WO2022224849A1 - Steel material for carbonitriding and carbonitrided steel material - Google Patents
Steel material for carbonitriding and carbonitrided steel material Download PDFInfo
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- WO2022224849A1 WO2022224849A1 PCT/JP2022/017420 JP2022017420W WO2022224849A1 WO 2022224849 A1 WO2022224849 A1 WO 2022224849A1 JP 2022017420 W JP2022017420 W JP 2022017420W WO 2022224849 A1 WO2022224849 A1 WO 2022224849A1
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- 238000005256 carbonitriding Methods 0.000 title claims abstract description 110
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 105
- 239000010959 steel Substances 0.000 title claims abstract description 105
- 239000000463 material Substances 0.000 title claims abstract description 93
- 239000012535 impurity Substances 0.000 claims abstract description 11
- 229910052742 iron Inorganic materials 0.000 claims abstract description 3
- 238000005496 tempering Methods 0.000 claims description 16
- 229910052799 carbon Inorganic materials 0.000 abstract description 7
- 229910052804 chromium Inorganic materials 0.000 abstract description 5
- 229910052757 nitrogen Inorganic materials 0.000 abstract description 5
- 229910052802 copper Inorganic materials 0.000 abstract description 3
- 229910052748 manganese Inorganic materials 0.000 abstract description 3
- 229910052750 molybdenum Inorganic materials 0.000 abstract description 3
- 229910052759 nickel Inorganic materials 0.000 abstract description 3
- 229910052698 phosphorus Inorganic materials 0.000 abstract description 3
- 229910052710 silicon Inorganic materials 0.000 abstract description 3
- 229910052782 aluminium Inorganic materials 0.000 abstract description 2
- 229910052717 sulfur Inorganic materials 0.000 abstract description 2
- 238000005255 carburizing Methods 0.000 description 16
- 238000000034 method Methods 0.000 description 12
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- 238000005121 nitriding Methods 0.000 description 11
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- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 1
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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
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
-
- 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
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
-
- 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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—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
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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
- C22C38/18—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
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- 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
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- 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
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- 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
Definitions
- the present invention relates to carbonitriding steel and carbonitriding steel.
- the fabric is a steel material with a specific composition, and in the region from the surface to a depth of 0.1 mm, the average C concentration Cs is 0.60 to 0.90%, the average N concentration
- a steel carbonitriding part is described, characterized in that Ns is 0.15 to 0.35%, Cs + Ns is 0.80 to 1.10%, and each component satisfies a specific relational expression.
- the bending fatigue strength and the surface fatigue strength are significantly superior to those manufactured by carburizing and quenching, which is the most typical surface hardening treatment, without a significant increase in cost. It is described that it is possible to provide carbonitrided steel parts that can meet the demands for parts weight reduction, miniaturization, and high stress load.
- Patent Document 3 describes a steel material for carbonitriding, which is characterized by having a specific composition and each component satisfying a specific relational expression. According to such a carbonitriding steel material, it is possible to provide a steel material that is excellent in workability into a part shape and has an excellent pitting life even if the polishing process after the carbonitriding treatment is omitted, and a part using the steel material. It is stated that it is possible.
- the base is a steel material having a specific composition
- the ratio of voids is less than 10% in a region from the surface to a depth of 5 ⁇ m
- the average C concentration Cave is 0.005 to 0.80%
- average N concentration Nave is 0.30 to 0.70%
- Cave + Nave is 0.50 to 1.40%. It is described that such steel parts have excellent surface fatigue strength and wear resistance, and can be used for parts such as gears, crankshafts, and camshafts of automobiles and industrial machinery. ing.
- Patent Document 5 includes a surface layer portion including a surface having a flat portion and an edge portion, and a core portion inside the surface layer portion, the core portion having a specific composition, and a depth from the flat portion
- the carbon concentration CP1 in the region up to 0.05 mm is 0.70 to 0.89%
- the nitrogen concentration is 0.10 to 0.80%
- the concentration CP2 is higher than the carbon concentration CP1 and 1.20% or less
- the Vickers hardness at a depth of 0.3 mm from the flat portion is HV650 or more
- the depth of the grain boundary oxide layer at the surface layer portion is is less than 3.0 ⁇ m and the core has a Vickers hardness of HV260 or higher.
- such a carbonitrided part can provide a carbonitrided part having a surface including a flat portion and an edge portion and having excellent bending fatigue strength and pitting strength.
- the sliding temperature of some parts may be higher than before (for example, about 300 to 500 degrees Celsius). Therefore, some members are required to be sufficiently hard even when exposed to high temperatures, that is, high temperature temper hardness.
- the present inventor found that the formation of CrN clusters greatly contributes to the improvement of the surface fatigue strength of carbonitriding, and that it is necessary to add Cr to a certain extent in order to sufficiently improve the surface fatigue strength.
- rice field Specifically, it was found that the addition of N is effective up to 300°C, and the addition of Cr and N is effective in the temperature range above 300°C.
- the inventors have found that the tempering hardness at high temperatures (about 300 to 500° C.) decreases depending on the amount of Cr and N added. That is, it has been found that it is difficult to improve both surface fatigue strength and high-temperature tempering hardness, and that these are in a trade-off relationship.
- An object of the present invention is to solve the above problems. That is, an object of the present invention is to provide a carbonitriding steel material having high surface fatigue strength and sufficiently high high-temperature tempering hardness, and a carbonitriding steel material obtained by carbonitriding the same.
- the present inventor has made intensive studies to solve the above problems, and completed the present invention.
- the present invention provides the following (1) to (7).
- Nb 0.001 to 0.08% by mass, V: 0.5% by mass or less, Ti: 0.05% by mass or less, and B: 0.0005 to 0.003% by mass
- Carbonitriding the steel material for carbonitriding according to any one of (1) to (6) above, Formula 1: Surface C concentration (% by mass) + 12/14 x Surface N concentration (% by mass) 0.6 to 1.4
- the present invention it is possible to provide a carbonitriding steel material having high surface fatigue strength and sufficiently high high-temperature tempering hardness, and a carbonitriding steel material obtained by carbonitriding the same.
- Example 4 It is a schematic side view of the small roller used in the Example. 4 is a graph showing the relationship between 500° C. tempering hardness and fatigue strength life ratio in Examples and Comparative Examples. 4 is a graph showing the relationship between 500° C. tempering hardness and seizure limit load ratio in Examples and Comparative Examples.
- the carbonitriding steel material of the present invention has C: 0.1 to 0.3% by mass, Si: 0.3% by mass or less, Mn: 0.4 to 2.0% by mass, and P: 0.03% by mass.
- S: 0.03% by mass or less Cu: 0.3% by mass or less, Ni: 2.5% by mass or less, Cr: 0.5 to 3.0% by mass, Mo: 0.001 to 1.0 % by mass, Al: 0.01 to 0.08% by mass, N: 0.005 to 0.03% by mass, the balance being Fe and unavoidable impurities.
- the carbonitriding steel material of the present invention is obtained by carbonitriding the steel material for carbonitriding treatment of the present invention. 6 to 1.4, Formula 2: 129.7805 ⁇ [Cr (mass%)] ⁇ 76.9797 ⁇ [Cr (mass%)] 2 + 339.3375 ⁇ [Surface N concentration (mass%)] ⁇ 539 .345 ⁇ [Surface N concentration (mass%)] 2 +181.4983 ⁇ [Cr (mass%)] ⁇ [Surface N concentration (mass%)]+437.
- the carbonitrided steel material has a hardness of 560 HV or more at a depth of 0.05 mm from the surface.
- the carbonitriding steel material of the present invention has a C content of 0.1 to 0.3% by mass, preferably 0.15 to 0.25% by mass. With such a C content, the hardenability of the carbonitriding steel material of the present invention is improved, and the hardness of the surface portion and the core portion is ensured. If the C content is too high, toughness and hot workability may deteriorate.
- the Si content in the carbonitriding steel material of the present invention is 0.3% by mass or less, preferably 0.01 to 0.24% by mass, and more preferably 0.01 to 0.17% by mass. More preferably, it is 0.01 to 0.16% by mass. With such a Si content, the precipitation of nitrides (Si 3 N 4 , SiMnN 2 , etc.) in the carbonitriding steel material of the present invention is suppressed, and a decrease in fatigue strength can be prevented.
- the Mn content in the carbonitriding steel material of the present invention is 0.4 to 2.0% by mass, preferably 0.5 to 2.0% by mass, and more preferably 0.53 to 2.0% by mass. More preferably, 0.5 to 1.8% by mass, more preferably 0.5 to 1.4% by mass, and 0.53 to 1.5% by mass is more preferred.
- Mn content the hardenability is improved, the core hardness is improved, and the fatigue strength is improved.
- machinability, hardenability and manufacturability are improved. If the Mn content is too low, the effect of improving hardenability cannot be obtained. Also, if the Mn content is too high, there is a possibility that the manufacturability will be impaired.
- the P content in the carbonitriding steel material of the present invention is 0.03% by mass or less, preferably 0.020% by mass or less.
- P is an impurity contained in steel, and segregates at grain boundaries to embrittle the steel. In particular, when the content exceeds 0.030% by mass, the degree of embrittlement may become significant. Therefore, the P content in the carbonitriding steel material of the present invention is set to 0.03% by mass or less.
- the S content in the carbonitriding steel material of the present invention is 0.03% by mass or less, preferably 0.020% by mass or less. Such a S content has the effect of forming MnS and improving the machinability. On the other hand, when the S content exceeds 0.030% by mass, coarse MnS tends to be formed and the hot forgeability and bending fatigue strength tend to decrease. Therefore, it is preferably 0.005 to 0.030% by mass. If more emphasis is placed on hot forgeability and bending fatigue strength, the S content is preferably 0.020% by mass or less.
- the Cu content in the carbonitriding steel material of the present invention is 0.3% by mass or less, preferably 0.001 to 0.3% by mass, and 0.03 to 0.3% by mass. is more preferable, and 0.03 to 0.25% by mass is even more preferable. With such a Cu content, the formation of carbides is suppressed and the hardenability is improved. If the Cu content is too high, the hot workability may deteriorate.
- Ni content in the carbonitriding steel material of the present invention is 2.5% by mass or less, preferably 0.01 to 0.6% by mass, and more preferably 0.05 to 0.6% by mass. more preferred. With such a Ni content, hardenability increases and toughness improves. In addition, it is a non-oxidizing element and can toughen the steel surface without increasing the depth of the grain boundary oxide layer during carburizing.
- the Cr content in the carbonitriding steel material of the present invention is 0.5 to 3.0% by mass, preferably 0.5 to 2.5% by mass, and more preferably 0.6 to 1.8% by mass. It is more preferable to have With such a Cr content, hardenability is improved, machinability is ensured, pitting fatigue strength is improved, and toughness is also improved. If the Cr content is too high, the hardness increases, the machinability decreases, and coarse Cr carbides are formed during carburizing, and coarse CrN is formed along grain boundaries during carbonitriding, Bending strength may decrease.
- the Mo content in the carbonitriding steel material of the present invention is 0.001 to 1.0% by mass, preferably 0.01 to 0.8% by mass, and 0.05 to 0.6% by mass. It is more preferable to have With such a Mo content, the hardenability is improved, so that the core hardness of the quenched part is improved, and the fatigue strength is improved. It also improves surface hardness and hardened layer hardness. If the Mo content is too low, the strength after hot forging increases, and machinability may deteriorate. On the other hand, if the Mo content is too high, there is a tendency to generate precipitation nucleation sites and promote the formation of precipitates such as carbonitrides. In addition, undissolved coarse carbonitrides and the like remain in the steel, and during carbonitriding and quenching, the coarse carbonitrides grow further and coarsen, which may reduce the fatigue strength.
- the Al content in the carbonitriding steel material of the present invention is 0.01 to 0.08% by mass, preferably 0.02 to 0.05% by mass. With such an Al content, Al easily bonds with N, forms AlN, refines crystal grains, and strengthens the steel. If the Al content is too high, there is a possibility that the machinability will decrease due to the formation of hard and coarse Al 2 O 3 , and Al 2 O 3 as large hard inclusions will become the origin of fatigue fracture, resulting in bending failure. It may cause a decrease in fatigue strength and pitting strength.
- the N content in the carbonitriding steel material of the present invention is 0.005 to 0.03% by mass, preferably 0.01 to 0.025% by mass, and more preferably 0.01 to 0.020% by mass. more preferably 0.01 to 0.015% by mass. With such an N content, the crystal grains are refined by the formation of nitrides, and the bending fatigue strength is improved. If the N content is too high, formation of coarse nitrides may reduce the toughness.
- the carbonitriding steel material of the present invention may contain Nb.
- the Nb content in the carbonitriding steel material of the present invention is preferably 0.001 to 0.08% by mass, more preferably 0.0015 to 0.06% by mass. With such an Nb content, fine precipitates (NbC) are generated, making it difficult for crystal grains to coarsen during carburizing.
- the carbonitriding steel material of the present invention may contain V.
- the V content in the carbonitriding steel material of the present invention is preferably 0.5% by mass or less, more preferably 0.25% by mass or less. With such a V content, V precipitates appear dispersedly, and the fracture characteristics are improved.
- the carbonitriding steel material of the present invention may contain Ti.
- the Ti content in the carbonitriding steel material of the present invention is preferably 0.05% by mass or less, more preferably 0.08% by mass or less, and 0.012 to 0.04% by mass. is more preferred. With such a Ti content, fine precipitates (TiC) are generated, making it difficult for crystal grains to coarsen during carburizing.
- the carbonitriding steel material of the present invention may contain B.
- the B content in the carbonitriding steel material of the present invention is preferably 0.0005 to 0.003% by mass, more preferably 0.0006 to 0.0025% by mass. With such a B content, the hardenability is greatly improved, and the crack workability is improved. If the B content is too high, BN is formed and the effect of improving the hardenability at deep portions is reduced.
- the steel material for carbonitriding treatment of the present invention contains C, Si, Mn, P, S, Cu, Ni, Cr, Mo, Al and N in the above contents, and further optionally includes Nb, V and Ti. and B may be contained at a specific content rate.
- the balance consists of Fe and unavoidable impurities.
- the unavoidable impurities mean components that may be mixed from raw materials or manufacturing processes even if they are not intentionally added.
- Specific examples of unavoidable impurities include O, As, and the like.
- the content of each component contained in the steel material for carbonitriding treatment of the present invention means the value obtained by measuring by the following method.
- Si, Mn, P, Cu, Ni, Cr, Mo, V, Ti, Nb are values determined by fluorescent X-ray analysis
- Al is by emission spectrometry
- O is dissolved in an inert gas-infrared absorption method
- C denote values determined by the combustion infrared absorption method.
- N means the value obtained by melting in an inert gas-thermal conduction method
- B means the value obtained by the emission spectroscopic analysis method.
- the method of manufacturing the carbonitriding steel material of the present invention is not particularly limited.
- the steel material for carbonitriding treatment of the present invention can be produced by a conventionally known method.
- the carbonitriding steel material of the present invention can be obtained by subjecting the steel material for carbonitriding treatment of the present invention having the above composition to carbonitriding treatment.
- the carbonitriding treatment is not particularly limited, and any carbonitriding treatment that can obtain the carbonitriding steel material of the present invention from the steel material for carbonitriding treatment of the present invention can be used. It's okay.
- the carbonitriding treatment X may be either gas carbonitriding or vacuum carbonitriding.
- various conditions of carbonitriding can be appropriately determined according to the surface layer hardness and tempering hardness required for carbonitriding parts, and are not particularly limited.
- CP is usually controlled to 0.5 to 1.0
- ammonia is used as the nitriding gas
- the ammonia flow rate, ammonia concentration in the furnace, diffusion time, and quenching temperature are adjusted.
- Hardening is performed by controlling the surface N concentration. Then, it is tempered by heating to 100° C. to 300° C. and holding for 1 to 3 hours.
- the carbonitriding steel material of the present invention will be described.
- the carbonitriding steel material of the present invention can be obtained by subjecting the steel material for carbonitriding treatment of the present invention as described above to a carbonitriding treatment (for example, the carbonitriding treatment X described above).
- the carbonitrided steel material of the present invention preferably has a surface C concentration of 0.4 to 0.8% by mass, more preferably 0.45 to 0.70% by mass.
- the surface C concentration means the C concentration obtained by applying the combustion-infrared absorption method to the obtained chips (turning powder) by scraping the carbonitriding steel material of the present invention from the surface to a depth of 100 ⁇ m. shall be
- the carbonitrided steel material of the present invention preferably has a surface N concentration of 0.25 to 0.8% by mass, more preferably 0.30 to 0.70% by mass.
- the surface N concentration means the N concentration obtained by cutting the carbonitrided steel material of the present invention from the surface to a depth of 100 ⁇ m and applying the fusion-thermal conductivity measurement to the obtained chips (turning powder). It shall be.
- the surface C concentration and the surface N concentration as described above satisfy the following formula 1.
- the calculation result of Equation 1 is preferably 0.7 to 1.2.
- the surface C concentration, the surface N concentration, and the Cr content as described above satisfy the following formula 2.
- Formula 2 129.7805 ⁇ [Cr (mass%)] ⁇ 76.9797 ⁇ [Cr (mass%)] 2 +339.3375 ⁇ [Surface N concentration (mass%)] ⁇ 539.345 ⁇ [Surface N concentration ( % by mass)] 2 +181.4983 ⁇ [Cr (% by mass)] ⁇ [Surface N concentration (% by mass)]+437.6799>560
- the carbonitriding steel material of the present invention obtained by subjecting the carbonitriding steel material of the present invention to the carbonitriding treatment X described above has a hardness of 600 HV or more at a depth of 0.05 mm from the surface. is preferred.
- the steel material for carbonitriding treatment of the present invention when the steel material for carbonitriding treatment of the present invention obtained by applying the carbonitriding treatment X described above is further subjected to tempering treatment at 500 ° C., a depth of 0.05 mm from the surface The hardness of the thin portion is 560 HV or more.
- steel ingot A was hot-rolled or hot-forged to obtain a round bar with a cross-sectional diameter of 125 mm, and then hot-forged to obtain a round bar with a cross-sectional diameter of 32 mm. Then, a normalizing treatment was applied (925° C. ⁇ 1 HrAC), and a round bar (length: 210 mm) with a cross-sectional diameter of 15 mm was cut out from the obtained round bar.
- the round bar was subjected to carburizing treatment and nitriding treatment to obtain a test piece.
- carburizing treatment was performed, and the nitriding treatment was not performed.
- the carburizing treatment is the following treatment.
- a round bar is placed in a gas carbonitriding furnace, a carburizing gas (propane gas is used as an enrichment gas) is introduced at a temperature of 930°C, and CP (carbon potential) is adjusted by adjusting the partial pressure of carbon monoxide and carbon dioxide. ) was controlled to 0.7, and carburization was carried out.
- a carburizing gas propane gas is used as an enrichment gas
- CP carbon potential
- the nitriding treatment is the following treatment. After the above carburizing treatment, the temperature of the round bar was lowered to 850° C., and ammonia gas was introduced as a nitriding gas while keeping the CP constant, and the nitriding treatment was performed. After the nitriding treatment, quenching was performed with semi-hot oil at 120°C. As the next treatment, the quenched round bar was placed in a furnace adjusted to 160° C. for 2 hours, heated, taken out of the furnace, and allowed to cool in a room for tempering.
- a round bar was produced from the above steel ingot A in the same process and machined to obtain a small rotor.
- the small roller 1 comprises a contact portion 2 having a diameter of 26 mm and a width of 28 mm and small diameter portions 4 having a diameter of 22 mm arranged on both sides thereof.
- the small rotor was subjected to carburizing treatment and nitriding treatment to obtain a test piece.
- a large roller was prepared as the opposite side of the test piece.
- the large roller was made of SUJ2 and was quenched and tempered so as to have HRC61.
- the radius of curvature of the large roller was set to 150R.
- a roller pitching test was performed.
- the test piece and the mating large roller are brought into contact with each other at various surface pressures of 2.0 to 4.0 GPa at a rotation speed of 3000 rpm, and a roller pitching tester is used to determine the slip rate: -100. %, and the load stress that does not cause pitting in 10 7 cycles was taken as the surface fatigue strength (pitting fatigue strength). Then, the surface fatigue strength against the vacuum carburized material of JIS SCR420 was determined for each test piece. That is, the fatigue strength life ratio means (surface fatigue strength of test piece/surface fatigue strength of vacuum carburized material of JIS SCR420). Results are shown in Tables 1 and 2.
- Seizure was determined at the time when the torque of the torque meter installed on the load side suddenly increased, and the load at that time was taken as the seizure load. Then, the surface fatigue strength against the vacuum carburized material of JIS SCR420 was determined for each test piece. That is, the seizure limit load ratio means "seizure load of test piece/seizure load of vacuum carburized material of JIS SCR420". The seizure limit load was measured for each of Examples 1-31 and Comparative Examples 1-19. The results are shown in Tables 3 and 4.
- FIG. 2 shows the relationship between the surface hardness when tempering at 500° C. shown in Tables 1 and 2 and the fatigue strength life ratio (life ratio under high-speed roller pitting conditions). From FIG. 2, it can be confirmed that the example is improved in all respects as compared with the comparative example.
- FIG. 3 shows the relationship between the surface hardness when tempering at 500° C. shown in Tables 1 and 2 and the seizure limit load ratio shown in Tables 3 and 4.
- FIG. 3 From FIG. 3, it can be confirmed that the example is improved in all respects as compared with the comparative example.
- the present invention it is possible to provide a carbonitriding steel material having high surface fatigue strength and sufficiently high high-temperature tempering hardness, and a carbonitriding steel material obtained by carbonitriding the same.
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Abstract
Description
これに関連する従来法として、例えば特許文献1~5に記載のものが挙げられる。 For example, high surface fatigue strength is required for steel parts such as gears and shafts for automobiles and industrial machinery. Therefore, conventionally, carbonitrided parts are used as such parts. Conventionally, it is widely known that surface fatigue strength is improved by carbonitriding steel materials.
Conventional methods related to this include, for example, those described in Patent Documents 1 to 5.
さらに、本発明者はCr、Nの添加量によっては高温(300~500℃程度)における焼戻し硬さが低下してしまうことを見出した。
すなわち、面疲労強度と高温焼戻し硬さとの両方を改善することは難しく、これらはトレードオフの関係にあることを見出した。 On the other hand, the present inventor found that the formation of CrN clusters greatly contributes to the improvement of the surface fatigue strength of carbonitriding, and that it is necessary to add Cr to a certain extent in order to sufficiently improve the surface fatigue strength. rice field. Specifically, it was found that the addition of N is effective up to 300°C, and the addition of Cr and N is effective in the temperature range above 300°C.
Furthermore, the inventors have found that the tempering hardness at high temperatures (about 300 to 500° C.) decreases depending on the amount of Cr and N added.
That is, it has been found that it is difficult to improve both surface fatigue strength and high-temperature tempering hardness, and that these are in a trade-off relationship.
すなわち、本発明の目的は、面疲労強度が高く、かつ、高温焼戻し硬さが十分に高い浸炭窒化処理用鋼材およびそれを浸炭窒化処理してなる浸炭窒化鋼材を提供することである。 An object of the present invention is to solve the above problems.
That is, an object of the present invention is to provide a carbonitriding steel material having high surface fatigue strength and sufficiently high high-temperature tempering hardness, and a carbonitriding steel material obtained by carbonitriding the same.
本発明は下記(1)~(7)である。
(1)C:0.1~0.3質量%、
Si:0.3質量%以下、
Mn:0.4~2.0質量%、
P:0.03質量%以下、
S:0.03質量%以下、
Cu:0.3質量%以下、
Ni:2.5質量%以下、
Cr:0.5~3.0質量%、
Mo:0.001~1.0質量%、
Al:0.01~0.08質量%、
N:0.005~0.03質量%、
で含有し、残部はFeおよび不可避的不純物からなり、
浸炭窒化を施すことで、
式1:表面C濃度(質量%)+12/14×表面N濃度(質量%)=0.6~1.4
を満たし、
式2:129.7805×[Cr(質量%)]-76.9797×[Cr(質量%)]2+339.3375×[表面N濃度(質量%)]-539.345×[表面N濃度(質量%)]2+181.4983×[Cr(質量%)]×[表面N濃度(質量%)]+437.6799>560
を満たし、
前記浸炭窒化を施した後に500℃で焼戻し処理を施した場合に、表面から0.05mmの深さの部分における硬さが560HV以上である浸炭窒化鋼材が得られる、浸炭窒化処理用鋼材。
(2)Nb:0.001~0.08質量%、
V:0.5質量%以下、
Ti:0.05質量%以下、および
B:0.0005~0.003質量%、
からなる群から選ばれる少なくとも一種をさらに含有する、上記(1)に記載の浸炭窒化処理用鋼材。
(3)C:0.15~0.25質量%、
Si:0.01~0.24質量%、
Mn:0.5~1.8質量%、
Cu:0.001~0.3質量%、
Ni:0.01~0.6質量%、
Cr:0.6~1.8質量%、
Mo:0.01~0.8質量%、
Al:0.02~0.05質量%、
N:0.01~0.025質量%、
で含有し、
Nb:0.0015~0.06質量%、
V:0.25質量%以下、
Ti:0.012~0.04質量%、および
B:0.0006~0.0025質量%、
からなる群から選ばれる少なくとも一種をさらに含有し、残部はFeおよび不可避的不純物からなり、
前記浸炭窒化を施すことで、
式1:表面C濃度(質量%)+12/14×表面N濃度(質量%)=0.7~1.2を満たす浸炭窒化処理鋼材が得られる、上記(1)または(2)に記載の浸炭窒化処理用鋼材。
(4)Cu:0.03~0.3質量%、
で含有する、上記(1)~(3)のいずれかに記載の浸炭窒化処理用鋼材。
(5)Si:0.01~0.17質量%、
で含有する、上記(1)~(4)のいずれかに記載の浸炭窒化処理用鋼材。
(6)Cu:0.03~0.25質量%、
で含有する、上記(1)~(5)のいずれかに記載の浸炭窒化処理用鋼材。
(7)上記(1)~(6)のいずれかに記載の浸炭窒化処理用鋼材を浸炭窒化処理してなり、
式1:表面C濃度(質量%)+12/14×表面N濃度(質量%)=0.6~1.4
を満たし、
式2:129.7805×[Cr(質量%)]-76.9797×[Cr(質量%)]2+339.3375×[表面N濃度(質量%)]-539.345×[表面N濃度(質量%)]2+181.4983×[Cr(質量%)]×[表面N濃度(質量%)]+437.6799>560
を満たし、
さらに500℃で焼戻し処理を施した場合に、表面から0.05mmの深さの部分における硬さが560HV以上となる、浸炭窒化鋼材。 The present inventor has made intensive studies to solve the above problems, and completed the present invention.
The present invention provides the following (1) to (7).
(1) C: 0.1 to 0.3% by mass,
Si: 0.3% by mass or less,
Mn: 0.4 to 2.0% by mass,
P: 0.03% by mass or less,
S: 0.03% by mass or less,
Cu: 0.3% by mass or less,
Ni: 2.5% by mass or less,
Cr: 0.5 to 3.0% by mass,
Mo: 0.001 to 1.0% by mass,
Al: 0.01 to 0.08% by mass,
N: 0.005 to 0.03% by mass,
and the balance consists of Fe and unavoidable impurities,
By applying carbonitriding,
Formula 1: Surface C concentration (% by mass) + 12/14 x Surface N concentration (% by mass) = 0.6 to 1.4
The filling,
Formula 2: 129.7805×[Cr (mass%)]−76.9797×[Cr (mass%)] 2 +339.3375×[Surface N concentration (mass%)]−539.345×[Surface N concentration ( % by mass)] 2 +181.4983×[Cr (% by mass)]×[Surface N concentration (% by mass)]+437.6799>560
The filling,
A steel material for carbonitriding treatment that provides a carbonitriding steel material having a hardness of 560 HV or more at a depth of 0.05 mm from the surface when tempering treatment is performed at 500° C. after the carbonitriding treatment.
(2) Nb: 0.001 to 0.08% by mass,
V: 0.5% by mass or less,
Ti: 0.05% by mass or less, and B: 0.0005 to 0.003% by mass,
The carbonitriding steel material according to (1) above, further containing at least one selected from the group consisting of:
(3) C: 0.15 to 0.25% by mass,
Si: 0.01 to 0.24% by mass,
Mn: 0.5 to 1.8% by mass,
Cu: 0.001 to 0.3% by mass,
Ni: 0.01 to 0.6% by mass,
Cr: 0.6 to 1.8% by mass,
Mo: 0.01 to 0.8% by mass,
Al: 0.02 to 0.05% by mass,
N: 0.01 to 0.025% by mass,
contains with
Nb: 0.0015 to 0.06% by mass,
V: 0.25% by mass or less,
Ti: 0.012 to 0.04% by mass, and B: 0.0006 to 0.0025% by mass,
further contains at least one selected from the group consisting of the balance consisting of Fe and inevitable impurities,
By applying the carbonitriding,
Formula 1: Surface C concentration (% by mass) + 12/14 x Surface N concentration (% by mass) = 0.7 to 1.2. Steel for carbonitriding.
(4) Cu: 0.03 to 0.3% by mass,
The steel material for carbonitriding treatment according to any one of the above (1) to (3), containing in.
(5) Si: 0.01 to 0.17% by mass,
The steel material for carbonitriding treatment according to any one of the above (1) to (4), containing in.
(6) Cu: 0.03 to 0.25% by mass,
The steel material for carbonitriding treatment according to any one of the above (1) to (5), containing in.
(7) Carbonitriding the steel material for carbonitriding according to any one of (1) to (6) above,
Formula 1: Surface C concentration (% by mass) + 12/14 x Surface N concentration (% by mass) = 0.6 to 1.4
The filling,
Formula 2: 129.7805×[Cr (mass%)]−76.9797×[Cr (mass%)] 2 +339.3375×[Surface N concentration (mass%)]−539.345×[Surface N concentration ( % by mass)] 2 +181.4983×[Cr (% by mass)]×[Surface N concentration (% by mass)]+437.6799>560
The filling,
A carbonitrided steel material which, when further tempered at 500° C., has a hardness of 560 HV or more at a depth of 0.05 mm from the surface.
本発明の浸炭窒化処理用鋼材は、C:0.1~0.3質量%、Si:0.3質量%以下、Mn:0.4~2.0質量%、P:0.03質量%以下、S:0.03質量%以下、Cu:0.3質量%以下、Ni:2.5質量%以下、Cr:0.5~3.0質量%、Mo:0.001~1.0質量%、Al:0.01~0.08質量%、N:0.005~0.03質量%、で含有し、残部はFeおよび不可避的不純物からなり、浸炭窒化を施すことで、式1:表面C濃度(質量%)+12/14×表面N濃度(質量%)=0.6~1.4を満たし、式2:129.7805×[Cr(質量%)]-76.9797×[Cr(質量%)]2+339.3375×[表面N濃度(質量%)]-539.345×[表面N濃度(質量%)]2+181.4983×[Cr(質量%)]×[表面N濃度(質量%)]+437.6799>560を満たし、前記浸炭窒化を施した後に500℃で焼戻し処理を施した場合に、表面から0.05mmの深さの部分における硬さが560HV以上である浸炭窒化鋼材が得られる、浸炭窒化処理用鋼材である。 The present invention will be described.
The carbonitriding steel material of the present invention has C: 0.1 to 0.3% by mass, Si: 0.3% by mass or less, Mn: 0.4 to 2.0% by mass, and P: 0.03% by mass. Below, S: 0.03% by mass or less, Cu: 0.3% by mass or less, Ni: 2.5% by mass or less, Cr: 0.5 to 3.0% by mass, Mo: 0.001 to 1.0 % by mass, Al: 0.01 to 0.08% by mass, N: 0.005 to 0.03% by mass, the balance being Fe and unavoidable impurities. : Surface C concentration (% by mass) + 12/14 x surface N concentration (% by mass) = 0.6 to 1.4, formula 2: 129.7805 x [Cr (mass%)] -76.9797 x [ Cr (mass%)] 2 + 339.3375 × [Surface N concentration (mass%)] - 539.345 × [Surface N concentration (mass%)] 2 + 181.4983 × [Cr (mass%)] × [Surface N Concentration (% by mass)]+437.6799>560, and when tempering is performed at 500° C. after the carbonitriding, the hardness at a depth of 0.05 mm from the surface is 560 HV or more. It is a carbonitriding steel material from which a carbonitriding steel material can be obtained.
本発明の浸炭窒化処理用鋼材におけるC含有率は0.1~0.3質量%であり、0.15~0.25質量%であることが好ましい。
このようなC含有率であると、本発明の浸炭窒化処理用鋼材の焼入れ性が向上し、また表面部および芯部の硬さが確保される。C含有率が高すぎると靭性および熱間加工性が低下する可能性がある。 <C>
The carbonitriding steel material of the present invention has a C content of 0.1 to 0.3% by mass, preferably 0.15 to 0.25% by mass.
With such a C content, the hardenability of the carbonitriding steel material of the present invention is improved, and the hardness of the surface portion and the core portion is ensured. If the C content is too high, toughness and hot workability may deteriorate.
本発明の浸炭窒化処理用鋼材におけるSi含有率は0.3質量%以下であり、0.01~0.24質量%であることが好ましく、0.01~0.17質量%であることがより好ましく、0.01~0.16質量%であることがさらに好ましい。
このようなSi含有率であると、本発明の浸炭窒化処理用鋼材での窒化物の析出(Si3N4、SiMnN2等)の析出が抑制され、疲労強度の低下を防ぐことができる。 <Si>
The Si content in the carbonitriding steel material of the present invention is 0.3% by mass or less, preferably 0.01 to 0.24% by mass, and more preferably 0.01 to 0.17% by mass. More preferably, it is 0.01 to 0.16% by mass.
With such a Si content, the precipitation of nitrides (Si 3 N 4 , SiMnN 2 , etc.) in the carbonitriding steel material of the present invention is suppressed, and a decrease in fatigue strength can be prevented.
本発明の浸炭窒化処理用鋼材におけるMn含有率は0.4~2.0質量%であり、0.5~2.0質量%であることが好ましく、0.53~2.0質量%であることがより好ましく、0.5~1.8質量%であることがより好ましく、0.5~1.4質量%であることがより好ましく、0.53~1.5質量%であることがさらに好ましい。
このようなMn含有率であると、焼入れ性が向上することで芯部硬さが向上し、疲労強度が向上する。また、切削性、焼入性、製造性が良好となる。Mn含有率が低すぎると焼入れ性向上効果が得られない。また、Mn含有率が高すぎると製造性を損なう可能性がある。 <Mn>
The Mn content in the carbonitriding steel material of the present invention is 0.4 to 2.0% by mass, preferably 0.5 to 2.0% by mass, and more preferably 0.53 to 2.0% by mass. More preferably, 0.5 to 1.8% by mass, more preferably 0.5 to 1.4% by mass, and 0.53 to 1.5% by mass is more preferred.
With such a Mn content, the hardenability is improved, the core hardness is improved, and the fatigue strength is improved. In addition, machinability, hardenability and manufacturability are improved. If the Mn content is too low, the effect of improving hardenability cannot be obtained. Also, if the Mn content is too high, there is a possibility that the manufacturability will be impaired.
本発明の浸炭窒化処理用鋼材におけるP含有率は0.03質量%以下であり、0.020質量%以下であることが好ましい。Pは鋼に含有される不純物であり、結晶粒界に偏析して鋼を脆化させ、特に、その含有量が0.030質量%を超えると、脆化の程度が著しくなる場合がある。従って、本発明の浸炭窒化処理用鋼材におけるP含有率は0.03質量%以下とする。 <P>
The P content in the carbonitriding steel material of the present invention is 0.03% by mass or less, preferably 0.020% by mass or less. P is an impurity contained in steel, and segregates at grain boundaries to embrittle the steel. In particular, when the content exceeds 0.030% by mass, the degree of embrittlement may become significant. Therefore, the P content in the carbonitriding steel material of the present invention is set to 0.03% by mass or less.
本発明の浸炭窒化処理用鋼材におけるS含有率は0.03質量%以下であり、0.020質量%以下であることが好ましい。
このようなS含有率であると、MnSを形成し、被削性を向上させる作用がある。一方で、Sの含有量が0.030質量%を超えると、粗大なMnSを形成して、熱間鍛造性および曲げ疲労強度が低下する傾向がある。そのため、0.005~0.030質量%であることが好ましい。熱間鍛造性および曲げ疲労強度をより重視する場合、Sの含有量は0.020質量%以下が好ましい。 <S>
The S content in the carbonitriding steel material of the present invention is 0.03% by mass or less, preferably 0.020% by mass or less.
Such a S content has the effect of forming MnS and improving the machinability. On the other hand, when the S content exceeds 0.030% by mass, coarse MnS tends to be formed and the hot forgeability and bending fatigue strength tend to decrease. Therefore, it is preferably 0.005 to 0.030% by mass. If more emphasis is placed on hot forgeability and bending fatigue strength, the S content is preferably 0.020% by mass or less.
本発明の浸炭窒化処理用鋼材におけるCu含有率は0.3質量%以下%であり、0.001~0.3質量%であることが好ましく、0.03~0.3質量%であることがより好ましく、0.03~0.25質量%であることがさらに好ましい。
このようなCu含有率であると炭化物の生成が抑制され、焼入れ性が向上する。Cu含有率が高すぎると熱間加工性が低下する可能性がある。 <Cu>
The Cu content in the carbonitriding steel material of the present invention is 0.3% by mass or less, preferably 0.001 to 0.3% by mass, and 0.03 to 0.3% by mass. is more preferable, and 0.03 to 0.25% by mass is even more preferable.
With such a Cu content, the formation of carbides is suppressed and the hardenability is improved. If the Cu content is too high, the hot workability may deteriorate.
本発明の浸炭窒化処理用鋼材におけるNi含有率は2.5質量%以下であり、0.01~0.6質量%であることが好ましく、0.05~0.6質量%であることがより好ましい。
このようなNi含有率であると焼入れ性が高まり、靭性が向上する。また、非酸化性の元素であり、浸炭時に粒界酸化層の深さを増大せずに鋼表面を強靭化することができる。 <Ni>
The Ni content in the carbonitriding steel material of the present invention is 2.5% by mass or less, preferably 0.01 to 0.6% by mass, and more preferably 0.05 to 0.6% by mass. more preferred.
With such a Ni content, hardenability increases and toughness improves. In addition, it is a non-oxidizing element and can toughen the steel surface without increasing the depth of the grain boundary oxide layer during carburizing.
本発明の浸炭窒化処理用鋼材におけるCr含有率は0.5~3.0質量%であり、0.5~2.5質量%であることが好ましく、0.6~1.8質量%であることがより好ましい。
このようなCr含有率であると焼入れ性が向上し、被切削性も確保され、ピッチング疲労強度が向上し、靭性も向上する。
Cr含有率が高すぎると、硬度大きくなり、被削性が低下し、また、浸炭時に粗大なCr炭化物が生成することで、また、浸炭窒化時に結晶粒界に沿って粗大なCrN生成し、曲げ強度が低下する可能性がある。 <Cr>
The Cr content in the carbonitriding steel material of the present invention is 0.5 to 3.0% by mass, preferably 0.5 to 2.5% by mass, and more preferably 0.6 to 1.8% by mass. It is more preferable to have
With such a Cr content, hardenability is improved, machinability is ensured, pitting fatigue strength is improved, and toughness is also improved.
If the Cr content is too high, the hardness increases, the machinability decreases, and coarse Cr carbides are formed during carburizing, and coarse CrN is formed along grain boundaries during carbonitriding, Bending strength may decrease.
本発明の浸炭窒化処理用鋼材におけるMo含有率は0.001~1.0質量%であり、0.01~0.8質量%であることが好ましく、0.05~0.6質量%であることがより好ましい。
このようなMo含有率であると、焼入れ性が向上することで焼入れ処理した部品の芯部硬さが向上し、疲労強度が向上する。また、表面硬さ及び硬化層硬さを向上させる。
Mo含有率が低すぎると熱間鍛造後の強度が高くなり、切削加工性が加工する可能性がある。また、Mo含有率が高すぎると、析出核生成サイトを生成し、炭窒化物等の析出物の生成を促進してしまう傾向がある。また、未固溶の粗大な炭窒化物等が鋼中に残存し、浸炭窒化焼入れ時において、粗大な炭窒化物がさらに成長し粗大化し、これにより疲労強度が低下する可能性がある。 <Mo>
The Mo content in the carbonitriding steel material of the present invention is 0.001 to 1.0% by mass, preferably 0.01 to 0.8% by mass, and 0.05 to 0.6% by mass. It is more preferable to have
With such a Mo content, the hardenability is improved, so that the core hardness of the quenched part is improved, and the fatigue strength is improved. It also improves surface hardness and hardened layer hardness.
If the Mo content is too low, the strength after hot forging increases, and machinability may deteriorate. On the other hand, if the Mo content is too high, there is a tendency to generate precipitation nucleation sites and promote the formation of precipitates such as carbonitrides. In addition, undissolved coarse carbonitrides and the like remain in the steel, and during carbonitriding and quenching, the coarse carbonitrides grow further and coarsen, which may reduce the fatigue strength.
本発明の浸炭窒化処理用鋼材におけるAl含有率は0.01~0.08質量%であり、0.02~0.05質量%であることが好ましい。
このようなAl含有率であると、AlはNと結合しやすく、AlNを形成し、結晶粒を微細化して鋼を強化する作用を奏する。
Al含有率が高すぎると、硬質で粗大なAl2O3の形成により被削性が低下する可能性があり、また、大型硬質介在物としてのAl2O3が疲労破壊の起点となり、曲げ疲労強度やピッチング強度の低下の原因となる可能性がある。 <Al>
The Al content in the carbonitriding steel material of the present invention is 0.01 to 0.08% by mass, preferably 0.02 to 0.05% by mass.
With such an Al content, Al easily bonds with N, forms AlN, refines crystal grains, and strengthens the steel.
If the Al content is too high, there is a possibility that the machinability will decrease due to the formation of hard and coarse Al 2 O 3 , and Al 2 O 3 as large hard inclusions will become the origin of fatigue fracture, resulting in bending failure. It may cause a decrease in fatigue strength and pitting strength.
本発明の浸炭窒化処理用鋼材におけるN含有率は0.005~0.03質量%であり、0.01~0.025質量%であることが好ましく、0.01~0.020質量%であることがより好ましく、0.01~0.015質量%であることがさらに好ましい。
このようなN含有率であると窒化物形成により結晶粒が微細化し、曲げ疲労強度が向上する。
N含有率が高すぎると粗大窒化物が形成することで靭性が低下する可能性がある。 <N>
The N content in the carbonitriding steel material of the present invention is 0.005 to 0.03% by mass, preferably 0.01 to 0.025% by mass, and more preferably 0.01 to 0.020% by mass. more preferably 0.01 to 0.015% by mass.
With such an N content, the crystal grains are refined by the formation of nitrides, and the bending fatigue strength is improved.
If the N content is too high, formation of coarse nitrides may reduce the toughness.
本発明の浸炭窒化処理用鋼材はNbを含んでもよい。
本発明の浸炭窒化処理用鋼材におけるNb含有率は0.001~0.08質量%であることが好ましく、0.0015~0.06質量%であることがより好ましい。
このようなNb含有率であると微細な析出物(NbC)が生成することで、浸炭時の結晶粒が粗大化し難くなる。 <Nb>
The carbonitriding steel material of the present invention may contain Nb.
The Nb content in the carbonitriding steel material of the present invention is preferably 0.001 to 0.08% by mass, more preferably 0.0015 to 0.06% by mass.
With such an Nb content, fine precipitates (NbC) are generated, making it difficult for crystal grains to coarsen during carburizing.
本発明の浸炭窒化処理用鋼材はVを含んでもよい。
本発明の浸炭窒化処理用鋼材におけるV含有率は0.5質量%以下であることが好ましく、0.25質量%以下であることがより好ましい。
このようなV含有率であるとV析出物が分散して現れ、破壊特性が向上する。 <V>
The carbonitriding steel material of the present invention may contain V.
The V content in the carbonitriding steel material of the present invention is preferably 0.5% by mass or less, more preferably 0.25% by mass or less.
With such a V content, V precipitates appear dispersedly, and the fracture characteristics are improved.
本発明の浸炭窒化処理用鋼材はTiを含んでもよい。
本発明の浸炭窒化処理用鋼材におけるTi含有率は0.05質量%以下であることが好ましく、0.08質量%以下であることがより好ましく、0.012~0.04質量%であることがさらに好ましい。
このようなTi含有率であると微細な析出物(TiC)が生成することで、浸炭時の結晶粒が粗大化し難くなる。 <Ti>
The carbonitriding steel material of the present invention may contain Ti.
The Ti content in the carbonitriding steel material of the present invention is preferably 0.05% by mass or less, more preferably 0.08% by mass or less, and 0.012 to 0.04% by mass. is more preferred.
With such a Ti content, fine precipitates (TiC) are generated, making it difficult for crystal grains to coarsen during carburizing.
本発明の浸炭窒化処理用鋼材はBを含んでもよい。
本発明の浸炭窒化処理用鋼材におけるB含有率は0.0005~0.003質量%であることが好ましく、0.0006~0.0025質量%であることがより好ましい。
このようなB含有率であると焼入れ性が大幅に向上し、また割れ加工性が改善する。
B含有率が高すぎると、BNを形成し、深部での焼入れ性向上の効果が低下する。 <B>
The carbonitriding steel material of the present invention may contain B.
The B content in the carbonitriding steel material of the present invention is preferably 0.0005 to 0.003% by mass, more preferably 0.0006 to 0.0025% by mass.
With such a B content, the hardenability is greatly improved, and the crack workability is improved.
If the B content is too high, BN is formed and the effect of improving the hardenability at deep portions is reduced.
ここで不可避的不純物とは、意図的に添加しなくても原料や製造過程から混入する可能性がある成分を意味する。不可避的不純物として、具体的にはO、As等が挙げられる。 The steel material for carbonitriding treatment of the present invention contains C, Si, Mn, P, S, Cu, Ni, Cr, Mo, Al and N in the above contents, and further optionally includes Nb, V and Ti. and B may be contained at a specific content rate. The balance consists of Fe and unavoidable impurities.
Here, the unavoidable impurities mean components that may be mixed from raw materials or manufacturing processes even if they are not intentionally added. Specific examples of unavoidable impurities include O, As, and the like.
Si、Mn、P、Cu、Ni、Cr、Mo、V、Ti、Nbは蛍光X線分析法によって求めた値、Alは発光分光分析法、Oは不活性ガス中溶解-赤外線吸収法、C、Sは燃焼赤外線吸収法によって求めた値を意味するものとする。また、Nは不活性ガス中融解-熱伝導法、Bは発光分光分析法によって求めた値を意味するものとする。 The content of each component contained in the steel material for carbonitriding treatment of the present invention means the value obtained by measuring by the following method.
Si, Mn, P, Cu, Ni, Cr, Mo, V, Ti, Nb are values determined by fluorescent X-ray analysis, Al is by emission spectrometry, O is dissolved in an inert gas-infrared absorption method, C , S denote values determined by the combustion infrared absorption method. Further, N means the value obtained by melting in an inert gas-thermal conduction method, and B means the value obtained by the emission spectroscopic analysis method.
ここで浸炭窒化処理は特に限定されず、本発明の浸炭窒化処理用鋼材から本発明の浸炭窒化鋼材を得ることができる浸炭窒化処理であればよいが、例えば次のような浸炭窒化処理Xであってよい。
浸炭窒化処理Xは、ガス浸炭窒化、真空浸炭窒化の何れでもよい。また、浸炭窒化処理の諸条件(浸炭温度、浸炭ガスの種類、浸炭ガス圧、浸炭工程での処理時間、拡散工程での処理時間、冷却工程での冷却速度、窒化工程での窒化ガス圧、アンモニアガス量、処理時間、焼入れ温度等)は、浸炭窒化部品において要求される表層部の硬さ、焼戻し硬さに応じて適宜決定でき、特に限定されない。例えば、ガス浸炭窒化処理では、通常CP=0.5~1.0に制御し、浸窒ガスとしてアンモニアを使用し、アンモニア流量、炉内アンモニア濃度、拡散時間、焼入れ温度を調整することで、表面N濃度を制御し、焼入れを実施する。その後、100℃~300℃に加熱、1~3時間保持し、焼戻しを実施する。 The carbonitriding steel material of the present invention can be obtained by subjecting the steel material for carbonitriding treatment of the present invention having the above composition to carbonitriding treatment.
Here, the carbonitriding treatment is not particularly limited, and any carbonitriding treatment that can obtain the carbonitriding steel material of the present invention from the steel material for carbonitriding treatment of the present invention can be used. It's okay.
The carbonitriding treatment X may be either gas carbonitriding or vacuum carbonitriding. In addition, various conditions of carbonitriding (carburizing temperature, type of carburizing gas, carburizing gas pressure, treatment time in the carburizing process, treatment time in the diffusion process, cooling rate in the cooling process, nitriding gas pressure in the nitriding process, Ammonia gas amount, treatment time, quenching temperature, etc.) can be appropriately determined according to the surface layer hardness and tempering hardness required for carbonitriding parts, and are not particularly limited. For example, in gas carbonitriding, CP is usually controlled to 0.5 to 1.0, ammonia is used as the nitriding gas, and the ammonia flow rate, ammonia concentration in the furnace, diffusion time, and quenching temperature are adjusted. Hardening is performed by controlling the surface N concentration. Then, it is tempered by heating to 100° C. to 300° C. and holding for 1 to 3 hours.
本発明の浸炭窒化鋼材は、上記のような本発明の浸炭窒化処理用鋼材について浸炭窒化処理(例えば上記の浸炭窒化処理X)を施すことで得ることができる。 The carbonitriding steel material of the present invention will be described.
The carbonitriding steel material of the present invention can be obtained by subjecting the steel material for carbonitriding treatment of the present invention as described above to a carbonitriding treatment (for example, the carbonitriding treatment X described above).
本発明の浸炭窒化鋼材において表面C濃度は0.4~0.8質量%であることが好ましく、0.45~0.70質量%であることがより好ましい。
ここで表面C濃度は、本発明の浸炭窒化鋼材を、その表面から100μmの深さまで削り、得られた切り屑(ダライ粉)について燃焼-赤外線吸収法を適用して求めたC濃度を意味するものとする。 <Surface C concentration>
The carbonitrided steel material of the present invention preferably has a surface C concentration of 0.4 to 0.8% by mass, more preferably 0.45 to 0.70% by mass.
Here, the surface C concentration means the C concentration obtained by applying the combustion-infrared absorption method to the obtained chips (turning powder) by scraping the carbonitriding steel material of the present invention from the surface to a depth of 100 μm. shall be
本発明の浸炭窒化鋼材において表面N濃度は0.25~0.8質量%であることが好ましく、0.30~0.70質量%であることがより好ましい。
ここで表面N濃度は、本発明の浸炭窒化鋼材を、その表面から100μmの深さまで削り、得られた切り屑(ダライ粉)について融解-熱伝導度測定を適用して求めたN濃度を意味するものとする。 <Surface N concentration>
The carbonitrided steel material of the present invention preferably has a surface N concentration of 0.25 to 0.8% by mass, more preferably 0.30 to 0.70% by mass.
Here, the surface N concentration means the N concentration obtained by cutting the carbonitrided steel material of the present invention from the surface to a depth of 100 μm and applying the fusion-thermal conductivity measurement to the obtained chips (turning powder). It shall be.
式1:表面C濃度(質量%)+12/14×表面N濃度(質量%)=0.6~1.4
式1の計算結果は0.7~1.2であることが好ましい。 In the carbonitrided steel material of the present invention, the surface C concentration and the surface N concentration as described above satisfy the following formula 1.
Formula 1: Surface C concentration (% by mass) + 12/14 x Surface N concentration (% by mass) = 0.6 to 1.4
The calculation result of Equation 1 is preferably 0.7 to 1.2.
式2:129.7805×[Cr(質量%)]-76.9797×[Cr(質量%)]2+339.3375×[表面N濃度(質量%)]-539.345×[表面N濃度(質量%)]2+181.4983×[Cr(質量%)]×[表面N濃度(質量%)]+437.6799>560 In the carbonitrided steel material of the present invention, the surface C concentration, the surface N concentration, and the Cr content as described above satisfy the following formula 2.
Formula 2: 129.7805×[Cr (mass%)]−76.9797×[Cr (mass%)] 2 +339.3375×[Surface N concentration (mass%)]−539.345×[Surface N concentration ( % by mass)] 2 +181.4983×[Cr (% by mass)]×[Surface N concentration (% by mass)]+437.6799>560
以下、本発明の実施例について説明する。
第1表に示す実施例1~31および比較例1~19の各々について、表1および表2に示す組成(単位は質量%であり、残部はFe及び不可避不純物)となるように原料を混合し、150kg高周波誘導炉を用いて溶製し、鋳造して鋼塊Aを得た。 <Production of test piece>
Examples of the present invention will be described below.
For each of Examples 1 to 31 and Comparative Examples 1 to 19 shown in Table 1, the raw materials were mixed so as to have the compositions shown in Tables 1 and 2 (the unit is mass%, the balance being Fe and unavoidable impurities). Then, a steel ingot A was obtained by melting using a 150 kg high-frequency induction furnace and casting.
ガス浸炭窒化炉へ丸棒を載置し、930℃の温度で浸炭ガス(エンリッチガスとしてプロパンガスを使用)を導入し、一酸化炭素と二酸化炭素の分圧を調整することでCP(カーボンポテンシャル)を0.7に制御し、浸炭を実施した。 Here, the carburizing treatment is the following treatment.
A round bar is placed in a gas carbonitriding furnace, a carburizing gas (propane gas is used as an enrichment gas) is introduced at a temperature of 930°C, and CP (carbon potential) is adjusted by adjusting the partial pressure of carbon monoxide and carbon dioxide. ) was controlled to 0.7, and carburization was carried out.
上記の浸炭処理を施した後の丸棒を850℃に降温し、CPを一定に保った状態で窒化ガスとしてアンモニアガスを導入し、窒化処理を実施した。なお、窒化処理を実施した後、120℃のセミホット油で焼入れを行った。さらに次の処理として、焼入れを施した後の丸棒を160℃に調整した炉内に2時間裁置して加熱した後、炉から出し、室内で放冷する焼戻し処理を実施した。 Further, the nitriding treatment is the following treatment.
After the above carburizing treatment, the temperature of the round bar was lowered to 850° C., and ammonia gas was introduced as a nitriding gas while keeping the CP constant, and the nitriding treatment was performed. After the nitriding treatment, quenching was performed with semi-hot oil at 120°C. As the next treatment, the quenched round bar was placed in a furnace adjusted to 160° C. for 2 hours, heated, taken out of the furnace, and allowed to cool in a room for tempering.
上記の浸炭処理および窒化処理を施した試験片(一部は浸炭処理のみを施した試験片)について、その表面から100μmの深さまでを削り、得られた切り屑(ダライ粉)におけるC濃度およびN濃度を測定した。C濃度の測定には燃焼-赤外線吸収法を用い、N濃度の測定には融解-熱伝導度測定を用いた。
結果を第1表に示す。 <Surface C density, surface N density>
For the above carburized and nitrided test pieces (some of which were only carburized), the surface was scraped to a depth of 100 μm, and the C concentration and N concentration was measured. A combustion-infrared absorption method was used to measure the C concentration, and a fusion-thermal conductivity measurement was used to measure the N concentration.
The results are shown in Table 1.
上記の浸炭処理および窒化処理を施した試験片(一部は浸炭処理のみを施した試験片)について、その表面を鏡面研磨し、表面から0.05mmの位置の硬さをJIS Z 2244に基づき、荷重2.94Nで測定した。
結果を表1および表2に示す。 <Surface hardness at room temperature>
For the above carburized and nitrided test pieces (some of which were only carburized), the surface was mirror-polished, and the hardness at a position 0.05 mm from the surface was measured according to JIS Z 2244. , and a load of 2.94N.
Results are shown in Tables 1 and 2.
上記の浸炭処理および窒化処理を施した試験片(一部は浸炭処理のみを施した試験片)を500℃に調整した炉内に3時間載置して加熱した後、炉から出し、室内で放冷する焼戻し処理を施した。そして、その後、その表面を鏡面研磨し、表面から0.05mmの位置の硬さをJIS Z 2244に基づき、荷重2.94Nで測定した。
結果を表1および表2に示す。 <Surface hardness when tempered at 500°C>
The above carburized and nitrided test pieces (some of which were only carburized) were placed in a furnace adjusted to 500 ° C. for 3 hours and heated, then taken out of the furnace and placed in a room. A tempering treatment was performed by standing to cool. After that, the surface was mirror-polished, and the hardness at a position 0.05 mm from the surface was measured with a load of 2.94 N based on JIS Z 2244.
Results are shown in Tables 1 and 2.
上記の鋼塊Aから同様の工程で丸棒を製造し、機械加工して小ロータを得た。小ローラ1は、図1に示すような直径26mm、幅28mmの接触部2、その両側に配置される直径22mmの小径部4からなる。
そして、小ロータについて浸炭処理および窒化処理を施して、試験片を得た。
次に、試験片の相手側となる大ローラを用意した。大ローラは材質がSUJ2でHRC61となるように焼入れ焼戻し処理を実施した。なお、大ローラの曲率半径は150Rとした。
そして、ローラピッチング試験を行った。ローラピッチング試験では、試験片と相手側大ローラとを2.0~4.0GPaの種々の面圧で、回転数:3000rpmで接触させ、ローラピッチング試験機を用いてそれらを滑り率:-100%で回転させ、107サイクルでピッチングを生じない負荷応力を面疲労強度(ピッチング疲労強度)とした。そしてJIS SCR420の真空浸炭材に対する面疲労強度を、ぞれぞれの試験片において求めた。すなわち、疲労強度寿命比は(試験片の面疲労強度/JIS SCR420の真空浸炭材の面疲労強度)を意味する。
結果を表1および表2に示す。 <Fatigue strength life ratio>
A round bar was produced from the above steel ingot A in the same process and machined to obtain a small rotor. As shown in FIG. 1, the small roller 1 comprises a contact portion 2 having a diameter of 26 mm and a width of 28 mm and small diameter portions 4 having a diameter of 22 mm arranged on both sides thereof.
Then, the small rotor was subjected to carburizing treatment and nitriding treatment to obtain a test piece.
Next, a large roller was prepared as the opposite side of the test piece. The large roller was made of SUJ2 and was quenched and tempered so as to have HRC61. The radius of curvature of the large roller was set to 150R.
Then, a roller pitching test was performed. In the roller pitching test, the test piece and the mating large roller are brought into contact with each other at various surface pressures of 2.0 to 4.0 GPa at a rotation speed of 3000 rpm, and a roller pitching tester is used to determine the slip rate: -100. %, and the load stress that does not cause pitting in 10 7 cycles was taken as the surface fatigue strength (pitting fatigue strength). Then, the surface fatigue strength against the vacuum carburized material of JIS SCR420 was determined for each test piece. That is, the fatigue strength life ratio means (surface fatigue strength of test piece/surface fatigue strength of vacuum carburized material of JIS SCR420).
Results are shown in Tables 1 and 2.
上記の鋼塊Aを機械加工して負荷ローラー側、試験ローラー側の二つの試験片を得た。
試験片は直径78mm、幅18mmからなり、負荷ローラー側の曲率半径は700Rとした。
そして、試験片について、浸炭処理および窒化処理を施して、試験片を得た。
そしてローラーピッチング試験機を用いて焼付き試験を行った。
焼付き試験では上記で作製した二つの試験片をあるすべり速度下(2.0~20.0m/s)で荷重を60秒ごとに0.05GPaずつ段階的に増加させた。
焼付き判定は、負荷側に設置したトルク計のトルクが急上昇した時点とし、その際の荷重を焼付き荷重とした。
そして、JIS SCR420の真空浸炭材に対する面疲労強度を、それぞれの試験片において求めた。
すなわち、焼付き限界荷重比は「試験片の焼付き荷重/JIS SCR420の真空浸炭材の焼付き荷重」を意味する。
実施例1~31および比較例1~19の各々について焼付き限界荷重を測定した。
結果を表3および表4に示す。 <Seizure limit load ratio>
Steel ingot A was machined to obtain two specimens, one on the load roller side and one on the test roller side.
The test piece had a diameter of 78 mm and a width of 18 mm, and the radius of curvature on the load roller side was 700R.
Then, the test piece was subjected to carburizing treatment and nitriding treatment to obtain a test piece.
Then, a seizure test was conducted using a roller pitting tester.
In the seizure test, the load was increased stepwise by 0.05 GPa every 60 seconds under a certain sliding speed (2.0 to 20.0 m/s) on the two test pieces prepared above.
Seizure was determined at the time when the torque of the torque meter installed on the load side suddenly increased, and the load at that time was taken as the seizure load.
Then, the surface fatigue strength against the vacuum carburized material of JIS SCR420 was determined for each test piece.
That is, the seizure limit load ratio means "seizure load of test piece/seizure load of vacuum carburized material of JIS SCR420".
The seizure limit load was measured for each of Examples 1-31 and Comparative Examples 1-19.
The results are shown in Tables 3 and 4.
図2から、実施例は比較例に対して、いずれもが向上していることを確認できる。 FIG. 2 shows the relationship between the surface hardness when tempering at 500° C. shown in Tables 1 and 2 and the fatigue strength life ratio (life ratio under high-speed roller pitting conditions).
From FIG. 2, it can be confirmed that the example is improved in all respects as compared with the comparative example.
図3から、実施例は比較例に対して、いずれもが向上していることを確認できる。 3 shows the relationship between the surface hardness when tempering at 500° C. shown in Tables 1 and 2 and the seizure limit load ratio shown in Tables 3 and 4. FIG.
From FIG. 3, it can be confirmed that the example is improved in all respects as compared with the comparative example.
2 接触部
4 小径部
1 small roller 2 contact part 4 small diameter part
Claims (7)
- C:0.1~0.3質量%、
Si:0.3質量%以下、
Mn:0.4~2.0質量%、
P:0.03質量%以下、
S:0.03質量%以下、
Cu:0.3質量%以下、
Ni:2.5質量%以下、
Cr:0.5~3.0質量%、
Mo:0.001~1.0質量%、
Al:0.01~0.08質量%、
N:0.005~0.03質量%、
で含有し、残部はFeおよび不可避的不純物からなり、
浸炭窒化を施すことで、
式1:表面C濃度(質量%)+12/14×表面N濃度(質量%)=0.6~1.4
を満たし、
式2:129.7805×[Cr(質量%)]-76.9797×[Cr(質量%)]2+339.3375×[表面N濃度(質量%)]-539.345×[表面N濃度(質量%)]2+181.4983×[Cr(質量%)]×[表面N濃度(質量%)]+437.6799>560
を満たし、
前記浸炭窒化を施した後に500℃で焼戻し処理を施した場合に、表面から0.05mmの深さの部分における硬さが560HV以上である浸炭窒化鋼材が得られる、浸炭窒化処理用鋼材。 C: 0.1 to 0.3% by mass,
Si: 0.3% by mass or less,
Mn: 0.4 to 2.0% by mass,
P: 0.03% by mass or less,
S: 0.03% by mass or less,
Cu: 0.3% by mass or less,
Ni: 2.5% by mass or less,
Cr: 0.5 to 3.0% by mass,
Mo: 0.001 to 1.0% by mass,
Al: 0.01 to 0.08% by mass,
N: 0.005 to 0.03% by mass,
and the balance consists of Fe and unavoidable impurities,
By applying carbonitriding,
Formula 1: Surface C concentration (% by mass) + 12/14 x Surface N concentration (% by mass) = 0.6 to 1.4
The filling,
Formula 2: 129.7805×[Cr (mass%)]−76.9797×[Cr (mass%)] 2 +339.3375×[Surface N concentration (mass%)]−539.345×[Surface N concentration ( % by mass)] 2 +181.4983×[Cr (% by mass)]×[Surface N concentration (% by mass)]+437.6799>560
The filling,
A steel material for carbonitriding treatment that provides a carbonitriding steel material having a hardness of 560 HV or more at a depth of 0.05 mm from the surface when tempering treatment is performed at 500° C. after the carbonitriding treatment. - Nb:0.001~0.08質量%、
V:0.5質量%以下、
Ti:0.05質量%以下、および
B:0.0005~0.003質量%、
からなる群から選ばれる少なくとも一種をさらに含有する、請求項1に記載の浸炭窒化処理用鋼材。 Nb: 0.001 to 0.08% by mass,
V: 0.5% by mass or less,
Ti: 0.05% by mass or less, and B: 0.0005 to 0.003% by mass,
The carbonitriding steel material according to claim 1, further comprising at least one selected from the group consisting of: - C:0.15~0.25質量%、
Si:0.01~0.24質量%、
Mn:0.5~1.8質量%、
Cu:0.001~0.3質量%、
Ni:0.01~0.6質量%、
Cr:0.6~1.8質量%、
Mo:0.01~0.8質量%、
Al:0.02~0.05質量%、
N:0.01~0.025質量%、
で含有し、
Nb:0.0015~0.06質量%、
V:0.25質量%以下、
Ti:0.012~0.04質量%、および
B:0.0006~0.0025質量%、
からなる群から選ばれる少なくとも一種をさらに含有し、残部はFeおよび不可避的不純物からなり、
前記浸炭窒化を施すことで、
式1:表面C濃度(質量%)+12/14×表面N濃度(質量%)=0.7~1.2を満たす浸炭窒化処理鋼材が得られる、請求項1または2に記載の浸炭窒化処理用鋼材。 C: 0.15 to 0.25% by mass,
Si: 0.01 to 0.24% by mass,
Mn: 0.5 to 1.8% by mass,
Cu: 0.001 to 0.3% by mass,
Ni: 0.01 to 0.6% by mass,
Cr: 0.6 to 1.8% by mass,
Mo: 0.01 to 0.8% by mass,
Al: 0.02 to 0.05% by mass,
N: 0.01 to 0.025% by mass,
contains with
Nb: 0.0015 to 0.06% by mass,
V: 0.25% by mass or less,
Ti: 0.012 to 0.04% by mass, and B: 0.0006 to 0.0025% by mass,
further contains at least one selected from the group consisting of the balance consisting of Fe and inevitable impurities,
By applying the carbonitriding,
The carbonitriding treatment according to claim 1 or 2, wherein a carbonitriding-treated steel material that satisfies Formula 1: surface C concentration (mass%) + 12/14 x surface N concentration (mass%) = 0.7 to 1.2 is obtained. steel material. - Cu:0.03~0.3質量%、
で含有する、請求項1~3のいずれか1項に記載の浸炭窒化処理用鋼材。 Cu: 0.03 to 0.3% by mass,
The steel material for carbonitriding treatment according to any one of claims 1 to 3, containing in. - Si:0.01~0.17質量%、
で含有する、請求項1~4のいずれか1項に記載の浸炭窒化処理用鋼材。 Si: 0.01 to 0.17% by mass,
The steel material for carbonitriding treatment according to any one of claims 1 to 4, containing in. - Cu:0.03~0.25質量%、
で含有する、請求項1~5のいずれか1項に記載の浸炭窒化処理用鋼材。 Cu: 0.03 to 0.25% by mass,
The steel material for carbonitriding treatment according to any one of claims 1 to 5, containing in. - 請求項1~6のいずれか1項に記載の浸炭窒化処理用鋼材を浸炭窒化処理してなり、
式1:表面C濃度(質量%)+12/14×表面N濃度(質量%)=0.6~1.4
を満たし、
式2:129.7805×[Cr(質量%)]-76.9797×[Cr(質量%)]2+339.3375×[表面N濃度(質量%)]-539.345×[表面N濃度(質量%)]2+181.4983×[Cr(質量%)]×[表面N濃度(質量%)]+437.6799>560
を満たし、
さらに500℃で焼戻し処理を施した場合に、表面から0.05mmの深さの部分における硬さが560HV以上となる、浸炭窒化鋼材。
Carbonitriding the steel material for carbonitriding according to any one of claims 1 to 6,
Formula 1: Surface C concentration (% by mass) + 12/14 x Surface N concentration (% by mass) = 0.6 to 1.4
The filling,
Formula 2: 129.7805×[Cr (mass%)]−76.9797×[Cr (mass%)] 2 +339.3375×[Surface N concentration (mass%)]−539.345×[Surface N concentration ( % by mass)] 2 +181.4983×[Cr (% by mass)]×[Surface N concentration (% by mass)]+437.6799>560
The filling,
A carbonitrided steel material which, when further tempered at 500° C., has a hardness of 560 HV or more at a depth of 0.05 mm from the surface.
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Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH08311603A (en) * | 1994-09-29 | 1996-11-26 | Nippon Seiko Kk | Rolling bearing |
JP2010070831A (en) * | 2008-09-22 | 2010-04-02 | Sumitomo Metal Ind Ltd | Carbonitrided component made of steel |
WO2016017162A1 (en) * | 2014-07-29 | 2016-02-04 | 新日鐵住金株式会社 | Steel for carbonitrided bearing |
JP2020029608A (en) * | 2018-08-24 | 2020-02-27 | 大同特殊鋼株式会社 | Steel for carbonitriding |
WO2020138458A1 (en) * | 2018-12-27 | 2020-07-02 | 日本製鉄株式会社 | Carbonitrided bearing component |
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- 2022-04-08 WO PCT/JP2022/017420 patent/WO2022224849A1/en active Application Filing
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Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH08311603A (en) * | 1994-09-29 | 1996-11-26 | Nippon Seiko Kk | Rolling bearing |
JP2010070831A (en) * | 2008-09-22 | 2010-04-02 | Sumitomo Metal Ind Ltd | Carbonitrided component made of steel |
WO2016017162A1 (en) * | 2014-07-29 | 2016-02-04 | 新日鐵住金株式会社 | Steel for carbonitrided bearing |
JP2020029608A (en) * | 2018-08-24 | 2020-02-27 | 大同特殊鋼株式会社 | Steel for carbonitriding |
WO2020138458A1 (en) * | 2018-12-27 | 2020-07-02 | 日本製鉄株式会社 | Carbonitrided bearing component |
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