WO2020004570A1 - Fil d'acier plat, et fil machine pour fil d'acier plat - Google Patents

Fil d'acier plat, et fil machine pour fil d'acier plat Download PDF

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Publication number
WO2020004570A1
WO2020004570A1 PCT/JP2019/025662 JP2019025662W WO2020004570A1 WO 2020004570 A1 WO2020004570 A1 WO 2020004570A1 JP 2019025662 W JP2019025662 W JP 2019025662W WO 2020004570 A1 WO2020004570 A1 WO 2020004570A1
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Prior art keywords
flat steel
steel wire
less
wire
stress corrosion
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PCT/JP2019/025662
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English (en)
Japanese (ja)
Inventor
直樹 松井
大羽　浩
新 磯
篠原　康浩
原　卓也
陽平 小山
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日本製鉄株式会社
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Priority to JP2020527649A priority Critical patent/JP6897876B2/ja
Publication of WO2020004570A1 publication Critical patent/WO2020004570A1/fr

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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
    • 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
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/20—Recycling

Definitions

  • the present invention relates to a flat steel wire and a wire rod for a flat steel wire.
  • Priority is claimed on Japanese Patent Application No. 2018-124644 filed on June 29, 2018, the content of which is incorporated herein by reference.
  • Flat steel wire is used as a reinforcing material for flexible pipes for transporting high-pressure fluids such as natural gas and crude oil.
  • high-pressure fluids such as natural gas and crude oil.
  • the mining depth tends to be deeper with the increase in oil demand, and there is an increasing demand for reinforcement of flexible pipes.
  • the flat steel wire used for the reinforcing material has a property of preventing hydrogen-induced cracking (HIC) from being caused by hydrogen-induced cracking.
  • HIC hydrogen-induced cracking
  • SSC sulfide stress corrosion cracking which is a property not to cause sulfide stress corrosion cracking (Sulfide Stress Corrosion Cracking; SSC) is required.
  • Patent Document 1 C: 0.25 to 0.60%, Si: more than 0.50 and less than 2.0%, Mn: 0.20 to 1.50%, S: 0. 015% or less, P: 0.015% or less, Cr: 0.005 to 1.50%, Al: 0.005 to 0.080%, and N: 0.0020 to 0.0080%. : 0 to 0.0050% and Mg: 0 to 0.0050%, one or two of which are contained so as to satisfy [Ca] + [Mg]> 0.20 ⁇ [S], and have a tensile strength.
  • Patent Document 2 discloses that, by mass%, C: 0.85% to 1.00%, Si: 0.80% to 1.30%, Mn: 0.30% to 0.90%, P : 0.017% or less, S: 0.010% or less, Cu: 0.20% or less, Al: 0% to 0.10%, Ti: 0% to 0.05%, B: 0% or more It contains 0.0040% or less, N: 0% or more and 0.0060% or less, Cr: 0% or more and 0.5% or less, and V: 0% or more and 0.50% or less.
  • the yield strength or 0.2% proof stress obtained by the tensile strength is 1600 MPa or more and 2000 MPa or less, and the tensile strength is
  • a flat steel wire has been proposed, wherein the flat steel wire has a torsion value of 12 or more obtained by a torsion test under a condition of 900 MPa or more, elongation at break of 2% or more, and a distance between chucks of 500 mm. .
  • Patent Document 1 The technology disclosed in Patent Document 1 is a flat steel wire that does not cause hydrogen-induced cracking in a sour environment with a pH of less than 5.5 even if the tensile strength exceeds 1000 MPa.
  • the present invention relates to a high-strength flat steel wire having a tensile strength of 1000 to 1350 MPa, and even in a harsh sour environment having a pH of less than 5.5, the surface of the flat steel wire is not subjected to a hydrogen-induced It is an object of the present invention to provide a flat steel wire which does not generate cracks and sulfide stress corrosion cracking and can be used as a reinforcing wire for a flexible pipe or the like having a deep mining depth and a wire for a flat steel wire suitable for the production thereof.
  • the present inventors conducted various studies on the effects of added elements on hydrogen-induced cracking and sulfide stress corrosion cracking in order to solve the above-mentioned problems, and obtained the following findings (a) to (d). Was.
  • Y1 No cracking occurs in the steel material at the time of primary drawing and subsequent flat pressing to a flat steel wire, and hydrogen-induced cracking and sulfide stress corrosion cracking do not occur in a sour environment having a pH of less than 5.5.
  • Y1 represented by the following formula ⁇ 1> must contain C, Si, Mn, Cr, Cu, and Ni in a range that satisfies the formula ⁇ 2>.
  • Y1 10 ⁇ ⁇ [C] ⁇ (1 + 0.8 ⁇ [Si]) ⁇ (1 + 3 ⁇ [Mn]) ⁇ (1 + 2 ⁇ [Cr]) ⁇ (1 + 0.8 ⁇ [Cu]) ⁇ (1 + 0.7 ⁇ [Ni]) ⁇ ...
  • the present invention has been completed based on the above findings, and the gist thereof is a flat steel wire shown in the following (1) to (6) and a wire rod for a flat steel wire shown in the following (7).
  • D represents the thickness (mm) of the flat steel wire.
  • the flat steel wire according to (1) wherein the flat steel wire contains one or more types selected from the group consisting of: (3) In mass%, Mo: 0.01 to 1.00%, B: 0.0002 to 0.0100%, The flat steel wire according to (1) or (2), wherein the flat steel wire contains one or two types selected from the group consisting of: (4) In mass%, REM: 0.0002 to 0.1000%, Zr: 0.0002 to 0.100%, Mg: 0.0002 to 0.0050%, The flat steel wire according to any one of (1) to (3), characterized by containing one or more kinds selected from the group consisting of: (5) The flat steel wire according to any one of (1) to (4), further comprising a tempered martensite structure.
  • the “impurity” in the “Fe and impurities” as the balance is a concept that includes, in addition to the components unintentionally contained in the steel material, other components contained within a range that does not impair the effects of the present invention.
  • the steel material is manufactured industrially, ore as a raw material, scrap, or a material mixed from a manufacturing environment is included.
  • the flat steel wire of the present invention has a high tensile strength of 1000 MPa or more and is unlikely to cause hydrogen-induced cracking and sulfide stress corrosion cracking even in a severe sour environment having a pH of less than 5.5. Can be used as reinforcement.
  • the wire for flat steel wire of the present invention is suitable for manufacturing such flat steel wire.
  • C 0.35 to 0.60%
  • C is an element that strengthens steel and must be contained in an amount of 0.35% or more.
  • the content of C In order to achieve both excellent hydrogen-induced cracking resistance and sulfide stress corrosion cracking resistance, a sufficiently high tensile strength is obtained even after high-temperature tempering treatment after quenching or heat treatment at high temperatures after processing into flat steel wire.
  • the content of C In order to secure the strength, the content of C must be 0.35% or more.
  • the content of C is preferably set to 0.38% or more, and more preferably 0.40% or more. However, when the content of C exceeds 0.60%, the strength of the joint becomes insufficient when flat steel wires are joined by welding.
  • a suitable C content is 0.35 to 0.60%.
  • the content is preferably 0.55% or less. In order to improve the material stress corrosion cracking resistance, it is desirable that the content is 0.50% or less.
  • Si more than 1.50% and less than 2.00% Si forms a solid solution in the matrix, improves the strength of the flat steel wire, and is effective in improving hydrogen-induced cracking resistance and sulfide stress corrosion cracking resistance.
  • Si In order to improve the resistance to sulfide stress corrosion cracking simultaneously with the resistance to hydrogen-induced cracking in a high-strength flat steel wire having a tensile strength exceeding 1000 MPa, Si must be contained in excess of 1.50%. However, when 2.00% or more is contained, problems occur such as cracking of the wire rod when flat-pressure processing is performed into a flat steel wire shape. Therefore, the content of Si is more than 1.50% and less than 2.00%.
  • the Si content should be 1.60% or more, and the Si content should be 1.70% or more. More preferred.
  • the content is preferably set to 1.80% or less.
  • Mn more than 0.65% and less than 1.50% Mn is an element necessary for enhancing the hardenability of steel and increasing the strength.
  • the content is set to be more than 0.65%.
  • the strength of the wire becomes too high, and there arises a problem that a crack occurs in the wire when it is processed into a flat steel wire. Therefore, the content of Mn in the present invention is more than 0.65% and less than 1.50%.
  • Mn when it is desired to further enhance the hardenability of the flat steel wire to suppress the bending of the wire or to increase the strength, Mn may be contained at least 0.70%, and may be contained at least 0.75%. More preferred. When it is desired to suppress cracking of the wire rod when working into a flat steel wire, Mn is preferably set to 1.30% or less, and more preferably 1.10% or less.
  • P 0.010% or less P is contained as an impurity.
  • the content of P exceeds 0.010%, hydrogen-induced cracking and sulfide stress corrosion cracking are likely to occur, and in a flat steel wire having a tensile strength exceeding 1000 MPa, in a severe sour environment having a pH of less than 5.5. Hydrogen-induced cracking and sulfide stress corrosion cracking cannot be suppressed.
  • the content of P is preferably 0.008% or less, and more preferably less than 0.005%.
  • the lower limit of the P content is not particularly limited. However, since excessive reduction leads to an increase in manufacturing cost, the lower limit of the P content may be set to 0.0005%.
  • S 0.010% or less S is contained as an impurity.
  • MnS becomes coarse and deteriorates the hydrogen-induced cracking resistance and the sulfide stress corrosion cracking resistance.
  • the S content is preferably 0.008% or less, and more preferably less than 0.005%.
  • the lower limit of the S content is not particularly limited. However, since excessive reduction leads to an increase in manufacturing cost, the lower limit of the S content may be set to 0.0005%.
  • Cr 0.005 to 0.60%
  • Cr is an element necessary for enhancing the hardenability of steel and increasing the strength, like Mn, and must be contained in an amount of 0.005% or more.
  • the appropriate Cr content in the present invention is 0.005 to 0.60%.
  • Cr may be contained at 0.05% or more, and more preferably at 0.10% or more.
  • the content is preferably 0.50% or less, and more preferably 0.40% or less.
  • Al 0.005 to 0.080% Al not only has a deoxidizing effect, but also combines with N to form AlN, and its pinning effect has the effect of refining austenite grains during hot rolling. It has the effect of improving sulfide stress corrosion cracking resistance. For this reason, Al must be contained at 0.005% or more. From the viewpoint of improving the hydrogen-induced cracking resistance and the sulfide stress corrosion cracking resistance, the Al content is desirably 0.015% or more, and more desirably 0.020% or more.
  • the content of Al is preferably 0.060% or less, and more preferably 0.050% or less.
  • N 0.0020 to 0.0080% N dissolves in the matrix and has the effect of improving the strength of the flat steel wire.
  • it combines with Al and Ti to form nitrides and carbonitrides, and has the effect of refining austenite grains during hot rolling, and has the effect of preventing hydrogen-induced cracking and sulfide stress corrosion of flat steel wires. It has the effect of improving cracking properties.
  • N must be contained at 0.0020% or more, and more preferably 0.0030% or more. However, even if it is excessively contained, the effect is not only saturated, but also the productivity is deteriorated such as generation of cracks at the time of casting the steel. Therefore, the N content needs to be 0.0080% or less. is there. In order to ensure stable manufacturability, the content is preferably 0.0060% or less, and further preferably 0.0050% or less.
  • Ca 0.0002-0.0050% Ca is dissolved in MnS and has the effect of finely dispersing MnS. By finely dispersing MnS, it is possible to improve the resistance to hydrogen-induced cracking and the resistance to sulfide stress corrosion cracking even in a flat steel wire having a tensile strength exceeding 1000 MPa. In order to obtain these effects by Ca, Ca should be contained at 0.0002% or more, and when a higher effect is desired, Ca should be contained at 0.0005% or more.
  • the appropriate Ca content is 0.0050% or less.
  • the Ca content is preferably 0.0030% or less, and more preferably 0.0025% or less.
  • Cu 0.05 to 0.80%
  • Ni 0.05 to 0.60%
  • Cu / Ni> In a range that satisfies the condition 1, Cu and Ni must be contained in a total amount of 0.10 to 1.00% (Equations ⁇ 5> and ⁇ 6>).
  • Cu 0.05 to 0.80%
  • Cu has an effect of improving the sulfide stress corrosion cracking resistance of a flat steel wire having a tensile strength exceeding 1000 MPa, and is an essential additive element in the present invention. It also has the effect of increasing the hardenability of steel.
  • the content In order to obtain the effect of improving the sulfide stress corrosion cracking resistance, the content must be 0.05% or more.
  • the content of Cu exceeds 0.80%, problems such as cracks occurring in the wire rod when processing into a flat steel wire occur. Therefore, the content of Cu is 0.05 to 0.80%. From the viewpoint of improving sulfide stress corrosion cracking resistance, the content of Cu contained is preferably 0.10% or more, and more preferably 0.20% or more.
  • the Cu content is preferably 0.70% or less, and more preferably 0.50% or less.
  • Cu must be contained together with Ni. If Cu is contained alone at less than 0.05% of Ni, surface flaws occur during the hot rolling process for producing a wire. This causes cracking during primary drawing and flat pressure processing on flat steel wires, which makes it difficult to form flat steel wires.
  • Ni 0.05 to 0.60%
  • Ni has an effect of improving the sulfide stress corrosion cracking resistance of a flat steel wire having a tensile strength exceeding 1000 MPa, and is an essential additive element in the present invention. It also has the effect of increasing the hardenability of steel.
  • the content In order to obtain the effect of improving the sulfide stress corrosion cracking resistance, the content must be 0.05% or more.
  • the Ni content exceeds 0.60%, the strength of the wire becomes too high, and the wire tends to crack when subjected to flat pressing to a flat steel wire. Further, even if it can be processed, problems such as sulfide stress corrosion cracking are likely to occur. Therefore, the content of Ni is 0.05 to 0.60%.
  • the Ni content is preferably 0.07% or more, and more preferably 0.10% or more.
  • the Ni content is preferably 0.50% or less, and more preferably 0.40% or less, in consideration of workability to a flat steel wire and sulfide corrosion cracking resistance. It is to be noted that Ni must be contained together with Cu, and when Cu is less than 0.05% and Ni is solely contained, the surface of the flat steel wire is subjected to a sour environment having a pH of less than 5.5 containing hydrogen sulfide. When tensile stress is applied to the steel sheet, fine cracks are likely to occur on the surface of the flat steel wire, and sulfide stress corrosion cracking resistance is reduced.
  • the Cu / Ni ratio is 1 or less, that is, the Ni content is equal to or more than the Cu content, when a tensile stress is applied to the flat steel wire surface in a sour environment containing hydrogen sulfide, the flat steel wire surface Fine cracks are likely to occur, and sulfide stress corrosion cracking resistance is reduced. Therefore, Cu and Ni must satisfy Cu / Ni> 1.
  • the Cu / Ni ratio is preferably 1.5 or more, and more preferably 2 or more. Cu and Ni only have to satisfy Cu / Ni> 1, and the upper limit of the Cu / Ni ratio is not limited. However, generation of surface flaws and processing into a flat steel wire in a hot rolling process for manufacturing a wire rod are performed. In consideration of the properties, the Cu / Ni ratio is preferably 5 or less.
  • the total content of Cu and Ni is less than 0.10%, the above effects cannot be obtained.
  • the total content of Cu and Ni exceeds 1.00%, the strength of the steel material becomes too high, and when the flat steel wire is flat-pressed, cracks occur in the wire, or the pH 5 containing hydrogen sulfide is increased.
  • the total content of Cu and Ni is preferably 0.20 or more, and more preferably 0.40 or more.
  • the total content of Cu and Ni is preferably 0.80% or less. , 0.50% or less is more preferable.
  • the Y1 value represented by the formula ⁇ 1> needs to satisfy the formula ⁇ 2>.
  • Y1 10 ⁇ ⁇ [C] ⁇ (1 + 0.8 ⁇ [Si]) ⁇ (1 + 3 ⁇ [Mn]) ⁇ (1 + 2 ⁇ [Cr]) ⁇ (1 + 0.8 ⁇ [Cu]) ⁇ (1 + 0.7 ⁇ [Ni]) ⁇
  • [C], [Si], [Mn], [Cr], [Cu], and [Ni] represent the content of each element in mass%
  • D is Indicates the thickness (mm) of the flat steel wire.
  • Y1 is in a range that can be used as a flat steel wire having a tensile strength exceeding 1000 MPa, and is not necessary to impart hardenability to obtain sufficient strength without causing cracks in the wire when flat-pressing flat steel wire. Parameters.
  • Y1 when manufacturing a flat steel wire, Y1 heats a flat steel wire having a thickness of D (mm) to a temperature of three or more points of Ac, and performs a quenching process. This is a parameter that affects the fraction of the martensite structure obtained at a certain D / 2 (mm) position.
  • the value of Y1 is expressed by using the thickness D (mm) of the flat steel wire to obtain a uniform tempered martensite structure. It is necessary to exceed D.
  • the cooling rate of the quenching treatment by oil cooling varies depending on the thickness D of the flat steel wire, but is generally about 30 to 50 ° C./sec.
  • the tensile strength of the flat steel wire is preferably 1100 MPa or more. However, when the tensile strength exceeds 1350 MPa, sulfide stress corrosion cracking occurs even when hydrogen-induced cracking does not occur.
  • the present invention controls the component segregation in the cross section perpendicular to the longitudinal direction of the wire rod by controlling the components and controlling the inclusions at the stage of melting the steel, and controlling the rolling and heating conditions.
  • the present invention removes the processing strain imparted when processing the flat steel wire by heat treatment, and reduces the tensile residual stress generated in the longitudinal direction of the surface of the flat steel wire.
  • the reason for reducing the residual tensile stress is that sulfide stress corrosion cracking occurs when the residual tensile stress measured in the longitudinal direction of the flat steel wire is 300 MPa or more. Therefore, when it is desired to suppress sulfide stress corrosion cracking in a severe sour environment having a pH of less than 5.5, the tensile residual stress in the longitudinal direction is preferably 250 MPa or less, and more preferably 100 MPa or less.
  • the production conditions of the flat steel wire are controlled, for example, heat treatment is performed after the flat steel wire is processed, and the tensile residual stress measured in the longitudinal direction of the flat steel wire is controlled.
  • a wire (a flat steel wire) is manufactured by the following manufacturing method.
  • a flat steel wire may be manufactured using it as a material.
  • the following manufacturing process is an example, and when a flat steel wire having a chemical composition and other requirements within the scope of the present invention is obtained by a process other than the following, the flat steel wire is included in the present invention.
  • the chemical components such as C, Si, Mn, etc. are adjusted, and the steel ingots and slabs that are melted and cast by a converter or an electric furnace, etc., are subjected to a slab rolling process to be a material for product rolling.
  • Slab Before the product rolling, that is, during or before the heating of the slab rolling, the cast steel slab is subjected to a heat treatment at a temperature of 1250 ° C. or more for 12 hours or more. Thereby, a part of MnS forms a solid solution to be refined, and component segregation of the wire after product rolling can be suppressed.
  • the slab is reheated and hot rolled, and finally finished into a bar or wire rod with a predetermined diameter.
  • the rolled wire (wire for flat steel wire) is processed into a flat steel wire after primary drawing. At this time, it is desirable that the total reduction in area when the rolled wire is processed into the flat steel wire is 80% or less.
  • the flat steel wire is adjusted to a predetermined size by cold rolling the primary drawn wire using a cold rolling mill. In the state where the flat steel wire is kept cold-rolled, the flat steel wire is subjected to heat treatment because the tensile residual stress generated in the longitudinal direction of the flat steel wire is large.
  • oil quenching and tempering at a temperature of 460 ° C. or more may be performed. In this case, a flat steel wire including a tempered martensite structure is manufactured.
  • a heating process may be performed in which the heating temperature is 460 ° C. or more and the temperature is A 1 point or less. In this case, a flat steel wire having a pearlite structure is produced.
  • both end faces in the thickness direction are parallel, and both end faces in the width direction have a semi-elliptical shape or an arc shape in a longitudinal vertical cross section, respectively.
  • the same shape may be finished by wire drawing using a deformed die. If the ratio of the maximum width to the thickness in the width direction of the flat steel wire, the width / thickness ratio is less than 2.5, the thickness is large relative to the width of the flat steel wire, so the bending that occurs on the surface when the flat steel wire is bent Stress increases, and sulfide stress corrosion cracking is likely to occur.
  • the flat steel wire when the flat steel wire is to be incorporated into a flexible pipe, it becomes difficult to bend the flat steel wire, which causes problems such as cracks.
  • the flat steel wire has a width / thickness ratio of more than 10, after the flat steel wire is cold-rolled or after the heat treatment of the flat steel wire, the flat steel wire is warped and may be incorporated into a flexible pipe. It becomes impossible or the tensile residual stress increases, and sulfide stress corrosion cracking occurs.
  • the high-strength flat steel wire of the present invention may contain, as necessary, Ti: 0 to 0.100%, Nb: 0 to 0.050%, V: 0 to 0.50%, Mo: 0 to 1.00%. , B: 0 to 0.0100%, REM: 0 to 0.1000%, Zr: 0 to 0.100%, and Mg: 0 to 0.0050% You may make it contain.
  • Percentages for optional components are% by weight.
  • Ti 0 to 0.100% Ti combines with N and C to form carbides, nitrides or carbonitrides, and has an effect of miniaturizing austenite grains during hot rolling due to their pinning effect. It may be included because it has the effect of improving the properties and resistance to sulfide stress corrosion cracking. In order to obtain this effect, the content of Ti may be 0.001% or more. From the viewpoint of improving the resistance to hydrogen-induced cracking and the resistance to sulfide stress corrosion cracking, the Ti content is desirably 0.005% or more, and more desirably 0.010% or more.
  • the content of Ti is preferably 0.050% or less, and more preferably 0.035% or less.
  • Nb 0 to 0.050% Nb combines with N and C to form carbides, nitrides or carbonitrides, and has an effect of miniaturizing austenite grains during hot rolling by their pinning effect. It may be included because it has the effect of improving the properties and resistance to sulfide stress corrosion cracking. In order to obtain this effect, Nb may be contained at 0.001% or more. From the viewpoint of improving the resistance to hydrogen-induced cracking and the resistance to sulfide stress corrosion cracking, the content of Nb is preferably 0.005% or more, and more preferably 0.010% or more.
  • the Nb content is preferably 0.035% or less, and more preferably 0.030% or less.
  • V 0 to 0.50%
  • V combines with C and N to form carbides, nitrides or carbonitrides, and can increase the strength of flat steel wires.
  • 0.01% or more of V may be contained.
  • the amount of V when contained is preferably 0.20% or less, and more preferably 0.10% or less.
  • the amount of V is preferably contained at 0.02% or more.
  • Mo 0 to 1.00%
  • Mo is an element that enhances the hardenability of steel, and may be contained. However, in order to obtain the effect of improving the hardenability, the content may be 0.01% or more. However, when the content of Mo exceeds 1.00%, the strength of the wire becomes too high, and there arises a problem that a crack occurs in the wire when it is processed into a flat steel wire. Therefore, when Mo is contained, the content of Mo is 0.01 to 1.00%. When Mo is contained from the viewpoint of improving the hardenability, the content of Mo is preferably 0.02% or more, and more preferably 0.05% or more. In consideration of the workability of the flat steel wire, the content of Mo when it is contained is preferably 0.50% or less, and more preferably 0.30% or less.
  • B 0 to 0.0100%
  • B is effective for increasing the hardenability of steel by adding a trace amount thereof, and may be contained in an amount of 0.0002% or more when an effect is desired. If the content exceeds 0.0100%, not only the effect is saturated, but also coarse nitride is generated, so that hydrogen-induced cracking and sulfide stress corrosion cracking are likely to occur. Therefore, when B is contained, the content of B is 0.0002 to 0.0100%. In order to further enhance the hardenability, the content of B may be set to 0.0005% or more, and more preferably 0.0010% or more. In consideration of hydrogen-induced cracking and sulfide stress corrosion cracking, the content of B in the case where B is contained is preferably 0.0050% or less, and more preferably 0.0030% or less.
  • REM 0 to 0.1000% REM is a general term for rare earth elements, and the content of REM is the total content of rare earth elements.
  • REM like Ca and Mg, has the effect of forming a solid solution in MnS and finely dispersing MnS. By dispersing MnS finely, resistance to hydrogen-induced cracking and resistance to sulfide stress corrosion cracking can be improved, and therefore MnS may be added.
  • REM should be contained at 0.0002% or more. To obtain higher effects, REM should be contained at 0.0005% or more. Just do it.
  • the content of REM when contained is 0.1000% or less.
  • the content of REM is preferably 0.0500% or less, and more preferably 0.030% or less.
  • Zr 0 to 0.100% Zr reacts with O to generate an oxide, and when added in a small amount, has an effect of finely dispersing the oxide and suppressing hydrogen-induced cracking and sulfide stress corrosion cracking. It may be added.
  • Zr should be contained at 0.0002% or more, and if a higher effect is desired, Zr should be contained at 0.001% or more. Just do it.
  • the content of Zr exceeds 0.100%, the effect is saturated and reacts with N and S in the steel to generate coarse nitrides and sulfides. Hydrogen-induced cracking and sulfide stress corrosion cracking resistance are reduced.
  • the content of Zr when it is contained is 0.100% or less.
  • the Zr content is preferably 0.080% or less, and more preferably 0.050% or less. preferable.
  • Mg 0-0.0050% Mg has an effect of forming a solid solution in MnS and finely dispersing MnS. By finely dispersing MnS, the hydrogen-induced cracking resistance and the sulfide stress corrosion cracking resistance can be improved even with a high-strength flat steel wire.
  • Mg may not be contained (Mg: 0%), in order to obtain the effect of suppressing hydrogen-induced cracking and sulfide stress corrosion cracking by Mg, Mg may be contained at 0.0002% or more. If a higher effect is desired, the content may be 0.0005% or more.
  • the proper content of Mg when it is contained is 0.0050% or less.
  • the Mg content is preferably 0.0030% or less, and more preferably 0.0025% or less.
  • Impurity is a concept that includes, in addition to components unintentionally contained in steel materials, other components contained within a range that does not impair the effects of the present invention, and industrially manufactures steel materials. At this time, ore, scrap as a raw material, or those mixed from a production environment or the like are included.
  • test Nos In order to produce flat steel wires having the same components but different tensile strengths and different tensile residual stresses in the longitudinal direction, test Nos.
  • A1 to A5 and A7 a flat steel wire cold-rolled to a width of 15 mm and a thickness of 5 mm using steel A was heated at 950 ° C. for 10 minutes, then immersed in cold oil and quenched. Tempering treatment was performed at a temperature of up to 600 ° C. for a predetermined time to produce flat steel wires having different tensile strengths.
  • Test No. A1 to A5 and A7 are flat steel wires containing a tempered martensite structure. Test No.
  • A6 and A8 a quenching treatment was not performed, and a heat treatment was performed at 450 ° C. and 580 ° C. for a predetermined time after cold rolling.
  • Test No. For A9 no heat treatment was performed after cold rolling.
  • Test No. A6, A8, and A9 are flat steel wires containing a pearlite structure.
  • Test No. B1 to B5 flat steel wires having different shapes were produced by using a wire rod obtained by rolling steel B and changing the width and thickness when cold rolling to flat steel wires after primary drawing.
  • Test No. B1 to B4 were processed into flat steel wires having different widths and thicknesses, heated at 950 ° C. for 10 minutes, immersed in cold oil, quenched, and tempered at 485 ° C.
  • a flat steel wire having substantially the same tensile strength but different width and thickness was produced.
  • Test No. For B5 a flat steel wire having a width of 18 mm and a thickness of 1.7 mm was prepared, heated at 950 ° C. for 10 minutes, immersed in cold oil and quenched, but a large warp occurred in the longitudinal direction of the flat steel wire. Subsequent tests were discontinued. Table 3 shows the heat treatment conditions after the cold rolling.
  • the drawn wire rod was rolled by a cold rolling mill to form a flat steel wire having a width of 15 mm, a thickness of 4 mm or a width of 15 mm, a thickness of 5 mm, a width of 15 mm, and a thickness of 3 mm.
  • Test No. For 1 to 26, 27, 29, 31, 33, 34, 36, 37, 39, 41, 42, 45 to 48, the formed flat steel wire was heated at 950 ° C. for 10 minutes after cold rolling. Thereafter, the steel sheet was immersed in cold oil to perform a quenching treatment, and a tempering treatment was performed at a temperature of 430 to 540 ° C. for 60 minutes. Test No.
  • Tables 3 and 4 show the results of the investigation.
  • an underline indicates that the property is out of the range of the present invention, and "-" indicates a test for investigating various properties due to cracking when processing into a flat steel wire or the like. Not performed.
  • the “longitudinal direction” refers to the thickness direction of the rolled flat steel wire, the length direction extending perpendicular to the width direction, and the “surface” refers to a depth of 50 ⁇ m from the surface of the flat steel wire toward the center of thickness. Point to the range.
  • the residual stress is measured by a known X-ray method. Specifically, an X-ray stress measurement method using X-ray diffraction is used in accordance with JIS B 2711 (2013).
  • the measurement was performed using the type of characteristic X-ray: MnK ⁇ ray, Cr filter, reference diffraction angle 2 ⁇ 0: 152.0 °, ⁇ angle: 14.0 °, X-ray stress constant K: -336 MPa / ° X-rays were irradiated parallel to the longitudinal direction with the center position in the width direction as the center, and a diffraction pattern was obtained. Further, the residual stress was measured at six locations on the surface of the flat steel wire in which the distance between the measurement positions was at least 450 mm or more in the longitudinal direction, and the average value was obtained.
  • the sample was fixed to a jig.
  • the pH of the solution was adjusted to 5.0 by using 5% NaCl + CH 3 COOH solution with HCl.
  • a mixed gas of hydrogen sulfide (H 2 S) and carbon dioxide (CO 2 ) is introduced, and immersed in the solution together with the 4-point bending jig fixing the flat steel wire to check for cracks. investigated.
  • the partial pressure of hydrogen sulfide is 0.01 MPa
  • the test temperature is 25 ° C.
  • the test time is 96 hours. After the test, the presence or absence of cracks in the flat steel wire was visually determined.
  • the longitudinal section at the position where the bending strain became maximum was filled with resin to check for the occurrence of minute cracks on the surface due to sulfide stress corrosion cracking. Then, the surface of the flat steel wire was inspected for the occurrence of minute cracks by an optical microscope. When a small crack having a depth of 20 ⁇ m or more was found on the surface of the flat steel wire, it was determined that sulfide stress corrosion cracking had occurred.
  • Test No. which is an example of the present invention.
  • A1 to A6 and B1 to B3 all satisfy the chemical components and the requirements of the present invention, and the production conditions of the steel material are appropriate. Therefore, the tensile strength is 1000 MPa or more, and hydrogen-induced cracking and sulfide No stress corrosion cracking occurred and no problem.
  • Test No. A7 has a tensile strength outside the range of the present invention, and sulfide stress corrosion cracking has occurred.
  • Test No. Test No. A8 performed only heat treatment without performing quenching treatment. A9 was not heat-treated after processing into a flat steel wire. In each case, the tensile residual stress exceeded 300 MPa, and hydrogen-induced cracking and sulfide stress corrosion cracking occurred.
  • Test No. In B4 the width / thickness ratio of the flat steel wire is out of the range of the present invention, and sulfide stress corrosion cracking has occurred.
  • Test No. B5 did not undergo a test such as a tensile test because a large warpage occurred in the longitudinal direction of the flat steel wire when the quenching treatment was performed.
  • Test No. which is an example of the present invention.
  • Nos. 1 to 26 all satisfy the chemical components and the requirements of the present invention and are suitable for steel production conditions. Therefore, the tensile strengths are all in the range of 1000 MPa to 1350 MPa, and hydrogen-induced cracking and sulfide corrosion cracking occur. Also has not occurred.
  • Test No. 28, 30, 32, 35, 38, 40, and 44 are the chemical components of steel, any one of the formulas ⁇ 5> and ⁇ 6>, or the value of Y1 does not satisfy the formula ⁇ 2>. , And when the flat steel wire was cold-rolled, the flat steel wire cracked. Therefore, the subsequent tests were stopped without performing the heat treatment. Test No.
  • Test No. 27 has a chemical component within the range of the present invention, but the value of Y1 does not satisfy the expression ⁇ 2>, and sulfide stress corrosion cracking has occurred.
  • Test No. No. 28 has a chemical component within the range of the present invention, but the value of Y1 does not satisfy the formula ⁇ 2>, cracks occur when processing into flat steel wire, and the test after heat treatment is stopped. I have. Test No. In No. 29, Cu and Ni are out of the range of the present invention, and sulfide stress corrosion cracking has occurred. Test No. In No. 30, Ni was out of the range of the present invention, and cracks occurred during processing into flat steel wires, and the tests after the heat treatment were stopped. Test No. In No.
  • Cu is out of the range of the present invention, and sulfide stress corrosion cracking has occurred.
  • Test No. In No. 32 Cu is out of the range of the present invention, and cracks occur when processing into flat steel wire, and the test after the heat treatment is stopped.
  • Test No. In No. 33 the Cu / Ni ratio was out of the range of the present invention, and sulfide stress corrosion cracking occurred.
  • Test No. In No. 34 Ni is out of the range of the present invention, and sulfide stress corrosion cracking has occurred.
  • Test No. In No. 35 the sum of Cu and Ni is out of the range of the present invention, a crack occurs when the flat steel wire is processed, and the test after the heat treatment is stopped. Test No. In Nos.
  • the N content is out of the range of the present invention, and hydrogen-induced cracking and sulfide stress corrosion cracking have occurred.
  • Test No. In No. 47 the Ca content is out of the range of the present invention, and hydrogen-induced cracking and sulfide stress corrosion cracking have occurred.
  • Test No. In No. 48 the content of S is out of the range of the present invention, and hydrogen-induced cracking and sulfide stress corrosion cracking have occurred.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

L'invention concerne un fil d'acier plat contenant, en % en masse, 0,35 à 0,60 % de C, plus de 1,50 % et moins de 2,00 % de Si, plus de 0,65 % et moins de 1,50 % de Mn, 0,010 % ou moins de S, 0,010 % ou moins de P, 0,005 à 0,60 % de Cr, 0,005 à 0,080 % d'Al, 0,0020 à 0,0080 % de N, 0,0002 à 0,0050 % de Ca, 0,05 à 0,80 % de Cu, et 0,05 à 0,60 % de Ni, le reste comprenant du Fe et des impuretés, Y1 représenté par l'expression <1> satisfaisant l'expression <2>, les expressions <5> et <6> étant satisfaites, la résistance à la traction étant comprise entre 1 000 et 1 350 MPa, la contrainte résiduelle de traction longitudinale étant inférieure ou égale à 300 MPa, et le rapport largeur/épaisseur étant compris entre 2,5 et 10.
PCT/JP2019/025662 2018-06-29 2019-06-27 Fil d'acier plat, et fil machine pour fil d'acier plat WO2020004570A1 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102570361B1 (ko) * 2022-07-19 2023-08-25 닛테츠 스테인레스 가부시키가이샤 고강도 스테인리스 강선 및 스프링

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001279381A (ja) * 2000-03-29 2001-10-10 Kobe Steel Ltd 耐縦割れ性に優れた高強度高靭性極細鋼線及びその製造方法
JP2016069705A (ja) * 2014-09-30 2016-05-09 株式会社神戸製鋼所 ボルト用鋼およびボルト
WO2017154930A1 (fr) * 2016-03-07 2017-09-14 新日鐵住金株式会社 Fil d'acier plat haute résistance présentant une résistance supérieure à la fissuration induite par l'hydrogène

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001279381A (ja) * 2000-03-29 2001-10-10 Kobe Steel Ltd 耐縦割れ性に優れた高強度高靭性極細鋼線及びその製造方法
JP2016069705A (ja) * 2014-09-30 2016-05-09 株式会社神戸製鋼所 ボルト用鋼およびボルト
WO2017154930A1 (fr) * 2016-03-07 2017-09-14 新日鐵住金株式会社 Fil d'acier plat haute résistance présentant une résistance supérieure à la fissuration induite par l'hydrogène

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102570361B1 (ko) * 2022-07-19 2023-08-25 닛테츠 스테인레스 가부시키가이샤 고강도 스테인리스 강선 및 스프링

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