TWI706820B - Spot welding electrode and spot welding method for aluminum alloy - Google Patents

Abstract

A spot welding electrode and a spot welding method for aluminum alloy are provided. The spot welding electrode includes a metal body having a welding end formed as a hemispherical shape; and a metal plating film covering the welding end of the metal body, wherein material of the metal plating film is different from that of the metal body, and the material of the metal plating film is nickel, cobalt or nickel cobalt alloy. The spot welding electrode is applied to perform the spot welding method for aluminum alloy. Thus, the strength of a welded portion of the aluminum alloy can be improved.

Description

Spot welding electrode parts and aluminum alloy spot welding method

The invention relates to a metal welding technology, in particular to a spot welding electrode piece and an aluminum alloy spot welding method that can be used for welding aluminum alloys.

The conventional automobile manufacturing process uses a large number of resistance spot welding technology, which has excellent reliability in the joint of steel structure car body, but resistance spot welding cannot be applied to aluminum alloy materials because of the low melting point and high thermal resistance of aluminum alloy. And high electrical impedance.

For example, if a conventional welding electrode (such as a copper electrode tip) is used to weld aluminum alloy, the part where the electrode contacts the aluminum alloy (such as the tip) will form a sticking phenomenon and reduce the life; in addition, the aluminum oxide on the surface of the aluminum alloy The layer will reduce the spot welding strength and fatigue strength. Therefore, the conventional aluminum alloy joining method is riveting or gluing.

In view of the above-mentioned sticking problem, which reduces the service life, although prior art attempts to propose solutions, such as: coating on aluminum alloy plates to reduce the degree of electrode sticking during spot welding, the workpiece to be welded (ie, aluminum alloy plate ) The surface degreasing operation is required before the coating process. If the size of the workpiece is different, the electroplating equipment needs to adopt different specifications.

In view of this, it is necessary to provide a solution that is different from the past to solve the problems of conventional technologies.

One object of the present invention is to provide a spot welding electrode assembly which uses a metal material with high electrical resistance as a coating to increase the welding temperature to remove oxidation and grease on the surface of the aluminum alloy, thereby increasing the tensile strength of the aluminum alloy welding part.

Another object of the present invention is to provide an aluminum alloy spot welding method, which uses spot welding electrode parts plated with a special metal with high electrical resistance for welding, so as to increase the welding temperature. In addition to oxidation and grease on the surface of the aluminum alloy, the tensile strength of the aluminum alloy welding part is improved.

An aspect of the present invention provides a spot welding electrode assembly, comprising: a metal body having a welding end, the welding end forming a hemispherical shape; and a metal coating covering the welding end of the metal body, the metal coating The material of is different from the material of the metal body, and the material of the metal coating is nickel, cobalt or nickel-cobalt alloy.

In an embodiment of the present invention, a center of the welding end portion can diffuse outward to form a contact plane.

In an embodiment of the present invention, a diameter of the contact plane may range from 4 to 8 mm.

In an embodiment of the present invention, the material of the metal body may be copper, chromium, zirconium or alloys thereof.

In an embodiment of the present invention, a thickness of the metal coating film may range from 10 to 15 microns.

Another aspect of the present invention provides an aluminum alloy spot welding method, which includes the steps of preparing two spot welding electrode parts, each spot welding electrode part includes a metal body and a metal coating, the metal body has a welding end, the The welding end forms a hemispherical shape, and the metal plating film covers the welding end of the metal body. The material of the metal plating film is different from that of the metal body. The material of the metal plating film is nickel, cobalt or nickel-cobalt alloy; The alloy plates overlap to form a to-be-welded area, and the to-be-welded area is placed between the two spot welding electrode parts; the metal coating of the two spot welding electrode parts abuts against the two aluminum alloy plates in the to-be-welded area Relative to two points; pressurize the two spot welding electrode components on the two aluminum alloy plates; energize the two spot welding electrode components until a weld nugget is generated on the two aluminum alloy plates to form a joint; and The spot welding electrode member is moved away from the joining member.

In an embodiment of the present invention, a pressure range for the two spot welding electrode components to pressurize the two aluminum alloy plates may be 200 to 350 kgf.

In an embodiment of the present invention, a current range for energizing the two spot welding electrode components may be between 5 and 25 kA.

In an embodiment of the present invention, the two-spot welding electrode assembly can perform a multi-stage energization process with different electrical parameters.

In an embodiment of the present invention, the center of one of the welding ends can spread outward A contact plane is formed.

In an embodiment of the present invention, a diameter of the contact plane may range from 4 to 8 mm.

In an embodiment of the present invention, the material of the metal body may be copper, chromium, zirconium or alloys thereof.

In an embodiment of the present invention, a thickness of the metal coating film may range from 10 to 15 microns.

The spot welding electrode part and the aluminum alloy spot welding method of the present invention coat the surface of the spot welding electrode part with a specific metal with high electrical resistance (such as nickel, cobalt, or nickel-cobalt alloy), which can improve spot welding The electrical resistance of the electrode part. During the spot welding process, the spot welding electrode part and the specific metal first generate resistance heat, which removes the oxide layer and grease on the surface of the aluminum alloy, and subsequently generates resistance between the aluminum alloy plates to be welded Heat causes the high-temperature melting and growth of weld nuggets between the aluminum alloy plates, and the contact surface between the spot welding electrode and the aluminum alloy continues to generate high temperature to provide additional energy to slow down the heat dissipation rate of the spot welding process, without the need for high welding Current and large-size spot welding electrode parts can completely shape the weld nugget, thereby obtaining metal joints with small welding diameters but high tensile strength, which is beneficial to improve the quality, efficiency and cost of existing metal joint processing.

1‧‧‧Metal body

11‧‧‧Welding end

12‧‧‧Contact plane

2‧‧‧Metal coating

C‧‧‧Nugget

E1‧‧‧Spot welding electrode parts

E2‧‧‧Spot welding electrode parts

J‧‧‧Joint

P1‧‧‧Aluminum alloy plate

P2‧‧‧Aluminum alloy plate

S1‧‧‧Welding preparation steps

S2‧‧‧Stacking steps

S3‧‧‧Abutment Steps

S4‧‧‧Pressure step

S5‧‧‧Power-on steps

S6‧‧‧Welding step

V1‧‧‧Power

V2‧‧‧Power

W‧‧‧Welding area

Figure 1: A three-dimensional schematic diagram of a spot welding electrode assembly of an embodiment of the present invention from an oblique upper perspective.

Figure 2: A schematic side sectional view of a spot welding electrode assembly according to an embodiment of the present invention.

Figure 3: A schematic flow chart of an aluminum alloy spot welding method according to an embodiment of the present invention.

Figure 4A: A schematic diagram of the welding preparation steps of an aluminum alloy spot welding method according to an embodiment of the present invention.

Figure 4B: A schematic diagram of the stacking steps of an aluminum alloy spot welding method according to an embodiment of the present invention.

Fig. 4C: A schematic diagram of abutting steps of an aluminum alloy spot welding method according to an embodiment of the present invention.

Fig. 4D: A schematic diagram of the pressing step of the aluminum alloy spot welding method according to an embodiment of the present invention.

Figure 4E: A schematic diagram of the energization steps of an aluminum alloy spot welding method according to an embodiment of the present invention.

Fig. 4F: A schematic diagram of a welding step of an aluminum alloy spot welding method according to an embodiment of the present invention.

Figure 5: Aluminum alloy spot welded by the aluminum alloy spot welding method according to an embodiment of the present invention The macroscopic and microscopic metallographic diagrams of the weld samples.

Fig. 6: A photo of a plurality of aluminum alloy spot welding samples formed by welding at least one welding spot by an aluminum alloy spot welding method according to an embodiment of the present invention.

Fig. 7A: A schematic diagram of the tensile strength test results of an aluminum alloy spot welding sample (1) formed by an aluminum alloy spot welding method according to an embodiment of the present invention.

Figure 7B: A schematic diagram of the tensile strength test results of the aluminum alloy spot welding sample (2) formed by the aluminum alloy spot welding method of an embodiment of the present invention.

Figure 7C: A schematic diagram of the tensile strength test results of the aluminum alloy spot welding sample (3) formed by three welding joints by the aluminum alloy spot welding method according to an embodiment of the present invention.

Figure 7D: A schematic diagram of the tensile strength test results of the aluminum alloy spot welding sample (4) formed by three welding joints by the aluminum alloy spot welding method according to an embodiment of the present invention.

Fig. 7E: A schematic diagram of the tensile strength test results of an aluminum alloy spot welding sample (5) formed by five welding points welded by an aluminum alloy spot welding method according to an embodiment of the present invention.

Fig. 7F: A schematic diagram of the tensile strength test results of an aluminum alloy spot welding sample (6) formed by five welding points welded by an aluminum alloy spot welding method according to an embodiment of the present invention.

In order to make the above and other objects, features, and advantages of the present invention more obvious and understandable, the following will specifically cite the preferred embodiments of the present invention, together with the accompanying drawings, and describe in detail as follows. Furthermore, the directional terms mentioned in the present invention, such as up, down, top, bottom, front, back, left, right, inside, outside, side, surrounding, center, horizontal, horizontal, vertical, vertical, axial, The radial direction, the uppermost layer or the lowermost layer, etc., are only the direction of reference to the attached drawings. Therefore, the directional terms used are used to describe and understand the present invention, rather than to limit the present invention.

Please refer to Figures 1 and 2, the spot welding electrode assembly of an embodiment of the present invention may include a metal body 1 and a metal coating 2. The metal body 1 has a welding end 11, and the welding end 11 can be formed The metal coating 2 covers the welding end 11 of the metal body 1, and the metal coating 2 can completely cover the welding end 11 of the hemispherical surface to facilitate the production of better welding results. Good welding effect; among them, the material of the metal coating 2 is different from the material of the metal body 1, and the material of the metal coating 2 can be nickel, cobalt, or nickel-cobalt alloy and other metal materials with high electrical resistance to improve electrical welding The temperature at the time. The following examples illustrate the implementation of the above-mentioned spot welding electrode assembly, but it is not limited thereto.

For example, the material of the metal body 1 can be a metal with good electrical and thermal conductivity, such as copper, chromium, zirconium or alloys thereof, etc., for example, copper can be used to cast a suitable metal body according to application requirements 1. To be used as an electrode for spot welding, for example: for welding aluminum alloy (AL5182-O/AL5754), but not limited to this, it can also be used for welding other metal materials, such as light metal with oxide film.

In addition, in one embodiment, as shown in FIG. 2, a center of the welding end portion 11 may diffuse outward to form a contact plane 12. For example, the diameter of the contact plane 12 may range from 4 to 8. Millimeters (mm), for example: 4, 5, 6, 7, 8 millimeters, etc. In this way, the contact plane 12 of the diameter range can be used to form solder joints of a specific size, which can avoid the situation of different solder joint sizes due to different operating conditions, and can produce better welding results. For example, if the diameter range is too large, If the welding temperature is not high enough, it will easily affect the welding effect; if the diameter range is too small, if the solder joint is too small, it will easily affect the tensile strength.

In addition, in one embodiment, as shown in Figure 2, a thickness of the metal coating 2 ranges from 10 to 15 microns (μm), for example: 10, 11, 12, 13, 14, 15 microns, etc. It is in accordance with economic benefits, but it is not limited to this, and can be fine-tuned according to actual needs.

In addition, referring to Figure 3, the aluminum alloy spot welding method of an embodiment of the present invention may include a welding preparation step S1, a stacking step S2, a contacting step S3, a pressing step S4, and an energizing step S5 and a welding step S6. Examples are as follows, but not limited to this.

As shown in Figures 3 and 4A, the welding preparation step S1 can prepare two spot welding electrode parts E1 and E2. As shown in Figures 1 and 2, each spot welding electrode part E1 and E2 can include a metal body 1 and a metal plating film 2, the metal body 1 has a welding end 11, the welding end 11 forms a hemispherical shape, the metal plating film 2 covers the welding end 11 of the metal body 1, and the material of the metal plating film 2 and The material of the metal body 1 is different, and the material of the metal coating 2 can be nickel, cobalt or nickel-cobalt alloy. For example, the metal coating 2 can be formed by an electroplating method. For example, in an electrolyte composed of nickel salt, conductive salt, pH buffer, and wetting agent, the anode plate is electrically connected to nickel, cobalt or nickel-cobalt alloy, and the cathode plate is electrically connected to the metal body 1 (such as the welding end 11) The direct current is then applied to facilitate the deposition of a uniform and dense metal coating 2 on the metal body 1 of the cathode plate.

In one embodiment, as shown in FIG. 4A, the metal coatings 2 of the two spot welding electrode elements E1 and E2 face each other to facilitate the subsequent electric welding process, for example: the two spot welding electrode The pole pieces E1 and E2 can be configured to face each other up and down (as shown in Figure 4A), but not limited to this. The two spot welding electrode parts E1 and E2 can be configured to face each other in other ways, such as left and right. Relatively equal.

As shown in Figures 3 and 4B, in the stacking step S2, two aluminum alloy plates P1, P2 can be overlapped to form a welding area W, and the welding area W is placed on the two spot welding electrode parts E1, E2 between. For example, the area to be spot welded of the two aluminum alloy plates P1 and P2 to be welded can be overlapped to form the area to be welded W, and placed between the two spot welding electrode parts E1 and E2, for example: A bracket places the two aluminum alloy plates P1 and P2 forming the area to be welded W between the two spot welding electrode parts E1 and E2, for subsequent electric welding process.

As shown in Figures 3 and 4C, the abutting step S3 can abut the metal coating 2 of the two spot welding electrode parts E1 and E2 against the two opposite sides of the two aluminum alloy plates P1 and P2 in the area to be welded W point. For example, the contact positions of the metal coating 2 of the two spot welding electrode parts E1 and E2 with the surfaces of the two aluminum alloy plates P1 and P2 can be located on the same axis as far as possible, for example: the metal coating on the contact plane 12 2 The contact of the two aluminum alloy plates P1 and P2 are located at two relative positions on a longitudinal axis to facilitate the subsequent electric welding process to form a better quality welding effect.

As shown in FIGS. 3 and 4D, in the pressing step S4, the two spot welding electrode parts E1 and E2 may be pressed against the two aluminum alloy plates P1 and P2. For example, before performing electric welding, a pre-pressurization process can be performed on the two aluminum alloy plates P1 and P2, for example: the two spot welding electrode parts E1 and E2 contact the positions of the two aluminum alloy plates P1 and P2 This pre-pressurization process is performed to facilitate the joining of metals. In an embodiment, a pressure range for the two spot welding electrode parts E1, E2 to press the two aluminum alloy plates P1, P2 may be 200 to 350 kilogram force (KgF), for example: 225, 250, 275, 300, 325 and 350 kg force, etc., but not limited to this, the pressure range can be fine-tuned according to actual needs.

As shown in FIGS. 3 and 4E, in the energization step S5, the two spot welding electrode parts E1 and E2 can be energized until the two aluminum alloy plates P1 and P2 generate a weld nugget C to form a joint J. For example, the two spot welding electrode parts E1 and E2 can be connected to power sources V1 and V2 respectively. For example, the power sources V1 and V2 can be alternating current (AC), direct current (DC), or pulse wave power sources (such as electrical signal amplitude). Between the two potentials, it appears in a cycle (cycle), etc., and provides positive and negative voltages to facilitate the generation of a current between the two spot welding electrode parts E1, E2 through the two aluminum alloy plates P1, P2.

In an embodiment, a current range in which the two spot welding electrode parts E1 and E2 are energized It can be between 5 to 25 kiloamperes, for example: 5, 10, 15, 18, 20, 22, 25 kiloamperes, etc.; the energization process can also adopt a multi-stage energization method to enable the two-spot welding electrode parts E1 and E2 Perform a multi-stage electrification process with different electrical parameters, for example: the first stage current (such as 20kA\2cycles) is used to heat the metal coating 2 of the spot welding electrode parts E1 and E2, so as to preheat the metal to be welded Treatment: remove the oxide film on the metal surface and degrease at high temperature, so there is no need to pre-treat the metal surface to be welded; the second stage of current (such as 18kA\5cycles) is used for welding and post heat treatment to cool the welding place Slowing down to avoid the occurrence of porosity is conducive to complete formation of the weld nugget C, so as to improve welding efficiency and quality, but not limited to this.

Thereby, the metal coating 2 can be heated to vaporize the aluminum alloy surface oxide film due to the passage of electric current. At the same time, the electric current can enter between the two aluminum alloy plates P1 and P2 through the surfaces of the two aluminum alloy plates P1 and P2. For example, after a period of electric welding (5-30 cycles), the aluminum alloy is melted at high temperature to generate resistance heat to form the weld nugget C, and the two aluminum alloy plates P1 and P2 are joined to form the joint J.

Please refer to Figure 5, which is the macroscopic and microscopic weld nugget metallographic diagram of the one-point welding sample formed by welding aluminum alloy by the above method embodiment, from the macroscopic weld nugget metallographic diagram (top of Figure 5) It can be seen that the weld nugget of the spot welding sample is indeed evenly distributed between the upper and lower two aluminum alloy plates; from the microscopic weld nugget metallographic diagram (bottom figure 5), it can be seen that the material properties of the weld nugget inside and outside of the spot welding sample Same and uniform distribution, the obtained weld nugget can be completely formed, the structure is fine, and the tensile and shear strength is greatly improved. Compared with the prior art, the above-mentioned embodiments of the present invention can solve the problems of cracks, loose nugget structure and nugget pores in the weld bead structure of conventional aluminum alloy spot welding, effectively improving the strength of aluminum alloy spot welding and having stable and reliable reproduction Sex.

As shown in FIGS. 3 and 4F, in the separation step S6, the two spot welding electrode parts E1 and E2 can be removed from the joining part J. For example, after the two aluminum alloy plates P1 and P2 are joined to form the joining member J, the two spot welding electrode members E1 and E2 can be removed from the joining member J.

Please refer to Figure 6, which is a photo of multiple aluminum alloy spot welding samples formed by the aluminum alloy spot welding method of the above embodiment of the present invention to form at least one solder joint. From left to right in the figure, a single solder joint is formed. Aluminum alloy spot welding samples (1), (2), aluminum alloy spot welding samples forming three solder joints (1), (2), aluminum alloy spot welding samples forming five solder joints (1), (2) ). Figures 7A to 7F are the tensile strength test results of six aluminum alloy spot welding samples from left to right corresponding to Figure 6 Schematic diagram, for example: use the model MTS-810 tensile testing machine, the tensile speed is 5 millimeters per minute (mm/min), etc., but not limited to this. It can be seen from Figures 7A and 7B that the tensile strength of a single solder joint is about 2.2 to 2.3 kilonewtons (kN); from Figures 7C and 7D, the tensile strength of the three solder joints is about 6 to 6.3kN. ; It can be seen from Figures 7E and 7F that the tensile strength of the five solder joints is about 6.3 to 7.3kN, and the tensile strength of 7.3kN leads to the damage of the base material (aluminum alloy).

It can be seen that the tensile strength of the five solder joints of the present invention has actually reached the tensile strength of the metal base material. Due to the complete weld nugget structure, it can almost exceed the aluminum alloy base material under the synergy of multiple solder joints. For example, comparing the aluminum alloy spot welding sample of the above-mentioned embodiment of the present invention with the ISO-18595 aluminum alloy resistance spot welding specification, the strength of a single solder joint is twice as large as the specification, and the weld nugget is smaller; multiple solder joints The strength grows in multiples, almost reaching the strength of the aluminum alloy base material.

Thereby, the spot welding electrode part and the aluminum alloy spot welding method of the above embodiments of the present invention can indeed produce a strong joining effect on aluminum alloy welding. The joining effect can also be applied to other metal joining applications, which is beneficial to improve existing metal joining. The quality of processing.

In summary, the spot welding electrode parts and aluminum alloy spot welding methods of the above-mentioned embodiments of the present invention are mainly based on coating the surface of the spot welding electrode parts with a layer of specific metal with high electrical resistance (such as nickel, cobalt, or nickel-cobalt alloy). ), the metal material can improve the electrical resistance of the spot welding electrode. During the spot welding process, the spot welding electrode and the specific metal first generate resistance heat to remove the oxide layer and grease on the surface of the aluminum alloy. Resistance heat is generated between the aluminum alloy plates to be welded, which causes the high-temperature melting and growth of weld nuggets between the aluminum alloy plates. The contact surface between the spot welding electrode and the aluminum alloy continues to generate high temperature to provide additional energy to slow down the spot welding process The heat dissipation rate is high, and the welding nugget can be formed completely without high welding current and large-size spot welding electrode parts, and then a metal joint with small welding diameter but high tensile strength can be obtained, which is beneficial to improve the existing metal joint processing Quality, efficiency and cost.

Although the present invention has been disclosed in preferred embodiments, it is not intended to limit the present invention. Anyone who is familiar with the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be subject to the scope of the attached patent application.

1‧‧‧Metal body

11‧‧‧Welding end

12‧‧‧Contact plane

2‧‧‧Metal coating

Claims (13)

A spot welding electrode assembly, comprising: a metal body with a welding end, the welding end forming a hemispherical shape; and a metal plating film covering the welding end of the metal body, the material of the metal plating film and the metal body The material is different, the metal coating material is nickel-cobalt alloy. The spot welding electrode assembly according to claim 1, wherein a center of the welding end diffuses outward to form a contact plane. The spot welding electrode assembly according to claim 2, wherein a diameter of the contact plane ranges from 4 to 8 mm. The spot welding electrode assembly according to claim 1, wherein the material of the metal body is copper, chromium, zirconium or alloys thereof. The spot welding electrode assembly according to claim 1, wherein a thickness of the metal coating film ranges from 10 to 15 microns. An aluminum alloy spot welding method, comprising the steps of preparing two spot welding electrode parts, each spot welding electrode part includes a metal body and a metal coating, the metal body has a welding end, and the welding end forms a hemispherical shape , The metal plating film covers the welding end of the metal body, the material of the metal plating film is different from the material of the metal body, the material of the metal plating film is a nickel-cobalt alloy; the two aluminum alloy plates are overlapped to form a welding area, and The to-be-welded area is placed between the two spot welding electrode parts; the metal coating of the two spot-welding electrode parts abuts the two spot welding electrode parts located in the to-be-welded area Two opposite points of the aluminum alloy plate; pressurize the two spot welding electrode components on the two aluminum alloy plates; energize the two spot welding electrode components until a weld nugget is generated on the two aluminum alloy plates to form a joint; And remove the two spot welding electrode member from the joining member. The aluminum alloy spot welding method according to claim 6, wherein a pressure range of the two-spot welding electrode assembly to pressurize the two aluminum alloy plate is 200 to 350 kgf. The aluminum alloy spot welding method according to claim 6, wherein a current range for energizing the two spot welding electrode components is between 5 and 25 kA. The aluminum alloy spot welding method according to claim 6, wherein the two spot welding electrode parts perform a multi-stage energization process with different electrical parameters. The aluminum alloy spot welding method according to claim 6, wherein a center of the welding end diffuses outward to form a contact plane. The aluminum alloy spot welding method according to claim 10, wherein a diameter of the contact plane ranges from 4 to 8 mm. The aluminum alloy spot welding method according to claim 6, wherein the material of the metal body is copper, chromium, zirconium or alloys thereof. The aluminum alloy spot welding method according to claim 6, wherein a thickness of the metal coating film ranges from 10 to 15 microns.

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