JP2002167647A - Si KILLED STEEL HAVING EXCELLENT FATIGUE STRENGTH AND ITS PRODUCTION METHOD - Google Patents
Si KILLED STEEL HAVING EXCELLENT FATIGUE STRENGTH AND ITS PRODUCTION METHODInfo
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- JP2002167647A JP2002167647A JP2000359368A JP2000359368A JP2002167647A JP 2002167647 A JP2002167647 A JP 2002167647A JP 2000359368 A JP2000359368 A JP 2000359368A JP 2000359368 A JP2000359368 A JP 2000359368A JP 2002167647 A JP2002167647 A JP 2002167647A
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Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、従来の鋼と比較し
て、有害な大型介在物が少なく、しかも残留した介在物
も延性のある介在物であり、かつその介在物は微細に分
散されたものであり、疲労強度に優れたＳｉ脱酸鋼およ
びその製造方法に関する。BACKGROUND OF THE INVENTION The present invention relates to a steel according to the present invention, which has less harmful large inclusions than conventional steels, and furthermore, the remaining inclusions are ductile inclusions, and the inclusions are finely dispersed. The present invention relates to a Si deoxidized steel excellent in fatigue strength and a method for producing the same.
【０００２】[0002]
【従来の技術】Ｓｉ脱酸鋼は、Ｓｉが鋼材としての必要
成分であると同時に、溶鋼中での酸素との親和力が大き
く鋼を脱酸する機能を有することから、強脱酸元素を含
有しない鋼に脱酸材として広く用いられている。2. Description of the Related Art Si-deoxidized steel contains a strongly deoxidized element because Si is a necessary component as a steel material and, at the same time, has a large affinity for oxygen in molten steel and has a function of deoxidizing steel. Widely used as a deoxidizer for steel that does not.
【０００３】一般にＳｉ脱酸鋼は、鋼中のＳｉ濃度がＡ
ｌ脱酸鋼のＡｌ濃度と比較して数倍ないし数十倍高い。
また、Ｓｉ脱酸鋼は、Ａｌ脱酸鋼よりも全酸素濃度が高
くなるが、介在物組成の制御が可能であるという利点が
ある。この利点を生かして、疲労強度向上に有害な介在
物の生成を抑制することが広く行われている。[0003] In general, Si deoxidized steel has an Si concentration of A
1 It is several times to several tens times higher than the Al concentration of deoxidized steel.
In addition, Si deoxidized steel has a higher total oxygen concentration than Al deoxidized steel, but has the advantage that the inclusion composition can be controlled. Taking advantage of this advantage, it has been widely practiced to suppress the generation of inclusions harmful to the improvement of fatigue strength.
【０００４】[0004]
【発明が解決しようとする課題】例えば、特公昭５４−
７２５２号公報には、線材用高炭素Ｓｉ脱酸鋼中のＳｉ
Ｏ2 −ＭｎＯ−Ａｌ2 Ｏ3 系の３元系非金属介在物を低
融点のスペサタイト領域に制御する技術が開示されてい
る。この技術は、介在物を低融点化することにより、熱
間圧延段階での介在物の伸展性を向上させ、線材加工時
の伸線性を良好にするものである。しかしながら、この
技術は全酸素濃度が高く介在物量が多いという問題があ
る。[Problems to be solved by the invention] For example,
No. 7252 discloses that Si in a high carbon Si deoxidized steel for a wire is used.
O 2 -MnO-Al 2 O 3 based techniques for controlling the ternary nonmetallic inclusions Supesataito region of the low melting point is disclosed. This technique improves the extensibility of inclusions in the hot rolling step by lowering the melting point of the inclusions and improves the drawability during wire processing. However, this technique has a problem that the total oxygen concentration is high and the amount of inclusions is large.
【０００５】また、特公昭５８−５６０２１号公報に
は、線材用の高炭素Ｓｉ脱酸鋼中の全酸素濃度が５０重
量ｐｐｍ以下、非粘性介在物インデックスが１５以下、
および介在物組成が硬度の低いロードナイト質を含む複
合酸化物からなることを特徴とする清浄鋼が開示されて
いる。しかしながら、この発明でのＳｉ脱酸鋼中の全酸
素濃度は３０〜４５ｐｐｍと高い水準にとどまってい
る。Japanese Patent Publication No. 58-56021 discloses that the total oxygen concentration in a high carbon Si deoxidized steel for a wire is 50 ppm by weight or less, the non-viscous inclusion index is 15 or less,
Further, a clean steel characterized in that the inclusion composition is composed of a composite oxide containing rhodonite having a low hardness is disclosed. However, the total oxygen concentration in the Si deoxidized steel according to the present invention is as high as 30 to 45 ppm.
【０００６】さらに、特公平６−７４４８４号公報に
は、介在物を無害化するという観点から介在物の長さ
（ｌ）と幅（ｄ）のアスペクト比（ｌ／ｄ）が５以下
で、組成がＳｉＯ2 ：２０〜６０％、ＭｎＯ：１０〜８
０％、およびＣａＯ：５０％以下、ＭｇＯ：１５％以下
の介在物であることを特徴とする冷間加工性および疲労
特性に優れた高清浄鋼が提案されている。また、特公平
６−７４４８５号公報には、同じアスペクト比で、組成
がＳｉＯ2 ：３５〜７５％、Ａｌ2 Ｏ3 ：３０％以下、
ＣａＯ：５０％以下、ＭｇＯ：２５％以下からなる介在
物であることを特徴とする冷間加工性および疲労特性に
優れた高清浄鋼が提案されている。これらは、熱間圧延
で残存している介在物であっても、その段階での形状と
組成を限定することにより、大型の有害介在物が存在す
る割合を小さくする技術と言える。しかしながら、これ
らの技術は、介在物低減には限界があり、疲労特性の向
上にも限界があった。Furthermore, Japanese Patent Publication No. 6-74484 discloses that from the viewpoint of detoxifying inclusions, the aspect ratio (l / d) of the length (l) and width (d) of the inclusion is 5 or less, composition of SiO 2: 20~60%, MnO: 10~8
A high clean steel excellent in cold workability and fatigue properties characterized by inclusions of 0%, CaO: 50% or less, and MgO: 15% or less has been proposed. Japanese Patent Publication No. 6-74485 discloses that the composition is SiO 2 : 35 to 75%, Al 2 O 3 : 30% or less at the same aspect ratio.
A highly clean steel excellent in cold workability and fatigue properties, characterized by inclusions of CaO: 50% or less and MgO: 25% or less, has been proposed. These can be said to be techniques for reducing the proportion of large harmful inclusions by limiting the shape and composition at that stage even if the inclusions remain during hot rolling. However, these techniques have a limit in reducing inclusions and a limit in improving fatigue characteristics.
【０００７】特公平４−８４９９号公報には、介在物を
さらに延性なものとする方法として、全酸素量、非粘性
介在物インデックスを規定し、さらに介在物成分のうち
ＳｉＯ2 、ＭｎＯ、ＭｇＯ、Ａｌ2 Ｏ3 、ＣａＯ、Ｔｉ
Ｏ2 組成を限定するとともに、さらにその他酸化物とし
てＶ、Ｂａ、Ｚｒ、Ｎａの酸化物および不可避的に混入
する酸化物を５％以下に制御した技術が提案されてい
る。この技術は、非粘性介在物組成を制御するために全
酸素濃度を１５ｐｐｍ以上とする必要があるため、介在
物量そのものを減じる、あるいは微細化するという機能
はない。In Japanese Patent Publication No. 4-8499, as a method for making inclusions more ductile, the total oxygen content and the non-viscous inclusion index are specified, and among the inclusion components, SiO 2 , MnO and MgO are included. , Al 2 O 3 , CaO, Ti
A technique has been proposed in which the composition of O 2 is limited and oxides of V, Ba, Zr, and Na and oxides inevitably mixed are controlled to 5% or less as other oxides. In this technique, since the total oxygen concentration needs to be 15 ppm or more in order to control the composition of the non-viscous inclusion, there is no function of reducing the amount of the inclusion itself or miniaturizing it.
【０００８】特許２６５４０９９号公報には、Ｓｉ脱酸
剤とアルカリ金属化合物を添加することにより、脱酸生
成物をアルカリ金属含有組成にコントロールする清浄鋼
の製造法が開示され、この方法によれば介在物にアルカ
リ金属化合物量を４〜２４％含有させることにより、
７．５μｍ以上の大型介在物量を減少させることができ
るとしている。この大型介在物が減少する理由は、アル
カリ金属化合物によるアルミナ系およびシリカ系介在物
の延性化により圧延過程で微細化されるためである。し
かしこの方法では、脱酸生成物に起因する介在物の組成
制御が考慮されていないことから、より有害なアルミナ
系介在物そのものを減ずるものではなく、しかもこれは
安定な酸化物であるため、容易には組成変化し難く、し
たがって非延性な組成で残存するおそれがある。また、
この方法はアルカリ金属化合物を直接溶鋼に添加するの
で、アルカリ金属の蒸発やそれによる発煙といった製造
法上の問題が避けられない。Japanese Patent No. 2654099 discloses a method for producing a clean steel in which a deoxidation product is controlled to an alkali metal-containing composition by adding a Si deoxidizing agent and an alkali metal compound. By allowing the inclusion to contain 4 to 24% of the alkali metal compound,
It is stated that the amount of large inclusions of 7.5 μm or more can be reduced. The reason why the large inclusions are reduced is that the alumina-based and silica-based inclusions are made ductile by the alkali metal compound to be refined in the rolling process. However, this method does not reduce the more harmful alumina-based inclusions themselves because the composition control of inclusions caused by deoxidation products is not considered, and since this is a stable oxide, The composition is difficult to change easily, and therefore, there is a possibility that the composition may remain in a non-ductile composition. Also,
In this method, since the alkali metal compound is directly added to the molten steel, problems in the production method such as evaporation of the alkali metal and fuming due to the evaporation are inevitable.
【０００９】本発明は、従来の鋼と比較して、有害な大
型介在物が少なく、しかも残留した介在物も延性のある
介在物であり、かつその介在物は微細に分散されたもの
であり、疲労強度に優れたＳｉ脱酸鋼およびその製造方
法を提供することにある。According to the present invention, as compared with conventional steel, there are fewer harmful large inclusions, and the remaining inclusions are ductile inclusions, and the inclusions are finely dispersed. Another object of the present invention is to provide a Si deoxidized steel excellent in fatigue strength and a method for producing the same.
【００１０】[0010]
【課題を解決するための手段】本発明者は、有害な大型
介在物の生成を抑制する等の検討を重ねた結果、下記の
知見を得た。Means for Solving the Problems The present inventor has made the following findings as a result of repeated studies on suppressing generation of harmful large inclusions.
【００１１】（Ａ）大型介在物の生成を防ぐには、介在
物量を抑制するとともに介在物を微細に分散させること
が有効である。微細な介在物が安定であるためには、溶
鉄との界面エネルギーが低いものが望ましく、介在物中
のＦｅＯ、ＭｎＯ濃度が高いものが良いと推察される。
しかしながら、介在物中でのこれらのＦｅＯ、ＭｎＯ濃
度が高くなると、溶鋼中の酸素ポテンシャルが高くな
り、介在物量の増加をまねくという問題を生じる。(A) In order to prevent the formation of large inclusions, it is effective to suppress the amount of inclusions and finely disperse the inclusions. In order for the fine inclusions to be stable, those having low interface energy with molten iron are desirable, and those having high concentrations of FeO and MnO in the inclusions are presumed to be good.
However, when the concentrations of FeO and MnO in the inclusions increase, the oxygen potential in the molten steel increases, which causes a problem of increasing the amount of inclusions.
【００１２】（Ｂ）延性のある介在物とするには、Ｓｉ
Ｏ2 を基本組成とする必要があるので、ＳｉＯ2 が主体
の介在物で、それら介在物の微細化を図るために、アル
カリ金属：Ｒ（Ｒ= Ｎａ、Ｋ、Ｌｉ）の酸化物（以下、
Ｒ2 Ｏともいう）を含有させればよいと着想した。(B) In order to make ductile inclusions, Si
Since it is necessary to use O 2 as a basic composition, the inclusions are mainly composed of SiO 2 , and in order to reduce the size of the inclusions, an oxide of an alkali metal: R (R = Na, K, Li) (hereinafter referred to as “O”) is used. ,
R 2 O).
【００１３】すなわち、ＳｉＯ2 系介在物にＲ2 Ｏが含
まれている状態は、ＦｅＯやＭｎＯが含まれている状態
に比べて溶鋼温度域で熱力学的により安定であり、溶鋼
との平衡酸素ポテンシャルが低い。一方、ＣａＯ、Ａｌ
2 Ｏ3 およびＭｇＯと比較すると、Ｒ2 Ｏは溶鋼温度域
で熱力学的により不安定であるため、ＳｉＯ2 系介在物
にＲ2 Ｏが含まれている状態は、ＳｉＯ2 系介在物にＣ
ａＯ、Ａｌ2 Ｏ3 およびＭｇＯが含まれている状態に比
較して溶鋼との反応性が高くなるため、界面エネルギー
が低くなる。この界面エネルギーの低下効果により、Ｒ
2 Ｏが含まれているＳｉＯ2 系介在物は微細化が可能と
なる。この結果、介在物起因の疲労強度の低下要因が低
減され、疲労強度に優れたＳｉ脱酸鋼が得られる。That is, the state in which R 2 O is contained in the SiO 2 -based inclusions is more thermodynamically stable in the temperature range of the molten steel than the state in which FeO or MnO is contained, and the equilibrium with the molten steel is obtained. Low oxygen potential. On the other hand, CaO, Al
Compared to 2 O 3 and MgO, for R 2 O is unstable thermodynamically more at the molten steel temperature range, the state of the SiO 2 type inclusions contain the R 2 O is the SiO 2 inclusions C
Since the reactivity with molten steel is higher than in the state containing aO, Al 2 O 3 and MgO, the interface energy is low. Due to this effect of lowering the interface energy, R
SiO 2 -based inclusions containing 2 O can be miniaturized. As a result, the cause of the decrease in fatigue strength due to inclusions is reduced, and Si-deoxidized steel excellent in fatigue strength is obtained.
【００１４】（Ｃ）このような良好な介在物を含有する
Ｓｉ脱酸鋼は、取鍋精錬におけるスラグ組成を適正な組
成に制御することにより得られる。本発明は、以上の知
見に基づいてなされたもので、その要旨は、下記のとお
りである。(C) The Si deoxidized steel containing such good inclusions can be obtained by controlling the slag composition in ladle refining to an appropriate composition. The present invention has been made based on the above findings, and the gist is as follows.
【００１５】(１）質量％でＡｌ：０．００３％以下、
Ｔｉ：０．００３％以下、Ｚｒ：０．００１０％以下お
よびＳｉ：０．０５〜４．０％含有するＳｉ脱酸鋼であ
って、かつ該Ｓｉ脱酸鋼中の介在物が質量％でＳｉ
Ｏ2 ：４５％以上、アルカリ金属Ｒ(Ｒ= Ｎａ、Ｋ、Ｌ
ｉ）の酸化物（Ｒ2 Ｏ）：０．５〜１０％含有すること
を特徴とする疲労強度に優れたＳｉ脱酸鋼。(1) Al: not more than 0.003% by mass%
A Si deoxidized steel containing 0.003% or less of Ti, 0.0010% or less of Zr, and 0.05 to 4.0% of Si, and the inclusions in the Si deoxidized steel are expressed in mass%. Si
O 2 : 45% or more, alkali metal R (R = Na, K, L
i oxide) (R 2 O): Excellent Si-deoxidized steel in fatigue strength, characterized in that it contains 0.5% to 10%.
【００１６】(２）前記Ｓｉ脱酸鋼が、更に、Ｃ：１．
２％以下、Ｍｎ：０．２０〜１．５０％、Ｏ：０．００
２０％以下含有することを特徴とする上記（１）に記載
の疲労強度に優れたＳｉ脱酸鋼。(2) The Si deoxidized steel further comprises C: 1.
2% or less, Mn: 0.20 to 1.50%, O: 0.00
The Si-deoxidized steel having excellent fatigue strength according to the above (1), which contains 20% or less.
【００１７】(３）前記Ｓｉ脱酸鋼が、更に、Ｃ：１．
２％以下、Ｍｎ：０．２０〜１．５０％、Ｏ：０．００
２０％以下、Ｃｒ：０．０５〜２．０％含有することを
特徴とする上記（１）に記載の疲労強度に優れたＳｉ脱
酸鋼。(3) The Si deoxidized steel further comprises C: 1.
2% or less, Mn: 0.20 to 1.50%, O: 0.00
The Si-deoxidized steel having excellent fatigue strength according to the above (1), which contains 20% or less and Cr: 0.05 to 2.0%.
【００１８】(４）前記Ｓｉ脱酸鋼が、更に、Ｃ：０．
１５％以下、Ｍｎ：０．１〜２．０％、Ｃｒ：４〜２０
％、Ｏ：０．００８０％以下含有することを特徴とする
上記（１）に記載の疲労強度に優れたＳｉ脱酸鋼。(4) The above-mentioned Si deoxidized steel further contains C: 0.
15% or less, Mn: 0.1 to 2.0%, Cr: 4 to 20
%, O: 0.0080% or less, wherein the Si-deoxidized steel having excellent fatigue strength according to the above (1).
【００１９】(５）上記（１）〜（４）のいずれかに記
載のＳｉ脱酸鋼を製造する方法であって、精錬炉から取
鍋に出鋼するときにＳｉ脱酸を行い、その後の取鍋スラ
グ精錬時のスラグ組成を質量％でＣａＯ：２０〜４５
％、ＳｉＯ2 ：２５〜６０％、ＭｇＯ：５〜１８％、Ａ
ｌ2 Ｏ3 ：１〜１２％、ＭｎＯ：０．２〜８％、アルカ
リ金属Ｒ（Ｒ= Ｎａ、Ｋ、Ｌｉ）の酸化物（Ｒ2 Ｏ）：
０．５〜１０％とすることを特徴とする疲労強度に優れ
たＳｉ脱酸鋼の製造方法。(5) A method for producing Si deoxidized steel according to any one of the above (1) to (4), wherein the Si is deoxidized when the steel is discharged from the refining furnace to the ladle. Ladle slag refining slag composition in mass% CaO: 20-45
%, SiO 2: 25~60%, MgO: 5~18%, A
l 2 O 3: 1~12%, MnO: 0.2~8%, alkali metal R (R = Na, K, Li) oxide (R 2 O):
A method for producing Si deoxidized steel having excellent fatigue strength, characterized in that the content is 0.5 to 10%.
【００２０】[0020]
【発明の実施の形態】介在物中の（ＳｉＯ2 ）濃度が４
５質量％（以下、単に％で質量％を表す）以上であれ
ば、非延性で有害なＡｌ2 Ｏ3 系介在物、ＭｇＯ・Ａｌ
2 Ｏ3 系介在物およびＭｇＯ系介在物の生成確率は確実
に減少する。望ましい介在物中の（ＳｉＯ2 ）濃度は７
０％以上である。BEST MODE FOR CARRYING OUT THE INVENTION The (SiO 2 ) concentration in inclusions is 4
If it is 5% by mass or more (hereinafter simply expressed as% by mass), it is non-ductile and harmful Al 2 O 3 -based inclusion, MgO · Al
The generation probability of 2 O 3 -based inclusions and MgO-based inclusions is definitely reduced. The preferred inclusion (SiO 2 ) concentration is 7
0% or more.
【００２１】このように介在物中の（ＳｉＯ2 ）濃度が
４５％以上と高い介在物は、圧延長手方向に著しく延伸
した形状ではないが、オーバルな鋭角のない形状であ
り、微細である限りにおいては、疲労強度に悪影響を及
ぼしにくい。As described above, the inclusions having a high (SiO 2 ) concentration of 45% or more in the inclusions are not remarkably elongated in the longitudinal direction of the rolling, but are fine without oval acute angles. As far as possible, it does not easily affect the fatigue strength.
【００２２】しかしながら、単に（ＳｉＯ2 ）濃度が高
い介在物が主体となった場合、これが１０μｍ以上の幅
を有する大きなものであれば、疲労強度に悪影響を及ぼ
す可能性が高い。また、（ＳｉＯ2 ）濃度が高い介在物
組成に制御すること自体は、介在物径を減少させる効果
はないし、また、（ＳｉＯ2 ）濃度が極端に高い介在物
は熱間圧延加工での延伸効果が期待できず、１０μｍ以
上の幅を有する介在物が圧延加工後でも存在する確率が
高い。However, in the case where only inclusions having a high (SiO 2 ) concentration are mainly used, if the inclusions are large having a width of 10 μm or more, there is a high possibility of adversely affecting the fatigue strength. Controlling the composition of the inclusions having a high (SiO 2 ) concentration has no effect of reducing the diameter of the inclusions, and inclusions having an extremely high (SiO 2 ) concentration are stretched by hot rolling. No effect can be expected, and there is a high probability that inclusions having a width of 10 μm or more exist even after rolling.
【００２３】そこで、この１０μｍ以上の幅を有するＳ
ｉＯ2 系介在物の生成を防ぐために、介在物を微細に分
散させる条件について、脱酸過程での溶鋼−酸化物間の
界面エネルギーから検討すると、Ｓｉ脱酸鋼で一般的な
ＳｉＯ2 −ＣａＯ−Ａｌ2 Ｏ 3 系介在物よりも、ＦｅＯ
やＭｎＯ濃度の高い介在物の方が微細に分散させるのに
有利となる。Therefore, the S having a width of 10 μm or more is
iOTwoInclusions are finely divided to prevent the formation of system inclusions.
The conditions for dispersing, between molten steel and oxide during the deoxidation process
Considering from the interfacial energy, the general characteristics of Si deoxidized steel
SiOTwo-CaO-AlTwoO ThreeFeO rather than system inclusions
And inclusions with high MnO concentration can be finely dispersed
This is advantageous.
【００２４】しかしながら、ＦｅＯやＭｎＯ濃度の高い
介在物を生成させるには、溶鋼中のＳｉ濃度を低く抑え
る必要があり、多くのＳｉ脱酸鋼には適用できず、また
弱脱酸になることから介在物個数はむしろ増加する。However, in order to generate inclusions having a high concentration of FeO or MnO, it is necessary to suppress the Si concentration in the molten steel to a low level. Therefore, the number of inclusions increases rather.
【００２５】そこで、ＳｉＯ2 系介在物に、介在物を微
細に分散させるのに有利になると考えられる強塩基性の
アルカリ金属酸化物（Ｒ2 Ｏ、Ｒ= Ｌｉ、Ｎａ、Ｋ）を
含有させることを前述の通り着想した。Therefore, a strongly basic alkali metal oxide (R 2 O, R = Li, Na, K), which is considered to be advantageous for finely dispersing the inclusions, is contained in the SiO 2 -based inclusions. This was conceived as described above.
【００２６】以下に、この着想を確認するために実施し
た模擬実験結果を示す。取鍋スラグ精錬を模擬すること
ができる雰囲気調整炉を用いて、種々のＳｉ脱酸鋼を１
５００〜１５６０℃で溶解した。The results of a simulation experiment conducted to confirm this idea will be described below. Using an atmosphere control furnace that can simulate ladle slag refining, various Si deoxidized steel
Melted at 500-1560 ° C.
【００２７】溶鋼を［Ｃ］：０．７０％、［Ｍｎ］：
０．２５％にそれぞれ成分調整後、所定成分のスラグを
添加し、取鍋スラグ精錬を行い、溶鋼温度を１５００〜
１５６０℃に保持した後、スラグが混入しないように炉
を傾動して得られた溶鋼を鋳造した。このようにして得
られた鋼塊（大きさ：２２０ｍｍφ×５００ｍｍ、質
量：１５０ｋｇ）を６５ｍｍφまで鍛圧し、さらに５．
５ｍｍφまで圧延加工した。[C]: 0.70% of molten steel, [Mn]:
After adjusting each component to 0.25%, slag of a predetermined component is added, ladle slag refining is performed, and the molten steel temperature is set to 1500 to 1500.
After maintaining at 1560 ° C., the molten steel obtained by tilting the furnace so as not to mix slag was cast. The steel ingot (size: 220 mmφ × 500 mm, mass: 150 kg) thus obtained was forged to 65 mmφ.
It was rolled to 5 mmφ.
【００２８】スラグの生成は、ＣａＯ−ＳｉＯ2 −Ｍｇ
Ｏ−Ａｌ2 Ｏ3 −Ｎａ2 Ｏ系を基本とするフラックスを
対象溶鋼質量ｋｇあたり１５ｇ使用して行い、スラグ中
のＮａ2 Ｏ濃度を８％とした。The slag is formed by CaO—SiO 2 —Mg
O-Al 2 O 3 -Na 2 O based flux was carried out with 15g used per target molten steel mass kg which is based, it was 8% of concentration of Na 2 O in the slag.
【００２９】圧延加工した試料から、長手方向断面に切
断、鏡面研磨して、内在する幅１μｍ以上の酸化物系介
在物を調査した。調査した酸化物系介在物は、すべて単
独または硫化物と複合した形態であり、組成については
そのうちの酸化物部分をエネルギー分散型Ｘ線マイクロ
アナライザで分析した。The rolled sample was cut into a longitudinal section, mirror-polished, and an internal oxide-based inclusion having a width of 1 μm or more was examined. The investigated oxide-based inclusions were all in the form of a single compound or a complex with a sulfide, and the oxide portion of the composition was analyzed with an energy dispersive X-ray microanalyzer.
【００３０】図１は、鋼中の［Ａｌ］濃度と介在物中の
（ＳｉＯ2 ）濃度との関係を示すグラフである。なお、
図中の●値は、観察した介在物（ｎ= ３０〜４０）中の
（ＳｉＯ2 ）濃度の平均値を、図中のエラーバーは、観
察した介在物（ｎ= ３０〜４０）中の最大値と最小値を
それぞれ示す（以下の図２〜５および８も同様）。FIG. 1 is a graph showing the relationship between the [Al] concentration in steel and the (SiO 2 ) concentration in inclusions. In addition,
The ● values in the figure indicate the average values of the (SiO 2 ) concentration in the observed inclusions (n = 30 to 40), and the error bars in the figures indicate the values in the observed inclusions (n = 30 to 40). The maximum value and the minimum value are shown (the same applies to FIGS. 2 to 5 and 8 below).
【００３１】同図に示すように、鋼中の［Ａｌ］濃度が
０．００３％以下で介在物中の（ＳｉＯ2 ）濃度が４５
％以上となる。また、鋼中の［Ａｌ］濃度が０．００１
％以下で介在物中の（ＳｉＯ2 ）濃度が７０％以上とな
る。As shown in the figure, the [Al] concentration in the steel is 0.003% or less and the (SiO 2 ) concentration in the inclusion is 45%.
% Or more. [Al] concentration in steel is 0.001.
% Or less, the (SiO 2 ) concentration in the inclusion becomes 70% or more.
【００３２】図２は、鋼中の［Ｔｉ］濃度と介在物中の
（ＳｉＯ2 ）濃度との関係を示すグラフである。同図に
示すように、鋼中の［Ｔｉ］濃度が０．００３％以下で
介在物中の（ＳｉＯ2 ）濃度が４５％以上となる。ま
た、鋼中の［Ｔｉ］濃度が０．００１％以下で介在物中
の（ＳｉＯ2 ）濃度が７０％以上となる図３は、鋼中の
［Ｚｒ］濃度と介在物中の（ＳｉＯ2 ）濃度との関係を
示すグラフである。FIG. 2 is a graph showing the relationship between the [Ti] concentration in steel and the (SiO 2 ) concentration in inclusions. As shown in the figure, when the [Ti] concentration in the steel is 0.003% or less, the (SiO 2 ) concentration in the inclusion becomes 45% or more. Also, Figure 3 is [Ti] concentration in the steel (SiO 2) concentration in inclusions in 0.001% or less is 70% or more, in the steel [Zr] concentration and inclusions of (SiO 2 4) is a graph showing the relationship with the concentration.
【００３３】同図に示すように、鋼中の［Ｚｒ］濃度が
０．００１０％以下で介在物中の（ＳｉＯ2 ）濃度が４
５％以上となる。また、鋼中の［Ｚｒ］濃度が０．００
０２％以下で介在物中の（ＳｉＯ2 ）濃度が７０％以上
となる次に、［Ａｌ］≦０．００３％、［Ｔｉ］≦０．
００３％および［Ｚｒ］≦０．００１０％である鋼を使
用して、［Ｓｉ］濃度を０．０３％から４．４％の範囲
に調整し、そのときの加工試料中に観察される介在物中
の（ＳｉＯ2 ）濃度および（Ｎａ2 Ｏ濃度）を分析し
た。As shown in the figure, the [Zr] concentration in the steel is 0.0010% or less and the (SiO 2 ) concentration in the inclusion is 4%.
It becomes 5% or more. [Zr] concentration in steel is 0.00
When the content of (SiO 2 ) in the inclusions is 70% or more when the content is 02% or less, [Al] ≦ 0.003% and [Ti] ≦ 0.
Using steel with 003% and [Zr] ≦ 0.0010%, the [Si] concentration was adjusted in the range of 0.03% to 4.4%, and the intervening observed in the processed sample at that time. The (SiO 2 ) concentration and (Na 2 O concentration) in the product were analyzed.
【００３４】図４は、鋼中の［Ｓｉ］濃度と介在物中の
（ＳｉＯ2 ）濃度との関係を示すグラフである。なお、
図中の●は、スラグにＮａ2 Ｏを８％配合したときの試
験結果を、○はＮａ2 Ｏを無添加としたときの試験結果
を、それぞれ示す。FIG. 4 is a graph showing the relationship between the [Si] concentration in steel and the (SiO 2 ) concentration in inclusions. In addition,
In the figure, ● indicates the test result when 8% of Na 2 O was added to the slag, and ○ indicates the test result when Na 2 O was not added.
【００３５】同図に示すように、スラグにＮａ2 Ｏの添
加有無に関係なく、鋼中の［Ｓｉ］濃度が０．０５〜
４．０％の範囲において、介在物中の（ＳｉＯ2 ）濃度
が４５％以上となる。As shown in the figure, regardless of whether Na 2 O is added to the slag, the [Si] concentration in the steel is 0.05 to
In the range of 4.0%, the (SiO 2 ) concentration in the inclusion becomes 45% or more.
【００３６】図５は、鋼中の［Ｓｉ］濃度と介在物中の
（Ｎａ2 Ｏ）濃度との関係を示すグラフである。なお、
図中の●は、スラグにＮａ2 Ｏを８％配合したときの試
験結果を、□はＮａ2 Ｏを無添加としたときの試験結果
を、それぞれ示す。FIG. 5 is a graph showing the relationship between the [Si] concentration in steel and the (Na 2 O) concentration in inclusions. In addition,
In the figure, ● indicates the test results when 8% of Na 2 O was added to the slag, and □ indicates the test results when Na 2 O was not added.
【００３７】同図に示すように、スラグにＮａ2 Ｏを８
％配合すると、鋼中の［Ｓｉ］濃度が０．０５〜４．０
％の範囲において、介在物中の（Ｎａ2 Ｏ）濃度が０.
５％以上となる。As shown in the figure, the Na 2 O in the slag 8
%, The [Si] concentration in the steel is 0.05 to 4.0.
%, The (Na 2 O) concentration in the inclusions is 0.1%.
It becomes 5% or more.
【００３８】次に、［Ｃ］：０．７０％、［Ｓｉ］：
０．２５％、［Ｍｎ］：０．５０％、［Ａｌ］：０．０
００４％、［Ｔｉ］：０．０００４％、［Ｚｒ］：０．
０００１％以下の鋼組成を有し、かつ介在物中の（Ｎａ
2 Ｏ）濃度が３．２〜３．６％を有するものについて、
ＳｉＯ2 濃度が４２％、５４％および７５％の３水準の
試料を作製し、前記の通り５．５ｍｍφまで圧延加工し
た。Next, [C]: 0.70%, [Si]:
0.25%, [Mn]: 0.50%, [Al]: 0.0
004%, [Ti]: 0.0004%, [Zr]: 0.
0001% or less steel composition and (Na
For those 2 O) concentration has a 3.2 to 3.6 percent,
Samples with three levels of SiO 2 concentration of 42%, 54% and 75% were prepared and rolled to 5.5 mmφ as described above.
【００３９】図６は、圧延方向断面における介在物の幅
の大きさとその度数分布との関係を示すグラフである。
なお、図中横軸に記載の例えば１〜２とは１〜２μｍ未
満を示し、２〜４とは２〜４μｍ未満をそれぞれ示す。FIG. 6 is a graph showing the relationship between the size of the inclusion width in the cross section in the rolling direction and its frequency distribution.
In addition, for example, 1-2 described on the horizontal axis in the drawing indicates less than 1-2 μm, and 2-4 indicates less than 2-4 μm, respectively.
【００４０】同図に示すように、介在物中の（Ｓｉ
Ｏ2 ）濃度が４２％では、Ｎａ2 Ｏを含有していても８
μｍ以上の介在物が有るのに対し、ＳｉＯ2 濃度が５４
％では、８μｍ未満となり、７５％では６μｍ未満であ
り、介在物が微細化する。As shown in FIG.
O 2 ) at a concentration of 42%, even if Na 2 O is contained,
μm or more, while the SiO 2 concentration is
%, It is less than 8 μm, and at 75%, it is less than 6 μm, and the inclusions are finer.
【００４１】同様に上記鋼組成で、介在物の組成が（Ｓ
ｉＯ2 ）７０％以上で、（Ｎａ2 Ｏ）濃度が０．３％、
１．８％、３．６％、９．７％の４水準の試料を作製
し、前記の通り５．５ｍｍφまで圧延加工した。Similarly, in the above steel composition, the composition of the inclusion is (S
iO 2 ) 70% or more, (Na 2 O) concentration 0.3%,
Samples of four levels of 1.8%, 3.6% and 9.7% were prepared and rolled to 5.5 mmφ as described above.
【００４２】図７は、介在物中の（Ｎａ2 Ｏ）濃度をパ
ラメータとした圧延方向断面における介在物の幅の大き
さとその度数分布との関係を示すグラフである。同図に
示すように、介在物中の（Ｎａ2 Ｏ）濃度が０．３％で
は、８μｍ以上の介在物が有るのに対し、（Ｎａ2 Ｏ）
濃度が１．８％では、８μｍ未満となり、３．６重量以
上％では６μｍ未満であり、介在物が微細化する。FIG. 7 is a graph showing the relationship between the width of the inclusions in the cross section in the rolling direction and the frequency distribution thereof with the (Na 2 O) concentration in the inclusions as a parameter. As shown in the figure, when the concentration of (Na 2 O) in inclusions is 0.3%, inclusions of 8 μm or more are present, while (Na 2 O)
When the concentration is 1.8%, the concentration is less than 8 μm, and when the concentration is 3.6% by weight or more, the concentration is less than 6 μm.
【００４３】さらに、詳しく介在物中のアルカリ金属酸
化物の濃度について試験検討したところ、アルカリ金属
酸化物の濃度は、０．５％以上で望ましくは３％以上で
介在物を微細に分散させる効果が認められた。Furthermore, when the concentration of the alkali metal oxide in the inclusions was examined in detail, the concentration of the alkali metal oxide was 0.5% or more, preferably 3% or more, and the effect of finely dispersing the inclusions was obtained. Was observed.
【００４４】しかし、その介在物を微細に分散させる効
果は約１０％で飽和する。一方、アルカリ金属酸化物
は、溶鋼脱酸が生じるような還元性雰囲気下で分解しや
すくなり、その結果、介在物中に約１０％を越えるアル
カリ金属酸化物を安定して維持させることは困難とな
る。However, the effect of finely dispersing the inclusions is saturated at about 10%. On the other hand, alkali metal oxides are easily decomposed in a reducing atmosphere where deoxidation of molten steel occurs, and as a result, it is difficult to stably maintain more than about 10% of alkali metal oxides in inclusions. Becomes
【００４５】本発明の優れた点は、Ｓｉ脱酸鋼のＳｉＯ
2 系介在物中にアルカリ金属酸化物を含有させれば、さ
まざまな鋼種に適用が可能となることである。そこで、
本発明を使用できる望ましい鋼種について以下に述べ
る。An excellent point of the present invention is that the SiO deoxidized steel is made of SiO.
If an alkali metal oxide is contained in the second inclusion, it can be applied to various steel types. Therefore,
Preferred steel types in which the present invention can be used are described below.
【００４６】その一には、Ｃ：１．２０％以下、Ｍｎ：
０．１０％〜１．５０％、およびＯ：０．００２０％以
下の組成を基本とする高炭素Ｓｉ脱酸鋼が望ましい。Ｃ
濃度の上限を１．２０％とした理由は、１．２０％を越
えると鋼自体が脆化し加工性が悪化するとともに、アル
カリ金属酸化物が溶鋼中の炭素によって分解しやすくな
るおそれがあるからである。One of them is that C: 1.20% or less, Mn:
High carbon Si deoxidized steel based on a composition of 0.10% to 1.50% and O: 0.0020% or less is desirable. C
The reason for setting the upper limit of the concentration to 1.20% is that if it exceeds 1.20%, the steel itself becomes brittle and the workability is deteriorated, and the alkali metal oxide may be easily decomposed by the carbon in the molten steel. It is.
【００４７】下限は特に限定されるものではないが、鋼
材強度を適度に保つには０．０５％以上とすることが望
ましい。Ｍｎ濃度の上限を１. ５％とした理由は、Ｍｎ
濃度が高くなるとＳｉ−Ｍｎ複合脱酸の影響が現れ始
め、Ｍｎ濃度が１．５％を越えると介在物中のＭｎＯ濃
度が１０％を越えて、介在物中のＳｉＯ2 濃度が７０％
以上となることが困難となるおそれがあるからである。
下限は介在物制御の観点から特にないが、鋼材の強度等
を鑑みれば、０．２０％以上とすることが望ましい。Although the lower limit is not particularly limited, it is preferable that the lower limit is 0.05% or more in order to keep the steel material strength at an appropriate level. The reason for setting the upper limit of the Mn concentration to 1.5% is that
When the concentration increases, the influence of the Si—Mn composite deoxidation starts to appear. When the Mn concentration exceeds 1.5%, the MnO concentration in the inclusions exceeds 10%, and the SiO 2 concentration in the inclusions increases to 70%.
This is because it may be difficult to achieve the above.
The lower limit is not particularly limited from the viewpoint of inclusion control, but is preferably 0.20% or more in view of the strength of the steel material and the like.
【００４８】Ｏ濃度の上限を０．００２０％とした理由
は、疲労強度の向上には、介在物量が少ないことが望ま
しいからである。また、上記高炭素Ｓｉ脱酸鋼に、Ｃｒ
を０．０５〜２．０％含有させた高炭素Ｃｒ含有Ｓｉ脱
酸鋼も望ましい。The reason why the upper limit of the O concentration is set to 0.0020% is that it is desirable to reduce the amount of inclusions in order to improve the fatigue strength. In addition, Cr is added to the high carbon Si deoxidized steel.
Is also desirable for high carbon Cr-containing Si deoxidized steel containing 0.05 to 2.0%.
【００４９】さらに、本発明は、Ｓｉ脱酸で溶製できる
フェライト系、あるいは、オーステナイト系ステンレス
鋼にも適用することができる。これらのステンレス鋼の
望ましいＣｒ濃度は４．０〜２０％である。Further, the present invention can be applied to a ferritic or austenitic stainless steel which can be produced by deoxidation of Si. The desirable Cr concentration of these stainless steels is 4.0 to 20%.
【００５０】Ｃｒが含有されると、Ｃｒと酸素の親和力
が強く脱酸処理が困難となるおそれがある。脱酸が不足
した場合には介在物が多量に残留して、本技術による介
在物形態制御をもってしても、疲労強度に影響が出る可
能性があることから、全酸素濃度を０．００８０％以下
にすることが望ましい。When Cr is contained, the affinity between Cr and oxygen is so strong that the deoxidizing treatment may be difficult. If the deoxidation is insufficient, a large amount of inclusions remain, and even if the inclusion morphology control according to the present technology can affect the fatigue strength, the total oxygen concentration is reduced to 0.0080%. It is desirable to make the following.
【００５１】なお、Ｃｒ濃度が８．０％以上では、上記
脱酸が不足するのを回避するために、Ｓｉ濃度が０．１
０％以上あることが望ましい。Ｃ濃度は、加工性と耐食
性とを両立させるために、０．１５％以下が望ましい。When the Cr concentration is 8.0% or more, the Si concentration is set to 0.1% in order to avoid the shortage of deoxidation.
Desirably, it is 0% or more. The C concentration is desirably 0.15% or less in order to achieve both workability and corrosion resistance.
【００５２】Ｍｎ濃度は、Ｓｉ脱酸の予備脱酸機能を持
たせるために、また強度を確保するために、０．１％以
上が望ましい。一方、Ｓｉ脱酸・Ｍｎ脱酸の複合脱酸効
果による介在物中のＳｉＯ2 濃度の低下を防止するため
には２．０％以下が望ましい。The Mn concentration is desirably 0.1% or more in order to provide a preliminary deoxidizing function for Si deoxidation and to secure strength. On the other hand, in order to prevent a decrease in the SiO 2 concentration in inclusions due to a combined deoxidation effect of Si deoxidation and Mn deoxidation, the content is preferably 2.0% or less.
【００５３】また、Ｎｉ濃度については、特に制限はな
く、オーステナイト系ステンレス鋼としての特徴を発揮
する組成においても本発明は適用できる。さらに、本発
明は、Ｓｉ脱酸鋼で溶製できるＶやＭｏを含む高強硬度
鋼や肌焼き鋼へも適用できる。すなわち、本発明におい
ては脱酸に影響を及ぼさない合金成分、例えばＶやＭｏ
は通常の鋼成分の範囲であればその効果を発揮すること
ができる。またＮｉ濃度についても特に制限はなく、そ
の効果を発揮することができる。The Ni concentration is not particularly limited, and the present invention can be applied to a composition exhibiting the characteristics of an austenitic stainless steel. Further, the present invention can be applied to a high-strength steel and a case hardened steel containing V and Mo which can be produced by deoxidizing steel. That is, in the present invention, alloy components that do not affect deoxidation, such as V and Mo
Can exert its effect as long as it is within the range of ordinary steel components. The Ni concentration is not particularly limited, and the effect can be exhibited.
【００５４】次に、介在物組成の制御方法について述べ
る。介在物組成は、基本的には溶鋼中の脱酸元素濃度お
よびスラグ組成によって制御することができる。Next, a method for controlling the composition of inclusions will be described. The inclusion composition can be basically controlled by the deoxidizing element concentration in the molten steel and the slag composition.
【００５５】スラグ組成はスラグ精錬のタイミング、添
加するフラックス組成および量、初期酸素濃度、精錬温
度にも影響されるためこれらを考慮する必要がある。Ｓ
ｉ添加の時期については、転炉あるいは電気炉といった
製鋼炉の出鋼前あるいは出鋼硫に対しての添加が望まし
い。その理由は、脱酸初期に生成する大型介在物が浮上
・除去するためである。The slag composition is affected by the timing of slag refining, the composition and amount of flux to be added, the initial oxygen concentration, and the refining temperature. S
Regarding the timing of i addition, it is desirable to add it before tapping or in tapping sulfur of a steelmaking furnace such as a converter or an electric furnace. The reason is that large inclusions generated in the early stage of deoxidation float and are removed.
【００５６】本発明で対象とするＳｉ脱酸鋼の溶製に際
し、製鋼炉からの流出スラグを取鍋中の溶鋼から除滓を
行い、あらためて溶鋼中にフラックス添加を行う。ここ
で最も重要な点は、フラックス添加取鍋精錬におけるス
ラグ組成である。In the production of the Si deoxidized steel, which is the subject of the present invention, the slag flowing out of the steelmaking furnace is subjected to the removal of slag from the molten steel in the ladle, and flux is added to the molten steel again. The most important point here is the slag composition in the ladle refining with flux addition.
【００５７】すなわち、この取鍋精錬段階において、Ｃ
ａＯ−ＳｉＯ2 −ＭｇＯ−Ａｌ2 Ｏ 3 −ＭｎＯ−Ｒ2 Ｏ
（Ｒ= Ｌｉ、Ｎａ、Ｋ）系スラグを用いる。スラグ中の
ＣａＯは熱的に安定なスラグを構成するための必須成分
であり、その濃度は２０％以上が望ましいが、４５％を
越えると、スラグ塩基度が高くなることにより、介在物
中のＣａＯ、ＭｇＯ等の塩基性成分、Ａｌ2 Ｏ3 等の中
性成分が高い濃度で安定となり、介在物中の（Ｓｉ
Ｏ2 ）濃度が４５％未満となるおそれがあり４５％以下
が望ましい。すなわち、スラグ中のＣａＯ濃度は２０〜
４５％が望ましい。That is, in this ladle refining stage, C
aO-SiOTwo-MgO-AlTwoO Three-MnO-RTwoO
(R = Li, Na, K) slag is used. In the slag
CaO is an essential component for constituting a thermally stable slag
The concentration is preferably 20% or more, but 45%
Beyond that, the slag basicity increases,
Basic components such as CaO and MgO, AlTwoOThreeInside
Content becomes stable at high concentration, and (Si
OTwo) Concentration may be less than 45% and not more than 45%
Is desirable. That is, the CaO concentration in the slag is 20 to
45% is desirable.
【００５８】スラグ中のＳｉＯ2 は、Ｓｉ脱酸鋼を安定
に溶製するための必須成分であり、その濃度が２５％未
満では、介在物中の（ＳｉＯ2 ）濃度が４５％未満とな
るおそれがあり、６０％を越えると取鍋耐火物の溶損が
生じるおそれがあるため、スラグ中のＳｉＯ2 濃度は２
５〜６０％が望ましい。The SiO 2 in the slag is an essential component for stably producing the Si deoxidized steel. If the concentration is less than 25%, the (SiO 2 ) concentration in the inclusions will be less than 45%. If it exceeds 60%, the ladle refractory may be melted, so that the SiO 2 concentration in the slag is 2%.
5 to 60% is desirable.
【００５９】スラグ中のＭｇＯは製鋼炉流出スラグ、耐
火物や副原料から入る不可避的適成分で極端に低減する
ことはコスト的に困難であり、また耐火物保護の観点か
らスラグ中のＭｇＯ濃度は５％以上が望ましいが、Ｍｇ
Ｏ濃度が１８％を越えると、介在物にＭｇＯ濃度が５０
％を越え、非延性介在物が発生するおそれがあり、スラ
グ中のＭｇＯ濃度は１８％以下が望ましい。すなわち、
スラグ中のＭｇＯ濃度は５〜１８％が望ましい。The MgO in the slag is an inevitable suitable component entering from the slag flowing out of the steelmaking furnace, refractories and auxiliary materials, and it is difficult to reduce it extremely in terms of cost. Is preferably 5% or more.
When the O concentration exceeds 18%, the inclusion has a MgO concentration of 50%.
%, Non-ductile inclusions may be generated, and the MgO concentration in the slag is desirably 18% or less. That is,
The MgO concentration in the slag is preferably 5 to 18%.
【００６０】スラグ中のＡｌ2 Ｏ3 は製鋼炉流出スラ
グ、耐火物や副原料から入る不可避的適成分で極端に低
減することはコスト的に困難であり、Ａｌ2 Ｏ3 濃度が
１２％を越えると介在物の（Ａｌ2 Ｏ3 ）濃度が３０％
を越え、非延性介在物が発生するおそれがあるため、ス
ラグ中のＡｌ2 Ｏ3 濃度は１〜１２％が望ましい。[0060] Al 2 O 3 in the slag is steelmaking furnace effluent slag, be extremely reduced by unavoidable suitable components entering from refractories and auxiliary raw material is cost difficult, 12% is the concentration of Al 2 O 3 If it exceeds, the (Al 2 O 3 ) concentration of the inclusion becomes 30%
Therefore, the concentration of Al 2 O 3 in the slag is desirably 1 to 12%, since non-ductile inclusions may be generated.
【００６１】スラグ中のＭｎＯは製鋼炉流出スラグ、合
金成分の脱酸から入る不可避的成分で極端に低減するこ
とはコスト的に困難であり、ＭｎＯ濃度が８％を越える
と全酸素濃度を下げることが困難となり、介在物量その
ものが増加するおそれがあるため、スラグ中のＭｎＯ濃
度は０．２〜８．０％が望ましい。MnO in the slag is an unavoidable component coming from the deoxidation of slag and alloy components flowing out of the steelmaking furnace, and it is difficult to reduce it extremely in terms of cost. If the MnO concentration exceeds 8%, the total oxygen concentration is reduced Therefore, the amount of inclusions itself may increase, so that the MnO concentration in the slag is desirably 0.2 to 8.0%.
【００６２】スラグ中のＲ2 Ｏは、スラグ中に０．５％
以上含有させることが望ましいが、Ｒ2 Ｏ濃度が１０％
を越えるとスラグ中であっても蒸発し易くなり、その蒸
発量が増加してダスト量が増加する等の問題が発生する
おそれがあり、スラグ中のＲ 2 Ｏ濃度は０．５〜１０％
が望ましい。R in slagTwoO is 0.5% in slag
It is desirable to containTwoO concentration is 10%
If it exceeds, it is easy to evaporate even in slag,
Problems such as an increase in the amount of dust and the amount of dust occur
There is a possibility that R in slag TwoO concentration is 0.5-10%
Is desirable.
【００６３】Ｒ2 Ｏ原料の代表例であるＮａ2 Ｏ原料
は、熱的に安定でコスト的にも有利な珪酸ソーダ、メタ
珪酸ソーダ、ソーダ灰、ソーダガラス等が望ましい。Ｒ
2 Ｏ原料の添加時期は特に制限はないが、スラグへの速
やかな溶解を図るため、添加フラックスとの同時添加、
または造滓後スラグへのＲ2 Ｏ原料の個別添加が望まし
い。The Na 2 O raw material, which is a typical example of the R 2 O raw material, is preferably sodium silicate, sodium metasilicate, soda ash, soda glass, etc., which are thermally stable and advantageous in cost. R
The timing of addition of the 2O raw material is not particularly limited. However, in order to dissolve the slag quickly, simultaneous addition with the added flux,
Alternatively, it is desirable to add the R 2 O raw material to the slag after slag making.
【００６４】スラグ精錬段階におけるＲ2 Ｏの過大な蒸
発を抑制するには、溶鋼温度を低くすることが有効であ
り、スラグ精錬時の溶鋼温度を１６００℃以下とするこ
とが望ましい。In order to suppress excessive evaporation of R 2 O in the slag refining stage, it is effective to lower the temperature of the molten steel, and it is desirable that the temperature of the molten steel during the slag refining be 1600 ° C. or less.
【００６５】なお、ＣａＦ2 の併用は、通常、スラグの
滓化性を改善する効果が期待できるので必要に応じて使
用すればよいが、本発明の効果に影響を及ぼさないた
め、ＣａＦ2 の濃度範囲を特に限定しない。In general, the combined use of CaF 2 can be used as necessary, since the effect of improving the slag-making properties of the slag can be expected. However, since the effect of the present invention is not affected, the use of CaF 2 is not affected. The concentration range is not particularly limited.
【００６６】また、不可避的成分としてスラグに含有さ
れるＦｅＯ濃度またはステンレス溶製時におけるスラグ
中のＣｒ2 Ｏ3 濃度は、スラグからの溶鋼再酸化を防ぐ
観点から極力低いことが有効であるが、それらの合計濃
度で５％以下とすることが望ましい。It is effective that the concentration of FeO contained in the slag as an unavoidable component or the concentration of Cr 2 O 3 in the slag at the time of melting stainless steel is as low as possible from the viewpoint of preventing reoxidation of molten steel from the slag. It is desirable that the total concentration thereof be 5% or less.
【００６７】次に、本発明のスラグ精錬の実施形態につ
いて、転炉( または電気炉) −取鍋精錬プロセスを模擬
した実験に沿って述べる。通常、Ｓｉ脱酸鋼は、転炉あ
るいは電気炉によって所期の目的炭素濃度および温度に
なるように酸素吹精された後、取鍋へ出鋼される。出鋼
時、Ｆｅ−Ｓｉ等のＳｉ源をＦｅ−Ｍｎ等のＭｎ源とと
もに添加することによりＳｉ脱酸される。Next, an embodiment of the slag refining of the present invention will be described along with an experiment simulating a converter (or electric furnace) -ladle refining process. Normally, Si deoxidized steel is subjected to oxygen blowing by a converter or an electric furnace so as to have a desired target carbon concentration and temperature, and then is discharged to a ladle. At the time of tapping, Si is deoxidized by adding a Si source such as Fe-Si together with a Mn source such as Fe-Mn.
【００６８】このＳｉ脱酸出鋼時の流出スラグを極力抑
制し、出鋼後に取鍋中の残滓を除去した後に所定組成の
フラックスを添加して造滓する。本発明は、この取鍋ス
ラグ精錬によって、Ｓｉ脱酸鋼中の介在物における（Ｓ
ｉＯ2 ）濃度および（Ｒ2 Ｏ）濃度を制御するものであ
り、前に述べたように本発明のＲはＬｉ、Ｎａ、Ｋであ
りこれらの効果は等価として扱えることから、（Ｎａ2
Ｏ）濃度を制御する方法について以下に説明する。The outflow slag during the deoxidation of Si is minimized, the residue in the ladle is removed after tapping, and a flux of a predetermined composition is added to produce the slag. According to the present invention, the ladle slag refining enables the inclusion of (S) in the inclusions in the Si deoxidized steel.
iO 2) is for controlling the concentration and (R 2 O) concentration, the R of the present invention as mentioned before Li, Na, or K from the handle these effects as an equivalent, (Na 2
O) A method for controlling the concentration will be described below.
【００６９】取鍋スラグ精錬機能を模擬した溶鋼量１５
ｋｇの試験装置により、溶鋼組成としては、Ｃ：０．４
５〜０．５５％、Ｍｎ：０．２０〜０．３０％を含むＳ
ｉ未添加鋼を１５２０〜１５６０℃で溶解した。ここで
出鋼を模擬してＳｉおよびＭｎ添加を行い、最終的にＳ
ｉ：０．２０〜０．３０％およびＭｎ：０．４５〜０．
５５％になるよう調整する。所定時間保持した後、種々
の組成に配合した合成スラグを添加した後、さらに所定
時間保持し、ボンブサンプラーで溶鋼から採取した試料
中の介在物組成とスラグ組成との関係を調査した。Molten steel amount 15 simulating ladle slag refining function
kg test equipment, C: 0.4 as molten steel composition
S containing 5 to 0.55%, Mn: 0.20 to 0.30%
i The non-added steel was melted at 1520 to 1560 ° C. Here, Si and Mn were added to simulate tapping, and finally S
i: 0.20 to 0.30% and Mn: 0.45 to 0.
Adjust to be 55%. After maintaining for a predetermined time, synthetic slag mixed with various compositions was added, and then further maintained for a predetermined time, and the relationship between the inclusion composition and the slag composition in a sample collected from molten steel with a bomb sampler was investigated.
【００７０】スラグの基本成分としては、ＣａＯ−Ｓｉ
Ｏ2 −Ａｌ2 Ｏ3 −ＭｇＯ−ＣａＦ 2 として、そこにＮ
ａ2 Ｏはその炭酸塩の試薬で配合した。図８は、Ｃａ
Ｏ：３３〜４０％、ＳｉＯ2 ：３３〜４０％、Ａｌ2 Ｏ
3 ：２〜５％、ＭｇＯ：１２〜１５％、残部にＣａ
Ｆ2 ：２〜５と不可避的に含まれるＦｅＯ、ＭｎＯおよ
びその他不純物を含有するスラグ中のＮａ2 Ｏ濃度と介
在物中のＮａ2 Ｏ濃度との関係を示すグラフである。The basic component of the slag is CaO—Si
OTwo-AlTwoOThree-MgO-CaF TwoAs there N
aTwoO was formulated with the carbonate reagent. FIG.
O: 33-40%, SiOTwo: 33-40%, AlTwoO
Three: 2 to 5%, MgO: 12 to 15%, the balance being Ca
FTwo: FeO, MnO and unavoidably contained as 2 to 5
In slag containing iron and other impuritiesTwoO concentration and mediation
Na in substanceTwoIt is a graph which shows the relationship with O concentration.
【００７１】同図に示すように、スラグ中のＮａ2 Ｏ濃
度の上昇とともに介在物中の（Ｎａ 2 Ｏ）濃度も上昇
し、その効果は１０％で飽和する。また、この試験の
際、１０％を越えて配合すると、スラグからの蒸発物が
著しく増加することが認められた。As shown in FIG.TwoO concentration
(Na) in inclusions with increasing degree TwoO) Concentration also rises
The effect saturates at 10%. In addition, this test
At this time, if it exceeds 10%, evaporation from slag will
A significant increase was observed.
【００７２】このように、この取鍋スラグ精錬によっ
て、Ｓｉ脱酸鋼中の介在物における（Ｒ2 Ｏ）濃度を任
意に制御することができる。As described above, the ladle slag refining can arbitrarily control the (R 2 O) concentration in the inclusions in the Si deoxidized steel.
【００７３】[0073]
【実施例】８０ｔ転炉で脱炭精錬を行った後、取鍋へ出
鋼する際に、Ｆｅ−ＳｉおよびＦｅ−Ｍｎ等の合金鉄お
よび加炭剤を適宜添加し、Ｓｉ脱酸および成分の調整を
行った。この際、後のスラグ組成制御をより効率良く行
うために、流出スラグを極力防止し、さらに、スラグド
ラッガーで除滓を行った。EXAMPLE After decarburization and refining in an 80-t converter, when steel is extracted to a ladle, ferrous alloys such as Fe-Si and Fe-Mn and a carburizing agent are appropriately added to deoxidize Si and remove components. Was adjusted. At this time, in order to more efficiently control the slag composition later, the outflow slag was prevented as much as possible, and the slag was removed with a slag dragger.
【００７４】その後あらためて造滓のためのフラックス
を添加し、所要の組成を有するスラグを形成せしめた。
フラックスとしては、製鋼で一般に用いられる生石灰
（ＣａＯ源）、珪砂（ＳｉＯ2 源）、ドロマイト（Ｍｇ
ＯおよびＣａＯ源）、蛍石（ＣａＦ2 ）等を適宜添加し
た。Thereafter, a flux for slag was added again to form a slag having a required composition.
Examples of the flux include quick lime (CaO source), silica sand (SiO 2 source), dolomite (Mg
O and CaO sources), fluorite (CaF 2 ) and the like were added as appropriate.
【００７５】また、Ａｌ2 Ｏ3 、ＦｅＯおよびＭｎＯ成
分は、残存スラグ、耐火物および脱酸生成物に由来し上
記スラグ中に混入した。ここで、スラグ中へのＲ2 Ｏ源
としては、Ｌｉ2 Ｏ、Ｎａ2 ＯおよびＫ2 Ｏがほぼ等価
な機能を有していることから、製鋼プロセスで利用しや
すく工業的規模の入手が可能なＮａ2 Ｏを含有する珪酸
ソーダを用いた。スラグ量は、溶鋼質量トン当たり約１
５ｋｇとなるようにした。この取鍋精錬時の温度は、１
５００℃〜１６００℃の範囲であった。The Al 2 O 3 , FeO and MnO components were derived from residual slag, refractories and deoxidized products and were mixed into the slag. Here, as the R 2 O source in the slag, since Li 2 O, Na 2 O and K 2 O have almost equivalent functions, they can be easily used in the steelmaking process and can be obtained on an industrial scale. Sodium silicate containing possible Na 2 O was used. The amount of slag is about 1 per ton of molten steel.
The weight was adjusted to 5 kg. The temperature during this ladle refining is 1
The range was from 500C to 1600C.
【００７６】上記条件下のスラグ精錬を約１０分間以上
実施した後、スラグが均一になった状態でスラグを採取
し組成を調べた。スラグ精錬をさらに約５分間以上実施
した後、常法にしたがい連続鋳造を行い、得られた鋳片
を常法にしたがい圧延を施し、５．５ｍｍφの線材を得
た。線材の長手方向断面に観察される介在物を無作為に
２０個以上選び、その組成をエネルギー分散型のＸ線マ
イクロアナライザーで調べ、その平均値を比較した。After performing slag refining under the above conditions for about 10 minutes or more, slag was sampled in a state where the slag was uniform, and the composition was examined. After slag refining was further performed for about 5 minutes or more, continuous casting was performed according to a conventional method, and the obtained slab was rolled according to a conventional method to obtain a 5.5 mmφ wire. Twenty or more inclusions observed in the longitudinal section of the wire were randomly selected, their compositions were examined with an energy dispersive X-ray microanalyzer, and their average values were compared.
【００７７】上記の方法により種々の組成を有する鋼材
を製造し、これらの圧延試料を用いて回転曲げ疲労試験
（１０7 回回転曲げ試験）を行った。各試料は、鋼種ご
とに焼き入れ焼き戻し等の同じ熱処理を施した。疲労強
度の評価は、温度は２０〜２５℃、湿度５０〜６０％の
条件下試験を行った。[0077] By the above method to produce a steel having various compositions were rotating bending fatigue test using these rolling samples (rotary bending test 10 7 times). Each sample was subjected to the same heat treatment such as quenching and tempering for each steel type. For the evaluation of the fatigue strength, a test was performed under the conditions of a temperature of 20 to 25 ° C. and a humidity of 50 to 60%.
【００７８】(実施例１）表１に高炭素Ｓｉ脱酸鋼の化
学組成および介在物の化学組成と疲労強度との関係を示
す。Example 1 Table 1 shows the relationship between the chemical composition of high carbon Si deoxidized steel, the chemical composition of inclusions, and fatigue strength.
【００７９】[0079]
【表１】 [Table 1]
【００８０】表１に示すように、高炭素Ｓｉ脱酸鋼の化
学組成がＡｌ≦０．００３％、Ｔｉ≦０．００３％およ
びＺｒ≦０．００１０％でＳｉが０．０５〜４．０％
で、かつ介在物中のＳｉＯ2 濃度が４５％以上、Ｎａ2
Ｏ濃度が０．５〜１０％である試料No. １〜5 の本発明
例は疲労強度が１０２３ＭＰａ以上と大きな値が得られ
たが、No.6〜10の比較例は疲労強度が７８０ＭＰａ以下
と比較的に小さな値しかえられなかった。As shown in Table 1, when the chemical composition of the high carbon Si deoxidized steel is Al ≦ 0.003%, Ti ≦ 0.003% and Zr ≦ 0.0010%, the content of Si is 0.05 to 4.0. %
And the SiO 2 concentration in the inclusions is 45% or more and Na 2
The samples of the present invention of sample Nos. 1 to 5 having an O concentration of 0.5 to 10% had a large fatigue strength of 1023 MPa or more, whereas the comparative examples of Nos. 6 to 10 had a fatigue strength of 780 MPa or less. And only a relatively small value was obtained.
【００８１】(実施例２）表２に高炭素Ｃｒ含有Ｓｉ脱
酸鋼の化学組成および介在物の化学組成と疲労強度との
関係を示す。Example 2 Table 2 shows the relationship between the chemical composition of high carbon Cr-containing Si deoxidized steel, the chemical composition of inclusions, and the fatigue strength.
【００８２】[0082]
【表２】 [Table 2]
【００８３】表２に示すように、高炭素Ｃｒ含有Ｓｉ脱
酸鋼の化学組成がＡｌ≦０．００３％、Ｔｉ≦０．００
３％およびＺｒ≦０．００１０％でＳｉが０．０５〜
４．０％で、かつ介在物中のＳｉＯ2 濃度が４５％以
上、Ｎａ2 Ｏ濃度が０．５〜１０％である試料No.11 〜
15の本発明例は疲労強度が１２２４ＭＰａ以上と大きな
値が得られたが、No.16 〜20の比較例は疲労強度が１０
４０ＭＰａ以下と比較的に小さな値しかえられなかっ
た。As shown in Table 2, the chemical composition of the high carbon Cr-containing Si deoxidized steel was such that Al ≦ 0.003% and Ti ≦ 0.003%.
3% and Zr ≦ 0.0010%, Si is 0.05 to
Sample No. 11 to 4.0%, in which the SiO 2 concentration in the inclusions is 45% or more and the Na 2 O concentration is 0.5 to 10%
The fifteen examples of the present invention had a large fatigue strength of 1224 MPa or more, while the comparative examples of Nos. 16 to 20 had a fatigue strength of 10
A relatively small value of 40 MPa or less was obtained.
【００８４】(実施例３）表３に中炭素Ｃｒ、Ｍｏ含有
Ｓｉ脱酸鋼の化学組成および介在物の化学組成と疲労強
度との関係を示す。Example 3 Table 3 shows the relationship between the chemical composition of medium carbon Cr and Mo-containing Si deoxidized steel, the chemical composition of inclusions, and the fatigue strength.
【００８５】[0085]
【表３】 [Table 3]
【００８６】表３に示すように、中炭素Ｃｒ、Ｍｏ含有
Ｓｉ脱酸鋼の化学組成がＡｌ≦０．００３％、Ｔｉ≦
０．００３％およびＺｒ≦０．００１０％でＳｉが０．
０５〜４．０％で、かつ介在物中のＳｉＯ2 濃度が４５
％以上、Ｎａ2 Ｏ濃度が０．５〜１０％である試料No.2
1 〜25の本発明例は疲労強度が６２８ＭＰａ以上と大き
な値が得られたが、No.26 〜30の比較例は疲労強度が５
０８ＭＰａ以下と比較的に小さな値しかえられなかっ
た。As shown in Table 3, the chemical composition of the medium carbon Cr and Mo containing Si deoxidized steel was such that Al ≦ 0.003%, Ti ≦
0.003% and Zr.ltoreq.0.0010% when Si is 0.1%.
And the SiO 2 concentration in the inclusions is 45 to 4.0%.
% Or more, and the Na 2 O concentration is 0.5 to 10%.
In the present invention examples 1 to 25, the fatigue strength was as large as 628 MPa or more, whereas in the comparative examples No. 26 to 30, the fatigue strength was 5
A relatively small value of 08 MPa or less was obtained.
【００８７】(実施例４）表４に中炭素Ｃｒ、Ｍｏ、Ｎ
ｉ含有Ｓｉ脱酸鋼の化学組成および介在物の化学組成と
疲労強度との関係を示す。Example 4 Table 4 shows that medium carbon Cr, Mo, N
4 shows the relationship between the chemical composition of i-containing Si deoxidized steel, the chemical composition of inclusions, and fatigue strength.
【００８８】[0088]
【表４】 [Table 4]
【００８９】表４に示すように、同脱酸鋼の化学組成が
Ａｌ≦０．００３％、Ｔｉ≦０．００３％およびＺｒ≦
０．００１０％でＳｉが０．０５〜４．０％で、かつ介
在物中のＳｉＯ2 濃度が４５％以上、Ｎａ2 Ｏ濃度が
０．５〜１０％である試料No.31 〜35の本発明例は疲労
強度が６０９ＭＰａ以上と大きな値が得られたが、No.3
6 〜40の比較例は疲労強度が５０８ＭＰａ以下と比較的
に小さな値しかえられなかった。As shown in Table 4, the chemical composition of the deoxidized steel was as follows: Al ≦ 0.003%, Ti ≦ 0.003%, and Zr ≦
Si is at 0.05 to 4.0 percent by 0.0010%, and SiO 2 concentration in inclusions at least 45%, Na 2 O concentration of the sample No.31 to 35 are 0.5% to 10% In the example of the present invention, the fatigue strength was as large as 609 MPa or more.
The comparative examples 6 to 40 had relatively small values of the fatigue strength of 508 MPa or less.
【００９０】(実施例５）表５に低炭素Ｃｒ系ステンレ
スＳｉ脱酸鋼の化学組成および介在物の化学組成と疲労
強度との関係を示す。Example 5 Table 5 shows the relationship between the chemical composition of low carbon Cr-based stainless steel deoxidized steel, the chemical composition of inclusions, and fatigue strength.
【００９１】[0091]
【表５】 [Table 5]
【００９２】表５に示すように、同脱酸鋼の化学組成が
Ａｌ≦０．００３％、Ｔｉ≦０．００３％およびＺｒ≦
０．００１０％でＳｉが０．０５〜４．０％で、かつ介
在物中のＳｉＯ2 濃度が４５％以上、Ｎａ2 Ｏ濃度が
０．５〜１０％である試料No.41 〜45の本発明例は疲労
強度が３３０ＭＰａ以上と大きな値が得られたが、No.3
6 〜40の比較例は疲労強度が３１１ＭＰａ以下と比較的
に小さな値しかえられなかった。As shown in Table 5, the chemical composition of the deoxidized steel was as follows: Al ≦ 0.003%, Ti ≦ 0.003%, and Zr ≦
Si is at 0.05 to 4.0 percent by 0.0010%, and SiO 2 concentration in inclusions at least 45%, Na 2 O concentration of the sample No.41 to 45 are 0.5% to 10% In the example of the present invention, the fatigue strength was as high as 330 MPa or more, but No. 3
The comparative examples 6 to 40 had a relatively small fatigue strength of 311 MPa or less.
【００９３】(実施例６）表６に低炭素Ｃｒ−Ｎｉ系ス
テンレスＳｉ脱酸鋼の化学組成および介在物の化学組成
と疲労強度との関係を示す。Example 6 Table 6 shows the chemical composition of low carbon Cr-Ni stainless steel Si deoxidized steel and the relationship between the chemical composition of inclusions and fatigue strength.
【００９４】[0094]
【表６】 [Table 6]
【００９５】表６に示すように、同脱酸鋼の化学組成が
Ａｌ≦０．００３％、Ｔｉ≦０．００３％およびＺｒ≦
０．００１０％でＳｉが０．０５〜４．０％で、かつ介
在物中のＳｉＯ2 濃度が４５％以上、Ｎａ2 Ｏ濃度が
０．５〜１０％である試料No.51 〜55の本発明例は疲労
強度が３５６ＭＰａ以上と大きな値が得られたが、No.5
6 〜60の比較例は疲労強度が３１１ＭＰａ以下と比較的
に小さな値しかえられなかった。As shown in Table 6, the chemical composition of the deoxidized steel was as follows: Al ≦ 0.003%, Ti ≦ 0.003%, and Zr ≦
Si is at 0.05 to 4.0 percent by 0.0010%, and SiO 2 concentration in inclusions at least 45%, Na 2 O concentration of the sample No.51 to 55 are 0.5% to 10% In the example of the present invention, the fatigue strength was as large as 356 MPa or more.
Comparative Examples 6 to 60 had relatively small values of fatigue strength of 311 MPa or less.
【００９６】[0096]
【発明の効果】本発明のＳｉ脱酸鋼は、従来の鋼と比較
して、有害な大型介在物が少なく、しかも残留した介在
物も延性のある介在物であり、かつその介在物は微細に
分散されたものであり、今までにない疲労強度に優れた
鋼種である。The Si deoxidized steel of the present invention has less harmful large inclusions than conventional steels, and the remaining inclusions are ductile inclusions, and the inclusions are fine. It is a type of steel that has an unprecedented fatigue strength.
【図１】鋼中の［Ａｌ］濃度と介在物中の（ＳｉＯ2 ）
濃度との関係を示すグラフである。FIG. 1 [Al] concentration in steel and (SiO 2 ) in inclusions
It is a graph which shows the relationship with a density.
【図２】鋼中の［Ｔｉ］濃度と介在物中の（ＳｉＯ2 ）
濃度との関係を示すグラフである。FIG. 2 [Ti] concentration in steel and (SiO 2 ) in inclusions
It is a graph which shows the relationship with a density.
【図３】鋼中の［Ｚｒ］濃度と介在物中の（ＳｉＯ2 ）
濃度との関係を示すグラフである。FIG. 3 [Zr] concentration in steel and (SiO 2 ) in inclusions
It is a graph which shows the relationship with a density.
【図４】鋼中の［Ｓｉ］濃度と介在物中の（ＳｉＯ2 ）
濃度との関係を示すグラフである。FIG. 4 [Si] concentration in steel and (SiO 2 ) in inclusions
It is a graph which shows the relationship with a density.
【図５】鋼中の［Ｓｉ］濃度と介在物中の（Ｎａ2 Ｏ）
濃度との関係を示すグラフである。FIG. 5: [Si] concentration in steel and (Na 2 O) in inclusions
It is a graph which shows the relationship with a density.
【図６】圧延方向断面における介在物の幅の大きさとそ
の度数分布との関係を示すグラフである。FIG. 6 is a graph showing the relationship between the width of inclusions in the cross section in the rolling direction and the frequency distribution thereof.
【図７】介在物中の（Ｎａ2 Ｏ）濃度をパラメータとし
た圧延方向断面における介在物の幅の大きさとその度数
分布との関係を示すグラフである。FIG. 7 is a graph showing the relationship between the width of inclusions in the cross section in the rolling direction and the frequency distribution thereof, using the (Na 2 O) concentration in the inclusions as a parameter.
【図８】ＣａＯ：３３〜４０％、ＳｉＯ2 ：３３〜４０
％、Ａｌ2 Ｏ3 ：２〜５％、ＭｇＯ：１２〜１５％、残
部にＣａＦ2 ：２〜５と不可避的に含まれるＦｅＯ、Ｍ
ｎＯおよびその他不純物を含有するスラグ中のＮａ2 Ｏ
濃度と介在物中のＮａ2Ｏ濃度との関係を示すグラフで
ある。FIG. 8: CaO: 33 to 40%, SiO 2 : 33 to 40
%, Al 2 O 3 : 2 to 5%, MgO: 12 to 15%, and the balance CaF 2 : 2 to 5 FeO and M inevitably contained.
Na 2 O in slag containing nO and other impurities
It is a graph showing the relationship between the concentration and the concentration of Na 2 O inclusions.
Claims (5)
ｉ：０．００３％以下、Ｚｒ：０．００１０％以下およ
びＳｉ：０．０５〜４．０％含有するＳｉ脱酸鋼であっ
て、かつ該Ｓｉ脱酸鋼中の介在物が質量％でＳｉＯ2 ：
４５％以上、アルカリ金属Ｒ（Ｒ= Ｎａ、Ｋ、Ｌｉ）の
酸化物（Ｒ2 Ｏ）：０．５〜１０％含有することを特徴
とする疲労強度に優れたＳｉ脱酸鋼。1. Al in mass%: 0.003% or less, T
i: a Si-deoxidized steel containing 0.003% or less, Zr: 0.0010% or less, and Si: 0.05 to 4.0%, and the inclusions in the Si-deoxidized steel are represented by mass%. SiO 2 :
45% or more, oxides of alkali metal R (R = Na, K, Li) (R 2 O): 0.5~10% containing Si deoxidized steel with excellent fatigue strength, characterized by.
以下、Ｍｎ：０．２０〜１．５０％、Ｏ：０．００２０
％以下含有することを特徴とする請求項１に記載の疲労
強度に優れたＳｉ脱酸鋼。2. The Si deoxidized steel further comprises C: 1.2%
Hereinafter, Mn: 0.20 to 1.50%, O: 0.0020
The Si deoxidized steel having excellent fatigue strength according to claim 1, wherein the content thereof is not more than%.
以下、Ｍｎ：０．２０〜１．５０％、Ｏ：０．００２０
％以下、Ｃｒ：０．０５〜２．０％含有することを特徴
とする請求項１に記載の疲労強度に優れたＳｉ脱酸鋼。3. The Si deoxidized steel further comprises C: 1.2%
Hereinafter, Mn: 0.20 to 1.50%, O: 0.0020
% Or less, Cr: 0.05 to 2.0%, Si deoxidized steel excellent in fatigue strength according to claim 1 characterized by the above-mentioned.
％以下、Ｍｎ：０．１〜２．０％、Ｃｒ：４〜２０％、
Ｏ：０．００８０％以下含有することを特徴とする請求
項１に記載の疲労強度に優れたＳｉ脱酸鋼。4. The Si deoxidized steel further comprises C: 0.15
% Or less, Mn: 0.1 to 2.0%, Cr: 4 to 20%,
The Si-deoxidized steel excellent in fatigue strength according to claim 1, wherein O: 0.0080% or less is contained.
酸鋼を製造する方法であって、精錬炉から取鍋に出鋼す
るときにＳｉ脱酸を行い、その後の取鍋スラグ精錬時の
スラグ組成を質量％でＣａＯ：２０〜４５％、Ｓｉ
Ｏ2 ：２５〜６０％、ＭｇＯ：５〜１８％、Ａｌ
2 Ｏ3 ：１〜１２％、ＭｎＯ：０．２〜８％、アルカリ
金属Ｒ（Ｒ= Ｎａ、Ｋ、Ｌｉ）の酸化物（Ｒ2 Ｏ）：
０．５〜１０％とすることを特徴とする疲労強度に優れ
たＳｉ脱酸鋼の製造方法。5. A method for producing a Si deoxidized steel according to claim 1, wherein when the steel is discharged from a refining furnace to a ladle, the Si deoxidation is performed, and then the ladle slag is produced. The slag composition at the time of refining is CaO: 20 to 45% by mass%, Si
O 2 : 25 to 60%, MgO: 5 to 18%, Al
2 O 3 : 1 to 12%, MnO: 0.2 to 8%, oxide (R 2 O) of alkali metal R (R = Na, K, Li):
A method for producing Si deoxidized steel having excellent fatigue strength, characterized in that the content is 0.5 to 10%.
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| JP3719131B2 (en) | 2005-11-24 |
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