WO2011078165A1 - High-strength spring steel - Google Patents

High-strength spring steel Download PDF

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Publication number
WO2011078165A1
WO2011078165A1 PCT/JP2010/073003 JP2010073003W WO2011078165A1 WO 2011078165 A1 WO2011078165 A1 WO 2011078165A1 JP 2010073003 W JP2010073003 W JP 2010073003W WO 2011078165 A1 WO2011078165 A1 WO 2011078165A1
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spring steel
strength
spring
steel
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PCT/JP2010/073003
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French (fr)
Japanese (ja)
Inventor
清佳 永松
知忠 丸尾
吉原 直
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株式会社神戸製鋼所
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Priority to EP10839395.0A priority Critical patent/EP2518175B1/en
Priority to BR112012014178A priority patent/BR112012014178A2/en
Priority to US13/511,541 priority patent/US20120285585A1/en
Priority to CN201080039360.2A priority patent/CN102482743B/en
Priority to ES10839395T priority patent/ES2709515T3/en
Publication of WO2011078165A1 publication Critical patent/WO2011078165A1/en
Priority to US15/286,065 priority patent/US20170022580A1/en

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    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D8/00Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D9/00Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/02Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for springs
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/002Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/34Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING 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
    • C21D7/00Modifying the physical properties of iron or steel by deformation
    • C21D7/02Modifying the physical properties of iron or steel by deformation by cold working
    • C21D7/04Modifying the physical properties of iron or steel by deformation by cold working of the surface
    • C21D7/06Modifying the physical properties of iron or steel by deformation by cold working of the surface by shot-peening or the like

Definitions

  • the present invention relates to a spring steel (spring steel) useful as a material for a coil spring, and more particularly to a spring steel used when manufacturing a coil spring, which has a tensile strength as it is quenched.
  • the present invention relates to a steel for springs of 1900 MPa class.
  • Such a coil spring is generally manufactured by drawing spring steel (wire), polishing, heating, coiling hot, quenching and tempering, and setting.
  • the quenching and tempering treatment after hot coiling is performed to adjust the strength of the spring.
  • heat treatment such as quenching and tempering, a large amount of CO 2 is exhausted.
  • CO 2 reduction has been strongly demanded as one of the measures for preventing global warming for the purpose of reducing the burden on the global environment. Therefore, it is required to reduce the CO 2 emission amount even in the manufacturing process of the coil spring.
  • Patent Document 1 proposes a steel for a stabilizer that is water-quenched immediately after hot forming and has improved normal temperature toughness and low temperature toughness while still being water-quenched without tempering.
  • the component composition is adjusted to a low C-high Mn-Cr system or a low C-high Mn-B-Cr system with one or more of Ti, V, and Nb added.
  • the stabilizer that is the subject of this Patent Document 1 is different from the coiling spring in the technical field.
  • the strength level is an 800 MPa class in which corrosion fatigue characteristics do not become a problem, and a high strength region where compatibility with the corrosion fatigue characteristics is required. (For example, a 1900 MPa class) spring is not related.
  • the strength of steel materials increases with increasing hardness, and toughness decreases with increasing hardness.
  • the toughness decreases when the strength of the steel material increases, but the spring material is required to have fracture characteristics that can withstand the severe use environment of the spring, and even in springs such as suspension springs with increased strength, In particular, it is necessary to ensure low temperature toughness, which is important for use in cold regions.
  • Patent Document 2 discloses that ductility and toughness have been improved in high-strength spring steel by adjusting various components
  • Patent Document 3 has improved hardness and toughness by adjusting various components. It is disclosed that a combined spring steel is obtained.
  • both Patent Documents 2 and 3 focus only on toughness at room temperature, and do not consider low-temperature toughness.
  • the toughness at low temperature is usually inferior to the toughness at normal temperature, and considering the normal temperature toughness disclosed in Patent Documents 2 and 3, the low-temperature toughness in the techniques of Patent Documents 2 and 3 is insufficient.
  • the present invention has been made paying attention to the above circumstances, and its purpose is to provide high strength and good corrosion fatigue characteristics even when tempering after quenching is omitted when processing into a coil spring.
  • An object of the present invention is to provide a spring steel that can produce a coil spring that is compatible and has excellent low-temperature toughness.
  • Another object of the present invention is to provide a spring obtained from this spring steel.
  • the high-strength spring steel according to the present invention that can solve the above-mentioned problems is C: 0.15 to 0.40% (meaning mass%, the same applies hereinafter), Si: 1 to 3.5%, Selected from the group consisting of Mn: 0.20 to 2.0%, Ti: 0.005 to 0.10%, Nb: 0.005 to 0.05%, and V: 0.25% or less At least one selected from the group consisting of Cr: 0.05 to 1.20%, P: 0.030% or less, S: 0.02% or less, the balance being iron and inevitable impurities, ), The carbon equivalent Ceq 1 is 0.55 or less.
  • the spring steel according to the present invention includes (a) Ni: 0.05 to 2% and Cu: 0.05 to 0.50%, (b) Ni: 0.15 to 2% and Cu: 0 as necessary. 0.05 to 0.50%, (c) B: 0.005% or less and / or Mo: 0.60% or less may be contained.
  • the spring steel of the present invention is selected from the group consisting of Ti: 0.035 to 0.10%, Nb: 0.005 to 0.05%, and V: 0.05 to 0.25%. It is also preferable that at least one kind is contained and the crystal grain size after quenching is 7.5 or more.
  • the spring steel is hot-coiled, quenched and quenched, and then set with the temper omitted, a spring that can achieve both of the above characteristics can be manufactured.
  • the spring steel of the present invention appropriately controls the element amount and blending balance of a specific alloy element, the tempering process after quenching is omitted when a coil spring is manufactured using this spring steel. Thus, it is possible to manufacture a spring having both high strength and good corrosion fatigue properties while still being quenched, and further having good low temperature toughness.
  • FIG. 1 is a graph showing the relationship between the carbon equivalent (Ceq 1 ) of the test piece obtained in Example 1 and the hydrogen embrittlement crack life.
  • FIG. 2 is a graph showing the relationship between the tensile strength and the low temperature toughness (vE- 50 ) of the test piece obtained in Example 2.
  • the present inventors When producing springs by coiling spring steel, the present inventors omit the tempering after quenching performed after coiling to achieve both high strength and good corrosion fatigue properties, and are excellent in low temperature toughness.
  • the types of basic alloy elements to be contained in the spring steel are limited to at least one of C, Si, Mn, Cr and Ti, Nb and V, or (i) Ni and Cu are further added to these element groups.
  • the spring steel of the present invention is particularly characterized in that the amount of C is lower than the amount of C used in ordinary spring steel.
  • the amount of C is lower than the amount of C used in ordinary spring steel.
  • the amount of carbide precipitated in the steel can be reduced, so that tempering after quenching that is performed in a normal spring manufacturing process can be omitted. That is, as described above, the spring is usually manufactured by drawing and polishing spring steel (wire rod), heating, hot coiling, quenching and tempering, and setting. After the setting, if necessary, coating is performed after shot peening.
  • the spring steel of the present invention has a reduced amount of C, the strength of the spring can be secured even if setting is performed without the tempering after quenching.
  • Si and Mn are positively added.
  • Si and Mn are easily available elements, and stable supply can be maintained even if the amount of Si and Mn is increased.
  • Si and Mn have the effect
  • the component composition of the spring steel is designed as follows, and the carbon equivalent Ceq 1 represented by the following formula (1) is set to 0.55 or less.
  • [] represents the content (% by mass) of each element in the steel.
  • the reason for setting the addition amount of each element and the reason for defining the carbon equivalent Ceq 1 are as follows.
  • the reason why C is 0.15% or more is to improve the hardenability and ensure the strength.
  • the reason why C is set to 0.40% or less is to prevent deterioration of toughness and corrosion fatigue characteristics.
  • the lower limit of the C amount is preferably 0.2% or more, more preferably 0.25% or more, and the upper limit of the C amount is preferably 0.35% or less, more preferably 0.34% or less, particularly preferably. It is 0.33% or less.
  • Si is 1% or more
  • Si is preferably 1.5% or more and 3.0% or less, more preferably 1.80% or more and 2.5% or less.
  • Mn is 0.20% or more
  • the hardenability is improved and the strength can be secured.
  • the formation of sulfide inclusions can suppress grain boundary embrittlement due to S and improve toughness and corrosion fatigue characteristics.
  • Mn is 2.0% or less, it is possible to prevent a supercooled structure from being generated and deteriorate toughness and corrosion fatigue characteristics.
  • production and coarsening of an excessive sulfide type inclusion can be suppressed, and it can prevent that toughness and a corrosion fatigue characteristic deteriorate.
  • the lower limit of the Mn amount is preferably 0.5% or more, more preferably 0.80% or more
  • the upper limit of the Mn amount is preferably 1.8% or less, particularly preferably 1.5% or less.
  • Ti is made 0.005% or more is to refine the prior austenite crystal grains after quenching, improve the strength and yield ratio, and improve the toughness and corrosion fatigue characteristics. By improving toughness, sag resistance can be improved.
  • the reason why Ti is made 0.10% or less is to prevent coarse inclusions (for example, Ti nitride) from precipitating and to suppress deterioration of corrosion fatigue characteristics.
  • the lower limit of the Ti amount is preferably 0.01% or more (particularly preferably 0.05% or more), and the upper limit of the Ti amount is preferably 0.080% or less, more preferably 0.07% or less. .
  • V is an element that effectively acts to further enhance the hardenability and increase the strength. In addition to enhancing toughness and improving sag resistance, it is an element that refines crystal grains to improve strength and proof stress ratio. In order to exert such an action, V is preferably contained in an amount of 0.05% or more, more preferably 0.08% or more, and further preferably 0.1% or more. However, when V is excessive, coarse carbonitrides are formed, and toughness and corrosion fatigue properties are deteriorated. Therefore, V is 0.25% or less, preferably 0.22% or less, more preferably 0.2% or less.
  • Nb is an element that contributes to improvement in sag resistance by increasing toughness, and is an element that refines crystal grains to improve strength and proof stress ratio.
  • the Nb amount is set to 0.005% or more.
  • the amount of Nb is preferably 0.008% or more, and more preferably 0.01% or more.
  • the Nb content is 0.05% or less.
  • the Nb amount is preferably 0.04% or less, more preferably 0.03% or less.
  • Ti, V and Nb may be added alone or in combination of two or more.
  • the contents of Ti, V, and Nb are Ti: 0.035 to 0.10%, Nb: 0.005 to 0.05%, and V: 0.05 to 0.25%, respectively. It is preferable to contain. Further, by containing Ti, V and Nb in such a range, the effect of crystal grain refinement can be effectively exhibited, and the crystal grain size after quenching can be set to 7.5 or more, Good low temperature toughness can be exhibited.
  • the grain size after quenching is more preferably 8.0 or more, and even more preferably 9.0 or more.
  • the low temperature toughness of the spring steel of the present invention is, for example, that Charpy absorbed energy at ⁇ 50 ° C. is 50 J / cm 2 or more, preferably 70 J / cm 2 or more, more preferably 80 J / cm 2 or more.
  • Cr When Cr is 0.05% or more, the steel matrix is strengthened by solid solution strengthening, and the hardenability is improved and the strength can be secured. Further, it is an element that contributes to the improvement of corrosion resistance by making the rust generated in the surface layer portion under the corrosive condition amorphous and dense.
  • Cr when Cr is 1.20% or less, the Ms point is lowered to prevent formation of a supercooled structure, and toughness and corrosion fatigue characteristics can be secured, and strength due to insufficient penetration of Cr carbide during quenching. And a decrease in hardness can be prevented.
  • Cr is preferably 0.1% or more and 1.10% or less, more preferably 0.5% or more and 1.05% or less.
  • the balance of the spring steel of the present invention is substantially iron.
  • steel contains unavoidable impurities brought in depending on the situation of materials such as iron raw materials (including scrap) and auxiliary materials, manufacturing equipment, and the like.
  • unavoidable impurities P is defined as 0.030% or less and S is defined as 0.02% or less. The reason for setting such a range is as follows.
  • P is set to 0.030% or less. The reason why P is set to 0.030% or less is to prevent segregation at the prior austenite grain boundaries and embrittle the grain boundaries, and to prevent deterioration of toughness and corrosion fatigue characteristics.
  • P is preferably 0.02% or less, more preferably 0.01% or less. The smaller the amount of P, the better. However, it is usually contained in an amount of about 0.001%.
  • S is set to 0.02% or less.
  • S is preferably 0.015% or less, particularly 0.01% or less.
  • P is preferably as small as P, but is usually contained in an amount of about 0.001%.
  • the total amount of P and S is preferably 0.015% or less, more preferably 0.010% or less.
  • the reason why the carbon equivalent Ceq 1 is 0.55 or less is that, when coiled spring steel is manufactured to produce a coil spring, the strength and corrosion fatigue characteristics of the spring are compatible even if the tempering treatment after quenching is omitted. Because. That is, the carbon equivalent Ceq 1 indicates the contribution of the alloy element that affects the hardness after quenching. By reducing this numerical value and omitting the tempering treatment after quenching, the core portion of the spring is obtained. Hardness can be secured and high strength can be achieved. In addition, by suppressing the carbon equivalent Ceq 1 to 0.55 or less, the dependence of the alloy elements can be reduced, and the stable supply ability can be improved.
  • the carbon equivalent Ceq 1 is preferably 0.53 or less, more preferably 0.50 or less.
  • the carbon equivalent Ceq 1 can be reduced in cost by designing the component so as to be as small as possible. However, in order to achieve both high strength and corrosion fatigue characteristics, it is necessary to add an alloy element to some extent. Therefore, the lower limit value of the carbon equivalent Ceq 1 is 0.30. In addition, in calculating the following formula (1), when there is an element that is not contained, the content of the element is assumed to be 0% by mass.
  • the spring steel of the present invention satisfies the above chemical composition and the carbon equivalent Ceq 1 , but contains Ni and Cu, or contains B and / or Mo with the aim of further improving the characteristics. It may be contained.
  • Ni and Cu When Ni and Cu are contained (that is, when Ni and Cu are used in combination), the Ni content is 0.05 to 2% and the Cu content is 0.05 to 0.50%.
  • the reason why Ni is set to 0.05% or more is to increase toughness, reduce defect sensitivity, and improve corrosion fatigue characteristics. Further, Ni has an effect of improving corrosion resistance by forming amorphous rust that is amorphous and dense, and also has an effect of improving the sag characteristic important as a spring characteristic.
  • Ni is preferably 0.15% or more and 2% or less, more preferably 0.18% or more and 1.5% or less, further preferably 0.20% or more and 1% or less, particularly 0.5%. It is as follows.
  • Cu is an element that is electrochemically noble than iron (noble) and therefore has the effect of densifying rust and improving corrosion resistance. Therefore, when Cu is contained, the amount of Cu is set to 0.05% or more. However, even if added excessively, the effect is saturated, and there is a possibility of causing embrittlement of the material due to hot rolling. Therefore, the upper limit of Cu content is 0.50% or less. Cu is preferably 0.1% or more and 0.4% or less, more preferably 0.15% or more (particularly 0.18% or more) and 0.3% or less.
  • B is an element that further enhances hardenability to increase grain boundary strength, enhance toughness and improve sag resistance, and further densify rust generated on the surface to improve corrosion resistance.
  • B is preferably contained in an amount of 0.0005% or more, more preferably 0.001% or more, and further preferably 0.0015% or more.
  • B is 0.005% or less, preferably 0.004% or less, more preferably 0.003% or less.
  • Mo is an element that increases toughness and contributes to improvement in sag resistance, and also ensures hardenability and increases the strength and toughness of steel.
  • the Mo amount is preferably 0.05% or more, more preferably 0.08% or more, and further preferably 0.10% or more.
  • the Mo content is preferably 0.60% or less, more preferably 0.50% or less, and still more preferably 0.35% or less.
  • B and Mo may be contained alone or in combination.
  • the spring steel according to the present invention is characterized in that the amount of each alloying element is strictly defined and the relationship between them is specified. If this spring steel is used, it is performed after coiling. A tempering treatment after quenching can be omitted, and a spring having both high strength with a tensile strength of 1900 MPa or more and good corrosion fatigue characteristics can be produced even when quenched. Moreover, low temperature toughness can be improved by controlling the content of elements (Ti, Nb and V) having a grain refinement action more strictly.
  • elements Ti, Nb and V
  • tempering means that the material is not heated to a temperature exceeding 350 ° C. after quenching.
  • the above setting may be performed cold or warm.
  • the temperature at the time of cold setting may be normal temperature, and the temperature at the time of cold setting may be about 200 to 250 ° C.
  • the conditions for shot peening and painting are not particularly limited, and conventional conditions can be adopted.
  • the spring thus obtained can achieve both high strength and good corrosion fatigue properties, and is also excellent in low temperature toughness.
  • the production conditions of the spring steel according to the present invention are not particularly limited, but in order to make the crystal grain size 7.5 or more which is a preferred embodiment of the present invention, for example, the heating temperature at the time of quenching is set to 925 ° C. or less, and the heating is performed. It is recommended that the time be 15 minutes or less.
  • the lower limit of the heating temperature and the heating time at the time of quenching is not particularly limited, the lower limit of the heating temperature is usually about 850 ° C., and the lower limit of the heating time is about 10 minutes.
  • Example 1 The steel of the chemical composition shown in Table 1 below (the balance is iron and inevitable impurities) was melted in a 150 kg vacuum melting furnace and held at 1200 ° C., then hot forged into a 155 mm square billet, This billet was hot-rolled to produce a spring steel (spring wire) having a diameter of 13.5 mm. The spring wire was subjected to a polishing rod process so that the diameter was 12.5 mm, and was then quenched after being cut to a length of 70 mm. Quenching was performed by heating at a temperature of 925 ° C. for 10 minutes and then placing in an oil bath at a temperature of 50 ° C. After quenching, a test piece having a width of 10 mm, a thickness of 1.5 mm and a length of 65 mm was cut out by machining.
  • Table 1 The steel of the chemical composition shown in Table 1 below (the balance is iron and inevitable impurities) was melted in a 150 kg vacuum melting furnace and held at 1200 ° C., then hot
  • Table 1 shows the results of calculating the amount of chemical components in the steel and the carbon equivalent (Ceq 1 ) calculated from the above formula (1).
  • the strength and corrosion fatigue properties of the test specimens were measured by simulating the setting performed cold or warm. That is, when simulating cold setting, the test piece was used for each test as it was, and when simulating warm setting, the test piece heated at 200 ° C. for 60 minutes was used for each test. Table 2 below shows which of the cold setting and the warm setting is simulated.
  • the corrosion fatigue characteristics were evaluated by conducting a hydrogen embrittlement cracking test.
  • a stress of 1400 MPa was applied to the above test piece by four-point bending, and this test piece was treated with sulfuric acid (0.5 mol / L) and potassium thiocyanate (KSCN; 0.01 mol / L).
  • the sample was immersed in a mixed aqueous solution, and a voltage of ⁇ 700 mV, which is lower than the SCE electrode, was applied using a potentiostat, and the time until cracking occurred (hereinafter referred to as hydrogen embrittlement crack life) was measured. did.
  • the measurement results of the hydrogen embrittlement cracking test are shown in Table 2 below. In the present invention, a case where the time until occurrence of cracking is 600 seconds or more is regarded as acceptable.
  • FIG. 1 shows the relationship between the carbon equivalent (Ceq 1 ) and the hydrogen embrittlement crack life (seconds).
  • the results of 1 to 15, 31, and 33 are indicated by ⁇ and No.
  • the results of 16 to 29, 32 are indicated by ⁇ and No.
  • the result of 30 (with tempering) is indicated by ⁇ .
  • No. 30 is an example of tempering after quenching.
  • the core hardness can be secured, the strength is high, the hydrogen embrittlement crack life is good, and the corrosion fatigue characteristics can be improved.
  • tempering is performed after quenching, CO 2 emissions cannot be reduced.
  • No. The component composition of No. 29 is the above No. This is an example similar to 30, but without tempering after quenching. In this example, the tempering process is omitted, so that the CO 2 emission can be reduced. However, since the carbon equivalent exceeds 0.55 and the alloy element amount is large, the tempering is omitted. The partial hardness becomes too hard, the toughness is lowered, the hydrogen embrittlement crack life is shortened, and the corrosion fatigue characteristics are deteriorated.
  • No. Nos. 16 to 28 and 32 are examples that do not satisfy the requirements defined in the present invention, and cannot achieve both high strength and good corrosion fatigue characteristics. That is, the carbon equivalent (Ceq 1 ) of the spring steel exceeds the range specified in the present invention, and the tempering after quenching is omitted, so that the CO 2 emission can be reduced, but the core hardness is hard. As a result, the toughness is lowered, the hydrogen embrittlement crack life is shortened, and the corrosion fatigue characteristics are deteriorated.
  • No. Nos. 1 to 15 and 33 are examples that satisfy the requirements defined in the present invention, and both high strength and good corrosion fatigue characteristics can be achieved. That is, after suppressing the carbon equivalent (Ceq 1 ) to 0.55 or less, and tempering after quenching is omitted, CO 2 emission can be reduced, and the core hardness can be appropriately secured. High strength can be achieved. In addition, the hydrogen embrittlement crack life is long, and the corrosion fatigue characteristics can be improved. Moreover, since the carbon equivalent (Ceq 1 ) of the spring steel is suppressed to 0.55 or less, the dependence of the alloy elements can be reduced, and stable supply can be realized. Therefore, when the spring steel of the present invention is used, the above No. 1 simulating the “UHS1900”. It can be seen that a spring exhibiting characteristics comparable to or higher than 30 can be provided.
  • Example 2 Steel materials having the chemical composition shown in Table 3 (the balance being iron and inevitable impurities) were melted in a 150 kg vacuum melting furnace, then cast by the ingot-making method or continuous casting method, and then 155 mm square by split rolling.
  • the billet was prepared, further hot-rolled, and processed into a wire having a diameter of 13.5 mm to obtain a test material.
  • These specimens were heated at a temperature of 925 ° C. for 10 minutes and then quenched in an oil bath at 50 ° C. No. Only 2-24 was tempered at 400 ° C. for 1 hour after the quenching.
  • No. in Table 4 2-1. No. 2-14 satisfies the requirements of the present invention, and in particular, the Ti, Nb, and V contents are appropriately adjusted, so that a steel having high strength and excellent low-temperature toughness could be realized.
  • No. 2-15 ⁇ No. No. 2-24 did not satisfy at least one of the requirements of the present invention, and thus toughness was insufficient.
  • No. 2-15 ⁇ No. No. 2-19 was an example in which the amount of C was excessive, and the low temperature toughness decreased due to the excessive increase in strength.
  • No. 2-23 and no. No. 2-24 is a steel grade corresponding to standard steel 9254.
  • No. 2-24 has been tempered after quenching.
  • No. No. 2-23 had a large amount of C and an excessively high strength, and did not contain any of Ti, Nb and V, so that the low temperature toughness decreased.
  • FIG. FIG. 2 is a graph showing the relationship between strength and low temperature toughness (Charpy absorbed energy at ⁇ 50 ° C.) for 2-1 to 2-24.
  • the results of 2-1 to 2-14 and 2-25 are indicated by ⁇ and No. 2-15 ⁇ No.
  • the results of Nos. 2-23 and 2-26 are indicated by ⁇ ,
  • the result of 2-24 was indicated by ⁇ .
  • all the steels satisfying the requirements of the present invention (indicated by ⁇ in FIG. 2) have a Charpy absorbed energy of 50 J / cm 2 or more and steels that do not satisfy any of the requirements of the present invention ( In FIG. 2, it can be seen that high toughness is achieved when compared at the same strength as indicated by ⁇ and ⁇ .

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Abstract

Provided is a spring steel that contains 0.15-0.40% carbon, 1-3.5% silicon, 0.20-2.0% manganese, 0.05-1.20% chromium, at most 0.030% phosphorus, at most 0.02% sulfur, and at least one of the following: 0.005-0.10% titanium, 0.005-0.05% niobium, and at most 0.25% vanadium. The remainder of said spring steel comprises iron and unavoidable impurities. The carbon equivalent (Ceq1) of the provided spring steel, as calculated by formula (1), is at most 0.55. (1) Ceq1 = [C] + 0.108×[Si] − 0.067×[Mn] + 0.024×[Cr] − 0.05×[Ni] + 0.074×[V] (In formula (1), each symbol in brackets represents the content (mass%) of the corresponding element.)

Description

高強度ばね用鋼High strength spring steel
 本発明は、コイルばねの素材として有用なばね用鋼(ばね鋼)に関するものであり、詳細には、コイルばねを製造する際に用いるばね用鋼であって、焼入れままの状態で引張強度が1900MPa級となるばね用鋼に関するものである。 TECHNICAL FIELD The present invention relates to a spring steel (spring steel) useful as a material for a coil spring, and more particularly to a spring steel used when manufacturing a coil spring, which has a tensile strength as it is quenched. The present invention relates to a steel for springs of 1900 MPa class.
 自動車等に用いられるばね(懸架ばねなど)には、排ガス低減や燃費向上のため軽量化が求められ、その一環として高強度化が指向されている。高強度化されたばねは、欠陥感受性が増し、例えば、融雪剤の付着により発生した腐食ピットからの破壊が生じやすくなり、腐食疲労による早期折損が問題となる。そこで高強度で、しかも腐食疲労特性に優れたばねが求められている。例えば、出願人がばね用鋼として先に開発した「UHS1900」は、ばね形状にコイリングした後、焼入れ焼戻しすることで、引張強度が1900MPa級と高強度でありながら、良好な腐食疲労特性を達成することができる。従ってこのばね用鋼から得られるコイルばねは、高強度と良好な腐食疲労特性を両立したものとなる。 For springs (suspension springs, etc.) used in automobiles and the like, weight reduction is required in order to reduce exhaust gas and improve fuel efficiency. Higher strength springs are more susceptible to defects, for example, are more likely to break from corrosion pits caused by the adhesion of snow melting agent, and there is a problem of early breakage due to corrosion fatigue. Therefore, a spring having high strength and excellent corrosion fatigue characteristics is required. For example, "UHS1900", which was previously developed as spring steel by the applicant, achieved good corrosion fatigue properties by coiling into a spring shape and then quenching and tempering, while the tensile strength was as high as 1900 MPa class. can do. Therefore, the coil spring obtained from this spring steel has both high strength and good corrosion fatigue characteristics.
 こうしたコイルばねは、一般的に、ばね用鋼(線材)を引抜き、磨棒した後、加熱し、熱間でコイリングした後、焼入れ、焼戻しを行い、セッチング(setting)して作製される。熱間コイリング後の焼入れ、焼戻し処理は、ばねの強度を調整するために行われる。焼入れ焼戻し処理のような熱処理時には、多くのCO2が排出されている。ところが、近年では、地球環境に対する負荷を低減することを目的とし、地球温暖化防止策の1つとしてCO2削減が強く求められている。そのため、コイルばねの製造工程においてもCO2の排出量を低減することが求められている。 Such a coil spring is generally manufactured by drawing spring steel (wire), polishing, heating, coiling hot, quenching and tempering, and setting. The quenching and tempering treatment after hot coiling is performed to adjust the strength of the spring. During heat treatment such as quenching and tempering, a large amount of CO 2 is exhausted. However, in recent years, CO 2 reduction has been strongly demanded as one of the measures for preventing global warming for the purpose of reducing the burden on the global environment. Therefore, it is required to reduce the CO 2 emission amount even in the manufacturing process of the coil spring.
 なお、特許文献1には、熱間成形後直ちに水焼入れし、焼戻しを行わない水焼入れままで、常温靱性と低温靱性を改善したスタビライザ用鋼が提案されている。このスタビライザ用鋼は、成分組成を低C-高Mn-Cr系、または低C-高Mn-B-Cr系にTi、V、Nbの一種または二種以上を添加したものに調整しているところに特徴がある。この特許文献1で対象としているスタビライザは、コイリングばねと技術分野が異なっており、例えば、強度レベルは腐食疲労特性が問題とならない800MPa級であり、腐食疲労特性との両立が求められる高強度域(例えば、1900MPa級)のばねとは関連がない。 In addition, Patent Document 1 proposes a steel for a stabilizer that is water-quenched immediately after hot forming and has improved normal temperature toughness and low temperature toughness while still being water-quenched without tempering. In this stabilizer steel, the component composition is adjusted to a low C-high Mn-Cr system or a low C-high Mn-B-Cr system with one or more of Ti, V, and Nb added. There is a feature. The stabilizer that is the subject of this Patent Document 1 is different from the coiling spring in the technical field. For example, the strength level is an 800 MPa class in which corrosion fatigue characteristics do not become a problem, and a high strength region where compatibility with the corrosion fatigue characteristics is required. (For example, a 1900 MPa class) spring is not related.
 また、一般に鉄鋼材料の強度は、硬度の上昇と共に増加し、また硬度が上昇すると靭性が低下する。つまり、鉄鋼材料の強度が増加すると靭性が低下するが、ばね用材料としては、ばねの過酷な使用環境に耐えうる破壊特性が要求され、高強度化された懸架ばね等のばねにおいても、靭性、特に寒冷地における使用で重要となる低温靭性を確保することが必要となる。 In general, the strength of steel materials increases with increasing hardness, and toughness decreases with increasing hardness. In other words, the toughness decreases when the strength of the steel material increases, but the spring material is required to have fracture characteristics that can withstand the severe use environment of the spring, and even in springs such as suspension springs with increased strength, In particular, it is necessary to ensure low temperature toughness, which is important for use in cold regions.
 例えば、特許文献2は各種成分を調節することによって、高強度ばね鋼において延性と靭性が改善されたことを開示しており、また特許文献3は各種成分を調節することによって、硬度と靭性を兼ね備えたばね鋼が得られたことを開示している。しかし、特許文献2および3はいずれも常温での靭性に着目するのみで、低温靭性については考慮されていない。低温での靭性は、通常、常温での靭性よりも劣るものであり、特許文献2および3に開示された常温靭性から考慮すると、特許文献2および3の技術における低温靭性は不十分である。 For example, Patent Document 2 discloses that ductility and toughness have been improved in high-strength spring steel by adjusting various components, and Patent Document 3 has improved hardness and toughness by adjusting various components. It is disclosed that a combined spring steel is obtained. However, both Patent Documents 2 and 3 focus only on toughness at room temperature, and do not consider low-temperature toughness. The toughness at low temperature is usually inferior to the toughness at normal temperature, and considering the normal temperature toughness disclosed in Patent Documents 2 and 3, the low-temperature toughness in the techniques of Patent Documents 2 and 3 is insufficient.
特許第4406341号公報Japanese Patent No. 4406341 特許第3577411号公報Japanese Patent No. 3577411 特許第3246733号公報Japanese Patent No. 3246733
 本発明は上記の様な事情に着目してなされたものであって、その目的は、コイルばねに加工する際に、焼入れ後の焼戻し処理を省略しても高強度と良好な腐食疲労特性を両立し、さらに低温靭性にも優れるコイルばねを製造できるばね用鋼を提供することにある。また、本発明の他の目的は、このばね用鋼から得られるばねを提供することにある。 The present invention has been made paying attention to the above circumstances, and its purpose is to provide high strength and good corrosion fatigue characteristics even when tempering after quenching is omitted when processing into a coil spring. An object of the present invention is to provide a spring steel that can produce a coil spring that is compatible and has excellent low-temperature toughness. Another object of the present invention is to provide a spring obtained from this spring steel.
 上記課題を解決することのできる本発明に係る高強度ばね用鋼は、C:0.15~0.40%(質量%の意味。以下、同じ。)、Si:1~3.5%、Mn:0.20~2.0%を含有するとともに、Ti:0.005~0.10%、Nb:0.005~0.05%、およびV:0.25%以下よりなる群から選択される少なくとも1種、Cr:0.05~1.20%、P:0.030%以下、S:0.02%以下を含有し、残部が鉄および不可避的不純物であり、下記式(1)で示される炭素等量Ceq1が0.55以下である。
Ceq1=[C]+0.108×[Si]-0.067×[Mn]+0.024×[Cr]-0.05×[Ni]+0.074×[V] ・・・(1)
(上記式(1)中、[ ]は各元素の含有量(質量%)を表す。)
The high-strength spring steel according to the present invention that can solve the above-mentioned problems is C: 0.15 to 0.40% (meaning mass%, the same applies hereinafter), Si: 1 to 3.5%, Selected from the group consisting of Mn: 0.20 to 2.0%, Ti: 0.005 to 0.10%, Nb: 0.005 to 0.05%, and V: 0.25% or less At least one selected from the group consisting of Cr: 0.05 to 1.20%, P: 0.030% or less, S: 0.02% or less, the balance being iron and inevitable impurities, ), The carbon equivalent Ceq 1 is 0.55 or less.
Ceq 1 = [C] + 0.108 × [Si] −0.067 × [Mn] + 0.024 × [Cr] −0.05 × [Ni] + 0.074 × [V] (1)
(In the above formula (1), [] represents the content (mass%) of each element.)
 本発明のばね用鋼は、必要に応じて(a)Ni:0.05~2%およびCu:0.05~0.50%、(b)Ni:0.15~2%およびCu:0.05~0.50%、(c)B:0.005%以下および/またはMo:0.60%以下を含有していてもよい。 The spring steel according to the present invention includes (a) Ni: 0.05 to 2% and Cu: 0.05 to 0.50%, (b) Ni: 0.15 to 2% and Cu: 0 as necessary. 0.05 to 0.50%, (c) B: 0.005% or less and / or Mo: 0.60% or less may be contained.
 また、本発明のばね用鋼は、Ti:0.035~0.10%、Nb:0.005~0.05%、およびV:0.05~0.25%よりなる群から選択される少なくとも1種を含有し、焼入れ後の結晶粒度が7.5番以上であることも好ましい。 The spring steel of the present invention is selected from the group consisting of Ti: 0.035 to 0.10%, Nb: 0.005 to 0.05%, and V: 0.05 to 0.25%. It is also preferable that at least one kind is contained and the crystal grain size after quenching is 7.5 or more.
 上記ばね用鋼を用い、このばね用鋼を熱間でコイリングし、焼入れした後、焼戻しを省略したままセッチングすれば、上記特性を両立できるばねを製造できる。 If the spring steel is hot-coiled, quenched and quenched, and then set with the temper omitted, a spring that can achieve both of the above characteristics can be manufactured.
 本発明のばね用鋼は、特定の合金元素の元素量と配合バランスを適切に制御しているため、このばね用鋼を用いてコイルばねを製造する際には、焼入れ後の焼戻し処理を省略することができ、焼入れままの状態で高強度と良好な腐食疲労特性を両立し、さらに良好な低温靭性を有するばねを製造できる。 Since the spring steel of the present invention appropriately controls the element amount and blending balance of a specific alloy element, the tempering process after quenching is omitted when a coil spring is manufactured using this spring steel. Thus, it is possible to manufacture a spring having both high strength and good corrosion fatigue properties while still being quenched, and further having good low temperature toughness.
図1は、実施例1で得られた試験片の炭素当量(Ceq1)と、水素脆化割れ寿命との関係を示すグラフである。FIG. 1 is a graph showing the relationship between the carbon equivalent (Ceq 1 ) of the test piece obtained in Example 1 and the hydrogen embrittlement crack life. 図2は、実施例2で得られた試験片の引張強度と低温靭性(vE-50)との関係を示すグラフである。FIG. 2 is a graph showing the relationship between the tensile strength and the low temperature toughness (vE- 50 ) of the test piece obtained in Example 2.
 本発明者らは、ばね用鋼をコイリングしてばねを製造するにあたり、コイリング後に行う焼入れ後の焼戻し処理を省略して高強度と良好な腐食疲労特性を両立し、さらに低温靭性にも優れるばねを製造できるばね用鋼を提供するために鋭意検討を重ねてきた。その結果、ばね用鋼に含有させる基本合金元素の種類をC、Si、Mn、Crと、Ti、NbおよびVの少なくとも1種に絞るか、これらの元素群にさらに(i)Ni、およびCuを加えたものか、また(ii)Bおよび/またはMoを加えたものに絞り、且つ、これらの元素のうち、C、Ti、Nb、V、Cr、Ni、およびCuの量はできるだけ低減する一方で、SiとMnを積極的に含有させれば、このばね用鋼をコイリングしてばねを製造する際に、焼入れ後の焼戻し処理を省略でき、焼入れままの状態で1900MPa級の引張強度と良好な腐食疲労特性を両立し、さらにTi、NbおよびVの含有量をより厳密に調整することによって低温靭性にも優れたばねを提供できることを見出し、本発明を完成した。 When producing springs by coiling spring steel, the present inventors omit the tempering after quenching performed after coiling to achieve both high strength and good corrosion fatigue properties, and are excellent in low temperature toughness. In order to provide spring steel that can be manufactured, we have made extensive studies. As a result, the types of basic alloy elements to be contained in the spring steel are limited to at least one of C, Si, Mn, Cr and Ti, Nb and V, or (i) Ni and Cu are further added to these element groups. Or (ii) those containing B and / or Mo, and among these elements, the amount of C, Ti, Nb, V, Cr, Ni, and Cu is reduced as much as possible On the other hand, if Si and Mn are positively contained, the tempering treatment after quenching can be omitted when the spring steel is coiled to produce a spring, and the tensile strength of 1900 MPa class can be obtained in the as-quenched state. The inventors have found that a spring excellent in low-temperature toughness can be provided by satisfying both good corrosion fatigue characteristics and more precisely adjusting the contents of Ti, Nb and V, thereby completing the present invention.
 本発明のばね用鋼では、特に、C量を、通常のばね用鋼に用いられるC量よりも低減しているところに特徴がある。C量を低減することで、鋼中に析出する炭化物量を低減できるため、通常のばね製造過程で行われている焼入れ後の焼戻しを省略できる。即ち、ばねは、上述したように、通常、ばね用鋼(線材)を引抜き、磨棒した後、加熱し、熱間でコイリングした後、焼入れ、焼戻しを行い、セッチングして作製される。セッチング後は、必要に応じて、ショットピーニングされた後、塗装が施される。しかし本発明のばね用鋼はC量を低減しているため、焼入れ後の焼戻しを省略してそのままセッチングしてもばねの強度を確保できる。 The spring steel of the present invention is particularly characterized in that the amount of C is lower than the amount of C used in ordinary spring steel. By reducing the amount of C, the amount of carbide precipitated in the steel can be reduced, so that tempering after quenching that is performed in a normal spring manufacturing process can be omitted. That is, as described above, the spring is usually manufactured by drawing and polishing spring steel (wire rod), heating, hot coiling, quenching and tempering, and setting. After the setting, if necessary, coating is performed after shot peening. However, since the spring steel of the present invention has a reduced amount of C, the strength of the spring can be secured even if setting is performed without the tempering after quenching.
 一方、本発明のばね用鋼では、SiとMnを積極的に添加している。SiとMnは、入手し易い元素であり、SiとMnを増量しても安定供給性を維持できる。また、SiとMnは、靱性を低下させることなく強度を高める作用を有するため、SiとMnを積極的に添加することによって高強度と良好な腐食疲労特性を両立できる。 On the other hand, in the spring steel of the present invention, Si and Mn are positively added. Si and Mn are easily available elements, and stable supply can be maintained even if the amount of Si and Mn is increased. Moreover, since Si and Mn have the effect | action which raises an intensity | strength, without reducing toughness, high intensity | strength and favorable corrosion fatigue characteristics can be made compatible by adding Si and Mn positively.
 以上の知見に基づきつつ、高強度と良好な腐食疲労特性を確実に両立するには、各元素の量を厳密に規定し、かつそれらの関係も規定する必要がある。即ち、本発明では、ばね用鋼の成分組成を次のように設計し、下記式(1)で示される炭素当量Ceq1を0.55以下とした。下記式(1)中、[ ]は鋼中の各元素の含有量(質量%)を表す。 Based on the above knowledge, in order to ensure both high strength and good corrosion fatigue properties, it is necessary to strictly define the amount of each element and also define the relationship between them. That is, in the present invention, the component composition of the spring steel is designed as follows, and the carbon equivalent Ceq 1 represented by the following formula (1) is set to 0.55 or less. In the following formula (1), [] represents the content (% by mass) of each element in the steel.
<ばね用鋼の成分組成>
 C:0.15~0.40%、Si:1~3.5%、Mn:0.20~2.0%を含有するとともに、Ti:0.005~0.10%、Nb:0.005~0.05%、およびV:0.25%以下よりなる群から選択される少なくとも1種、Cr:0.05~1.20%
 Ceq1=[C]+0.108×[Si]-0.067×[Mn]+0.024×[Cr]-0.05×[Ni]+0.074×[V] ・・・(1)
 各元素の添加量設定理由と、炭素当量Ceq1の規定理由は以下の通りである。
<Composition composition of spring steel>
C: 0.15 to 0.40%, Si: 1 to 3.5%, Mn: 0.20 to 2.0%, Ti: 0.005 to 0.10%, Nb: 0.0. 005 to 0.05%, and V: at least one selected from the group consisting of 0.25% or less, Cr: 0.05 to 1.20%
Ceq 1 = [C] + 0.108 × [Si] −0.067 × [Mn] + 0.024 × [Cr] −0.05 × [Ni] + 0.074 × [V] (1)
The reason for setting the addition amount of each element and the reason for defining the carbon equivalent Ceq 1 are as follows.
 Cを0.15%以上としたのは、焼入れ性を高め、強度を確保するためである。また、Cを0.40%以下としたのは、靱性と腐食疲労特性の劣化を防止するためである。C量の下限は、好ましくは0.2%以上、より好ましくは0.25%以上であり、C量の上限は好ましくは0.35%以下、より好ましくは0.34%以下、特に好ましくは0.33%以下である。 The reason why C is 0.15% or more is to improve the hardenability and ensure the strength. The reason why C is set to 0.40% or less is to prevent deterioration of toughness and corrosion fatigue characteristics. The lower limit of the C amount is preferably 0.2% or more, more preferably 0.25% or more, and the upper limit of the C amount is preferably 0.35% or less, more preferably 0.34% or less, particularly preferably. It is 0.33% or less.
 Siを1%以上としたのは、Siを固溶強化元素として作用させ、強度を確保するためである。Siが1%未満では、マトリックス強度が不足する。一方、Si量が過剰になると、焼入れ加熱時に炭化物の溶け込みが不十分となり、均一にオーステナイト化させるためにより高温の加熱が必要となって表面の脱炭が進み、ばねの疲労特性が悪くなる。そこで、Siを3.5%以下とすることによって、前記した脱炭の抑制や粒界酸化などの発生を抑制でき、異常組織が生成して強度が低下するのを防止できる。Siは、好ましくは1.5%以上、3.0%以下、より好ましくは1.80%以上、2.5%以下である。 The reason why Si is 1% or more is to make Si act as a solid solution strengthening element to ensure strength. If Si is less than 1%, the matrix strength is insufficient. On the other hand, when the amount of Si becomes excessive, the carbides are not sufficiently dissolved during quenching and heating, and high temperature heating is required for uniform austenitization, so that surface decarburization proceeds and the fatigue characteristics of the spring deteriorate. Therefore, by setting Si to 3.5% or less, it is possible to suppress the above-described decarburization and the occurrence of grain boundary oxidation, etc., and it is possible to prevent the formation of an abnormal structure and a decrease in strength. Si is preferably 1.5% or more and 3.0% or less, more preferably 1.80% or more and 2.5% or less.
 Mnは、0.20%以上とすることで焼入れ性を高め、強度を確保できる。さらに硫化物系介在物が生成することでSによる粒界脆化を抑制し、靭性と腐食疲労特性を向上させることができる。また、Mnは、2.0%以下とすることで過冷組織が発生し、靱性と腐食疲労特性が劣化するのを防止できる。また、過剰な硫化物系介在物の生成や粗大化を抑制し、靭性と腐食疲労特性が劣化するのを防止できる。Mn量の下限は、好ましくは0.5%以上、より好ましくは0.80%以上であり、Mn量の上限は好ましくは1.8%以下、特に好ましくは1.5%以下である。 When Mn is 0.20% or more, the hardenability is improved and the strength can be secured. Further, the formation of sulfide inclusions can suppress grain boundary embrittlement due to S and improve toughness and corrosion fatigue characteristics. Further, when Mn is 2.0% or less, it is possible to prevent a supercooled structure from being generated and deteriorate toughness and corrosion fatigue characteristics. Moreover, generation | occurrence | production and coarsening of an excessive sulfide type inclusion can be suppressed, and it can prevent that toughness and a corrosion fatigue characteristic deteriorate. The lower limit of the Mn amount is preferably 0.5% or more, more preferably 0.80% or more, and the upper limit of the Mn amount is preferably 1.8% or less, particularly preferably 1.5% or less.
 Tiを0.005%以上としたのは、焼入れ後の旧オーステナイト結晶粒を微細化し、強度や耐力比を向上させ、靱性と腐食疲労特性を向上させるためである。靭性を向上させることによって耐へたり性(sag resistance)を向上させることができる。また、Tiを0.10%以下としたのは、粗大な介在物(例えば、Ti窒化物)が析出するのを防止し、腐食疲労特性の劣化を抑制するためである。Ti量の下限は、好ましくは0.01%以上(特に好ましくは0.05%以上)であり、Ti量の上限は、好ましくは0.080%以下、より好ましくは0.07%以下である。 The reason why Ti is made 0.005% or more is to refine the prior austenite crystal grains after quenching, improve the strength and yield ratio, and improve the toughness and corrosion fatigue characteristics. By improving toughness, sag resistance can be improved. The reason why Ti is made 0.10% or less is to prevent coarse inclusions (for example, Ti nitride) from precipitating and to suppress deterioration of corrosion fatigue characteristics. The lower limit of the Ti amount is preferably 0.01% or more (particularly preferably 0.05% or more), and the upper limit of the Ti amount is preferably 0.080% or less, more preferably 0.07% or less. .
 Vは、焼入れ性を一段と高めて強度を高めるのに有効に作用する元素である。また靭性を高めて耐へたり性の向上に寄与する他、結晶粒を微細化して強度や耐力比を向上させる元素である。こうした作用を発揮させるには、Vは0.05%以上含有させることが好ましく、より好ましくは0.08%以上、更に好ましくは0.1%以上である。しかしVが過剰になると粗大な炭窒化物を形成し、靱性と腐食疲労特性が劣化する。従ってVは0.25%以下、好ましくは0.22%以下、より好ましくは0.2%以下である。 V is an element that effectively acts to further enhance the hardenability and increase the strength. In addition to enhancing toughness and improving sag resistance, it is an element that refines crystal grains to improve strength and proof stress ratio. In order to exert such an action, V is preferably contained in an amount of 0.05% or more, more preferably 0.08% or more, and further preferably 0.1% or more. However, when V is excessive, coarse carbonitrides are formed, and toughness and corrosion fatigue properties are deteriorated. Therefore, V is 0.25% or less, preferably 0.22% or less, more preferably 0.2% or less.
 Nbは、靭性を高めて耐へたり性の向上に寄与する元素であり、また結晶粒を微細化して強度や耐力比を向上させる元素である。こうした作用を発揮させるために、Nb量は0.005%以上とする。Nb量は好ましくは0.008%以上であり、より好ましくは0.01%以上である。一方、Nb量が過剰になると靭性に悪影響を及ぼす。従ってNb量は0.05%以下とする。Nb量は好ましくは0.04%以下であり、より好ましくは0.03%以下である。 Nb is an element that contributes to improvement in sag resistance by increasing toughness, and is an element that refines crystal grains to improve strength and proof stress ratio. In order to exert such an effect, the Nb amount is set to 0.005% or more. The amount of Nb is preferably 0.008% or more, and more preferably 0.01% or more. On the other hand, if the amount of Nb is excessive, the toughness is adversely affected. Therefore, the Nb content is 0.05% or less. The Nb amount is preferably 0.04% or less, more preferably 0.03% or less.
 Ti、VおよびNbは単独で添加しても良いし、二種以上を組み合わせて添加しても良い。Ti、VおよびNbの含有量はそれぞれ、Ti:0.035~0.10%、Nb:0.005~0.05%、V:0.05~0.25%として、これらの少なくとも1種を含有させることが好ましい。また、この様な範囲でTi、VおよびNbを含有させることによって、結晶粒微細化効果を有効に発揮することができ、焼入れ後の結晶粒度を7.5番以上とすることができる結果、良好な低温靭性を発揮することができる。焼入れ後の結晶粒度は、より好ましくは8.0番以上であり、さらに好ましくは9.0番以上である。本発明のばね用鋼の低温靭性は、例えば-50℃でのシャルピー吸収エネルギーが50J/cm2以上であり、好ましくは70J/cm2以上、より好ましくは80J/cm2以上である。 Ti, V and Nb may be added alone or in combination of two or more. The contents of Ti, V, and Nb are Ti: 0.035 to 0.10%, Nb: 0.005 to 0.05%, and V: 0.05 to 0.25%, respectively. It is preferable to contain. Further, by containing Ti, V and Nb in such a range, the effect of crystal grain refinement can be effectively exhibited, and the crystal grain size after quenching can be set to 7.5 or more, Good low temperature toughness can be exhibited. The grain size after quenching is more preferably 8.0 or more, and even more preferably 9.0 or more. The low temperature toughness of the spring steel of the present invention is, for example, that Charpy absorbed energy at −50 ° C. is 50 J / cm 2 or more, preferably 70 J / cm 2 or more, more preferably 80 J / cm 2 or more.
 Crは、0.05%以上とすることで固溶強化により鋼マトリックスを強化させると共に、焼入れ性を向上させて強度を確保できる。また、腐食条件下で表層部に生成する錆を非晶質で緻密なものとし、耐食性の向上に寄与する元素である。一方Crは、1.20%以下とすることでMs点が低下して過冷組織が生成するのを防止し、靱性と腐食疲労特性を確保できまた、焼入れ時のCr炭化物の溶け込み不足による強度や硬さの減少を防止することができる。Crは、好ましくは0.1%以上、1.10%以下、より好ましくは0.5%以上、1.05%以下である。 When Cr is 0.05% or more, the steel matrix is strengthened by solid solution strengthening, and the hardenability is improved and the strength can be secured. Further, it is an element that contributes to the improvement of corrosion resistance by making the rust generated in the surface layer portion under the corrosive condition amorphous and dense. On the other hand, when Cr is 1.20% or less, the Ms point is lowered to prevent formation of a supercooled structure, and toughness and corrosion fatigue characteristics can be secured, and strength due to insufficient penetration of Cr carbide during quenching. And a decrease in hardness can be prevented. Cr is preferably 0.1% or more and 1.10% or less, more preferably 0.5% or more and 1.05% or less.
 本発明のばね用鋼の残部は、実質的に鉄である。但し、鉄原料(スクラップを含む)や副原料などの資材、製造設備等の状況によって持ち込まれる不可避不純物が鋼中に含まれることは、当然に許容される。不可避不純物のうち、特にPは0.030%以下、Sは0.02%以下と定めた。このような範囲を定めた理由は以下の通りである。 The balance of the spring steel of the present invention is substantially iron. However, it is naturally allowed that steel contains unavoidable impurities brought in depending on the situation of materials such as iron raw materials (including scrap) and auxiliary materials, manufacturing equipment, and the like. Among unavoidable impurities, P is defined as 0.030% or less and S is defined as 0.02% or less. The reason for setting such a range is as follows.
 Pを0.030%以下としたのは、旧オーステナイト粒界に偏析して粒界を脆化させるのを抑制し、靱性と腐食疲労特性を劣化させるのを防止するためである。Pは、好ましくは0.02%以下、より好ましくは0.01%以下である。Pは少なければ少ない程好ましいが、通常0.001%程度含まれる。 The reason why P is set to 0.030% or less is to prevent segregation at the prior austenite grain boundaries and embrittle the grain boundaries, and to prevent deterioration of toughness and corrosion fatigue characteristics. P is preferably 0.02% or less, more preferably 0.01% or less. The smaller the amount of P, the better. However, it is usually contained in an amount of about 0.001%.
 Sを0.02%以下としたのは、鋼中に硫化物系介在物を形成し、これが粗大化して腐食疲労特性が低下するのを防止するためである。Sは、好ましくは0.015%以下、特に0.01%以下である。SもPと同様に少なければ少ない程好ましいが、通常0.001%程度含まれる。 The reason why S is set to 0.02% or less is to prevent sulfide inclusions from forming in the steel and coarsening the steel to deteriorate the corrosion fatigue characteristics. S is preferably 0.015% or less, particularly 0.01% or less. Like S, P is preferably as small as P, but is usually contained in an amount of about 0.001%.
 PとSの合計量は0.015%以下とすることが好ましく、より好ましくは0.010%以下である。 The total amount of P and S is preferably 0.015% or less, more preferably 0.010% or less.
 上記炭素当量Ceq1を0.55以下としたのは、ばね用鋼をコイリングしてコイルばねを製造する際に、焼入れ後の焼戻し処理を省略してもばねの強度と腐食疲労特性を両立するためである。即ち、上記炭素当量Ceq1は、焼入れ後の硬さに影響を及ぼす合金元素の寄与度を示しており、この数値を小さくしたうえで焼入れ後の焼戻し処理を省略することで、ばねの芯部硬さを確保でき、高強度化を達成できる。また、上記炭素当量Ceq1を0.55以下に抑えることで、合金元素の依存度を下げることができ、安定供給性を高めることができる。上記炭素当量Ceq1は、好ましくは0.53以下、より好ましくは0.50以下である。なお、上記炭素当量Ceq1は、できるだけ小さくなるように成分設計する方がコスト削減できるが、高強度と腐食疲労特性を両立するには合金元素をある程度添加する必要がある。従って炭素当量Ceq1の下限値は0.30である。なお、下記式(1)を計算するにあたり、含有されない元素がある場合は、その元素の含有量は0質量%として計算するものとする。 The reason why the carbon equivalent Ceq 1 is 0.55 or less is that, when coiled spring steel is manufactured to produce a coil spring, the strength and corrosion fatigue characteristics of the spring are compatible even if the tempering treatment after quenching is omitted. Because. That is, the carbon equivalent Ceq 1 indicates the contribution of the alloy element that affects the hardness after quenching. By reducing this numerical value and omitting the tempering treatment after quenching, the core portion of the spring is obtained. Hardness can be secured and high strength can be achieved. In addition, by suppressing the carbon equivalent Ceq 1 to 0.55 or less, the dependence of the alloy elements can be reduced, and the stable supply ability can be improved. The carbon equivalent Ceq 1 is preferably 0.53 or less, more preferably 0.50 or less. The carbon equivalent Ceq 1 can be reduced in cost by designing the component so as to be as small as possible. However, in order to achieve both high strength and corrosion fatigue characteristics, it is necessary to add an alloy element to some extent. Therefore, the lower limit value of the carbon equivalent Ceq 1 is 0.30. In addition, in calculating the following formula (1), when there is an element that is not contained, the content of the element is assumed to be 0% by mass.
 本発明のばね用鋼は、上記化学成分組成と、上記炭素当量Ceq1を満足するものであるが、更なる特性の改善を狙って、NiおよびCuを含有したり、Bおよび/またはMoを含有しても良い。 The spring steel of the present invention satisfies the above chemical composition and the carbon equivalent Ceq 1 , but contains Ni and Cu, or contains B and / or Mo with the aim of further improving the characteristics. It may be contained.
 NiおよびCuを含有(すなわち、NiとCuの併用)する場合は、Ni量を0.05~2%、Cu量を0.05~0.50%とする。Niを0.05%以上としたのは、靱性を高め、欠陥感受性を低減して腐食疲労特性を向上させるためである。また、Niは生成する錆を非晶質で緻密なものとして耐食性を高める作用があり、さらにばね特性として重要なへたり特性を改善する作用も有している。一方、Niを2%以下とすることでMs点が低下して過冷組織が生成するのを防止し、靱性と腐食疲労特性を確保できる。Niは、好ましくは0.15%以上、2%以下であり、より好ましくは0.18%以上、1.5%以下、さらに好ましくは0.20%以上、1%以下、特に0.5%以下である。 When Ni and Cu are contained (that is, when Ni and Cu are used in combination), the Ni content is 0.05 to 2% and the Cu content is 0.05 to 0.50%. The reason why Ni is set to 0.05% or more is to increase toughness, reduce defect sensitivity, and improve corrosion fatigue characteristics. Further, Ni has an effect of improving corrosion resistance by forming amorphous rust that is amorphous and dense, and also has an effect of improving the sag characteristic important as a spring characteristic. On the other hand, by setting Ni to 2% or less, it is possible to prevent the formation of a supercooled structure by lowering the Ms point, and toughness and corrosion fatigue characteristics can be ensured. Ni is preferably 0.15% or more and 2% or less, more preferably 0.18% or more and 1.5% or less, further preferably 0.20% or more and 1% or less, particularly 0.5%. It is as follows.
 Cuは電気化学的に鉄より貴な(Noble)元素であるため錆を緻密化して耐食性を向上させる作用を有する元素である。そこでCuを含有する場合は、Cu量を0.05%以上とする。しかし過剰に添加してもその効果は飽和し、むしろ熱間圧延による素材の脆化を引き起こす恐れがある。そこでCu量の上限は0.50%以下とした。Cuは、好ましくは0.1%以上、0.4%以下、より好ましくは0.15%以上(特に0.18%以上)、0.3%以下である。 Cu is an element that is electrochemically noble than iron (noble) and therefore has the effect of densifying rust and improving corrosion resistance. Therefore, when Cu is contained, the amount of Cu is set to 0.05% or more. However, even if added excessively, the effect is saturated, and there is a possibility of causing embrittlement of the material due to hot rolling. Therefore, the upper limit of Cu content is 0.50% or less. Cu is preferably 0.1% or more and 0.4% or less, more preferably 0.15% or more (particularly 0.18% or more) and 0.3% or less.
 Bは、焼入れ性を一段と高めて粒界強度を高め、靭性を高めて耐へたり性を向上させ、さらに表面に生成する錆を緻密化して耐食性を向上させる元素である。こうした作用を発揮させるには、Bは0.0005%以上含有させることが好ましく、より好ましくは0.001%以上、更に好ましくは0.0015%以上である。しかしBが過剰になると上記効果が飽和する他、粗大な炭窒化物を形成し、靱性と腐食疲労特性が劣化する。従ってBは0.005%以下、好ましくは0.004%以下、より好ましくは0.003%以下である。 B is an element that further enhances hardenability to increase grain boundary strength, enhance toughness and improve sag resistance, and further densify rust generated on the surface to improve corrosion resistance. In order to exert such an effect, B is preferably contained in an amount of 0.0005% or more, more preferably 0.001% or more, and further preferably 0.0015% or more. However, when B is excessive, the above effect is saturated and coarse carbonitride is formed, resulting in deterioration of toughness and corrosion fatigue characteristics. Therefore, B is 0.005% or less, preferably 0.004% or less, more preferably 0.003% or less.
 Moは、靭性を高めて耐へたり性の向上に寄与する元素であり、また焼入性を確保して、鋼の強度と靭性を高める元素である。こうした作用を有効に発揮させるためMo量は0.05%以上とすることが好ましく、より好ましくは0.08%以上であり、さらに好ましくは0.10%以上である。一方、Mo量が過剰になっても上記効果は飽和する。そこでMo量は0.60%以下とすることが好ましく、より好ましくは0.50%以下、さらに好ましくは0.35%以下である。BおよびMoは、単独で含有しても良いし、併用しても良い。 Mo is an element that increases toughness and contributes to improvement in sag resistance, and also ensures hardenability and increases the strength and toughness of steel. In order to effectively exhibit these actions, the Mo amount is preferably 0.05% or more, more preferably 0.08% or more, and further preferably 0.10% or more. On the other hand, even if the amount of Mo becomes excessive, the above effect is saturated. Therefore, the Mo content is preferably 0.60% or less, more preferably 0.50% or less, and still more preferably 0.35% or less. B and Mo may be contained alone or in combination.
 以上説明したように、本発明のばね用鋼は、各合金元素量を厳密に規定すると共に、それらの関係を規定しているところに特徴があり、このばね用鋼を用いれば、コイリング後に行う焼入れ後の焼戻し処理を省略でき、焼入れままでも引張強度が1900MPa以上の高強度と良好な腐食疲労特性を両立したばねを製造できる。また、結晶粒微細化作用のある元素(Ti、NbおよびV)の含有量をより厳密に制御することによって、低温靭性を向上させることができる。以下、上記ばね用鋼からばねを製造するときの方法について説明する。 As described above, the spring steel according to the present invention is characterized in that the amount of each alloying element is strictly defined and the relationship between them is specified. If this spring steel is used, it is performed after coiling. A tempering treatment after quenching can be omitted, and a spring having both high strength with a tensile strength of 1900 MPa or more and good corrosion fatigue characteristics can be produced even when quenched. Moreover, low temperature toughness can be improved by controlling the content of elements (Ti, Nb and V) having a grain refinement action more strictly. Hereinafter, a method for manufacturing a spring from the spring steel will be described.
 本発明のばね用鋼からばねを製造するにあたっては、焼入れ後の焼戻しを省略する必要がある。即ち、上記化学成分組成を満足するばね用鋼(線材)を、引抜き、磨棒した後、加熱し、熱間でコイリングしてばね形状に成形し、焼入れするまでは従来と同じであるが、焼入れ後、焼戻しを省略したままセッチングする必要がある。本発明のばね用鋼は、C量を従来のばね用鋼よりも低減しているため、焼入れ後に焼戻しすると、軟化し過ぎて靱性と腐食疲労特性が劣化する。従って焼入れ後の焼戻しは省略する必要がある。 When manufacturing a spring from the spring steel of the present invention, it is necessary to omit tempering after quenching. That is, it is the same as before until the spring steel (wire) satisfying the above chemical composition is drawn, polished, heated, coiled hot, formed into a spring shape, and quenched. After quenching, it is necessary to perform setting while omitting tempering. Since the spring steel of the present invention has a C content lower than that of the conventional spring steel, when it is tempered after quenching, it is too soft and deteriorates toughness and corrosion fatigue characteristics. Therefore, it is necessary to omit tempering after quenching.
 ここで、「焼戻しの省略」とは、焼入れ後に、350℃を超える温度に加熱されないことを意味している。 Here, “omission of tempering” means that the material is not heated to a temperature exceeding 350 ° C. after quenching.
 上記セッチングは、冷間で行ってもよいし、温間で行ってもよい。冷間セッチングするときの温度は、常温とすればよく、温間セッチングするときの温度は、200~250℃程度とすればよい。 The above setting may be performed cold or warm. The temperature at the time of cold setting may be normal temperature, and the temperature at the time of cold setting may be about 200 to 250 ° C.
 セッチング後は、必要に応じて、ショットピーニングした後、塗装してもよい。ショットピーニングと塗装の条件は特に限定されず、常法の条件を採用できる。 After setting, if necessary, you may paint after shot peening. The conditions for shot peening and painting are not particularly limited, and conventional conditions can be adopted.
 こうして得られるばねは、高強度と良好な腐食疲労特性を両立でき、さらに低温靭性にも優れている。 The spring thus obtained can achieve both high strength and good corrosion fatigue properties, and is also excellent in low temperature toughness.
 本発明に係るばね用鋼の製造条件は特に限定されないが、本発明の好ましい態様である結晶粒度を7.5番以上とするためには、例えば焼入れ時の加熱温度を925℃以下とし、加熱時間を15分以下とすることが推奨される。前記焼入れ時の加熱温度および加熱時間の下限は特に限定されないが、通常、加熱温度の下限は850℃程度、加熱時間の下限は10分程度である。 The production conditions of the spring steel according to the present invention are not particularly limited, but in order to make the crystal grain size 7.5 or more which is a preferred embodiment of the present invention, for example, the heating temperature at the time of quenching is set to 925 ° C. or less, and the heating is performed. It is recommended that the time be 15 minutes or less. Although the lower limit of the heating temperature and the heating time at the time of quenching is not particularly limited, the lower limit of the heating temperature is usually about 850 ° C., and the lower limit of the heating time is about 10 minutes.
 以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも勿論可能であり、それらはいずれも本発明の技術的範囲に包含される。 EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.
実施例1
 下記表1に示す化学成分組成の鋼(残部は、鉄および不可避不純物)を150kgの真空溶解炉にて溶製してから1200℃で保持した後、熱間鍛造して155mm角のビレットにし、このビレットを熱間圧延して直径13.5mmのばね用鋼(ばね用線材)を作製した。このばね用線材に、直径が12.5mmとなるように磨棒加工を施した後、長さ70mmに切断してから焼入れを行った。焼入れは、温度925℃で10分間加熱した後、温度50℃の油浴に入れて行った。焼入れ後、機械加工して幅10mm×厚さ1.5mm×長さ65mmの試験片を切り出した。
Example 1
The steel of the chemical composition shown in Table 1 below (the balance is iron and inevitable impurities) was melted in a 150 kg vacuum melting furnace and held at 1200 ° C., then hot forged into a 155 mm square billet, This billet was hot-rolled to produce a spring steel (spring wire) having a diameter of 13.5 mm. The spring wire was subjected to a polishing rod process so that the diameter was 12.5 mm, and was then quenched after being cut to a length of 70 mm. Quenching was performed by heating at a temperature of 925 ° C. for 10 minutes and then placing in an oil bath at a temperature of 50 ° C. After quenching, a test piece having a width of 10 mm, a thickness of 1.5 mm and a length of 65 mm was cut out by machining.
 表1に示したNo.29とNo.30は、神戸製鋼所(KOBE STEEL,LTD)製のばね用線材「UHS1900」を模擬したデータであり、これらのうちNo.30は、焼入れ後、400℃で1時間保持して焼戻しを行ってから上記と同じ条件で機械加工して試験片を作製した。表2に、焼戻しの有無を示す。 No. shown in Table 1. 29 and No. 30 is data simulating a spring wire “UHS1900” manufactured by Kobe Steel (KOBEKSTEEL, LTD). No. 30 was quenched and held at 400 ° C. for 1 hour for tempering and then machined under the same conditions as above to prepare a test piece. Table 2 shows the presence or absence of tempering.
 また、鋼中の化学成分量と、上記式(1)から算出される炭素当量(Ceq1)を算出した結果を下記表1に示す。 Table 1 below shows the results of calculating the amount of chemical components in the steel and the carbon equivalent (Ceq 1 ) calculated from the above formula (1).
 得られた試験片の強度と腐食疲労特性を以下のようにして調べた。 The strength and corrosion fatigue properties of the obtained specimens were examined as follows.
 試験片の強度と腐食疲労特性は、セッチングを冷間または温間で行うことを模擬して測定した。即ち、冷間セッチングを模擬する場合は、上記試験片をそのまま各試験に用い、温間セッチングを模擬する場合は、上記試験片を200℃で60分間加熱したものを各試験に用いた。冷間セッチングと温間セッチングのどちらを模擬したかを下記表2に示す。 The strength and corrosion fatigue properties of the test specimens were measured by simulating the setting performed cold or warm. That is, when simulating cold setting, the test piece was used for each test as it was, and when simulating warm setting, the test piece heated at 200 ° C. for 60 minutes was used for each test. Table 2 below shows which of the cold setting and the warm setting is simulated.
<強度>
 試験片の強度は、試験片の硬さをロックウェル硬さ試験機で、Cスケールで測定して評価した。C硬さの測定結果を下記表2に示す。本発明では、HRCが51以上を合格とする。
<Strength>
The strength of the test piece was evaluated by measuring the hardness of the test piece with a Rockwell hardness tester on a C scale. The measurement results of C hardness are shown in Table 2 below. In the present invention, an HRC of 51 or more is considered acceptable.
<腐食疲労特性>
 腐食疲労特性は、水素脆化割れ試験を行って評価した。水素脆化割れ試験は、上記試験片に対して4点曲げによって1400MPaの応力を作用させながら、この試験片を硫酸(0.5mol/L)とチオシアン酸カリウム(KSCN;0.01mol/L)の混合水溶液に浸漬し、ポテンショスタットを用いてSCE電極よりも卑(Lower)である-700mVの電圧をかけ、割れが発生するまでの時間(以下、水素脆化割れ寿命と呼ぶ。)を測定した。水素脆化割れ試験の測定結果を下記表2に示す。本発明では、割れ発生までの時間が600秒以上の場合を合格とする。
<Corrosion fatigue characteristics>
The corrosion fatigue characteristics were evaluated by conducting a hydrogen embrittlement cracking test. In the hydrogen embrittlement cracking test, a stress of 1400 MPa was applied to the above test piece by four-point bending, and this test piece was treated with sulfuric acid (0.5 mol / L) and potassium thiocyanate (KSCN; 0.01 mol / L). The sample was immersed in a mixed aqueous solution, and a voltage of −700 mV, which is lower than the SCE electrode, was applied using a potentiostat, and the time until cracking occurred (hereinafter referred to as hydrogen embrittlement crack life) was measured. did. The measurement results of the hydrogen embrittlement cracking test are shown in Table 2 below. In the present invention, a case where the time until occurrence of cracking is 600 seconds or more is regarded as acceptable.
 なお、HRCが51以上、割れ発生までの時間が600秒以上という基準は、焼入れ後に焼戻しを行って得られた従来の懸架ばね(下記表2のNo.30)と同等以上の特性を有していることを意味している。 In addition, the standard that HRC is 51 or more and the time until crack generation is 600 seconds or more has the same or better characteristics as a conventional suspension spring (No. 30 in Table 2 below) obtained by tempering after quenching. It means that
 図1に、炭素当量(Ceq1)と水素脆化割れ寿命(秒)との関係を示す。図1では、No.1~15、31、33の結果を□で、No.16~29、32の結果を●で、No.30(焼戻し有り)の結果を○で示した。 FIG. 1 shows the relationship between the carbon equivalent (Ceq 1 ) and the hydrogen embrittlement crack life (seconds). In FIG. The results of 1 to 15, 31, and 33 are indicated by □ and No. The results of 16 to 29, 32 are indicated by ● and No. The result of 30 (with tempering) is indicated by ○.
 図1から明らかなように、炭素当量(Ceq1)を小さくした方が、水素脆化割れ寿命を長くすることができ、腐食疲労特性を改善できる傾向が読み取れる。 As is apparent from FIG. 1, it can be seen that the hydrogen embrittlement crack life can be extended and the corrosion fatigue characteristics can be improved by reducing the carbon equivalent (Ceq 1 ).
 表2から次のように考察できる。 From Table 2, it can be considered as follows.
 No.30は、焼入れ後に焼戻しを行った例である。この例では、芯部硬さを確保できており、強度が高く、また水素脆化割れ寿命も良好で、腐食疲労特性を改善できている。しかし焼入れ後に焼戻し処理しているため、CO2排出量を削減できない。 No. 30 is an example of tempering after quenching. In this example, the core hardness can be secured, the strength is high, the hydrogen embrittlement crack life is good, and the corrosion fatigue characteristics can be improved. However, since tempering is performed after quenching, CO 2 emissions cannot be reduced.
 No.29の成分組成は上記No.30に類似しているが、焼入れ後の焼戻しを省略した例である。この例では、焼戻し処理を省略しているためCO2排出量を削減できるが、炭素当量が0.55を超えており、合金元素量が多いにもかかわらず焼戻しを省略しているため、芯部硬さが硬くなり過ぎて靱性が低下し、水素脆化割れ寿命が短くなって腐食疲労特性が劣化している。 No. The component composition of No. 29 is the above No. This is an example similar to 30, but without tempering after quenching. In this example, the tempering process is omitted, so that the CO 2 emission can be reduced. However, since the carbon equivalent exceeds 0.55 and the alloy element amount is large, the tempering is omitted. The partial hardness becomes too hard, the toughness is lowered, the hydrogen embrittlement crack life is shortened, and the corrosion fatigue characteristics are deteriorated.
 No.16~28、32は、本発明で規定する要件を満足しない例であり、高強度と良好な腐食疲労特性を両立できていない。即ち、ばね用鋼の炭素当量(Ceq1)が本発明で規定する範囲を超えており、しかも焼入れ後の焼戻しを省略しているためCO2排出量を削減できるが、芯部硬さが硬くなり過ぎて靱性が低下し、水素脆化割れ寿命が短くなって腐食疲労特性が劣化している。 No. Nos. 16 to 28 and 32 are examples that do not satisfy the requirements defined in the present invention, and cannot achieve both high strength and good corrosion fatigue characteristics. That is, the carbon equivalent (Ceq 1 ) of the spring steel exceeds the range specified in the present invention, and the tempering after quenching is omitted, so that the CO 2 emission can be reduced, but the core hardness is hard. As a result, the toughness is lowered, the hydrogen embrittlement crack life is shortened, and the corrosion fatigue characteristics are deteriorated.
 No.1~15、33は、本発明で規定する要件を満足する例であり、高強度と良好な腐食疲労特性を両立できている。即ち、炭素当量(Ceq1)を0.55以下に抑えたうえで、焼入れ後の焼戻しを省略しているためCO2排出量を削減でき、しかも芯部硬さを適度に確保できており、高強度を達成できている。また、水素脆化割れ寿命も長く、腐食疲労特性も改善できている。しかも、ばね用鋼の炭素当量(Ceq1)を0.55以下に抑えているため、合金元素の依存度を下げることができており、安定供給を実現できる。従って、本発明のばね用鋼を用いれば、上記「UHS1900」を模擬した上記No.30と同程度か、それ以上の特性を発揮するばねを提供できることが分かる。 No. Nos. 1 to 15 and 33 are examples that satisfy the requirements defined in the present invention, and both high strength and good corrosion fatigue characteristics can be achieved. That is, after suppressing the carbon equivalent (Ceq 1 ) to 0.55 or less, and tempering after quenching is omitted, CO 2 emission can be reduced, and the core hardness can be appropriately secured. High strength can be achieved. In addition, the hydrogen embrittlement crack life is long, and the corrosion fatigue characteristics can be improved. Moreover, since the carbon equivalent (Ceq 1 ) of the spring steel is suppressed to 0.55 or less, the dependence of the alloy elements can be reduced, and stable supply can be realized. Therefore, when the spring steel of the present invention is used, the above No. 1 simulating the “UHS1900”. It can be seen that a spring exhibiting characteristics comparable to or higher than 30 can be provided.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
実施例2
 表3に示す化学成分組成の鋼材(残部は、鉄および不可避不純物)を150kgの真空溶解炉にて溶製した後、造塊法または連続鋳造法によって鋳造し、その後、分塊圧延によって155mm角のビレットを作成し、さらに熱間圧延して直径13.5mmの線材に加工して供試材とした。これら供試材を、温度925℃で10分間加熱した後、50℃の油浴に入れて焼入れを行った。No.2-24のみ、前記焼入れ後に400℃で1時間の焼戻し処理を行った。
Example 2
Steel materials having the chemical composition shown in Table 3 (the balance being iron and inevitable impurities) were melted in a 150 kg vacuum melting furnace, then cast by the ingot-making method or continuous casting method, and then 155 mm square by split rolling. The billet was prepared, further hot-rolled, and processed into a wire having a diameter of 13.5 mm to obtain a test material. These specimens were heated at a temperature of 925 ° C. for 10 minutes and then quenched in an oil bath at 50 ° C. No. Only 2-24 was tempered at 400 ° C. for 1 hour after the quenching.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
<低温靭性>
 上記焼入れ後の供試材から、2mmUノッチ付衝撃試験片を採取し、JIS Z2242に従って、-50℃でのシャルピー吸収エネルギー(vE-50)を求めた。試験は各鋼種につき2本ずつ行い、平均値を各鋼種のシャルピー吸収エネルギーとした。
<Low temperature toughness>
An impact test piece with a 2 mm U notch was taken from the specimen after quenching, and Charpy absorbed energy (vE -50 ) at -50 ° C was determined according to JIS Z2242. Two tests were performed for each steel type, and the average value was defined as the Charpy absorbed energy of each steel type.
<結晶粒度番号>
 上記焼入れ後の供試材の、D/4位置(Dは線材の直径)において、任意の15mm2の領域を光学顕微鏡で観察し(倍率:400倍)、JIS G0551に従って結晶粒度番号を測定した。測定は2視野について行い、これらの平均値をオーステナイト結晶粒度とした。
<Grain size number>
At the D / 4 position (D is the diameter of the wire) of the specimen after quenching, an arbitrary 15 mm 2 region was observed with an optical microscope (magnification: 400 times), and the crystal grain size number was measured according to JIS G0551. . The measurement was performed for two fields of view, and the average of these values was defined as the austenite grain size.
 結果を表4に示す。 The results are shown in Table 4.
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
 表4のNo.2-1~No.2-14は、本発明の要件を満たし、特にTi、NbおよびV量が適切に調整されているため、高強度で、かつ低温靭性に優れる鋼が実現できた。 No. in Table 4 2-1. No. 2-14 satisfies the requirements of the present invention, and in particular, the Ti, Nb, and V contents are appropriately adjusted, so that a steel having high strength and excellent low-temperature toughness could be realized.
 一方、No.2-15~No.2-24は、本発明の要件の少なくともいずれかを満たしていないため、靭性が不十分であった。 On the other hand, No. 2-15 ~ No. No. 2-24 did not satisfy at least one of the requirements of the present invention, and thus toughness was insufficient.
 No.2-15~No.2-19は、C量が過剰であった例であり、強度が上昇しすぎることによって低温靭性が低下した。 No. 2-15 ~ No. No. 2-19 was an example in which the amount of C was excessive, and the low temperature toughness decreased due to the excessive increase in strength.
 No.2-20~No.2-22は、Ti、NbおよびVのいずれも含有しないため、結晶粒微細化効果が発揮されず、低温靭性が低下した。 No. 2-20 ~ No. Since 2-22 does not contain any of Ti, Nb and V, the effect of refining crystal grains was not exhibited, and the low temperature toughness was lowered.
 No.2-23およびNo.2-24はいずれも規格鋼の9254に相当する鋼種であり、No.2-24は焼入れ後に焼戻し処理を行ったものである。No.2-23はC量が多く強度が上昇しすぎたことと、Ti、NbおよびVのいずれも含有しないため、低温靭性が低下した。また、No.2-24は、焼戻し処理をしたため強度はNo.2-23に比べて低下しているが、Ti、NbおよびVのいずれも含有しないため、低温靭性が低下した。 No. 2-23 and no. No. 2-24 is a steel grade corresponding to standard steel 9254. No. 2-24 has been tempered after quenching. No. No. 2-23 had a large amount of C and an excessively high strength, and did not contain any of Ti, Nb and V, so that the low temperature toughness decreased. No. Since No. 2-24 was tempered, its strength was No. 2-24. Although it is lower than that of 2-23, since it does not contain any of Ti, Nb and V, the low temperature toughness is reduced.
 図2は、No.2-1~2-24について、強度と低温靭性(-50℃でのシャルピー吸収エネルギー)の関係を示したグラフである。図2ではNo.2-1~2-14、2-25の結果を□で、No.2-15~No.2-23、2-26の結果を●で、No.2-24の結果を○で示した。図2によれば本発明の要件を満たす鋼(図2中、□で示す)は、いずれもシャルピー吸収エネルギーが50J/cm2以上であるとともに、本発明の要件のいずれかを満たさない鋼(図2中、●および○で示す)に比べて同じ強度で比較した場合に高靭性を達成していることが分かる。 FIG. FIG. 2 is a graph showing the relationship between strength and low temperature toughness (Charpy absorbed energy at −50 ° C.) for 2-1 to 2-24. In FIG. The results of 2-1 to 2-14 and 2-25 are indicated by □ and No. 2-15 ~ No. The results of Nos. 2-23 and 2-26 are indicated by ●, The result of 2-24 was indicated by ○. According to FIG. 2, all the steels satisfying the requirements of the present invention (indicated by □ in FIG. 2) have a Charpy absorbed energy of 50 J / cm 2 or more and steels that do not satisfy any of the requirements of the present invention ( In FIG. 2, it can be seen that high toughness is achieved when compared at the same strength as indicated by ● and ○.

Claims (6)

  1. C:0.15~0.40%(質量%の意味。以下、同じ。)、
    Si:1~3.5%、
    Mn:0.20~2.0%を含有するとともに、
    Ti:0.005~0.10%、Nb:0.005~0.05%、およびV:0.25%以下よりなる群から選択される少なくとも1種、
    Cr:0.05~1.20%、
    P:0.030%以下、
    S:0.02%以下を含有し、残部が鉄および不可避的不純物であり、
     下記式(1)で示される炭素等量Ceq1が0.55以下であることを特徴とする焼戻しを省略した高強度ばね用鋼。
    Ceq1=[C]+0.108×[Si]-0.067×[Mn]+0.024×[Cr]-0.05×[Ni]+0.074×[V] ・・・(1)
    (上記式(1)中、[ ]は各元素の含有量(質量%)を表す。)
    C: 0.15 to 0.40% (meaning mass%, hereinafter the same)
    Si: 1 to 3.5%,
    Containing Mn: 0.20 to 2.0%,
    At least one selected from the group consisting of Ti: 0.005 to 0.10%, Nb: 0.005 to 0.05%, and V: 0.25% or less,
    Cr: 0.05 to 1.20%,
    P: 0.030% or less,
    S: 0.02% or less, the balance is iron and inevitable impurities,
    A high strength spring steel without tempering, characterized in that the carbon equivalent Ceq 1 represented by the following formula (1) is 0.55 or less.
    Ceq 1 = [C] + 0.108 × [Si] −0.067 × [Mn] + 0.024 × [Cr] −0.05 × [Ni] + 0.074 × [V] (1)
    (In the above formula (1), [] represents the content (mass%) of each element.)
  2.  更に、
     Ni:0.05~2%およびCu:0.05~0.50%を含有する請求項1に記載の高強度ばね用鋼。
    Furthermore,
    The high-strength spring steel according to claim 1, containing Ni: 0.05-2% and Cu: 0.05-0.50%.
  3.  Ni:0.15~2%を含有する請求項2に記載の高強度ばね用鋼。 The steel for high strength springs according to claim 2, containing Ni: 0.15 to 2%.
  4.  Ti:0.035~0.10%、Nb:0.005~0.05%、およびV:0.05~0.25%よりなる群から選択される少なくとも1種を含有し、
     焼入れ後の結晶粒度が7.5番以上である請求項1に記載の高強度ばね用鋼。
    Containing at least one selected from the group consisting of Ti: 0.035 to 0.10%, Nb: 0.005 to 0.05%, and V: 0.05 to 0.25%,
    The steel for high strength springs according to claim 1, wherein the grain size after quenching is 7.5 or more.
  5.  更に、
     B:0.005%以下および/またはMo:0.60%以下を含有する請求項1に記載の高強度ばね用鋼。
    Furthermore,
    The steel for high-strength springs according to claim 1, containing B: 0.005% or less and / or Mo: 0.60% or less.
  6.  請求項1~5のいずれかに記載のばね用鋼を熱間でコイリングし、焼入れした後、焼戻しを省略したままセッチングすることを特徴とする腐食疲労特性に優れた高強度ばねの製造方法。 A method for producing a high-strength spring excellent in corrosion fatigue characteristics, characterized in that the spring steel according to any one of claims 1 to 5 is hot-coiled, quenched, and then set while omitting tempering.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2811198A4 (en) * 2012-01-31 2016-01-06 Nhk Spring Co Ltd Ring-shaped spring and method for manufacturing same

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2014198874A (en) 2013-03-29 2014-10-23 株式会社神戸製鋼所 Steel material excellent in corrosion resistance and magnetic properties and method of producing the same
JP6477007B2 (en) * 2015-02-26 2019-03-06 愛知製鋼株式会社 Leaf spring and manufacturing method thereof
CN105088081B (en) * 2015-08-28 2018-03-13 浙江美力汽车弹簧有限公司 The manufacturing process of stabiliser bar
CN105112774B (en) * 2015-08-28 2017-12-01 浙江美力科技股份有限公司 The air-cooled hardening spring steel of the low middle carbon microalloy of high-strength tenacity and its shaping and Technology for Heating Processing
KR101795277B1 (en) * 2016-06-21 2017-11-08 현대자동차주식회사 High strength spring steel having excellent corrosion resistance
KR101795278B1 (en) * 2016-06-21 2017-11-08 현대자동차주식회사 Ultra high strength spring steel
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JP2020076154A (en) * 2020-01-07 2020-05-21 日本発條株式会社 Method for producing spring for suspension
CN114134411B (en) * 2021-10-12 2022-07-29 江阴兴澄特种钢铁有限公司 Spheroidized annealed steel for low-temperature-resistant high-strength ball screw and manufacturing method thereof

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH11323495A (en) * 1998-05-13 1999-11-26 Kobe Steel Ltd Non-heat treated rolled wire steel or rod steel for spring
JP2001049337A (en) * 1999-08-05 2001-02-20 Kobe Steel Ltd Production of high strength spring excellent in fatigue strength
JP3246733B2 (en) 1999-10-29 2002-01-15 三菱製鋼室蘭特殊鋼株式会社 High strength spring steel
JP2004263247A (en) * 2003-02-28 2004-09-24 Daido Steel Co Ltd Steel for cold-formed spring
JP3577411B2 (en) 1997-05-12 2004-10-13 新日本製鐵株式会社 High toughness spring steel
JP2009046764A (en) * 2007-07-20 2009-03-05 Kobe Steel Ltd Steel wire material for spring having excellent corrosion fatigue property
JP4406341B2 (en) 2004-09-22 2010-01-27 Jfe条鋼株式会社 Manufacturing method of high strength stabilizer with excellent toughness

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61276952A (en) * 1985-06-01 1986-12-06 Nissan Motor Co Ltd Tough and hard steel
JPS62267420A (en) * 1986-05-13 1987-11-20 Kobe Steel Ltd Manufacture of high tension and high toughness wire rod having superior delayed fracture resistance
JPH0830246B2 (en) * 1987-03-05 1996-03-27 大同特殊鋼株式会社 High strength spring steel
JPH0892696A (en) * 1994-09-26 1996-04-09 Nippon Steel Corp High strength bainitic rail
US5776267A (en) * 1995-10-27 1998-07-07 Kabushiki Kaisha Kobe Seiko Sho Spring steel with excellent resistance to hydrogen embrittlement and fatigue
JP3966493B2 (en) * 1999-05-26 2007-08-29 新日本製鐵株式会社 Cold forging wire and method for producing the same
JP3968011B2 (en) * 2002-05-27 2007-08-29 新日本製鐵株式会社 High strength steel excellent in low temperature toughness and weld heat affected zone toughness, method for producing the same and method for producing high strength steel pipe
CA2531615A1 (en) * 2004-12-28 2006-06-28 Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) High strength thin steel sheet having high hydrogen embrittlement resisting property
JP4476863B2 (en) * 2005-04-11 2010-06-09 株式会社神戸製鋼所 Steel wire for cold forming springs with excellent corrosion resistance
JP5064060B2 (en) * 2007-02-22 2012-10-31 新日本製鐵株式会社 Steel wire for high-strength spring, high-strength spring, and manufacturing method thereof
JP5306845B2 (en) * 2009-02-12 2013-10-02 Jfe条鋼株式会社 Steel for vehicle high strength stabilizer excellent in corrosion resistance and low temperature toughness, its manufacturing method and stabilizer
JP5324311B2 (en) * 2009-05-15 2013-10-23 株式会社神戸製鋼所 Hollow seamless pipe for high strength springs

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3577411B2 (en) 1997-05-12 2004-10-13 新日本製鐵株式会社 High toughness spring steel
JPH11323495A (en) * 1998-05-13 1999-11-26 Kobe Steel Ltd Non-heat treated rolled wire steel or rod steel for spring
JP2001049337A (en) * 1999-08-05 2001-02-20 Kobe Steel Ltd Production of high strength spring excellent in fatigue strength
JP3246733B2 (en) 1999-10-29 2002-01-15 三菱製鋼室蘭特殊鋼株式会社 High strength spring steel
JP2004263247A (en) * 2003-02-28 2004-09-24 Daido Steel Co Ltd Steel for cold-formed spring
JP4406341B2 (en) 2004-09-22 2010-01-27 Jfe条鋼株式会社 Manufacturing method of high strength stabilizer with excellent toughness
JP2009046764A (en) * 2007-07-20 2009-03-05 Kobe Steel Ltd Steel wire material for spring having excellent corrosion fatigue property

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2811198A4 (en) * 2012-01-31 2016-01-06 Nhk Spring Co Ltd Ring-shaped spring and method for manufacturing same

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US20120285585A1 (en) 2012-11-15
EP2518175A4 (en) 2015-12-02
JP6027302B2 (en) 2016-11-16
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