JPH08109415A - Production of low carbon cold rolled steel sheet - Google Patents
Production of low carbon cold rolled steel sheetInfo
- Publication number
- JPH08109415A JPH08109415A JP24945394A JP24945394A JPH08109415A JP H08109415 A JPH08109415 A JP H08109415A JP 24945394 A JP24945394 A JP 24945394A JP 24945394 A JP24945394 A JP 24945394A JP H08109415 A JPH08109415 A JP H08109415A
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- cooling
- aging
- annealing
- cold rolled
- cooling rate
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- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、連続焼鈍による低炭素
冷延鋼板の製造方法に関し、特に耐時効性に優れた軟質
冷延鋼板を非常に短い過時効処理によって製造する方法
を提供しようとするものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a low carbon cold-rolled steel sheet by continuous annealing, and particularly to provide a method for producing a soft cold-rolled steel sheet having excellent aging resistance by a very short overaging treatment. To do.
【０００２】[0002]
【従来の技術】一般に、連続焼鈍材において歪時効を防
ぐためには連続焼鈍のような短時間の過時効処理で固溶
炭素を十分に析出させる必要があるが、そのためには固
溶炭素の析出サイトとなる炭化物を粒内に微細分散さ
せ、析出に必要な拡散距離を短くすることが有効である
ことが知られている。一方、粒内炭化物密度の増加は材
料の硬質化を招くことから、耐時効性に優れた軟質冷延
鋼板の製造には粒内炭化物密度の適正化に努力が傾けら
れている。2. Description of the Related Art Generally, in order to prevent strain aging in a continuously annealed material, it is necessary to sufficiently precipitate solid solution carbon by a short time overaging treatment such as continuous annealing. For that purpose, precipitation of solid solution carbon is required. It is known that it is effective to finely disperse carbides that become sites into grains to shorten the diffusion distance required for precipitation. On the other hand, since an increase in the intragranular carbide density leads to hardening of the material, efforts are being made to optimize the intragranular carbide density in the production of a soft cold-rolled steel sheet having excellent aging resistance.
【０００３】ところで、時効性の改善方法については近
年、連続焼鈍過程における冷却および過時効処理の適正
化により固溶炭素を低減させ時効性を抑制する発明が数
多く成されている。By the way, in recent years, regarding the method of improving the aging property, many inventions for suppressing the aging property by reducing the solid solution carbon by optimizing the cooling and the overaging treatment in the continuous annealing process have been made.
【０００４】結晶粒内炭化物の析出は核生成と成長段階
とに分けられることから、それぞれの段階について適正
化を行った例として、特開昭60−165321号公報、特公昭
63−49726 号公報、特開昭61−276935号公報、特開平２
−93025 号公報、特開平４−327 号公報、特開平５−59
445 号公報に示されるように、焼鈍後急冷してからの粒
内炭化物の核生成を促進するために過時効温度より低い
温度まで一旦冷却し、核生成を促進させ、その後再加熱
して過時効処理を行い炭化物の成長を促進させる製造方
法が提案されている。Since the precipitation of carbides in crystal grains is divided into nucleation and growth stages, examples of optimizing each stage are disclosed in JP-A-60-165321.
63-49726, JP-A-61-276935, JP-A-2
-93025, JP 4-327, JP 5-59
As shown in Japanese Patent No. 445, in order to promote the nucleation of intragranular carbide after quenching after annealing, it is once cooled to a temperature lower than the overaging temperature, the nucleation is promoted, and then reheating is performed. A manufacturing method has been proposed in which aging treatment is performed to promote the growth of carbides.
【０００５】しかし、これらの手法は時効性改善には有
効であるものの急冷後の再加熱には特別な設備が必要と
なり、またエネルギーコストの増加につながるという欠
点を有する。さらに、これらの実施例では過時効処理に
2.5 分以上10分以下という長い時間を要している。However, although these methods are effective for improving the aging property, they have the drawbacks that special equipment is required for reheating after quenching and the energy cost is increased. Furthermore, these examples provide overage treatment.
It takes a long time from 2.5 minutes to 10 minutes.
【０００６】短時間の過時効処理による遅時効化を提案
する例としては、特開昭58−48632号公報があり、それ
には再結晶焼鈍に続いて水焼入れを行い、その後30秒以
上の過時効処理を施すことにより耐時効性に優れた軟質
鋼板を得る製造方法が示されている。しかし、この場合
には常温付近から再加熱するため著しいエネルギーコス
ト増加を招く。As an example of proposing a delayed aging by a short-term overaging treatment, there is JP-A-58-48632, in which recrystallization annealing is followed by water quenching, and then overaging for 30 seconds or more. A manufacturing method for obtaining a soft steel sheet having excellent aging resistance by performing an aging treatment is disclosed. However, in this case, reheating from around room temperature causes a significant increase in energy cost.
【０００７】また、再加熱を伴わずに短時間の過時効処
理により遅時効化を図る製造方法が特開昭58−52429 号
公報に示されている。しかし、この公報の実施例の第１
表のＥの試料特性は100 ℃×60分の人工促進時効後の降
伏点伸び (YP−El) が1.0 ％であり、耐ストレッチャー
ストレインという観点から0.3 ％以下とする必要がある
ので充分な耐時効性が得られているとはいえない。Further, Japanese Patent Application Laid-Open No. 58-52429 discloses a manufacturing method for effecting delayed aging by overaging for a short time without reheating. However, the first embodiment of this publication
The sample characteristics of E in the table are sufficient because the yield point elongation (YP-El) after artificial accelerated aging at 100 ° C x 60 minutes is 1.0%, and it is necessary to set it to 0.3% or less from the viewpoint of stretcher strain resistance. It cannot be said that aging resistance is obtained.
【０００８】[0008]
【発明が解決しようとする課題】本発明の目的は、上記
した従来法の問題点に鑑み、1.5 分以上の非常に短い過
時効処理により耐時効性に優れた軟質冷延鋼板の製造方
法を提供することである。SUMMARY OF THE INVENTION In view of the above-mentioned problems of the conventional method, an object of the present invention is to provide a method for producing a soft cold-rolled steel sheet excellent in aging resistance by an extremely short overaging treatment of 1.5 minutes or more. Is to provide.
【０００９】[0009]
【課題を解決するための手段】本発明者等は、連続焼鈍
による耐時効性に優れた軟質冷延鋼板の製造方法に関し
て種々の検討を行ったところ、成分の適正化を行うこと
により比較的低温域から著しい粒成長が生じることを見
い出し、これにより粒界近傍の炭化物無析出帯の体積を
低減させ、非常に短い時間の過時効処理を施すだけで遅
時効化の実現を可能にすることを知り、本発明を完成し
た。[Means for Solving the Problems] The inventors of the present invention have made various studies on a method for producing a soft cold-rolled steel sheet having excellent aging resistance by continuous annealing. Finding that remarkable grain growth occurs from low temperature range, thereby reducing the volume of carbide-free zone near the grain boundary, and making it possible to realize delayed aging only by performing overaging treatment for a very short time. And completed the present invention.
【００１０】本発明の要旨とするところは、重量％で、
Ｃ：0.010 〜0.025 ％、Mn：0.05〜0.25％、Ｓ：0.003
〜0.020 ％、sol.Al：0.01〜0.10％、Ｎ：0.0030％以
下、Ｂ：0.0003〜0.0030％ 残部鉄および不可避的不純物から成る鋼組成を有する鋼
を、通常の熱間圧延−酸洗−冷間圧延を行い、続いて連
続焼鈍において820 ℃以上880 ℃以下で20秒以上60秒以
下の再結晶焼鈍することにより結晶粒寸法がJIS G 0552
で定義される結晶粒度番号で6.5 以上8.0 以下とし、65
0 〜740 ℃まで７℃/s以下の冷却速度で徐冷し、325 〜
375 ℃まで80〜250 ℃/sの冷却速度で冷却した後、その
冷却終点温度から保定を含む0.5 ℃/s以下の冷却速度
で、好ましくは1.5 分以上3.0 分以下の過時効処理を行
うことを特徴とする耐時効性に優れた軟質の低炭素冷延
鋼板の製造方法である。The gist of the present invention is that, in% by weight,
C: 0.010 to 0.025%, Mn: 0.05 to 0.25%, S: 0.003
~ 0.020%, sol.Al: 0.01-0.10%, N: 0.0030% or less, B: 0.0003-0.0030% Steel having a steel composition consisting of the balance iron and unavoidable impurities is usually hot-rolled-pickled-cooled. Rolling is performed, and then continuous annealing is performed at a temperature of 820 ° C to 880 ° C for 20 seconds to 60 seconds, which results in a crystal grain size of JIS G 0552
The grain size number defined by
Gradually cool from 0 to 740 ℃ at a cooling rate of 7 ℃ / s, 325 to
After cooling to 375 ° C at a cooling rate of 80 to 250 ° C / s, perform overaging treatment for 1.5 minutes to 3.0 minutes at a cooling rate of 0.5 ° C / s or less including retention from the cooling end temperature. Is a method for producing a soft low carbon cold-rolled steel sheet having excellent aging resistance.
【００１１】[0011]
【作用】本発明のＣ、Mn、Ｓ、sol.Al、Ｎ、Ｂの各成分
について数値限定した理由について述べる。The reason for numerically limiting each component of C, Mn, S, sol.Al, N and B of the present invention will be described.
【００１２】Ｃ:Ｃの下限は時効性の観点から制限され
る。すなわち、少なすぎる場合には過時効析出にあたっ
て焼鈍後の冷却速度を大きくしてもＣの過飽和度が増加
しないため粒内炭化物の析出駆動力が得られないので0.
010 ％を下限とする。また、上限は粒成長性の観点から
制限され、0.025 ％超とすると焼鈍過程において粒成長
性が阻害されるため、820 ℃以上の高温焼鈍を行っても
結晶粒度番号を8.0 以下にすることは困難となる。好ま
しくは、0.012 〜0.020 である。The lower limit of C: C is limited from the viewpoint of aging. That is, when the amount is too small, the driving force for precipitation of intragranular carbide cannot be obtained because the supersaturation degree of C does not increase even if the cooling rate after annealing during overaging precipitation is increased.
The lower limit is 010%. Also, the upper limit is limited from the viewpoint of grain growth property, and if it exceeds 0.025%, grain growth property is hindered in the annealing process, so even if high temperature annealing at 820 ° C or higher is performed, it is not possible to set the grain size number to 8.0 or less. It will be difficult. It is preferably 0.012 to 0.020.
【００１３】Mn、Ｓ:MnおよびＳは粒内炭化物の析出核
として重要であることから、Mnを0.05％以上、Ｓを0.00
3 ％以上とする。また、Mnが多い場合には材料の硬質化
を招くことから0.25％以下とし、Ｓは熱間脆性の観点か
ら0.020 ％以下とする。好ましくは、Mnは0.08〜0.15
％、Ｓは0.005 〜0.010 ％である。Mn, S: Mn and S are important as precipitation nuclei for intragranular carbides, so Mn is 0.05% or more and S is 0.00% or more.
3% or more. Further, if the Mn content is large, the material is hardened, so the content is 0.25% or less, and the content of S is 0.020% or less from the viewpoint of hot brittleness. Preferably, Mn is 0.08 to 0.15
%, S is 0.005 to 0.010%.
【００１４】Al:AlはAlN 形成を促進させるために必要
であることから下限を0.01％とする。また、多すぎると
材料の硬質化を招くので上限を0.10％とする。好ましく
は、0.015 〜0.04％である。Al: Al is necessary to promote the formation of AlN, so the lower limit is made 0.01%. Further, if the amount is too large, the material is hardened, so the upper limit is made 0.10%. It is preferably 0.015 to 0.04%.
【００１５】Ｎ:Ｎは加工性の面から少ない方が好まし
いが、製鋼コストの上昇を防ぐために上限を0.0030％と
する。好ましくは、0.0010〜0.0020％である。It is preferable that N: N is small in terms of workability, but the upper limit is made 0.0030% in order to prevent an increase in steelmaking cost. Preferably, it is 0.0010 to 0.0020%.
【００１６】Ｂ：Ｂは本発明の主要構成因子であり、Al
より窒化物形成能が高くBNを形成し焼鈍前の残留固体Ｎ
を低減させることにより焼鈍後の粒成長性を向上させ
る。したがって、この効果を得るために下限を0.0003％
とする。しかし過剰なＢは固溶Ｂとなり逆に焼鈍時の粒
成長を阻害するので上限を0.0030％とする。好ましく
は、0.0005〜0.0020％である。B: B is the main constituent factor of the present invention, and Al
Higher nitride forming ability, forming BN and remaining solid N before annealing
The grain growth property after annealing is improved by reducing Therefore, the lower limit is 0.0003% to obtain this effect.
And However, excess B becomes solid solution B and conversely hinders grain growth during annealing, so the upper limit is made 0.0030%. Preferably, it is 0.0005 to 0.0020%.
【００１７】次に、本発明の連続焼鈍条件の限定理由を
述べる。 再結晶焼鈍:連続焼鈍の急冷過程において、粒界近傍の
固溶Ｃは粒界への拡散・炭化物析出に伴い減少してしま
う。このことより粒界近傍では十分な過飽和度が達成さ
れずに炭化物無析出帯が生じる。この炭化物無析出帯に
おける固溶Ｃは析出サイトまでの距離が長くなるため、
長時間の過時効処理を要するようになる。Next, the reasons for limiting the continuous annealing conditions of the present invention will be described. Recrystallization annealing: In the rapid cooling process of continuous annealing, the solid solution C near the grain boundary decreases with diffusion into the grain boundary and carbide precipitation. As a result, a sufficient degree of supersaturation cannot be achieved in the vicinity of the grain boundary, and a carbide-free zone occurs. Since the solid solution C in the carbide-free precipitation zone has a longer distance to the precipitation site,
It requires long-term overaging treatment.
【００１８】したがって、例えば1.5 分程度の過時効処
理により遅時効化を実現すべく炭化物無析出帯の体積を
減少させるため、820 ℃以上880 ℃以下で20秒以上60秒
以下の再結晶焼鈍を行い結晶粒度番号 (JIS G 0552) を
6.5以上8.0 以下として結晶粒界面積を減少させる。Therefore, for example, in order to reduce the volume of the carbide-free precipitate zone in order to achieve delayed aging by overaging for about 1.5 minutes, recrystallization annealing at 820 ° C to 880 ° C for 20 seconds to 60 seconds is performed. The grain size number (JIS G 0552)
The grain boundary area is reduced to 6.5 or more and 8.0 or less.
【００１９】焼鈍温度の上限を880 ℃にしたのはこれを
超えて高くした場合には結晶方位のランダム化により特
性劣化を招くためである。また焼鈍処理設備の長大化お
よびエネルギーコストの増加を防ぐために焼鈍時間の上
限を60秒とした。結晶粒は大きい方が望ましいが、粗粒
化による肌荒れを防ぐために結晶粒度番号で6.5 以上と
する。The upper limit of the annealing temperature is set to 880 ° C. because if it is set higher than this, the characteristics are deteriorated due to randomization of crystal orientation. In addition, the upper limit of the annealing time was set to 60 seconds in order to prevent the annealing treatment equipment from becoming longer and the energy cost from increasing. Larger crystal grains are preferred, but the grain size number should be 6.5 or more to prevent rough skin due to coarsening.
【００２０】一次冷却処理:再結晶処理の終了後は650
〜740 ℃まで７℃/S以下の冷却速度で徐冷するが、これ
はＣの固溶量を高め、次に続く急冷、過時効における粒
内炭化物析出に必要とされるＣの過飽和度を確保するた
めに行うもので、フェライト中へのＣの固溶限の関係か
ら急冷開始温度が650 ℃より低い場合あるいは740 ℃よ
り高い場合には十分な固溶Ｃの過飽和度が得られないた
め、より長時間の過時効処理を要する。したがって、好
ましくは、この急冷開始温度を650 〜740 ℃とする。Primary cooling treatment: 650 after completion of recrystallization treatment
It is gradually cooled to ~ 740 ℃ at a cooling rate of 7 ℃ / S or less, but this increases the solid solution amount of C, and the supersaturation degree of C required for precipitation of intragranular carbide in the subsequent rapid cooling and overaging. This is done for the purpose of ensuring that, because of the solid solubility limit of C in ferrite, if the quenching start temperature is lower than 650 ° C or higher than 740 ° C, a sufficient degree of supersaturation of solid solution C cannot be obtained. , Requires a longer overaging treatment. Therefore, the quenching start temperature is preferably 650 to 740 ° C.
【００２１】二次冷却処理:次に、急速冷却を行なっ
て、粒内炭化物析出を可能にする過飽和速度を達成させ
るが、冷却速度が80℃/sより小さい場合には粒内炭化物
密度が低下するため長い過時効処理時間を要するように
なる。また、250 ℃/sより大きくなると粒内炭化物が微
細に分散するため降伏強度を増加させ、延性を低下させ
る。したがって冷却速度は80〜250 ℃/sとする。好まし
くは、冷却速度は100 〜180 ℃/Sである。Secondary cooling treatment: Next, rapid cooling is carried out to achieve a supersaturation rate that enables precipitation of carbides in the grain, but if the cooling rate is less than 80 ° C./s, the density of carbides in the grain decreases. Therefore, a long overaging treatment time is required. On the other hand, if it exceeds 250 ° C / s, the intragranular carbide is finely dispersed, so that the yield strength is increased and the ductility is decreased. Therefore, the cooling rate is 80-250 ° C / s. Preferably, the cooling rate is 100-180 ° C / S.
【００２２】過時効処理:二次冷却処理の冷却終点温度
および過時効温度は粒内炭化物の分布と成長を決定す
る。冷却終点温度が375 ℃より高い場合には固溶Ｃの拡
散は十分に確保できるが固溶Ｃの溶解度が大きいため固
溶Ｃの低減が十分に行われない。また325 ℃より低い場
合には固溶Ｃの拡散が不十分となり固溶Ｃが大量に残留
してしまう。これより急冷終点温度は325 〜375 ℃とす
る。Over-aging treatment: The cooling end temperature and over-aging temperature of the secondary cooling treatment determine the distribution and growth of intragranular carbide. When the cooling end temperature is higher than 375 ° C., the diffusion of the solid solution C can be sufficiently secured, but the solubility of the solid solution C is large, so that the solid solution C cannot be sufficiently reduced. On the other hand, when the temperature is lower than 325 ° C., the solid solution C is not sufficiently diffused and a large amount of the solid solution C remains. From this, the end temperature of quenching shall be 325-375 ° C.
【００２３】過時効過程における冷却速度が0.5 ℃/sよ
り大きい場合には固溶Ｃの析出サイトまでの拡散が不十
分となり時効性が劣化するので0.5 ℃/s以下の傾斜過時
効または等温時効を適用する。すなわち、本発明におい
て過時効処理は保定処理も包含する内容である。If the cooling rate in the overaging process is higher than 0.5 ° C./s, the diffusion of the solid solution C to the precipitation site is insufficient and the aging property is deteriorated. Therefore, the gradient overaging or isothermal aging of 0.5 ° C./s or less is performed. Apply. That is, in the present invention, the overaging treatment includes the retention treatment.
【００２４】本発明の場合、過時効処理に要する時間
は、1.5 分以上3.0 分以下であれば十分である。換言す
れば、本発明によれば1.5 〜3.0 分という短時間の過時
効処理でも優れた耐時効性が実現されるということであ
る。もちろんそれ以上の時間をかけて過時効処理を行っ
てもよいが、経済的観点からは不必要であろう。In the case of the present invention, it is sufficient that the time required for the overaging treatment is 1.5 minutes or more and 3.0 minutes or less. In other words, according to the present invention, excellent aging resistance can be achieved even by overaging treatment for a short time of 1.5 to 3.0 minutes. Of course, overaging may be carried out over a longer period of time, but it may be unnecessary from an economical point of view.
【００２５】ここに、上述のような本発明における連続
焼鈍条件の限定理由について実験例に基づいてさらに補
足すると次の通りである。Here, the reason for limiting the continuous annealing conditions in the present invention as described above will be further supplemented based on experimental examples.
【００２６】図１は、本発明で規定する範囲内の鋼につ
いての降伏点伸びと焼付硬化性との一般的関係を示すグ
ラフである。時効性は、人工促進時効後の降伏点伸びや
焼付硬化性でもって評価される。すなわち、100 ℃×60
分の人工促進時効後の降伏点伸び (YP−El) や、２％予
歪後に170 ℃×20分の人工促進時効を行い、この時効前
後における降伏強度の上昇分で定義される焼付硬化性
(以下BHと称する) で評価され、耐ストレッチャースト
レインの観点から時効後でYP−Elを0.3 ％以下にする必
要がある。この観点から図１の結果からは、遅時効とみ
なすには、BHで35N/mm2 以下とすることが必要であるこ
とがわかる。FIG. 1 is a graph showing the general relationship between yield point elongation and bake hardenability for steels within the range specified by the present invention. The aging property is evaluated by the yield point elongation and the bake hardenability after artificial acceleration aging. That is, 100 ℃ x 60
Min. Yield point elongation after artificial accelerated aging (YP-El) and 2% pre-strain after artificial aging at 170 ° C for 20 minutes, and bake hardenability defined by the increase in yield strength before and after this aging.
(Hereinafter referred to as BH), it is necessary to set YP-El to 0.3% or less after aging from the viewpoint of stretcher strain resistance. From this point of view, it can be seen from the results of FIG. 1 that it is necessary to set the BH to 35 N / mm 2 or less in order to consider it as the delayed aging.
【００２７】次に、焼鈍温度と結晶粒度番号とのBHの関
係を調べるために後述する表１に示す化学成分の鋼ｃと
鋼ｇについて粒成長性と時効性を調査した。焼鈍均熱時
間を30秒とし、700 ℃まで４℃/sで徐冷し、100 ℃/sで
急冷した後、350 ℃で1.5 分の過時効処理を行った。Next, in order to investigate the relationship between BH between the annealing temperature and the grain size number, grain growth and aging of steels c and g having chemical compositions shown in Table 1 described later were investigated. Annealing soaking time was 30 seconds, slow cooling to 700 ° C at 4 ° C / s, rapid cooling to 100 ° C / s, and overaging treatment at 350 ° C for 1.5 minutes.
【００２８】結果は図２に示すが、これより、鋼ｃのよ
うに成分が上記範囲にある場合には800 ℃付近から著し
い粒成長が生じ、820 ℃以上という比較的低温域で結晶
粒度番号8.0 以下を実現し、BHで35N/mm2 以下とするこ
とが可能であることがわかる。また、鋼ｇはＢ以外は上
記成分範囲にあるが、著しい粒成長は確認されず、結晶
粒度番号8.0 以下とするには880 ℃超の高温焼鈍を施す
必要があり実質上困難である。The results are shown in FIG. 2. From this, when the composition is in the above range as in steel c, remarkable grain growth occurs from around 800 ° C., and the grain size number is relatively low at 820 ° C. or higher. It can be seen that it is possible to achieve 8.0 or less and BH of 35 N / mm 2 or less. Although steel g is in the above-mentioned composition range except for B, no remarkable grain growth is confirmed, and it is practically difficult to perform high temperature annealing above 880 ° C to obtain a grain size of 8.0 or less.
【００２９】さらに、適切な過時効処理時間を求めるた
めに、同じく表１の鋼ｃについて焼鈍温度830 ℃で、均
熱時間を30秒とし、700 ℃まで４℃/sで徐冷し、350 ℃
まで100 ℃/sで急冷し、過時効処理温度を350 ℃とする
連続焼鈍を行った。Further, in order to obtain an appropriate overaging treatment time, similarly for steel c in Table 1, the annealing temperature was 830 ° C., the soaking time was 30 seconds, and the steel was slowly cooled to 700 ° C. at 4 ° C./s, and 350 ℃
Was quenched at 100 ℃ / s, and continuous annealing was performed at an overaging temperature of 350 ℃.
【００３０】結果を図３に示すが、これからも分かるよ
うに、1.5 分未満の過時効処理では、BHは35N/mm2 より
大きくなっており時効性の改善が不十分であり、1.5 分
以上の過時効時間を要することがわかる。また３分より
長く過時効処理を行っても時効性改善の効果は小さく、
過時効処理設備の長大化やエネルギーコストの増加を防
ぐために過時効処理時間の上限を３分とした。次に、以
上のような本発明の作用効果について実施例をもってさ
らに具体的に説明する。The results are shown in FIG. 3. As can be seen from the results, BH was more than 35 N / mm 2 in the overaging treatment for less than 1.5 minutes, and the improvement of the aging was insufficient, and therefore 1.5 minutes or more. It can be seen that the overaging time is required. In addition, the effect of improving the aging effect is small even if the overaging treatment is performed for more than 3 minutes
The upper limit of the overaging treatment time was set to 3 minutes in order to prevent the overaging treatment equipment from being lengthened and the energy cost from increasing. Next, the effects of the present invention as described above will be described more specifically with reference to Examples.
【００３１】[0031]
(実施例１)表１に示す化学成分を有する鋼を溶製し、連
続鋳造法によってスラブを製造した後、熱間圧延で870
〜920 ℃で仕上圧延を行い板厚を3.5 mmとし、鋼ａ〜ｈ
については630 ℃、鋼ｉについては720 ℃でコイルに巻
取った。その後酸洗し、0.8 mmまで冷間圧延を行い、連
続焼鈍を行った。(Example 1) Steel having the chemical composition shown in Table 1 was melted, and a slab was manufactured by a continuous casting method, followed by hot rolling to produce 870.
Finish rolling at ~ 920 ℃, plate thickness 3.5 mm, steel a ~ h
At 630 ° C. for steel i and 720 ° C. for steel i. After that, it was pickled, cold-rolled to 0.8 mm, and continuously annealed.
【００３２】連続焼鈍条件は焼鈍温度830 ℃で、均熱時
間を30秒とし、700 ℃まで４℃/sで徐冷し、350 ℃まで
100 ℃/sで急冷し、350 ℃で1.5 分間の過時効処理を行
った。その後1.2 ％の伸び率でスキンパス圧延を行っ
た。試験として結晶粒度番号とBH値を求めた。この結果
を表２に示す。The continuous annealing conditions were an annealing temperature of 830 ° C., a soaking time of 30 seconds, slow cooling to 700 ° C. at 4 ° C./s, to 350 ° C.
It was quenched at 100 ° C / s and overaged at 350 ° C for 1.5 minutes. After that, skin pass rolling was performed at an elongation of 1.2%. As a test, the grain size number and BH value were obtained. The results are shown in Table 2.
【００３３】鋼ｅおよび鋼ｆは、Ｃ以外は本発明の成分
域内にあるが、鋼ｅの場合にはＣが低いことによる粒内
炭化物の析出が不十分となり、鋼ｆの場合にはＣが若干
高いために粒成長が不十分となり、共に時効性が劣化し
ている。Steel e and steel f are within the composition range of the present invention except for C, but in the case of steel e, the precipitation of intragranular carbide due to the low content of C is insufficient, and in the case of steel f, C The grain growth is insufficient due to the slightly high value, and the aging property is deteriorated in both cases.
【００３４】鋼ｇおよび鋼ｈは、Ｂ以外は本発明の成分
域内にあるが、鋼ｇの場合にはＢの添加がなされていな
いため粒成長不足となり、鋼ｈの場合にはＢ添加量が多
すぎるため粒成長が阻害され時効性が劣る。鋼ｉではＣ
が多く、さらにＢの添加がなされていないため粒成長が
悪く時効性も悪い。Steel g and steel h are within the composition range of the present invention except for B, but in the case of steel g, grain growth is insufficient because B is not added, and in the case of steel h, the amount of B added is Is too much, grain growth is hindered and aging is inferior. C for steel i
However, grain growth is poor and aging is also poor because B is not added.
【００３５】鋼ａ〜ｄの成分は本発明域内にあり、十分
な粒成長により1.5 分の過時効処理でBH35N/mm2 以下と
なっており十分に時効性が改善されている。The components of steels a to d are within the range of the present invention, and due to sufficient grain growth, BH is 35 N / mm 2 or less after over-aging treatment for 1.5 minutes, and the aging property is sufficiently improved.
【００３６】(実施例２)表１に示す鋼ｃを実施例１と同
様の製造条件により得られた冷延鋼板を用いて時効性に
及ぼす連続焼鈍条件影響を調査した。各焼鈍条件とその
特性を表３に示す。試験方法については実施例１と同様
である。(Example 2) The effect of continuous annealing conditions on the aging property of steel c shown in Table 1 was investigated using a cold-rolled steel sheet obtained under the same manufacturing conditions as in Example 1. Table 3 shows each annealing condition and its characteristics. The test method is the same as in Example 1.
【００３７】熱処理条件１では焼鈍温度が低いために粒
成長が不足し、時効性の劣化が認められる。熱処理条件
２〜５では、冷却終点温度および過時効処理温度が適正
温度から外れているため時効性が悪い。熱処理条件６で
は、過時効処理時間が短すぎるため時効性の改善が不十
分である。Under the heat treatment condition 1, since the annealing temperature is low, grain growth is insufficient and deterioration of aging property is observed. Under the heat treatment conditions 2 to 5, the cooling end point temperature and the overaging treatment temperature deviate from the proper temperatures, so that the aging property is poor. Under the heat treatment condition 6, the overaging treatment time is too short, so that the improvement of the aging property is insufficient.
【００３８】熱処理条件７〜９は本発明焼鈍条件であ
り、十分な粒成長により1.5 分以上の非常に短い過時効
処理によりBH35N/mm2 以下となっており遅時効化が実現
されている。The heat treatment conditions 7 to 9 are the annealing conditions of the present invention, and BH35N / mm 2 or less is achieved by the extremely short overaging treatment of 1.5 minutes or more due to sufficient grain growth, and delayed aging is realized.
【００３９】[0039]
【表１】 [Table 1]
【００４０】[0040]
【表２】 [Table 2]
【００４１】[0041]
【表３】 [Table 3]
【００４２】[0042]
【発明の効果】本発明は、鋼組成の調整と連続焼鈍熱サ
イクルの適正化により、短時間の過時効処理により耐時
効性に優れた軟質冷延鋼板を製造することを可能とし、
再加熱等に必要な装置の増設やコストの増加を防ぎ生産
性を向上させる等の効果を有する優れた発明である。INDUSTRIAL APPLICABILITY The present invention makes it possible to produce a soft cold-rolled steel sheet excellent in aging resistance by a short-time overaging treatment by adjusting the steel composition and optimizing the continuous annealing heat cycle,
This is an excellent invention that has the effects of increasing the number of devices required for reheating, preventing an increase in cost, and improving productivity.
【図面の簡単な説明】[Brief description of drawings]
【図１】BHと時効処理後のYP−ELの関係を示すグラフで
ある。FIG. 1 is a graph showing the relationship between BH and YP-EL after aging treatment.
【図２】各成分の鋼について結晶粒度番号とBHに及ぼす
焼鈍温度の影響を示すグラフである。FIG. 2 is a graph showing the effect of annealing temperature on grain size number and BH for steels of each component.
【図３】BHに及ぼす過時効処理時間の影響を示すグラフ
である。FIG. 3 is a graph showing the effect of overaging treatment time on BH.
Claims (1)
〜0.020 ％、 sol.Al：0.01〜0.10％、Ｎ：0.0030％以下、Ｂ：0.0003
〜0.0030％ 残部鉄および不可避的不純物から成る鋼組成を有する鋼
を、通常の熱間圧延−酸洗−冷間圧延を行い、続いて連
続焼鈍において820 ℃以上880 ℃以下で20秒以上60秒以
下の再結晶焼鈍することにより結晶粒寸法をJIS G 0552
で定義される結晶粒度番号で6.5 以上8.0 以下とし、次
いで650 〜740 ℃まで７℃/s以下の冷却速度で徐冷し、
さらに325 〜375 ℃まで80〜250 ℃/sの冷却速度で冷却
した後、その冷却終点温度から保定を含む0.5 ℃/s以下
の冷却速度で過時効処理を行うことを特徴とする耐時効
性に優れた軟質の低炭素冷延鋼板の製造方法。1. By weight%, C: 0.010 to 0.025%, Mn: 0.05 to 0.25%, S: 0.003
~ 0.020%, sol.Al: 0.01 ~ 0.10%, N: 0.0030% or less, B: 0.0003
~ 0.0030% Steel having a steel composition consisting of balance iron and unavoidable impurities is subjected to normal hot rolling-pickling-cold rolling, followed by continuous annealing at 820 ° C to 880 ° C for 20 seconds to 60 seconds. The crystal grain size was changed to JIS G 0552 by performing the following recrystallization annealing.
The grain size number is defined as 6.5 or more and 8.0 or less, and then gradually cooled from 650 to 740 ° C at a cooling rate of 7 ° C / s or less,
Furthermore, after cooling from 325 to 375 ° C at a cooling rate of 80 to 250 ° C / s, overaging treatment is performed from the cooling end temperature at a cooling rate of 0.5 ° C / s or less that includes retention. A method for producing a low carbon cold rolled steel sheet which is excellent in softness.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24945394A JP2953323B2 (en) | 1994-10-14 | 1994-10-14 | Manufacturing method of low carbon cold rolled steel sheet |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24945394A JP2953323B2 (en) | 1994-10-14 | 1994-10-14 | Manufacturing method of low carbon cold rolled steel sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH08109415A true JPH08109415A (en) | 1996-04-30 |
| JP2953323B2 JP2953323B2 (en) | 1999-09-27 |
Family
ID=17193193
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24945394A Expired - Fee Related JP2953323B2 (en) | 1994-10-14 | 1994-10-14 | Manufacturing method of low carbon cold rolled steel sheet |
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| Country | Link |
|---|---|
| JP (1) | JP2953323B2 (en) |
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1994
- 1994-10-14 JP JP24945394A patent/JP2953323B2/en not_active Expired - Fee Related
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| Publication number | Publication date |
|---|---|
| JP2953323B2 (en) | 1999-09-27 |
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