CN116275437A

CN116275437A - Resistance spot welding method and system

Info

Publication number: CN116275437A
Application number: CN202310490748.3A
Authority: CN
Inventors: 韩晓辉; 张志毅; 徐野; 叶结和; 李刚卿
Original assignee: CRRC Qingdao Sifang Co Ltd
Current assignee: CRRC Qingdao Sifang Co Ltd
Priority date: 2023-04-28
Filing date: 2023-04-28
Publication date: 2023-06-23

Abstract

The invention relates to the technical field of welding, and provides a resistance spot welding method and a system, wherein the method comprises the following steps: at least two plates with thickness differences are selected, and a conductive silver base layer is formed on one side of the plate with the thinnest thickness. And (3) moving the plate with the thinnest thickness to a gluing feeding area and coating the adhesive on the other side of the plate with the thinnest thickness by a preset gluing procedure. And (3) moving the glued plate to an assembly area and bonding the rest plates. Selecting a test plate matched with the plate, performing test welding on the test plate, generating welding technological parameters of formal welding based on a welding result, performing resistance spot welding on the bonded plate by using a welding technology, monitoring welding quality in real time in the process of resistance spot welding, and adjusting the welding technological parameters based on the monitored welding quality. And carrying out surface treatment on welding spots on the surface of the welded plate.

Description

Resistance spot welding method and system

Technical Field

The invention relates to the technical field of welding, in particular to a resistance spot welding method and a system.

Background

The resistance spot welding method has stable welding quality and high production efficiency, and has wide application in the manufacturing fields of railway vehicles, automobiles, electronics, household appliances and the like. The current resistance spot welding process also has the technical problems of low sheet side penetration rate, insufficient air tightness after welding forming and the like, so a brand new resistance spot welding method is needed to solve the technical problems.

Disclosure of Invention

The invention provides a resistance spot welding method which is used for solving the technical problems of low side penetration rate and insufficient air tightness after welding forming of a thin plate in the prior art and realizing uniform penetration and good air tightness.

The invention also provides a resistance spot welding system.

The invention provides a resistance spot welding method, which comprises the following steps:

selecting at least two plates with thickness difference, and forming a conductive silver base layer on one side of the plate with the thinnest thickness;

moving the plate with the thinnest thickness to a gluing feeding area and coating an adhesive on the other side of the plate with the thinnest thickness by a preset gluing procedure;

moving the glued plate to an assembly area and bonding the rest plates;

selecting a test plate matched with the plate, performing test welding on the test plate, generating welding process parameters of formal welding based on a welding result, performing resistance spot welding on the bonded plate by using the welding process, monitoring welding quality in real time in the process of resistance spot welding, and adjusting the welding process parameters based on the monitored welding quality;

and carrying out surface treatment on welding spots on the surface of the welded plate.

According to the resistance spot welding method provided by the invention, the step of selecting at least two plates with thickness difference and forming the conductive silver base layer on one side of the plate with the thinnest thickness comprises the following steps:

Selecting two plates with thickness difference, wherein the two plates are a thin plate and a thick plate respectively, coating a conductive silver-based material on the outer surface of the thin plate, forming a conductive silver base layer with the thickness of 10-20 micrometers, and attaching the thick plate to one side of the thin plate far away from the conductive silver base;

wherein the thickness of the thin plate is t ₁ The thickness of the thick plate is t ₂ ；

Wherein 2t ₁ ＞t ₂ ＞t ₁ The thickness of the backing plate is 0.3 millimeter;

or, t ₂ ＞3t ₁ The thickness of the backing plate is 0.5 mm.

selecting three plates with thickness difference, wherein the three plates are a thin plate, a thicker plate and a thick plate respectively, coating a conductive silver-based material on the outer surface of the thin plate, forming a conductive silver base layer with the thickness of 10-20 micrometers, and attaching the thick plate and the thicker plate to one side of the thin plate far away from the conductive silver base;

wherein the thickness of the thin plate is t ₃ The thickness of the thicker plate is t ₄ The thickness of the thick plate is t ₅ ；

Wherein t is ₅ ＞t ₄ ＞t ₃ And t ₅ ＞3t ₃ The thickness of the backing plate is 0.8 mm.

According to the resistance spot welding method provided by the invention, the step of moving the thinnest plate to the gluing feeding area and coating the adhesive on the other side of the thinnest plate by a preset gluing procedure comprises the following steps:

and establishing a gluing program based on assembly logic between boards, grabbing the board with the thinnest thickness to a gluing feeding area based on the gluing program, identifying the position of the board in the gluing feeding area, moving the position of the board to a preset point position of the gluing feeding area, selecting a corresponding gluing unit based on the gluing program, identifying a glue seam of the board positioned at the preset point position through an identification unit assembled on the gluing unit, and gluing the other side of the board with the thinnest thickness along the glue seam by using the gluing unit through the gluing program.

According to the resistance spot welding method provided by the invention, the step of moving the glued plate to the assembly area and bonding the rest plates comprises the following steps:

the plate coated with the adhesive is identified by the identification unit, the plate is grabbed by the assembly robot and moved to the assembly area, the grabbed rest plates on the assembly robot are attached to the plate coated with the adhesive, the flexible compression unit is adopted to compress at least two plates, the assembly robot grabs the scraping plates, and the scraping plates are utilized to scrape the adhesive overflowing from the edges of the at least two plates.

According to the resistance spot welding method provided by the invention, the step of selecting the test plate matched with the plate, performing test welding on the test plate and generating welding process parameters of formal welding based on welding results comprises the following steps:

establishing a relational database of a welding process and welding quality, utilizing an identification component to identify a test board matched with a board, grabbing the corresponding test board to a welding platform through a grabbing component, performing test welding on the test board on the welding platform based on the welding process in the relational database, and performing performance test after the test welding is finished;

if the performance test is qualified, taking the current welding process parameters as the welding process parameters of the formal welding;

if the performance test is not qualified, the current welding process parameters are adjusted, then test welding is continued until the performance test is qualified, and the welding process parameters of formal welding are output;

wherein, the step of performance test comprises the following steps: continuously spot-welding three welding spots on at least three pairs of test boards respectively, tearing the last welding spot of each pair of test boards, and measuring the nugget diameter of the torn welding spot;

the performance test step further comprises: cutting the welding spots along the X-axis direction and the Y-axis direction at the welding spots of the test plate to obtain a nugget appearance section inside the welding spots of the test plate, amplifying the nugget appearance section by a plurality of times to generate a macroscopic section, and overlapping and comparing the macroscopic section with a section digital model.

According to the resistance spot welding method provided by the invention, the step of performing resistance spot welding on the bonded plates by using the welding process comprises the following steps:

bonding and fixing the backing plate on the outer surface of the conductive silver base layer in at least one mode of bonding, fixture fixing and fastener fixing, selecting a first electrode rod and a second electrode rod with different diameters, respectively arranging the first electrode rod and the second electrode rod on the outer side of the backing plate and the outer side of the rest of plates, setting a welding spot distance, a welding spot-to-edge distance, welding current, welding time, cooling time, pulse number, holding time and electrode pressure based on thickness parameters of a thinner plate in the two outermost plates, and welding at least two plates through the first electrode rod and the second electrode rod in a preset welding current, welding time, cooling time, pulse number, holding time and electrode pressure;

wherein the diameter of the first electrode rod is smaller than the diameter of the second electrode rod.

According to the resistance spot welding method provided by the invention, the welding quality is monitored in real time in the resistance spot welding process, and the welding process parameter is adjusted based on the monitored welding quality, and the method comprises the following steps:

Establishing a relational database of welding process and welding quality;

acquiring a gap parameter between at least two plates before welding, and adjusting a pre-pressure value before welding based on comparison of the gap parameter and a gap threshold value in the relational database;

acquiring expansion volume parameters of nuggets at welding points in the welding process, and adjusting welding parameters in the welding process based on comparison of the expansion volume parameters and nugget expansion thresholds in the relational database;

and acquiring nugget quality parameters of nuggets at welding spots after welding is finished, and adjusting post-processing parameters after welding based on comparison of the nugget quality parameters and nugget quality thresholds in the relational database.

According to the resistance spot welding method provided by the invention, the step of carrying out surface treatment on the welding spots on the surface of the welded plate comprises the following steps:

carrying out electrolysis mark elimination on welding spots on the surface of the plate;

on the basis of the plate qualified in electrolytic mark elimination, the surface of the plate is integrally passivated;

the surface of the plate is cleaned to clean the electrolytic marking fluid and the electrolytic passivation fluid attached to the surface of the plate.

The present invention also provides a resistance spot welding system comprising:

a central control unit, a central control unit and a control unit,

the selecting unit is electrically connected with the central control unit and is used for selecting at least two plates with thickness difference;

The coating unit is electrically connected with the central control unit and is used for forming a conductive silver base layer on one side of the plate with the thinnest thickness;

the gluing unit is electrically connected with the central control unit and is used for moving the plate with the thinnest thickness to a gluing feeding area and coating an adhesive on the other side of the plate with the thinnest thickness by a preset gluing procedure;

the assembly unit is electrically connected with the central control unit and is used for moving the glued plate to an assembly area and bonding the rest plate;

the test welding unit is electrically connected with the central control unit and is used for selecting a test plate matched with the plate, performing test welding on the test plate and generating welding process parameters of formal welding based on a welding result;

the formal welding unit is electrically connected with the central control unit and is used for performing resistance spot welding on the bonded plates by the welding process;

the monitoring and adjusting unit is electrically connected with the central control unit and is used for monitoring welding quality in real time in the process of resistance spot welding and adjusting welding process parameters based on the monitored welding quality;

and the surface treatment unit is electrically connected with the central control unit and is used for carrying out surface treatment on welding spots on the surface of the welded plate.

According to the resistance spot welding method provided by the embodiment of the invention, the resistivity of the sheet side can be improved through the arrangement of the conductive silver base layer so as to improve the nuclear forming capability, thereby improving the penetration rate of the sheet side, and the welded sheet has good air tightness by adopting a mode of bonding before spot welding, so that the engineering limit of unsealing of spot welding of a railway vehicle body is broken through, welding process parameters are adjusted in real time in the welding process so as to ensure the quality after welding, and surface treatment is performed after the welding is finished so that the sheet can meet the use requirement.

According to the resistance spot welding system provided by the embodiment of the invention, the resistivity of the sheet side can be improved through the arrangement of the conductive silver base layer so as to improve the nuclear forming capability, thereby improving the penetration rate of the sheet side, and the welded sheet has good air tightness by adopting a mode of bonding before spot welding, so that the engineering limitation of unsealing of spot welding of a railway vehicle body is broken through, welding process parameters are adjusted in real time in the welding process so as to ensure the quality after welding, and surface treatment is performed after the welding is finished so that the sheet can meet the use requirement.

Drawings

In order to more clearly illustrate the invention or the technical solutions of the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the invention, and other drawings can be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic flow chart of a resistance spot welding method provided by the invention;

FIG. 2 is a schematic diagram of a resistance spot welding system according to the present invention;

FIG. 3 is a schematic diagram of the principle of gap measurement of two plates by laser according to the invention;

FIG. 4 is a schematic view of a photosensitive element according to the present invention;

fig. 5 is a schematic view showing a state in which the first electrode rod and the second electrode rod weld two plates;

FIG. 6 is a graph of weld spot spacing versus nugget diameter for a resistance spot welding method provided by the present invention versus a conventional welding method;

FIG. 7 is a graph of weld spot spacing versus maximum force with pull shear for a resistance spot welding method and a conventional welding method provided by the present invention;

FIG. 8 is a schematic view of the path of electrolytic trace out in the present invention;

fig. 9 is a schematic diagram of the path of the overall passivation in the present invention.

Detailed Description

Embodiments of the present invention are described in further detail below with reference to the accompanying drawings and examples. The following examples are illustrative of the invention but are not intended to limit the scope of the invention.

The resistance spot welding method of the present invention is described below with reference to fig. 1-9, including the steps of:

s100, selecting at least two plates with thickness differences, and forming a conductive silver base layer on one side of the plate with the thinnest thickness.

And S200, moving the plate with the thinnest thickness to a gluing and feeding area, and coating an adhesive on the other side of the plate with the thinnest thickness by a preset gluing procedure.

And S300, moving the glued plate to an assembly area and bonding the rest plates.

S400, selecting a test plate matched with the plate, performing test welding on the test plate, generating welding technological parameters of formal welding based on a welding result, performing resistance spot welding on the bonded plate by using a welding technology, monitoring welding quality in real time in the process of resistance spot welding, and adjusting the welding technological parameters based on the monitored welding quality.

S500, carrying out surface treatment on welding spots on the surface of the welded plate.

In the embodiment, the resistivity of the sheet side can be improved through arrangement of the conductive silver base layer to improve the nuclear forming capability, so that the penetration rate of the sheet side is improved, the welded sheet has good air tightness by adopting a mode of bonding before spot welding, the engineering limitation that the spot welding of the railway vehicle body is not sealed is broken through, welding process parameters are adjusted in real time in the welding process to ensure the quality after welding, and surface treatment is performed after the welding is finished to enable the sheet to meet the use requirement.

The main component of the conductive silver base layer is silver tin oxide (AgSnO ₂ ) The silver tin oxide can improve the contact resistance of the material surface, so that the resistivity of the plate side with the thinnest thickness is improved, and under the condition of the same spot welding parameters, the nucleation capacity is stronger as the contact resistance is larger, so that the nucleation capacity of the sheet side is improved, and the penetration rate of the sheet side is increased.

In this embodiment, the step of selecting at least two plates having a thickness difference, and forming a conductive silver-based layer on one side of the plate having the thinnest thickness, includes: two plates with thickness difference are selected, wherein the two plates are a thin plate and a thick plate respectively, the outer surface of the thin plate is coated with a conductive silver-based material, a conductive silver base layer with the thickness of 10-20 micrometers is formed, and the thick plate is attached to one side of the thin plate far away from the conductive silver base layer.

When the two plates are welded, the thin plate can be placed above the thick plate, and the upper surface of the thin plate is coated with the conductive silver-based material, so that the conductive silver base layer is formed. In the welding process, the conductive silver base layer can improve the contact resistance of the sheet side, and improve the nucleation capacity of the sheet side, so that the nugget is positioned at the joint of the sheet and the thick plate, the penetration rate of the sheet side is improved, and the welding quality is improved. The fusion rate can be increased from original 20% to 50% by matching the backing plate on the outer surface of the conductive silver base layer and the first electrode rod and the second electrode rod which are asymmetrically arranged.

The thickness of the thin plate is t ₁ The thickness of the thick plate is t ₂ . When 2t ₁ ＞t ₂ ＞t ₁ The thickness of the backing plate was 0.3mm. When t ₂ ＞3t ₁ The thickness of the backing plate was 0.5mm. The thickness of the backing plate will vary based on the thickness of the thin and thick plates. When the thickness of the thick plate is slightly larger than that of the thin plate (it is to be noted that the thickness of the thick plate is slightly larger than that of the thin plate by at least 3 mm), the thickness of the backing plate can be set to be 0.3mm, and the backing plate has the best effect of reducing the heat dissipation speed of the thin plate side and meets the welding requirement. When the thickness of the thick plate is far greater than that of the thin plate, the backing plate can be used forThe thickness of the backing plate is set to be 0.5mm, the effect of reducing the heat dissipation speed of the backing plate on the sheet side is optimal, and the welding requirement is met.

In this embodiment, the step of selecting at least two plates having a thickness difference, and forming a conductive silver-based layer on one side of the plate having the thinnest thickness, includes:

three plates with thickness difference are selected, wherein the three plates are a thin plate, a thicker plate and a thick plate respectively, the outer surface of the thin plate is coated with a conductive silver-based material, a conductive silver base layer with the thickness of 10-20 micrometers is formed, and the thick plate and the thicker plate are attached to one side of the thin plate far away from the conductive silver base.

When the three plates are welded, the thin plate can be placed above the thick plate, the thicker plate is placed below the thick plate, so that the thick plate is clamped between the thin plate and the thicker plate, and the upper surface of the thin plate is coated with the conductive silver-based material, so that the conductive silver base layer is formed. In the welding process, the conductive silver base layer can improve the contact resistance of the thin plate side, improve the nucleation capacity of the thin plate side, enable the thick plate to be penetrated in the nucleation process, enable the thin plate and the thicker plate to be penetrated towards one side of the thick plate, improve the penetration rate of the thin plate side and improve the welding quality. The fusion rate can be increased from original 20% to 50% by matching the backing plate on the outer surface of the conductive silver base layer and the first electrode rod and the second electrode rod which are asymmetrically arranged.

The thickness of the thin plate is t ₃ The thickness of the thicker plate is t ₄ The thickness of the thick plate is t ₅ . Wherein, when t ₅ ＞t ₄ ＞t ₃ And t ₅ ＞3t ₃ The thickness of the backing plate was 0.8mm. At this time, the pad plate has the best effect of reducing the heat dissipation speed of the sheet side, and meets the welding requirement.

In this embodiment, the step of moving the thinnest plate to the glue feeding area and coating the adhesive on the other side of the thinnest plate by a preset glue coating procedure includes:

the method comprises the steps of establishing a gluing program based on assembly logic between boards, grabbing the board with the thinnest thickness to a gluing feeding area based on the gluing program, identifying the position of the board in the gluing feeding area, moving the position of the board to a preset point of the gluing feeding area, selecting a corresponding gluing unit based on the gluing program, identifying a glue seam of the board located at the preset point through an identification unit assembled on the gluing unit, and gluing the other side of the board with the thinnest thickness along the glue seam by using the gluing unit through the gluing program.

Snatch the panel that this rubber coating needs to use based on the rubber coating procedure to shift the panel to the rubber coating material loading district, correct its position after the position of rubber coating material loading district discernment panel, make the panel be located the default position, so that follow-up accurate rubber coating, then select the rubber coating unit to glue the panel along the glue line based on the rubber coating procedure, realize the automatic rubber coating of panel, so that carry out subsequent process.

Each plate is respectively implanted with a radio frequency identification chip, each radio frequency identification chip corresponds to the parameter information of each plate, the radio frequency identification chip has a wave emitting function and can continuously emit signals, and in the following steps, signals emitted by the radio frequency identification chips are received through a signal receiver, so that part information can be converted into electric signals and transmitted to the grabbing unit, and the grabbing unit can grab the corresponding plates conveniently.

The parameter information of the plate comprises at least one parameter of a material parameter, a thickness parameter and a specification parameter of the plate. The radio frequency identification chip with the material, the thickness and the specification is implanted into the plate so as to convert the information of the plate into an electric signal and transmit the electric signal to the part grabbing unit, and the grabbing unit grabs the plate to the gluing and feeding area according to the existing procedure.

The step of identifying the position of the plate in the gluing and feeding area and moving the position of the plate to a preset point position of the gluing and feeding area comprises the following steps:

the coating material loading area is provided with a three-dimensional positioning sensing unit and a position adjusting unit, the position of the plate in the coating material loading area is identified by the three-dimensional positioning sensing unit, and the plate is adjusted to a preset point position of the coating material loading area by the position adjusting unit.

The three-dimensional positioning sensing unit comprises a three-dimensional positioning sensor, the position adjusting unit comprises a three-dimensional adjusting rod, the position of the plate initially placed in the coating material loading area is identified through the three-dimensional positioning sensor, the position deviation between the position of the plate and the reference point is judged based on the identified position, and the three-dimensional adjusting rod is triggered to adjust the position of the plate based on the position deviation, so that the plate can be located in a preset point position, and subsequent coating is facilitated.

Selecting a corresponding gluing unit based on a gluing procedure, and identifying the glue line of the plate positioned at the preset point position through an identification unit assembled on the gluing unit, wherein the step comprises the following steps:

based on a gluing program, a gun changing disc of a gluing robot grabs a corresponding glue gun, a visual identification unit is assembled on the glue gun, and the glue seam position and the glue seam size of the plate positioned at a preset point position are identified through the visual identification unit.

Based on the influence of manufacturing errors of each plate, the sizes of different plates are fluctuated, so that the glue coating position and the filling amount of each plate are different, the glue joint position and the glue joint size of the plates are identified based on real-time visual identification, and the glue outlet speed of a gun nozzle can be adjusted according to the glue joint position and the glue joint size, so that a proper amount of adhesive can be filled in each glue joint. Based on subsequent resistance spot welds, the identified glue line location will correspond to the subsequent spot weld location, as will the glue line size.

According to the automatic gluing method provided by the invention, the step of gluing the plate positioned at the preset point position along the glue line by using the gluing unit through a gluing procedure comprises the following steps:

and assembling a plastic gun nozzle on the glue gun, and driving the glue gun to move along the glue line by a glue coating robot and coating glue on the plate positioned at the preset point, wherein the glue coating robot adjusts the glue outlet speed of the glue gun based on different glue line sizes.

The plastic gun nozzle can avoid the gun nozzle from scratching the surface of the plate, and particularly for a railway vehicle, the gun nozzle can be prevented from damaging the vehicle body. The glue gun moves along the glue line and glues the board, and the real-time identification of visual identification unit on the technical glue gun can adjust the play glue speed of glue gun constantly based on the glue line size of discernment to ensure that every position glue line can all fill appropriate amount of adhesive. Wherein, the single-point gluing amount of the glue gun is 1.0 gram, and the gluing diameter is 4.5-5.0 mm. In the range of the single-point gluing quantity and the gluing diameter, the best air tightness after the subsequent resistance spot welding is finished can be ensured, and the bonding effect between at least two plates is best.

In this example, the adhesive was prepared using the compounded rubber, titanium pigment and conductive carbon black together as the base materials. The formed adhesive has good smearing performance and initial adhesion, and does not flow in each spot welding station. The spot welding stations referred to herein include stations in a horizontal, vertical, inverted, and the like state.

The adhesive can also facilitate accurate control of the adhesive outlet diameter, can carry out subsequent spot welding within three days after the adhesive is coated, can withstand the impact and corrosion of pretreatment liquid and electrophoretic liquid, and ensures no collapsibility and no pollution. And has certain compatibility for arc welding, flame repairing and restoring technology and the like. The adhesive also has stronger conductivity, does not influence the quality of subsequent spot welding, and has certain tolerance on the cleaning degree of the surface of the plate. Meanwhile, the flame retardant has higher flame retardance, can not generate bright fire in a spot welding environment at 1000 ℃, and keeps better stability and sealing performance. The adhesive is nontoxic and odorless, and does not influence the health of operators. The overflowed spot welding sealant is convenient to clean. Meanwhile, the product has good storage stability and has a shelf life of up to 180 days.

In this embodiment, the step of moving the glued board to the assembly area and bonding the remaining board includes:

The plates are mutually bonded by grabbing through the assembly robot, when the plates are bonded, the adhesive overflows from the plates, and the scraping plate is utilized to scrape the adhesive, so that the edge of the plates is ensured to be clean.

In this embodiment, a test board adapted to a board is selected, test welding is performed on the test board, and welding process parameters of formal welding are generated based on welding results, including:

and establishing a relational database of the welding process and the welding quality, identifying the test board matched with the board by utilizing the identification component, grabbing the corresponding test board to the welding platform by utilizing the grabbing component, performing test welding on the test board on the welding platform based on the welding process in the relational database, and performing performance test after the test welding is finished. And if the performance test is qualified, taking the current welding process parameters as the welding process parameters of the formal welding. If the performance test is not qualified, the current welding process parameters are adjusted, then the test welding is continued until the performance test is qualified, and the welding process parameters of the formal welding are output. Wherein, the step of performance test comprises: and continuously spot-welding three welding spots on at least three pairs of test boards respectively, tearing the last welding spot of each pair of test boards, and measuring the nugget diameter of the torn welding spot. And if the diameter of the nugget meets the requirement, the performance test is qualified. If the diameter of the nugget does not meet the requirement, the performance test is not qualified. The performance testing step further comprises: cutting the welding spots along the X-axis direction and the Y-axis direction at the welding spots of the test plate to obtain a nugget appearance section inside the welding spots of the test plate, amplifying the nugget appearance section by a plurality of times to generate a macroscopic section, and overlapping and comparing the macroscopic section with a section digital model. And if the result of the coincidence comparison meets the requirement, the performance test is qualified. If the result of the coincidence comparison does not meet the requirement, the performance test is not qualified.

The test board is matched with the plate, namely the material of the test board is the same as that of the plate. Meanwhile, in order to facilitate experimental welding, the sizes of the test plates can be the same. For example, a plurality of test panels having a size of 40mmX200mm are selected, respectively. The test boards with the same size can also ensure that each test board after spot welding can be accurately placed on a tearing tester and a section cutting test bed by a robot for performance test.

The actual macroscopic morphology of the cross section can be obtained by adopting a method of cross section sectioning test, specifically, the morphology of the molten core cross section is amplified under a microscope of 60 times, the macroscopic cross section is obtained, and whether the morphology of the molten core meets the standard requirement is rapidly judged based on the coincidence comparison of the macroscopic cross section and the cross section digital model. The method mainly judges whether the nugget diameter is in an allowable range, whether the penetration rate is in an allowable range, whether the maximum limit of the core part defect meets the requirements and the like.

In this embodiment, the step of trial welding generally includes: identifying test boards, determining the assembly sequence of the test boards, grabbing the test boards, spot welding the test boards, grabbing the welded test boards, performing a three-point tearing test, performing a cross section sectioning test, and outputting results.

In this embodiment, the step of performing resistance spot welding on the bonded sheet material by using a welding process includes: attaching a fixed backing plate on the outer surface of a conductive silver base layer in at least one of bonding, fixture fixing and fastener fixing modes, selecting a first electrode rod and a second electrode rod with different diameters, respectively arranging the first electrode rod and the second electrode rod on the outer side of the backing plate and the outer side of the rest of plates, setting a welding spot distance, a welding spot-to-edge distance, welding current, welding time, cooling time, pulse number, holding time and electrode pressure based on thickness parameters of a thinner plate in the two outermost plates, and welding at least two plates through the first electrode rod and the second electrode rod in a preset welding current, welding time, cooling time, pulse number, holding time and electrode pressure; wherein the diameter of the first electrode rod is smaller than the diameter of the second electrode rod.

By forming the conductive silver base layer on the outer side of the thinnest plate, the resistivity of the thin plate side can be improved to improve the nuclear forming capability, so that the penetration rate of the thin plate side is improved; the plates are bonded by using the adhesive and then welded later, so that the welded plates have good air tightness, and the engineering limitation that the spot welding of the railway vehicle body is not sealed is broken through; the heat dissipation speed of the sheet side during spot welding can be reduced by adding the backing plate, and the penetration rate of the sheet side is improved; meanwhile, spot welding is performed based on the first electrode rods and the second electrode rods with different diameters, and the first electrode rod with smaller diameters is located on the sheet side, so that the heat dissipation speed of the sheet side is lower, molten core is offset to the sheet side, and the penetration rate of the sheet side is improved. Through the cooperation of the modes, the air tightness is improved, the penetration rate of the sheet side is improved to 50% from 20% originally, the penetration rate is greatly improved, the welding between the plates is more stable, and the product quality is improved.

An electrode with the diameter of 8mm and the spherical radius of the end part of 200mm is selected as a first electrode rod, an electrode with the diameter of 16mm and the spherical radius of the end part of 200mm is selected as a second electrode rod, the first electrode rod and the second electrode rod are respectively arranged on the outer side of the backing plate and the outer sides of other plates, and at least two plates are welded through the first electrode rod and the second electrode rod according to preset current intensity, preset welding time and preset cooling time.

Based on the 8mm first electrode rod and the 16mm second electrode rod, the first electrode rod is located on the thin plate side, the falling electrode rod is located on the thick plate side or the thicker plate side, the heat dissipation speed of the thin plate side is lower, the nuggets are offset to the thin plate side, and the penetration rate of the thin plate side is improved.

Based on the thickness of the outermost sheet, the parameters of the set pad spacing, pad-to-edge spacing are as follows:

as shown in fig. 6 and 7, when the pitch of the welding spots is about 38mm, the nugget diameter after welding and the maximum force of pulling and shearing are reduced, and thus the pitch value of the interval 36-40 is discarded in the determination of the pitch of the welding spots.

The fixture is fixed by adopting a clamping fixture, and the clamping fixture can clamp the base plate and the plate at the edge of the base plate so as to fix the position of the base plate. The fastener can adopt clamping locking piece, can carry out the centre gripping to two at the edge department of backing plate and panel to realize the fixed position of backing plate.

The thickness of the backing plate is 0.3-0.8mm. The thickness of the backing plate may be specifically selected according to the aforementioned plate thickness parameters. The backing plate with a corresponding shape can be selected according to the shape characteristics of the spot welding part, for example, a strip backing plate, a wafer backing plate and the like. The backing plate can be made of stainless steel or red copper material, and the material of the backing plate can be adaptively adjusted according to the material of the plate.

In this embodiment, the welding quality is monitored in real time during the resistance spot welding, and the step of adjusting the welding process parameters based on the monitored welding quality includes:

acquiring gap parameters between at least two plates before welding, and adjusting a pre-welding pre-pressure value based on comparison of the gap parameters and gap threshold values in a relational database;

acquiring expansion volume parameters of nuggets at welding points in the welding process, and adjusting welding parameters in the welding process based on comparison of the expansion volume parameters and nugget expansion threshold values in a relational database;

and acquiring nugget quality parameters of nuggets at welding spots after welding is completed, and adjusting post-processing parameters after welding based on comparison of the nugget quality parameters and nugget quality thresholds in a relational database.

A relational database is established based on the welding process and the welding quality, welding process parameters of formal welding are determined according to data in the relational database and experimental welding results, and then the welding process parameters of each stage are adjusted in real time based on real-time monitoring data before, during and after welding. Specifically, the pre-pressure value before welding is adjusted according to the comparison between the gap parameter monitored in real time before welding and the gap threshold value, so that the gap between the plates is ensured to meet the welding quality requirement; according to the comparison between the nugget expansion volume monitored in real time during welding and the nugget expansion threshold, each welding parameter during welding is adjusted to ensure that the welding quality requirement is met; and comparing the nugget quality parameter monitored in real time after welding with a nugget quality threshold value to judge whether to adjust the post-processing parameter so as to ensure that the welding quality requirement is met.

The gap value between the plates can be adjusted according to the magnitude of the pre-pressure value before welding. The gap value between the plates has a critical influence on the quality of the spot welding splashing and the inner nugget, and the gap is too large to cause the appearance quality problems of the spot welding splashing, deformation and the like and the nugget inner quality problems of the nugget diameter which does not reach or is lack to exceed the standard and the like, and the spot welding quality is improved by adjusting the gap value of the plate. When the pre-pressure value increases, the gap value between at least two plates can be reduced; when the pre-pressure value is reduced, the gap value between at least two plates may be increased.

During welding, welding parameters can influence the quality of the nucleation, particularly the expansion volume parameter of the nugget, and in the welding process, whether the welding parameters need to be adjusted is judged based on the expansion volume parameter of the nugget. Specifically, the adjusted welding parameters include welding current, welding pressure, electrode pressure, welding time, cooling time, hold time, and pulse number.

After welding, it is determined whether post-treatment is required or not and the specific manner of the post-treatment based on the shape after welding.

In this embodiment, the step of establishing a relational database of welding process and welding quality specifically includes:

The method comprises the steps of establishing a relation database of pre-pressure, clearance threshold and welding quality before welding, establishing a relation database of welding parameters, nugget expansion threshold and welding quality in welding, and establishing a relation database of post-processing parameters, nugget quality threshold and welding quality after welding.

It is understood that the relational databases include pre-weld relational databases of pre-stress-gap threshold-weld quality, mid-weld relational databases of weld parameters-nugget expansion threshold-weld quality, and post-process relational databases of post-nugget quality threshold-weld quality.

The pre-pressure value is correlated with the gap value, and when the pre-pressure value increases, the gap value between at least two plates decreases; when the pre-pressure value decreases, the gap value between at least two plates increases. For example, when the gap parameter monitored in real time is 50mm (millimeter), and the gap threshold is within 30mm, it is indicated that the gap between the plates is too large at this time, and the gap between the plates needs to be adjusted in time to ensure the subsequent welding quality. At this time, the gap between the plates is compressed by increasing the pre-pressure before welding so that there is a greater pressure between at least two plates to reduce the gap, and when the gap parameter monitored in real time is 30mm or less, the subsequent step is performed while maintaining the current pre-pressure value.

The method comprises the steps of obtaining a clearance parameter between at least two plates before welding, and adjusting a pre-welding pre-pressure value based on comparison of the clearance parameter and a clearance threshold value in a relational database, wherein the steps specifically comprise:

and transmitting laser to at least two plates at a first position, respectively reflecting the laser on the surfaces of the at least two plates to form at least two beams of reflected light, respectively receiving the at least two beams of reflected light by using a photosensitive element at a second position, correspondingly forming at least two photosensitive positions on the photosensitive element by the at least two beams of reflected light, and calculating a gap value between the at least two plates based on the interval between the at least two photosensitive positions. If the gap value is smaller than or equal to the gap threshold value in the relational database, the pre-pressure value before welding does not need to be adjusted. And if the clearance value is larger than the clearance threshold value in the relational database, the pre-pressure value before welding is improved.

For two plates, as shown in fig. 3 and 4, the first plate 310 may be placed on a working table, and then the laser emitting unit 330 emits laser, where the reflected light is reflected on the surface of the first plate 310 and then received at the first photosensitive position 350 of the photosensitive element 340, and at this time, the point of the first photosensitive position 350 is marked. Then, the second plate 320 is placed on the surface of the first plate 310, the second plate 320 is attached to the first plate 310 with a preset pre-pressure value, and then the laser is emitted by the laser emitting unit 330, and the reflected light is received at the second photosensitive position 360 of the photosensitive element 340 after the laser is reflected on the surface of the second plate 320, and at this time, the point of the second photosensitive position 360 is marked. The gap value between the first plate 310 and the second plate 320 is calculated based on the distance between the first photosensitive position 350 and the second photosensitive position 360 and through the light reflection angle and the like. If the clearance value is greater than the clearance threshold, the pre-pressure value is raised and the measurement is performed again until the clearance value meets the clearance threshold.

If the two plates are transparent weldments, laser light may pass through the plates. At this time, the first plate 310 is placed on the table, and then the second plate 320 is directly placed on the first plate 310, and the second plate 320 and the first plate 310 are bonded with each other at a predetermined pre-pressure value. The laser emitting unit 330 may emit laser, where the laser is reflected on the surface of the first plate 310 and then reflected at the first photosensitive position 350 of the photosensitive element 340, and the laser passes through the first plate 310 and is reflected at the position of the second plate 320, where the laser is reflected on the surface of the second plate 320 and then reflected at the second photosensitive position 360 of the photosensitive element 340, the point of the first photosensitive position 350 and the point of the second photosensitive position 360 are recorded, and the gap value between the first plate 310 and the second plate 320 is calculated based on the distance between the first photosensitive position 350 and the second photosensitive position 360 and the angle of reflection of the light. If the clearance value is greater than the clearance threshold, the pre-pressure value is raised and the measurement is performed again until the clearance value meets the clearance threshold.

Judging whether the pre-pressure value before welding needs to be adjusted based on the value of the clearance parameter, and reducing the clearance value between at least two plates when the pre-pressure value is increased; when the pre-pressure value is reduced, the gap value between at least two plates may be increased.

In one embodiment, when the real-time monitored gap parameter is 80mm and the gap threshold is within 40mm, the gap between the plates is too large, and the gap between the plates needs to be adjusted in time to ensure the subsequent welding quality. At this time, the gap between the plates is compressed by increasing the pre-pressure before welding so that there is a greater pressure between at least two plates to reduce the gap, and when the gap parameter monitored in real time is 40mm or less, the subsequent step is performed while maintaining the current pre-pressure value.

Welding at least two plates by using welding process parameters and adjusted pre-pressure values, acquiring expansion volume parameters of nuggets at welding spots in the welding process, and adjusting the welding process parameters in real time based on comparison of the expansion volume parameters and nugget expansion threshold values in a relational database, wherein the method specifically comprises the following steps of:

and welding at least two plates by using the welding process parameters and the adjusted precompression value, adding an expansion displacement sensor at the welding end of the welding mechanism, acquiring the expansion volume parameters of the nuggets at the welding spots in real time by using the expansion displacement sensor, and judging whether to adjust the welding process parameters based on the comparison of the expansion volume parameters and the nugget expansion threshold values in the relational database. If the expansion volume parameter is within the range of the nugget expansion threshold in the relational database, no adjustment of the welding parameters is required. And if the expansion volume parameter is outside the range of the nugget expansion threshold in the relational database, adjusting at least one parameter of welding current, welding pressure, electrode pressure, welding time, cooling time, holding time and pulse number based on the relational database.

Specifically, an expansion displacement sensor is additionally arranged on the welding tongs to monitor the fused expansion volume value in real time, and the detected expansion volume value can directly reflect the fused expansion volume parameter. Based on real-time monitoring, the data monitored by the expansion displacement sensor can be fed back to the terminal in real time, the terminal can compare the expansion volume value fed back with the nugget expansion threshold value in the relational database in the terminal, and after the comparison and judgment, the result is fed back synchronously so as to make an instruction whether the welding parameters need to be adjusted or not.

It is understood that the welding parameters include at least one of welding current, welding pressure, electrode pressure, welding time, cooling time, hold time, and pulse number. During welding, it is determined whether or not adjustment of welding current, welding pressure, electrode pressure, welding time, cooling time, holding time, and number of pulses is required based on the expansion volume parameter detected in real time. For example, based on changes in the expansion volume parameter, the welding current may be increased, the welding pressure may be increased, the electrode pressure may be increased, the welding time may be prolonged, the cooling time may be prolonged, the holding time may be prolonged, and the number of pulses may be increased.

In one embodiment, the pre-pressure may be set to 3kN, the spot welding current may be set to 9KA, the welding time may be set to 180ms, the cooling time may be set to 30ms, the number of pulses may be set to 2, the hold time may be set to 600ms, and the electrode pressure may be set to 5.6kN.

The method comprises the steps of obtaining nugget quality parameters of nuggets at welding spots after welding, and adjusting post-processing parameters after welding based on comparison of the nugget quality parameters and nugget quality thresholds in a relational database, wherein the steps specifically comprise:

scanning the X-axis direction and the Y-axis direction of each welding spot by using a laser ranging device to form a rectangular scanning area, performing height ranging on all detection points in the rectangular scanning area, generating a three-dimensional contour by matching with the numerical value of the X-axis direction and the numerical value of the Y-axis direction, and calculating at least one parameter of pit depth and contour diameter at the nugget based on the three-dimensional contour. If the pit depth and the profile diameter are within the range of the pit depth threshold and the profile diameter threshold in the relational database, no post-processing is required. And if the pit depth and the contour diameter are out of the ranges of the pit depth threshold value and the contour diameter threshold value in the relational database, performing post-treatment processing on the welding part.

And scanning each welding spot along the X-axis direction and the Y-axis direction to generate a rectangular scanning area of the welding spot on a horizontal plane, and performing height ranging in the rectangular scanning area, namely scanning along the Z-axis, so as to generate a three-dimensional contour at the welding spot based on the coordinate points of the X-axis, the Y-axis and the Z-axis. Based on the obtained three-dimensional profile, at least one parameter of pit depth and profile diameter at the nugget can be directly calculated. To determine the nugget quality based on at least one parameter of pit depth, profile diameter.

The X-axis direction may be a length direction of the welding platform, the Y-axis direction may be a width direction of the welding platform, and the Z-axis direction may be a height direction of the welding platform.

Acquiring nugget quality parameters of nuggets at welding spots after welding, and adjusting post-processing parameters after welding based on comparison of the nugget quality parameters and nugget quality thresholds in a relational database, wherein the method specifically further comprises the following steps:

and (3) carrying out ultrasonic scanning along the welding spot area by using an ultrasonic scanning device, and calculating at least one parameter of the nugget diameter and the quality defect at the nugget based on the ultrasonic scanning result. If the nugget diameter and the mass defect are within the range of the nugget diameter threshold and the mass defect threshold in the relational database, no post-processing is needed. And if the nugget diameter and the quality defect are out of the range of the nugget diameter threshold and the quality defect threshold in the relational database, performing post-processing on the welding part.

And directly displaying the result of the position of the welding point nugget by utilizing ultrasonic scanning, thereby calculating at least one parameter of nugget diameter and quality defect, and judging nugget quality based on the at least one parameter of nugget diameter and quality defect.

The ultrasonic scanning scans all welding spots by clamping an ultrasonic C scanning probe through a robot, scanning tracks are distributed spirally along the welding spot area, internal quality information such as nugget diameter, quality defect and the like is extracted according to the ultrasonic scanning result, and whether the internal quality of the welding spots is qualified or not is judged based on a comparison mode.

the portal crane is arranged along the welding platform, the portal crane is provided with the light pen measuring instrument and the laser tracker, the Leika laser tracker can be adopted, a size coordinate system is constructed by combining the sheet materials, the light pen measuring instrument and the laser tracker are driven to measure each welding point based on the movement of the portal crane, and the measuring result can be combined with the size coordinate system to generate at least one parameter of the large-span size and the form and position tolerance of each welding point. If the large span size and the form tolerance are within the range of the large span size threshold and the form tolerance threshold in the relational database, no post-processing is needed. And if the large-span size and the form tolerance are out of the range of the large-span size threshold and the form tolerance threshold in the relational database, performing post-processing on the welding part.

The gantry crane is a gantry crane, and the sliding rails of the gantry crane are arranged along the length direction of the welding platform, so that the arrangement direction of the sliding rails of the gantry crane is the same as the welding direction. It can be understood that the portal crane spans the width direction of the welding platform, and the portal crane can drive the light pen measuring instrument and the laser tracker to monitor each welding spot in real time along the welding direction in sequence in the process of sliding along the sliding rail. After the dimensional coordinate system of the plate member is combined, the large dimensions of the plate are all unified into one coordinate system, and large span dimensions and form and position tolerances such as length, width, height, deflection, diagonal and flatness are generated according to the characteristics of detection results of different welding spots. And judging whether post-processing is needed or not based on comparison of the large-span size and the form tolerance with a large-span size threshold and a form tolerance threshold respectively.

The laser measurement mode is adopted, so that the measurement accuracy can reach 0.15mm, the detection time of the whole size of a single vehicle body is shortened to 1.5h (hours), and the detection efficiency is improved by more than 30%.

In this embodiment, on the one hand, the nugget mass is reacted based on the generated three-dimensional profile, on the other hand, the nugget mass is reacted based on the result of ultrasonic scanning, and on the other hand, the nugget mass is reacted by means of laser measurement or the like, and the nugget mass is reacted jointly from three aspects, so that comprehensive judgment is facilitated.

In this embodiment, the step of performing surface treatment on the welding points on the surface of the welded plate includes: and carrying out electrolytic trace elimination on the welding spots on the surface of the plate. And (3) carrying out integral passivation on the surface of the plate based on the plate qualified in electrolytic mark elimination. The surface of the plate is cleaned to clean the electrolytic marking fluid and the electrolytic passivation fluid attached to the surface of the plate.

In the embodiment, the oxidation color of the welding spot on the surface of the plate after the resistance spot welding is finished is eliminated through electrolytic mark elimination, the chromatic aberration formed between the welding spot after the mark elimination and the surface of the plate is eliminated through a passivation step, the corrosion resistance of the plate in the welding spot area can be improved, the uniformity and consistency of the plate can be maintained, the commercialized effect is ensured, the surface of the plate is cleaned through a cleaning step, the electrolytic mark elimination liquid and the electrolytic passivation liquid remained on the surface of the plate are cleaned, and the cleanliness of the surface of the plate is ensured. By adopting the method, the oxidation color can be quickly and conveniently eliminated after the spot welding of the plate, the chromatic aberration can be eliminated, the corrosion resistance of the plate can be improved, the quality of surface treatment can be ensured, and the efficiency of surface treatment can be improved.

The electrolytic mark elimination and the integral passivation are based on the electrochemical principle, and the mark elimination brush head and the passivation group brush head are respectively assembled through the driving unit to respectively form an electrolytic device in the electrolytic mark elimination stage and an electrolytic device in the integral passivation stage. After the oxidation color of the surface of the welding spot after the completion of the resistance spot welding is eliminated, the chromatic aberration between the welding spot and the surface of the side wall base metal after the elimination of the mark is eliminated, the corrosion resistance of a side wall welding area is improved, the uniform commercialization effect of the exposed parts of the non-coated stainless steel vehicle is ensured, the vehicle delivery is carried out after the cleaning is finished, and the vehicle delivery state is ensured.

The step of carrying out electrolysis mark elimination on welding spots on the surface of the plate comprises the following steps:

and selecting a mark removing program based on the oxidation degree of the welding spots on the surface of the plate, grabbing a mark removing brush head by using a driving unit, introducing electrolytic mark removing liquid into the mark removing brush head, and grinding the welding spots on the surface of the plate and the area around the welding spots by using the driving unit to drive the mark removing brush head based on the mark removing program until the surface of the plate has metallic luster.

It is understood that the plate surface is qualified for electrolytic mark elimination after metallic luster is generated. When the metal luster is generated on the surface of the plate, the electrolysis mark elimination is stopped, and the influence of white spots generated on the surface of the welding spot and the mark elimination effect caused by overlong grinding time is avoided.

A step of selecting a mark removal program based on the degree of oxidation at the weld points on the surface of the sheet material, comprising:

the oxidation degree of the welding spots on the surface of the plate is divided into mild oxidation of the outer circle of the welding spots, moderate oxidation of the outer circle of the welding spots and overall heavy oxidation of the welding spots. Based on the light oxidation of the outer ring of the welding spot, the trace eliminating brush head grinds the welding spot on the surface of the plate and the area around the welding spot with the first grinding power. Based on the moderate oxidation of the outer ring of the welding spot, the trace eliminating brush head grinds the welding spot on the surface of the plate and the area around the welding spot with the second grinding power. And (3) grinding the welding spots and the surrounding areas of the welding spots on the surface of the plate by the mark eliminating brush head at a third grinding power based on the overall heavy oxidation of the welding spots. Wherein the first grinding power is smaller than the second grinding power, and the second grinding power is smaller than the third grinding power. The first grinding power is 220 watts (W), the second grinding power is 500 watts, the third grinding power is 750 watts, and the electrolytic trace removing liquid comprises 10% sodium gluconate solution, so that the surface treatment process is environment-friendly and waste liquid recovery is not needed.

The method comprises the steps of enabling a driving unit to drive a mark eliminating brush head to grind welding spots on the surface of a plate and areas around the welding spots based on a mark eliminating program until the surface of the plate generates metallic luster, and comprises the following steps:

based on the mark eliminating program, the driving unit drives the mark eliminating brush head to grind the welding spot on the surface of the plate and the area around the welding spot within the range of 6 mm from the edge of the welding spot, wherein after the electrolytic mark eliminating liquid of the mark eliminating brush head reacts with the surface of the welding spot, the driving unit drives the mark eliminating brush head to grind the welding spot on the surface of the plate, after the metal luster is generated at the welding spot, the driving unit drives the mark eliminating brush head to conduct multistage circular motion by taking the welding spot as the circle center and grind the area around the welding spot on the surface of the plate through the mark eliminating brush head, the radius of each stage of circular motion is gradually increased along the direction from the welding spot to the area around the welding spot, and the rotation direction of each stage of circular motion is the same.

As shown in FIG. 8, which is a schematic diagram of a path of multistage circular motion, the welding spots and the annular region of the welding spot edge 6m are subjected to trace removal grinding, so that the thorough electrolytic trace removal is ensured, and the oxidation colors of the welding spots and the surrounding regions of the welding spots are all removed.

The method comprises the steps that firstly, a mark eliminating brush head moves to the position of a welding spot to carry out electrolytic mark elimination on the welding spot, after the electrolytic mark elimination at the welding spot is qualified, the welding spot is used as the circle center to drive the mark eliminating brush head to carry out circular motion with the radius of R1, when the electrolytic mark elimination at the corresponding position of the range is qualified, the welding spot is used as the circle center to drive the mark eliminating brush head to carry out circular motion with the radius of R2, wherein R2 is larger than R1, so that the radius of the circular motion is gradually increased, and the electrolytic mark elimination of the welding spot and an annular area with the edge of 6 mm is gradually completed. The circular motion of each stage corresponds to a circular motion under a radius value, for example, the circular motion with the radius R1 may be defined as a first stage circular motion, the circular motion with the radius R2 may be defined as a second stage circular motion, the circular motion with the radius R3 may be defined as a third stage circular motion, and so on, the driving unit drives the trace-removing brush head to perform a multi-stage circular motion and grinds a region around the welding point on the surface of the board by using the trace-removing brush head. The rotation direction of each stage of circular motion is the same, so that the shapes of the exposed base materials of the oxide layers at all positions are approximately the same after the treatment is finished, and the attractiveness is ensured.

The step of carrying out integral passivation on the surface of the plate comprises the following steps:

setting a passivation path based on the shape of the plate and the positions of welding spots, grabbing a passivation group brush head by using a driving unit, introducing electrolytic passivation solution into the passivation group brush head, and after the electrolytic passivation solution of the passivation group brush head reacts with the surface of the plate, carrying out integral passivation on the surface of the plate by the passivation group brush head along the passivation path at a preset passivation speed and a preset passivation power, wherein the passivation group brush head stays at the position of each welding spot for a preset passivation time.

In this example, the preset passivation rate was 1 minute per meter (m/min), the preset passivation power was 500 watts, the preset passivation time was 30 seconds (S), and the electrolytic passivation solution included an 8% citric acid solution. The driving unit drives the passivation group brush head to move along the passivation path at the speed of 1 minute per meter, and stays for 30 seconds at the position of each welding spot respectively, and after passivation along the passivation path is finished, the driving unit drives the passivation group brush head to automatically return to the original position at the idle speed. The citric acid solution with the solute mass fraction of 8% is used as the electrolytic passivation solution, so that the surface treatment process is environment-friendly and waste liquid recovery is not needed.

As shown in fig. 9, the passivation path comprises a plurality of segments of U-shaped paths connected in sequence, and the passivation path passes through each of the solder joints of the sheet surface. The direction of the line matching arrow indicates the passivation path and direction, and the driving unit drives the passivation group brush head to integrally passivate the surface of the plate along the path, so that each position can be ensured to be subjected to surface passivation treatment through electrolytic passivation liquid.

A step of cleaning a surface of a sheet material to clean an electrolytic marking fluid and an electrolytic passivation fluid attached to the surface of the sheet material, comprising: and cleaning the surface of the plate by adopting a spraying mode so as to flush and clean the electrolytic trace removing liquid and the electrolytic passivation liquid attached to the surface of the plate.

Taking the side wall of the railway vehicle as an example, the whole vehicle can be sprayed and cleaned in a spraying mode after the side wall is assembled, so that the electrolytic mark elimination and the whole passivation share one set of cleaning system and cleaning flow, the arrangement of cleaning units is reduced, the cleaning flow is shortened, and the surface treatment time is shortened.

On the other hand, as shown in fig. 2, the invention also provides a resistance spot welding system, which comprises a central control unit, a selection unit, a coating unit, a gluing unit, an assembling unit, a test welding unit, a formal welding unit, a monitoring and adjusting unit and a surface treatment unit. The selecting unit is electrically connected with the central control unit and is used for selecting at least two plates with thickness differences. The coating unit is electrically connected with the central control unit and is used for forming a conductive silver base layer on one side of the plate with the thinnest thickness. The gluing unit is electrically connected with the central control unit and is used for moving the plate with the thinnest thickness to the gluing feeding area and coating the adhesive on the other side of the plate with the thinnest thickness by a preset gluing procedure. The assembly unit is electrically connected with the central control unit and is used for moving the glued plate to the assembly area and bonding the rest plates. The test welding unit is electrically connected with the central control unit and is used for selecting a test plate matched with the plate, performing test welding on the test plate and generating welding process parameters of formal welding based on welding results. The formal welding unit is electrically connected with the central control unit and is used for performing resistance spot welding on the bonded plates through a welding process. The monitoring and adjusting unit is electrically connected with the central control unit and is used for monitoring welding quality in real time in the process of resistance spot welding and adjusting welding process parameters based on the monitored welding quality. The surface treatment unit is electrically connected with the central control unit and is used for carrying out surface treatment on welding spots on the surface of the welded plate.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of resistance spot welding comprising the steps of:

moving the glued plate to an assembly area and bonding the rest plates;

2. The resistance spot welding method according to claim 1, wherein said selecting at least two sheets having a thickness difference, the step of forming a conductive silver-based layer on one of the thinnest sheets, comprises:

or, t ₂ ＞3t ₁ The thickness of the backing plate is 0.5 mm.

3. The resistance spot welding method according to claim 1, wherein said selecting at least two sheets having a thickness difference, the step of forming a conductive silver-based layer on one of the thinnest sheets, comprises:

4. The resistance spot welding method according to claim 1, wherein the step of moving the thinnest sheet material to the glue application area and applying an adhesive to the other side of the thinnest sheet material in a preset glue application program includes:

5. The resistance spot welding method according to claim 1, wherein the step of moving the rubberized sheet material to the assembly area and bonding the remaining sheet material comprises:

6. The resistance spot welding method according to claim 1, wherein the steps of selecting a test panel adapted to a plate material, performing trial welding on the test panel, and generating welding process parameters of the formal welding based on the welding result, include:

7. The resistance spot welding method according to claim 1, wherein the step of resistance spot welding the bonded sheet material by the welding process comprises:

8. The resistance spot welding method according to claim 1, wherein the step of monitoring the welding quality in real time during the resistance spot welding and adjusting the welding process parameters based on the monitored welding quality comprises:

Establishing a relational database of welding process and welding quality;

9. The resistance spot welding method according to any one of claims 1 to 8, wherein the step of surface-treating the welding spot on the surface of the welded plate member comprises:

10. A resistance spot welding system, comprising:

a central control unit, a central control unit and a control unit,