KR101172676B1 - Welding condition creation method of spot welding - Google Patents

Abstract

The present invention relates to a method for setting the welding conditions of spot welding, and in detail, it is possible to present the optimum spot welding working conditions according to the corresponding spot welding operation in response to the change in the thickness of the plate during spot welding according to various changes of the processed product. It is intended to provide a database.

The present invention includes a spot welding quality evaluation system for detecting the welding state at the time of spot welding in real time to determine the appropriateness of the weld state; The welding time range is welded by gradually increasing the welding time of a metal plate of a certain thickness in a welding environment that supplies a predetermined welding current and is subjected to a constant pressing force, and the spot welding quality evaluation system performs proper welding in the corresponding welding environment. A first step of acquiring data for the first step; After acquiring data on the range of welding time for proper welding in any welding environment through the first process, the welding current is increased by a predetermined value to change the welding environment, and the process proceeds to the first process in the changed welding environment. A second process of acquiring data on a range of welding time at which proper welding is performed; After acquiring data on the range of welding time for proper welding in the changed welding environment through the second process, the welding pressure is increased by a predetermined value to change the welding environment, and the process proceeds to the first process in the changed welding environment. A third step of acquiring data on a range of welding times at which proper welding is made; And after acquiring data on the range of welding time at which the proper welding is performed in the changed welding environment through the third process, changing the welding environment by increasing a predetermined thickness of the weld plate, and proceeding to the first process. And a fourth process of acquiring data on the range of welding time at which proper welding is performed in the welding environment.

Spot welding, pressing force, welding current, time, adequacy

Description

How to set welding conditions for spot welding {WELDING CONDITION CREATION METHOD OF SPOT WELDING}

1 is an exemplary configuration of a spot welding quality evaluation system for the application of the present invention

2 is a graph showing a measurement example using FIG.

3 is an exemplary view showing a principle of quality evaluation according to the change of dynamic resistance of the spot welding quality evaluation system shown in FIG.

4 is an operation flowchart of a welding condition setting process for improving the spot welding quality according to the present invention

Figure 5 is a schematic diagram showing a process of inspecting the weld quality through the peel test in the conventional spot welding

The present invention relates to a method for setting the welding conditions of spot welding, and in detail, it is possible to present the optimum spot welding working conditions according to the corresponding spot welding operation in response to the change in the thickness of the plate during spot welding according to various changes of the processed product. It is intended to provide a database.

In general, spot welding (spot welding) is a welding method belonging to the electric resistance welding, a method of welding while applying pressure using heat generated when the current flows through the metal. When the two metals to be joined to each other are flowed while applying an appropriate mechanical pressure, heat of resistance is generated, which uses the property of joining the pressure parts, which is a very popular welding method for automobile body assembly.

Spot welding is a welding method that is widely used, accounting for about 95% of the total number of 3500 ~ 4000 elements in a passenger car.

However, as various kinds of surface-treated plated steel sheets are widely used due to the anti-rusting regulation of automobile bodies, the spot weldability is remarkably degraded due to the influence of the plating layer. For this reason, the evaluation of weld quality and weldability to maintain the body strength Is an important issue.

On the other hand, in spot welding used for assembling sheet metal parts in automobile manufacturing lines, the evaluation of weldability includes peel test, tensile shear test, and cross tensile test related to joint strength. And the results of experiments such as measuring the nugget diameter of spot welds.

FIG. 5 is a schematic diagram illustrating a step of inspecting welding quality through a peel test in conventional spot welding. As shown, mechanical force is applied to expose the nugget 3 to two welded materials 1 and 2. In addition, the weld quality is determined by visually observing the size and fracture state of the nugget 3 appearing at this time.

However, the welding quality inspection as described above is destructive sample inspection, and even if it is judged to be defective, it is impossible to correct, and it is difficult to improve the quality of welding because it is impossible to identify the cause of the quality defect, There was a time consuming problem.

Moreover, in general, spot welding generates resistance heat when a current is flowed while putting two metals to be joined together under an appropriate mechanical pressure. This is because the pressure portion is bonded to each other. Conditions can be expressed as pressing force, time, and amount of current flowing.

On the other hand, the welding conditions are also changed according to the thickness of the plate, the above-mentioned conventional inspection method, even if the welding quality is excellent, it is difficult to database the data on the conditions for performing the welding, moreover, the plate Since the welding condition is set based on the manual of the spot welding system judged to be appropriate according to the material and the thickness of the material, there is a problem that there is no standard that can be adapted to various changes in the processed product.

That is, when the welding condition of the spot welding system is to be set, the welding condition is set by the skilled person and the condition is reset by the test as shown in FIG. This breakdown method causes a problem of loss of work. Therefore, only a rough welding condition is recorded in the process of preparing a method, and a realistic welding condition cannot be recorded.

The present invention corrects the problems described above, and uses a spot welding quality evaluation system to change the thickness of a plate having any material (for example, from 0.5 t to 10 t) while applying the spot welding of the plate at each thickness. We have obtained the welding conditions for the area experimentally, and made a database to respond to the change in the thickness of the plate during spot welding, so that the optimum spot welding work conditions can be suggested according to the spot welding operation. It is an object to provide a method for setting welding conditions.

In order to achieve the above object, the present invention provides a method for setting welding conditions in spot welding for joining two metals to be joined by heat generated at a portion pressurized by conducting a constant current under a constant mechanical pressure. A spot welding quality evaluation system for detecting a welding state in real time to determine whether the welding state is appropriate; The welding time range is welded by gradually increasing the welding time of a metal plate of a certain thickness in a welding environment that supplies a predetermined welding current and is subjected to a constant pressing force, and the spot welding quality evaluation system performs proper welding in the corresponding welding environment. A first step of acquiring data for the first step; After acquiring data on the range of welding time for proper welding in any welding environment through the first process, the welding current is increased by a predetermined value to change the welding environment, and the process proceeds to the first process in the changed welding environment. A second process of acquiring data on a range of welding time at which proper welding is performed; After acquiring data on the range of welding time for proper welding in the changed welding environment through the second process, the welding pressure is increased by a predetermined value to change the welding environment, and the process proceeds to the first process in the changed welding environment. A third step of acquiring data on a range of welding times at which proper welding is made; And after acquiring data on the range of welding time at which the proper welding is performed in the changed welding environment through the third process, changing the welding environment by increasing the thickness of the weld plate by a predetermined value, and proceeding to the first process to change the welding. It comprises the 4th process of acquiring the data about the range of the welding time which a suitable welding is performed in environment.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

First of all, the present invention is not limited to the description below, but may be interpreted in advance by a finite element method (FEM), and in the following, the spot welding quality evaluation system described in Korean Patent No. 10-0482487 This is an example of using the configuration.

FIG. 1 is a diagram illustrating a configuration of a spot welding quality evaluation system according to the present invention, FIG. 2 is a graph showing a measurement example using FIG. 1, and FIG. 3 is a diagram of the spot welding quality evaluation system shown in FIG. 1. It is an exemplary figure which shows the principle of quality evaluation by the change of a copper resistance.

Referring to the configuration of the spot welding quality evaluation system shown in FIG. 1, the current to be welded 10 is joined to each other, and two current electrodes 20 are used to flow a current while applying an appropriate mechanical pressure. By applying a welding to the site under pressure, the wire 30 is attached to both ends of the two electrodes to measure the voltage between the both ends of the electrode, the current sensor 210 is attached to the electrode to the current After measuring the to measure the variation in resistance generated when welding the voltage signal based on the current signal.

More specifically, the voltage measuring unit 100 is connected to both ends of the electrode to measure the voltage; A current measuring unit 200 connected to one of the electrodes to measure current; The divider 300 is connected to the voltage measuring unit 100 and the current measuring unit 200 and divides the voltage signal and the current signal to calculate a resistance value.

The voltage measuring unit (100) of the configuration includes a differential amplifier (110) connected to both ends of the electrode; A variable gain amplifier (120) connected to the differential amplifier (110); It consists of a full wave rectifier (130) connected to the change gain amplifier (120).

In addition, the current measuring unit 200, the current sensor 210 is provided on one side of the electrode; An attenuator / voltage follower 220 connected to the current sensor 210; An integrator 230 connected to the attenuator / voltage follower 220; A change gain amplifier 240 connected to the integrator 230; It is composed of a full-wave rectifier 250 connected to the change gain amplifier 240, so that the divider 300 to divide the output signal of the voltage measuring unit 100 and the current measuring unit 200 Adjust and rectify.

On the other hand, the other end of the divider 300, the low pass filter 400 for filtering only the necessary signal of the measured resistance value; An output unit 500 for displaying the signal is further configured, and the output unit 500 displays a change in resistance over time as a graph (see FIG. 2), thereby changing the resistance in real time during welding. Make sure you know.

At this time, referring to the accompanying drawings, the quality evaluation principle according to the change in the dynamic resistance of the spot welding quality evaluation system used in the present invention, the dynamic resistance (dynamic resistance) is a time change in the resistance of the weld as the welding cycle proceeds As discussed above, the dynamic resistance value shown in FIG. 3 is an indicator of the quality of the actual welded portion by showing the progress of welding.

In the step I of FIG. 3, as the initial current is energized, contaminants on the metal surface collapse, thereby rapidly decreasing resistance. This interval occurs within a few ms and is difficult to observe in typical welding conditions without preheating.

Subsequently, in stages II and III, as the uneven portion of the contact surface disappears, the contact area through which current flows increases, the resistance decreases, and the specific resistance increases due to the temperature rise of the contact portion. Therefore, after the two resistance changes are equilibrated and become the poles, the copper resistance increases again due to the increase in the specific resistance.

Subsequently, in step IV, melting of the contact portion starts, and an increase in specific resistance due to temperature increases and becomes equilibrium with a decrease in resistance due to an increase in the conduction area due to the expansion of the melt part and a shortening of the conduction distance due to plastic deformation.

Finally, in the V stage, the thickness reduction due to the growth and plastic deformation of the melt nugget is noticeable as the IV peak passes, and the dynamic resistance is significantly reduced. After that, when the solid metal around the nuggets under pressure can no longer support the molten metal, an intermediate explosion occurs, which causes a discontinuous decrease in dynamic resistance.

Based on the analysis of the welding state according to the general resistance change, the quality of the welding can be evaluated by using the measurement of the actual dynamic resistance value.

That is, the signal 1 of FIG. 2 shows a dynamic resistance signal at the time of proper welding quality, and shows a moderate slope to a moderate peak value, but the signal 2 lacks a resistance string so that nuggets cannot be formed properly. It indicates a bad state.

In addition, signal 3 is interpreted as an abnormality in welding quality due to spattering caused by excessive heat.

As mentioned above, the quality of the welded state can be evaluated using the measured value of a copper resistance.

Therefore, the data on the spot welding condition (magnitude of current, time, pressing force) when the signal # 1 of FIG. 2 is detected can be obtained for one sheet.

The data obtained in this way is changed to a thickness of, for example, 0.5t to 10t, and the optimum spot welding condition for each thickness is obtained and made into a database.

Referring to FIG. 5 attached to the database formation process, a test model for acquiring an optimum welding condition for spot welding operation is set in step S101.

Spot welding is to join two metals to be joined by heat generated at a portion which is pressurized by applying a constant current under constant mechanical pressure. In step S102, the thickness of the welding plate is initially set, and in step S103, welding is performed. The pressing force of the sheet is initially set. In step S104, the welding current for welding the sheet is initially set, and in step S105, the welding time of the sheet is initially set.

When the initial setting for the welding working environment is completed through the process of steps S102 to S105, the process proceeds to step S106 to perform a spot welding operation.

At this time, while the process of step S106 is being performed, it is determined in step S107 whether or not the welding state has entered a range recognized as an appropriate state through the spot welding quality evaluation system described with reference to FIGS. 1 to 3. If it is determined that it is not properly made, the process proceeds to step S108 to increase the welding time, and the process proceeds to step S105 to change the welding time of the sheet material from the previous setting value.

On the other hand, if it is determined in step S107 that the current welding state has entered a range recognized as an appropriate state, the process proceeds to step S109 to store data on the working environment set through the processes of steps S102 to S105.

Subsequently, it is determined in step S110 whether the welding state through the above-described process is out of a range recognized as an appropriate state, which is to acquire data on the range of welding time at which proper welding is performed in the corresponding welding environment. An appropriate range of welding is detected in the range of welding time.

At this time, the data of the thickness of the welding plate, the pressing force of the welding plate, and the welding current for welding have already been obtained as values of the preceding conditions for the welding working environment through the processes of steps S102 to S104.

Thereafter, as a prerequisite for the welding working environment through the process of step S112, it is determined whether the data has been acquired through all the data regarding the change in the welding current, and when it is determined that the data is not completed, the process proceeds to step S113 and the data on the welding time. Is initialized and the welding current is increased to proceed to step S104.

Therefore, the data on the welding time for the changed welding current is obtained.

On the other hand, if it is judged that all the data of the possible range for the welding current have been acquired through the process of step S112, the process proceeds to step S114 and data is acquired through all the data regarding the change in the pressing force as a prerequisite for the welding working environment. If it is judged that it has not been completed and judged that it has not been completed, the process proceeds to step S115 to initialize the data on the welding time and the welding current, and increases the pressing force, and then proceeds to step S103.

Therefore, the welding current and the welding time for the changed pressing force are acquired.

On the other hand, if it is judged that all the data in the possible range for the change in the pressing conditions have been acquired through the process of step S114, the process proceeds to step S116 and all the data for the change in the thickness of the plate as a prerequisite for the welding working environment are obtained. If it is determined that the data acquisition has been completed, and it is determined that the data has not been completed, the process proceeds to step S117 to initialize the data on the welding time, the welding current and the welding force, increases the thickness of the plate, and then proceeds to step S103.

Therefore, the welding current and the welding time for the changed pressing force are acquired.

Through this process, in the process of step S118, data of three-dimensional welding conditions for welding current, time, and pressing force with respect to the change in the thickness of the plate is acquired.

While the invention has been shown and described in connection with specific embodiments thereof, it will be appreciated that various modifications and changes can be made without departing from the spirit and scope of the invention as indicated by the claims. Anyone who owns it can easily find out.

As described above, the present invention can provide a database for presenting an optimum spot welding operation condition according to the spot welding operation in response to the thickness change of the spot welding plate according to various changes in the production process product. It can shorten the period and maintain the uniformity of quality.

Claims (1)

In the welding condition setting method for spot welding in which two metals to be joined are joined by heat generated at a portion pressurized by applying a constant current while a constant mechanical pressure is applied, A spot welding quality evaluation system for detecting a welding state in real time to determine whether the welding state is appropriate; The welding time range is welded by gradually increasing the welding time of a metal plate of a certain thickness in a welding environment that supplies a predetermined welding current and is subjected to a constant pressing force, and the spot welding quality evaluation system performs proper welding in the corresponding welding environment. A first step of acquiring data for the first step; After acquiring data on the range of welding time for proper welding in any welding environment through the first process, the welding current is increased by a predetermined value to change the welding environment, and the process proceeds to the first process in the changed welding environment. A second process of acquiring data on a range of welding time at which proper welding is performed; After acquiring data on the range of welding time for proper welding in the changed welding environment through the second process, the welding pressure is increased by a predetermined value to change the welding environment, and the process proceeds to the first process in the changed welding environment. A third step of acquiring data on a range of welding times at which proper welding is made; And After acquiring data on the range of welding time for proper welding in the changed welding environment through the third process, the thickness of the welding plate is increased by a predetermined value to change the welding environment, and the process proceeds to the first process. And a fourth process of acquiring data on the range of welding time at which the proper welding is performed in the welding process.

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