CN109794670B - Dissimilar metal material resistance rivet welding system of light alloy and steel and welding method thereof - Google Patents

Abstract

A resistance riveting welding system for dissimilar metal materials of light alloy and steel and a welding method thereof, wherein semi-hollow steel nails with customizable composition are used to directly weld dissimilar materials without pre-punching, so that light alloy plates to be connected, The semi-hollow steel nail and the steel plate to be connected are partially melted to form a weld nugget of aluminum-steel mixture to obtain a joint of dissimilar materials; the rivet adopts a semi-hollow structure to accommodate part of the light alloy plate to be connected, and a smaller rivet design can be used; The taper-angle steel nails directly pierce the light alloy plate to be connected, eliminating the existing hole-making process; through the local melting of the light alloy plate to be connected, the semi-hollow steel nail and the steel plate to be connected, a high-strength aluminum-steel mixture weld nugget is formed to improve the efficiency of the welding process. Joint performance: The joint performance is improved by adjusting the ratio of each element in the weld nugget by the crushing length of the nail legs and the alloying elements in the rivet cavity. The invention simplifies the production process, improves the production efficiency, reduces the cost and improves the joint performance.

Description

Dissimilar metal material resistance riveting welding system and welding method of light alloy and steel

technical field

The invention relates to a technology in the field of connection of dissimilar metal materials, in particular to a resistance riveting welding system for dissimilar metal materials of light alloy and steel and a welding method thereof.

Background technique

Lightweight car body is an effective means of energy saving and emission reduction in the modern automobile industry. With the attention of major automobile companies, light alloys and ultra-high-strength steels are widely used in car body manufacturing. As a traditional point connection method for body assembly, resistance spot welding is applied to traditional steel body welding due to its advantages of high joint strength, low energy consumption and fast cycle time. However, the application of light alloy materials such as aluminum and magnesium alloys poses great challenges to the traditional point joining technology. Due to the large difference in thermophysical properties between light alloys and steel, it is inevitable to form hard and brittle intermetallic compounds during fusion welding. , which makes it difficult to realize the effective connection of dissimilar metal materials by the traditional resistance spot welding process. The above problems make the self-piercing riveting based on the principle of cold forming the most important connection technology for the current hybrid car body. However, limited by the hardness of the rivet and the tonnage of the riveting equipment, when some high-strength and high-hardness materials such as advanced high-strength steel or ultra-high-strength steel are connected, the rivet legs will be severely thickened during the self-piercing riveting process, and effective mechanical interaction cannot be obtained. Lock. The existing resistance unit welding technology combines the characteristics of riveting and spot welding to convert the problem of dissimilar metal connection into the same metal welding problem, and can realize the reliable connection of light metal and ultra-high-strength steel. However, this method requires an additional blanking process, and the process is cumbersome, resulting in increased process cost and reduced production efficiency. Moreover, it is difficult to accurately place the nails in the punching holes during welding, and the quality controllability is poor.

SUMMARY OF THE INVENTION

Aiming at the above-mentioned deficiencies in the prior art, the present invention proposes a resistance riveting system and a welding method for dissimilar metal materials of light alloy and steel, using semi-hollow steel nails with customizable compositions to directly The dissimilar materials are welded, so that the light alloy plate to be connected, the semi-hollow steel nail and the steel plate to be connected are melted in the open cavity to form a metal mixture weld nugget, and a high-strength dissimilar material connection joint is obtained.

The present invention is achieved through the following technical solutions:

The invention relates to a resistance riveting welding system for dissimilar metal materials of light alloy and steel, comprising from top to bottom: an upper electrode, a semi-hollow steel nail, a light alloy plate to be connected, a steel plate to be connected and a lower electrode.

The light alloy plates to be connected are at least one layer, and are arranged adjacently when multiple layers of light alloy plates to be connected are used.

The steel plate to be connected can only be one layer, and must be arranged on the lower electrode side. If it is multi-layer, the intermediate layer must have process holes.

The semi-hollow steel nail includes: a nail cap, a nail leg and a taper angle connected in sequence, wherein: the nail cap and the nail leg form an open cavity, and the height of the open cavity is greater than or equal to the thickness of the light alloy plate to be connected .

The top surface of the nail cap is a circular plane, and the bottom surface is provided with grooves or inclinations distributed along the circumferential direction, and the cross-section of the groove is an arc or a rectangle.

said

The length of the nail legs is 1.2-2.5 times the total thickness of the light alloy sheet to be connected.

The inner side of the open inner cavity can be modified by adding trace alloying elements to the joint.

The taper angle can pierce the light alloy plate to be connected and make close contact with the steel plate to be connected under the action of current and electrode pressure.

The present invention relates to the resistance riveting welding method of the above system, comprising the following steps:

Step 1) Preloading stage: place the semi-hollow steel nail on the light alloy side of the combination of the plates to be connected, and apply pre-pressure through the upper electrode and the lower electrode to make the semi-hollow steel nail, the light alloy plate to be connected, and the steel plate to be connected between the contact and form a conductive path;

Step 2) Piercing stage: applying welding current to soften the light alloy plate to be connected, the semi-hollow steel nail pierces the light alloy plate to be connected under the action of electrode pressure, and is in close contact with the steel plate to be connected;

Step 3) Welding stage: changing the electrode pressure and current to generate resistance heat for a certain duration, so that the steel plate to be connected, the lower end of the steel nail and the light alloy plate material retained in the cavity are melted in the open cavity of the steel nail;

Step 4) Cooling stage: the holding pressure is applied through the electrode cap, and the nugget solidifies under the action of the water-cooled copper electrode to form a riveted joint.

The said close contact with the steel plate to be connected is determined by any one of the following operations or a combination thereof:

a) The displacement of the steel nail is 1.0 to 1.2 times the thickness of the light alloy plate to be connected;

b) The time of the puncture phase is set empirically.

For the cooling phase, the starting time of the cooling phase is determined by adopting any one of the following operations or a combination thereof:

a) The bottom surface of the nail cap is in contact with the light alloy plate material to be connected;

b) Set the time of the welding stage based on experience.

The light alloy plate material retained in the cavity refers to the light alloy plate material to be connected that is retained in the cavity of the semi-hollow steel nail during the puncturing stage.

technical effect

Compared with the prior art, the rivet of the present invention adopts a semi-hollow structure, which can accommodate part of the light alloy plate to be connected, so a smaller rivet design can be adopted; the steel nail with a tapered angle is used to directly pierce the light alloy plate to be connected, Eliminates the hole-making process of traditional technology; through the local melting of the light alloy plate to be connected, the semi-hollow steel nail and the steel plate to be connected, a high-strength aluminum-steel mixture weld nugget is formed to improve the joint performance; at the same time, the length of the nail leg can be crushed And the alloying elements inside the rivet cavity regulate the proportion of each element of the weld nugget, thereby improving the joint performance. In general, the present invention simplifies the production process, improves the production efficiency, reduces the cost, and improves the joint performance.

Description of drawings

Fig. 1 is the semi-hollow steel nail structure schematic diagram of the present invention;

In the figure: a and b are the structural schematic diagrams of the semi-hollow steel nail; c is the cross-sectional view of the semi-hollow steel nail;

Figure 2 is a schematic diagram of the welding process;

In the figure: a is a schematic diagram of the pre-pressing stage; b and c are schematic diagrams of the intermediate process of puncturing and the end of puncturing; d and e are schematic diagrams of the welding stage; f is a schematic diagram of the cooling process; Alloy plate 108, steel plate to be connected 109, semi-hollow steel nail 110, light alloy plate to be connected 111 and weld nugget 112 retained in the cavity;

Fig. 3 is the schematic diagram of electrode pressure and welding current changing with time in welding process;

Fig. 4 is the schematic diagram of embodiment 1 weld nugget;

5 is a schematic cross-sectional view of the semi-hollow steel nail in Example 2;

Fig. 6 is the schematic diagram of embodiment 2 weld nugget;

FIG. 7 is a schematic cross-sectional view of the semi-hollow steel nail in Example 3. FIG.

Detailed ways

Example 1

As shown in FIG. 1 , the semi-hollow steel nail 110 used in this embodiment includes a nail cap 101 , a nail leg 102 and a taper angle 103 connected in sequence, wherein the nail cap 101 and the nail leg 102 form an open cavity 105 .

The diameter of the nail cap 101 is 10mm, the height is 2mm, the inclination angle of the bottom surface 104 is 15°, and the radius of the chamfer is 0.8mm.

The shape of the cavity 105 is a cylinder, the diameter of the cylinder is 3.4mm, and the height is 2.2mm.

The outer diameter of the nail legs 102 is 5.3 mm and the height is 2.9 mm.

The cross section of the taper angle 103 is an equilateral triangle.

The light alloy plates 108 to be connected in this embodiment are AA6061-T6 aluminum alloy plates with a thickness of 1 mm, and the steel plates 109 to be connected are PHS ultra-high strength steels with a thickness of 1.55 mm.

As shown in FIG. 2 , this embodiment realizes the connection between the light alloy plate 108 to be connected and the steel plate 109 to be connected through the following four stages:

Step 1) Preloading stage: place the semi-hollow steel nail 110 on the light alloy plate 108 to be connected, and apply pre-pressure through the upper electrode 106 and the lower electrode 107 to make the semi-hollow steel nail 110, the light alloy plate 108 to be connected, and the to-be-connected Contact between the steel plates 109 forms a conductive path;

Step 2) Piercing stage: applying welding current to soften the light alloy plates 108 to be connected, the semi-hollow steel nails 110 pierce the light alloy plates 108 to be connected under the action of electrode pressure, and are in close contact with the steel plates 109 to be connected;

Step 3) Welding stage: change the electrode pressure and current, and generate resistance heat for a certain duration, so as to realize the open end of the steel nail 109 to be connected, the lower end of the semi-hollow steel nail 110 and the light alloy plate material 111 retained in the cavity. Melting in cavity 105;

Step 4) Cooling stage: the holding pressure is applied through the electrode cap, and the nugget 112 solidifies under the action of the water-cooled copper electrode to form a riveted joint.

In this embodiment, the pre-pressure is 2kN, the piercing current is 10kA, the time is 30ms, the welding current is 8kA, the time is 200ms, and the welding force is still 2kN.

In this embodiment, the determination method of the close contact between the semi-hollow steel nail 110 and the steel plate 109 to be connected is that the displacement of the semi-hollow steel nail exceeds 1.1 mm.

The start of the cooling phase is determined by the bottom surface of the nail cap being in contact with the light alloy plate material to be connected. .

As shown in FIG. 4 , the aluminum-steel mixture weld nugget formed in this example. The average tensile shear strength of the joint is 4094.7kN, and the fracture mode is pull-out fracture.

Example 2

As shown in FIG. 5 , the semi-hollow steel nail 110 used in this embodiment is compared with Embodiment 1: the inclination angle of the bottom surface 104 of the nail cap 101 is 5°, the height of the cavity 105 is 2.8 mm, and the height of the nail legs 102 is 1.8 mm. mm, the section of the taper angle 103 is a right triangle.

The light alloy plate 108 to be connected and the steel plate 109 to be connected used in this embodiment are the same as those in the first embodiment.

As shown in FIG. 2 , this embodiment realizes the connection between the light alloy plate 108 to be connected and the steel plate 109 to be connected through the following four stages:

Step 1) Preloading stage: place the semi-hollow steel nail 110 on the light alloy plate 108 to be connected, and apply pre-pressure through the upper electrode 106 and the lower electrode 107 to make the semi-hollow steel nail 110, the light alloy plate 108 to be connected, and the to-be-connected Contact between the steel plates 109 forms a conductive path;

Step 2) Piercing stage: applying welding current to soften the light alloy plates 108 to be connected, the semi-hollow steel nails 110 pierce the light alloy plates 108 to be connected under the action of electrode pressure, and are in close contact with the steel plates 109 to be connected;

Step 3) Welding stage: change the electrode pressure and current, and generate resistance heat for a certain duration, so as to realize the open end of the steel nail 109 to be connected, the lower end of the semi-hollow steel nail 110 and the light alloy plate material 111 retained in the cavity. Melting in cavity 105;

Step 4) Cooling stage: the holding pressure is applied through the electrode cap, and the nugget 112 solidifies under the action of the water-cooled copper electrode to form a riveted joint. In this embodiment, the pre-pressure is 3kN, the piercing current is 10kA, the time is 30ms, the welding current is 8kA, the time is 300ms, and the welding force is 2kN.

In this embodiment, the determination method of the close contact between the semi-hollow steel nail 110 and the steel plate 109 to be connected is that the displacement of the semi-hollow steel nail exceeds 1.1 mm.

The start of the cooling phase is determined by the bottom surface of the nail cap being in contact with the light alloy plate material to be connected.

As shown in FIG. 6 , for the aluminum-steel mixture weld nugget formed in this example, the average tensile shear strength of the joint is 3090.4 kN, and the fracture modes are all pull-out fractures.

Example 3

As shown in FIG. 7 , the semi-hollow steel nail 110 used in this embodiment includes: a nail cap 101 , a nail leg 102 and a taper angle 103 connected in sequence, wherein the nail cap 101 and the nail leg 102 form an open cavity 105 .

The diameter of the upper surface of the nail cap 101 is 7.8 mm, the diameter of the lower surface is 10.8 mm, and the height is 2 mm. The radius of the arc groove on the bottom surface 104 of the nail cap 101 is 0.8 mm.

The shape of the cavity 105 is a truncated cone, the sectional inclination angle of the truncated cone is 69°, the diameter of the lower end is 5mm, and the height is 2.2mm.

The cross-section of the taper angle 103 is an isosceles triangle with an apex of 140°.

In the present embodiment, the determination method of the close contact between the semi-hollow steel nail 110 and the steel plate 109 to be connected is based on experience, and the time of the puncturing stage is set to be 30 ms.

The way of judging the completion of the welding stage is to set the welding stage time as 200ms according to experience.

Other implementations of this embodiment are the same as those of Embodiment 1.

The aluminum-steel mixture weld nugget formed in this example has an average tensile shear strength of 4758.9 kN, and the fracture mode is pull-out fracture.

Compared with the prior art, the present invention has the advantages that: the bottom surface of the nail cap is designed as a groove or an inclined structure, and the extruded metal liquid can be contained in the nail cap during welding, so as to ensure the appearance of the welded joint; It is designed as a semi-hollow structure with a certain wall thickness, which can accommodate the excess light metal at the lower end of the leg to prevent molten metal from splashing and reduce the deformation of the joint. The flexibility of the process is increased; the light alloy plate to be connected is penetrated by direct welding, the process of making holes is omitted by the simple welding process, and the process time is shorter than 1s; the tensile shear strength can reach 4758.9kN, compared with the same conditions The tensile shear strength of the lower resistance unit welded joint 3200.6kN is increased by about 48%.

The above-mentioned specific implementation can be partially adjusted by those skilled in the art in different ways without departing from the principle and purpose of the present invention. The protection scope of the present invention is based on the claims and is not limited by the above-mentioned specific implementation. Each implementation within the scope is bound by the present invention.

Claims (2)

1. A light alloy-steel resistance riveting method for dissimilar metal materials, characterized in that the dissimilar materials are directly welded by using semi-hollow steel nails with customizable compositions without pre-punching, so that the light alloy plates to be connected are welded. , The semi-hollow steel nail and the steel plate to be connected are locally melted to form a metal mixture weld nugget to obtain a high-strength dissimilar material connection joint; The semi-hollow steel nail includes: a nail cap, a nail leg and a taper angle connected in sequence, wherein: the nail cap and the nail leg form an open cavity, and the height of the open cavity is greater than or equal to the thickness of the light alloy plate to be connected ; The length of the nail legs is 1.2 to 2.5 times the total thickness of the light alloy sheet to be connected; The riveting welding method is realized by a resistance riveting welding system of dissimilar metal materials, the system includes from top to bottom: an upper electrode, a semi-hollow steel nail, a light alloy plate to be connected, a steel plate to be connected, and a lower electrode; The dissimilar material connection joints are connected by the following methods: Step 1) Preloading stage: place the semi-hollow steel nail on the light alloy side of the combination of the plates to be connected, and apply pre-pressure through the upper electrode and the lower electrode to make the semi-hollow steel nail, the light alloy plate to be connected, and the steel plate to be connected between the contact and form a conductive path; Step 2) Piercing stage: applying welding current to soften the light alloy plate to be connected, the semi-hollow steel nail pierces the light alloy plate to be connected under the action of electrode pressure, and is in close contact with the steel plate to be connected; Step 3) Welding stage: changing the electrode pressure and current to generate resistance heat for a certain duration, so that the steel plate to be connected, the lower end of the steel nail and the light alloy plate material retained in the cavity are melted in the open cavity of the steel nail; Step 4) Cooling stage: the holding pressure is applied through the electrode cap, and the nugget solidifies under the action of the water-cooled copper electrode to form a riveted joint. 2. The electric resistance riveting welding method according to claim 1, characterized in that, the said steel plate is in close contact with the steel plate to be connected, and its contact determination method adopts any one of the following operations or a combination thereof to determine to prevent the steel nail from crushing : a) The displacement of the steel nail is 1.0 to 1.2 times the thickness of the light alloy plate to be connected; b) Set the time of the piercing phase according to experience; The cooling stage start determination method is determined by any one of the following operations or a combination thereof, so as to prevent excessive softening and thinning of the nail cap to be connected to the light alloy plate: a) The bottom surface of the nail cap is in contact with the light alloy plate material to be connected; b) Set the time of the welding stage based on experience.

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