JP2672605C

JP2672605C -

Info

Publication number: JP2672605C
Authority: JP
Original assignee: Nippon Steel Corp
Current assignee: Nippon Steel Corp
Publication date: 1999-08-23

Description

【発明の詳細な説明】〔産業上の利用分野〕本発明は、溶銑の脱珪，脱燐，脱硫などの溶銑予備処理に使用する鍋，浸漬槽
，インジェクションランスなどの耐火構造体の稼働部を成形する不定形耐火物に
関する。〔従来の技術〕例えば上記浸漬槽のフリーボードなどの芯金入り耐火構造体は、第１図に示す
ように、スタッド３を設けた鉄管，鉄筋，鉄芯等の芯金２を有し、この芯金２を
例えば、シャモット質，アルミナ質，スピネル質，ＭｇＯ質，Ａｌ₂Ｏ₃−ＳｉＣ
質，Ａｌ₂Ｏ₃−ＳｉＣ質等の不定形耐火物１で被覆成形した構造になっている。〔発明が解決しようとする課題〕ところが、この溶銑予備処理稼働部を構成する不定形耐火物は亀裂発生が起こ
り易く、亀裂が一旦発生すると、その伝播，拡大が早く、地金を耐火構造体に侵
入させてしまう。その結果、芯金を溶損させ該不定形耐火物を脱落させてしまう
等、該耐火構造体の寿命を著しく短いものにしていた。上述のような不定形耐火物の脱落の原因である亀裂の発生は、従来から熱スポ
ーリングに伴うものと考えられており、そのため、稼働部の耐火物としては線膨
張係数が小さく、熱衝撃抵抗性に優れた耐火材料の適用が種々検討されたが、亀
裂発生防止の効果は小さく、問題解決に至っていない。本発明において解決すべき課題は、耐火構造体の芯金の熱膨張変形や機械的応力による動きに追随変形可能で、亀裂の発生を防止できる不定形耐火物を提供し
、これによって耐火構造体の長寿命化を図ることにある。〔課題を解決するための手段〕本発明は、このような耐火構造体における亀裂発生の主要因が、単純な熱サイ
クルに起因する熱スポーリングによるものではなく、芯金の熱膨張及び使用中の
振動や機械的衝撃、さらに溶銑，溶鋼による浮力に伴う芯金変形による影響が大
であるという知見に基づいて完成した。すなわち、本発明の溶銑予備処理用耐火構造体の不定形耐火物は、炭化珪素５
〜４０重量％、炭素材料１〜５重量％、ロー石及び／又は珪石原料を２〜３０重
量％，アルミナ系セメント結合材を５〜２０重量％，残部は実質的に骨材として
アルミナ系原料もしくはムライト原料からなる。〔作用〕本発明の不定形耐火物は、溶銑処理用の耐火構造体の芯金として通常用いられ
ているＳＳ４１鋼材と極めて近似した線膨張係数を有するロー石，珪石等の高膨
張性原料を配合することによって、芯金の膨張変形に追随変形するようになり、
これによって亀裂の発生を抑制し、発生した亀裂は熱間において閉塞してそれ以
上の伝播，拡大を防止するものである。即ち、アルミナ，炭素材料及び炭化珪素を加えたものに、２〜３０重量％の高
膨張性のロー石等のシリカ−アルミナ質、及び珪石等のシリカ質原料等を配合す
ることによって、ロー石あるいは珪石原料中のシリカ（ＳｉＯ₂）成分は、成形
，乾燥後の溶銑予備処理にて加熱されると、α−石英からβ−石英、さらにクリ
ストバライトへの変態を起こして、高温膨張と高残存膨張性を発揮する。このた
め、不定形耐火物施工成形体は芯金の熱膨張等にも追随変形し、亀裂発生，伝播
が防止される。また、亀裂が発生しても、高温下におけるＳｉＯ₂のブローチン
グ（ＳｉＯ₂ガラスの生成，融着）により亀裂の先端を閉塞することができる。しかし、シリカあるいはシリカ−アルミナ質原料の使用によりＳｉＯ₂成分の
ガラス化による不定形耐火物の低気孔化による炭素原料と炭化珪素原料粉末の酸化防止が図られるが、３０重量％超に使用量を増すと逆に耐スポーリング性及び
スラグに対する耐食性は著しく低下する。また、２重量％未満であると、前記作
用が得られない。また、本発明の不定形耐火物を構成する骨材としては、シャモット，ムライト
，電融アルミナ，焼結アルミナ，アンダリュサイト等のアルミナ系原料、マグネ
シア，スピネル，ジルコン，ジルコニア，溶融シリカ等の原料の他、前記のごと
く、ロー石あるいは珪石の使用により耐食性，耐スポーリング性がやや劣化する
ことから、それを補うため、特に炭素材料並びに炭化珪素を配合する。炭素材料は１〜５重量％配合することによって、スラグと濡れにくいことによ
る耐食性や、熱伝導が良いことによる耐スポーリング性の向上に寄与するもので
ある。炭素材料としては種々の炭素質材料が使用できるが、特に耐食性の点から
、天然や人造の黒鉛のような結晶質のもの、あるいはタール，ピッチ等の不定形
黒鉛等の黒鉛が好ましい。配合割合が５重量％超では、酸化損耗を受けた時、組織が粗（ポーラス）にな
り、かえって耐食性が悪くなる。一方、１重量％未満では、ほとんど耐食性の向
上に寄与せず、スラグの浸潤を起こし易くなるため好ましくない。また、炭化珪素は５〜４０重量％配合することによって、炭素材料の酸化を抑
制して炭素材料の高耐食性，高耐スポーリング性を発揮させるために配合される
が、４０重量％を超えると炭化珪素原料の酸化によりＳｉＯ₂を生成して耐食性
及び機械的強度の劣化を招くため好ましくない。また、５重量％未満であると不
定形耐火物の耐熱衝撃性を低下させ、スポーリングによる損傷を受け易くなるた
め、その効果が期待できない。また、バインダー（結合剤）としては、アルミナ系セメントを５〜２０重量％
配合することによって、前記各原料の均一混合と良好な結合を可能とするが、よ
り熱間強度を向上したい場合は低融点物質を生成し易いセメントを減量し、活性
アルミナ，シリカフラワー等の超微粉原料を２〜１０重量％配合してもよく、ヘ
キサメタリン酸ソーダ等分散剤を添加する。このバインダーの配合割合は５重量％未満であると熱間強度が低く、構造体として耐用性に劣るため好ましくない。
また、２０重量％を超えると熱間強度は増大するものの、耐食性は著しく低下し
、また、芯金との膨張にも追随できず、亀裂の発生も増大するため好ましくない
。〔実施例〕溶銑鍋内の溶銑（３４０ｔ，１４００℃）に下端開口部を所定深さ浸漬して、
上部を排気ダクト等に連通させた脱燐，脱硫処理用の円筒状のフリーボードの該
浸漬槽の内外壁を形成する耐火物について使用した。第１表のＮｏ．１〜９に本発明例の不定形耐火物の組成と特性及び使用結果を
示す。比較のために、ロー石，珪石等の原料を含まない従来の不定形耐火物（比
較例Ｎｏ．１）及び本発明の配合割合範囲外の不定形耐火物（比較例Ｎｏ．２〜
Ｎｏ．１１）の組成と特性及び使用結果を示す。なお、フリーボードの内径は２
９４０ｍｍ、外径は３６００ｍｍ、高さ８５００ｍｍ、内外壁各厚み２００ｍｍ
，１１０ｍｍ、芯金は円筒状であり、厚み２０ｍｍのＳＳ４１の鋼板である。第１表に見られるように、実施例１〜９の熱膨張特性は、芯金であるＳＳ４１
と略同等である。第２図には実施例４，６，７の熱膨張率（％）曲線を比較例１
及び芯金ＳＳ４１のそれぞれと比べて示す通り、本発明例が優れた特性と効果を
有することが分かる。〔発明の効果〕本発明の不定形耐火物は、以下の効果を奏するものである。１）芯金と略近い熱膨張係数を有するものであるので、芯金の熱膨張により発生
する構造体内の内部応力が極めて小さくなる。２）ロー石もしくは珪石の粒周辺には、他の骨材原料あるいは、マトリックスと
の膨張差から微細な欠陥（隙間）が生じ、亀裂の分散及び内部応力を抑制する。３）芯金の熱膨張による内部応力抑制及び応力吸収能向上に効果的であり、溶銑
処理用構造体としては不可欠な耐食性，耐熱衝撃性、さらには亀裂伝播が拡大し
難い特性等優れた効果をもたらす。DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a working part of a refractory structure such as a pot, a dipping tank, and an injection lance used for hot metal pretreatment such as desiliconization, dephosphorization, and desulfurization of hot metal. The present invention relates to an irregular-shaped refractory for molding a refractory. [Prior Art] For example, a refractory structure containing a metal core such as a freeboard of the above-mentioned immersion tank has a metal core 2 such as an iron tube, a reinforcing bar, and an iron core provided with a stud 3, as shown in FIG. This core 2 is made of, for example, chamotte, alumina, spinel, MgO, Al ₂ O ₃ —SiC
Quality has become coated molded structure monolithic refractory 1 such Al ₂ O ₃ -SiC quality. [Problems to be Solved by the Invention] However, the amorphous refractory constituting the hot metal pretreatment working part is liable to cracks, and once cracks occur, the propagation and expansion of the cracks are fast, and the ingot is connected to the refractory structure. Invade. As a result, the life of the refractory structure is significantly shortened, for example, the core metal is melted and the irregular refractory is dropped off. The occurrence of cracks, which are the cause of the detachment of irregular shaped refractories as described above, has conventionally been considered to be due to thermal spalling. Various applications of a refractory material having excellent resistance have been studied, but the effect of preventing the occurrence of cracks is small and the problem has not been solved. The problem to be solved in the present invention is to provide an irregular-shaped refractory which can be deformed to follow the movement of the core metal of the refractory structure due to thermal expansion deformation or mechanical stress, and which can prevent the occurrence of cracks. The purpose is to extend the service life. [Means for Solving the Problems] The present invention is based on the finding that the main factor of crack generation in such a refractory structure is not due to thermal spalling caused by a simple thermal cycle, but to thermal expansion and use of a cored bar. It was completed based on the knowledge that the influence of the core metal deformation due to the buoyancy of hot metal and molten steel was great, as well as the vibration and mechanical shock of the steel. That is, the amorphous refractory of the refractory structure for hot metal pretreatment of the present invention is made of silicon carbide 5
-40% by weight, 1-5% by weight of carbon material, 2-30% by weight of raw stone and / or silica material, 5-20% by weight of alumina cement binder, and the balance being substantially alumina material as aggregate Alternatively, it is made of mullite material. [Function] The amorphous refractory of the present invention is a high-expansion raw material such as lozenge or silica stone having a linear expansion coefficient extremely similar to SS41 steel which is generally used as a core metal of a refractory structure for treating hot metal. By blending, it will deform following the expansion deformation of the core metal,
As a result, the generation of cracks is suppressed, and the generated cracks are closed during hot to prevent further propagation and expansion. That is, by adding 2 to 30% by weight of a silica-alumina material such as a high-expansion lozenge and a siliceous raw material such as a silica stone to a material obtained by adding alumina, a carbon material and silicon carbide, Alternatively, when the silica (SiO ₂ ) component in the quartzite raw material is heated in the hot metal pretreatment after forming and drying, it undergoes transformation from α-quartz to β-quartz and further to cristobalite, resulting in high-temperature expansion and high residue. Exhibits swelling properties. For this reason, the irregularly shaped refractory molded article is deformed following the thermal expansion of the core metal, etc., thereby preventing crack generation and propagation. Further, even if a crack occurs, the tip of the crack can be closed by broaching (generation and fusion of SiO ₂ glass) of SiO _{2 at} a high temperature. However, the use of silica or silica-alumina raw material prevents the oxidation of the carbon raw material and the silicon carbide raw material powder by reducing the porosity of the amorphous refractory by vitrification of the SiO ₂ component. On the contrary, spalling resistance and corrosion resistance to slag are remarkably reduced. On the other hand, if the content is less than 2% by weight, the above effect cannot be obtained. Examples of the aggregate constituting the amorphous refractory of the present invention include alumina-based raw materials such as chamotte, mullite, fused alumina, sintered alumina, andalusite, and magnesia, spinel, zircon, zirconia, fused silica, and the like. In addition to the raw materials, as described above, the corrosion resistance and spalling resistance are slightly deteriorated due to the use of lozenge or silica stone. To compensate for such deterioration, a carbon material and silicon carbide are particularly blended. When the carbon material is blended in an amount of 1 to 5% by weight, it contributes to the improvement of corrosion resistance due to being hardly wet with slag and the improvement of spalling resistance due to good heat conduction. As the carbon material, various carbonaceous materials can be used. In particular, from the viewpoint of corrosion resistance, a crystalline material such as natural or artificial graphite, or graphite such as amorphous graphite such as tar or pitch is preferable. If the mixing ratio is more than 5% by weight, the structure becomes coarse (porous) when oxidized and worn, and the corrosion resistance is rather deteriorated. On the other hand, if it is less than 1% by weight, it hardly contributes to improvement of corrosion resistance and slag is easily infiltrated, which is not preferable. Also, silicon carbide is blended in an amount of 5 to 40% by weight to suppress oxidation of the carbon material and exhibit high corrosion resistance and high spalling resistance of the carbon material. Oxidation of the silicon carbide raw material generates SiO ₂ , resulting in deterioration of corrosion resistance and mechanical strength, which is not preferable. On the other hand, if the content is less than 5% by weight, the thermal shock resistance of the amorphous refractory decreases, and the refractory is easily damaged by spalling, so that the effect cannot be expected. Further, as a binder (binder), 5 to 20% by weight of an alumina cement is used.
The compounding enables uniform mixing and good bonding of the respective raw materials, but when it is desired to further improve the hot strength, the amount of cement that easily produces a low-melting substance is reduced, and activated alumina, silica flour, etc. The fine powder raw material may be blended in an amount of 2 to 10% by weight, and a dispersant such as sodium hexametaphosphate is added. If the compounding ratio of the binder is less than 5% by weight, the hot strength is low and the durability of the structure is poor, which is not preferable.
On the other hand, if the content exceeds 20% by weight, although the hot strength is increased, the corrosion resistance is remarkably reduced, and furthermore, it cannot follow the expansion with the cored bar, and the generation of cracks is undesirably increased. [Example] A lower end opening was immersed in hot metal (340t, 1400 ° C) in a hot metal pot to a predetermined depth,
The refractory material used to form the inner and outer walls of the immersion tank of a cylindrical freeboard for dephosphorization and desulfurization treatment whose upper part was communicated with an exhaust duct or the like was used. No. 1 in Table 1. 1 to 9 show the composition, characteristics and use results of the amorphous refractory of the present invention. For comparison, a conventional amorphous refractory (Comparative Example No. 1) containing no raw materials such as lozenge and silica stone and an amorphous refractory (Comparative Example Nos.
No. The composition, characteristics and use results of 11) are shown. The free board has an inner diameter of 2
940mm, outer diameter 3600mm, height 8500mm, inner and outer wall thickness 200mm
, 110 mm, the core metal is a cylindrical shape, and is a SS41 steel plate having a thickness of 20 mm. As can be seen from Table 1, the thermal expansion characteristics of Examples 1 to 9 are as follows:
Is approximately equivalent to FIG. 2 shows the thermal expansion coefficient (%) curves of Examples 4, 6, and 7 in Comparative Example 1.
As can be seen from comparison with each of the metal core SS41 and the core metal SS41, it can be seen that the examples of the present invention have excellent characteristics and effects. [Effect of the Invention] The amorphous refractory of the present invention has the following effects. 1) Since it has a thermal expansion coefficient substantially similar to that of the metal core, the internal stress in the structure caused by the thermal expansion of the metal core becomes extremely small. 2) A fine defect (gap) is generated around the grain of the raw stone or silica stone due to a difference in expansion from other aggregate raw materials or the matrix, thereby suppressing crack dispersion and internal stress. 3) It is effective in suppressing internal stress and improving stress absorption by thermal expansion of the core metal, and has excellent effects such as corrosion resistance and thermal shock resistance, which are indispensable as a structure for hot metal processing, and characteristics that crack propagation is difficult to expand. Bring.

【図面の簡単な説明】第１図は本発明の対象となる耐火構造体の一例を示す図である。第２図は本発
明の不定形耐火物の熱膨張曲線を示すグラフである。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing an example of a refractory structure to which the present invention is applied. FIG. 2 is a graph showing a thermal expansion curve of the amorphous refractory of the present invention.

Claims

[Claims] 1. 5 to 40% by weight of silicon carbide, 1 to 5% by weight of carbon material, 2 to 30% by weight of raw stone and / or silica material , 5 to 20% by weight of alumina-based cement binder , the balance being substantially aggregate An amorphous refractory for a refractory structure for hot metal pretreatment characterized by blending an alumina-based material or a mullite material.