JP2006312771A - Wire rod superior in cold forgeability and manufacturing method therefor - Google Patents
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Abstract
Description
本発明は、冷間鍛造に供する鋼材（線材）に関するものであり、特に鍛造中の温度上昇による時効硬化が少なく鍛造性に優れた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 steel material (wire material) to be subjected to cold forging, and particularly to a wire material that has little age hardening due to a temperature rise during forging and excellent forgeability and a method for producing the same.
最近の冷間鍛造機の加工速度の高速化に伴い、鍛造ダイの長寿命化が冷間鍛造性に関して重要な要素とされている。鍛造ダイの長寿命化には冷間鍛造加工時の時効を抑制することが必要とされており、従来、時効を抑制するために、例えば、特許文献１に開示されているように、Ｎ及びＣを固定して鋼材の時効化を抑制するためのＴｉを０．１％程度添加した線材などを供することが提案されている。
しかし、上記鋼材（線材）は延性が優れているため、伸び易く剪断加工時に容易に剪断されず、破断面にばりが生成するなどの問題が生じ、その結果、成型加工された製品形状に不具合が生じるなどの問題点を有していた。 However, because the above steel (wire) is excellent in ductility, it is easy to stretch and is not easily sheared during shearing, resulting in problems such as flashing on the fracture surface, resulting in defects in the shape of the molded product. There was a problem such as.
また、前記ばりの生成を解決するためにＳを添加することが有効とされているが、ＴｉとＳは化合し易く容易にＴｉＳとなるため、時効の抑制に有効なＴｉ量が減少し、時効の抑制を効率よく行うことができないという問題が生じていた。この問題を解決するために、Ｔｉを多量に添加する必要が生じ、益々、コストが高くなるとの問題があった。また、Ｔｉを大量に使用すると、化成処理性の変化、例えば燐酸亜鉛処理の場合、被覆の厚みの低下、結晶成長の抑制による、冷間鍛造前の伸線加工時における伸線潤滑剤のキャリア効果の低下などが生じるという問題を抱えていた。 In addition, it is effective to add S to solve the generation of the flash, but Ti and S are easily combined and become TiS easily, so the amount of Ti effective for suppressing aging is reduced, There has been a problem that aging cannot be efficiently controlled. In order to solve this problem, it is necessary to add a large amount of Ti, and there is a problem that the cost becomes higher. Also, when Ti is used in large quantities, the carrier of the wire drawing lubricant during wire drawing before cold forging due to a change in chemical conversion treatment, for example, in the case of zinc phosphate treatment, by reducing the coating thickness and suppressing crystal growth It had a problem that the effect was reduced.
本願発明は、今後の省資源化の動向に伴い、工具寿命の延長および成形不良による歩留まり低下の改善を図るため、優れた冷間鍛造性を有する鋼材とその製造方法を提供することを目的とするものであり、鋼の成分の最適化とそれに適応した製造方法により前記問題点を解決するものである。 The invention of the present application aims to provide a steel material having excellent cold forgeability and a method for producing the same in order to improve the yield reduction due to the extension of the tool life and the molding failure in accordance with the trend of resource saving in the future. Therefore, the above-mentioned problems are solved by optimizing the components of the steel and manufacturing methods adapted thereto.
本発明者らは、上記課題を解決すべく、Ｓとの親和性が小さく、ＣやＮとの親和性が高いＮｂをＴｉの換わりに鋼に添加すれば、ＳとＮｂとの化合を防止して成型不良による歩留まり低下を改善することができるばかりでなく、Ｎｂによる固溶Ｃ及びＮの固定によって時効抑制を図ることが可能となり、結果として工具寿命を延長させて、冷間鍛造性をより向上させることができるのではないかと考えた。そこで、本発明者らは、Ｔｉの換わりにＮｂを用い、Ｃ、Ｓｉ、Ｍｎ、Ｐ、Ｓ、Ｎｂ、Ｎ等の元素の量が異なる様々な鋼を線材圧延し、その後、任意の温度範囲で巻き取った後、任意の温度で恒温変態処理を行い、得られた線材の時効特性（時効指数）を調べた。その結果、鋼材の時効を効率よく抑制させるためには、Ｔｉの換わりにＮｂを単に添加するだけでは不十分であり、ＮｂとＣ＋Ｎとの質量比が７以上必要であることを見出した。また、その後の調査により、時効抑制効果が優れていた鋼材（特に線材）の組織の９０％以上が擬似パーライトであることがわかった。このことから、優れた時効抑制効果を得るためには、例えば、鋼材（特に線材）を所定の温度範囲内で恒温変態処理等を施して、鋼材の組織の９０％以上を擬似パーライトにすることが必要であることが示された。このようにして、本発明者らは本発明を完成するに至った。 In order to solve the above-mentioned problems, the present inventors can prevent the combination of S and Nb by adding Nb having a low affinity with S and a high affinity with C or N to steel instead of Ti. In addition to improving yield reduction due to molding defects, it is possible to suppress aging by fixing solute C and N with Nb, resulting in extended tool life and cold forgeability. I thought it could be improved. Therefore, the present inventors use Nb instead of Ti, wire-roll various steels having different amounts of elements such as C, Si, Mn, P, S, Nb, and N, and then, in an arbitrary temperature range. After being wound at, a constant temperature transformation treatment was performed at an arbitrary temperature, and the aging characteristics (aging index) of the obtained wire were examined. As a result, in order to efficiently suppress the aging of the steel material, it has been found that it is not sufficient to simply add Nb instead of Ti, and a mass ratio of Nb and C + N of 7 or more is necessary. Further, it was found from the subsequent investigation that 90% or more of the structure of the steel material (particularly, wire) that was excellent in the effect of suppressing aging was pseudo pearlite. From this, in order to obtain an excellent effect of suppressing aging, for example, a steel material (particularly a wire) is subjected to a constant temperature transformation treatment within a predetermined temperature range, and 90% or more of the structure of the steel material is made to be pseudo pearlite. Was shown to be necessary. Thus, the present inventors have completed the present invention.
すなわち、本願発明の要旨は、以下のとおりである。
1) 質量％で、
Ｃ：０．０６％以下，
Ｓｉ：０．４０％以下，
Ｍｎ：０．１０〜０．６％，
Ｐ：０．０１０％以下，
Ｓ：０．００８〜０．０２０％以下，
Ｎｂ：０．０６〜１．１０％，
残部が鉄及び不可避的不純物からなり、かつ、
Ｎを、質量％でＮｂ／(Ｃ＋Ｎ)≧７を満足する範囲内で含む鋼からなり、
組織が擬似パーライト≧９０％であることを特徴とする冷間鍛造性に優れた線材。
That is, the gist of the present invention is as follows.
1)% by mass
C: 0.06% or less,
Si: 0.40% or less,
Mn: 0.10 to 0.6%,
P: 0.010% or less,
S: 0.008 to 0.020% or less,
Nb: 0.06 to 1.10%,
The balance consists of iron and inevitable impurities, and
Made of steel containing N in a range satisfying Nb / (C + N) ≧ 7 by mass%,
A wire rod excellent in cold forgeability, characterized in that the structure is pseudo pearlite ≧ 90%.
2) 前記鋼が、更に質量％で、
Ｂ：０．００１〜０．０１０％
Ｖ：０．００８〜０．０３０％
を含有することを特徴とする1)に記載の冷間鍛造性に優れた線材。
2) The steel is further mass%,
B: 0.001 to 0.010%
V: 0.008 to 0.030%
1. A wire rod having excellent cold forgeability as described in 1), which comprises
3) 1)乃至2)に記載の鋼を線材圧延し、
８５０℃〜９００℃の温度で巻き取った後５００〜５５０℃の温度で恒温変態させることを特徴とする冷間鍛造性に優れた線材の製造方法。
3) Wire-rolling the steel described in 1) to 2),
A method for producing a wire material excellent in cold forgeability, characterized by being wound at a temperature of 850 ° C to 900 ° C and then isothermally transformed at a temperature of 500 to 550 ° C.
本発明は、Ｔｉに換えてＣ及びＮとの親和力が強く、且つ、Ｓとの親和力が小さいＮｂ元素を適正に用いることにより時効を抑制し工具寿命の延長を図ることが可能となる。更に、切断時の切り離れ性を高めるためのＳが有効に作用するために、成形不良も低減可能となり冷間鍛造性の向上という顕著な効果を示す。また、本発明によれば省資源化が可能となる。 In the present invention, it is possible to suppress the aging and to extend the tool life by appropriately using Nb element having a strong affinity with C and N instead of Ti and having a small affinity with S. Furthermore, since S for improving the detachability at the time of cutting acts effectively, it is possible to reduce molding defects and to show a remarkable effect of improving the cold forgeability. Further, according to the present invention, it is possible to save resources.
まず、本発明の鋼成分の質量％の範囲の限定理由について以下に述べる。 First, the reason for limiting the mass% range of the steel component of the present invention will be described below.
Ｃ：０．０６％以下
Ｃは鋼の強度を高めるために必要な元素であるが、その含有量が高いと冷間鍛造時の加工硬化が大きくなり、冷間鍛造性が低下するばかりか、伸線時の加工性も低下する。また、Ｃ含有量が大きいと、Ｎｂもそれに見合うだけの量を添加する必要があり経済的に不利となるため、Ｃ量の上限を０．０６％とした。
C: 0.06% or less C is an element necessary for increasing the strength of steel, but if its content is high, work hardening at the time of cold forging increases, and cold forgeability decreases, The workability during wire drawing also decreases. Further, if the C content is large, Nb also needs to be added in an amount commensurate with it, and this is economically disadvantageous, so the upper limit of the C content is set to 0.06%.
Ｓｉ：０．４０％以下
Ｓｉは固溶硬化により鋼の強度を高めるために有効な元素である。しかし、その反面、Ｓｉ含有量が多すぎると強度上昇による変形抵抗が増加し、かえって加工性を損なうこととなるため、Ｓｉ量の上限を０．４０％とした。
Si: 0.40% or less Si is an effective element for increasing the strength of steel by solid solution hardening. However, on the other hand, if the Si content is too large, the deformation resistance due to the increase in strength increases and the workability is deteriorated. Therefore, the upper limit of the Si content is set to 0.40%.
Ｍｎ：０．１０〜０．６％
Ｍｎは脱酸元素として有効で、Ｍｎが少ないと十分に脱酸を行うことができず鋳造段階で気泡性の欠陥が生じ、線材圧延後の表面疵が多発する。そこで、本発明においては、Ｍｎ量の下限を０．１０％とした。また、Ｍｎは鋼の強度を高める元素としても有効であるが、Ｍｎ含有量が多すぎると過度の強度上昇により加工性を劣化させるため、Ｍｎ量の上限を０．６０％とした。
Mn: 0.10 to 0.6%
Mn is effective as a deoxidizing element, and if Mn is small, deoxidation cannot be performed sufficiently, resulting in bubble defects at the casting stage, and surface defects after wire rod rolling occur frequently. Therefore, in the present invention, the lower limit of the amount of Mn is set to 0.10%. Mn is also effective as an element for increasing the strength of steel. However, if the Mn content is too large, the workability is deteriorated due to an excessive increase in strength, so the upper limit of the Mn content is set to 0.60%.
Ｐ：０．０１０％以下
Ｐは鋼材の延性を劣化させるので、本発明のように細径まで伸線するような場合、Ｐ含有量を低減させる必要がある。また、Ｐは偏析を生じ易い元素である。そこで、本発明においては、Ｐ量の上限を０．０１０％とした。
P: 0.010% or less Since P deteriorates the ductility of the steel material, it is necessary to reduce the P content when drawing to a small diameter as in the present invention. P is an element that easily causes segregation. Therefore, in the present invention, the upper limit of the P amount is set to 0.010%.
Ｓ：０．００８〜０．０２０％以下
Ｓは切断時のばりの生成を防止するために必要な元素であるが、その含有量が多すぎるとかえって加工性の低下をもたらすこととなる。そこで、本発明においては、Ｓ量の上限を０．０２０％とした。しかしながら、Ｓ含有量が少なすぎると切断時のばりが発生し易くなったりメカニカルデスケーリング性が劣化するなどの不具合が生じるため、Ｓ量の下限を０．００８％とした。
S: 0.008 to 0.020% or less S is an element necessary for preventing the generation of flash during cutting. However, if the content is too large, the workability is deteriorated. Therefore, in the present invention, the upper limit of the amount of S is set to 0.020%. However, if the S content is too small, defects such as the occurrence of flash during cutting and mechanical descaling properties are deteriorated, so the lower limit of the S content is set to 0.008%.
Ｎｂ：０．０６〜１．１０％
Ｎｂは窒化物、炭化物形成元素であり、固溶ＣやＮの固定を行って時効を抑制させるために有効な元素である。また、ＮｂはＴｉと異なり硫化物形成能が極めて弱いため、切断性能を高めるためにＳ添加を行ってもＮｂはＳと結合せずＣやＮと結合するため効率よく時効の抑制が可能である。そこで、本発明においては、Ｎｂを０．０６％以上添加することとした。しかしながら、Ｎｂを過剰に添加しても、時効抑制効果が飽和して経済的に不利となるため、Ｎｂ量の上限を１．１０％にした。
Nb: 0.06 to 1.10%
Nb is a nitride and carbide forming element, and is an element effective for fixing solute C and N to suppress aging. In addition, unlike Ti, Nb has a very low ability to form sulfides, so even if S is added to improve cutting performance, Nb does not bind to S but binds to C or N, so that aging can be suppressed efficiently. is there. Therefore, in the present invention, 0.06% or more of Nb is added. However, even if Nb is added excessively, the effect of suppressing aging is saturated and it is economically disadvantageous, so the upper limit of the Nb content is set to 1.10%.
Ｎ：Ｎｂ／(Ｃ＋Ｎ)≧７を満足する範囲内
上述のように、本発明者らの基本的かつ系統的な検討の結果、鋼材の時効硬化を効率よく抑制させるためには、ＮｂとＣ＋Ｎとの質量比が７以上有することが必要であることが明らかになった。従って、本発明においては、Ｎ量をＮｂ量及びＣ量との関係において調節することとした。ここで、ＮｂとＣ＋Ｎとの質量比を７以上としたのは、本実施例により、ＮｂとＣ＋Ｎとの質量比が７以上である場合に時効特性（時効指数）が０．５kgf/mm2以下となり、充分な時効抑制効果を発現できるためである。また、ＮｂとＣ＋Ｎとの質量比の上限は経済的な理由により必然的に決まるので特に設けないこととするが、省資源化の観点から１０程度以下であることが好ましい。なお、上記時効指数（Aging Index）は、図２に示すように、引張試験機で１２％の予歪みを付与した後に１００℃×１時間の人工時効処理を行い、除荷重前の応力と時効後の応力との差を算出することによって求めた。
N: Within a range satisfying Nb / (C + N) ≧ 7 As described above, as a result of basic and systematic studies by the present inventors, in order to efficiently suppress the age hardening of steel materials, Nb and C + N It became clear that it is necessary to have a mass ratio of 7 or more. Therefore, in the present invention, the N amount is adjusted in relation to the Nb amount and the C amount. Here, the mass ratio between Nb and C + N was set to 7 or more according to this example, when the mass ratio between Nb and C + N was 7 or more, the aging characteristic (aging index) was 0.5 kgf / mm 2. This is because the following effects can be obtained and sufficient aging suppression effects can be expressed. The upper limit of the mass ratio of Nb and C + N is inevitably determined for economic reasons and is not particularly provided, but is preferably about 10 or less from the viewpoint of resource saving. As shown in FIG. 2, the above aging index (Aging Index) is obtained by applying an artificial aging treatment of 100 ° C. × 1 hour after applying a pre-strain of 12% with a tensile tester to determine the stress and aging before unloading. It calculated | required by calculating the difference with later stress.
なお、本発明においては、上記の元素以外に必要に応じてＢ、Ｖ等を鋼にさらに添加することとしてもよい。これにより、Ｎｂの添加量を減少させても本願発明の効果を発揮させることができると考えられるからである。これにより、Ｎｂ量を削減することができるので、省資源化を図ることが可能となる。 In addition, in this invention, it is good also as adding B, V, etc. to steel further as needed other than said element. This is because it is considered that the effect of the present invention can be exhibited even if the amount of Nb added is reduced. Thereby, since the amount of Nb can be reduced, resource saving can be achieved.
Ｂ：０．００１〜０．０１０％
Ｂは固溶Ｃ及びＮを固定する作用を有することから、Ｎｂ量を減少させてもＢを添加することにより時効を抑制させることができると考えられる。従って、ＣおよびＮを固定する効果が現れる０．００１％をＢ量の下限とした。しかしながら、Ｂの添加量が多すぎると粒界脆化を生じさせるため、Ｂ量の上限を０．０１０％とした。
B: 0.001 to 0.010%
Since B has an action of fixing solute C and N, it is considered that aging can be suppressed by adding B even if the amount of Nb is decreased. Therefore, 0.001% where the effect of fixing C and N appears is taken as the lower limit of the B amount. However, if the amount of B added is too large, grain boundary embrittlement occurs, so the upper limit of the amount of B is set to 0.010%.
Ｖ：０．００８〜０．０３０％
ＶもＢと同様に、固溶Ｃ及びＮを固定する作用を有することから、Ｎｂ量を減少させてもＶを添加することにより時効を抑制させることができると考えられる。従って、ＣおよびＮを固定する効果が期待できる０．００８％をＶ量の下限とした。しかしながら、Ｖの添加量が多すぎると引張強度を上昇させ、かえって冷間鍛造性を悪化させるため、Ｖ量の上限を０．０３０％とした。
V: 0.008 to 0.030%
V, like B, has the effect of fixing solute C and N, so it is considered that aging can be suppressed by adding V even if the amount of Nb is decreased. Therefore, 0.008% at which the effect of fixing C and N can be expected is taken as the lower limit of the V amount. However, if the addition amount of V is too large, the tensile strength is increased and the cold forgeability is deteriorated. Therefore, the upper limit of the V amount is set to 0.030%.
次に、本発明の鋼材（例えば、線材）が、９０％以上の擬似パーライト組織を有することを条件とした理由について説明する。 Next, the reason why the steel material (for example, wire) of the present invention has a pseudo pearlite structure of 90% or more will be described.
本発明者らの調査の結果、時効抑制効果が優れていた鋼材は、９０％以上が擬似パーライト組織であることが明らかになった。このことから、優れた時効抑制効果、すなわち、優れた冷間鍛造性を獲得するためには、鋼材の組織を９０％以上擬似パーライトにすることが必要であると考えられた。そこで、本発明においては、組織が９０％以上擬似パーライトであることを条件とした。 As a result of the investigation by the present inventors, it has been clarified that 90% or more of the steel material having an excellent effect of suppressing aging has a pseudo pearlite structure. From this, in order to obtain an excellent aging suppression effect, that is, excellent cold forgeability, it was considered necessary to make the steel structure 90% or more pseudo pearlite. Therefore, in the present invention, the condition is that the structure is 90% or more pseudo pearlite.
次に、本願発明の鋼材（線材）の製造方法について説明する。
本願発明の線材の製造は、上述の成分を含む鋼を線材圧延し、巻き取りを行った後、恒温変態処理を施すことにより行うことができる。前記線材の捲き取りは、８５０〜９００℃の温度範囲内で行うことが好ましい。なお、巻き取り温度を８５０℃以上としたのは、８５０℃未満では、引張強度が上昇してしまい冷間鍛造性が悪化するためである。また、巻き取り温度を９００℃以下としたのは、９００℃超では、スケールオフ量が増大し歩留が悪化するためである。
Next, the manufacturing method of the steel material (wire material) of this invention is demonstrated.
The production of the wire of the present invention can be carried out by subjecting the steel containing the above-mentioned components to wire rolling and winding, and then subjecting it to a constant temperature transformation treatment. It is preferable that the wire is scraped off within a temperature range of 850 to 900 ° C. The reason why the winding temperature is set to 850 ° C. or more is that if it is less than 850 ° C., the tensile strength increases and the cold forgeability deteriorates. The reason why the winding temperature is set to 900 ° C. or less is that when it exceeds 900 ° C., the amount of scale-off increases and the yield deteriorates.
また、前記線材の恒温変態処理は、５００〜５５０℃の温度範囲内で行うことが好ましい。これにより、組織を擬似パーライト化することが可能となり、これによって鍛造時の加工性を向上させることができるようになる。なお、恒温変態温度を５００℃以上としたのは、５００℃未満では、変態に要する時間が長くなるからである。また恒温変態温度を５５０℃以下としたのは、５５０℃超では、設備の耐火性が問題となるためである。 Moreover, it is preferable to perform the isothermal transformation process of the said wire within the temperature range of 500-550 degreeC. Thereby, it becomes possible to make a structure | tissue into pseudo pearlite, and it becomes possible to improve the workability at the time of forging by this. The reason why the constant temperature transformation temperature is 500 ° C. or more is that if it is less than 500 ° C., the time required for transformation becomes long. The reason why the constant temperature transformation temperature is set to 550 ° C. or less is that if it exceeds 550 ° C., the fire resistance of the equipment becomes a problem.
なお、本実施の形態においては、上述の成分を含む鋼を線材圧延し、巻き取りを行った後、恒温変態処理を施すことにより本願発明の線材を製造することとしているが、恒温変態処理後に冷却処理を施すこととしてもよい。前記冷却処理としては、例えば、水冷、空冷、放冷等の処理を挙げることができるが、これらに特に限定されるものではない。 In the present embodiment, the wire containing the above-mentioned components is rolled, wound, and then subjected to a constant temperature transformation treatment to produce the wire material of the present invention, but after the constant temperature transformation treatment It is good also as performing a cooling process. Examples of the cooling treatment include water cooling, air cooling, and natural cooling, but are not particularly limited thereto.
以下に本発明を実施例によって具体的に説明する。なお、これらの実施例は本発明を説明するためのものであって、本発明の範囲を限定するものではない。 Hereinafter, the present invention will be specifically described by way of examples. These examples are for explaining the present invention, and do not limit the scope of the present invention.
表１に示すように、各成分を含む鋼を２５０ｔｏｎ転炉で溶製し、連続鋳造により断面サイズ３００×５００ｍｍのブルームを形成し、更に分塊圧延により１２５ｍｍ角のビレットにした後、線材圧延により５．５ｍｍの線材とし、表１に示す温度で巻き取りを行い、その後、表１に示す温度でインライン熱処理により恒温変態させた。なお、従来法においては、線材圧延により５．５ｍｍの線材とした後、ステルモア冷却を実施した。その結果得られた線材（水準Ｎｏ．１〜１２）について時効指数（Aging Index）を求め評価した。 As shown in Table 1, steel containing each component is melted in a 250 ton converter, a bloom having a cross-sectional size of 300 × 500 mm is formed by continuous casting, and further, a billet of 125 mm square is formed by block rolling, followed by wire rolling. Then, the wire was wound at the temperature shown in Table 1 and then subjected to isothermal transformation by in-line heat treatment at the temperature shown in Table 1. In addition, in the conventional method, after making it a 5.5-mm wire by wire rolling, Stemmore cooling was implemented. The aging index (Aging Index) was calculated | required and evaluated about the obtained wire (level No. 1-12).
その結果を表１に示す。また、Ｎｂの質量とＣ＋Ｎの質量との比も併せて表１に示す。
［表１］
[Table 1]
本発明法による水準Ｎｏ１〜６は引張強度（ＴＳ）が低く、Aging Indexが全て０.５kgf/mm2以下の値を示しており、加工硬化が生じ難いことを示した。
これに対して、比較法による水準Ｎｏ７〜９はAging Indexの値が２．８〜５．２kgf/mm2の値を示し、０．５kgf/mm2を超えており、十分な時効抑制効果を得ることができないことがわかった。このことは、Ｎｂの添加量がＣおよびＮ量に対して適正な量よりも少なかったことによるものではないかと考えられた。換言すればＮｂによりＣおよびＮを十分固定していないことを意味している。
このことから、鋼におけるＮｂの質量がＣ＋Ｎの質量に対して７以上なければ、優れた時効抑制効果が得られないことが示唆された。
Levels Nos. 1 to 6 according to the present invention have low tensile strength (TS) and all Aging Index values of 0.5 kgf / mm 2 or less, indicating that work hardening is unlikely to occur.
In contrast, the value of the level No7~9 the Aging Index by the comparison method indicates the value of 2.8~5.2kgf / mm 2, are over 0.5 kgf / mm 2, a sufficient aging inhibition effect I knew I couldn't get it. This was thought to be due to the fact that the amount of Nb added was less than the appropriate amount for C and N. In other words, it means that C and N are not sufficiently fixed by Nb.
From this, it was suggested that unless the mass of Nb in the steel is 7 or more with respect to the mass of C + N, an excellent aging suppression effect cannot be obtained.
一方、従来法による水準Ｎｏ１０〜１２は、Aging Indexの値が６．０kgf/mm2を超えており、十分な時効抑制効果を得ることができないことがわかった。これは、Ｎｂフリーであるため、ＣおよびＮの固定ができないこと、及び、擬似パーライト組織が９０％には満たなかったことによるものであることが示された。このことから、従来法による線材は冷間鍛造中に時効硬化による変形抵抗の上昇が生じやすくなることを示している。 On the other hand, levels No. 10 to 12 according to the conventional method have an Aging Index value of more than 6.0 kgf / mm 2, and it has been found that sufficient aging suppression effects cannot be obtained. This is because Nb-free, C and N cannot be fixed, and the pseudo pearlite structure was less than 90%. From this, it is shown that the wire rod according to the conventional method is likely to increase in deformation resistance due to age hardening during cold forging.
以上の結果から、鋼材の時効を効率よく抑制させるためには、ＮｂとＣ＋Ｎとの質量比が７以上必要であること、及び、鋼材の組織の９０％以上が擬似パーライトであることが少なくとも必要であることが明らかになった。 From the above results, in order to efficiently suppress the aging of the steel material, the mass ratio of Nb and C + N is required to be 7 or more, and at least 90% of the structure of the steel material is required to be pseudo pearlite. It became clear that.
Claims (3)
Ｃ：０．０６％以下，
Ｓｉ：０．４０％以下，
Ｍｎ：０．１０〜０．６％，
Ｐ：０．０１０％以下，
Ｓ：０．００８〜０．０２０％以下，
Ｎｂ：０．０６〜１．１０％，
残部が鉄及び不可避的不純物からなり、かつ、
Ｎを、質量％でＮｂ／(Ｃ＋Ｎ)≧７を満足する範囲内で含む鋼からなり、
組織が擬似パーライト≧９０％であることを特徴とする冷間鍛造性に優れた線材。 % By mass
C: 0.06% or less,
Si: 0.40% or less,
Mn: 0.10 to 0.6%,
P: 0.010% or less,
S: 0.008 to 0.020% or less,
Nb: 0.06 to 1.10%,
The balance consists of iron and inevitable impurities, and
Made of steel containing N in a range satisfying Nb / (C + N) ≧ 7 by mass%,
A wire rod excellent in cold forgeability, characterized in that the structure is pseudo pearlite ≧ 90%.
Ｂ：０．００１〜０．０１０％
Ｖ：０．００８〜０．０３０％
を含有することを特徴とする請求項１記載の冷間鍛造性に優れた線材。 The steel is further mass%,
B: 0.001 to 0.010%
V: 0.008 to 0.030%
The wire rod excellent in cold forgeability according to claim 1.
８５０℃〜９００℃の温度で巻き取った後５００〜５５０℃の温度で恒温変態させることを特徴とする冷間鍛造性に優れた線材の製造方法。
The steel according to claim 1 or 2 is wire-rolled,
A method for producing a wire material excellent in cold forgeability, characterized by being wound at a temperature of 850 ° C to 900 ° C and then isothermally transformed at a temperature of 500 to 550 ° C.
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| CN114918250A (en) * | 2022-05-21 | 2022-08-19 | 湖南华菱湘潭钢铁有限公司 | Production method for reducing aging time of high-carbon wire rod |
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| JPS60169545A (en) * | 1984-02-10 | 1985-09-03 | Nippon Steel Corp | Mild steel wire rod with high suitability to mechanical descaling |
| JPH03287743A (en) * | 1990-04-04 | 1991-12-18 | Nippon Steel Corp | Low carbon nonaging wire rod excellent in machinability and workability |
| JPH08295932A (en) * | 1995-04-21 | 1996-11-12 | Nippon Steel Corp | High strength steel wire excellent in fatigue characteristic |
| JPH1053814A (en) * | 1996-06-05 | 1998-02-24 | Kobe Steel Ltd | High strength hot rolled steel material excellent in weldability, and high strength steel wire and high strength bar steel using the same |
| JP2003013174A (en) * | 2001-06-28 | 2003-01-15 | Nippon Steel Corp | Steel product with little decrease in toughness caused by plastic deformation, and manufacturing method therefor |
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Patent Citations (6)
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|---|---|---|---|---|
| JPS59162249A (en) * | 1983-03-08 | 1984-09-13 | Nippon Steel Corp | Mild steel wire rod |
| JPS60169545A (en) * | 1984-02-10 | 1985-09-03 | Nippon Steel Corp | Mild steel wire rod with high suitability to mechanical descaling |
| JPH03287743A (en) * | 1990-04-04 | 1991-12-18 | Nippon Steel Corp | Low carbon nonaging wire rod excellent in machinability and workability |
| JPH08295932A (en) * | 1995-04-21 | 1996-11-12 | Nippon Steel Corp | High strength steel wire excellent in fatigue characteristic |
| JPH1053814A (en) * | 1996-06-05 | 1998-02-24 | Kobe Steel Ltd | High strength hot rolled steel material excellent in weldability, and high strength steel wire and high strength bar steel using the same |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN114918250A (en) * | 2022-05-21 | 2022-08-19 | 湖南华菱湘潭钢铁有限公司 | Production method for reducing aging time of high-carbon wire rod |
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