PROCESS FOR ACHIEVING PROPER WELD QUALITY IN COURSE OF THE WELDING OPERATION, MARKING THE FAULTS ON THE WORKPIECES AND CERTIFYING THE QUALITY

Abstract: Process for maintaining weld quality marking the fault spots (25) on the workpiece, in course of which momentary values of arc current and arc voltage (1, 2) are continuously measured and from the values, drop frequency and arc outputs (4, 6) are continuously calculated. The measured and calculated values are compared with empirically determined optimal values (8). The averages of absolute values and signals representing the directions are defined (9), furtheron the quotient of the duration of deviations and predetermined duration is formed. If averages and quotients fall between a first and a second limit value (11), a warning signal is given for the welder (23), whereas, if averages are surpassing the second limit simultaneously the fault spot is marked on the workpiece (25).

Description: Process for achieving proper weld quality in course of the welding operation, marking the faults on the workpieces and certifying the quality The invention relates to a process which enables maintenance of proper weld quality in course of welding operation by calling the atten¬ tion- of the worker to the failure prior to occur- ing. urtheron, the process is well suitable for marking the failure spots on the workpiece and by recording continuously input signals and processed signals Cfailure signals) for the demonstration of quality. In course of producing steel structures quality of the welding fastening the single elements of the structure to each other decisively determines the quality of said structures, accordingly, a con¬ siderable part of productional costs are alloted to welding and testing thereof. In addition to high costs, this fact fundamentally influences transit time, since only few welders are able to produce faultless welds being in compliance with the high qualitative demands. Costs and transit time are fur¬ ther increased by the necessity that for the sake of control welds are to be subjected to an 2>ray examination and after having corrected the faults, control with a repeated X-ray examination is also imperative. Correction, however, may result/, in dama¬ ges in the basic material causing premature failure of the structures i.e. reduction of loadability. Up to now it has been tried to eliminate said problems so that are welding apparatuses have been set possibly optimally and provided with means regulating the process during operation, this method proved unsuccessful, in particular under adverse cir- cumstances. In the patent HU 164 536 a process for setting of welding apparatuses is described. This patent starts from the conception that melting of the welding electrodes, accordingly welding proper¬ ties are fundamentally determined by the electric parameters of the welding process Cwelding voltage and arc current, relative period of short-circuit¬ ing and drop frequency, both to be calculated there- from). By measuring the arc current and voltage welding parameters belonging to the given task are determined, thereafter, by changing inductive re¬ sistance of the welding apparatus optimal values of the velocity of current changing are adjusted. The welder performs his work with this optimally set apparatus. According to the patent US 4103 141 it is not sufficient to set once the welding apparatus prior to beginning the welding process, but it has to be regulated continuously, during the process in order to keep the values of arc voltage and arc current within a predetermined range, whereby welding of proper quality can be obtained. An equipment is also known which controls the welder himself while working. Such an equipment is disclosed i the patent US 40 β 3075. With this solution by means ό£ measur¬ ing stations having been installed on the single. ork- ing places a centrally located computer controls and records the activity of the single workers (maximally for 100 working places). The computer registers the number of arc ignitions, duration of continuous weld¬ ing, the parameters and consumed electric energy. The previously described patents examine bu the process of welding and did not yield a satisfac¬ tory solution; in course of practice the experience could be gained, in so far as even with optimally adjusted and controlling (semi-automatic) apparatuses only well qualified welders are able to make a fault¬ less weld and even in this case qualification can be negatively influenced by tiredness, inattention, bad conditions etc., as a consequence control X-ray exa¬ minations of considerable number cannot be omitted. The known apparatus controlling the welders themselves did not yield the solution needed either, as it controls practically the power and efficiency of the worker and his discipline of labour but quali¬ tative welds are not at all assured. Experiences having been gained in course of long years' practice are unambiguously showing that weld quality primarly depends on the welder him¬ self and only secondarly on the apparatus used, as inproper function of the apparatus or smaller errors of adjusting can be equalized by the knowledge, ex¬ perience and manual skill of the welder, at the same time, if these qualifications are missing even with the optimally adjusted apparatus weld faults will occur. Welders perform fundamental welding phases using a plurality of individual methods, so e.g. with different handpositions, all influencing the result of the welding and quality of welding. Analysing the work of welders, a general working method can be de- termined, representing the working system of highly qualified welders. Our invention was elaborated on basis of the parameters corresponding to this general system, the application of which can trained to the welders in course- of qualifying in a rather short time. Accordingly, our intention is to solve the following tasks by using the process according to the invention: - increasing "knowledge and manual skill" of the welders by means of informative warning signals - forecast of the physical fitness of the welder on basis of the procents of faults at the beginning of the shift - signalizat on of momentary faults at the welder and other controlstations, e«g. at the foreman - signalization the possibility of making a faulty welding i.e. marking it on the workpiece (accord¬ ingly nondestructive testing can be restricted to these parts) - certifying of proper welding quality - qualifying the welder. Eealization of the aims set is based on the following recognitions: a) for every welding operation an optimal working poi can be determined (empirically) on the curve arc current-arc voltage and there is an optimal arc output, i.e. interval; b) similarly, there exist an optimal short-circuit time and drop frequency, i.e. an interval; c) the welds prepared will be of proper quality, if average values of the arc-parameters (current, voltage, drop frequency, relative shor^circuit ti me and arc output) are falling into th determined environment of the optimum points, whl,le if they are coincident or lie outside thereof, a faulty weld will be probably made; d) a faulty weld can be reckoned with, if velocity of deviation of the average of the arc-parameters is reaching a critical value; e) comparing the difference between momentary values and optima with total time and extrapolating their tendency, condition of the welder can be presignallized, i.e. expectable percent of faults can be predetermined. Accordingly, our invention relates to a process for the maintenance of weld quality during operation, marking of the faultspots on the workpieces and certifying of quality. In course of the process momentary values of arc current and arc voltage being characteristic for the welding process are continous- ly measured and on the basis of measured data relati¬ ve short circuit time of the arc, drop frequency and arc output are continuously calculated. The essence of the invention lies in that both measured and calculated values are compared with empirically determined optimal values, while absolute values and signals representing the directions, as wel as duration of deviations are determined, thereafter the averages of absolute values and signals' represent- ing the direction are formed related to a pre-deter- mined period, furtheron quotient of the duration of deviations and pre-determined duration is formed. Average values and said quotient are re¬ gistered. Simultaneously with recording we examine the proportion of the absolute values to a first and second limit-value. In case, if these absolute values are falling between the first and second limit values an alarming signal is given for the welder. In case, if averages are surpassing the second limit value, a further alarming signal is given, simultaneously the workpiece is marked, as long as the averages are falling below the second limit value. In course of the process according to the invention the freβhly formed average of the absolute values and quotient of duration are compared with the • previously formed and recorded average and quotient. Velocity of change is also determined and in case, if a third limit value is surpassed, a warning signal is given before average values would surpass the first average value. In accordance with the invention - to be able to perform pre-signalisation - we are counting the number of surpassings of the first and second li¬ mit values, respectively, related to a longer span of time, let us say, to an hour, and in case, if these surpassed a further limit value, each, a signal is gi¬ ven. Determination of possible fault places is performed so, that in addition to fault markings ti e- -marking arc is also marked on the workpiece. Markers relating to time and faults, respectively, are made with dyestuffs of different colour. When giving the warning signals, a signal each is given in dependence of the average of signals the directions. The invention will be detailed by means of the drawings enclosed, wherein a possible version of the process is specified. While welding, momentary values of arc current and arc voltage characterizing welding process are measured by means of the arc current sensor 1 and arc voltage sensor 2 having been connected to the out put terminals of the arc welding apparatus supplying welding current. Prom the momentary values having bee measured relative shortcircuit time, drop frequency and momentary value of arc output are measured by mea of the drop frequency signal forming unit 4, the unit 5 generating short circuit signal and the unit 6 cal¬ culating arc output; measuring is continuously per- formed. Signals representing momentary values are led " to the signal inputs of unit 7 forming the differen¬ ce. Reference signal inputs of the unit 7 are connect¬ ed to the outputs of the unit 8 yielding the optimal value, delivering the optimal arc parameter values of a given welding task having been determined empi¬ rically. By the aid of the difference forming unit 7 we compare the measured and calculated values of the ' arc parameters with the relating optimal values, si¬ multaneously determining absolute values of deviation and belonging directions. Signals are forwarded part¬ ly to the unit 9, forming the average, partly to the unit 15 defining period of deviation. Absolute value and average of the direc¬ tions are formed, in the unit 9, forming the average for an empirically fixed period, which can change in dependence of the task set. Average values and direc¬ tions having been formed are led partly to the inputs of the comparing unit 11, the inputs of the recorder 19 and partly to the inputs of the memory 10. By means of the memory 10 average values and signals representing the directions of deviations are stored provisionally, while the recording unit 19 serves for the final storing. Said signals are led to the display 29 displaying the type of the fault occured and to one of the inputs of the comparator 14. Comparator 11 examines, whether the averages are falling between a first and a second limit value, respectively, or surpass the second li itf value• Li¬ mit value signals are supplied by the first limit value transmitter 12 and the second limit value trans¬ mitter 13. In case, if average fall into the range between the first and second limit value, a warning signal is omitted. In addition, the given warning signal depends on the average directional sign of the deviations, accordingly, if average lies below the optimal values, a warning signal I is given, while if it lies above it, a warning signal II will be released on the first and second output of the com¬ parator 11. If the welder operates around the opti- al values, no signal if given. By the aid of the warning signal trans¬ mitters 3, respectively, 23 having been installed in¬ to the face shield of the welder the warning signals I, respectively II are transmitted, calling the atten- tion of the welder to the expectable occurence of fault and giving the proposed method of avoiding, in such a manner welders with inferior qualification can also prepare welds of proper quality. In case, if averages surpassed the second limit value, on the third output of the comparative unit 11 a warning signal III is released. Warning sig¬ nal III appears on the working place on the fault dis¬ play 22 and the display 28 displaying the type of fault, simultaneously averages of deviations of weld- ing parameters also appear; while the fault signal exists, the fault marker 25 is marking the faulty weld ing on the working pieces with a dystuff marking. Recorder 19 serves for the documentation of the complete welding process which records the average of deviations of the welding parameters, warning sig¬ nals I and II and fault signal III in dependence of time. In order to be able to identify recordings of the recorder 19 with the weld on the workp eces, mark¬ ing unit 24 marks the time on the working piece with a different colour. As already mentioned before, the outputs of the unit 7 forming the difference are also connect¬ ed to the inputs of the unit 15 defining deviation time. On the outputs of the unit 15 time signals will exist as long as the given welding parameter deviates from the optimal value. Said time signals indicating timely dif¬ ference are led to the quotient forming unit 16, wherein quotients of duration of deviation are formed related to a predetermined span of time. Output sig¬ nals of the quotient forming unit 16 are led partly to the inputs of the memory 10, partly to the compa¬ rator 14 and partly to the inputs of the extrapolat¬ ing unit 28. Accordingly, in the memory 10 average values, signals representing the directions and quo¬ tients of timely deviations are stored; in the next period said stored signals are compared with the i- dentical signals just formed by means of the compara¬ tor 14. By means of the differential quotient forming unit 17 velocity of change of the signals represent¬ ing the result of comparison is determined, thereafter velocity signals obtained are compared with the limit signals delivered by the basic signal transmitter 32 in the comparator 18; in case, if velocity signals sur passed the limit signal, warning signal I, respecti¬ vely, II are omitted in dependence of the character of the directional sign of the momentary average of the welding parameter deviation in accordance with the directional signs 17 introduced. In such a manner the welder can be warned prior to surpassing the first limit value. Warning signals I and II, as well as fault signals III are led into the counter 20, the number of the signals arriving during an hour is counted. In course of counting fault signal III is considered with a multiple averaging as a three-fourfold value, number of signals appearing within an hour are compar¬ ed in the comparative unit 26 with the limit signal delivered by the limit value transmitter 27; in case of a positive result deterioration of quality is sig- nailed on the unit 30. By determining the quantity of several differing limit signals both the work¬ piece and the welder can be qualified. Output signal of the counter 20 is led to the outer input of the extrapolating unit 28, to the first input of which the signals of the quotients in¬ dicating the duration of fault are led. By means of the extrapolating unit 28, on basis of the develop¬ ment of said signals, at the beginning of the shift, e.g. at the end of the first working hour, conclusions can be made in respect to the quality of faults to be expected during the whole working time. Said value is indicated by the unit 31 indicating the magnitude of the faults to be expected, thus informing the fore- man about the condition of the welder on this speci¬ fic working day. Co-ordinated operation of the equipment de¬ mands a plurality of time signals, the transmitter 21 delivers the required time signals a ... k. It becomes obvious that warning signals I and II emitted in due time in accordance with the invention enable the welder to avoid faulty welds, as warning signals appear so, as to enable avoiding the faults; the informations delivered give the di- rectives for changing work performance in a positive direction, as a consequence, after a short period of training awelder with an inferior qualification and less experience is also able to make #elds of first class quality, which could be made ptherwise - without the solution according to the invention - only by a highly qualified welder with a long expe¬ rience. It goes without saying that the invention involves several additional advantages, as e.g. by marking the reduced faults, duration of non-destruc- tive tests can shortened, expenses are reduced, as * $ JR OM Λ only the marked sections are to be tested, why, for the others weld quality is documented in the regis¬ ter.

Claims: C l a i s 1. Process for maintaining weld quality during welding operation, marking the fault spots on the workpiece and certifyin " of quality, incourse of which momentary values of arc current and arc voltage characterizing manual or mechanized welding process are continuously measured and from the values thus obtained relative short circuit time of the arc, drop frequency and arc outputs (powers) are con¬ tinuously calculated, c h a r a c t e r i z e d in that measured and calculated values are compared with empirically determined optimal values, thus defining absolute values and signals representing the direc- tions of deviations, as well as duration of deviations thereafter - related to a predetermined span of time - averages of absolute values and signals repre senting the directions are defined, furtheron the quotient of the duration of deviations and pre-deter- mined duration is formed; averages and quotients are recorded and simultaneously averages of the absolute values are related to a first and second limit value and in case, if they fall between the first and se¬ cond limit value, a warning signal is given for the welder, whereas, if averages are surpassing the se¬ cond limit value a further signal is given and simul¬ taneously fault spot is marked on the workpiece as long as averages are reduced below the sedond limit value. *' 2. Process as claimed in claim * 1, c h a ¬ r a c t e r i z e d in that momentary formed average of absolute values and quotient of durations are com¬ pared with previously formed average and quotient, thus determining velocity of change and in case, if a third limit value is surpassed, a warning signal OMPI is given, before average values could surpass the first limit value. 3. Process as claimed in claim 1 or 2, c h a r a c t e r i z e d in that number of sur- passings of the first and second limit values relat¬ ed for a larger span of time, e.g. an hour is counted and in case, if these surpassed a further limit value each, a signal is emitted. 4. Process as claimed in any of the claims 1 to 3, c h a r a c t e r i z e d in that in addi¬ tion to marking the fault spots, time-markers pro- time units are also applied onto the working piece. 5. Process as claimed in claim 4, c h a ¬ r a c t e r i z e d in that marking of faults and time-markers are of different colour, using diffe¬ rent d stuffs. 6. Process as claimed in claims 1 to 4, c h a r a c t e r i z e d in that when surpassing the first limit value, in addition to the given warn- ing signal a signal each is given in dependence of the average of the signals representing the direc¬ tions. f

Inventors: LUKACS LASZLO, MOLNAR LASZLO, RETFALVI FERENC, SZAPPANOS ADAM, TOTH LASZLO, LUKACS, LASZLO, MOLNAR, LASZLO, RETFALVI, FERENC, SZAPPANOS, ADAM, TOTH, LASZLO
Applicants: KOHASZATI GYAREPITOE VALLALAT
Application year: 1984
Main classification: B23K9
IPC codes: B23K9