Welding Quality Detection Method, Device, Machine, and Storage Medium

Abstract

Provided is a welding quality detection method that solves problems such as low detection efficiency, high cost, and inability to meet comprehensive detection needs. 【Solution means】The present application provides a welding quality detection method including the steps of continuously applying a detection voltage to a welding location during the cooling stage after power failure in metal material welding, detecting a detection current corresponding to the detection voltage, calculating a resistance value of the welding location during the cooling stage based on the detection voltage and the detection current, and determining the welding quality based on the initial value, intermediate value, and end value of the resistance value. In the present application, the resistance change in the cooling process of the nugget is measured and analyzed, and the relationship between the resistivity and temperature of the metal material is utilized to indirectly represent the heat accumulated in the nugget, and further realize the detection and evaluation of resistance spot welding quality.

Description

Technical Field

[0001] This application belongs to the field of welding quality detection, and particularly relates to a welding quality detection method, device, equipment, and storage medium.

Background Art

[0002] Resistance welding technology 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 electrodes and uses the resistance of the welded part of the workpiece and the contact resistance at the interface to apply a large current. Under the combined action of Joule heat and pressure, the interface of the workpiece is melted to form a nugget. When the nugget cools, the welding process is completed. This is a high-efficiency, low-cost, and high-speed metal connection method. However, although resistance spot welding is a widely used technology, it is difficult to detect the welding quality 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. As a result, the size of the nugget fluctuates, and furthermore, Welding quality problems such as defects and spatter occur.

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

[0005] To solve these problems, non-destructive detection methods such as ultrasonic detection and infrared detection have been introduced. They are widely used because they can keep the workpiece intact, save material costs, are convenient to use, and do not harm the human body. However, methods such as ultrasonic detection and infrared detection still have problems such as high cost and low efficiency. They require the operation of professional detectors and have a low degree of automation. In addition, both the current destructive detection methods and non-destructive detection methods cannot meet the needs of comprehensive detection.

[0006] Patent Document 1 (the corresponding application of CN115392132A) discloses a technique for detecting abnormalities in welding quality using deep learning. However, since the technique in this document uses deep learning, it is necessary to construct a complex processing system.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] An object of the present application is to provide a welding quality detection method, apparatus, device, and storage medium that solve the problems in the above-mentioned prior art, such as low detection efficiency, high cost, and inability to meet the needs of comprehensive detection.

Means for Solving the Problems

[0009] The present application provides a welding quality detection method applied to a welding apparatus. The working process of the welding apparatus includes a welding stage and a cooling stage after the welding current stops. A detection voltage is applied to the welding location starting from the moment the welding current stops, and the step ends when the temperature of the welding location reaches a preset threshold value; a step of obtaining a detection current generated according to the detection voltage applied to the welding location; a step of calculating the resistance value of the welding location that continuously changes in the cooling stage based on the detection voltage and the detection current; and a step of determining whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location.

[0010] Also, in the step of determining whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location, Generate a first resistance curve based on the continuously changing resistance value, Generate a second resistance curve based on the resistance value of a qualified welding location that continuously changes in the cooling stage, Compare the first resistance curve and the second resistance curve to determine the presence or absence of a welding defect.

[0011] Also, in the step of determining whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location, Among the continuously changing resistance values, if the initial value is smaller than the initial value of a qualified welding location, the descending speed of the intermediate value is Small less than the descending speed of the intermediate value of a qualified welding location, and the end value is larger than the end value of a qualified welding location, and the difference between the initial value and the end value is smaller than a first threshold value, then Welding it is determined as defective.

[0012] Also, in the step of determining whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location, Among the continuously changing resistance values, if the difference between the initial value and the initial value of the qualified welding location is less than the second threshold, the rate of decrease of the intermediate value is greater than the rate of decrease of the intermediate value of the qualified welding location, the end value is less than the end value of the qualified welding location, and the difference between the initial value and the end value is less than the third threshold, it is determined as spatter.

[0013] Also, in the step of determining whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of the qualified welding location, Generate a first resistance curve based on the continuously changing resistance value, Judge the welding quality based on the change trend of the first resistance curve.

[0014] Also, in the step of determining whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of the qualified welding location, Among the resistance values that continuously change at the qualified welding location, count the qualified initial value, qualified intermediate value, and qualified end value, and obtain the resistance value change range of the qualified initial value, qualified intermediate value, and qualified end value based on the statistical result, Compare the initial value, intermediate value, and end value in the resistance value that continuously changes at the measured welding location with the resistance value change range, and judge the welding quality based on the comparison result.

[0015] Also, in the step of starting to apply a voltage to the welding location from the stop of the welding current and ending when the temperature of the welding location reaches a preset threshold, Apply a voltage to the welding location through both poles of the welding gun.

[0016] This application also includes a voltage module that starts to apply a detection voltage to the welding location from the stop of the welding current and ends when the temperature of the welding location reaches a preset threshold, A detection module that obtains the detection current generated by the detection voltage applied to the welding location, A calculation module that calculates the resistance value of the welding location that continuously changes in the cooling stage based on the detection voltage and the detection current, A judgment module that determines whether there is a welding defect in a welded portion based on the change tendency of the resistance value or the comparison result with the resistance value of a qualified welded portion, To provide a welding quality detection device including

[0017] This application also includes a memory that stores a program executable by a computer that implements the above welding quality detection method, A step of calling a program executable by a computer, starting to apply a detection voltage to a welded portion from the time when the welding current stops, and ending when the temperature of the welded portion reaches a preset threshold value; a step of obtaining a detection current generated according to the detection voltage applied to the welded portion; a step of calculating the resistance value of the welded portion that continuously changes in the cooling stage based on the detection voltage and the detection current; and a step of determining whether there is a welding defect in the welded portion based on the change tendency of the resistance value or the comparison result with the resistance value of a qualified welded portion, and a processor that executes To provide a welding quality detection device including

[0018] This application also provides a storage medium in which a program executable by a computer is stored, and the program executable by the computer is called by a processor and used to execute the steps of the above welding quality detection method.

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

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out 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 by the embodiments and can be implemented in various forms. These embodiments are provided so that those skilled in the art can more fully understand the present disclosure.

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

[0023] Resistance welding is a widely applied welding technique. Its basic principle is to apply a certain voltage between workpieces and utilize the resistance heat generated when current flows through the workpieces to melt the contact surfaces of the workpieces, thereby realizing the connection between the workpieces. The key points of this welding method are the generation and control of heat, and these heats are determined by current, resistance, and welding time.

[0024] The generation of welding heat is represented by the formula Q = I 2 Rt. Here, Q is the amount of heat generated, I is the welding current, R is the resistance between the electrodes, and t is the welding time. The resistance between the electrodes mainly consists of the resistance of the workpiece itself, the contact resistance between the workpieces, and the contact resistance between the electrode and the workpiece. The welding current and welding time can be preset according to the welding process in order to achieve the desired welding effect.

[0025] The resistivity of the workpiece is one of the important physical properties, which determines the magnitude of the resistance generated in the workpiece when current flows. The resistivity increases with the increase in temperature and decreases with the decrease in temperature. The resistance between the electrodes can reflect the contact state between the electrode and the workpiece, the metallurgical process, and the changes in physical properties during the welding process, and can further indirectly represent the quality of the welded joint.

[0026] The resistance spot welding process can be divided into two stages: the welding stage of applying pressure and current, and the cooling stage of cutting off the power supply and maintaining the pressure. In the welding stage, the workpiece is melted by the resistance heat to form a nugget that gradually becomes larger. In the cooling stage, the nugget is cooled under pressure and solidifies to form a stable welded connection. The size of the nugget volume directly affects the quality of the weld point. If it is too large, spatter defects are likely to occur. If it is too small, Welding it may become defective.

[0027] The cooling process of resistance spot welding is a process in which the liquid metal nugget crystallizes and solidifies under pressure and continuously cools 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. When the temperature of the nugget is high and the volume is large, more heat is accumulated and the cooling rate is slow. Conversely, when the temperature of the nugget is low and the volume is small, the cooling rate is fast.

[0028] If the temperature of the nugget is too high and the volume is too large, spatter defects are likely to occur, a large amount of heat accumulated in the nugget is lost, and the cooling rate in the cooling process becomes fast. Conversely, if the temperature of the nugget is too low and the volume is too small, the heat accumulated in the nugget is low, and when the cooling rate in the cooling process is faster than that of a normal weld point, Welding defect defects are likely to occur. When the nugget is cooled to room temperature, the temperature stops changing and the resistance tends to stabilize.

[0029] The cooling characteristics of resistance welding are closely related to the heat stored in the nugget. Also, since the heat stored in the nugget is related to the temperature and volume of the nugget, the cooling characteristics of spot welding can indirectly reflect the quality of the weld point. By observing and analyzing the characteristics of the cooling process, the quality of the weld point can be evaluated, providing a basis for the optimization of 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, it is a welding defect evaluation method including the following steps. S101. Start applying a detection voltage to the welding location from the time when the welding current stops, and end when the temperature of the welding location reaches a preset threshold value. S102. Obtain a detection current generated according to the detection voltage applied to the welding location. S103. Calculate the resistance value of the welding location that continuously changes in the cooling stage based on the detection voltage and the detection current. S104. Determine whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location.

[0032] In step S101, as shown in FIG. 2, at both ends of the electrode of the welding apparatus, the voltage change between the electrodes is detected in real time with a voltage detection line. In step S102, a current detection line and its apparatus are attached at an appropriate position of the secondary loop to detect the change in current. In step S103, in the power-off holding stage (cooling stage) of resistance spot welding, the nugget is the main heat source, and its heat is dissipated to the electrode, the workpiece, and the surrounding air. Since the resistivity of the electrode and the nugget is closely related to the temperature, as the temperature decreases, the resistivity also decreases accordingly. Therefore, by detecting the resistance change of the electrode and the nugget, the temperature change in the cooling process of the nugget can be indirectly reflected, and the determination of the quality of the welding point becomes possible.

[0033] In the power-off holding stage of resistance spot welding, a small voltage and current are applied through the detection line. Since these current and voltage values are much smaller than the current (thousands to tens of thousands of amperes) used during welding, they do not have a significant impact on the crystal structure and mechanical properties of the nugget.

[0034] In the power-off holding stage, record the measured voltage value and current value. The voltage value and current value may be recorded at regular time intervals (for example, at the millisecond level), or may be intermittent recordings (for example, at important times such as the initial, middle, and end).

[0035] Calculate the resistance value using the recorded voltage value and current value according to Ohm's law (R = V / I).

[0036] In step S104, the characteristics of the resistance curve including the change situations of the initial value, intermediate value, and end value of the resistance are analyzed to determine the welding quality.

[0037] In the cooling stage of welding, at least the initial value at the start of welding, the intermediate value in the welding process, and the end value at the end of welding of the welding point are recorded.

[0038] Compare the resistance value with the resistance value at the same time of a known qualified welding point to find the difference. If this difference (deviation) exceeds the deviation range allowed for a normal welding point, this welding point can be determined as unqualified.

[0039] In addition to simple numerical comparison, based on the initial value, intermediate value, and end value of the resistance value recorded in the cooling stage of welding, a curve of the change of the resistance value over time (referred to as the first curve) is generated. Compare the generated first curve with the curve of the change of the resistance value over time of the preset qualified welding location (referred to as the second curve). The second curve is obtained based on a large amount of experimental data and experience, and represents the change trend of the resistance value in an ideal or qualified welding process. By comparing the two curves, it is possible to determine whether the welding quality is qualified.

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

[0041] Figure 3 shows the determination of quality problems.

[0042] Welding Defect L1: Welding The defect is due to the low temperature, small volume, small heat contained, and small melting region of the slug, leading to such characteristics of the resistance curve L1. Therefore, when the initial value is smaller than that of the qualified welding point, the descent rate of the intermediate value is slower than that of the qualified welding point, Small and the end value is larger than that of the qualified welding point, and the difference between the initial value and the end value is smaller than the first preset threshold, Welding it is determined as a defect.

[0043] Spatter L2: When spatter occurs, the spattered metal takes away the heat of the slug, reducing the metal in the slug region and causing the resistance curve to drop rapidly. The resistance at the end of spatter is smaller than that of a normal welding point. Therefore, when the difference between the initial value and the initial value of the qualified welding point is smaller than the second preset threshold, the descent rate of the intermediate value is larger than that of the qualified welding point, the end value is smaller than that of the qualified welding point, and the difference between the initial value and the end value is smaller than the third threshold, it is determined as spatter.

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

[0045] Continuing to refer to Figure 3, the analysis of other situations includes the following. Slug too large L3: The starting resistance value is equivalent to that of the qualified welding point, the cooling rate is slow, it reaches room temperature gently, the end resistance value is smaller than that of the qualified welding point, and the difference between the initial resistance value and the end resistance value is large. Slug too small: Similar to the Welding curve of the above defect.

[0046] In short, if the resistance value of the resistance corresponding to the time in the cooling process exceeds the tolerance range L4, it is a non - qualified welding point. Specifically, it is necessary to accurately analyze what kind of welding point it is, and it is a qualified welding point within the range.

[0047] To obtain the measured values of voltage and current at the above-mentioned three time points of initial, intermediate, and end, and calculate the obtained resistance value, the following steps are included. (1) When the welding current ends and the test current starts, immediately obtain the measured value (R1). (2) At the intermediate value (T2) of the power-off holding time, obtain the measured value (R2). (3) When the resistance change is almost stable (T3), that is, at the end time of the power-off holding, obtain the measured value (R3).

[0048] Furthermore, a plurality of measured values (R) can be obtained at regular time intervals (for example, 1 ms), and the first curve of the resistance change over time can be plotted.

[0049] Statistically calculate the measured values of the qualified weld points obtained under the same welding process and conditions. Based on the statistical results, determine the resistance change range at the corresponding time in the cooling process of the qualified weld points.

[0050] Compare the resistance value of the measured weld point obtained in the cooling process with the resistance at the corresponding time in the cooling process of the qualified weld points under the same welding process and conditions. If the resistance value of the measured weld point is within the fluctuation range shown by L4 in Figure 3, it is determined as a qualified weld point; otherwise, it is determined as an unqualified weld point. Deeply analyze the characteristics of the records or curves determined as unqualified weld points, and Welding further determine whether there are defects, spatter, or other welding defects in the unqualified weld points.

[0051] In this application, by utilizing the cooling characteristics of the welding point and measuring the resistance value, the temperature change in the cooling process of the nugget is represented, and quality determination is realized by comparing it with the resistance value in the cooling process of a normal welding point. This technology can detect all welding points in real time on the production line, ensuring complete coverage without leaving dead ends. The detection process is rapid, can be easily automated without manual intervention, perfectly conforms to the on-site production rhythm, and does not cause production delays.

[0052] In this application, detection is performed in the cooling stage, with few elements affected by external factors, a stable heat dissipation process, and the heat accumulated in the welding nugget during the welding process can be effectively embodied. By measuring the resistance value to represent the temperature change in the nugget cooling process and comparing it with the resistance value in the cooling process of a normal welding point, quality determination is realized, eliminating the need to add a separate sensor, effectively reducing additional costs, and saving investment. This application can be effectively used for both AC welding and DC welding, with a wide range of applications.

[0053] In addition, the method of the present invention is compatible with multiple types of metal materials and has high material compatibility.

[0054] This application also provides a welding defect evaluation device, a voltage module that continuously applies a detection voltage to the welding location in the cooling stage after the welding of the metal material is completed and the welding current stops, a detection module that detects the detection current corresponding to the detection voltage, a calculation module that calculates the continuous resistance value of the welding location based on the detection voltage and the detection current, a judgment module that determines the welding quality based on the initial value, intermediate value, and end value of the resistance value, and includes.

[0055] This application also provides a welding defect evaluation instrument, a memory that stores a computer-executable program of the above welding defect evaluation method, Call a computer-executable program, and in the cooling stage after the welding of the metal material is completed and the welding current stops, continuously apply a detection voltage to the welding location, detect a detection current corresponding to the detection voltage, calculate a continuous resistance value of the welding location based on the detection voltage and the detection current, and determine the welding quality based on the initial value, intermediate value, and end value of the resistance value. A processor that executes the steps; including.

[0056] The present application also provides a storage medium in which a computer-executable program is stored, and the computer-executable program is called by a processor and used to execute the steps of the above welding defect evaluation method.

Claims

1. A welding quality detection method applied to a welding device, wherein the working process of the welding device includes a welding stage and a cooling stage after the welding current stops. A step of starting to apply a detection voltage to the welding location from the time when the welding current stops and ending when the temperature of the welding location reaches a preset threshold value. A step of obtaining a detection current generated by the detection voltage applied to the welding location. A step of calculating the resistance value of the welding location that continuously changes in the cooling stage based on the detection voltage and the detection current. Among the continuously changing resistance values, if the initial value is smaller than the initial value of a qualified welding location, the falling speed of the intermediate value is smaller than the falling speed of the intermediate value of a qualified welding location, the end value is larger than the end value of a qualified welding location, and the difference between the initial value and the end value is smaller than a first threshold value, it is determined as a welding defect. A step of determining whether there is a welding defect in the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location. A welding quality detection method characterized by including the above.

2. In the step of determining whether there is a welding defect in the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location. Generating a first resistance curve based on the continuously changing resistance value. Generating a second resistance curve based on the resistance value of a qualified welding location that continuously changes in the cooling stage. Comparing the first resistance curve and the second resistance curve to determine the presence or absence of a welding defect. The welding quality detection method according to Claim 1, characterized by the above.

3. In the step of determining whether there is a welding defect in the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location. Among the continuously changing resistance values, if the difference between the initial value and the initial value of a qualified welding location is smaller than a second threshold value, the falling speed of the intermediate value is larger than the falling speed of the intermediate value of a qualified welding location, the end value is smaller than the end value of a qualified welding location, and the difference between the initial value and the end value is smaller than a third threshold value, it is determined as spatter. The welding quality detection method according to Claim 1, characterized by the above.

4. In the step of determining whether there is a welding defect in the welding location based on the change trend of the resistance value or the comparison result with the resistance value of a qualified welding location. Generating a first resistance curve based on the continuously changing resistance value. Determining the welding quality based on the change trend of the first resistance curve The welding quality detection method according to claim 1, characterized in that.

5. In the step of determining whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of the qualified welding location, Among the resistance values that continuously change at the qualified welding location, the qualified initial value, the qualified intermediate value, and the qualified end value are statistically analyzed, and based on the statistical results, the resistance value change ranges of the qualified initial value, the qualified intermediate value, and the qualified end value are obtained. The initial value, the intermediate value, and the end value in the resistance value that continuously changes at the measured welding location are compared with the resistance value change range, and the welding quality is determined based on the comparison result. The welding quality detection method according to claim 1, characterized in that.

6. In the step of starting to apply a voltage to the welding location from when the welding current stops and ending when the temperature of the welding location reaches a preset threshold value, Applying the voltage to the welding location via both poles of the welding gun. The welding quality detection method according to claim 1, characterized in that.

7. A voltage module that starts to apply a detection voltage to the welding location from when the welding current stops and ends when the temperature of the welding location reaches a preset threshold value, A detection module that acquires a detection current generated by the detection voltage applied to the welding location, A calculation module that calculates the resistance value of the welding location that continuously changes in the cooling stage based on the detection voltage and the detection current, Among the continuously changing resistance values, if the initial value is smaller than the initial value of the qualified welding location, the descent rate of the intermediate value is smaller than the descent rate of the intermediate value of the qualified welding location, the end value is larger than the end value of the qualified welding location, and the difference between the initial value and the end value is smaller than the first threshold value, it is determined that the welding is defective. A judgment module that determines whether there is a welding defect at the welding location based on the change trend of the resistance value or the comparison result with the resistance value of the qualified welding location. A welding quality detection device, characterized by including.

8. A memory that stores a computer-executable program for implementing the welding quality detection method according to any one of claims 1 to 6. Calling a program executable by the computer, starting to apply a detection voltage to the welding location from the time when the welding current stops, and ending when the temperature of the welding location reaches a preset threshold value; obtaining a detection current generated according to the detection voltage applied to the welding location; calculating a resistance value of the welding location that continuously changes in the cooling stage based on the detection voltage and the detection current; among the continuously changing resistance values, when the initial value is smaller than the initial value of a qualified welding location, the descending speed of the intermediate value is smaller than the descending speed of the intermediate value of a qualified welding location, the end value is larger than the end value of a qualified welding location, and the difference between the initial value and the end value is smaller than a first threshold value, determining whether there is a welding defect at the welding location based on the change tendency of the resistance value or the comparison result with the resistance value of a qualified welding location; a processor that executes the above steps; A welding quality detection device, characterized by including the above.

9. A program executable by a computer is stored, and the program executable by the computer is called by a processor and used to execute the steps of the welding quality detection method according to any one of claims 1 to 6. A storage medium, characterized by the above.

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