JPS6059018A - Production of cu-added steel having excellent weldability and low-temperature toughness - Google Patents

Abstract

PURPOSE:To obtain a Cu-added steel having excellent strength, toughness and welding characteristic by heating a continuous casting billet contg. C, Si, Mn, Nb, Cu, Al and S respectively at prescribed ratios at a low temp. and rolling said steel under specific conditions then cooling the rolled steel and subjecting the same to a tempering treatment. CONSTITUTION:A continuous casting billet contg. 0.005-0.090% C, <=0.6% Si, 0.6-2.2% Mn, 0.005-0.08% Nb, 0.5-1.5% Cu, 0.005-0.08% Al and <=0.003% S and consisting of the balance Fe and unavoidable impurities is treated in the following way: The billet is heated to <=1,150 deg.C, more particularly to the Ac3 transformation point or above to fine the austenite grains in the stage of heating. The billet after the heating treatment is rolled at the cumulative draft at <=900 deg.C limited to >=60% and the finishing temp. limited to <=800 deg.C to improve considerably the strength and toughness of the steel sheet. The steel sheet after rolling is subjected to tempering at >=500 deg.C and the Ac1 point or below after said steel is allowed to cool or is forcibly cooled, by which the Cu-added steel having the intended excellent weldability and low-temp. toughness is obtd.

Description

【発明の詳細な説明】 （産業上の利用分野） 本発明は溶接性及び低温靭性の優れたＣｕ添加高張力鋼
の製造法に関するものである。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for producing Cu-added high-strength steel having excellent weldability and low-temperature toughness.

近年、経済性、安全性等の面から溶接構造物（建築、圧
力容器、造船、ラインパイプなど）における高張力鋼の
使用は多岐にわたシ、溶接性高張力鋼の需要は鋼板、条
鋼、シームレスパイプ等として着実な増加を示している
。溶接構造物に使用される鋼は当然のことながら高強度
に加え、安全性、作業性の面から、低温靭性と優れた溶
接性’ｋＩ７１’せもつことが要求される。In recent years, the use of high-strength steel in welded structures (architecture, pressure vessels, shipbuilding, line pipes, etc.) has expanded from the viewpoint of economy and safety, and the demand for weldable high-strength steel is increasing in steel plates, bars, It is showing steady increase as seamless pipe etc. Steel used for welded structures is naturally required to have high strength, as well as low temperature toughness and excellent weldability 'kI71' from the standpoint of safety and workability.

（従来技術） Ｃｕは古くよシ時効硬化作用を有する元素として知られ
ており、鋼にＣｕ　ｆ約０．５％以上添加し、適当な熱
処理を行なうことによシ、容易に高強度を得ることがで
きる。このため、Ｃｕ添加鋼では低炭素当量（Ｃｅｑ）
、低Ｃでも高強度化が達成可能である。しかし、Ｃｕ添
加鋼（Ｃｕ″＞０．５％）は現在、低温靭性及び溶接性
が必要な高張力鋼にはほとんど使用されていない。この
理由は製造上熱間圧延中にＣｕ−クラックを起こすこと
あるいは材質上時効による強度上昇によって低温靭性が
著しく劣化するなどのためである。(Prior art) Cu has long been known as an element that has an age-hardening effect, and high strength can be easily obtained by adding about 0.5% or more of Cu f to steel and performing appropriate heat treatment. be able to. For this reason, Cu-added steel has a low carbon equivalent (Ceq)
, high strength can be achieved even at low C. However, Cu-added steel (Cu''>0.5%) is currently hardly used for high-strength steel that requires low-temperature toughness and weldability. This is because the low-temperature toughness is significantly deteriorated due to the aging of the material and the strength increase due to aging.

（本発明の目的） そこで本発゛明はＣｕ添加鋼の大きな特徴である低Ｃ１
低Ｃｅｑでも高強度が得られる特徴を生かすため、製造
上、材質上の問題点を解決し、溶接性及び低温靭性の優
れたＣｕ添加高張力鋼を製造しようとするものである。(Objective of the present invention) Therefore, the present invention aims to achieve low C1, which is a major feature of Cu-added steel.
In order to take advantage of the feature that high strength can be obtained even at low Ceq, we aim to solve manufacturing and material problems and produce a Cu-added high-strength steel with excellent weldability and low-temperature toughness.

（発明の要旨） 本発明の要旨とするところは以下の通りである。(Summary of the invention) The gist of the present invention is as follows.

（１）　Ｃ：０．００５〜０．０９０チ、Ｓｉ：０．６
％以下、Ｍｎ　’：　０．６−２．２％、Ｎｂ：０．０
０５〜０．０８％。(1) C: 0.005-0.090chi, Si: 0.6
% or less, Mn': 0.6-2.2%, Nb: 0.0
05-0.08%.

Ｃｕ　：　０．５−１．５％、ＡＡ：０．００５〜０．
０８％。Cu: 0.5-1.5%, AA: 0.005-0.
08%.

Ｓ：０．００３係以下 全含有し、残部鉄及び不可避的不純物よりなる鋼片を１
１５０Ｃ以下の温度に加熱し、その後の圧延にあたって
９００？Ｓ以下の累積圧下率が６０％以上でかつ仕上温
度８００Ｃ以下の圧延を行ない、放冷または強制冷却後
５００　ＩＴ以上Ａｃ１以下の温度で焼戻しを行なうこ
と全特徴とする溶接性および低温靭性の優れたＣｕ添加
鋼の製造法。S: 1 piece of steel containing 0.003% or less, with the remainder consisting of iron and unavoidable impurities.
It is heated to a temperature of 150C or less, and then rolled to a temperature of 900℃. Rolling is carried out at a cumulative reduction rate of S or less of 60% or more and a finishing temperature of 800C or less, and after cooling or forced cooling, tempering is performed at a temperature of 500IT or more and Ac1 or less.All features are excellent weldability and low temperature toughness. A method for producing Cu-added steel.

（２）　Ｃ：０．００５〜０．０９０％、Ｓｉ：０．６
％以下、Ｍｕ　：　０．６〜２．２　％　＊　Ｎｂ　：
　０．０　Ｏ５〜０．０８％。(2) C: 0.005-0.090%, Si: 0.6
% or less, Mu: 0.6-2.2% *Nb:
0.0 O5-0.08%.

Ｃｕ　：　０．５−１．５％、　Ｍ：０．００５〜０．
０８％。Cu: 0.5-1.5%, M: 0.005-0.
08%.

Ｓ：０．００３％以下 全含有し、さらに Ｃｒ　：　０．１〜０．５％、Ｎｉ　：　０．１〜２．
０％。S: 0.003% or less total content, further Cr: 0.1-0.5%, Ni: 0.1-2.
0%.

Ｍｏ　：　０．０５〜０．３％、Ｖ：０．０１−０．１
０係。Mo: 0.05-0.3%, V: 0.01-0.1
0 person in charge.

Ｔｉ：０．００５〜０．０２５％、Ｂ：０．０００５〜
０．００２％、Ｃａ　：　０．０００５−０．００５％
。Ti: 0.005~0.025%, B: 0.0005~
0.002%, Ca: 0.0005-0.005%
.

ＲＥＭ：０．００３〜０．０３％の１種または２種以上 全含有し、残部鉄及び不可避的不純物よりなる鋼片を１
１５０ｔＺ’以下の温度に加熱し、その後の圧延にあた
って９０００以下の累積圧下率が６０％以−ヒでかつ仕
上温度８００ｔＺ’以下の圧延を行ない、放冷または強
制冷却後５０００以上Ａｃｌ　以下の温度で焼戻しを行
なうことを特徴とする溶接性および低温・靭性の優れた
Ｃｕ添加鋼の製造法 である。REM: 1 piece of steel containing 0.003 to 0.03% of one or more types, with the balance consisting of iron and unavoidable impurities.
Heating to a temperature of 150 tZ' or less, subsequent rolling with a cumulative reduction rate of 9,000 or less and a finishing temperature of 800 tZ' or less, followed by cooling or forced cooling at a temperature of 5,000 or more ACl or less. This is a method for producing Cu-added steel with excellent weldability, low temperature and toughness, which is characterized by performing tempering.

即ち、本発明法の特徴とするところは、（１）ＣＬＩ’
ｅ　０．５％以上添加し、圧延後焼戻し処理を行なうこ
とによるＣｕの時効析出硬化全利用するこ吉、（２）そ
れにともなうＣ含有量、Ｃｅｑの低減による溶接性の向
上、（３）Ｎｂ添加及び低温加熱後の制御圧延冷却によ
る圧延組織の細粒化にある。That is, the features of the method of the present invention are (1) CLI'
Adding 0.5% or more of e and performing tempering treatment after rolling makes full use of age precipitation hardening of Cu. (2) Improved weldability due to the associated reduction of C content and Ceq. (3) Nb The purpose is to refine the rolled structure by controlled rolling cooling after addition and low-temperature heating.

一般的に鋼中にＣｕ　ｋ添加すると、（１）熱間圧延中
の鋼表面におけるＣｕ−クラックの発生、（２）溶接熱
影響部（ＨＡＺ）の粒界割れ、（３）Ｃｕの析出硬化に
ともなう低温靭性の劣化などの欠点を有するものである
が、本発明ではＣｕの析出硬化を有効に利用して強度、
靭性、溶接性共に優れた鋼を安価に製造するには、これ
らの欠点全克服せねばならない。Generally, when Cu is added to steel, (1) Cu cracks occur on the steel surface during hot rolling, (2) intergranular cracking in the weld heat affected zone (HAZ), and (3) Cu precipitation hardening occurs. However, in the present invention, the precipitation hardening of Cu is effectively used to improve strength and toughness.
In order to produce steel with excellent toughness and weldability at a low cost, all of these drawbacks must be overcome.

そこで本発明法では、■熱間圧延中の鋼表面眞おけるＣ
ｕ−クラック発生防止のため、低温加熱の採用、低Ｓ化
（０，００３％以下）によって、Ｃｕの低融点化合物の
生成を少なくし、■ＨＡＺの粒界割れ発生防止のために
■と同様像Ｓ化を行ない、■Ｃｕの析出硬化による低温
靭性劣化を防ぐためにＮｂ添加、低温加熱の採用に加え
て、９００ｔＺ’以下のオーステナイト未再結晶域で十
分な圧下（６０％以上）を加え、８００Ｃ以下で圧延を
終了しミクロ組織の細粒化全徹底した。Therefore, in the method of the present invention, ■ C on the steel surface during hot rolling is
In order to prevent the occurrence of u-cracks, low-temperature heating and low S content (0,003% or less) are used to reduce the formation of low-melting Cu compounds. In order to prevent low-temperature toughness deterioration due to precipitation hardening of Cu, in addition to adding Nb and employing low-temperature heating, sufficient reduction (60% or more) is applied in the austenite non-recrystallized region of 900 tZ' or less. The rolling was completed at 800C or lower to thoroughly refine the microstructure.

（発明の構成） 次に本発明の構成要件について説明する。(Structure of the invention) Next, the constituent elements of the present invention will be explained.

Ｃは、溶接性及び溶接部靭性改善のため０．００５〜０
．０９０％に限定した。一般に小人熱溶接部は硬化しや
すく、各種の溶接割れが発生する。これを防ぐためには
鋼の硬化性を低めることが有効であり、これは溶接部靭
性の改善にも効果的である。C is 0.005 to 0 to improve weldability and weld toughness.
．． It was limited to 090%. In general, dwarf heat welds tend to harden and various weld cracks occur. In order to prevent this, it is effective to reduce the hardenability of steel, which is also effective in improving the toughness of the weld zone.

このためＣ含有量の上限を０．０９０％とした。しかし
ながら、Ｃｕの析出硬化作用を利用するといってもあま
りにも極端なＣ含有量の低減は母材及び溶接部の強度を
低下させるため、下限’ｉｏ、００５チに限定した。最
も望ましいＣ含有量は０．０２〜０．０６％である。Therefore, the upper limit of the C content was set to 0.090%. However, even though the precipitation hardening effect of Cu is utilized, too extreme a reduction in the C content lowers the strength of the base metal and the welded part, so the lower limit was limited to 'io, 005chi. The most desirable C content is 0.02-0.06%.

Ｓｉは脱酸上、・鋼に必然的に含有される元素であるが
、Ｓｌは溶接性及び溶接部の靭性対策上好ましくない元
素であるため、０，６％以下とした。Si is an element that is inevitably contained in steel for deoxidation purposes, but since Sl is an unfavorable element from the viewpoint of weldability and toughness of welded parts, it was set to 0.6% or less.

Ｍζは０．６％未満ではＨＡＺ　（熱影響部）軟化が大
きいこと及び母材の強度靭性が劣化するため下限を０．
６チとした。一方Ｍｎが多過ぎると溶接性及びＨＡＺ靭
性が急激に低下するため、上限を２．２係とした。If Mζ is less than 0.6%, the HAZ (heat affected zone) softens significantly and the strength and toughness of the base metal deteriorates, so the lower limit is set to 0.6%.
It was set at 6. On the other hand, if there is too much Mn, weldability and HAZ toughness will drop sharply, so the upper limit was set to 2.2.

不純物であるＳｉ０．００３％以下に限定した理由は、
母材及び溶接部の吸収エネルギーを高めるためである。The reason for limiting the impurity Si to 0.003% or less is as follows.
This is to increase the energy absorbed by the base metal and the weld.

前述の如（、Ｃｕ添加による鋼表面におけるＣｕ−クラ
ック、ＨＡＺの粒界割れ防止のためＳ’ｒ０．００３％
以下とした。Ｃｕ添加鋼では０．００２％以下とするこ
とが特に効果的である。As mentioned above (S'r0.003% to prevent Cu cracks on the steel surface due to Cu addition and intergranular cracking in HAZ)
The following was made. For Cu-added steel, it is particularly effective to limit the content to 0.002% or less.

Ｍは脱酸上、この種のキルド鋼に必然的に含有される元
素であるが、ＡＡ　ｔｏｔａｌ　０．００５％未満では
脱酸が不十分となり、母材靭性が劣化するため下限ｉ０
．００５％とした。一方Ａ９ｔｏｔａｌが０．０８％を
超えるとＨＡ　Ｚの靭性が劣化するため上限を０．０８
係とした。M is an element that is inevitably contained in this type of killed steel for deoxidation, but if the AA total is less than 0.005%, deoxidation will be insufficient and the base material toughness will deteriorate, so the lower limit i0
．． 005%. On the other hand, if A9total exceeds 0.08%, the toughness of HAZ will deteriorate, so the upper limit should be set at 0.08%.
I was in charge.

Ｃｕは耐環境腐食性に効果がある他、本発明鋼の如き、
低Ｃ９低Ｃｅｑ鋼において析出硬化によシ強度を向上さ
せる貴重な元素である。そのため材質上の効果を得るた
めに下限ｉ０．５％とした。In addition to being effective in environmental corrosion resistance, Cu, such as the steel of the present invention,
It is a valuable element that improves the strength of low C9 low Ceq steel through precipitation hardening. Therefore, the lower limit i was set at 0.5% in order to obtain an effect on the material quality.

しかし１．５％を超えると、本発明の条件内であっても
鋼の熱間圧延中のＣｕ−クラック、ＨＡＺの粒界割れが
顕著になり、製造は難しくなる。このため上限を１．５
チとした。However, if it exceeds 1.5%, Cu-cracks during hot rolling of steel and intergranular cracking in HAZ become noticeable even within the conditions of the present invention, making manufacturing difficult. Therefore, the upper limit is set to 1.5
It was hot.

Ｎｂは圧延組織の細粒化と析出硬化のために含有させる
もので、強度、靭性全共に向上させる重要な元素である
が、０．００５％未満では十分にその効果が得られず、
また０、０８１を超えると溶接性及び溶接部靭性に有害
であるためその範囲ン＝０．００５〜０，０８％に制限
した。Nb is included for grain refinement and precipitation hardening of the rolling structure, and is an important element that improves both strength and toughness, but if it is less than 0.005%, the effect cannot be obtained sufficiently.
Moreover, since exceeding 0.081 is harmful to weldability and weld toughness, the range is limited to 0.005 to 0.08%.

特許請求の範囲第２項に示した第２の発明においては、
第１項に示した第１の発明の鋼の成分及び製造プロセス
に、さらにＴｉ：０．００５〜０．０２５チ、Ｖ：０．
０１〜０１０％、　Ｎｉ　：　０．１〜２．０％。In the second invention shown in claim 2,
In addition to the composition and manufacturing process of the steel of the first invention shown in Section 1, Ti: 0.005 to 0.025 Ti, V: 0.
01-010%, Ni: 0.1-2.0%.

Ｃｒ　：　０．１〜０．５％、　Ｍｏ　：　０．０５〜
０．３％ＩＢ二０．０００５−０．００２％、Ｃａ　：
　０．０００５〜０．００５％。Cr: 0.1~0.5%, Mo: 0.05~
0.3% IB2 0.0005-0.002%, Ca:
0.0005-0.005%.

ＲＥＭ　：　０．００３〜０．０３％の１種または２種
以上を含有するものである。REM: Contains one or more of 0.003 to 0.03%.

Ｔ１は、圧延組織及びＨＡＺの細粒化に有効な元素であ
って、Ｎ’ｉ’ｌ’ｉＮとして固定しＢの焼入性向上効
果を十分に発揮させる他、鋼片中に微細析出したＴｉＮ
　（０，０５μ以下）は加熱時のオーステナイト粒を細
粒化し、圧延組織の細粒化に有効である。また鋼板中に
存在する微ａｌＴＩＮは溶接時にＨＡＺ組織を細粒化す
る。しかしながら、通常の製鋼法で生成する粗大なＴｉ
Ｎは靭性に対し悪影響を与える。従ってＴｉ　ｋ添加し
て母材及びＨＡＺの靭性向上に役立てるためには、Ｔｉ
Ｎ（ｉ７微細析出させることが重要である。このために
’［’ｉ　ｆ　Ｏ，００５〜０．０２５％に限定する。T1 is an element effective in refining the rolling structure and HAZ, and is fixed as N'i'l'iN to fully exhibit the hardenability improvement effect of B, and is also finely precipitated in the steel slab. TiN
(0.05 μm or less) is effective in refining austenite grains during heating and refining the rolling structure. Furthermore, the fine AlTIN present in the steel plate refines the HAZ structure during welding. However, coarse Ti produced by normal steelmaking methods
N has a negative effect on toughness. Therefore, in order to improve the toughness of the base metal and HAZ by adding Ti, it is necessary to add Ti.
It is important to finely precipitate N (i7). For this purpose, it is limited to 005 to 0.025%.

Ｔｉの下限は母材及びＨＡＺの靭性を向上させるための
必要最小量であシ、また上限はこれを超えると通常の製
造工程では微細なＴｉＮが得られず母材及びＨＡ　Ｚ靭
性を劣化させるためである。The lower limit of Ti is the minimum amount necessary to improve the toughness of the base material and HAZ, and the upper limit is the minimum amount necessary to improve the toughness of the base material and HAZ, and if the upper limit is exceeded, fine TiN cannot be obtained in the normal manufacturing process and the toughness of the base material and HAZ deteriorates. It's for a reason.

■は、本発明鋼の圧延細織の細粒化と析出硬化のために
添加するもので強度、靭性を共に向上させる元素である
。しかし、００１％未満では十分にその効果が得られず
、また溶接性及び溶接部靭性の点からその上限を０．１
０％とした。(2) is an element added to refine the rolled weave and precipitation harden the steel of the present invention, and is an element that improves both strength and toughness. However, if it is less than 0.01%, the effect cannot be sufficiently obtained, and from the viewpoint of weldability and weld toughness, the upper limit is set at 0.1%.
It was set to 0%.

Ｎｉは溶接性に悪影響を、与えることなしに母材２．０
％を超えると悪影響が出るため上限’ｔ１．０％とした
。また、ＮｉはＣｕ添加鋼において、ｃｕ添加量のＡ以
上添加するとＣｕ−クラックの防止に有効な元素である
。Ni can be applied to base metal 2.0 without adversely affecting weldability.
If it exceeds 1.0%, it will have an adverse effect, so the upper limit was set at 1.0%. Further, in Cu-added steel, Ni is an element effective in preventing Cu-cracks when added in a Cu addition amount of A or more.

Ｃｒは圧延組織のベイナイト化を促進し、強度、靭性を
向上させる他、耐環境腐食性を有し安価な元素であるた
め、その利用価値は高い。しかし多量に添加すると溶接
部の硬化性全増大させ、靭性及び耐割れ性の低下を招き
好ましくない。そこで上限’（ｚ　０．５％とし、下限
は添加による材質上の効果が得られるための必要最小量
とすることが望ましく０．１％とした。Cr promotes bainiticization of the rolled structure, improves strength and toughness, and is an inexpensive element that has environmental corrosion resistance, so its utility value is high. However, if it is added in a large amount, it will increase the hardenability of the welded part, resulting in a decrease in toughness and cracking resistance, which is not preferable. Therefore, the upper limit'(z) was set at 0.5%, and the lower limit was set at 0.1%, which is preferably the minimum amount necessary to obtain the effect of addition on the material quality.

Ｍｏは本発明鋼の強度を向上させる元素であるが、多き
に失すると母材及び溶接部靭性、溶接性が劣化するため
、上限全０．３％とし、下限は必要最小量の０．０５％
とした。Mo is an element that improves the strength of the steel of the present invention, but if too much is lost, the toughness and weldability of the base metal and weld zone will deteriorate, so the upper limit is set at 0.3% in total, and the lower limit is the minimum necessary amount of 0.05%. %
And so.

Ｂは微量で圧延組織のベイナイト化に有効でかつ安価な
元素である。しかし、Ｂは溶接部靭性、溶接性にとって
極めて有害であり、これは本発明鋼の如き低Ｃ鋼におい
ても同様である。このためＢの含有量についてはとシわ
け十分な配慮が必要である。Ｂ量が多いとＨＡ　Ｚが硬
化するだけでなく、オーステナイト粒界にＢ化合物が生
成し、粒界強度が低下するためである。したがってＢ量
の上限’ｒ０．００２％とする。一方、Ｂの焼入性の安
定確保のためには少な（とも０．０００５％が必要であ
る。B is a small amount of an element that is effective in converting the rolled structure into bainite and is inexpensive. However, B is extremely harmful to weld toughness and weldability, and this is true even in low C steels such as the steel of the present invention. Therefore, sufficient consideration must be given to the content of B. This is because a large amount of B not only hardens the HAZ but also produces B compounds at austenite grain boundaries, resulting in a decrease in grain boundary strength. Therefore, the upper limit of the B amount 'r is set to 0.002%. On the other hand, in order to ensure stable hardenability of B, a small amount (both 0.0005%) is required.

ＲＥＭ（希土類金属）、ＣａはＭｎＳを球状化させ衝撃
値を向上させる他、制御圧延（ＣＲ）によって延伸化し
たＭｎＳと水素による欠陥の発生を防止する。ＲＥＭの
含有量については０００１％未満であると実用上効果が
なく、また０、０３％を越えて添加するとＲＥＭ、−８
またはＲＥＭ−０−８が大量に生成して大型介在物とな
り、鋼板の靭性のみならず清浄度を損いかつ溶接性に対
し悪影響を及ぼす。またＲＥＭはＳとの相関において靭
性向上、安定化に効果があシ、この最適範囲は（ＲＥＭ
％）／（８％）で１〜１０である。よってＲＥＭの範囲
１ｏ、ｏ　０３〜０．０．３％とした。Ｃａについても
ＲＥＭと同様の効果をもちその有効範囲は０．０００５
〜０．００５％である。特にＣａ添加は本発明鋼の如き
、Ｃｕ添加鋼における熱間圧延中のＣｕ−クラック、Ｈ
ＡＺ割れの防止に極めて有効であり、低Ｓ化と共にＣａ
添加が好ましい。REM (rare earth metal) and Ca make MnS spheroidal and improve the impact value, and also prevent the occurrence of defects caused by hydrogen and MnS stretched by controlled rolling (CR). Regarding REM content, if it is less than 0.001%, it has no practical effect, and if it is added in excess of 0.03%, REM, -8
Alternatively, REM-0-8 is generated in large quantities and becomes large inclusions, impairing not only the toughness but also the cleanliness of the steel plate and having a negative effect on weldability. In addition, REM is effective in improving and stabilizing toughness in relation to S, and this optimal range is (REM
%)/(8%) is 1 to 10. Therefore, the range of REM was set to 1o, o 03 to 0.0.3%. Ca has the same effect as REM, and its effective range is 0.0005
~0.005%. In particular, Ca addition can cause Cu-cracks during hot rolling in Cu-added steel such as the steel of the present invention, and
It is extremely effective in preventing AZ cracking, and reduces Ca as well as lowering S.
Addition is preferred.

この鋼は不純物としてＰ、Ｎ、０’（５含む。通常レベ
ルはＰ≦０．０３０％、Ｎ＜０．００８０％、０≦ｏ、
ｏｏｓ％であるが、Ｃｕ添加鋼においては特に製造上、
材質上可能な限シ低減する必要がある。This steel contains P, N, 0' (5) as impurities. Normal levels are P≦0.030%, N<0.0080%, 0≦o,
oos%, but in Cu-added steel, especially in manufacturing,
It is necessary to reduce this as much as possible based on the material.

望ましい量は、Ｐ＜０．０１０％、Ｎ≦０．００４０チ
、０≦０．００３０％である。Desirable amounts are P<0.010%, N≦0.0040%, and 0≦0.0030%.

以上の如（成分系を限定しても製造条件が不適当であれ
ば、優れた強度、靭性を得ることができない。このため
加熱圧延条件も合わせて限定する。Even if the component system is limited as described above, if the manufacturing conditions are inappropriate, excellent strength and toughness cannot be obtained.For this reason, the hot rolling conditions are also limited.

まず加熱温度についてであるが、Ｃｕ添加鋼における鋼
表面のＣｕ−クラック発生金防ぐためには、低温加熱が
効果的であり、このため上限１１１５０Ｃとした。また
加熱温度’ｅ１１５０Ｃ以下好ましくはＡｃ３変態点以
上とすることによって加熱時のオーステナイト粒が細粒
となり低温靭性も改善される。しかし、加熱後のオース
テナイト粒を如何に細粒化しても単に圧延しただけでは
高強度と優れた低温靭性溶接性をもった鋼板を製造する
ことは難しい。それ故、圧延条件についても制限を加え
る。First, regarding the heating temperature, in order to prevent Cu-cracks from occurring on the steel surface in Cu-added steel, low-temperature heating is effective, and therefore the upper limit was set at 11150C. In addition, by setting the heating temperature to less than 1150C, preferably more than Ac3 transformation point, the austenite grains become finer during heating, and low temperature toughness is also improved. However, no matter how fine the austenite grains are after heating, it is difficult to produce a steel sheet with high strength and excellent low-temperature toughness and weldability simply by rolling. Therefore, restrictions are also placed on the rolling conditions.

本発明では圧延条件として９０００以下の累積圧下率を
６０％以上かつ仕上温度’１８００１：以下と限定した
。この条件に従えば鋼板の強度、靭性は大幅に向上する
。以下圧延条件の限定理由について述べる。まず９００
Ｃ以下の累積圧下率が６０％以上であると、フェライト
粒が著しく小さくなり強度と靭性が大幅に向上する。し
かし、累積圧下率が６０％未満であると高強度と優れた
靭性全得ることができない。一方９００Ｃ以下の累積圧
下率が６０％以上であっても、仕上温度が５ｏｏｃｉ超
えると優れた強度と靭性をもつ鋼板が製造できない。仕
上温度’１８０００以下とすることによって、フェライ
ト粒の細粒化は著しく促進され、強度、靭性の両方の向
上または靭性を劣化させずに強度全向上させることがで
きる。In the present invention, the rolling conditions are limited to a cumulative reduction rate of 9000 or less, 60% or more, and a finishing temperature of '18001: or less. If these conditions are followed, the strength and toughness of the steel plate will be significantly improved. The reason for limiting the rolling conditions will be described below. First 900
When the cumulative rolling reduction ratio below C is 60% or more, the ferrite grains become significantly smaller and the strength and toughness are significantly improved. However, if the cumulative rolling reduction is less than 60%, high strength and excellent toughness cannot be obtained. On the other hand, even if the cumulative rolling reduction of 900C or less is 60% or more, if the finishing temperature exceeds 500C, a steel plate with excellent strength and toughness cannot be produced. By setting the finishing temperature to 18,000 or less, the refinement of ferrite grains is significantly promoted, and both strength and toughness can be improved, or the strength can be completely improved without deteriorating toughness.

また、本発明鋼の成分範囲、加熱圧延条件であれば、フ
ェライト−オーステナイト域あるいはフェライト域で相
当量の圧延を行なっても低温靭性は良好であシ、強度を
高めるために有効である。Moreover, within the range of the composition of the steel of the present invention and under hot rolling conditions, low-temperature toughness remains good even if a considerable amount of rolling is performed in the ferrite-austenite region or ferrite region, which is effective for increasing strength.

圧延後の冷却においては、放冷でもよいが、スプレー水
、ミストあるいは空気で強制冷却することは圧延組織の
ベイナイト化、細粒化をはかる上で非常に効果的である
。Ｃｕの析出硬化による強度向上をはかるために、圧延
、冷却後鋼板を５００Ｃ以上Ａｃｌ以下の温度で焼戻し
を行なう。この場合焼戻し温度５００Ｃ未満ではＣｕの
析出硬化が充分に達成できず、又焼戻し温度Ａｃ、超に
なると変態′ｆｆ：開始し析出効果が消失する。Cooling after rolling may be done by leaving it to cool, but forced cooling with spray water, mist, or air is very effective in turning the rolled structure into bainite and refining the grains. In order to improve the strength by precipitation hardening of Cu, the steel plate is tempered at a temperature of 500 C or more and ACl or less after rolling and cooling. In this case, if the tempering temperature is less than 500C, sufficient precipitation hardening of Cu cannot be achieved, and if the tempering temperature exceeds Ac, transformation 'ff: starts and the precipitation effect disappears.

また、本発明の焼戻し作業は脱水素、島状マルテンサン
トの分解による降伏点の向上にも有効である。Furthermore, the tempering operation of the present invention is also effective in improving the yield point through dehydrogenation and decomposition of island-like martensanths.

実施例 次に本発明の実施例について述べる。Example Next, examples of the present invention will be described.

転炉一連鋳工程で製造した種々の化学成分の鋼片を用い
、加熱、圧延、冷却条件の異なる板厚１４〜３０１１８
の鋼板を製造した。大部分の鋼板は圧延後に焼戻し処理
を行なっており、一部のものは圧延、４母材および溶接
部の機械的性質について調べた。結果を表１に示す。表
中の鋼１〜６は本発明鋼であり、鋼７〜１２は比較鋼で
ある。鋼７はＣが上限値を超え、Ｃｕが下限値に満たな
いものであり、低温における衝撃特性が劣り、溶接部の
最高硬さが著しく高い。鋼８はＣｕが下限値に満たず、
低温靭性、溶接性は良好であるが、強度が化学成分に比
して必ずしも十分でない。鋼９は加熱温度及びＳ量が上
限値を超え、熱間圧延中にＣｕ−クラックが発生し、製
品にならない。鋼１０は強度は厚肉にもかかわらず十分
比ているが、９００Ｃ以下の累積圧下率が下限値に満た
ないために低温での衝撃特性が劣っている。鋼１１．１
２は圧延、冷却後焼戻しを行なっていないものである。Using steel slabs of various chemical compositions produced in a continuous converter casting process, plate thicknesses of 14 to 30118 are produced under different heating, rolling, and cooling conditions.
steel plates were manufactured. Most of the steel plates were tempered after rolling, and some of them were examined for mechanical properties of rolling, base metals, and welds. The results are shown in Table 1. Steels 1 to 6 in the table are the steels of the present invention, and steels 7 to 12 are comparative steels. Steel 7 has C exceeding the upper limit and Cu less than the lower limit, and has poor impact properties at low temperatures and extremely high maximum hardness of the welded part. Steel 8 has Cu less than the lower limit,
It has good low-temperature toughness and weldability, but its strength is not necessarily sufficient compared to its chemical composition. In Steel 9, the heating temperature and S amount exceeded the upper limit values, Cu-cracks occurred during hot rolling, and the product could not be produced. Steel 10 has sufficient strength despite its thick wall thickness, but its impact properties at low temperatures are poor because the cumulative rolling reduction below 900C is below the lower limit. steel 11.1
Sample No. 2 was not tempered after rolling and cooling.

鋼１１ではその化学成分１ｔこ比して強度が低（、また
鋼１２では、圧延後水冷のため強度は高いが低温靭性が
著しく劣る。Steel 11 has low strength compared to its chemical composition of 1 ton (and steel 12 has high strength because it is water-cooled after rolling, but its low-temperature toughness is significantly inferior).

本発明鋼の鋼１〜６については母材における強度、低温
衝撃特性及び溶接部靭性、最高硬さ共に優れている。Steels 1 to 6 of the invention steels are excellent in strength in the base metal, low-temperature impact properties, weld zone toughness, and maximum hardness.

以上の実施例からもわかるように、本発明は特定成分の
調音低温加熱し、特定の圧延条件で圧延後、放冷または
強制冷却全行ない、その後焼戻し処理を行なった状態で
、強度、靭性及び溶接特性のバランスの著しく優れた鋼
板の製造を可能ならしめるものであって工業上大きなメ
リットが得られる。As can be seen from the above examples, the present invention is capable of improving the strength, toughness and This makes it possible to manufacture steel plates with extremely well-balanced welding properties, which provides a great industrial advantage.

千に左上ｉｆｊ　Ｔｆ丁ｇ）（自発） ＩＹＪ和５和平９年１月３ ０日庁長官　若　杉　和　夫　殿 １、ＪＩ件の表示 昭和５８年特許願第１４１１７７号 ２、発明の名称 溶接性および低温靭性の優れたＣｕ添加鋼の製造法 ３、補正をする者 事件との関係　出願人 住所　東京都千代田区大手町二丁目６番３号名称　（６
６５）新日本製鐵株式会社 ４、代　理　人 ５、補正の対象　明細書の特許請求の範囲および発明の
詳細な説明 ８、補正の内容 （１）明細書の特許請求の範囲の記載を別紙の通り訂正
する。1,000 upper left ifj Tf chog) (self-motivated) IYJ January 30, 1999 Director General Kazuo Wakasugi 1, Indication of JI Patent Application No. 141177 1983 2, Name of Invention Weldability and Manufacturing method of Cu-added steel with excellent low-temperature toughness 3, relationship with the amended case Applicant Address 2-6-3 Otemachi, Chiyoda-ku, Tokyo Name (6
65) Nippon Steel Corporation 4, Agent 5, Subject of amendment Claims of the specification and Detailed explanation of the invention 8, Contents of amendment (1) Attached statement of claims of the specification Correct as follows.

（２）明細書第１１頁６行の「である。」の次に「しか
し、本発明法では低温加熱などの採用によってＮｉ添加
量をＮｉ＜Ｃｕ／２とすることが可能であり安価に含Ｃ
ｕ鋼を製造できる。」を追加する。(2) On page 11, line 6 of the specification, next to “is.” “However, in the method of the present invention, by employing low-temperature heating, it is possible to make the amount of Ni added Ni<Cu/2, and it is possible to reduce the cost.” Contains C
U steel can be manufactured. ” is added.

（３）明細書第１４頁１〜２行の「される。」の次に「
この場合、特に加熱温度を１０５０°Ｃ以下とすればＮ
１を添加しなくてもＣｕ−クラックが防止でき、製造コ
スト上極めて好ましいものとなる。」を挿入する。(3) On page 14 of the specification, lines 1-2, after “will be”, “
In this case, especially if the heating temperature is 1050°C or less, N
Even without adding 1, Cu-cracks can be prevented, which is extremely preferable in terms of manufacturing cost. ” is inserted.

２、特許請求の範囲 （＋）　Ｃ：　０．００５〜０．０９０Ｌ　Ｓ　ｉ　：
　０．６％以下。2. Claims (+) C: 0.005-0.090L Si:
0.6% or less.

Ｍｎ　：　０．８−２．２％、　Ｎｂ　：　０．００５
〜０．０８％　。Mn: 0.8-2.2%, Nb: 0.005
~0.08%.

Ｃｕ　：　０．５〜１．５Ｌ　Ａｉ　：　０．００５〜
０．０８ｇ　。Cu: 0.5~1.5L Ai: 0.005~
0.08g.

Ｓ　：　０．００３１以下 を含有し、残部鉄及び不可避的不純物よりなる鋼片を１
１５０°Ｃ以下の温度に加熱し、その後の圧延にあたっ
て８００°Ｃ以下の累積圧下率が６０％以上でかつ仕上
温度８００°Ｃ以下の圧延を行ない、放冷または強制冷
却後５００°Ｃ以上Ａ＋４以下の温度で焼戻しを行なう
ことを特徴とする溶接性および低温靭性の優れたＣｕ添
加鋼の製造法。S: 1 piece of steel containing 0.0031 or less, the balance consisting of iron and unavoidable impurities
Heating to a temperature of 150°C or less, subsequent rolling with a cumulative reduction rate of 60% or more at 800°C or less and a finishing temperature of 800°C or less, and after cooling or forced cooling to 500°C or more A+4 A method for producing Cu-added steel having excellent weldability and low-temperature toughness, the method comprising tempering at the following temperature.

（２）　Ｃ：　０．００５〜０．０９０％、　Ｓ　ｉ　
：　０．６％以下。(2) C: 0.005-0.090%, Si
: 0.6% or less.

Ｍｎ　：　Ｏ，ｆｌ−２，２％、　Ｎｂ　：　０．００
５−０．０８％　。Mn: O, fl-2, 2%, Nb: 0.00
5-0.08%.

Ｃｕ　：　０．５〜１．５％、　ＡＪＩ−：　０．００
５〜０．０８％　。Cu: 0.5-1.5%, AJI-: 0.00
5-0.08%.

Ｓ　：　０．００３Ｘ以下 を含有し、さらに Ｃｒ　：　０．１〜０．５＄、　Ｎｉ　：　０．１−２
．ＯＬＭｏ　：　０．０５−０．３％、　Ｖ　：　０．
０１〜０．１０％　。Contains S: 0.003X or less, further Cr: 0.1-0.5$, Ni: 0.1-2
．． OLMo: 0.05-0.3%, V: 0.
01-0.10%.

Ｔ　ｉ　：　０．００５〜０．０２５Ｌ　Ｂ　：　０．
０００５〜０．００２Ｘ。T i : 0.005-0.025L B : 0.
0005-0.002X.

Ｃａ　：　０．０００５−０．００５％、ＲＥＭ　：　
０−００３〜０．０３％の１種または２種以上 を含有し、残部鉄及び不可避的不純物よりな旦Ｎｉを添
加する場合はＮｉ＜Ｃｕ／２を満足する細片を１１５０
℃以下の温度に加熱し、その後の圧延にあたって８００
°Ｃ以下の累積圧下率が６０％以上でかつ仕上温度８０
０℃以下の圧延を行ない、放冷または強制冷却後５００
°Ｃ以上Ａｃｌ以下の温度で焼戻しを行なうことを特徴
とする溶接性および低温靭性の優れたＣｕ添加鋼の製造
法。Ca: 0.0005-0.005%, REM:
0-003 to 0.03% of one or more types, and when Ni is added once the balance is iron and unavoidable impurities, the strip satisfying Ni<Cu/2 is 1150.
℃ or less, and then rolled at 800℃.
The cumulative reduction rate below °C is 60% or more and the finishing temperature is 80%.
500℃ after rolling at 0℃ or less and cooling by cooling or forced cooling.
A method for producing Cu-added steel with excellent weldability and low-temperature toughness, characterized by performing tempering at a temperature of not less than °C and not more than ACl.

手続補正書（自発） 昭和５９年１０月７．２日 特許庁長官　志　賀　学　殿 １、事件の表示 昭和５８年特許願第１４１１７７号 ２、発明の名称 溶接性および低温靭性の優れたＣｕ添加鋼の製造法 ３、補正をする者 事件との関係　出願人 住所　東京都千代田区大手町二丁目６番３号名称　（６
６５）新日本製鐵株式会社 ４代　理　人 ５、補正の対象 明細書の特許請求の範囲および発明の詳細な説明 ６、補正の内容 （１）明細書の特許請求の範囲を、俗の如く補正する。Procedural amendment (voluntary) October 7, 1980 Manabu Shiga, Commissioner of the Patent Office1, Indication of the case, Patent Application No. 141177, filed in 1982, Title of the invention: Cu addition with excellent weldability and low-temperature toughness Steel manufacturing method 3, relationship with the amended case Applicant address 2-6-3 Otemachi, Chiyoda-ku, Tokyo Name (6
65) Nippon Steel Corporation 4 Agent 5. Claims of the specification to be amended and detailed description of the invention 6. Contents of the amendment (1) The scope of claims of the specification should be to correct.

［特許請求の範囲 （１）　Ｃ：　０．００５〜０．０９０１Ｅ、　Ｓ　ｉ
　：　０．６＄以下。[Claim (1) C: 0.005 to 0.0901E, Si
: Less than 0.6$.

Ｍｎ　：　０．８〜２．２％、　Ｎｂ　：　０．００５
−０．０８％　。Mn: 0.8-2.2%, Nb: 0.005
-0.08%.

Ｃｕ　：　０．５−１．５％、　Ａｉ　：　０．００５
〜０．０８％　。Cu: 0.5-1.5%, Ai: 0.005
~0.08%.

Ｓ　：　０．００３％以下 を含有し、残部鉄及び不可避的不純物よりなる連、°１
゛法によ番゛シた鋼片を１１５０℃以下の温度に加熱し
、その後の圧延にあたって９００℃以下の累積圧下率が
６０％以上でかつ仕上温度８００℃以下の圧延を行ない
、放冷または強制冷却後５００°Ｃ以上Ａｃ１　以下の
温度で焼戻しを行なうことを特徴とする溶接性および低
温靭性の優れたＣｕ添加鋼の製造法。S: Contains 0.003% or less, the balance consisting of iron and unavoidable impurities, °1
A steel billet numbered by the above method is heated to a temperature of 1150°C or less, and then rolled with a cumulative reduction of 60% or more at 900°C or less and a finishing temperature of 800°C or less, and then left to cool or A method for producing Cu-added steel with excellent weldability and low-temperature toughness, which comprises tempering at a temperature of 500°C or more and Ac1 or less after forced cooling.

（２）　Ｃ：　０．００５−０．０９０％、　Ｓ　ｉ　
：　０．１４以下。(2) C: 0.005-0.090%, Si
: 0.14 or less.

Ｍｎ　：　０．８〜２．２ｚ、Ｎｂ　：　０．００５〜
０．０８！　。Mn: 0.8~2.2z, Nb: 0.005~
0.08! .

Ｃｕ　：　０．５〜１．５％、　ＡＮ　：　０．００５
−０．０８Ｋ　。Cu: 0.5-1.5%, AN: 0.005
-0.08K.

Ｓ　：　０．００３％以下 を含有し、さらに Ｃｒ　：　０．１〜０．５％、Ｎｉ　：　０．１〜２．
０％。S: 0.003% or less, Cr: 0.1-0.5%, Ni: 0.1-2.
0%.

Ｍｏ　＋　０．０５−０．３％　、、Ｖ　：　０．０１
〜０．１０％　。Mo + 0.05-0.3%, V: 0.01
~0.10%.

Ｔｉ　：　０．００５−０．０２５Ｌ　Ｂ　：　０．０
００５〜０．００２Ｋ。Ti: 0.005-0.025L B: 0.0
005-0.002K.

Ｃａ　：　０．０００５〜０．００５ｚ、ＨＥＭ　：　
０．００３〜０．０３Ｘの１種または２種以上 を含有し、残部鉄及び不可避的不純物よりなりＮｉを添
加する場合はＮｉ＜Ｃｕ／２を満足する’ＪＬＭｌ＋　
告りによし・パ′シた鋼片を１１５０°Ｃ以下の温度に
加熱し、その後の圧延にあたって９００°Ｃ以下の累積
川下率が６０％以上でかつ仕上温度８００℃以下の圧延
を行ない、放冷または強制冷却後５００℃以、１−ＡＣ
＋以下の温度で焼戻しを行なうことを特徴とする溶接性
および低温靭性の倹れたＣｕ添加鋼の製造法。」 （２）明細書第４頁１２行口〜１３行［Ｊの「よりなる
鋼片を」を「よりなる連続鋳造法により製造した鋼片を
」と補正する。Ca: 0.0005~0.005z, HEM:
'JLMl+' containing one or more of 0.003 to 0.03
Heating the steel billet that has been cured and sealed to a temperature of 1150°C or less, and then rolling it at a cumulative downstream rate of 60% or more at 900°C or less and at a finishing temperature of 800°C or less, 500℃ or higher after natural cooling or forced cooling, 1-AC
A method for producing Cu-added steel with good weldability and low-temperature toughness, characterized by tempering at a temperature of + or lower. ” (2) Page 4 of the specification, lines 12 to 13 [Correct “a steel billet made of” in J to “a steel billet manufactured by a continuous casting method”.

（３）同第５頁１行目のｒＭｕ　：　０．８〜２．２ｚ
、ＪをｒＭｎ　：　０．ｆｌ−２，２％、Ｊと補正する
。(3) rMu on page 5, line 1: 0.8 to 2.2z
, J rMn: 0. Correct as fl-2, 2% and J.

（４）同第５頁１１行１１〜１２行目の［よりなる鋼片
を」を「よりなる連＃Ｏ１！鋳造法により製造した鋼片
を」と補正する。(4) On page 5, line 11, line 11-12, ``A steel billet made of'' is corrected to ``A steel billet made by the casting method''.

（５）同第６頁１５行目の「、低温加熱」を「、連続鋳
造スラブの低温加熱」と補正する。(5) "Low-temperature heating" on page 6, line 15 is corrected to "Low-temperature heating of continuous casting slab."

（６）同第１３）ｔ１５行目〜１６行目の「ない。・・
・・・・Ｃｕ添加鋼に」を以下の如く補正する。(6) No. 13) t Lines 15 to 16: “No...
...Cu-added steel" shall be corrected as follows.

「ない。このため製造条件も合わせて限定する。"No. For this reason, we will also limit the manufacturing conditions.

まず、鋼片の製造法であるが、従来の造塊−分塊法では
、Ｃｕ添加鋼に発生するＣｕ−クランクを防＋ｈするこ
とができないため、連続鋳造法によって製造することを
限定した。即ち、造塊−分塊法では、概ね１２００℃以
上の均熱、圧延工程が必須であり、鋼表面におけるスケ
ール発生が大となるためＣｕ−クラックが発生する。し
かし、均熱温度を低温（１１５０°Ｃ）以下とすると、
大型鋼塊では灼熱までに長時間を必要とし、工業化は不
可能である。First, regarding the manufacturing method of the steel billet, since the conventional ingot-blowing method cannot prevent Cu-crank which occurs in Cu-added steel, we have limited the manufacturing method to the continuous casting method. That is, in the ingot-blowing method, soaking at a temperature of approximately 1200° C. or higher and rolling steps are essential, which increases scale generation on the steel surface, resulting in Cu-cracks. However, if the soaking temperature is lower than a low temperature (1150°C),
Large steel ingots require a long time to reach scorching heat, making industrialization impossible.

次に加熱温度についてであるが、Ｃｕ添加鋼に」 （７）同第１５頁１１行目の「を行なう。」の後に次の
文を挿入する。Next, regarding the heating temperature, for Cu-added steel.'' (7) Insert the following sentence after ``Carry out.'' on page 15, line 11.

「鋼板を冷間加工により成形して製造した鋼管（例えば
ＵＯ鋼管）を同様の焼戻し温度で焼戻ししてもよい。」"A steel pipe (for example, a UO steel pipe) manufactured by forming a steel plate by cold working may be tempered at a similar tempering temperature."

Claims (1)

【特許請求の範囲】 １、Ｃ：０．００５〜０．０９０％、Ｓｉ：０．６チ以
下、Ｍｎ　：　０．６〜２．’２　％＋　Ｎｂ　：　Ｏ
，’００５〜０．０８　％。 Ｃｕ　：　０．５〜１．５％、ｕ：ｏ、ｏｏ！５〜ｏ、
ｏｓ％。 Ｓ：０．００３チ以下 全含有し、残部鉄及び不可避的不純物よシなる鋼片’ｉ
ｌ　１５　ＱＣ以下の温度に加熱し、その後の圧延にあ
たって９００Ｃ以下の累積圧下率が６０％以上でかつ仕
上温度８０００以下の圧延を行ない、放冷または強制冷
却後５００Ｃ以上Ａｃ１　以下の温度で焼戻しを行なう
ことを特徴とする溶接性および低温靭性の優れたＣｕ添
加鋼の製造法。 ２、　０：０．００５〜０．０９０％、Ｓｉ：０．６％
以下。 Ｍｎ：０．６〜２．２％、Ｎｂ：０．００５〜０．０８
０％。 Ｃｕ　：　０．５−１．５％、ＡＲ，：ｏ、００５〜０
．０８％。 Ｓ：０．００３％以下 １ｒを含有し、さらに Ｃｒ　：　０．１−０．５％、Ｎｉ：Ｏ１１〜２．０　
％　、Ｍｏ　：　−０，０，５〜０．３％、Ｖ　：　０
．０１〜０．１０　％、Ｔｉ　：０．００５〜０．０２
５％、Ｂ：０．０００５〜０．００２％。 Ｃａ　：０．０００５〜０．００５％−、、ＲＥＭ：　
０．００３〜０．０３％の１種または２種以上 を含有し、残部鉄及び不可避的不純物よりなる鋼Ｊｉｉ
ｌ１５０Ｃ以下の温厚に加熱し、その後の圧延にあたっ
て９００Ｃ以下の累積圧下率が６０％以上でかつ仕上温
度８００Ｃ以下の圧延を行ない、放冷または強′□制冷
却後５００Ｃ以上Ａｃ４以下の温度で焼戻しを行なうこ
とを特徴とする溶接性および低温靭性の優れたＣｕ添加
鋼の製造法。[Claims] 1. C: 0.005 to 0.090%, Si: 0.6 or less, Mn: 0.6 to 2. '2%+Nb: O
,'005~0.08%. Cu: 0.5-1.5%, u:o, oo! 5~o,
os%. S: A steel piece containing 0.003 or less iron, with the balance free of iron and unavoidable impurities.
l Heated to a temperature of 15 QC or less, then rolled with a cumulative reduction of 60% or more at 900C or less and a finishing temperature of 8000 or less, and after cooling or forced cooling, tempering at a temperature of 500C or more and Ac1 or less. A method for producing Cu-added steel having excellent weldability and low-temperature toughness. 2. 0:0.005-0.090%, Si:0.6%
below. Mn: 0.6-2.2%, Nb: 0.005-0.08
0%. Cu: 0.5-1.5%, AR, :o, 005-0
．． 08%. Contains S: 0.003% or less 1r, further Cr: 0.1-0.5%, Ni: O11-2.0
%, Mo: -0.0.5~0.3%, V: 0
．． 01-0.10%, Ti: 0.005-0.02
5%, B: 0.0005-0.002%. Ca: 0.0005-0.005%-, REM:
Steel Jii containing 0.003 to 0.03% of one or more kinds, with the balance consisting of iron and inevitable impurities
The product is heated to a temperature of 150C or less, then rolled with a cumulative reduction rate of 60% or more at 900C or less and a finishing temperature of 800C or less, and then allowed to cool or forced cooling and then tempered at a temperature of 500C or more and Ac4 or less. A method for producing Cu-added steel having excellent weldability and low-temperature toughness, the method comprising: