EP3112491A1 - Matériau laminé pour ressort de haute résistance et fil pour ressort de haute résistance - Google Patents

Matériau laminé pour ressort de haute résistance et fil pour ressort de haute résistance Download PDF

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EP3112491A1
EP3112491A1 EP15755898.2A EP15755898A EP3112491A1 EP 3112491 A1 EP3112491 A1 EP 3112491A1 EP 15755898 A EP15755898 A EP 15755898A EP 3112491 A1 EP3112491 A1 EP 3112491A1
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amount
hydrogen
wire
rolled material
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EP3112491A4 (fr
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Atsuhiko TAKEDA
Tomokazu Masuda
Sho Takayama
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Kobe Steel Ltd
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Kobe Steel Ltd
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    • 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
    • C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
    • 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
    • C21D9/02—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for springs
    • 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
    • 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
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
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    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • 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
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • 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
    • 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
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • 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
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • 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
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • 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
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
    • 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
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/008—Martensite
    • 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
    • C21D3/00—Diffusion processes for extraction of non-metals; Furnaces therefor
    • C21D3/02—Extraction of non-metals
    • C21D3/06—Extraction of hydrogen
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires

Definitions

  • the present invention relates to a rolled material for high strength spring, and a wire for high strength spring using the same. More particularly, the present invention relates to a rolled material and a wire for high strength spring, which are useful as raw materials of high strength springs that are used in a state of being subjected to refining, namely, quenching and tempering, particularly a rolled material having excellent in corrosion fatigue properties after quench and temper, which are excellent in corrosion fatigue properties even though a tensile strength is a high strength in a range of 1,900 MPa or more after wire drawing.
  • Coil springs used in automobiles for example, a valve spring and a suspension spring used in the engine, suspension, and the like are required to reduce the weight and to increase the strength so as to achieve exhaust gas reduction an improvement in fuel economy.
  • the spring imparted with high strength is likely to cause hydrogen brittleness because of its poor toughness and ductility, leading to degradation of corrosion fatigue properties. Therefore, the steel wire (hereinafter, the steel wire is sometimes referred to as a wire) for high strength spring used in the manufacture of a spring is required to have excellent corrosion fatigue properties. Hydrogen generated by corrosion enters into a steel and may lead to embrittlement of a steel material, thus causing corrosion fatigue fracture, so that there is a need to improve corrosion resistance and hydrogen embrittlement resistance of the steel material so as to improve corrosion fatigue properties.
  • Patent Document 1 discloses technology in which a wire material is cold-drawn and then the structure is adjusted by quenching and tempering through high frequency incuction heating.
  • a structural fraction of pearlite is set at 30% or less and a structural fraction composed of martensite and bainite is set at 70% or more and then cold drawing is performed at a predetermined area reduction rate, followed by quenching and tempering to thereby reduce the insoluble carbides, leading to an improvement in delayed fracture properties.
  • Patent Document 2 a rolled wire material is subjected to wire drawing, followed by a quenching and tempering treatment through high frequency induction heating in Examples. This technology focuses primarily on achievement of the reconciliation of high strength and coiling properties, and gives no consideration to corrosion fatigue properties.
  • Patent Document 3 proposes a hot rolled wire material having excellent wire drawability under high degree wire drawing conditions.
  • Patent Document 3 focuses only on wire drawability during special processing such as high degree wire drawing, and also gives no consideration to corrosion fatigue properties after quenching and tempering, which becomes most important in a suspension spring.
  • the present invention has been made, and it is an object thereof is. to provide a rolled material, which is a material for high strength spring of hot coiling and cold coiling, and also can exhibit excellent corrosion fatigue properties after quenching and tempering even when suppressing the addition amount of an alloying element; and a wire for high strength spring obtained from such a rolled material.
  • the present invention that can solve the foregoing problems provides a rolled material for high strength spring, including, in % by mass:
  • a major axis and a minor axis of an oxide inclusion are respectively measured by observing using an electron probe micro analyzer (EPMA), and an average of the major axis and the minor axis of the oxide inclusion, namely, a value obtained by dividing the sum of the major axis and the minor axis by 2 is regarded as an average diameter.
  • Inclusions exhibiting this average of 25 ⁇ m or more are objects that are subjected to measurement of the number in the present invention.
  • the rolled material for high strength spring of the present invention further includes, in % by mass, at least one of following (a) to (d):
  • the present invention also include a wire for high strength spring, including any of chemical components of the steel mentioned above, wherein an area ratio of tempered martensite is 80% or more, and a tensile strength,is 1,900 MPa or more.
  • oxide inclusions in the rolled material are reduced and the amount of nondiffusible hydrogen is suppressed without adding a large amount of an alloying element, thus making it possible to exhibit excellent corrosion fatigue properties after quenching and tempering.
  • a rolled material it is possible to improve corrosion fatigue properties of the wire even when suppressing the cost of steel materials, thus making it possible to supply a high strength spring which is very unlikely to cause corrosion fatigue fracture, for example, a coil spring such as a suspension spring that is one of automobile components, at a cheap price.
  • Fig. 1 is a graph showing an influence of the number of inclusions and an amount of nondiffusible hydrogen in a rolled material on corrosion fatigue properties.
  • the number of oxide inclusions having an average diameter of 25 ⁇ m or more is set at 30 or less per 100 g of a steel material (hereinafter sometimes referred to as "30 or less per 100 g).
  • the number of oxide inclusions is preferably 20 or less per 100 g, and more preferably 10 or less per 100 g. To improve corrosion fatigue properties, there is no need to set the lower limit of the number of oxide inclusions.
  • the lower limit is preferably 2 or more per 100 g in view of industrial production.
  • Oxide inclusions having an average diameter of 25 ⁇ m or more serve as fracture starting point that is a stress concentration source, thus degrading corrosion fatigue properties, whereas, oxide inclusions having an average diameter of less than 25 ⁇ m do not exert an adverse influence on corrosion fatigue properties.
  • the amount of nondiffusible hydrogen is set at 0.40 ppm by mass or less. If a large amount of nondiffusible hydrogen exists in the rolled material, the amount of nondiffusible hydrogen also increases in the wire after quenching and tempering. If a large amount of nondiffusible hydrogen exists in the wire, a permissible amount of hydrogen, which further enters until the steel material embrittles, decreases. Therefore, even though a small amount of hydrogen entered during use as a spring, embrittlement of the steel material occurs and early fracture is likely to occur, resulting in degraded hydrogen embrittlement resistance.
  • the amount of nondiffusible hydrogen is preferably 0.35 ppm by mass or less, and more preferably 0.30 ppm by mass or less- The less the amount of nondiffusible hydrogen, the better. However, it is difficult to set at 0 ppm by mass and the lower limit is about 0.01 ppm by mass.
  • the amount of nondiffusible hydrogen is an amount of hydrogen measured by the method mentioned in Examples below, and specifically means the total amount of hydrogen released at 300 to 600°C when the temperature of a steel material is raised at 100°C/hour.
  • the rolled material for high strength spring according to the present invention is a low alloy steel in which the content of an alloying element is suppressed, and the chemical composition is as follows.
  • the present invention also includes a wire obtained by wire-drawing the above-mentioned rolled material, followed by quenching and tempering, and the chemical composition is the same as that of the rolled material.
  • chemical composition means % by mass.
  • C is an element that is required to ensure the strength of a wire for spring, and is also required to generate fine carbides that serve as hydrogen trapping sites. From such a viewpoint, the amount of C was determined in a range of 0.39% or more.
  • the lower limit of the amount of C is preferably 0.45% or more, and more preferably 0.50% or more. Excessive C amount, however, might generate coarse residual austenite and non-solid soluted carbides after quenching and tempering, which further degrades hydrogen embrittlement resistance.
  • C is an element that degrades corrosion resistance, so that there is a need to suppress the amount of C so as to enhance corrosion fatigue properties of a spring product such as a suspension spring which is a final product. From such a viewpoint, the amount of C was determined in a range of 0.65% or less.
  • the upper limit of the amount of C is preferably 0.62% or less, and more preferably 0.60% or less.
  • Si is an element that is required to ensure the strength of a wire for spring, and also exhibits the effect of refining carbides. To effectively exhibit these effects, the amount of Si was determined in a range of 1.5% or more.
  • the lower limit of the amount of Si is preferably 1.7% or more, and more preferably 1.9% or more.
  • Si is also an element that accelerates decarburization
  • excessive Si amount accelerates formation of a decarburized layer on a surface of a wire rod, thus requiring the peeling step for removal of the decarburized layer, resulting in increased manufacturing costs.
  • Non-solid solution carbides also increase, thus degrading hydrogen embrittlement resistance. From such a viewpoint, the amount of Si was determined in a range of 2.5% or less.
  • the upper limit of the amount of Si is preferably 2.3% or less, more preferably 2.2% or less, and still more preferably 2.1% or less.
  • Mn is an element that is employed as a deoxidizing element and reacts with S, which is a harmful element in a steel, to form MnS, and is useful for detoxication of S. Mn is also an element that contributes to an improvement in strength. To effectively exhibit these effects, the amount of Mn was determined in a range of 0.15% or more.
  • the lower limit of the amount of Mn is preferably 0.2% or more, and more preferably 0.3% or more. Excessive Mn amount, however, degrades toughness, thus causing embrittlement of a steel material. From such a viewpoint, the amount of Mn was determined in a range of 1.2% or less.
  • the upper-limit of the amount of Mn is preferably 1.0% or less, and more preferably 0.85% or less.
  • P is a harmful element that degrades ductility such as coiling properties of a rolled material such as a wire rod, and the amount thereof is preferably as small as possible. P is likely to segregate in grain boundaries to cause grain boundary embrittlement, and hydrogen is likely to cause fracture of grain boundaries, thus exerting an adverse influence on hydrogen embrittlement resistance. From such a viewpoint, the amount of P was determined in a range of 0.015% or less. The upper limit of the amount of P is preferably 0.010% or less, and more preferably 0.008% or less. The amount of P is preferably as small as possible, and is contained usually about 0.001%.
  • S is a harmful element that degrades ductility such as coiling properties of a rolled material, and the amount thereof is preferably as small as possible. S is likely to segregate in grain boundaries to cause grain boundary embrittlement, and hydrogen is likely to cause fracture of grain boundaries, thus exerting an adverse influence on hydrogen embrittlement resistance. From such a viewpoint, the amount of S was determined in a range of 0.015% or less. The upper limit of the amount of S is preferably 0.010% or less, and more preferably 0.008% or less. The amount of S is preferably as small as possible', and is usually contained about 0.001%.
  • Al is mainly added as a deoxidizing element. This element reacts with N to form AlN to thereby detoxicate solid-soluted N, and also contributes to refining of the structure. To adequately exhibit these effects, the amount of Al was determined in a range of 0.001% or more.
  • the lower limit of the amount of Al is preferably 0.002% or more, and more preferably 0.005% or more.
  • Al is an element that accelerates decarburization, like Si, there is a need to suppress the amount of Al in a steel for spring, which includes a large amount of Si. Therefore, in the present invention, the amount of Al was determined in a range of 0.1% or less.
  • the upper limit of the amount of Al is preferably 0.07% or less, more preferably 0.030% or less, and particularly preferably 0.020% or less.
  • Cu is an element that is effective in suppressing surface decarburization and improving corrosion resistance. Therefore, the amount of Cu was determined in a range of 0.10% or more.
  • the lower limit of the amount of Cu is preferably 0.15% or more, and more preferably 0.20% or more. Excessive Cu amount, however, causes cracks during hot working and increases costs. Therefore, the amount of Cu was determined in a range of 0.80% or less.
  • the upper limit of the amount of Cu is preferably 0.70% or less, and more preferably 0.60% or less.
  • the amount of Cu is preferably 0.48% or less, 0.35% or less, and 0.30% or less.
  • Ni is an element that is effective in suppressing surface decarburization and improving corrosion resistance. Therefore, the amount of Ni was determined in a range of 0.10% or more.
  • the lower limit of the amount of Ni is preferably 0.15% or more, and more preferably 0.20% or more. Excessive Ni amount, however, increases costs. Therefore, the amount of Ni was determined in a range of 0.80% or less.
  • the upper limit of the amount of Ni is preferably 0.70% or less, and more preferably 0.60% or less.
  • the amount of Ni is preferably 0.48% or less, 0.35% or less, and 0.30% or less.
  • oxide inclusions such as Al 2 O 3 , SiO 2 , CaO, MgO and TiO 2 are formed. Oxide inclusions are hard, and thus strain is generated around oxide inclusions due to a difference in hardness with a material around oxide inclusions. Hydrogen accumulated on the strain causes embrittlement of grain boundaries around the oxide inclusions. Therefore, reducing the amount of oxygen is important to improve corrosion fatigue properties. Therefore, the upper limit of the amount of O was set.at 0.0010% or less. The upper limit is preferably 0.0008% or less, and more preferably 0.0006% or less. Whereas, the lower limit of the amount of O is generally 0.0002% or more on industrial production.
  • the rolled material for spring of the present invention has the chemical composition mentioned above and can achieve excellent coiling properties and hydrogen embrittlement resistance while having high strength. Elements mentioned below may be further included for the purpose of improving corrosion resistance according to application.
  • Cr is an element that is effective in improving corrosion resistance. To effectively exhibit these effects, the amount of Cr is preferably 0.05% or more, more preferably 0.08% or more, and still more preferably 0.10% or more. However, Cr is an element that has a strong tendency to form carbides, and forms peculiar carbides in a steel material and is likely to be dissolved in cementite in a high concentration. It is effective to include a small amount of Cr, however, the heating time of the quenching step decreases in high frequency induction heating, leading to insufficient austenitizing of dissolving carbide, cementite, and the like into a matrix.
  • the amount of Cr is preferably 1.2% or less, more preferably 0.8% or less, and still more preferably 0.6% or less.
  • Ti is an element that is useful to react with S to form sulfide to thereby detoxicate S. Ti also has the effect of refining the structure by forming carbonitride. To effectively exhibit these effects, the amount of Ti is preferably 0.02% or more, more preferably 0.05% or more, and still more preferably 0.06% or more. Excessive Ti amount, however, may form coarse Ti sulfide, thus degrading ductility. Therefore, the amount of Ti is preferably 0.13% or less. From a viewpoint of cost reduction, the amount of Ti is preferably 0.10% or less, and more preferably 0.09% or less.
  • B is an element that improve hardenability and strengthens prior austenite crystal grain boundaries, and also contributes to suppression of fracture.
  • the amount of B is preferably 0.0005% or more, and more preferably 0.0010% or more. Excessive B amount, however, causes saturation of the above effects, so that the amount of B is preferably 0.01% or less, more preferably 0.0050% or less, and still more preferably 0.0040% or less.
  • Nb is an element that forms carbonitride together with C and N, and mainly contributes to refining of the structure.
  • the amount of Nb is preferably 0.003% or more, more preferably 0.005% or more, and still more preferably 0.01% or more. Excessive Nb amount, however, form coarse carbonitride, thus degrading ductility of a steel material. Therefore, the amount of Nb is preferably 0.1% or less. From a viewpoint of cost reduction, the amount is preferably set at 0.07% or less.
  • Mo is also an element that forms carbonitride together with C and N, and contributes to refining of the structure.
  • Mo is an element that is also effective in ensuring the strength after tempering.
  • the amount of Mo is preferably 0.15% or more, more preferably 0.20% or more, and still more preferably 0.25% or more. Excessive Mo amount, however, form coarse carbonitride, thus degrading ductility, for example, coiling properties of a steel material. Therefore, the amount of Mo is preferably 0.5% or less, and more preferably 0.4% or less.
  • Nb and Mo may be included individually, or both of them may be included in combination.
  • the rolled material of the present invention includes N as inevitable impurities, and the amount of it is preferably adjusted in a range mentioned below.
  • N is an element included in inevitable impurities. As the amount of N increases, it forms coarse nitride together with Ti and Al, thus exerting an adverse influence on fatigue properties. Therefore, the amount of N is preferably as small as possible.
  • the amount of N is, for example, 0.007% or less, and more preferably 0.005% or less. Meanwhile, if the amount of N is too reduced, productivity is drastically degraded. N forms nitride together with Al to thereby contribute to refining of crystal grains. From such a viewpoint, the amount of N is preferably 0.001% or more, more preferably 0.002% or more, and still more preferably 0.003% or more.
  • a method for producing a rolled material of the present invention will be described below.
  • it is possible to control the amount of nondiffusible hydrogen of the rolled material by adjusting at least one of (A) the amount of hydrogen in a molten steel stage, (B) the homogenizing treatment temperature and time before blooming, and (C) the cooling rate in a range of 400 to 100°C after hot rolling.
  • the method of reducing the amount of hydrogen in the steel include a method of adjusting in a molten steel stage, a method of adjusting in a stage of a continuously cast material at 1,000°C or higher after solidification, a method of adjusting in a heating stage before hot rolling, a method of adjusting in a heated stage during hot rolling, and a method of adjusting in a cooling stage after rolling. It is particularly preferred to perform at least one of treatments for reducing nondiffusible hydrogen (A) to (C) mentioned below.
  • coiling temperature TL after hot rolling there is no particular limitation on the coiling temperature TL after hot rolling, and cooling conditions beyond a temperature range of 400 to 100°C after coiling.
  • the coiling temperature TL can be set, for example, in a range of 900°C or higher and 1,000°C or lower, and is preferably 910°C or higher, and more preferably 930°C or higher.
  • An average cooling rate at the coiling temperature of TL to 650°C can be set in a range of 2°C/second or more and 5°C/second or less.
  • the lower limit of the average cooling rate at the coiling temperature of TL to 650°C is preferably 2.3°C/second or more, and more preferably 2.5°C/second or more.
  • the upper limit of the average cooling rate at the coiling temperature of TL to 650°C is preferably 4.5°C/second or less, and more preferably 4°C/second or less.
  • the average cooling rate at 650 to 400°C can be set at 2°C/second or less.
  • the average cooling rate at 650 to 400°C is preferably 1.5°C/second or less, and more preferably 1°C/second or less.
  • a wire is manufactured by wire processing, namely, wire drawing of the rolled material mentioned above.
  • wire processing namely, wire drawing of the rolled material mentioned above.
  • quenching and tempering by high frequency induction heating are performed after wire drawing, and such a wire is also included in the present invention.
  • a high strength wire having a tensile strength of 1,900 MPa or more can be obtained by subjecting the rolled material to wire working, namely, wire drawing, followed by quenching and tempering by high frequency induction heating. Specifically, the rolled material is subjected to wire drawing at an area reduction rate of about 5 to 35%, followed by quenching at about 900 to 1,000°C and further tempering at about 300 to 520°C.
  • the quenching temperature is preferably 900°C or higher so as to sufficiently perform austenitizing, and preferably 1,000°C or lower so as to prevent grain coarsening.
  • the heating temperature for tempering may be set at an appropriate temperature in a range of 300 to 520°C according to a target value of a wire strength. When quenching and tempering are performed by high frequency induction heating, quenching and tempering times are respectively in a range of about 10 to 60 seconds.
  • the tempered martensite structure has 80 area% or more. As a result of increasing the proportions of non-solid-soluted ferrite and residual austenite, the strength decreases.
  • the tempered martensite structure preferably has 88 area% or more. To set the proportion of the tempered martensite structure at 80 area% or more, it is preferable that the material is heated to 900°C or higher when heating before quenching, followed by sufficient austenitizing and further cooling to 100°C or lower by water cooling or oil cooling.
  • the thus obtained wire of the present invention can realize a high tensile strength in a range of 1,900 MPa or more.
  • the tensile strength is usually selected in a range of 1,900 MPa to 2,200 MPa.
  • the upper limit is about 2,500 MPa.
  • the wire of the present invention can exhibit corrosion fatigue properties even at a high strength in a range of 1,900 MPa or more because of use of the rolled material of the present invention.
  • Each of steel materials having chemical compositions shown in Tables 1 to 3 was melted by melting in a converter and then subjecting to continuous casting and a homogenizing treatment at 1,100°C or higher. After the homogenizing treatment, blooming was performed, followed by heating at 1,000 to 1,280°C and further hot rolling to obtain a rolled material having a diameter of 14.3 mm, namely, a wire rod. It is as shown in Tables 4 to 6 below whether or not a degassing treatment of a molten steel by the above-mentioned material is implemented, and whether or not cooling is implemented after coiling, namely, whether or not cooling at an average cooling rate of 0.5°C/second or less is implemented at 400 to 100°C after rolling. The amount of O in the molten steel shown in Tables 4 to 6 was adjusted by controlling the degree of deoxidizing with aluminum and silicon.
  • the coiling temperature TL after hot rolling was set at 950°C, and other cooling after coiling was performed at an average cooling rate of 4°C/second at a temperature in a range of TL to 650°C, and performed at an average cooling rate of 1°C/second at a temperature in a range of 650 to 400°C.
  • the homogenizing treatment is performed at 1,100°C for 10 hours or more.
  • the time of the homogenizing treatment at 1,100°C is less than 10 hours.
  • a specimen measuring 20 mm in width ⁇ 40 mm in length was cut out from the rolled material, namely, wire rod. After raising the temperature of the specimen at a temperature rise rate of 100°C/hour, a hydrogen release amount at 300 to 600°C was measured using a gas chromatogram, and the hydrogen release amount was regarded as the amount of nondiffusible hydrogen.
  • the number of oxide inclusions was determined by the following procedure: an average of the results of examination of six rolled material samples each having 50 g in weight was determined, followed by conversion into the number per 100 g. The number-of inclusions was examined by an acid dissolution method. Each sample (50 g) was dissolved with an acid and inclusions, remaining without being dissolved, was allowed to remain.on a filter paper. Inclusions having an average diameter of 25 ⁇ m or more were sorted by EPMA, analyzed by energy dispersive X-ray spectrometry (EDX), and then oxide inclusions were sorted.
  • EDX energy dispersive X-ray spectrometry
  • the number of oxide inclusions having an average diameter of 25 ⁇ m or more was measured and an average thereof was determined, followed by conversion into the number per 100 g of a steel material.
  • nitric acid adjusted so as not to dissolve oxide inclusions was.used for dissolution with an acid.
  • An average diameter of oxide inclusions means an average of a major axis and a minor axis, namely, the value obtained by dividing the sum of the major axis and the minor axis by 2.
  • oxygen was removed by sufficiently perform vacuum degassing when melting in a converter.
  • wire drawing namely, cold drawing to thereby reduce to a diameter of 12.5 mm
  • quenching and tempering An area reduction rate of wire drawing is about 23.6%, and the conditions of quenching and tempering are as follows.
  • a wire was cut into a' predetermined length and a tensile test was performed at a distance between chucks of 200 mm and a tensile speed of 5 mm/minute in accordance with JIS Z2241 (2011).
  • Corrosion fatigue properties were evaluated by fracture life after subjecting to a corrosion treatment and performing the Ono-type rotating-bending fatigue test.
  • Each wire.subjected to quenching and tempering was cut to fabricate a No. 1 test specimen (JIS Z 2274(1978)).
  • the parallel part of this test specimen was polished using a sand paper of No. 800.
  • a test was carried out without shot peening of a surface. First, the test specimen thus processed was subjected to a corrosion treatment under the following conditions.
  • the samples of test Nos. 17 to 31 shown in Table 5 are inferior in corrosion fatigue properties because at least any one of requirements of chemical composition of a steel material, the number of oxide inclusions and the amount of nondiffusible hydrogen defined in the present invention is invalid.
  • test Nos. 17 and 18 are examples using steels Nos. 17 ad 18 that contains neither Cu nor Ni added therein, or do not meet the defined lower limit, and thus corrosion fatigue properties were degraded.
  • insufficient deoxidizing treatment leads to excess amount of O in the steel, so that the number of oxide inclusions in the rolled material.increased and corrosion fatigue properties were degraded.
  • Fig. 1 an influence of the number of oxide inclusions and the amount of nondiffusible hydrogen in the rolled material on corrosion fatigue properties is shown in Fig. 1 .
  • invented examples denote samples of test Nos. 1 to 16 in Table 4 and comparative examples (expressed by the symbol “x” (cross)) denote samples of test Nos. 19 to 31 in Table 5, and the number of oxide inclusions in the rolled material was mentioned as "Number of Inclusions".
  • the rolled material and the wire of the present invention are industrially useful since they can be suitably used for coil springs that are used in automobiles, for example, a valve spring, a suspension spring, and the like that are used in the engine, suspension, and the like.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Thermal Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Strip Materials And Filament Materials (AREA)
  • Springs (AREA)
EP15755898.2A 2014-02-28 2015-02-03 Matériau laminé pour ressort de haute résistance et fil pour ressort de haute résistance Withdrawn EP3112491A4 (fr)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3088551A4 (fr) * 2013-12-27 2017-08-23 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Matiériau d'acier laminé pour ressort à haute résistance et câble pour ressort à haute résistance l'utilisant

Families Citing this family (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6458927B2 (ja) * 2014-10-07 2019-01-30 大同特殊鋼株式会社 線材圧延性に優れた高強度ばね鋼
CN105543652B (zh) * 2015-12-21 2018-02-09 武钢集团昆明钢铁股份有限公司 一种用于制造行车车轮的锻件钢钢水及其冶炼方法
JP6693532B2 (ja) 2016-01-26 2020-05-13 日本製鉄株式会社 ばね鋼
KR101889172B1 (ko) * 2016-12-12 2018-08-16 주식회사 포스코 응력부식 저항성이 우수한 고강도 스프링용 강선 및 그 제조방법
EP3640357A4 (fr) * 2017-06-15 2020-09-30 Nippon Steel Corporation Fil laminé pour acier à ressort
KR20190139941A (ko) * 2017-06-23 2019-12-18 닛폰세이테츠 가부시키가이샤 고강도 강 부재
TW201945559A (zh) * 2018-05-01 2019-12-01 日商日本製鐵股份有限公司 鋅系鍍敷鋼板及其製造方法
US11828698B2 (en) * 2018-11-30 2023-11-28 Nsk Ltd. Ambient-hydrogen-level assessment method and white-structure-damage-likelihood prediction method
CN109735771A (zh) * 2019-03-19 2019-05-10 马鞍山钢铁股份有限公司 一种具有优良疲劳性能和耐蚀性能的高强度弹簧用钢及其生产方法
CN114555850B (zh) * 2019-10-16 2022-11-01 日本制铁株式会社 减震器弹簧
CN111118398A (zh) * 2020-01-19 2020-05-08 石家庄钢铁有限责任公司 一种高淬透性高强度低温韧性弹簧钢及其生产方法
KR102141331B1 (ko) * 2020-03-19 2020-08-04 주식회사 샤크컴퍼니 강선을 이용하여 만든 파이프형 금속 탄성체 및 그 제조 방법과 이를 이용한 낚시릴의 텐션조정노브
WO2022047714A1 (fr) * 2020-09-03 2022-03-10 Nv Bekaert Sa Câblé d'acier pour le renforcement du caoutchouc
CN112853220A (zh) * 2021-01-08 2021-05-28 江苏省沙钢钢铁研究院有限公司 2000MPa级弹簧用盘条及其生产方法
CN113930681B (zh) * 2021-09-29 2022-12-02 武汉钢铁有限公司 一种高淬透性高疲劳寿命耐低温弹簧扁钢及其生产方法
CN115125446A (zh) * 2022-06-28 2022-09-30 浙江伊思灵双第弹簧有限公司 一种汽车用高疲劳性能弹簧及其制备方法
CN121204562A (zh) * 2025-11-27 2025-12-26 马鞍山钢铁有限公司 一种具有高疲劳性能的弹簧钢、制造方法及热处理方法

Family Cites Families (21)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5776267A (en) * 1995-10-27 1998-07-07 Kabushiki Kaisha Kobe Seiko Sho Spring steel with excellent resistance to hydrogen embrittlement and fatigue
JP3764715B2 (ja) 2002-10-22 2006-04-12 新日本製鐵株式会社 高強度冷間成形ばね用鋼線とその製造方法
KR20050103981A (ko) * 2003-03-28 2005-11-01 가부시키가이샤 고베 세이코쇼 내 셋팅성 및 피로특성이 우수한 스프링용 강
JP4280123B2 (ja) * 2003-07-01 2009-06-17 株式会社神戸製鋼所 耐腐食疲労性に優れたばね用鋼
JP4393335B2 (ja) * 2004-10-01 2010-01-06 株式会社神戸製鋼所 疲労強度または冷間加工性に優れた高清浄度鋼の製造方法
JP4555768B2 (ja) 2004-11-30 2010-10-06 新日本製鐵株式会社 高強度ばね用鋼線
JP4423253B2 (ja) * 2005-11-02 2010-03-03 株式会社神戸製鋼所 耐水素脆化特性に優れたばね用鋼、並びに該鋼から得られる鋼線及びばね
JP4027956B2 (ja) * 2006-01-23 2007-12-26 株式会社神戸製鋼所 耐脆性破壊特性に優れた高強度ばね鋼およびその製造方法
JP4393467B2 (ja) 2006-02-28 2010-01-06 株式会社神戸製鋼所 強伸線加工用の熱間圧延線材およびその製造方法
US8613809B2 (en) * 2006-06-09 2013-12-24 Kobe Steel, Ltd. High cleanliness spring steel and high cleanliness spring excellent in fatigue properties
JP4134203B2 (ja) * 2006-06-09 2008-08-20 株式会社神戸製鋼所 疲労特性に優れた高清浄度ばね用鋼および高清浄度ばね
US8734599B2 (en) * 2006-10-11 2014-05-27 Posco Steel wire rod for high strength and high toughness spring having excellent cold workability, method for producing the same and method for producing spring by using the same
KR100833051B1 (ko) * 2006-12-20 2008-05-27 주식회사 포스코 고강도 스프링용 강선재, 상기 강선재의 제조방법
CN102268604A (zh) * 2007-07-20 2011-12-07 株式会社神户制钢所 弹簧用钢线材及其制造方法
JP4847988B2 (ja) * 2007-07-20 2011-12-28 株式会社神戸製鋼所 腐食疲労特性に優れたばね用線材
JP4900516B2 (ja) * 2010-03-29 2012-03-21 Ｊｆｅスチール株式会社 ばね鋼およびその製造方法
JP5655627B2 (ja) * 2011-02-24 2015-01-21 新日鐵住金株式会社 耐水素脆化特性に優れた高強度ばね用鋼
CN102560046A (zh) * 2012-02-21 2012-07-11 南京钢铁股份有限公司 一种弹簧钢线材表面脱碳的控制方法
JP5364859B1 (ja) * 2012-05-31 2013-12-11 株式会社神戸製鋼所 コイリング性と耐水素脆性に優れた高強度ばね用鋼線およびその製造方法
CN103484781B (zh) * 2013-09-26 2016-06-01 宝山钢铁股份有限公司 一种高强高韧性弹簧钢及其制造方法
JP6212473B2 (ja) * 2013-12-27 2017-10-11 株式会社神戸製鋼所 高強度ばね用圧延材及びこれを用いた高強度ばね用ワイヤ

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3088551A4 (fr) * 2013-12-27 2017-08-23 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Matiériau d'acier laminé pour ressort à haute résistance et câble pour ressort à haute résistance l'utilisant

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MX2016011156A (es) 2016-12-09
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TWI535856B (zh) 2016-06-01
CN106062229A (zh) 2016-10-26
WO2015129403A1 (fr) 2015-09-03
EP3112491A4 (fr) 2017-11-15
KR20180112882A (ko) 2018-10-12
KR20160119216A (ko) 2016-10-12
TW201540845A (zh) 2015-11-01
US20170058376A1 (en) 2017-03-02

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