JP2016112576A - Slide plate and producing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize stabile high tolerance in alumina-carbon slide plate by stably suppressing damage in an edge part due to heat spalling upon heating 2 surfaces of the slide plate.SOLUTION: An alumina-carbon slide plate of the present invention has a chemical composition which is composed of 1 to 20 mass% of ZrOcontent, 0.5 to 4.5 mass% of SiOcontent, 1 to 10 mass% of C content, 2.5 mass% or less (comprising zero) in total content of FeO, TiO, MgO, CaO, VO, 6.5 mass% or less (comprising zero) of the component other than ZrO, SiO, C, FeO, TiO, MgO, CaO, VO, NaO and AlO, 0.2 mass% or less (comprising zero) of NaO content, and the balance AlO.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a slide plate used in a ladle, tundish, and the like, and a method for manufacturing the slide plate.

  The slide plate is a refractory material used for ladle and tundish bottoms and used to control the flow rate of molten steel. The slide plate is perforated, two or three are stacked, the slide plates are slid and moved to change the opening of the hole, and the flow rate of the molten steel is adjusted. Due to the severe usage conditions, the slide plate is required to have spalling resistance, wear resistance, and corrosion resistance, and an alumina-carbon material is widely used.

  There are four types of damage to the slide plate: (A) crack, (B) expansion of inner hole, (C) sliding surface damage, and (D) edge damage. Edge damage refers to a portion where the sliding surface of the plate and the inner hole are in contact with each other, and refers to damage to that portion. Among the above damages, the edge damage is enlarged, making it difficult to control the flow rate of the molten steel, and it is easy for the molten steel to bite between the slide plate surfaces during sliding, which may lead to leakage steel between the surfaces. It can be said that it is an important damage. In other words, suppression of edge damage is important for improving the productivity of steel and preventing troubles.

  FIG. 1 is a schematic view of a slide plate composed of an upper plate (1) and a lower plate (2), and a molten steel flow (3) flows through the inner holes of the upper plate (1) and the lower plate (2). It has become. As shown in FIG. 1, when the opening of the sliding nozzle is reduced, the edge portion of the inner hole is heated from the two directions of the sliding surface (upper surface or lower surface) and the inner hole surface. Thereby, a very large thermal stress is applied, cracks (5) in a direction parallel to the working surface are generated, and the edge (4) is lost during use. This is considered to be the cause of edge damage. In particular, in a sliding nozzle plate for a ladle, the ratio of draw casting (casting with a small opening) is high, and the edge portion (4) is easily damaged.

  Generally, reduction of edge damage is considered to require reduction in elastic modulus, reduction in thermal expansion coefficient, and increase in fracture energy, and various countermeasures have been conventionally taken. For example, in Patent Document 1, alumina, carbon or alumina, mullite, carbon is used as a main raw material, zirconia having a particle size of 0.4 to 300 μm is added to the outer layer in an amount of 1 to 30 wt%, and an appropriate amount of binder is added and kneaded. A method for producing a sliding nozzle plate is disclosed in which after the molding, reduction firing is performed at 1000 to 1500 ° C. According to Patent Document 1, it is said that the obtained sliding nozzle plate is more likely to generate fine cracks in the sliding nozzle plate due to expansion / contraction due to the phase transition of zirconia, and the edge portion chipping is reduced. This is considered to be due to the low elastic modulus due to the generation of microcracks due to the phase transition of zirconia, and as a result, the spalling resistance is improved.

In Patent Document 2, the main mineral phase is composed of corundum, tetragonal zirconia and monoclinic zirconia, the amount of Al ₂ O ₃ is 40 to 80 wt%, the amount of ZrO ₂ is 20 to 60 wt%, and other coexisting components are 5 wt. Disclosed is a method for producing a sliding nozzle plate, characterized in that 5 to 60 wt% of Al ₂ O ₃ —ZrO ₂ -based molten raw material having a chemical composition of less than 5% is blended, kneaded, and fired after molding. . According to Patent Document 2, it is possible to improve the spalling resistance by generating microcracks by adding 5 to 60 wt% of fine powder of Al ₂ O ₃ —ZrO ₂ -based molten raw material and improving fracture energy. I can do it.

Further, Patent Document 3 discloses that silicon nitride powder is 0.2 to 10.0% by weight in a blend of at least one refractory aggregate material of alumina, silica, zirconia, magnesia and spinel, and a carbonaceous material. And a landing nozzle plate characterized in that 0.1 to 8.0% by weight of at least one metal is added as an antioxidant. According to Patent Document 3, corrosion resistance, heat spalling resistance, and oxidation resistance can be ensured by increasing the hot strength while maintaining a low elastic modulus. However, the silicon nitride powder is unstable in a CO atmosphere at the time of actual use, and there is a problem that the hot strength is reduced due to the generation of SiO ₂ .

  In addition, in Patent Document 4, alumina zirconia grains and zirconia mullite grains are used in combination with one or more refractory raw materials of aggregate raw materials such as alumina, silica, magnesia and spinel as the raw material composition of the sliding nozzle plate, In addition, one or more of carbides, borides, nitrides and / or metals as antioxidants are added, kneaded to form a sliding nozzle plate, and then reduced firing is performed. (Claim 1): The ratio of zirconia mullite (ZM) to AZ: ZM = 1: 0.2 to 1: 1 with respect to 10.0 to 50.0% by weight of alumina zirconia (AZ) A method for manufacturing the sliding nozzle plate (claim 2) is disclosed. According to Patent Document 4, a sliding nozzle plate having improved corrosion resistance and heat-sparability can be obtained by using alumina zirconia grains and zirconia mullite grains in the above ratio.

JP 58-20777 A JP 63-112456 A JP 2004-9059 A JP 2006-26728 A

  As described above, conventionally, a sliding plate of a sliding nozzle is based on an alumina-carbon refractory, and in order to meet required properties such as heat spalling resistance and corrosion resistance, an alumina-zirconia raw material, zirconia- The material composition includes mullite raw material and the like and also includes additives such as metals. Such a material is generally applied as a slide plate, and relatively good results have been obtained. However, when the slide plate made of the above material is applied to the actual machine, its use results vary, and even if it is used in the same equipment, its service life varies. Some of them ended, and there were many demands from users for stable durability rather than unstable longevity, so further improvement was necessary.

  Accordingly, an object of the present invention is to stably suppress damage to the edge portion due to thermal spalling during two-side heating of the slide plate, and to stably increase the durability of the alumina-carbonaceous slide plate.

The inventors diligently investigated various requirements such as the selection of raw materials, manufacturing methods, and conditions of use in actual equipment, as to the cause of variation even when the same material alumina-carbon slide plate is used in the same apparatus. , Explored the cause.
As a result, it was found that there is a correlation between the life of the slide plate and the amount of Na ₂ O contained in the slide plate, and that the life is shortened when the amount of Na ₂ O is large. When manufacturing a slide plate, it is common to manufacture using many raw materials from which a particle size and a composition differ. The Na 2 _O content of the impurities contained in raw materials thereof, Na 2 _O content in the slide plate is determined. Furthermore, the Na ₂ O content and the hot strength are correlated, and it was also found that the hot strength decreases when the Na ₂ O content is large. As a result of the analysis of the cause, as described above, the edge portion of the slide plate is easily heated to the inside of the plate by two-sided heating, and the presence of a large amount of Na ₂ O component reacts with the Al ₂ O ₃ component and the SiO ₂ component. As a result, a large amount of liquid phase is generated, and the hot strength decreases. As a result, it was concluded that the spalling resistance was lowered and cracks occurred at the edge.

Through these searches, the present inventors have found that it is possible to obtain a stable slide plate life by keeping the amount of Na ₂ O contained in the alumina-carbonaceous slide plate low. Succeeded in stabilizing.
On the other hand, if the amount of Na ₂ O contained in the alumina-carbonaceous slide plate can be reduced compared with the conventional art, the present inventors can obtain a slide plate having a longer life and a stable life. I thought it would be possible. Thus, when a raw material was carefully selected and a slide plate in which the amount of Na ₂ O in the slide plate was further reduced was prototyped and used, it was found that a longer life and a stable life could be obtained.
Based on this discovery, the present inventors have arrived at the present invention.

That is, the alumina-carbonaceous slide plate of the present invention has a chemical composition of ZrO ₂ content of 1 to 20 mass%, SiO ₂ content of 0.5 to 4.5 mass%, and C content of 1 to 10 mass. %, Fe ₂ O ₃ , TiO ₂ , MgO, CaO, V ₂ O ₅ content is 2.5% by mass or less (including zero) in total amount, ZrO ₂ , SiO ₂ , C, Fe ₂ O ₃ , TiO ₂ , MgO, CaO, V ₂ O ₅ , Na ₂ O and Al ₂ O ₃ other component content is 6.5% by mass or less (including zero), Na ₂ O content is 0.2% by mass or less (Including zero), and the remainder is made of Al ₂ O ₃ .

The alumina-carbonaceous slide plate has a chemical composition of ZrO ₂ content of 1 to 20% by mass, SiO ₂ content of 0.5 to 4.5% by mass, C content of 1 to 10% by mass, Fe ₂ O ₃ , TiO ₂ , MgO, CaO, V ₂ O ₅ content is 2.5% by mass or less (including zero) in total, ZrO ₂ , SiO ₂ , C, Fe ₂ O ₃ , TiO ₂ , The content of other components excluding MgO, CaO, V ₂ O ₅ , Na ₂ O and Al ₂ O ₃ is 6.5% by mass or less (including zero), and the content of Na ₂ O is 0.2% by mass or less (zero) And the raw material is blended so that the remainder becomes Al ₂ O ₃ .

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to suppress stably the damage of the edge part by the heat spalling at the time of the 2 surface heating of a slide plate, and to obtain a stable high durability alumina-carbonaceous slide plate.

It is the schematic of a slide plate.

The alumina-carbonaceous slide plate of the present invention is characterized in that the Na ₂ O content is 0.20% by mass or less (including zero). When the Na ₂ O content exceeds 0.20% by mass, Na ₂ O reacts with the Al ₂ O ₃ component and the SiO ₂ component contained in the alumina-carbonaceous slide plate to produce a low melting point material, The strength is lowered, and as a result, the heat spalling property is lowered, which is not preferable. The Na ₂ O content is more preferably 0.15% by mass or less (including zero), and even more preferably 0.10% by mass or less (including zero).

Here, the Na ₂ O component contained in the alumina-carbonaceous slide plate is derived from the Na ₂ O component as an impurity contained in the alumina-carbonaceous slide plate raw material. Further, the Na ₂ O component as an impurity is mainly derived from an artificially produced Al ₂ O ₃ containing raw material used for an alumina-carbonaceous slide plate, that is, an alumina raw material, an alumina-zirconia raw material, or a zirconia-mullite raw material. To do. In the alumina-carbonaceous slide plate, the Al ₂ O ₃ -containing natural raw material is rarely used, but the Na ₂ O content in the Al ₂ O ₃ -containing natural raw material used is not so large. That is, the origin of the Na ₂ O component in the Al ₂ O ₃ -containing raw material is in its production method. Usually, the Al ₂ O ₃ -containing raw material used for the slide plate is manufactured using calcined alumina manufactured by the Bayer method. In the Bayer method, since bauxite as a raw material is dissolved using NaOH in the production process, the calcined alumina obtained therefrom usually contains a Na ₂ O component.

When the calcined alumina raw material produced by the Bayer method is used as a refractory, the Na ₂ O content does not become a big problem, and generally 0.25 to 0.6 mass% of Na ₂ O is included. Using this calcined alumina as a raw material, sintered alumina raw material, fused alumina raw material, fused alumina-zirconia raw material, fused zirconia-mullite raw material and the like are manufactured, and the Na ₂ O content is Al ₂ O ₃ containing Although it varies depending on the amount, it generally contains 0.05 to 0.6% by mass of Na ₂ O.

Conventionally, when using the raw materials as described above for an alumina-carbonaceous slide plate, the Na ₂ O content is not particularly considered. For example, in the case of an alumina raw material, the Na ₂ O content is as described above. Even if it differs from 0.25 to 0.6% by mass, it has been handled and blended as a replaceable raw material of the same grade. This is the reason for the above-mentioned variation in the life of the slide plate.

Therefore, when manufacturing the alumina-carbonaceous slide plate, when blending the raw materials, the Na ₂ O content in each blended raw material is examined in advance, and the Na ₂ O content as a whole is 0.20 mass. The content of Na ₂ O in the slide plate can be adjusted to 0.20% by mass or less (including zero) by determining and adjusting the blending raw material so as to be not more than% (including zero).

The amount of Na ₂ O contained in calcined alumina can be reduced. For electronic ceramic materials that require high functionality and high reliability, and structural ceramic materials that require high temperature and high strength, A calcined alumina called low soda-alumina having a Na ₂ O content reduced to 0.00 to 0.10% by mass is used. By using sintered alumina or electrofused alumina made from such low soda / alumina, the Na ₂ O content can be further reduced.

Examples of the alumina raw material used in the present invention include sintered alumina or electrofused alumina, calcined alumina, brown alumina, alumina-zirconia raw material, zirconia-mullite raw material, etc. as a raw material containing alumina. More preferably, low-soda sintered alumina or electrofused alumina is used, and one having a Na ₂ O content of 0.10% by mass or less (including zero) is preferably used.

In addition, even if it is an alumina raw material containing Fe ₂ O ₃ , TiO ₂ , MgO, CaO, V ₂ O ₅ in a total amount of 5% by mass or less, the Na ₂ O content is 0.10% by mass or less (including zero) ) Can also be used as an alumina raw material. When Fe ₂ O ₃ , TiO ₂ , MgO, CaO, and V ₂ O ₅ are more than 5% by mass, the hot strength is greatly reduced due to the liquid phase generated hot, and the generated liquid phase is cooled between the plates during cooling. This is because there is a high possibility that it will solidify and weld and cause damage to the sliding surface. The content of Fe ₂ O ₃ , TiO ₂ , MgO, CaO, and V ₂ O _{5 in the} alumina raw material is preferably 3% by mass or less.

Next, the ZrO ₂ content of the alumina-carbonaceous slide plate of the present invention is in the range of 1 to 20% by mass. The ZrO ₂ component contains monoclinic ZrO ₂ , so that the volume shrinks due to the phase transition from the monoclinic system to the tetragonal system at a high temperature, and conversely, the tetragonal system changes to the monoclinic crystal by returning to a low temperature. Microcracks are generated by volume expansion when returning to the system, and the elastic modulus is lowered. In addition, the raw material containing zirconia is characterized by high corrosion resistance. For this reason, when the ZrO ₂ content is less than 1% by mass, the effects of reducing the elastic modulus and improving the corrosion resistance are small. On the other hand, if the ZrO ₂ content exceeds 20% by mass, the thermal expansion and contraction due to the phase transition becomes excessive and causes a decrease in strength. The ZrO ₂ content is preferably in the range of 2 to 15% by mass.

Here, alumina of the present invention - as the zirconia-containing raw material that can be used in preparing the carbonaceous slide plate, for example, ZrO ₂ content of 15 to 45 wt%, _Al 2 _{O 3} content of 50 to 85 wt% And a fused zirconia-mullite raw material having a ZrO ₂ content of 25-45 mass% and a mullite of 55-75 mass%.

Furthermore, the alumina of the present invention - SiO ₂ content of the carbonaceous slide plate is in the range of 0.5 to 4.5 wt%. The SiO ₂ component is derived from zirconia-mullite raw material, zircon and the like. When SiO ₂ content exceeds 4.5 mass%, increases the amount of liquid phase produced in the hot, hot strength is lowered, the corrosion resistance is lowered. Furthermore, it is not preferable because the generated liquid phase is likely to solidify and weld between the plates during cooling and cause damage to the sliding surface. On the other hand, when the SiO ₂ content is less than 0.5% by mass, the elastic modulus is increased, which is not preferable. The SiO ₂ content is preferably in the range of 0.5 to 3% by mass.

  The C content of the alumina-carbonaceous slide plate of the present invention is in the range of 1 to 10% by mass. When the C content is less than 1% by mass, the spalling resistance is poor, and when it exceeds 10% by mass, the strength and corrosion resistance decrease, which is not preferable. The C content is preferably in the range of 2 to 7% by mass. In addition, the pyrolytic residual carbon amount (residual carbon amount) derived from the organic binder used at the time of molding is also included in the C content. Here, the amount of residual coal is measured based on the fixed carbon measurement method in JIS K 6910 (phenol resin test method).

  Here, as a carbon raw material which can be used when manufacturing the alumina-carbonaceous slide plate of this invention, graphite, carbon black, etc. can be mentioned, for example. Moreover, as an organic binder, a phenol resin, a furan resin, a pitch etc. can be mentioned, for example.

Furthermore, the content of Fe ₂ O ₃ , TiO ₂ , MgO, CaO, and V ₂ O _{5 in} the alumina-carbonaceous slide plate of the present invention is 2.5% by mass or less (including zero) in total. When the content of Fe ₂ O ₃ , TiO ₂ , MgO, CaO, V ₂ O _5, etc. exceeds 2.5% by mass, the hot strength is greatly reduced due to the liquid phase generated hot, and the corrosion resistance is also reduced. . Furthermore, it is because there is a high possibility that the generated liquid phase is solidified and welded between the plates during cooling and causes damage to the sliding surface. The Fe ₂ O ₃ , TiO ₂ , MgO, CaO, and V ₂ O ₅ contents are preferably 2% by mass or less (including zero) in total.

Further, the alumina of the present invention - in carbonaceous slide _plate, other components except for _{ZrO 2, SiO 2, C,} Fe 2 O 3, TiO 2, MgO, CaO, V 2 O 5, Na 2 O and _Al 2 _{O 3} The content is 6.5% by mass or less (including zero). If the content of other components exceeds 6.5% by mass, the elastic modulus increases, which is not preferable. The content of other components is preferably 6.0% by mass or less (including zero).

In the alumina-carbonaceous slide plate of the present invention, the balance excluding the above-described components and inevitable impurities is an Al ₂ O ₃ component.

In addition to the above raw materials, the alumina-carbonaceous slide plate of the present invention includes metals (Si, Al, etc.), carbides (SiC, B ₄ C, Al ₄ C ₃ etc.), nitrides (BN, AlN, etc.) Can be blended in a total amount of 7% by mass or less.

  The alumina-carbonaceous slide plate of the present invention can be produced by ordinary plate production processes such as weighing, kneading, molding, drying, firing or non-firing, pitch and tar impregnation. Specifically, 1 to 5% by mass of a binder is added to the raw material and kneaded to form a plate shape. Although it does not specifically limit about the heat processing conditions with respect to a molded object, Generally, it dries at 100-400 degreeC. When making it into a baked product, after the said heat processing, it bakes at 1000-1400 degreeC in a reducing atmosphere or a non-oxidizing atmosphere. The plate refractory obtained through such a manufacturing process is subjected to pitch impregnation treatment and heat treatment to obtain a final product.

  The alumina-carbonaceous slide plate of the present invention is a material suitable for use in a ladle, but can also be used for tundish.

Example 1
The raw material composition and chemical composition of the product of the present invention and the comparative product are shown in Tables 1 and 2, and Table 3 shows the chemical composition of the raw materials used.
Each raw material is weighed at the blending ratio shown in Table 1 and Table 2, and 3% by weight phenol resin is added and kneaded with an outer shell, which is then formed into a slide plate shape with a vacuum hydraulic press and dried at 200 ° C. Then, the sample was obtained by reduction firing at 1300 ° C. The residual carbon amount of the phenol resin was 35%, and the total carbon amount was set together with the added carbon raw material. Various characteristics of the obtained sample are shown in Tables 1 and 2.

Details of the evaluation items in the table are as follows:
“Normal temperature bending strength and hot bending strength” is a bending strength at normal temperature and 1400 ° C., and in accordance with JIS R 2656 (Test method for hot bending strength of refractory bricks), a square column of 25 × 25 × 150 mm is used. Used for measurement.
The “elastic modulus” was obtained by a grindsonic method using an MK5 manufactured by JWLEMMENS-ELEKTONIKA and calculating from the natural frequency generated by applying an impact to the test piece.
“Corrosion resistance” was evaluated by the lining erosion method using a high-frequency induction furnace. The erosion test was performed for 4 hours by floating slag having a composition of CaO: Al ₂ O ₃ = 6: 4 on steel melted at 1550 to 1600 ° C., and changing the slag every hour. Corrosion resistance is expressed as an index with the product 2 of the present invention as a standard 100, and the larger the number, the higher the corrosion resistance.
In addition, the suitable ranges of normal temperature bending strength, hot bending strength, elastic modulus, and corrosion resistance index are 13 MPa or more, 13 MPa or more, 85 GPa or less, and 86 or more, respectively.

As apparent from Table 1 above, all of the products of the present invention have a high ordinary temperature bending strength, a high hot bending strength, an excessively high elastic modulus, an excellent heat spalling resistance, and an excellent corrosion resistance. It had the characteristics.
On the other hand, each comparison product is out of range. Comparative Example 1 because the content of Na 2 _O is large, hot strength was decreased. Comparative product 2 also had a high Na ₂ O content and had a low hot bending strength. Comparative product 3 had a higher Na ₂ O content, the hot strength was lowered, and the corrosion resistance was further lowered. Since the comparative product 4 did not contain the ZrO ₂ component, the elastic modulus was increased. Since the comparative product 5 had a large ZrO ₂ content, the room temperature bending strength and the hot bending strength were reduced. Since the comparative product 6 has a low SiO ₂ content, it has a high elastic modulus. Since the comparative product 7 had a large SiO ₂ content, the hot bending strength was lowered. Since the comparative product 8 had a C content of zero, it had a high elastic modulus. Since the comparative product 9 had a large C content, the ordinary temperature bending strength and the hot bending strength were lowered, and the corrosion resistance was further lowered. Since the comparative product 10 had a large content of Fe ₂ O ₃ , TiO ₂ , MgO, CaO, and V ₂ O ₅ , the hot bending strength was lowered and the corrosion resistance was also lowered. Since the comparative product 11 has a large amount of other components, it has a high elastic modulus.
As described above, the superiority of the alumina-carbonaceous slide plate of the present invention is clear.

Example 2
Using the present invention product 2 and the comparative product 1 having different Na ₂ O contents, an actual furnace test was conducted using a 250 t pan as a ladle slide plate and ordinary steel. In each case, 10 sets were tested, and the product 2 of the present invention had an average useful life of 8.2 ch, whereas the comparative product 1 was 6.3 ch. The product 1 of the present invention having a Na ₂ O content of 0.10% by mass has improved durability by 30% compared to the comparative product 1 having a Na ₂ O content of 0.24% by mass.

1 Upper plate 2 Lower plate 3 Molten steel flow 4 Edge part 5 Crack

Claims (2)

In the alumina-carbonaceous slide plate, the chemical composition has a ZrO ₂ content of 1 to 20% by mass, a SiO ₂ content of 0.5 to 4.5% by mass, a C content of 1 to 10% by mass, Fe ₂ O ₃ , TiO ₂ , MgO, CaO, V ₂ O ₅ content is 2.5% by mass or less (including zero) in total, ZrO ₂ , SiO ₂ , C, Fe ₂ O ₃ , TiO ₂ , MgO, CaO , V ₂ O ₅ , Na ₂ O and Al ₂ O ₃ other component content is 6.5% by mass or less (including zero), Na ₂ O content is 0.2% by mass or less (including zero) An alumina-carbonaceous slide plate, wherein the balance is made of Al ₂ O ₃ . Alumina as claimed in claim 1, wherein - in the production method of the carbonaceous slide plate, ZrO ₂ content of 1 to 20 mass% as chemical composition, SiO ₂ content of 0.5 to 4.5 wt%, the C content 1 10 _wt% (including _{zero) Fe 2 O 3, TiO 2} , MgO, CaO, V 2 O 5 content of more than 2.5 mass% in total _{amount, ZrO 2, SiO 2, C} , Fe 2 O ₃ , TiO ₂ , MgO, CaO, V ₂ O ₅ , Na ₂ O and Al ₂ O ₃ other than the content of 6.5% by mass (including zero), Na ₂ O content of 0.2 A method for producing a slide plate, characterized in that raw materials are blended so as to be less than or equal to mass% (including zero) and the remainder being Al ₂ O ₃ .

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