Electrode device for resistance spot welding with adjustable current distribution and welding method

Abstract

The present application relates to a kind of adjustable resistance spot welding electrode device of current distribution and welding method, belong to the field of welding process control.First, second and third level core electrode is coaxially installed in the concentric cavity of electrode body, independently or combined under hydraulic control to work on the surface of welding workpiece, different point core electrode combination constitutes different electrically conductive path, thereby leading to the difference of current distribution in the internal welding workpiece, under the balance condition of resistance heat production, heat dissipation, the spot welding nugget formed has different cross-sectional profile form.The present application takes sleeve type combination electrode device with special structure as core, by controlling the compacted state of each level core electrode, changes the current distribution in the internal workpiece, so that spot welding joint can obtain nugget with different geometric form, realizes the flexible adjustment of spot welding current distribution under the premise of not replacing electrode, significantly improves resistance spot welding quality and production efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of welding process control, in particular to the current density distribution adjustment and control technology in resistance spot welding process, and more particularly to a current distribution adjustable resistance spot welding electrode device and a welding method. BACKGROUND

[0002] In the field of equipment manufacturing such as automobile and rail passenger car, resistance spot welding, as a welding process with high efficiency, low cost and stable welding quality, is widely used in the lap welding structure of thin plates. In the spot welding process, the workpieces are assembled into a lap structure and placed between upper and lower electrodes; the upper and lower electrodes apply a certain pressing force to the workpieces and pass a large current for a short time. Under the action of resistance heat, a certain amount of molten metal is formed inside the workpiece pressing area, and after cooling, it forms an isolated circular spot weld (nugget) connecting the plate layers.

[0003] The geometry of the spot welding nugget determines the mechanical properties of the welded joint. The geometry of the spot welding nugget (diameter, thickness, etc.) depends on the current distribution inside the workpiece during welding. Currently, in industrial production, the electrodes of resistance spot welding equipment are generally fixed in size. When other welding conditions (workpiece thickness combination, electrode pressure, welding current, etc.) are determined, the current distribution inside the workpiece during welding is also fixed. When the welding object changes, the flexibility of nugget size adjustment and welding quality control is poor. Therefore, how to achieve flexible adjustment of spot welding current distribution without changing the electrode is an important means to improve the quality and production efficiency of resistance spot welding, and is also a technical problem to be solved at present. SUMMARY

[0004] The present application aims to provide a current distribution adjustable resistance spot welding electrode device and a welding method, which solves the above-mentioned problems existing in the prior art. The present application takes a sleeve type combined electrode device as the core, and quickly adjusts the contact state of the electrode end face and the workpiece according to the needs in welding production, thereby changing the path of the welding current from the electrode to the workpiece, and effectively adjusting the current distribution state inside the workpiece, achieving the purpose of changing and controlling the geometric shape of the nugget inside the workpiece. The flexible adjustment of spot welding current distribution is achieved without changing the electrode, which significantly improves the quality and production efficiency of resistance spot welding.

[0005] The above-mentioned purposes of the present application are achieved by the following technical solutions:

[0006] The electrode device for resistance spot welding with adjustable current distribution comprises an electrode body 1, a primary core electrode 2, a secondary core electrode 3, a tertiary core electrode 4, and a locking nut 5. During the welding process, the primary core electrode 2, the secondary core electrode 3, and the tertiary core electrode 4 of the electrode device are coaxially installed in the concentric cavities of the electrode body 1, and can be independently or combined used to work on the surface of the welding workpiece under the hydraulic control. Different combinations of the core electrodes result in different conductive paths, thereby causing differences in the current distribution inside the welding workpiece. Under the balance condition of resistance heat generation and dissipation, the spot welding nuggets formed have different cross-sectional profile morphologies.

[0007] The electrode body 1 is cylindrical, and the end thereof is provided with a tapered mounting hole 11 connected with the electrode rod of the spot welding equipment to transmit the welding current, the electrode pressing force, and the cooling water. The diameter and the taper of the mounting hole 11 are matched with the end size of the electrode guide rod of the spot welding equipment. The side surface of the electrode body 1 is provided with a primary oil inlet hole 12, a secondary oil inlet hole 13, and a tertiary oil inlet hole 14 connected with the hydraulic working station of the spot welding equipment through the hydraulic pipeline. The inside of the electrode body 1 is provided with a primary concentric cavity 15, a secondary concentric cavity 16, and a tertiary concentric cavity 17 respectively assembling the primary core electrode 2, the secondary core electrode 3, and the tertiary core electrode 4. The hydraulic oil is delivered to the primary concentric cavity 15, the secondary concentric cavity 16, and the tertiary concentric cavity 17 inside the electrode body 1 through the primary oil inlet hole 12, the secondary oil inlet hole 13, the tertiary oil inlet hole 14, and the oil passage inside the electrode body 1. The front end of the electrode body 1 is provided with a sealing thread 18 matched with the locking nut 5 to fasten the installation of the core electrodes.

[0008] The front end of the primary core electrode 2 is cylindrical, the front end of the secondary core electrode 3 and the tertiary core electrode 4 is cylindrical, and the rear end of the primary core electrode 2, the secondary core electrode 3, and the tertiary core electrode 4 is provided with a circular flange. During the work, the flange end surface of the core electrode is acted on by the hydraulic oil delivered by the primary oil inlet hole 12, the secondary oil inlet hole 13, and the tertiary oil inlet hole 14, and the core electrode is pushed to move axially.

[0009] Another object of the present application is to provide a current distribution adjustable resistance spot welding electrode welding method, in which each level of core electrode is pressed to the workpiece under the action of hydraulic oil during resistance spot welding; each level of core electrode can be independently pressed or freely combined for pressing; when only one level of core electrode 2 is pressed for welding, the welding current can only pass through the end face of the one level of core electrode to enter the welding workpiece, and the current distribution in the workpiece is concentrated, at this time the fusion nucleus formed by welding has an elliptical cross section, a smaller diameter and a larger thickness; when the one level of core electrode 2 and the two level of core electrode 3 are pressed together for welding, the welding current can pass through the end face of the one level of core electrode 2 and the two level of core electrode 3 to enter the welding workpiece, and the current distribution in the workpiece is more dispersed compared with the one level of core electrode 2 being pressed alone, at this time the fusion nucleus formed by welding has a larger diameter and a smaller thickness; when the one level of core electrode 2, the two level of core electrode 3 and the three level of core electrode 4 are pressed together for welding, the welding current can pass through the end face of all core electrodes to enter the welding workpiece, and the current distribution in the workpiece is the most dispersed, at this time the fusion nucleus formed by welding has the largest diameter and the smallest thickness; when only the two level of core electrode 3 or the three level of core electrode 4 is pressed alone or the two are combined for welding, the contact surface between the electrode and the workpiece is annular, and the current path in the workpiece is also annular, at this time the fusion nucleus formed has a dumbbell shape.

[0010] The present application has the advantages that: in view of the control requirements of the current distribution in the workpiece and the fusion nucleus shape in the resistance spot welding process, the sleeve type combined electrode device with a special structure is used as the core, the pressing state of each level of core electrode is controlled, the current distribution in the workpiece is changed, and thus the spot welding joint can obtain fusion nuclei with different geometric shapes to meet the adjustment and control of different connection states of the resistance spot welding joint. BRIEF DESCRIPTION OF DRAWINGS

[0011] The drawings described herein are used to provide further understanding of the present application, form a part of the present application, and the illustrative examples of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0012] Figure 1 The structure schematic diagram of the current distribution adjustable resistance spot welding electrode device of the present application;

[0013] Figure 2 The assembly schematic diagram of each part of the current distribution adjustable resistance spot welding electrode device of the present application;

[0014] Figure 3 The structure schematic diagram of the electrode body of the present application;

[0015] Figure 4 The working schematic diagram of the current distribution adjustable resistance spot welding electrode device of the present application;

[0016] Figure 5Figure for the welding nugget shape of different core electrode combination of the present application;

[0017] Figure 6 Figure for the welding nugget cross section of the elliptical type of the present application;

[0018] Figure 7 Figure for the welding nugget cross section of the dumbbell type of the present application.

[0019] In the figure: 1, electrode body; 2, primary core electrode; 3, secondary core electrode; 4, tertiary core electrode; 5, locking nut; 11, mounting hole; 12, primary oil inlet hole; 13, secondary oil inlet hole; 14, tertiary oil inlet hole; 15, primary concentric cavity; 16, secondary concentric cavity; 17, tertiary concentric cavity; 18, sealing thread. DETAILED DESCRIPTION

[0020] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0021] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0022] Referring to Figures 1 to 7 As shown in the figure, the current distribution adjustable resistance spot welding electrode device and welding method of the present application, the geometric size of the spot welding nugget determines the mechanical properties of the welded joint. The geometric size (diameter, thickness, etc.) of the spot welding nugget depends on the current distribution state inside the workpiece during the welding process. The present application takes the sleeve type combined electrode device as the core, and quickly adjusts the contact state of the electrode end face and the workpiece according to the needs in the welding production, so as to change the path of the welding current from the electrode to the workpiece, and then effectively adjust the current distribution state inside the workpiece, so as to achieve the purpose of changing and controlling the geometric shape of the nugget inside the workpiece.

[0023] Referring to Figures 1 to 3 As shown in the figure, the current distribution adjustable resistance spot welding electrode device of the present application is composed of an electrode body 1, a primary core electrode 2, a secondary core electrode 3, a tertiary core electrode 4, and a locking nut 5. The electrode body 1 is cylindrical, and the end is provided with a tapered mounting hole 11, which is connected with the electrode rod of the spot welding equipment during work, and transmits the welding current, electrode pressing force and cooling water. The mounting hole 11 can be processed into different diameters and tapers to adapt to the end size of the electrode guide rod of different spot welding equipment.

[0024] The electrode body 1 is provided with a first oil inlet hole 12, a second oil inlet hole 13 and a third oil inlet hole 14, which are connected with the hydraulic working station of the spot welding equipment through hydraulic pipelines. The electrode body 1 is internally provided with three concentric cavities (a first concentric cavity 15, a second concentric cavity 16 and a third concentric cavity 17) for assembling a first core electrode 2, a second core electrode 3 and a third core electrode 4. Hydraulic oil is delivered into the three concentric cavities in the electrode body 1 through the first oil inlet hole 12, the second oil inlet hole 13, the third oil inlet hole 14 and the oil passage in the electrode body 1; and the electrode body 1 is provided with a sealing thread 18 at the front end for mounting a locking nut 5 to install the core electrodes (the first core electrode 2, the second core electrode 3 and the third core electrode 4).

[0025] The front end of the first core electrode 2 is cylindrical, the front ends of the second core electrode 3 and the third core electrode 4 are cylindrical, and the first core electrode 2, the second core electrode 3 and the third core electrode 4 are coaxially installed in the concentric cavities of the electrode body 1; the rear ends of the first, second and third core electrodes are all provided with circular flanges, which form a piston cooperation structure with the side walls of the concentric cavities of the electrode body 1 during operation, and the hydraulic oil delivered through the oil inlet holes acts on the flange end faces of the corresponding core electrodes to push the core electrodes to move axially. The core electrodes are extended and retracted along the electrode axis under the action of the hydraulic oil to apply a pressing force to the workpiece and perform welding.

[0026] Referring to Figure 4 As shown in the drawings, the current distribution adjustable resistance spot welding electrode welding method of the application can press the workpiece through the action of the core electrodes under the action of the hydraulic oil during the resistance spot welding process; each core electrode can be independently pressed or freely combined to press. When the welding conditions (workpiece thickness combination, electrode pressure, welding current, etc.) are fixed, the conductive paths formed by different combinations of core electrodes are different, resulting in differences in the current distribution in the welded workpiece. Under the balance condition of resistance heat generation and dissipation, the spot welding nuggets formed have different cross-sectional profile shapes.

[0027] Referring to Figure 5 When only the first core electrode 2 is pressed to perform welding, the welding current can only enter the welded workpiece through the end face of the first core electrode 2, and the current distribution in the workpiece is concentrated, so that the cross section of the welding nugget formed is elliptical, the diameter is small, and the thickness is large; when the first core electrode 2 and the second core electrode 3 are pressed to perform welding, the welding current can enter the welded workpiece through the end faces of the first core electrode 2 and the second core electrode 3, and the current distribution in the workpiece is relatively dispersed compared with the case where only the first core electrode 2 is pressed, so that the diameter of the welding nugget formed is increased, and the thickness is reduced; when the first core electrode 2, the second core electrode 3 and the third core electrode 4 are pressed to perform welding, the welding current can enter the welded workpiece through the end faces of all the core electrodes, and the current distribution in the workpiece is the most dispersed, so that the diameter of the welding nugget formed is the largest, and the thickness is the smallest.

[0028] When only the secondary core electrode 3 or the tertiary core electrode 4 is independently pressed or both are combined to be pressed and welded, the contact surface of the electrode and the workpiece is annular, the current path in the workpiece is also annular, and the formed nugget shape is dumbbell-shaped.

[0029] When the spot-welded joint has different nugget shapes, the forming quality such as the penetration rate, the nugget diameter, and the surface indentation is obviously different, and the bearing capacity is also different. The present application can prepare resistance spot-welded joints with different forming characteristics under the condition of not changing the welding equipment by reasonably matching the welding parameters and the pressing mode of the electrode, and the process adaptability and flexibility are prominent.

[0030] Example 1:

[0031] The resistance spot welding process for the rail car body parts is taken as an example for description as follows:

[0032] (1) The welding material is SUS301L stainless steel, and the plate thickness combination is 1 mm+1 mm. The diameter of the primary core electrode is Φ3 mm, the inner diameter of the secondary core electrode 3 is Φ3 mm, the outer diameter is Φ5 mm, the inner diameter of the tertiary core electrode 4 is Φ5 mm, and the outer diameter is Φ8 mm. The welding current is 12 kA, and the welding time is 400 ms.

[0033] (2) Before welding, the sleeve-type electrode device of the present application is first installed at the end of the electrode guide rod of the spot-welding equipment, and the oil inlet holes of each stage are connected with the hydraulic system of the spot-welding equipment through pipelines. Through oil pressure control, the primary core electrode 2 and the secondary core electrode 3 are combined to be pressed, the secondary core electrode 3 and the tertiary core electrode 4 are combined to be pressed, and welding is implemented, respectively, to obtain an elliptical cross-section nugget (diameter 5.8 mm) and a dumbbell-shaped cross-section nugget (diameter 8.0 mm), as shown in Figure 6 and Figure 7 .

[0034] The above description is only preferred examples of the present application and is not used to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made to the present application shall be included in the protection scope of the present application.

Claims

1. A method of resistance spot welding with an electrode having an adjustable current distribution, characterized in that: The sleeve type combined electrode device is used for quickly adjusting the contact state between the electrode end face and the workpiece in the welding production, thereby changing the path of the welding current from the electrode to the workpiece, and effectively adjusting the current distribution state in the workpiece, changing and controlling the geometric shape of the nugget in the workpiece; the sleeve type combined electrode device comprises an electrode body (1), a first-stage core electrode (2), a second-stage core electrode (3), a third-stage core electrode (4) and a locking nut (5), the first-stage core electrode (2), the second-stage core electrode (3) and the third-stage core electrode (4) are coaxially arranged in the concentric cavities of the electrode body (1), in the welding process, the core electrodes of the electrode device are independently or combinedly used for the workpiece surface under the hydraulic control, the conductive paths formed by the different point core electrode combinations are different, thereby causing the difference of the current distribution in the workpiece, under the balance condition of the resistance heat generation and heat dissipation, the spot welding nugget formed has different cross-sectional profile shapes; In the resistance spot welding process, the core electrodes are pressed to the workpiece under the action of the hydraulic oil; each core electrode can be independently pressed or freely combined to be pressed; when only the first-stage core electrode (2) is pressed to perform the welding, the welding current can only enter the workpiece through the end face of the first-stage core electrode, the current distribution in the workpiece is concentrated, at this time, the cross section of the nugget formed by the welding is elliptical, the diameter is small, and the thickness is large; when the first-stage core electrode (2) and the second-stage core electrode (3) are jointly pressed to perform the welding, the welding current can enter the workpiece through the end faces of the first-stage core electrode (2) and the second-stage core electrode (3), compared with the first-stage core electrode (2) being independently pressed, the current distribution in the workpiece is more dispersed, at this time, the diameter of the nugget formed by the welding is increased, and the thickness is reduced; when the first-stage core electrode (2), the second-stage core electrode (3) and the third-stage core electrode (4) are jointly pressed to perform the welding, the welding current can enter the workpiece through the end faces of all the core electrodes, the current distribution in the workpiece is the most dispersed, at this time, the diameter of the nugget formed by the welding is the largest, and the thickness is the smallest; when only the second-stage core electrode (3) or the third-stage core electrode (4) is independently pressed or the two are combined to be pressed to perform the welding, the contact surface of the electrode and the workpiece is annular, the current path in the workpiece is also annular, at this time, the nugget formed is dumbbell-shaped; The electrode body (1) is cylindrical, the end is provided with a tapered mounting hole (11), which is connected with the electrode rod of the spot welding equipment in the working state, and transmits the welding current, the electrode pressing force and the cooling water; the mounting hole (11) can be processed into different diameters and tapers to adapt to the end part size of the electrode guide rod of different spot welding equipment; the side surface of the electrode body (1) is provided with a first-stage oil inlet hole (12), a second-stage oil inlet hole (13) and a third-stage oil inlet hole (14), which are connected with the hydraulic working station of the spot welding equipment through the hydraulic pipeline; the inside of the electrode body (1) is provided with three concentric cavities for assembling the first-stage core electrode (2), the second-stage core electrode (3) and the third-stage core electrode (4); the hydraulic oil is delivered to the three concentric cavities in the inside of the electrode body (1) through the oil passage in the inside of the electrode body (1); The front end of the electrode body is provided with a sealing thread for installing a locking nut to fasten the core electrodes.

2. The resistance spot welding electrode method of claim 1, wherein: The front end of the first core electrode (2) is cylindrical, the front end of the second core electrode (3) and the third core electrode (4) is cylindrical, and the third core electrode is coaxially installed in the concentric cavity of the electrode body (1). The rear end of the core electrode is provided with a circular flange, which forms a piston matching structure with the side wall of the concentric cavity of the electrode body during work. The hydraulic oil delivered by the oil inlet holes acts on the flange end face of the corresponding core electrode, so as to push the core electrode to move axially.

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