CN104114733A - Soft-nitriding steel and soft-nitrided component using steel as material - Google Patents
Soft-nitriding steel and soft-nitrided component using steel as material Download PDFInfo
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- CN104114733A CN104114733A CN201380009412.5A CN201380009412A CN104114733A CN 104114733 A CN104114733 A CN 104114733A CN 201380009412 A CN201380009412 A CN 201380009412A CN 104114733 A CN104114733 A CN 104114733A
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- tufftride
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- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 75
- 239000010959 steel Substances 0.000 title claims abstract description 75
- 239000000463 material Substances 0.000 title claims abstract description 51
- 238000005121 nitriding Methods 0.000 title abstract description 11
- 229910001563 bainite Inorganic materials 0.000 claims abstract description 38
- 239000002244 precipitate Substances 0.000 claims description 30
- 229910052758 niobium Inorganic materials 0.000 claims description 19
- 229910052720 vanadium Inorganic materials 0.000 claims description 19
- 239000012535 impurity Substances 0.000 claims description 5
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- 229910052804 chromium Inorganic materials 0.000 claims description 4
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 239000000203 mixture Substances 0.000 abstract description 9
- 238000012545 processing Methods 0.000 description 28
- 238000001556 precipitation Methods 0.000 description 21
- 238000005096 rolling process Methods 0.000 description 14
- 238000001816 cooling Methods 0.000 description 13
- 238000010438 heat treatment Methods 0.000 description 10
- 238000012360 testing method Methods 0.000 description 10
- 238000005255 carburizing Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 9
- 238000000034 method Methods 0.000 description 8
- 238000005242 forging Methods 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 238000010791 quenching Methods 0.000 description 5
- 239000006104 solid solution Substances 0.000 description 5
- 229910052719 titanium Inorganic materials 0.000 description 5
- 230000005540 biological transmission Effects 0.000 description 4
- 239000007789 gas Substances 0.000 description 4
- 238000003754 machining Methods 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 230000000171 quenching effect Effects 0.000 description 4
- 230000000996 additive effect Effects 0.000 description 3
- 229910052802 copper Inorganic materials 0.000 description 3
- 229910052757 nitrogen Inorganic materials 0.000 description 3
- 230000008520 organization Effects 0.000 description 3
- 229910001562 pearlite Inorganic materials 0.000 description 3
- 238000004881 precipitation hardening Methods 0.000 description 3
- 230000000630 rising effect Effects 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910001566 austenite Inorganic materials 0.000 description 2
- 238000005452 bending Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000010273 cold forging Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 238000005520 cutting process Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000006185 dispersion Substances 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
- 238000009863 impact test Methods 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 230000009466 transformation Effects 0.000 description 2
- 238000007514 turning Methods 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- 229910003310 Ni-Al Inorganic materials 0.000 description 1
- 229910011214 Ti—Mo Inorganic materials 0.000 description 1
- 229910001315 Tool steel Inorganic materials 0.000 description 1
- 238000000441 X-ray spectroscopy Methods 0.000 description 1
- 230000001133 acceleration Effects 0.000 description 1
- 238000003483 aging Methods 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000009661 fatigue test Methods 0.000 description 1
- KHYBPSFKEHXSLX-UHFFFAOYSA-N iminotitanium Chemical class [Ti]=N KHYBPSFKEHXSLX-UHFFFAOYSA-N 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000005764 inhibitory process Effects 0.000 description 1
- 238000007689 inspection Methods 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000003973 paint Substances 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 238000005204 segregation Methods 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000005496 tempering Methods 0.000 description 1
- 238000007669 thermal treatment Methods 0.000 description 1
Classifications
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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
-
- 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
- C21D6/002—Heat treatment of ferrous alloys containing Cr
-
- 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
- C22C38/22—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
- C22C38/32—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
- C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of 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
- C22C38/60—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
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/002—Bainite
Abstract
The present invention can provide soft-nitriding steel which has a predefined component composition and, before soft nitriding, excellent machinability by having a structure in which the bainite area ratio prior to soft nitriding is greater than 50%, and after soft nitriding, strength/toughness equal to that of a carburized material of conventional steel, for example, SCr420 steel and provides more superior fatigue characteristics.
Description
Technical field
The present invention relates to tufftride steel and the tufftride parts using this steel as former material, particularly relate to after tufftride material of excellent fatigue characteristics, preferably as tufftride steel and the tufftride parts using this steel as former material of automobile, construction Machines.
Background technology
For the machine structural parts such as the gear of automobile, require good fatigue characteristic, convention is to implement surface hardening processing.As surface hardening processing, know have carburizing treatment, high-frequency quenching process and nitriding treatment.
Carburizing treatment makes C infiltrate, spread in the austenitic area of high temperature, therefore, can obtain darker hardening depth, and for improving, fatigue strength is effective.
But, owing to producing thermal treatment strain, be therefore difficult to be applied to the parts that require strict dimensional precision from viewpoints such as solemn silence.
High-frequency quenching processing is the processing of skin section being quenched by high-frequency induction heating, poor with carburizing treatment same size precision.
Nitriding treatment is at Ac
1in the temperature range below transformation temperature, make that nitrogen infiltrates, thereby diffusion improves the processing of surface hardness, but the treatment time reach 50～100 hours, and after processing need the more crisp compound layer on top layer to remove.
Therefore, developed with the treatment temp of nitriding treatment same degree under carry out the tufftride processing of nitrogenize with the short period of time, be widely used as object with parts etc. taking physical construction in recent years.Make N and C infiltrate simultaneously, spread and make case-hardened processing thereby tufftride processing is the temperature range within the scope of 500～600 DEG C, compared with existing nitriding treatment, can make the treatment time is below half.
But, in carburizing treatment, can make core hardness raise by quench hardening, on the other hand, in tufftride is processed, owing to processing at the temperature below the transformation temperature of steel, therefore core hardness does not raise, and compared with carburizing treatment material, it is poor that tufftride is processed the fatigue strength of material.
Process the fatigue strength of material in order to improve tufftride, conventionally before tufftride by quenching, temper raises core hardness, but the fatigue strength obtaining is difficult to be called fully, and manufacturing cost rising, machinability also reduces.
In order to solve such problem, following technical scheme is proposed: the one-tenth of steel is grouped into the one-tenth that is set as containing Ni, Al, Cr, Ti and is grouped into, in the time of tufftride, for core, utilize Ni-Al, Ni-Ti series intermetallic compound or Cu compound to make its age hardening, for surface, make nitride or the carbide precipitation-hardening in nitride layer (patent documentation 1, patent documentation 2) of Cr, Al, Ti etc.
In patent documentation 3, record following technical scheme: by forge hot, the steel that contains 0.5～2%Cu is forged after extension, carry out air cooling and form solid solution have the ferrite subject organization of Cu, in the tufftrides of 580 DEG C × 120 minutes are processed, Cu is separated out, and then the also precipitation-hardening of coupling Ti, V, Nb carbonitride, thereby after processing, tufftride forms the steel that possesses good Flexural fatigue.In patent documentation 4, disclose and be dispersed with Ti-Mo carbide and be further dispersed with therein one or more the tufftride steel of carbide comprising in Nb, V, W.
Prior art document
Patent documentation
Patent documentation 1: Japanese kokai publication hei 5-59488 communique
Patent documentation 2: Japanese kokai publication hei 7-138701 communique
Patent documentation 3: TOHKEMY 2002-69572 communique
Patent documentation 4: TOHKEMY 2010-163671 communique
Summary of the invention
Invent problem to be solved
But, although the tufftride steel described in patent documentation 1,2 has improved bending fatigue strength by the precipitation-hardening of Cu etc., but the guaranteeing of processibility is difficult to be called fully, and the tufftride steel described in patent documentation 3 need to add relatively large Cu, Ti, V, Nb, and production cost is high.Tufftride described in patent documentation 4 contains relatively large Ti, Mo with steel, therefore has the problem that production cost is high.
Therefore, the object of the present invention is to provide a kind of tufftride steel and the tufftride parts using this steel as former material, this tufftride has the character that hardness is low and machinability is good before tufftride with steel, core hardness can be improved by tufftride processing, and the tufftride parts of material of excellent fatigue characteristics can be manufactured less expensively.
For the method for dealing with problems
In order to address the above problem, the impact that contriver brings the fatigue characteristic after the tufftride of steel for tissue, composition conducts in-depth research.Result obtains following opinion: the steel that the V that contains specified quantitative, Nb are organized as steel composition and before using bainite subject organization as tufftride are implemented tufftride processing, utilize temperature now to raise, make Precipitation in the core tissue of fine precipitate beyond the skin section of tufftride, improve thus core hardness, if like this, can obtain good fatigue characteristic after tufftride.
The present invention further studies based on above-mentioned opinion and obtains, and its feature is as follows.
1. a tufftride steel, in quality %, contain C:0.01% above and lower than 0.10%, Si:1.0% following, Mn:0.5～3.0%, Cr:0.30～3.0%, Mo:0.005～0.4%, V:0.02～0.5%, Nb:0.003～0.15%, Al:0.005～0.2%, S:0.06% is following, P:0.02% is following and B:0.0003～0.01%, surplus is made up of Fe and inevitable impurity, and described tufftride has the tissue that bainite area occupation ratio is greater than 50% before tufftride with steel.
2. the tufftride steel as described in above-mentioned 1 wherein, after tufftride, disperses to separate out the precipitate that contains V, Nb in Bainite Phases of Some.
3. tufftride parts, it uses steel as former material using the tufftride described in above-mentioned 1 or 2.
Invention effect
According to the present invention, can obtain tufftride steel and the tufftride parts using this steel as former material, steel excellent in machinability before tufftride for this tufftride, after tufftride, there is intensity and the toughness equal with the carburized material of for example SCr420 steel of existing steel, also possess good fatigue characteristic, the present invention is industrially exceedingly useful.
Brief description of the drawings
Fig. 1 represents for manufacturing the schematic diagram of the manufacturing process of tufftride parts with tufftride of the present invention steel.
Embodiment
Below tufftride of the present invention is become to be grouped into and to create conditions with the microstructure of steel and describe.
1. microstructure
Make the bainite area occupation ratio of the microstructure before tufftride be greater than 50%, and after tufftride, be formed in Bainite Phases of Some disperse to separate out have V, the tissue of Nb precipitate.Be that bainite area occupation ratio is greater than 50% bainite subject organization in the case of making parent phase before tufftride, compared with the situation of ferrite-pearlite tissue, significantly suppressed V, the generation of Nb precipitate in parent phase.As a result, can suppress that V, Nb precipitate separate out before tufftride and the hardness of the steel that causes raises, the machinability conventionally carrying out before tufftride is improved.In addition, if it is implemented to tufftride processing, when skin section is nitrided, in the core bainite structure beyond the nitrogenize portion of top layer, V, Nb precipitate Precipitation, thus core hardness is raise.As a result, the fatigue strength after tufftride and intensity significantly improve.
It should be noted that, in the present invention, bainite area occupation ratio is greater than 50% tissue and refers to that the area occupation ratio of observing bainite structure (phase) in (the opticmicroscope structure observations of 200 times) at section structure is greater than 50%.Preferably make the area occupation ratio of bainite structure be greater than 60%, more preferably greater than 80%.In addition, as the V separating out, Nb precipitate, be preferably dispersed with the nano-precipitation that particle diameter is less than 10nm in bainite structure.From the viewpoint of abundant precipitation strength, V, Nb precipitate that further preferably this particle diameter is less than 10nm are at every 1 μ m
2middle existence is more than 500.
2. become to be grouped into
The restriction reason being grouped into the one-tenth in steel for tufftride of the present invention describes.Below, the % of composition of steel is quality %.
More than C:0.01% and lower than 0.10%
C adds with guaranteeing intensity in order to generate bainite structure.C addition is lower than 0.01% time, and bainite growing amount reduces, and V, Nb precipitate amount reduce simultaneously, are difficult to guarantee intensity.On the other hand, if add more than 0.10% C, the hardness of bainite structure increases, and machinability declines.Therefore, C addition is set as more than 0.01% and lower than in 0.10% scope.More preferably more than 0.03% and lower than 0.10%.
Below Si:1.0%
Si is for deoxidation effectively and generate bainite structure and add, if Si addition is greater than 1.0%, and can be because the solution hardening of ferrite and bainite structure causes machinability and cold-workability variation.Therefore, Si addition is set as below 1.0%.More preferably below 0.5%.More preferably below 0.3%.In addition, in order to make Si effectively contribute to deoxidation, preferably Si addition is set as more than 0.01%.
Mn：0.5～3.0％
Mn adds in order effectively to generate bainite structure and raising intensity.Mn addition is lower than 0.5% time, and bainite structure growing amount reduces, and generates V, Nb precipitate, and therefore before tufftride, hardness increases, and tufftride V after treatment, Nb precipitate growing amount reduce simultaneously, lower hardness after tufftride and be difficult to guarantee intensity.On the other hand, if Mn addition is greater than 3.0%, can make machinability and cold-workability variation.Therefore, Mn addition is set as in 0.5～3.0% scope.More preferably more than 0.5% and below 2.5%.More preferably more than 0.6% and below 2.0%.
Cr：0.30～3.0％
Cr adds in order effectively to generate bainite structure.Cr addition is lower than 0.30% time, and bainite structure growing amount reduces, and generates V, Nb precipitate, and therefore before tufftride, hardness increases, and tufftride V after treatment, Nb precipitate growing amount reduce simultaneously, lower hardness after tufftride and be difficult to guarantee intensity.On the other hand, if Cr addition is greater than 3.0%, can make machinability and cold-workability variation.Therefore, Cr addition is set as in 0.30～3.0% scope.More preferably more than 0.5% and below 2.0%.More preferably more than 0.5% and below 1.5%.
V：0.02～0.5％
Thereby V is the temperature during by tufftride to raise and form the important element that nano-precipitation makes core hardness increase, intensity is improved together with Nb.If V addition is lower than 0.02%, additive effect is poor.On the other hand, if V addition is greater than 0.5%, can cause precipitate coarsening.Therefore, V addition is set as in 0.02～0.5% scope.More preferably more than 0.03% and below 0.3%.More preferably more than 0.03% and below 0.25%.
Nb：0.003～0.15％
The temperature of Nb during by tufftride raises and form nano-precipitation together with V, for increasing core hardness, to improve for fatigue strength be extremely effective element.If Nb addition is lower than 0.003%, additive effect is poor.On the other hand, if Nb addition is greater than 0.15%, precipitate coarsening.Therefore, Nb addition is set as in 0.003～0.15% scope.More preferably more than 0.02% and below 0.12%.
Mo：0.005～0.4％
Making V, the fine effect of separating out the intensity that improves tufftride processing material of Nb precipitate thereby Mo has, is important element in the present invention.In addition, Mo is also effective for generating bainite structure.Add more than 0.005% in order to improve intensity, but owing to being expensive element, be greater than 0.4% if add, can cause the rising of composition cost.Therefore, Mo addition is set as in 0.005～0.4% scope.More preferably 0.01～0.3%.More preferably 0.04～0.2%.
Al：0.005～0.2％
Al is effective element for the surface hardness and the effective case depth that improve after tufftride, add on one's own initiative.In addition, the austenite crystal growth during by inhibition forge hot makes to organize miniaturization, being also useful element aspect raising toughness, therefore adds more than 0.005%.On the other hand, be greater than 0.2% even if contain, its effect is also saturated, can produce on the contrary and cause the disadvantageous effect that composition cost raises.Therefore, Al addition is set as in 0.005～0.2% scope.Be preferably greater than 0.020% and be below 0.1%.Further be preferably greater than 0.020% and be below 0.040%.
Below S:0.06%
S forms MnS and the useful element that improves machinability in steel, if but content is greater than 0.06% infringement toughness.Therefore, S addition is set as below 0.06%.Be preferably below 0.04%.In addition, the effect improving in order to show machinability that S brings, is preferably set as S addition more than 0.002%.
Below P:0.02%
P makes grain-boundary strength reduce in austenite grain boundary generation segregation, cause thus intensity, toughness drop.Therefore, P content preferably reduces as far as possible, but allows to 0.02%.Therefore, P content is set as below 0.02%.In addition, P is needed expensive lower than 0.001%, be therefore reduced to 0.001% industrial.
B：0.0003～0.01％
B has the effect that promotes that bainite structure generates.If B addition is lower than 0.0003%, additive effect is poor.On the other hand, even if add the B that is greater than 0.01%, its effect is also saturated, can cause the rising of composition cost.Therefore, B addition is set as in 0.0003～0.01% scope.More preferably be set as more than 0.0010% and below 0.01%.
It should be noted that, the effect generating in order to be promoted bainite structure, preferably B is solid-solubilized in steel.But the in the situation that of there is solid solution N in steel, the B in steel is consumed by the formation of BN, when B exists with the form of BN in steel, be helpless to the raising of hardening capacity.Therefore, there is solid solution N in steel time, B preferably adds by the amount more than amount that formation consumed of BN, and preferably between the amount of the B in steel (%B) and N amount (%N), makes the relation that following (1) formula represents set up.
％B≥％N/14×10.8+0.0003---(1)
Tufftride of the present invention is with in steel, after forging or when the machinability that makes tufftride process material improves, can add and be selected from more than one in Pb≤0.2%, Bi≤0.02%.It should be noted that, effect of the present invention can't and have or not interpolation impaired because of the content of these elements.
In addition, tufftride of the present invention is with in steel, and the surplus beyond above-mentioned interpolation element is Fe and inevitable impurity, especially Ti, not only the precipitation strength of V, Nb is brought to detrimentally affect, and core hardness is reduced, and therefore will not contain as far as possible.Preferably lower than 0.010%, further preferably lower than 0.005%.
3. create conditions
Fig. 1 represents to manufacture the schematic diagram of the manufacturing process of tufftride parts with tufftride of the present invention steel.
In Fig. 1, S1 represents the manufacturing process as the bar steel of former material, and S2 represents to carry operation, and S3 represents goods (tufftride parts) finishing step.
That is, in bar steel manufacturing process (S1), steel ingot is carried out hot rolling and makes bar steel, in the laggard luggage fortune of quality inspection.Then, after shipment, for the bar steel that is transferred (S2), in goods (tufftride parts) finishing steps (S3), above-mentioned bar steel is cut into predetermined size, carry out forge hot or cold forging, make after desired shape by the machining such as bit bore, turning as required, carry out tufftride processing and making articles.
In addition, sometimes directly by the machining such as turning, bit bore, hot-finished material is finish-machined to desired shape, then carries out tufftride processing and making articles.It should be noted that, in the situation of forge hot, after forge hot, can also carry out cold straightening.In addition, sometimes to end article paint, the overlay film processing such as plating.Below to preferably creating conditions and describe.
Rolling Heating temperature
Rolling Heating temperature is preferably set in the scope of 950～1250 DEG C.This be because, tufftride of the present invention is with in steel, in order not damage forging owing to separating out nano-precipitation in rolling stock (as the bar steel of the former material of hot-forged parts), solid solution when residual carbide is in hot rolling making in the time of fusing.
,, while making rolling Heating temperature lower than 950 DEG C, from when fusing, residual carbide is difficult to solid solution.On the other hand, if rolling Heating temperature higher than 1250 DEG C, coarse grains, forge property easy variation.Therefore, rolling Heating temperature is preferably set in the scope of 950 DEG C～1250 DEG C.
Rolling end temp
Rolling end temp is preferably set to more than 800 DEG C.This be because, rolling end temp is during lower than 800 DEG C, can generate ferritic structure, therefore, as subsequent handling, particularly implement tufftride after cold forging or machining in the situation that, be disadvantageous for obtain being greater than 50% bainite structure using area occupation ratio after tufftride as parent phase.In addition also because, if rolling end temp lower than 800 DEG C, rolling load is high, the roundness variation of rolling stock.Therefore, rolling end temp is preferably set to more than 800 DEG C.
Speed of cooling
Thereby preferably specify to make nano-precipitation to separate out before forging to the speed of cooling after rolling and do not damage forging.The speed of cooling that preferably can obtain the critical cooling rate (0.5 DEG C/sec) of nano-precipitation to be greater than in 700～550 DEG C of the Precipitation Temperature scopes of nano-precipitation is carried out cooling.
Tufftride processing (separating out processing)
Using obtained bar steel as former material, after forging, make component shape by machining etc.Then, carry out tufftride processing.For the nano-precipitation that contains V, Nb is separated out, tufftride is preferably set as tufftride treatment temp in the scope of 550～700 DEG C, will be set as in the treatment time more than 10 minutes in processing.This be because, if lower than 550 DEG C, can not obtain the precipitate of q.s, on the other hand, if higher than 700 DEG C, reach austenitic area and be difficult to carry out tufftride.In addition, the scope of 550～630 DEG C more preferably.In addition, the treatment time being set as 10 minutes is because can obtain V, the Nb precipitate of q.s above.
It should be noted that, in the situation that using forge hot, be to be greater than 50% bainite structure and the cold straightening from forge hot and the viewpoint of machinability in area occupation ratio in order to make parent phase after tufftride, preferably the Heating temperature in the time making forge hot be in the scope of 950～1250 DEG C, make to forge end temp be more than 800 DEG C and make to forge after speed of cooling be greater than under the condition of 0.5 DEG C/sec and carry out forge hot, so that nano-precipitation can not be separated out.
Embodiment
Then, by embodiment, the present invention is further described.
The steel (steel No.1～17) of composition shown in 150kg table 1 is carried out to melting in vacuum melting furnace, to be rolled in the condition of 1150 DEG C of heating, 970 DEG C of end, then, be cooled to room temperature with the speed of cooling of 0.9 DEG C/sec, the bar steel of preparation 50mm φ.No.17 is current material JISSCr420.It should be noted that, for all steel in table 1, all initiatively do not add P.Therefore, the P content in table 1 represents the value of sneaking into as inevitable impurity.In addition, with regard to Ti, adding for the steel No.14 in table 1 and steel No.15, is not initiatively to add for steel No.1～13 and steel No.16～17.Therefore,, in table 1, the Ti content of steel No.1～13 and steel No.16～17 all represents the value of sneaking into as inevitable impurity.
These former materials to be further heated to after 1200 DEG C, at 1100 DEG C, to carry out forge hot, make 30mm φ, be cooled to room temperature with the speed of cooling of 0.8 DEG C/sec, and in order comparing, a part to be cooled to room temperature with the speed of cooling of 0.1 DEG C/sec.
For above-mentioned former material, carry out the investigation of structure observation, measurement of hardness and machinability.Structure observation is to utilize opticmicroscope pair cross-section observe and identify core tissue, and exists the former material of Bainite Phases of Some to obtain the area percent of the Bainite Phases of Some of core to core.In addition, machinability is tested and is evaluated by bit cutting.Particularly, forge hot material is cut into 20mm thickness, using the material of gained as test materials, utilize the straight shank drill of the 6mm φ of JIS rapid tool steel SKH51 to open communicating pores with the condition of feeding: 0.15mm/rev, rotating speed: 795rpm at 5 places in every 1 cross section, with till total hole count that drill bit can not cut evaluate.
In addition, measurement of hardness is to use Vickers hardness tester with the test load of 100g, the hardness of core to be investigated.
Steel No.1～16th, further implements gas soft nitriding processing to forge hot material, and steel No.17 implements gas cementation processing to forge hot material.Gas soft nitriding is processed and is passed through at NH
3: N
2: CO
2under the atmosphere of=50:45:5, be heated to 570～620 DEG C and keep carrying out for 3.5 hours.Gas cementation process with at 930 DEG C, carry out at 850 DEG C, keeping after carburizing in 3 hours 40 minutes, then carry out the such condition of oil cooling and implement, and then at 170 DEG C, carry out the tempering of 1 hour.
For these heat treatment materials, carry out observation, the impact characteristics of structure observation, measurement of hardness, precipitate and investigate and fatigue characteristic investigation.
Structure observation is to utilize opticmicroscope pair cross-section observe and core tissue is identified, and exists the heat treatment material of Bainite Phases of Some to obtain the area percent of Bainite Phases of Some to core.
The measurement of hardness of tufftride material and carburized material has carried out the mensuration for core hardness and surface hardness.Surface hardness is measured in the position apart from surperficial 0.02mm, and effective case depth is defined as and reaches measuring apart from the surperficial degree of depth of HV400.In addition, make sample used for transmission electron microscope observation by the electropolishing method that uses two spray methods from the core of tufftride material and carburized material, for obtained sample, the transmission electron microscope that uses acceleration voltage to be set as 200kV carries out the observation of precipitate.And then, obtain the composition of the precipitate of observing by energy dispersion type x-ray spectrometry device (EDX).
The evaluation of impact characteristics is undertaken by Charpy impact test, obtains impact value (J/cm
2).Test film uses notched test film (R:10mm, the degree of depth: 2mm).It should be noted that, this notched test film cuts from forge hot material, and cut test film is implemented after above-mentioned tufftride processing or carburizing treatment, for Charpy impact test.
In addition, fatigue characteristic evaluation is undertaken by little wild formula rotary bending fatigue test, obtains safe range of stress.As test film, use notched test film (breach R:1.0mm, notch diameter: 8mm, stress concentration factor: 1.8).Cut this test film from forge hot material, implement after above-mentioned tufftride processing or carburizing treatment, for test.
Test-results shown in table 2.No.1～6 are that example, No.7～17 are that comparative example, No.18 are the conventional example that uses JIS SCr420 steel.
As shown in Table 2, the material obtaining than conventional example (No.18) being carried out to carburizing and quenching, temper, it is better that the tufftride of No.1～6 is processed the fatigue strength of material.The bit cutting processibility that the tufftride of No.1～6 is processed front former material (forge hot material) is more than equal rank with current material in practical.In addition, utilize transmission electron microscope observation and EDX to form to precipitate the result of investigating and be, process in material in the tufftride of No.1～6, can confirm every 1 μ m in Bainite Phases of Some
2disperse to separate out the nano-precipitation that 500 particle diameters that contain above V, Nb are less than 10nm.Can think according to this result, the precipitation strength bringing by above-mentioned nano-precipitation according to tufftride processing material of the present invention demonstrates high-fatigue strength.
On the other hand, the chemical constitution of comparative example No.7～17 or the microstructure obtaining outside the scope of the invention, therefore fatigue strength or drill bit poor in processability.
Particularly No.7, because the speed of cooling after forge hot is slow, therefore fatigue strength is low compared with example.At this, the result of the transmission electron microscope observation of No.7 is, do not observe the dispersion that particle diameter is less than the nano-precipitation of 10nm and separates out, and observe the thick precipitate of particle diameter much larger than 10nm.Can think according to this result, the precipitate of generation is thick is like this reason that fatigue strength reduces.That is, can not obtain desired bainite structure if the speed of cooling after forge hot is slow, before tufftride, generate thick precipitate, the growing amount of tufftride nano-precipitation after treatment reduces, and result causes precipitation strength insufficient.
The C amount of No.8 exceeds outside the scope of the invention, and therefore the hardness of bainite structure increases, and drill bit processibility reduces.
Si, the Mn amount of No.9 exceeds outside the scope of the invention, and therefore the hardness of forge hot material is high, and drill bit processibility is reduced to approximately 1/5 of current material.
The Mn amount of No.10 is low to moderate outside the scope of the invention, before tufftride (after forge hot) generate ferrite-pearlite tissue and make the area occupation ratio reduction of bainite structure, in tissue, separate out V, Nb precipitate, therefore the hardness before tufftride increases, and drill bit processibility reduces.
The Cr amount of No.11 is low to moderate outside the scope of the invention, before tufftride (after forge hot) generate ferrite-pearlite tissue and make the area occupation ratio reduction of bainite structure, in tissue, separate out V, Nb precipitate, therefore the hardness before tufftride increases, and drill bit processibility reduces.
The Mo amount of No.12 is low to moderate outside the scope of the invention, and therefore tufftride nano-precipitation amount after treatment is few, can not obtain sufficient core hardness, and therefore fatigue strength is lower than conventional example.
V, the Nb of No.13 are low to moderate outside the scope of the invention, and therefore tufftride precipitate amount after treatment is few, can not obtain sufficient core hardness, and therefore fatigue strength is lower than current material.
The Nb of No.14 is low to moderate outside the scope of the invention, and therefore tufftride precipitate amount after treatment is few, therefore, can not obtain sufficient core hardness, and fatigue strength is lower than current material.
No.15 and No.16 have added Ti, and the amount of separating out of the precipitate that therefore tufftride contains V, Nb after processing is few, therefore, can not obtain sufficient core hardness, and fatigue strength is lower than current material.In addition, impact value is also shown as low value.
The Al of No.17 is low to moderate outside the scope of the invention, and therefore tufftride surface hardness after treatment and effective case depth are low, and therefore fatigue strength is lower than current material.
Claims (3)
1. a tufftride steel, in quality %, contain C:0.01% above and lower than 0.10%, Si:1.0% following, Mn:0.5～3.0%, Cr:0.30～3.0%, Mo:0.005～0.4%, V:0.02～0.5%, Nb:0.003～0.15%, Al:0.005～0.2%, S:0.06% is following, P:0.02% is following and B:0.0003～0.01%, surplus is made up of Fe and inevitable impurity, and described tufftride has the tissue that bainite area occupation ratio is greater than 50% before tufftride with steel.
2. tufftride steel as claimed in claim 1 wherein, after tufftride, disperses to separate out the precipitate that contains V, Nb in Bainite Phases of Some.
3. tufftride parts, it uses steel as former material using the tufftride described in claim 1 or 2.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
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| JP2012031031 | 2012-02-15 | ||
| JP2012-031031 | 2012-02-15 | ||
| PCT/JP2013/000838 WO2013121794A1 (en) | 2012-02-15 | 2013-02-15 | Soft-nitriding steel and soft-nitrided component using steel as material |
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| CN104114733A true CN104114733A (en) | 2014-10-22 |
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| US (1) | US20150020926A1 (en) |
| EP (1) | EP2816128B1 (en) |
| JP (1) | JP5449626B1 (en) |
| KR (1) | KR20140129081A (en) |
| CN (1) | CN104114733A (en) |
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| CN107406942A (en) * | 2015-03-24 | 2017-11-28 | 杰富意钢铁株式会社 | Tufftride steel and part and its manufacture method |
| CN110036129A (en) * | 2016-11-30 | 2019-07-19 | 杰富意钢铁株式会社 | Tufftride steel and component |
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| JP5767594B2 (en) * | 2012-02-15 | 2015-08-19 | Ｊｆｅ条鋼株式会社 | Steel for nitriding and nitriding member using the same |
| EP2835130A1 (en) * | 2013-08-05 | 2015-02-11 | Polichem SA | Composition for skin anti-ageing treatment |
| WO2015140235A1 (en) * | 2014-03-18 | 2015-09-24 | Innomaq 21, Sociedad Limitada | Extremely high conductivity low cost steel |
| JP6431456B2 (en) * | 2014-09-05 | 2018-11-28 | Ｊｆｅスチール株式会社 | Soft nitriding steel and parts, and methods for producing them |
| JP6225965B2 (en) * | 2014-09-05 | 2017-11-08 | Ｊｆｅスチール株式会社 | Soft nitriding steel and parts, and methods for producing them |
| CN104975160A (en) * | 2015-06-18 | 2015-10-14 | 柳州科尔特锻造机械有限公司 | Thermal treatment method for driving and driven bevel gears |
| JP6477614B2 (en) * | 2016-06-30 | 2019-03-06 | Ｊｆｅスチール株式会社 | Steel for soft nitriding and parts and method for manufacturing them |
| US11625844B2 (en) * | 2020-05-11 | 2023-04-11 | The Boeing Company | Rapid effective case depth measurement of a metal component using physical surface conditioning |
| WO2024003593A1 (en) * | 2022-06-28 | 2024-01-04 | Arcelormittal | Forged part of steel and a method of manufacturing thereof |
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Also Published As
| Publication number | Publication date |
|---|---|
| EP2816128A4 (en) | 2015-05-20 |
| EP2816128B1 (en) | 2019-02-06 |
| WO2013121794A1 (en) | 2013-08-22 |
| JPWO2013121794A1 (en) | 2015-05-11 |
| KR20140129081A (en) | 2014-11-06 |
| MY177826A (en) | 2020-09-23 |
| US20150020926A1 (en) | 2015-01-22 |
| EP2816128A1 (en) | 2014-12-24 |
| WO2013121794A8 (en) | 2014-07-17 |
| JP5449626B1 (en) | 2014-03-19 |
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