JP2001089817A - Method of manufacturing hot rolled steel plate excellent in longitudinal crack resistance - Google Patents
Method of manufacturing hot rolled steel plate excellent in longitudinal crack resistanceInfo
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- JP2001089817A JP2001089817A JP26504399A JP26504399A JP2001089817A JP 2001089817 A JP2001089817 A JP 2001089817A JP 26504399 A JP26504399 A JP 26504399A JP 26504399 A JP26504399 A JP 26504399A JP 2001089817 A JP2001089817 A JP 2001089817A
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- rolling
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- Heat Treatment Of Sheet Steel (AREA)
- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、特にコンプレッサ
ーカバーなど深絞り性が要求される部位に適用される軟
質熱延鋼板の製造方法に係り、深絞り加工後の部材に衝
撃が加わっても脆性的な破壊をしない、即ち、耐たて割
れ性に優れた深絞り用熱延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 method for producing a soft hot-rolled steel sheet which is applied particularly to a portion requiring deep drawing such as a compressor cover, and is fragile even if an impact is applied to a member after deep drawing. The present invention relates to a method for producing a hot-rolled steel sheet for deep drawing, which does not cause permanent breakage, that is, has excellent vertical cracking resistance.
【０００２】[0002]
【従来の技術】従来、深絞り用熱延鋼板の成形性、耐た
て割れ性に関し、様々な検討が成されてきた。2. Description of the Related Art Various studies have hitherto been made on the formability and warp resistance of hot-rolled steel sheets for deep drawing.
【０００３】例えば、極低炭素鋼にＴｉを添加し成形性
を向上させるとともに、耐２次加工脆性のためＣを意図
的に鋼中に固溶させ、且つＢを添加する技術（特公平５
−８８２９９号公報）、あるいは、低炭素鋼を結晶粒微
細化のため、仕上げ圧延をＡｒ3変態点直上で行い、適
正な温度範囲で巻き取る方法（特開平２−２０９４２３
号公報）や、Ａｒ3変態点以下の温度で仕上げ圧延を行
い、深絞りに好ましい集合組織を得ようという方法など
である。[0003] For example, a technique of adding Ti to ultra-low carbon steel to improve formability, intentionally dissolving C in steel due to secondary work embrittlement resistance and adding B (Japanese Patent Publication No.
Japanese Patent Application Laid-Open No. 2-209423) or a method in which low-carbon steel is subjected to finish rolling just above the Ar 3 transformation point and refined in a proper temperature range in order to refine crystal grains.
Publication) and finish rolling at a temperature equal to or lower than the Ar 3 transformation point to obtain a texture preferable for deep drawing.
【０００４】しかし、Ａｒ3変態点以下での仕上げ圧延
は、圧延荷重が大きくなってしまい、製造上好ましくな
い。また、その場合、フェライト粒が大きくなり、耐た
て割れ性が劣化するとともに、深絞り時の異方性が大き
くなる。[0004] However, finish rolling at a temperature lower than the Ar 3 transformation point increases the rolling load, and is not preferable in production. In that case, the ferrite grains become large, the warp resistance is deteriorated, and the anisotropy during deep drawing becomes large.
【０００５】極低炭素鋼にＴｉ、Ｎｂなどを添加して成
形性を向上させ、且つ、耐たて割れ性のためＰなどを低
減し、固溶Ｃを残存させ、Ｂを添加するという方法があ
る。これは主としてフェライト粒界を強化し、粒界での
割れ、即ち、粒界割れを防止しようという技術である。
しかし、近年深絞り熱延鋼板に対する耐たて割れ性の要
求が厳しくなってきており、粒界割れ対策のみでは対応
できなくなってきている。即ち、たて割れ発生品を観察
すると、粒界割れではなく、結晶粒内で破壊する劈開割
れのことが多い。[0005] A method in which Ti, Nb, etc. are added to ultra-low carbon steel to improve the formability, and P, etc. are reduced due to the resistance to warp cracking, solute C remains, and B is added. There is. This is a technique for strengthening ferrite grain boundaries and preventing cracks at grain boundaries, that is, grain boundary cracks.
However, in recent years, the demand for the resistance to vertical cracking of deep drawn hot rolled steel sheets has become strict, and it is no longer possible to cope with only grain boundary cracking measures. That is, when observing a product in which a vertical crack is generated, it is often the case that the crack is not a grain boundary crack but a fracture in a crystal grain.
【０００６】ここで、仕上げ温度を、Ａｒ3変態点直上
まで下げて仕上げを行うなどして結晶粒を微細化する技
術は、粒界割れのみならず、劈開割れにも効果がある。
しかし、それだけでは、近年、益々厳しくなっている耐
たて割れ性の要求に応えることが出来なくなってきてい
る。Here, the technique of making the crystal grains fine by lowering the finishing temperature to just above the Ar 3 transformation point is effective not only for grain boundary cracking but also for cleavage cracking.
However, it is no longer possible to meet the increasingly severe demand for warp resistance in recent years.
【０００７】更に、特開平１０−１８３２５５号公報に
は、ｒ値の面内異方性を低減するため熱延時の集合組織
制御を行うという技術が開示されている。しかし、この
技術は、圧延時の摩擦係数を下げるため熱延時に潤滑を
施す必要があり、コスト面から不利なだけでなく、大量
生産も困難である。Furthermore, Japanese Patent Application Laid-Open No. 10-183255 discloses a technique of controlling the texture during hot rolling in order to reduce the in-plane anisotropy of the r value. However, this technique requires lubrication at the time of hot rolling in order to reduce the friction coefficient at the time of rolling, which is disadvantageous not only in terms of cost but also mass production.
【０００８】[0008]
【発明が解決しようとする課題】本発明は、このような
課題を解決するためになされてもので、耐たて割れ性に
優れた熱延鋼板、特に板厚が４ｍｍ以上といった厚物の
熱延鋼板の製造方法を提供することを目的とする。DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and is intended to provide a hot-rolled steel sheet having excellent resistance to warp cracking, in particular, a heat-rolled steel sheet having a thickness of 4 mm or more. An object of the present invention is to provide a method for manufacturing a rolled steel sheet.
【０００９】[0009]
【課題を解決するための手段】前述したごとく、近年、
耐たて割れ性に対する要求は厳しくなってきており、且
つ、ユーザーで発生するたて割れは、劈開破壊が多くな
ってきている。そこで、耐たて割れ性改善には、成分適
性化による粒界破壊対策に加えて結晶粒制御が重要と考
えられる。As mentioned above, in recent years,
The demand for the resistance to warp cracking is becoming severe, and the cracks generated by the user are increasing the number of cleavage fractures. Therefore, in order to improve the vertical cracking resistance, it is considered important to control the crystal grains in addition to the countermeasures against grain boundary destruction by optimizing the components.
【００１０】劈開破壊の場合、フェライト粒界で破壊の
方向が変化することから、微細粒の方が劈開破壊しにく
い。このため、従来より低温仕上げによる細粒化が図ら
れてきたが、それでも耐たて割れ性は十分とは言えなか
った。その理由は、以下のように考えられる。低温仕上
げを行うと、仕上げ圧延の後段側においてオーステナイ
ト粒が再結晶を起こしにくくなる。このため、仕上げ圧
延後、歪の蓄積した展伸したオーステナイト粒から複数
のフェライト粒に変態する。変態後のフェライト粒の結
晶方位は、変態前のオーステナイト粒の影響を受けるた
め、これらの複数生成したフェライト粒の結晶方位は比
較的揃ってしまう。結晶方位の揃ったフェライト粒の粒
界は劈開破壊を抑制しにくく、劈開破壊が発生しやすく
なると考えられる。近年、コンプレッサーカバーなどは
大型化が進み、例えば４ｍｍ以上というように比較的厚
い鋼板板厚の材料が求められるようになってきた。この
ような厚物の鋼板は圧延中の温度低下が小さいため、仕
上げ温度（圧延終了温度）を低下させるためには仕上げ
圧延中の温度を薄物材よりも更に低下させる必要があ
り、前記の影響が大きくなりがちである。In the case of cleavage fracture, since the direction of fracture changes at the ferrite grain boundary, the fine grains are less likely to undergo cleavage fracture. For this reason, grain refinement by low-temperature finishing has been conventionally attempted, but the cracking resistance was still insufficient. The reason is considered as follows. When the low-temperature finishing is performed, the austenite grains are less likely to recrystallize on the subsequent stage of the finish rolling. For this reason, after the finish rolling, the expanded austenite grains having accumulated strain are transformed into a plurality of ferrite grains. Since the crystal orientation of the ferrite grains after the transformation is affected by the austenite grains before the transformation, the crystal orientations of the plurality of ferrite grains formed are relatively uniform. The grain boundaries of ferrite grains having a uniform crystal orientation are unlikely to suppress cleavage destruction, and it is considered that cleavage destruction is likely to occur. In recent years, compressor covers and the like have been increased in size, and a material having a relatively thick steel plate thickness of, for example, 4 mm or more has been required. Such a thick steel sheet has a small temperature drop during rolling, and therefore, in order to lower the finishing temperature (rolling end temperature), it is necessary to further lower the temperature during finishing rolling as compared with a thin material. Tends to be large.
【００１１】これらの課題を解決するため、低温仕上げ
による結晶粒微細化に加えて仕上げ圧延における前段強
圧下により集合組織を弱くすることが考えられる。この
方法を以下に示す。仕上げ圧延前段部では温度が高くオ
ーステナイトの再結晶が起こりやすいことを利用し、前
段強圧下により仕上げ圧延前段部で微細な等軸な再結晶
オーステナイ粒を生成させる。更に、仕上げ圧延後段で
の圧下率を下げ、オーステナイト粒内の歪の蓄積を小さ
くすることにより、オーステナイト粒界からのフェライ
トの変態を促進する。オーステナイト粒界から変態した
フェライト粒は、元のオーステナイト粒の影響を受けに
くいため、比較的ランダムな方位となり、耐たて割れ性
に優れると考えられる。また、トータル（熱間仕上げ圧
延全体）の仕上げ圧下率が大きくなると仕上げ圧延後段
部での圧下率も大きくなりがちであるため、トータルの
圧下率の上限を規定する。なお。このような前段強圧下
の効果は、再結晶挙動に影響されるものであるから、Ｃ
等の成分の影響を受ける。本発明方法は、後述する成分
範囲において効果の大きいものである。[0011] In order to solve these problems, it is conceivable to weaken the texture by applying a high pressure in the first stage in the finish rolling, in addition to the refinement of crystal grains by low-temperature finishing. This method is described below. Utilizing the fact that the temperature is high and the austenite recrystallization is likely to occur in the pre-rolling stage, fine pre-rolling is used to generate fine equiaxed recrystallized austenite grains in the pre-rolling stage. Further, the transformation of ferrite from austenite grain boundaries is promoted by lowering the rolling reduction in the latter stage of finish rolling and reducing the accumulation of strain in austenite grains. Ferrite grains transformed from the austenite grain boundaries are less likely to be affected by the original austenite grains, and therefore have a relatively random orientation, and are considered to have excellent warp resistance. Further, when the total reduction ratio of the whole (the entire hot finish rolling) increases, the reduction ratio in the subsequent stage of the finish rolling tends to increase, so the upper limit of the total reduction ratio is defined. In addition. Such an effect of the first stage under high pressure is affected by the recrystallization behavior.
And other components. The method of the present invention is highly effective in the component ranges described below.
【００１２】このようにして発明した耐たて割れ性に優
れた熱延鋼板の製造方法を以下に示す。A method of manufacturing a hot-rolled steel sheet having excellent resistance to warp cracking invented in this manner will be described below.
【００１３】請求項１記載の発明は、Ｃ：０．００１〜
０．０３ｗｔ．％、Ｓｉ：０〜０．５ｗｔ．％、Ｍｎ：
０〜２ｗｔ．％、Ｐ：０．０２ｗｔ．％以下、Ｓ：０．
０２ｗｔ．％以下、ｓｏｌ．Ａｌ：０．１ｗｔ．％以下
及びＮ：０．００５ｗｔ．％以下を含有する鋼からなる
スラブを熱間仕上げ圧延するに際し、トータルの仕上げ
圧延率が９５％以下で、且つ、（Ａｒ3変態点＋７０
℃）以上の温度範囲でのトータル圧下率が５５％以上
で、且つ、仕上げ温度がＡｒ3変態点〜（Ａｒ3変態点＋
４０℃）の温度範囲内で圧延することに特徴を有するも
のである。According to the first aspect of the present invention, C: 0.001 to
0.03 wt. %, Si: 0 to 0.5 wt. %, Mn:
0 to 2 wt. %, P: 0.02 wt. % Or less, S: 0.
02 wt. % Or less, sol. Al: 0.1 wt. % And N: 0.005 wt. % Of the steel having a total finish rolling ratio of 95% or less and (Ar 3 transformation point +70).
° C) or more, the total draft in the temperature range of 55% or more, and the finishing temperature is from the Ar 3 transformation point to the (Ar 3 transformation point +
(40 ° C.).
【００１４】請求項２記載の発明は、Ｃ：０．００１〜
０．０３ｗｔ．％、Ｓｉ：０〜０．５ｗｔ．％、Ｍｎ：
０〜２ｗｔ．％、Ｐ：０．０２ｗｔ．％以下、Ｓ：０．
０２ｗｔ．％以下、ｓｏｌ．Ａｌ：０．１ｗｔ．％以下
及びＮ：０．００５ｗｔ．％以下を含有し、更に、Ｔ
ｉ：０．００５〜０．１ｗｔ．％、Ｎｂ：０．００５〜
０．０５ｗｔ．％、Ｚｒ：０．００５〜０．０５ｗｔ．
％及びＶ：０．００５〜０．０５ｗｔ．％のうちの少な
くとも１種を含有する鋼からなるスラブを熱間仕上げ圧
延するに際し、トータルの仕上げ圧延率が９５％以下
で、且つ、（Ａｒ3変態点＋７０℃）以上の温度範囲で
のトータル圧下率が５５％以上で、且つ、仕上げ温度が
Ａｒ3変態点〜（Ａｒ3変態点＋４０℃）の温度範囲内で
圧延することに特徴を有するものである。According to a second aspect of the present invention, C: 0.001 to
0.03 wt. %, Si: 0 to 0.5 wt. %, Mn:
0 to 2 wt. %, P: 0.02 wt. % Or less, S: 0.
02 wt. % Or less, sol. Al: 0.1 wt. % And N: 0.005 wt. % Or less.
i: 0.005 to 0.1 wt. %, Nb: 0.005 to
0.05 wt. %, Zr: 0.005 to 0.05 wt.
% And V: 0.005 to 0.05 wt. % In hot finish rolling of a slab made of steel containing at least one of the steels having a total finish reduction ratio of 95% or less and a temperature range of (Ar 3 transformation point + 70 ° C.) or more. Rolling is performed at a rolling reduction of 55% or more and a finishing temperature within a temperature range from the Ar 3 transformation point to (Ar 3 transformation point + 40 ° C.).
【００１５】請求項３記載の発明は、請求項１又は２に
示す成分に、更に、Ｂ：０．０００２〜０．００５ｗ
ｔ．％を含有する鋼からなるスラブを熱間仕上げ圧延す
るに際し、トータルの仕上げ圧延率が９５％以下で、且
つ、（Ａｒ3変態点＋７０℃）以上の温度範囲でのトー
タル圧下率が５５％以上で、且つ、仕上げ温度がＡｒ3
変態点〜（Ａｒ3変態点＋４０℃）の温度範囲内で圧延
することに特徴を有するものである。According to a third aspect of the present invention, there is provided the composition according to the first or second aspect, further comprising B: 0.0002 to 0.005 w.
t. % In hot finish rolling of a slab made of steel containing at least 95% and a total draft of 55% or more in a temperature range of (Ar 3 transformation point + 70 ° C.) or more. And the finishing temperature is Ar 3
Rolling is performed within the temperature range from the transformation point to (Ar 3 transformation point + 40 ° C.).
【００１６】以下に、成分及び製造条件の限定理油につ
いて説明する。Hereinafter, the limiting oils of the components and the production conditions will be described.
【００１７】Ｃ：０．００１〜０．０３ｗｔ．％ Ｃの含有量が０.０３ｗｔ．％を超えると鋼板の延性が
低下すると共に降伏強度及び引張強度が増大し、成形性
が劣化する。一方、固溶Ｃが存在した方がフェライト粒
界が強化され、耐たて割れ性に対して有効であり、０．
００１ｗｔ．％以上添加すべきである。好ましい範囲
は、０．００４０〜０．００８０ｗｔ．％である。C: 0.001 to 0.03 wt. % C content is 0.03 wt. %, The ductility of the steel sheet decreases, the yield strength and the tensile strength increase, and the formability deteriorates. On the other hand, the presence of solid solution C strengthens the ferrite grain boundaries and is effective for warp crack resistance.
001 wt. % Should be added. The preferred range is 0.0040 to 0.0080 wt. %.
【００１８】Ｓｉ：０〜０．５ｗｔ．％ Ｓｉ量が多くなると鋼板強度が上昇し、成形性が劣化す
ると共に、耐たて割れ性も劣化するので、Ｓｉ量は０．
５ｗｔ．％以下とすべきである。好ましい範囲としては
０．０３ｗｔ．％以下である。本発明においてＳｉは必
ずしも必要ではないため、下限は設けない（０ｗｔ．％
も含む）。Si: 0 to 0.5 wt. When the amount of Si increases, the strength of the steel sheet increases, the formability deteriorates, and the resistance to vertical cracking also deteriorates.
5 wt. %. A preferable range is 0.03 wt. % Or less. In the present invention, since Si is not necessarily required, no lower limit is provided (0 wt.%
Including).
【００１９】Ｍｎ：０〜２ｗｔ．％ Ｍｎは、Ｓｉと同様、鋼板の強度を上昇させ、成形性、
耐たて割れ性を劣化させるので、２ｗｔ．％以下とすべ
きである。Ｍｎ量は０ｗｔ．％でもかまわないが、製鋼
上の精錬コストから０．０５ｗｔ．％以上が好ましい。
また、強度、耐たて割れ性の観点から０．３ｗｔ．％以
下が好ましい。Mn: 0 to 2 wt. % Mn, like Si, increases the strength of the steel sheet,
2 wt. %. The amount of Mn is 0 wt. %, But 0.05 wt. % Or more is preferable.
Further, from the viewpoint of strength and resistance to warp cracking, 0.3 wt. % Or less is preferable.
【００２０】Ｐ：０．０２ｗｔ．％以下 Ｐ量が多いと鋼板が脆化しやすくなり、耐たて割れ性が
不利になるため、０．０２ｗｔ．％以下とすべきであ
る。好ましい範囲は、０．０１５ｗｔ．％以下である。P: 0.02 wt. % Or less When the amount of P is large, the steel sheet is easily embrittled and the resistance to warp cracking is disadvantageous. %. The preferred range is 0.015 wt. % Or less.
【００２１】Ｓ：０．０２ｗｔ．％以下 Ｓの含有量が０．０２ｗｔ．％を超えると介在物が多く
なり、耐たて割れ性が劣化するため、０．０２ｗｔ．％
以下とすべきである。好ましい範囲は、０．００５ｗ
ｔ．％以下である。S: 0.02 wt. % Or less S content is 0.02 wt. %, The amount of inclusions increases and the warp resistance deteriorates. %
Should be: The preferred range is 0.005w
t. % Or less.
【００２２】ｓｏｌ．Ａｌ：０．１ｗｔ．％以下 ｓｏｌ．Ａｌは、鋼の脱酸を安定して行うために必要に
応じて添加する。ｓｏｌ．Ａｌ量が多くなると鋼板の強
度が上昇し、成形性、耐たて割れ性が劣化するため、
０．１ｗｔ．％以下とすべきである。好ましい範囲は、
０．０１〜０．０５ｗｔ．％である。Sol. Al: 0.1 wt. % Or less sol. Al is added as needed to stably deoxidize the steel. sol. When the amount of Al increases, the strength of the steel sheet increases, and formability and warp resistance deteriorate,
0.1 wt. %. The preferred range is
0.01 to 0.05 wt. %.
【００２３】Ｎ：０．００５ｗｔ．％以下 Ｎ含有量が０．００５ｗｔ．％を超えると低延性、高強
度となり、耐たて割れ性も劣化するため、０．００５ｗ
ｔ．％以下とすべきである。好ましい範囲は、０．００
３０ｗｔ．％以下である。N: 0.005 wt. % Or less N content is 0.005 wt. %, The ductility becomes low and the strength becomes high, and the warp resistance deteriorates.
t. %. The preferred range is 0.00
30 wt. % Or less.
【００２４】なお、Ｐ、Ｓ、ｓｏｌ．Ａｌ、Ｎは不可避
物であり、「ｗｔ．％以下」の表示とした。Note that P, S, sol. Al and N are inevitable substances and are indicated as "wt.% Or less".
【００２５】Ｔｉ：０．００５〜０．１ｗｔ．％、Ｎ
ｂ：０．００５〜０．０５ｗｔ．％、Ｚｒ：０．００５
〜０．０５ｗｔ．％、Ｖ：０．００５〜０．０５ｗｔ．
％ Ｔｉ、Ｎｂ、Ｚｒ、Ｖは、鋼板の成形性の向上のため、
１種又は２種以上を適宜添加する。少なすぎる添加は、
成形性の向上が認められない。一方、多すぎる添加は鋼
板中のＣをほとんど固定してしまい、粒界のＣ量が減少
することから耐たて割れ性が劣化する。好ましい範囲と
しては、それぞれ、Ｔｉ：（４８／３２）Ｓ＋（４８／
１４）Ｎ以上、（４８／１２）Ｃ＋（４８／３２）Ｓ＋
（４８／１４）Ｎ以下、Ｎｂ：（９３／１４）Ｎ以上、
（９３／１２）Ｃ＋（９３／１４）Ｎ以下、Ｚｒ（９１
／３２）Ｓ＋（９１／１４）Ｎ以上、（９１／１２）Ｃ
＋（９１／３２）Ｓ＋（９１／１４）Ｎ以下、Ｖ：（５
１／１４）Ｎ以上、（５１／１２）Ｃ＋（５１／１４）
Ｎ以下である。これらの元素はいずれも成形性の向上に
効果があるが、コスト面からＴｉ単独添加が最も好まし
い。Ti: 0.005 to 0.1 wt. %, N
b: 0.005 to 0.05 wt. %, Zr: 0.005
~ 0.05 wt. %, V: 0.005 to 0.05 wt.
% Ti, Nb, Zr, and V are for improving the formability of the steel sheet.
One or two or more are appropriately added. Too little addition
No improvement in moldability is observed. On the other hand, if the addition is too large, C in the steel sheet is almost fixed, and the amount of C at the grain boundaries decreases, so that the cracking resistance deteriorates. Preferred ranges are Ti: (48/32) S + (48 /
14) N or more, (48/12) C + (48/32) S +
(48/14) N or less, Nb: (93/14) N or more,
(93/12) C + (93/14) N or less, Zr (91
/ 32) S + (91/14) N or more, (91/12) C
+ (91/32) S + (91/14) N or less, V: (5
1/14) N or more, (51/12) C + (51/14)
N or less. Each of these elements is effective in improving the formability, but it is most preferable to add Ti alone from the viewpoint of cost.
【００２６】Ｂ：０．０００２〜０．００５ｗｔ．％ Ｂは結晶粒界に偏析し、粒界を強化することにより耐た
て割れ性に効果が有るため、適宜添加する。この効果の
ためには、０．０００２ｗｔ．％以上の添加が必要であ
るが、多すぎるとその効果が飽和し、鋼板が硬化して耐
たて割れ性が劣化するため、０．００５ｗｔ．％以下と
すべきである。好ましい範囲は、０．００１０〜０．０
０２０ｗｔ．％である。B: 0.0002 to 0.005 wt. % B segregates at the crystal grain boundaries and strengthens the grain boundaries, which has an effect on warp crack resistance. For this effect, 0.0002 wt. % Or more is necessary, but if it is too much, the effect is saturated, the steel sheet hardens and the cracking resistance deteriorates. %. The preferred range is 0.0010 to 0.0
020 wt. %.
【００２７】その他の元素については、本発明の効果を
妨げない範囲で含有することができる。例えば、介在物
の形状制御による成形性の向上のためにＣａを０．００
６ｗｔ．％以下、ＲＥＭ：０．１ｗｔ．％以下、耐食性
向上などのため、Ｓｎ：０．１ｗｔ．％以下、Ｃｕ：
０．５ｗｔ．％以下、Ｃｒ：０．８ｗｔ．％以下、Ｎ
ｉ：０．５ｗｔ．％以下、Ｗ：０．５ｗｔ．％以下、Ｍ
ｏ：０．７ｗｔ．％以下の範囲内で適宜添加しても本発
明の効果が妨げられることはない。Other elements can be contained within a range not to impair the effects of the present invention. For example, in order to improve the formability by controlling the shape of inclusions, Ca is added in an amount of 0.00%.
6 wt. % Or less, REM: 0.1 wt. %, Sn: 0.1 wt. % Or less, Cu:
0.5 wt. % Or less, Cr: 0.8 wt. % Or less, N
i: 0.5 wt. % Or less, W: 0.5 wt. % Or less, M
o: 0.7 wt. % Does not hinder the effect of the present invention.
【００２８】こうした成分を含有する鋼を仕上げ圧延す
るに際しては、鋼を溶製後粗バーあるいは粗バー相当の
厚みの薄スラブを製造する。その製法は特に限定しない
が、通常は、鋼を溶製後、連続鋳造あるいは造塊−分塊
圧延によりスラブとなし、そのまま直接あるいは加熱炉
で再加熱して粗圧延することにより粗バーを、又は、溶
製後、連続鋳造により粗バー相当の厚みを有する薄スラ
ブを、製造する。When the steel containing such components is finish-rolled, the steel is melted and then a rough bar or a thin slab having a thickness equivalent to the rough bar is manufactured. Although the production method is not particularly limited, usually, after smelting the steel, a continuous casting or ingot-forming into a slab by ingot-rolling, the raw bar is directly heated or re-heated in a heating furnace to obtain a rough bar. Alternatively, after smelting, a thin slab having a thickness equivalent to a rough bar is manufactured by continuous casting.
【００２９】スラブの再加熱を行う場合は、スケール欠
陥の発生防止及び仕上げ圧延前のオーステナイト粒の微
細化を図る上で、１２５０℃以下の低温加熱が好まし
い。When the slab is reheated, low-temperature heating of 1250 ° C. or less is preferable in order to prevent the occurrence of scale defects and to refine the austenite grains before finish rolling.
【００３０】熱間仕上げ圧延の仕上げ温度（＝圧延終了
温度）は、前述したように結晶粒微細化のため、Ａｒ3
変態点以上から（Ａｒ3変態点＋４０℃）以下、の温度
範囲で行うべきである。仕上げ温度がＡｒ3変態点未満
では、フェライトに変態してから圧延が行なわれるた
め、フェライト粒が大きくなり、また、展伸するため材
質の異方性が大きくなる。（Ａｒ3変態点＋４０℃）を
超える仕上げ温度では、仕上げ後のフェライトの粒成長
によりフェライトが大きくなり、耐たて割れ性が劣化す
る。細粒化と集合組織を弱くすることを両立させるた
め、トータルの仕上げ圧延率｛「熱間仕上げ圧延全体
（トータル）の圧下率」｝が９５％以下で、且つ、（Ａ
ｒ3変態点＋７０℃）以上の温度範囲でのトータル圧下
率が５５％以上、好ましくは６０％以上になるように
（前段強圧下で）仕上げ圧延する。仕上げ圧延の前段で
強圧下を行うことにより、オーステナイト粒を微細化
し、変態後のフェライト粒の微細化を図る一方、後段の
圧下率を低減することにより、オーステナイト粒の歪の
蓄積を抑制し、集合組織を改善することができる。この
ような前段強圧下による効果は、歪による再結晶を制御
する技術であるため仕上げ温度に依存し、低温仕上げで
特に効果が大きくなるものである。As described above, the finishing temperature of the hot finish rolling (= rolling end temperature) is set to Ar 3
It should be carried out in a temperature range from the transformation point or more to (Ar 3 transformation point + 40 ° C.) or less. If the finishing temperature is lower than the Ar 3 transformation point, the ferrite is transformed after being transformed into ferrite, so that the ferrite grains become large, and the material is anisotropic due to expansion. At a finishing temperature exceeding (Ar 3 transformation point + 40 ° C.), the ferrite becomes large due to the growth of ferrite grains after finishing, and the cracking resistance deteriorates. In order to achieve both grain refinement and weakening of the texture, the total finish rolling ratio {"the overall reduction ratio of hot finish rolling"} is 95% or less, and (A
Finish rolling is performed so that the total draft in the temperature range of (r 3 transformation point + 70 ° C.) or more is 55% or more, and preferably 60% or more (under the first-stage strong rolling). By performing strong rolling in the previous stage of finish rolling, the austenite grains are refined and ferrite grains after transformation are refined, while reducing the rolling reduction in the latter stage suppresses the accumulation of strain of austenite grains, The texture can be improved. Such an effect of the first-stage high pressure depends on the finishing temperature because it is a technique for controlling recrystallization due to strain, and the effect is particularly large at low-temperature finishing.
【００３１】なお、仕上げ温度を制御するため、粗バー
や薄スラブを仕上げ圧延前に加熱することや、粗バーを
仕上げ圧延に先立ち、巻き取るという方法も本発明を妨
げるものではない。特に、粗バーや薄スラブを加熱する
方法では、粗バーや薄スラブの長手方向の温度分布に応
じて加熱条件を変化させることが可能であり、鋼帯の仕
上げ温度の安定化が容易である。また、粗バーや薄スラ
ブを長手方向に加熱することに加えて、必要に応じてエ
ッジヒーターを併用することについても、本発明を妨げ
ることはない。In order to control the finishing temperature, a method of heating the rough bar or the thin slab before the finish rolling or a method of winding the rough bar before the finish rolling does not hinder the present invention. In particular, in the method of heating the coarse bar or the thin slab, the heating condition can be changed according to the temperature distribution in the longitudinal direction of the coarse bar or the thin slab, and it is easy to stabilize the finishing temperature of the steel strip. . Further, in addition to heating the coarse bar or the thin slab in the longitudinal direction, the use of an edge heater as needed does not disturb the present invention.
【００３２】仕上げの圧延速度は一定にする必要が無
く、仕上げ温度の均一化などを目的として加速圧延など
を施してもよい。The finishing rolling speed does not need to be constant, and accelerated rolling may be performed for the purpose of making the finishing temperature uniform.
【００３３】仕上げ圧延後、巻き取るまでは特に規定す
るものではないが、フェライト粒成長を抑えるため、３
０℃／ｓ以上の速度で冷却するのが好ましい。しかし、
速すぎる冷却は、温度制御が困難となるため、１００℃
／ｓ以下の冷却速度が好ましい。巻取り温度についても
特に規定するわけではないが、成形性、フェライト粒成
長性を考慮して、５５０℃以上から６４０℃以下の温度
範囲での巻取りが好ましい。After finish rolling, there is no particular limitation until winding up.
It is preferable to cool at a rate of 0 ° C./s or more. But,
Too fast cooling makes it difficult to control the temperature.
/ S or less is preferred. Although the winding temperature is not particularly limited, winding in a temperature range of 550 ° C. or more to 640 ° C. or less is preferable in consideration of formability and ferrite grain growth.
【００３４】[0034]
【実施例】表１に示す本発明範囲内の成分を有する鋼ａ
〜ｈを溶製し、連続鋳造により厚さ約２５０ｍｍのスラ
ブを製造し、１１９０℃に加熱後、粗圧延機により厚さ
４０ｍｍの粗バーに圧延した。次いで、表２に示す条件
で、この粗バーを板厚４．５ｍｍに仕上げ圧延し、６２
０℃で巻き取った。仕上げ圧延のトータルの仕上げ圧延
率は８９％であった。そして、このようにして調製した
鋼帯Ｎｏ．１〜２４の長手方向中央部の幅中央部よりサ
ンプル採取した。DESCRIPTION OF THE PREFERRED EMBODIMENTS Steel a having components shown in Table 1 within the scope of the present invention
~ H was melted, a slab having a thickness of about 250 mm was produced by continuous casting, heated to 1190 ° C, and then rolled into a coarse bar having a thickness of 40 mm by a rough rolling mill. Then, under the conditions shown in Table 2, this coarse bar was finish-rolled to a plate thickness of 4.5 mm,
Wound at 0 ° C. The total finish rolling ratio of the finish rolling was 89%. And, the steel strip No. Samples were taken from the center of the width at the center in the longitudinal direction of 1 to 24.
【００３５】耐たて割れ性に関しては、各サンプルから
φ１１０ｍｍのブランクを採取し、φ５０ｍｍのポンチ
で円筒絞りを行い、端部の耳取り加工を施した後、各試
験温度で１１ｋｇの重りを高さ１ｍから落下させる落重
試験を行い、カップの割れ発生の有無で耐たて割れ性を
評価した。その結果を表２に示す。表２には、試験条
件：Ａｒ3変態点＋７０℃以上でのトータル圧下率、仕
上げ温度（＝仕上げ圧延の圧延終了温度）−Ａｒ3変態
点、及び、たて割れ遷移温度を記載した。たて割れ遷移
温度とは、３回上記試験を実施しても、たて割れが発生
しなかった温度を示す。Regarding the resistance to warp cracking, a blank of φ110 mm was sampled from each sample, subjected to cylindrical drawing with a punch of φ50 mm, and subjected to edge lubrication. Then, a weight of 11 kg was increased at each test temperature. A drop test was conducted by dropping the cup from a height of 1 m, and the resistance to warp cracking was evaluated based on whether or not the cup was cracked. Table 2 shows the results. Table 2 shows the test conditions: Ar 3 transformation point + total rolling reduction at 70 ° C. or higher, finishing temperature (= rolling end temperature of finish rolling) −Ar 3 transformation point, and vertical crack transition temperature. The vertical crack transition temperature indicates a temperature at which vertical cracks did not occur even after the above test was performed three times.
【００３６】[0036]
【表１】 [Table 1]
【００３７】[0037]
【表２】 [Table 2]
【００３８】それぞれの鋼ａ〜ｈにおいて、（Ａｒ3変
態点＋７０℃）以上の温度で５５％以上の圧下を行い、
且つ、仕上げ温度がＡｒ3変態点〜（Ａｒ3変態点+４０
℃）の温度範囲であった本発明鋼帯１、４、７、１０、
１３、１６、１９、２２は、いずれも他の鋼帯よりも立
て割れ遷移温度が低く、耐たて割れ性が良好であった。In each of the steels a to h, a reduction of 55% or more is performed at a temperature of (Ar 3 transformation point + 70 ° C.) or more,
And the finishing temperature is from Ar 3 transformation point to (Ar 3 transformation point +40)
° C) of the present invention steel strip 1, 4, 7, 10,
13, 16, 19, and 22 all had lower vertical crack transition temperatures than the other steel strips, and had good vertical crack resistance.
【００３９】例えば、鋼ａにおいては、鋼帯１はたて割
れ遷移温度が−９０℃と、鋼帯２（−６０℃）及び鋼帯
３（−５５℃）よりも低く、耐たて割れ性が良好である
ことが分かる。他の鋼ｂ〜ｈについても同様である。For example, in steel a, steel strip 1 has a vertical crack transition temperature of -90 ° C., which is lower than steel strip 2 (−60 ° C.) and steel strip 3 (−55 ° C.). It can be seen that the properties are good. The same applies to other steels b to h.
【００４０】（Ａｒ3変態点＋７０℃以上）の温度で５
５％未満の圧下を行った鋼帯（表２中に〇印で表示）及
び、仕上げ温度が（Ａｒ3変態点+４０℃）を超えて高か
った鋼帯（同△印で表示）、仕上げ温度がＡｒ3変態点
未満の鋼帯（同×印で表示）は、いずれも耐たて割れ性
が本発明よりも劣化していた。At a temperature of (Ar 3 transformation point + 70 ° C. or more), 5
A steel strip subjected to a reduction of less than 5% (indicated by “〇” in Table 2), a steel strip whose finishing temperature was higher than (Ar 3 transformation point + 40 ° C.) (indicated by “△”), finishing The steel strip having a temperature lower than the Ar 3 transformation point (indicated by the symbol x) had lower warp resistance than the present invention.
【００４１】[0041]
【発明の効果】本発明は以上説明したように構成されて
いるので、耐たて割れ性に優れた深絞り用熱延鋼板、特
に板厚が４ｍｍ以上の厚物の熱延鋼板の製造方法を提供
でき、かくして有用な効果がもたらされる。Since the present invention is constructed as described above, a method for producing a hot-rolled steel sheet for deep drawing excellent in warp resistance, particularly a hot-rolled steel sheet having a thickness of 4 mm or more. And thus a useful effect is brought about.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 高東 啓嗣 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 (72)発明者 山本 徹夫 東京都千代田区丸の内一丁目１番２号 日 本鋼管株式会社内 Ｆターム(参考） 4K032 AA01 AA02 AA04 AA16 AA21 AA22 AA27 AA29 AA31 AA35 AA36 AA39 BA01 CA02 CA03 CB02 CC03 CD03 4K037 EA01 EA02 EA04 EA05 EA15 EA18 EA19 EA23 EA25 EA27 EA31 EA32 EA35 EB02 EB06 FA02 FA03 FC03 FC07 FD04 FE02 JA02 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Keiji Takato 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Inside Nihon Kokan Co., Ltd. (72) Inventor Tetsuo Yamamoto 1-1-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) in Nippon Kokan Co., Ltd. FD04 FE02 JA02
Claims (3)
ｉ：０〜０．５ｗｔ．％、Ｍｎ：０〜２ｗｔ．％、Ｐ：
０．０２ｗｔ．％以下、Ｓ：０．０２ｗｔ．％以下、ｓ
ｏｌ．Ａｌ：０．１ｗｔ．％以下及びＮ：０．００５ｗ
ｔ．％以下を含有する鋼からなるスラブを熱間仕上げ圧
延するに際し、トータルの仕上げ圧延率が９５％以下
で、且つ、（Ａｒ3変態点＋７０℃）以上の温度範囲で
のトータル圧下率が５５％以上で、且つ、仕上げ温度が
Ａｒ3変態点〜（Ａｒ3変態点＋４０℃）の温度範囲内で
圧延することを特徴とする耐たて割れ性に優れた熱延鋼
板の製造方法。1. C: 0.001 to 0.03 wt. %, S
i: 0 to 0.5 wt. %, Mn: 0 to 2 wt. %, P:
0.02 wt. % Or less, S: 0.02 wt. % Or less, s
ol. Al: 0.1 wt. % Or less and N: 0.005w
t. % In hot finish rolling of a steel slab containing not more than 95%, and a total reduction of 55% in a temperature range of not less than 95% and (Ar 3 transformation point + 70 ° C.) or more. A method for producing a hot-rolled steel sheet having excellent resistance to cracking, characterized by rolling at a finishing temperature within the temperature range from the Ar 3 transformation point to (Ar 3 transformation point + 40 ° C.).
ｉ：０〜０．５ｗｔ．％、Ｍｎ：０〜２ｗｔ．％、Ｐ：
０．０２ｗｔ．％以下、Ｓ：０．０２ｗｔ．％以下、ｓ
ｏｌ．Ａｌ：０．１ｗｔ．％以下及びＮ：０．００５ｗ
ｔ．％以下を含有し、更に、Ｔｉ：０．００５〜０．１
ｗｔ．％、Ｎｂ：０．００５〜０．０５ｗｔ．％、Ｚ
ｒ：０．００５〜０．０５ｗｔ．％及びＶ：０．００５
〜０．０５ｗｔ．％のうちの少なくとも１種を含有する
鋼からなるスラブを熱間仕上げ圧延するに際し、トータ
ルの仕上げ圧延率が９５％以下で、且つ、（Ａｒ3変態
点＋７０℃）以上の温度範囲でのトータル圧下率が５５
％以上で、且つ、仕上げ温度がＡｒ3変態点〜（Ａｒ3変
態点＋４０℃）の温度範囲内で圧延することを特徴とす
る耐たて割れ性に優れた熱延鋼板の製造方法。2. C: 0.001 to 0.03 wt. %, S
i: 0 to 0.5 wt. %, Mn: 0 to 2 wt. %, P:
0.02 wt. % Or less, S: 0.02 wt. % Or less, s
ol. Al: 0.1 wt. % Or less and N: 0.005w
t. % Or less, and further, Ti: 0.005 to 0.1
wt. %, Nb: 0.005 to 0.05 wt. %, Z
r: 0.005 to 0.05 wt. % And V: 0.005
~ 0.05 wt. % In hot finish rolling of a slab made of steel containing at least one of the steels having a total finish reduction ratio of 95% or less and a temperature range of (Ar 3 transformation point + 70 ° C.) or more. Reduction rate 55
%, And the finishing temperature is rolled in a temperature range from the Ar 3 transformation point to (Ar 3 transformation point + 40 ° C.).
Ｂ：０．０００２〜０．００５ｗｔ．％を含有する鋼か
らなるスラブを熱間仕上げ圧延するに際し、トータルの
仕上げ圧延率が９５％以下で、且つ、（Ａｒ3変態点＋
７０℃）以上の温度範囲でのトータル圧下率が５５％以
上で、且つ、仕上げ温度がＡｒ3変態点〜（Ａｒ3変態点
＋４０℃）の温度範囲内で圧延することを特徴とする請
求項１又は２記載の耐たて割れ性に優れた熱延鋼板の製
造方法。3. The composition according to claim 1, further comprising:
B: 0.0002 to 0.005 wt. % In hot finish rolling of a slab made of steel containing at least 95% or less, and (Ar 3 transformation point +
The rolling is performed at a total draft of 55% or more in a temperature range of 70 ° C. or higher and a finishing temperature in a temperature range of Ar 3 transformation point to (Ar 3 transformation point + 40 ° C.). 3. The method for producing a hot-rolled steel sheet having excellent warp resistance according to 1 or 2.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26504399A JP3855556B2 (en) | 1999-09-20 | 1999-09-20 | Manufacturing method of hot-rolled steel sheet with excellent warp resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26504399A JP3855556B2 (en) | 1999-09-20 | 1999-09-20 | Manufacturing method of hot-rolled steel sheet with excellent warp resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2001089817A true JP2001089817A (en) | 2001-04-03 |
| JP3855556B2 JP3855556B2 (en) | 2006-12-13 |
Family
ID=17411798
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26504399A Expired - Fee Related JP3855556B2 (en) | 1999-09-20 | 1999-09-20 | Manufacturing method of hot-rolled steel sheet with excellent warp resistance |
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| Country | Link |
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| JP (1) | JP3855556B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104169018A (en) * | 2012-03-30 | 2014-11-26 | 株式会社神户制钢所 | Manufacturing method for hot press-molded steel member, and hot press-molded steel member |
-
1999
- 1999-09-20 JP JP26504399A patent/JP3855556B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104169018A (en) * | 2012-03-30 | 2014-11-26 | 株式会社神户制钢所 | Manufacturing method for hot press-molded steel member, and hot press-molded steel member |
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| Publication number | Publication date |
|---|---|
| JP3855556B2 (en) | 2006-12-13 |
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