JP2000301306A - Cast slab excellent in quality and working characteristic and steel material worked from this slab - Google Patents
Cast slab excellent in quality and working characteristic and steel material worked from this slabInfo
- Publication number
- JP2000301306A JP2000301306A JP11367399A JP11367399A JP2000301306A JP 2000301306 A JP2000301306 A JP 2000301306A JP 11367399 A JP11367399 A JP 11367399A JP 11367399 A JP11367399 A JP 11367399A JP 2000301306 A JP2000301306 A JP 2000301306A
- Authority
- JP
- Japan
- Prior art keywords
- slab
- inclusions
- molten steel
- steel
- rolling
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、均一な凝固組織を
備え、割れや中心偏析等の欠陥が少なく、加工特性に優
れた鋳片及びその鋳片を加工した鋼材に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slab having a uniform solidification structure, having few defects such as cracks and center segregation, and having excellent processing characteristics, and a steel material obtained by processing the slab.
【０００２】[0002]
【従来の技術】従来、鋳片は、溶鋼を振動式鋳型やベル
トキャスター、ストリップキャスター等を用いて、スラ
ブ、ブルーム、ビレット、薄肉鋳片等に鋳造し、これを
所定のサイズに切断して製造される。更に、前記鋳片を
加熱炉等を用いて加熱した後に、粗圧延や仕上げ圧延等
の加工が施され、鋼板や形鋼等が製造される。しかし、
図５に示すように、鋳片の表層（表層部）には、鋳型に
より急激に冷却されて凝固した細かい組織のチル晶が形
成され、このチル晶より内側に大きな柱状晶が形成され
る。この表層部は、柱状晶の境界にミクロ偏析が存在
し、このミクロ偏析の部位は、脆い特性を有し、鋳型に
よる冷却や収縮の不均一性によって鋳片の表層に割れや
へこみ疵等の表面欠陥が生じる。更に、内部は、表層部
よりも冷却が緩慢になり、柱状晶、あるいは大きい等軸
晶が生成し、境界に表層部と同様のミクロ偏析が存在す
る。このミクロ偏析は、表層部と同様に脆い特性を有
し、内部が凝固する際の熱収縮や鋳片のバルジングや曲
げ戻し矯正等の機械的な応力により内部割れが生じ易く
なる。一方、内部の等軸晶の粒径が大きい場合は、凝固
が進行するにつれて、内部に溶鋼の供給不足に起因する
空洞（ザク）や溶鋼の流動に起因する中心偏析（偏析）
等の内部欠陥が生じて鋳片の品質を損なうことになる。
鋳片に発生した表面欠陥は、研削等の手入れの増加や屑
化等により歩留りの低下を招き、この鋳片をそのまま用
いて粗圧延や仕上げ圧延等の加工を行った場合は、鋳片
に生じた表面欠陥に加えて、内部割れやザク、偏析等の
内部欠陥が鋼材に残存して、ＵＳＴ不合格や強度低下あ
るいは外観の悪化等を招き、鋼材の手入れの増加や屑化
等の問題が生じる。この対策として、鋳片の凝固組織を
微細な等軸晶にし、鋳片と、それを加工して得られる鋼
材の表面及び内部欠陥を防止することが試みられてい
る。鋳片の凝固組織を微細化する方法としては、１）溶
鋼の温度を低くして低温鋳造する、２）凝固過程の溶鋼
を電磁攪拌する、３）溶鋼が凝固する際に凝固核となる
金属や酸化物を添加する、又は、これ等１）〜３）を組
合せて行うことが知られている。2. Description of the Related Art Conventionally, cast slab is cast from molten steel into a slab, bloom, billet, thin cast slab, or the like using a vibration mold, belt caster, strip caster, or the like, and cut into a predetermined size. Manufactured. Further, after the slab is heated using a heating furnace or the like, processing such as rough rolling and finish rolling is performed to produce a steel plate, a shaped steel, and the like. But,
As shown in FIG. 5, on the surface layer (surface layer portion) of the slab, a chilled crystal having a fine structure solidified by rapid cooling by a mold is formed, and a large columnar crystal is formed inside the chilled crystal. This surface layer has micro-segregation at the boundary of columnar crystals, and the site of this micro-segregation has brittle characteristics, and the surface of the slab has cracks and dents due to unevenness of cooling and shrinkage by the mold. Surface defects occur. Further, the inside is cooled more slowly than the surface layer, columnar crystals or large equiaxed crystals are generated, and microsegregation similar to the surface layer exists at the boundary. This micro-segregation has brittle properties like the surface layer portion, and internal cracks are easily generated due to heat shrinkage at the time of solidification of the inside, mechanical stress such as bulging of the slab and correction of bending back. On the other hand, when the particle size of the equiaxed crystal inside is large, as solidification progresses, cavities (Zaku) caused by insufficient supply of molten steel and center segregation (segregation) caused by flow of molten steel.
And other internal defects, which impair the quality of the slab.
Surface defects that occur in the slab cause a decrease in yield due to increased care such as grinding and debris, etc.If this slab is used as it is for rough rolling or finish rolling, In addition to the generated surface defects, internal defects such as internal cracks, zags, segregation, etc., remain in the steel material, causing UST rejection, a decrease in strength, or a deterioration in appearance, and an increase in the care of the steel material and problems such as waste. Occurs. As a countermeasure, attempts have been made to make the solidified structure of the slab into a fine equiaxed crystal to prevent the surface and internal defects of the slab and the steel material obtained by processing the slab. As methods for refining the solidification structure of the slab, 1) lower the temperature of the molten steel and cast it at a low temperature. 2) electromagnetically stir the molten steel in the solidification process. It is known to add a metal or an oxide, or to combine these methods 1) to 3).
【０００３】低温鋳造の具体例としては、例えば特開平
７−８４６１７号公報に記載されているように、溶鋼を
連続鋳造する際に、過熱温度（実際の溶鋼温度からこの
溶鋼の液相温度を差し引いた温度）を４０℃以下にして
鋳型内で冷却しながら引き抜きを行って、凝固した鋳片
の等軸晶の割合を７０％以上にして、フェライト系ステ
ンレス鋼板に発生するリジングを防止している。更に、
溶鋼の電磁攪拌については、特開昭５０−１６６１６号
公報に記載されているように、凝固過程の溶鋼に電磁攪
拌を行って、成長する柱状晶の先端を切断し、柱状晶の
切断片を凝固核として利用し、鋳片の凝固組織の等軸晶
を６０％以上にしてリジングを防止している。また、特
開昭５３−９０１２９号公報には、溶鋼が凝固する際に
凝固核となる金属や酸化物の添加と電磁攪拌を組合せ
て、鋳片の厚み方向の全断面の凝固組織を殆ど等軸晶に
することが行われている。As a specific example of low-temperature casting, for example, as described in Japanese Patent Application Laid-Open No. 7-84617, when a molten steel is continuously cast, the superheat temperature (the liquidus temperature of the molten steel is calculated from the actual molten steel temperature). The temperature is reduced to 40 ° C. or less, and drawing is performed while cooling in a mold. The ratio of equiaxed crystals in the solidified slab is increased to 70% or more to prevent ridging generated in a ferritic stainless steel sheet. I have. Furthermore,
Regarding the electromagnetic stirring of molten steel, as described in Japanese Patent Application Laid-Open No. 50-16616, the molten steel in the solidification process is subjected to electromagnetic stirring to cut off the tips of the growing columnar crystals and cut the columnar crystals into pieces. Utilizing as solidification nuclei, ridging is prevented by making the equiaxed crystal of the solidified structure of the slab 60% or more. Japanese Unexamined Patent Publication No. 53-90129 discloses that the addition of a metal or oxide as a solidification nucleus when molten steel is solidified is combined with electromagnetic stirring to substantially reduce the solidified structure of the entire cross section in the thickness direction of the slab. Axialization has been performed.
【０００４】[0004]
【発明が解決しようとする課題】しかしながら、特開平
７−８４６１７号公報では、過熱温度を低くしているた
め、鋳造途中に溶鋼が凝固してノズル詰まりや地金の付
着を生じて鋳造が困難になったり、溶鋼の粘性が増加し
て介在物の浮上が阻害され、介在物に起因した欠陥等が
発生するため、十分な等軸晶を備えた鋳片ができるまで
に過熱温度を低くすることが困難である。更に、表面及
び内部欠陥を防止し、且つ加工性に優れた鋳片を製造す
るために、表層から内部に至る等軸晶を如何なる粒径と
し、鋳片の凝固組織をどのように均一にすれば良いかに
ついて明確でない。また、特開昭５０−１６６１６号公
報では、鋳型を出た鋳片に電磁攪拌を行うため、鋳片の
表層部に柱状晶が存在し、この柱状晶に起因した割れや
へこみ疵等の表面欠陥、あるいは圧延等の加工を施した
鋼材に、ヘゲ疵や割れ疵に加えてリジング等の表面欠陥
が発生する。更に、特開昭５３−９０１２９号公報で
は、鋳型内の溶鋼に凝固核になる金属や酸化物を添加
し、金属や酸化物が溶解する近傍の溶鋼を電磁攪拌して
いるので、鋳片の表層部には、柱状晶が存在しており、
特開昭５０−１６６１６号公報に記載された方法と同様
の表面欠陥が生じる。しかも、凝固組織を等軸晶にする
際に、電磁攪拌を行う位置や攪拌推力により、等軸晶が
形成される範囲や等軸晶の大きさが異なる難点がある。
このように、従来の方法では、均一な凝固組織にした無
欠陥の鋳片を得ることが困難であり、この鋳片を用いて
圧延等の加工性を高め、欠陥の少ない良品質の鋼材を得
ることができないという問題がある。また、無欠陥の加
工性の良い鋳片を安定して工業的に製造するには、如何
なる凝固組織にすれば良いかについて明確にされていな
い。However, in Japanese Patent Application Laid-Open No. 7-84617, since the superheating temperature is low, the molten steel solidifies during casting, causing nozzle clogging and sticking of metal, making casting difficult. Or increase the viscosity of the molten steel, hindering the floating of inclusions and causing defects and the like caused by inclusions, so lower the superheating temperature until a slab with sufficient equiaxed crystals is formed It is difficult. Furthermore, in order to prevent surface and internal defects and to produce cast slabs with excellent workability, the equiaxed crystal from the surface layer to the inside is made to have any particle size, and how the solidified structure of the cast slab is uniformly reduced. It is not clear what to do. In Japanese Patent Application Laid-Open No. Sho 50-16616, columnar crystals are present on the surface layer of the cast slab because electromagnetic stirring is performed on the cast slab from the mold, and surface such as cracks and dents caused by the columnar crystals are present. Defects or surface defects such as ridging, in addition to barges and cracks, occur in steel materials that have been subjected to processing such as rolling. Further, in Japanese Patent Application Laid-Open No. 53-90129, a metal or oxide that becomes a solidification nucleus is added to molten steel in a mold, and molten steel in the vicinity where the metal or oxide is dissolved is electromagnetically stirred. Columnar crystals exist in the surface layer,
The same surface defects as in the method described in JP-A-50-16616 occur. In addition, when the solidified structure is made into an equiaxed crystal, there is a problem that the range in which the equiaxed crystal is formed and the size of the equiaxed crystal are different depending on the position where the electromagnetic stirring is performed and the stirring thrust.
As described above, in the conventional method, it is difficult to obtain a defect-free slab having a uniform solidified structure, and the workability such as rolling is enhanced by using the slab to produce a high-quality steel material with few defects. There is a problem that cannot be obtained. In addition, it is not clear what solidification structure should be used to stably and industrially produce a defect-free cast slab with good workability.
【０００５】本発明はかかる事情に鑑みてなされたもの
で、鋳片を微細で均一な凝固組織にし、割れ、へこみ疵
や中心偏析等の表面及び内部欠陥を抑制し、圧延等の加
工性が高く、鋼材に発生する欠陥を少なくした品質と加
工特性に優れた鋳片及びそれを加工した鋼材を提供する
ことを目的とする。The present invention has been made in view of such circumstances, and has a slab having a fine and uniform solidification structure, suppressing surface and internal defects such as cracks, dents and center segregation, and having a workability such as rolling. It is an object of the present invention to provide a slab which is high in quality and processing characteristics with reduced defects generated in steel material, and a steel material obtained by processing the same.
【０００６】[0006]
【課題を解決するための手段】前記目的に沿う本発明に
係る品質と加工特性に優れた鋳片は、溶鋼の凝固時に形
成されるδフェライトとの格子整合度が６％以下の介在
物を１００個／ｃｍ2 以上含有している。これにより、
格子整合度が小さい、即ちδフェライトとの格子整合度
の良好な介在物は、凝固核を効率良く生成する接種核と
して作用し、多数の凝固核を形成して凝固組織を微細に
でき、表層及び内部のミクロ偏析を小さくして、鋳型等
の冷却の不均一や収縮歪み等に対する割れ抵抗を良好に
し、凝固後におけるピンニング作用（凝固直後における
結晶粒の成長を抑制する）により、凝固組織の粗大化を
抑制して、より安定した微細な凝固組織を保つことがで
きる。更に、この鋳片を用いることで、圧延等の加工を
行った際に、圧下した方向に容易に変形して加工性を高
めることができる。なお、δフェライトとの格子整合度
が６％以下の介在物の個数が１００個／ｃｍ 2 未満にな
ると、凝固核が少なくなる。また、ピンニング作用が十
分でなくなるので、鋳片の凝固組織が大きくなり、表面
欠陥及び内部欠陥が発生する。According to the present invention, there is provided the present invention having the above object.
The slab with such high quality and processing characteristics is formed during solidification of molten steel.
Interposition with a lattice matching degree of 6% or less with the formed δ ferrite
100 pieces / cmTwo It is contained above. This allows
Lattice matching degree is small, that is, lattice matching degree with δ ferrite
Good inclusions are inoculated nuclei that efficiently generate coagulation nuclei.
Acts to form numerous coagulation nuclei to finely solidify the coagulated tissue.
Can reduce surface and internal micro-segregation
Crack resistance against uneven cooling and shrinkage strain
And pinning action after coagulation (immediately after coagulation
(Inhibit the growth of crystal grains.)
To maintain a more stable and fine solidified structure.
Wear. Furthermore, by using this slab, processing such as rolling can be performed.
When it is performed, it is easily deformed in the direction of reduction to improve workability.
Can be The degree of lattice matching with δ ferrite
Is 100% / cm Two Less than
Then, coagulation nuclei decrease. Also, the pinning action is
The solidification structure of the slab becomes large,
Defects and internal defects occur.
【０００７】ここで、前記鋳片に含有した前記介在物の
内、大きさが１０μｍ以下の介在物を１００個／ｃｍ2
以上含有すること好ましい。このように細かい介在物に
しているので、凝固核を効率良く生成し、ピンニング作
用を高めて微細で均一な凝固組織にし、圧延等の加工を
行った際の加工性を高め、鋼材に発生するヘゲ疵や表面
割れ、しわ疵等の表面欠陥及び内部欠陥を抑制できる。
介在物の大きさが１０μｍより大きいと、溶鋼が凝固す
る際に凝固核としての働きが弱くなる。有効な凝固核の
数が減少して凝固組織が粗大化するのを抑制できない。Here, among the inclusions contained in the slab, 100 inclusions / cm 2 having a size of 10 μm or less are included.
It is preferable to contain the above. Since such fine inclusions are used, solidification nuclei are efficiently generated, the pinning action is enhanced to form a fine and uniform solidification structure, and the workability when rolling or other processing is performed is increased, and the steel is generated. Surface defects and internal defects such as barbed flaws, surface cracks, and wrinkles can be suppressed.
If the size of the inclusions is larger than 10 μm, the function as a solidification nucleus when the molten steel solidifies becomes weak. It is not possible to prevent the number of effective coagulation nuclei from decreasing and the coagulated tissue from becoming coarse.
【０００８】また、前記溶鋼の凝固初晶がδフェライト
の鋼種であっても良い。鋳片の冷却中に相変態を生じ、
凝固後、又は冷却中にフェライト以外の組織となる鋼種
であっても、δフェライトの凝固核の生成を促進するの
で、凝固組織を微細で均一な凝固組織にできる。その結
果、冷却後の組織を微細にできる。The solidified primary crystal of the molten steel may be a δ ferrite steel type. Phase transformation occurs during cooling of the slab,
Even if the steel type becomes a structure other than ferrite after solidification or during cooling, since the formation of solidification nuclei of δ ferrite is promoted, the solidified structure can be made into a fine and uniform solidified structure. As a result, the structure after cooling can be made fine.
【０００９】前記目的に沿う本発明に係る鋼材は、溶鋼
の凝固時に形成されるδフェライトとの格子整合度が６
％以下の介在物を１００個／ｃｍ2 以上含有した鋳片を
加熱した後に、圧延等の加工を施している。この鋼材
は、均一で微細な凝固組織の鋳片を加工するので、凝固
組織に起因した表面及び内部欠陥を少なくし、圧下する
方向に変形がし易くなり圧延等の加工性を高めることが
できる。そして、加工後の鋼材に発生するヘゲ疵や割れ
等の表面欠陥及びザクや中心偏析（偏析）等の内部欠陥
を抑制できる。凝固時に形成されるδフェライトとの格
子整合度が６％以下の介在物が１００個／ｃｍ2 より少
ないと、凝固核が少なくなる。また、ピンニング作用が
十分でなくなるので、鋳片の凝固組織が大きくなり、表
面欠陥及び内部欠陥が発生したり、鋳片の加工性等が悪
くなる。The steel according to the present invention, which meets the above object, has a degree of lattice matching with δ ferrite formed during solidification of molten steel of 6%.
% Of the slab containing at least 100 inclusions / cm 2 or less is subjected to processing such as rolling. Since this steel material is processed into a cast slab having a uniform and fine solidification structure, the surface and internal defects caused by the solidification structure are reduced, and it is easy to be deformed in the rolling direction, so that workability such as rolling can be improved. . In addition, surface defects such as scabs and cracks generated in the steel material after processing, and internal defects such as zag and center segregation (segregation) can be suppressed. If the number of inclusions having a degree of lattice matching with δ ferrite formed at the time of solidification of 6% or less is less than 100 / cm 2 , the number of solidified nuclei decreases. In addition, since the pinning action is not sufficient, the solidification structure of the slab becomes large, surface defects and internal defects occur, and the workability of the slab deteriorates.
【００１０】ここで、前記鋳片に含有した介在物の内、
１０μｍ以下の大きさの介在物を１００個／ｃｍ2 以上
含有することが好ましい。従って、凝固組織をより微細
で均一にしているので、圧下する方向に容易に変形して
圧延等の加工性をより良好にし、加工時あるいは加工後
に発生する欠陥を防止できる。介在物の大きさが１０μ
ｍより大きいと、溶鋼が凝固する際に凝固核としての働
きが弱くなるので、有効な凝固核の数が減少して凝固組
織が粗大化し易くなり、加工性が低下したり表面及び内
部欠陥が発生し易くなる。Here, among the inclusions contained in the slab,
It is preferable to contain 100 inclusions / cm 2 or more of inclusions having a size of 10 μm or less. Therefore, since the solidified structure is made finer and more uniform, it can be easily deformed in the rolling direction to improve the workability of rolling and the like, and defects occurring during or after processing can be prevented. Inclusion size is 10μ
When it is larger than m, the function as solidification nuclei when the molten steel is solidified is weakened, so the number of effective solidification nuclei decreases, the solidification structure easily becomes coarse, workability decreases, and surface and internal defects are reduced. It is easy to occur.
【００１１】[0011]
【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。図１は本発明の一実施の形態に係る
品質と加工特性に優れた鋳片を鋳造する連続鋳造装置の
全体断面図、図２は１０μｍ以下の介在物個数と鋳片の
等軸晶率（％）の関係を表すグラフ、図３は鋳片の厚み
方向の断面における凝固組織の模式図、図４は鋳片の厚
み方向の断面における凝固組織の模式図である。まず、
図１を参照して、本発明の一実施の形態に係る品質と加
工特性に優れた鋳片を鋳造するための連続鋳造装置１０
について説明する。連続鋳造装置１０は、タンディッシ
ュ１１に貯湯された溶鋼１２を浸漬ノズル１３から鋳型
１４に注湯し、鋳型１４の冷却により溶鋼１２を凝固さ
せながら、支持セグメント１５に設けた図示しない冷却
水ノズルから冷却水を散水し、凝固が進行しつつある鋳
片１６を圧下セグメント１７により圧下してからピンチ
ロール１８により引き抜きを行う。そして、所定のサイ
ズに切断された鋳片１６は後工程に搬送され、図示しな
い加熱炉、均熱炉等で加熱されてから圧延等の加工が施
され、鋼材が製造される。DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is an overall sectional view of a continuous casting apparatus for casting a slab excellent in quality and processing characteristics according to an embodiment of the present invention. FIG. 2 is a diagram showing the number of inclusions of 10 μm or less and the equiaxed crystal ratio of the slab ( %), FIG. 3 is a schematic diagram of a solidified structure in a cross section in the thickness direction of the slab, and FIG. 4 is a schematic diagram of a solidified structure in a cross section in the thickness direction of the slab. First,
Referring to FIG. 1, a continuous casting apparatus 10 for casting a slab excellent in quality and working characteristics according to one embodiment of the present invention.
Will be described. The continuous casting device 10 pours the molten steel 12 stored in the tundish 11 from the immersion nozzle 13 into the mold 14, and solidifies the molten steel 12 by cooling the mold 14, and a cooling water nozzle (not shown) provided on the support segment 15. Then, cooling water is sprinkled from the slab, the slab 16 that is undergoing solidification is reduced by the reduction segment 17, and then drawn out by the pinch roll 18. Then, the cast slab 16 cut to a predetermined size is conveyed to a subsequent step, and is heated in a heating furnace (not shown), a soaking furnace, or the like, and then subjected to a process such as rolling to produce a steel material.
【００１２】次に、連続鋳造装置１０によって鋳造され
る品質と加工特性に優れた鋳片１６について説明する。
タンディッシュ１１に設けた浸漬ノズル１３から鋳型１
４に注湯された凝固初晶（溶鋼１２が固まる時に最初に
でる相）がδフェライトの鋼種である溶鋼（クロム１３
重量％を含有するフェライト系ステンレス溶鋼）１２
は、鋳型１４により冷却され、図示しない凝固殻を形成
して鋳片１６となり、支持セグメント１５を下流側へ進
むにつれて、散水する冷却水によって抜熱され、順次凝
固殻の厚みを増しながら、途中で圧下セグメント１７に
より圧下され、完全に凝固する。Next, a slab 16 excellent in quality and processing characteristics cast by the continuous casting apparatus 10 will be described.
From the immersion nozzle 13 provided in the tundish 11, the mold 1
The molten solid (chromium 13) is a δ ferrite steel grade whose solidified primary crystal (the first phase when molten steel 12 solidifies) poured into
Ferritic stainless steel molten steel containing 12% by weight) 12
Is cooled by the mold 14 to form a solidified shell (not shown) to form a slab 16, and as the support segment 15 proceeds downstream, the heat is removed by the cooling water to be sprinkled, thereby increasing the thickness of the solidified shell in the middle. , And is reduced by the reduction segment 17 to be completely solidified.
【００１３】ここで、鋳片の表面及び内部欠陥を防止す
るために、溶鋼１２が凝固する際にδフェライトとの格
子整合度が６％以下の介在物を１００個／ｃｍ2 以上に
なるように溶鋼１２に含有させる。この介在物は、溶鋼
１２中に含有するＯ（酸素）、Ｃ（炭素）、Ｎ（窒
素）、Ｓ（硫黄）やＳｉＯ2 等の酸化物と反応して介在
物を形成する金属を用いるか、あるいは介在物そのもの
を溶鋼１２に添加することによって、溶鋼１２に含有さ
せる。前記金属が溶鋼１２と反応して生成した物（介在
物）、あるいは添加した介在物は、溶鋼１２中に１００
μｍ以下の種々の大きさの介在物を形成し、溶鋼１２が
凝固する際の凝固核として働き、多数の凝固を開始する
起点になる。更に、ピンニング作用により凝固組織の成
長が抑制され、微細な凝固組織の鋳片１６にすることが
できる。特に、分散性の良いものを用いて、鋳型１４内
の溶鋼１２の吐出流による攪拌や鋳型１４に電磁攪拌装
置を配置して攪拌を行うことにより、大きさが１０μｍ
以下の介在物を１００個／ｃｍ2 以上形成させると、前
述した凝固核とそのピンニング作用をより顕著に発現し
て、図２に示すように、等軸晶率が６０％以上の凝固組
織の鋳片１６を得ることができる。図３は、鋳片１６の
厚み方向の断面における凝固組織の模式図であり、鋳片
１６の内部に微細な等軸晶の組織が形成されており、表
層部においても柱状晶の成長が抑制されて小さくなって
おり優れた凝固組織を得ることができた。そして、１０
μｍ以下の介在物を多くすることで、図４に示すよう
に、鋳片１６の表層部から内部にいたる全断面の凝固組
織をより微細で均一な等軸晶とすることができる。Here, in order to prevent the surface and internal defects of the slab, when the molten steel 12 solidifies, the inclusions having a lattice matching degree with δ ferrite of 6% or less become 100 pieces / cm 2 or more. To the molten steel 12. For this inclusion, a metal that forms an inclusion by reacting with an oxide such as O (oxygen), C (carbon), N (nitrogen), S (sulfur), or SiO 2 contained in the molten steel 12 is used. Alternatively, the inclusions are added to the molten steel 12 by adding the inclusions to the molten steel 12. The product (inclusion) generated by the reaction of the metal with the molten steel 12 or the added inclusion is 100% in the molten steel 12.
Inclusions of various sizes of μm or less are formed, function as solidification nuclei when the molten steel 12 solidifies, and serve as a starting point for starting many solidifications. Further, the growth of the solidified structure is suppressed by the pinning action, and the cast piece 16 having a fine solidified structure can be obtained. In particular, by using a material having good dispersibility, stirring by the discharge flow of the molten steel 12 in the mold 14 and stirring by disposing an electromagnetic stirrer in the mold 14 to achieve a size of 10 μm
When the following inclusions are formed in an amount of 100 pieces / cm 2 or more, the above-described solidification nuclei and the pinning action thereof are more remarkably expressed, and as shown in FIG. A slab 16 can be obtained. FIG. 3 is a schematic diagram of a solidification structure in a cross section in the thickness direction of the slab 16, in which a fine equiaxed crystal structure is formed inside the slab 16, and the growth of columnar crystals is suppressed even in the surface layer portion. As a result, an excellent solidified structure was obtained. And 10
By increasing the number of inclusions of μm or less, as shown in FIG. 4, the solidified structure of the entire cross section from the surface layer portion to the inside of the slab 16 can be made into a finer and more uniform equiaxed crystal.
【００１４】微細な等軸晶を備えた鋳片１６は、割れ抵
抗が強いので、鋳片１６の表面に発生する割れやへこみ
疵等の表面欠陥を防止することができる。更に、鋳片１
６の内部も脆いミクロ偏析部が少なく熱収縮や何らかの
応力が生じた際に、内部割れ等の発生が少なく、しか
も、内部の溶鋼１２の供給不足に起因する空洞や偏析等
の内部欠陥の発生も防止できる。また、圧延等の加工を
行う際に、鋳片１６の微細な等軸晶が圧下する方向に容
易に変形して加工性をより高めることができる。しか
も、加工性が良いので圧延等の加工を行った後に、しわ
疵（ローピング、リジング、エッジシーム）等の表面欠
陥を防止でき、鋳片１６及び圧延等の加工に起因する割
れ等の内部欠陥の発生も解消できる。Since the slab 16 having fine equiaxed crystals has high cracking resistance, surface defects such as cracks and dents generated on the surface of the slab 16 can be prevented. Furthermore, slab 1
6 also has few brittle micro-segregated portions, so that when heat shrinkage or some kind of stress occurs, the occurrence of internal cracks and the like is small, and the occurrence of internal defects such as voids and segregation due to insufficient supply of molten steel 12 inside. Can also be prevented. Further, when processing such as rolling is performed, the fine equiaxed crystals of the slab 16 are easily deformed in a direction in which the slab is reduced, so that workability can be further improved. Moreover, since the workability is good, surface defects such as wrinkles (roping, ridging, edge seam) can be prevented after processing such as rolling, and internal defects such as cracks caused by the casting 16 and processing such as rolling can be prevented. The occurrence can also be eliminated.
【００１５】フェライト系鋼種に用いる介在物を形成す
るには、金属Ｍｇ、Ｍｇ合金、Ｔｉ、Ｃｅ、Ｃａ、Ｚｒ
等の金属や金属の化合物を用い、溶鋼中のＯ、Ｃ、Ｎ、
ＳやＳｉＯ2 等の酸化物と反応させて金属化合物（介在
物）を形成する。溶鋼に添加する介在物としては、Ｍｇ
Ｏ、ＭｇＡｌ2 Ｏ4 、ＴｉＮ、ＣｅＳ、Ｃｅ2 Ｏ3 、Ｃ
ａＳ、ＺｒＯ2 、ＴｉＣ、ＶＮ等のδフェライトとの格
子整合度（格子歪み係数）が６％以下のものを用い、溶
鋼に添加した際の分散性や凝固核の生成の安定性から、
特にＭｇＯ、ＭｇＡｌ2 Ｏ4 、ＴｉＮがより好ましい。
なお、δフェライトとの格子整合度は、溶鋼が凝固して
生成されるδフェライトの格子定数と金属化合物の格子
定数の差を溶鋼の凝固核の格子定数で除した値であり、
この値が小さい程凝固核の生成が良好になる。In order to form inclusions used in ferritic steel types, metallic Mg, Mg alloy, Ti, Ce, Ca, Zr
O, C, N, etc. in molten steel using metals and metal compounds such as
It reacts with oxides such as S and SiO 2 to form metal compounds (inclusions). As an inclusion to be added to molten steel, Mg
O, MgAl 2 O 4 , TiN, CeS, Ce 2 O 3 , C
aS, ZrO 2 , TiC, VN, etc., having a lattice matching degree (lattice strain coefficient) of 6% or less with δ ferrite, and from the dispersibility when added to molten steel and the stability of solidification nucleus generation,
Particularly, MgO, MgAl 2 O 4 and TiN are more preferable.
The degree of lattice matching with δ ferrite is a value obtained by dividing the difference between the lattice constant of δ ferrite generated by solidification of molten steel and the lattice constant of a metal compound by the lattice constant of solidification nuclei of molten steel,
The smaller this value, the better the formation of solidification nuclei.
【００１６】鋳片の介在物の個数を測定するには、ＳＥ
Ｍ（Ｓｃａｎｎｉｎｇ・Ｅｌｅｃｔｒｏｎ・Ｍｉｃｒｏ
ｓｃｏｐｅ）やスライム法等を用いて単位面積当たりの
１０μｍ以下の大きさを有する介在物の個数を数える。
金属化合物の大きさは、ＳＥＭ等の電子顕微鏡により全
断面の介在物を観察して、それぞれの介在物の最大直径
と最小直径を平均した値をその介在物の大きさにする。
一方、スライム法の場合は、鋳片の全断面の一部を切り
出して、この切り出し片を溶解してから介在物を分級し
て取り出し、それぞれの介在物の最大直径と最小直径を
平均した値により大きさを判定し、その大きさごとの個
数を求める。また、等軸晶の大きさは、溶鋼が凝固する
際に生じる溶鋼の溶質成分の固液分配に起因するミクロ
偏析を境界とする凝固組織単位の大きさであり、凝固し
た鋳片をその厚み方向の断面が出るように、切断してそ
の断面を研磨してから、例えばピクリン酸を用いてミク
ロ偏析部をエッチングして、この凝固組織を１〜１０倍
に拡大してから画像処理等により求めることができる。To measure the number of inclusions in the slab, use SE
M (Scanning / Electron / Micro)
The number of inclusions having a size of 10 μm or less per unit area is counted by using a scoping method or a slime method.
The size of the metal compound is determined by observing inclusions in all cross sections with an electron microscope such as an SEM and averaging the maximum diameter and the minimum diameter of each inclusion to determine the size of the inclusion.
On the other hand, in the case of the slime method, a part of the entire cross section of the cast piece is cut out, the cut piece is melted, the inclusions are classified and taken out, and a value obtained by averaging the maximum diameter and the minimum diameter of each inclusion. Is used to determine the size, and the number of each size is determined. The size of the equiaxed crystal is the size of a solidification structure unit bounded by microsegregation caused by solid-liquid distribution of solute components of the molten steel that occurs when the molten steel is solidified. After cutting and polishing the cross-section so that the cross section in the direction appears, the micro-segregated part is etched using, for example, picric acid, and the solidified structure is enlarged 1 to 10 times, and then subjected to image processing or the like. You can ask.
【００１７】また、このような介在物を含有した鋳片１
６を連続鋳造するには、タンディッシュ１１内の溶鋼１
２に、溶鋼１２中の酸素あるいは酸化物であるＦｅＯ、
ＳｉＯ 2 、ＭｎＯ、窒素、炭素等と反応させて、Ｍｇ
Ｏ、ＭｇＡｌ2 Ｏ4 、ＴｉＮ、ＴｉＣ、等の介在物を形
成する金属あるいは直接に前記の介在物を添加する。特
に、金属ＭｇあるいはＭｇ合金を溶鋼１２に添加して、
溶鋼１２中にＭｇＯの単体あるいはＭｇＯを含有する複
合の酸化物からなる介在物を形成させると溶鋼１２中で
の介在物の分散性を向上できるのでより好ましい結果が
得られる。例えば、Ｍｇ等の金属を例にした場合は、溶
鋼に対して、０．００２〜０．１００重量％に相当する
金属ＭｇあるいはＭｇ合金を添加する。更に、添加方法
は、Ｍｇ、又はＭｇ合金を溶鋼１２に直接添加するか、
あるいはＭｇ、又はＭｇ合金を薄鋼で覆った線状に加工
したワイヤーを連続的に供給することができる。添加量
が０．００２重量％未満では、凝固核が不足するので、
微細な凝固組織が得られ難くなる。また、ピンニング効
果が小さくなるので、凝固後の凝固組織の成長の抑制効
果が減少し微細な凝固組織が得られない。一方、０．１
００重量％を超えると、凝固核の生成が飽和し、合金コ
ストの上昇や鋳片１６の内部の総酸化物量が増加して耐
食性等が低下する。また、凝固初晶がδフェライトにな
る鋼種である溶鋼１２としては、例えば、クロムを１３
〜１７重量％を含有したＳＵＳステンレス等がある。こ
のようにして鋳造された鋳片１６は、凝固組織が均一で
あり、表面及び内部欠陥の抑制に優れ、良好な加工特性
を備えている。更に、鋳片１６は、振動鋳型式の連続鋳
造の他に、造塊法やベルトキャスター、双ロール等の鋳
造法により鋳造することができる。また、鋳片１６とし
ては、例えば連続鋳造により鋳造されたもので、厚みを
１００ｍｍ以上にすると、表層から内部にいたる凝固組
織中の等軸晶を容易に調整でき、微細化による効果も大
きいので好ましい結果が得られる。このように、鋳造さ
れた鋳片１６は、ピンチロール１８により引き抜かれ
て、図示しない切断機により所定のサイズに切断されて
から圧延等の後工程に搬送される。Further, the slab 1 containing such inclusions
In order to continuously cast 6, molten steel 1 in tundish 11
2, FeO which is oxygen or oxide in the molten steel 12,
SiO Two , MnO, nitrogen, carbon, etc.
O, MgAlTwo OFour , TiN, TiC, etc.
The metal to be formed or the above-mentioned inclusions are added directly. Special
In addition, metal Mg or Mg alloy is added to molten steel 12,
The molten steel 12 contains MgO alone or a compound containing MgO.
When the inclusions made of the combined oxides are formed,
More favorable results because the dispersibility of the inclusions can be improved.
can get. For example, in the case of a metal such as Mg,
Corresponds to 0.002 to 0.100% by weight based on steel
Metallic Mg or Mg alloy is added. Furthermore, the addition method
Is to add Mg or Mg alloy directly to molten steel 12,
Alternatively, process Mg or Mg alloy into a line covered with thin steel
Can be supplied continuously. Amount added
If the content is less than 0.002% by weight, coagulation nuclei are insufficient.
It becomes difficult to obtain a fine solidified structure. In addition, the pinning effect
The effect of suppressing the growth of coagulated tissue after coagulation
Fruits are reduced and a fine solidified structure cannot be obtained. On the other hand, 0.1
If the content exceeds 00% by weight, the formation of solidification nuclei is saturated, and
And the total oxide content inside the slab 16 increases,
Eating habits etc. decrease. Also, the solidification primary crystal becomes δ ferrite.
As the molten steel 12 as a steel type, for example,
SUS stainless steel containing about 17% by weight. This
The slab 16 cast as described above has a uniform solidification structure.
Yes, excellent in suppressing surface and internal defects, good processing characteristics
It has. Further, the slab 16 is a continuous casting type of a vibration mold.
In addition to casting, ingot casting, casting of belt casters, twin rolls, etc.
It can be cast by a manufacturing method. In addition, cast slab 16
For example, it is cast by continuous casting,
If it is 100mm or more, solidification from the surface layer to the inside
Equiaxed crystals during weaving can be easily adjusted and the effect of miniaturization is great.
Preferred results are obtained. Thus, cast
The cast slab 16 is pulled out by a pinch roll 18.
Is cut to a predetermined size by a cutting machine (not shown).
To a subsequent step such as rolling.
【００１８】次に、本発明の一実施の形態に係る鋼材に
ついて説明する。本発明の鋼材は、前述した鋳片１６を
図示しない加熱炉や均熱炉等により１１５０〜１２５０
℃に加熱した後、圧延等の加工を施して厚板や薄板、形
鋼等に加工される。この鋼材は、加工に用いる鋳片１６
の凝固組織を表層から内部にわたり微細にし、脆いミク
ロ偏析を小さくしているので、割れ抵抗が強くなり、加
工中や加工後に生じる割れやヘゲ等の表面欠陥を少なく
できる。更に、内部においても、内部割れや未凝固溶鋼
の凝固収縮による空洞、溶鋼１２の流動による中心偏析
等を抑制しているので、鋼材に発生する鋳片や圧延等の
加工に起因する内部欠陥を少なくできる。しかも、微細
で均一な凝固組織を備えた鋳片１６は、絞り加工（ｒ
値）等の加工特性に優れており、容易に鋳片１６を加工
することができ、加工後の溶接部の靭性にも優れてい
る。特に、分散性が良く、大きさが１０μｍ以下の介在
物を多く形成させた鋳片１６に、圧延等の加工を施した
鋼材は、より微細な等軸晶で均一な鋳片１６を加熱、加
工をするので、鋼材の表面に発生するヘゲ疵や割れ等が
発生するのを確実に防止でき、圧下方向に容易に変形し
て絞り加工等の加工特性がより向上できる。Next, a steel material according to an embodiment of the present invention will be described. The steel material of the present invention is obtained by converting the above-mentioned slab 16 to 1150 to 1250 by a heating furnace or a soaking furnace (not shown).
After heating to ° C., it is processed into a thick plate, a thin plate, a shaped steel, etc. by performing processing such as rolling. This steel material is used as a cast slab 16 for processing.
Since the solidification structure of the steel is made fine from the surface layer to the inside and brittle microsegregation is reduced, cracking resistance is increased, and surface defects such as cracks and scabs generated during and after processing can be reduced. Further, also inside, since internal cracks, cavities due to solidification shrinkage of unsolidified molten steel, center segregation due to the flow of molten steel 12, and the like are suppressed, internal defects caused by processing such as slabs and rolling generated in steel materials are reduced. Can be reduced. Moreover, the slab 16 having a fine and uniform solidification structure is drawn (r
Value), the casting slab 16 can be easily processed, and the toughness of the weld after processing is also excellent. In particular, a steel material that has been subjected to processing such as rolling on a slab 16 in which a large number of inclusions having a good dispersibility and a size of 10 μm or less are formed, heats a uniform slab 16 with finer equiaxed crystals, Since the working is performed, it is possible to reliably prevent the occurrence of barbed flaws, cracks, and the like generated on the surface of the steel material, and it is possible to easily deform in the drafting direction to further improve the processing characteristics such as drawing.
【００１９】[0019]
【実施例】次に、本発明の一実施の形態に係る品質と加
工特性に優れた鋳片及びこの鋳片を用いて圧延加工を行
った鋼材の実施例について説明する。タンディッシュ内
の溶鋼に、金属Ｍｇを０．００５重量％添加してから、
幅１２００ｍｍ、厚み２５０ｍｍの内寸法の鋳型に連続
鋳造を行ない、鋳型による冷却と支持セグメントからの
散水により、鋳片を冷却して凝固させ、圧下セグメント
を用いて３〜７ｍｍの圧下を行って、ピンチロールで引
き抜きを行った。そして、鋳片を切断して厚み方向の断
面の凝固組織の等軸晶率、平均等軸晶径（ｍｍ）、表層
及び内部欠陥の調査と、その鋳片を１２５０℃に加熱し
てから圧延し、鋼材の表層及び内部欠陥と加工特性を調
査し、結果を表１に示した。EXAMPLES Next, examples of a slab excellent in quality and working characteristics according to one embodiment of the present invention and a steel material rolled using the slab will be described. After adding 0.005% by weight of metallic Mg to molten steel in the tundish,
Continuous casting is performed on a mold having an inner size of 1200 mm in width and 250 mm in thickness, and the slab is cooled and solidified by cooling by the mold and water sprinkling from the support segment, and a reduction of 3 to 7 mm is performed by using a reduction segment. The sheet was pulled out with a pinch roll. Then, the slab is cut to investigate the equiaxed crystal ratio, average equiaxed crystal diameter (mm), surface layer and internal defects of the solidified structure in the cross section in the thickness direction, and the slab is heated to 1250 ° C. and then rolled. Then, the surface layer and internal defects of the steel material and the processing characteristics were investigated, and the results are shown in Table 1.
【００２０】実施例１は、フェライト鋼の鋳片に含有さ
れるδフェライトとの格子整合度が６％以下の介在物の
個数を１０４個／ｃｍ2 にし、その介在物のサイズを１
０μｍ以上にし、等軸晶率を６２％、平均等軸晶径を
１．８ｍｍにした鋳片であり、表層に形成したミクロ偏
析を小さくでき、割れやへこみ疵等の表面欠陥の発生が
少なく（○）、割れ、ザクや中心偏析（偏析）等の内部
欠陥も少なかった（○）。更に、この鋳片を用いて圧延
した鋼材は、表層にリジングやエッジシーム疵等が少な
く（○）、割れ、ザクや偏析等の内部欠陥も少なく
（○）、凝固組織及びミクロ偏析が小さいので、圧下す
る方位に変形し易く加工性の指標であるｒ値等が良い
（○）結果であった。実施例２は、フェライト鋼の鋳片
に含有されるδフェライトとの格子整合度が６％以下の
介在物の個数を１４１個／ｃｍ2 にし、その介在物のサ
イズを１０μｍ以下にし、等軸晶率を８１％、平均等軸
晶径を１．３ｍｍにした鋳片であり、表層に形成したミ
クロ偏析を小さくでき、割れやへこみ疵等の表面欠陥の
発生が無く（◎）、内部欠陥である割れ、ザクや偏析等
の内部欠陥も無かった（◎）。更に、この鋳片を用いて
圧延した鋼材は、表層にリジングやエッジシーム疵等が
無く（◎）、割れ、ザクや偏析等の内部欠陥も無く
（◎）、凝固組織及びミクロ偏析が小さいので、圧下す
る方位に変形し易く加工性の指標であるｒ値等が良い
（◎）結果であった。In Example 1, the number of inclusions having a lattice matching degree of 6% or less with δ-ferrite contained in a slab of ferritic steel was 104 / cm 2 , and the size of the inclusions was 1
It is a slab having 0 μm or more, an equiaxed crystal ratio of 62%, and an average equiaxed crystal diameter of 1.8 mm. The microsegregation formed on the surface layer can be reduced, and the occurrence of surface defects such as cracks and dents is small. (○), and few internal defects such as cracks, zags and center segregation (segregation) were also observed (）). Furthermore, since the steel material rolled using this slab has few ridging and edge seam flaws on the surface layer (）), few internal defects such as cracks, zags and segregation (○), and has a small solidification structure and micro segregation. It was easy to be deformed in the direction of rolling down, and the r value and the like which are indicators of workability were good (○). In Example 2, the number of inclusions having a lattice matching degree of 6% or less with δ ferrite contained in a slab of ferritic steel was 141 / cm 2 , the size of the inclusions was 10 μm or less, A slab having a crystallinity of 81% and an average equiaxed crystal diameter of 1.3 mm. The microsegregation formed on the surface layer can be reduced, no surface defects such as cracks and dents are generated (◎), and internal defects are generated. There were no internal defects such as cracks, zags and segregation (◎). Furthermore, the steel material rolled using this slab has no ridging or edge seam flaws on the surface layer (◎), no internal defects such as cracks, zags and segregation (◎), and has a small solidification structure and micro segregation. It was easy to be deformed in the direction of rolling down, and the r value and the like which are indicators of workability were good (良 い).
【００２１】[0021]
【表１】 [Table 1]
【００２２】これに対して、比較例１は、鋳片に含有さ
れる介在物の個数を７０個／ｃｍ2 にし、その介在物の
サイズを１０μｍ以下にした場合であり、等軸晶率を２
７％、平均等軸晶径が２．５ｍｍに大きくなった鋳片で
あり、表層に形成したミクロ偏析が大きく、割れやへこ
み疵等の表面欠陥が発生し（×）、鋳片の内部に割れや
空洞、偏析等の内部欠陥が生じて悪い（×）結果になっ
た。更に、この鋳片を用いて圧延した鋼材は、表層にヘ
ゲ疵、リジングやエッジシーム疵等が発生し（×）、割
れや空洞、偏析等の内部欠陥も生じ（×）、圧下する方
位に変形し難く加工性の指標であるｒ値等が悪い（×）
結果であった。比較例２は、鋳片の単位面積当たりに存
在する金属化合物の内で、１０μｍ以下の金属化合物の
個数が、表層部で４５個／ｃｍ2 、内部で４５個／ｃｍ
2 にした鋳片であり、表層部の最大等軸晶粒径及び内部
の最大等軸晶粒径が大きくなった鋳片であり、割れやへ
こみ疵等の表面及び割れ、ザクや偏析等の内部欠陥も発
生して悪い（×）結果となった。更に、この鋳片を用い
て圧延した鋼材は、ヘゲ疵及び割れの表面欠陥及び割
れ、ザクや偏析等の内部欠陥が発生して悪く（×）、加
工性の指標であるｒ値も悪い（×）結果であった。On the other hand, in Comparative Example 1, the number of inclusions contained in the slab was set to 70 / cm 2 and the size of the inclusions was set to 10 μm or less. 2
7%, a slab having an average equiaxed crystal diameter of as large as 2.5 mm. The microsegregation formed on the surface layer is large, and surface defects such as cracks and dents occur (×). Internal defects such as cracks, cavities, and segregation occurred, resulting in a poor (X) result. Further, in the steel material rolled using this slab, barge flaws, ridging and edge seam flaws are generated on the surface layer (×), and internal defects such as cracks, cavities, segregation are also generated (×), and the rolling direction is reduced. Difficult to deform and bad in r-value, which is an index of workability (x)
It was a result. In Comparative Example 2, the number of metal compounds having a size of 10 μm or less among the metal compounds existing per unit area of the slab was 45 / cm 2 in the surface layer portion and 45 / cm 2 in the inside.
A slab which was 2, the maximum equiaxed Akiratsubu diameter and the maximum equiaxed Akiratsubu diameter cast increased pieces inside the surface layer portion, the surface and cracks such as cracks and dents flaws, Zaku and segregation Internal defects also occurred, resulting in a bad (x) result. Furthermore, the steel material rolled using this slab is poor (x) due to surface defects and cracks such as barbs and cracks, and internal defects such as zag and segregation, and the r value as an index of workability is poor. (X) The result was obtained.
【００２３】なお、介在物を形成する物として、Ｍｇ
Ｏ、ＭｇＡｌ2 Ｏ4 、ＴｉＮ、ＴｉＣを０．０６重量％
添加した鋳片及びこの鋳片に圧延等の加工を施した鋼材
についても凝固組織の等軸晶の大きさと、表層及び内部
欠陥の調査と、その鋳片を１２５０℃に加熱してから圧
延し、鋼材の表層及び内部欠陥と加工特性を調査したが
いずれも良い結果であった。In addition, as a substance forming the inclusion, Mg
0.06% by weight of O, MgAl 2 O 4 , TiN and TiC
Regarding the added slab and the steel material that has been subjected to processing such as rolling, the slab is also subjected to rolling, etc., the equiaxed crystal size of the solidification structure, the surface layer and internal defects are investigated, and the slab is heated to 1250 ° C. and then rolled. The surface layer and internal defects of the steel material and the processing characteristics were investigated, and all were good results.
【００２４】以上、本発明の一実施の形態を説明した
が、本発明は、上記した形態に限定されるものでなく、
要旨を逸脱しない条件の変更等は全て本発明の適用範囲
である。例えば、介在物を形成する金属あるいはＭｇ
Ｏ、ＭｇＡｌ2 Ｏ4 、ＴｉＮ、ＴｉＣをタンディッシュ
以外に、取鍋や鋳型内の溶鋼に添加することもできる。
更に、介在物を形成する物を添加し、これに低温鋳造や
電磁攪拌あるいはこれ等を組合せて鋳造することもでき
る。Although the embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment.
All changes in conditions that do not depart from the gist are within the scope of the present invention. For example, metal forming inclusions or Mg
O, MgAl 2 O 4 , TiN, and TiC can be added to the molten steel in the ladle and the mold other than the tundish.
Further, it is also possible to add a substance that forms inclusions and cast the mixture by low-temperature casting, electromagnetic stirring, or a combination thereof.
【００２５】[0025]
【発明の効果】請求項１〜３記載の品質と加工特性に優
れた鋳片においては、溶鋼の凝固時に形成されるδフェ
ライトとの格子整合度が６％以下の介在物が１００個／
ｃｍ2 以上含有されているので、鋳片の凝固組織を微細
で均一にでき、鋳片に生じる割れやへこみ疵等の表面欠
陥及び内部割れや空洞（ザク）、中心偏析等の内部欠陥
を抑制して、手入れや屑化等が少なく、歩留りの高い品
質に優れた鋳片を製造できる。更に、圧延等の加工を行
った際に、表面及び内部欠陥が少なく、圧下方向に対す
る変形を容易にして圧延等の加工性を高めこともでき
る。In the slab having excellent quality and working characteristics according to the first to third aspects, 100 inclusions having a lattice matching degree of 6% or less with δ ferrite formed at the time of solidification of molten steel /
cm 2 or more, the solidification structure of the slab can be made fine and uniform, and surface defects such as cracks and dents generated in the slab and internal defects such as internal cracks, cavities, and center segregation can be suppressed. As a result, it is possible to manufacture a cast piece having little quality, such as care and debris, and high yield. Furthermore, when processing such as rolling is performed, surface and internal defects are small, and deformation in the rolling direction is facilitated, so that workability such as rolling can be improved.
【００２６】特に、請求項２記載の品質と加工特性に優
れた鋳片においては、１０μｍ以下の大きさの介在物が
１００個／ｃｍ2 以上含有されているので、安定して微
細で均一な凝固組織にすることができ、表面及び内部欠
陥をより確実に防止でき、研削等の手入れや屑化等をな
くして歩留りをより向上でき、圧延等の加工性をより高
め、溶接等を行った際に靱性を向上することができる。In particular, in the slab excellent in quality and working characteristics according to the second aspect, since inclusions having a size of 10 μm or less are included in an amount of 100 or more / cm 2, it is stable and fine and uniform. Solidified structure, surface and internal defects can be more reliably prevented, maintenance such as grinding and debris can be eliminated, yield can be further improved, workability such as rolling can be further improved, welding etc. have been performed In this case, the toughness can be improved.
【００２７】請求項３記載の品質と加工特性に優れた鋳
片においては、溶鋼の凝固初晶がδフェライトの鋼種で
あるので、粗大化し易い鋳片の凝固組織を微細で均一に
することができ、表面及び内部欠陥を抑制しながら、圧
延等の加工性を良好にできる。In the slab having excellent quality and working characteristics according to the third aspect, since the solidified primary crystal of the molten steel is a δ ferrite steel type, the solidified structure of the slab which is easily coarsened can be made fine and uniform. The processability such as rolling can be improved while suppressing surface and internal defects.
【００２８】請求項４及び５記載の鋼材においては、溶
鋼の凝固時に形成されるδフェライトとの格子整合度が
６％以下の介在物を１００個／ｃｍ2 以上含有した鋳片
を加熱した後に、圧延等の加工を施しているので、圧延
等の加工性を高めることができ、加工後の鋼材に発生す
るヘゲ疵や割れ等の表面欠陥及びザクや偏析等の内部欠
陥を少なくして、鋼材の手入れの増加や屑化等を防止し
て良製品の歩留りを向上できる。In the steel material according to the fourth and fifth aspects, after heating a slab containing at least 100 inclusions / cm 2 having a lattice matching degree of 6% or less with δ ferrite formed during solidification of molten steel, Since it is subjected to processing such as rolling, it is possible to enhance the workability of rolling and the like, and to reduce surface defects such as barbed scratches and cracks and internal defects such as zags and segregation which occur in the processed steel material. In addition, it is possible to prevent an increase in the maintenance of the steel material and to prevent the scrap from being scrapped, thereby improving the yield of good products.
【００２９】特に、請求項５記載の鋼材においては、１
０μｍ以下の大きさの介在物が１００個／ｃｍ2 以上含
有された鋳片を加熱した後に、圧延等の加工を施してい
るので、圧延等の加工性をより良好にし、加工時あるい
は加工後に発生する表面欠陥及び内部欠陥をより確実に
無くし、良製品の歩留りや靱性等の品質特性をより向上
できる。In particular, in the steel material according to claim 5, 1
After heating the cast slab containing 100 μm / cm 2 or more inclusions having a size of 0 μm or less, the slab is subjected to processing such as rolling. Surface defects and internal defects that occur are more reliably eliminated, and quality characteristics such as yield and toughness of good products can be further improved.
【図１】本発明の一実施の形態に係る品質と加工特性に
優れた鋳片を鋳造する連続鋳造装置の全体断面図であ
る。FIG. 1 is an overall sectional view of a continuous casting apparatus for casting a slab excellent in quality and processing characteristics according to an embodiment of the present invention.
【図２】１０μｍ以下の介在物の個数と鋳片の等軸晶率
の関係を表すグラフである。FIG. 2 is a graph showing the relationship between the number of inclusions of 10 μm or less and the equiaxed crystal ratio of a slab.
【図３】鋳片の厚み方向の断面における凝固組織の模式
図である。FIG. 3 is a schematic view of a solidified structure in a cross section in a thickness direction of a slab.
【図４】鋳片の厚み方向の断面における凝固組織の模式
図である。FIG. 4 is a schematic diagram of a solidified structure in a cross section in a thickness direction of a slab.
【図５】従来の鋳片の厚み方向の断面における凝固組織
の模式図である。FIG. 5 is a schematic view of a solidified structure in a cross section in the thickness direction of a conventional slab.
１０：連続鋳造装置、１１：タンディッシュ、１２：溶
鋼、１３：浸漬ノズル、１４：鋳型、１５：支持セグメ
ント、１６：鋳片、１７：圧下セグメント、１８：ピン
チロール10: continuous casting apparatus, 11: tundish, 12: molten steel, 13: immersion nozzle, 14: mold, 15: support segment, 16: cast piece, 17: reduction segment, 18: pinch roll
フロントページの続き (72)発明者 三浦 龍介 福岡県北九州市戸畑区飛幡町１番１号 新 日本製鐵株式会社八幡製鐵所内 (72)発明者 阿部 雅之 福岡県北九州市戸畑区飛幡町１番１号 新 日本製鐵株式会社八幡製鐵所内 Ｆターム(参考） 4E004 MC00 Continuing from the front page (72) Inventor Ryusuke Miura 1-1-1, Hibata-cho, Tobata-ku, Kitakyushu-shi, Fukuoka New Nippon Steel Corporation Yawata Works (72) Inventor Masayuki Abe 1-Hibatacho, Tobata-ku, Kitakyushu-shi, Fukuoka No. 1 New Nippon Steel Corporation Yawata Works F-term (reference) 4E004 MC00
Claims (5)
との格子整合度が６％以下の介在物を１００個／ｃｍ2
以上含有していることを特徴とする品質と加工特性に優
れた鋳片。1. Inclusions having a lattice matching degree of 6% or less with δ ferrite formed at the time of solidification of molten steel are 100 / cm 2.
A slab excellent in quality and processing characteristics characterized by containing above.
鋳片において、前記介在物の内、１０μｍ以下の大きさ
の介在物が１００個／ｃｍ2 以上含有されていることを
特徴とする品質と加工特性に優れた鋳片。2. The slab according to claim 1, wherein the slab has excellent quality and processing characteristics, wherein at least 100 inclusions / cm 2 having a size of 10 μm or less are contained among the inclusions. Slab with excellent quality and processing characteristics.
優れた鋳片において、前記溶鋼の凝固初晶がδフェライ
トの鋼種であることを特徴とする品質と加工特性に優れ
た鋳片。3. A slab having excellent quality and working characteristics according to claim 1, wherein the solidified primary crystal of the molten steel is a δ ferrite steel type. .
との格子整合度が６％以下の介在物を１００個／ｃｍ2
以上含有した鋳片を加熱した後に、圧延等の加工を施し
たことを特徴とする鋼材。4. Inclusions having a lattice matching degree of 6% or less with δ ferrite formed at the time of solidification of molten steel are 100 / cm 2.
A steel material characterized by being subjected to processing such as rolling after heating a slab containing the above.
に含有した介在物の内、１０μｍ以下の大きさの介在物
が１００個／ｃｍ2 以上含有されていることを特徴とす
る鋼材。5. The steel material according to claim 4, wherein, among the inclusions contained in said slab, at least 100 inclusions / cm 2 having a size of 10 μm or less are contained.
Priority Applications (17)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11367399A JP2000301306A (en) | 1999-04-21 | 1999-04-21 | Cast slab excellent in quality and working characteristic and steel material worked from this slab |
| KR1020057018257A KR100706973B1 (en) | 1999-04-08 | 2000-04-07 | Cast steel piece with fine solidification sturcture and excellent forming characteristics and steel product and seamless steel pipe produced by using the same |
| CNB2005100068043A CN1321766C (en) | 1999-04-08 | 2000-04-07 | Cast steel and steel material with excellent workability, method for processing molten steel therefor and method for manufacturing the cast steel and steel material |
| RU2001101464/02A RU2228235C2 (en) | 1999-04-08 | 2000-04-07 | Steel casting (variants) and steel material with improved workability, method for processing melt steel (variants) and method for making steel casting and steel material |
| AU36746/00A AU753777B2 (en) | 1999-04-08 | 2000-04-07 | Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof |
| US09/719,206 US6585799B1 (en) | 1999-04-08 | 2000-04-07 | Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof |
| KR1020007013895A KR100550678B1 (en) | 1999-04-08 | 2000-04-07 | Method for treatment of molten steel for making solidification structure of cast steel piece fine |
| EP00915437A EP1099498A4 (en) | 1999-04-08 | 2000-04-07 | Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof |
| EP07005688.2A EP1803512B1 (en) | 1999-04-08 | 2000-04-07 | Cast steel with excellent workability and method for manufacturing the cast steel |
| EP10186292.8A EP2292352B1 (en) | 1999-04-08 | 2000-04-07 | Method for processing molten steel for cast steel and steel material with excellent workability |
| CN 00800836 CN1258413C (en) | 1999-04-08 | 2000-04-07 | Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof |
| EP10186277.9A EP2308616B1 (en) | 1999-04-08 | 2000-04-07 | Cast steel and steel material with excellent workability, method for processing molten steel therefor and method for manufacturing the cast steel and steel material |
| EP10186285.2A EP2308617B1 (en) | 1999-04-08 | 2000-04-07 | Method for processing molten steel |
| PCT/JP2000/002296 WO2000061322A1 (en) | 1999-04-08 | 2000-04-07 | Cast steel piece and steel product excellent in forming characteristics and method for treatment of molted steel therefor and method for production thereof |
| CA002334352A CA2334352C (en) | 1999-04-08 | 2000-04-07 | Cast steel piece and steel material with excellent workability, method for processing molten steel therefor and method for manufacutring the cast steel and steel material |
| TW89106564A TW434059B (en) | 1999-04-08 | 2000-04-08 | Cast strip and steel material with excellent workability, and method for processing molten steel therefor and method for manufacturing the strip and material |
| US10/222,362 US6918969B2 (en) | 1999-04-08 | 2002-08-16 | Cast steel and steel material with excellent workability, method for processing molten steel therefor and method for manufacturing the cast steel and steel material |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11367399A JP2000301306A (en) | 1999-04-21 | 1999-04-21 | Cast slab excellent in quality and working characteristic and steel material worked from this slab |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000301306A true JP2000301306A (en) | 2000-10-31 |
Family
ID=14618275
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11367399A Pending JP2000301306A (en) | 1999-04-08 | 1999-04-21 | Cast slab excellent in quality and working characteristic and steel material worked from this slab |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000301306A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017018515A1 (en) * | 2015-07-29 | 2017-02-02 | 新日鐵住金株式会社 | Titanium material for hot rolling |
| CN115144259A (en) * | 2022-08-30 | 2022-10-04 | 张家港广大特材股份有限公司 | Method and system for detecting deformation resistance of steel |
-
1999
- 1999-04-21 JP JP11367399A patent/JP2000301306A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2017018515A1 (en) * | 2015-07-29 | 2017-02-02 | 新日鐵住金株式会社 | Titanium material for hot rolling |
| JPWO2017018515A1 (en) * | 2015-07-29 | 2017-12-28 | 新日鐵住金株式会社 | Titanium material for hot rolling |
| CN115144259A (en) * | 2022-08-30 | 2022-10-04 | 张家港广大特材股份有限公司 | Method and system for detecting deformation resistance of steel |
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