JP2000319070A - Impact resistant refractory and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give both strength and impact resistance at a room temp. and a high temp. by preparing refractory containing a specific quantity of acicular aluminum nitride specified in the diameter. SOLUTION: The refractory containing 5 wt.% acicular aluminum nitride having 0.1-2 mm diameter is prepared. The ratio of the length to the diameter of the acicular aluminum nitride is preferably >=3. When the acicular aluminum nitride is used as short fiber, the length is desirably about >=50 mm. The acicular aluminum nitride contains 100 wt.% AlN and preferably >=60 wt.%. The residual part except AIM in the acicular aluminum nitride is oxynitride of AlON, SiAlON, Si2N2O, one or more kinds of oxides selected from Al2O3, MHO, TiO2, ZrO2, Cr2O3, SiO2, Y2O3, CeO2 and Sc2O3, and a multiple oxide of Mgo.Al2 O3, 3Al2O3.2SiO2 or 9Al203.2B2O3 can be incorporated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a refractory mainly resistant to mechanical or thermal shock.

[0002]

2. Description of the Related Art Refractories are often used in environments subject to mechanical or thermal shock. For example, in a hot metal ladle, in the early stage of receiving the hot metal, the hot metal contact portion receives both mechanical shock and thermal shock due to the collision of the hot metal. In a converter, in addition to the same impact, a mechanical impact is also applied when scrap is charged. Nozzles for continuous casting of steel are exposed to thermal shock generated by contact of molten steel exceeding 1500 ° C. in the early stage of casting. In a slab heating furnace, an impact load is repeatedly applied to the furnace bottom as the slab moves.

[0003] Refractories are required to withstand such mechanical or thermal shocks. In order to meet this demand, there is known a method of adding particles having a large anisotropy, for example, various fibers to prevent breakage due to impact. This is because when the tip of the generated crack collides with a highly anisotropic particle, the particle becomes a bridge crossing the crack and prevents the crack from growing. The larger the anisotropy of the particles, the more difficult it is for the particles to escape from the matrix, and the greater the effect of inhibiting the propagation of cracks. From such a viewpoint, various fibers are selected as particles having large anisotropy.

[0004] JP-A-4-37450, in order to provide a nozzle for wide thin slab casting rich endurance, identify CaO · ZrO ₂ fibers casting nozzle material mainly containing zirconia over graphite vol% It is proposed to be added. In other words, CaO / ZrO ₂ fiber is used as a casting nozzle raw material containing zirconia graphite as a main component.
Manufacture wide and thin slab casting nozzles by adding ~ 20Vol%. 1~6μ a fiber diameter of CaO · ZrO ₂ fibers added
m and the fiber length is 60 to 150 μm. It says that it can provide a nozzle with high bending strength, high breaking energy and high thermal shock resistance.

Japanese Patent Application Laid-Open No. 55-15952 discloses that
Proposal of castable refractories that are obtained by adding a binder such as alumina cement to castable refractories to which stainless steel fiber is added, and have no significant reduction in bending strength and thermal shock resistance and significantly improved compressive strength are doing.

Japanese Unexamined Patent Publication No. 5-139854 discloses a high refractory material suitable for a non-sintering upper nozzle having high spalling resistance for immersion nozzles, which satisfies the requirements for improvement of spalling resistance and corrosion resistance accompanying multiple casting of molten steel. To provide refractory aggregate 85
~ 95wt% (wt%) and 5 ~ 15wt% organic binder, 0.1mm ~ 2m diameter obtained by chatter vibration cutting
It has been proposed to add 1 to 10% by weight of one or more kinds of Al fibers or Al alloy fibers having a length of 5 mm to 50 mm.

[0007]

THE INVENTION to be solved INVENTION CaO · ZrO ₂ fiber, mullite fiber, conventional ceramic fiber typified by alumina fibers thinner than a diameter 10 [mu] m, length is 50 to 200 [mu] m. When such fine particles having large anisotropy are mixed with ceramic fine powder having small anisotropy constituting a matrix, the fibers constitute a fine network, which hinders the filling of the ceramic fine powder. Then, it causes a decrease in the packing density and a decrease in the sintering density. As a result, although the impact resistance can be improved,
There is a disadvantage that the material strength is reduced.

On the other hand, conventional metal fibers are:
Diameter 0.1 to 2mm, thicker than ceramic fiber.
Even when blended with the same volume fraction as the ceramic fiber, the network of the fiber is coarse and does not hinder the filling of the ceramic fine powder constituting the matrix. Therefore, a high sintering density is secured, and the impact resistance can be improved without lowering the strength of the matrix. However, the heat resistance of the fiber is limited. The melting point of aluminum is as low as 660 ° C., and the melting point of an aluminum alloy to which Si, Mg or the like is added is further reduced. Therefore, although the effect of reducing the strain due to the thermal shock by plastic deformation can be expected, a decrease in the high-temperature strength is inevitable. Stainless steel fiber has a melting point of 1500
It is better than aluminum or aluminum alloy fiber because it exceeds ℃, but cannot withstand long-term use at high temperature.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a refractory to which anisotropic particles are added, which has both strength at normal temperature and high temperature and impact resistance. To provide.

[0010]

Means for Solving the Problems The present inventor has adopted, as anisotropic particles, acicular aluminum nitride, which is an acicular substance containing AlN as a main component, and a refractory in which this is dispersed is at room temperature and at high temperature. The inventors have found that the material has both strength and impact resistance and completed the present invention.

That is, according to the present invention, first of all, the diameter is 0.1 mm.
Provided is a refractory characterized by containing at least 5% by weight of 1 to 2 mm acicular aluminum nitride.

The present invention secondly provides a refractory characterized in that the ratio between the length and the diameter of the acicular aluminum nitride is 3 or more.

[0013] Thirdly, the present invention provides the refractory, wherein the acicular aluminum nitride contains 60 wt% or more of AlN.

[0014] Fourth, the present invention relates to a fourth aspect of the present invention wherein at least 60 wt% of the portion other than the acicular aluminum nitride is made of AlN, BN, AlON, SiAl.
_{ON, Al 2 O 3, MgAl} 2 O 4, 3Al 2 O 3 · 2SiO 2, 9Al 2 O 3 · 2B 2 O 3,
Providing _{MgO, MgCr 2 O 4, SiO} 2, ZrO 2, CaO · ZrO 2, B 4 C, the refractory of which is a one or two or more compounds selected from among C .

[0015] Fifth, the present invention provides a refractory of the above four items by heating a filled body or molded body containing acicular aluminum in a nitriding atmosphere to convert the acicular aluminum into acicular aluminum nitride. And a method for producing a refractory.

Here, the acicular aluminum nitride may be acicular in shape, and the shape of the cross section is not limited. That is, circular,
It may be elliptical, polygonal, or even irregular.
Further, the area and shape of the cross section may change in the longitudinal direction of the needle. The needle-shaped aluminum nitride functions to prevent the cracks generated when a thermal or mechanical impact is applied to the refractory, thereby preventing the refractory from breaking. In order for this function to work sufficiently, it is necessary that both the maximum value and the minimum value of the diameter of the cross section are in the range of 0.1 to 2 mm. If the diameter is less than 0.1 mm, cracks that have collided with the acicular aluminum nitride are not preferable because a phenomenon in which the acicular aluminum nitride is pulled out and continues to grow further becomes noticeable. Diameter
When a certain percentage of thick needle-like aluminum nitride exceeding 2 mm is dispersed in the refractory structure, the number is reduced compared to the case of fine needle-like aluminum nitride, and the impact resistance is locally inferior due to uneven structure. It is not preferable because a portion is generated. The length is preferably at least three times the maximum value of the diameter of the arbitrarily selected cross section. If the length is less than three times the diameter, a crack that has collided with the acicular aluminum nitride increases the possibility that the acicular aluminum nitride is pulled out and continues to grow. The impact resistance is remarkably improved by adding 5 wt% or more of the needle-like aluminum nitride having such a crack propagation preventing function to the refractory. The acicular aluminum nitride may be 100 wt%.

The acicular aluminum nitride is mainly composed of AlN.
Needle-like substance. AlN for heat resistance, corrosion resistance and wear resistance
Excellent compound, chemical up to 2300 ℃ in inert atmosphere
It is stable. In addition, high-temperature oxidizing atmosphere of 1000 ° C or more
Al ON or Al_TwoO_Three1600 ° C
And there is no major decline. AlN is hot metal, molten steel, molten
For molten metal such as aluminum, corrosive gas such as chloride
Excellent corrosion resistance. Also resistant to mechanical wear
It is known. From this point of view, acicular aluminum nitride
It is preferable that the aluminum contains AlN at 60 wt% or more. AlN100wt%
May be. Excluding AlN in acicular aluminum nitride
The rest is AlON, SiAlON, Si_TwoN_TwoOxynitrides represented by O,
Al_TwoO_Three, MgO, TiO_Two, ZrO_Two, Cr_TwoO_Three, SiO_Two, Y_TwoO_Three, CeO_Two, S
c_TwoO_ThreeOne or more oxides selected from
Complex oxidation containing at least one of these oxides
Object, such as MgO / Al_TwoO_Three, 3Al_TwoO_Three・ 2SiO_Two, 9Al_TwoO_Three・ 2B_TwoO_Three
May enter. Also, MgB_Two, CaB₆, TiB_Two, ZrB_Two, Al
B_Two, AlB₁₂One or more hoes selected from
Compounds may enter. Also, B_FourC, TiC, ZrC, Cr_ThreeC_Two, Al
_FourC _ThreeOne or more carbides selected from among SiC
May enter. Also, TiN, ZrN, Cr_TwoN, Si_ThreeN_FourInside
One or more nitrides selected from
No. C may be included because it has excellent thermal shock resistance. S
Aluminum containing elements such as i, Mg, and Fe as alloy components
Alloy or pure aluminum may be contained.

The refractory may be constituted by the needle-like aluminum nitride alone, but may be combined with other components.
In this case, the portion other than the acicular aluminum nitride is preferably a compound having excellent heat resistance, corrosion resistance, and wear resistance.From this viewpoint, AlN, BN, AlON, SiAlON, Al ₂ O ₃ ,
_{MgAl 2 O 4, 3Al 2 O} 3 · 2SiO 2, 9Al 2 O 3 · 2B 2 O 3, MgO, MgCr 2 O
₄ , 60% by weight or more of one or more compounds selected from among SiO ₂ , ZrO ₂ , CaO.ZrO ₂ , B ₄ C, and C. These compounds may be 100 wt% of the portion other than the acicular aluminum nitride.

Further, another compound may be blended as long as it is less than 40% by weight. That is, TiO ₂ , Cr ₂ O ₃ , Y ₂ O ₃ , Ce
One or more oxides selected from O ₂ and Sc ₂ O ₃ , and a composite oxide containing at least one of these oxides may be included. Also, MgB ₂ , CaB ₆ , TiB ₂ , Zr
One or more borides selected from B ₂ , AlB ₂ and AlB ₁₂ may be contained. Also, TiC, ZrC, Cr ₃ C ₂ , A
l ₄ C _3, it may contain one or more carbides selected from among SiC. Further, one or a plurality of nitrides selected from TiN, ZrN, Cr ₂ N, and Si ₃ N ₄ may be contained. An oxynitride represented by Si ₂ N ₂ O may be contained. Further, metal Al and metal Si may be contained. It may be an aluminum alloy containing 0.2 to 10 wt% of an element such as Si, Mg, Fe or the like as an alloy component, or may be pure aluminum. These metals absorb the oxygen that enters when the refractory is used by oxidation and prevent the progress of oxidation.

These components are dispersed between the acicular aluminum nitride dispersed in the refractory structure as particles having a shape different from that of the acicular aluminum nitride, and are dispersed in the refractory as a dispersed phase different from the acicular aluminum nitride. Different functions may be provided. Further, it may serve as a continuous phase of fine crystal grains to bind the dispersed phase.

The acicular aluminum nitride may exist as short fibers randomly dispersed in the refractory structure, or may exist as continuous fibers regularly arranged.

As described above, both the maximum value and the minimum value of the diameter of the acicular aluminum nitride cross section are in the range of 0.1 to 2 mm, and the length is equal to the maximum value of the diameter of the arbitrarily selected cross section.
The length is preferably three times or more, and when the acicular aluminum nitride is used as short fibers, the length is preferably 50 mm or less. The shorter the short fibers, the more uniform the dispersion, and the longer the short fibers, the more uneven the dispersion.
If it exceeds 50 mm, the dispersion tends to be non-uniform, the strength of the material varies depending on the manufacturing method, and the reliability of the material tends to be impaired.

The present inventor has found that a material in which the acicular aluminum nitride having a length of 50 mm or less is dispersed in a continuous phase containing AlN, BN, and B ₄ C is suitable for hot metal, molten steel, and molten slag exceeding 1500 ° C. Excellent corrosion resistance and directly without preheating,
They have been found to have excellent thermal shock resistance without breaking even when immersed in these melts. Here, by setting the acicular aluminum nitride to 5 wt% or more, excellent thermal shock resistance will be exhibited, but if it exceeds 65 wt%, pores will increase in the material and the strength of the material and its variation will be reduced. It is not preferable because the increased disadvantage becomes remarkable. The portion excluding acicular aluminum nitride accounts for 35 to 95 wt%,
The composition of this portion can ensure corrosion resistance to the molten metal by setting AlN to 5 wt% or more.

Further, by setting the BN content to 10 wt% or more, corrosion resistance to molten slag can be ensured. Also, B ₄ C is 400
It is preferably present at 3 wt% or more because it oxidizes from the temperature of ° C. to form a melt of B ₂ O ₃ , fills the pores in the surface layer of the refractory, prevents intrusion of oxygen into the inside and prevents deterioration of the refractory. Thermal shock resistance, corrosion resistance, the range of composition of the continuous phase for collateral oxidation resistance is 5~50wt% AlN, 10~80wt% BN, 3~30wt% B 4 C. The continuous phase containing such components in such amounts may contain other components as long as it is less than 10 wt%. Other components include Al ₂ O ₃ , SiO ₂ , MgO, ZrO ₂ , TiO ₂ , Cr ₂ O ₃ , Y ₂ O ₃ , CeO
₂ , one or more oxides selected from Sc ₂ O ₃ , and a composite oxide containing at least one of these oxides may be included.

[0025] In other _{words, MgO · Al 2 O 3,} 3Al 2 O 3 · 2SiO 2, 9
Al ₂ O ₃ .2B ₂ O ₃ , MgO.Cr ₂ O ₃ , and CaO.ZrO ₂ .
Further, one or a plurality of borides selected from MgB ₂ , CaB ₆ , TiB ₂ , ZrB ₂ , AlB ₂ , and AlB ₁₂ may be contained. _{Further, TiC, ZrC, Cr 3 C} 2, Al 4 C 3, may contain one or more carbides selected from among SiC. Further, one or a plurality of nitrides selected from TiN, ZrN, Cr ₂ N, and Si ₃ N ₄ may be contained. AlON, SiAlON, Si
_An oxynitride represented by ₂ N ₂ O may be contained. Also metal
Al or metal Si may be contained. Also, C may be included.
Among the above listed non-oxides and metals, all play a role in preventing the deterioration of the refractory by absorbing oxygen entering from the outside as an oxide in the surface layer of the refractory. Since such a function is working, even if C enters, the oxidation consumption of C hardly progresses. Under such conditions, C is preferable because it improves the thermal shock resistance by lowering the coefficient of thermal expansion and the Young's modulus of the material. This refractory is suitable as a transport pipe for various molten metals such as iron, aluminum, zinc or the like or a molten slag, a flow control valve, a thermocouple protection pipe, and a gas injection lance. It is also suitable as a crucible for various molten metals and a ceramic mold for casting.

A needle-shaped aluminum nitride having a length of 50 mm or less
It may be dispersed at a high content of not less than wt% to form a refractory. In this case, the content may be 100% by weight or less than 10% by weight may be combined with a component selected from the above-mentioned components. Such a material has a high content of acicular aluminum nitride, and is extremely resistant to impact.

Also, the acicular aluminum nitride may be regularly arranged. For example, they are arranged in one direction. Also, for example, they are arranged so as to have a high porosity in a mesh form. Also, for example, they are arranged in a plain weave so as to have a low porosity. Components selected from the above-mentioned components may be combined with the regularly arranged needle-like aluminum nitride at less than 10% by weight. Such materials are extremely resistant to impacts because of the large weight fraction of acicular aluminum nitride.

Conventional refractories have difficulty in having both room temperature and high temperature strength and impact resistance, and have a disadvantage in impact resistance. However, this problem is solved by the refractory containing acicular aluminum nitride according to the present invention. It is done.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS There is no particular limitation on the method for producing the refractory containing acicular aluminum nitride described above.
Although acicular aluminum nitride may be produced by sintering using the starting main material, the following method is preferred. That is, Al
The main starting material is acicular aluminum whose main component is
The raw material containing the acicular aluminum is filled into a mold to form a filled body or a molded body having shape retention, and then heated in a nitriding atmosphere to convert the acicular aluminum into acicular aluminum nitride. It is.

According to this method, commercially available acicular aluminum which is easily available can be used, and there is an advantage that acicular aluminum nitride can be easily obtained by nitriding.

The acicular aluminum may be pure aluminum. Elements such as Si, Mg, Fe, etc. as alloy components 0.2 to 10 wt%
Aluminum alloy may be included. The acicular aluminum may be completely nitrided, or a metal may remain inside.

The acicular aluminum as the starting material may be an aggregate of unconstrained needles. It may be a molded product obtained by press-molding acicular aluminum in advance. It may be a mesh. It may be a woven fabric.

[0033]

[Example 1] An example in which an immersion nozzle is manufactured using the refractory of the present invention will be described.

A needle-shaped aluminum having a diameter of 0.6 mm, a length of 15 mm, and a circular cross section containing 2.5 wt% of Mg was prepared. Further, Al powder having a particle size of 74 μm or less and B ₄ C powder having a particle size of 44 μm or less were prepared. Acicular aluminum 40.0wt%, Al powder 38.0wt%, B ₄ C
The powder was mixed at a mixing ratio of 22.0 wt% to obtain a mixed powder.

Separately, a graphite mold having a square of 25 mm on a side and a cavity of 230 mm in length was prepared. The mixed powder was vibration-filled into the graphite mold to obtain a packing having a packing density of 1.55 g / cm ³ . This filled body shaped by a graphite mold was placed in a nitriding furnace. The temperature was raised to 1750 ° C. at a rate of 10 ° C./min while maintaining the nitrogen pressure at 9.1 kg / cm ² .

The prism-shaped sintered body obtained by releasing the mold was increased in weight by 49.7% by the nitriding treatment, and had a bulk density of 2.00 g /
It was cm ^3. The weight increase is due to the nitridation of Al and B ₄ C. AlN is 35.
It was estimated to be 7 wt% and dispersed. The composition of the acicular aluminum nitride is 8.7 wt% Al, 90.8 wt% AlN, 0.5 wt% Al
₂ O ₃ estimated. The composition of the continuous phase is 52.8 wt% AlN, 25.9 wt%
_{BN, 8.4wt% B 4 C,} 3.1wt% C, 0.6wt% Al 2 O 3, was estimated to be 9.2 wt% Al. The three-point bending strength of this sintered body is 230 kg / cm at room temperature.
^{2. It} was 190 kg / cm ² at 1500 ° C, indicating that the strength was maintained up to high temperatures.

When the prism was immersed in a two-phase melt of molten slag and molten steel at 1550 ° C. and kept for 1 hour, the melting loss was small and the wall loss was only 0.3 mm at the maximum.

The same material is used in the same manner and has an inner diameter of 95 mm and an outer diameter of 14 mm.
A 4 mm, 790 mm long immersion nozzle with two discharge ports was prototyped.
The material was immersed in molten steel, and the thermal shock resistance of the material was evaluated based on whether or not breakage occurred. Room temperature immersion nozzle at 1550 ° C
Immersed in molten steel (material SS400), held for 1 minute, pulled up and allowed to cool. It was confirmed from the appearance observation that there was no crack and the structure was sound.

As described above, by dispersing the acicular aluminum nitride obtained by nitriding the acicular aluminum in the material structure, the fracture toughness is improved, and the immersion nozzle can withstand severe thermal shock. It is. This material has excellent corrosion resistance to molten metal and molten slag, maintains strength up to high temperatures, and has excellent impact resistance.

Comparative Example 1 A comparative example in which an immersion nozzle was manufactured will be described.

Al coarse powder having a particle size range of 74 to 2000 μm, particle size 74 μm
The following Al powder and B ₄ C powder having a particle size of 44 μm or less were prepared. Al
A mixed powder was obtained by mixing 40.0 wt% of coarse powder, 38.0 wt% of Al powder and 22.0 wt% of B ₄ C powder.

Separately, a graphite mold having a cavity of 25 mm square and 230 mm length was prepared. The graphite powder was vibration-filled with the mixed powder to obtain a packing having a packing density of 1.59 g / cm ³ . This filled body shaped by a graphite mold was placed in a nitriding furnace. While maintaining the nitrogen pressure at 9.1 kg / cm ² , the temperature was raised to 1750 ° C. at a rate of 10 ° C./min.

The prism-shaped sintered body obtained by releasing the mold was increased in weight by 47.7% by the nitriding treatment, and had a bulk density of 1.98 g /
It was cm ^3. The weight increase is due to the nitridation of Al and B ₄ C. AlN is 35.
It was estimated to be 7 wt% and dispersed. The composition of the continuous phase is
52.8wt% AlN, 25.9wt% BN, 8.4wt% B 4 C, 3.1wt% C, 0.6wt% A
It was estimated that l ₂ O _{3 was} 9.2 wt% Al. The three-point bending strength of this sintered body was 240 kg / cm ^{2 at} room temperature and 200 kg / cm ² at 1500 ° C., indicating that the strength was maintained up to high temperatures.

When this prism was immersed in a two-phase melt of molten slag and molten steel at 1550 ° C. and held for 1 hour, the melting loss was small and the wall thickness was reduced to only 0.3 mm at the maximum.

An inner diameter of 95 mm and an outer diameter of 14
A 4 mm, 790 mm long immersion nozzle with two discharge ports was prototyped.
The material was immersed in molten steel, and the thermal shock resistance of the material was evaluated based on whether or not breakage occurred. Room temperature immersion nozzle at 1550 ° C
When it was immersed in molten steel (material SS400), held for 1 minute, and then pulled up, a crack was generated on the surface of the immersed part, and the surface was broken by propagation.

[Example 2] An example in which a molten metal transport pipe was manufactured using the refractory of the present invention will be described.

A needle-shaped aluminum having a diameter of 0.6 mm, a length of 230 mm and a circular cross section containing 2.5 wt% of Mg was prepared. This is Mg
It is an aluminum alloy containing 2.5 wt%.

Separately, a graphite mold having a square of 25 mm on a side and a cavity of 230 mm in length was prepared. The graphite mold was filled with the acicular aluminum to obtain a packing having a packing density of 1.89 g / cm ³ . The filled body shaped by a graphite mold was placed in a nitriding furnace. While maintaining the nitrogen pressure at 9.1 kg / cm ² , the temperature was raised to 1200 ° C. at a rate of 10 ° C./min.

The bulk density of the prismatic sintered body obtained by releasing the mold was 2.73 g / cm ³ . This composition is 38.
0wt% Al, 60.1wt% AlN, was estimated to 1.9wt% Al ₂ O _3. The Mg compound was presumed to have volatilized and was not confirmed by X-ray diffraction. The three-point bending strength of this sintered body at room temperature is 1050 kg / cm ² , 1
It was 950 kg / cm ² at 500 ° C, indicating that relatively high strength was maintained up to high temperatures.

A needle-shaped aluminum having a diameter of 0.6 mm, a length of 950 mm and a circular cross section containing 2.5 wt% of Mg was prepared. This is Mg
It is an aluminum alloy containing 2.5 wt%. Using this material, a molten metal transport tube having an inner diameter of 55 mm, an outer diameter of 100 mm, and a length of 950 mm was prototyped in the same manner. The material was immersed in hot metal, and the thermal shock resistance of this material was evaluated based on whether or not fracture occurred. The molten metal transport tube at room temperature was immersed in hot metal at 1520 ° C., held for 1 minute, pulled up and allowed to cool. It was confirmed from the appearance observation that there was no crack and the structure was sound.

That is, since the acicular aluminum nitride obtained by nitriding the acicular aluminum constitutes the material, the fracture toughness is improved, and the immersion nozzle can withstand severe thermal shock. This material maintains strength up to high temperatures and has excellent impact resistance.

[Comparative Example 2] A comparative example in which a molten metal transport pipe was manufactured will be described.

An Al powder having a particle size of 74 μm or less was prepared. Separately, a graphite mold having a 25 mm square side and a 230 mm long cavity was prepared. The graphite powder was vibration-filled with the mixed powder to obtain a packing having a packing density of 1.62 g / cm ³ . The filled body shaped by a graphite mold was placed in a nitriding furnace. 1200 ° C at a heating rate of 10 ° C / min while maintaining a nitrogen pressure of 9.1 kg / cm ²
The temperature was maintained at this temperature for 3 hours and then allowed to cool. Blowing of aluminum was seen from the gap of the mold of the processed product, and the bulk density of the obtained prismatic sintered body was 2.03 g / cm ³ . This is mainly composed of AlN and Al, the composition is 60.2 wt% Al, 3
9.2 wt% AlN, was estimated to 0.6wt% Al ₂ O _3. The Mg compound was presumed to have volatilized and was not confirmed. The three-point bending strength of this sintered body was 550 kg / cm ^{2 at} room temperature and 150 kg / cm ² at 1500 ° C., and the strength was significantly reduced at high temperatures.

As described above, it was found that it was difficult to sufficiently advance nitriding using only the Al powder as a raw material. For this reason, the trial production of the molten metal transport tube was abandoned. In other words, by using acicular aluminum as a raw material as in Example 2, sufficient progress of nitriding becomes possible, and high-temperature strength can be exhibited.

[Example 3] An example in which a molten metal transport pipe was manufactured using the refractory of the present invention will be described.

A needle-shaped aluminum having a diameter of 0.6 mm, a length of 950 mm and a circular cross section containing 2.5 wt% of Mg was prepared. This was attached and spread on an aluminum foil having a thickness of 50 μm and a width of 950 mm with an organic adhesive. The aluminum foil side is wrapped around a graphite rod with an outer diameter of 55 mm and a length of 1000 mm so that the aluminum foil is in close contact with the graphite.
A 50 mm layer was formed. Further, an aluminum foil having a thickness of 50 μm and a width of 950 mm was wound once, and an organic adhesive was applied to the overlapped portion and fixed. This was placed in a nitriding furnace. Nitrogen pressure 9.1k
While maintaining g / cm ² , the temperature was raised to 1800 ° C. at a rate of 10 ° C./min. A graphite rod was pulled out, and a molten metal transport pipe having an inner diameter of 55 mm, an outer diameter of 105 mm, and a length of 970 mm was prototyped. Weight gain of nitride is 45%, the composition was estimated 8.7wt% Al, 90.8wt% AlN, and 0.5wt% Al ₂ O _3.
The material was immersed in hot metal, and the thermal shock resistance of this material was evaluated based on whether or not fracture occurred. The molten metal transport tube at room temperature was immersed in hot metal at 1520 ° C., held for 1 minute, pulled up and allowed to cool. It was confirmed from the appearance observation that there was no crack and the structure was sound.

That is, since the acicular aluminum nitride obtained by nitriding the acicular aluminum constitutes the material, the fracture toughness is improved, and the immersion nozzle can withstand severe thermal shock.

[Example 4] An example of a prismatic refractory of the present invention will be described.

A needle-shaped aluminum having a diameter of 0.6 mm, a length of 230 mm and a circular cross section containing 2.5 wt% of Mg was prepared. This was filled in a graphite mold having a cavity of 230 mm in length with a square cross section of 25 mm on a side. The filling amount was 276 g. Three such packings were placed in a nitriding furnace. While maintaining the nitrogen pressure at 9.1 kg / cm ² , the temperature was raised to 1550 ° C. at a rate of 10 ° C./min. The mold was released to obtain a prism.
It consists of an aggregate of acicular aluminum nitride, the weight increase by nitriding is 34.5%, the composition is 21.2 wt% Al, 75.1 wt
% AlN, it was estimated to 3.7wt% Al ₂ O _3. When the three-point bending strength at room temperature, 800 ° C and 1200 ° C was measured using this prism,
^They are 153 kg / cm ² , 140 kg / cm ² and 122 kg / cm ² , respectively.
The decrease in strength with increasing temperature was relatively small and the heat resistance was sufficient.

[Example 5] An example of a prismatic refractory of the present invention will be described.

A needle-shaped aluminum having a diameter of 0.6 mm, a length of 230 mm and a circular cross section containing 2.5 wt% of Mg was prepared. This was filled in a graphite mold having a cavity of 230 mm in length with a square cross section of 25 mm on a side. The filling amount was 276 g. Three such packings were placed in a nitriding furnace. While maintaining the nitrogen pressure at 9.1 kg / cm ² , the temperature was raised to 1200 ° C. at a rate of 10 ° C./min. The mold was released to obtain a prism.
It consists of an aggregate of acicular aluminum nitride, the weight increase by nitriding is 22.2%, the composition is 42.8wt% Al, 53.2wt
% AlN, it was estimated to 4.0wt% Al ₂ O _3. When the three-point bending strength at room temperature, 800 ° C and 1200 ° C was measured using this prism,
^They were 153 kg / cm ² , 110 kg / cm ² and 15 kg / cm ² , respectively.
If the temperature exceeds 1000 ° C., the strength is extremely reduced and the heat resistance becomes insufficient, so the application is limited to 1000 ° C. or less.

In Examples 4 and 5, refractories containing AlN and Al as main components were taken up. However, even if components other than Al listed above were used as components other than AlN, the degree of difference was the same. And the heat resistance decreases with the decrease in AlN. Therefore, acicular aluminum nitride can be used depending on the application temperature even if the AlN is less than 60 wt%, but 60 wt%
It is more preferable to make the above.

As described above, in the five embodiments, needle-like aluminum nitride is present in the sintered body, which prevents the crack of the sintered body by preventing the growth of cracks generated by the impact. In the comparative example in which no acicular aluminum nitride was present in the sintered body, the sintered body was damaged by the impact. Also, AlN in the acicular aluminum nitride is 60 wt%
By doing so, higher-temperature strength can be ensured.

[0064]

As described above, according to the present invention, a refractory having both impact resistance and strength at room temperature and high temperature can be provided by including needle-like aluminum nitride, which can be hardly damaged by impact. can do.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4G001 BA01 BA03 BA04 BA06 BA14 BA23 BA61 BA63 BB01 BB03 BB04 BB06 BB14 BB23 BB33 BB36 BB51 BB52 BB60 BB63 BC11 BC13 BC44 BC45 BC49 BD04 BD07 BD14 BD16 BE21 BE22 BE23

Claims (5)

[Claims] 1. An acicular aluminum nitride having a diameter of 0.1 to 2 mm
Refractory characterized by containing 5wt% or more. 2. The refractory according to claim 1, wherein the ratio between the length and the diameter of the acicular aluminum nitride is 3 or more. 3. The refractory according to claim 1, wherein the acicular aluminum nitride contains 60 wt% or more of AlN. 4. The part other than the acicular aluminum nitride
Above 60 wt% is, AlN, BN, AlON, SiAlON , Al 2 O 3, MgAl
_{2 O 4, 3Al 2 O 3} · 2SiO 2, 9Al 2 O 3 · 2B 2 O 3, MgO, MgCr 2 O 4, S
The compound is one or more compounds selected from iO ₂ , ZrO ₂ , CaO.ZrO ₂ , B ₄ C, and C.
A refractory according to any one of claims 3 to 4. 5. The method for producing a refractory according to claim 1, wherein the filler or the molded body containing acicular aluminum is heated in a nitriding atmosphere. A method for producing a refractory, comprising producing acicular aluminum by converting acicular aluminum into acicular aluminum nitride.