JP3015305B2 - Nozzle for continuous casting of steel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum killed steel (hereinafter simply referred to as "steel" ) for an immersion nozzle, a long nozzle or the like.
)) .

[0002]

2. Description of the Related Art In continuous casting of Al-killed steel, Al ₂ O ₃ —S which has been excellent in corrosion resistance and spall resistance has been conventionally used.
iO ₂ -C quality nozzles are most widely used. However, clogging of the nozzle inner tube due to adhesion of Al ₂ O ₃ inclusions generated by Al deoxidation in steel has become a problem.

[0003] The blocking mechanism is as follows. First, in a refractory at a high temperature, Si used as a refractory raw material is used.
The reaction of the formula (1) occurs between O ₂ and C. The generated SiO (gas: hereinafter referred to as “(g)”) and CO (g) diffuse into the interface between the nozzle and the molten steel, and react with Al in the molten steel according to the equations (2) and (3). Causes alumina to be generated on the working surface of the nozzle and fused to the nozzle surface,
l ₂ O ₃ sets the stage for inclusion adhesion:

Embedded image SiO ₂ (s) + C (s) = SiO (g) + CO (g) (1)

## STR2 ## 3SiO (g) +2 Al = Al 2 O 3 (s) +3 Si (2)

Embedded image 3CO (g) +2 Al = Al ₂ O ₃ (s) +3 C (3)

In the above formula, (s) is a solid phase,
(G) represents a gaseous phase, and Al , Si , and C represent Al , Si , and C in a molten state in molten steel, respectively.

[0005] As the adhesion of alumina inclusions progresses, the nozzle is blocked. This not only shortens the service life of the nozzle, but also hinders the continuous casting operation.

In order to solve the above problem, a method of coating the inner hole of the immersion nozzle with a refractory material not containing C for the purpose of eliminating the reaction of the formula (1), that is, a method of coating the inner surface of the runner of the immersion nozzle with the runner. _{al 2 O 3, MnO 2,} MgO, CaO, immersion nozzle for continuous casting which is disposed a refractory obtained by adding SiO ₂ alone or combined to is disclosed in JP-a-51-54836. However, S described in the publication as desirable
In the region of 90 to 99% by weight of iO ₂ , the following (4)
By the reaction shown in the formula, alumina is generated on the working surface of the nozzle in the same manner as in formulas (1) to (3), and fused to the nozzle surface,
The starting point for the adhesion of Al ₂ O ₃ inclusions in steel:

Embedded image _{3SiO 2 (s) +4 Al =} 2Al 2 O 3 (s) +3 Si (4)

As a countermeasure for this, Si exceeding 5% by weight is used.
O ₂ free of, Al ₂ O ₃ (or MgO, ZrO ₂₎ is a carbonless high alumina refractory than 90% by weight is disclosed in Japanese Patent Laid-Open No. 3-243258. Also,
JP-A-5-154628 discloses an alumina content of 9%.
It has a refractory composition containing 9% by weight or more of alumina clinker as a main component, an alumina content of 70% by weight or more, a carbon content of less than 1% by weight, and a silica content of less than 1% by weight, and 0.21 mm A continuous casting nozzle bore having the following particle size composition occupying 20 to 70% by weight is disclosed.

[0008] In order to prepare these inner holes, a method of simultaneously press-forming the raw material composition for the inner body and the raw material composition for the nozzle body, or the method for forming the raw material for the inner body on the previously formed nozzle body is used. There is a method of interior filling of the formulation. However, in any of the methods, the coefficient of thermal expansion of the carbon-less material constituting the inner hole body to be internally filled is remarkably large as compared with the coefficient of thermal expansion of the carbon-containing material of the nozzle body. And cracking during use.

[0009]

In order to solve this problem, in the latter manufacturing method, a nozzle body is formed of a refractory material containing a carbon source, and a portion through which molten steel passes and a portion in contact with the molten steel are formed by a carbon source. In the continuous casting nozzle coated with a refractory material that does not contain, the coating portion of the refractory material that does not contain the carbon source is the inner hole straight body part, the lower part of the inner hole, the discharge hole part and the outer peripheral part immersed in the molten steel, The covering portion is formed by a cylindrical shape of a refractory material containing no carbon, and the cylindrical body is connected to the straight body portion through a joint having a thickness of 0.5 to 2.0 mm, and the bottom of the inner hole and the discharge hole are formed. Japanese Patent Application Laid-Open No. 8-57601 discloses a continuous casting nozzle characterized in that the nozzle is provided with a joint having a thickness of 1 to 5 mm. However, in this case, there is a disadvantage that molten steel invades from the joint portion and the inner hole body is likely to be lost during casting.

Accordingly, an object of the present invention is to provide a nozzle for continuous casting of steel, which has both the effect of suppressing the adhesion of Al ₂ O ₃ inclusions and the resistance to spalling.

[0011]

That is, the nozzle for continuous casting of steel according to the present invention is characterized in that, in the nozzle for continuous casting of steel, at least a portion in contact with the inner hole of the nozzle and / or the molten steel contains 5 to 10 SiO _2. % By weight, 90 to 95 Al ₂ O ₃
% By weight, the main mineral phase is mullite and corundum and / or β-alumina, in a simple form
Of SiO ₂ is absent, and the particle size is
It is characterized by being composed of an Al ₂ O ₃ —SiO ₂ -based refractory material produced using a refractory raw material having a particle size ratio of not more than 00 μm and not less than 80% by weight.

[0012]

Further, the nozzle for continuous casting of steel of the present invention comprises:
The Al ₂ O ₃ —SiO ₂ refractory material is characterized by being produced using mullite as a SiO ₂ -containing refractory raw material.

[0014]

Further, the nozzle for continuous casting of steel of the present invention comprises:
The Al ₂ O ₃ —SiO ₂ refractory material is disposed in the inner hole of the nozzle at a thickness of ₂ to 10 mm.

Further, the nozzle for continuous casting of steel of the present invention comprises:
The Al ₂ O ₃ —SiO ₂ refractory material is provided at a portion in contact with the molten steel with a thickness of ₂ to 10 mm.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
Nozzle for continuous casting of steel of the present invention (hereinafter simply referred to as “nozzle”
At least a portion in contact with the inner hole of the nozzle and / or the molten steel has 5 to 10% by weight of SiO ₂ and A
Al ₂ O _{3 in} which l ₂ O ₃ has a chemical composition of 90 to 95% by weight
There is characterized in that is constituted from -SiO ₂ refractory material, further, the main mineral phase of Al ₂ O ₃ -SiO ₂ -based refractory material is characterized in mullite and corundum and / or β- alumina.

In the Al ₂ O ₃ —SiO ₂ refractory material, if the content of SiO ₂ is less than 5% by weight, that is, if the content of Al ₂ O ₃ exceeds 95% by weight, the proportion of silica in the refractory is too small, ie, If the proportion of alumina is too high, the spall resistance of the refractory is significantly reduced, which is not desirable.

As is well known, as SiO ₂ increases, that is, as Al ₂ O ₃ decreases, Al ₂ O ₃ —S
The spall resistance of the iO ₂ refractory is improved. However, S
When iO ₂ is more than 10% by weight, that is, Al ₂ O ₃ is less than 90% by weight, the clogging of the nozzle becomes large as described in Examples below.

Accordingly, the Al ₂ O ₃ − used in the present invention is
The composition of the SiO ₂ based _refractory, SiO 2 5 to 10 wt%, A
Desirably, the content of l ₂ O ₃ is in the range of 90 to 95% by weight.

Also, Al ₂ O ₃ —SiO ₂ refractories include:
Inevitable impurities (carbon, CaO, etc.) caused by a binder or the like blended when molding the raw material mixture, inevitable impurities (TiO ₂ , MgO, Na ₂ O caused by β-alumina, K ₂ O) may be present, but this unavoidable impurity is acceptable if its amount is 2% by weight or less.

That is, in the nozzle of the present invention, the Al ₂ O ₃ —SiO ₂ refractory material constituting at least the inner hole of the nozzle and / or the portion in contact with the molten steel is substantially Al ₂ O _3.
And it is composed of SiO _2, because the carbon is a substantially absence, the (1) it is possible to suppress the reaction to (3), thereby preventing clogging of the nozzle by the alumina inclusion be able to.

Further, the Al ₂ O ₃ —SiO used in the present invention
_{In the 2} type refractory material, since the SiO ₂ is contained not in a simple form but as mullite (3Al ₂ O ₃ .2SiO ₂ ), the thermodynamic activity of the SiO ₂ is significantly reduced,
The reactivity between Al in the molten steel and SiO _{2 in the} refractory material is (4)
It is significantly smaller than the reaction shown in the equation. As a result, when mullite is applied to the material of the nozzle, adhesion of alumina due to the reaction between the molten steel and the refractory material is significantly reduced.

Al ₂ O ₃ —Si used for the nozzle of the present invention
The O ₂ -based refractory material may be applied to the inner hole of a continuous casting nozzle such as a long nozzle and an immersion nozzle and / or a portion in contact with molten steel, and the entire continuous casting nozzle such as a long nozzle and an immersion nozzle. May be used for

When the entire nozzle is composed only of an Al ₂ O ₃ —SiO ₂ refractory material, a predetermined refractory raw material may be a polysaccharide such as phenolic resin or molasses or a cellulosic refractory such as CMC. It can be manufactured by kneading with a binder generally used when manufacturing a product, molding into a predetermined nozzle shape by CIP or the like, drying and firing. Further, the refractory raw material can be produced by casting, press-fitting, drying and, in some cases, firing.

Depending on the type of the binder, for example, carbon such as phenol resin due to the binder and CaO due to cement may be mixed, but the amount thereof is small and can be regarded as inevitable impurities. There is no particular problem if these unavoidable impurities are 2% by weight or less in total with the unavoidable impurities caused by the starting material.

In the case where an Al ₂ O ₃ —SiO ₂ refractory material is provided in the inner hole of the nozzle and / or the portion in contact with the molten steel, the formation of the inner hole of the nozzle and / or the portion in contact with the molten steel is performed in the following manner. (1) Simultaneously press-molding the raw material composition of the Al ₂ O ₃ —SiO ₂ -based refractory material constituting the portion (a) and the raw material composition of the refractory material constituting the nozzle body to form a predetermined nozzle shape (simultaneous molding) Method) or a method of internally filling a preformed nozzle body with a compound of a refractory raw material forming an Al ₂ O ₃ —SiO ₂ refractory constituting an inner hole and / or a portion in contact with molten steel (interior). Method). An alumina-carbon refractory material conventionally used as a refractory material constituting the nozzle body (base),
Materials such as zirconia-carbon refractory materials can be used.

The distribution pattern of the refractory material in the nozzle of the present invention is shown in FIGS. Here, FIGS.
The ZrO ₂ -C-based refractory material is arranged in the powder line portion of the immersion nozzle. The powder line portion is a zone in contact with the mold powder having a high erodibility during use of the immersion nozzle, and therefore, the Al ₂ O ₃ -C
The powder line portion is reinforced with a ZrO ₂ -C type refractory material having excellent corrosion resistance. Incidentally, Al ₂ O ₃ -C refractory materials and ZrO ₂ -C refractory material can be used and the conventional composition, Al ₂ O ₃ -
For C-based refractory materials, for example, Al ₂ O ₃ 30 to 90
Weight%, SiO ₂ 0~35 weight%, C10~35 weight%
Can be used, and Zr
In the O ₂ -C refractory material, when using the CaO-stabilized ZrO _2, for example, ZrO ₂ from 66 to 88 wt%, C
Those having a composition of 2 to 4% by weight of aO and 10 to 30% by weight of C can be used. In general, CaO-stabilized ZrO ₂ is widely used as a ZrO ₂ raw material. In addition, MgO-stabilized ZrO ₂ , Y ₂ O ₃ -stabilized ZrO ₂
O ₂ , badderite and the like can be used.

In the case of simultaneous molding, a raw material composition of a refractory material constituting a nozzle body such as alumina-carbon kneaded with a polysaccharide such as a phenol resin or molasses as a binder, and an inner hole and / or A raw material mixture of Al ₂ O ₃ —SiO ₂ refractory material constituting a portion in contact with molten steel is filled in a predetermined position of a mold, molded by CIP or the like,
After drying, it can be made into an unfired product or fired.

In the case of the interior method, a kneaded raw material mixture is cast into a nozzle body prepared in advance by a conventional method using a binder such as cement, silicate, or phosphate, followed by press molding. , Drying, and firing in some cases, or may be manufactured by pressure molding, pouring or press-fitting into a nozzle body (base body) prepared in advance by a conventional method. And / or a portion in contact with molten steel).

Al ₂ O ₃ —Si constituting the nozzle of the present invention
Raw materials used to form the O ₂ -based refractory material include silica-based materials (such as cristobalite, quartz, and silica glass), mullite materials, and alumina materials (corundum,
In addition to (β-alumina), a raw material mainly composed of two components of Al ₂ O ₃ —SiO ₂ can be used. Any of the raw materials may be either an electrofused raw material, a sintered raw material or a natural raw material.

The whole nozzle of the present invention is made of Al ₂ O ₃ —SiO ₂
When it is made only of a refractory material or when it is made through a firing step by a simultaneous molding method, a silica-based material can be used.However, it is necessary to sufficiently react the alumina-based material and the silica material during firing to produce mullite. There are 12
A firing temperature of 00 ° C. or higher is required. However, if the mullite generation reaction is insufficient, a silica-based raw material may remain. Therefore, it is more preferable to use a mullite or alumina-based raw material as a starting material. In this case, 250
There is no particular problem with unsintered products dried at a temperature of not less than ° C. In addition,
The content of unavoidable impurities such as MgO and TiO ₂ in the starting material is 2% by weight in total with the above unavoidable impurities caused by the binder for the purpose of preventing oversintering at the time of using the nozzle.
The following is desirable.

The starting material used has a particle size of 100
The particle size is preferably 0 μm or less, and more preferably, the particle size ratio of 500 μm or less is 80% by weight or more. Maximum particle size is 100
When the particle size ratio of more than 0 μm or 500 μm or more exceeds 20% by weight, the maximum particle size with respect to the thickness of the nozzle becomes too large, resulting in embrittlement of the refractory structure during use and dropout of particles.

When the Al ₂ O ₃ —SiO ₂ refractory material is used separately from other refractory materials, the Al ₂ O ₃ —Si
The thickness of the O ₂ -based refractory material is desirably in the range of _{2 to 10} mm. If the thickness is less than 2 mm, it is not desirable because it may be damaged during use and the original function may not be exhibited. If it exceeds 10 mm, the difference in thermal expansion from the refractory material constituting the nozzle body (base) may be reduced. Undesirably, cracks originating from the cracks occur (deterioration of spall resistance).

[0035]

The spalling test and the alumina adhesion test for each sample of the following examples and comparative examples will be described. In the spalling tests in Examples 1 and 2, the samples were heated to 1500 ° C. in an electric furnace and then evaluated for the occurrence of cracks after water cooling. Ten samples were prepared and evaluated by the number of samples having cracks. Alumina adhesion test, 1 wt% aluminum in 1550 ° C molten steel
The sample was dissolved, and the sample was immersed in the sample for 60 minutes. The evaluation was made based on the thickness of the alumina adhered to the immersion part.

Example 1 A phenol resin or molasses was added as a binder to a mixture of the starting materials shown in Table 1 below, and kneaded.
CIP molding at 0 kgf / cm ² ,
After drying for 1 hour, baking at 1400 ° C for 3 hours
A test sample having a shape of mm, outer diameter of 55 mm and length of 400 mm was prepared. Nozzle characteristics were evaluated by performing physical characteristics, alumina adhesion test and spalling test.

[0037]

[Table 1]

In Table 1, the symbols in the starting material and the mineral phase column after firing are A: corundum, β: β-alumina, M:
Mullite, S: silica glass, C: cristobalite,
G: represents graphite. The symbols in the binder column represent F: phenolic resin and T: molasses, respectively.

In Table 1, the bending strength is the strength at 1400 ° C., and the coefficient of thermal expansion is the value at 1000 ° C. The symbol * indicates that the refractory has fallen off.

[0040] Al ₂ O ₃ what was blended 99% by weight (Comparative Product 1), spalling resistance is markedly inferior, also, SiO ₂
(Comparative products 2 and 3) in which 90% by weight or 15% by weight was blended, the refractory fell off, and Al
_{In the case of 2} O ₃ —SiO ₂ —C (Comparative product 4), the alumina adhesion was remarkably poor. However, the products 1 to 4 of the present invention may be either alumina-resistant or spall-resistant, and no refractory was dropped off.

Example 2 A phenol resin was added as a binder to a mixture of the starting materials shown in Table 2 below, kneaded, and kneaded at 1000 kgf / cm.
CIP molding at ² and drying at 250 ° C for 3 hours, then 1400
C. for 3 hours to prepare a test sample having an inner diameter of 30 mm, an outer diameter of 55 mm, and a length of 400 mm.
Nozzle characteristics were evaluated by performing physical characteristics, alumina adhesion test and spalling test. In Table 2, the bending strength is the strength at 1400 ° C, and the thermal expansion coefficient is the value at 1000 ° C.

[0042]

[Table 2] In addition, * in a table | surface shows that the refractory has fallen off.

When the maximum particle size of the starting material exceeded 1000 μm, or when the particle size ratio of 500 μm or more exceeded 20% by weight, particles fell off from the nozzle sample. Therefore, it is understood that the desirable particle size of the raw material is 1000 μm or less, and the particle size ratio of 500 μm or less is 80% by weight or more.

Example 3 A nozzle (nozzle) in which the alumina-carbon refractory material of Comparative Product 4 shown in Table 1 above was used as the main body material of the nozzle, and the product 2 of the present invention shown in Table 1 was used as the material of the nozzle inner hole. Outer diameter 130
mm, inner diameter 70 mm, length 600 mm) by changing the thickness of the inner hole member material (1 mm, 2 mm, 5 mm, 10 mm,
12 mm, but the nozzle thickness was constant). The sample was obtained by simultaneous molding by CIP molding, drying at 250 ° C. for 3 hours, and then firing at 1000 ° C. for 3 hours. The distribution pattern is as shown in FIG.

With respect to the test sample of the obtained nozzle, when dipped in steel containing 1% by weight of Al dissolved at 1550 ° C. in a high-frequency induction furnace for 3 hours, the spall resistance was evaluated by the presence or absence of cracks. Corrosion resistance was compared based on the amount of erosion of each part. Ten test samples were prepared, and the spall resistance was determined by the number of cracked test samples.
The amount of erosion was evaluated by the average erosion depth of the inner hole.
Table 3 shows the test results.

[0046]

[Table 3]

As can be seen from Table 3, if the thickness of the inner hole is less than 2 mm, the interior part may be melted during casting.
In addition, it was found that when the thickness exceeds 10 mm, the spall resistance is significantly reduced.

Example 4 Alumina-carbon refractory material and ZrO ₂ -C refractory material (CaO-stabilized Zr) of Comparative Product 4 shown in Table 1 above
O ₂ 80% by weight, graphite 20% by weight)
A firing nozzle (nozzle body) having a shape of 30 mm, an inner diameter of 70 mm, and a length of 600 mm was prepared. 64 wt% of corundum and 28 wt% of mullite (raw material particle size
300 [mu] m) high alumina cement (CaO: 25 wt%, Al ₂ O _3: 75 wt%) 8% by weight was added, and cast to a thickness of as 5mm shown in Fig. The obtained molded body was dried at 250 ° C. for 3 hours and fired at 1000 ° C. for 3 hours to prepare a test sample of an immersion nozzle. In addition,
The distribution pattern is as shown in FIG.

The composition of the obtained Al ₂ O ₃ —SiO ₂ refractory material was 90% by weight of Al ₂ O _{3 and} 8% by weight of SiO _2.
And CaO2 percent by weight, the major mineral phase is mullite and corundum, Al ₂ O ₃ -SiO ₂ -CaO-based glass had coexist slightly. The test sample of the obtained nozzle was evaluated by the amount of erosion and the spall resistance test under the same conditions as in Example 3 above. Table 4 shows the test results.

[0050]

[Table 4]

When the results in Table 4 were compared with those in Table 3, it was found that no significant damage was caused if the content of inevitable impurities in the refractory material was 2% by weight or less.

Example 5 In order to evaluate the effect of the nozzle of the present invention, an actual machine test was performed. Al ₂ O ₃ -C of the immersion nozzle of the product 9 of the present invention shown in Table 3 and the comparative product 4 of Table 1 having the distribution pattern shown in FIG.
A comparative nozzle of a conventional product, in which the refractory material based on ZrO2-C used in Example 4 was used, was tested. The test was conducted on a low carbon aluminum killed steel [composition (% by weight), C: 0.04, Si: 0.03, Mn: 0.2,
P: 0.01, S: 0.01, Al: 0.05] at a casting temperature of 1580 ° C. The thickness of the maximum inclusion adhesion layer of the inner tube after casting for 210 minutes is 2.0 mm for the nozzle of the present invention 9 while the nozzle of the comparative product is 12 mm, and a significant alumina adhesion reduction effect is obtained. Was seen.

[0053]

By using the nozzle of the present invention, nozzle blockages due to the adhesion of Al ₂ O ₃ inclusions during Al Miki shield steel casting is greatly suppressed, it can continuously casting prolonged the aluminum-killed steel Becomes

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a material distribution pattern of a nozzle according to the present invention.

FIG. 2 is a view showing another embodiment of the material distribution pattern of the nozzle of the present invention.

FIG. 3 is a view showing another embodiment of the material distribution pattern of the nozzle of the present invention.

FIG. 4 is a view showing another embodiment of the material distribution pattern of the nozzle of the present invention.

FIG. 5 is a view showing a material distribution pattern of a conventional nozzle.

[Explanation of symbols]

1 Al ₂ O ₃ -SiO ₂ refractory material ₂ Al 2 O ₃ -C refractory material 3 ZrO ₂ -C refractory material

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-214258 (JP, A) JP-A-7-51819 (JP, A) JP-A-4-37453 (JP, A) JP-A-3- 243258 (JP, A) Japanese Utility Model 63-202462 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) B22D 11/10

Claims (4)

(57) [Claims] 1. A nozzle for continuous casting of steel, wherein at least a portion in contact with an inner hole of the nozzle and / or molten steel is S.
iO ₂ has a chemical composition of 5 to 10% by weight, Al ₂ O ₃ has a chemical composition of 90 to 95% by weight, the main mineral phase is mullite and corundum and / or β-alumina, and S in a simple form
iO ₂ is absent, particle size is less than 1000 μm and 500
nozzle for continuous casting of aluminum-killed steel, characterized in that the particle size ratio of less μm are composed of Al ₂ O ₃ -SiO ₂ system refractory material which is manufactured using a refractory raw material is 80 wt% or more. 2. An Al ₂ O ₃ —SiO ₂ based refractory material comprising S
iO as _2-containing refractory raw material, those made using mullite, claim 1 continuous casting nozzle of the aluminum-killed steel according. 3. An Al ₂ O ₃ —SiO ₂ -based refractory material comprising
2. A nozzle having a thickness of 10 mm disposed in an inner hole of the nozzle.
Or a nozzle for continuous casting of aluminum killed steel according to 2 above. 4. An Al ₂ O ₃ —SiO ₂ based refractory material comprising
3. The nozzle for continuous casting of aluminum-killed steel according to claim 1, wherein the nozzle is disposed at a portion having a thickness of 10 mm and in contact with the molten steel.