JPH09143612A - High strength hot rolled steel plate member low in yield ratio - Google Patents
High strength hot rolled steel plate member low in yield ratioInfo
- Publication number
- JPH09143612A JPH09143612A JP32837095A JP32837095A JPH09143612A JP H09143612 A JPH09143612 A JP H09143612A JP 32837095 A JP32837095 A JP 32837095A JP 32837095 A JP32837095 A JP 32837095A JP H09143612 A JPH09143612 A JP H09143612A
- Authority
- JP
- Japan
- Prior art keywords
- less
- hot
- yield ratio
- rolled steel
- ferrite
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 65
- 239000010959 steel Substances 0.000 title claims abstract description 65
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 18
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 18
- 229910001566 austenite Inorganic materials 0.000 claims abstract description 13
- 238000005482 strain hardening Methods 0.000 claims abstract description 12
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 239000000126 substance Substances 0.000 claims abstract description 7
- 239000012535 impurity Substances 0.000 claims abstract description 4
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 4
- 239000000203 mixture Substances 0.000 claims description 12
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 238000005098 hot rolling Methods 0.000 abstract description 8
- 229910052799 carbon Inorganic materials 0.000 abstract description 5
- 229910052757 nitrogen Inorganic materials 0.000 abstract 1
- 230000000694 effects Effects 0.000 description 11
- 238000003303 reheating Methods 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 5
- 229910001563 bainite Inorganic materials 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 230000009466 transformation Effects 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 238000004881 precipitation hardening Methods 0.000 description 3
- 238000004804 winding Methods 0.000 description 3
- 238000010276 construction Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 238000010583 slow cooling Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 238000003466 welding Methods 0.000 description 2
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000004035 construction material Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229910001562 pearlite Inorganic materials 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【発明が属する技術分野】本発明は、強度クラスが５４
０Ｎ／mm2 級以上、７８０Ｎ／mm2 級以下の降伏比の低
い、高強度熱延鋼板部材に関し、ホイールなどの自動車
足まわり部材や建築用部材などの構造用熱間加工部材と
して利用される。TECHNICAL FIELD The present invention has a strength class of 54.
High-strength hot-rolled steel plate members with a low yield ratio of 0 N / mm 2 class or more and 780 N / mm 2 class or less, and are used as structural hot-working members such as automobile suspension materials such as wheels and construction materials. .
【０００２】[0002]
【従来の技術】従来、低降伏比化を目的とした熱延綱板
は、例えば自動車用鋼板ではＤＰ鋼に示される様に成形
性（形状凍結性）や衝撃性の向上を目的として開発され
ているが、このような鋼板により加工形成された部材の
降伏比は高くなり、衝撃特性や部材としての材質均質性
に劣り、十分な品質を有しているとは言えない。2. Description of the Related Art Conventionally, hot-rolled steel sheet for the purpose of lowering the yield ratio has been developed for the purpose of improving formability (shape freezing) and impact resistance as shown in DP steel for automobile steel sheets, for example. However, the yield ratio of the member processed and formed from such a steel sheet is high, the impact property and the material homogeneity as the member are poor, and it cannot be said that the member has sufficient quality.
【０００３】また、建築用熱延鋼板では、従来、一般構
造用圧延鋼材（ＪＩＳ Ｇ ３１０１）、溶接構造用圧
延鋼材（ＪＩＳ Ｇ ３１０６）等が広く利用されてき
たが、最近、構造物の安全性向上のため、特に耐震特性
を向上させるために降伏比の低下が望まれ、建築構造用
圧延鋼材（ＪＩＳ Ｇ ３１３６）が制定され、降伏比
が規定されるに至っている。しかし、建築用熱延鋼板部
材として、例えば、熱延鋼帯を冷間加工によって管状に
成形し、開口縁部を電気抵抗溶接して鋼管を得、その後
この鋼管に冷間加工を施して成形加工された鋼板部材
は、冷間加工による成形の際の加工硬化により降伏点が
上昇し、降伏比が高くなる。また、衝撃値も著しく低下
する。特に冷間加工の厳しい部分においては材質の劣化
が大きく、降伏比が９０％以上となることも珍しくな
い。As the hot rolled steel sheet for construction, conventionally, rolled steel for general structure (JIS G 3101) and rolled steel for welded structure (JIS G 3106) have been widely used. In order to improve the property, especially in order to improve the seismic resistance, it is desired to lower the yield ratio, and a rolled steel material for building structures (JIS G 3136) has been established, and the yield ratio has been specified. However, as a hot-rolled steel plate member for construction, for example, a hot-rolled steel strip is formed into a tubular shape by cold working, an opening edge is electrically resistance welded to obtain a steel pipe, and then this steel pipe is subjected to cold working to be formed. The worked steel plate member has a higher yield point and a higher yield ratio due to work hardening during forming by cold working. Also, the impact value is significantly reduced. In particular, it is not uncommon for the yield ratio to be 90% or more because the material is greatly deteriorated in the cold-worked portion.
【０００４】[0004]
【発明が解決しようとする課題】このため、降伏比の上
昇を押さえる対策が種々なされているが、降伏比の低減
には限度があるのが実情である。例えば、特開平４−３
２３３１９号公報には、冷間加工の厳しい部分のみを加
熱して部材全体の降伏比を低減させる方法が記載されて
いるが、この方法では、平板部の加熱が不十分となり、
冷間加工で生じた歪が残存すると共に加熱部との温度差
に起因して熱歪が発生し、このため加工の厳しい部分と
平板部とに強度差が生じると共に降伏比の低減効果、衝
撃値の向上効果が小さい。For this reason, various measures have been taken to suppress the increase in the yield ratio, but there is a limit to the reduction in the yield ratio. For example, Japanese Patent Laid-Open No. 4-3
In Japanese Patent No. 23319, there is described a method of heating only a portion subjected to severe cold working to reduce the yield ratio of the entire member, but with this method, heating of the flat plate portion becomes insufficient,
The strain generated by cold working remains and thermal strain occurs due to the temperature difference with the heating part.Therefore, strength difference occurs between the severely worked part and the flat plate part, and the yield ratio reduction effect and impact. The effect of improving the value is small.
【０００５】また、高強度化のために冷間加工後、焼入
焼戻し処理を施す製造方法もあるが、この方法では、部
材の組織が焼戻しマルテンサイトとなるため、降伏比が
高くなる。There is also a manufacturing method in which quenching and tempering treatment is carried out after cold working for increasing the strength, but in this method, since the structure of the member becomes tempered martensite, the yield ratio becomes high.
【０００６】また、厚板鋼板では、降伏比を低くするた
めにフェライトとマルテンサイト（フェライト＋マルテ
ンサイト）の混合組織とした鋼板を部材原板として使用
することも行われているが、原板を合わせて、合わせ部
を溶接するなどの方法により鋼板部材を製造しているた
め、溶接部を含む部材コーナ部では原板のフェライト＋
マルテンサイト組織が得られない。このため、降伏比が
低くならず、また溶接軟化も生じるという問題がある。In the case of thick steel plates, steel plates having a mixed structure of ferrite and martensite (ferrite + martensite) have been used as raw material plates for lowering the yield ratio. Since the steel plate members are manufactured by welding the joints, etc., at the member corners including the welded parts, the ferrite +
Martensite structure cannot be obtained. For this reason, there are problems that the yield ratio is not lowered and welding softening occurs.
【０００７】本発明はかかる問題に鑑みなされたもの
で、降伏比が低くかつ高強度を有する構造用熱延鋼板部
材を提供することを発明の課題としている。The present invention has been made in view of the above problems, and an object of the invention is to provide a structural hot-rolled steel plate member having a low yield ratio and high strength.
【０００８】[0008]
【課題を解決するための手段】本発明の高強度熱延鋼板
部材は、化学組成が重量％で、Ｃ：0.05〜0.25％、 S
i：0.01〜1.0 ％、Mn：0.50〜2.0 ％、 Ｐ：0.05％以
下、Ｓ：0.03％以下、 sol.Al：0.08％以下 Ｎ：0.01％以下を含み、残部がＦｅ及び不可避的不純物
からなる鋼を、熱間圧延して巻取り、その後鋼板を冷間
加工した後、フェライト・オーステナイト共存温度域に
再加熱し、この温度域で熱間成形加工を行い、冷却後の
組織がフェライトとマルテンサイトとが主体の混合組織
とされたものである。ここで、フェライトとマルテンサ
イトが主体の混合組織とは、マルテンサイト量の５０％
未満のベイナイトが組織中に一部含まれていてもよいこ
とを意味するものである。The high-strength hot-rolled steel sheet member of the present invention has a chemical composition of wt%, C: 0.05 to 0.25%, S
i: 0.01-1.0%, Mn: 0.50-2.0%, P: 0.05% or less, S: 0.03% or less, sol.Al: 0.08% or less N: 0.01% or less, the balance consisting of Fe and unavoidable impurities The steel is hot-rolled and wound, and then the steel sheet is cold-worked, then reheated to the ferrite / austenite coexistence temperature range, hot-formed in this temperature range, and the microstructure after cooling is ferrite and martensite. The site is a mixed organization of the main body. Here, the mixed structure mainly composed of ferrite and martensite means 50% of the amount of martensite.
It means that less than bainite may be partially contained in the structure.
【０００９】前記鋼板部材の化学組成としては、前記成
分の他、更に必要に応じて、下記成分の内、一種以上を
含有してもよい。Cr：0.05〜0.80％、 Ni：0.50％以
下、Mo：0.40％以下、 Nb：0.08％以下、Ｖ：0.30％
以下、 Ti：0.10％以下、Ｂ：0.0005〜0.0050％、C
a：0.006 ％以下As the chemical composition of the steel plate member, in addition to the above-mentioned components, one or more of the following components may be contained, if desired. Cr: 0.05 to 0.80%, Ni: 0.50% or less, Mo: 0.40% or less, Nb: 0.08% or less, V: 0.30%
Below, Ti: 0.10% or less, B: 0.0005 to 0.0050%, C
a: 0.006% or less
【００１０】本発明によれば、原板となる熱延鋼板の化
学組成のみならず、その製造条件引いては熱間加工後の
組織を適切に調整したので、熱間成形加工後の引張強度
（ＴＳ）が５４０Ｎ／mm2 以上の高強度を有し、かつそ
の降伏比が８０％以下の低降伏比の熱延鋼板部材が得ら
れる。According to the present invention, not only the chemical composition of the hot-rolled steel sheet to be used as the original sheet but also the production conditions are properly adjusted to the microstructure after hot working, so that the tensile strength after hot forming ( A hot-rolled steel sheet member having a high yield strength (TS) of 540 N / mm 2 or more and a low yield ratio of 80% or less can be obtained.
【００１１】[0011]
【発明の実施の形態】まず、本発明における熱延鋼板部
材の鋼組成の限定理由について説明する。以下、単位は
wt％である。 Ｃ：０．０５〜０．２５％ Ｃは鋼板の強度を高めるために有効な元素である。０．
０５％未満ではその作用が過少であり、−方０．２５％
を越えると溶接性及び靭性が著しく劣化するようにな
る。よって下限を０．０５％、上限を０．２５％とす
る。好ましくは０．０８〜０．２０％である。BEST MODE FOR CARRYING OUT THE INVENTION First, the reasons for limiting the steel composition of the hot-rolled steel sheet member according to the present invention will be described. Below, the unit is
wt%. C: 0.05 to 0.25% C is an element effective for increasing the strength of the steel sheet. 0.
If it is less than 05%, its action is too small, and it is 0.25%.
If it exceeds the range, the weldability and toughness will be significantly deteriorated. Therefore, the lower limit is 0.05% and the upper limit is 0.25%. It is preferably 0.08 to 0.20%.
【００１２】Ｓｉ：０．０１〜１．００％ Ｓｉは溶鋼の脱酸作用を有し、また熱間加工後の冷却段
階で固溶強化作用により強度、延性を向上させる。０．
０１％未満ではかかる作用が過少であり、一方１．００
％を越えると熱間圧延段階でＳｉスケールが発生し易く
なり、鋼板表面性状が劣化するようになる。よって下限
を０．０１％、上限を１．００％とする。Si: 0.01 to 1.00% Si has a deoxidizing action on molten steel, and also improves strength and ductility by a solid solution strengthening action in a cooling stage after hot working. 0.
If it is less than 01%, such an effect is too small, while on the other hand, 1.00
If it exceeds%, Si scale is likely to be generated in the hot rolling stage, and the steel sheet surface properties are deteriorated. Therefore, the lower limit is 0.01% and the upper limit is 1.00%.
【００１３】Ｍｎ：０．５０〜２．００％ ＭｎはＣ、Ｓｉと同様に強度を高める元素であって、熱
間加工後の冷却により強度を高めるための必須の元素で
ある。０．５０％未満ではかかる作用が過少であり、
２．００％を越えると帯状組織を生成させ、圧延方向の
延性を劣化させる。よって、下限を０．５０％、上限を
２．００％とする。Mn: 0.50 to 2.00% Mn is an element that enhances the strength like C and Si, and is an essential element for enhancing the strength by cooling after hot working. If it is less than 0.50%, the effect is too small,
If it exceeds 2.00%, a band-like structure is formed and ductility in the rolling direction is deteriorated. Therefore, the lower limit is 0.50% and the upper limit is 2.00%.
【００１４】Ｐ：０．０５％以下 Ｓ：０．０３％以下 Ｐ、Ｓは靭性を劣化させるので少ない程よく、許容限度
として、それぞれ上限を０．０５％、０．０３％とす
る。P: 0.05% or less S: 0.03% or less P and S deteriorate the toughness, so the smaller the better, the upper limits are 0.05% and 0.03%, respectively.
【００１５】sol.Ａｌ：０．０８％以下 Ａｌは鋼の脱酸剤として添加されるが、多量に添加され
ると鋼の清浄度が悪くなり、更に靭性も低下するので、
その上限をsol.（固溶）Ａｌで０．０８％とする。Sol.Al: 0.08% or less Al is added as a deoxidizing agent for steel, but if added in a large amount, the cleanliness of the steel deteriorates and the toughness also deteriorates.
The upper limit of sol. (Solid solution) Al is 0.08%.
【００１６】Ｎ：０．０１％以下 Ｎは延性、溶接性を劣化させるので少ない程よく、その
上限を０．０１％とする。本発明に用いる鋼は上記成分
のほか残部Ｆｅおよび不可避的不純物からなるが、強度
や靭性などをより一層向上させるため、更に下記成分の
うち一種以上を必要に応じて含有させることができる。N: 0.01% or less N decreases the ductility and weldability, so the less the better, the upper limit is made 0.01%. The steel used in the present invention comprises, in addition to the above components, the balance Fe and unavoidable impurities, but in order to further improve strength and toughness, one or more of the following components can be further contained, if necessary.
【００１７】Ｃｒ：０．０５〜０．８０％ Ｃｒは析出硬化等により鋼の強度を高めるのに有効であ
り、特に再加熱後の強度特性の改善に有効である。この
効果を得るためには、０．０５％以上が必要であり、一
方多量に含有させると、低温靭性、溶接性を劣化させる
ので、上限を０．８０％とする。Cr: 0.05 to 0.80% Cr is effective in increasing the strength of steel by precipitation hardening and the like, and is particularly effective in improving the strength characteristics after reheating. To obtain this effect, 0.05% or more is necessary. On the other hand, if contained in a large amount, low temperature toughness and weldability are deteriorated, so the upper limit is made 0.80%.
【００１８】Ｍｏ：０．４０％以下 ＭｏはＣｒと同様、鋼の強度を高めるのに有効であり、
特に再加熱後の強度特性の改善や高温強度特性の改善に
有効である。しかし、多量に含有させると溶接性を劣化
させ、またコストの上昇を招来するので、上限を０．４
０％とする。Mo: 0.40% or less Mo, like Cr, is effective in increasing the strength of steel,
Particularly, it is effective for improving the strength characteristics after reheating and for improving the high temperature strength characteristics. However, if contained in a large amount, the weldability deteriorates and the cost increases, so the upper limit is 0.4.
0%.
【００１９】Ｎｂ：０．０８％以下 Ｎｂは析出硬化等により鋼の強度を高めるのに有効であ
り、また結晶粒度の微細化に有効であるが、多く含有さ
せると溶接性を劣化させるので、上限を０．０８％とす
る。Nb: 0.08% or less Nb is effective in increasing the strength of the steel by precipitation hardening and is also effective in refining the grain size, but if it is contained in a large amount, the weldability is deteriorated. The upper limit is 0.08%.
【００２０】Ｖ：０．３０％以下 Ｖは析出硬化等により鋼の強度を高めるのに有効であ
り、特に再加熱後の強度特性の改善に有効であるが、多
く添加すると溶接性を劣化させるので、上限を０．３０
％とする。V: 0.30% or less V is effective for increasing the strength of steel by precipitation hardening and the like, and is particularly effective for improving the strength characteristics after reheating, but if added in a large amount, it deteriorates the weldability. Therefore, the upper limit is 0.30
%.
【００２１】Ｔｉ：０．１０％以下 Ｔｉは鋼の強度を高めるとともに、ＴｉＮを形成しオー
ステナイト粒の微細化に効果があり、靭性の向上に有効
であるが、多く添加すると溶接性を劣化させるので、上
限を０．１０％とする。Ti: 0.10% or less Ti enhances the strength of steel and forms TiN, which is effective in refining austenite grains and is effective in improving toughness, but if added in large amounts, it deteriorates weldability. Therefore, the upper limit is made 0.10%.
【００２２】Ｂ：０．０００５〜０．００５０％ Ｂは微量添加で強度を高めるのに有効であるとともに、
焼入れ性を著しく高める効果を有する。０．０００５％
未満ではかかる作用が過少であり、一方多く添加すると
Ｂ化合物を生成して靭性を劣化させるので、上限を０．
００５０％とする。B: 0.0005 to 0.0050% B is effective for increasing the strength by adding a trace amount, and
It has the effect of significantly increasing the hardenability. 0.0005%
If it is less than 1, the effect is too small, while if added in a large amount, a B compound is formed and the toughness is deteriorated.
0050%.
【００２３】Ｃａ：０．００６％以下 Ｃａは硫化物の形態を展伸状から球状にする形態制御を
通して、機械的異方性を小さくし、延性、靭性を改善す
る作用がある。しかし、多く添加すると鋼中の非金属介
在物の増大により、延性、靭性が却って低下するように
なるので、上限を０．００６％とする。Ca: 0.006% or less Ca has the effect of reducing the mechanical anisotropy and improving the ductility and toughness through morphology control of changing the form of sulfide from expanded to spherical. However, if a large amount is added, the ductility and toughness rather decrease due to the increase of non-metallic inclusions in the steel, so the upper limit is made 0.006%.
【００２４】本発明の熱延鋼板部材は、上記成分を有す
る鋼を熱間圧延して巻取り、その後鋼板を冷間加工した
後、フェライト・オーステナイト共存温度域に７００〜
９５０℃に再加熱し、この温度域で熱間成形加工を行
い、冷却後の組織をフェライトとマルテンサイトを主体
とした混合組織としたものである。The hot-rolled steel sheet member of the present invention is obtained by hot rolling a steel having the above-mentioned components, winding the steel, cold working the steel sheet, and then adding the steel in the ferrite-austenite coexistence temperature range of 700 to 700.
Reheating is performed at 950 ° C., hot forming is performed in this temperature range, and the structure after cooling is a mixed structure mainly composed of ferrite and martensite.
【００２５】熱間圧延は、スラブを連続鋳造後直ちに圧
延（直接圧延）してもよく、あるいは鋳塊を加熱後、圧
延してもよいが、熱間圧延時の加熱温度は、１１００〜
１３００℃が好ましい。１１００℃未満になるとＮｂな
どによる強度の向上作用が不足し、一方１３００℃を越
えるとオーステナイトの粗大化が生じ、靭性が劣化する
ようになる。もっとも、上記範囲外の加熱温度でも本発
明の所期の効果が得られるため、この範囲に限定されな
い。In the hot rolling, the slab may be rolled immediately after continuous casting (direct rolling), or the ingot may be heated and then rolled, but the heating temperature during hot rolling is 1100 to 1100.
1300 ° C. is preferred. If it is less than 1100 ° C, the effect of improving strength due to Nb or the like is insufficient, while if it exceeds 1300 ° C, austenite is coarsened and toughness deteriorates. However, since the desired effect of the present invention can be obtained even at a heating temperature outside the above range, the heating temperature is not limited to this range.
【００２６】熱間圧延の仕上温度は冷間での成形加工が
可能となる範囲でよく、特に規定されないが、好ましく
は変態点直上の８００℃から８５０℃がよい。熱間圧延
後の巻取温度についても、特に規定されないが、巻取温
度が極端に低いと、低温変態生成組織が多くなり、強度
が著しく上昇し、冷間加工性が著しく劣化するようにな
る。また巻取温度が通常より極端に高くなると表面性状
（粒界酸化）が著しくなる。このため、巻取温度範囲と
して通常の約４００〜６５０℃で行えばよい。The finishing temperature of hot rolling may be in a range that allows cold forming and is not particularly limited, but preferably 800 ° C to 850 ° C just above the transformation point. The take-up temperature after hot rolling is also not particularly specified, but if the take-up temperature is extremely low, the low-temperature transformation forming structure increases, the strength remarkably increases, and the cold workability deteriorates significantly. . Further, when the winding temperature becomes extremely higher than usual, the surface properties (grain boundary oxidation) become remarkable. Therefore, the winding temperature range may be about 400 to 650 ° C.
【００２７】巻き取られた鋼板は、巻き戻されて、適宜
の冷間加工、例えばロールフォーミングにより所定の形
状に成形加工した後、Ａc1点以上のフェライト・オース
テナイト共存温度域、通常７００〜９５０℃の温度域に
再加熱し、熱間加工により角管などの適宜の部材形状に
成形した後、冷却して部材の金属組織をフェライトとマ
ルテンサイトを主体とした混合組織とする。フェライト
とマルテンサイトを主体とした混合組織とは、マルテン
サイト量の５０％未満、特に２５％以下の少量のベイナ
イトが組織中に一部含まれていてもよいことを意味する
ものである。かかる組織にすることにより、熱間成形加
工後の部材の降伏比を低くすることができ、また均質な
優れた材質が得られる。The rolled steel sheet is rewound and subjected to an appropriate cold working, for example, forming into a predetermined shape by roll forming, and then a temperature range of Ac / one ferrite / austenite coexistence, usually 700 to 950. After being reheated to a temperature range of ° C and formed into an appropriate member shape such as a square tube by hot working, the metal structure of the member is cooled to obtain a mixed structure mainly composed of ferrite and martensite. The mixed structure mainly composed of ferrite and martensite means that a small amount of bainite of less than 50%, especially 25% or less of the amount of martensite may be partially contained in the structure. With such a structure, the yield ratio of the member after hot forming can be lowered, and a homogeneous and excellent material can be obtained.
【００２８】再加熱温度がフェライト・オーステナイト
共存温度未満ではオーステナイトが生成しないため、そ
の後の熱間加工処理によってもマルテンサイトが生成せ
ず、部材の組織がフェライト＋マルテンサイトを主体と
したものにならず、降伏強度の低い熱延鋼板部材が得ら
れない。また、フェライト・オーステナイト共存温度を
越えると、再加熱時に鋼組織はほとんどオーステナイト
化するために、オーステナイトへのＣの濃縮が生じず、
熱間加工後の比較的緩慢な冷却速度ではマルテンサイト
が生成せず、熱延鋼板部材において目標組織が得られな
い。本発明ではフェライト・オーステナイト共存温度域
で熱間加工を行うため、オーステナイトにＣの濃縮が生
じて、マルテンサイト変態点が低下し、熱間加工後、比
較的緩慢な冷却速度でも変態が生じ、通常、空冷あるい
は衝風空冷により所期の混合組織を得ることができる。If the reheating temperature is lower than the ferrite / austenite coexisting temperature, austenite is not formed. Therefore, martensite is not formed even by the subsequent hot working, and if the structure of the member is mainly composed of ferrite + martensite. Therefore, a hot-rolled steel sheet member having a low yield strength cannot be obtained. Further, when the temperature exceeds the coexistence temperature of ferrite and austenite, the steel structure is almost austenized during reheating, so that C is not concentrated in austenite.
Martensite is not generated at a relatively slow cooling rate after hot working, and the target structure cannot be obtained in the hot rolled steel sheet member. In the present invention, since hot working is performed in the ferrite / austenite coexisting temperature range, concentration of C occurs in austenite, the martensite transformation point decreases, and after hot working, transformation occurs even at a relatively slow cooling rate, Usually, the desired mixed structure can be obtained by air cooling or air blow cooling.
【００２９】[0029]
【実施例】表１に示した化学組成を有する鋼種No. Ａ〜
Ｇ（本発明鋼）、Ｈ〜Ｉ（比較鋼）の供試鋼を溶製し、
熱間圧延して巻取り、板厚１２ｍｍの熱延鋼板を製造し
た。この鋼板を用いて冷間加工（圧下率７％の冷間圧
延）を施した後、種々の温度に再加熱して熱間加工（圧
下率１０％の熱間圧延）を施し、空冷した。熱間加工後
の鋼板部材について、金属組織、引張特性、衝撃特性を
調べた結果を表２に示す。EXAMPLES Steel grades No. A to have the chemical composition shown in Table 1
G (inventive steel), HI (comparative steel) sample steels are melted,
It was hot rolled and wound to produce a hot rolled steel sheet having a plate thickness of 12 mm. After cold working (cold rolling with a rolling reduction of 7%) using this steel sheet, it was reheated to various temperatures, hot worked (hot rolling with a rolling reduction of 10%), and air-cooled. Table 2 shows the results of examining the metal structure, tensile properties, and impact properties of the steel sheet member after hot working.
【００３０】[0030]
【表１】 [Table 1]
【００３１】[0031]
【表２】 [Table 2]
【００３２】表２より、実施例にかかる試料No. ｌ〜８
では、熱間加工後の引張強さが５９０〜７８０Ｎ／mm2
で、降伏比が７２〜７８％であり、高強度低降伏比の部
材が得られている。また、衝撃値も３４Ｊ以上であり、
優れた靭性を有していることが分かる。尚、No. ８では
ベイナイトが一部（面積率でマルテンサイト量の約２５
％）生成したが、少量であるため、特性の劣化は生じな
かった。From Table 2, sample Nos. 1 to 8 according to the embodiment
Then, the tensile strength after hot working is 590 to 780 N / mm 2
The yield ratio is 72 to 78%, and a member having high strength and low yield ratio is obtained. Also, the impact value is 34J or more,
It can be seen that it has excellent toughness. In No. 8, some bainite (about 25% of martensite in area ratio)
%) Was produced, but since it was a small amount, the characteristics did not deteriorate.
【００３３】これに対し、比較例である試料No. ９〜１
１は鋼成分が本発明の成分範囲内であるが、再加熱温度
が本発明範囲から外れているために、組織がフェライト
＋パーライトの混合組織となり、降伏比が８４〜８６％
と高くなっている。また、比較例の試料No. １２〜１５
は、成分が本発明の鋼成分範囲から外れているために、
本発明範囲内の再加熱を行っても、フェライト＋ベイナ
イト組織となり、降伏比が８４〜８９％と高い。On the other hand, sample Nos. 9 to 1 which are comparative examples
In No. 1, the steel composition is within the composition range of the present invention, but since the reheating temperature is out of the range of the present invention, the structure becomes a mixed structure of ferrite + pearlite, and the yield ratio is 84 to 86%.
It is high. In addition, sample Nos. 12 to 15 of comparative examples
Because the composition is out of the steel composition range of the present invention,
Even if it is reheated within the range of the present invention, it becomes a ferrite + bainite structure, and the yield ratio is as high as 84 to 89%.
【００３４】[0034]
【発明の効果】本発明の熱延鋼板部材によれば、熱間加
工後の強度が５４０Ｎ／mm2 以上と高く、しかも降伏比
が８０％以下に止まり、低降伏比、高強度の構造用鋼板
部材として好適である。EFFECT OF THE INVENTION According to the hot-rolled steel sheet member of the present invention, the strength after hot working is as high as 540 N / mm 2 or more, and the yield ratio is 80% or less. It is suitable as a steel plate member.
Claims (2)
からなる鋼を、熱間圧延して巻取り、その後鋼板を冷間
加工した後、フェライト・オーステナイト共存温度域に
再加熱し、この温度域で熱間成形加工を行い、冷却後の
組織がフェライトとマルテンサイトが主体の混合組織と
されたことを特徴とする降伏比の低い高強度熱延鋼板部
材。1. A chemical composition, by weight, C: 0.05 to 0.25%, Si: 0.01 to 1.0%, Mn: 0.50 to 2.0%, P: 0.05% or less, S: 0.03% or less, sol.Al: 0.08% or less N: 0.01% or less of N, 0.01% or less, the balance Fe and unavoidable impurities, hot-rolled and wound, after cold working the steel sheet, reheated to the ferrite-austenite coexistence temperature range A high-strength hot-rolled steel sheet member having a low yield ratio, which is obtained by performing hot forming in this temperature range, and the structure after cooling is a mixed structure mainly composed of ferrite and martensite.
学組成が重量％で、 Cr：0.05〜0.80％、 Ni：0.50％以下、 Mo：0.40％以下、 Nb：0.08％以下、 Ｖ：0.30％以下、 Ti：0.10％以下、 Ｂ：0.0005〜0.0050％、Ca：0.006 ％以下のうち一種以
上を含有する請求項１に記載した降伏比の低い高強度熱
延鋼板部材。2. The composition as set forth in claim 1, wherein the chemical composition is wt%, Cr: 0.05 to 0.80%, Ni: 0.50% or less, Mo: 0.40% or less, Nb: 0.08% or less, V: The high-strength hot-rolled steel sheet member having a low yield ratio according to claim 1, containing one or more of 0.30% or less, Ti: 0.10% or less, B: 0.0005 to 0.0050%, and Ca: 0.006% or less.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32837095A JPH09143612A (en) | 1995-11-21 | 1995-11-21 | High strength hot rolled steel plate member low in yield ratio |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP32837095A JPH09143612A (en) | 1995-11-21 | 1995-11-21 | High strength hot rolled steel plate member low in yield ratio |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09143612A true JPH09143612A (en) | 1997-06-03 |
Family
ID=18209498
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP32837095A Pending JPH09143612A (en) | 1995-11-21 | 1995-11-21 | High strength hot rolled steel plate member low in yield ratio |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09143612A (en) |
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|---|---|---|---|---|
| JPH11114624A (en) * | 1997-10-07 | 1999-04-27 | Sumitomo Metal Ind Ltd | Method of manufacturing non-heat treated high workability ERW steel pipe |
| WO2002101099A1 (en) | 2001-06-07 | 2002-12-19 | Jfe Steel Corporation | High tensile hot-rolled steel sheet excellent in resistance to scuff on mold and in fatigue characteristics |
| WO2002103071A1 (en) * | 2001-06-19 | 2002-12-27 | Jfe Steel Corporation | High tensile hot rolled steel sheet excellent in shape freezing property and endurance fatigue characteristics after forming |
| JP2004124221A (en) * | 2002-10-07 | 2004-04-22 | Nippon Steel Corp | Steel sheet with excellent curability after hot forming and method of using the same |
| JP2005271018A (en) * | 2004-03-24 | 2005-10-06 | Nippon Steel Corp | Hot forming method and high strength hot formed parts with excellent strength after forming |
| EP2287344A1 (en) * | 2005-09-21 | 2011-02-23 | ArcelorMittal France | Method of manufacturing multi phase microstructured steel piece |
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| CN104630629A (en) * | 2015-03-06 | 2015-05-20 | 河北普阳钢铁有限公司 | Automotive axle housing steel and preparation method thereof |
| GB2548175A (en) * | 2016-03-09 | 2017-09-13 | Goodwin Plc | A steel, a welding consumable and a cast steel product |
| CN116790971A (en) * | 2022-03-18 | 2023-09-22 | 上海梅山钢铁股份有限公司 | Low yield ratio hot rolled steel plate with 750 MPa-level tensile strength and manufacturing method thereof |
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-
1995
- 1995-11-21 JP JP32837095A patent/JPH09143612A/en active Pending
Cited By (18)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH11114624A (en) * | 1997-10-07 | 1999-04-27 | Sumitomo Metal Ind Ltd | Method of manufacturing non-heat treated high workability ERW steel pipe |
| WO2002101099A1 (en) | 2001-06-07 | 2002-12-19 | Jfe Steel Corporation | High tensile hot-rolled steel sheet excellent in resistance to scuff on mold and in fatigue characteristics |
| EP1394276A4 (en) * | 2001-06-07 | 2006-01-18 | Jfe Steel Corp | High tensile hot-rolled steel sheet excellent in resistance to scuff on mold andin fatigue characteristics |
| US7485194B2 (en) | 2001-06-07 | 2009-02-03 | Jfe Steel Corporation | High tensile hot-rolled steel sheet excellent in resistance to scuff on mold and in fatigue characteristics |
| WO2002103071A1 (en) * | 2001-06-19 | 2002-12-27 | Jfe Steel Corporation | High tensile hot rolled steel sheet excellent in shape freezing property and endurance fatigue characteristics after forming |
| JP2004124221A (en) * | 2002-10-07 | 2004-04-22 | Nippon Steel Corp | Steel sheet with excellent curability after hot forming and method of using the same |
| JP2005271018A (en) * | 2004-03-24 | 2005-10-06 | Nippon Steel Corp | Hot forming method and high strength hot formed parts with excellent strength after forming |
| US8114227B2 (en) * | 2005-09-21 | 2012-02-14 | Arcelormittal France | Method for making a steel part of multiphase microstructure |
| EP2287344A1 (en) * | 2005-09-21 | 2011-02-23 | ArcelorMittal France | Method of manufacturing multi phase microstructured steel piece |
| US10294557B2 (en) | 2005-09-21 | 2019-05-21 | Arcelormittal France | Method for making a steel part of multiphase microstructure |
| WO2012169639A1 (en) * | 2011-06-10 | 2012-12-13 | 株式会社神戸製鋼所 | Hot press molded article, method for producing same, and thin steel sheet for hot press molding |
| CN103597106A (en) * | 2011-06-10 | 2014-02-19 | 株式会社神户制钢所 | Hot press molded article, method for producing same, and thin steel sheet for hot press molding |
| CN104220619A (en) * | 2012-04-12 | 2014-12-17 | 杰富意钢铁株式会社 | Hot-rolled steel plate for square steel tube for use as building structural member and process for producing same |
| CN104630629A (en) * | 2015-03-06 | 2015-05-20 | 河北普阳钢铁有限公司 | Automotive axle housing steel and preparation method thereof |
| GB2548175A (en) * | 2016-03-09 | 2017-09-13 | Goodwin Plc | A steel, a welding consumable and a cast steel product |
| GB2548175B (en) * | 2016-03-09 | 2018-10-03 | Goodwin Plc | A steel, a welding consumable and a cast steel product |
| CN116790971A (en) * | 2022-03-18 | 2023-09-22 | 上海梅山钢铁股份有限公司 | Low yield ratio hot rolled steel plate with 750 MPa-level tensile strength and manufacturing method thereof |
| CN118237457A (en) * | 2024-03-06 | 2024-06-25 | 广东省科学院新材料研究所 | Hot forming steel and preparation method thereof |
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