JPH0140895B2 - - Google Patents
Info
- Publication number
- JPH0140895B2 JPH0140895B2 JP14634881A JP14634881A JPH0140895B2 JP H0140895 B2 JPH0140895 B2 JP H0140895B2 JP 14634881 A JP14634881 A JP 14634881A JP 14634881 A JP14634881 A JP 14634881A JP H0140895 B2 JPH0140895 B2 JP H0140895B2
- Authority
- JP
- Japan
- Prior art keywords
- less
- present
- steel
- annealing
- temperature
- 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
- 238000000137 annealing Methods 0.000 claims description 30
- 229910000831 Steel Inorganic materials 0.000 claims description 24
- 239000010959 steel Substances 0.000 claims description 24
- 238000001953 recrystallisation Methods 0.000 claims description 12
- 239000010960 cold rolled steel Substances 0.000 claims description 9
- 238000005097 cold rolling Methods 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 9
- 238000000034 method Methods 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 239000000203 mixture Substances 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 description 14
- 238000005098 hot rolling Methods 0.000 description 13
- 238000012545 processing Methods 0.000 description 8
- 229910052782 aluminium Inorganic materials 0.000 description 6
- 238000004804 winding Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 229910000655 Killed steel Inorganic materials 0.000 description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 4
- 239000000463 material Substances 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 238000007796 conventional method Methods 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000005554 pickling Methods 0.000 description 3
- 238000005336 cracking Methods 0.000 description 2
- 238000005261 decarburization Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 238000009849 vacuum degassing Methods 0.000 description 2
- 230000032683 aging Effects 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 239000013256 coordination polymer Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 230000014509 gene expression Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000004381 surface treatment Methods 0.000 description 1
- 238000009864 tensile test Methods 0.000 description 1
- 239000005028 tinplate Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0426—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0421—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the working steps
- C21D8/0436—Cold rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/04—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing
- C21D8/0447—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips to produce plates or strips for deep-drawing characterised by the heat treatment
- C21D8/0473—Final recrystallisation annealing
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Description
本発明は傑出した張出し性と優れた深絞り性を
有し、かつプレス後の二次加工性の優れた極低C
アルミキルド冷延鋼板の製造法に関するものであ
る。
張出し性、深絞り性の優れた冷延鋼板として従
来下記の三つの製造法がある。
(イ) アルミキルド鋼をオープンコイルで脱炭焼鈍
したもの。
(ロ) 極低Cアルミキルド鋼を箱焼鈍あるいは連続
焼鈍して製造したもの。
(ハ) 極低Cアルミキルド鋼にTiあるいはNbを添
加したもの。
まず(イ)では再結晶焼鈍の加熱時にAlNの析出
を有効に活用して優れた深絞り性を付与し、さら
に脱炭処理によつて鋼中Cを低減させて張出し性
を向上させるものである。そのため通常N量が
40ppm以上、Al量も0.02〜0.08%を含有させ、ス
ラブ加熱温度もAlNを完全に溶体化させるため
に通常1200℃以上の高温加熱が必須であり、かつ
再結晶焼鈍の加熱速度も徐加熱(10〜40℃/hr程
度)が必要であり、また脱炭にも長時間を要す
る。従つて生産性も悪く省エネルギーの点からも
好ましくない。
(ロ)では脱C焼鈍こそ不要であるが、箱焼鈍で製
造する場合、上記(イ)と全く同一方法で製造するた
め、上記箱焼鈍法と同じ欠点を有している。また
(ロ)で連続焼鈍で製造する場合は、高温捲取を行な
わないと所期の特性が得られない。そのため高温
捲取に起因する熱延板の酸洗性の低下およびコイ
ルトツプ、ボトム部の材質劣化の問題がある。
また(ハ)は箱焼鈍、連続焼鈍どちらでも製造でき
るが、特殊元素の添加によりコスト高となりまた
張出し性は(イ),(ロ)に比して劣つている。
さらに従来の(イ),(ロ)および(ハ)では下記共通の欠
点を有している。すなわち張出し深絞り用冷延鋼
板は、きびしいプレス加工に供するため、低加工
度の時には余り問題とならない二次加工性(プレ
ス加工後の加工品の靭性を云い、二次加工性が悪
いと加工品に脆性的な割れを生じる)が問題視さ
れるが、特に極低C材は2次加工性が一般に悪
く、上記いずれの鋼板もこの二次加工性に問題を
有していた。
本発明者らは、これら上記欠点を解決すべく
種々研究した結果、本発明を完成した。
即ち本発明の要旨は重量%としてC:0.005%
以下、Mn:0.5%以下、Al:0.005〜0.05%、P:
0.008%以下、N:0.0025%以下とし、かつP
4C、P+5N:0.0175%以下、残部が鉄および不
可避的不純物からなる組成の鋼を850℃以上で熱
間圧延し、50%以上の冷延率の冷延を行ない、更
に再結晶温度以上、A3点以下の温度で、連続焼
鈍または箱焼鈍することを特徴とする冷延鋼板の
製造法にあり、更に上記鋼にTi:0.10%以下、
Nb:0.10%以下、B:0.003%以下のうち1種又
は2種以上を含有せしめた冷延鋼板の製造法にあ
る。
以下本発明について詳細に説明する。
まず本発明を構成する鋼成分について説明す
る。
本発明の最も重要な構成要件はC.PとNを密接
不可分の関係として特定することにある。まず本
発明ではC,PおよびN量をそれぞれC:0.005
%以下、P:0.008%以下、N:0.0025%以下に
特定し、さらにP4C、P+5N0.0175%の条
件式を満足しなければならない。これらの条件は
張出し性、深絞り性および二次加工性を同時に良
好ならしめるためのものである。以下これをより
詳細に説明する。
まずC量の上限値0.005%は優れた張出し性お
よび深絞り性を得るために定めた。従来から加工
性を良くするためには、Cは極力少ない方が良い
ことが知られており、0.01%以下の極低C鋼が製
造されているが、Cが0.005%を超えると、焼鈍
後CがFe3Cとして析出せず、鋼中に過飽和に固
溶し、時効性が大きくなり本発明の特徴を失う。
また単にC量を低くしただけではプレス加工後に
二次加工割れが発生しやすくなる。例えばCを
0.005%以下にすればプレス加工の程度が余り大
きくなくても、二次加工割れが発生することが知
られている。本発明では絞り比3.5程度のきびし
いプレス加工を行つても二次加工割れを生じない
ようにするためP量を0.008%以下に限定すると
同時にP4CとなるようC量の低下とともにP
量も低減させることが有効であることが多数の実
験結果より判明した。なおこのP量をC量の低減
にともなつて低減させることは、後述のようにP
量低減による深絞り性、張出し性向上にも大きく
寄与する。したがつて本発明ではC量の低減は同
時にP量の低減にもつながるので、その効果は従
来鋼より著しく大きくなる。なお本発明の特徴を
最大限に発揮するにはC量を0.004%以下、P
3cとすることが好ましい。
PおよびN量の限定も本発明では極めて重要な
意義を有する。
第1図は1例としてC:0.003〜0.004%、
Mn:0.20〜0.25%、Al:0.01〜0.04%の組成の鋼
のP量、N量と二次加工性の関係を、第2図はP
量、N量と値、伸びの関係を示したもので、い
ずれも多数の実験の平均値の等高線で表示してい
る。なお図中P量の上限値についてはC≒0.0035
%としてP:0.14%(P=4C)で表示している。
他の製造条件は次の通りである。
熱延スラブ加熱温度 1050〜1200℃
熱延仕上温度 890℃以上
熱延捲取温度 550〜650℃
冷間圧延率 80〜85%
焼鈍条件 750℃×1分(連続焼鈍方式)
調質圧延率 1.0%
なお第1図の二次加工試験は種々の絞り比のカ
ツプを絞り、0℃で逆円錐形ポンチでカツプの押
拡げを行ない、その際カツプに脆性割れが発生す
るか否かを調査し、脆性割れの発生しない最大の
絞り比で二次加工性を評価し、この値が大きい程
二次加工性が優れていることを示す。第1図中の
数字は二次加工割れが発生しない最大の絞り比を
示し、この数値の大きいもの程二次加工性が優れ
ている。
第2図の実線は伸び、破線は値を示し、数字
はそれぞれ伸び、値である。
第1図、第2図からわかるように、Pは単に二
次加工性に影響を与えるのみでなく、張出し性と
強い相関を持つ伸びおよび深絞り性と強い相関を
持つ値にも影響し、P0.008%で伸びの向上
効果が極めて大きくなり、同時にP量低減につれ
r値も向上する。
またNについてもN量低減により二次加工性が
向上するという新事実も判明し、さらにN
25ppm以下で値も急激に向上し、伸びも向上す
る。
本発明では張出し性、深絞り性と二次加工性を
バランスさせ、且つ最高度にその性能を発揮させ
るためP0.008%、20.0025%かつP+5N
0.0175%に限定する。これにより伸び52%以上、
r値1.6以上、二次加工割れの限界絞り比が3.5以
上を確保できる。勿論P,Nをさらに低減するこ
とによつて、これらの特性を一段と向上し、P
0.010%、N0.0020%にすることによつて最高
級の張出し性、深絞り性および二次加工性を有す
る冷延鋼板が製造できる。
Mnは熱間圧延時のSによる熱間脆性を防止す
るため、0.05%程度は必要であるが、Mn/S
15の条件を安定して満足するために、下限を0.10
%とすることが好ましい。一方0.5%を超えると
鋼板が硬質化し、本発明の特徴をそこなう。本発
明の特徴を最大限に発揮するMn量は0.40%以下
である。
Alは本発明では再結晶焼鈍時のAlNを利用し
ない点が従来法と特徴的に異なる。Al量は、キ
ルド鋼とするため少なくとも0.005%必要である。
一方Al量が0.05%を超えると鋼板が若干硬質化
し、またコスト上昇をもたらす。好ましい範囲は
0.010〜0.040%である。
Sについては特に規定しないが、熱間脆性を防
止するため、通常行なわれているようにMn/S
15とすることが好ましい。
以上本発明の基本成分について述べたが、基本
成分に加えて、Ti,Nb,Bを適宜加えることが
できる。
Ti,Nb,BはそれぞれNまたはCと結合する
ので低C、低Nを指向する本発明ではこれらの元
素添加によつて本発明の特徴をさらに向上させ
る。これら元素を添加する場合はTi0.10%、
Nb0.10%、B0.0030%のうち1種また2種以
上とするが、これら上限値超ではその効果は飽和
し、鋼が高価となる。
本発明の鋼片(スラブ)は転炉、電気炉など通
常の溶解炉で溶製され、さらに真空脱ガス処理に
より溶製された溶鋼を造塊、分塊または連続鋳造
される。
熱延条件は本発明では仕上温度が850℃以上で
あれば良く、スラブ加熱温度、捲取温度によつて
本発明の特徴はなんら影響されない。したがつて
加熱温度は自由であるが、省エネルギーの点から
1200℃以下で加熱することが望ましい。また連続
鋳造、分塊圧延された熱片を直接熱間圧延しても
良い。また連続鋳造、分塊圧延された熱片を加熱
炉に装入するホツトチヤージを行つても良い。
本発明の特徴をより発揮させるためには、仕上
熱延での仕上入口温度1000℃以下とし、なるべく
低温域での圧下率を大きくすることによつて(よ
り好ましくは最終2パスでの全圧下率が40%以
上)、また熱延終了後直ちに30℃/sec以上の強制
冷却することが望ましい。実施例で述べるが熱延
仕上入口温度を1000℃以下にすると深絞り性の指
標である値が向上することがわかる。この効果
をより発揮するためにはスラブ加熱温度を1100℃
以下にすることが好ましい。
この理由は定かでないが、本発明のような極低
C鋼に通常の熱延では熱延後の結晶粒が粗粒とな
りやすい。一方熱延を低温で行ない、直ちに強制
冷却を開始すれば熱延後の結晶粒が細粒になり、
この熱延板の細粒化の効果により、値が向上す
るものと考えられる。
捲取温度によつて本発明の特徴はなんら影響さ
れないが、酸洗性向上の点から550〜650℃とする
ことが好ましい(捲取温度が高温であると酸化皮
膜が厚くなり、酸洗性を悪くする)。
熱延されたコイルは続いて脱スケールされ、冷
間圧延に供される。
冷間圧延率は通常行なわれているように50%以
上の冷間圧延が施される。しかし本発明鋼では冷
間圧延率が通常の鋼より高い方が加工性が向上す
るので冷間圧延率は73%以上とすることが好まし
い。
焼鈍は連続焼鈍でも箱焼鈍でも良い。連続焼鈍
は通常行なわれているように再結晶温度以上A3
点以下で再結晶処理を行ない、ついて冷却必要に
応じて過時効処理を施す。代表的焼鈍条件は700
〜800℃で3分以下の再結晶処理をした後冷却す
る。過時効処理を行う場合には200〜450℃で5分
以下の処理が施される。
箱焼鈍の場合は再結晶温度以上、A3点以下の
再結晶処理を行なうが、本発明では加熱速度は従
来法と異なり特に徐加熱しなくても良い。代表的
焼鈍条件は650〜750℃で1〜5hrで再結晶処理を
行なう。
焼鈍された鋼板は必要に応じて調質圧延され成
品に供される。また本発明の方法で製造された鋼
板は、表面処理されても本発明の特徴をなんら損
なわないので、ブリキ、Znメツキ、ターンメツ
キ鋼板にも適用される。
実施例
第1表に示す鋼を転炉で溶製し、さらに真空脱
ガス処理によつて、C量を所定量まで低減し、連
続鋳造によつてスラブにされ、1050〜1200℃で加
熱後、第1表に示す条件で熱延し、ついて脱スケ
ール後、0.8mmまで冷間圧延して、焼鈍し、1.5%
の調質圧延を行つた。
得られた冷延鋼板の材質特性を同じく第1表に
示す。
引張試験片はJIS5号試験片を用い、二次加工性
は種々の絞り比で深絞りされた円筒を0℃で逆円
錐ダイスで押拡げし、脆性割れを発生しない最大
の絞り比で表わした。
本発明の範囲内で製造された鋼板は、張出し性
と強い相関のある伸び、深絞り性と強い相関のあ
る値が極めて優れているばかりでなく、二次加
工性も極めて優れており、最上級のプレス成形性
を有していると云える。
コイルNo.3と4,13と14は、熱延仕上入口温度
以外はまつたく同一条件で製造されているにもか
かわらず、値が大きく異なつている。すなわち
熱延仕上入口温度を100℃以下にすることにより
r値が大巾に向上することがわかる。
本発明の範囲からいずれかの一つの条件がはず
れても、張出し性、深絞り性、二次加工性の内い
ずれかの特性が劣つていることがわかる。
本発明は従来のものに比し、下記の傑出した特
徴を有する。
(イ) プレス加工後の二次加工性が優れているばか
りでなく、張出し性が従来のものより著しく向
上している。また深絞り性も従来のものと同等
以上である。
(ロ) スラブ加熱温度依存性がほとんどなく、した
がつてスラブ低温加熱が可能である。
(ハ) 焼鈍方式に左右されずに製造が可能で、箱焼
鈍法あるいはオープンコイル焼鈍法の場合で
は、従来のように徐加熱の必要がないので生産
性が向上する。また連続焼鈍法では高温捲取の
必要がなく、650℃以下の低温捲取が可能であ
る。したがつて材質のバラツキ、酸洗性の低下
もない。
The present invention has outstanding stretchability, excellent deep drawability, and ultra-low C with excellent secondary workability after pressing.
This invention relates to a method for producing aluminum killed cold rolled steel sheets. There are three conventional manufacturing methods for cold-rolled steel sheets with excellent stretchability and deep drawability. (a) Aluminum killed steel decarburized and annealed using an open coil. (b) Manufactured by box annealing or continuous annealing of ultra-low C aluminum killed steel. (c) Ultra-low C aluminum killed steel with Ti or Nb added. First, in (a), the precipitation of AlN is effectively utilized during heating during recrystallization annealing to impart excellent deep drawability, and furthermore, the C content in the steel is reduced through decarburization treatment to improve stretchability. be. Therefore, the amount of N is usually
40 ppm or more, the Al content is 0.02 to 0.08%, and the slab heating temperature is normally 1200°C or higher to completely solutionize the AlN, and the heating rate for recrystallization annealing is also slow heating ( 10 to 40℃/hr), and decarburization also takes a long time. Therefore, productivity is poor and it is not preferable from the point of view of energy saving. (b) does not require C-removal annealing, but when manufactured by box annealing, it has the same drawbacks as the box annealing method because it is manufactured using the same method as in (a) above. Also
When manufacturing by continuous annealing in (b), the desired properties cannot be obtained unless high-temperature winding is performed. Therefore, there are problems such as a decrease in the pickling properties of the hot-rolled sheet and deterioration of the material of the coil top and bottom parts due to high-temperature winding. Also, (c) can be manufactured by either box annealing or continuous annealing, but the addition of special elements increases the cost and the overhang properties are inferior to (a) and (b). Furthermore, conventional methods (a), (b), and (c) have the following common drawbacks. In other words, cold-rolled steel sheets for overhang deep drawing are subjected to severe press working, so secondary workability (referring to the toughness of the processed product after press working) is not a problem when the degree of work is low. However, ultra-low C materials in particular generally have poor secondary workability, and all of the above-mentioned steel sheets had problems with this secondary workability. The present inventors completed the present invention as a result of various studies to solve the above-mentioned drawbacks. That is, the gist of the present invention is that C: 0.005% by weight.
Below, Mn: 0.5% or less, Al: 0.005-0.05%, P:
0.008% or less, N: 0.0025% or less, and P
4C, P+5N: Steel with a composition of 0.0175% or less, the balance consisting of iron and unavoidable impurities, is hot rolled at 850°C or higher, cold rolled at a cold rolling rate of 50% or higher, and then at a recrystallization temperature or higher, A A method for manufacturing cold rolled steel sheets characterized by continuous annealing or box annealing at a temperature of 3 points or less, and further including Ti: 0.10% or less in the above steel.
A method for manufacturing a cold-rolled steel sheet containing one or more of Nb: 0.10% or less and B: 0.003% or less. The present invention will be explained in detail below. First, the steel components constituting the present invention will be explained. The most important component of the present invention is to specify CP and N as a close and inseparable relationship. First, in the present invention, the amounts of C, P and N are each C: 0.005.
% or less, P: 0.008% or less, N: 0.0025% or less, and the conditional expressions of P4C and P+5N0.0175% must be satisfied. These conditions are intended to improve stretchability, deep drawability, and secondary workability at the same time. This will be explained in more detail below. First, an upper limit of 0.005% for the amount of C was set in order to obtain excellent stretchability and deep drawability. It has long been known that in order to improve workability, it is better to have as little C as possible, and ultra-low C steel with 0.01% or less is manufactured, but if C exceeds 0.005%, C does not precipitate as Fe 3 C, but forms a supersaturated solid solution in the steel, increases aging resistance, and loses the characteristics of the present invention.
Moreover, if the amount of C is simply reduced, secondary processing cracks are likely to occur after press working. For example, C
It is known that if the content is 0.005% or less, secondary processing cracks will occur even if the degree of press working is not too great. In the present invention, in order to prevent secondary processing cracks even when performing severe press working with a drawing ratio of about 3.5, the P content is limited to 0.008% or less, and at the same time, as the C content decreases, the P content becomes P4C.
Numerous experimental results have shown that it is effective to also reduce the amount. Note that reducing the amount of P along with the reduction of the amount of C means reducing the amount of P as described below.
It also greatly contributes to improving deep drawability and stretchability by reducing the amount of steel. Therefore, in the present invention, since the reduction in the amount of C also leads to the reduction in the amount of P, the effect is significantly greater than in conventional steels. In order to maximize the characteristics of the present invention, the amount of C should be 0.004% or less, and the amount of P should be 0.004% or less.
3c is preferable. Limiting the amounts of P and N also has extremely important significance in the present invention. Figure 1 shows an example of C: 0.003-0.004%,
Figure 2 shows the relationship between the P content, N content and secondary workability of steel with a composition of Mn: 0.20~0.25% and Al: 0.01~0.04%.
It shows the relationship between N content, N content, value, and elongation, all of which are expressed as contour lines of the average value of a large number of experiments. In addition, the upper limit of P amount in the figure is C≒0.0035.
It is expressed as a percentage of P: 0.14% (P=4C). Other manufacturing conditions are as follows. Hot-rolled slab heating temperature 1050-1200℃ Hot-rolling finishing temperature 890℃ or higher Hot-rolling temperature 550-650℃ Cold rolling rate 80-85% Annealing conditions 750℃ x 1 minute (continuous annealing method) Temper rolling rate 1.0 % In the secondary processing test shown in Figure 1, cups with various drawing ratios were drawn, and the cups were expanded using an inverted conical punch at 0℃, and it was investigated whether brittle cracks occurred in the cups. The secondary workability is evaluated at the maximum drawing ratio at which no brittle cracks occur, and the larger this value is, the better the secondary workability is. The numbers in FIG. 1 indicate the maximum drawing ratios at which secondary processing cracks do not occur, and the larger this number is, the better the secondary processing properties are. In FIG. 2, solid lines indicate elongation, dashed lines indicate values, and numbers indicate elongation and values, respectively. As can be seen from Figures 1 and 2, P not only affects secondary workability, but also affects elongation, which has a strong correlation with stretchability, and values that have a strong correlation with deep drawability. At 0.008% P, the effect of improving elongation becomes extremely large, and at the same time, as the amount of P decreases, the r value also improves. Regarding N, a new fact was also discovered that reducing the amount of N improves secondary workability.
Below 25ppm, the value increases rapidly and the elongation also improves. In the present invention, in order to balance stretchability, deep drawability and secondary workability, and to maximize performance, P0.008%, 20.0025% and P+5N are used.
Limited to 0.0175%. This resulted in an elongation of over 52%,
It is possible to ensure an r value of 1.6 or more and a critical drawing ratio for secondary processing cracking of 3.5 or more. Of course, by further reducing P and N, these characteristics can be further improved, and P
By setting N to 0.010% and N to 0.0020%, a cold rolled steel sheet having the highest quality stretchability, deep drawability and secondary workability can be manufactured. Mn is required at about 0.05% to prevent hot embrittlement caused by S during hot rolling, but Mn/S
In order to stably satisfy the conditions of 15, the lower limit is set to 0.10.
% is preferable. On the other hand, if it exceeds 0.5%, the steel plate becomes hard and the characteristics of the present invention are impaired. The amount of Mn that maximizes the characteristics of the present invention is 0.40% or less. Al is uniquely different from conventional methods in that AlN is not used during recrystallization annealing in the present invention. The amount of Al is required to be at least 0.005% in order to obtain killed steel.
On the other hand, if the Al content exceeds 0.05%, the steel plate becomes slightly hard and costs increase. The preferred range is
It is 0.010-0.040%. Although S is not specified, Mn/S is commonly used to prevent hot embrittlement.
It is preferable to set it to 15. The basic components of the present invention have been described above, but in addition to the basic components, Ti, Nb, and B can be added as appropriate. Ti, Nb, and B bond with N or C, respectively, so in the present invention, which aims at low C and low N, the features of the present invention are further improved by adding these elements. When adding these elements, Ti0.10%,
One or more of Nb 0.10% and B 0.0030% may be used, but if these upper limits are exceeded, the effect will be saturated and the steel will become expensive. The steel billets (slabs) of the present invention are melted in a normal melting furnace such as a converter or an electric furnace, and the molten steel melted by vacuum degassing is then ingot-formed, bloomed, or continuously cast. In the present invention, the hot rolling conditions are sufficient as long as the finishing temperature is 850°C or higher, and the characteristics of the present invention are not affected by the slab heating temperature and winding temperature. Therefore, the heating temperature is free, but from the point of view of energy saving
It is desirable to heat at 1200℃ or less. Alternatively, hot pieces that have been continuously cast or bloomed may be directly hot rolled. Alternatively, hot charging may be performed in which continuously cast and bloomed hot pieces are charged into a heating furnace. In order to make the most of the features of the present invention, the finishing inlet temperature during finishing hot rolling should be 1000°C or less, and the reduction rate should be as large as possible in the low temperature range (more preferably, the total rolling reduction in the final two passes should be lowered). 40% or more), and it is desirable to perform forced cooling at 30°C/sec or more immediately after hot rolling. As described in the examples, it can be seen that when the hot rolling finishing inlet temperature is set to 1000°C or less, the value, which is an index of deep drawability, improves. In order to make the most of this effect, the slab heating temperature should be set to 1100℃.
It is preferable to do the following. The reason for this is not clear, but when the ultra-low C steel of the present invention is subjected to normal hot rolling, the crystal grains after hot rolling tend to become coarse. On the other hand, if hot rolling is performed at a low temperature and forced cooling is started immediately, the grains after hot rolling will become finer.
It is thought that the value improves due to the effect of making the grains of the hot-rolled sheet finer. Although the features of the present invention are not affected by the winding temperature, it is preferably 550 to 650°C from the viewpoint of improving pickling properties. make things worse). The hot rolled coil is subsequently descaled and subjected to cold rolling. Cold rolling is carried out at a cold rolling rate of 50% or more, as is commonly practiced. However, in the steel of the present invention, the workability is improved when the cold rolling rate is higher than that of ordinary steel, so the cold rolling rate is preferably 73% or more. Annealing may be continuous annealing or box annealing. Continuous annealing is performed above the recrystallization temperature A 3 as is normally done.
Recrystallization treatment is performed below the temperature, followed by cooling and, if necessary, overaging treatment. Typical annealing conditions are 700
After performing recrystallization treatment at ~800°C for 3 minutes or less, it is cooled. When performing overaging treatment, the treatment is performed at 200 to 450°C for 5 minutes or less. In the case of box annealing, recrystallization treatment is performed above the recrystallization temperature and below the A3 point, but in the present invention, the heating rate is different from the conventional method and there is no particular need for gradual heating. Typical annealing conditions include recrystallization at 650-750°C for 1-5 hours. The annealed steel plate is subjected to skin pass rolling as required and is then used as a finished product. Further, since the steel sheet manufactured by the method of the present invention does not lose any of the features of the present invention even if it is subjected to surface treatment, it can also be applied to tinplate, Zn-plated, and turn-plated steel sheets. Example The steel shown in Table 1 is melted in a converter, the amount of C is reduced to a predetermined amount by vacuum degassing treatment, the slab is made by continuous casting, and after heating at 1050 to 1200 ° C. , hot rolled under the conditions shown in Table 1, descaled, cold rolled to 0.8 mm, annealed, 1.5%
Temper rolling was carried out. The material properties of the obtained cold rolled steel sheet are also shown in Table 1. The tensile test piece used was a JIS No. 5 test piece, and the secondary workability was measured by expanding cylinders that had been deep drawn at various drawing ratios using an inverted conical die at 0°C, and using the maximum drawing ratio that did not cause brittle cracking. . Steel sheets manufactured within the scope of the present invention not only have extremely excellent elongation, which has a strong correlation with stretchability, and values that have a strong correlation with deep drawability, but also have extremely excellent secondary workability, and are the best. It can be said that it has superior press formability. Coil Nos. 3 and 4, 13 and 14 have significantly different values even though they were manufactured under exactly the same conditions except for the hot rolling finishing inlet temperature. That is, it can be seen that the r value is greatly improved by reducing the hot rolling finishing inlet temperature to 100°C or less. It can be seen that even if any one condition deviates from the scope of the present invention, any one of the properties of stretchability, deep drawability, and secondary workability is inferior. The present invention has the following outstanding features compared to the prior art. (a) Not only is the secondary workability after press working excellent, but the stretchability is significantly improved compared to conventional products. Also, the deep drawability is equal to or better than that of conventional products. (b) There is almost no dependence on the slab heating temperature, so it is possible to heat the slab at a low temperature. (c) Manufacture is possible regardless of the annealing method, and in the case of box annealing or open coil annealing, there is no need for gradual heating as in the past, improving productivity. Furthermore, the continuous annealing method does not require high-temperature winding, and low-temperature winding of 650°C or less is possible. Therefore, there is no variation in material quality and no deterioration in pickling properties.
【表】【table】
【表】
* 二次加工割れの発生しない最大の絞り比
[Table] * Maximum drawing ratio without secondary processing cracks
第1図は二次加工性とP量、N量の関係を示す
図、第2図は伸び、値とP量、N量の関係を示
す図である。
FIG. 1 is a diagram showing the relationship between secondary workability and the amount of P and the amount of N, and FIG. 2 is a diagram showing the relationship between the elongation value and the amount of P and N.
Claims (1)
以下、Al:0.005〜0.05%、N:0.0025%以下、
P:0.008%以下とし、かつP4C、P+5N:
0.0175%以下、残部が鉄および不可避的不純物か
らなる組成の鋼を850℃以上で熱間圧延し、50%
以上の冷延率の冷延を行ない、更に再結晶温度以
上、A3点以下の温度で、連続焼鈍または箱焼鈍
することを特徴とする冷延鋼板の製造法。 2 重量%としてC:0.005%以下、Mn:0.50%
以下、Al:0.005〜0.05%、N:0.0025%以下、
P:0.008%以下とし、かつP4C、P+5N:
0.0175%以下であつて、Ti:0.10%以下、Nb:
0.10%以下、B:0.003%以下のうち1種または
2種以上を含み、残部が鉄および不可避的不純物
からなる組成の鋼を850℃以上で熱間圧延し、50
%以上の冷延率を行ない、更に再結晶温度以上、
A3点以下の温度で連続焼鈍または箱焼鈍するこ
とを特徴とする冷延鋼板の製造法。[Claims] 1. C: 0.005% or less, Mn: 0.5% as weight%
Below, Al: 0.005 to 0.05%, N: 0.0025% or less,
P: 0.008% or less, and P4C, P+5N:
Steel with a composition of 0.0175% or less and the balance consisting of iron and unavoidable impurities is hot rolled at 850℃ or higher to produce 50%
A method for producing a cold-rolled steel sheet, which is characterized in that cold rolling is performed at a cold-rolling rate of the above, and then continuous annealing or box annealing is performed at a temperature above the recrystallization temperature and below A 3 points. 2 C: 0.005% or less, Mn: 0.50% as weight%
Below, Al: 0.005 to 0.05%, N: 0.0025% or less,
P: 0.008% or less, and P4C, P+5N:
0.0175% or less, Ti: 0.10% or less, Nb:
0.10% or less, B: 0.003% or less, and the balance is iron and unavoidable impurities, hot rolled at 850℃ or higher,
% or more, and furthermore, the recrystallization temperature or more,
A A method for manufacturing cold rolled steel sheets characterized by continuous annealing or box annealing at temperatures below 3 points.
Priority Applications (5)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14634881A JPS5848633A (en) | 1981-09-18 | 1981-09-18 | Production of cold rolled steel plate having excellent press formability |
DE8282108598T DE3271669D1 (en) | 1981-09-18 | 1982-09-17 | Method for producing a cold rolled steel sheet |
EP82108598A EP0075292B2 (en) | 1981-09-18 | 1982-09-17 | Method for producing a cold rolled steel sheet |
US06/776,097 US4627881A (en) | 1981-09-18 | 1985-09-16 | Cold rolled steel sheet having excellent press formability and method for producing the same |
US06/894,255 US4678522A (en) | 1981-09-18 | 1986-08-07 | Cold rolled steel sheet having excellent press formability and method for producing the same |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP14634881A JPS5848633A (en) | 1981-09-18 | 1981-09-18 | Production of cold rolled steel plate having excellent press formability |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS5848633A JPS5848633A (en) | 1983-03-22 |
JPH0140895B2 true JPH0140895B2 (en) | 1989-09-01 |
Family
ID=15405669
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP14634881A Granted JPS5848633A (en) | 1981-09-18 | 1981-09-18 | Production of cold rolled steel plate having excellent press formability |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS5848633A (en) |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS59173223A (en) * | 1983-03-23 | 1984-10-01 | Sumitomo Metal Ind Ltd | Preparation of grade cold rolled steel plate for processing |
JPS60221526A (en) * | 1984-04-17 | 1985-11-06 | Nippon Kokan Kk <Nkk> | Manufacture of cold rolled steel sheet with superior deep drawability and ductility |
JPS60243226A (en) * | 1984-05-15 | 1985-12-03 | Kawasaki Steel Corp | Method and device for controlling quality of hot rolled material |
JPS61276927A (en) * | 1985-05-31 | 1986-12-06 | Kawasaki Steel Corp | Production of cold rolled steel sheet having good deep drawability |
JPH0617517B2 (en) * | 1986-02-08 | 1994-03-09 | 日新製鋼株式会社 | Manufacturing method of cold rolled steel sheet with excellent press workability |
JPS62227043A (en) * | 1986-03-28 | 1987-10-06 | Sumitomo Metal Ind Ltd | Manufacture of cold-rolled steel sheet for deep drawing reduced in anisotropy |
JPH0753889B2 (en) * | 1986-10-15 | 1995-06-07 | 川崎製鉄株式会社 | Method for manufacturing cold rolled steel sheet for thick ultra deep drawing |
JP4559918B2 (en) | 2004-06-18 | 2010-10-13 | 新日本製鐵株式会社 | Steel plate for tin and tin free steel excellent in workability and method for producing the same |
CN110714170B (en) * | 2019-10-23 | 2021-03-19 | 首钢集团有限公司 | High-nitrogen cold-rolled steel and preparation method and application thereof |
-
1981
- 1981-09-18 JP JP14634881A patent/JPS5848633A/en active Granted
Also Published As
Publication number | Publication date |
---|---|
JPS5848633A (en) | 1983-03-22 |
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