JPH0369979B2 - - Google Patents
Info
- Publication number
- JPH0369979B2 JPH0369979B2 JP2576788A JP2576788A JPH0369979B2 JP H0369979 B2 JPH0369979 B2 JP H0369979B2 JP 2576788 A JP2576788 A JP 2576788A JP 2576788 A JP2576788 A JP 2576788A JP H0369979 B2 JPH0369979 B2 JP H0369979B2
- Authority
- JP
- Japan
- Prior art keywords
- temperature
- strength
- hot
- rolled steel
- less
- 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.)
- Expired
Links
- 229910000831 Steel Inorganic materials 0.000 claims description 85
- 239000010959 steel Substances 0.000 claims description 85
- 238000010438 heat treatment Methods 0.000 claims description 28
- 238000004519 manufacturing process Methods 0.000 claims description 10
- 229910001562 pearlite Inorganic materials 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 9
- 229910000859 α-Fe Inorganic materials 0.000 claims description 9
- 238000004804 winding Methods 0.000 claims description 7
- 238000005098 hot rolling Methods 0.000 claims description 5
- 238000005096 rolling process Methods 0.000 claims description 3
- 239000010949 copper Substances 0.000 description 33
- 230000000694 effects Effects 0.000 description 10
- 238000001556 precipitation Methods 0.000 description 8
- 239000006104 solid solution Substances 0.000 description 8
- 229910052799 carbon Inorganic materials 0.000 description 6
- 229910052802 copper Inorganic materials 0.000 description 5
- 238000005728 strengthening Methods 0.000 description 5
- 230000032683 aging Effects 0.000 description 4
- 230000007423 decrease Effects 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 4
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 239000012467 final product Substances 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- 230000001376 precipitating effect Effects 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 238000005482 strain hardening Methods 0.000 description 2
- 230000035882 stress Effects 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000881 Cu alloy Inorganic materials 0.000 description 1
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910001563 bainite Inorganic materials 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000008094 contradictory effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 229910000734 martensite Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000010791 quenching Methods 0.000 description 1
- 230000000171 quenching effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 238000003466 welding Methods 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Description
（産業上の利用分野）
本発明は極めて加工度の高い成形性と同時に高
い製品の強度が要求される利用分野に提供する熱
延鋼板およびその製造方法に関するものである。
（従来の技術）
従来の加工用熱延高強度鋼板は炭素量約0.03％
以上であり、その炭素を利用した焼入れによる組
織強化のほかにMn、Si、Ｐ等の固溶体強化元素
を添加したりTiやNb等の炭窒化物による析出強
化を活用して製造されるのが通常である。
このようにして得られた高強度鋼板は引張強さ
が高くなるに従い加工性、特に延性が低くなつて
いく。従つて高強度と同時に高い加工性を確保す
ることはできない。
高強度と同時に高い加工性を確保しなければな
らないという相矛盾する課題に十分に応える技術
は見当たらない。一つの理想と思われる技術は、
冷間加工変形をするときは鋼板の強度が低いと同
時に加工性、特に延性が十分に高く、加工が終了
した後にその加工品の強度が高くなるとすれば最
終製品として複雑な加工部品になると共に強固な
部品になることになる。この考え方に従つた技術
の例は、例えば、特公昭57−17049号公報などに
みられる。この場合では、Cuの固溶状態からそ
れの析出状態への変化を利用している。即ち、強
度の低いうちに加工しておきその後の熱処理によ
つてCuを析出させることによつて加工部品の強
度を上げようとするものである。
しかしながら、特公昭57−17049号公報に見ら
れる固溶したCuを熱処理によつて析出させ鋼板
の強度をあげることおよび熱処理条件等は古くか
ら周知の技術である。それは例えばAlloys of
iron and copper（McGRAW−HILL BOOK
COMPANY、Inc.、1934）に明記されている。
（発明が解決しようとする課題）
最近の高加工性熱延鋼板の材質特性にたいする
利用者側からの要求の度合は益々高くなりつつあ
る。即ち、益々の高加工変形を必要とする複雑な
形状部品がふえていることと、鋼板の利用者側で
の変形加工工程を出来る限り少なくして低コスト
化を計る必要性が近年とみに増えているためであ
る。従つて、前述の特公昭57−17049号公報記載
の技術内容では到底鋼板の利用者側の要求を満た
すものではない。
利用者側からの高加工性熱延鋼板にたいする最
近の強い要求の一つは、最終製品の超高強度化で
ある。例えば、従来では、引張強度で45Kgｆ／mm2
程度の部品を最近では60Kgｆ／mm2以上の強度を持
つた鋼板で製造したいと言う要求である。従つ
て、この鋼板の超高強度化と同時に高加工性を同
時に満たす技術を開発する必要がある。
その次は鋼板の変形加工時の極めて高い変形加
工性能が要求されていることである。これは最終
部品の形状が益々複雑になつてきておりこれに応
えうる鋼板を提供しなくてはならないことであ
る。また、利用者側での加工工程数を減らしたい
という要望も強くそのためにも極めて高い変形加
工性能をもつた鋼板を提供しなくてはならなくな
つている。
さらには、利用者側での熱処理工程の簡素化の
必要性である。当然、低コスト化を指向する部品
メーカーとしては、短時間で熱処理が済み生産性
を一層高める必要がある。
これらの最近の鋼板利用者側からの新しい鋼板
にたいする要求に対して従来技術では満足に応え
うるものではない。本発明ではそれらの要求に答
える技術を開発したものである。
（課題を解決するための手段）
先ず、本発明の対象である加工用熱延鋼板につ
いて説明する。
本発明の加工用熱延鋼板は、以下の理由により
C0.0005〜0.015％、Mn0.05〜0.5％、S0.001〜
0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、N0.0050％以下、sol.Al0.002〜
0.10％、その他不可避的元素からなり、かつパー
ライトの発生を回避した主としてフエライト単相
からなることを基本とし、これに必要に応じて
Ti、Nbの一種または二種を、更にはNiを含有さ
せることもある。
先ず、Ｃについて説明する。本発明者等は、
Cu添加鋼に種々の元素を単独あるいは複合添加
した熱延鋼板の研究を行つた結果、Cuの析出に
よる強度上昇量がＣ量により変化し、Ｃ量を低減
することによつて従来知られていたCuの析出に
よる強度上昇量よりも遥かに大きな強度上昇量が
得られる事を新規に知見した。第１図はMn0.15
％、Si0.02％、S0.015％、P0.01％、N0.0020％、
sol.Al0.03％、Cu1.3％を含む鋼を基本成分とし、
Ｃ量を0.0015％〜0.0465％の範囲で変化させた鋼
を溶製し、1050℃で加熱後、A3点以上で熱間圧
延を終了し板厚3.0mmとし、300℃で巻き取つた時
のＣ量と引張強さの関係を示すグラフであり、図
中、曲線ａは300℃で巻き取つたままの熱延鋼板
の場合、曲線ｂはその熱延鋼板を600℃で10分間
熱処理した場合を示す。曲線ａと曲線ｂの差が
Cuの析出による強度上昇量であり、Ｃ量が0.025
％以上では強度上昇量は約15Kgｆ／mm2であるのに
対し、Ｃ量が0.015％以下では強度上昇量は約20
Kgｆ／mm2と極めて大きな強度上昇量が得られる。
Ｃ量が0.015％を境に巻き取つたままの熱延鋼板
の引強さに大きな変化が認められるが、この強度
差はＣの固溶強化だけでは説明できない。この強
度差に対応してＣ量が0.015％を境に巻き取つた
ままの熱延鋼板の伸びにも大きな変化が認められ
る。第２図は第１図と同じ1.3％Cu含有熱延鋼板
の伸びとＣ量の関係を示すグラフである。同図よ
り、Ｃ量を0.015％以下に制御する事により極め
て高い延性を確保し得る事が認められる。このた
めＣ量の上限を0.015％とする。
このようにＣ量が0.015％以下の場合、延性が
高く且つ熱処理による強度上昇量が大きくなる理
由は未だ明らかではないが、敢えて推測すれば以
下の如く考える事ができる。即ち、Cuは鋼中で
偏析しCuの含有量はフエライト中とパーライト
中では異なり、パーライト中の方が高い。このた
めパーライト中のCuはフエライト中のCuに比べ
平衡固溶度に対する過飽和度が大きく析出し易い
状態にある。従つて300℃という低温で巻き取つ
た場合でも、Ｃ量が高くパーライトが存在する場
合にはCuが一部析出し硬質化する。これに対し
Ｃ量が低くパーライトが存在せずフエライト単相
の場合には、Cuが過飽和な状態で固溶され硬質
化しない。これらの熱延板を600℃程度の高温で
熱処理すると過飽和状態にあつたCuの十分な析
出が起こり強度が上昇するものと想定される。
この様にＣ量は極めて高い強度上昇量と極めて
高い延性を確保するためには極力低減させること
が必要である。Ｃ量の下限は工業的に溶製しうる
限界の0.0005％とする。逆にＣ量が0.015％を越
えると強度上昇量と延性はさがると同時に、加工
前の鋼板を製造するときに熱延の巻き取り温度に
対する制限が発生する。即ち、焼入れ組織が発生
して加工前の鋼板の延性を下げるからである。従
つて、Ｃ量は0.0005〜0.015％の範囲とする。
Ｐは鋼板の強度を上げる元素としてその必要強
度レベルに応じて添加する。しかし、0.001％未
満ではその効果はなく、一方0.100％を越えると
鋼板の二次加工割れが発生するのでそれを上限と
する。尚、この範囲のＰの添加はCuの添加とと
もに鋼板の耐食性能を高めるのに有効である。
Siは鋼板の強度を上げる元素としてその必要強
度レベルに応じて添加する。しかし、0.005％未
満ではその効果はなく、一方1.0％を越えると熱
間圧延工程におけるスケールの発生が著しく、鋼
板の表面性状を劣化させるためその上限を1.0％
とする。
Mn量は鋼板の加工性を高めるためには低いほ
うが好ましく、上限を0.5％とする。Mn量があま
り低くなりすぎると鋼板の表面疵が発生し易くな
るのでその下限を0.05％とする。
Ｓ量は鋼板の加工性を高めるためには低いほう
が好ましく、上限を0.030％とする。下限は工業
的に溶製しうる限界の0.001％とする。
Ｎ量は加工性を高めるためにも低いほうが好ま
しく0.0050％以下とする。
Cu量は加工前では固溶状態にしておき、加工
後の熱処理によりCuを析出させて強度をあげる。
第３図は極低炭素鋼にCuを添加した鋼の熱処理
時間（熱処理時間550℃）による強度上昇量（熱
処理後の引張強さ−熱延まま引張強さ）をCuを
パラメータとして示すグラフであり、図中、曲線
ａはCu2.06％、曲線ｂはCu1.68％、曲線ｃは
Cu1.38％、曲線ｄはCu0.71％の場合である。同図
よりCu1.0％未満では曲線ｄの如く強度の上昇量
は不十分である。
Ti0.01〜0.2％、Nb0.005〜0.2％の一種または
二種を添加するとＣとＮはこれらによつて固定さ
れ、得られる鋼板は非時効性の鋼板になる。非時
効性鋼板になると時効による延性の低下はなくな
り、一層の高延性鋼板が得られることになる。
Niは鋼板の表面品質を高品位に保ち、熱間脆
性を防止するのに有効である。0.15％未満ではそ
の効果はなく、一方0.45％を超えると効果が飽和
するうえに、Niが高価なため経済性が損なわれ
る。
sol.AlはAlキルドを得るために必要な0.002〜
0.10％の範囲にあればよい。0.002％未満では効
果がなく、一方0.10％を超えると効果が飽和す
る。
次ぎに本発明鋼板の製造方法における熱間圧延
工程についてであるが、連鋳機から直送された高
温鋳片または、加熱によつてえられた高温鋳片を
Ar3以上の温度で熱間圧延をおこない、その後、
500℃以下の温度で巻き取る。圧延終了温度が
Ar3未満ではフエライト粒にひずみが加わり加工
性が劣化する。上限については工業的に実施しう
る限界である1000℃とする。巻取温度について
は、500℃を越える温度で巻き取るとCuの析出が
起こり、加工性の良い軟質鋼板が得られない。本
発明ではＣ量を制限して巻取段階でのCuの析出
を抑制しており、500℃以下の温度で巻取ること
により大部分のCuを過飽和固溶の状態に保ちう
る。しかし500℃を越える温度で巻取るとCuの析
出が起こり硬質化するため、巻取温度の上限を
500℃とする。全てのCuを固溶状態に保つには巻
取温度を350℃以下とする。従来の鋼のようにＣ
量もしくはMn量が高い場合には、低温で巻取る
とマルテンサイト相もしくはベイナイト相という
変態による硬質相が生成し硬質化するため、これ
を避けるために巻取温度に下限を設けなければな
らない。本発明鋼はＣ量およびMn量を低く制御
し、焼き入れ性を著しく抑えているため巻取温度
の冶金学的な下限温度はない。但し、100℃未満
で巻取ると巻形状が悪くなり、これに起因する表
面品質の劣化を招くため、好ましくは巻取温度を
350℃以下、100℃以上とする。
得られた熱延板は成形加工後に熱処理を施して
その強度を高めるが、熱処理作業性からみると出
来るだけ低温で然も短時間の熱処理で終了させる
ことが極めて大切である。本発明ではこの点につ
いても十分な検討を加え短時間の熱処理でその目
的が達成されるようにしたものである。
次ぎに実施例をあげて本発明を具体的に説明す
る。
実施例 １
第１表に示したＡからＬまでの鋼片を同表に示
す加熱温度で加熱、熱延し、巻き取り、板厚3.0
mmの熱延鋼板を得た。またその機械的性質を示
す。その鋼板に変形加工は施さずに熱処理を与え
た場合の機械的性質を第２表に示す。
第１表および第２表に示す通り、本発明鋼は加
工時は極めて優れた延性を持つており、極めて短
時間の熱処理で引張強度が著しく上昇する。Cu
の固溶強化能は１％当たり約４Kgｆ／mm2であり、
極低炭素鋼にCuを2.11％添加した鋼Ａは熱延まま
での強度は低く極めて高い延性を有し、且つ600
℃で10分という短時間の熱処理で25Kgｆ／mm2以上
の強度上昇が可能である。Siを添加した鋼Ｃ、Ｐ
を添加した鋼Ｄは熱延ままでの強度が高いが良好
な延性を有しており、熱処理による強度上昇も大
きい。Ti、Nbを単独もしくは複合添加した鋼
Ｂ、Ｅ、Ｆ、Ｊ、Ｋ及びＬは時効後の伸びの低下
がなく、一層の高延性鋼板となつている。これに
対し比較鋼Ｇ及びＩはＣ量が高く加工時の延性が
劣り、比較鋼ＨはCu量が少なく本発明の目的と
する短時間の熱処理では引張強度の上昇が見られ
ない。
(Industrial Field of Application) The present invention relates to a hot-rolled steel sheet and a method for manufacturing the same, which are used in fields of application that require extremely high formability and high product strength. (Conventional technology) Conventional hot-rolled high-strength steel sheets for processing have a carbon content of approximately 0.03%.
As mentioned above, in addition to strengthening the structure by quenching using carbon, it is manufactured by adding solid solution strengthening elements such as Mn, Si, P, etc., or by utilizing precipitation strengthening with carbonitrides such as Ti and Nb. Normal. As the tensile strength of the high-strength steel sheet obtained in this manner increases, the workability, especially the ductility thereof, decreases. Therefore, it is not possible to ensure high strength and high workability at the same time. No technology has yet been found that satisfactorily addresses the contradictory issues of having to ensure both high strength and high workability. One technique that is considered ideal is
When deforming by cold working, the strength of the steel sheet is low and at the same time the workability, especially the ductility, is sufficiently high, and if the strength of the workpiece increases after the work is completed, the final product will be a complex workpiece. It will become a strong part. An example of a technique based on this idea can be found in, for example, Japanese Patent Publication No. 17049/1983. In this case, the change from Cu's solid solution state to its precipitation state is utilized. That is, it attempts to increase the strength of processed parts by processing them while their strength is still low and precipitating Cu through subsequent heat treatment. However, the technique of increasing the strength of a steel plate by precipitating solid-dissolved Cu through heat treatment and the heat treatment conditions, etc., as disclosed in Japanese Patent Publication No. 57-17049, has been well known for a long time. For example, Alloys of
iron and copper (McGRAW−HILL BOOK
COMPANY, Inc., 1934). (Problems to be Solved by the Invention) Recently, demands from users regarding the material properties of highly workable hot-rolled steel sheets are becoming increasingly high. In other words, the number of parts with complex shapes that require increasingly high processing deformation has increased, and the need to reduce costs by minimizing the deformation process on the steel sheet user side has increased in recent years. This is because there is. Therefore, the technical contents described in the above-mentioned Japanese Patent Publication No. 17049/1987 do not meet the requirements of steel sheet users. One of the recent strong demands from users for highly formable hot-rolled steel sheets is for the final product to have ultra-high strength. For example, in the past, the tensile strength was 45Kgf/mm 2
Recently, there has been a demand for manufacturing parts with steel plates with a strength of 60 kgf/mm 2 or more. Therefore, it is necessary to develop a technology that simultaneously increases the strength of this steel sheet and provides high workability. Next is the need for extremely high deformation performance when deforming steel plates. This means that the shapes of final parts are becoming more and more complex, and it is necessary to provide steel plates that can meet these demands. In addition, there is a strong desire to reduce the number of processing steps on the user side, and for this purpose, it is necessary to provide steel sheets with extremely high deformation processing performance. Furthermore, there is a need to simplify the heat treatment process on the user side. Naturally, as a parts manufacturer aiming to reduce costs, it is necessary to further increase productivity by completing heat treatment in a short time. Conventional techniques cannot satisfactorily meet these recent demands for new steel sheets from steel sheet users. The present invention has developed a technology to meet these demands. (Means for Solving the Problems) First, a hot-rolled steel sheet for processing, which is an object of the present invention, will be explained. The hot-rolled steel sheet for processing of the present invention is advantageous for the following reasons.
C0.0005~0.015%, Mn0.05~0.5%, S0.001~
0.030%, Cu1.0~2.2%, P0.001~0.100%,
Si0.005~1.0%, N0.0050% or less, sol.Al0.002~
0.10% and other unavoidable elements, and is mainly composed of a single phase of ferrite that avoids the generation of pearlite.
One or both of Ti and Nb may be contained, and Ni may also be contained. First, C will be explained. The inventors,
As a result of research on hot-rolled steel sheets in which various elements were added singly or in combination to Cu-added steel, we found that the amount of strength increase due to Cu precipitation changes depending on the C content, which was previously known by reducing the C content. It was newly discovered that a much larger increase in strength can be obtained than that due to the precipitation of Cu. Figure 1 shows Mn0.15
%, Si0.02%, S0.015%, P0.01%, N0.0020%,
The basic component is steel containing sol.Al0.03% and Cu1.3%,
Steel with C content varied in the range of 0.0015% to 0.0465% is melted, heated at 1050℃, hot rolled at A 3 points or higher to a plate thickness of 3.0mm, and rolled at 300℃. This is a graph showing the relationship between C content and tensile strength, in which curve a is a hot-rolled steel sheet that has been rolled up at 300℃, and curve b is a hot-rolled steel sheet that has been heat-treated at 600℃ for 10 minutes. Indicate the case. The difference between curve a and curve b is
This is the amount of strength increase due to Cu precipitation, and the amount of C is 0.025
% or more, the strength increase is approximately 15Kgf/mm 2 , whereas when the C content is 0.015% or less, the strength increase is approximately 20Kgf/mm2.
An extremely large strength increase of Kgf/mm 2 can be obtained.
A large change in the tensile strength of the as-rolled hot-rolled steel sheet is observed when the C content reaches 0.015%, but this strength difference cannot be explained only by the solid solution strengthening of C. Corresponding to this difference in strength, there is a large change in the elongation of the hot-rolled steel sheet when the C content reaches 0.015%. FIG. 2 is a graph showing the relationship between elongation and C content of a hot rolled steel sheet containing 1.3% Cu, which is the same as FIG. 1. From the same figure, it is recognized that extremely high ductility can be ensured by controlling the C content to 0.015% or less. For this reason, the upper limit of the amount of C is set at 0.015%. It is not yet clear why when the C content is 0.015% or less, the ductility is high and the increase in strength due to heat treatment is large, but if we dare to speculate, we can think of it as follows. That is, Cu segregates in steel, and the Cu content differs between ferrite and pearlite, and is higher in pearlite. For this reason, Cu in pearlite has a higher degree of supersaturation relative to the equilibrium solid solubility than Cu in ferrite, making it easier to precipitate. Therefore, even when rolled at a low temperature of 300°C, if the C content is high and pearlite is present, some Cu will precipitate and become hard. On the other hand, in the case where the C content is low and pearlite is not present and there is a single ferrite phase, Cu is dissolved as a solid solution in a supersaturated state and does not harden. It is assumed that when these hot-rolled sheets are heat-treated at a high temperature of about 600°C, sufficient precipitation of supersaturated Cu occurs, resulting in an increase in strength. As described above, it is necessary to reduce the amount of C as much as possible in order to ensure an extremely high increase in strength and extremely high ductility. The lower limit of the amount of C is 0.0005%, which is the limit that can be produced industrially. On the other hand, if the C content exceeds 0.015%, the amount of increase in strength and ductility will decrease, and at the same time, there will be restrictions on the winding temperature of the hot roll when manufacturing a steel plate before processing. That is, this is because a hardened structure is generated and reduces the ductility of the steel sheet before processing. Therefore, the amount of C is set in the range of 0.0005 to 0.015%. P is an element that increases the strength of the steel sheet and is added depending on the required strength level. However, if it is less than 0.001%, there is no effect, and if it exceeds 0.100%, secondary processing cracks will occur in the steel plate, so this is the upper limit. Incidentally, addition of P in this range is effective in improving the corrosion resistance performance of the steel sheet along with addition of Cu. Si is an element that increases the strength of steel sheets and is added depending on the required strength level. However, if it is less than 0.005%, there is no effect, while if it exceeds 1.0%, scale will occur during the hot rolling process, and the surface quality of the steel plate will deteriorate, so the upper limit is set at 1.0%.
shall be. The lower the Mn content, the better, in order to improve the workability of the steel sheet, and the upper limit is set to 0.5%. If the Mn content is too low, surface flaws will easily occur on the steel sheet, so the lower limit is set at 0.05%. In order to improve the workability of the steel plate, it is preferable that the amount of S is low, and the upper limit is set to 0.030%. The lower limit is 0.001%, which is the limit that can be produced industrially. In order to improve workability, the amount of N is preferably as low as 0.0050% or less. The amount of Cu is kept in a solid solution state before processing, and the strength is increased by precipitating Cu through heat treatment after processing.
Figure 3 is a graph showing the amount of increase in strength (tensile strength after heat treatment - tensile strength as hot rolled) due to heat treatment time (heat treatment time 550℃) of ultra-low carbon steel with Cu added, using Cu as a parameter. In the figure, curve a is Cu2.06%, curve b is Cu1.68%, and curve c is Cu2.06%.
Curve d is for Cu 1.38% and Cu 0.71%. As shown in the figure, if Cu is less than 1.0%, the amount of increase in strength is insufficient as shown by curve d. When one or both of Ti 0.01 to 0.2% and Nb 0.005 to 0.2% are added, C and N are fixed by these, and the obtained steel plate becomes a non-aging steel plate. When the steel plate becomes a non-aging steel plate, there is no decrease in ductility due to aging, and a steel plate with even higher ductility can be obtained. Ni is effective in keeping the surface quality of steel sheets high and preventing hot embrittlement. If it is less than 0.15%, there is no effect, while if it exceeds 0.45%, the effect will be saturated and the cost of Ni will be poor, since Ni is expensive. sol.Al is 0.002~ required to get Al killed
It should be within the range of 0.10%. If it is less than 0.002%, there is no effect, while if it exceeds 0.10%, the effect is saturated. Next, regarding the hot rolling process in the manufacturing method of the steel sheet of the present invention, high-temperature slabs directly delivered from a continuous casting machine or high-temperature slabs obtained by heating are used.
Hot rolling is carried out at a temperature of Ar 3 or higher, and then
Roll up at a temperature below 500℃. The rolling end temperature is
If Ar is less than 3 , strain will be added to the ferrite grains and workability will deteriorate. The upper limit shall be 1000°C, which is the industrially practical limit. Regarding the coiling temperature, if the steel is coiled at a temperature exceeding 500°C, Cu will precipitate, making it impossible to obtain a soft steel sheet with good workability. In the present invention, the amount of C is limited to suppress the precipitation of Cu at the winding stage, and by winding at a temperature of 500° C. or lower, most of the Cu can be kept in a supersaturated solid solution state. However, if the coiling temperature exceeds 500℃, Cu will precipitate and become hard, so the upper limit of the coiling temperature should be set.
The temperature shall be 500℃. To keep all Cu in solid solution, the coiling temperature should be 350°C or less. C like conventional steel
When the Mn content or the Mn content is high, a hard phase called martensitic phase or bainite phase is generated due to transformation and becomes hard when coiled at a low temperature.To avoid this, a lower limit must be set for the coiling temperature. In the steel of the present invention, the C content and Mn content are controlled to be low, and the hardenability is significantly suppressed, so there is no metallurgical lower limit temperature for the coiling temperature. However, if the winding temperature is lower than 100℃, the winding shape will become poor and this will lead to deterioration of the surface quality, so it is preferable to lower the winding temperature.
The temperature shall be below 350℃ and above 100℃. The obtained hot-rolled sheet is subjected to heat treatment after forming to increase its strength, but from the viewpoint of heat treatment workability, it is extremely important to complete the heat treatment at as low a temperature as possible and in a short time. In the present invention, sufficient consideration has been given to this point so that the object can be achieved with a short heat treatment. Next, the present invention will be specifically explained with reference to Examples. Example 1 Steel slabs A to L shown in Table 1 were heated at the heating temperatures shown in the same table, hot-rolled, and rolled to a thickness of 3.0.
A hot rolled steel plate of mm was obtained. It also shows its mechanical properties. Table 2 shows the mechanical properties when the steel plate was heat treated without being deformed. As shown in Tables 1 and 2, the steel of the present invention has extremely excellent ductility during processing, and its tensile strength increases significantly with extremely short heat treatment. Cu
The solid solution strengthening ability of is approximately 4Kgf/ mm2 per 1%,
Steel A, which is an ultra-low carbon steel with 2.11% Cu added, has low strength as hot-rolled and extremely high ductility.
It is possible to increase the strength by 25Kgf/mm 2 or more with a short heat treatment at ℃ for 10 minutes. Si-added steel C, P
Steel D with the addition of is high in strength as hot-rolled, but has good ductility, and its strength increases greatly through heat treatment. Steels B, E, F, J, K, and L, to which Ti and Nb were added singly or in combination, showed no decrease in elongation after aging, making them steel sheets with even higher ductility. On the other hand, Comparative Steels G and I have a high C content and are inferior in ductility during processing, and Comparative Steel H has a low Cu content and does not show an increase in tensile strength during short-time heat treatment, which is the objective of the present invention.
【表】【table】
【表】【table】
【表】
実施例 ２
第３表に示す組成の鋼No.１およびNo.２を熱間圧
延して板厚3.0mmの熱延鋼板を得た、これらの鋼
板を圧力容器に成形加工した。圧力容器はプレス
加工および溶接後、内部応力を除去するため630
℃程度の温度で応力除去焼鈍が行われる。この鋼
板を圧力容器に成形加工した後、サンプルを切り
出した。切り出したサンプルの板厚歪は約26％で
あつた。このサンプルの引張強さおよび630℃で
５分間の熱処理後の引張強さを第４表に示す。同
表中の強度上昇量△TSは、プレス成形および熱
処理後の引張強さから、熱延ままの引張強さを引
いた値である。比較鋼は加工後の熱処理により大
幅に軟化しているのに対し、本発明鋼は加工後の
熱処理により更なる強度上昇が達成されている。[Table] Example 2 Steels No. 1 and No. 2 having the compositions shown in Table 3 were hot rolled to obtain hot rolled steel plates with a thickness of 3.0 mm. These steel plates were formed into a pressure vessel. 630 to remove internal stress after pressing and welding the pressure vessel.
Stress relief annealing is performed at a temperature of approximately 0.9°C. After forming this steel plate into a pressure vessel, a sample was cut out. The plate thickness distortion of the cut sample was approximately 26%. Table 4 shows the tensile strength of this sample and the tensile strength after heat treatment at 630°C for 5 minutes. The amount of increase in strength ΔTS in the same table is the value obtained by subtracting the tensile strength as hot rolled from the tensile strength after press forming and heat treatment. While the comparative steel was significantly softened by the heat treatment after working, the steel of the present invention achieved a further increase in strength by the heat treatment after working.
【表】【table】
【表】【table】
【表】
（発明の効果）
本発明は、極めて良好な冷間加工性を有すると
共に、最終製品で必要とされる高い強度が冷間加
工後の短時間の熱処理により達成され得る新規な
熱延鋼板を提供するものであり、またかかる熱延
鋼板を成分規制および熱延鋼板の巻取温度の制御
という簡便な手段により製造しうる新規な方法を
提供するものであるから、鋼板利用者側からの新
たな要求に十分応えうるものであり、産業上裨益
するところが極めて大である。[Table] (Effects of the Invention) The present invention provides a novel hot rolled product that has extremely good cold workability and can achieve the high strength required for the final product by a short heat treatment after cold working. Since it provides steel sheets and a new method for manufacturing such hot-rolled steel sheets by simple means of regulating the composition and controlling the coiling temperature of the hot-rolled steel sheets, it is important for steel sheet users to It can fully meet the new demands of the world, and the industrial benefits are extremely large.
第１図は熱延鋼板の強度に及ぼすＣ量の影響
を、Cuの析出の為の熱処理の前後で示すグラフ、
第２図は熱延鋼板の延性に及ぼすＣ量の影響を示
すグラフ、第３図は極低炭素鋼熱延鋼板の強度上
昇量に及ぼす熱処理時間の影響をCu量をパラメ
ーターとして示すグラフである。
Figure 1 is a graph showing the effect of C content on the strength of hot rolled steel sheets before and after heat treatment for Cu precipitation.
Figure 2 is a graph showing the effect of C content on the ductility of hot-rolled steel sheets, and Figure 3 is a graph showing the effect of heat treatment time on the strength increase of ultra-low carbon steel hot-rolled steel sheets using Cu content as a parameter. .
Claims (1)
〜0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、N0.0050％以下、sol.Al0.002〜
0.10％を含有し、残部Fe及び不可避的元素からな
り、パーライトの発生を回避した主としてフエラ
イト単相からなることを特徴とする冷間加工性の
極めて優れた高強度熱延鋼板。 ２ C0.0005〜0.015％、Mn0.05〜0.5％、S0.001
〜0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、N0.0050％以下、sol.Al0.002〜
0.10％に加えて、Ti0.01〜0.2％、またはNb0.005
〜0.2％の一種もしくは二種を含有し、残部Fe及
び不可避的元素からなり、パーライトの発生を回
避した主としてフエライト単相からなることを特
徴とする冷間加工性の極めて優れた高強度熱延鋼
板。 ３ C0.0005〜0.015％、Mn0.05〜0.5％、S0.001
〜0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、Ni0.15〜0.45％、N0.0050％以
下、sol.Al0.002〜0.10％を含有し、残部Fe及び不
可避的元素からなり、パーライトの発生を回避し
た主としてフエライト単相からなることを特徴と
する冷間加工性の極めて優れた高強度熱延鋼板。 ４ C0.0005〜0.015％、Mn0.05〜0.5％、S0.001
〜0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、Ni0.15〜0.45％、N0.0050％以
下、sol.Al0.002〜0.10％に加えて、Ti0.01〜0.2
％、またはNb0.005〜0.2％の一種もしくは二種を
含有し、残部Fe及び不可避的元素からなり、パ
ーライトの発生を回避した主としてフエライト単
相からなることを特徴とする冷間加工性の極めて
優れた高強度熱延鋼板。 ５ C0.0005〜0.015％、Mn0.05〜0.5％、S0.001
〜0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、N0.0050％以下、sol.Al0.002〜
0.10％を含有し、残部Fe及び不可避的元素からな
る鋼を、Ar3以上1000℃以下の温度で熱間圧延
し、得られた熱間圧延鋼帯を500℃以下100℃以上
の温度で巻き取ることを特徴とする冷間加工性の
極めて優れた高強度熱延鋼板の製造方法。 ６ C0.0005〜0.015％、Mn0.05〜0.5％、S0.001
〜0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、N0.0050％以下、sol.Al0.002〜
0.10％に加えて、Ti0.01〜0.2％、またはNb0.005
〜0.2％の一種もしくは二種を含有し、残部Fe及
び不可避的元素からなる鋼を、Ar3以上1000℃以
下の温度で熱間圧延し、得られた熱間圧延鋼帯を
500℃以下100℃以上の温度で巻き取ることを特徴
とする冷間加工性の極めて優れた高強度熱延鋼板
の製造方法。 ７ C0.0005〜0.015％、Mn0.05〜0.5％、S0.001
〜0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、Ni0.15〜0.45％、N0.0050％以
下、sol.Al0.002〜0.10％を含有し、残部Fe及び不
可避的元素からなる鋼を、Ar3以上1000℃以下の
温度で熱間圧延し、得られた熱間圧延鋼帯を500
℃以下100℃以上の温度で巻き取ることを特徴と
する冷間加工性の極めて優れた高強度熱延鋼板の
製造方法。 ８ C0.0005〜0.015％、Mn0.05〜0.5％、S0.001
〜0.030％、Cu1.0〜2.2％、P0.001〜0.100％、
Si0.005〜1.0％、Ni0.15〜0.45％、N0.0050％以
下、sol.Al0.002〜0.10％に加えて、Ti0.01〜0.2
％、またはNb0.005〜0.2％の一種もしくは二種を
含有し、残部Fe及び不可避的元素からなる鋼を、
Ar3以上1000℃以下の温度で熱間圧延し、得られ
た熱間圧延鋼帯を500℃以下100℃以上の温度で巻
き取ることを特徴とする冷間加工性の極めて優れ
た高強度熱延鋼板の製造方法。 ９ 特許請求の範囲第５項〜第８項の何れか１項
に記載の方法において、熱間圧延後の巻取温度を
350℃以下100℃以上とすることを特徴とする冷間
加工性の極めて優れた高強度熱延鋼板の製造方
法。[Claims] 1 C0.0005-0.015%, Mn0.05-0.5%, S0.001
~0.030%, Cu1.0~2.2%, P0.001~0.100%,
Si0.005~1.0%, N0.0050% or less, sol.Al0.002~
A high-strength hot-rolled steel sheet with extremely excellent cold workability, characterized by containing 0.10%, the balance being Fe and unavoidable elements, and mainly consisting of a single phase of ferrite, avoiding the generation of pearlite. 2 C0.0005~0.015%, Mn0.05~0.5%, S0.001
~0.030%, Cu1.0~2.2%, P0.001~0.100%,
Si0.005~1.0%, N0.0050% or less, sol.Al0.002~
0.10% plus Ti0.01~0.2% or Nb0.005
A high-strength hot rolled roll with extremely excellent cold workability, containing ~0.2% of one or two of the above elements, with the balance consisting of Fe and other unavoidable elements, and consisting mainly of a single phase of ferrite, avoiding the generation of pearlite. steel plate. 3 C0.0005~0.015%, Mn0.05~0.5%, S0.001
~0.030%, Cu1.0~2.2%, P0.001~0.100%,
Contains 0.005~1.0% of Si, 0.15~0.45% of Ni, 0.0050% of N or less, 0.002~0.10% of sol.Al, and the balance consists of Fe and other unavoidable elements, mainly consisting of ferrite, avoiding the generation of pearlite. A high-strength hot-rolled steel sheet with extremely excellent cold workability characterized by a structure consisting of three phases. 4 C0.0005~0.015%, Mn0.05~0.5%, S0.001
~0.030%, Cu1.0~2.2%, P0.001~0.100%,
Si0.005~1.0%, Ni0.15~0.45%, N0.0050% or less, sol.Al0.002~0.10%, plus Ti0.01~0.2
%, or 0.005 to 0.2% of Nb, and the balance is Fe and other unavoidable elements, and has excellent cold workability, characterized by being mainly composed of a single ferrite phase that avoids the generation of pearlite. Excellent high strength hot rolled steel plate. 5 C0.0005~0.015%, Mn0.05~0.5%, S0.001
~0.030%, Cu1.0~2.2%, P0.001~0.100%,
Si0.005~1.0%, N0.0050% or less, sol.Al0.002~
A steel containing 0.10% Ar with the balance consisting of Fe and unavoidable elements is hot rolled at a temperature of 3 or more and 1000°C or less, and the obtained hot rolled steel strip is rolled at a temperature of 500°C or more and 100°C or more. A method for producing a high-strength hot-rolled steel sheet with extremely excellent cold workability. 6 C0.0005~0.015%, Mn0.05~0.5%, S0.001
~0.030%, Cu1.0~2.2%, P0.001~0.100%,
Si0.005~1.0%, N0.0050% or less, sol.Al0.002~
0.10% plus Ti0.01~0.2% or Nb0.005
A steel containing up to 0.2% of one or two types of Ar, with the balance consisting of Fe and unavoidable elements, is hot rolled at a temperature of 3 to 1000℃, and the resulting hot rolled steel strip is
A method for producing high-strength hot-rolled steel sheets with extremely excellent cold workability, characterized by rolling at a temperature of 500°C or lower and 100°C or higher. 7 C0.0005~0.015%, Mn0.05~0.5%, S0.001
~0.030%, Cu1.0~2.2%, P0.001~0.100%,
Steel containing 0.005 to 1.0% Si, 0.15 to 0.45% Ni, 0.0050% or less N, 0.002 to 0.10% sol.Al, and the balance consisting of Fe and unavoidable elements, is heated at a temperature of Ar 3 to 1000℃. The resulting hot rolled steel strip is hot rolled at a temperature of 500
A method for producing a high-strength hot rolled steel sheet with extremely excellent cold workability, characterized by rolling at a temperature of 100°C or lower. 8 C0.0005~0.015%, Mn0.05~0.5%, S0.001
~0.030%, Cu1.0~2.2%, P0.001~0.100%,
Si0.005~1.0%, Ni0.15~0.45%, N0.0050% or less, sol.Al0.002~0.10%, plus Ti0.01~0.2
%, or one or two of Nb0.005-0.2%, with the balance consisting of Fe and unavoidable elements,
High-strength heat treatment with extremely excellent cold workability, characterized by hot rolling at a temperature of Ar 3 or higher and 1000°C or lower, and then winding the resulting hot rolled steel strip at a temperature of 500°C or higher and 100°C or higher. Method for manufacturing rolled steel plate. 9 In the method according to any one of claims 5 to 8, the coiling temperature after hot rolling is
A method for producing a high-strength hot-rolled steel sheet with extremely excellent cold workability, characterized in that the temperature is 350°C or lower and 100°C or higher.
Priority Applications (5)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2576788A JPS6479347A (en) | 1988-02-08 | 1988-02-08 | High strength hot rolled steel plate having drastically excellent cold workability and its manufacture |
| PCT/JP1988/000639 WO1988010318A1 (en) | 1987-06-26 | 1988-06-27 | High-strength, hot-rolled steel sheet having excellent cold workability and process for its production |
| EP88906041A EP0322463B1 (en) | 1987-06-26 | 1988-06-27 | Heat treatment hardenable hot rolled steel sheet having excellent cold workability and process for its production |
| DE88906041T DE3881002T2 (en) | 1987-06-26 | 1988-06-27 | THROUGH HEAT TREATMENT, HARDENABLE HOT ROLLED STEEL FINE SHEET WITH EXCELLENT COLD FORMABILITY AND METHOD FOR THE PRODUCTION THEREOF. |
| US07/320,265 US4925500A (en) | 1987-06-26 | 1988-06-27 | High-strength hot-rolled steel sheet having remarkably excellent cold workability and process for manufacturing the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2576788A JPS6479347A (en) | 1988-02-08 | 1988-02-08 | High strength hot rolled steel plate having drastically excellent cold workability and its manufacture |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS6479347A JPS6479347A (en) | 1989-03-24 |
| JPH0369979B2 true JPH0369979B2 (en) | 1991-11-06 |
Family
ID=12174989
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2576788A Granted JPS6479347A (en) | 1987-06-26 | 1988-02-08 | High strength hot rolled steel plate having drastically excellent cold workability and its manufacture |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS6479347A (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0639616B2 (en) * | 1988-10-13 | 1994-05-25 | 住友金属工業株式会社 | Method for producing hot rolled steel sheet with excellent workability |
| KR20020049920A (en) * | 2000-12-20 | 2002-06-26 | 이구택 | A method for manufacturing hot-rolled steel sheet without the edge defects |
-
1988
- 1988-02-08 JP JP2576788A patent/JPS6479347A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS6479347A (en) | 1989-03-24 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR101594670B1 (en) | Cold-rolled steel sheet and galvanized steel sheet having excellent ductility and method for manufacturing thereof | |
| CN109328241B (en) | Ultrahigh-strength and high-ductility steel sheet having excellent yield strength and method for producing same | |
| JP2010121213A (en) | Method for manufacturing high-strength low-specific gravity steel sheet excellent in ductility | |
| US4961793A (en) | High-strength cold-rolled steel sheet having high r value and process for manufacturing the same | |
| JP2008297570A (en) | Low yield ratio steel sheet | |
| JP3879440B2 (en) | Manufacturing method of high strength cold-rolled steel sheet | |
| JP2000273577A (en) | High tensile strength hot rolled steel plate excellent in stretch-flanging workability and material stability and its production | |
| JP3422865B2 (en) | Method for producing high-strength martensitic stainless steel member | |
| JP3280692B2 (en) | Manufacturing method of high strength cold rolled steel sheet for deep drawing | |
| JPS61113724A (en) | Manufacture of cold rolled steel sheet extremely superior in press formability | |
| JPH0369979B2 (en) | ||
| JP3043519B2 (en) | Manufacturing method of high strength hot rolled steel sheet | |
| JP4507364B2 (en) | Manufacturing method of high strength hot-rolled steel sheet | |
| JP3806958B2 (en) | Manufacturing method of high-tensile hot-rolled steel sheet | |
| JP3299287B2 (en) | High strength steel sheet for forming and its manufacturing method | |
| JP2618563B2 (en) | High strength electric resistance welded steel pipe which is hardly softened in welding heat affected zone and method of manufacturing the same | |
| JPH02145747A (en) | Hot rolled steel sheet for deep drawing and its manufacture | |
| JP2002105540A (en) | Method for producing high strength hot rolled steel sheet | |
| JP2003013176A (en) | High-ductility cold-rolled steel sheet superior in press formability and strain aging hardening characterisitics, and manufacturing method therefor | |
| JPH0320407A (en) | Method for preventing oxidation of grain boundary in high strength cold-rolled steel sheet | |
| JPS5935414B2 (en) | Manufacturing method of high-strength steel with excellent weldability | |
| KR100544737B1 (en) | Blackplates with excellent formability and method for manufacturing thereof | |
| JPS61157660A (en) | Nonageable cold rolled steel sheet for deep drawing and its manufacture | |
| JP2002121646A (en) | High workability and high strength hot rolled steel sheet having small variation of material in coil and its production method | |
| JPH05247588A (en) | Cr-based ultrahigh tensile strength resistance welded steel tube excellent in ductility |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Year of fee payment: 16 Free format text: PAYMENT UNTIL: 20071106 |
|
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Year of fee payment: 17 Free format text: PAYMENT UNTIL: 20081106 |
|
| EXPY | Cancellation because of completion of term | ||
| FPAY | Renewal fee payment (prs date is renewal date of database) |
Free format text: PAYMENT UNTIL: 20081106 Year of fee payment: 17 |