JPH0550150A - Method for warm pressforming and manufacture of steel sheet for above - Google Patents

Method for warm pressforming and manufacture of steel sheet for above

Info

Publication number
JPH0550150A
JPH0550150A JP3231225A JP23122591A JPH0550150A JP H0550150 A JPH0550150 A JP H0550150A JP 3231225 A JP3231225 A JP 3231225A JP 23122591 A JP23122591 A JP 23122591A JP H0550150 A JPH0550150 A JP H0550150A
Authority
JP
Japan
Prior art keywords
steel sheet
temperature
press forming
press
warm
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.)
Withdrawn
Application number
JP3231225A
Other languages
Japanese (ja)
Inventor
Ichiro Tsukatani
一郎 塚谷
Shoji Okamoto
昭二 岡本
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Kobe Steel Ltd
Original Assignee
Kobe Steel Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Kobe Steel Ltd filed Critical Kobe Steel Ltd
Priority to JP3231225A priority Critical patent/JPH0550150A/en
Publication of JPH0550150A publication Critical patent/JPH0550150A/en
Withdrawn legal-status Critical Current

Links

Abstract

PURPOSE:To present a warm press forming method of high baking hardening type steel sheet and a manufacture of steel sheet for warm press forming so that any stretcher strain in not generated by making the thin steel sheet which can obtain a baking hardening amount >=4kgf/mm<2> after working feasible to the press working condition without adding expensive alloy element even if an ordinary temperature aging degradation is occurred. CONSTITUTION:On the case for press forming the steel sheet that the steel material contains, by weight %, 0.003-0.03C, <=1 S, 0.05-1 Mn, and 0.01-0.1 acid soluble Al, is hot rolled and cold rolled, then annealed with harmonic heating in the temperature range of over than the re-crystallyzing temperature, <=850 deg.C by continuously annealing, then cooled until the room temperature with a cooling velocity of >=20 deg.C/sec or executed with a super aging treatment of <=10min on the cooling way, and manufactured, it is worked in the temperature range of 75-250 deg.C, and with the strain velocity of >=10<-2>.

Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【産業上の利用分野】本発明は焼付硬化性の極めて優れ
た薄鋼板をプレス成形する際に、ストレッチャーストレ
インと呼ばれる不均一変形等を生じない温間プレス成形
法及び温間プレス成形に適した薄鋼板の製造法に関する
ものである。
BACKGROUND OF THE INVENTION The present invention is suitable for a warm press forming method and a warm press forming which do not cause nonuniform deformation called stretcher strain when press forming a thin steel sheet having extremely excellent bake hardenability. The present invention relates to a method for manufacturing a thin steel sheet.

【0002】[0002]

【従来の技術】薄鋼板、例えば冷延鋼板等の加工素材
は、一般に加工時には加工し易いように軟質であること
が要求され、加工後製品となってからは強度の高いこと
が要求される。例えば自動車外板を例にとると、複雑な
形状のプレス加工が容易に行えるような軟質性が要求さ
れる一方では、加工後の寸法精度がスプリングバックや
歪み等によって悪くならないような低降伏応力鋼板を用
いるのが一般的である。しかしながら低降伏応力鋼板を
用いたドアやフード等の大型部品は、加工硬化が期待で
きないため外力に対して極めて変形し易いという問題が
あった。このような問題に対処するため、従前は低炭素
リムド鋼板において塗装焼付け時の窒素の析出硬化によ
る強度の上昇を利用してきたが、近年は焼付硬化性を有
する低炭素Alキルド冷延鋼板を用いるのが一般的な傾
向である。該低炭素Alキルド冷延鋼板は一般に非時効
性でプレス成形性も良好であるが、焼付硬化量が上記低
炭素リムド鋼を用いた場合に比べて少ない。従って低炭
素Alキルド冷延鋼板に対してリムド鋼並み又はそれ以
上の焼付硬化量が得られるならば、自動車業界の要望で
ある自動車の軽量化に対するメリットは非常に大きい。
このような実用化の困難な性質を有する冷延鋼板として
は、従来から種々の鋼板が開発されている。
2. Description of the Related Art A work material such as a thin steel plate, for example, a cold-rolled steel plate, is generally required to be soft so that it can be easily processed at the time of processing, and is required to have high strength after being a processed product. .. For example, in the case of automobile skins, softness is required so that complicated shapes can be easily pressed, while low yield stress that does not deteriorate the dimensional accuracy after processing due to springback or strain. It is common to use a steel plate. However, large parts such as doors and hoods using low yield stress steel plates have a problem that they are extremely likely to be deformed by external force because work hardening cannot be expected. In order to deal with such a problem, in the past, the increase in strength due to the precipitation hardening of nitrogen at the time of paint baking in low carbon rimmed steel sheets has been utilized, but in recent years, low carbon Al-killed cold rolled steel sheets having bake hardenability have been used. Is the general tendency. The low carbon Al-killed cold-rolled steel sheet is generally non-aging and has good press formability, but the bake hardening amount is smaller than that when the above low carbon rimmed steel is used. Therefore, if a bake hardening amount equal to or higher than that of a rimmed steel can be obtained with respect to a low carbon Al killed cold rolled steel sheet, there is a great advantage in reducing the weight of an automobile which is a demand of the automobile industry.
As a cold-rolled steel sheet having such properties that are difficult to put into practical use, various steel sheets have been conventionally developed.

【0003】焼付硬化性は塗料を焼付けする時の熱的影
響、例えば170 ℃×20分で析出する鉄炭化物によって析
出硬化する性質であるが、低炭素Alキルド冷延鋼板に
おける硬化量は焼鈍後存在する固溶炭素量にほぼ依存す
る。連続焼鈍で鋼を製造する場合は加熱及び均熱後に急
速冷却されるため、強力な炭化物形成元素(例えばTi
等)が含まれていない低炭素Alキルド冷延鋼板のよう
な鋼では、箱焼鈍材に比べ最終製品に固溶炭素を多く残
存させやすく、焼付硬化性を得るうえでは有利である
が、その代り耐時効性が劣化するという大きな欠点があ
る。このため低炭素Alキルド冷延鋼板等においては、
製造直後では箱焼鈍材と同等な材質レベルを有していて
も、例えば数カ月後のプレス加工時には時効による材質
劣化及び降伏点伸びの回復が生じて、割れやストレッチ
ャーストレイン等のプレス成形上のトラブルを生じる場
合が多かった。これらの原因は後述するように、プレス
条件が必ずしも最適ではなかったためである。ストレッ
チャーストレイン等の発生の有無は常温時効指数で評価
され、一般的に該指数を3kgf/mm2 以下にする必要があ
り、鉄鋼メーカーはこのような鋼板を提供することに腐
心してきた。
Bake hardenability is a property of precipitation hardening due to thermal influence when baking a paint, for example, iron carbide that precipitates at 170 ° C. × 20 minutes, but the hardening amount in a low carbon Al killed cold rolled steel sheet is after annealing. Almost depends on the amount of solid solution carbon present. When steel is manufactured by continuous annealing, it is rapidly cooled after heating and soaking, so that strong carbide-forming elements (such as Ti
Steels such as low carbon Al-killed cold rolled steel sheets that do not contain () etc. are more likely to leave a large amount of solute carbon in the final product than the box annealed material and are advantageous in obtaining bake hardenability. Instead, there is a major drawback that the aging resistance deteriorates. Therefore, in low carbon Al killed cold rolled steel sheets,
Even if the material has a material level equivalent to that of a box annealed material immediately after production, material deterioration due to aging and recovery of yield point elongation occur, for example, during press working several months later, and cracking, stretcher strain, etc. It often caused trouble. These causes are because the press conditions were not always optimum, as will be described later. The presence or absence of stretcher strain is evaluated by the room temperature aging index, and the index generally needs to be 3 kgf / mm 2 or less, and steel manufacturers have been keen to provide such a steel sheet.

【0004】時効性に関しては、連続焼鈍のように時間
的に制約された中で非時効化の効果を上げるには、原理
的には再結晶焼鈍の後、固溶炭素の多い状態から冷却速
度1000℃/秒以上で急冷し次いで焼戻せばよいのである
が、この場合焼入ひずみ等の各種欠陥の導入・凍結、場
合によっては急冷組織を形成すると共にフェライト粒内
に析出した炭化物の影響もこれらに重畳して、極度の硬
質化ひいては加工性の大幅な劣化を招くことになる。一
方、再結晶後、ガス単独もしくはガスとスチームの混気
を用いて1〜300 ℃/秒程度の比較的遅い冷却速度で冷
却して400 ℃程度の過時効を行えば鋼板は軟質化するが
時効性はかなり劣るものとなる。このことを避ける目的
で過時効温度を低くすると過時効処理に要する時間が長
引き、よって生産能率の低下およびコストアップを招
く。要するに上記のように非時効化を図ることは製品段
階での固溶炭素量を減少させることがあるから必然的に
焼付硬化性を劣化させることになる。
Regarding the aging property, in order to improve the effect of non-aging in a time-constrained condition such as continuous annealing, in principle, after recrystallization annealing, the cooling rate is changed from the state in which solute carbon is abundant. It is only necessary to quench at 1000 ° C / sec or more and then temper, but in this case the introduction and freezing of various defects such as quenching strain, and in some cases the formation of a quenched structure and the effect of carbides precipitated in ferrite grains If superposed on these, it will lead to extremely hardening and, consequently, a great deterioration in workability. On the other hand, after recrystallization, if the gas is cooled alone or a mixture of gas and steam is used for cooling at a relatively slow cooling rate of about 1 to 300 ° C / sec and overaging at about 400 ° C, the steel sheet softens. The prescription is considerably inferior. If the overaging temperature is lowered for the purpose of avoiding this, the time required for the overaging treatment is prolonged, resulting in a decrease in production efficiency and an increase in cost. In short, since non-aging as described above may reduce the amount of solute carbon in the product stage, it necessarily deteriorates the bake hardenability.

【0005】一方で特開昭59-53651号には、連続焼鈍に
よって500 ℃以上720 ℃以下の温度範囲で最大5分間均
熱後5℃/秒以上で急冷し、固溶Cと固溶Nをその和で
8ppm 以上含むことを特徴とする冷延鋼板の製造法が開
示されているが、当該公報には鋼板が温間プレス成形性
に優れ且つ高強度化すると記載されている。しかしなが
ら「温間」に関して温度条件が具体的に限定されておら
ず、実施例において300 ℃での温間プレス成形の結果が
示されているが、300 ℃もの高温下では潤滑剤の粘度低
下によりプレス成形時に潤滑効果が得られないばかり
か、鋼板の表面に酸化皮膜を形成し、化成処理性や塗装
性を劣化させる。さらに本発明で開示するようにストレ
ッチャーストレインと呼ばれる不均一変形などの発生と
重要にかかわってくるにもかかわらず、プレス成形速度
に関しては全く記載されていない。即ち当該製法では綺
麗な外観を持ったプレス成形品は得られないものと推測
される。また当該公報には「プレス成形によって高強度
化する」と記述されているが、具体的には10%の塑性加
工ひずみによる加工硬化のことであり、本発明の様な外
力に対する変形抵抗、すなわち耐デント性が問題となる
自動車のドアやフードなどの部位での変形ひずみ量の2
%程度でそのような加工硬化が得られるとは期待できな
い。
On the other hand, in JP-A-59-53651, continuous annealing is performed in a temperature range of 500 ° C. or higher and 720 ° C. or lower for a maximum of 5 minutes, followed by rapid cooling at 5 ° C./second or higher to obtain a solid solution C and a solid solution N. Is disclosed in a total amount of 8 ppm or more, but a method for manufacturing a cold-rolled steel sheet is disclosed, and the publication describes that the steel sheet has excellent warm press formability and high strength. However, the temperature conditions for "warm" are not specifically limited, and the results of warm press molding at 300 ° C are shown in the examples. Not only the lubrication effect cannot be obtained at the time of press forming, but an oxide film is formed on the surface of the steel sheet, which deteriorates the chemical conversion treatment property and the paintability. Further, as disclosed in the present invention, although it is related to the occurrence of nonuniform deformation called stretcher strain and the like, the press forming speed is not described at all. That is, it is presumed that a press-molded product having a beautiful appearance cannot be obtained by the manufacturing method. Further, in the publication, it is described that “the strength is increased by press molding”, but specifically, it means work hardening by a plastic working strain of 10%, that is, the deformation resistance against an external force as in the present invention, that is, The amount of deformation strain at parts such as automobile doors and hoods where dent resistance is a problem
%, It cannot be expected that such work hardening will be obtained.

【0006】以上のように、高い焼付硬化性が得られる
冷延鋼板をストレッチャーストレインなどの発生なしに
プレス成形し、更に加工性を同時に満たすことは不可能
とみなされてきた。
As described above, it has been regarded as impossible to press-form a cold-rolled steel sheet having a high bake hardenability without causing stretcher strains and further satisfy workability at the same time.

【0007】[0007]

【発明が解決しようとする課題】本発明は上記事情に着
目してなされたものであり、その目的は高価な合金用元
素を添加することなしに加工(例えばプレス加工)後の
焼付硬化量が4kgf/mm2以上得られる薄鋼板(例えば低
炭素Alキルド冷延鋼板)が、常温時効劣化したとして
も、そのプレス加工条件を適切なものとすることにより
ストレッチャーストレインを生じさせない様な温間プレ
ス成形法及び温間プレス成形用薄鋼板の製造法を提供し
ようとするものである。
The present invention has been made in view of the above circumstances, and an object thereof is to obtain a bake hardening amount after working (for example, press working) without adding an expensive alloying element. Even if a thin steel sheet (for example, a low carbon Al killed cold rolled steel sheet) with a yield of 4 kgf / mm 2 or more is aged at room temperature, it can be warmed so that stretcher strain does not occur by adjusting the press working conditions appropriately. It is intended to provide a press forming method and a method for manufacturing a thin steel sheet for warm press forming.

【0008】[0008]

【課題を解決するための手段】上記目的を達成した本発
明とは、薄鋼板をプレス成形するに際し、75〜 250℃の
温度範囲で、10-2以上のひずみ速度で加工することを要
旨とするものであるが、中でもC:0.003 〜0.03重量
%、Si:1重量%以下、Mn:0.05〜1重量%及び酸
可溶Al:0.01〜0.1 重量%を含有する鋼材を熱間圧延
及び冷間圧延した後、連続焼鈍によって再結晶温度以上
850 ℃以下の温度範囲で均熱焼鈍し、次いで20℃/秒以
上の冷却速度で室温まで冷却するか、あるいは冷却途中
10分以下の過時効処理を行って作製した薄鋼板を前記温
間プレス成形法に供することが特に推奨される。尚上記
条件に従って製造した薄鋼板は、前記以外の条件からな
る温間プレス成形に供することも可能である。
Means for Solving the Problems The present invention that has achieved the above object is that, when press forming a thin steel sheet, it is processed at a strain rate of 10 -2 or more in a temperature range of 75 to 250 ° C. In particular, steel materials containing C: 0.003 to 0.03% by weight, Si: 1% by weight or less, Mn: 0.05 to 1% by weight and acid-soluble Al: 0.01 to 0.1% by weight are hot-rolled and cold-rolled. After re-rolling for a long time, continuous annealing causes recrystallization temperature or higher
Soaking annealing in the temperature range of 850 ℃ or less, then cooling to room temperature at a cooling rate of 20 ℃ / sec or more, or during cooling
It is particularly recommended to subject the thin steel sheet produced by performing overaging treatment for 10 minutes or less to the warm press forming method. The thin steel sheet manufactured under the above conditions can be subjected to warm press forming under conditions other than the above.

【0009】[0009]

【作用】本発明の目的を達成できる温間プレス成形条件
は、プレス時の鋼板のひずみ速度が10-2以上、プレス時
の鋼板の温度が75〜250 ℃であることを必須とし、特に
鋼成分がC:0.003 〜0.03重量%、Si:1重量%以
下、Mn:0.05〜1重量%及び酸可溶Al:0.01〜0.1
重量%であるもの、更に好ましくはP:0.1 重量%以
下、N:0.007 重量%以下を含有する鋼を用いるのが好
適である。実験結果に即して説明すると、まず通常の条
件でプレス成形した場合にはストレッチャーストレイン
を発生すると考えられる常温時効指数が5kgf/mm2 であ
る鋼板(供試材:表1の鋼番2、及び比較例として鋼番
11)を調質圧延後、降伏点伸びが発生するまで十分に時
効させたのち、プレス成形時のひずみ速度及び加熱温度
を仮に想定した条件で引張試験を行ったところ、図示す
る様な結果が得られた(表1〜3参照)。即ち図1〜3
に示すように、常温で且つ極めて低速で引張試験した場
合には、リューダス変形による降伏点伸びが発生し、且
つ降伏応力も高いが、引張試験温度を高め、さらに引張
速度を増大(自動車車体内外板に成形する時のプレス成
形速度に相当)すると、応力−ひずみ曲線が連続降伏化
すると共に降伏応力が低下する。このことは常温時効指
数が3kgf/mm2 以上の鋼板であってもプレス成形時の温
度を高め、更にその速度を最適な条件にすることにより
ストレッチャーストレインを発生せずにプレス成形でき
ることを意味している。
The warm press forming conditions capable of achieving the object of the present invention require that the strain rate of the steel sheet during pressing is 10 -2 or more, and the temperature of the steel sheet during pressing is 75 to 250 ° C. The components are C: 0.003 to 0.03% by weight, Si: 1% by weight or less, Mn: 0.05 to 1% by weight, and acid-soluble Al: 0.01 to 0.1%.
It is preferable to use a steel containing the content of P: 0.1% by weight or less, more preferably N: 0.007% by weight or less. To explain according to the experimental results, first, a steel plate with a room temperature aging index of 5 kgf / mm 2, which is considered to generate stretcher strain when press-formed under normal conditions (test material: steel No. 2 in Table 1). , And steel numbers as comparative examples
After temper rolling of 11), after sufficiently aging until elongation at yield occurred, a tensile test was performed under the conditions that assumed the strain rate and heating temperature during press forming, and the results shown in the figure were obtained. Obtained (see Tables 1 to 3). That is, FIGS.
As shown in, when tensile tests are performed at room temperature and extremely low speed, yield point elongation occurs due to Ludas deformation and yield stress is high, but the tensile test temperature is increased and the tensile speed is further increased (inside and outside the automobile body). Corresponding to the press forming speed when forming into a plate), the stress-strain curve is continuously yielded and the yield stress is reduced. This means that even steel sheets with a room temperature aging index of 3 kgf / mm 2 or higher can be press-formed without causing stretcher strain by raising the temperature during press-forming and adjusting the speed to an optimum condition. is doing.

【0010】[0010]

【表1】 [Table 1]

【0011】[0011]

【表2】 [Table 2]

【0012】[0012]

【表3】 [Table 3]

【0013】さらに図3よりこの鋼板は本質的には多量
の固溶炭素を含有するため自動車等のドアやフードなど
の成形歪み量に相当する2%ひずみを与えた後の170 ℃
×20分の塗装焼付け時の硬化量は8kgf/mm2 という極め
て高い値を示す。即ち加工時には軟らかくて加工し易
く、加工後の製品としては強度が高いという理想的プレ
ス成形品を得ることができる。
Further, from FIG. 3, since this steel sheet essentially contains a large amount of solute carbon, 170 ° C. after being subjected to 2% strain corresponding to the amount of forming strain of doors and hoods of automobiles, etc.
The amount of curing at the time of baking the paint for 20 minutes shows an extremely high value of 8 kgf / mm 2 . That is, it is possible to obtain an ideal press-molded product that is soft during processing and easy to process, and has high strength as a product after processing.

【0014】尚比較例として用いた鋼番11は連続焼鈍後
の固溶炭素量が4ppm であり、従って常温時効指数も2
kgf/mm2 と低く、図2に示すようにプレス成形条件内で
は、鋼番2と同様にストレッチャーストレインを発生し
ないが、塗装焼付け時の硬化量は4kgf/mm2 以下と低
い。
Steel No. 11 used as a comparative example has a solid solution carbon content of 4 ppm after continuous annealing, and therefore has a room temperature aging index of 2 as well.
It is as low as kgf / mm 2, and as shown in Fig. 2, under the press forming conditions, stretcher strain does not occur as in Steel No. 2, but the amount of hardening during baking is as low as 4 kgf / mm 2 or less.

【0015】また温間プレス成形するに際し、プレスさ
れる薄鋼板を予め加熱して温度を高めても良いし、プレ
ス型内にヒーター等を組み込んで間接的に薄鋼板を加熱
しながらプレス成形してもよい。プレス型内へヒーター
等の加熱手段を組み込む手段は特に限定しない。尚本発
明に係る温間プレス成形法は冷延鋼板に限定されず、溶
融亜鉛めっき鋼板や合金化めっき鋼板等の表面処理鋼板
にも容易に適用することができる。
In the warm press forming, the thin steel plate to be pressed may be heated in advance to raise the temperature, or a heater or the like may be incorporated in the press die to indirectly press the thin steel plate for heating. May be. Means for incorporating heating means such as a heater into the press die is not particularly limited. The warm press forming method according to the present invention is not limited to cold-rolled steel sheets and can be easily applied to surface-treated steel sheets such as hot-dip galvanized steel sheets and alloyed steel sheets.

【0016】薄鋼板の成分限定理由を記すと、C量は0.
003 〜0.03重量%であれば、温間プレス成形時にストレ
ッチャーストレインを発生せず、更に塗装焼付け時に4
kgf/mm2 以上の硬化量を得ることができる。即ち0.003
重量%以下では連続焼鈍後に炭素を十分に固溶させるこ
とができず、塗装焼付硬化性が発揮できない。またC量
が0.03重量%以上ではその効果が飽和するばかりか良好
な深絞り性を確保することができない。Siは加工性を
劣化させることなく必要な強化性を確保するためには有
効な元素であり、その観点からは添加量の制限はない
が、あまり過剰のSi量は合金化溶融亜鉛めっき鋼板と
してのめっき密着性を劣化させるため1重量%を上限と
する。Mnは鋼の熱間脆性を防止するため0.05重量%以
上必要であるが、多量のMn添加はプレス加工性とりわ
け深絞り性の劣化を招くのでその上限は1重量%とす
る。酸可溶性Alは鋼中のNを固定してNによる過大な
常温時効を防止し、固溶炭素のみによる焼付硬化性を得
る上で重要である。その目的では0.01重量%以上が必要
であり、0.1 重量%以上含有してもNを固定する量は超
えるし、Nを固定した残りは加工性を劣化させるため酸
可溶Alの範囲は0.01〜0.1 重量%とする。
The reason for limiting the composition of the thin steel sheet is as follows.
If it is 003 to 0.03% by weight, stretcher strain does not occur during warm press molding, and it is 4 at the time of paint baking.
A curing amount of kgf / mm 2 or more can be obtained. That is 0.003
If it is less than 10% by weight, carbon cannot be sufficiently dissolved as a solid solution after continuous annealing, and the coating bake hardenability cannot be exhibited. On the other hand, when the C content is 0.03% by weight or more, not only the effect is saturated but also good deep drawability cannot be secured. Si is an effective element for ensuring the necessary strengthening property without deteriorating the workability, and there is no limit to the amount added from that point of view, but an excessively large amount of Si is an alloyed hot dip galvanized steel sheet. The upper limit is 1% by weight in order to deteriorate the plating adhesion of. Mn is required to be 0.05% by weight or more in order to prevent hot embrittlement of steel, but addition of a large amount of Mn causes deterioration of press workability, especially deep drawability, so the upper limit is made 1% by weight. The acid-soluble Al is important for fixing N in the steel, preventing excessive room temperature aging due to N, and obtaining bake hardenability only by solid solution carbon. For that purpose, 0.01% by weight or more is necessary. Even if 0.1% by weight or more is contained, the amount of N fixed is exceeded, and the remaining N-immobilized residue deteriorates workability. 0.1% by weight.

【0017】その他の元素については特に制限しない
が、代表的元素について好適範囲を示すと、まずPはS
iと同様加工性を劣化させることなく必要な強化を確保
する目的に有効な元素であるばかりでなく、連続焼鈍に
おける均熱後の冷却速度の違いによる固溶炭素量のばら
つき、ひいては塗装焼付硬化量のばらつきを少なくする
効果がある。しかしながら0.1 重量%を超えると強度と
延性のバランスが劣化するのでこれを上限とする。Nは
その量が多いほど材質が劣化する。即ち熱延後、高温で
の巻取処理により析出するAlNの粗大化を図ったとし
ても焼鈍時に高い結晶粒成長性を得るには不十分なサイ
ズであるため、N量の増加に伴うAlN析出量の増大は
材質を劣化させる。このような観点からN量は0.07重量
%以下とする。
The other elements are not particularly limited, but when the preferable range is shown for the typical elements, P is S
Similar to i, it is not only an effective element for the purpose of ensuring the necessary strengthening without deteriorating the workability, but also the variation in the amount of solute carbon due to the difference in the cooling rate after soaking in continuous annealing, and eventually the coating bake hardening. It has the effect of reducing variation in the amount. However, if it exceeds 0.1% by weight, the balance between strength and ductility deteriorates, so this is the upper limit. As the amount of N increases, the material deteriorates. That is, after the hot rolling, even if the AlN precipitated by high-temperature coiling is coarsened, the size is not sufficient to obtain high crystal grain growth during annealing. Increasing the amount deteriorates the material. From this viewpoint, the N content is 0.07% by weight or less.

【0018】連続焼鈍条件を再結晶温度以上、好ましく
は720 ℃以上850 ℃以下の温度範囲で最大5分間の均熱
焼鈍し、その後20℃/秒以上の冷却速度で室温付近まで
冷却するか、もしくは冷却途中の過時効処理を300 〜50
0 ℃で10分以下としたのは、4kgf/mm2 以上の塗装焼付
硬化量を得るための固溶炭素を連続焼鈍後5ppm以上含
有させるためである。即ち固溶炭素量が5ppm 以下では
充分な塗装焼付け硬化性が得られないからである。
A continuous annealing condition is a recrystallization temperature or higher, preferably a soaking anneal for a maximum of 5 minutes in a temperature range of 720 ° C. or higher and 850 ° C. or lower, followed by cooling to near room temperature at a cooling rate of 20 ° C./sec or higher, or Alternatively, the overaging treatment during cooling is 300 to 50
The reason why the temperature was set to 10 minutes or less at 0 ° C. is to contain 5 ppm or more of solid solution carbon for obtaining a coating bake hardening amount of 4 kgf / mm 2 or more after continuous annealing. That is, if the amount of solute carbon is 5 ppm or less, sufficient paint bake hardenability cannot be obtained.

【0019】次に本発明におけるもっとも重要なプレス
条件限定の理由を以下に示す。プレス成形時の温度が75
℃未満、及びひずみ速度が10-2未満では、3kgf/mm2
上の常温時効指数を示すような高固溶炭素量の鋼板にお
いてはストレッチャーストレインを発生するため、これ
らを下限としている。一方プレス温度は400 ℃程度まで
上昇させても効果は得られるが、プレス成形時に塗布す
る潤滑剤の効果が得られないばかりか、プレス成形品の
表面に酸化皮膜を形成し、化成処理性や塗装性が劣化す
るため250 ℃を上限としている。また、ひずみ速度は10
-2以上あれば効果が得られるため、実用上差しつかえな
ければ上限は限定しない。
Next, the reasons for limiting the most important pressing conditions in the present invention are shown below. The temperature during press molding is 75
When the temperature is lower than 0 ° C and the strain rate is lower than 10 -2 , stretcher strain is generated in a steel sheet having a high solid solution carbon content that exhibits a room temperature aging index of 3 kgf / mm 2 or more, so these are the lower limits. On the other hand, although the effect can be obtained even if the press temperature is raised to about 400 ° C, not only the effect of the lubricant applied at the time of press molding cannot be obtained, but also an oxide film is formed on the surface of the press molded product, resulting in chemical conversion treatment and Since the paintability deteriorates, the upper limit is 250 ° C. The strain rate is 10
-Because the effect is obtained if it is 2 or more, the upper limit is not limited unless it is practically acceptable.

【0020】以上のようにプレス成形時に温度を高め、
且つその速度を最適な条件にすることによって、常温時
効指数が3kgf/mm2 以上であってもストレッチャースト
レインを発生せずにプレス成形でき、更に塗装焼付け時
に高い硬化量を得ることができる。
As described above, the temperature is raised during press molding,
Further, by adjusting the speed to an optimum condition, even if the room temperature aging index is 3 kgf / mm 2 or more, press molding can be performed without generating a stretcher strain, and a high curing amount can be obtained during coating baking.

【0021】[0021]

【実施例】表1に示す化学成分から成る連続鍛造スラブ
を製造した。これらの鋼塊を加熱温度1230℃、仕上げ温
度900 ℃で熱間圧延し、仕上がり後570 〜630 ℃の温度
範囲で巻取り、熱延鋼帯とした。更に約73%の圧下率で
鋼帯を0.8mm に冷間圧延し、これらを表2に示している
条件で冷延鋼板を製造した。なお、鋼番1〜10は実施例
であり、鋼番11〜16は比較例で、詳しくは鋼番11〜12は
連続焼鈍条件が請求範囲外のもの、鋼番13〜16は成分が
請求範囲を逸脱するものである。
Example A continuous forged slab having the chemical components shown in Table 1 was produced. These steel ingots were hot-rolled at a heating temperature of 1230 ° C and a finishing temperature of 900 ° C, and after finishing, wound in a temperature range of 570 to 630 ° C to obtain hot-rolled steel strips. Further, the steel strip was cold-rolled to 0.8 mm with a rolling reduction of about 73%, and cold-rolled steel sheets were manufactured under the conditions shown in Table 2. Steel Nos. 1 to 10 are examples, Steel Nos. 11 to 16 are comparative examples, and in detail, Steel Nos. 11 to 12 are those whose continuous annealing conditions are out of the claimed range, and Steel Nos. 13 to 16 are the components. It is out of the range.

【0022】表2に本発明により得られた鋼板と従来鋼
板との特性を併記した。本発明の鋼板はプレス成形時に
ストレッチャーストレインを発生しないと推定できる、
即ち降伏点伸びの発生がなく、かつその時の降伏応力も
低く、さらに4kgf/mm2 以上の焼付硬化性が得られてい
る。
Table 2 shows the characteristics of the steel sheet obtained according to the present invention and the conventional steel sheet. It can be estimated that the steel sheet of the present invention does not generate stretcher strain during press forming,
That is, no yield point elongation occurs, the yield stress at that time is low, and a bake hardenability of 4 kgf / mm 2 or more is obtained.

【0023】表3に本発明の鋼番2の冷延鋼板を供して
本発明のプレス成形法と従来の成形法を用いて得られた
プレス成形鋼板の特性を比較併記した。本発明の請求範
囲内でプレス成形することによりストレッチャーストレ
インを発生することなく、且つその時の降伏応力も低
く、更に4kgf/mm2 以上の焼付硬化性が得られている。
Table 3 shows the characteristics of the press-formed steel sheet obtained by applying the cold-rolled steel sheet of Steel No. 2 of the present invention and using the press-forming method of the present invention and the conventional forming method. By press molding within the scope of the present invention, stretcher strain is not generated, the yield stress at that time is low, and bake hardenability of 4 kgf / mm 2 or more is obtained.

【0024】[0024]

【発明の効果】本発明は以上のように構成されているの
で、高価な合金元素を添加することなしに加工後の焼付
硬化量を4kgf/mm2 以上が高め得る薄鋼板を、常温時効
劣化したとしてもそのプレス加工条件を適したものとす
ることによりストレッチャーストレインを生じさせない
高焼付硬化型薄鋼板の温間プレス成形法及び温間プレス
成形用薄鋼板の製造法が提供できることとなった。本発
明の方法により、プレス成形することによって綺麗な外
観を有し、かつ高い焼付硬化量の増大に基づく優れた耐
デント性を有する自動車用パネルが得られる。
EFFECTS OF THE INVENTION Since the present invention is constituted as described above, a thin steel sheet capable of increasing the bake hardening amount after processing to 4 kgf / mm 2 or more without adding an expensive alloy element is aged at room temperature. Even if it does, it is possible to provide a warm press-forming method for high bake hardening type steel sheet that does not cause stretcher strain and a method for producing a warm press forming sheet steel by making the press working conditions suitable. .. According to the method of the present invention, an automobile panel having a beautiful appearance by press molding and having excellent dent resistance due to a high increase in bake hardening amount can be obtained.

【図面の簡単な説明】[Brief description of drawings]

【図1】実施例の降伏点伸び等の発生条件および塗装焼
付硬化量におよぼす温度−ひずみ速度の影響を示す図で
ある。
FIG. 1 is a diagram showing the influence of temperature-strain rate on the occurrence conditions of yield point elongation and the like and the amount of paint bake hardening in Examples.

【図2】比較例の降伏点伸び等の発生条件および塗装焼
付硬化量におよぼす温度−ひずみ速度の影響を示す図で
ある。
FIG. 2 is a diagram showing the influence of temperature-strain rate on the occurrence conditions of yield point elongation and the like and the amount of baking and hardening of coating in a comparative example.

【図3】室温および150 ℃引張試験時の応力におよぼす
ひずみ速度の影響を示す図である。
FIG. 3 is a diagram showing the effect of strain rate on stress at room temperature and 150 ° C. tensile test.

───────────────────────────────────────────────────── フロントページの続き (51)Int.Cl.5 識別記号 庁内整理番号 FI 技術表示箇所 // C22C 38/00 301 A 7217−4K 38/06 ─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. 5 Identification number Office reference number FI technical display location // C22C 38/00 301 A 7217-4K 38/06

Claims (3)

【特許請求の範囲】[Claims] 【請求項1】 薄鋼板をプレス成形するに際し、75〜 2
50℃の温度範囲で、10-2以上のひずみ速度で加工するこ
とを特徴とする温間プレス成形法。
1. When press-forming a thin steel sheet, 75-2
A warm press forming method characterized by processing at a strain rate of 10 -2 or more in a temperature range of 50 ° C.
【請求項2】 C:0.003 〜0.03重量%、Si:1重量
%以下、Mn:0.05〜1重量%及び酸可溶Al:0.01〜
0.1 重量%を含有する鋼材を熱間圧延及び冷間圧延した
後、連続焼鈍によって再結晶温度以上850 ℃以下の温度
範囲で均熱焼鈍し、次いで20℃/秒以上の冷却速度で室
温まで冷却するか、あるいは冷却途中10分以下の過時効
処理を行って作製した薄鋼板を請求項1記載の方法でプ
レス成形することを特徴とする温間プレス成形法。
2. C: 0.003 to 0.03 wt%, Si: 1 wt% or less, Mn: 0.05 to 1 wt% and acid-soluble Al: 0.01 to
After hot-rolling and cold-rolling a steel material containing 0.1% by weight, it is soak-annealed in a temperature range of recrystallization temperature to 850 ℃ or less by continuous annealing, and then cooled to room temperature at a cooling rate of 20 ℃ / sec or more. Alternatively, a warm press forming method is characterized in that a thin steel sheet produced by performing overaging treatment for 10 minutes or less during cooling is press formed by the method according to claim 1.
【請求項3】 C:0.003 〜0.03重量%、Si:1重量
%以下、Mn:0.05〜1重量%及び酸可溶Al:0.01〜
0.1 重量%を含有する鋼材を熱間圧延及び冷間圧延した
後、連続焼鈍によって再結晶温度以上850 ℃以下の温度
範囲で均熱焼鈍し、次いで20℃/秒以上の冷却速度で室
温まで冷却するか、あるいは冷却途中10分以下の過時効
処理を行うことを特徴とする温間プレス成形用薄鋼板の
製造法。
3. C: 0.003 to 0.03 wt%, Si: 1 wt% or less, Mn: 0.05 to 1 wt% and acid-soluble Al: 0.01 to
After hot-rolling and cold-rolling a steel material containing 0.1% by weight, it is soak-annealed in a temperature range of recrystallization temperature to 850 ℃ or less by continuous annealing, and then cooled to room temperature at a cooling rate of 20 ℃ / sec or more. Or a method for manufacturing a thin steel sheet for warm press forming, which comprises performing overaging treatment for 10 minutes or less during cooling.
JP3231225A 1991-08-16 1991-08-16 Method for warm pressforming and manufacture of steel sheet for above Withdrawn JPH0550150A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP3231225A JPH0550150A (en) 1991-08-16 1991-08-16 Method for warm pressforming and manufacture of steel sheet for above

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP3231225A JPH0550150A (en) 1991-08-16 1991-08-16 Method for warm pressforming and manufacture of steel sheet for above

Publications (1)

Publication Number Publication Date
JPH0550150A true JPH0550150A (en) 1993-03-02

Family

ID=16920284

Family Applications (1)

Application Number Title Priority Date Filing Date
JP3231225A Withdrawn JPH0550150A (en) 1991-08-16 1991-08-16 Method for warm pressforming and manufacture of steel sheet for above

Country Status (1)

Country Link
JP (1) JPH0550150A (en)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05308143A (en) * 1992-09-18 1993-11-19 Sharp Corp Solar battery
JP2008111189A (en) * 2006-10-03 2008-05-15 Nisshin Steel Co Ltd Hot-work method of hot dip plated steel sheet and hot-work formed article
JP2011230189A (en) * 2010-04-09 2011-11-17 Jfe Steel Corp Warm press forming method
JP2012153962A (en) * 2011-01-28 2012-08-16 Jfe Steel Corp Method of manufacturing member excellent in shape fixability

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05308143A (en) * 1992-09-18 1993-11-19 Sharp Corp Solar battery
JP2008111189A (en) * 2006-10-03 2008-05-15 Nisshin Steel Co Ltd Hot-work method of hot dip plated steel sheet and hot-work formed article
JP2011230189A (en) * 2010-04-09 2011-11-17 Jfe Steel Corp Warm press forming method
JP2012153962A (en) * 2011-01-28 2012-08-16 Jfe Steel Corp Method of manufacturing member excellent in shape fixability

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