JP4475724B2

JP4475724B2 - Method for manufacturing amorphous refractory having a close-packed structure excellent in strength and spall resistance

Info

Publication number: JP4475724B2
Application number: JP2000082940A
Authority: JP
Inventors: 章弘新保; 剛松井; 利弘礒部; 英俊神尾
Original assignee: Nippon Steel Corp; Krosaki Harima Corp
Current assignee: Nippon Steel Corp; Krosaki Harima Corp
Priority date: 2000-03-23
Filing date: 2000-03-23
Publication date: 2010-06-09
Anticipated expiration: 2020-03-23
Also published as: JP2001261456A

Description

【０００１】
【発明の属する技術分野】
本発明は、金属精錬用等の窯炉に使用される不定形耐火物の製造方法に関する。
【０００２】
【従来の技術】
不定形耐火物は省エネルギー、省力化の観点から定形耐火物に替わり金属精錬用等の窯炉に広く使用されている。しかしながら真空脱ガス、溶鋼鍋精錬および連続鋳造等の技術向上から高級鋼種が精錬されるようになり、操業温度上昇や溶鋼接触時間の延長等で不定形耐火物の寿命にとり厳しい環境となっている。さらに、ライニング部位によっては不定形耐火物に熱的衝撃や機械的衝撃が加わり、従来の材質改善だけでは寿命の延長が期待できない現状である。これに対し、特開昭61-215268 号公報に記載のように、不定形耐火物の構造を粒径10mm未満の母材に表面を被覆処理した粗大粒耐火物材を施し均一分散させ、強度・耐スポール性・粉体の充填性を向上させる技術が開示されている。この技術では粗大粒の均一分布が可能であるが、母材中の充填構造は考慮されておらず、母材からの強度低下、構造スポールに問題がある。また、特開昭61-97161号公報や特開平1-320265号公報には、原料粉の粒径分布がアンドレアゼン式を満たす耐火物をそれぞれ提示し、耐スポール性と耐磨耗性を向上させたことを開示している。これらの先行技術は、アンドレアゼン式を基に各原料粉体の質量配合を求めることを特徴としている。もともとアンドレアゼン式は粉体が密充填をとる充填式であるが、各粉体の比重が異なるため質量配合で粉を充填しても理想的な密充填構造がとれないことが考えられる。
【０００３】
従って、不定形耐火物の既存技術においては原料粉の粒度構成を基にした密充填構造設計の材料はない。
【０００４】
【発明が解決しようとする課題】
高温中での熱的衝撃や機械的衝撃が不定形耐火物に働く場合、材料中の欠陥等に応力集中が発生し、その結果亀裂が発生する。さらに、衝撃が繰り返されると亀裂は伸展し、不定形耐火物が損傷・破壊されてゆく。この亀裂を拡大させないために、粗大粒を混在させて亀裂伸展の抵抗作用を発現させて不定形耐火物の高耐用化を可能にしたが、母材中に発生した亀裂が溶鋼に接触する稼働面に露出していると溶鋼やスラグ浸潤を伴う構造的なスポールを誘発しやすい問題がある。
【０００５】
本発明は、上述した従来の不定形耐火物の問題を解決すべく発明されたものであり、不定形耐火物の母材中の亀裂発生・伸展を抑制し、さらに強度・耐スポール性を向上させる不定形耐火物の製造方法を提供することを目的とする。
【０００６】
【課題を解決するための手段】
本発明の不定形耐火物はかかる状況に鑑みなされたものである。その要旨とするところは、（１）アルミナを含有する不定形耐火物の製造方法において、前記不定形耐火物はアルミナ−マグネシア質不定形耐火物、又は、アルミナ−スピネル質不定形耐火物であって、粒径10mm以上の粗大粒を除いた耐火骨材の粒径分布を複数に分け、それらの体積配合割合を、前記複数に分けた粒径分布毎にアンドレアゼン分布式
P=100(X/D)ⁿ
D:最大径
P:粒径Ｘ以下の粒子％
n=0.15〜0.35
を基に算出し、当該算出された粒度分布毎の体積配合割合から、前記複数に分けた粒径分布毎に予め添加質量割合が定められた耐火骨材の体積配合割合への換算値を差し引くことにより、残部の耐火骨材の粒径分布毎の体積割合を定めて、耐火骨材の配合割合を決定して配合することを特徴とする強度および耐スポール性に優れた密充填構造を有する不定形耐火物の製造方法である。特に、（２）アルミナーマグネシア質不定形耐火物の場合は、粒径10mm未満の耐火骨材が、前記複数に分けた粒径分布毎に予め添加質量割合が定められた耐火骨材であるマグネシア、シリカ、及びアルミナセメントと、残部のアルミナとからなり、質量％でマグネシア：3 ％〜15％、シリカ：0.2 ％〜1.5 ％、アルミナセメント：4 ％〜12％を含有することを特徴とし、さらに（３）アルミナースピネル質不定形耐火物の場合は、粒径10mm未満の耐火骨材が、前記複数に分けた粒径分布毎に予め添加質量割合が定められた耐火骨材であるスピネル及びアルミナセメントと、残部のアルミナとからなり、質量％で、スピネル：10％〜40％：アルミナセメント：4 ％〜15％を含有することを特徴する不定形耐火物の製造方法である。
【０００７】
【発明の実施の形態】
本発明では、アルミナを含有する不定形耐火物において、粒径10mm以上の粗大粒を除いた耐火骨材の粒径分布を複数に分けた際に、分類したそれらの体積配合がアンドレアゼン分布式を基に定められ母材が密充填構造になっていることが特徴である。先ず、母材中の耐火骨材の粒径分布を複数に分けるとは、それぞれの耐火骨材をあらかじめ２種類以上の平均粒径のグループに分類することを意味する。次に、アルミナを含有する不定形耐火物中の10mm以上の粗大粒を除いた耐火骨材の総体積量を材料設計の見地から定めておく。その総量100 体積部に対して、各平均粒径の耐火骨材の体積割合をアンドレアゼン分布式により算出する。先述したように、耐火物の従来技術では本式を適用して質量割合を求めているが、これは同じ比重で平均粒径が幾つかに分類できる粉が閉空間を充填する場合に適している。しかしながら、実際の耐火物は比重の異なる複数種類の粉体を充填するため、体積割合として算出した方がより密充填構造をとることが可能となる。ここでアンドレアゼン分布式とは、構成する各粒子径が連続的に変化する連続粒子径において、その粒子径が密充填をとる時の充填式として知られ、下式のようになる。
【０００８】
P=100(X/D)ⁿ
ここで、D ：最大径、P ：粒子径X 以下の割合% 、n ：係数
本発明のように耐火骨材の粒径が２種類以上に分類される場合は、最初に一番大きな粒径(D) グループと二番目に大きい粒径(X) グループに分け、これらの粒径をアンドレアゼン式に代入し、二番目に大きい粒子径以下全体の体積割合(P) を求める。次に、３種類以上に分類される場合は、二番目に大きい粒子径以下を大小の２グループに分け先述と同じ要領で算出し、この操作を順次繰り返す。これより既知の平均粒径の各耐火骨材に対する体積割合を求めることができる。さらに、耐火骨材の中で特定の粉の粒径と添加量が予め定まっている場合でも、残部をアンドレアゼン式にて定めることを可能にする。例えば、前記（２）および（３）に記載のアルミナーマグネシア質とアルミナースピネル質不定形耐火物についてそれぞれ説明する。アルミナーマグネシア質不定形耐火物の場合、マグネシアが5 質量％以上であれば、耐火骨材中のアルミナとマグネシアが熱間で反応し耐溶損性向上に役立つスピネルが生成することが知られている。この不定形耐火物は耐火骨材が主としてアルミナで構成されているので、マグネシアの添加量が生成スピネルの量を決定する。一方、マグネシアが15質量% を超えると未反応マグネシアが焼結体中に残り、低強度や水和反応を引き起こしやすくなるので、本発明では適量のスピネル相が生成する量に対してマグネシアを5 〜15質量% と定めた。また、シリカはスピネル反応を促進させる目的で添加する。添加量0.2 〜1.5 質量% に対して、0.2 質量% より少ない場合スピネル反応を促進する働きが弱く、1.5 質量% より多いと熱間強度が低下する。さらに、アルミナセメントは母材あるいはそれと粗大粒を連結させる作用がある。母材中に一様に分布する量として、4 〜12質量% がアルミナーマグネシア質不定形耐火物には最適である。このように新たに生成する相の生成量のコントロールや、ある目的で機能を付与させる場合、それに関与する粉体量と粒径を定める必要がある。ここで、事前に添加量（体積）が決まる粉体とこれと同じ粒径で他の耐火骨材の体積割合は、上述のアンドレアゼン分布式で求めた体積割合から既知の粉体が占める体積部を差し引いて求めればよい。次に、アルミナースピネル質不定形耐火物は、耐火物原料となるスピネル粉の量が、耐溶損性の観点から適正添加量が予め求まる。例えば、スピネル粉が10質量% より少ないと耐溶損性に劣り、40質量% を超えると熱間弾性率が高く熱衝撃に弱くなるので10〜40質量% とする。さらに、アルミナセメントが4 質量% より少ないと部材の強度低下を引き起こし、15質量% より多いと溶損性に優れる耐火骨材の占める割合が小さくなり耐溶損性に劣る不定形耐火物となるので、4 〜15質量% とする。従って、スピネル粉やアルミナセメントの粒子径と同じ他の耐火物骨材の体積割合は、アンドレアゼン分布式で求めた体積割合から既知のスピネル粉が占める体積部を差し引いて求めればよい。
【０００９】
ここで、アンドレアゼン分布式の係数ｎを0.15〜0.35と設定したのは、最小粒子径側の粒子が適当な大きさとなり粉体が均一分散すること、かつ不定形耐火物の施工時に使用する水分が乾燥して蒸発する際の気孔通路が確保できる等効率的な密充填構造が形成できるからである。係数ｎが0.35より大きくなると最小粒子径が大きすぎるため粉体が均一分散せず、かつ比較的大きな気孔が分布する傾向のため、その結果密充填構造がとれず強度の低い構造体となる。一方、係数ｎが0.15より小さくなると最小粒子径側の粒子が小さくなり、水蒸気が抜ける気孔通路が小さくなりすぎる。このため、不定形耐火物の使用時に残留水分による爆裂を誘発しやすくなる。なお、本発明において、アンドレアゼン分布式に基づく体積割合の算出に、粒径10mm以上の粗大粒を含めなかったのは、母材すなわち粒径10mm以下の耐火骨材領域部の方が不定形耐火物全体の強度・スポール向上に大きく影響するためである。
【００１０】
【実施例】
（実施例１）
表１に示す原料粉をアンドレアゼン分布式にて配合を算出した。具体的には、質量％で粗大粒アルミナ (粒径：15±5mm)を外掛けで20% 、そしてスピネル (粒径： 1mm以下)10%、微粉スピネル（粒径： 0.075mm以下)10%、アルミナセメント10% 等をあらかじめ設定し、残りの粗粒アルミナ、中粒アルミナ、微粉アルミナの質量割合を求めた。
【００１１】
最初にスピネル（粒径： 1mm以下) 、微粉スピネル（粒径： 0.075mm以下) 、アルミナセメントの質量割合を体積割合に換算した。換算式は下式の通りである。
（体積割合）＝（原料の質量割合）／100 ／（嵩比重）……（１）
本実施例１では、密充填の熱衝撃性に及ぼす影響を調査する目的のため、予め原料粉の粒度をある範囲内に整えた。
【００１２】
次に、粗大粒アルミナを除いた部を100 体積部とし、粗粒アルミナ、中粒アルミナ、微粉アルミナの体積割合をアンドレアゼン分布式の係数ｎ＝０．３として求める。先ず、粒径：1 〜5mm の原料粉の体積割合(P1)と粒径：1mm 以下の原料粉の体積割合（Ｐ２）を２グループに分ける。アンドレアゼン分布式よりＰ２は、
P2=100×(1/5)^0.3=61.7% ………（２）
したがって、Ｐ１すなわち粗粒アルミナは、
（粗粒アルミナ）＝P1＝ 100−61.7=38.3% ………（３）
となる。同様にして粒径：1 〜0.075mm の原料粉(P3)と粒径：0.075mm 以下の原料粉 (P4) の体積割合を求める。
【００１３】
P4=P2 ×(0.075/1)^0.3=28.4% ………（４）
となる。ここで、P4には微粉スピネルを2.7%とアルミナセメントを2.6%含むので微粉アルミナは、
（微粉アルミナ）＝P4−2.7 −2.6=23.1% ………（５）
となる。さらに、粒径：1 〜0.075mm の原料粉は、
P3=P2 −P4=33.3% ………（６）
となる。同様に、P3にはスピネルを2.7%含むので中粒アルミナは、
（中粒アルミナ）＝P3−2.7=30.6% ………（７）
となる。以上で求めた各原料粉の体積割合を式（１）により質量割合に換算し、粗粒・中粒・微粉アルミナの総質量から表１の太枠の質量割合を求めた。
【００１４】
アンドレアゼン分布式の係数ｎ=0.5の場合も上述と同様に体積割合から質量割合を求めた。ｎ=0.3とｎ=0.5それぞれの配合割合の不定形耐火物を350 ℃の温度で乾燥した後、圧縮試験を行い破壊強さを求めたところ、ｎ=0.3が33.2MPa に対しｎ=0.5のそれは21.3MPa と小さかった。ｎ=0.3の方が密充填構造を有したため圧縮強さが大きかった。
【００１５】
【表１】

【００１６】
（実施例２）
アンドレアゼン分布式の係数ｎを0.1 、0.18、0.25、0.3 そして0.4 のそれぞれに対し、粒径：1 〜5mm の粗粒アルミナ、粒径：0.075 〜1mm の中粒アルミナ、そして粒径：0.075mm 以下の微粉アルミナをアンドレアゼン分布式により配合割合を算出し、アルミナーマグネシア質及びアルミナースピネル質不定形耐火物の見掛け気孔率、曲げ強さ、そして耐熱スポーリング性から最適なｎ値を求めた。式（１）において、マグネシアの嵩比重：3.6g/cm³、シリカの嵩密度：2g/cm³とし、その他は実施例１と同じ値を用いて体積割合を求めた。なお、粗大粒アルミナ（粒径：10-20mm ）、マグネシア、アルミナセメント、スピネルそしてシリカは表２のように予め設定した。耐スポーリング試験は、1500℃の温度で３時間加熱焼成した耐火物を、1500℃の温度で0.5 時間加熱した後、コンプレッサーより空気を吹き込み0.5 時間の強制空冷を行い熱衝撃を与える操作を６回繰り返した。冷却後、試料切断面の亀裂発生状況を観察し、5mm 以下の微小亀裂を◎、5 〜10mmの小亀裂を○、そして10mm以上の大亀裂を△とした。表２に示すように、いずれのアルミナ系不定形耐火物とも、ｎ値が0.15〜0.35の範囲で低気孔率で曲げ強さが高く、かつ耐熱スポーリング性が良好であった。このことから、本発明の不定形耐火物において、ｎ値が0.15〜0.35の範囲で母材が良好な充填構造が形成することがわかった。
【００１７】
【表２】

【００１８】
（実施例３）
表２のアルミナーマグネシア質不定形耐火物のサンプルＣ（ｎ値＝0.25) を、溶鋼取鍋の湯当たり部にてその耐用性を評価した。比較材としてｎ値＝0.4 のサンプルＦも同様に評価した。耐用性として、鍋の溶鋼受鋼から排鋼を1 チャージ (ch) として50チャージ (ch) 終了後の湯当たり部の残厚から損耗速度を求めた。その結果、サンプルＣが2.3mm/chに対し、比較材サンプルＦのそれは4.2mm/chであった。より密充填構造を有するサンプルの方が耐用性が良好であった。
【００１９】
（実施例４）
表２のアルミナースピネル質不定形耐火物のサンプルＩ（ｎ値＝0.25) を、溶鋼取鍋の側壁部にてその耐用性を評価した。比較材としてｎ値＝0.4 のサンプルＬも同様に評価した。耐用性として、鍋の溶鋼受鋼から排鋼を1 チャージ (ch) として50チャージ (ch) 終了後の湯当たり部の残厚から損耗速度を求めた。その結果、サンプルＩが0.2mm/chに対し、比較材サンプルＬのそれは0.4mm/chであった。実施例３と同様に、より密充填構造を有するサンプルの方が耐用性が良好であった。
【００２０】
【発明の効果】
本発明の製造方法で製造された不定形耐火物は、以上の実施例の試験結果が示すように優れた耐用性が得られる。その結果、本発明の不定形耐火物は金属精錬容器の一つである溶鋼取鍋の湯当たり部や側壁部の寿命を延長し、耐火物原単位の低減等に寄与する。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing an amorphous refractory used in a furnace for metal refining and the like.
[0002]
[Prior art]
Amorphous refractories are widely used in kiln furnaces for metal refining in place of regular refractories from the viewpoint of energy saving and labor saving. However, high-grade steel grades have been refined due to technological improvements such as vacuum degassing, ladle refining and continuous casting, and it has become a severe environment for the life of amorphous refractories due to increased operating temperature and extended molten steel contact time. . In addition, depending on the lining part, thermal and mechanical impacts are applied to the irregular refractory, and it is not possible to expect an extension of the life only by improving the conventional material. On the other hand, as described in JP-A-61-215268, the structure of the irregular refractory is uniformly dispersed by applying a coarse refractory material whose surface is coated on a base material having a particle diameter of less than 10 mm,・ Technologies for improving the spall resistance and powder filling properties are disclosed. Although this technique enables uniform distribution of coarse grains, the filling structure in the base material is not taken into consideration, and there are problems with strength reduction from the base material and structural spars. In addition, JP-A-61-97161 and JP-A-1-320265 show refractories that satisfy the Andreazen formula in the particle size distribution of the raw powder, thereby improving the spall resistance and wear resistance. Disclosed. These prior arts are characterized in that mass blending of each raw material powder is obtained based on the Andreazen formula. Originally, the Andreazen method is a packing type in which powders are closely packed, but since the specific gravity of each powder is different, it is considered that an ideal close-packed structure cannot be obtained even if powders are filled by mass blending.
[0003]
Therefore, in the existing technology for amorphous refractories, there is no material with a tightly packed structure design based on the particle size structure of the raw material powder.
[0004]
[Problems to be solved by the invention]
When a thermal shock or mechanical shock at high temperatures acts on an irregular refractory, stress concentration occurs in defects in the material, resulting in cracks. In addition, when the impact is repeated, the crack expands, and the amorphous refractory is damaged and destroyed. In order to prevent this crack from spreading, coarse grains were mixed to develop the resistance to crack extension, enabling high durability of the amorphous refractory. When exposed to the surface, there is a problem that it is easy to induce structural spalls with molten steel and slag infiltration.
[0005]
The present invention was invented to solve the above-mentioned problems of the conventional amorphous refractories, suppressing the occurrence of cracks and extension in the base material of the irregular refractories, and further improving the strength and spall resistance. and to provide a method for producing castable refractory that is.
[0006]
[Means for Solving the Problems]
The amorphous refractory of the present invention has been made in view of such a situation. The gist of the invention is (1) In the method for producing an amorphous refractory containing alumina, the amorphous refractory is an alumina-magnesia amorphous refractory or an alumina-spinel amorphous refractory. The particle size distribution of the refractory aggregate excluding coarse particles with a particle size of 10 mm or more is divided into a plurality of parts, and the volume blending ratio thereof is an Andreasen distribution formula for each of the divided particle size distributions.
P = 100 (X / D) ⁿ
D: Maximum diameter
P:% of particle diameter X or less
n = 0.15-0.35
And based on the calculated volume mixing ratio for each particle size distribution, subtract the converted value to the volume mixing ratio of the refractory aggregate for which the added mass ratio is determined in advance for each of the plurality of particle size distributions By determining the volume ratio for each particle size distribution of the remainder of the refractory aggregate, the mixture ratio of the refractory aggregate is determined and blended, and has a tightly packed structure with excellent strength and spall resistance This is a method for producing an amorphous refractory. In particular, in the case of (2) alumina-magnesia amorphous refractory, the refractory aggregate having a particle size of less than 10 mm is a refractory aggregate in which the added mass ratio is determined in advance for each of the plurality of particle size distributions. magnesia consists silica, and alumina cement, and the remainder of alumina, magnesia mass%: 3% to 15%, silica: 0.2% to 1.5%, alumina cement: wherein that you containing 4% to 12% (3) In the case of an alumina-spinel amorphous refractory, the refractory aggregate with a particle size of less than 10 mm is a refractory aggregate with a pre-determined mass ratio for each of the divided particle size distributions. consists of a certain spinel and alumina cement, with the remainder of the alumina, by mass%, spinel: 10% to 40%: alumina cement: in the manufacturing method of monolithic refractories which features that you containing 4% to 15% is there.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
In the present invention, in the amorphous refractory containing alumina, when the particle size distribution of the refractory aggregate excluding coarse particles having a particle size of 10 mm or more is divided into a plurality, the classified volume composition is an Andreasen distribution formula. The base material is characterized in that it has a close-packed structure. First, dividing the particle size distribution of the refractory aggregates in the base material into a plurality means that the respective refractory aggregates are classified into groups of two or more average particle diameters in advance. Next, the total volume of the refractory aggregate excluding coarse particles of 10 mm or more in the amorphous refractory containing alumina is determined from the viewpoint of material design. The volume ratio of the refractory aggregate of each average particle diameter is calculated by the Andreazen distribution formula with respect to 100 parts by volume of the total amount. As described above, in the conventional technology of refractory, the mass ratio is obtained by applying this formula, but this is suitable when powder with the same specific gravity that can be classified into several average particle sizes fills the closed space. Yes. However, since an actual refractory is filled with a plurality of types of powders having different specific gravities, a more densely packed structure can be obtained by calculating the volume ratio. Here, the Andreasen distribution equation is known as a packing equation when the particle size is close packed in a continuous particle size in which each particle size continuously changes, and is represented by the following equation.
[0008]
P = 100 (X / D) ⁿ
Here, D: maximum diameter, P: percentage% of particle diameter X or less, n: coefficient When the particle size of the refractory aggregate is classified into two or more types as in the present invention, the largest particle size is the first. Divide into (D) group and second largest particle size (X) group, and substituting these particle sizes into the Andreasen equation to find the volume fraction (P) of the whole below the second largest particle size. Next, when it is classified into three or more types, the second largest particle size or less is divided into two large and small groups and calculated in the same manner as described above, and this operation is sequentially repeated. From this, the volume ratio for each refractory aggregate having a known average particle diameter can be determined. Furthermore, even when the particle size and the amount of the specific powder in the refractory aggregate are determined in advance, the remainder can be determined by the Andreazen method. For example, the alumina-magnesia and the alumina-spinel amorphous refractories described in (2) and (3) will be described. In the case of alumina-magnesia amorphous refractories, if magnesia is 5% by mass or more, it is known that alumina and magnesia in the refractory aggregate reacts hot to produce spinel that helps improve resistance to melting. Yes. In this amorphous refractory, since the refractory aggregate is mainly composed of alumina, the amount of magnesia added determines the amount of spinel produced. On the other hand, when magnesia exceeds 15% by mass, unreacted magnesia remains in the sintered body and easily causes low strength and hydration reaction. It was defined as ˜15% by mass. Silica is added for the purpose of promoting the spinel reaction. When the amount is less than 0.2% by mass relative to the added amount of 0.2 to 1.5% by mass, the function of promoting the spinel reaction is weak, and when it is more than 1.5% by mass, the hot strength decreases. Furthermore, the alumina cement has an effect of connecting the base material or coarse particles with the base material. As an amount uniformly distributed in the base material, 4 to 12% by mass is optimal for alumina-magnesia amorphous refractories. As described above, when the amount of newly generated phase is controlled or when a function is given for a certain purpose, it is necessary to determine the amount of powder and the particle size involved in the function. Here, the volume ratio of the powder whose addition amount (volume) is determined in advance and the other refractory aggregate with the same particle size is the volume occupied by the known powder from the volume ratio determined by the above-described Andreasen distribution formula. What is necessary is just to subtract the part. Next, for the alumina-spinel amorphous refractory, the appropriate amount of spinel powder as the refractory raw material is determined in advance from the viewpoint of resistance to erosion. For example, if the spinel powder is less than 10% by mass, the melt resistance is inferior, and if it exceeds 40% by mass, the hot elastic modulus is high and weak against thermal shock. Furthermore, if the amount of alumina cement is less than 4% by mass, the strength of the member will be reduced, and if it is more than 15% by mass, the proportion of the refractory aggregate with excellent melt resistance will be small, resulting in an amorphous refractory with poor melt resistance. 4 to 15% by mass. Therefore, the volume ratio of other refractory aggregates having the same particle diameter as that of spinel powder or alumina cement may be obtained by subtracting the volume part occupied by the known spinel powder from the volume ratio obtained by the Andreasen distribution formula.
[0009]
Here, the coefficient n of the Andreasen distribution equation is set to 0.15 to 0.35 because the particles on the minimum particle diameter side have an appropriate size and the powder is uniformly dispersed, and is used for the construction of the irregular refractory. This is because it is possible to form an efficient close-packing structure that can secure a pore passage when moisture dries and evaporates. When the coefficient n is larger than 0.35, the minimum particle diameter is too large, so that the powder is not uniformly dispersed and relatively large pores tend to be distributed. As a result, a densely packed structure cannot be obtained, resulting in a structure having low strength. On the other hand, when the coefficient n is smaller than 0.15, the particles on the minimum particle diameter side become small, and the pore passage through which water vapor escapes becomes too small. For this reason, it becomes easy to induce the explosion by the residual water | moisture content at the time of use of an amorphous refractory. In the present invention, the calculation of the volume ratio based on the Andreasen distribution formula does not include coarse particles having a particle size of 10 mm or more, but the base material, that is, the refractory aggregate region having a particle size of 10 mm or less is more irregular. This is because it greatly affects the strength and spall improvement of the entire refractory.
[0010]
【Example】
Example 1
The blending of the raw material powders shown in Table 1 was calculated by the Andreazen distribution formula. Specifically, 20% by mass of coarse alumina (particle size: 15 ± 5mm) and 10% spinel (particle size: 1mm or less) 10%, fine spinel (particle size: 0.075mm or less) 10% Alumina cement 10% and the like were set in advance, and the mass ratio of the remaining coarse alumina, medium alumina, and fine alumina was determined.
[0011]
First, the mass proportions of spinel (particle size: 1 mm or less), fine spinel (particle size: 0.075 mm or less), and alumina cement were converted to volume proportions. The conversion formula is as follows.
(Volume ratio) = (mass ratio of raw material) / 100 / (bulk specific gravity) (1)
In Example 1, the particle size of the raw material powder was adjusted in a certain range in advance for the purpose of investigating the influence of close packing on the thermal shock resistance.
[0012]
Next, the part excluding coarse-grained alumina is taken as 100 parts by volume, and the volume ratio of coarse-grained alumina, medium-grained alumina, and fine-grained alumina is determined as the coefficient n = 0.3 of the Andreasen distribution equation. First, the volume ratio (P1) of the raw material powder having a particle diameter of 1 to 5 mm and the volume ratio (P2) of the raw powder having a particle diameter of 1 mm or less are divided into two groups. From the Andreazen distribution equation, P2 is
P2 = 100 × (1/5) ^0.3 = 61.7% ……… (2)
Therefore, P1 or coarse-grained alumina is
(Coarse Alumina) = P1 = 100−61.7 = 38.3% (3)
It becomes. Similarly, the volume ratio of the raw material powder (P3) having a particle size of 1 to 0.075 mm and the raw material powder (P4) having a particle size of 0.075 mm or less is obtained.
[0013]
P4 = P2 × (0.075 / 1) ^0.3 = 28.4% ……… (4)
It becomes. Here, P4 contains 2.7% fine spinel and 2.6% alumina cement.
(Fine powder alumina) = P4−2.7 −2.6 = 23.1% ……… （5）
It becomes. Furthermore, the raw material powder with a particle size of 1 to 0.075mm is
P3 = P2 −P4 = 33.3% ……… （6）
It becomes. Similarly, P3 contains 2.7% spinel, so medium-grained alumina is
(Medium Alumina) = P3−2.7 = 30.6% ……… （7）
It becomes. The volume ratio of each raw material powder obtained above was converted into a mass ratio by the formula (1), and the mass ratio of the thick frame in Table 1 was calculated from the total mass of coarse particles, medium particles, and fine powder alumina.
[0014]
In the case of the coefficient n = 0.5 of the Andreasen distribution formula, the mass ratio was obtained from the volume ratio in the same manner as described above. After drying amorphous refractories with a blending ratio of n = 0.3 and n = 0.5 at a temperature of 350 ° C, a compression test was conducted to determine the breaking strength. As a result, n = 0.3 was 33.2 MPa and n = 0.5. It was as small as 21.3MPa. Since n = 0.3 had a tightly packed structure, the compressive strength was larger.
[0015]
[Table 1]

[0016]
(Example 2)
For the coefficient n of the Andreasen distribution formula, 0.1, 0.18, 0.25, 0.3 and 0.4, respectively, coarse particle alumina with particle size: 1-5mm, medium particle alumina with particle size: 0.075-1mm, and particle size: 0.075mm Calculate the blend ratio of the following fine powdered alumina by the Andreasen distribution formula, and find the optimum n value from the apparent porosity, bending strength, and heat-resistant spalling properties of alumina-magnesia and alumina-spinel amorphous refractories It was. In the formula (1), the volume ratio of magnesia was 3.6 g / cm ³ , the bulk density of silica was 2 g / cm ³ , and the other volume ratios were obtained using the same values as in Example 1. The coarse alumina (particle size: 10-20 mm), magnesia, alumina cement, spinel and silica were preset as shown in Table 2. In the spalling resistance test, the refractory heated and fired at 1500 ° C for 3 hours is heated at 1500 ° C for 0.5 hours, then blown with air from the compressor and subjected to forced air cooling for 0.5 hours to give a thermal shock 6 Repeated times. After cooling, the crack occurrence state on the cut surface of the sample was observed. A small crack of 5 mm or less was marked with ◎, a small crack of 5 to 10 mm was marked with ○, and a large crack of 10 mm or more was marked with Δ. As shown in Table 2, all of the alumina-based amorphous refractories had a low porosity, a high bending strength, and a good heat spalling property when the n value was in the range of 0.15 to 0.35. From this, it was found that in the amorphous refractory according to the present invention, a filling structure with a good base material is formed when the n value is in the range of 0.15 to 0.35.
[0017]
[Table 2]

[0018]
(Example 3)
The durability of the sample C (n value = 0.25) of the alumina-magnesia amorphous refractory shown in Table 2 was evaluated at the hot water contact portion of the molten steel ladle. Sample F having an n value = 0.4 was also evaluated in the same manner as a comparative material. As the durability, the wear rate was calculated from the remaining thickness of the hot metal after 50 charges (ch), with the discharged steel as 1 charge (ch) from the molten steel receiving steel of the pan. As a result, the sample C was 2.3 mm / ch while the comparative material sample F was 4.2 mm / ch. The sample having a tighter packed structure had better durability.
[0019]
Example 4
The durability of the sample I (n value = 0.25) of the alumina-spinel amorphous refractory shown in Table 2 was evaluated at the side wall of the molten steel ladle. As a comparative material, a sample L having an n value = 0.4 was also evaluated in the same manner. As the durability, the wear rate was calculated from the remaining thickness of the hot metal after 50 charges (ch), with the discharged steel as 1 charge (ch) from the molten steel receiving steel of the pan. As a result, the sample I was 0.2 mm / ch while the comparative sample L was 0.4 mm / ch. Similar to Example 3, the sample having a more closely packed structure had better durability.
[0020]
【The invention's effect】
The amorphous refractory manufactured by the manufacturing method of the present invention has excellent durability as shown by the test results of the above examples. As a result, the amorphous refractory according to the present invention extends the life of the hot water contact portion and the side wall portion of the molten steel ladle which is one of the metal refining vessels, and contributes to the reduction of the refractory unit.

Claims

In the method for producing an amorphous refractory containing alumina,
The amorphous refractory is an alumina-magnesia amorphous refractory or an alumina-spinel amorphous refractory,
Dividing the particle size distribution of the refractory aggregate excluding coarse particles with a particle size of 10 mm or more into multiple parts,
The volume blending ratio is determined for each of the plurality of divided particle size distributions by the Andreasen distribution formula P = 100 (X / D) ⁿ
D: Maximum diameter,
P: particles having a particle size X or less (%),
n = 0.15 to 0.35
Calculated based on the,
By subtracting a conversion value from the calculated volume mixing ratio for each particle size distribution to the volume mixing ratio of the refractory aggregate in which the added mass ratio is determined in advance for each of the divided particle size distributions, the remaining fire resistance Production of amorphous refractories having a tightly packed structure with excellent strength and spall resistance, characterized by determining the volume ratio of each aggregate particle size distribution and determining the blend ratio of the refractory aggregate Method.

The amorphous refractory is an alumina-magnesia amorphous refractory, and the refractory aggregate having a particle size of less than 10 mm is a refractory aggregate in which an addition mass ratio is determined in advance for each of the divided particle size distributions. characterized in that it contains 4% to 12%: magnesia, silica, and alumina cement consists of a balance of alumina, by mass%, magnesia 3% to 15%, silica: 0.2% to 1.5%, alumina cement The method for producing an amorphous refractory having a close-packed structure excellent in strength and spall resistance according to claim 1.

The amorphous refractory is an alumina-spinel amorphous refractory, and the refractory aggregate having a particle size of less than 10 mm is a refractory aggregate in which an addition mass ratio is determined in advance for each of the divided particle size distributions. consists of a spinel and alumina cement, with the remainder of the alumina, by mass%, spinel: 10% to 40%, alumina cement: strength and spalling of claim 1, wherein the containing 4% to 15% A method for producing an amorphous refractory having a tightly packed structure with excellent properties.