SU768581A1 - Apparatus for quality control of spot contact welding - Google Patents

Description

The invention relates to the processing and welding of materials and can be used to control the quality of welded joints in the process of their implementation by resistance spot, seam and relief welding. A device for quality control of spot welding is known in which during the execution of welding of each point, the quality of joints is determined from its basic parameters to the geometric dimensions of the cast core of point f 1. This device is based on a mathematical model of the process of resistance spot welding, which establishes a quantitative dependence of the dimensions of a cast core point on the basic parameters of the welding mode. The closest to the invention of the technical essence and the achieved result is a device for controlling the quality of resistance spot welding, comprising a sensor unit, a unit for calculating the diameter of a weld point, a unit for calculating the depth of mutual melting of parts and a display unit, connected in series, and the output of the unit for calculating the core diameter The weld point is connected to the second input of the display unit 12. The quality control of spot welded joints is carried out by this device according to the diameter of the core point and the depth of mutual penetration of parts directly during welding on the basis of information about changes in process parameters. The low accuracy of the control by the known device is due to the fact that the quality of welding is determined by two parameters of the zone of mutual melting of the parts being joined - the diameter of the cast core and the depth of mutual melting of the parts. At the same time, the quality of welding — the strength of the joints — depends both on the size of the core point and on the internal defects in the zone of mutual melting of the parts being joined. One of the serious and difficult internal macrodefects of a welded joint is the discontinuity of the metal of the cast zone in the form of pores, cavities and cracks, which reduce the fatigue durability of the joints and, consequently, the efficiency of welded structures. The aim of the invention is to improve the accuracy with entrol quality of welded joints. This is achieved by the fact that a block for calculating the forging force of compression of the electrodes and an analyzer of the dimensions of the weld point are introduced into the proposed device, with the first output. The welded point dimensions analyzer is connected to the output of the weld point core diameter calculator; the second input is connected to the output of the calculator of the mutual penetration section of details of the welded point dimensions analyzer to the third input of the display unit; the input unit for calculating the forging compression force of the electrodes under; It is connected to the output of the sensor unit, and the output of the calculating unit of the forging force to compress the electrodes is connected to the input of an analyzer for the dimensions of the weld point and to the fourth input of the display unit. FIG. 1 shows a functional block diagram of devices for controlling the quality of resistance spot welding; in fig. 2, a – z is a cylogram of the process of spot welding. The device contains a block 1 of a sensor for the process parameters, which includes a sensor 2 of the welding current, a sensor 3 for the voltage drop across the electrodes, and a sensor 4 for the compression force of the electrodes. All sensors are installed on the contact welding machine: not (not shown in the figures). The sensor unit 1, unit 5 for calculating the diameter of the weld point core, unit 6 for calculating the depth of mutual details of the details and display unit 7 are connected in series, and the output of the unit; 5, the core diameter calculation is connected to the second input of the display unit 7. ,;.: The compression forging force calculation unit 8 of the electrodes is connected to. Output of sensor 2 of svarnozgo tbka and sensor 4 of the force: compression of the elec- trodes, and its outputs are connected to the display unit 7 and to the analyzer 9 dimensions of the weld point. The analyzer is equipped with 9 inputs. It is also connected to the output of block 5 for calculating the diameter of the saarna point and to the output of block 6 for calculating the depth of the penetration melting of parts, and the output for the third input of block 7 signals. : /; ; -. ,,., -, ".., .. Block 8 is designed to measure directly during the welding of each Point of the forging force of compression of the electrodes and the time of its inclusion, to compare them with the optimal values of Emi parameters, when installed on the welding machine, provide The formation of point connections without internal macrodefects in (cracks, pores and cavities) and, in the case of rtcdone, at least a single Icc is measured, the value of the error signal on the unit 9 of the analyzer of the geometric dimensions of the cast point core. . The unit 8 for measuring and comparing the forging force of compressing the electrodes and the time it is turned on contains a storage element .10 for storing the forging force for compressing the electrodes, connected by this input elements 11 and 12 of the comparison, the second of which is connected to the input of the element 10 via a differentiating capacitor chain 13 and resistor 14. The second inputs of the elements 11 and 12 are connected to the source 15 of the reference voltage. The output of the element 12 is connected to the trigger 16, which is connected to the electronic key 17 connected to the pulse generator 18. The output of the key 17 is connected to the first input of the pulse counter 19, the second input of which is connected to the output of the comparison element 11, and the output of the pulse counter 19 is connected to the input of the decoder 20, the output of which is connected to the display unit 7. The input of the decoder 20 is also connected to the reference element 21, connected with. element 22 OR and block 23 settings. The storage element 10 is connected to the comparison element 24 associated with the OR element 22. The trigger 16 is connected to the synchronization element 25, which is connected to the welding current sensor 2. . The analyzer 9 dimensions of the weld point is designed to determine directly during the execution of the weld and the volume of the molten point core, comparing it with the minimum volume of the NKJTall. In which the formation of internal macrodefects in the cast core of the weld point is possible, and when the last signal is exceeded, the display unit 7 is signaled to signal a spot welding defect in case of deviation from the set values of the compression force of the electrodes or the time of its activation. Block 9 contains serially connected multiplication element 26, comparison element 27, setpoint element 28 and element 29 AND connected to element 27 of comparison, the second input is connected to the output of element 22 OR, and output of element 29 AND is connected to one of the inputs of block 7 indications. : The device works as follows. The unit 5 calculates the diameter of the core point by the current parameters of the process measured by the sensors 2,3 4 directly during welding, and the basis of the unit 6 calculates the depth of the mutual melting of the parts. The voltages from the output of the blocks 5 and, proportional to the diameter of the core, the glasses and the depth of mutual reproduction of the parts, respectively, are transferred to the block 7, which is produced. the indication in the ten-fold code of the quality parameters of the welded joint (the diameter of the point frame in millimeters, the depth of the mutual melting of the parts as a percentage of their diameter) and their recording on paper tape. At the same time, block 9, namely, the multiplication element 26, according to the parameters of the zone of mutual melting of connected parts calculated by blocks 5 and 6, of the diameter of the point core and: the depth of the mutual melting of the parts determines the volume of the molten metal of the point core. The voltage from the output of the element 26, proportional to the volume of the molten metal of the point core calculated directly during welding, is fed to the input of the comparison element 27 and is compared to the voltage that is fed to its second input from the element 28 of the settings, which forms a signal proportional to the minimum volume metal, at which the formation of internal macrodefects in the cast core of the weld point is possible. The magnitude of the latter is determined from the results of experimental and statistical processing of X-ray and metallographic analyzes of welded points from materials of various grades and thicknesses 1. Moreover, the internal defects of the type of cracks, pores, and crayfish are revealed with the help of X-ray translucency, the minimum volume of the cast core, at which they can be formed, by metallographic means. In case the voltage from the output of the element 26 exceeds in magnitude the voltage coming from the element 28 to the comparison element 27, then a high level signal is generated at its output, which is fed to the input of the logic element 29 I. the same level at its second input, which is produced by logic element 22 OR block 8 when the forging force of the electrodes is compressed or when it is turned on beyond the maximum permissible values of the parameters, results in a low level signal at the element output. This signal is sent to the 7th display, where the signaling of a spot welding defect is made, for example, in the form of a luminous inscription on the display panel of the block. CRACKING IS POSSIBLE. Measurement directly at the welding process of each point of the forging force of electrode compression, its activation time and comparing them with the maximum values of the mode parameters, at which the formation of point connections without internal defects, is carried out by block 8 as follows. When the compression force FC increases (, on the electrodes of the welding machine (see Fig. 2, a), the signal from sensor 4 of unit 1 is fed to the input of the comparison element 11 and through the differentiating chain to the input element: 12 comparison. When decelerating the signal from the sensor The 4 switching threshold level of the comparison elements, which is set by the SOURCE 15 of the reference voltage and selected from the noise immunity condition of the latter, at the output of the elements 11 and 12 (in Fig. 2, b and in, respectively) a potential corresponding to a high output level is established. A high voltage level at the output of element 11- is maintained until the compression force is completely removed from the electrodes, and at the output of element 12 - for a time determined by the constant time of the differentiating chain.The leading edge of the Pulse from the output of element 11 is set to zero the counter 19 pulses, and from the output of element 12, setting trigger zero to 16. (Fig. 2, e). When welding current Uj is turned on, synchronization element 25 (Fig. 2, d), the signal from sensor 2 detects: a pulse that sets a trigger 16 in position., which corresponds to a high an equal voltage at its output unit. In this case, a high voltage level from a single output of the trigger 16 opens the electronic key 17 and switches the output of the generator 18 pulses (Fig. 2, e) to the input of the pulse counter 19. Thus, since the start of the welding current, the following is made: filling the counter of 19 pulses, i.e. conversion of the measured time to the number of pulses. When the forging force F is compressed by the electrodes (moment of time ty,, Fig. 2, a) by differentiating the signal from sensor 4 by element 12, a pulse is again generated, the leading edge of KOTOpofo corresponds to the moment of pressing the forging force of electrodes. : by this. the trigger 16 is shifted to the position O, and at its single output a potential is established which corresponds to the low output level (Fig. 2, e). The electronic key 17 is closed and thereby stops the flow of pulses to the input of the count 19 pulses (Fig. 2, g). The number of pulses, recorded by the counter, is converted by the decoder 20 into a descriptive code, which from its output goes down to block 7 to indicate the time when the forging force of pressing the electrodes is turned on. The time measurement is produced in seconds. Simultaneously, the pulse code from the output of the counter 19 pulses arrives

to the input of the comparison element 21 and compares with the CBd & k corresponding to

zhdaj bsc uyenyv1KNYucheni forging effort compression electrodes. The latter is formed by the element 23 yctabOK. In case the measured time is larger than the life of the parameter deviation permitted by the production, the comparison element 21 generates a signal that is outputted from its output to one of the inputs of the logic element 22 OR, and then to the input of the logic element 29 AND block 9. The output signal the logical element 22 OR in the presence of a cast point core indicates a defect in the welded joint, since it is known that the inclusion of a forging force to compress the electrodes after a specified time leads to the formation of internal pores, cancer ovini cracks.

The measurement of the forging force of compression eeeKtrbdov produced by the storage element 10, the input of which receives a signal from the sensor 4 force., Compression of the electrodes. As a storage element, well-known analogue signals can be used.

; scheyah; storing the amplitudes of the signals on the capacitors (the peak-detector-type detection circuitry) or the decisive amplifier in the inertial-link mode. Dia; gram voltage at the output of storage element 10 is shown in FIG. 2.3, the output of the storage element of the iO voltage, proportional to: the forging force of compressing the electrodes, goes to block 7, where it is converted from analogue form to digital and indicated on the display in decimal code. The measurement of the forging force of the compression of electrodes is made in kilograms.

In addition, unit 8 compares the stresses proportional to the measured and specified compression forging compressors for the voltage that is applied to the reference element 24 compared to the response from the output of the storage element 10 and the element 23 of the settings. In case measured in the process

in pffi to fHee in sitShe 7 akat Wr ayyo ktrodov. does not exceed the value of the parameter that was set before starting up for its change in production conditions; a comparison element 24 forms an impulse on the logical element 22 OR. Lastly, a pulse is generated at block 9 and, as in the previous case, in the presence of a cast point core, block 7 signals a defect in the scrolling defect, as a reduction in forging

The EFFORT of compression of the electrodes, as well as of the Г 3 Г Я Я test in the application time, leads to the formation of macrodefects of the welded joint.

Optimum values of forging - - 5ySh Compress electrodes and time

its inclusion depends on the brand of the material being welded, the thickness of the parts, the welding mode and the type of contact machine. The optimal values, as well as the values of permissible 1x deviations by the parameter under the conditions of production, under which the formation of point connections without internal macrodefects is ensured, are chosen experimentally when welding prototypes. Defaces such as cracks, pores, cavities and splash in spot welding are detected by X-ray.

It is advisable to use the device for 100% non-destructive testing of the quality of welded joints in the process of their implementation mainly in the manufacture of critical welded structures in the aircraft industry, shipbuilding and other parts of the engineering industry.

The introduction of devices in production will reduce the HopivM of existing labor-intensive control methods (X-ray examination, metallographic analysis and mechanical testing) and increase the cost-effectiveness and productivity of resistance welding. At 100% quality control of point joints, the omission of rejected points will be excluded, due to which the operational reliability of welded structures will be significantly increased.

Formula of Invention

A device for monitoring the quality of resistance spot welding, containing a sensor unit, a welded point core diameter calculating unit, a unit for calculating the depth of interdissusion of parts and a display unit connected in series, the output of the welded point core calculating unit, connected to the second input of the display unit. In order to improve the accuracy of quality control of welded joints, a block for calculating the forging force of compression of the electrodes and the analyzer of the dimensions of the welded point were introduced, while The first input of the welded point dimensions analyzer is connected to the output of the core dimension block of the weld point, the second input is to the output of the mutual penetration depth calculator, the output of the welded point dimensions analyzer is connected to the third input of the display unit, the input of the forging compression unit of the electrodes is connected to the output of the sensor unit, and the output of the calculating unit of the forging force of compression of the electrodes is connected to the third input of the dimension analyzer welded

points and with the fourth input of the display unit.

Sources of information taken into account in the examination

1. USSR Author's Certificate No. 405679, cl. On 23 K 11/24, 1973 ..

2. USSR author's certificate

No. 478701, cl. B 23 K 11/24, 03/22/74,

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Claims (1)

Claim A device for monitoring the quality of spot resistance welding, comprising a sensor unit, a unit for calculating the diameter of the core of the weld point, a unit for calculating the depth of mutual penetration of parts, and an indication unit connected in series, the output of the unit for calculating the diameter of the core of the weld point being connected to the second input of the display unit,. l and with. I mean that, in order to improve the accuracy of quality control of welded joints, a unit for calculating the forging force of compression of the electrodes and an analyzer of the dimensions of the weld point were introduced, while the first input of the analyzer of dimensions of the weld point is connected to the output of the unit for calculating the diameter of the core of the weld point, and the second input to the output unit for calculating the depth of mutual penetration of parts, the output of the size analyzer of the weld point is to the third input of the display unit, the input of the unit for computing the forging force of compression of the electrodes is connected to the output of the sensor unit and the output of the block for calculating the forging force of compression of the electrodes is connected to the third input of the size analyzer of the weld point and to the fourth input of the display unit.