Threaded drawing screw for interference connection and manufacturing method thereof

Abstract

The invention discloses a threaded blind rivet for interference connection and a manufacturing method of the threaded blind rivet. The blind rivet comprises a core rod, a rivet sleeve, an interference lining, a rivet body and a driving nut. Wherein the nail body head part is connected with the outer wall surface of the nail body main body part through a first outer rounded corner transition surface, the inner wall surface of the lining head part is connected with the inner wall surface of the lining main body part through an inner rounded corner transition surface, and the outer wall surface of the lining head part is connected with the outer wall surface of the lining main body part through a second outer rounded corner transition surface; in a fastening state, the screw body conical part is attached to the lining conical part, the lining conical part is inserted into the screw sleeve, the first outer fillet transition face is attached to the inner fillet transition face, and the second outer fillet transition face can be attached to an inlet of the mounting hole. According to the invention, the stress at the joint of the nail body head and the nail body main body can be improved, the risk of deformation and fracture of the nail body head is reduced, the mechanical properties such as fatigue of the whole structure are improved, and the fastening degree and the bearing capacity of threaded nail pulling installation are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of fasteners, and in particular to a threaded pull-out nail for interference connection and a manufacturing method thereof. Background Art

[0002] In aviation and aerospace vehicles, due to the strict control of their own weight, in order to reduce weight, many use composite materials as the body material, and the installation space is often small, and workers cannot successfully install. In this case, a single-sided riveted threaded rivet (also called a core-pulling rivet) is usually used to achieve the installation of the sandwich structure. When using the existing threaded rivet, first insert the assembled threaded rivet into the preset installation hole, and then drive the driving nut under the drive of the installation tool to pull the core rod outward, so that the nail sleeve is deformed and a large foot is formed. The core rod is broken from the broken neck groove, so that the large foot of the nail sleeve cooperates with the nail head of the nail body to lock the sandwich structure, so as to achieve the effect of tightening. Because the driving nut constantly squeezes the nail head of the nail body during the installation process, the nail head of the nail body is easily deformed, resulting in a loose fit between the nail body and the entrance of the installation hole and a gap, and even the nail head of the nail body is broken, causing the thread to fail. Summary of the invention

[0003] The purpose of the present invention is to provide a threaded pull-out nail for interference connection and a manufacturing method thereof, so as to solve the technical problem that the nail head of the nail body of the current threaded pull-out nail is easily deformed and broken.

[0004] The above-mentioned purpose of the present invention can be achieved by adopting the following technical solutions:

[0005] The present invention provides a threaded screw for interference connection, comprising a core rod, a screw sleeve, an interference bushing, a screw body and a drive nut, wherein the first end of the core rod is provided with a core rod head, the screw sleeve, the interference bushing, the screw body and the drive nut are sequentially sleeved on the core rod from the second end of the core rod, the first end of the screw sleeve abuts against the core rod head, the second end of the screw sleeve is sleeved on the first end of the interference bushing, the second end of the interference bushing is sleeved on the first end of the screw body, and the second end of the screw body abuts against the drive nut; wherein the interference bushing has a bushing cone portion, a bushing main body portion and a bushing head sequentially connected from the first end to the second end thereof, and the screw body has The nail body cone, nail body main body and nail body head are connected in sequence from the first end to the second end; the nail body head is connected to the outer wall surface of the nail body main body through a first outer rounded corner transition surface, the inner wall surface of the bushing head is connected to the inner wall surface of the bushing main body through an inner rounded corner transition surface, and the outer wall surface of the bushing head is connected to the outer wall surface of the bushing main body through a second outer rounded corner transition surface; when the interference connection is in the tightened state of the threaded pull-out nail, the nail body cone is fitted with the bushing cone, the bushing cone is inserted into the nail sleeve, the first outer rounded corner transition surface is fitted with the inner rounded corner transition surface, and the second outer rounded corner transition surface can fit with the entrance of the mounting hole.

[0006] In an embodiment of the present invention, the nail body head has a first abutting plane abutting against the drive nut.

[0007] In an embodiment of the present invention, the drive nut has a second abutting plane abutting against the first abutting plane, and the second abutting plane has a friction texture layer for increasing friction.

[0008] In an embodiment of the present invention, the interference connection threaded puller nail further comprises an insert, the second end of the nail sleeve is provided with a step hole, and the insert and one end of the cone portion of the bushing are sequentially inserted into the step hole.

[0009] The present invention also provides a method for manufacturing a threaded pull-out nail for interference connection, the manufacturing method comprising processing and manufacturing the core rod, nail sleeve, interference bushing, nail body and drive nut of the above-mentioned threaded pull-out nail for interference connection; wherein the manufacturing of the nail body comprises the following steps: preparing a nail body blank; upsetting the nail body blank to form a nail body head, a first outer rounded transition surface, a nail body main body and a nail body cone to obtain a nail body semi-finished product; machining a through hole in the nail body semi-finished product; tapping the inner wall surface of the through hole to form an inner nut surface; grinding the outer wall surfaces of the nail body main body and the nail body cone of the nail body semi-finished product; and heat treating the nail body semi-finished product. Processing; rolling the first outer rounded corner transition surface of the semi-finished nail body; surface treating the semi-finished nail body to obtain the finished nail body; wherein, the manufacture of the interference bushing specifically includes the following steps: preparing a bushing blank; upsetting the bushing blank to form a bushing head, a second outer rounded corner transition surface, an inner rounded corner transition surface and a bushing rod to obtain a bushing semi-finished product; rolling the end of the bushing rod away from the bushing head to form a bushing cone, and the other end of the bushing rod constitutes the bushing body; heat treating the semi-finished bushing; surface treating the semi-finished bushing to obtain the finished interference bushing.

[0010] In an embodiment of the present invention, the first outer rounded corner transition surface of the semi-finished nail body is rolled, including: using a matching rolling tool to roll the first outer rounded corner transition surface of the semi-finished nail body; wherein the rolling force of the rolling tool is 40Kgf~80Kgf, the rotation speed of the semi-finished nail body is 300r / min~700r / min, and the rolling time of the rolling tool is 0.1s~1.0s.

[0011] In an embodiment of the present invention, the semi-finished bushing is heat treated, comprising the following steps: vacuum water quenching the semi-finished bushing at a heating temperature of 600°C to 720°C; keeping the semi-finished bushing warm for 10min to 20min; water quenching the semi-finished bushing, and controlling the transfer time of the semi-finished bushing to be less than 8S.

[0012] In an embodiment of the present invention, the manufacture of the drive nut includes the following steps: preparing a semi-finished nut product: using a powder metallurgy near-net forming method to prepare a semi-finished nut product having a nut hole and a friction texture layer formed on one end plane from a powder raw material; heat treating the semi-finished nut product; and surface treating the semi-finished nut product to obtain a finished product of the drive nut.

[0013] In an embodiment of the present invention, the powder raw material includes 0.25% to 0.45% by weight of Mo, 0.38% to 0.48% by weight of C, 0.20% to 0.37% by weight of Si, 0.40% to 0.70% by weight of Mn, 0.05% to 0.15% by weight of Cu and the remaining Fe, and the powder diameter of the powder raw material is 10μm to 80μm.

[0014] In an embodiment of the present invention, the step of preparing a nut semi-finished product includes the following steps: placing the powder raw material in a matching mold, and then placing the mold in a hydraulic press for molding; wherein the molding pressure is 30Mpa~100Mpa, and the molding holding time is 2s~20s; placing the molded nut semi-finished product in a sintering furnace, heating it to 1100℃~1300℃ at a heating rate of 100℃ / min~300℃ / min for sintering, and then keeping it warm for 1h~5h and then cooling it with the furnace.

[0015] The characteristics and advantages of the present invention are:

[0016] The threaded pull-out nail for interference connection and the manufacturing method thereof of the present invention are connected by setting a first outer rounded corner transition surface between the nail body head and the nail body body, and setting an inner rounded corner transition surface between the bushing head and the bushing body of the interference bushing, so that the first outer rounded corner transition surface and the inner rounded corner transition surface are matched in the tightened state, thereby improving the force at the connection between the nail body head and the nail body body, reducing the risk of deformation and fracture of the nail body head, and improving the fatigue and other mechanical properties of the overall structure of the threaded pull-out nail, and rolling the first outer rounded corner transition surface during the manufacturing process of the nail body, thereby further improving the mechanical properties of the first outer rounded corner transition surface; in addition, by setting a second outer rounded corner transition surface between the bushing head and the bushing body of the interference bushing, the second outer rounded corner transition surface is matched with the entrance of the mounting hole in the tightened state, which not only improves the tightness and bearing capacity of the threaded pull-out nail installation, thereby facilitating further improving the fatigue and other mechanical properties of the overall structure, but also avoids the risk of increasing the structure being oxidized and corroded due to residual gas between the interference bushing and the mounting hole, and also avoids the safety hazard caused by the internal and external pressure difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0018] Figure 1It is a schematic structural diagram of the threaded pull-out nail for interference connection in the present invention.

[0019] Figure 2 It is a schematic diagram of the threaded screw for interference connection in the present invention in a tightened state.

[0020] Figure 3 It is a partial longitudinal cross-sectional schematic diagram of the nail body in the present invention.

[0021] Figure 4 It is a schematic diagram of the structure of the interference bushing in the present invention.

[0022] Figure 5 It is a schematic diagram of the first abutment plane of the nail body head in the present invention.

[0023] Figure 6 It is a partial longitudinal section schematic diagram of the driving nut in the present invention.

[0024] Figure 7 It is a schematic diagram of the second abutment plane of the drive nut in the present invention.

[0025] Figure 8 It is a structural schematic diagram of the semi-finished bushing in the present invention.

[0026] Fig. 9 It is a schematic structural diagram of the nail sleeve in the present invention.

[0027] Fig.10 It is a cross-sectional view of the nail sleeve, the core rod and the insert after being assembled in the present invention.

[0028] Fig.11 It is the metallographic structure diagram of the main deformation section in the nail sleeve of the present invention.

[0029] Fig.12 It is the metallographic structure diagram of the transition deformation section in the nail sleeve of the present invention.

[0030] Fig.13 The figure is a metallographic structure diagram of the support section in the nail sleeve of the present invention.

[0031] In the figure:

[0032] 1. Core rod; 11. Core rod head;

[0033] 2. nail sleeve; 21. step hole; 22. perforation; 23. closing portion; 24. main deformation section; 25. transition deformation section; 26. support section; 27. first length section; 28. second length section; 29. ​​third length section;

[0034] 3. Interference bushing; 31. Bushing head; 32. Bushing body; 33. Bushing cone; 34. Inner rounded corner transition surface; 35. Second outer rounded corner transition surface;

[0035] 4. nail body; 41. nail body head; 42. nail body main body; 43. nail body cone; 44. first outer rounded corner transition surface; 45. first abutment plane; 46. nail body threaded hole; 47. internal threaded surface;

[0036] 5. driving nut; 51. second abutting plane; 52. nut threaded hole; 53. abutting boss;

[0037] 6. Inserts;

[0038] 7. Sandwich structure; 71. Mounting hole;

[0039] 8. Semi-finished bushing; 81. Bushing rod. DETAILED DESCRIPTION

[0040] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] Implementation Method 1

[0042] Combination Figures 1 to 4 As shown, the present invention provides a threaded screw for interference connection, comprising a core rod 1, a screw sleeve 2, an interference bushing 3, a screw body 4 and a driving nut 5. The first end of the core rod 1 is provided with a core rod head 11, the screw sleeve 2, the interference bushing 3, the screw body 4 and the driving nut 5 are sequentially sleeved on the core rod 1 from the second end of the core rod 1, the first end of the screw sleeve 2 is abutted against the core rod head 11, the second end of the screw sleeve 2 is sleeved on the first end of the interference bushing 3, the second end of the interference bushing 3 is sleeved on the first end of the screw body 4, and the second end of the screw body 4 is abutted against the driving nut 5; wherein the interference bushing 3 has a bushing cone 33, a bushing main body 32 and a bushing head 31 sequentially connected from the first end to the second end thereof, and the screw body 4 has a bushing cone 33, a bushing main body 32 and a bushing head 31 sequentially connected from the first end thereof ... The nail body cone 43, the nail body main body 42 and the nail body head 41 are connected in sequence to the second end; the nail body head 41 is connected to the outer wall surface of the nail body main body 42 through the first outer rounded corner transition surface 44, the inner wall surface of the bushing head 31 is connected to the inner wall surface of the bushing main body 32 through the inner rounded corner transition surface 34, and the outer wall surface of the bushing head 31 is connected to the outer wall surface of the bushing main body 32 through the second outer rounded corner transition surface 35; when the interference connection is in the tightening state of the threaded screw, the nail body cone 43 is fitted with the bushing cone 33, the bushing cone 33 is inserted into the nail sleeve 2, the first outer rounded corner transition surface 44 is fitted with the inner rounded corner transition surface 34, and the second outer rounded corner transition surface 35 can fit with the entrance of the mounting hole 71.

[0043] The interference connection threaded screw of the present invention is connected by setting a first outer rounded corner transition surface 44 between the nail body head 41 and the nail body main body 42 of the nail body 4, and setting an inner rounded corner transition surface 34 between the bushing head 31 and the bushing main body 32 of the interference bushing 3, so that the first outer rounded corner transition surface 44 fits with the inner rounded corner transition surface 34 in the tightened state, thereby improving the force at the connection between the nail body head 41 and the nail body main body 42, reducing the risk of deformation and fracture of the nail body head 41, and improving the fatigue of the overall structure of the threaded screw. Mechanical properties; in addition, by setting a second outer rounded corner transition surface 35 between the bushing head 31 and the bushing body 32 of the interference bushing 3, the second outer rounded corner transition surface 35 is fit with the entrance of the mounting hole 71 in the tightened state, which not only improves the tightness and load-bearing capacity of the threaded screw installation, thereby facilitating further improving the fatigue and other mechanical properties of the overall structure, but also avoids the risk of increased oxidation corrosion of the structure due to residual gas between the interference bushing 3 and the mounting hole 71, and also avoids the safety hazards caused by the internal and external pressure differences.

[0044] In order to further enhance the above beneficial effects, in some embodiments of the present invention, the radius range of the first outer rounded corner transition surface 44 is 0.5mm to 0.7mm; the radius range of the inner rounded corner transition surface 34 is 0.9mm to 1.4mm; the radius range of the second outer rounded corner transition surface 35 is 0.8mm to 1.3mm.

[0045] Specifically, the first end and the second end of each component are both opposite ends of each component in the axial direction. The core rod 1 has an external threaded surface, and the nail body 4 and the driving nut 5 are both provided with threaded holes that match the external threaded surface of the core rod 1, wherein the threaded hole of the nail body 4 is recorded as the nail body threaded hole 46, and the threaded hole of the driving nut 5 is recorded as the nut threaded hole 52 ( Figure 6 ). The core rod 1 is also provided with a neck-breaking groove for breaking in a tightened state. The bushing taper 33 is gradually set from the second end of the interference bushing 3 to the first end to guide the second end of the nail sleeve 2; the nail body taper 43 is gradually set from the second end of the nail body 4 to the first end to guide the insertion into the bushing taper 33. In this embodiment, in order to achieve more precise interference installation, the wall thickness of the interference bushing is only 0.25mm.

[0046] In addition, combined Figure 1 , Fig. 9 and Fig.10As shown, the threaded screw for interference connection also includes an insert 6, and the second end of the nail sleeve 2 is provided with a step hole 21. The insert 6 and one end of the bushing cone 33 are sequentially inserted into the step hole 21. The insert 6 can reduce the friction resistance between the nail sleeve 2 and the nail body 4 and the core rod 1, and is conducive to expanding the deformation of the nail sleeve 2. Among them, the first end of the nail sleeve 2 can form a closing portion 23 after the nail sleeve 2 and the core rod 1 are assembled. The second end of the nail sleeve 2 is provided with a step hole 21 for installing the insert 6, and the length l1 of the insert 6 is less than the length L0 of the step hole 21. The nail sleeve 2 forms a main deformation section 24, a transition deformation section 25 and a support section 26 from its second end to the first end.

[0047] Combination Figure 1 and Figure 2 As shown, in the embodiment of the present invention, the installation process of the threaded screw for interference connection is as follows:

[0048] The nail body 4 is squeezed into the stage: the assembled interference connection threaded screw is inserted into the mounting hole 71 of the sandwich structure 7, and then the driving nut 5 is fixed with the installation tool, and the core rod 1 is rotated. The nail body cone 43 and the nail body main body 42 of the nail body 4 are squeezed into the bushing cone 33 and the bushing main body 32 of the interference bushing 3 along the axial direction of the interference bushing 3 by the rotation and the top pressure of the driving nut 5; wherein, since the outer diameter of the nail body cone 43 of the nail body 4 is larger than the inner diameter of the bushing cone 33 of the interference bushing 3, and the outer diameter of the nail body main body 42 is larger than the inner diameter of the bushing main body 32, the nail body 4 will expand outwards to squeeze the interference bushing 3 during the squeezing process, so that the interference bushing 3 will expand outwards to squeeze the hole wall of the mounting hole 71, thereby obtaining a predetermined interference amount, so that the nail body 4, the interference bushing 3 and the mounting hole 71 are closely matched;

[0049] Large foot forming stage: during the process of the nail body 4 squeezing into the bushing, the friction between the outer wall of the nail body 4 and the inner wall of the bushing gradually increases, so that the contact pressure between the nail sleeve 2 and the interference bushing 3 also gradually increases. When the contact pressure reaches a certain level, the nail sleeve 2 and the insert 6 are formed upward along the bushing cone 33 of the interference bushing 3. During this process, the squeezing action of the nail body 4 and the forming process of the nail sleeve 2 are carried out simultaneously; wherein, as the nail body 4 squeezes into the interference bushing 3, the second end of the nail sleeve 2 contacts the inner side surface of the sandwich structure 7, and then driven by the rotation of the core rod 1, the core rod 1 continues to be pulled outward, and the nail sleeve 2 is deformed under the top pressure of the sandwich structure 7 and the core rod head 11, and a large foot is formed.

[0050] Neck groove fracture stage: during the large base foot forming process, the rotation torque of the core rod 1 increases due to the increase in resistance. When the rotation torque exceeds the force that the neck groove can withstand, the neck groove of the core rod 1 breaks, thereby completing the installation of the threaded screw for interference connection and realizing the fastening of the sandwich structure 7.

[0051] like Figure 3 and Figure 5 As shown, in order to further reduce the risk of deformation and fracture of the nail body head 41, in an embodiment of the present invention, the nail body head 41 has a first abutting plane 45 abutting against the drive nut 5, that is, the nail body head 41 does not have a groove structure such as a cross, flower or other shape at the entrance of the nail body threaded hole 46; on the one hand, it can avoid the structural strength of the nail body head 41 being reduced by grooving, and increase the wall thickness at the first outer rounded corner transition surface 44, thereby further reducing the risk of deformation and fracture of the nail body head 41; on the other hand, it can reduce the expansion and extrusion of the nail body head 41 caused by the drive nut 5 directly abutting against the groove structure, thereby also helping to reduce the risk of deformation and fracture of the nail body head 41; on the other hand, it can reduce the distance between the fracture surface of the core rod 1 and the first abutting plane 45 of the nail body head 41, reduce the depression of the installation surface, and improve the flatness of the installation. For example, in this embodiment, the distance between the fracture surface of the core rod 1 and the first abutting plane 45 of the nail body head 41 can be controlled within 0.3 mm.

[0052] like Figure 6 and Figure 7 As shown, the drive nut 5 has a second abutting plane 51 abutting against the first abutting plane 45, and the second abutting plane 51 has a friction texture layer for increasing friction. By setting the second abutting plane 51 to abut against the first abutting plane 45 and setting the friction texture layer, the contact area and friction between the drive nut 5 and the nail body head 41 can be effectively increased, which facilitates the drive nut 5 and the nail body 4 to be relatively fixed and screwed together with the core rod 1. Specifically, the first end of the drive nut 5 is provided with an abutting boss 53, and the end surface of the abutting boss 53 constitutes a second abutting platform.

[0053] Implementation Method 2

[0054] Combination Figure 1 As shown, the present invention also provides a method for manufacturing a threaded screw for interference connection, the manufacturing method comprising processing and manufacturing a core rod 1, a screw sleeve 2, an interference bushing 3, a screw body 4 and a driving nut 5 of the threaded screw for interference connection. The specific structure, working principle and beneficial effects of the threaded screw for interference connection in this embodiment are the same as those of the threaded screw for interference connection in the first embodiment, and will not be repeated here.

[0055] Combination Figure 3 As shown, in the manufacturing method of the present invention, the manufacturing of the nail body 4 includes the following steps:

[0056] Step S101, preparing a nail body blank; specifically, the nail body blank can be made of TC4 titanium alloy coiled wire with a coating.

[0057] Step S102, upsetting the nail body blank to form a nail body head 41, a first outer rounded corner transition surface 44, a nail body main body 42 and a nail body tapered portion 43, to obtain a semi-finished nail body; specifically, placing the nail body blank in a warm upsetting machine and upsetting the nail body head 41, the first outer rounded corner transition surface 44, the nail body main body 42 and the nail body tapered portion 43 at one time through a corresponding upsetting mold, to obtain a semi-finished nail body.

[0058] After step S102, step S103 may be performed to clean the semi-finished nail body; specifically, the semi-finished nail body is placed in a corresponding vibration polishing machine to remove surface dirt and raw material coating generated by upsetting.

[0059] Step S104, machining a through hole in the semi-finished nail body product; specifically, drilling a through hole along the axial direction of the semi-finished nail body product.

[0060] Step S105 , tapping the inner wall surface of the through hole to form an inner nut surface; specifically, using a special tap to process the inner wall surface of the through hole into an internal thread surface 47 , so that the through hole forms a nail body threaded hole 46 .

[0061] Step S106, grinding the outer wall surfaces of the nail body main body 42 and the nail body cone 43 of the semi-finished nail body so that the outer diameters of the nail body main body 42 and the nail body cone 43 meet the design requirements; specifically, placing the nail body main body 42 and the nail body cone 43 of the semi-finished nail body on a centerless grinder for grinding; as in this embodiment, the tolerance of the outer diameter of the nail body main body 42 and the outer diameter of the nail body cone 43 is controlled at 0.005mm.

[0062] Step S107, heat-treating the semi-finished nail body to improve the mechanical properties of the semi-finished nail body; specifically, firstly subjecting the semi-finished nail body to solution heat treatment at a temperature of 900°C to 980°C, and keeping it warm for 30min to 60min, and then water-cooling; then placing the semi-finished nail body in a vacuum aging furnace at 480°C to 580°C, keeping it warm for 4h to 6h, and then cooling it with the furnace.

[0063] Step S108, rolling the first rounded corner transition surface 44 of the semi-finished nail body, on the one hand, so that the size of the first rounded corner transition surface 44 meets the design requirements, and on the other hand, further improves the mechanical properties of the first rounded corner transition surface 44; specifically, a matching rolling tool is used to roll the first rounded corner transition surface 44 of the semi-finished nail body; wherein the rolling force of the rolling tool is 40Kgf~80Kgf, the speed of the semi-finished nail body is 300r / min~700r / min, and the rolling time of the rolling tool is 0.1s~1.0s. The rolling tool and the semi-finished nail body can be installed on a three-wheeled fully automatic fillet strengthening machine, and then the first rounded corner transition surface 44 of the semi-finished nail body can be rolled by the rolling tool.

[0064] Step S109, surface treatment is performed on the semi-finished nail body to obtain the finished nail body 4; specifically, the semi-finished nail body is sandblasted to remove surface impurities, increase the roughness, and enhance the coating adhesion; then the surface is passivated or coated with lubricants such as aluminum and molybdenum disulfide to obtain the finished nail body 4.

[0065] Combination Figure 4 and Figure 8 As shown, in the manufacturing method of the present invention, the manufacturing of the interference bushing 3 specifically includes the following steps:

[0066] Step 201, prepare a bushing blank; specifically, the bushing blank can be made of high-temperature alloy wire rods such as GH2132 or GH3030 with a strength level of 900Mpa to 1100Mpa.

[0067] Step 202, upsetting the bushing blank to form a bushing head 31, a second outer rounded transition surface 35, an inner rounded transition surface 34 and a bushing rod 81, to obtain a bushing semi-finished product 8; specifically, the bushing blank is processed into the bushing semi-finished product 8 by a multi-station cold upsetting method.

[0068] Step 203, roll-form the bushing taper 33 at one end of the bushing rod 81 away from the bushing head 31, and the other end of the bushing rod 81 constitutes the bushing body 32; specifically, use a conical rolling cutter and a female mold with a conical convex portion, wherein the shape and outer diameter of the conical convex portion are consistent with the designed shape and designed inner diameter of the bushing taper 33, and then roll-form the bushing taper 33 on a special lathe.

[0069] Step 204, heat-treating the semi-finished bushing 8; specifically, performing vacuum water quenching treatment on the semi-finished bushing 8 at a heating temperature of 600°C to 720°C; keeping the semi-finished bushing 8 warm for 10min to 20min; performing water quenching treatment on the semi-finished bushing 8, and controlling the transfer time of the semi-finished bushing 8 to be less than 8s.

[0070] Step 205 , subjecting the semi-finished bushing 8 to surface treatment to obtain a finished interference bushing 3 ; specifically, subjecting the semi-finished bushing 8 after heat treatment to surface passivation treatment, and then subjecting it to molybdenum disulfide coating treatment to obtain a finished interference bushing 3 .

[0071] Combination Figure 6 and Figure 7 As shown, in the manufacturing method of the present invention, the manufacturing of the drive nut 5 includes the following steps:

[0072] Step 301, prepare a nut semi-finished product: use a powder metallurgy near-net forming method to prepare a nut semi-finished product having a nut threaded hole 52 and a friction texture layer formed on one end plane from a powder raw material; specifically, the powder raw material includes 0.25% to 0.45% by weight of Mo, 0.38% to 0.48% by weight of C, 0.20% to 0.37% by weight of Si, 0.40% to 0.70% by weight of Mn, 0.05% to 0.15% by weight of Cu and the remaining Fe, and the powder diameter of the powder raw material is 10μm to 80μm. The powder raw material is placed in a matching mold, wherein the mold is provided with a threaded inner mold core matching the design shape and design size of the nut threaded hole 52, and then the mold is placed in a hydraulic press for molding; wherein the molding pressure is 30Mpa~100Mpa, and the molding holding time is 2s~20s; the molded nut semi-finished product is placed in a sintering furnace, heated to 1100℃~1300℃ at a heating rate of 100℃ / min~300℃ / min for sintering, and then kept warm for 1h~5h and then cooled with the furnace.

[0073] Step 302, heat treatment is performed on the semi-finished nut product; specifically, first, solution heat treatment is performed: the semi-finished nut product is placed in a vacuum solution furnace at 850°C to 1050°C for 45min to 60min, and then oil-cooled; then tempering treatment is performed: the semi-finished nut product after solution heat treatment is placed in a vacuum furnace at 150°C to 300°C for 1h to 2h, and then air-cooled. In this embodiment, the hardness of the semi-finished nut product after heat treatment reaches 45HRC to 50HRC.

[0074] Step 303, surface treatment is performed on the semi-finished nut to obtain the finished drive nut 5; specifically, the semi-finished nut after heat treatment is subjected to surface coating (such as nickel plating, zinc plating or chrome plating) to obtain the finished drive nut 5.

[0075] Combination Fig. 9 and Fig.10 As shown, in the manufacturing method of the present invention, the outer wall surface of the manufactured nail sleeve 2 is generally a cylindrical surface, that is, the closing portion 23 is not formed, and the nail sleeve 2 is also formed with a through hole 22 that is connected to the step hole 21 and extends to the first end of the nail sleeve 2. When the nail sleeve 2 is assembled with the core rod 1, that is, the nail sleeve 2 is sleeved on the core rod 1, the first end of the nail sleeve 2 (that is, the end of the nail sleeve 2 that abuts against the core rod head 11 of the core rod 1) can be horizontally squeezed (that is, radially compressed inwardly) to form a closing portion 23 with increased strength and hardness at the first end of the nail sleeve 2. The outer diameter of the closing portion 23 is smaller than the outer diameter of the main body of the nail sleeve 2. The length of the closing portion 23 is not specifically limited and can be adjusted according to the outer diameter of the nail sleeve 2. For example, the larger the outer diameter of the nail sleeve 2, the longer the length of the closing portion 23 is, and the smaller the outer diameter of the nail sleeve 2 is, the shorter the length of the closing portion 23 is.

[0076] In the manufacturing method of the present invention, the manufacturing of the nail sleeve 2 includes the following steps:

[0077] Step 401, preparing nail sleeve blanks;

[0078] Step 402, machining a stepped hole 21 at one end of the nail sleeve blank to obtain a nail sleeve semi-finished product;

[0079] Step 403, dividing the semi-finished nail sleeve into a first length section 27, a second length section 28 and a third length section 29 in sequence from one end of the semi-finished nail sleeve near the step hole 21 to the other end of the semi-finished nail sleeve; wherein the length L1 of the first length section 27 is greater than the length l1 of the insert 6, the second length section 28 is connected to the first length section 27, and the length L3 of the third length section 29 is greater than the length l2 of the closing portion 23;

[0080] Step 404, heat treating the first length segment 27 of the semi-finished nail sleeve at a first heating temperature, and heat treating the second length segment 28 of the semi-finished nail sleeve at a second heating temperature; wherein the first heating temperature is higher than the second heating temperature; after heat treating the first length segment 27 and the second length segment 28, the semi-finished nail sleeve is cryogenically treated, so that the first length segment 27 constitutes the main deformation segment 24 of the nail sleeve 2, the second length segment 28 constitutes the transition deformation segment 25 of the nail sleeve 2, and the third length segment 29 constitutes the support segment 26 of the nail sleeve 2.

[0081] The present invention divides the nail sleeve semi-finished product into a first length section 27, a second length section 28 and a third length section 29, and designs the length of each length section, and then heat-treats the first length section 27 and the second length section 28 at different heating temperatures. Since the heating temperature of the first length section 27 is higher than the heating temperature of the second length section 28, the third length section 29 is not heat-treated, so that the strength of the first length section 27 becomes lower and the plasticity becomes better. The main deformation section 24 of the nail sleeve 2 is formed by the length section, and expansion deformation occurs during the installation process of the threaded nail, thereby reducing the installation driving force and resistance of the threaded nail, thereby facilitating the installation of the threaded nail. The second length segment 28 has a lower strength and plasticity than the first length segment 27, and the transition deformation segment 25 of the nail sleeve 2 is formed by the length segment, which is convenient for forming the bell-shaped pier head of the nail sleeve 2. The third length segment 29 can maintain high strength and is used as the supporting segment 26 of the nail sleeve 2, so that it can bear the axial force applied by the core rod 1 during the installation process of the threaded nail. Therefore, the present invention can form a unique three-stage incremental structure of low strength-medium strength-high strength from the second end to the first end of the nail sleeve 2, so that the length segments of different strengths can play their due role, improve the quality stability of the product, and ensure that the pier head of the riveted installation of the threaded nail is in a bell tower shape.

[0082] refer to Fig. 9As shown, in an embodiment of the present invention, preparing a nail sleeve blank includes: using a tube body to cut and process into a nail sleeve blank; wherein the nail sleeve blank has an axially penetrating through hole. Specifically, the tube body is a hard stainless steel tube, and the tensile strength of the hard stainless steel tube is 800Mpa to 1050Mpa, ensuring that the support section 26 formed by the third length section 29 that is not subsequently heat treated has high strength. The length of the nail sleeve blank is substantially the same as the designed length of the nail sleeve 2. The inner diameter of the through hole is substantially the same as the designed inner diameter of the through hole 22 of the nail sleeve 2. Further, in the preparation step of the semi-finished nail sleeve, one end of the through hole of the nail sleeve blank is expanded by lathing to form a step hole 21, and the other end of the through hole constitutes a through hole 22. That is to say, the semi-finished nail sleeve is completely identical in shape and size to the finished nail sleeve 2 obtained in the end before heat treatment.

[0083] Combination Fig. 9 and Fig.10 As shown, in the embodiment of the present invention, the length of the first length segment 27 is L1, the length of the insert 6 is l1, and the relationship is: 0.5mm≤(L1-l1)≤2.0mm; the length of the third length segment 29 is L3, the length of the closing portion 23 is l2, and the relationship is: 1.5mm≤(L3-l2)≤5.5mm. The length of the second length segment 28 is L2, which is equal to the total length of the semi-finished nail sleeve (that is, the length L of the nail sleeve 2) minus the sum of the length L1 of the first length segment 27 and the length L3 of the third length segment 29.

[0084] Combination Figure 1 As shown, in an embodiment of the present invention, the first heating temperature is 950°C to 1050°C, and the second heating temperature is 850°C to 950°C. Preferably, the heating methods for heat treatment of the first length segment 27 and the second length segment 28 are both induction heating, that is, electromagnetic induction heating. The segmented heat treatment of the semi-finished nail sleeve by induction heating can ensure that the heating temperatures of the first length segment 27 and the second length segment 28 are accurate and do not affect each other, and can also avoid the third length segment 29 being heated and affecting its organization. It is suitable for the heat treatment of large quantities of semi-finished nail sleeves, which is beneficial to improve the manufacturing efficiency of large quantities of nail sleeves 2, and is also suitable for the heat treatment of small quantities of semi-finished nail sleeves, with low energy consumption and high cost performance, which is beneficial to reduce the manufacturing cost of small quantities of nail sleeves 2.

[0085] Specifically, heat treating the first length segment 27 includes: sleeve a first induction heating coil outside the first length segment 27 for induction heating; wherein the length of the first induction heating coil is equal to the length L1 of the first length segment 27. Heat treating the second length segment 28 includes: sleeve a second induction heating coil outside the second length segment 28 for induction heating; wherein the length of the second induction heating coil is equal to the length L2 of the second length segment 28.

[0086] refer to Fig. 9 As shown, in an embodiment of the present invention, performing cryogenic treatment on the semi-finished nail sleeve product includes: placing the semi-finished nail sleeve product in a cold box for cryogenic treatment; wherein the cold box is filled with liquid nitrogen, and the temperature in the cold box is -90°C.

[0087] In addition, after heat treatment of the first length section 27 and the second length section 28 and before cryogenic treatment of the semi-finished nail sleeve, the method further includes: blowing inert gas to the semi-finished nail sleeve to rapidly cool the semi-finished nail sleeve, wherein the inert gas includes but is not limited to argon.

[0088] refer to Fig. 9 As shown, in the embodiment of the present invention, the first length segment 27 and the second length segment 28 can be heat-treated separately and then air-cooled separately, for example, the first length segment 27 is first heat-treated at the first heating temperature by the first induction heating coil, and then the semi-finished nail sleeve is air-cooled, and then the second length segment 28 is heat-treated at the second heating temperature by the second induction heating coil, and then the semi-finished nail sleeve is air-cooled. The first length segment 27 and the second length segment 28 can also be heat-treated at the same time and then air-cooled at the same time, for example, the first induction heating coil is sleeved outside the first length segment 27, and the second induction heating coil is sleeved outside the second length segment 28, so as to achieve the simultaneous heat treatment of the first length segment 27 and the second length segment 28 at the corresponding heating temperature, and then the semi-finished nail sleeve is air-cooled.

[0089] Before heat treating the first length section 27 and the second length section 28, the method further includes: cleaning the surface dirt of the nail sleeve semi-finished product; after deep freezing the nail sleeve semi-finished product, the method further includes: performing surface lubrication treatment on the nail sleeve semi-finished product; wherein the surface lubrication treatment includes but is not limited to coating the surface of the nail sleeve semi-finished product with aviation aluminum paint or molybdenum disulfide-based lubricant.

[0090] refer to Fig. 9 and Fig.10 As shown, in order to better understand and implement the manufacture of the nail sleeve 2 in the present invention, two specific embodiments are provided:

[0091] In a specific embodiment, a nail sleeve 2 with an outer diameter of 5 mm and a length L of 10 mm is prepared, and the length l1 of the insert 6 configured for the nail sleeve 2 is 2.2 mm to 2.6 mm, and the length l2 of the preformed closing portion 23 is 0.5 mm to 1.5 mm. The length of the semi-finished nail sleeve is 10 mm, and the length L0 of the step hole 21 is 3.5 mm; the semi-finished nail sleeve is divided into a first length section 27 with a length L1 of 3.5 mm to 4.0 mm, a second length section 28 with a length L2 of 3 mm, and a third length section 29 with a length L3 of 3.0 mm to 3.5 mm from the end face of the first end where the step hole 21 is provided to the end face of the second end of the semi-finished nail sleeve in sequence; the first length section 27 of the semi-finished nail sleeve is heated to 1000° C. to 1150° C. by a first induction heating coil with a length of 3.5 mm to 4.0 mm, and then cooled by air blowing; the second length tube of the semi-finished nail sleeve is heated to 900° C. to 950° C. by a second induction heating coil with a length of 3 mm, and then cooled by air blowing; the semi-finished nail sleeve after heat treatment and cooling is placed in a cold box at -90° C. for deep cooling.

[0092] In another specific embodiment, a nail sleeve 2 with an outer diameter of 8 mm and a length L of 14 mm is prepared, and the length l1 of the insert 6 configured for the nail sleeve 2 is 3.6 mm to 3.9 mm, and the length l2 of the preformed closing portion 23 is 1.5 mm to 2.5 mm. The length of the semi-finished nail sleeve is 14 mm, and the length L0 of the step hole 21 is 4.5 mm; the semi-finished nail sleeve is divided into a first length section 27 with a length L1 of 4.5 mm to 5.0 mm, a second length section 28 with a length L2 of 2.5 mm to 3.0 mm, and a third length section 29 with a length L3 of 6.0 mm to 7.0 mm from the end face of the first end of the semi-finished nail sleeve where the step hole 21 is provided to the end face of the second end of the semi-finished nail sleeve in sequence; the first length section 27 of the semi-finished nail sleeve is heated to 1000° C. to 1150° C. by a first induction heating coil with a length of 4.5 mm to 5.0 mm, and then cooled by air blowing; the second length tube of the semi-finished nail sleeve is heated to 900° C. to 950° C. by a second induction heating coil with a length of 2.5 mm to 3.0 mm, and then cooled by air blowing; the semi-finished nail sleeve after heat treatment and cooling is placed in a cold box at -90° C. for deep cooling.

[0093] The nail sleeve 2 obtained in the above two specific embodiments has a hardness of 156Hv for the main deformation section 24 corresponding to the first length section 27, a hardness of 256Hv for the transition deformation section 25 corresponding to the second length section 28, and a hardness of 350Hv for the support section 26 corresponding to the third length section 29. Figures 11 to 13It can be seen from the metallographic structures of each section that the main deformation section 24 and the transition deformation section 25 are both low-hardness austenite structures obtained after heat treatment. The main deformation section 24 has a small hardness value and the corresponding structure has large grains. The transition deformation section 25 has the second-best hardness and the corresponding grains are finer. The support section 26 has the highest hardness and the corresponding grains are relatively small and has a deformed martensite structure with high strength and hardness.

[0094] In addition, the manufacture of the core rod 1 may be the same as in the prior art and will not be described in detail herein.

[0095] The above are only several embodiments of the present invention. Those skilled in the art may make various changes or modifications to the embodiments of the present invention based on the contents disclosed in the application documents without departing from the spirit and scope of the present invention.

Claims

1. A threaded screw for interference connection, characterized in that: It comprises a core rod, a nail sleeve, an interference bushing, a nail body and a driving nut, wherein the first end of the core rod is provided with a core rod head, the nail sleeve, the interference bushing, the nail body and the driving nut are sequentially sleeved on the core rod from the second end of the core rod, the first end of the nail sleeve abuts against the core rod head, the second end of the nail sleeve is sleeved on the first end of the interference bushing, the second end of the interference bushing is sleeved on the first end of the nail body, and the second end of the nail body abuts against the driving nut; The interference bushing comprises a bushing cone portion, a bushing body portion and a bushing head portion connected in sequence from the first end to the second end thereof, and the nail body comprises a nail body cone portion, a nail body body portion and a nail body head portion connected in sequence from the first end to the second end thereof; The nail body head is connected to the outer wall surface of the nail body main body through a first outer rounded corner transition surface, the inner wall surface of the bushing head is connected to the inner wall surface of the bushing main body through an inner rounded corner transition surface, and the outer wall surface of the bushing head is connected to the outer wall surface of the bushing main body through a second outer rounded corner transition surface; When the interference connection threaded screw is in a tightened state, the tapered portion of the screw body fits with the tapered portion of the bushing, the tapered portion of the bushing is inserted into the screw sleeve, the first outer rounded corner transition surface fits with the inner rounded corner transition surface, and the second outer rounded corner transition surface can fit with the entrance of the mounting hole.

2. The threaded screw for interference connection according to claim 1, characterized in that: The nail body head has a first abutting plane abutting against the drive nut.

3. The threaded screw for interference connection according to claim 2, characterized in that: The drive nut has a second abutting plane abutting against the first abutting plane, and the second abutting plane has a friction texture layer for increasing friction.

4. The threaded screw for interference connection according to claim 1, characterized in that: The threaded pull-out nail for interference connection also includes an insert, a second end of the nail sleeve is provided with a step hole, and the insert and one end of the cone portion of the bushing are inserted into the step hole in sequence.

5. A method for manufacturing a threaded screw for interference connection, characterized in that: The manufacturing method comprises processing and manufacturing a core rod, a nail sleeve, an interference bushing, a nail body and a drive nut of a threaded screw for interference connection according to any one of claims 1 to 4; The manufacturing of the nail body includes the following steps: Preparing nail body blanks; The nail body blank is upset to form a nail body head, a first rounded transition surface, a nail body main body and a nail body taper to obtain a nail body semi-finished product; machining a through hole in the semi-finished nail body; tapping the inner wall surface of the through hole to form an inner nut surface; Grinding the outer wall surfaces of the nail body main body and the nail body cone of the semi-finished nail body; performing heat treatment on the semi-finished nail body; Rolling the first rounded corner transition surface of the semi-finished nail body; Performing surface treatment on the semi-finished nail body to obtain the finished nail body; The manufacturing of the interference bushing specifically includes the following steps: Prepare bushing blanks; The bushing blank is upset to form a bushing head, a second outer rounded transition surface, an inner rounded transition surface, and a bushing stem to obtain a bushing semi-finished product; The end of the bushing stem away from the bushing head is roll-formed to form a bushing cone, and the other end of the bushing stem forms a bushing body; heat treating the semi-finished bushing; The semi-finished bushing is subjected to surface treatment to obtain the finished interference bushing.

6. The method for manufacturing a threaded screw for interference connection according to claim 5, characterized in that: The first outer rounded corner transition surface of the semi-finished nail body is rolled, including: using a matching rolling tool to roll the first outer rounded corner transition surface of the semi-finished nail body; wherein the rolling force of the rolling tool is 40Kgf~80Kgf, the rotation speed of the semi-finished nail body is 300r / min~700r / min, and the rolling time of the rolling tool is 0.1s~1.0s.

7. The method for manufacturing a threaded screw for interference connection according to claim 5, characterized in that: The semi-finished bushing is subjected to heat treatment, comprising the following steps: Performing vacuum water quenching treatment on the semi-finished bushing at a heating temperature of 600° C. to 720° C.; Keeping the semi-finished bushing warm for 10 to 20 minutes; The semi-finished bushing is subjected to water quenching treatment, and the transfer time of the semi-finished bushing is controlled to be less than 8s.

8. The method for manufacturing a threaded screw for interference connection according to claim 5, characterized in that: The manufacturing of the drive nut comprises the following steps: Preparing a semi-finished nut product: using a powder metallurgy near-net forming method to prepare a semi-finished nut product having a nut hole and a friction texture layer formed on one end plane from a powder raw material; performing heat treatment on the semi-finished nut product; The semi-finished nut is subjected to surface treatment to obtain the finished drive nut.

9. The method for manufacturing a threaded screw for interference connection according to claim 8, characterized in that: The powder raw material includes 0.25% to 0.45% by weight of Mo, 0.38% to 0.48% by weight of C, 0.20% to 0.37% by weight of Si, 0.40% to 0.70% by weight of Mn, 0.05% to 0.15% by weight of Cu and the remaining Fe, and the powder diameter of the powder raw material is 10μm to 80μm.

10. The method for manufacturing a threaded screw for interference connection according to claim 8, characterized in that: The step of preparing the semi-finished nut product comprises the following steps: The powder raw material is placed in a matching mold, and then the mold is placed in a hydraulic press for molding; wherein the molding pressure is 30Mpa to 100Mpa, and the molding holding time is 2s to 20s; The molded semi-finished nut is placed in a sintering furnace, heated to 1100°C to 1300°C at a heating rate of 100°C / min to 300°C / min for sintering, and then kept warm for 1h to 5h before cooling with the furnace.

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