Improved resistance welding electrode cap

Abstract

An improved resistance welding electrode cap is arranged at the end of the electrode rod, comprising: a ring-shaped permanent magnet arranged at the outer edge of the end, a thin-walled high-resistivity magnetic conductive interlayer and an electrode copper core arranged in the electrode cap in sequence, and a cavity arranged at the top end for circulating cooling water, the upper end of the thin-walled high-resistivity magnetic conductive interlayer is in contact with the cooling water in the cavity, the lower end is flush with the end face of the electrode cap and the ring-shaped permanent magnet, and three current density distribution areas are formed between the electrode end face and the workpiece to be welded, i.e. the ring-shaped permanent magnet area with the smallest current density, the interlayer inner area, and the permanent magnet inner area and the interlayer outer area with the largest current density. By embedding the thin-walled high-resistivity magnetic conductive interlayer in the electrode cap, the current density distribution is changed to reduce the current density of the central part of the electrode, thereby reducing the heat generation in the central area while ensuring the heat generation in the central area, reducing the maximum indentation depth of the central area, and reducing the surface indentation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of resistance welding, and particularly relates to an improved resistance welding electrode cap capable of reducing unevenness of a galvanized welding point surface. BACKGROUND

[0002] In addition to reducing the surface indentation depth, the existing resistance welding electrode cap also needs to control the zinc protrusion phenomenon of the galvanized welding point surface. Since the existing resistance spot welding electrode cap does not change the internal current density distribution of the electrode cap by changing the internal structure of the electrode cap, some liquid zinc is expelled to the surrounding and quickly solidified by heat dissipation during the welding process due to the action of the welding current and the electrode pressure, forming a zinc ring and causing unevenly distributed protruding parts in the zinc ring, i.e. zinc protrusion. SUMMARY

[0003] The present application proposes an improved resistance welding electrode cap to solve the above problems in the prior art. The improved resistance welding electrode cap is provided with a ring-shaped permanent magnet at the edge end of the electrode cap and a thin-walled high-resistivity magnetic conductive interlayer in the interior, so that the current density of the center and the outer part of the electrode is reduced, the heat generation in the center and the outer part is reduced while the overall heat generation is ensured, the maximum surface indentation depth of the center area is reduced, and the irregular zinc protrusion in the outer area is improved.

[0004] The present application is implemented by the following technical solutions:

[0005] The present application relates to an improved resistance welding electrode cap arranged at the end of an electrode rod, which comprises a ring-shaped permanent magnet arranged at the outer edge of the end, a thin-walled high-resistivity magnetic conductive interlayer and an electrode copper core arranged in the interior of the electrode cap in sequence, and a cavity arranged at the top end for flowing cooling water. The upper end of the thin-walled high-resistivity magnetic 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 ring-shaped permanent magnet. Three current density distribution areas are formed between the electrode end face and the workpiece to be welded, i.e. the ring-shaped permanent magnet area with the smallest current density, the interlayer interior area, and the permanent magnet interior and interlayer exterior area with the largest current density. The lower end face of the ring-shaped permanent magnet is slightly higher than the electrode end face and reduces the nugget thickness by stirring through the magnetic field of the ring-shaped permanent magnet, thereby significantly reducing the indentation depth and the surface zinc protrusion.

[0006] The upper end of the thin-walled high-resistivity magnetic 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 ring-shaped permanent magnet.

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

[0008] The axis of the thin-walled high-resistivity magnetic conductive 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 is in interference fit with the inner diameter of the thin-wall high-resistivity magnetic conductive interlayer, and the central axis of the electrode copper core coincides with the central axes of the thin-wall high-resistivity magnetic 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 direction or the radial direction of the electrode rod. If the electrode cap is arranged on one side, that is, only one electrode cap is arranged or both electrode caps are arranged on the same side of the workpiece to be welded, the annular permanent magnet unit is an axial magnetization magnet unit combination. If the electrode cap is arranged on two sides, that is, the two electrode caps are arranged on the upper and lower surfaces of the workpiece to be welded, the annular permanent magnet units installed in the upper and lower electrode caps have the same polarity, and the permanent magnets in the upper and lower electrodes have the same polarity and are pressed against each other to generate a stronger radial magnetic field during welding.

[0012] The axis of the annular permanent magnet coincides with the axes of the electrode cap body, the electrode copper core and the thin-wall high-resistivity magnetic conductive interlayer, so that the magnetic conductive interlayer can gather and guide the magnetic field to the fusion nucleus action area, and the effective radial magnetic field strength of the fusion nucleus area is enhanced.

[0013] The lower end surface of the annular permanent magnet is slightly higher than the electrode end surface, that is, the lower end surface of the annular permanent magnet is higher than the lowest point of the electrode end surface, so that the lowest point of the electrode end surface contacts the workpiece to be welded first during welding, the annular permanent magnet is pressed against the plate, and the effect of locking the welding area is achieved, thereby overcoming the splashing and zinc bulging phenomena during welding. The specific height difference can be adjusted according to the type and mechanical properties of the workpiece to be welded.

[0014] The magnetic field stirring refers to that the annular permanent magnet preferably adopts high-temperature-resistant neodymium iron boron, the demagnetization temperature of which is greater than 80 DEG C, the residual magnetic strength thereof is greater than 0.8 Br / T, and the coercive force thereof is greater than 500 Hcb / kA / m. The permanent magnet unit needs to be treated with a surface insulating coating to reduce the electrical conductivity.

[0015] Technical effects

[0016] The electrode end surface combination structure is improved, and the thin-wall high-resistivity magnetic conductive interlayer is arranged, so that the outer edge of the permanent magnet structure at the outer edge of the electrode end surface can press the welding area during welding, thereby flattening the outside zinc bulging and reducing splashing, and the thickness of the fusion nucleus and the surface indentation can be reduced under the action of the magnetic field. The thin-wall high-resistivity magnetic conductive interlayer can change the current density distribution in the electrode cap while ensuring the magnetic control technical effect and the heat conduction effect, thereby reducing the heat generation in the center and the outside area while ensuring the overall heat generation, and further reducing the maximum indentation depth in the center area. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1Structure diagram of the present application;

[0018] Figure: a is the working diagram of the electrode cap device, b is the front view of the electrode cap device; 1 electrode cap, 2 thin-walled high-resistivity magnetic conductive interlayer, 3 copper core inside the interlayer electrode, 4 annular permanent magnet, 5 workpiece to be welded, 6 cooling water flow direction;

[0019] Figure 2 Thin-walled high-resistivity magnetic conductive interlayer inside the electrode cap of Example 1;

[0020] Figure: a is the front view of the magnetic conductive interlayer, b is the left view of the magnetic conductive interlayer, c is the top view of the magnetic conductive interlayer, d is the front three-axis view of the magnetic conductive interlayer;

[0021] Figure 3 The schematic diagram of the current density distribution between the electrode end face and the workpiece to be welded of Example 1;

[0022] Figure 4 Annular permanent magnet unit of Example 1;

[0023] Figure: a is the front view of the annular permanent magnet, b is the left view of the annular permanent magnet, c is the top view of the annular permanent magnet, d is the front three-axis view of the annular permanent magnet;

[0024] Figure 5 The schematic diagram of the height difference between the electrode end face and the lower surface of the annular permanent magnet of Example 1;

[0025] Figure 6 The schematic diagram of the magnetic field formed by the magnetic field source of Example 1;

[0026] Figure 7 The comparative diagram of the zinc convexity and spatter of the weld surface indentation of Example 1;

[0027] Figure: a is the weld surface indentation of the ordinary resistance spot welding electrode cap, b is the weld surface indentation of the 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 the ordinary resistance spot welding electrode cap, ii is the zinc convexity defect in the weld surface indentation of the ordinary resistance spot welding electrode cap;

[0028] Figure 8 The comparative diagram of the weld indentation depth of Examples 1, 2 and 3;

[0029] Figure: a is the weld indentation depth comparative diagram of Example 1, b is the weld indentation depth comparative diagram of Example 2 shape 2, c is the weld indentation depth comparative diagram of Example 3; i is the weld indentation depth curve of the ordinary resistance spot welding electrode cap in the weld indentation depth comparative diagram, ii is the weld indentation depth curve of the resistance welding electrode cap that can reduce the unevenness of the galvanized weld surface;

[0030] Figure 9This is a front view of a thin-walled, high-resistivity magnetic interlayer with different shapes, as shown in Example 2. Detailed Implementation

[0031] Example 1

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] The electrode cap 1 is made of chromium zirconium copper, and the diameter of the electrode end face is 6mm.

[0038] In this embodiment, the workpiece 5 to be welded is galvanized high-strength steel DP590+Z, with a thickness matching of 2mm+2mm.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] Table 1

[0046]

[0047] 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.

[0048] Example 2

[0049] 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.

[0050] By adjusting the thickness of the thin-walled large-resistivity magnetic conductive interlayer, the surface indentation is further reduced, specifically: when the thickness of the thin-walled large-resistivity magnetic conductive interlayer increases, the resistivity of the interlayer increases, the current density in the center electrode copper core is further reduced, the heat generation in the center part is reduced, the thickness of the center part of the nugget is further reduced, and the surface indentation is further reduced.

[0051] The corresponding thin-walled large-resistivity magnetic conductive interlayer thickness recommendation when welding the common galvanized steel plate combination (the same plate type) is shown in Table 2

[0052] Table 2

[0053]

[0054] The electrode cap with different thin-walled large-resistivity magnetic conductive interlayer shapes can achieve the same effect as Example 1 in reducing surface indentation, reducing spatter and zinc bulging phenomenon, and guiding and concentrating magnetic field, as shown in Figure 8 b.

[0055] Example 3

[0056] The difference between this embodiment and Examples 1 and 2 is that the width of the annular permanent magnet unit can be adjusted according to different electrode end face sizes to achieve the desired spatter, zinc bulging control effect, and the specific size is shown in Table 3.

[0057] Table 3

[0058]

[0059] Compared with the prior art, this embodiment has the same effect as Examples 1 and 2, which can effectively reduce surface indentation, reduce spatter phenomenon, guide and concentrate magnetic field, and solve the problem of zinc bulging.

[0060] Compared with the prior art, the present application solves the problem of zinc bulging by flattening the zinc barium annular permanent magnet melted during welding, and effectively suppresses the external spatter. During welding, the thin-walled large-resistivity magnetic conductive interlayer changes the current density inside the electrode cap, forming a special annular nugget, which reduces the maximum surface indentation depth without significantly increasing the surface indentation diameter.

[0061] The above specific embodiments can be adjusted in different ways by those skilled in the art without departing from the principles and purposes of the present application, and the protection scope of the present application is subject to the claims and is not limited by the above specific embodiments, and each implementation within the scope is subject to the constraints of the present application.

Claims

1. An improved resistance welding electrode cap, which is provided at the end of an electrode rod, characterized in that, The application relates to a welding electrode, which comprises a ring-shaped permanent magnet arranged at the outer edge of the end, a thin-wall high-resistivity magnetic-conducting interlayer and an electrode copper core arranged in the electrode cap in sequence, and a cavity arranged at the top end for flowing cooling water, the upper end of the thin-wall high-resistivity magnetic-conducting interlayer is in contact with the cooling water in the cavity, the lower end is flush with the end surface of the electrode cap and the ring-shaped permanent magnet, and three current density distribution areas are formed between the electrode end surface and the workpiece to be welded, i.e. a ring-shaped permanent magnet area with the minimum current density, an internal area of the interlayer, and an internal area of the permanent magnet and an external area of the interlayer with the maximum current density. The thin-wall high-resistivity magnetic-conducting interlayer is a single-layer columnar hollow interlayer, the thickness of the high-resistivity magnetic-conducting material is less than or equal to 0.5 mm, and the inner diameter is less than or equal to half of the diameter of the electrode end surface.

2. The improved resistance welding electrode cap of claim 1 wherein, The axis of the thin-wall high-resistivity magnetic-conducting interlayer is coincident with the central axis of the electrode cap body.

3. The improved resistance welding electrode cap of claim 1 or 2, wherein, The electrode copper core is in interference fit with the inner diameter of the thin-wall high-resistivity magnetic-conducting interlayer, and the central axis of the electrode copper core is coincident with the central axes of the thin-wall high-resistivity magnetic-conducting interlayer and the electrode cap body.

4. The improved resistance welding electrode cap of claim 1 wherein, The lower surface of the ring-shaped permanent magnet is higher than the electrode end surface, the electrode end surface is first in contact with the plate to produce deformation in the welding process, and the ring-shaped permanent magnet is then pressed against the edge of the welding area.

5. The improved resistance welding electrode cap of claim 1 wherein, The axis of the ring-shaped permanent magnet is coincident with the axes of the electrode cap, the electrode copper core and the thin-wall high-resistivity magnetic-conducting interlayer, so that the magnetic-conducting interlayer can gather and guide the magnetic field to the molten core action area and enhance the effective radial magnetic field strength of the molten core area.

6. The improved resistance welding electrode cap of claim 1 or 5 wherein, The magnetization direction of the ring-shaped permanent magnet is along the axial direction or the radial direction of the electrode rod; if the electrode cap is arranged on one side, i.e. only one electrode cap is arranged or both electrode caps are arranged on the same side of the workpiece to be welded, the ring-shaped permanent magnet unit is a combination of axial magnetization magnet units; if the electrode cap is arranged on two sides, i.e. two electrode caps are arranged on the upper and lower surfaces of the workpiece to be welded, the ring-shaped permanent magnet units installed in the upper and lower electrode caps have the same polarity, the permanent magnets in the upper and lower electrodes are opposite in polarity during welding, and a stronger radial magnetic field is generated by mutual extrusion.

7. The improved resistance welding electrode cap of claim 1 or 5 wherein, The ring-shaped permanent magnet is made of high-temperature-resistant neodymium iron boron, the demagnetization temperature of which is greater than 80 DEG C, the residual magnetism intensity is greater than 0.8 Br / T, and the coercive force is greater than 500 Hcb / kA / m; the permanent magnet unit needs to be treated by a surface insulation coating to reduce the conductivity.

8. The improved resistance welding electrode cap of claims 1 or 5, wherein, ​

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