JPH08158006A - High strength steel excellent in toughness in weld heat-affected zone - Google Patents
High strength steel excellent in toughness in weld heat-affected zoneInfo
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- JPH08158006A JPH08158006A JP30237294A JP30237294A JPH08158006A JP H08158006 A JPH08158006 A JP H08158006A JP 30237294 A JP30237294 A JP 30237294A JP 30237294 A JP30237294 A JP 30237294A JP H08158006 A JPH08158006 A JP H08158006A
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Abstract
Description
【0001】[0001]
【産業上の利用分野】本発明は、船舶、海洋構造物、低
温用タンク、橋梁等の溶接構造物に使用される、特に、
溶接熱影響部(以下、HAZと略称する)の靭性が優れ
た高強度鋼に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used for welded structures such as ships, offshore structures, low temperature tanks and bridges.
The present invention relates to a high-strength steel having excellent toughness in a heat-affected zone (hereinafter abbreviated as HAZ).
【0002】[0002]
【従来の技術】従来より、鋼製構造物の溶接継手部にお
けるHAZの靭性が、母材部分に比べて著しく劣化する
ことが問題であり、このHAZ靭性の改善は緊急の課題
となっている。現在までに、HAZ靭性の改善手段は種
々提案されており、例えば、TiN、BN等の窒化物を
利用した鋼や、特開昭62−109948号公報、特開
平1−159356号公報、特開平3−162522号
公報、特開平4−99248号公報等に見られるような
Ti酸化物を利用した鋼が提案されている。2. Description of the Related Art Conventionally, it has been a problem that the HAZ toughness at a welded joint portion of a steel structure is significantly deteriorated as compared with the base metal portion, and improvement of this HAZ toughness has become an urgent issue. . To date, various means for improving HAZ toughness have been proposed, for example, steel using nitrides such as TiN and BN, JP 62-109948 A, JP 1-159356 A, and JP H09-159356 A. There is proposed a steel using a Ti oxide as disclosed in JP-A-3-162522 and JP-A-4-99248.
【0003】Ti酸化物の利用は、TiN粒子がHAZ
の溶融線近傍で約1400℃以上の高温に加熱されたと
きに溶解してしまう問題を解決するために考えられた手
法であり、約1400℃以上の高温に加熱された部分で
の靭性劣化を小さくするのに有効である。また、HAZ
に生成する上部ベイナイト組織や島状マルテンサイト
が、HAZ靭性に有害であることから、これらの組織生
成を低減させるために、C量や合金元素量、炭素当量
(Ceq)を少なくすることが有効であるが、反面、H
AZの強度が低下するという問題がある。The use of Ti oxide is that TiN particles are HAZ.
This is a method considered to solve the problem of melting when heated to a high temperature of about 1400 ° C or higher in the vicinity of the melting line of, and toughness deterioration in a portion heated to a high temperature of about 1400 ° C or higher is caused. It is effective in reducing the size. Also, HAZ
Since the upper bainite structure and island-like martensite that are generated in the HAZ are harmful to the HAZ toughness, it is effective to reduce the amount of C, the amount of alloying elements and the carbon equivalent (Ceq) in order to reduce the formation of these structures. However, on the other hand, H
There is a problem that the strength of AZ decreases.
【0004】[0004]
【発明が解決しようとする課題】Ti酸化物を利用した
場合、1400℃以上に加熱された微小領域でのHAZ
靭性の劣化を防止できる可能性はあるが、HAZ全域で
必ずしも良好な靭性が得られるわけではなく、1350
℃以下に加熱された大部分のHAZ領域での靭性は、窒
化物を利用した場合と比較してほとんど改善されない
か、あるいはむしろ劣化する場合もある。When Ti oxide is used, HAZ in a minute region heated to 1400 ° C. or higher is used.
Although it is possible to prevent deterioration of toughness, good toughness is not always obtained in the entire HAZ, and 1350
The toughness in most of the HAZ region heated to below 0 ° C may be hardly improved, or even deteriorated, as compared with the case of utilizing the nitride.
【0005】また、高強度の鋼板では合金元素を多量に
含有させる必要性があるため、HAZ靭性の劣化が大き
く、素材の高強度化とHAZ靭性改善という相反する特
性をいかにして向上させるかが問題である。鋼板の高強
度化のために、一般的にNbが利用されるが、Nbは鋼
のHAZ靭性を劣化させるため、HAZ靭性の要求が厳
しい鋼板では通常Nbを極力添加しないようにしてい
る。本発明は、前記した従来技術における問題点を解消
し、鋼の高強度化に有効なNbを積極的に添加しながら
HAZ靭性も向上させることにより、船舶、海洋構造
物、低温用タンク、橋梁等の溶接構造物に使用されるH
AZ靭性が優れた高強度鋼を提供することを目的として
いる。Further, since it is necessary to add a large amount of alloying elements to a high-strength steel sheet, the HAZ toughness is greatly deteriorated, and how to improve the contradictory characteristics of high strength and HAZ toughness improvement of the material. Is a problem. Nb is generally used to increase the strength of the steel sheet, but Nb deteriorates the HAZ toughness of the steel, so that Nb is usually not added as much as possible in the steel sheet where the HAZ toughness is strictly required. The present invention solves the above-mentioned problems in the prior art and improves the HAZ toughness while positively adding Nb that is effective for increasing the strength of steel, and thereby improves the HAZ toughness of ships, marine structures, low temperature tanks and bridges. H used for welded structures such as
It is intended to provide a high strength steel having excellent AZ toughness.
【0006】[0006]
【課題を解決するための手段】上記目的を達成するた
め、本発明者等は鋭意研究を重ねた結果、母材となる鋼
中のC量とNb量の最適バランスとともに、各合金元素
の最適添加量ならびに鋼板中の介在物、析出粒子の大き
さ、個数が、鋼の高強度化とHAZ靭性向上に密接に関
連することを知見し、本発明を完成するに至った。前記
知見に基づいてなされた本発明は、以下の8の態様を要
旨とするものである。[Means for Solving the Problems] In order to achieve the above-mentioned object, the inventors of the present invention have conducted extensive studies, and as a result, have found that the optimum balance of C content and Nb content in steel as a base material and the optimal balance of each alloying element. The inventors have found that the addition amount and the size and number of inclusions and precipitated particles in the steel sheet are closely related to the high strength of the steel and the improvement of HAZ toughness, and have completed the present invention. The present invention made based on the above findings has the following eight aspects.
【0007】第1発明 重量%で、C:0.02〜0.15%,Si:0.00
5〜0.50%,Mn:0.8〜2.0%,P≦0.0
10%,S≦0.003%,Al:0.005〜0.0
5%,Nb:0.005〜0.060%,Ti:0.0
05〜0.02%,N:0.003〜0.015%,O
≦0.0030%を含有し、残部Feおよび不可避不純
物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb≧0.30 C+Mn/6≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とするHAZの靭性が優れた高強度鋼。First invention C: 0.02 to 0.15% by weight, Si: 0.00
5 to 0.50%, Mn: 0.8 to 2.0%, P ≦ 0.0
10%, S ≦ 0.003%, Al: 0.005-0.0
5%, Nb: 0.005 to 0.060%, Ti: 0.0
05-0.02%, N: 0.003-0.015%, O
≦ 0.0030%, balance Fe and unavoidable impurities, and −0.375C + 0.035 ≦ Nb ≦ −0.375C +
0.065 C + Mn / 6 + 1.7 Nb ≧ 0.30 Satisfaction of C + Mn / 6 ≦ 0.36, center segregation portion of steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel excellent in toughness of HAZ, characterized in that the number of oxide / nitride precipitates of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 piece / mm 2 .
【0008】第2発明 重量%で、C:0.02〜0.15%,Si:0.00
5〜0.50%,Mn:0.8〜2.0%,P≦0.0
10%,S≦0.003%,Al:0.005〜0.0
5%,Nb:0.005〜0.060%,Ti:0.0
05〜0.02%,B:0.0003〜0.0030
%,N:0.003〜0.015%,O≦0.0030
%を含有し、残部Feおよび不可避不純物からなり、か
つ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+20B≧0.30 C+Mn/6≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とするHAZの靭性が優れた高強度鋼。Second invention C: 0.02 to 0.15% by weight, Si: 0.00
5 to 0.50%, Mn: 0.8 to 2.0%, P ≦ 0.0
10%, S ≦ 0.003%, Al: 0.005-0.0
5%, Nb: 0.005 to 0.060%, Ti: 0.0
05-0.02%, B: 0.0003-0.0030
%, N: 0.003 to 0.015%, O ≦ 0.0030
%, With the balance being Fe and unavoidable impurities, and -0.375C + 0.035≤Nb≤-0.375C +.
0.065 C + Mn / 6 + 1.7 Nb + 20B ≧ 0.30 C + Mn / 6 ≦ 0.36 is satisfied, and the center segregated portion (sheet thickness / 50) mm thickness of the steel sheet × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel excellent in toughness of HAZ, characterized in that the number of oxide / nitride precipitates of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 piece / mm 2 .
【0009】第3発明 重量%で、C:0.02〜0.15%,Si:0.00
5〜0.50%,Mn:0.8〜2.0%,P≦0.0
10%,S≦0.003%,Al:0.005〜0.0
5%,Nb:0.005〜0.060%,Ti:0.0
05〜0.02%,N:0.003〜0.015%,O
≦0.0030%を含有し、さらに,Cu:0.05〜
2.0%,Ni:0.05〜3.5%,Cr:0.01
〜0.5%,Mo:0.01〜0.5%,V:0.00
5〜0.10%の内から選んだ1種または2種以上を含
有し、残部Feおよび不可避不純物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+(Cu+Ni)/15+
(Cr+Mo)/10+V/2.5≧0.30 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+
V)/5≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とするHAZの靭性が優れた高強度鋼。Third invention C: 0.02 to 0.15% by weight, Si: 0.00
5 to 0.50%, Mn: 0.8 to 2.0%, P ≦ 0.0
10%, S ≦ 0.003%, Al: 0.005-0.0
5%, Nb: 0.005 to 0.060%, Ti: 0.0
05-0.02%, N: 0.003-0.015%, O
≦ 0.0030%, further, Cu: 0.05 ~
2.0%, Ni: 0.05 to 3.5%, Cr: 0.01
~ 0.5%, Mo: 0.01 to 0.5%, V: 0.00
5 to 0.10% selected from the group consisting of one or more selected from the balance Fe and inevitable impurities, and -0.375C + 0.035≤Nb≤-0.375C +.
0.065 C + Mn / 6 + 1.7 Nb + (Cu + Ni) / 15 +
(Cr + Mo) /10+V/2.5≧0.30 C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo +
V) /5≦0.36 is satisfied, and the center segregated portion of the steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel excellent in toughness of HAZ, characterized in that the number of oxide / nitride precipitates of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 piece / mm 2 .
【0010】第4発明 重量%で、C:0.02〜0.15%,Si:0.00
5〜0.50%,Mn:0.8〜2.0%,P≦0.0
10%,S≦0.003%,Al:0.005〜0.0
5%,Nb:0.005〜0.060%,Ti:0.0
05〜0.02%,B:0.0003〜0.0030
%,N:0.003〜0.015%,O≦0.0030
%を含有し、さらに,Cu:0.05〜2.0%,N
i:0.05〜3.5%,Cr:0.01〜0.5%,
Mo:0.01〜0.5%,V:0.005〜0.10
%の内から選んだ1種または2種以上を含有し、残部F
eおよび不可避不純物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+(Cu+Ni)/15+
(Cr+Mo)/10+V/2.5+20B≧0.30 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+
V)/5≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とするHAZの靭性が優れた高強度鋼。Fourth invention C: 0.02 to 0.15%, Si: 0.00 by weight%
5 to 0.50%, Mn: 0.8 to 2.0%, P ≦ 0.0
10%, S ≦ 0.003%, Al: 0.005-0.0
5%, Nb: 0.005 to 0.060%, Ti: 0.0
05-0.02%, B: 0.0003-0.0030
%, N: 0.003 to 0.015%, O ≦ 0.0030
%, Further, Cu: 0.05 to 2.0%, N
i: 0.05 to 3.5%, Cr: 0.01 to 0.5%,
Mo: 0.01-0.5%, V: 0.005-0.10
%, Containing 1 or 2 or more selected from the
e and unavoidable impurities, and is −0.375C + 0.035 ≦ Nb ≦ −0.375C +
0.065 C + Mn / 6 + 1.7 Nb + (Cu + Ni) / 15 +
(Cr + Mo) /10+V/2.5+20B≧0.30 C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo +
V) /5≦0.36 is satisfied, and the center segregated portion of the steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel excellent in toughness of HAZ, characterized in that the number of oxide / nitride precipitates of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 piece / mm 2 .
【0011】第5発明 重量%で、C:0.02〜0.15%,Si:0.00
5〜0.50%,Mn:0.8〜2.0%,P≦0.0
10%,S≦0.003%,Al:0.005〜0.0
5%,Nb:0.005〜0.060%,Ti:0.0
05〜0.02%,N:0.003〜0.015%,O
≦0.0030%を含有し、さらに、Ca:0.000
5〜0.0030%,REM:0.005〜0.050
%の内から選んだ1種または2種以上を含有し、残部F
eおよび不可避不純物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb≧0.30 C+Mn/6≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とするHAZの靭性が優れた高強度鋼。Fifth Invention C: 0.02 to 0.15% by weight%, Si: 0.00
5 to 0.50%, Mn: 0.8 to 2.0%, P ≦ 0.0
10%, S ≦ 0.003%, Al: 0.005-0.0
5%, Nb: 0.005 to 0.060%, Ti: 0.0
05-0.02%, N: 0.003-0.015%, O
≦ 0.0030%, further Ca: 0.000
5 to 0.0030%, REM: 0.005 to 0.050
%, Containing 1 or 2 or more selected from the
e and unavoidable impurities, and is −0.375C + 0.035 ≦ Nb ≦ −0.375C +
0.065 C + Mn / 6 + 1.7 Nb ≧ 0.30 Satisfaction of C + Mn / 6 ≦ 0.36, center segregation portion of steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel excellent in toughness of HAZ, characterized in that the number of oxide / nitride precipitates of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 piece / mm 2 .
【0012】第6発明 重量%で、C:0.02〜0.15%,Si:0.00
5〜0.50%,Mn:0.8〜2.0%,P≦0.0
10%,S≦0.003%,Al:0.005〜0.0
5%,Nb:0.005〜0.060%,Ti:0.0
05〜0.02%,B:0.0003〜0.0030
%,N:0.003〜0.015%,O≦0.0030
%を含有し、さらに、Ca:0.0005〜0.003
0%,REM:0.005〜0.050%の内から選ん
だ1種または2種以上を含有し、残部Feおよび不可避
不純物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+20B≧0.30 C+Mn/6≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とするHAZの靭性が優れた高強度鋼。Sixth Invention C: 0.02 to 0.15% by weight, Si: 0.00
5 to 0.50%, Mn: 0.8 to 2.0%, P ≦ 0.0
10%, S ≦ 0.003%, Al: 0.005-0.0
5%, Nb: 0.005 to 0.060%, Ti: 0.0
05-0.02%, B: 0.0003-0.0030
%, N: 0.003 to 0.015%, O ≦ 0.0030
%, And further Ca: 0.0005 to 0.003
0%, REM: 0.005 to 0.050%, containing one or more selected from the group consisting of the balance Fe and inevitable impurities, and -0.375C + 0.035≤Nb≤-0. 375C +
0.065 C + Mn / 6 + 1.7 Nb + 20B ≧ 0.30 C + Mn / 6 ≦ 0.36 is satisfied, and the center segregated portion (sheet thickness / 50) mm thickness of the steel sheet × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel excellent in toughness of HAZ, characterized in that the number of oxide / nitride precipitates of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 piece / mm 2 .
【0013】第7発明 重量%で、C:0.02〜0.15%,Si:0.00
5〜0.50%,Mn:0.8〜2.0%,P≦0.0
10%,S≦0.003%,Al:0.005〜0.0
5%,Nb:0.005〜0.060%,Ti:0.0
05〜0.02%,N:0.003〜0.015%,O
≦0.0030%を含有し、さらに,Cu:0.05〜
2.0%,Ni:0.05〜3.5%,Cr:0.01
〜0.5%,Mo:0.01〜0.5%,V:0.00
5〜0.10%の内から選んだ1種または2種以上を含
有し、さらに、Ca:0.0005〜0.0030%,
REM:0.005〜0.050%の内から選んだ1種
または2種以上を含有し、残部Feおよび不可避不純物
からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+(Cu+Ni)/15+
(Cr+Mo)/10+V/2.5≧0.30 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+
V)/5≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とするHAZの靭性が優れた高強度鋼。Seventh Invention C: 0.02 to 0.15% by weight%, Si: 0.00
5 to 0.50%, Mn: 0.8 to 2.0%, P ≦ 0.0
10%, S ≦ 0.003%, Al: 0.005-0.0
5%, Nb: 0.005 to 0.060%, Ti: 0.0
05-0.02%, N: 0.003-0.015%, O
≦ 0.0030%, further, Cu: 0.05 ~
2.0%, Ni: 0.05 to 3.5%, Cr: 0.01
~ 0.5%, Mo: 0.01 to 0.5%, V: 0.00
5 to 0.10%, one or more selected from, and further contains Ca: 0.0005 to 0.0030%,
REM: contains one or more selected from 0.005 to 0.050%, consists of balance Fe and unavoidable impurities, and -0.375C + 0.035≤Nb≤-0.375C +
0.065 C + Mn / 6 + 1.7 Nb + (Cu + Ni) / 15 +
(Cr + Mo) /10+V/2.5≧0.30 C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo +
V) /5≦0.36 is satisfied, and the center segregated portion of the steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel excellent in toughness of HAZ, characterized in that the number of oxide / nitride precipitates of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 piece / mm 2 .
【0014】第8発明 重量%で、C:0.02〜0.15%,Si:0.00
5〜0.50%,Mn:0.8〜2.0%,P≦0.0
10%,S≦0.003%,Al:0.005〜0.0
5%,Nb:0.005〜0.060%,Ti:0.0
05〜0.02%,B:0.0003〜0.0030
%,N:0.003〜0.015%,O≦0.0030
%を含有し、さらに,Cu:0.05〜2.0%,N
i:0.05〜3.5%,Cr:0.01〜0.5%,
Mo:0.01〜0.5%,V:0.005〜0.10
%の内から選んだ1種または2種以上を含有し、さら
に、Ca:0.0005〜0.0030%,REM:
0.005〜0.050%の内から選んだ1種または2
種以上を含有し、残部Feおよび不可避不純物からな
り、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+(Cu+Ni)/15+
(Cr+Mo)/10+V/2.5+20B≧0.30 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+
V)/5≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とするHAZの靭性が優れた高強度鋼。Eighth invention C: 0.02 to 0.15% by weight, Si: 0.00
5 to 0.50%, Mn: 0.8 to 2.0%, P ≦ 0.0
10%, S ≦ 0.003%, Al: 0.005-0.0
5%, Nb: 0.005 to 0.060%, Ti: 0.0
05-0.02%, B: 0.0003-0.0030
%, N: 0.003 to 0.015%, O ≦ 0.0030
%, Further, Cu: 0.05 to 2.0%, N
i: 0.05 to 3.5%, Cr: 0.01 to 0.5%,
Mo: 0.01-0.5%, V: 0.005-0.10
%, One or two or more selected from%, and further Ca: 0.0005 to 0.0030%, REM:
1 or 2 selected from 0.005 to 0.050%
Containing at least one species, consisting of balance Fe and unavoidable impurities, and -0.375C + 0.035≤Nb≤-0.375C +
0.065 C + Mn / 6 + 1.7 Nb + (Cu + Ni) / 15 +
(Cr + Mo) /10+V/2.5+20B≧0.30 C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo +
V) /5≦0.36 is satisfied, and the center segregated portion of the steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel excellent in toughness of HAZ, characterized in that the number of oxide / nitride precipitates of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 piece / mm 2 .
【0015】[0015]
【作用】本発明の構成と作用を説明する。本発明に係る
鋼の化学成分組成範囲の限定理由を説明するが、ここに
示す化学成分含有量は溶鋼での成分分析値または鋼板の
中心偏析部を除外した部分の成分分析値である。 C:Cは、HAZにおいて島状マルテンサイトの量を増
加させ、HAZ靭性に有害な元素であるとともに溶接性
を阻害するため少ないほうが望ましく、上限を0.15
%とする。また、含有量が0.02%未満では、鋼の所
定強度を確保することができない。よって、C含有量は
0.02〜0.15%とする。好ましくは0.03〜
0.09%が良い。The structure and operation of the present invention will be described. The reason for limiting the chemical composition range of the steel according to the present invention will be described. The chemical content shown here is a component analysis value in molten steel or a component analysis value of a portion excluding the central segregation portion of the steel sheet. C: C increases the amount of island martensite in the HAZ, is an element harmful to the HAZ toughness, and hinders weldability.
%. Further, if the content is less than 0.02%, the predetermined strength of steel cannot be secured. Therefore, the C content is 0.02 to 0.15%. Preferably from 0.03
0.09% is good.
【0016】Si:Siは鋼の脱酸と強化に対して有用
な元素であり、含有量が0.005%未満ではその効果
がなく、また0.50%を超えて過剰に含有させると鋼
の溶接性及び靭性が劣化する。したがってSi含有量は
0.005〜0.50%とする。 Mn:Mnは、鋼の強度を上昇させるのに有効な元素で
あるが、その含有量が0.8%未満では十分な強度が得
られず、また、2.0%を超えて含有させると、鋼の溶
接性を劣化させる。よってMn含有量は、0.8〜2.
0%とする。Si: Si is an element useful for deoxidizing and strengthening steel, and if the content is less than 0.005%, its effect is not exerted, and if it exceeds 0.50%, it is steel. Weldability and toughness of the steel deteriorate. Therefore, the Si content is set to 0.005 to 0.50%. Mn: Mn is an element effective in increasing the strength of steel, but if its content is less than 0.8%, sufficient strength cannot be obtained, and if it exceeds 2.0%, it is contained. , Deteriorates the weldability of steel. Therefore, the Mn content is 0.8-2.
0%
【0017】P:Pは偏析しやすい元素であり、結晶粒
開に偏析して靭性を劣化させる。よって、P含有量は
0.010%以下とする。 S:SはMnS介在物を生成して、靭性や板厚方向の延
性を劣化させるため、S含有量を0.003%以下とす
る。 Al:Alは脱酸元素であり、含有量が0.005%未
満ではその効果が少なく、また、0.05%を超えて過
剰に添加すると、アルミナ系の粗大な介在物を生成して
それが破壊の起点となり、靭性を劣化させる。よって、
Al含有量は0.005〜0.05%とする。P: P is an element which easily segregates and segregates into the open grains to deteriorate the toughness. Therefore, the P content is set to 0.010% or less. S: S forms MnS inclusions and deteriorates toughness and ductility in the plate thickness direction, so the S content is made 0.003% or less. Al: Al is a deoxidizing element, and if the content is less than 0.005%, its effect is small, and if it is added in excess of more than 0.05%, coarse alumina-based inclusions are produced. Becomes the starting point of fracture and deteriorates toughness. Therefore,
The Al content is 0.005 to 0.05%.
【0018】Nb:Nbは、Cと相俟って本発明におい
て重要な元素である。Nbは鋼の強度上昇に極めて有効
であり、また、圧延時に温度制御することによりオース
テナイト粒径の微細化及びオーステナイト粒内への歪の
導入を促進することができ、冷却後のフェライト粒径を
微細化して母材の靭性向上にも有効である。前記の効果
を得るためには0.005%以上含有させることが必要
である。一方、含有量が0.060%を超えるとNb炭
窒化物の析出量が多くなり過ぎてHAZ靭性が劣化るた
め、Nb含有量は0.005〜0.060%とする。Nb: Nb, together with C, is an important element in the present invention. Nb is extremely effective in increasing the strength of steel, and by controlling the temperature during rolling, it is possible to promote the refinement of the austenite grain size and the introduction of strain into the austenite grains, and to reduce the ferrite grain size after cooling. It is also effective in improving the toughness of the base material by making it finer. In order to obtain the above effect, it is necessary to contain 0.005% or more. On the other hand, if the content exceeds 0.060%, the precipitation amount of Nb carbonitrides becomes too large and the HAZ toughness deteriorates, so the Nb content is made 0.005 to 0.060%.
【0019】Ti:Tiは、HAZの靭性向上に効果の
ある重要な元素であり、鋼組織中に析出したTiNが、
溶接により加熱されたときのオーステナイト粒の粗大化
を防止し、フェライト変態を促進する。含有量が0.0
05%未満ではこの効果はなく、また、0.020%を
超えて多量に添加すると靭性が劣化する。よって、Ti
含有量は0.005〜0.020%とする。Ti: Ti is an important element effective in improving the HAZ toughness, and TiN precipitated in the steel structure is
It prevents coarsening of austenite grains when heated by welding and promotes ferrite transformation. Content is 0.0
If it is less than 05%, this effect is not obtained, and if it is added in excess of 0.020%, the toughness deteriorates. Therefore, Ti
The content is 0.005 to 0.020%.
【0020】N:NはTiとともにTiNを生成させ、
HAZのオーステナイト粒径の粗大化を抑制してフェラ
イト生成を促進させることによりHAZ靭性を向上させ
る効果を有する元素であり、含有量が0.003%未満
ではこのような効果はない。また、N含有量が多いほど
オーステナイト粒径が微細化し靭性向上に有効である
が、0.015%を超えて含有すると、靭性に有害なフ
リーN量が増大するため逆に靭性が劣化する。よって、
N含有量は0.003〜0.015%とする。N: N produces TiN together with Ti,
It is an element having an effect of improving the HAZ toughness by suppressing coarsening of the austenite grain size of HAZ and promoting ferrite formation. If the content is less than 0.003%, such an effect does not occur. Further, as the N content increases, the austenite grain size becomes finer and it is effective for improving the toughness. However, if the N content exceeds 0.015%, the toughness-deteriorating free N content increases, and conversely the toughness deteriorates. Therefore,
The N content is 0.003 to 0.015%.
【0021】O:Oは、HAZのオーステナイト粒径の
粗大化を防止するTi酸化物を生成させるためには有効
であるが、0.0030%を超えて含有すると粗大な酸
化物系の介在物が多量に生成するため、その酸化物が破
壊発生の起点となり靭性を劣化させる。よって、O含有
量を0.0030%以下とする。O: O is effective for forming a Ti oxide which prevents coarsening of the austenite grain size of HAZ, but if it is contained in excess of 0.0030%, it is a coarse oxide-based inclusion. Since a large amount is generated, the oxide becomes a starting point of fracture generation and deteriorates toughness. Therefore, the O content is set to 0.0030% or less.
【0022】以上説明した成分元素以外に、本発明に係
るHAZ靭性が優れた高強度鋼ではBを含有させること
ができる。 B:Bは母材の強度を上昇させるとともに、HAZの
内、1400℃以上に加熱された部分でTiNが溶解し
た場合でも、冷却過程でBNを析出させ、オーステナイ
ト粒内からのフェライト変態を促進させることができ
る。この効果を得るためには、B含有量は0.0003
%以上必要である。しかし、0.0030%以上多量に
添加すると靭性を劣化させる。よって、B含有量は0.
0003〜0.0030%とする。In addition to the constituent elements described above, B can be contained in the high-strength steel having excellent HAZ toughness according to the present invention. B: B not only increases the strength of the base metal but also precipitates BN in the cooling process and promotes ferrite transformation from within the austenite grains even when TiN is melted in the part of HAZ heated to 1400 ° C or higher. Can be made. To obtain this effect, the B content is 0.0003.
% Or more is required. However, if added in a large amount of 0.0030% or more, the toughness deteriorates. Therefore, the B content is 0.
0003 to 0.0030%.
【0023】さらに本発明鋼には、強度上昇のためC
u、Ni、Cr、Mo、Vの内から1種または2種以上
を含有させることができる。 Cu:Cuは強度上昇に有効であり、0.6%未満の添
加では固溶強化、0.6%以上の添加では時効析出強化
作用を活用することができ、大幅な強度上昇も可能であ
る。含有量が0.05%未満ではこの効果はなく、2.
0%を超えて多量に含有すると靭性を低下させる。よっ
て、Cu含有量は0.05〜2.0%とする。Further, in the steel of the present invention, due to the increase in strength, C
One or more of u, Ni, Cr, Mo and V may be contained. Cu: Cu is effective for increasing the strength. Addition of less than 0.6% can utilize the solid solution strengthening, and addition of 0.6% or more can utilize the aging precipitation strengthening effect, and can also significantly increase the strength. . If the content is less than 0.05%, this effect does not occur.
If it is contained in a large amount exceeding 0%, the toughness is reduced. Therefore, the Cu content is 0.05 to 2.0%.
【0024】Ni:Niは母材靭性を向上させるととも
に強度上昇に有効である。含有量が0.05%未満では
この効果はなく、また、高価であるため3.5%以下と
する必要がある。よってNi含有量は0.05〜3.5
%とする。 Cr:Crは強度上昇に有効な元素であり、含有量が
0.01%未満ではこのような効果は少なく、また、
0.50%を超えて多量に含有させると溶接性を阻害す
るようになる。よってCr含有量は0.01〜0.50
%とする。Ni: Ni improves the toughness of the base material and is effective for increasing the strength. If the content is less than 0.05%, this effect does not occur, and since it is expensive, it must be 3.5% or less. Therefore, the Ni content is 0.05 to 3.5.
%. Cr: Cr is an element effective for increasing strength, and if the content is less than 0.01%, such an effect is small, and
If it is contained in a large amount exceeding 0.50%, the weldability is impaired. Therefore, the Cr content is 0.01 to 0.50.
%.
【0025】Mo:Moは強度上昇に有効な元素であ
り、含有量が0.01%未満ではこのような効果は少な
く、また、0.50%を超えて多量に含有させると溶接
性を阻害するようになる。よってMo含有量は0.01
〜0.50%とする。 V:Vは強度上昇に有効な元素であり、含有量が0.0
1%未満ではこのような効果は少なく、また、0.50
%を超えて多量に含有させると溶接性、靭性を阻害する
ようになる。よってV含有量は0.01〜0.50%と
する。Mo: Mo is an element effective for increasing the strength, and if the content is less than 0.01%, such an effect is small, and if it exceeds 0.50% in a large amount, the weldability is impaired. Come to do. Therefore, the Mo content is 0.01
~ 0.50%. V: V is an element effective in increasing strength, and its content is 0.0
If it is less than 1%, such an effect is small and 0.50.
If it is contained in a large amount in excess of%, the weldability and toughness will be impaired. Therefore, the V content is set to 0.01 to 0.50%.
【0026】本発明鋼は、介在物の形態制御をするため
Ca、REMの内から1種または2種を含有させること
ができる。 Ca:Caは、破壊発生の起点となる介在物を低減し、
微細化し、形態制御することによって、HAZ靭性を向
上させる効果のある元素である。特に、有害なAl2 O
3 (アルミナ)系の粗大な介在物を溶鋼中で凝集浮上さ
せる効果があり、アルミナ系介在物の量を低減させると
ともに微細に分散させる。また、MnS介在物の形態制
御をする。含有量が0.0005%未満ではこのような
効果はなく、0.003%を超えて含有させるとCaと
アルミナの複合した極めて粗大な介在物が生じる。よっ
て、Ca含有量は0.0005〜0.0030%とす
る。 REM:REMはMnS介在物の形態制御に効果があ
る。含有量が0.005%未満ではこの効果は少なく、
また、0.050%を超えて含有させると有害な粗大介
在物を生成させる。よって、REM含有量は0.005
〜0.050%とする。The steel of the present invention may contain one or two of Ca and REM for controlling the morphology of inclusions. Ca: Ca reduces inclusions that are the starting point of fracture occurrence,
It is an element effective in improving the HAZ toughness by refining and controlling the morphology. Particularly harmful Al 2 O
3 It has the effect of flocculating coarse (Alumina) -based inclusions in molten steel, reducing the amount of alumina-based inclusions and finely dispersing them. Also, the morphology of MnS inclusions is controlled. If the content is less than 0.0005%, there is no such effect, and if the content exceeds 0.003%, an extremely coarse inclusion of Ca and alumina is generated. Therefore, the Ca content is 0.0005 to 0.0030%. REM: REM is effective in controlling the morphology of MnS inclusions. If the content is less than 0.005%, this effect is small,
Further, if contained in excess of 0.050%, harmful coarse inclusions are generated. Therefore, the REM content is 0.005
~ 0.050%.
【0027】一般的に、Nbは、鋼の溶接部の靭性を著
しく害する元素として、極力小量の添加に制限する必要
があるといわれている。しかし、これはC含有量が比較
的多い場合であり、C含有量が0.06%程度よりも少
ない場合には逆にHAZのフェライト結晶粒径の粗大化
を防止する作用が強くなり、むしろNb含有量を増加さ
せたほうがHAZ靭性は良好になる。つまり、Nb含有
量はC含有量とのバランスで決定する必要がある。It is generally said that Nb is an element that significantly impairs the toughness of the welded portion of steel, and it is necessary to limit the addition of Nb to the smallest possible amount. However, this is the case where the C content is relatively large, and when the C content is less than about 0.06%, the effect of preventing coarsening of the ferrite crystal grain size of the HAZ becomes stronger, rather. The HAZ toughness becomes better as the Nb content is increased. That is, the Nb content needs to be determined in balance with the C content.
【0028】本発明鋼においては、前記NbとCの含有
量バランスを次の数式によって明確化した。 −0.375C+0.035≦Nb≦−0.375c+0.065 ……… 例えば、C含有量が0.04%のとき、Nb含有量は
0.02〜0.05%、C含有量が0.08%のとき、
Nb含有量は0.005〜0.035%、C含有量が
0.12%のときNb含有量は0.02%以下とする必
要がある。これは、HAZ靭性の優れた高強度鋼とする
ための極めて重要なポイントである。In the steel of the present invention, the balance of Nb and C contents was clarified by the following mathematical formula. −0.375C + 0.035 ≦ Nb ≦ −0.375c + 0.065 For example, when the C content is 0.04%, the Nb content is 0.02 to 0.05% and the C content is 0. When it is 08%,
When the Nb content is 0.005 to 0.035% and the C content is 0.12%, the Nb content needs to be 0.02% or less. This is an extremely important point for producing a high strength steel having excellent HAZ toughness.
【0029】次に、本発明のHAZ靭性が優れた高強度
鋼は、成分元素の含有量を次の数式の範囲内に限定しな
ければならない。まず、十分な高強度を得るため、 C+Mn/6+(Cu+Ni)/15+(Cr+Mo)/10+V/2.5 +20B≧0.30 ……… を満足しなければならない。また、優れたHAZ靭性を
得るためには、 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+V)≦0.36…… を満足しなければならない。本発明鋼は、これら、
、式をすべて満足する成分含有量に調整されていな
ければならない。Next, in the high strength steel of the present invention having excellent HAZ toughness, the content of the constituent elements must be limited within the range of the following formula. First, in order to obtain a sufficiently high strength, C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo) /10+V/2.5+20B≧0.30 ... Must be satisfied. Further, in order to obtain excellent HAZ toughness, C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo + V) ≦ 0.36 ... Must be satisfied. The present invention steel, these,
, The content of ingredients must be adjusted to satisfy all the formulas.
【0030】鋼板の中心偏析部は、成分元素が濃縮され
ているためその部分が硬化し、脆化するために破壊発生
の起点となる。中心偏析部の成分は分析する領域によっ
て大きく異なり、EPMAやCMAによる微小領域での
分析では高濃度の分析結果となる。本発明鋼では、鋼板
の中心偏析部をマクロエッチした後、もっとも偏析して
いる部分(板厚/50)mm厚×10mm×10mmに
おける平均化学分析値を中心偏析部の成分とする。偏析
元素にはC、P、Mn等があるが、硬化量を表すC元素
の濃度を採用し、偏析の程度は鋼材の平均C濃度との比
を用いた。At the center segregated portion of the steel sheet, the constituent elements are concentrated, so that the portion hardens and becomes brittle, and becomes a starting point of fracture occurrence. The components of the central segregation portion greatly differ depending on the area to be analyzed, and a high-concentration analysis result is obtained by analysis in a minute area by EPMA or CMA. In the steel of the present invention, after the center segregation portion of the steel sheet is macro-etched, the average chemical analysis value in the most segregated portion (sheet thickness / 50) mm thickness × 10 mm × 10 mm is used as the component of the center segregation portion. Although segregation elements include C, P, Mn, etc., the concentration of C element that represents the amount of hardening was adopted, and the degree of segregation was based on the ratio with the average C concentration of steel.
【0031】ここで、鋼材の平均C濃度とは、溶鋼での
成分分析値または鋼材の中心偏析部を除外した部分の成
分分析値である。中心偏析は無いに越したことはない
が、現実の鋼材では連続鋳造の凝固過程で中心部が最後
に凝固するため、中心偏析を皆無とすることは不可能で
ある。したがって、本発明鋼では、HAZ靭性に有害と
なる中心偏析の程度を明確に規定した。すなわち、中心
偏析部のC濃度が鋼材の平均C濃度の1.2倍を超える
場合は、マクロ組織上でも明確に黒い線が現われ、その
部分が破壊発生の起点となる場合が多いため、鋼板の中
心偏析部(板厚/50)mm厚×10mm×10mmの
平均化学分析値のC濃度が鋼材の平均C濃度の1.2倍
以下とする。Here, the average C concentration of the steel material is a component analysis value in molten steel or a component analysis value of a portion excluding the center segregated portion of the steel material. There is no such thing as center segregation, but in actual steel materials, it is impossible to eliminate center segregation because the center solidifies last in the solidification process of continuous casting. Therefore, in the steel of the present invention, the degree of center segregation, which is harmful to HAZ toughness, was clearly defined. That is, when the C concentration of the central segregation portion exceeds 1.2 times the average C concentration of the steel material, a clear black line appears on the macrostructure, and that portion often becomes the starting point of fracture occurrence. The C concentration of the average chemical analysis value of the center segregated portion (plate thickness / 50) mm thickness × 10 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material.
【0032】鋼中に非金属介在物が存在している場合、
これが破壊の発生点となることがある。特に、比較的大
きな介在物や連なった介在物では、溶接熱が加わった場
合その熱と応力によって界面が剥離し、破壊が発生し易
くなる。この点から、HAZ靭性の優れた鋼では非金属
介在物は少ない方が望ましい。一般的に介在物の量を評
価する手法として、JIS G 0555の「鋼の非金
属介在物の顕微鏡試験方法」で定められている清浄度が
ある。つまり、接眼鏡に縦、横各々20本の格子線を持
つ顕微鏡を用い、倍率400倍で60視野観察し、介在
物によって占められた格子点中心の数を測定し、次の式
によって介在物の占める面積百分率を算出し、それを清
浄度(d%)とする。 d=n÷(p+f)×100 ここで、p:視野内のガラス板上の総格子点数 f:視野数 n:f個の視野における全介在物によって占められる格
子点中心の数If non-metallic inclusions are present in the steel,
This may be the point of destruction. Particularly, in the case of relatively large inclusions or a series of inclusions, when welding heat is applied, the interface is separated due to the heat and stress, and breakage easily occurs. From this point, it is desirable that the steel having excellent HAZ toughness has few nonmetallic inclusions. Generally, as a method for evaluating the amount of inclusions, there is a cleanliness degree defined by JIS G 0555 "Microscopic test method for non-metallic inclusions in steel". That is, using a microscope having 20 grid lines in each of the vertical and horizontal directions, observe 60 fields of view at a magnification of 400 times, measure the number of center points of the grid points occupied by inclusions, and calculate the inclusions by the following formula. The area percentage occupied by is calculated and used as the cleanliness (d%). d = n ÷ (p + f) × 100 where p: total number of lattice points on the glass plate in the visual field f: number of visual fields n: number of lattice point centers occupied by all inclusions in f visual fields
【0033】例えば、60視野内で1個の介在物のみが
1格子点に掛かるような極めて清浄度の良好な場合に、
清浄度d=0.004%となる。この清浄度が0.03
%を超える場合には靭性が劣化するため、JIS規格で
測定される介在物の清浄度を0.03%以下とする。For example, in the case where the cleanliness is very good such that only one inclusion hangs over one grid point in 60 fields of view,
The cleanliness d is 0.004%. This cleanliness is 0.03
%, The toughness deteriorates, so the cleanliness of inclusions measured according to JIS standard is 0.03% or less.
【0034】また、比較的微細な平均直径5μm以下の
酸化物系介在物(酸化物系析出物)は、先に述べたよう
に1400℃以上に加熱されるHAZでのオーステナイ
ト粒内からのフェライト変態を促進するために有効であ
るが、平均直径10μm以上の酸化物系介在物は、破壊
の起点となる場合があり有害である。この平均直径10
μm以上の酸化物系介在物の存在頻度が1個/1mm2
を超える場合には、HAZ靭性が劣化するため、鋼板断
面で観察される平均直径10μm以上の酸化物系介在物
の個数を1個以下/1mm2 とする。The relatively fine oxide-based inclusions (oxide-based precipitates) having an average diameter of 5 μm or less are ferrite from the austenite grains in the HAZ heated to 1400 ° C. or higher as described above. Although effective for promoting transformation, oxide-based inclusions having an average diameter of 10 μm or more are harmful as they may be the starting point of fracture. This average diameter 10
Existence frequency of oxide inclusions of μm or more is 1 piece / 1 mm 2
If it exceeds 1.0, the HAZ toughness deteriorates, so the number of oxide inclusions having an average diameter of 10 μm or more observed in the steel plate cross section is set to 1 or less / 1 mm 2 .
【0035】一方、平均直径5μm以下の酸化物および
窒化物の微細析出物は、HAZにおいてオーステナイト
結晶粒の粗大化抑制とオーステナイト粒内からのフェラ
イト生成を促進し、HAZ靭性を向上させる。この効果
を得るためには、平均直径0.05〜5μmの酸化物お
よび窒化物の析出物の個数が100個以上/1mm2必
要である。On the other hand, fine precipitates of oxides and nitrides having an average diameter of 5 μm or less promote the suppression of coarsening of austenite crystal grains in the HAZ and the promotion of ferrite formation from within the austenite grains to improve the HAZ toughness. To obtain this effect, the number of oxide and nitride precipitates having an average diameter of 0.05 to 5 μm must be 100 or more / 1 mm 2 .
【0036】従来技術での酸化物系介在物は、製鋼工程
でのAl脱酸、Ti脱酸で生成するものや、スラグや鋳
造フラックス等から混入する場合等がある。これらの介
在物は数百μmから1mm以上に及ぶもの迄あり、10
μm以上の介在物は、通常の製鋼法では2個以上/1m
m2 存在している。特にTi脱酸では、こうした粗大な
介在物が多く生成し易い。この粗大な介在物を低減させ
るためには、脱ガス処理を十分行い、生成した酸化物を
凝集浮上させることが必要である。The oxide inclusions in the prior art may be produced by Al deoxidation or Ti deoxidation in the steelmaking process, or may be mixed in from slag, casting flux or the like. These inclusions range from several hundred μm to over 1 mm, and 10
Inclusions of μm or more are 2 or more / 1m in the ordinary steelmaking method.
m 2 exists. In particular, Ti deoxidation is likely to produce many such coarse inclusions. In order to reduce the coarse inclusions, it is necessary to perform a sufficient degassing process to cause the produced oxide to flocculate and float.
【0037】また、平均直径5μm以下の微細析出物
は、Tiを主成分とする窒化物、酸化物がHAZ靱性改
善に有効であるため対象となる。微細析出物を多く生成
させるためには、TI,Nを適正バランスで含有させる
ことや、凝固冷却速度を速くすることが必要であり、造
塊でなく連続鋳造で製造する必要がある。Fine precipitates having an average diameter of 5 μm or less are targeted because nitrides and oxides containing Ti as a main component are effective in improving the HAZ toughness. In order to generate a large amount of fine precipitates, it is necessary to contain TI and N in an appropriate balance and to increase the solidification cooling rate, and it is necessary to manufacture by continuous casting instead of ingot casting.
【0038】本発明鋼を製造する方法は特に限定するも
のではないが、高強度化を図るためには熱間圧延後の加
速冷却または直接焼入(DQ)等の水冷をすることが望
ましく、冷却後の焼き戻し(テンパー)は行なっても行
なわなくてもよい。また、圧延後空冷のままでも、その
後焼き入れ・焼き戻しの熱処理を行なってもかまわな
い。The method for producing the steel of the present invention is not particularly limited, but it is desirable to carry out accelerated cooling after hot rolling or water cooling such as direct quenching (DQ) in order to achieve high strength. Tempering after cooling may or may not be performed. Further, after rolling, it may be air-cooled or may be heat-treated by quenching and tempering.
【0039】[0039]
【実施例】本発明の実施例を説明するが、これによって
本発明は何等限定されるものではない。 実施例 実施例における介在物、析出物個数の作り分けは、脱酸
方法、脱ガス条件、鋳造条件、鋳片採取位置等を変える
ことによって行った。下記の表1および表2に示す合金
成分および成分含有割合の鋼を常法により溶製後、連続
鋳造を行ない、製造された鋳片を加熱・圧延・冷却を行
なって供試鋼板を作製した。EXAMPLES Examples of the present invention will be described, but the present invention is not limited thereto. Example The number of inclusions and the number of precipitates in the examples were made differently by changing the deoxidizing method, the degassing conditions, the casting conditions, the slab sampling position, and the like. Steels having the alloy components and component content ratios shown in Tables 1 and 2 below were melted by a conventional method, then continuously cast, and the manufactured slabs were heated, rolled, and cooled to produce test steel sheets. .
【0040】[0040]
【表1】 [Table 1]
【0041】[0041]
【表2】 [Table 2]
【0042】これらの鋼板から、中心偏析部の成分分
析、鋼板断面の介在物観察および引張試験、シャルピー
衝撃試験を行ない、さらに、1パスの大入熱溶接後、板
厚中央部から試験片を採取し、溶融線でHAZと溶接金
属が1対1に分割されるボンド部にノッチを入れ、−4
0℃でシャルピー衝撃試験を行なった。表3に成分割合
の条件を表すパラメータを、表4に試験結果をそれぞれ
示す。From these steel sheets, the component analysis of the central segregation portion, the observation of inclusions in the steel sheet cross section, the tensile test and the Charpy impact test were conducted, and after one pass of large heat input welding, the test piece was taken from the center portion of the plate thickness. Take a sample, make a notch in the bond where the HAZ and weld metal are divided 1: 1 at the fusion line, -4
A Charpy impact test was performed at 0 ° C. Table 3 shows the parameters indicating the conditions of the component ratios, and Table 4 shows the test results.
【0043】[0043]
【表3】 [Table 3]
【0044】[0044]
【表4】 [Table 4]
【0045】前記の表から、本発明鋼が高強度、高靭性
かつ溶接継手部で優れたシャルピー衝撃特性を有してい
ることがわかる。すなわち、本発明鋼は母材引張強さが
510MPa以上かつ、大入熱溶接継手ボンド部の−4
0℃におけるシャルピー衝撃吸収エネルギーが90J以
上と優れたHAZ靭性を有している。From the above table, it can be seen that the steel of the present invention has high strength, high toughness and excellent Charpy impact characteristics in the welded joint. That is, the steel of the present invention has a base metal tensile strength of 510 MPa or more and a high heat input welded joint bond portion of -4.
It has excellent HAZ toughness with a Charpy impact absorbed energy of 90 J or more at 0 ° C.
【0046】これに対して比較鋼BAはC含有量が高
く、比較鋼BBはNb含有量がC濃度に応じた上限値を
超えているため溶接継手ボンド部の靭性が低い。比較鋼
BCは各成分元素の含有量は条件を満足しているが、成
分元素の含有量の割合から計算される強度パラメータが
下限値より低く、また比較鋼BDはNb含有量がC濃度
に応じた下限値より低いとともに強度パラメータも低い
ため、強度が低く、溶接継手部の靭性も低い。比較鋼B
EはTi含有量が低いため、溶接継手部の靭性が低い。
比較鋼BFはN含有量が低いため、TiNの生成が十分
でなく、溶接継手部の靭性が低い。比較鋼BGはO含有
量が高いため介在物の生成が多く、溶接継手部の靭性が
低い。また、比較鋼A2、B2、C2、L2、N2は各
成分元素量は全ての条件を満足しているが、中心偏析の
程度がきついため、溶接継手部の靭性が低い。比較鋼A
3、B3、C3、L3、N3は各成分元素量は全ての条
件を満足しているが、平均直径10μm以上の介在物が
多いため、溶接継手部の靭性が低い。On the other hand, the comparative steel BA has a high C content, and the comparative steel BB has a Nb content exceeding the upper limit corresponding to the C concentration, so that the toughness of the welded joint is low. The comparative steel BC satisfies the conditions for the content of each component element, but the strength parameter calculated from the ratio of the content of the component elements is lower than the lower limit value, and the comparative steel BD has the Nb content at the C concentration. Since the strength parameter is lower than the corresponding lower limit value and the strength parameter is also low, the strength is low and the toughness of the welded joint is also low. Comparative steel B
Since E has a low Ti content, the toughness of the welded joint is low.
Since the comparative steel BF has a low N content, TiN is not sufficiently produced and the toughness of the welded joint is low. Since the comparative steel BG has a high O content, a large amount of inclusions are formed and the toughness of the welded joint is low. Further, the comparative steels A2, B2, C2, L2, and N2 satisfy all the conditions for the amounts of the respective constituent elements, but the degree of center segregation is so severe that the toughness of the welded joint is low. Comparative steel A
3, B3, C3, L3, and N3 satisfy all the conditions for the amount of each elemental element, but the toughness of the welded joint is low because there are many inclusions having an average diameter of 10 μm or more.
【0047】[0047]
【発明の効果】本発明は以上説明したように構成されて
いるから、鋼板として引張強さ510MPa以上の高強
度を保持するとともに大入熱溶接継手部において優れた
靭性を有することが可能となり、産業上極めて有用な発
明である。EFFECTS OF THE INVENTION Since the present invention is constituted as described above, it is possible to maintain high tensile strength of 510 MPa or more as a steel sheet and to have excellent toughness in a large heat input welded joint portion. This is an extremely useful invention in industry.
Claims (8)
Si:0.005〜0.50%,Mn:0.8〜2.0
%,P≦0.010%,S≦0.003%,Al:0.
005〜0.05%,Nb:0.005〜0.060
%,Ti:0.005〜0.02%,N:0.003〜
0.015%,O≦0.0030%を含有し、残部Fe
および不可避不純物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb≧0.30 C+Mn/6≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とする溶接熱影響部の靭性が優れた高強度鋼。1. C: 0.02 to 0.15% by weight,
Si: 0.005 to 0.50%, Mn: 0.8 to 2.0
%, P ≦ 0.010%, S ≦ 0.003%, Al: 0.
005-0.05%, Nb: 0.005-0.060
%, Ti: 0.005 to 0.02%, N: 0.003 to
0.015%, O ≦ 0.0030%, balance Fe
And unavoidable impurities, and -0.375C + 0.035≤Nb≤-0.375C +
0.065 C + Mn / 6 + 1.7 Nb ≧ 0.30 Satisfaction of C + Mn / 6 ≦ 0.36, center segregation portion of steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel with excellent toughness in the heat-affected zone of welding, characterized in that the number of precipitates of oxides and nitrides of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 pieces / mm 2 .
Si:0.005〜0.50%,Mn:0.8〜2.0
%,P≦0.010%,S≦0.003%,Al:0.
005〜0.05%,Nb:0.005〜0.060
%,Ti:0.005〜0.02%,B:0.0003
〜0.0030%,N:0.003〜0.015%,O
≦0.0030%を含有し、残部Feおよび不可避不純
物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+20B≧0.30 C+Mn/6≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とする溶接熱影響部の靭性が優れた高強度鋼。2. C .: 0.02 to 0.15% by weight,
Si: 0.005 to 0.50%, Mn: 0.8 to 2.0
%, P ≦ 0.010%, S ≦ 0.003%, Al: 0.
005-0.05%, Nb: 0.005-0.060
%, Ti: 0.005 to 0.02%, B: 0.0003
~ 0.0030%, N: 0.003 to 0.015%, O
≦ 0.0030%, balance Fe and unavoidable impurities, and −0.375C + 0.035 ≦ Nb ≦ −0.375C +
0.065 C + Mn / 6 + 1.7 Nb + 20B ≧ 0.30 C + Mn / 6 ≦ 0.36 is satisfied, and the center segregated portion (sheet thickness / 50) mm thickness of the steel sheet × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel with excellent toughness in the heat-affected zone of welding, characterized in that the number of precipitates of oxides and nitrides of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 pieces / mm 2 .
Si:0.005〜0.50%,Mn:0.8〜2.0
%,P≦0.010%,S≦0.003%,Al:0.
005〜0.05%,Nb:0.005〜0.060
%,Ti:0.005〜0.02%,N:0.003〜
0.015%,O≦0.0030%を含有し、さらに,
Cu:0.05〜2.0%,Ni:0.05〜3.5
%,Cr:0.01〜0.5%,Mo:0.01〜0.
5%,V:0.005〜0.10%の内から選んだ1種
または2種以上を含有し、残部Feおよび不可避不純物
からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+(Cu+Ni)/15+
(Cr+Mo)/10+V/2.5≧0.30 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+
V)/5≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とする溶接熱影響部の靭性が優れた高強度鋼。3. C: 0.02 to 0.15% by weight,
Si: 0.005 to 0.50%, Mn: 0.8 to 2.0
%, P ≦ 0.010%, S ≦ 0.003%, Al: 0.
005-0.05%, Nb: 0.005-0.060
%, Ti: 0.005 to 0.02%, N: 0.003 to
0.015%, O ≦ 0.0030%, and
Cu: 0.05-2.0%, Ni: 0.05-3.5
%, Cr: 0.01 to 0.5%, Mo: 0.01 to 0.
5%, V: 0.005 to 0.10%, containing 1 or 2 or more kinds, consisting of the balance Fe and unavoidable impurities, and -0.375C + 0.035≤Nb≤-0. 375C +
0.065 C + Mn / 6 + 1.7 Nb + (Cu + Ni) / 15 +
(Cr + Mo) /10+V/2.5≧0.30 C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo +
V) /5≦0.36 is satisfied, and the center segregated portion of the steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel with excellent toughness in the heat-affected zone of welding, characterized in that the number of precipitates of oxides and nitrides of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 pieces / mm 2 .
Si:0.005〜0.50%,Mn:0.8〜2.0
%,P≦0.010%,S≦0.003%,Al:0.
005〜0.05%,Nb:0.005〜0.060
%,Ti:0.005〜0.02%,B:0.0003
〜0.0030%,N:0.003〜0.015%,O
≦0.0030%を含有し、さらに,Cu:0.05〜
2.0%,Ni:0.05〜3.5%,Cr:0.01
〜0.5%,Mo:0.01〜0.5%,V:0.00
5〜0.10%の内から選んだ1種または2種以上を含
有し、残部Feおよび不可避不純物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+(Cu+Ni)/15+
(Cr+Mo)/10+V/2.5+20B≧0.30 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+
V)/5≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とする溶接熱影響部の靭性が優れた高強度鋼。4. C: 0.02 to 0.15% by weight,
Si: 0.005 to 0.50%, Mn: 0.8 to 2.0
%, P ≦ 0.010%, S ≦ 0.003%, Al: 0.
005-0.05%, Nb: 0.005-0.060
%, Ti: 0.005 to 0.02%, B: 0.0003
~ 0.0030%, N: 0.003 to 0.015%, O
≦ 0.0030%, further, Cu: 0.05 ~
2.0%, Ni: 0.05 to 3.5%, Cr: 0.01
~ 0.5%, Mo: 0.01 to 0.5%, V: 0.00
5 to 0.10% selected from the group consisting of one or more selected from the balance Fe and inevitable impurities, and -0.375C + 0.035≤Nb≤-0.375C +.
0.065 C + Mn / 6 + 1.7 Nb + (Cu + Ni) / 15 +
(Cr + Mo) /10+V/2.5+20B≧0.30 C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo +
V) /5≦0.36 is satisfied, and the center segregated portion of the steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel with excellent toughness in the heat-affected zone of welding, characterized in that the number of precipitates of oxides and nitrides of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 pieces / mm 2 .
Si:0.005〜0.50%,Mn:0.8〜2.0
%,P≦0.010%,S≦0.003%,Al:0.
005〜0.05%,Nb:0.005〜0.060
%,Ti:0.005〜0.02%,N:0.003〜
0.015%,O≦0.0030%を含有し、さらに、
Ca:0.0005〜0.0030%,REM:0.0
05〜0.050%の内から選んだ1種または2種以上
を含有し、残部Feおよび不可避不純物からなり、か
つ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb≧0.30 C+Mn/6≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とする溶接熱影響部の靭性が優れた高強度鋼。5. C .: 0.02 to 0.15% by weight,
Si: 0.005 to 0.50%, Mn: 0.8 to 2.0
%, P ≦ 0.010%, S ≦ 0.003%, Al: 0.
005-0.05%, Nb: 0.005-0.060
%, Ti: 0.005 to 0.02%, N: 0.003 to
0.015%, O ≦ 0.0030%, and
Ca: 0.0005 to 0.0030%, REM: 0.0
It contains one or more selected from the range of 0.05 to 0.050%, consists of the balance Fe and unavoidable impurities, and -0.375C + 0.035≤Nb≤-0.375C +.
0.065 C + Mn / 6 + 1.7 Nb ≧ 0.30 Satisfaction of C + Mn / 6 ≦ 0.36, center segregation portion of steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel with excellent toughness in the heat-affected zone of welding, characterized in that the number of precipitates of oxides and nitrides of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 pieces / mm 2 .
Si:0.005〜0.50%,Mn:0.8〜2.0
%,P≦0.010%,S≦0.003%,Al:0.
005〜0.05%,Nb:0.005〜0.060
%,Ti:0.005〜0.02%,B:0.0003
〜0.0030%,N:0.003〜0.015%,O
≦0.0030%を含有し、さらに、Ca:0.000
5〜0.0030%,REM:0.005〜0.050
%の内から選んだ1種または2種以上を含有し、残部F
eおよび不可避不純物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+20B≧0.30 C+Mn/6≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とする溶接熱影響部の靭性が優れた高強度鋼。6. C: 0.02 to 0.15% by weight,
Si: 0.005 to 0.50%, Mn: 0.8 to 2.0
%, P ≦ 0.010%, S ≦ 0.003%, Al: 0.
005-0.05%, Nb: 0.005-0.060
%, Ti: 0.005 to 0.02%, B: 0.0003
~ 0.0030%, N: 0.003 to 0.015%, O
≦ 0.0030%, further Ca: 0.000
5 to 0.0030%, REM: 0.005 to 0.050
%, Containing 1 or 2 or more selected from the
e and unavoidable impurities, and is −0.375C + 0.035 ≦ Nb ≦ −0.375C +
0.065 C + Mn / 6 + 1.7 Nb + 20B ≧ 0.30 C + Mn / 6 ≦ 0.36 is satisfied, and the center segregated portion (sheet thickness / 50) mm thickness of the steel sheet × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel with excellent toughness in the heat-affected zone of welding, characterized in that the number of precipitates of oxides and nitrides of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 pieces / mm 2 .
Si:0.005〜0.50%,Mn:0.8〜2.0
%,P≦0.010%,S≦0.003%,Al:0.
005〜0.05%,Nb:0.005〜0.060
%,Ti:0.005〜0.02%,N:0.003〜
0.015%,O≦0.0030%を含有し、さらに,
Cu:0.05〜2.0%,Ni:0.05〜3.5
%,Cr:0.01〜0.5%,Mo:0.01〜0.
5%,V:0.005〜0.10%の内から選んだ1種
または2種以上を含有し、さらに、Ca:0.0005
〜0.0030%,REM:0.005〜0.050%
の内から選んだ1種または2種以上を含有し、残部Fe
および不可避不純物からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+(Cu+Ni)/15+
(Cr+Mo)/10+V/2.5≧0.30 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+
V)/5≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とする溶接熱影響部の靭性が優れた高強度鋼。7. C .: 0.02 to 0.15% by weight,
Si: 0.005 to 0.50%, Mn: 0.8 to 2.0
%, P ≦ 0.010%, S ≦ 0.003%, Al: 0.
005-0.05%, Nb: 0.005-0.060
%, Ti: 0.005 to 0.02%, N: 0.003 to
0.015%, O ≦ 0.0030%, and
Cu: 0.05-2.0%, Ni: 0.05-3.5
%, Cr: 0.01 to 0.5%, Mo: 0.01 to 0.
5%, V: 0.005 to 0.10%, containing 1 or 2 or more selected, and further Ca: 0.0005
~ 0.0030%, REM: 0.005-0.050%
Containing one or more selected from the balance Fe
And unavoidable impurities, and -0.375C + 0.035≤Nb≤-0.375C +
0.065 C + Mn / 6 + 1.7 Nb + (Cu + Ni) / 15 +
(Cr + Mo) /10+V/2.5≧0.30 C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo +
V) /5≦0.36 is satisfied, and the center segregated portion of the steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel with excellent toughness in the heat-affected zone of welding, characterized in that the number of precipitates of oxides and nitrides of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 pieces / mm 2 .
Si:0.005〜0.50%,Mn:0.8〜2.0
%,P≦0.010%,S≦0.003%,Al:0.
005〜0.05%,Nb:0.005〜0.060
%,Ti:0.005〜0.02%,B:0.0003
〜0.0030%,N:0.003〜0.015%,O
≦0.0030%を含有し、さらに,Cu:0.05〜
2.0%,Ni:0.05〜3.5%,Cr:0.01
〜0.5%,Mo:0.01〜0.5%,V:0.00
5〜0.10%の内から選んだ1種または2種以上を含
有し、さらに、Ca:0.0005〜0.0030%,
REM:0.005〜0.050%の内から選んだ1種
または2種以上を含有し、残部Feおよび不可避不純物
からなり、かつ、 −0.375C+0.035≦Nb≦−0.375C+
0.065 C+Mn/6+1.7Nb+(Cu+Ni)/15+
(Cr+Mo)/10+V/2.5+20B≧0.30 C+Mn/6+(Cu+Ni)/15+(Cr+Mo+
V)/5≦0.36 を満足し、鋼板の中心偏析部(板厚/50)mm厚×1
0mm×10mmの平均化学分析値のC濃度が、鋼材の
平均C濃度の1.2倍以下、JIS規格で測定される介
在物の清浄度が0.03%以下、かつ鋼板断面で観察さ
れる平均直径10μm以上の酸化物系介在物の個数が1
個以下/1mm2 、0.05〜5μmの酸化物及び窒化
物の析出物の個数が100個以上/1mm2 であること
を特徴とする溶接熱影響部の靭性が優れた高強度鋼。8. C: 0.02 to 0.15% by weight,
Si: 0.005 to 0.50%, Mn: 0.8 to 2.0
%, P ≦ 0.010%, S ≦ 0.003%, Al: 0.
005-0.05%, Nb: 0.005-0.060
%, Ti: 0.005 to 0.02%, B: 0.0003
~ 0.0030%, N: 0.003 to 0.015%, O
≦ 0.0030%, further, Cu: 0.05 ~
2.0%, Ni: 0.05 to 3.5%, Cr: 0.01
~ 0.5%, Mo: 0.01 to 0.5%, V: 0.00
5 to 0.10%, one or more selected from, and further contains Ca: 0.0005 to 0.0030%,
REM: contains one or more selected from 0.005 to 0.050%, consists of balance Fe and unavoidable impurities, and -0.375C + 0.035≤Nb≤-0.375C +
0.065 C + Mn / 6 + 1.7 Nb + (Cu + Ni) / 15 +
(Cr + Mo) /10+V/2.5+20B≧0.30 C + Mn / 6 + (Cu + Ni) / 15 + (Cr + Mo +
V) /5≦0.36 is satisfied, and the center segregated portion of the steel sheet (sheet thickness / 50) mm thickness × 1
The C concentration of the average chemical analysis value of 0 mm × 10 mm is 1.2 times or less of the average C concentration of the steel material, the cleanliness of inclusions measured by JIS standard is 0.03% or less, and it is observed in the steel plate cross section. The number of oxide inclusions with an average diameter of 10 μm or more is 1
A high-strength steel with excellent toughness in the heat-affected zone of welding, characterized in that the number of precipitates of oxides and nitrides of not more than 1 piece / mm 2 and 0.05 to 5 μm is not less than 100 pieces / mm 2 .
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP30237294A JPH08158006A (en) | 1994-12-06 | 1994-12-06 | High strength steel excellent in toughness in weld heat-affected zone |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP30237294A JPH08158006A (en) | 1994-12-06 | 1994-12-06 | High strength steel excellent in toughness in weld heat-affected zone |
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Publication Number | Publication Date |
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JPH08158006A true JPH08158006A (en) | 1996-06-18 |
Family
ID=17908113
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Application Number | Title | Priority Date | Filing Date |
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JP30237294A Pending JPH08158006A (en) | 1994-12-06 | 1994-12-06 | High strength steel excellent in toughness in weld heat-affected zone |
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