【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鋳造用
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。また、溶融シリカ質の耐火物
でスライデイングノズル装置の摺動盤や固定盤を
構成すると、地金や介在物が差し込んだ時の滑り
性が悪化し、摺動盤による円滑な溶鋼流量制御が
困難となる。
これに対して、本発明者は上記欠点を克服すべ
く鋭意研究した結果、窒化ホウ素、窒化ケイ素及
び炭素の化学組成とし、かつこれらの成分の配合
割合を規制することによつて、熱膨張率が低く抑
えられ、予熱せずにスポーリング発生を防止で
き、しかも上記窒化物自体の濡れ難い性質と低熱
伝導性及び窒素ガスの放出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防止でき、更に窒素ホウ
素の配合による固体潤滑作用により滑り性を改善
した鋳造用ノズル等に適した鋳造用窒化物質耐火
物を見い出した。
即ち、本発明は重量比にて窒化ホウ素45〜90
％、窒化ケイ素５〜40％及び炭素３〜15％の成分
組成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ホウ素
は耐蝕性の向上、熱膨張率の低減化と共にそれ自
体濡れ難い性質を有する他に、高温の熱影響によ
り炭素等と反応して金属炭化物等の主成、窒素ガ
スの放出によるカーテンの形成（濡れ性の改善）
に寄与し、更に固体潤滑作用を備える。かかる窒
化ホウ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、窒化ホウ素
の配合効果が十分期待できなくなり、かといつて
その量が90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
し易い酸化ホウ素の量が多くなり耐蝕性の低下を
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ケイ
素は熱膨張率の低減化に寄与し、更にそれ自体濡
れ難い性質を有すると共に高温の熱影響により炭
素等と反応して金属炭化物等の生成、窒素ガスの
放出によりカーテンを形成して溶鋼に対する濡れ
性を改善するものである。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５
重量％未満にすると、窒化ケイ素の配合効果を十
分期待できなくなり、かといつてその量が45重量
％を越えると、酸化によつて溶損し易い酸化ケイ
素の量が多くなり、耐蝕性の低下を招くからであ
る。
本発明に係る耐火物の他の成分である炭素は、
耐スポーリング性の向上と、スラグパラダーに対
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するからで
ある。
次に本発明の実施例を説明する。
実施例 １〜３
下記表に示す３種の成分組成の耐火原料粉100
重量部にフエノールレジン８重量部を夫夫添加
し、充分ねつ合し、更に造粒した。次いで、これ
ら造粒物をノズル形状のゴム型に充填し、アイソ
タクテイクプレス成形を行ない脱型した後、乾
燥、焼成して３種の連続鋳造用浸漬ノズルを製造
した。
しかして、得られた各浸漬ノズルを鋳造用鋳型
内に浸漬し、溶鋼を連続鋳造し、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
の曲げ強さ、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
料粉から得た浸漬ノズル（参考例）、アルミ―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 for casting used in 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. In addition, if the sliding plate or fixed plate of a sliding nozzle device is made of fused siliceous refractory, the slipperiness will deteriorate when metal or inclusions are inserted, making it difficult for the sliding plate to smoothly control the flow rate of molten steel. It becomes difficult. On the other hand, as a result of intensive research to overcome the above-mentioned drawbacks, the inventors of the present invention have developed a chemical composition of boron nitride, silicon nitride, and carbon, and by regulating the blending ratio of these components, the coefficient of thermal expansion has been reduced. It is possible to suppress the occurrence of spalling without preheating, and to increase the contact angle with molten steel, which improves wettability with molten steel due to the hard-to-wet property of the nitride itself, low thermal conductivity, and release of nitrogen gas. We have found a nitride refractory for casting that is suitable for casting nozzles and the like, which can prevent nonmetallic inclusions from clogging the nozzle, and has improved slipperiness due to the solid lubricating action of nitrogen-boron. That is, the present invention has boron nitride of 45 to 90% by weight.
%, silicon nitride 5-40%, and carbon 3-15%. Boron nitride, which is the main 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 by itself. Formation of a curtain by releasing nitrogen gas (improving wettability)
It also has a solid lubricating effect. The reason for limiting the blending ratio of boron nitride to the above range is that if the amount is less than 40% by weight, the effect of boron nitride cannot be expected to be sufficient; This is because not only will the amount of refractory components blended become smaller, making it impossible to take full advantage of their effects, but also the amount of boron oxide, which is easily eroded by oxidation, will increase, leading to a decrease in corrosion resistance. Silicon nitride, which is another component of the refractory according to the present invention, contributes to reducing the coefficient of thermal expansion, and also has properties that are difficult to wet by itself, and reacts with carbon etc. under the influence of high temperature heat to form metal carbides etc. , which improves the wettability of molten steel by forming a curtain by releasing nitrogen gas. The reason for limiting the blending ratio of silicon nitride to the above range is that the amount
If the amount is less than 45% by weight, the effect of silicon nitride cannot be fully expected, and if the amount exceeds 45% by weight, the amount of silicon oxide that is easily eroded by oxidation increases, resulting in a decrease in corrosion resistance. Because it invites you. Carbon, which is another component of the refractory according to the present invention, is
Used to improve spalling resistance and wettability to slag pallader. The reason for limiting the blending ratio of carbon to the above range is that if the amount is less than 3% by weight, a sufficient carbon blending effect cannot be expected, whereas if the amount exceeds 15% by weight, contact with molten steel may occur. This is because the corners are lowered, making it easier to get wet, and the material is more likely to be eroded and damaged. Next, examples of the present invention will be described. Examples 1 to 3 Refractory raw material powder 100 with the three component compositions shown in the table below
8 parts by weight of phenol resin was added to each part by weight, thoroughly kneaded, and further granulated. Next, these granules were filled into a nozzle-shaped rubber mold, subjected to isotactic press molding, removed from the mold, dried, and fired to produce three types of continuous casting immersion nozzles. Each of the obtained immersion nozzles was immersed in a casting mold to continuously cast molten steel, and the amount of erosion on the inner wall of the nozzle hole after casting and the contact angle (wettability) of the 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 bending strength and porosity of the nozzle. In addition, the table also lists the physical properties of an immersed nozzle (reference example) obtained from raw material powder outside the composition range of the present invention and an aluminum-carbon immersed nozzle (comparative example).
【表】
上記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ホウ素
や窒化ケイ素の接触角が夫々125゜，130゜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
明の浸漬ノズルは溶鋼に対する溶損性が優れてい
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
金属介在物の付着によるノズル閉塞を起こした。
なお、本発明と同成分組成でも、それら成分の配
合範囲が逸脱した浸漬ノズル（参考例）では低熱
膨張性や溶鋼に対する接触角の点では本発明のノ
ズルと変わらないが、熱伝導率が大きくなつた
り、溶鋼に対して溶損し易くなる。
また、上記表中の実施例１〜３の組成割合の原
料粉を用いてスライデイングノズル装置の摺動盤
と固定盤を造り、これらの摺動性を調べたとこ
ろ、窒化ホウ素の配合による固体潤滑作用によつ
て良好な滑り性を発揮でき、溶鋼の流量調整を円
滑に行なうことができた。
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、溶鋼中の非金属介
在物の付着によるノズル閉塞を防止でき、更に固
体潤滑作用に滑り性が良好で鋳造用ノズルやスラ
イデイングノズル装置の固定盤、摺動盤に適した
鋳造用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 made of the refractory of the present invention was able to suppress the coefficient of thermal expansion lower than the conventional alumina-carbon based immersion nozzle, and was able to improve the spalling resistance. . 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 boron nitride and silicon nitride, which constitute the immersion nozzle, have contact angles of 125° and 130°, respectively, making them essentially difficult to wet, and their decomposition produces a curtain of nitrogen gas. The immersion nozzle of the present invention has excellent erosion resistance against molten steel. Because the immersion nozzle of the comparative example had the above-mentioned easy wettability and high thermal conductivity, the nozzle was clogged due to adhesion of molten steel and nonmetallic inclusions as shown in the same table.
Note that even with the same component composition as the present invention, a submerged nozzle (reference example) in which the blending range of these components deviates from that of the present invention is the same as the nozzle of the present invention in terms of low thermal expansion and contact angle with molten steel, but the thermal conductivity is large. It becomes susceptible to rusting and melting damage from molten steel. In addition, when the sliding plate and fixed plate of a sliding nozzle device were made using raw material powders having the composition ratios of Examples 1 to 3 in the table above, and the sliding properties of these plates were investigated, it was found that the solid by blending boron nitride. The lubrication effect provided good sliding properties, and the flow rate of molten steel could be adjusted smoothly. As detailed above, according to the present invention, spalling can be prevented without preheating, nozzle clogging due to adhesion of non-metallic inclusions in molten steel can be prevented, and the solid lubricant has good sliding properties, making it suitable for casting. It is possible to provide a nitride refractory for casting suitable for fixed plates and sliding plates of nozzles and sliding nozzle devices.