JP3310064B2 - Good burring high strength steel sheet with excellent fatigue resistance - Google Patents
Good burring high strength steel sheet with excellent fatigue resistanceInfo
- Publication number
- JP3310064B2 JP3310064B2 JP24160793A JP24160793A JP3310064B2 JP 3310064 B2 JP3310064 B2 JP 3310064B2 JP 24160793 A JP24160793 A JP 24160793A JP 24160793 A JP24160793 A JP 24160793A JP 3310064 B2 JP3310064 B2 JP 3310064B2
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- JP
- Japan
- Prior art keywords
- less
- steel sheet
- fatigue resistance
- burring
- excellent fatigue
- 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.)
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Description
【０００１】[0001]
【産業上の利用分野】本発明は耐疲労特性、耐バーリン
グ性に優れた高張力鋼板に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-tensile steel sheet having excellent fatigue resistance and burring resistance.
【０００２】[0002]
【従来の技術】自動車の足回り部品の中には強度、特に
疲労強度が高く、かつ優れたバーリング性（穴広げ性）
を要請される材料がある。高バーリング性を達成する方
法として組織の均質化が有効であることが明らかにな
り、ベーナイト組織を主体とした高バーリング鋼板が最
近開発された。また、組織はフェライトで、その中に微
細な析出物を生成させ析出強化を図った高バーリング高
張力鋼板も開発されている。しかし、これらの鋼の疲労
特性は引張強度に対して１／２程度であり優れた耐疲労
特性を有するとはいえない。2. Description of the Related Art Some underbody parts of automobiles have high strength, particularly high fatigue strength, and excellent burring properties (hole expanding properties).
There are materials that are required. It has been clarified that homogenization of the structure is effective as a method for achieving high burring properties, and high burring steel sheets mainly composed of bainite structure have recently been developed. In addition, a high burring and high tensile strength steel sheet having a microstructure of ferrite, which forms fine precipitates therein and strengthens precipitation has been developed. However, the fatigue properties of these steels are about 1/2 of the tensile strength, and cannot be said to have excellent fatigue resistance properties.
【０００３】一方、表面近傍層だけをハイテン化するこ
とにより耐疲労特性を向上させることができることが、
クラッド鋼板や浸炭処理あるいは窒化処理した鋼でよく
知られており、例えば特開平３−２４３７５７号公報に
浸炭，窒化処理により、表面近傍の強度の高い冷延鋼板
及びその製造方法が開示されている。しかし、バーリン
グ性については全く考慮されておらず、優れた強度とバ
ーリング性のバランスを考えた窒化鋼板ならびにその製
造方法について全く開示されていないだけでなく、示唆
する結果も提示されていない。On the other hand, the fact that the fatigue resistance can be improved by increasing the tensile strength of only the layer near the surface,
It is well known that a clad steel sheet or a carburized or nitrided steel is known. For example, JP-A-3-243775 discloses a cold-rolled steel sheet having a high strength near the surface by carburizing and nitriding and a method for producing the same. . However, the burring property is not considered at all, and the nitrided steel sheet and the method for producing the same in consideration of the balance between excellent strength and burring property are not disclosed at all, and no suggestive results are presented.
【０００４】[0004]
【発明が解決しようとする課題】本発明は、表層部を特
定の強化組織にすることにより優れた耐疲労特性とバー
リング性を共有する高張力鋼板を提供するものである。SUMMARY OF THE INVENTION An object of the present invention is to provide a high-strength steel sheet which has excellent fatigue resistance and burring properties by forming a surface layer having a specific strengthened structure.
【０００５】[0005]
【課題を解決するための手段】本発明者らは優れた耐疲
労特性とバーリング性を同時に満足する鋼板について検
討を重ね、母材を窒化物形成元素を含むＩＦ鋼（固溶
Ｃ，ＮをＴｉ，Ｎｂ等で固定した鋼）とし、表層近傍部
に特定の大きさの窒化物を分散析出させることにより両
特性を同時に満足する鋼板を得られることを見いだし
た。Means for Solving the Problems The present inventors have repeatedly studied steel sheets satisfying both excellent fatigue resistance characteristics and burring properties, and determined that the base material was an IF steel containing a nitride-forming element (solid solution C, N). Steel fixed with Ti, Nb, etc.), and by dispersing and depositing a nitride of a specific size in the vicinity of the surface layer, it has been found that a steel sheet satisfying both characteristics can be obtained at the same time.
【０００６】すなわち、本発明の要旨とするところは、
重量比でＣ ：０．０１％以下、 Ｎ：０．０１％
以下、Ｍｎ：３％以下、 Ｓｉ：２％以下、
Ｐ ：０．２％以下、 Ａｌ：０．００５％以
上、０．５％以下、Ｍｎ，Ｓｉ，Ｐ量がＭｎ（wt%)＋
１．５Ｓｉ（wt%)＋１０Ｐ（wt%)＞１を満足し、またＴ
ｉ及びＮｂのいずれか一方または双方が５５×｛Ｔｉ／
４８＋Ｎｂ／９３−（Ｃ／１２＋Ｎ／１４＋Ｓ／３２)}
＞０．０１の条件式を満足するように含有し、必要に応
じＢを０．０００２％以上、０．００５％以下含み、残
部Ｆｅ及び不可避的不純物からなり、表層から０．１５
mmまでの領域のＮが重量比で０．０５％以下であり、平
均粒径が１００オングストローム以下のＴｉＮあるいは
ＮｂＮの総和の原子分率が１０-4以上であることを特徴
とする耐疲労特性に優れた良バーリング性高張力鋼板。That is, the gist of the present invention is as follows.
C: 0.01% or less by weight ratio, N: 0.01%
Hereinafter, Mn: 3% or less, Si: 2% or less,
P: 0.2% or less, Al: 0.005% or more, 0.5% or less, Mn, Si, P content is Mn (wt%) +
1.5Si (wt%) + 10P (wt%)> 1
One or both of i and Nb is 55 × ΔTi /
48 + Nb / 93- (C / 12 + N / 14 + S / 32)}
> 0.01 is contained so as to satisfy the conditional expression, and if necessary, B is contained at 0.0002% or more and 0.005% or less, and the balance consists of Fe and unavoidable impurities.
Fatigue resistance characteristics in which N in a region up to mm is 0.05% or less by weight, and the total atomic fraction of TiN or NbN having an average particle size of 100 Å or less is 10 -4 or more. Good burring and high tensile strength steel sheet with excellent properties.
【０００７】以下に、本発明について詳細に説明する。
本発明の成分の限定理由は次の通りである。Ｔｉ及びＮ
ｂのいずれか一方または双方を５５×｛Ｔｉ／４８＋Ｎ
ｂ／９３−（Ｃ／１２＋Ｎ／１４＋Ｓ／３２)}＞０．０
１なる条件を満足するように限定したのは、鋼中のＣ及
びＮを析出物の形で固定し、均質な組織と形成し、バー
リング性を高めると共に、強力な窒化物形成元素である
Ｔｉ，Ｎｂを適量固溶状態で残し、窒化等の析出処理を
した際、表層部に窒化物を微細に析出させ耐疲労特性を
向上させるためである。Hereinafter, the present invention will be described in detail.
The reasons for limiting the components of the present invention are as follows. Ti and N
b or 55 × 双方 Ti / 48 + N
b / 93- (C / 12 + N / 14 + S / 32)}> 0.0
The reason for satisfying the condition (1) is that C and N in the steel are fixed in the form of precipitates, form a homogeneous structure, enhance burring properties, and have a strong nitride-forming element, Ti. , And Nb are left in a solid solution state, and when a precipitation treatment such as nitridation is performed, nitrides are finely precipitated on the surface layer to improve fatigue resistance.
【０００８】表層から０．１５mmまでの平均Ｎ量を０．
０５％以下としたのは、Ｎ量が０．０５％以上になると
表層が脆くなり耐疲労特性が劣化するためである。ま
た、この層に存在するＴｉＮあるいはＮｂＮの平均粒径
の上限を１００オングストロームとしたのは、析出物の
大きさがこれ以上になると疲労強度比、バーリング性の
両方が劣化し良好な疲労強度比−バーリング性バランス
が得られないためである。尚疲労強度比−バーリング性
のバランスは、疲労強度比とバーリング性の積で表わ
し、その積が１．４以上ならばバーリング性バランスが
良好であるとした。また、特に疲労強度比が劣化し、良
好な疲労強度比−バーリング性バランスが得られないの
で析出物の量の下限を原子分率で１０-4以上とした。こ
のような表層部の析出物の制御を達成する手段はいろい
ろ考えられるが、経済的な方法として窒化処理は有効な
手段の１つである。ここで称するＴｉＮ，ＮｂＮは一般
にはＮの分率が極めて高いＴｉあるいはＮｂの炭窒化物
である。一方、母材の平均Ｎ量を０．０１％以下とした
のは、これ以上の添加は加工性の劣化をもたらすからで
ある。The average N amount from the surface layer to 0.15 mm is set to 0.
The reason for setting the content to 05% or less is that if the N content is 0.05% or more, the surface layer becomes brittle and the fatigue resistance deteriorates. Further, the upper limit of the average particle diameter of TiN or NbN present in this layer was set to 100 Å because when the size of the precipitates became larger than this, both the fatigue strength ratio and the burring property deteriorated, and the good fatigue strength ratio was obtained. -It is because burring balance cannot be obtained. The balance between the fatigue strength ratio and the burring property is represented by the product of the fatigue strength ratio and the burring property. If the product is 1.4 or more, the burring property balance is determined to be good. Further, since the fatigue strength ratio is particularly deteriorated and a good fatigue strength ratio-burring property balance cannot be obtained, the lower limit of the amount of precipitates is set to 10 -4 or more in terms of atomic fraction. There are various means for achieving such control of the precipitates on the surface layer, but nitriding is one of the effective means as an economical method. TiN and NbN referred to herein are generally carbon nitrides of Ti or Nb having an extremely high N fraction. On the other hand, the reason why the average N amount of the base material is set to 0.01% or less is that the addition of more than this causes deterioration in workability.
【０００９】Ｃ：０．０１％以下としたのはこれらの量
を超えて、Ｃを添加すると製品の加工性を損なうのみな
らず５５×｛Ｔｉ／４８＋Ｎｂ／９３−（Ｃ／１２＋Ｎ
／１４＋Ｓ／３２）｝＞０．０１の条件式を満足せしめ
るに必要なＴｉあるいはＮｂの量が多くなり、不必要に
製造コストが高くなるためである。尚他の成分として、
強度向上のために通常含まれる成分すなわち、Ｓｉ，Ｍ
ｎ，Ｐの上限をそれぞれＳｉ：２％以下、Ｍｎ：３％以
下、Ｐ：０．２％以下としたのは、これ以上の添加は加
工性を劣化するためである。また、下限をＭｎ（wt%)＋
１．５Ｓｉ（wt%)＋１０Ｐ（wt%)＞１の条件式で限定し
たのは足回り部品として必要な強度を確保するためであ
る。C: 0.01% or less exceeds these amounts. When C is added, not only does the workability of the product deteriorate, but also 55 × ΔTi / 48 + Nb / 93- (C / 12 + N
/14+S/32)｝>0.01 because the amount of Ti or Nb required to satisfy the conditional expression increases, and the manufacturing cost unnecessarily increases. As other components,
Components usually included for improving strength, namely, Si, M
The upper limits of n and P are set to Si: 2% or less, Mn: 3% or less, and P: 0.2% or less, respectively. The lower limit is Mn (wt%) +
The reason why the conditional expression of 1.5Si (wt%) + 10P (wt%)> 1 is used is to secure the strength required for the underbody parts.
【００１０】また、Ｂの添加は２次加工性を高めるの
で、必要に応じ０．０００２％以上のＢを添加すること
は効果的であるが、０．００５０％以上になると加工性
の劣化が著しくなるので、上限は０．００５０％とす
る。Ａｌは溶鋼での確実な脱酸を可能にするために少な
くとも０．００５％の添加が必要であるが、過度の添加
は加工性を劣化するので上限を０．５％とした。[0010] Further, the addition of B enhances the secondary workability, so it is effective to add B in an amount of 0.0002% or more, if necessary. However, when it exceeds 0.0050%, the workability deteriorates. Therefore, the upper limit is set to 0.0050%. Al must be added in an amount of at least 0.005% in order to enable reliable deoxidation in molten steel, but an excessive addition deteriorates the workability, so the upper limit was made 0.5%.
【００１１】本発明鋼を溶融めっき鋼板、電気めっき鋼
板等の表面処理鋼板として使用することは本発明の趣旨
を何ら損ずるものではない。また、本発明鋼は熱延鋼板
としても、冷延鋼板としても適用できる。Use of the steel of the present invention as a surface-treated steel sheet such as a hot-dip coated steel sheet or an electroplated steel sheet does not impair the purpose of the present invention. Further, the steel of the present invention can be applied as both a hot-rolled steel sheet and a cold-rolled steel sheet.
【００１２】[0012]
【実施例】本発明の実施例を、比較例と共に説明する。
表１に示した成分組成を有する材料を用いて様々な機械
試験をした結果を表２に示す。ここでの材料は、連続鋳
造スラブを１２００℃に加熱し、約９３０℃で仕上圧延
した４mm厚の熱延板を６０％冷延し、連続焼鈍の前半で
８００℃で３０秒の再結晶焼鈍をし、その後窒化処理を
したものと同じ温度で仕上げた２．５mmの熱延板を窒化
処理したものである。表２中、疲労強度は１０7 回の繰
り返し実験で破壊を起こさない負荷応力である。穴広げ
比はブランク径Ｄの鋼板に円錐ポンチを押し入れ、割れ
の発生が観察されたときの穴の径ｄの比ｄ／Ｄで表わ
す。EXAMPLES Examples of the present invention will be described together with comparative examples.
Table 2 shows the results of various mechanical tests using materials having the component compositions shown in Table 1. The material used here was a continuous cast slab heated to 1200 ° C., a hot-rolled 4 mm-thick plate finished and rolled at about 930 ° C. was cold rolled by 60%, and recrystallization annealing was performed at 800 ° C. for 30 seconds in the first half of continuous annealing. Then, a hot-rolled sheet of 2.5 mm finished at the same temperature as that obtained by nitriding was subjected to nitriding. In Table 2, the fatigue strength is the load stress which does not cause breakdown in 10 7 replicate experiments. The hole expansion ratio is expressed by the ratio d / D of the hole diameter d when cracks are observed when a conical punch is pressed into a steel plate having a blank diameter D.
【００１３】実験番号１，２，３，６，７は本発明鋼で
耐疲労特性−バーリング性バランスが優れている。この
うち、実験番号１，６は熱延鋼板、実験番号２，７は冷
延鋼板、実験番号３は窒化後、連続して４５０℃の溶融
亜鉛の入ったポットに通板した後５５０℃で約２０秒間
の加熱をして、亜鉛めっき層の合金化を行なった冷延鋼
板である。Test Nos. 1, 2, 3, 6, and 7 are steels of the present invention and have an excellent balance between fatigue resistance and burring properties. Of these, Experiment Nos. 1 and 6 were hot rolled steel sheets, Experiment Nos. 2 and 7 were cold rolled steel sheets, and Experiment No. 3 was nitrided and continuously passed through a pot containing molten zinc at 450 ° C. and then at 550 ° C. This is a cold-rolled steel sheet which has been heated for about 20 seconds to alloy the galvanized layer.
【００１４】実験番号４は表層部の窒素物の平均粒径が
本発明の範囲外で優れた耐疲労特性−バーリング性バラ
ンスが得られなかった。また、実験番号５では表層部の
窒化物の原子分率が本発明の範囲外で優れた耐疲労特性
−バーリング性バランスが得られなかった。実験番号８
は固溶Ｔｉが十分存在せず窒化処理によって微細な析出
物を最適に析出させることができなかったため優れた耐
疲労特性−バーリング性バランスが得られなかった。実
験番号９は比較材で高バーリング熱延鋼板として市販さ
れている材料で、穴広げ比は高いが疲労特性は優れてい
るとはいえない。また、実験番号１０は４５０MPa 級の
熱延鋼板を窒化処理したものであるが、Ｃが多く、パー
ライトが部分的に析出したためか穴広げ性が悪く、優れ
た耐疲労特性−バーリング性バランスが得られなかっ
た。In Experiment No. 4, when the average particle size of nitrogen in the surface layer was out of the range of the present invention, an excellent balance between fatigue resistance and burring property could not be obtained. Further, in Experiment No. 5, an excellent balance between fatigue resistance and burring property could not be obtained when the atomic fraction of nitride in the surface portion was out of the range of the present invention. Experiment number 8
No sufficient amount of solid-solution Ti was present, and fine precipitates could not be optimally deposited by nitriding treatment, so that an excellent balance between fatigue resistance and burring properties could not be obtained. Experiment No. 9 is a comparative material that is commercially available as a high burring hot-rolled steel sheet and has a high hole expansion ratio, but cannot be said to have excellent fatigue properties. In Experiment No. 10, a 450 MPa class hot rolled steel sheet was subjected to nitriding treatment. However, since C was large and pearlite was partially precipitated, the hole expanding property was poor, and an excellent fatigue resistance-burring property balance was obtained. I couldn't.
【００１５】[0015]
【表１】 [Table 1]
【００１６】[0016]
【表２】 [Table 2]
【００１７】[0017]
【表３】 [Table 3]
【００１８】[0018]
【発明の効果】本発明は、自動車の足回り部品でよく要
求される耐疲労特性と高バーリング性の両方を兼ね備え
た鋼板を、比較的安価に提供するもので工業的に価値の
高い発明である。Industrial Applicability The present invention provides a steel plate having both fatigue resistance and high burring properties, which are often required for underbody parts of automobiles, at a relatively low cost, and is an invention of industrial value. is there.
Claims (2)
０Ｐ（wt%)＞１ を満足し、またＴｉ及びＮｂのいずれか一方または双方
を５５×｛Ｔｉ／４８＋Ｎｂ／９３−（Ｃ／１２＋Ｎ／
１４＋Ｓ／３２）｝＞０．０１の条件式を満足するよう
に含有し、残部Ｆｅ及び不可避的不純物からなり、表層
から０．１５mmまでの領域のＮが重量比で０．０５％以
下であり、平均粒径が１００オングストローム以下のＴ
ｉＮあるいはＮｂＮの総和の原子分率が１０-4以上であ
ることを特徴とする耐疲労特性に優れた良バーリング性
高張力鋼板。1. C: 0.01% or less, N: 0.01% or less, Mn: 3% or less, Si: 2% or less, P: 0.2% or less, Al: 0.005% by weight ratio Not less than 0.5% and the amount of Mn, Si, and P is Mn (wt%) + 1.5Si (wt%) + 1
0P (wt%)> 1 and one or both of Ti and Nb is 55 × ΔTi / 48 + Nb / 93− (C / 12 + N /
14 + S / 32)｝> 0.01 so as to satisfy the conditional expression, the balance being Fe and unavoidable impurities, and N in the region from the surface layer to 0.15 mm in a weight ratio of 0.05% or less. , T having an average particle size of 100 Å or less
A good burring high-tensile steel sheet having excellent fatigue resistance characteristics, wherein the total atomic fraction of iN or NbN is 10 -4 or more.
０Ｐ（wt%)＞１ を満足し、またＴｉ及びＮｂのいずれか一方または双方
を５５×｛Ｔｉ／４８＋Ｎｂ／９３−（Ｃ／１２＋Ｎ／
１４＋Ｓ／３２）｝＞０．０１の条件式を満足するよう
に含有し、残部Ｆｅ及び不可避的不純物からなり、表層
から０．１５mmまでの領域のＮが重量比で０．０５％以
下であり、平均粒径が１００オングストローム以下のＴ
ｉＮあるいはＮｂＮの総和の原子分率が１０-4以上であ
ることを特徴とする耐疲労特性に優れた良バーリング性
高張力鋼板。2. C: 0.01% or less, N: 0.01% or less, Mn: 3% or less, Si: 2% or less, P: 0.2% or less, Al: 0.005% by weight ratio Above, 0.5% or less, B: 0.0002% or more, 0.005% or less, Mn, Si, P content is Mn (wt%) + 1.5Si (wt%) + 1
0P (wt%)> 1 and one or both of Ti and Nb is 55 × ΔTi / 48 + Nb / 93− (C / 12 + N /
14 + S / 32)｝> 0.01 so as to satisfy the conditional expression, the balance being Fe and unavoidable impurities, and N in the region from the surface layer to 0.15 mm in a weight ratio of 0.05% or less. , T having an average particle size of 100 Å or less
A good burring high-tensile steel sheet having excellent fatigue resistance characteristics, wherein the total atomic fraction of iN or NbN is 10 -4 or more.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24160793A JP3310064B2 (en) | 1993-09-28 | 1993-09-28 | Good burring high strength steel sheet with excellent fatigue resistance |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24160793A JP3310064B2 (en) | 1993-09-28 | 1993-09-28 | Good burring high strength steel sheet with excellent fatigue resistance |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0790483A JPH0790483A (en) | 1995-04-04 |
| JP3310064B2 true JP3310064B2 (en) | 2002-07-29 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24160793A Expired - Fee Related JP3310064B2 (en) | 1993-09-28 | 1993-09-28 | Good burring high strength steel sheet with excellent fatigue resistance |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3310064B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104114731B (en) | 2012-02-17 | 2016-03-02 | 新日铁住金株式会社 | Steel plate, plated steel sheet and their manufacture method |
| CN111979537B (en) * | 2020-07-01 | 2022-08-30 | 燕山大学 | W 18 Cr 4 VCo 5 High-speed steel roll surface modification material and modification method |
-
1993
- 1993-09-28 JP JP24160793A patent/JP3310064B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0790483A (en) | 1995-04-04 |
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