JPS61136633A - Manufacture of unnormalized high tensile strength steel - Google Patents

Abstract

PURPOSE:To improve weldability and toughness at low temp., by subjecting the steel containing prescribed percentage of C, Si, Mn, Al, S, Nb, Ti, etc., to hot rolling and then to heat treatment under prescribed conditions. CONSTITUTION:The steel containing, by weight, 0.005-0.2% C, 0.05-0.5% Si, 0.5-2% Mn, 0.005-0.08% Al, <=0.01% S, or further containing >=one kind among <=0.1% Nb, <=0.1% Ti, <=0.1% V, <=1% Ni, <=0.5% Cu, <=0.5% Cr, and <=0.5% Mo, or the like, is refined. This steel is hot-rolled, and cooled in the temp. range of 650-500 deg.C at 4-30 deg.C/S cooling rate, which is then cooled with >=40 deg.C water from the above temp. range to the temp. range of 500-200 deg.C, followed by air cooling or slow cooling.

Description

【発明の詳細な説明】 （産業上の利用分野） 溶接性と低温じん性に優れる非調質高張力鋼板の製造に
関連してこの明細書で述べる技術内容は、とくに鋼板内
のひずみ及び材質特性のばらつきが少ない加速冷却の手
法についての開発研究の成果に基いて上記特性を兼備し
た高張力鋼を有利に製造する方法を確立し、下記の如き
使途における非調質鋼板の適合を図るところにある。[Detailed Description of the Invention] (Industrial Application Field) The technical content described in this specification in connection with the production of non-temperature high-strength steel sheets that are excellent in weldability and low-temperature toughness is particularly focused on the strain and material quality of steel sheets. Based on the results of research and development on accelerated cooling methods with less variation in properties, we have established a method to advantageously produce high-strength steel that has the above properties, and are working to make non-tempered steel sheets suitable for the following uses. It is in.

従来溶接施工が必然的に伴われて、しかも低温じん性の
要求もきびしい高張力厚鋼板、例えば造船用高張力鋼板
や、タンク用圧力容器用鋼板、さらには寒冷地向はライ
ンパイプ用鋼板などは焼ならし、焼入焼戻し処理によっ
て製造するを例としているが、熱処理その他の経費の高
騰により製造費が嵩む欠点が看過できない。High-strength steel plates that conventionally require welding and have strict requirements for low-temperature toughness, such as high-strength steel plates for shipbuilding, steel plates for pressure vessels for tanks, and even steel plates for line pipes for cold regions. Although this is an example of manufacturing by normalizing, quenching and tempering, the drawback of increasing manufacturing costs due to the rise in heat treatment and other costs cannot be overlooked.

これに反し熱処理を施さない、いわゆる非調質で高張力
化、高じん性化をはかる製造方法としては、制御圧延（
以下ＣＲと記す）による方法の実施も普及しつつあるが
、ＣＲの仕上げ温度を下げようとすると圧延能率が著し
く劣化するばかりか、得られた鋼板のシャルピー衝撃破
面にセバレーシツンが発生するようになるため、適用鋼
種の拡大が難しいところに問題を残す。On the other hand, controlled rolling (
The implementation of the method (hereinafter referred to as CR) is also becoming popular, but if you try to lower the finishing temperature of CR, not only will the rolling efficiency deteriorate significantly, but also the resulting steel plate will have severe damage on the Charpy impact fracture surface. Therefore, the problem remains that it is difficult to expand the applicable steel types.

（従来の技術） ＣＲによる上記問題を改善すべく、低温域までのＣＲを
必要とせずに高張力化と高じん性化を目指す企てには、
例えば特開昭５７−１３４５１４号公報の如き圧延後に
加速冷却を施す方法がある。(Prior art) In order to improve the above-mentioned problems caused by CR, attempts are made to achieve high tensile strength and high toughness without requiring CR down to a low temperature range.
For example, there is a method of applying accelerated cooling after rolling, as disclosed in Japanese Unexamined Patent Publication No. 57-134514.

しかし乍ら加速冷却法により、じん性の劣化を少なくし
乍ら高強度化（高Ｔ、Ｓ、化）を図るには、加速冷却の
冷却停止温度を５００℃以下にすることによってのみ可
能なところ、冷却停止温度が５００以下の場合には、冷
却速度が急増するため、目標とする冷却停止温度に制御
することが困難となって、しばしば鋼板の長手方向、巾
方向に冷却むらが生じ、ひずみ及び材質特性の均一な鋼
板を製造することは困難であった。However, in order to achieve high strength (high T, S,) while minimizing deterioration of toughness using the accelerated cooling method, it is possible only by reducing the cooling stop temperature of accelerated cooling to 500℃ or less. However, when the cooling stop temperature is 500 or less, the cooling rate increases rapidly, making it difficult to control the cooling stop temperature to the target, often causing uneven cooling in the longitudinal and width directions of the steel plate. It has been difficult to produce steel plates with uniform strain and material properties.

また特開昭５７−１４３４３１号又は特開５８−６１２
２４号公報にも冷却停止温度を５００℃以下にしている
例がみられるけれども、ひずみ及び材質特性の均一な鋼
板を製造することは困難であった。Also, JP-A-57-143431 or JP-A-58-612
Although there is an example in Publication No. 24 in which the cooling stop temperature is set to 500° C. or lower, it is difficult to manufacture a steel plate with uniform strain and material properties.

（発明が解決しようとする問題点） 上記した従来技術の問題点を解決して、鋼板内にひずみ
及び材質特性のばらつきが少なく、溶接性と低温じん性
に優れる高張力鋼を、調質処理によらずとも安定して製
造できる方法を提供することがこの発明の目的である。(Problems to be Solved by the Invention) By solving the above-mentioned problems of the prior art, a high-strength steel with less variation in strain and material properties within the steel plate and excellent weldability and low-temperature toughness can be processed by heat treatment. It is an object of the present invention to provide a method that can be stably manufactured without relying on the method.

（問題点を解決するための手段） この発明はＣ：　０．００５〜０．２０ｗｔ％。(Means for solving problems) In this invention, C: 0.005 to 0.20 wt%.

Ｓｔ　：　０．０５　〜０．５０ｗｔ％。St: 0.05 to 0.50 wt%.

Ｍｎ　：　０．５　〜２．Ｏｗｔ％。Mn: 0.5 ~ 2. Owt%.

Ａｔ　：　０．００５〜０．０８詩ｔ％。At: 0.005-0.08 t%.

Ｓ　：　０．０１ｗｔ％以下。S: 0.01wt% or less.

を含有する組成或いは、更にＮｂ、Ｔｉ＋Ｖ＋Ｃｕ、Ｎ
ｉ＋ＣｒｔとＭｏのうちの少なくとも１種、及び／又は
ＣａとＲＨＮとのうち少くとも１種を、 Ｎｂにあっては０．１０Ｍｔ％以下、 Ｔｉにあっては０．１０ｗｔ％以下、 ■にあっては０．１０ｗｔ％以下、 Ｎｉにあっては１，０ｗｔ％以下、 Ｃｕ、Ｃｒ＋Ｍｏにあってはそれぞれ０．５ｗｔ％以下
、そして、 Ｃａにあっては０．０１０ｗｔ％以下 ＲＥＭにあっては０．０１０ｗｔ％以下で含有する成分
組成にて溶製した鋼を熱間圧延し、ただちに６５０〜５
００℃の温度域を４〜ｂ却速度で冷却し、さらに該温度
域から５００〜２００℃の温度域までを４０℃以上の温
度の水で冷却し、引続き空冷ないし徐冷することを特徴
とする溶接性と低温じん性の優れる非調質高張力鋼の製
造方法である。or further Nb, Ti+V+Cu, N
i + At least one of Crt and Mo and/or at least one of Ca and RHN, Nb at 0.10 Mt% or less, Ti at 0.10 wt% or less, 0.10wt% or less for Ni, 1.0wt% or less for Cu, 0.5wt% or less for Cu, Cr+Mo, and 0.010wt% or less for Ca. A steel melted with a composition containing 0.010 wt% or less is hot rolled and immediately
The temperature range of 00°C is cooled at a cooling rate of 4 to 200°C, and the temperature range from this temperature range to 500°C to 200°C is further cooled with water at a temperature of 40°C or higher, and then air cooling or slow cooling is performed. This is a method for manufacturing non-temperature high-strength steel with excellent weldability and low-temperature toughness.

発明者らは、鋼板内の冷却むらを少なくしてしかも有利
に鋼板の高強度化を図る方法について種々検討した結果
、圧延終了後加速冷却を実施する際、５００℃未満の冷
却をその温度が４０℃以上の水を使用することにより、
冷却停止温度のばらつきがほとんど解消され、そのため
、冷却むらが少なくなって鋼板のひずみの解消と、ひい
ては材質のばらつきの著しい軽減がもたらされ、しかも
４０℃以上の温水による冷却に拘らず高強度化が図れる
ことを新たに知見した。As a result of various studies on methods for reducing uneven cooling within a steel sheet and advantageously increasing the strength of the steel sheet, the inventors found that when performing accelerated cooling after rolling, the temperature is lower than 500°C. By using water above 40℃,
Variations in the cooling stop temperature are almost eliminated, which reduces uneven cooling, eliminates distortion in the steel plate, and significantly reduces variations in material quality.Moreover, it maintains high strength even when cooled with hot water of 40℃ or higher. We have newly discovered that it is possible to achieve

第１図はＣＲ直後に加速冷却を行った時の板厚中心部に
おける冷却速度を水温をパラメータとして示したもので
ある。FIG. 1 shows the cooling rate at the center of the plate thickness when accelerated cooling is performed immediately after CR, using water temperature as a parameter.

水温２５℃では約５００℃、水温８０℃では３００℃か
ら冷却速度が急激に速くなっており、これは鋼板表面で
の冷却挙動が膜沸騰から核沸騰に遷移する特異現象のた
め熱流束が急激に上昇するためと考えられる。At a water temperature of 25°C, the cooling rate rapidly increases from approximately 500°C, and at a water temperature of 80°C, the cooling rate rapidly increases from 300°C. This is due to a unique phenomenon in which the cooling behavior at the steel plate surface transitions from film boiling to nucleate boiling, and the heat flux rapidly increases. This is thought to be due to the increase in

発明者らは従来、通常の水温で加速冷却を続けた場合そ
の冷却停止温度を５００℃以下にして高強度化を図ろう
とすると、該冷却停止温度域が膜沸騰から核沸騰に遷移
する領域にあるため、冷却停正時の鋼板表面は温度差を
生じやすくしかも核沸騰の部分は水切りが容易でなく、
そのため鋼板のひずみおよび、材質のばらつきを生じや
すいことそのため、制御を正確に行うのに設備上多くの
工夫、投資が必要になることを解明した。The inventors have conventionally found that when accelerated cooling is continued at normal water temperature, when trying to increase the strength by reducing the cooling stop temperature to 500°C or less, the cooling stop temperature range shifts from film boiling to nucleate boiling. Because of this, the surface of the steel plate is prone to temperature differences when the cooling is stopped, and it is difficult to drain water from the nucleate boiling area.
As a result, it was found that distortion of the steel plate and variations in material quality are likely to occur, and that a large amount of equipment and investment is required to achieve accurate control.

これに反し、水温を上昇させて冷却すると膜沸騰領域が
低温側に拡張し、５００℃以下で冷却を停止させても冷
却停止時には鋼板表面は引続き膜沸騰領域が持続される
ため、鋼板上の水は容易に除去できてしかも温度むらも
少い。従って鋼板のひずみ、材質のばらつきも生じにく
いことが確認された。On the other hand, when cooling by raising the water temperature, the film boiling region expands to the lower temperature side. Water can be easily removed and there is little temperature variation. Therefore, it was confirmed that distortion of the steel plate and variation in material quality were less likely to occur.

次に発明者らは、圧延終了後の加速冷却につき、その後
半の冷却に際して水温を変える実験を行ったところ、水
温を上昇させることによりその冷却速度が遅（なるにも
かかわらず、従来法と同等の強度しん性が得られること
を知見した。Next, the inventors conducted an experiment in which the water temperature was changed during the latter half of the accelerated cooling after the completion of rolling, and found that increasing the water temperature slowed down the cooling rate (although it was slower than the conventional method). It was found that the same strength and toughness could be obtained.

第２図は、Ｃ：　０．０７ｗｔ％＋　Ｓｉ：　０−３　
ｗｔ％。Figure 2 shows C: 0.07wt% + Si: 0-3
wt%.

Ｍｎ　：　１．６ｗｔ％、＾ｌ　！　０．０３ｗｔ％、
　　Ｓ　：０．００２ｗｔ％。Mn: 1.6wt%, ^l! 0.03wt%,
S: 0.002wt%.

Ｎ　：　０．００５ｗｔ％、　Ｎｂ　：　０．０４ｗｔ
％、　　Ｖ　：　０．０４ｗｔ％。N: 0.005wt%, Nb: 0.04wt
%, V: 0.04wt%.

Ｃｕ　：　　０．２ｗｔ％、およびＮｉ　：　　０．２
ｗｔ％を含む組成の鋼をＣＲ後直ちに７００〜４５０℃
の種々な各温度域までを１０℃／Ｓの冷却速度で加速冷
却し、さらにそれらの停止温度から４００℃までの温度
域は水温を８０℃にして冷却を続行したとき（前者）の
機械的性質の変化（Ｏ印）を第１段階冷却停止温度に対
する関係で示す。Cu: 0.2wt%, and Ni: 0.2
700-450℃ immediately after CR of steel with a composition including wt%
accelerated cooling at a cooling rate of 10°C/S up to various temperature ranges, and furthermore, for the temperature range from the stop temperature to 400°C, the mechanical Changes in properties (marked with O) are shown in relation to the first stage cooling stop temperature.

比較法として上記と同じ＜ＣＲ後７００〜３００℃の種
々な各温度までを１０℃／Ｓの冷却速度にて加速冷却し
その後空冷したとき（後者）の機械的性質の変化（０印
）もあわせて第２図に示す。As a comparative method, changes in mechanical properties (marked 0) when accelerated cooling to various temperatures of 700 to 300 °C after CR at a cooling rate of 10 °C/S and then air cooling (latter) were also performed. It is also shown in Figure 2.

両者ともに冷却停止温度の低下とともにＴ、Ｓ、は段階
的に上昇の傾向にあるが、前者は冷却停止温度７００〜
４５０℃の領域において、後者の４５０℃以下に及ぶ加
速冷却を行った比較鋼と比べて、じん性の劣化なしに引
張強さを４〜１３ｋｇｆ／ｍｍ”より上昇させることが
できた。In both cases, T and S tend to increase gradually as the cooling stop temperature decreases, but in the former case, the cooling stop temperature is 700~
In the 450°C region, the tensile strength could be increased from 4 to 13 kgf/mm'' without deterioration of toughness compared to the latter comparative steel which was subjected to accelerated cooling to 450°C or less.

この発明では５００〜２００℃の範囲の第２段階加速冷
却の冷却水の温度を４０℃以上にすることにより、鋼板
の幅方向、長さ方向における温度むらが少なくなって最
終目標の冷却停止温度に均一にかつ容易に停止させるこ
とができること、さらに冷却停止時には鋼板表面は膜沸
騰域にあり、水切りが簡単なため、鋼板内の冷却停止温
度のばらつきが少なくなり、ひずみ及び材質特性のばら
つきの少ない鋼板を容易に製造できることが究明された
のである。In this invention, by setting the temperature of the cooling water in the second stage accelerated cooling in the range of 500 to 200 degrees Celsius to 40 degrees Celsius or higher, temperature unevenness in the width direction and length direction of the steel plate is reduced, and the final target cooling stop temperature is achieved. Furthermore, since the surface of the steel plate is in the film boiling region when cooling is stopped, it is easy to drain water, which reduces the variation in the cooling stop temperature within the steel plate, and reduces the variation in strain and material properties. It was discovered that it was possible to easily manufacture a small amount of steel plate.

（作　用） まず１段階目の冷却としては４〜ｂ 速度で６５０〜５００℃の温度域まで加速冷却するがそ
の理由は、 γ−α変態後のフェライト粒の成長を押えて、じん性を
向上させること、そして、 パーライト組成となる変態域をベイナイト組成に変態さ
せることにより引張強度を上昇させること、 にあるが、冷却速度が４℃／Ｓ未満ではベイナイト組成
の生成効果がなく、一方３０℃／Ｓを越えると塊状のベ
イナイトやマルテンサイト組成が生成して著しくしん性
を劣化させるのでこの段階における冷却速度は４〜ｂ 次に冷却停止温度を６５０〜５００℃と限定する理由は
、６５０℃を越える温度では、フェライト細粒効果及び
ベイナイト組成の生成効果がないためであり、さらに冷
却停止温度が５００℃未満では鋼板表面の冷却挙動につ
き膜沸騰から各沸騰に遷移する特異現象のために、冷却
速度が急激に速くなってもはやこの発明に従う２段階冷
却を適用しても最終冷却停止温度のばらつきを少なくと
ることは困難となる。(Function) First, the first stage of cooling is accelerated cooling to a temperature range of 650 to 500°C at a rate of 4 to 50°C.The reason for this is to suppress the growth of ferrite grains after the γ-α transformation and improve the toughness. and to increase the tensile strength by transforming the transformation region that has a pearlite composition to a bainite composition. However, if the cooling rate is less than 4°C/S, there is no effect of forming a bainite composition; If the temperature exceeds ℃/S, bulky bainite and martensite compositions will be generated, which will significantly deteriorate the toughness, so the cooling rate at this stage should be 4~b Next, the reason why the cooling stop temperature is limited to 650~500℃ is that At temperatures exceeding ℃, there is no ferrite fine grain effect and bainite composition formation effect, and furthermore, when the cooling stop temperature is lower than 500℃, there is a peculiar phenomenon in the cooling behavior of the steel sheet surface that transitions from film boiling to individual boiling. As the cooling rate increases rapidly, it becomes difficult to reduce the variation in the final cooling stop temperature even if the two-stage cooling according to the present invention is applied.

ちなみにＣＲ直後に１０℃／Ｓの冷却速度で加速冷却を
行ったとき板厚中心部における冷却曲線の変曲点がほぼ
５００℃に相当し上記の特異現象が裏付けられた。Incidentally, when accelerated cooling was performed at a cooling rate of 10°C/S immediately after CR, the inflection point of the cooling curve at the center of the plate thickness corresponded to approximately 500°C, confirming the above-mentioned peculiar phenomenon.

従って第１段階目の冷却停止温度は６５０〜５００　ｔ
の範囲内にする必要がある。Therefore, the cooling stop temperature in the first stage is 650 to 500 t.
Must be within the range.

次に第２段階の冷却制御は５００〜２００℃の温度域ま
で４０℃以上の温度の水で冷却するが、その理由につい
ては、第２段階目の冷却停止温度に至るべき範囲を４０
℃以上の水で冷却することにより、鋼板内の長さ方向、
巾方向の冷却停止温度むらを少なくすること、さらに冷
却停止温度を低くすることにより、マルテンサイトを生
成させ強度上昇させることにある。Next, the second stage of cooling control uses water at a temperature of 40°C or higher to cool down to a temperature range of 500 to 200°C.
By cooling with water above ℃, the longitudinal direction inside the steel plate,
The objective is to reduce the unevenness of the cooling stop temperature in the width direction and further lowering the cooling stop temperature to generate martensite and increase the strength.

水温が４０℃以下だと実質上膜沸騰域が低温側に拡大し
ないので水温は４０℃以上とする必要がある。If the water temperature is 40°C or lower, the film boiling region will not substantially expand to the lower temperature side, so the water temperature needs to be 40°C or higher.

次に冷却停止温度を５００〜２００℃と限定する理由は
、５００℃を越える温度ではマルテンサイト組成の生成
効果がないためであり、さらに冷却停止温度が２００℃
未満のように低すぎる温度まで加速冷却を施すと水素の
除去が十分できないため水素欠陥が起きるので冷却停止
温度は５００〜２００℃の範囲内にする必要がある。Next, the reason why the cooling stop temperature is limited to 500 to 200°C is that there is no effect of producing martensite composition at temperatures exceeding 500°C, and furthermore, the cooling stop temperature is limited to 200°C.
If accelerated cooling is performed to a temperature that is too low, such as below, hydrogen cannot be removed sufficiently and hydrogen defects will occur, so the cooling stop temperature must be within the range of 500 to 200°C.

また加速冷却を上記のようにして完了したあと２００℃
以上の温度から空冷もしくは徐冷するのは水素の除去を
容易にし、水素欠陥を防止するためである。In addition, after completing accelerated cooling as described above,
The reason for performing air cooling or gradual cooling from the above temperature is to facilitate the removal of hydrogen and prevent hydrogen defects.

次にこの発明の方法を適用して所期の効果を得るために
適合する好ましい鋼成分および圧延条件の具体例を述べ
る。Next, specific examples of preferred steel compositions and rolling conditions suitable for applying the method of the present invention and obtaining desired effects will be described.

まず鋼成分としては Ｃ：　０．００５〜０．２０鍔ｔ％、　Ｓｉ　：　０．
０５〜０．５０ｗｔ％Ｍｎ　：　０．５　〜２．Ｏｗｔ
％、　Ａｔ　：　０．００５〜０．０８ｗｔ％Ｓ　：　
０．０１ｗｔ％以下 を含有する組成或いは更に、Ｎｂ、ＴｉｔＶ、Ｃｕ＋Ｎ
ｉ＋Ｃｒ。First, the steel components are C: 0.005 to 0.20 t%, Si: 0.
05-0.50wt%Mn: 0.5-2. Owt
%, At: 0.005-0.08wt%S:
A composition containing 0.01 wt% or less, or in addition, Nb, TitV, Cu+N
i+Cr.

とＭｏのうち少なくとも１種、及び／またはＣａとＲＥ
Ｍとのうち少くとも１種を Ｎｂにあっては０．１　ｗｔ％以下 Ｔｉにあっては０．１　ｗｔ％以下 ■にあっては０．１　ｗｔ％以下 Ｎｉにあっては１．０　ｗｔ％以下 Ｃｕ、Ｃｒ＋Ｍｏにあってはそれぞれ０．５ｗｔ％以下
そして、 Ｃａにあっては０．０１０　ｗｔ％以下ＲＥＭにあって
は０．１０ｗｔ％以下 を含有する組成とすることが必要である。and at least one of Mo, and/or Ca and RE
At least one of M and M is 0.1 wt% or less for Nb, 0.1 wt% or less for Ti, 0.1 wt% or less for Ni, or 1.0 for Ni. It is necessary to create a composition containing 0.5 wt% or less for each of Cu and Cr+Mo, 0.010 wt% or less for Ca, and 0.10 wt% or less for REM. .

またこの発明においてはじん性を改善する目的からＮｂ
含有鋼にあっては（八ｒ３　＋　１５０）　℃〜＾ｒ１
間で少なくとも５０％以上、Ｎｂを含有していない鋼で
はＡｒ＝〜Ａｒｘ＋７０℃の温度範囲で少なくとも３０
％の圧下を必要とし、また圧延仕上温度はこれもじん性
の面から（Ａｒｓ　　４０℃）以上が好ましい。In addition, in this invention, for the purpose of improving toughness, Nb
For containing steel (8r3 + 150) ℃~^r1
At least 50% or more in between, and at least 30% in the temperature range of Ar=~Arx+70℃ for steels that do not contain
% of rolling reduction is required, and the rolling finish temperature is preferably at least (Ars 40°C) from the viewpoint of toughness.

Ｃ： Ｃは０．００５　ｗｔ％未満では鋼板強度が不足し、ま
た溶接熱影響部（以下１１ＡＺと記す）の軟化を来し、
一方０．２０％を越えると母材のじん性が劣化するとと
もに溶接部の硬化に加え、耐割れ性の劣化も著しくなる
ので、Ｃは０．００５〜０．２０ｗｔ％の範囲内にする
必要がある。C: If C is less than 0.005 wt%, the steel sheet strength will be insufficient and the weld heat affected zone (hereinafter referred to as 11AZ) will become softened.
On the other hand, if it exceeds 0.20%, the toughness of the base metal deteriorates, the weld hardens, and the cracking resistance deteriorates significantly, so C must be within the range of 0.005 to 0.20wt%. There is.

Ｓｉ　： Ｓｉは鋼精錬時に脱酸上必然的に含有される元素である
が、０．１ｗｔ％未満では母材じん性が不足し、一方０
．５ｗｔ％を越えると鋼の清浄度が劣化してじん性低下
の原因になるので、Ｓｉは０．１〜０．５％１ｔ％の範
囲内にする必要がある。Si: Si is an element that is inevitably included for deoxidation during steel refining, but if it is less than 0.1 wt%, the base material toughness will be insufficient;
．． If it exceeds 5 wt%, the cleanliness of the steel deteriorates and causes a decrease in toughness, so Si needs to be in the range of 0.1 to 0.5% and 1t%.

Ｍｎ： Ｍｎは０．８ｗｔ％未満では鋼板の強度およびじん性が
不足し、さらにＨＡＺ軟化が顕著となり、一方２．Ｏｗ
ｔ％を越えるとＨＡＺのじん性が劣化するので、Ｍｎは
０．８〜２．０ｗｔ％の範囲内にする必要がある。Mn: If Mn is less than 0.8 wt%, the strength and toughness of the steel sheet will be insufficient, and HAZ softening will become significant. Ow
If it exceeds t%, the toughness of the HAZ deteriorates, so Mn needs to be in the range of 0.8 to 2.0wt%.

ＡＩ＝ 鋼の脱酸上最低０．００５ｗｔ％のＡｌを固溶するよう
含有させることが必要であり、一方０．０８ｗｔ％を越
えるとＨＡＺのじん性のみならず溶接金属のしん性も著
しく劣化するので、ＡＩは０．００５〜０．８％１ｔ％
の範囲内にする必要がある。AI = It is necessary to contain at least 0.005wt% of Al as a solid solution for deoxidizing the steel.On the other hand, if it exceeds 0.08wt%, not only the toughness of the HAZ but also the toughness of the weld metal will deteriorate significantly. Therefore, AI is 0.005~0.8%1t%
Must be within the range.

Ｓ　： Ｓは０．０１０ｗｔ％を越えると、圧延と直角方向の吸
収エネルギーが著しく低下するので、０．０１０％１ｔ
％以下に制限する必要がある。S: If S exceeds 0.010 wt%, the absorbed energy in the direction perpendicular to rolling will decrease significantly, so 0.010% 1 t
% or less.

以上の成分組成においてこの発明の方法による所期した
硬化を奏するがその他以下に掲げる各群の成分がそれら
の添加目的の下で含有される場合にあっても、この発明
による効果の達成を妨げることはない。Although the above component composition achieves the desired curing by the method of this invention, even if other components of each group listed below are included for the purpose of their addition, it may prevent the achievement of the effects of this invention. Never.

第１群成分 Ｎｂ： Ｎｂはフェライトの細粒化に効果があるが、Ｑ、１ｗｔ
χを越えると溶接時に溶接金属中に拡散し、溶接金属の
しん性を低下させるので、Ｎｂは０．１ｗｔ％以下に限
定した。First group component Nb: Nb is effective in refining ferrite grains, but Q, 1wt
If Nb exceeds χ, it will diffuse into the weld metal during welding and reduce the toughness of the weld metal, so Nb was limited to 0.1 wt% or less.

Ｔｉ： Ｔｉは母材の強度を向上させるが０．１０ｗｔ％を越え
ると母材のじん性を著しく劣化させるので０．１０％１
ｔ％以下に限定した。Ti: Ti improves the strength of the base material, but if it exceeds 0.10 wt%, it will significantly deteriorate the toughness of the base material, so 0.10%1
It was limited to t% or less.

Ｖ　： ■は鋼板の母材の強度とじん性向上、継手強度確保のた
めむしろ０．０１Ｈｔ％以上の含有を可とするが、０．
１０ｗｔ％を越えると母材およびＨＡＺのじん性を著し
く劣化させるので、■は０．１０ｗｔ％以下の範囲内に
制限する。V: In order to improve the strength and toughness of the base material of the steel plate and ensure the strength of the joint, the content of V: 0.01Ht% or more is allowed, but 0.
If it exceeds 10 wt%, the toughness of the base material and HAZ will be significantly deteriorated, so ① is limited to 0.10 wt% or less.

Ｃｕ： Ｃｕは後述のＮｉとほぼ同様の効果があるだけでなく、
耐食性の向上にも寄与するが、０．５１１ｔχを越える
と熱間圧延中にクランクが発生しゃなくなり、鋼板の表
面性状が劣化するので、０．５ｗｔ％以下にする必要が
ある。Cu: Cu not only has almost the same effect as Ni, which will be described later, but also
It also contributes to improving corrosion resistance, but if it exceeds 0.511tχ, cranks will no longer occur during hot rolling and the surface quality of the steel sheet will deteriorate, so it is necessary to keep it below 0.5wt%.

Ｃｒ： Ｃｒは鋼板の母材強度と継手強度確保のために含有させ
得るが、０．５ｗｔχを越えると母材のじん性ばかりか
溶接部じん性にも悪影響が生じるので、０．５ｗｔ％以
下にする必要がある。Cr: Cr can be included to ensure the strength of the base metal of the steel plate and the strength of the joint, but if it exceeds 0.5wtχ, it will adversely affect not only the toughness of the base metal but also the toughness of the weld zone, so it should be 0.5wt% or less. It is necessary to

Ｎｉ　： ＮｉはＨＡＺ、の硬化性およびじん性に悪い影響を与え
ることな（、母材の強度、じん性を向上させるのに有用
であるが、０．５ｗｔχを越えて含有させるのは製造コ
ストの上昇を招くので、０．５ｗｔ％以下にする。Ni: Ni does not have a negative effect on the hardenability and toughness of the HAZ (and is useful for improving the strength and toughness of the base material, but containing more than 0.5wtχ increases manufacturing costs. Therefore, the amount should be 0.5 wt% or less.

ＭＯ： Ｍｏは圧延時の１粒を整粒となし、なおかつ微細なベイ
ナイトを生成するので強度、じん性の向上に有用である
が、０．５ｗｔχを越える必要はなく、却って製造コス
トの上昇を招く不利を来すのでＭＯは０．５ｗｔ％以下
に限定する。MO: Mo is useful for improving strength and toughness because it treats each grain as a regular grain during rolling and also produces fine bainite, but it is not necessary to exceed 0.5wtχ, and on the contrary, it increases manufacturing costs. Since this may cause disadvantages, MO is limited to 0.5 wt% or less.

第２群成分 Ｃａ： Ｃａは０．００２ｗｔχ程度の微量にてＭｎＳの形態制
御に効果をもたらし鋼板の圧延と直角方向のしん性向上
に有効であるが、０．０１０ｗｔχを越えると鋼の清浄
度が悪くなり内部欠陥の原因となるので、０．０１０ｗ
ｔ％以下の範囲に限定とした。2nd group component Ca: Ca is effective in controlling the morphology of MnS in a small amount of about 0.002wtχ and is effective in improving the toughness of the steel plate in the direction perpendicular to rolling, but when it exceeds 0.010wtχ, it affects the cleanliness of the steel. 0.010w as this will deteriorate and cause internal defects.
It was limited to a range of t% or less.

ＲＥＭ　　： ＲＢＭは０．００４ｗｔχ程度の微量にてやはり１ＩＩ
ｎｓの形態制御効果をあられし鋼板の圧延と直角方向の
じ°　ん性向上にを効であるが、０．０１０ｗｔχを越
えると鋼の清浄度が悪くなるほかにアーク溶接の面でも
不利があるので、０．０１０ｗｔ％以下の範囲に限定し
た。REM: RBM is still 1II at a trace amount of about 0.004wtχ
The shape control effect of ns is effective in improving the rolling and perpendicular toughness of steel sheets, but if it exceeds 0.010wtχ, the cleanliness of the steel deteriorates and there are also disadvantages in terms of arc welding. Therefore, the content was limited to 0.010 wt% or less.

以上の限定の理由から明らかなように第１群成分は主と
して強度増強、第２群成分は専らじん住改善に関し、そ
れぞれ同効成分と見なされる。As is clear from the above-mentioned limitations, the first group ingredients are mainly concerned with strength enhancement, and the second group ingredients are mainly concerned with improving living conditions, and are considered to be the same effective ingredients.

（実施例） 表１成分組成を示した供試鋼（Ａ）〜（１）を表２に示
す圧延−冷却条件により処理して、その鋼板の機械的性
質等を調査した結果を表２にまとめて示した。(Example) Test steels (A) to (1) whose compositions are shown in Table 1 were processed under the rolling-cooling conditions shown in Table 2, and the mechanical properties of the steel sheets were investigated. Table 2 shows the results. Shown all together.

表２において試験阻１〜５は、表１の供試鋼（Ａ）のス
ラブに種々の加熱−圧延−冷却条件により何れも板厚１
６ｍｍの製品としたものであり、また試験漱１１〜１６
は表１における供試鋼（Ｇ）のスラブに種々の加熱−圧
延−冷却条件により何れも板厚１６ｍｍの製品としたも
ので、さらに試験！ｌｈ６〜１０は表１の供試鋼ＣＢ）
〜（Ｆ）についての加熱−圧延−冷却条件および板厚の
異なる事例の成績も示しである。In Table 2, test results 1 to 5 were applied to the slab of test steel (A) in Table 1 under various heating-rolling-cooling conditions.
The product was 6 mm thick, and the test strain 11 to 16 was
The slabs of test steel (G) in Table 1 were subjected to various heating-rolling-cooling conditions to produce products with a thickness of 16 mm, and were further tested! lh6-10 are test steel CB in Table 1)
The results of cases with different heating-rolling-cooling conditions and plate thicknesses for ~(F) are also shown.

まず試験Ｎｌｌは圧延後の加速冷却を施していないため
、引張強さが低い。また問丸２は圧延後の加速冷却を６
００℃で停止しているため引張強さが低い。　゛ 次に試験１１ｈ３および１１は５００℃未満の４００℃
まで単一の冷却速度にて加速冷却を施した例（水温を変
化させなかった例に担当する）で鋼板内のひずみおよび
材質特性にばらつきが発生した。First, test Nll was not subjected to accelerated cooling after rolling, so its tensile strength was low. Question 2 is about accelerated cooling after rolling.
The tensile strength is low because it stops at 00°C.゛Next, tests 11h3 and 11 were conducted at 400°C below 500°C.
In an example in which accelerated cooling was performed at a single cooling rate up to (this is an example in which the water temperature was not changed), variations occurred in the strain and material properties within the steel plate.

隘１２は（Ａｒ、＋１５０℃）　〜Ａｒ、の温度域での
圧下率が少ない（２０％）のためしん性が劣化している
。In case 12, the reduction rate in the temperature range of (Ar, +150°C) to Ar is small (20%), so the toughness is deteriorated.

またＮａ１６は１００℃まで冷却したため水素割れが発
生した。これらに対しＮ１４，５．６（Ｎｂ非含を鋼）
およびｌ１ｂ１３，１４．１５　（Ｎｂ鋼）はこの発明
の要件とするところに従い製造したため高い強度と十分
な低温じん性を有しさらに鋼板内の材質ばらつきが少゛
なくかつひずみもない。Further, hydrogen cracking occurred in Na16 because it was cooled to 100°C. In contrast to these, N14,5.6 (Nb-free steel)
and l1b13,14.15 (Nb steel) were manufactured in accordance with the requirements of the present invention, so they have high strength and sufficient low-temperature toughness, and furthermore, there is little material variation within the steel plate and there is no distortion.

次に試験１ｌｋＬ７〜１０および１０．１７は板厚が１
６〜４０ｍｍの鋼板で何れも低温じん性の優れた鋼板の
製造事例であり、この発明の構成要件をすべて満足して
いるため、目標とする強度と低温じん性が、低い炭素当
量で実現でき、また材質のばらつき台よびひずみのまっ
たくない鋼板が得られている。Next, for tests 1lkL7 to 10 and 10.17, the plate thickness was 1
These are examples of manufacturing steel plates with a thickness of 6 to 40 mm and excellent low-temperature toughness, and as they satisfy all the constituent requirements of this invention, the target strength and low-temperature toughness can be achieved with a low carbon equivalent. In addition, a steel plate with no material variation or distortion was obtained.

（発明の効果） 以上述べたように圧延後の加速冷却に際しこの発明の方
法によれば、鋼板のひずみ、材質のばらつきについて特
に装置上の工夫を要せずして単に、第２段冷却の水温を
上昇させるだけで、強度しん性のすぐれた鋼板を容易に
得ることができ、また材質のばらつき及びひずみのまっ
たくない鋼板が得られる。(Effects of the Invention) As described above, according to the method of the present invention during accelerated cooling after rolling, strain in the steel plate and variations in material quality can be reduced by simply performing the second stage cooling without requiring any special device measures. By simply increasing the water temperature, a steel plate with excellent strength and toughness can be easily obtained, and a steel plate with no variation in material quality or distortion can be obtained.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は冷却曲線図、 第２図はＣＲ直後の加速冷却の冷却停止温度が強度しん
性に及ぼす影響の比較グラフである。 第１図 縛Ｍ（紗）Figure 1 is a cooling curve diagram, and Figure 2 is a comparison graph of the influence of the cooling stop temperature of accelerated cooling immediately after CR on strength toughness. Figure 1: Bound M (shape)

Claims (1)

【特許請求の範囲】 １、Ｃ：０．００５〜０．２０ｗｔ％、 Ｓｉ：０．０５〜０．５０ｗｔ％、 Ｍｎ：０．５〜２．０ｗｔ％、 Ａｌ：０．００５〜０．０８ｗｔ％、 Ｓ：０．０１ｗｔ％以下、 を含有する組成或いは、更にＮｂ、Ｔｉ、Ｖ、Ｃｕ、Ｎ
ｉ、Ｃｒ、とＭｏのうちの少なくとも１種、及び／又は
ＣａとＲＥＭとのうち少くとも１種を、 Ｎｂにあっては０．１０ｗｔ％以下、 Ｔｉにあっては０．１０ｗｔ％以下、 Ｖにあっては０．１０ｗｔ％以下、 Ｎｉにあっては１．０ｗｔ％以下、 Ｃｕ、Ｃｒ、Ｍｏにあってはそれぞれ０．５ｗｔ％以下
、そして、 Ｃａにあっては０．０１０ｗｔ％以下 ＲＥＭにあっては０．０１０ｗｔ％以下 で含有する成分組成にて溶製した鋼を熱間圧延し、ただ
ちに６５０〜５００℃の温度域を４〜３０℃／ｓの冷却
速度で冷却し、さらに該温度域から５００〜２００℃の
温度域までを、４０℃以上の温度の水で冷却し、引続き
空冷ないし徐冷することを特徴とする溶接性と低温じん
性の優れる非調質高張力鋼の製造方法。[Claims] 1. C: 0.005 to 0.20 wt%, Si: 0.05 to 0.50 wt%, Mn: 0.5 to 2.0 wt%, Al: 0.005 to 0.08 wt%. %, S: 0.01 wt% or less, or further containing Nb, Ti, V, Cu, N
i, Cr, and at least one of Mo, and/or at least one of Ca and REM, Nb is 0.10 wt% or less, Ti is 0.10 wt% or less, 0.10wt% or less for V, 1.0wt% or less for Ni, 0.5wt% or less for each of Cu, Cr, and Mo, and 0.010wt% or less for Ca. In REM, steel melted with a composition containing 0.010 wt% or less is hot rolled, immediately cooled in a temperature range of 650 to 500 ° C at a cooling rate of 4 to 30 ° C / s, and further A non-thermal high tensile steel with excellent weldability and low-temperature toughness, characterized by cooling with water at a temperature of 40°C or higher from the above temperature range to a temperature range of 500 to 200°C, followed by air cooling or slow cooling. manufacturing method.