JP4216642B2 - Immersion nozzle and continuous casting method using the same - Google Patents

Immersion nozzle and continuous casting method using the same Download PDF

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JP4216642B2
JP4216642B2 JP2003142473A JP2003142473A JP4216642B2 JP 4216642 B2 JP4216642 B2 JP 4216642B2 JP 2003142473 A JP2003142473 A JP 2003142473A JP 2003142473 A JP2003142473 A JP 2003142473A JP 4216642 B2 JP4216642 B2 JP 4216642B2
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molten steel
immersion nozzle
ratio
discharge
inner diameter
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JP2004344900A (en
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健一 森
祐二 平本
新一 福永
淳平 小西
隆 諸星
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Nippon Steel Corp
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Nippon Steel Corp
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Description

【0001】
【発明の属する技術分野】
本発明は、連続鋳造において溶融金属を鋳型に注入するための浸漬ノズル及びこれを用いた連続鋳造方法に関し、詳しくは浸漬ノズルの吐出口から鋳型内に放出される溶鋼流を緩慢で均一な流れにし、溶鋼流に随伴する気泡や介在物の深部への侵入を抑制して、高速鋳造を可能にすることができる浸漬ノズル及びこれを用いた連続鋳造方法に関する。
【0002】
【従来の技術】
従来、連続鋳造において、溶融金属を鋳型に注湯する際、鋳型内に吐出する溶鋼の流れを緩慢かつ均一にする浸漬ノズル(連続鋳造用浸漬ノズルとも言う)として、以下のものが開示されている。
例えば、特許文献1に開示された浸漬ノズルは、浸漬ノズルの左右に上下一対の吐出口をそれぞれ設け、しかも上下の吐出口間の距離Dを、D<L−Z−64Y−370としたものである。ここで、Lはモールド長さ、Yはスループット、Zはモールド上端からメニスカスに至るまでの距離である。
この式は、パウダーの巻き込みを防止するため、吐出口の上端からメニスカスに至るまでの距離Xを設定した式、即ちX>80(0.8Y−1)と、ブレークアウトの発生を防止するための式、即ちD<L−(X+Z+450)に基づいて求めた式である。
また、特許文献2に開示された浸漬ノズルは、吐出口を側方に長めに突出させて、この突出口にCaOを主成分とした格子状、棒状等のCaO含有体を取付け、清浄鋼を鋳造できるものである。
そして、特許文献3に開示された浸漬ノズルは、この浸漬ノズルの下部に、側面に複数の小径の吐出口が形成された拡径したボックスが設けられたもので、各吐出口から溶鋼を吐出させることで、吐出流を分散させて溶鋼の流速を低減するものである。
【0003】
【特許文献1】
特開平2−187240号公報
【特許文献2】
実開昭63−85358号公報
【特許文献3】
実開昭60−71462号公報
【0004】
【発明が解決しようとする課題】
しかしながら、特許文献1の浸漬ノズルは、吐出口を、横長かつ高さ方向に2孔に限定しているため、2孔の間隔が近い場合には、吐出口から出た後の流れが合流し、溶鋼を2孔から分散させて吐出させた効果が無くなる。一方、2孔の間隔が広い場合には、溶鋼の高さ方向の圧力差によって上下の吐出口を通過する流量のバランスが崩れ、即ち下側の吐出口からの流量が大きくなって、吐出流速が大きくなるため、溶鋼を2孔から分散させて吐出させた効果が小さくなる。
このため、溶鋼の流れを、緩慢かつ均一にできず、耐火物との反応生成物や溶鋼中の酸化物である介在物が鋳片の深部に侵入し、鋳片の品質を悪くしていた。
【0005】
また、特許文献2の浸漬ノズルは、吐出口を側方に延長することで、吐出する溶鋼の流れの方向を定めることができるが、その傾斜角度が下向きであれば、溶鋼の流れによって介在物を鋳型内深くまで持ち込み、浮上させることができなくなるため、清浄鋼を得ることができない。一方、その傾斜角度が上向きであれば、上向き流の流速を低減できず、その流れに伴ってパウダーを巻き込むため、やはり清浄鋼を得ることができない。また、吐出流速を低減して、介在物、パウダーの巻き込みを防止するためには、格子あるいは棒の隙間の流路を適度な大きさに設定する必要があるが、その部分については規定されていない。そして、CaOは、溶鋼中のAl23 などの酸化物と反応し溶損して次第に失われるため、CaOを主成分としたのみでは、鋳造時間全体にわたって本構造の効果を持続することは困難である。
【0006】
特許文献3の浸漬ノズルでは、溶鋼の落下力が細孔に直接作用するため、吐出部から吐出する溶鋼の流れを緩慢かつ均一にできない。また、下部に設けられた吐出口によって下向き流が形成されるため、下降流が強くなり、気泡や介在物が鋳片の深部に侵入し、集積して内部表層欠陥の要因になる。
特に、主吐出口の外側に空間部を設け、更に外側に複数の小径の吐出口が配置されているため、構造が複雑になり、製造コストが高くなる。なお、ボックスの周辺部に形成された吐出口から吐出する溶鋼流になる程、その流れを拘束することが困難であるため、吐出した溶鋼流が放射状に拡散する。一方、ボックスの中央部に形成された吐出口から吐出する溶鋼流は、ボックスの周辺部から吐出する溶鋼流によって拘束される。このため、各吐出口からの溶鋼流速が、中央部で強く、外周部で弱くなり、各吐出口から吐出する溶鋼流を適正な均一流速にすることができず、しかも複数の吐出口で均一な流速分布を形成できないなどの問題がある。
本発明はかかる事情に鑑みてなされたもので、鋳型内の溶鋼の流れを緩慢にし、かつ均一な流れを形成して、気泡や介在物欠陥を防止して高速鋳造を可能にする浸漬ノズル及びこれを用いた連続鋳造方法を提供することを目的とする。
【0007】
【課題を解決するための手段】
前記目的に沿う第1の発明に係る浸漬ノズルは、溶鋼が上から下に通過する筒状部と、該筒状部の下部に設けられ、前記溶鋼を横方向に吐出可能な左右対となる吐出口とを有し、前記筒状部の下部を除く部分の内径D1と前記各吐出口間の間隔D2との比D2/D1が0.8〜1.2である浸漬ノズルにおいて、
前記各吐出口の少なくとも上部及び下部のいずれか一方又は双方には、前記各吐出口から吐出した前記溶鋼の流れを誘導可能なひさし部が設けられ、しかも前記吐出口には、前記溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられ、一方側の前記吐出口の内断面積S1と、前記複数の小孔の総断面積S2との比S1/S2が2〜5.5であり、しかも前記小孔の内径dと前記筒状部の前記内径D1との比D1/dが2〜8であり、
更に、前記吐出部は、ドロマイトクリンカーを骨材の一部に使用し、CaO成分の含有量W1とMgO成分の含有量W2との質量比W1/W2が0.46〜3.0、かつMgO成分を30〜70質量%含み、しかも炭素成分を1〜10質量%含み、SiO 2 及びFe 2 3 の各含有率がいずれも3質量%以下となる耐火物で構成されている。
このように、各吐出口の少なくとも上部及び下部のいずれか一方又は双方には、ひさし部が設けられているので、下降流の形成を抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制できる。
また、筒状部の下部を除く部分の内径D1と各吐出間の間隔D2との比D2/D1を0.8〜1.2に設定するので、浸漬ノズルの形状を複雑化することなく単純化できる。
【0008】
ここで、内径D1と間隔D2との比D2/D1が0.8より小さくなる場合、内径D1に対して間隔D2が小さくなり過ぎるため、筒状部内に落下した溶鋼の落下力が吐出口に直接作用し、下降流の形成が抑制できず、気泡及び介在物が鋳片の深部に侵入する。一方、内径D1と間隔D2との比D2/D1が1.2より大きくなる場合、内径D1に対して間隔D2が大きくなり過ぎるため、浸漬ノズルの形状が複雑になり、強度の低下や耐火物コストの上昇を招く。
以上のことから、浸漬ノズルの形状を単純化でき、しかも気泡及び介在物が鋳片の深部に侵入することを防止するため、内径D1と間隔D2との比D2/D1を、好ましくは0.85〜1.15、更には0.9〜1.1にすることが好ましい。
【0009】
前記目的に沿う第2の発明に係る浸漬ノズルは、第1の発明に係る浸漬ノズルにおいて、前記ひさし部の突出長さL1と前記筒状部の前記内径D1との比L1/D1が0.5〜2であって、前記ひさし部の幅Wと前記筒状部の前記内径D1との比W/D1が1〜3である。
このように、ひさし部の突出長さL1と筒状部の内径D1との比L1/D1、及びひさし部の幅Wと筒状部の内径D1との比W/D1をそれぞれ設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止できる。
【0010】
ここで、ひさし部の突出長さL1と筒状部の内径D1との比L1/D1が大きい程、下降流の形成を抑制する効果が大きくなるが、比L1/D1が2を超える場合、ひさし部の先端から例えば鋳型の短辺部材までの距離が小さくなり過ぎ、短辺部材への衝突流速が上昇して下降流速が上昇し、下降流の形成を抑制できない。一方、比L1/D1が0.5より小さい場合、ひさし部による下降流の形成を抑制する効果が小さくなる。
以上のことから、ひさし部による下降流の形成を抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止するためには、ひさし部の突出長さL1と筒状部の内径D1との比L1/D1を、好ましくは0.8〜1.7、更には1〜1.5に設定することが好ましい。
【0011】
また、ひさし部の幅Wと筒状部の内径D1との比W/D1が大きい程、下降流の形成を抑制する効果が大きくなるが、比W/D1が3を超える場合、ひさし部の両側端から例えば鋳型の長辺部材までの距離が小さくなり過ぎ、長辺部材への衝突流速が上昇して下降流速が上昇し、下降流の形成を抑制できない。一方、比W/D1が1より小さい場合、ひさし部による下降流の形成を抑制する効果が小さくなる。
以上のことから、ひさし部による下降流の形成を抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止するためには、ひさし部の幅Wと筒状部の内径D1との比W/D1を、好ましくは1.1〜2.5、更には1.2〜2に設定することが好ましい。
【0012】
前記目的に沿う第3の発明に係る浸漬ノズルは、第1及び第2の発明に係る浸漬ノズルにおいて、前記吐出口の基端から前記ひさし部の先端へかけての流路長さL2と、前記筒状部の前記内径D1との比L2/D1が1〜2である。
このように、吐出口の基端からひさし部の先端へかけての流路長さL2と、筒状部の内径D1との比L2/D1を設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止できる。
ここで、流路長さL2と筒状部の内径D1との比L2/D1が大きい程、下降流の形成を抑制する効果が大きくなるが、比L2/D1が2を超える場合、ひさし部の先端から例えば鋳型の短辺部材までの距離が小さくなり過ぎ、短辺部材への衝突流速が上昇して下降流速が上昇し、下降流の形成を抑制できない。一方、比L2/D1が1より小さい場合、ひさし部による下降流の形成を抑制する効果が小さくなる。
以上のことから、ひさし部による下降流の形成を抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止するためには、流路長さL2と筒状部の内径D1との比L2/D1を、好ましくは1.2〜1.8、更には1.3〜1.7に設定することが好ましい。
【0013】
前記目的に沿う第の発明に係る浸漬ノズルは、前記各吐出口には、前記溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられている。
このように、各吐出口には、溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられているので、複数の小孔によって吐出流を広範囲に分散することができ、吐出する溶鋼の低流速化を図ることができる。
【0014】
前記目的に沿う第の発明に係る浸漬ノズルは、第1及び第2の発明に係る浸漬ノズルにおいて、前記吐出部の前端から前記ひさし部の先端へかけての流路長さL3と、前記筒状部の前記内径D1との比L3/D1が1〜2である。
このように、吐出部の前端からひさし部の先端へかけての流路長さL3と、筒状部の内径D1との比L3/D1を設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止できる。
ここで、流路長さL3と筒状部の内径D1との比L3/D1が大きい程、下降流の形成を抑制する効果が大きくなるが、比L3/D1が2を超える場合、ひさし部の先端から例えば鋳型の短辺部材までの距離が小さくなり過ぎ、短辺部材への衝突流速が上昇して下降流速が上昇し、下降流の形成を抑制できない。一方、比L3/D1が1より小さい場合、ひさし部による下降流の形成を抑制する効果が小さくなる。
以上のことから、ひさし部による下降流の形成を抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止するためには、流路長さL3と筒状部の内径D1との比L3/D1を、好ましくは1.2〜1.8、更には1.3〜1.7に設定することが好ましい。
【0015】
前記目的に沿う第の発明に係る浸漬ノズルは、一方側の前記吐出口の内断面積S1と、前記複数の小孔の総断面積S2との比S1/S2が5.5である。
このように、一方側の吐出口の内断面積S1と、複数の小孔の総断面積S2との比S1/S2を設定するので、各小孔から吐出する溶鋼の流速を均一にでき、しかも吐出した溶鋼が鋳型内壁に衝突して形成される反転流の悪影響を抑制できる。
ここで、内断面積S1と総断面積S2の比S1/S2が6.5を超える場合、小孔から吐出する溶鋼の流れが十分拡散せず、一部で吸い込み流を生じるなど、均一な流速を得ることができない。一方、比S1/S2が1より小さい場合、小孔からの溶鋼流が合体して吐出流が強くなり過ぎ、反転流の悪影響が発生する。
以上のことから、均一な流速を得ることができ、しかも反転流の悪影響を抑制、更には防止するためには、内断面積S1と総断面積S2の比S1/S2を、2〜5.5、更には3〜5に設定することが好ましい。
【0016】
前記目的に沿う第の発明に係る浸漬ノズルは、前記小孔の内径dと前記筒状部の前記内径D1との比D1/dが2〜8である。
このように、小孔の内径dと筒状部の内径D1との比D1/dを設定するので、小孔による圧損を増加させて溶鋼の流速を低減でき、更に溶鋼の二次メニスカス位置(筒状部内の溶鋼の湯面位置)を上昇できるため、吐出部の上端部と下端部との間の溶鋼の圧力差を小さくでき、溶鋼の流量を吐出部の高さ方向に均一にできる。
【0017】
ここで、小孔の内径dと筒状部の内径D1との比D1/dが8を超える場合、筒状部の内径D1に対して小孔の内径dが小さくなり過ぎるため、溶鋼中の介在物の付着により各小孔に閉塞を生じるか、あるいは小孔の内径dに対して筒状部の内径D1が大きくなり、鋳型内でのクリアランスが確保できない。一方、比D1/dが2より小さい場合、小孔による圧損が小さくなり、流速低減効果を得ることができなくなる。
以上のことから、各小孔に閉塞を生じさせることなく、鋳型内でのクリアランスを確保し、しかも吐出部から吐出する溶鋼の流速低減効果を得るためには、小孔の内径dと筒状部の内径D1との比D1/dを、好ましくは2〜6、更には2〜5に設定することが好ましい。
【0018】
前記目的に沿う第の発明に係る浸漬ノズルは、第〜第の発明に係る浸漬ノズルにおいて、前記複数の小孔の総断面積S2と、前記筒状部の内断面積S3との比S3/S2が0.5〜1.5である。
このように、複数の小孔の総断面積S2と、筒状部の内断面積S3との比S3/S2を設定するので、複数の小孔から吐出する溶鋼の平均の吐出流速を低減し、しかもパウダーの巻き込み、気泡、介在物の侵入深さの増大を抑制、更には防止できる。
ここで、総断面積S2と内断面積S3との比S3/S2が1.5を超える場合、内断面積S3に対する小孔の総断面積S2が小さくなり過ぎ、複数の小孔から吐出する溶鋼の平均の吐出流速を低減することができない。一方、比S3/S2が0.5より小さい場合、内断面積S3に対する小孔の総断面積S2が大きくなり過ぎ、小孔による圧損の付与効果が減少するため、例えば吐出口を浸漬深さの浅い位置あるいは深い位置に設ける必要性が生じ、パウダーの巻き込み、気泡、介在物の侵入深さの増大の起因となる。
以上のことから、複数の小孔から吐出する溶鋼の平均の吐出流速を低減し、しかもパウダーの巻き込み、気泡、介在物の侵入深さの増大を抑制、更には防止するためには、総断面積S2と内断面積S3との比S3/S2を、好ましくは0.7〜1.3、更には0.8〜1.2に設定することが好ましい。
【0019】
前記目的に沿う第の発明に係る浸漬ノズルは、前記吐出部はドロマイトを主体とする耐火物で構成されている。
ここで、ドロマイトとは、CaO成分とMgO成分を含有するものであり、溶鋼中のAlが酸化することで生成するAl23や、溶鋼中に含まれるAl23が、その表面に付着した場合、CaO成分とAl23とが反応して低融点の化合物、即ちAl23−CaO系液相を形成できるものである。
これにより、例えば小孔にAl23が付着しても、小孔の内側面(溶鋼接触面、稼働面とも言う)にAl23−CaO系液相が形成され、これが小孔を流れる溶鋼によって下流側へ流されるので、アルミナ系介在物による小孔の孔詰まりを防止できる。
【0021】
前記目的に沿う第の発明に係る浸漬ノズルは、第1〜第の発明に係る浸漬ノズルにおいて、前記筒状部の下部を除く部分には、縮径部が設けられている。
このように、筒状部の下部を除く部分に縮径部を設けるので、筒状部内に落下する溶鋼の落下力を縮径部で吸収できる。
【0022】
前記目的に沿う第の発明に係る浸漬ノズルは、第1〜第の発明に係る浸漬ノズルにおいて、前記筒状部の下部を除く部分には、前記溶鋼を通過させる複数の貫通孔を備えた整流部材が設けられている。
このように、筒状部の下部を除く部分に複数の貫通孔を備えた整流部材を設けるので、筒状部内に落下する溶鋼の落下力を整流部材で吸収でき、しかも整流部材の各貫通孔によって整流部材を通過する溶鋼の落下流を均一化できる。
【0023】
前記目的に沿う第の発明に係る連続鋳造方法は、溶鋼が上から下に通過する筒状部の内径D1と、該筒状部の下部に設けられ、前記溶鋼を横方向に吐出可能な左右対となる吐出口間の間隔D2との比D2/D1が0.8〜1.2であり、前記各吐出口の少なくとも上部及び下部のいずれか一方又は双方に、前記各吐出口から吐出した前記溶鋼の流れを誘導可能なひさし部が設けられ、しかも前記吐出口に前記溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられ、一方側の前記吐出口の内断面積S1と、前記複数の小孔の総断面積S2との比S1/S2が2〜5.5であり、前記小孔の内径dと前記筒状部の前記内径D1との比D1/dが2〜8であり、更に、前記吐出部が、ドロマイトクリンカーを骨材の一部に使用し、CaO成分の含有量W1とMgO成分の含有量W2との質量比W1/W2が0.46〜3.0、かつMgO成分を30〜70質量%含み、しかも炭素成分を1〜10質量%含み、SiO 2 及びFe 2 3 の各含有率がいずれも3質量%以下となる耐火物で構成された浸漬ノズルを介して、鋳型内に前記溶鋼を注湯し、該溶鋼を凝固させながら0.6m/min以上の鋳造速度で前記鋳型から引き抜く。
このように、上記した構成の浸漬ノズルを使用して、鋳型に溶鋼を注湯することにより、鋳型内に形成される吐出口からの溶鋼の吐出流を緩慢、かつ均一な流れにでき、形成される下向き流を弱く、しかも、偏流のない均一な流れにできるので、筒状部との反応生成物や溶鋼中の酸化物である介在物が鋳片の深部に侵入するのを抑制できる。
ここで、鋳造速度を0.6m/min以上にすることにより、鋳片の表層や内部欠陥の無い鋳片を製造できるが、生産性をより高め、鋳片を高温度で加熱炉などの後工程に供給して熱エネルギーを有効に活用するには、鋳造速度を0.8m/min以上にすることが好ましく、更には1.0m/min以上にすることが好ましい。一方、上限値については規定していないが、溶鋼の凝固を行う例えば連続鋳造設備の冷却能力を考慮すれば、例えば2.3m/min以下の鋳造速度で鋳造するのが良い。
【0024】
前記目的に沿う第の発明に係る連続鋳造方法は、第の発明に係る連続鋳造方法において、前記ひさし部の傾斜角度を水平状態に対して上向き10度から下向き35度の範囲に設定し、前記吐出口をメニスカス位置から150〜350mmの範囲で前記鋳型中の前記溶鋼に浸漬させ、アルゴンガスの吹き込み量を0.2〜20NL/minにする。
このように、ひさし部の傾斜角度、及び鋳型内の溶鋼への浸漬ノズルの浸漬深さ、及びアルゴンガスの吹き込み量を規定することで、各吐出口から吐出する溶鋼の上向き流及び下向き流の速度を抑制することができ、上向き流に起因する湯面変動やパウダー巻き込みによる欠陥、下向き流に起因する気泡や介在物の鋳片深部への侵入を抑制することができる。しかも、溶鋼の吐出流の偏流が無いので、例えばひさし部の傾斜角度を従来よりも広い範囲に設定でき、同時に浸漬深さをメニスカス位置から150〜350mmの範囲にして、安定した高速鋳造が可能になる。
【0025】
ここで、ひさし部の傾斜角度が水平位置に対して上向き10度を超える場合、上向き流による湯面の変動やパウダーの巻き込みを生じる。一方、ひさし部の傾斜角度が水平位置に対して下向き35度を超える場合、下向き流が強くなり、この下向き流に随伴する介在物や気泡が鋳片の深部に侵入し、鋳片の内部欠陥の要因になり、高品質の鋳片を製造できない。
以上のことから、高品質の鋳片を製造するためには、ひさし部の傾斜角度を、水平位置に対して上向き5度から下向き20度の範囲とすることが好ましく、更には水平位置に対して上向き5度から下向き15度の範囲とすることが好ましい。
【0026】
また、例えば、浸漬ノズルの吐出口の上端部の浸漬深さが150mmより浅くなる場合、各吐出口から吐出する溶鋼の上向き流が湯面に作用し、湯面変動やパウダーの巻き込みの原因になる。一方、浸漬深さが350mmを超える場合、溶鋼の下向き流が強くなり、気泡や介在物を鋳片の深部に随伴し、その浮上を阻害して鋳片の内部の品質が低下する。
以上のことから、高品質の鋳片を製造するためには、浸漬ノズルの吐出口の上端部の浸漬深さを200〜300mmとすることが好ましく、更には200〜250mmとすることが好ましい。
【0027】
そして、アルゴンガス(Arガスとも言う)の吹き込み量が0.2NL/minより少なくなれば、Arガス気泡による浸漬ノズルの閉鎖防止効果が減少し、かつArガス気泡による介在物の浮上促進効果が減少する。一方、吹き込み量が20NL/minより多くなると、浸漬ノズルの閉鎖防止効果を良好にできるが、Arガス気泡の増加による湯面の変動やパウダーの巻き込み、凝固殻への気泡の捕捉、鋳片内部への気泡の侵入などの問題が発生し、鋳片の品質低下を招く恐れがある。
以上のことから、Arガスの吹き込み量を、好ましくは0.2〜10NL/min、より好ましくは0.2〜5NL/minに設定することで、Arガスの気泡の浮上力を活用し、浸漬ノズルの含有成分であるCaO成分と反応して生成した低融点のAl23 −CaO系の生成物の浮上促進を図り、清浄度の高い鋳片を製造する。
【0028】
前記目的に沿う第10の発明に係る連続鋳造方法は、第及び第の発明に係る連続鋳造方法において、前記ひさし部の突出長さL1と前記筒状部の前記内径D1との比L1/D1が0.5〜2であって、前記ひさし部の幅Wと前記筒状部の前記内径D1との比W/D1が1〜3である。
このように、ひさし部の突出長さL1と筒状部の内径D1との比L1/D1、及びひさし部の幅Wと筒状部の内径D1との比W/D1をそれぞれ設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止できる。
【0029】
前記目的に沿う第11の発明に係る連続鋳造方法は、第〜第10の発明に係る連続鋳造方法において、前記吐出口の基端から前記ひさし部の先端へかけての流路長さL2と、前記筒状部の前記内径D1との比L2/D1が1〜2である。
このように、吐出口の基端からひさし部の先端へかけての流路長さL2と、筒状部の内径D1との比L2/D1を設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止できる。
【0030】
前記目的に沿う第の発明に係る連続鋳造方法は、前記各吐出口には、前記溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられている。
このように、各吐出口には、溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられているので、複数の小孔によって吐出流を広範囲に分散することができ、吐出する溶鋼の低流速化を図ることができる。
【0031】
前記目的に沿う第12の発明に係る連続鋳造方法は、第8〜第10の発明に係る連続鋳造方法において、前記吐出部の前端から前記ひさし部の先端へかけての流路長さL3と、前記筒状部の前記内径D1との比L3/D1が1〜2である。
このように、吐出部の前端からひさし部の先端へかけての流路長さL3と、筒状部の内径D1との比L3/D1を設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止できる。
【0032】
前記目的に沿う第の発明に係る連続鋳造方法は、一方側の前記吐出口の内断面積S1と、前記複数の小孔の総断面積S2との比S1/S2が5.5である。
このように、一方側の吐出口の内断面積S1と、複数の小孔の総断面積S2との比S1/S2を設定するので、各小孔から吐出する溶鋼の流速を均一にでき、しかも反転流の悪影響を抑制できる。
【0033】
前記目的に沿う第の発明に係る連続鋳造方法は、前記小孔の内径dと前記筒状部の前記内径D1との比D1/dが2〜8である。
このように、小孔の内径dと筒状部の内径D1との比D1/dを設定するので、小孔による圧損を増加させて溶鋼の流速を低減でき、更に溶鋼の二次メニスカス位置を上昇できるため、吐出部の上端部と下端部との間の溶鋼の圧力差を小さくでき、溶鋼の流量を吐出部の高さ方向に均一にできる。
【0034】
前記目的に沿う第13の発明に係る連続鋳造方法は、第〜第12の発明に係る連続鋳造方法において、前記複数の小孔の総断面積S2と、前記筒状部の内断面積S3との比S3/S2が0.5〜1.5である。
このように、複数の小孔の総断面積S2と、筒状部の内断面積S3との比S3/S2を設定するので、複数の小孔から吐出する溶鋼の平均の吐出流速を低減し、しかもパウダーの巻き込み、気泡、介在物の侵入深さの増大を抑制、更には防止できる。
【0035】
前記目的に沿う第の発明に係る連続鋳造方法は、前記吐出部はドロマイトを主体とする耐火物で構成されている。
これにより、例えば小孔にAl23が付着しても、小孔の内側面にAl23−CaO系液相が形成され、これが小孔を流れる溶鋼によって下流側へ流されるので、アルミナ系介在物による小孔の孔詰まりを防止できる。
【0037】
前記目的に沿う第14の発明に係る連続鋳造方法は、第〜第13の発明に係る連続鋳造方法において、前記筒状部の下部を除く部分には、縮径部が設けられている。
このように、筒状部の下部を除く部分に縮径部を設けるので、筒状部内に落下する溶鋼の落下力を縮径部で吸収できる。
【0038】
前記目的に沿う第15の発明に係る連続鋳造方法は、第〜第14の発明に係る連続鋳造方法において、前記筒状部の下部を除く部分には、前記溶鋼を通過させる複数の貫通孔を備えた整流部材が設けられている。
このように、筒状部の下部を除く部分に複数の貫通孔を備えた整流部材を設けるので、筒状部内に落下する溶鋼の落下力を整流部材で吸収でき、しかも整流部材の各貫通孔によって整流部材を通過する溶鋼の落下流を均一化できる。
【0039】
即ち、本発明者らは、従来のように2つの孔を備えた浸漬ノズルにおいて、鋳造速度の増加に伴い、鋳型近傍の下降流の流速が増加し、気泡、介在物の侵入深さが増加することにより鋳片内部に欠陥が増加するという課題に対し、改善に取り組み、吐出流を低流速化し安定化した流れを得るためのノズル構造の検討を行った結果、本発明の浸漬ノズル及びこれを用いた連続鋳造方法により低流速で均一な吐出流が得られることを確認した。
【0040】
【発明の実施の形態】
続いて、添付した図面を参照しつつ、本発明を具体化した実施の形態につき説明し、本発明の理解に供する。
ここに、図1(A)、(B)はそれぞれ本発明の第1の実施の形態に係る浸漬ノズルの側断面図、平面図、図2は本発明の第2の実施の形態に係る浸漬ノズルの側断面図、図3は本発明の第3の実施の形態に係る浸漬ノズルの側断面図、図4(A)、(B)はそれぞれ本発明の第4の実施の形態に係る浸漬ノズルの側断面図、平面図、図5は同浸漬ノズルの吐出部の正面図、図6は本発明の第1の実施の形態に係る浸漬ノズルを用いた連続鋳造方法の説明図、図7(A)〜(C)はそれぞれ第1の従来例に係る浸漬ノズルの使用状態の説明図、第2の従来例に係る浸漬ノズルの使用状態の説明図、第1の実施例に係る浸漬ノズルの使用状態の説明図、図8は製造した鋳片中の気泡侵入量の説明図、図9は(A)、(B)はそれぞれ第1の従来例に係る浸漬ノズルの使用状態の説明図、第2の実施例に係る浸漬ノズルの使用状態の説明図、図10は製造した鋳片中の気泡侵入量の説明図、図11は製造した鋳片の不具合発生指数と鋳造速度との関係を示す説明図である。
【0041】
図1(A)、(B)に示すように、本発明の第1の実施の形態に係る浸漬ノズル(連続鋳造用浸漬ノズルとも言う)10は、溶鋼11が上から下に通過する筒状部12と、筒状部12の下部に設けられ、溶鋼11を横方向に吐出可能な左右対となる吐出口13、14とを有し、筒状部12の下部を除く部分の内径D1(例えば、50〜90mm)と各吐出口13、14間の間隔(各吐出口13、14の基端間の間隔)D2との比D2/D1が0.8〜1.2となったものである。以下、詳しく説明する。
【0042】
この各吐出口13、14は、正面視して矩形状となったもので、筒状部12を中心としてその両側部にそれぞれ配置され、しかも各吐出口13、14の上部に、筒状部12から前方に突出した状態のひさし部15、16が設けられている。なお、各ひさし部15、16は、各吐出口13、14から吐出した溶鋼の流れを誘導するものである。
ここで、各ひさし部15、16の筒状部12からの突出長さL1と、筒状部12の内径D1との比L1/D1は0.5〜2に設定され、またひさし部15、16の幅Wと筒状部12の内径D1との比W/D1は1〜3に設定されている。なお、各吐出口13、14の基端、即ち筒状部12の内側面から、ひさし部15、16の先端へかけての流路長さL2と、筒状部12の内径D1との比L2/D1は、1〜2の範囲に設定されている。
【0043】
この各ひさし部15、16の傾斜角度θは、水平位置に対して上向き10度から下向き35度の範囲に設定されている。このように、ひさし部15、16の傾斜角度を変更することで、各吐出口13、14から吐出する溶鋼11の流れの方向を容易に変えることができるので、溶鋼11の流れを容易に安定化することができ、しかも鋼種や鋳造条件に適応した鋳造を行うことが可能になる。
なお、筒状部12は、従来から使用されている浸漬ノズル用の耐火物、例えばアルミナ黒鉛質耐火物(AG)を用いて形成することができる。
【0044】
また、図2に示すように、本発明の第2の実施の形態に係る浸漬ノズル23は、筒状部20の下部を除く部分、即ち筒状部20の内部に存在する溶鋼11の湯面位置(二次メニスカス位置)21より例えば50〜300mm上方の筒状部20の内周部に、その内径D3が筒状部20の内径D1よりも小さな縮径部22(例えば、1/2×D1≦D3<D1)を設けている。なお、筒状部20は、縮径部22を設けたこと以外、筒状部12と略同様の構成である。
これにより、落下する溶鋼11を縮径部22の段差部分に衝突させ、溶鋼11の落下エネルギーを減衰することができる。
【0045】
また、図3に示すように、本発明の第3の実施の形態に係る浸漬ノズル26は、筒状部24の内部に存在する溶鋼11の湯面位置(二次メニスカス位置)21より例えば50〜300mm上方の筒状部24の内周部に、整流部材25を設けている。
ここで、筒状部24の内部には、内径が僅かに(例えば、5〜10mm)縮径して段差を備える係止部27が設けられ、この係止部27の上面に、整流部材25の下面を当接させて配置している。なお、筒状部24は、係止部27を設けたこと以外、筒状部12と略同様の構成である。
【0046】
この整流部材25は、外形が円柱状に構成されたものであり、整流部材25の軸心を中心として略等角度に設けられ、しかも整流部材21の軸心方向に形成された溶鋼11が通過可能な複数(例えば、4以上)の貫通孔28が設けられている。このため、各貫通孔28の内側面が稼働面(以下、溶鋼接触面とも言う)となる。
これにより、浸漬ノズル26内に落下してきた溶鋼11を、浸漬ノズル26内の溶鋼11の湯面に直接衝突させることなく、整流部材25で溶鋼11の落下エネルギーを一旦減衰した後、各貫通孔28で分散させて更に下流側へ供給できるので、浸漬ノズル26内の湯面の変動を抑制できる。
なお、前記した整流部材25を、ドロマイトを主体とした耐火物で構成することが好ましく、この場合、前記したように、少なくとも筒状部24と整流部材25とが接する部分に、ジルコニア系のモルタルを使用する。
【0047】
次に、本発明の第4の実施の形態に係る浸漬ノズル(連続鋳造用浸漬ノズルとも言う)30について説明する。
図4(A)、(B)に示すように、浸漬ノズル30は、溶鋼11が上から下に通過する筒状部31と、筒状部31の下部に設けられ、溶鋼11を横方向に吐出可能な左右対となる吐出口32、33とを有したものである。
【0048】
この各吐出口32、33は、正面視して矩形状となったもので、筒状部31を中心としてその両側部にそれぞれ配置され、しかも各吐出口32、33の上部、下部、及び両側部には、筒状部31から両側方向に突出して各吐出口32、33を囲んだひさし部34、35が設けられている。
ここで、ひさし部34、35の筒状部31からの突出長さL1と、筒状部31の内径D1との比L1/D1は0.5〜2に設定され、またひさし部34、35の幅Wと筒状部31の内径D1との比W/D1は1〜3に設定されている。このように、各吐出口32、33は、前記した大きさのひさし部34、35に囲まれているので、気泡の巻き込みを低減できると共に、吐出流の乱れも低減できる。
また、各ひさし部34、35の傾斜角度θは、水平位置に対して上向き10度から下向き35度の範囲に設定されている。このように、ひさし部34、35の傾斜角度θを変更することで、各吐出口32、33から吐出する溶鋼11の流れの方向を容易に変えることができるので、溶鋼11の流れを容易に安定化することができ、しかも鋼種や鋳造条件に適応した鋳造を行うことが可能になる。
【0049】
図4(A)、(B)、図5に示すように、各吐出口32、33には、実質的に同一の内径dを有し、溶鋼11を吐出可能で、しかも上端部から下端部へかけて分散されて配置された複数(例えば、5〜20個)の小孔36が形成された吐出部37、38が設けられている。
ここで、筒状部31の下部を除く部分の内径D1(例えば、50〜90mm)と各吐出口32、33間、即ち吐出部37、38間の間隔D2との比D2/D1は、0.8〜1.2に設定され、また吐出部37、38の前端からひさし部34、35の先端へかけての流路長さL3と、筒状部31の内径D1との比L3/D1は、1〜2に設定されている。
また、一方側の吐出口32の内断面積S1と、複数の小孔36の総断面積S2との比S1/S2は、1〜6.5に設定され、小孔36の内径dと筒状部31の内径D1との比D1/dは2〜8に設定され、しかも複数の小孔36の総断面積S2と、筒状部31の内断面積S3との比S3/S2は0.5〜1.5に設定されている。
【0050】
なお、各吐出部37、38は実質的に同一の構成であるため、以下一方側の吐出部37についてのみ説明する。
吐出部37は、ドロマイトを主体とした耐火物で構成されている。
この吐出部37を構成する耐火物は、例えばCaO成分の含有量W1とMgO成分の含有量W2との質量比W1/W2が0.46〜3.0であって、しかもMgO成分が30〜70質量%含まれたものである。なお、この耐火物中には、炭素成分が1〜10質量%含有されている。また、この耐火物には、CaO成分及びMgO成分を除いた残部成分の含有量W3に対するCaO成分の含有量W1の質量比W1/W3が2〜30で、特に、残部成分中のSiO2 及びFe23 の各含有率がいずれも3質量%以下となるように調整されている。
【0051】
この耐火物は、上記した組成を満足するように、ドロマイトクリンカーを骨材の一部に使用し、これに例えば粒径が0.5mm以下のMgO粒子を3〜30質量%添加し、更に結合材として、例えばフェノール樹脂を添加して調整することができる。
そして、上記した耐火物から、複数の小孔を予め形成した吐出部を形成し、フェノール樹脂を硬化処理することにより、吐出部37を形成することができる。
また、筒状部31は、従来から使用されている浸漬ノズル用の耐火物、例えばアルミナ黒鉛質耐火物を用いて形成することができる。
なお、アルミナ黒鉛質耐火物とドロマイトとは反応するため、少なくとも筒状部31と吐出部37とが接する部分に、ジルコニア系のモルタルを使用する。なお、筒状部自体をジルコニア黒鉛質耐火物で構成することも可能である。
【0052】
このように、吐出部37はドロマイトを主体とする耐火物で構成されているので、複数の小孔36へのAl23 の付着や堆積を、従来と比較して抑制、更には防止できる。
また、吐出部37は、アルミナ黒鉛質耐火物又はジルコニア黒鉛質耐火物(ZG)を主体とし、炭素成分及び珪素成分のいずれか一方又は双方の含有量が1質量%以下となった耐火物で構成することも可能である。
これにより、溶鋼11を各小孔36から吐出させ、溶鋼11の流れを広範囲に分散させて低流速とした後、ひさし部34、35により各吐出口32、33の前方へ誘導できる。
【0053】
続いて、本発明の第1の実施の形態に係る浸漬ノズル10を用いた連続鋳造方法について説明する。
図6に示すように、溶鋼11をタンディッシュ40に入れ、更にタンディッシュ40の下方に設けた浸漬ノズル10を介して鋳型41に注湯した。なお、鋳型41は、例えば250mm×1000〜1800mmの断面矩形状のものである。そして、鋳型41による冷却と支持セグメント42に設けた冷却水ノズルからの散水による冷却によって、凝固殻(凝固シェル)43を生成させ、凝固殻43の成長を促進しながら、軽圧下セグメント44の複数の押圧ロール(図示しない)によって圧下を行い、ピンチロール45により0.6m/min以上の鋳造速度で鋳型41から引き抜き、鋳片46を鋳造する。
【0054】
なお、浸漬ノズル10は、浸漬ノズル10の各吐出口13、14の上端部が、例えばメニスカス(湯面)位置から150〜350mmの範囲の深さで、鋳型41中の溶鋼11に浸漬するように配置し固定されている。また、浸漬ノズル10中に、アルゴンガスを吹き込む場合は、タンディッシュ40に設けられた上ノズル及びスライディングノズル(SN)プレートを介して浸漬ノズル10に吹き込まれるアルゴンガス量、及びスリットを介して浸漬ノズル10に吹き込まれるアルゴンガス量の総量で、例えば0.2〜20NL/minに調整する。
【0055】
なお、浸漬ノズル10の代わりに、浸漬ノズル30を使用した場合、各吐出部37、38の複数の小孔36から鋳型41内へ溶鋼11を吐出させることで、溶鋼11中のAlから生成したAl23 は、各小孔36の内側面である稼動面に付着するが、付着したAl23 がドロマイトクリンカー内のCaOと反応して低融点のAl23 −CaO系液相が形成され、また過剰なAl23 −CaO系液相の形成が抑えられ、しかも耐火物の消化も抑えることができる。
また、ドロマイトクリンカーの結晶粒子の粒界にSiO2 及びFe23 が存在することで、ドロマイトクリンカー内のCaOと反応して低融点の化合物を形成し、CaOの移動を活発化させると共に、CaOの反応性を向上させることができる。そして、稼動面側に形成されるMgOリッチな層により、稼動面側の耐食性を向上できる。
これにより、溶鋼11の吐出流を緩慢にし、かつ均一な流速分布にすることができ、湯面変動の抑制や、パウダー巻き込みの防止ができ、吐出流に随伴して鋳片の深部に侵入する気泡、介在物などに起因した鋳片の品質欠陥を防止することができる。
【0056】
【実施例】
前記した実施の形態に係る連続鋳造方法を適用し、試験を行った結果について説明する。
図7に、鋳型41内で形成される溶鋼の流れの状態について示す。
前記した浸漬ノズル10のひさし部を上向きに傾斜させた第1の実施例に係る浸漬ノズル50を使用した場合、図7(C)に示すように、鋳型41内に形成される各吐出口51、52からの溶鋼11の吐出流を緩慢、かつ均一な流れにでき、形成される溶鋼11の下向き流を弱く、しかも、偏流のない均一な流れにできる。また、発生した上向きの吐出流は、各ひさし部53、54に衝突し、その流速が低減される。
【0057】
一方、筒状部55の下部に、その軸心を下向きに傾斜させ、溶鋼11を下斜め方向に吐出可能な各吐出口56、57をそれぞれ設けた第1の従来例に係る浸漬ノズル58を使用した場合、図7(A)に示すように、下向き流の流速を低減できない。これにより、強い下向き流に随伴する気泡や介在物が鋳片の深部に侵入するため、鋳片内部の気泡や介在に起因する欠陥を防止できず、鋳片の品質低下を招いたり、鋳片を安定に製造できない問題が発生する。
また、筒状部60の下部に、その軸心を上向きに傾斜させ、溶鋼11を上斜め方向に吐出可能な各吐出口61、62をそれぞれ設けた第2の従来例に係る浸漬ノズル63を使用した場合、図7(B)に示すように、下向き流の流速を低減できるが、上向き流の流速が低減できない。このため、上向き流による湯面の変動やパウダー巻き込みが生じ、鋳片内部の気泡や介在に起因する欠陥を防止できず、鋳片の品質低下を招いたり、鋳片を安定に製造できない問題が発生する。
【0058】
ここで、第1の従来例に係る浸漬ノズル58、及び第1の実施例に係る浸漬ノズル50をそれぞれ使用して製造した鋳片中に含まれる気泡侵入量の比較を、図8に示す。なお、気泡侵入量指数は、第1の従来例の浸漬ノズル58を使用して、鋳造速度を1.0(m/分)とした場合に製造した鋳片中の気泡量を100としたものであり、その指数が高くなる程、鋳変中に多くの気泡が存在し、鋳片の品質が低下することを示している。
第1の従来例に係る浸漬ノズル58を使用して鋳造を行った場合、鋳造速度を1.0(m/分)から1.6(m/分)に上昇させることで、気泡侵入量指数が1.6倍に増加する。一方、第1の実施例に係る浸漬ノズル50を使用して鋳造を行った場合、鋳造速度が1.0(m/分)のときで気泡侵入量指数は60となり、浸漬ノズル58と比較して大幅に低減できたことが分かる。また、鋳造速度を1.6(m/分)に上昇させても、気泡侵入量指数は80程度であり、浸漬ノズル58と比較して約半分程度にできたことが分かる。
以上のことから、第1の実施例に係る浸漬ノズル50を使用することで、各吐出口51、52からの溶鋼11の吐出流の偏流を抑制し、更には防止して、高品質の鋳片を従来よりも高速度で鋳造できる。
【0059】
続いて、図9(A)、(B)にそれぞれ、前記した第1の従来例に係る浸漬ノズル58、及び前記した浸漬ノズル30と略同様の構成である第2の実施例に係る浸漬ノズル65を使用した場合における鋳型41内で形成される溶鋼11の流れの状態について示す。
第2の実施例に係る浸漬ノズル65を使用した場合、図9(B)に示すように、鋳型41内に形成される各吐出口66、67からの溶鋼11の吐出流を緩慢、かつ均一な流れにでき、形成される溶鋼11の下向き流を弱く、しかも、偏流のない均一な流れにできる。
一方、第1の従来例に係る浸漬ノズル58を使用した場合、図9(A)に示すように、下向き流の流速を低減できない。これにより、強い下向き流に随伴する気泡や介在物が鋳片の深部に侵入するため、鋳片内部の気泡や介在に起因する欠陥を防止できず、鋳片の品質低下を招いたり、鋳片を安定に製造できない問題が発生する。
【0060】
ここで、第1の従来例に係る浸漬ノズル58、及び第2の実施例に係る浸漬ノズル65をそれぞれ使用して製造した鋳片中に含まれる気泡侵入量の比較を、図10に示す。
第2の実施例に係る浸漬ノズル65を使用して鋳造を行った場合、鋳造速度が1.0(m/分)のときで気泡侵入量指数は40となり、浸漬ノズル58と比較して大幅に低減できることが分かる。また、鋳造速度を1.6(m/分)に上昇させても、気泡侵入量指数は50程度であり、高速鋳造でも高品質の鋳片を製造できることが分かる。
以上のことから、第2の実施例に係る浸漬ノズル65を使用することで、各吐出口66、67からの溶鋼11の吐出流の偏流を抑制し、更には防止して、更に高品質の鋳片を従来よりも高速度で鋳造できる。
【0061】
続いて、図11に、第1の実施の形態に係る浸漬ノズル10の比L1/D1及び比L2/D1のみを、前記した範囲から外した実施例に係る浸漬ノズルと、前記した第1の従来例に係る浸漬ノズル58とを使用して製造した鋳片の不具合(不良品)発生指数と鋳造速度との関係を示す。なお、鋳片の不具合発生指数とは、所定期間内に製造した鋳片(10〜20本の鋳片)に対する不具合の発生割合を示しており、1に近づくほど不具合が多く発生していることを示している。ここで、試験は、表1に示すように、ひさし部の傾斜角度、浸漬ノズルの浸漬深さ、及びアルゴンガス(Arガス)の吹き込み量の各条件をそれぞれ変化させて行った。
【0062】
【表1】

Figure 0004216642
【0063】
図11に示すように、浸漬ノズルは、ひさし部の傾斜角度(上向き10度から下向き35度の範囲)、浸漬ノズルの浸漬深さ(150〜350mm)、及びアルゴンガス(Arガス)の吹き込み量(0.2〜20NL/分)の各条件を変化させても、不具合の発生率が0.35未満となっており、高品質の鋳片を製造できることを確認できた。なお、不具合の発生率は、鋳片の引き抜き速度が0.5〜1.7(mm/分)の範囲においても殆ど変わらず、やはり高品質の鋳片を製造できることを確認できた。
【0064】
一方、第1の従来例に係る浸漬ノズル58は、図11に示すように、鋳片の引き抜き速度が低速になる程、即ち0.7(mm/分)未満の場合、鋳片にヘゲ、スリバ等が発生し、鋳片表層の品質を低下させる。また、鋳片の引き抜き速度が高速になる程、即ち1.5(mm/分)を超える場合、鋳片に、気泡、介在物等の起因による内部欠陥が発生する。
従って、不具合の発生率が、実施例に係る浸漬ノズルと比較して、大幅に高くなることが分かる。
以上のことから、実施例に係る浸漬ノズルを使用することで、鋳型内の溶鋼の流れを緩慢にし、かつ均一な流れを形成して、気泡や介在物欠陥を防止して高速鋳造を可能にできる。
【0065】
なお、前記した第2、第3の実施の形態に係る浸漬ノズル23、26の比L1/D1のみを、前記した範囲から外した各浸漬ノズルでは、図11に示した結果よりも不具合の発生率を10%低減できた。
また、前記した第1の実施の形態に係る浸漬ノズル10では、図11に示した結果よりも不具合の発生率を20%低減できた。
このように、吐出流の緩慢化及び均一化を図って溶鋼を鋳型内に吐出できるので、鋳型内の溶鋼の流れを緩慢にし、かつ均一な流れを形成して、気泡や介在物欠陥を防止して高速鋳造を可能にする。
【0066】
以上、本発明を、実施の形態を参照して説明してきたが、本発明は何ら上記した実施の形態に記載の構成に限定されるものではなく、特許請求の範囲に記載されている事項の範囲内で考えられるその他の実施の形態や変形例も含むものである。例えば、前記したそれぞれの実施の形態や変形例の一部又は全部を組合せて本発明の浸漬ノズル及びこれを用いた連続鋳造方法を構成する場合も本発明の権利範囲に含まれる。
前記実施の形態においては、各吐出口の上部のみにひさし部を設けた場合、また各吐出口の上部、下部、及び両側部に、各吐出口を囲むようにひさし部を設けた場合について説明した。しかし、ひさし部は各吐出口の少なくとも上部及び下部のいずれか一方又は双方に設けられればよいため、ひさし部を各吐出口の下部のみ、又は上部及び下部のみに設けることも可能である。
そして、前記実施の形態においては、ひさし部の幅を筒状部の外径と実質的に同じにした場合について説明したが、筒状部の外径よりも側方に突出した状態で設けることも可能である。
【0067】
【発明の効果】
請求項1〜記載の浸漬ノズル、及び請求項15記載の連続鋳造方法においては、鋳型内に形成される吐出口からの溶鋼の吐出流を緩慢、かつ均一な流れにでき、形成される溶鋼の下向き流を弱く、しかも、偏流のない均一な流れにできる。これにより、下向き流の減衰と均一化によって鋳片深部へ侵入する気泡や介在物を減少させることができ、鋳片の欠陥を防止できる。また、極端な上向きの吐出流の発生を抑制できるので、湯面の変動を回避してパウダーの巻き込みなどの欠陥や湯面近傍への熱供給を適正にして、安定した鋳造が可能になる。そして、鋳片の凝固殻の内側のウォッシング効果を積極的に発現して、凝固殻に捕捉される気泡や介在物を速やかに浮上させて、表層部の欠陥を減少することができる。更に、吐出流を緩慢にできるので、高速鋳造が可能になり、鋳造の生産性を向上できる。なお、ひさし部により吐出口から吐出する溶鋼の拡散を抑制して、均一な流れにすることができる。
従って、気泡や介在物欠陥を防止した高品質の鋳片を効率的、かつ経済的に安定して製造できる。
また、例えばひさし部の傾斜角度を変えることにより、溶鋼の吐出流の吐出方向(吐出角度)を容易に変更することができるので、浸漬ノズルの構造を簡素化でき、しかも従来のような例えばボックス部を設ける必要性が無くなるので、耐火物、製造の両コストを低減でき経済的である。
【0068】
特に、請求項2記載の浸漬ノズル、及び請求項10記載の連続鋳造方法においては、ひさし部の突出長さL1と筒状部の内径D1との比L1/D1、及びひさし部の幅Wと筒状部の内径D1との比W/D1をそれぞれ設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止できる。これにより、吐出口から吐出する溶鋼の拡散を抑制、更には防止して、更に均一な流れにすることができる。
【0069】
請求項3記載の浸漬ノズル、及び請求項11記載の連続鋳造方法においては、吐出口の基端からひさし部の先端へかけての流路長さL2と、筒状部の内径D1との比L2/D1を設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止でき、高品質の鋳変を製造できる。
【0070】
請求項記載の浸漬ノズル、及び請求項記載の連続鋳造方法においては、各吐出口に溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられているので、複数の小孔によって吐出流を広範囲に分散することができ、吐出する溶鋼の低流速化を図ることができる。これにより、吐出部から吐出する溶鋼の流れを、緩慢で、かつ偏流の無い流れにすることができる。
【0071】
請求項記載の浸漬ノズル、及び請求項12記載の連続鋳造方法においては、吐出部の前端からひさし部の先端へかけての流路長さL3と、筒状部の内径D1との比L3/D1を設定するので、下降流の形成を更に抑制して、気泡及び介在物が鋳片の深部に侵入することを抑制、更には防止でき、高品質の鋳変を製造できる。
【0072】
請求項記載の浸漬ノズル、及び請求項記載の連続鋳造方法においては、一方側の吐出口の内断面積S1と、複数の小孔の総断面積S2との比S1/S2を設定するので、各小孔から吐出する溶鋼の流速を均一にでき、しかも反転流の悪影響を抑制できる。
【0073】
請求項記載の浸漬ノズル、及び請求項記載の連続鋳造方法においては、小孔による圧損を増加させて溶鋼の流速を低減でき、更に溶鋼の二次メニスカス位置を上昇できるため、吐出部の上端部と下端部との間の溶鋼の圧力差を小さくでき、溶鋼の流量を吐出部の高さ方向に均一にできる。これにより、溶鋼の圧損の変動の解消と、吐出口からの溶鋼の吐出流の合体によって吐出流が強くなり、鋳型内壁に衝突して反転する下向き、上向きの溶鋼の流れを抑制して、気泡や介在物の深部への侵入を防止できる。
【0074】
請求項記載の浸漬ノズル、及び請求項13記載の連続鋳造方法においては、複数の小孔から吐出する溶鋼の流速を低減でき、しかも、例えば、パウダーの巻き込み、気泡、介在物の侵入深さを、従来よりも浅くできるので、気泡欠陥や介在物欠陥を防止した高品質の鋳片を製造できる。
【0075】
請求項記載の浸漬ノズル、及び請求項記載の連続鋳造方法においては、吐出部の材質がドロマイトを主体としているので、例えば貫通孔にAl23が付着しても、貫通孔の内側面にAl23−CaO系液相が形成され、これが貫通孔を流れる溶鋼によって下流側へ流されるので、従来のようなアルミナ系介在物による小孔の孔詰まりを防止でき、製造する鋳片の品質を向上できる。
【0077】
請求項記載の浸漬ノズル、及び請求項14記載の連続鋳造方法においては、筒状部の下部を除く部分に縮径部を設けるので、筒状部内に落下する溶鋼の落下力を縮径部で吸収でき、従来発生していた吐出流の偏流を抑制でき、良好な品質を備えた鋳片を製造できる。
【0078】
請求項記載の浸漬ノズル、及び請求項15記載の連続鋳造方法においては、筒状部内に落下する溶鋼の落下力を整流部材で吸収でき、しかも整流部材の各貫通孔によって整流部材を通過する溶鋼の落下流を均一化できるので、従来発生していた吐出流の偏流を更に抑制でき、良好な品質を備えた鋳片を製造できる。
【0079】
請求項記載の連続鋳造方法においては、ひさし部の傾斜角度、及び鋳型内の溶鋼への浸漬ノズルの浸漬深さを規定することで、吐出口から吐出する溶鋼の上向き流及び下向き流の速度を抑制することができるので、上向き流に起因する湯面変動やパウダー巻き込みによる欠陥、下向き流に起因する気泡や介在物の鋳片深部への侵入を抑制することができ、高品質の鋳片を製造できる。しかも、溶鋼の吐出流の偏流が無いので、例えばひさし部の傾斜角度を従来よりも広い範囲に設定でき、同時に浸漬深さをメニスカス位置から150〜350mmの範囲にして、安定した高速鋳造が可能になり、生産性を高めることができる。
【図面の簡単な説明】
【図1】(A)、(B)はそれぞれ本発明の第1の実施の形態に係る浸漬ノズルの側断面図、平面図である。
【図2】本発明の第2の実施の形態に係る浸漬ノズルの側断面図である。
【図3】本発明の第3の実施の形態に係る浸漬ノズルの側断面図である。
【図4】(A)、(B)はそれぞれ本発明の第4の実施の形態に係る浸漬ノズルの側断面図、平面図である。
【図5】同浸漬ノズルの吐出部の正面図である。
【図6】本発明の第1の実施の形態に係る浸漬ノズルを用いた連続鋳造方法の説明図である。
【図7】(A)〜(C)はそれぞれ第1の従来例に係る浸漬ノズルの使用状態の説明図、第2の従来例に係る浸漬ノズルの使用状態の説明図、第1の実施例に係る浸漬ノズルの使用状態の説明図である。
【図8】製造した鋳片中の気泡侵入量の説明図である。
【図9】(A)、(B)はそれぞれ第1の従来例に係る浸漬ノズルの使用状態の説明図、第2の実施例に係る浸漬ノズルの使用状態の説明図である。
【図10】製造した鋳片中の気泡侵入量の説明図である。
【図11】製造した鋳片の不具合発生指数と鋳造速度との関係を示す説明図である。
【符号の説明】
10:浸漬ノズル、11:溶鋼、12:筒状部、13、14:吐出口、15、16:ひさし部、20:筒状部、21:湯面位置、22:縮径部、23:浸漬ノズル、24:筒状部、25:整流部材、26:浸漬ノズル、27:係止部、28:貫通孔、30:浸漬ノズル、31:筒状部、32、33:吐出口、34、35:ひさし部、36:小孔、37、38:吐出部、40:タンディッシュ、41:鋳型、42:支持セグメント、43:凝固殻、44:軽圧下セグメント、45:ピンチロール、46:鋳片、50:浸漬ノズル、51、52:吐出口、53、54:ひさし部、55:筒状部、56、57:吐出口、58:浸漬ノズル、60:筒状部、61、62:吐出口、63、65:浸漬ノズル、66、67:吐出口[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an immersion nozzle for injecting molten metal into a mold in continuous casting and a continuous casting method using the same, and more specifically, a slow and uniform flow of a molten steel flow discharged from the discharge port of the immersion nozzle into the mold. In addition, the present invention relates to a submerged nozzle capable of suppressing high-speed casting by suppressing intrusion of bubbles and inclusions accompanying the molten steel flow into a deep portion, and a continuous casting method using the same.
[0002]
[Prior art]
Conventionally, in continuous casting, when pouring molten metal into a mold, the following is disclosed as an immersion nozzle (also referred to as an immersion nozzle for continuous casting) that makes the flow of molten steel discharged into the mold slow and uniform. Yes.
For example, the immersion nozzle disclosed in Patent Document 1 is provided with a pair of upper and lower discharge ports on the left and right sides of the immersion nozzle, and the distance D between the upper and lower discharge ports is D <LZ-64Y-370 It is. Here, L is the mold length, Y is the throughput, and Z is the distance from the upper end of the mold to the meniscus.
In order to prevent the entrainment of the powder, this formula sets the distance X from the upper end of the discharge port to the meniscus, that is, X> 80 (0.8Y−1), and prevents the occurrence of breakout. That is, an expression obtained based on D <L− (X + Z + 450).
In addition, the immersion nozzle disclosed in Patent Document 2 has a discharge port that protrudes sideways, and a CaO-containing body such as a lattice or bar shape mainly composed of CaO is attached to the protrusion, and clean steel is used. It can be cast.
The immersion nozzle disclosed in Patent Document 3 is provided with an enlarged box having a plurality of small-diameter discharge ports formed on the side surface at the bottom of the immersion nozzle, and discharges molten steel from each discharge port. By doing so, the discharge flow is dispersed to reduce the flow velocity of the molten steel.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2-187240
[Patent Document 2]
Japanese Utility Model Publication No. 63-85358
[Patent Document 3]
Japanese Utility Model Publication No. 60-71462
[0004]
[Problems to be solved by the invention]
However, since the submerged nozzle of Patent Document 1 has a discharge port that is horizontally long and limited to two holes in the height direction, when the interval between the two holes is close, the flow after the discharge port merges. The effect of discharging the molten steel from the two holes is lost. On the other hand, when the interval between the two holes is wide, the balance of the flow rate passing through the upper and lower discharge ports is lost due to the pressure difference in the height direction of the molten steel, that is, the flow rate from the lower discharge port is increased, resulting in a discharge flow velocity. Therefore, the effect that the molten steel is dispersed and discharged from the two holes is reduced.
For this reason, the flow of the molten steel could not be made slow and uniform, and the reaction product with the refractory and inclusions that were oxides in the molten steel penetrated into the deep part of the slab, which deteriorated the quality of the slab. .
[0005]
Moreover, the immersion nozzle of patent document 2 can determine the direction of the flow of the molten steel to be discharged by extending the discharge port to the side. However, if the inclination angle is downward, the inclusion is caused by the flow of the molten steel. Can not be brought deep into the mold and floated, so that clean steel cannot be obtained. On the other hand, if the inclination angle is upward, the flow velocity of the upward flow cannot be reduced, and powder is entrained along with the flow, so that clean steel cannot be obtained. In addition, in order to reduce the discharge flow rate and prevent inclusions and powder from getting involved, it is necessary to set the flow path between the lattices or the gaps of the bars to an appropriate size. Absent. And CaO is Al in molten steel2 OThree It is difficult to maintain the effect of this structure over the entire casting time only by using CaO as a main component.
[0006]
In the immersion nozzle of Patent Document 3, since the dropping force of the molten steel acts directly on the pores, the flow of the molten steel discharged from the discharge portion cannot be made slow and uniform. Further, since the downward flow is formed by the discharge port provided in the lower part, the downward flow becomes strong, and bubbles and inclusions penetrate into the deep part of the slab and accumulate to cause internal surface layer defects.
In particular, since a space portion is provided outside the main discharge port and a plurality of small-diameter discharge ports are arranged on the outside, the structure becomes complicated and the manufacturing cost increases. In addition, since it becomes difficult to restrain the flow, so that it becomes the molten steel flow discharged from the discharge port formed in the peripheral part of the box, the discharged molten steel flow diffuses radially. On the other hand, the molten steel flow discharged from the discharge port formed in the central portion of the box is restrained by the molten steel flow discharged from the peripheral portion of the box. For this reason, the molten steel flow velocity from each discharge port is strong at the center and weak at the outer periphery, and the molten steel flow discharged from each discharge port cannot be made to an appropriate uniform flow velocity, and is uniform at a plurality of discharge ports. There is a problem that a simple flow velocity distribution cannot be formed.
The present invention has been made in view of such circumstances, and an immersion nozzle that slows the flow of molten steel in a mold and forms a uniform flow to prevent bubbles and inclusion defects and enable high-speed casting, and It aims at providing the continuous casting method using this.
[0007]
[Means for Solving the Problems]
The immersion nozzle according to the first aspect of the present invention is provided in a cylindrical part through which molten steel passes from the top to the bottom and a left and right pair provided at the lower part of the cylindrical part and capable of discharging the molten steel in the lateral direction. With discharge portThe ratio D2 / D1 between the inner diameter D1 of the portion excluding the lower portion of the cylindrical portion and the interval D2 between the discharge ports is 0.8 to 1.2.In the immersion nozzle,
At least one or both of the upper and lower portions of each discharge port is provided with an eaves portion capable of guiding the flow of the molten steel discharged from each discharge port,Moreover, the discharge port is provided with a discharge portion in which a plurality of small holes capable of discharging the molten steel are formed, and an inner cross-sectional area S1 of the discharge port on one side and a total cross-sectional area S2 of the plurality of small holes. And the ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion is 2-8,
Furthermore, the discharge part uses dolomite clinker as a part of the aggregate, the mass ratio W1 / W2 of the CaO component content W1 and the MgO component content W2 is 0.46 to 3.0, and MgO 30 to 70% by mass of the component, and 1 to 10% by mass of the carbon component, SiO 2 And Fe 2 O Three Each content of is composed of refractory that is 3% by mass or lessThe
Thus, since at least one or both of the upper and lower portions of each discharge port are provided with eaves, the formation of a downward flow is suppressed and bubbles and inclusions enter the deep portion of the slab. Can be suppressed.
Further, the inner diameter D1 of each portion excluding the lower portion of the cylindrical portion and each dischargemouthSince the ratio D2 / D1 to the interval D2 is set to 0.8 to 1.2, the shape of the immersion nozzle can be simplified without complicating it.
[0008]
Here, when the ratio D2 / D1 between the inner diameter D1 and the distance D2 is smaller than 0.8, the distance D2 becomes too small with respect to the inner diameter D1, so that the dropping force of the molten steel that has fallen into the cylindrical portion is applied to the discharge port. Directly acting, the formation of the downward flow cannot be suppressed, and bubbles and inclusions penetrate into the deep part of the slab. On the other hand, when the ratio D2 / D1 between the inner diameter D1 and the distance D2 is larger than 1.2, the distance D2 becomes too large with respect to the inner diameter D1, so that the shape of the immersion nozzle becomes complicated, and the strength decreases and the refractory material Increases costs.
In view of the above, the ratio D2 / D1 of the inner diameter D1 and the distance D2 is preferably set to 0. 0 in order to simplify the shape of the immersion nozzle and to prevent bubbles and inclusions from entering the deep part of the slab. It is preferably 85 to 1.15, more preferably 0.9 to 1.1.
[0009]
In the immersion nozzle according to the second aspect of the invention, the ratio L1 / D1 between the protrusion length L1 of the eaves portion and the inner diameter D1 of the cylindrical portion is 0.00. The ratio W / D1 between the width W of the eaves portion and the inner diameter D1 of the tubular portion is 1 to 3.
Thus, the ratio L1 / D1 between the protrusion length L1 of the eaves part and the inner diameter D1 of the cylindrical part, and the ratio W / D1 of the eaves part width W and the inner diameter D1 of the cylindrical part are set. It is possible to further suppress the formation of the downward flow, and to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab.
[0010]
Here, the larger the ratio L1 / D1 between the protrusion length L1 of the eaves part and the inner diameter D1 of the cylindrical part, the greater the effect of suppressing the formation of the downward flow, but when the ratio L1 / D1 exceeds 2, For example, the distance from the tip of the eaves portion to the short side member of the mold becomes too small, the collision flow velocity against the short side member increases, the downward flow velocity increases, and the formation of the downward flow cannot be suppressed. On the other hand, when the ratio L1 / D1 is smaller than 0.5, the effect of suppressing the formation of the downward flow by the eaves part becomes small.
From the above, in order to suppress the formation of the downward flow by the eaves part and to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab, the protrusion length L1 of the eaves part and the tube The ratio L1 / D1 with the inner diameter D1 of the shape portion is preferably set to 0.8 to 1.7, more preferably 1 to 1.5.
[0011]
In addition, the larger the ratio W / D1 between the width W of the eaves part and the inner diameter D1 of the cylindrical part, the greater the effect of suppressing the formation of the downward flow, but when the ratio W / D1 exceeds 3, the ratio of the eaves part For example, the distance from both side ends to the long side member of the mold becomes too small, the collision flow velocity to the long side member rises, the descending flow velocity rises, and the formation of the downward flow cannot be suppressed. On the other hand, when the ratio W / D1 is smaller than 1, the effect of suppressing the formation of the downward flow by the eaves part becomes small.
From the above, in order to suppress the formation of the downward flow by the eaves part and to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab, the width W of the eaves part and the cylindrical part The ratio W / D1 to the inner diameter D1 is preferably set to 1.1 to 2.5, more preferably 1.2 to 2.
[0012]
The immersion nozzle according to the third aspect of the invention that meets the above-described object is the immersion nozzle according to the first and second aspects, wherein the flow path length L2 extends from the base end of the discharge port to the tip of the eaves part, Ratio L2 / D1 with the said internal diameter D1 of the said cylindrical part is 1-2.
Thus, since the ratio L2 / D1 between the flow path length L2 from the base end of the discharge port to the tip of the eaves portion and the inner diameter D1 of the cylindrical portion is set, the formation of the downward flow is further suppressed. Thus, it is possible to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab.
Here, the larger the ratio L2 / D1 between the flow path length L2 and the inner diameter D1 of the cylindrical portion, the greater the effect of suppressing the formation of the downward flow, but when the ratio L2 / D1 exceeds 2, the eaves portion For example, the distance from the tip of the mold to the short side member of the mold becomes too small, the collision flow velocity to the short side member increases, the downward flow velocity increases, and the formation of the downward flow cannot be suppressed. On the other hand, when the ratio L2 / D1 is smaller than 1, the effect of suppressing the formation of the downward flow by the eaves part becomes small.
From the above, in order to suppress the formation of the downward flow by the eaves part and to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab, the flow path length L2 and the cylindrical part The ratio L2 / D1 with respect to the inner diameter D1 is preferably set to 1.2 to 1.8, more preferably 1.3 to 1.7.
[0013]
In line with the purpose1In the immersion nozzle according to the invention, each of the discharge ports is provided with a discharge portion in which a plurality of small holes capable of discharging the molten steel are formed.
Thus, since each discharge port is provided with a discharge portion in which a plurality of small holes capable of discharging molten steel are formed, the discharge flow can be dispersed over a wide range by the plurality of small holes and discharged. The flow velocity of molten steel can be reduced.
[0014]
In line with the purpose4The immersion nozzle according to the invention is the first1 and 2In the immersion nozzle according to the invention, the ratio L3 / D1 of the flow path length L3 from the front end of the discharge part to the tip of the eaves part and the inner diameter D1 of the cylindrical part is 1-2. .
Thus, since the ratio L3 / D1 between the flow path length L3 from the front end of the discharge part to the tip of the eaves part and the inner diameter D1 of the cylindrical part is set, the formation of the downward flow is further suppressed. It is possible to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab.
Here, the larger the ratio L3 / D1 between the flow path length L3 and the inner diameter D1 of the cylindrical portion, the greater the effect of suppressing the formation of the downward flow, but when the ratio L3 / D1 exceeds 2, the eaves portion For example, the distance from the tip of the mold to the short side member of the mold becomes too small, the collision flow velocity to the short side member increases, the downward flow velocity increases, and the formation of the downward flow cannot be suppressed. On the other hand, when the ratio L3 / D1 is smaller than 1, the effect of suppressing the formation of the downward flow by the eaves part becomes small.
From the above, in order to suppress the formation of the downward flow by the eaves part and to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab, the flow path length L3 and the cylindrical part The ratio L3 / D1 with the inner diameter D1 is preferably set to 1.2 to 1.8, more preferably 1.3 to 1.7.
[0015]
In line with the purpose1The immersion nozzle according to the invention has a ratio S1 / S2 between the inner cross-sectional area S1 of the discharge port on one side and the total cross-sectional area S2 of the plurality of small holes.2~5.5It is.
Thus, since the ratio S1 / S2 of the inner cross-sectional area S1 of the discharge port on one side and the total cross-sectional area S2 of the plurality of small holes is set, the flow rate of the molten steel discharged from each small hole can be made uniform. Moreover, the adverse effect of the reversal flow formed by the discharged molten steel colliding with the inner wall of the mold can be suppressed.
Here, when the ratio S1 / S2 of the inner cross-sectional area S1 and the total cross-sectional area S2 exceeds 6.5, the flow of the molten steel discharged from the small holes is not sufficiently diffused, and a suction flow is generated in a part and the like. The flow rate cannot be obtained. On the other hand, when the ratio S1 / S2 is smaller than 1, the molten steel flow from the small holes merges, the discharge flow becomes too strong, and the adverse effect of the reverse flow occurs.
From the above, in order to obtain a uniform flow velocity and to suppress or prevent the adverse effect of the reverse flow, the ratio S1 / S2 of the inner sectional area S1 to the total sectional area S2 is set to 2-5. 5 and more preferably 3 to 5.
[0016]
In line with the purpose1In the immersion nozzle according to the invention, a ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion is 2 to 8.
Thus, since the ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion is set, the pressure loss due to the small hole can be increased, the flow velocity of the molten steel can be reduced, and the secondary meniscus position of the molten steel ( Since the molten steel surface position in the cylindrical portion can be raised, the pressure difference of the molten steel between the upper end portion and the lower end portion of the discharge portion can be reduced, and the flow rate of the molten steel can be made uniform in the height direction of the discharge portion.
[0017]
Here, when the ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion exceeds 8, the inner diameter d of the small hole becomes too small with respect to the inner diameter D1 of the cylindrical portion. Each small hole is blocked by the inclusions, or the inner diameter D1 of the cylindrical portion is larger than the inner diameter d of the small hole, so that the clearance in the mold cannot be secured. On the other hand, when the ratio D1 / d is smaller than 2, the pressure loss due to the small holes becomes small, and the flow velocity reduction effect cannot be obtained.
From the above, in order to ensure clearance in the mold without causing clogging of each small hole and to obtain the effect of reducing the flow rate of the molten steel discharged from the discharge portion, the inner diameter d of the small hole and the tubular shape The ratio D1 / d with respect to the inner diameter D1 of the part is preferably set to 2 to 6, more preferably 2 to 5.
[0018]
In line with the purpose5The immersion nozzle according to the invention is the first1No.4In the immersion nozzle according to the invention, a ratio S3 / S2 between the total cross-sectional area S2 of the plurality of small holes and the inner cross-sectional area S3 of the cylindrical portion is 0.5 to 1.5.
Thus, since the ratio S3 / S2 of the total cross-sectional area S2 of the plurality of small holes and the inner cross-sectional area S3 of the cylindrical portion is set, the average discharge flow rate of the molten steel discharged from the plurality of small holes is reduced. Moreover, it is possible to suppress and further prevent an increase in the penetration depth of powder, bubbles, and inclusions.
Here, when the ratio S3 / S2 of the total cross-sectional area S2 to the inner cross-sectional area S3 exceeds 1.5, the total cross-sectional area S2 of the small holes with respect to the inner cross-sectional area S3 becomes too small, and discharge is performed from a plurality of small holes. The average discharge flow rate of molten steel cannot be reduced. On the other hand, when the ratio S3 / S2 is smaller than 0.5, the total cross-sectional area S2 of the small holes with respect to the inner cross-sectional area S3 becomes too large, and the effect of imparting pressure loss due to the small holes is reduced. Therefore, it is necessary to provide at a shallow position or deep position, which causes an increase in the penetration depth of powder, bubbles, and inclusions.
From the above, in order to reduce the average discharge flow rate of molten steel discharged from a plurality of small holes, and to suppress and further prevent the increase of the penetration depth of powder, bubbles and inclusions, The ratio S3 / S2 between the area S2 and the inner cross-sectional area S3 is preferably set to 0.7 to 1.3, more preferably 0.8 to 1.2.
[0019]
In line with the purpose1In the immersion nozzle according to the invention, the discharge portion is made of a refractory material mainly composed of dolomite.
Here, dolomite contains a CaO component and a MgO component, and is generated by the oxidation of Al in molten steel.2OThreeAnd Al contained in molten steel2OThreeIs attached to the surface, CaO component and Al2OThreeReacts with a low melting point compound, that is, Al2OThree-A CaO-based liquid phase can be formed.
As a result, for example, Al2OThreeAl is attached to the inner surface of the small hole (also referred to as molten steel contact surface or working surface).2OThreeSince the CaO-based liquid phase is formed and flows downstream by the molten steel flowing through the small holes, it is possible to prevent clogging of the small holes due to the alumina inclusions.
[0021]
In line with the purpose6The immersion nozzle according to the invention is first to first.5The immersion nozzle which concerns on this invention WHEREIN: The diameter reduction part is provided in the part except the lower part of the said cylindrical part.
Thus, since the reduced diameter portion is provided in the portion other than the lower portion of the cylindrical portion, the dropping force of the molten steel falling into the cylindrical portion can be absorbed by the reduced diameter portion.
[0022]
In line with the purpose7The immersion nozzle according to the invention is first to first.6The immersion nozzle which concerns on this invention WHEREIN: The rectification | straightening member provided with the several through-hole which lets the said molten steel pass is provided in the part except the lower part of the said cylindrical part.
As described above, since the rectifying member having a plurality of through holes is provided in a portion other than the lower portion of the cylindrical portion, the dropping force of the molten steel falling into the cylindrical portion can be absorbed by the rectifying member, and each through hole of the rectifying member can be absorbed. By this, the falling flow of the molten steel passing through the rectifying member can be made uniform.
[0023]
In line with the purpose8The continuous casting method according to the invention includes an inner diameter D1 of a cylindrical portion through which molten steel passes from the top to the bottom, and a discharge port that is provided at the lower portion of the cylindrical portion and forms a left and right pair capable of discharging the molten steel in a lateral direction. The ratio D2 / D1 with the interval D2 between is 0.8 to 1.2, and the flow of the molten steel discharged from each discharge port is at least one or both of the upper and lower portions of each discharge port. Inductable eaves part is providedIn addition, a discharge portion in which a plurality of small holes capable of discharging the molten steel is formed in the discharge port, an inner cross-sectional area S1 of the discharge port on one side, and a total cross-sectional area S2 of the plurality of small holes, The ratio S1 / S2 is 2 to 5.5, the ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion is 2 to 8, and the discharge section is dolomite Using clinker as part of the aggregate, the mass ratio W1 / W2 of the CaO component content W1 and the MgO component content W2 is 0.46 to 3.0, and the MgO component is 30 to 70% by mass Moreover, it contains 1 to 10% by mass of a carbon component, and SiO 2 And Fe 2 O Three Each content of is composed of refractory that is 3% by mass or lessThe molten steel is poured into the mold through the immersion nozzle, and the molten steel is pulled out from the mold at a casting speed of 0.6 m / min or more while solidifying the molten steel.
In this way, by using the immersion nozzle configured as described above and pouring molten steel into the mold, the molten steel discharge flow from the discharge port formed in the mold can be made slow and uniform and formed. Since the downward flow is weak and can be a uniform flow without uneven flow, it is possible to suppress the inclusion of reaction products with the cylindrical portion and inclusions which are oxides in the molten steel into the deep portion of the slab.
Here, by setting the casting speed to 0.6 m / min or more, it is possible to manufacture a slab having no slab surface layer or internal defects. However, the productivity is improved and the slab is heated at a high temperature after a heating furnace or the like. In order to effectively use the thermal energy by supplying it to the process, the casting speed is preferably 0.8 m / min or more, and more preferably 1.0 m / min or more. On the other hand, although an upper limit is not specified, it is preferable to cast at a casting speed of 2.3 m / min or less, for example, considering the cooling capacity of a continuous casting facility that solidifies molten steel.
[0024]
In line with the purpose9The continuous casting method according to the invention is8In the continuous casting method according to the invention, an inclination angle of the eaves portion is set in a range of 10 degrees upward to 35 degrees downward with respect to a horizontal state, and the discharge port is set in a range of 150 to 350 mm from the meniscus position in the mold. In the molten steel, the amount of argon gas blown is 0.2 to 20 NL / min.
In this way, by defining the inclination angle of the eaves part, the immersion depth of the immersion nozzle into the molten steel in the mold, and the amount of argon gas blown in, the upward and downward flow of the molten steel discharged from each discharge port The speed can be suppressed, and defects due to fluctuations in the molten metal surface caused by upward flow and powder entrainment, and intrusion of bubbles and inclusions due to downward flow into the deep part of the slab can be suppressed. Moreover, since there is no drift in the discharge flow of molten steel, for example, the inclination angle of the eaves can be set in a wider range than before, and at the same time the immersion depth can be set in the range of 150 to 350 mm from the meniscus position, enabling stable high speed casting. become.
[0025]
Here, when the inclination angle of the eaves part exceeds 10 degrees upward with respect to the horizontal position, fluctuation of the molten metal surface or entrainment of powder occurs due to the upward flow. On the other hand, when the inclination angle of the eaves part exceeds 35 degrees downward with respect to the horizontal position, the downward flow becomes strong, and inclusions and bubbles accompanying the downward flow penetrate into the deep part of the slab, and internal defects of the slab This makes it impossible to produce high quality slabs.
From the above, in order to manufacture a high quality slab, it is preferable that the inclination angle of the eaves part is in the range of 5 degrees upward to 20 degrees downward relative to the horizontal position, and further to the horizontal position. It is preferable that the angle be in the range of 5 degrees upward to 15 degrees downward.
[0026]
For example, when the immersion depth of the upper end of the discharge port of the immersion nozzle becomes shallower than 150 mm, the upward flow of the molten steel discharged from each discharge port acts on the molten metal surface, causing the molten metal surface fluctuation and powder entrainment. Become. On the other hand, when the immersion depth exceeds 350 mm, the downward flow of the molten steel becomes strong, air bubbles and inclusions accompany the deep part of the slab, hindering its floating, and lowering the quality inside the slab.
From the above, in order to produce a high quality slab, the immersion depth at the upper end of the discharge port of the immersion nozzle is preferably 200 to 300 mm, and more preferably 200 to 250 mm.
[0027]
If the amount of argon gas (also referred to as Ar gas) is less than 0.2 NL / min, the effect of preventing the closing of the immersion nozzle by Ar gas bubbles is reduced and the effect of promoting the floating of inclusions by Ar gas bubbles is achieved. Decrease. On the other hand, when the blowing amount is higher than 20 NL / min, the effect of preventing the closing of the immersion nozzle can be improved. However, the fluctuation of the molten metal surface due to the increase of Ar gas bubbles, the entrainment of powder, the trapping of bubbles in the solidified shell, This may cause problems such as the intrusion of bubbles into the slab, leading to deterioration of the quality of the slab.
From the above, the amount of Ar gas blown is preferably set to 0.2 to 10 NL / min, more preferably 0.2 to 5 NL / min, so that the levitation force of the bubbles of Ar gas can be utilized to immerse the gas. Low melting point Al produced by reaction with CaO component, which is a component of the nozzle2 OThree -Promoting the floating of CaO-based products and producing slabs with high cleanliness.
[0028]
In line with the purpose10The continuous casting method according to the invention is8And the second9In the continuous casting method according to the invention, the ratio L1 / D1 between the projection length L1 of the eaves part and the inner diameter D1 of the tubular part is 0.5 to 2, and the width W of the eaves part and the Ratio W / D1 with the said internal diameter D1 of a cylindrical part is 1-3.
Thus, the ratio L1 / D1 between the protrusion length L1 of the eaves part and the inner diameter D1 of the cylindrical part, and the ratio W / D1 of the eaves part width W and the inner diameter D1 of the cylindrical part are set. It is possible to further suppress the formation of the downward flow, and to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab.
[0029]
In line with the purpose11The continuous casting method according to the invention is8No.10In the continuous casting method according to the invention, the ratio L2 / D1 of the flow path length L2 from the base end of the discharge port to the tip of the eaves part and the inner diameter D1 of the cylindrical part is 1-2. It is.
Thus, since the ratio L2 / D1 between the flow path length L2 from the base end of the discharge port to the tip of the eaves portion and the inner diameter D1 of the cylindrical portion is set, the formation of the downward flow is further suppressed. Thus, it is possible to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab.
[0030]
In line with the purpose8In the continuous casting method according to the invention, each of the discharge ports is provided with a discharge portion in which a plurality of small holes capable of discharging the molten steel are formed.
Thus, since each discharge port is provided with a discharge portion in which a plurality of small holes capable of discharging molten steel are formed, the discharge flow can be dispersed over a wide range by the plurality of small holes and discharged. The flow velocity of molten steel can be reduced.
[0031]
In line with the purpose12The continuous casting method according to the invention is8th to 10thIn the continuous casting method according to the invention, the ratio L3 / D1 of the flow path length L3 from the front end of the discharge part to the tip of the eaves part and the inner diameter D1 of the cylindrical part is 1-2. is there.
Thus, since the ratio L3 / D1 between the flow path length L3 from the front end of the discharge part to the tip of the eaves part and the inner diameter D1 of the cylindrical part is set, the formation of the downward flow is further suppressed. It is possible to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab.
[0032]
In line with the purpose8In the continuous casting method according to the invention, the ratio S1 / S2 between the inner cross-sectional area S1 of the discharge port on one side and the total cross-sectional area S2 of the plurality of small holes is2~5.5It is.
Thus, since the ratio S1 / S2 of the inner cross-sectional area S1 of the discharge port on one side and the total cross-sectional area S2 of the plurality of small holes is set, the flow rate of the molten steel discharged from each small hole can be made uniform. Moreover, the adverse effect of the reverse flow can be suppressed.
[0033]
In line with the purpose8In the continuous casting method according to the invention, a ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion is 2 to 8.
Thus, since the ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion is set, the pressure loss due to the small hole can be increased, the flow velocity of the molten steel can be reduced, and the secondary meniscus position of the molten steel can be set. Since it can raise, the pressure difference of the molten steel between the upper end part and lower end part of a discharge part can be made small, and the flow volume of molten steel can be made uniform in the height direction of a discharge part.
[0034]
In line with the purpose13The continuous casting method according to the invention is8No.12In the continuous casting method according to the invention, the ratio S3 / S2 between the total cross-sectional area S2 of the plurality of small holes and the inner cross-sectional area S3 of the cylindrical portion is 0.5 to 1.5.
Thus, since the ratio S3 / S2 of the total cross-sectional area S2 of the plurality of small holes and the inner cross-sectional area S3 of the cylindrical portion is set, the average discharge flow rate of the molten steel discharged from the plurality of small holes is reduced. Moreover, it is possible to suppress and further prevent an increase in the penetration depth of powder, bubbles, and inclusions.
[0035]
In line with the purpose8In the continuous casting method according to the invention, the discharge part is made of a refractory material mainly composed of dolomite.
As a result, for example, Al2OThreeEven if it adheres, Al on the inner surface of the small hole2OThreeSince the CaO-based liquid phase is formed and flows downstream by the molten steel flowing through the small holes, it is possible to prevent clogging of the small holes due to the alumina inclusions.
[0037]
In line with the purpose14The continuous casting method according to the invention is8No.13In the continuous casting method according to the invention, a reduced diameter portion is provided in a portion excluding the lower portion of the cylindrical portion.
Thus, since the reduced diameter portion is provided in the portion other than the lower portion of the cylindrical portion, the dropping force of the molten steel falling into the cylindrical portion can be absorbed by the reduced diameter portion.
[0038]
In line with the purpose15The continuous casting method according to the invention is8No.14In the continuous casting method according to the invention, a rectifying member having a plurality of through holes through which the molten steel passes is provided in a portion excluding the lower portion of the cylindrical portion.
As described above, since the rectifying member having a plurality of through holes is provided in a portion other than the lower portion of the cylindrical portion, the dropping force of the molten steel falling into the cylindrical portion can be absorbed by the rectifying member, and each through hole of the rectifying member can be absorbed. By this, the falling flow of the molten steel passing through the rectifying member can be made uniform.
[0039]
That is, the inventors of the present invention have a conventional immersion nozzle with two holes. As the casting speed increases, the flow velocity of the downflow near the mold increases and the penetration depth of bubbles and inclusions increases. As a result of studying the nozzle structure to obtain a stabilized flow by reducing the discharge flow rate, the submerged nozzle of the present invention and this It was confirmed that a uniform discharge flow can be obtained at a low flow rate by a continuous casting method using a slag.
[0040]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIGS. 1A and 1B are respectively a side sectional view and a plan view of an immersion nozzle according to the first embodiment of the present invention, and FIG. 2 is an immersion according to the second embodiment of the present invention. 3 is a side sectional view of the nozzle, FIG. 3 is a side sectional view of the immersion nozzle according to the third embodiment of the present invention, and FIGS. 4A and 4B are immersion according to the fourth embodiment of the present invention. FIG. 5 is a front view of a discharge portion of the immersion nozzle, FIG. 6 is an explanatory view of a continuous casting method using the immersion nozzle according to the first embodiment of the present invention, and FIG. (A)-(C) is explanatory drawing of the use condition of the immersion nozzle which concerns on a 1st prior art example, respectively, The explanatory drawing of the use condition of the immersion nozzle which concerns on a 2nd prior art example, The immersion nozzle which concerns on a 1st Example FIG. 8 is an explanatory view of the amount of bubble intrusion in the manufactured slab, FIG. 9 is (A), (B) is the first conventional one, respectively. FIG. 10 is an explanatory view of the state of use of the immersion nozzle according to the second embodiment, FIG. 10 is an explanatory view of the state of use of the immersion nozzle according to the second embodiment, FIG. 10 is an explanatory view of the amount of bubble penetration in the manufactured slab, and FIG. It is explanatory drawing which shows the relationship between this malfunction occurrence index and casting speed.
[0041]
As shown in FIGS. 1 (A) and 1 (B), an immersion nozzle (also referred to as a continuous casting immersion nozzle) 10 according to the first embodiment of the present invention has a cylindrical shape through which molten steel 11 passes from top to bottom. A portion 12 and a discharge port 13 and 14 which are provided at the lower portion of the cylindrical portion 12 and which are left and right pairs capable of discharging the molten steel 11 in the lateral direction, and an inner diameter D1 ( For example, a ratio D2 / D1 of 50 to 90 mm) and a distance between the discharge ports 13 and 14 (a distance between the base ends of the discharge ports 13 and 14) D2 is 0.8 to 1.2. is there. This will be described in detail below.
[0042]
Each of the discharge ports 13 and 14 has a rectangular shape when viewed from the front. The discharge ports 13 and 14 are respectively disposed on both sides of the tubular portion 12 as a center, and the tubular portions are disposed above the discharge ports 13 and 14. Eaves portions 15 and 16 projecting forward from 12 are provided. In addition, each eaves part 15 and 16 guides the flow of the molten steel discharged from each discharge port 13 and 14.
Here, the ratio L1 / D1 between the protruding length L1 of the eaves 15 and 16 from the tubular portion 12 and the inner diameter D1 of the tubular portion 12 is set to 0.5 to 2, and the eaves 15 The ratio W / D1 between the width W of 16 and the inner diameter D1 of the cylindrical portion 12 is set to 1 to 3. In addition, the ratio between the flow path length L2 from the base end of each discharge port 13 and 14, ie, the inner surface of the cylindrical part 12, to the tip of the eaves parts 15 and 16, and the inner diameter D1 of the cylindrical part 12 L2 / D1 is set in the range of 1-2.
[0043]
The inclination angle θ of each of the eaves 15 and 16 is set in a range of 10 degrees upward to 35 degrees downward with respect to the horizontal position. In this way, by changing the inclination angle of the eaves 15 and 16, the flow direction of the molten steel 11 discharged from the discharge ports 13 and 14 can be easily changed, so that the flow of the molten steel 11 can be easily stabilized. In addition, it is possible to perform casting adapted to the steel type and casting conditions.
In addition, the cylindrical part 12 can be formed using the refractory for immersion nozzles conventionally used, for example, an alumina graphite refractory (AG).
[0044]
Moreover, as shown in FIG. 2, the immersion nozzle 23 which concerns on the 2nd Embodiment of this invention is a part except the lower part of the cylindrical part 20, ie, the hot_water | molten_metal surface of the molten steel 11 which exists in the inside of the cylindrical part 20. As shown in FIG. On the inner peripheral portion of the cylindrical portion 20, for example, 50 to 300 mm above the position (secondary meniscus position) 21, the reduced diameter portion 22 (for example, 1/2 ×) whose inner diameter D3 is smaller than the inner diameter D1 of the cylindrical portion 20. D1 ≦ D3 <D1) is provided. The cylindrical portion 20 has substantially the same configuration as the cylindrical portion 12 except that the reduced diameter portion 22 is provided.
Thereby, the falling molten steel 11 can collide with the level | step-difference part of the reduced diameter part 22, and the fall energy of the molten steel 11 can be attenuated.
[0045]
Further, as shown in FIG. 3, the immersion nozzle 26 according to the third embodiment of the present invention is, for example, 50 than the molten metal surface position (secondary meniscus position) 21 of the molten steel 11 existing inside the cylindrical portion 24. A rectifying member 25 is provided on the inner peripheral portion of the cylindrical portion 24 that is ˜300 mm above.
Here, inside the cylindrical part 24, there is provided a locking part 27 having an inner diameter slightly reduced (for example, 5 to 10 mm) and having a step, and a rectifying member 25 is provided on the upper surface of the locking part 27. The lower surface of this is placed in contact. The cylindrical portion 24 has substantially the same configuration as the cylindrical portion 12 except that the locking portion 27 is provided.
[0046]
The rectifying member 25 has a cylindrical outer shape, and is provided at substantially equal angles with the axial center of the rectifying member 25 as the center, and the molten steel 11 formed in the axial direction of the rectifying member 21 passes therethrough. A plurality of possible through holes 28 (for example, 4 or more) are provided. For this reason, the inner side surface of each through-hole 28 becomes an operation surface (hereinafter also referred to as a molten steel contact surface).
As a result, the molten steel 11 that has fallen into the immersion nozzle 26 is not directly collided with the molten metal surface of the molten steel 11 in the immersion nozzle 26, and after the decay energy of the molten steel 11 is once attenuated by the rectifying member 25, Since it can disperse | distribute by 28 and can supply further downstream, the fluctuation | variation of the hot_water | molten_metal surface in the immersion nozzle 26 can be suppressed.
The rectifying member 25 is preferably made of a refractory mainly composed of dolomite. In this case, at least a portion where the cylindrical portion 24 and the rectifying member 25 are in contact with each other, as described above, a zirconia-based mortar. Is used.
[0047]
Next, an immersion nozzle (also referred to as a continuous casting immersion nozzle) 30 according to a fourth embodiment of the present invention will be described.
As shown in FIGS. 4A and 4B, the immersion nozzle 30 is provided in a cylindrical portion 31 through which the molten steel 11 passes from top to bottom, and a lower portion of the cylindrical portion 31, and the molten steel 11 extends in the lateral direction. It has the discharge ports 32 and 33 which become the right and left pair which can discharge.
[0048]
Each of the discharge ports 32 and 33 has a rectangular shape when viewed from the front, and is disposed on both sides of the tubular portion 31 as a center, and the upper, lower, and both sides of each of the discharge ports 32 and 33. The part is provided with eaves parts 34 and 35 that project from the cylindrical part 31 in both directions and surround the discharge ports 32 and 33.
Here, the ratio L1 / D1 between the protruding length L1 of the eaves 34 and 35 from the tubular portion 31 and the inner diameter D1 of the tubular portion 31 is set to 0.5 to 2, and the eaves 34 and 35 are also set. The ratio W / D1 between the width W of the cylindrical portion 31 and the inner diameter D1 of the cylindrical portion 31 is set to 1 to 3. As described above, since each of the discharge ports 32 and 33 is surrounded by the eaves portions 34 and 35 having the above-described size, it is possible to reduce the entrainment of bubbles and the disturbance of the discharge flow.
Further, the inclination angle θ of the eaves portions 34 and 35 is set in a range of 10 degrees upward to 35 degrees downward with respect to the horizontal position. In this way, by changing the inclination angle θ of the eaves 34 and 35, the flow direction of the molten steel 11 discharged from the discharge ports 32 and 33 can be easily changed, so that the flow of the molten steel 11 can be easily performed. It is possible to stabilize the casting, and it is possible to perform casting adapted to the steel type and casting conditions.
[0049]
As shown in FIGS. 4 (A), 4 (B), and 5, the discharge ports 32 and 33 have substantially the same inner diameter d, can discharge the molten steel 11, and the upper end portion to the lower end portion. Discharge portions 37 and 38 in which a plurality of (for example, 5 to 20) small holes 36 are disposed so as to be dispersed are provided.
Here, the ratio D2 / D1 between the inner diameter D1 (for example, 50 to 90 mm) of the portion excluding the lower portion of the cylindrical portion 31 and the interval between the discharge ports 32 and 33, that is, the interval D2 between the discharge portions 37 and 38, is 0. .8 to 1.2, and the ratio L3 / D1 between the flow path length L3 from the front ends of the discharge portions 37 and 38 to the tips of the eaves portions 34 and 35 and the inner diameter D1 of the cylindrical portion 31. Is set to 1-2.
The ratio S1 / S2 between the inner cross-sectional area S1 of the discharge port 32 on one side and the total cross-sectional area S2 of the plurality of small holes 36 is set to 1 to 6.5, and the inner diameter d of the small hole 36 and the cylinder The ratio D1 / d with respect to the inner diameter D1 of the cylindrical portion 31 is set to 2 to 8, and the ratio S3 / S2 between the total sectional area S2 of the plurality of small holes 36 and the inner sectional area S3 of the cylindrical portion 31 is 0. .5 to 1.5.
[0050]
Since each of the discharge units 37 and 38 has substantially the same configuration, only the discharge unit 37 on one side will be described below.
The discharge part 37 is comprised with the refractory material which made dolomite the main body.
The refractory constituting the discharge unit 37 has, for example, a mass ratio W1 / W2 of the CaO component content W1 and the MgO component content W2 of 0.46 to 3.0, and the MgO component of 30 to 30. 70 mass% is contained. In addition, in this refractory material, 1-10 mass% of carbon components are contained. Further, in this refractory, the mass ratio W1 / W3 of the content W1 of the CaO component to the content W3 of the remaining component excluding the CaO component and the MgO component is 2 to 30, in particular, SiO in the remaining component.2 And Fe2 OThree Each content of is adjusted to be 3% by mass or less.
[0051]
In order to satisfy the above-described composition, this refractory uses dolomite clinker as a part of the aggregate, and, for example, 3 to 30% by mass of MgO particles having a particle size of 0.5 mm or less are added thereto, and further bonded. As a material, for example, a phenol resin can be added and adjusted.
And the discharge part 37 can be formed by forming the discharge part which formed several small holes previously from the above-mentioned refractory material, and hardening-processing a phenol resin.
Moreover, the cylindrical part 31 can be formed using the refractory material for immersion nozzles conventionally used, for example, an alumina graphite refractory material.
Since the alumina graphite refractory and dolomite react, zirconia-based mortar is used at least at the portion where the cylindrical portion 31 and the discharge portion 37 are in contact with each other. In addition, it is also possible to comprise cylindrical part itself with a zirconia graphite refractory.
[0052]
Thus, since the discharge part 37 is comprised with the refractory material which has dolomite as a main body, Al to several small holes 36 is carried out.2 OThree Can be suppressed and further prevented as compared with the prior art.
Moreover, the discharge part 37 is a refractory mainly composed of alumina graphite refractory or zirconia graphite refractory (ZG), and the content of one or both of the carbon component and the silicon component is 1% by mass or less. It is also possible to configure.
Thereby, after the molten steel 11 is discharged from each small hole 36 and the flow of the molten steel 11 is dispersed over a wide range so as to have a low flow rate, it can be guided to the front of the discharge ports 32 and 33 by the eaves portions 34 and 35.
[0053]
Then, the continuous casting method using the immersion nozzle 10 which concerns on the 1st Embodiment of this invention is demonstrated.
As shown in FIG. 6, the molten steel 11 was put in the tundish 40 and further poured into the mold 41 through the immersion nozzle 10 provided below the tundish 40. In addition, the casting_mold | template 41 is a cross-sectional rectangular shape of 250 mm x 1000-1800 mm, for example. The solidified shell (solidified shell) 43 is generated by cooling with the mold 41 and cooling with water spray from the cooling water nozzle provided on the support segment 42, and the growth of the solidified shell 43 is promoted. A pressing roll (not shown) is used for reduction, and the pinch roll 45 is pulled out from the mold 41 at a casting speed of 0.6 m / min or more to cast a slab 46.
[0054]
The immersion nozzle 10 is so arranged that the upper ends of the discharge ports 13 and 14 of the immersion nozzle 10 are immersed in the molten steel 11 in the mold 41 at a depth in the range of, for example, 150 to 350 mm from the meniscus (water surface) position. Placed and fixed. In addition, when argon gas is blown into the immersion nozzle 10, the amount of argon gas blown into the immersion nozzle 10 through the upper nozzle and sliding nozzle (SN) plate provided in the tundish 40, and immersion through the slits. The total amount of argon gas blown into the nozzle 10 is adjusted to, for example, 0.2 to 20 NL / min.
[0055]
In addition, when the immersion nozzle 30 was used instead of the immersion nozzle 10, it was produced | generated from Al in the molten steel 11 by discharging the molten steel 11 into the casting_mold | template 41 from the some small hole 36 of each discharge part 37 and 38. Al2 OThree Adheres to the working surface which is the inner surface of each small hole 36, but the adhered Al2 OThree Reacts with CaO in the dolomite clinker to lower the melting point of Al2 OThree -CaO-based liquid phase is formed, and excess Al2 OThree Formation of the -CaO-based liquid phase can be suppressed, and digestion of the refractory can also be suppressed.
In addition, SiO grain at grain boundaries of dolomite clinker crystal particles2 And Fe2 OThree By being present, it reacts with CaO in the dolomite clinker to form a low-melting compound, activates the movement of CaO, and improves the reactivity of CaO. The corrosion resistance on the operating surface side can be improved by the MgO-rich layer formed on the operating surface side.
Thereby, the discharge flow of the molten steel 11 can be made slow and the flow velocity distribution can be made uniform, the fluctuation of the molten metal surface can be suppressed, and the entrainment of the powder can be prevented, and it penetrates into the deep part of the slab accompanying the discharge flow. It is possible to prevent slab quality defects caused by bubbles, inclusions, and the like.
[0056]
【Example】
The result of applying the continuous casting method according to the above-described embodiment and performing a test will be described.
In FIG. 7, it shows about the state of the flow of the molten steel formed in the casting_mold | template 41. FIG.
When the immersion nozzle 50 according to the first embodiment in which the eaves portion of the immersion nozzle 10 is inclined upward is used, each discharge port 51 formed in the mold 41 is shown in FIG. 7C. 52, the discharge flow of the molten steel 11 can be made slow and uniform, and the downward flow of the formed molten steel 11 can be made weak and uniform with no uneven flow. Further, the generated upward discharge flow collides with the eaves portions 53 and 54, and the flow velocity is reduced.
[0057]
On the other hand, an immersion nozzle 58 according to the first conventional example is provided at the lower part of the cylindrical portion 55, with the discharge ports 56 and 57 each having an axis inclined downward and capable of discharging the molten steel 11 in a downward oblique direction. When used, the downward flow velocity cannot be reduced as shown in FIG. As a result, bubbles and inclusions accompanying the strong downward flow penetrate into the deep part of the slab, so that defects caused by bubbles and inclusions inside the slab cannot be prevented, resulting in deterioration of the slab quality, The problem that can not be manufactured stably occurs.
In addition, an immersion nozzle 63 according to the second conventional example is provided at the lower part of the cylindrical part 60, the axis of which is inclined upward, and the respective discharge ports 61 and 62 capable of discharging the molten steel 11 in an obliquely upward direction are provided. When used, as shown in FIG. 7B, the flow velocity of the downward flow can be reduced, but the flow velocity of the upward flow cannot be reduced. For this reason, fluctuations in the molten metal surface and powder entrainment due to upward flow occur, and it is not possible to prevent defects due to bubbles and interposition inside the slab, leading to deterioration in the quality of the slab, and inability to stably manufacture the slab. appear.
[0058]
Here, FIG. 8 shows a comparison of the amount of bubble intrusion contained in the slab manufactured using the immersion nozzle 58 according to the first conventional example and the immersion nozzle 50 according to the first embodiment. In addition, the bubble penetration amount index is obtained by setting the amount of bubbles in a slab manufactured to 100 when the casting speed is 1.0 (m / min) using the immersion nozzle 58 of the first conventional example. The higher the index is, the more bubbles are present during the casting change, indicating that the quality of the slab is lowered.
When casting is performed using the immersion nozzle 58 according to the first conventional example, the bubble penetration amount index is increased by increasing the casting speed from 1.0 (m / min) to 1.6 (m / min). Increases 1.6 times. On the other hand, when casting is performed using the immersion nozzle 50 according to the first embodiment, the bubble penetration index is 60 when the casting speed is 1.0 (m / min), which is compared with the immersion nozzle 58. It can be seen that the reduction can be achieved. It can also be seen that even when the casting speed was increased to 1.6 (m / min), the bubble penetration amount index was about 80, which was about half that of the immersion nozzle 58.
From the above, by using the immersion nozzle 50 according to the first embodiment, it is possible to suppress and further prevent the drift of the discharge flow of the molten steel 11 from the discharge ports 51 and 52, and to produce a high-quality casting. The piece can be cast at a higher speed than before.
[0059]
Subsequently, in FIGS. 9A and 9B, the immersion nozzle 58 according to the first conventional example and the immersion nozzle according to the second embodiment having substantially the same configuration as the immersion nozzle 30 described above, respectively. It shows about the state of the flow of the molten steel 11 formed in the casting_mold | template 41 at the time of using 65. FIG.
When the immersion nozzle 65 according to the second embodiment is used, the discharge flow of the molten steel 11 from the discharge ports 66 and 67 formed in the mold 41 is slow and uniform as shown in FIG. 9B. Therefore, the downward flow of the molten steel 11 to be formed can be weakened and the flow can be made uniform without drift.
On the other hand, when the immersion nozzle 58 according to the first conventional example is used, the flow velocity of the downward flow cannot be reduced as shown in FIG. As a result, bubbles and inclusions accompanying the strong downward flow penetrate into the deep part of the slab, so that defects caused by bubbles and inclusions inside the slab cannot be prevented, resulting in deterioration of the slab quality, The problem that can not be manufactured stably occurs.
[0060]
Here, FIG. 10 shows a comparison of the amount of bubble intrusion contained in the slab manufactured using the immersion nozzle 58 according to the first conventional example and the immersion nozzle 65 according to the second embodiment.
When casting is performed using the immersion nozzle 65 according to the second embodiment, the bubble penetration index is 40 when the casting speed is 1.0 (m / min), which is significantly larger than that of the immersion nozzle 58. It can be seen that it can be reduced. Moreover, even if it raises a casting speed to 1.6 (m / min), the bubble penetration | invasion amount index | exponent is about 50, and it turns out that a high quality slab can be manufactured also by high-speed casting.
From the above, by using the immersion nozzle 65 according to the second embodiment, the uneven flow of the discharge flow of the molten steel 11 from each discharge port 66, 67 is suppressed, further prevented, and further improved in quality. The slab can be cast at a higher speed than before.
[0061]
Subsequently, FIG. 11 shows the immersion nozzle according to the example in which only the ratio L1 / D1 and the ratio L2 / D1 of the immersion nozzle 10 according to the first embodiment are excluded from the above-described range. The relationship of the malfunction (defective product) generation | occurrence | production index of a slab manufactured using the immersion nozzle 58 which concerns on a prior art example, and a casting speed is shown. In addition, the defect occurrence index of the slab indicates the occurrence ratio of defects with respect to the slab (10 to 20 slabs) manufactured within a predetermined period. Is shown. Here, as shown in Table 1, the test was performed by changing each condition of the inclination angle of the eaves portion, the immersion depth of the immersion nozzle, and the amount of argon gas (Ar gas) blown.
[0062]
[Table 1]
Figure 0004216642
[0063]
As shown in FIG. 11, the immersion nozzle has an inclination angle of the eaves part (range of 10 degrees upward to 35 degrees downward), the immersion depth of the immersion nozzle (150 to 350 mm), and the amount of argon gas (Ar gas) blown in Even if each condition (0.2 to 20 NL / min) was changed, the failure rate was less than 0.35, and it was confirmed that a high-quality slab could be produced. In addition, it was confirmed that the occurrence rate of defects hardly changed even when the drawing speed of the slab was in the range of 0.5 to 1.7 (mm / min), and that a high-quality slab could be produced.
[0064]
On the other hand, the immersion nozzle 58 according to the first conventional example, as shown in FIG. 11, has a stagnation on the slab when the drawing speed of the slab becomes lower, that is, less than 0.7 (mm / min). Sliver and the like are generated, and the quality of the slab surface layer is lowered. Further, when the drawing speed of the slab becomes higher, that is, when the slab exceeds 1.5 (mm / min), internal defects due to bubbles, inclusions and the like are generated in the slab.
Therefore, it can be seen that the occurrence rate of defects is significantly higher than that of the immersion nozzle according to the example.
From the above, by using the immersion nozzle according to the embodiment, the flow of the molten steel in the mold is slowed down and a uniform flow is formed, which prevents high-speed casting by preventing bubbles and inclusion defects. it can.
[0065]
Incidentally, in each of the immersion nozzles in which only the ratio L1 / D1 of the immersion nozzles 23 and 26 according to the second and third embodiments described above is excluded from the above-described range, a problem is generated more than the result shown in FIG. The rate could be reduced by 10%.
Moreover, in the immersion nozzle 10 which concerns on above-described 1st Embodiment, the malfunction occurrence rate was able to be reduced 20% rather than the result shown in FIG.
In this way, the molten steel can be discharged into the mold by slowing and uniforming the discharge flow, so that the molten steel flow in the mold is slowed down and a uniform flow is formed to prevent bubbles and inclusion defects. To enable high speed casting.
[0066]
As described above, the present invention has been described with reference to the embodiment. However, the present invention is not limited to the configuration described in the above embodiment, and the matters described in the scope of claims. Other embodiments and modifications conceivable within the scope are also included. For example, a case where the immersion nozzle of the present invention and a continuous casting method using the same are configured by combining some or all of the above-described embodiments and modifications are also included in the scope of the right of the present invention.
In the above-described embodiment, a description is given of a case where an eaves portion is provided only at the upper portion of each discharge port, and a case where an eave portion is provided so as to surround each discharge port at the upper portion, lower portion, and both side portions of each discharge port. did. However, since the eaves portion only needs to be provided in at least one or both of the upper and lower portions of each discharge port, the eaves portion can be provided only in the lower portion of each discharge port, or only in the upper portion and lower portion.
And in the said embodiment, although the case where the width | variety of an eaves part was made substantially the same as the outer diameter of a cylindrical part was demonstrated, it provides in the state protruded to the side rather than the outer diameter of a cylindrical part. Is also possible.
[0067]
【The invention's effect】
Claims 1 to7Immersion nozzle according to claim, and claim8~15In the described continuous casting method, the discharge flow of the molten steel from the discharge port formed in the mold can be made slow and uniform flow, the downward flow of the formed molten steel is weak, and there is no uniform flow. Can be. Thereby, the bubble and inclusion which penetrate | invade into a slab deep part can be reduced by attenuation | damping and equalization of a downward flow, and the defect of a slab can be prevented. In addition, since the generation of an extremely upward discharge flow can be suppressed, stable casting can be achieved by avoiding fluctuations in the molten metal surface and appropriately supplying defects such as entrainment of powder and heat supply to the vicinity of the molten metal surface. Then, the washing effect inside the solidified shell of the slab can be positively expressed, and bubbles and inclusions trapped in the solidified shell can be promptly floated to reduce defects in the surface layer portion. Furthermore, since the discharge flow can be made slow, high-speed casting becomes possible, and casting productivity can be improved. In addition, it can be made a uniform flow by suppressing the diffusion of the molten steel discharged from the discharge port by the eaves portion.
Therefore, a high-quality slab in which bubbles and inclusion defects are prevented can be produced efficiently and economically stably.
In addition, for example, by changing the inclination angle of the eaves part, the discharge direction (discharge angle) of the discharge flow of molten steel can be easily changed, so that the structure of the immersion nozzle can be simplified and, for example, a conventional box Since there is no need to provide a part, both refractory and manufacturing costs can be reduced, which is economical.
[0068]
In particular, an immersion nozzle according to claim 2, and claim10In the described continuous casting method, the ratio L1 / D1 between the protrusion length L1 of the eaves portion and the inner diameter D1 of the cylindrical portion, and the ratio W / D1 of the eaves portion width W and the inner diameter D1 of the cylindrical portion are respectively set. Therefore, it is possible to further suppress the formation of the downward flow and to suppress and further prevent the bubbles and inclusions from entering the deep part of the slab. Thereby, diffusion of the molten steel discharged from the discharge port can be suppressed, further prevented, and a more uniform flow can be achieved.
[0069]
An immersion nozzle according to claim 3, and claim11In the described continuous casting method, the ratio L2 / D1 between the flow path length L2 from the base end of the discharge port to the tip of the eaves portion and the inner diameter D1 of the cylindrical portion is set, so that the downward flow is formed. Can be further suppressed, and air bubbles and inclusions can be suppressed and further prevented from penetrating into the deep part of the slab, and a high quality casting can be produced.
[0070]
Claim1Immersion nozzle according to claim, and claim8In the continuous casting method described, since each discharge port is provided with a discharge portion formed with a plurality of small holes capable of discharging molten steel, the discharge flow can be widely dispersed by the plurality of small holes, The flow velocity of the molten steel to be discharged can be reduced. Thereby, the flow of the molten steel discharged from a discharge part can be made into the flow which is slow and does not have a drift.
[0071]
Claim4Immersion nozzle according to claim, and claim12In the continuous casting method described, since the ratio L3 / D1 between the flow path length L3 from the front end of the discharge portion to the tip of the eaves portion and the inner diameter D1 of the cylindrical portion is set, the downward flow is formed. Further suppressing, it is possible to suppress and further prevent bubbles and inclusions from penetrating into the deep part of the slab, thereby producing a high quality casting change.
[0072]
Claim1Immersion nozzle according to claim, and claim8In the described continuous casting method, since the ratio S1 / S2 between the inner cross-sectional area S1 of the discharge port on one side and the total cross-sectional area S2 of the plurality of small holes is set, the flow rate of the molten steel discharged from each small hole is set to It can be made uniform and the adverse effect of the reverse flow can be suppressed.
[0073]
Claim1Immersion nozzle according to claim, and claim8In the described continuous casting method, the pressure loss due to the small holes can be increased to reduce the flow velocity of the molten steel, and the secondary meniscus position of the molten steel can be raised, so the pressure of the molten steel between the upper end and the lower end of the discharge portion The difference can be reduced, and the flow rate of the molten steel can be made uniform in the height direction of the discharge part. This eliminates fluctuations in the pressure loss of the molten steel and combines the discharge flow of molten steel from the discharge port, strengthening the discharge flow, suppressing the downward and upward flow of molten steel that collides with the inner wall of the mold and suppresses the flow of bubbles. And the penetration of inclusions into the deep part can be prevented.
[0074]
Claim5Immersion nozzle according to claim, and claim13In the described continuous casting method, the flow rate of molten steel discharged from a plurality of small holes can be reduced, and further, for example, the entrapment depth of powder, bubbles and inclusions can be made shallower than before, so that bubble defects and High quality slabs with no inclusion defects can be produced.
[0075]
Claim1Immersion nozzle according to claim, and claim8In the described continuous casting method, since the material of the discharge part is mainly dolomite, for example, the through hole is made of Al.2OThreeEven if it adheres to the inner surface of the through-hole, Al2OThreeSince a CaO-based liquid phase is formed and is flowed downstream by molten steel flowing through the through-holes, it is possible to prevent clogging of small holes due to alumina-based inclusions as in the past, and to improve the quality of the slab to be manufactured .
[0077]
Claim6Immersion nozzle according to claim, and claim14In the described continuous casting method, since the reduced diameter portion is provided in the portion excluding the lower portion of the cylindrical portion, the dropping force of the molten steel falling into the cylindrical portion can be absorbed by the reduced diameter portion, and the discharge flow that has been generated conventionally can be absorbed. It is possible to suppress drift and manufacture a slab having good quality.
[0078]
Claim7Immersion nozzle according to claim, and claim15In the continuous casting method described above, since the dropping force of the molten steel falling into the cylindrical portion can be absorbed by the rectifying member, and the falling flow of the molten steel passing through the rectifying member can be made uniform by the respective through holes of the rectifying member, it is generated conventionally. It is possible to further suppress the uneven flow of the discharge flow, and to produce a slab having good quality.
[0079]
Claim9In the described continuous casting method, by controlling the inclination angle of the eaves part and the immersion depth of the immersion nozzle in the molten steel in the mold, the speed of the upward and downward flow of the molten steel discharged from the discharge port is suppressed. As a result, it is possible to suppress defects due to fluctuations in the molten metal surface due to upward flow, powder entrainment, intrusion of bubbles and inclusions due to downward flow into the deep part of the slab, and high quality slabs can be manufactured. . Moreover, since there is no drift in the discharge flow of molten steel, for example, the inclination angle of the eaves can be set in a wider range than before, and at the same time the immersion depth can be set in the range of 150 to 350 mm from the meniscus position, enabling stable high speed casting. And increase productivity.
[Brief description of the drawings]
FIGS. 1A and 1B are a side sectional view and a plan view, respectively, of an immersion nozzle according to a first embodiment of the present invention.
FIG. 2 is a side sectional view of an immersion nozzle according to a second embodiment of the present invention.
FIG. 3 is a side sectional view of an immersion nozzle according to a third embodiment of the present invention.
4A and 4B are a side sectional view and a plan view of an immersion nozzle according to a fourth embodiment of the present invention, respectively.
FIG. 5 is a front view of a discharge unit of the immersion nozzle.
FIG. 6 is an explanatory diagram of a continuous casting method using an immersion nozzle according to the first embodiment of the present invention.
FIGS. 7A to 7C are explanatory diagrams of the usage state of the immersion nozzle according to the first conventional example, the explanatory diagrams of the usage state of the immersion nozzle according to the second conventional example, and the first embodiment. It is explanatory drawing of the use condition of the immersion nozzle which concerns on.
FIG. 8 is an explanatory diagram of the amount of bubble intrusion in the manufactured slab.
FIGS. 9A and 9B are explanatory diagrams of the usage state of the immersion nozzle according to the first conventional example, and are explanatory diagrams of the usage state of the immersion nozzle according to the second embodiment, respectively.
FIG. 10 is an explanatory diagram of the amount of bubble penetration in the manufactured slab.
FIG. 11 is an explanatory diagram showing a relationship between a defect occurrence index and a casting speed of a manufactured slab.
[Explanation of symbols]
10: immersion nozzle, 11: molten steel, 12: cylindrical part, 13, 14: discharge port, 15, 16: eaves part, 20: cylindrical part, 21: hot water surface position, 22: reduced diameter part, 23: immersion Nozzle, 24: cylindrical part, 25: rectifying member, 26: immersion nozzle, 27: locking part, 28: through-hole, 30: immersion nozzle, 31: cylindrical part, 32, 33: discharge port, 34, 35 : Eaves part, 36: small hole, 37, 38: discharge part, 40: tundish, 41: mold, 42: support segment, 43: solidified shell, 44: segment under light pressure, 45: pinch roll, 46: slab , 50: immersion nozzle, 51, 52: discharge port, 53, 54: eaves portion, 55: cylindrical portion, 56, 57: discharge port, 58: immersion nozzle, 60: cylindrical portion, 61, 62: discharge port 63, 65: immersion nozzle, 66, 67: discharge port

Claims (15)

溶鋼が上から下に通過する筒状部と、該筒状部の下部に設けられ、前記溶鋼を横方向に吐出可能な左右対となる吐出口とを有し、前記筒状部の下部を除く部分の内径D1と前記各吐出口間の間隔D2との比D2/D1が0.8〜1.2である浸漬ノズルにおいて、
前記各吐出口の少なくとも上部及び下部のいずれか一方又は双方には、前記各吐出口から吐出した前記溶鋼の流れを誘導可能なひさし部が設けられ、しかも前記吐出口には、前記溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられ、一方側の前記吐出口の内断面積S1と、前記複数の小孔の総断面積S2との比S1/S2が2〜5.5であり、しかも前記小孔の内径dと前記筒状部の前記内径D1との比D1/dが2〜8であり、
更に、前記吐出部は、ドロマイトクリンカーを骨材の一部に使用し、CaO成分の含有量W1とMgO成分の含有量W2との質量比W1/W2が0.46〜3.0、かつMgO成分を30〜70質量%含み、しかも炭素成分を1〜10質量%含み、SiO 2 及びFe 2 3 の各含有率がいずれも3質量%以下となる耐火物で構成されていることを特徴とする浸漬ノズル。
A cylindrical portion which molten steel passes from top to bottom, is provided in the lower portion of the cylindrical portion, possess a discharge port wherein the molten steel in the horizontal direction to enable discharge of the right and left pair, a lower portion of the cylindrical portion In the immersion nozzle in which the ratio D2 / D1 between the inner diameter D1 of the removed portion and the interval D2 between the discharge ports is 0.8 to 1.2 ,
At least one or both of the upper and lower portions of each discharge port is provided with an eaves portion capable of guiding the flow of the molten steel discharged from each discharge port, and the molten steel is discharged to the discharge port. A discharge portion having a plurality of possible small holes is provided, and a ratio S1 / S2 between the inner cross-sectional area S1 of the discharge port on one side and the total cross-sectional area S2 of the plurality of small holes is 2 to 5. 5 and the ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion is 2 to 8,
Furthermore, the discharge part uses dolomite clinker as a part of the aggregate, the mass ratio W1 / W2 of the CaO component content W1 and the MgO component content W2 is 0.46 to 3.0, and MgO comprise components 30 to 70 wt%, yet contains 1 to 10 wt% of carbon component, characterized Rukoto each content of SiO 2 and Fe 2 O 3 is it consists of a refractory material comprising a both 3 wt% or less Immersion nozzle.
請求項1記載の浸漬ノズルにおいて、前記ひさし部の突出長さL1と前記筒状部の前記内径D1との比L1/D1が0.5〜2であって、前記ひさし部の幅Wと前記筒状部の前記内径D1との比W/D1が1〜3であることを特徴とする浸漬ノズル。  The immersion nozzle according to claim 1, wherein a ratio L1 / D1 between a protruding length L1 of the eaves portion and the inner diameter D1 of the tubular portion is 0.5 to 2, and the width W of the eaves portion and the The immersion nozzle, wherein the ratio W / D1 of the cylindrical portion to the inner diameter D1 is 1 to 3. 請求項1及び2のいずれか1項に記載の浸漬ノズルにおいて、前記吐出口の基端から前記ひさし部の先端へかけての流路長さL2と、前記筒状部の前記内径D1との比L2/D1が1〜2であることを特徴とする浸漬ノズル。  The immersion nozzle according to any one of claims 1 and 2, wherein a flow path length L2 from a base end of the discharge port to a tip end of the eaves portion and the inner diameter D1 of the cylindrical portion. An immersion nozzle, wherein the ratio L2 / D1 is 1-2. 請求項1及び2のいずれか1項に記載の浸漬ノズルにおいて、前記吐出部の前端から前記ひさし部の先端へかけての流路長さL3と、前記筒状部の前記内径D1との比L3/D1が1〜2であることを特徴とする浸漬ノズル。The immersion nozzle according to any one of claims 1 and 2 , wherein a ratio between a flow path length L3 from a front end of the discharge part to a tip of the eaves part and the inner diameter D1 of the cylindrical part. L3 / D1 is 1-2, the immersion nozzle characterized by the above-mentioned. 請求項のいずれか1項に記載の浸漬ノズルにおいて、前記複数の小孔の総断面積S2と、前記筒状部の内断面積S3との比S3/S2が0.5〜1.5であることを特徴とする浸漬ノズル。The immersion nozzle according to any one of claims 1 to 4 , wherein a ratio S3 / S2 between a total cross-sectional area S2 of the plurality of small holes and an inner cross-sectional area S3 of the cylindrical portion is 0.5 to 1. A submerged nozzle characterized in that it is .5. 請求項1〜のいずれか1項に記載の浸漬ノズルにおいて、前記筒状部の下部を除く部分には、縮径部が設けられていることを特徴とする浸漬ノズル。The immersion nozzle according to any one of claims 1 to 5 , wherein a reduced diameter portion is provided in a portion excluding a lower portion of the cylindrical portion. 請求項1〜のいずれか1項に記載の浸漬ノズルにおいて、前記筒状部の下部を除く部分には、前記溶鋼を通過させる複数の貫通孔を備えた整流部材が設けられていることを特徴とする浸漬ノズル。The immersion nozzle according to any one of claims 1 to 6 , wherein a portion other than a lower portion of the cylindrical portion is provided with a rectifying member having a plurality of through holes through which the molten steel passes. A featured immersion nozzle. 溶鋼が上から下に通過する筒状部の内径D1と、該筒状部の下部に設けられ、前記溶鋼を横方向に吐出可能な左右対となる吐出口間の間隔D2との比D2/D1が0.8〜1.2であり、前記各吐出口の少なくとも上部及び下部のいずれか一方又は双方に、前記各吐出口から吐出した前記溶鋼の流れを誘導可能なひさし部が設けられ、しかも前記吐出口に前記溶鋼を吐出可能な複数の小孔が形成された吐出部が設けられ、一方側の前記吐出口の内断面積S1と、前記複数の小孔の総断面積S2との比S1/S2が2〜5.5であり、前記小孔の内径dと前記筒状部の前記内径D1との比D1/dが2〜8であり、更に、前記吐出部が、ドロマイトクリンカーを骨材の一部に使用し、CaO成分の含有量W1とMgO成分の含有量W2との質量比W1/W2が0.46〜3.0、かつMgO成分を30〜70質量%含み、しかも炭素成分を1〜10質量%含み、SiO 2 及びFe 2 3 の各含有率がいずれも3質量%以下となる耐火物で構成された浸漬ノズルを介して、鋳型内に前記溶鋼を注湯し、該溶鋼を凝固させながら0.6m/min以上の鋳造速度で前記鋳型から引き抜くことを特徴とする連続鋳造方法。Ratio D2 / of the inner diameter D1 of the cylindrical part through which the molten steel passes from the top to the bottom and the interval D2 between the left and right discharge ports provided at the lower part of the cylindrical part and capable of discharging the molten steel in the lateral direction D1 is 0.8 to 1.2, and at least one or both of the upper and lower portions of each discharge port is provided with an eaves portion capable of guiding the flow of the molten steel discharged from each discharge port , And the discharge part in which the some small hole which can discharge the said molten steel was formed in the said discharge port is provided, and internal cross-sectional area S1 of the said discharge port of one side, and total cross-sectional area S2 of the said some small hole The ratio S1 / S2 is 2 to 5.5, the ratio D1 / d between the inner diameter d of the small hole and the inner diameter D1 of the cylindrical portion is 2 to 8, and the discharge section is a dolomite clinker Is used as part of the aggregate, and the mass of the CaO component content W1 and the MgO component content W2 W1 / W2 is 0.46 to 3.0, and comprises an MgO component 30 to 70 mass%, yet contains 1 to 10 wt% of carbon component, 3 both the content of SiO 2 and Fe 2 O 3 mass The molten steel is poured into a mold through an immersion nozzle composed of a refractory that is less than or equal to%, and the molten steel is solidified and pulled out from the mold at a casting speed of 0.6 m / min or more. Continuous casting method. 請求項記載の連続鋳造方法において、前記ひさし部の傾斜角度を水平状態に対して上向き10度から下向き35度の範囲に設定し、前記吐出口をメニスカス位置から150〜350mmの範囲で前記鋳型中の前記溶鋼に浸漬させ、アルゴンガスの吹き込み量を0.2〜20NL/minにすることを特徴とする連続鋳造方法。9. The continuous casting method according to claim 8 , wherein an inclination angle of the eaves portion is set in a range of 10 degrees upward to 35 degrees downward with respect to a horizontal state, and the discharge port is set in a range of 150 to 350 mm from a meniscus position. A continuous casting method, wherein the molten steel is immersed in the molten steel, and an argon gas blowing rate is 0.2 to 20 NL / min. 請求項及びのいずれか1項に記載の連続鋳造方法において、前記ひさし部の突出長さL1と前記筒状部の前記内径D1との比L1/D1が0.5〜2であって、前記ひさし部の幅Wと前記筒状部の前記内径D1との比W/D1が1〜3であることを特徴とする連続鋳造方法。In continuous casting method according to any one of claims 8 and 9, and the ratio L1 / D1 of the inner diameter D1 of the cylindrical portion and the projecting length L1 of the eaves portion is a 0.5-2 The continuous casting method is characterized in that a ratio W / D1 of the width W of the eaves part and the inner diameter D1 of the cylindrical part is 1 to 3. 請求項10のいずれか1項に記載の連続鋳造方法において、前記吐出口の基端から前記ひさし部の先端へかけての流路長さL2と、前記筒状部の前記内径D1との比L2/D1が1〜2であることを特徴とする連続鋳造方法。In the continuous casting method according to any one of claims 8 to 10 , the flow path length L2 from the base end of the discharge port to the tip of the eaves part, and the inner diameter D1 of the cylindrical part The ratio L2 / D1 of the continuous casting method is 1-2. 請求項8〜10のいずれか1項に記載の連続鋳造方法において、前記吐出部の前端から前記ひさし部の先端へかけての流路長さL3と、前記筒状部の前記内径D1との比L3/D1が1〜2であることを特徴とする連続鋳造方法。The continuous casting method according to any one of claims 8 to 10 , wherein a flow path length L3 from a front end of the discharge part to a tip of the eaves part and the inner diameter D1 of the cylindrical part Ratio L3 / D1 is 1-2, The continuous casting method characterized by the above-mentioned. 請求項12のいずれか1項に記載の連続鋳造方法において、前記複数の小孔の総断面積S2と、前記筒状部の内断面積S3との比S3/S2が0.5〜1.5であることを特徴とする連続鋳造方法。The continuous casting method according to any one of claims 8 to 12 , wherein a ratio S3 / S2 between the total cross-sectional area S2 of the plurality of small holes and the inner cross-sectional area S3 of the cylindrical portion is 0.5 to 0.5. A continuous casting method characterized by being 1.5. 請求項13のいずれか1項に記載の連続鋳造方法において、前記筒状部の下部を除く部分には、縮径部が設けられていることを特徴とする連続鋳造方法。The continuous casting method according to any one of claims 8 to 13 , wherein a reduced diameter portion is provided in a portion excluding a lower portion of the cylindrical portion. 請求項14のいずれか1項に記載の連続鋳造方法において、前記筒状部の下部を除く部分には、前記溶鋼を通過させる複数の貫通孔を備えた整流部材が設けられていることを特徴とする連続鋳造方法。The continuous casting method according to any one of claims 8 to 14 , wherein a portion of the cylindrical portion excluding a lower portion is provided with a rectifying member having a plurality of through holes through which the molten steel passes. A continuous casting method characterized by the above.
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