Spot welding implementation method for aluminum alloy and dissimilar materials

Abstract

The invention discloses a spot welding implementation method for an aluminum alloy and a dissimilar material, and belongs to the technical field of spot welding of dissimilar materials. The method comprises the steps that a first prefabricated hole and a second prefabricated hole are aligned, and a friction sleeve is inserted into the first prefabricated hole in a matched mode; a sealing push rod is cooperatively arranged in the friction sleeve; an expansion plug is arranged in the second prefabricated hole in a matched mode, spot welding filler is arranged at the upper end of the expansion plug in a matched mode, and an inverted buckle protrusion is arranged at the top; the sealing push rod and the friction sleeve are controlled to rotate, the sealing push rod is pushed downwards to drive the spot welding filler to rotate and rub with the expansion plug to generate heat, the spot welding filler is softened and expanded outwards, and the outer circle face of the friction sleeve rubs with the first prefabricated hole to generate heat to be softened; and the friction sleeve is controlled to move upwards, the spot welding filler is softened and flows outwards to extrude the inverted buckle protrusion so that the inverted buckle protrusion can be mechanically locked with the lower side base material, and the spot welding filler gradually flows to the inner surface of the first prefabricated hole and is welded to the inner surface of the first prefabricated hole till the lower end face of the sealing push rod and the lower end face of the friction sleeve both reach the upper surface of the upper side base material.

Description

Technical Field

[0001] The invention belongs to the technical field of spot welding of dissimilar materials, and in particular relates to a method for implementing spot welding of aluminum alloy and dissimilar materials. Background Art

[0002] Aluminum alloy, as a widely used lightweight alloy, has incomparable advantages in many fields, especially in the body manufacturing of new energy vehicles and rail trains. In the manufacture of these aluminum alloy bodies, in order to meet the performance and safety requirements of the body, it is inevitable to use steel alloys with better strength and copper alloys with better conductivity as other components, which inevitably encounters problems in the connection between aluminum alloys, aluminum alloys and steel alloys, and aluminum alloys and copper alloys. Due to the inherent characteristics of aluminum alloys, its welding performance is poor, especially when welding with dissimilar materials, it is difficult to obtain reliable performance, which largely restricts its further development and application.

[0003] Traditional resistance spot welding, laser welding, melting welding, and stir friction welding are prone to problems such as holes and thermal cracks in spot welding of different types of aluminum alloys. Spot welding between aluminum alloys and copper alloys is prone to problems such as thermal cracks and brittle intermetallic compounds on the bonding surface. Spot welding between aluminum alloys and steel alloys is prone to welding failures and brittle intermetallic compounds on the bonding surface. These problems are currently difficult to solve. Although bolting and riveting can avoid the problems of welding, they bring more weight, obvious protrusions on the surface, and short fatigue life. For some structural parts, this greatly limits its application. Therefore, it is particularly important to achieve a high-quality spot welding between aluminum alloys and dissimilar materials while keeping the spot welding surface smooth and level without protrusions. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a method for spot welding an aluminum alloy and dissimilar materials, which solves the problems in the prior art.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A method for spot welding an aluminum alloy and a dissimilar material comprises the following steps:

[0007] The first prefabricated hole of the upper substrate and the second prefabricated hole of the lower substrate are aligned vertically, and a friction sleeve is inserted into the first prefabricated hole, and the lower end surface of the friction sleeve contacts the upper surface of the lower substrate; a sealing push rod is provided in the friction sleeve, and an extrusion ring is provided on the outer side of the friction sleeve, and under the action of external force, the lower end surface of the extrusion ring can be closely attached to the upper end surface of the upper substrate; an expansion plug is provided in the second prefabricated hole, and a spot welding filler is provided on the upper end of the expansion plug, and an undercut protrusion is provided on the top of the expansion plug;

[0008] The sealing push rod and the friction sleeve are controlled to rotate, and the sealing push rod is pushed downward at the same time to drive the spot welding filler to rotate and generate heat by friction between the expansion plug, so that the spot welding filler softens and expands outwards, and the outer cylindrical surface of the friction sleeve and the first prefabricated hole generate heat and soften by friction;

[0009] The friction sleeve is controlled to move upward, and the spot welding filler softens and flows outward to squeeze the undercut protrusion to mechanically lock it with the lower substrate. The spot welding filler gradually flows to the inner surface of the first prefabricated hole and welds with it until the lower end surface of the sealing push rod and the lower end surface of the friction sleeve reach the upper surface of the upper substrate.

[0010] Furthermore, the upper substrate is made of aluminum alloy, and the softening temperature of the lower substrate is not less than the softening temperature of the upper substrate.

[0011] Furthermore, the sealing push rod, the friction sleeve and the extrusion ring are coaxially clearance-matched, and the clearance is between 0.015 mm and 0.03 mm.

[0012] Furthermore, the diameter d of the sealing push rod 3 and the outer diameter of the friction sleeve d 4 The ratio is between 1.1 and 1.2.

[0013] Furthermore, the diameter of the first prefabricated hole is d 1 , d 1 With d 4 The ratio is between 0.95 and 0.99.

[0014] Furthermore, the second prefabricated hole is a tapered hole with a small top and a large bottom, and a minimum diameter of d 2 , the minimum diameter of the second prefabricated hole d 2 Smaller than the diameter d of the first prefabricated hole (41) 1 .

[0015] Furthermore, the diameter of the undercut protrusion is the same as the minimum diameter of the second prefabricated hole, both of which are d 2 .

[0016] Furthermore, the expansion plug is tapered as a whole, and the tapered surface of the expansion plug is provided with coaxial concave rings, the number of which is 2 to 6.

[0017] Furthermore, a conical groove is formed at the upper end of the expansion plug, and a conical surface matching the conical groove is formed at the lower end of the spot welding filler.

[0018] Furthermore, the softening temperature of the expansion plug is not less than the softening temperature of the upper substrate; and the material of the spot welding filler is the same as that of the upper substrate.

[0019] Beneficial effects of the present invention:

[0020] 1. The present invention achieves that there is no melting and excessive material exchange between the materials to be spot-welded by the cooperation of the expansion plug and the spot welding filler, and no obvious material flow and high temperature occur at the contact interface between the two, which can effectively avoid the generation of brittle intermetallic compounds due to different material properties. The spot welding filler produces high-quality solid-phase welding with the upper substrate under high temperature and extrusion flow. At the same time, it is mechanically locked and welded with the expansion plug through the undercut protrusion. The expansion plug is mechanically locked with the lower substrate through conical cooperation. In this form, high-quality spot welding of the upper substrate and the lower substrate is completed. When subjected to shear load, the bearing surface of the spot welding area is located at the expansion plug, which can provide higher shear strength.

[0021] 2. The present invention can realize spot welding of aluminum alloy and dissimilar materials with large differences and difficult to form metallurgical bonding. When the upper substrate is aluminum alloy, spot welding can be realized without considering what kind of dissimilar material the lower substrate is, which is impossible to achieve with existing spot welding processes.

[0022] 3. The surface of the spot welding area of ​​the present invention is flat and smooth, without protrusions and depressions, and no subsequent processing is required; when spot welding is completed, the expansion plug is flush with the lower surface of the lower substrate, and the spot welding filler is flush with the upper surface of the upper substrate. At the same time, the spot welding filler becomes flat and smooth under the high-speed rotation and extrusion of the sealing push rod and the friction sleeve, which is difficult to achieve with the current existing spot welding and connection processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 It is a schematic flow chart of the electric welding implementation method of the present invention;

[0025] Figure 2 It is a schematic diagram of the positions of the components after the electric welding of the present invention is completed;

[0026] Figure 3 It is a schematic diagram of the relative positions of the sealing push rod, the friction sleeve and the extrusion ring of the present invention;

[0027] Figure 4 is a schematic diagram of the upper substrate and its preformed holes of the present invention;

[0028] Figure 5 is a schematic diagram of the lower substrate and its preformed holes of the present invention;

[0029] Figure 6 is an expansion plug of the present invention and a schematic diagram of its structure;

[0030] Figure 7 It is a spot welding filler of the present invention and a schematic diagram of its structure;

[0031] In the figure: 1-sealing push rod, 2-friction sleeve, 3-extrusion ring, 4-upper substrate, 5-lower substrate, 6-expansion plug, 7-spot welding filler, 41-first prefabricated hole, 51-second prefabricated hole, 61-undercut protrusion, 62-coaxial concave ring, 63-conical groove. DETAILED DESCRIPTION

[0032] 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.

[0033] like Figure 1 As shown, a method for spot welding an aluminum alloy and a dissimilar material comprises the following steps:

[0034] S1, spot welding component assembly;

[0035] like Figure 2 As shown, the first prefabricated hole 41 of the upper substrate 4 and the second prefabricated hole 51 of the lower substrate 5 are aligned vertically, and the friction sleeve 2 is inserted into the first prefabricated hole 41, and the lower end surface of the friction sleeve 2 contacts the upper surface of the lower substrate 5; a sealing push rod 1 is provided in the friction sleeve 2, and an extrusion ring 3 is provided on the outer side of the friction sleeve 2. Under the action of external force, the lower end surface of the extrusion ring 3 can be closely attached to the upper end surface of the upper substrate 4; an expansion plug 6 is provided in the second prefabricated hole 51, and a conical groove 63 is provided at the upper end of the expansion plug 6, and a spot welding filler 7 is placed in the conical groove 63, and an undercut protrusion 61 is provided on the top of the expansion plug 6;

[0036] In this embodiment, the upper substrate 4 is made of aluminum alloy, and the lower substrate 5 is made of steel alloy. In other embodiments, the lower substrate 5 can also be made of high entropy alloy, tungsten alloy, titanium alloy, copper alloy, magnesium alloy, aluminum alloy or zinc alloy, as long as the softening temperature of the lower substrate 5 is not less than the softening temperature of the upper substrate 4.

[0037] like Figure 3 As shown, the sealing push rod 1, the friction sleeve 2, and the extrusion ring 3 are coaxially matched, and the matching clearance is between 0.015mm and 0.03mm. The sealing push rod 1 and the friction sleeve 2 can perform independent rotational and axial movements. In order to ensure sufficient strength and better spot welding effect, the diameter d of the sealing push rod 1 is 3 and the outer diameter of the friction sleeve d4 The ratio is strictly controlled between 1.1 and 1.2. The extrusion ring 3 is always coaxially installed on the outside of the friction sleeve 2 and is pressed against the upper plane of the upper substrate 4 by external force.

[0038] like Figure 4 As shown, the diameter of the first prefabricated hole 41 of the upper substrate 4 is d 1 , the diameter of the first prefabricated hole d 1 Smaller than the outer diameter d of the friction sleeve 2 4 , the ratio between the two is between 0.95 and 0.99;

[0039] like Figure 5 As shown, the second prefabricated hole 51 of the lower substrate 5 is a tapered hole with a small top and a large bottom, a taper of Z, and a minimum diameter of d 2 The minimum diameter d of the second preformed hole 51 2 Smaller than the diameter d of the first prefabricated hole 41 1 .

[0040] like Figure 6 As shown, the expansion plug 6 is tapered as a whole, and the tapered end surface (top) with a smaller diameter is provided with an undercut protrusion 61 which is easily deformed outwards and has a diameter of d 2 ; Taper Z of expansion plug 6 1 Matching with the taper Z of the second prefabricated hole 51; the material of the expansion plug 6 can be selected according to demand, including but not limited to various types of high entropy alloys, steel alloys, tungsten alloys, titanium alloys, copper alloys, magnesium alloys, aluminum alloys, zinc alloys and other materials, as long as its softening temperature is not less than the softening temperature of the upper substrate 4.

[0041] like Figure 7 As shown, the lower end of the spot welding filler 7 is provided with a conical surface, and can cooperate with the conical groove 63, and the taper of both is Z 2 The material of the spot welding filler 7 can be selected according to the needs, including but not limited to any type of material of the same alloy as the upper substrate 4, and the material that is closer to or the same as the upper substrate 4 is preferably selected.

[0042] The diameter of the undercut protrusion 61 is equal to the minimum diameter of the second prefabricated hole 51, which is d 2 The conical surface is provided with a coaxial concave ring 62, the number of which is generally set to 2 to 6 according to the thickness of the lower substrate 5. Its function is to improve the bonding strength between the undercut protrusion 6 and the lower substrate 5. When spot welding is performed, the coaxial concave ring 62 can produce a slight deformation to increase the taper Z 1 The matching degree with taper Z ensures the final spot welding quality. At the same time, the taper Z is reduced. 1 Reduce the difficulty of processing and manufacturing and save costs.

[0043] In some other embodiments, in order to ensure a higher quality fit, the taper Z 1 It can be slightly smaller than the taper Z.

[0044] S2, the sealing push rod 1 and the friction sleeve 2 are rotated at high speed by external force, and the sealing push rod 1 is pushed downward at the same time to drive the spot welding filler 7 to rotate and generate friction heat with the expansion plug 6. At this time, the spot welding filler 7 is gradually softened and expands outward under the pressure of the sealing push rod 1, and the outer cylindrical surface of the friction sleeve 2 and the first prefabricated hole 41 of the upper substrate 4 generate friction heat to soften the first prefabricated hole;

[0045] S3, control the friction sleeve 2 to move upward, the spot welding filler 7 is fully softened and flows outward to squeeze the undercut protrusion 61 of the expansion sleeve 6 to mechanically lock it with the lower substrate 5, and the spot welding filler 7 gradually flows to the inner surface of the first prefabricated hole 41 of the upper substrate 4 and welds it; until the lower end surface of the sealing push rod 1 and the lower end surface of the friction sleeve 2 reach the upper surface of the upper substrate 4, the spot welding is completed.

[0046] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0047] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A method for spot welding of aluminum alloy and dissimilar materials, characterized in that: The following steps are involved: The first prefabricated hole (41) of the upper substrate (4) and the second prefabricated hole (51) of the lower substrate (5) are aligned vertically, and a friction sleeve (2) is inserted into the first prefabricated hole (41), so that the lower end surface of the friction sleeve (2) contacts the upper surface of the lower substrate (5); a sealing push rod (1) is arranged in the friction sleeve (2), and an extrusion ring (3) is arranged on the outer side of the friction sleeve (1), and under the action of external force, the lower end surface of the extrusion ring (3) can be closely attached to the upper end surface of the upper substrate (4); an expansion plug (6) is arranged in the second prefabricated hole (51), and a spot welding filler (7) is arranged at the upper end of the expansion plug (6), and an undercut protrusion (61) is arranged at the top of the expansion plug (6); The sealing push rod (1) and the friction sleeve (2) are controlled to rotate, and the sealing push rod (1) is pushed downward to drive the spot welding filler (7) to rotate and generate heat by friction with the expansion plug (6), so that the spot welding filler (7) softens and expands outwards, and the outer cylindrical surface of the friction sleeve (2) and the first prefabricated hole (41) generate heat and soften by friction; The friction sleeve (2) is controlled to move upward, the spot welding filler (7) softens and flows outward to squeeze the undercut protrusion (61) so that it is mechanically locked with the lower substrate (5), and the spot welding filler (7) gradually flows to the inner surface of the first prefabricated hole (41) and welds with it until the lower end surface of the sealing push rod (1) and the lower end surface of the friction sleeve (2) both reach the upper surface of the upper substrate (4).

2. The method for spot welding of aluminum alloy and dissimilar materials according to claim 1, characterized in that: The upper substrate (4) is made of aluminum alloy, and the softening temperature of the lower substrate (5) is not less than the softening temperature of the upper substrate (4).

3. The spot welding method for aluminum alloy and dissimilar materials according to claim 1, characterized in that: The sealing push rod (1), the friction sleeve (2) and the extrusion ring (3) are coaxially clearance-matched, and the clearance is between 0.015 mm and 0.03 mm.

4. The spot welding method for aluminum alloy and dissimilar materials according to claim 1, characterized in that: The ratio of the diameter d3 of the sealing push rod (1) to the outer diameter d4 of the friction sleeve (2) is between 1.1 and 1.

2.

5. The spot welding method for aluminum alloy and dissimilar materials according to claim 4, characterized in that: The diameter of the first prefabricated hole (41) is d1, and the ratio of d1 to d4 is between 0.95 and 0.

99.

6. The method for spot welding of aluminum alloy and dissimilar materials according to claim 5, characterized in that: The second preformed hole (51) is a tapered hole that is smaller at the top and larger at the bottom, and has a minimum diameter of d2. The minimum diameter d2 of the second preformed hole (51) is smaller than the diameter d1 of the first preformed hole (41).

7. The method for spot welding of aluminum alloy and dissimilar materials according to claim 6, characterized in that: The diameter of the undercut protrusion (61) is the same as the minimum diameter of the second prefabricated hole (51), both being d2.

8. The method for spot welding of aluminum alloy and dissimilar materials according to claim 6, characterized in that: The expansion plug (6) is in a cone shape as a whole, and the cone surface of the expansion plug (6) is provided with coaxial concave rings (62), the number of which is 2 to 6.

9. The method for spot welding of aluminum alloy and dissimilar materials according to claim 1, characterized in that: The upper end of the expansion plug (6) is provided with a conical groove (63), and the lower end of the spot welding filler (7) is provided with a conical surface matching the conical groove (63).

10. The method for spot welding of aluminum alloy and dissimilar materials according to claim 1, characterized in that: The softening temperature of the expansion plug (6) is not less than the softening temperature of the upper substrate (4); and the material of the spot welding filler (7) is the same as that of the upper substrate (4).

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