JPH0515953A - Immersion nozzle for continuous casting - Google Patents
Immersion nozzle for continuous castingInfo
- Publication number
- JPH0515953A JPH0515953A JP19365791A JP19365791A JPH0515953A JP H0515953 A JPH0515953 A JP H0515953A JP 19365791 A JP19365791 A JP 19365791A JP 19365791 A JP19365791 A JP 19365791A JP H0515953 A JPH0515953 A JP H0515953A
- Authority
- JP
- Japan
- Prior art keywords
- nozzle
- immersion nozzle
- gas
- gas blowing
- continuous casting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Landscapes
- Continuous Casting (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、鋼の連続鋳造におい
て、溶鋼をタンディッシュからモールド内へ鋳込むため
に使用されるガス吹き込み型浸漬ノズルに関するもので
ある。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas injection type immersion nozzle used for casting molten steel from a tundish into a mold in continuous casting of steel.
【０００２】[0002]
【従来の技術】現在、連続鋳造においては、溶鋼を酸化
させることなくタンディッシュからモールド内に供給す
るために、浸漬ノズルが利用されている。浸漬ノズルの
材質としては、アルミナ及び炭素を主体とし、これに２
０ｗｔ％程度のシリカを含有するものが主流となってい
る。このような浸漬ノズルでは、鋳造時間の経過ととも
に鋼中析出物のアルミナ及び地金がノズル内壁に付着
し、激しい場合にはノズル閉塞を引き起こし鋳造を停止
する場合もあった。この問題を解決する手段の１つとし
て、例えば、特公昭５８−３４６７号公報に示されるよ
うに、浸漬ノズル内孔と同心円となる多孔質の筒状耐火
物（内孔体）を浸漬ノズル本体に内挿し、この多孔質耐
火物内壁からＡｒその他の不活性ガスを吹き込むことが
知られている。しかし、本方法により吹き込まれたＡｒ
ガスは、一部モールド内で浮上中に凝固界面に捕捉さ
れ、気泡として鋳片内に残留する。この気泡は、大きな
ものほど熱間圧延、冷間圧延後も圧着されず、鋼板表面
にふくれ欠陥として現れる。ここで、ふくれ欠陥とは熱
間圧延、冷間圧延後の鋼板表面に現れる欠陥で、幅１〜
４ｍｍ、長さ数ｍｍに***した、あるいはこれら数ｍｍ
の***が点状に連続し３００ｍｍにも渡って連なったも
のをいう。このふくれ欠陥は鋼板中の炭素濃度を極力低
下させた、例えば炭素濃度が５０ｐｐｍ以下の極低炭素
鋼において、製品中の固溶炭素を析出物として固定させ
るためにＴｉを添加させた鋼種にとりわけ多く発生し、
製品歩留まりの大幅な低下を招いている。そこで、浸漬
ノズルの閉塞防止を確実に享受しつつ、ふくれ欠陥の発
生を抑制するために、溶鋼トン当たり４Ｎｌ以下に制限
したＡｒと残余Ｎ2との混合ガスを用い、鋳片内部に捕
捉されるガス気泡に基づく１ｍｍφ以上のピンホール数
をトン当たり１０個以内に低減させる方法（特開昭６２
−３８７４７号公報）が報告され効果を発揮している。Immersion nozzles are currently used in continuous casting to feed molten steel into a mold from a tundish without oxidizing it. The material of the dipping nozzle is mainly alumina and carbon, and 2
Those containing about 0 wt% silica are the mainstream. In such a dipping nozzle, alumina and metal ingots deposited in steel adhere to the inner wall of the nozzle as the casting time elapses, and in severe cases, nozzle clogging may occur and casting may be stopped. As one of means for solving this problem, for example, as shown in Japanese Patent Publication No. 58-3467, a porous cylindrical refractory (inner hole body) which is concentric with the inner hole of the immersion nozzle is provided with a main body of the immersion nozzle. It is known to insert Ar and other inert gas from the inner wall of the porous refractory. However, Ar blown by this method
Part of the gas is trapped at the solidification interface while floating in the mold and remains in the slab as bubbles. The larger the bubbles, the more they are not pressed after hot rolling and cold rolling, and appear as swelling defects on the surface of the steel sheet. Here, the blistering defect is a defect that appears on the surface of the steel sheet after hot rolling or cold rolling, and has a width of 1 to 1.
4 mm, length of several mm, or several mm
It means that the ridges are continuous in a dot shape and extend over 300 mm. This swelling defect is caused especially in the steel type in which Ti is added in order to fix the solid solution carbon in the product as the precipitate in the extremely low carbon steel in which the carbon concentration in the steel sheet is reduced as much as possible, for example, in the extremely low carbon steel having the carbon concentration of 50 ppm or less. Many occur,
This leads to a significant decrease in product yield. Therefore, in order to reliably enjoy the prevention of blockage of the immersion nozzle and to suppress the occurrence of blistering defects, a mixed gas of Ar and the residual N 2 which is limited to 4 Nl or less per ton of molten steel is used and trapped inside the slab. A method of reducing the number of pinholes of 1 mmφ or more due to gas bubbles to 10 or less per ton (JP-A-62-62
No. 38,747) has been reported and is effective.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、浸漬ノ
ズルからＮ2ガスを吹き込んだ場合には、特に鋳造速度
が速くなりＮ2気泡が鋳片の奥深くまで持ち込まれ溶鋼
との接触時間が長くなると、溶鋼中に吸収され、既に存
在する以上に溶鋼中窒素濃度が増加する。この窒素成分
は、凝固段階及び冷却段階において種々の窒化物として
鋼材中に析出してくるため、薄鋼板の加工性、成形性に
支障をきたす恐れがあり、極力低いほうが好ましい。し
たがって、鋼材特性の一層の向上が望まれる今日にあっ
ては、窒素濃度が現状以上に増加した場合には、材質を
確保するために添加合金の量が増加し、精錬上のコスト
増加をまぬがれない。これらの問題点を鑑み、本発明
は、ノズル閉塞の防止に必要なガス吹き込み流量を確保
した上で、大幅な精錬コストの増加もなく、また鋼材の
材質を損ねることなく、常に安定してふくれ欠陥のない
加工用鋼板素材を鋳造できる連続鋳造用浸漬ノズルを提
供することを目的とするものである。However, when N 2 gas is blown from the immersion nozzle, the casting speed becomes particularly high, and N 2 bubbles are brought deep into the slab and the contact time with molten steel becomes long, It is absorbed in molten steel and the nitrogen concentration in molten steel increases more than it already exists. Since this nitrogen component precipitates in the steel material as various nitrides during the solidification step and the cooling step, it may impair the workability and formability of the thin steel sheet, and it is preferably as low as possible. Therefore, in the present day when further improvement of steel material properties is desired, when the nitrogen concentration increases beyond the current level, the amount of the additive alloy increases in order to secure the material, and the refining cost increase is avoided. Absent. In view of these problems, the present invention secures a gas blowing flow rate necessary for preventing nozzle clogging, does not significantly increase refining cost, and does not damage the material of the steel material, and constantly blisters. An object of the present invention is to provide a dipping nozzle for continuous casting that can cast a steel sheet material for processing without defects.
【０００４】[0004]
【課題を解決するための手段】本発明は、アルミナ黒鉛
質ガス吹き込み型浸漬ノズルにおいて、ガス吹き込み部
にあたる内孔体のシリカ含有率を５ｗｔ％以下とし、且
つ使用前の冷間通気量を圧力１ｋｇｆ／ｃｍ2において
０．０５〜０．１Ｎｌ／ｍｉｎ／ｃｍ2に形成したこと
を特徴とする連続鋳造用浸漬ノズルに関するものであ
る。The present invention relates to an alumina-graphite gas-blowing type immersion nozzle, in which the silica content of the inner pores corresponding to the gas-blowing portion is 5 wt% or less, and the cold aeration amount before use is set to a pressure. The present invention relates to a continuous casting immersion nozzle, which is formed at 0.05 to 0.1 Nl / min / cm 2 at 1 kgf / cm 2 .
【０００５】[0005]
【作用】発明者等は、ノズル閉塞を防止するための浸漬
ノズルからのＡｒガス吹き込みは従来どおり積極的に実
施し、その上でふくれ欠陥につながらない熱延、冷延鋼
板用鋳片を鋳造できる連続鋳造用浸漬ノズルの研究開発
を続けてきた。鋳片内に捕捉された気泡は、大きなもの
ほど熱間圧延、冷間圧延後にふくれ欠陥につながり易
い。そこで、本発明者等は浸漬ノズル内孔体の劣化によ
るＡｒ気泡径の粗大化がふくれ欠陥発生の原因と考え、
特に欠陥発生率の高いＴｉを含有する極低炭素鋼を鋳造
した浸漬ノズルについて詳細な調査を行った。水中での
Ａｒガス吹き込み試験では、未使用内孔体の平均気泡径
が０．３ｍｍであるのに対し、Ｔｉを含有する極低炭素
鋼を鋳造した内孔体では平均気泡径が２．０ｍｍにも達
していた。また、気泡径が粗大化する原因を明らかにす
るために、浸漬ノズルから内孔体部を切り出し、溶鋼接
触面の組織観察及びＥＰＭＡによる面分析を行った。こ
れにより、内孔体中に含まれているシリカが溶鋼中のＴ
ｉにより還元され、組織中から消失することで、Ａｒ気
泡径が粗大化していることを見出した。したがって、Ｔ
ｉを含有する極低炭素鋼に発生するふくれ欠陥を防止す
るためには、内孔体中のシリカ含有率を０とし、生成す
るＡｒ気泡の粗大化を抑制することが有効となる。The inventors of the present invention can positively inject Ar gas from the dipping nozzle to prevent nozzle blockage as in the conventional case, and can cast a slab for hot-rolled or cold-rolled steel sheet that does not lead to blistering defects. We have continued research and development of immersion nozzles for continuous casting. The larger the bubbles trapped in the slab, the more easily they will lead to blistering defects after hot rolling and cold rolling. Therefore, the present inventors consider that the coarsening of the Ar bubble diameter due to the deterioration of the submerged nozzle inner hole causes the swelling defect,
Particularly, a detailed investigation was conducted on the immersion nozzle cast from an ultra-low carbon steel containing Ti, which has a high defect occurrence rate. In an Ar gas blowing test in water, the average pore diameter of the unused inner pores was 0.3 mm, whereas the average pore diameter of the inner pores cast from the ultra-low carbon steel containing Ti was 2.0 mm. Had also reached. In addition, in order to clarify the cause of the coarsening of the bubble diameter, the inner hole portion was cut out from the immersion nozzle, the structure of the molten steel contact surface was observed, and the surface analysis by EPMA was performed. As a result, the silica contained in the inner pores is
It was found that the Ar bubble diameter is coarsened by being reduced by i and disappearing from the tissue. Therefore, T
In order to prevent the blistering defect that occurs in the ultra low carbon steel containing i, it is effective to set the silica content in the inner pores to 0 and suppress the coarsening of the generated Ar bubbles.
【０００６】しかしながら、内孔体にシリカを含有しな
いアルミナ黒鉛質ノズル（以下、シリカレスノズルと略
す）を用いて溶鋼を鋳造した場合、内孔体に亀裂が発生
し長時間の使用に耐えない。そこで、本発明者等は種々
の実験、研究を繰り返し、シリカレスノズルに割れが発
生する機構を解明した。シリカレスノズルでは、低膨張
性のシリカを含まない内孔体の熱膨張率が高くなってい
るのに対し、浸漬ノズル本体には耐スポーリング性確保
の観点からシリカが添加されており、内孔体に比べて熱
膨張率が小さく抑えられている。その結果、内孔体は低
膨張のノズル本体から拘束され熱膨張できなくなるた
め、内孔体に圧縮応力が発生すると共に耐火物組織が引
き締まり緻密化する。これが原因となり、内孔体の通気
抵抗が増すため、Ａｒガスの吹き込み圧力が上昇し、ノ
ズルの割れ発生限界を超えることになる。したがって、
シリカレスノズルでは、鋳造時のＡｒガス吹き込み圧力
がノズルの割れ発生限界を超えないように、通気抵抗を
予め小さくしておく必要がある。However, when molten steel is cast by using an alumina graphite nozzle (hereinafter abbreviated as silica-less nozzle) that does not contain silica in the inner hole, cracks occur in the inner hole and it cannot withstand long-term use. .. Therefore, the present inventors have repeated various experiments and studies to elucidate the mechanism of cracking in the silicaless nozzle. In the silicaless nozzle, the coefficient of thermal expansion of the inner pore body that does not contain low-expansion silica is high, whereas silica is added to the immersion nozzle body from the viewpoint of ensuring spalling resistance. The coefficient of thermal expansion is smaller than that of the hole body. As a result, the inner hole body is constrained by the low expansion nozzle body and cannot be thermally expanded, so that compressive stress is generated in the inner hole body and the refractory structure is tightened and densified. Due to this, the ventilation resistance of the inner hole increases, so that the blowing pressure of Ar gas rises, and the cracking limit of the nozzle is exceeded. Therefore,
In the silicaless nozzle, it is necessary to reduce the ventilation resistance in advance so that the Ar gas blowing pressure during casting does not exceed the crack occurrence limit of the nozzle.
【０００７】そこで、シリカレスノズルの通気抵抗を下
げ、割れ発生を防止する方法について、以下に詳しく述
べる。本発明者等は、冷間状態で１ｋｇｆ／ｃｍ2の吹
き込み圧力をかけ、使用前のノズルに通気する単位面
積、単位時間当たりのＡｒガス流量を測定し、これをガ
ス吹き込み型浸漬ノズルの通気特性（通気抵抗）を示す
指標（以下、冷間通気量）として利用している。この冷
間通気量は鋳造時のＡｒガス吹き込み圧力と相関があ
り、冷間通気量が多いものほどＡｒガス吹き込み圧力は
小さくなる。したがって、シリカレスノズルでは使用前
ノズルの冷間通気量を従来ノズルよりも高い範囲に設定
し、鋳造時のＡｒガス吹き込み圧力が割れ発生限界を超
えないようにすることで、常に安定した割れ発生防止が
可能となる。なお、従来ノズルでは、シリカ消失による
気孔径及び気孔率増大を補償するために緻密な組織を有
する内孔体が使用され、見掛け気孔率で１８．０〜１
９．５％程度、冷間通気量で０．０２〜０．０４Nl／mi
n／cｍ2程度であった。Therefore, a method of lowering the ventilation resistance of the silicaless nozzle and preventing the occurrence of cracks will be described in detail below. The inventors of the present invention applied a blowing pressure of 1 kgf / cm 2 in a cold state, measured a unit area for aeration of a nozzle before use, and an Ar gas flow rate per unit time, and measured the ventilation rate of a gas injection type immersion nozzle. It is used as an index (hereinafter referred to as cold air flow rate) indicating the characteristic (air flow resistance). This cold air flow rate has a correlation with the Ar gas blowing pressure during casting, and the higher the cold air flow rate, the smaller the Ar gas blowing pressure. Therefore, in the silicaless nozzle, the cold air flow rate of the nozzle before use is set to a range higher than that of the conventional nozzle so that the Ar gas blowing pressure during casting does not exceed the crack generation limit, so that stable crack generation is always achieved. Prevention is possible. In the conventional nozzle, an internal pore body having a dense structure is used to compensate for an increase in pore size and porosity due to the disappearance of silica, and an apparent porosity of 18.0 to 1
About 9.5%, 0.02-0.04Nl / mi in cold air flow
It was about n / cm 2 .
【０００８】図１は、ノズルの冷間通気量と鋳造時のＡ
ｒガス吹き込み圧力の関係を示す。鋳造後の浸漬ノズル
をオフラインで試験したところ、割れ発生の限界圧力は
１．７ｋｇｆ／ｃｍ2程度であった。このため、浸漬ノ
ズルの割れ発生を防止するためには、図１から分かるよ
うに冷間通気量は０．０５Ｎｌ／ｍｉｎ／ｃｍ2以上に
する必要がある。また、使用前ノズルの冷間通気量を大
きくすると、必然的に内孔体の気孔径も大きくなり生成
するＡｒ気泡径が粗大化する。図２は、水中へのＡｒガ
ス吹き込み試験により求めた使用前ノズルの気泡径と冷
間通気量の関係を示す。この図から分かるように、冷間
通気量はＡｒ気泡が粗大化し始める０．１Ｎｌ／ｍｉｎ
／ｃｍ2以下にする必要がある。なお、冷間通気量の制
御については、浸漬ノズル内孔体に添加するバインダー
量を調整することで十分可能である。FIG. 1 shows the cold air flow rate of the nozzle and A at the time of casting.
The relationship of r gas blowing pressure is shown. When the immersion nozzle after casting was tested offline, the critical pressure for cracking was about 1.7 kgf / cm 2 . Therefore, in order to prevent cracking of the immersion nozzle, it is necessary to set the cold air flow rate to 0.05 Nl / min / cm 2 or more, as can be seen from FIG. Further, when the cold air flow rate of the pre-use nozzle is increased, the pore size of the inner hole body is inevitably increased and the diameter of the Ar bubble generated is coarsened. FIG. 2 shows the relationship between the bubble diameter of the nozzle before use and the cold air flow rate, which was obtained by an Ar gas blowing test into water. As can be seen from this figure, the cold air flow rate is 0.1 Nl / min when Ar bubbles start to coarsen.
/ Cm 2 or less. It should be noted that the control of the cold aeration amount can be sufficiently performed by adjusting the amount of the binder added to the immersion nozzle inner hole body.
【０００９】以上の方法で決定された冷間通気量を有す
るシリカレスノズルは、耐蝕性及び耐スポーリング性を
損ねることなく、内孔体の気孔率増大及び気孔径拡大を
抑制し、微細な気泡を安定して吹き込むことができるた
め、ふくれ欠陥防止に非常に有効な浸漬ノズルを提供で
きる。The silicaless nozzle having the cold air flow rate determined by the above method suppresses the increase in the porosity and the increase in the pore diameter of the inner pore body without impairing the corrosion resistance and the spalling resistance, and the Since bubbles can be stably blown in, it is possible to provide an immersion nozzle that is extremely effective in preventing blistering defects.
【００１０】アルミナは耐蝕性を付与する役割を持ち、
内孔体への好ましい配合率は３０〜８０ｗｔ％である。
３０ｗｔ％未満では耐蝕性が劣化し、８０ｗｔ％を超え
ると熱膨張率が大きくなり耐スポーリング性が低下する
ためである。また、耐蝕性の面から内孔体にシリカを含
有しないことが望ましいが、必要な場合には５ｗｔ％以
下に限って添加しても良い。これは、シリカ含有率が５
ｗｔ％を超えると、気孔率及び気孔径が増大し安定なＡ
ｒガス吹き込みができなくなるため、ふくれ欠陥が発生
するからである。Alumina has a role of imparting corrosion resistance,
The preferable blending ratio in the inner pore body is 30 to 80 wt%.
This is because if it is less than 30 wt%, the corrosion resistance deteriorates, and if it exceeds 80 wt%, the coefficient of thermal expansion increases and the spalling resistance decreases. Further, from the viewpoint of corrosion resistance, it is desirable that the inner pore body does not contain silica, but if necessary, it may be added in an amount of 5 wt% or less. It has a silica content of 5
If it exceeds wt%, the porosity and pore diameter increase and stable A
This is because it is impossible to blow the r gas, so that a blistering defect occurs.
【００１１】黒鉛は熱伝導率が極めて高く、また溶鋼と
非常に濡れ難い性質を有することから、本発明では耐蝕
性を低下させない範囲で黒鉛を添加し、溶鋼やパウダー
の浸漬ノズル気孔内への侵入を防止すると共に耐スポー
リング性を向上させる。黒鉛の配合範囲については５〜
５０ｗｔ％程度が好ましい。５ｗｔ％未満では耐スポー
リング性に劣り、５０ｗｔ％を超えると黒鉛の酸化や溶
鋼中への溶出により溶鋼及び溶融パウダーに対する耐蝕
性が低下する。また、高熱伝導率のためノズル詰まりを
生ずる恐れもある。Since graphite has a very high thermal conductivity and is very hard to wet with molten steel, graphite is added to the present invention within the range where the corrosion resistance is not lowered, and molten steel or powder is immersed in the pores of the immersion nozzle. Prevents intrusion and improves spalling resistance. About the blending range of graphite is 5
About 50 wt% is preferable. If it is less than 5 wt%, the spalling resistance is inferior, and if it exceeds 50 wt%, the corrosion resistance to molten steel and molten powder deteriorates due to the oxidation of graphite and the elution into molten steel. In addition, the high thermal conductivity may cause nozzle clogging.
【００１２】浸漬ノズル内孔体の基本的な構成成分は以
上であるが、この他にもノズル材質への添加物として既
に知られている材料を、本発明の効果を損なわない範囲
で含有させてもよい。その材料としては、例えば炭化珪
素、ジルコニア、ジルコン、各種金属粉等である。これ
ら構成成分から成る耐火物を用いて、ノズル内孔体を構
成する際、ノズル本体に関しても同一材料を使用するこ
とが望ましいが、溶鋼と接触しない部分に関しては、従
来のシリカを含有する組成の材料を用いることもでき、
また両者の中間的な材質を介在させることも可能であ
る。さらに、浸漬ノズル内孔体の厚みは一概に規定でき
るものではないが、浸漬ノズル厚みの１／２以下にする
ことが望ましい。１／２以上では耐スポーリング性を低
下させる。逆に薄くすると通気流量が安定せず、ガス吹
き込み効果が十分に得られなくなるため６ｍｍ以上が好
ましい。The basic constituent components of the inner hole of the submerged nozzle are as described above. In addition to these, other materials already known as additives to the nozzle material are contained within a range that does not impair the effects of the present invention. May be. Examples of the material thereof include silicon carbide, zirconia, zircon, and various metal powders. It is desirable to use the same material for the nozzle body when constructing the nozzle inner hole body using a refractory composed of these constituents, but for the part that does not come into contact with the molten steel, the conventional composition containing silica Materials can also be used,
It is also possible to interpose a material intermediate between the two. Further, although the thickness of the submerged nozzle inner hole cannot be unconditionally specified, it is preferably set to 1/2 or less of the submerged nozzle thickness. If it is 1/2 or more, the spalling resistance is deteriorated. On the contrary, if the thickness is made thin, the ventilation flow rate is not stable and the gas blowing effect cannot be sufficiently obtained, so 6 mm or more is preferable.
【００１３】[0013]
【実施例】以下に、実施例及び比較例を挙げて、本発明
について説明する。表２に示した原料含有物に樹脂バイ
ンダーとしてフェノール樹脂を添加して混練し、アイソ
スタティックプレスを用いて１．０ｔ／ｃｍ2の圧力で
ノズル形状に成形した。EXAMPLES The present invention will be described below with reference to Examples and Comparative Examples. Phenol resin was added as a resin binder to the raw material-containing materials shown in Table 2 and kneaded, and was molded into a nozzle shape using an isostatic press at a pressure of 1.0 t / cm 2 .
【００１４】[0014]
【表１】 [Table 1]
【００１５】さらに、この成形体を１２００℃の温度で
還元焼成し、連続鋳造用ガス吹き込み型浸漬ノズル（内
径９０ｍｍφ、吐出孔径７０ｍｍφ、吐出孔角度３５度
の逆Ｙ型ノズル）を作製した。なお、浸漬ノズル内孔体
の厚みは１３ｍｍと、冷間通気量及び見掛け気孔率は表
１に示す通りである。このようにして得られた浸漬ノズ
ルを用いてＴｉを０．０８ｗｔ％含有する炭素濃度３０
ｐｐｍの極低炭素鋼を４００分間鋳造した。この際、Ａ
ｒガス吹き込み流量は溶鋼トン当たり６Ｎｌに一定とし
た。本発明の実施例及び比較例とも鋳造寸法は厚み２４
５ｍｍ×幅１５００ｍｍで、８５００ｍｍ長さに切断し
て１コイル単位とした。このスラブを常法により熱間圧
延、冷間圧延し、最終的に０．７ｍｍ×幅１５００ｍｍ
コイルの冷延鋼板とした。ふくれ欠陥防止に対する浸漬
ノズル耐火物の評価は、鋳造後ノズルの水中でのＡｒ吹
き込み試験により得られた気泡径と冷間圧延後の検査ラ
インで目視観察を行い１コイル当たりに発生するふくれ
欠陥の個数（ふくれ欠陥指標）により評価した。また、
耐スポーリング性については、鋳造時のＡｒガス吹き込
み圧力と浸漬ノズルに亀裂が生じた時間を指標として評
価した。表２に、実施例及び比較例の品質評価結果を示
す。Further, this molded body was reduction-fired at a temperature of 1200 ° C. to prepare a continuous casting gas injection type immersion nozzle (inner diameter 90 mmφ, discharge hole diameter 70 mmφ, reverse Y-shaped nozzle with discharge hole angle 35 °). The thickness of the submerged nozzle inner hole was 13 mm, and the cold air permeability and the apparent porosity are as shown in Table 1. Using the immersion nozzle thus obtained, a carbon concentration of 30 containing Ti of 0.08 wt% was obtained.
Ultra low carbon steel of ppm was cast for 400 minutes. At this time, A
The flow rate of the r gas blown was constant at 6 Nl per ton of molten steel. In both the example and the comparative example of the present invention, the casting size is 24
5 mm × width 1500 mm, cut into length 8500 mm to make one coil unit. This slab is hot-rolled and cold-rolled by a conventional method, and finally 0.7 mm x width 1500 mm.
The coil was used as a cold rolled steel sheet. Evaluation of the immersion nozzle refractory for blistering defect prevention was performed by visually observing the bubble diameter obtained by the Ar blowing test in the nozzle of the water after casting and the inspection line after cold rolling to check for blistering defects generated per coil. It was evaluated by the number (bulge defect index). Also,
The spalling resistance was evaluated by using the Ar gas blowing pressure during casting and the time at which the immersion nozzle was cracked as an index. Table 2 shows the quality evaluation results of the examples and comparative examples.
【００１６】[0016]
【表２】 [Table 2]
【００１７】表２に示す如く、実施例は何れの浸漬ノズ
ルも、内孔体のシリカ含有率を５ｗｔ％以下とし、且つ
使用前の冷間通気量を０．０５〜１．０ｋｇ／ｃｍ2の
範囲に制御したため、ノズルに亀裂が発生することなく
耐スポーリング性は良好であった。また、鋳造後ノズル
の水中でのＡｒ気泡径は０．５ｍｍ以下に抑えられ、ふ
くれ欠陥は全く発生しなかった。これに対し、比較例１
のノズルは使用前の冷間通気量を小さくしたため、Ａｒ
ガスの吹き込み圧力が１．９２ｋｇｆ／ｃｍ2と高くな
り、鋳造開始後３５０分で内孔体に亀裂が発生した。ま
た、比較例２のノズルは、逆に使用前の冷間通気量が大
き過ぎたため、鋳造後のＡｒ気泡径が０．９ｍｍと大き
くなりふくれ欠陥が発生した。さらに、比較例４は内孔
体のシリカ含有率が５ｗｔ％を超えたため、シリカと溶
鋼中Ｔｉとの反応が顕著になり気孔径が拡大した。この
ため、Ａｒガスの吹き込み圧力が０．６２ｋｇｆ／ｃｍ
2と小さくなると共に、Ａｒ気泡が粗大化しふくれ欠陥
が多発した。As shown in Table 2, in each of the immersion nozzles of the Examples, the silica content of the inner pores was 5 wt% or less, and the cold ventilation before use was 0.05 to 1.0 kg / cm 2. Since it was controlled within the range of 1, the spalling resistance was good without cracking in the nozzle. Further, the diameter of Ar bubbles in the water of the nozzle after casting was suppressed to 0.5 mm or less, and no blistering defect occurred. On the other hand, Comparative Example 1
Nozzle of Ar has reduced the cold air flow before use.
The gas blowing pressure became as high as 1.92 kgf / cm 2, and cracks occurred in the inner hole 350 minutes after the start of casting. On the contrary, in the nozzle of Comparative Example 2, since the cold air flow rate before use was too large, the Ar bubble diameter after casting was as large as 0.9 mm and a blister defect occurred. Furthermore, in Comparative Example 4, since the silica content of the inner pores exceeded 5 wt%, the reaction between silica and Ti in the molten steel became remarkable, and the pore diameter was expanded. Therefore, the blowing pressure of Ar gas is 0.62 kgf / cm.
As it became as small as 2 , the Ar bubbles became coarse and many swelling defects occurred.
【００１８】[0018]
【発明の効果】以上に説明したように、本発明の連続鋳
造用浸漬ノズルによれば、耐蝕性及び耐スポーリング性
を確保した上で、内孔体から微細な気泡を安定して吹き
込むことができる。したがって、ふくれ欠陥の防止に留
まらず、気泡による介在物の浮上分離効果及びノズル閉
塞の防止効果をより効率的に行うことができる。以上の
効果により、連続鋳造法で製造される鋼板の品質は非常
に安定し、歩留まりも格段に向上する。As described above, according to the immersion nozzle for continuous casting of the present invention, the corrosion resistance and the spalling resistance are ensured and the fine air bubbles are stably blown from the inner hole. You can Therefore, the effect of floating and separating inclusions by bubbles and the effect of preventing nozzle clogging can be more efficiently performed in addition to the prevention of blistering defects. Due to the above effects, the quality of the steel sheet produced by the continuous casting method is very stable and the yield is significantly improved.
【図１】ノズルの冷間通気量と鋳造時のＡｒガス吹き込
み圧力の関係を示す説明図、FIG. 1 is an explanatory diagram showing the relationship between the cold air flow rate of a nozzle and the Ar gas blowing pressure during casting,
【図２】水中へのＡｒガス吹き込み試験により求めた使
用前ノズルの気泡径と冷間通気量の関係を示す説明図。FIG. 2 is an explanatory view showing a relationship between a bubble diameter of a nozzle before use and a cold air flow amount obtained by an Ar gas blowing test into water.
Claims (1)
ルにおいて、ガス吹き込み部にあたる内孔体のシリカ含
有率を５ｗｔ％以下とし、且つ使用前の冷間通気量を圧
力１ｋｇｆ／ｃｍ2において０．０５〜０．１Ｎｌ／ｍ
ｉｎ／ｃｍ2に形成したことを特徴とする連続鋳造用浸
漬ノズル。Claim: What is claimed is: 1. In an alumina-graphite gas-blowing type immersion nozzle, the silica content of the inner pores corresponding to the gas-blowing portion is 5 wt% or less, and the cold aeration rate before use is 1 kgf / pressure. 0.05 to 0.1 Nl / m in cm 2
An immersion nozzle for continuous casting, characterized by being formed at in / cm 2 .
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19365791A JPH0515953A (en) | 1991-07-09 | 1991-07-09 | Immersion nozzle for continuous casting |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19365791A JPH0515953A (en) | 1991-07-09 | 1991-07-09 | Immersion nozzle for continuous casting |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0515953A true JPH0515953A (en) | 1993-01-26 |
Family
ID=16311599
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP19365791A Pending JPH0515953A (en) | 1991-07-09 | 1991-07-09 | Immersion nozzle for continuous casting |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0515953A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2020171937A (en) * | 2019-04-10 | 2020-10-22 | 日本製鉄株式会社 | Method for preheating continuous-casting nozzle |
-
1991
- 1991-07-09 JP JP19365791A patent/JPH0515953A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2020171937A (en) * | 2019-04-10 | 2020-10-22 | 日本製鉄株式会社 | Method for preheating continuous-casting nozzle |
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