JP2009527638A - Steel wire rod excellent in cold workability and hardenability, and manufacturing method thereof - Google Patents

Steel wire rod excellent in cold workability and hardenability, and manufacturing method thereof Download PDF

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JP2009527638A
JP2009527638A JP2008548379A JP2008548379A JP2009527638A JP 2009527638 A JP2009527638 A JP 2009527638A JP 2008548379 A JP2008548379 A JP 2008548379A JP 2008548379 A JP2008548379 A JP 2008548379A JP 2009527638 A JP2009527638 A JP 2009527638A
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JP4966316B2 (en
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サン−ウ チョイ
ダク−ラク リー
サン−ヨン リー
ヨ−アン ユン
モ−チャン カン
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ポスコ
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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32Ferrous alloys, e.g. steel alloys containing chromium with boron
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/001Ferrous alloys, e.g. steel alloys containing N
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium

Abstract

【課題】本発明は、冷間加工用素材に用いられる鋼線材の製造方法に関するもので、より詳細には線材の状態で球状化熱処理を省略しても素材の強度が大幅に低く冷間加工が容易な反面、その後焼入れ処理により強度を大幅に上昇することができる冷間加工性及び焼入れ性に優れた鋼線材及びその製造方法に関するものである。
【解決手段】本発明の鋼線材は、C:0.1〜0.4重量%、Si:0.3〜1.5重量%、Mn:0.3〜1.7重量%、P:0.015重量%以下、S:0.015重量%以下、Cr:0.05〜1.7重量%、Al:0.05重量%以下、B:0.001〜0.005重量%、Ti:0.01〜0.05重量%、N:0.015重量%以下、残部Fe及びその他不可避な不純物からなることを特徴とする。
【選択図】図1
The present invention relates to a method for producing a steel wire used for a material for cold working, and more specifically, the strength of the material is greatly reduced even if the spheroidizing heat treatment is omitted in the state of the wire. The present invention relates to a steel wire material excellent in cold workability and hardenability, which can greatly increase the strength by subsequent quenching, and a method for producing the same.
The steel wire rod according to the present invention comprises C: 0.1 to 0.4 wt%, Si: 0.3 to 1.5 wt%, Mn: 0.3 to 1.7 wt%, P: 0 0.015 wt% or less, S: 0.015 wt% or less, Cr: 0.05 to 1.7 wt%, Al: 0.05 wt% or less, B: 0.001 to 0.005 wt%, Ti: It consists of 0.01 to 0.05% by weight, N: 0.015% by weight or less, the remainder Fe and other inevitable impurities.
[Selection] Figure 1

Description

本発明は、冷間加工用素材に用いられる鋼線材の製造方法に関するもので、より詳細には、線材状態で球状化熱処理を省略しても素材の強度が大幅に低く冷間加工が容易な反面、その後焼入れ処理により強度を大幅に上昇することができる冷間加工性及び焼入れ性に優れた鋼線材及びその製造方法に関するものである。   The present invention relates to a method of manufacturing a steel wire used for a material for cold working, and more specifically, the strength of the material is significantly low and cold working is easy even if the spheroidizing heat treatment is omitted in the wire state. On the other hand, the present invention relates to a steel wire rod excellent in cold workability and hardenability, which can greatly increase the strength by quenching, and a method for producing the same.
一般に、冷間加工は、熱間加工や切削加工に比べ生産性が高いため、ボルト、ナット、ネジ等の機械部品や自動車部品等を効率的に製造する方法として広く用いられている。   In general, since cold work has higher productivity than hot work or cutting, it is widely used as a method for efficiently producing machine parts such as bolts, nuts, and screws, automobile parts, and the like.
上記のような冷間加工は、特別な昇温過程や切削過程なく、素材にそのまま鍛造加工を行うものであるため、上記冷間加工に用いられる鋼素材は冷間加工に適合な物性を有することが求められる。即ち、低い外力によっても十分に変形することができるように素材の引張強度が低いことが求められ、また、冷間で深加工時にも素材が破壊されないよう延性に優れることが求められる。   Since the cold working as described above is forging the material as it is without any special heating process or cutting process, the steel material used for the cold working has physical properties suitable for cold working. Is required. That is, it is required that the material has a low tensile strength so that it can be sufficiently deformed even by a low external force, and that it is required to have excellent ductility so that the material is not broken even during cold deep processing.
しかし、冷間加工により生産される部品は上述のように、主にボルト、ナット、ネジ等の機械部品や自動車部品であるため、高い強度を有することが求められる。   However, as described above, parts produced by cold working are mainly machine parts such as bolts, nuts, and screws, and automobile parts, and thus are required to have high strength.
つまり、優れた冷間加工用素材は、冷間加工前には低い強度及び高い延性を有することが求められるが、最終製品では高い強度を有しなければならない。二つの性質は同時に満たすことができないものであるため、段階別に適切な処理をして、求められる物性を満たす必要がある。通常、冷間加工され最終製品の形状を有する部品は、強度を高めるために通常焼入れ過程を経る。焼入れにより部品の強度は上昇するようになるが、所望の強度規格を満たすために鋼材の内部には焼入れ性を高めることができる元素が適正水準含まれるようにする。   In other words, an excellent cold work material is required to have low strength and high ductility before cold work, but the final product must have high strength. Since the two properties cannot be satisfied at the same time, it is necessary to perform appropriate processing for each stage to satisfy the required physical properties. Usually, a cold-worked part having the shape of the final product undergoes a normal quenching process to increase strength. Although the strength of the parts increases by quenching, an element that can enhance the hardenability is contained in the steel material in order to satisfy a desired strength standard.
従来は、鋼の焼入れ性を向上させるために鋼材の内部に炭素を多量に含ませる方法を用いた。炭素は、代表的な焼入れ性向上元素で焼入れ熱処理により部品の強度は大幅向上するになる。   Conventionally, in order to improve the hardenability of steel, a method of containing a large amount of carbon inside the steel material has been used. Carbon is a typical hardenability-enhancing element, and the strength of parts is greatly improved by quenching heat treatment.
しかし、炭素が多量に含まれた鋼材は、焼入れ処理をしなくても硬度及び強度が高く冷間鍛造にそのまま用いるのには適切でないため、特別な処理が必要である。即ち、炭素が鋼材内部に固溶されている場合は、鋼材の固溶強化の原因となって鋼材の強度が上昇し、その結果冷間加工時、工具寿命を減少させる上、延性が足らず素材に亀裂が発生する等の問題が発生するようになる。   However, a steel material containing a large amount of carbon has a high hardness and strength and is not suitable for use in cold forging as it is without being subjected to a quenching treatment, and therefore requires special treatment. That is, when carbon is dissolved in the steel material, the strength of the steel material increases as a result of the solid solution strengthening of the steel material. As a result, the tool life is reduced during cold working and the material is not ductile. Problems such as cracks occur.
従って、上記炭素が多量に含まれた鋼材を冷間加工に用いる場合は、冷間加工時、炭素により加工性が減少することを防ぐために炭素を球状のセメンタイト形態で析出し、鋼の基地内部に炭素が固溶され固溶強化を起こすことを抑える工程が先行する必要がある。上記球状のセメンタイトを析出させる工程を球状化熱処理という。   Therefore, when using a steel material containing a large amount of carbon for cold working, carbon is precipitated in the form of spherical cementite in order to prevent the workability from being reduced by carbon during cold working. Therefore, it is necessary to precede the step of suppressing the solid solution of carbon and causing solid solution strengthening. The step of precipitating the spherical cementite is called spheroidizing heat treatment.
そのため、炭素が多量に含まれた鋼線材を用いて高強度の部品に加工するためには、球状化熱処理−冷間加工−焼入れ過程を経るようになり、最終的に鋼部品の靭性を向上させるために焼頓熱処理を行う場合もある。   Therefore, in order to process steel parts containing a large amount of carbon into high-strength parts, the process of spheroidizing heat treatment-cold working-quenching process is finally performed, and the toughness of steel parts is finally improved. In some cases, incineration heat treatment is performed.
しかし、上記球状化熱処理のためには数時間〜数十時間の熱処理時間がかかるため、生産性が低下する上、製造費用が上昇する問題が発生する可能性があるため、球状化熱処理はなるべく省略したほうが好ましい。   However, since the heat treatment time of several hours to several tens of hours is required for the spheroidizing heat treatment, there is a possibility that the productivity may be lowered and the manufacturing cost may be increased. It is preferable to omit it.
上記のような問題点を解決するために、特許文献1は重量%でB:0.0055%以下、Zr:0.035%以下のうち、少なくとも一方を含み、またN:0.0005〜0.0070%を含むと共に、B、Zr及びNが−0.001≦[N]−1.3[B]−0.15[Zr]≦0.0020を満たすことにより、フェライト結晶粒の微細化を抑制することを特徴とする室温又は加工発熱領域の変形抵抗の上昇が抑制される鋼線材の製造方法を提示している。   In order to solve the above problems, Patent Document 1 includes at least one of B: 0.0055% or less and Zr: 0.035% or less by weight%, and N: 0.0005-0. .0070% and B, Zr, and N satisfy −0.001 ≦ [N] −1.3 [B] −0.15 [Zr] ≦ 0.0020, so that the ferrite crystal grains can be refined. The present invention proposes a method for manufacturing a steel wire rod that suppresses an increase in deformation resistance in a room temperature or a heat generation region, which is characterized by suppressing the above.
この技術の場合、BやZrを添加して固溶C及び固溶Nを固定化しフェライト結晶粒の微細化を抑制して冷間加工時、変形抵抗の上昇を抑制することを特徴とする。しかし、球状化熱処理が省略された鋼材の冷間加工で最も重要なことは、冷間加工前の素材の引張強度であるが、この発明はこのような点を見過ごしているという問題を有している。即ち、冷間加工前、素材の引張強度が低いほど変形エネルギーが低くなり加工に有利になるが、フェライト結晶粒、微細化の抑制のみでは素材の強度を低下させるのに限界があり、その結果、球状化熱処理を実施せず、冷間加工するとき、工具寿命の低下や素材に亀裂が発生するという問題がある。   In the case of this technique, B or Zr is added to fix solute C and solute N, thereby suppressing the refinement of ferrite crystal grains and suppressing an increase in deformation resistance during cold working. However, the most important thing in the cold working of steel materials in which the spheroidizing heat treatment is omitted is the tensile strength of the material before the cold working, but this invention has a problem that this point is overlooked. ing. That is, before cold working, the lower the tensile strength of the material, the lower the deformation energy, which is advantageous for processing, but there is a limit to reducing the strength of the material only by suppressing ferrite crystal grains and refinement, and as a result When cold working without performing spheroidizing heat treatment, there is a problem that the tool life is reduced and cracks occur in the material.
日本特開2001−303189号Japanese Unexamined Patent Publication No. 2001-303189
本発明は、上記の問題を解消するためのもので、球状化熱処理を行わなくても十分に低い強度を有し冷間加工に有利である上、その後焼入れ処理時強度が大幅に向上することができる冷間加工性及び焼入れ性に優れた鋼線材及びこのような鋼線材を製造する方法を提供することをその目的とする。   The present invention is for solving the above-mentioned problems, and has a sufficiently low strength without performing a spheroidizing heat treatment, which is advantageous for cold working, and the strength during the subsequent quenching process is greatly improved. It is an object of the present invention to provide a steel wire rod excellent in cold workability and hardenability and a method for producing such a steel wire rod.
上記目的を達成するための本発明の鋼線材は、C:0.1〜0.4重量%、Si:0.3〜1.5重量%、Mn:0.3〜1.7重量%、P:0.015重量%以下、S:0.015重量%以下、Cr:0.05〜1.7重量%、Al:0.05重量%以下、B:0.001〜0.005重量%、Ti:0.01〜0.05重量%、N:0.015重量%以下、残部Fe及びその他不可避な不純物からなることを特徴とする。   In order to achieve the above object, the steel wire rod of the present invention includes C: 0.1 to 0.4% by weight, Si: 0.3 to 1.5% by weight, Mn: 0.3 to 1.7% by weight, P: 0.015 wt% or less, S: 0.015 wt% or less, Cr: 0.05 to 1.7 wt%, Al: 0.05 wt% or less, B: 0.001 to 0.005 wt% Ti: 0.01 to 0.05% by weight, N: 0.015% by weight or less, remaining Fe and other inevitable impurities.
このとき、上記TiとNの原子量比Ti/Nが1.39以上で、BとCrの重量基準含量比B/Crが0.04以下であることが好ましい。   At this time, it is preferable that the atomic weight ratio Ti / N of Ti and N is 1.39 or more and the weight-based content ratio B / Cr of B and Cr is 0.04 or less.
そして、上記鋼線材はフェライトとパーライトからなる内部組織を有することがよい。   The steel wire preferably has an internal structure made of ferrite and pearlite.
このとき、上記内部組織のうちフェライトの分率が50%以上であることが効果的である。   At this time, it is effective that the ferrite fraction in the internal structure is 50% or more.
また、上記内部組織のうちベイナイトとマルテンサイトの分率の和が0.5%以下であることが好ましい。   Moreover, it is preferable that the sum of the fraction of a bainite and a martensite is 0.5% or less among the said internal structures.
上記鋼線材の冷間加工性を確保するためには、関係式
TS(MPa)=258+959*[C]+112*[Si]+111*[Mn]+5*[Cr]+439*[Ti]−0.7*[フェライト分率]
で表される引張強度が590MPa以下であることがよい。
In order to ensure the cold workability of the steel wire rod, the relational expression TS (MPa) = 258 + 959 * [C] + 112 * [Si] + 111 * [Mn] + 5 * [Cr] + 439 * [Ti] -0. 7 * [Ferrite fraction]
It is preferable that the tensile strength represented by 590MPa or less.
上記の有利な効果を有する鋼線材を製造するための本発明の製造方法は、C:0.1〜0.4重量%、Si:0.3〜1.5重量%、Mn:0.3〜1.7重量%、P:0.015重量%以下、S:0.015重量%以下、Cr:0.05〜1.7重量%、Al:0.05重量%以下、B:0.001〜0.005重量%、Ti:0.01〜0.05重量%、N:0.015重量%以下、残部Fe及びその他不可避な不純物からなる鋼片を1000〜1100℃で加熱した後、圧延し、0.1〜5℃/secの冷却速度で500℃以下の温度まで冷却することを特徴とする。   The production method of the present invention for producing the steel wire having the above advantageous effects is as follows: C: 0.1 to 0.4% by weight, Si: 0.3 to 1.5% by weight, Mn: 0.3 1.7% by weight, P: 0.015% by weight or less, S: 0.015% by weight or less, Cr: 0.05-1.7% by weight, Al: 0.05% by weight or less, B: 0.005% or less. After heating a steel slab consisting of 001 to 0.005 wt%, Ti: 0.01 to 0.05 wt%, N: 0.015 wt% or less, the balance Fe and other inevitable impurities at 1000 to 1100 ° C, It rolls and it cools to the temperature of 500 degrees C or less with the cooling rate of 0.1-5 degrees C / sec.
そして、上記圧延時、仕上げ圧延終了温度は850℃以下であることがよい。   And at the time of the said rolling, it is good for finish rolling completion | finish temperature to be 850 degrees C or less.
また、上記TiとNの原子量比Ti/Nが1.39以上で、BとCrの重量基準含量比B/Crが0.04以下のとき、本発明の鋼線材の有利な効果を確保することに効果的である。 Moreover, when the atomic weight ratio Ti / N of Ti and N is 1.39 or more and the weight-based content ratio B / Cr of B and Cr is 0.04 or less, the advantageous effect of the steel wire rod of the present invention is ensured. It is particularly effective.
そして、上記製造された鋼線材は、関係式
TS(MPa)=258+959*[C]+112*[Si]+111*[Mn]+5*[Cr]+439*[Ti]−0.7*[フェライト分率]
で表される引張強度が590MPa以下であることが好ましい。
The manufactured steel wire has the following relation: TS (MPa) = 258 + 959 * [C] + 112 * [Si] + 111 * [Mn] + 5 * [Cr] + 439 * [Ti] −0.7 * [ferrite content rate]
It is preferable that the tensile strength represented by is 590 MPa or less.
上述のように、本発明による場合は、冷間加工のための熱処理工程を省略しても冷間圧組成に優れた鋼部品及びその製造方法を提供することができる。   As described above, according to the present invention, it is possible to provide a steel part excellent in cold pressure composition and a method for manufacturing the same even if the heat treatment step for cold working is omitted.
本発明により製造された鋼部品は、機械部品、自動車部品、建築構造用材料等高強度が求められる多様な分野に用いることができる。   The steel parts produced according to the present invention can be used in various fields where high strength is required, such as machine parts, automobile parts, and materials for building structures.
以下で、本発明を詳細に説明する。   The present invention is described in detail below.
本発明の発明者は、本発明の鋼線材を製造するに先立って、本発明で目的とする鋼線材の好ましい物性として引張強度が590MPa以下で、焼入れによる強度の上昇量が100MPa以上でなければならないことを把握し、上記のような条件を満たす鋼線材及びその製造方法を確立しようとした。   Prior to the production of the steel wire of the present invention, the inventor of the present invention should have a tensile strength of 590 MPa or less as a preferred physical property of the steel wire intended in the present invention and an increase in strength by quenching of 100 MPa or more. We tried to establish a steel wire that satisfies the above conditions and a method for manufacturing the same.
(鋼線材の組成)
本発明で提供する鋼線材は、冷間加工性及び焼入れ性の向上のため、以下で規定した範囲で各成分元素を含む必要がある。以下で説明する各成分元素の含量は、特別な表示がない限り、全て重量%を示すものである。本発明者らは、線材状態では球状化熱処理を行わなくても冷間鍛造性を高めるために、低い強度を有し、焼入れ焼き戻しされた後には、高い引張強度を有することができるようにするためには鋼材の焼入れ性が大きく向上されることができる組成を有することが重要であるということが分かった。
(Composition of steel wire)
The steel wire provided by the present invention needs to contain each component element in the range specified below in order to improve cold workability and hardenability. Unless otherwise indicated, the content of each component element described below indicates% by weight. In order to improve cold forgeability without performing spheroidizing heat treatment in the wire state, the present inventors have low strength and can have high tensile strength after quenching and tempering. In order to do so, it has been found that it is important to have a composition that can greatly improve the hardenability of the steel.
このため、図1にグラフで示したように、複数の主要元素を含む鋼成分系に対して焼入れ性の向上効果を確認するために880℃で加熱し油冷させる方式で、予備試験した結果、主要元素に、C−Si−Mn−Cr−Bが共に含まれている鋼成分界の焼入れ性が最もよいということが分かった。グラフに示された焼入れ性は、焼入れ前の線材の硬度対比焼入れ焼き戻しされた部品の硬度が何%上昇したかを示す指標である。   Therefore, as shown in the graph of FIG. 1, in order to confirm the effect of improving the hardenability with respect to the steel component system containing a plurality of main elements, the result of the preliminary test by heating at 880 ° C. and oil cooling. It has been found that the hardenability of the steel component boundary in which C—Si—Mn—Cr—B is contained in the main elements is the best. The hardenability shown in the graph is an index indicating how much the hardness of the part subjected to quenching and tempering has increased by the hardness of the wire before quenching.
C:0.1〜0.4重量%
炭素(C)が過多に添加されると、鋼の冷間加工性が減少するようになるため、適切な範囲で添加される必要がある。即ち、若し炭素含量が0.4重量%を超える場合は、パーライト分率が50%以上になり、冷間加工性を減少させる。逆に炭素含量が低すぎて0.1重量%未満の場合は焼入れ性が減少し最終製品の素材の強度や疲労強度等が悪化する。従って、炭素含量は0.1〜0.4重量%であることが好ましい。
C: 0.1 to 0.4% by weight
If carbon (C) is added excessively, the cold workability of steel will decrease, so it needs to be added in an appropriate range. That is, when the carbon content exceeds 0.4% by weight, the pearlite fraction becomes 50% or more, and the cold workability is reduced. On the other hand, if the carbon content is too low and less than 0.1% by weight, the hardenability is reduced, and the strength and fatigue strength of the material of the final product are deteriorated. Therefore, the carbon content is preferably 0.1 to 0.4% by weight.
Si:0.3〜1.5重量%
ケイ素(Si)は、通常、製鋼過程で脱酸を行う上、製品段階では製品強度を確保する役割をする。しかし、上記Siの含量が1.5重量%以上であれば、冷間加工時、変形抵抗を大きく増加させ、冷間圧組成を急激に落とすため好ましくなく、含量が0.3重量%以下になると、焼入れ焼き戻し処理後、最終製品で必要とする強度を得ることが困難である上、圧延後鋼材内部のフェライト分率が50%以上になることが困難であるため、ケイ素はその含量を0.3−1.5重量%に設定することが好ましい。
Si: 0.3 to 1.5% by weight
Silicon (Si) usually performs deoxidation in the steelmaking process, and plays a role of ensuring product strength at the product stage. However, if the Si content is 1.5% by weight or more, the deformation resistance is greatly increased during cold working, and the cold pressure composition is drastically dropped. Then, after quenching and tempering, it is difficult to obtain the strength required for the final product, and it is difficult for the ferrite fraction in the steel material after rolling to be 50% or more. It is preferable to set to 0.3 to 1.5% by weight.
Mn:0.3〜1.7重量%
マンガン(Mn)は鋼の焼入れ性を増加させ、衝撃靭性を低下させることなく鋼の強度を高める。添加量が0.3重量%以下であればこのような効果を得ることが困難で、添加量が1.7重量%以上になると、熱間圧延後、線材引張強度が過多に増加して冷間圧組成を減少させるため、マンガンの添加範囲は0.3−1.7重量%に制限することが好ましい。
Mn: 0.3 to 1.7% by weight
Manganese (Mn) increases the hardenability of the steel and increases the strength of the steel without reducing impact toughness. If the addition amount is 0.3% by weight or less, it is difficult to obtain such an effect. If the addition amount is 1.7% by weight or more, after hot rolling, the wire tensile strength increases excessively and the cooling is reduced. In order to reduce the intermediate pressure composition, the addition range of manganese is preferably limited to 0.3 to 1.7% by weight.
P:0.015重量%以下
リン(P)は粒界に偏析され鋼の靭性及び水素破壊抵抗性を落とすため、その含量を0.015重量%以下に制限することが好ましい。
P: 0.015% by weight or less Phosphorus (P) is segregated at grain boundaries and decreases the toughness and hydrogen fracture resistance of the steel. Therefore, the content is preferably limited to 0.015% by weight or less.
S:0.015重量%以下
硫黄(S)は粒界に偏析され鋼の靭性及び水素破壊抵抗性を減少させるため、その含量を0.015重量%以下に制限することが好ましい。
S: 0.015 wt% or less Sulfur (S) is segregated at the grain boundaries and decreases the toughness and hydrogen fracture resistance of the steel. Therefore, the content is preferably limited to 0.015 wt% or less.
Cr:0.05〜1.7重量%
クロム(Cr)は、鋼の焼入れ性を増加させ焼入れ処理後、安定的なマルテンサイト組織を得ることができるように、マルテンサイトの急激な軟化を抑制し鋼の強度を増加させる作用をする元素で、その含量が少ないとこのような効果を得ることが困難で、添加量が多いとその効果が飽和されるため、上記クロムの含量は0.05−1.7重量%に設定することが好ましい。
Cr: 0.05 to 1.7% by weight
Chromium (Cr) is an element that acts to increase the strength of steel by suppressing the rapid softening of martensite so that a stable martensite structure can be obtained after quenching by increasing the hardenability of steel. If the content is small, it is difficult to obtain such an effect. If the content is large, the effect is saturated. Therefore, the chromium content may be set to 0.05 to 1.7% by weight. preferable.
Al:0.05重量%以下
アルミニウム(Al)は、脱酸に有用な元素であるため、0.05%以下までは添加することができる。
Al: 0.05% by weight or less Aluminum (Al) is an element useful for deoxidation, so it can be added up to 0.05% or less.
B:0.001〜0.005重量%
ボロン(B)は少量の添加で焼入れ性を大幅に向上させる元素であるため、炭素量を減少させても、同じ鋼の中で焼入れ性を得ることができる。0.005重量%以上か、0.001重量%以下の添加の場合、焼入れ性が急激に落ちるため、上記ボロンの量は0.001〜0.005重量%に設定することが好ましい。
B: 0.001 to 0.005% by weight
Boron (B) is an element that greatly improves the hardenability when added in a small amount. Therefore, hardenability can be obtained in the same steel even if the carbon content is reduced. In the case of addition of 0.005% by weight or more or 0.001% by weight or less, the hardenability is drastically lowered. Therefore, the amount of boron is preferably set to 0.001 to 0.005% by weight.
Ti:0.01〜0.05重量%
チタニウム(Ti)は、窒素を固定させボロンの焼入れ性効果を確保するために必要な元素で焼入れ処理時、過熱するときオーステナイトの結晶粒成長を抑制し製品の疲労破綻を抑制することができる。このような効果を発揮させるためには少なくとも0.01重量%以上含ませる必要がある。また、0.05重量%を超える場合はTi系析出物及び固溶による線材強度の上昇及び冷間圧組成に問題が発生する。従って、チタニウムの含量は0.01〜0.05%が好ましい。
Ti: 0.01 to 0.05% by weight
Titanium (Ti) is an element necessary for fixing nitrogen and securing the hardenability effect of boron, and can suppress austenite crystal grain growth and suppress fatigue failure of the product when it is overheated during quenching. In order to exhibit such an effect, it is necessary to contain at least 0.01% by weight or more. On the other hand, when the content exceeds 0.05% by weight, a problem occurs in Ti-based precipitates and wire strength increase due to solid solution and cold pressure composition. Therefore, the titanium content is preferably 0.01 to 0.05%.
N:0.015重量%以下
窒素は、ボロンと反応しBNを形成しやすい元素である。従って、窒素の含量はなるべく低いことがよく、0.015重量%を超えて含まれると十分な焼入れ効果を得ることが困難である。
N: 0.015 wt% or less Nitrogen is an element that easily reacts with boron to form BN. Therefore, the nitrogen content should be as low as possible, and if it exceeds 0.015% by weight, it is difficult to obtain a sufficient quenching effect.
Ti/N:1.39以上(原子数比、以下省略)
上述のように、窒素はボロンと結合し有効ボロン量(Beff)を減少させて鋼線材の焼入れ性を害する元素であるため、なるべく少なく含まれることが好ましい。しかし、窒素は製鋼段階で容易に除去することができる元素ではないため、他の方法で窒素の活動度を減少させることが効果的である。即ち、窒素と親和力を有する元素にチタニウムを挙げることができるが、上記チタニウムが窒素と共に含まれている場合、TiN等を形成し窒素の活動度を減少させることができる。窒素の活動度が減少する場合、BNを形成させる駆動力が弱くなるため、結局、有効ボロン量が高くなり鋼線材の焼入れ性の向上に効果的である。上記のように窒素の活動度を減少させ有効ボロン量を増大させるためにはTi/Nの比率が1.39以上である必要がある。若し、Ti/Nが1.39未満の場合十分な窒素の固定効果が表れず焼入れ性の向上効果が十分でなくなるからである。
Ti / N: 1.39 or more (atomic ratio, omitted below)
As described above, nitrogen is an element that binds to boron and reduces the effective boron content (B eff ) to impair the hardenability of the steel wire, so it is preferably contained as little as possible. However, since nitrogen is not an element that can be easily removed in the steelmaking stage, it is effective to reduce the nitrogen activity by other methods. That is, titanium can be cited as an element having an affinity for nitrogen, but when the titanium is contained together with nitrogen, TiN or the like can be formed to reduce the activity of nitrogen. When the activity of nitrogen is reduced, the driving force for forming BN is weakened. As a result, the effective boron amount is increased, which is effective in improving the hardenability of the steel wire. As described above, in order to decrease the activity of nitrogen and increase the effective boron amount, the Ti / N ratio needs to be 1.39 or more. If Ti / N is less than 1.39, a sufficient nitrogen fixing effect does not appear and the effect of improving the hardenability becomes insufficient.
B/Cr:0.04以下(重量比、以下省略)
本発明の発明者らは、鋼線材の焼入れ性を高めるための因子に対して研究した結果、ボロンが単独で含まれている場合よりクロムと共に含まれている場合の方が、焼入れ性の向上効果が優れるということが分かった。上記のクロムとボロンの関係はB/Crの比で0.04以下であることが好ましい。
B / Cr: 0.04 or less (weight ratio, hereinafter omitted)
The inventors of the present invention have studied the factors for improving the hardenability of the steel wire, and as a result, the hardenability is improved when boron is included together with chromium rather than when it is included alone. It turns out that the effect is excellent. The relationship between chromium and boron is preferably 0.04 or less in terms of B / Cr ratio.
(組織)
本発明で対象とする鋼線材は、内部にフェライトが面積分率で50%以上含まれることが好ましい。即ち、若しフェライト以外の組織が50%以上含まれる場合は鋼材の強度が増加し加工性が悪化するためである。特に、マルテンサイトとベイナイトは面積分率の和が0.5%以下であることが好ましい。上記マルテンサイトとベイナイトのような硬質組織が鋼線材の段階で形成される場合、線材の加工性を著しく落とすためである。従って、本発明で提供される鋼線材の好ましい内部組織はフェライト、パーライト等を主に含む組織で、フェライトの面積比率が50%以上で、残りのパーライト等を含みマルテンサイトとベイナイトの面積比率の和は0.5%以下の組織である。
(Organization)
The steel wire material targeted by the present invention preferably contains 50% or more of ferrite in the area fraction. That is, if the structure other than ferrite is contained by 50% or more, the strength of the steel material increases and the workability deteriorates. In particular, martensite and bainite preferably have a sum of area fractions of 0.5% or less. This is because when a hard structure such as martensite and bainite is formed at the stage of the steel wire rod, the workability of the wire rod is remarkably lowered. Therefore, the preferred internal structure of the steel wire provided by the present invention is a structure mainly containing ferrite, pearlite, etc., and the area ratio of ferrite is 50% or more, and the area ratio of martensite and bainite including the remaining pearlite. The sum is an organization of 0.5% or less.
(製造方法)
上述したように、本発明で目的とする50%以上のフェライト及び0.5%以下のベイナイト+マルテンサイト、残りパーライトの微細組織を得るためには、以下のような線材の製造条件にしなければならい。鋼片の加熱温度は通常の線材の過熱温度で1000〜1100℃の範囲にし、仕上げ圧延温度は圧延中の素材のオーステナイトの結晶粒を微細化するために、最終圧延後、素材の温度が850℃以下で熱間圧延されなければならない。圧延された素材は、微細化された結晶粒からフェライトの核生成を促し、線材の冷却中、フェライト分率を増大させるために500℃まで0.1〜5℃/secで冷却する必要がある。
(Production method)
As described above, in order to obtain the microstructure of 50% or more of ferrite and 0.5% or less of bainite + martensite and the remaining pearlite as intended in the present invention, the production conditions for the wire must be as follows: Goodbye. The heating temperature of the steel slab is in the range of 1000 to 1100 ° C., which is the normal heating temperature of the wire, and the final rolling temperature is 850 after final rolling in order to refine the austenite crystal grains of the material being rolled. It must be hot rolled below ℃. The rolled material needs to be cooled to 500 ° C. at 0.1 to 5 ° C./sec in order to promote ferrite nucleation from the refined crystal grains and increase the ferrite fraction during cooling of the wire. .
鋼片再加熱温度:1000〜1100℃
鋼片の再加熱温度は1000〜1100℃範囲であることが好ましい。これは通常の線材加熱操業と同一条件である。
Billet reheating temperature: 1000-1100 ° C
The reheating temperature of the steel slab is preferably in the range of 1000 to 1100 ° C. This is the same condition as a normal wire heating operation.
線材の冷却速度:0.01〜5℃/sec
鋼片を線材形状で熱間圧延した後、冷却時の線材冷却速度は、0.01〜5℃/secであることが好ましい。即ち、上述したように本発明の鋼部品は冷間加工により製造されるもので、冷間加工前の線材強度が高すぎると変形抵抗が高くなり、ダイスの寿命が低下する等の問題が発生する可能性がある。従って、線材はなるべく徐々に除冷パターンで冷却することが好ましい。若し、線材冷却速度が5℃/sec以上の場合には上述したように線材の強度が高くなり冷間加工時不利で、冷却速度の下限を0.01℃/secに限定した理由は現実的にその以下の冷却速度で鋼材を冷却することが困難であるためである。
Wire cooling rate: 0.01 to 5 ° C./sec
After the steel slab is hot-rolled in the shape of a wire, the wire cooling rate during cooling is preferably 0.01 to 5 ° C./sec. That is, as described above, the steel parts of the present invention are manufactured by cold working, and if the wire strength before cold working is too high, the deformation resistance increases and the life of the die decreases. there's a possibility that. Therefore, it is preferable that the wire is gradually cooled by a cooling pattern as much as possible. If the wire cooling rate is 5 ° C./sec or more, the strength of the wire becomes high as described above, which is disadvantageous during cold working, and the reason why the lower limit of the cooling rate is limited to 0.01 ° C./sec is a reality. This is because it is difficult to cool the steel material at a lower cooling rate.
線材の冷却停止温度:500℃以下
線材を冷却する時500℃以下までは上記で限定した冷却速度で制御冷却を行わなければならない。線材の温度が500℃以下になると、これ以上内部組織の変化や強度上昇の要因がなく、続けて除冷条件を維持する場合、生産性が悪くなるため、制御冷却は500℃以下で停止する。
Cooling stop temperature of wire: 500 ° C. or less When cooling the wire, controlled cooling must be performed at a cooling rate limited to 500 ° C. or less. When the temperature of the wire becomes 500 ° C. or less, there is no further change in the internal structure or increase in strength, and if the cooling condition is continuously maintained, the productivity deteriorates, so the controlled cooling stops at 500 ° C. or less. .
上記のような線材の製造方法で線材の仕上げ圧延温度は850℃以下の温度で圧延することがより好ましい。仕上げ圧延温度を上記範囲に制限する理由は微細な結晶粒を得るためであり、850℃を超える温度で仕上げ圧延する場合は結晶粒が粗大化する。結晶粒が粗大である場合、その後冷却過程でフェライト核生成の場所が減少しフェライトの分率が増加し、また、マルテンサイトとベイナイトの分率が増加するため、好ましくない。   It is more preferable that the finish rolling temperature of the wire is rolled at a temperature of 850 ° C. or less in the method for producing a wire as described above. The reason for limiting the finish rolling temperature to the above range is to obtain fine crystal grains, and when the finish rolling is performed at a temperature exceeding 850 ° C., the crystal grains become coarse. When the crystal grains are coarse, the location of ferrite nucleation decreases in the subsequent cooling process, the ferrite fraction increases, and the martensite and bainite fractions increase.
上記の全ての条件で線材を製造する場合、引張強度が590MPa以下の線材を得ることができる。   When producing a wire under all the above conditions, a wire having a tensile strength of 590 MPa or less can be obtained.
(実施例)
以下、下記の実施例に基づき本発明をより具体的に説明する。但し、下記の実施例は本発明をより詳細に説明するためのもので、本発明の権利範囲を制限するためのものではない。
(Example)
Hereinafter, the present invention will be described more specifically based on the following examples. However, the following examples are for explaining the present invention in more detail, and are not intended to limit the scope of rights of the present invention.
表1は実施例と比較例の成分を示す。全ての場合、P、Sは製鋼作業時0.02重量%以下になるように管理して製造した。   Table 1 shows the components of Examples and Comparative Examples. In all cases, P and S were controlled and manufactured so as to be 0.02% by weight or less during the steelmaking operation.
上記表1中、実施例1乃至実施例7は、本発明で規定する条件を全て満たす組成を有しているものを示したものである。   In Table 1 above, Examples 1 to 7 show those having compositions that satisfy all of the conditions defined in the present invention.
しかし、比較例1の場合は、CとSi含量が規定値から外れ本発明で有利に添加するCr、B、Ti等を全く添加しない場合を示す。比較例2は、Ti含量が上限を超える場合を示し、比較例3と比較例5はSi含量が本発明の規定に達していない場合を示し、比較例4はSiとTi含量が本発明の規格から外れる場合を示す。そして、比較例6はCrが添加されていない場合を、比較例7はBとTiが添加されていない場合を示す。   However, in the case of Comparative Example 1, the C and Si contents deviate from the specified values, and the case where Cr, B, Ti, etc. that are advantageously added in the present invention are not added is shown. Comparative Example 2 shows the case where the Ti content exceeds the upper limit, Comparative Example 3 and Comparative Example 5 show the case where the Si content does not reach the provisions of the present invention, and Comparative Example 4 shows that the Si and Ti contents are Indicates a case that falls outside the standard. And the comparative example 6 shows the case where Cr is not added, and the comparative example 7 shows the case where B and Ti are not added.
上記表1の成分を有する素材から表2の条件で線材の製造をした。   Wires were produced from the materials having the components shown in Table 1 under the conditions shown in Table 2.
上記条件中、本発明の組成に該当しない比較例1乃至比較例6は全て本発明の製造方法で製造し組成上の効果を比較した。但し、比較例1は冷却停止温度を本発明で規定した500℃より高い温度にした場合で冷却停止温度の効果も比較した。   Under the above conditions, Comparative Examples 1 to 6 which do not correspond to the composition of the present invention were all manufactured by the manufacturing method of the present invention, and the effects on the composition were compared. However, Comparative Example 1 also compared the effect of the cooling stop temperature when the cooling stop temperature was set to a temperature higher than 500 ° C. defined in the present invention.
又、実施例中でも製造条件の影響を観察するために実施例4と実施例5は、仕上げ圧延温度が非常に高い場合について試験した結果を示した。   Moreover, in order to observe the influence of manufacturing conditions also in an Example, Example 4 and Example 5 showed the result tested about the case where finish rolling temperature is very high.
実施例1乃至実施例3及び実施例6と実施例7は、本発明で規定する条件を全て満たす製造方法を示したものである。   Examples 1 to 3 and Examples 6 and 7 show manufacturing methods that satisfy all of the conditions defined in the present invention.
上記条件で製造された線材に対して物性分析をした結果及び上記線材を用いて特別な球状化熱処理なく冷間鍛造してボルト形状に加工した後、焼入れ焼き戻しした結果を表3に示した。焼入れ条件と焼き戻し条件は本発明では特に限定されず、通常のボルト焼入れ、焼き戻し条件に合わせて実施すればよい。   Table 3 shows the results of physical property analysis on the wire manufactured under the above conditions and the results of quench forging and tempering after cold forging without special spheroidizing heat treatment using the wire and processing into a bolt shape. . Quenching conditions and tempering conditions are not particularly limited in the present invention, and may be carried out in accordance with normal bolt quenching and tempering conditions.
上記表3で分かるように、本発明で規定する組成と本発明の製造条件を全て満たす実施例1乃至実施例3及び実施例6と実施例7の場合は、フェライト分率が50%を超えてベイナイト+マルテンサイト分率が0.5%未満の組織を有する。このような場合、線材の引張強度は全て550MPa以下で、ダイス一つで製造可能なボルト数が99000回を上回るもので、特別な球状化熱処理なくそのまま冷間鍛造加工するのに適合な物性を有する。   As can be seen from Table 3 above, in the case of Examples 1 to 3 and Examples 6 and 7, which satisfy all of the composition defined in the present invention and the production conditions of the present invention, the ferrite fraction exceeds 50%. The bainite + martensite fraction has a structure of less than 0.5%. In such a case, the tensile strengths of the wires are all 550 MPa or less, and the number of bolts that can be manufactured with one die exceeds 99000 times, and the physical properties suitable for cold forging as it is without special spheroidizing heat treatment. Have.
しかし、本発明の組成を満たしても線材の仕上げ圧延温度が高かった実施例4及び実施例5の場合は粗大な結晶粒によりフェライトの分率が減少しベイナイト+マルテンサイトの分率が増加し冷間鍛造性が減少する問題点を見せた。   However, in the case of Example 4 and Example 5 in which the finish rolling temperature of the wire was high even if the composition of the present invention was satisfied, the fraction of ferrite decreased due to coarse crystal grains, and the fraction of bainite + martensite increased. It showed the problem that cold forgeability decreased.
そして、本発明の組成を満たさない比較例1乃至比較例7の場合は本発明で規定する全ての製造条件に従い製造されたが、内部にマルテンサイトとベイナイトが多量に形成されている上、線材の強度が600MPa以上に高いため、そのまま冷間鍛造を実施することが困難であるということが分かる。また、これらを用いて冷間加工する時、ダイスの寿命も著しく減少するということが分かりその後焼入れ焼き戻し後の強度の上昇量もそれ程高くないことが分かる。   And in the case of the comparative example 1 thru | or the comparative example 7 which does not satisfy | fill the composition of this invention, although it manufactured according to all the manufacturing conditions prescribed | regulated by this invention, a martensite and a bainite are formed in large quantities inside, and a wire rod It can be seen that it is difficult to carry out cold forging as it is because the strength of is higher than 600 MPa. Further, when cold working using these, it is found that the life of the die is remarkably reduced, and it is understood that the increase in strength after quenching and tempering is not so high.
上記結果を総合すると、フェライト分率が増加する程、そしてマルテンサイトとベイナイトの分率和が減少する程、線材の冷間圧組成が増加することが分かる。冷間圧組成を確保することができる適切なフェライト分率は50%以上、ベイナイトとマルテンサイトの分率和は0.5%以上であることが確認できた。   From the above results, it can be seen that the cold pressure composition of the wire increases as the ferrite fraction increases and as the sum of the fractions of martensite and bainite decreases. It was confirmed that the proper ferrite fraction capable of securing the cold pressure composition was 50% or more, and the sum of the fractions of bainite and martensite was 0.5% or more.
図2に本発明により製造された実施例1と通常冷間鍛造用鋼に開発された鋼で球状化熱処理を経た後、冷間鍛造に用いられるSWRCH45という規格の鋼のダイスの寿命を比較した結果をグラフに示した。グラフで分かるように球状化熱処理を実施した鋼に比べ本発明により製造された実施例1の結果は、略同等な水準と示され、これにより本発明の鋼線材及びその製造方法が優れていることが確認できた。   FIG. 2 compares the life of dies of a standard steel called SWRCH45 used for cold forging after spheroidizing heat treatment in Example 1 manufactured according to the present invention and steel developed for normal cold forging. The results are shown in the graph. As can be seen from the graph, the result of Example 1 manufactured according to the present invention compared to the steel subjected to the spheroidizing heat treatment is shown to be substantially the same level, and thus the steel wire of the present invention and the manufacturing method thereof are excellent. I was able to confirm.
また、図1に各組成の影響を観察するために設計成分系別焼入れ性を比較した結果を示した。図1のC−Mnは比較例1、C−Mn−Bは比較例6、C−Mn−Crは比較例7、そしてC−Mn−Cr−Bは実施例2を夫々示す。図1で分かるように、実施例2の場合が焼入れ性が最も優れていることが分かる。   Moreover, in order to observe the influence of each composition in FIG. 1, the result of having compared the hardenability according to design component system was shown. In FIG. 1, C-Mn represents Comparative Example 1, C-Mn-B represents Comparative Example 6, C-Mn-Cr represents Comparative Example 7, and C-Mn-Cr-B represents Example 2. As can be seen from FIG. 1, it can be seen that the hardenability is the best in Example 2.
本発明者らは、上記結果を綜合して線材の引張強度と鋼組成の影響を観察した結果、下記の関係式のような回帰式を得ることができた。   As a result of observing the influence of the tensile strength of the wire and the steel composition by combining the above results, the present inventors were able to obtain a regression equation such as the following relational expression.
TS(MPa)=258+959*[C]+112*[Si]+111*[Mn]+5*[Cr]+439*[Ti]−0.7*[フェライト分率]   TS (MPa) = 258 + 959 * [C] + 112 * [Si] + 111 * [Mn] + 5 * [Cr] + 439 * [Ti] −0.7 * [ferrite fraction]
上記の回帰式を利用する場合、線材の段階における引張強度をある程度は予め予測することができるので、これに合わせて組成と製造方法を予め選び線材の製造に用いることができる。従って、本発明で目的とする590MPa以下の線材の製造に効果的である。上記回帰式からみて、線材の引張強度を低めるためにはC、Si、Mn、Cr、Ti等の含量を制限する必要がある。しかし、このような元素を制限する場合、焼入れ性が確保されないため、ボルト加工後の強度確保が難しいという矛盾が発生する。このような問題を解決するために、本発明で選んだ元素がBで、この元素は線材の引張強度を上昇させず、ボルトの強度確保に有用な元素である。   When the above regression equation is used, the tensile strength at the wire stage can be predicted to some extent in advance, so that the composition and the production method can be selected in advance and used for the production of the wire. Therefore, it is effective for producing a wire material of 590 MPa or less, which is the object of the present invention. From the above regression equation, it is necessary to limit the contents of C, Si, Mn, Cr, Ti, etc. in order to reduce the tensile strength of the wire. However, when such elements are limited, the hardenability is not ensured, and thus there is a contradiction that it is difficult to ensure the strength after bolt processing. In order to solve such a problem, the element selected in the present invention is B, and this element does not increase the tensile strength of the wire and is a useful element for securing the strength of the bolt.
発明鋼と従来鋼の冷間ダイスの寿命を比較した結果を示したグラフである。It is the graph which showed the result of having compared the life of the cold die of invention steel and conventional steel. 発明鋼と比較鋼の焼入れ性を比較した結果を示したグラフである。It is the graph which showed the result of having compared the hardenability of invention steel and comparative steel.

Claims (10)

  1. C:0.1〜0.4重量%、Si:0.3〜1.5重量%、Mn:0.3〜1.7重量%、P:0.015重量%以下、S:0.015重量%以下、Cr:0.05〜1.7重量%、Al:0.05重量%以下、B:0.001〜0.005重量%、Ti:0.01〜0.05重量%、N:0.015重量%以下、残部Fe及びその他不可避な不純物からなることを特徴とする冷間加工性及び焼入れ性に優れた鋼線材。   C: 0.1 to 0.4 wt%, Si: 0.3 to 1.5 wt%, Mn: 0.3 to 1.7 wt%, P: 0.015 wt% or less, S: 0.015 % By weight, Cr: 0.05 to 1.7% by weight, Al: 0.05% by weight or less, B: 0.001 to 0.005% by weight, Ti: 0.01 to 0.05% by weight, N : A steel wire excellent in cold workability and hardenability, characterized by comprising 0.015% by weight or less, the balance Fe and other inevitable impurities.
  2. 前記TiとNの原子量比Ti/Nが1.39以上で、BとCrの重量基準含量比B/Crが0.04以下であることを特徴とする請求項1に記載の冷間加工性及び焼入れ性に優れた鋼線材。   2. The cold workability according to claim 1, wherein the atomic weight ratio Ti / N of Ti and N is 1.39 or more and the weight-based content ratio B / Cr of B and Cr is 0.04 or less. Steel wire rod with excellent hardenability.
  3. フェライトとパーライトからなる内部組織を有することを特徴とする請求項1または請求項2に記載の冷間加工性及び焼入れ性に優れた鋼線材。   The steel wire rod excellent in cold workability and hardenability according to claim 1 or 2, wherein the steel wire rod has an internal structure composed of ferrite and pearlite.
  4. 前記内部組織のうちフェライトの分率が50%以上であることを特徴とする請求項3に記載の冷間加工性及び焼入れ性に優れた鋼線材。   The steel wire rod excellent in cold workability and hardenability according to claim 3, wherein a fraction of ferrite in the internal structure is 50% or more.
  5. 前記内部組織のうちベイナイトとマルテンサイトの分率の和が0.5%以下であることを特徴とする請求項4に記載の冷間加工性及び焼入れ性に優れた鋼線材。   The steel wire rod excellent in cold workability and hardenability according to claim 4, wherein the sum of the fraction of bainite and martensite in the internal structure is 0.5% or less.
  6. 関係式
    TS(MPa)=258+959*[C]+112*[Si]+111*[Mn]+5*[Cr]+439*[Ti]−0.7*[フェライト分率]
    で表される引張強度が590MPa以下であることを特徴とする請求項5に記載の冷間加工性及び焼入れ性に優れた鋼線材。
    Relational expression TS (MPa) = 258 + 959 * [C] + 112 * [Si] + 111 * [Mn] + 5 * [Cr] + 439 * [Ti] −0.7 * [ferrite fraction]
    The steel wire rod excellent in cold workability and hardenability according to claim 5, wherein the tensile strength represented by the formula (1) is 590 MPa or less.
  7. C:0.1〜0.4重量%、Si:0.3〜1.5重量%、Mn:0.3〜1.7重量%、P:0.015重量%以下、S:0.015重量%以下、Cr:0.05〜1.7重量%、Al:0.05重量%以下、B:0.001〜0.005重量%、Ti:0.01〜0.05重量%、N:0.015重量%以下、残部Fe及びその他不可避な不純物からなる鋼片を1000〜1100℃で加熱した後、圧延し、0.1〜5℃/secの冷却速度で500℃以下の温度まで冷却することを特徴とする冷間加工性及び焼入れ性に優れた鋼線材の製造方法。   C: 0.1 to 0.4 wt%, Si: 0.3 to 1.5 wt%, Mn: 0.3 to 1.7 wt%, P: 0.015 wt% or less, S: 0.015 % By weight, Cr: 0.05 to 1.7% by weight, Al: 0.05% by weight or less, B: 0.001 to 0.005% by weight, Ti: 0.01 to 0.05% by weight, N : A steel slab composed of 0.015% by weight or less, the balance Fe and other inevitable impurities is heated at 1000 to 1100 ° C., and then rolled, to a temperature of 500 ° C. or less at a cooling rate of 0.1 to 5 ° C./sec A method for producing a steel wire excellent in cold workability and hardenability characterized by cooling.
  8. 前記圧延時、仕上げ圧延終了温度は850℃以下であることを特徴とする請求項7に記載の冷間加工性及び焼入れ性に優れた鋼線材の製造方法。   The method for producing a steel wire excellent in cold workability and hardenability according to claim 7, wherein the finish rolling finish temperature is 850 ° C. or lower during the rolling.
  9. 前記TiとNの原子量比Ti/Nが1.39以上で、BとCrの重量基準含量比B/Crが0.04以下であることを特徴とする請求項7または請求項8に記載の冷間加工性及び焼入れ性に優れた鋼線材の製造方法。   9. The atomic weight ratio Ti / N of Ti and N is 1.39 or more, and the weight-based content ratio B / Cr of B and Cr is 0.04 or less. A method for producing a steel wire rod excellent in cold workability and hardenability.
  10. 前記製造された鋼線材は、関係式
    TS(MPa)=258+959*[C]+112*[Si]+111*[Mn]+5*[Cr]+439*[Ti]−0.7*[フェライト分率]
    で表される引張強度が590MPa以下であることを特徴とする請求項7または請求項8に記載の冷間加工性及び焼入れ性に優れた鋼線材の製造方法。

    The manufactured steel wire has a relational expression TS (MPa) = 258 + 959 * [C] + 112 * [Si] + 111 * [Mn] + 5 * [Cr] + 439 * [Ti] −0.7 * [ferrite fraction]
    The manufacturing method of the steel wire material excellent in cold workability and hardenability of Claim 7 or Claim 8 characterized by the above-mentioned.

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KR20200063384A (en) * 2018-11-27 2020-06-05 주식회사 포스코 Steel wire rod having excellent spheroidizing heat treatment properties and method of manufacturing the same
KR102131529B1 (en) * 2018-11-27 2020-07-08 주식회사 포스코 Steel wire rod having excellent spheroidizing heat treatment properties and method of manufacturing the same
KR102131530B1 (en) * 2018-11-27 2020-07-08 주식회사 포스코 Steel wire rod having excellent spheroidizing heat treatment properties and method of manufacturing the same

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WO2007074986A1 (en) 2007-07-05
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