JP2000265240A - Carbon steel sheet excellent in fine blankability - Google Patents

Carbon steel sheet excellent in fine blankability

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Publication number
JP2000265240A
JP2000265240A JP6949999A JP6949999A JP2000265240A JP 2000265240 A JP2000265240 A JP 2000265240A JP 6949999 A JP6949999 A JP 6949999A JP 6949999 A JP6949999 A JP 6949999A JP 2000265240 A JP2000265240 A JP 2000265240A
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JP
Japan
Prior art keywords
weight
less
carbide
steel sheet
notch
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.)
Granted
Application number
JP6949999A
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Japanese (ja)
Other versions
JP4465057B2 (en
Inventor
Hiroyuki Jufuku
博之 壽福
Naoto Okubo
直人 大久保
Terushi Hiramatsu
昭史 平松
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Nippon Steel Nisshin Co Ltd
Original Assignee
Nisshin Steel Co Ltd
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Publication date
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Priority to JP06949999A priority Critical patent/JP4465057B2/en
Publication of JP2000265240A publication Critical patent/JP2000265240A/en
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Publication of JP4465057B2 publication Critical patent/JP4465057B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Abstract

PROBLEM TO BE SOLVED: To improve fine blankability by providing a specific composition consisting of C, Si, Mn, P, total Al, and the balance essentially Fe, also providing a structure in which carbides of a specific spheroidizing rate and a specific average grain size are dispersed through a ferritic matrix, and regulating notch tensile elongation to a specific value or above. SOLUTION: The steel sheet has a composition consisting of, by weight, 0.15-0.90% C, <=0.4% Si, 0.3-1.0% Mn, <=0.03% P, <=0.10% total Al, and the balance essentially Fe and also has a structure in which carbides of >=80% spheroidizing rate and 0.4-1.0 μm average grain size are dispersed through a ferritic matrix. Further, when tensile test is performed by using a test piece which is prepared by providing a V-notch of 45 deg. opening angle and 2 mm depth to width-directional both sides in the central position, in a longitudinal direction, of the parallel part of a JIS No.5 tensile test piece, the notch tensile elongation represented as an elongation percentage after breaking based on 10 mm gauge length in the central part in the longitudinal direction of the parallel part is regulated to >=20%.

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、精密打抜き加工性に優
れ、形状精度の良好な各種機械部品等として使用される
高炭素鋼板に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high carbon steel sheet which is excellent in precision punching workability and is used as various mechanical parts having good shape accuracy.

【０００２】[0002]

【従来の技術】複雑形状をもち高い寸法精度，耐摩耗性
が要求されるギア等の機械部品は、中炭素鋼や高炭素鋼
を素材とし、切削加工等によって成形仕上げされた後、
焼入れ焼戻し等の必要な熱処理を施すことにより製造さ
れてきた。しかし、切削加工では製造コストが高くつく
ため、切削加工を精密打抜き加工に置き換えることが最
近検討されている。精密打抜きは、通常の打抜きと異な
りほぼ１００％の剪断面が得られるので、低炭素鋼を素
材として比較的簡単な形状の部品製造に従来から使用さ
れてきた。ところが、ギア等の複雑且つ高寸法精度が要
求される部品の精密打抜きでは、加工方法の技術改善に
加え、素材としても従来よりも精密打抜き性，特に精密
打抜き面性状に優れた中炭素鋼板や高炭素鋼板に対する
要求が高くなってきている。2. Description of the Related Art Gears and other mechanical parts that have complex shapes and require high dimensional accuracy and wear resistance are made of medium-carbon steel or high-carbon steel, and are formed and finished by cutting.
It has been manufactured by performing necessary heat treatment such as quenching and tempering. However, since the manufacturing cost is high in the cutting process, replacing the cutting process with a precision punching process has recently been studied. Since the precision punching can obtain a shear surface of almost 100% unlike the normal punching, it has been conventionally used for manufacturing parts having a relatively simple shape using low carbon steel as a raw material. However, in precision punching of parts such as gears that require complex and high dimensional accuracy, in addition to technological improvement of the processing method, medium-carbon steel sheets, which are superior in precision punching properties, especially precision punching surface properties, as materials, and The demand for high carbon steel sheets is increasing.

【０００３】精密打抜き性に優れた中・高炭素鋼として
は、Ｔｉ添加，熱延条件及び焼鈍条件の制御によりセメ
ンタイトを球状化した鋼材（特公昭６２−２００８号公
報），セメンタイトの粒径制御に併せてＮｉ添加により
精密打抜き加工時の破断を抑制した鋼材（特開平９−８
７８０５号公報）等が知られている。しかし、何れもＴ
ｉ，Ｎｉ等の添加を必要とするため一般的な中・高炭素
鋼板に適用できない。また、特公昭５８−７３４号公報
では、０．０１重量％以下に低Ｓ化することによりＭｎ
Ｓ系介在物を低減すると共に、Ｃａ−Ａｌ添加によって
脱硫の促進及び硫化物の形態制御を図り、材料の異方性
を抑え、精密打抜き加工性を改善している。しかし、Ｓ
量の低減及びＣａ−Ａｌ添加が必要なため、製造コスト
の上昇が避けられない。[0003] As medium and high carbon steels having excellent precision punching properties, steel materials in which cementite is spheroidized by controlling Ti addition, hot rolling conditions and annealing conditions (Japanese Patent Publication No. 62-2008), and grain size control of cementite In addition to the above, a steel material in which breakage during precision punching is suppressed by the addition of Ni (Japanese Patent Laid-Open No. 9-8)
No. 7805) and the like. However, T
Since it requires the addition of i, Ni, etc., it cannot be applied to general medium and high carbon steel sheets. In Japanese Patent Publication No. 58-734, Mn is reduced by reducing the S content to 0.01% by weight or less.
In addition to reducing S-based inclusions, the addition of Ca-Al promotes desulfurization and controls the morphology of sulfides, suppresses the anisotropy of the material, and improves precision punching workability. However, S
Since it is necessary to reduce the amount and to add Ca-Al, an increase in manufacturing cost is inevitable.

【０００４】更に、特開昭５８−１０４１６０号公報，
特公平３−２９４２号公報，特公平５−１４７６４号公
報等では、精密打抜き性及び熱処理性を改善した鋼板が
紹介されている。しかし、Ｃ量が０．１９重量％以下の
低い値に設定されており、Ｃ含有量が高い中・高炭素鋼
板の精密打抜き性を改善する手段は具体化されていな
い。また、熱処理性の改善及び炭化物の微細化を狙って
Ｂを添加しているため、一般の中高炭素鋼に比較して製
造コストが高くなる。金型寿命に関しては、通常の打抜
き加工を対象とする金型寿命の改善策は従来から種々提
案されている（特公昭６２−５９１６７号公報，特公平
２−１９１７３号公報，特開平３−４４４４７号公報，
特開平４−２３５２５２号公報）。しかし、精密打抜き
加工で要求される精密打抜き面をほぼ１００％剪断面と
する条件下で金型寿命を改善する手段は明らかにされて
いない。Further, Japanese Patent Application Laid-Open No. 58-104160,
JP-B-3-2942, JP-B-5-14764, and the like introduce steel sheets having improved precision punching properties and heat treatment properties. However, the C content is set to a low value of 0.19% by weight or less, and no means has been embodied for improving the precision punching property of a medium / high carbon steel sheet having a high C content. Further, since B is added for the purpose of improving the heat treatment property and miniaturizing the carbide, the production cost is higher than that of general medium-high carbon steel. Regarding the mold life, various measures for improving the mold life for ordinary punching have been conventionally proposed (JP-B-62-59167, JP-B-2-19173, JP-A-3-44447). No.,
JP-A-4-235252). However, no means has been disclosed for improving the mold life under the condition that the precision punched surface required for precision punching has a nearly 100% shear surface.

【０００５】[0005]

【発明が解決しようとする課題】精密打抜き性，なかで
も精密打抜き面性状に優れた素材のニーズが高くなって
きており、一層精密打抜き性に優れた中・高炭素鋼板が
要求されているにも拘わらず、一般的な中・高炭素の鋼
種で精密打抜き性を改善する手法、更には金型寿命を改
善する方法が確立されていない。これは、精密打抜き性
を満足させるに足る鋼板の好適な材料特性，その材料特
性に見合った金属組織等が未解明なことが一つの理由と
して挙げられる。本発明は、このような問題を解消すべ
く案出されたものであり、Ｃ含有量：０．１５〜０．９
０重量％の中・高炭素鋼板において切欠き引張伸びが精
密打抜き性に密接な関係をもつことに着目し、炭化物の
析出形態を制御することにより、精密打抜き性に優れ、
良好な形状精度の部品に打抜き加工できる中・高炭素鋼
板を提供することを目的とする。The need for a material excellent in precision punching properties, in particular, precision punching surface properties has been increasing, and medium and high carbon steel sheets having even higher precision punching properties have been demanded. Nevertheless, there has not been established a method for improving precision punching properties and a method for improving the mold life of general medium and high carbon steel types. One of the reasons for this is that the suitable material properties of the steel sheet that satisfies the precision punching property and the metal structure suitable for the material properties are unknown. The present invention has been devised to solve such a problem, and has a C content of 0.15 to 0.9.
Focusing on the fact that notch tensile elongation has a close relationship with precision punching properties in medium and high carbon steel sheets of 0% by weight, and by controlling the precipitation form of carbide, it is excellent in precision punching properties,
It is an object of the present invention to provide a medium- and high-carbon steel sheet that can be stamped into parts having good shape accuracy.

【０００６】[0006]

【課題を解決するための手段】本発明の高炭素鋼板は、
その目的を達成するため、Ｃ：０．１５〜０．９０重量
％，Ｓｉ：０．４重量％以下，Ｍｎ：０．３〜１．０重
量％，Ｐ：０．０３重量％以下，全Ａｌ：０．１０重量
％以下，残部が実質的にＦｅの組成をもち、球状化率８
０％以上，平均粒径０．４〜１．０μｍの炭化物がフェ
ライトマトリックスに分散した組織をもち、ＪＩＳ５号
引張試験片の平行部長手方向中央位置における幅方向両
サイドに開き角４５度，深さ２ｍｍのＶノッチを入れた
試験片を用いて引張試験し、平行部長手方向中央部の標
点間距離１０ｍｍに対する破断後の伸び率として表わさ
れる切欠き引張伸びが２０％以上であることを特徴とす
る。この炭素鋼板は、更にＣｒ：１．２重量％以下，Ｍ
ｏ：０．３重量％以下，Ｃｕ：０．３重量％以下，Ｎ
ｉ：２．０重量％以下，Ｎ：０．０１重量％以下の１種
又は２種以上を含むことができる。また、Ｔｉ：０．０
１〜０．０５重量％及びＢ：０．０００５〜０．００５
０重量％，Ｃａ：０．０１重量％以下を含むこともでき
る。Ｓ含有量は、０．０１重量％以下に規制することが
好ましい。The high carbon steel sheet of the present invention comprises:
In order to achieve the object, C: 0.15 to 0.90% by weight, Si: 0.4% by weight or less, Mn: 0.3 to 1.0% by weight, P: 0.03% by weight or less, Al: 0.10% by weight or less, the balance substantially has a composition of Fe, and a spheroidization ratio of 8
It has a structure in which carbides of 0% or more and an average particle size of 0.4 to 1.0 μm are dispersed in a ferrite matrix. A tensile test was performed using a test piece having a V notch of 2 mm in length, and the notch tensile elongation expressed as the elongation percentage after fracture with respect to a distance of 10 mm between the gauges at the center in the longitudinal direction of the parallel portion was 20% or more. Features. This carbon steel sheet further contains Cr: 1.2% by weight or less, M
o: 0.3% by weight or less, Cu: 0.3% by weight or less, N
One or more of i: 2.0% by weight or less and N: 0.01% by weight or less can be contained. Also, Ti: 0.0
1 to 0.05% by weight and B: 0.0005 to 0.005
0 wt%, Ca: 0.01 wt% or less. The S content is preferably regulated to 0.01% by weight or less.

【０００７】金型の長寿命化には、ＪＩＳ ５号引張試
験で得られる引張強さＴＳ及び切欠き引張伸びＥｌV 値
で定義されるＤ値［＝（３×ＥｌV 2＋１８×ＥｌV ）／
ＴＳ］を３以上とすることが有効である。炭化物球状化
率は、鋼板断面の金属組織を観察するとき、炭化物総数
が３００個以上の領域を観察視野にとり、最大長さｐを
特定し、最大長さｐと直角方向の最大長さｑとの比ｐ／
ｑが３未満の炭化物（以下、球状化炭化物という）の個
数が観察視野内の炭化物総数に占める割合（％）で表わ
される。また、炭化物平均粒径は、同じ炭化物総数３０
０個以上の観察視野において個々の炭化物について測定
した円相当径を全測定炭化物で平均した値で表わされ
る。To extend the life of the mold, a D value [= (3 × El V 2 + 18 × El V) defined by a tensile strength TS and a notch tensile elongation El V obtained in a JIS No. 5 tensile test. ) /
[TS] is 3 or more. When observing the metallographic structure of the cross section of the steel sheet, the carbide spheroidization ratio takes the region where the total number of carbides is 300 or more in the observation visual field, specifies the maximum length p, and determines the maximum length p and the maximum length q in the direction perpendicular to the perpendicular direction. Ratio p /
The number of carbides having q less than 3 (hereinafter referred to as spheroidized carbides) is expressed as a ratio (%) to the total number of carbides in the observation visual field. In addition, the average carbide particle diameter is 30
It is represented by a value obtained by averaging the equivalent circle diameters of individual carbides measured in zero or more observation fields for all the measured carbides.

【０００８】[0008]

【作用】本発明者等は、一般的な中・高炭素鋼板の精密
打抜き性を向上させる方法を種々検討したところ、精密
打抜き時の剪断面率が局部延性の指標の一つである切欠
き引張伸びと密接な相関関係にあること、鋼板中の炭化
物分散形態に剪断面率が大きく依存していることを見出
した。そして、炭化物を球状化し、炭化物の平均粒径を
大きくすると、精密打抜き時の剪断面率が大きくなるこ
とを解明した。更には、炭化物の分散形態を制御する
と、部品成形後に施される焼入れ焼戻し，高周波焼入れ
焼戻し等の熱処理性を阻害しない範囲で精密打抜き性が
十分に改善されることが判った。The present inventors have studied various methods for improving the precision punching properties of general medium- and high-carbon steel sheets, and found that the notch in which the shearing area ratio during precision punching is one of the indicators of local ductility is used. It has been found that there is a close correlation with the tensile elongation, and that the shear ratio is greatly dependent on the carbide dispersion form in the steel sheet. Then, it was clarified that when the carbide was made spherical and the average particle diameter of the carbide was increased, the shear surface ratio at the time of precision punching was increased. Further, it has been found that when the dispersion form of the carbide is controlled, the precision punching property is sufficiently improved within a range that does not hinder the heat treatment properties such as quenching and tempering and induction quenching and tempering performed after forming the part.

【０００９】精密打抜き加工時に発生する割れや亀裂
は、加工変形中に発生した非常に局所的な欠陥を起点と
し、加工変形の進行に伴って素材内部を伝播した結果で
あると考えられる。中・高炭素鋼板においては、欠陥生
成原因として炭化物（セメンタイト），ＭｎＳ系介在物
等を起点とするミクロボイドの発生・成長が挙げられ
る。このような前提に立つとき、加工変形時にミクロボ
イドの発生・成長を可能な限り抑制できる金属組織の調
整及び介在物の低減が精密打抜き性の改善に有効である
といえる。ミクロボイドの発生・成長を抑制すること
は、精密打抜き性を向上させることにもなる。実際に切
欠き引張試験に供した試験片のミクロボイドを観察する
と、ミクロボイドの発生・成長が金属組織の形態に大き
く影響され、精密打抜き加工時のミクロボイドの発生・
成長に酷似していた。このことからしても、精密打抜き
時の剪断面率と切欠き引張伸びとの間に密接な関係があ
ることが窺がわれる。It is considered that the cracks and cracks generated during the precision punching work originate from very local defects generated during the working deformation and propagate through the inside of the material as the working deformation progresses. In medium and high carbon steel sheets, the generation and growth of microvoids originating from carbides (cementite), MnS-based inclusions, and the like can be cited as defects. Under such a premise, it can be said that adjustment of the metal structure and reduction of inclusions that can suppress generation and growth of microvoids as much as possible during working deformation are effective for improving precision punching. Suppressing the generation and growth of microvoids also improves the precision punching property. When observing the microvoids of the test specimens actually subjected to the notch tensile test, the generation and growth of microvoids were greatly affected by the morphology of the metallographic structure.
It was very similar to growth. This suggests that there is a close relationship between the shear area ratio during precision punching and the notch tensile elongation.

【００１０】金型は、繰返しの打抜き作業によって摩耗
し、かえりの増加，破断面の発生等として打抜き品に摩
耗の影響が現れる。金型寿命は、一般的に打抜き品に規
定されている以上のかえりや破断面の発生で判定されて
おり、破断面が発生し難い素材ほど金型寿命が良好であ
るといえる。この点、切欠き引張伸びＥｌV 値が高い材
料ほど、破断面の発生が抑制されるため金型寿命が良好
であると推察される。金型寿命は、精密打抜き時の荷重
ーストローク曲線で囲まれる面積、すなわち剪断エネル
ギにも大きく影響される。具体的には、剪断エネルギが
低い材料ほど金型にかかる負担が軽減され、型摩耗の程
度が小さくなる。剪断エネルギは、素材の引張強さと良
好な相関関係にあり、引張強さの上昇に伴って剪断エネ
ルギが直線的に増加することを考慮すると、引張強さの
低下が金型寿命の改善に有効であると考えられる。そこ
で、本発明者等は、ＥｌV 値及び引張強さＴＳが金型寿
命に及ぼす影響を種々調査・研究した。その結果、Ｄ値
［＝（３×ＥｌV 2＋１８×ＥｌV ）／ＴＳ］を３以上に
するとき、金型寿命が顕著に改善されることを見出し
た。[0010] The die is worn by repeated punching operations, and the effect of wear on the punched product appears as an increase in burrs, generation of a fractured surface, and the like. The mold life is generally determined by the occurrence of burrs or fractured surfaces that are greater than those specified for punched products, and it can be said that a material with a less likely fracture surface has a better mold life. In this regard, it is inferred that the higher the notch tensile elongation El V value is, the better the mold life is because the occurrence of a fracture surface is suppressed. The mold life is greatly affected by the area surrounded by the load-stroke curve at the time of precision punching, that is, the shear energy. Specifically, the load on the mold is reduced as the material has lower shear energy, and the degree of mold wear is reduced. The shear energy has a good correlation with the tensile strength of the material, and considering that the shear energy increases linearly with increasing tensile strength, a decrease in tensile strength is effective for improving the mold life. It is considered to be. Therefore, the present inventors have conducted various investigations and studies on the effects of the El V value and the tensile strength TS on the mold life. As a result, it was found that when the D value [= (3 × El V 2 + 18 × El V ) / TS] is 3 or more, the mold life is remarkably improved.

【００１１】［成分・組成］本発明では、Ｃ：０．１５
〜０．９０重量％を含む中・高炭素高鋼を対象としてい
る。Ｃは、炭素鋼において最も基本となる合金成分であ
り、含有量の如何に応じて焼入れ硬さ，炭化物量等が大
きく変動する。Ｃ含有量が０．１５重量％未満では、各
種機械構造用部品に適用する上で十分な焼入れ硬さが得
られない。逆に０．９０重量％を超えるＣ含有量では、
熱延後の靭性低下により鋼帯の製造性・取扱い性が悪化
すると共に、焼鈍後においても十分な延性が得られない
ため、加工度の高い部品への適用が困難になる。したが
って、本発明では適度な焼入れ硬さ及び加工性を兼ね備
えた鋼板を得るために、Ｃ含有量が０．１５〜０．９０
重量％の範囲にある鋼材を対象としている。なお、Ｃ含
有量が低くなるほど精密打抜き性が一層改善されるた
め、精密打抜き性が特に重視される用途では０．１５〜
０．５０重量％の範囲にＣ含有量を設定することが好ま
しい。[Components / Composition] In the present invention, C: 0.15
It is intended for medium and high carbon high steel containing up to 0.90% by weight. C is the most basic alloy component in carbon steel, and the quenching hardness, the amount of carbide, and the like greatly vary depending on the content. If the C content is less than 0.15% by weight, sufficient quench hardness cannot be obtained for application to various mechanical structural parts. Conversely, at a C content exceeding 0.90% by weight,
Due to the decrease in toughness after hot rolling, the manufacturability and handleability of the steel strip are deteriorated, and sufficient ductility is not obtained even after annealing, so that application to parts with high workability becomes difficult. Therefore, in the present invention, in order to obtain a steel sheet having both appropriate quenching hardness and workability, the C content is 0.15 to 0.90.
For steel materials in the range of weight%. The precision punching property is further improved as the C content becomes lower.
It is preferable to set the C content in the range of 0.50% by weight.

【００１２】Ｓｉは、局部延性に対し大きな影響を及ぼ
す合金成分である。過剰量のＳｉを添加すると、固溶強
化作用によってフェライトが硬化し、成形加工時に割れ
を発生させる原因になる。過剰なＳｉ添加は、製造過程
で鋼板表面におけるスケール疵の発生を助長し、表面品
質を低下させる原因にもなる。そこで、Ｓｉ含有量の上
限を０．４０重量％に規定し、特に精密打抜き性が要求
される用途では０．２０重量％以下に規制することが好
ましい。Ｍｎは、鋼板の焼入れ性を改善し、強靭化にも
有効な合金成分である。十分な焼入れ性を確保するため
には、０．３重量％以上のＭｎ量が必要である。しか
し、１．０重量％を超える多量のＭｎが含まれるとフェ
ライトが硬化し、精密打抜き性が劣化する。Ｐは、延性
及び靭性に悪影響を及ぼす成分であることから、上限を
０．０３重量％に規定する。Ａｌは、溶鋼の脱酸剤とし
て添加される成分であるが、鋼中の全Ａｌ量が０．１重
量％を超えると鋼材の清浄度が損われ、鋼板表面に疵が
発生し易くなる。[0012] Si is an alloy component that has a large effect on local ductility. When an excessive amount of Si is added, the ferrite is hardened by a solid solution strengthening action, which causes cracks during molding. Excessive Si addition promotes the generation of scale flaws on the steel sheet surface during the manufacturing process, and also causes the surface quality to deteriorate. Therefore, it is preferable to set the upper limit of the Si content to 0.40% by weight, and particularly to 0.20% by weight or less for applications requiring precision punching. Mn is an alloy component that improves the hardenability of a steel sheet and is also effective for toughening. In order to ensure sufficient hardenability, an Mn content of 0.3% by weight or more is required. However, when a large amount of Mn exceeding 1.0% by weight is contained, the ferrite is hardened and the precision punching property is deteriorated. Since P is a component that adversely affects ductility and toughness, the upper limit is defined as 0.03% by weight. Al is a component added as a deoxidizing agent for molten steel. However, if the total Al content in the steel exceeds 0.1% by weight, the cleanliness of the steel material is impaired, and the surface of the steel sheet is liable to have flaws.

【００１３】熱処理特性を改善するため、Ｃｒ，Ｍｏ，
Ｃｕ，Ｎｉの１種又は２種以上が必要に応じて添加され
る。Ｃｒは、焼入れ性の改善に有効であり、焼戻し軟化
抵抗を大きくする作用を呈する。しかし、１．２重量％
を超える多量のＣｒが含まれると、焼鈍後も軟化し難
く、却って精密打抜き性が低下する。したがって、Ｃｒ
を添加する場合には、Ｃｒ含有量の上限を１．２重量％
に設定する。Ｍｏは、少量の添加でＣｒと同様に焼入れ
性及び焼戻し軟化抵抗を改善する作用を呈する。しか
し、０．３重量％を超える多量のＭｏが含まれると、焼
鈍によっても軟質化し難く、却って焼入れ前のプレス成
形性や精密打抜き性が低下する。したがって、Ｍｏを添
加する場合には、Ｍｏ含有量の上限を０．３重量％に設
定する。In order to improve the heat treatment characteristics, Cr, Mo,
One or more of Cu and Ni are added as needed. Cr is effective in improving hardenability and has the effect of increasing temper softening resistance. However, 1.2% by weight
If a large amount of Cr exceeds that, it is difficult to soften even after annealing, and the precision punching property is rather deteriorated. Therefore, Cr
, The upper limit of the Cr content is 1.2% by weight.
Set to. Mo has an effect of improving the quenchability and the tempering softening resistance similarly to Cr with a small amount of addition. However, when Mo is contained in a large amount exceeding 0.3% by weight, it is difficult to soften even by annealing, and the press formability before quenching and the precision punching property are rather deteriorated. Therefore, when adding Mo, the upper limit of the Mo content is set to 0.3% by weight.

【００１４】Ｃｕは、熱延中に生成される酸化スケール
の剥離性を向上させ、鋼板の表面品質を改善する作用を
呈する。しかし、０．３重量％を超える多量のＣｕが含
まれると、溶融金属脆化に起因して鋼板表面に微細なク
ラックが発生し易くなる。Ｃｕを添加する場合、０．１
０〜０．１５重量％の範囲が好ましい。Ｎｉは、焼入れ
性を改善すると共に、低温靭性の向上に有効な合金成分
である。また、Ｃｕ添加に起因する溶融金属脆化の悪影
響を打ち消す作用も呈する。溶融金属脆化の防止には、
０．２重量％以上のＣｕを添加する場合、Ｃｕ添加量と
当量程度のＮｉを添加することが有効である。しかし、
２．０重量％を超える多量のＮｉを添加すると、焼鈍に
よっても軟質化し難く、却って焼入れ前のプレス加工性
や精密打抜き性が低下する。Cu has the effect of improving the releasability of oxide scale generated during hot rolling and improving the surface quality of a steel sheet. However, when a large amount of Cu exceeding 0.3% by weight is included, fine cracks are easily generated on the steel sheet surface due to the embrittlement of the molten metal. When adding Cu, 0.1
A range of 0 to 0.15% by weight is preferred. Ni is an alloy component effective for improving hardenability and improving low-temperature toughness. In addition, it also has the effect of counteracting the adverse effect of embrittlement of molten metal due to the addition of Cu. To prevent molten metal embrittlement,
When adding 0.2% by weight or more of Cu, it is effective to add Ni in an amount equivalent to the amount of Cu added. But,
When a large amount of Ni exceeding 2.0% by weight is added, it is difficult to soften even by annealing, and the press workability before quenching and the precision punching property are rather deteriorated.

【００１５】更に、焼入れ性を改善するため、Ｔｉ，
Ｎ，Ｂを添加できる。Ｔｉは、溶鋼の脱酸調整に使用さ
れる合金成分であり、脱窒作用も呈する。また、鋼板に
固溶しているＮを窒化物として固定するため、焼入れ性
改善に必要な有効Ｂ量が確保される。Ｔｉ添加で生成し
た炭窒化物は、焼入れ時の結晶粒粗大化を防止する作用
を呈する。これらの作用を安定して得るためには、少な
くとも０．０１重量％以上のＴｉ含有量が必要である。
しかし、０．０５重量％を超える過剰量のＴｉが含まれ
ると、経済的に不利になる。Ｎは、Ｔｉと結合してＴｉ
Ｎを形成し、焼入れ時の結晶粒微細化に有効な合金成分
である。しかし、０．０１重量％を超えるＮ含有量で
は、鋼材の延性が低下する。また、過剰量のＮは、Ｂと
結合し焼入れ性改善に有効なＢ量を消費する。Ｂは、ご
く微量の添加でＣｒ，Ｍｏと同様に焼入れ性を改善す
る。焼入れ性改善効果は０．０００５重量％以上のＢ含
有量で顕著になるが、０．００５０重量％で飽和する。Further, in order to improve hardenability, Ti,
N and B can be added. Ti is an alloy component used for adjusting deoxidation of molten steel, and also exhibits a denitrifying effect. Further, since N dissolved in the steel sheet is fixed as nitride, an effective B amount necessary for improving hardenability is secured. The carbonitride generated by the addition of Ti has an effect of preventing coarsening of crystal grains during quenching. In order to stably obtain these effects, a Ti content of at least 0.01% by weight or more is required.
However, if an excessive amount of Ti exceeding 0.05% by weight is contained, it is economically disadvantageous. N combines with Ti to form Ti
This is an alloy component that forms N and is effective in refining crystal grains during quenching. However, if the N content exceeds 0.01% by weight, the ductility of the steel material decreases. Further, an excessive amount of N combines with B and consumes an effective amount of B for improving hardenability. B improves the hardenability similarly to Cr and Mo with a very small amount of addition. The hardenability improving effect becomes significant at a B content of 0.0005% by weight or more, but saturates at 0.0050% by weight.

【００１６】精密打抜き性は、Ｓ含有量を規制し、Ｃａ
を添加することによっても改善される。Ｓは、ＭｎＳ系
介在物を生成する成分である。ＭｎＳ系介在物の量が多
くなると精密打抜き性が劣化するので、鋼中のＳ量は可
能な限り低減することが好ましいが、本発明で規定する
炭化物形態が得られる限り、極低Ｓ化を要することなく
一般的な市販鋼に対しても精密打抜き性改善の効果は得
られる。しかし、Ｃ含有量が０．８重量％近くまで高く
なった場合でも高い精密打抜き性を安定して確保するた
めには、Ｓ含有量を０．０１重量％以下に低減した鋼を
使用することが好ましい。ＭｎＳ系介在物は、Ｃａ添加
により効果的に形態制御される。通常のＭｎＳ系介在物
は、細長い形状を呈し、精密打抜き時にミクロボイド生
成の起点になり易い。これに対し、Ｃａ添加した鋼材で
はＭｎ，Ｓ，Ｃａの複合介在物となり、介在物が球状化
するためミクロボイドの発生が抑えられる。しかし、
０．０１重量％を超える過剰量のＣａを添加すると、介
在物の粗大化に起因する弊害が現れるようになる。した
がって、Ｃａを添加する場合、Ｃａ含有量の上限を０．
０１重量％に設定する。The precision punching ability regulates the S content,
Can also be improved by adding. S is a component that generates MnS-based inclusions. As the amount of MnS-based inclusions increases, the precision punching property deteriorates. Therefore, it is preferable to reduce the S content in steel as much as possible. The effect of improving the precision punching property can be obtained even for general commercial steel without necessity. However, in order to stably maintain high precision punching properties even when the C content is increased to nearly 0.8% by weight, use steel whose S content is reduced to 0.01% by weight or less. Is preferred. The morphology of the MnS-based inclusions is effectively controlled by adding Ca. Ordinary MnS-based inclusions have an elongated shape and tend to be the starting point of microvoid formation during precision punching. On the other hand, the Ca-added steel material becomes a composite inclusion of Mn, S, and Ca, and the inclusion is spheroidized, thereby suppressing the generation of microvoids. But,
When an excessive amount of Ca exceeding 0.01% by weight is added, a problem caused by coarsening of inclusions appears. Therefore, when adding Ca, the upper limit of the Ca content is set to 0.1.
Set to 01% by weight.

【００１７】［炭化物の球状化率］炭化物球状化率は、
「球状化した炭化物」が全炭化物に占める割合を示す。
本件明細書では、鋼板断面の金属組織観察視野で最大長
さｐとそれに直交する方向の最大長さｑの比ｐ／ｑが３
未満の炭化物を「球状化した炭化物」として扱った。た
とえば、再生パーライトにおける炭化物では、ほとんど
ｐ／ｑ≧３の炭化物である。他方、Ａｃ1 変態点以上の
加熱で残留した未溶解炭化物を起点として成長した炭化
物では、比ｐ／ｑが３未満になる。炭化物の形状を立体
的に正確に捉えて規定することは難しく、製品鋼板の適
否を判定する上でも煩雑である。これに対し、鋼板断面
の平面的な金属組織を観察することは容易である。本発
明者等は、鋼板断面の金属組織の中で観察される炭化物
形状について比ｐ／ｑを用いて球状化の程度を捉えたと
き、鋼板の精密打抜き性に対する炭化物形状の影響を適
切に評価できることを確認した。そして、種々の実験結
果から、比ｐ／ｑが３未満の「球状化した炭化物」の数
が全炭化物数の８０％以上を占め、更には平均炭化物粒
径を特定範囲に調整するとき、鋼板が高い精密打抜き性
を示すことを見出した。[Spheroidization rate of carbide]
The ratio of “spheroidized carbide” to the total carbide is shown.
In the present specification, the ratio p / q of the maximum length p and the maximum length q in the direction orthogonal to the maximum length p in the metallographic observation field of view of the steel sheet cross section is 3
Less than the carbides were treated as "spheroidized carbides". For example, the carbide in the recycled pearlite is almost the carbide of p / q ≧ 3. On the other hand, in the carbide grown from the undissolved carbide remaining after heating at the Ac 1 transformation point or higher, the ratio p / q is less than 3. It is difficult to accurately determine the shape of the carbide by three-dimensionally grasping it, and it is also troublesome to determine the suitability of the product steel sheet. On the other hand, it is easy to observe the planar metal structure of the steel plate cross section. The present inventors have appropriately evaluated the influence of the carbide shape on the precision punching property of a steel sheet when the degree of spheroidization of the carbide shape observed in the metal structure of the steel sheet cross section is determined using the ratio p / q. I confirmed that I can do it. According to various experimental results, when the number of “spheroidized carbides” having a ratio p / q of less than 3 accounts for 80% or more of the total number of carbides, and further when adjusting the average carbide particle size to a specific range, Shows high precision punching properties.

【００１８】炭化物球状化率を高めると精密打抜き性が
向上することは、球状化率の高い炭化物は加工時にミク
ロボイドの生成起点になりにくいことが原因であると推
察される。炭化物球状化率の低い鋼板では、分散してい
る炭化物のうち、たとえば再生パーライトの炭化物のよ
うに球状化が不充分な炭化物は、周囲のフェライト粒と
の変形能が異なる。そのため、球状化不充分な炭化物が
ミクロボイドの生成起点となり、ミクロボイドの生成・
連結を助長させて割れ発生に至るものと考えられる。し
たがって、精密打抜き性の改善には、平均炭化物粒径の
調整と相俟って鋼板の炭化物球状化率を８０％以上にす
ることが有効である。The reason why the precision punching property is improved when the carbide spheroidization rate is increased is presumed to be that carbides having a high spheroidization rate are unlikely to be the starting points of microvoid formation during processing. In a steel sheet having a low carbide spheroidization rate, among the dispersed carbides, a carbide having insufficient spheroidization, such as carbide of recycled pearlite, has a different deformability from surrounding ferrite grains. For this reason, insufficient spheroidized carbide becomes the starting point of microvoid formation,
It is considered that the connection is promoted to cause cracking. Therefore, in order to improve the precision punching property, it is effective to adjust the carbide spheroidization ratio of the steel sheet to 80% or more in combination with the adjustment of the average carbide particle size.

【００１９】［炭化物の平均粒径］精密打抜き性は、炭
化物の平均粒径を大きくすることによっても顕著に改善
される。平均粒径の増大は、鋼中の炭素量は一定である
ことから炭化物総数の減少を意味する。炭化物総数の減
少は、個々の炭化物を起点として生成したミクロボイド
の連結を抑制し、結果として精密打抜き性の顕著な向上
に寄与するものと推察される。他方、高周波焼入れのよ
うな短時間加熱による焼入れでは、炭化物を十分に固溶
させる上から、炭化物の粒径が小さいほど焼入れ性が良
くなる。精密打抜き性と焼入れ性の向上は、このように
炭化物の粒径変化に関して相反する挙動を採る。そこ
で、精密打抜き性及び焼入れ性の双方を満足させるため
には、平均炭化物粒径を厳格に規定することが必要であ
る。[Average Particle Size of Carbide] The precision punching property can be significantly improved by increasing the average particle size of carbide. An increase in the average grain size means a decrease in the total number of carbides because the amount of carbon in the steel is constant. It is presumed that the reduction in the total number of carbides suppresses the connection of microvoids generated from the individual carbides, and consequently contributes to remarkable improvement in precision punching. On the other hand, in quenching by short-time heating such as induction quenching, in order to sufficiently dissolve the carbide, the smaller the particle size of the carbide, the better the hardenability. The improvement of the precision punching property and the quenching property adopts the conflicting behavior with respect to the change in the particle size of the carbide. Therefore, in order to satisfy both the precision punching property and the hardenability, it is necessary to strictly define the average carbide particle size.

【００２０】平均炭化物粒径は、鋼板断面の金属組織を
観察するとき、観察視野にある個々の炭化物について測
定した円相当径を全測定炭化物で平均した値で示され
る。具体的には、個々の炭化物について面積を測定し、
得られた面積から円相当径を算出する。炭化物の面積
は、画像処理装置を用いて容易に測定できる。測定した
全ての炭化物の円相当径の総和を求め、総和を測定炭化
物の総数で除した値を平均炭化物粒径とする。数値の信
頼性を高めるためには、測定炭化物総数が３００個以上
となる観察視野を選定することが好ましい。本発明者等
による詳細な精密打抜き実験の結果、炭化物球状化率を
８０％以上，平均炭化物粒径を０．４μｍ以上とすると
き、優れた精密打抜き性を示す鋼板が得られることが判
った。しかし、加工後に高周波焼入れする場合に焼入れ
性を確保する上では、平均炭化物粒径を１．０μｍ以下
に抑える必要がある。したがって、本発明では、鋼板中
の平均炭化物粒径を０．４〜１．０μｍの範囲に規定し
た。The average carbide particle size is represented by a value obtained by averaging the equivalent circle diameters measured for individual carbides in the observation field of view when observing the metal structure in the cross section of the steel sheet with all the measured carbides. Specifically, measure the area of each carbide,
The equivalent circle diameter is calculated from the obtained area. The area of the carbide can be easily measured using an image processing device. The sum of the circle equivalent diameters of all the measured carbides is determined, and the value obtained by dividing the sum by the total number of the measured carbides is defined as the average carbide particle size. In order to increase the reliability of the numerical values, it is preferable to select an observation visual field in which the total number of measured carbides is 300 or more. As a result of detailed precision punching experiments by the present inventors, it has been found that when the carbide spheroidization ratio is 80% or more and the average carbide particle size is 0.4 μm or more, a steel sheet exhibiting excellent precision punchability can be obtained. . However, in order to ensure hardenability when induction hardening is performed after processing, it is necessary to suppress the average carbide particle size to 1.0 μm or less. Therefore, in the present invention, the average carbide particle size in the steel sheet is specified in the range of 0.4 to 1.0 μm.

【００２１】以上のような特性をもつ鋼板は、焼鈍方法
の改良によって製造される。たとえば、ＡC1変態点直下
での短時間均熱，ＡC1変態点直下〜ＡC1変態点直上の温
度域での加熱を組み合わせた焼鈍等が採用される。具体
的には、中炭素鋼の場合、（ＡC1−５０℃）〜（ＡC1未
満の温度）の温度域に熱延鋼板又は冷延鋼板を１０時間
以上保持する焼鈍により、本発明で規定した適正な金属
組織をもつ鋼板が製造される。高炭素鋼の場合、前記焼
鈍の長時間実施や焼鈍に先立った冷間圧延により精密打
抜き性に好適な組織をもつ鋼板が製造される。また、
（ＡC1−５０℃）〜（ＡC1未満の温度）の温度域に熱延
鋼板を０．５時間以上保持する１段目の加熱、ＡC1〜
（ＡC1＋１００℃）の温度域に０．５〜２０時間保持す
る２段目の加熱、次いで（Ａr1−５０℃）〜Ａr1の温度
域に２〜２０時間保持する３段目の加熱を連続させ、２
段目の保持温度から３段目の保持温度への冷却速度を５
〜３０℃／時間とする３段階焼鈍によって、或いは冷延
鋼板に３段階焼鈍を施すことにより、精密打抜き性に好
適な金属組織をもつ鋼板が製造される。A steel sheet having the above characteristics is manufactured by improving the annealing method. For example, a short time just below A C1 transformation point soaking, annealing or the like which combines the heating in the temperature range just above A C1 transformation point just below to A C1 transformation point is employed. Specifically, in the case of a medium carbon steel, it is specified in the present invention by annealing in which a hot-rolled steel sheet or a cold-rolled steel sheet is kept in a temperature range of (A C1 -50 ° C.) to (a temperature lower than A C1 ) for 10 hours or more. A steel sheet having a proper metal structure is manufactured. In the case of high-carbon steel, a steel sheet having a structure suitable for precision punching is manufactured by performing the annealing for a long time or performing cold rolling prior to the annealing. Also,
(A C1 -50 ° C.) ~ temperature range the heating of the first stage which holds more than 0.5 hours hot rolled steel sheet of (A temperature below C1), A C1 ~
Second stage heating maintained at (A C1 + 100 ° C.) temperature range for 0.5-20 hours, then third stage heating maintained at (A r1 -50 ° C.)-A r1 temperature range for 2-20 hours And 2
The cooling rate from the holding temperature of the third stage to the holding temperature of the third stage is 5
By performing three-step annealing at ３０30 ° C./hour or by performing three-step annealing on a cold-rolled steel sheet, a steel sheet having a metal structure suitable for precision punching is manufactured.

【００２２】[0022]

【実施例１】表１の成分・組成をもつ鋼を溶製し、板厚
４．０ｍｍの熱延板を製造した。熱延中にコイル巻取り
温度を種々変更することにより熱延組織を変化させた。
得られた熱延板を酸洗した後、種々の条件で焼鈍し、一
部については冷間圧延後に焼鈍し、鋼板の炭化物球状化
率及び炭化物平均粒径を変化させた。表２中、試験番号
３，７，１６では、巻取り温度５８０〜６３０℃で熱延
板を製造した後、酸洗し、ＡC1変態点以下の７００℃に
１５時間保持して空冷する焼鈍を施した。試験番号８，
１０，１３，１５では、巻取り温度５８０〜６３０℃で
熱延板を製造した後、酸洗し、６９０℃×４時間保持→
７３０℃×４時間保持→速度１０℃／時で冷却→６９０
℃×４時間保持→６５０℃まで速度１０℃／時で冷却→
空冷の焼鈍を施した。試験番号１４では、巻取り温度５
８０〜６３０℃で熱延板を製造した後、酸洗し、６９０
℃×４時間保持→７７０℃×４時間保持→速度１０℃／
時で冷却→７１０℃×８時間保持→６５０℃まで速度１
０℃／時で冷却→空冷の焼鈍を施した。試験番号９，１
１では、巻取り温度５８０〜６３０℃で熱延板を製造し
た後、酸洗し、圧下率４０％で冷間圧延し、６９０℃×
４時間保持→７３０℃×４時間保持→速度１０℃／時で
冷却→６９０℃×４時間保持→６５０℃まで速度１０℃
／時で冷却→空冷の焼鈍を施した。Example 1 Steel having the components and compositions shown in Table 1 was melted to produce a hot-rolled sheet having a thickness of 4.0 mm. The hot rolling structure was changed by variously changing the coil winding temperature during hot rolling.
The obtained hot-rolled sheet was pickled, then annealed under various conditions, and partly annealed after cold rolling, thereby changing the carbide spheroidization ratio and the carbide average particle diameter of the steel sheet. In Table 2, in Test Nos. 3, 7, and 16, annealing was performed after producing a hot-rolled sheet at a winding temperature of 580 to 630 ° C., pickling, holding at 700 ° C. below the A C1 transformation point for 15 hours, and air cooling. Was given. Test number 8,
In 10, 13, and 15, after manufacturing a hot-rolled sheet at a winding temperature of 580 to 630 ° C., pickling and holding at 690 ° C. × 4 hours →
Hold at 730 ° C x 4 hours → Cool at 10 ° C / hour → 690
℃ x 4 hours → Cool to 650 ° C at a rate of 10 ° C / hour →
Air-cooled annealing was performed. In test number 14, the winding temperature 5
After producing a hot-rolled sheet at 80 to 630 ° C, it is pickled and 690
℃ ℃ 4 hours hold → 770 ℃ × 4 hours hold → speed 10 ℃ /
Cool at time → 710 ° C x 8 hours hold → Speed 1 to 650 ° C
Cooling at 0 ° C./hour→annealing by air cooling was performed. Test number 9.1
In No. 1, a hot-rolled sheet was manufactured at a winding temperature of 580 to 630 ° C., then pickled, cold-rolled at a reduction of 40%, and 690 ° C. ×
Hold for 4 hours → 730 ° C × 4 hours hold → Cool at 10 ° C / hour → 690 ° C × 4 hours hold → 10 ° C to 650 ° C
/ Hour cooling → air cooling annealing.

【００２３】 [0023]

【００２４】表面研削等で板厚を最終的に２．０ｍｍに
調整した後、引張試験，切欠き引張試験，精密打抜き性
評価試験及び高周波焼入れ試験に供した。炭化物球状化
率は、走査型電子顕微鏡を用いて鋼板断面の一定領域を
観察し、総数３００〜１０００個の炭化物が析出してい
る部分を観察領域として選定した。炭化物の最大長さｐ
とその直角方向の最大長さｑとの比ｐ／ｑが３未満とな
るものを「球状化した炭化物」としてカウントし、測定
炭化物総数に占める「球状化した炭化物」の数の割合を
炭化物球状化率として算出した。平均炭化物粒径は、炭
化物球状化率の測定と同じ観察視野を画像処理し、ここ
の炭化物の円相当径を算出し、算出結果を全測定炭化物
で平均化することにより求めた。After finally adjusting the plate thickness to 2.0 mm by surface grinding or the like, it was subjected to a tensile test, a notch tensile test, a precision punching property evaluation test and an induction hardening test. The carbide spheroidization ratio was determined by observing a predetermined region of the steel plate cross section using a scanning electron microscope and selecting a portion where a total of 300 to 1000 carbides were precipitated as an observation region. Maximum length of carbide p
Those having a ratio p / q of less than 3 to the maximum length q in the perpendicular direction are counted as “spheroidized carbides”, and the ratio of the number of “spheroidized carbides” to the total number of measured carbides is defined as carbide spheres. It was calculated as the conversion rate. The average carbide particle diameter was determined by performing image processing on the same observation visual field as in the measurement of the carbide spheroidization ratio, calculating the equivalent circle diameter of the carbide, and averaging the calculation results with all the measured carbides.

【００２５】引張試験にはＪＩＳ５号試験片を用い、平
行部の標点間距離を５０ｍｍに設定した。切欠き引張試
験では、ＪＩＳ５号引張り試験片の平行部長手方向中央
位置における幅方向両側に開き角４５度，深さ２ｍｍの
Ｖノッチを入れた試験片を使用した。平行部長手方向中
央部の標点間距離１０ｍｍに対する伸び率を破断後に測
定し、得られた伸び率を切欠き引張伸びＥｌV とした。
ＥｌV 値は局部延性を示す指標であり、通常の引張試験
で（全伸び）−（均一伸び）として求められる局部伸び
に比較し、より精度良く局部延性を定量的に評価でき
る。精密打抜き性評価試験では、先端角度９０度，先端
アール１．０ｍｍのギア歯をもつ加工品が得られる評価
用金型を使用し、加工品１００個中の全ギア歯の破断面
率を調査することにより、精密打抜き面性状を評価し
た。破断面率は、精密打抜き面の板厚に対する破断面長
さの比率で求めた。For the tensile test, a JIS No. 5 test piece was used, and the distance between the reference points of the parallel portions was set to 50 mm. In the notch tensile test, a test piece having a V-notch with an opening angle of 45 degrees and a depth of 2 mm at both sides in the width direction at the center in the longitudinal direction of the parallel portion of the JIS No. 5 tensile test piece was used. The elongation percentage with respect to the gauge length of 10 mm at the central part in the longitudinal direction of the parallel portion was measured after breaking, and the obtained elongation percentage was defined as notch tensile elongation El V.
The El V value is an index indicating local ductility, and the local ductility can be quantitatively evaluated with higher accuracy than the local elongation obtained as (total elongation) − (uniform elongation) in a normal tensile test. In the precision punching property evaluation test, the fracture surface ratio of all gear teeth in 100 processed products was investigated using an evaluation die that can obtain a processed product having gear teeth with a tip angle of 90 degrees and a radius of 1.0 mm. Then, the precision punched surface properties were evaluated. The fracture surface ratio was determined by the ratio of the fracture surface length to the thickness of the precision punched surface.

【００２６】高周波焼入れ試験では、鋼板から切り出し
た直径５ｍｍ，長さ１０ｍｍの試験片を高周波加熱して
９００℃に５秒間保持した後、水焼入れし、焼入れ後の
硬さを測定することにより焼入れ性を評価した。表２の
調査結果にみられるように、試験番号１は、高いＥｌV
値を示し精密打抜き面性状に優れていたが、Ｃ含有量が
０．１重量％未満の鋼Ｂ１を使用しているため加工後の
熱処理で焼入れ不良が発生した。他方、試験番号２で
は、０．９重量％を超えるＣを含む鋼Ｂ２を使用したた
め、加工性が著しく悪く、加工後の焼入れにおいても焼
き割れが発生した。In the induction hardening test, a test piece cut from a steel plate and having a diameter of 5 mm and a length of 10 mm was induction-heated and maintained at 900 ° C. for 5 seconds, then water-quenched, and the hardness after quenching was measured. The sex was evaluated. As can be seen from the survey results in Table 2, Test No. 1 showed a high El V
Although the value was excellent and the precision punched surface properties were excellent, since the steel B1 having a C content of less than 0.1% by weight was used, poor quenching occurred in the heat treatment after processing. On the other hand, in Test No. 2, since steel B2 containing C exceeding 0.9% by weight was used, workability was remarkably poor, and quenching cracks occurred even after quenching after working.

【００２７】Ｂ１，Ｂ２以外の鋼を使用し、炭化物球状
化率，平均炭化物粒径及びＥｌV 値が本発明で規定した
条件を満足する本発明例（試験番号３，７〜１１，１３
〜１６）では、Ｃ含有量が同レベルの比較例に比べ何れ
も精密打抜き面性状に優れ、高周波焼入れ性にも優れて
いた。なかでも、特にＳ量を低減し、Ｃａ添加した鋼Ａ
８を使用した試験番号１６では、同じＣ含有量で炭化物
球状化率及び平均炭化物粒径が同等の試験番号７に比較
して精密打抜き面性状が大きく向上していた。これに対
し、炭化物球状化率が不足し、平均炭化物粒径も小さ
く、ＥｌV 値が低い試験番号４では、精密打抜き面性状
が大きく劣化した。炭化物球状化率は高いが平均炭化物
粒径が小さくＥｌV 値も低い試験番号５では、精密打抜
き面性状が劣化した。逆に、炭化物球状化率は低いが、
平均炭化物粒径が大きくＥｌV 値が低い試験番号６で
も、精密打抜き面性状が劣化した。また、平均炭化物粒
径が１．０μｍを超えている試験番号１２では、同じＣ
含有量の試験番号１１に比較して高周波焼入れ後の硬さ
が低く、焼入れ不良が生じた。以上の結果から、炭化物
球状化率，平均炭化物粒径及びＥｌV 値が本発明で規定
した条件を満足するとき、優れた精密打抜き性が得られ
ることが判る。Examples of the present invention in which steels other than B1 and B2 are used and the degree of carbide spheroidization, average carbide particle size and El V value satisfy the conditions specified in the present invention (test numbers 3, 7 to 11, 13).
In Nos. To 16), all were superior in precision punched surface properties and in induction hardening properties as compared with Comparative Examples having the same C content. Among them, steel A with reduced S content and Ca added
In Test No. 16 using No. 8, the precision punched surface properties were greatly improved as compared with Test No. 7 in which the carbide spheroidization ratio and the average carbide particle size were the same at the same C content. On the other hand, in Test No. 4 in which the carbide spheroidization ratio was insufficient, the average carbide particle size was small, and the El V value was low, the properties of the precision punched surface were significantly deteriorated. In Test No. 5, in which the carbide spheroidization ratio was high but the average carbide particle size was small and the El V value was low, the precision punched surface properties were deteriorated. Conversely, although the carbide spheroidization rate is low,
Even in Test No. 6 in which the average carbide particle size was large and the El V value was low, the precision punched surface properties were deteriorated. In Test No. 12 in which the average carbide particle size exceeds 1.0 μm, the same C
The hardness after induction hardening was lower than that of Test No. 11 for the content, and poor quenching occurred. From the above results, it can be seen that when the carbide spheroidization ratio, the average carbide particle size, and the El V value satisfy the conditions specified in the present invention, excellent precision punching properties can be obtained.

【００２８】 [0028]

【００２９】[0029]

【実施例２】表３の成分・組成をもつ鋼を溶製し、板厚
４．０ｍｍの熱延板を製造した。熱延中にコイル巻取り
温度を種々変更することにより熱延組織を変化させた。
得られた熱延板を酸洗した後、種々の条件で焼鈍し、一
部については冷間圧延後に焼鈍し、鋼板の炭化物球状化
率及び炭化物平均粒径を変化させた。表４中、試験番号
２３，２８，３４，３８では、巻取り温度５８０〜６３
０℃で熱延板を製造した後、酸洗し、Ａｃ1 変態点以下
の７００℃に１５時間保持して空冷する焼鈍を施した。
試験番号２７では、巻取り温度５８０〜６３０℃で熱延
鋼板を製造した後、酸洗し、６８０℃で１０時間保持し
て空冷する焼鈍を施した。試験番号２９，３１，３５，
３７では、巻取り温度５８０〜６３０℃で熱延板を製造
した後、酸洗し、６９０℃×４時間保持→７３０℃×４
時間保持→速度１０℃／時で冷却→６９０℃×４時間保
持→６５０℃まで速度１０℃／時で冷却→空冷の焼鈍を
施した。試験番号３６では、巻取り温度５８０〜６３０
℃で熱延板を製造した後、酸洗し、６９０℃×４時間保
持→７７０℃×４時間保持→速度１０℃／時で冷却→７
１０℃×８時間保持→６５０℃まで速度１０℃／時で冷
却→空冷の焼鈍を施した。試験番号３０，３２では、巻
取り温度５８０〜６３０℃で熱延板を製造した後、酸洗
し、圧下率４０％で冷間圧延し、６９０℃×４時間保持
→７３０℃×４時間保持→速度１０℃／時で冷却→６９
０℃×４時間保持→６５０℃まで速度１０℃／時で冷却
→空冷の焼鈍を施した。Example 2 Steel having the components and compositions shown in Table 3 was melted to produce a hot-rolled sheet having a thickness of 4.0 mm. The hot rolling structure was changed by variously changing the coil winding temperature during hot rolling.
The obtained hot-rolled sheet was pickled, then annealed under various conditions, and partly annealed after cold rolling, thereby changing the carbide spheroidization ratio and the carbide average particle diameter of the steel sheet. In Table 4, in the test numbers 23, 28, 34, and 38, the winding temperatures 580 to 63
After producing a hot-rolled sheet at 0 ° C., the sheet was pickled, and then annealed by holding at 700 ° C. below the Ac 1 transformation point for 15 hours and air cooling.
In Test No. 27, after producing a hot-rolled steel sheet at a winding temperature of 580 to 630 ° C., it was subjected to an acid washing, an annealing at 680 ° C. for 10 hours, and air cooling. Test numbers 29, 31, 35,
In No. 37, after manufacturing a hot-rolled sheet at a winding temperature of 580 to 630 ° C., pickling and holding at 690 ° C. × 4 hours → 730 ° C. × 4
Time holding → cooling at a rate of 10 ° C./hour→holding at 690 ° C. × 4 hours → cooling to 650 ° C. at a rate of 10 ° C./hour→annealing by air cooling. In test number 36, the winding temperature was 580 to 630.
After producing a hot-rolled sheet at ℃, pickling and holding at 690 ° C × 4 hours → holding at 770 ° C × 4 hours → cooling at a rate of 10 ° C / hour → 7
Hold at 10 ° C. × 8 hours → cool at 650 ° C. at a rate of 10 ° C./hour→anneal by air cooling. In Test Nos. 30 and 32, after manufacturing a hot-rolled sheet at a winding temperature of 580 to 630 ° C., pickling, cold rolling at a reduction of 40%, and holding at 690 ° C. × 4 hours → holding at 730 ° C. × 4 hours → Cool at a rate of 10 ° C / hour → 69
Holding at 0 ° C. × 4 hours → cooling to 650 ° C. at a rate of 10 ° C./hour→annealing by air cooling.

【００３０】 [0030]

【００３１】表面研削等で板厚を最終的に２．０ｍｍに
調整した後、実施例１と同様に引張試験，切欠き引張試
験，精密打抜き性評価試験及び高周波焼入れ試験に供し
た。併せて切欠き引張試験及びＪＩＳ ５号引張試験片
を用いた通常の引張試験で測定された切欠き引張伸びＥ
ｌV 値及び引張強さＴＳからＤ値［＝（３×ＥｌV 2＋１
８×ＥｌV ）／ＴＳ］を算出した。また、５０００回の
プレス実験をした後で精密打抜き面の破断面率を測定す
ることにより金型寿命を判定した。なお、５０００回の
プレス実験に使用した金型は、初期の金型と同じ状態に
なるように補修した。表４の調査結果にみられるよう
に、試験番号２１は、高いＥｌV 値を示し精密打抜き面
性状に優れていたが、Ｃ含有量が０．１重量％未満の鋼
Ｄ１を使用しているため加工後の熱処理で焼入れ不良が
発生した。他方、試験番号２２では、０．９重量％を超
えるＣを含む鋼Ｄ２を使用したため、加工性が著しく悪
く、加工後の焼入れにおいても焼き割れが発生した。After the sheet thickness was finally adjusted to 2.0 mm by surface grinding or the like, it was subjected to a tensile test, a notch tensile test, a precision punching property evaluation test and an induction hardening test in the same manner as in Example 1. In addition, the notch tensile elongation E measured by a notch tensile test and a normal tensile test using a JIS No. 5 tensile test piece.
From the 1 V value and the tensile strength TS, the D value [= (3 × El V 2 +1)
8 × El V ) / TS] was calculated. After 5000 press experiments, the mold life was determined by measuring the fracture surface area of the precision punched surface. The mold used for 5000 press experiments was repaired so as to be in the same state as the initial mold. As can be seen from the investigation results in Table 4, Test No. 21 exhibited a high El V value and was excellent in precision punched surface properties, but steel D1 having a C content of less than 0.1% by weight was used. Therefore, quenching failure occurred in the heat treatment after processing. On the other hand, in Test No. 22, since steel D2 containing C exceeding 0.9% by weight was used, workability was remarkably poor, and quenching cracking occurred even after quenching after working.

【００３２】Ｄ１，Ｄ２以外の鋼を使用し、炭化物球状
化率，平均炭化物粒径及びＥｌV 値が本発明で規定した
条件を満足する本発明例のうち、Ｄ値が３以上を満足し
た試験番号２３，２８〜３２，３５〜３８では、Ｃ含有
量が同レベルの比較例に比べ何れも精密打抜き面性状に
優れ、金型寿命及び高周波焼入れ性にも優れていた。な
かでも、特にＳ量を低減し、Ｃａ添加した鋼Ｃ８を使用
した試験番号３８では、同じＣ含有量で炭化物球状化率
及び平均炭化物粒径が同等の試験番号２８に比較してＥ
ｌV 値が高く、精密打抜き面性状，金型寿命共に優れて
いた。炭化物球状化率が不足し、平均炭化物粒径も小さ
く、ＥｌV 値が低い試験番号２４では、同程度のＣを含
む鋼種に比較して精密打抜き面性状が大きく劣化した。
炭化物球状化率は高いが平均炭化物粒径が小さくＥｌV
値も低い試験番号２５では、精密打抜き面性状が劣化し
た。逆に、炭化物球状化率は低いが、平均炭化物粒径が
大きくＥｌV 値が低い試験番号２６でも、精密打抜き面
性状が劣化した。[0032] Using the D1, D2 other than steel, carbide spheroidization ratio, average carbide grain size and El V values of inventive examples satisfying the conditions specified in the present invention, satisfied the D value is 3 or more In Test Nos. 23, 28 to 32, and 35 to 38, the C content was excellent in precision punched surface properties, the mold life and the induction hardening properties as compared with Comparative Examples having the same level. In particular, in Test No. 38 using steel C8 in which the S content was reduced and Ca was added, compared to Test No. 28 in which the carbide spheroidization rate and the average carbide particle size were the same at the same C content,
l V value is high, fine blanking surface properties, they were excellent in mold life both. In Test No. 24, in which the carbide spheroidization ratio was insufficient, the average carbide particle size was small, and the El V value was low, the precision punched surface properties were significantly deteriorated as compared with steel types containing the same degree of C.
Carbide spheroidization ratio is high average carbide grain size is small El V
In test number 25 having a low value, the precision punched surface properties were deteriorated. Conversely, even though Test No. 26 had a low carbide spheroidization ratio but a large average carbide particle size and a low El V value, the precision punched surface properties were deteriorated.

【００３３】金型寿命についてみると、Ｄ値が３に達し
ない試験番号２７，３４では、５０００回後の精密打抜
き面性状が最初の打抜き品に比較して破断面率が高くな
っている。また、平均炭化物粒径が１．０μｍを超えて
いる試験番号３３では、同じＣ含有量の試験番号３２に
比較して高周波焼入れ後の硬さが低く、焼入れ不良が生
じた。以上の結果から、炭化物球状化率，平均炭化物粒
径及，ＥｌV 値及びＤ値が本発明で規定した条件を満足
するとき、優れた精密打抜き性が得られ、しかも金型が
長寿命化されることが判る。With respect to the life of the mold, in Test Nos. 27 and 34 in which the D value does not reach 3, the precision punched surface properties after 5,000 times have a higher fracture surface ratio than the first punched product. In Test No. 33 in which the average carbide particle size exceeds 1.0 μm, the hardness after induction hardening was lower than that in Test No. 32 having the same C content, and poor quenching occurred. From the above results, when the carbide spheroidization ratio, the average carbide particle size, the El V value and the D value satisfy the conditions specified in the present invention, excellent precision punching properties are obtained, and the mold has a long life. It turns out that it is done.

【００３４】 [0034]

【００３５】[0035]

【発明の効果】以上に説明したように、本発明の炭素鋼
板は、球状化率及び平均粒径が規定された炭化物が分散
した組織をもち、局部延性の指標である切欠き引張伸び
を調整することにより、精密打抜き性が改善されてい
る。更に、引張強さとの関連で切欠き引張伸びを制御す
ることにより、金型寿命も改善される。更には、精密打
抜き加工後に焼入れすると、焼入れ不良を発生させるこ
となく各種部品に要求される強度が付与される。このよ
うにして、本発明に従った中炭素鋼板又は高炭素鋼板
は、従来の炭素鋼板に比較して優れた精密打抜き加工性
を活用し、複雑形状の自動車部品，各種機械部品等の素
材として広範な分野で使用される。また、部品加工後に
高周波焼入れが適用されるため、生産性も向上する。As described above, the carbon steel sheet of the present invention has a structure in which carbide having a defined spheroidization ratio and average particle size is dispersed, and adjusts the notch tensile elongation which is an index of local ductility. By doing so, the precision punching property is improved. Further, by controlling the notch tensile elongation in relation to tensile strength, mold life is also improved. Furthermore, when quenching is performed after precision punching, strength required for various components is imparted without causing quenching failure. As described above, the medium carbon steel sheet or the high carbon steel sheet according to the present invention utilizes the superior precision punching workability as compared with the conventional carbon steel sheet, and is used as a material for automobile parts having various shapes and various machine parts. Used in a wide range of fields. Further, since the induction hardening is applied after the parts are processed, the productivity is also improved.

Claims (6)

【特許請求の範囲】[Claims] 【請求項１】 Ｃ：０．１５〜０．９０重量％，Ｓｉ：
０．４重量％以下，Ｍｎ：０．３〜１．０重量％，Ｐ：
０．０３重量％以下，全Ａｌ：０．１０重量％以下，残
部が実質的にＦｅの組成をもち、球状化率８０％以上，
平均粒径０．４〜１．０μｍの炭化物がフェライトマト
リックスに分散した組織をもち、ＪＩＳ５号引張試験片
の平行部長手方向中央位置における幅方向両サイドに開
き角４５度，深さ２ｍｍのＶノッチを入れた試験片を用
いて引張試験し、平行部長手方向中央部の標点間距離１
０ｍｍに対する破断後の伸び率として表わされる切欠き
引張伸びが２０％以上である精密打抜き性に優れた高炭
素鋼板。C: 0.15 to 0.90% by weight, Si:
0.4% by weight or less, Mn: 0.3 to 1.0% by weight, P:
0.03% by weight or less, total Al: 0.10% by weight or less, the balance substantially has a Fe composition, and the spheroidization ratio is 80% or more;
V has a structure in which carbides having an average particle size of 0.4 to 1.0 μm are dispersed in a ferrite matrix, and has an opening angle of 45 ° and a depth of 2 mm on both sides in the width direction at the center in the longitudinal direction of the parallel portion of the JIS No. 5 tensile test piece. A tensile test was performed using a notched test piece, and the distance between the gauge points at the center in the longitudinal direction of the parallel portion was 1
A high carbon steel sheet excellent in precision punching properties, having a notch tensile elongation expressed as an elongation percentage after fracture with respect to 0 mm of 20% or more. 【請求項２】 Ｃ：０．１５〜０．９０重量％，Ｓｉ：
０．４０重量％以下，Ｍｎ：０．３〜１．０重量％以
下，Ｐ：０．０３重量％以下，全Ａｌ：０．１０重量％
以下を含み、更にＣｒ：１．２重量％以下，Ｍｏ：０．
３重量％以下，Ｃｕ：０．３重量％以下，Ｎｉ：２．０
重量％以下の１種又は２種以上を含み、残部が実質的に
Ｆｅの組成をもち、平均粒径０．４〜１．０μｍで炭化
物球状化率８０％以上の炭化物がフェライトマトリック
スに分散した組織をもち、ＪＩＳ５号引張試験片の平行
部長手方向中央位置における幅方向両サイドに開き角４
５度，深さ２ｍｍのＶノッチを入れた試験片を用いて引
張試験し、平行部長手方向中央部の標点間距離１０ｍｍ
に対する破断後の伸び率として表わされる切欠き引張伸
びＥｌV が２０％以上である精密打抜き性に優れた高炭
素鋼板。2. C: 0.15 to 0.90% by weight, Si:
0.40 wt% or less, Mn: 0.3 to 1.0 wt% or less, P: 0.03 wt% or less, total Al: 0.10 wt%
And Cr: 1.2% by weight or less;
3% by weight or less, Cu: 0.3% by weight or less, Ni: 2.0
% Or less, and the balance substantially has the composition of Fe, and the carbide having an average particle diameter of 0.4 to 1.0 μm and a carbide spheroidization ratio of 80% or more is dispersed in the ferrite matrix. Opening angle 4 on both sides in the width direction at the center in the longitudinal direction of the parallel part of JIS No. 5 tensile test piece
A tensile test was performed using a test piece having a V notch of 5 degrees and a depth of 2 mm, and the distance between the gauge points at the center in the longitudinal direction of the parallel portion was 10 mm.
A high-carbon steel sheet excellent in precision punching properties, having a notch tensile elongation El V expressed as an elongation percentage after rupture of at least 20%. 【請求項３】 Ｃ：０．１５〜０．９０重量％，Ｓｉ：
０．４重量％以下，Ｍｎ：０．３〜１．０重量％，Ｐ：
０．０３重量％以下，全Ａｌ：０．１０重量％以下，Ｔ
ｉ：０．０１〜０．０５重量％，Ｂ：０．０００５〜
０．００５０重量％，Ｎ：０．０１重量％以下，残部が
実質的にＦｅの組成をもち、球状化率８０％以上，平均
粒径０．４〜１．０μｍの炭化物がフェライトマトリッ
クスに分散した組織をもち、ＪＩＳ５号引張試験片の平
行部長手方向中央位置における幅方向両サイドに開き角
４５度，深さ２ｍｍのＶノッチを入れた試験片を用いて
引張試験し、平行部長手方向中央部の標点間距離１０ｍ
ｍに対する破断後の伸び率として表わされる切欠き引張
伸びが２０％以上である精密打抜き性に優れた高炭素鋼
板。3. C: 0.15 to 0.90% by weight, Si:
0.4% by weight or less, Mn: 0.3 to 1.0% by weight, P:
0.03% by weight or less, total Al: 0.10% by weight or less, T
i: 0.01 to 0.05% by weight, B: 0.0005 to
0.0050% by weight, N: 0.01% by weight or less, balance substantially has Fe composition, spheroidization ratio is 80% or more, and carbide having an average particle size of 0.4 to 1.0 μm is dispersed in the ferrite matrix. A tensile test was carried out using a test piece having a V-notch with an opening angle of 45 degrees and a depth of 2 mm on both sides in the width direction at the center in the longitudinal direction of the parallel portion of the JIS No. 5 tensile test piece, 10m distance between gauges in the center
A high-carbon steel sheet excellent in precision punching properties, having a notch tensile elongation expressed as an elongation after fracture with respect to m of 20% or more. 【請求項４】 Ｃ：０．１５〜０．９０重量％，Ｓｉ：
０．４０重量％以下，Ｍｎ：０．３〜１．０重量％以
下，Ｐ：０．０３重量％以下，全Ａｌ：０．１０重量％
以下，Ｔｉ：０．０１〜０．０５重量％，Ｂ：０．００
０５〜０．００５０重量％，Ｎ：０．０１重量％以下を
含み、更にＣｒ：１．２重量％以下，Ｍｏ：０．３重量
％以下，Ｃｕ：０．３重量％以下，Ｎｉ：２．０重量％
以下の１種又は２種以上を含み、残部が実質的にＦｅの
組成をもち、平均粒径０．４〜１．０μｍで炭化物球状
化率８０％以上の炭化物がフェライトマトリックスに分
散した組織をもち、ＪＩＳ５号引張試験片の平行部長手
方向中央位置における幅方向両サイドに開き角４５度，
深さ２ｍｍのＶノッチを入れた試験片を用いて引張試験
し、平行部長手方向中央部の標点間距離１０ｍｍに対す
る破断後の伸び率として表わされる切欠き引張伸びが２
０％以上である精密打抜き性に優れた高炭素鋼板。4. C: 0.15 to 0.90% by weight, Si:
0.40 wt% or less, Mn: 0.3 to 1.0 wt% or less, P: 0.03 wt% or less, total Al: 0.10 wt%
Hereinafter, Ti: 0.01 to 0.05% by weight, B: 0.00
0.05 to 0.0050 wt%, N: 0.01 wt% or less, Cr: 1.2 wt% or less, Mo: 0.3 wt% or less, Cu: 0.3 wt% or less, Ni: 2 0.0% by weight
One or two or more of the following, the balance substantially has a composition of Fe, an average particle diameter of 0.4 to 1.0 μm, and a structure in which carbide having a carbide spheroidization ratio of 80% or more is dispersed in a ferrite matrix. The JIS No. 5 tensile test piece has an opening angle of 45 degrees on both sides in the width direction at the center in the longitudinal direction of the parallel part,
A tensile test was performed using a test piece having a V notch having a depth of 2 mm, and the notch tensile elongation expressed as an elongation percentage after fracture with respect to a distance of 10 mm between the gauge points at the center in the longitudinal direction of the parallel portion was 2 mm.
High carbon steel sheet excellent in precision punching property of 0% or more. 【請求項５】 更にＣａ：０．０１重量％以下を含む請
求項１〜４の何れかに記載の精密打抜き性に優れた高炭
素鋼板。5. The high carbon steel sheet according to claim 1, further comprising Ca: 0.01% by weight or less. 【請求項６】 ＪＩＳ ５号引張試験で得られる引張強
さＴＳ及び切欠き引張伸びＥｌV 値で定義されるＤ値
［＝（３×ＥｌV 2＋１８×ＥｌV ）／ＴＳ］が３以上で
ある請求項１〜５の何れかに記載の精密打抜き性に優れ
た高炭素鋼板。6. A D value [= (3 × El V 2 + 18 × El V ) / TS] defined by a tensile strength TS and a notch tensile elongation El V obtained in a JIS No. 5 tensile test of 3 or more. The high-carbon steel sheet excellent in precision punchability according to any one of claims 1 to 5.
JP06949999A 1999-03-16 1999-03-16 High carbon steel sheet for precision punching Expired - Fee Related JP4465057B2 (en)

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