JP3658037B2 - Melting method of low Al ultra low sulfur steel - Google Patents
Melting method of low Al ultra low sulfur steel Download PDFInfo
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- JP3658037B2 JP3658037B2 JP08524195A JP8524195A JP3658037B2 JP 3658037 B2 JP3658037 B2 JP 3658037B2 JP 08524195 A JP08524195 A JP 08524195A JP 8524195 A JP8524195 A JP 8524195A JP 3658037 B2 JP3658037 B2 JP 3658037B2
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
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Description
【０００１】
【産業上の利用分野】
本発明は、脱酸剤としてＡｌ合金をほとんど用いず、Ｓ含有量が限定された、低炭素鋼であり、主たる用途は厚板またはパイプである、低Ａｌ極低硫鋼の溶製方法に関する。
【０００２】
【従来の技術】
近年、海洋構造物、船舶、ラインパイプ等の高級鋼に要求される材質特性は益々厳しくなっている。特に、耐水素誘起割れ特性、耐硫化物応力腐食割れ特性ならびに溶接部における低温靭性の抜本的改善が望まれる。耐水素誘起割れ特性、耐硫化物応力腐食割れ特性を満足するためには、溶鋼中のＳを低減し、Ｃａを添加することによって、有害介在物であるＭｎＳの生成を抑制することが必要である。
また、低温靭性の向上を図るためには、高炭素マルテンサイトの生成を抑制することが必須であり、そのためには、溶鋼中のＡｌ濃度の低減が有効である。
【０００３】
低Ａｌ鋼（Ａｌ≦０．００５mass％）を脱硫処理を行なう場合、脱硫処理前に溶鋼にＡｌを添加して溶鋼中の溶解酸素濃度を低減し、脱硫剤を添加して脱硫処理を行なった後、酸素を溶鋼中に吹込み溶鋼中のＡｌを酸化除去する方法が特開平４−１８３８１２号公報に開示されている。この方法では酸素吹込み時に生成する多量のＡｌ2 Ｏ3 系の非金属介在物が生成し溶鋼の酸素濃度が高くなり、溶鋼清浄性が悪化する問題がある。
【０００４】
一般に、Ａｌ脱酸鋼の取鍋スラグはＣａＯ，Ａｌ2 Ｏ3 が主成分であり、脱硫能と流動性を考慮し、（mass％ＣａＯ）／（mass％Ａｌ2 Ｏ3 ）が１．５〜３程度に制御されている。
【０００５】
Ａｌ2 Ｏ3 濃度が高いと、スラグから溶鋼へＡｌが還元され、溶鋼中のＡｌ濃度が上昇し、本鋼材のＡｌ≦０．００５mass％の製造が困難となる。Ａｌ2 Ｏ3 濃度が低く、ＣａＯ濃度が高くなるとスラグの溶融温度が上昇し、溶鋼温度である、１５５０〜１６００℃において固体スラグとなり、反応性が著しく悪化し、低硫鋼の製造が困難となる。
【０００６】
したがって、この鋼材の製造では、溶鋼中のＡｌ濃度を低減しつつ、脱硫処理を行うことが可能なスラグ組成を明らかにする必要がある。
なお、本発明では、Ｃ含有量が高くなると靭性が低下するためにＣは０．２０mass％以下の鋼材を対象とした。
【０００７】
【発明が解決しようとする課題】
本発明の目的は、スラグ組成を制御することにより、低Ａｌ、低Ｓ鋼（Ａｌ≦０．００５ｍａｓｓ％、Ｓ≦０．００１ｍａｓｓ％を含む鋼）を溶製する方法を提供することである。
【０００８】
【課題を解決するための手段】
本発明の要旨は、Ｃ≦０．２０ｍａｓｓ％、Ａｌ≦０．００５ｍａｓｓ％、Ｓ≦０．００１ｍａｓｓ％を含む鋼材を製造する方法において、Ａｌ２Ｏ３≦２０ｍａｓｓ％、ＭｇＯ＝５〜１５ｍａｓｓ％、（ｍａｓｓ％ＣａＯ）／（ｍａｓｓ％ＳｉＯ２）＝２．５〜４．０の取鍋スラグ組成に制御し、Ｓ≦０．００１ｍａｓｓ％の低Ａｌ極低硫鋼の溶製方法である。
【０００９】
以下に、低Ａｌ、低Ｓ鋼（Ａｌ≦０．００５ｍａｓｓ％、Ｓ≦０．００１ｍａｓｓ％を含む鋼）を溶製する方法を説明する。
脱硫能を表すスラグの塩基度、（ｍａｓｓ％ＣａＯ）／（ｍａｓｓ％ＳｉＯ２）（以下Ｃ／Ｓと記述）とＳ濃度の関係をＡｌ２Ｏ３濃度別に図１に示す。塩基度の増加とともにＳは低減するが、Ｃ／Ｓ＞４では、その効果は低減する。スラグの溶融温度が上昇し、スラグ・メタルの反応性が悪化する。
【００１０】
Ａｌ濃度に関して、スラグのＡｌ2 Ｏ3 濃度の影響を、図２に示す。Ａｌ2 Ｏ3 濃度の上昇に伴い、Ａｌ濃度は上昇し、塩基度が高い程上昇が大きい。Ａｌ2 Ｏ3 濃度を２０mass％以下にすることが必要である。
【００１１】
ＭｇＯ濃度を制御することにより、スラグの反応速度を向上させるための、溶融温度を制御する。図３に、スラグ中のＭｇＯ濃度をスラグの液相率の関係を示す。ＭｇＯ濃度が低いと液相率が低いが、ＭｇＯ濃度の増加とともに液相率が増加し、５mass％でほぼ液相が１００％である。ＭｇＯ濃度の増加とともに液相率の変化は小さいが、１５mass％を超えると固体析出物が晶出するために、液相率が低減する。また、液相率と鋼材のＳ濃度の関係を図４に示す。液相率が低下するＭｇＯ濃度が５mass％未満、１５mass％を超える濃度においてはスラグとの反応が低下するために鋼材のＳ濃度が上昇する。したがって、ＭｇＯ濃度を５〜１５mass％に制御する。
【００１２】
【実施例】
以下に、本発明の実施例を表１に示す。
本発明の実施例（１）〜（５）では、Ａｌ≦０．００５mass％、Ｓ≦０．００１mass％の鋼材を製造できた。しかし比較例である（６）〜（１５）では（８）〜（１５）がＳ＞０．００１mass％となって目的を達せず、（７），（８）もＡｌ2 Ｏ3 ＞２０mass％となって目的が達成されなかった。
【００１３】
【表１】
【発明の効果】
以上の如く本発明によれば、Ｃ≦０．２０ｍａｓｓ％、Ａｌ≦０．００５ｍａｓｓ％、Ｓ≦０．００１ｍａｓｓ％を含む鋼材を製造する方法において、安定して、０．００１０ｍａｓｓ％以下の硫黄の鋼材を製造できた。
【図面の簡単な説明】
【図１】スラグ中の（mass％ＣａＯ）／（mass％ＳｉＯ2 ）と鋼材のＳ濃度の関係。
【図２】スラグ中の（mass％Ａｌ2 Ｏ3 ）と鋼材のＡｌ濃度の関係。
【図３】スラグ中の（mass％ＭｇＯ）とスラグの液相率の関係。
【図４】スラグ中の（mass％ＭｇＯ）と鋼材のＳ濃度の関係。[0001]
[Industrial application fields]
The present invention relates to a method for melting low Al ultra-low sulfur steel, which is a low carbon steel that uses almost no Al alloy as a deoxidizer and has a limited S content, and whose main application is a thick plate or pipe. .
[0002]
[Prior art]
In recent years, material properties required for high-grade steel such as offshore structures, ships, and line pipes have become increasingly severe. In particular, drastic improvements in resistance to hydrogen induced cracking, resistance to sulfide stress corrosion cracking, and low temperature toughness in welds are desired. In order to satisfy the resistance to hydrogen-induced cracking and the resistance to sulfide stress corrosion cracking, it is necessary to suppress the generation of MnS, which is a harmful inclusion, by reducing S in the molten steel and adding Ca. is there.
Moreover, in order to improve low temperature toughness, it is essential to suppress the formation of high carbon martensite, and for that purpose, it is effective to reduce the Al concentration in the molten steel.
[0003]
When desulfurizing low Al steel (Al ≦ 0.005 mass%), Al was added to the molten steel before the desulfurizing treatment to reduce the dissolved oxygen concentration in the molten steel, and desulfurizing treatment was performed by adding a desulfurizing agent. Subsequently, Japanese Patent Laid-Open No. 4-183812 discloses a method in which oxygen is blown into molten steel and Al in the molten steel is oxidized and removed. In this method, there is a problem that a large amount of non-metallic inclusions of Al 2 O 3 produced when oxygen is blown is generated, the oxygen concentration of the molten steel is increased, and the cleanliness of the molten steel is deteriorated.
[0004]
In general, the ladle slag of Al deoxidized steel is mainly composed of CaO and Al 2 O 3 , and (mass% CaO) / (mass% Al 2 O 3 ) is 1.5 in consideration of desulfurization ability and fluidity. It is controlled to about ~ 3.
[0005]
When the Al 2 O 3 concentration is high, Al is reduced from the slag to the molten steel, the Al concentration in the molten steel increases, and it becomes difficult to produce Al ≦ 0.005 mass% of the steel material. When the Al 2 O 3 concentration is low and the CaO concentration is high, the melting temperature of the slag rises, and the molten steel temperature becomes solid slag at 1550 to 1600 ° C., the reactivity is remarkably deteriorated, and the production of low-sulfur steel is difficult. Become.
[0006]
Therefore, in the production of this steel material, it is necessary to clarify a slag composition that can be desulfurized while reducing the Al concentration in the molten steel.
In the present invention, since the toughness is lowered when the C content is high, C is targeted for steel materials with 0.20 mass% or less.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to provide a method for melting low Al, low S steel (steel containing Al ≦ 0.005 mass%, S ≦ 0.001 mass%) by controlling the slag composition.
[0008]
[Means for Solving the Problems]
Gist of the present invention, C ≦ 0.20mass%, Al ≦ 0.005mass%, a process for the preparation of including steel material to S ≦ 0.001mass%, Al 2 O 3 ≦ 20mass%, MgO = 5~15mass %, (Mass% CaO) / (mass% SiO 2 ) = 2.5 to 4.0 ladle slag composition, S ≦ 0.001 mass% low Al ultra-low sulfur steel melting method .
[0009]
Hereinafter, a method of melting low Al and low S steel (steel containing Al ≦ 0.005 mass%, S ≦ 0.001 mass%) will be described.
FIG. 1 shows the relationship between the basicity of slag representing desulfurization ability, (mass% CaO) / (mass% SiO 2 ) (hereinafter referred to as C / S) and the S concentration for each Al 2 O 3 concentration. S decreases with increasing basicity, but the effect decreases with C / S> 4. The melting temperature of slag rises, and the reactivity of slag metal deteriorates.
[0010]
FIG. 2 shows the influence of the Al 2 O 3 concentration of the slag on the Al concentration. As the Al 2 O 3 concentration increases, the Al concentration increases. The higher the basicity, the greater the increase. It is necessary to make the Al 2 O 3 concentration 20 mass% or less.
[0011]
By controlling the MgO concentration, the melting temperature for controlling the reaction rate of slag is controlled. FIG. 3 shows the relationship between the MgO concentration in the slag and the liquid phase ratio of the slag. When the MgO concentration is low, the liquid phase ratio is low. However, as the MgO concentration increases, the liquid phase ratio increases, and at 5 mass%, the liquid phase is almost 100%. Although the change in the liquid phase ratio is small as the MgO concentration increases, the solid phase is crystallized when it exceeds 15 mass%, so that the liquid phase ratio decreases. Moreover, the relationship between a liquid phase rate and S concentration of steel materials is shown in FIG. When the MgO concentration at which the liquid phase ratio is reduced is less than 5 mass% or more than 15 mass%, the reaction with slag is reduced, so that the S concentration of the steel material is increased. Therefore, the MgO concentration is controlled to 5 to 15 mass%.
[0012]
【Example】
Examples of the present invention are shown in Table 1 below.
In Example (1)-(5) of this invention, the steel materials of Al <= 0.005mass% and S <= 0.001mass% were able to be manufactured. However, in comparative examples (6) to (15), (8) to (15) are not achieved because S> 0.001 mass%, and (7) and (8) are also Al 2 O 3 > 20 mass%. The purpose was not achieved.
[0013]
[Table 1]
【The invention's effect】
According to the above, as the present invention, C ≦ 0.20mass%, Al ≦ 0.005mass%, the S ≦ 0.001% in the method for producing a including steel material, stably, following 0.0010Mass% Sulfur steel could be manufactured.
[Brief description of the drawings]
FIG. 1 shows the relationship between (mass% CaO) / (mass% SiO 2 ) in slag and the S concentration of steel.
[Fig. 2] Relationship between (mass% Al 2 O 3 ) in slag and Al concentration of steel.
FIG. 3 shows the relationship between (mass% MgO) in slag and the liquid phase rate of slag.
FIG. 4 shows the relationship between (mass% MgO) in slag and the S concentration of steel.
Claims (1)
Ａｌ≦０．００５ｍａｓｓ％、
Ｓ≦０．００１ｍａｓｓ％、
を含む鋼材を製造する方法において、Ａｌ２Ｏ３≦２０ｍａｓｓ％、ＭｇＯ＝５〜１５ｍａｓｓ％、（ｍａｓｓ％ＣａＯ）／（ｍａｓｓ％ＳｉＯ２）＝２．５〜４．０の取鍋スラグ組成に制御し、Ｓ≦０．００１ｍａｓｓ％の低Ａｌ極低硫鋼の溶製方法。C ≦ 0.20 mass%,
Al ≦ 0.005 mass%,
S ≦ 0.001 mass%,
A process for the preparation of including steel material to, Al 2 O 3 ≦ 20mass% , MgO = 5~15mass%, (mass% CaO) / ladle slag (mass% SiO 2) = 2.5~4.0 A method for producing a low Al ultra-low-sulfur steel having a composition controlled to S ≦ 0.001 mass%.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08524195A JP3658037B2 (en) | 1995-04-11 | 1995-04-11 | Melting method of low Al ultra low sulfur steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08524195A JP3658037B2 (en) | 1995-04-11 | 1995-04-11 | Melting method of low Al ultra low sulfur steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08283825A JPH08283825A (en) | 1996-10-29 |
| JP3658037B2 true JP3658037B2 (en) | 2005-06-08 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP08524195A Expired - Fee Related JP3658037B2 (en) | 1995-04-11 | 1995-04-11 | Melting method of low Al ultra low sulfur steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3658037B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100530063B1 (en) * | 2001-12-13 | 2005-11-22 | 주식회사 포스코 | Method for Manufacturing Steel Including Aluminum and Sulfur |
-
1995
- 1995-04-11 JP JP08524195A patent/JP3658037B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| JPH08283825A (en) | 1996-10-29 |
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