Anti-fatigue automobile accessory bolt and heat treatment processing technology thereof

Abstract

The invention discloses an anti-fatigue automobile accessory bolt and a heat treatment processing technology thereof, and relates to the technical field of bolt production. Comprising the steps that the anti-fatigue automobile accessory bolt to be machined is cleaned and dried; the cleaned to-be-machined anti-fatigue automobile accessory bolt is heated and subjected to heat preservation through the heating box and then rapidly cooled, and in the heating and heat preservation process, the continuous position change of the to-be-machined anti-fatigue automobile accessory bolt is kept; cleaning and drying the to-be-processed anti-fatigue automobile accessory bolt again; the anti-fatigue automobile accessory bolt to be machined is quenched and then rapidly immersed in a quenching oil bath to be cooled; and the quenched anti-fatigue automobile accessory bolt to be machined is tempered, and finally natural cooling is conducted, so that the finished anti-fatigue automobile accessory bolt is obtained. In the bolt heating process, the bolts are kept moving continuously, the positions of the bolts are exchanged, the heating uniformity of the bolts is improved, and the problem that heating equipment and the positions of the bolts are heated unevenly is solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bolt production, in particular to an anti-fatigue automobile accessory bolt and a heat treatment processing technology thereof. BACKGROUND

[0002] Bolt heat treatment is a key process to improve its performance, generally including quenching and tempering two steps. Quenching is to heat the bolt above the critical temperature, and after holding, it is rapidly cooled to make the internal organization into high-hardness martensite, which greatly improves the strength and hardness. But the bolt is brittle after quenching, and needs to be tempered. It is heated to an appropriate temperature and cooled after holding for a period of time, which can eliminate internal stress, adjust hardness and toughness, so that the bolt has sufficient strength and good toughness to meet the needs of different working conditions.

[0003] The process of heat treatment is different, and the improvement of bolt performance will be different. For example, the patent with publication number CN119372438A discloses a bolt heat treatment device and process, which includes a heat treatment box, the inner wall of the heat treatment box is symmetrically provided with two bidirectional drive rods, two heat insulation plates are threadedly sleeved between the two bidirectional drive rods, and the two heat insulation plates are respectively movably inserted into the left and right sides of the heat treatment box. When the bolt holder moves, the guide rod slides along the inner wall of the guide groove, so that the bolt holder shakes left and right, and the bolt is shaken to shake off the debris on its surface. At the same time, the debris is collected by the heat insulation plate, and the possibility of affecting the heat treatment effect of the bolt by the debris is reduced. Through the toothed plate, the bidirectional drive rod is rotated, and the heat insulation plate is moved, so that the heat treatment box is opened, and the bolt holder is moved to the lower side of the heat insulation plate, and the heat insulation plate is reset by continuing to move the toothed plate, so that the heat treatment box is sealed, and the possibility of heat loss is reduced.

[0004] During the heat treatment of the bolt, it is necessary to ensure that each bolt is uniformly heated to ensure the heat treatment effect of the bolt. However, the above process and the existing heat treatment process do not move the bolt relatively during the heating process of the bolt, which is difficult to improve the problem of uneven heating caused by the heating equipment itself and the position of the bolt, and the heat treatment effect is poor. SUMMARY

[0005] The purpose of the present application is to provide an anti-fatigue automobile accessory bolt heat treatment processing technology to solve the problems raised in the background art.

[0006] To achieve the above purpose, the present application provides the following technical scheme: an anti-fatigue automobile accessory bolt heat treatment processing technology, comprising: S1: washing and drying the anti-fatigue automobile accessory bolt to be processed; S2: The cleaned anti-fatigue steam fitting bolt to be processed is heated to 870-890 DEG C by a heating box and is kept for 60-75 min, and then is rapidly cooled down. During the heating and keeping, the anti-fatigue steam fitting bolt to be processed is kept in continuous position change; S3: The anti-fatigue steam fitting bolt to be processed is cleaned and dried again, and then is heated to 560-580 DEG C, and is kept for 80-90 min, and then is cooled down; S4: The anti-fatigue steam fitting bolt to be processed is quenched, the quenching temperature is 860-880 DEG C, the heating time is 30-45 min, and then is rapidly immersed into a quenching oil pool for cooling; S5: The quenched anti-fatigue steam fitting bolt to be processed is tempered, the tempering temperature is 330-350 DEG C, the heating time is 100-120 min, and then is naturally cooled down to obtain the finished anti-fatigue steam fitting bolt.

[0007] Preferably, the heating box comprises a box body, a cylindrical heating cavity is arranged inside the box body, heating resistance wires are arranged inside the sidewall of the box body, a cover body is arranged at the upper end of the box body, a bottom disc is rotatably arranged at the bottom of the cylindrical heating cavity, a driving motor for driving the rotation of the bottom disc is mounted at the bottom of the box body, a support base is arranged inside the box body, the support base is placed above the bottom disc, a positioning mechanism is arranged on the support base, a plurality of circumferentially distributed storage racks are arranged above the support base, and a plurality of storage discs for placing bolts are arranged on the storage racks.

[0008] Preferably, the positioning mechanism comprises a plurality of positioning rods fixed on the bottom disc, the positioning rods are circumferentially distributed, a plurality of positioning grooves are formed at the edge of the support base and have the same number as the positioning rods, and the positioning rods are respectively located inside the corresponding positioning grooves.

[0009] Preferably, the storage racks are composed of a plurality of short rods stacked together, positioning sleeves are arranged at the upper ends of the short rods, the bottoms of the short rods can be inserted into the positioning sleeves, the storage discs are fixed on the short rods, a plurality of circumferentially distributed round holes are formed in the upper surface of the support base, the bottom of the lowermost short rod is rotatably inserted into the round hole, the cover body is located inside the cylindrical heating cavity, and the heating resistance wires can be controlled to be turned on and off in layers.

[0010] Preferably, a tooth ring is fixed at the center position of the lower surface of the cover body, a plug rod is inserted into the uppermost positioning sleeve, a gear is fixed at the upper end of the plug rod, the gear is engaged with the tooth ring, a vertical groove is formed in the inner wall of the box body, a protrusion is arranged at the edge of the cover body, and the protrusion is located inside the vertical groove.

[0011] Preferably, a center hole is formed at the middle position of the cover body, and a center rod is arranged at the upper end of the support base and penetrates through the center hole.

[0012] Preferably, a handle is arranged at the upper end of the cover body.

[0013] Based on the same inventive concept, an anti-fatigue automobile accessory bolt is also provided, which is prepared by the anti-fatigue automobile accessory bolt heat treatment process described above, and the anti-fatigue automobile accessory bolt to be processed is a low-alloy high-strength steel, and the components thereof comprise, by mass percentage, C 0.18-0.23%, Si 0.15-0.35%, Mn 1.2-1.6%, Cr 0.8-1.2%, Mo 0.15-0.25%, V 0.05-0.12%, B 0.001-0.005%, and the balance is Fe. After quenching + low-temperature tempering treatment, the core hardness of the anti-fatigue automobile accessory bolt to be processed is 38-42 HRC, and the surface compressive stress is greater than or equal to 500 MPa.

[0014] Preferably, the surface of the anti-fatigue automobile accessory bolt to be processed is sequentially covered from inside to outside with: A nanocrystallized nickel-phosphorus alloy plating layer, the thickness of which is 3-8 microns, the grain size of which is less than or equal to 50 nanometers, and the hardness of which is greater than or equal to 600 HV; A rare earth modified zinc-nickel alloy plating layer, the rare earth element content of which is 0.5-2 wt%, and the thickness of which is 10-15 microns; A composite lubricating plating layer containing graphite-like carbon, the thickness of which is 1-3 microns, and the friction coefficient of which is less than or equal to 0.12; The nanocrystallized nickel-phosphorus alloy plating layer, the rare earth modified zinc-nickel alloy plating layer, and the composite lubricating plating layer are formed by a pulse electrodeposition process, the total thickness of which is not more than 25 microns, and the interlayer bonding strength of which is greater than or equal to 35 MPa.

[0015] Preferably, the composite lubricating plating layer also contains nanometer titanium dioxide particles, the particle size of which is 20-50 nanometers, and the content of which is 0.5-1.5 wt%; The fluctuation value of the friction coefficient of the composite lubricating plating layer is not more than 0.03 within the temperature range of -40 DEG C to 150 DEG C, and the salt spray corrosion resistance time is greater than or equal to 1000 hours.

[0016] Compared with the prior art, the beneficial effects of the present application are: By heating the box, the bolts are kept moving and exchanging positions between the bolts during heating, heat preservation and natural cooling, thereby improving the heating uniformity of the bolts and reducing the problem of uneven heating caused by the heating equipment itself and the bolt positions.

[0017] At the same time, the cover body cannot rotate due to the limiting action of the protrusions and the vertical grooves, and the gear will roll along the tooth ring while the support base rotates, thereby driving the multiple short rods stacked below to rotate, so as to realize the rotation of the storage disc, and further change the movement trajectory of the bolts in combination with multiple rotation modes, thereby further improving the heating uniformity.

[0018] In addition, different numbers of short rods can be stacked according to the number of bolts, and then the cover is covered on the upper end of the plurality of short rods, the heating space of the cylindrical heating cavity is reduced, and the heating resistance wire of the appropriate height of the bottom is turned on, so that the heat treatment effect is ensured and the energy consumption is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 It is a structure schematic view of the heating box in the application; Figure 2 It is a structure schematic view of the bottom structure of the heating box in the application; Figure 3 It is a structure schematic view of the bottom structure of the cover in the application; Figure 4 It is a structure schematic view of the bracket base and the bottom disc in the application; Figure 5 It is a structure schematic view of the short rod and the gear in the application; Figure 6 It is a structure schematic view of the anti-fatigue automobile accessory bolt in the application.

[0020] In the figure: 1, box body; 2, bottom disc; 3, driving motor; 4, bracket base; 5, storage disc; 6, positioning groove; 7, positioning rod; 8, short rod; 9, positioning sleeve; 10, round hole; 11, cover; 12, gear; 13, insertion rod; 14, tooth ring; 15, protruding block; 16, vertical groove; 17, center rod; 18, center hole; 19, handle; 20, anti-fatigue automobile accessory bolt to be processed. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0022] As shown in the figure, the application provides an anti-fatigue automobile accessory bolt heat treatment processing process, which comprises: Figures 1-3 S1: cleaning and drying the anti-fatigue automobile accessory bolt to be processed 20; S2: heating the cleaned anti-fatigue automobile accessory bolt to be processed 20 to 870-890 DEG C by a heating box and keeping warm for 60-75 min, and then rapidly cooling, and in the heating and keeping warm process, the position of the anti-fatigue automobile accessory bolt to be processed 20 is kept changing; ​S3: The anti-fatigue steam fitting bolt 20 to be processed is washed and dried again, and then heated to 560-580°C, and after 80-90 min of heat preservation, it is cooled; S4: The anti-fatigue steam fitting bolt 20 to be processed is quenched, the quenching temperature is 860-880°C, the heating time is 30-45 min, and then it is quickly immersed in a quenching oil pool for cooling; S5: The quenched anti-fatigue steam fitting bolt 20 to be processed is tempered, the tempering temperature is 330-350°C, the heating time is 100-120 min, and finally it is naturally cooled to obtain the finished anti-fatigue steam fitting bolt.

[0023] It should be noted that the following heating box is used in this embodiment. During heating, heat preservation and natural cooling, the bolts are kept moving, the positions of the bolts are exchanged, the heating uniformity of the bolts is improved, and the problem of uneven heating caused by the heating equipment itself and the position of the bolts is reduced.

[0024] As shown in Figures 1-6 , the heating box comprises a box body 1, a cylindrical heating cavity (not marked in the figure) is arranged inside the box body 1, heating resistance wires (not shown in the figure) are arranged inside the side wall of the box body 1, a cover 11 is arranged at the upper end of the box body 1, a bottom disc 2 is rotatably arranged at the bottom of the cylindrical heating cavity, a driving motor 3 for driving the bottom disc 2 to rotate is mounted at the bottom of the box body 1, a support base 4 is arranged inside the box body 1, the support base 4 is placed above the bottom disc 2, a positioning mechanism is arranged on the support base 4, a plurality of circumferentially distributed storage racks are arranged above the support base 4, and a plurality of storage discs 5 for placing bolts are arranged on the storage racks.

[0025] It should be noted that a temperature sensor (not shown in the figure) is also arranged inside the box body 1. In use, the bolts are placed in the storage discs 5, then the support base 4 is placed on the bottom disc 2 and connected through the positioning mechanism, heated by the heating resistance wires, and the bottom disc 2 is driven to rotate by the driving motor 3, so as to drive the plurality of storage discs 5 to rotate, so that the bolts rotate inside the box body 1, improve the heating uniformity of the bolts, and improve the heat treatment effect.

[0026] As shown in Figure 4 , the positioning mechanism comprises a plurality of positioning rods 7 fixed on the bottom disc 2, the plurality of positioning rods 7 are circumferentially distributed, a plurality of positioning grooves 6 are formed in the edges of the support base 4, and the number of the positioning grooves 6 is the same as that of the positioning rods 7, and the positioning rods 7 are respectively located inside the corresponding positioning grooves 6.

[0027] It should be noted that the position of the support base 4 is limited by the positioning grooves 6 and the positioning rods 7, and at the same time, the support base 4 can always rotate with the bottom disc 2. When the support base 4 is put in or taken out, the support base 4 can be directly moved upward, which is convenient to use.

[0028] As Figure 4 and Figure 5 shown, the storage rack is composed of a plurality of short rods 8 stacked, the upper end of the short rod 8 is provided with a positioning sleeve 9, and the bottom of the short rod 8 can be inserted into the positioning sleeve 9, the storage disc 5 is fixed on the short rod 8, a plurality of circular holes 10 are arranged on the upper surface of the support base 4, and the bottom of the lowermost short rod 8 is rotatably inserted into the circular hole 10, the cover body 11 is located on the inner side of the cylindrical heating cavity, and the heating resistance wire can be controlled by layering.

[0029] It should be noted that different numbers of short rods 8 can be stacked according to the number of bolts, and then the cover body 11 is placed on the upper end of the plurality of short rods 8, the heating space of the cylindrical heating cavity is reduced, and the heating resistance wire of the appropriate height at the bottom is turned on, which ensures the heat treatment effect while reducing energy consumption.

[0030] As Figure 1 , Figure 3 and Figure 5 shown, the lower surface of the cover body 11 is fixed with a tooth ring 14 at the center position, and the uppermost positioning sleeve 9 is provided with a plug rod 13, the upper end of the plug rod 13 is fixed with a gear 12, and the gear 12 is engaged with the tooth ring 14, a vertical groove 16 is arranged on the inner wall of the box body 1, and the edge of the cover body 11 is provided with a lug 15, and the lug 15 is located on the inner side of the vertical groove 16.

[0031] It should be noted that the cover body 11 cannot rotate due to the limiting action of the lug 15 and the vertical groove 16, and the gear 12 will roll along the tooth ring 14 while the support base 4 rotates, and the plurality of short rods 8 stacked below are driven to rotate by the plug rod 13, so as to realize the rotation of the storage disc 5, and further combined with various rotating modes, the movement track of the bolt is changed, and the heating uniformity is further improved.

[0032] As Figure 1 , Figure 3 and Figure 4 shown, a center hole 18 is arranged at the middle position of the cover body 11, and a center rod 17 is arranged at the upper end of the support base 4, and the center rod 17 penetrates the center hole 18.

[0033] It should be noted that in use, the bolt is placed in the storage disc 5 outside the box body 1, and then the support base 4 is placed into the box body 1 through the center rod 17, and after heating, the support base 4 and the bolt are also taken out through the center rod 17, which is convenient and practical.

[0034] As Figure 1 shown, the upper end of the cover body 11 is provided with a handle 19.

[0035] It should be noted that the handle 19 is more convenient for taking and placing the cover body 11, and is more convenient to use.

[0036] Referring again Figure 6 The application further provides a fatigue-resistant steam component bolt prepared by the heat treatment process of the fatigue-resistant steam component bolt, wherein the fatigue-resistant steam component bolt 20 is made of low-alloy high-strength steel, and the components of the low-alloy high-strength steel include, in percentage by mass, C 0.18-0.23%, Si 0.15-0.35%, Mn 1.2-1.6%, Cr 0.8-1.2%, Mo 0.15-0.25%, V 0.05-0.12%, B 0.001-0.005%, and the balance of Fe. After the quenching and low-temperature tempering treatment, the fatigue-resistant steam component bolt 20 has a core hardness of 38-42 HRC and a surface compressive stress of ≥500 MPa.

[0037] In the application, Cr, Mo and V micro-alloying can form fine carbides such as Cr7C3, Mo2C and VC, hinder dislocation movement and inhibit fatigue crack initiation; the addition of B element can cause the segregation of B element at the grain boundary, improve the grain boundary bonding force and delay the crack propagation along the grain boundary; the solid solution strengthening effect of Mn and Si is to improve the yield strength of the base material by the interaction between the solid solution atoms and dislocations, and the yield strength can be ≥900 MPa. After quenching, martensite structure is obtained, surface compressive stress is generated, tensile stress in the external load is offset, and the fatigue crack propagation rate is reduced; after low-temperature tempering, the quenching stress is eliminated, the toughness is improved while the high hardness is maintained, and brittle fracture is avoided.

[0038] The surface of the fatigue-resistant steam component bolt 20 is sequentially covered from inside to outside with: A nanocrystallized nickel-phosphorus alloy plating layer with a thickness of 3-8 μm, a grain size of ≤50 nm and a hardness of ≥600 HV; A rare earth modified zinc-nickel alloy plating layer with a rare earth element content of 0.5-2 wt% and a thickness of 10-15 μm; A composite lubricating plating layer containing graphite-like carbon with a thickness of 1-3 μm and a friction coefficient of ≤0.12; The nanocrystallized nickel-phosphorus alloy plating layer, the rare earth modified zinc-nickel alloy plating layer and the composite lubricating plating layer are formed by a pulse electrodeposition process, the total thickness is not more than 25 μm, and the interlayer bonding strength is ≥35 MPa.

[0039] The nanocrystallized nickel-phosphorus alloy plating layer has a nanocrystalline structure of ≤50 nm, a high grain boundary density, hindered dislocation movement and a hardness of ≥600 HV, and effectively disperses stress concentration on the surface of the bolt. The high-frequency pulse current refines the grains and simultaneously enhances the metallurgical bonding between the plating layer and the base material, and the bonding strength can be ≥35 MPa.

[0040] The rare earth modified zinc-nickel alloy coating, whose rare earth elements can be La and Ce, can reduce porosity and improve corrosion resistance by adsorbing at coating defects. In addition, the zinc-nickel alloy can form a dense corrosion product film to block the penetration of corrosive media.

[0041] The graphite-like carbon-containing composite lubricating coating can be graphite-like carbon + nano-TiO2 composite lubricating coating. The graphite-like carbon provides self-lubricating properties to reduce fretting wear during bolt assembly and service. The nano-TiO2 particle size can be 20-50 nm: stable structure at high temperature, inhibiting oxidation of the lubricating film, ensuring that the friction coefficient fluctuation is ≤0.03 in the range of -40℃ to 150℃, and the salt spray corrosion resistance time is ≥1000 hours.

[0042] The base material of the anti-fatigue automotive fastener bolt is micro-alloyed + nanocrystalline coating, which increases the fatigue limit by about 25%, and the surface compressive stress and high hardness coating work together to extend the fatigue life by 1.8-2.5 times. The friction coefficient is reduced to below 0.12, and the fretting wear volume is reduced by more than 60%. At 150℃ high temperature, it still maintains low friction, avoiding seizure or loosening due to lubrication failure. It can meet the long-term service needs of automotive chassis bolts in salt spray and moisture environments.

[0043] Although embodiments of the present application have been shown and described, it is to be understood that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present application, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A heat treatment process for anti-fatigue automotive fastener bolts, characterized by, The utility model relates to an anti-fatigue steam fitting bolt processing device and method, and belongs to the field of anti-fatigue steam fitting bolt processing. S1: the anti-fatigue steam fitting bolt (20) to be processed is washed and dried; S2: the anti-fatigue steam fitting bolt (20) to be processed is heated to 870-890 DEG C through a heating box and is kept warm for 60-75 min, and then is rapidly cooled down, and in the heating and keeping warm process, the anti-fatigue steam fitting bolt (20) to be processed is kept in continuous position change; The heating box comprises a box body (1), a cylindrical heating cavity is arranged in the box body (1), heating resistance wires are arranged in the side wall of the box body (1), a cover body (11) is arranged at the upper end of the box body (1), a bottom disc (2) is rotatably arranged at the bottom of the cylindrical heating cavity, a driving motor (3) for driving the bottom disc (2) to rotate is mounted at the bottom of the box body (1), a support base (4) is arranged in the box body (1), the support base (4) is placed above the bottom disc (2), a positioning mechanism is arranged on the support base (4), a plurality of circumferentially distributed storage racks are arranged above the support base (4), and a plurality of storage trays (5) for placing bolts are arranged on the storage racks. The positioning mechanism comprises a plurality of positioning rods (7) fixed on the bottom disc (2), the positioning rods (7) are circumferentially distributed, a plurality of positioning grooves (6) are formed in the edge of the support base (4) and are the same in number as the positioning rods (7), and the positioning rods (7) are respectively located inside the corresponding positioning grooves (6); S3: the anti-fatigue steam fitting bolt (20) to be processed is washed and dried again, and then is heated to 560-580 DEG C, and is kept warm for 80-90 min before being cooled down; S4: the anti-fatigue steam fitting bolt (20) to be processed is quenched, the quenching temperature is 860-880 DEG C, the heating time is 30-45 min, and then the anti-fatigue steam fitting bolt (20) to be processed is rapidly immersed in a quenching oil pool to be cooled down; S5: the anti-fatigue steam fitting bolt (20) to be processed is tempered after being quenched, the tempering temperature is 330-350 DEG C, the heating time is 100-120 min, and finally, the anti-fatigue steam fitting bolt (20) to be processed is naturally cooled down to obtain an anti-fatigue steam fitting bolt product.

2. The heat treatment process for anti-fatigue automotive fastener bolts according to claim 1, characterized in that: The storage racks are composed of a plurality of short rods (8) stacked together, positioning sleeves (9) are arranged at the upper ends of the short rods (8), the bottoms of the short rods (8) can be inserted into the positioning sleeves (9), the storage trays (5) are fixed on the short rods (8), a plurality of circumferentially distributed round holes (10) are formed in the upper surface of the support base (4), the bottoms of the lowermost short rods (8) are rotatably inserted into the round holes (10), the cover body (11) is located inside the cylindrical heating cavity, and the heating resistance wires can be controlled to be turned on and turned off in layers.

3. The heat treatment process for anti-fatigue automotive fastener bolts of claim 2, wherein: A tooth ring (14) is fixed to the center of the lower surface of the cover body (11), an insertion rod (13) is inserted into the uppermost positioning sleeve (9), a gear (12) is fixed to the upper end of the insertion rod (13), the gear (12) is engaged with the tooth ring (14), vertical grooves (16) are formed in the inner wall of the box body (1), and protrusions (15) are arranged at the edge of the cover body (11) and located inside the vertical grooves (16).

4. The heat treatment process for anti-fatigue automotive fastener bolts of claim 1, wherein: The middle position of the cover body (11) is provided with a center hole (18), and the upper end of the support base (4) is provided with a center rod (17) penetrating through the center hole (18).

5. The heat treatment process for anti-fatigue automotive fastener bolts of claim 1, wherein: The upper end of the cover body (11) is provided with a handle (19).

6. A fatigue resistant automotive fastener prepared by the heat treatment process of claim 1, wherein: The to-be-processed fatigue-resistant automobile accessory bolt (20) is made of low-alloy high-strength steel, and its components include, by mass percentage, C 0.18-0.23%, Si 0.15-0.35%, Mn 1.2-1.6%, Cr 0.8-1.2%, Mo 0.15-0.25%, V 0.05-0.12%, B 0.001-0.005%, and the balance of Fe. After quenching and low-temperature tempering treatment, the to-be-processed fatigue-resistant automobile accessory bolt (20) has a core hardness of 38-42 HRC and a surface compressive stress of ≥500 MPa.

7. The fatigue resistant automotive fastener of claim 6, wherein: The surface of the to-be-processed fatigue-resistant automobile accessory bolt (20) is sequentially covered from inside to outside with: A nanocrystallized nickel-phosphorus alloy plating layer with a thickness of 3-8 μm, a grain size of ≤50 nm, and a hardness of ≥600 HV; A rare earth modified zinc-nickel alloy plating layer with a rare earth element content of 0.5-2 wt% and a thickness of 10-15 μm; A composite lubricating plating layer containing graphite-like carbon with a thickness of 1-3 μm and a friction coefficient of ≤0.12; The nanocrystallized nickel-phosphorus alloy plating layer, the rare earth modified zinc-nickel alloy plating layer, and the composite lubricating plating layer are formed by a pulse electrodeposition process, have a total thickness of not more than 25 μm, and have an interlayer bonding strength of ≥35 MPa.

8. The fatigue resistant automotive fastener of claim 7, wherein: The composite lubricating plating layer also contains nanometer titanium dioxide particles with a particle size of 20-50 nm and a content of 0.5-1.5 wt%; The composite lubricating plating layer has a friction coefficient fluctuation value of not more than 0.03 within a temperature range of -40°C to 150°C and a salt spray corrosion resistance of ≥1000 hours.

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