JP2000288693A - Ingot having excellent quality characteristic and steel using it - Google Patents
Ingot having excellent quality characteristic and steel using itInfo
- Publication number
- JP2000288693A JP2000288693A JP10237999A JP10237999A JP2000288693A JP 2000288693 A JP2000288693 A JP 2000288693A JP 10237999 A JP10237999 A JP 10237999A JP 10237999 A JP10237999 A JP 10237999A JP 2000288693 A JP2000288693 A JP 2000288693A
- Authority
- JP
- Japan
- Prior art keywords
- slab
- molten steel
- surface layer
- solidification
- metal compound
- 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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Links
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- Continuous Casting (AREA)
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
備え表面や内部欠陥等の発生が少なく、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 less surface and internal defects, 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、薄肉鋳片等に連続鋳造し、これを所
定のサイズに切断して製造される。さらに、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
の加工を施すことにより、鋼板や形鋼等の鋼材が製造さ
れる。しかし、この鋳片は、溶鋼を凝固させるため、そ
の過程において、冷却や凝固収縮の不均一等により表面
に割れやへこみ疵等の表面欠陥が生じたり、内部の凝固
収縮時に未凝固溶鋼が流動することによって、内部割れ
や空洞（ザク）、中心偏析（偏析）等の内部欠陥が生じ
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と内部割れやザク、偏析等の内部
欠陥が鋼板や形鋼等の鋼材に残存して、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。2. Description of the Related Art Conventionally, cast slabs are manufactured by continuously casting molten steel into slabs, blooms, billets, thin cast slabs and the like using a mold, a belt caster, a strip caster, or the like, and cutting the cast slab to a predetermined size. Is done. Further, after the slab is heated using a heating furnace or the like, roughing rolling, finishing rolling, or the like is performed, thereby producing a steel material such as a steel plate or a shaped steel. However, since this slab solidifies molten steel, surface defects such as cracks and dents occur on the surface due to uneven cooling and solidification shrinkage in the process, and unsolidified molten steel flows during internal solidification shrinkage. This causes internal defects such as internal cracks, cavities (Zaku), and center segregation (segregation). Surface defects generated in the slab cause a decrease in yield due to an increase in care such as grinding and debris, etc.When processing such as rough rolling or finish rolling using this slab as it is,
Internal defects such as surface defects and internal cracks, zags, segregation, etc. generated in the slab remain in steel materials such as steel plates and shaped steels, causing UST rejection, reduced strength or deterioration of appearance, etc., and increased care of steel materials And problems such as scraping occur.
【０００３】この対策として、凝固する鋳片の結晶組織
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。鋳片の凝固組織中の等軸晶を微細化するには、１）
溶鋼の温度を低くした低温鋳造する、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等の方法、あるいはこれ等
１）〜３）を組合せて行う等の方法が知られている。低
温鋳造の具体例としては、例えば、特開平７−８４６１
７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５３−９
０１２９号公報には、溶鋼が凝固する際に凝固核となる
金属酸化物の添加と電磁攪拌を組合せて、鋳片の厚み方
向の全断面における凝固組織を殆ど等軸晶にすることが
提案されている。As a countermeasure, attempts have been made to make the crystal structure of the solidified 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. To refine equiaxed crystals in the solidification structure of cast slabs 1)
Low-temperature casting with the temperature of the molten steel lowered; 2) electromagnetic stirring of the molten steel in the solidification process; 3) a method of adding a metal or oxide which becomes a solidification nucleus when the molten steel is solidified; There is known a method in which 3) is performed in combination. As a specific example of low-temperature casting, for example, Japanese Patent Application Laid-Open No. 7-8461.
As described in Japanese Patent Publication No. 7, when the molten steel is continuously cast, the superheat temperature (the temperature obtained by subtracting the liquidus temperature of the molten steel from the actual molten steel temperature) is set to 40 ° C. or less while cooling in the mold. By drawing, the ratio of equiaxed crystals in the solidified slab is made 70% or more to prevent ridging generated in the ferritic stainless steel sheet. Further, regarding the electromagnetic stirring of molten steel, as described in JP-A-50-16616, electromagnetic stirring is performed on molten steel in a solidification process,
The tip of the growing columnar crystal is cut, and the cut piece of the columnar crystal is used as a solidification nucleus, and the equiaxed crystal of the solidified structure of the cast slab is made 60% or more to prevent ridging. Also, JP-A-53-9
No. 0129 proposes that the addition of a metal oxide serving as a solidification nucleus when molten steel solidifies is combined with electromagnetic stirring to make the solidified structure in the entire cross section in the thickness direction of the slab almost equiaxed. ing.
【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
生し、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
技術的に明確な条件が提示されていない。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、酸化物が溶解終了位置近傍の溶鋼
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。特に、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
って等軸晶が形成される範囲や等軸晶の大きさが異なる
欠点がある。このように、凝固組織の等軸晶化を図る従
来の方法では、均一な凝固組織にして無欠陥の鋳片を得
ることが困難であり、鋳片に生じる割れ、中心偏析（偏
析）等の表面及び内部欠陥を抑制できない。更に、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り、しか
も、無欠陥の鋳片と、その加工性の良い鋳片を安定して
工業的に製造するには、如何なる均一な凝固組織にすれ
ば良いかについて明確でなかった。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, causing defects etc. due to inclusions, and lowering the superheating temperature until a slab with sufficient equiaxed crystals is produced. Have difficulty. 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. No clear technical terms are provided. 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, JP-A-53-
In Japanese Patent No. 90129, a metal or an oxide serving as a solidification nucleus is added to molten steel in a mold, and the molten steel in the vicinity of the melting end position is subjected to electromagnetic stirring, so that columnar crystals are formed on the surface layer of the slab. And the same surface defects as in the method described in JP-A-50-16616. In particular, when the solidified structure is made into an equiaxed crystal, there is a disadvantage that the position where electromagnetic stirring is performed, the range in which the equiaxed crystal is formed by the stirring thrust, and the size of the equiaxed crystal are different. As described above, it is difficult to obtain a defect-free cast slab with a uniform solidified structure by a conventional method for equiaxed crystallization of a solidified structure, and it is difficult to obtain cracks, center segregation (segregation), and the like generated in the slab. Surface and internal defects cannot be suppressed. Furthermore, there is a problem that the workability of rolling or the like is enhanced by using this slab, and a high-quality steel material with few defects cannot be obtained. It was not clear what uniform solidification structure should be used for stable industrial production.
【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、割れや偏析等の
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、耐食性等が良好な品質特
性に優れた鋳片及びそれを用い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 the above circumstances, and has a slab having a fine and uniform solidified structure, suppressing surface and internal defects such as cracks and segregation, and has high workability such as rolling, and has been used for steel materials. It is an object of the present invention to provide a cast slab with reduced defects and excellent quality characteristics such as good corrosion resistance and the like and a steel material using 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
係る品質特性に優れた鋳片は、溶鋼が凝固する際に凝固
核を形成する金属又は金属化合物を前記溶鋼に添加して
鋳造した鋳片において、該鋳片の表層部に含まれる大き
さが１０μｍ以下の金属化合物の個数に対して、該表層
部より内部に含まれる大きさが１０μｍ以下の金属化合
物の個数を１．３倍以上にしている。これにより、金属
を添加して生成した金属化合物、又は直接溶鋼に添加し
た金属化合物のうち、１０μｍ以下の大きさの金属化合
物の個数を鋳片の内部側で多くしているので、溶鋼が凝
固する際に凝固核として働き、凝固組織の等軸晶径を小
さくして粒界のミクロ偏析を抑制する。また、金属化合
物は、ピンニング作用により凝固後の等軸晶の粗大化を
抑制することができる。そして、凝固過程の歪み及び応
力による割れやへこみ疵、介在物等に起因する表面欠陥
を防止し、鋳片のバルジングや曲げ戻し矯正等により加
えられる歪みに対する内部割れへの抵抗を強め、凝固時
の収縮を小さくして流動性を良くし、空洞（ザク）や偏
析等の内部欠陥の発生を抑制する。しかも、内部に比べ
て表層部の金属化合物を少なくしているので、圧延等の
加工を行った際に、介在物に起因する表面欠陥が少なく
なり、耐食性や加工性等を良好にできる。なお、表層部
とは、表層より１０％を超えて表層より２５％までの範
囲をいう。この範囲を外れると、表層部が薄くなり過ぎ
て金属化合物の多い内部が表層に近くなったり、内部の
金属化合物の個数が増加し、表層部を微細な凝固組織に
できず、鋳片に加工を施した際に金属化合物に起因する
欠陥が生じ易くなる。According to the present invention, there is provided a slab excellent in quality characteristics according to the present invention, wherein a metal or a metal compound which forms a solidification nucleus when molten steel is solidified is added to the molten steel for casting. In the slab, the number of metal compounds having a size of 10 μm or less contained inside the surface layer portion is 1.3 times the number of metal compounds having a size of 10 μm or less contained in the surface layer portion of the slab. That's it. As a result, the number of metal compounds having a size of 10 μm or less among the metal compounds formed by adding the metal or the metal compounds directly added to the molten steel is increased inside the slab, so that the molten steel is solidified. In this case, it acts as a solidification nucleus to reduce the equiaxed crystal diameter of the solidified structure and suppress microsegregation at grain boundaries. Moreover, the metal compound can suppress the coarsening of the equiaxed crystal after solidification by the pinning action. Also, it prevents cracks and dents due to strain and stress in the solidification process, surface defects caused by inclusions, etc., and strengthens resistance to internal cracks due to strain applied by bulging and straightening of slabs, etc. To reduce the shrinkage and improve the fluidity, and to suppress the occurrence of internal defects such as cavities and segregation. In addition, since the metal compound in the surface layer portion is reduced as compared with the inside, when processing such as rolling is performed, surface defects due to inclusions are reduced, and corrosion resistance, workability, and the like can be improved. In addition, the surface layer portion means a range of more than 10% from the surface layer to 25% from the surface layer. If it is out of this range, the surface layer becomes too thin, and the inside with a large amount of metal compounds becomes close to the surface, or the number of metal compounds in the inside increases, and the surface layer cannot be formed into a fine solidified structure, and is processed into a slab. , Defects due to the metal compound are likely to occur.
【０００７】ここで、前記溶鋼に含まれる金属化合物と
前記鋳片の凝固時に形成するδフェライトとの格子整合
度を６％以下にしても良い。これにより、鋳片に対する
凝固核の形成能が高くなり微細な凝固組織が得られ、表
層部及び内部のミクロ偏析を小さくできる。しかも、圧
下方向に対する変形が容易になり、加工及び品質特性に
優れた鋳片を安定して製造できる。Here, the degree of lattice matching between the metal compound contained in the molten steel and the δ ferrite formed during the solidification of the slab may be 6% or less. As a result, the ability to form solidification nuclei on the slab is increased, a fine solidified structure is obtained, and microsegregation in the surface layer and inside can be reduced. In addition, deformation in the rolling direction is facilitated, and a cast piece excellent in processing and quality characteristics can be stably manufactured.
【０００８】更に、前記溶鋼に含まれる金属化合物をＭ
ｇＯを含有する酸化物にすることができる。ＭｇＯを含
む酸化物を形成させることにより、溶鋼中における分散
性が高くなり、凝固核の生成能に優れた多数の細かい酸
化物を形成することができる。Further, the metal compound contained in the molten steel is M
It can be an oxide containing gO. By forming an oxide containing MgO, dispersibility in molten steel is increased, and a large number of fine oxides having excellent ability to generate solidification nuclei can be formed.
【０００９】また、前記鋳片をフェライト系ステンレス
鋼とすることができる。これは、粗大化し易い凝固組織
を微細な等軸晶に容易にすることができる。Further, the slab may be made of ferritic stainless steel. This can facilitate the formation of a solidified structure that is likely to be coarsened into fine equiaxed crystals.
【００１０】前記目的に沿う本発明の鋼材は、溶鋼が凝
固する際に凝固核を形成する金属又は金属化合物を前記
溶鋼に添加して鋳造した鋳片において、該鋳片の表層部
に含まれる大きさが１０μｍ以下の金属化合物の個数に
対して、該表層部より内部に含まれる大きさが１０μｍ
以下の金属化合物の個数を１．３倍以上にした前記鋳片
を加熱した後に、圧延等の加工を施している。この鋼材
は、鋳片を圧下する方向に変形し易くして圧延等の加工
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空洞や偏析等の内部欠陥を抑制
することができる。しかも、介在物に起因した表面及び
内部欠陥を少なくし、耐食性等が向上できる。[0010] The steel material of the present invention meeting the above object is included in the surface layer of the cast slab, in which a metal or a metal compound which forms a solidification nucleus when the molten steel is solidified is added to the molten steel and cast. With respect to the number of metal compounds having a size of 10 μm or less, the size contained within the surface layer portion is 10 μm.
After heating the cast slab having the number of the following metal compounds 1.3 times or more, it is subjected to processing such as rolling. This steel material can be easily deformed in the direction of rolling down the slab to enhance workability such as rolling, and surface defects such as barges and cracks generated in the processed steel material and internal defects such as cavities and segregation. Defects can be suppressed. In addition, surface and internal defects caused by inclusions are reduced, and corrosion resistance and the like can be improved.
【００１１】ここで、前記溶鋼に含まれる金属化合物と
前記鋳片の凝固時に形成されるδフェライトとの格子整
合度を６％以下とすることもできる。従って、溶鋼中で
の分散性が良くなり、小さい凝固核を形成して凝固組織
をより微細で均一にして、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できる。Here, the degree of lattice matching between the metal compound contained in the molten steel and the δ ferrite formed during solidification of the slab may be 6% or less. Therefore, the dispersibility in the molten steel is improved, a small solidification nucleus is formed, the solidification structure is made finer and more uniform, and the material is easily deformed in the rolling direction, so that workability such as rolling can be further improved.
【００１２】[0012]
【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６０％以上が微細な等軸晶である同鋳片の
厚み方向の断面における凝固組織の模式図、図３は全断
面が微細な等軸晶である同鋳片の厚み方向の断面におけ
る凝固組織の模式図、図４は従来例に係る鋳片の厚み方
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特性に優
れた鋳片を鋳造する連続鋳造装置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とな
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 characteristics according to one embodiment of the present invention, and FIG. 2 is a thickness direction of the slab having 60% or more of fine equiaxed crystals. FIG. 3 is a schematic view of a solidified structure in a cross section in the thickness direction of the slab, in which the entire cross section is a fine equiaxed crystal, and FIG. It is a schematic diagram of the solidification structure in a cross section. First, FIG.
A continuous casting apparatus 10 for casting a slab excellent in quality characteristics according to an embodiment of the present invention will be described with reference to FIG. Continuous casting apparatus 10 pours molten steel 12 stored in tundish 11 from immersion nozzle 13 into mold 14,
While solidifying the molten steel 12 by cooling the mold 14, cooling water is sprinkled from a cooling water nozzle (not shown) provided on the support segment 15, and the slab 16 whose solidification is progressing is reduced by the reduction segment 17 and then pinch rolled. Withdrawing 18 is performed. Then, the cast slab 16 cut to a predetermined size is conveyed to a post-process, heated in a heating furnace (not shown), a soaking furnace, or the like, and then subjected to processing such as rolling to be a steel material.
【００１３】次に、連続鋳造装置１０で連続鋳造される
品質特性に優れた鋳片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１４に注湯
された溶鋼（クロム１３〜１７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の下流側に進むにつれて、冷却水によっ
て抜熱され、徐々に凝固殻の厚みを増しながら圧下セグ
メント１７により圧下されて後、完全に凝固する。図４
に示すように従来例に係る凝固した鋳片の凝固組織で
は、表層（表層部）に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と、このチル晶の内側に形成さ
れた大きな結晶組織の柱状晶とからなる。この表層部
は、柱状晶の粒界にミクロ偏析が存在する。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（内層部）は、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、粒界
にミクロ偏析が形成される。このミクロ偏析は、表層部
と同様に脆い特性を有し、鋳片のバルジングや曲げ戻し
矯正等により加えられる歪みによって、内部割れが生じ
易くなる。また、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、内部に空洞（ザク）や溶鋼の
流動に起因する中心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。Next, the slab 16 which is continuously cast by the continuous casting apparatus 10 and has excellent quality characteristics will be described. Molten steel (ferritic stainless steel molten steel containing 13 to 17% by weight of chromium) poured into a mold 14 from an immersion nozzle 13 provided in a tundish 11 is cooled by the mold 14 to form a solidified shell (not shown). As the cast slab 16 advances to the downstream side of the support segment 15, the heat is removed by the cooling water, and the solidified shell is gradually reduced in thickness while gradually increasing the thickness of the solidified shell, and then completely solidified. FIG.
As shown in the figure, in the solidified structure of the solidified cast slab according to the conventional example, a chill crystal having a fine structure solidified by being rapidly cooled by a mold on a surface layer (surface layer portion) and a large crystal formed inside the chill crystal It consists of columnar crystals. This surface layer has micro-segregation at the grain boundaries of columnar crystals. The micro-segregated portion has brittle characteristics, and surface defects such as cracks and dents occur on the surface layer of the slab due to unevenness of cooling and shrinkage by the mold. Further, cooling is slow inside (inner layer portion), columnar crystals or large equiaxed crystals are generated, and micro-segregation is formed at grain boundaries. This micro-segregation has brittle characteristics like the surface layer portion, and internal cracks are easily generated by strain applied by bulging or bending back straightening of the slab. Also, if the particle size of the equiaxed crystal inside is large,
As the solidification progresses, internal defects such as cavities (Zaku) and center segregation due to the flow of molten steel are generated therein, which impairs the quality of the slab.
【００１４】従って、本発明では表面及び内部欠陥を防
止するために、溶鋼１２中に含有するＯ、Ｃ、Ｎや酸化
物等と反応して金属化合物を形成する金属、あるいは金
属化合物そのものを溶鋼１２に添加して、鋳片１６が凝
固する際に、凝固核を形成する。しかし、溶鋼１２中に
は、種々の大きさの金属化合物が形成され、金属化合物
の大きさが１０μｍを超えると、溶鋼１２が凝固する際
の凝固核になり難く、ピンニング作用による凝固後の等
軸晶の粗大化の抑制を発現できず凝固組織の微細化が図
れない。従って、分散性の良いものを用い、大きさが１
０μｍ以下の金属化合物を多く形成させることが重要で
ある。更に、この１０μｍ以下の金属化合物は、鋳片１
６の表層部に存在する個数に比べて、鋳片１６の内部に
存在する単位面積当たりの個数を１．３倍以上にしてい
る。この理由は、表層部では、冷却が迅速に行われ、凝
固核となる金属化合物が比較的少なくても微細な等軸晶
の凝固組織にすることができるためである。更に、鋳片
１６の内部は、１０μｍ以下の金属化合物の個数を表層
部の１．３倍以上にすることで、この金属化合物による
凝固核としての働きと、ピンニング作用をより強化して
等軸晶の粗大化を抑制し、微細な等軸晶を備えた凝固組
織にすることができる。図２にその結果を示すが、鋳片
１６の厚み方向の断面における凝固組織の６０％以上を
微細な組織にすることができ、表層部の柱状晶も小さく
抑制され品質特性の良好な鋳片１６が得られた。また、
図３のように、鋳片１６の表層部から内部にいたる全断
面の凝固組織を微細な等軸晶で、且つ均一なものにする
こともできる。そして、この鋳片１６は、凝固過程の歪
み及び応力による割れやへこみ疵と介在物等に起因する
表面欠陥を防止でき、しかも、鋳片１６のバルジングや
曲げ戻し矯正等により加えられる歪みに対する内部割れ
への抵抗を強め、凝固時の収縮を小さくして流動性を良
くし、空洞（ザク）や偏析等の内部欠陥の発生を抑制す
ることができる。特に、これ等の鋳片１６は、凝固核と
なる金属化合物の個数を表層部に少なく、内部に多くし
ているので、薄板や形鋼等の加工した際に、介在物に起
因する表面のヘゲ疵、割れ等の表面欠陥を抑制し、金属
化合物が薄板や形鋼等の表面に露出したり、表層近傍に
存在することに起因する耐食性の低下等も防止できる。
表層部に対して鋳片１６の内部の単位面積当たりの個数
が１．３倍より少なくなると、凝固組織を微細化するた
めの凝固核が不足してピンニング作用が低下し、凝固組
織が粗大化し、均一な凝固組織が得らず、鋳造時の鋳型
１４の冷却や凝固過程の不均一冷却等による応力や内部
の収縮等による割れやへこみ疵等の表面欠陥、空洞、偏
析等の内部欠陥が発生し、圧延等の加工を行う際に加工
性が阻害される。Accordingly, in the present invention, in order to prevent surface and internal defects, the metal which reacts with O, C, N, oxides and the like contained in the molten steel 12 to form a metal compound or the metal compound itself is molten steel. 12 to form solidification nuclei when the slab 16 solidifies. However, metal compounds of various sizes are formed in the molten steel 12, and when the size of the metal compound exceeds 10 μm, it is difficult for the molten steel 12 to become a solidification nucleus when solidifying, and after solidification due to a pinning action. Suppression of coarsening of the axis crystal cannot be achieved, and the solidification structure cannot be refined. Therefore, a material having good dispersibility and a size of 1
It is important to form a large number of metal compounds of 0 μm or less. Further, the metal compound having a size of 10 μm or less is
The number per unit area existing inside the cast piece 16 is 1.3 times or more as compared with the number existing in the surface layer portion of No. 6. The reason for this is that, in the surface layer portion, cooling is rapidly performed, and a fine equiaxed crystal solidification structure can be obtained even with a relatively small amount of a metal compound serving as a solidification nucleus. Further, the number of metal compounds of 10 μm or less in the inside of the cast slab 16 is set to be 1.3 times or more of the surface layer portion. Crystallization can be suppressed and a solidified structure having fine equiaxed crystals can be obtained. The results are shown in FIG. 2. As shown in FIG. 2, 60% or more of the solidified structure in the cross section in the thickness direction of the slab 16 can be made a fine structure, and the columnar crystals in the surface layer portion are suppressed to be small, and the slab has good quality characteristics. 16 were obtained. Also,
As shown in FIG. 3, 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 fine equiaxed crystal and uniform. The slab 16 can prevent surface defects caused by cracks and dents and inclusions due to distortion and stress in the solidification process, and furthermore, the slab 16 has an internal resistance to distortion applied by bulging or bending back correction of the slab 16. The resistance to cracks is increased, the shrinkage during solidification is reduced, the fluidity is improved, and the occurrence of internal defects such as voids and segregation can be suppressed. In particular, these cast slabs 16 have a small number of metal compounds serving as solidification nuclei in the surface layer and have a large number inside, so that when a thin plate, shaped steel, or the like is processed, the surface caused by inclusions is reduced. Surface defects such as barbed flaws and cracks can be suppressed, and it is possible to prevent the metal compound from being exposed on the surface of a thin plate or a shaped steel or the like and from being reduced in corrosion resistance due to being present near the surface layer.
If the number per unit area of the inside of the slab 16 with respect to the surface layer portion is less than 1.3 times, the number of solidification nuclei for refining the solidification structure is insufficient, the pinning action is reduced, and the solidification structure becomes coarse. In addition, a uniform solidification structure cannot be obtained, and surface defects such as cracks and dents due to stress due to cooling of the mold 14 during casting and uneven cooling during the solidification process, internal shrinkage, etc., and internal defects such as cavities and segregation. It occurs and the workability is impaired when performing processing such as rolling.
【００１５】溶鋼１２に含まれる金属化合物としては、
ＭｇＯ、ＭｇＡｌ2 Ｏ4 、ＴｉＮ、ＣｅＳ、Ｃｅ2 Ｏ
3 、ＣａＳ、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％以下のもを用
い、溶鋼１２に添加した際の分散性や凝固核の生成の安
定性から、ＭｇＯ、ＭｇＡｌ2 Ｏ4 、ＴｉＮがより好ま
しい。更に、溶鋼１２に添加する金属としては、金属Ｍ
ｇ、Ｍｇ合金、Ｔｉ、Ｃｅ、Ｃａ、Ｚｒ等の金属を用
い、溶鋼１２中のＯ（酸素）やＣ（炭素）、Ｎ（窒
素）、ＳｉＯ2 等の酸化物と反応して前述した金属化合
物を形成するものが使用でき、これ等の金属を含む金属
化合物を用いることもできる。なお、δフェライトとの
格子整合度は、一般に用いられているもので、溶鋼１２
が凝固して生成される結晶核の格子定数と金属化合物の
格子定数の差を溶鋼１２の凝固結晶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能が良好と
なる。The metal compounds contained in the molten steel 12 include:
MgO, MgAl 2 O 4 , TiN, CeS, Ce 2 O
3. Dispersibility and stability of formation of solidification nuclei when added to molten steel 12 using a lattice matching degree (lattice strain coefficient) of 6% or less with δ ferrite such as CaS, ZrO 2 , TiC, VN, etc. Therefore, MgO, MgAl 2 O 4 , and TiN are more preferable. Further, the metal added to the molten steel 12 is a metal M
g, a Mg alloy, a metal such as Ti, Ce, Ca, Zr, etc., and reacts with an oxide such as O (oxygen), C (carbon), N (nitrogen), SiO 2, etc. Those which form compounds can be used, and metal compounds containing these metals can also be used. Note that the degree of lattice matching with δ ferrite is a commonly used one,
Is the value obtained by dividing the difference between the lattice constant of the crystal nucleus formed by solidification and the lattice constant of the metal compound by the lattice constant of the solidified crystal nucleus of the molten steel 12. The smaller this value is, the better the ability to generate the solidified nucleus is. Become.
【００１６】また、鋳片１６の金属化合物の個数を測定
するには、ＳＥＭ（Ｓｃａｎｎｉｎｇ・Ｅｌｅｃｔｒｏ
ｎ・Ｍｉｃｒｏｓｃｏｐｅ）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金属化合
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金属化合物を観察して、それ
ぞれの金属化合物の最大直径と最小直径を平均した値を
その金属化合物の大きさとする。一方、スライム法の場
合は、鋳片１６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金属化合物を分級して取り出し、
それぞれの金属化合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。In order to measure the number of metal compounds in the slab 16, a scanning electron (SEM) is used.
The number of metal compounds having a size of 10 μm or less per unit area is counted by using a method such as n-microscope or slime method. The size of the metal compound is determined by observing the metal compound in all cross sections with an electron microscope such as an SEM and averaging the maximum diameter and the minimum diameter of each metal compound as the size of the metal compound. On the other hand, in the case of the slime method, a part of the entire cross section of the cast piece 16 is cut out, and the cut out piece is melted, and then the metal compound is classified and taken out.
The size is determined by averaging the maximum diameter and the minimum diameter of each metal compound, and the number for each size is determined.
【００１７】また、このような金属化合物を含む鋳片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、金属Ｍｇ、Ｍｇ合金、Ｔｉ、Ｃｅ、Ｃａ、Ｚｒ等
を添加し、溶鋼１２中の酸素あるいは酸化物であるＦｅ
Ｏ、ＳｉＯ2 、ＭｎＯ、窒素、炭素等と反応させて、Ｍ
ｇＯ、ＭｇＡｌ2 Ｏ4 、ＴｉＮ、ＴｉＣ、等の金属化合
物を形成させる。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を形成させると溶鋼１２
中での金属化合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、０．００２〜０．０１０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、凝固核の絶対
量が不足し、凝固核及びピンニング効果が小さくなり、
微細な凝固組織が得られ難くなる。一方、０．０１０重
量％を超えると、凝固核の形成効果が飽和し、合金コス
トの上昇や鋳片１６の内部の総合酸化物量が増加して耐
食性等が低下する。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、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が、厚みが
１００ｍｍ以上になると、介在物（金属化合物）の分布
の調整がし易くなり、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るので好ましく、鋳造におい
ても例えば両端が貫通した鋳型を用いた垂直あるいは湾
曲型の連続鋳造により鋳造されたものの方が微細化によ
る効果も大きくなり、好ましい結果が得られる。Further, a slab 1 containing such a metal compound is used.
In order to continuously cast 6, molten steel 1 in tundish 11
2, metal Mg, Mg alloy, Ti, Ce, Ca, Zr and the like are added, and oxygen or oxide Fe in the molten steel 12 is added.
O, SiO 2 , MnO, nitrogen, carbon, etc.
Metal compounds such as gO, MgAl 2 O 4 , TiN, and TiC are formed. In particular, when metallic Mg or Mg alloy is added to molten steel 12 to form MgO alone or a composite oxide containing MgO,
Since the dispersibility of the metal compound therein can be improved, more preferable results can be obtained. For example, when a metal such as Mg is taken as an example, 0.002 to 0.010% by weight of metallic Mg or Mg alloy is added to molten steel. Furthermore,
As an addition method, Mg or a Mg alloy can be directly added to the molten steel 12, or a wire formed by covering the Mg or the Mg alloy with thin steel can be continuously supplied. When the addition amount is less than 0.002% by weight, the absolute amount of the coagulation nuclei is insufficient, and the coagulation nuclei and the pinning effect are reduced,
It becomes difficult to obtain a fine solidified structure. On the other hand, when the content exceeds 0.010% by weight, the effect of forming solidification nuclei is saturated, the alloy cost increases, the total amount of oxide inside the slab 16 increases, and the corrosion resistance and the like decrease. The slab 16 thus cast
Has a uniform solidification structure, is excellent in suppressing surface and internal defects, and has good processing characteristics. Furthermore, the slab 16
Can be cast by a casting method such as an ingot casting method, a belt caster, or a twin roll, in addition to continuous casting. However, when the thickness is 100 mm or more, the distribution of inclusions (metal compounds) is easily adjusted. It is preferable because the equiaxed crystal in the solidified structure from the surface layer to the inside can be easily adjusted.In casting, for example, the one cast by vertical or curved continuous casting using a mold having both ends penetrated is more refined. The effect is increased, and a favorable result is obtained.
【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、鋳片１６に、大きさ
が１０μｍ以下の金属化合物を多く形成させており、そ
の含有する個数が、鋳片１６の表層部の単位面積当たり
に存在する個数に比べて、内部の単位面積当たりの存在
する個数を１．３倍以上にした鋳片１６を用いて、図示
しない加熱炉や均熱炉等により１１５０〜１２５０℃に
加熱を行った後、圧延等の加工を施して薄板、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ており、粒界に存
在する脆いミクロ偏析を小さくしているので、ミクロ偏
析部の割れ抵抗が増して、割れやヘゲ等の表面欠陥の少
ない鋼材にできる。更に、内部においても、割れや未凝
固溶鋼の凝固収縮によるザク、溶鋼１２の流動による偏
析等を抑制しているので、鋼材に発生する鋳片に起因す
る内部欠陥や圧延等の加工に起因する内部割れ（割れ）
等の内部欠陥を少なくできる。しかも、この鋳片１６
は、延び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、加工後の靭性にも優れている。特
に、δフェライトとの格子整合度が６％以下の金属化合
物を形成する金属、あるいは金属化合物を溶鋼１２に添
加した場合は、有効に働く凝固核の形成とピンニング作
用を積極的に発現させて、微細の等軸晶にした鋳片１６
にしているので、圧下方向に容易に変形して延び等の加
工特性に優れている。しかも、表層部の金属化合物を少
なくしているので、鋼材の表面に発生するヘゲ疵の発生
を防止し、鋼材に含有する金属化合物に起因する耐食性
の低下等をより確実に抑制することができる。Next, a steel material according to an embodiment of the present invention will be described. In the steel material of the present invention, a large number of metal compounds having a size of 10 μm or less are formed on the slab 16, and the number of contained metal compounds is smaller than the number present per unit area of the surface layer portion of the slab 16. After using a slab 16 whose number per existing unit area is 1.3 times or more, it is heated to 1150 to 1250 ° C. by a heating furnace or a soaking furnace (not shown), and then processed such as rolling. And processed into thin plates, shaped steel, etc. In this steel material, the solidification structure of the slab 16 used for processing is fine from the surface layer to the inside, and the brittle micro-segregation existing at the grain boundary is reduced, so that the cracking resistance of the micro-segregated portion increases, and A steel material with few surface defects such as barbs can be formed. Furthermore, since cracks and cracks, seizures due to solidification shrinkage of unsolidified molten steel, and segregation due to the flow of molten steel 12 are suppressed, internal defects caused by cast slabs generated in the steel material and processing such as rolling are caused. Internal crack (crack)
And other internal defects. Moreover, this slab 16
Has excellent processing characteristics such as elongation, can easily process the cast slab 16, and has excellent toughness after processing. In particular, when a metal that forms a metal compound having a lattice matching degree of 6% or less with δ ferrite or a metal compound is added to the molten steel 12, the formation of effective solidification nuclei and the pinning action are positively developed. , A fine equiaxed cast slab 16
Therefore, it is easily deformed in the drafting direction and has excellent processing characteristics such as elongation. Moreover, since the amount of the metal compound in the surface layer is reduced, it is possible to prevent the occurrence of barbed flaws generated on the surface of the steel material, and to more reliably suppress a decrease in corrosion resistance caused by the metal compound contained in the steel material. it can.
【００１９】[0019]
【実施例】次に、本発明に係る鋳片及びこの鋳片を用い
て圧延加工を行った鋼材の製造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、サイズが幅１２００ｍｍ、厚み２５
０ｍｍ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
を行ってからピンチロールにより引き抜きを行った。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
晶の大きさと、表層及び内部欠陥の調査を行い、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。なお、等軸晶の大きさ
は、溶鋼が凝固する際に、溶鋼の溶質成分が固液分配に
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
用いてミクロ偏析の境界をエッチングして、このマクロ
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。実施例１は、鋳片に含有した金属化合
物のうち、１０μｍ以下の金属化合物の個数が表層部で
５０個／ｃｍ2 、内部で６６個／ｃｍ2 にし、良好な等
軸晶が形成された鋳片であり、表層に形成したミクロ偏
析を小さくでき、割れやへこみ疵の発生やリジングやエ
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、この鋳片を用いて圧延した鋼材は、表層の
リジングやエッジシーム疵等、更に割れ、ザクや偏析等
の内部欠陥も少なく良好（○）であり、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
時の深絞りの指標であるｒ値等が良い（○）結果であっ
た。EXAMPLE Next, an example of manufacturing a slab according to 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 a tundish, the size is 1200 mm wide and 25 mm thick.
Continuous casting is performed on a mold having an inner dimension of 0 mm, and the slab is cooled and solidified by cooling with the mold and water sprinkling from the supporting segment. After the slab is reduced by 3 to 7 mm using the rolling segment, it is pulled out with a pinch roll. Was done. Then, the slab is cut, the size of the equiaxed crystal of the solidification structure in the cross section in the thickness direction, the surface layer and the internal defects are investigated, and the slab is heated to 1250 ° C., and then rolled. The internal defects and processing characteristics were investigated. The size of the equiaxed crystal is the size of the solidification structure unit bounded by the microsegregation caused by the solid-liquid distribution of the solute component of the molten steel when the molten steel solidifies, and in the thickness direction of the solidified slab. So that the cross section of
After cutting and polishing the cross section, the boundary of micro segregation is etched using, for example, picric acid, and the macro structure can be obtained by image processing or the like after expanding the macro structure 1 to 10 times. Example 1, of the metal compound contained in the slab, 50 number of the following metal compounds 10μm is the surface layer portion / cm 2, internally to 66 / cm 2, good equiaxed crystals are formed It is a slab, can reduce micro-segregation formed on the surface layer, has few occurrences of cracks and dent flaws, ridging and edge seam flaws, and has few internal defects such as cracks, zags and segregation, and is rolled using this slab. The steel material is good (○) with few internal defects such as ridging and edge seam flaws on the surface layer and further cracks, zags and segregation, and has a small solidification structure and micro-segregation. The r value as an index of the aperture was a good (良 い) result.
【００２０】実施例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
数を表層部で９５個／ｃｍ2 、内部で１３０個／ｃｍ2
にし、良好な等軸晶が形成された鋳片であり、表層に形
成したミクロ偏析を小さくでき、割れやへこみ疵の発生
や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、この鋳片を用いて圧延した
鋼材は、表層のリジングやエッジシーム疵等、及び割
れ、ザクや偏析等の内部欠陥も少なく良好（○）であ
り、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ｒ値等が良い（○）結果であった。[0020] Example 2, among the metal compounds present per unit area of the slab 95 or the number of the following metal compounds 10μm in surface layer portion / cm 2, 130 pieces inside / cm 2
It is a slab in which good equiaxed crystals are formed, the micro segregation formed on the surface layer can be reduced, the occurrence of cracks and dents, the occurrence of ridging and edge seam etc. is small, and internal defects such as cracks, stagnation and segregation The steel material rolled using this slab is good (○) with few internal defects such as ridging and edge seam flaws on the surface layer, and cracks, zags and segregation, and has a small solidification structure and micro segregation. The result was easy to be deformed to the direction of rolling down and the r value was good (良 い).
【００２１】[0021]
【表１】 [Table 1]
【００２２】これに対して、比較例１は、鋳片の単位面
積当たりに存在する金属化合物のうち、１０μｍ以下の
金属化合物の個数を、表層部で４５個／ｃｍ2 、内部で
４６個／ｃｍ2 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
内部欠陥が発生し、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（×）、ｒ値も悪い（×）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
を、表層部で９７個／ｃｍ2 、内部で１１６個／ｃｍ2
にした鋳片であり、表層部及び内部の等軸晶粒径が小さ
くなった鋳片であり、鋳片及び鋼材に発生する表面及び
内部欠陥について良い（○）結果となったが、ｒ値が悪
い（×）結果となった。On the other hand, in Comparative Example 1, 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 46 / cm 2 in the inside. cm 2 , a slab having a larger maximum equiaxed grain size in the surface layer and an inner largest equiaxed grain size, such as cracks and dents, and cracks, seizures, etc. Internal defects occur, and the steel material rolled using this slab
Surface defects such as barbs and cracks, internal defects such as cracks and segregation, and the like were bad (×), and the r value was also poor (×). Comparative Example 2 Among the metal compounds present per unit area of the slab, the number of the following metal compound 10 [mu] m, 97 pieces in the surface layer portion / cm 2, 116 pieces inside / cm 2
This is a slab with reduced equiaxed grain size in the surface layer and inside, and good (○) results were obtained for the surface and internal defects occurring in the slab and steel material. Was bad (x).
【００２３】なお、実施例１及び実施例２と同様の１０
μｍ以下の金属化合物の個数比を有し、金属化合物とし
て、ＭｇＯ、ＭｇＡｌ2 Ｏ4 、ＴｉＮ、ＴｉＣを０．０
６重量％添加した鋳片及びこの鋳片を圧延等の加工を施
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を行い、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
性を調査したが良好な結果であった。It should be noted that the same tenth embodiment as in the first and second embodiments is used.
It has a number ratio of the metal compound of not more than μm, and MgO, MgAl 2 O 4 , TiN and TiC are 0.0
For the cast slab to which 6% by weight was added and the steel obtained by subjecting the cast slab to processing such as rolling, the size of the equiaxed crystal of the solidification structure, the surface layer and internal defects were investigated, and the cast slab was heated to 1250 ° C. After rolling, the surface layer and internal defects of the steel material and the processing characteristics were examined, but good results were obtained.
【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、前記実施の形態では鋳片の厚み方向の
表層部と内部の金属化合物の個数について説明したが、
鋳片の幅方向の表層部と内部の１０μｍ以下の金属化合
物の個数についても、表層部に比べて内部の金属化合物
の個数を１．３倍以上の同じ条件にすることができる。
更に、鋳片の金属化合物の大きさや個数の調整方法とし
ては、浸漬ノズルからの溶鋼の吐出流等により最期に凝
固する部位を洗浄することにより、表層部に少なく、内
部に多くすることができ、１０μｍ以下の金属化合物の
個数についても溶鋼に攪拌力を付与したり、分散性の良
いＭｇＯを含む金属化合物を形成することにより調整す
ることができる。また、低温鋳造や電磁攪拌あるいはこ
れ等を組合せて用いることもできる。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, in the above embodiment, the number of the metal compound in the surface layer portion and the inside in the thickness direction of the slab was described.
Regarding the number of metal compounds of 10 μm or less in the surface layer portion in the width direction of the slab and the inside, the number of metal compounds in the inside can be 1.3 times or more the same condition as in the surface layer portion.
Furthermore, as a method for adjusting the size and number of the metal compounds in the slab, by washing the part that is finally solidified by the discharge flow of molten steel from the immersion nozzle, it can be reduced to the surface layer and increased to the inside. The number of metal compounds having a particle size of 10 μm or less can be adjusted by applying a stirring force to molten steel or by forming a metal compound containing MgO having good dispersibility. Further, low-temperature casting, electromagnetic stirring, or a combination thereof can be used.
【００２５】[0025]
【発明の効果】請求項１〜４記載の品質特性に優れた鋳
片においては、溶鋼が凝固する際に凝固核を形成する金
属又は金属化合物を溶鋼に添加して鋳造した鋳片におい
て、鋳片の表層部に含まれる大きさが１０μｍ以下の金
属化合物の個数に対して、表層部より内部に含まれる大
きさが１０μｍ以下の金属化合物の個数を１．３倍以上
にしているので、粒界のミクロ偏析を抑制して凝固過程
の歪みや応力による割れやへこみ疵、介在物等に起因す
る表面欠陥を抑制し、空洞や偏析等の内部欠陥の発生を
防止でき、鋳片の手入れや屑化を抑制して歩留りや品質
等の向上が達成できる。しかも、表層部の金属化合物が
少ないので、圧延等の加工を行った際に、介在物に起因
する表面欠陥の発生を少なくし、金属化合物に起因する
耐食性や加工性が低下するのを防止して、品質特性に優
れた鋼材を製造することができる。According to the present invention, there is provided a slab having excellent quality characteristics, wherein a metal or a metal compound which forms a solidification nucleus when the molten steel is solidified is added to the molten steel. Since the number of metal compounds having a size of 10 μm or less contained inside the surface layer is 1.3 times or more the number of metal compounds having a size of 10 μm or less contained in the surface portion of the piece, It suppresses micro-segregation in the boundary, suppresses cracks and dents due to distortion and stress in the solidification process, surface defects caused by inclusions, etc., and prevents the occurrence of internal defects such as cavities and segregation, Improvement in yield, quality, etc. can be achieved by suppressing waste. In addition, since the metal compound in the surface layer is small, the occurrence of surface defects caused by inclusions during processing such as rolling is reduced, and the corrosion resistance and workability caused by the metal compound are prevented from being reduced. Thus, a steel material having excellent quality characteristics can be manufactured.
【００２６】特に、請求項２記載の品質特性に優れた鋳
片においては、金属化合物と鋳片の凝固時に形成される
δフェライトとの格子整合度を６％以下にしているの
で、凝固核の形成能が高く、少ない金属化合物で微細な
凝固組織にでき、過剰の金属化合物による表面及び内部
欠陥を防止し、加工した鋼材の耐食性や加工性を向上で
きる。In particular, in the slab excellent in quality characteristics according to the second aspect, since the degree of lattice matching between the metal compound and the δ ferrite formed at the time of solidification of the slab is 6% or less, the solidification nucleus of the solidification nucleus is reduced. It has a high forming ability and can form a fine solidified structure with a small amount of metal compound, can prevent surface and internal defects due to excessive metal compound, and can improve the corrosion resistance and workability of the processed steel material.
【００２７】請求項３記載の品質特性に優れた鋳片にお
いては、金属化合物がＭｇＯを含有する酸化物であるの
で、溶鋼中における金属化合物の分散性を高くし、多数
の細かい凝固核を形成させて微細な凝固組織にすること
ができ、凝集した金属化合物（介在物）による欠陥を防
止し、加工された鋼材の耐食性などが向上できる。In the slab having excellent quality characteristics according to the third aspect, since the metal compound is an oxide containing MgO, the dispersibility of the metal compound in the molten steel is increased to form a large number of fine solidification nuclei. As a result, a fine solidified structure can be obtained, defects due to agglomerated metal compounds (inclusions) can be prevented, and the corrosion resistance of the processed steel material can be improved.
【００２８】請求項４記載の品質特性に優れた鋳片にお
いては、鋳片がフェライト系ステンレス鋼であるので、
鋳片の割れやへこみ疵等の表面欠陥を安定して防止し、
しかも、圧延等の加工を施した際に鋼材の表面に発生す
るリジング等をより確実に防止できる。In the slab having excellent quality characteristics according to claim 4, the slab is a ferritic stainless steel.
Stable prevention of surface defects such as cracks and dents in slabs,
In addition, ridging or the like generated on the surface of the steel material when rolling or other processing is performed can be more reliably prevented.
【００２９】請求項５及び６記載の鋼材においては、溶
鋼が凝固する際に凝固核を形成する金属又は金属化合物
を溶鋼に添加して鋳造した鋳片において、鋳片の表層部
に含まれる大きさが１０μｍ以下の金属化合物の個数に
対して、表層部より内部に含まれる大きさが１０μｍ以
下の金属化合物の個数を１．３倍以上にした鋳片を加熱
した後に、圧延等の加工を施したので、圧延等の加工性
が高くなり、加工時あるいは加工後に発生するリジング
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、鋼材の手入れや屑化等の防止による製品等の歩留
りの向上と、耐食性や品質特性に優れた鋼材を製造する
ことができる。In the steel material according to the fifth and sixth aspects, in a slab cast by adding a metal or a metal compound which forms a solidification nucleus when the molten steel is solidified, the size included in the surface layer portion of the slab After heating a slab in which the number of metal compounds having a size of 10 μm or less included in the surface layer portion is 1.3 times or more with respect to the number of metal compounds having a size of 10 μm or less, processing such as rolling is performed. As a result, the workability of rolling and other processes is increased, surface defects such as ridging and cracks generated during or after processing and internal defects such as zags and segregation are reduced. Thus, it is possible to produce a steel material having an improved yield and excellent corrosion resistance and quality characteristics.
【００３０】特に、請求項６記載の鋼材においては、金
属化合物と鋳片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％以下であるので、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て、安定した耐食性及
び品質特性に優れた鋼材にできる。In particular, in the steel material according to the sixth aspect, since the degree of lattice matching between the metal compound and the δ ferrite formed during the solidification of the slab is 6% or less, the workability such as rolling can be improved. Surface defects and internal defects generated during or after processing are more reliably eliminated, and a steel material having stable corrosion resistance and excellent quality characteristics can be obtained.
【図１】本発明の一実施の形態に係る品質特性に優れた
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 characteristics according to an embodiment of the present invention.
【図２】６０％以上が微細な等軸晶である同鋳片の厚み
方向の断面における凝固組織の模式図である。FIG. 2 is a schematic diagram of a solidification structure in a cross section in a thickness direction of the cast slab in which 60% or more are fine equiaxed crystals.
【図３】全断面が微細な等軸晶である同鋳片の厚み方向
の断面における凝固組織の模式図である。FIG. 3 is a schematic diagram of a solidified structure in a cross section in a thickness direction of the slab having a fine equiaxed crystal in all cross sections.
【図４】従来例に係る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 according to a conventional example.
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
Claims (6)
属又は金属化合物を前記溶鋼に添加して鋳造した鋳片に
おいて、該鋳片の表層部に含まれる大きさが１０μｍ以
下の金属化合物の個数に対して、該表層部より内部に含
まれる大きさが１０μｍ以下の金属化合物の個数が１．
３倍以上であることを特徴とする品質特性に優れた鋳
片。1. A slab cast by adding a metal or a metal compound that forms a solidification nucleus when the molten steel solidifies to the molten steel, wherein the metal compound contained in the surface layer portion of the slab is 10 μm or less. The number of metal compounds having a size of 10 μm or less contained inside the surface layer portion is 1.
A slab excellent in quality characteristics characterized by being three times or more.
おいて、前記溶鋼に含まれる金属化合物と前記鋳片の凝
固時に形成されるδフェライトとの格子整合度が６％以
下である品質特性に優れた鋳片。2. The slab having excellent quality characteristics according to claim 1, wherein the degree of lattice matching between a metal compound contained in the molten steel and δ ferrite formed during solidification of the slab is 6% or less. A slab with excellent properties.
鋳片において、前記溶鋼に含まれる金属化合物がＭｇＯ
を含有する酸化物である品質特性に優れた鋳片。3. The slab according to claim 1, wherein the metal compound contained in the molten steel is MgO.
A slab excellent in quality characteristics which is an oxide containing.
質特性に優れた鋳片において、前記鋳片がフェライト系
ステンレス鋼である品質特性に優れた鋳片。4. The slab having excellent quality characteristics according to claim 1, wherein the slab is a ferritic stainless steel.
属又は金属化合物を前記溶鋼に添加して鋳造した鋳片に
おいて、該鋳片の表層部に含まれる大きさが１０μｍ以
下の金属化合物の個数に対して、該表層部より内部に含
まれる大きさが１０μｍ以下の金属化合物の個数を１．
３倍以上にした前記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。5. A slab cast by adding a metal or a metal compound that forms a solidification nucleus when the molten steel solidifies to the molten steel, wherein the metal compound contained in the surface layer portion of the slab has a size of 10 μm or less. The number of the metal compounds having a size of 10 μm or less contained from the surface layer portion with respect to the number of 1.
A steel material characterized by being subjected to processing such as rolling after heating the slab 3 times or more.
に含まれる金属化合物と前記鋳片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％以下である鋼材。6. The steel material according to claim 5, wherein the degree of lattice matching between the metal compound contained in the molten steel and the δ ferrite formed during the solidification of the slab is 6% or less.
Priority Applications (17)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10237999A JP2000288693A (en) | 1999-04-09 | 1999-04-09 | Ingot having excellent quality characteristic and steel using it |
| 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 |
| KR1020007013895A KR100550678B1 (en) | 1999-04-08 | 2000-04-07 | Method for treatment of molten steel for making solidification structure of cast steel piece fine |
| 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 |
| 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 |
| 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 |
| EP10186292.8A EP2292352B1 (en) | 1999-04-08 | 2000-04-07 | Method for processing molten steel for cast steel and steel material with excellent workability |
| 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 |
| 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 |
| 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 |
| 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 |
|---|---|---|---|
| JP10237999A JP2000288693A (en) | 1999-04-09 | 1999-04-09 | Ingot having excellent quality characteristic and steel using it |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000288693A true JP2000288693A (en) | 2000-10-17 |
Family
ID=14325832
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10237999A Pending JP2000288693A (en) | 1999-04-08 | 1999-04-09 | Ingot having excellent quality characteristic and steel using it |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000288693A (en) |
-
1999
- 1999-04-09 JP JP10237999A patent/JP2000288693A/en active Pending
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