JP2016074978A - High strength pc steel twisted wire excellent in stress corrosion property - Google Patents

High strength pc steel twisted wire excellent in stress corrosion property Download PDF

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JP2016074978A
JP2016074978A JP2015182674A JP2015182674A JP2016074978A JP 2016074978 A JP2016074978 A JP 2016074978A JP 2015182674 A JP2015182674 A JP 2015182674A JP 2015182674 A JP2015182674 A JP 2015182674A JP 2016074978 A JP2016074978 A JP 2016074978A
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wire
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鎭 永 鄭
Jin Young Jung
鎭 永 鄭
煥 承 諸
Hwan Seung Je
煥 承 諸
辰 鎬 金
Jin Ho Kim
辰 鎬 金
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Kiswire Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • E—FIXED CONSTRUCTIONS
    • E04—BUILDING
    • E04C—STRUCTURAL ELEMENTS; BUILDING MATERIALS
    • E04C5/00—Reinforcing elements, e.g. for concrete; Auxiliary elements therefor
    • E04C5/08—Members specially adapted to be used in prestressed constructions

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Abstract

PROBLEM TO BE SOLVED: To provide a high strength PC steel twisted wire excellent in stress corrosion property.SOLUTION: In a high strength PC steel twisted wire excellent in stress corrosion property manufactured by twisting 6 outer layer wires on a center wire and the center wire and the outer layer wires consist of a high carbon steel containing C:0.9 to 1.2 wt.%, Mn:0.4 to 0.7 wt.%, Si:1.0 to 1.5 wt.%, Cr:0.4 to 0.7 wt.%, S:0.01 wt.% or less (excluding 0%), P:0.01 wt.% or less (excluding 0%) and the balance Fe with inevitable impurities. The high strength PC steel twisted wire has a spheroidized structure layer by at least 10 μm depth from a surface of the steel twisted wire.SELECTED DRAWING: Figure 1

Description

本発明は、応力腐食特性にすぐれる高強度ＰＣ鋼撚線（strand）に係り、特に、高強度であり、耐応力腐食特性、及び水素脆性に対する抵抗性にすぐれる高強度ＰＣ鋼撚線に関する。   The present invention relates to a high-strength PC steel stranded wire having excellent stress corrosion characteristics, and particularly to a high-strength PC steel stranded wire having high strength, excellent stress corrosion resistance, and resistance to hydrogen embrittlement. .

今日の建築物や構造物に必須に使用されているコンクリートは、大きく見て、ＲＣ（reinforced concrete）とＰＣ（pre-stressed concrete）とに区分され、最近では、徐々にＰＣを利用した土木建築が目立ち始めている。ＲＣとは、構造物建築において、構造物の形態内に鉄筋を配し、鉄線で連結した後、その上にコンクリートを注いだ後、養生させて得られたものであり、ＰＣは、鋼線や鋼撚線に引っ張り応力を付与した状態で、セメント混合物を注いだ後、養生させて得られたものである。前記鉄筋、鋼線などは、衝撃に脆弱な特性を有するコンクリートに耐性を付与する役割を行うという点においては同一である。   The concrete used in today's buildings and structures is broadly divided into RC (reinforced concrete) and PC (pre-stressed concrete). Recently, civil engineering architecture using PC gradually. Is starting to stand out. RC is obtained by placing reinforcing bars in the form of a structure, connecting them with steel wires, pouring concrete onto them, and curing them. PC is a steel wire. It was obtained by pouring a cement mixture in a state where tensile stress was applied to a steel stranded wire and curing. The reinforcing bars, steel wires, and the like are the same in that they play a role of imparting resistance to concrete having characteristics that are vulnerable to impact.

また、ＰＣは、内圧・外圧によって生じる引っ張り応力を、鋼撚線による圧縮応力によって相殺させるために、ＰＣ鋼撚線は、非常に大きい圧力にも十分に耐えられるように、耐久年限にかけて一定の圧縮応力を付与しなければならない。   In addition, since the PC cancels the tensile stress caused by the internal and external pressures by the compressive stress caused by the steel stranded wire, the PC steel stranded wire has a constant over the endurance period so that it can sufficiently withstand a very large pressure. Compressive stress must be applied.

しかし、ＰＣ鋼撚線のクンクリトをなすセメントには、混和剤の一種であるＡＥ（air entraining）減水剤が含有されるために、セメント内には、１，０００〜３，０００ｐｐｍのチオシアン酸イオン（ＳＣＮ−）が含有され、該チオシアン酸イオンが、応力下で鋼線の水素脆性及び応力腐食亀裂を引き起こすことにより、鋼線の早期破壊をもたらし、結局、ＰＣ鋼撚線の寿命を縮めるという問題がある。それにもかかわらず、最近のＰＣ鋼撚線は、さらに高圧化、軽量化及び長長寿命化が要求されており、ＰＣ鋼撚線の水素脆性及び応力腐食亀裂に対する抵抗性向上は、非常に重要な解決課題になっている実情である。 However, since the cement forming the PC steel twisted wire contains an AE (air entraining) water reducing agent, which is a kind of admixture, 1,000 to 3,000 ppm of thiocyanate ion is contained in the cement. (SCN − ) is contained, and the thiocyanate ion causes hydrogen wire embrittlement and stress corrosion cracking of the steel wire under stress, thereby leading to the early breakage of the steel wire and eventually shortening the life of the PC steel stranded wire. There's a problem. Nonetheless, recent PC steel stranded wires are required to have higher pressure, lighter weight, and longer life, and it is very important to improve the resistance of PC steel stranded wires to hydrogen embrittlement and stress corrosion cracking. It is a fact that has become a problem to solve.

従来、応力腐食亀裂及び水素脆性に対する敏感度を低下させる方法として、特許文献１には、鋼線表面に、高防食合成樹脂被膜を形成する方法などが提示されているが、被膜の厚みが５０μｍ以下である場合には、大きい防錆効果がないだけではなく、外部衝撃によって、容易に被膜が損傷される可能性がある。   Conventionally, as a method for reducing the sensitivity to stress corrosion cracking and hydrogen embrittlement, Patent Document 1 has proposed a method of forming a highly anticorrosive synthetic resin coating on the surface of a steel wire, but the thickness of the coating is 50 μm. In the case of the following, not only there is not a large rust prevention effect, but the coating may be easily damaged by an external impact.

また、特許文献２には、ボロン及びチタンを添加させ、ボロン，チタン−炭窒化物を形成し、水素の拡散を抑制し、応力腐食亀裂抵抗性を向上させる技術が提案されたが、合金の追加によって、追加費用が生じるという短所がある。   Patent Document 2 proposes a technique for adding boron and titanium to form boron, titanium-carbonitride, suppressing hydrogen diffusion, and improving stress corrosion crack resistance. There is a disadvantage that additional costs arise due to the addition.

一方、特許文献３では、鋼線にショットピーニング処理を施すことにより、表面に圧縮残留応力を取り入れ、水素脆性及び応力腐食特性を改善させることができることが提案されている。   On the other hand, Patent Document 3 proposes that by applying shot peening to a steel wire, compressive residual stress can be taken into the surface and hydrogen embrittlement and stress corrosion characteristics can be improved.

韓国公開特許第１９９９−００５５２１６号Korean Published Patent No. 1999-0055216 韓国公開特許第２００４−０１０７７８６号Korean Published Patent No. 2004-0107786 韓国公開特許第２００３−００４５８２７号Korean Published Patent No. 2003-0045827

本発明は、高強度であり、耐応力腐食特性、及び水素脆性に対する抵抗性にすぐれる高強度ＰＣ鋼撚線を提供することをその目的とする。   An object of the present invention is to provide a high-strength PC steel stranded wire having high strength, excellent stress corrosion resistance, and excellent resistance to hydrogen embrittlement.

本発明による応力腐食特性にすぐれる高強度ＰＣ鋼撚線は、１本の中心線に６本の外層線を撚ってなるＰＣ鋼撚線において、前記中心線及び前記外層線は、Ｃ：０．９〜１．２重量％、Ｍｎ：０．４〜０．７重量％、Ｓｉ：１．０〜１．５重量％、Ｃｒ：０．４〜０．７重量％、Ｓ：０．０１重量％以下（０％を含まず）、Ｐ：０．０１重量％以下（０％を含まず）、並びに残りは、Ｆｅ及び不可避な不純物を含んだ高炭素鋼からなり、前記鋼撚線の表面から少なくとも１０μｍの深さまで、球状化組織層を有することを特徴とする。   The high-strength PC steel stranded wire having excellent stress corrosion characteristics according to the present invention is a PC steel stranded wire obtained by twisting six outer layer wires on one center line, and the center line and the outer layer wire are C: 0.9 to 1.2% by weight, Mn: 0.4 to 0.7% by weight, Si: 1.0 to 1.5% by weight, Cr: 0.4 to 0.7% by weight, S: 0.0. 01% by weight or less (excluding 0%), P: 0.01% by weight or less (not including 0%), and the remainder is made of high carbon steel containing Fe and inevitable impurities, It is characterized by having a spheroidized tissue layer from the surface to a depth of at least 10 μm.

前記中心線及び前記外層線が撚られて延線された後、４１０℃ないし５００℃の温度で応力緩和熱処理を行い、前記応力緩和熱処理によって、水素含量が１０ｐｐｍ以下であることが望ましい。   After the center line and the outer layer wire are twisted and extended, a stress relaxation heat treatment is performed at a temperature of 410 ° C. to 500 ° C., and the hydrogen content is preferably 10 ppm or less by the stress relaxation heat treatment.

また、前記中心線及び前記外層線の伸線時、伸線加工率が１４％ないし２３％に加工されることが望ましい。   Further, it is preferable that the drawing rate is 14% to 23% when the center line and the outer layer wire are drawn.

また、前記中心線及び前記外層線の伸線工程が複数回にわたって遂行される場合、各回の伸線加工率は、１４％ないし２３％であることが望ましい。   Further, when the drawing process of the center line and the outer layer wire is performed a plurality of times, it is preferable that the drawing rate of each time is 14% to 23%.

本発明による応力腐食特性にすぐれる高強度ＰＣ鋼撚線は、高強度ながら、応力腐食亀裂及び水素脆性に対する抵抗性にすぐれる。   The high-strength PC steel stranded wire having excellent stress corrosion properties according to the present invention is excellent in resistance to stress corrosion cracking and hydrogen embrittlement while having high strength.

本発明の実施例による高強度ＰＣ鋼撚線の断面図である。It is sectional drawing of the high strength PC steel twisted wire by the Example of this invention. 本発明の実施例及び比較例の実験的結果比較表である。It is an experimental result comparison table of the Example and comparative example of this invention.

以下、本発明による望ましい実施例について、添付された図面を参照して詳細に説明する。   Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

図１は、本発明の実施例による高強度ＰＣ（pre-stressed concrete）鋼撚線の断面図であり、図２は、本発明の実施例及び比較例の実験的結果比較表である。   FIG. 1 is a cross-sectional view of a high-strength PC (pre-stressed concrete) steel stranded wire according to an embodiment of the present invention, and FIG. 2 is an experimental result comparison table of the embodiment of the present invention and a comparative example.

本発明による、応力腐食特性にすぐれる高強度ＰＣ鋼撚線３０は、１本の中心線１０に、６本の外層線２０を撚ってなるＰＣ鋼撚線に係り、前記中心線１０と外層線２０とに使用される線材の組成物によって強度を高め、球状化組織を深く確保し、水素が内部で侵透することができないように、表面に閉じ込めるトラップピング作用を行い、応力腐食亀裂及び水素脆性に対する抵抗性を顕著に向上させる。   The high-strength PC steel stranded wire 30 having excellent stress corrosion characteristics according to the present invention relates to a PC steel stranded wire obtained by twisting six outer layer wires 20 to one center line 10, and the center line 10 and Strength is increased by the composition of the wire used for the outer layer wire 20, a spheroidized structure is secured deeply, a trapping action is performed to confine the surface so that hydrogen cannot penetrate inside, and stress corrosion cracking And the resistance to hydrogen embrittlement is significantly improved.

また、応力緩和熱処理の温度条件を強化し、水素含量を制限して応力腐食特性を向上させ、中心線１０及び外層線２０の伸線工程時、伸線加工量を一定範囲内に限定し、ねじれ特性にすぐれ、螺旋亀裂を発生させない高強度ＰＣ鋼撚線３０に関する。   In addition, the temperature condition of the stress relaxation heat treatment is strengthened, the hydrogen content is limited to improve the stress corrosion characteristics, and the drawing process amount of the center line 10 and the outer layer wire 20 is limited to a certain range during the drawing process. The present invention relates to a high-strength PC steel stranded wire 30 that has excellent torsional characteristics and does not generate a spiral crack.

具体的には、前記中心線１０及び前記外層線２０は、Ｃ：０．９〜１．２重量％、Ｍｎ：０．４〜０．７重量％、Ｓｉ：１．０〜１．５重量％、Ｃｒ：０．４〜０．７重量％、Ｓ：０．０１重量％以下（０％を含まず）、Ｐ：０．０１重量％以下（０％を含まず）、並びに残りは、Ｆｅ及び不可避な不純物を含んだ高炭素鋼からなり、前記鋼撚線の表面から少なくとも１０μｍの深さまで、球状化組織層を有するように形成される。   Specifically, the center line 10 and the outer layer line 20 are C: 0.9 to 1.2% by weight, Mn: 0.4 to 0.7% by weight, Si: 1.0 to 1.5% by weight. %, Cr: 0.4 to 0.7% by weight, S: 0.01% by weight or less (not including 0%), P: 0.01% by weight or less (not including 0%), and the rest It consists of high carbon steel containing Fe and inevitable impurities, and is formed to have a spheroidized structure layer from the surface of the steel stranded wire to a depth of at least 10 μm.

前記炭素（Ｃ）は、鋼の強度を高める最も効果的でありながら、経済的な元素であり、鋼がパーライト組織中のセメンタイトを形成する元素である。炭素含量が増加するほど、高強度であるセメンタイトの分率が増大し、パーライトラメラ間隔が微細になって強度が上昇する。   The carbon (C) is the most effective but economical element for increasing the strength of the steel, and the steel is an element for forming cementite in the pearlite structure. As the carbon content increases, the fraction of cementite, which is high strength, increases, the pearlite lamella spacing becomes finer, and the strength increases.

本発明の実施例によれば、炭素含量を０．９重量％以上にし、２，１６０ＭＰａ以上の高引っ張り強度を確保する。炭素含量が１．２重量％を超える場合、初析（pro-eutectoid）セメンタイトの析出が憂慮され、伸線に必要な軟性が急激に低下するために、炭素の含量範囲は、０．９重量％ないし１．２重量％にする。   According to the embodiment of the present invention, the carbon content is set to 0.9% by weight or more, and a high tensile strength of 2,160 MPa or more is ensured. When the carbon content exceeds 1.2% by weight, precipitation of pro-eutectoid cementite is a concern, and the softness necessary for wire drawing decreases rapidly, so the carbon content range is 0.9% by weight. % To 1.2% by weight.

マンガン（Ｍｎ）は、フェライト組織に、鋼の強度を強化させ、小粒性を増大させてパーライト変態を遅延させる元素であり、若干遅い冷却速度でも、微細パーライト組織を確保しやすくするために、０．４重量％以上添加し、過度なマンガンは、中心に偏析が発生し、中心部にマルテンサイト組織を発生させ、伸線性を阻害するために、その上限を０．７％とする。   Manganese (Mn) is an element that reinforces the strength of the steel in the ferrite structure, increases the grain size and delays the pearlite transformation, and in order to make it easy to secure a fine pearlite structure even at a slightly slow cooling rate, 0 More than 4% by weight is added, and excessive manganese causes segregation at the center, a martensite structure at the center, and obstructs the drawability, so the upper limit is made 0.7%.

ケイ素（Ｓｉ）は、パーライト中のフェライトを固溶強化する元素であり、高強度化に効果的であり、亜鉛または亜鉛−アルミニウム合金のメッキ時、セメンタイトの分解を抑制し、強度低下を防止する役割を行う。従って、高強度化のために１．０重量％以上添加することが必要であり、１．５重量％を超える場合には、フェライトの軟性を急激に低下させ、表面組織欠陥を誘発するので、その上限を１．５重量％にする。   Silicon (Si) is an element that solidifies and strengthens ferrite in pearlite, and is effective for increasing the strength. It suppresses the decomposition of cementite and prevents a decrease in strength when plating zinc or zinc-aluminum alloy. Perform a role. Therefore, it is necessary to add 1.0% by weight or more in order to increase the strength, and if it exceeds 1.5% by weight, the softness of the ferrite is drastically reduced and surface texture defects are induced. The upper limit is 1.5% by weight.

クロム（Ｃｒ）は、パーライトラメラ層状間隔を微細化させ、強度及び軟性と共に、セメンタイトの分解を抑制する効果があり、クロムの含量が０．４重量％未満である場合には、十分な強度を得ることができず、０．７重量％超過時には、恒温変態終了時間が長くなって生産性が落ち、マルテンサイト組織を誘発する可能性が高くなる。従って、クロムは、０．４〜０．７重量％範囲で添加する。   Chromium (Cr) has the effect of suppressing the decomposition of cementite as well as the strength and softness of the pearlite lamellar layer spacing, and when the chromium content is less than 0.4% by weight, sufficient strength is obtained. When it cannot be obtained and exceeds 0.7% by weight, the end time of the isothermal transformation is prolonged, the productivity is lowered, and the possibility of inducing a martensite structure is increased. Therefore, chromium is added in the range of 0.4 to 0.7% by weight.

硫黄（Ｓ）は、０．０１重量％を超える場合、低融点析出物の形態で結晶粒界に析出され、熱間脆化を誘発するので、０．０１重量％以下に添加することが望ましい。   When sulfur (S) exceeds 0.01% by weight, it is precipitated at the grain boundary in the form of a low melting point precipitate and induces hot embrittlement, so it is desirable to add it to 0.01% by weight or less. .

リン（Ｐ）は、０．０１重量％を超える場合、柱状晶間に偏析されて熱間脆化を起こし、冷間伸線内に亀裂を誘発するので、０．０１重量％以下で添加することが望ましい。   When phosphorus (P) exceeds 0.01% by weight, it is segregated between columnar crystals to cause hot embrittlement and induces cracks in the cold wire drawing, so it is added at 0.01% by weight or less. It is desirable.

本発明の高強度ＰＣ鋼撚線３０を構成する中心線１０及び外層線２０は、前記組成物以外の残りは、鉄（Ｆｅ）、及びその他不可避に添加される不純物からなる。   The center line 10 and the outer layer wire 20 constituting the high-strength PC steel stranded wire 30 of the present invention are made of iron (Fe) and other impurities inevitably added, except for the above composition.

前記のような成分によって製造される中心線１０及び外層線２０を利用して、鋼撚線を製造する。１本の中心線１０に、６個の外層線２０を撚って延線して鋼撚線が製造され、本実施例による応力腐食特性にすぐれる高強度ＰＣ鋼撚線３０は、表面から１０μｍまで、球状化組織層を有するように形成される。   A steel stranded wire is manufactured using the center line 10 and the outer layer wire 20 manufactured by the above components. A steel stranded wire is manufactured by twisting and extending six outer layer wires 20 to one central wire 10, and the high-strength PC steel stranded wire 30 having excellent stress corrosion characteristics according to this embodiment is formed from the surface. It is formed to have a spheroidized tissue layer up to 10 μm.

前記球状化組織層は、中心線１０に外層線２０を撚って延線した後、応力緩和（stress relieving）熱処理を行う過程で形成され、表面組織を球状化させて形成される粒状セメンタイト炭化物が水素浸透を防止し、応力腐食特性を向上させる。本発明によれば、ＰＣ鋼撚線は、表面から１０μｍまで球状化組織層を有するように形成される。   The spheroidized structure layer is formed in the process of performing stress relieving heat treatment after twisting the outer layer wire 20 around the center line 10 and forming a spheroidized cementite carbide formed by spheroidizing the surface structure. Prevents hydrogen permeation and improves stress corrosion properties. According to the present invention, the PC steel stranded wire is formed to have a spheroidized structure layer from the surface to 10 μm.

また、本発明の実施例による応力腐食特性にすぐれる高強度ＰＣ鋼撚線３０は、鋼撚線を構成する中心線１０及び外層線２０の伸線時、伸線加工率が１４％ないし２３％に加工される。   Further, the high strength PC steel stranded wire 30 having excellent stress corrosion characteristics according to the embodiment of the present invention has a wire drawing ratio of 14% to 23 when the center wire 10 and the outer layer wire 20 constituting the steel stranded wire are drawn. %.

伸線加工率を前記範囲内にすることにより、引っ張り強度が２，１６０Ｍｐａ以上である中心線１０及び外層線２０を製造することができる。望ましくは、該伸線は、複数回にわたって遂行され、各回当たり伸線加工率（パス当たり伸線加工率）が１４％ないし２３％で加工される。パス当たり伸線加工率が１４％以上である場合、引っ張り強度２，１６０Ｍｐａを確保することができる。一方、パス当たり伸線加工率が２３％を超える場合には、小線のねじれ特性が低下し、螺旋亀裂が発生し、鋼撚線を製造した場合、疲労特性と延伸率とが低下する。従って、中心線１０と外層線２０との伸線時、伸線加工率は、１４％ないし２３％にする。   By making the wire drawing rate within the above range, the center line 10 and the outer layer wire 20 having a tensile strength of 2,160 Mpa or more can be produced. Preferably, the drawing is performed a plurality of times, and the drawing is performed at a drawing rate (drawing rate per pass) of 14% to 23%. When the drawing rate per pass is 14% or more, a tensile strength of 2,160 Mpa can be secured. On the other hand, when the wire drawing rate per pass exceeds 23%, the twisting characteristics of the small wires are reduced, the spiral cracks are generated, and when the steel stranded wire is manufactured, the fatigue characteristics and the drawing ratio are reduced. Therefore, when the center line 10 and the outer layer wire 20 are drawn, the drawing rate is 14% to 23%.

また、本発明の実施例による応力腐食特性にすぐれる高強度ＰＣ鋼撚線３０は、前記のように製造される中心線１０に外層線２０を撚って延線した後、４１０℃ないし５００℃の温度で応力緩和熱処理を行い、前記応力緩和熱処理によって、水素含量を１０ｐｐｍ以下にする。   In addition, the high strength PC steel stranded wire 30 having excellent stress corrosion characteristics according to the embodiment of the present invention is obtained by twisting the outer layer wire 20 around the center line 10 manufactured as described above, and then 410 ° C. to 500 ° C. Stress relaxation heat treatment is performed at a temperature of ° C., and the hydrogen content is reduced to 10 ppm or less by the stress relaxation heat treatment.

従来、応力緩和熱処理の温度は、３００℃ないし４００℃の範囲内で行われていたところに比べ、本発明の実施例による応力腐食特性にすぐれる高強度ＰＣ鋼撚線３０は、応力緩和熱処理温度を昇温させ、水素含量を１０ｐｐｍ以下になるように制限し、応力腐食特性を向上させる。   Conventionally, the high-strength PC steel stranded wire 30 having excellent stress corrosion characteristics according to the embodiment of the present invention is compared with the stress relaxation heat treatment performed at a temperature of 300 ° C. to 400 ° C. The temperature is raised and the hydrogen content is limited to 10 ppm or less to improve the stress corrosion characteristics.

以下、前述のような応力腐食特性にすぐれる高強度ＰＣ鋼撚線３０の作用及び効果について、下記比較例を参考にして詳細に説明する。   Hereinafter, the action and effect of the high-strength PC steel stranded wire 30 having excellent stress corrosion characteristics as described above will be described in detail with reference to the following comparative example.

本発明の実施例及び比較例１ないし３で使用された中心線１０及び外層線２０としては、重量％で、炭素（Ｃ）：０．９８％、マンガン（Ｍｎ）：０．５％、ケイ素（Ｓｉ）：１．３％、クロム（Ｃｒ）：０．６％、リン（Ｐ）：０．００９％、硫黄（Ｓ）：０．０１％を含み、残りが、鉄（Ｆｅ）及びその他不可避な不純物からなる鋼を使用した。前記成分からなる線材に対して、恒温変態熱処理を施して冷間伸線を実施する。冷間伸線後、１本の中心線１０と、６本の外層線２０とを撚る延線工程を介して、適当な型付率、ピッチ、荷重を付与した。   As the center line 10 and the outer layer line 20 used in the examples of the present invention and the comparative examples 1 to 3, carbon (C): 0.98%, manganese (Mn): 0.5%, silicon by weight% (Si): 1.3%, chromium (Cr): 0.6%, phosphorus (P): 0.009%, sulfur (S): 0.01%, the remainder being iron (Fe) and others Steel made of inevitable impurities was used. The wire rod composed of the above components is subjected to isothermal transformation heat treatment to perform cold drawing. After the cold wire drawing, an appropriate molding rate, pitch, and load were applied through a wire drawing process in which one center line 10 and six outer layer wires 20 were twisted.

比較例１ないし３の応力緩和熱処理温度は、従来のＰＣ鋼撚線製造時の熱処理温度である３００℃ないし４００℃の範囲内で選択され、本発明の実施例による応力緩和熱処理温度は、従来のＰＣ鋼撚線製造時の応力緩和熱処理温度より昇温された４１０℃ないし５００℃の条件で熱処理を行った。   The stress relaxation heat treatment temperature of Comparative Examples 1 to 3 is selected within the range of 300 ° C. to 400 ° C., which is the heat treatment temperature at the time of conventional PC steel stranded wire production. The heat treatment was performed under conditions of 410 ° C. to 500 ° C., which was raised from the stress relaxation heat treatment temperature during the production of the PC steel stranded wire.

また、本発明の実施例による線材の伸線加工量を２３％以下にし、延線工程時、応力緩和熱処理の温度を４１０℃〜５００℃で処理し、引っ張り荷重、延伸率、ＦＩＴ試験結果を測定した。また、比較例１ないし３の伸線加工量は、本発明の実施例と類似して、３％以下にした。   Further, the wire drawing amount of the wire according to the embodiment of the present invention is set to 23% or less, and the temperature of the stress relaxation heat treatment is treated at 410 ° C. to 500 ° C. during the wire drawing process, and the tensile load, the draw ratio, and the FIT test result are obtained. It was measured. Further, the amount of wire drawing in Comparative Examples 1 to 3 was set to 3% or less, similar to the example of the present invention.

図２は、実施例、及び比較例１ないし３の測定結果を記録したものであり、鋼撚線の引っ張り荷重（ｋＮ）、延伸率（％）測定は、Instron ５０トン引っ張り試験機器で測定し、水素含量はＬｅｃｏ ＲＨ−４０２ hydrogen Determinatorと利用し、ｐｐｍ単位で測定した。また、表面組織は、ＦＥ−ＳＥＭ（Hitachi Ｓ−４８００）で観察した。   FIG. 2 is a record of the measurement results of Examples and Comparative Examples 1 to 3, and the tensile load (kN) and the draw ratio (%) of the steel stranded wire were measured with an Instron 50-ton tensile test equipment. The hydrogen content was measured in ppm using a Leco RH-402 hydrogen Determinator. The surface texture was observed with FE-SEM (Hitachi S-4800).

そして、鋼撚線使用中にその寿命が来るまで受ける鋼撚線の水素脆性及び応力腐食亀裂の環境に対する抵抗性を評価する試験方法として、ＦＩＰ（ＦＩＰ：Federation Internationale de la Precontrainte）試験方法が広く使用されている。ＦＩＰ試験は、ＩＳＯ １５６３０−３及びｐｒＥＮ１０１３８−３を参考にし、５０±１℃に維持される鋼撚線を、２０％ ＮＨ４ＳＣＮ（チオシアン酸）溶液に沈積させた後、規格切断荷重（ＵＴＳ）の８０％に該当する引っ張り荷重を付与した状態を維持しながら、鋼撚線が破断に至る時間（最小２時間）で、水素脆性及び応力腐食亀裂に対する抵抗性を評価する試験である。 As a test method for evaluating the resistance to the environment of hydrogen embrittlement and stress corrosion cracking of steel stranded wire that is subjected to the life of the steel stranded wire until its end of life, FIP (FIP: Federation Internationale de la Precontrainte) test method is widely used. It is used. The FIP test refers to ISO 15630-3 and prEN10138-3, and after steel strands maintained at 50 ± 1 ° C. are deposited in a 20% NH 4 SCN (thiocyanic acid) solution, the standard breaking load (UTS) This is a test for evaluating the resistance to hydrogen embrittlement and stress corrosion cracking in the time until the steel stranded wire breaks (minimum 2 hours) while maintaining a state where a tensile load corresponding to 80% of the above is applied.

図２から分かるように、実施例は比較例１ないし３に比べて高い延伸率を示し、球状化組織の深さが比較例１ないし３に比べて深く、水素含量が１０ｐｐｍ以下であるということを確認することができる。低い水素含量、及び深く形成される球状化組織は、水素脆性及び応力腐食亀裂に対する抵抗性を向上させ、ＦＩＰ試験の最小破断時間を延長させるという効果を提供する。また、高い延伸率は、高い耐性を示し、ねじれにすぐれるという効果を提供する。   As can be seen from FIG. 2, the example shows a higher stretch ratio than Comparative Examples 1 to 3, the depth of the spheroidized structure is deeper than Comparative Examples 1 to 3, and the hydrogen content is 10 ppm or less. Can be confirmed. The low hydrogen content and deeply formed spheroid structure provide the effect of improving resistance to hydrogen embrittlement and stress corrosion cracking and extending the minimum rupture time of the FIP test. Moreover, a high stretch ratio shows the high tolerance and provides the effect that it is excellent in a twist.

以上、本発明について、望ましい実施例を挙げて詳細に説明したが、本発明は、前記実施例に限定されるものではなく、本発明の範疇を外れない範囲内でさまざまな多くの変形が提供される。   The present invention has been described in detail with reference to preferred embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be provided without departing from the scope of the present invention. Is done.

本発明の応力腐食特性にすぐれる高強度ＰＣ鋼撚線は、例えば、建築構造関連の技術分野に効果的に適用可能である。   The high-strength PC steel stranded wire excellent in stress corrosion characteristics of the present invention can be effectively applied to, for example, technical fields related to building structures.

１０ 中心線
２０ 外層線
３０ 高強度ＰＣ鋼撚線
10 Center line 20 Outer layer wire 30 High strength PC steel stranded wire

Claims (4)

１本の中心線に６本の外層線を撚ってなるＰＣ鋼撚線において、
前記中心線及び前記外層線は、Ｃ：０．９〜１．２重量％、Ｍｎ：０．４〜０．７重量％、Ｓｉ：１．０〜１．５重量％、Ｃｒ：０．４〜０．７重量％、Ｓ：０．０１重量％以下（０％を含まず）、Ｐ：０．０１重量％以下（０％を含まず）、並びに残りは、Ｆｅ及び不可避な不純物を含んだ高炭素鋼からなり、
前記鋼撚線の表面から少なくとも１０μｍの深さまで、球状化組織層を有することを特徴とする応力腐食特性にすぐれる高強度ＰＣ鋼撚線。 In a PC steel stranded wire in which six outer layer wires are twisted on one center line,
The center line and the outer layer line are: C: 0.9 to 1.2 wt%, Mn: 0.4 to 0.7 wt%, Si: 1.0 to 1.5 wt%, Cr: 0.4 ~ 0.7 wt%, S: 0.01 wt% or less (not including 0%), P: 0.01 wt% or less (not including 0%), and the remainder includes Fe and inevitable impurities Made of high carbon steel,
A high-strength PC steel stranded wire having excellent stress corrosion characteristics, characterized by having a spheroidized structure layer from the surface of the steel stranded wire to a depth of at least 10 μm. 前記中心線と前記外層線とが撚られて延線された後、４１０℃ないし５００℃の温度で応力緩和熱処理を行い、前記応力緩和熱処理によって、水素含量が１０ｐｐｍ以下であることを特徴とする請求項１に記載の応力腐食特性にすぐれる高強度ＰＣ鋼撚線。   After the center line and the outer layer wire are twisted and extended, a stress relaxation heat treatment is performed at a temperature of 410 ° C. to 500 ° C., and the hydrogen content is 10 ppm or less by the stress relaxation heat treatment. A high-strength PC steel stranded wire having excellent stress corrosion characteristics according to claim 1. 前記中心線と前記外層線との伸線時、伸線加工率が１４％ないし２３％に加工されることを特徴とする請求項１に記載の応力腐食特性にすぐれる高強度ＰＣ鋼撚線。   The high-strength PC steel stranded wire with excellent stress corrosion characteristics according to claim 1, wherein a drawing rate is 14% to 23% when the center line and the outer layer wire are drawn. . 前記中心線と前記外層線との伸線工程が複数回にわたって遂行される場合、各回の伸線加工率は、１４％ないし２３％であることを特徴とする請求項１に記載の応力腐食特性にすぐれる高強度ＰＣ鋼撚線。
2. The stress corrosion characteristic according to claim 1, wherein when the drawing process of the center line and the outer layer wire is performed a plurality of times, a drawing rate of each time is 14% to 23%. Excellent high-strength PC steel stranded wire.
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