JP6947591B2 - Electrodes for spot welding - Google Patents

Description

The present invention relates to a spot welding electrodes.

Spot welding (or lap resistance welding, point welding, etc.) is performed in each field of industry. In this spot welding, a superposed metal member (material to be welded) is sandwiched between the tips of a pair of electrodes and heated and welded.

Various types of commercially available electrodes (electrodes for spot welding) used in spot welding are available, and the most suitable one is selected according to the material of the material to be welded and the welding conditions. Can be used. Further, for example, as in Patent Documents 1 to 5, various devices have been devised for the electrodes are also known.

Japanese Unexamined Patent Publication No. 4-118177 Japanese Unexamined Patent Publication No. 10-225776 Japanese Unexamined Patent Publication No. 2001-179464 Japanese Unexamined Patent Publication No. 2000-71078 Japanese Unexamined Patent Publication No. 2006-55898

For example, when the material to be welded is a zinc-plated steel plate or a zinc-plated steel plate, when spot welding is performed, the plating component dissolves from the material to be welded and causes an alloying reaction with the electrode, so that the material is plated. There is a problem that the tip of the electrode is significantly worn or deformed as compared with the bare steel plate, and the life of the electrode is shortened accordingly.

Further, although Patent Document 1 proposes an electrode suitable for a composite coated plate, it does not extend the life of the electrode when a galvanized steel sheet or a galvanized steel sheet is spot welded. In Patent Document 2, a notch is provided at the tip of the electrode, but since the notch is troublesome to process and difficult to reuse by cutting (dressing), a galvanized steel sheet or a galvanized steel sheet is used. It is difficult to use it for spot welding. In Patent Document 3, the tip of the electrode is D-shaped in order to improve the formation delay of the nugget (molten solidification part) in spot welding, but when spot welding a galvanized steel sheet or a zinc-plated steel sheet, the electrode It wasn't something that would extend life. In Patent Document 4 and Patent Document 5, the radii of curvature of the tips of the upper and lower electrodes are made different in order to prevent the occurrence of indentations and welding dust, but in this case, electrodes having different radii of curvature are used. Various types must be prepared, which increases cost and labor.

Therefore, an object of the present invention is mainly to solve the above-mentioned problems.

In order to solve the above problems, in the present invention, the electrode body for spot welding using the material to be welded as a galvanized steel plate or a galvanized steel plate is made of chrome copper and has a CR type tip portion. the radius of curvature R of the R portion of the distal end portion, 27 mm ≦ R <75 mm der is, the thickness t of the R moiety, wherein the spot welding electrodes that have a 0.3 mm <t ≦ 0.9 mm ..

According to the present invention, the electrode life can be extended when the material to be welded is spot welded as a galvanized steel sheet or a galvanized steel sheet according to the above configuration.

It is a figure which shows the welding apparatus which concerns on this embodiment. (A) is a C type, (b) is an R type, and (c) is a current CR type spot welding electrode. It is a graph which shows the transition state of the joint shear strength (shear strength) and contact area by the number of weldings when the CR type spot welding electrode of FIG. 2C is used. (A) is a CR type spot welding electrode according to this embodiment, (b) is another CR type spot welding electrode according to this embodiment, and (a) is a current CR type spot welding electrode. It shows. It is a graph which shows the state of the transition of the joint shear strength by the number of weldings using each CR type spot welding electrode of FIGS. 4A to 4C. It is a graph which shows the relationship between the joint shear strength and the contact area in each CR type spot welding electrode of FIGS. 4A to 4C.

Hereinafter, the present embodiment will be described in detail with reference to the drawings.
1 to 6 are for explaining this embodiment.

<Structure> The configuration will be described below.

FIG. 1 shows a welding device 1 that performs spot welding (lap resistance welding, point welding, etc.). In spot welding, the overlapped metal members (materials 2 and 3 to be welded) are sandwiched between the tips 5 of the pair of electrodes 4, and electric current is applied (current is applied) between the pair of electrodes 4. Then, the materials to be welded 2 and 3 are heated and welded.

The electrode 4 (spot welding electrode) for spot welding includes, for example, a C type (conical cone type) as shown in FIG. 2 (a) and an R type (conical cone type) as shown in FIG. 2 (b). Various types such as a CR type (conical cone radius type) having a C portion 6 (conical base portion) and an R portion 7 (radius portion) as shown in FIG. 2 (c). Is commercially available. Then, it is common to select and use the most suitable electrode 4 from commercially available electrodes 4 according to the material of the materials to be welded 2 and 3 and the welding condition.

Therefore, the materials to be welded 2 and 3 are used as galvanized steel sheets or galvanized steel sheets, and the zinc-plated steel sheets or zinc-plated steel sheets are, for example, the C-type electrode 4 of FIG. 2 (a) and FIG. 2 (c). When spot welding was actually performed using the CR type electrode 4 of the above, for example, the CR type electrode 4 had a bonding shear strength of 66 kN, whereas the C type electrode 4 was bonded. The shear strength was 22 kN. Therefore, it was confirmed that the CR type electrode 4 can obtain a larger joint shear strength (or shear strength) at the welded joint than the C type electrode 4, and at least a galvanized steel plate or a galvanized type. It was found that it is better to use the CR type electrode 4 when spot welding a steel plate.

However, when spot welding is performed on a zinc-plated steel sheet or a zinc-plated steel sheet having a large total thickness (6.3 mm to 10 mm) using a generally available CR type electrode 4, the electrode life is extended. Since it was not sufficient, it is required to extend the electrode life.

Therefore, when the above-mentioned CR type electrode 4 was investigated, as shown in FIG. 3, the tip portion 5 of the spot welding electrode was consumed (due to melting, deformation, deterioration, etc.) by repeated welding. It was confirmed that the contact area with the materials to be welded 2 and 3 increased, and the joint shear strength of the welded joint decreased accordingly.

Therefore, there is a clear correlation between the increase in the contact area with respect to the materials to be welded 2 and 3 and the decrease in the joint shear strength of the welded joint. Further, the contact area and the joint shear strength of the welded joint are determined by the presence or absence of the R portion 7 and the magnitude of the radius of curvature R of the R portion 7 from the comparison between the C-type electrode 4 and the CR-type electrode 4 described above. It is presumed that it has an effect. The current CR type electrode 4 has a radius of curvature R of the R portion 7 of 75 mm (R75).

The diameter (tip diameter) of the tip portion 5 of the electrode 4 is defined as the energization diameter and substantially coincides with the nugget diameter. The tip diameter of a general electrode 4 is 6Φ to 10Φ or the like, but when spot welding is performed on a galvanized steel sheet or a galvanized steel sheet having a large total thickness (total thickness: 6.3 mm to 10 mm). Since the required nugget diameter is larger than that of a general one, it is desired that the tip diameter of the electrode 4 is also increased to 14Φ or the like.

Therefore, in this embodiment, the spot welding electrode has the following configuration.

(1) The electrode body of the spot welding electrode (electrode 4) for performing spot welding by using the materials to be welded 2 and 3 as a zinc-plated steel plate or a zinc-plated steel plate is made of chrome copper. Then, as shown in FIG. 4, the electrode body shall have a CR type tip portion 5. Further, the radius of curvature R of the R portion 7 of the tip portion 5 is set to 27 mm ≦ R <75 mm.

Here, FIG. 4A is a spot welding electrode according to this embodiment, in which the radius of curvature R of the R portion 7 is 27 mm (R27). FIG. 4B is another spot welding electrode according to this embodiment, in which the radius of curvature R of the R portion 7 is 40 mm (R40). FIG. 4C shows a current CR type electrode 4 as a comparative example, and the radius of curvature R of the R portion 7 is 75 mm (R75).

Then, when each of these spot welding electrodes was used to actually perform spot welding on the galvanized steel plate or the galvanized steel plate as the materials to be welded 2 and 3, and compared, welding was performed by repeating welding. The transition of the weld shear strength of the joint portion is shown in FIG.

The welding conditions at this time are as follows.
Target steel plate: Galvanized steel plate (ZAM-plated t3.2-4.0t joint) Target plate thickness (total thickness of lap joint): 6.3 to 10mm Number of welds: 200 times Current value: 18.5kA Pressurization: 9kN Squeeze time: 35cylce slow Time: 3cycle Energizing time: 115cycle Holding time: 50cycle

According to FIG. 5, it was confirmed that the smaller the radius of curvature R, the higher the position of the line showing the transition of the joint shear strength and the gentler the gradient of the line. That is, it was confirmed that the joint shear strength increased in the order of R27, R40, and R75, and the decrease in the joint shear strength for each welding in the order of R27, R40, and R75 also decreased (R27 (-). 2kN) <R40 (-4kN) <R75 (-5kN).

Then, when the value of the joint shear strength which is the electrode life is set as the reference strength (broken line in FIG. 5), the electrode 4 of R40 is 50 times or more with respect to the electrode 4 of R75, and the electrode 4 of R27 is 100 times. It was confirmed that the electrode life was extended more than once.

In addition, as a matter that is almost common to each spot welding electrode, the joint shear strength that connects the first welding and the 200th welding in a straight line around the 50th welding (at the beginning of welding). It was confirmed that the actual weld shear strength tends to be higher than the average transition line (thin line in FIG. 5). This is because the contact area with the materials to be welded 2 and 3 is still small at the initial stage of welding, so that the current density increases and the formation speed of the nugget 9 (molten solidification part: see FIG. 1) increases, so that the nugget 9 is efficient. It is presumed that it is because it is well formed.

The radius of curvature R of the R portion 7 of the tip portion 5 of the electrode 4 is set to 27 mm because, as shown in FIG. 6, dust and welding increase as the radius of curvature R decreases. This is because it was judged that it is practically difficult to make the radius of curvature R smaller than 27 mm.

(2) The thickness t of the R portion 7 of the tip portion 5 of the CR type electrode 4 may be 0.3 mm <t ≦ 0.9 mm.

Here, as shown in FIG. 4A, in the case of the spot welding electrode (R27) in which the radius of curvature R of the R portion 7 is 27 mm, the thickness t of the R portion 7 is 0.9 mm. Further, as shown in FIG. 4B, in the case of another spot welding electrode (R40) in which the radius of curvature R of the R portion 7 is 40 mm, the thickness t of the R portion 7 is 0.6 mm. On the other hand, as shown in FIG. 4C, in the case of the CR type electrode 4 (R75) in which the radius of curvature R of the R portion 7 is 75 mm, the thickness t of the R portion 7 is 0.3 mm. ..

In this way, by making the thickness t of the R portion 7 thicker (thickening) than that of the current CR type electrode 4, the thickening of the R portion 7 consumes the electrode 4 until it reaches the end of its life. The amount of parts that can be made (consumable allowance) can be increased.

(3) the contact area S with respect to the material to be welded and third R part 7 of the distal end portion 5 of the CR type electrode 4 may be a 19.0mm ² ≦ S <34.8mm ^2.

Here, as shown in FIG. 4A, in the case of the spot welding electrode (R27) in which the radius of curvature R of the R portion 7 is 27 mm, the initial contact area S of the R portion 7 with respect to the materials to be welded 2 and 3 S. Is 19.0 mm ² . Further, as shown in FIG. 4B, in the case of another spot welding electrode (R40) in which the radius of curvature R of the R portion 7 is 40 mm, the initial contact area of the R portion 7 with respect to the materials to be welded 2 and 3 is achieved. S is 23.5 mm ² . On the other hand, as shown in FIG. 4C, in the case of the CR type electrode 4 (R75) having the radius of curvature R of the R portion 7 having a radius of curvature R of 75 mm, the initial contact area of the R portion 7 with respect to the materials to be welded 2 and 3 S is 34.8 mm ² .

In this way, by making the contact area S of the R portion 7 with respect to the welded materials 2 and 3 smaller than that of the current CR type electrode 4, the current density can be increased.

When the contact area of each spot welding electrode with respect to the materials to be welded 2 and 3 at the time of the 50th welding described above was measured, R27 was 74 mm ² , R40 was 81 mm ² , and R75 was 86 mm ^2. , The initial contact area was small. As described above, as the initial contact area becomes smaller, the current density increases and the formation speed of the nugget 9 increases, so that the nugget 9 can be formed more efficiently.

(4) The inclination angle α of the C portion 6 of the tip portion 5 of the CR type electrode 4 may be 25 °.

Here, the inclination angle α of the C portion 6 of the tip portion 5 is the angle of the outer peripheral surface (conical surface) of the truncated cone-shaped C portion 6 with respect to the bottom surface of the C portion 6. As a result, the diameter of the tip portion 5 of the C portion 6 can be made larger than the general tip diameter (6Φ to 10Φ) (14Φ), the radius of curvature R, the thickness t, and the contact area of the R portion 7 of the tip portion 5 can be increased. It is advantageous to set S as described above.

The diameter of the tip 5 of the C portion 6 is set to 14Φ or the like because the total thickness is larger than that of a general one (6.3 mm to 10 mm), and it is made of a galvanized steel plate or a galvanized steel plate to be welded. This is so that a nugget 9 having a sufficient size can be formed with respect to the materials 2 and 3.

(5) Then, the welding apparatus 1 may be provided with the above-mentioned spot welding electrode (electrode 4).

Here, as shown in FIG. 1, the welding apparatus 1 is provided with spot welding electrodes (electrodes 4) that can be arranged to face each other on both surfaces of the overlapped materials 2 and 3, and is located between a pair of spot welding electrodes. The welding power supply 11 is connected to the above. A pair of spot welding electrodes having the same shape and size are used.

The welding device 1 is used, for example, when assembling a steel-framed building unit used in the unit construction method. Pillars and beams (ceiling beams, floor beams) made of galvanized steel sheets or galvanized steel sheets are used for the unit frame that forms the framework of the building unit. Since the columns and beams constituting the unit frame are thick, the total thickness is larger than that of the materials to be welded 2 and 3 to which spot welding is generally performed (6.3 mm to 10 mm). However, the target of use of the welding device 1 is not limited to the unit frame.

(6) Welding is performed using the welding device 1 provided with the above-mentioned spot welding electrode (electrode 4).

Here, the welding method is, for example, a method of constructing a unit frame by spot welding a joint piece (connecting member) and a beam attached to a pillar of a building unit made of a galvanized steel plate or a galvanized steel plate. Become. However, the application target of the welding method is not limited to the unit frame.

<Action / Effect> According to this example, the following action / effect can be obtained.

(Effect 1) The electrode body of the spot welding electrode (electrode 4) for spot welding the materials to be welded 2 and 3 was made of chrome copper. As a result, even when the materials to be welded 2 and 3 are zinc-plated steel plates or zinc-plated steel plates, the plating components dissolved from the materials to be welded 2 and 3 by spot welding react with the electrode 4 (the electrode body). Therefore, it is possible to suppress wear and deformation of the tip portion 5 of the electrode body. Therefore, it is possible to obtain an electrode for spot welding suitable for spot welding on a galvanized steel sheet or a galvanized steel sheet.

Further, the electrode body of the spot welding electrode (electrode 4) has a CR type tip portion 5. As a result, the merits of the C-shaped electrode 4 (for example, good maintainability of the tip shape) and the merits of the R-shaped electrode 4 (for example, good dressing workability for cutting the tip shape) and a pair of merits. It is possible to have both good compensation characteristics for the misalignment of the pressure shafts between the electrodes 4 and good compensation characteristics for the misalignment of the contact angles between the electrodes 4 and the materials to be welded 2 and 3.

Further, the radius of curvature R of the R portion 7 of the tip portion 5 of the CR type electrode 4 was set to 27 mm ≦ R <75 mm. As a result, it is possible to obtain an electrode 4 having an optimum shape in which the radius of curvature R of the R portion 7 is smaller than that of the current CR type electrode 4 (for example, R75).

Then, in the spot welding electrode, the life is reached when the proper nugget 9 cannot be obtained and the joint shear strength of the welded joint becomes less than the reference value.

At this time, the tip portion 5 of the spot welding electrode is consumed (melted, deformed, deteriorated, etc.) by repeating welding, and the radius of curvature R of the R portion 7 gradually increases. The joint shear strength of the welded joint gradually decreases. Therefore, it is considered that there is a correlation between the increase in the radius of curvature R of the R portion 7 and the decrease in the joint shear strength of the welded joint.

Therefore, by setting the radius of curvature R of the R portion 7 to 27 mm ≦ R <75 mm, as described above, the radius of curvature R of the R portion 7 becomes smaller than that of the current CR type electrode 4 (for example, R75). Therefore, it is possible to secure a large range (diameter expandable allowance) in which the radius of curvature R can change before the electrode 4 reaches the end of its life. As a result, the spot welding electrode can obtain a stable joint shear strength at the welded joint portion with respect to long-term use, and the electrode life can be extended (life extension) by that amount.

Further, since the electrode life can be extended only by using the radius of curvature R of the R portion 7 of 27 mm ≦ R <75 mm, the electrode 4 having a special shape can be used or the tip portion 5 of the electrode 4 can be processed. It can be used as it is without any special effort or cost. Further, since the same electrodes 4 can be used for both the upper and lower surfaces, no extra labor and cost are required.

As described above, by extending the electrode life, it is possible to reduce the number of replacements of the spot welding electrode, increase the welding efficiency, and reduce the welding cost.

(Action Effect 2) The thickness t of the R portion 7 of the tip portion 5 of the CR type electrode 4 may be 0.3 mm <t ≦ 0.9 mm. By setting the thickness t of the R portion 7 to 0.3 mm <t ≦ 0.9 mm in this way, the thickness t of the R portion 7 becomes thicker than that of the current CR type electrode 4 (for example, R75) (for example, R75). Thicken). Therefore, the amount of the portion (consumable allowance) that can be consumed before the electrode 4 reaches the end of its life can be increased by the thickening of the R portion 7. Therefore, the life of the electrode can be extended. Further, it can be expected that the large thickness t of the R portion 7 or the large consumable allowance itself contributes to the suppression of electrode wear.

Since the consumable allowance of the electrode 4 is large, there is a margin or a margin with respect to the reference strength (of the joint shear strength) which is the life of the electrode. Therefore, for example, the applied current is intentionally increased to form the nugget 9. It will be possible to devise new ways of energizing, such as promoting it. This makes it possible to develop a new method of energization that can shorten the welding time and extend the life of the electrodes.

The contact area S with respect to the material to be welded and third R part 7 of the distal end portion 5 of the (Operation and Effect 3) CR-type electrode 4 may be a 19.0mm ² ≦ S <34.8mm ^2. Thus, the contact area S with respect to the welding material 2,3 in the R moiety 7, by a 19.0mm ² ≦ S <34.8mm ^2, the current CR-type electrode 4 (e.g., R75) than The contact area S of the R portion 7 with respect to the welded materials 2 and 3 can be reduced. Therefore, the current density increases and the formation speed of the nugget 9 increases, so that a large nugget 9 can be efficiently formed, or a nugget 9 having an appropriate size can be obtained even if the applied current is lowered. You will be able to form. As a result, the life of the electrode can be extended.

(Action Effect 4) The inclination angle α of the C portion 6 of the tip portion 5 of the CR type electrode 4 may be 25 °. In this way, by setting the inclination angle α of the C portion 6 of the tip portion 5 to 25 °, it is possible to facilitate the shape of the R portion of the tip portion 5 as described above.

(Action and Effect 5) By providing the above-mentioned spot welding electrode (electrode 4), the welding apparatus 1 can obtain the same action and effect as the above-mentioned spot welding electrode (for example, the life extension effect of the electrode 4). can.

(Action Effect 6) By using the above-mentioned spot welding electrode in the welding method, the same action and effect as the above-mentioned spot welding electrode (for example, the life extension effect of the electrode 4) can be obtained.

Although the embodiments of the present invention have been described in detail with reference to the drawings, the embodiments are merely examples of the present invention. Therefore, the present invention is not limited only to the configuration of the embodiment, and it goes without saying that the present invention includes a design change or the like within a range that does not deviate from the gist of the present invention. Further, for example, when a plurality of configurations are included in each embodiment, it goes without saying that possible combinations of these configurations are included even if there is no particular description. Further, when a plurality of examples and modifications are disclosed as those of the present invention in the embodiment, possible combinations of configurations straddling these are included even if there is no particular description. Of course. Further, it goes without saying that the configuration depicted in the drawings is included even if there is no particular description. Furthermore, when there is a term such as "etc.", it is used to mean that it includes the equivalent. In addition, when there are terms such as "almost", "about", and "degree", they are used to mean that they include those with a range and accuracy that are generally accepted.

1 Welding device 2 Welded material 3 Welded material 4 Electrode 5 Tip part 6 C part 7 R part R Radius of curvature S Contact area t Thickness α Tilt angle

Claims (3)

The electrode body for spot welding using a galvanized steel plate or a galvanized steel plate as the material to be welded is made of chrome copper and has a CR type tip portion, and the radius of curvature R of the R portion of the tip portion is 27 mm ≦ R <Ri 75mm der, the thickness t of the R moiety is, 0.3 mm <spot welding electrode, characterized that you have a t ≦ 0.9 mm. In the spot welding electrode according to claim 1,
The contact area S with respect to the welding material in the R moiety is, 19.0 mm ² ≦ S <spot welding electrode, characterized in that it has a 34.8 mm ^2. In the spot welding electrode according to claim 1 or 2.
An electrode for spot welding, wherein the inclination angle α of the C portion of the tip portion is 25 °.

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