resistance to thermal shock increases.

-Example 1-Using the raw materials having the analysis values shown in Table 1, the dipping nozzles for continuous casting were manufactured with the formulations shown in Table 2.
After kneading the required amount of each raw material, 1200 by rubber press
It was molded at a pressure of kg / cm ² , dried at about 260 ° C, and then baked at 1000 ° C in a non-oxidizing atmosphere. Table 3 shows the physical properties and characteristic values of the obtained continuous casting immersion nozzle.

The measurement was performed by the following method.

Spar test A cylindrical test piece with an outer diameter of 200 mm and a length of 250 mm was cut out from the nozzle shape and heated in an electric furnace at 1400 ° C x 1 hr.
The presence or absence of crevices was observed. Those without cracks were evaluated as ◯, and those with cracks were evaluated as x.

b. Alumina adhesion test A test piece of 20 x 20 x 150 mm was cut out and immersed in a high-frequency furnace in which 5 kg of steel was melted. Immediately after immersion, 15 minutes later, 30 minutes later, each 10 g of aluminum was charged, and 60 minutes after the beginning. The thickness of the deposited alumina was measured. No adhesion was evaluated as ◯, partial adhesion of 0.5 mm or less was evaluated as Δ, and adhesion of 0.5 mm or less was evaluated as x.

The thickness of the reaction layer of the test piece working surface after the alumina deposition test was observed with a reflection microscope to measure the far that the decomposition of C _a ZrO ₃ of fused ZrO ₂ · C a _O material particles.

c. Molten steel erosion test A test piece (50 × 50 × 50m immersed in molten steel of a high frequency furnace
m), while applying a vibration of 1500 cycles per minute with a vibration device 1
Hold at 600 ℃ × 1hr. The amount of melting loss (mm) was measured.

d. Others The standard refractory test method based on JIS was used.

No.1~3 in Table 2 and Table 3, ZrO ₂ · _C a O
In case of active S _i O ₂ content involved in the reaction of DenTorubutsu are different, No.1 those using S _i O ₂ content of about 1 wt% of the conventional product, No.2 is the present invention those S _i O ₂ content of fused material in the ZrO ₂ · C a _O is equal to or less than 0.4 wt% in the examples, No.3 is S _i O of ZrO ₂ · in C a _O DenTorubutsu in Comparative example ₂ Content is about 2.0 wt%. The No.4 and 5, the metal silicon or S _i to No.2
C is added to each.

There is no great difference in the physical properties of these materials. Al ₂ O
₃ Although the appearance of the test piece not observed adhesion of Al ₂ O ₃ reaction of approximately C _a ZrO ₃ when examined by microscopy and X-ray microanalyzer after immersion deposition test is doing. That is, for C _a ZrO ₃ ingredients indicates the angular grasshoppers particle form was pulverized, since C _a ZrO ₃ is rounded with comminuted when reacted with S _i O ₂ or Al ₂ O _3, this phenomenon It is possible to measure the reaction layer thickness. Of low _{S i} O ₂ No.2
In Al ₂ O ₃ is not promoted only react to the portion that has penetrated, the reaction layer is thin unaffected zone layer only is C _a ZrO ₃ remains intact. In contrast, the reaction layer carry a C _a ZrO ₃ is decomposed rounded unaffected zone layer by the S _i O ₂ often No.1 and No.3~5 S _i O ₂ is thick, simultaneously unaffected zone The difference between the layer and the reaction layer becomes difficult to discern, and the amount of melting loss increases. 3 (A) (B) (C) shows the grain structure of the quality layer after immersion in molten steel in the No. 1, No. 2 and No. 4 alumina adhesion tests. Is a micrograph showing the state of the raw material layer is clear.

-Example 2-In the actual manufacture of the nozzle, the refractory according to the present invention may be entirely used as in Example 1, but as shown in FIG. The refractory 1 according to the present invention is used on the lower side of the nozzle including the 10 discharge holes 4 and the wall surface of the inner hole 5, that is, at least in the portion in contact with molten steel, and the upper side of the nozzle is made of Al ₂ O ₃ -C material. Refractory 2,
The powder line portion 6 may be made of ZrO ₂ -C quality refractory material 3, respectively.

The conventional refractory material obtained by the No. 1 formulation in Table 2 is formed of aluminum killed material in the conventional nozzle which is formed on the lower and inner wall surfaces including the discharge holes of the nozzle of the same shape as the nozzle shown in FIG. Continuous casting of steel or aluminum silicon killed steel with a life of 7 charges on average, out of 100
The obstruction was reached at a rate of 2.5. However, when the refractory material obtained by blending No. 2 which is an example of the present invention was used, alumina adhesion did not occur at all in the same target steel type, corrosion resistance was good, and at least 8 charges were possible. .

[Brief description of drawings]

Figure 1 _{ZrO 2 -C a O-Al 2} O 3 is in the refractory of the present invention
Which shows the existence range of the analytical value of the reaction layer after the operation shown in the distribution state diagram of the three components of the low-melting-point system, FIG. Figure (A) (B)
(C) is a micrograph showing the particle structure of the raw material layer of the immersion nozzle after immersion in molten steel. 1 …… Example refractory 2 …… Al ₂ O ₃ -C quality refractory 3 …… ZrO ₂ -C quality refractory 4 …… Discharge hole 5 …… Inner hole 6 …… Powder line 10 …… Dip nozzle

Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical location C04B 35/52 (72) Inventor Yoichi Yokoyama 1-3-1, Niihama, Arai-cho, Takasago-shi, Hyogo Harima Ceramics Co., Ltd. (72) Inventor Masami Nishikawa 1-3-1 Niihama, Arai-cho, Takasago, Hyogo Prefecture Harima Ceramics Co., Ltd.

Claims (2)

[Claims] 1. A refractory at least a portion in contact with molten steel is
O _{2, C} a O, and ZrO ₂ -C _a O-C refractories composed mainly of C, 0.3 wt active _{S i} O ₂ content of the refractory composition
% Or less, a continuous casting immersion nozzle. 2. A mineral composition C _a ZrO ₃ and cubic Zr
It has a O _2, and containing less 0.4 wt% of S _i O ₂ fused ZrO ₂
· C a _O feedstock 50～95Wt% and graphite 5-50 wt%, and kneaded by adding a binder to the process and this mixture is mixed with city method of immersion nozzle having a step of firing after molding.