WO2017038436A1 - Fil d'acier pour pièces d'une structure mécanique - Google Patents

Fil d'acier pour pièces d'une structure mécanique Download PDF

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Publication number
WO2017038436A1
WO2017038436A1 PCT/JP2016/073770 JP2016073770W WO2017038436A1 WO 2017038436 A1 WO2017038436 A1 WO 2017038436A1 JP 2016073770 W JP2016073770 W JP 2016073770W WO 2017038436 A1 WO2017038436 A1 WO 2017038436A1
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cementite
steel wire
steel
average
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PCT/JP2016/073770
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English (en)
Japanese (ja)
Inventor
雄基 佐々木
琢哉 高知
政道 千葉
昌之 坂田
昌吾 村上
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株式会社神戸製鋼所
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Priority claimed from JP2016124960A external-priority patent/JP2017048459A/ja
Application filed by 株式会社神戸製鋼所 filed Critical 株式会社神戸製鋼所
Publication of WO2017038436A1 publication Critical patent/WO2017038436A1/fr

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • 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
    • C21D1/26—Methods of annealing
    • C21D1/32—Soft annealing, e.g. spheroidising
    • 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

Definitions

  • the present invention relates to a steel wire used as a material for machine structural parts. More specifically, the wire rod manufactured by temper rolling is subjected to spheroidizing annealing and then cold-worked, so the deformation resistance during cold working is low, crack resistance is good, and cold workability is good.
  • the present invention relates to a steel wire useful as a material for machine structural parts.
  • a "wire” is used for the meaning of a rolled wire, and points out the linear steel material cooled to room temperature after hot rolling.
  • the “steel wire” refers to a linear steel material obtained by subjecting the rolled wire material to a tempering treatment such as spheroidizing annealing.
  • spheroidizing annealing is usually applied to hot rolled wire rods such as carbon steel and alloy steel for the purpose of imparting cold workability.
  • hot rolled wire rods such as carbon steel and alloy steel
  • the strength is adjusted to obtain a machine structural part.
  • the life of the mold can be improved by lowering the deformation resistance of the steel wire.
  • the yield improvement of various components can be expected by improving the crack resistance of the steel wire.
  • the metal structure is substantially composed of ferrite grains and spherical carbides, and the ferrite grains have an average particle size of 15 ⁇ m or more, and the spherical carbides have an average particle size of 0.1. 8 ⁇ m or less, the maximum particle size is 4.0 ⁇ m or less, and the number per 1 mm 2 is 0.5 ⁇ 10 6 ⁇ C% to 5.0 ⁇ 10 6 ⁇ C%.
  • a steel wire technique in which the maximum distance between spherical carbides having a particle size of 0.1 ⁇ m or more is 10 ⁇ m or less is disclosed.
  • the average particle diameter of ferrite in the region from the surface to 20% of the cross-sectional radius, is 3 to 15 ⁇ m, the average particle diameter is 0.3 to 0.6 ⁇ m, and the average aspect ratio is 2. 5 or less spherical cementite is contained at a number density of 7 ⁇ 10 5 pieces / mm 2 or less, and the value obtained by dividing the standard deviation of the area ratio of cementite by the average area ratio of cementite is 0.25 or less.
  • the average particle diameter of ferrite In the inner region from 75% of the radius to the center, the average particle diameter of ferrite is 20 ⁇ m or more, and the steel wire rod / steel bar has excellent cold workability and contains spherical cementite having an average particle diameter of 0.3 ⁇ m or more.
  • Patent Document 3 includes a ferrite structure having an average particle diameter of 15 ⁇ m or less, and spherical cementite having an average aspect ratio of 3 or less and an average particle diameter of 0.6 ⁇ m or less, and the number of the spherical cementite is 1 mm.
  • a technique of steel wire rods having a cold workability of 1.0 ⁇ 10 6 ⁇ C content (%) or more per 2 is disclosed.
  • An object of the present invention is to provide a steel wire for machine structural parts capable of reducing deformation resistance during cold working, improving crack resistance, and exhibiting excellent cold workability.
  • the steel wire for machine structural parts according to the embodiment of the present invention that has solved the above problems is in mass%, C: 0.3 to 0.6%, Si: 0.05 to 0.5%, Mn: 0.2 to 1.7%, P: more than 0%, 0.03% or less, S: 0.001 to 0.05%, Al: 0.01 to 0.1%, and N: 0 to 0.015 %,
  • the balance is composed of iron and inevitable impurities, the steel microstructure is composed of ferrite and cementite, the balance is composed of impurities, and the average equivalent circle diameter of the bcc-Fe crystal grains is 15 ⁇ m or less,
  • the main point is that the number of cementite per 25 ⁇ m 2 satisfies 2.0 ⁇ 10 ⁇ [C%] or less. However, [C%] indicates the C content in mass%.
  • the steel wire further comprises, in mass%, Cr: more than 0%, 0.5% or less, Cu: more than 0%, 0.25% or less, Ni: more than 0%, 0 0.5% or less, Mo: more than 0%, 0.25% or less, and B: more than 0%, containing 0.01% or less, and satisfying the following formula (X) To do. [Cr%] + [Cu%] + [Ni%] + [Mo%] ⁇ 0.75 (X) However, [Cr%], [Cu%], [Ni%], and [Mo%] respectively indicate the contents of Cr, Cu, Ni, and Mo expressed in mass%.
  • the number ratio of cementite having an aspect ratio of 3.0 or less in the metal structure is 70% or more with respect to the total cementite number.
  • the chemical composition is appropriately adjusted, the steel microstructure contains ferrite and cementite, and the balance is made of impurities, and bcc (body-centered cubic) : Body-centered cubic lattice)-by controlling the average equivalent circle diameter of Fe crystal grains (hereinafter sometimes simply referred to as "bcc-Fe average grain diameter") to be small and reducing the number of cementite per 25 ⁇ m 2 Further, it is possible to provide a steel wire that realizes an improvement in crack resistance as well as a reduction in deformation resistance.
  • the present inventors have studied from various angles in order to realize a steel wire that has both improved deformation resistance and reduced deformation resistance during cold working. As a result, it was found that the ductility is improved and the crack resistance is improved by controlling the average particle size of bcc-Fe to be small during cold working. Further, the present inventors have found that as the number density of cementite is higher, the deformation resistance is increased by the dispersion strengthening mechanism, and further, macro cracks are formed by connecting the voids starting from the cementite.
  • the metal structure of a steel wire for machine structural parts according to an embodiment of the present invention (hereinafter sometimes simply referred to as “steel wire”) contains ferrite and cementite, and the balance is impurities.
  • the steel wire according to the embodiment of the present invention is obtained by spheroidizing and annealing a rolled wire, and changes to a spheroidized structure mainly composed of ferrite and cementite by spheroidizing annealing.
  • the steel metal structure contains ferrite and cementite, and the balance is made of impurities. As a result, the deformation resistance of the steel is reduced and the cold workability is improved.
  • a preferable total area ratio of ferrite and cementite with respect to the entire metal structure is 97% or more, more preferably 98% or more, and further preferably 99% or more.
  • the impurities include compounds such as AlN.
  • the compound can be tolerated as long as it does not adversely affect cold workability.
  • the preferred area ratio of the compound with respect to the total metal structure is less than about 3%.
  • a pearlite structure before spheroidizing annealing may be included as long as the cold workability is not adversely affected.
  • Average equivalent circle diameter of bcc-Fe crystal grains 15 ⁇ m or less
  • the average equivalent circle diameter (bcc-Fe average grain diameter) of bcc-Fe crystal grains of steel wire is 15 ⁇ m or less to improve ductility and during cold working Generation of cracks can be suppressed.
  • the bcc-Fe average particle diameter is preferably 13 ⁇ m or less, more preferably 11 ⁇ m or less.
  • the bcc-Fe average particle diameter is preferably 5 ⁇ m or more in consideration of production costs.
  • the standard for the size of the bcc-Fe crystal grains to be measured is not particularly limited, but the size that can be discriminated by the measurement method described later is the minimum size. Specifically, a size of 1 ⁇ m or more is a measurement target.
  • the circle equivalent diameter of a crystal grain means the diameter of the circle of the same area as each crystal grain.
  • the metal structure to be controlled by the above-described average bcc-Fe grain size is bcc-Fe crystal grains surrounded by a large-angle grain boundary in which the orientation difference between two adjacent crystal grains is larger than 15 °. This is because the effect on cold workability is small at the small-angle grain boundary where the orientation difference is 15 ° or less.
  • the above-mentioned “azimuth difference” is also called “deviation angle” or “bevel angle”, and the EBSP method (Electron BackScatter diffraction Pattern method) may be employed for measuring the orientation difference.
  • Number of cementite per 25 ⁇ m 2 2.0 ⁇ 10 ⁇ [C%] or less
  • the number of cementite per 25 ⁇ m 2 in the metal structure is 2.0 ⁇ 10 ⁇ [C %] Or less.
  • the number of cementite per 25 ⁇ m 2 is preferably 1.8 ⁇ 10 ⁇ [C%] or less, more preferably 1.6 ⁇ 10 ⁇ [C%] or less.
  • the number of cementite per 25 ⁇ m 2 is preferably 0.6 ⁇ 10 ⁇ [C%] or more in consideration of productivity.
  • size of the cementite used as a measuring object is not specifically limited, The size of the cementite which can be discriminate
  • the steel wire according to the embodiment of the present invention has a number ratio of cementite having an aspect ratio of 3.0 or less to the total number of cementites (hereinafter simply referred to as “aspect ratio”).
  • the ratio of the cementite with a ratio of 3.0 or less ”(sometimes referred to as“ the ratio of cementite ”) is preferably 70% or more.
  • the aspect ratio of cementite decreases, voids originating from the cementite become more difficult to generate. Therefore, macro cracks can be further suppressed by increasing the number ratio of cementite having a small aspect ratio.
  • the number ratio of cementite having an aspect ratio of 3.0 or less is more preferably 75% or more, still more preferably 80% or more, still more preferably 90% or more, and most preferably 100%.
  • size of the cementite used as a measuring object is not specifically limited. However, similarly to the above-described measurement of the number of cementites per 25 ⁇ m 2 , the size of the cementite that can be discriminated by the measurement method of the cementite ratio with an aspect ratio of 3.0 or less described later is the minimum size. Specifically, cementite having an equivalent circle diameter of 0.1 ⁇ m or more is a measurement target.
  • the aspect ratio of cementite is a value obtained by dividing the length of the major axis of the equivalent ellipse by the length of the minor axis of the equivalent ellipse when the cementite shape is an equivalent ellipse.
  • the equivalent ellipse is an ellipse having the same area as the target cementite and having the same moment of inertia as the target cementite.
  • Media Cybernetics, Inc. which will be described later. You may obtain
  • the embodiment of the present invention is intended for a steel wire used as a material for a machine structural component, and may have a normal chemical composition as a steel wire for a machine structural component.
  • the appropriate range of chemical components and the reasons for limiting the range are as follows.
  • “%” for the chemical component composition means mass%.
  • C 0.3 to 0.6%
  • the C content is preferably 0.32% or more, and more preferably 0.34% or more. However, if C is excessively contained, the strength is increased and the cold workability is lowered, so that it is necessary to be 0.6% or less.
  • the C content is preferably 0.55% or less, more preferably 0.50% or less.
  • Si 0.05 to 0.5% Si is useful as a deoxidizing element and an element for improving the strength of the final product by solid solution hardening.
  • the Si content was set to 0.05% or more.
  • the Si content is preferably 0.07% or more, and more preferably 0.10% or more.
  • the Si content is set to 0.5% or less.
  • the Si content is preferably 0.45% or less, more preferably 0.40% or less.
  • P more than 0% and 0.03% or less
  • P is an element inevitably contained in steel, causes segregation of grain boundaries in steel, and causes ductility deterioration. Therefore, the P content is set to 0.03% or less.
  • the P content is preferably 0.02% or less, more preferably 0.017% or less, and still more preferably 0.01% or less. The smaller the P content, the better. However, there may be a case where approximately 0.001% remains due to restrictions on the manufacturing process.
  • S 0.001 to 0.05%
  • S is an element inevitably contained in the steel, and is present as MnS in the steel and deteriorates ductility. Therefore, S is an element harmful to cold workability. Therefore, the S content is set to 0.05% or less.
  • the S content is preferably 0.04% or less, and more preferably 0.03% or less. However, since S has the effect
  • the S content is preferably 0.002% or more, and more preferably 0.003% or more.
  • Al 0.01 to 0.1%
  • Al is useful as a deoxidizing element and is useful for fixing solute N present in steel as AlN.
  • the Al content is determined to be 0.01% or more.
  • the Al content is preferably 0.013% or more, and more preferably 0.015% or more.
  • the Al content is determined to be 0.1% or less. Al content becomes like this. Preferably it is 0.090% or less, More preferably, it is 0.080% or less.
  • N 0 to 0.015%
  • N is an element inevitably contained in the steel.
  • the N content is set to 0.015% or less.
  • the N content is preferably 0.013% or less, and more preferably 0.010% or less.
  • the N content is preferably as low as possible, and is most preferably 0%, but it may remain about 0.001% due to restrictions on the manufacturing process.
  • the basic components of the steel wire according to the embodiment of the present invention are as described above, and the balance is substantially iron.
  • substantially iron means that the presence of trace components such as Sb and Zn, for example, other than iron, which does not inhibit the characteristics of the present invention, and that other than P, S, N, etc. It means that inevitable impurities such as O and H may be included.
  • the following elements may be selectively contained as necessary. Depending on the type of the selected arbitrary element (selected component), the characteristics of the steel wire are further improved. As described above, P, S, and N are elements inevitably contained (unavoidable impurities), but their composition ranges are separately defined as described above. For this reason, in the present specification, “inevitable impurities” included as the balance mean elements inevitably included except for elements whose composition range is separately defined.
  • Cr more than 0%, 0.5% or less
  • Cu more than 0%, 0.25% or less
  • Ni more than 0%, 0.25% or less
  • Mo more than 0%, 0.25% or less
  • B One or more selected from the group consisting of more than 0% and less than 0.01% Cr, Cu, Ni, Mo and B all increase the strength of the final product by improving the hardenability of the steel. It is an effective element. If necessary, these elements may be contained alone or in combination of two or more. Such effects increase as the content of these elements increases.
  • a preferable content for effectively exhibiting the above-described effect is such that the Cr content is 0.015% or more, more preferably 0.020% or more.
  • the preferable contents of Cu, Ni and Mo are all 0.02% or more, more preferably 0.05% or more.
  • the preferable content of B is 0.0003% or more, more preferably 0.0005% or more.
  • the Cr content is preferably 0.5% or less, and the Cu, Ni and Mo contents are preferably 0.25% or less.
  • a more preferable content of Cr is 0.45% or less, and further preferably 0.40% or less.
  • the more preferable contents of Cu, Ni and Mo are all 0.22% or less, more preferably 0.20% or less.
  • the B content is preferably 0.01% or less.
  • a more preferable content of B is 0.007% or less, more preferably 0.005% or less.
  • the steel wire according to the embodiment of the present invention may contain Ti in a range of more than 0% and 0.1% or less, if necessary. Since Ti forms a compound with N, solid solution N can be reduced by containing Ti. Therefore, the steel wire can be made softer.
  • the content of Ti is preferably 0.01% or more, more preferably 0.02% or more. On the other hand, if the Ti content is excessive, the hardness of the steel wire may increase due to the compound formed. Therefore, the preferable Ti content is 0.1% or less, more preferably 0.08% or less, and still more preferably 0.05% or less.
  • the steel wire according to the embodiment of the present invention is obtained by spheroidizing and annealing a rolled wire. Therefore, in order to appropriately control the metal structure after spheroidizing annealing as described above, it is preferable to appropriately control the spheroidizing annealing conditions described later. However, in order to ensure the above-described structure form by spheroidizing annealing, it is preferable to further appropriately control the production conditions (that is, rolling conditions) of the rolled wire rod. By controlling the rolling conditions, the microstructure of the rolled wire can be in a state where the bcc-Fe average particle diameter can be easily reduced and the number density of cementite can be easily reduced after spheroidizing annealing.
  • the finish rolling temperature at the time of hot rolling the steel that satisfies the above-described component composition it is preferable to adjust the finish rolling temperature at the time of hot rolling the steel that satisfies the above-described component composition, and to appropriately adjust the cooling rate and the temperature range with three subsequent cooling rates. .
  • the metal structure before spheroidizing annealing has pearlite and ferrite as the main phase, the crystal grains are refined, and the proeutectoid ferrite crystal grains are equiaxed.
  • the average lamellar interval can be set to a predetermined value or less.
  • the rolling wire manufacturing conditions for this are as follows: (a) finish rolling at 800 ° C. or more and 1000 ° C.
  • first cooling with an average cooling rate of 7 ° C./sec or more (b) first cooling with an average cooling rate of 7 ° C./sec or more, and (c) average cooling rate of 1 Second cooling at a rate of not less than 5 ° C / second and not more than 5 ° C / second, and (d) a third cooling having an average cooling rate faster than that of the second cooling and not less than 5 ° C / second in this order,
  • the end of the first cooling and the start of the second cooling are performed within a range of 700 to 750 ° C.
  • the end of the second cooling and the start of the third cooling are performed within a range of 600 to 650 ° C.
  • the third The end of cooling is preferably set to 500 ° C. or lower.
  • the finish rolling temperature is preferably 1000 ° C. or less.
  • the finish rolling temperature is more preferably 970 ° C. or less, and further preferably 940 ° C. or less.
  • the number ratio of cementite having an aspect ratio of 3.0 or less after spheroidizing annealing is further increased by performing finish rolling at 970 ° C. or less, which is a more preferable finish rolling temperature, and performing spheroidizing annealing under appropriate conditions described later. It tends to be higher.
  • the finish rolling temperature is more preferably 830 ° C. or higher, and further preferably 860 ° C. or higher.
  • the first cooling starts from 800 ° C. or more and 1000 ° C. or less, which is the finish rolling temperature, and ends in the temperature range of 700 to 750 ° C.
  • the average cooling rate in the first cooling is preferably 7 ° C./second or more.
  • the average cooling rate of the first cooling is more preferably 10 ° C./second or more, and further preferably 20 ° C./second or more.
  • the average lamellar spacing of the pearlite of the rolled wire rod is made as narrow as possible, the cementite is easily dissolved during spheroidizing annealing, and no spherical cementite nuclei are left in the grains ( That is, the number density of spherical cementite nuclei remaining in the grains is reduced).
  • the third cooling starts from a temperature range of 600 to 650 ° C. and ends at 500 ° C. or less.
  • the third cooling is faster than the second cooling and at an average cooling rate of 5 ° C./second or more.
  • the average cooling rate of the third cooling is more preferably 10 ° C./second or more, and further preferably 20 ° C./second or more.
  • the upper limit of the average cooling rate of the third cooling is not particularly limited, but is preferably 200 ° C./second or less as a practical range.
  • the cooling rate may be changed as long as the average cooling rate is 5 ° C./second or more.
  • finish temperature of 3rd cooling is not specifically limited, For example, it is 200 degreeC or more.
  • the average cooling rate of cooling is often slower than the average cooling rate of the third cooling.
  • the area reduction rate at that time may be, for example, 30% or less.
  • the area reduction rate is preferably 30% or less.
  • the lower limit of the area reduction rate is not particularly limited, but the effect is preferably obtained by setting it to 2% or more.
  • a spheroidizing annealing condition to be applied to a rolled wire manufactured under the preferable conditions as described above for example, when heating from room temperature to 740 ° C. in an atmospheric furnace as SA1 described later, at least from 500 ° C. to 740 ° C. Is heated at an average heating rate of 50 ° C / hour or more, then heated to 750 ° C at an average heating rate of 2 to 5 ° C / hour, held at 750 ° C for 10 to 60 minutes, and then at an average cooling rate of 20 ° C / hour or more. It is preferably cooled to 720 ° C., cooled to 700 ° C.
  • the spheroidizing annealing condition used in the embodiment of the present invention is not limited to this.
  • the average heating rate from at least 500 ° C. to 740 ° C. is set to 50 ° C./hour or more, thereby suppressing the grain growth of the metal structure.
  • the average heating rate at this time is more preferably 60 ° C./hour or more.
  • the average heating rate is preferably 200 ° C./hour or less, more preferably 150 ° C./hour or less.
  • the holding time at this time is more preferably 20 minutes or more and 50 minutes or less.
  • the average cooling rate at this time is more preferably 30 ° C./hour or more.
  • the average cooling rate is preferably 100 ° C./hour or less.
  • the average cooling rate at this time is more preferably 4 ° C./hour or more and 6 ° C./hour or less.
  • the average cooling rate at this time is more preferably 9 ° C./hour or more and 11 ° C./hour or less.
  • normal cooling such as cooling may be performed to cool to room temperature.
  • the average cooling rate for cooling is often slower than the average cooling rate from 700 ° C to 640 ° C.
  • Embodiments of the present invention are not limited by the following examples, and can be implemented with appropriate modifications within a range that can be adapted to the gist described above. It is included in the technical scope of the embodiment.
  • this annealing condition is abbreviated as “SA1”.
  • (B) Repeat SA1 five times. Note that the second and subsequent heating of SA2 (that is, the heating during the annealing of the second to fifth SA1 conditions in the annealing of SA2 that repeats SA1 five times) started at 640 ° C. Hereinafter, this annealing condition is abbreviated as “SA2”.
  • (C) When heating from room temperature to 710 ° C., heating from room temperature to 500 ° C.
  • this annealing condition is abbreviated as “SA3”.
  • the annealing conditions SA1 and SA2 are preferable annealing conditions of the embodiment of the present invention, and the annealing condition SA3 is an example in which the heating temperature (holding temperature) is low and not properly controlled.
  • the cross section (that is, in the radial direction of the wire)
  • the resin was embedded so that the cut cross-section could be observed, and the cut surface was mirror-polished with emery paper and diamond buff.
  • the position of D / 4 was measured in the radial direction from the outer peripheral surface of the steel wire.
  • the bcc-Fe crystal grain diameter was measured using an EBSP analyzer and an FE-SEM. As an analysis tool, OIM software of TSL Solutions Inc. was used. When the crystal grain difference is defined as a boundary where the crystal orientation difference (also referred to as “bevel”) exceeds 15 °, that is, a large-angle grain boundary, and the area of the bcc-Fe crystal grain is converted into a circle The average value of the diameters, that is, the average equivalent circle diameter was calculated. The measurement area at this time was 200 ⁇ m ⁇ 400 ⁇ m, and the measurement step was 1.0 ⁇ m. Measurement points having a confidence index (Confidence Index) indicating the reliability of the measurement direction of 0.1 or less were deleted (ie, excluded) from the analysis target.
  • Confidence Index Confidence Index
  • cementite ratio with an aspect ratio of 3.0 or less In measuring the cementite ratio with an aspect ratio of 3.0 or less, the measurement was performed based on the photograph taken in (3) above. Specifically, the aspect ratios of all cementites in the five photographs were measured by image analysis, and the average value of the ratios of the number of cementites having an aspect ratio of 3.0 or less to the total number of cementites in the five visual fields was determined. The total cementite and the cementite with an aspect ratio of 3.0 or less were targeted for those in which the entire cementite was shown in the photograph, and those that were not partially visible in the photograph. From the average value, a cementite ratio with an aspect ratio of 3.0 or less was calculated. The minimum equivalent circle diameter of the cementite to be measured was 0.1 ⁇ m.
  • Target deformation resistance 400 ⁇ Ceq + 430 (1)
  • Ceq [C%] + 0.2 ⁇ [Si%] + 0.2 ⁇ [Mn%]
  • [C%] and [Mn%] are C, Si and Mn, respectively. Content (mass%) is shown.
  • the crack occurrence rate was measured by performing a cold forging test with a processing rate of 60% under the same conditions as in (5) above, and observing the surface of each sample with a stereomicroscope at a magnification of 20 times. It was performed 5 times and the presence or absence of surface cracks was measured. Then, the “number of samples having surface cracks” was divided by 5 to obtain the average. The target crack generation rate for all steel types was 20% or less.
  • test no. 1, 2, 4 to 8, 10, 11, 13 to 16, 18 to 20, 22 to 25, 37, 38, 40, and 41 are examples that satisfy all of the requirements defined in the embodiments of the present invention. It can be seen that both a reduction in deformation resistance and an improvement in crack resistance are achieved. Although not shown in Table 3, test no. FE-SEM observation of the metal structures 1 to 36 confirms that all contain ferrite and cementite in a total ratio of 99 area% or more.
  • test No. which performed both SA1 and SA2 annealing conditions. 1 and 2 (steel type A), test no. 7 and 8 (steel type E), test no. 10 and 11 (steel type F), test no. 15 and 16 (steel type I), test no. 19 and 20 (steel grade K), test no. 24 and 25 (steel grade N), and test no. Focusing on 37 and 38 (steel type V), in any case, when annealing SA2 was repeated 5 times compared to SA1, at least one of deformation resistance and crack generation rate was further reduced.
  • test no. 11 (steel type F) is an example in which the number ratio of cementite having an aspect ratio of 3.0 or less satisfies the preferable requirements of the embodiment of the present invention. Therefore, the test No. in which the number ratio of cementite is not properly controlled. Compared to 10 (steel type F), the crack generation rate was further reduced.
  • Test No. 3 is an example in which spheroidizing annealing was performed using SA3 whose conditions were not appropriate using steel type A in Tables 1 and 2. Therefore, the number of cementite per 25 ⁇ m 2 is larger than the specified value, and the deformation resistance and crack occurrence rate do not reach the target values.
  • Test No. No. 9 is an example in which spheroidizing annealing was performed using SA3 whose conditions are not appropriate using steel type E in Tables 1 and 2. Therefore, the number of cementite per 25 ⁇ m 2 is larger than the specified value, and the deformation resistance does not reach the target value.
  • Test No. No. 12 is an example in which spheroidizing annealing was performed with SA3 whose conditions were not appropriate using the steel type F in Tables 1 and 2. Therefore, the number of cementite per 25 ⁇ m 2 is larger than the specified value, and the deformation resistance and crack occurrence rate do not reach the target values.
  • Test No. No. 17 is an example in which spheroidizing annealing was performed using SA3 whose conditions were not appropriate using steel type I in Tables 1 and 2. Therefore, the number of cementite per 25 ⁇ m 2 is larger than the specified value, and the deformation resistance and crack occurrence rate do not reach the target values.
  • Test No. No. 21 is an example in which spheroidizing annealing was performed using SA3 whose conditions are not appropriate using the steel type K shown in Tables 1 and 2. Therefore, the number of cementite per 25 ⁇ m 2 is larger than the specified value, and the deformation resistance does not reach the target value.
  • Test No. No. 26 is an example in which spheroidizing annealing was performed with SA3 whose conditions were not appropriate using the steel type N in Tables 1 and 2. Therefore, the number of cementite per 25 ⁇ m 2 is larger than the specified value, and the deformation resistance and crack occurrence rate do not reach the target values.
  • Test No. 27 is an example using the steel type O of Tables 1 and 2 with an excessive Mn content. For this reason, appropriate hot rolling and spheroidizing annealing of SA1 were performed, but the deformation resistance did not reach the target value.
  • Test No. No. 28 is an example using the steel type O in Tables 1 and 2 with an excessive Mn content. Therefore, although appropriate hot rolling and spheroidizing annealing of SA2 were performed, the deformation resistance did not reach the target value.
  • Test No. 29 is an example using the steel type P in Tables 1 and 2 with an excessive Cr content. For this reason, appropriate hot rolling and spheroidizing annealing of SA1 were performed, but the deformation resistance did not reach the target value.
  • Test No. 30 is an example using the steel type P of Tables 1 and 2 with an excessive Cr content. Therefore, although appropriate hot rolling and spheroidizing annealing of SA2 were performed, the deformation resistance did not reach the target value.
  • Test No. 31 is an example using the steel types Q of Tables 1 and 2 having a high finish rolling temperature at the time of rolling wire production. For this reason, appropriate spheroidizing annealing of SA1 was performed, but the average bcc-Fe particle diameter was coarser than the specified value, and the crack generation rate did not reach the target value.
  • Test No. 32 is an example using the steel types R of Tables 1 and 2 in which the cooling rate of the first cooling during the production of the rolled wire rod is slow and the cooling rate of the third cooling is slow. Therefore, although appropriate spheroidizing annealing of SA1 was performed, the average particle diameter of bcc-Fe was coarser than the specified value, and the number of cementites per 25 ⁇ m 2 was larger than the specified value. The target value has not been reached.
  • Test No. 33 is an example using the steel types S of Tables 1 and 2 in which the cooling rate of the second cooling during the production of the rolled wire rod is fast and the cooling rate of the third cooling is the same as the cooling rate of the second cooling. Therefore, although appropriate SA1 spheroidizing annealing was performed, the number of cementite per 25 ⁇ m 2 was larger than the specified value, and the deformation resistance did not reach the target value.
  • Test No. 34 is an example using the steel types T of Tables 1 and 2 having a high finish rolling temperature during the production of the rolled wire rod. Therefore, appropriate spheroidizing annealing of SA1 was performed, but the bcc-Fe average particle diameter was coarser than the specified value, and the crack generation rate did not reach the target value.
  • Test No. No. 35 uses the steel type U of Tables 1 and 2 that has a high finish rolling temperature at the time of rolling wire production, a high cooling rate of the second cooling, and does not perform the third cooling. This is an example. Therefore, the average particle diameter of bcc-Fe is coarser than the specified value, fine cementite is uniformly dispersed, the number of cementites per 25 ⁇ m 2 is larger than the specified value, and the deformation resistance and crack occurrence rate are the target values. Not reached.
  • Test No. No. 36 uses the steel type U of Tables 1 and 2 that has a high finish rolling temperature during the production of the rolled wire, the second cooling rate is high, and the third cooling is not performed, and the spheroidizing annealing is performed with SA5 where the conditions are not appropriate.
  • SA5 the spheroidizing annealing
  • Test No. 39 is an example in which spheroidizing annealing was performed using SA3 whose conditions are not appropriate using steel type V in Table 1.
  • the number of cementites around 25 ⁇ m 2 is larger than the predetermined value, and the deformation resistance does not reach the target value.
  • Steel wires for machine structural parts are various machine structural parts such as automobile parts and construction machine parts manufactured by cold working such as cold forging, cold forging and cold rolling. It is suitably used for the material.
  • these mechanical structural parts include bolts, screws, nuts, sockets, ball joints, inner tubes, torsion bars, clutch cases, cages, housings, hubs, covers, cases, washers, tappets, saddles, bulgs, Inner case, clutch, sleeve, outer race, sprocket, core, stator, anvil, spider, rocker arm, body, flange, drum, fitting, connector, pulley, metal fitting, yoke, base, valve lifter, spark plug, pinion gear, steering Examples include mechanical parts such as shafts and common rails, and electrical parts.
  • a steel wire according to an embodiment of the present invention is industrially useful as a steel wire for a high-strength mechanical structural component that is preferably used as a material for the mechanical structural component.
  • Excellent cold workability can be exhibited by low deformation resistance at room temperature and by suppressing cracking of the material.
  • Aspect 1 % By mass C: 0.3 to 0.6%, Si: 0.05 to 0.5%, Mn: 0.2 to 1.7%, P: more than 0%, 0.03% or less, S: 0.001 to 0.05%, Al: 0.01 to 0.1% and N: 0 to 0.015%, respectively, the balance consisting of iron and inevitable impurities,
  • the metallographic structure of the steel contains ferrite and cementite, the balance is made of impurities, the average equivalent circle diameter of the bcc-Fe crystal grains is 15 ⁇ m or less, and the number of cementite per 25 ⁇ m 2 is 2.0 ⁇ 10 ⁇ [C %] Steel wires for machine structural parts that are less than the number.
  • [C%] indicates the C content in mass%.
  • -Aspect 2 Furthermore, in mass%, Cr: more than 0%, 0.5% or less, Cu: more than 0%, 0.25% or less, Ni: more than 0%, 0.25% or less, It is described in the aspect 1 which contains 1 or more types selected from the group which consists of Mo: more than 0%, 0.25% or less and B: more than 0%, 0.01% or less, and satisfy
  • the present application includes a Japanese patent application with a filing date of September 3, 2015, Japanese Patent Application No. 2015-173962, and a Japanese patent application with a filing date of June 23, 2016, Japanese Patent Application No. 2016- Japanese Patent Application No. 2015-173962 and Japanese Patent Application No. 2016-124960 are incorporated herein by reference with a priority claim based on No. 124960.

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

Abstract

La présente invention concerne un fil d'acier pour pièces d'une structure mécanique dont la résistance à la déformation est réduite au cours d'un travail à froid, qui présente une meilleure résistance à la fissuration et peut présenter une excellente aptitude au travail à froid. Le fil d'acier pour pièces d'une structure mécanique d'après la présente invention contient, en % en masse, de 0,3 à 0,6 % de C, de 0,05 à 0,5 % de Si, de 0,2 à 1,7 % de Mn, de plus de 0 % à au maximum 0,03 % de P, de 0,001 à 0,05 % de S, de 0,01 à 0,1 % d'Al et de 0 à 0,015 % de N, le reste étant constitué de fer et des inévitables impuretés. Dans le fil d'acier, la structure métallique de l'acier contient de la ferrite et de la cémentite, le reste étant constitué d'impuretés. Dans le fil d'acier, le diamètre de cercle équivalent moyen des grains de cristal bcc-Fe est inférieur ou égal à 15 µm et le nombre de grains de cémentite par 25 μm2 est inférieur ou égal à 2,0 × 10 × [C%].
PCT/JP2016/073770 2015-09-03 2016-08-12 Fil d'acier pour pièces d'une structure mécanique WO2017038436A1 (fr)

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
JP2015173962 2015-09-03
JP2015-173962 2015-09-03
JP2016124960A JP2017048459A (ja) 2015-09-03 2016-06-23 機械構造部品用鋼線
JP2016-124960 2016-06-23

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2021509151A (ja) * 2017-12-26 2021-03-18 ポスコＰｏｓｃｏ 冷間圧造用線材、これを用いた加工品、およびこれらの製造方法
CN112522632A (zh) * 2020-12-09 2021-03-19 苏州莱特复合材料有限公司 一种粉末冶金耐磨定子及其生产工艺

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001011575A (ja) * 1999-06-30 2001-01-16 Nippon Steel Corp 冷間加工性に優れた機械構造用棒鋼・鋼線及びその製造方法
JP2009275250A (ja) * 2008-05-13 2009-11-26 Nippon Steel Corp 冷間加工性に優れた鋼線材およびその製造方法
WO2011108459A1 (fr) * 2010-03-02 2011-09-09 新日本製鐵株式会社 Fil d'acier avec d'excellentes caractéristiques de forgeage à froid, et procédé de fabrication associé
JP2012140674A (ja) * 2010-12-28 2012-07-26 Kobe Steel Ltd 冷間鍛造性に優れた鋼材、及びその製造方法
WO2015194411A1 (fr) * 2014-06-16 2015-12-23 株式会社神戸製鋼所 Acier pour une structure mécanique pour un travail à froid, et son procédé de fabrication

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001011575A (ja) * 1999-06-30 2001-01-16 Nippon Steel Corp 冷間加工性に優れた機械構造用棒鋼・鋼線及びその製造方法
JP2009275250A (ja) * 2008-05-13 2009-11-26 Nippon Steel Corp 冷間加工性に優れた鋼線材およびその製造方法
WO2011108459A1 (fr) * 2010-03-02 2011-09-09 新日本製鐵株式会社 Fil d'acier avec d'excellentes caractéristiques de forgeage à froid, et procédé de fabrication associé
JP2012140674A (ja) * 2010-12-28 2012-07-26 Kobe Steel Ltd 冷間鍛造性に優れた鋼材、及びその製造方法
WO2015194411A1 (fr) * 2014-06-16 2015-12-23 株式会社神戸製鋼所 Acier pour une structure mécanique pour un travail à froid, et son procédé de fabrication

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2021509151A (ja) * 2017-12-26 2021-03-18 ポスコＰｏｓｃｏ 冷間圧造用線材、これを用いた加工品、およびこれらの製造方法
US11441202B2 (en) 2017-12-26 2022-09-13 Posco Wire rod for cold heading, processed product using same, and manufacturing method therefor
JP7300451B2 (ja) 2017-12-26 2023-06-29 ポスコ カンパニー リミテッド 冷間圧造用線材、これを用いた加工品、およびこれらの製造方法
CN112522632A (zh) * 2020-12-09 2021-03-19 苏州莱特复合材料有限公司 一种粉末冶金耐磨定子及其生产工艺

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