JP3094148B2 - Manufacturing method of lightweight refractory - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightweight refractory, and more particularly to a lightweight refractory suitable for a sintering jig (hereinafter referred to as a "setter") used in a powder metallurgy manufacturing process and a method for producing the same.

[0002]

2. Description of the Related Art In a powder metallurgy manufacturing process, a firing step is indispensable for sintering a compact and sufficiently exhibiting the properties to be possessed by a metal. The setter plays a vital role in getting enough. This setter is generally configured by placing a SUS304 tray on a mullite base. However, the above-mentioned mainstream setter has a problem that the product adheres to SUS304, and the mullite base plate has a bending strength of 3.9 MPa, which is high enough to have no practical problem.
Since the density is as high as 3.0 g / cm ³ , the heating efficiency is poor and there is a problem from the viewpoint of energy saving. In particular, recently, products have been miniaturized, and the weight of the object to be fired tends to be smaller than that of the setter, and the ratio of setter heating to firing fuel economy cannot be ignored.

The present invention has been made in view of the above circumstances, and provides a refractory material which is reduced in weight while maintaining thermal shock resistance, particularly suitable for setters, for the purpose of energy saving and cost reduction in powder metallurgy. The purpose is to:

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to provide (1) hydraulic alumina, talc and sericite as main components.
Refractory raw material powder, alumina fiber, aluminum
Nasilica ceramic fiber and aluminum borate
A fiber component consisting of a mixture of whiskers, and aramidoff
With at least one of fiber or carbon fiber
Is mixed with water to form a slurry.
After the slurry is dewatered and formed, it is fired to form aluminum borate.
Vaporizing and decomposing the boron oxide component of whiskers
And (2) a method for producing a lightweight refractory according to the above (1), wherein smectite is added to the refractory raw material powder .

According to the above configuration, the following operation and effect can be obtained. By using alumina fiber, alumina siliceous ceramic fiber and aluminum borate whisker together, the mullite whisker is uniformly present in the matrix in a state where the mullite whisker enters the gap where the alumina fiber and the alumina siliceous ceramic fiber are entangled by firing. Because of the structure, the reinforcing effect of these fiber components is further enhanced, and uniform reinforcement is obtained over the entire lightweight refractory. The matrix is cordierite with excellent heat resistance and thermal shock resistance. In addition, the aluminum oxide borate whisker decomposes the boron oxide component by firing, and the remaining alumina component converts the silica component (talc, ) To form mullite whiskers with excellent heat resistance, so that the resulting lightweight refractory has extremely high thermal stability. Aluminum borate whiskers are less expensive than alumina whiskers conventionally used for this type of refractory and mullite whiskers as raw materials, and are easily available from the market. The aramid fiber increases the handling strength of a dewatered molded product (hereinafter referred to as a raw material molded product), and also prevents carbonization during firing and generation of cracks in the fired molded product. In addition, since they are eventually lost and become pores, this contributes to a reduction in the weight of the fired body. Carbon fiber performs almost the same function. Hydraulic alumina also functions as an inorganic binder in addition to forming a matrix, and further increases the handling strength of the raw material molded article due to a synergistic effect with the action of the aramid fiber as described above. The addition of smectite increases the viscosity of the slurry, increases the shearing force during mixing during slurry preparation, improves the dispersibility of the starting material, and causes a gelling reaction with hydraulic alumina to form a raw material compact. Acceleration is accelerated.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a method for producing a lightweight refractory of the present invention will be described in detail. The lightweight refractory of the present invention is a fiber component comprising a mixture of hydraulic alumina, raw powder mainly composed of talc and sericite, alumina fiber, alumina siliceous ceramic fiber and aluminum borate whisker, and aramid fiber or carbon fiber. A starting material containing at least one of the following is mixed with water to form a slurry, and the slurry is subjected to dehydration molding and then calcined at a high temperature in the air to form aluminum borate.
It is obtained by vaporizing and decomposing the boron oxide component of the whisker .

The composition of the raw material powder is preferably such that hydraulic alumina, talc and sericite account for 50 to 90% by weight, especially 70 to 80% by weight of the starting material in total. The mixing ratio of hydraulic alumina, talc and sericite is 65:20:15 to 20:55:15, particularly 50: 3.
The ratio is preferably 8:12 to 55:35:10. In the composition of the raw material powder, if it is outside the above range,
The production of cordierite which becomes a matrix of lightweight refractories is hindered, and the high heat resistance and thermal shock resistance of cordierite cannot be sufficiently obtained. The average particle diameter of each component constituting the raw material powder is 3 to 30 μm, particularly 5 to 1 μm.
Preferably it is 5 μm.

The fiber component consisting of alumina fiber, alumina siliceous ceramic fiber and aluminum borate whisker is used to prepare a slurry by mixing the alumina fiber and alumina siliceous ceramic fiber with each other when preparing a slurry by mixing with water. Aluminum borate whiskers enter into the slurry and are uniformly dispersed in the slurry. Therefore, when a green compact and a fired body (that is, the same as the lightweight refractory of the present invention) are obtained, these fiber components are uniformly entangled with each other in the cordierite matrix and fired. Increases mechanical strength throughout the body. In particular, aluminum borate whis
The boron oxide component of the car is vaporized and decomposed, leaving
Lumina component reacts with silica component in raw material and has excellent heat resistance
Mullite whiskers for lightweight refractory thermal
Increase stability. The mixing ratio of alumina fiber, alumina siliceous ceramic fiber and aluminum borate whisker is preferably 85: 10: 5 to 5:65:30, particularly preferably 40:48:12 to 30:52:18. Outside this range, the effect of reinforcing the fired body cannot be sufficiently obtained. The size of the aluminum borate whisker is not particularly limited, but is preferably 10 to 30 μm at the major axis.

For the purpose of weight reduction, aramid fiber or carbon fiber may be used alone or in a mixture of two or more at an arbitrary ratio. They are,
It decomposes and disappears by firing, becomes pores in the fired body, and is uniformly distributed to reduce the density of the fired body. Further, the compounding amount is 3 to 30% by weight in the starting material, preferably 5 to 30% by weight.
12% by weight is blended. If less than the above amount, does not contribute to weight reduction of the fired body, while more than the above range,
The ratio of the pores in the fired body becomes too large, and the bending strength is lowered, which is not preferable. The size of the aramid fiber and the carbon fiber is not particularly limited, but is preferably 6 to 18 μm at the major axis.

[0010] The starting material contains the above-mentioned raw material powder, fiber component and aramid fiber or carbon fiber as essential components, but smectite powder may be added. Since smectite is clayey, it can function as a viscosity modifier when formed into a water slurry and can improve the dispersibility of the slurry. In addition, it improves the formability and shape stability when forming a raw material molded body, and promotes the curing of the raw material molded body by causing a gelling reaction with hydraulic alumina. Furthermore, this smectite can prevent cracks and breakage of the raw material molded body during firing, and can improve the mechanical strength of the fired body. The amount of smectite to be added is preferably 0.5 to 8% by weight, particularly preferably 1 to 4% by weight, based on the starting material.

Then, the above-mentioned starting material is mixed with water to form a slurry, and a slurry obtained by dehydration molding is fired at a predetermined temperature to form a slurry of aluminum borate whisker.
A lightweight refractory can be obtained by vaporizing and decomposing the iodine component . Here, the mixing ratio of the starting material and water in the slurry is not particularly limited as long as it does not hinder the molding. However, as the ratio of water increases, the density of the fired body tends to decrease. The dehydration molding is performed, for example, by heating in a drying oven at 50 ° C. for 1 hour in a state where the slurry is poured into a mold, removing the mold, and further heating and drying in a drying oven at 100 ° C. for 1 hour. Then, the raw material molded body is fired at a predetermined temperature. The sintering temperature is a temperature required for the generation of cordierite and the decomposition and disappearance of the aramid fiber or carbon fiber. This temperature varies depending on the composition of the starting materials, and generally, as the firing temperature increases, the shrinkage ratio of the sintered body increases and the density tends to increase. It is preferable to set the firing temperature in consideration of the above. In the present invention, a practically preferable density of 0.8 kg / c as a setter
m ³ or less, and for the purpose of obtaining a bending strength 5.0 MPa, in order to satisfy these, in the above-mentioned preferred raw material composition, firing temperature is approximately 1350 to 1450 ° C.
It is.

The lightweight refractory of the present invention obtained as described above has a cordierite matrix as a matrix, in which the fiber components are uniformly dispersed in a state of being entangled with each other. When smectite is added, smectite is not formed. It has a structure in which the particles are uniformly dispersed, and the pores generated by the disappearance of the aramid fiber or the carbon fiber by firing are uniformly distributed.

Now, the present invention will be described in further detail with reference to Examples. At a ratio shown in Table 1, the starting material and water were stirred for 2 minutes using a stirrer to prepare a slurry.

[0014]

[Table 1]

Then, the slurry is placed in a metal frame (120 × 120).
× 10 mm), and the surface was smoothed using a SUS iron. In addition, a glass cloth was spread on the bottom to improve the releasability, and machine oil was applied to a metal frame. Next, the metal frame into which the slurry was poured was placed in a drying oven at 50 ° C. for 1 hour.
After heating for one hour, it was removed from the metal frame and the glass cloth, and further heated and dried in a drying furnace at 100 ° C. for one hour to form a molded body. In Example 2, the obtained molded body was impregnated with 200% by weight of colloidal silica (solid content: 20%), and then dried again to obtain a raw material molded body. The dehydrated raw material molded body was fired by using a HLF 2035 type high temperature electric furnace manufactured by Hiroki Co., Ltd. while maintaining the temperature in the air for 30 minutes while changing the temperature. The firing conditions were rapid heating and rapid cooling.

The density and shrinkage of the obtained fired body were measured, and a three-point bending test was performed using an Autograph AG-A type manufactured by Shimadzu Corporation. The lower fulcrum distance is 50 mm and the crosshead speed is 0.5 mm /
min. The measurement results are shown in FIGS. Both Example 1 and Example 2 have bending strength equal to or higher than that of the conventional product composed of the mullite base plate and SUS, and the density is significantly reduced.

[0017]

As described above, according to the present invention, the following effects can be obtained, and the present invention can be suitably applied to a setter. By using alumina fiber, alumina siliceous ceramic fiber and aluminum borate whisker together, the mullite whisker is uniformly present in the matrix in a state where the mullite whisker enters the gap where the alumina fiber and the alumina siliceous ceramic fiber are entangled by firing. To become an organization,
The reinforcing effect by these fiber components is further increased, and uniform reinforcement is obtained over the entire lightweight refractory. The matrix is cordierite with excellent heat resistance and thermal shock resistance. In addition, the aluminum oxide borate whisker decomposes the boron oxide component by firing, and the remaining alumina component converts the silica component (talc, ) To form mullite whiskers with excellent heat resistance, so that the resulting lightweight refractory has extremely high thermal stability. Aluminum borate whiskers are less expensive than alumina whiskers conventionally used for this type of refractory and mullite whiskers as raw materials, and are easily available from the market. The aramid fiber increases the handling strength of the dewatered molded article and also prevents carbonization during firing and the occurrence of cracks in the fired molded article. In addition, since they are eventually lost and become pores, this contributes to a reduction in the weight of the fired body. Carbon fiber performs almost the same function. Hydraulic alumina also functions as an inorganic binder in addition to forming a matrix, and further increases the handling strength of the raw material molded article due to a synergistic effect with the action of the aramid fiber as described above. By adding smectite, the viscosity of the slurry is increased, the shearing force during mixing during the preparation of the slurry is increased, and the dispersibility of the starting material is improved. Acceleration is accelerated.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the firing temperature and the density, bending strength and shrinkage of the obtained fired body in Example 1.

FIG. 2 is a graph showing the relationship between the firing temperature and the density, bending strength and shrinkage of the obtained fired body in Example 2.

Continuation of the front page (73) Patent holder 595109708 Napac Co., Ltd. 1-32-2, Iizaka, Komagane-shi, Nagano Prefecture (72) Inventor Fumitake Nishiyama 2-2-3, Tambajima, Nagano-shi, Nagano Prefecture (72) Inventor Yajima Yoichi Kazama 1374-15, Oaza, Nagano City, Nagano Prefecture (72) Inventor Mikio Tsukahara 1-1, Kokuradai, Inzai-machi, Inba-gun, Chiba Prefecture (72) Inventor Rikio Fukuda 708-4, Mure-mura, Murai-mura, Kamiminochi-gun, Nagano Prefecture (72) Inventor Kiyoo Tatebayashi 3893 Higashi-Terao, Matsushiro-cho, Nagano City, Nagano Prefecture (72) Inventor Akira Suzuki 6-24, Rinoki, Komagane-shi, Nagano Prefecture (56) References JP-A-5-270943 (JP, A) JP-A-5-279143 ( JP, A) JP-A-1-167281 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C04B 38/06 C04B 38/00 304 C04B 35/64 C04B 35/80

Claims (2)

(57) [Claims] 1. Hydraulic alumina, talc and sericite
Refractory raw material powder mainly composed of
ー 、 Alumina siliceous ceramic fiber and boric acid
A fiber component consisting of a mixture of aluminum whiskers,
Less aramid fiber or carbon fiber
And a mixture of the starting material containing water and water
After dehydration molding of this slurry, baking
Boron oxide component of aluminum whisker is vaporized and separated
A method for producing a lightweight refractory, comprising: 2. A smectite is added to said refractory raw material powder.
The method for producing a lightweight refractory according to claim 1, wherein the refractory is added.