JP5466829B2 - Continuous casting mold and steel continuous casting method - Google Patents
Continuous casting mold and steel continuous casting method Download PDFInfo
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- JP5466829B2 JP5466829B2 JP2008092032A JP2008092032A JP5466829B2 JP 5466829 B2 JP5466829 B2 JP 5466829B2 JP 2008092032 A JP2008092032 A JP 2008092032A JP 2008092032 A JP2008092032 A JP 2008092032A JP 5466829 B2 JP5466829 B2 JP 5466829B2
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- 230000000052 comparative effect Effects 0.000 description 3
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- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910000655 Killed steel Inorganic materials 0.000 description 2
- RQMIWLMVTCKXAQ-UHFFFAOYSA-N [AlH3].[C] Chemical compound [AlH3].[C] RQMIWLMVTCKXAQ-UHFFFAOYSA-N 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
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- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 1
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
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Description
本発明は、連続鋳造用鋳型及び鋼の連続鋳造方法に係り、特に、厳格な表面品質が要求される自動車用鋼板や飲料缶用鋼板の素材として使用する、厚みが150mm以上、500mm以下の、一般的に中厚スラブから普通厚スラブと呼ばれる厚みのスラブ(鋳片)を鋳造する際に用いるのに好適であり、ブレークアウトや鋳型の異常損耗等の操業トラブルを回避することのできる連続鋳造用鋳型、及び、これを用いた鋼の連続鋳造方法に関する。 The present invention relates to a continuous casting mold and a continuous casting method of steel, and particularly, used as a material for steel plates for automobiles and beverage cans, which require strict surface quality, and has a thickness of 150 mm or more and 500 mm or less. Continuous casting that is suitable for casting slabs with a thickness generally called medium thickness slabs (slabs) and avoids operational troubles such as breakout and abnormal mold wear. The present invention relates to a casting mold and a steel continuous casting method using the same.
自動車用鋼板、特に自動車用製品の外板部となる箇所に使用される鋼板や、飲料缶等に使用される鋼板では、表面の美麗さや塗装性、ラミネート性等が求められる。自動車用鋼板や飲料缶用鋼板として使用される極低炭素アルミキルド鋼、乃至、低炭素アルミキルド鋼は、その精錬過程で酸素を使用して溶鋼中の炭素を酸化除去する工程が不可欠であるため、この工程で溶鋼中に溶存した酸素を、更にアルミニウム等の脱酸剤で脱酸する工程が必要となる。この脱酸工程において、溶鋼中の溶存酸素が前記脱酸剤と結合して、脱酸生成物であるアルミナ等を生じ、これが溶鋼中に非金属介在物として残存する。 In steel plates for automobiles, particularly steel plates used in places serving as the outer plate of automobile products, and steel plates used in beverage cans and the like, surface beauty, paintability, laminate properties, and the like are required. Because ultra-low carbon aluminum killed steel or low carbon aluminum killed steel used as steel plates for automobiles and beverage cans, the process of oxidizing and removing carbon in molten steel using oxygen in the refining process is indispensable. A step of deoxidizing oxygen dissolved in the molten steel in this step with a deoxidizer such as aluminum is required. In this deoxidation step, dissolved oxygen in the molten steel combines with the deoxidizing agent to produce deoxidation products such as alumina, which remains as nonmetallic inclusions in the molten steel.
このような非金属介在物がスラブの表面近傍に存在すると、スラブを熱間圧延及び冷間圧延して薄鋼板とした場合に、鋼板の表面にヘゲや膨れ等の欠陥を生じるので好ましくない。又、脱酸生成物以外にも、連続鋳造時に、図1に例示する鋳型(モールド)30内の溶鋼表面に添加するモールドパウダや、タンディッシュ20から鋳型30内に溶鋼8を供給するための浸漬ノズル22の詰まり防止のために供給されるアルゴンガスの気泡が溶鋼中に巻き込まれたものが、気泡単独、あるいは、脱酸生成物と合体した気泡として溶鋼中に残存しても、上記の脱酸生成物と同様な表面欠陥を持たらすことが知られている。図において、9はスラブ、40は2次冷却帯のロールである。
If such non-metallic inclusions are present in the vicinity of the surface of the slab, when the slab is hot-rolled and cold-rolled into a thin steel plate, defects such as swells and blisters occur on the surface of the steel plate, which is not preferable. . In addition to the deoxidation product, a mold powder added to the surface of the molten steel in the mold (mold) 30 illustrated in FIG. 1 or the
従って、自動車用鋼板や飲料缶用鋼板として使用するスラブでは、スラブ中への非金属介在物やモールドパウダ等の捕捉を大幅に減少させる必要がある。 Therefore, in a slab used as a steel plate for automobiles or a steel plate for beverage cans, it is necessary to greatly reduce the capture of non-metallic inclusions, mold powders and the like in the slab.
又、前述したアルミナを主体とした脱酸生成物は、タンディッシュ20から鋳型30へ溶鋼8を供給する際に用いる耐火物製の浸漬ノズル22に付着し、溶鋼流動を阻害して、スラブ品質の低下を引き起こすことも知られている。そこで、浸漬ノズル22へのアルミナ付着を防止するために様々な対策が採られているが充分ではない。
Further, the above-mentioned deoxidation product mainly composed of alumina adheres to the
そのため、薄スラブ連続鋳造プロセスのように、厚みの小さい鋳型30にノズルを挿入するため、浸漬ノズル22の内径、外径や吐出穴を小さくしなければならない場合には、浸漬ノズル22へのアルミナ付着を防止するために、鋼中にカルシウム等を添加している。しかしながら、カルシウム添加鋼は、鋼中に存在する介在物を粗大化したり、鋼の材質特性(延びや絞り性)を悪化させるために、自動車用鋼板として用いることができない。
Therefore, when inserting the nozzle into the
又、薄スラブ連続鋳造プロセスでは、鋳型の断面積が普通厚連続鋳造プロセスに比べて小さく、普通厚連続鋳造プロセスのように、介在物の浮遊機会が多くない。そのため、介在物やモールドパウダの捕捉量が増えてしまう。 In the thin slab continuous casting process, the cross-sectional area of the mold is smaller than that in the normal thickness continuous casting process, and there are not many opportunities for floating inclusions unlike the normal thickness continuous casting process. As a result, the amount of inclusions and mold powder captured increases.
更に、薄スラブ連続鋳造プロセスは、普通厚連続鋳造プロセスに比べて、鋳造速度は概ね速いものの、製造されるスラブの厚みが薄いために、鋼の重量を基準とした生産性を比較すると劣っている。 Furthermore, the thin slab continuous casting process is generally faster than the normal thick continuous casting process, but the thickness of the slab to be manufactured is thin, so the productivity based on the weight of the steel is inferior. Yes.
これに対して、全体を厚くすると、連鋳機内で完全に凝固を完了させるために必要な鋳造長さが増大するために鋳造速度を速められないと共に、スラブの厚みが増えると後工程の圧延における加熱炉での加熱時間の増大、圧延荷重の増大等の生産性を阻害する要因にもなる。 On the other hand, if the entire thickness is increased, the casting length required for complete solidification within the continuous casting machine is increased, so that the casting speed cannot be increased. It becomes a factor which inhibits productivity, such as increase in the heating time in a heating furnace, and increase in rolling load.
そこで特許文献1、2には、浸漬ノズル22の吐出口を扁平形状とし、浸漬ノズル22と鋳型壁面の間隔を50mm以上確保することが提案されている。
Therefore,
上記のように薄スラブ連続鋳造プロセスは、普通厚連続鋳造プロセスで必要となる分塊工程や熱間圧延工程が不要になるという利点はあるものの、製造可能な鋼種も限定され、本発明の主目的である自動車用外板用途向けのスラブを製造出来ないのが現状である。よって、品質上も、生産性の観点からも、有利なプロセスとは言えなかった。 As described above, the thin slab continuous casting process has the advantage that the bundling process and the hot rolling process that are normally required in the thick continuous casting process are not required, but the types of steel that can be produced are limited, and the main feature of the present invention is as follows. The present condition is that the slab for the outer plate | board use for vehicles which is the objective cannot be manufactured. Therefore, it was not an advantageous process from the viewpoint of quality and productivity.
これに対して普通厚連続鋳造プロセスでは、スラブを製造する段階で、上記したような鋼板の表面欠陥の原因となるスラブ表層欠陥の発生を防止する試みがこれまでになされてきた。以下に例を挙げる。 On the other hand, in the normal thickness continuous casting process, attempts have been made so far to prevent the occurrence of slab surface layer defects that cause the surface defects of the steel sheet as described above at the stage of manufacturing the slab. Examples are given below.
(1)鋳型内での溶鋼中からの脱酸生成物、モールドパウダあるいは気泡等の浮上・分離を促進すべく、垂直部を有する連鋳機で鋳造する。 (1) Casting is performed by a continuous casting machine having a vertical portion in order to promote the floating / separation of deoxidation products, mold powder, bubbles, etc. from the molten steel in the mold.
(2)モールドパウダの粘度を大きくして、溶鋼中へのモールドパウダの巻き込みを減少させる。 (2) Increase the viscosity of the mold powder to reduce the entrainment of the mold powder into the molten steel.
(3)電磁力により、メニスカス近傍に水平方向の流れを付与し、溶鋼内に浮遊する異物が凝固シェルに捕捉されるのを防止する(溶鋼流動による洗浄効果)(特許文献3等)。
(3) By applying an electromagnetic force, a horizontal flow is applied in the vicinity of the meniscus to prevent foreign matters floating in the molten steel from being trapped by the solidified shell (cleaning effect by molten steel flow) (
しかしながら、特許文献1や2に記載の技術では、特殊な扁平形状の浸漬ノズルを用いる必要があり、浸漬ノズルから鋳型内ヘの溶鋼流入が円滑で無くなる可能性がある。
However, in the techniques described in
又、上記の従来技術(1)〜(3)は、次に述べるような問題を残していた。 In addition, the conventional techniques (1) to (3) described above have left the following problems.
(1)のように、垂直部を有する連鋳機で生産したスラブであっても、近年ますます厳しくなっている表面厳格材の品質要求に応えることのできる品質レベルには達せられない。 As in (1), even a slab produced by a continuous casting machine having a vertical part cannot reach a quality level that can meet the quality requirements of strict surface strictors that have become increasingly severe in recent years.
(2)のように、モールドパウダの粘性を大きくした場合、モールドパウダが鋳型の潤滑に十分に寄与できず、鋳型内のシェル拘束、更にはブレークアウト発生等の危険が高まってしまい、望ましくない。 When the viscosity of the mold powder is increased as in (2), the mold powder cannot sufficiently contribute to the lubrication of the mold, which increases the risk of restraint of the shell in the mold and the occurrence of breakout, which is not desirable. .
(3)のように、メニスカス近傍で溶鋼流動を与えて介在物を洗浄しようとした場合、逆にメニスカスでのモールドパウダ巻き込みを増加させる懸念が生じる。又、凝固シェルへの熱伝達が促進されるため、凝固シェルの成長が阻害される。その結果、鋳型出口近傍で溶鋼静圧によるスラブ短辺バルジングが顕著になり、甚だしい場合には、シェル再溶解によるブレークアウトの発生に繋がり、鋳造の安定操業が阻害されるという問題があった。 As shown in (3), when it is attempted to clean the inclusions by applying a molten steel flow in the vicinity of the meniscus, there is a concern that mold powder entrainment at the meniscus is increased. Moreover, since heat transfer to the solidified shell is promoted, the growth of the solidified shell is inhibited. As a result, slab short-side bulging due to the molten steel static pressure becomes prominent near the mold outlet. In severe cases, breakout occurs due to shell remelting, which hinders stable casting operation.
上記のような技術に対しての問題点を解決するべく、(a)スラブ中の介在物(脱酸生成物、モールドパウダ、気泡等)を浮上除去する機会を多くするために、普通厚の鋳型において、鋳型中央部の厚みを増加することで、鋳型内の銅板表面側から、スラブ内部へ進行する凝固シェルに捕捉される介在物の個数を減少させることが可能となり、又、凝固シェルの凝固収縮量以上の変形を凝固シェルに与えない構造とすることで、凝固シェルへの負荷が増大して、凝固シェルの座屈、変形、あるいは凝固中の溶鋼の漏洩(いわゆるブレークアウト)等を避けることができる。又、(b)鋳型の下端部の厚みを上端部よりも減少させるため、鋳型の通過した後の2次冷却帯における連鋳機内の冷却能は相対的に低下しない。更に、(c)鋳型下端厚みと同様の冷却が実現できるため、スラブの生産性は確保される。結果として、(d)下工程に搬送するスラブの厚みが増加しないため、熱延加熱炉工程、厚板加熱炉工程での燃料原単価負荷も増大しない、等を実現させる技術として、一対の長辺面と一対の短辺面で形成され、溶鋼の入口側及び出口側が開放されている連続鋳造用鋳型であって、入口側の断面積が出口側の断面積より大きく、相対する長辺鋳型間距離が鋳造方向に縮小すると共に出口側は矩形形状であり、出口側の相対する長辺鋳型間距離が150mm以上、500mm以下である連続鋳造用鋳型を使用する。 In order to solve the problems with the technology as described above, (a) in order to increase the opportunity to float and remove inclusions (deoxidation products, mold powder, bubbles, etc.) in the slab, In the mold, by increasing the thickness of the mold center, it is possible to reduce the number of inclusions trapped in the solidified shell that proceeds from the copper plate surface side in the mold to the inside of the slab. By adopting a structure that does not give the solidified shell more deformation than the solidification shrinkage, the load on the solidified shell increases, causing buckling of the solidified shell, deformation, or leakage of molten steel during solidification (so-called breakout). Can be avoided. Further, (b) since the thickness of the lower end portion of the mold is made smaller than that of the upper end portion, the cooling capacity in the continuous casting machine in the secondary cooling zone after the mold has passed does not relatively decrease. Furthermore, since (c) cooling similar to the mold lower end thickness can be realized, slab productivity is ensured. As a result, (d) since the thickness of the slab transported to the lower process does not increase, the fuel unit price load in the hot rolling heating furnace process and the thick plate heating furnace process does not increase. A continuous casting mold formed of a side surface and a pair of short side surfaces, with the inlet side and outlet side of the molten steel being open, wherein the cross-sectional area on the inlet side is larger than the cross-sectional area on the outlet side, and the opposed long-side molds The casting distance is reduced in the casting direction, the outlet side has a rectangular shape, and a continuous casting mold having a distance between opposed long side molds on the outlet side of 150 mm or more and 500 mm or less is used.
この鋳型は、図2に示す如く、一対の長辺(30a)面と一対の短辺(30b)面で形成され、溶鋼の入口側(図2(B)…メニスカス位置)及び出口側(図2(C))が開放されており、入口側の断面積が出口側の断面積より大きい。出口側は、図2(C)に示す如く、長方形形状であり、出口側の相対する長辺鋳型間距離T2が150mm以上、500mm以下とされている。 As shown in FIG. 2, this mold is formed by a pair of long sides (30a) and a pair of short sides (30b), and the molten steel inlet side (FIG. 2B ... meniscus position) and outlet side (figure 2). 2 (C)) is open, and the sectional area on the inlet side is larger than the sectional area on the outlet side. As shown in FIG. 2C, the outlet side has a rectangular shape, and the distance T2 between the long side molds facing each other on the outlet side is 150 mm or more and 500 mm or less.
鋳型内の厚み拡大領域の形状は、図2(B)に示す如く、幅中央を最大厚として短辺方向に暫時減少する曲線を構成している。更に、厚み拡大領域の相対する長辺鋳型間距離は鋳造方向に向かって縮小し、鋳型入口側から距離Hで長方形形状になる。 As shown in FIG. 2B, the shape of the thickness expansion region in the mold forms a curve that decreases for a while in the short side direction with the maximum width at the center of the width. Furthermore, the distance between the long side molds opposite to each other in the thickness expansion region decreases toward the casting direction, and becomes a rectangular shape at a distance H from the mold inlet side.
図2(B)に示す厚み拡大領域の幅B1は、介在物浮上等の観点から、なるべく短辺近くにまで設けることが望ましいが、両端部近傍が平行とされているのは、幅変更に対応できるようにするためである。 The width B1 of the enlarged thickness region shown in FIG. 2B is desirably provided as close to the short side as possible from the viewpoint of inclusion floating, etc. This is in order to be able to cope.
前記鋳型30は、図1に示した如く、連鋳機に組み込まれて、スラブ9の連続鋳造に用いられる。
As shown in FIG. 1, the
上記の鋳型を用いて鋳造操業を重ねたところ、短辺近傍の凝固シェルの破断、鋳型の異常損耗、鋳型に過大な負荷が作用したことに起因する鋳型オシレーションの振動異常、更には、短辺近傍部からのブレークアウト等の重大なトラブルが発生した。それら、トラブルはいずれも、両短辺側の長辺平行部長が比較的小さい場合に発生していた。 When the casting operation was repeated using the above mold, the solidification shell near the short side was broken, the mold was worn abnormally, the mold oscillation was abnormal due to excessive load acting on the mold, and the short Serious troubles such as breakout from the neighborhood occurred. Both of these troubles occurred when the long side parallel part length on both short sides was relatively small.
本発明は、スラブの表面品質向上を目的に実施している厚み拡大領域を有する鋳型での鋳造操業において、上記のトラブルを確実に防止することを目的としている。 An object of the present invention is to surely prevent the above-described troubles in a casting operation with a mold having an enlarged thickness region, which is carried out for the purpose of improving the surface quality of a slab.
本発明者等は、上記の課題を解決するために、トラブル発生時の条件や鋳片の調査等を鋭意実施した結果なされたものであり、本発明は、一対の長辺面と一対の短辺面で形成され、溶鋼の入口側及び出口側が開放されている連続鋳造用鋳型であって、入口側の長辺中央部に、短辺側の平行部より広い厚み拡大領域が設けられ、入口側の断面積が出口側の断面積より大きく、相対する長辺鋳型間距離が鋳造方向に縮小すると共に出口側は矩形形状であり、出口側の相対する長辺鋳型間距離T2が150mm以上、500mm以下である連続鋳造用鋳型において、短辺側長辺平行部長Dmが、前記厚み拡大領域が完了するまで下式で表される短辺凝固シェル厚Dsよりも大であり、且つ、T2より小であることを特徴とする連続鋳造用鋳型及びその鋳型を用いた鋼の連続鋳造方法である。
Ds=k√(L/Vc)
ここで、k:定数(mm/min0.5)
L:メニスカスからの鋳込み方向の距離(m)
Vc:鋳造速度(m/min)
In order to solve the above-mentioned problems, the present inventors have been made as a result of diligently investigating conditions at the time of trouble occurrence and investigating slabs, and the present invention includes a pair of long side surfaces and a pair of short sides. It is a continuous casting mold formed on the side surface and having an inlet side and an outlet side of the molten steel open, and has a wider thickness expansion region at the center of the long side on the inlet side than the parallel part on the short side, The cross-sectional area on the side is larger than the cross-sectional area on the outlet side, the distance between the long side molds facing each other is reduced in the casting direction, and the outlet side is rectangular, and the distance T2 between the long side molds facing the outlet side is 150 mm or more, in the continuous casting mold is 500mm or less, the short side long side parallel director Dm is a larger than the short side solidified shell thickness Ds of the following formula to the thickness larger area is completed, and,
Ds = k√ (L / Vc)
Here, k: constant (mm / min 0.5 )
L: Distance in the casting direction from the meniscus (m)
Vc: Casting speed (m / min)
上記関係は、次式で表わすこともできる。
Dm>k√(L/Vc) …(1)
ここで、Dm:短辺側長辺平行部長(mm)、k:定数(mm/min0.5)、L:メニスカスからの鋳込み方向の距離(m)、Vc:鋳造速度(m/min)である。
The above relationship can also be expressed by the following equation.
Dm> k√ (L / Vc) (1)
Here, Dm: short side long side parallel part length (mm), k: constant (mm / min 0.5 ), L: distance in the casting direction from the meniscus (m), Vc: casting speed (m / min) It is.
本発明を用いることにより、浮上除去する鋳型内気泡・介在物除去によって、自動車用鋼板や、飲料缶等に使用される品質厳格材の表面品質を向上することが可能となる厚み拡大領域を有する鋳型での鋳造をトラブルなく操業できるようになる。 By using the present invention, by removing bubbles and inclusions in the mold to be lifted and removed, it has a thickness expansion region that makes it possible to improve the surface quality of quality steel materials used in automobile steel plates, beverage cans, etc. It becomes possible to operate casting with mold without any trouble.
以下図面を参照して、本発明に至った経緯及び実施形態を詳細に説明する。 Hereinafter, the background and embodiments leading to the present invention will be described in detail with reference to the drawings.
図3及び図4は、鋳型長辺面の短辺側近傍の短辺凝固シェルと長辺面厚み拡大部との位置関係を模式的に示した図である。図3は、操業トラブルが発生しなかった本発明の場合、図4は、操業トラブルが発生した比較例の場合の図である。 3 and 4 are diagrams schematically showing the positional relationship between the short-side solidified shell in the vicinity of the short side of the mold long-side surface and the long-side surface thickness enlarged portion. FIG. 3 is a diagram in the case of the present invention in which no operation trouble has occurred, and FIG. 4 is a diagram in the case of a comparative example in which an operation trouble has occurred.
図3の本発明の場合、メニスカスから成長している短辺凝固シェル9bの厚さDsが、鋳型長辺30aの短辺30b近傍に設けた平行部長Dmを超過することなく、厚み拡大領域下端を通過している。この場合、短辺凝固シェル9bは、鋳込み方向に向かって縮小する厚み拡大領域で発生する厚み方向の圧縮変形を受けることなく、鋳型を通過することになる。
In the case of the present invention of FIG. 3, the thickness Ds of the short-side solidified
一方、図4の比較例の場合、メニスカスから成長している短辺凝固シェル9bの厚さDsが、鋳型長辺30aの短辺30b近傍に設けた平行部長Dmを超過しており、超過した以降の短辺凝固シェル9bは、図4(A)に示すように、厚み拡大領域に達しており、引き抜きに際して、完全に凝固しているシェルを圧縮変形させる必要があるため、鋳型及び鋳片凝固シェルに過大な荷重が作用することになる。
On the other hand, in the case of the comparative example of FIG. 4, the thickness Ds of the short side solidified
このことが原因で、先に述べた、短辺近傍の凝固シェルの破断、鋳型の異常損耗、鋳型に過大な負荷が作用したことに起因する鋳型オシレーションの振動異常、更には、短辺近傍部からのブレークアウト等が発生していたのである。 Because of this, as mentioned above, fracture of the solidified shell near the short side, abnormal wear of the mold, abnormal vibration of the mold oscillation due to excessive load acting on the mold, and also near the short side There was a breakout from the department.
従って、上記トラブルを防止するためには、常に図3の状態、即ち、短辺30b側に設ける長辺平行部長Dmを、厚み拡大領域が完了するまでの短辺凝固シェル厚Dsよりも大きく設定する必要があることが判明した。
Therefore, in order to prevent the above trouble, the state shown in FIG. 3, that is, the long side parallel portion length Dm provided on the
短辺凝固シェル厚Dsは鋼種や鋳込み速度等で変化するが、次式
Ds=k√t=k√(L/Vc) …(2)
で近似することができる。ここで、Dm:短辺側長辺平行部長(mm)、k:定数(mm/min0.5)、t:鋳造時間(min)、L:メニスカスからの鋳込み方向の距離(m)、Vc:鋳造速度(m/min)であり、kは例えばブレークアウトした時の鋳片凝固シェルの厚み分布の調査により求めることができる。
Although the short side solidified shell thickness Ds varies depending on the steel type, the casting speed, etc., the following formula: Ds = k√t = k√ (L / Vc) (2)
Can be approximated by Here, Dm: short side long side parallel part length (mm), k: constant (mm / min 0.5 ), t: casting time (min), L: distance in the casting direction from the meniscus (m), Vc : Casting speed (m / min), and k can be obtained, for example, by investigating the thickness distribution of the slab solidified shell when breakout occurs.
従って、
Dm>k√(L/Vc) …(1)
を常に満足する、短辺側長辺平行部長Dmを設けることにより、上記課題が解決されるのである。
Therefore,
Dm> k√ (L / Vc) (1)
By providing the short side long side parallel part length Dm that always satisfies the above, the above problem is solved.
なお、kの求め方はブレークアウトに基づく場合に限らず、鋳型温度の測定値に基づいた伝熱計算などにより求めることも可能であり、限定されるものでない。 The method of obtaining k is not limited to the case based on the breakout, and can be obtained by heat transfer calculation based on the measured value of the mold temperature, and is not limited.
鋳型全長さ950mm、垂直部長さ2.5m、湾曲半径8.0mである垂直曲げ型連鋳機を用いて、鋳造試験を行なった。連鋳機(鋳型先端から機端まで)の長さは42mである。引き抜き速度を1.5〜2.5m/minの間で変更した。 A casting test was performed using a vertical bending type continuous casting machine having a total mold length of 950 mm, a vertical portion length of 2.5 m, and a bending radius of 8.0 m. The length of the continuous casting machine (from the mold tip to the machine end) is 42 m. The drawing speed was changed between 1.5 and 2.5 m / min.
鋼種は、極低炭素鋼(C:0.002%、Si:0.03%、Mn:0.2%、P:0.01%、S:0.01%)にて試験を行なった。 The steel type was tested with ultra-low carbon steel (C: 0.002%, Si: 0.03%, Mn: 0.2%, P: 0.01%, S: 0.01%).
使用した鋳型は、全幅(図2(C)中W2)が1600mm、鋳型上端厚肉部の厚み(図2(B)中T1)が300mm、鋳型上端薄肉部の厚み(図2(B)中A1)が220mm、鋳型下端薄肉部の厚み(図2(C)中T2)が220mm、鋳型上端から厚み拡大領域下端までの距離(図2(A)中H)が0.75m、鋳型上端からメニスカスまでが100mm(メニスカスから厚み拡大領域下端までの距離が0.65m)である。 The used mold has a total width (W2 in FIG. 2C) of 1600 mm, the thickness of the thick part at the upper end of the mold (T1 in FIG. 2B) is 300 mm, and the thickness of the thin part at the upper end of the mold (in FIG. 2B). A1) is 220 mm, the thickness of the thin part at the lower end of the mold (T2 in FIG. 2C) is 220 mm, the distance from the upper end of the mold to the lower end of the enlarged thickness area (H in FIG. 2A) is 0.75 m, from the upper end of the mold The distance to the meniscus is 100 mm (the distance from the meniscus to the lower end of the thickness expansion region is 0.65 m).
上記条件において、k=23とし、鋳型短辺側長辺平行部長Dmを0〜20mmまで変更した鋳型を製作し、200トン/ヒートの実験鋳造を行なった。各実験においては、鋳造中の鋳型オシレーションの振動波形の記録を行なうと共に、製造した鋳片表面の表面観察、鋳造後の鋳型内面の損傷有無の観察を行なった。 Under the above conditions, a mold was produced in which k = 23 and the mold short side long side parallel part length Dm was changed from 0 to 20 mm, and experimental casting was performed at 200 tons / heat. In each experiment, the vibration waveform of the mold oscillation during casting was recorded, the surface of the manufactured slab surface was observed, and the presence or absence of damage on the inner surface of the mold after casting was observed.
図5に実験条件及び結果をまとめて示す。本発明の規定する短辺側長辺平行部を設けた場合は、オシレーション異常、凝固シェル破断、鋳型の異常損耗・傷のいずれも発生せず、健全な鋳片を得ることが可能であった。 FIG. 5 summarizes the experimental conditions and results. When the short side long side parallel part defined by the present invention is provided, it is possible to obtain a sound slab without any occurrence of oscillation abnormality, solidified shell fracture, and abnormal wear and damage of the mold. It was.
なお、本実施例では、短辺側長辺平行部長Dmを鋳込み方向一定とした鋳型を用いたが、本発明はそれに限定されるものではなく、(1)式を満足させながら、鋳造方向にDmを変化させる方法も包含するものである。 In this example, a mold was used in which the short side side long side parallel part length Dm was constant in the casting direction. However, the present invention is not limited to this and in the casting direction while satisfying the expression (1). A method of changing Dm is also included.
8…溶鋼
9…鋳片
9b…短辺凝固シェル
30…鋳型
30a…鋳型長辺
30b…鋳型短辺
8 ...
Claims (2)
入口側の長辺中央部に、短辺側の平行部より広い厚み拡大領域が設けられ、
入口側の断面積が出口側の断面積より大きく、相対する長辺鋳型間距離が鋳造方向に縮小すると共に出口側は矩形形状であり、出口側の相対する長辺鋳型間距離T2が150mm以上、500mm以下である連続鋳造用鋳型において、
短辺側長辺平行部長Dmが、前記厚み拡大領域が完了するまで下式で表される短辺凝固シェル厚Dsよりも大であり、且つ、T2より小であることを特徴とする連続鋳造用鋳型。
Ds=k√(L/Vc)
ここで、k:定数(mm/min0.5)
L:メニスカスからの鋳込み方向の距離(m)
Vc:鋳造速度(m/min) A continuous casting mold that is formed of a pair of long side surfaces and a pair of short side surfaces, with the inlet side and the outlet side of the molten steel being open,
In the central part of the long side on the entrance side, there is a wider thickness expansion region than the parallel part on the short side,
The cross-sectional area on the inlet side is larger than the cross-sectional area on the outlet side, the distance between the long side molds facing each other is reduced in the casting direction, and the outlet side is rectangular, and the distance T2 between the long side molds facing each other on the outlet side is 150 mm or more. In a continuous casting mold that is 500 mm or less,
Continuous short side long side parallel director Dm is the is greater than the short sides solidified shell thickness Ds of the following formula to a thickness larger area is completed, and, characterized in that it is smaller than T 2 Casting mold.
Ds = k√ (L / Vc)
Here, k: constant (mm / min 0.5 )
L: Distance in the casting direction from the meniscus (m)
Vc: Casting speed (m / min)
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