JP2735376B2 - Method for producing cold-rolled steel sheet for processing having excellent aging and BH properties and having surface distortion resistance and dent resistance - Google Patents
Method for producing cold-rolled steel sheet for processing having excellent aging and BH properties and having surface distortion resistance and dent resistanceInfo
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- JP2735376B2 JP2735376B2 JP26640990A JP26640990A JP2735376B2 JP 2735376 B2 JP2735376 B2 JP 2735376B2 JP 26640990 A JP26640990 A JP 26640990A JP 26640990 A JP26640990 A JP 26640990A JP 2735376 B2 JP2735376 B2 JP 2735376B2
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Description
【発明の詳細な説明】 （産業上の利用分野） 本発明は実質非時効が要求され、かつBH性、耐面歪み
性、耐デント性を有する加工性に優れた冷延鋼板の製造
方法に関するものである。The present invention relates to a method for producing a cold-rolled steel sheet which is required to be substantially non-ageable and has excellent workability having BH property, surface distortion resistance and dent resistance. Things.
（従来の技術） 実質非時効でかつBH性を付加する方法として極低炭素
鋼にTi,Nbなどを添加し、固溶Ｃ量を制御したり（特開
昭59−38337号、特開昭59−31827号公報）、ＮとＳ量を
調整し、析出物の生成を制御する方法（特開昭61−2675
7号、特開昭62−7822号公報）などが知られている。(Prior Art) As a method of adding substantially non-aging and BH properties, the amount of dissolved C can be controlled by adding Ti, Nb or the like to ultra-low carbon steel (JP-A-59-38337, JP-A-59-38337). 59-31827), a method of controlling the amounts of N and S to control the formation of precipitates (JP-A-61-2675).
No. 7, JP-A-62-7822) and the like.
しかし、このような鋼では耐面歪み性はあるが耐デン
ト性は劣り、自動車用の外板として適用すると成形後外
力を加えると形状が容易に崩れる欠点がある。一方、耐
デント性を向上させるには降伏点を高くすることが効果
的であることが知られているが、この場合逆に面歪みが
生じやすく、耐面歪み性、耐デント性の両方の特性が優
れた鋼板は知られていない。However, such steels have surface distortion resistance but poor dent resistance, and have a drawback that when applied as an outer plate for an automobile, the shape is easily broken when an external force is applied after molding. On the other hand, it is known that increasing the yield point is effective for improving the dent resistance. However, in this case, the surface distortion tends to occur, and conversely, both the surface distortion resistance and the dent resistance are improved. No steel sheet with excellent properties is known.
（発明が解決しようとする課題） 本発明は従来相反する特性である耐面歪み性と耐デン
ト性の両方の特性を有し、かつ実質非時効でBH性を持つ
冷延鋼板の製造方法を提供することを目的としてなされ
た。(Problems to be Solved by the Invention) The present invention relates to a method for producing a cold-rolled steel sheet having both surface distortion resistance and dent resistance, which are contradictory characteristics, and having substantially non-aging and BH properties. Made for the purpose of providing.
（課題を解決するための手段） 本発明の要旨とする処は二種の成分材からなる複層構
造を有する鋼板の製造において、一層成分（Ａ成分）材
をC:0.04wt％〜0.2wt％、Mn:0.5wt％〜3wt％、Si:3wt％
以下、P:0.1wt％以下を含む鋼とし、他層成分（Ｂ成
分）材をC:0.05wt％以下、N:0.02wt％以下で、かつ、該
Ｃ及びＮの添加量がTi,Zr及びNbの一種あるいは二種以
上の添加量の合計とC/12＋N/14＜1.2（Ti/48＋Zr/91＋N
b/93）の関係にある鋼として二層以上の複層構造を有す
る鋼材となし、該鋼材を両成分鋼のAr3変態点以上で熱
延し、酸洗、冷延後、Ａ成分材のAc1変態点以上で、か
つＢ成分材のAc1変態点以下の温度に加熱し、平均冷却
速度（以下、冷却速度を冷速という）20℃/sec以上で40
0℃以下まで冷却する加工用冷延鋼板の製造方法であ
る。(Means for Solving the Problems) The gist of the present invention is to produce a steel sheet having a multilayer structure composed of two types of component materials, wherein one component (A component) material is C: 0.04 wt% to 0.2 wt%. %, Mn: 0.5wt% ~ 3wt%, Si: 3wt%
Hereinafter, steel containing P: 0.1 wt% or less, the other layer component (B component) material is C: 0.05 wt% or less, N: 0.02 wt% or less, and the added amount of C and N is Ti, Zr. And the total amount of one or more of Nb and C / 12 + N / 14 <1.2 (Ti / 48 + Zr / 91 + N
b / 93) steel as a steel having a multi-layer structure of two or more layers, hot-rolling the steel above the Ar 3 transformation point of both components steel, pickling, cold rolling, and in the Ac 1 transformation point or more, and heated to Ac 1 transformation point in the temperature of the B component material, the average cooling rate 40 (hereinafter, the cooling rate of Hiyasoku) 20 ° C. / sec or higher
This is a method for producing a cold-rolled steel sheet for processing to be cooled to 0 ° C. or lower.
以下に、本発明を詳細に説明する。 Hereinafter, the present invention will be described in detail.
発明者らは研究を重ねた結果、耐面歪み性と耐デント
性の両方の特性を付加するこが、鋼板を異なった成分の
複層構造にすることによって達成できる可能性を見いだ
した。そのうえ、実質非時効でかつBH性を有する加工性
に優れた複層鋼板としてDP鋼（フェライト組織中に高硬
度の変態相を分散析出させた二相鋼）とIF鋼（極低炭素
鋼にTiなどの炭窒化物形成元素を添加して鉄中の侵入型
元素を炭窒化物の形で析出処理した鋼）の組み合わせが
有望なことが明らかになった。また、両鋼を複層構造に
したことにより各鋼の単体での製造では現われなかった
現象も起こることがわかった。As a result of repeated studies, the inventors have found that it is possible to add both properties of surface distortion resistance and dent resistance by making a steel sheet into a multilayer structure having different components. In addition, DP steel (a dual-phase steel in which a high-hardness transformation phase is dispersed and precipitated in a ferrite structure) and IF steel (an ultra-low carbon steel) It has been clarified that a combination of a steel in which an interstitial element in iron is precipitated in the form of carbonitride by adding a carbonitride forming element such as Ti) is promising. In addition, it was found that a phenomenon that did not appear in the production of each steel alone also occurred due to the fact that both steels had a multilayer structure.
次に、以上の知見に基づく本発明の限定理由を述べ
る。Next, the reasons for limiting the present invention based on the above findings will be described.
まず、本発明における鋼の成分の限定理由について説
明する。First, the reasons for limiting the components of steel in the present invention will be described.
Ａ成分材の成分はDP鋼を製造することを前提としたも
ので、Ｃは第二相を得るのに必要な元素で、Ｃが0.04wt
％未満である場合は二相組織が得られない。一方、Ｃを
0.2wt％を超えて含有させると溶接性に支障を来たすと
ともに目的とする二相組織が得られなくなる。The composition of the A component material is based on the premise that DP steel is manufactured. C is an element necessary for obtaining the second phase, and C is 0.04 wt.
%, A two-phase structure cannot be obtained. On the other hand, C
If the content exceeds 0.2 wt%, the weldability is impaired and the desired two-phase structure cannot be obtained.
Mnも第二相の生成に寄与する。Mn含有量の下限0.5wt
％は5wt％以上のマルテンサイトを生成させるのに必要
な最小値である。一方、Mnを3wt％を超えて含有させる
と目的とする二相組織が得られなくなる。Mn also contributes to the formation of the second phase. Lower limit of Mn content 0.5wt
% Is the minimum required to produce more than 5 wt% martensite. On the other hand, if Mn is contained in an amount exceeding 3 wt%, the desired two-phase structure cannot be obtained.
Siの適量の添加は二相組織を得るには好ましいが、3w
t％を超えて添加すると熱間圧延時にオーステナイト単
相組織にならず、圧延後目的とする二相組織が得られな
くなる。The addition of an appropriate amount of Si is preferable to obtain a two-phase structure, but 3w
If it is added in excess of t%, the austenite single phase structure will not be formed during hot rolling, and the desired two-phase structure cannot be obtained after rolling.
Ｐの適量の添加も二相組織を得るには好ましいが、0.
1wt％超添加すると熱間加工割れが起きやすくなる。The addition of an appropriate amount of P is also preferable to obtain a two-phase structure,
Addition of more than 1 wt% tends to cause hot working cracks.
V,Ni,Cr,Mo,Cu,Ti,Nb,Bの添加は本発明のＡ成分材の
必須の条件ではないが、これらの元素の添加は組織の微
細化あるいは鋼材の焼き入れ性の向上に寄与するので選
択的に添加することは本発明の主旨に反しない。また、
脱酸を目的にしたAlの添加も同様に本発明の主旨に反し
ない。しかし、これらの元素の添加量が過度になるとコ
スト高になるので、これらの元素の合計添加量の上限1w
t％とする。The addition of V, Ni, Cr, Mo, Cu, Ti, Nb, and B is not an essential condition of the component A of the present invention, but the addition of these elements can make the structure finer or improve the hardenability of steel. Therefore, the selective addition does not violate the gist of the present invention. Also,
The addition of Al for the purpose of deoxidation similarly does not contradict the gist of the present invention. However, if the addition amount of these elements is excessive, the cost increases, so the upper limit of the total addition amount of these elements 1w
t%.
Ｂ成分材の成分はIF鋼を製造することを前提としたも
ので、本発明方法において、C/12＋N/14＜1.2（Ti/48＋
Zr/91＋Nb/93）の条件式により鋼の成分を限定した理由
は、この条件を満たすことにより、実質非時効でかつ優
れた深絞り特性が得られるためである。金属学的には、
該条件を満足する鋼はTi,Nb,Zrにより炭窒化物が形成さ
れ、固溶Ｃ及びＮが減少し、これが時効性及び深絞り性
に有利に作用したと考えられる。The component of the B component material is based on the premise that IF steel is manufactured. In the method of the present invention, C / 12 + N / 14 <1.2 (Ti / 48 +
The reason for limiting the composition of the steel by the conditional expression (Zr / 91 + Nb / 93) is that satisfying this condition provides substantially non-aging and excellent deep drawing characteristics. Metallurgically,
It is considered that in the steel satisfying the conditions, a carbonitride is formed by Ti, Nb, and Zr, and solute C and N are reduced, which advantageously acts on aging and deep drawability.
また、Ｃ量を0.5wt％以下、Ｎ量を0.02wt％以下に限
定したのは、これ以上C,Nが添加されると加工性が悪く
なるばかりでなく、上記の条件式を満足するためのTi,N
b,Zrの必要量が多くなり高価になるためである。Further, the C content is limited to 0.5 wt% or less and the N content is limited to 0.02 wt% or less. When C and N are further added, not only the workability is deteriorated but also the above-mentioned conditional expression is satisfied. Ti, N
This is because the required amounts of b and Zr increase and the cost increases.
Ｂ鋼の成分はIF鋼にすることが主旨で、強度の調整に
Mn,Si,P,Cr,Niなどを添加するのは本発明の主旨に反す
るものではない。また、二次加工割れの防止にＢを添加
することも本発明の主旨に反しない。The main purpose of B steel is to use IF steel.
The addition of Mn, Si, P, Cr, Ni, etc. does not depart from the gist of the present invention. Further, the addition of B for preventing secondary working cracks does not contradict the gist of the present invention.
本発明で記した複層構造はＡ−Ｂ−ＡあるいはＢ−Ａ
−Ｂのサンドウィッチ構造、Ａ−Ｂの二層構造又はその
繰り返しの多層構造を総括したものを意味する。また、
各層の板厚比は必要な強度によって変化することがで
き、本発明において特に限定しない。The multilayer structure described in the present invention is ABA or BA.
-B sandwich structure, AB double-layer structure or a repetitive multilayer structure. Also,
The thickness ratio of each layer can be changed depending on the required strength, and is not particularly limited in the present invention.
次に、製造条件の限定理由について説明する。 Next, the reasons for limiting the manufacturing conditions will be described.
熱延の仕上温度の下限を両鋼のAr3変態点以上とした
のは、これより低い温度で熱延を終了すると最終製品板
の加工性が著しく劣化するためである。これは、Ar3変
態点以下の温度で圧延すると強い集合組織が形成され、
それがその後の冷延、焼鈍後の集合組織にも影響を与
え、深絞り性に好ましい集合組織の発達を抑制するため
と考られる。The reason for setting the lower limit of the finishing temperature of hot rolling to be equal to or higher than the Ar 3 transformation point of both steels is that when hot rolling is completed at a lower temperature, the workability of the final product sheet is significantly deteriorated. This is because when rolled at a temperature below the Ar 3 transformation point, a strong texture is formed,
This is considered to affect the texture after the subsequent cold rolling and annealing, and to suppress the development of the texture favorable for deep drawability.
冷延後の焼鈍温度をＡ成分材のAc1変態点以上で、か
つＢ成分のAc1変態点未満と限定したのは、焼鈍温度が
Ａ成分材のAc1変態点以下では、Ａ成分材がDP組織にな
らず、目的とする二相組織が得られない為である。ま
た、焼鈍温度がＢ成分材のAc1変態点を超えるとＢ成分
材に形成されていた深絞り性に好ましい集合組織が変態
により壊され、加工性が著しく劣化する。The annealing temperature after cold rolling at least Ac 1 transformation point of the A component material, and was restricted with Ac less than 1 transformation point of the B component, the following Ac 1 transformation point of the annealing temperature the A component material, component A material However, this does not result in a DP structure, and the desired two-phase structure cannot be obtained. On the other hand, if the annealing temperature exceeds the Ac 1 transformation point of the B component material, the texture formed in the B component material that is preferable for deep drawing properties is broken by the transformation, and the workability is significantly deteriorated.
上記の焼鈍温度から400℃までの平均冷速を20℃/sec
としたのは、これより小さい冷速ではＡ成分材が目的と
する二相組織にならないためである。Average cooling rate from the above annealing temperature to 400 ° C is 20 ° C / sec
The reason for this is that at a lower cooling speed, the component A material does not have the desired two-phase structure.
（実 施 例） 表１に示す成分の鋼を、表２に示す条件で製造した。
表１中のAc1及びAr3は１℃/secで昇降温したときのデー
タより求めた。(Example) Steel having the components shown in Table 1 was produced under the conditions shown in Table 2.
Ac 1 and Ar 3 in Table 1 were determined from data when the temperature was raised and lowered at 1 ° C./sec.
得られた特性を表２に示す。ここで、層構造とはａか
らｉの鋼の層状組織の組み合せを示すもので、その板厚
分率を同表の板厚分率比に示す。板厚は0.8mmである。Table 2 shows the obtained characteristics. Here, the layer structure indicates a combination of the layered structures of the steels a to i, and the plate thickness fraction is shown in the plate thickness ratio in the same table. The thickness is 0.8 mm.
面歪みの指数としてはYPが25kg f/mm2になると面歪み
に問題が生じる。また、実質非時効の目安とは、引張試
験時のストレッチャーストレイン（st−st）の生成の有
無で判断した。BH性は170℃で20分の熱処理前後の降伏
点の差によって表した。耐デント性の指標は図１に示す
実験装置により鋼板に負荷を与えた後、残った凹み量で
もって表した。As an index of surface distortion, when YP is 25 kg f / mm 2 , a problem occurs in surface distortion. In addition, the standard of substantially non-aging was determined by the presence or absence of the formation of a stretcher strain (st-st) during the tensile test. The BH property was represented by the difference in yield point before and after heat treatment at 170 ° C for 20 minutes. The index of dent resistance was represented by the amount of dents remaining after a load was applied to the steel sheet by the experimental device shown in FIG.
実験番号1,2は単層材で１はDP材、２はIF鋼である。
１はYPが高いため面歪みが大きく、値（平均ｒ値）も
小さいため加工性が悪い。２は加工性は良いが耐デント
性が悪い。実験３から６は同じ材料を用いて製造プロセ
ス条件を検討した結果である。 Experiment numbers 1 and 2 are single layer materials, 1 is DP material, and 2 is IF steel.
In No. 1, workability is poor because surface distortion is large due to high YP and the value (average r value) is small. No. 2 has good workability but poor dent resistance. Experiments 3 to 6 are the results of examining the manufacturing process conditions using the same material.
３は本発明の範囲内で時効性、BH性、耐デント性、深
絞り性の全ての面で優れた特性を示す。No. 3 shows excellent properties in all aspects of aging, BH properties, dent resistance and deep drawability within the scope of the present invention.
４は焼鈍後の冷速が小さいため表層の組織がフェライ
ト／パーライト組織になり、それが原因でst−stが生成
した。５は焼鈍温度が低く過ぎ、表層はフェライトと炭
化物の再結晶組織を示し、内層は加工組織を呈し、加工
性が劣る。６は熱延仕上温度が低いため、深絞り性に好
ましい集合組織の形成が妨げられた。In No. 4, since the cooling rate after annealing was low, the structure of the surface layer became a ferrite / pearlite structure, and as a result, st-st was generated. In No. 5, the annealing temperature is too low, the surface layer shows a recrystallized structure of ferrite and carbide, the inner layer shows a processed structure, and the workability is poor. No. 6 had a low hot rolling finish temperature, which prevented formation of a texture preferred for deep drawability.
実験７は板厚比を変えた例であるが、実験３と同様に
優れた特性を示す。実験８はサンドウイッチ構造でな
い、二層構造の例で、この場合も優れた特性を示す。実
験８の耐デント性の試験はａ材が下に来るようにして実
験を行なった。Experiment 7 is an example in which the plate thickness ratio was changed, but shows excellent characteristics as in Experiment 3. Experiment 8 is an example of a two-layer structure without a sandwich structure, which also shows excellent characteristics. In the test for dent resistance in Experiment 8, the experiment was carried out with the material a placed below.
実験９から13は種々の鋼種の組み合わせの結果を示
す。９から11までは本発明の範囲内の鋼種の組み合わせ
で、優れた特性を示す。Experiments 9 to 13 show the results of various combinations of steel types. 9 to 11 are combinations of steel types within the range of the present invention and show excellent characteristics.
12は内層が本発明の成分範囲を満たさない例で加工法
の著しい劣化を示す。13は表層が本発明の成分範囲を満
たさない例で、組織がDPにならずst−stが生じた。12 is an example in which the inner layer does not satisfy the component range of the present invention, and shows remarkable deterioration of the processing method. 13 is an example in which the surface layer does not satisfy the component range of the present invention, in which the structure did not become DP and st-st occurred.
実験14は内層がDPで表層がIF鋼の組み合わせである
が、内層がIFで表層がDP鋼の組み合わせと同様に優れた
特性を示した。In Experiment 14, although the inner layer was DP and the surface layer was a combination of IF steel, the inner layer was IF and the surface layer was as excellent as the combination of DP steel.
実験３から14までは圧延の圧着により複層鋼板を製造
し、実験15では鋳込みにより複層鋼板を製造し、それを
圧延した結果であるが、複層鋼鈑の製造方法に限定され
ず、本発明の範囲を満たすことにより優れた特性が得ら
れることを示す。In Experiments 3 to 14, the results were obtained by producing a multi-layer steel sheet by rolling compression bonding, and in Experiment 15 by producing a multi-layer steel sheet by casting and rolling it. It shows that excellent characteristics can be obtained by satisfying the range of the present invention.
また、実験9,10の材料については冷延後、溶融亜鉛め
っき及び合金化処理を行なったがパウダリングは良好で
あった。The materials of Experiments 9 and 10 were subjected to hot-dip galvanizing and alloying after cold rolling, but the powdering was good.
（発明の効果） 本発明は、いままで不可能と考えられていた耐面歪み
性と耐デント性の両特性を同時に満足する鋼を実質非時
効でかつBH性をも備えた形で提供するもので、自動車用
の外板などに広く使用でき、産業上極めて大きな効果が
期待される。(Effects of the Invention) The present invention provides a steel which simultaneously satisfies both the characteristics of surface distortion resistance and dent resistance, which have been considered impossible so far, in the form of substantially non-aging and also having BH property. It can be widely used for outer panels of automobiles and the like, and is expected to have extremely large industrial effects.
第１図は耐デント性の測定の実験方法の概要を示した斜
視図である。FIG. 1 is a perspective view showing an outline of an experimental method for measuring dent resistance.
Claims (1)
板の製造において、一層成分（Ａ成分）材を C :0.04〜0.2wt％、 Mn:0.5 〜3wt％、 Si:3wt％以下、 P :0.1wt％以下 を含む鋼とし、他層成分（Ｂ成分）材を C:0.05wt％以下、 N:0.02wt％以下 で、かつ、該Ｃ及びＮの添加量がTi,Zr及びNbの一種あ
るいは二種以上の添加量の合計とC/12＋N/14＜1.2（Ti/
48＋Zr/91＋Nb/93）の関係にある鋼として二層以上の複
層構造を有する鋼材となし、該鋼材を両成分鋼のAr3変
態点以上で熱延し、酸洗、冷延後、Ａ成分材のAc1変態
点以上で、かつＢ成分材のAc1変態点以下の温度に加熱
し、平均冷却速度20℃/sec以上で400℃以下まで冷却す
ることを特徴とする時効性、BH性に優れ、かつ耐面歪み
性、耐デント性を有する加工用冷延鋼板の製造方法。1. In the manufacture of a steel sheet having a multilayer structure composed of two kinds of component materials, one component (A component) material is C: 0.04 to 0.2 wt%, Mn: 0.5 to 3 wt%, Si: 3 wt% or less. , P: 0.1 wt% or less, the other layer component (B component) material is C: 0.05 wt% or less, N: 0.02 wt% or less, and the added amount of C and N is Ti, Zr and The total amount of one or more of Nb and C / 12 + N / 14 <1.2 (Ti /
48 + Zr / 91 + Nb / 93) as a steel having a multilayer structure of two or more layers, hot-rolling the steel at the Ar 3 transformation point or higher of both components steel, pickling, cold rolling, and Aging, characterized by heating to a temperature above the Ac 1 transformation point of the component material and below the Ac 1 transformation point of the B component material, and cooling to 400 ° C. or less at an average cooling rate of 20 ° C./sec or more. Of cold-rolled steel sheets for processing, which have excellent heat resistance, surface distortion resistance and dent resistance.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26640990A JP2735376B2 (en) | 1990-10-05 | 1990-10-05 | Method for producing cold-rolled steel sheet for processing having excellent aging and BH properties and having surface distortion resistance and dent resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26640990A JP2735376B2 (en) | 1990-10-05 | 1990-10-05 | Method for producing cold-rolled steel sheet for processing having excellent aging and BH properties and having surface distortion resistance and dent resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04143227A JPH04143227A (en) | 1992-05-18 |
| JP2735376B2 true JP2735376B2 (en) | 1998-04-02 |
Family
ID=17430535
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26640990A Expired - Fee Related JP2735376B2 (en) | 1990-10-05 | 1990-10-05 | Method for producing cold-rolled steel sheet for processing having excellent aging and BH properties and having surface distortion resistance and dent resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2735376B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2665884B2 (en) * | 1994-07-19 | 1997-10-22 | 新日本製鐵株式会社 | Steel sheet with excellent dent resistance, fatigue properties, surface distortion resistance and workability |
-
1990
- 1990-10-05 JP JP26640990A patent/JP2735376B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04143227A (en) | 1992-05-18 |
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