JP2944540B2 - Manufacturing method of direct quenching high strength steel sheet with excellent toughness - Google Patents
Manufacturing method of direct quenching high strength steel sheet with excellent toughnessInfo
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- JP2944540B2 JP2944540B2 JP30037496A JP30037496A JP2944540B2 JP 2944540 B2 JP2944540 B2 JP 2944540B2 JP 30037496 A JP30037496 A JP 30037496A JP 30037496 A JP30037496 A JP 30037496A JP 2944540 B2 JP2944540 B2 JP 2944540B2
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Description
【発明の詳細な説明】DETAILED DESCRIPTION OF THE INVENTION
【０００１】[0001]
【発明の属する技術分野】本発明は、直接焼入型高張力
鋼板の製造技術分野に属し、さらに詳しくは、タンク、
橋梁、ペンストック等に用いられる引張強さ588N/mm2(6
0kgf/mm2) 以上の調質高張力鋼板を直接焼入法にて製造
する場合に、良好な母材靱性を確保するための製造技術
分野に属するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention belongs to the technical field of manufacturing a direct quenching type high-tensile steel sheet,
Tensile strength 588 N / mm 2 (6
0 kgf / mm 2 ) It belongs to the field of manufacturing technology for ensuring good base metal toughness when a tempered high-strength steel sheet having a hardness of 0 kgf / mm 2 or more is manufactured by the direct quenching method.
【０００２】[0002]
【従来の技術】熱延鋼板に対して圧延後直ちに焼入れす
る、いわゆる直接焼入法では、従来の再加熱焼入法と比
べて、焼入性が向上する利点があるが、その反面、靱性
が劣化する欠点がある。この靱性劣化の理由は以下のと
おりである。2. Description of the Related Art The so-called direct quenching method, in which a hot-rolled steel sheet is quenched immediately after rolling, has the advantage of improving the hardenability as compared with the conventional reheating quenching method. Has the disadvantage of deteriorating. The reason for the deterioration of toughness is as follows.
【０００３】通常、直接焼入装置は仕上圧延機と離れた
位置にあるため、圧延終了後、焼入れまでの間に鋼板の
温度低下が避けられない。そこで、焼入温度確保の観点
から、その温度低下を見込んで高温で仕上圧延を行うた
め、焼入れ前のオーステナイト粒が粗大となり、焼入組
織も粗く、靱性が劣化する。Usually, since the direct quenching device is located at a position away from the finish rolling mill, the temperature of the steel sheet is unavoidably reduced from the end of rolling to the time of quenching. Therefore, from the viewpoint of securing the quenching temperature, the finish rolling is performed at a high temperature in anticipation of the temperature decrease, so that the austenite grains before quenching become coarse, the quenched structure is coarse, and the toughness is deteriorated.
【０００４】ところで、直接焼入適用鋼板の靱性を改善
する方法としては、未再結晶域からの焼入れにより、焼
入れ組織を微細化する方法が提案されている。すなわ
ち、未再結晶組織を得るために、(1) 特開昭57-152422
号公報、同61-23715号公報及び同61-295320 号公報に記
載されているように、Nb、Ti、V 等の特定の元素を加え
て、所定の温度域で30％以上圧下する方法、また(2) 特
開昭63-33521号公報に記載されているように、特定の元
素を加える代わりに、低温圧延を行う方法などがある。As a method for improving the toughness of a steel sheet to which direct quenching is applied, a method has been proposed in which the quenched structure is refined by quenching from an unrecrystallized region. That is, in order to obtain an unrecrystallized structure, (1) JP-A-57-152422
As described in JP-A-61-23715 and JP-A-61-295320, a method of adding a specific element such as Nb, Ti, V, etc., and reducing the pressure by 30% or more in a predetermined temperature range, Also, as described in (2) JP-A-63-33521, there is a method of performing low-temperature rolling instead of adding a specific element.
【０００５】[0005]
【発明が解決しようとする課題】B は微量の添加で鋼の
焼入性を高める元素であるが、B 添加鋼に前記(1) 或い
は(2) の方法を適用する場合、以下に述べるような焼入
不足に起因する靱性劣化の問題が生じることがある。B is an element that enhances the hardenability of steel with a small amount of addition. When the above method (1) or (2) is applied to B-added steel, the following is required. In some cases, a problem of toughness deterioration due to insufficient quenching may occur.
【０００６】まず、B 添加鋼に(1) の方法を適用する場
合、粒界に偏析する固溶B 量がある濃度以上の時のみ、
焼入性向上の効果を発揮させることから、過度の組織の
微細化は、粒界の面積を増大させることになり、粒界に
おける固溶B 量の濃度が必要量を下回り、焼入性を低下
させることになる。焼入性の低下は、焼入組織がマルテ
ンサイト＋下部ベイナイトの混合組織から、上部ベイナ
イト組織になり、靱性を劣化させる。First, when the method (1) is applied to B-added steel, only when the amount of solute B segregated at the grain boundary is above a certain concentration,
Since the effect of improving hardenability is exerted, excessive micronization of the structure increases the area of the grain boundary, and the concentration of the solute B in the grain boundary falls below the required amount, and the hardenability decreases. Will be reduced. The decrease in hardenability changes the quenching structure from a mixed structure of martensite + lower bainite to an upper bainite structure, and deteriorates toughness.
【０００７】また、(2) の方法では、未再結晶組織を得
るために、圧延仕上温度を 800〜900 ℃の低い温度に制
限しているが、この温度範囲では、圧延終了から焼入れ
までの鋼板搬送時間の経過と共にBN及びFe23(CB)6 が形
成され、粒界の固溶B 量が減少する。したがって、B の
焼入性向上効果が有効に利用できるのは、圧延終了から
60秒までの短時間のみである。そのため、鋼板を先端か
ら順次焼き入れる通常の直接焼入において、長尺の鋼板
の後端を焼入れるまでに60秒以上要することから、後端
では十分に焼きが入らず、鋼板長手方向に材質が不均一
になる。In the method (2), the rolling finish temperature is limited to a low temperature of 800 to 900 ° C. in order to obtain an unrecrystallized structure. BN and Fe 23 (CB) 6 are formed with the passage of the steel sheet, and the amount of solute B at the grain boundaries decreases. Therefore, the effect of improving the hardenability of B can be effectively used only after the end of rolling.
Only a short time up to 60 seconds. Therefore, in normal direct quenching, in which the steel sheet is sequentially quenched from the front end, it takes 60 seconds or more to quench the rear end of the long steel sheet. Becomes uneven.
【０００８】本発明は、上記従来技術の問題点を解決す
るためになされたものであって、調質高張力鋼板を直接
焼入法にて製造する場合に良好な母材靱性を確保できる
方法を提供することを目的とするものである。The present invention has been made in order to solve the above-mentioned problems of the prior art, and is a method capable of securing good base material toughness when a tempered high-strength steel sheet is manufactured by a direct quenching method. The purpose is to provide.
【０００９】[0009]
【課題を解決するための手段】上記のように、B を添加
した調質高張力鋼板の未再結晶域での圧延による靱性改
善方法の問題点は、組織を必要以上に微細化すること及
び鋼板搬送時の温度が低いことから、焼きが十分に入ら
ないことにある。As described above, the problem of the method for improving the toughness of a tempered high-strength steel sheet to which B is added by rolling in the unrecrystallized region is that the structure is unnecessarily refined and Since the temperature at the time of transporting the steel sheet is low, baking is not sufficiently performed.
【００１０】そこで、本発明者らは、これらの問題点に
ついて鋭意研究を重ねた結果、組織の必要以上の微細化
を防ぐためには、圧延時に過度の圧下をとらないこと、
そして鋼板搬送時にBNなどの形成を抑えて必要な固溶B
量を確保するためには、Nbを添加し未再結晶域を高温側
に拡げ、その高い未再結晶温度で仕上圧延を行い、搬送
中の温度を確保することが有効であることを見い出し、
ここにB 添加鋼の直接焼入れ時の靱性改善方法を発明し
たものである。The inventors of the present invention have conducted intensive studies on these problems. As a result, in order to prevent the microstructure from being unnecessarily refined, it is necessary to prevent excessive reduction during rolling.
The necessary solid solution B by suppressing the formation of BN etc.
In order to secure the amount, Nb was added, the unrecrystallized region was expanded to the high temperature side, finish rolling was performed at the high unrecrystallized temperature, and it was found that it was effective to secure the temperature during transportation.
Here, a method for improving the toughness of B-added steel during direct quenching was invented.
【００１１】すなわち、本発明に係わる靱性の優れた直
接焼入型高張力鋼板の製造方法は、C:0.03〜0.20％、 S
i:0.10〜0.40％、 Mn:0.50〜2.00％、Nb:0.010〜0.040
％、B:0.0005〜0.0020％、N:0.0050％以下及びAl:0.020
〜0.080 ％を含み、さらに Cu:0.10〜1.00％、 Ni:0.10
〜3.00％、 Cr:0.10〜1.00％、 Mo:0.05〜1.00％、 V:
0.005〜0.100 ％及びTi:0.005〜0.020 ％のうちの１種
又は２種以上を含み、残部がFe及び不可避的不純物より
なる鋼を1150〜1300℃に加熱し、 900〜950 ℃の温度に
おいて10％以上30％未満の圧下率で圧延を終了した後、
120秒以内に、且つ 850℃以上の温度から焼入れを開始
し、 200℃以下まで急冷して、その後、Ａc1点以下で焼
もどし処理を施すことを特徴とするものである。That is, the method for producing a direct-quenching type high-tensile steel sheet having excellent toughness according to the present invention comprises: C: 0.03 to 0.20%,
i: 0.10 ~ 0.40%, Mn: 0.50 ~ 2.00%, Nb: 0.010 ~ 0.040
%, B: 0.0005 to 0.0020%, N: 0.0050% or less and Al: 0.020
~ 0.080%, Cu: 0.10 ~ 1.00%, Ni: 0.10
~ 3.00%, Cr: 0.10 ~ 1.00%, Mo: 0.05 ~ 1.00%, V:
A steel containing one or more of 0.005 to 0.100% and Ti: 0.005 to 0.020%, with the balance being Fe and unavoidable impurities, is heated to 1150 to 1300 ° C. After rolling at a rolling reduction of 30% or more and less than 30%,
Within 120 seconds, and starts quenched from 850 ° C. or higher, and rapidly cooled to 200 ° C. or less, then, is characterized in performing a tempering treatment in the following point Ac.
【００１２】[0012]
【発明の実施の形態】まず、本発明における化学成分の
限定理由について説明する。C は焼入性と強度確保のた
めに必要な元素であるが、0.03％未満ではこれらの効果
は期待できず、また0.20％を超えて含有すると溶接性及
び靱性を劣化させる。したがって、C 含有量は0.03〜0.
20％の範囲とする。DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the reasons for limiting chemical components in the present invention will be described. C is an element necessary for securing hardenability and strength. However, if less than 0.03%, these effects cannot be expected, and if it exceeds 0.20%, weldability and toughness are deteriorated. Therefore, the C content is 0.03--0.
20% range.
【００１３】Siは脱酸に必要な元素であるが、0.10％未
満ではこの効果が少なく、また0.40％を超えて含有する
と溶接性及び靱性の劣化を招く。したがって、Si含有量
は0.10〜0.40％の範囲とする。[0013] Si is an element necessary for deoxidation. If Si is less than 0.10%, this effect is small, and if it exceeds 0.40%, weldability and toughness are deteriorated. Therefore, the Si content is in the range of 0.10 to 0.40%.
【００１４】Mnは焼入性を確保するために必要な元素で
あるが、0.50％未満ではその効果が少なく、また2.00％
を超えて含有すると溶接性及び靱性の劣化を招く。した
がって、Mn含有量は0.50〜2.00％の範囲とする。Mn is an element necessary for ensuring hardenability, but if its content is less than 0.50%, its effect is small, and 2.00%
If it is contained in excess of, the weldability and the toughness will deteriorate. Therefore, the Mn content is in the range of 0.50 to 2.00%.
【００１５】Nbは加工オーステナイトの再結晶を抑制す
るために必要な元素である。しかし、0.010 ％未満では
この効果が少なく、また0.040 ％を超えて含有すると前
記効果が飽和する上に、かえって靱性劣化を招く。した
がって、Nb含有量は 0.010〜0.040 ％の範囲とする。Nb is an element necessary for suppressing recrystallization of processed austenite. However, if the content is less than 0.010%, this effect is small. If the content exceeds 0.040%, the above effect is saturated and the toughness is rather deteriorated. Therefore, the Nb content is in the range of 0.010 to 0.040%.
【００１６】B は焼入性向上に重要な元素である。しか
し、0.0005％未満ではその効果が少なく、また0.0020％
を超えて含有するとBN及びFe23(CB)6 を多量に生成して
靱性を劣化させる。したがって、B 含有量は0.0005〜0.
0020％の範囲とする。B is an important element for improving hardenability. However, less than 0.0005% is less effective, and 0.0020%
If it is contained in excess of BN, BN and Fe 23 (CB) 6 are generated in large amounts, and the toughness is deteriorated. Therefore, the content of B is 0.0005-0.
0020%.
【００１７】N はB と結合して固溶B 量を減少させ、0.
0050％を超えるとB の焼入性向上効果を阻害する。した
がって、N 含有量は0.0050％以下とする。N combines with B to reduce the amount of solute B,
If it exceeds 0050%, the effect of improving the hardenability of B is impaired. Therefore, the N content should be 0.0050% or less.
【００１８】Alは脱酸と結晶粒の微細化に必要な元素で
あるが、0.020 ％未満ではこれらの効果が少なく、また
0.080 ％を超えて含有すると介在物の増加により靱性が
劣化する。したがって、Al含有量は0.020 〜0.080 ％の
範囲とする。Al is an element necessary for deoxidation and grain refinement. If less than 0.020%, these effects are small.
If the content exceeds 0.080%, toughness deteriorates due to an increase in inclusions. Therefore, the Al content is in the range of 0.020 to 0.080%.
【００１９】以上の元素を必須成分とするが、以下に示
す元素のうち１種又は２種以上を含有させる。The above elements are essential components, but one or more of the following elements are contained.
【００２０】Cuは強度を確保するために必要な元素であ
るが、0.10％未満ではその効果が少なく、また1.00％を
超えて含有すると熱間加工時に割れが発生し、且つ溶接
性を劣化させる。したがって、Cu含有量は0.10〜1.00％
の範囲とする。[0020] Cu is an element necessary for securing strength, but if its content is less than 0.10%, its effect is small, and if it exceeds 1.00%, cracks occur during hot working and the weldability deteriorates. . Therefore, the Cu content is 0.10-1.00%
Range.
【００２１】Niは焼入性と低温靱性を確保する元素であ
るが、0.10％未満ではこれらの効果が少なく、また3.00
％を超えて含有させても、これらの効果は飽和する上
に、経済的な観点より好ましくない。したがって、Ni含
有量は0.10〜3.00％の範囲とする。Ni is an element that secures hardenability and low-temperature toughness. However, if it is less than 0.10%, these effects are small, and 3.00%.
%, These effects are saturated and are not preferable from an economic viewpoint. Therefore, the Ni content is in the range of 0.10 to 3.00%.
【００２２】Crは焼入性を確保する元素であるが、0.10
％未満ではその効果が少なく、また1.00％を超えて含有
すると溶接性を劣化させる。したがって、Cr含有量は0.
10〜1.00％の範囲とする。Cr is an element that secures hardenability.
%, The effect is small, and if it exceeds 1.00%, the weldability deteriorates. Therefore, the Cr content is 0.
The range is 10 to 1.00%.
【００２３】Moは焼入性と焼もどし軟化抵抗を確保する
ための元素であるが、0.05％未満ではこれらの効果が少
なく、また1.00％を超えて含有すると溶接性が劣化す
る。したがって、Moの含有量は0.05〜1.00％の範囲とす
る。Mo is an element for securing hardenability and tempering softening resistance. However, if it is less than 0.05%, these effects are small, and if it exceeds 1.00%, the weldability deteriorates. Therefore, the content of Mo is in the range of 0.05 to 1.00%.
【００２４】V は焼もどし軟化抵抗を確保するための元
素であるが、0.005 ％未満ではこの効果が得られず、ま
た0.100 ％を超えて含有すると母材靱性の劣化を招く。
したがって、V 含有量は 0.005〜0.100 ％の範囲とす
る。V is an element for securing the resistance to tempering and softening. If V is less than 0.005%, this effect cannot be obtained. If V exceeds 0.100%, the toughness of the base material is deteriorated.
Therefore, the V content is in the range of 0.005 to 0.100%.
【００２５】TiはN をTiN として固定し、B と結合する
N 量を減少させ、B の焼入性向上効果を確保するための
元素であるが、0.005 ％未満ではその効果が少なく、ま
た0.020 ％を超えて含有すると母材靱性を劣化させる。
したがって、Ti含有量は0.005 〜0.020 ％の範囲とす
る。Ti fixes N as TiN and combines with B
It is an element for reducing the amount of N and securing the effect of improving the hardenability of B. However, if it is less than 0.005%, the effect is small, and if it exceeds 0.020%, the base material toughness is deteriorated.
Therefore, the Ti content is in the range of 0.005 to 0.020%.
【００２６】次に、本発明における製造条件について説
明する。まず、スラブ加熱温度は、Nbの炭窒化物を完全
に固溶させ、Nbが再結晶抑制効果を発揮するように1150
℃以上とする。また結晶粒粗大化防止の観点より、1300
℃以下とする。Next, the manufacturing conditions in the present invention will be described. First, the slab heating temperature was set to 1150 so that the carbonitride of Nb was completely dissolved and Nb exerted the recrystallization suppressing effect.
C or higher. Also, from the viewpoint of preventing crystal grain coarsening, 1300
It should be below ° C.
【００２７】仕上圧延は、仕上温度 900〜950 ℃におけ
る圧下率が10％以上30％未満の条件で行う必要がある。
その理由を図１及び図２に基づいて説明する。The finish rolling needs to be performed under the condition that the rolling reduction at the finishing temperature of 900 to 950 ° C. is 10% or more and less than 30%.
The reason will be described with reference to FIGS.
【００２８】図１は靱性に及ぼす仕上温度の影響を示し
たものである。なお、図１は0.15％C-0.25％Si-1.50 ％
Mn-0.035％Al-0.0010 ％B-0.0030％N 鋼 (Nb無添加鋼)
とこれに0.030 ％Nbを添加したNb添加鋼について、板厚
25mm、最終圧下率12％、搬送時間70秒の条件で、仕上温
度を変化させて製造した場合である。FIG. 1 shows the effect of the finishing temperature on the toughness. Figure 1 shows 0.15% C-0.25% Si-1.50%
Mn-0.035% Al-0.0010% B-0.0030% N steel (Nb-free steel)
And Nb-added steel with 0.030% Nb added to it
This is a case where the device is manufactured under the conditions of 25 mm, a final draft of 12%, and a transfer time of 70 seconds while changing the finishing temperature.
【００２９】図１より、破面遷移温度が -80℃以下の優
れた靱性を示す鋼は、Nb添加鋼で仕上温度 900〜950 ℃
の範囲にあって未再結晶組織を有する場合であることが
わかる。しかし、仕上温度が 900℃未満では焼入れ不足
となり、また 950℃を超えると結晶粒粗大化により靱性
が劣化する。From FIG. 1, it can be seen that a steel exhibiting excellent toughness having a fracture surface transition temperature of -80 ° C. or less is a Nb-added steel having a finishing temperature of 900 to 950 ° C.
It can be seen that this is the case in which it has a non-recrystallized structure. However, if the finishing temperature is lower than 900 ° C, quenching is insufficient, and if it exceeds 950 ° C, the toughness deteriorates due to coarsening of crystal grains.
【００３０】図２は靱性に及ぼす 900〜950 ℃での圧下
率の影響を示したものである。なお、図２は0.15％C-0.
25％Si-1.50 ％Mn-0.035％Al-0.030％Nb-0.0010 ％B-0.
0030％N 鋼について、板厚25mm、搬送時間70秒の条件
で、 900〜950 ℃の間での圧下率を変化させて製造した
場合である。FIG. 2 shows the effect of the rolling reduction at 900 to 950 ° C. on the toughness. Figure 2 shows 0.15% C-0.
25% Si-1.50% Mn-0.035% Al-0.030% Nb-0.0010% B-0.
This is the case where 0030% N steel is manufactured under the conditions of a plate thickness of 25 mm and a transfer time of 70 seconds while changing the rolling reduction between 900 and 950 ° C.
【００３１】図２より、靱性が良好な鋼は圧下率が10％
以上30％未満の場合であることがわかる。しかし、圧下
率が10％未満では再結晶して粗粒になるために靱性が劣
化し、また圧下率が30％以上では過剰に変形帯が導入さ
れて焼入性が低下するために靱性が劣化する。以上のこ
とより、良好な靱性を得るために、仕上圧延は 900〜95
0 ℃での圧下率を10％以上30％未満の条件とする。FIG. 2 shows that the steel with good toughness has a rolling reduction of 10%.
It turns out that it is the case of more than 30%. However, if the rolling reduction is less than 10%, the toughness deteriorates due to recrystallization to coarse grains, and if the rolling reduction is more than 30%, excessive deformation zones are introduced and the hardenability decreases, resulting in a decrease in toughness. to degrade. From the above, in order to obtain good toughness, finish rolling is 900-95
The rolling reduction at 0 ° C is 10% or more and less than 30%.
【００３２】圧延後の搬送時間は、 120秒以内とする必
要がある。その理由を図３に基づいて説明する。図３は
靱性に及ぼす搬送時間の影響を示したものである。な
お、図３は0.15％C-0.25％Si-1.50 ％Mn-0.035％Al-0.1
5 ％Cr-0.08 ％Mo-0.030％Nb-0.0010 ％B-0.0030％N 鋼
について、板厚38mm、仕上温度 930℃、最終圧下率12
％、 950℃以下累積圧下率25％の条件で、搬送時間を変
化させて製造した場合である。The transport time after rolling must be within 120 seconds. The reason will be described with reference to FIG. FIG. 3 shows the effect of the transport time on the toughness. FIG. 3 shows 0.15% C-0.25% Si-1.50% Mn-0.035% Al-0.1
5% Cr-0.08% Mo-0.030% Nb-0.0010% B-0.0030% N For steel, plate thickness 38mm, finishing temperature 930 ℃, final draft 12
%, 950 ° C. or less, and a rolling reduction of 25% under the condition of a cumulative rolling reduction of 25%.
【００３３】図３より、搬送時間が 120秒を超えると、
靱性が急激に劣化することが明らかである。したがっ
て、BNやFe23(CB)6 の生成を防ぎ、焼入性を確保するた
めに、搬送時間を 120秒以内とする。According to FIG. 3, when the transport time exceeds 120 seconds,
It is clear that the toughness deteriorates rapidly. Therefore, in order to prevent the generation of BN and Fe 23 (CB) 6 and to ensure hardenability, the transfer time is set within 120 seconds.
【００３４】次いで焼入れするが、焼入れ温度は 850℃
以上とし、 200℃以下まで急冷する必要がある。その理
由を図４に基づいて説明する。図４は靱性に及ぼす焼入
温度の影響を示したものである。なお、図４は0.15％C-
0.25％Si-1.50 ％Mn-0.035％Al-0.15 ％Cr-0.08 ％Mo-
0.030％Nb-0.0010 ％B-0.0030％N 鋼について、板厚38m
m、仕上温度 910℃、最終圧下率12％、 950℃以下累積
圧下率25％、搬送時間 120秒の条件で、焼入温度を変化
させて製造した場合である。Next, quenching is performed at a quenching temperature of 850 ° C.
It is necessary to rapidly cool to 200 ° C or less. The reason will be described with reference to FIG. FIG. 4 shows the effect of the quenching temperature on the toughness. Fig. 4 shows 0.15% C-
0.25% Si-1.50% Mn-0.035% Al-0.15% Cr-0.08% Mo-
0.030% Nb-0.0010% B-0.0030% N Steel thickness 38m
m, finishing temperature 910 ° C, final rolling reduction 12%, cumulative rolling reduction 25% or less at 950 ° C or less, and transfer time 120 seconds, with the quenching temperature varied.
【００３５】図４より、焼入温度が 850℃未満では靱性
が急激に劣化することがわかる。したがって、BNやFe23
(CB)6 の生成を防ぎ、焼入性を確保する観点より、焼入
温度は 850℃以上とする。また、焼入れ時にマルテンサ
イト変態或いはベイナイト変態を完了させ、良好な焼入
組織を得るために、急冷は 200℃以下までとする。焼入
れ後、Ａc1点以下で焼きもどし処理を施す。FIG. 4 shows that when the quenching temperature is lower than 850 ° C., the toughness is rapidly deteriorated. Therefore, BN and Fe 23
From the viewpoint of preventing the formation of (CB) 6 and ensuring hardenability, the quenching temperature is 850 ° C or higher. In order to complete martensitic transformation or bainite transformation at the time of quenching and to obtain a good quenched structure, rapid cooling is performed to 200 ° C. or less. After quenching, a tempering treatment is performed with one or less Ac.
【００３６】このように、鋼の化学成分、製造条件、特
に 900〜950 ℃の間での圧下率を規制することにより、
靱性の優れた高張力鋼板を得ることができるのである。Thus, by regulating the chemical composition of the steel and the production conditions, particularly the rolling reduction between 900 and 950 ° C.,
Thus, a high-tensile steel sheet having excellent toughness can be obtained.
【００３７】次に本発明の実施例を示す。なお、図１〜
図４に示した試験例も本発明の実施例足りうることは言
うまでもない。Next, examples of the present invention will be described. In addition, FIG.
It goes without saying that the test example shown in FIG. 4 is sufficient for the embodiment of the present invention.
【００３８】[0038]
【実施例】表１に示す化学成分を有する供試鋼につい
て、表２に示す条件で熱間圧延、直接焼入れを施し、焼
きもどし(640℃) を施した。得られた鋼板の機械的性質
（引張強さ、破面遷移温度）を第２表に併記する。な
お、破面遷移温度については、試験片を板厚ｔの１／２
の位置でＣ方向のものを採取し、衝撃試験に供して、破
面遷移温度を求めた。EXAMPLES Test steels having the chemical components shown in Table 1 were subjected to hot rolling, direct quenching and tempering (640 ° C.) under the conditions shown in Table 2. Table 2 also shows the mechanical properties (tensile strength, fracture surface transition temperature) of the obtained steel sheet. In addition, about the fracture surface transition temperature, the test piece was １ ／ of the plate thickness t.
The sample in the direction C was sampled at the position of, and subjected to an impact test to determine the fracture surface transition temperature.
【００３９】表２より明らかなように、本発明例No.1〜
No.4はいずれも破面遷移温度が低く、優れた靱性を示
し、また引張強さも588N/mm2(60kgf/mm2) 以上が得られ
ている。一方、少なくとも化学成分、製造条件のいずれ
かが本発明範囲外の比較例は、強度は得られているもの
の、破面遷移温度が高く、靱性が劣化している。As is clear from Table 2, the present invention examples No. 1 to No. 1
No. 4 shows a low fracture surface transition temperature, excellent toughness, and a tensile strength of 588 N / mm 2 (60 kgf / mm 2 ) or more. On the other hand, in Comparative Examples in which at least one of the chemical components and the production conditions are out of the range of the present invention, although the strength is obtained, the fracture surface transition temperature is high and the toughness is deteriorated.
【００４０】[0040]
【表１】 [Table 1]
【００４１】[0041]
【表２】 [Table 2]
【００４２】[0042]
【発明の効果】以上詳述したように、本発明によれば、
直接焼入法にて588N/mm2(60kgf/mm2)以上の調質高張力
鋼板を製造するに際し、化学成分を特にB 添加のもとで
調整すると共に、圧延条件、搬送時間を規制するので、
良好な母材靱性を確保できる。したがって、タンク、橋
梁、ペンストック等に用いられる引張強さ588N/mm2(60k
gf/mm2) 以上の調質高張力鋼板の製造に適している。As described in detail above, according to the present invention,
When manufacturing tempered high-strength steel sheets of 588 N / mm 2 (60 kgf / mm 2 ) or more by the direct quenching method, adjust the chemical composition especially under the addition of B, and regulate the rolling conditions and transport time. So
Good base metal toughness can be secured. Therefore, tensile strength of 588 N / mm 2 (60k
gf / mm 2 ) Suitable for the production of tempered high-strength steel sheets of above.
【図１】靱性に及ぼす仕上温度の影響を示す図である。FIG. 1 is a diagram showing the effect of finishing temperature on toughness.
【図２】靱性に及ぼす 900〜950 ℃での圧下率の影響を
示す図である。FIG. 2 is a view showing the effect of the rolling reduction at 900 to 950 ° C. on the toughness.
【図３】靱性に及ぼす搬送時間の影響を示す図である。FIG. 3 is a diagram showing the influence of the transport time on the toughness.
【図４】靱性に及ぼす焼入温度の影響を示す図である。FIG. 4 is a diagram showing the effect of quenching temperature on toughness.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 昭61−136622（ＪＰ，Ａ) 特開 昭61−48517（ＪＰ，Ａ) 特開 昭59−100214（ＪＰ，Ａ) 特開 昭63−33521（ＪＰ，Ａ) 特開 昭61−23715（ＪＰ，Ａ) (58)調査した分野(Int.Cl.6，ＤＢ名) C21D 8/02 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-136622 (JP, A) JP-A-61-48517 (JP, A) JP-A-59-100214 (JP, A) JP-A-63-100 33521 (JP, A) JP-A-61-2715 (JP, A) (58) Fields investigated (Int. Cl. 6 , DB name) C21D 8/02
Claims (1)
％、 Si:0.10〜0.40％、 Mn:0.50〜2.00％、Nb:0.010〜
0.040 ％、B:0.0005〜0.0020％、N:0.0050％以下及びA
l:0.020〜0.080 ％を含み、さらに Cu:0.10〜1.00％、
Ni:0.10〜3.00％、 Cr:0.10〜1.00％、 Mo:0.05〜1.00
％、 V:0.005〜0.100 ％及びTi:0.005〜0.020 ％のうち
の１種又は２種以上を含み、残部がFe及び不可避的不純
物よりなる鋼を1150〜1300℃に加熱し、 900〜950 ℃の
温度において10％以上30％未満の圧下率で圧延を終了し
た後、 120秒以内に、且つ 850℃以上の温度から焼入れ
を開始し、 200℃以下まで急冷して、その後、Ａc1点以
下で焼もどし処理を施すことを特徴とする靱性の優れた
直接焼入型高張力鋼板の製造方法。C. 0.03 to 0.20 in mass% (hereinafter the same).
%, Si: 0.10 ~ 0.40%, Mn: 0.50 ~ 2.00%, Nb: 0.010 ~
0.040%, B: 0.0005-0.0020%, N: 0.0050% or less and A
l: 0.020 ~ 0.080%, Cu: 0.10 ~ 1.00%,
Ni: 0.10 to 3.00%, Cr: 0.10 to 1.00%, Mo: 0.05 to 1.00
%, V: 0.005 to 0.100% and Ti: 0.005 to 0.020%, the steel containing one or more kinds and the balance consisting of Fe and unavoidable impurities is heated to 1150 to 1300 ° C, and 900 to 950 ° C. After rolling at a temperature of 10% or more and less than 30% at a temperature of, quenching is started within 120 seconds and at a temperature of 850 ° C or more, quenched to 200 ° C or less, then Ac 1 point or less A method for producing a direct-quenched high-strength steel sheet having excellent toughness, characterized by performing a tempering treatment at a temperature.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30037496A JP2944540B2 (en) | 1996-11-12 | 1996-11-12 | Manufacturing method of direct quenching high strength steel sheet with excellent toughness |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP30037496A JP2944540B2 (en) | 1996-11-12 | 1996-11-12 | Manufacturing method of direct quenching high strength steel sheet with excellent toughness |
Related Parent Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2305689A Division JP2655901B2 (en) | 1989-02-01 | 1989-02-01 | Manufacturing method of direct quenching type high strength steel sheet with excellent toughness |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH09256049A JPH09256049A (en) | 1997-09-30 |
| JP2944540B2 true JP2944540B2 (en) | 1999-09-06 |
Family
ID=17884019
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP30037496A Expired - Lifetime JP2944540B2 (en) | 1996-11-12 | 1996-11-12 | Manufacturing method of direct quenching high strength steel sheet with excellent toughness |
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| Country | Link |
|---|---|
| JP (1) | JP2944540B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004106573A1 (en) * | 2003-05-28 | 2004-12-09 | Sumitomo Metal Industries, Ltd. | Method for hot forming and hot formed member |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4735191B2 (en) * | 2005-10-27 | 2011-07-27 | Ｊｆｅスチール株式会社 | Abrasion resistant steel plate with excellent low temperature toughness and method for producing the same |
-
1996
- 1996-11-12 JP JP30037496A patent/JP2944540B2/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2004106573A1 (en) * | 2003-05-28 | 2004-12-09 | Sumitomo Metal Industries, Ltd. | Method for hot forming and hot formed member |
| US7559998B2 (en) | 2003-05-28 | 2009-07-14 | Sumitomo Metal Industries, Ltd. | Hot forming method and a hot formed member |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH09256049A (en) | 1997-09-30 |
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