Refractory for casting, nozzle for casting and sliding nozzle plate using same

Abstract

A refractory to be used repeatedly or for a long period of time, such as a refractory for casting, especially a nozzle for casting and an SN plate, has improved tolerance. The refractory for casting contains Al.sub.4O.sub.4C in the range of 15 to 60% by mass, both inclusive, an Al component as a metal in the range of 1.2 to 10.0% by mass, both inclusive, and a balance including Al.sub.2O.sub.3, a free C, and other refractory component; a sum of Al.sub.4O.sub.4C, Al.sub.2O.sub.3, and the Al component as a metal is 85% or more by mass; and a content of Al.sub.4O.sub.4C (Al.sub.4O.sub.4C), a content of the Al component as a metal (Al), and a content of the free carbon (C). The contact of the free carbon satisfies the following Equation 1 and Equation 2:
1.0C/(Al.sub.4O.sub.4C0.038+Al0.33)(Equation 1)
and
1.0C/(Al.sub.4O.sub.4C0.13+Al0.67)(Equation 2).

Claims

1. A refractory for casting, wherein the refractory for casting contains Al.sub.4O.sub.4C in the range of 15 to 60% by mass, both inclusive, an Al component as a metal in the range of 1.2 to 10.0% by mass, both inclusive, and a balance comprising Al.sub.2O.sub.3, a free C, and other refractory component; a sum of Al.sub.4O.sub.4C, Al.sub.2O.sub.3, and the Al component as a metal is 85% or more by mass; and a content of Al.sub.4O.sub.4C (Al.sub.4O.sub.4C), a content of the Al component as a metal (Al), and a content of the free C (C) satisfy following Equation 1 and Equation 2:
1.0C/(Al.sub.4O.sub.4C0.038+Al0.33)Equation 1
1.0C/(Al.sub.4O.sub.4C0.13+Al0.67)Equation 2.

2. The refractory for casting according to claim 1, wherein the Al.sub.4O.sub.4C is derived from an Al.sub.4O.sub.4C-containing raw material particle produced by an electromelting method.

3. The refractory for casting according to claim 2, wherein a size of an Al.sub.4O.sub.4C crystal in the Al.sub.4O.sub.4C-containing raw material particle is 20 m or more as an average diameter when a cross section of the Al.sub.4O.sub.4C crystal is converted to a circle.

4. The refractory for casting according to claim 1, wherein the other refractory component in the balance is one or more of the following materials: MgO, SiO.sub.2, a tetragonal or a monoclinic ZrO.sub.2, SiC, B.sub.4C, BN, Si.sub.3N.sub.4, and a metal Si.

5. The refractory for casting according to claim 1, wherein a metal Si is contained therein with a weight ratio of the metal Si to the Al component as a metal in the range of 0.1 to 2, both inclusive.

6. A nozzle for casting or a plate for a sliding nozzle, wherein the refractory for casting according to claim 1 is arranged in part or all of the nozzle for casting or of the plate for a sliding nozzle.

7. The refractory for casting according to claim 2, wherein the other refractory component in the balance is one or more of the following materials: MgO, SiO.sub.2, a tetragonal or a monoclinic ZrO.sub.2, SiC, B.sub.4C, BN, Si.sub.3N.sub.4, and a metal Si.

8. The refractory for casting according to claim 3, wherein the other refractory component in the balance is one or more of the following materials: MgO, SiO.sub.2, a tetragonal or a monoclinic ZrO.sub.2, SiC, B.sub.4C, BN, S.sub.3N.sub.4, and a metal Si.

9. The refractory for casting according to claim 2, wherein a metal Si is contained therein with a weight ratio of the metal Si to the Al component as a metal in the range of 0.1 to 2, both inclusive.

10. The refractory for casting according to claim 3, wherein a metal Si is contained therein with a weight ratio of the metal Si to the Al component as a metal in the range of 0.1 to 2, both inclusive.

11. The refractory for casting according to claim 4, wherein the metal Si is contained therein with a weight ratio of the metal Si to the Al component as a metal in the range of 0.1 to 2, both inclusive.

12. The refractory for casting according to claim 7, wherein the metal Si is contained therein with a weight ratio of the metal Si to the Al component as a metal in the range of 0.1 to 2, both inclusive.

13. The refractory for casting according to claim 8, wherein the metal Si is contained therein with a weight ratio of the metal Si to the Al component as a metal in the range of 0.1 to 2, both inclusive.

14. A nozzle for casting or a plate for a sliding nozzle, wherein the refractory for casting according to claim 2 is arranged in part or all of the nozzle for casting or of the plate for a sliding nozzle.

15. A nozzle for casting or a plate for a sliding nozzle, wherein the refractory for casting according to claim 3 is arranged in part or all of the nozzle for casting or of the plate for a sliding nozzle.

16. A nozzle for casting or a plate for a sliding nozzle, wherein the refractory for casting according to claim 4 is arranged in part or all of the nozzle for casting or of the plate for a sliding nozzle.

17. A nozzle for casting or a plate for a sliding nozzle, wherein the refractory for casting according to claim 5 is arranged in part or all of the nozzle for casting or of the plate for a sliding nozzle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is an example of the experimental results illustrating the relationship between the modulus and the volume ratio of the free C to Al.sub.4O.sub.4C in the refractory.

(2) FIG. 2 is an experimental example illustrating the relationship between the addition amount of carbon black (free C) and the rate of change by baking.

(3) FIG. 3 is an example of the experimental results illustrating the relationship between the average particle diameter of Al.sub.2O.sub.3 and the thickness of the C layer thereof (C/Al.sub.4O.sub.4C in volume ratio and mass ratio) (this illustrates Table 1 by a graph).

(4) FIG. 4 is an example of the experimental results illustrating the relationship between the average particle diameter of Al.sub.4O.sub.4C and the thickness of the C layer thereof (C/Al.sub.4O.sub.4C in volume ratio and mass ratio) (this illustrates Table 2 by a graph).

(5) FIG. 5 is a conceptual diagram illustrating the range of the content of Al.sub.4O.sub.4C and the amount of the free carbon of the present invention (the range determined by the Equation 1 and the Equation 2).

DESCRIPTION OF THE EMBODIMENTS

(6) With regard to the Al.sub.4O.sub.4C-containing raw material particle to be used in the present invention, a size of the particle diameter thereof, a classification, a blending ratio, and the like may be selected in accordance with individual conditions and needs including the form of the refractory to be applied. For example, the particles are classified into the class of 5 to 3 mm, the class of 3 to 1 mm, and the class of 1 to 0 mm or to 0.074 mm or more; and then, these may be applied with an arbitrary ratio thereof. In order to enhance the effect to decrease the thermal expansion rate of the refractory, it is preferable to use the Al.sub.4O.sub.4C-containing raw material, which is of a low expansion in itself, as a relatively large particle, a so-called coarse aggregate. Al.sub.4O.sub.4C is preferably in a ball-like form or in a form near to it; however, a plate-like form may be used as well.

(7) The size of the Al.sub.4O.sub.4C crystal in the Al.sub.4O.sub.4C-containing raw material particle is preferably 20 m or more as an average diameter when a cross section of Al.sub.4O.sub.4C crystal is converted to a circle. The larger the crystal diameter of Al.sub.4O.sub.4C in the Al.sub.4O.sub.4C-containing raw material particle is, the more the change of Al.sub.4O.sub.4C to Al.sub.2O.sub.3 can be suppressed even in the use condition of a long period of time, so that more amount of Al.sub.4O.sub.4C can persist.

(8) The Al.sub.4O.sub.4C-containing raw material particle is preferably an electromelted raw material melted by an arc, wherein a main constituting component of the electromelted raw material is preferably Al.sub.4O.sub.4C and a corundum (Al.sub.2O.sub.3). With a conventional sintering method, productivity of the Al.sub.4O.sub.4C-containing raw material is low, so that an actual industrialization thereof is difficult; and in addition, production of the raw material capable of becoming a dense aggregate having a large crystal diameter of Al.sub.4O.sub.4C is difficult. On the contrary, productivity of the electromelted raw material obtained by an arc melting is high, and also a dense aggregate raw material of Al.sub.4O.sub.4C having an arbitrary particle size with a large crystal diameter can be obtained. Because of a high density as mentioned above, the contact area with an oxygen and a carbon monoxide is so small even under the conditions of high temperature and of oxidation so that the oxidation and change of Al.sub.4O.sub.4C to an alumina can be suppressed, and therefore a low thermal expansion rate can persist for a long period of time. In addition, because a main constituting component other than Al.sub.4O.sub.4C is a corundum (Al.sub.2O.sub.3), a high corrosion resistance can persist. Further, when the composition is made such that the electromelted Al.sub.4O.sub.4C-containing raw material may include a coarse particle having the size of, for example, 0.5 mm or more, mainly including, for example, regions of a so-called medium particle and coarse particle with the size of them being about 20 m or more, the effect of the refractory to decrease the thermal expansion rate can be enhanced, so that the characteristics of the low thermal expansion rate can persist for a long period of time. At the same time, progress in the change of Al.sub.4O.sub.4C to an alumina under the use condition for a long period of time can be suppressed (slowed).

(9) With regard to the form of the metal aluminum which is the source of the Al component as a metal, any of a ball-like form, a flake-like form, and a fiber-like form may be used. In addition, it may also be used as an alloy with Si or Mg.

(10) In the case that the refractory for casting of the present invention is baked in the temperature range of not lower than 660 C., the form of the metal aluminum to be used is preferably a ball-like form or a fiber-like form including an atomized powder which has a small specific surface area and can remain even until a comparatively high temperature region; and also, the grain size thereof is preferably 0.074 mm or more in terms of an average particle diameter with the amount thereof being in the range of 30 to 90 parts by mass, both inclusive, on the basis of 100 parts by mass of the metal aluminum to be used.

(11) Because the volume expansion is smaller when an aluminum carbide is produced from the metal aluminum as compared with the case of producing an alumina therefrom, in order to suppress the densification and increase in the modulus, which are caused by the reactions of the metal aluminum, naturally it is preferable to produce the aluminum carbide rather than producing the alumina. Supposed that all of the metal aluminum contained therein (Al component as a metal) produces the aluminum carbide, it can be said that as shown in the Equation 4, the contents therein may be 3 moles of C relative to 4 moles of Al, namely 0.33% by mass of C relative to 1.1% by mass of Al, namely of the free C.

(12) However, slaking of the aluminum carbide as illustrated in the Equation 11 can take place under a condition such as the repeat use condition including a process in which important portions including, for example, a contacting surface with a melted steel and a moving surface of the plate refractory are exposed, regardless of a high temperature state and a low temperature state of not higher than several hundred Celsius, to a water vapor derived from an air or the like, as well as especially in the case that a large amount of the metal aluminum is present in the refractory; and as a result, destruction and the like of the refractory organization can occasionally occur.
Al.sub.4C.sub.3+6H.sub.2O=4Al(OH).sub.3+3CO+9/2H.sub.2Equation 11

(13) Under the condition of a general single use or the condition in which slaking of the aluminum carbide does not take place even in the use for a long period of time, namely under the condition of generally not higher than about 200 C. or under the use condition in which the slaking reaction with a water vapor does not take place, there is no adverse effect by production of the aluminum carbide, although these conditions are different depending on the organization, structure, composition, and the like of the refractory as well as the environment around the refractory; and therefore, production of the aluminum carbide itself is desirable.

(14) Other than the conditions as mentioned above, under the condition including the repeat use, namely under the condition such that the slaking reaction of the aluminum carbide can take place, it is preferable to have a small amount of a metal Si or of an SiO.sub.2 component contained therein so as to suppress this slaking reaction. By replacing a part of Al in the aluminum carbide with Si, the resistance to the slaking can be obtained.

(15) Under the condition including the repeat use in the way as mentioned above, it is preferable that the refractory of the present invention contain a metal Si in the range of 0.5 to 10% by mass, both inclusive, as the mass ratio relative to the Al component as a metal, or a weight ratio of metal Si to Al component as a metal in the range of 0.1 to 2, both inclusive.

(16) With regard to the aggregate other than Al.sub.4O.sub.4C, it is desirable to make Al.sub.2O.sub.3 as a main component. In the refractory of the present invention, the sum of the contents of Al.sub.4O.sub.4C, the Al component as a metal, and Al.sub.2O.sub.3 needs to be 85% or more, wherein it is desirable that a main component in the balance be the free C, a carbide, a nitride, a boride, or the like, or a refractory component containing a metal including silicon and magnesia.

(17) Other refractory component as the balance after the contents of Al.sub.4O.sub.4C, the Al component as a metal, and Al.sub.2O.sub.3 with minimum sum thereof being 85% by mass and the content of the free C based on the Equation 1 and Equation 2 is a carbide, a boride, a nitride, a metal including Si and Mg, or an oxide including magnesia as well as a small amount of zirconia and silica.

(18) As described above, in order to enhance the corrosion resistance to a slag and so forth, the infiltration resistance, the oxidation resistance, and the like, the balance may contain a carbide, a boride, a nitride, or the like. However, if the balance contains a large amount of a carbide, a boride, a nitride, or the like, an attrition by oxidation of these substances themselves or an attrition due to dissolution into a melted steel becomes large, thereby leading to a large attrition of the refractory. Also, if a large amount of a metal including Si and Mg is contained (for example, all of the balance), sintering of the refractory organization takes place notably, resulting in a decrease in the thermal shock resistance by an increase in the modulus or the like, thereby leading to an increase in the attrition including a crack and a destruction. If the content of the component including a zirconia or a silica is large, these are reduced to cause facilitation of the organization deterioration and the attrition. If the content of a magnesia is large, because not only the magnesia itself has a large thermal expansion rate when this is present as a periclase, but also a reaction with an alumina in the refractory generates a spinel-forming reaction which shows a large expansion behavior, resulting in an increase in a crack and an attrition due to a decrease in the thermal shock resistances. However, if the raw material contains the magnesia which has already been converted to a spinel, this may be treated in the same way as the alumina raw material.

(19) With regard to these oxide components as a mineral, a -alumina, a spinel, a mullite, a clay, a kaolinite, a monoclinic zirconia, a tetragonal zirconia, a glass layer, or the like may be contained therein. In order to prevent an eccentric expansion behavior along with metamorphosis, zirconia is preferably monoclinic or tetragonal.

(20) The method for producing the refractory of the present invention will be shown by taking the SN plate as an example. The SN plate applied with the refractory of the present invention can be obtained by a general production method of a SN plate.

(21) Namely, the production method includes: a step of mixing, with a prescribed particle size composition, an aggregate particle containing Al.sub.2O.sub.3 as a main component, a metal aluminum, a carbonaceous base aggregate, and other refractory raw materials constituting a balance thereof; a step of adding thereto an organic binder including a phenol resin which forms a carbon bond, followed by kneading the resulting mixture; a step of molding to a prescribed form of the SN plate; a step of drying and carrying out a heat treatment; and a step of processing a surface and so forth. Detailed condition in each of these steps can be optimized by an arbitrary design in accordance with individual conditions. The heat treatment is carried out preferably in a non-oxidative atmosphere, while more preferably in an inert gas atmosphere.

EXAMPLES

(22) An organic binder was added to an Al.sub.4O.sub.4C-containing raw material, an alumina-based raw material, a metal aluminum, a carbonaceous raw material, and other fire resistant aggregate; and then, the resulting mixture was kneaded, molded to a refractory form by an oil press, dried, and then subjected to a heat treatment at a prescribed temperature to obtain a refractory. With regard to the Al.sub.4O.sub.4C-containing raw material, except for later-mentioned Example D (Table 6), an electromelted raw material particle containing Al.sub.4O.sub.4C and corundum as main components was used, wherein the electromelted raw material particle had the maximum particle diameter (top size) of 1 mm with 50 m of the Al.sub.4O.sub.4C crystal size as an average diameter when a cross section of Al.sub.4O.sub.4C crystal was converted to a circle.

(23) The composition of the refractory thus obtained was analyzed in the way as described below.

(24) In the refractory composition, Al.sub.4O.sub.4C, Al.sub.2O.sub.3 (corundum), Al (Al component as a metal), and Si were quantified by an internal standard method with an X-ray diffraction; and when a standard sample was not available, quantification was made with a profile by a Rietveld method. The free C (F. C.) and the total C (TOTAL C) were quantified in conformity with JIS-R-2012. Other components, namely, ZrO.sub.2, SiO.sub.2, and MgO, were quantified by a fluorescent X-ray in conformity with JIS-R-2216.

(25) A specimen having a prescribed form was cut out from the obtained refractory; and the following evaluations were carried out for each specimen. (1) Bulk specific gravity: this was measured in conformity with JIS-R-2205. (2) Thermal expansion rate: this was measured in conformity with JIS-R-2207.

(26) As for evaluation of conformity for the repeat use or multiple use, the oxidative abrasion resistance test and the thermal shock resistance test were carried out with a method in which heating under an oxidative atmosphere and cooling were repeated for 3 times, and also the slaking (hydration) test was carried out.

(27) Specific evaluation contents are described below. (3) Oxidative abrasion resistance: the specimen was subjected to a heat treatment under an atmospheric air at 1000 C. for 2 hours by using a rotary furnace, and then cooled; this operation was repeated for three times. In conformity with a BS (British Standard) abrasion method, the specimen after oxidation was blasted with an abrasive grain to quantify the abrasion amount. Then, this abrasion amount was expressed by an index relative to Comparative Example 6 (see, Table 5) as 100. It can be said that when the index is smaller, the oxidative abrasion resistance is higher. (4) Thermal shock resistance: in order to evaluate the thermal shock resistance after change of the organization upon heat receiving, the specimen was subjected to a heat treatment under a non-oxidative atmosphere in an electric furnace at 1400 C. for 3 hours, and thereafter, soaked in a melted iron at 1600 C. for 3 minutes by using a high-frequency induction furnace, and then cooled. This evaluation was repeated for three times to evaluate the state of the specimen after the evaluation. (5) Slaking resistance: the specimen with the form of 50 mm50 mm50 mm was heated under a non-oxidative atmosphere at 1400 C. for 3 hours, and then it was cooled to room temperature; thereafter, this specimen was kept under a humidified condition with 0.49 MPa at 150 C. for three hours by using an autoclave in conformity with the slaking test of a magnesia clinker described in the Gakushin method 4, and then, the appearance of the specimen after the test was evaluated.

Example A

(28) Example A illustrates the examples in which the content of Al.sub.4O.sub.4C in the refractory was studied. In Table 3, the compositions of each Example and the results thereof are summarized.

(29) TABLE-US-00003 TABLE 3 Compar- Compar- Compar- ative ative ative Exam- Exam- Exam- Exam- Exam- Exam- ple 1 ple 2 ple 1 ple 2 ple 3 ple 3 Refractory composition (% by mass) Al.sub.4O.sub.4C 14 15 38 60 62 Al.sub.2O.sub.3 90 75 71 48 25 25 Al 5 3 5 5 4 5 F.C. 3 2 4 3 5 6 Al.sub.4O.sub.4C + Al.sub.2O.sub.3 + Al 95 92 91 91 89 92 TOTAL C 3.0 2.9 4.9 6.3 8.7 9.8 Others (% by mass) ZrO.sub.2 SiO.sub.2 2 2 3 2 3 2 MgO ZrO.sub.2 + SiO.sub.2 + MgO 2 2 3 2 3 2 Others (except for 2 6 5 6 6 2 F.C.) total Grand total 100.0 100.0 100.0 100.0 100.0 100.0 C/(Al.sub.4O.sub.4C 0.038 + 1.82 1.31 1.80 1.29 1.39 1.50 0.33 Al) C/(Al.sub.4O.sub.4C 0.13 + 0.90 0.52 0.75 0.48 0.48 0.53 0.67 Al) Evaluation results Bulk specific gravity 3.30 3.12 3.10 2.88 2.62 2.60 Thermal expansion 0.88 0.67 0.64 0.55 0.44 0.43 rate (%) at 1000 C. Oxidative abrasion 70 70 60 55 40 45 resistance (index) Thermal shock Large Large Medium Faint Medium Large resistance crack crack crack crack crack crack

(30) Comparative Example 1 not containing Al.sub.4O.sub.4C but mainly containing Al.sub.2O.sub.3 was taken as the typical example of the conventional technology. It can be seen that the thermal expansion rate tends to decrease notably with an increase in the content of Al.sub.4O.sub.4C. In Comparative Example 2 containing 14% by mass of Al.sub.4O.sub.4C, the thermal expansion rate becomes lower as compared with Comparative Example 1 as the conventional technology, but the thermal shock resistance after receiving the heat treatment is not sufficient. The oxidative abrasion resistance thereof is as same as that of Comparative Example 1, but the thermal shock resistance is not sufficient when considering the use condition including the repeat use for a long period of time.

(31) It can be seen that in Examples 1 to 3 containing 15 to 60% by mass of Al.sub.4O.sub.4C, both the thermal shock resistance and the oxidative abrasion resistance are improved, and thus, these can withstand the conditions including the repeat use. In Comparative Example 3 containing 62% by mass of Al.sub.4O.sub.4C, the oxidative abrasion resistance is improved significantly as compared with Comparative Example 1 as the conventional technology, but this shows the tendency of decrease in the thermal shock resistance.

Example B

(32) Example B illustrates the examples in which the total content of Al.sub.4O.sub.4C, Al.sub.2O.sub.3, and Al component as a metal in the refractory was studied. In Table 4, the compositions of each Example and the results thereof are summarized.

(33) TABLE-US-00004 TABLE 4 Compar- ative Exam- Exam- Exam- Exam- Exam- ple 4 ple 4 ple 5 ple 1 ple 3 Refractory composition (% by mass) Al.sub.4O.sub.4C 20 20 20 15 60 Al.sub.2O.sub.3 58 60 60 71 25 Al 5 5 5 5 4 F.C. 5 5 5 4 5 Al.sub.4O.sub.4C + Al.sub.2O.sub.3 + Al 83 85 85 91 89 TOTAL C 6.2 6.2 6.2 4.9 8.7 Others (% by mass) ZrO.sub.2 7 4 SiO.sub.2 3 3 3 3 3 MgO ZrO.sub.2 + SiO.sub.2 + MgO 10 7 3 3 3 Others (except for 12 10 10 5 6 F.C.) total Grand total 100.0 100.0 100.0 100.0 100.0 C/(Al.sub.4O.sub.4C 0.038 + 2.07 2.07 2.07 1.80 1.39 0.33 Al) C/(Al.sub.4O.sub.4C 0.13 + 0.84 0.84 0.84 0.75 0.48 0.67 Al) Evaluation results Bulk specific gravity 3.04 3.02 3.01 3.10 2.62 Thermal expansion 0.60 0.61 0.61 0.64 0.44 rate (%) at 1000 C. Oxidative abrasion 80 70 60 60 40 resistance (index) Thermal shock Collapse Medium Small Medium Medium resistance crack crack crack crack

(34) Comparative Example 4, in which the content of ZrO.sub.2 in the refractory was 7% by mass and the foregoing total content was 83% by mass, resulted in a collapse in the thermal shock resistance test. This collapse is presumably caused by formation of ZrC and slaking thereof. However, in Example 4 in which 4% by mass of ZrO.sub.2 was contained and the foregoing total content was 85% by mass, there was no collapse; and it can be seen that this can be used even under the condition of the repeat use. Besides Example 4, also in Example 5, Example 1, and Example 3, in all of which the total contents were 85% or more by mass, the oxidative abrasion resistance was excellent, so that these can be used even under the condition of the repeat use.

Example C

(35) Example C illustrates the examples in which the Equation 1 and the Equation 2 in relation with the content of the free C were studied. In Table 5, the compositions of each Example and the results thereof are summarized.

(36) TABLE-US-00005 TABLE 5 Compar- Compar- ative ative Exam- Exam- Exam- Exam- Exam- Exam- Exam- Exam- ple 5 ple 6 ple 1 ple 7 ple 8 ple 6 ple 9 ple 10 Refractory composition (% by mass) Al.sub.4O.sub.4C 20 38 15 50 38 20 16 16 Al.sub.2O.sub.3 66 48 71 40 48 65 62 75 Al 7 5 5 1.2 4 2 9 1 F.C. 3 3.1 4 5 7.6 5 8 1.5 Al.sub.4O.sub.4C + Al.sub.2O.sub.3 + Al 93 91 91 91.2 90 87 87 92 TOTAL C 4.2 5.4 4.9 8.1 9.9 6.2 9.0 2.5 Others (% by mass) ZrO.sub.2 SiO.sub.2 2 3 3 3 2 2 3 3 MgO ZrO.sub.2 + SiO.sub.2 + MgO 2 3 3 3 2 2 3 3 Others (except for 4 5.9 5 3.8 2.4 8 5 6.5 F.C.) total Grand total 100.0 100.0 100.0 100.0 100.0 100.0 100.0 100.0 C/(Al.sub.4O.sub.4C 0.038 + 0.98 1.00 1.80 2.18 2.75 3.52 2.24 1.60 0.33 Al) C/(Al.sub.4O.sub.4C 0.13 + 0.41 0.37 0.75 0.68 1.00 1.27 0.99 0.55 0.67 Al) Evaluation results Bulk specific gravity 3.05 2.90 3.10 2.73 2.86 3.03 3.02 3.10 Thermal expansion 0.62 0.56 0.64 0.45 0.54 0.60 0.63 0.65 rate (%) at 1000 C. Oxidative abrasion 35 48 60 75 80 100 50 70 resistance (index) Thermal shock Large Faint Medium Faint Faint Small Small Medium resistance crack crack crack crack crack crack crack crack Compar- Compar- Compar- Compar- ative ative ative ative Exam- Exam- Exam- Exam- Exam- Exam- ple 7 ple 8 ple 11 ple 9 ple 12 ple 10 Refractory composition (% by mass) Al.sub.4O.sub.4C 16 16 58 58 58 58 Al.sub.2O.sub.3 60 75 18 16 30 35 Al 10 0.5 9 10 0.5 0.5 F.C. 10 0.5 13 16 3.5 2 Al.sub.4O.sub.4C + Al.sub.2O.sub.3 + Al 86 91.5 85 84 88.5 93.5 TOTAL C 10.0 1.5 16.6 19.6 7.1 5.6 Others (% by mass) ZrO.sub.2 SiO.sub.2 3 3 1 3 3 MgO ZrO.sub.2 + SiO.sub.2 + MgO 3 3 1 3 3 Others (except for 4 8 2 8 4.5 F.C.) total Grand total 100.0 100.0 100.0 100.0 100.0 100.0 C/(Al.sub.4O.sub.4C 0.038 + 2.56 0.65 2.51 2.91 1.48 0.84 0.33 Al) C/(Al.sub.4O.sub.4C 0.13 + 1.14 0.21 0.96 1.12 0.44 0.25 0.67 Al) Evaluation results Bulk specific gravity 3.01 3.11 2.70 2.68 2.73 2.75 Thermal expansion 0.62 0.66 0.45 0.44 0.47 0.49 rate (%) at 1000 C. Oxidative abrasion 105 60 60 110 40 55 resistance (index) Thermal shock Medium Large Faint Faint Medium Large resistance crack crack crack crack crack crack

(37) Examples 6 to 12 and Example 1, all of which satisfy the Equation 1 and the Equation 2, are excellent in both the thermal shock resistance and the oxidative abrasion resistance. On the contrary, Comparative Example 5, Comparative Example 8, and Comparative Example 10, all of which do not satisfy the Equation 1 which is significantly influential to the thermal shock resistance, are excellent in the oxidative abrasion resistance but are low in the thermal shock resistance. On the other hand, Comparative Example 6, Comparative Example 7, and Comparative Example 9, all of which do not satisfy the Equation 2 which is significantly influential to the oxidative abrasion resistance, are excellent in the thermal shock resistance but are significantly low in the oxidative abrasion resistance.

Example D

(38) Example D illustrates the examples in which by using an Al.sub.4O.sub.4C-containing raw material, the effects of the production method of this raw material, of the crystal size of the Al.sub.4O.sub.4C crystal, and of the particle size of the raw material thereof (top size) were studied. In Table 6, the compositions of each Example and the results thereof are summarized. Meanwhile, the crystal size (dimensions of the crystal) of the Al.sub.4O.sub.4C crystal means an average diameter when a cross section of the Al.sub.4O.sub.4C crystal is converted to a circle. In other words, the crystal size here means an average value of each circle's diameter when a cross section of each of the Al.sub.4O.sub.4C crystals is converted to a circle.

(39) TABLE-US-00006 TABLE 6 Exam- Exam- Exam- Exam- Exam- Exam- ple 13 ple 14 ple 15 ple 16 ple 5 ple 17 Production method of Melting Sintering Melting Melting Melting Melting Al.sub.4O.sub.4C-containing method method method method method method raw material Refractory composition (% by mass) Al.sub.4O.sub.4C 20 20 20 20 20 20 Al.sub.2O.sub.3 60 60 60 60 60 60 Al 5 5 5 5 5 5 F.C. 5 5 5 5 5 5 Al.sub.4O.sub.4C + Al.sub.2O.sub.3 + Al 85 85 85 85 85 85 TOTAL C 6.2 6.2 6.2 6.2 6.2 6.2 Others (% by mass) ZrO.sub.2 SiO.sub.2 3 3 3 3 3 3 Others total 10 10 10 10 10 10 Grand total 100.0 100.0 100.0 100.0 100.0 100.0 C/(Al.sub.4O.sub.4C 0.057 + 2.07 2.07 2.07 2.07 2.07 2.07 0.33 Al) C/(Al.sub.4O.sub.4C 0.13 + 0.87 0.87 0.87 0.87 0.87 0.87 0.67 Al) Top size of Al4O4C-containing raw material (mm) 3 (good) 1 0.5 0.21 0.074 Crystal size of 20 5 15 20 50 50 Al.sub.4O.sub.4C (m) Evaluation results Bulk specific gravity 3.12 3.13 3.12 3.09 3.01 3.11 Thermal expansion 0.64 0.65 0.63 0.60 0.61 0.62 rate (%) at 1000 C. Oxidative abrasion 75 55 70 55 60 60 resistance (index) Thermal shock Medium Medium Medium Small Small Small resistance crack crack crack crack crack crack

(40) Examples 13, 16, 5, and 17 illustrate the examples in which the raw materials produced by a melting method (arc melting method) with the top size thereof being 0.21 mm or more and the crystal size of the Al.sub.4O.sub.4C crystal being 20 m or more were used; and Example 14 illustrates the example in which the raw material produced by a sintering method with the top size thereof being 0.074 mm and the crystal size of the Al.sub.4O.sub.4C crystal being 5 m was used.

(41) Because the raw material in Example 14 is produced by a sintering method, the crystal size of the Al.sub.4O.sub.4C crystal is 5 m, so small and fine; and thus, the lowering effect to the thermal expansion rate is small. Moreover, because the reaction to Al.sub.2O.sub.3 (conversion to a corundum) is facilitated by the heat treatment, the thermal expansion rate and the modulus are increased, thereby leading to a slight decrease in the thermal shock resistance even though the content of Al.sub.4O.sub.4C is 20% by mass.

(42) Example 15 illustrates the example in which the Al.sub.4O.sub.4C raw material produced by a melting method (arc melting method) is so small and fine with the crystal size of the Al.sub.4O.sub.4C crystal being 15 m; and thus, the lowering effect to the thermal expansion rate is somewhat small. Moreover, because the reaction to Al.sub.2O.sub.3 (conversion to a corundum) is facilitated by the heat treatment, the thermal expansion rate and the modulus are increased, thereby leading to a slight decrease in the thermal shock resistance even though the content of Al.sub.4O.sub.4C is 20% by mass.

Example E

(43) Example E illustrates the examples in which the effects of a metal Si were studied. In Table 7, the compositions of each Example and the results thereof are summarized.

(44) TABLE-US-00007 TABLE 7 Exam- Exam- Exam- Exam- Exam- Exam- ple 18 ple 19 ple 20 ple 21 ple 22 ple 23 Refractory composition (% by mass) Al.sub.4O.sub.4C 40 40 40 40 40 40 Al.sub.2O.sub.3 45 40 45 40 40 40 Al 5 5 5 5 5 5 Si 0.4 0.5 5 10 11 F.C. 5 5 5 5 5 4 Si/Al(%) 0 8 10 100 200 220 Al.sub.4O.sub.4C + Al.sub.2O.sub.3 + Al 90 85 90 85 85 85 TOTAL C 7.5 7.5 7.5 6.5 Others (% by mass) SiO.sub.2 1 1 1 1 1 MgO ZrO.sub.2 + SiO.sub.2 + 1 1 1.5 1 11 11 MgO + Si Others (except for 5 9.6 4.5 5 0 0 F.C.) total Grand total 100.0 100.0 100.0 100.0 100.0 100.0 C/(Al.sub.4O.sub.4C 0.038 + 1.58 1.58 1.58 1.58 1.58 1.26 0.33 Al) C/(Al.sub.4O.sub.4C 0.13 + 0.58 0.58 0.58 0.58 0.58 0.47 0.67 Al) Evaluation results Bulk specific gravity 2.83 2.88 2.82 2.87 2.82 2.82 Thermal expansion 0.54 0.53 0.53 0.52 0.53 0.53 rate (%) at 1000 C. Oxidative abrasion 57 55 52 35 45 40 resistance (index) Thermal shock Faint Faint Faint Faint Small Medium resistance crack crack crack crack crack crack Slaking resistance Medium Small No No No No crack crack change change change change

(45) In Example 18 in which the metal Si was not contained, a medium crack was formed in the test with an autoclave. And, in Example 15 in which 8% by mass of the metal Si relative to the Al component as a metal was contained, a small crack was formed in the test with an autoclave. On the other hand, in Examples 20 to 22 in which a weight ratio of metal Si to Al component as a metal in the range of 0.1 to 2 was contained, there was no change in the test with an autoclave, thereby giving good results. In Example 23 in which a weight ratio of metal Si to Al component as a metal in the range of 0.1 to 2 was contained, the test with an autoclave gave a good result without no change; however, the thermal chock resistance was slightly decreased even though the content of Al.sub.4O.sub.4C was 20% by mass. It is presumed that this result was obtained because the metal Si further formed a strong bond.

Example F

(46) Example F illustrates the examples in which the refractory of the present invention was applied to the SN plate so as to test in an actual SN device. In Table 8, the compositions of each Example and the results thereof are summarized.

(47) TABLE-US-00008 TABLE 8 Compar- Compar- ative ative Exam- Exam- Exam- ple 24 ple 11 ple 12 Refractory composition (% by mass) ZrO.sub.2 7.0 6.0 SiO.sub.2 4.5 5.5 Al.sub.4O.sub.4C 40.0 Al.sub.2O.sub.3 45.0 78.0 77.0 Al 5.0 2.0 Si 1.0 0.1 B.sub.4C 1.0 1.0 1.0 SiC 1.0 2.0 4.0 F.C. 5.0 6.0 3.0 Al.sub.4O.sub.4C + Al.sub.2O.sub.3 + Al 90.0 90.0 90.0 TOTAL C 7.5 6.6 4.2 Others total 2.0 1.5 1.4 Grand total 100.0 100.0 100.0 C/(Al.sub.4O.sub.4C 0.057 + 1.27 0.33 Al) C/(Al.sub.4O.sub.4C 0.13 + 0.58 0.67 Al) Top size of Al.sub.4O.sub.4C- 1 mm containing raw material Evaluation results Bulk specific gravity 2.82 3.35 3.28 Thermal expansion 0.53 0.78 0.75 rate (%) at 1000 C. Actual furnace use result A Number of use 11ch 7ch 8ch Casting time 440 min 280 min 320 min (TOTAL) Use result Excellent Very rough Edge surface defect Use of reproduced actual furnace use result A Number of use 10ch 7ch Formation of crack Casting time 400 min 280 min (impossible (TOTAL) to reproduce) Use result Excellent Very rough surface Actual furnace use result B Number of use 7ch 5ch 5ch Casting time 840 min 600 min 600 min (TOTAL) Use result Excellent Very rough Edge surface defect

(48) In Table 8, the use condition shown in Actual furnace use result A is the condition in which the refractory is used as the SN plated for a ladle of 250 tons with the average casting time per 1 ch of about 40 minutes and with the multiple use of 8 ch or more. In Use of reproduced actual furnace use result A shows the results of the use of the reproduced SN plate which was obtained by a reproduction of the SN plate used in the actual furnace use result A, wherein the reproduction is made by reprocessing the actually used SN palate, followed by interpolating a ring thereto, and then followed by polishing the moving surface thereof.

(49) On the other hand, the use condition shown in Actual furnace use result B is the condition in which the refractory is used as the SN plate for a ladle of 300 tons with the average casting time per 1 ch of 120 minutes and with the use of 5 ch or more, thus for a long period of time in casting with the total time of 500 minutes or more.

(50) In Comparative Example 11 using the refractory of a conventional technology not containing the metal Al and so forth, a large attrition (surface roughness) was caused in the moving surface in any of the use conditions. Therefore, an adequate tolerance could not be obtained. In Comparative Example 12 using the same conventional material but containing the metal Al and so forth, in both the actual furnace use results A and B, not only a large crack but also an edge defect was formed. Therefore, an adequate tolerance could not be obtained. Further, under the use condition of the reproduced actual furnace use result A, a crack was formed during the time of processing the SN plate after the use thereof; and thus, the reproduction thereof could not be achieved. This is presumably due to slaking of the aluminum carbide.

(51) On the contrary, in Example 24, under any of the conditions, both the attrition of the moving surface (surface roughness) and the crack were not serious, and an adequate tolerance was obtained.