JP2002361372A - CASTING METHOD FOR HIGH Cr-CONTAINING STEEL - Google Patents
CASTING METHOD FOR HIGH Cr-CONTAINING STEELInfo
- Publication number
- JP2002361372A JP2002361372A JP2001173089A JP2001173089A JP2002361372A JP 2002361372 A JP2002361372 A JP 2002361372A JP 2001173089 A JP2001173089 A JP 2001173089A JP 2001173089 A JP2001173089 A JP 2001173089A JP 2002361372 A JP2002361372 A JP 2002361372A
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- Japan
- Prior art keywords
- steel
- slab
- steel ingot
- ingot
- casting
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、高Ｃｒ含有鋼の造
塊法による鋼塊または連続鋳造法による鋳片を得るため
の鋳造方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting method for obtaining an ingot of a high Cr content steel by an ingot method or a slab by a continuous casting method.
【０００２】[0002]
【従来の技術】油井用鋼管、ボイラーなどの熱伝達用鋼
管、プラスチック用金型などに用いられる高Ｃｒ含有率
の合金鋼またはフェライト系ステンレス鋼では、それら
の素材として、通常の造塊法による鋼塊または連続鋳造
法による鋳片が用いられている。鋼塊および鋳片は、分
塊圧延および／または鍛造工程を経て、いったんビレッ
トに熱間加工された後、熱間加工されて上記最終製品と
なる。2. Description of the Related Art Alloy steels or ferritic stainless steels having a high Cr content used in steel pipes for oil wells, steel pipes for heat transfer such as boilers, molds for plastics, etc., are prepared by a conventional ingot casting method. A steel ingot or a slab by a continuous casting method is used. The ingots and slabs are subjected to slab rolling and / or forging processes and then once hot-worked into billets, and then hot-worked to become the final product.
【０００３】これら高Ｃｒ含有率の合金鋼またはフェラ
イト系ステンレス鋼の鋼塊および鋳片の内部には、ザク
またはセンターキャビティと呼ばれる凝固収縮に起因す
る内部欠陥（以下、単に内部欠陥と記す場合がある）が
発生しやすい。とくに高Ｃｒ含有率の溶鋼が凝固する際
の凝固収縮は大きく、鋼塊または鋳片の厚さ方向中心部
近傍に粗大なポロシティが生成し、これらポロシティが
集まってこれら内部欠陥が生成する。鋼塊または鋳片の
内部に粗大な内部欠陥が存在すると、鋼塊または鋳片を
熱間加工した際に、ビレットおよび最終製品にまで、こ
れら鋼塊または鋳片の内部欠陥が残存しやすい。[0003] Internal defects caused by solidification shrinkage called Zaku or center cavity (hereinafter sometimes referred to simply as internal defects) are present in the ingots and slabs of alloy steels or ferritic stainless steels having a high Cr content. Yes) is easy to occur. In particular, solidification shrinkage when molten steel having a high Cr content solidifies is large, and coarse porosity is generated near the center in the thickness direction of the steel ingot or slab, and these porosity is collected to generate these internal defects. If there are coarse internal defects inside the steel ingot or slab, when the steel ingot or slab is hot-worked, the internal defects in the steel ingot or slab tend to remain in the billet and the final product.
【０００４】そこで、鋼塊のこれら内部欠陥の発生を防
止するために、Ｎｉ基超合金などには、ＥＳＲ、ＶＡＲ
といった再溶解法が適用されているが、通常の造塊法に
比べて、製造コストが著しく高い。また、従来から造塊
用鋳型の形状変更などが実施されてきたが、鋳型テーパ
変更程度の鋳型形状変更だけでは、鋼塊の内部欠陥の低
減に対する効果は小さく、鋼塊に粗大なザクが生成しや
すい。[0004] Therefore, in order to prevent the occurrence of these internal defects in the steel ingot, Ni-based superalloys and the like include ESR and VAR.
Such a remelting method is applied, but the production cost is significantly higher than that of a normal ingot making method. In addition, changes in the shape of ingot casting molds have been carried out, but changing the shape of the mold only by changing the shape of the mold taper has little effect on the reduction of internal defects in the steel ingot, and a coarse zaku is generated in the steel ingot. It's easy to do.
【０００５】また、鋳片のこれら内部欠陥の発生を防止
するために、内部に未凝固部が存在する鋳片に圧下を加
え、内部欠陥を圧着する方法が採られている。たとえ
ば、特開平７−１０８３５８号公報には、丸ビレット鋳
片の連続鋳造において、内部に未凝固部が存在する間
に、楕円の長径方向に鋳片を圧下し、その後、丸ビレッ
トが真円となるように再度鋳片を圧下する方法が提案さ
れている。この方法は、厚さ方向両側の凝固界面を圧着
させることにより、これら内部欠陥の発生を防止する方
法である。Further, in order to prevent the occurrence of these internal defects in the slab, a method has been adopted in which a slab having an unsolidified portion therein is pressed down to press the internal defects. For example, Japanese Patent Application Laid-Open No. 7-108358 discloses that in continuous casting of round billet slab, while an unsolidified portion is present, the slab is rolled down in the major axis direction of the ellipse. A method has been proposed in which the slab is reduced again so that This method is to prevent the occurrence of these internal defects by pressing the solidification interfaces on both sides in the thickness direction.
【０００６】この特開平７−１０８３５８号公報で提案
された方法は、鋳片だけでなく、鋼塊にも適用でき、こ
れら鋼塊または鋳片の内部欠陥の発生の防止に効果的で
あると期待される。また、この方法では、圧下すること
によって、鋼塊または鋳片の内部に負偏析部が形成され
やすい。この負偏析部は、鋼塊または鋳片を熱間加工し
た後のビレットに残存し、さらにビレットを熱間加工し
た最終製品にまで残存しやすい。ただし、これら残存し
た負偏析部は、通常の炭素鋼の最終製品の機械的性質な
どに、とくに悪い影響を与えない。The method proposed in Japanese Patent Application Laid-Open No. Hei 7-108358 can be applied not only to cast slabs but also to steel ingots, and is effective in preventing the occurrence of internal defects in these steel ingots or cast slabs. Be expected. Further, in this method, the negative segregation portion is easily formed in the steel ingot or the slab by rolling down. The negatively segregated portion remains in the billet after hot working of the steel ingot or slab, and is likely to remain in the final product obtained by hot working the billet. However, these remaining negative segregation portions do not particularly adversely affect the mechanical properties of the final carbon steel product.
【０００７】しかし、この特開平７−１０８３５８号公
報で提案された鋳片を圧下する方法を、Ｃｒ含有率が５
質量％以上の合金鋼またはフェライト系ステンレス鋼の
鋼塊または鋳片に適用すると、ビレットおよび最終製品
に残存した負偏析部に、微細な割れが多く発生し、最終
製品の機械的性質などの目標性能を満足できないという
問題があった。However, the method of rolling down a slab proposed in Japanese Patent Application Laid-Open No.
When applied to ingots or slabs of alloy steels or ferritic stainless steels with a mass% or more, many fine cracks are generated in the billet and the negative segregation part remaining in the final product, and the target such as mechanical properties of the final product There was a problem that the performance could not be satisfied.
【０００８】[0008]
【発明が解決しようとする課題】本発明は、高Ｃｒ含有
鋼において、ザクまたはセンターキャビティと呼ばれる
凝固収縮に起因する内部欠陥の発生のない鋼塊または鋳
片を得るための鋳造方法を提供することを目的とする。SUMMARY OF THE INVENTION The present invention provides a casting method for obtaining a steel ingot or a slab in a high Cr-containing steel free from internal defects caused by solidification shrinkage called "Zaku" or "center cavity". The purpose is to:
【０００９】[0009]
【課題を解決するための手段】本発明の要旨は、Ｃｒを
５〜２０質量％、Ｃを０．０５〜０．３質量％含有する
溶鋼を鋳造し、鋼塊または鋳片の内部に未凝固部が存在
する間に鋼塊または鋳片の外表面をその厚さ方向に圧下
することにより、鋼塊または鋳片の内部の厚さ方向両側
の凝固殻を圧着させ、凝固後の鋼塊または鋳片の内部の
厚さ方向中心部近傍に負偏析部を形成させる鋳造方法で
あって、上記溶鋼の水素含有率を４ｐｐｍ以下とする高
Ｃｒ含有鋼の鋳造方法にある。SUMMARY OF THE INVENTION The gist of the present invention is to cast a molten steel containing 5 to 20% by mass of Cr and 0.05 to 0.3% by mass of C, and leave the molten steel in a steel ingot or slab. By pressing down the outer surface of the steel ingot or slab in the thickness direction while the solidified portion exists, the solidified shells on both sides in the thickness direction inside the steel ingot or slab are pressed, and the solidified steel ingot Alternatively, there is provided a casting method for forming a negatively segregated portion in the vicinity of the center in the thickness direction of the slab, wherein the molten steel has a hydrogen content of 4 ppm or less.
【００１０】本発明で規定する「Ｃｒを５〜２０質量
％、Ｃを０．０５〜０．３質量％含有する溶鋼」とは、
上記ＣｒおよびＣ以外に、必要に応じて、質量％で、Ｓ
ｉ：０．０５〜０．４％、Ｍｎ：０．２〜２％、ｓｏ
ｌ．Ａｌ：０．１％以下、Ｍｏ：１．５％以下、Ｎｉ：
１．５％以下、Ｃｕ：１．５％以下、Ｔｉ：０．１％以
下、Ｎｂ：０．１％以下およびＶ：０．１％以下のうち
の１種または２種以上を含有し、残部がＦｅおよび不純
物からなる合金鋼またはフェライト系ステンレス鋼の溶
鋼を意味する。また、そのうちのフェライト系ステンレ
ス鋼の溶鋼とは、Ｃｒ含有率が１３質量％以上の鋼の溶
鋼を意味する。[0010] The term "molten steel containing 5 to 20% by mass of Cr and 0.05 to 0.3% by mass of C" as defined in the present invention means:
In addition to the above Cr and C, if necessary, by mass%, S
i: 0.05 to 0.4%, Mn: 0.2 to 2%, so
l. Al: 0.1% or less, Mo: 1.5% or less, Ni:
1.5% or less, Cu: 1.5% or less, Ti: 0.1% or less, Nb: 0.1% or less, and V: one or more of 0.1% or less, The remainder means molten steel of alloy steel or ferritic stainless steel consisting of Fe and impurities. Further, the molten steel of ferritic stainless steel means a molten steel of steel having a Cr content of 13% by mass or more.
【００１１】また、本発明で規定する「鋼塊」とは、い
わゆる造塊法によって鋳造された鋼塊を、また「鋳片」
とは、連続鋳造鋳片で鋳造された鋳片を意味する。さら
に、本発明で規定する「鋳造方法」とは、造塊法または
連続鋳造方法を意味する。[0011] The "steel ingot" defined in the present invention means a steel ingot cast by a so-called ingot-making method, or a "slab".
Means a slab cast with a continuous cast slab. Further, the “casting method” defined in the present invention means an ingot casting method or a continuous casting method.
【００１２】内部に未凝固部が存在する状態で、鋼塊ま
たは鋳片の内部の厚さ方向両側の凝固殻を圧着させる程
度に、鋼塊または鋳片の外表面に圧下を加え、これら内
部欠陥を圧着する方法は、鋼塊および鋳片の内部欠陥の
発生を防止するために、効果的な方法である。In a state where an unsolidified portion is present inside, the outer surface of the steel ingot or the slab is pressed down to the extent that the solidified shells on both sides in the thickness direction of the steel ingot or the slab are pressed together. The method of crimping a defect is an effective method for preventing the occurrence of internal defects in a steel ingot and a slab.
【００１３】しかし、Ｃｒ含有率が５質量％以上の合金
鋼またはフェライト系ステンレス鋼の鋼塊または鋳片に
上記方法を適用した場合、鋼塊または鋳片に負偏析部が
生成し、さらにビレットおよび最終製品にまで残存した
負偏析部に、微細な割れが著しく発生し、最終製品の機
械的性質などの目標性能を満足できない。そこで、これ
らの割れの生成機構およびその防止方法を検討した結
果、鋳造する際に用いる溶鋼の水素含有率を４ｐｐｍ以
下とすることにより、この割れを防止できることがわか
った。以下に、その詳細を説明する。However, when the above method is applied to a steel ingot or a slab of an alloy steel or a ferritic stainless steel having a Cr content of 5% by mass or more, a negative segregation is formed in the steel ingot or the slab and the billet is further increased. Further, minute cracks are remarkably generated in the negative segregated portion remaining even in the final product, and the target performance such as mechanical properties of the final product cannot be satisfied. Therefore, as a result of examining the mechanism of generation of these cracks and the method of preventing them, it was found that the cracks can be prevented by setting the hydrogen content of molten steel used for casting to 4 ppm or less. The details will be described below.
【００１４】通常の炭素鋼などの鋼塊または鋳片を、内
部に未凝固部が存在する状態で、厚さ方向両側の凝固殻
を圧着させる程度に圧下した場合にも、鋼塊または鋳片
の内部に負偏析部が生成する。厚さ方向両側の凝固殻を
圧着させることにより、凝固界面近傍のデンドライト樹
間に存在する、Ｃ、Ｐ、Ｍｎ、Ｓ、Ｃｒなどの成分が濃
化した未凝固の溶鋼が絞り出され、絞り出された後のデ
ンドライト組織は、そのまま圧着して、圧下時に既に凝
固完了していた凝固組織より成分含有率の低い負偏析状
態の凝固組織（負偏析部）となる。[0014] Even when an ingot or slab of ordinary carbon steel or the like is pressed down to the extent that the solidified shells on both sides in the thickness direction are pressed in a state where an unsolidified portion is present inside, the ingot or slab is , A negative segregation part is generated inside. By pressing the solidified shells on both sides in the thickness direction, unsolidified molten steel in which components such as C, P, Mn, S, and Cr exist between dendrite trees near the solidification interface is squeezed out and drawn. The dendrite structure after being discharged is pressed as it is to form a solidified structure (negative segregated portion) in a negatively segregated state having a lower component content than the solidified structure that has already been solidified at the time of reduction.
【００１５】とくに、質量％で、Ｃｒを５〜２０％、Ｃ
を０．０５〜０．３％含有する合金鋼またはフェライト
系ステンレス鋼の溶鋼を鋳造し、未凝固部を含む鋼塊ま
たは鋳片を圧下する際には、著しい負偏析の凝固組織が
発生しやすい。このように負偏析部の形成された鋼塊ま
たは鋳片を、高温状態のまま、または、いったん室温近
傍まで冷却後に加熱した後、熱間加工して、ビレットな
どの中間素材を製造する際、これら熱間加工したビレッ
トに負偏析部が残存し、その残存した負偏析部に粗大な
フェライト組織（以下、単にフェライトと記す）が生成
し、そのフェライトに沿って微細な割れが発生すること
がわかった。これらビレットに残存した負偏析部および
負偏析部に発生した微細な割れが、最終製品にまで残存
する。In particular, 5% to 20% of Cr,
Of alloy steel or ferritic stainless steel containing 0.05 to 0.3% by volume and rolling down a steel ingot or slab containing an unsolidified portion, a solidified structure of remarkable negative segregation occurs. Cheap. The steel ingot or slab in which the negative segregation portion was formed in this way, in a high-temperature state, or after once heating after cooling to around room temperature, hot working, when producing an intermediate material such as a billet, Negative segregated portions remain in these hot-worked billets, and coarse ferrite structures (hereinafter simply referred to as ferrites) are formed in the remaining negative segregated portions, and fine cracks may occur along the ferrite. all right. The negative segregated portions remaining in these billets and the fine cracks generated in the negative segregated portions remain in the final product.
【００１６】本発明が対象とする合金鋼またはフェライ
ト系ステンレス鋼では、鋼塊または鋳片を圧下すること
により形成させた負偏析部において、各成分の平均的な
含有率に対して、どの程度含有率が低いか、つまり、ど
の程度の負偏析状態かは、成分元素により相違する。In the alloy steel or ferritic stainless steel to which the present invention is applied, in the negative segregation portion formed by rolling down a steel ingot or a slab, how much the average content of each component is reduced. Whether the content is low, that is, the degree of negative segregation, depends on the component elements.
【００１７】Ｃは、もともと偏析しやすい元素であるた
め、凝固界面が圧着する程度に圧下すると、圧下された
部分の負偏析状態が著しく、平均的なＣ含有率の５０〜
８０％の含有率にまで負偏析（含有率が低下）すること
がわかった。一方、Ｃｒは、上記Ｃに比べ偏析しにく
く、平均的なＣｒ含有率の９５〜９８％の含有率にまで
しか低下しないことがわかった。Since C is an element that is easily segregated from the beginning, when the solidification interface is reduced to the extent that it is pressed, the negatively segregated state of the reduced part is remarkable, and the average C content is 50 to 50%.
It was found that the negative segregation (the content decreased) up to the content of 80%. On the other hand, it was found that Cr is less likely to segregate than the above-mentioned C, and is reduced only to an average Cr content of 95 to 98%.
【００１８】Ｃは、オーステナイト安定化元素であり、
負偏析部においてＣ含有率が低下すると、その凝固組織
はフェライトとなる。一方、Ｃｒは、フェライト安定化
元素であり、とくに、含有率が５質量％以上の合金鋼ま
たはフェライト系ステンレス鋼では、凝固組織は安定し
てフェライトとなり、さらに、負偏析部におけるＣｒ含
有率の低下はわずかなので、負偏析部の凝固組織は安定
してフェライトとなりやすい。C is an austenite stabilizing element,
When the C content decreases in the negative segregation part, the solidified structure becomes ferrite. On the other hand, Cr is a ferrite stabilizing element. In particular, in an alloy steel or a ferritic stainless steel having a content of 5% by mass or more, the solidification structure becomes stably ferrite, and the Cr content in the negative segregation portion is further reduced. Since the decrease is slight, the solidified structure of the negative segregation portion is liable to become ferrite stably.
【００１９】上記のことから、鋼塊または鋳片の負偏析
部におけるＣ含有率の低下した部分では、外側をオース
テナイト組織（以下、単にオーステナイトと記す）に取
り囲まれた状態で島状にフェライトが存在する凝固組織
となる。このような島状のフェライトは、鋳造直後の高
温状態で生成し、その後の冷却過程を経て、室温状態の
鋼塊または鋳片まで残存する。From the above, in the portion where the C content is reduced in the negatively segregated portion of the steel ingot or slab, the ferrite is island-shaped with the outside surrounded by an austenitic structure (hereinafter simply referred to as austenite). The coagulated tissue is present. Such island-like ferrite is generated in a high temperature state immediately after casting, and after a cooling process, remains as a steel ingot or a slab at room temperature.
【００２０】ところで、オーステナイトに比べ、フェラ
イト中の水素溶解度は低く、かつフェライト中の水素の
拡散速度は速い。鋼塊または鋳片の温度が鋳造直後のよ
うに高温状態であれば、オーステナイト中でもフェライ
ト中でも、水素は固溶しているが、その後の冷却過程で
温度が低下するにつれて、オーステナイトおよびフェラ
イトにおける水素溶解度は低下し、水素溶解度の小さな
フェライトにおいて、オーステナイトよりも先に固溶限
界に達する。固溶限界に達したフェライト中の水素原子
は水素溶解度の高いオーステナイト中に拡散するが、フ
ェライト中に比べてオーステナイト中における水素の拡
散速度が遅いので、これら水素原子は、フェライト中に
存在する微細な空隙中に水素ガスとして残留する。微細
な空隙は、結晶粒界、非金属介在物と地の組織（マトリ
ックス）との異相接合部、ミクロポロシティなどに通常
存在する。By the way, as compared with austenite, the solubility of hydrogen in ferrite is low, and the diffusion rate of hydrogen in ferrite is high. If the temperature of the ingot or slab is high, such as immediately after casting, hydrogen is dissolved in both austenite and ferrite, but as the temperature decreases in the subsequent cooling process, the hydrogen solubility in austenite and ferrite decreases. Decreases, and reaches the solid solubility limit in ferrite having a low hydrogen solubility before austenite. Hydrogen atoms in ferrite that has reached the solid solution limit diffuse into austenite, which has high hydrogen solubility, but the diffusion rate of hydrogen in austenite is slower than in ferrite. Remains as hydrogen gas in the voids. Fine voids are usually present at grain boundaries, at heterogeneous junctions between nonmetallic inclusions and the ground structure (matrix), at microporosity, and the like.
【００２１】鋼塊または鋳片を鋳造直後の高温状態のま
ま引き続き、または、室温までいったん冷却した後に加
熱し、熱間圧延または熱間鍛造などの熱間加工を加える
と、上記フェライト中の微細な空隙中の水素ガスの圧力
が高くなり、フェライトの強度が小さいことから、フェ
ライト中の微細な空隙を起点に割れが発生する。この割
れが、負偏析部に発生する微細な割れである。When the steel ingot or slab is continuously heated in a high temperature state immediately after casting, or once cooled to room temperature and then heated and subjected to hot working such as hot rolling or hot forging, the fine particles in the ferrite are reduced. Since the pressure of the hydrogen gas in the voids increases and the strength of the ferrite is low, cracks are generated starting from the fine voids in the ferrite. This crack is a fine crack generated in the negative segregation part.
【００２２】負偏析部の割れの生成機構と防止対策の検
討の結果、鋳造する溶鋼の水素含有率を４ｐｐｍ以下と
することにより、鋼塊または鋳片を熱間加工した後のビ
レット、およびそのビレットを用いて熱間加工した最終
製品の冷却過程において、６００〜８００℃程度の低温
まで、フェライト中の溶解度以下となる状態を保てるこ
と、さらに、水素含有率が過飽和に達しても、上記温度
程度では、水素の拡散速度は遅く、微細な空隙への水素
ガスの放散は実質的に問題のない程度にしか起こらない
ことがわかった。As a result of studying the mechanism of generation of cracks in the negative segregation zone and measures to prevent it, the hydrogen content of the molten steel to be cast was set to 4 ppm or less, so that the billet after hot working of the steel ingot or slab, and its billet. In the cooling process of the final product hot-worked using a billet, it is possible to keep the state of solubility in ferrite up to a low temperature of about 600 to 800 ° C. Further, even if the hydrogen content reaches supersaturation, the above temperature is maintained. It has been found that the diffusion rate of hydrogen is so low that the hydrogen gas is diffused into the fine voids only to the extent that there is substantially no problem.
【００２３】したがって、本発明が対象とする高Ｃｒ含
有率の合金鋼またはフェライト系ステンレス鋼の溶鋼を
鋳造する際に、溶鋼の水素含有率を４ｐｐｍ以下とする
ことによって、鋼塊または鋳片を熱間加工したビレット
および最終製品において、鋼塊または鋳片に形成させた
負偏析部に起因する割れの発生を防止することができ
る。Therefore, when casting a molten steel of alloy steel or ferritic stainless steel having a high Cr content, which is a target of the present invention, the hydrogen content of the molten steel is set to 4 ppm or less, whereby the steel ingot or slab can be formed. In the hot-worked billet and the final product, it is possible to prevent the occurrence of cracks due to the negatively segregated portions formed in the steel ingot or slab.
【００２４】[0024]
【発明の実施の形態】本発明が対象とする鋳造方法に
は、いわゆる鋼塊を鋳造する造塊法と、連続鋳造方法と
がある。まず、本発明を実施する場合の造塊法による鋼
塊の例について、以下に説明する。図１は、内部に未凝
固部が存在する間に、鋼塊の外表面を厚さ方向に圧下す
る状況の例を示す模式図である。未凝固部３が存在する
鋼塊１を造塊用鋳型（図示していない）から引き抜き、
この鋼塊を吊り具６で吊りながら、油圧プレス装置（図
示していない）のシリンダ５の先端に設けた金具４で、
凝固殻２が圧着するように、鋼塊の外表面を両側から厚
さ方向に圧下している状況を示す。DESCRIPTION OF THE PREFERRED EMBODIMENTS Casting methods to which the present invention is applied include a so-called ingot casting method for casting a steel ingot and a continuous casting method. First, an example of a steel ingot by the ingot-making method in the case of carrying out the present invention will be described below. FIG. 1 is a schematic diagram showing an example of a situation in which the outer surface of a steel ingot is pressed down in the thickness direction while an unsolidified portion exists inside. The steel ingot 1 in which the unsolidified portion 3 exists is pulled out from an ingot casting mold (not shown),
While hanging this steel ingot with the hanging tool 6, the metal fitting 4 provided at the tip of the cylinder 5 of the hydraulic press device (not shown)
This shows a situation where the outer surface of the steel ingot is pressed down from both sides in the thickness direction so that the solidified shell 2 is pressed.
【００２５】対象とする鋼塊の大きさは、３ｔ程度以上
の鋼塊に適用するのが効果的である。３ｔの鋼塊で、水
平断面形状が長方形の場合、高さが２０００ｍｍで、水
平断面の厚さ４００ｍｍ、幅５００ｍｍ程度の大きさと
なる。また、水平断面形状が円形の鋼塊の場合は、高さ
２０００ｍｍ、直径５００ｍｍ程度の大きさとなる。It is effective to apply the target steel ingot to a steel ingot of about 3 t or more. In the case of a 3t steel ingot having a rectangular cross section, the height is 2000 mm, the thickness of the horizontal cross section is 400 mm, and the width is about 500 mm. Further, in the case of a circular steel ingot having a horizontal cross-sectional shape, the size is about 2000 mm in height and about 500 mm in diameter.
【００２６】圧下装置には、一般的な油圧プレス装置な
どを用いればよい。また、鋼塊を圧下する治具、すなわ
ち金型の大きさおよび形状は、鋼塊の大きさ、形状、圧
下する回数などで決めればよい。３ｔ程度以上の鋼塊の
場合、たとえば鋼塊と接する面の形状が、縦２００〜４
００ｍｍ、横５００〜１０００ｍｍ程度の長方形の金型
を用いることができる。その際、鋼塊と接する金型のコ
ーナー部分には丸味をもたせるのがよい。丸味をもたせ
ると、鋼塊の表面に圧下による疵が発生しにくい。鋼塊
の横断面形状が円形の場合には、鋼塊と接する金型の内
面形状を疑似円形状としてもよい。A general hydraulic press device or the like may be used as the pressing device. Also, the size and shape of the jig for rolling down the steel ingot, that is, the mold, may be determined by the size and shape of the steel ingot, the number of times of rolling down, and the like. In the case of a steel ingot of about 3t or more, for example, the shape of the surface in contact with the steel ingot is 200 to 4 in length.
A rectangular mold having a size of about 00 mm and a width of about 500 to 1000 mm can be used. At this time, it is preferable that the corner of the mold in contact with the steel ingot be rounded. When the roundness is imparted, the surface of the steel ingot is less likely to have scratches due to the rolling. When the cross section of the steel ingot is circular, the inner surface shape of the mold in contact with the steel ingot may be a pseudo circular shape.
【００２７】圧下する鋼塊の側面とは、水平断面形状が
長方形の場合には、両側の長辺側であり、正方形の場合
には、相対する側面である。円形の鋼塊の場合には、鋼
塊の中心軸を挟んで相対する位置である。The side surfaces of the steel ingot to be reduced are long sides on both sides when the horizontal sectional shape is rectangular, and are opposite side surfaces when the horizontal sectional shape is square. In the case of a circular steel ingot, the position is opposite to the central axis of the steel ingot.
【００２８】圧下する際、鋼塊の高さ方向で、少なくと
も未凝固部が存在する領域に相当する位置の側面を圧下
するのがよい。さらに、複数回圧下する場合に、鋼塊の
高さ方向の位置における圧下の順番は、上方からでもよ
いし、下方からでもよいし、高さの中央部近傍から圧下
を開始しても構わない。When rolling down, it is preferable to roll down at least the side surface in the height direction of the steel ingot at a position corresponding to the region where the unsolidified portion exists. Furthermore, when rolling down a plurality of times, the order of rolling at the position in the height direction of the steel ingot may be from above, may be from below, or may be started from near the center of the height. .
【００２９】圧下を開始する時期は、たとえば、水平断
面形状が長方形である鋼塊の両側の長辺側を圧下する場
合、未凝固部の厚さが、両長辺間の距離、すなわち鋼塊
の厚さの１５〜４０％程度となる時期が望ましい。ま
た、水平断面形状が円形である鋼塊の相対する２方向か
ら鋼塊の側面を圧下する場合も、未凝固部の直径が鋼塊
の直径の１５〜４０％程度となる時期が望ましい。When the rolling is started, for example, when rolling down the long sides of both sides of a steel ingot having a rectangular horizontal cross-sectional shape, the thickness of the unsolidified portion depends on the distance between the two long sides, ie, the steel ingot. It is desirable to have a time when the thickness becomes about 15 to 40% of the thickness. Also, when the side surfaces of the steel ingot are reduced from two opposite directions of the steel ingot having a circular horizontal cross-sectional shape, it is desirable that the unsolidified portion has a diameter of about 15 to 40% of the diameter of the steel ingot.
【００３０】具体的には、たとえば、一般的に用いられ
ている凝固厚さＤ（ｍｍ）と凝固時間Ｔ（分）との間の
関係式であるＤ＝Ｋ×Ｔ１／２ （一般的にルート則と
言う）を用いて、圧下を開始する時期を求めることがで
きる。ただし、Ｋは凝固係数で、造塊用鋳型の質量、溶
鋼の注入温度などで決まる係数である。一般的には、ほ
ぼ２０〜３０（ｍｍ×分−１／２）の値である。鋳型内
に注入した溶鋼にトレーサーを添加することにより、こ
のＫ値を確認することができる。More specifically, for example, D = K × T 1/2 (general expression) which is a relational expression between a commonly used solidification thickness D (mm) and a solidification time T (minutes) The time to start the reduction can be determined using the route rule. Here, K is a solidification coefficient, which is a coefficient determined by the mass of the ingot casting mold, the molten steel injection temperature, and the like. Generally, it is a value of approximately 20 to 30 (mm × minute− ／ ). This K value can be confirmed by adding a tracer to the molten steel injected into the mold.
【００３１】鋼塊内部の未凝固部の厚さが上記程度にな
る時期においては、鋼塊の上部も凝固が進行することに
より凝固殻が形成され、鋼塊内部の未凝固部は閉じこめ
られた状態となる。この状態で鋼塊の両側の長辺側を圧
下する場合には、内部の未凝固の溶鋼は鋼塊の外部に漏
れることはない。圧下することによって減少する未凝固
部の体積に相当する容量だけ、既に凝固した凝固殻が変
形するとともに、未凝固部の溶鋼の凝固が促進されるか
らである。At the time when the thickness of the unsolidified portion inside the steel ingot reaches the above-mentioned level, solidification of the upper portion of the steel ingot progresses to form a solidified shell, and the unsolidified portion inside the steel ingot is confined. State. When the long sides of both sides of the steel ingot are lowered in this state, the unsolidified molten steel inside does not leak to the outside of the steel ingot. This is because the solidified shell already solidified is deformed by the volume corresponding to the volume of the unsolidified portion that is reduced by the rolling, and the solidification of the molten steel in the unsolidified portion is promoted.
【００３２】圧下を開始する時期における鋼塊の表面温
度は６００〜１０００℃程度とするのが望ましい。６０
０℃未満では、鋼塊の凝固殻の強度が高いため、圧下が
困難となるので、圧下の効果が発揮できない。また、過
大な圧下装置を用いるのは現実的でない。１０００℃を
超える場合には、鋼塊の凝固殻の強度が低いため、圧下
の効果を十分発揮できない。なお、鋼塊の表面温度は、
鋼塊の側面の圧下される部分の温度とすることが望まし
く、放射温度計などにより測定できる。It is desirable that the surface temperature of the steel ingot at the time of starting the rolling be about 600 to 1000 ° C. 60
If the temperature is lower than 0 ° C., since the strength of the solidified shell of the steel ingot is high, it is difficult to reduce the steel. Further, it is not practical to use an excessively low rolling device. When the temperature exceeds 1000 ° C., the strength of the solidified shell of the steel ingot is low, so that the rolling effect cannot be sufficiently exhibited. The surface temperature of the ingot is
It is desirable to use the temperature of the part to be reduced on the side surface of the steel ingot, which can be measured by a radiation thermometer or the like.
【００３３】鋼塊内部の厚さ方向両側の凝固殻を圧着さ
せ、凝固後の鋼塊内部の厚さ方向中心部近傍に負偏析部
を形成させるように鋼塊を圧下する。その際の必要な圧
下量は、事前に鋳造試験により確認するのがよい。これ
は、造塊用鋳型、鋼塊などの大きさによって、必要な圧
下量が変化するからであるが、少なくとも圧下開始時の
未凝固部の厚さ以上の圧下量とする。The solidified shells on both sides in the thickness direction inside the steel ingot are pressed together, and the steel ingot is lowered so as to form a negatively segregated portion near the center in the thickness direction inside the solidified steel ingot. The amount of reduction required at that time is preferably confirmed in advance by a casting test. This is because the required amount of reduction varies depending on the size of the ingot casting mold, the steel ingot, and the like. However, the amount of reduction is at least the thickness of the unsolidified portion at the start of the reduction.
【００３４】鋼塊内部の厚さ方向両側の凝固殻を圧着さ
せることにより、凝固後の鋼塊内部の厚さ方向中心部近
傍に負偏析部を形成させることができる。その際、鋼塊
の厚さ方向における負偏析部の厚さは、鋼塊の大きさに
もよるが、圧下した方向における圧下後の鋼塊の厚さま
たは直径の１５〜４０％が望ましい。By pressing the solidified shells on both sides in the thickness direction inside the steel ingot, a negative segregation portion can be formed near the center in the thickness direction inside the solidified steel ingot. At this time, the thickness of the negatively segregated portion in the thickness direction of the steel ingot depends on the size of the steel ingot, but is desirably 15 to 40% of the thickness or diameter of the steel ingot in the reduced direction.
【００３５】つぎに、本発明を実施する場合の連続鋳造
方法による鋳片の例について、以下に説明する。本発明
が対象とする油井用鋼管、熱伝達用鋼管、プラスチック
用金型などに用いられる素材を連続鋳造する場合、湾曲
型、垂直型または垂直曲げ型のブルーム連続鋳造機か、
または、水平式連続鋳造機を用いて、横断面形状が正方
形または長方形のブルーム鋳片か、または丸形状の丸鋳
片が、通常、鋳造される。ブルーム鋳片または丸鋳片の
大きさは、通常、長方形のブルーム鋳片で縦３００ｍ
ｍ、横４００ｍｍ程度、丸鋳片で直径２００〜３００ｍ
ｍ程度である。以下では、水平式連続鋳造機を用いて、
丸鋳片を鋳造する場合の例を説明する。Next, an example of a slab by the continuous casting method when the present invention is carried out will be described below. When continuously casting materials used for oil well steel pipes, heat transfer steel pipes, plastic molds, and the like, which are targeted by the present invention, a curved, vertical or vertical bending type bloom continuous caster,
Alternatively, bloom cast pieces having a square or rectangular cross section or round cast pieces having a round shape are usually cast using a horizontal continuous caster. Bloom slabs or round slabs are usually rectangular bloom slabs and 300m long
m, width about 400mm, round cast slab diameter 200-300m
m. In the following, using a horizontal continuous casting machine,
An example of casting a round slab will be described.
【００３６】図２は、内部に未凝固部が存在する間に、
水平式連続鋳造機を用いて鋳造された丸鋳片を圧下する
状況の例を示す模式図である。取鍋７内の溶鋼１５は、
ロングノズル８を経てタンデイッシュ９内に注入され、
フィードノズル１０を介して鋳型１１内に供給される。
鋳型内で形成された凝固殻１７は、さらに冷却用ノズル
１２から吹き付けられる冷却水で冷却される。未凝固部
１６を含む鋳片は、ガイドロール１３で案内されなが
ら、ピンチロール１４により圧下され、また、鋳片１８
はピンチロールによって引き抜かれる。圧下位置におけ
る鋳片内部の未凝固部の溶鋼は、圧下により、順次その
上流側に排出される。FIG. 2 shows that while an unsolidified portion exists inside,
It is a schematic diagram which shows the example of the situation which rolls down the round cast piece cast using the horizontal continuous casting machine. The molten steel 15 in the ladle 7
Injected into tundish 9 via long nozzle 8,
It is supplied into the mold 11 through the feed nozzle 10.
The solidified shell 17 formed in the mold is further cooled by cooling water blown from the cooling nozzle 12. The slab including the unsolidified portion 16 is pressed down by the pinch roll 14 while being guided by the guide roll 13, and the slab 18
Is pulled out by a pinch roll. The molten steel in the unsolidified portion inside the slab at the rolling down position is sequentially discharged to the upstream side by rolling down.
【００３７】圧下装置として、通常配置されているピン
チロールを用いることができる。通常、ピンチロールは
上下方向または水平方向にロール対として相対する位置
に配置されているので、丸鋳片を効果的に圧下できる。
また、丸鋳片を引き抜きながら、連続的に圧下すること
ができる。As the pressing-down device, a pinch roll which is usually arranged can be used. Usually, since the pinch rolls are arranged at positions facing each other as a pair of rolls in the vertical direction or the horizontal direction, the round cast slab can be effectively reduced.
Further, it is possible to continuously reduce the pressure while pulling out the round slab.
【００３８】連続鋳造機では配置されたピンチロールの
位置は、通常、固定式であるので、圧下するピンチロー
ルの位置における丸鋳片内部の未凝固部の直径を、たと
えば、鋳造速度と二次冷却の比水量条件で調整するのが
よい。In a continuous casting machine, the position of the pinch rolls arranged is usually of a fixed type, so that the diameter of the unsolidified portion inside the round cast at the position of the pinch roll to be reduced is determined by, for example, the casting speed and the secondary speed. It is preferable to adjust the specific water volume condition for cooling.
【００３９】圧下するピンチロールの位置における丸鋳
片内部の未凝固部の直径は、丸鋳片の直径の１０〜３０
％程度となる時期が望ましい。未凝固部の直径は、凝固
伝熱解析方法により計算で求めることができ、また、予
め、連続鋳造用鋳型内に注入した溶鋼にトレーサーを添
加する試験により求めることができる。The diameter of the unsolidified portion inside the round slab at the position of the pinch roll to be reduced is 10 to 30 times the diameter of the round slab.
% Is desirable. The diameter of the unsolidified portion can be determined by calculation using a solidification heat transfer analysis method, or can be determined by a test in which a tracer is added to molten steel previously poured into a continuous casting mold.
【００４０】圧下を開始する時期における丸鋳片の表面
温度は６００〜１０００℃程度とするのが望ましい。６
００℃未満では、丸鋳片の凝固殻の強度が高いため、圧
下が困難となるので、圧下の効果が発揮できない。１０
００℃を超える場合には、丸鋳片の凝固殻の強度が低い
ため、圧下の効果を十分発揮できない。なお、丸鋳片の
表面温度は、放射温度計などにより測定できる。It is desirable that the surface temperature of the round slab at the time of starting the rolling be about 600 to 1000 ° C. 6
If the temperature is lower than 00 ° C., since the strength of the solidified shell of the round cast piece is high, it is difficult to reduce the rolling. 10
When the temperature exceeds 00 ° C., the strength of the solidified shell of the round slab is low, so that the rolling effect cannot be sufficiently exhibited. The surface temperature of the round slab can be measured with a radiation thermometer or the like.
【００４１】丸鋳片内部の厚さ方向両側の凝固殻を圧着
させ、凝固後の丸鋳片内部の厚さ方向中心部近傍に負偏
析部を形成させるように丸鋳片を圧下する。その際の必
要な圧下量は、事前に鋳造試験により確認するのがよ
い。これは、丸鋳片の大きさなどによって、必要な圧下
量が変化するからであるが、少なくとも圧下開始時の未
凝固部の直径以上の圧下量とする。The solidified shells on both sides in the thickness direction inside the round slab are pressed together, and the round slab is reduced so as to form a negative segregation part near the center in the thickness direction inside the solidified round slab. The amount of reduction required at that time is preferably confirmed in advance by a casting test. This is because the required amount of reduction varies depending on the size of the round slab or the like, but the amount of reduction is at least as large as the diameter of the unsolidified portion at the start of the reduction.
【００４２】丸鋳片内部の厚さ方向両側の凝固殻を圧着
させることにより、凝固後の丸鋳片内部の厚さ方向中心
部近傍に負偏析部を形成させることができる。その際、
丸鋳片の厚さ方向における負偏析部の厚さは、丸鋳片の
大きさにもよるが、圧下した方向における圧下後の丸鋳
片の厚さまたは直径の１０〜３０％が望ましい。By crimping the solidified shells on both sides in the thickness direction inside the round slab, a negative segregation portion can be formed near the center in the thickness direction inside the solidified round slab. that time,
The thickness of the negatively segregated portion in the thickness direction of the round slab depends on the size of the round slab, but is desirably 10 to 30% of the thickness or diameter of the round slab after rolling in the reduced direction.
【００４３】つぎに、本発明が対象とする鋼について、
以下に説明する。油井用鋼管、ボイラーなどの熱伝達用
鋼管、プラスチック用金型などに用いられる鋼として
は、通常、耐食性、耐酸化性、優れた高温強度、靱性な
どから、Ｃｒ含有率が５〜１２％程度の合金鋼、また
は、Ｃｒ含有率が１３〜２０％程度のフェライト系ステ
ンレス鋼が用いられている。また、これら合金鋼および
フェライト系ステンレス鋼には、炭化物を形成させて高
温強度を増加させるために、Ｃが０．０５〜０．３％程
度含有されている。Next, regarding the steel targeted by the present invention,
This will be described below. Steels used for oil well steel pipes, heat transfer steel pipes such as boilers, plastic molds, and the like, usually have a Cr content of about 5 to 12% from the viewpoint of corrosion resistance, oxidation resistance, excellent high-temperature strength, and toughness. Alloy steel or a ferritic stainless steel having a Cr content of about 13 to 20% is used. Further, in these alloy steels and ferritic stainless steels, C is contained in an amount of about 0.05 to 0.3% in order to increase the high-temperature strength by forming carbides.
【００４４】上記程度にＣｒおよびＣを含有する合金鋼
またはフェライト系ステンレス鋼では、前述のとおり、
溶鋼を鋳造し、内部に未凝固部が存在する状態で、鋼塊
または鋳片を圧下する際には、鋼塊または鋳片に負偏析
の凝固組織が発生する。負偏析部の発生した鋼塊または
鋳片を熱間加工して、ビレットを製造し、さらにビレッ
トを熱間加工して最終製品を製造する際に、ビレットお
よび最終製品に負偏析部が残存する。この残存した負偏
析部に粗大なフェライトが生成し、そのフェライトに沿
って微細な割れが発生しやすい。In the case of alloy steel or ferritic stainless steel containing Cr and C to the above extent, as described above,
When a molten steel is cast and a steel ingot or a slab is reduced in a state where an unsolidified portion is present therein, a solidified structure of negative segregation is generated in the steel ingot or the slab. Hot-worked steel ingots or slabs with negative segregated parts to produce billets, and when hot-working billets to produce final products, negative segregated parts remain in billets and final products . Coarse ferrite is generated in the remaining negative segregation portion, and fine cracks are easily generated along the ferrite.
【００４５】したがって、本発明が対象とする鋼は、本
発明の方法を適用するのに好適であるので、Ｃｒを５〜
２０質量％、Ｃを０．０５〜０．３質量％含有する合金
鋼またはフェライト系ステンレス鋼とする。Therefore, the steel targeted by the present invention is suitable for applying the method of the present invention,
An alloy steel or ferritic stainless steel containing 20% by mass and 0.05 to 0.3% by mass of C is used.
【００４６】本発明の対象とする合金鋼またはフェライ
ト系ステンレス鋼は、上記ＣｒおよびＣ以外に、必要に
応じて、質量％で、Ｓｉ：０．０５〜０．４％、Ｍｎ：
０．２〜２％、ｓｏｌ．Ａｌ：０．１％以下、Ｍｏ：
１．５％以下、Ｎｉ：１．５％以下、Ｃｕ：１．５％以
下、Ｔｉ：０．１％以下、Ｎｂ：０．１％以下および
Ｖ：０．１％以下のうちの１種または２種以上を含有
し、残部がＦｅおよび不純物からなる鋼とする。The alloy steel or ferritic stainless steel to be used in the present invention may contain, as required, Si: 0.05 to 0.4%, Mn:
0.2-2%, sol. Al: 0.1% or less, Mo:
One of the following: 1.5% or less, Ni: 1.5% or less, Cu: 1.5% or less, Ti: 0.1% or less, Nb: 0.1% or less, and V: 0.1% or less Alternatively, steel containing two or more kinds, the balance being Fe and impurities.
【００４７】Ｓｉおよびｓｏｌ．Ａｌは、主として溶鋼
の脱酸のために含有され、また、Ｍｎ、Ｍｏ、Ｎｉ、Ｃ
ｕ、Ｔｉ、ＮｂおよびＶの元素は、鋼の強度、靱性など
の機械的性質の改善を目的として含有される。また、こ
れらの元素は、上記の範囲内の含有率であれば、鋼塊ま
たは鋳片の負偏析部の形成への影響はない。Si and sol. Al is mainly contained for deoxidation of molten steel, and Mn, Mo, Ni, C
The elements u, Ti, Nb and V are contained for the purpose of improving mechanical properties such as strength and toughness of steel. In addition, as long as the content of these elements is within the above range, there is no effect on the formation of the negative segregation part of the steel ingot or slab.
【００４８】本発明が対象とする合金鋼またはフェライ
ト系ステンレス鋼の溶鋼を鋳造し、内部に未凝固部が存
在する間に鋼塊または鋳片の外表面をその厚さ方向に圧
下することにより、鋼塊または鋳片の内部の厚さ方向両
側の凝固殻を圧着させ、凝固後の鋼塊または鋳片の内部
の厚さ方向中心部近傍に負偏析部を形成させる際、本発
明の方法では、溶鋼の水素含有率を４ｐｐｍ以下とす
る。A molten steel of an alloy steel or a ferritic stainless steel to which the present invention is applied is cast, and the outer surface of a steel ingot or slab is reduced in the thickness direction while an unsolidified portion is present therein. The method of the present invention, when crimping the solidified shells on both sides in the thickness direction inside the steel ingot or slab and forming a negative segregation part near the center in the thickness direction inside the solidified steel ingot or slab. Then, the hydrogen content of the molten steel is set to 4 ppm or less.
【００４９】溶鋼の水素含有率を４ｐｐｍ以下とするこ
とにより、鋼塊または鋳片を熱間加工したビレット、お
よびそのビレットを熱間加工した最終製品において、残
存した負偏析部における微細な割れの発生を防止できる
のは、前述のとおりである。By setting the hydrogen content of the molten steel to 4 ppm or less, in a billet obtained by hot working a steel ingot or a slab and in a final product obtained by hot working the billet, fine cracks in the remaining negative segregation portion are reduced. The occurrence can be prevented as described above.
【００５０】[0050]
【実施例】電気炉で原料を溶解した後、ＡＯＤ法と称さ
れるアルゴン−酸素脱炭法により溶鋼を精錬して、Ｃｒ
含有率が、質量％で、５％、９％および１３％の３水準
の合金鋼またはフェライト系ステンレス鋼の溶鋼を溶製
した。また、ＡＯＤ法による精錬の際に、溶鋼の脱水素
を行い溶鋼中の水素含有率を調整した。溶製した溶鋼の
水素含有率は後述する表２および表３に示し、その他の
化学組成を表１に示す。EXAMPLE After melting the raw material in an electric furnace, the molten steel was refined by an argon-oxygen decarburization method called AOD method,
Molten steel of three levels of alloy steel or ferritic stainless steel having a content of 5%, 9% and 13% by mass was produced. In addition, during refining by the AOD method, the molten steel was dehydrogenated to adjust the hydrogen content in the molten steel. The hydrogen content of the smelted molten steel is shown in Tables 2 and 3 below, and other chemical compositions are shown in Table 1.
【００５１】[0051]
【表１】 実施例１の試験では、図１に示す装置構成の例の圧下装
置を用いて、未凝固部を含む鋼塊の側面を圧下した。ま
た、実施例２の試験では、図２に示す装置構成の例の水
平式連続鋳造機を用いて、ピンチロールにより未凝固部
を含む丸鋳片を圧下した。それぞれ鋼塊または丸鋳片の
鋳造および圧下の条件は後述する。[Table 1] In the test of Example 1, the side surface of the steel ingot including the unsolidified portion was reduced by using the reduction device of the example of the device configuration shown in FIG. Further, in the test of Example 2, a round cast piece including an unsolidified portion was pressed down by a pinch roll using a horizontal continuous casting machine having an apparatus configuration shown in FIG. The conditions for casting and rolling the ingot or round slab, respectively, will be described later.
【００５２】凝固後の鋼塊または丸鋳片の厚さ方向中心
部近傍に負偏析部が生成するように、内部の厚さ方向両
側の凝固殻を圧着させる程度に未凝固部を含む鋼塊また
は丸鋳片を圧下する際、実際に負偏析部が生成したかど
うかについて、以下のように事前に確認した。The solidified steel ingot or the ingot including the unsolidified portion to the extent that the solidified shells on both sides in the thickness direction are pressed so that a negative segregation portion is formed near the center in the thickness direction of the solidified ingot or round slab. Alternatively, whether or not a negative segregation part was actually generated when rolling down the round slab was confirmed in advance as follows.
【００５３】すなわち、鋳造した直後の鋼塊または丸鋳
片の内部に未凝固部が残存する状態で、それぞれ鋲打ち
試験を行い、未凝固部の厚さまたは直径を測定した。ま
た、凝固伝熱解析により、鋼塊または丸鋳片の鋳造条件
と未凝固部の厚さまたは直径を求めた。これら鋲打ち試
験結果と解析結果とがよく一致することを確認した。ま
た、未凝固部を含む鋼塊または丸鋳片を圧下したことに
よる負偏析の凝固組織の確認は、鋼塊または丸鋳片の厚
さ中心部を含む縦断サンプルを採取し、その縦断面のマ
クロ組織観察を行って、負偏析部の生成状況を確認し
た。その事前確認試験により、未凝固部の厚さまたは直
径の１．２〜２．５倍の厚さまたは直径に相当する量を
圧下することにより、負偏析の凝固組織が生成すること
がわかった。鋼塊または丸鋳片の外表面を圧下しても、
実際に鋼塊または丸鋳片の厚さ中心部が圧下される、い
わゆる圧下浸透性は１００％ではないことによる。実際
の実施例の鋳造試験では、凝固伝熱解析による未凝固部
の厚さまたは直径の値を用いて、圧下条件を変更した。 （実施例１）表１に示す化学組成の溶鋼中の水素含有率
を、ＡＯＤ法による精錬の際に調整した後に、通常の下
注ぎ造塊法により、水平断面が５００ｍｍの正方形で、
高さが２０００ｍｍの鋼塊に鋳造した。その際、湯面上
に通常用いられる保温剤を添加した。その後、約１時間
経過してから、内部に未凝固部が存在する状態で、造塊
用鋳型より鋼塊を引き抜き、横型油圧プレス装置を用い
て金型で鋼塊の側面を両側から圧下した。圧下開始時の
鋼塊の表面温度は８４０〜８８０℃程度とした。また、
圧下力は最大１０００ｔに設定した。That is, in a state where the unsolidified portion remains in the steel ingot or the round slab immediately after casting, a tacking test was performed, and the thickness or diameter of the unsolidified portion was measured. Further, the casting conditions of the steel ingot or the round slab and the thickness or diameter of the unsolidified portion were obtained by the solidification heat transfer analysis. It was confirmed that the results of these tacking tests and the analysis results were in good agreement. In addition, to confirm the solidification structure of negative segregation by rolling down the steel ingot or round slab including the unsolidified portion, a longitudinal sample including the center of the thickness of the steel ingot or round slab was collected, and Macrostructure observation was performed to confirm the formation state of the negatively segregated portion. According to the preliminary confirmation test, it was found that a negatively segregated solidified structure was generated by reducing an amount corresponding to a thickness or diameter 1.2 to 2.5 times the thickness or diameter of the unsolidified portion. . Even if the outer surface of the ingot or round slab is reduced,
This is because the central part of the thickness of the ingot or round slab is actually reduced, that is, the so-called reduction permeability is not 100%. In the casting test of the actual example, the rolling condition was changed using the thickness or diameter of the unsolidified portion by the solidification heat transfer analysis. (Example 1) After adjusting the hydrogen content in the molten steel having the chemical composition shown in Table 1 at the time of refining by the AOD method, a horizontal cross section of 500 mm square was obtained by a usual underpour ingot casting method.
It was cast into a steel ingot having a height of 2000 mm. At that time, a warming agent usually used was added to the surface of the hot water. After about one hour, the steel ingot was pulled out of the ingot casting mold in a state where the unsolidified portion was present inside, and the side face of the steel ingot was pressed down from both sides by a mold using a horizontal hydraulic press. . The surface temperature of the steel ingot at the start of rolling was set to about 840 to 880 ° C. Also,
The rolling force was set to a maximum of 1000 t.
【００５４】鋼塊を圧下する両側の金型の、それぞれの
大きさは、縦３００ｍｍ、横１０００ｍｍで、鋼塊の未
凝固部の位置を金型により両側から圧下した。その際、
鋼塊の未凝固部の下側から上側に向けて、順次金型を押
し当て、鋼塊の全高さを圧下した。鋼塊を圧下するため
の油圧シリンダの圧下速度は約１〜１．４ｍｍ／秒と
し、圧下後は、圧下速度と同じ速度で金型を開放するこ
とにより、約４分以内に圧下を完了した。鋼塊の上部も
凝固が進行しているので、鋼塊内部の未凝固部の溶鋼が
鋼塊の外に漏れることはなかった。The sizes of the molds on both sides for rolling down the steel ingot were 300 mm in length and 1000 mm in width, and the position of the unsolidified portion of the ingot was pressed down from both sides by the mold. that time,
The mold was pressed in order from the lower side to the upper side of the unsolidified portion of the steel ingot to reduce the entire height of the steel ingot. The rolling speed of the hydraulic cylinder for rolling down the steel ingot was about 1 to 1.4 mm / sec. After rolling down, the mold was opened at the same speed as the rolling speed, and the rolling was completed within about 4 minutes. . Since the solidification of the upper part of the steel ingot also progressed, the molten steel in the unsolidified portion inside the steel ingot did not leak out of the steel ingot.
【００５５】圧下完了後に鋼塊を室温近傍まで冷却した
後、鋼塊の高さの１／２で２分割し、１本の鋼塊は、厚
さ中心部で縦断して縦断サンプルを採取し、縦断面をマ
クロ組織観察によりザクまたはセンターキャビティであ
る内部欠陥の発生状況と負偏析部の発生の有無を調査し
た。これら内部欠陥の発生状況は、縦断サンプルの縦断
面に目視で観察される内部欠陥の存在範囲を確認し、最
も大きな内部欠陥の形状を円または楕円の形状に近似
し、その直径または長径を存在範囲径として評価した。After the completion of the rolling, the steel ingot was cooled to around room temperature, and then divided into two at a half of the height of the steel ingot. Then, by observing the macrostructure of the longitudinal section, the occurrence state of internal defects as zaku or center cavity and the presence / absence of negative segregation were investigated. The state of occurrence of these internal defects is confirmed by visually confirming the existence range of the internal defects that are visually observed in the longitudinal section of the longitudinal sample, approximating the shape of the largest internal defect to a circle or ellipse, and determining the diameter or major diameter. It was evaluated as a range diameter.
【００５６】残りの１本は、１１００〜１２００℃に加
熱後、鍛造加工して直径３００ｍｍの丸鋼片とした。得
られた丸鋼片を厚さ中心部で縦断して縦断サンプルを採
取し、縦断面をマクロ組織観察により負偏析部の割れの
発生の有無を調査した。試験条件および試験結果を表２
に示す。The remaining one was heated to 1100 to 1200 ° C. and forged to form a round steel slab having a diameter of 300 mm. The obtained round steel slab was traversed at the center in the thickness direction, a longitudinal sample was taken, and the longitudinal section was examined for macro-structure observation to determine whether or not cracks occurred in the negative segregation part. Table 2 shows test conditions and test results.
Shown in
【００５７】[0057]
【表２】 本発明例の試験Ｎｏ．１〜Ｎｏ．９では、Ｃｒ含有率が
およそ５〜１３質量％、Ｃ含有率がおよそ０．０５〜
０．２質量％の合金鋼またはフェライト系ステンレス鋼
の溶鋼を、水素含有率が全て４ｐｐｍ以下になるように
調整した後、鋼塊に鋳造し、未凝固部を含む鋼塊を圧下
した。鋼塊の圧下に際し、未凝固部の厚さを超える圧下
量でそれぞれ鋼塊を圧下した。いずれの試験Ｎｏ．１〜
Ｎｏ．９でも、鋼塊において、負偏析部の形成が確認で
きた。また、試験Ｎｏ．６およびＮｏ．９で、鋼塊にわ
ずかに内部欠陥が発生したが、問題となる大きさではな
く、その他の試験では、内部欠陥は発生しなかった。負
偏析部の形成が確認できたことから、鋼塊の厚さ中心部
まで、効果的に圧下されたことがわかった。さらに、鋼
塊を熱間鍛造した後の丸鋼片では、負偏析部に割れは発
生しなかった。これは、溶鋼の水素含有率を４ｐｐｍ以
下とした効果である。[Table 2] Test No. of the present invention example. 1 to No. In No. 9, the Cr content was about 5 to 13% by mass, and the C content was about 0.05 to
After adjusting the hydrogen content of all alloy steel or ferritic stainless steel of 0.2 mass% to 4 ppm or less, the steel ingot was cast and the steel ingot including the unsolidified portion was lowered. In rolling the steel ingot, the steel ingot was lowered by a reduction amount exceeding the thickness of the unsolidified portion. In each test No. 1 to
No. Also in No. 9, formation of a negatively segregated portion was confirmed in the steel ingot. Test No. 6 and no. At 9, the steel ingot had slight internal defects, but not the size of the problem, and in other tests no internal defects occurred. The formation of the negative segregation was confirmed, indicating that the steel was effectively reduced to the center of the thickness of the ingot. Further, in the round slab after hot forging of the steel ingot, no crack occurred in the negative segregation part. This is an effect of reducing the hydrogen content of the molten steel to 4 ppm or less.
【００５８】比較例の試験Ｎｏ．１０、Ｎｏ．１３およ
びＮｏ．１６では、Ｃｒ含有率がおよそ５〜１３質量
％、Ｃ含有率がおよそ０．０５〜０．２質量％の合金鋼
またはフェライト系ステンレス鋼の溶鋼を、水素含有率
が全て４ｐｐｍ以下になるように調整した後、鋼塊に鋳
造し、未凝固部を含む鋼塊を圧下した。鋼塊の圧下に際
し、未凝固部の厚さより小さい圧下量で鋼塊を圧下し
た。この圧下の条件は、本発明で規定する条件を満たし
ていない。これら試験Ｎｏ．１０、Ｎｏ．１３およびＮ
ｏ．１６では、圧下量が小さいので、鋼塊に負偏析部を
形成できず、また存在範囲径が２５〜３８ｍｍの著しく
大きな内部欠陥が発生した。Test No. of Comparative Example 10, No. 13 and No. In No. 16, the molten steel of the alloy steel or the ferritic stainless steel having the Cr content of about 5 to 13% by mass and the C content of about 0.05 to 0.2% by mass has a hydrogen content of 4 ppm or less. Then, the steel ingot was cast into a steel ingot, and the steel ingot including the unsolidified portion was reduced. In rolling the steel ingot, the steel ingot was reduced by a reduction amount smaller than the thickness of the unsolidified portion. The conditions for this reduction do not satisfy the conditions specified in the present invention. These test Nos. 10, No. 13 and N
o. In No. 16, since the amount of reduction was small, a negative segregation part could not be formed in the steel ingot, and an extremely large internal defect having an existing range diameter of 25 to 38 mm occurred.
【００５９】比較例の試験Ｎｏ．１１、Ｎｏ．１２、Ｎ
ｏ．１４、Ｎｏ．１５、Ｎｏ．１７およびＮｏ．１８で
は、Ｃｒ含有率がおよそ５〜１３質量％、Ｃ含有率がお
よそ０．０５〜０．２質量％の合金鋼またはフェライト
系ステンレス鋼の溶鋼を、水素含有率が全て４ｐｐｍを
超えて５〜７ｐｐｍとなるように調整した後、鋼塊に鋳
造し、未凝固部を含む鋼塊を圧下した。これら溶鋼中の
水素含有率は、本発明で規定する条件を外れている。鋼
塊の圧下に際し、未凝固部の厚さを超える圧下量で鋼塊
を圧下した。これら試験Ｎｏ．１１、Ｎｏ．１２、Ｎ
ｏ．１４、Ｎｏ．１５、Ｎｏ．１７およびＮｏ．１８で
は、圧下量を未凝固部の厚さよりも大きくしたので、鋼
塊において負偏析部の形成が確認され、また、内部欠陥
は、試験Ｎｏ．１７で小さい内部欠陥が発生した以外
は、発生しなかった。しかし、鋼塊を熱間鍛造した後の
丸鋼片では、負偏析部に割れの発生が認められた。これ
は、溶鋼の水素含有率を５〜７ｐｐｍと高くしたためで
ある。 （実施例２）表１に示す化学組成の溶鋼中の水素含有率
を、ＡＯＤ法による精錬の際に調整した後に、水平式連
続鋳造機を用いて、横断面形状が直径２６０ｍｍの丸鋳
片に鋳造した。直径３５０ｍｍの大きさのピンチロール
により未凝固部を含む丸鋳片を圧下する際、鋳造速度を
０．６〜０．８５ｍ／分、丸鋳片の二次冷却の比水量を
０．６〜１．０リットル／ｋｇ−鋼の範囲内でそれぞれ
変化させ、未凝固部の直径を変化させて、丸鋳片を圧下
した。圧下開始時の丸鋳片の表面温度は８６０〜８９０
℃とした。圧下時の圧下反力は最大で２５０ｔであっ
た。Test No. of Comparative Example 11, No. 12, N
o. 14, No. 15, No. 17 and No. In No. 18, a molten steel of an alloy steel or a ferritic stainless steel having a Cr content of about 5 to 13% by mass and a C content of about 0.05 to 0.2% by mass was added to a steel having a hydrogen content exceeding 4 ppm and 5%. After adjusting so as to be about 7 ppm, it was cast into a steel ingot, and the steel ingot including an unsolidified portion was lowered. The hydrogen content in these molten steels is outside the conditions specified in the present invention. In rolling the steel ingot, the steel ingot was reduced by a reduction amount exceeding the thickness of the unsolidified portion. These test Nos. 11, No. 12, N
o. 14, No. 15, No. 17 and No. In No. 18, since the amount of reduction was larger than the thickness of the unsolidified portion, the formation of a negative segregation portion in the steel ingot was confirmed. No small defects were generated except for the small internal defect in No. 17. However, in the round slab after hot forging of the ingot, cracking was observed in the negative segregation part. This is because the hydrogen content of the molten steel was increased to 5 to 7 ppm. Example 2 After adjusting the hydrogen content in molten steel having the chemical composition shown in Table 1 at the time of refining by the AOD method, using a horizontal continuous caster, a round slab having a cross-sectional shape of 260 mm in diameter was used. Cast into. When a round slab including an unsolidified portion is rolled down by a pinch roll having a diameter of 350 mm, the casting speed is 0.6 to 0.85 m / min, and the specific water amount of the secondary cooling of the round slab is 0.6 to 0.8 mm. The round slab was reduced by changing the diameter of the unsolidified portion in the range of 1.0 liter / kg-steel. The surface temperature of the round slab at the start of rolling is 860-890.
° C. The rolling reaction force during rolling was 250 t at the maximum.
【００６０】得られた圧下後の丸鋳片から各２ｍ長さの
丸鋳片サンプルを採取し、１本の丸鋳片は、厚さ中心部
で縦断して縦断サンプルを採取し、縦断面をマクロ組織
観察によりザクまたはセンターキャビティである内部欠
陥の発生状況と負偏析部の発生の有無を調査した。これ
ら内部欠陥の発生状況は、縦断サンプルの縦断面に目視
で観察される内部欠陥の存在範囲を確認し、前述のとお
り、その存在範囲径を求めた。From the obtained round cast slab after rolling, a round cast slab sample having a length of 2 m was collected, and one round slab was cut longitudinally at the center of the thickness to obtain a longitudinal sample. The occurrence of internal defects (Zaku or center cavity) and the presence or absence of negative segregation were investigated by macrostructure observation. Regarding the state of occurrence of these internal defects, the existence range of the internal defects visually observed in the longitudinal section of the longitudinal sample was confirmed, and the existence range diameter was obtained as described above.
【００６１】残りの１本は、１１００〜１２００℃に加
熱後、鍛造加工して直径１５０ｍｍの丸鋼片とした。得
られた丸鋼片を厚さ中心部で縦断して縦断サンプルを採
取し、前述のとおり、負偏析部の割れの発生の有無を調
査した。試験条件および試験結果を表３に示す。The remaining one was heated to 1100 to 1200 ° C. and forged to obtain a round bar having a diameter of 150 mm. The obtained round steel slab was traversed at the center in the thickness direction, a longitudinal sample was taken, and as described above, the presence or absence of occurrence of cracks in the negative segregation portion was examined. Table 3 shows the test conditions and test results.
【００６２】[0062]
【表３】 本発明例の試験Ｎｏ．１９〜Ｎｏ．２７では、Ｃｒ含有
率がおよそ５〜１３質量％、Ｃ含有率がおよそ０．０５
〜０．２質量％の合金鋼またはフェライト系ステンレス
鋼の溶鋼を、水素含有率が全て４ｐｐｍ以下になるよう
に調整した後、丸鋳片に鋳造し、未凝固部を含む丸鋳片
をピンチロールで圧下した。これらの試験では、鋳造速
度を０．６０〜０．８５ｍ／分、丸鋳片の二次冷却の比
水量を０．６〜１．０リットル／ｋｇ−鋼とすることに
より、未凝固部の直径を２０〜３３ｍｍとした。丸鋳片
の圧下に際し、未凝固部直径を超える圧下量で丸鋳片を
圧下した。いずれの試験Ｎｏ．１９〜Ｎｏ．２７でも、
丸鋳片において負偏析部の形成が確認された。また、試
験Ｎｏ．２０、Ｎｏ．２２およびＮｏ．２７で、丸鋳片
にわずかに内部欠陥が発生したが、問題となる大きさで
はなく、その他の試験では、内部欠陥は発生しなかっ
た。丸鋳片において負偏析部の形成が確認されたことか
ら、丸鋳片の厚さ中心部まで、効果的に圧下されたこと
がわかった。さらに、丸鋳片を熱間鍛造した後の丸鋼片
では、負偏析部に割れは発生しなかった。これは、溶鋼
の水素含有率を４ｐｐｍ以下とした効果である。[Table 3] Test No. of the present invention example. 19-No. 27, the Cr content is about 5 to 13% by mass, and the C content is about 0.05
~ 0.2 mass% of molten steel of alloy steel or ferritic stainless steel is adjusted to have a hydrogen content of 4 ppm or less, and then cast into round cast pieces, and the round cast pieces including unsolidified portions are pinched. Rolled down. In these tests, by setting the casting speed to 0.60 to 0.85 m / min and the specific water volume of the secondary cooling of the round slab to 0.6 to 1.0 liter / kg-steel, The diameter was 20 to 33 mm. In rolling down the round slab, the round slab was reduced by a reduction amount exceeding the diameter of the unsolidified portion. In each test No. 19-No. 27,
The formation of a negative segregation part was confirmed in the round slab. Test No. 20, no. 22 and No. At 27, the round slab had some internal defects, but not the size of the problem, and other tests did not show any internal defects. The formation of the negative segregation portion in the round slab was confirmed, indicating that the pressure was effectively reduced down to the center of the thickness of the round slab. Furthermore, in the round slab after hot forging the round slab, no crack occurred in the negative segregation part. This is an effect of reducing the hydrogen content of the molten steel to 4 ppm or less.
【００６３】比較例の試験Ｎｏ．２８、Ｎｏ．３１およ
びＮｏ．３４では、Ｃｒ含有率がおよそ５〜１３質量
％、Ｃ含有率がおよそ０．０５〜０．２質量％の合金鋼
またはフェライト系ステンレス鋼の溶鋼を、水素含有率
が全て４ｐｐｍ以下になるように調整した後、丸鋳片に
鋳造し、未凝固部を含む丸鋳片を圧下した。丸鋳片の圧
下に際し、未凝固部直径より小さい圧下量で丸鋳片を圧
下した。この圧下の条件は、本発明で規定する条件を満
たしていない。これら試験Ｎｏ．２８、Ｎｏ．３１およ
びＮｏ．３４では、圧下量が小さいので、丸鋳片に負偏
析部は形成されず、また１５〜２２ｍｍの著しく大きな
内部欠陥が発生した。Test No. of Comparative Example 28, no. 31 and No. 31. In No. 34, a molten steel of an alloy steel or a ferritic stainless steel having a Cr content of about 5 to 13% by mass and a C content of about 0.05 to 0.2% by mass has a hydrogen content of 4 ppm or less. , And cast into a round slab, and the round slab including the unsolidified portion was lowered. In rolling down the round slab, the round slab was reduced by a reduction amount smaller than the diameter of the unsolidified portion. The conditions for this reduction do not satisfy the conditions specified in the present invention. These test Nos. 28, no. 31 and No. 31. In No. 34, since the rolling reduction was small, no negative segregation portion was formed in the round slab, and an extremely large internal defect of 15 to 22 mm occurred.
【００６４】比較例の試験Ｎｏ．２９、Ｎｏ．３０、Ｎ
ｏ．３２、Ｎｏ．３３、Ｎｏ．３５およびＮｏ．３６で
は、Ｃｒ含有率がおよそ５〜１３質量％、Ｃ含有率がお
よそ０．０５〜０．２質量％の合金鋼またはフェライト
系ステンレス鋼の溶鋼を、水素含有率が全て４ｐｐｍを
超えて５〜７ｐｐｍとなるように調整した後、丸鋳片に
鋳造し、未凝固部を含む丸鋳片を圧下した。これら溶鋼
中の水素含有率は、本発明で規定する条件を外れてい
る。丸鋳片の圧下に際し、未凝固部の厚さを超える圧下
量で丸鋳片を圧下した。これら試験Ｎｏ．２９、Ｎｏ．
３０、Ｎｏ．３２、Ｎｏ．３３、Ｎｏ．３５およびＮ
ｏ．３６では、圧下量を未凝固部の厚さよりも大きくし
たので、丸鋳片において負偏析部の形成が確認され、ま
た、内部欠陥は発生しなかった。しかし、丸鋳片を熱間
鍛造した後の丸鋼片では、負偏析部に割れの発生が認め
られた。これは、溶鋼の水素含有率を５〜７ｐｐｍと高
くしたためである。Test No. of Comparative Example 29, no. 30, N
o. 32, no. 33, no. No. 35 and No. 35. In No. 36, a molten steel of an alloy steel or a ferritic stainless steel having a Cr content of about 5 to 13% by mass and a C content of about 0.05 to 0.2% by mass was added to a steel having a hydrogen content of more than 4 ppm and 5%. After adjusting to be about 7 ppm, it was cast into a round slab, and the round slab including the unsolidified portion was lowered. The hydrogen content in these molten steels is outside the conditions specified in the present invention. In rolling down the round slab, the round slab was reduced by a reduction amount exceeding the thickness of the unsolidified portion. These test Nos. 29, no.
30, no. 32, no. 33, no. 35 and N
o. In No. 36, since the amount of reduction was larger than the thickness of the unsolidified portion, formation of a negative segregation portion was confirmed in the round cast slab, and no internal defect occurred. However, in the round slab after hot forging of the round slab, the occurrence of cracks in the negative segregation was observed. This is because the hydrogen content of the molten steel was increased to 5 to 7 ppm.
【００６５】[0065]
【発明の効果】本発明の方法の適用により、高Ｃｒ含有
率の合金鋼またはフェライト系ステンレス鋼において、
ザクまたはセンターキャビティと呼ばれる凝固収縮に起
因する内部欠陥の発生のない、さらに、形成させた負偏
析部に微細な割れの発生のない内部品質の良好な鋼塊ま
たは鋳片を得ることができる。According to the method of the present invention, a high Cr content alloy steel or ferritic stainless steel
It is possible to obtain a steel ingot or a slab of good internal quality without generation of internal defects due to solidification shrinkage called Zaku or center cavity and without generation of fine cracks in the formed negative segregation portion.
【図１】内部に未凝固部が存在する間に、鋼塊の外表面
を厚さ方向に圧下する状況の例を示す模式図である。FIG. 1 is a schematic diagram showing an example of a situation where an outer surface of a steel ingot is pressed down in a thickness direction while an unsolidified portion is present therein.
【図２】内部に未凝固部が存在する間に、水平式連続鋳
造機を用いて鋳造された鋳片を圧下する状況の例を示す
模式図である。FIG. 2 is a schematic diagram showing an example of a situation in which a slab cast using a horizontal continuous casting machine is reduced while an unsolidified portion is present therein.
１：鋼塊 ２：凝固殻 ３：
未凝固部 ４：金具 ５：シリンダ ６：
吊り具 ７：取鍋 ８：ロングノズル ９：
タンデイッシュ １０：フィードノズル １１：鋳型 １
２：冷却用ノズル １３：ガイドロール １４：ピンチロール １
５：溶鋼 １６：未凝固部 １７：凝固殻 １
８：鋳片1: Steel ingot 2: Solidified shell 3:
Unsolidified part 4: Metal fittings 5: Cylinder 6:
Hanging tool 7: Ladle 8: Long nozzle 9:
Tundish 10: Feed nozzle 11: Mold 1
2: Cooling nozzle 13: Guide roll 14: Pinch roll 1
5: molten steel 16: unsolidified part 17: solidified shell 1
8: cast slab
Claims (1)
０．３質量％含有する溶鋼を鋳造し、鋼塊または鋳片の
内部に未凝固部が存在する間に鋼塊または鋳片の外表面
をその厚さ方向に圧下することにより、鋼塊または鋳片
の内部の厚さ方向両側の凝固殻を圧着させ、凝固後の鋼
塊または鋳片の内部の厚さ方向中心部近傍に負偏析部を
形成させる鋳造方法であって、上記溶鋼の水素含有率を
４ｐｐｍ以下とすることを特徴とする高Ｃｒ含有鋼の鋳
造方法。(1) 5 to 20% by mass of Cr and 0.05 to
By casting molten steel containing 0.3% by mass and rolling down the outer surface of the steel ingot or slab in the thickness direction while an unsolidified portion exists inside the steel ingot or slab, A casting method in which solidified shells on both sides in the thickness direction of the slab are pressure-bonded to form a negative segregation portion near the center in the thickness direction of the solidified steel ingot or slab, A method for casting high Cr content steel, wherein the content is 4 ppm or less.
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|---|---|---|---|
| JP2001173089A JP3671868B2 (en) | 2001-06-07 | 2001-06-07 | Method for casting high Cr steel |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2001173089A JP3671868B2 (en) | 2001-06-07 | 2001-06-07 | Method for casting high Cr steel |
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| JP3671868B2 JP3671868B2 (en) | 2005-07-13 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7156151B2 (en) | 2003-10-10 | 2007-01-02 | Nucor Corporation | Casting steel strip |
| JP2007275903A (en) * | 2006-04-03 | 2007-10-25 | Sumitomo Metal Ind Ltd | Method for casting stainless steel or high alloy steel |
| US7484551B2 (en) | 2003-10-10 | 2009-02-03 | Nucor Corporation | Casting steel strip |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5327006B2 (en) * | 2009-11-09 | 2013-10-30 | 新日鐵住金株式会社 | Steel continuous casting method and extra-thick steel plate |
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|---|---|---|---|---|
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| JPH0559617B2 (en) * | 1988-03-09 | 1993-08-31 | Fujitsu Ltd | |
| JPH09300053A (en) * | 1996-05-16 | 1997-11-25 | Nkk Corp | Production of chromium alloy steel round cast billet |
| JP2000061602A (en) * | 1998-08-26 | 2000-02-29 | Sumitomo Metal Ind Ltd | Continuously cast slab and continuous casting method |
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2001
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|---|---|---|---|---|
| JPH0559617B2 (en) * | 1988-03-09 | 1993-08-31 | Fujitsu Ltd | |
| JPH0559167A (en) * | 1991-08-30 | 1993-03-09 | Ube Ind Ltd | Production of 2-pyrrolidone polymer |
| JPH09300053A (en) * | 1996-05-16 | 1997-11-25 | Nkk Corp | Production of chromium alloy steel round cast billet |
| JP2000061602A (en) * | 1998-08-26 | 2000-02-29 | Sumitomo Metal Ind Ltd | Continuously cast slab and continuous casting method |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7156151B2 (en) | 2003-10-10 | 2007-01-02 | Nucor Corporation | Casting steel strip |
| US7484551B2 (en) | 2003-10-10 | 2009-02-03 | Nucor Corporation | Casting steel strip |
| JP2007275903A (en) * | 2006-04-03 | 2007-10-25 | Sumitomo Metal Ind Ltd | Method for casting stainless steel or high alloy steel |
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| JP3671868B2 (en) | 2005-07-13 |
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