JP2000264739A - PRODUCTION OF SINTERED POWDER AND AlN-BN REFRACTORY MATERIAL - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sintered powder having a specified low porosity, a specified composition consisting of AlN, BN and B4C and packing property by heating a filled body or a compact of a powdery mixture containing a powdery source of Al and B4C powder to a specified temperature in an atmosphere of N2 and comminuting the resulting sintered compact. SOLUTION: The sintered powder contains >=80 wt.%, in total, of 2-95 wt.% AlN, 4-73 wt.% BN and 1-25 wt. % B4C and has <=30% porosity. A powdery source of Al and B4C powder are prepared and mixed. The powdery source of Al may be metal Al or an Al alloy and may contain Mg and Si as alloying elements. The powdery mixture is filled into a graphite vessel to form a filled body or it is compacted to form a compact having shape retentivity. The filled body or the compact is heated to 1,300-2,300 deg.C under 0-10 kg/cm2 pressure of nitrogen. By the progress of nitriding, A/N and BN are formed and the porosity of the resulting sintered compact can be controlled to <=30% because of high density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a sintered powder and, particularly, an AlN-BN refractory material having excellent corrosion resistance to molten materials such as molten metal and molten slag.

[0002]

2. Description of the Related Art As is well known, hexagonal boron nitride (B
N) has high thermal conductivity, excellent electrical insulation and excellent lubricity, and is composed of iron, copper, nickel, zinc, gallium, arsenic,
It is known as a chemically stable material that does not react with molten materials such as glass and cryolite. The boron nitride is stable up to 900 ° C. in air and up to 2200 ° C. in an inert gas, and has a low Young's modulus so that it is easily elastically deformed and resistant to thermal shock. Further, since boron nitride has a low hardness, it has a feature that, like metal, machining such as cutting and grinding can be easily performed.

[0003] On the other hand, aluminum nitride (AlN) is also known as a material having high thermal conductivity and excellent corrosion resistance to various molten metals typified by molten steel, similarly to the above-mentioned boron nitride. Also, aluminum nitride is different from soft boron nitride in that it has relatively high rigidity and hardness, and thus has excellent wear resistance.

[0004] Therefore, when boron nitride and aluminum nitride are combined, a composite material having both thermal shock resistance, machinability and abrasion resistance and excellent corrosion resistance to molten metal and molten slag can be obtained. Thus, AlN-BN
Composite materials are known for use as various refractories for casting.

[0005] For example, Japanese Patent Application Laid-Open No. 63-84750 relates to a nozzle for continuous casting of steel.
Parts by weight, 10 to 40 parts by weight of aluminum nitride and graphite 1
A nozzle for continuous casting characterized by mixing 0 to 30 parts by weight is disclosed. As an effect of the invention, it is stated that a nozzle in which boron nitride, aluminum nitride and graphite are blended in a predetermined ratio has a low wettability to molten steel, so that it is possible to prevent inclusions from adhering to the inner surface of the nozzle.

On the other hand, Japanese Patent Application Laid-Open No. Hei 6-238409 relates to a ceramic mold for continuous casting, in which at least the solidification point of molten steel on the inner wall surface which comes into contact with molten steel is AlN.
Disclosed is a nozzle for continuous casting of a Ni-Cr-Fe-based steel material, which can be cast over a long period of time by using a sintered AlN-BN having a content of 30% by weight or more to form a steel material having a good surface condition. .

As a method of manufacturing the AlN-BN sintered body, a method of adding a thermosetting organic binder such as a phenol resin and baking to bond the raw material particles from residual carbon is well known. By applying this method, after sintering,
The AlN and BN particles are bonded by carbon. This carbon is amorphous and rich in reactivity, and starts oxidizing at about 350 ° C. when exposed to air. Then, the binder disappears due to this oxidation, and the structure of the sintered body collapses. Conventionally, it has been known to add an antioxidant such as metal Si, Al, or SiC as a countermeasure for this. However, although these antioxidants can delay the loss of the carbon binder, they cannot. This is a disadvantage of thermosetting binders.

Further, a method is known in which AlN powder and BN powder are used as main raw materials, and a sintering aid such as Y ₂ O ₃ is added thereto to form and sinter. For example, JP-A-1-246178
Japanese Patent Publication No. JP-A-2005-64131 relates to a method for manufacturing a refractory for molten steel,
Mixed weight% of BN powder and 30 to 80 wt% of AlN powder and 0.1 to 8% by weight of Y ₂ O ₃ powder, molding, to produce a continuous casting nozzle such as by baking in a non-oxidizing atmosphere Is disclosed.

[0009]

However, since AlN and BN powders as main raw materials are expensive, AlN-BN powder is required.
Based refractory materials are expensive. For this reason, AlN-BN refractory materials are rarely put to practical use despite having excellent properties.

The present invention has been made in view of such circumstances, and does not use expensive AlN powder or BN powder, but uses inexpensive Al powder or B ₄ C powder and involves sintering accompanied by nitriding reaction. and to obtain a sintered powder good filling property mainly comprising AlN-BN-B ₄ C by.

Further, according to the present invention, by adding an Al powder to a sintered powder and performing sintering accompanied by nitridation again, it is possible to produce an AlN-BN refractory material at a lower cost than before.
An object of the present invention is to provide a method for producing an 1N-BN refractory material.

[0012]

According to the present invention, AlN is reduced to 2 to 2.
95% by weight, BN ₄ to 73% by weight, B ₄ C 1 to 25
80% by weight of AlN, BN and B ₄ C in total
The present invention provides a sintered powder containing the above, and having a porosity of 30% or less.

[0013] Second, a filled or molded body of a mixed powder containing an Al source powder and a B ₄ C powder is placed in a nitrogen atmosphere at 1300 to 1300.
The present invention provides a sintered powder obtained by heating to a temperature of 2300 ° C. to form a sintered body, and then pulverizing the sintered body.

Third, 2 to 95% by weight of AlN and 4 to 7%
3% by weight of BN and 1 to 25% by weight of B ₄ C
A sintered powder characterized by being obtained by using a sintered body containing not less than 30% by weight and having a porosity of not more than 30% as a refractory for casting, and then collecting and pulverizing it.

Fourth, 2 to 95% by weight of AlN and 4 to 7
3% by weight of BN and 1 to 25% by weight of B ₄ C
A sintered powder characterized by being obtained by using a sintered body containing not less than 30% by weight and having a porosity of not more than 30% as an immersion nozzle, and then collecting and pulverizing it.

Fifthly, the AlN-BN is characterized in that the filler or the compact of the mixture of the raw material powder and the binder containing 30% by weight or more of the sintered powder is heated and sintered in a non-oxidizing atmosphere. A method for producing a refractory material is provided.

Sixth, 10 to 40% by weight of the Al source powder having a metal content of 95 parts by weight or more and 30% by weight or more of the sintered powder of claim 1 to 4, and the Al source powder and the sintered powder Of a mixed powder containing 70% by weight in total in a nitrogen atmosphere to produce AlN, thereby producing an AlN-BN refractory material.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
In the present invention, the particles constituting the sintered powder are AlN and B
It is desirable that the total of the three components of N and B ₄ C be 80% by weight or more. Here, AlN imparts corrosion resistance to the molten metal and resistance to abrasion due to the flow of the molten metal, and BN imparts thermal shock resistance and corrosion resistance to the molten slag to the AlN-BN refractory material. In addition, B ₄ C is oxidized at 450 ° C. or higher to generate a B ₂ O ₃ melt to close the pores and prevent further oxidation of the sintered body. Note that B ₄ C also has the effect of promoting the sintering of BN, and as a result, functions to increase the strength of the sintered powder. Therefore, the above three components are indispensable for constituting the above-mentioned basic characteristics of the AlN-BN refractory material, and it is preferable that the total of the three components is at least 80% by weight or more. Further, the respective features of the three components is most effectively exhibited, the composition such that 2 to 95% by weight of AlN and 4-73% by weight of BN and 1 to 25 wt% of B ₄ C Is preferably restricted.

The above three components may be added in a total amount of 100% by weight, and if less than 20% by weight, other compounds may be blended. As other compounds, for example,
AlON, SiAlON, Al ₂ O ₃ , MgAl
_{2 O 4, 3Al 2 O 3} · 2SiO 2, 9Al 2 O 3 · 2
One or more compounds selected from B ₂ O ₃ , Ti
O ₂ , ZrO ₂ , Cr ₂ O ₃ , SiO ₂ , Y ₂ O ₃ , C
One or more oxides selected from eO ₂ and Sc ₂ O ₃ , and a composite oxide containing at least one of these oxides may be included.

In addition, MgB_Two, CaB₆, TiB_Two, Z
rB_Two, AlB_TwoOne or more selected from
Borides may enter. Furthermore, TiC, ZrC, Cr
_ThreeC _Two, Al_FourC_ThreeOr one selected from SiC
May contain a plurality of carbides. Furthermore, TiN,
ZrN, Cr_TwoN, Si_ThreeN_Four, Mg_ThreeN_FourChoose from
One or more selected nitrides may be included. Ma
The Si_TwoN_TwoOxynitrides typified by O may enter
No. Metal Al and metal Si absorb oxygen invading the sintered body.
Al_TwoO_ThreeInstead of closing the pores and invading oxygen inside.
This is preferable because it prevents entry. Carbon C has excellent thermal shock resistance
You may enter.

The porosity of the sintered powder is preferably 30% or less. The reason for this is that if the porosity exceeds 30%, the powder is brittle, and the strength of the AlN-BN refractory material produced by sintering the raw material powder including the sintered powder is reduced.

Incidentally, in order to produce the sintered powder,
First, a mixed powder containing an Al source powder and a B ₄ C powder is prepared. Here, the mixed powder may be composed of only the Al source powder and the B ₄ C powder, or the other compound may be mixed within a range satisfying the constraint on the composition of the sintered powder. The Al source powder may be Al alone or an aluminum alloy. As an alloy element, for example, Mg,
Si may enter. When the metal content of the Al source powder contains nonmetals such as oxides and nitrides, the bonding force due to nitridation is reduced. Therefore, the metal content is preferably 95% by weight or more.

The mixed powder is filled into a container made of, for example, graphite to form a filled body, or is pressed to form a molded body having shape retention. It is preferable that the density of the filled body or the molded body is high as long as the penetration of nitrogen into the inside is not hindered. However, the porosity of the obtained sintered body is adjusted to be 30% or less.

The filled or sintered body is subjected to a nitrogen pressure of 0 to 10 k.
It is preferable to heat to a temperature of 1300 to 2300 ° C. at g / cm ² (gauge pressure). The reason is 1300 ° C
If it is less than ₃ , nitriding of B ₄ C is difficult to proceed, and if it exceeds 2300 ° C., heat generated by the nitriding reaction melts B ₄ C to inhibit nitriding. The reactions that proceed are as follows.

Al + 1 / 2N ₂ → AlNB ₄ C + 2N ₂ → 4BN + C A part of C may be dissolved in unreacted B ₄ C. Further, a carbide such as Al ₄ C ₃ may be generated.

It is known that commercially available boron nitride powder is extremely bulky and has a tap density as extremely small as 0.2 to 0.5 g / cm ³ . For this reason, when commercially available boron nitride powder is blended, the packing density of the mixed powder is reduced, and the density of the sintered body must be reduced. On the other hand, when the sintering accompanied by the above reaction is applied, the porosity of the sintered body can be suppressed to 30% or less by the sintering promoting action of AlN and B ₄ C. As a result, the sintered powder obtained by pulverizing the sintered body has a tap density of 1 g / cm ³ or more even when a condition containing a large amount of BN is selected, and has extremely high filling properties as compared with commercially available boron nitride powder. It is well suited as a raw material for producing sintered bodies.

As a pulverizer for pulverizing the sintered body, for example, a jaw crusher, a ball mill, and a roll mill can be applied. The particle size of the sintered powder is selected according to the characteristics required for the sintered body as the final product, that is, the AlN-BN refractory material, and is, for example, 1 mm or less.

For the sintering of the sintered powder, a thermosetting resin represented by a phenol resin may be applied as a binder. In this case, as described above, CO, H ₂ , N ₂ ,
The binder is thermally decomposed in a non-oxidizing atmosphere containing a gas such as Ar as a main component, and the bond by the remaining carbon is developed. Further, metal Al may be used as a binder. In this case, as described above, the AlN bond is developed by nitriding. In any case, an AlN-BN refractory material is manufactured by heating and sintering a filled body or a molded body of a mixture of a raw material powder containing 30% by weight or more of a sintered powder and a binder in a non-oxidizing atmosphere. .

Among the two kinds of binders, metal Al
Reaction sintering using as a binder is more preferable.
The reason for this is that bonding with AlN generated by nitriding metal Al is much better in oxidation resistance and corrosion resistance to molten metal than C bonding with thermosetting resin. That is, the main constituent component AlN,
Both BN and B ₄ C absorb oxygen invading from the outside by oxidation at the surface layer of the sintered body and prevent intrusion into the inside, so that they are not easily damaged by oxidation.

The Al is added to the sintered powder in an amount of 30 to 90% by weight.
10 to 40% by weight of the source powder, and the sintered powder and Al
In the same manner as described above, a filled body or a molded body is formed from a mixed powder containing a total of 70% by weight or more of the source powder, and Al is nitrided, and the generated AlN is used as a bonding force to form a sintered body.

In order to give strength to the sintered body, it is preferable that the Al source powder is 10% by weight or more. Therefore, the content of the sintered powder is limited to 90% by weight or less. On the other hand, if the Al source powder is added in an amount exceeding 40% by weight, the thermal shock resistance is undesirably reduced. Further, in order to take advantage of the characteristics of BN, the content of the sintered powder is preferably 30% by weight or more. Further, the total amount of the sintering powder and the Al source powder may be 100% by weight, or if it is less than 30% by weight, the other compounds may be blended to realize various characteristics. .

Next, the sun according to the embodiment of the present invention will be described with reference to FIG. First, an Al source powder and a B4 C powder are mixed in a predetermined mixture. Subsequently, the mixture is supplied to a molding die, and molding is performed by adding a predetermined factor. Thereafter, the compact is placed in a furnace and heated in a nitrogen atmosphere. As a result, Al and B ₄
As the nitriding of C proceeds, a sintered body mainly composed of B ₄ C which has not reacted with Al and BN is generated. Further, after cooling the sintered body, the sintered body is pulverized to a predetermined particle size. Thus, Al
N-BN-B ₄ C sintered powder.

Next, the sintering powder and the Al source powder are mixed in a predetermined composition. Subsequently, the mixture is filled into a graphite mold having a cavity of a submerged nozzle while applying vibration. Further, the packing is placed in a furnace and heated in a nitrogen atmosphere. As a result, the nitridation of Al progresses to produce Al,
This serves as a binder and unreacted B ₄ C with Al and BN.
Sintered body containing Al as a main component, that is, AlN-BN with AlN bond
-B ₄ C sintered immersion nozzle is completed in the mold. here,
In the second stage sintering, a thermosetting organic binder such as a phenol resin may be used as the binder. In this case, C bond of AlN-BN-B ₄ C sintered immersion nozzle can.

After the two-stage sintering process,
95% by weight of AlN and 4 to 73% by weight of BN and 1 to 25
It is possible to obtain a sintered body containing B ₄ C in an amount of 80% by weight or more and having a porosity of 30% or less. Used as a refractory for casting.

Next, the second embodiment of the present invention will be described with reference to FIGS.
An embodiment will be described. AlN-BN-B shown in FIG.
_{The 4} C sintering immersion nozzle 1 is used on an actual machine with a surface provided with a heat insulating material by a known method. Molten steel at 1530 to 1600 ° C. flows into the inner hole of the immersion nozzle 1 from the upper inlet 2, and flows out of the discharge hole 3 into a mold (not shown).
Immediately above the discharge hole 3 on the outer surface of the immersion nozzle 1 is in contact with the molten slag of the mold powder. In the process of using the actual machine, metal and nonmetallic inclusions remain on the inner and outer surfaces depending on conditions, and slag also adheres to the outer surface.

After use, the immersion nozzle 1 was recovered, and FIG.
Heat insulating material as shown in, the foreign matter was pulverized after the predetermined particle size removed, AlN-BN-B ₄ C sintered powder is played. Subsequently, the sintered powder and the Al source powder are mixed at a predetermined ratio to obtain a mixture. Thereafter, the mixture is filled into a graphite mold having a cavity of a dipping nozzle while applying vibration to obtain a filled body. Thereafter, the packing is placed in a furnace and heated in a nitrogen atmosphere. As a result, the nitridation of Al proceeds to generate AlN, which serves as a binder to form AlN.
And BN and a sintered body containing B ₄ C as a main component, ie, A
lN-BN-B ₄ C sintered immersion nozzle is completed in the mold. Here, in the second-stage sintering, a thermosetting organic binder such as a phenol resin may be used as a binder. In this case, C bond of AlN-BN-B ₄ C sintered immersion nozzle can.

FIG. 7 shows a conventional immersion nozzle.
Performance of the present invention is AlN-BN-B_FourC sintered material
Is partially applied. Figure 7
The nozzle body 11 is made of Al_TwoO_Three-SiO_TwoMainly -C
Made of C-bonded AG material,
The contact portion 12 is made of ZrO having relatively good corrosion resistance._Two-SiC-C
And a C-bonded ZG material whose main component is FIG.
Is AlN-BN-B _FourStraight tube part 13 made of C sintered material
Are arranged in the inner hole of the nozzle body 11. to this
Non-metallic inclusions such as ingots and alumina
Is suppressed.

FIG. 5 shows a configuration in which a straight pipe portion 14 made of an AlN-BN-B ₄ C sintered material is arranged so as to reach the inner hole of the nozzle body 11 around the discharge hole 3. In this case, the AlN-BN-
The inner wall to which the B ₄ C sintered material is applied can further thoroughly prevent nonmetallic inclusions such as metal and alumina from adhering.

FIG. 6 shows an example in which a molten slag contact portion 15 made of an AlN-BN-B ₄ C sintered material is arranged on the outer peripheral portion of the nozzle body 11. In this case, erosion by the molten slag is suppressed, and the life of the immersion nozzle can be improved.

In the embodiments shown in FIGS. 4 to 6, there are several options for the manufacturing method. one,
Keep incorporated into AlN-BN-B ₄ C material portions fabricated by a mold in advance AlN bond, filling the raw material powder obtained by adding phenol resin as a starting material, the molding is subjected to a non-oxidizing atmosphere sintering , C-bonds. Also, including the AlN-BN-B ₄ C material portion may be the entire and C bonds.

[0041]

Embodiments of the present invention will be described below. (Example 1) In this Example 1, an example of manufacturing the AlN-BN-B ₄ C sintered powder of Al source powder and B ₄ C powder as a raw material. First, 105 μm or less is 100% by weight,
and Al atomized powder metals Al content 99.97 wt% or more m is 20% by weight of the particle size, the B ₄ C content 96.7 wt% of B ₄ C powder below 98.5% by weight of particle size 44 .mu.m,
Each was mixed at a ratio of 28% by weight and 72% by weight to obtain a mixed powder. Next, the mixed powder was filled in a mold and molded under pressure at a molding pressure of 120 kg / cm ² . The obtained molded body had a bulk density of 1.58 g / cm ³ . Further, the compact was heated under a nitrogen pressure of 9.1 kg / cm ^{2 at} a pressure of 19 kg / cm ^2.
The temperature was raised to 00 ° C., kept for 4 hours, and allowed to cool.

In the obtained sintered body, a weight increase of 66.6% by weight was caused by nitriding, and volume expansion was also observed. The bulk density of the sintered body was 1.91 g / cm ³ , and the porosity was 19.0% in terms of open porosity. The composition was 26.1% by weight AlN, 52.7% by weight BN, 14.9% by weight B
₄ C, 6.4% by weight C. This sintered body was ground to 3.35 mm or less with a jaw crusher to obtain a sintered powder. The particle size of this sintered powder is 1 to 3.35 mm.
7% by weight, 0.25 to 1 mm is 26.3% by weight, 0.2
56.0 mm or less was 36.0% by weight.

Table 1 below shows the mixing ratio of the raw material powder, the shape imparting, the nitriding conditions, the bulk density, the porosity and the composition of the sintered body, the particle size of the sintered powder, and the tap in Example 1 and Example 2 described later. Indicates the density.

[0044]

[Table 1]

Thus, according to Example 1, although the sintered powder contains BN as much as 52.7% by weight,
The tap density was as high as 1.24 g / cm ³ , and the filling property was good. On the other hand, it is known that commercially available boron nitride powder is extremely bulky and has a tap density of as small as 0.2 to 0.5 g / cm ³ . For this reason, when commercially available boron nitride powder is blended, the packing density of the mixed powder is reduced, and the density of the sintered body must be reduced.

(Embodiment 2) First, 105 μm or less
0% by weight, particle size of 20% by weight of 37μm or more
99.97% by weight of Al atomized powder and 44 μm
The following are 98.5% by weight with a particle size of 98.5% by weight and a B ₄ C content of 96.7% by weight.
Of B ₄ C powders were mixed at a ratio of 5% by weight and 95% by weight, respectively, to obtain a mixed powder. Next, the mixed powder was filled in a mold and molded under pressure at a molding pressure of 120 kg / cm ² . The obtained molded body had a bulk density of 1.55 g / cm ³ . Further, the molded body was heated to 1900 ° C. under pressurized nitrogen at a nitrogen pressure of 9.1 kg / cm ² , held for 4 hours, and allowed to cool.

The obtained sintered body was increased in weight by 60.4% by weight due to nitriding, and volume expansion was also observed. The bulk density of the sintered body was 1.68 g / cm ³ , and the porosity was 23.1% in terms of open porosity. The composition was 4.7% by weight.
AlN, 64.3% by weight BN, 23.2% by weight B ₄ C,
It was 7.8% by weight C. This sintered body was ground to 3.35 mm or less with a jaw crusher to obtain a sintered powder. The particle size of the sintered powder is 35.2% by weight for 1 to 3.35 mm, 19.6% by weight for 0.25 to 1 mm, 0.25 mm.
The following was 45.2% by weight.

According to the second embodiment, the sintered powder is B
Despite containing as much as 64.3% by weight of N, the tap density was as high as 1.09 g / cm ³ and the filling property was good.

(Embodiment 3) First, 105 μm or less
0% by weight, particle size of 20% by weight of 37μm or more
99.97% by weight of Al atomized powder and Example 2
15% by weight and 85% by weight of the sintered powder obtained in
To obtain a mixed powder. Next, this mixed powder was filled into a graphite mold having a cavity in the shape of a immersion nozzle for continuous casting of slab production and vibrated to obtain a filled body. Here, the packing density of the mixed powder was 1.48 g / cm ³ . Further, the temperature of the above-mentioned filled body was raised to 1900 ° C. under pressurized nitrogen at a nitrogen pressure of 9.1 kg / cm ² , kept for 4 hours, and allowed to cool.

The bulk density of the sample collected from the immersion nozzle was 1.70 g / cm ³ , and the porosity was 2 in open porosity.
It was 8.7%. The composition was 24.0% by weight Al
N, 50.9 wt% BN, 18.4 wt% B ₄ C, 6.
It was 2% by weight C. Furthermore, the 4-point bending strength is 1.70k
g / mm ² .

Table 2 below shows, in Example 3, the mixing ratio of the raw material powder, the shape imparting, the nitriding conditions, the bulk density, the porosity and the composition of the sintered body, the grain size of the sintered powder, and the four-point bending strength. .

[0052]

[Table 2]

In fact, the above immersion nozzle was arranged on an actual machine and 5
It passed through 00T molten steel and was used for slab production. When the immersion nozzle was recovered and observed, there was little adhesion of alumina to the inner surface of the nozzle, and erosion by molten slag on the outer surface was slight. As described above, the immersion nozzle was able to suppress the adhesion of inclusions that adversely affect the quality of the product, and could be expected to treat a large amount of molten steel.

(Embodiment 4) First, in Embodiment 3, used in actual machine
After removing the insulation material from the collected immersion nozzle,
Foreign matter such as slag was removed. Next, crush into small pieces and
-Pulverized to less than 3.35mm by crusher and regenerated
A sintered powder was obtained. Subsequently, the regenerated sintered powder,
The sintered powder obtained in Step 2 and the Al atomized powder were
65% by weight, 20% by weight and 15% by weight are mixed,
A mixed powder was obtained. Next, this mixed powder is used for slab production.
Graphite with a cavity in the shape of a submerged nozzle for continuous casting
The mold was filled and vibrated to obtain a filled body. Where the mixed powder
The packing density is 1.56 g / cm ^ThreeMet. In addition, the charge
Filled with nitrogen pressure 9.1kg / cm^Two19 under pressurized nitrogen
The temperature was raised to 00 ° C., kept for 4 hours, and allowed to cool.

The bulk density of the sample collected from the immersion nozzle was 1.82 g / cm ³ , and the porosity was 2 in open porosity.
7.7%. The composition was 35.1% by weight Al
N, 43.0 wt% BN, 15.5 wt% B ₄ C, 5.
It was 3% by weight C. Furthermore, the 4-point bending strength is 1.96k
g / mm ² .

Table 3 below shows the compounding ratio of the raw material powder, shape imparting, nitriding conditions, bulk density, porosity and composition of the sintered body, grain size of the sintered powder, and four-point bending strength in Example 4. .

[0057]

[Table 3]

In fact, the above immersion nozzle was arranged on an actual machine and 5
It passed through 00T molten steel and was used for slab production. When the immersion nozzle was recovered and observed, there was little adhesion of alumina to the inner surface of the nozzle, and erosion by molten slag on the outer surface was slight. As described above, the immersion nozzle was able to suppress the adhesion of inclusions that adversely affect the quality of the product, and could be expected to treat a large amount of molten steel.

[0059]

As described in detail above, according to the present invention,
Sintering accompanied by nitridation reaction using inexpensive Al powder and B ₄ C powder without using expensive AlN powder and BN powder, and sintering with good filling properties containing AlN-BN-B ₄ C as a main component. A sintered powder can be obtained.

A sintered body obtained by adding Al powder to such a sintered powder and performing sintering with nitridation again has excellent performance as a refractory for casting. A conventional AlN-BN refractory material can be manufactured at low cost.

[Brief description of the drawings]

FIG. 1 shows an AlN-BN-B according to an embodiment of the present invention.
₄ shows a flow chart of a C sintering immersion method of manufacturing a nozzle.

FIG. 2 shows an AlN-BN- according to another embodiment of the present invention.
1 shows a flowchart of a method for manufacturing a B ₄ C sintered immersion nozzle.

FIG. 3 shows a cross-sectional view of an AlN-BN-B ₄ C sintered immersion nozzle.

FIG. 4 is a sectional view of an immersion nozzle in which a straight pipe portion made of an AlN-BN-B ₄ C sintered material is disposed in an inner hole of a nozzle body.

FIG. 5 is a sectional view of an immersion nozzle in which a straight pipe portion made of an AlN-BN-B ₄ C sintered material is arranged in an inner hole of the nozzle body so as to reach around a discharge hole.

FIG. 6 is a sectional view of an immersion nozzle in which a molten slag contact portion made of an AlN-BN-B ₄ C sintered material is arranged on an outer peripheral portion of the nozzle body.

FIG. 7 shows a sectional view of a conventional immersion nozzle.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Sintering immersion nozzle, 2 ... Upper entrance, 3 ... Discharge hole, 11 ... Nozzle main body, 12 ... Melt slag contact part, 13, 14 ... Straight pipe part.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G001 BA23 BA33 BA36 BA60 BA63 BB23 BB33 BB36 BB60 BC13 BC45 BC52 BC71 BD07 BD14 BD37 BE31 BE33 4G030 AA46 AA50 AA51 AA60 BA25 BA27 BA30 BA33 CA07 GA03 GA13 GA24

Claims (6)

[Claims] 1. An AlN content of 2 to 95% by weight and a BN content of 4 to 7%.
3% by weight, 1 to 25% by weight of B ₄ C, and AlN and BN
And B ₄ C in total of 80% by weight or more and a porosity of 30%
A sintered powder characterized by the following. 2. A packed or molded body of a mixed powder containing an Al source powder and a B ₄ C powder is placed in a nitrogen atmosphere at 1300 to 230
A sintered powder obtained by heating to a temperature of 0 ° C. to form a sintered body, and then pulverizing the sintered body. 3. A total of 80% by weight of 2 to 95% by weight of AlN, 4 to 73% by weight of BN and 1 to 25% by weight of B ₄ C.
A sintered powder characterized by being obtained by using a sintered body containing the above and having a porosity of 30% or less as a refractory for casting, and then collecting and pulverizing it. _{4. A} total of 80% by weight of 2-95% by weight of AlN, 4-73% by weight of BN and 1-25% by weight of B ₄ C.
A sintered powder characterized by being obtained by using a sintered body containing the above and having a porosity of 30% or less as an immersion nozzle, and then collecting and pulverizing the sintered body. 5. A method for heating and sintering a filled or molded body of a mixture of a raw material powder and a binder containing 30% by weight or more of the sintered powder according to claim 1 in a non-oxidizing atmosphere. A method for producing an AlN-BN refractory material. 6. An Al source powder having a metal content of 95 parts by weight or more
A filled or molded body of a mixed powder containing 0 to 40% by weight, 30% by weight or more of the sintered powder according to claims 1 to 4, and 70% by weight in total of the Al source powder and the sintered powder. Characterized in that AlN is generated by heating in
-A method for producing a BN-based refractory material.