JP2530392B2 - Heat resistant ceramics - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat resistant ceramic used as a refractory material for a furnace wall of an industrial waste melting furnace, a mold weir of a continuous thin plate casting facility, and the like.

[0002]

2. Description of the Related Art Conventionally, a melting furnace for industrial waste, a furnace wall or a thin plate series
Refractory materials used for mold weirs of continuous casting equipment are harsh
Since it is used under conditions, its material is silicon nitride (S
i₃N _Four) Or boron nitride (BN) or a mixture of both
(Si₃N_Four+ BN) has been mainly used. this
The material properties of these materials are shown in Table 1.

[0003]

[Table 1]

[0004]

However, as can be seen from Table 1, among the above-mentioned conventional materials, Si ₃ N ₄ has a good heat resistance of ⊚, but a low thermal shock resistance of Δ. It was Further, for BN and the mixture (Si ₃ N ₄ + BN), the heat resistance and thermal shock resistance may be ⊚, but for the wear resistance, BN is ×, the mixture (Si ₃ N ₄ + BN)
Has a defect such as poor thermal shock resistance. This wear resistance is not necessarily sufficient even with Si ₃ N ₄ and is not necessarily sufficient, which is attributed to the low hardness.

Here, the inventors of the present invention have disclosed in Japanese Patent Laid-Open No. 2-111.
In Japanese Patent Application No. 664 and Japanese Patent Application No. 2-217363, a mixture (Si ₃ N ₃₎ is used as a refractory material for continuous casting equipment.
We have proposed a refractory for continuous casting equipment and a method for producing the refractory that satisfies the required heat resistance, thermal shock resistance and abrasion resistance by adding titanium, zirconium, hafnium boride or nitride to ( ₄ + BN). However, when this refractory for continuous casting equipment is exposed to a high temperature atmosphere for a long period of time, it has a problem in that it is inferior in oxidation resistance and causes a large reduction in wall thickness during use. This means that, as shown in Table 1,
The above conventional refractory members Si ₃ N ₄ , BN, Si ₃ N
_{The same} applies to ₄ + BN.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a heat resistant ceramic which is a material having excellent heat resistance, thermal shock resistance and wear resistance, and excellent oxidation resistance. Is.

[0007]

[Means for Solving the Problems] To solve the above problems
The heat-resistant ceramics of the present invention are₂O₃, Y
₂O ₃, MgO, MgAl₂O_Four, ZrO₂, Si
O₂, ZrSiO_FourOne or more oxides selected from
5-20% by weight, BN 3-25% by weight, titanium,
Rom, zirconium, niobium, molybdenum, tantalum,
One or more silicifications selected from tungsten suicides
Content of 4 to 20% by weight, the balance being Si₃N_FourComposed of
It is characterized by being done.

[0008]

With the above structure, Si ₃ N _{4 which is} a high strength heat resistant material
As the base material, there is no problem in heat resistance. Also, Al
₂ O ₃ , Y ₂ O ₃ , MgO, MgAl ₂ O ₄ , Zr
Since the addition amount of one or more kinds of oxides selected from O ₂ , SiO ₂ , and ZrSiO _{4 was set} to 5 to 20% by weight, the sintered state was good, there was no problem in strength, and the coefficient of thermal expansion was It exerts a good function as a sintering aid without deterioration of thermal shock resistance due to increase. Furthermore, since the amount of BN added is 3 to 25% by weight, the effect of imparting thermal shock resistance is sufficiently exerted, and the thermal shock resistance does not deteriorate due to an increase in the coefficient of thermal expansion. Furthermore, since 4 to 20% by weight of one or more kinds of silicides selected from titanium, chromium, zirconium, niobium, molybdenum, tantalum, and tungsten silicide is used, wear resistance due to hardness and during use The effect of the silicide that imparts the oxidation resistance that causes the thickness reduction is satisfactorily exhibited, and the thermal shock resistance is not deteriorated due to the increase in the thermal expansion coefficient.

[0009]

EXAMPLES The conditions for use as a refractory member of a mold weir of a melting furnace wall and a thin plate continuous casting facility are the following four points.

Bending strength is 5 Kgf / mm ² or more. Thermal shock resistance of 650 ° C or higher. Vickers hardness of 600 or more.

The change in weight after oxidation for 500 hours in the atmosphere at 1400 ° C. is 10% or less. In order to satisfy the above four conditions, the heat-resistant ceramics of the present invention uses Si ₃ N ₄ which is a high-strength heat-resistant material as a base material, and imparts BN that imparts thermal shock resistance and abrasion resistance and oxidation resistance to it. Contains at least one silicide selected from silicides of titanium (Ti), chromium (Cr), zirconium (Zr), niobium (Nb), molybdenum (Mo), tantalum (Ta), and tungsten (W). To do.

Al ₂ O ₃ , Y ₂ O ₃ , MgO, M
All of gAl ₂ O ₄ , ZrO ₂ , SiO ₂ , and ZrSiO ₄ are sintering aids of Si ₃ N ₄ , and if the content is 5% by weight or less, insufficient sintering will result in low strength. %, The thermal shock resistance deteriorates due to an increase in the coefficient of thermal expansion, so Al ₂ O ₃ , Y ₂ O ₃ , MgO, MgAl ₂ O
The optimum composition of one or more kinds of oxides selected from ₄ , ZrO ₂ , SiO ₂ , and ZrSiO _{4 is set} to 5 to 20% by weight.
Further, if BN is less than 3% by weight, the effect of imparting thermal shock resistance becomes insufficient, and if it is more than 25% by weight, the strength is lowered. Therefore, the optimum composition of BN is 3 to 25%. It was set to% by weight. Furthermore, titanium (Ti), chromium (C
r), zirconium (Zr), niobium (Nb), molybdenum (Mo), tantalum (Ta), tungsten (W)
Silicide is a substance that imparts oxidation resistance, but when it is 4% by weight or less, the effects of abrasion resistance and oxidation resistance become insufficient, and when it is 20% by weight or more, the coefficient of thermal expansion Since the thermal shock resistance is deteriorated by the increase, the optimum composition of one or more kinds of silicides selected from the respective silicides is set to 4 to 20% by weight.

Next, concrete experimental examples carried out to determine the optimum composition will be described. First, Si ₃ N ₄
Powder (particle size 0.8 μm), Al ₂ O ₃ powder (particle size 0.5 μm
m), MgO powder (particle size 0.5 μm), BN powder (particle size 1
μm), and further TiSi ₂ , CrSi ₂ , ZrS
_{i 2, NbSi 2, MOSi 2} , TaSi 2, WSi 2
Each powder (particle size 1 μm) of Sample No. 1 to
It is blended so as to have 23 material compositions (% by weight).

Then, it was ball milled for 16 hours in ethanol. After drying this slurry at 120 ° C for 10 hours,
Uniaxial molding was performed in a mold having a diameter of 100 mm at a pressure of 300 Kgf / cm ² , and further CIP molding was performed at a pressure of 3 ton / cm ² . Then, this molded body was heated at 1770 ° C. with 1.5 atm of N ₂
Each sample in Table 2 was obtained by sintering in an atmosphere for 2 hours.

Regarding the sintered body thus obtained,
Bending strength at room temperature, thermal shock resistance, Vickers hardness (abrasion resistance), and oxidation test at 1400 ° C in air for 24 hours were carried out to measure the weight change (oxidation resistance) before and after the test. Furthermore, the measurement results and the above-mentioned conditions (bending strength of 5 Kgf / mm ² or more, thermal shock resistance of 650 ° C. or more,
The Vickers hardness was 600 or more, and the weight change after oxidation for 500 hours in the air at 1400 ° C was 10% or less). The above experimental results are shown in Table 2 as the physical properties of the materials, and the evaluation is shown by ◯ when the above conditions 1 to 4 are satisfied, and by x when the conditions are not satisfied.

[0016]

[Table 2]

Here, the sample No. Nos. 1 to 5 are experiments for determining the optimum amount of the sintering aid in the Si ₃ N ₄ sintered body using Al ₂ O ₃ and MgO as the sintering aid.
In Table 2, sample No. Sample Nos. 1 and 5 are sample Nos. 2 to 4, the bending strength and the thermal shock resistance are particularly inferior in the physical properties, and the composition of the sintering aid (Al ₂ O ₃ + MgO) is 10% by weight. No. 3 has the most excellent physical properties especially in bending strength and thermal shock resistance. Therefore,
When the range of the optimum addition amount of the sintering aid is determined by graphing the above experimental results and the respective conditions, the optimum range is 5 to 20% by weight.

In addition, the sample No. 6 to 11 are
The optimum composition of the sintering aid is 10% by weight of sample No. This is an experiment for determining the optimum addition amount of BN in order to impart thermal shock resistance, based on the value of 3. Sample No. of Table 2 In Nos. 6 to 11, the greater the weight percentage of BN, the better the thermal shock resistance, but the worse the weight change (%) after the oxidation test, the bending strength and the Vickers hardness. B
Sample No. with N of 2% by weight In the case of No. 6, the amount of BN added was too small and the effect of imparting thermal shock resistance was insufficient.
That is, the sample No. Thermal shock resistance of 6 is 600 ℃,
It is lower than the standard value of conditions of 650 ℃. If the amount of BN added is too large, that is, if 20 or 30% by weight of the sample N
o. In the cases of 10 and 11, the bending strength and Vickers hardness are suddenly deteriorated. However, the bending strength of sample No. 20 is 20% by weight. No. 10 has 5 Kgf / mm ² , which satisfies the condition bending strength of 5 Kgf / mm ² or more. When the range of the optimum addition amount of BN is determined by plotting the above experimental results and the respective conditions, the optimum range is 3 to 25% by weight.

In addition, the sample No. In the case of 12 to 17, 10% by weight, which is the optimum composition of the sintering aid, and BN
10% by weight of sample No. This is an experiment in which the influence of the compounding amount of MoSi ₂ which is a silicide of molybdenum (Mo) was examined on the basis of 9. Sample No. of Table 2 In 12 to 17, M
The larger the amount of oSi ₂ compounded, the better the Vickers hardness and the weight change (%) after the oxidation test, but the poorer the bending strength and the thermal shock resistance. When the compounding amount of MoSi ₂ which is a silicide is too small, that is, 1,
2% by weight of sample No. In the case of 12 and 13, the oxidation resistance function was not fully exerted, and the weight change (%) after the oxidation test
Is 20% and 15%, and does not satisfy the condition standard value of 10% or less. Moreover, when the compounding amount of MoSi ₂ which is a silicide is too large, that is, 30 wt% of the sample No. In the case of 17, the bending strength is 3 Kgf / mm ² ,
This does not satisfy the required flexural strength of 5 Kgf / mm ² or more, and also has a thermal shock resistance of 600 ° C., which does not satisfy the required thermal shock resistance of 650 ° C. or more. In addition, the sample No. Those of 14 to 16 satisfy each standard value, and the judgment is ◯. When the range of the compounding amount of the silicide is determined by graphing the above experimental results and the respective conditions, the optimum range is 4 to 20% by weight.

Further, sample No. In the case of 18 to 23, the sintering aid has an optimum composition of 10% by weight and the BN is 10%.
Wt.% And 5 wt. 14 as a reference, instead of MoSi ₂ which is a silicide, ZrSi ₂ , WSi ₂ , TiSi ₂ , NbSi ₂ , which are silicides,
TaSi _2, CrSi ₂ and the experimental added respectively. In this case, the sample No. 18 to 23 satisfy each standard value and the judgment is ◯.

Further, the sample N of this embodiment shown in Table 2 is used.
o. 15 and the sample No. of the comparative example. A case where an endurance test is actually performed using a material having predetermined physical properties such as 3, 9 will be described. First, each material is cut into a size of 25 mm × 50 mm × thickness 10 mm to prepare two samples, one of which is fitted into the furnace wall of a slag melting furnace containing iron oxide,
The slag was melted at 1400 ° C. Then, the sample is
Contacted with molten slag for hours. Further, the other sample was fitted in the weir of the mold part for continuous casting, and 350 kg of stainless (SUS304) steel was cast. Then, Table 3 shows the results of visual observation of the ceramics samples after completion of melting and casting.

[0022]

[Table 3]

In Table 3, when visually observing whether or not cracks have occurred after the melting and casting durability tests,
Table 2 Sample No. Only 3 (Si ₃ N ₄ ) had cracks (Δ). In addition, when examining the degree of wear in the casting durability test, Table 2 Sample No. 3 (Si ₃ N ₄ ) and Table 2 Sample No. In 9 (Si ₃ N ₄ + BN), there was a considerable change (Δ) compared with before the test. Further, the commercially available hot-pressed product (BN) was changed (x) so that its shape could not be retained. Furthermore, when examining the degree of reactivity in the melting test, Table 2 sample No. 3 (Si ₃ N
Only ₄ ) was slightly changed (○) compared to before the test.

As described above, in the result of the durability test, the sample No. No. 15 indicates that there is no problem with respect to each judgment item, that is, cracking, wear, and reactivity. In addition, ⊚ indicates that there is no great difference in the shape and the like of the sample compared to before the test.

[0025]

As described above, according to the present invention, Si ₃ N ₄ which is a high-strength heat-resistant material is used as a base material, and BN which imparts thermal shock resistance and abrasion resistance and oxidation resistance are imparted to the base material. By adding an appropriate amount of one or more silicates selected from titanium, chromium, zirconium, niobium, molybdenum, tantalum, and tungsten silicates, the fire resistance of the melting furnace wall and mold weirs of thin plate continuous casting equipment, etc. Conditions for use as a member (bending strength of 5 Kgf / mm ² or more, thermal shock resistance of 650 ° C or more, Vickers hardness of 60
0 or more, the weight change after oxidation for 500 hours in the atmosphere of 1400 ℃
It is possible to obtain a refractory member which is excellent in heat resistance, thermal shock resistance and wear resistance, and excellent in oxidation resistance.

Claims (1)

(57) [Claims] 1. Al ₂ O ₃ , Y ₂ O ₃ , MgO, MgAl
5 to 20% by weight of one or more kinds of oxides selected from ₂ O ₄ , ZrO ₂ , SiO ₂ and ZrSiO ₄ , and 3 to BN.
25% by weight of titanium, chromium, zirconium, niobium,
Containing 4 to 20% by weight of one or more kinds of silicides selected from molybdenum, tantalum, and tungsten silicides,
A heat-resistant ceramics characterized in that the balance is composed of Si ₃ N ₄ .