CN116652434A - Welded joint and method of manufacturing the same - Google Patents

Abstract

The invention belongs to the technical field of mechanical processing, and in particular relates to a welded joint and a manufacturing method thereof, which are used to solve the technical problem of low fatigue strength of the welded joint. The welding joint includes at least two plates stacked in sequence, a nugget fixedly connecting the two adjacent plates, and a nail-shaped piece, which is pressed into at least part of the stacked direction of the at least two plates. In the plate and each nugget, the corresponding plate and the nugget are formed with accommodating holes suitable for the nail-shaped piece, and at least the edge region of the nugget away from the nail-shaped piece has compressive residual stress. Inhibit the generation and growth of cracks by compressing residual stress, improve fatigue strength, and reduce fatigue fracture of welded joints.

Description

Welded joint and method of manufacturing the same

technical field

The embodiments of the present invention relate to the technical field of mechanical processing, and in particular to a welded joint and a manufacturing method thereof.

Background technique

In the automobile industry in recent years, in order to improve the fuel consumption and safety of automobiles, thin-walled high-strength steel sheets are usually used for body parts and other parts, and the overlapped joints are connected by spot welding to form welded joints. . Among them, spot welding connects multiple high-tensile steel plates that are overlapped by electrodes, and pressurizes them through the electrodes, and at the same time passes high current to the electrodes in a short period of time to form a nugget, thereby fixing and connecting multiple high-tensile steel plates , no filling material is required during the connection process, high production efficiency and easy automation. However, the fatigue strength of welded joints is usually low.

Contents of the invention

In view of the above problems, embodiments of the present invention provide a welded joint and a manufacturing method thereof, so as to improve the fatigue strength of the welded joint.

A first aspect of an embodiment of the present invention provides a welded joint, which includes at least two plates stacked in sequence, a nugget fixedly connecting two adjacent plates, and a nail, the nail The shape piece is pressed into at least part of the plate piece and each of the nuggets along the stacking direction of the at least two plate pieces, so that the nail-like shape is formed in the corresponding plate piece and the nugget. A receiving hole adapted to a piece, and at least an edge region of the nugget far away from the nail-like piece has a compressive residual stress.

In some possible embodiments, the direction of the compressive residual stress is perpendicular to the stacking direction of at least two plates.

In some possible embodiments, the compressive residual stress is radially distributed relative to the axis of the nail.

In some possible embodiments, the hardness of the nail is greater than that of the plate and greater than that of the nugget, and the axis of the nail coincides with the center of the nugget.

In some possible embodiments, the first surface of the at least two plates is formed with the receiving hole, the second surface is formed with a protrusion, the protrusion is arranged opposite to the receiving hole, and the first The surface is disposed opposite to the second surface along the stacking direction of the at least two boards.

In some possible embodiments, the nail-shaped piece is self-piercing riveted with the corresponding plate piece and the nugget, and the nail-shaped piece includes a self-piercing rivet.

In some possible embodiments, the self-piercing rivet includes a rivet foot, and a rivet head connected to one end of the rivet foot, the rivet head is located in one of the plates, and the end surface away from the rivet foot is exposed , the rivet foot penetrates the nugget and the plate between the rivet head and the nugget, and presses the edge region of the nugget.

In some possible embodiments, the at least two boards include a first board and a second board, and the nail is located in the first board and passes through the first board and the second board. The nugget extends into the second plate, and the edge region of the nugget away from the nail has the compressive residual stress.

The welded joint of the embodiment of the present invention has at least the following advantages:

A welded joint according to an embodiment of the present invention comprises a nail pressed into at least two plates, and the nail penetrates at least part of the plates and each nugget such that at least the edge region of the nugget away from the nail It has compressive residual stress to inhibit the generation and growth of cracks, improve fatigue strength and reduce fatigue fracture of welded joints.

A second aspect of an embodiment of the present invention provides a method for manufacturing a welded joint, which includes:

Stacking at least two plates in sequence to form a part to be welded;

Welding the parts to be welded to form a welded part, a nugget is formed in the welded part, and the nugget is fixedly connected to two adjacent plates, and along the overlapping of the at least two plates direction, the piece to be welded has a first surface and a second surface oppositely arranged;

A nail is driven from the first surface to form a welded joint, the nail penetrates the nugget and the plate on the side of the nugget close to the first surface to form In the accommodating hole, at least an edge region of the nugget far away from the nail has compressive residual stress.

In some possible examples, driving a spike from the first surface includes:

the spike is mounted within a male tool and the weld is placed between the male tool and the female tool, the male tool in contact with the first surface;

The male mold tool drives the nail-shaped piece into the welded piece, the nail-shaped piece and the welded piece are plastically deformed, and the second surface is attached to the female mold tool to form a Protrusions that match the die tool described above.

The manufacturing method of the welded joint in the embodiment of the present invention has at least the following advantages:

In the manufacturing method in the embodiment of the present invention, at least two plates are stacked in sequence and then welded to form a nugget between two adjacent plates, and the nail-shaped nail-shaped piece penetrates the nugget And the corresponding plate, so that at least the edge region of the nugget far away from the nail has compressive residual stress, so as to inhibit the generation and growth of cracks, improve the fatigue strength, and reduce the fatigue fracture of the welded joint.

In addition to the technical problems solved by the embodiments of the present invention described above, the technical features constituting the technical solutions, and the beneficial effects brought by the technical features of these technical solutions, the welded joints and manufacturing methods provided by the embodiments of the present invention can Other technical problems to be solved, other technical features included in the technical solution, and the beneficial effects brought by these technical features will be further described in detail in the specific implementation manner.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

1 is a schematic diagram of tensile residual stress of a nugget in a welded joint in the related art;

2 is a schematic diagram of a fatigue crack in the related art;

Fig. 3 is the structural representation of the welding joint in the embodiment of the present invention;

Fig. 4 is a schematic diagram of the position before the nail-shaped part is pressed into the plate in the embodiment of the present invention;

Fig. 5 is a schematic diagram of the position of the nail-shaped part after being pressed into the plate in the embodiment of the present invention;

Fig. 6 is the top view of the plate and nugget used for testing in the embodiment of the present invention;

Fig. 7 is the side view of the plate and nugget used for testing in the embodiment of the present invention;

Fig. 8 is a schematic diagram of fatigue test results in an embodiment of the present invention.

Explanation of reference signs:

1-plate;

2 - nugget;

3 - nails;

4- Punch tool;

5- Die tool;

6 - first surface;

7 - second surface;

8- Raised.

Detailed ways

In the related art, the fatigue strength of welded joints is generally low. The inventors have found that the reason is that: referring to Fig. 1 and Fig. 2, during welding, the molten metal undergoes volume expansion due to martensitic transformation, but after subsequent solidification Thermal shrinkage occurs during cooling. Due to the shrinkage of the nugget 2, in the edge region of the nugget 2 and the nearby plate 1, a balanced stress state as shown in FIG. 1 is formed, and finally the edge region of the nugget 2 is in a state of tensile residual stress. As shown in Figure 2, the edge region of the nugget 2 has crack openings in the same direction as the tensile stress (X direction shown in Figure 2), and fatigue cracks are generated near the melt, and the fatigue cracks are directed toward the plate thickness direction (Figure 2 2 shown in the Y direction) grows, and when the fatigue crack develops to the surface of the plate 1, fatigue fracture occurs. The tensile residual stress is affected by the shape of the edge region of the nugget 2, even if the strength of the plate 1 is increased, the fatigue strength of the welded joint will not increase accordingly.

To this end, an embodiment of the present invention provides a welded joint and a manufacturing method thereof, by pressing a nail-like piece into at least two plates, and the nail-like piece penetrates at least part of the plates and each nugget, so that the nugget At least the edge region far away from the nail-shaped piece has compressive residual stress to inhibit the generation and growth of cracks, improve the fatigue strength, and reduce the fatigue fracture of the welded joint.

In order to make the above objects, features and advantages of the embodiments of the present invention more obvious and understandable, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Apparently, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Referring to FIG. 3 , an embodiment of the present invention provides a welded joint, which includes at least two plates 1 stacked in sequence, a nugget 2 that fixedly connects two adjacent plates 1 , and a nail 3 . Wherein, the number of plates 1 may be two or more, and these plates 1 are stacked in sequence and have overlapping areas, so as to be clamped by electrodes and form a nugget 2 . The stacking direction of these boards 1 is the board thickness direction, the stacking sequence of these boards 1 is related to their connection relationship, and the boards 1 that need to be fixedly connected are in contact.

The plate 1 can be a steel plate or an aluminum alloy plate, etc., and its thickness is relatively thin. When the plate 1 is a steel plate, it can be a mild steel plate, a high-tensile steel plate, an ultra-high-tensile steel plate, etc., and its thickness is usually less than or equal to 4mm. When the plate 1 is an aluminum alloy plate, its material may be 5000 series aluminum alloy, 6000 series aluminum alloy, etc., and its thickness is usually less than or equal to 3mm.

Two adjacent plates 1 are fixedly connected by a nugget 2 , and the nugget 2 can be formed by heating the plates 1 . When the number of plates 1 is greater than two, the nugget 2 is located in the central part of the overall thickness of the plates 1 and is fixedly connected to each plate 1 . Wherein, the thickness direction of the nugget 2 is the overlapping direction of at least two plates 1, that is, the depth direction of the penetration depth, and the radial direction of the nugget 2 is perpendicular to the thickness direction of the nugget 2, so that the nugget 2 The direction in which the center extends radially, and the diameter of the nugget is the maximum length of the nugget 2 along the radial direction.

Continuing to refer to FIG. 3 , the nail-shaped part 3 is pressed into at least part of the plate 1 and each nugget 2 along the stacking direction of the plate 1 (ie, the thickness direction), so that the corresponding plate 1 and the nugget 2 are formed to accommodate The hole, the receiving hole is adapted to the nail-like piece 3 to accommodate the nail-like piece 3. The inside of the nugget 2 and the plate 1 has a new structure, and the edge region of the nugget 2 is in a state of compressive residual stress.

Wherein, along the stacking direction of at least two panels 1, one end of the stacked panels 1 is a press-in end (such as the upper end shown in FIG. 3 ), and the nail-shaped part 3 is pressed into the panel 1 by the press-in end. and nugget 2. The nail 3 runs through each nugget 2 and the corresponding plate 1 , for example, the nail 3 runs through each plate 1 on the side of the nugget 2 close to the press-in end, so as to realize the penetration of the nugget 2 .

Due to the extrusion of the nail 3 , both the nugget 2 and the inside of the plate 1 undergo plastic deformation, and at least the edge region of the nugget 2 away from the nail 3 has compressive residual stress. Compared with tensile residual stress, compressive residual stress can inhibit the generation and growth of cracks, which can not only improve the static strength and dynamic strength of welded joints, such as improving impact strength, but also improve fatigue strength and reduce fatigue fracture of welded joints. At the same time, the nail-shaped part 3 will also undergo plastic deformation to form a mechanical interlocking structure with the plate part 1 and the nugget 2 to ensure the firmness of the connection.

Wherein, the hardness of the nail 3 is greater than that of the plate 1 and greater than that of the nugget 2 , so as to realize the pressing of the nail 3 and the formation of the receiving hole. The nail 3 is located in the center of the nugget 2, for example, the nail 3 is located in the center of the nugget 2, that is, the axis of the nail 3 coincides with the center of the nugget 2, so that the edge area of the nugget 2 is affected. The force is more uniform. The compressive residual stress is radially distributed relative to the axis of the nail 3, so that the compressive residual stress in the edge area is distributed around the axis of the nail 3. The edge areas all have compressive residual stress, and the compressive residual stress in the edge area is relatively uniform.

Referring to FIG. 3 , the direction of the compressive residual stress is perpendicular to the stacking direction of at least two plates 1 , that is, the direction of the compressive residual stress is consistent with the rolling direction of the plates 1 . Since cracks usually open in the rolling direction (X direction shown in Figure 2) and grow and develop in the plate thickness direction (Y direction shown in Figure 2), by making the direction of the compressive residual stress coincide with the radial direction of the nugget 2 (that is, consistent with the rolling direction of the plate 1), the tensile residual stress in the rolling direction disappears, and the compressive residual stress is maintained in the vertical direction of the crack growth, which is beneficial to keep the opening of the crack closed, and can more effectively suppress crack.

In some examples, the nail-shaped piece 3 is self-piercing riveting (SPR for short) between the corresponding plate piece 1 and the nugget 2 , and the nail-shaped piece 3 includes a self-pierce rivet. That is, the self-piercing rivet is directly pressed into the plate 1 and the nugget 2 through the power provided by the hydraulic cylinder or the servo motor. The plate 1, the nugget 2 and the self-piercing rivet all reflect plastic deformation under pressure, thereby forming a stable connection.

The self-piercing rivet can be a cylindrical rivet. Specifically, the self-piercing rivet includes a rivet foot and a rivet head connected to one end of the rivet foot. The rivet head is located in a plate 1 and exposed at the end face away from the rivet foot. The rivet foot penetrates the nugget 2, and the plate 1 between the rivet head and the nugget 2, and squeezes the edge area of the nugget 2. Wherein, the rivet head may be cylindrical, and the rivet feet are turned outwards to securely connect the plate 1 . When there are multiple rivet feet, the distance between adjacent rivet feet increases along the direction away from the rivet head.

Continue to refer to Fig. 3, at least two plates 1 form a stack, and the nail 3 is pressed into the first surface 6 (for example, the upper surface) of the at least two plates 1 (ie, the stack), and the first surface 6 forms an accommodating hole. The second surface 7 (for example, the lower surface) of at least two boards 1 (ie, laminates) facing away from the first surface 6 forms a protrusion 8, the protrusion 8 is opposite to the receiving hole, and the first surface 6 and the second surface 7 Opposite along the stacking direction of at least two boards 1 .

Wherein, in the stack formed by at least two boards 1 , the two surfaces of the two boards 1 on both sides facing away from each other are the first surface 6 and the second surface 7 respectively. The nail-shaped part 3 is located in the stack formed by at least two board parts 1, one end of which is exposed and the other end is not exposed.

In some possible examples, each of the plate 1 and the nugget 2 is formed with a protruding portion facing the second surface 7 , and the protruding portion of the plate 1 at the bottom of the receiving hole forms a protrusion 8 . During the pressing process of the nail-shaped part 3, a pressure consistent with the pressing direction (for example, vertically downward) is generated on each plate 1 and nugget 2, and each plate 1 and nugget 2 produce corresponding deformation under the pressure , forming a protrusion consistent with the pressing direction. The protruding portion of the outermost panel 1 away from the opening direction of the receiving hole is the protrusion 8 of the stack formed by at least two panels 1 .

In the example of the self-piercing riveting of the nail-shaped part 3 with the plate 1 and the nugget 2, referring to Fig. 4 and Fig. Between the die tool 5 and the at least two plates 1, the plate 1 close to the punch tool 4 is the top plate, and the plate 1 close to the die tool 5 is the bottom plate. Through the punch tool 4, the self-piercing rivet will self-pierce through the top plate and each nugget 2, and enter the bottom plate, and the rivet foot expands to a certain diameter in the bottom plate, and the material of the bottom plate flows into the die tool 5 to form a Matching bumps.

In some possible examples, the at least two boards 1 include a first board and a second board, and the first board is arranged on the second board. There are two plates 1, and a nugget 2 is fixedly connected to the first plate and the second plate. The nail 3 is located in the first plate, runs through the first plate 1 and the nugget 2 , and extends into the second plate, and the edge region of the nugget 2 away from the nail 3 has compressive residual stress. The compressive residual stress is perpendicular to the stacking direction of the first plate and the second plate, so that the welded joint has higher fatigue strength.

In order to study the fatigue strength of the welded joint in the embodiment of the present invention, taking two plates 1 as an example, the welded joint A that is only welded, the welded joint B that is compressed after welding, and the welded joint (welded joint) of the embodiment of the present invention Post-self-piercing riveted welded joints) C performed tensile shear fatigue strength tests.

Specifically, referring to Fig. 6 and Fig. 7, the two stacked plates 1 are both 780MPa-grade cold-rolled steel plates (DP780), with a size of 1.8mmx38mmx125mm, where 125mm is the length L1 of the plate 1, and 1.8mm is the plate The thickness t of 1, 38cm, is the width L3 of the board 1, and is the length L2 of the overlapping area of the two boards 1. Correspondingly, the total length L4 of the two boards 1 after stacking is 212mm.

The diameter of the nugget 2 is φ7.5mm. The specific welding conditions are as follows: use a conical-R-shaped electrode with a diameter of 20mm, a front diameter of φ8mm (R40), an electrode pressure of 4.4kN, a welding current of 7.7kA, and a power-on time of 490ms. After the two plates 1 are welded under the above conditions, a welded joint A only welded is obtained.

Compression processing was performed on the welded joint A obtained only by welding using a universal testing machine and a boron steel cylindrical punch (φ10 mm). Specifically, the central axis of the punch is kept consistent with the center of the nugget 2, pressure is applied from the plate surface in the direction of plate thickness, the maximum load is 100kN, and the hold time is 10 seconds to obtain a welded joint B compressed after welding.

A hard rivet (φ5×L6mm, 540HV) was used to perform self-piercing riveting on the welded joint A obtained only by welding. The central axis of the hard rivet is consistent with the center of the nugget 2, and it is driven into the plate thickness direction from the plate surface. The maximum load when driving is 82kN, and a welded joint C with self-piercing riveting after welding is obtained.

Fatigue tests were performed on welded joint A, welded joint B and welded joint C. Specifically, using a servo-hydraulic fatigue testing machine, frequency f=60Hz, stress ratio R≈0, cycle number 1× ¹⁰⁷ times is defined as the fatigue endurance limit, LN (load amplitude-rupture cycle number) line diagram production, etc. Evaluation of fatigue results is based on ISO-14324.

Referring to Figure 8, the time intensity of welded joint C under each load is the largest, and the L-N line graph moves to the upper right. Compared with welded joint B, the fatigue strength of welded joint C is high and stable, that is, the deviation of the test structure of welded joint C under the same load is small. In the comparison of the fatigue endurance limit (1×107 times the maximum load without breaking), the welded joint C is 2.9 times that of the welded joint A, and compared with the welded joint B, the welded joint C is improved by 2 times. Therefore, the fatigue strength of the welded joint in the embodiment of the present invention is significantly improved.

To sum up, the welded joint in the embodiment of the present invention includes a nail-like piece 3 pressed into at least two plates 1, and the nail-like piece 3 penetrates at least part of the plate 1 and each nugget 2, so that the nugget 2 At least the edge region far away from the nail-shaped part 3 has compressive residual stress, so as to inhibit the generation and growth of cracks, improve the fatigue strength, and reduce the fatigue fracture of the welded joint.

The embodiment of the present invention also provides a method for manufacturing a welded joint, referring to Figures 3 to 5, the manufacturing method specifically includes the following steps:

Step S100: stack at least two plate parts in sequence to form a part to be welded.

Wherein, the number of plate parts 1 may be two or more, and these plate parts 1 are stacked in sequence and have overlapping areas to form parts to be welded. The stacking direction of these boards 1 is the board thickness direction, the stacking sequence of these boards 1 is related to their connection relationship, and the boards 1 that need to be fixedly connected are in contact.

The plate 1 can be a steel plate or an aluminum alloy plate, etc., and its thickness is relatively thin. Exemplarily, the plate 1 may be a mild steel plate, a high-tensile steel plate, an ultra-high-tensile steel plate, a 5000-series aluminum alloy, a 6000-series aluminum alloy or the like. The materials of the boards 1 can be the same or different.

Step S200: Weld the parts to be welded to form a welded part. A nugget is formed in the welded part, and the nugget is fixedly connected to two adjacent plates. Along the stacking direction of at least two plates, the welded part has a first first surface and second surface.

Use the electrodes to clamp the parts to be welded, and apply pressure and electricity to the electrodes to perform spot welding, so that the parts to be welded form welded parts. A nugget 2 is formed centering on the contact surface of two adjacent plates 1 in the weldment, so as to fix the corresponding two plates 1 . Along the stacking direction of at least two plates 1 , the welded part has a first surface 6 (upper surface shown in FIG. 4 ) and a second surface 7 (lower surface shown in FIG. 4 ) which are oppositely disposed. Welding conditions during spot welding (such as welding current, energized test machine, pressurized size, etc.) can be adjusted according to the needs of the process.

Step S300: Driving a nail-like piece from the first surface to form a welded joint, the nail-like piece penetrates the nugget and the plate on the side of the nugget close to the first surface to form a receiving hole, the nugget is at least far away from the nail The edge region of the shape has compressive residual stress.

Drive the nail 3 from the first surface 6 of the weldment to form a welded joint, the nail 3 penetrates the nugget 2, and the plate 1 on the side of the nugget 2 near the first surface 6, so that the corresponding plate Accommodating holes are formed in the element 1 and the nugget 2, and the accommodating holes are adapted to the nail-shaped element 3. The accommodating hole is a blind hole, that is, the bottom of the accommodating hole is located in one of the panels 1 , for example, the bottom of the accommodating hole is located in the panel 1 farthest from the opening of the accommodating hole.

The hardness of the nail 3 is greater than that of the plate 1 and greater than that of the nugget 2 , so as to realize the pressing of the nail 3 and the formation of the receiving hole. The nail 3 is located in the center of the nugget 2, for example, the nail 3 is located in the center of the nugget 2, that is, the axis of the nail 3 coincides with the center of the nugget 2, so that the edge area of the nugget 2 is affected. The force is more uniform. The compressive residual stress is radially distributed relative to the axis of the nail 3, so that the compressive residual stress in the edge area is distributed around the axis of the nail 3. The edge areas all have compressive residual stress, and the compressive residual stress in the edge area is relatively uniform.

After the nail-shaped part 3 is driven into the weldment, the direction of the compressive residual stress in the nugget 2 is perpendicular to the stacking direction of at least two plates 1, that is, the direction of the compressive residual stress is consistent with the rolling direction of the plates 1, so that The tensile residual stress in the rolling direction disappears, and the compressive residual stress is maintained in the vertical direction of crack growth, which is beneficial to keep the opening of the crack closed, and can suppress the crack more effectively.

Wherein, the nail-shaped part 3 can be riveted into the weldment by self-piercing. Specifically, in some possible implementations, driving the nail-shaped part from the first surface (step S300) includes:

Step S301: the nail-shaped part is installed in the punch tool, and the welding part is placed between the punch tool and the die tool, and the punch tool is in contact with the first surface.

Referring to FIG. 4 , the nail 3 is located on the punch tool 4 and the punch tool 4 is in contact with the first surface 6 of the weldment, so that the nail 3 also remains in contact with the first surface 6 of the weld. The die tool 5 is in contact with the second surface 7 of the weldment, the weldment is located between the punch tool 4 and the die tool 5, and the first surface 6 and the second surface 7 are respectively close to the punch tool 4 and the die tool 5. Wherein, the male mold tool 4 and the female mold tool 5 are arranged oppositely, and the second surface 7 of the welding part is exposed in the cavity of the female mold tool 5 .

Step S302: The male tool drives the nail into the weldment, the nail and the weld are plastically deformed, and the second surface is attached to the die tool to form a protrusion matching the die tool.

The punch tool 4 pushes the nail 3 through the first surface 6 of the weldment and into the weldment. The nail 3 is plastically deformed to form a mechanical interlocking structure with the weldment. The weldment is plastically deformed, and the material of a layer of plate 1 in the weldment that is in contact with the die tool 5 enters the die tool 5, so that the second surface 7 of the weldment is attached to the die tool 5, forming a joint with the die tool 5 Compatible protrusions, and the welding piece and the nail-shaped piece 3 form a welding joint at the same time.

To sum up, in the method for manufacturing a welded joint in the embodiment of the present invention, at least two plates 1 are stacked sequentially and then welded to form a nugget 2 between two adjacent plates 1, and through The nail-shaped nail-shaped piece 3 penetrates the nugget 2 and the corresponding plate 1, so that at least the edge region of the nugget 2 far away from the nail-shaped piece 3 has compressive residual stress, so as to inhibit the generation and growth of cracks, improve the fatigue strength, and reduce Fatigue fracture of welded joints.

Each embodiment or implementation manner in this specification is described in a progressive manner, each embodiment focuses on the differences from other embodiments, and the same and similar parts of each embodiment can be referred to each other.

Those skilled in the art should understand that in the disclosure of the present invention, the terms "vertical", "transverse", "upper", "lower", "front", "rear", "left", "right", " The orientation or positional relationship indicated by "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, which are only for the convenience of describing the present invention and simplified description, rather than indicating or implying that the system or element referred to must have a specific orientation, be constructed and operate in a specific orientation, so the above terms should not be construed as limiting the present invention.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "exemplary embodiments", "examples", "specific examples", or "some examples" etc. mean that the embodiments are combined A specific feature, structure, material, or characteristic described or exemplified is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. The welding joint is characterized by comprising at least two plates which are sequentially overlapped, a nugget fixedly connecting the two adjacent plates, and a nail-shaped piece, wherein the nail-shaped piece is pressed into at least part of the plates and each nugget along the overlapped direction of the at least two plates, so that accommodating holes matched with the nail-shaped piece are formed in the corresponding plates and the nugget, and at least the edge area far away from the nail-shaped piece in the nugget is provided with compressive residual stress.

2. The welded joint according to claim 1, wherein the direction of the compressive residual stress is perpendicular to the stacking direction of at least two plates.

3. The welded joint of claim 1, wherein the compressive residual stress is radially distributed relative to the axis of the spike.

4. The welded joint of claim 1, wherein the spike has a hardness greater than the hardness of the plate and greater than the hardness of the nugget, the spike axis coinciding with the center of the nugget.

5. The welded joint according to any one of claims 1 to 4, wherein the receiving hole is formed in a first surface of the at least two plates, a projection is formed in a second surface, the projection is disposed opposite to the receiving hole, and the first surface and the second surface are disposed opposite to each other in a stacking direction of the at least two plates.

6. The welded joint according to any one of claims 1-4, wherein the spike comprises a self-piercing rivet between the spike and the respective plate and nugget.

7. The welded joint of claim 6 wherein said self-piercing rivet includes a rivet foot and a rivet head attached to one end of said rivet foot, said rivet head being located within one of said plates and being exposed at an end face remote from said rivet foot, said rivet foot extending through said nugget and said plate between said rivet head and said nugget and compressing said edge region of said nugget.

8. A welded joint according to any one of claims 1-3, wherein the at least two plates comprise a first plate and a second plate, the spike being located in the first plate and extending through the first plate and the nugget and into the second plate, the nugget having the compressive residual stress away from an edge region of the spike.

9. A method of manufacturing a welded joint, comprising:

sequentially superposing at least two plates to form a piece to be welded;

welding the to-be-welded piece to form a welding piece, wherein a nugget is formed in the welding piece, the nugget is fixedly connected with two adjacent plate pieces, and the to-be-welded piece is provided with a first surface and a second surface which are oppositely arranged along the stacking direction of the at least two plate pieces;

driving a nail from the first surface to form a welded joint, the nail penetrating the nugget, and the plate on a side of the nugget adjacent to the first surface to form a receiving hole, the nugget having compressive residual stress in at least an edge region thereof remote from the nail.

10. The method of manufacturing of claim 9, wherein driving the spike from the first surface comprises:

the spike is mounted within a punch tool and the weld is placed between the punch tool and a die tool, the punch tool being in contact with the first surface;

the male die tool drives the spike-shaped piece into the welding piece, the spike-shaped piece and the welding piece are plastically deformed, and the second surface is attached to the female die tool to form a protruding head matched with the female die tool.