GB2173185A - Carbon-containing refractories - Google Patents

Abstract

The refractories include 2 to 15 wt.% metal fibers obtained by chatter-vibration cutting, the fibers having a length of 2 to 10 mm and a diameter of 0.03 to 0.2 mm. The refractories may be composite refractory structures such as long nozzles, immersion nozzles, upper and lower nozzles of sliding nozzle devices in continuous casting, plates of sliding nozzle devices, and nozzles for steel making converter tuyeres. The addition of the metal fibers leads to firm integration of the interface of different refractory materials in the structures, resulting in improved spalling resistance.

Description

SPECIFICATION Carbon-containing refractories This invention relates to carbon-containing refractories applicable to refractory structures requiring high thermal-shock-resistance and high mechanical strength.

For example, such refractory structures as long nozzles used for connecting a molten-steel ladle with a tundish or the tundish with a mold, immersion nozzles, upper and lower nozzles of sliding nozzle devices (slide closure devices), plates of sliding nozzle devices, or tuyeres of convertors are subjected to a considerable temperature difference within the inside of the structure during working or servicing, so that considerable thermal stress occurs in the structure due to the difference of expansion rates in different parts of the structure. Furthermore, such refractory structures are subjected to external mechanical stress such as vibration caused by molten steel flow or mechanical sliding movement.

Accordingly, the refractories for constituting such structures must have excellent thermal-shockresistance. Furthermore, the refractories must have excellent wear-resistance properties and oxidationresistance properties capable of resisting severe wear, e.g. due to molten steel flow.

In addition, when a nozzle is used as such refractory structure with a condition that the bottom end thereof is immersed in a molten steel, it is also necessary that the nozzle has sufficient slag erosion-resistance properties capable of resisting to the erosion by the molten slag existing on the surface of the molten steel.

As materials applicable to such refractory structures, conventionally, several materials with improved properties have been developed to cope with the change of the working or service condition which becomes severer year by year.

For example, in terms of long nozzles or immersion nozzles made of alumina-graphite, to improve the properties of such nozzles, it has been proposed to control the thickness of the flakes of flaky graphite contained therein, or to add carbon fibers or to add specific raw materials containing zirconia. Aithough such proposals have been effective for improving the thermal-shock-resistance and the wear resistance, they are not effective to prevent the rupture or breaking of the nozzles, which cause the most detrimental accidents in service.

Although the addition of carbon fibers has been expected to prevent the above rupture or breakings, it has not achieved any noticeable effect since the dispersion of the carbon fibers in the matrix or inner structure of the alumina-graphite is extremely difficult.

In terms of the sliding nozzles, to cope with the working or service condition of sliding nozzles which becomes severer along with the improvement of continuous casting technology such as multi-stage continuous castings, the materials which have improved wear or abrasion resistance with the inclusion of Al powders or Mg powders have been proposed and the materials have been widely used in actual working or servicing.

However, such materials also cannot cope with the current tendency of nozzles to become elongated and thin so that the rupture or breaking of nozzles have occurred.

Furthermore, in terms of the plates used for sliding nozzle'devices, materials having high wear or abrasion resistance which contain metal powders of low-fusion points such as Al powders or Mg powders or powders of alloys of such metals or carbon fibers have been proposed.

However, such materials are not effective for preventing the development of the cracks.

What are desired are refractories having high durability which can resolve the above-mentioned defects of the conventional refractories used for producing refractory structures such as continuous casting nozzles.

The present invention is based on the finding that metal fibers which are obtained by chatter-vibration cutting have a triangular cross section as shown in Figures (a), (b), and (c) of the accompanying drawings, the surfaces of the fibers are considerably deformed, and such fibers have a favourable affinity with the internal structure of the refractories and the joint strength of such fibers with the internal structure of the refractories, namely the resistance against the mechanical stress, is increased.Although metal fibers have been produced by other methods, such as a method which produces metal fibers by cutting wires after drawing or a melt extraction method, those fibers have a nearly circular cross section and have only slight indentations and protrusions on the surface thereof and, therefore, those fibers cannot be expected to have such effect as to be able to join or integrate the internal structure of the refractories, as fibers obtained by chatter-vibration cutting can.

In addition, it has heretofore been difficult to economicaily manufacture fibers having a diameter of 0.2 mm or less in conventional means. Whereas, according to the chatter-vibration cutting method, fibers having a diameter of 30 pm or so may inexpensively be obtained, and so it is possible to make the aspect ratio larger. The shape of the section of thefibers in the chatter-vibration cutting method or scrape-vibration cutting method is a complicated triangular form; the diameter of such a fiber with a deformed triangular section is defined as the diameter of a circle having the same cross-sectional area as the fiber.

The length of the fibers obtained by the chatter-vibration cutting method, used in this invention, is within the range of 2 to 10 mm. If thefibers are shorter than 2 mm, the integration effect thereof is insufficient, but on the contrary, if they are longer than 10 mm, it is difficult or is practically impossible to mold the refractory materials. The diameter of the fibers is preferably within the range of 30 to 200 lim. If the diameter is less than 30 pm, dispersion of the fibers is difficult as the fibers are entangled together, but on the contrary, if the diameter is largerthan 200 um, the aspect ratio becomes substantially small, and accordingly the desired effect cannot be attained.

Any kinds of metal may be used for the fibers obtained by the chatter-vibration cutting method, and in particular, a metal having a high melting point such as a cast iron, an ordinary steel, or a special steel, e.g.

Ni-Cr steel, Cr-Mo steel, Cr steel, Cr-V steel, etc. or stainless steel; an Fe-base alloy or ferro-alloy is preferred, as they have an excellent strength from a normal temperature to a moderately high temperature and they are relatively low-priced.

Metal fibers having a low melting point may also be used, such as Al-fibers, Al-fiber-containing Al-alloy fibers, Mg-fibers, etc.

The metal fibers obtained by chatter-vibration cutting method can be used in a single form or a mixture including several kinds of metal fibers depending upon the purpose of the usage. It is especially effective to use metal fibers of different kinds with different fusion points.

The total amount of the said metal fibers to be added is preferably 2 to 15 wt.% of the amount of the refractory aggregate. If the content of the metal fibers is less than 2 wt.%, sufficient strength and spalling-resistance cannot be attained, but on the contrary, if the content thereof exceeds 15 wot(%, the ratio of the metal fibers in the matrix is too large and thus the properties of the refractory materials are lowered and any noticeable improvement on the spalling-resistance cannot be attained. Moreover, blending and molding operation is difficult, and thus refractory products of good quality cannot be obtained thereby.

Any desired refractory aggregates may freely be used in this invention, including, for example, silica, alumina, silica-alumina, magnesia, spinel, zirconia, zircon, chrome minerals, SiC, Si3N4, B4C, BN, carbon such as graphite and amorphous carbon, etc.

In manufacture of the refractory structures, individual components are first prepared in accordance with the necessary characteristics which are required by the parts of the refractory structures to be manufactured, and then, these are blended to obtain mixtures, which are simultaneously molded to form the structure which may satisfy the respective objects. The metal fibers may be used in any part of the structure depending on the condition of the usage of the structure. For example, in terms of a long nozzle, the metal fibers can be used throughout the entire body of the long nozzle or only at the upper or neck portion thereof where the mechanical stress concentrates. Thereafter, if necessary, the thus formed parts are fired in a reducing atmosphere to remove volatile components therefrom.According to the use of the refractory structures to be formed, it is also possible to mold articles as still retaining organic binders such as pitch, phenol resin, etc.

In order to prevent Fe-base alloy fibers from being oxidized or from being reacted with any oxides, organic materials should be used as binding agent, and in addition, the aggregate preferably contains 2 wt.% or more carbon in all.

The organic binders are preferably those containing a large amount of a residual carbon,and in this connection, phenol and furan resins are preferable in view of cost, which, however, does not imply any limitation whatsoever to those organic binders.

The refractory material compositions of this invention may further contain, if necessary, metal powders of a low melting point such as Al, Mg, Zn, Sn, or the like metal particles having a diameter of 0.5 mm or less, in an amount of 2 to 15 wt.% of the amount of the refractory aggregate, whereby decrease of the strength in the middle temperature range may completely be prevented. (The addition of such low melting point-metal powders is disclosed in Japanese Laid-Open Patent Publication No. 55-65348.) According to this invention, it has now been found that the combined use of these metal powders and the above mentioned metal fibers results in the obtaining of non-fired or fired molded refractory structures having good properties and good spalling-resistance.

The compositions of this invention, comprising the components as mentioned above, may be molded, hardened, and fired, if necessary, in a conventional manner, whereby non-fired or fired refractory structures having high spalling-resistance of this invention can be obtained.

The composite refractory materials of this invention contain fibers obtained by chatter-vibration cutting method and having a section with acute-angled corners and a surface with a complicated and rugged shape.

The incorporation of said fibers has further developed the reinforcement of the refractory matrix oyer a prior art to add conventional fibers. In addition, even though each of the structural parts is made of a different refractory material, any crack does not occur in the interface of the parts made of different refractory materials, as the incorporated fibers act to integrate the interface. Thus, the life and the durability of the refractory structures of this invention are apparently and noticeably improved.

Brief description of the drawings Figure 1 shows shapes of sections of steel fibers obtained by chatter-vibration cutting method, which are microscopic views with 200-times magnification. Figures 2 and 3 show structures of nozzles for continuous casting, which are embodiments of refractory structures of this invention. Figure 2 is an immersion nozzle, and Figure 3 is a long nozzle. In these drawings, (1) is a body, (2) is a powder part, (3) is a gate part, and (4) is a slag part.

Description ofpreferred embodiments This invention was applied to the immersion nozzle and the long nozzle as shown in Figures 2 and 3, respectively, and the effects thereby attained are explained hereunder, in comparison with those made of conventional composite refractory materials. Compositions and properties of materials used hereunder are given in Tables 1 and 2 to follow.

In Table 1, each "Note" is as follows: Note 1: Electrofused zirconia-mullite (awl203 48 wt.%- ZrO2 36 wt.% - SiO2 16 wt.%) Note 2: Fibre A: SS41, by chatter-vibration cutting, 90 pm x 6 mm.

Fibre B: FOD50, by chatter-vibration cutting,090 pm x 6 mm.

Fibre C: SUS430, by drawn-wire cutting, pr300 Cim x 20 mm.

Note 3: Samples were fired with a coke breeze in a tunnel kiln, at 900"C for 10 hours, and thereafter the dimensional variation (%) was measured.

Note 4: Samples were immersed in a pig iron at 16000C in a high frequency induction furnace fdr 1 minute and 30 seconds, and thereafter cooled in water for 20 seconds. Each modules of elasticity before and after said treatment was measured, E0 being before treatment and E1 being after treatment, and the spalling-resistance in each sample was represented by the ratio of R=E1/E0. In Table 1; S means R 0.95: A means 0.95 > R > 0.90; B means 0.90 > R 3 0.80; and C means R < 0.80. From the view point of practical use, the rank of A or more is preferred, and the rank of B may also be acceptable, for practical use so far as the condition in use is appropriately selected.

Note 5: Each sample was used as a lining layer in a high frequency induction furnace, and SS41 was fed thereinto and fused at 1600"C and kept as such for 60 minutes. Afterwards, the molten loss in each sample was measured and then the erosion-resistance of each sample was evaluated therefrom. The loss index (L) was determined as follows: The sample Al has the loss index (L) of 100; and S means L < 95; A means 95 S L < 105; B means 105 < L < 115; and C means L m115.

Note 6: Each sample was immersed in a mixture of an electrolytic iron and a powder in a criptol electric furnace at 1 6000C for 60 minutes. Afterwards, the loss index in each sample was calculated, whereupon the loss index of the sample ZI was 100.

In Tables 2, "Note 2" and "Note 6" are different from those in Table 1, and are as follows: Note 2: Aluminium flakes (44 um or less) were used.

Note 6: Each sample having a shape of 40 x 40 x 40 mm was treated in an electric furnace at 800"C for 3 hours, and thereafter the thickness (mm) of the formed oxide layer in each sample was measured.

Other "Notes" in Table 2 are the same as those in Table 1.

In every sample in Tables 1 and 2, the raw materials were well blended and then pressed with a rubber press at a pressure of 1200 kg/cm2 to form the determined shape. The thus molded sampies were then fired in a tunnel kiln having a reducing atmosphere at 900"C.

TABLE 1

Al A2 A3 A4 Z1 Z2 Z3 Graphite crude powder 15 15 15 15 5 5 10 Graphite fine powder 10 10 10 10 - - 5 Sintered alumina 0.5-0.1 (mm) 10 10 10 10 - - Sintered alumina 0.04S0 20 20 20 20 - - Electrofused alumina 0.044-0 20 20 20 20 - - Electrofused zirconia 0.0.1 (mm) - - - - 50 45 40 g Electrofused zirconia 0.070 - - 40 40 40 40 CO ZRM(Notel) 0.5-0.1 (mm) 20 13 13 13 - - ~ Silicone 0.074-0 1 5 5 5 5 5 5 o n E Fibre A (Note 2) 7 7 - - - 5 0 O Fibre B 7 7 Fibre C - - - 7 - - Phenol resin +10 +10 +10 +10 +6 +6 +8 Firing shrinkage percentage (%) -1.3 -0.9 -0.9 -1.0 -0.6 -0.6 -0.9 (Note 3) (after fired at 900"C) Bulk density 2.38 2.46 2.45 2.48 3.60 3.65 3.10 Porosity (%) 16.8 17.9 18.1 17.4 15.8 16.6 16.3 .t Thermal expansion percentage (%) +0.41 +0.45 +0.42 +0.48 +50 +0.53 +0.43 (at 1 000'C) o X Spalling-resistance (Note 4) A S S C C A B Corrosion-resistance (Note 5) A A A A 100 103 155 (Note 6) TABLE 2

A5 A6 A7 A8 Graphite crude powder 15 14 10 10 Graphite fine powder 15 14 10 10 Sintered alumina 0.5-0.1 (mm) 10 7 15 15 Sintered alumina 0.044-0 35 32 35 35 Fused Fusedsilica 0.4-0.1 (mm) 15 14 10 5 ZRM(Notel) 1) 0.4-0.1 10 9 10 5 o Aluminium flake (Note 2) - - 5 5 0 m Silicone 0.07S0 (mm) 5 5 F O Fibre A (Note 3) 3) 10 - 10 Phenol resin +12 +12 +11 +11 Firing shrinkage percentage (%) -1.1 -1.0 +0 -0.6 (after fired at 900"C) Bulk density 2.23 2.36 2.30 2.45 Porosity (%) 17.8 18.5 17.2 17.6 Thermal expansion percentage (%) +0.25 +0.31 +0.40 +0.43 (at 1000 C) 0 t Spalling-resistance (Note 4) A S A S Q o X Corrosion-resistance (Note 5) A A S A Oxidation-resistance (Note 6) (800"C x 3hrs) Thickness of oxide layer (mm) 5.2 3.8 0.1 0.1 Example 1 Al in Table 1 was used as the material of the body (1) referring to Figure 2 and Z1 in Table 1 as the material of the powder part (2) and these (1) and (2) were integrally formed by simultaneous molding method. This was then sunk in a coke breeze in a tunnel kiln and fired at 900"C therein, to obtain a conventional nozzle structure.After the firing, however, the interface between the body and the powder part was cracked, and the firing yield was 85%. On the other hand, the same nozzle was formed by using the combination of A2 and Z2, according to the same step of simultaneous molding followed by firing. After the firing, no crack occurred in the latter manufactured nozzle, and thus, the firing yield thereof was 100%.

Example 2 The conventional nozzle comprising the combination of Al as the body (1) referring to Figure 2 and Z1 as the powder part (2), as formed in the above Example 1, was practically used in a continuous casting of a steel. In the result, the interface peeled in places in the form of a ring and partly cracked, resulting in an occurrence of accidents. Apart from this, Z3 which has a similar expansion characteristic to Al was used as the material of the powder part. In the latter case, however, the erosion-resistance of said part is insufficient and the life of the nozzle lasted for only three charges. On the other hand, the nozzle was manufactured by simultaneous molding of the combination of A2 and Z2 according to this invention, each containing fibers obtained by chatter-vibration cutting method. Thus manufactured nozzle was used in continuous steel casting, whereupon no peeling occurred, and the life thereof lasted sufficiently for 6 charges.

Next, A4 was substituted for A2, the former A4 containing fibers C obtained by cutting drawn-wires, to manufacture the nozzle. This was used analogously, whereupon the interface of A4 and A7 cracked. This result means that the addition of said fibers C is not effective.

Example 3 The long nozzle as shown in Figure 3 has heretobefore been manufactured by simultaneous molding of the body (1), the gate part (3) and the slag part (4) to obtain said long nozzle having an integrated structure, whereupon A5 of Table 2 was used for the body (1), A7 having good oxidation-resistance was used for the gate part (3), and Z3 of Table 1 having good erosion-resistance was used for the slag part (4). However, the long nozzle thus manufactured in a conventional manner has some problems in practical use, in that the interface of the different materials in the nozzle was cracked during the use, due to the expansion difference therebetween, sometimes resulting in occurrence of accidents.

Then, the nozzle of the same shape as above was manufactured by using A6 for the body (1), A8 for the gate part (3) and Z2 for the slag part (4), the Z2 containing fibers A having a diameter of 90 pom and a length of 6 mm and this was practically used. In the result, no crack occurred.

Example 4 5 wt.% of a phenol resin was added to a refractory aggregate comprising 35 wt.% of a synthetic mullite (produced by Naigai Taika Co.), 60 wt.% of a sintered alumina and 5 wt.% of a clay, and blended to obtain a composition. 3 wt.% of steel fibers having a diameter of 0.09 mm and a length of 6 mm obtained by chatter-vibration cutting and 2 wt.% of aluminium fibers obtained by chatter-vibration cutting having a diameter of 0.03 mm and a length of 3 mm, said weight ratio being an apparent weight ratio to the refractory aggregate, were added to the above prepared composition and then molded and hardened at 200"C for 24 hours, to obtain a non-fired refractory material to be used for a lower nozzle part of a sliding nozzle.

As Comparative Example 4-1, in the same manner as in the above Example 4, with the exception that steel and aluminium fibers were not added, another non-fired refractory material to be used for said lower nozzle part of the sliding nozzle was manufactured.

Properties of these refractory materials obtained in said Example 4 and Comparative Example are shown in the following Table 3. Comparing the refractory material of Example 4 with that of Comparative Example 1 from the results in said Table 3, it is confirmed that the time till the occurrence of crack is longer in the former than the latter and that the development of the crack is slower in the former than the latter.

TABLE 3 Example 4 Comparative Example 4-1 Apparent density 3.23 3.28 Bulk density 2.96 3.00 Apparent porosity (%) 8.4 8.5 Compressive strength (kg/cm2) 1325 1390 Spalling test* 2min.30sec. 1 min.30sec.

(time of crack occurrence) *The pour orifice of the lower nozzle part of the sliding nozzle was rapidly heated with a flame of 1500"C, and thus the test was carried out.

Example5 5 wt.% of a phenol resin and 1 wt.% of an aluminium powder having a grain diameter of 0.2 mm or less were added to a refractory aggregate comprising 15 wt.% of a quartz glass, 60 wt.% of an electrofused alumina, 20 wt.% of a flaky graphite and 5 wt.% of a mixture of Si powder and SiC; and 5 wt.% (to the refractory aggregate) of stainless steel fibers obtained by the chatter-vibration cutting having diameter of 0.1 mm and a length of 6 mm and 3 wt.% of aluminium fibers obtained by the chatter-vibration cutting having a diameter of 0.1 mm and a length of 3 mm were further added thereto, and then molded and hardened at 200"C for 24 hours, to obtain a non-fired long nozzle for a ladle.

As the comparative Example 5-1, in the same manner as in the above Example 5, with the exception that aluminium fibers were not added, another non-fired refractory material was obtained. And as Comparative Example 5-2, in the same manner as in the above Example 5, with the exception that stainless steel fibers were not added but 5 wt.% of aluminium fibers only were added, still another nonfired refractory material was obtained.

Properties of the non-fired refractory materials obtained in the above Example 5, Comparative Example 5-1 and Comparative Example 5-2 are shown in the following Table 4. As being clear from the results given in said Table 4, it is confirmed that the refractory material of Example 5 is free from the occurrence of cracks and has good spalling-resistance. In a practical test using a ladle of 300t, the long nozzle of Example 5 was confirmed to last for 6 charges without occurrence of crack. This result is fully comparable to a long nozzle of a fired material now is used in this field.

TABLE 4 Example Comparative Comparative 5 Example 5-1 Example 5-2 Apparent density 2.63 2.66 2.61 Bulk density 2.42 2.46 2.39 Apparent porosity (%) 8.2 7.6 8.1 Compressive strength 520 630 450 (kg/cm2) Spalling test* No crack 30min.30sec. 25min.05sec.

(time of crack 60 min.

occurrence) 2 times *A cylindrical part of 200 mm long was cut from the long nozzle, and the pour orifice thereof was rapidly heated with a flame of 1500 C.

Example 6 5 wt.% of a phenol resin was added to a refractory aggregate comprising 80 wt.% of sintered alumina, 10 wt.% of synthetic mullite and 5 wt.% of carbon, and blended to obtain a composition. 2.5 wt.% of stainless steel fibers obtained by the chatter-vibration cutting having a diameter of 0.06 mm and a length of 3 mm and 4 wt.% of aluminium fibers having a diameter of 0.03 mm and a length of 1.5 mm were added to the obtained composition, the weight ratio being to the amount of the refractory aggregate, and then blended, molded, and hardened at 200"C for 24 hours, to obtain a non-fired sliding nozzle plate brick.

As Comparative Example 6-1, in the same manner as in the above Example 6, with the exception that 5 wt.% of stainless steel fibers having the same diameter and the same length as those of said Example 6 and 7 wt.% of aluminium fibers were used, the total content of said metal fibers being more than'10 wt.%; another non-fired plate was obtained. During kneading the composition, however, aggregated granules were formed.

As the next Comparative Example 6-2, in the same manner as in the above Example 6, with the exception that stainless steel fibers were not added, still another non-fired plate was obtained.

As further another Comparative Example 6-3, in the same manner as in the above Example 6, with the exception that 0.5 wt.% of stainless steel fibers and 0.3 wt.% of aluminium fibers were added, the total content of said metal fibers being less than 1 wt.%, still another nonfired plate was obtained.

Properties of these non-fired plates obtained in the above Example 6 and Comparative Examples 6-1 to 6-3 are as shown in the following Table 5, together with the practical test results of each sample.

TABLE 5 Example 6 Comparative Comparative Comparative Example 6-1 Example 6-2 Example 6-3 Apparent density 3.57 3.51 3.68 3.45 Bulk density 3.15 3.07 3.23 2.98 Apparent porosity (%) 11.8 12.5 12.2 13.6 Compressive strength (kg/cm2) 1350 1200 1300 1100 Bending strength (kg/cm2) 650 550 400 200 Practical test result Used as SN Used as SN Used as SN Used as SN of 300t of 300t of 300t of 300t ladle in ladle in ladle in ladle in converter, converter, converter, converter, n=20 n=6 n=5 n=5 5.5 heats 3.2 heats 3.0 heats 3.0 heats Durable Extreme Extreme Extreme with no adhesion of development damage on trouble metal of crack slide surface SN:Sliding nozzle Example 7 25 wt.% of a phenol resin was added to a refractory aggregate comprising 75 wt.% of a sea water magnesia of high purity, 20 wt.% of a sintered spinel and 5 wt.% of carbon, and blended to obtain a composition. 4 wt.% of stainless steel fibers obtained by the chatter-vibration cutting having a diameter of 0.06 mm and a length of 6 mm and 3 wt.% of Al-Mg alloy fibers (Mg = 50 wt.%) having a diameter of 0.09 mm and a length of 3 mm, the weight ratio being an apparent weight ratio to the amount of the refractory aggregate, were added to the obtained composition, and then blended, molded, and hardened, to obtain a non-fired basic plate.

As Comparative Example 7-1, in the same manner as in the above Example 7, with the exception that stainless stool fibers were not added, another non-fired plate was obtained.

Properties of these plates obtained in said Example 7 and Comparative Example 4 are given in the following Table 6.

TABLE 6 Example 7 Comparative Example 7-1 Apparent density 3.21 3.15 Bulk density 3.04 2.99 Apparent porosity (%) 5.3 4.9 Compressive 1450 1525 strength (kg/cm2) Bending 450 280 strength (kg/cm2) Practical test Used as SN of 200t Used as SN of 200t result ladle in converter. ladle in converter.

S-containing, ' S-containing, free-cutting steel, free-cutting steel, n=5 (C; 0.1, S; 0.25) n=3 (C; 0.1, S; 0.25) 3.5 heats Durable with 2.3 heats Development no penetrated crack of cracks SN: Sliding nozzle

Claims (9)

1. A carbon-containing refractory including metal fibers obtained by chatter-vibration cutting in an amount of 2 to 15 wt.%, the fibers having a length of 2 to 10 mm and a diameter of 0.03 to 0.2 mm.

2. A refractory as claimed in claim 1, wherein the metal fibers comprise two or more kinds of metal fibers, each kind having a different melting point.

3. A refractory as claimed in claim 1 or 2, wherein the carbon content is within the range of 2 to 50 wt.%.

4. A refractory as claimed in claim 3, wherein the carbon content is 10 wt.% or more, and at least 80 wt.% of the carbon is a flaky graphite.

5. A refractory as claimed in any preceding claim, wherein up to 10 wt.% of a metal powder having a melting point of 1000"C or lower is incorporated, in addition to the metal fibers.

6. A refractory as claimed in any preceding claim, wherein the refractory aggregate and powder components, other than metal fibers, metal powders, and carbon, comprise raw materials selected from Al2O3, SiO2, ZrO2, MgO, and CaO, and/or two or more kinds of crystals and inevitable glass phase raw materials, and/or one or more kinds of carbides and/or nitrides which are used in ceramics.

7. A refractory as claimed in any preceding claim, wherein an organic binder is used in the manufacture ofthe refractory.

8. A refractory as claimed in any preceding claim, which has been treated at a heat treatment temperature of 1300"C or lower.

9. A refractory as claimed in any preceding claim, substantially as described in any of the Examples given.