CN100590209C - Hot-forged products excellent in fatigue strength, process for production thereof, and machine structural parts - Google Patents
Hot-forged products excellent in fatigue strength, process for production thereof, and machine structural parts Download PDFInfo
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- CN100590209C CN100590209C CN200680010358A CN200680010358A CN100590209C CN 100590209 C CN100590209 C CN 100590209C CN 200680010358 A CN200680010358 A CN 200680010358A CN 200680010358 A CN200680010358 A CN 200680010358A CN 100590209 C CN100590209 C CN 100590209C
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Abstract
Hot-forged products obtained by suitably controlling the structure in the hot-forging step, which are improved in the fatigue strength, that is a factor required for withstanding high stress caused bythe weight reduction and/or compactification of hot-forged products, by, e.g., 20% or above as compared with hot-forged products obtained by conventional processes and which exhibit excellent machinability in the machining conducted after hot forging not only in the portions not requiring high fatigue strength but also in the other portions and can be therefore easily finished, more specifically,a hot-forged product having a hardened portion introduced by partial cooling after hot forging and a nonhardened portion, wherein Vickers hardness (V<SUB>1</SUB>) of the hardened portion and Vickershardness (V<SUB>2</SUB>) of the nonhardened portion satisfy the relationship: (V<SUB>1</SUB> - V<SUB>2</SUB>)/V<SUB>2</SUB> = 0.1 to 0.8.
Description
Technical field
The present invention relates to in as with the hot-forged products of engine parts such as the wheel arrangements such as trolley part, for example constant-speed universal coupling and wheel hub that use steel, bent axle as half-finished hot-forged products, particularly the excellent in fatigue strength machine structural parts of representative, before the precision work.
Background technology
Be used for the wheel arrangement of automobile, the product made from steel of engine parts, carry out forge hot usually earlier, carry out precision work by machining then and make.In recent years, with respect to the product of such use,, require to improve fatigue strength in order to realize making as the required miniaturization of the automobile lightweight of its application, thin-walled property.
For example,, whole forged article is quenched after in patent documentation 1, disclosing forge hot as the technology of the fatigue strength that improves hot-forged products, and the manufacture method of the high-fatigue strength hot-forged products by temper precipitation strength matrix.
Patent documentation 1: No. 3100492 communique of patent
But in patent documentation 1 described method, owing to after forge hot whole parts are directly cooled off, thereby the hardness of whole parts uprises, and do not require that the workability at the position of fatigue strength reduces.That is, the machine structural parts of such use after forming shape of product substantially by forge hot, is implemented the precision work that the top layer of this hot-forged products is cut all sidedly usually and is made.Therefore, in the manufacturing of this machine structural parts,, when the hardness of whole parts uprises, must reduce machinability, become big problem though machining and surface grinding are indispensable.
And, need carry out temper in addition in order to carry out precipitation strength to handle, thus not preferred from energy-conservation viewpoint yet.
Summary of the invention
The present invention develops in view of the above problems, its purpose is to provide a kind of hot-forged products by following favourable manufacture method: by suitably control tissue in the forge hot operation, making lightweight, densification because of forged article cause producing stress increases desired fatigue strength and has the forged article that is better than being obtained by existing method for example more than 20%, and be not only the part that does not require fatigue strength, machinability when other parts are in addition implemented machining after forge hot is also good, carries out precision work easily.
Therefore, contriver etc. especially in regard to implement the result that part refrigerative situation is studied with keen determination after forge hot, draw (I) as follows conclusion to (III) in order to reach above-mentioned purpose:
(I) part of the special requirement fatigue strength of hot-forged products is cooled off and partly quenched, the hardness rate of rise of this part can make the fatigue strength as parts improve more than 20% 10% when above.
(II) and, implement the part of incomplete quench by part cooling, because of uncooled position possess heat tempered result voluntarily, can obtain and the existing identical effect of temper of carrying out additional process.And, in order to obtain this effect, this voluntarily tempering satisfy specific parameter.
(III) therefore, owing to carry out tempering again after need not forged article is cooled to room temperature, thereby can make the high-fatigue strength parts with being dirt cheap.
The present invention is based on above-mentioned conclusion proposition.
That is, primary structure of the present invention is as described below:
1. a hot-forged products is characterized in that, has the sclerosis portion that imports by the part after forge hot cooling and non-sclerosis portion, the Vickers' hardness V of the Vickers' hardness V1 of the described sclerosis portion in the surface and described non-sclerosis portion
2Satisfy with following formula (1):
(V
1-V
2)/V
2：0.1～0.8——(1)。
2. according to above-mentioned 1 described hot-forged products, wherein, described sclerosis portion is made of martensitic stucture and/or bainite structure.
3. machine structural parts wherein, is implemented final cold working and is made above-mentioned 1 or 2 described hot-forged products.
4. the manufacture method of a hot-forged products is characterized in that, the forged article that obtains for implementing forge hot partly carries out with the speed more than the 20 ℃/s from A
C3Be cooled to A more than+100 ℃
C1Cooling process below-150 ℃ is then by being no more than A
ClBackheat in the temperature province of point is implemented tempering to this part.
5. according to the manufacture method of above-mentioned 4 described hot-forged products, wherein, the tempering of being undertaken by described backheat, after stopping described cooling, up to reach in the temperature-fall period after backheat 300 ℃ during, according to every Δ T
nThe medial temperature t of second
n(K), satisfy 65≤H≤85 by Parameter H with following formula (2) definition:
H＝log
10∑10
fn——(2)
Wherein, f
n=log Δ t
n-1.597 * 10
4/ T
n+ 100.
According to the present invention, can on the basis that keeps good machinability, realize the high high-fatigue strengthization more than 20% of the existing hot-forged products of fatigue ratio.
Description of drawings
Fig. 1 is the synoptic diagram of the temperature course in the backheat.
Fig. 2 is expression Parameter H and (V
1-V
2)/V
2Between the figure of relation.
Fig. 3 is the process picture sheet of the order of expression forge hot.
Fig. 4 is the figure of the main points of expression flexural fatigue state test.
Wherein, the label declaration among Fig. 3 is as follows:
1 hot-forged products 1
1a flange root
The 1b shaft end
Embodiment
Hot-forged products of the present invention importantly, has the sclerosis portion that imports by the part after forge hot cooling and the non-sclerosis portion except that sclerosis portion, the Vickers' hardness V of the above-mentioned sclerosis portion in the surface
1Vickers' hardness V with above-mentioned non-sclerosis portion
2Satisfy following formula:
(V
1-V
2)/V
2：0.1～0.8。
That is, at (V
1-V
2)/V
2Ratio less than 0.1 time, the intensity of sclerosis portion rises less, can not be improved the effect of fatigue strength fully.On the other hand, at (V
1-V
2)/V
2Ratio surpass at 0.8 o'clock, it is too high that hardness becomes, cold-workabilities such as machinability significantly reduce.Particularly, in the present invention, owing to directly carry out incomplete quench after forge hot, machining after this is indispensable, thereby importantly makes (V
1-V
2)/V
2Below 0.8.Optimum range is 0.2～0.6.
Above-mentioned sclerosis portion with this difference of hardness is made of martensitic stucture and/or bainite structure, but not the part bainite structure is also sneaked into sometimes based on ferritic structure and/or pearlitic structure by sclerosis portion.
Above hot-forged products is directly to carry out incomplete quench after forge hot, obtains through tempering voluntarily then, and through after this cutting precision work and become machine structural parts.
Then, to being used for making (V
1-V
2)/V
2: creating conditions of 0.1～0.8 hot-forged products describes.
That is, copy the general manufacture method of this parts, to the heating of the former material of steel and import warm forming machine and implement forge hot, importantly,, partly carry out with the above speed of 20 ℃/s from A to the forged article that obtains like this
C3Be cooled to A more than+100 ℃
C1Cooling process below-150 ℃.That is, by make the position that requires high-fatigue strength after the forge hot with the above speed of 20 ℃/s from A
C3Be cooled to A more than+100 ℃
C1Below-150 ℃, the ferrite that suppresses in the process of cooling generates, and can make tissue become martensite and/or bainite.
At this, from A
C3More than+100 ℃ to A
C1The part refrigerative reason that temperature province below-150 ℃ is carried out after the forge hot is, in order to obtain sufficient backheat effect, A after cooling
C3Cooling more than+100 ℃ is indispensable, is cooled to A
C1-150 ℃ with next be in order to suppress ferritic generation.
And, make in the said temperature zone speed of cooling 20 ℃/more than the s, be in order to suppress the ferrite transformation in the process of cooling, to make tissue become martensite and/or bainite.
Then, importantly, the backheat by the heat of possessing based on these parts carries out is being no more than A continuously
C1Carry out tempering in the temperature province of point.That is,, backheat surpasses A because of making tempering temperature
ClDuring point, become austenite once more by organizing of incomplete quench formation, and in process of cooling after this, become the ferrite-pearlite tissue.In order to prevent this situation, importantly, be no more than A
C1The temperature province of point is carried out tempering.
And, the tempering of being undertaken by above-mentioned backheat, preferably, after stopping above-mentioned cooling, up to reach in the temperature-fall period after backheat 300 ℃ during, according to every Δ t
nThe medial temperature T of second
n(K), the Parameter H by following formula (2) definition satisfies 65≤H≤85:
H＝log
10∑10
fn ——(2)
Wherein, f
n=log Δ t
n-1.597 * 10
4/ T
n+ 100.
At this, the temperature course when Fig. 1 represents the backheat of part cooling end.T when as shown in Figure 1, the cooling of the cooling curve after cooling stops to stop
1To the temperature-fall period after backheat, reach 300 ℃ moment t
2, obtain each Δ t
nInterior medial temperature T
n(K), apply it to above-mentioned (2) formula and determine Parameter H.At this moment, because the temperature T in the drawing process voluntarily
nChange continuously, thereby establish Δ t
nBelow 0.5 second and find the solution.
Represent above-mentioned ratio (V at Fig. 2
1-V
2)/V
2And the relation between the Parameter H.As shown in Figure 2, Parameter H is closely related with hardness ratio, during Parameter H less than 65, because the tempering effect is insufficient, thereby hardness ratio (V
1-V
2)/V
2Surpass 0.8, machinability is a problem.And Parameter H surpasses at 85 o'clock, overbate owing to become, thereby (V
1-V
2)/V
2Less than 0.1, the effect of the fatigue strength that can not be improved.
As mentioned above, obtain hot-forged products of the present invention, do not form, but recommend following one-tenth to be grouped into as preferred component though do not rely on composition can under prescribed condition, implement the part cooling process:
C:0.3～0.9 quality %
C is an element essential when improving the intensity of steel.Owing to can not get necessary strength during C quantity not sufficient 0.3 quality %, and cause the reduction of machinability, fatigue strength and forging property when surpassing 0.9 quality %, thereby 0.3～0.9 quality % is made as preferable range.
Si:0.01～1.2 quality %
Si not only plays a role as reductor, but also help to improve effectively intensity, because this effect is insufficient when containing quantity not sufficient 0.01 quality %, causes the reduction of forging property, cold-workability when surpassing 1.2 quality %, thereby 0.01～1.2 quality % is made as preferable range.
Mn:0.01～2.0 quality %
Mn not only improves intensity, also helps to improve effectively fatigue strength, but since when containing quantity not sufficient 0.01 quality % this effect insufficient, make forging property, machinability variation when surpassing 2.0 quality %, thereby 0.01～2.0 quality % be made as preferable range.
More than be preferred basal component, requiring further to improve under the situation of fatigue strength, also can suitably contain following element:
Mo:0.05～0.60 quality %
Mo is to suppressing the useful element of growth of ferrite particles, needs at least more than 0.05 quality % for this reason, but because addition causes the machinability variation when surpassing 0.60 quality %, thereby be preferably 0.05～0.60 quality %.
Al:0.01～0.06 quality %
Al plays a role as the reductor of steel.But, because this effect deficiency when containing quantity not sufficient 0.01 quality % causes the reduction of machinability and fatigue strength when surpassing 0.06 quality %, thereby is preferably 0.01～0.06 quality %.
Ti:0.005～0.050 quality %
Ti is that blockage effect by TiN is to making the useful element of crystal grain granular, in order to obtain this effect, need add at least more than the 0.005 quality %, cause the reduction of fatigue strength when surpassing 0.050 quality %, thereby be preferably the scope of 0.005～0.050 quality % owing to addition.
Below the Ni:1.0 quality %
Ni is the crackle effective elements that intensity is risen and produces when preventing to add Cu, though preferably must add 0.05 quality %, because the Ni that adds amount causes hardening crack when surpassing 1.0 quality % easily, thereby preferably, is limited in below the 1.0 quality %.
Below the Cr:1.0 quality %
Cr rises effectively to intensity, though preferably add more than the 0.05 quality %, but when surpassing 1.0 quality % owing to addition, make carbide stable and promote the generation of remaining carbide, grain-boundary strength is reduced, and cause the reduction of fatigue strength, thereby preferably, be limited in below the 1.0 quality %.
Below the V:0.1 quality %
V is a carbide forming element, is that performance is by blocking the element of organizing the granular effect that produces.The preferred interpolation more than the 0.005 quality %, but since when surpassing 0.1 quality % effect saturated, thereby preferably, be limited in 0.1 quality %.
Below the Cu:1.0 quality %
Because Cu is the element that intensity is improved by solution strengthening, precipitation strength, and effective to the raising of hardenability, thereby preferably add more than the 0.1 quality %, but because the crackle of content when hot-work taking place when surpassing 1.0 quality %, thereby preferably, be limited in below the 1.0 quality %.
Below the Nb:0.05 quality %
Nb separates out as carbide or carbonitride, has the effect that suppresses crystal grain-growth by obstruction, preferably add more than the 0.005 quality %, but since addition when surpassing 0.05 quality % this effect saturated, thereby preferably, be limited in below the 0.05 quality %.
Below the Ca:0.008 quality %
Ca has by making the inclusion englobement improve the effect of fatigue characteristic.The preferred interpolation more than the 0.001 quality %, but make the trend that inclusion is thick, make the fatigue characteristic variation because addition has when surpassing 0.008 quality %, thereby preferably, be limited in below the 0.008 quality %.
Below the B:0.004 quality %
B not only can separate out in crystal boundary and improve fatigue strength by grain-boundary strengthening, also helps raising intensity.The preferred interpolation more than the 0.003 quality %, but since addition when surpassing 0.004 quality % this effect saturated, thereby preferably, be limited in below the 0.008 quality %.
In addition, surplus is Fe and unavoidable impurities.As unavoidable impurities, can enumerate P, S, O and N.
Embodiment
Melt out the steel that chemical ingredients shown in the table 1 is formed with the vacuum melting stove, and be cast as the steel ingot of 100kg.Then, by forge hot steel ingot is made the rolling bar steel of 65mm φ.After should rolling bar steel being heated to 1000～1200 ℃, implementing forge hots shown in Figure 3,3 stages and form the hot-forged products 1 of the flange shown in (d) that has Fig. 3.After this forge hot, only flange root 1a is carried out the part cooling at once, put cold then.
Wherein, the temperature of forge hot is measured by radiation thermometer, at flange root 1a thermopair is installed after the forge hot, measures temperature course, thereby can recover Parameter H in calculating.In this calculates, establish Δ t=0.5 second, temperature T is used the medial temperature (K) in each Δ t.
About the hot-forged products that obtains like this, implement structure observation, measurement of hardness, the test of flexural fatigue state and cutting test according to following main points.In order to compare, also make forged article by normally used forge hot-air cooling technology and forge hot in the past-all Q-tempering technology.After all quenching, carry out the temper of 600 ℃ * 1h of tempering temperature.And,, further carry out high-frequency quenching and handle in the part of forge hot-air cooling material.
At first, during tissues observed, cut out the sample that is used for tissues observed from the flange root 1a and the shaft end 1b of the hot-forged products that obtains, and with opticmicroscope and its nitric acid ethanol corrosion structure of electron microscope observation.
During Vickers' hardness is measured, respectively in the Vickers' hardness of having measured 1mm under epidermis under the load of 300g from flange root 1a and shaft end 1b.
And, in the flexural fatigue device experiment, as shown in Figure 4, by standing bolt hot-forged products is installed on the turning axle, with main points applied load shown in Figure 4, and with the rotation of the rotating speed of 800rpm the time, at the flange part applied load, carrying out long duration test, thereby obtain the durable time at 120 hours fatigue strength.
Machinability in the cutting test is estimated by periphery is implemented cutting.That is, use sintered carbide tools P10, with cutting speed 200m/min, incision 0.25mm and feeding 0.5mm/rev and spray lubricant and implement, by by implementing cutting and whole parts being cut the required time estimate.At this moment, establishing the time t1 required time required with respect to the cutting of existing forge hot-air cooling process materials is t2, estimates with (t2-t1)/t1.
In table 2, No.1～5,14,16,18 and 20 are example of the present invention, can improve machinability in the fatigue strength that improves than the manufactured materials in the existing technology more than 25%.
No.6 and 7, lower in cooling beginning temperature, voluntarily under the situation that tempering parameter H is lower, the insufficient and hardness of the tempering of sclerosis portion rises bigger, thus machinability is poor.No.8 since cooling to stop temperature higher, thereby the quenching effect of tissue is insufficient, thereby can not improve fatigue strength.No.9 because Parameter H surpasses 85, thereby can not fully make fatigue strength rise.No.10, the speed of cooling after the forge hot is insufficient, can not obtain sufficient sclerotic tissue, thereby can not improve fatigue strength.No.11 is the comparative example of being made by existing general thermal forging technology.No.12 is the steel that all quenches after the forge hot, can not improve fatigue strength, and machinability is relatively poor.No.13 is the local steel that carries out quench treatment after the forge hot, can not improve fatigue strength, and machinability is relatively poor.No.11,15,17,19 and 21 is steel of being made by existing technology, is used for carrying out fatigue strength relatively with local cooling material.
Claims (4)
1. a hot-forged products is characterized in that, has the sclerosis portion that imports by the part after forge hot cooling and non-sclerosis portion, the Vickers' hardness V of the described sclerosis portion in the surface
1Vickers' hardness V with described non-sclerosis portion
2Satisfy with following formula (1):
(V
1-V
2)/V
2：0.1～0.8——(1)。
2. hot-forged products according to claim 1, wherein, described sclerosis portion is made of martensitic stucture and/or bainite structure.
3. machine structural parts wherein, is implemented final cold working and is made claim 1 or 2 described hot-forged products.
4. the manufacture method of a hot-forged products is characterized in that, the forged article that obtains for implementing forge hot partly carries out with the speed more than the 20 ℃/s from A
C3Be cooled to A more than+100 ℃
C1Cooling process below-150 ℃ is then by being no more than A
C1Backheat in the temperature province of point is implemented tempering to this part, wherein, after stopping described cooling, up to reach in the temperature-fall period after backheat 300 ℃ during, according to every Δ t
nSecond be the medial temperature T of unit with K
n, making by the Parameter H with following formula (2) definition is 65≤H≤85:
H＝log
10∑10
fn——(2)
Wherein, f
n=log Δ t
n-1.597 * 10
4/ T
n+ 100.
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2005190220 | 2005-06-29 | ||
| JP190220/2005 | 2005-06-29 | ||
| JP205170/2005 | 2005-07-14 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101151381A CN101151381A (en) | 2008-03-26 |
| CN100590209C true CN100590209C (en) | 2010-02-17 |
Family
ID=39251263
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN200680010358A Expired - Fee Related CN100590209C (en) | 2005-06-29 | 2006-06-05 | Hot-forged products excellent in fatigue strength, process for production thereof, and machine structural parts |
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| Country | Link |
|---|---|
| CN (1) | CN100590209C (en) |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101942549B (en) * | 2010-05-27 | 2013-02-27 | 德阳市秦南铸锻钢制造有限公司 | Heat treatment process for adjusting valve disc forge piece of supercritical steam turbine unit |
| JP5786968B2 (en) * | 2012-01-31 | 2015-09-30 | 日産自動車株式会社 | Manufacturing method of forged products |
| CN105385816A (en) * | 2015-10-27 | 2016-03-09 | 浙江万向精工有限公司 | Forging waste heat normalizing process for hub bearing unit ferrule |
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2006
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| CN101151381A (en) | 2008-03-26 |
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Granted publication date: 20100217 |