JP2000080418A - Production of thin steel sheet for working - Google Patents
Production of thin steel sheet for workingInfo
- Publication number
- JP2000080418A JP2000080418A JP24975198A JP24975198A JP2000080418A JP 2000080418 A JP2000080418 A JP 2000080418A JP 24975198 A JP24975198 A JP 24975198A JP 24975198 A JP24975198 A JP 24975198A JP 2000080418 A JP2000080418 A JP 2000080418A
- Authority
- JP
- Japan
- Prior art keywords
- steel
- steel sheet
- iron
- heat treatment
- rolling
- 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.)
- Granted
Links
Landscapes
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、自動車のボディー
等の構造用部品などのように、構造上の強度が必要とさ
れる箇所に適用される薄鋼板であって、部分的な短時間
熱処理により成形性が向上する加工用薄鋼板の製造方法
に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin steel sheet applied to a place where structural strength is required, such as a structural part such as a body of an automobile, etc. The present invention relates to a method for producing a thin steel sheet for processing, the formability of which is improved.
【０００２】[0002]
【従来の技術】構造用部品の軽量化、高強度化を図るた
めに、通常、高強度鋼板の成形が試みられる。しかし、
高強度鋼板は、降伏応力が高く延性に乏しいためプレス
成形性に難があり、成形性を改善する検討が行われてい
る。例えば、プレス前に軟質で、その後の電着塗装時の
焼付過程で硬化する焼付硬化鋼板や、成形完了後に、高
エネルギー密度のビームの照射を行い、硬化させる方法
がある。2. Description of the Related Art In order to reduce the weight and increase the strength of structural parts, molding of a high-strength steel sheet is usually attempted. But,
High-strength steel sheets have high yield stress and poor ductility, and thus have difficulty in press formability, and studies are being made to improve formability. For example, there is a baking hardened steel sheet which is soft before pressing and hardens during the baking process during the subsequent electrodeposition coating, or a method of hardening by irradiating a high energy density beam after completion of forming.
【０００３】焼付硬化鋼板は焼付後の降伏応力を高める
が、変形強度自体は高々５％程度しか上昇せず、強度の
絶対量が不足する。また成形完了後に、高エネルギー密
度のビームの照射を行い、硬化させる方法としては、例
えば、特開昭６１−９９６２９号公報のように成形後に
レーザー照射する方法が開示されている。しかしなが
ら、この場合３次元的に照射するため、処理設備が経済
的に高価なものとなる上、鋼の変態による熱歪みによる
精度の狂いが非常に大きなものとなる。[0003] A bake hardened steel sheet increases the yield stress after baking, but the deformation strength itself increases by only about 5%, and the absolute amount of strength is insufficient. Further, as a method of irradiating and curing a beam of high energy density after completion of molding, for example, a method of irradiating a laser after molding as disclosed in JP-A-61-99629 is disclosed. However, in this case, since the irradiation is performed three-dimensionally, the processing equipment becomes economically expensive, and in addition, the deviation in accuracy due to thermal distortion due to the transformation of steel becomes extremely large.
【０００４】そこで、鋼板の状態で強度が必要な部分だ
け強化し、成形性が必要なところは軟質にする方法が考
えだされた。例えば、特開昭６０−２３８４２４号公報
は、鋼板に部分的にレーザー照射して焼入組織にし、硬
質部と軟質部を両方存在させ、成形は軟質部で行い、硬
質部で強度を持たせる方法が開示されている。しかしな
がら、硬質化に鋼の変態を利用するため、変態歪みによ
る鋼板の変形は避けられない。また、変態硬質部と軟質
部の硬度差が著しく、変形能に差がありすぎるため、そ
の境界から、破断することが多く、必ずしも成形性の向
上を図ることはできなかった。また、特開平９−８７７
３７号公報にはアークまたはレーザーを部分的に高張力
鋼板に照射して溶融し、鋼板の軟質化を図る方法が開示
されている。しかしながら、この方法も鋼を変態させる
ため、変態歪みの影響を避けることはできない。鋼の変
態を利用しない方法としては、例えば、特開平９−１４
３５５４号公報が開示されている。鋼板に塑性歪みを加
えておき、部分的に８００℃以上の熱処理をすることに
より、回復又は再結晶をおこさせ、軟質化する方法であ
る。しかしながら、この方法も８００℃以上に加熱する
ため、鋼板の熱歪みの問題があり、また、塑性歪みを利
用するため、硬質部の延性が著しく劣化する欠点があ
り、必ずしも高強度のプレス成形体を得るための問題解
決とはなっていない。[0004] Therefore, a method has been conceived in which a steel sheet is reinforced only in a portion where strength is required, and is softened where a formability is required. For example, Japanese Patent Application Laid-Open No. 60-238424 discloses that a steel sheet is partially irradiated with a laser to form a quenched structure so that both a hard part and a soft part are present, and the forming is performed in the soft part and the hard part has strength. A method is disclosed. However, since the transformation of steel is used for hardening, deformation of the steel sheet due to transformation strain is inevitable. Further, since the hardness difference between the transformed hard part and the soft part is remarkable, and the deformability is too different, breakage often occurs at the boundary, and it was not always possible to improve the formability. Also, Japanese Patent Application Laid-Open No. 9-877
No. 37 discloses a method in which a high-tensile steel sheet is partially irradiated with an arc or a laser and melted to soften the steel sheet. However, since this method also transforms the steel, the effect of transformation strain cannot be avoided. As a method not utilizing the transformation of steel, for example, Japanese Unexamined Patent Publication No. 9-14
No. 3554 is disclosed. This is a method in which plastic strain is applied to a steel sheet, and a heat treatment is partially performed at 800 ° C. or higher to cause recovery or recrystallization, thereby softening the steel sheet. However, this method also has a problem of thermal distortion of a steel sheet because it is heated to 800 ° C. or higher, and has a disadvantage that ductility of a hard portion is significantly deteriorated because of utilizing plastic strain, and a high-strength press-formed product is not necessarily required. It is not a problem solution to get
【０００５】また、テーラードブランク (例えばApplic
ation of Laser-Beam-Welded SheetMetal, SAE Technic
al Paper Series, 890853, 1989）のように、一枚板に
軟質部と硬質部を造り分けるのではなく、レーザー溶接
等の手段で、接合し一枚板に仕上げる方法がある。しか
しながら、この方法においても接合部が溶接により硬化
するのは避けられず、成形上の障害となる。また溶接に
より接合するため、材料を細かく接合する事は難しい。[0005] Tailored blanks (for example, Applic
ation of Laser-Beam-Welded SheetMetal, SAE Technic
al Paper Series, 890853, 1989), there is a method in which a soft part and a hard part are not separately formed on a single plate, but are joined by laser welding or the like to finish the single plate. However, even in this method, it is inevitable that the joint is hardened by welding, which is an obstacle to molding. In addition, since they are joined by welding, it is difficult to join the materials finely.
【０００６】このように、高強度の構造用部品を製造す
るにあたっては、未だ最適な方法が得られていない。そ
こで、高強度鋼板を、軟鋼板のように容易にプレス成形
等の加工成形ができる鋼板の製造方法が強く求められて
いた。As described above, an optimum method for producing a high-strength structural component has not yet been obtained. Therefore, there has been a strong demand for a method of manufacturing a steel sheet that can be easily formed by press-forming or the like, such as a mild steel sheet, from a high-strength steel sheet.
【０００７】[0007]
【発明が解決しようとする課題】本発明者らは、上記の
ような問題点を解決するべく、薄鋼板からなる各種成形
材料およびその製造方法、成形性を向上させる熱処理、
最適成形法など鋭意研究を行った。SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present inventors have made various molding materials made of thin steel sheet, a method for producing the same, a heat treatment for improving formability,
We worked diligently on the optimal molding method.
【０００８】[0008]
【課題を解決するための手段】本発明者らは、短時間熱
処理に限定すれば、例えば０．１〜７．０mmの薄鋼板で
熱伝導を極力押さえ、局所的な熱処理が可能な事を見い
出し、また特定の組織、成分をもつ鋼を用いれば、その
短時間熱処理の範囲で鋼の材質を著しく変えられる事を
見出した。さらに局所的な熱処理を成形時の変形が必要
な部分に施すと驚くほど成形性が向上する事を新たに発
見した。本発明は、この成形性向上を目的とする短時間
熱処理に最適な材料を追求し更にその材料を得るための
方法について鋭意一般研究を行い、成し遂げたものであ
る。Means for Solving the Problems If the present invention is limited to a short-time heat treatment, for example, a thin steel plate having a thickness of 0.1 to 7.0 mm suppresses heat conduction as much as possible, and can perform a local heat treatment. It was also found that if a steel having a specific structure and composition was used, the material of the steel could be significantly changed within the range of the short-time heat treatment. Furthermore, it was newly discovered that when a local heat treatment is applied to a portion requiring deformation during molding, the moldability is surprisingly improved. The present invention has been accomplished by pursuing an optimum material for a short-time heat treatment for the purpose of improving the formability, and conducting intensive general research on a method for obtaining the material.
【０００９】その要旨は、（１）重量比で Ｃ：０．０００５％〜０．２５％ Ｓｉ：０．０１％〜３．０％ Ｍｎ：０．０１％〜３．０％ Ｐ：０．００２％〜０．２０％ Ｓ：０．００１％〜０．０３％ Ｎ：０．０００２％〜０．０２％ を含有する鋼において、さらに、Ｍｏ，Ｎｂ，Ｔｉ，
Ｖ，Ｃｒ，Ｂの１種または２種以上を重量％で、 Ｋ／Ｙ≧０．７７、 K=｛TS(MPa)-(280+390*C+98*Si+65*Mn+882*P+207*A1+98
0*Ti+2000*Nb+980*V+200*Mo+38*Ni+55*Cu+22*Cr)｝、 Y=｛30* √Si+40*√Mn+80*√Mo+4* √Ni+35*√Nb+40*√
Ti+55*√V+40* √Cr+70*√P+500*√B ｝、 の範囲で含有した鋼に、熱延を施すに際し、圧延終了
後、６５０℃以上７７０℃以下の温度から２０℃／sec
以上の速さで３００℃以下まで冷却を施して、鋼のミク
ロ組織のうち、鉄炭化物、鉄窒化物、鉄炭窒化物の１種
または２種以上の合計の割合が１０個／μｍ2 以上含ま
れる結晶粒が、占積率で７％以上とする成形性向上熱処
理能に優れた加工用熱延鋼板の製造方法、（２）（１）
に記載の成分を有する鋼に、熱延を施すに際し、圧延終
了後、（Ａｒｌ＋２０) ℃以上の温度から２０℃／sec
以上の速さで３００℃以下まで冷却を施して、鋼のミク
ロ組織のうち、ベイナイト、マルテンサイト、の１種ま
たは２種以上の合計の割合が、占積率で７％以上とする
成形性向上熱処理能に優れた加工用熱延鋼板の製造方
法、（３）（１）に記載の成分を有する鋼に、熱延、脱
スケール処理、冷延を施し、ついで冷延鋼板に連続焼鈍
後冷却を施すに際し、６５０℃以上７７０℃以下の温度
から２０℃／sec 以上の速さで３００℃以下まで冷却を
施し、更に過時効処理を施さないか、または３００℃以
下の過時効処理を施して、鋼のミクロ組織のうち、鉄炭
化物、鉄窒化物、鉄炭窒化物の１種または２種以上の合
計の割合が１０個／μｍ2 以上含まれる結晶粒が、占積
率で７％以上とする成形性向上熱処理能に優れた加工用
冷延鋼板の製造方法、（４）（１）に記載の成分を有す
る鋼に、熱延、脱スケール処理、冷延を施し、ついで冷
延鋼板に連続焼鈍後冷却を施すに際し、（Ａｒｌ＋２
０) ℃以上の温度から２０℃／sec 以上の速さで３００
℃以下まで冷却を施し、更に過時効処理を施さないか、
または３００℃以下の過時効処理を施して、鋼のミクロ
組織のうち、ベイナイト、マルテンサイト、の１種また
は２種以上の合計の割合が、占積率で７％以上とする成
形性向上熱処理能に優れた加工用冷延鋼板の製造方法、
及び（５）（１）に記載の成分を含有し、さらに、鋼の
ミクロ組織のうち、鉄炭化物、鉄窒化物、鉄炭窒化物の
１種または２種以上の合計の割合が１０個／μｍ2 以上
含まれる結晶粒、ベイナイト、マルテンサイト、の１種
または２種以上の合計の割合が、占積率で７％以上であ
る鋼板に、Ａｃｌ点以下３０sec 以内の局部的な熱処理
を施して局部的に軟質化させる事を特徴とする部分軟化
加工用薄鋼板の製造方法、である。The gist is as follows: (1) C: 0.0005% to 0.25% Si: 0.01% to 3.0% Mn: 0.01% to 3.0% P: 0. 002% to 0.20% S: 0.001% to 0.03% N: 0.0002% to 0.02% In the steel containing Mo, Nb, Ti,
K / Y ≧ 0.77, K = ＢTS (MPa) − (280 + 390 * C + 98 * Si + 65 * Mn + 882 *) P + 207 * A1 + 98
0 * Ti + 2000 * Nb + 980 * V + 200 * Mo + 38 * Ni + 55 * Cu + 22 * Cr)｝, Y = ｛30 * √Si + 40 * √Mn + 80 * √Mo + 4 * √Ni + 35 * √Nb + 40 * √
When hot rolling is performed on steel containing Ti + 55 * + V + 40 * √Cr + 70 * √P + 500 * √B｝, from the temperature of 650 ° C or more and 770 ° C or less after rolling is completed. 20 ° C / sec
The steel is cooled to 300 ° C. or less at the above speed, and the total ratio of one or more of iron carbide, iron nitride, and iron carbonitride in the microstructure of the steel is 10 pieces / μm 2 or more. (2) (1) A method for producing a hot-rolled steel sheet for processing excellent in formability improvement and heat treatment ability in which the contained crystal grains are 7% or more in space factor.
When hot rolling is performed on steel having the components described in (1), after rolling is completed, a temperature of (Arl + 20) ° C. or higher and 20 ° C./sec.
Cooling to 300 ° C. or less at the above speed to form a steel microstructure in which the total ratio of one or more of bainite and martensite is 7% or more in space factor. (3) A method for producing a hot-rolled steel sheet for processing having excellent heat treatment ability, (3) subjecting the steel having the components described in (1) to hot-rolling, descaling treatment, and cold-rolling, and then continuously annealing the cold-rolled steel sheet At the time of cooling, it is cooled from a temperature of 650 ° C. to 770 ° C. to 300 ° C. or less at a speed of 20 ° C./sec or more, and is not further overaged, or is overaged at 300 ° C. or less. In the steel microstructure, crystal grains containing at least 10 / μm 2 or more in total of one or more of iron carbide, iron nitride, and iron carbonitride at a space factor of 7% Method for producing a cold-rolled steel sheet for processing excellent in formability improvement heat treatment ability as described above, The steel having the components described in 4) (1), hot-rolling, descaling, when subjected to cold rolling, then subjected to continuous annealing after cooling to cold rolled steel sheet, (Arl + 2
0) 300 ° C at a rate of 20 ° C / sec or more from a temperature of
Cool to below ℃, do not further overage treatment,
Or, heat treatment for improving formability is performed by performing an overaging treatment at 300 ° C. or less so that the total proportion of one or more of bainite and martensite in the steel microstructure is 7% or more in space factor. Manufacturing method of cold rolled steel sheet for processing with excellent performance,
And (5) the composition according to (1), further comprising, in the steel microstructure, a total ratio of one or more of iron carbide, iron nitride, and iron carbonitride is 10 / A steel sheet having a occupation ratio of 7% or more of a total of one or more of crystal grains, bainite, and martensite containing μm 2 or more is subjected to local heat treatment within 30 seconds or less from the Acl point. A method for producing a thin steel sheet for partial softening, characterized by locally softening the steel sheet.
【００１０】ここで成形性向上熱処理能とは、鋼板のＡ
ｃｌ変態点以下の熱処理温度で３０sec 以内の短時間熱
処理により鋼板の引張り強さが変化する能力のことをい
う。この熱処理に限定すれば、０．１〜７．０mmの薄鋼
板で熱歪みを極力少なく抑える事ができ、また変態歪み
も生じ難い。さらに熱伝導も抑えられるので、約１mmの
分解能で熱処理を施す事ができる。また、この熱処理に
より引張り強さが変化する変化量としては、５％以上引
張り強さが変化することが、望ましい。この鋼板を用い
て局部的に熱処理を行うと鋼板全体の強度はほとんど変
化することなく、成形性が著しく向上する。たとえば、
変形が必要である部分に局部的に熱処理を行うと、変形
が必要である部分の強度が下がり変形が容易に生じ、成
形性が向上する。[0010] Here, the heat treatment ability for improving formability is defined as A
The ability to change the tensile strength of a steel sheet by short-time heat treatment within 30 seconds at a heat treatment temperature below the cl transformation point. If limited to this heat treatment, thermal distortion can be suppressed as small as possible with a thin steel sheet of 0.1 to 7.0 mm, and transformation distortion hardly occurs. Further, since heat conduction is suppressed, heat treatment can be performed with a resolution of about 1 mm. Further, it is desirable that the amount of change in the tensile strength by the heat treatment be changed by 5% or more. When heat treatment is locally performed using this steel sheet, the formability is significantly improved without substantially changing the strength of the entire steel sheet. For example,
When heat treatment is locally performed on a portion requiring deformation, the strength of the portion requiring deformation is reduced, and deformation is easily caused, thereby improving the formability.
【００１１】[0011]
【発明の実施の形態】本研究者らは、最強度鋼板の成形
性を向上させるＡｃｌ変態点以下の温度で３０sec 以内
の局部熱処理で強度が大きく変わる鋼板組織、鋼板成分
について鋭意研究を行ったところ、鋼の鉄炭化物、鉄窒
化物、および鉄炭窒化物の大きさを制御してやれば、Ａ
ｃｌ変態点以下の温度で３０sec 以内の熱処理で即座に
鉄炭化物、鉄窒化物、および鉄炭窒化物を溶解または粗
大化し、鋼板の強度を下げられる事を見出した。BEST MODE FOR CARRYING OUT THE INVENTION The present inventors have conducted intensive studies on the structure and composition of a steel sheet whose strength is greatly changed by local heat treatment within 30 seconds at a temperature below the Acl transformation point to improve the formability of the strongest steel sheet. However, if the size of iron carbide, iron nitride and iron carbonitride of steel is controlled, A
It has been found that iron carbide, iron nitride, and iron carbonitride can be immediately dissolved or coarsened by a heat treatment within 30 sec at a temperature below the cl transformation point, and the strength of the steel sheet can be reduced.
【００１２】またマルテンサイトも同様な効果がある事
を見出した。さらに鋼板の強度の変化量は、鉄炭化物、
鉄窒化物、および鉄炭窒化物を微細に含む組織、ベイナ
イト組織、マルテンサイト組織の割合に影響され、占積
率で７％以上の分率がある時、その効果が大きい事を見
出した。さらに、鋼板の強度の低下量が鋼板の化学成分
にも大きく依存し、 Ｋ／Ｙ≧０．７７、 K=｛TS(MPa)-(280+390*C+98*Si+65*Mn+882*P+207*A1+98
0*Ti+2000*Nb+980*V+200*Mo+38*Ni+55*Cu+22*Cr)｝、 Y=｛30* √Si+40*√Mn+80*√Mo+4* √Ni+35*√Nb+40*√
Ti+55*√V+40* √Cr+70*√P+500*√B ｝、 の範囲に限定する事によって鋼板の強度の低下量を大き
くできる事を見出した。It has also been found that martensite has a similar effect. Furthermore, the change in the strength of the steel sheet is
It has been found that the effect is large when there is a fraction of 7% or more in the space factor, which is affected by the proportions of the microstructure containing iron nitride and iron carbonitride, bainite microstructure, and martensite microstructure. Furthermore, the amount of reduction in the strength of the steel sheet also depends greatly on the chemical composition of the steel sheet, and K / Y ≧ 0.77, K = ｛TS (MPa)-(280 + 390 * C + 98 * Si + 65 * Mn + 882 * P + 207 * A1 + 98
0 * Ti + 2000 * Nb + 980 * V + 200 * Mo + 38 * Ni + 55 * Cu + 22 * Cr)｝, Y = ｛30 * √Si + 40 * √Mn + 80 * √Mo + 4 * √Ni + 35 * √Nb + 40 * √
It has been found that the strength reduction of the steel sheet can be increased by limiting the range of Ti + 55 * √V + 40 * √Cr + 70 * √P + 500 * √B｝.
【００１３】そこで、該鋼板をえるための製造法につい
ても鋭意研究を行い、熱延条件、焼鈍条件、冷却条件な
どについて詳細な検討を行い、最適な製造法を見出し
た。以下に本発明を詳細に説明する。まず、本発明法に
よって得られる鋼板の組織について説明する。本発明法
により鉄炭化物、鉄窒化物、鉄炭窒化物の１種または２
種以上の合計の割合が１０個／μｍ2 以上含まれる結晶
粒および、ベイナイト、マルテンサイトを占積率で７％
以上である組織を得る事が出来る。本発明法でえられた
鋼板は、成形性向上熱処理としてＡｃｌ変態点以下の温
度で３０sec 以内の局部熱処理を行い、部分的に軟化さ
せる。そのため、低温短時間で強度が変わる必要がある
ので、鋼の中で移動速度の早いＣ，Ｎの拡散現象を利用
するのが最も適しており、鉄炭化物または鉄窒化物また
は鉄炭窒化物および、ベイナイト、マルテンサイトを利
用するのが最も有効である。[0013] Accordingly, the present inventors have conducted intensive research on the manufacturing method for obtaining the steel sheet, and have conducted detailed studies on hot rolling conditions, annealing conditions, cooling conditions, and the like, and have found an optimum manufacturing method. Hereinafter, the present invention will be described in detail. First, the structure of the steel sheet obtained by the method of the present invention will be described. According to the method of the present invention, one or two of iron carbide, iron nitride, iron carbonitride
7% or more of crystal grains, bainite, and martensite having a total ratio of 10 or more seeds / μm 2 or more in a space factor of
The above organization can be obtained. The steel sheet obtained by the method of the present invention is partially softened by performing a local heat treatment at a temperature lower than the Acl transformation point within 30 seconds as a heat treatment for improving formability. Therefore, it is necessary to change the strength in a short time at a low temperature, and it is most suitable to use the diffusion phenomenon of C and N, which has a high moving speed in steel, and to use iron carbide or iron nitride or iron carbonitride and , Bainite and martensite are most effective.
【００１４】鉄炭化物、鉄窒化物、鉄炭窒化物の１種ま
たは２種以上の合計の割合が１０個／μｍ2 以上含まれ
る結晶粒があると鋼は析出強化により高強度化する事が
できる。一方この鉄炭化物または鉄窒化物または鉄炭窒
化物は、短時間熱処理により溶解、粗大化して容易に低
強度化する事ができる。ベイナイトまたはマルテンサイ
トは鋼を変態強化により高強度化する事ができる。一方
ベイナイトまたはマルテンサイトは短時間熱処理により
容易に焼き戻されて、粗大な炭化物が析出し、低強度化
する事ができる。鋼板を局部的に低強度化するために
は、短時間熱処理で強度の変化する組織を体積割合で一
定割合以上含有する事が必要である。すなわち、鉄炭化
物、鉄窒化物、鉄炭窒化物の１種または２種以上の合計
の割合が１０個／μｍ2 以上含まれる結晶粒、ベイナイ
ト、マルテンサイト組織が鋼全体の割合の中で一定割合
以上ある事が必要である。鉄炭化物、鉄窒化物、鉄炭窒
化物の１種または２種以上の合計の割合が１０個／μｍ
2 以上含まれる結晶粒、ベイナイト、マルテンサイト組
織は、鋼の他の組織（例えば、微細な炭窒化物を含まな
いフェライトやパーライト等）に比べ、強度が高いので
鋼板の強度に対する寄与度が大きく、合計の体積割合
が、おおむね７％以上あれば、短時間熱処理したときに
鋼板の強度を５％以上変化させる事ができる。鉄炭化
物、鉄窒化物、鉄炭窒化物の１種または２種以上の合計
の割合が１０個／μｍ2 以上含まれる結晶粒、ベイナイ
ト、マルテンサイト組織の強度および短時間熱処理によ
り強度の変化する軟化量は、これらの組織中に含まれる
炭素量、窒素量により異なり、炭素量、窒素量が多い場
合には、これら組織の体積割合が７％以下のときでも、
鋼板の強度は５％以上変化させる事ができる。しかしな
がら、通常薄鋼板として使用される炭素量（wt％Ｃ≦
０．２５) 、窒素量（wt％Ｎ≦０．０２) 範囲では、鉄
炭化物、鉄窒化物、鉄炭窒化物の１種または２種以上の
合計の割合が１０個／μｍ2 以上含まれる結晶粒、ベイ
ナイト、マルテンサイト組織が体積割合で合計７％以上
のとき、鋼板の強度は５％以上変化させる事ができるの
で、７％を下限とする。If there is a crystal grain containing one or more of iron carbide, iron nitride and iron carbonitride in a total ratio of at least 10 / μm 2 , the steel may be strengthened by precipitation strengthening. it can. On the other hand, the iron carbide, iron nitride, or iron carbonitride can be easily melted and coarsened by a short-time heat treatment to reduce the strength. Bainite or martensite can increase the strength of steel by transformation strengthening. On the other hand, bainite or martensite can be easily tempered by a short-time heat treatment, and coarse carbides can be precipitated to lower the strength. In order to locally reduce the strength of the steel sheet, it is necessary to contain a structure whose strength changes by a short-time heat treatment at a certain volume ratio or more. That is, the crystal grains, bainite, and martensite structures in which the total ratio of one or more of iron carbide, iron nitride, and iron carbonitride is 10 or more / μm 2 or more are constant in the ratio of the entire steel. It is necessary that there be more than a percentage. The total ratio of one or more of iron carbide, iron nitride, and iron carbonitride is 10 / μm
The crystal grains, bainite, and martensite structures contained in two or more steels have higher strengths than other structures of the steel (for example, ferrite and pearlite that do not contain fine carbonitrides), and thus contribute more to the strength of the steel plate. If the total volume ratio is about 7% or more, the strength of the steel sheet can be changed by 5% or more when heat-treated for a short time. The strength of crystal grains, bainite, martensite structure containing 10 or more μm 2 or more in total of one or more of iron carbide, iron nitride and iron carbonitride, and the strength changes by short-time heat treatment The amount of softening varies depending on the amount of carbon and nitrogen contained in these tissues. When the amount of carbon and nitrogen is large, even when the volume ratio of these tissues is 7% or less,
The strength of the steel sheet can be changed by 5% or more. However, the amount of carbon (wt% C ≦
0.25) and the amount of nitrogen (wt% N ≦ 0.02) in the range of at least one of iron carbide, iron nitride, iron carbonitride, or a total of at least 10 / μm 2. When the crystal grains, bainite, and martensite structures are 7% or more in total by volume, the strength of the steel sheet can be changed by 5% or more. Therefore, the lower limit is 7%.
【００１５】また、鉄炭化物、鉄窒化物、鉄炭窒化物の
１種または２種以上の合計の割合が１０個／μｍ2 以上
含まれる結晶粒、ベイナイト、マルテンサイト組織の体
積割合が増えれば増えるほど、鋼板の強度を変化させる
ことが容易になるので、上限は規定しないが、加工性は
劣化していくので、加工部品に応じて体積割合を調整し
ておく事が望ましい。Further, if the volume ratio of crystal grains, bainite, and martensite structures containing 10 or more μm 2 or more of one or more of iron carbide, iron nitride, and iron carbonitride is increased. As the number increases, the strength of the steel sheet can be easily changed. Therefore, the upper limit is not specified. However, since the workability deteriorates, it is desirable to adjust the volume ratio according to the processed part.
【００１６】ここで言う鉄炭化物とはセメンタイト、ε
炭化物、χ炭化物、鉄−炭素コンプレックスなどの鉄炭
素化合物、鉄窒化物とはＦｅ4 Ｎ，Ｆｅ16Ｎ2 、鉄−窒
素コンプレックスなどの鉄窒素化合物、鉄炭窒化物とは
鉄炭化合物や鉄窒化物が混合した形態や、鉄炭化合物の
一部のＣがＮに置き換わったもの、鉄窒化物の一部のＮ
がＣに置き換わったもの等を指す。The iron carbide mentioned here is cementite, ε
Iron-carbon compounds such as carbides, carbides, iron-carbon complexes, iron nitrides are Fe 4 N, Fe 16 N 2 , iron-nitrogen compounds such as iron-nitrogen complexes, and iron carbonitrides are iron-carbon compounds and iron Nitride mixed form, iron carbon compounds with some C replaced by N, iron nitride with some N
Is replaced with C, etc.
【００１７】図１に鉄炭化物、鉄窒化物、鉄炭窒化物の
１種または２種以上の合計の割合が１０個／μｍ2 以上
含まれる結晶粒、ベイナイト、マルテンサイト組織の合
計の占積率と鋼板強度の低下比の関係を示す。鉄炭化
物、鉄窒化物、鉄炭窒化物の１種または２種以上の合計
の割合が１０個／μｍ2 以上含まれる結晶粒の割合は、
顕微鏡視野内の結晶粒ごとの鉄炭化物または鉄窒化物ま
たは鉄炭窒化物の個数を数え、１０個／μｍ2 以上含ま
れる結晶粒個数および平均結晶粒径を測定する事により
占積率を算出した。また、ベイナイト、マルテンサイト
の占積率も顕微鏡視野内の個数および平均サイズを測定
する事により算出した。強度測定は、ＪＩＳ５号引張試
験片を作成し、４００℃で３０秒の熱処理を行った後、
室温まで冷却し、その後室温で引張試験を行った。この
時の引張試験強度の低下量（ΔＴＳ）を熱処理前のＴＳ
で割った値を強度低下比として示した。鉄炭化物、鉄窒
化物、鉄炭窒化物の１種または２種以上の合計の割合が
１０個／μｍ2 以上含まれる結晶粒、ベイナイト、マル
テンサイト組織の合計の占積率が７％以上のとき、鋼板
強度の低下比が著しいことが分かる。FIG. 1 shows the occupation of crystal grains, bainite, and martensitic structures in which the total ratio of one or more of iron carbide, iron nitride and iron carbonitride is 10 or more / μm 2 or more. The relationship between the rate and the reduction ratio of the steel sheet strength is shown. The ratio of the crystal grains in which the total ratio of one or more of iron carbide, iron nitride, and iron carbonitride is 10 or more / μm 2 is:
Calculate the space factor by counting the number of iron carbide, iron nitride or iron carbonitride in each crystal grain in the microscope field of view and measuring the number of crystal grains and the average crystal grain size of 10 / μm 2 or more. did. Further, the space factor of bainite and martensite was also calculated by measuring the number and average size in the visual field of the microscope. For the strength measurement, a JIS No. 5 tensile test piece was prepared and heat-treated at 400 ° C. for 30 seconds.
After cooling to room temperature, a tensile test was performed at room temperature. At this time, the amount of decrease in the tensile test strength (ΔTS)
The value divided by is shown as the strength reduction ratio. Iron carbide, iron nitride, iron carbonitride, the total ratio of one or two or more of the crystal grains, bainite, and martensitic microstructures containing 10 or more μm 2 or more is 7% or more. At this time, it is understood that the reduction ratio of the steel sheet strength is remarkable.
【００１８】次に、鉄炭化物、鉄窒化物、鉄炭窒化物の
１種または２種以上の合計の割合が１０個／μｍ2 以上
含まれる結晶粒、ベイナイト、マルテンサイト組織の合
計の占積率が７％以上であることを特徴とする鋼板の製
造方法について詳細に説明する。まず、鋼のミクロ組織
のうち、鉄炭化物、鉄窒化物、鉄炭窒化物の１種または
２種以上の合計の割合が１０個／μｍ2 以上含まれる結
晶粒を占積率で７％以上得る好適な方法についてのべ
る。Next, the occupation of the crystal grains, bainite, and martensitic structures in which the total ratio of one or more of iron carbide, iron nitride, and iron carbonitride is 10 or more / μm 2 or more. A method for producing a steel sheet having a rate of 7% or more will be described in detail. First, in the microstructure of steel, crystal grains containing at least 10 / μm 2 of one or more of iron carbide, iron nitride, and iron carbonitride in a total space ratio of 7% or more are included. The preferred method of obtaining is described.
【００１９】熱延鋼板を製造する場合、熱延を施すに際
し、圧延終了後、６５０℃以上７７０℃以下の温度から
２０℃／sec 以上の速さで３００℃以下まで冷却を施
す。これは、６５０℃以上７７０℃以下の温度で、Ｃま
たはＮの固溶量が最大になり、過飽和度が高まるためで
ある。この温度域から、２０℃／sec 以上の冷却を施
し、ＣまたはＮの過飽和度が高いまま３００℃以下に冷
却、巻取を行うと、鉄炭化物、鉄窒化物、鉄炭窒化物の
１種または２種以上の合計の割合が１０個／μｍ2以上
含まれる結晶粒が、占積率で７％以上含む熱延鋼板を得
る事ができる。これは、鉄炭化物または鉄窒化物または
鉄炭窒化物の析出の駆動力が非常に高いので微細に析出
するためと考えられる。In the case of producing a hot-rolled steel sheet, at the time of hot rolling, after the rolling is completed, the steel sheet is cooled from a temperature of 650 ° C. or more and 770 ° C. or less to 300 ° C. or less at a speed of 20 ° C./sec or more. This is because at a temperature of 650 ° C. or more and 770 ° C. or less, the amount of solid solution of C or N is maximized and the degree of supersaturation is increased. From this temperature range, cooling at a rate of 20 ° C / sec or more, cooling to 300 ° C or less while supersaturation of C or N is high, and winding and performing one type of iron carbide, iron nitride, iron carbonitride Alternatively, it is possible to obtain a hot-rolled steel sheet in which crystal grains having a total ratio of two or more of 10 / μm 2 or more have a space factor of 7% or more. This is considered to be because the driving force for precipitation of iron carbide, iron nitride or iron carbonitride is extremely high, so that the precipitate is finely precipitated.
【００２０】冷延鋼板を製造する場合、熱延、脱スケー
ル処理、冷延を施し、ついで冷延鋼板に連続焼鈍後冷却
を施すに際し、６５０℃以上７７０℃以下の温度から２
０℃／sec 以上の速さで３００℃以下まで冷却を施し、
更に過時効処理を施さないか、または３００℃以下の過
時効処理を施す。これは、熱延鋼板と同様に、６５０℃
以上７７０℃以下の温度で、ＣまたはＮの固溶量が最大
になり、過飽和度が高まるためである。この温度域か
ら、２０℃／sec 以上の冷却を施し、ＣまたはＮの過飽
和度が高いまま３００℃以下に冷却すると、鉄炭化物、
鉄窒化物、鉄炭窒化物の１種または２種以上の合計の割
合が１０個／μｍ2 以上含まれる結晶粒が、占積率で７
％以上含む熱延鋼板を得る事ができる。これは、鉄炭化
物または鉄窒化物または鉄炭窒化物の析出の駆動力が非
常に高いので微細に析出するためと考えられる。冷延鋼
板の場合は、過時効処理を施す場合があるが、過時効処
理によって、鉄炭化物、鉄窒化物、鉄炭窒化物の１種ま
たは２種以上の合計の割合が１０個／μｍ2 以上含まれ
る結晶粒が失われるので、その後、過時効処理を施さな
いか、または過時効処理を施したとしても、３００℃以
下の過時効処理を施す必要がある。When a cold-rolled steel sheet is manufactured, it is subjected to hot rolling, descaling treatment and cold rolling, and then to continuous cold annealing of the cold-rolled steel sheet.
Cooling to 300 ° C or less at a speed of 0 ° C / sec or more,
Further, no overaging treatment is performed, or an overaging treatment at 300 ° C. or less is performed. This is similar to hot-rolled steel plate at 650 ° C.
At a temperature of 770 ° C. or lower, the amount of solid solution of C or N is maximized, and the degree of supersaturation is increased. From this temperature range, cooling at 20 ° C./sec or more is performed, and when the supersaturation degree of C or N is high and cooled to 300 ° C. or less, iron carbide,
A crystal grain having a total ratio of one or more of iron nitride and iron carbonitride of 10 or more / μm 2 or more in a space factor of 7
% Can be obtained. This is considered to be because the driving force for precipitation of iron carbide, iron nitride or iron carbonitride is extremely high, so that the precipitate is finely precipitated. In the case of a cold-rolled steel sheet, an overaging treatment may be performed. However, the overaging treatment reduces the ratio of one or more of iron carbide, iron nitride, and iron carbonitride to 10 / μm 2. Since the crystal grains contained above are lost, it is necessary to perform no overaging treatment after that, or to carry out overaging treatment at 300 ° C. or lower even if the overaging treatment is performed.
【００２１】ついで、鋼のミクロ組織のうち、ベイナイ
ト、マルテンサイトの１種または２種以上の合計の割合
が、占積率で７％以上を得る方法についてのべる。熱延
鋼板を製造する場合、熱延を施すに際し、圧延終了後、
（Ａｒｌ＋２０）℃以上の温度から２０℃／sec 以上の
速さで３００℃以下まで冷却を施す。ベイナイト、マル
テンサイトを７％以上得るためには、オーステナイトを
７％以上含む温度域からの冷却が必要である。従って、
（Ａｒｌ＋２０）℃以上の温度域から冷却をする必要が
ある。冷却速度は、２０℃／sec 以上の速さで冷却する
と、低温まで、オーステナイトを未変態のまま冷却で
き、低温変態生成物であるベイナイトまたはマルテンサ
イトを得る事ができる。ベイナイトを得るためには、約
５００℃以下、マルテンサイトを得るためには、Ｍｓ点
以下まで冷却すればよいが、焼戻により強度が低下して
しまうので、焼戻により強度が低下しないように３００
℃以下まで冷却し３００℃以下を巻取を行う必要があ
る。Next, a method for obtaining a ratio of one or more of bainite and martensite in the steel microstructure of 7% or more in the space factor will be described. When manufacturing hot-rolled steel sheet, when performing hot rolling, after rolling,
Cooling is performed from a temperature of (Arl + 20) ° C. or more to 300 ° C. or less at a speed of 20 ° C./sec or more. In order to obtain at least 7% of bainite and martensite, it is necessary to cool from a temperature range containing at least 7% of austenite. Therefore,
It is necessary to cool from a temperature range of (Arl + 20) ° C. or higher. By cooling at a cooling rate of 20 ° C./sec or more, austenite can be cooled to a low temperature in an untransformed state, and bainite or martensite, which is a low-temperature transformation product, can be obtained. In order to obtain bainite, the temperature may be cooled to about 500 ° C. or lower, and to obtain martensite, the temperature may be lowered to the Ms point or lower. However, the strength is reduced by tempering. 300
It is necessary to cool to 300 ° C. or less and wind up to 300 ° C. or less.
【００２２】冷延鋼板を製造する場合、熱延、脱スケー
ル処理、冷延を施し、ついで冷延鋼板に連続焼鈍後冷却
を施すに際し、（Ａｒｌ＋２０）℃以上の温度から２０
℃／sec 以上の速さで３００℃以下まで冷却を施し、更
に過時効処理を施さないか、または３００℃以下の過時
効処理を施す。ベイナイト、マルテンサイトを７％以上
得るためには、オーステナイトを７％以上含む温度域か
らの冷却が必要である。従って、（Ａｒｌ＋２０）℃以
上の温度域から冷却をする必要がある。冷却速度は、２
０℃／sec 以上の速さで冷却すると、低温まで、オース
テナイトを未変態のまま冷却でき、低温変態生成物であ
るベイナイトまたはマルテンサイトを得る事ができる。
ベイナイトを得るためには、約５００℃以下、マルテン
サイトを得るためには、Ｍｓ点以下まで冷却すればよい
が、焼戻により強度が低下してしまうので、焼戻により
強度が低下しないように３００℃以下まで冷却を行う必
要がある。また過時効処理を施すと、過時効処理により
ベイナイトまたはマルテンサイトが焼き戻されてしま
い、強度低下を引き起こすので、過時効処理を施さない
か、施したとしても３００℃以下の温度域で過時効処理
を施すことが必要である。When a cold-rolled steel sheet is manufactured, it is subjected to hot rolling, descaling treatment and cold rolling, and then to continuous cold annealing of the cold-rolled steel sheet.
Cool to 300 ° C. or lower at a speed of not lower than 300 ° C./sec, and do not further perform overaging, or perform overaging at 300 ° C. or lower. In order to obtain at least 7% of bainite and martensite, it is necessary to cool from a temperature range containing at least 7% of austenite. Therefore, it is necessary to cool from a temperature range of (Arl + 20) ° C. or higher. The cooling rate is 2
When cooled at a rate of 0 ° C./sec or more, austenite can be cooled to a low temperature without being transformed, and bainite or martensite which is a low-temperature transformation product can be obtained.
In order to obtain bainite, the temperature may be cooled to about 500 ° C. or lower, and to obtain martensite, the temperature may be lowered to the Ms point or lower. However, the strength is reduced by tempering. It is necessary to cool to 300 ° C. or less. If the overaging treatment is performed, bainite or martensite is tempered by the overaging treatment, and the strength is reduced. Therefore, the overaging treatment is not performed, or even if it is performed, the overaging is performed in a temperature range of 300 ° C or less. It is necessary to perform processing.
【００２３】次に鋼の成分を限定する理由について述べ
る。Ｃは、本発明である鉄炭化物または鉄炭窒化物が１
０個／μｍ2 以上含まれる結晶粒、ベイナイト、マルテ
ンサイト組織を得るために、必須の元素である。含有量
が多くなると、上記組織を得やすくなるが、溶接性は劣
化する。従って０．２５％以下とする。また、０．００
０５％未満では、鉄炭化物、鉄窒化物、鉄炭窒化物の１
種または２種以上の合計の割合が１０個／μｍ2 以上含
まれる結晶粒、ベイナイト、マルテンサイト組織を得る
ための製造コスト、合金コストが増大し、製造コストが
飛躍的に上がり経済的でなくなるので、０．０００５％
を下限とする。Next, the reasons for limiting the components of steel will be described. C is 1% of the iron carbide or iron carbonitride of the present invention.
It is an essential element for obtaining a crystal grain, bainite, and martensite structure containing 0 / μm 2 or more. When the content is large, the above structure is easily obtained, but the weldability is deteriorated. Therefore, it is set to 0.25% or less. Also, 0.00
If less than 05%, one of iron carbide, iron nitride, iron carbonitride
Species or the total proportion of the two or more are 10 / [mu] m 2 or more Included grain, bainite, manufacturing cost for obtaining the martensite structure, the alloy cost increases, the manufacturing cost is not dramatically increases economically So 0.0005%
Is the lower limit.
【００２４】Ｓｉは、０．０１％未満では、熱処理の
際、強度を上昇させる効果が少ないので、０．０１％を
下限とする。好ましくは、０．２％以上である。３．０
％を超えると加工性は劣化するので、３．０％を上限と
する。Ｍｎは、強度確保のために使用されるが、０．０
１％未満では、製造コストが飛躍的に上がり経済的でな
くなるので、０．０１％を下限とし、３．０％を超える
と加工性は劣化するので、３．０％を上限とする。If the content of Si is less than 0.01%, the effect of increasing the strength during heat treatment is small, so the lower limit is 0.01%. Preferably, it is at least 0.2%. 3.0
%, The workability deteriorates, so the upper limit is 3.0%. Mn is used for securing strength, but 0.0
If it is less than 1%, the production cost increases dramatically and it becomes uneconomical, so the lower limit is 0.01%. If it exceeds 3.0%, the workability deteriorates, so the upper limit is 3.0%.
【００２５】Ｐは、０．００２％未満では、熱処理の
際、強度を上昇させる効果が少ないので、０．００２％
を下限とする。好ましくは、０．０２％以上である。
０．２０％を超えると靱性が著しく悪化して脆化するの
で、０．２０％を上限とする。Ｓは、０．００１％未満
では製造コストが飛躍的に上がり経済的でなくなるの
で、０．００１％を下限とし、０．０３％を超えると熱
間圧延時に赤熱脆性を起こし、表面で割れる、いわゆ
る、熱間脆性を起こすため、０．０３％を上限とする。If P is less than 0.002%, the effect of increasing the strength during heat treatment is small, so that P is 0.002%.
Is the lower limit. Preferably, it is at least 0.02%.
If it exceeds 0.20%, the toughness deteriorates remarkably and the material becomes brittle, so the upper limit is 0.20%. If S is less than 0.001%, the production cost is dramatically increased and it is not economical, so the lower limit is 0.001%, and if it exceeds 0.03%, red hot embrittlement occurs at the time of hot rolling and cracks at the surface. To cause so-called hot embrittlement, the upper limit is made 0.03%.
【００２６】Ｎは、０．０００２％未満では製造コスト
が飛躍的に上がり経済的でなくなるので、０．０００２
％を下限とし、０．０２％を超えると加工性が劣化して
くるので、０．０２％を上限とする。また、本発明で
は、Ｃ，Ｓｉ，Ｍｎ，Ｍｏ，Ｎｉ，Ａｌ，Ｃｕ，Ｎｂ，
Ｔｉ，Ｖ，Ｃｒ，Ｐ，Ｂを次式の範囲で含有させると効
果が著しい。If N is less than 0.0002%, the production cost increases dramatically and becomes uneconomical.
% Is made the lower limit, and if it exceeds 0.02%, the workability deteriorates. Therefore, the upper limit is made 0.02%. In the present invention, C, Si, Mn, Mo, Ni, Al, Cu, Nb,
The effect is remarkable when Ti, V, Cr, P and B are contained in the range of the following formula.
【００２７】Ｋ／Ｙ≧０．７７、 K=｛TS(MPa)-(280+390*C+98*Si+65*Mn+882*P+207*Al+98
0*Ti+2000*Nb+980*V+200*Mo+38*Ni+55*Cu+22*Cr)｝、 Y=｛30* √Si+40*√Mn+80*√Mo+4* √Ni+35*√Nb+40*√
Ti+55*√V+40* √Cr+70*√P+500*√B ｝、 ＴＳ(MPa）は鋼の引張強度(MPa）である。K / Y ≧ 0.77, K = ｛TS (MPa) − (280 + 390 * C + 98 * Si + 65 * Mn + 882 * P + 207 * Al + 98
0 * Ti + 2000 * Nb + 980 * V + 200 * Mo + 38 * Ni + 55 * Cu + 22 * Cr)｝, Y = ｛30 * √Si + 40 * √Mn + 80 * √Mo + 4 * √Ni + 35 * √Nb + 40 * √
Ti + 55 * √V + 40 * √Cr + 70 * √P + 500 * √B｝, TS (MPa) is the tensile strength (MPa) of steel.
【００２８】本発明法によって得られる鋼板の使用にあ
たっては、成形性向上熱処理として、Ａｃｌ以下の温度
で、かつ３０秒以内の熱処理をされる。上式のＫ値はＡ
ｃｌ以下の温度で熱処理を行う事から、おもに規定され
るものであり、上式のＹ値は３０秒以内の時間内で熱処
理を行う事から、おもに規定されるものである。In using the steel sheet obtained by the method of the present invention, a heat treatment at a temperature of not more than Acl and within 30 seconds is performed as a heat treatment for improving formability. The K value in the above equation is A
Since the heat treatment is performed at a temperature of not more than cl, it is mainly specified, and the Y value in the above formula is mainly specified because the heat treatment is performed within a time period of 30 seconds or less.
【００２９】まず、上式のＫ値について説明する。Ｃ，
Ｓｉ，Ｍｎ，Ｐ，Ａｌ，Ｔｉ，Ｎｂ，Ｖ，Ｍｏ，Ｎｉ，
Ｃｕ，Ｃｒは鋼を強化する元素である。これらの元素
は、固溶強化、析出強化、変態強化など、様々な硬化メ
カニズムにより直接的または間接的に作用し、鋼を強化
する。本発明ではＡｃｌ変態点以下の温度で熱処理によ
り鋼の強度を軟化させ低強度にする。軟化量は熱処理時
間が増加するにつれて増加するが、どんなに長時間熱処
理しても鋼が軟化しない強度分があることが判明した。
この軟化しない強度分は鋼の成分に大きく依存し、MPa
単位で (280+390*C+98*Si+65*Mn+882*P+207*Al+980*Ti+2000*Nb
+980*V+200*Mo+38*Ni+55*Cu+22*Cr) で表せる事が分かった。この軟化しない強度分は、成分
によって異なり、単位重量あたり、Ｎｂが最も効果が大
きく、ついでＴｉ，Ｐの順となる。この効果の寄与度
が、請求項１に示した式の第一項の元素の前に付与され
た係数である。すなわち、この係数が、Ｃの場合３９
０、Ｓｉの場合９８、Ｍｎの場合６５、Ｐの場合８８
２、Ａｌの場合２０７、Ｔｉの場合９８０、Ｎｂの場合
２０００、Ｖの場合９８０、Ｍｏの場合２００、Ｎｉの
場合３８、Ｃｕの場合５５、Ｃｒの場合２２である事が
判明した。First, the K value in the above equation will be described. C,
Si, Mn, P, Al, Ti, Nb, V, Mo, Ni,
Cu and Cr are elements that strengthen steel. These elements act directly or indirectly by various hardening mechanisms such as solid solution strengthening, precipitation strengthening, and transformation strengthening to strengthen the steel. In the present invention, the strength of the steel is softened by heat treatment at a temperature equal to or lower than the Acl transformation point to reduce the strength. Although the amount of softening increases as the heat treatment time increases, it has been found that there is a part of the steel that does not soften even if the heat treatment is performed for a long time.
This non-softening strength depends greatly on the steel composition,
Unit: (280 + 390 * C + 98 * Si + 65 * Mn + 882 * P + 207 * Al + 980 * Ti + 2000 * Nb
+ 980 * V + 200 * Mo + 38 * Ni + 55 * Cu + 22 * Cr). The non-softening strength varies depending on the component, and Nb has the largest effect per unit weight, followed by Ti and P. The degree of contribution of this effect is a coefficient given before the element of the first term in the formula shown in claim 1. That is, when this coefficient is C, 39
0, 98 for Si, 65 for Mn, 88 for P
2, 207 for Al, 980 for Ti, 2000 for Nb, 980 for V, 200 for Mo, 38 for Ni, 55 for Cu, and 22 for Cr.
【００３０】従って、Ａｃｌ変態点以下の温度の熱処理
で強度が変化しうる鋼の強度分としては ｛TS(MPa)-(280+390*C+98*Si+65*Mn+882*P+207*Al+980*
Ti+2000*Nb+980*V+200*Mo+38*Ni+55*Cu+22*Cr)｝ で表され、この値をＫとして定義している。Therefore, the strength of the steel whose strength can be changed by heat treatment at a temperature lower than the Acl transformation point is as follows: TS (MPa) − (280 + 390 * C + 98 * Si + 65 * Mn + 882 * P + 207 * Al + 980 *
Ti + 2000 * Nb + 980 * V + 200 * Mo + 38 * Ni + 55 * Cu + 22 * Cr)｝, and this value is defined as K.
【００３１】次に上式のＹ値について説明する。Ｓｉ，
Ｍｎ，Ｍｏ，Ｎｉ，Ｎｂ，Ｔｉ，Ｖ，Ｃｒ，Ｐ，Ｂは鋼
の軟化速度に影響を及ぼす元素であり、鉄炭化物、鉄窒
化物、鉄炭窒化物の溶解、粗大化やベイナイト組織、マ
ルテンサイト組織の軟化を遅らせる元素である。そのた
め、これらの元素が一定量以上含まれると短時間熱処理
により鋼を軟化させる事ができない。この効果は、鋼の
成分、含有量に大きく依存し、 ｛30* √Si+40*√Mn+80*√Mo+4* √Ni+35*√Nb+40*√Ti
+55*√V+40* √Cr+70*√P+500*√B ｝ に比例する事が分かった。この値をＹとして定義してい
る。Next, the Y value in the above equation will be described. Si,
Mn, Mo, Ni, Nb, Ti, V, Cr, P, and B are elements that affect the softening rate of steel, and dissolve iron carbide, iron nitride, iron carbonitride, coarsen, bainite, It is an element that delays the softening of the martensite structure. Therefore, if these elements are contained in a certain amount or more, the steel cannot be softened by a short-time heat treatment. This effect largely depends on the composition and content of the steel, ｛30 * √Si + 40 * √Mn + 80 * √Mo + 4 * √Ni + 35 * √Nb + 40 * √Ti
+ 55 * √V + 40 * √Cr + 70 * √P + 500 * √B｝ This value is defined as Y.
【００３２】この効果代は、成分によって異なり、単位
重量あたり、Ｂが最も効果が大きく、ついでＭｏ，Ｐの
順となる。この効果の寄与度が、請求項１に示した式の
第二項の元素の前に付与された係数である。すなわち、
この係数が、Ｓｉの場合３０、Ｍｎの場合４０、Ｍｏの
場合８０、Ｎｉの場合４、Ｎｂの場合３５、Ｔｉの場合
４０、Ｖの場合５５、Ｃｒの場合４０、Ｐの場合７０、
Ｂの場合５００である事が判明した。The effect cost varies depending on the components. B has the largest effect per unit weight, followed by Mo and P. The degree of contribution of this effect is a coefficient given before the element of the second term in the formula shown in claim 1. That is,
This coefficient is 30 for Si, 40 for Mn, 80 for Mo, 4 for Ni, 35 for Nb, 40 for Ti, 55 for V, 40 for Cr, 70 for P,
In the case of B, it turned out to be 500.
【００３３】また、この効果は、含有元素の濃度の平方
根に比例する事が明らかとなった。このメカニズムは明
らかではないが、これらの元素とＣ，Ｎ、転位、空孔と
の相互作用により、鉄炭化物、鉄窒化物、鉄炭窒化物の
溶解、粗大化を遅らしたり、ベイナイトやマルテンサイ
トからの炭化物の析出や転位の回復を抑制し、ベイナイ
トやマルテンサイトの軟化を遅らせるからだと思われ
る。It was also found that this effect is proportional to the square root of the concentration of the contained element. Although the mechanism is not clear, the interaction of these elements with C, N, dislocations, and vacancies delays the dissolution and coarsening of iron carbide, iron nitride, and iron carbonitride, and prevents the formation of bainite or martensite. Presumably, this suppresses the precipitation of carbides from sites and the recovery of dislocations, and delays the softening of bainite and martensite.
【００３４】また、さらに本発明の重要な点は、鋼の組
織を限定し、鋼の強度のうち軟化しない強度分と鋼の軟
化を遅らせる元素量を上手くバランスさせることによ
り、成形性向上熱処理にすぐれた鋼板を実現したことで
ある。すなわち、Ｋ値とＹ値の比が０．７７以上となる
とき、短時間熱処理で鋼の強度を５％変化させる事に成
功した。Further, an important point of the present invention is that the structure of the steel is limited, and the balance between the strength of the steel that does not soften and the amount of the element that delays the softening of the steel is well-balanced. It is the realization of an excellent steel plate. That is, when the ratio between the K value and the Y value is 0.77 or more, the strength of the steel was successfully changed by 5% by a short-time heat treatment.
【００３５】この事を式で表現した場合、 Ｋ／Ｙ≧０．７７、 K=｛TS(MPa)-(280+390*C+98*Si+65*Mn+882*P+207*Al+98
0*Ti+2000*Nb+980*V+200*Mo+38*Ni+55*Cu+22*Cr)｝、 Y=｛30* √Si+40*√Mn+80*√Mo+4* √Ni+35*√Nb+40*√
Ti+55*√V+40* √Cr+70*√P+500*√B ｝、 の範囲であるとき、成形性向上熱処理に優れた鋼板とす
る事ができる。図２に上記説明の概念図をしめす。When this is expressed by an equation, K / Y ≧ 0.77, K = ｛TS (MPa) − (280 + 390 * C + 98 * Si + 65 * Mn + 882 * P + 207 * Al +98
0 * Ti + 2000 * Nb + 980 * V + 200 * Mo + 38 * Ni + 55 * Cu + 22 * Cr)｝, Y = ｛30 * √Si + 40 * √Mn + 80 * √Mo + 4 * √Ni + 35 * √Nb + 40 * √
When it is in the range of Ti + 55 * 40V + 40 * √Cr + 70 * √P + 500 * √B｝, it is possible to obtain a steel sheet excellent in heat treatment for improving formability. FIG. 2 shows a conceptual diagram of the above description.
【００３６】また、種々の濃度の鋼を用い、短時間熱処
理を行ったときの鋼板の強度の低下比を図３に示す。強
度測定は、ＪＩＳ５号引張試験片を作成し、４００℃で
３０秒の熱処理を行った後、室温まで冷却し、その後室
温で引張試験を行った。この時の引張試験強度の低下量
（ΔＴＳ）を熱処理前のＴＳで割った値を強度低下比と
して示した。FIG. 3 shows the reduction ratio of the strength of the steel sheet when heat treatment was performed for a short time using steels of various concentrations. For strength measurement, a JIS No. 5 tensile test piece was prepared, heat-treated at 400 ° C. for 30 seconds, cooled to room temperature, and then subjected to a tensile test at room temperature. The value obtained by dividing the amount of decrease in the tensile test strength (ΔTS) at this time by TS before the heat treatment was shown as a strength decrease ratio.
【００３７】図３より、Ｋ／Ｙが０．７７を下回ると、
効果が殆ど認められず、０．７７以上で５％以上の鋼板
の強度低下が得られることが分かる。本発明法によって
得られる成形性向上熱処理能に優れた加工用薄鋼板と
は、上記組織、組成を満たすものならば、熱延鋼板、冷
延鋼板、溶融亜鉛めっき鋼板、合金化溶融亜鉛めっき鋼
板、電気亜鉛めっき鋼板でもかまわない。According to FIG. 3, when K / Y falls below 0.77,
The effect is hardly recognized, and it can be seen that the strength of the steel sheet is reduced by 5% or more at 0.77 or more. The thin steel sheet for processing obtained by the method of the present invention, which has excellent formability and heat treatment ability, is a hot-rolled steel sheet, a cold-rolled steel sheet, a hot-dip galvanized steel sheet, a galvannealed steel sheet if it satisfies the above structure and composition. Alternatively, an electrogalvanized steel sheet may be used.
【００３８】亜鉛めっき鋼板の場合、亜鉛めっき層の劣
化を防ぐため、５５０℃以下の温度で成形性向上熱処理
を施すことが必要であるが、本発明法によってえられる
鋼板を用いれば、十分可能である。また、板厚も限定さ
れるものではないが、０．４〜６mmで特に有効である。
本発明法で得られた鋼板をプレス成形するにあたって
は、鋼板を部品形状に合わせてブランキングを行ない、
成形前にプレスで加工の厳しいところに局部的に成形性
向上熱処理を施す。熱処理は部分的であるが、鋼板全体
の成形性は著しく向上し、複雑な形状の高強度プレス成
形体を得る事ができる。In the case of a galvanized steel sheet, it is necessary to perform a heat treatment for improving formability at a temperature of 550 ° C. or less in order to prevent deterioration of the galvanized layer, but using a steel sheet obtained by the method of the present invention is sufficiently possible. It is. The thickness is not particularly limited, but is particularly effective at 0.4 to 6 mm.
In press-forming the steel sheet obtained by the method of the present invention, the steel sheet is blanked according to the part shape,
Before forming, heat treatment for improving formability is locally applied to places where processing is severe with a press. Although the heat treatment is partial, the formability of the entire steel sheet is significantly improved, and a high-strength press-formed body having a complicated shape can be obtained.
【００３９】次に部分軟化加工用薄鋼板の製造法につい
て述べる。本発明で得られた鋼板は、プレス成形前でな
く、事前に部品に合わせたパターンで成形性向上熱処理
を施して鋼板を部分的に軟化させ、鋼板面内に二次元的
に１mm2 以上の単位でパターン化された軟質部と硬質部
を作ることができる。この部分軟化鋼板の製造方法は、
本発明法によって得られた鋼板に、Ａｃｌ点以下３０se
c 以内の局部的な熱処理を施して局部的に軟質化させる
事にある。あらかじめ部品形状にあわせて必要部位を軟
質化しておくと、部品形状に鋼板を切り出した後、個別
に成形性向上熱処理をする必要がないので、部品の部分
熱処理製造工程を減らす事ができ、特殊なプレス製造設
備が要らず、通常設備で複雑な形状の高強度プレス成形
体を得る事ができる。Next, a method of manufacturing a thin steel sheet for partial softening will be described. The steel sheet obtained by the present invention is not subjected to press forming, but is subjected to a heat treatment for improving formability in a pattern according to a part in advance to partially soften the steel sheet, and two-dimensionally more than 1 mm 2 in the steel sheet surface. Soft parts and hard parts patterned in units can be produced. The manufacturing method of this partially softened steel sheet is
The steel sheet obtained by the method of the present invention has an Acl point of 30
(c) Local heat treatment is performed to soften locally. If the necessary parts are softened in advance according to the shape of the part, it is not necessary to individually heat the formability after cutting the steel sheet into the part shape. No complicated press manufacturing equipment is required, and a high-strength press formed body having a complicated shape can be obtained with ordinary equipment.
【００４０】局部的な熱処理はＡｃｌ点以下３０sec で
行う。熱処理温度は、高ければ高いほど、鋼板強度は低
下して軟質化するが、温度をＡｃｌ変態点以上に上げる
と変態歪みにより鋼板の形状が著しく悪化するので、Ａ
ｃｌ変態点上限とする。また、亜鉛めっき鋼板を熱処理
する際には熱処理を施してからめっきを施すか、めっき
後に局所的な熱処理を施す。熱処理を施してから亜鉛め
っきを施す場合には、鋼板が軟質化しない低温で溶融め
っきを施すか、または、電気めっきを施して鋼板強度が
変化しないように配慮する必要がある。また亜鉛めっき
を施してから、局部熱処理する場合には、亜鉛めっきが
変質しない５５０℃以下の熱処理を施す事が、望まし
い。また、熱処理時間は、長ければ長いほど、鋼板強度
は低下して軟質化するが、熱伝導により軟質にしたい所
以外にも熱が伝わり、軟質化し、硬質部と軟質部のパタ
ーン化の精度が著しく悪くなるので、３０sec 以内の熱
処理とする。The local heat treatment is performed within 30 seconds below the Acl point. The higher the heat treatment temperature, the lower the steel sheet strength and soften, but if the temperature is raised above the Acl transformation point, the shape of the steel sheet is significantly deteriorated by the transformation strain.
cl transformation point upper limit. When heat-treating a galvanized steel sheet, heat treatment is performed before plating, or local heat treatment is performed after plating. When galvanizing is performed after heat treatment, it is necessary to apply hot-dip galvanizing at a low temperature at which the steel sheet does not soften or to perform electroplating so that the strength of the steel sheet does not change. When performing local heat treatment after zinc plating, it is preferable to perform heat treatment at 550 ° C. or less where the zinc plating does not deteriorate. In addition, the longer the heat treatment time, the lower the steel sheet strength and softens as the heat treatment time increases.However, heat is transmitted to places other than the place where softening is desired by heat conduction, the heat is softened, and the patterning accuracy of the hard part and the soft part is improved. The heat treatment is performed for 30 seconds or less because the temperature becomes extremely bad.
【００４１】図４にパターン例をしめす。本発明の部分
軟化鋼板の製造法は、このパターン例に限定されること
なく部品形状に合わせたパターン化をする事が出来る。FIG. 4 shows an example of a pattern. The method for manufacturing a partially softened steel sheet according to the present invention is not limited to this pattern example, but can be patterned according to the component shape.
【００４２】[0042]
【実施例】実施例１ 以下に、本発明を実施例に基づいて具体的に説明する。
表１に示す成分の鋼を溶製し、常法に従い連続鋳造でス
ラブとした。そして、加熱炉中で１２００℃まで加熱
し、８８０℃の仕上げ温度で、熱間圧延を行い、５００
℃の温度で巻取り、ついで、酸洗を施し熱延鋼板とし
た。Embodiment 1 The present invention will be specifically described below based on embodiments.
Steels having the components shown in Table 1 were melted and continuously cast into slabs according to a conventional method. Then, it is heated to 1200 ° C. in a heating furnace, hot-rolled at a finishing temperature of 880 ° C., and
It was wound at a temperature of ° C and then pickled to obtain a hot-rolled steel sheet.
【００４３】更に、６０％の圧下率で冷間圧延を行った
後、８３０℃×６０秒の再結晶焼鈍を行い、７００℃ま
で徐冷し、その後１００℃／sec の冷却速度、２５０℃
の温度まで冷却し、１．２mmの冷延鋼板となした。この
とき得られた鋼の組織を表１に併記する。また、一部は
電気亜鉛めっきを施し、鋼板の表層に亜鉛層を付与し
た。Further, after cold rolling was performed at a rolling reduction of 60%, recrystallization annealing was performed at 830 ° C. × 60 seconds, and gradually cooled to 700 ° C., and then at a cooling rate of 100 ° C./sec, 250 ° C.
To a cold rolled steel sheet of 1.2 mm. Table 1 also shows the steel structure obtained at this time. In addition, a part was electrogalvanized to provide a zinc layer on the surface layer of the steel sheet.
【００４４】得られた冷延鋼板をＪＩＳ５号引張試験片
に加工し、機械的特性値（熱処理なし）の評価を行っ
た。また、別途、ＪＩＳ５号引張試験片を作成し、４５
０℃×１０sec の熱処理を行い、機械的特性値（熱処理
あり）の評価を行った。また、別途、該鋼板を９０ψ〜
１２０ψの円盤に打ち抜き、２５℃に保たれた５０ψの
円筒ポンチ、内径５４ψのダイスを用い深絞り成形を行
った。しわ押さえ圧を変え、深絞り成形が可能な限界絞
り比を求めた。一部の円盤はフランジ相当部を短時間熱
処理する目的で、４５０℃に加熱された内径６０ψのダ
イスで円盤の周辺部を挟み込んで軟質化し、図５に示す
ような局部的に材料強度の変化した円盤を作成した。そ
の後、熱処理無しの円盤と同様に、２５℃に保たれた５
０ψの円筒ポンチ、内径５４ψのダイスを用い深絞り成
形を行った。The obtained cold-rolled steel sheet was processed into a JIS No. 5 tensile test piece, and the mechanical properties (without heat treatment) were evaluated. Separately, a JIS No. 5 tensile test piece was created and 45
Heat treatment was performed at 0 ° C. × 10 sec, and the mechanical property values (with heat treatment) were evaluated. Separately, the steel sheet is 90 ° ~
The sheet was punched into a 120 ° disk, and deep drawing was performed using a 50 ° cylindrical punch kept at 25 ° C. and a die having an inner diameter of 54 °. By changing the wrinkle holding pressure, the limit drawing ratio at which deep drawing was possible was determined. Some disks are softened by sandwiching the periphery of the disk with a 60 ° inner diameter die heated to 450 ° C for the purpose of heat-treating the flange-equivalent portion for a short period of time. Created a disc. After that, as in the case of the disk without heat treatment, 5
Deep drawing was performed using a 0 ° cylindrical punch and a 54 ° inner diameter die.
【００４５】以上の結果を表１に併記する。表１から明
らかなように、本発明によって得られた鋼板を用いれ
ば、短時間熱処理で材料強度を５％以上軟質にする事が
でき、成形性向上熱処理を行ったとき、成形性を向上さ
せる事ができる。 実施例２ 以下に、本発明を実施例に基づいて具体的に説明する。The above results are also shown in Table 1. As is clear from Table 1, when the steel sheet obtained according to the present invention is used, the material strength can be softened by 5% or more in a short time heat treatment, and the formability is improved when the formability improvement heat treatment is performed. Can do things. Example 2 Hereinafter, the present invention will be specifically described based on examples.
【００４６】表２に示す成分の鋼を溶製し、常法に従い
連続鋳造でスラブとした。そして、加熱炉中で１２００
℃まで加熱し、８８０℃の仕上げ温度で、熱間圧延を行
い、表２に示す冷却開始温度、冷却速度、冷却終点温度
で冷却を行い、巻取り、ついで、酸洗を施し熱延鋼板と
した。また別途、更に、６０％の圧下率で冷間圧延を行
った後、８３０℃×６０秒の再結晶焼鈍を行い、徐冷
し、その後表３に示す冷却開始温度、冷却速度、冷却終
点温度まで冷却し、冷延鋼板となした。Steels having the components shown in Table 2 were melted and continuously cast into slabs according to a conventional method. Then, in a heating furnace, 1200
C., hot-rolled at a finishing temperature of 880 ° C., cooled at a cooling start temperature, a cooling rate, and a cooling end point temperature shown in Table 2, wound up, and then subjected to pickling to form a hot-rolled steel sheet. did. Separately, after further performing cold rolling at a rolling reduction of 60%, performing recrystallization annealing at 830 ° C. × 60 seconds, gradually cooling, and thereafter, a cooling start temperature, a cooling rate, and a cooling end point temperature shown in Table 3. And cooled to a cold rolled steel sheet.
【００４７】得られた熱延鋼板、冷延鋼板のミクロ組織
のうち鉄炭化物、鉄窒化物、鉄炭窒化物の１種または２
種以上の合計の割合が１０個／μｍ2 以上含まれる結晶
粒、ベイナイト、マルテンサイトの合計の体積分率を表
３に示す。本発明法で鉄炭化物、鉄窒化物、鉄炭窒化物
の１種または２種以上の合計の割合が１０個／μｍ2 以
上含まれる結晶粒、ベイナイト、マルテンサイトの合計
の体積分率が７％以上である鋼板を得られることが分か
る。One or two of iron carbide, iron nitride and iron carbonitride in the microstructure of the obtained hot rolled steel sheet and cold rolled steel sheet.
Table 3 shows the total volume fraction of crystal grains, bainite, and martensite having a total ratio of 10 or more seeds / μm 2 or more. In the method of the present invention, the total volume fraction of crystal grains, bainite, and martensite containing 10 or more μm 2 or more of one or more of iron carbide, iron nitride, and iron carbonitride is 7 % Can be obtained.
【００４８】また得られた熱延鋼板、冷延鋼板をＪＩＳ
５号引張試験片に加工し、機械的特性値（熱処理なし）
の評価を行った。また、別途、ＪＩＳ５号引張試験片を
作成し、４５０℃×１０sec の熱処理を行い、機械的特
性値（熱処理あり）の評価を行った。また、別途、該鋼
板を９０ψ〜１２０ψの円盤に打ち抜き、２５℃に保た
れた５０ψの円筒ポンチ、内径５４ψのダイスを用い深
絞り成形を行った。しわ押さえ圧を変え、深絞り成形が
可能な限界絞り比を求めた。一部の円盤はフランジ相当
部を短時間熱処理する目的で、４５０℃に加熱された内
径６０ψのダイスで円盤の周辺部を挟み込んで軟質化
し、図５に示すような局部的に材料強度の変化した円盤
を作成した。その後、熱処理無しの円盤と同様に、２５
℃に保たれた５０ψの円筒ポンチ、内径５４ψのダイス
を用い深絞り成形を行った。Further, the obtained hot-rolled steel sheet and cold-rolled steel sheet were subjected to JIS.
Processed into No. 5 tensile test piece, mechanical property value (no heat treatment)
Was evaluated. Separately, a JIS No. 5 tensile test piece was prepared, heat-treated at 450 ° C. × 10 sec, and mechanical property values (with heat treatment) were evaluated. Separately, the steel sheet was punched into a 90 ° to 120 ° disk, and deep drawing was performed using a 50 ° cylindrical punch maintained at 25 ° C. and a 54 ° inner diameter die. By changing the wrinkle holding pressure, the limit drawing ratio at which deep drawing was possible was determined. Some disks are softened by sandwiching the periphery of the disk with a 60 ° inner diameter die heated to 450 ° C for the purpose of heat-treating the flange-equivalent portion for a short period of time. Created a disc. Then, as with the disc without heat treatment, 25
Deep drawing was performed using a 50 ° cylindrical punch maintained at a temperature of 50 ° C. and a 54 ° inner diameter die.
【００４９】以上の結果を表２に併記する。表３から明
らかなように、本発明法を用いれば、鉄炭化物、鉄窒化
物、鉄炭窒化物の１種または２種以上の合計の割合が１
０個／μｍ2 以上含まれる結晶粒、ベイナイト、マルテ
ンサイトの合計の体積分率が７％以上であり、短時間熱
処理で材料強度を５％以上軟質にする事ができ、成形性
向上熱処理を行ったとき、成形性を向上させる事ができ
る鋼板を製造する事ができる。The above results are also shown in Table 2. As is clear from Table 3, when the method of the present invention is used, the ratio of one or more of iron carbide, iron nitride and iron carbonitride is 1
The total volume fraction of crystal grains, bainite, and martensite containing 0 grains / μm 2 or more is 7% or more, and the material strength can be softened by 5% or more by short-time heat treatment. When performed, it is possible to produce a steel sheet capable of improving formability.
【００５０】[0050]
【表１】 [Table 1]
【００５１】[0051]
【表２】 [Table 2]
【００５２】[0052]
【表３】 [Table 3]
【００５３】[0053]
【表４】 [Table 4]
【００５４】[0054]
【表５】 [Table 5]
【図１】鉄炭化物、鉄窒化物、鉄炭窒化物の１種または
２種以上の合計の割合が１０個／μｍ2 以上含まれる結
晶粒、ベイナイト、マルテンサイトの合計の体積分率と
鋼板強度の低下比（ΔＴＳ／ＴＳ）の関係を説明する概
念図である。FIG. 1 shows the total volume fraction of steel grains, bainite, and martensite containing 10 or more μm 2 or more of one or more of iron carbide, iron nitride, and iron carbonitride, and a steel sheet. It is a conceptual diagram explaining the relationship of the intensity reduction ratio ((DELTA) TS / TS).
【図２】鋼板強度、Ｋ値、Ｙ値、熱処理により可能な強
度の低下量の関係を説明する概念図である。FIG. 2 is a conceptual diagram illustrating a relationship among a steel sheet strength, a K value, a Y value, and a decrease in strength that can be performed by heat treatment.
【図３】Ｋ値、Ｙ値の比（Ｋ／Ｙ）と４００℃×３０se
c の熱処理による鋼板の強度低下比（ΔＴＳ／ＴＳ）を
示す図である。[FIG. 3] Ratio of K value and Y value (K / Y) and 400 ° C. × 30se
It is a figure which shows the intensity | strength reduction ratio ((DELTA) TS / TS) of a steel plate by heat processing of c.
【図４】部分軟化鋼板の軟質部硬質部のパターン例を示
す図である。FIG. 4 is a diagram showing an example of a pattern of a soft portion and a hard portion of a partially softened steel sheet.
【図５】円盤状鋼板を局部加熱する装置と局部加熱され
た円盤を示す図である。FIG. 5 is a diagram showing an apparatus for locally heating a disk-shaped steel plate and a disk that has been locally heated.
１…部分軟化鋼板 ２…ブランク（切り板） ３…プレス部品 ４…側面から見た４５０℃に加熱したダイス ５…側面から見た円盤状の鋼板 ６…上から見た円盤の未加熱部 ７…上から見た円盤の加熱部 Ａ…軟質部 Ｂ…硬質部 DESCRIPTION OF SYMBOLS 1 ... Partially softened steel plate 2 ... Blank (cut plate) 3 ... Pressed part 4 ... Die heated to 450 degreeC seen from the side 5 ... Disk-shaped steel plate seen from the side 6 ... Unheated part of the disk seen from the top 7 … Heating part of disk as seen from above A… Soft part B… Hard part
─────────────────────────────────────────────────────
────────────────────────────────────────────────── ───
【手続補正書】[Procedure amendment]
【提出日】平成１０年１２月１７日（１９９８．１２．
１７）[Submission date] December 17, 1998 (1998.12.
17)
【手続補正１】[Procedure amendment 1]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】請求項１[Correction target item name] Claim 1
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【手続補正２】[Procedure amendment 2]
【補正対象書類名】明細書[Document name to be amended] Statement
【補正対象項目名】０００９[Correction target item name] 0009
【補正方法】変更[Correction method] Change
【補正内容】[Correction contents]
【０００９】その要旨は、（１）重量比で Ｃ：０．０００５％〜０．２５％ Ｓｉ：０．０１％〜３．０％ Ｍｎ：０．０１％〜３．０％ Ｐ：０．００２％〜０．２０％ Ｓ：０．００１％〜０．０３％ Ｎ：０．０００２％〜０．０２％ を含有する鋼において、さらに、Ｍｏ，Ａｌ，Ｎｉ，Ｃ
ｕ，Ｎｂ，Ｔｉ，Ｖ，Ｃｒ，Ｂの１種または２種以上を
重量％で、 Ｋ／Ｙ≧０．７７、 K=｛TS(MPa)-(280+390*C+98*Si+65*Mn+882*P+207*A1+98
0*Ti+2000*Nb+980*V+200*Mo+38*Ni+55*Cu+22*Cr)｝、 Y=｛30* √Si+40*√Mn+80*√Mo+4* √Ni+35*√Nb+40*√
Ti+55*√V+40* √Cr+70*√P+500*√B ｝、 の範囲で含有した鋼に、熱延を施すに際し、圧延終了
後、６５０℃以上７７０℃以下の温度から２０℃／sec
以上の速さで３００℃以下まで冷却を施して、鋼のミク
ロ組織のうち、鉄炭化物、鉄窒化物、鉄炭窒化物の１種
または２種以上の合計の割合が１０個／μｍ2 以上含ま
れる結晶粒が、占積率で７％以上とする成形性向上熱処
理能に優れた加工用熱延鋼板の製造方法、（２）（１）
に記載の成分を有する鋼に、熱延を施すに際し、圧延終
了後、（Ａｒｌ＋２０) ℃以上の温度から２０℃／sec
以上の速さで３００℃以下まで冷却を施して、鋼のミク
ロ組織のうち、ベイナイト、マルテンサイト、の１種ま
たは２種以上の合計の割合が、占積率で７％以上とする
成形性向上熱処理能に優れた加工用熱延鋼板の製造方
法、（３）（１）に記載の成分を有する鋼に、熱延、脱
スケール処理、冷延を施し、ついで冷延鋼板に連続焼鈍
後冷却を施すに際し、６５０℃以上７７０℃以下の温度
から２０℃／sec 以上の速さで３００℃以下まで冷却を
施し、更に過時効処理を施さないか、または３００℃以
下の過時効処理を施して、鋼のミクロ組織のうち、鉄炭
化物、鉄窒化物、鉄炭窒化物の１種または２種以上の合
計の割合が１０個／μｍ2 以上含まれる結晶粒が、占積
率で７％以上とする成形性向上熱処理能に優れた加工用
冷延鋼板の製造方法、（４）（１）に記載の成分を有す
る鋼に、熱延、脱スケール処理、冷延を施し、ついで冷
延鋼板に連続焼鈍後冷却を施すに際し、（Ａｒｌ＋２
０) ℃以上の温度から２０℃／sec 以上の速さで３００
℃以下まで冷却を施し、更に過時効処理を施さないか、
または３００℃以下の過時効処理を施して、鋼のミクロ
組織のうち、ベイナイト、マルテンサイト、の１種また
は２種以上の合計の割合が、占積率で７％以上とする成
形性向上熱処理能に優れた加工用冷延鋼板の製造方法、
及び（５）（１）に記載の成分を含有し、さらに、鋼の
ミクロ組織のうち、鉄炭化物、鉄窒化物、鉄炭窒化物の
１種または２種以上の合計の割合が１０個／μｍ2 以上
含まれる結晶粒、ベイナイト、マルテンサイト、の１種
または２種以上の合計の割合が、占積率で７％以上であ
る鋼板に、Ａｃｌ点以下３０sec 以内の局部的な熱処理
を施して局部的に軟質化させる事を特徴とする部分軟化
加工用薄鋼板の製造方法、である。The gist is as follows: (1) C: 0.0005% to 0.25% Si: 0.01% to 3.0% Mn: 0.01% to 3.0% P: 0. 002% to 0.20% S: 0.001% to 0.03% N: 0.0002% to 0.02% In the steel containing Mo, Al, Ni, C
One or more of u, Nb, Ti, V, Cr, and B are expressed in terms of% by weight, and K / Y ≧ 0.77, K = MPTS (MPa) − (280 + 390 * C + 98 * Si + 65 * Mn + 882 * P + 207 * A1 + 98
0 * Ti + 2000 * Nb + 980 * V + 200 * Mo + 38 * Ni + 55 * Cu + 22 * Cr)｝, Y = ｛30 * √Si + 40 * √Mn + 80 * √Mo + 4 * √Ni + 35 * √Nb + 40 * √
When hot rolling is performed on steel containing Ti + 55 * + V + 40 * √Cr + 70 * √P + 500 * √B｝, from the temperature of 650 ° C or more and 770 ° C or less after rolling is completed. 20 ° C / sec
The steel is cooled to 300 ° C. or less at the above speed, and the total ratio of one or more of iron carbide, iron nitride, and iron carbonitride in the microstructure of the steel is 10 pieces / μm 2 or more. (2) (1) A method for producing a hot-rolled steel sheet for processing excellent in formability improvement and heat treatment ability in which the contained crystal grains are 7% or more in space factor.
When hot rolling is performed on steel having the components described in (1), after rolling is completed, a temperature of (Arl + 20) ° C. or higher and 20 ° C./sec.
Cooling to 300 ° C or lower at the above speed to form a steel microstructure in which the total ratio of one or more of bainite and martensite is 7% or more in space factor. (3) A method for producing a hot-rolled steel sheet for processing having excellent heat treatment ability, (3) subjecting the steel having the components described in (1) to hot-rolling, descaling treatment, and cold-rolling, and then continuously annealing the cold-rolled steel sheet At the time of cooling, it is cooled from a temperature of 650 ° C. to 770 ° C. to 300 ° C. or less at a speed of 20 ° C./sec or more, and is not further overaged, or is overaged at 300 ° C. or less. In the steel microstructure, crystal grains containing at least 10 / μm 2 or more in total of one or more of iron carbide, iron nitride, and iron carbonitride at a space factor of 7% Method for producing a cold-rolled steel sheet for processing excellent in formability improvement heat treatment ability as described above, The steel having the components described in 4) (1), hot-rolling, descaling, when subjected to cold rolling, then subjected to continuous annealing after cooling to cold rolled steel sheet, (Arl + 2
0) 300 ° C at a rate of 20 ° C / sec or more from a temperature of
Cool down to below ℃ and do not further overage
Or, heat treatment for improving formability is performed by performing an overaging treatment at a temperature of 300 ° C. or less so that the total ratio of one or more of bainite and martensite in the steel microstructure is 7% or more in space factor. Manufacturing method of cold rolled steel sheet for processing with excellent performance,
And (5) the composition according to (1), further comprising, in the microstructure of the steel, a total ratio of one or more of iron carbide, iron nitride, and iron carbonitride is 10 / A steel sheet in which one or more of the crystal grains, bainite, and martensite contained in μm 2 or more have a space factor of 7% or more is subjected to local heat treatment within 30 seconds or less from the Acl point. A method for producing a thin steel sheet for partial softening, characterized by locally softening the steel sheet.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 岡本 力 愛知県東海市東海町５−３ 新日本製鐵株 式会社名古屋製鐵所内 (72)発明者 山崎 一正 愛知県東海市東海町５−３ 新日本製鐵株 式会社名古屋製鐵所内 Ｆターム(参考） 4K037 EA02 EA04 EA05 EA06 EA12 EA15 EA16 EA17 EA18 EA19 EA23 EA25 EA27 EA28 EA31 EA32 EB02 EB06 EB09 FA02 FC04 FD03 FD04 FE01 FJ04 FJ05 FK03 FL01 JA01 JA07 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Riki Okamoto 5-3 Tokai-cho, Tokai-city, Aichi Prefecture Inside Nippon Steel Corporation Nagoya Works (72) Inventor Kazumasa Yamazaki 5--Tokai-cho, Tokai-city, Aichi Prefecture 3 F-term in Nagoya Works, Nippon Steel Corporation (reference) 4K037 EA02 EA04 EA05 EA06 EA12 EA15 EA16 EA17 EA18 EA19 EA23 EA25 EA27 EA28 EA31 EA32 EB02 EB06 EB09 FA02 FC04 FD01 FE01 F03 FL04
Claims (5)
Ｖ，Ｃｒ，Ｂの１種または２種以上を重量％で、 Ｋ／Ｙ≧０．７７、 K=｛TS(MPa)-(280+390*C+98*Si+65*Mn+882*P+207*A1+98
0*Ti+2000*Nb+980*V+200*Mo+38*Ni+55*Cu+22*Cr)｝、 Y=｛30* √Si+40*√Mn+80*√Mo+4* √Ni+35*√Nb+40*√
Ti+55*√V+40* √Cr+70*√P+500*√B ｝、 の範囲で含有した鋼に、熱延を施すに際し、圧延終了
後、６５０℃以上７７０℃以下の温度から２０℃／sec
以上の速さで３００℃以下まで冷却を施して、鋼のミク
ロ組織のうち、鉄炭化物、鉄窒化物、鉄炭窒化物の１種
または２種以上の合計の割合が１０個／μｍ2 以上含ま
れる結晶粒が、占積率で７％以上とする成形性向上熱処
理能に優れた加工用熱延鋼板の製造方法。1. Weight ratio of C: 0.0005% to 0.25% Si: 0.01% to 3.0% Mn: 0.01% to 3.0% P: 0.002% to 0.3% 20% S: 0.001% to 0.03% N: 0.0002% to 0.02% In the steel containing Mo, Nb, Ti,
K / Y ≧ 0.77, K = ＢTS (MPa) − (280 + 390 * C + 98 * Si + 65 * Mn + 882 *) P + 207 * A1 + 98
0 * Ti + 2000 * Nb + 980 * V + 200 * Mo + 38 * Ni + 55 * Cu + 22 * Cr)｝, Y = ｛30 * √Si + 40 * √Mn + 80 * √Mo + 4 * √Ni + 35 * √Nb + 40 * √
When hot rolling is performed on steel containing Ti + 55 * + V + 40 * √Cr + 70 * √P + 500 * √B｝, from the temperature of 650 ° C or more and 770 ° C or less after rolling is completed. 20 ° C / sec
The steel is cooled to 300 ° C. or less at the above speed, and the total ratio of one or more of iron carbide, iron nitride, and iron carbonitride in the microstructure of the steel is 10 pieces / μm 2 or more. A method for producing a hot-rolled steel sheet for processing excellent in formability improving heat treatment ability in which the contained crystal grains have a space factor of 7% or more.
延を施すに際し、圧延終了後、（Ａｒｌ＋２０) ℃以上
の温度から２０℃／sec 以上の速さで３００℃以下まで
冷却を施して、鋼のミクロ組織のうち、ベイナイト、マ
ルテンサイト、の１種または２種以上の合計の割合が、
占積率で７％以上とする成形性向上熱処理能に優れた加
工用熱延鋼板の製造方法。2. When hot rolling is performed on steel having the composition described in claim 1, after completion of rolling, the steel is cooled from a temperature of (Arl + 20) ° C. or more to 300 ° C. or less at a speed of 20 ° C./sec or more. The ratio of the total of one or more of bainite and martensite in the microstructure of the steel,
A method for producing a hot-rolled steel sheet for processing excellent in formability improvement heat treatment ability with an occupation ratio of 7% or more.
延、脱スケール処理、冷延を施し、ついで冷延鋼板に連
続焼鈍後冷却を施すに際し、６５０℃以上７７０℃以下
の温度から２０℃／sec 以上の速さで３００℃以下まで
冷却を施し、更に過時効処理を施さないか、または３０
０℃以下の過時効処理を施して、鋼のミクロ組織のう
ち、鉄炭化物、鉄窒化物、鉄炭窒化物の１種または２種
以上の合計の割合が１０個／μｍ2 以上含まれる結晶粒
が、占積率で７％以上とする成形性向上熱処理能に優れ
た加工用冷延鋼板の製造方法。3. A steel having the composition according to claim 1, which is subjected to hot rolling, descaling treatment, and cold rolling, and then to continuous cold annealing of the cold rolled steel sheet, followed by cooling at a temperature of 650 ° C. or more and 770 ° C. or less. From 20 ° C / sec to 300 ° C or lower, and no further overaging treatment or 30 ° C
A crystal that has been subjected to overage treatment at 0 ° C. or less to contain at least 10 / μm 2 or more of a total of one or more of iron carbide, iron nitride, and iron carbonitride in the microstructure of steel. A method for producing a cold-rolled steel sheet for processing having excellent formability improvement heat treatment ability in which grains have an occupying ratio of 7% or more.
延、脱スケール処理、冷延を施し、ついで冷延鋼板に連
続焼鈍後冷却を施すに際し、（Ａｒｌ＋２０) ℃以上の
温度から２０℃／sec 以上の速さで３００℃以下まで冷
却を施し、更に過時効処理を施さないか、または３００
℃以下の過時効処理を施して、鋼のミクロ組織のうち、
ベイナイト、マルテンサイト、の１種または２種以上の
合計の割合が、占積率で７％以上とする成形性向上熱処
理能に優れた加工用冷延鋼板の製造方法。4. A steel having the composition according to claim 1, which is subjected to hot rolling, descaling, and cold rolling, and then to continuous annealing of the cold-rolled steel sheet, followed by cooling at a temperature of (A1 + 20) ° C. or higher. Cool to 300 ° C or less at a speed of 20 ° C / sec or more, and do not further overage, or
Under the aging treatment below ℃, of the steel microstructure,
A method for producing a cold-rolled steel sheet for processing excellent in formability improving heat treatment ability in which the total ratio of one or more of bainite and martensite is 7% or more in space factor.
に、鋼のミクロ組織のうち、鉄炭化物、鉄窒化物、鉄炭
窒化物の１種または２種以上の合計の割合が１０個／μ
ｍ2 以上含まれる結晶粒、ベイナイト、マルテンサイ
ト、の１種または２種以上の合計の割合が、占積率で７
％以上である鋼板に、Ａｃｌ点以下３０sec 以内の局部
的な熱処理を施して局部的に軟質化させる事を特徴とす
る部分軟化加工用薄鋼板の製造方法。5. The steel according to claim 1, further comprising at least one of iron carbide, iron nitride and iron carbonitride in a microstructure of the steel. / Μ
The ratio of one or more of the crystal grains, bainite and martensite contained in m 2 or more is 7 in space factor.
% Of the steel sheet having a percentage of not less than Acl point and a local heat treatment within 30 seconds of the Acl point to locally soften the steel sheet.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24975198A JP3993703B2 (en) | 1998-09-03 | 1998-09-03 | Manufacturing method of thin steel sheet for processing |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24975198A JP3993703B2 (en) | 1998-09-03 | 1998-09-03 | Manufacturing method of thin steel sheet for processing |
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| Publication Number | Publication Date |
|---|---|
| JP2000080418A true JP2000080418A (en) | 2000-03-21 |
| JP3993703B2 JP3993703B2 (en) | 2007-10-17 |
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ID=17197690
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|---|---|---|---|
| JP24975198A Expired - Fee Related JP3993703B2 (en) | 1998-09-03 | 1998-09-03 | Manufacturing method of thin steel sheet for processing |
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| Country | Link |
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| JP (1) | JP3993703B2 (en) |
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