JP2004149348A - Low-carbon high-zirconia-based electrocast refractory, and method of producing the same - Google Patents

Low-carbon high-zirconia-based electrocast refractory, and method of producing the same Download PDF

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JP2004149348A
JP2004149348A JP2002315295A JP2002315295A JP2004149348A JP 2004149348 A JP2004149348 A JP 2004149348A JP 2002315295 A JP2002315295 A JP 2002315295A JP 2002315295 A JP2002315295 A JP 2002315295A JP 2004149348 A JP2004149348 A JP 2004149348A
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zirconia
refractory
carbon
electroformed refractory
heat
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JP4275384B2 (en
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Nobuo Tomura
信雄 戸村
Yasuo Misu
安雄 三須
Shozo Seo
省三 瀬尾
Kimio Hirata
公男 平田
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Saint Gobain TM KK
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Saint Gobain TM KK
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-zirconia-based electrocast refractory which contains a very small amount of carbon and thereby exhibits less foaming property to molten glass, and a method of producing the same. <P>SOLUTION: The high-zirconia-based electrocast refractory is produced by blending raw materials so that the chemical components of an electrocast material are, by weight, 85-96% ZrO<SB>2</SB>, 3-10% SiO<SB>2</SB>and 0.5-2% Al<SB>2</SB>O<SB>3</SB>, then melting the obtained blend, electrocasting the resulting melt by using a template composed of refractory particles free from carbon, and gradually cooling. The content of carbon in the refractory is ≤150 ppm. <P>COPYRIGHT: (C)2004,JPO

Description

【0001】
【産業上の利用分野】
本発明は、ガラス溶融炉に適した高ジルコニア質電鋳耐火物、とくに炭素(C)含有量の少ない高ジルコニア質電鋳耐火物とその製造方法に関する。
【0002】
【従来の技術】
電鋳耐火物は、原料を溶融し、溶融物を所定形状の鋳型に鋳造し、これを徐冷することによって製造される。従って、焼成法による耐火物とは組織、製造方法とも異なる非常に緻密な耐火物として知られている。
【0003】
このような電鋳耐火物の中で、ジルコニア含有量が85〜96重量%である高ジルコニア質電鋳耐火物は、ジルコニアの結晶と僅かのガラス相からなり、あらゆる種類の溶融ガラスに対し耐食性に極めて優れており、溶融ガラスとの界面に反応層を作らない性質を持つことから、ガラス中にストーンやコードと呼ばれる欠陥を発生させることがない。
【0004】
こういった理由で、ジルコニア含有量が85〜96重量%である高ジルコニア質電鋳耐火物は、高品質のガラスを製造するのに特に適している。
【0005】
そのような高ジルコニア質電鋳耐火物において、その大部分を占めるジルコニア結晶は、800〜1200℃で急激な体積変化を伴って単斜晶系と正方晶系の可逆的な変態を起こすことがよく知られている。
【0006】
それゆえ、製作の際に亀裂のない高ジルコニア質電鋳耐火物を得るためには、この変態に伴う応力をいかにして緩和させるかが大きな課題である。
【0007】
この課題を解決するために、従来、いろいろとガラス相の改善について提案がなされ、ある程度改善されている。
【0008】
しかしながら、高ジルコニア質電鋳耐火物は、ガラス溶融炉に使用する際、溶融ガラスに対して泡を発生させる原因となっていた。さらに、熱衝撃に弱く、操炉初期の熱上げの際に、比較的低い300〜600℃で剥離や破断が生じることもあった。
【0009】
これらの欠点を取り除く為に、種々の改良がなされてきた。例えば、特開平6−183832号公報では、MgOを加えることによつて発泡性や熱衝撃性を改善している。また、特公平4−4271号公報では原料中に含まれるFeやCuなどの不純物を少なくすることによって、発泡性を改善している。また、特開平8−277162号公報では、ガラス相の膨張係数を低下させ残留応力の適正化を図り、使用時の熱衝撃によって剥離を生じないように改善している。
【0010】
【発明が解決しようとする課題】
高ジルコニア質電鋳耐火物は、一般に、珪砂などの徐冷材中に埋設したカーボン鋳型に溶湯を鋳造し、そのまま徐冷して製作されている。
【0011】
しかし、この方法では、耐火物がカーボンによる還元作用を受け、得られる耐火物の酸素濃度が理論値より少ない不飽和酸化物になりやすく、かつ、カーボン鋳型による浸炭作用で、耐火物中に炭素を含有した状態となってしまう。
【0012】
このような高ジルコニア質電鋳耐火物は、使用されるガラス溶融炉において、ガラス中に気泡を生じさせてガラス製品の品質を低下させる。
【0013】
また、この気泡の発生を防止する対策の一つとして、耐火物の周囲に白金を被覆することがある。
【0014】
しかし、炭素を含有した状態の高ジルコニア質電鋳耐火物は、白金と接触すると白金を劣化させることがある。
【0015】
前述の各公報に示された発明においても、改善度合いが不十分であり、また、製造工程が複雑で高価になるという欠点があった。
【0016】
本発明の目的は、このような従来の問題点を克服し、ガラス溶融炉に適した高ジルコニア質電鋳耐火物、とくに、炭素の含有量が極めて少なく、その為に溶融ガラスに対して発泡性の少ない特徴をもつ高ジルコニア質電鋳耐火物及びその製造方法を提供することである。
【0017】
【課題を解決するための手段】
本発明者らは、高ジルコニア質電鋳耐火物において、耐火物の不純物を含む化学組成と、その耐火物を使用してガラスを溶融したときの、ガラス中に発生する泡の数との関係について鋭意研究を重ねた結果、前記ガラス中における泡の発生が、耐火物中に含まれる炭素含有量に大きく依存することを見出し、この知見に基づいて本発明をなすに至った。
【0018】
本発明の解決手段を例示すると、請求項1〜11に記載の高ジルコニア質電鋳耐火物とその製造方法である。
【0019】
本発明の好適な解決手段により提供された高ジルコニア質電鋳耐火物は、耐火物の化学組成が、ZrO成分85〜96重量%、SiO成分3〜10重量%、Alが0.5〜2重量%であって、且つ、C(炭素)が150ppm以下であることを特徴とする。
【0020】
また、本発明の好適な解決手段により提供された高ジルコニア質電鋳耐火物の製造方法は、鋳造物の化学組成が、ZrO85〜96重量%、SiO3〜10重量%、Al0.5〜2重量%となるように原料を配合し、溶融し、炭素を含まない耐熱性粒子からなる鋳型によって鋳造し、徐冷することを特徴とする。
【0021】
【発明の実施の形態】
本発明は、高ジルコニア質電鋳耐火物に含まれる炭素に着目し、溶融ガラスに対して低発泡性であるように改良した。すなわち、耐火物に含まれる炭素の量を少なくするという構成により、発泡を少なくする効果を得た。
【0022】
本発明は、ZrOが85〜96重量%であり、SiOが3〜10重量%であり、Alが0.5〜2重量%である高ジルコニア質電鋳耐火物を改良して、ガラス類の溶融に有効に作用するようにした。
【0023】
本発明は、高ジルコニア質電鋳耐火物に含まれる炭素を150ppm以下、より好ましくは100ppm以下とすることにより、発泡を顕著に少なくするものである。高ジルコニア質電鋳耐火物に含まれる炭素が150ppmを超えると、溶融ガラスに対して発泡性が改善されにくい。発泡が少なくなる効果は、ガラスの種類にもよるが、ソーダライムガラスにおいて特に顕著である。
【0024】
高ジルコニア質電鋳耐火物に含まれる炭素が少ないと、発泡性を改善する他に、高ジルコニア質電鋳耐火物に白金を被覆して使用する際に、白金の劣化を防ぐ意味でも重要な役割を果たす。使用した白金が劣化すると、回収が困難になり、白金の再使用が困難となる。
【0025】
次に、本発明の電鋳耐火物の、C(炭素)以外の化学組成について説明する。
【0026】
ZrO成分濃度は、85〜96重量%が好ましい。96重量%より高くなる と、得られる電鋳耐火物に亀裂が生じることがある。また、85重量%未満になると、得られる電鋳耐火物の、溶融ガラスに対する耐食性が低下する。
【0027】
SiO成分濃度は、3〜10重量%が好ましい。SiO成分は、高ジルコニア質電鋳耐火物のガラス相の網目形成成分として必須であり、鋳造したとき、亀裂のない高ジルコニア質電鋳耐火物を得るのに十分なガラス相を形成するためには、少なくとも3重量%以上のSiO成分が必要である。また、SiO成分濃度が10重量%よりも高くなると、得られる電鋳耐火物の溶融ガラスに対する耐食性が低下する。
【0028】
また、Al成分は、ガラス相の粘度を調節するための重要な役割を果たしている。
【0029】
高ジルコニア質電鋳耐火物は、ジルコニア結晶相とガラス相より構成される。ジルコニア結晶には前記のように変態による体積変化が生じるが、このジルコニア結晶の体積変化を、ガラス相が緩衝するためには、ジルコニア結晶の変態温度域におけるガラス相の粘度を適度な範囲としなければならない。前記ガラス相の粘度が適度な範囲から外れると、得られる電鋳耐火物に亀裂が発生する傾向が強くなる。そこで、本発明者らは、Al成分濃度と得られる電鋳耐火物の亀裂の有無について鋭意検討を重ねた結果、耐火物の炭素含有量を150ppm以下とするために、後述する材質の鋳型に鋳造して本発明の電鋳耐火物を得る場合、耐火物のAl成分濃度が0.5〜2重量であれば、亀裂のない電鋳耐火物が得られることを見出した。また、Al成分濃度が0.5重量%よりも低くなると、得られる電鋳耐火物の耐食性が低下することがあり、Al成分濃度が2重量%よりも高くなると、後述する材質の鋳型に鋳造したとき、得られる電鋳耐火物のガラス相の一部が結晶化し、亀裂が生じることがある。
【0030】
したがって、本発明の高ジルコニア質電鋳耐火物に含まれる化学成分は、ZrOが85〜96重量%であり、SiOが3〜10重量%であり、Alが0.5〜2重量%であり、Cが150ppm以下である。
【0031】
次に、本発明の高ジルコニア質電鋳耐火物の製造方法の一例を示す。
【0032】
所定の原料配合物を電気炉にて溶融し、この溶融物を、徐冷材に埋設した炭素を含まない耐熱性粒子からなる鋳型によって鋳造し、鋳造後も徐冷材の中に埋設しておき十分に徐冷する。
【0033】
この製造方法を用いると、高ジルコニア質電鋳耐火物中の炭素含有量を容易かつ確実に150ppm以下に低減できる。これは従来のカーボン鋳型を用いる製造方法では実現し難い。
【0034】
鋳型は炭素を含まない耐熱性粒子を有機質或は無機質バインダーで結合したものを使用する。
【0035】
炭素を含む耐熱性粒子とは、例えばSiC粒子のように、化学組成としてC(炭素)を含む。そして、本発明の炭素を含まない耐熱性粒子とは、化学組成として実質的にCを含有しない粒子であり、不純物として微量のCを含んでいても良い。
【0036】
この耐熱性粒子は、機械的強度と耐熱性に優れていて、炭素を含まない無機粒子が使用できる。このような好ましい耐熱性粒子としては、例えば、アルミナ、ジルコニア、マグネシア、ジルコンなどの粒子がある。これらの耐熱性粒子は、高純度のものが、更に耐熱性に優れていて、より好ましい。
【0037】
耐熱性粒子の材質としては、特にジルコニア粒子が好ましい。ジルコニア粒子を用いると、断熱性に優れ、鋳造物の酸化が進み、炭素含有量が100ppm以下の高ジルコニア質電鋳耐火物が得られて、発泡特性が顕著に優れている。
【0038】
耐熱性粒子として、その他に、アルミナ質、高ジルコニア質またはアルミナジルコニアシリカ質等の各種電鋳耐火物を粉砕した粒子が好ましく使用できる。これらの粒子は、炭素を含まず、十分な機械的強度と耐熱性が得られて理想的である。
【0039】
また、耐熱性粒子の粒径は0.1〜5mmとするのが望ましい。粒径が0.1mm未満の粒子を含むと、鋳型は鋳造時の溶湯によって比較的溶融し易い上、鋳型作製の際に多量のバインダーを必要とする。また、粒径が5mmを超える粒子を含むと、十分な鋳型の強度を確保し難い。
【0040】
バインダーとしては、有機質或いは無機質の各種バインダーが使用できる。特に無機バインダーはC(炭素)を含まないことから好ましく使用できる。無機バインダーのなかでも珪酸ソーダ水溶液が特に好ましい。
【0041】
また、鋳型は、熱伝導率が10W/mK以下であることが好ましい。熱伝導率が低いと、鋳造後、長時間にわたって鋳造物の温度が高く、例えば電極から混入したC(炭素)が酸化され易くなり、結果としてCの少ない高ジルコニア質電鋳耐火物が得られる。この理由により、熱伝導率は10W/mK以下であることが好ましい。
【0042】
【実施例】
本発明の高ジルコニア質電鋳耐火物を次のようにして作製した。
【0043】
脱珪ジルコニアに、SiO、Al、その他の粉末原料を所定の割合で加 え、これらを混合後、アーク電気炉で溶融し、別に準備した珪砂の中に埋設した鋳型によって鋳造し、そのまま徐冷した。
【0044】
鋳型は、実験例2〜5では各種耐熱性粒子に珪酸ソーダ水溶液を4重量%添加し、混練し、50mmの厚さに造型した後に熱硬化して作製し、実験例1ではカーボン板を使用して作製した。
【0045】
耐熱性粒子としては、粒径が0.2〜5mmである、電融アルミナ、マグネシアクリンカー、ジルコンサンド、ジルコニアを用いた。
【0046】
鋳型は製品部分の内寸法が100×300×350mmで、その上部に内寸法が180×300×150mmの押し湯部分を一体に接続したものである。
【0047】
徐冷後、製品部分を押し湯部分から切り離して試験耐火物として使用した。得られた試験耐火物はいずれも外観上亀裂はなかった。
【0048】
この試験耐火物の化学成分はZrOが93.8重量%、SiOが4.5重量%、Alが1.3重量%、NaOが0.2重量%であった。
【0049】
表1は、各実験例に用いた鋳型の材質、鋳型の熱伝導率(W/mK)、試験耐火物の炭素含有量、各種ガラスの発泡試験による発泡数および白金回収の難易を示す。
【0050】
【表1】

Figure 2004149348
実験例2〜5は、本発明の実施例であるが、実験例1は、Cの含有量が170ppmであって、比較例である。
【0051】
炭素量は、試験耐火物の鋳込み面から約25mmの部分を切り出し、これを試料として、JIS G1211の全炭素定量方法−高周波誘導加熱炉燃焼−赤外線吸収法により測定した。
【0052】
発泡は次の方法で試験した。各試験耐火物の鋳造面から約15mm内部の3箇所から直径33mm、厚さ8mmの大きさの試験片を切り出し、この試験片を直径65mmの白金るつぼ内で溶融した30gの3種類のガラスの中に浸漬し、温度1400℃にて4時間保持した。試験後に白金るつぼの外周部分を水冷により急冷し、その後、試験片の中央部分15×15mmの上部ガラスに残った泡を数えた。この泡の数をcmあたりに換算して発泡数とした。
【0053】
白金回収の難易は、耐火物に白金を巻いて使用した後に、白金を回収する際の容易性を示す。
【0054】
実験例1に示すようにカーボン板の鋳型の熱伝導率は100W/mKと大きく、得られる耐火物の炭素含有量が170ppmであり、発泡試験後のガラスの発泡数は大きいものであった。しかしながら、実験例2〜5に示すように、炭素を含まない耐熱性粒子を用いた鋳型は熱伝導率が10W/mK以下と小さく、得られる耐火物の炭素含有量が150ppm以下であり、発泡試験後のガラスの発泡数は、より小さくなった。特に、実験例1と実験例5の比較からわかるように、ジルコニア粒を用いた鋳型は熱伝導率が1W/mKと極めて小さく、得られる耐火物の炭素含有量が100ppm以下であり、カーボン板を使用した鋳型に鋳造して得られた耐火物に比べ、発泡試験後のガラスの発泡数が1/2以下となった。
【0055】
また、実験例2〜5に示すように、耐火物の炭素含有量が150ppm以下であると、耐火物に白金を巻いて使用した後の、白金の回収が容易であった。しかしながら、実験例1に示すように、耐火物の炭素含有量が150ppmを超えると、耐火物に白金を巻いて使用した後は、白金が脆弱となり、その回収が困難であった。
【0056】
【発明の効果】
本発明の高ジルコニア質電鋳耐火物は、含まれる炭素が少ないため、発泡性が大きく改善されている。耐火物に起因する発泡が抑制されるためにガラスの品質向上に多大な効果をもたらすことが可能となる。
【0057】
さらに、本発明の高ジルコニア質電鋳耐火物は、高ジルコニア質電鋳耐火物に白金を被覆して使用する際に、白金の劣化を防ぎ、白金の回収を容易にする。[0001]
[Industrial applications]
The present invention relates to a high zirconia electroformed refractory suitable for a glass melting furnace, particularly to a high zirconia electroformed refractory having a low carbon (C) content and a method for producing the same.
[0002]
[Prior art]
An electroformed refractory is produced by melting a raw material, casting the molten product in a mold having a predetermined shape, and gradually cooling the molten product. Therefore, it is known as a very dense refractory having a different structure and a different production method from the refractory obtained by the firing method.
[0003]
Among such electroformed refractories, the high zirconia electroformed refractory having a zirconia content of 85 to 96% by weight is composed of zirconia crystals and a slight glass phase, and has a corrosion resistance to all kinds of molten glass. And has the property of not forming a reaction layer at the interface with the molten glass, so that defects called stones or cords do not occur in the glass.
[0004]
For these reasons, high zirconia electroformed refractories having a zirconia content of 85 to 96% by weight are particularly suitable for producing high quality glass.
[0005]
In such a high zirconia electroformed refractory, the zirconia crystal occupying most of the refractory may undergo a reversible transformation between a monoclinic system and a tetragonal system with a rapid volume change at 800 to 1200 ° C. well known.
[0006]
Therefore, in order to obtain a high zirconia electroformed refractory free of cracks during production, it is a major issue how to relieve the stress accompanying this transformation.
[0007]
In order to solve this problem, various proposals have been made on the improvement of the glass phase, and some improvements have been made.
[0008]
However, the high zirconia electroformed refractory causes bubbles to be generated in the molten glass when used in a glass melting furnace. Furthermore, it is vulnerable to thermal shock, and peeling or breaking may occur at a relatively low temperature of 300 to 600 ° C. when the heat is raised in the early stage of the furnace operation.
[0009]
Various improvements have been made to eliminate these disadvantages. For example, in JP-A-6-183832, foamability and thermal shock resistance are improved by adding MgO. In Japanese Patent Publication No. 4-4271, the foamability is improved by reducing impurities such as Fe and Cu contained in the raw material. Further, in Japanese Patent Application Laid-Open No. 8-277162, the expansion coefficient of the glass phase is reduced to optimize the residual stress, and improvement is made so as not to cause peeling due to thermal shock during use.
[0010]
[Problems to be solved by the invention]
In general, high-zirconia electroformed refractories are manufactured by casting a molten metal in a carbon mold buried in a gradually cooled material such as silica sand and gradually cooling the molten metal as it is.
[0011]
However, in this method, the refractory is subjected to a reducing action by carbon, and the resulting refractory tends to become an unsaturated oxide having an oxygen concentration lower than the theoretical value. Will be contained.
[0012]
Such a high zirconia electroformed refractory causes bubbles in the glass in a glass melting furnace to be used, thereby deteriorating the quality of the glass product.
[0013]
In addition, as one of measures for preventing the generation of bubbles, there is a case where platinum is coated around the refractory.
[0014]
However, a high zirconia electroformed refractory containing carbon may deteriorate platinum when it comes into contact with platinum.
[0015]
The inventions disclosed in the above publications also have the drawback that the degree of improvement is insufficient, and that the manufacturing process is complicated and expensive.
[0016]
An object of the present invention is to overcome such conventional problems and to provide a highly zirconia-based electroformed refractory suitable for a glass melting furnace, in particular, having a very low carbon content, and therefore foaming the molten glass. An object of the present invention is to provide a high-zirconia electroformed refractory having a characteristic of low resistance and a method for producing the same.
[0017]
[Means for Solving the Problems]
The present inventors have found that, in a high zirconia electroformed refractory, the relationship between the chemical composition containing impurities of the refractory and the number of bubbles generated in the glass when the glass is melted using the refractory. As a result of diligent studies, the present inventors have found that the generation of bubbles in the glass greatly depends on the carbon content contained in the refractory, and have made the present invention based on this finding.
[0018]
An example of the solution of the present invention is a high zirconia electroformed refractory according to claims 1 to 11 and a method for producing the same.
[0019]
High-zirconia electrocast refractories provided by suitable solutions of the present invention, the chemical composition of the refractory, ZrO 2 component 85-96 wt%, SiO 2 component 3 to 10% by weight, Al 2 O 3 0.5 to 2% by weight and C (carbon) is 150 ppm or less.
[0020]
Further, in the method for producing a high zirconia electroformed refractory provided by a preferred solution according to the present invention, the chemical composition of the casting is 85 to 96% by weight of ZrO 2 , 3 to 10% by weight of SiO 2 , and Al 2 It is characterized in that raw materials are blended so as to be 0.5 to 2% by weight of O 3 , melted, cast by a mold made of heat-resistant particles not containing carbon, and gradually cooled.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention focuses on carbon contained in a high zirconia electroformed refractory and has improved the molten glass to have low foaming properties. That is, the effect of reducing foaming was obtained by the configuration of reducing the amount of carbon contained in the refractory.
[0022]
The present invention, ZrO 2 is 85 to 96 wt%, SiO 2 is 3 to 10 wt%, Al 2 O 3 is to improve the high-zirconia electrocast refractories 0.5-2 wt% Thus, it effectively acts on the melting of glasses.
[0023]
In the present invention, foaming is remarkably reduced by setting the carbon contained in the high zirconia electroformed refractory to 150 ppm or less, more preferably 100 ppm or less. If the carbon content in the high zirconia electroformed refractory exceeds 150 ppm, the foaming property of the molten glass is hardly improved. The effect of reducing foaming is particularly remarkable in soda lime glass, depending on the type of glass.
[0024]
If the carbon content of the high zirconia electroformed refractory is low, in addition to improving the foamability, it is also important in preventing platinum degradation when using high zirconia electroformed refractory coated with platinum. Play a role. If the platinum used deteriorates, it becomes difficult to recover the platinum, and it becomes difficult to reuse the platinum.
[0025]
Next, the chemical composition other than C (carbon) of the electroformed refractory of the present invention will be described.
[0026]
The ZrO 2 component concentration is preferably from 85 to 96% by weight. If it exceeds 96% by weight, cracks may occur in the obtained electroformed refractory. When the content is less than 85% by weight, the corrosion resistance of the obtained electroformed refractory to molten glass decreases.
[0027]
The SiO 2 component concentration is preferably 3 to 10% by weight. The SiO 2 component is indispensable as a network forming component of the glass phase of the high zirconia electroformed refractory, and when cast, forms a glass phase sufficient to obtain a crack-free high zirconia electroformed refractory. Requires at least 3% by weight or more of the SiO 2 component. On the other hand, when the SiO 2 component concentration is higher than 10% by weight, the corrosion resistance of the obtained electroformed refractory to molten glass decreases.
[0028]
In addition, the Al 2 O 3 component plays an important role for adjusting the viscosity of the glass phase.
[0029]
The high zirconia electroformed refractory is composed of a zirconia crystal phase and a glass phase. As described above, the zirconia crystal undergoes a volume change due to transformation, but in order for the glass phase to buffer the volume change of the zirconia crystal, the viscosity of the glass phase in the transformation temperature range of the zirconia crystal must be within an appropriate range. Must. If the viscosity of the glass phase is out of an appropriate range, the resulting electroformed refractory tends to have cracks. The present inventors have conducted intensive studies on the Al 2 O 3 component concentration and the presence or absence of cracks in the obtained electroformed refractory. As a result, in order to reduce the carbon content of the refractory to 150 ppm or less, the following materials were used. In the case of obtaining the electroformed refractory of the present invention by casting in a mold of the present invention, it has been found that if the Al 2 O 3 component concentration of the refractory is 0.5 to 2% by weight, a crack-free electroformed refractory can be obtained. Was. Further, when the concentration of the Al 2 O 3 component is lower than 0.5% by weight, the corrosion resistance of the obtained electroformed refractory may be reduced. When the concentration of the Al 2 O 3 component is higher than 2% by weight, it will be described later. When cast into a mold of a suitable material, a part of the glass phase of the obtained electroformed refractory may crystallize and cracks may occur.
[0030]
Accordingly, the chemical components contained in the high-zirconia electrocast refractories of the present invention, ZrO 2 is 85 to 96 wt%, a SiO 2 is 3 to 10 wt%, 0.5 is Al 2 O 3 2% by weight, and C is 150 ppm or less.
[0031]
Next, an example of a method for producing a high zirconia electroformed refractory of the present invention will be described.
[0032]
The specified raw material mixture is melted in an electric furnace, and the melt is cast in a mold made of carbon-free heat-resistant particles embedded in the gradually cooled material. Let cool.
[0033]
By using this manufacturing method, the carbon content in the high-zirconia electroformed refractory can be easily and reliably reduced to 150 ppm or less. This is difficult to achieve with a conventional manufacturing method using a carbon mold.
[0034]
As the template, use is made of heat-resistant particles that do not contain carbon and bound with an organic or inorganic binder.
[0035]
The heat-resistant particles containing carbon include C (carbon) as a chemical composition, for example, like SiC particles. The heat-resistant particles that do not contain carbon according to the present invention are particles that do not substantially contain C as a chemical composition, and may contain trace amounts of C as impurities.
[0036]
The heat-resistant particles are excellent in mechanical strength and heat resistance, and inorganic particles containing no carbon can be used. Such preferable heat-resistant particles include, for example, particles of alumina, zirconia, magnesia, zircon and the like. These heat-resistant particles are more preferably high-purity particles because they have more excellent heat resistance.
[0037]
As the material of the heat-resistant particles, zirconia particles are particularly preferable. When zirconia particles are used, the heat insulation property is excellent, the oxidation of the casting proceeds, and a high zirconia electroformed refractory having a carbon content of 100 ppm or less is obtained, and the foaming characteristics are remarkably excellent.
[0038]
In addition, as the heat resistant particles, particles obtained by pulverizing various electroformed refractories such as alumina, high zirconia, and alumina zirconia silica can be preferably used. These particles are ideal because they do not contain carbon and have sufficient mechanical strength and heat resistance.
[0039]
Further, the particle size of the heat-resistant particles is desirably 0.1 to 5 mm. When particles having a particle size of less than 0.1 mm are included, the mold is relatively easily melted by the molten metal at the time of casting, and a large amount of binder is required when the mold is produced. In addition, when particles having a particle size exceeding 5 mm are included, it is difficult to secure sufficient strength of the mold.
[0040]
As the binder, various organic or inorganic binders can be used. In particular, an inorganic binder can be preferably used because it does not contain C (carbon). Among the inorganic binders, an aqueous sodium silicate solution is particularly preferred.
[0041]
The mold preferably has a thermal conductivity of 10 W / mK or less. If the thermal conductivity is low, the temperature of the casting is high for a long time after casting, and for example, C (carbon) mixed from the electrode is easily oxidized, and as a result, a high zirconia electroformed refractory containing less C is obtained. . For this reason, the thermal conductivity is preferably 10 W / mK or less.
[0042]
【Example】
A high zirconia electroformed refractory of the present invention was produced as follows.
[0043]
SiO 2 , Al 2 O 3 , and other powdered raw materials are added to desiliconized zirconia at a predetermined ratio, mixed, melted in an electric arc furnace, and cast by a mold embedded in separately prepared silica sand. , And then slowly cooled.
[0044]
In Experimental Examples 2 to 5, a 4% by weight aqueous sodium silicate solution was added to various heat-resistant particles, kneaded, molded to a thickness of 50 mm, and then heat-cured. In Experimental Example 1, a carbon plate was used. It was produced.
[0045]
As the heat-resistant particles, fused alumina, magnesia clinker, zircon sand, and zirconia having a particle size of 0.2 to 5 mm were used.
[0046]
The mold has a product portion having an inner size of 100 × 300 × 350 mm, and a top portion having an inner size of 180 × 300 × 150 mm integrally connected thereto.
[0047]
After slow cooling, the product part was cut off from the riser part and used as a test refractory. All of the test refractories obtained had no cracks in appearance.
[0048]
The chemical components of this test refractory were 93.8% by weight of ZrO 2, 4.5% by weight of SiO 2 , 1.3% by weight of Al 2 O 3 and 0.2% by weight of Na 2 O.
[0049]
Table 1 shows the material of the mold, the thermal conductivity (W / mK) of the mold, the carbon content of the test refractory, the number of foams by the foaming test of various glasses, and the difficulty of platinum recovery used in each experimental example.
[0050]
[Table 1]
Figure 2004149348
Experimental Examples 2 to 5 are examples of the present invention, while Experimental Example 1 is a comparative example in which the C content is 170 ppm.
[0051]
The amount of carbon was measured by cutting out a portion of about 25 mm from the casting surface of the test refractory and using this as a sample by the total carbon determination method of JIS G1211-high-frequency induction heating furnace combustion-infrared absorption method.
[0052]
Foaming was tested in the following manner. A test piece having a diameter of 33 mm and a thickness of 8 mm was cut out from three places within about 15 mm from the casting surface of each test refractory, and the test pieces were melted in a 65-mm-diameter platinum crucible. And kept at a temperature of 1400 ° C. for 4 hours. After the test, the outer peripheral portion of the platinum crucible was quenched by water cooling, and then the number of bubbles remaining on the upper glass of 15 × 15 mm in the central portion of the test piece was counted. The number of the foams was converted per cm 2 to obtain the number of foams.
[0053]
The difficulty of platinum recovery refers to the ease with which platinum is recovered after platinum is wound around a refractory.
[0054]
As shown in Experimental Example 1, the thermal conductivity of the carbon plate mold was as large as 100 W / mK, the carbon content of the obtained refractory was 170 ppm, and the number of foams in the glass after the foaming test was large. However, as shown in Experimental Examples 2 to 5, the mold using the heat-resistant particles containing no carbon has a small thermal conductivity of 10 W / mK or less, the obtained refractory has a carbon content of 150 ppm or less, and has a foaming property. The foaming number of the glass after the test became smaller. In particular, as can be seen from a comparison between Experimental Example 1 and Experimental Example 5, the mold using zirconia particles has an extremely low thermal conductivity of 1 W / mK, the obtained refractory has a carbon content of 100 ppm or less, and a carbon plate. The number of foams of the glass after the foaming test was 以下 or less as compared with the refractory obtained by casting in a mold using.
[0055]
Further, as shown in Experimental Examples 2 to 5, when the carbon content of the refractory was 150 ppm or less, it was easy to recover platinum after using the refractory by winding platinum around it. However, as shown in Experimental Example 1, when the carbon content of the refractory exceeded 150 ppm, platinum was fragile after the refractory was wound around platinum, and it was difficult to recover the platinum.
[0056]
【The invention's effect】
Since the high zirconia electroformed refractory of the present invention contains a small amount of carbon, the foamability is greatly improved. Since the foaming caused by the refractory is suppressed, it is possible to bring a great effect for improving the quality of the glass.
[0057]
Furthermore, the high zirconia electroformed refractory of the present invention prevents the deterioration of platinum and facilitates the recovery of platinum when the high zirconia electroformed refractory is coated with platinum and used.

Claims (11)

化学成分として、ZrOが85〜96重量%であり、Si Oが3〜10重量%であり、Alが0.5〜2重量%であり、Cが150 ppm以下であることを特徴とする高ジルコニア質電鋳耐火物。As chemical components that, ZrO 2 is 85 to 96 wt%, Si O 2 is 3 to 10 wt% are Al 2 O 3 is 0.5 to 2 wt%, C is 0.99 ppm or less A high zirconia electroformed refractory characterized by the following. 電鋳耐火物が、炭素を含まない耐熱性粒子からなる鋳型によって鋳造されたものであることを特徴とする請求項1に記載の高ジルコニア質電鋳耐火物。2. The high-zirconia electroformed refractory according to claim 1, wherein the electroformed refractory is cast by a mold made of heat-resistant particles containing no carbon. 鋳型が、炭素を含まない耐熱性粒子と無機結合材からなることを特徴とする請求項2に記載の高ジルコニア質電鋳耐火物。The high zirconia electroformed refractory according to claim 2, wherein the mold comprises heat-resistant particles not containing carbon and an inorganic binder. 炭素を含まない耐熱性粒子がジルコニアであることを特徴とする請求項2または3のいずれか1項に記載の高ジルコニア質電鋳耐火物。The high-zirconia electroformed refractory according to any one of claims 2 to 3, wherein the heat-resistant particles containing no carbon are zirconia. 無機結合材が珪酸ソーダであることを特徴とする請求項3に記載の高ジルコニア質電鋳耐火物。The high zirconia electroformed refractory according to claim 3, wherein the inorganic binder is sodium silicate. 鋳型の熱伝導率が10W/mK以下であることを特徴とする請求項2または3のいずれか1項に記載の高ジルコニア質電鋳耐火物。The high zirconia electroformed refractory according to any one of claims 2 and 3, wherein the mold has a thermal conductivity of 10 W / mK or less. 鋳造物の化学成分が、ZrO85〜96重量%、SiO3〜10重量%、Al0.5〜2重量%となるように原料を配合し、溶融し、炭素を含まない耐熱性粒子からなる鋳型によって鋳造し、徐冷することを特徴とする高ジルコニア質電鋳耐火物の製造方法。Chemical composition of the castings, ZrO 2 85 to 96 wt%, SiO 2 3 to 10% by weight, blended with the raw material so that the Al 2 O 3 0.5 to 2 wt%, melt and no carbon A method for producing a highly zirconia-based electroformed refractory, comprising casting by a mold made of heat-resistant particles and gradually cooling. 鋳型が、炭素を含まない耐熱性粒子と無機結合材からなることを特徴とする請求項7に記載の高ジルコニア質電鋳耐火物の製造方法。The method for producing a high-zirconia electroformed refractory according to claim 7, wherein the mold is made of heat-resistant particles containing no carbon and an inorganic binder. 炭素を含まない耐熱性粒子がジルコニアであることを特徴とする請求項7または8のいずれか1項に記載の高ジルコニア質電鋳耐火物の製造方法。9. The method for producing a high zirconia electroformed refractory according to claim 7, wherein the heat-resistant particles containing no carbon are zirconia. 無機結合材が珪酸ソーダであることを特徴とする請求項8に記載の高ジルコニア質電鋳耐火物の製造方法。The method for producing a high zirconia electroformed refractory according to claim 8, wherein the inorganic binder is sodium silicate. 鋳型の熱伝導率が10W/mK以下であることを特徴とする請求項7または8のいずれか1項に記載の高ジルコニア質電鋳耐火物の製造方法。The method for producing a high-zirconia electroformed refractory according to any one of claims 7 and 8, wherein the heat conductivity of the mold is 10 W / mK or less.
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10407349B2 (en) 2015-04-24 2019-09-10 Corning Incorporated Bonded zirconia refractories and methods for making the same

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10407349B2 (en) 2015-04-24 2019-09-10 Corning Incorporated Bonded zirconia refractories and methods for making the same

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