CN100359033C - Superfine grain steel having nitrided layer - Google Patents
Superfine grain steel having nitrided layer Download PDFInfo
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- CN100359033C CN100359033C CNB2003801015127A CN200380101512A CN100359033C CN 100359033 C CN100359033 C CN 100359033C CN B2003801015127 A CNB2003801015127 A CN B2003801015127A CN 200380101512 A CN200380101512 A CN 200380101512A CN 100359033 C CN100359033 C CN 100359033C
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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
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
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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
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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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
- C23C8/24—Nitriding
- C23C8/26—Nitriding of ferrous surfaces
Abstract
An ultra fine grain steel has a ferrite grain structure having an average grain size of 3 mum or less and has a nitride layer formed on a surface of the steel. The nitride layer is formed without adding an alloy element such as Cr or Mo that is expensive and detrimental to recycling. Fatigue strength is enhanced by the nitride layer.
Description
Technical field
The application's invention relates to the ultra tiny crystal grain steel with nitride layer.It when in more detail, the application's invention relates to the recirculation of high prices such as not adding Cr, Mo deleterious alloying element and form the ultra tiny crystal grain steel with nitride layer of nitride layer, high-fatigue strengthization.
Background technology
In the metal member made that bears bending, twisting stress of turning axle etc., from the surface that exposes fatigue cracking can take place because of heavily stressed, will cause repeated stress failure soon.Therefore, making surface hardening, high-fatigue strengthization, is effective to the whole high-fatigue strengthization of parts.In addition, from wear resistance, corrosion proof viewpoint, it also is effective making surface hardening.This also is same for the very little ultra tiny crystal grain steel with high strength, high tenacity (for example, with reference to Patent Document 1) of ferrite crystal grain diameter.
Always, study being used for case-hardened nitrogenize, but the necessary for this reason alloying element that adds Cr, Mo, Ti, Nb etc. heats maintenance 0.5～100 hour down at 450 ℃～590 ℃, generate the nitride (for example, with reference to Non-Patent Document 1) of these alloying elements.Now, when making the pure iron nitrogenize, only stay in the level that forms the membranaceous iron-nitride of number μ m to tens μ m thickness on its surface, be no more than about high Hv250 with ammonia.Even portion separates out iron-nitride hardly or separates out a little and also give sclerosis hardly within it.
And, harmful during recirculation in addition because the alloying element of Cr, Mo etc. is a high valence elements, so wish to avoid its interpolation.
Deleterious alloying element when in light of this situation, the application's the invention problem that must solve provides the recirculation of high prices such as not adding Cr, Mo and form the ultra tiny crystal grain steel with nitride layer of nitride layer, high-fatigue strengthization.
[Patent Document 1] spy opens the 2000-309850 communique
[Non-Patent Document 1] Sang Yuanxiu is capable, Ph D dissertation " about the research of the surfaction of the iron alloy that utilizes plasma body ", in November, 1992, Kyoto University
Summary of the invention
In order to solve above-mentioned problem, the application's invention provides a kind of ultra tiny crystal grain steel with nitride layer, it is characterized in that, has the following ferrite crystal grain tissue of average crystal grain diameter 3 μ m, forms nitride layer from the teeth outwards.
In addition, the application's invention is as dividing other embodiment to provide: by separating out of carbide or growing up of any mode of the interpolation of solid solution element or the dual mode crystal grain when suppressing nitrogenize; C content is more than the 0.01 quality %; At least a element that interpolation is selected from the group that is made of Mn, Cr, Mo, Ti, Nb, V and P; Mn content is more than the 0.4 quality %; P content is more than the 0.035 quality %; The content that is Cr, Mo, Ti, Nb, V is aggregated in the following carbon steel of 0.1 quality %; Safe range of stress is more than 1.6 times of Vickers' hardness of mother metal; The molding, parts or the member that form by ultra tiny crystal grain steel with above nitride layer.
Embodiment below is shown, the ultra tiny crystal grain steel of the nitride layer of the invention with the application is described simultaneously in further detail.
Description of drawings
Fig. 1 is that the Fe-C-Mn that is illustrated in pecvd nitride under 550 ℃ * 26 hours the condition is the photo of FB-SBM of the nitride layer tissue of 0.002C coarse-grained steel.
Fig. 2 is that the Fe-C-Mn that is illustrated in pecvd nitride under 550 ℃ * 26 hours the condition is that 0.002C coarse-grained steel and Fe-C-Mn are the column graphic representation of the Vickers' hardness on the starting material of the ultra tiny crystal grain steel of 0.05C and nitride layer surface.
Fig. 3 is that expression Fe-C-Mn is the graphic representation of the Hardness Distribution after the nitrogenize in the fatiguespecimen of the ultra tiny crystal grain steel of 0.05C.
Fig. 4 is that the Fe-C-Mn that is illustrated in pecvd nitride under 550 ℃ * 26 hours the condition is the photo of the FE-SBM of the mother metal matrix after the nitrogenize of 0.05C ultra micro crystal grain steel.
Fig. 5 is that to contain the Fe-C-Mn-Si that Mn measures 0.37 quality % be the graphic representation of the Hardness Distribution of 0.25C coarse-grained steel after nitrogenize under 500 ℃ * 16 hours the condition in expression.
Fig. 6 is that to contain the Fe-C-Mn-Si that Mn measures 0.83 quality % be the graphic representation of the Hardness Distribution of 0.45C coarse-grained steel after nitrogenize under 500 ℃ * 16 hours the condition in expression.
Fig. 7 be expression relatively Fe-C-Mn be result's the graphic representation of the fatigue test of the starting material of the ultra tiny crystal grain steel of 0.05C and nitride material.
Fig. 8 is that expression Fe-C-Mn-Si is the graphic representation that the grain growth that is produced by Fe3C of ultra tiny crystal grain steel suppresses effect.
Fig. 9 (a) and (b) are to represent that respectively Fe-C-Mn-Si is the photo of the FE-SEM of the mother metal tissue before the nitrogenize of the ultra tiny crystal grain steel of 0.15C, the ultra tiny crystal grain steel of 0.45C.
Figure 10 is expression to Fe-C-Mn-Si is to add the graphic representation that grain growth in the ultra tiny crystal grain steel of 0.15C-0.1P of P of 0.1 quality % suppresses effect in the ultra tiny crystal grain steel of 0.15C.
Figure 11 represents that making Fe-C-Mn-Si is the graphic representation of the Hardness Distribution after the ultra tiny crystal grain steel 0.45C-0.1P nitrogenize.
Embodiment
The simple ultra tiny crystal grain steel of forming with the following ferrite crystal grain tissue of average crystal grain diameter 3 μ m, by at ammonia atmosphere or contain in the atmosphere of ammonia and under 450 ℃～590 ℃ temperature, kept 0.5～100 hour, form nitride layer on its surface, make surface hardening, high-fatigue strengthization.
Here, so-called ferrite crystal grain tissue is meant the tissue based on ferrite crystal grain.This means, ferrite crystal grain is organized no matter be ferritic single phase structure can or contain carbide as the 2nd phase, perlite, martensite, austenite etc.
In addition, in the ultra tiny crystal grain steel with nitride layer of the application's invention, Mn content preferably is taken as more than the 0.4 quality %.The Fe-C-Mn system of Mn content 0.37 quality % or the ultra tiny crystal grain steel of Fe-C-Mn-Si system make surface hardening by 500 ℃, 16 hours nitrogenize meeting, but are difficult to form dark hardened layer.The occasion of Mn content 0.83 quality % makes the surface hardening of ultra tiny crystal grain steel, forms dark nitride layer.Therefore, in common steel as add the Mn of minimum 0.4 quality % at the countermeasure of MnS.Consider above factor, preferred Mn content is taken as more than the 0.4 quality % in the ultra tiny crystal grain steel with nitride layer of the application's invention.
Grain growth takes place in C content when keeping for a long time under the temperature of ultra tiny crystal grain steel about 550 ℃ of 0.05 quality %～0.15 quality %, ultra tiny crystal grain is organized and lost original shape easily.Therefore, in the high-fatigue strength method of the steel of the application's invention, can be by improving C content, separate out carbide such as Fe3C, NbC, TiC or add P (phosphorus), V (vanadium) solid solution element of etc.ing or with this two kinds of methods preventions or inhibition grain growth.For example, nitrogenize to 26 for a long time hour under the temperature about 500 ℃.By so long-time nitrogenize, can form darker, to the effective nitride layer of high-fatigue strengthization.Preferred C content is more than 0.05 quality %.In addition, P content preferably is taken as more than the 0.035 quality %.
Usually, considering tired occasion, the hardened layer that is produced by nitrogenize, is that nitride layer is about 0.5mm～1.0mm, makes surperficial adequately hardened occasion, the mother metal matrix generation repeated stress failure in coarse-grained steel under the nitride layer.Generally, the fatigue strength of nitride material integral body is decided by the stress of the starting point portion of repeated stress failure and the intensity of being weighed by the fatigue strength of mother metal matrix, but the ultra tiny crystal grain steel with nitride layer of the application's invention can obtain more than the high fatigue strength of fatigue strength by above-mentioned rule expectation.Why be like this because ultra tiny crystal grain steel is higher than the hardenability of the nitride layer of coarse-grained steel by the nitride layer that nitrogenize forms.Therefore, ultra tiny crystal grain steel not only can have high strength, high tenacity simultaneously, and can give high-fatigue strength by nitrogenize.
In addition, the rising of surface hardness is associated with the raising of wear resistance, that is to say, gives nitride layer big stress under compression, and remaining stress under compression can be offset the tensile stress that produces by sliding, and what the tensile stress of ultra tiny crystal grain steel surface load can be relative is little.In addition, because the ultra tiny crystal grain steel with nitride layer of the application's invention can stop or suppress the growing up of crystal grain nitriding temperature under, so, also be difficult to cause the deterioration of characteristic even for heat because of the generation that rubs.Therefore, the ultra tiny crystal grain steel with nitride layer of the application's invention can show good wear resistance.
The ultra tiny crystal grain steel with nitride layer of the application's invention can be block, pulverous any.
When the powdered steel that makes Fe-C-Mn system or Fe-C-Mn-Si be was carried out nitrogenize, the nitride layer that the intensity of powder shows and blocky ultra tiny crystal grain steel forms was with the intensity of degree.Therefore, the blocks that obtains by sintering nitrogenize powder can become more high-intensity material.This occasion for example can make nitrogen, ammonia separately or blended gas or add in its any gas in stress under compression in 2 atmosphere gas below the air pressure, more than the load 0.1MPa of hydrogen, total pressure, the temperature range below 1200 ℃ and carry out sintering.In addition, when carrying out sintering, need not to be all powder, for example, can sneak into pure iron powder as sintering aid by nitrogenize.In addition, the particle diameter that uses powdered steel is the occasion of the following powder of 20 μ m, in order to manifest the inhibition effect of above-mentioned grain growth, can add the ceramic powder such as TiN, TiC of the following particle diameter of 2 μ m.
Like this, the ultra tiny crystal grain steel with nitride layer of the application's invention is also given high-fatigue strength, good wear resistance except high strength, high tenacity, can be widely used in various molding, parts, member and expects practicability.
(embodiment)
Table 1
(a) coarse-grained steel
| Material | C | Si | Mn | P | S | Ferrite crystal grain diameter (μ m) | |
| Fe-C-Mn | 0.002C | 0.002 | 0.01 | 1.98 | 0.001 | 0.002 | 20.0 |
| Fe-C-Mn-Si | 0.25C | 0.27 | 0.23 | 0.37 | 0.008 | 0.030 | 20.0 |
| 0.45C | 0.43 | 0.22 | 0.83 | 0.017 | 0.016 | - | |
(b) ultra tiny crystal grain steel
| Material | C | Si | Mn | P | S | Ferrite crystal grain diameter (μ m) | |
| Fe-C-Mn | 0.05C | 0.05 | 0.01 | 1.98 | 0.021 | 0.001 | 1.7 |
| Fe-C-Mn-Si | 0.15C | 0.14 | 0.31 | 1.51 | 0.001 | 0.001 | 0.5 |
| 0.45C | 0.43 | 0.31 | 1.50 | 0.001 | 0.001 | 0.7 | |
| 0.76C | 0.76 | 0.31 | 1.43 | 0.012 | 0.004 | 0.5 | |
| 0.90C | 0.89 | 0.30 | 1.51 | 0.002 | 0.001 | 0.5 | |
| 0.15C-0.1P | 0.14 | 0.30 | 1.48 | 0.093 | 0.001 | 0.6 | |
| 0.45C-0.1P | 0.45 | 0.30 | 1.49 | 0.100 | 0.001 | 0.5 | |
Table 2
(a) coarse-grained steel
| Material | Tensile strength (MPa) | Breaking elongation (%) | Vickers' hardness | |
| Fe-C-Mn | 0.002C | - | - | 114 |
| Fe-C-Mn-Si | 0.25C | 511 | 34 | 155 |
| 0.45C | 706 | 25 | 230 | |
(b) ultra tiny crystal grain steel
| Material | Tensile strength (MPa) | Breaking elongation (%) | Vickers' hardness | |
| Fe-C-Mn | 0.05C | 645 | 13 | 216 |
| Fe-C-Mn-Si | 0.15C | 842 | 17 | 286 |
| 0.45C | 952 | 17 | 300 | |
| 0.75C | 1143 | 12 | 360 | |
| 0.90C | - | - | 364 | |
| 0.15C-0.1P | 926 | 13 | 308 | |
| 0.45C-0.1P | 1048 | 15 | 339 | |
The chemical ingredients and the ferrite crystal grain diameter of the material that table 1 expression is used in an embodiment, table 2 expression mechanical properties.Fe-C-Mn is that coarse-grained steel 0.002C and Fe-C-Mn-Si are that its ferrite crystal grain diameter of coarse-grained steel 0.25C is about 20 μ m, has ferrite, pearlitic structure.Making Fe-C-Mn-Si is coarse-grained steel 0.45C tempering, has martensitic stucture.Ultra tiny crystal grain steel has fine ferrite crystal grain and carbide dispersive ferritic structure.For so ultra tiny crystal grain steel, rolling by grooved roll, be configured as the square steel of 18mm * 18mm.
As shown in table 2 such, at Fe-C-Mn is that ultra tiny crystal grain steel 0.05C and Fe-C-Mn-Si are among coarse-grained steel 0.15C, 0.45C, 0.75C, the 0.90C, increase along with carbon content, such shown in Fig. 9 (a) and (b), the granulous carbide increases, thereby the precipitation strength by carbide, tensile strength and Vickers' hardness increase.At Fe-C-Mn-Si is among ultra tiny crystal grain steel 0.15C-0.1P and the 0.45C-0.1P, and when comparing with the ultra tiny crystal grain steel that does not add P with identical C content, its tensile strength and Vickers' hardness increase.This is that the solution strengthening effect of P causes.
Making Fe-C-Mn is that 0.002C coarse-grained steel and Fe-C-Mn are that the ultra tiny crystal grain steel of 0.05C is plasma nitrided under 550 ℃ * 26 hours condition.Fig. 1 is that Fe-C-Mn is the photo of FE-SEM of the nitride layer tissue of 0.002C coarse-grained steel.Can confirm the muscle shape nitride that in ferrite crystal grain, forms by the photo of this FE-SEM.
Fig. 2 is that expression Fe-C-Mn is that 0.002C coarse-grained steel and Fe-C-Mn are the column graphic representation of the Vickers' hardness on the starting material of the ultra tiny crystal grain steel of 0.05C and nitride layer surface.Vickers' hardness is measured by the loading that applies 1kg on the surface of the plate of plasma nitrided thick 1mm.Can confirm that even the simple Fe-C-Mn that forms is a steel, also can be hardened by nitrogenize, ultra tiny crystal grain hardening of steel degree is bigger.
Fig. 3 is that expression Fe-C-Mn is the graphic representation of the Hardness Distribution after the nitrogenize of fatiguespecimen of the ultra tiny crystal grain steel of 0.05C.Nitridation conditions is same as described above 550 ℃ * 26 hours plasma nitrided, and the diameter of phi that fatiguespecimen is taken as test portion is the sand clock and watch type of 6mm.Carry out under the loading that is determined at 0.2kg of Vickers' hardness.Hardness Distribution by the curve representation of Fig. 3 can be inferred about the about 1mm of nitride layer.In addition; can confirm; the raw-material hardness of mother metal matrix after the nitrogenize before than nitrogenize reduces; can think that this is because mother metal matrix coarse-grain granulation during nitrogenize; in fact as being confirmed by the photo of the FE-SEM of the mother metal matrix after the nitrogenize shown in Figure 4, thickization of ferrite crystal grain diameter is to the size of 5 μ m～10 μ m.
Fig. 5, Fig. 6 are that the Fe-C-Mn-Si that represents to add respectively 0.37 quality %, 0.83 quality %Mn is the graphic representation of 0.25C, the Hardness Distribution of 0.45C coarse-grained steel (diameter all is the round steel of 16mm) after nitrogenize under 500 ℃ * 16 hours the condition.Same with pure iron, be that surface hardness increases in the 0.25C coarse-grained steel of 0.37 quality % at Mn content, but the inside hardness beyond on the surface does not improve.In contrast, can confirm, be that inner hardness also improves in the coarse-grained steel of 0.45C of 0.83 quality % at Mn content, forms the dark nitride layer about 1mm.Can think, even be that steel also can nitrogenize to Fe-C-Mn-Si.In addition, as shown in table 1, its Mn content of coarse-grained steel of all other and fine grained steel and all forms nitride layer about 1mm more than 1.43 quality %.Therefore, can think that in order to form dark effective nitride layer in the ultra tiny crystal grain steel of the simple composition that Fe-C-Mn is, Fe-C-Mn-Si is, to be hardened layer, Mn content must be more than the 0.37 quality %.
Fig. 7 be expression relatively Fe-C-Mn be result's the graphic representation of the fatigue test of the starting material of the ultra tiny crystal grain steel of 0.05C and nitride material.Using the diameter of phi of Ke Laozi type rotating bending fatigue machine and test portion in fatigue test is the sand clock and watch type sample of 6mm.In addition, the surface of nitride material is removed about 0.1mm the defective that causes when removing nitrogenize by grinding.Can be confirmed that by Fig. 7 although its thickization of mother metal matrix of nitride material, its fatigue strength also improves greatly than starting material, is 375MPa with respect to raw-material safe range of stress, the safe range of stress of nitride material is 640MPa.The hardness of the mother metal matrix of nitride material is about HV160, when using following empirical formula:
Safe range of stress=1.6 * Vickers' hardness
The safe range of stress that can infer mother metal is 1.6 * 160=256[MPa].With the thickness of nitride layer be taken as 1mm, when considering the stress gradient in the rotating bending test of sample of diameter of phi 6mm (radius 3mm), the stress amplitude σ a ' that acts under the nitride layer is σ a '/σ a=(3-1)/3 ≈ 0.67 with respect to surperficial nominal stress amplitude sigma a.Therefore, the safe range of stress of the nitride material of being estimated by mother metal matrix hardness and stress gradient is 256/0.67=382[MPa] about, but the safe range of stress of actual nitride material is aforesaid 640MPa, can confirm, carry out more than the big high-fatigue strengthization of safe range of stress by the anticipation of mother metal matrix hardness.When calculating, represent that by result shown in Figure 3 the nitrogenize degree of depth with the starting material same rigidity is about 0.6mm, σ a '/σ a=(3-0.6)/3=0.8 with the 376MPa of the safe range of stress starting material measured with above-mentioned same estimated service life.Therefore, the safe range of stress of the nitride material of prediction is 375/0.8=469[MPa].Can think that the safe range of stress 640MPa of actual nitride material is bigger than this anticipation value.
As mentioned above, even ultra tiny crystal grain steel for its fatigue strength, also can obtain the effect of tangible nitrogenize along with how many meeting coarse-grain granulations of nitrogenize.But when considering actual component pieces,, keep intensity even preferably also will keep ultra tiny crystal grain tissue by the nitrogenize mother metal.
In addition, Fig. 8 is the result who represents the grain growth effect research that is produced by Fe3C.Specifically, using by Fe-C-Mn-Si is that the diameter of the test portion that does of ultra tiny crystal grain steel is the sample of 6mm, and the high temperature during blank nitriding keeps for a long time, measures and uses common electric furnace 500 ℃ of changes in hardness that keep down after 30 hours.Like that, in the low 0.05C of C content (0.05C quality %) ultra tiny crystal grain steel and the ultra tiny crystal grain steel of 0.15C (0.15C quality %), when high temperature kept about 3 hours, hardness was reduced to about HV200, can confirm the coarse-grain granulation shown in Fig. 8 graphic representation.In contrast, in the ultra tiny crystal grain steel of the high 0.45C of C content (0.45C quality %), even keep 30 hours, its hardness also only reduces a little, does not show the omen of coarse-grain granulation.Even, also can obtain same result for the ultra tiny crystal grain steel of 0.75C, the ultra tiny crystal grain steel of 0.90C.
Fig. 9 (a) and (b) are to represent that respectively Fe-C-Mn-Si is the photo of the FE-SEM of the mother metal tissue before the nitrogenize of the ultra tiny crystal grain steel of 0.15C, the ultra tiny crystal grain steel of 0.45C.As mentioned above, in the ultra tiny crystal grain steel of 0.45C, separate out many Fe3C (white spot).Can infer, by the grain growth inhibition effect of such Fe3C precipitate, the ultra tiny crystal grain steel of 0.45C is the coarse-grain granulation not.In addition, can confirm that the ferrite crystal grain diameter is below the 1 μ m in two kinds of ultra tiny crystal grain steel.
Figure 10 is expression to Fe-C-Mn-Si is to add the graphic representation that grain growth in the ultra tiny crystal grain steel of 0.15C-0.1P of P of 0.1 quality % suppresses effect in the ultra tiny crystal grain steel of 0.15C.As Figure 10 confirms, to compare with the ultra tiny crystal grain steel of 0.15C, the hardness of the ultra tiny crystal grain steel of 0.15C-0.1P only reduces a little, can suppress the coarse-grain granulation.Can infer, this is because the grain growth that the P of solid solution produces suppresses effect.
Be that the grain growth by carbide or solid solution element suppresses effect can stop or suppress the coarse-grain granulation, keeps ultra tiny crystal grain tissue, the nitrogenize for a long time to keep high-intensity original state by above its conclusion as a result.
Validity for the nitrogenize of the ultra tiny crystal grain steel further confirming to utilize grain growth to suppress effect, to make the Fe-C-Mn-Si that utilizes the Fe3C precipitate be ultra tiny crystal grain steel 0.45C, utilize P solid solution 0.15C-0.1P and utilize its two side's the actual nitrogenize of 0.45C-0.1P, carry out fatigue test.The plasma nitrided of 500 ℃ * 16 hours conditions got in nitrogenize.In fatigue test, the diameter of use-testing portion is sand clock and watch type sample and the Ke Laozi type rotating bending test machine of 6mm, carries out stagewise as unit 107 times with per 1 sample and tests, and only obtains safe range of stress.Figure 11 represents that making Fe-C-Mn-Si is the graphic representation of the Hardness Distribution after the ultra tiny crystal grain steel 0.45C-0.1P nitrogenize.As confirming by this graphic representation shown in Figure 11, in the nitride material of 0.45C-0.1P, even the mother metal matrix also can show about HV300, can keep ultra tiny crystal grain tissue.In addition, the fatigue test results of each nitride material is shown in table 3.
Table 3
| Safe range of stress (MPa) | |||||
| 0.45C | 0.15C-0.1P | 0.45C-0.1P | |||
| Fe-C-Mn-Si | Starting material | 500 | 520 | 580 | |
| |
700 | 700 | 780 | ||
Safe range of stress after the nitrogenize is 700MPa to the ultra tiny crystal grain steel of 0.45C, is 780MPa to the ultra tiny crystal grain steel of 0.15C-0.1P, is 700MPa to the ultra tiny crystal grain steel of 0.45C-0.1P.As shown in table 2, be 300,308,339 owing to divide the Vickers' hardness of other mother metal matrix, so the ratio of the Vickers' hardness of safe range of stress/mother metal matrix is respectively 2.33,2.53,2.06, all more than 1.6.
, be the repeated stress failure of surperficial starting point with respect to ultra tiny crystal grain steel 0.45C and 0.15C-0.1P, the repeated stress failure that the ultra tiny crystal grain steel of 0.45C-0.1P is an inner clamps foreign material starting point.Can think, because like this, in ultra tiny crystal grain steel 0.45C and 0.15C-0.1P, obtain the original safe range of stress that nitrided structure has, and as mentioned above, the ultra tiny crystal grain steel of 0.45C-0.1P is to reduce because of the repeated stress failure that inclusion starting point type takes place causes safe range of stress.For example, as long as utilize high purification technology etc. to make the size decreases of inclusion, the repeated stress failure of inclusion starting point type do not take place, again because the hardness height of the ultra tiny crystal grain steel of 0.45C-0.1P, then just can expect to obtain to be higher than the safe range of stress of the 780MPa of the ultra tiny crystal grain steel of 0.15C-0.1P.
In addition, hardness is high more can obtain good wear resistance more.As shown in Figure 2, the hardness of starting material and nitride layer poor, a side of ultra tiny crystal grain steel is bigger more than 2 times than coarse-grained steel.In other words, this means that when making ultra tiny crystal grain steel nitrogenize, the raising of the hardness that causes is more than the value of coarse-grain granulation steel expectation, ultra tiny crystal grain steel has good wear resistance.In addition, from Fig. 2 and Figure 11 more as can be seen, because the interpolation of solid solution elements such as the separating out of the carbide of Fe3C etc., P can improve the hardness of nitride layer respectively by precipitation strength, solution strengthening, so further improved the wear resistance of ultra tiny crystal grain steel.
In addition, as Fig. 8, Figure 10 and shown in Figure 11, even under nitriding temperature, crystal grain is not grown up yet.Can think that because like this, even produce heat by friction, also can keep ultra tiny crystal grain tissue with respect to reaching to rise to the temperature of the surface of friction of nitriding temperature degree, intensity does not reduce or reduces to be lacked, and can obtain good wear resistance.
Self-evident, the application's invention is not to being limited by above embodiment and embodiment.Also can various modes be arranged for details such as the chemical ingredients of steel, nitridation conditions, nitrogenize modes.
As described above in detail, deleterious alloying element in the time of can providing the recirculation of high prices such as not adding Cr, Mo by the application's invention and form the ultra tiny crystal grain steel with nitride layer of nitride layer, high-fatigue strengthization.
Claims (4)
1. ultra tiny crystal grain steel with nitride layer, it is characterized in that, has the following ferrite crystal grain tissue of average crystal grain diameter 3 μ m, the thickness that forms nitride layer and nitride layer on the surface of steel is 0.5-1mm, the chemical constitution of this ultra tiny crystal grain steel is: comprise C, Mn and the surplus of forming by Fe and unavoidable impurities, wherein C content is that the above and Mn content of 0.05 quality % is more than the 0.83 quality %, perhaps the chemical constitution of this ultra tiny crystal grain steel is: comprise C, Mn, Si and the surplus of forming by Fe and unavoidable impurities, wherein C content is that the above and Mn content of 0.05 quality % is more than the 0.83 quality %, and unit is that the safe range of stress of MPa is more than 1.6 times of Vickers' hardness Hv of mother metal.
2. the ultra tiny crystal grain steel with nitride layer according to claim 1, it is characterized in that, the average crystal grain diameter of ferrite crystal grain tissue is below the 1 μ m, the chemical constitution of this ultra tiny crystal grain steel is: the surplus that comprises C, Mn, Si and be made up of Fe and unavoidable impurities, wherein C content is 0.45-0.90 quality %.
3. the ultra tiny crystal grain steel with nitride layer according to claim 2 is characterized in that P content is more than the 0.035 quality %.
4. a molding, parts or member is characterized in that, are formed by each described ultra tiny crystal grain steel with nitride layer of claim 1-3.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP303658/2002 | 2002-10-17 | ||
| JP2002303658A JP3931230B2 (en) | 2002-10-17 | 2002-10-17 | Ultrafine grained steel with nitrided layer |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1705762A CN1705762A (en) | 2005-12-07 |
| CN100359033C true CN100359033C (en) | 2008-01-02 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CNB2003801015127A Expired - Fee Related CN100359033C (en) | 2002-10-17 | 2003-10-17 | Superfine grain steel having nitrided layer |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US20050241733A1 (en) |
| EP (1) | EP1580291A4 (en) |
| JP (1) | JP3931230B2 (en) |
| KR (1) | KR20050067184A (en) |
| CN (1) | CN100359033C (en) |
| WO (1) | WO2004035850A1 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8070888B2 (en) * | 2005-02-28 | 2011-12-06 | National Institute For Materials Science | High strength formed article comprising hyperfine grain structure steel and manufacturing method of the same |
| JP4009313B2 (en) * | 2006-03-17 | 2007-11-14 | 株式会社神戸製鋼所 | High strength steel material excellent in weldability and method for producing the same |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07216497A (en) * | 1994-02-03 | 1995-08-15 | Sumitomo Metal Ind Ltd | Steel sheet or steel sheet parts with high fatigue strength and their production |
| JPH10219393A (en) * | 1997-02-04 | 1998-08-18 | Sumitomo Metal Ind Ltd | Steel material for soft-nitriding, soft-nitrided parts, and their production |
| JP2000246301A (en) * | 1999-02-26 | 2000-09-12 | Natl Res Inst For Metals | Method of manufacturing p-added low-carbon steel of high strength and high toughness |
| JP2001073035A (en) * | 1999-08-31 | 2001-03-21 | Natl Res Inst For Metals | Production of steel having superfine structure |
| JP2001234239A (en) * | 2000-02-25 | 2001-08-28 | National Institute For Materials Science | Producing method for superfine-grained ferritic structure steel |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5917167B2 (en) * | 1980-06-09 | 1984-04-19 | 株式会社不二越 | How to harden steel |
| JP2979987B2 (en) * | 1994-12-20 | 1999-11-22 | 住友金属工業株式会社 | Steel for soft nitriding |
| KR100536827B1 (en) * | 1997-09-22 | 2006-02-28 | 카가쿠기쥬쯔죠 킨조쿠자이료 기쥬쯔켄큐죠 | Ultra-fine grain steel and method thereof |
| JP2000080435A (en) * | 1998-08-31 | 2000-03-21 | Japan Science & Technology Corp | High strength p-added steel and its production |
| US6386810B1 (en) * | 1999-05-21 | 2002-05-14 | Hiroshi Onoe | High strength screw |
| JP4374196B2 (en) * | 2002-02-19 | 2009-12-02 | 新日本製鐵株式会社 | High-strength steel sheet having fine structure excellent in workability, plating property and toughness, and method for producing the same |
-
2002
- 2002-10-17 JP JP2002303658A patent/JP3931230B2/en not_active Expired - Lifetime
-
2003
- 2003-10-17 CN CNB2003801015127A patent/CN100359033C/en not_active Expired - Fee Related
- 2003-10-17 KR KR1020057006535A patent/KR20050067184A/en active Search and Examination
- 2003-10-17 EP EP03808902A patent/EP1580291A4/en not_active Withdrawn
- 2003-10-17 WO PCT/JP2003/013308 patent/WO2004035850A1/en active Application Filing
- 2003-10-17 US US10/531,319 patent/US20050241733A1/en not_active Abandoned
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH07216497A (en) * | 1994-02-03 | 1995-08-15 | Sumitomo Metal Ind Ltd | Steel sheet or steel sheet parts with high fatigue strength and their production |
| JPH10219393A (en) * | 1997-02-04 | 1998-08-18 | Sumitomo Metal Ind Ltd | Steel material for soft-nitriding, soft-nitrided parts, and their production |
| JP2000246301A (en) * | 1999-02-26 | 2000-09-12 | Natl Res Inst For Metals | Method of manufacturing p-added low-carbon steel of high strength and high toughness |
| JP2001073035A (en) * | 1999-08-31 | 2001-03-21 | Natl Res Inst For Metals | Production of steel having superfine structure |
| JP2001234239A (en) * | 2000-02-25 | 2001-08-28 | National Institute For Materials Science | Producing method for superfine-grained ferritic structure steel |
Also Published As
| Publication number | Publication date |
|---|---|
| EP1580291A4 (en) | 2006-01-18 |
| JP3931230B2 (en) | 2007-06-13 |
| KR20050067184A (en) | 2005-06-30 |
| EP1580291A1 (en) | 2005-09-28 |
| WO2004035850A1 (en) | 2004-04-29 |
| CN1705762A (en) | 2005-12-07 |
| JP2004137561A (en) | 2004-05-13 |
| US20050241733A1 (en) | 2005-11-03 |
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