JP2000199029A - Steel sheet and steel pipe excellent in carbon dioxide corrosion resistance and sulfide stress cracking resistance and production thereof - Google Patents
Steel sheet and steel pipe excellent in carbon dioxide corrosion resistance and sulfide stress cracking resistance and production thereofInfo
- Publication number
- JP2000199029A JP2000199029A JP11002049A JP204999A JP2000199029A JP 2000199029 A JP2000199029 A JP 2000199029A JP 11002049 A JP11002049 A JP 11002049A JP 204999 A JP204999 A JP 204999A JP 2000199029 A JP2000199029 A JP 2000199029A
- Authority
- JP
- Japan
- Prior art keywords
- carbon dioxide
- resistance
- steel sheet
- sulfide stress
- steel
- 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.)
- Withdrawn
Links
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、ラインパイプにお
いて、耐炭酸ガス腐食性と耐硫化物応力割れ性に優れた
ラインパイプ用鋼板および鋼管に関わるものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel pipe and a steel pipe for a line pipe which are excellent in carbon dioxide gas corrosion resistance and sulfide stress cracking resistance.
【０００２】[0002]
【従来の技術】近年、天然ガスは炭酸ガスと共に硫化水
素を随伴する資源も対象とされるようになり、従来適用
されてきた炭素鋼や低合金鋼等の油井管、或いはライン
パイプでは、炭酸ガスに対する耐食性（以下、耐炭酸ガ
ス腐食性という）又は硫化水素に対する耐食性（以下、
耐硫化物応力腐食割れ性という）の点で問題となる事例
が発生している。2. Description of the Related Art In recent years, natural gas has become a target for resources accompanied by hydrogen sulfide together with carbon dioxide gas. Corrosion resistance to gas (hereinafter, referred to as carbon dioxide corrosion resistance) or corrosion resistance to hydrogen sulfide (hereinafter, referred to as
(Sulfide stress corrosion cracking resistance).
【０００３】炭酸ガスと共に硫化水素が混入する天然ガ
ス資源に適用する油井管、或いはラインパイプとして
は、従来、炭酸ガスや硫化水素の分圧が低い場合は、比
較的耐食性（耐炭酸ガス腐食性と耐硫化物応力腐食割れ
性）が優れた低合金鋼を適用するが、それらの分圧が高
い場合は、ステンレス鋼等の高合金鋼を使用してきた。
このような炭酸ガスと硫化水素が共存する天然ガス環境
下では、炭酸ガスに起因する全面腐食と共に硫化水素に
起因する硫化物応力腐食割れが腐食形態となる。[0003] Conventionally, oil well pipes or line pipes applied to natural gas resources in which hydrogen sulfide is mixed with carbon dioxide gas have relatively low corrosion resistance (carbon dioxide corrosion resistance) when the partial pressure of carbon dioxide gas or hydrogen sulfide is low. And low sulfide stress corrosion cracking resistance), but when their partial pressure is high, high alloy steel such as stainless steel has been used.
In a natural gas environment in which carbon dioxide and hydrogen sulfide coexist, sulfide stress corrosion cracking due to hydrogen sulfide and corrosion morphology due to hydrogen sulfide take the form of corrosion.
【０００４】耐硫化物応力腐食割れの向上を目的とする
低合金ラインパイプ用鋼板もしくは鋼管については既に
多くの先行技術が開示されている。例えば、特開昭５８
−６９６１号公報には、Ｍｎ，Ｐ，Ｃの含有量を制御す
ることによって、また特開昭６３−４７３５２号公報に
は、Ｃｕを添加し、中心偏析組織の硬度を規制すること
によって、さらに、特開昭５５−１２８５３６号公報に
はＣａ等を添加して介在物の形状を制御することによっ
て、それぞれ耐水素誘起割れ（ＨＩＣ）性を改善した鋼
が開示されている。[0004] Many prior arts have already been disclosed for steel plates or pipes for low alloy line pipes for the purpose of improving sulfide stress corrosion cracking resistance. For example, Japanese Patent Application Laid-Open
In JP-A-6961, the content of Mn, P, and C is controlled, and in JP-A-63-47352, Cu is added to regulate the hardness of the central segregation structure. JP-A-55-128536 discloses steels in which the shape of inclusions is controlled by adding Ca or the like to thereby improve the resistance to hydrogen-induced cracking (HIC).
【０００５】また、従来、炭酸ガス環境においては、全
面腐食量を低減させるためにＣｒの添加が有効であるこ
とは公知であり、例えば特公昭５３−１８６６３号公報
には、Ｃｒを含有する耐炭酸ガス腐食性に優れた油井管
用鋼が開示されている。さらに、特公平７−１０６４５
５号公報には耐炭酸ガス腐食性に優れたパイプライン用
鋼管およびその円周溶接部の溶接方法に関する内容が開
示されている。Further, it has been known that the addition of Cr is effective in reducing the overall corrosion amount in a carbon dioxide gas environment. For example, Japanese Patent Publication No. 53-18663 discloses a resistance to Cr containing Cr. An oil country tubular steel excellent in carbon dioxide gas corrosion is disclosed. In addition, Tokuhei 7-10645
No. 5 discloses a steel pipe for a pipeline excellent in carbon dioxide gas corrosion resistance and a method for welding a circumferentially welded portion thereof.
【０００６】しかし、これらの従来技術では、炭酸ガス
と硫化水素が共存する天然ガス環境下において、耐硫化
物応力割れ性と耐全面腐食性を共に満足できるレベルに
改善させることはできなかった。また、これらの従来技
術では、硫化物応力腐食割れの発生条件が解明されてい
ないため、応力腐食割れを定量的に抑制する技術として
確立されていなかった。However, these conventional techniques cannot improve both the resistance to sulfide stress cracking and the resistance to general corrosion in a natural gas environment in which carbon dioxide and hydrogen sulfide coexist. Further, in these conventional techniques, since the conditions under which sulfide stress corrosion cracking occurs are not clarified, a technique for quantitatively suppressing stress corrosion cracking has not been established.
【０００７】[0007]
【発明が解決しようとする課題】本発明は、炭酸ガスと
共に硫化水素が共存する環境において使用する鋼に関し
て、先に述べた従来技術の問題点に対処する耐炭酸ガス
腐食性および耐硫化物応力腐食割れ性の優れた性能を有
する鋼板および鋼管とその製造方法を提供することを目
的とするものである。SUMMARY OF THE INVENTION The present invention is directed to a steel for use in an environment where hydrogen sulfide coexists with carbon dioxide, which addresses the above-mentioned problems of the prior art with respect to carbon dioxide corrosion resistance and sulfide stress. It is an object of the present invention to provide a steel sheet and a steel pipe having excellent performance of corrosion cracking and a method for producing the same.
【０００８】[0008]
【課題を解決するための手段】発明者らは、上記課題を
達成するために鋭意検討を行った結果、従来、耐炭酸ガ
ス腐食性を向上させるために用いられてきたＣｒの添加
は、炭酸ガスと硫化水素が共存する環境下では、必ずし
も多量に添加することは好ましくなく、Ｃｒ添加量が１
％を越える領域では、かえって炭酸ガス起因の全面腐食
量を増加させ、さらに耐硫化物応力腐食割れ性も低下さ
せることがわかった。Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the addition of Cr, which has been conventionally used for improving the corrosion resistance to carbon dioxide gas, is limited to the addition of carbon dioxide. In an environment where gas and hydrogen sulfide coexist, it is not always desirable to add a large amount,
%, It was found that the amount of overall corrosion caused by carbon dioxide gas was increased and the resistance to sulfide stress corrosion cracking was also reduced.
【０００９】さらに本発明者らは、炭酸ガスと硫化水素
が共存する環境下では、Ｃｒと共にＣｕの複合添加が炭
酸ガス起因の全面腐食量の低減に有効であること、かつ
硫化水素起因の耐硫化物応力割れ性を向上させるには硫
化物の圧延断面方向の最大長さ（ａ）と中心偏析帯の最
高硬さ（Ｈｖ）が０．００２１（Ｈｖ）＋１／４ｌｏｇ
（ａ）−０．９≦０の関係式を満足するように硫化物の
サイズと中心偏析帯の硬さを制御することが極めて重要
であることを見いだした。Further, the present inventors have found that in an environment where carbon dioxide gas and hydrogen sulfide coexist, the combined addition of Cu with Cr is effective in reducing the overall corrosion amount caused by carbon dioxide gas, and the resistance to hydrogen sulfide is reduced. In order to improve the sulfide stress cracking property, the maximum length (a) of the sulfide in the rolling section direction and the maximum hardness (Hv) of the center segregation zone are 0.0021 (Hv) + ／ log.
(A) It has been found that it is extremely important to control the size of the sulfide and the hardness of the central segregation zone so as to satisfy the relational expression of -0.9 ≦ 0.
【００１０】本発明は、これらの知見に基づいてなされ
たものであり、すなわち、本発明鋼の要旨は次の通りで
ある。 （１）重量％で、Ｃ ：０．０１〜０．１０％、Ｓｉ：
０．０２〜０．５０％、Ｍｎ：０．６〜２．０％、Ｐ
：≦０．０３０％、Ｓ ：≦０．０３０％、Ｃｒ：
０．１〜１．０％、Ｃｕ：０．１〜１．５％、Ａｌ：≦
０．０５％、を含有し、残部が鉄および不可避的不純物
からなり、かつ介在物の圧延断面方向の最大長さ（ａ）
と中心偏析帯の最高硬さ（Ｈｖ）が下記の関係式を満た
すことを特徴とする耐炭酸ガス腐食性および耐硫化物応
力割れ性に優れた鋼板。The present invention has been made based on these findings, that is, the gist of the steel of the present invention is as follows. (1) By weight%, C: 0.01 to 0.10%, Si:
0.02 to 0.50%, Mn: 0.6 to 2.0%, P
: ≦ 0.030%, S: ≦ 0.030%, Cr:
0.1-1.0%, Cu: 0.1-1.5%, Al: ≦
0.05%, the balance being iron and unavoidable impurities, and the maximum length of inclusions in the rolling section direction (a)
And a steel sheet having excellent carbon dioxide corrosion resistance and sulfide stress cracking resistance, characterized in that the maximum hardness (Hv) of the center segregation zone satisfies the following relational expression.
【００１１】０．００２１（Ｈｖ）＋１／４ｌｏｇ
（ａ）−０．９≦０ （２）さらに、重量％で、Ｔｉ：０．００５〜０．０５
０％、Ｍｇ：０．０００１〜０．００５０％、Ｏ ：
０．０００５〜０．００８０％、を含み、かつ重量％
で、Ｚｒ：０．００５〜０．０５０％、Ｔａ：０．００
５〜０．０５０％、のうちの１種または２種を含有する
ことを特徴とする上記（１）に記載の耐炭酸ガス腐食性
および耐硫化物応力割れ性に優れた鋼板。0.0021 (Hv) + ／ log
(A) −0.9 ≦ 0 (2) Further, in weight%, Ti: 0.005 to 0.05
0%, Mg: 0.0001 to 0.0050%, O:
0.0005 to 0.0080%, and by weight
And Zr: 0.005 to 0.050%, Ta: 0.00
The steel sheet having excellent carbon dioxide corrosion resistance and sulfide stress cracking resistance according to the above (1), wherein the steel sheet contains one or two of 5 to 0.050%.
【００１２】（３）さらに、重量％で、Ｎｂ：０．００
５〜０．１０％、Ｖ ：０．００５〜０．１０％、Ｎｉ
：０．０５〜２．０％、Ｍｏ ：０．０２〜１．５０
％、Ｂ ：０．０００３〜０．００３０％、のうちの
１種または２種以上を含有することを特徴とする上記
（１）または（２）の何れか１つの項に記載の耐炭酸ガ
スおよび耐硫化物応力割れ性に優れた鋼板。(3) Further, by weight%, Nb: 0.00
5 to 0.10%, V: 0.005 to 0.10%, Ni
: 0.05 to 2.0%, Mo: 0.02 to 1.50
%, B: 0.0003% to 0.0030% of the carbon dioxide resistant gas according to any one of the above items (1) and (2), wherein one or more types are contained. And steel sheet with excellent sulfide stress cracking resistance.
【００１３】（４）さらに、重量％で、Ｃａ ：０．０
００５〜０．００５％、ＲＥＭ：０．０００５〜０．０
０５％、のうちの１種または２種を含有することを特徴
とする上記（１）〜（３）の何れか１つの項に記載の耐
炭酸ガス腐食性および耐硫化物応力割れ性に優れた鋼
板。(4) Further, in terms of% by weight, Ca: 0.0
005-0.005%, REM: 0.0005-0.0
Excellent in carbon dioxide gas corrosion resistance and sulfide stress cracking resistance as described in any one of the above items (1) to (3), characterized by containing one or two of the above. Steel plate.
【００１４】（５）重量％で、Ｃ ：０．０１〜０．１
０％、Ｓｉ：０．０２〜０．５０％、Ｍｎ：０．６〜
２．０％、Ｐ ：≦０．０３０％、Ｓ ：≦０．０３０
％、Ｃｒ：０．１〜１．０％、Ｃｕ：０．１〜１．５
％、Ａｌ：≦０．０５％、を含有し、残部が鉄および不
可避的不純物からなる鋼片を１０００℃以上の温度に加
熱し、圧延終了温度がＡｒ３変態点以上なるように圧延
後、Ａｒ３変態点以上の温度から水冷を開始し、３００
℃以上６００℃以下の温度で水冷を停止することを特徴
とする耐炭酸ガスおよび耐硫化物応力割れ性に優れた鋼
板の製造方法。(5) C: 0.01-0.1% by weight
0%, Si: 0.02 to 0.50%, Mn: 0.6 to
2.0%, P: ≦ 0.030%, S: ≦ 0.030
%, Cr: 0.1 to 1.0%, Cu: 0.1 to 1.5
%, Al: ≦ 0.05%, and the balance is heated to a temperature of 1000 ° C. or more, the balance being iron and unavoidable impurities. Water cooling is started from the temperature above the transformation point,
A method for producing a steel sheet excellent in carbon dioxide gas resistance and sulfide stress cracking resistance, wherein water cooling is stopped at a temperature of not lower than 600C and not higher than 600C.
【００１５】（６）鋼片の成分として、さらに、重量％
で、Ｔｉ：０．００５〜０．０５０％、Ｍｇ：０．００
０１〜０．００５０％、Ｏ ：０．０００５〜０．００
８０％、を含み、かつ重量％で、Ｚｒ：０．００５〜
０．０５０％、Ｔａ：０．００５〜０．０５０％、のう
ちの１種または２種以上を含有することを特徴とする上
記（４）に記載の耐炭酸ガスおよび耐硫化物応力割れ性
に優れた鋼板の製造方法。(6) As a component of the billet, further,
And Ti: 0.005 to 0.050%, Mg: 0.00
01-0.0050%, O: 0.0005-0.00
80%, and by weight%, Zr: 0.005 to
0.050%, Ta: 0.005 to 0.050%, one or more of which are contained, the carbon dioxide resistance and the sulfide stress crack resistance according to the above (4), Excellent steel plate manufacturing method.
【００１６】（７）鋼片の成分として、さらに、重量％
で、Ｎｂ：０．００５〜０．１０％、Ｖ ：０．００５
〜０．１０％、Ｎｉ：０．０５〜２．０％、Ｍｏ：０．
０２〜１．５０％、Ｂ ：０．０００３〜０．００３０
％、のうち１種または２種以上を含有することを特徴と
する上記（５）または（６）の何れか１つの項に記載の
耐炭酸ガスおよび耐硫化物応力割れ性に優れた鋼板の製
造方法。(7) As a component of the billet, further,
And Nb: 0.005 to 0.10%, V: 0.005
-0.10%, Ni: 0.05-2.0%, Mo: 0.
02-1.50%, B: 0.0003-0.0030
% Of the steel sheet having excellent carbon dioxide gas resistance and sulfide stress cracking resistance according to any one of the above items (5) and (6), wherein Production method.
【００１７】（８）鋼片の成分として、さらに、重量％
で、Ｃａ ：０．０００５〜０．００５％、ＲＥＭ：
０．０００５〜０．００５％、のうちの１種または２種
を含有することを特徴とする上記（５）〜（７）の何れ
か１つの項に記載の耐炭酸ガスおよび耐硫化物応力割れ
性に優れた鋼板の製造方法。(8) As a component of the billet, further,
And Ca: 0.0005-0.005%, REM:
0.005 to 0.005%, wherein one or two of the above components are contained, and the carbon dioxide resistance and the sulfide resistance described in any one of the above items (5) to (7) are included. A method for manufacturing steel sheets with excellent cracking properties.
【００１８】（９）上記（１）から（４）の何れか１つ
に記載の鋼板を冷間成形後、溶接を施したことを特徴と
する耐炭酸ガス腐食性および耐硫化物応力腐食割れ性に
優れた鋼管。(9) The steel sheet according to any one of (1) to (4) is cold-formed, and then subjected to welding. Steel pipe with excellent properties.
【００１９】[0019]
【発明の実施の形態】図１は、Ｃｕを０．５％含有する
Ｘ６５ラインパイプ用鋼板を用いて、炭酸ガスと硫化水
素の共存環境下で実施した腐食試験の結果であり、鋼板
中のＣｒ含有量（wt％）と腐食速度（mm／ｙ）の関係を
示したものである。図中に示した点線（腐食速度＝０．
５mm／ｙ）は、使用限界腐食量を示す。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the results of a corrosion test conducted using a steel sheet for X65 line pipe containing 0.5% of Cu in an environment where carbon dioxide gas and hydrogen sulfide coexist. It shows the relationship between the Cr content (wt%) and the corrosion rate (mm / y). The dotted line shown in the figure (corrosion rate = 0.
5 mm / y) indicates the use limit corrosion amount.
【００２０】図１からＣｕとＣｒが複合添加された鋼の
腐食速度は、Ｃｕ共存下でＣｒ含有量が１wt％を超える
とむしろ腐食量が増加し、耐腐食性を向上させるための
Ｃｒ添加量の最適範囲は０．１〜１．０wt％であること
がわかる。図２は、様々な硫化水素分圧（ＰH2S ）およ
びpHの腐食環境下におけるＸ６５ラインパイプの鋼中水
素量を示す。FIG. 1 shows that the corrosion rate of steel with a complex addition of Cu and Cr is increased when the Cr content exceeds 1 wt% in the coexistence of Cu. It can be seen that the optimal range for the amount is 0.1-1.0 wt%. FIG. 2 shows the hydrogen content in the steel of the X65 line pipe under corrosive environments of various hydrogen sulfide partial pressures (P H2S ) and pH.
【００２１】ここで、試験は、様々の硫化水素分圧（Ｐ
H2S )(MPa)およびpHの環境下で９６時間試験片を浸漬さ
せ後、その試験片を４５℃グリセリンバスに７２時間浸
漬させて鋼中の水素量〔Ｈ０〕(ppm）を測定したもので
ある。また図２に示すプロットは全て割れが発生しなか
ったものであり、図中の記号（●○△）は、鋼種の違い
である。Here, the tests were carried out at various hydrogen sulfide partial pressures (P
A test piece was immersed in an environment of H2S ) (MPa) and pH for 96 hours, and then the test piece was immersed in a 45 ° C glycerin bath for 72 hours to measure the amount of hydrogen [H0] (ppm) in steel. is there. In addition, all plots shown in FIG. 2 show no cracks, and the symbols (●) in the figure indicate the difference in steel type.
【００２２】鋼中水素量は硫化水素分圧（ＰH2S ）の対
数の０．５倍に比例し、pHの−０．１５倍に比例する。
従って、図２において、鋼中水素量を（０．５ｌｏｇＰ
H2S−０．１５pH）で整理した。図２より制御圧延・制
御冷却したＸ６５ラインパイプの鋼中水素量〔Ｈ０〕(p
pm）と硫化水素分圧（ＰH2S )(MPa)およびpHとの関係
は、（１）式のように表される。The amount of hydrogen in steel is proportional to 0.5 times the logarithm of the partial pressure of hydrogen sulfide (P H2S ), and is proportional to -0.15 times the pH.
Therefore, in FIG. 2, the amount of hydrogen in the steel was set to (0.5 log P
H2S -0.15 pH). From FIG. 2, the hydrogen content [H0] (p
pm) and the partial pressure of hydrogen sulfide (P H2S ) (MPa) and pH are expressed as in equation (1).
【００２３】 〔Ｈ０〕＝３．１＋０．５６ｌｏｇＰH2S −０．１７pH （１） ここで、ＰH2S は硫化水素分圧（MPa)を意味する。図３
は、割れ限界水素量〔Ｈcrit〕(ppm）と介在物の圧延断
面方向の最大長さ（ａ）（μｍ）と中心偏析帯の最高硬
さの関係式を示したものである。破壊力学の式より割れ
限界水素量は介在物の長さの対数の１／４倍に比例する
ことが知られている。そこで、様々な鋼種において水素
誘起割れ試験を行い、その時の中心偏析帯の最高硬さ、
割れ限界水素量とさらに微小な水素誘起割れ（ＨＩＣ）
の起点（この場合の起点はほとんどがＭｎＳである）の
圧延断面方向の最大長さを求めた。その結果より、割れ
限界水素量〔Ｈcrit〕(ppm）と硫化物の圧延断面方向の
最大長さ（ａ）（μｍ）及び中心偏析帯の最高硬さ（Ｈ
ｖ）の関係は、（２）式のように表される。[0023] [H0] = 3.1 + 0.56logP H2S -0.17pH (1 ) where, P H2 S means hydrogen sulfide partial pressure (MPa). FIG.
Shows the relational expression between the crack limit hydrogen content [H crit ] (ppm), the maximum length (a) (μm) of the inclusion in the rolling section direction, and the maximum hardness of the central segregation zone. From the equation of fracture mechanics, it is known that the critical hydrogen content of cracking is proportional to 1/4 times the logarithm of the length of inclusions. Therefore, a hydrogen-induced cracking test was performed on various steel types, and the highest hardness of the central segregation zone at that time,
Cracking limit hydrogen content and even smaller hydrogen-induced cracking (HIC)
(The starting point in this case is almost always MnS) in the rolling section direction. From the results, it can be seen that the critical hydrogen content [H crit ] (ppm), the maximum length (a) (μm) of the sulfide in the rolling section direction, and the maximum hardness (H) of the central segregation zone
The relationship of v) is expressed as in equation (2).
【００２４】 ｌｏｇ〔Ｈcrit〕＝（１．２−０．００２１Ｈｖ）−０．２５ｌｏｇ（ａ）（ ２） （１）式および（２）式から、様々な硫化水素分圧およ
びpHの腐食環境下において硫化物応力腐食割れを抑制す
るための硫化物の限界サイズおよび限界中心偏析硬さが
導き出せることが可能になった。Log [H crit ] = (1.2-0.0021 Hv) -0.25 log (a) (2) From the equations (1) and (2), the corrosive environment at various hydrogen sulfide partial pressures and pHs Under this condition, it is possible to derive the critical size and critical center segregation hardness of sulfide for suppressing sulfide stress corrosion cracking.
【００２５】（１）式から最も厳しい腐食環境すなわち
ＮＡＣＥ環境（硫化水素分圧；０．１MPa, pH ; ３．
０）での鋼中水素量は２．０ppm であるので、ＮＡＣＥ
環境下での水素誘起割れが発生しない介在物の大きさと
中心偏析帯の最高硬さの関係式は（２）式より（３）式
のようになる。 ０．００２１Ｈｖ＋０．２５ｌｏｇａ−０．９≦０ （３） 従って、硫化物のサイズを出来る限り小さくし、中心偏
析帯の硬さを出来る限り低くすることによって、すべて
の硫化水素環境中で水素誘起割れが発生しなくなること
がわかる。From the equation (1), the most severe corrosive environment, that is, the NACE environment (hydrogen sulfide partial pressure; 0.1 MPa, pH;
Since the amount of hydrogen in steel in (0) is 2.0 ppm, NACE
The relational expression between the size of the inclusion where hydrogen-induced cracking does not occur under the environment and the maximum hardness of the central segregation zone is as shown in equation (3) from equation (2). 0.0021Hv + 0.25loga-0.9 ≦ 0 (3) Accordingly, by reducing the size of the sulfide as much as possible and making the hardness of the central segregation zone as low as possible, hydrogen-induced cracking can be achieved in all hydrogen sulfide environments. It can be seen that no longer occurs.
【００２６】ここで、硫化物の圧延断面方向の最大長さ
（ａ）とは、圧延断面全域に分布するＭｎＳの圧延方向
の長さの最大値を示す。通常は中心偏析帯に分布するＭ
ｎＳの圧延方向長さの最大値を示す。また、中心偏析帯
とは、板厚断面方向で、例えばＭｎ等の合金元素濃度が
その他の領域よりも高くなる領域を示す。通常は板厚断
面での中心部に存在する。Here, the maximum length (a) of the sulfide in the rolling section direction indicates the maximum value of the length in the rolling direction of MnS distributed over the entire rolling section. Usually, M distributed in the central segregation zone
It shows the maximum value of nS in the rolling direction. In addition, the center segregation zone indicates a region in which the concentration of an alloy element such as Mn is higher than other regions in the thickness direction of the cross section. Usually, it exists at the center in the thickness section.
【００２７】次に、硫化物を具体的に微細化させる方法
を以下に示す。発明者らの研究により酸化物および窒化
物が存在すると硫化物の優先核として硫化物が析出し、
酸化物もしくは窒化物を微細分散させれば硫化物もさら
に微細分散することが判明した。これは、析出する全硫
化物のＭｎ量とＳ量は一定であるためである。Next, a method for specifically refining sulfides will be described below. According to the study of the inventors, when oxides and nitrides are present, sulfides precipitate as preferential nuclei of sulfides,
It has been found that if oxides or nitrides are finely dispersed, sulfides are also finely dispersed. This is because the amount of Mn and the amount of S in all the sulfides precipitated are constant.
【００２８】また、Ｍｇ酸化物はあらゆる酸化物の中で
最も凝集しにくいため、酸化物を微細分散させるために
はＭｇを用いるのが最も有効であることが判明した。従
来からＭｇは強脱酸剤、脱硫剤として鋼の清浄度を高め
ることが知られているが、その酸化物が微細に分散する
ことは知られていなかった。本発明者らは、強脱酸剤で
あり、且つ凝集粗大化が起こりにくいＭｇの性質を利用
し、製鋼工程で他の弱脱酸剤との添加順序および添加量
を制御することで、生成する酸化物の微細分散が可能で
あることを見いだした。Further, since Mg oxide is the least likely to aggregate among all oxides, it has been found that Mg is most effective for finely dispersing the oxide. Conventionally, Mg has been known as a strong deoxidizing agent and a desulfurizing agent to increase the cleanliness of steel, but it has not been known that its oxide is finely dispersed. The present inventors made use of the property of Mg, which is a strong deoxidizing agent and hardly causes agglomeration, to control the order and amount of addition with other weak deoxidizing agents in the steelmaking process to produce It has been found that fine dispersion of oxides is possible.
【００２９】以下に、本発明の詳細について説明する。
本発明者らは、Ｔｉと共に他の弱脱酸剤により弱脱酸し
た溶鋼中に強脱酸剤のＭｇを添加した場合の酸化物の状
態を系統的に調査した。その結果、Ｔｉと共に、Ｔａ，
Ｚｒ等の他の弱脱酸剤を１種あるいは２種以上添加した
後、さらにＡｌおよびＭｇをある条件下で添加した場合
は、Ｔｉを単独で添加する場合に比較して、生成する酸
化物の粒子数増加及びサイズの微細化がなされることが
分かった。また、生成する酸化物と詳細に観察したとこ
ろ、比較的大きな（粒子径：０．２〜５．０μｍ）Ｍｇ
含有酸化物と超微細な（粒子径：０．００５〜０．１μ
ｍ）Ｍｇ含有酸化物あるいはＭｇＯが生成されることを
分かった。The details of the present invention will be described below.
The present inventors systematically investigated the state of the oxide when Mg, a strong deoxidizer, was added to molten steel weakly deoxidized with another weak deoxidizer together with Ti. As a result, together with Ti, Ta,
When one or more other weak deoxidizing agents such as Zr are added, and then Al and Mg are further added under certain conditions, the resulting oxides are produced more than when Ti is added alone. It was found that the number of particles and the size of the particles were reduced. Further, when the oxides formed were observed in detail, it was found that the oxides were relatively large (particle diameter: 0.2 to 5.0 μm).
Containing oxide and ultrafine (particle size: 0.005 to 0.1μ)
m) It was found that Mg-containing oxide or MgO was generated.
【００３０】これらのうちで、比較的粒径の大きいＭｇ
含有酸化物は、先に添加したＴｉ，Ｔａ，Ｚｒなどの弱
脱酸剤が、一旦、酸化物として生成するが、その後、こ
れらの酸化剤よりも脱酸力の強いＭｇやＡｌ等の強脱酸
剤の添加により、既に生成された酸化物がこれらの強脱
酸剤により還元され、最終的に粒径が０．２から５．０
μｍのＭｇ含有酸化物が生成されるものと思われる。Of these, Mg having a relatively large particle size
In the contained oxide, the weak deoxidizing agent such as Ti, Ta, or Zr previously added is once generated as an oxide, and thereafter, the strong deoxidizing agent such as Mg or Al has a stronger deoxidizing power than these oxidizing agents. By the addition of the deoxidizing agent, the already formed oxides are reduced by these strong deoxidizing agents, and finally the particle size becomes 0.2 to 5.0.
It is believed that a μm Mg-containing oxide is produced.
【００３１】一方、超微細な酸化物は、先に添加したＴ
ａやＴｉやＺｒ等の弱脱酸剤の酸化物の生成後に、残存
する溶存酸素と、ＭｇやＡｌとの酸化反応によって生成
したものと思われる。この際、Ｔｉを１種単独で添加す
る場合に比べて、Ｔｉと共にＴａやＺｒ等の弱脱酸剤を
１種又は２種以上添加する場合には、酸化物粒径がより
微細になるが、これは、弱脱酸剤の複合添加による溶存
酸素量の低下に加えて、溶存酸素の溶鋼中での分布の均
一化によって、生成する酸化物の凝集粗大化が抑制され
るためと推定される。On the other hand, the ultrafine oxide is obtained by adding the previously added T
It is presumed that after the formation of the oxide of the weak deoxidizing agent such as a, Ti or Zr, the remaining dissolved oxygen was formed by an oxidation reaction with Mg or Al. At this time, when one or two or more weak deoxidizing agents such as Ta and Zr are added together with Ti as compared with the case where Ti is added alone, the oxide particle size becomes finer. This is presumed to be due to the fact that, in addition to the reduction of the dissolved oxygen amount due to the combined addition of the weak deoxidizer, the distribution of the dissolved oxygen in the molten steel is made uniform, thereby suppressing the agglomeration of the generated oxide. You.
【００３２】以上のように、予めＴｉと共にＴａ及びＺ
ｒ等のその他の弱脱酸剤を１種以上添加することによ
り、溶鋼中の残存酵素量を調節するとともに、先に生成
したＴｉ，Ｔａ，Ｚｒの単独酸化物又はそれらの複合酸
化物をＡｌとＭｇの強酸化物で還元することによって、
Ｔｉ，Ｔａ，Ｚｒ等とＭｇとの複合酸化物またはＭｇＯ
酸化物を溶鋼中に微細に分散することができる。As described above, Ta and Z are previously set together with Ti.
By adding one or more other weak deoxidizing agents such as r, the amount of the residual enzyme in the molten steel is adjusted, and the previously generated single oxide of Ti, Ta, Zr or a composite oxide thereof is converted to Al. And reduction with a strong oxide of Mg,
Complex oxide of Mg with Ti, Ta, Zr, etc. or MgO
The oxide can be finely dispersed in the molten steel.
【００３３】予めＴｉと共にＴａ及びＺｒ等のその他の
弱脱酸剤を１種又は２種以上複合添加する場合は、生成
酸化物の凝集粗大化の防止のために、脱酸力の弱い方か
ら例えば、Ｔａ，ＴｉまたはＴｉ，Ｚｒの順序で添加す
るのが好ましい。また、ＡｌとＭｇの最適な添加量は、
Ｔｉ，Ｔａ，Ｚｒ等による弱脱酸後の溶鋼中に存在する
酸素量などに依存するが、残存酸素濃度を調整するため
のＴｉやＴａやＺｒ等の弱脱酸剤の添加量に応じて、Ａ
ｌやＭｇ添加量を適正な範囲で制御すれば良い。When one or more other weak deoxidizing agents such as Ta and Zr are added together with Ti in advance, in order to prevent the formed oxide from agglomerating and coarsening, the weaker deoxidizing agent is used. For example, it is preferable to add Ta and Ti or Ti and Zr in this order. The optimal addition amount of Al and Mg is
It depends on the amount of oxygen present in the molten steel after weak deoxidation by Ti, Ta, Zr, etc., but depends on the amount of weak deoxidizing agent such as Ti, Ta, Zr, etc. for adjusting the residual oxygen concentration. , A
What is necessary is just to control l and Mg addition amount in an appropriate range.
【００３４】なお、使用するＭｇの脱酸剤は、金属Ｍ
ｇ，Ｍｇ合金などの何れを用いても良い。このようにし
て鋼中に微細分散されたＭｇ含有酸化物は、鋳造時ある
いはその後の冷却過程や再加熱−熱間工程中に硫化物お
よび窒化物の優先核生成サイトになるため、硫化物応力
腐食割れの原因になるＭｎ含有硫化物の粗大化を抑制
し、Ｍｎ含有硫化物を微細分散することが可能となる。The deoxidizing agent for Mg used is metal M
Any of g and Mg alloys may be used. Since the Mg-containing oxide finely dispersed in the steel becomes a preferential nucleation site for sulfides and nitrides during casting or during a cooling process or a reheating-hot process, sulfide stress is reduced. It is possible to suppress the coarsening of the Mn-containing sulfide, which causes corrosion cracking, and to finely disperse the Mn-containing sulfide.
【００３５】以下に本発明の成分の限定理由について述
べる。 Ｃ：鋼における母材強度を向上させる基本的な元素とし
て欠かせない元素であり、その有効な下限として０．０
１％以上の添加が必要であるが、０．１０％を越える過
剰の添加では、微細な低温変態組織を形成する可能性が
あり、これが水素誘起割れもしくは硫化物応力腐食割れ
性の低下を招くので、その上限を０．１０％とした。The reasons for limiting the components of the present invention are described below. C: Element indispensable as a basic element for improving the base metal strength in steel, and 0.0 as an effective lower limit thereof
Addition of 1% or more is necessary, but excessive addition exceeding 0.10% may form a fine low-temperature transformation structure, which leads to a decrease in hydrogen-induced cracking or sulfide stress corrosion cracking. Therefore, the upper limit was set to 0.10%.
【００３６】Ｓｉ：製鋼上脱酸元素として必要な元素で
あり、鋼中に０．０２％以上の添加が必要であるが、
０．５％を越えるとＨＡＺ靱性を低下させるのでそれを
上限とする。 Ｍｎ：母材の強度および靱性の確保に必要な元素である
が、２．０％を越えると水素誘起割れ性あるいは硫化物
応力割れ性を著しく阻害するが、逆に０．６％未満で
は、母材の強度確保が困難になるために、その範囲を
０．６〜２．０％とする。Si: an element necessary as a deoxidizing element in steel making, and it is necessary to add 0.02% or more to steel.
If it exceeds 0.5%, the HAZ toughness is reduced, so the upper limit is made. Mn: an element necessary for securing the strength and toughness of the base material. If it exceeds 2.0%, hydrogen-induced cracking property or sulfide stress cracking property is significantly impaired. Since it is difficult to secure the strength of the base material, the range is set to 0.6 to 2.0%.
【００３７】Ｐ：鋼の靱性に影響を与える元素であり、
０．０３０％を越えて含有すると鋼材の母材だけでなく
ＨＡＺの靱性を著しく阻害するのでその含有される上限
を０．０３０％とした。 Ｓ：０．０３０％を越えて過剰に添加されると粗大な硫
化物の生成の原因となり、耐水素誘起割れ性、耐応力腐
食割れ性を著しく低下させるためその含有される上限を
０．００３０％とした。P: an element that affects the toughness of steel,
When the content exceeds 0.030%, not only the base material of the steel material but also the toughness of HAZ is significantly impaired, so the upper limit of the content is set to 0.030%. S: Excessive addition exceeding 0.030% causes the formation of coarse sulfides and significantly reduces the resistance to hydrogen-induced cracking and the resistance to stress corrosion cracking. %.
【００３８】Ｃｒ：本発明が適用される炭酸ガスと硫化
水素を含有する環境において全面腐食を抑制するために
は有効な元素である。本発明では、耐応力腐食割れ性を
向上させるためにＣｕと共に添加することを要件とする
が、この場合、炭酸ガスに起因する全面腐食の限界腐食
量（０．５mm／ｙ）以下とするためには、Ｃｒ含有量の
下限を０．１％とする必要がある。また、Ｃｕ共存下で
の多量のＣｒ量は腐食量を増加させるのでＣｒ添加量の
上限を１．０％とする。Cr: an element effective for suppressing general corrosion in an environment containing carbon dioxide and hydrogen sulfide to which the present invention is applied. In the present invention, in order to improve the stress corrosion cracking resistance, it is required to be added together with Cu. In this case, in order to reduce the total corrosion limit (0.5 mm / y) due to carbon dioxide gas to 0.5 mm / y or less. Requires the lower limit of the Cr content to be 0.1%. Further, since a large amount of Cr in the presence of Cu increases the amount of corrosion, the upper limit of the amount of added Cr is set to 1.0%.
【００３９】Ｃｕ：炭酸ガスと硫化水素を含有する環境
において有効な元素であるが、多量の添加は熱間加工と
溶接性の低下を招く。０．０５％未満では効果がなく、
１．５％を越えると鋼片加熱時や溶接時に割れを生じや
すくする。従って、その含有量を０．０５〜１．５％以
下とする。 Ａｌ：通常脱酸材として添加されるが、本発明において
は、０．０５％越えて添加されるとＭｇの添加の効果を
阻害するために、これを上限とした。Cu: an element effective in an environment containing carbon dioxide gas and hydrogen sulfide, but the addition of a large amount causes hot working and deterioration of weldability. Less than 0.05% has no effect,
If it exceeds 1.5%, cracks are likely to occur during heating of the slab or welding. Therefore, the content is set to 0.05 to 1.5% or less. Al: Usually added as a deoxidizing agent, but in the present invention, if added over 0.05%, the effect of the addition of Mg is impaired, so the upper limit was set.
【００４０】Ｍｇ：主に脱酸材として添加されるが、
０．００５０％を越えて添加されると、粗大な酸化物が
生成し易くなり、母材およびＨＡＺ靱性の低下をもたら
す。しかしながら、０．０００１％未満の添加では、ピ
ニング粒子として必要な酸化物の生成が十分に期待でき
なくなるため、その添加範囲を０．０００１〜０．００
５０％と限定する。Mg: mainly added as a deoxidizer,
If it is added in excess of 0.0050%, coarse oxides are likely to be formed, resulting in a decrease in base material and HAZ toughness. However, if the addition is less than 0.0001%, the formation of oxides required as pinning particles cannot be sufficiently expected, so the addition range is 0.0001 to 0.00.
Limited to 50%.
【００４１】Ｔｉ：脱酸材として、さらには窒化物形成
元素として結晶粒の細粒化に効果を発揮する元素である
が、多量の添加は炭化物の形成による靱性の著しい低下
をもたらすために、その上限を０．０５０％にする必要
があるが、所定の効果を得るためには０．００３％以上
の添加が必要であり、その範囲を０．００５〜０．０５
０％とする。Ti: an element that exerts an effect on grain refinement of crystal grains as a deoxidizing material and also as a nitride-forming element, but when added in a large amount, the formation of carbides causes a significant decrease in toughness. The upper limit must be 0.050%, but in order to obtain a predetermined effect, 0.003% or more must be added, and the range is 0.005 to 0.05.
0%.
【００４２】Ｚｒ，Ｔａ：上記Ｔｉと同様に脱酸材とし
て用い、Ｔｉとともに本発明具現化のために必須の元素
であり、その効果はＴｉと同時に添加されることで初め
て発揮される。また、それ自身炭化物形成能力が高いた
めＯ量およびＴｉ／Ｎ比を考えて、適切な量にする必要
がある。すなわち、Ｔｉと同様に多量の添加は炭化物の
形成による靱性の著しい低下をもたらすために、その上
限を０．０５０％にする制限するが、所定の効果を得る
ためには０．０００１％以上の添加が必要であり、その
範囲を０．０００１〜０．０５％とする。Zr, Ta: Used as a deoxidizing material in the same manner as Ti, and is an essential element for realizing the present invention together with Ti. The effect is exhibited only when added simultaneously with Ti. In addition, since the carbide itself has a high ability to form carbides, it is necessary to consider the amount of O and the Ti / N ratio to make the amount appropriate. That is, as in the case of Ti, the addition of a large amount causes a remarkable decrease in toughness due to the formation of carbides. Therefore, the upper limit is limited to 0.050%, but in order to obtain a predetermined effect, 0.0001% or more. Addition is necessary, and the range is made 0.0001 to 0.05%.
【００４３】Ｏ：硫化物の生成サイトとなるＭｇ含有酸
化物を生成させるための必須元素である。０．０００５
未満では酸化物の個数が十分とはならないために、０．
０００５％を下限値とする。一方、０．００８０％を越
えて添加されると、粗大な酸化物が生成し易くなり、硫
化物の微細分散効果が得られず、また母材およびＨＡＺ
靱性の低下をもたらす。従って、上限値を０．００８０
％とした。O: an essential element for generating an Mg-containing oxide serving as a sulfide generation site. 0.0005
If it is less than 0.1, the number of oxides will not be sufficient.
0005% is the lower limit. On the other hand, if it is added in excess of 0.0080%, coarse oxides are likely to be formed, and the effect of fine dispersion of sulfide cannot be obtained.
This leads to a decrease in toughness. Therefore, the upper limit is 0.0080
%.
【００４４】なお、本発明においては、強度および靱性
を改善するために、Ｎｂ，Ｖ，Ｎｉ，Ｍｏ，Ｂの中から
１種または２種以上を選択的に添加してもよい。Ｎｂ，
Ｖは炭化物、窒化物を形成し強度の向上に効果がある元
素であるが、０．００５％以下の添加ではその効果がな
く、０．１０％を越える添加では、逆に靱性の低下を招
くために、その範囲を０．００５〜０．１０％以下とす
る。In the present invention, one or more of Nb, V, Ni, Mo, and B may be selectively added in order to improve strength and toughness. Nb,
V is an element that forms carbides and nitrides and is effective in improving the strength, but has no effect when added in an amount of 0.005% or less, and conversely causes a decrease in toughness when added in an amount exceeding 0.10%. Therefore, the range is made 0.005 to 0.10% or less.
【００４５】Ｎｉ：靱性および強度の改善に有効な元素
であり、その効果を得るためには０．０５％以上の添加
が必要であるが、２．０％以上の添加では溶接性が低下
するために、その上限を２．０％とする。 Ｍｏ：焼入れ性を向上させると同時に、炭窒化物を形成
し強度を改善する元素であり、その効果を得るために
は、０．０２％以上の添加が必要になるが、１．５０％
を越えた多量の添加は必要以上の強化とともに、靱性の
著しい低下をもたらすために、その範囲を０．０５〜
０．５０％以下とする。Ni: an element effective for improving toughness and strength. To obtain the effect, addition of 0.05% or more is necessary, but addition of 2.0% or more lowers weldability. Therefore, the upper limit is set to 2.0%. Mo: an element that forms a carbonitride and improves the strength at the same time as improving the hardenability. To obtain the effect, it is necessary to add 0.02% or more, but 1.50%
The addition of a large amount exceeds the required amount, together with unnecessarily strengthening, causes a marked decrease in toughness.
0.50% or less.
【００４６】Ｂ：一般に、固溶すると焼入れ性を増加さ
せるが、またＢＮとして固溶Ｎを低下させ、溶接熱影響
部の靱性を向上させる元素である。従って、０．０００
５％以上の添加でその効果を利用できるが、過剰の添加
は、靱性の低下を招くために、その上限を０．００３０
％とする。さらに、本発明では、硫化物の形態制御のた
めに、Ｃａ及びＲＥＭを１種又は２種選択的に添加する
ことができる。B: Generally, quenching properties are increased when a solid solution is formed. However, BN is an element that reduces solid solution N and improves the toughness of the heat affected zone. Therefore, 0.000
The effect can be utilized with the addition of 5% or more. However, the excessive addition causes a decrease in toughness.
%. Further, in the present invention, one or two kinds of Ca and REM can be selectively added for controlling the form of sulfide.
【００４７】Ｃａ及びＲＥＭは硫化物を生成することに
より伸長ＭｎＳの生成を抑制し、鋼材の板厚方向の特
性、特に耐ラメラティアー性を改善するが、０．０００
５％未満では、この効果が得られないので下限値を０．
０００５％にする必要がある。また、０．００３０％を
越えると、Ｃａ及びＲＥＭの酸化物個数が増加し、超微
細なＭｇ含有酸化物の個数が低下するため、その上限を
０．００３０％とする。Ca and REM suppress the formation of elongation MnS by forming sulfides and improve the properties in the thickness direction of the steel material, particularly the lamella tear resistance, but 0.000%.
If it is less than 5%, this effect cannot be obtained, so the lower limit is set to 0.
0005%. If the content exceeds 0.0030%, the number of oxides of Ca and REM increases, and the number of ultrafine Mg-containing oxides decreases. Therefore, the upper limit is made 0.0030%.
【００４８】さらに、本発明では、鋼板の耐硫化物応力
腐食割れ性を向上させるために、組織中のＭｎＳ等のＭ
ｎ含有硫化物の圧延断面最大長さ（ａ）と中心偏析帯の
最大硬さ（Ｈｖ）が０．００２１（Ｈｖ）＋０．２５ｌ
ｏｇ（ａ）−０．９０≦０の関係式を満足することを要
件とする。ここで、ａは、ＭｎＳ等のＭｎ含有硫化物の
圧延断面方向の最大長さを示す。また、Ｈｖは、中心偏
析帯の最高硬さを示す。Further, in the present invention, in order to improve the sulfide stress corrosion cracking resistance of the steel sheet, M
The maximum cross-sectional length (a) of the n-containing sulfide and the maximum hardness (Hv) of the central segregation zone are 0.0021 (Hv) +0.25 l.
og (a) −0.90 ≦ 0. Here, a indicates the maximum length of the Mn-containing sulfide such as MnS in the rolling section direction. Hv indicates the highest hardness of the central segregation zone.
【００４９】次に、本発明の鋼板の製造方法について述
べる。本発明では、上記の０．００２１（Ｈｖ）＋０．
２５ｌｏｇ（ａ）−０．９０≦０の関係式を満たす鋼板
中の硫化物の圧延断面最大長さ（ａ）と中心偏析帯の最
大硬さ（Ｈｖ）を得るために、以下のように加熱、圧
延、冷却条件を規定する必要がある。Next, a method for manufacturing a steel sheet according to the present invention will be described. In the present invention, the above 0.0021 (Hv) +0.
In order to obtain the maximum rolled cross-sectional length (a) of sulfide and the maximum hardness (Hv) of the central segregation zone in a steel sheet satisfying the relational expression of 25 log (a)-0.90 ≤ 0, heating is performed as follows. , Rolling and cooling conditions need to be defined.
【００５０】加熱温度は、加熱時にＴｉ，Ｎｂ等の強化
元素を充分に固溶させるために１０００℃以上に限定す
る。圧延終了温度および圧延後の水冷開始温度は、Ａｒ
３未満になるとフェライトが生成し、フェライト周辺に
硬化組織が生成することにより、水素誘起割れ性および
硫化物応力割れ性を劣化させるためにＡｒ３以上に規定
する。The heating temperature is limited to 1000 ° C. or more in order to sufficiently dissolve the strengthening elements such as Ti and Nb during heating. The rolling end temperature and the water cooling start temperature after the rolling are Ar
When the value is less than 3, ferrite is formed, and a hardened structure is formed around the ferrite, thereby deteriorating the hydrogen-induced cracking property and the sulfide stress cracking property.
【００５１】また、水冷停止温度は、３００℃未満にす
ると低温変態生成物が生じ、６００℃を超えると硬化組
織が生成し、いずれの場合にも水素誘起割れ性、硫化物
応力割れ性を劣化させるために３００℃以上６００℃以
下に規定する。以上に示した鋼板の製造方法を採用する
と中心偏析の硬さ（Ｈｖ）が低減できるので、０．００
２１（Ｈｖ）＋０．２５ｌｏｇ（ａ）−０．９０≦０を
満足させやすくする。When the water cooling stop temperature is less than 300 ° C., a low-temperature transformation product is generated, and when it exceeds 600 ° C., a hardened structure is formed, and in any case, the hydrogen-induced cracking property and the sulfide stress cracking property are deteriorated. For this purpose, the temperature is specified to be 300 ° C. or more and 600 ° C. or less. Since the hardness (Hv) of the center segregation can be reduced by adopting the manufacturing method of the steel sheet described above,
21 (Hv) + 0.25log (a) −0.90 ≦ 0 is easily satisfied.
【００５２】なお、本発明では、上記の製造方法で得ら
れた鋼板を用いて、更に冷間成形してＯ形状に変形後、
溶接を行い、その後、真円度を出すために拡管を行って
得られた鋼管も対象とする。In the present invention, the steel sheet obtained by the above manufacturing method is further cold-formed and deformed into an O shape.
Steel pipes obtained by welding and then expanding the pipes to achieve roundness are also included.
【００５３】[0053]
【実施例】（実施例１）次に、本発明の実施例について
述べる。転炉による溶製、連続鋳造を経て得られた表１
に示す化学成分を含有する鋼片を用いて、表１に示す製
造条件で熱間圧延を行い、厚さ２０mmの厚鋼板を製造し
た。この鋼板を更に冷間成形、溶接、拡管を行い、ＵＯ
Ｅ鋼管とした。この時の降伏強度は４５０〜５５０MPa
の範囲に調整している。(Embodiment 1) Next, an embodiment of the present invention will be described. Table 1 obtained through melting and continuous casting by a converter
Using a steel slab containing the chemical components shown in Table 1, hot rolling was performed under the manufacturing conditions shown in Table 1 to produce a thick steel plate having a thickness of 20 mm. This steel sheet is further cold-formed, welded and expanded, and the UO
An E steel pipe was used. The yield strength at this time is 450-550MPa
Is adjusted to the range.
【００５４】これらの鋼板の耐全面腐食性を評価するた
めに、鋼板表面より３mmｔ×１５mmＷ×２０mmＬの鋼板
を切り出し、機械研磨後＃３２０エメリー研磨を行っ
た。その後、８％ＮａＣｌ溶液（硫化水素分圧０．００
１MPa ，ＣＯ2 分圧０．１MPa，pH３．８の溶液）中に
浸漬させて、その腐食量を求めた。試験時間は９６時間
である。In order to evaluate the overall corrosion resistance of these steel sheets, a steel sheet of 3 mmt × 15 mmW × 20 mmL was cut out from the surface of the steel sheet, and subjected to mechanical polishing and # 320 emery polishing. Then, an 8% NaCl solution (hydrogen sulfide partial pressure 0.00
1 MPa, CO 2 partial pressure 0.1 MPa, pH 3.8 solution) to determine the amount of corrosion. The test time is 96 hours.
【００５５】また、耐水素誘起割れ性を評価するため
に、鋼板の中心部より１９mmｔ×２０mmＷ×１００mmＬ
の鋼板を切り出し、機械研磨後＃３２０エメリー研磨を
行った。その後、ＮＡＣＥ溶液（硫化水素分圧０．１MP
a ，pH３．０の溶液）中に浸漬させた。試験時間は９６
時間である。試験終了後、４５℃のグリセリン液中に７
２時間浸漬させ、鋼中水素量を測定した。その後ＵＳＴ
にて割れの発生有無をＵＳＴで測定し、割れ断面面積率
（ＣＡＲ）を求めた。Further, in order to evaluate the resistance to hydrogen-induced cracking, the center of the steel sheet was 19 mmt × 20 mmW × 100 mmL.
Was cut out, mechanically polished and # 320 emery polished. Then, a NACE solution (hydrogen sulfide partial pressure 0.1MPa)
a, pH 3.0 solution). Testing time is 96
Time. After the test is completed, put 7% in glycerin solution at 45 ° C.
After immersion for 2 hours, the amount of hydrogen in the steel was measured. Then UST
The presence or absence of cracks was measured by UST, and the crack sectional area ratio (CAR) was determined.
【００５６】また、耐水素誘起割れ性の発生した部分を
液体窒素により破面出しを行い、介在物の組成および介
在物の圧延方向の長さを測定し、中心偏析帯の最高硬さ
を求めた。鋼１〜１４は本発明例を示す。表１から明ら
かなように、これらの鋼板およびＵＯＥ鋼管は、本発明
で規定する硫化物の圧延断面方向の最大長さ（ａ）と中
心偏析帯の最高硬さ（Ｈｖ）の式で満足し、硫化水素と
炭酸ガスが存在する環境下での腐食速度が０．５mm／ｙ
以下でかつ、ＮＡＣＥ溶液中でも水素誘起割れが発生し
ない。Further, the portion where the hydrogen-induced cracking resistance was generated was fractured by liquid nitrogen, the composition of the inclusions and the length of the inclusions in the rolling direction were measured, and the maximum hardness of the central segregation zone was determined. Was. Steels 1 to 14 show examples of the present invention. As apparent from Table 1, these steel sheets and UOE steel pipes are satisfied by the formulas of the maximum length (a) of the sulfide in the rolling section direction and the maximum hardness (Hv) of the center segregation zone specified in the present invention. Corrosion rate in an environment where hydrogen sulfide and carbon dioxide gas are present is 0.5 mm / y
No hydrogen-induced cracking occurs even in a NACE solution.
【００５７】それに対し、鋼１５〜２４は本発明の範囲
から逸脱した比較例を示す。すなわち、鋼１５，１６，
１７，１８，１９は基本成分の内、それぞれＭｎ，Ｓ，
Ｃ，Ｃｒ，Ｃｕの元素が、発明の用件を越えて添加され
ている例であり、鋼２０，２１はＣｒまたはＣｕが添加
されていない例である。鋼２２，２３，２４はＭｇ，
Ｏ，Ｔｉがそれぞれ過剰に添加されている。On the other hand, steels 15 to 24 show comparative examples which deviate from the scope of the present invention. That is, steel 15, 16,
17, 18, and 19 represent Mn, S, and
This is an example in which elements C, Cr, and Cu are added beyond the scope of the invention, and steels 20, 21 are examples in which Cr or Cu is not added. Steels 22, 23 and 24 are made of Mg,
O and Ti are excessively added.
【００５８】特に、比較鋼の１５，１６，１７はＭｎＳ
の最大長さが７００〜１０００μｍとかなり大きいこ
と、１５，１７，１８，１９の中心偏析最高硬さが２９
０〜３５０Ｈｖと高いので０．００２１Ｈｖ−０．２５
ｌｏｇ（ａ）−０．９≦０の式を満足しないために水素
誘起割れが発生した。さらに１８，１９は炭酸ガスと硫
化水素共存下での腐食速度が０．５mm／ｙを越えてい
る。In particular, the comparative steels 15, 16, and 17 were MnS
Has a very large maximum length of 700 to 1000 μm, and the maximum segregation center hardness of 15, 17, 18, and 19 is 29.
0.0021Hv-0.25 because it is as high as 0 to 350Hv
Since the expression of log (a) -0.9 ≦ 0 was not satisfied, hydrogen-induced cracking occurred. Further, in Examples 18 and 19, the corrosion rate in the coexistence of carbon dioxide and hydrogen sulfide exceeded 0.5 mm / y.
【００５９】また、鋼２２〜２４は微細な酸化物も多く
存在しているが、過剰のＭｇあるいはＯが添加された事
に起因することによる粗大な介在物が存在したためであ
る。鋼２５，２６は水冷停止温度が３００〜６００℃の
範囲に入っていないために硬化組織が生成し、中心偏析
硬さが硬くなったため水素誘起割れが発生した。The steels 22 to 24 also have many fine oxides, but have coarse inclusions due to the addition of excessive Mg or O. Steels 25 and 26 had hardened structures because the water cooling stop temperature was not in the range of 300 to 600 ° C., and hydrogen-induced cracking occurred because the center segregation hardness was high.
【００６０】[0060]
【表１】 [Table 1]
【００６１】[0061]
【表２】 [Table 2]
【００６２】（実施例２）転炉でＴｉ，Ｍｇ以外の合金
を添加する。ＴｉおよびＭｇの添加は２次精錬で行う。
Ｔｉを添加した１０分後にＭｇ合金を溶鋼中に吹き込
む。さらに１０分後に連続鋳造を行い、スラブにする。
スラブを例えば１２００℃に加熱し、中心部が１２００
℃に到達した６０分後にスラブを抽出し、１０００〜１
１００℃の温度域で１００mmまで粗圧延を行った後、９
５０℃の温度域で２０mmまで厚板での仕上げ圧延を行
う。その後９００℃で水冷を開始し、４５０℃で停止さ
せる。このような製造条件を採用したことにより、硫化
物が微細化され、中心偏析帯の硬さも低減されたことに
より、得られた鋼板は圧延断面方向の硫化物の長さの最
大（ａ）と中心偏析帯の最高硬さ（Ｈｖ）の関係式を満
足していた。(Example 2) In a converter, an alloy other than Ti and Mg is added. The addition of Ti and Mg is performed by secondary refining.
Ten minutes after the addition of Ti, the Mg alloy is blown into the molten steel. After another 10 minutes, continuous casting is performed to form a slab.
The slab is heated, for example, to 1200 ° C.
The slab was extracted 60 minutes after the temperature reached
After rough rolling to 100mm in the temperature range of 100 ° C, 9
Finish rolling is performed on a thick plate up to 20 mm in a temperature range of 50 ° C. Thereafter, water cooling is started at 900 ° C and stopped at 450 ° C. By adopting such manufacturing conditions, the sulfides are refined and the hardness of the central segregation zone is also reduced, so that the obtained steel sheet has a maximum sulfide length (a) in the rolling section direction. The relational expression of the maximum hardness (Hv) of the center segregation zone was satisfied.
【００６３】この鋼板を冷間形成し、仮づけ溶接、内外
面溶接を行う。この時の入熱量は例えば３．５ｋＪ／c
m、溶接速度は１．８mm／min である。その後拡管を行
い、ＵＯＥ鋼管とした。この鋼管を実施例１に示す炭酸
ガス環境下での腐食試験および水素誘起割れ試験を行
い、炭酸ガス環境下での腐食試験は０．５mm／ｙ以下で
かつ、ＮＡＣＥ溶液でも水素誘起割れが発生しなかっ
た。This steel sheet is cold-formed, and tack welding and inner / outer surface welding are performed. The heat input at this time is, for example, 3.5 kJ / c.
m, the welding speed is 1.8 mm / min. Thereafter, expansion was performed to obtain a UOE steel pipe. This steel pipe was subjected to a corrosion test and a hydrogen-induced cracking test in a carbon dioxide gas environment as shown in Example 1. The corrosion test in a carbon dioxide gas environment was 0.5 mm / y or less, and hydrogen-induced cracking occurred even in a NACE solution. Did not.
【００６４】[0064]
【発明の効果】本発明により、炭酸ガスおよび硫化水素
の共存環境下において優れた耐炭酸ガス腐食性と耐水素
誘起割れ性、耐応力腐食割れ性を有するラインパイプ用
鋼板および鋼管を提供することが可能となった。According to the present invention, there is provided a steel plate and a steel pipe for a line pipe having excellent carbon dioxide gas corrosion resistance, hydrogen-induced cracking resistance, and stress corrosion cracking resistance in an environment where carbon dioxide and hydrogen sulfide coexist. Became possible.
【図１】炭酸ガスと硫化水素環境における腐食量に及ぼ
すＣｒ量の影響を示す図。FIG. 1 is a diagram showing the effect of the amount of Cr on the amount of corrosion in an environment of carbon dioxide and hydrogen sulfide.
【図２】様々な硫化水素分圧およびpHにおけるＸ６５ラ
インパイプの鋼中水素量との関係を示す図。FIG. 2 is a graph showing the relationship between the hydrogen content in steel of an X65 line pipe at various hydrogen sulfide partial pressures and pHs.
【図３】割れ限界水素量〔Ｈcrit〕と介在物の大きさ
（ａ）と中心偏析帯の最高硬さの関係式を示す図。FIG. 3 is a view showing a relational expression between a crack limit hydrogen content [H crit ], the size (a) of inclusions, and the maximum hardness of a central segregation zone.
───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.7 識別記号 ＦＩ テーマコート゛(参考） Ｃ２２Ｃ 38/54 Ｃ２２Ｃ 38/54 (72)発明者 植森 龍治 千葉県富津市新富20−１ 新日本製鐵株式 会社技術開発本部内 (72)発明者 為広 博 千葉県富津市新富20−１ 新日本製鐵株式 会社技術開発本部内 Ｆターム(参考） 4K032 AA01 AA02 AA04 AA05 AA11 AA12 AA14 AA15 AA16 AA17 AA19 AA20 AA22 AA23 AA26 AA27 AA29 AA31 AA33 AA35 AA36 AA39 BA01 CA02 CA03 CC04 CD06 ──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. 7 Identification symbol FI Theme coat ゛ (Reference) C22C 38/54 C22C 38/54 (72) Inventor Ryuji Uemori 20-1 Shintomi, Futtsu City, Chiba Prefecture Made in New Japan (72) Hiroshi Tamehiro, Inventor 20-1 Shintomi, Futtsu-shi, Chiba F-term (reference) in Nippon Steel Corporation Technology Development Division 4K032 AA01 AA02 AA04 AA05 AA11 AA12 AA14 AA15 AA16 AA17 AA19 AA20 AA22 AA23 AA26 AA27 AA29 AA31 AA33 AA35 AA36 AA39 BA01 CA02 CA03 CC04 CD06
Claims (9)
つ介在物の圧延断面方向の最大長さ（ａ）と中心偏析帯
の最高硬さ（Ｈｖ）が下記の関係式を満たすことを特徴
とする耐炭酸ガス腐食性および耐硫化物応力割れ性に優
れた鋼板。 ０．００２１（Ｈｖ）＋１／４ｌｏｇ（ａ）−０．９≦
０C: 0.01 to 0.1%, Si: 0.02 to 0.5%, Mn: 0.6 to 2%, P: ≦ 0.03%, S: ≦ 0.03%, Cr: 0.1-1%, Cu: 0.1-1.5%, Al: ≦ 0.05%, the balance being iron and unavoidable impurities and intervening Excellent in carbon dioxide gas corrosion resistance and sulfide stress cracking resistance, characterized in that the maximum length (a) in the rolling section direction of the product and the maximum hardness (Hv) of the center segregation zone satisfy the following relational expression. steel sheet. 0.0021 (Hv) + ／ log (a) −0.9 ≦
0
求項１に記載の耐炭酸ガス腐食性および耐硫化物応力割
れ性に優れた鋼板。2. The composition according to claim 2, further comprising: Ti: 0.005 to 0.05%, Mg: 0.0001 to 0.005%, O: 0.0005 to 0.008%, and% by weight. The corrosion resistant carbon dioxide gas according to claim 1, wherein one or two of Zr: 0.005 to 0.05% and Ta: 0.005 to 0.05% are contained. Steel sheet with excellent resistance and sulfide stress cracking resistance.
る請求項１または請求項２の何れかの項に記載の耐炭酸
ガスおよび耐硫化物応力割れ性に優れた鋼板。Further, Nb: 0.005 to 0.1%, V: 0.005 to 0.1%, Ni: 0.05 to 2%, Mo: 0.02 to 1.0% by weight%. 5%, B: 0.0003% to 0.003%, wherein at least one of them is contained, and the carbon dioxide resistant gas according to any one of claims 1 and 2, and Steel sheet with excellent sulfide stress cracking resistance.
求項１〜請求項３の何れか１つの項に記載の耐炭酸ガス
腐食性および耐硫化物応力割れ性に優れた鋼板。4. The composition according to claim 1, further comprising at least one of Ca: 0.0005 to 0.005% and REM: 0.0005 to 0.005% by weight. The steel sheet according to any one of claims 1 to 3, which is excellent in carbon dioxide gas corrosion resistance and sulfide stress cracking resistance.
を１０００℃以上の温度に加熱し、圧延終了温度がＡｒ
３変態点以上なるように圧延後、Ａｒ３変態点以上の温
度から水冷を開始し、３００℃以上６００℃以下の温度
で水冷を停止することを特徴とする耐炭酸ガスおよび耐
硫化物応力割れ性に優れた鋼板の製造方法。5. In% by weight, C: 0.01 to 0.1%, Si: 0.02 to 0.5%, Mn: 0.6 to 2%, P: ≦ 0.03%, S: ≦ 0.03%, Cr: 0.1-1%, Cu: 0.1-1.5%, Al: ≦ 0.05%, with the balance being iron and unavoidable impurities. Heat to a temperature of 1000 ° C. or higher and finish the rolling at Ar
After rolling to at least three transformation points, water cooling is started at a temperature of at least Ar3 transformation point, and water cooling is stopped at a temperature of at least 300 ° C. and at most 600 ° C., which is resistant to carbon dioxide and sulfide stress cracking. Excellent steel plate manufacturing method.
る請求項４に記載の耐炭酸ガスおよび耐硫化物応力割れ
性に優れた鋼板の製造方法。6. The steel slab further contains, by weight, Ti: 0.005 to 0.05%, Mg: 0.0001 to 0.005%, O: 0.0005 to 0.008%, And at least one of Zr: 0.005 to 0.050% and Ta: 0.005 to 0.05% by weight. The method for producing a steel sheet having excellent carbon dioxide gas resistance and sulfide stress crack resistance described in 1.
請求項５または請求項６の何れか１つの項に記載の耐炭
酸ガスおよび耐硫化物応力割れ性に優れた鋼板の製造方
法。7. As a component of the billet, Nb: 0.005 to 0.1%, V: 0.005 to 0.1%, Ni: 0.05 to 2%, Mo: 0.02 to 1.5%, B: 0.0003 to 0.003%, wherein one or more of the following are contained: any one of claims 5 or 6, A method for producing a steel sheet having excellent resistance to carbon dioxide and sulfide stress cracking as described.
求項５〜請求項７の何れか１つの項に記載の耐炭酸ガス
および耐硫化物応力割れ性に優れた鋼板の製造方法。8. The steel slab further contains one or two of Ca: 0.0005 to 0.005% and REM: 0.0005 to 0.005% by weight. The method for producing a steel sheet excellent in carbon dioxide gas resistance and sulfide stress cracking resistance according to any one of claims 5 to 7, characterized in that:
の鋼板を冷間成形後、溶接を施したことを特徴とする耐
炭酸ガス腐食性および耐硫化物応力腐食割れ性に優れた
鋼管。9. The steel sheet according to claim 1, which is cold-formed and then welded, and has excellent carbon dioxide gas corrosion resistance and sulfide stress corrosion cracking resistance. Steel pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11002049A JP2000199029A (en) | 1999-01-07 | 1999-01-07 | Steel sheet and steel pipe excellent in carbon dioxide corrosion resistance and sulfide stress cracking resistance and production thereof |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11002049A JP2000199029A (en) | 1999-01-07 | 1999-01-07 | Steel sheet and steel pipe excellent in carbon dioxide corrosion resistance and sulfide stress cracking resistance and production thereof |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2000199029A true JP2000199029A (en) | 2000-07-18 |
Family
ID=11518488
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11002049A Withdrawn JP2000199029A (en) | 1999-01-07 | 1999-01-07 | Steel sheet and steel pipe excellent in carbon dioxide corrosion resistance and sulfide stress cracking resistance and production thereof |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2000199029A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002137058A (en) * | 2000-10-26 | 2002-05-14 | Kawasaki Steel Corp | Production method for corrosion-resistant, high-strength oil well steel pipe joint and high-strength oil well steel pipe joint |
| WO2004106572A1 (en) * | 2003-05-28 | 2004-12-09 | Sumitomo Metal Industries, Ltd. | Oil well steel pipe to be placed under ground and be expanded |
| JP2009221534A (en) * | 2008-03-15 | 2009-10-01 | Jfe Steel Corp | Steel sheet for line pipe |
| CN103160753A (en) * | 2011-12-14 | 2013-06-19 | 鞍钢股份有限公司 | Zr-containing sulfuric acid dew point corrosion resistant steel plate and manufacturing method thereof |
| TWI427160B (en) * | 2008-03-04 | 2014-02-21 | Kobe Steel Ltd | Corrosion resistance of the ship with excellent steel |
| CN108546884A (en) * | 2018-06-20 | 2018-09-18 | 南京钢铁股份有限公司 | A kind of acid-resistant pipeline steel and pipe-making method |
| CN108866432A (en) * | 2018-06-20 | 2018-11-23 | 南京钢铁股份有限公司 | A kind of acid-resistant pipeline steel and smelting process |
| CN108893677A (en) * | 2018-06-20 | 2018-11-27 | 南京钢铁股份有限公司 | A kind of acid-resistant pipeline steel and production method |
| CN114381664A (en) * | 2021-12-22 | 2022-04-22 | 南阳汉冶特钢有限公司 | Production method of thick X80MS steel plate for corrosion-resistant pipeline |
-
1999
- 1999-01-07 JP JP11002049A patent/JP2000199029A/en not_active Withdrawn
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002137058A (en) * | 2000-10-26 | 2002-05-14 | Kawasaki Steel Corp | Production method for corrosion-resistant, high-strength oil well steel pipe joint and high-strength oil well steel pipe joint |
| WO2004106572A1 (en) * | 2003-05-28 | 2004-12-09 | Sumitomo Metal Industries, Ltd. | Oil well steel pipe to be placed under ground and be expanded |
| US7082992B2 (en) | 2003-05-28 | 2006-08-01 | Sumitomo Metal Industries, Ltd. | Oil well steel pipe for embedding-expanding |
| EA008418B1 (en) * | 2003-05-28 | 2007-04-27 | Сумитомо Метал Индастриз, Лтд. | Oil well steel pipe to be placed under ground and be expanded |
| TWI427160B (en) * | 2008-03-04 | 2014-02-21 | Kobe Steel Ltd | Corrosion resistance of the ship with excellent steel |
| JP2009221534A (en) * | 2008-03-15 | 2009-10-01 | Jfe Steel Corp | Steel sheet for line pipe |
| CN103160753A (en) * | 2011-12-14 | 2013-06-19 | 鞍钢股份有限公司 | Zr-containing sulfuric acid dew point corrosion resistant steel plate and manufacturing method thereof |
| CN108546884A (en) * | 2018-06-20 | 2018-09-18 | 南京钢铁股份有限公司 | A kind of acid-resistant pipeline steel and pipe-making method |
| CN108866432A (en) * | 2018-06-20 | 2018-11-23 | 南京钢铁股份有限公司 | A kind of acid-resistant pipeline steel and smelting process |
| CN108893677A (en) * | 2018-06-20 | 2018-11-27 | 南京钢铁股份有限公司 | A kind of acid-resistant pipeline steel and production method |
| CN114381664A (en) * | 2021-12-22 | 2022-04-22 | 南阳汉冶特钢有限公司 | Production method of thick X80MS steel plate for corrosion-resistant pipeline |
| CN114381664B (en) * | 2021-12-22 | 2022-11-22 | 南阳汉冶特钢有限公司 | Production method of thick X80MS steel plate for corrosion-resistant pipeline |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP1546417B1 (en) | High strength seamless steel pipe excellent in hydrogen-induced cracking resistance and its production method | |
| KR101331976B1 (en) | Method of manufacturing sheet steel for thick-walled sour-resistant line pipe of excellent toughness | |
| JP3898814B2 (en) | Continuous cast slab for high strength steel with excellent low temperature toughness and its manufacturing method, and high strength steel with excellent low temperature toughness | |
| JP7147960B2 (en) | Steel plate and its manufacturing method | |
| JP2009197327A (en) | Hollow member and method for production thereof | |
| JP4700740B2 (en) | Manufacturing method of steel plate for sour line pipe | |
| JP2001152248A (en) | Method for producing high tensile strength steel plate and steel pipe excellent in low temperature toughness | |
| JP2000345281A (en) | Low alloy heat resistant steel excellent in weldability and low temperature toughness, and its production | |
| WO2006132441A1 (en) | Oil well pipe for expandable-tube use excellent in toughness after pipe expansion and process for producing the same | |
| JP2000199029A (en) | Steel sheet and steel pipe excellent in carbon dioxide corrosion resistance and sulfide stress cracking resistance and production thereof | |
| JP2000160245A (en) | Production of high strength steel excellent in hic resistance | |
| JP2002129281A (en) | High tensile strength steel for welding structure excellent in fatigue resistance in weld zone and its production method | |
| JP2001234238A (en) | Producing method for highly wear resistant and high toughness rail | |
| JP2007138210A (en) | Steel sheet for high strength line pipe in with reduced lowering of yield stress caused by bauschinger effect and its production method | |
| JP2000256777A (en) | High tensile strength steel plate excellent in strength and low temperature toughness | |
| JP2002047531A (en) | High tensile strength steel for welded structure having excellent fatigue characteristic and its production method | |
| CN109778070B (en) | Steel plate and production method thereof | |
| JP2002348609A (en) | Method for manufacturing steel with high strength for line pipe superior in hic resistance | |
| JP2001140041A (en) | Chromium stainless steel with double layer structure for spring and producing method therefor | |
| JPS6043433A (en) | Manufacture of clad steel plate with superior corrosion resistance and toughness | |
| JP2003328080A (en) | High-strength steel pipe superior in low-temperature toughness and deformability, and method for manufacturing steel plate for steel pipe | |
| JPH09137253A (en) | High tensile strength steel excellent in stress corrosion cracking resistance and low temperature toughness and its production | |
| JP4038166B2 (en) | Steel plate excellent in earthquake resistance and weldability and manufacturing method thereof | |
| JP2003293039A (en) | Method for producing high strength steel plate and steel pipe with low content of coarse crystal grin and having excellent low temperature toughness | |
| JPH03211230A (en) | Production of low alloy steel for line pipe with high corrosion resistance |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A300 | Withdrawal of application because of no request for examination |
Free format text: JAPANESE INTERMEDIATE CODE: A300 Effective date: 20060307 |