Electrode cap for resistance spot welding

Abstract

The application discloses an electrode cap for resistance spot welding, which comprises a front end part, a trunk part and a transition part. The front end part is the part that first contacts the material to be welded during welding, and the outer arc surface of the front end part is formed by rotating a preset circular arc as a generatrix and taking the central axis of the electrode cap as a rotation center. The bottom of the trunk part is provided with a cavity, and the electrode cap is assembled with an electrode rod through the cavity. The outer cylindrical surface of the trunk part is formed by rotating a preset straight line as a generatrix and taking the central axis of the electrode cap as a rotation center. One end of the transition part is connected with the front end part, and the other end of the transition part is connected with the top of the trunk part. The outer arc surface of the transition part is formed by rotating a preset arc line as a generatrix and taking the central axis of the electrode cap as a rotation center, and the preset circular arc and the preset arc line are tangent. The application solves the technical problem of brittle cracks of liquid metal in the welding joint.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of welding, and particularly relates to an electrode cap for resistance spot welding. BACKGROUND

[0002] Resistance spot welding is the most widely used welding process in vehicle body welding. In resistance spot welding, resistance heat generated by the electrode cap is used to melt the welding material, so as to form a spot joint between the welding materials, and then complete the welding.

[0003] Advanced high-strength steel is an important material for realizing automobile lightweighting and ensuring automobile safety. In the resistance spot welding process of galvanized high-strength steel plates, liquid metal embrittlement (LME) cracking phenomenon caused by liquid zinc occurs. One of the reasons is that the electrode cap itself has a design problem, and the spot joint surface in contact with the electrode cap is prone to stress concentration, which causes deep electrode indentation on the spot joint surface, and then leads to the liquid metal embrittlement cracking phenomenon. The liquid metal embrittlement cracking will reduce the mechanical properties of the spot joint, making it difficult to ensure product quality and affecting the practical application of advanced high-strength steel. Therefore, the existence of liquid metal embrittlement cracking in the spot joint is a technical problem to be solved. SUMMARY

[0004] The electrode cap for resistance spot welding provided by the embodiments of the application solves the technical problem of liquid metal embrittlement cracking in the spot joint.

[0005] In a first aspect, the embodiments of the application provide an electrode cap for resistance spot welding, which comprises: a front end portion, the front end portion being a portion that first contacts the welding material during welding, an outer shape of the front end portion being an arc surface formed by rotating a preset circular arc as a generatrix and a central axis of the electrode cap as a rotation center; a trunk portion, a bottom of the trunk portion being provided with a cavity, the electrode cap being assembled with an electrode rod through the cavity, an outer shape of the trunk portion being a cylinder formed by rotating a preset straight line as a generatrix and the central axis of the electrode cap as a rotation center; and a transition portion, one end of the transition portion being connected with the front end portion, the other end of the transition portion being connected with a top of the trunk portion, an outer shape of the transition portion being an arc surface formed by rotating a preset arc line as a generatrix and the central axis of the electrode cap as a rotation center, the preset circular arc and the preset arc line being tangent.

[0006] In combination with the first aspect of the application, in some embodiments, the preset arc line is tangent to the preset straight line.

[0007] In some embodiments of the first aspect of the application, the first curvature radius of the preset arc is 40-500 mm, and the chord length of the outer arc surface of the front end portion is 5-12 mm.

[0008] In some embodiments of the first aspect of the application, the cylindrical outer diameter of the trunk portion is 12-20 mm, and the total length of the electrode cap is 20-30 mm.

[0009] In some embodiments of the first aspect of the application, the preset arc is a constant-curvature arc, and the second curvature radius of the preset arc satisfies the following relationship:

[0010] [R1×(D2-D1)] / (2R1-D1)≤R2<R1;

[0011] wherein R1 is the first curvature radius, R2 is the second curvature radius, D1 is the chord length, and D2 is the cylindrical outer diameter.

[0012] In some embodiments of the first aspect of the application, the geometric dimensions of the electrode cap satisfy the following relationship:

[0013] (R1-R2) / R1=2A / D1;

[0014] (R1-L+B) 2 +A 2 =(R1-R2) 2 ;

[0015] wherein R1 is the first curvature radius, R2 is the second curvature radius, D1 is the chord length, L is the total length of the electrode cap, A is the distance between the center of the preset arc and the central axis of the electrode cap, and B is the distance between the center of the preset arc and the bottom end of the electrode cap.

[0016] In some embodiments of the first aspect of the application, the preset arc is a variable-curvature arc.

[0017] In some embodiments of the first aspect of the application, the variable-curvature arc is an Archimedes spiral, which is represented by a Cartesian coordinate equation of polar coordinate transformation as follows:

[0018] x(θ)=a×θ×sin(θ);

[0019] y(θ)=a×θ×cos(θ);

[0020] wherein a and θ are both parameters of the Cartesian coordinate equation.

[0021] In combination with the first aspect of the present application, in some embodiments, the geometric size of the electrode cap satisfies the following relationship:

[0022]

[0023] a≥(D2-D1)÷(2θ×sin(θ));

[0024] wherein the a and the θ are parameters of the Cartesian coordinate equation, D1 is the chord length, D2 is the outer diameter of the cylinder, and R1 is the first radius of curvature.

[0025] In combination with the first aspect of the present application, in some embodiments, the material of the electrode cap is a copper alloy, the copper alloy includes at least one of chromium, zirconium and aluminum, in the case that the copper alloy includes chromium, the content of chromium is 0.5% to 1.5%; in the case that the copper alloy includes zirconium, the content of zirconium is 0.2% to 1.0%; in the case that the copper alloy includes aluminum, the content of aluminum is 0.3% to 1.0%.

[0026] The one or more technical solutions provided in the embodiments of the present application at least achieve the following technical effects or advantages:

[0027] The electrode cap for resistance spot welding in the embodiments of the present application comprises: a front end portion, which is a portion that first contacts a material to be welded during welding, and the outer shape curved surface of the front end portion is formed by rotating a preset circular arc as a generatrix and taking the central axis of the electrode cap as a rotation center; a trunk portion, which is provided with a cavity at the bottom, and the electrode cap is assembled with an electrode rod through the cavity, and the outer shape cylinder of the trunk portion is formed by rotating a preset straight line as a generatrix and taking the central axis of the electrode cap as a rotation center; and a transition portion, one end of which is connected with the front end portion and the other end of which is connected with the top of the trunk portion, and the outer shape curved surface of the transition portion is formed by rotating a preset arc line as a generatrix and taking the central axis of the electrode cap as a rotation center, and the preset circular arc and the preset arc line are tangent. The outer shape curved surface of the front end portion is formed by rotating a preset circular arc as a generatrix and taking the central axis of the electrode cap as a rotation center, the outer shape curved surface of the transition portion is formed by rotating a preset arc line as a generatrix and taking the central axis of the electrode cap as a rotation center, and the preset circular arc and the preset arc line are tangent, so that the transition between the front end portion and the transition portion of the electrode cap is continuous, the shape of the electrode cap is avoided from being suddenly changed, the possibility of stress concentration on the surface of a spot joint is reduced, the possibility of a deep electrode indentation on the surface of the spot joint is reduced, and the possibility of brittle cracks of liquid metal in the spot joint is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiments description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those of ordinary skill in the art without any creative effort based on these drawings.

[0029] Figure 1 A schematic diagram of the electrode cap for resistance spot welding in the embodiments of the present application.

[0030] Figure 2 A schematic diagram of the various dimensions of the electrode cap for resistance spot welding in the embodiments of the present application when the preset arc line is a constant-curvature circular arc.

[0031] Figure 3 A plurality of schematic diagrams of the geometric dimension features of the electrode cap for resistance spot welding in the embodiments of the present application when the preset arc line is a constant-curvature circular arc.

[0032] Figure 4 A schematic diagram of the Archimedes spiral in the embodiments of the present application.

[0033] Figure 5 A plurality of schematic diagrams of the geometric dimension features of the electrode cap for resistance spot welding in the embodiments of the present application when the preset arc line is an Archimedes spiral. DETAILED DESCRIPTION

[0034] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without any creative effort fall within the scope of protection of the present application.

[0035] In the present application, the description such as "first", "second", etc. is only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the fact that the technical solutions can be realized by those of ordinary skill in the art. When the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, and is not within the scope of protection claimed by the present application.

[0036] Figure 1 A schematic diagram of the electrode cap for resistance spot welding in the embodiments of the present application. Reference Figure 1As shown, the electrode cap provided by the embodiment of the present application comprises: a front end part 10, which is the part first contacted with the material to be welded when welding, and the profiled arc surface of the front end part 10 is formed by rotating a preset circular arc 110 as a generatrix and the central axis 40 of the electrode cap as a rotation center; a trunk part 20, which is provided with a cavity 210 at the bottom, and the electrode cap is assembled with the electrode rod through the cavity 210, and the profiled cylinder of the trunk part 20 is formed by rotating a preset straight line 220 as a generatrix and the central axis 40 of the electrode cap as a rotation center; and a transition part 30, one end of which is connected with the front end part 10 and the other end of which is connected with the top of the trunk part 20, and the profiled arc surface of the transition part 30 is formed by rotating a preset arc line 310 as a generatrix and the central axis 40 of the electrode cap as a rotation center, and the preset circular arc 110 and the preset arc line 310 are tangent.

[0037] In some embodiments, the preset arc line 310 is tangent to the preset straight line 220.

[0038] It should be noted that, in the case that the preset circular arc 110 and the preset arc line 310 are tangent, the preset arc line 310 is further limited to be tangent to the preset straight line 220, so that the transition of the geometric profile of the electrode cap is more continuous, further reducing the possibility of stress concentration on the surface of the welded joint and the possibility of deep electrode indentation on the surface of the welded joint, and further reducing the possibility of liquid metal brittle crack of the welded joint. Therefore, the mechanical properties of the welded joint are further improved.

[0039] In some embodiments, the first curvature radius of the preset circular arc 110 is 40-500 mm, and the chord length of the profiled arc surface of the front end part 10 is 5-12 mm.

[0040] In some embodiments, the cylindrical outer diameter of the trunk part 20 is 12-20 mm, and the total length of the electrode cap is 20-30 mm.

[0041] In some embodiments, the preset arc line 310 can be a constant-curvature circular arc, and the second curvature radius of the preset arc line 310 satisfies the following relationship:

[0042] [R1×(D2-D1)] / (2R1-D1)≤R2<R1;

[0043] Wherein, as shown in the accompanying drawings, Figure 1 As shown, R1 is the first curvature radius, R2 is the second curvature radius, D1 is the chord length, and D2 is the cylindrical outer diameter.

[0044] As shown in the accompanying drawings, Figure 2 As shown, Figure 2This is a schematic diagram illustrating the dimensions of the electrode cap for resistance spot welding in an embodiment of the present invention when the preset arc 310 is a circular arc of constant curvature. When the preset arc 310 is a circular arc of constant curvature, the geometric dimensions of the electrode cap satisfy the following relationship:

[0045] (R1-R2) / R1 = 2A / D1;

[0046] (R1-L+B) 2 +A 2 =(R1-R2) 2 ;

[0047] Among them, reference Figure 1 and Figure 2 As shown, R1 is the first radius of curvature, R2 is the second radius of curvature, D1 is the chord length, L is the total length of the electrode cap, A is the distance between the center of the circle corresponding to the preset arc 310 and the central axis 40 of the electrode cap, and B is the distance between the center of the circle corresponding to the preset arc 310 and the bottom of the electrode cap.

[0048] It should be noted that by limiting the aforementioned geometric dimensions and the second radius of curvature, the geometric shape of the electrode cap is further optimized, thereby improving the mechanical properties of the solder joint. It should also be noted that if [R1×(D2-D1)] / (2R1-D1)=R2, it ensures that the preset arc 310 is tangent to the preset straight line 220, and that the preset circular arc 110 is tangent to the preset arc 310. Furthermore, through multiple physical verifications, it has been shown that when the second radius of curvature is smaller than the first radius of curvature, the mechanical properties of the solder joint are significantly improved.

[0049] refer to Figure 3 As shown, Figure 3 These are various schematic diagrams illustrating the geometric dimensions of the electrode cap for resistance spot welding in embodiments of the present invention when the preset arc is a circular arc with a constant curvature.

[0050] Figure 3 (a) The electrode cap shown has a total length of 23 mm, a chord length of 6 mm for the outer arc surface of the front end portion 10, a first radius of curvature of 40 mm, an outer diameter of 16 mm, a second radius of curvature of 5.41 mm, a distance of 2.59 mm between the center of the preset arc 310 and the central axis 40 of the electrode cap, and a distance of 17.5 mm between the center of the preset arc 310 and the bottom of the electrode cap. In this embodiment, the transition portion 30 of the electrode cap is tangent to both the front end portion 10 and the torso portion 20.

[0051] Figure 3(b) the electrode cap shown, the total length of the electrode cap is 23 mm, the chord length of the outer arc surface of the front end portion 10 is 6 mm, the first curvature radius is 80 mm, the outer diameter of the cylinder is 16 mm, the second curvature radius is 5.19 mm, the distance between the center of the preset arc line 310 and the central axis 40 of the electrode cap is 2.81 mm, the distance between the center of the preset arc line 310 and the bottom end of the electrode cap is 17.75 mm, and the transition portion 30 of the electrode cap in this embodiment is tangent to the front end portion 10 and the trunk portion 20 at the same time.

[0052] Figure 3 (c) the electrode cap shown, the total length of the electrode cap is 23 mm, the chord length of the outer arc surface of the front end portion 10 is 6 mm, the first curvature radius is 40 mm, the outer diameter of the cylinder is 16 mm, the second curvature radius is 12 mm, the distance between the center of the preset arc line 310 and the central axis 40 of the electrode cap is 2.10 mm, the distance between the center of the preset arc line 310 and the bottom end of the electrode cap is 10.92 mm, and the transition portion 30 of the electrode cap in this embodiment is tangent to the front end portion 10.

[0053] Figure 3 (d) the electrode cap shown, the total length of the electrode cap is 23 mm, the chord length of the outer arc surface of the front end portion 10 is 8 mm, the first curvature radius is 40 mm, the outer diameter of the cylinder is 16 mm, the second curvature radius is 4.44 mm, the distance between the center of the preset arc line 310 and the central axis 40 of the electrode cap is 3.56 mm, the distance between the center of the preset arc line 310 and the bottom end of the electrode cap is 18.38 mm, and the transition portion 30 of the electrode cap in this embodiment is tangent to the front end portion 10 and the trunk portion 20 at the same time.

[0054] Figure 3 (e) the electrode cap shown, the total length of the electrode cap is 23 mm, the chord length of the outer arc surface of the front end portion 10 is 8 mm, the first curvature radius is 80 mm, the outer diameter of the cylinder is 16 mm, the second curvature radius is 4.21 mm, the distance between the center of the preset arc line 310 and the central axis 40 of the electrode cap is 3.79 mm, the distance between the center of the preset arc line 310 and the bottom end of the electrode cap is 18.69 mm, and the transition portion 30 of the electrode cap in this embodiment is tangent to the front end portion 10 and the trunk portion 20 at the same time.

[0055] Figure 3(f) the electrode cap shown, the total length of the electrode cap is 23 mm, the chord length of the arc-shaped outer shape of the front end portion 10 is 8 mm, the first curvature radius is 80 mm, the cylindrical outer diameter is 16 mm, the second curvature radius is 12 mm, the distance between the center of the preset arc 310 corresponding arc and the central axis 40 of the electrode cap is 3.40 mm, the distance between the center of the preset arc 310 corresponding arc and the bottom end of the electrode cap is 10.91 mm, and the transition portion 30 of the electrode cap in the embodiment is tangent to the front end portion 10.

[0056] In some embodiments, the preset arc 310 can be a variable curvature arc. The variable curvature arc can be an Archimedes spiral, which can be expressed by the following Cartesian coordinate equation of polar coordinate transformation:

[0057] x(θ)=a×θ×sin(θ);

[0058] y(θ)=a×θ×cos(θ);

[0059] wherein a and θ are parameters of the Cartesian coordinate equation. Specifically, a is the distance moved by the moving point in each rotation period, which is a constant value, and θ is the angle of rotation of the ray.

[0060] In the case where the variable curvature arc is an Archimedes spiral, the geometric dimensions of the electrode cap satisfy the following relationships:

[0061]

[0062] a≥(D2-D1)÷(2θ×sin(θ));

[0063] wherein a and θ are parameters of the Cartesian coordinate equation, D1 is the chord length, D2 is the cylindrical outer diameter, and R1 is the first curvature radius.

[0064] It should be noted that by limiting the above geometric dimensions and limiting the variable curvature arc, the geometric shape of the electrode cap is further optimized, thereby improving the mechanical properties of the solder joint. Through multiple physical verifications, in the case where the preset arc 310 is a variable curvature arc, the mechanical properties of the solder joint of the present embodiment are significantly improved compared to the ordinary electrode cap formed solder joint.

[0065] Reference Figure 4 shown, Figure 4 is a schematic diagram of the Archimedes spiral in the embodiment of the present application. The point P on the Archimedes spiral is the tangent point of the preset arc 310 and the preset circular arc 110, and the origin of the coordinate system in which the Archimedes spiral is located is O. When the transition portion 30 is tangent to the trunk portion 20, the point O is the intersection point of the generatrix of the transition portion 30 and the generatrix of the trunk portion 20, i.e. the tangent point. Reference Figure 5 shown, Figure 5These are various schematic diagrams illustrating the geometric dimensions of the electrode cap for resistance spot welding in embodiments of the present invention when the preset arc is an Archimedean spiral.

[0066] Figure 5 The electrode cap shown in (a) has a total length of 23 mm, a chord length of 6 mm for the outer arc surface of the front end portion 10, a first radius of curvature of 40 mm, an outer diameter of 16 mm, and a rotation angle of θ at generatrix point P of the transition portion 30. p = 46.59°, x-coordinate of point P p The value is 5mm, and the ordinate of point P is y. p The diameter is 4.73 mm, the helix constant a = 8.47, and the transition portion 30 of the electrode cap in this embodiment is tangent to both the front end portion 10 and the torso portion 20.

[0067] Figure 5 (b) The electrode cap shown has a total length of 23 mm, a chord length of 6 mm for the outer arc surface of the front end portion 10, a first radius of curvature of 80 mm, an outer diameter of 16 mm, and a rotation angle of θ at generatrix point P of the transition portion 30. p = 47.94°, x-coordinate of point P p The value is 5mm, and the ordinate of point P is y. p The diameter is 4.51 mm, the helix constant a = 8.05, and the transition portion 30 of the electrode cap in this embodiment is tangent to both the front end portion 10 and the torso portion 20.

[0068] Figure 5 (c) shows an electrode cap with a total length of 23 mm, a chord length of 6 mm for the outer arc surface of the front end portion 10, a first radius of curvature of 40 mm, an outer diameter of 16 mm, and a rotation angle θ at generatrix point P of the transition portion 30. p = 46.59°, x-coordinate of point P p The value is 20mm, and the ordinate of point P is y. p The diameter is 18.92 mm, the helix constant a = 33.86, and the transition portion 30 of the electrode cap in this embodiment is tangent to the front end portion 10.

[0069] Figure 5 The electrode cap shown in (d) has a total length of 23 mm, a chord length of 8 mm for the outer arc surface of the front end portion 10, a first radius of curvature of 40 mm, an outer diameter of 16 mm, and a rotation angle of θ at generatrix point P of the transition portion 30. p = 45.69°, x-coordinate of point P p The value is 4mm, and the ordinate of point P is y. p The diameter is 3.90 mm, the helix constant a = 7.01, and the transition portion 30 of the electrode cap in this embodiment is tangent to both the front end portion 10 and the torso portion 20.

[0070] Figure 5 The electrode cap shown in (e) has a total length of 23 mm, a chord length of 8 mm for the outer arc surface of the front end portion 10, a first radius of curvature of 80 mm, an outer diameter of 16 mm, and a rotation angle of θ at generatrix point P of the transition portion 30. p = 47.94°, x-coordinate of point P p The value is 4mm, and the ordinate of point P is y. p The diameter is 3.67 mm, the helix constant a = 6.55, and the transition portion 30 of the electrode cap in this embodiment is tangent to both the front end portion 10 and the torso portion 20.

[0071] Figure 5 (f) shows an electrode cap with a total length of 23 mm, a chord length of 8 mm for the outer arc surface of the front end portion 10, a first radius of curvature of 80 mm, an outer diameter of 16 mm, and a rotation angle θ at generatrix point P of the transition portion 30. p = 47.94°, x-coordinate of point P p The value is 20mm, and the ordinate of point P is y. p The diameter is 18.34 mm, the helix constant a = 32.74, and the transition portion 30 of the electrode cap in this embodiment is tangent to the front end portion 10.

[0072] In some embodiments, the electrode cap is made of a copper alloy, which includes at least one of chromium, zirconium, and aluminum. When the copper alloy includes chromium, the chromium content is 0.5% to 1.5%; when the copper alloy includes zirconium, the zirconium content is 0.2% to 1.0%; and when the copper alloy includes aluminum, the aluminum content is 0.3% to 1.0%.

[0073] It should be noted that the advanced high-strength steel is an important material for realizing the light weight and safety of the automobile. In order to meet the corrosion resistance requirement of the material, the galvanizing treatment is performed on the surface of the high-strength steel during production. The resistance spot welding is the most widely used welding process in the welding of the automobile body. In order to obtain the mechanical properties superior to those of the traditional steel plate, the advanced high-strength steel inevitably has a higher alloy element content, which affects the welding performance. For example, in the resistance spot welding process of the galvanized high-strength steel plate, the LME (Liquid metal embrittlement) crack phenomenon caused by the liquid zinc occurs, resulting in a large number of cracks on the surface and inside of the welded joint, and the LME crack can cause the risk of the reduction of the mechanical properties of the welded joint. Therefore, this problem seriously affects the practical application of the advanced high-strength steel in the automobile. The shape and size of the electrode cap are important factors affecting the occurrence of the LME crack. If a dome radius (DR) type electrode cap having an end face with a diameter of φ6 or φ8 is used, the geometric shape transition between the front end portion 10 and the transition portion 30 of the electrode cap is discontinuous, which can cause the deep electrode indentation, the large stress concentration on the surface of the welded joint, and the LME crack in the portion.

[0074] The electrode cap for resistance spot welding in the embodiment of the application comprises: a front end portion 10, which is the portion first contacting the material to be welded during welding, and the outer arc surface of the front end portion 10 is formed by rotating a preset circular arc 110 as a generatrix and the central axis 40 of the electrode cap as a rotation center; a trunk portion 20, which is provided with a cavity 210 at the bottom, and the electrode cap is assembled with the electrode rod through the cavity 210, and the outer cylindrical surface of the trunk portion 20 is formed by rotating a preset straight line 220 as a generatrix and the central axis 40 of the electrode cap as a rotation center; and a transition portion 30, which is connected with the front end portion 10 at one end and connected with the top of the trunk portion 20 at the other end, and the outer arc surface of the transition portion 30 is formed by rotating a preset arc line 310 as a generatrix and the central axis 40 of the electrode cap as a rotation center, and the preset circular arc 110 and the preset arc line 310 are tangent. The outer arc surface of the front end portion 10 is formed by rotating the preset circular arc 110 as a generatrix and the central axis 40 of the electrode cap as a rotation center, and the outer arc surface of the transition portion 30 is formed by rotating the preset arc line 310 as a generatrix and the central axis 40 of the electrode cap as a rotation center, and since the preset circular arc 110 and the preset arc line 310 are tangent, the transition between the front end portion 10 and the transition portion 30 of the electrode cap is continuous, the shape of the electrode cap is avoided from being suddenly changed, the possibility of the stress concentration on the surface of the welded joint is reduced, the possibility of the deep electrode indentation on the surface of the welded joint is reduced, and the possibility of the LME crack in the welded joint is reduced.

[0075] The above merely provides the embodiments of the present application but are not intended to limit the present application. Based on the above teachings, one skilled in the art will be able to devise various modifications and variations without departing from the spirit and scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall fall within the scope of claims of the present application.

Claims

1. An electrode cap for resistance spot welding, characterized in that, The electrode cap includes: The front end is the part that first contacts the material to be welded during welding. The outer arc surface of the front end is formed by rotating around a preset circular arc as the generatrix and the central axis of the electrode cap as the center of rotation. The torso portion has a cavity at its bottom, through which the electrode cap is assembled with the electrode rod. The cylindrical shape of the torso portion is formed by rotating around a preset straight line as the generatrix and the central axis of the electrode cap as the center of rotation. The transition section has one end connected to the front end section and the other end connected to the top of the torso section. The outer arc surface of the transition section is formed by rotating around the central axis of the electrode cap with a preset arc as the generatrix. The preset arc is tangent to the preset arc. Wherein, the preset arc is tangent to the preset straight line; the preset arc is a circular arc with a constant curvature, and the second radius of curvature of the preset arc satisfies the following relationship: [R1×(D2-D1)] / (2R1-D1)≤R2<R1; Wherein, R1 is the first radius of curvature of the preset arc, R2 is the second radius of curvature, D1 is the chord length of the outer arc surface of the front end part, and D2 is the outer diameter of the cylinder of the torso part.

2. The electrode cap for resistance spot welding according to claim 1, characterized in that, The first radius of curvature of the preset arc is 40-500mm, and the chord length of the outer arc surface of the front end is 5-12mm.

3. The electrode cap for resistance spot welding according to claim 2, characterized in that, The cylindrical outer diameter of the torso portion is 12–20 mm, and the total length of the electrode cap is 20–30 mm.

4. The electrode cap for resistance spot welding according to claim 1, characterized in that, The geometric dimensions of the electrode cap satisfy the following relationship: (R1-R2) / R1=2A / D1; (R1-L+B) 2 +A 2 =(R1-R2) 2 ; Wherein, R1 is the first radius of curvature, R2 is the second radius of curvature, D1 is the chord length, L is the total length of the electrode cap, A is the distance between the center of the circle corresponding to the preset arc and the central axis of the electrode cap, and B is the distance between the center of the circle corresponding to the preset arc and the bottom of the electrode cap.

5. The electrode cap for resistance spot welding according to claim 3, characterized in that, The preset arc is a variable curvature arc; the variable curvature arc is an Archimedean spiral, and the Archimedean spiral is represented by the Cartesian coordinate equation of polar coordinate transformation as follows: x(θ) = a × θ × sin(θ); y(θ) = a × θ × cos(θ); Where a and θ are parameters of the Cartesian coordinate equation; The geometric dimensions of the electrode cap satisfy the following relationship: Wherein, a and θ are parameters of the Cartesian coordinate equation, D1 is the chord length, D2 is the outer diameter of the cylinder, and R1 is the first radius of curvature.

6. The electrode cap for resistance spot welding according to any one of claims 1-5, characterized in that, The electrode cap is made of a copper alloy, which includes at least one of chromium, zirconium, and aluminum. When the copper alloy includes chromium, the chromium content is 0.5% to 1.5%; When the copper alloy includes zirconium, the zirconium content is 0.2% to 1.0%; In the case where the copper alloy includes aluminum, the aluminum content is 0.3% to 1.0%.

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