JP4485615B2 - Corrosion-resistant spinel sintered body and heat treatment member comprising the same - Google Patents

Description

【００３２】
【表２】

【００３３】
【表３】

【００３４】
【表４】

【００３５】
【発明の効果】
本発明のスピネル質焼結体は、耐食性、耐熱衝撃性及び耐久性にすぐれるため圧電体、誘電体、セラミックコンデンサー等の電子部品の焼成用部材として有効に用いることができる。特にＰｂＯを含有するＰＺＴの焼成における焼成用部材として用いると、ＰｂＯに対する耐食性がすぐれるため被焼成物の組成変化が非常に少ないことから好適である。さらに、金属及び合金の溶解用ルツボとしても有効である。また、すぐれた耐食性を利用して、例えばバーナーノズル、炉心管、ラジアントチューブ、ヒーターサポートチューブ、特に廃棄物焼成炉及び溶融炉等に使用される測温用保護管及び燃焼ガス配管の内張り材としても有効に用いることができる。
【００３６】
以下に本発明の実施態様を列挙する。
（１）（ａ）含有量が９４ｖｏｌ％以上のスピネル結晶からなり、（ｂ）Ａｌ_２Ｏ_３とＭｇＯの合計量が９８重量％以上、（ｃ）Ａｌ_２Ｏ_３／ＭｇＯ（重量比）が６５／３５〜８０／２０、（ｄ）ＺｒＯ_２が２重量％以下、（ｅ）かさ密度が３．４０ｇ／ｃｍ^３以上、（ｆ）平均結晶粒径が３μｍ以上、であることを特徴とする耐食性スピネル質焼結体。
（２）前記Ａｌ_２Ｏ_３とＭｇＯの１部が少量のＣａＯで置換されたものである前項（１）記載の耐食性スピネル質焼結体。
（３）前記ＣａＯの含有量がＡｌ_２Ｏ_３とＭｇＯとＣａＯとの合計量に対し０．５重量％以下である前項（２）記載の耐食性スピネル質焼結体。
（４）前記ＣａＯの含有量がＡｌ_２Ｏ_３とＭｇＯとＣａＯとの合計量に対し０．０５〜０．３重量％である前項（３）記載の耐食性スピネル質焼結体。
（５）Ａｌ_２Ｏ_３とＭｇＯの含有量が全量の９８重量％になるようにアルミニウム化合物とマグネシウム化合物とを、水を用いて湿式で均一に混合し、乾燥させた後、１０００〜１５００℃で合成し、スピネル結晶相量が、７０ｖｏｌ％以上であるスピネル粉体を得、得られたスピネル粉体を湿式により粉砕・分散した後、乾燥し、成形粉体を得、これを用いて所望の形状に成形し、得られた成形体を１５００〜１７５０℃で焼成することを特徴とする耐食性スピネル質焼結体の製造方法。
【図面の簡単な説明】
【図１】実施例１のスピネル質焼結体のＸ線回折チャートである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a corrosion-resistant spinel sintered body and a heat treatment member using the same and having excellent heat resistance and corrosion resistance.
[0002]
[Prior art and its problems]
Piezoelectric materials are often used for frequency control of filters and resonators, and ceramics such as PZT (lead zirconate titanate) are used. PZT contains PbO, and PbO vapor is generated during the firing process. Therefore, from the viewpoint of corrosion resistance, the firing container used for pre-firing synthesis of PZT powder or the firing of the molded body or a member that may be touched by PbO vapor, Heat treatment members such as MgO and Al ₂ O ₃ are used. However, although MgO material has excellent corrosion resistance against PbO, it has poor thermal shock resistance and thus has a disadvantage of poor productivity. Although Al ₂ O ₃ material is superior to MgO material in terms of thermal shock resistance, It has the disadvantage of being inferior in corrosion resistance to PbO.
[0003]
Therefore, in the invention described in Japanese Patent Application Laid-Open No. 10-7470, a heat-treating member having an excellent corrosion resistance to PbO, a large thermal shock resistance, and a molar ratio of MgO to Al ₂ O ₃ of 1.0 or more. Is disclosed. However, the quality of corrosion resistance, thermal shock resistance and durability greatly affects not only the crystal phase composing the sintered body, but also the second component, impurity components and amount thereof, sintered body density, crystal grain size, etc. Therefore, even this invention was not fully satisfactory.
[0004]
On the other hand, recently, harmful gases such as dioxins generated during the firing of waste have become a problem from the viewpoint of environmental destruction. Therefore, waste is incinerated, incineration ash is melted, and vitrification is performed so that harmful components are not released. However, since the incinerated ash melt and the gas generated from the melt are highly corrosive, the components used in the melting furnace, such as the temperature measuring protective tube for controlling the temperature inside the furnace, the filler, etc. are corroded, and the short term There was a problem that it could not be used between the two, and had to be replaced and replenished frequently.
[0005]
In view of the above, a ceramic sintered body having excellent corrosion resistance and thermal shock resistance has been desired.
[0006]
[Problems to be solved by the invention]
The object of the present invention is to have excellent heat resistance and corrosion resistance against alkalis and heavy metals such as PbO, and also excellent corrosion resistance against slag generated from waste incineration ash melting furnaces and corrosive harmful gases. The object is to provide a spinel sintered body and a heat treatment member comprising the same.
[0007]
[Means for Solving the Problems]
The present inventor has conducted extensive studies in view of the above situation, and as a result, in a spinel sintered body containing Al ₂ O ₃ / MgO as a main component and containing a specific weight ratio, ZrO ₂ It was found that a ceramic sintered body having excellent corrosion resistance and a heat treatment member can be obtained by adjusting the bulk density and the average crystal grain size to an appropriate range by containing a specific amount of the present invention, and completed the present invention. .
[0008]
That is, the first of the present invention is: (a) the content of spinel crystals is 94 vol% or more, and (b) the total amount of Al ₂ O ₃ , MgO and CaO is 98 wt% or more, CaO is 0.05 to 0.5 wt%, (c) Al ₂ O ₃ / MgO (weight ratio) is 65/35 to 80/20, and (d) ZrO ₂ is 0.05 to ₂ wt%. And (e) a bulk density of 3.40 g / cm ³ or more, and (f) an average crystal grain size of 3 μm or more.
[0009]
The second of the present invention relates to a heat treatment member comprising the corrosion-resistant spinel sintered body.
[0010]
The heat-treating member having excellent heat resistance and corrosion resistance in the present invention refers to various members used in or around containers such as containers for storing heat-treated materials used in the heat treatment of various materials or various firing furnaces and melting furnaces. Specifically, for example, firing containers, setters, metal melting crucibles, glass melting containers, slag melting crucibles, single crystal growing crucibles, fluorescent lamps used for calcining synthesis of ceramic powder and firing of molded bodies It refers to a vessel for heat treatment of body materials, a core tube for a tubular furnace, a radiant tube, a heater support tube, a temperature measuring protective tube, a gas blowing tube, a gas sampling tube, a lining furnace material, and the like. Furthermore, since it is excellent in heat resistance and corrosion resistance, it can be sufficiently used for a gas transport pipe.
[0011]
Each requirement to be satisfied by the corrosion-resistant spinel sintered body of the present invention will be described in detail below.
[0012]
The requirement (a) in the present invention is that it is composed of a spinel crystal having a content of 94 vol% or more . The spinel crystal is not a collection of individual crystals of _Al 2 _{O 3} and MgO, a crystal of a compound of _Al 2 _{O 3} and MgO. If the spinel sintered body contains an Al ₂ O ₃ crystal phase, the corrosion resistance against PbO or alkali is lowered, which is not preferable. Moreover, it is not preferable that the MgO crystal phase is contained because the thermal shock resistance is lowered.
[0013]
The requirement (b) in the present invention is that the total amount of Al ₂ O ₃ , MgO and CaO is 98% by weight or more. In the present invention, the total amount of Al ₂ O ₃ , MgO and CaO needs to be 98% by weight or more, preferably 98.5% by weight or more. When the total amount of Al ₂ O ₃ , MgO and CaO is less than 98% by weight, the amount of impurities increases, so that a lot of second phase or glass phase is present at the spinel grain boundaries, and corrosion resistance and mechanical properties are increased. This is not preferable because of a decrease in the thickness.
[0014]
In the present invention, it is essential that the total amount of _Al 2 _O 3, MgO and CaO account for at least 98 wt% of the total. CaO is contained in an amount of 0.05 to 0.5% by weight , more preferably 0.05 to 0.3% by weight , based on the total amount of Al ₂ O ₃ , MgO and CaO. In this case, it is needless to say that the total amount of Al ₂ O ₃ , MgO and CaO occupies 98% by weight or more of the whole. CaO is effective in improving the sinterability, but if it exceeds 0.5% by weight, corrosion resistance is lowered, which is not preferable.
[0015]
The requirement of (c) in the present invention is that the weight ratio of Al ₂ O ₃ / MgO is 65/35 to 80/20, and the weight ratio is particularly 67/33 to 75/25. preferable. When the weight ratio of Al ₂ O ₃ / MgO is less than 65/35, the amount of MgO crystal phase in the sintered body increases, and corrosion resistance and mechanical characteristics, particularly thermal shock resistance and thermal fatigue characteristics are increased. Since it falls, it is not preferable. On the other hand, when the weight ratio of Al ₂ O ₃ / MgO exceeds 80/20, the amount of the Al ₂ O ₃ crystal phase in the sintered body increases, and the corrosion resistance is lowered.
[0016]
In the present invention, the presence / absence and content of Al ₂ O ₃ crystal phase and MgO crystal phase can be determined by X-ray diffraction by the following method. Specifically, the sintered body was pulverized with a mortar to such an extent that no grain was felt on the fingertips, and the obtained powder sample was measured by X-ray diffraction, and whether or not Al ₂ O ₃ crystal phase and MgO crystal phase existed, and The content is calculated by the following formula.
[0017]
[Expression 1]
Al ₂ O ₃ crystal phase amount (vol%) =
{IA (113) / [IS (311) + IA (113) + IM (200)]} × 100
(Where IA (113) is the peak height of the Al ₂ O ₃ crystal diffraction peak (113), IS (311) is the peak height of the spinel crystal diffraction peak (311), and IM (200) is the MgO crystal diffraction peak. (Shows the peak height of (200).)
[Expression 2]
MgO crystal phase amount (vol%) =
{IM (200) / [IS (311) + IA (113) + IM (200)]} × 100
(Where IM (200) is the peak height of the MgO crystal diffraction peak (200), IA (113) is the peak height of the Al ₂ O ₃ crystal diffraction peak (113), and IS (311) is the spinel crystal diffraction peak. (Shows the peak height of (311).)
[Equation 3]
Spinel crystal phase amount (vol%) = 100−Al ₂ O ₃ crystal phase amount−MgO crystal phase amount
In the present invention, the respective crystal phase amounts of Al ₂ O ₃ and MgO obtained from the X-ray diffraction can be allowed up to 3 vol%. Therefore, the present invention includes a case of containing up to 3 vol% of each of these crystal phases in addition to the spinel crystal, and in the present specification, these are generically defined as a spinel sintered body .
[0019]
The requirement (d) in the present invention is that ZrO ₂ is contained in an amount of 2% by weight or less. In the present invention, ZrO ₂ needs to be 0.05 to ₂ % by weight , more preferably 0.05 to 1.5% by weight . ZrO ₂ is dissolved in the spinel crystal, or exists in the grains and at the grain boundaries, and is effective in improving mechanical properties, particularly thermal shock resistance, and further improving corrosion resistance, particularly corrosion resistance against PZT. When the content of ZrO ₂ exceeds 2% by weight, it is not preferable because distortion and micro cracks are generated inside the sintered body due to repeated heating and cooling due to the difference in thermal expansion, leading to cracks, and further, corrosion resistance is reduced. Therefore, it is not preferable. In addition, stabilizers such as Y ₂ O ₃ , MgO, and CaO may be dissolved in ZrO ₂ .
[0020]
The requirement (e) in the present invention is that the bulk density is 3.40 g / cm ³ or more, but preferably 3.45 g / cm ³ or more. Even if the above requirements (a) to (d) are satisfied, if the bulk density is less than 3.40 g / cm ³ , many pores exist inside the sintered body, and the pores are the starting points. The corrosion reaction progresses and the corrosion resistance is lowered, which is not preferable. Further, the mechanical properties and the thermal shock resistance are deteriorated, which is not preferable.
[0021]
The requirement (f) in the present invention is that the average crystal grain size is 3 μm or more, preferably 5 μm or more. When the average crystal grain size is less than 3 μm, not only is the corrosion resistance lowered, but it is not preferable because deformation at high temperature and thermal fatigue are likely to occur.
[0022]
The corrosion-resistant spinel sintered body of the present invention can be produced by various methods. An example is shown below.
[0023]
Aluminum compound (for example, alumina, aluminum hydroxide) and magnesium compound (for example, magnesia, magnesium carbonate) are uniformly mixed with water so that the content of Al ₂ O ₃ and MgO becomes a predetermined weight ratio. And dried and then synthesized at 1000 to 1500 ° C. to obtain spinel powder. The amount of the spinel crystal phase of the synthesized spinel powder needs to be 70 vol% or more, and more preferably 80 vol% or more. When the spinel crystal phase amount is less than 70 vol%, the microstructure of the obtained sintered body becomes non-uniform, which leads to deterioration of corrosion resistance and mechanical properties. Components other than Al ₂ O ₃ and MgO may be added in the form of a compound such as a hydroxide during mixing of the aluminum compound and the magnesia compound, or a hydroxide during pulverization / dispersion of the synthetic powder described later. Further, it may be added in the form of carbonate, oxide or the like. The obtained synthetic powder is pulverized and dispersed by a wet process. The specific surface area of the obtained pulverized powder is ^{2 to 20} m ² / g, more preferably 4 to 15 m ² / g. When the pulverized powder particle size is outside these ranges, the moldability is lowered, the sintered bulk density is lowered, and the obtained sintered body contains many defects, so that the corrosion resistance and the mechanical properties are lowered. Therefore, it is not preferable. When adopting a method such as press molding or rubber press molding as a molding method, a known molding aid (for example, wax emulsion, PVA, acrylic resin, etc.) is added to the pulverized / dispersed slurry as necessary, and a spray dryer or the like is added. It is dried by a known method to produce a molded powder, which is then molded. In addition, when adopting the casting method, a known binder (for example, wax emulsion, acrylic resin, etc.) is added to the pulverized / dispersed slurry as required, and the waste mud is cast and filled using a gypsum mold or a resin mold. Molded by casting or pressure casting. Furthermore, when adopting an extrusion molding method, the pulverized / dispersed slurry is dried, sized, and mixed with water, a binder (for example, methylcellulose), a plasticizer (for example, polyethylene glycol), a lubricant (for example). For example, stearic acid or the like is mixed to prepare a clay, and extrusion molding is performed. A sintered body can be obtained by firing the molded body obtained as described above at 1500 to 1750 ° C, more preferably 1600 to 1700 ° C.
[0024]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited thereto.
[0025]
Example 1
Alumina having a purity of 99.8% by weight and magnesium carbonate having a MgO content of 98% by weight are wet-mixed in the proportions shown in Table 1, dried, synthesized at 1400 ° C. for 2 hours, and the obtained spinel powder is mixed with ZrO. ₂ and CaO were added in the proportions shown in Table 1, and were pulverized and dispersed in a wet manner. Next, 3% by weight of the wax emulsion was added to the obtained slurry, and dried with a spray dryer to obtain a molded powder. Using this powder, it was molded from a mold at a molding pressure of 1 tonf / cm ² and fired at 1600-1750 ° C. to obtain a 25 × 25 × 5 mm sample. Moreover, it cast-molded by the gypsum type | mold using the slurry grind | pulverized and disperse | distributed by wet, and baked on the same conditions as the above, and produced the square container of external shape 100x100x80mm (wall thickness 5mm).
[0026]
Table 2 shows the chemical composition and characteristics of the obtained sintered body. Sample No. 1 to 7 are spinel sintered bodies of the present invention. 8 to 15 are comparative products that do not satisfy at least one of the requirements of the present invention. Sample No. An X-ray diffraction chart of the sintered body of No. 7 is shown in FIG. 1, and it was proved that this sintered body was composed only of the spinel crystal phase.
[0027]
Next, a PZT molded body having a diameter of 25 mm and a thickness of 3 mm was placed on the sample obtained above, and a 63 g alumina block was placed on the PZT molded body, and the alumina firing container [SSA made by Nikkato Co., Ltd. -S], capped and sealed, and heat treated twice at 1300 ° C. in an electric furnace. The sample after the heat treatment was cut, mirror finished, and the penetration depth of PbO was measured by EDX. The measurement results are shown in Table 2.
[0028]
The spinel sintered body with excellent corrosion resistance of the present invention exhibits excellent corrosion resistance with an erosion depth of 0.5 mm or less with respect to PbO, but a sintered body that does not satisfy even one of the requirements of the present invention is It is clear that its corrosion resistance is inferior.
[0029]
Example 2
Sample No. in Table 1 Thermal shock tests were conducted on 2, 6, 9 and 13. The test was put in a square container containing 40-mesh fused zirconia powder in an electric furnace heated and held at 1000 ° C., held for 30 minutes, taken out to room temperature, cooled, and then cracked by fluorescence flaw detection. It was done by the method of examining. The results of repeating the above test 10 times are shown in Table 3. The spinel sintered body of the present invention has no thermal cracking even after 10 repeated thermal shock tests, and has excellent thermal shock resistance compared to a sintered body that does not satisfy any of the requirements of the present invention. Is clear.
[0030]
Example 3
Sample No. in Table 1 4, 7, 8 and 12 were subjected to a corrosion resistance test against general waste incinerated ash. In the test, the incinerated ash containing limestone was put in an alumina container [SSA-S manufactured by Nikkato Co., Ltd.], and a sintered body of 25 × 25 × 5 mm was embedded therein, and 72 ° C. at 1400 ° C. in an electric furnace. Hold for hours and cool in furnace. A sample after firing was cut out, mirror finished, and Ca and Si line analysis was performed by EDX to measure the erosion depth. The results are shown in Table 4. The spinel sintered body of the present invention exhibits excellent corrosion resistance with an erosion depth of 0.35 mm or less, and a sintered body that does not satisfy even one of the requirements of the present invention is inferior in corrosion resistance.
[0031]
[Table 1]

[0032]
[Table 2]

[0033]
[Table 3]

[0034]
[Table 4]

[0035]
【The invention's effect】
Since the spinel sintered body of the present invention is excellent in corrosion resistance, thermal shock resistance and durability, it can be effectively used as a member for firing electronic parts such as piezoelectric bodies, dielectric bodies and ceramic capacitors. In particular, when used as a firing member in firing PZT containing PbO, the corrosion resistance to PbO is excellent, so that the composition change of the material to be fired is very small. Furthermore, it is also effective as a crucible for melting metals and alloys. In addition, using excellent corrosion resistance, for example, as a lining material for temperature measuring protection tubes and combustion gas pipes used in burner nozzles, furnace core tubes, radiant tubes, heater support tubes, especially waste firing furnaces and melting furnaces, etc. Can also be used effectively.
[0036]
The embodiments of the present invention are listed below.
(1) (a) It consists of a spinel crystal whose content is 94 vol% or more , (b) The total amount of Al ₂ O ₃ and MgO is 98 wt% or more, and (c) Al ₂ O ₃ / MgO (weight ratio) is 65 / 35-80 / 20, (d) ₂ % by weight or less of ZrO ₂ , (e) a bulk density of 3.40 g / cm ³ or more, and (f) an average crystal grain size of 3 μm or more. Corrosion-resistant spinel sintered body.
(2) The corrosion-resistant spinel sintered body according to (1), wherein a part of the Al ₂ O ₃ and MgO is substituted with a small amount of CaO.
(3) The corrosion-resistant spinel sintered body according to (2), wherein the content of CaO is 0.5% by weight or less with respect to the total amount of Al ₂ O ₃ , MgO, and CaO.
(4) The corrosion-resistant spinel sintered body according to (3), wherein the content of CaO is 0.05 to 0.3% by weight with respect to the total amount of Al ₂ O ₃ , MgO, and CaO.
(5) The aluminum compound and the magnesium compound are uniformly mixed with water so that the content of Al ₂ O ₃ and MgO is 98% by weight of the total amount and dried, and then 1000 to 1500 ° C. To obtain a spinel powder having a spinel crystal phase amount of 70 vol% or more, pulverize and disperse the obtained spinel powder by a wet process, and then dry to obtain a molded powder. A method for producing a corrosion-resistant spinel sintered body, characterized in that the molded body obtained by molding is sintered at 1500 to 1750 ° C.
[Brief description of the drawings]
1 is an X-ray diffraction chart of a spinel sintered body of Example 1. FIG.

Claims (2)

(A) The content of spinel crystals is 94 vol% or more , (b) the total amount of Al ₂ O ₃ , MgO and CaO is 98 wt% or more. 5% by weight, (c) Al ₂ O ₃ / MgO (weight ratio) 65/35 to 80/20, (d) ZrO ₂ 0.05 to ₂ % by weight, (e) Bulk density 3 .40 g / cm ³ or more and (f) an average crystal grain size of 3 μm or more.   A heat-treating member comprising the corrosion-resistant spinel sintered body according to claim 1.

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