CN112375883A - Anti-fatigue strengthening method for crankshaft journal - Google Patents
Anti-fatigue strengthening method for crankshaft journal Download PDFInfo
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- CN112375883A CN112375883A CN202011271559.XA CN202011271559A CN112375883A CN 112375883 A CN112375883 A CN 112375883A CN 202011271559 A CN202011271559 A CN 202011271559A CN 112375883 A CN112375883 A CN 112375883A
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- 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
- C21D7/00—Modifying the physical properties of iron or steel by deformation
- C21D7/02—Modifying the physical properties of iron or steel by deformation by cold working
- C21D7/04—Modifying the physical properties of iron or steel by deformation by cold working of the surface
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- Crystallography & Structural Chemistry (AREA)
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- Organic Chemistry (AREA)
- Shafts, Cranks, Connecting Bars, And Related Bearings (AREA)
Abstract
The invention discloses an anti-fatigue strengthening method of a crankshaft journal, which comprises the following steps: s1: processing a surface structure on the surface of a crankshaft journal, wherein the surface structure is a concave-convex texture with a peak-valley height difference of 6-40 microns; s2: the surface structure is processed before the rolling strengthening treatment, so that after the rolling strengthening treatment is adopted, a larger and deeper residual compressive stress layer and a residual compressive stress with preset directionality can be generated on the surface of a crankshaft journal, the value of the residual compressive stress on the outermost surface is increased, the effect of the rolling strengthening is enhanced, the surface layer of the crankshaft journal is easier to generate severe plastic deformation and grain refinement, and the preparation of an ultrafine grain or nanocrystalline surface layer material is facilitated.
Description
Technical Field
The invention relates to the technical field of crankshaft processing, in particular to an anti-fatigue strengthening method for a crankshaft journal.
Background
The emission standard of an automobile engine becomes the focus of global automobile industry attention, low emission and less pollution are inevitable trends of automobile engine development, therefore, the engine supercharging and supercharging intercooling technology comes along with the development of the engine supercharging and supercharging intercooling technology, the requirement on the fatigue strength of an engine crankshaft is higher and higher, the corresponding crankshaft strengthening technology is developed rapidly in recent years, and the most obvious effect is the crankshaft rolling strengthening technology.
The rolling strengthening technology has the following characteristics: first, the depth of the strengthening layer that can be produced is small, limited by the hertzian contact deformation. Secondly, the maximum residual compressive stress is not generally at the outermost surface but at a subsurface of a certain depth, but fatigue cracks are often generated at the surface of the material. Thirdly, the residual stress is isotropic in the plane parallel to the surface, but the working stress of the actual part and structure is generally directional. And fourthly, due to the three-dimensional compressive stress effect of Hertz contact, the grain refinement based on the violent plastic deformation mechanism is difficult. The above characteristics limit the strengthening effect that can be achieved by the rolling strengthening technology.
Disclosure of Invention
The invention provides an anti-fatigue strengthening method for a crankshaft journal.
In order to achieve the purpose, the invention provides the following technical scheme:
a method for fatigue-resisting and strengthening a crankshaft journal comprises the following steps:
s1: processing a surface structure on the surface of a crankshaft journal, wherein the surface structure is a concave-convex texture with a peak-valley height difference of 6-40 microns;
s2: and (3) rolling and strengthening treatment to extrude the concave-convex texture to generate shearing deformation so as to reduce the height difference between the peaks and the valleys of the concave-convex texture to 1-8 microns.
Preferably, the uneven texture has isotropy and is arranged regularly, or has isotropy and is arranged randomly.
Preferably, the concave-convex texture is parallel straight ripples or parallel curved ripples, and the wavelength is 2-5 times of the height difference between peaks and valleys.
Preferably, the waveform is a sine wave, a cosine wave, a sawtooth wave, an inverted trapezoidal wave, an orthotrapezoidal wave, a double trapezoidal wave, an inverted arc wave and/or an orthoarc wave.
Preferably, the concavo-convex texture is a convex body or a notch.
Preferably, in step S2, the crankshaft journal at one end is fixedly connected to the journal clamping tool, the crankshaft bell crank is clamped by the balance weight clamp, the journal clamping tool is clamped by the spindle chuck, the crankshaft journal at the other end is pressed by the ejector pin, the crankshaft rotation center, the ejector pin and the journal clamping tool rotation center are consistent, and the outer circle of the crankshaft journal is roll-processed by the hob.
Preferably, the cutting speed of the hob is 155 m/min-165 m/min, the feeding speed of the hob is 0.08 mm/rotation-0.12 mm/rotation, and the cutter head of the hob is a diamond cutter head.
Preferably, step S1 is preceded by performing oil removal, rust removal, cleaning and drying on the surface of the crankshaft journal.
The invention has the beneficial effects that:
the surface structure is processed before the rolling strengthening treatment, so that after the rolling strengthening treatment is adopted, a larger and deeper residual compressive stress layer and residual compressive stress with preset directionality can be generated on the surface of the crankshaft journal, and the value of the outermost residual compressive stress is increased, so that the rolling strengthening effect is enhanced, the surface layer of the crankshaft journal is easier to generate severe plastic deformation and grain refinement, and the preparation of an ultrafine grain or nanocrystalline surface layer material is facilitated.
Description of the drawings:
FIG. 1 is a schematic diagram of a parallel straight corrugation structure according to the present invention;
FIG. 2 is a schematic structural view of a parallel curved corrugation according to the present invention;
FIG. 3 is a longitudinal sectional wave representation of a surface structure;
FIG. 4 is a schematic structural diagram of a convex body of the present invention;
FIG. 5 is a structural view of a score of the present invention;
FIG. 6 is a schematic view of a hob colliding with a smooth surface of a crankshaft journal to generate plastic deformation;
FIG. 7 is a schematic view of the plastic deformation of the hob caused by contact and collision with the surface structure;
FIG. 8 is a graph showing a distribution curve of compressive residual stress.
In the drawings: 1-crankshaft journal, 2-surface structure, 3-waveform, 4-peak, 5-trough, 6-surface structure transverse, 7-surface structure longitudinal, 8-hob, 9-plastic deformation, 10-crankshaft journal with processed surface structure residual compressive stress curve generated after rolling strengthening treatment, 11-crankshaft journal with unprocessed surface structure residual compressive stress curve generated after rolling strengthening treatment, 12-residual compressive stress surface value, 13-residual compressive stress maximum value, 14-peak-valley height difference (h), 15-wavelength (L), 16-waveform angle (d), 17-waveform back dip angle (beta), 18-sine/cosine wave, 19-sawtooth wave, 20-inverted trapezoidal wave, 21-orthotrapezoidal wave, 22-double trapezoidal wave, 23-inverted arc type wave and 24-positive arc type wave.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first embodiment is as follows:
a method for fatigue-resisting and strengthening a crankshaft journal comprises the following steps:
firstly, the surface of a crankshaft journal is subjected to oil removal, rust removal, cleaning and drying treatment, and is polished by abrasive paper until the surface is smooth and clean and has roughness.
Next, as shown in fig. 1 and 2, a surface structure 2 is processed on the surface of the crankshaft journal 1, wherein the surface structure 2 is a concave-convex texture with a peak-to-valley height difference of 6-40 microns. Specifically, in this embodiment, the concave-convex textures have isotropy and are arranged regularly, and preferably, the concave-convex textures are parallel straight ripples as shown in fig. 1, or the concave-convex textures are parallel curved ripples as shown in fig. 2. That is, the uneven texture is a waveform 3 having a peak-to-valley height difference 14 (i.e., a height difference between the peak 4 and the valley 5) and a wavelength 15, and the wavelength 15 is 2 to 5 times the peak-to-valley height difference 14. Further, as shown in fig. 3, the waveform 3 of the uneven texture may be a sine/cosine wave 18, a sawtooth wave 19, an inverted trapezoidal wave 20, a regular trapezoidal wave 21, a double trapezoidal wave 22, an inverted arc wave 23, and a regular arc wave 24, but is not limited to the above waveform 3. The surface structure 2 can be obtained by turning, milling, grinding, wire brushing, sand blasting, chemical etching and laser etching, but is not limited to the above methods.
In other embodiments, the concave-convex texture has isotropy and is randomly arranged, and preferably, the concave-convex texture is convex as shown in fig. 4, or the concave-convex texture is concave as shown in fig. 5.
Finally, carry out the roll extrusion strengthening treatment to the bent axle journal 1 that processes out surface structure 2, press from both sides bent axle journal 1 and the journal of one end and press from both sides tight frock fixed connection, the bent axle crank throw presss from both sides tightly with balanced weight anchor clamps, the journal presss from both sides tight frock and presss from both sides tightly through the main shaft chuck, with the bent axle journal 1 of the other end through the thimble top to guarantee that bent axle centre of gyration, thimble and journal press from both sides tight frock centre of gyration unanimous, carry out roll-forming to bent axle journal excircle with hobbing cutter 8, hobbing cutter 8 extrusion concave-convex texture produces shear deformation, makes concave-convex texture's peak valley difference in height reduce to 1 ~ 8 microns, in order to prevent surface structure 2 to.
As shown in fig. 6, when the hob 8 collides with the smooth surface of the crankshaft journal 1, the portion immediately below the contact area is in a three-way compressive stress state due to the combined action of hertzian contact and friction, which is not favorable for causing plastic deformation of the contact surface.
As shown in FIG. 7, when the surface structure 2 is processed on the surface of the crankshaft journal 1, the hob 8 firstly presses the peaks 4 of the surface structure to cause the material at the peaks 4 to try to be pressed in, and the material at the troughs 5 can be extruded to a certain extent, so as to generate a 'peak-off valley-filling' effect, reduce or eliminate the initial roughness formed by the surface structure 2, make the peaks 4 more prone to generate shear deformation, increase the stress deflection, reduce the three-way compressive stress, make the contact surface more prone to generate plastic deformation 9, increase the grain refinement and work hardening effects generated by the surface rolling strengthening, and be more suitable for processing surface grain or nano-grained layer.
Meanwhile, when the surface structure 2 is parallel straight corrugation or parallel curved corrugation, and the hob 8 and the surface structure 2 are in contact collision, the constraint effect of the longitudinal direction 7 of the surface structure on deformation is weaker than that of the transverse direction 6 of the surface structure, so that larger plastic deformation and larger residual compressive stress can be generated in the longitudinal direction 7 of the surface structure, and the residual compressive stress on the surface has preset directionality. That is, when the surface structure 2 is a parallel straight corrugation or a parallel curved corrugation, the plastic deformation 9 is generated with a directivity in relation to the surface structure 2, so that the surface residual compressive stress has a predetermined directivity, and the residual compressive stress generated in the longitudinal direction 7 of the surface structure is larger than the residual compressive stress generated in the transverse direction 6 of the surface structure.
As shown in fig. 8, when the hob 8 makes contact collision with the smooth surface of the crankshaft journal 1, the value 12 of the surface of the outermost residual compressive stress is small because the plastic deformation of the material immediately adjacent to the contact surface is relatively small. The crankshaft journal 1 with the surface structure 2 is processed to enable the maximum plastic deformation to be closer to the surface after the rolling strengthening treatment, so that the surface value 12 of the residual compressive stress on the outermost surface is increased, and the maximum value 13 of the residual compressive stress is closer to the surface. That is, the residual compressive stress curve 11 generated after the rolling strengthening treatment of the crankshaft journal with an unprocessed surface structure is not suitable for exerting the fatigue resistance of the material. The residual compressive stress curve 10 generated after the crankshaft journal 1 of the prefabricated surface structure 2 is subjected to rolling strengthening treatment enhances the rolling strengthening effect. That is to say, the surface structure 2 will alleviate the hertzian contact three-dimensional compressive stress, increase shear stress and shear strain, make the crankshaft journal 1 produce plastic deformation more easily to produce bigger residual compressive stress, simultaneously, the biggest residual compressive stress is closer to the crankshaft journal 1 surface, produces ultra-fine grain or nanocrystalline because of violent plastic deformation more easily.
Example two:
parts of this embodiment that are the same as those of the first embodiment are not described again, except that:
the surface structure 2 is machined by turning, milling or grinding on a common machine tool or a numerical control machine tool. First, the feed rate is determined from the peak-to-valley height difference 14 and the wavelength 15 of the surface structure 2 by selecting or customizing the appropriate tool according to the material used for the crankshaft journal 1. Secondly, after the prefabrication of the surface structure 2 is finished, surface rolling strengthening treatment is carried out in the shortest possible time to prevent oxidation or corrosion, the cutting speed of a hob is 155-165 m/min, the feeding speed of the hob is 0.08-0.12 mm/r, and the cutter head of the hob is a diamond cutter head.
Aiming at the anti-fatigue strengthening treatment, when a machining method is adopted to prefabricate a parallel straight ripple surface structure or a parallel curved ripple surface structure, the longitudinal direction 7 of the surface structure needs to be consistent with the working main stress direction of a crankshaft journal so as to ensure better subsequent strengthening effect.
Example three:
the peak-to-valley height difference 14 of the surface structure 2 is different according to different materials and rolling strengthening treatment, and the selection principle is as follows: the surface roughness of the prefabricated surface structure 2 after the rolling strengthening treatment is not more than that of the smooth surface after the rolling strengthening treatment, so that additional stress concentration caused by the prefabricated surface structure 2 is avoided. At the same time, the higher the material hardness, the higher the peak to valley height difference 14 of the desired preformed surface structure 2. The higher the rolling strength, the higher the peak to valley height difference 14 of the desired preformed surface structure 2. Further, the roughness is detected using a roughness meter or a surface profiler, but is not limited to the above method.
Experiment one:
a high-strength steel (strength limit 1300 MPa-1600 MPa) bar-shaped test piece is selected, a sawtooth wave surface structure with a prefabricated peak-valley height difference of 30 mu m is machined, a hob is adopted for cutting at 160m/min, and the feeding speed of the hob is 0.09 mm/r. After rolling strengthening, the surface roughness is reduced to 3-4 μm by measurement. Compared with a smooth surface part with an unprepared surface structure, the surface microhardness of the roll-strengthened preformed sawtooth wave surface structure is improved by 6%, the residual surface compressive stress is increased by 15-20%, the stress ratio is-1, and the rotary bending fatigue life under the stress amplitude of 900-1100 MPa is improved by 15-50%.
Experiment two:
a high-strength aluminum alloy rod-shaped test piece is selected, a convex surface structure with 20 mu m of peak-valley height difference is prefabricated by turning, the cutting speed of a hob is 160m/min, and the feeding speed of the hob is 0.09 mm/rotation. After rolling strengthening, the surface roughness is reduced to 2-3 μm by measurement. Compared with a smooth surface part with an unprepared surface structure, the surface microhardness of the prefabricated convex body surface structure after roll strengthening is improved by 6.8%, the surface residual compressive stress is increased by 15-18%, the stress ratio is-1, and the rotary bending fatigue life under the stress amplitude of 900-1100 MPa is improved by 25-50%.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (8)
1. A method for fatigue-resisting and strengthening a crankshaft journal is characterized by comprising the following steps:
s1: processing a surface structure on the surface of a crankshaft journal, wherein the surface structure is a concave-convex texture with a peak-valley height difference of 6-40 microns;
s2: and (3) rolling and strengthening treatment to extrude the concave-convex texture to generate shearing deformation so as to reduce the height difference between the peaks and the valleys of the concave-convex texture to 1-8 microns.
2. The method of claim 1, wherein the asperities are isotropic and regularly arranged or isotropic and randomly arranged.
3. The method of claim 2, wherein the uneven texture is parallel straight or parallel curved corrugation and the wavelength is 2-5 times of the difference between the peak and the valley heights.
4. The method of claim 3, wherein the waveform is a sine wave, a cosine wave, a sawtooth wave, an inverted trapezoidal wave, a regular trapezoidal wave, a double trapezoidal wave, an inverted arc wave, and/or a regular arc wave.
5. The method of claim 2, wherein the asperities are protrusions or indentations.
6. The method for fatigue-resistance strengthening of the crank journal according to any one of claims 2 to 5, wherein in step S2, the crank journal at one end is fixedly connected to a journal clamping tool, the crank throw of the crank is clamped by a balance weight clamp, the journal clamping tool is clamped by a spindle chuck, the crank journal at the other end is pressed by an ejector pin, and the outer circle of the crank journal is roll-processed by a hob cutter while ensuring the rotation center of the crank, the ejector pin and the rotation center of the journal clamping tool to be the same.
7. The method of claim 6, wherein the hob is operated at a cutting speed of 155m/min to 165m/min, the hob is operated at a feeding speed of 0.08 mm/rpm to 0.12 mm/rpm, and the hob head is a diamond head.
8. The method of claim 7, wherein the step S1 is preceded by degreasing, descaling, cleaning, and drying the surface of the crankshaft journal.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202011271559.XA CN112375883A (en) | 2020-11-13 | 2020-11-13 | Anti-fatigue strengthening method for crankshaft journal |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011271559.XA CN112375883A (en) | 2020-11-13 | 2020-11-13 | Anti-fatigue strengthening method for crankshaft journal |
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| CN112375883A true CN112375883A (en) | 2021-02-19 |
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| CN202011271559.XA Pending CN112375883A (en) | 2020-11-13 | 2020-11-13 | Anti-fatigue strengthening method for crankshaft journal |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114182076A (en) * | 2021-12-10 | 2022-03-15 | 北京理工大学 | Ultrasonic rolling surface residual stress regulation and control method by prefabricating surface processing texture |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1546276A (en) * | 2003-12-11 | 2004-11-17 | 东风汽车有限公司 | Crankshaft rolling strengthening process |
| CN102501037A (en) * | 2011-11-08 | 2012-06-20 | 沃得重型机床（中国）有限公司 | Machining method for crankshaft |
| CN105886728A (en) * | 2016-05-05 | 2016-08-24 | 中国人民解放军装甲兵工程学院 | Method for improving mechanical surface strengthening effect |
| CN107470872A (en) * | 2017-10-20 | 2017-12-15 | 湖州正德轻工机械有限公司 | A kind of processing method of bent axle |
-
2020
- 2020-11-13 CN CN202011271559.XA patent/CN112375883A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1546276A (en) * | 2003-12-11 | 2004-11-17 | 东风汽车有限公司 | Crankshaft rolling strengthening process |
| CN102501037A (en) * | 2011-11-08 | 2012-06-20 | 沃得重型机床（中国）有限公司 | Machining method for crankshaft |
| CN105886728A (en) * | 2016-05-05 | 2016-08-24 | 中国人民解放军装甲兵工程学院 | Method for improving mechanical surface strengthening effect |
| CN107470872A (en) * | 2017-10-20 | 2017-12-15 | 湖州正德轻工机械有限公司 | A kind of processing method of bent axle |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114182076A (en) * | 2021-12-10 | 2022-03-15 | 北京理工大学 | Ultrasonic rolling surface residual stress regulation and control method by prefabricating surface processing texture |
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Application publication date: 20210219 |
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