JP5157657B2 - High-strength steel plate with excellent toughness in heat-affected zone of large heat input welding - Google Patents
High-strength steel plate with excellent toughness in heat-affected zone of large heat input welding Download PDFInfo
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- JP5157657B2 JP5157657B2 JP2008148738A JP2008148738A JP5157657B2 JP 5157657 B2 JP5157657 B2 JP 5157657B2 JP 2008148738 A JP2008148738 A JP 2008148738A JP 2008148738 A JP2008148738 A JP 2008148738A JP 5157657 B2 JP5157657 B2 JP 5157657B2
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- 229910000831 Steel Inorganic materials 0.000 title claims description 24
- 239000010959 steel Substances 0.000 title claims description 24
- 238000003466 welding Methods 0.000 title description 13
- 229910052804 chromium Inorganic materials 0.000 claims description 12
- 229910052748 manganese Inorganic materials 0.000 claims description 12
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 239000000203 mixture Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- 230000009466 transformation Effects 0.000 description 6
- 229910001566 austenite Inorganic materials 0.000 description 5
- 229910001563 bainite Inorganic materials 0.000 description 5
- 230000007423 decrease Effects 0.000 description 4
- 230000000087 stabilizing effect Effects 0.000 description 4
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 3
- 239000010953 base metal Substances 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000009863 impact test Methods 0.000 description 3
- 229910052759 nickel Inorganic materials 0.000 description 3
- 230000006641 stabilisation Effects 0.000 description 3
- 238000011105 stabilization Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 229910052750 molybdenum Inorganic materials 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 238000009628 steelmaking Methods 0.000 description 2
- 238000009864 tensile test Methods 0.000 description 2
- 229910000851 Alloy steel Inorganic materials 0.000 description 1
- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000005098 hot rolling Methods 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
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Description
本発明は、大入熱溶接熱影響部の靭性に優れた高強度鋼板に関し、特に５００ｋＪ／ｃｍを超える大入熱溶接を施した場合であっても、溶接熱影響部の靭性に優れる、引張強度が４９０ＭＰａ以上のものに関する。 The present invention relates to a high-strength steel plate excellent in toughness of a heat input zone affected by high heat input, and in particular, tensile strength excellent in toughness of the heat affected zone even when subjected to high heat input exceeding 500 kJ / cm. It relates to a material having a strength of 490 MPa or more.
建築構造物の一つであるボックス柱の組み立て溶接に適用されるサブマージアーク溶接やエレクトロスラグ溶接等では、施工高能率化のため、５００ｋJ／ｃｍを超える大入熱溶接が施されることがある。 In submerged arc welding and electroslag welding, which are applied to assembly welding of box columns, which is one of the building structures, large heat input welding exceeding 500 kJ / cm may be performed to improve construction efficiency. .
鋼材を溶接すると、溶接入熱の増大に伴い、溶接熱影響部組織（以下、ＨＡＺ）が粗大化して靭性が低下するため、従来より種々の靭性改善技術が提案されている。 When steel materials are welded, as the welding heat input increases, the weld heat-affected zone structure (hereinafter referred to as HAZ) becomes coarse and the toughness decreases, so that various toughness improving techniques have been proposed conventionally.
例えば、特許文献１は大入熱溶接熱影響部の靭性に優れた高張力鋼板に関し、鋼組成を極低Ｃ化して島状マルテンサイト（以下、ＭＡ）の生成を抑制し、焼入れ性向上元素であるＭｎ，ＮｉおよびＣｒの含有量を適正化してγ粒界でのフェライトの生成を押えて粒内における変態組織のブロックサイズを微細化し、ＨＡＺ靭性の劣化を抑制することが開示されている。
しかしながら、特許文献１記載の大入熱溶接熱影響部の靭性に優れた高張力鋼板は、ＨＡＺ靭性を改善するため成分組成においてＮｉ添加を必須とし、最近の高合金鋼やステンレス鋼の需要増加によるＮｉ価格の高騰で、建築など大量に使用される用途には適用しがたくなっている。 However, the high-tensile steel plate with excellent toughness of the high heat input welding heat-affected zone described in Patent Document 1 requires the addition of Ni in the component composition in order to improve the HAZ toughness, and the recent increase in demand for high alloy steel and stainless steel Due to soaring Ni prices, it is difficult to apply to large-scale uses such as architecture.
そこで、本発明は、Ｎｉ，Ｍｏ，及びＮｂなど高価な合金元素を用いず、比較的安価なＭｎやＣｒの添加により大入熱溶接のＨＡＺ靭性に優れる、引張強度が４９０ＭＰａ以上の高張力鋼板を提供することを目的とする。 Therefore, the present invention does not use expensive alloy elements such as Ni, Mo, and Nb, and is excellent in HAZ toughness for high heat input welding by adding relatively inexpensive Mn and Cr, and has a tensile strength of 490 MPa or more. The purpose is to provide.
本発明者等は大入熱溶接ＨＡＺの靭性に及ぼす成分組成の影響について鋭意検討し、その結果、安定して高い靭性を確保するためには、１．Ｃ含有量を０．０３％以下に極低Ｃ化してＭＡ（島状マルテンサイト）の生成を抑制し、Ｍｎ，Cｒを添加して変態点温度を低下させＨＡＺ全体を均一なベイナイト組織とすること、２．更に、ＭｎとＣｒを同時に添加して、Ｍｎ量に対してＣｒ量を適正にすること、が有効なことを見出した。本発明は得られた知見を基に更に検討を加えてなされたもので、すなわち、本発明は、
１． 質量％で、Ｃ：０．０１〜０．０３％、Ｓｉ：０．５％以下、Ｍｎ：２．３〜３．５％、Ｃｒ：１．０〜２．５％、Ａｌ：０．０５％以下、Ｔｉ：０．００５〜０．０５０％を含有し、３５Ｃｒ＋８Ｍｎ≧６３、且つ６Ｃｒ＋４Ｍｎ≦２４を満足し、残部鉄及び不可避的不純物からなることを特徴とする大入熱溶接熱影響部の靭性に優れた高強度鋼板。但し、上記式中のＣｒ，Ｍｎはそれぞれの元素の含有量（質量％）を示す。
The present inventors diligently studied the influence of the component composition on the toughness of the high heat input welding HAZ, and as a result, in order to ensure high toughness stably, 1. C content is extremely reduced to 0.03% or less to suppress the formation of MA (island martensite), and Mn and Cr are added to lower the transformation point temperature to make the entire HAZ uniform bainite structure. 2. Furthermore, it has been found that it is effective to add Mn and Cr at the same time to make the Cr amount appropriate with respect to the Mn amount. The present invention was made by further study based on the obtained knowledge, that is, the present invention is
1. In mass%, C: 0.01 to 0.03%, Si: 0.5% or less, Mn: 2.3 to 3.5%, Cr: 1.0 to 2.5%, Al: 0.05 % Of Ti, 0.005 to 0.050%, satisfying 35Cr + 8Mn ≧ 63 and 6Cr + 4Mn ≦ 24, and comprising the balance iron and inevitable impurities, High strength steel plate with excellent toughness. However, Cr and Mn in the above formulas indicate the content (% by mass) of each element.
本発明によれば、５００ｋＪ／ｃｍを超える大入熱溶接を施した場合にも、優れたＨＡＺ靭性が確保される高強度鋼板が得られるので、ボックス柱などの建築構造物の安全性を高め、且つ高能率で製造でき産業上極めて有用である。 According to the present invention, even when high heat input welding exceeding 500 kJ / cm is performed, a high-strength steel sheet that ensures excellent HAZ toughness is obtained, so that the safety of building structures such as box columns is increased. In addition, it can be manufactured with high efficiency and is extremely useful in industry.
また、本発明に係る高強度鋼板は、近年、高騰しているＮｉ，Ｍｏなど高価な合金元素を添加する必要がないので経済性にも優れる。 Further, the high-strength steel sheet according to the present invention is excellent in economical efficiency because it is not necessary to add expensive alloy elements such as Ni and Mo, which have been rising in recent years.
本発明では成分組成を規定する。説明において％は、質量％とする。
Ｃ：０．０１〜０．０３％
Ｃは、母材強度を確保するとともに、γ粒の粗大化を抑制してＨＡＺ靭性を確保するために必要で、当該効果を発揮させるため、０．０１％以上を添加する。一方、Ｃ量が過剰になるとＭＡが増大してＨＡＺ靭性が劣化するようになるので０．０３％以下とする。
In the present invention, the component composition is defined. In the description,% is mass%.
C: 0.01 to 0.03%
C is necessary for securing the strength of the base material and suppressing the coarsening of the γ grains to ensure the HAZ toughness. In order to exhibit the effect, 0.01% or more is added. On the other hand, if the amount of C becomes excessive, MA increases and the HAZ toughness deteriorates, so the content is made 0.03% or less.
Ｓｉ：０．５０％以下
Ｓｉは、製鋼時の脱酸に必要な元素であるが、脱酸の目的を達すれば、添加量は少なくて良く、一方、０．５０％を超えて過剰に添加するとＭＡが増大してＨＡＺ靭性が劣化するため、０．５０％以下とする。
Si: 0.50% or less Si is an element necessary for deoxidation at the time of steelmaking. However, if the purpose of deoxidation is achieved, the addition amount may be small, while over 0.50% is added excessively. Then, since MA increases and HAZ toughness deteriorates, it is 0.50% or less.
Ｍｎ：２．３〜３．５％
Ｍｎは、強力なオーステナイト安定化元素で、変態温度を低下させて母材の強度を確保するのに有用で、また、ベイナイト変態を促進するため、２．３％以上を添加する。一方、Ｍｎ量が過剰になるとＨＡＺが硬化してＨＡＺ靭性が低下するようになるので、３．５％以下とする。
Mn: 2.3 to 3.5%
Mn is a strong austenite stabilizing element, useful for lowering the transformation temperature to ensure the strength of the base material, and 2.3% or more is added to promote bainite transformation. On the other hand, if the amount of Mn becomes excessive, the HAZ hardens and the HAZ toughness decreases, so the content is made 3.5% or less.
Ｃｒ：１．０〜２．５％
Ｃｒは、焼入れ性を向上させて母材の強度や靭性を確保するのに有用な元素で、また、フェライト安定化元素のため、Ｍｎによるオーステナイトの過度の安定化を防止し、ＭＡの発生を防止する。このような効果を得るため、１．０％以上添加する。
Cr: 1.0-2.5%
Cr is an element useful for improving the hardenability and ensuring the strength and toughness of the base metal, and because it is a ferrite stabilizing element, it prevents excessive stabilization of austenite by Mn and prevents the generation of MA. To prevent. In order to obtain such an effect, 1.0% or more is added.
一方、Ｃｒが過剰に存在すると、ＨＡＺの硬度が増大してＨＡＺ靭性が劣化するので、２．５％以下とする。 On the other hand, if Cr is present excessively, the hardness of the HAZ increases and the HAZ toughness deteriorates, so the content is made 2.5% or less.
Ａｌ：０．０５％以下
Ａｌは、製鋼時の脱酸に必要な元素であるが、脱酸の目的が達成されれば添加量は少なくても良く、一方、過剰になると、アルミナ等の粗大介在物が増加して、母材靭性が劣化し、ＭＡも増加してＨＡＺ靭性も劣化させるようになるので、０．０５％以下とする。
Al: 0.05% or less Al is an element necessary for deoxidation at the time of steelmaking. However, if the purpose of deoxidation is achieved, the amount added may be small. Inclusions increase, base metal toughness deteriorates, MA also increases and HAZ toughness deteriorates, so 0.05% or less.
Ｔｉ：０．００５〜０．０５０％
Ｔｉは、Ｎと結合してＴｉＮを形成する。ＴｉＮは、ＨＡＺのγ粒の成長を抑制し、ＨＡＺ靭性を向上させるため、このような効果が得られるように０．００５％以上、好ましくは０．０１０％以上を添加する。一方、Ｔｉが過剰になるとＴｉＮが粗大化し、母材靭性、ＨＡＺ靭性が共に劣化するので、０．０５０％以下とする。好ましくは、０．０２５％以下である。
Ti: 0.005 to 0.050%
Ti combines with N to form TiN. TiN suppresses the growth of HAZ γ grains and improves the HAZ toughness, so 0.005% or more, preferably 0.010% or more is added so as to obtain such an effect. On the other hand, when Ti becomes excessive, TiN becomes coarse and both the base material toughness and the HAZ toughness deteriorate, so the content is made 0.050% or less. Preferably, it is 0.025% or less.
３５Ｃｒ＋８Ｍｎ≧６３、且つ、６Ｃｒ＋４Ｍｎ≦２４
これらのパラメータ式は、上記成分範囲で構成される鋼の、大入熱溶接ＨＡＺにおけるＭＡの生成量を少なくすると共に、ＨＡＺの硬さを低減して靭性を優れたものとするためのものである。
35Cr + 8Mn ≧ 63 and 6Cr + 4Mn ≦ 24
These parameter formulas are for reducing the amount of MA generated in the high heat input welding HAZ of the steel composed of the above component ranges, and reducing the hardness of the HAZ to make the toughness excellent. is there.
Ｍｎは強力なオーステナイト安定化元素であり変態温度を低下させてベイナイト変態を促進する。しかし、Ｍｎ単独で添加した場合は、ベイナイトラス間にＭＡが析出してＨＡＺ靭性が低下する。 Mn is a strong austenite stabilizing element and promotes bainite transformation by lowering the transformation temperature. However, when Mn is added alone, MA precipitates between the bainite laths and the HAZ toughness decreases.
Ｍｎと共にフェライト安定化元素であるＣｒを添加すると、Ｍｎ添加による過度のオーステナイトの安定化が緩和され、ベイナイトラス間のＭＡは減少し、ＨＡＺ靭性に優れる領域が現出する。しかし、Ｃｒを更に添加すると焼入れ性が高まってＨＡＺの硬さが増大してＨＡＺ靭性は低下する。 When Cr, which is a ferrite stabilizing element, is added together with Mn, excessive stabilization of austenite due to the addition of Mn is alleviated, MA between bainite laths is reduced, and a region excellent in HAZ toughness appears. However, when Cr is further added, the hardenability is increased, the hardness of the HAZ is increased, and the HAZ toughness is decreased.
そこで、本発明では、ＭｎとＣｒの添加量を、上述した個々の添加量の範囲内で、３５Ｃｒ＋８Ｍｎ≧６３、且つ６Ｃｒ＋４Ｍｎ≦２４を満足するように規定する。 Therefore, in the present invention, the addition amounts of Mn and Cr are defined so as to satisfy 35Cr + 8Mn ≧ 63 and 6Cr + 4Mn ≦ 24 within the range of the individual addition amounts described above.
ＭｎとＣｒの添加量が、３５Ｃｒ＋８Ｍｎ≧６３を満足する場合、Ｍｎ添加によるオーステナイトの過度の安定化が防止されて、ＭＡの発生が抑制されＨＡＺ靭性が向上する。 When the addition amount of Mn and Cr satisfies 35Cr + 8Mn ≧ 63, excessive stabilization of austenite due to the addition of Mn is prevented, generation of MA is suppressed, and HAZ toughness is improved.
一方、６Ｃｒ＋４Ｍｎ＞２４となる場合、ＨＡＺ硬さが硬くなりすぎてＨＡＺ靭性が低下するようになるので、６Ｃｒ＋４Ｍｎ≦２４とする。尚、これらの式においてＣｒ，Ｍｎは添加量（質量％）とする。 On the other hand, when 6Cr + 4Mn> 24, the HAZ hardness becomes too hard and the HAZ toughness decreases, so 6Cr + 4Mn ≦ 24. In these formulas, Cr and Mn are added amounts (mass%).
本発明に係る鋼板は、常法により溶製、熱間圧延して製造することが可能である。以下、実施例を用いて本発明をより具体的に説明する。 The steel sheet according to the present invention can be manufactured by melting and hot rolling by a conventional method. Hereinafter, the present invention will be described more specifically with reference to examples.
表１に示す成分組成の鋼を溶製しインゴットとした後、１２００℃に加熱し、板厚１３ｍｍまで熱間圧延を行って供試鋼板とし、母材強度とＨＡＺ靭性の評価を行った。 Steels having the component compositions shown in Table 1 were melted into ingots, heated to 1200 ° C., hot-rolled to a plate thickness of 13 mm to obtain test steel plates, and the base metal strength and HAZ toughness were evaluated.
１．母材強度
各鋼板から採取した丸棒試験片（ＡＳＴＭ−Ｆ型）について、ＪＩＳＺ２２４１に準じて引張試験を行い、降伏強度（ＹＳ），引張強度（ＴＳ），伸び（ＥＬ）を測定した。丸棒試験片（ＡＳＴＭ−Ｆ型）は圧延方向から採取した。得られた引張強度が４９０ＭＰａ以上のものを本発明範囲内とした。
1. Base material strength A round bar test piece (ASTM-F type) collected from each steel plate was subjected to a tensile test according to JISZ2241, and yield strength (YS), tensile strength (TS), and elongation (EL) were measured. A round bar specimen (ASTM-F type) was taken from the rolling direction. The obtained tensile strength of 490 MPa or more was made within the scope of the present invention.
２．ＨＡＺ靭性
ＨＡＺ靭性の評価を再現熱サイクルシャルピー衝撃試験により行った。熱サイクルは、スキンプレート材（５０ｍｍ厚）とダイヤフラム材（５０ｍｍ厚）を組み合わせ、溶接入熱５００ｋＪ／ｃｍのエレクトロスラグ溶接を行った場合のボンド近傍のＨＡＺにおけるものを模擬したもので、１４００℃で１秒間保持し、８００−５００℃の冷却時間を５１０秒とした。
2. HAZ toughness HAZ toughness was evaluated by a reproducible thermal cycle Charpy impact test. The thermal cycle is a simulation of the HAZ in the vicinity of the bond when electroslag welding with a heat input of 500 kJ / cm is performed by combining a skin plate material (50 mm thickness) and a diaphragm material (50 mm thickness). At 800 to 500 ° C. for 510 seconds.
圧延方向から採取した１２ｍｍ厚さ×１２ｍｍ幅の角棒状試験片に高周波誘導加熱装置で上述した熱サイクルを付与した後、ＪＩＳＺ２３２０２のＶノッチ試験片を３本採取して、ＪＩＳＺ２２４２に準じてシャルピー衝撃試験を行った。 After applying the thermal cycle described above with a high-frequency induction heating device to a 12 mm thick x 12 mm wide square bar specimen taken from the rolling direction, three V-notch specimens of JISZ2322 were collected, and Charpy impact was performed according to JISZ2242. A test was conducted.
シャルピー衝撃試験は試験温度を０℃として各鋼板について３本の試験片で行った。３本における吸収エネルギー（ｖＥ０）の最低値が５０Ｊ以上、３本の吸収エネルギー（ｖＥ０）の平均値が１００Ｊ以上をＨＡＺ靭性に優れるもの（本発明範囲内）とした。 The Charpy impact test was performed with three test pieces for each steel plate at a test temperature of 0 ° C. The minimum value of the absorbed energy (vE 0 ) of the three pieces was 50 J or more, and the average value of the three absorbed energy (vE 0 ) was 100 J or more, which was excellent in HAZ toughness (within the scope of the present invention).
表２に引張試験結果およびシャルピー衝撃試験結果を示す。供試鋼の記号は表１と表２で同じものとする。 Table 2 shows the tensile test results and the Charpy impact test results. The symbol of the test steel is the same in Table 1 and Table 2.
供試鋼Ｋ１，Ｖ３，Ｖ４，Ｗ２、W３、Ｗ４は本発明鋼で、引張強度４９０ＭＰａ以上の高強度と、３本における吸収エネルギー（ｖＥ０）の最低値が５０Ｊ以上、３本の吸収エネルギー（ｖＥ０）の平均値が１００Ｊ以上の優れたＨＡＺ靭性が得られた。 Test steels K1, V3, V4, W2, W3, and W4 are steels of the present invention, high strength with a tensile strength of 490 MPa or more, and the minimum value of absorbed energy (vE 0 ) at 3 is 50 J or more and 3 absorbed energy Excellent HAZ toughness having an average value of (vE 0 ) of 100 J or more was obtained.
一方、供試鋼Ｃ１，Ｃ２，Ｃ３，Ｃ４は成分組成においてＣｒの添加がなく、Ｍｎのみが添加された比較例で、供試鋼Ｃ１，Ｃ２は母材のＴＳが４９０ＭＰａ未満で強度が不足し、供試鋼Ｃ３，Ｃ４は母材のＴＳは十分であるが、ＨＡＺ靭性が劣っていた。 On the other hand, the test steels C1, C2, C3 and C4 are comparative examples in which Cr is not added in the component composition and only Mn is added. However, the sample steels C3 and C4 had sufficient base TS, but had poor HAZ toughness.
供試鋼Ｆ１，Ｆ２，Ｆ３，Ｆ４は成分組成においてＣｒとＭｎの両者が添加されているが、６Ｃｒ＋４Ｍｎ＞２４のためＨＡＺ靭性が劣っていた。 In the test steels F1, F2, F3, and F4, both Cr and Mn were added in the composition, but HAZ toughness was inferior because 6Cr + 4Mn> 24.
供試鋼Ｋ２、Ｋ３，Ｋ４は成分組成においてＣｒが本発明範囲を超えて過剰に添加され、６Ｃｒ＋４Ｍｎ＞２４のためＨＡＺ靭性が劣っていた。 In the test steels K2, K3, and K4, Cr was excessively added in the component composition exceeding the range of the present invention, and HAZ toughness was inferior because 6Cr + 4Mn> 24.
供試鋼Ｖ１，Ｖ２、Ｗ１は成分組成においてＣｒの添加量が本発明範囲未満で、３５Ｃｒ＋８Ｍｎ≧６３を満足せず、ＨＡＺ靭性が劣っていた。 In the test steels V1, V2, and W1, the amount of Cr added in the composition was less than the range of the present invention, 35Cr + 8Mn ≧ 63 was not satisfied, and the HAZ toughness was inferior.
Claims (1)
但し、上記式中のＣｒ，Ｍｎはそれぞれの元素の含有量（質量％）を示す。 In mass%, C: 0.01 to 0.03%, Si: 0.5% or less, Mn: 2.3 to 3.5%, Cr: 1.0 to 2.5%, Al: 0.05 % Of Ti, 0.005 to 0.050%, satisfying 35Cr + 8Mn ≧ 63 and 6Cr + 4Mn ≦ 24, and comprising the balance iron and inevitable impurities, High strength steel plate with excellent toughness.
However, Cr and Mn in the above formulas indicate the content (% by mass) of each element.
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