EP3770291B1 - Stahl - Google Patents

Stahl Download PDF

Info

Publication number
EP3770291B1
EP3770291B1 EP19772012.1A EP19772012A EP3770291B1 EP 3770291 B1 EP3770291 B1 EP 3770291B1 EP 19772012 A EP19772012 A EP 19772012A EP 3770291 B1 EP3770291 B1 EP 3770291B1
Authority
EP
European Patent Office
Prior art keywords
steel
content
ferrite
fraction
bainite
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
EP19772012.1A
Other languages
English (en)
French (fr)
Other versions
EP3770291A4 (de
EP3770291A1 (de
Inventor
Tatsuya Koyama
Yutaka Neishi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Publication of EP3770291A1 publication Critical patent/EP3770291A1/de
Publication of EP3770291A4 publication Critical patent/EP3770291A4/de
Application granted granted Critical
Publication of EP3770291B1 publication Critical patent/EP3770291B1/de
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/32—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for gear wheels, worm wheels, or the like
    • 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
    • C21D1/06—Surface hardening
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/26—Methods of annealing
    • 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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/007—Heat treatment of ferrous alloys containing Co
    • 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
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/20—Ferrous alloys, e.g. steel alloys containing chromium with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/22—Ferrous alloys, e.g. steel alloys containing chromium with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/26—Ferrous alloys, e.g. steel alloys containing chromium with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/30—Ferrous alloys, e.g. steel alloys containing chromium with cobalt
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/32—Ferrous alloys, e.g. steel alloys containing chromium with boron
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/02—Pretreatment of the material to be coated
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/20—Carburising
    • C23C8/22—Carburising of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/28—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases more than one element being applied in one step
    • C23C8/30—Carbo-nitriding
    • C23C8/32—Carbo-nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/80—After-treatment
    • 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
    • C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
    • C21D1/58—Oils
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • 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
    • C21D2261/00—Machining or cutting being involved
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys

Definitions

  • the present invention relates to steel.
  • gears for use in automobiles, construction machinery, industrial machinery, and the like are generally used after receiving carburizing hardening after machining.
  • quietness during operation has been more strongly demanded than before, and thus an increase in the dimensional accuracy of gears, especially the dimensional accuracy of teeth, has been demanded.
  • the dimensional accuracy of gear teeth is attributable to deformation associated with heat treatment during carburizing hardening (hereinafter referred to as thermal strain). Since this thermal strain varies and is not uniform for each gear tooth, a symmetrical shape is lost in the same gear, and thus vibrations are created during use, thus losing quietness. Accordingly, demands exist for stabilizing thermal strain on gear teeth so as to provide a symmetrical shape.
  • Patent Document 1 discloses a technology for providing steel having excellent cold forgeability and temper softening resistance. However, Patent Document 1 does not provide a technology for stabilizing thermal strain on gear teeth during carburizing hardening, which is an object of the present invention.
  • Patent Document 2 discloses a technology for providing a hot-rolled steel bar or wire rod composed of a ferrite-pearlite structure, ferrite-pearlite-bainite structure, or ferrite-bainite structure, wherein the standard deviation of ferrite fractions at the time when randomly selected 15 viewing fields of a transverse cross-section are observed and measured with the area per one viewing field being 62500 ⁇ m 2 is 0.10 or less; and when a region from the surface to one-fifth of the radius and a region from the center to one-fifth of the radius in the transverse cross-section are observed, in each of the regions, the amount of Al precipitating as AlN is 0.005% or less, and the density in terms of the number of AlN having a diameter of 100 nm or larger is 5/100 ⁇ m 2 or less.
  • Patent Document 2 uses a pearlite structure to reduce the standard deviation of ferrite fractions. That is to say, according to the technology of Patent Document 2, it is not possible to sufficiently reduce the standard deviation of ferrite fractions while controlling the structures so as not to substantially include pearlite.
  • An object of the present invention is to provide steel that stabilizes thermal strain on gear teeth during carburizing hardening.
  • thermal strain on the teeth of a gear manufactured by carburizing hardening can be stabilized.
  • Figure 1 is a schematic cross-sectional view of steel for explaining the positions for measuring the average ferrite fraction and the standard deviation of the ferrite fraction.
  • the present inventors have conducted diligent research on a method for stabilizing thermal strain on the teeth of a gear after carburizing hardening. As a result, it was found that the thermal strain is stabilized by increasing the uniformity of structures in a region of steel that becomes teeth after machining. Accordingly, concerning a method for making uniform the structures of a region corresponding to the gear teeth in steel, the inventors further investigated the effect of changing the chemical components of steel and the manufacturing method. As a result, it was found that by configuring the steel components to be in predetermined ranges and then controlling the casting method and the post-rolling cooling rate, the structures of a region corresponding to the gear teeth in steel can be uniform.
  • the cross-sectional area of casting, the casting rate, and the average cooling rate of the surface from the beginning of casting to the correction point are controlled in a combined manner. This makes it possible to homogenize the cast structures of a region in a bloom that eventually becomes gear teeth. Moreover, concerning the control of the post-rolling cooling rate, the cooling rate of the steel surface is controlled. This makes it possible to homogenize the structures of a region in steel that corresponds to the gear teeth.
  • the C content affects the hardness of the non-carburized portion of a gear. In order to ensure a required hardness, the C content is 0.17% or more. On the other hand, when the C content is excessive, the hardness of the non-carburized portion after carburization is high, resulting in poor impact strength, and thus the C content is 0.21 % or less.
  • the preferable lower limit of the C content is 0.175%, 0.18%, 0.185%, or 0.19%.
  • the preferable upper limit of the C content is 0.205%, 0.200%, 0.195%, or 0.19%.
  • Si is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel.
  • the Si content needs to be within the range of 0.40 to 0.60%.
  • the preferable lower limit of the Si content is 0.42%, 0.45%, 0.48%, or 0.50%.
  • the preferable upper limit of the Si content is 0.58%, 0.55%, 0.53%, or 0.51%.
  • Mn is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel.
  • the Mn content needs to be 0.25% or more.
  • the Mn content is 0.50% or less.
  • the preferable lower limit of the Mn content is 0.27%, 0.30%, 0.32%, or 0.35%.
  • the preferable upper limit of the Mn content is 0.48%, 0.45%, 0.42%, or 0.40%.
  • Cr is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel.
  • the Cr content needs to be within the range of 1.35 to 1.55%.
  • the preferable lower limit of the Cr content is 1.37%, 1.40%, 1.42%, or 1.45%.
  • the preferable upper limit of the Cr content is 1.53%, 1.50%, 1.49%, or 1.47%.
  • Mo is an element, the amount of which needs to be strictly limited in steel in order to homogenize the structures of a region corresponding to the teeth of machined gear steel.
  • Mo When Mo is contained in steel together with Nb, which will be described below, Mo suppresses pearlite transformation by increasing the hardenability of steel, and also suppresses coarse austenite crystal grains during the heating of steel. This makes it possible to suitably control hardenability, and obtain the desired bainite structure by suppressing martensite transformation.
  • the Mo content is excessive, the amount of ferrite in steel is insufficient, and the amounts of bainite and the like are increased, resulting in poor workability. In order to obtain the above-described effect, the Mo content needs to be within the range of 0.20 to 0.40%.
  • the preferable lower limit of the Mo content is 0.22%, 0.25%, 0.28%, or 0.30%.
  • the preferable upper limit of the Mo content is 0.38%, 0.35%, 0.32%, or 0.30%.
  • S forms MnS in steel, thereby increasing the machinability of steel.
  • a S content comparable to that of commonly used steel for machine structural use is needed.
  • the S content needs to be within the range of 0.010 to 0.05%.
  • the preferable lower limit of the S content is 0.012%, 0.014%, 0.020%, or 0.022%.
  • the preferable upper limit of the S content is 0.035%, 0.030%, 0.028%, or 0.025%.
  • N has a crystal grain refining effect by forming compounds with Al, Ti, V, Cr, and the like, and thus needs to be contained in an amount of 0.005% or more.
  • N exceeds 0.020%, compounds are coarse, and the crystal grain refining effect cannot be obtained.
  • the N content needs to be within the range of 0.005 to 0.020%.
  • the preferable lower limit of the N content is 0.0055%, 0.0060%, 0.007%, or 0.010%.
  • the preferable upper limit of the N content is 0.018%, 0.015%, 0.012%, or 0.010%.
  • Al is an element effective for the deoxidation of steel, and is an element that binds to N to form nitride and refine crystal grains.
  • the preferable lower limit of the Al content is 0.004%, 0.007%, 0.010%, or 0.020%.
  • the preferable upper limit of the Al content is 0.080%, 0.050%, 0.040%, or 0.030%.
  • Nb is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect. Also, Nb when contained in steel together with Mo exerts the above-described synergistic effect (the effect of suppressing pearlite transformation and martensite transformation). When the Nb content is less than 0.001%, this effect is insufficient. When the Nb content exceeds 0.030%, carbonitride is coarse, and this effect cannot be sufficiently obtained. For the above reason, the Nb content needs to be 0.001 to 0.030%. The preferable lower limit of the Nb content is 0.005%, 0.010%, 0.012%, or 0.015%. The preferable upper limit of the Nb content is 0.028%, 0.025%, 0.022%, or 0.020%.
  • the O content forms oxide in steel and acts as an inclusion to reduce fatigue strength, and thus the O content is limited to 0.005% or less.
  • the preferable upper limit of the O content is 0.003%, 0.002%, 0.0015%, or 0.001%. Since a smaller O content is more preferable, the lower limit of the O content is 0%. However, removing O more than necessary results in increased manufacturing costs. Accordingly, the lower limit of the O content may be 0.0001 %, 0.0002%, 0.0005%, or 0.0008%.
  • the P content is limited to 0.03% or less.
  • the preferable upper limit of the P content is 0.025%, 0.023%, 0.020%, or 0.015%. Since a smaller P content is more preferable, the lower limit of the P content is 0%. However, removing P more than necessary results in increased manufacturing costs. Accordingly, the substantial lower limit of the P content is usually about 0.004% or more.
  • the lower limit of the P content may be 0.005%, 0.007%, 0.010%, or 0.012%.
  • Steel according to the present invention may further contain one or two or more selected from the group consisting of Ni, Cu, Co, W, V, Ti, and B in place of a part of Fe in order to increase hardenability or the crystal grain refining effect.
  • the lower limit when these elements are not contained is 0%.
  • Ni is an element effective for imparting necessary hardenability to steel.
  • the Ni content is preferably 0.01% or more.
  • the Ni content exceeds 3.0%, the amount of residual austenite after hardening is large, resulting in poor hardness.
  • the Ni content is 3.0% or less and more preferably 0.01 to 3.0%.
  • the upper limit of the Ni content is more preferably 2.0% and even more preferably 1.8%.
  • a more preferable lower limit of the Ni content is 0.1% and more preferably 0.3%.
  • the Cu is an element effective for increasing the hardenability of steel.
  • the Cu content is preferably 0.01% or more.
  • the Cu content exceeds 1.0%, hot ductility is impaired. Accordingly, the Cu content is 1.0% or less and more preferably 0.01 to 1.0%.
  • a more preferable lower limit of the Cu content is 0.05% and even more preferably 0.1%.
  • Co is an element effective for increasing the hardenability of steel.
  • the Co content is preferably 0.01% or more.
  • the Co content exceeds 3.0%, the effect is saturated. Accordingly, the Co content is 3.0% or less and more preferably 0.01 to 3.0%.
  • a more preferable lower limit of the Co content is 0.05% and even more preferably 0.1%.
  • W is an element effective for increasing the hardenability of steel.
  • the W content is preferably 0.01% or more.
  • the W content exceeds 1.0%, the effect is saturated. Accordingly, the W content is 1.0% or less and more preferably 0.01 to 1.0%.
  • a more preferable lower limit of the W content is 0.05% and even more preferably 0.1 %.
  • V is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect.
  • the V content is preferably 0.01 % or more.
  • the V content exceeds 0.3%, compounds are coarse, and the crystal grain refining effect cannot be obtained. Accordingly, the V content is 0.3% or less and more preferably 0.01 to 0.3%.
  • a more preferable lower limit of the V content is 0.1% and even more preferably 0.15%.
  • Ti is an element that produces fine compounds with C and N in steel and provides a crystal grain refining effect.
  • the Ti content is preferably 0.001% or more.
  • the Ti content exceeds 0.3%, the effect is saturated.
  • the Ti content is 0.3% or less and more preferably 0.001 to 0.3%.
  • a more preferable upper limit of the Ti content is 0.25% and even more preferably 0.2%.
  • B functions to suppress the grain boundary segregation of P.
  • B also has the effect of increasing grain boundary strength and intragranular strength and the effect of increasing hardenability, and these effects increase the fatigue strength of steel.
  • the B content is preferably 0.0001% or more.
  • the B content exceeds 0.005%, the effect is saturated.
  • the B content is 0.005% or less and preferably 0.0001 to 0.005%.
  • a more preferable upper limit of the B content is 0.0045% and even more preferably 0.004%.
  • the chemical composition of steel according to the present invention may further contain one or two or more selected from the group consisting of Pb, Bi, Ca, Mg, Zr, Te, and rare earth elements (REMs) in place of a part of Fe.
  • Pb Pb
  • Bi Bi
  • Ca Ca
  • Mg Mg
  • Zr Te
  • REMs rare earth elements
  • Pb is an element that increases machinability by being molten and embrittled during cutting.
  • the Pb content is preferably 0.01% or more.
  • a more preferable lower limit of the Pb content is 0.05% and even more preferably 0.1 %.
  • the preferable upper limit of Pb is 0.4% and even more preferably 0.3%.
  • Bi is an element that increases machinability due to finely dispersed sulfide.
  • the Bi content is preferably 0.0001 % or more.
  • the Bi content is 0.5% and more preferably 0.0001 to 0.5%.
  • a more preferable lower limit is 0.0001 % and even more preferably 0.001%.
  • the preferable upper limit of Bi is 0.4% and even more preferably 0.3%.
  • the Ca is an element effective for the deoxidation of steel and reduces the Al 2 O 3 content in oxide.
  • the Ca content is preferably 0.0001 % or more.
  • the Ca content exceeds 0.01 %, a large amount of Cacontaining coarse oxide appears and causes a shortened rolling fatigue life.
  • the Ca content needs to be within the range of 0.0001 to 0.01%.
  • the preferable lower limit of the Ca content is 0.0003% and more preferably 0.0005%.
  • the preferable upper limit of the Ca content is 0.008% and more preferably 0.006%.
  • Mg is a deoxidizing element and produces oxide in steel. Moreover, Mgbased oxide formed by Mg likely becomes a nucleus for crystallization and/or precipitation of MnS. Also, the sulfide of Mg makes MnS spherical by becoming a complex sulfide of Mn and Mg. Thus, Mg is an element effective for controlling the dispersion of MnS and improving machinability. In order to obtain this effect, the Mg content is preferably 0.0001% or more. However, when the Mg content exceeds 0.01%, a large amount of MgS is produced, and the machinability of steel decreases.
  • the Mg content needs to be 0.01% or less.
  • the preferable upper limit of the Mg content is 0.008% and more preferably 0.006%.
  • the preferable lower limit of the Mg content is 0.0005% and more preferably 0.001%.
  • Zr is a deoxidizing element and forms oxide. Moreover, Zr-based oxide formed by Zr likely becomes a nucleus for crystallization and/or precipitation of MnS. Thus, Zr is an element effective for controlling the dispersion of MnS and improving machinability.
  • the Zr content is preferably 0.0001% or more. However, when the amount of Zr exceeds 0.05%, the effect is saturated. Thus, in order to obtain the above-described effect by containing Zr, the Zr content is 0.05% or less and more preferably 0.0001 to 0.05%.
  • the preferable upper limit of the Zr content is 0.04% and more preferably 0.03%.
  • the preferable lower limit of the Zr content is 0.0005% and more preferably 0.001%.
  • Te promotes the spheroidization of MnS and thus improves the machinability of steel.
  • the Te content is preferably 0.0001% or more.
  • the Te content is 0.1% or less and more preferably 0.0001 to 0.1%.
  • the preferable upper limit of the Te content is 0.08% and more preferably 0.06%.
  • the preferable lower limit of the Te content is 0.0005% and more preferably 0.001%.
  • Rare earth element 0 to 0.005%
  • Rare earth elements are elements that promote the production of MnS by producing sulfide in steel and this sulfide becoming a precipitation nucleus for MnS, and improve the machinability of steel.
  • the total amount of rare earth elements is preferably 0.0001 % or more.
  • the total amount of rare earth elements exceeds 0.005%, sulfide is coarse, reducing the fatigue strength of steel. Accordingly, the total amount of rare earth elements is 0.005% or less and more preferably 0.0001 to 0.005%.
  • the preferable upper limit of the total amount of rare earth elements is 0.004% and more preferably 0.003%.
  • the preferable lower limit of the total amount of rare earth elements is 0.0005% and more preferably 0.001%.
  • the rare earth element as used herein is a collective term referring to 17 elements including 15 elements from lanthanum (La) with atomic number 57 to lutetium (Lu) with atomic number 71 in addition to yttrium (Y) and scandium (Sc) in the periodic table.
  • the amount of rare earth elements means the total amount of one or two or more of these elements.
  • Steel according to the present invention contains the above-described alloying components, and the balance includes Fe and impurities. Elements other than the above-described alloying components are allowable in steel as impurities from raw materials and manufacturing equipment as long as the amounts thereof do not affect the properties of steel.
  • the region of steel corresponding to the gear teeth is a region including a part from the tooth tip to the tooth root of a gear after forging or cutting, and is a region satisfying 0.7R ⁇ r ⁇ 0.9R in rolled steel, wherein r is the distance from the center of the cross-section of steel that is perpendicular to the length direction, and R is a circle equivalent radius in the cross-section of steel that is perpendicular to the length direction of steel.
  • the uniform structures suitable for improvement of thermal strain are structures including ferrite and bainite, and that the structure fractions are in suitable ranges.
  • the thermal strain was stabilized when, in the 0.7R ⁇ r ⁇ 0.9R region, the average value of the ferrite fraction (average fraction) in terms of area ratio is in the range of 40 to 70%, the total of the average fractions of structures other than ferrite and bainite is 0% or more and 3% or less on average, the balance includes bainite, and the standard deviation of the average ferrite fraction in the 0.7R ⁇ r ⁇ 0.9R range is 4% or less, as determined by the measurement method described below.
  • a fraction with respect to a metal structure means the average value of a structure fraction (unit: area%) in the cross-section of steel determined by the means described below.
  • the "fraction” does not mean an average value in the entirety of a cross-section but means the fraction in each measured visual field, as will be described below.
  • the preferable lower limit of the ferrite fraction is 42% and more preferably 45%.
  • the preferable upper limit of the ferrite fraction is 68% and more preferably 65%.
  • a lower standard deviation of the ferrite fraction in the 0.7R ⁇ r ⁇ 0.9R range is more preferable, and thus the lower limit is 0%.
  • the preferable upper limit of the standard deviation of the ferrite fraction in the 0.7R ⁇ r ⁇ 0.9R range is 3.5% and more preferably 3%.
  • "bainite” means, among the structures obtained by heating steel to form an austenite single phase structure and then cooling it to room temperature by continuous cooling, a structure excluding a ferrite structure, a pearlite structure, and a martensite structure, and means a collective term referring to an upper bainite structure, a lower bainite structure, or a mixed structure of an upper bainite structure and a lower bainite structure.
  • pearlite is contained in the structures of steel according to the present invention because it deteriorates carburizing hardenability.
  • steel composed of mixed structures of ferrite, pearlite, and bainite is carburizing-hardened, the austenite crystal grain structure in a region corresponding to the teeth becomes non-uniform during heating. Accordingly, deformation after carburizing hardening, i.e., thermal strain, is increased.
  • the area ratio of pearlite needs to be limited as much as possible.
  • the total of structures other than ferrite and bainite is specified to be 0% or more and 3% or less.
  • steel according to the present invention is steel having a ferrite-bainite structure.
  • the points where the circumferences having 0.7R + 0.25 mm, 0.8R, and 0.9R - 0.25 mm intersect straight lines radially dividing, from the center of the cross-section of steel, the cross-section into eight equal parts (central angle 45°) were regarded as measurement points, and rectangular regions having 0.5 mm ⁇ 1 mm 0.5 mm 2 were regarded as measurement regions such that the respective measurement points were at the centers of the rectangles. There are 24 measurement regions.
  • the ferrite fraction and the standard deviation of the ferrite fraction in the 0.7R ⁇ r ⁇ 0.9R range were determined by observation using an optical microscope with respect to a sample obtained by mirror-polishing the cross-section of steel and corroding it with nital.
  • each measurement region of the nitalcorroded sample was visually observed, and in each measurement region, the 0.5 mm 2 area in an image captured at 100 observation magnification (captured at 400 observation magnification when the boundary of structures is unclear) was binarized using image processing software Winroof 2015 so as to have ferrite and bainite as bright regions to derive the area ratios of the bright regions, and thereby the ferrite fraction and the bainite fraction of each measurement region were obtained.
  • the area obtained by excluding the area of non-metallic structures such as MnS from the test area was regarded as an evaluated area, and the respective proportions of the areas of the ferrite structure and the bainite structure relative to the evaluated area were regarded as the area ratios of the ferrite structure and the bainite structure.
  • the average value of the ferrite fraction of the 24 measurement regions was regarded as the ferrite fraction, and the average value of the bainite fraction of the 24 measurement regions was regarded as the bainite fraction.
  • the area ratio of structures other than ferrite and bainite were determined by 100 - (Ferrite fraction + Bainite fraction).
  • the standard deviation of the ferrite fraction in the 24 measurement points was regarded as the standard deviation of the ferrite fraction of the 0.7R ⁇ r ⁇ 0.9R range.
  • V is the casting rate, and the unit is m/min
  • A is the casting size (the cross-sectional area of the bloom), and the unit is mm 2
  • C is the average cooling rate of the bloom from immediately after casting to the bending correction point.
  • the average cooling rate of the bloom is a value obtained by dividing the temperature difference between the casting temperature of molten steel and the surface temperature of the bloom at the bending correction point by the time required to reach the correction point from immediately below the mold.
  • the unit is °C/min.
  • the bending correction point is a position where the shape of the bloom is corrected from a curved shape to a straight shape in curved continuous casting.
  • the range of V ⁇ A 0.5 /C needs to be controlled to 6.0 to 20.0.
  • the preferable lower limit is 6.2 or more and more preferably 6.5 or more.
  • the preferable upper limit is 19.0 or less and more preferably 18.0 or less. It is impossible to actually measure the internal temperature during casting, but the use of this formula enables the internal temperature to be estimated in consideration of the items that can be actually measured and the casting size, thereby enabling cast control of a region corresponding to the gear teeth during casting.
  • post-rolling cooling it is important to control the average cooling rate when the surface temperature of steel during cooling is between 800°C and 300°C.
  • a uniform structure can be obtained by controlling the average cooling rate to 0.1 to 1.0°C/sec when the surface temperature of steel is between 800°C and 300°C, and, moreover, the ferrite fraction can be within a predetermined range. When the average cooling rate exceeds this range, a uniform structure cannot be obtained, and thermal strain is increased.
  • the preferable lower limit of the post-rolling cooling rate is 0.15°C/sec or faster and more preferably 0.2°C/sec or faster.
  • the preferable upper limit of the post-rolling cooling rate is 0.9°C/sec or slower and more preferably 0.8°C/sec or slower.
  • Molten steel is cast using a curved continuous casting machine (a casting step).
  • the mold size, the casting rate, and the cooling rate during casting are controlled as described above, and are desirably in the following ranges from the viewpoint of productivity.
  • the mold size is 30000 mm 2 or more and 400000 mm 2 or less, the casting rate is 0.2 m/min or faster and 3.0 m/min or slower, and the cooling rate from casting to the correction point is 4.0°C/min or faster and 100°C/min or slower.
  • the bloom obtained by the casting step is subjected to bloom rolling to obtain a billet (a bloom-rolling step).
  • the heating temperature during bloom rolling is desirably 1100°C or higher.
  • a more preferable heating temperature is 1200°C or higher.
  • an excessively high heating temperature results in coarse crystal grains, and thus the upper limit of the heating temperature is desirably 1280°C.
  • the bloom-rolling reduction of area is desirably 30% or more and more preferably 40% or more.
  • bar rolling or wire rod rolling is performed.
  • the heating temperature of bar rolling or wire rod rolling is desirably 1100°C or higher.
  • a more preferable heating temperature is 1150°C or higher.
  • an excessively high heating temperature results in coarse crystal grains, and thus the upper limit of the heating temperature is desirably 1250°C.
  • the post-rolling cooling rate is controlled such that the average cooling rate when the surface temperature of steel is between 800°C and 300°C is 0.1 to 1.0°C/sec.
  • a carburized gear is obtained by performing machining on the above steel to form a gear shape and then performing carburizing hardening and tempering.
  • a method for forming a gear shape hot forging, cold forging, cutting, or grindstone processing may be performed. Also, in order to increase workability, normalizing and annealing may be performed. Moreover, these may be combined.
  • carburizing hardening any carburizing method such as gas carburizing and vacuum carburizing can be used. Moreover, carbonitriding may be performed. Any type of gear may be created, such as spur gears, helical gears, bevel gears, external teeth, and internal teeth.
  • Test Nos.1 to 19 of the inventive examples had good thermal strain.
  • Test Nos. 20 to 23, 33, and 34 of the comparative examples good thermal strain was not obtained because the chemical component ranges were outside the scope of the present invention.
  • any one or more of the ferrite fraction, the fractions of structures other than ferrite and bainite, and the variation in ferrite fraction were outside the scope of the invention, and thus it was not possible to suppress the variation in helix deviation.
  • molten steels having the chemical components shown in Steel Nos. 1, 3, and 24 of Table 1 were cast under the conditions shown in Production Conditions 1 to 12 of Table 2 to obtain blooms. Thereafter, the blooms were heated to 1250°C and bloom-rolled to obtain billets having 162 mm per side. These billets were heated to 1200°C, bar-rolled to have a shape (a post-rolling diameter) shown in Production Conditions 1 to 12 of Table 2, and cooled under the cooling conditions shown in the same table to obtain steels 1, 24 to 32, 35, and 36.
  • Test Nos. 1, 24 to 32, 35, and 36 of Table 3 Test No. 32 is a test example corresponding to Production No. 1 of PCT International Publication No. WO 2014/171472 .
  • Test Nos. 1 and 24 to 28 of the inventive examples had good thermal strain.
  • the production conditions were not desirable in Test Nos. 29 to 32, 35, and 36 of the comparative examples, good thermal strain was not obtained.
  • Test No. 35 the variation in ferrite fraction was excessive. This is presumably because the post-rolling cooling rate was too fast, and thus it was not possible to achieve structural uniformity. Accordingly, in Test No. 35, it was not possible to suppress the variation in helix deviation.
  • Test No. 36 the fraction of a structure other than ferrite and bainite was excessive.
  • the structure other than ferrite and bainite was pearlite. This is presumably because V ⁇ A 0.5 /C was too small, thus it was not possible to eliminate segregation, and moreover the post-rolling cooling rate was too small. Accordingly, in Test No. 36, it was not possible to suppress the variation in helix deviation.
  • Test No. 36 the variation in ferrite fraction was suppressed despite V ⁇ A 0.5 /C being too small. This is considered to be because the structure included pearlite. However, pearlite also causes an increased variation in helix deviation, and thus it cannot be said that the steel of Test No. 36 is steel that stabilizes thermal strain.
  • Blank columns indicate elements which are not positively included.
  • Underlins indicate values outside of the scope of the present invention. Blank columns indicate elements which are not positively included. Underlines indicate values outside of the desireble manufacturing conditions.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Articles (AREA)

Claims (3)

  1. Ein Stahl, umfassend, in Massen-%:
    C: 0,17 bis 0,21%,
    Si: 0,40 bis 0,60%,
    Mn: 0,25 bis 0,50%,
    Cr: 1,35 bis 1,55%,
    Mo: 0,20 bis 0,40%,
    S: 0,010 bis 0,05%,
    N: 0,005 bis 0,020%,
    Al: 0,001% bis 0,100%,
    Nb: 0,001 bis 0,030%,
    Ni: 0 bis 3,0%,
    Cu: 0 bis 1,0%,
    Co: 0 bis 3,0%,
    W: 0 bis 1,0%,
    V: 0 bis 0,3%,
    Ti: 0 bis 0,3%,
    B: 0 bis 0,005%,
    O: 0,005% oder weniger,
    P: 0,03% oder weniger,
    Pb: 0 bis 0,5%,
    Bi: 0 bis 0,5%,
    Ca: 0 bis 0,01%,
    Mg: 0 bis 0,01%,
    Zr: 0 bis 0,05%,
    Te: 0 bis 0,1%,
    Seltenerdelement: 0 bis 0,005%, und
    einen Rest, bei dem es sich um Fe und Verunreinigungen handelt, wobei in einem Bereich, in dem ein Abstand r von der Mitte eines Querschnitts senkrecht zu einer Längsrichtung den folgenden Ausdruck erfüllt, Strukturen Ferrit und Bainit umfassen, ein durchschnittlicher Anteil des Ferrits in einem Bereich von 40 bis 70%,
    ausgedrückt als Flächenverhältnis, liegt, ein gesamter durchschnittlicher Anteil der Strukturen, die von dem Ferrit und dem Bainit verschieden sind, im Durchschnitt 0% oder mehr und 3% oder weniger beträgt, und ein Rest Bainit beinhaltet;
    eine Standardabweichung eines Ferritanteils in dem Bereich 4% oder weniger beträgt: 0,7 R ≤ r ≤ 0,9 R
    Figure imgb0004
    wobei R einen flächengleichen Kreisradius des Stahls darstellt,
    der Stahl in Form eines Stahlstabes oder Walzdrahts mit einem kreisförmigen Querschnitt vorliegt, und
    der durchschnittliche Ferritanteil und die Standardabweichung des Ferritanteils wie in der Beschreibung ausgeführt bestimmt werden.
  2. Der Stahl nach Anspruch 1, welcher, in Massen-%, eines oder zwei oder mehrere aus:
    Ni: 0,01 bis 3,0%,
    Cu: 0,01 bis 1,0%,
    Co: 0,01 bis 3,0%,
    W: 0,01 bis 1,0%,
    V: 0,01 bis 0,3%,
    Ti: 0,001 bis 0,3% und
    B: 0,0001 bis 0,005%
    umfasst.
  3. Der Stahl nach Anspruch 1 oder Anspruch 2, welcher, in Massen-%, eines oder zwei oder mehrere aus:
    Pb: 0,01 bis 0,5%,
    Bi: 0,0001 bis 0,5%,
    Ca: 0,0001 bis 0,01%,
    Mg: 0,0001 bis 0,01%,
    Zr: 0,0001 bis 0,05%,
    Te: 0,0001 bis 0,1% und
    Seltenerdelement: 0,0001 bis 0,005% umfasst.
EP19772012.1A 2018-03-23 2019-03-20 Stahl Active EP3770291B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2018056867 2018-03-23
PCT/JP2019/011847 WO2019182054A1 (ja) 2018-03-23 2019-03-20 鋼材

Publications (3)

Publication Number Publication Date
EP3770291A1 EP3770291A1 (de) 2021-01-27
EP3770291A4 EP3770291A4 (de) 2021-12-22
EP3770291B1 true EP3770291B1 (de) 2024-01-17

Family

ID=67986215

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19772012.1A Active EP3770291B1 (de) 2018-03-23 2019-03-20 Stahl

Country Status (6)

Country Link
US (1) US20200407815A1 (de)
EP (1) EP3770291B1 (de)
JP (1) JP6919762B2 (de)
KR (1) KR102463278B1 (de)
CN (1) CN111868281B (de)
WO (1) WO2019182054A1 (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116209782A (zh) * 2020-09-30 2023-06-02 日本制铁株式会社 钢材
CN116234938A (zh) * 2020-09-30 2023-06-06 日本制铁株式会社 钢材

Family Cites Families (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998023784A1 (fr) * 1996-11-25 1998-06-04 Sumitomo Metal Industries, Ltd. Acier d'excellente usinabilite et composant usine
JP4050829B2 (ja) * 1998-07-30 2008-02-20 新日本製鐵株式会社 転動疲労特性に優れた浸炭材
JP2006097066A (ja) * 2004-09-29 2006-04-13 Jfe Bars & Shapes Corp 肌焼鋼
JP4528363B1 (ja) * 2009-04-06 2010-08-18 新日本製鐵株式会社 冷間加工性、切削性、浸炭焼入れ後の疲労特性に優れた肌焼鋼及びその製造方法
CN102597290A (zh) 2009-11-05 2012-07-18 住友金属工业株式会社 热轧棒钢或线材
JP5397247B2 (ja) * 2010-02-02 2014-01-22 新日鐵住金株式会社 熱間圧延棒鋼または線材
EP2662462A1 (de) * 2012-05-07 2013-11-13 Valls Besitz GmbH Niedertemperatur-härtbare Stahle mit ausgezeichneter Bearbeitbarkeit
JP6073167B2 (ja) * 2013-03-25 2017-02-01 株式会社神戸製鋼所 面疲労強度と冷間鍛造性に優れた肌焼用鋼材
WO2014171472A1 (ja) 2013-04-18 2014-10-23 新日鐵住金株式会社 肌焼用鋼材と肌焼鋼部品
CN107406943B (zh) * 2015-03-31 2019-06-07 新日铁住金株式会社 表面硬化钢部件
JP6713394B2 (ja) 2016-09-30 2020-06-24 株式会社Ｎｔｔドコモ 制御装置、基地局装置、通信システム及び通信方法

Also Published As

Publication number Publication date
KR102463278B1 (ko) 2022-11-07
JPWO2019182054A1 (ja) 2020-12-17
EP3770291A4 (de) 2021-12-22
WO2019182054A1 (ja) 2019-09-26
US20200407815A1 (en) 2020-12-31
EP3770291A1 (de) 2021-01-27
CN111868281A (zh) 2020-10-30
JP6919762B2 (ja) 2021-08-18
KR20200118854A (ko) 2020-10-16
CN111868281B (zh) 2022-05-10

Similar Documents

Publication Publication Date Title
KR101826458B1 (ko) 베어링 부품
EP2003222B1 (de) Ein gehärteter und vergüteter stahl für den einsatz als feder
KR100968938B1 (ko) 고강도 스프링용 강 및 고강도 스프링용 열처리 강선
EP3305930A1 (de) Stahlblech und verfahren zur herstellung davon
WO2013151009A1 (ja) 冷間鍛造性に優れた鋼線材または棒鋼
EP2418296A1 (de) Stahl zum einsatzhärten mit hervorragender kaltumformbarkeit und zerspanbarkeit und hervorragenden ermüdungseigenschaften nach aufkohlung und abschreckung und herstellungsverfahren dafür
JP5736936B2 (ja) 熱間圧延棒鋼または線材、および冷間鍛造用鋼線の製造方法
US9187797B2 (en) Steel part for machine structural use and manufacturing method thereof
EP3342892A1 (de) Stahl für mechanische strukturen zur kaltbearbeitung und herstellungsverfahren dafür
US8926767B2 (en) Steel part for machine structural use and manufacturing method thereof
JP4464862B2 (ja) 耐結晶粒粗大化特性と冷間加工性に優れた軟化焼鈍の省略可能な肌焼用鋼
JP2010163671A (ja) 軟窒化用鋼
JP2010150566A (ja) 真空浸炭または真空浸炭窒化用の鋼材
EP3770291B1 (de) Stahl
JP4464861B2 (ja) 耐結晶粒粗大化特性と冷間加工性に優れた肌焼用鋼
EP3173500B1 (de) Warmbearbeitungswerkzeugmaterial, verfahren zur herstellung des warmbearbeitungswerkzeugs und warmbearbeitungswerkzeug
EP3211106B1 (de) Stahlwalzdraht für lager mit hervorragenden zieheigenschaften und spulenformbarkeit nach dem ziehen
EP3279361B1 (de) Warmgewalzter stab oder warmgewalzter walzdraht, komponente und herstellungsverfahren für warmgewalzten stab oder warmgewalzten walzdraht
EP3483293A1 (de) Walzdraht
JP7200646B2 (ja) 浸炭部品、浸炭部品用の素形材、及び、それらの製造方法
KR20220087978A (ko) 절삭성 및 연자성이 우수한 흑연화 열처리용 선재 및 흑연강
JP5098486B2 (ja) 浸炭部品の製造方法

Legal Events

Date Code Title Description
STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE INTERNATIONAL PUBLICATION HAS BEEN MADE

PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: REQUEST FOR EXAMINATION WAS MADE

17P Request for examination filed

Effective date: 20200925

AK Designated contracting states

Kind code of ref document: A1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

AX Request for extension of the european patent

Extension state: BA ME

DAV Request for validation of the european patent (deleted)
DAX Request for extension of the european patent (deleted)
A4 Supplementary search report drawn up and despatched

Effective date: 20211119

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: EXAMINATION IS IN PROGRESS

17Q First examination report despatched

Effective date: 20230310

REG Reference to a national code

Ref country code: DE

Ref legal event code: R079

Ref document number: 602019045252

Country of ref document: DE

Free format text: PREVIOUS MAIN CLASS: C22C0038000000

Ipc: C21D0009320000

Ref country code: DE

Ref legal event code: R079

Free format text: PREVIOUS MAIN CLASS: C22C0038000000

Ipc: C21D0009320000

RIC1 Information provided on ipc code assigned before grant

Ipc: C21D 1/58 20060101ALN20230613BHEP

Ipc: C22C 38/48 20060101ALI20230613BHEP

Ipc: C22C 38/32 20060101ALI20230613BHEP

Ipc: C22C 38/30 20060101ALI20230613BHEP

Ipc: C22C 38/28 20060101ALI20230613BHEP

Ipc: C22C 38/26 20060101ALI20230613BHEP

Ipc: C22C 38/24 20060101ALI20230613BHEP

Ipc: C22C 38/20 20060101ALI20230613BHEP

Ipc: C22C 38/04 20060101ALI20230613BHEP

Ipc: C22C 38/00 20060101ALI20230613BHEP

Ipc: C22C 38/02 20060101ALI20230613BHEP

Ipc: C21D 9/00 20060101ALI20230613BHEP

Ipc: C21D 1/76 20060101ALI20230613BHEP

Ipc: C21D 1/26 20060101ALI20230613BHEP

Ipc: C21D 1/18 20060101ALI20230613BHEP

Ipc: C22C 38/60 20060101ALI20230613BHEP

Ipc: B22D 11/00 20060101ALI20230613BHEP

Ipc: B22D 11/20 20060101ALI20230613BHEP

Ipc: B22D 11/22 20060101ALI20230613BHEP

Ipc: C21D 1/06 20060101ALI20230613BHEP

Ipc: C21D 8/06 20060101ALI20230613BHEP

Ipc: C21D 9/32 20060101AFI20230613BHEP

GRAP Despatch of communication of intention to grant a patent

Free format text: ORIGINAL CODE: EPIDOSNIGR1

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: GRANT OF PATENT IS INTENDED

RIC1 Information provided on ipc code assigned before grant

Ipc: C21D 1/58 20060101ALN20230710BHEP

Ipc: C22C 38/48 20060101ALI20230710BHEP

Ipc: C22C 38/32 20060101ALI20230710BHEP

Ipc: C22C 38/30 20060101ALI20230710BHEP

Ipc: C22C 38/28 20060101ALI20230710BHEP

Ipc: C22C 38/26 20060101ALI20230710BHEP

Ipc: C22C 38/24 20060101ALI20230710BHEP

Ipc: C22C 38/20 20060101ALI20230710BHEP

Ipc: C22C 38/04 20060101ALI20230710BHEP

Ipc: C22C 38/00 20060101ALI20230710BHEP

Ipc: C22C 38/02 20060101ALI20230710BHEP

Ipc: C21D 9/00 20060101ALI20230710BHEP

Ipc: C21D 1/76 20060101ALI20230710BHEP

Ipc: C21D 1/26 20060101ALI20230710BHEP

Ipc: C21D 1/18 20060101ALI20230710BHEP

Ipc: C22C 38/60 20060101ALI20230710BHEP

Ipc: B22D 11/00 20060101ALI20230710BHEP

Ipc: B22D 11/20 20060101ALI20230710BHEP

Ipc: B22D 11/22 20060101ALI20230710BHEP

Ipc: C21D 1/06 20060101ALI20230710BHEP

Ipc: C21D 8/06 20060101ALI20230710BHEP

Ipc: C21D 9/32 20060101AFI20230710BHEP

INTG Intention to grant announced

Effective date: 20230811

RIC1 Information provided on ipc code assigned before grant

Ipc: C21D 1/58 20060101ALN20230803BHEP

Ipc: C22C 38/48 20060101ALI20230803BHEP

Ipc: C22C 38/32 20060101ALI20230803BHEP

Ipc: C22C 38/30 20060101ALI20230803BHEP

Ipc: C22C 38/28 20060101ALI20230803BHEP

Ipc: C22C 38/26 20060101ALI20230803BHEP

Ipc: C22C 38/24 20060101ALI20230803BHEP

Ipc: C22C 38/20 20060101ALI20230803BHEP

Ipc: C22C 38/04 20060101ALI20230803BHEP

Ipc: C22C 38/00 20060101ALI20230803BHEP

Ipc: C22C 38/02 20060101ALI20230803BHEP

Ipc: C21D 9/00 20060101ALI20230803BHEP

Ipc: C21D 1/76 20060101ALI20230803BHEP

Ipc: C21D 1/26 20060101ALI20230803BHEP

Ipc: C21D 1/18 20060101ALI20230803BHEP

Ipc: C22C 38/60 20060101ALI20230803BHEP

Ipc: B22D 11/00 20060101ALI20230803BHEP

Ipc: B22D 11/20 20060101ALI20230803BHEP

Ipc: B22D 11/22 20060101ALI20230803BHEP

Ipc: C21D 1/06 20060101ALI20230803BHEP

Ipc: C21D 8/06 20060101ALI20230803BHEP

Ipc: C21D 9/32 20060101AFI20230803BHEP

RIN1 Information on inventor provided before grant (corrected)

Inventor name: NEISHI, YUTAKA

Inventor name: KOYAMA, TATSUYA

GRAS Grant fee paid

Free format text: ORIGINAL CODE: EPIDOSNIGR3

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: THE PATENT HAS BEEN GRANTED

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

REG Reference to a national code

Ref country code: GB

Ref legal event code: FG4D

REG Reference to a national code

Ref country code: CH

Ref legal event code: EP

REG Reference to a national code

Ref country code: DE

Ref legal event code: R096

Ref document number: 602019045252

Country of ref document: DE

REG Reference to a national code

Ref country code: IE

Ref legal event code: FG4D

REG Reference to a national code

Ref country code: SE

Ref legal event code: TRGR

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 20240325

Year of fee payment: 6

REG Reference to a national code

Ref country code: LT

Ref legal event code: MG9D

REG Reference to a national code

Ref country code: NL

Ref legal event code: MP

Effective date: 20240117