Welding quality detection method and apparatus, device and storage medium

Abstract

To provide a welding quality detection method for solving problems such as low detection efficiency, high cost, and incapability of satisfying comprehensive detection needs.SOLUTION: The present application provides a welding quality detection method, comprising: continuously applying a detection voltage to a welding position in a cooling stage of metal material welding after a power outage; detecting a detection current corresponding to the detection voltage; calculating a resistance value of the welding position in the cooling stage according to the detection voltage and the detection current; and determining welding quality according to an initial value, an intermediate value and an end value of the resistance value. In the present application, the resistance change of the welding ball during the cooling process is measured and analyzed, and the heat accumulated in the welding ball is indirectly represented by using the relationship between the resistivity and the temperature of the metal material, thereby realizing the detection and evaluation of the resistance spot welding quality.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present application relates to the field of weld quality detection, and more particularly to a method, apparatus, device and storage medium for detecting weld quality. [Background technology]

[0002] Resistance welding is an efficient welding method that does not require metal filling and includes four forms: spot welding, seam welding, projection welding, and butt welding.

[0003] Resistance spot welding applies voltage through an electrode, utilizing the resistance of the workpiece weld and the contact resistance at the interface. Under high current conditions, the interface of the workpieces is melted through the combined action of Joule heat and pressure to form a nugget. The welding process is completed once the nugget cools. This is a highly efficient, low-cost, and fast method for joining metals. However, while resistance spot welding is a widely used technique, the welding quality is difficult to detect because the connection area is hidden and cannot be visually inspected. In actual production, various factors such as electrode wear, fitting gap, and contamination on the workpiece surface affect the stability of the welding process, resulting in variations in nugget size and even quality issues such as poor soldering and spatter.

[0004] Currently, there are two types of detection methods: destructive and non-destructive. Destructive detection methods, such as manual cutting inspection, indentation depth measurement, and metal structure analysis, have the disadvantages of low detection efficiency, high cost, and difficulty in online implementation.

[0005] To solve these problems, non-destructive detection methods such as ultrasonic detection and infrared detection have been introduced, which have been widely used due to their features of leaving the workpiece intact, saving material costs, being easy to use, and not harming the human body. However, ultrasonic detection, infrared detection, and other methods still have problems such as high cost and low efficiency, require the operation of professional detectors, and have a low degree of automation. In addition, neither the current destructive nor non-destructive detection methods can meet all detection needs.

[0006] Patent Document 1 (corresponding application to CN115392132A) discloses a technology for detecting abnormalities in welding quality using deep learning. However, because the technology in this document uses deep learning, it is necessary to build a complex processing system. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2023-044713 Summary of the Invention [Problem to be solved by the invention]

[0008] The present application aims to provide a welding quality detection method, device, equipment, and storage medium that solve the problems of the above-mentioned prior art, such as low detection efficiency, high cost, and inability to meet all detection needs. [Means for solving the problem]

[0009] The present application provides a welding quality detection method applicable to a welding device, wherein the working process of the welding device includes a welding stage and a cooling stage after the welding current is stopped, and includes the steps of: starting to apply a detection voltage to the welding point when the welding current is stopped and ending when the temperature of the welding point reaches a preset threshold; acquiring a detection current generated in response to the detection voltage applied to the welding point; calculating a resistance value of the welding point which changes continuously during the cooling stage based on the detection voltage and the detection current; and determining whether there is a welding defect in the welding point based on the change trend of the resistance value or a comparison result with the resistance value of a pass-welded point.

[0010] Further, in the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, generating a first resistance curve based on the continuously varying resistance value; generating a second resistance curve based on the resistance value of the accepted weld that changes continuously during the cooling stage; The first resistance curve and the second resistance curve are compared to determine whether or not there is a welding defect.

[0011] Further, in the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, If the continuously changing resistance values ​​have an initial value smaller than the initial value of a passable weld, a rate of decline of the intermediate value greater than the rate of decline of the intermediate value of a passable weld, an end value greater than the end value of a passable weld, and the difference between the initial value and the end value is smaller than a first threshold, the soldering is determined to be defective.

[0012] Further, in the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, Among the continuously changing resistance values, if the difference between the initial value and the initial value of a passable welded area is smaller than a second threshold, the rate of decline of the intermediate value is greater than the rate of decline of the intermediate value of a passable welded area, the end value is smaller than the end value of a passable welded area, and the difference between the initial value and the end value is smaller than a third threshold, it is determined to be spatter.

[0013] Further, in the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, generating a first resistance curve based on the continuously varying resistance value; The weld quality is determined based on the change trend of the first resistance curve.

[0014] Further, in the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, Among the resistance values ​​that continuously change at the passing welded portion, the passing initial value, the passing intermediate value, and the passing final value are statistically calculated, and the range of change in the resistance values ​​of the passing initial value, the passing intermediate value, and the passing final value is determined based on the statistical results. The initial, intermediate and final values ​​of the continuously changing resistance at the welded portion to be measured are compared with the resistance change range, and the weld quality is judged based on the comparison results.

[0015] In addition, in the step of starting to apply a voltage to the welding point when the welding current is stopped and ending the application when the temperature of the welding point reaches a preset threshold value, A voltage is applied to the weld via both poles of the welding gun.

[0016] The present application also provides a voltage module that starts applying a detection voltage to the welding point when the welding current is stopped and ends when the temperature of the welding point reaches a preset threshold; a detection module for acquiring a detection current generated by a detection voltage applied to a welding point; a calculation module for calculating the resistance value of the welding point, which continuously changes during the cooling stage, based on the detected voltage and the detected current; a judgment module for judging whether the welded portion has a welding defect based on the change trend of the resistance value or the result of comparison with the resistance value of a pass-welded portion; A welding quality detection device including:

[0017] The present application also provides a method for detecting welding quality, comprising: a memory for storing a program executable by a computer to perform the above-described welding quality detection method; a processor that executes the steps of calling a program executable by a computer, starting to apply a detection voltage to the welding point when the welding current stops and ending the application when the temperature of the welding point reaches a preset threshold, obtaining a detection current generated in response to the detection voltage applied to the welding point, calculating a resistance value of the welding point that changes continuously during the cooling stage based on the detection voltage and the detection current, and determining whether or not there is a welding defect in the welding point based on the change trend of the resistance value or a comparison result with the resistance value of a pass-welded point; The present invention provides a welding quality detection device including:

[0018] The present application also provides a storage medium having a computer-executable program stored thereon, the computer-executable program being called by a processor and used to perform the steps of the above-described weld quality detection method.

[0019] In this application, the resistance change during the cooling process of the nugget is measured and analyzed, and the relationship between the resistivity and temperature of the metal material is used to indirectly represent the heat accumulated in the nugget, and further realize the detection and evaluation of the resistance spot welding quality. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a schematic diagram of a welding defect evaluation flow in the present application. [Figure 2] FIG. 2 is a schematic diagram illustrating the attachment position of a voltage detection line according to the present application. [Figure 3] FIG. 1 is a comparison diagram of weld quality problem curves in the present application. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, exemplary embodiments of the present disclosure will be described in more detail with reference to the drawings. It should be understood that the present disclosure is not limited to the embodiments and can be realized in various forms. These embodiments are provided to enable those skilled in the art to more fully understand the present disclosure.

[0022] The present application relates to the field of resistance welding quality detection, and the technical problem to be solved is how to quickly and conveniently detect welding quality.

[0023] Resistance welding is a widely used welding technique whose basic principle is to apply a constant voltage between workpieces and use the resistance heat generated when current flows through the workpieces to melt the contact surfaces of the workpieces, thereby achieving a connection between the workpieces. The key to this welding method is the generation and control of heat, which is determined by the current, resistance, and welding time.

[0024] The generation of welding heat is calculated by the formula Q=I 2 It is expressed as Rt, where Q is the amount of heat generated, I is the welding current, R is the inter-electrode resistance, and t is the welding time. The inter-electrode resistance is mainly composed of the resistance of the workpiece itself, the contact resistance between the workpiece, and the contact resistance between the electrode and workpiece. The welding current and welding time can be preset according to the welding process to achieve the desired welding effect.

[0025] The resistivity of a workpiece is an important physical property that determines the resistance that occurs in the workpiece when current is passed through it. Resistivity increases with increasing temperature and decreases with decreasing temperature. The interelectrode resistance can reflect the contact condition between the electrode and workpiece during the welding process, the changes in the metallurgical process and physical properties, and can also indirectly represent the quality of the weld.

[0026] The resistance spot welding process is divided into two stages: the welding stage with applied pressure and current, and the cooling stage with no applied pressure. During the welding stage, the workpiece is melted by resistive heat to form a gradually growing nugget. During the cooling stage, the nugget solidifies under pressure, forming a stable weld. The size of the nugget directly affects the quality of the weld; if it is too large, spatter defects are likely to occur, while if it is too small, soldering failure may occur.

[0027] The cooling process in resistance spot welding involves the liquid metal nugget crystallizing and solidifying under pressure, then continuously cooling to room temperature. This process involves phase change and plastic deformation, and the cooling rate is closely related to the temperature and volume of the nugget. The heat absorbed by the nugget and the heat dissipation conditions affect the cooling process. If the nugget temperature is high and its volume is large, more heat will be accumulated and the cooling rate will be slow. Conversely, if the nugget temperature is low and its volume is small, the cooling rate will be fast.

[0028] If the nugget temperature is too high and its volume is too large, spatter defects are likely to occur, and the nugget loses a large amount of accumulated heat, resulting in a rapid cooling rate. Conversely, if the nugget temperature is too low and its volume is too small, the nugget loses less accumulated heat and the cooling rate is faster than that of a normal welding point, which can lead to poor soldering. Once the nugget cools to room temperature, its temperature will no longer change and its resistance will tend to stabilize.

[0029] The cooling characteristics of resistance welding are closely related to the heat stored in the nugget, and the heat stored in the nugget is related to the temperature and volume of the nugget, so the cooling characteristics of spot welding can indirectly reflect the quality of the weld. By observing and analyzing the characteristics of the cooling process, the quality of the weld can be evaluated, providing a basis for optimizing the welding process and quality control.

[0030] Based on the above principle, the present application proposes a welding quality detection method, device, equipment and storage medium.

[0031] Referring to FIG. 1, a method for evaluating weld defects includes the following steps: S101: When the welding current is stopped, a detection voltage is applied to the welding point, and the application ends when the temperature of the welding point reaches a preset threshold value. S102: Obtain a detected current generated in response to a detected voltage applied to a welding point. S103, calculating the resistance value of the welding point which changes continuously during the cooling stage based on the detected voltage and the detected current. S104: Determine whether there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass-welded portion.

[0032] In step S101, as shown in FIG. 2, a voltage change between the electrodes of the welding device is detected in real time by a voltage detection line. In step S102, a current detection line and its device are attached to an appropriate position of the secondary loop to detect a change in current. In step S103, during the cooling phase (stop-hold phase) of resistance spot welding, the nugget acts as the main heat source, dissipating heat to the electrode, workpiece, and surrounding air. Because the resistivity of the electrode and nugget is closely related to temperature, the resistivity decreases accordingly as the temperature decreases. Therefore, detecting the change in resistance of the electrode and nugget can indirectly reflect the temperature change during the nugget cooling process, enabling the quality of the weld to be determined.

[0033] During the hold-off phase of resistance spot welding, a small voltage and current are applied through the detection wire. These current and voltage values ​​are much smaller than the current used during welding (thousands to tens of thousands of amperes), so they do not significantly affect the crystal structure or mechanical properties of the nugget.

[0034] During the power outage maintenance phase, the measured voltage and current values ​​are recorded. The voltage and current values ​​may be recorded at regular intervals (e.g., millisecond level) or intermittently (e.g., at important times such as the beginning, middle, and end).

[0035] The resistance is calculated using the recorded voltage and current values ​​according to Ohm's law (R=V / I).

[0036] In step S104, the characteristics of the resistance curve, including the changes in the initial, intermediate and final values ​​of the resistance, are analyzed to determine the welding quality.

[0037] During the cooling phase of the weld, at least the initial value of the weld at the start of the weld, intermediate values ​​during the welding process, and final values ​​at the end of the weld are recorded.

[0038] The resistance value is compared to the resistance value of a known good weld at the same time to find any differences. If this difference (deviation) exceeds the range of deviation allowed for a normal weld, the weld can be determined to be unacceptable.

[0039] In addition to simple numerical comparison, a curve of the resistance over time (referred to as the first curve) is generated based on the initial, intermediate and final resistance values ​​recorded during the cooling phase of the weld. The generated first curve is compared with a predetermined time-dependent change curve of the resistance value of a pass-welded portion (referred to as the second curve). The second curve was derived from a large amount of experimental data and experience and represents the trend of resistance change in an ideal or acceptable welding process. By comparing the two curves, it can be determined whether the weld quality is acceptable.

[0040] In addition to directly comparing the curves, the change trend of the first curve is also analyzed. The slope of the curve can represent the change trend, and the change in slope can reflect the speed and stability of the resistance change. If the slope of the first curve is stable or changes as expected during the welding process, this may indicate acceptable weld quality. Conversely, if the change in slope is abnormal or unstable, this may indicate a problem with the weld quality.

[0041] FIG. 3 shows the determination of quality issues.

[0042] Soldering failure L1: A soldering failure is caused by a nugget with low temperature, small volume, small contained heat, and small melting area, which leads to this feature of the resistance curve L1. Therefore, if the initial value is smaller than the initial value of a passing weld, the rate of fall of the median value is greater than the rate of fall of the median value of a passing weld, the end value is greater than the end value of a passing weld, and the difference between the initial value and the end value is less than the first preset threshold, then the soldering is determined to be poor.

[0043] Spatter L2: When spatter occurs, the spattered metal absorbs heat from the nugget, reducing the metal in the nugget area and causing the resistance curve to drop rapidly. The resistance at the end of spattering is smaller than that of a normal weld. Therefore, if the difference between the initial value and the initial value of a passing weld is less than a second preset threshold, the rate of fall of the median value is greater than the rate of fall of the median value of a passing weld, the end value is less than the end value of a passing weld, and the difference between the initial value and the end value is less than a third threshold, it is determined to be spatter.

[0044] The first threshold, the second threshold, and the third threshold are parameters that can be set according to different materials and environments in accordance with the actual situation, and are therefore not limited to specific numerical values.

[0045] Continuing to refer to Figure 3, analysis of other situations includes the following: L3: The nugget is too large. The initial resistance is equal to that of the acceptable welding point, the cooling rate is slow, the temperature reaches room temperature slowly, the final resistance is smaller than that of the acceptable welding point, and the difference between the initial resistance and the final resistance is large. Nugget too small: Similar to the poor soldering curve above.

[0046] In short, if the resistance value of the resistance response time during the cooling process exceeds the tolerance range L4, it is a failed welding point. The specific type of welding point needs to be accurately analyzed, and within the range, it is a passed welding point.

[0047] The steps of obtaining voltage and current measurements at the three initial, intermediate, and final time points and calculating the obtained resistance value include the following: (1) When the welding current is terminated and the test current is initiated, a measurement value (R1) is immediately obtained. (2) At the midpoint of the power outage pressure holding time (T2), a measurement value (R2) is obtained. (3) When the resistance change is almost stable (T3), that is, when the power outage pressure maintenance ends, a measurement value (R3) is obtained.

[0048] Furthermore, multiple measurements (R) can be taken at regular time intervals (for example, 1 ms) and a first curve of the change in resistance over time can be plotted.

[0049] The measured values ​​of the acceptable welding points obtained under the same welding process and conditions are statistically calculated, and the range of resistance change at the corresponding time during the cooling process of the acceptable welding points is determined based on the statistical results.

[0050] The resistance value of the measured weld obtained during the cooling process is compared with the resistance at the corresponding time during the cooling process of a pass weld under the same welding process and conditions. If the resistance value of the weld to be measured is within the variation range indicated by L4 in FIG. 3, it is judged to be a pass weld, and if not, it is judged to be a fail weld. The characteristics of the records or curves identified as failed welds are then analyzed in depth to further determine whether poor soldering, spatter or other welding defects exist at the failed welds.

[0051] This application utilizes the cooling characteristics of the weld points, measures the resistance to represent the temperature change during the nugget cooling process, and compares it with the resistance of a normal weld point during the cooling process to determine quality. This technology can detect all weld points on the production line in real time, leaving no dead ends and ensuring complete coverage. The detection process is fast and manual, making it easy to automate detection, perfectly fitting into the production rhythm of the site and preventing production delays.

[0052] In the present invention, detection is performed during the cooling stage, with fewer external influences and a stable heat dissipation process, effectively realizing the heat accumulated in the weld nugget during the welding process. The temperature change during the nugget cooling process is represented by measuring the resistance value, and quality is determined by comparing it with the resistance value during the cooling process of a normal weld point. This eliminates the need for additional sensors, effectively reducing additional costs and investment. The present invention can be effectively used in both AC and DC welding, and has a wide range of applications.

[0053] Furthermore, the method of the present invention is compatible with a variety of metal materials and has high material compatibility.

[0054] The present application also provides a welding defect evaluation device, a voltage module for continuously applying a detection voltage to the welding point during a cooling phase after welding of the metallic materials is completed and the welding current is stopped; a detection module for detecting a detection current corresponding to the detection voltage; a calculation module for calculating a continuous resistance value of the welding point based on the detected voltage and the detected current; a determination module for determining the weld quality based on the initial, intermediate, and final resistance values; Includes.

[0055] The present application also provides a weld defect evaluation device, a memory for storing a computer-executable program for the welding defect evaluation method; a processor that calls a computer-executable program and executes the steps of: continuously applying a detection voltage to a welding point during a cooling stage after welding of the metallic materials is completed and the welding current is stopped; detecting a detection current corresponding to the detection voltage; calculating successive resistance values ​​of the welding point based on the detection voltage and the detection current; and determining the welding quality based on the initial, intermediate, and final resistance values; Includes.

[0056] The present application also provides a storage medium having a computer-executable program stored therein, the computer-executable program being called by a processor and used to execute the steps of the above-described weld defect evaluation method.

Claims

1. A welding quality detection method applied to a welding device, wherein an operation process of the welding device includes a welding stage and a cooling stage after stopping a welding current; a step of starting to apply a detection voltage to the welding point when the welding current is stopped and terminating the application when the temperature of the welding point reaches a preset threshold value; obtaining a detected current generated by the detected voltage applied to the welding point; calculating a resistance value of the welding point that continuously changes during the cooling stage based on the detected voltage and the detected current; a step of determining whether the welded portion has a welding defect based on the change trend of the resistance value or the result of comparison with the resistance value of a passable welded portion, wherein the welded portion is determined to have a soldering defect if, among the continuously changing resistance values, the initial value is smaller than the initial value of a passable welded portion, the rate of decline of the median value is greater than the rate of decline of the median value of a passable welded portion, the end value is greater than the end value of a passable welded portion, and the difference between the initial value and the end value is smaller than a first threshold value; A welding quality detection method comprising:

2. In the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, generating a first resistance curve based on the continuously varying resistance value; generating a second resistance curve based on the resistance value of the accepted weld that changes continuously during the cooling stage; comparing the first resistance curve with the second resistance curve to determine whether or not there is a welding defect; 2. The method for detecting weld quality according to claim 1.

3. In the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, Among the continuously changing resistance values, if the difference between the initial value and the initial value of a passable welded portion is smaller than a second threshold value, the rate of decline of the median value is greater than the rate of decline of the median value of a passable welded portion, the end value is smaller than the end value of a passable welded portion, and the difference between the initial value and the end value is smaller than a third threshold value, it is determined to be spatter.

2. The method for detecting weld quality according to claim 1.

4. In the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, generating a first resistance curve based on the continuously varying resistance value; determining the welding quality based on the change trend of the first resistance curve; 2. The method for detecting weld quality according to claim 1.

5. In the step of determining whether or not there is a welding defect in the welded portion based on the change trend of the resistance value or the result of comparison with the resistance value of a pass welded portion, Among the resistance values ​​that continuously change at the passing welded portion, statistical analysis is performed on the passing initial value, the passing intermediate value, and the passing final value, and the range of change in resistance values ​​of the passing initial value, the passing intermediate value, and the passing final value is determined based on the statistical results; comparing the initial value, intermediate value, and final value of the resistance value that continuously changes at the welding point to be measured with the resistance value change range, and determining the welding quality based on the comparison result; 2. The method for detecting weld quality according to claim 1.

6. In the step of starting to apply a voltage to a welding point when the welding current is stopped and ending the application when the temperature of the welding point reaches a preset threshold value, applying the voltage to the welding point via both poles of a welding gun; 2. The method for detecting weld quality according to claim 1.

7. a voltage module that applies a detection voltage to the welding point starting from the time when the welding current is stopped and ending when the temperature of the welding point reaches a predetermined threshold; a detection module for acquiring a detection current generated by the detection voltage applied to the welding point; a calculation module for calculating a resistance value of the welding point that continuously changes during a cooling stage based on the detected voltage and the detected current; Among the continuously changing resistance values, if the initial value is smaller than the initial value of a passable welded portion, the rate of decline of the intermediate value is greater than the rate of decline of the intermediate value of a passable welded portion, the end value is greater than the end value of a passable welded portion, and the difference between the initial value and the end value is smaller than a first threshold value, it is determined that the soldering is defective. a judgment module for judging whether the welding portion has a welding defect based on the change trend of the resistance value or a comparison result with the resistance value of a pass-welded portion; A welding quality detection device comprising:

8. a memory for storing a program executable by a computer that implements the welding quality detection method according to any one of claims 1 to 6; a processor that executes the steps of calling a program executable by the computer, starting to apply a detection voltage to the welded point when the welding current stops and ending the application when the temperature of the welded point reaches a preset threshold, acquiring a detection current generated in response to the detection voltage applied to the welded point, calculating a resistance value of the welded point that changes continuously during the cooling phase based on the detection voltage and the detection current, and determining whether or not there is a welding defect at the welded point based on a change trend of the resistance value or a comparison result with the resistance value of a pass-welded point, where the welded point is determined to have a soldering defect if, among the continuously changing resistance values, the initial value is smaller than the initial value of a pass-welded point, the rate of decline of the median value is greater than the rate of decline of the median value of a pass-welded point, the end value is greater than the end value of a pass-welded point, and the difference between the initial value and the end value is smaller than a first threshold; 1. A weld quality detection device comprising:

9. a computer-executable program is stored, the computer-executable program being called by a processor and used to perform the steps of the weld quality detection method according to any one of claims 1 to 6; A storage medium characterized by:

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