JPH0776377B2 - Manufacturing method of high strength steel plate with excellent low temperature toughness - Google Patents
Manufacturing method of high strength steel plate with excellent low temperature toughnessInfo
- Publication number
- JPH0776377B2 JPH0776377B2 JP62054171A JP5417187A JPH0776377B2 JP H0776377 B2 JPH0776377 B2 JP H0776377B2 JP 62054171 A JP62054171 A JP 62054171A JP 5417187 A JP5417187 A JP 5417187A JP H0776377 B2 JPH0776377 B2 JP H0776377B2
- Authority
- JP
- Japan
- Prior art keywords
- rolling
- austenite
- low temperature
- temperature toughness
- steel plate
- 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.)
- Expired - Lifetime
Links
Landscapes
- Heat Treatment Of Steel (AREA)
Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は低温靭性の優れた高強度厚鋼板の製造法に関す
るもので、特に連続鋳造鋳片の熱間圧延に用いる厚板ミ
ルに適用することが望ましい製造法に係る。TECHNICAL FIELD The present invention relates to a method for producing a high-strength steel plate having excellent low temperature toughness, and is particularly applied to a plate mill used for hot rolling of continuously cast slabs. Relates to a desirable manufacturing method.
（従来の技術） 加工熱処理技術の進歩に伴い、高張力鋼の低温靭性改善
のためには、鋳片の加熱温度の低温化による初期オース
テナイト粒の粗大化抑制,Nb,Ni等の合金元素添加及び制
御圧延，加速冷却によるミクロ組織の微細化等が行なわ
れている。特に、制御圧延時のオーステナイト未再結晶
域での圧延は転位密度の増加，変形帯の導入を促進し、
変態後のフェライト粒を微細化するため、低温靭性の改
善に極めて有効である。オーステナイト未再結晶域圧延
での１パス当たりの圧下率の下限を設けたものとしては
特公昭56−4610がある。これは、含Nb鋼板の製造におい
て、圧延温度域，圧下率等を規定することにより高靭化
を図っている。しかし、板厚が19mm以下と薄く、圧延に
よる圧下量が十分にとれているにもかかわらず、シャル
ピー衝撃特性における50％延性破面遷移温度（vTsある
いはvTrs）は−70〜−90程度である。また、TS（抗張
力）が60kg/mm2程度となると、衝撃特性は劣化する傾向
にある。(Conventional technology) In order to improve the low temperature toughness of high-strength steel with the progress of thermomechanical processing technology, the coarsening of initial austenite grains is suppressed by lowering the heating temperature of the slab, and the addition of alloying elements such as Nb and Ni. In addition, the microstructure is refined by controlled rolling and accelerated cooling. In particular, rolling in the austenite unrecrystallized region during controlled rolling promotes an increase in dislocation density and the introduction of deformation zones,
Since the ferrite grains after transformation are made finer, it is extremely effective in improving the low temperature toughness. Japanese Patent Publication No. 56-4610 has a lower limit of the rolling reduction per pass in the austenite unrecrystallized region rolling. This is intended to increase the toughness by specifying the rolling temperature range, reduction ratio, etc. in the production of Nb-containing steel sheet. However, even though the plate thickness is as thin as 19 mm or less and the amount of reduction by rolling is sufficient, the 50% ductile fracture surface transition temperature (vTs or vTrs) in Charpy impact characteristics is about -70 to -90. . Further, when the TS (tensile strength) is about 60 kg / mm 2 , the impact properties tend to deteriorate.
（発明が解決しようとする問題点） 前述のように従来の技術ではTS 60kg/mm2未満の鋼でも
低温靭性が不十分で、また、TS 60kg/mm2を超える高強
度鋼においては、低温靭性の劣化が避けられない。ま
た、極厚鋼板についても、板厚中心部の衝撃特性が劣る
という欠点が解決されないものである。本発明は、TS 6
0kg/mm2未満の鋼は言うまでもなく、TS 60kg/mm2以上の
鋼においても格段に優れた低温靭性を有すること及び、
極厚高強度鋼板における板厚中心部の低温靭性の改善，
強度，靭性バランスの改善を目的としている。(Invention Problems to be Solved it) is insufficient low temperature toughness in the aforementioned manner TS 60 kg / mm 2 lower than the steel in the prior art, In the high strength steel exceeding TS 60 kg / mm 2, the low-temperature Degradation of toughness is inevitable. Further, with respect to the extremely thick steel plate, the drawback that the impact property at the central portion of the plate thickness is inferior cannot be solved. The present invention is TS 6
Not only steels with a weight of less than 0 kg / mm 2 , but also steels with a weight of TS 60 kg / mm 2 or more have significantly low temperature toughness, and
Improvement of low temperature toughness at the center of thickness of extra-thick high strength steel plate,
The purpose is to improve the balance of strength and toughness.
（問題点を解決する手段） 本発明の要旨は連続鋳造法によって製造した鋳片の熱間
圧延に際して、オーステナイト再結晶域で累積圧下量40
％以上の圧延を行ない、続いて850℃以下650以上のオー
ステナイト未再結晶域において、累積圧下量を50％以上
とし、かつ圧延最終５パスにおいて圧下率15％以上の圧
下を３回以上加え、その後直ちに加速冷却することを特
徴とする低温靭性の優れた高強度厚鋼板の製造法であ
る。(Means for Solving Problems) The gist of the present invention is to reduce the cumulative rolling reduction amount in the austenite recrystallization region during hot rolling of a slab produced by a continuous casting method.
%, Then, in the austenite unrecrystallized region of 850 ° C. or lower and 650 ° C. or higher, the cumulative rolling reduction is 50% or more, and the rolling reduction of 15% or more is applied three times or more in the final five passes of rolling, This is a method for producing a high-strength thick steel sheet having excellent low-temperature toughness, which is characterized by accelerated cooling immediately thereafter.
以下、本発明について詳しく説明する。Hereinafter, the present invention will be described in detail.
通常、厚鋼板の製造においては材質面ばかりでなく圧延
工程における圧延能率上、その圧延温度域は650〜1250
℃程度に限定される。これらの温度域の中でオーステナ
イト再結晶域，未再結晶域の境界は800〜1000℃程度の
間にあり、鋼の化学成分，加熱圧延条件によって変化す
るものである。オーステナイト再結晶域は、再結晶を行
なうことによりオーステナイトが微細化する領域であ
り、高温圧延においては再結晶オーステナイトは成長し
やすいため低温域での圧延による再結晶が望ましい。ま
た、低温靭性を向上させるためには粗大粒の生成を防止
し、整細粒オーステナイト組織を得る必要があるが、そ
のためにはまずオーステナイト再結晶域で累積圧下量40
％以上としなければならない。この条件に従えば、再結
晶したオーステナイトはかなり細粒になっているが、低
温靭性の向上にはより一層オーステナイト組織を微細化
し、フェライト核生成サイトを増加させる必要がある。
そのためには850℃以下650℃以上のオーステナイト未再
結晶域で累積圧下量50％以上かつ圧延最終５パスにおい
て圧下率15％以上の圧下を３回以上加える必要がある。
この条件に従って圧延を行なえばオーステナイトの延伸
化による粒界面積の増加、粒内への変形帯の導入、双晶
境界の活性化等によりフェライト核生成サイトは著しく
増加し、γ−α変態後のフェライト（あるいはベイナイ
ト，パーライト）組織は極めて微細化するため、優れた
低温靭性が得られるとともに強度の上昇も期待できる。Usually, in the production of thick steel plate, the rolling temperature range is 650 to 1250 in terms of not only the material quality but also the rolling efficiency in the rolling process.
Limited to about ℃. The boundary between the austenite recrystallized region and the non-recrystallized region is in the range of 800 to 1000 ° C in these temperature regions, and it changes depending on the chemical composition of the steel and the heating and rolling conditions. The austenite recrystallization region is a region in which austenite is refined by performing recrystallization, and since recrystallized austenite easily grows in high temperature rolling, recrystallization by rolling in a low temperature region is desirable. In order to improve the low temperature toughness, it is necessary to prevent the formation of coarse grains and obtain a fine-grained austenite structure.
Must be at least%. According to this condition, the recrystallized austenite is considerably fine grained, but in order to improve the low temperature toughness, it is necessary to further refine the austenite structure and increase the ferrite nucleation site.
For that purpose, it is necessary to apply the rolling reduction of 50% or more in the austenite unrecrystallized region of 850 ° C. or more and 650 ° C. or more and the rolling reduction of 15% or more in the final five passes of rolling at least three times.
If rolling is performed according to this condition, the ferrite nucleation site is remarkably increased due to an increase in the grain boundary area due to the austenite stretching, the introduction of a deformation zone into the grain, the activation of twin boundaries, etc. Since the ferrite (or bainite, pearlite) structure becomes extremely fine, excellent low-temperature toughness can be obtained and an increase in strength can be expected.
しかし、850℃を超える温度での圧延では、オーステナ
イトが部分的に再結晶するためフェライト核生成サイト
を増加させる効果が少ない。また、650℃未満の温度で
の圧延は二相域圧延のため結晶粒を極度に加工し、転位
密度増加による強度上昇は図れるものの、低温靭性は著
しく劣化するとともに、圧延方向とそれと直角方向との
材質の差が著しく増大する。そのため、オーステナイト
未再結晶域の圧延は850℃以下650℃以上で行なう必要が
ある。又、累積圧下量50％未満ではオーステナイト延伸
化による粒内の累積歪が不十分で圧下率によらず変形
帯，双晶境界の密度の増加が期待できない。オーステナ
イト未再結晶域の圧下量、温度が一定の場合、圧下率が
大きい方が粒内の変形帯密度、双晶境界密度が増加す
る。しかし材質改善効果が得られる圧下率の下限は15％
であり、かつ圧延最終５パスにおいて３パス以上行なう
ことが必要である。最終５パスにおいても15％以上の圧
下が３パス未満では以上のような効果は得られない。However, rolling at temperatures above 850 ° C has little effect of increasing ferrite nucleation sites because austenite is partially recrystallized. Also, rolling at a temperature of less than 650 ° C is a two-phase region rolling, so the crystal grains are extremely processed, and although the strength can be increased by increasing the dislocation density, the low temperature toughness significantly deteriorates and the rolling direction and the direction perpendicular to it The difference in the materials of the materials significantly increases. Therefore, rolling in the austenite unrecrystallized region must be performed at 850 ° C or lower and 650 ° C or higher. On the other hand, if the cumulative rolling reduction is less than 50%, the cumulative strain in the grain due to the austenite stretching is insufficient, and it is not possible to expect an increase in the deformation zone and the density of twin boundaries regardless of the rolling reduction. When the amount of reduction and temperature in the austenite unrecrystallized region are constant, the larger the reduction rate, the higher the deformation zone density within the grain and the twin boundary density. However, the lower limit of the reduction rate at which the material improvement effect is obtained is 15%
And it is necessary to perform three or more passes in the final five passes of rolling. Even in the final 5 passes, if the reduction of 15% or more is less than 3 passes, the above effect cannot be obtained.
さらに、圧延終了後の鋼板は加速冷却しなければならな
い。加速冷却は、フェライト粒の成長を抑制しフェライ
ト粒の微細化を行なうため低温靭性は向上する。また、
変態強化、加工オーステナイトの凍結を行なうことがで
き、著しい強度上昇が図れ、強度、靭性バランスの飛躍
的向上が図れる。Further, the steel sheet after the rolling has to be accelerated cooled. Accelerated cooling improves the low temperature toughness by suppressing the growth of ferrite grains and refining the ferrite grains. Also,
The transformation can be strengthened and the processed austenite can be frozen, the strength can be remarkably increased, and the balance of strength and toughness can be dramatically improved.
加速冷却の条件については特に規定するものではない
が、圧延直後直ちに冷却速度:5℃/s〜40℃/sで行なうこ
とが望ましい。加速冷却は途中停止の有無を問わない。
また、冷却後の鋼板を500℃以上Ac1温度以下に焼戻処理
することも何ら本発明鋼の特性を損なうものではない。The conditions for accelerated cooling are not particularly specified, but it is desirable to perform the cooling rate immediately after rolling at a cooling rate of 5 ° C / s to 40 ° C / s. Accelerated cooling may or may not be stopped midway.
Further, tempering the cooled steel sheet to a temperature of 500 ° C. or higher and an Ac 1 temperature or lower does not impair the characteristics of the steel of the present invention.
（実施例） 次に、本発明の実施例について述べる。(Example) Next, the Example of this invention is described.
第１表は連続鋳造によって製造した鋳片から厚鋼板を製
造した再の供試鋼の化学成分を示す。第２表には製造条
件を、第３表には厚鋼板の材質特性を示す。第２表，第
３表中鋼１〜10は本発明法で製造した鋼であり、鋼11〜
16は従来法で製造した比較鋼である。本発明法で製造し
た鋼はいずれも従来法で製造した鋼に比べて高強度かつ
高靭性であり、板厚50mm以上の厚鋼板においても板厚中
心部（1/2t）の低温靭性に優れている。Table 1 shows the chemical composition of the re-tested steel from which a thick steel plate was produced from a slab produced by continuous casting. Table 2 shows the manufacturing conditions, and Table 3 shows the material properties of the thick steel plate. Steels 1 to 10 in Tables 2 and 3 are steels produced by the method of the present invention.
16 is a comparative steel manufactured by the conventional method. All of the steels manufactured by the method of the present invention have higher strength and higher toughness than steels manufactured by the conventional method, and are excellent in low-temperature toughness at the center part (1 / 2t) of plate thickness even in thick steel plates with a plate thickness of 50 mm or more. ing.
Ａ成分の鋼11は、圧延の終段で圧下率15％以上の圧下が
３回に満たないものである。そのため、強度が低いばか
りでなくフェライト粒の微細化が不十分なため低温靭性
も劣る。Ｂ成分の鋼12はオーステナイト再結晶域の累積
圧下量が40％に満たないため、オーステナイトの再結晶
が不十分でオーステナイト粒は粗大なままである。この
結果、オーステナイト未再結晶域での圧延を十分に行な
っても鋼板での低温靭性は劣る。Ｄ成分の鋼13は圧延後
に加速冷却を行なわなかったため、変態強化が十分でな
いばかりでなくフェライト粒の微細化も不十分となり、
強度，低温靭性ともに劣る。Ｅ成分の鋼14は850以下650
℃以上のオーステナイト未再結晶域における累積圧下量
が50％以下のため、また、Ｆ成分の鋼15はオーステナイ
ト未再結晶域の圧延開始温度が850℃より高いため、転
位密度の増加，フェライト核生成サイトの増加が不十分
となり、強度低温靭性ともに劣る。Ｇ成分の鋼16はオー
ステナイト未再結晶域の圧延終了温度が650℃より低く
結晶粒の極度の加工のため、低温靭性は著しく劣る。The steel 11 of the A component has a rolling reduction of 15% or more at the final stage of rolling less than three times. Therefore, not only the strength is low, but also the low temperature toughness is poor because the ferrite grains are not sufficiently refined. Since the cumulative reduction amount of the B component steel 12 is less than 40% in the austenite recrystallization region, recrystallization of austenite is insufficient and the austenite grains remain coarse. As a result, the low temperature toughness of the steel sheet is inferior even if the rolling in the austenite unrecrystallized region is sufficiently performed. Since the D component steel 13 was not subjected to accelerated cooling after rolling, not only the transformation strengthening was insufficient, but also the ferrite grains were not sufficiently refined,
Both strength and low temperature toughness are inferior. E component steel 14 is 850 or less 650
Since the cumulative rolling reduction in the austenite unrecrystallized region above ℃ is less than 50% and the rolling start temperature of the F component steel 15 is higher than 850 ° C in the austenite unrecrystallized region, the dislocation density increases and the ferrite nuclei increase. The increase in the number of production sites is insufficient, resulting in poor strength and low temperature toughness. The G component steel 16 has a rolling end temperature in the austenite unrecrystallized region lower than 650 ° C. and is extremely poor in low temperature toughness due to extreme working of crystal grains.
（発明の効果） 本発明により製造された厚鋼板は従来の鋼に比べて格段
に優れた高強度高靭性となり、本発明による利益は大で
ある。(Effect of the Invention) The thick steel plate manufactured according to the present invention has significantly higher strength and toughness as compared with the conventional steel, and the benefits of the present invention are great.
Claims (1)
延に際して、オーステナイト再結晶域で累積圧下量40％
以上の圧延を行ない、続いて850℃以下650以上のオース
テナイト未再結晶域において、累積圧下量を50％以上と
し、かつ圧延最終５パスにおいて圧下率15％以上の圧下
を３回以上加え、その後直ちに加速冷却することを特徴
とする低温靭性の優れた高強度厚鋼板の製造法。1. A hot rolling of a slab produced by a continuous casting method, in which the cumulative rolling reduction is 40% in the austenite recrystallization region.
The above rolling was performed, and then, in the austenite unrecrystallized region of 850 ° C or lower and 650 or higher, the cumulative rolling reduction was set to 50% or more, and the rolling reduction of 15% or more was applied three or more times in the final five passes of the rolling. A method for producing a high-strength steel plate with excellent low-temperature toughness, characterized by immediate accelerated cooling.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62054171A JPH0776377B2 (en) | 1987-03-11 | 1987-03-11 | Manufacturing method of high strength steel plate with excellent low temperature toughness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP62054171A JPH0776377B2 (en) | 1987-03-11 | 1987-03-11 | Manufacturing method of high strength steel plate with excellent low temperature toughness |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS63223124A JPS63223124A (en) | 1988-09-16 |
| JPH0776377B2 true JPH0776377B2 (en) | 1995-08-16 |
Family
ID=12963095
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP62054171A Expired - Lifetime JPH0776377B2 (en) | 1987-03-11 | 1987-03-11 | Manufacturing method of high strength steel plate with excellent low temperature toughness |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0776377B2 (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01230713A (en) * | 1988-03-08 | 1989-09-14 | Nippon Steel Corp | Production of high-strength and high-toughness steel having excellent stress corrosion cracking resistance |
| CN102941227A (en) * | 2012-10-29 | 2013-02-27 | 唐山建龙实业有限公司 | Production process for middle-width hot rolling strip steel for cold rolling |
| CN114042773B (en) * | 2021-10-18 | 2023-06-23 | 山西太钢不锈钢股份有限公司 | Method for improving tissue uniformity of stainless steel super-thick plate |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS564610A (en) * | 1979-06-26 | 1981-01-19 | Sumitomo Chem Co Ltd | Curable resin composition |
| JPS57134514A (en) * | 1981-02-12 | 1982-08-19 | Kawasaki Steel Corp | Production of high-tensile steel of superior low- temperature toughness and weldability |
-
1987
- 1987-03-11 JP JP62054171A patent/JPH0776377B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPS63223124A (en) | 1988-09-16 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP3990725B2 (en) | High strength duplex steel sheet with excellent toughness and weldability | |
| JP3554505B2 (en) | Hot-rolled wire rod / steel bar for machine structure and manufacturing method thereof | |
| JPH11140582A (en) | High toughness thick steel plate excellent in toughness in weld heat-affected zone, and its production | |
| JP3314295B2 (en) | Method of manufacturing thick steel plate with excellent low temperature toughness | |
| KR0142274B1 (en) | Sheet steel excellent in flanging capability and process for producing the same | |
| JP3851147B2 (en) | Non-tempered high strength and high toughness forged product and its manufacturing method | |
| JP2003147479A (en) | Non-heatteated high strength and high toughness forging, and production method therefor | |
| JP3922805B2 (en) | Manufacturing method of high-tensile steel with excellent low-temperature toughness | |
| JP4405026B2 (en) | Method for producing high-tensile strength steel with fine grain | |
| KR970009087B1 (en) | Method for manufacturing strong and touch thick steel plate | |
| JPS625212B2 (en) | ||
| JPH10306315A (en) | Production of non-heat treated high tensile-strength steel excellent in low temperature toughness | |
| JPH0776377B2 (en) | Manufacturing method of high strength steel plate with excellent low temperature toughness | |
| JPH04358023A (en) | Production of high strength steel | |
| JPH06299237A (en) | Manufacture of high tension steel sheet | |
| KR100946051B1 (en) | Method for manufacturing the good weldability and high strength thick plate steel | |
| JP3462922B2 (en) | Manufacturing method of high strength steel sheet with excellent strength and toughness | |
| JP3212348B2 (en) | Manufacturing method of fine grain thick steel plate | |
| JP2003147480A (en) | Non-heatteated high strength and high toughness forging, and production method therefor | |
| KR100256357B1 (en) | The manufacturing method for high strength steel sheet with cu precipitation hardening type | |
| KR100530076B1 (en) | Drawing High Strength Steel Sheet With Secondary Working Brittleness Resistance and Press Formability and A Method for Manufacturing thereof | |
| JP2579721B2 (en) | Manufacturing method of tough steel | |
| JPH07242940A (en) | Production of low yield ratio high tensile strength steel by rapid tempering | |
| JPH062903B2 (en) | Manufacturing method of thick steel plate with excellent toughness | |
| JP2001329315A (en) | Method for producing steel plate excellent in toughness |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |