US20130118655A1 - Spring and manufacture method thereof - Google Patents

Spring and manufacture method thereof Download PDF

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Publication number
US20130118655A1
US20130118655A1 US13/811,152 US201113811152A US2013118655A1 US 20130118655 A1 US20130118655 A1 US 20130118655A1 US 201113811152 A US201113811152 A US 201113811152A US 2013118655 A1 US2013118655 A1 US 2013118655A1
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Prior art keywords
spring
wire rod
point
cross
less
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Abandoned
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US13/811,152
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English (en)
Inventor
Takeshi Suzuki
Yoshiki Ono
Shimpei Kurokawa
Kosuke Shibairi
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NHK Spring Co Ltd
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NHK Spring Co Ltd
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Priority claimed from JP2010175593A external-priority patent/JP5523241B2/ja
Priority claimed from JP2010260615A external-priority patent/JP5683230B2/ja
Application filed by NHK Spring Co Ltd filed Critical NHK Spring Co Ltd
Assigned to NHK SPRING CO., LTD. reassignment NHK SPRING CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KUROKAWA, SHIMPEI, ONO, YOSHIKI, SHIBAIRI, KOSUKE, SUZUKI, TAKESHI
Publication of US20130118655A1 publication Critical patent/US20130118655A1/en
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F1/00—Springs
    • F16F1/02—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant
    • F16F1/021—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant characterised by their composition, e.g. comprising materials providing for particular spring properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24C—ABRASIVE OR RELATED BLASTING WITH PARTICULATE MATERIAL
    • B24C1/00—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods
    • B24C1/10—Methods for use of abrasive blasting for producing particular effects; Use of auxiliary equipment in connection with such methods for compacting surfaces, e.g. shot-peening
    • 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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • 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
    • C21D7/00—Modifying the physical properties of iron or steel by deformation
    • C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
    • C21D7/04—Modifying the physical properties of iron or steel by deformation by cold working of the surface
    • C21D7/06—Modifying the physical properties of iron or steel by deformation by cold working of the surface by shot-peening or the like
    • 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
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • 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
    • 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
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F1/00—Springs
    • F16F1/02—Springs made of steel or other material having low internal friction; Wound, torsion, leaf, cup, ring or the like springs, the material of the spring not being relevant
    • F16F1/04—Wound springs
    • F16F1/06—Wound springs with turns lying in cylindrical surfaces
    • 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
    • C21D2211/001—Austenite
    • 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
    • C21D2211/002—Bainite
    • 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

Definitions

  • the present invention relates to a spring with superior fatigue resistance and superior sag resistance, and relates to a production method therefor.
  • materials for valve springs for automobile engines may include oil tempered carbon steel wires (SWO-V), oil tempered chromium-vanadium steel wires (SWOCV-V), and oil tempered chromium-silicon steel wires (SWOSC-V), which are specified in the Japanese Industrial Standards (JIS).
  • the oil tempered chromium-silicon steel wires are conventionally widely used in view of the fatigue resistance and the sag resistance. In recent years, reduction in weight of the valve spring is strongly desired in order to improve fuel efficiency of automobiles, and there is a trend of increasing tensile strength in spring wire so as to increase design stress of the valve spring.
  • notch sensitivity to cracks and defects such as inclusions is greatly increased according to the increase in the strength of the spring wire. Therefore, such a spring wire is more likely to break during cold spring forming (coiling) and for brittle fracture to occur while in use.
  • high compressive residual stress may be provided on a surface layer of a spring wire from a surface to deep inside the spring wire.
  • shot peening is widely used for providing compressive residual stress on a surface layer of a spring wire in order to improve the fatigue resistance of a spring.
  • the thickness of the compressive residual stress layer is a distance from the surface to a position where the compressive residual stress is zero, which is hereinafter called “thickness”.
  • a spring with superior fatigue resistance is disclosed in Japanese Unexamined Patent Application Laid-open No. 64-83644.
  • This spring is produced by using an oil tempered wire rod in which an element such as V is added in the chemical composition of the steel that is specified in the JIS.
  • the additional element increases toughness of the steel material by refining crystal grains and thereby improves the fatigue resistance; however, this increases the material cost.
  • a spring made of a silicon killed steel wire with superior fatigue characteristics is disclosed in Japanese Unexamined Patent Application Laid-open No. 2008-163423.
  • the spring is obtained by coiling a steel material in which the amounts of Ba, Al, Si, Mg, and Ca are adjusted. In order to add these elements in balanced amounts, the process of steel refining is very difficult to control, whereby the production cost is high.
  • a spring with superior fatigue strength is disclosed in Japanese Unexamined Patent Application Laid-open No. 2005-120479.
  • the chemical composition of the steel is adjusted, and grain size is decreased while the size of inclusions is decreased because the inclusions may become starting points of fatigue failure.
  • the practical strength is required of lightweight and high strength valve springs of recent years.
  • a method of further performing a nitriding treatment for obtaining higher fatigue strength is disclosed in Japanese Unexamined Patent Application Laid-open No. 2005-120479.
  • the nitriding treatment can increase the surface hardness, whereby the fatigue resistance may be improved.
  • iron nitrides are formed on a surface layer and must be completely removed after the nitriding treatment, because the iron nitrides may cause decrease in the fatigue strength. Therefore, the production process is complicated, and the cost of the nitriding treatment is high, whereby the production cost is high.
  • a spring which is made of a hard-drawn wire and has superior fatigue strength, is disclosed in Japanese Patent No. 4330306.
  • the hard-drawn wire is a drawn wire rod of a pearlite structure or a mixed structure of ferrite and pearlite.
  • the spring is formed by coiling the hard-drawn wire and then controlling a residual stress difference between the inner diameter side and the outer diameter side of the spring so as to be not more than 500 MPa. According to the technique disclosed in Japanese Patent No. 4330306, quenching treatment and tempering treatment are not necessary, whereas these treatments are generally widely used for producing oil tempered wires, whereby the costs therefor are decreased.
  • the chemical composition of the steel in order to control the residual stress difference so as to be not more than 500 MPa, the chemical composition of the steel must be adjusted, and the steel must be annealed at not less than 400° C. after it is coiled. Accordingly, the strength of the steel is decreased, and it is therefore difficult to obtain a high strength spring that meets recent requirements.
  • a spring steel wire with superior cold formability and high fatigue strength is disclosed in Japanese Unexamined Patent Application Laid-open No. 2-57637.
  • This spring steel wire is obtained by adding Mo, V, and the like, to a chemical composition of a spring steel that is specified in the JIS and by austempering treatment.
  • the yield ratio ratio of yield strength to tensile strength
  • the yield ratio is set to be not more than 0.85 in order to decrease tensile residual stress that may remain at the inner diameter side of a coil spring after the spring steel wire is cold formed.
  • a technique for improving the fatigue resistance and the sag resistance is disclosed in Japanese Unexamined Patent Application Laid-open No. 2004-315967.
  • concentrations mainly of Cr and Si are increased in a composition of a spring steel that is specified in the JIS, whereby quenchability and resistance to temper softening are improved.
  • some degree of the sag resistance is improved, but the material cost is increased by highly alloying.
  • a technique for improving the sag resistance is disclosed in Japanese Unexamined Patent Application Laid-open No. 2007-302950.
  • a concentration mainly of Cr is increased and V is added in a composition of a spring steel that is specified in the JIS.
  • size, density per area, and composition, of cementite are specified so as to obtain precipitation strengthening effect of fine cementite and to prevent decomposition of the cementite during low-temperature annealing and nitriding.
  • the material cost is increased by highly alloying, and the conditions of quenching and tempering must be strictly controlled so as to obtain the predetermined cementite structure. Accordingly, the production cost is increased.
  • the present invention has been completed so as to solve the problems in the conventional techniques, and an object of the present invention is to provide a spring with superior fatigue resistance and a production method therefor.
  • the spring is produced by decreasing the material cost in a simplified process.
  • the present invention has been completed so as to solve the problems in the conventional techniques, and another object of the present invention is to provide a spring with superior sag resistance and a production method therefor.
  • the spring is produced by decreasing the material cost in a simplified process.
  • the inventors of the present invention conducted intensive research on fatigue strength of a valve spring with high strength.
  • the inventors of the present invention had the following idea. That is, by adjusting the composition of a spring steel and annealing conditions that are provided after coiling, some degree of residual stress, which is generated after the coiling, can be decreased.
  • it is difficult to completely remove the effect of the residual stress with respect to the fatigue strength while high strength of the spring steel is maintained.
  • it is effective to heat a spring wire to an austenitizing temperature so that the residual stress, which is generated by coiling, is substantially zero, after it is coiled.
  • the inventors of the present invention found the following.
  • a coil spring in which high compressive residual stress is provided from a surface to deep inside, may be made of an inexpensive material such as an oil tempered wire that is specified in the JIS, a hard-drawn wire having the same composition as that of the oil tempered wire, or the like.
  • the coil spring is produced by performing ordinary shot peening in a later step without a special complicated heat treatment step as long as an appropriate heat history condition is selected so as to form a predetermined structure and predetermined concentrations of alloying elements are set.
  • the coil spring has high fatigue resistance corresponding to the requirements of the markets even when a nitriding treatment is not performed, whereas the nitriding treatment is usually performed. Accordingly, the processing cost is decreased, and the process is simplified.
  • the present invention provides a first spring that has been completed based on the above findings, and the spring consists of, by mass %, 0.5 to 0.7% of C, 1.0 to 2.0 % of Si, 0.1 to 1.0 % of Mn, 0.1 to 1.0 % of Cr, not more than 0.035% of P, not more than 0.035% of S, and the balance of Fe and inevitable impurities.
  • the spring has a structure including not less than 65% of bainite and 4 to 13% of residual austenite by area ratio in a cross section, and the residual austenite contains carbon at an average concentration of 0.65 to 1.7%.
  • the spring has a compressive residual stress layer in a cross section from a surface to a depth of 0.35 mm to D/4, in which D (mm) is a circle-equivalent diameter of the cross section.
  • the compressive residual stress layer has maximum compressive residual stress of 800 to 2000 MPa.
  • the spring has a center portion with hardness of 550 to 650 HV in a cross section and has a high hardness layer with greater hardness than the center portion by 50 to 500 HV from a surface to a depth of 0.05 to 0.3 mm.
  • the present invention provides a first production method for a spring, and the method includes a step of preparing a wire rod, a step of forming the wire rod into a shape of a spring, a heat treatment step, and a shot peening step of shooting shot at the wire rod after the heat treatment step.
  • the wire rod consists of, by mass %, 0.5 to 0.7% of C, 1.0 to 2.0% of Si, 0.1 to 1.0% of Mn, 0.1 to 1.0% of Cr, not more than 0.035% of P, not more than 0.035% of S, and the balance of Fe and inevitable impurities.
  • the wire rod is austenitized at a temperature of Ac3 point to (Ac3 point+250° C.) and is cooled at a cooling rate of not less than 20° C./second. Then, the wire rod is held at a temperature of Ms point to (Ms point+60° C.) for not less than 400 seconds and is cooled to room temperature at a cooling rate of not less than 20° C./second.
  • the Ac3 point is a boundary temperature at which a structure is transformed from a two-phase region of ferrite and austenite to a single-phase region of austenite during heating.
  • the Ms point is a temperature at which generation of martensite starts during cooling.
  • the “center portion” is a center portion of a circle of a circular cross section or a center of gravity of a shape of a cross section other than the circular cross section, such as a rectangular shape, an ellipse shape, or the like.
  • the inventors of the present invention conducted intensive research on the sag resistance of a coil spring in conditions at around 120° C.
  • Sag of a spring which is designed so as to withstand high stress of maximum shear stress of approximately 1400 MPa, is affected primarily by dislocation glide. Therefore, the amount of sag is smaller when lower net stress is applied to a spring wire.
  • the net stress is combined stress of stress, which remains in the spring wire even when no load is applied, and stress which is applied to the spring wire when load is applied. That is, tensile residual stress, which is generated by strain that remains after the cold coiling, adversely affects the sag resistance and is therefore preferably small.
  • the tensile residual stress that is generated after the cold coiling can be decreased by annealing and is decreased with the increase in the annealing temperature.
  • the material is softened accordingly, and there is a limit to increase in the resistance to temper softening by adjusting the composition. Therefore, it is essentially difficult to completely remove tensile residual stress while high strength of the spring steel is maintained by the annealing.
  • the inventors of the present invention reached the following conclusion. That is, it is effective for a coiled spring wire to be heated to an austenitizing temperature that is a high temperature so as to substantially completely remove the residual stress, which is generated by coiling, and then the structure of the coiled spring is improved.
  • strain aging which is performed by providing strain and low-temperature annealing, is generally widely used.
  • dislocation density is increased by providing strain, whereby some dislocations cross with or cut in forest dislocations and generate jogs and kinks. Some of the jogs and the kinks are immobilized and prevent movement of subsequent movable dislocations. In this case, movable dislocations are increased to some degree.
  • heating is performed so that solid-solved atoms such as carbon accumulate and surround the movable dislocations, whereby movement of the dislocations is prevented. If the movable dislocation density is too high, the number of the accumulated solid-solved atoms per length of dislocation is decreased, and the effects of the strain aging are decreased. Accordingly, the movable dislocation density needs to be preliminarily appropriately controlled before the aging is performed.
  • a conventional oil tempered wire has a metal structure in which martensite is tempered and has a mixed structure of ferrite with low carbon concentrations and cementite (Fe 3 C) due to the tempering temperature (hereinafter called a “tempered martensite structure”).
  • tempered martensite structure There may be cases in which austenite of a high temperature phase remains in the structure. Therefore, most carbon atoms are used for forming cementite, and the movable dislocation density with respect to the solid-solved atoms in ferrite is high, whereby it is difficult to improve the sag resistance by the strain aging.
  • the inventors of the present invention conducted intensive research and found the following. That is, by forming a structure so as to be made primarily of fine bainite with superior ductility after the coiling, greater plastic strain is provided without decreasing fatigue resistance compared with a case using a conventional tempered martensite structure. In this case, the movable dislocation density, which adversely affects the sag resistance, is decreased, whereby the movable dislocations are efficiently firmly fixed by the strain aging. Moreover, by providing a great amount of plastic strain in a setting step, large compressive residual stress is generated inside a spring wire and improves the sag resistance and the fatigue resistance. The setting step will be described later.
  • the inventors of the present invention focused on dispersion strengthening of a second phase in a metal structure and found the following. That is, the sag resistance is improved by dispersing fine residual austenite with high carbon concentrations in the structure, which is made primarily of fine bainite, at high density. In this case, the residual austenite prevents the movement of the dislocations. In general, since austenite that remains in the tempered martensite structure contains carbon at concentrations approximately equal to an average carbon concentration of a base phase, the residual austenite has low strength and thereby has been expected to adversely affect the sag resistance.
  • the inventors of the present invention found the following. That is, by setting the carbon concentration in the residual austenite high so as to be greater than an average carbon concentration in a base phase, the strength of the residual austenite is improved. Therefore, this residual austenite does not adversely affect the sag resistance. In contrast, this residual austenite is effective for improving the sag resistance and the fatigue resistance. This is because effects of deformation-induced martensitic transformation (accompanying large volume expansion) are obtained by the residual austenite with high carbon concentrations when a surface layer is plastically deformed by shot peening. As a result, compressive residual stress in the surface layer of a spring wire is more increased compared with a conventional case.
  • the effects of the completely removal of the tensile residual stress, which remains after the cold coiling, by austenitizing heating, and the effects of the deformation-induced transformation of the residual austenite, are obtained. Therefore, a compressive residual stress layer is foimed on a surface layer from a surface to deep inside by shot peening in a later step.
  • the structure in the entirety of the steel material, the structure is formed of fine bainite with superior ductility, and an immobilized rate of the movable dislocations is increased by the strain aging.
  • fine residual austenite with high strength is dispersed from the surface layer to the inside, whereby the effect for pinning dislocations is improved. Accordingly, fatigue resistance and sag resistance that are greater than those of an oil tempered wire are balanced.
  • a coil spring may be made of an inexpensive material such as an oil tempered wire that is specified in the JIS, a hard-drawn wire having the same composition as that of the oil tempered wire, or the like.
  • the coil spring is produced by performing ordinary shot peening and setting in later steps without a special complicated heat treatment step as long as an appropriate heat history condition is selected so as to fo a predetermined structure and predetermined concentrations of alloying elements are set.
  • the coil spring has high sag resistance corresponding to the requirements of the markets even when a nitriding treatment is not performed, whereas the nitriding treatment is generally performed. Accordingly, the processing cost is decreased, and the process is simplified.
  • the present invention also provides a second spring in which the residual austenite has an average circle-equivalent grain diameter of not more than 3 ⁇ m in the first spring.
  • the present invention also provides a second production method for a spring, and this method includes a step of preparing a wire rod, a step of forming the wire rod into a shape of a spring, a heat treatment step, and a shot peening step of shooting shot at the wire rod after the heat treatment step.
  • the wire rod consists of, by mass %, 0.5 to 0.7% of C, 1.0 to 2.0% of Si, 0.1 to 1.0% of Mn, 0.1 to 1.0% of Cr, not more than 0.035% of P, not more than 0.035% of S, and the balance of Fe and inevitable impurities.
  • the wire rod is austenitized at a temperature of Ac3 point to (Ac3 point+250° C.) and is cooled at a cooling rate of not less than 20° C./second. Then, the wire rod is held at a temperature of (Ms point ⁇ 20° C.) to (Ms point+60° C.) for not less than 400 seconds and is cooled to room temperature.
  • a spring with superior fatigue resistance is obtained without performing a complicated heat treatment and a surface hardening treatment by using a spring wire which is easily available.
  • the spring wire does not contain expensive alloying elements and has a composition of a spring steel that is specified in the JIS.
  • the spring has a high hardness layer and a thick high compressive residual stress layer on a surface layer.
  • the spring of the present invention has superior recycling efficiency because the amounts of the alloying elements are small.
  • the production process is simple, and processing time is decreased, whereby productivity is improved and energy is saved.
  • a spring with superior sag resistance is obtained without performing a complicated heat treatment and a surface hardening treatment by using a spring wire which is easily available.
  • the spring wire does not contain expensive alloying elements and has a composition of a spring steel that is specified in the JIS.
  • the spring has a high hardness area and a thick high compressive residual stress layer on a surface layer.
  • the spring of the present invention has superior recycling efficiency because the amounts of the alloying elements are small.
  • the production process is simple, and processing time is decreased, whereby productivity is improved and energy is saved.
  • FIG. 1A shows a result of observation of a reflection electron image (SEM (Scanning Electron Microscopy)) of a structure of a practical example of the present invention.
  • FIG. 1B shows a result of measurement of carbon element map (FE-EPMA (Field Emission Electron Probe Micro Analyzer)).
  • FIG. 1C shows a result of measurement of a crystal structure (phase) map (EBSD (Electron Backscatter Diffraction)).
  • FIG. 1D is a graph showing a result of analysis of carbon concentration at line LH in FIG. 1B .
  • C is important for obtaining high strength of not less than 1800 MPa and a predetermined ratio of residual austenite at room temperature. In order to obtain these effects, it is necessary to add C at not less than 0.5%. On the other hand, if the concentration of C is excessive, the ratio of residual austenite, which is a soft phase, is excessively increased, whereby predetermined strength is difficult to obtain. Therefore, the amount of C is set to be not more than 0.7%.
  • Si prevents generation of carbides from austenite matrix when C migrates from bainitic ferrite, which forms the bainite, to austenite. Therefore, Si is an essential element for obtaining predetermined residual austenite in which C is solid solved at high concentration. In addition, Si has a solid solution strengthening effect and is effective for obtaining high strength. In order to obtain these effects, not less than 1.0% of Si is necessary. In contrast, if the concentration of Si is excessive, the ratio of soft residual austenite is increased, whereby the strength is decreased. Accordingly, the concentration of Si is set to be not more than 2.0%.
  • Mn is added as a deoxidizing element during refining and stabilizes austenite.
  • the concentration of Mn is set to be not more than 1.0%.
  • Cr improves the quenchability of a steel material and facilitates strengthening. Moreover, Cr delays pearlitic transformation, whereby bainite structure is reliably obtained during cooling after the austenitizing heating, by preventing generation of pearlite structure. Therefore, it is necessary to add Cr at not less than 0.1%. On the other hand, if Cr is added at more than 1.0%, iron carbides are easily generated, and it is difficult to generate residual austenite. Accordingly, the concentration of Cr is set to be not more than 1.0 %.
  • the concentrations of P and S are desirably lower, but decrease in the concentrations of P and S is expensive in refining because they are impurities. Accordingly, the upper limits of the concentrations of P and S are set to be 0.035%.
  • the concentrations of P and S are preferably not more than 0.01%.
  • the “cross section” is a cross section that orthogonally crosses a longitudinal direction of a spring wire.
  • Bainite not less than 65%
  • Bainite is a metal structure that is obtained by isothermally transforming an austenitized steel material at a temperature range of not more than approximately 550° C. and more than a martensitic transformation start temperature. Bainite is composed of bainitic ferrite and iron carbide. Since the bainitic ferrite as a matrix has high dislocation density, and the iron carbide has a precipitation strengthening effect, bainitic structure improves the strength of the steel material. In the production method for a spring in the First Embodiment, a steel containing Si at high concentration is used and is held at a temperature of Ms point to (Ms point+60° C.), whereby coarsening of the iron carbide is prevented.
  • the bainite structure has a structure in which fine iron carbide is precipitated in the matrix of the bainitic ferrite, whereby grain boundary strength is not greatly decreased, and ductility and toughness are not greatly decreased although the steel material has high strength.
  • bainite is an essential structure for obtaining high strength and high ductility, and the area ratio thereof is preferably higher. In order to obtain high strength and high ductility as described in the present invention, not less than 65% of the area ratio of the bainite is required.
  • austenite that is not transformed during the isothermal holding becomes martensite or residual austenite by being subsequently cooled to room temperature.
  • Residual austenite increases ductility and toughness by TRIP (Transformation-induced plasticity) phenomenon and is thereby effective for decreasing notch sensitivity. Moreover, the residual austenite expands in volume at a stress concentrated portion of an end of a crack by deformation (strain)-induced martensitic transformation, and compressive stress is applied by binding force of surroundings thereof, whereby degree of stress concentration is decreased, and growth rate of the crack is decreased. Furthermore, the residual austenite is transformed into martensite by deformation-induced transformation in a shot peening step. In this case, the residual austenite expands in volume, whereby high compressive residual stress is provided on a surface layer to deep inside.
  • TRIP Transformation-induced plasticity
  • the surface layer that is processed by the shot peening contains residual austenite at a lower ratio than that of the inside, but not less than 4% of the ratio of residual austenite is necessary in a cross section in order to obtain the effect for preventing growth of cracks.
  • the ratio of residual austenite is set to be not more than 13%.
  • martensite is not essential but can be included at an area ratio of 5 to 30% so as to obtain predetermined tensile strength. If the area ratio of martensite exceeds 30%, high strength is obtained, but the notch sensitivity is increased, whereby superior fatigue resistance is not obtained.
  • Compressive residual stress is provided on a surface layer primarily by shot peening.
  • higher compressive residual stress is provided to deep inside by the deformation-induced martensitic transformation of the residual austenite that exists in the steel material.
  • the thickness of the compressive residual stress layer on the surface layer from a surface is set to be 0.35 mm to D/4, in which D (mm) is a circle-equivalent diameter of a cross section.
  • the compressive residual stress layer is made so as to have maximum compressive residual stress of 800 to 2000 MPa.
  • the maximum compressive residual stress is desirably higher in order to prevent generation and growth of fatigue cracks, and not less than 800 MPa of the maximum compressive residual stress is necessary in consideration of using the spring by setting high design stress.
  • the upper limit of the maximum compressive residual stress is set to be 2000 MPa.
  • the hardness at the center of a cross section of a spring wire is set to be not more than 650 HV.
  • a high hardness layer on the surface layer of the spring is effective for preventing generation of cracks and needs to have greater Vickers hardness than the center (center of gravity) by not less than 50 HV.
  • the upper limit of the difference in the hardness between the high hardness layer and the center is set to be not more than 500 HV.
  • not less than 0.05 mm of the thickness of the high hardness layer is necessary in order to prevent generation of cracks.
  • the thickness of the high hardness layer is set to be not more than 0.3 mm.
  • the spring of the present invention is produced as follows. After the steel material having the above-described chemical composition is coiled, both end surfaces of the coiled steel material are ground. Then, the coiled steel material is subjected to a heat treatment step. In the heat treatment step, the coiled steel material is austenitized at a temperature of Ac3 point to (Ac3 point+250° C.) and is cooled at a cooling rate of not less than 20° C./second. The coiled steel material is then held at a temperature of Ms point to (Ms point+60° C.) for not less than 400 seconds and is cooled to room temperature at a cooling rate of not less than 20° C./second.
  • the coiled steel material is subjected to shot peening.
  • the structure of the steel material before it is heated to not less than Ac3 point is not specifically limited.
  • a hot forged steel bar or a drawn steel bar may be used as the steel material.
  • each of the steps will be described, and reasons for limitations are also described as necessary.
  • the coiling step is a step of cold fottaing the steel material into a predetermined coil shape.
  • the forming may be performed by using a spring forming machine (coiling machine) or by using a cored bar.
  • the present invention is not limited to a coil spring and can be applied to any spring such as a plate spring, a torsion bar, a stabilizer, or the like.
  • both end surfaces of the coiled steel material are ground so as to be flat surfaces that are perpendicular to an axis thereof. This step is performed as necessary.
  • the coiled steel material is austenitized and is cooled, and it is then isothermally held and is cooled.
  • the isothermal holding may be performed by immersing the coiled steel material into a salt bath, for example, but it does not have to be performed by using the salt bath and may be performed by another method, such as a method of using a lead bath.
  • the structure of the steel material before it is austenitized is not specifically limited. For example, a hot forged steel bar or a drawn steel bar may be used as the steel material.
  • the austenitizing temperature is set at a temperature of Ac3 point to (Ac3 point+250° C.).
  • the austenitizing temperature is lower than Ac3 point, the coiled steel material is not austenitized, and a predetermined structure is not obtained. On the other hand, if the austenitizing temperature exceeds (Ac3 point+250° C.), diameters of prior austenite grains tend to be increased, whereby the ductility may be decreased.
  • the rate of cooling the coiled steel material to the isothermal holding temperature after the austenitizing is desirably higher, and the cooling needs to be performed at a cooling rate of not less than 20° C./second, preferably, not less than 50° C./second. If the cooling rate is less than 20° C./second, pearlite is generated during the cooling, and the structure that is described in the present invention is not obtained.
  • the isothermal holding temperature needs to be set at a temperature of Ms point to (Ms point+60° C.), which is a very important parameter to be controlled in the production method for the spring of the present invention.
  • the isothermal holding temperature is less than an Ms point, martensite, which is generated at an initial stage of the transformation, prevents improvement of the ductility, and the ratio of bainite that is described in the present invention is not obtained.
  • the isothermal holding temperature exceeds (Ms point+60° C.)
  • the ratio of residual austenite is excessively increased, whereby the tensile strength is decreased, and strength sufficient to withstand a load as a spring is not obtained.
  • the isothermal holding time needs to be set at not less than 400 seconds, which is also a very important parameter to be controlled in the production method for the spring of the present invention.
  • the holding time is less than 400 seconds, bainitic transformation hardly proceeds, whereby the ratio of martensite is increased whereas the ratio of bainite is decreased, and the structure that is described in the present invention is not obtained.
  • the holding time is desirably not more than 3 hours.
  • the cooling rate after the isothermal holding is preferably higher in order to obtain a uniform structure and needs to be set at not less than 20° C./second, preferably, not less than 50° C./second. Specifically, oil cooling or water cooling is preferable. On the other hand, if the cooling rate is less than 20° C./second, the structure tends to differ between the surface of the steel material and the inside, whereby the structure that is described in the present invention may not be obtained.
  • Shot peening is a method of providing compressive residual stress on a surface of the coiled steel material by colliding a shot of metal or sand on the coiled steel material, whereby the sag resistance and the fatigue resistance of the spring are improved.
  • higher compressive residual stress is provided to deep inside by the deformation-induced martensitic transformation of the residual austenite.
  • the shot peening may be performed by using a shot of cut wires, steel balls, high hardness particles such as of the FeCrB type, or the like.
  • the degree of the compressive residual stress can be adjusted by a sphere-equivalent diameter of the shot, shooting speed, shooting time, and a multistep shooting process.
  • the residual austenite occurs deformation-induced transformation and is transformed into martensite with higher strength.
  • the volume expansion occurs according to the transformation, whereby high compressive residual stress is provided, and the effect for pinning the dislocations is further increased. Accordingly, the sag resistance is further improved.
  • a setting step is optionally performed by providing plastic strain to the coiled steel material so as to improve the elastic limit and to decrease the amount of sag (amount of permanent set) while in use.
  • the setting hot setting
  • the sag resistance is further improved.
  • the residual austenite undergoes deformation-induced transformation and is transformed into martensite with higher strength.
  • the volume expansion occurs according to the transformation, whereby high compressive residual stress is provided, and the effect for pinning the dislocations is more increased. Accordingly, the sag resistance is further improved.
  • the chemical composition of a steel material and various characteristics in a cross section of a spring wire for the spring in the Second Embodiment of the present invention are the same as in the case of the First Embodiment. Moreover, the area ratios of the structures in a cross section are the same as in the case of the First Embodiment, except that an average circle-equivalent grain diameter of the residual austenite is limited. Therefore, only this difference will be described.
  • the residual austenite with high carbon concentration has high strength, and the effect for pinning the dislocations is obtained by dispersing fine residual austenite grains with high strength, whereby the sag resistance is improved. If an average circle-equivalent grain diameter of the residual austenite exceeds 3 ⁇ m, fine residual austenite is not sufficiently dispersed, whereby the effect for pinning the dislocations is not sufficiently obtained.
  • the production method for the spring in the Second Embodiment of the present invention is the same as that in the First Embodiment except that the isothermal holding is performed at a temperature of (Ms point ⁇ 20° C.) to (Ms point+60° C.) in the heat treatment step. Therefore, only this difference is described as follows.
  • the isothermal holding temperature needs to be set at a temperature of (Ms point ⁇ 20° C.) to (Ms point+60° C.), which is a very important parameter to be controlled in the production method for obtaining the spring steel and the spring of the present invention. If the isothermal holding temperature is less than (Ms point ⁇ 20° C.), martensite is excessively generated in an initial stage of the transformation and prevents improvement of the ductility, and bainite is not obtained at an area ratio of not less than 65%.
  • An austempered wire rod having a composition shown in Table 1 was prepared and was cold coiled into a predetermined shape by a coiling machine, whereby coiled wire rods are obtained.
  • the coiled wire rods were subjected to a heat treatment at a condition shown in Table 3.
  • the coiled wire rods were heated to a temperature of Ac3 point to (Ac3 point+250° C.) in a heating furnace and were austenitized.
  • the coiled wire rods were held in a salt bath, which was held at a temperature T (° C.), for a time t (seconds) and were cooled.
  • the temperature T and the time t are shown in Table 3.
  • the coiled wire rods were subjected to shot peening.
  • round cut wires with a sphere-equivalent diameter of 0.8 mm were used in a first step.
  • round cut wires with a sphere-equivalent diameter of 0.45 mm, and particles of sand with a sphere-equivalent diameter of 0.1 mm were used in a second step and a third step, respectively.
  • springs were produced, and specifications of the springs are shown in Table 2.
  • Various characteristics were investigated in the following manner with respect to the springs, and results thereof are shown in Table 3.
  • Phases in the structure were identified as follows. A cross section of a sample was polished, and the sample was immersed in a nital (a solution of 3% nitric acid and alcohol) for a few seconds. In the structure of the cross section, bainite is easily corroded by the nital and thereby appears black or gray in an optical micrograph. On the other hand, martensite and residual austenite have high corrosion resistance to the nital and thereby appears white in an optical micrograph. By using these functions, an image of an optical micrograph is processed, whereby the ratio of bainite (black portions and gray portions) and the total ratio of martensite and residual austenite (white portion) were measured.
  • a nital a solution of 3% nitric acid and alcohol
  • the ratio of residual austenite was measured by using an X-ray diffraction method with respect to a buff finished sample.
  • the ratio of martensite is calculated by subtracting the ratio of residual austenite, which was obtained by the X-ray diffraction method, from the total ratio of martensite and residual austenite, which was obtained by using the optical micrograph.
  • the average carbon concentration in the residual austenite was calculated from the following relational expression by using lattice constant a (nm).
  • the lattice constant was measured from each of diffraction peak angles of ( 111 ), ( 200 ), ( 220 ), and ( 311 ) by X-ray diffraction.
  • FIG. 1A to 1D show results of evaluating an area that existed at a depth of 1.025 mm from the outer circumferential surface toward the center of a cross section of the wire spring of a sample No. 3 of a practical example of the present invention.
  • FIG. 1A shows a result of observation of a reflection electron image (SEM (Scanning Electron Microscopy)).
  • FIG. 1B shows a result of measurement of carbon element map (FE-SPMA (Field Emission Electron Probe Micro Analyzer)).
  • FIG. 1C shows a result of measurement of crystal structure (phase) map (EBSD (Electron Backscatter Diffraction)).
  • FIG. 1A shows a result of observation of a reflection electron image (SEM (Scanning Electron Microscopy)).
  • FIG. 1B shows a result of measurement of carbon element map (FE-SPMA (Field Emission Electron Probe Micro Analyzer)).
  • FIG. 1C shows a result of measurement of crystal structure (phase) map (EBSD (
  • FIG. 1D shows a result of analysis of carbon concentration at line I-II in FIG. 1B .
  • the carbon concentration differed in each of the residual austenite, and it was approximately 1.2 to 1.5% in the area A in FIG. 1B and was approximately 1.3 to 1.7% in the area B in FIG. 1B .
  • These carbon concentrations are approximately equal to the average carbon concentration of 1.22% that was measured by X-ray diffraction. Accordingly, the method of measuring the carbon concentration in the residual austenite by X-ray diffraction is reasonable.
  • Vickers hardness was measured at five points around the center portion of a cross section of the spring, and an average thereof was calculated as Vickers hardness at the center portion.
  • Vickers hardness was measured from the outer circumferential surface toward the center of a cross section of the steel material, and a thickness of a high hardness layer, which had greater Vickers hardness than the center by 50 to 500 HV, from the surface was measured.
  • Residual stress was measured with respect to the outer circumferential surface of the steel material by using the X-ray diffraction method. Then, the entire surface of the steel material was chemically polished, and the above measurement was performed again. By repeating these steps, a residual stress distribution in a depth direction was obtained.
  • a fatigue test was performed at average stress ⁇ m of 735 MPa and stress amplitude ⁇ a of 637 MPa.
  • the sample that resisted more than 1 ⁇ 10 7 times was determined to have superior fatigue resistance and is represented by “Good” in Table 3.
  • the sample that broke before 1 ⁇ 10 7 times was performed was determined to have inferior fatigue resistance and is represented by “Bad” in Table 3.
  • the results of investigating various characteristics are shown in Table 3.
  • the isothermal holding time was short in the heat treatment step, whereby the ratio of martensite was high.
  • the ratio of bainite was small, whereby the hardness at the center portion was excessively increased.
  • the isothermal holding temperature was too high in the heat treatment step, whereby the ratio of residual austenite was excessively increased, and the hardness at the center portion was too low.
  • the residual austenite was transfouned into deformation-induced martensite, binding force of surroundings thereof was low because the hardness was low, whereby the compressive residual stress was low, and the compressive residual stress layer was thin.
  • ⁇ -Fe phase was identified in a crystal structure map that was obtained by the EBSD method. Then, circle-equivalent diameters of residual austenite grains were measured by using an image processing software.
  • Sag test was performed as follows. The sample was fixed while it was compressed by applying a load so that maximum shear stress was 1372 MPa, and it was immersed in silicone oil at 120° C. Then, 48 hours after the sample was immersed, the sample was taken out from the silicone oil, and the load was removed when the sample was cooled down to room temperature. A load, which was applied so that the spring was compressed to a predetermined height, was measured before and after the sag test, and a decreased amount AP of the load was obtained. The decreased amount ⁇ P was substituted into the following formula, and residual shear strain ( ⁇ ) was calculated as the amount of sag.
  • D represents an average coil diameter
  • d represents a wire diameter
  • the sample having the residual shear strain of not more than 10 ⁇ 10 ⁇ 4 was determined to have excellent sag resistance and is represented by “Very good” in Table 4.
  • the sample having the residual shear strain of greater than 10 ⁇ 10 ⁇ 4 and not more than 15 ⁇ 10 ⁇ 4 was determined to have superior sag resistance and is represented by “Good” in Table 4.
  • the sample having the residual shear strain of greater than 15 ⁇ 10 ⁇ 4 was determined to have inferior sag resistance and is represented by “Bad” in Table 4. The results of investigating various characteristics are shown in Table 4.
  • the samples Nos. 6, 8, and 11, which did not satisfy the conditions of the present invention had the following defects. That is, in the sample No. 6, the isothermal holding temperature was lower than (Ms point ⁇ 20° C.) in the heat treatment step, whereby martensite, which was generated in an initial stage of the transformation, excessively increased the hardness at the center potion, and the ductility was decreased. In addition, the carbon concentration in the residual austenite was low, whereby the strength of the residual austenite was low. As a result, the sag resistance was inferior.
  • the isothermal holding time was short in the heat treatment step, whereby the ratio of bainite was low.
  • the ratio of martensite was high, whereby the hardness at the center portion was excessively increased.
  • the carbon concentration in the residual austenite was low. Accordingly, the sag resistance was inferior.
  • the volume expansion according to the deformation-induced martensitic transformation was relatively small, whereby the compressive residual stress was low, and the compressive residual stress layer was thin.
  • the isothermal holding temperature was too high in the heat treatment step, whereby precipitation of carbides was decreased, and the carbon concentration in the austenite was excessively increased.
  • the Ms point was greatly decreased, and austenite was stabilized, whereby the ratio of residual austenite was excessively increased, and the hardness at the center portion was too low.
  • the isothermal holding temperature was too high, coarse bainite was precipitated, whereby the average diameter of residual austenite grains exceeded 3 ⁇ m.
  • the sag resistance was inferior.
  • the residual austenite underwent volume expansion due to deformation-induced martensitic transformation, binding force of surroundings thereof was low because the hardness was low, whereby the compressive residual stress was low, and the compressive residual stress layer was thin.
  • the present invention can be applied to springs that are required to have high fatigue resistance, such as valve springs for automobile engines, or the like. Moreover, the present invention can be applied to any springs such as coils, plate springs, torsion bars, stabilizers, or the like.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120024436A1 (en) * 2009-03-25 2012-02-02 Nhk Spring Co., Ltd. High-strength and high-ductility steel for spring, method for producing same, and spring
US20160208875A1 (en) * 2013-10-28 2016-07-21 Chuo Hatsujo Kabushiki Kaisha Spring and method for manufacturing the spring

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2013159802A (ja) * 2012-02-02 2013-08-19 Nhk Spring Co Ltd コイルばねおよびその製造方法
CN104057262B (zh) * 2014-07-02 2016-04-06 安庆谢德尔汽车零部件有限公司 一种高效的螺旋弹簧打样处理方法
WO2021075501A1 (fr) * 2019-10-16 2021-04-22 日本製鉄株式会社 Ressort de soupape
KR102318037B1 (ko) * 2019-12-17 2021-10-27 주식회사 포스코 냉간가공성이 우수한 선재 및 그 제조방법
US20230085279A1 (en) * 2020-02-21 2023-03-16 Nippon Steel Corporation Steel wire
CN113186377B (zh) * 2021-04-26 2022-02-01 二重（德阳）重型装备有限公司 降低锻件残余应力的热处理方法

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63312917A (ja) * 1987-06-16 1988-12-21 Nisshin Steel Co Ltd ばね性と延性の優れた高強度鋼板の製造方法
US5282906A (en) * 1992-01-16 1994-02-01 Inland Steel Company Steel bar and method for producing same
US20060169367A1 (en) * 2005-01-28 2006-08-03 Kabushiki Kaisha Kobe Seiko Sho(Kobe Steel, Ltd.) High strength spring steel having excellent hydrogen embrittlement resistance
US20060201588A1 (en) * 2003-03-28 2006-09-14 Sumie Suda Steel wire for high strength spring excellent in workability and high strength spring
US20060225819A1 (en) * 2005-04-11 2006-10-12 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Steel wire for cold-formed spring excellent in corrosion resistance and method for producing the same
US20100175795A1 (en) * 2006-10-11 2010-07-15 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
WO2010110041A1 (fr) * 2009-03-25 2010-09-30 日本発條株式会社 Acier de grande résistance et de grande ductilité pour un ressort, procédé de fabrication de celui-ci et ressort

Family Cites Families (23)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3847678A (en) * 1972-11-16 1974-11-12 Bethlehem Steel Corp Helical steel spring and method
JP2613601B2 (ja) 1987-09-25 1997-05-28 日産自動車株式会社 高強度スプリング
JPH0257637A (ja) 1988-08-23 1990-02-27 Nippon Steel Corp 高疲労強度ばねの製造方法及びそれに用いるばね用鋼線
CA2002138C (fr) 1988-11-08 1999-12-14 Susumu Yamamoto Ressort helicoidal haute resistance et methode de fabrication correspondante
JP2775778B2 (ja) * 1988-11-08 1998-07-16 住友電気工業株式会社 高強度コイルばねおよびその製造方法
JP3034543B2 (ja) * 1990-01-19 2000-04-17 日新製鋼株式会社 強靭な高強度鋼の製造方法
JPH07179936A (ja) 1993-12-24 1995-07-18 Aichi Steel Works Ltd 熱へたり性に優れた薄板ばね用鋼
JP3405391B2 (ja) * 1997-09-04 2003-05-12 住友電気工業株式会社 ばね用オイルテンパー線およびその製造方法
JP3548419B2 (ja) * 1998-04-15 2004-07-28 新日本製鐵株式会社 高強度鋼線
JP2001220650A (ja) * 1999-11-30 2001-08-14 Sumitomo Electric Ind Ltd 鋼線、ばね及びそれらの製造方法
JP4188582B2 (ja) * 2001-02-09 2008-11-26 株式会社神戸製鋼所 加工性に優れた高強度鋼板およびその製造方法
JP3930715B2 (ja) * 2001-09-28 2007-06-13 中央発條株式会社 高強度ばね
JP4330306B2 (ja) 2002-04-02 2009-09-16 株式会社神戸製鋼所 疲労強度に優れた硬引きばね
EP1491647B1 (fr) 2002-04-02 2006-07-26 Kabushiki Kaisha Kobe Seiko Sho Fil d'acier pour un ressort etire presentant d'excellentes caracteristiques de resistance a la fatigue et au tassement
JP2004315967A (ja) 2003-03-28 2004-11-11 Kobe Steel Ltd 耐へたり性及び疲労特性に優れたばね用鋼
JP4252351B2 (ja) * 2003-04-18 2009-04-08 中央発條株式会社 高疲労強度及び高腐食疲労強度を有する冷間成形ばね及び該ばね用鋼
JP2005120479A (ja) 2004-10-25 2005-05-12 Togo Seisakusho Corp 高強度ばねおよびその製造方法
KR101011565B1 (ko) * 2005-06-29 2011-01-27 신닛뽄세이테쯔 카부시키카이샤 신선 특성이 우수한 고강도 선재 및 그 제조 방법
JP4423254B2 (ja) * 2005-12-02 2010-03-03 株式会社神戸製鋼所 コイリング性と耐水素脆化特性に優れた高強度ばね鋼線
JP4868935B2 (ja) 2006-05-11 2012-02-01 株式会社神戸製鋼所 耐へたり性に優れた高強度ばね用鋼線
KR100797327B1 (ko) * 2006-10-11 2008-01-22 주식회사 포스코 냉간가공성이 우수한 고강도, 고인성 스프링용 강선재,상기 강선재의 제조방법 및 상기 강선재로부터 스프링을제조하는 방법
KR101146842B1 (ko) 2006-12-28 2012-05-16 가부시키가이샤 고베 세이코쇼 Ｓｉ 킬드강 선재 및 스프링
JP4177403B2 (ja) 2006-12-28 2008-11-05 株式会社神戸製鋼所 疲労特性に優れたＳｉキルド鋼線材およびばね

Patent Citations (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS63312917A (ja) * 1987-06-16 1988-12-21 Nisshin Steel Co Ltd ばね性と延性の優れた高強度鋼板の製造方法
US5282906A (en) * 1992-01-16 1994-02-01 Inland Steel Company Steel bar and method for producing same
US20060201588A1 (en) * 2003-03-28 2006-09-14 Sumie Suda Steel wire for high strength spring excellent in workability and high strength spring
US20060169367A1 (en) * 2005-01-28 2006-08-03 Kabushiki Kaisha Kobe Seiko Sho(Kobe Steel, Ltd.) High strength spring steel having excellent hydrogen embrittlement resistance
US20060225819A1 (en) * 2005-04-11 2006-10-12 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) Steel wire for cold-formed spring excellent in corrosion resistance and method for producing the same
US20100175795A1 (en) * 2006-10-11 2010-07-15 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
WO2010110041A1 (fr) * 2009-03-25 2010-09-30 日本発條株式会社 Acier de grande résistance et de grande ductilité pour un ressort, procédé de fabrication de celui-ci et ressort
US20120024436A1 (en) * 2009-03-25 2012-02-02 Nhk Spring Co., Ltd. High-strength and high-ductility steel for spring, method for producing same, and spring

Non-Patent Citations (5)

* Cited by examiner, † Cited by third party
Title
JP 63-312917 machine translation *
M. Ayada, K. Inoue, N. Tsuji, Y. Saito. "Mechanical properties of spring wire drawn and tempered at lower bainite region." Tetsu to Hagane (1999) 85(8), 605-612. *
Shah. “The Hand Book on Mechanical Maintenance.” http://practicalmaintenance.net/?p=1345. Accessed April 14, 2016. *
T. Jinbo, T. Jiwara, S. Suda, N. Ibaraki. "High strength, oil-tempered steel wire for valve springs manufactured by rapid heating mono-strand process". Kobelco Technology Review No. 27 Nov. 2007. Pages 23-27. *
WO 2010/110041 machine translation *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120024436A1 (en) * 2009-03-25 2012-02-02 Nhk Spring Co., Ltd. High-strength and high-ductility steel for spring, method for producing same, and spring
US8926768B2 (en) * 2009-03-25 2015-01-06 Nhk Spring Co., Ltd. High-strength and high-ductility steel for spring, method for producing same, and spring
US20160208875A1 (en) * 2013-10-28 2016-07-21 Chuo Hatsujo Kabushiki Kaisha Spring and method for manufacturing the spring

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EP2602350A4 (fr) 2015-06-24
EP2602350B8 (fr) 2018-03-21
US20190390727A1 (en) 2019-12-26
CN103025904B (zh) 2015-04-01
US11378147B2 (en) 2022-07-05
CN103025904A (zh) 2013-04-03
EP2602350A1 (fr) 2013-06-12
EP2602350B1 (fr) 2018-01-03
ES2664812T3 (es) 2018-04-23
WO2012018144A1 (fr) 2012-02-09
KR20130137137A (ko) 2013-12-16

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