JPH0143006B2 - - Google Patents
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- Publication number
- JPH0143006B2 JPH0143006B2 JP15318781A JP15318781A JPH0143006B2 JP H0143006 B2 JPH0143006 B2 JP H0143006B2 JP 15318781 A JP15318781 A JP 15318781A JP 15318781 A JP15318781 A JP 15318781A JP H0143006 B2 JPH0143006 B2 JP H0143006B2
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- Prior art keywords
- less
- temperature
- strength
- toughness
- hot
- Prior art date
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- 229910000831 Steel Inorganic materials 0.000 claims description 42
- 239000010959 steel Substances 0.000 claims description 42
- 238000001816 cooling Methods 0.000 claims description 14
- 238000010438 heat treatment Methods 0.000 claims description 12
- 238000004519 manufacturing process Methods 0.000 claims description 12
- 238000004804 winding Methods 0.000 claims description 10
- 229910052720 vanadium Inorganic materials 0.000 claims description 6
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910052759 nickel Inorganic materials 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 230000000694 effects Effects 0.000 description 19
- 238000005096 rolling process Methods 0.000 description 12
- 238000005098 hot rolling Methods 0.000 description 10
- 230000009466 transformation Effects 0.000 description 9
- 238000000034 method Methods 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- 229910001563 bainite Inorganic materials 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 238000000926 separation method Methods 0.000 description 5
- 229910000859 α-Fe Inorganic materials 0.000 description 5
- 229910001562 pearlite Inorganic materials 0.000 description 4
- 229910000746 Structural steel Inorganic materials 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910052758 niobium Inorganic materials 0.000 description 2
- 238000004881 precipitation hardening Methods 0.000 description 2
- 230000002787 reinforcement Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 230000007704 transition Effects 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
- 229910001035 Soft ferrite Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000005266 casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Description
この発明は、特にラインパイプ、あるいはその
他構造物などの高い強度と低温靭性が要求される
分野で使用するのに適した板厚：4.5mm以上を有
する厚肉の高張力熱延鋼板の製造法に関するもの
である。
一般に、Nb含有の構造用鋼板は、変態後の冷
却時にフエライト地へNb炭化物が析出すること
による強度上昇効果によつて高強度を有すること
から、高強度が要求されるラインパイプなどの製
造に用いられている。しかし、前記のNb含有構
造用鋼板の製造に際しては、熱履歴によつて析出
硬化の度合が微妙に変化し、かつ靭性も大きく影
響されることから、種々の厳格な圧延条件および
巻取条件を設定しなければならず、しかもこのよ
うに厳しい条件設定を行なつても、得られる鋼板
強度の上限が低かつたり、あるいは良好な靭性を
確保することができないなどの問題点があるもの
であつた。
そこで、これら従来Nb含有構造用鋼板の製造
法にみられる問題点を解決し、もつて強度および
靭性ともによりすぐれた熱延鋼板を安定して製造
する方法として、例えば特公昭50−25892号公報
にみられる方法が提案されている。この方法は、
Nb含有鋼に熱間圧延を施し、Ar3変態点以上の
温度で熱間圧延を終了した後、680〜500℃の温度
範囲で巻取ることを特徴とし、巻取温度を著しく
低くすると上部ベイナイト組織が混入して靭性に
有害であるとして、巻取温度の下限を500℃と定
めたものである。この方法によれば、強度、靭
性、および溶接性の良好な高張力熱延鋼板を比較
的安定して製造することができるけれども、鋼素
材として所定量のNb成分を含有したものを用い
ることが必須であるばかりでなく、圧延に際して
は、加熱温度、圧延温度、および巻取温度を比較
的高い条件に設定して圧延を行なわなければなら
ないために、製造コストが高くなるばかりでな
く、スケールの多発による公害および冷却のため
のコイル置場の問題がある。
本発明者等は、上述のような観点から、従来高
張力熱延鋼板の製造法のもつ問題点を解決し、も
つて強度、靭性、および溶接性のともにすぐれた
熱延鋼板を、低エネルギで、スケールによる損失
も少なく、生産性高く、かつ安定して製造すべく
鋭意研究を行なつた結果、
(a) 所定の成分組成の鋼を、熱間圧延終了後、冷
却速度を３℃／sec以上として480〜Ms点の温
度範囲内の温度まで急冷してから巻取ると、鋼
板は高強度を有するようになること。
(b) 上記(a)項に示される低温巻取の場合でも、ス
ラブを850〜1000℃の温度範囲内の温度に加熱
してオーステナイト粒を微細化し、引続いて熱
間圧延におけるAr3変態点以下の温度域におけ
る圧下率が30％以上となる条件で圧延を行なえ
ば、シヤルピー破面上にセパレーシヨンが多数
発生するようになり、この場合、一般に述べら
れているように割れ先端の三軸応力が減少する
ことにより、ベイナイト組織などの変態による
強化組織が混入しても決してシヤルピー破面遷
移温度（低温靭性）が上昇（劣化）しないこ
と。この事実は、第１図に示される実験結果か
らも裏付けられるものである。すなわち、第１
図は、Ｃ：0.15％、Si：0.30％、Mn：1.35％、
sol.Al：0.03％、Feおよび不可避不純物からな
る組成を有する鋼より、加熱温度：1250℃と
950℃、熱間圧延における全圧下率：90％、圧
延終了後巻取までの冷却速度：５℃／secの条
件で、熱延シミユレーシヨン実験を行なつて板
厚：11mmの熱延鋼板を製造し、この結果得られ
た鋼板の強度および靭性に及ぼす仕上温度と巻
取温度の影響を測定し、グラフ化したものであ
る。第１図から、巻取温度については、400℃
巻取にて最も高い降伏点となることが明白であ
り、これは自己焼なましベイナイト組織が混入
するためであると考えられる。また、100℃巻
取は、Ms点以下の巻取となるため降伏現象が
消失して低降伏点となり、さらに600℃巻取で
は軟質なフエライトとパーライトの混合組織と
なるためやはり低降伏点となることが示されて
いる。一方、シヤルピー破面遷移温度に関して
は、950℃加熱、400℃巻取で、特にAr3変態点
以下の温度域での圧下率が30％以上の強圧下を
行なつた場合にはセパレーシヨンが多発して大
巾な靭性向上が認められることが明らかであ
る。なお、熱間圧延がAr1変態点以下の温度で
終了した場合でも、温間加工フエライトが、圧
延後の急冷および低温巻取により軟化が抑制さ
れる結果、強度上昇効果が現われるのである。
以上の結果から、すぐれた強靭性鋼を得るため
には、加熱温度、圧延条件、および巻取温度を
上記の通り組合せ限定することが必須であるこ
とがわかる。これらの事実はNb添加鋼および
Ｖ添加鋼にても同様に確認されている。以上(a)
および(b)項に示される知見を得たのである。
したがつて、この発明は、上記知見にもとづい
てなされたものであつて、重量％で、
Ｃ：0.02〜0.25％、Si：0.60％以下、Mn：0.5
〜2.2％、Ｓ：0.010％以下、sol.Al：0.10％以下を
含有し、さらに必要に応じて、
Nb：0.15％以下、Ｖ：0.15％以下、Ti：0.15％
以下、Ｂ：0.010％以下、Cu：1.0％以下、Ni：
1.0％以下、およびCr：1.0％以下のうちの１種ま
たは２種以上からなる強度改善成分を含有し、さ
らにまた必要に応じて、
Ca：0.010％以下を含有し、
残りがFeと不可避不純物からなる組成を有す
る鋼を、850〜1000℃の温度範囲内の温度に加熱
してオーステナイト粒の微細化をはかり、ついで
熱間圧延を施し、特にこの熱間圧延ではAr3変態
点以下の温度域における圧下率を30％以上とする
ことによつて温間加工集合組織を十分に発達さ
せ、シヤルピー試験等の破壊破面に見られるセパ
レーシヨンを多数作つて靭性を向上させ、引続い
て３℃／sec以上の冷却速度で480〜Ms点の温度
範囲内の温度まで急冷し、巻取ることによつて、
温間加工フエライトの軟化を抑制した状態で、自
己焼もどし低温変態生成物を形成して強度上昇を
はかり、もつて高強度および高靭性を有する熱延
鋼板を得ることに特徴を有するものである。
つぎに、この発明の高張力熱延鋼板の製造法に
おいて、高の成分組成、加熱温度、圧下率、冷却
速度、および巻取温度を上記の通りに限定した理
由を説明する。
Ａ 鋼の成分組成
(a) Ｃ
Ｃ成分には、低温巻取時に生じるベイナイ
ト組織、微細パーライト組織の体積率を増加
して鋼を強化する作用があるほか、鋼の溶製
を容易にする作用があるが、その含有量が
0.02重量％未満では前記作用に所望の効果が
得られず、一方0.25％を越えて含有させると
溶接熱影響部に靭性劣化が生じるようになる
ことから、その含有量を0.02〜0.25％と定め
た。
(b) Si
Si成分には、素地に固溶して、これを硬化
し、もつて鋼の強度を上昇させる作用がある
が、0.60％を越えて含有させると溶接性が劣
化するようになることから、その含有量を
0.60％以下と定めた。
(c) Mn
Mn成分には、変態強化、パーライト強化
などにより強度を向上させる作用があるが、
その含有量が0.5％未満では所望の強度向上
効果を確保することができず、一方2.2％を
越えて含有させると溶接性が劣化するように
なることから、その含有量を0.5〜2.2％と定
めた。
(d) Ｓ
Ｓ成分には、Mnと結合してＡ系介在物を
形成し、横方向のシヤルピー吸収エネルギを
低下せしめる作用があり、この作用は、その
含有量が0.010％を越えると著しくなること
から、その含有量の上限値を0.010％と定め
た。
(e) sol.Al
Alは脱酸剤として必要な成分であるが、
sol.Al含有量で0.10％を越えると靭性に悪影
響を及ぼすようになることから、その含有量
を0.10％以下と定めた。
(f) Nb、Ｖ、およびTi
これらの成分には、Ｃと結合し、炭化物を
形成して鋼を析出硬化させ、もつて強度を向
上させる作用があるので、特に高強度が要求
される場合に必要に応じて含有されるが、
0.15％を越えて含有させてもより一層の強度
向上効果が現われないことから、経済性をも
考慮して、それぞれの含有量を、Nb：0.15
％以下、Ｖ：0.15％以下、およびTi：0.15％
以下と定めた。
(g) Ｂ
Ｂ成分は、微量添加で鋼の焼入れ性を改善
して強度を向上させる作用をもつので、Nb、
Ｖ、およびTiと同様に高強度が要求される
場合に必要に応じて含有され、特に低温巻取
を行なうこの発明の方法における鋼の構成成
分として有効な成分であるが、0.010％を越
えて含有しても、より一段の強度向上効果は
現われないことから、その含有量を0.010％
以下と定めた。
(h) Cu、Ni、およびCr
これらの成分にもMn、Nb、Ｖ、および
Tiと同様に強度を改善する作用があるので、
必要に応じて含有されるが、それぞれその含
有量が1.0％を越えると溶接性が大巾に劣化
するようになることから、それぞれの含有量
をCu：1.0％以下、Ni：1.0％以下、および
Cr：1.0％以下と定めた。
(i) Ca
Ca成分には、MnS系のＡ系介在物と、
Al2O3のＢ系介在物をＣ系介在物に変化させ
て、横方向の大巾な吸収エネルギの向上をは
かり、もつて靭性を改善する作用があるの
で、特に高靭性が要求される場合に必要に応
じて含有されるが、0.010％を越えて含有さ
せると実質的に介在物量が多くなりすぎて好
ましくないので、その含有量を0.010％以下
と定めた。
Ｂ 加熱温度
加熱温度が1000℃を越えると、オーステナイ
トの細粒化があまり進行せず、低温巻取時に粗
大なベイナイトが混入して、セパレーシヨンに
よる靭性向上効果を利用しても鋼板の靭性レベ
ルに限度を生じるようになり、一方850℃未満
の加熱温度ではオーステナイト化が不十分であ
ることから、加熱温度を850〜1000℃と定めた。
Ｃ 圧下率
Ar3変態点以下の温度域における圧下率が30
％未満では、フエライトの加工量が少なくて板
面における（100）の集合組織の発達が少なく、
セパレーシヨンの発生が少なくなつて、靭性向
上効果が少なくなることから、その圧下率を30
％以上と定めた。
Ｄ 冷却速度と巻取温度
３℃／sec未満の冷却速度では、冷却が遅す
ぎて480℃を越えた温度での高温巻取と同等の
軟質なフエライトとパーライトの混合組織とな
つて高強度が得られず、またMs点未満の低温
巻取を行なうと降伏現象の消失した硬化組織と
なつて、やはり高い降伏点が得られないことか
ら、圧延後、３℃／sec以上の冷却速度で480〜
Ms点の温度範囲内の温度まで急冷し、この温
度で巻取る必要があるのである。
つぎに、この発明の方法を実施例により比較例
と対比しながら説明する。
実施例
それぞれ第１表に示される成分組成をもつた鋼
を溶製し、鋳造してスラブとした後、同じく第１
表にそれぞれ示される条件にて熱延シミユレーシ
ヨン実験圧延により熱間圧延を行なうことによつ
て、いずれも板厚：11mmを有する本発明熱延鋼板
１〜10および比較熱延鋼板１〜５をそれぞれ製造
した。なお、比較熱延鋼板１〜５は、いずれも熱
延条件のうちのいずれかの条件（第１表に※印を
付した条件）がこの発明の範囲から外れた条件で
製造されたものである。
ついで、この結果得られた本発明熱延鋼板１〜
10および比較熱延鋼板１〜５からJIS5号お
This invention is a method for producing a thick high-strength hot-rolled steel plate having a thickness of 4.5 mm or more, which is particularly suitable for use in fields where high strength and low-temperature toughness are required, such as line pipes and other structures. It is related to. In general, Nb-containing structural steel sheets have high strength due to the strength-increasing effect of Nb carbide precipitated in the ferrite layer during cooling after transformation, so they are suitable for manufacturing line pipes that require high strength. It is used. However, when manufacturing the above-mentioned Nb-containing structural steel sheets, the degree of precipitation hardening changes slightly depending on the thermal history, and the toughness is also greatly affected, so various strict rolling and winding conditions are required. Moreover, even if such strict conditions are set, there are problems such as the upper limit of the strength of the steel sheet that can be obtained is low or it is not possible to ensure good toughness. Ta. Therefore, as a method to solve the problems seen in the conventional manufacturing method of Nb-containing structural steel sheets and to stably manufacture hot rolled steel sheets with better strength and toughness, for example, Japanese Patent Publication No. 50-25892 A method has been proposed. This method is
It is characterized by hot rolling Nb-containing steel, finishing the hot rolling at a temperature higher than the Ar 3 transformation point, and then coiling it at a temperature range of 680 to 500℃.If the coiling temperature is significantly lowered, upper bainite The lower limit of the winding temperature was set at 500°C because it is considered that the structure is mixed in and is harmful to the toughness. According to this method, high-strength hot-rolled steel sheets with good strength, toughness, and weldability can be produced relatively stably, but it is difficult to use a steel material containing a predetermined amount of Nb. Not only is this necessary, but when rolling, heating temperature, rolling temperature, and coiling temperature must be set at relatively high conditions, which not only increases manufacturing costs but also reduces scale. There are problems with frequent pollution and a place to store coils for cooling. From the above-mentioned viewpoints, the present inventors have solved the problems of conventional methods of manufacturing high-tensile hot-rolled steel sheets, and produced hot-rolled steel sheets with excellent strength, toughness, and weldability that can be produced using low energy. As a result of intensive research to achieve stable manufacturing with less loss due to scale and high productivity, we found that (a) steel with a specified composition was cooled at a cooling rate of 3°C/3°C after hot rolling. If the steel plate is rapidly cooled to a temperature within the temperature range of 480 to Ms point as sec or more and then coiled, the steel plate will have high strength. (b) Even in the case of low-temperature coiling as described in item (a) above, the slab is heated to a temperature within the temperature range of 850 to 1000°C to refine the austenite grains, followed by Ar 3 transformation during hot rolling. If rolling is carried out under conditions where the reduction rate is 30% or more in the temperature range below 30%, many separations will occur on the fractured surface of the shear pee. By reducing the axial stress, the shearpy fracture transition temperature (low-temperature toughness) never increases (deteriorates) even if a reinforcing structure due to transformation such as bainite structure is mixed in. This fact is also supported by the experimental results shown in FIG. That is, the first
The figure shows C: 0.15%, Si: 0.30%, Mn: 1.35%,
From steel with a composition consisting of sol.Al: 0.03%, Fe and unavoidable impurities, heating temperature: 1250℃
A hot-rolled steel plate with a thickness of 11 mm was produced by conducting a hot rolling simulation experiment under the conditions of 950°C, total reduction rate in hot rolling: 90%, and cooling rate after rolling until coiling: 5°C/sec. The influence of finishing temperature and coiling temperature on the strength and toughness of the resulting steel sheet was measured and graphed. From Figure 1, the winding temperature is 400℃.
It is clear that the highest yield point is obtained during winding, and this is thought to be due to the inclusion of self-annealed bainite structure. In addition, when winding at 100°C, the yield phenomenon disappears and the yield point is lower because the winding temperature is below the Ms point, and furthermore, when winding at 600°C, a mixed structure of soft ferrite and pearlite results in a low yield point. It has been shown that On the other hand, regarding the shear pie fracture surface transition temperature, when heating at 950°C and winding at 400°C, especially when applying strong pressure with a reduction rate of 30% or more in the temperature range below the Ar 3 transformation point, the separation will decrease. It is clear that a significant improvement in toughness is observed with multiple occurrences. Note that even if the hot rolling is completed at a temperature below the Ar 1 transformation point, the softening of the warm-worked ferrite is suppressed by rapid cooling and low-temperature coiling after rolling, resulting in an effect of increasing strength.
From the above results, it can be seen that in order to obtain a steel with excellent toughness, it is essential to limit the combination of heating temperature, rolling conditions, and coiling temperature as described above. These facts have been similarly confirmed for Nb-added steel and V-added steel. or more (a)
And we obtained the findings shown in section (b). Therefore, this invention was made based on the above knowledge, and in weight percent, C: 0.02 to 0.25%, Si: 0.60% or less, Mn: 0.5
~2.2%, S: 0.010% or less, sol.Al: 0.10% or less, and if necessary, Nb: 0.15% or less, V: 0.15% or less, Ti: 0.15%
Below, B: 0.010% or less, Cu: 1.0% or less, Ni:
Contains a strength improving component consisting of one or more of the following: 1.0% or less, and Cr: 1.0% or less, and further contains Ca: 0.010% or less, with the remainder being Fe and unavoidable impurities. A steel having a composition of By setting the rolling reduction ratio in the area to 30% or more, the warm working texture is sufficiently developed, and the toughness is improved by creating many separations that can be seen on the fracture surface of the shear py test. By rapidly cooling to a temperature within the temperature range of 480 to Ms point at a cooling rate of ℃/sec or more and winding it,
It is characterized in that it aims to increase its strength by forming self-tempering low-temperature transformation products while suppressing the softening of warm-worked ferrite, thereby obtaining a hot-rolled steel sheet with high strength and high toughness. . Next, in the method for producing a high-strength hot-rolled steel sheet of the present invention, the reason why the component composition, heating temperature, rolling reduction rate, cooling rate, and coiling temperature are limited as described above will be explained. A Composition of steel (a) C The C component has the effect of strengthening the steel by increasing the volume fraction of the bainite structure and fine pearlite structure that occur during low-temperature coiling, and also has the effect of facilitating the melting of steel. However, its content is
If the content is less than 0.02% by weight, the desired effect cannot be obtained, while if the content exceeds 0.25%, toughness will occur in the weld heat affected zone, so the content is set at 0.02 to 0.25%. Ta. (b) Si The Si component has the effect of forming a solid solution in the base material, hardening it, and increasing the strength of the steel, but if it is contained in excess of 0.60%, weldability will deteriorate. Therefore, the content
It is set at 0.60% or less. (c) Mn The Mn component has the effect of improving strength through transformation reinforcement, pearlite reinforcement, etc.
If the content is less than 0.5%, the desired strength improvement effect cannot be secured, while if the content exceeds 2.2%, weldability will deteriorate, so the content should be set at 0.5 to 2.2%. Established. (d) S The S component has the effect of combining with Mn to form A-based inclusions and lowering the lateral Charpy absorption energy, and this effect becomes significant when its content exceeds 0.010%. Therefore, the upper limit of its content was set at 0.010%. (e) sol.Al Al is a necessary component as a deoxidizing agent,
If the sol.Al content exceeds 0.10%, it will have a negative effect on toughness, so the content was set at 0.10% or less. (f) Nb, V, and Ti These components have the effect of combining with C, forming carbides, precipitation hardening the steel, and improving its strength, especially when high strength is required. Contained as necessary,
Even if the content exceeds 0.15%, no further strength improvement effect will be obtained, so in consideration of economic efficiency, the respective contents were reduced to Nb: 0.15%.
% or less, V: 0.15% or less, and Ti: 0.15%
It was determined as follows. (g) B The B component has the effect of improving the hardenability of steel and increasing its strength when added in small amounts, so Nb,
Like V and Ti, it is contained as necessary when high strength is required, and is an effective component of the steel in the method of this invention, which involves low-temperature coiling, but in excess of 0.010%. Even if it is contained, there is no further strength improvement effect, so the content was reduced to 0.010%.
It was determined as follows. (h) Cu, Ni, and Cr These components also include Mn, Nb, V, and
Like Ti, it has the effect of improving strength.
They are contained as necessary, but if their content exceeds 1.0%, weldability will deteriorate significantly, so the respective contents should be set to Cu: 1.0% or less, Ni: 1.0% or less, and
Cr: Set at 1.0% or less. (i) Ca The Ca component includes MnS-based A-based inclusions,
Particularly high toughness is required because the B-based inclusions in Al 2 O 3 are changed to C-based inclusions, which greatly improves absorbed energy in the lateral direction, thereby improving toughness. Although it may be contained if necessary, if it is contained in excess of 0.010%, the amount of inclusions will become substantially too large, which is undesirable, so the content is set at 0.010% or less. B Heating temperature If the heating temperature exceeds 1000℃, austenite grain refinement will not proceed much, and coarse bainite will be mixed in during low-temperature coiling, and the toughness level of the steel sheet will deteriorate even if the toughness improvement effect of separation is used. On the other hand, since austenitization is insufficient at a heating temperature of less than 850°C, the heating temperature was set at 850 to 1000°C. C Reduction rate Ar 3 The reduction rate in the temperature range below the transformation point is 30
If it is less than %, the amount of ferrite processed is small and the (100) texture on the plate surface is poorly developed.
Since the occurrence of separation is reduced and the effect of improving toughness is reduced, the rolling reduction ratio is reduced to 30%.
% or more. D. Cooling rate and coiling temperature If the cooling rate is less than 3℃/sec, the cooling will be too slow, resulting in a soft mixed structure of ferrite and pearlite that is equivalent to high-temperature coiling at a temperature exceeding 480℃, resulting in high strength. Moreover, if the coiling is performed at a low temperature below the Ms point, a hardened structure with no yielding phenomenon will result, and a high yield point will not be obtained. ~
It is necessary to rapidly cool the material to a temperature within the temperature range of the Ms point and then wind it at this temperature. Next, the method of the present invention will be explained using examples and comparing with comparative examples. Example After melting steel having the composition shown in Table 1 and casting it into a slab,
Hot rolled steel sheets 1 to 10 of the present invention and comparative hot rolled steel sheets 1 to 5, each having a thickness of 11 mm, were obtained by hot rolling by hot rolling simulation experiment rolling under the conditions shown in the table. Manufactured. Note that Comparative Hot Rolled Steel Sheets 1 to 5 were all manufactured under conditions in which any of the hot rolling conditions (conditions marked with * in Table 1) were outside the scope of this invention. be. Next, the hot rolled steel sheets 1 to 1 of the present invention obtained as a result
10 and comparative hot rolled steel sheets 1 to 5 to JIS No. 5 or
【表】
よび２mmＶノツチJIS4号シヤルピー試験片を切り
出し、引張り特性および衝撃特性を測定した。こ
の測定結果を第１表に合せて示した。
第１表に示される結果から、本発明熱延鋼板１
〜10は、いずれも高強度および高靭性を合せもつ
のに対して、この発明の範囲から外れた条件で製
造された比較熱延鋼板は、強度および靭性の少な
くともいずれかの性質が劣つていることが明らか
である。また、溶接性試験でも本発明鋼板１〜10
は良好な結果を示すものであつた。
上述のように、この発明の方法によれば、高価
な合金元素を多量に必要とすることなく、しかも
いずれも低い加熱温度、圧延温度、および巻取温
度にて高強度並びにすぐれた靭性および溶接性を
有する厚肉熱延鋼板を製造することができ、大巾
な製造コストの低減をはかることができるなど工
業上有用な効果がもたらされるのである。[Table] A 2 mm V-notch JIS No. 4 sharpie test piece was cut out, and the tensile properties and impact properties were measured. The measurement results are also shown in Table 1. From the results shown in Table 1, the hot rolled steel sheet 1 of the present invention
-10 have both high strength and high toughness, whereas comparative hot rolled steel sheets manufactured under conditions outside the scope of this invention are inferior in at least one of strength and toughness. That is clear. In addition, in the weldability test, steel sheets of the present invention 1 to 10
showed good results. As mentioned above, according to the method of the present invention, high strength and excellent toughness and welding can be achieved at low heating, rolling, and coiling temperatures without requiring large amounts of expensive alloying elements. This brings about industrially useful effects such as being able to produce thick-walled hot-rolled steel sheets with high properties and significantly reducing manufacturing costs.
第１図は鋼の強度と靭性に及ぼす仕上温度と巻
取温度の影響を示した線図である。
FIG. 1 is a diagram showing the influence of finishing temperature and coiling temperature on the strength and toughness of steel.
Claims (1)
0.5〜2.2％、Ｓ：0.010％以下、sol.Al：0.10％以
下を含有し、残りがFeと不可避不純物からなる
組成（以上重量％）を有する鋼を、850〜1000℃
の温度範囲内の温度に加熱した後、Ar3変態点以
下の温度域における圧下率が30％以上となる条件
で圧延を行ない、圧延後、480℃〜Ms点の温度範
囲内の温度まで３℃／sec以上の冷却速度で急冷
し、巻取ることを特徴とする低温靭性にすぐれた
厚肉高張力熱延鋼板の製造法。 ２ Ｃ：0.02〜0.25％、Si：0.60％以下、Mn：
0.5〜2.2％、Ｓ：0.010％以下、sol.Al：0.10％以
下を含有し、さらにNb：0.15％以下、Ｖ：0.15％
以下、Ti：0.15％以下、Ｂ：0.010％以下、Cu：
1.0％以下、Ni：1.0％以下、Cr：1.0％以下、お
よびCa：0.010％以下のうちの１種または２種以
上を含有し、残りがFeと不可避不純物からなる
組成（以上重量％）を有する鋼を、850〜1000℃
の温度範囲内の温度に加熱した後、Ar3変態点以
下の温度域における圧下率が30％以上となる条件
で圧延を行ない、圧延後、480〜Ms点の温度範囲
内の温度まで３℃／sec以上の冷却速度で急冷し、
巻取ることを特徴とする低温靭性にすぐれた厚肉
高張力熱延鋼板の製造法。[Claims] 1 C: 0.02 to 0.25%, Si: 0.60% or less, Mn:
Steel containing 0.5-2.2%, S: 0.010% or less, sol.Al: 0.10% or less, and the remainder consisting of Fe and unavoidable impurities (weight %) at 850-1000℃
After heating to a temperature within the temperature range of A method for producing thick-walled, high-strength hot-rolled steel sheets with excellent low-temperature toughness, characterized by rapid cooling at a cooling rate of ℃/sec or higher and coiling. 2 C: 0.02-0.25%, Si: 0.60% or less, Mn:
Contains 0.5 to 2.2%, S: 0.010% or less, sol.Al: 0.10% or less, and further Nb: 0.15% or less, V: 0.15%
Below, Ti: 0.15% or less, B: 0.010% or less, Cu:
1.0% or less, Ni: 1.0% or less, Cr: 1.0% or less, and Ca: 0.010% or less. Steel with 850~1000℃
After heating to a temperature within a temperature range of Rapid cooling at a cooling rate of /sec or more,
A method for producing thick-walled, high-tensile, hot-rolled steel sheets with excellent low-temperature toughness, characterized by winding.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15318781A JPS5855529A (en) | 1981-09-28 | 1981-09-28 | Preparation of thick high-tensile strength hot-rolled steel sheet excellent in low-temperature toughness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15318781A JPS5855529A (en) | 1981-09-28 | 1981-09-28 | Preparation of thick high-tensile strength hot-rolled steel sheet excellent in low-temperature toughness |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5855529A JPS5855529A (en) | 1983-04-01 |
| JPH0143006B2 true JPH0143006B2 (en) | 1989-09-18 |
Family
ID=15556942
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15318781A Granted JPS5855529A (en) | 1981-09-28 | 1981-09-28 | Preparation of thick high-tensile strength hot-rolled steel sheet excellent in low-temperature toughness |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5855529A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2011052282A (en) * | 2009-09-02 | 2011-03-17 | Sumitomo Metal Ind Ltd | Method for designing steel component of thick steel plate |
| CN114134415A (en) * | 2021-11-15 | 2022-03-04 | 山东钢铁集团日照有限公司 | Low-temperature high-toughness low-alloy medium-thickness steel plate and preparation method thereof |
-
1981
- 1981-09-28 JP JP15318781A patent/JPS5855529A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5855529A (en) | 1983-04-01 |
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