KR100590616B1 - Method for spot welding metal plates by surface friction welding process - Google Patents

Abstract

The present invention relates to a spot welding method of a metal sheet, comprising: a spot welding method of two metal sheets; Stacking the joint surfaces of the two joint members up and down with each other and firmly fixing the joint surfaces; Positioning a round bar probe for high-speed rotation made of a material more rigid than the joining member to a joining request line; Generating frictional heat while rapidly rotating the probe on the surface of the bonding member located at the top, and forcibly exerting extreme plastic flow on the surface of the bonding member; It is configured to bond the two joining members by allowing the generated plastic flow to penetrate into the joining member located at the bottom, and the spot welding while moving the probe horizontally at regular intervals.

According to the present invention, even in spot welding of a poorly welded metal sheet, it provides an advantage that easy welding can be performed in a very good quality without leaving a welding defect in the welding portion.

Description

Spot welding method of metal plate by surface moving friction welding method METMETOD FOR SPOT WELDING METAL PLATES BY SURFACE FRICTION WELDING PROCESS

1 is a schematic view showing a spot welding process of a metal plate using the surface movement friction welding method according to the present invention,

Figure 2 is an appearance photograph of the bonding material spot welded AZ31 magnesium alloy sheet material having a thickness of 1.0mm according to an embodiment of the present invention,

Figure 3 is a cross-sectional photograph after spot welding of the AZ31 magnesium alloy sheet thickness of 1.0mm according to the embodiment of the present invention,

Figure 4 is a cross-sectional photograph after spot welding of a 5052 aluminum alloy plate having a thickness of 0.5mm in accordance with an embodiment of the present invention.

♧ description of the symbols for the main parts of the drawing ♧

1,2 ... bonding member 3 .... probe

4 .... welding 5 .... firing area

The present invention relates to a spot welding method of a metal sheet, and more particularly, to spot weld two metal sheets, it is possible to easily weld a poorly welded metal material without maintaining welding defects such as keyholes. The present invention relates to a spot welding method for a metal sheet by surface moving friction welding.

In general, in case of spot welding by overlapping two thin metal plates, electrodes are contacted on the upper and lower sides of the junction and then energized to melt the material by the heat generated by the electrical resistance of the material itself. Spot welding method is mainly used.

However, it has been recognized that spot welding is impossible due to the disadvantage that the physical properties of the joint are significantly reduced when the aluminum alloy or magnesium alloy is bonded by spot welding except for relatively easy spot welding.

However, aluminum alloy or magnesium alloy plate is expected to be applied to environmentally friendly lightweight automobiles in the future, and because it is widely used in the form of a thin plate, an appropriate spot welding method is required.

Recently, friction stir welding methods using friction of non-consumable tools and bonding materials (WO 93/10935, WO 95/26254) have been disclosed due to the efforts of many efforts to easily bond such poorly welded metal materials.

The disclosed friction stir welding method is achieved by rotating the rod-shaped hard material tool consisting of a special type of probe pin and shoulder at high speed and interfering with the bonding material in contact with the probe pin and the shoulder when the probe pin is inserted into the joint portion of the bonding material. The heat is generated, and the frictional heat softens the material around the probe pin, thereby mixing and joining together by forced plastic flow by the rotation of the probe pin.

However, if the spot welding through the friction stir welding method as described above, the key hole is formed in the welded portion due to the probe pin inserted into the joining member, which in turn causes serious welding.

Therefore, in order to prevent the formation of such a keyhole during spot welding, the probe pin and the shoulder must be driven independently, and the joining member must be prevented from being discharged to the outside during joining. Therefore, a casing surrounding the tool must be provided. It becomes very complicated.

On the other hand, unlike the friction stir welding method described above, the surface movement friction welding method that enables the joining of a metal plate without forming a key hole, because it uses friction on the surface of the bonding material and processing heat caused by plastic deformation without using a probe pin. (Korean Patent Application No. 2003-68113: hereafter referred to as 'Pre-Application') has been disclosed by the applicant.

However, despite the prior application by the present applicant, no method has been studied for spot welding the sheet metal by using it, and no technology has been disclosed so that research for active application in this field is urgently needed. It is requested.

The present invention has been created by the necessity as described above, in particular, while simplifying the welding device for spot welding of poorly welded alloy sheet, such as aluminum alloy sheet or magnesium alloy sheet, while ensuring a very easy weldability and further improve the weld quality. Its main purpose is to provide a spot welding method for sheet metal by surface movement friction welding.

The present invention, in order to achieve the above technical problem, a method of spot welding two metal plate; Stacking the joint surfaces of the two joint members up and down with each other and firmly fixing the joint surfaces; Positioning a round bar probe for high-speed rotation made of a material more rigid than the joining member to a joining request line; Generating frictional heat while rapidly rotating the probe on the surface of the bonding member located at the top, and forcibly exerting extreme plastic flow on the surface of the bonding member; The plastic flow of the metal sheet by the surface movement friction welding method comprising the step of welding the probe while the horizontal movement of the probe at the same time at the same time to bond the two joining members so that the generated plastic flow is penetrated into the joining member located in the lower portion It is a technical feature to provide a spot welding method.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment according to the present invention.

1 is a schematic view showing a spot welding process of a metal sheet using the surface friction friction welding method according to the invention, Figure 2 is a photograph of the appearance of the bonding material spot welded AZ31 magnesium alloy plate with a thickness of 1.0mm according to an embodiment of the present invention 3 is a cross-sectional photograph after spot welding of an AZ31 magnesium alloy sheet having a thickness of 1.0 mm according to an embodiment of the present invention, and FIG. 4 is a cross-sectional photograph after spot welding of a 5052 aluminum alloy sheet having a thickness of 0.5 mm according to an embodiment of the present invention. to be.

As shown in FIG. 1, first, a pair of joining members 1 and 2, preferably metal sheets, are disposed in an overlapping state.

Then, the rod-shaped probe 3 having no probe pin inserted into the joining members 1 and 2 is formed on the surface of the joining member 1 positioned at the upper part at a constant pressure while rotating at high speed so as to generate appropriate frictional heat. Placed in contact.

Subsequently, the probe 3 moves along the joining request line while maintaining a predetermined interval, wherein the joining member 1 in contact with the probe 3 softens due to frictional heat and processing heat generated by plastic deformation. Will be.

At the same time, the high-speed rotation of the probe 3 causes extreme plastic flow, and as a result, the plastic flow penetrates into the interior of the joint member 2 located below the joint member 1, thereby joining these joint members. The overlapped portions of (1, 2) are joined to form a welded portion (4).

At this time, the plastic region 5 generated by the high-speed rotation of the round bar-shaped probe 3 is approximately equal to the area of the bottom of the probe 3 directly under the probe 3, that is, on the surface of the joining member 1, but gradually toward the inside of the material. The width gradually decreases.

Therefore, spot welding (bonding) between the metal sheets, that is, the two joining members 1 and 2, is possible only when the firing region 5 is secured to an appropriate depth, where the depth of the firing region 5 is determined by the probe 3. ) Is directly related to the diameter of Equation 1, and is represented by Equation 1 below (this is well described in the applicant's prior application technology).

[Equation 1]

D ≥ 8 × t1

Here, t1 represents the thickness of the joining member 1, D represents the diameter of the probe (3).

That is, the larger the diameter D of the probe 3, the thicker the thickness t1 of the joining member 1 capable of spot welding, but the larger the width of the welded portion 4 is. In addition, as the coefficient of friction between the joining member 1 and the probe 3 increases, plastic flow is more likely to occur, and the depth of the firing region 5 becomes deeper.

Therefore, in order to increase the coefficient of friction of the probe (3) to make the irregularities of various shapes on the lower surface of the probe (3) in contact with the joining member (1) can be a great help in obtaining easier bonding.

In addition, since most of the metal sheet is smooth with almost no irregularities and is thin by natural or artificial oxidation, it is covered with an oxide, and thus the overlapping in this state is not only easy to join but also causes a high rate of defects.

Therefore, if necessary, by forming an unevenness while removing the oxide covered on the joining surface of the metal sheet to be overlapped for spot welding by using an appropriate method, it is possible to make spot welding easier and lower the defective rate.

In summary, the present invention undergoes a step of firmly fixing the joining surfaces of the two joining members 1 and 2 to the top and bottom of each other, and then uses the round bar for high-speed rotation made of a material more solid than the joining members 1 and 2. Positioning the probe 3 on the joint request line, and then generating frictional heat while rotating the probe 3 at a high speed on the surface of the joint member 1 located above. The surface of 2) is subjected to a forced and extreme plastic flow, and the plastic flow generated in this way is allowed to penetrate into the joint member 2 located at the lower portion so that the two joint members 1, 2 are spot welded. After the step is performed, the two bonding members 1 and 2 are finally joined while horizontally moving the probe 3 by a predetermined interval.

As a result, according to the present invention, unlike the friction stir welding method, probe pins penetrating into the joining members 1 and 2 do not exist, so that friction is only present on the surface of the joining member 1 in contact with the probe 3. It is also characterized in that the plastic flow due to the high-speed rotation of the probe 3 is penetrated to the inside of the bonding member 2 located in the lower portion to be bonded to each other.

Therefore, according to the present invention, defects such as key holes due to the probe pins do not exist in the welded portion, thereby improving the welding quality.

Furthermore, in order to smoothly penetrate the plastic flow, as shown in Equation 1 above, at least eight diameters of the probe 3 should be maintained at least 8 times the thickness of the bonding member 1 in contact therewith. Unevenness may be formed on the bottom surface of the probe 3, and it is required to form some unevenness while removing oxides adhered to the surfaces of the joining members 1 and 2 by an appropriate method.

EXAMPLE

The surface of the AZ31 magnesium alloy plate having a thickness of 1.0 mm each subjected to surface friction friction welding under the conditions according to the present invention and then spot welded is shown in FIG. 2, and a photograph of the cross section is shown in FIG. 3.

In addition, after spot welding a 5052 aluminum alloy sheet having a thickness of 0.5mm each in the same manner, the cross section was taken and shown in FIG.

At this time, the diameter of the probe was 5mm when the thickness of the plate is 0.5mm, 10mm was used when the thickness of the plate is 1.0mm.

As a result, as shown in Figures 3 to 4 it can be confirmed that the spot welding can be easily performed even in the case of poorly welded metal sheet material, the bonding quality is also excellent.

As described in detail above, according to the present invention, even in spot welding of a poorly welded metal sheet, it is possible to secure a very good quality without leaving a welding defect at the end of the welding, and furthermore, it is possible to easily weld through a simple welding equipment. Provide advantages.

Claims (4)

A method of spot welding two metal sheets; Stacking the joint surfaces of the two joint members up and down with each other and firmly fixing the joint surfaces; Positioning a round bar probe for high-speed rotation made of a material more rigid than the joining member to a joining request line; Generating frictional heat while rapidly rotating the probe on the surface of the bonding member located at the top, and forcibly exerting extreme plastic flow on the surface of the bonding member; In the surface moving friction welding method comprising the step of welding the generated plastic flow is penetrated into the bonding member located in the lower portion to bond the two bonding members and at the same time while horizontally moving the probe at a predetermined interval. Spot welding method of metal sheet by welding. The method according to claim 1, The method of spot welding of a metal plate material by the surface movement friction welding method which removes the oxide adhering to the joining surface of the said metal plate material, forms a little unevenness | corrugation, and superimposes and fixes the said metal plate material. The method according to claim 1, The probe has a diameter that satisfies the relationship according to the following equation, characterized in that the spot welding method of a metal sheet material by the surface movement friction welding method. D ≥ 8 × t1 (D is the diameter of the probe, t1 is the thickness of the joint member in contact with the probe) The method according to claim 1, The bottom surface of the probe is processed in the form of fine grooves to increase the coefficient of friction characterized in that the spot welding method of the sheet metal material by the surface movement friction welding method characterized in that formed.

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