【発明の詳細な説明】[Detailed description of the invention]
本発明は鋳造用ノズル等に使用される窒化物質
耐火物に関する。
従来、この種の用途の耐火物としては、アルミ
ナ―黒鉛質耐火物や溶融シリカ質耐火物が知られ
ている。しかしながら、アルミナ―黒鉛質のノズ
ルでは熱伝導率が高く、溶鋼の鋳込み中において
温度低下が原因と思われる鋼の付着やそれに伴な
う非金属介在物の析出によりノズル閉塞を招く欠
点があつた。しかも、熱膨張率が高く、耐スポー
リング性に欠けるという難点があつた。一方、溶
融シリカ質のノズルではマンガンを多く含む溶鋼
を鋳込むのに使用すると、溶損が激しく短期間で
使用できなくなる。
これに対し、本発明者は上記欠点を克服すべく
鋭意研究した結果、窒化ケイ素、窒化アルミニウ
ム及び炭素の化学組成とし、かつこれら成分の配
合割合を規制することによつて、熱膨張率が抵く
抑えられ、予熱せずにスポーリング発生を防止で
き、上記窒化物自体の濡れ難い性質と低熱伝導性
により溶鋼との濡れ性を改善する接触角を大きく
して溶鋼中の非金属介在物の付着、ノズル閉塞を
阻止でき、更に溶鋼に対する耐溶損性の良好な鋳
造用ノズル等に適した窒化物質耐火物を見い出し
た。
すなわち、本発明は重量割合にて、窒化ケイ素
40〜80％、窒化アルミニウム５〜45％及び炭素３
〜15％の化学成分からなることを特徴とするもの
である。
本発明に係る耐火物の主成分である窒化ケイ素
は熱膨張率の低減化、それ自体溶鋼に濡れ難い性
質と低熱伝導性を有する他、高温の熱影響により
炭素等と反応して金属炭化物の生成、窒素ガスの
放出によるカーテン形成（濡れ性の改善）に寄与
するものである。かかる窒化ケイ素の配合割合を
上記範囲に限定した理由は、その量を40重量％未
満にすると、窒化ケイ素の配合効果が十分期待で
きず、かといつてその量が80重量％を越えると、
他の耐火物成分の配合量が少なくなり、それらの
効果を十分生かすことができなくなるばかりか、
酸化によつて溶損し易く、非金属介在物と付着し
易い酸化ケイ素の量が多くなり、耐蝕性の低下、
濡れ性の悪化を招くからである。
本発明に係る耐火物の他の成分である窒化アル
ミニウムは耐蝕性の向上、熱膨張率の低減化と共
に、それ自体溶鋼に濡れ難い性質と低熱伝導性を
有する他、高温の熱影響により炭素等と反応して
金属炭化物の生成、窒素ガスの放出によるカーテ
ン形成（濡れ性の改善）に寄与するものである。
かかる窒化アルミニウムの配合割合を上記範囲に
限定した理由は、その量を５重量％未満にする
と、窒化アルミニウムの配合効果を十分期待でき
ず、かといつてその量が45重量％を越えると、酸
化によつて非金属介在物と付着し易いアルミナの
量が多くなり、濡れ性がかえつて悪化するからで
ある。
本発明に係る耐火物の他の成分である炭素は耐
スボーリング性の向上と、スラグパウダーに対す
る濡れ性を改善するために用いられる。かかる炭
素の配合割合を上記範囲に限定した理由は、その
量を３重量％未満にすると、炭素の配合効果を十
分期待できなくなり、かといつてその量が15重量
％を越えると、溶鋼との接触角を低下させて濡れ
易くし、かつ溶損され易い性質が顕在化するから
である。
次に、本発明の実施例を説明する。
実施例
下記表に示す成分組成の耐火原料粉100重量部
にフエノールレジン８重量部を添加し、充分ねつ
合し、更に造粒した。次いで、この造粒物をノズ
ル形状のゴム型に充填し、アイソタクテイツクプ
レス成形を行ない脱型した後、乾燥、焼成して連
続鋳造用浸漬ノズルを製造した。
しかして、得られた浸漬ノズルを鋳造用鋳型内
に浸漬し、アルミキルド鋼を連続鋳造し、鋳造後
のノズル孔内壁の溶損量及びノズル孔内壁への溶
鋼の接触角（濡れ性）を調べた。その結果を同表
にノズルの曲が強さ、気孔率等の物性を合わせて
併記した。また、表中には本発明の成分組成範囲
外の原料粉から前記と同様な方法で得た浸漬ノズ
ル（参考例１，２）、アルミナ―炭素質の浸漬ノ
ズル（比較例）の物性等についても併記した。
The present invention relates to a nitride refractory used for casting nozzles and the like. Conventionally, alumina-graphite refractories and fused silica refractories have been known as refractories for this type of use. However, alumina-graphite nozzles have a high thermal conductivity, and have the disadvantage of causing nozzle clogging due to steel adhesion and the accompanying precipitation of nonmetallic inclusions, which are thought to be caused by temperature drop during molten steel pouring. . Moreover, it had the disadvantages of a high coefficient of thermal expansion and a lack of spalling resistance. On the other hand, when a fused silica nozzle is used to cast molten steel containing a large amount of manganese, it suffers from severe melting and becomes unusable in a short period of time. On the other hand, as a result of intensive research to overcome the above-mentioned drawbacks, the inventors of the present invention found that the coefficient of thermal expansion could be reduced by adopting a chemical composition of silicon nitride, aluminum nitride, and carbon, and by regulating the blending ratio of these components. The non-metallic inclusions in the molten steel can be prevented by increasing the contact angle, which can prevent spalling without preheating and improve wettability with molten steel due to the hard-to-wet property and low thermal conductivity of the nitride itself. We have found a nitride refractory suitable for casting nozzles, etc., which can prevent adhesion and nozzle clogging, and has good erosion resistance against molten steel. That is, in the present invention, silicon nitride is
40-80%, aluminum nitride 5-45% and carbon 3
It is characterized by consisting of ~15% chemical components. Silicon nitride, which is the main component of the refractory according to the present invention, has a reduced coefficient of thermal expansion, is difficult to wet with molten steel, and has low thermal conductivity. This contributes to curtain formation (improvement of wettability) by generation and release of nitrogen gas. The reason for limiting the blending ratio of silicon nitride to the above range is that if the amount is less than 40% by weight, the effect of silicon nitride cannot be expected to be sufficient, whereas if the amount exceeds 80% by weight,
Not only will the amount of other refractory components reduced, making it impossible to fully utilize their effects, but
The amount of silicon oxide, which is easily damaged by oxidation and adheres to non-metallic inclusions, increases, resulting in a decrease in corrosion resistance.
This is because it leads to deterioration of wettability. Aluminum nitride, which is another component of the refractory according to the present invention, not only has improved corrosion resistance and a reduced coefficient of thermal expansion, but also has properties that are difficult to wet with molten steel and low thermal conductivity. This contributes to the formation of metal carbides and the formation of a curtain (improving wettability) by releasing nitrogen gas.
The reason why the proportion of aluminum nitride is limited to the above range is that if the quantity is less than 5% by weight, the effect of aluminum nitride cannot be expected to be sufficient, whereas if the quantity exceeds 45% by weight, oxidation This is because the amount of alumina, which tends to adhere to non-metallic inclusions, increases, and the wettability worsens. Carbon, which is another component of the refractory according to the present invention, is used to improve the sagging resistance and the wettability to slag powder. The reason why the blending ratio of carbon is limited to the above range is that if the amount is less than 3% by weight, the effect of carbon blending cannot be expected to be sufficient, while if the amount exceeds 15% by weight, it will not interact with the molten steel. This is because the contact angle is lowered, making it easier to wet, and the property of being easily eroded and damaged becomes apparent. Next, examples of the present invention will be described. Example 8 parts by weight of phenol resin were added to 100 parts by weight of refractory raw material powder having the composition shown in the table below, thoroughly kneaded, and further granulated. Next, this granulated material was filled into a nozzle-shaped rubber mold, subjected to isotactic press molding, removed from the mold, dried, and fired to produce a continuous casting immersion nozzle. The obtained immersion nozzle was immersed in a casting mold to continuously cast aluminum killed steel, and the amount of erosion on the inner wall of the nozzle hole after casting and the contact angle (wettability) of molten steel on the inner wall of the nozzle hole were investigated. Ta. The results are also listed in the same table along with physical properties such as nozzle bending strength and porosity. In addition, the table also shows the physical properties of immersed nozzles (Reference Examples 1 and 2) and alumina-carbon immersed nozzles (Comparative Example) obtained from raw material powder outside the composition range of the present invention in the same manner as above. Also listed.
【表】
上表から明らかな如く、本発明の耐火物からな
る浸漬ノズル（実施例）は従来のアルミナ―炭素
系の浸漬ノズルに比べて熱膨張率を低く抑えるこ
とができ、耐スポーリング性を改善できた。本発
明の耐火物からなる浸漬ノズルは溶鋼に対する接
触角が大きく濡れ難い性質を有すると共に、熱伝
導率が従来の浸漬ノズルに比べて著しく小さいた
めに溶鋼中の非金属介在物の付着、ノズル閉塞を
防止できた。これは、浸漬ノズルを構成する窒化
ケイ素や窒化アルミニウムの接触角が夫々130
゜，135゜で本質的に濡れ難く、かつその分解に
より窒素ガスのカーテンが生成されることによる
ものである。本発明の浸漬ノズルは窒化アルミニ
ウム等の配合により溶鋼に対する耐溶損性が優れ
ている。比較例の浸漬ノズルは上述の濡れ易い性
質と熱伝導率が大きいことから、同表の如く溶鋼
や非金属介在物によるノズル閉塞を起こした。な
お、本発明と同組成でも窒化アルミニウムが本発
明の目的とする範囲を越えた浸漬ノズル（参考例
１）では、その分解により生成したアルミナに起
因すると思われるノズル孔内壁への非金属介在物
の付着が大きくなつた。また、窒化ケイ素が本発
明の目的とする範囲を越えた浸漬ノズル（参考例
２）では、その酸化分解により多量生成したシリ
カに起因すると思われるノズル孔内壁の溶損が顕
著に現われた。
以上詳述した如く、本発明によれば予熱せずに
スポーリング発生を防止でき、かつ溶鋼中の非金
属介在物の付着によるノズル閉塞及び同溶鋼等に
よる溶損を著しく抑制でき、もつて高寿命、連続
鋳造が可能な鋳造用ノズルに適した窒化物質耐火
物を提供できるものである。[Table] As is clear from the above table, the immersion nozzle (Example) made of the refractory of the present invention can suppress the coefficient of thermal expansion lower than the conventional alumina-carbon based immersion nozzle, and has excellent spalling resistance. was able to improve. The immersed nozzle made of the refractory of the present invention has a large contact angle with molten steel and is difficult to wet, and has a significantly lower thermal conductivity than conventional immersed nozzles, resulting in the adhesion of non-metallic inclusions in the molten steel and nozzle clogging. could be prevented. This is because the contact angle of silicon nitride and aluminum nitride, which make up the immersion nozzle, is 130
This is because it is essentially difficult to wet at an angle of 135° and its decomposition produces a curtain of nitrogen gas. The immersion nozzle of the present invention has excellent erosion resistance against molten steel due to the combination of aluminum nitride and the like. Because the immersion nozzle of the comparative example had the above-mentioned wettability and high thermal conductivity, the nozzle was clogged by molten steel and nonmetallic inclusions as shown in the same table. In addition, in a submerged nozzle (Reference Example 1) in which the aluminum nitride content exceeds the target range of the present invention even though the composition is the same as that of the present invention, non-metallic inclusions may be formed on the inner wall of the nozzle hole, which is thought to be caused by alumina generated by its decomposition. The amount of adhesion has increased. In addition, in the immersion nozzle (Reference Example 2) in which the content of silicon nitride exceeded the range targeted by the present invention, there was significant melting damage on the inner wall of the nozzle hole, which was thought to be caused by a large amount of silica produced due to its oxidative decomposition. As detailed above, according to the present invention, it is possible to prevent the occurrence of spalling without preheating, and it is possible to significantly suppress nozzle clogging due to the adhesion of non-metallic inclusions in molten steel and melting loss due to the molten steel. It is possible to provide a nitride refractory suitable for casting nozzles that have a long life and are capable of continuous casting.