JPS624826A - Manufacture of high strength and toughness steel plate for line pipe superior in characteristic for stopping unstable ductility fracture propagation - Google Patents
Manufacture of high strength and toughness steel plate for line pipe superior in characteristic for stopping unstable ductility fracture propagationInfo
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- JPS624826A JPS624826A JP14521185A JP14521185A JPS624826A JP S624826 A JPS624826 A JP S624826A JP 14521185 A JP14521185 A JP 14521185A JP 14521185 A JP14521185 A JP 14521185A JP S624826 A JPS624826 A JP S624826A
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Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
本発明は、不安定延性破壊伝播停止特性にすぐれた高強
度高靭性ラインパイプ用鋼板の製造方法に関し、詳しく
は、シャルピー吸収エネルギー値が高く、且つ、高い強
度と低い遷移温度を有して、圧延ままにて、例えば、天
然ガス等の気体の輸送ラインパイプ用鋼板として用いる
ことができる不安定延性破壊伝播停止特性にすぐれた高
強度高靭性ラインパイプ用鋼板の製造方法に関する。Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a high-strength, high-toughness steel plate for line pipes that has excellent properties of unstable ductile fracture propagation arrest. In addition, it has high strength and low transition temperature, and can be used as a steel plate for transportation line pipes for gases such as natural gas, for example, in the as-rolled state. The present invention relates to a method for producing a tough steel plate for line pipes.
（従来の技術）
天然ガス等の気体の輸送用ラインパイプの耐破壊設計に
おいては、脆性破壊のみならず、不安定延性破壊に対す
る配慮も必要とされる。即ち、天然ガス等の気体は、液
体に比較して圧縮比が大きく、且つ、その減圧速度が遅
いために、脆性破壊よりも速度の遅い延性破壊も伝播し
やすいからである。(Prior Art) In the fracture-resistant design of line pipes for transporting gases such as natural gas, it is necessary to consider not only brittle fracture but also unstable ductile fracture. That is, gases such as natural gas have a higher compression ratio than liquids and have a slower rate of decompression, so ductile fractures, which are slower than brittle fractures, are more likely to propagate.
脆性破壊は、材料の遷移温度以下の領域で生じるので、
パイプの使用温度を材料の遷移温度以上とすれば、長距
離伝播の脆性破壊を防止し得る。Because brittle fracture occurs below the material's transition temperature,
If the operating temperature of the pipe is higher than the transition temperature of the material, brittle fracture propagating over long distances can be prevented.
しかし、不安定延性破壊は、材料の遷移温度以上におい
ても発生伝播する。この不安定延性破壊の伝播防止に関
してば、パイプの設計周方向応力に応じて、材料がある
一定値以上のシャルピー吸収エネルギーを有することが
必要とされている。即ち、不安定延性破壊の伝播を防止
するには、パイプの使用温度において、高いシャルピー
吸収エネルギーを有する鋼板の使用が不可欠である。However, unstable ductile fracture occurs and propagates even above the transition temperature of the material. In order to prevent the propagation of unstable ductile fracture, the material is required to have a Charpy absorbed energy of a certain value or more, depending on the designed circumferential stress of the pipe. That is, in order to prevent the propagation of unstable ductile fracture, it is essential to use a steel plate that has a high Charpy absorbed energy at the temperature at which the pipe is used.
従来、Ｘ７０級以上の高強度高靭性ラインパイプ用鋼板
は、所謂制御圧延法にて製造されており、この方法によ
れば、結晶粒の微細化によって圧延ままにて鋼板に所定
の強度とすぐれた靭性、即ち、耐脆性破壊特性を付与す
ることができる。また、近年においては、所謂加速冷却
法によっても、この種の鋼板が製造され始めている。こ
の方法による場合も、鋼板の耐脆性破壊特性は、加速冷
却工程の前に行なわれる制御圧延工程によって付与され
るものであり、従って、その高靭性化機構は、制御圧延
法と基本的に同じである。Conventionally, high-strength, high-toughness steel sheets for line pipes of grade X70 or higher have been manufactured by the so-called controlled rolling method. According to this method, the steel sheets are given a predetermined strength and excellent properties in the as-rolled state by refining the grains. It is possible to impart additional toughness, that is, brittle fracture resistance. In recent years, this type of steel sheet has also begun to be manufactured by the so-called accelerated cooling method. Even when using this method, the brittle fracture resistance of the steel sheet is imparted by the controlled rolling process that is performed before the accelerated cooling process, and therefore, the mechanism for increasing toughness is basically the same as that of the controlled rolling process. It is.
これら制御圧延法又は加速冷却法によって製造される鋼
板は、圧延仕上温度を下げ、未再結晶域での圧下を十分
にとり、結晶粒を微細化することによって、高靭性を確
保しているため、遷移温度は著しく低温側に位置するが
、一方において、シャルピー吸収エネルギーは、−穀圧
延材や調質材に比べて著しく低い。換言すれば、従来の
制御圧延法或いは加速冷却法によって製造されている高
強度高靭性ラインパイプ用鋼板は、すぐれた脆性破壊伝
播停止特性を有しているが、不安定延性破壊伝播停止特
性に著しく劣る。この結果、天然ガスラインパイプへの
これら鋼板の使用が制限されている。Steel sheets manufactured by these controlled rolling methods or accelerated cooling methods have high toughness by lowering the rolling finish temperature, sufficiently reducing the rolling in the non-recrystallized area, and refining the grains. The transition temperature is significantly lower, but on the other hand, the Charpy absorbed energy is significantly lower than that of grain-rolled materials and tempered materials. In other words, high-strength, high-toughness steel sheets for line pipes manufactured by conventional controlled rolling or accelerated cooling methods have excellent brittle fracture propagation arresting properties, but they have poor ductile fracture propagation arresting properties. Significantly inferior. As a result, the use of these steel plates in natural gas line pipes is limited.
（発明の目的）
本発明者らは、気体用ラインパイプ用鋼板における上記
した問題を解決するために、圧延ままにてすぐれた不安
定延性破壊伝播停止特性と脆性破壊特性とを兼ね備えた
高強度ラインパイプ用鋼板を得るべく、鋭意研究した結
果、所定の化学組成を有する鋼を所定の条件下に圧延し
、冷却して、鋼板の主要組織を微細ベイナイトとするこ
とによって、シャルピー吸収エネルギーが飛躍的に向上
すると共に、遷移温度も顕著に改善された鋼板を得るこ
とができることを見出して、本発明に至ったものである
。(Purpose of the Invention) In order to solve the above-mentioned problems in steel plates for gas line pipes, the present inventors have developed a high-strength steel plate that combines excellent unstable ductile fracture propagation arresting properties and brittle fracture properties in as-rolled condition. As a result of intensive research to obtain steel plates for line pipes, we found that by rolling steel with a specific chemical composition under specific conditions and cooling it to make the main structure of the steel plate fine bainite, the Charpy absorbed energy dramatically increased. The inventors have discovered that it is possible to obtain a steel plate with significantly improved transition temperature as well as improved thermal stability, and have thus arrived at the present invention.
従って、本発明は、不安定延性破壊伝播停止特性にすぐ
れた高強度高靭性ラインパイプ用鋼板の製造方法を提供
することを目的とする。Accordingly, an object of the present invention is to provide a method for producing a high-strength, high-toughness steel plate for line pipes that has excellent characteristics of arresting unstable ductile fracture propagation.
（発明の構成）
本発明による不安定延性破壊伝播停止特性にすぐれた高
強度高靭性ラインパイプ用鋼板の製造方法は、重量％で
Ｃ０．０１〜０．０６％、
Ｓｉ０．５０％以下、
Ｍｎ １．５〜２．５％、
Ｓ ０．００６％以下、
Ｎｂ ０．００５〜０゜０８０％、
Ｔｉ ０．００５〜０．０３０％、
Ｂ ０．０００５〜０．００３０％、Ａβ ０．０
０５〜０．０６０％、
Ｎ ０．００１５〜ｏ、 ｏ ｏ ｓ ｏ％、残部
鉄及び不可避的不純物よりなるスラブをＡｒ２〜Ａｒｚ
＋ １００℃の温度範囲で熱間圧延を終了し、その後
直ちに５℃／秒以上の冷却速度で加速冷却を行ない、４
００℃以下の温度で加速冷却を停止して、主要組織をベ
イナイトとすることを特徴とする。(Structure of the Invention) The method for producing a high strength, high toughness steel plate for line pipes having excellent unstable ductile fracture propagation arresting properties according to the present invention comprises: C0.01 to 0.06%, Si 0.50% or less, Mn in weight%. 1.5-2.5%, S 0.006% or less, Nb 0.005-0°080%, Ti 0.005-0.030%, B 0.0005-0.0030%, Aβ 0.0
Ar2~Arz
Hot rolling is finished in a temperature range of +100°C, and then accelerated cooling is immediately performed at a cooling rate of 5°C/second or more, and 4
It is characterized in that accelerated cooling is stopped at a temperature of 00° C. or lower, and the main structure is bainite.
本発明の方法によるかかる鋼板は、降伏強度５０ ｋｇ
ｆ／ｍｍ”以上、降伏比８５％以下、シャルピー吸収エ
ネルギー（ｖＬ４ｏ） １０ｋｇｆ−ｍ以上、及び破面
遷移温度（νＴｒｓ）−８０℃以下を有する。Such a steel plate according to the method of the invention has a yield strength of 50 kg
f/mm" or more, yield ratio of 85% or less, Charpy absorbed energy (vL4o) of 10 kgf-m or more, and fracture surface transition temperature (vTrs) of -80°C or less.
以下、本発明について詳細に説明する。The present invention will be explained in detail below.
本発明者らは、圧延ままにて高いシャルピー吸収エネル
ギーに加えて、低い遷移温度と高い降伏強度を同時に鋼
板に付与するには、圧延後の冷却によって鋼板の主要組
織を微細ベイナイトとすると共に、靭性を劣化させる島
状マルテンサイトの生成を極力抑えることが有効である
ことを見出した。そこで、本発明の方法においては、圧
延後の加速冷却によって鋼板の主要組織が微細ベイナイ
トとなるように十分な焼入れ性を有し、且つ、シャルピ
ー吸収エネルギーを低下させる非金属介在物の少ないス
ラブを製造し得るように、スラブの化学組成を下記のと
おりに規定する。The present inventors believe that in order to simultaneously impart high Charpy absorbed energy, low transition temperature, and high yield strength to a steel sheet in the as-rolled state, the main structure of the steel sheet should be made into fine bainite by cooling after rolling, and It has been found that it is effective to suppress the formation of island martensite that deteriorates toughness as much as possible. Therefore, in the method of the present invention, a slab is produced which has sufficient hardenability so that the main structure of the steel sheet becomes fine bainite by accelerated cooling after rolling, and has few nonmetallic inclusions that reduce Charpy absorbed energy. The chemical composition of the slab is defined as follows so that it can be manufactured.
Ｃは、靭性を劣化させる島状マルテンサイトの生成を抑
制するために、その添加量を０．０６％以下とする。し
かし、鋼の強度を確保するために、０．０１％以上を添
加する必要がある。The amount of C added is 0.06% or less in order to suppress the formation of island martensite that deteriorates toughness. However, in order to ensure the strength of steel, it is necessary to add 0.01% or more.
Ｓｔは、製鋼時の脱酸剤として必要であるが、過多に添
加するときは靭性を低下させるので、添加量の上限を０
．５０％とする。St is necessary as a deoxidizing agent during steel manufacturing, but when added in excess it reduces toughness, so the upper limit of the amount added is set to 0.
．． It shall be 50%.
Ｍｎは、焼入れ性を確保するために、本発明においては
１．５％以上を添加することが必要であるが、過多に添
加するときは、溶接性を劣化させるので、添加量の上限
を２．５％とする。In the present invention, it is necessary to add Mn in an amount of 1.5% or more in order to ensure hardenability, but since adding too much Mn deteriorates weldability, the upper limit of the amount added is set at 2. .5%.
Ｓは、シャルピー吸収エネルギーを低下させる元素であ
るので、本発明においては、Ｓの含有量は０．００６％
以下とする。S is an element that lowers Charpy absorption energy, so in the present invention, the S content is 0.006%.
The following shall apply.
Ｎｂは、強度及び靭性の向上に有効であるが、添加量が
０．００５％よりも少ないときは、この効果に乏しく、
一方、０．０８０％を越えて過多に添加するときは、溶
接熱影響部の靭性が劣化する。Nb is effective in improving strength and toughness, but when the amount added is less than 0.005%, this effect is poor,
On the other hand, when added in excess of 0.080%, the toughness of the weld heat affected zone deteriorates.
従って、本発明においては、その添加量を０．００５〜
０．０８０％の範囲とする。Therefore, in the present invention, the amount added is 0.005~
The range is 0.080%.
Ｔｉは、Ｎを固定することによって、Ｂの焼入れ性を確
保すると共に、結晶粒を微細化して靭性を向上させる効
果を有する。このような効果を有効に得るためには、少
なくとも０．００５％を添加することが必要であるが、
０．０３０％を越えて多量に添加するときは、却って靭
性を低下させる。Ti has the effect of securing the hardenability of B by fixing N, and also improves toughness by refining crystal grains. In order to effectively obtain such an effect, it is necessary to add at least 0.005%,
When added in a large amount exceeding 0.030%, the toughness is actually reduced.
Ｂは、微量の添加にて綱の焼入れ性を高める元素であり
、本発明においては、０．０００５％以上を添加するこ
とが必要である。しかし、０．００３０％を越える量を
添加するときは、靭性を劣化させる。B is an element that improves the hardenability of steel when added in a trace amount, and in the present invention, it is necessary to add 0.0005% or more. However, when added in an amount exceeding 0.0030%, toughness deteriorates.
Ａβは、製鋼時の脱酸剤として、また、結晶粒を微細化
して靭性を向上させる効果を有する。かかる効果を有効
に発揮させるには、０．００５％以上を添加することが
必要であるが、過度に添加するときは、非金属介在物の
増加をもたらし、シャルピー吸収エネルギーを低下させ
るので、上限を０．００６０％とする。Aβ acts as a deoxidizing agent during steel manufacturing, and has the effect of improving toughness by refining crystal grains. In order to effectively exhibit this effect, it is necessary to add 0.005% or more; however, if excessively added, nonmetallic inclusions will increase and the Charpy absorbed energy will decrease, so the upper limit is set. is 0.0060%.
Ｎは、窒化物として結晶粒を微細化し、靭性を向上させ
る効果を有する。この効果を有効に得るためには、０．
００１５％以上を添加する必要があるが、０．００５０
％を越えて過多に添加するときは、Ｂの焼入れ性向上効
果を阻害する。N, as a nitride, has the effect of making crystal grains finer and improving toughness. In order to effectively obtain this effect, 0.
It is necessary to add 0.0015% or more, but 0.0050%
When added in excess of more than %, the hardenability improvement effect of B is inhibited.
本発明の方法においては、鋼スラブは、上記した元素に
加えて、
Ｃｕ０．５％以下、
Ｎｉ２．０％以下、
Ｃｒ１．０％以下、
Ｍｏ０．５％以下、
Ｖ ０．１５％以下、及び
Ｃａ ０．００５％以下
よりなる群から選ばれる少なくとも１種の元素を含有す
ることができる。In the method of the present invention, the steel slab contains, in addition to the above-mentioned elements, Cu 0.5% or less, Ni 2.0% or less, Cr 1.0% or less, Mo 0.5% or less, V 0.15% or less, and It can contain at least one element selected from the group consisting of Ca 0.005% or less.
Ｃｕは、強度の向上に有効であるが、過多に添加すると
きは、靭性を劣化させるので、添加量の上限を０．５％
とする。Cu is effective in improving strength, but when added in excess, it deteriorates toughness, so the upper limit of the amount added is set at 0.5%.
shall be.
Ｎｉも、強度及び靭性の向上に効果を有するが、多量の
添加は得られる鋼板の経済性を損なうので、添加量の上
限を２．０％とする。Ni is also effective in improving strength and toughness, but adding a large amount impairs the economic efficiency of the resulting steel sheet, so the upper limit of the amount added is set at 2.0%.
Ｃｒ及びＭｏも強度の向上に有効である。しかし、過多
の添加は溶接性を劣化させるので、添加量の上限は、Ｃ
ｒについては１．０％、Ｍｏについては０．５％とする
。Cr and Mo are also effective in improving strength. However, since excessive addition deteriorates weldability, the upper limit of the amount of C added is
It is assumed that r is 1.0% and Mo is 0.5%.
■は、鋼の強度向上に効果を有するが、０．１５％を越
えて過多に添加するときは、その効果が飽和するのみな
らず、却って靭性を劣化させるので、添加量の上限を０
．１５％とする。(2) has the effect of improving the strength of steel, but when added in excess of 0.15%, the effect not only saturates, but also deteriorates the toughness, so the upper limit of the addition amount should be set to 0.
．． It shall be 15%.
Ｃａは、シャルピー吸収エネルギーの改善に効果を有す
る。しかし、ｏ、 ｏ ｏ ｓ ｏ％を越えて添加して
も、効果が飽和するのみならず、非金属介在物量を増加
させて、却ってシャルピー吸収エネルギーを低下させる
場合もあるので、添加量の上限を０．００５０％とする
。Ca has an effect on improving Charpy absorbed energy. However, adding more than o, o o so o% not only saturates the effect, but also increases the amount of nonmetallic inclusions, which may even reduce the Charpy absorption energy, so the upper limit of the amount added is is set to 0.0050%.
次に、本発明による製造方法を説明する。Next, the manufacturing method according to the present invention will be explained.
本発明の方法は、上記した化学組成を有する鋼スラブを
Ａｒ３〜Ａｒ、＋ １００℃の温度範囲で熱間圧延を終
了し、その後直ちに５℃／秒以上の冷却速度で加速冷却
を行ない、４００℃以下の温度でこの加速冷却を停止し
て、主要組織を微細ベイナイトとする。The method of the present invention involves hot rolling a steel slab having the above-mentioned chemical composition in a temperature range of Ar3 to Ar and +100°C, and then immediately performing accelerated cooling at a cooling rate of 5°C/sec or more, This accelerated cooling is stopped at a temperature below .degree. C., and the main structure becomes fine bainite.
本発明者らは、本発明による化学組成を有する鋼スラブ
として、代表的に
Ｃ０．０４％、
Ｓｉ０．３０％、
Ｍｎ １．９５％、
Ｓ ０．００４％、
Ｎｂ ０．０４９％、
Ｔｉ０．０１２％、
Ｂ ０．００１）％、
Ａ４２ ０．００３５％、
Ｎ ０．（１０４０％、
残部鉄及び不可避的不純物よりなるスラブについて、鋼
板の機械的性質に及ぼす製造条件の影響を調べた。The present inventors typically used a steel slab having a chemical composition according to the present invention as C0.04%, Si0.30%, Mn 1.95%, S 0.004%, Nb 0.049%, Ti0. 012%, B 0.001)%, A42 0.0035%, N 0. (1040%, balance iron and unavoidable impurities) The influence of manufacturing conditions on the mechanical properties of the steel plate was investigated.
先ず、上記スラブを板厚１９ｍに熱間圧延し、圧延終了
後に直ちに８〜ｂ
て４００℃以下の温度まで加速冷却を行なって、圧延仕
上温度の影響を調べた。−４０℃におけるシャルピー吸
収エネルギー（ＶＥ−４゜）及び破面遷移温度（ｖＴｒ
ｓ）と圧延仕上温度との関係を第１図に示す。尚、上記
鋼のＡｒ＝は７４５℃である。First, the above-mentioned slab was hot rolled to a thickness of 19 m, and immediately after the rolling was completed, accelerated cooling was performed to a temperature of 400° C. or lower to examine the influence of the finishing temperature of rolling. Charpy absorbed energy (VE-4°) and fracture surface transition temperature (vTr
Fig. 1 shows the relationship between s) and rolling finish temperature. Incidentally, Ar= of the above steel is 745°C.
圧延仕上温度がＡｒ３＋ １００℃よりも高いときは、
ｖＥ、ｏは１０ｋｇ１ｍ以上であるが、ｖＴｒｓは一８
０℃に達しない。一方、圧延仕上温度がＡｒｚよりも低
いときは、逆に、ｖＴｒｓは−８０”Ｃ以下であるが、
ＶＥ−４゜は１０ｋｇｆ−ｍを満足しない。即ち、本発
明の方法においては、鋼板に圧延ままにて１０ｋｇｆ−
ｍ以上のｖＥ−、、と−８０℃以下のｖＴｒｓを与える
ためには、鋼スラブをＡｒ３〜Ａｒｔ＋ １００℃の温
度範囲で熱間圧延を終了することが必要である。When the rolling finish temperature is higher than Ar3+ 100℃,
vE, o is more than 10 kg 1 m, but vTrs is 18
Does not reach 0℃. On the other hand, when the finishing rolling temperature is lower than Arz, vTrs is -80"C or less, but
VE-4° does not satisfy 10 kgf-m. That is, in the method of the present invention, 10 kgf-
In order to provide vE-, ., of m or more and vTrs of -80°C or less, it is necessary to complete the hot rolling of the steel slab in a temperature range of Ar3 to Art+ 100°C.
次に、本発明の方法においては、圧延後、直ちに鋼板を
５℃／秒以上の冷却速度にて加速冷却して、鋼板の主要
組織を微細ベイナイトとすることによって、高いシャル
ピー吸収エネルギーとすぐれた破面遷移温度及び高い降
伏強度を得る。Next, in the method of the present invention, immediately after rolling, the steel plate is acceleratedly cooled at a cooling rate of 5°C/second or more to make the main structure of the steel plate fine bainite. Obtain fracture surface transition temperature and high yield strength.
上記鋼スラブを板厚１９ｔｌに熱間圧延し、圧延終了後
に直ちに５℃／秒以上の冷却速度にて所定の温度まで加
速冷却を行なって、冷却停止温度がｖＥ−ａ。及びｖＴ
ｒｓに及ぼす影響を第２図に示す。The above-mentioned steel slab was hot-rolled to a plate thickness of 19 tl, and immediately after the rolling was completed, it was acceleratedly cooled to a predetermined temperature at a cooling rate of 5° C./sec or more, so that the cooling stop temperature was vE-a. and vT
Figure 2 shows the effect on rs.
冷却停止温度が４００℃よりも高いときは、得られる鋼
板における組織中の微細ベイナイトの占める割合が著し
く少ないので、ｖＥ、ｏ及びｖＴｒｓ共に著しく劣化し
、ｖＥ−ａ。は１０ｋｇｆ・ｍを満足せず、また、−８
０℃以下のｖＴｒｓが得られない。When the cooling stop temperature is higher than 400°C, the proportion of fine bainite in the structure of the obtained steel sheet is extremely small, so vE, o and vTrs are all significantly deteriorated, resulting in vE-a. does not satisfy 10 kgf・m, and -8
vTrs below 0°C cannot be obtained.
しかし、本発明に従って、冷却停止温度を４００℃以下
とすることによって、１０ｋｇｆ−ｍ以上のｖ Ｅ −
４０と共に、−８０℃以下のｖＴｒｓを同時に得ること
ができる。特に好ましい冷却停止温度は４００〜２００
℃の範囲である。However, according to the present invention, by setting the cooling stop temperature to 400°C or less, v E − of 10 kgf-m or more
40 and vTrs of −80° C. or lower can be obtained at the same time. Particularly preferable cooling stop temperature is 400 to 200
℃ range.
（発明の効果）
以上のように、本発明によれば、所定の化学組成を有す
る綱を所定の条件の下に圧延し、加速冷却して、島状マ
ルテンサイトの生成を極力抑えて、鋼板の主要組織を微
細ベイナイトとすることによって、シャルピー吸収エネ
ルギーを飛躍的に向上させる同時に、遷移温度も顕著に
改善して、圧延ままにてすぐれた不安定延性破壊伝播停
止特性と脆性破壊特性とを兼ね備え、従って、気体輸送
ラインパイプに使用するに好適である高強度高靭性であ
って、且つ、不安定延性破壊伝播停止特性にすぐれた鋼
板を得ることができる。(Effects of the Invention) As described above, according to the present invention, a steel having a predetermined chemical composition is rolled under predetermined conditions, accelerated cooling is performed, and the formation of island-shaped martensite is suppressed as much as possible to produce a steel sheet. By making the main structure fine bainite, the Charpy absorbed energy is dramatically improved, and at the same time, the transition temperature is also significantly improved, resulting in excellent unstable ductile fracture propagation arrest characteristics and brittle fracture characteristics in as-rolled condition. Therefore, it is possible to obtain a steel plate having high strength and high toughness suitable for use in gas transportation line pipes, and excellent unstable ductile fracture propagation arresting properties.
（実施例）
以下に実施例を挙げて本発明を説明するが、本発明はこ
れら実施例によって何ら限定されるものではない。(Examples) The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples in any way.
実施例
表に示す化学組成を有する本発明鋼及び比較鋼をＩ Ｌ
５０ ｃの温度に加熱した後、表に示すように、所定
の仕上温度にて熱間圧延を終了し、その後、直ちに表に
示す冷却速度にて加速冷却して、本発明による鋼板を製
造した。The invention steel and comparative steel having the chemical compositions shown in the Example Table were
After heating to a temperature of 50 °C, hot rolling was completed at a predetermined finishing temperature as shown in the table, and then immediately accelerated cooling was performed at a cooling rate shown in the table to produce a steel plate according to the present invention. .
このようにして得られた鋼板の機械的性質及び鋼板組織
における微細ベイナイトの割合を示す。The mechanical properties of the steel sheet thus obtained and the proportion of fine bainite in the steel sheet structure are shown.
本発明による鋼板は、いずれも微細へイナイトが７０％
以上を占め、降伏強度５０ ｋｇｆ／ｍｍ２以上、降伏
比８５％以下、ＶＥ−４０１０ｋｇｆ−ｍ以上、ｖＴｒ
ｓ −８０℃以下である。The steel sheets according to the present invention each contain 70% fine heinite.
yield strength of 50 kgf/mm2 or more, yield ratio of 85% or less, VE-4010 kgf-m or more, vTr
s -80°C or lower.
比較鋼８は、圧延仕上温度が低いためにｖＥ−ａ。Comparative Steel 8 was vE-a because the rolling finish temperature was low.
が低く、比較鋼９は、圧延仕上温度が高いためにｖＴｒ
ｓが高い。比較鋼１０は冷却停止温度が高いために、Ｖ
Ｅ −ａ。及びｖＴｒｓ共に不十分である。is low, and comparative steel 9 has a high vTr due to the high finishing temperature of rolling.
s is high. Comparative steel 10 has a high cooling stop temperature, so V
E-a. and vTrs are both insufficient.
また、比較鋼１）は、冷却速度が遅いので、微細ベイナ
イト組織を得ることができず、ｖ Ｅ −ａ。及びｖＴ
ｒｓ共に不十分である。In addition, in comparison steel 1), since the cooling rate was slow, a fine bainite structure could not be obtained, and v E -a. and vT
Both rs and rs are insufficient.
また、比較鋼１４は、Ｃ量が過多である結果、島状マル
テンサイトが生成し、靭性が著しく劣化している。比較
鋼１５は、Ｎ量が過多であるので、Ｂの焼入れ性を阻害
し、その結果、靭性が低下している。また、鋼板Ｍｉ織
における微細ベイナイト量も少ない。Furthermore, in Comparative Steel 14, as a result of the excessive amount of C, island-shaped martensite is generated, and the toughness is significantly deteriorated. Comparative Steel 15 has an excessive amount of N, which inhibits the hardenability of B, resulting in a decrease in toughness. Furthermore, the amount of fine bainite in the Mi weave of the steel sheet is also small.
第１図は、本発明で規定する化学組成を有する鋼スラブ
の圧延仕上温度と一４０℃におけるシャルピー吸収エネ
ルギー（νＢ −４゜）及び破面遷移温度（ｖＴｒｓ）
との関係を示すグラフ、第２図は、加速冷却停止温度と
ｖＥ−４゜及びｖＴｒｓとの関係を示すグラフである。
特許出願人 株式会社神戸製鋼所
代理人 弁理士 牧 野 逸 部
第１図Figure 1 shows the rolling finish temperature, Charpy absorbed energy (νB -4°) and fracture surface transition temperature (vTrs) at -40°C of a steel slab having the chemical composition specified in the present invention.
FIG. 2 is a graph showing the relationship between accelerated cooling stop temperature and vE-4° and vTrs. Patent applicant: Kobe Steel, Ltd. Representative: Patent attorney: Ittsu Makino Department Figure 1
Claims (2)
Ａｒ＿３＋１００℃の温度範囲で熱間圧延を終了し、そ
の後直ちに５℃／秒以上の冷却速度で加速冷却を行ない
、４００℃以下の温度で加速冷却を停止して、主要組織
を微細ベイナイトとすることを特徴とする不安定延性破
壊伝播停止特性にすぐれた高強度高靭性ラインパイプ用
鋼板の製造方法。(1) C0.01-0.06% by weight, Si 0.50% or less, Mn 1.5-2.5%, S 0.006% or less, Nb 0.005-0.080%, Ti 0.005-0 A slab consisting of .030%, B0.0005~0.0030%, Al0.005~0.060%, N0.0015~0.0050%, balance iron and inevitable impurities is Ar_3~
Finish hot rolling in the temperature range of Ar_3+100°C, then immediately perform accelerated cooling at a cooling rate of 5°C/second or more, and stop accelerated cooling at a temperature of 400°C or less to make the main structure fine bainite. A method for manufacturing a high-strength, high-toughness steel plate for line pipes with excellent unstable ductile fracture propagation arresting characteristics.
、 残部鉄及び不可避的不純物よりなるスラブをＡｒ＿３〜
Ａｒ＿３＋１００℃の温度範囲で熱間圧延を終了し、そ
の後直ちに５℃／秒以上の冷却速度で加速冷却を行ない
、４００℃以下の温度で加速冷却を停止して、主要組織
を微細ベイナイトとすることを特徴とする不安定延性破
壊伝播停止特性にすぐれた高強度高靭性ラインパイプ用
鋼板の製造方法。(2) In weight% (a) C0.01-0.06%, Si0.50% or less, Mn1.5-2.5%, S0.006% or less, Nb0.005-0.080%, Ti0. 005-0.030%, B0.0005-0.0030%, Al0.005-0.060%, and N0.0015-0.0050%, furthermore, (b) Cu0.5% or less, Ni2 0% or less, Cr1.0% or less, Mo0.5% or less, V0.15% or less, and Ca0.005% or less, with the balance being iron and inevitable impurities. More slabs Ar_3~
Finish hot rolling in the temperature range of Ar_3+100°C, then immediately perform accelerated cooling at a cooling rate of 5°C/second or more, and stop accelerated cooling at a temperature of 400°C or less to make the main structure fine bainite. A method for manufacturing a high-strength, high-toughness steel plate for line pipes with excellent unstable ductile fracture propagation arresting characteristics.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14521185A JPS624826A (en) | 1985-07-01 | 1985-07-01 | Manufacture of high strength and toughness steel plate for line pipe superior in characteristic for stopping unstable ductility fracture propagation |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14521185A JPS624826A (en) | 1985-07-01 | 1985-07-01 | Manufacture of high strength and toughness steel plate for line pipe superior in characteristic for stopping unstable ductility fracture propagation |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPS624826A true JPS624826A (en) | 1987-01-10 |
Family
ID=15379946
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14521185A Pending JPS624826A (en) | 1985-07-01 | 1985-07-01 | Manufacture of high strength and toughness steel plate for line pipe superior in characteristic for stopping unstable ductility fracture propagation |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS624826A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05271860A (en) * | 1992-03-25 | 1993-10-19 | Nippon Steel Corp | Structural steel excellent in brittle fracture resistance and its production |
| KR100435446B1 (en) * | 1996-11-07 | 2004-09-04 | 주식회사 포스코 | Method for manufacturing steel in which toughness at low temperature required in ultra-cold area is greatly improved while maintaining 60 kgf/mm¬2 or more tensile strength by means of controlling alloy composition, hot rolling and cooling conditions of steel properly |
| WO2007136019A1 (en) | 2006-05-24 | 2007-11-29 | Nippon Steel Corporation | High-strength steel pipe with excellent unsusceptibility to strain aging for line piping, high-strength steel plate for line piping, and processes for producing these |
| WO2008004680A1 (en) | 2006-07-04 | 2008-01-10 | Nippon Steel Corporation | High-strength steel pipe with excellent low-temperature toughness for line pipe, high-strength steel plate for line pipe, and processes for producing these |
| WO2008069289A1 (en) | 2006-11-30 | 2008-06-12 | Nippon Steel Corporation | Weld steel pipe with excellent low-temperature toughness for high-strength line pipe and process for producing the same |
| EP2060643A1 (en) * | 2006-12-20 | 2009-05-20 | Nippon Steel Corporation | Steel excelling in toughness at region affected by welding heat |
| US8039118B2 (en) | 2006-11-30 | 2011-10-18 | Nippon Steel Corporation | Welded steel pipe for high strength line pipe superior in low temperature toughness and method of production of the same |
| CN109385576A (en) * | 2017-08-04 | 2019-02-26 | 上海梅山钢铁股份有限公司 | A kind of inexpensive X65 pipe line steel and its manufacturing method based on magnesium processing |
| CN112981241A (en) * | 2021-01-29 | 2021-06-18 | 邯郸钢铁集团有限责任公司 | Production method of economical single-refining drop hammer-protecting pipeline steel |
-
1985
- 1985-07-01 JP JP14521185A patent/JPS624826A/en active Pending
Cited By (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH05271860A (en) * | 1992-03-25 | 1993-10-19 | Nippon Steel Corp | Structural steel excellent in brittle fracture resistance and its production |
| KR100435446B1 (en) * | 1996-11-07 | 2004-09-04 | 주식회사 포스코 | Method for manufacturing steel in which toughness at low temperature required in ultra-cold area is greatly improved while maintaining 60 kgf/mm¬2 or more tensile strength by means of controlling alloy composition, hot rolling and cooling conditions of steel properly |
| WO2007136019A1 (en) | 2006-05-24 | 2007-11-29 | Nippon Steel Corporation | High-strength steel pipe with excellent unsusceptibility to strain aging for line piping, high-strength steel plate for line piping, and processes for producing these |
| WO2008004680A1 (en) | 2006-07-04 | 2008-01-10 | Nippon Steel Corporation | High-strength steel pipe with excellent low-temperature toughness for line pipe, high-strength steel plate for line pipe, and processes for producing these |
| US8764918B2 (en) | 2006-07-04 | 2014-07-01 | Nippon Steel & Sumitomo Metal Corporation | High strength steel pipe for line pipe superior in low temperature toughness and high strength steel plate for line pipe and methods of production of the same |
| US9719615B2 (en) | 2006-07-04 | 2017-08-01 | Nippon Steel & Sumitomo Metal Corporation | High strength steel pipe for line pipe superior in low temperature toughness and high strength steel plate for line pipe and methods of production of the same |
| WO2008069289A1 (en) | 2006-11-30 | 2008-06-12 | Nippon Steel Corporation | Weld steel pipe with excellent low-temperature toughness for high-strength line pipe and process for producing the same |
| US8039118B2 (en) | 2006-11-30 | 2011-10-18 | Nippon Steel Corporation | Welded steel pipe for high strength line pipe superior in low temperature toughness and method of production of the same |
| EP2060643A1 (en) * | 2006-12-20 | 2009-05-20 | Nippon Steel Corporation | Steel excelling in toughness at region affected by welding heat |
| EP2060643A4 (en) * | 2006-12-20 | 2010-12-01 | Nippon Steel Corp | Steel excelling in toughness at region affected by welding heat |
| CN109385576A (en) * | 2017-08-04 | 2019-02-26 | 上海梅山钢铁股份有限公司 | A kind of inexpensive X65 pipe line steel and its manufacturing method based on magnesium processing |
| CN112981241A (en) * | 2021-01-29 | 2021-06-18 | 邯郸钢铁集团有限责任公司 | Production method of economical single-refining drop hammer-protecting pipeline steel |
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