Improved resistance welding electrode cap

Abstract

An improved resistance welding electrode cap is arranged at the tail end of an electrode stem and comprises an annular permanent magnet arranged on the outer edge of the end portion, a thin-wall large-resistivity magnetic conductive interlayer and an electrode copper core which are sequentially arranged in the electrode cap, and a cavity formed in the top end and used for circulating cooling water. The upper end of the thin-wall large-resistivity magnetic conductive interlayer makes contact with cooling water in the cavity, the lower end of the thin-wall large-resistivity magnetic conductive interlayer is flush with the end face of the electrode cap and the annular permanent magnet, and three current density distribution areas are formed between the end face of the electrode and the workpiece to be welded. The annular permanent magnet area and the interlayer inner area are the annular permanent magnet area with the minimum current density, and the permanent magnet inner area and the interlayer outer area with the maximum current density are the annular permanent magnet area and the interlayer outer area. The thin-wall high-resistivity magnetic conductive interlayer is arranged in the electrode cap, and the current density distribution is changed to reduce the current density of the center part of the electrode, so that the heat production of the center area is reduced while the heat production of the center area is ensured, the maximum indentation depth of the center area is reduced, and the surface indentation is reduced.

Description

Technical Field

[0001] This invention relates to a technology in the field of resistance welding, specifically an improved resistance welding electrode cap that can reduce the surface unevenness of galvanized weld joints. Background Technology

[0002] In addition to reducing the surface indentation depth, existing resistance welding electrode caps also urgently need to address the control of zinc protrusion on the surface of galvanized weld joints to ensure surface smoothness. Because existing resistance spot welding electrode caps do not alter the internal current density distribution by changing the internal structure, during welding, due to the welding current and electrode pressure, some liquid zinc is displaced to the surrounding area and rapidly heats up and solidifies, forming a zinc ring. This results in unevenly distributed protrusions within the zinc ring, known as zinc protrusions. Summary of the Invention

[0003] To address the aforementioned shortcomings of existing technologies, this invention proposes an improved resistance welding electrode cap. By setting an annular permanent magnet at the edge of the electrode cap and a thin-walled, high-resistivity magnetically conductive interlayer inside, the current density in the center and outer parts of the electrode is reduced. This reduces heat generation in the center and outer regions while ensuring overall heat generation, thereby reducing the maximum surface indentation depth in the center region and improving the irregular zinc protrusions in the outer region.

[0004] This invention is achieved through the following technical solution:

[0005] This invention relates to an improved resistance welding electrode cap, which is disposed at the end of an electrode rod and includes: an annular permanent magnet disposed at the outer edge of the end, a thin-walled, high-resistivity magnetically conductive interlayer and an electrode copper core disposed sequentially inside the electrode cap, and a cavity disposed at the top for cooling water to circulate. The upper end of the thin-walled, high-resistivity magnetically conductive interlayer is in contact with the cooling water in the cavity, and the lower end is flush with the end face of the electrode cap and the annular permanent magnet. Three current density distribution regions are formed between the electrode end face and the workpiece to be welded: the annular permanent magnet region with the lowest current density, the interlayer region, and the permanent magnet interior and interlayer exterior regions with the highest current density. The lower end face of the annular permanent magnet is slightly higher than the electrode end face, and the magnetic field of the annular permanent magnet is used to stir and reduce the thickness of the weld nugget, thereby significantly reducing the indentation depth and surface zinc protrusion.

[0006] The upper end of the thin-walled, high-resistivity magnetic interlayer is in contact with the cooling water in the cavity, and the lower end is flush with the end face of the electrode cap and the annular permanent magnet.

[0007] The thin-walled, high-resistivity magnetic interlayer is made of a high-resistivity magnetic material with a thickness of less than or equal to 0.5 mm and an inner diameter less than or equal to half the diameter of the electrode end face.

[0008] The axis of the thin-walled, high-resistivity magnetic interlayer coincides with the central axis of the electrode cap body.

[0009] The electrode copper core is made of copper alloy. The electrode copper core and the inner diameter of the thin-walled high resistivity magnetically conductive interlayer form an interference fit. The central axis of the electrode copper core coincides with the central axis of the thin-walled high resistivity magnetically conductive interlayer and the electrode cap body.

[0010] The side taper of the cavity is 1:10.

[0011] The magnetization direction of the annular permanent magnet is along the axial or radial direction of the electrode rod. If the electrode cap is arranged on one side, that is, only one electrode cap or both electrode caps are set on the same side of the workpiece to be welded, the annular permanent magnet unit is a combination of magnet units that are magnetized axially; if the electrode cap is arranged on both sides, that is, the two electrode caps are respectively set on the upper and lower sides of the workpiece to be welded, the annular permanent magnet units installed in the upper and lower electrode caps have the same polarity, and during welding, the permanent magnets in the upper and lower electrodes face each other with the same pole, and squeeze each other to generate a stronger radial magnetic field.

[0012] The axis of the ring-shaped permanent magnet coincides with the axis of the electrode cap body, the electrode copper core and the thin-walled high resistivity magnetically conductive interlayer, so as to facilitate the magnetically conductive interlayer to gather and guide the magnetic field to the melting nucleus region, thereby enhancing the effective radial magnetic field strength of the melting nucleus region.

[0013] The lower end face of the annular permanent magnet being slightly higher than the electrode end face means that the lower end face of the annular permanent magnet is higher than the lowest point of the electrode end face. This ensures that during welding, the lowest point of the electrode end face contacts the workpiece first, and then the annular permanent magnet presses against the plate, thereby achieving the effect of locking the welding area and overcoming spatter and zinc protrusion during the welding process. The specific height difference can be adjusted according to the type and mechanical properties of the material to be welded.

[0014] The aforementioned magnetic field stirring refers to the following: the ring-shaped permanent magnet is preferably made of high-temperature resistant neodymium iron boron, with a demagnetization temperature greater than 80℃, a remanence greater than 0.8Br / T, and a coercivity greater than 500Hcb / kA / m. The permanent magnet unit needs to undergo surface insulating coating treatment to reduce conductivity. Technical effect

[0015] This invention improves the electrode end face combination structure and sets up a thin-walled, high-resistivity magnetically conductive interlayer. The outer edge of the permanent magnet structure at the outer edge of the electrode end face can press the welding area during welding, thereby flattening the outer zinc protrusion and reducing spatter. At the same time, under the action of the magnetic field, the thickness of the weld nugget can be reduced, and the surface indentation can be reduced. The thin-walled, high-resistivity magnetically conductive interlayer can change the current density distribution inside the electrode cap while ensuring the magnetic control technology effect and heat conduction effect. In this way, while ensuring the overall heat generation, the heat generation in the center and outer regions is reduced, and the maximum indentation depth in the center region is further reduced. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the present invention;

[0017] In the figure: a is a schematic diagram of the electrode cap device in operation, b is a front view of the electrode cap device; 1 electrode cap, 2 thin-walled high resistivity magnetic interlayer, 3 copper electrode core inside the interlayer, 4 ring-shaped permanent magnet, 5 workpiece to be welded, 6 cooling water flow direction;

[0018] Figure 2 The electrode cap of Example 1 has a thin-walled, high-resistivity magnetic interlayer.

[0019] In the figure: a is the front view of the magnetically conductive interlayer, b is the left view of the magnetically conductive interlayer, c is the top view of the magnetically conductive interlayer, and d is the orthogonal triaxial view of the magnetically conductive interlayer;

[0020] Figure 3 This is a schematic diagram of the current density distribution between the electrode end face and the workpiece to be welded in Example 1;

[0021] Figure 4 The annular permanent magnet unit of Example 1;

[0022] In the figure: a is the front view of the ring-shaped permanent magnet, b is the left view of the ring-shaped permanent magnet, c is the top view of the ring-shaped permanent magnet, and d is the orthogonal triaxial view of the ring-shaped permanent magnet;

[0023] Figure 5 This is a schematic diagram showing the height difference between the electrode end face and the lower surface of the annular permanent magnet in Example 1.

[0024] Figure 6 This is a schematic diagram of the magnetic field generated by the magnetic field source in Example 1;

[0025] Figure 7 Comparison of zinc indentation and spatter on the surface of the weld joint in Example 1;

[0026] In the figure: a is the weld surface indentation of a common resistance spot welding electrode cap; b is the weld surface indentation of a resistance welding electrode cap that can reduce the unevenness of the galvanized weld surface; i is the spatter defect in the weld surface indentation of a common resistance spot welding electrode cap; ii is the zinc protrusion defect in the weld surface indentation of a common resistance spot welding electrode cap.

[0027] Figure 8 Comparison of solder joint indentation depths for Examples 1, 2, and 3;

[0028] In the figure: a is a comparison diagram of the weld indentation depth of Example 1, b is a comparison diagram of the weld indentation depth of Shape 2 in Example 2, c is a comparison diagram of the weld indentation depth of Example 3; i is the weld indentation depth curve of ordinary resistance spot welding electrode cap in the comparison diagram of weld indentation depth, ii is the weld indentation depth curve of resistance welding electrode cap that can reduce the unevenness of galvanized weld surface;

[0029] Figure 9 This is a front view of a thin-walled, high-resistivity magnetic interlayer with different shapes, as shown in Example 2. Detailed Implementation Example 1

[0030] like Figure 1 As shown, this embodiment relates to a resistance welding electrode cap that can reduce the unevenness of the galvanized weld joint surface. It is symmetrically arranged on the upper and lower sides of the workpiece 5 to be welded, and includes: an annular permanent magnet 4 located at the end, a thin-walled high resistivity magnetically conductive interlayer 2 and an electrode copper core 3 arranged sequentially inside the electrode cap 1.

[0031] The thin-walled, high-resistivity magnetically conductive interlayer 2 is embedded in the electrode cap 1 by interference fit. The inner diameter of the thin-walled, high-resistivity magnetically conductive interlayer 2 is 2mm, the wall thickness is 0.5mm, the lower end coincides with the electrode end face, and the upper end coincides with the lower surface of the cavity.

[0032] The electrode copper core 3 is embedded inside the insulating magnetic interlayer 2 by interference fit. The diameter of the electrode copper core 3 is 2mm, the lower end coincides with the electrode end face, and the upper end coincides with the lower surface of the cavity.

[0033] The ring-shaped permanent magnet 4 is fixed to the bottom of the electrode cap 1 by an interference fit. The cross-sectional width of the ring-shaped permanent magnet 4 is 3mm, and its inner diameter forms an interference fit with the electrode cap body.

[0034] The lower end face of the ring-shaped permanent magnet 4 is higher than the lowest point of the electrode end face, ensuring that the lowest point of the electrode end face contacts the workpiece to be welded first during welding, and the outer edge is chamfered C2.

[0035] The electrode cap 1 is made of chromium zirconium copper, and the diameter of the electrode end face is 6mm.

[0036] In this embodiment, the workpiece 5 to be welded is galvanized high-strength steel DP590+Z, with a thickness matching of 2mm+2mm.

[0037] like Figure 1 As shown in b, the cooling water is in direct contact with the thin-walled, high-resistivity magnetic interlayer 2, and its flow direction is shown in 6, which makes the convective heat transfer more complete and improves the heat dissipation capacity.

[0038] like Figure 2 As shown, the thin-walled, high-resistivity magnetically conductive interlayer 2 in this embodiment is a single-layer columnar hollow interlayer used to constrain the magnetic field distribution, so that the magnetic field is concentrated in the melting nucleus region.

[0039] like Figure 3 As shown, under the action of the thin-walled, high-resistivity magnetic interlayer 2, the current density distribution between the electrode end face and the workpiece to be welded becomes that the current density is high outside the interlayer and low inside the interlayer.

[0040] like Figure 5As shown, in this embodiment, the lower surface of the annular permanent magnet 4 is higher than the lowest point of the electrode end face, so as to ensure that after the electrode end face contacts the workpiece 5 to be welded during welding, the lower surface of the annular permanent magnet 4 can also press the workpiece 5 to be welded, thereby reducing spatter.

[0041] like Figure 6 As shown, the annular permanent magnet is axially magnetized, with the lower part, i.e., the side near the plate, being the N pole; and the upper part, i.e., the side near the electrode rod, being the S pole. The corresponding lower electrode device has the same electrode cap and permanent magnet unit, with the magnetization direction being the upper part, i.e., the side near the plate, being the N pole; and the lower part, i.e., the side near the electrode rod, being the S pole.

[0042] In this embodiment, a welding alternating current of 9kA, a welding pressure of 3kN, a pre-pressure time of 100ms, a welding time of 270ms, and a holding pressure time of 250ms were used. A WTC steel welding machine was used to compare the surface quality of an improved resistance welding electrode cap that can reduce the surface unevenness of galvanized weld points and an ordinary chromium-zirconium-copper resistance welding electrode cap with the same diameter, using the same welding process parameters, namely a welding current of 9kA, a time of 270ms, and a pressure of 3kN. The results are shown in Table 1.

[0043] Table 1

[0044] like Figure 7 As shown in a and b, the galvanized weld indentation obtained using a regular electrode cap under the above welding process parameters exhibits obvious spatter and zinc protrusion, while the galvanized weld indentation obtained using a resistance welding electrode cap that reduces surface unevenness of the galvanized weld shows no spatter or zinc protrusion. Meanwhile, as... Figure 8 As shown in Figure a, the surface indentation depth of the galvanized weld joint obtained by using a resistance welding electrode cap that reduces surface unevenness of the galvanized weld joint is reduced by an average of 40.4% compared to the surface indentation depth of a conventional electrode cap. Compared to existing technologies, the magnetic control technology used in this embodiment does not require any device to be applied to the outside of the electrode rod and is not constrained by station limitations. The magnetic field generated by the annular permanent magnet is concentrated inside the weld nugget area under the guidance of the magnetically conductive interlayer, reducing the waste of magnetic force. Example 2

[0045] The difference from Example 1 is that the thin-walled, high-resistivity magnetic interlayer in this example can be adjusted in shape and thickness according to different requirements for current density distribution and heat conduction. For example, different shapes can be set while ensuring that the cross-sectional shape at any position is circular. Three recommended shapes are as follows: Figure 9 As shown.

[0046] The surface indentation can be further reduced by adjusting the thickness of the thin-walled, high-resistivity magnetic interlayer. Specifically, when the thickness of the thin-walled, high-resistivity magnetic interlayer increases, the resistivity of the interlayer increases, the current density in the copper core of the central electrode further decreases, the heat generation in the central part decreases, and the thickness of the molten core in the central part further decreases, thus further reducing the surface indentation.

[0047] Table 2 shows the recommended thickness of the corresponding thin-walled, high-resistivity magnetic interlayer for welding common galvanized steel sheet combinations (same sheet type).

[0048] Table 2

[0049] Electrode caps with different shapes of thin-walled, high-resistivity magnetically conductive interlayers can achieve the same effects as in Example 1 in reducing surface indentation, spattering, zinc protrusion, and magnetic field concentration. Figure 8 As shown in b. Example 3

[0050] The difference between this embodiment and Embodiments 1 and 2 is that the width of its annular permanent magnet unit can be adjusted according to different electrode end face sizes to achieve ideal splashing and zinc protrusion control effects. The specific dimensions are shown in Table 3.

[0051] Table 3

[0052] Compared with the prior art, this embodiment has the same effect as embodiments 1 and 2, which can effectively reduce surface indentation, reduce splashing, guide and concentrate the magnetic field, and solve the zinc protrusion problem.

[0053] Compared with existing technologies, this invention solves the zinc bulge problem by flattening the molten zinc-barium annular permanent magnet during welding and effectively suppresses external spatter. During welding, the thin-walled, high-resistivity magnetic interlayer changes the current density inside the electrode cap, forming a special annular weld nugget. This reduces the maximum indentation depth on the surface without significantly increasing the indentation diameter.

[0054] The above-described specific implementations can be partially adjusted by those skilled in the art in different ways without departing from the principles and purpose of the present invention. The scope of protection of the present invention is defined by the claims and is not limited to the above-described specific implementations. All implementation schemes within the scope of the claims are bound by the present invention.

Claims

1. An improved resistance welding electrode cap, which is disposed at the end of an electrode rod, characterized in that, include: An annular permanent magnet is located at the outer edge of the end, a thin-walled, high-resistivity magnetically conductive interlayer and an electrode copper core are sequentially arranged inside the electrode cap, and a cavity at the top for cooling water to flow through. The upper end of the thin-walled, high-resistivity magnetically conductive interlayer is in contact with the cooling water in the cavity, and the lower end is flush with the end face of the electrode cap and the annular permanent magnet. Three current density distribution regions are formed between the electrode end face and the workpiece to be welded: the annular permanent magnet region with the lowest current density, the interlayer region, and the permanent magnet region with the highest current density, and the interlayer region.

2. The improved resistance welding electrode cap according to claim 1, characterized in that, The thin-walled, high-resistivity magnetic interlayer is a single-layer columnar hollow interlayer with a thickness of less than or equal to 0.5 mm of high-resistivity magnetic material and an inner diameter less than or equal to half the diameter of the electrode end face.

3. The improved resistance welding electrode cap according to claim 1 or 2, characterized in that, The axis of the thin-walled, high-resistivity magnetic interlayer coincides with the central axis of the electrode cap body.

4. The improved resistance welding electrode cap according to claim 1, characterized in that, The electrode copper core and the inner diameter of the thin-walled, high-resistivity magnetically conductive interlayer form an interference fit, and the central axis of the electrode copper core coincides with the central axis of the thin-walled, high-resistivity magnetically conductive interlayer and the electrode cap body.

5. The improved resistance welding electrode cap according to claim 1, characterized in that, The lower surface of the ring-shaped permanent magnet is higher than the electrode end face. During the welding process, the electrode end face first contacts the plate and deforms, and then the ring-shaped permanent magnet presses against the edge of the welding area.

6. The improved resistance welding electrode cap according to claim 1 or 5, characterized in that, The axis of the ring-shaped permanent magnet coincides with the axis of the electrode cap, the electrode copper core, and the thin-walled, high-resistivity magnetically conductive interlayer, so that the magnetically conductive interlayer can gather and guide the magnetic field to the melting nucleus region, thereby enhancing the effective radial magnetic field strength of the melting nucleus region.

7. The improved resistance welding electrode cap according to claim 1 or 5, characterized in that, The magnetization direction of the annular permanent magnet is along the axial or radial direction of the electrode rod. If the electrode cap is arranged on one side, that is, only one electrode cap or both electrode caps are set on the same side of the workpiece to be welded, the annular permanent magnet unit is a combination of magnet units that are magnetized axially. If the electrode cap is arranged on both sides, that is, the two electrode caps are set on the upper and lower sides of the workpiece to be welded respectively, and the annular permanent magnet units installed in the upper and lower electrode caps have the same polarity. During welding, the permanent magnets in the upper and lower electrodes face each other with the same pole and squeeze each other to generate a stronger radial magnetic field.

8. The improved resistance welding electrode cap according to claim 1 or 5, characterized in that, The magnetic field stirring refers to the following: the annular permanent magnet is made of high-temperature resistant neodymium iron boron with a demagnetization temperature greater than 80℃, a remanence greater than 0.8Br / T, and a coercivity greater than 500Hcb / kA / m. The permanent magnet unit needs to undergo surface insulating coating treatment to reduce conductivity.

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