JPH11193418A - Manufacture of high strength cold rolled steel sheet excellent in flatness characteristic - Google Patents
Manufacture of high strength cold rolled steel sheet excellent in flatness characteristicInfo
- Publication number
- JPH11193418A JPH11193418A JP9369318A JP36931897A JPH11193418A JP H11193418 A JPH11193418 A JP H11193418A JP 9369318 A JP9369318 A JP 9369318A JP 36931897 A JP36931897 A JP 36931897A JP H11193418 A JPH11193418 A JP H11193418A
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- Japan
- Prior art keywords
- steel sheet
- strength cold
- rolled steel
- pressure
- annealing
- 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.)
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Abstract
Description
【０００１】[0001]
【発明が属する技術分野】本発明は連続焼鈍工程で、焼
き入れ処理が施される複合組織型の高強度冷延鋼板の製
造方法に関し、特に焼き入れの際に生じる平坦性劣化の
改善に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength cold-rolled steel sheet of a composite structure which is subjected to a quenching treatment in a continuous annealing step, and more particularly to an improvement in flatness deterioration occurring during quenching. It is.
【０００２】[0002]
【従来の技術】近年、例えば、自動車の安全性の向上と
燃費節減のための軽量化要求への高まりを背景として、
高強度冷延鋼板が強度部材として使用されている。特に
安全性の向上を目的とする場合、７８０Ｎ／mm2 を越え
る非常に高い引張強さを有する高強度鋼板が使用される
に及んでいる。もっとも、自動車用鋼板の場合、単に強
度が高ければよいというものではなく、良好な加工性も
要求される。なお、高強度鋼板の場合、加工性は強度と
伸びのバランスで評価され、強度が高く、伸びの大きい
鋼板が好適である。2. Description of the Related Art In recent years, for example, against the background of increasing demand for lighter weight for improving the safety of automobiles and reducing fuel consumption,
High strength cold rolled steel sheets are used as strength members. Particularly for the purpose of improving safety, high-strength steel sheets having a very high tensile strength exceeding 780 N / mm 2 have been used. However, in the case of a steel sheet for an automobile, it is not only that the strength is simply high, but also good workability is required. In the case of a high-strength steel sheet, workability is evaluated based on a balance between strength and elongation, and a steel sheet having high strength and large elongation is preferable.
【０００３】近年、熱間制御圧延技術や連続焼鈍技術の
普及に伴って、焼鈍後に焼き入れを行い、マルテンサイ
トやベイナイトのような硬い低温変態生成物を生成さ
せ、この強化能を利用することで強度−延性バランスに
優れる複合組織型の高強度冷延鋼板が製造されるに至っ
ている。なお、連続焼鈍という場合は、冷間圧延後の再
結晶焼鈍のみならず、その後の焼き入れ処理、過時効処
理（焼戻処理）を含めて連続的に処理する一連の工程を
意味する。In recent years, with the spread of hot controlled rolling technology and continuous annealing technology, quenching is performed after annealing to generate hard low-temperature transformation products such as martensite and bainite, and to utilize this strengthening ability. Thus, a composite structure type high-strength cold-rolled steel sheet excellent in strength-ductility balance has been produced. The term “continuous annealing” means a series of steps of not only recrystallization annealing after cold rolling, but also continuous processing including subsequent quenching and overaging (tempering).
【０００４】このような複合組織型の鋼板を製造する方
法としては、連続焼鈍以外に箱焼鈍による方法がある
が、箱焼鈍の場合は、Ａr1点以上の再結晶温度からの冷
却速度が遅いために、Ｍｎ等のオーステナイト安定化元
素を多量に添加する必要があり、生産効率が劣る上に製
造コスト高を招く。As a method for producing such a composite structure type steel sheet, there is a method using box annealing other than continuous annealing. In the case of box annealing, the cooling rate from the recrystallization temperature of Ar 1 point or more is slow. Therefore, it is necessary to add a large amount of an austenite stabilizing element such as Mn, so that the production efficiency is deteriorated and the production cost is increased.
【０００５】一方、連続焼鈍の場合は、再結晶焼鈍後の
冷却速度を大きくとることができるため、上記のような
オーステナイト安定化元素の添加を低減することができ
る。再結晶焼鈍後の急冷手段としては、水焼き入れ、ロ
ール冷却又は気水冷却を適用することができるが、実用
的には冷却速度が非常に速い水焼き入れが有利である。On the other hand, in the case of continuous annealing, since the cooling rate after recrystallization annealing can be increased, the addition of the austenite stabilizing element as described above can be reduced. As quenching means after recrystallization annealing, water quenching, roll cooling, or steam-water cooling can be applied, but practically, water quenching with a very high cooling rate is advantageous.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、冷間圧
延後の連続焼鈍過程において、焼鈍後の高温の鋼板に焼
き入れを施す際、図３に示すように、鋼板の板幅方向に
円弧状の反りが発生し、鋼板形状の平坦性が劣化する。
特に、冷却速度の非常に速い水焼き入れを行う場合、平
坦性の劣化が著しい。However, in the continuous annealing process after cold rolling, when quenching a hot steel sheet after annealing, as shown in FIG. Warpage occurs and the flatness of the steel sheet shape deteriorates.
In particular, when water quenching with a very high cooling rate is performed, the flatness is significantly deteriorated.
【０００７】平坦性の劣化は加工の際に搬送トラブルを
引き起こす原因となる。特に、加工方法の代表例である
プレス加工においては、複数の工程を順次プレスして加
工する場合が多く、その工程間は機械的に搬送されるこ
とが通例であるため、鋼板形状が悪いと、搬送トラブル
を発生させ、加工効率を著しく低下させる。なお、連続
焼鈍における高温からの急速冷却によるストリップ形状
の劣化防止については、例えば特開平４−２８９１２０
号公報に見られるように、組織制御により改善しようと
いう試みもあるが、十分とは言えないのが現状である。[0007] Deterioration of flatness causes transport trouble during processing. In particular, in press working, which is a typical example of the working method, in many cases, a plurality of steps are sequentially pressed and worked, and it is customary that the steps are mechanically conveyed. In addition, a transfer trouble occurs and the processing efficiency is remarkably reduced. In order to prevent strip shape deterioration due to rapid cooling from a high temperature in continuous annealing, see, for example, Japanese Patent Application Laid-Open No. 4-289120.
As described in Japanese Patent Laid-Open Publication No. H10-107, there is an attempt to improve by organizational control, but at present it is not enough.
【０００８】本発明はかかる問題に鑑みなされたもの
で、焼き入れ工程を伴う連続焼鈍により平坦性に優れた
高強度冷延鋼板を製造する方法を提供するものである。
また、７８０Ｎ／mm2 以上の引張強さを有し、良好な加
工性を備え、かつ平坦性にも優れた高強度冷延鋼板の製
造方法を提供するものである。The present invention has been made in view of such a problem, and provides a method for producing a high-strength cold-rolled steel sheet having excellent flatness by continuous annealing accompanied by a quenching step.
Another object of the present invention is to provide a method for producing a high-strength cold-rolled steel sheet having a tensile strength of 780 N / mm 2 or more, having good workability and excellent flatness.
【０００９】[0009]
【課題を解決するための手段】本発明の高強度冷延鋼板
の製造方法は、冷間圧延後の鋼板を連続焼鈍するに際
し、焼鈍後に焼き入れ、その後過時効処理を行う高強度
冷延鋼板の製造方法において、焼き入れの際に鋼板の表
裏面の少なくとも幅方向の全域に渡って５００Ｎ／ｍ2
以上の圧力で加圧するものである。SUMMARY OF THE INVENTION The method for producing a high-strength cold-rolled steel sheet according to the present invention is a high-strength cold-rolled steel sheet which is subjected to continuous annealing of a cold-rolled steel sheet, then quenched after annealing, and then overaged. The quenching process, at least over the entire width direction of the front and back surfaces of the steel sheet at 500 N / m 2
Pressurization is performed with the above pressure.
【００１０】この発明によれば、焼き入れの際に、鋼板
に５００Ｎ／ｍ2 以上の圧力が付加されるので、焼き入
れの際に変形した鋼板部分が付与された圧力により平坦
状に矯正されるため、鋼板の平坦性が改善される。水焼
き入れの場合、鋼板形状の劣化が他の焼き入れ法に比し
て大きいが、この場合でも形状矯正のための加圧時間は
０．２秒以上あればよい。焼き入れ方法としては、水焼
き入れに限らず、ロール冷却、気水冷却であってもよ
い。水焼き入れの際の鋼板加圧方法は後述するが、ロー
ル冷却の場合には冷却ロールに巻き付けられた鋼板に高
圧ガスを吹き付ける等すればよく、また気水冷却の場合
には冷却水の噴霧媒体として使用するガスを高圧化し、
鋼板の表裏面に対して噴霧状の気水を吹き付ける等すれ
ばよい。According to the present invention, a pressure of 500 N / m 2 or more is applied to the steel sheet at the time of quenching, so that the steel sheet portion deformed at the time of quenching is straightened by the applied pressure. Therefore, the flatness of the steel sheet is improved. In the case of water quenching, the deterioration of the steel sheet shape is greater than in other quenching methods, but even in this case, the pressurizing time for shape correction may be 0.2 seconds or more. The quenching method is not limited to water quenching, but may be roll cooling or air-water cooling. The method of pressurizing the steel sheet during water quenching will be described later. In the case of roll cooling, a high-pressure gas may be sprayed on a steel sheet wound around a cooling roll, and in the case of air-water cooling, cooling water is sprayed. The pressure of the gas used as a medium is increased,
What is necessary is just to spray atomized water on the front and back surfaces of the steel plate.
【００１１】図１は、下記成分の熱延鋼板（板幅１１０
０mm、板厚１．８mm）を８５０℃で再結晶焼鈍後、７１
０℃から種々の圧力を付加して水焼き入れを行い、その
後２００℃で過時効処理（この際、鋼板に通板方向の張
力を付与して、４．９Ｎ／mm2 の引張応力を与えた。）
を行った際の圧力と鋼板の浮き高さδとの関係を示す図
であり、圧力が５００Ｎ／ｍ2 以上、好ましくは８００
Ｎ／ｍ2 以上で浮き高さが小さくなっていることがわか
る。なお、浮さ高さδは、板幅１１００mmのストリップ
を全幅のまま長さ方向に５００mm長さで切断し、図３に
示すように、これを定盤上に載置したとき、定盤から鋼
板の最大高さまでの大きさをいう。 鋼板成分（wt％、残部実質的にＦｅ） Ｃ：０．１３％、Ｓｉ：０．４５％、Ｍｎ：１．９０
％、Ｐ：０．００５％、Ｓ：０．００１％、Ａｌ：０．
０４０％FIG. 1 shows a hot-rolled steel sheet (sheet width 110) having the following components.
0 mm, sheet thickness 1.8 mm) after recrystallization annealing at 850 ° C.
Water quenching is performed by applying various pressures from 0 ° C., and then over-aging treatment is performed at 200 ° C. (At this time, a tensile force of 4.9 N / mm 2 is given by applying a tensile force in the passing direction to the steel sheet. .)
FIG. 6 is a diagram showing a relationship between the pressure when the pressure is applied and the floating height δ of the steel sheet, where the pressure is 500 N / m 2 or more, and preferably 800
It can be seen that the floating height becomes smaller at N / m 2 or more. The floating height δ was determined by cutting a strip having a width of 1100 mm in the length direction and cutting it at a length of 500 mm while keeping the entire width, and as shown in FIG. The size up to the maximum height of the steel sheet. Steel plate component (wt%, balance substantially Fe) C: 0.13%, Si: 0.45%, Mn: 1.90
%, P: 0.005%, S: 0.001%, Al: 0.
040%
【００１２】焼き入れの際の鋼板への加圧は、図４に示
すように、水槽内に鋼板１の表裏面に対向するようにジ
ェットノズルを多数備えた一対の冷却水噴射装置２，２
を設け、ジェットノズルより高圧水を噴射することで冷
却水噴射装置２，２間に高圧域を形成し、該高圧域に鋼
板１を通板して圧力を付加した。図中、３は搬送方向変
換用ローラである。なお、水槽内に入った鋼板１は、高
温であるため鋼板表面に沸騰膜が生じ、前記高圧域に到
達して始めて実質的に急冷されて焼き入れられる。本例
では鋼板１の高圧域の通過時間を約１．０秒とした。As shown in FIG. 4, the pressurization of the steel sheet during quenching is performed by a pair of cooling water injection devices 2 and 2 provided with a large number of jet nozzles in the water tank so as to face the front and back surfaces of the steel sheet 1.
And a high-pressure region was formed between the cooling water injection devices 2 and 2 by injecting high-pressure water from a jet nozzle, and a steel sheet 1 was passed through the high-pressure region to apply pressure. In the drawing, reference numeral 3 denotes a transport direction changing roller. Since the steel sheet 1 in the water tank has a high temperature, a boiling film is formed on the surface of the steel sheet, and the steel sheet 1 is substantially rapidly cooled and quenched only after reaching the high pressure range. In this example, the passage time of the steel sheet 1 in the high pressure range was set to about 1.0 second.
【００１３】鋼板の平坦性をより一層改善するには、過
時効処理の際に、加熱された鋼板に７．４Ｎ／mm2 以上
の引張応力を付与するのがよい。なお、この応力は、例
えば連続焼鈍ラインの過時効ゾーン前後に設けられたロ
ールの回転速度（周速）を調整して鋼板の通板方向の張
力を制御することにより調整することができる。To further improve the flatness of the steel sheet, it is preferable to apply a tensile stress of 7.4 N / mm 2 or more to the heated steel sheet during the overaging treatment. This stress can be adjusted, for example, by adjusting the rotation speed (peripheral speed) of a roll provided before and after the overaging zone of the continuous annealing line to control the tension in the sheet passing direction of the steel sheet.
【００１４】図２は、上記熱延鋼板を８５０℃で再結晶
焼鈍後、７１０℃から５００Ｎ／ｍ2 の圧力を付加（加
圧時間１秒）して水焼き入れを行い、その後２００℃で
過時効処理を行った際の、過時効処理時に鋼板の通板方
向に付与した張力による応力（引張応力）と鋼板の浮き
高さδとの関係を示す図であり、張力が４．９Ｎ／m
m2、好ましくは７．４Ｎ／mm2 以上、より好ましくは
９．８Ｎ／mm2 以上で浮き高さが非常に小さくなってい
ることがわかる。なお、鋼板の引張応力は鋼板に作用す
る張力に基づいて算出した。FIG. 2 shows that the hot-rolled steel sheet is recrystallized and annealed at 850 ° C., and then subjected to water quenching by applying a pressure of 500 N / m 2 from 710 ° C. (pressing time: 1 second). It is a figure which shows the relationship between the stress (tensile stress) by the tension | tensile_strength given to the threading direction of the steel plate at the time of an overaging process at the time of an overaging process, and the floating height (delta) of a steel plate, and tension is 4.9N / m
m 2, preferably 7.4 N / mm 2 or more, more preferably it can be seen that the height float at 9.8 N / mm 2 or more is very small. In addition, the tensile stress of the steel plate was calculated based on the tension acting on the steel plate.
【００１５】請求項２に記載した発明は、引張強さが７
８０Ｎ／mm2 以上で、良好な加工性を有し、しかも鋼板
平坦性に優れた高強度冷延鋼板の製造方法を提供するも
のであり、重量％で、Ｃ ：０．０８〜０．３０％、Ｓ
ｉ：０．１〜２．５％、Ｍｎ：０．５〜２．５％、Ｐ：
０．１５％以下、Ｓ：０．０１％以下、sol.Ａｌ：０．
１％以下、残部Ｆｅ及び不可避的不純物からなる鋼を熱
間圧延するに際して、Ａr3点以上の温度にて仕上圧延
し、４５０〜７００℃で巻き取り、これを酸洗し、冷間
圧延率３０％以上にて冷間圧延を行った後、再結晶焼鈍
するに際して、Ａc1点以上に加熱後、８００〜４５０℃
まで強制空冷し、鋼板表裏面の少なくとも幅方向の全域
に渡って５００Ｎ／ｍ2 以上の圧力で加圧しながら１０
０℃／ｓ以上の冷却速度で焼き入れし、１８０〜４５０
℃の温度範囲で過時効処理を施すことを特徴とする。According to the second aspect of the present invention, the tensile strength is 7
The present invention provides a method for producing a high-strength cold-rolled steel sheet having good workability at 80 N / mm 2 or more and excellent in flatness of the steel sheet. C: 0.08 to 0.30 by weight%. %, S
i: 0.1 to 2.5%, Mn: 0.5 to 2.5%, P:
0.15% or less, S: 0.01% or less, sol.
When hot rolling steel containing 1% or less and the balance of Fe and unavoidable impurities, finish rolling at a temperature of 3 points or more of Ar, winding up at 450 to 700 ° C, pickling this, and cold rolling reduction After performing cold rolling at 30% or more, when performing recrystallization annealing, after heating to one or more Ac, 800 to 450 ° C.
Forced air cooling, and pressurizing at a pressure of 500 N / m 2 or more over at least the entire width direction of the front and back surfaces of the steel sheet.
Quenching at a cooling rate of 0 ° C./s or more, 180 to 450
The overaging treatment is performed in a temperature range of ° C.
【００１６】まず、本発明の成分限定理由について説明
する。 Ｃ：０．０８〜０．３０％ Ｃは再結晶焼鈍後の焼き入れ時の急冷によって、低温変
態生成相を生成させるために必要であり、７８０Ｎ／mm
2 以上の引張強さを確保するに必要な十分な量の低温変
態生成相を得るためには、少なくとも０．０８％が必要
がある。強度を高める観点からは多いほどよいが、反
面、過多に添加すると延性やスポット溶接性、更には耐
遅れ破壊特性が劣るようになるので、添加量の上限を
０．３０％とする。First, the reasons for limiting the components of the present invention will be described. C: 0.08 to 0.30% C is necessary for generating a low-temperature transformation generation phase by quenching during quenching after recrystallization annealing, and is 780 N / mm.
At least 0.08% is necessary to obtain a sufficient amount of the low-temperature transformation forming phase necessary to secure a tensile strength of 2 or more. From the viewpoint of increasing the strength, the more it is, the better. However, on the other hand, if it is added excessively, the ductility, spot weldability, and further the delayed fracture resistance become inferior, so the upper limit of the addition is made 0.30%.
【００１７】Ｓｉ：０．１〜２．５％ Ｓｉは鋼の延性、特に局部延性を劣化させることなく、
鋼の強度を高めることができる元素である。かかる効果
を有効に発揮させるためには、添加量を０．１％以上と
することが必要である。一方、２．５％を越えると鋼の
製造コストを高めるほか、適正な再結晶温度域を高温に
するので、上限を２．５％とする。Si: 0.1 to 2.5% Si is used without deteriorating the ductility of steel, particularly, local ductility.
It is an element that can increase the strength of steel. In order to effectively exhibit such an effect, it is necessary to set the addition amount to 0.1% or more. On the other hand, if it exceeds 2.5%, the production cost of steel is increased, and an appropriate recrystallization temperature range is raised. Therefore, the upper limit is made 2.5%.
【００１８】Ｍｎ：０．５〜２．５％ Ｍｎはオーステナイト相を安定化し、冷却過程において
低温変態生成物、特に主としてマルテンサイトからなる
低温変態生成物の生成を容易にする。このため、少なく
とも０．５％を添加することが必要である。しかし、過
多に添加するとオーステナイト相への濃化による第２相
体積率が増加して、Ｃの濃縮が弱まることから、添加量
の上限を２．５重量％とする。Mn: 0.5 to 2.5% Mn stabilizes the austenite phase and facilitates the formation of a low-temperature transformation product, particularly a low-temperature transformation product mainly composed of martensite, in the cooling process. For this reason, it is necessary to add at least 0.5%. However, excessive addition increases the volume ratio of the second phase due to concentration into the austenite phase and weakens the concentration of C. Therefore, the upper limit of the addition amount is set to 2.5% by weight.
【００１９】Ｐ：０．１５％以下 Ｐは鋼の高強度化には有効であるものの、過多に添加す
ると鋼板の加工性やスポット溶接性の低下を招くので、
上限を０．１５％とする。P: 0.15% or less P is effective in increasing the strength of steel, but excessive addition of P causes a reduction in workability and spot weldability of the steel sheet.
The upper limit is set to 0.15%.
【００２０】Ｓ：０．０１％以下 Ｓは硫化物系介在物を形成し、該介在物は金属との間で
電位差を生じ、腐食の起点となったり、曲げ加工性等を
劣化させるので、上限を０．０１％とする。S: 0.01% or less S forms sulfide-based inclusions, and the inclusions cause a potential difference between the metal and the metal, and serve as a starting point of corrosion and deteriorate bending workability. The upper limit is set to 0.01%.
【００２１】sol.Ａｌ：０．１％以下 Ａｌは、脱酸剤として使用されるものであるが、過多に
添加すると鋼の清浄度を悪化させるので、上限を０．１
％とする。Sol. Al: 0.1% or less Al is used as a deoxidizing agent. However, excessive addition of Al deteriorates the cleanliness of the steel.
%.
【００２２】本発明において用いる鋼は上記成分を基本
成分とし、残部実質的にＦｅで形成されるが、曲率半径
の小さい曲げ加工性すなわち局部延性を向上させるた
め、請求項３に記載したように下記Ｃａを添加すること
ができる。The steel used in the present invention contains the above components as basic components, and the balance is substantially formed of Fe. However, in order to improve the bending workability with a small radius of curvature, that is, the local ductility, the steel according to the third aspect of the present invention is described. The following Ca can be added.
【００２３】Ｃａ：０．００１〜０．０１０％ Ｃａは鋼中の非金属介在物を球状化して鋼の局部延性や
靱性を高める効果を有する。更に、Ｃａはマトリックス
中に固溶させることにより、粒界破壊を防止して、水素
脆化を抑制する効果を有する。また、耐食性を向上させ
る効果も有する。これらの効果を有効に発揮させるため
には、０．００１％以上が必要である。しかし、過多に
添加するとＣａ系の粗大介在物を生成して、加工性を低
下させるようになるため、上限を０．０１０％とする。Ca: 0.001 to 0.010% Ca has the effect of spheroidizing nonmetallic inclusions in steel to increase the local ductility and toughness of the steel. Further, Ca has an effect of preventing grain boundary destruction and suppressing hydrogen embrittlement by forming a solid solution in the matrix. It also has the effect of improving corrosion resistance. In order to exhibit these effects effectively, 0.001% or more is necessary. However, if added in excessive amounts, Ca-based coarse inclusions are formed and workability is reduced, so the upper limit is made 0.010%.
【００２４】さらに、鋼板の機械的特性を向上させるた
め、前記基本成分又は／及びこれにＣａを添加した鋼成
分に、下記Ｃｕ，ＮｉからなるＡ群、Ｂ，Ｃｒ，Ｍｏか
らなるＢ群、Ｔｉ，Ｎｂ，ＶからなるＣ群のうち少なく
とも１群から選択された１種以上の成分を含有すること
ができる。すなわち、下記(1) 〜(3) の組成とすること
ができる。 (1) 基本成分又は基本成分に前記Ｃａ添加成分のほか、
さらにＡ群から選択された１種以上の成分。 (2) 基本成分、基本成分に前記Ｃａ添加成分又は上記
(1) の成分のほか、さらにＢ群から選択された１種以上
の成分。 (3) 基本成分、基本成分に前記Ｃａ添加成分、上記(1)
又は(2) の成分のほか、さらにＣ群から選択された１種
以上の成分。Further, in order to improve the mechanical properties of the steel sheet, the basic component or / and the steel component obtained by adding Ca to the basic component and / or the steel component include the following A group consisting of Cu and Ni, B group consisting of B, Cr and Mo, It can contain one or more components selected from at least one of the group C consisting of Ti, Nb, and V. That is, the following compositions (1) to (3) can be obtained. (1) In addition to the basic component or the Ca-added component to the basic component,
At least one component selected from Group A. (2) Basic component, the above-mentioned Ca added component to the basic component or the above
In addition to the component (1), one or more components further selected from the group B. (3) Basic component, the Ca-added component to the basic component, (1)
Or one or more components selected from the group C in addition to the component (2).
【００２５】Ｃｕ：０．１０〜３．００％ Ｃｕは生成錆を緻密化して、大気腐食環境下における鋼
の腐食速度を著しく低減する。また、Ｃｕは電気化学的
に鉄よりも貴であることから、上記作用と共に相乗的に
鋼の耐食性を向上させ、水素脆性を抑制して耐遅れ破壊
性を向上させる。このような効果を有効に得るために
は、少なくとも０．１０％を添加することが必要であ
る。一方、Ｃｕは熱間圧延時の脆化を引き起こすおそれ
があるので、添加量の上限を３．００％とする。このよ
うな熱間圧延時の脆化を抑制するために、等量程度のＮ
ｉを併せて添加することが好ましい。実用上の観点か
ら、Ｃｕ含有量は０．２０〜２．００％の範囲が好まし
い。Cu: 0.10 to 3.00% Cu densifies the formed rust and remarkably reduces the corrosion rate of steel in an atmospheric corrosion environment. Further, since Cu is electrochemically nobler than iron, Cu improves the corrosion resistance of steel synergistically with the above-mentioned action, suppresses hydrogen embrittlement, and improves delayed fracture resistance. In order to effectively obtain such an effect, it is necessary to add at least 0.10%. On the other hand, since Cu may cause embrittlement during hot rolling, the upper limit of the addition amount is set to 3.00%. In order to suppress such embrittlement during hot rolling, an equivalent amount of N
It is preferable to add i together. From the viewpoint of practical use, the Cu content is preferably in the range of 0.20 to 2.00%.
【００２６】Ｎｉ：０．１０〜４．００％ ＮｉはＣｕと同様、０．１０％以上を添加することによ
って、生成錆の緻密化により、鋼の耐食性を向上させ、
水素脆性を抑制して耐遅れ破壊性を向上させる作用を有
する。しかし、過多に添加すると、残留オーステナイト
の増加による引張強さの低下原因となるので、上限を
４．００％とする。しかし、Ｎｉは高価な金属であり、
経済性の点を考慮すれば、好ましい添加範囲は、０．２
０〜２．００％である。なお、ＮｉはＣｕ添加による熱
間脆性を抑制する効果を有するので、Ｃｕと等量程度添
加するのが好ましい。Ni: 0.10 to 4.00% Ni is added in an amount of 0.10% or more in the same manner as Cu to improve the corrosion resistance of the steel by densification of generated rust,
It has the effect of suppressing hydrogen embrittlement and improving delayed fracture resistance. However, an excessive addition causes a decrease in tensile strength due to an increase in retained austenite, so the upper limit is made 4.00%. However, Ni is an expensive metal,
Considering the economics, the preferred range of addition is 0.2
0 to 2.00%. Since Ni has the effect of suppressing hot brittleness due to the addition of Cu, it is preferable to add about the same amount as Cu.
【００２７】Ｂ：０．０００３〜０．００６０％ ＢはＣｒ、Ｍｏと同様、鋼の焼き入れ性を高めるのに有
効な元素であり、その作用を有効に発揮させるために
は、０．０００３％以上含有させる必要がある。一方、
過剰に添加すると鋼の延性が低下するので、上限を０．
００６０％とする。B: 0.0003% to 0.0060% B, like Cr and Mo, is an element effective for improving the hardenability of steel. % Or more. on the other hand,
Excessive addition lowers the ductility of the steel, so the upper limit is set to 0.
0060%.
【００２８】 Ｃｒ：０．０５〜１．０％、Ｍｏ：０．０５〜０．６％ ＣｒおよびＭｏはＭｎと同様に鋼の焼入れ性を高め、高
強度化に有効な低温変態生成物を得やすくする元素であ
り、各々０．０５％よりも少ないとその効果が過少であ
る。一方、多すぎると延性の低下を招く。また、これら
の元素は高価であるので経済性を考慮して、Ｃｒの上限
を１．０％、Ｍｏの上限を０．６％とする。Cr: 0.05 to 1.0%, Mo: 0.05 to 0.6% Cr and Mo, like Mn, enhance the hardenability of steel and provide a low-temperature transformation product that is effective for increasing strength. These elements make it easy to obtain, and if each is less than 0.05%, the effect is too small. On the other hand, if it is too large, the ductility is reduced. In addition, since these elements are expensive, the upper limit of Cr is set to 1.0% and the upper limit of Mo is set to 0.6% in consideration of economy.
【００２９】Ｔｉ，Ｎｂ，Ｖ：各々０．０１〜０．２％ Ｔｉ，Ｎｂ及びＶは、Ｃ及びＮと析出物を形成し、強化
元素として有効であるとともに、熱間圧延板の結晶粒を
微細化し、延性を向上させる効果を有する。特にＴｉ
は、生成錆の緻密化による耐食性をも向上させ、耐水素
脆化特性の改善に有効である。この効果を有効に発現さ
せるためには、それぞれの元素について０．０１％を添
加することが必要であるが、しかし、過多に添加すると
延性を劣化させるので、その上限を０．２％とする。Ti, Nb, V: 0.01 to 0.2% each Ti, Nb and V form precipitates with C and N, are effective as strengthening elements, and have crystal grains of a hot-rolled sheet. Has the effect of miniaturizing and improving ductility. Especially Ti
Is effective in improving corrosion resistance due to densification of formed rust and improving hydrogen embrittlement resistance. In order to effectively exhibit this effect, it is necessary to add 0.01% for each element. However, since excessive addition deteriorates ductility, the upper limit is made 0.2%. .
【００３０】次に、製造条件について説明する。まず、
上記鋼を造塊又は連続鋳造によりスラブとし、これを熱
間圧延するに際してＡr3点以上の温度にて仕上圧延を終
了し、４５０〜７００℃で巻き取り、フェライトと体積
率４０％以上の低温変態生成物とからなる複合組織を得
るようにする。低温変態生成物とは、マルテンサイト、
ベイナイト又はこれらの混合物をいう。第２相（低温変
態生成物の組織）の量は、７０体積％以下に止めるのが
よい。７０％を越えると、熱間圧延板の強度が高くなり
すぎ、冷間圧延が困難となると共に、冷間圧延及び焼鈍
後の第２相におけるＣ濃度が低下し、強度−伸びバラン
スが低下するようになる。また、巻取温度が７００℃を
超えると熱延板がバンド組織を呈し易くなり、最終製品
の加工性を劣化させる。Next, the manufacturing conditions will be described. First,
The above steel is made into a slab by ingot casting or continuous casting, and when hot-rolled, finish rolling is completed at a temperature of Ar 3 or more, wound up at 450 to 700 ° C, and ferrite and a low temperature of 40% or more in volume ratio. A composite structure composed of a transformation product is obtained. Low-temperature transformation products include martensite,
Bainite or a mixture thereof. The amount of the second phase (structure of the low-temperature transformation product) should be kept to 70% by volume or less. If it exceeds 70%, the strength of the hot-rolled sheet becomes too high, and cold rolling becomes difficult. In addition, the C concentration in the second phase after cold rolling and annealing decreases, and the strength-elongation balance decreases. Become like On the other hand, if the winding temperature exceeds 700 ° C., the hot-rolled sheet tends to exhibit a band structure, and the workability of the final product is deteriorated.
【００３１】次に、上記のようにして得られた熱延鋼板
を酸洗し、後の焼鈍工程での再結晶を促進するため３０
％以上の冷間圧延率にて冷間圧延を行う。冷間圧延後、
連続焼鈍を行うに際し、加熱温度をＡc1点以上として加
熱し、焼鈍過程においてオーステナイト相を形成させ
る。次いで焼入開始温度の８００〜４５０℃までを強制
空冷する。焼入開始温度を８００℃を越える高温にする
必要がなく、４５０℃未満ではフェライト生成量が６０
体積％を越えるようになり、焼き入れ後の低温変態生成
物量が４０体積％未満となり、７８０Ｎ／mm2 以上の高
強度が得られないようになる。Next, the hot-rolled steel sheet obtained as described above is pickled, and is used for promoting recrystallization in a subsequent annealing step.
Cold rolling is performed at a cold rolling rate of at least%. After cold rolling,
In performing the continuous annealing, the heating is performed with the heating temperature set to one or more Ac to form an austenite phase in the annealing process. Next, forced air cooling is performed to a quenching start temperature of 800 to 450 ° C. It is not necessary to set the quenching start temperature to a high temperature exceeding 800 ° C.
% By volume, the amount of the low-temperature transformation product after quenching is less than 40% by volume, and a high strength of 780 N / mm 2 or more cannot be obtained.
【００３２】強制空冷後、鋼板表裏面の少なくとも幅方
向の全域に渡って５００Ｎ／ｍ2以上の圧力を付与しな
がら、焼き入れし、オーステナイト相を第２相に変態さ
せる。焼き入れの際に、所定の圧力を付加することで、
急速冷却に伴うストリップ形状の劣化（幅方向の反り）
を防止することができる。焼き入れは、１００℃／ｓ以
上の冷却速度が得られる適宜の冷却手段により急冷すれ
ばよい。１００℃／ｓ未満では、十分に硬い低温変態生
成物を得ることがでさないばかりでなく、過時効処理前
のフェライト中の固溶炭素量が少なくなり、後述する過
時効処理によって、フェライト中の固溶炭素量を十分に
低くし難くなる。もっとも、実操業上は可能な限り急冷
することができる水焼き入れが好ましい。After the forced air cooling, the steel sheet is quenched while applying a pressure of 500 N / m 2 or more over at least the entire width direction of the front and back surfaces of the steel sheet to transform the austenite phase into the second phase. At the time of quenching, by applying a predetermined pressure,
Deterioration of strip shape due to rapid cooling (warpage in width direction)
Can be prevented. The quenching may be quenched by an appropriate cooling means capable of obtaining a cooling rate of 100 ° C./s or more. When the temperature is less than 100 ° C./s, not only a sufficiently hard low-temperature transformation product cannot be obtained, but also the amount of solute carbon in the ferrite before the overaging treatment is reduced. Becomes difficult to sufficiently lower the amount of solute carbon. However, in actual operation, water quenching that can be cooled as quickly as possible is preferable.
【００３３】焼き入れ後、フェライト中に固溶したＣを
析出させ、延性の改善を図るために、１８０〜４５０℃
の温度範囲で過時効処理を施す。この過時効処理温度が
１８０℃よりも低いときは、フェライト中の炭化物が十
分に析出せず、延性が劣化する。一方、過時効処理温度
が４５０℃よりも高いときは、マルテンサイトが焼き戻
されて強度が著しく低下するのみならず、加熱コスト高
を招く。過時効温度での保持時間は１秒〜１０分間程度
でよい。なお、すでに説明したとおり、この過時効処理
の際に４．９Ｎ／mm2 以上、好ましくは７．４Ｎ／mm2
以上、より好ましくは９．８Ｎ／mm2 以上の引張応力を
鋼板に付与することで、平坦性がより一層向上する。After quenching, the solid solution C is precipitated in the ferrite, and in order to improve the ductility, the temperature is set at 180 to 450 ° C.
Overage treatment in the temperature range of When the overaging temperature is lower than 180 ° C., carbides in the ferrite do not sufficiently precipitate, and the ductility deteriorates. On the other hand, when the overaging treatment temperature is higher than 450 ° C., martensite is tempered and not only the strength is remarkably reduced, but also the heating cost is increased. The holding time at the overaging temperature may be about 1 second to 10 minutes. Incidentally, as already described, 4.9 N / mm 2 or more at the time of the overaging, preferably 7.4 N / mm 2
As described above, more preferably, the flatness is further improved by applying a tensile stress of 9.8 N / mm 2 or more to the steel sheet.
【００３４】以上の鋼成分、製造条件を満足することに
より、金属組織が６０体積％以下のフェライト相と残部
低温変態生成物からなり、７８０Ｎ／mm2 以上引張強さ
を有し、良好な加工性と平坦性を備えた高強度冷延鋼板
を得ることができる。By satisfying the above steel components and the production conditions, the metal structure is composed of a ferrite phase of 60% by volume or less and a low-temperature transformation product, and has a tensile strength of 780 N / mm 2 or more. A high-strength cold-rolled steel sheet having excellent properties and flatness can be obtained.
【００３５】[0035]
【実施例】〔実施例Ａ〕表１に示す化学組成を有する鋼
を転炉で出鋼した後、連続鋳造によりスラブとなし、こ
れを表２に示す熱延条件で厚さ２．８mmの熱延鋼板を得
て、酸洗後、厚さ１．２mmに冷間圧延し、次いで、水焼
き入れ型の連続焼鈍設備において、表２に示す種々の条
件にて連続焼鈍及び過時効処理を施した。水焼き入れの
際の付加圧力の加圧時間（鋼板が水槽内の高圧域を通過
するに要する時間）は１秒であり、過時効処理（処理時
間５９５秒）の際の鋼板の通板方向の引張応力を４．９
Ｎ／mm2 とした。なお、表１の備考における「発明
鋼」、「比較鋼」は請求項２〜４の発明の対象鋼につい
ていうものである。[Example A] A steel having a chemical composition shown in Table 1 was tapped in a converter and then turned into a slab by continuous casting. The slab having a thickness of 2.8 mm was obtained under the hot rolling conditions shown in Table 2. Obtain a hot-rolled steel sheet, cold-roll it to a thickness of 1.2 mm after pickling, and then perform continuous annealing and overage treatment under various conditions shown in Table 2 in a water-quenching type continuous annealing facility. gave. The pressurizing time (time required for the steel sheet to pass through the high-pressure area in the water tank) of the additional pressure during the water quenching is 1 second, and the passing direction of the steel sheet during the overaging treatment (processing time 595 seconds). 4.9 tensile stress
N / mm 2 . In addition, "invention steel" and "comparative steel" in the remarks in Table 1 refer to steels targeted by the inventions of claims 2 to 4.
【００３６】[0036]
【表１】 [Table 1]
【００３７】このようにして得られた鋼板について、機
械的性質、最小曲げ半径および耐遅れ破壊特性、鋼板の
平坦性を調べた。機械的性質は、ＪＩＳ５号引張り試験
片を作製し、引張試験により求めた。材料の局部伸びを
引張試験の応力−歪み線図から求めることは非常に困難
であるので、局部延性（伸びフランジ性）を調べるため
に、上記引張試験以外にＶ曲げ試験を行い、その時の曲
げ半径を０〜１０mmの間で種々変化させ、材料が破断せ
ずに曲げ加工がでさる限界の曲げ半径（最小曲げ半径）
を求めた。材料の耐遅れ破壊特性はＵ曲げ加工部材を塩
酸浸漬することで評価した。これは短冊試験片を曲げ半
径１５mmでＵ曲げ加工を行い、次いで曲げ外表面のひず
みとヤング率で応力を制御しながら、１０００Ｎ／mm2
の残留応力を付与した状態で０．１規定の塩酸に浸漬
し、１０００時間までの割れの発生の有無で評価した。
鋼板の平坦性は、板幅１１００mmのストリップを全幅の
まま長さ方向に５００mm長さで切断し、これを定盤上に
載置し、このとき生じた浮さ高さδにより評価した。The thus obtained steel sheet was examined for mechanical properties, minimum bending radius and delayed fracture resistance, and flatness of the steel sheet. The mechanical properties were determined by preparing a JIS No. 5 tensile test piece and performing a tensile test. Since it is very difficult to determine the local elongation of the material from the stress-strain diagram of the tensile test, a V-bending test was conducted in addition to the tensile test to check the local ductility (stretch flangeability). The minimum bending radius (minimum bending radius) where the radius can be varied between 0 and 10 mm and the material can be bent without breaking.
I asked. The delayed fracture resistance of the material was evaluated by immersing the U-bent member in hydrochloric acid. In this method, a strip test piece is subjected to a U-bending process at a bending radius of 15 mm, and then the stress is controlled by the strain and the Young's modulus of the outer surface of the bending while controlling the stress to 1000 N / mm 2.
The sample was immersed in 0.1 N hydrochloric acid in a state where the residual stress was applied, and evaluated by the presence or absence of cracking for up to 1000 hours.
The flatness of the steel sheet was evaluated by measuring a strip having a width of 1100 mm, cutting the strip in its length direction at a length of 500 mm in a length direction, placing the strip on a platen, and generating a floating height δ at this time.
【００３８】機械的性質、最小曲げ半径および鋼板の平
坦性の調査結果を表２に併せて示す。耐遅れ破壊特性に
ついては、Ｃ含有量が発明範囲外の試料No. １９を除
き、割れの発生は認められなかった。なお、表２の各試
料は請求項１の発明に対しては全て発明例であるが、備
考に記載した発明例、比較例は請求項２〜４の発明に対
するものである。The results of the investigation of the mechanical properties, minimum bending radius and flatness of the steel sheet are also shown in Table 2. Regarding the delayed fracture resistance, no cracking was observed except for Sample No. 19 in which the C content was out of the range of the invention. In addition, each sample of Table 2 is an invention example for the invention of claim 1, but the invention examples and comparative examples described in the remarks are for the inventions of claims 2 to 4.
【００３９】[0039]
【表２】 [Table 2]
【００４０】表２に示す各試料は、焼き入れの際、１８
８７Ｎ／ｍ2 の圧力を付加したものであり、例えば引張
強さが１９００Ｎ／mm2 台の試料No. １９においても浮
き高さは９mmに止まっており、良好な平坦性が得られて
いる。Each sample shown in Table 2 was subjected to 18
A pressure of 87 N / m 2 was applied. For example, even in Sample No. 19 having a tensile strength of the order of 1900 N / mm 2 , the floating height was only 9 mm, and good flatness was obtained.
【００４１】もっとも、表２の各試料は、熱延条件、焼
鈍条件についても発明条件を満足するものであるが、発
明鋼を用いた試料No. １〜１５は、比較鋼を用いた試料
No.１６〜２２に比して、良好な曲げ加工性や延性が得
られている。例えば、引張強さが１３００Ｎ／mm2 台の
試料No. ８とNo. １８を比較すると、平坦性は同等であ
るが、No. １８は伸び、局部延性に劣ることがわかる。
また、No. ２１は引張強さが７８０Ｎ／mm2 未満で強度
不足であり、No. １９は先に記載したとおり、耐遅れ破
壊性に劣る。Although each of the samples in Table 2 satisfies the invention conditions with respect to the hot rolling conditions and the annealing conditions, Sample Nos. 1 to 15 using the invention steels are samples using the comparative steels.
As compared with Nos. 16 to 22, good bending workability and ductility were obtained. For example, comparing Sample No. 8 with Sample No. 18 having a tensile strength of 1300 N / mm 2 units, it can be seen that the flatness is the same, but that Sample No. 18 is elongated and inferior in local ductility.
In addition, No. 21 has insufficient tensile strength with a tensile strength of less than 780 N / mm 2 , and No. 19 is inferior in delayed fracture resistance as described above.
【００４２】〔実施例Ｂ〕実施例Ａの表１に示す化学組
成を有する鋼種Ｂ，Ｄ，Ｅ，Ｌ，Ｎ（発明鋼）を転炉で
出鋼した後、連続鋳造によりスラブとなし、これを表３
に示す熱延条件で厚さ２．８mmの熱延鋼板を得て、酸洗
後、厚さ１．２mmに冷間圧延し、次いで、水焼き入れ型
の連続焼鈍設備において、表３に示す種々の条件にて連
続焼鈍及び過時効処理を施した。実施例Ａと同様、水焼
き入れの際の付加圧力の加圧時間を１秒とし、過時効処
理（処理時間５９５秒）の際の鋼板の通板方向の引張応
力を４．９Ｎ／mm2 とした。このようにして得られた鋼
板の機械的性質、最小曲げ半径、浮き高さを実施例Ａと
同様にして求めた。その結果を表３に示す。なお、表３
において、試料No. ４、７、１２、１６、１９を除く各
試料は請求項１の発明に対して発明例であるが、備考に
記載した発明例、比較例は請求項２〜４の発明に対する
ものである。Example B Steel types B, D, E, L, and N (inventive steels) having the chemical compositions shown in Table 1 of Example A were tapped in a converter, and then continuously cast to form a slab. This is shown in Table 3.
A hot-rolled steel sheet having a thickness of 2.8 mm was obtained under the hot-rolling conditions shown in Table 1. After pickling, the sheet was cold-rolled to a thickness of 1.2 mm. Continuous annealing and overaging treatment were performed under various conditions. As in Example A, the pressurizing time of the additional pressure during water quenching was 1 second, and the tensile stress in the sheet passing direction of the steel sheet during the overaging treatment (processing time 595 seconds) was 4.9 N / mm 2. And The mechanical properties, minimum bending radius and floating height of the steel sheet thus obtained were determined in the same manner as in Example A. Table 3 shows the results. Table 3
In the above, each sample except for sample Nos. 4, 7, 12, 16, and 19 is an invention example with respect to the invention of claim 1, but the invention examples and comparative examples described in the remarks are inventions of claims 2 to 4. Is for
【００４３】[0043]
【表３】 [Table 3]
【００４４】表３から、焼き入れの際の付加圧力が本発
明範囲未満の試料No. ４、７、１２、１６、１９（比較
例）は鋼板形状が劣っているが、他の試料は付加圧力が
本発明条件を満足しており、いずれも浮き高さが小さ
い。From Table 3, it can be seen that Sample Nos. 4, 7, 12, 16, and 19 (Comparative Examples) in which the additional pressure during quenching was less than the range of the present invention were inferior in the steel plate shape, while the other samples were not added. The pressure satisfies the conditions of the present invention, and each of them has a small floating height.
【００４５】もっとも、鋼成分、熱延条件、連続焼鈍条
件のいずれも発明条件（請求項２〜４）を満足する発明
例と比較して、鋼成分が発明範囲内にあるものの、例え
ば熱延巻取温度が発明範囲外の試料No. ２、８、１３、
２１では全伸びや最小曲げ半径が劣っている。また、焼
き入れの際の付加圧力が本発明範囲未満の試料No. ４、
７、１２、１６、１９は鋼板形状が劣っている。また、
低温変態生成物の量が本発明範囲からはずれている試料
No. ３は引張強さが７５０Ｎ／mm2 台に止まっている。Although the steel components, hot rolling conditions, and continuous annealing conditions are all within the scope of the invention as compared with the invention examples satisfying the invention conditions (claims 2 to 4), for example, hot rolling is performed. Sample No. 2, 8, 13, whose winding temperature is out of the range of the invention
21 is inferior in total elongation and minimum bending radius. Sample No. 4 in which the additional pressure during quenching was less than the range of the present invention,
7, 12, 16 and 19 are inferior in steel plate shape. Also,
Sample in which the amount of low-temperature transformation product is out of the range of the present invention
No. 3 has a tensile strength of only 750 N / mm 2 .
【００４６】〔実施例Ｃ〕実施例Ｂと同様、実施例Ａの
表１に示す化学組成を有する鋼種Ｂ，Ｄ，Ｅ，Ｌ，Ｎの
スラブを表４に示す熱延条件で厚さ２．８mmの熱延鋼板
を得て、酸洗後、厚さ１．２mmに冷間圧延し、次いで、
水焼き入れ型の連続焼鈍設備において、表４に示す種々
の条件にて連続焼鈍及び過時効処理（処理時間５９５
秒）を施した。水焼き入れの際の付加圧力の加圧時間は
実施例Ａと同様１秒とし、過時効処理時に鋼板に種々の
引張応力（表４中の付加応力）を付加した。このように
して得られた鋼板の機械的性質、最小曲げ半径、浮き高
さを実施例Ａと同様にして求めた。その結果を表４に併
せて示す。なお、表４において、備考に記載した発明
例、比較例は請求項２〜４の条件を満足し、かつ請求項
５の条件を満足する発明に対するものである。[Example C] As in Example B, slabs of steel types B, D, E, L and N having the chemical compositions shown in Table 1 of Example A were subjected to hot rolling under the conditions shown in Table 4 to a thickness of 2 mm. .8 mm hot rolled steel sheet, pickled, cold rolled to a thickness of 1.2 mm,
In the water-quenching type continuous annealing equipment, continuous annealing and overaging treatment (treatment time 595) were performed under various conditions shown in Table 4.
Seconds). The pressurizing time of the additional pressure during water quenching was 1 second as in Example A, and various tensile stresses (additional stresses in Table 4) were applied to the steel sheet during the overaging treatment. The mechanical properties, minimum bending radius and floating height of the steel sheet thus obtained were determined in the same manner as in Example A. The results are shown in Table 4. In addition, in Table 4, the invention examples and comparative examples described in the remarks are for the invention that satisfies the conditions of claims 2 to 4 and satisfies the conditions of claim 5.
【００４７】[0047]
【表４】 [Table 4]
【００４８】表４から、焼き入れの際の付加圧力が本発
明範囲未満の試料No. ４、７、１２、１６、１９（比較
例）は鋼板形状が劣っているが、他の試料は付加圧力が
本発明条件を満足しており、いずれも浮き高さが小さ
い。特に、過時効時の引張応力の低いNo. ２に比して、
１４．７Ｎ／mm2 を付与した他の試料は鋼板の平坦性が
非常に良好である。From Table 4, it can be seen that Sample Nos. 4, 7, 12, 16, and 19 (Comparative Examples) in which the additional pressure during quenching was less than the range of the present invention were inferior in the steel plate shape, while the other samples were not added. The pressure satisfies the conditions of the present invention, and each of them has a small floating height. In particular, compared to No. 2, which has a low tensile stress during overaging,
The other samples provided with 14.7 N / mm 2 have very good flatness of the steel sheet.
【００４９】[0049]
【発明の効果】以上のように、本発明によれば、連続焼
鈍の焼き入れの際に５００Ｎ／ｍ2 以上の圧力で鋼板を
加圧するので、焼き入れの際に生じる鋼板幅方向の反り
を有効に抑制することができ、平坦性の良好な高強度冷
延鋼板を得ることができる。As described above, according to the present invention, since the steel sheet is pressurized with a pressure of 500 N / m 2 or more during the quenching in the continuous annealing, the warpage in the width direction of the steel sheet caused during the quenching is reduced. A high strength cold-rolled steel sheet that can be effectively suppressed and has good flatness can be obtained.
【００５０】また、請求項２〜４の発明によれば、７８
０Ｎ／mm2 以上の引張強さを有しながら、良好な加工性
と平坦性を備えた高強度冷延鋼板を得ることができる。
特に請求項３に記載したように所定量のＣａを添加する
ことで、従来に比して優れた局部延性を確保することが
できる。このため、例えば、自動車のバンパーやドアの
補強部打の強度上昇や軽量化のために好適に用いること
ができる。According to the second to fourth aspects of the present invention, 78
A high-strength cold-rolled steel sheet having good workability and flatness can be obtained while having a tensile strength of 0 N / mm 2 or more.
Particularly, by adding a predetermined amount of Ca as described in claim 3, it is possible to secure excellent local ductility as compared with the related art. For this reason, it can be suitably used, for example, for increasing the strength and reducing the weight of the bumper or door of the automobile.
【００５１】また、過時効処理の際に鋼板に４．９Ｎ／
mm2 以上の引張応力を付与することにより、鋼板の平坦
性を向上させることができる。Further, at the time of overaging treatment, 4.9 N /
By applying a tensile stress of at least mm 2 , the flatness of the steel sheet can be improved.
【図１】連続焼鈍工程において焼鈍後の水焼き入れの際
に鋼板に付加した圧力と鋼板の浮き高さとの関係を示す
図である。FIG. 1 is a view showing a relationship between a pressure applied to a steel sheet and a floating height of the steel sheet during water quenching after annealing in a continuous annealing step.
【図２】連続焼鈍工程において過時効処理の際に鋼板に
付加した張力による応力と鋼板の浮き高さとの関係を示
す図である。FIG. 2 is a view showing a relationship between stress caused by tension applied to a steel sheet during overaging treatment in a continuous annealing step and a floating height of the steel sheet.
【図３】連続焼鈍工程において焼き入れられた複合組織
型の高強度冷延鋼板の変形状態および浮き高さδを示す
要部断面斜視図である。FIG. 3 is a cross-sectional perspective view of a relevant part showing a deformed state and a floating height δ of a composite structure type high-strength cold-rolled steel sheet quenched in a continuous annealing step.
【図４】水焼き入れの際の鋼板加圧要領を示す説明図で
ある。FIG. 4 is an explanatory diagram showing a steel sheet pressurizing procedure at the time of water quenching.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 山本 貴之 兵庫県加古川市金沢町１番地 株式会社神 戸製鋼所加古川製鉄所内 (72)発明者 斉藤 玄人 兵庫県加古川市金沢町１番地 株式会社神 戸製鋼所加古川製鉄所内 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takayuki Yamamoto 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Inside Kobe Steel Works Kakogawa Works (72) Inventor Gento Saito 1 Kanazawacho, Kakogawa City, Hyogo Prefecture Kobe Corporation Inside the steel mill Kakogawa Works
Claims (5)
し、焼鈍後に焼き入れ、その後過時効処理を行う高強度
冷延鋼板の製造方法において、 焼き入れの際に鋼板表裏面の少なくとも幅方向の全域に
渡って５００Ｎ／ｍ2以上の圧力で加圧する平坦性に優
れた高強度冷延鋼板の製造方法。1. A method for producing a high-strength cold-rolled steel sheet, comprising the steps of quenching after annealing and then performing overaging treatment when continuously annealing a steel sheet after cold rolling. A method for producing a high-strength cold-rolled steel sheet having excellent flatness, in which pressure is applied at a pressure of 500 N / m 2 or more over the entire region.
％、Ｓｉ：０．１〜２．５％、Ｍｎ：０．５〜２．５
％、Ｐ：０．１５％以下、Ｓ：０．０１％以下、sol.Ａ
ｌ：０．１％以下、残部Ｆｅ及び不可避的不純物からな
る鋼を熱間圧延するに際して、Ａr3点以上の温度にて仕
上圧延し、４５０〜７００℃で巻き取り、これを酸洗
し、冷間圧延率３０％以上にて冷間圧延を行った後、再
結晶焼鈍するに際して、Ａc1点以上に加熱後、８００〜
４５０℃まで強制空冷し、鋼板表裏面の少なくとも幅方
向の全域に渡って５００Ｎ／ｍ2 以上の圧力で加圧しな
がら１００℃／ｓ以上の冷却速度で焼き入れし、１８０
〜４５０℃の温度範囲で過時効処理を施す平坦性に優れ
た高強度冷延鋼板の製造方法。2. C: 0.08 to 0.30% by weight
%, Si: 0.1 to 2.5%, Mn: 0.5 to 2.5
%, P: 0.15% or less, S: 0.01% or less, sol.A
l: When hot rolling a steel consisting of 0.1% or less, with the balance being Fe and unavoidable impurities, finish rolling at a temperature of at least 3 points of Ar, winding up at 450 to 700 ° C, pickling this, After cold rolling at a cold rolling reduction of 30% or more, when recrystallization annealing, after heating to one or more Ac, 800 to
Forcibly air-cooled to 450 ° C., and quenched at a cooling rate of 100 ° C./s or more while applying a pressure of 500 N / m 2 or more over at least the entire width direction of the front and back surfaces of the steel sheet.
A method for producing a high-strength cold-rolled steel sheet having excellent flatness, which is subjected to an overaging treatment in a temperature range of -450 ° C.
〜０．０１０％を含有する請求項２に記載した平坦性に
優れた高強度冷延鋼板の製造方法。3. The steel component further contains Ca: 0.001.
The method for producing a high-strength cold-rolled steel sheet having excellent flatness according to claim 2, containing 0.010% to 0.010%.
３．００％，Ｎｉ：０．１０〜４．００％からなるＡ
群、Ｂ：０．０００３〜０．００６０％，Ｃｒ：０．０
５〜１．０％，Ｍｏ：０．０５〜０．６％からなるＢ
群、Ｔｉ：０．０１〜０．２％，Ｎｂ：０．０１〜０．
２％，Ｖ：０．０１〜０．２％からなるＣ群の少なくと
も１群から選択される１種以上の成分を含有する請求項
２又は３に記載した平坦性に優れた高強度冷延鋼板の製
造方法。4. The steel component further includes Cu: 0.10 to 0.10.
A consisting of 3.00% and Ni: 0.10 to 4.00%
Group, B: 0.0003 to 0.0060%, Cr: 0.0
B consisting of 5 to 1.0%, Mo: 0.05 to 0.6%
Group, Ti: 0.01-0.2%, Nb: 0.01-0.
4. The high-strength cold-rolled sheet having excellent flatness according to claim 2 or 3, containing at least one component selected from at least one group of group C consisting of 2% and V: 0.01 to 0.2%. Steel plate manufacturing method.
以上の引張応力を付与する請求項１〜４のいずれか１項
に記載した平坦性に優れた高強度冷延鋼板の製造方法。5. A steel sheet having an overageing treatment of 4.9 N / mm 2
The method for producing a high-strength cold-rolled steel sheet excellent in flatness according to any one of claims 1 to 4, wherein the tensile stress is applied.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9369318A JPH11193418A (en) | 1997-12-29 | 1997-12-29 | Manufacture of high strength cold rolled steel sheet excellent in flatness characteristic |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP9369318A JPH11193418A (en) | 1997-12-29 | 1997-12-29 | Manufacture of high strength cold rolled steel sheet excellent in flatness characteristic |
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| Publication Number | Publication Date |
|---|---|
| JPH11193418A true JPH11193418A (en) | 1999-07-21 |
Family
ID=18494125
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP9369318A Pending JPH11193418A (en) | 1997-12-29 | 1997-12-29 | Manufacture of high strength cold rolled steel sheet excellent in flatness characteristic |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH11193418A (en) |
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