SK363792A3 - Method of quality following of weld by a fusion welding - Google Patents

Abstract

In the mash-seam welding of sheet-metal panels (11, 12) with overlapping edges between electrode rollers (13, 14), the welding quality, provided that the process parameters (pressing force F of the electrode rollers, feed speed v, current intensity I through the welding point) are adhered to or regulated, is also dependent on the overlapping width (b) of the panel edges which is present at the welding point. Since it is difficult to measure the actual overlap during production, instead the thickness (ts) of the welded seam is recorded. With given workpiece data and associated welding parameters, this thickness is in direct relation to the overlap width (b). The functional relation ts = f(b) can be determined empirically and makes it possible to define the actual value of the overlap on the basis of the measured seam thickness. The thickness measurement can be carried out either at the welding point by measuring the spacing of the electrode rollers (displacement transmitter 16) or on the finished welded seam (measuring device 17). Instead of the relation ts = f(b), the relation between ts and another operating variable can also be evaluated in a similar way. <IMAGE>

Description

Technical field

In fusion seam welding of a metal sheet between cylindrical electrodes, it is necessary and usual for continuous process control and quality monitoring to measure continuously and / or continuously. manage the following working variables:

- the pressing force (F) of the cylindrical electrodes,

feed rate (v) and

- current intensity (I) during welding.

The given values of these variables are - for a particular workpiece - based on the determined offset width (b) of the edges of the sheets to be welded and are determined before welding while the sheets are aligned and clamped in place. All of the independent working variables listed must be within certain limits to achieve the required quality weld.

BACKGROUND OF THE INVENTION

However, the continuous measurement or control of various work variables over time. Welding is simple and can - depending on the type of variable - present different degrees of difficulty. Therefore, in order to overcome this disadvantage, in one of the methods used, the weld seam temperature of the passing workpiece is measured as an excess variable as soon as it exits the cylindrical electrodes. In conjunction with the essential data, this is intended to increase the reliability of the tracking function. However, in order to be truly reliable, this temperature measurement must be a controller under certain pre-determined conditions, since it may be difficult to install a measuring device, e.g. infrared sensor.

In order to achieve a good weld or create a sufficient welding melt in the seam area, it is also of particular importance that the determined offset width is actually established in the welding station. However, misalignment may already occur with five alignment of the metal sheet and exposure to the load, or deviations may occur when feeding the workpiece between the cylindrical electrodes. It is therefore very difficult and hardly possible to measure the true offset value during the passage or immediately after the cylindrical electrodes.

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION The object of the present invention, in conjunction with the above method of fusion seam welding, is to propose a method suitable for industrial use which permits to significantly extend operational quality control in a manner that is achievable. According to the invention, this object is achieved by recording the seam weld thickness during the welding operation and derives the weld quality criterion from a predetermined relationship between the weld thickness values and one of the - independent - initially changed operating variables.

There are many tried and tested ways to record the seam thickness and calibration does not present any significant difficulties. The seam thickness can be measured directly or indirectly according to the working need, or alternatively at the point of origin by measuring the distance or displacement of the cylindrical electrodes. In the second, it might be necessary to make corrections for the variations in thickness that occur! in cooling and solidifying the area, but this is usually taken into account when determining the particular functional relationship used.

In practicing the method of the invention, it is possible to start by deriving a criterion by comparing the weld thickness values with the values of other operating variables that are determined from (specifically used) predetermined relationships. However, it is also possible to take primary comparisons of the set values and the actual seam thickness value as such, the set values being determined by these interrelations.

The particular relationship used can be determined in advance empirically for a given workpiece and work parameters. The method according to the invention is particularly suitable for the operational calculation of the edge offset width value which, as explained above, cannot be measured directly.

Mark dependent claims! Foreign embodiments according to claim 1.

Overview of the figures in the drawing

An exemplary embodiment of the method of the invention is shown in the accompanying drawing, the main aspect being the relationship between the thickness of the seam weld and the offset width; Fig. 1 shows a schematic of a fusion seam welding apparatus with cylindrical electrodes and a workpiece to be welded; Fig. 2 is a front view of two offset sheet metal sheets prior to welding; Fig. 3 is a similar view of the sheets joined by welding; and Fig. 4 shows a typical, empirically determined functional relationship between the offset width b and the seam weld thickness ts.

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DETAILED DESCRIPTION OF THE INVENTION

Highly simplified and schematic of the device of Fig. 1 with cylindrical electrodes fusion seam welding (sheet metal type 11,12). Sheet metal sheets 11.12 align and clamp with offset ends as shown by welding

13. 14 is used for resistance welding to be welded is shown in FIG. As shown in FIG. 1, the lower cylindrical electrode 14 is fixed, while the upper cylindrical electrode 22 can slide on the workpiece and exert a compressive force F, e.g. *, using the hydraulic cylinder system 15. During the welding process, the working variables - the pushing force (F) of the cylindrical electrodes 13, L4, the feed rate (v) of the workpiece and the current intensity (I) of the weld joint - are smoothly measured and sorted as in the known manner. based on predetermined slant adjustment control b edge edge board 11.12 sheet. When welding the edges of the sheet 11, the current passing between the cylindrical electrodes 13.14 and the corresponding heating of the sheet material lying between them in the so-called &quot; in the welding core of the method is that the material is simultaneously deformed by the pressing force F to form a fusible seam 10 (FIG. 3), the thickness ts of which is substantially less than the sum of the thicknesses t1 and t2 of the sheet 12, 12. ). The extent to which the material is deformed depends on the three variables listed above and the actual offset width b (actual value) in the weld. With these three working variables, other variables can be measured as slope as the slope. weld temperature 2 * 2 at the exit of the cylindrical electrodes 13.14 and controlled as needed.

The continuous recording of the real values of the work variables constitutes an important criterion in quality control, i. if these actual values deviate unacceptably, it must be inferred from this that the weld quality is inadequate and the workpiece must be discarded.

However, as has been said before, the practical Mekit is not real

An arrow b repositioning the edges of a blackboard during transportation. In order to make a definitive conclusion about the true value of the offset length and hence the quality of the work, a certain relationship between the offset width b is used in the present invention. the thickness s of the seam weld 10 as shown in FIG. 4 for one particular example. The relationship between the offset width b and the resulting weld thickness ts can be used

Determine empirically beforehand for different workpieces and operating parameters.

It has been found that this relationship - at least in production-related areas - is always unambiguous and makes the weld thickness an excellent substitute variable for the offset width. In other words, the seam weld thickness ts is measured on the workpiece and this relationship is used to determine the true value of the offset width b. In order to achieve a clear good / bad criterion for the quality of the function monitoring, the tolerance range T of the weld thickness corresponding to the offset range B of the offset can be determined. The previous criterion can be derived either by determining whether. the values found for b lie or do not lie within the tolerance range of B or by a clear determination of whether ts lies or does not lie within the tolerance range of T (given point range).

The relation ts = 1 (b) used is determined in each case in advance using a series of tests in the appropriate ranges and using the given workpiece data (sheet thickness, material, etc.) and the respective working parameters. There are various options for grinding the welding process. How the thickness ts during the run is shown in c

1, the distance between the cylindrical electrodes 13, 14 or otherwise of the position of the movable cylindrical electrode 13 can be measured automatically using the position encoder 16 (displacement sensor). However, once the workpiece leaves the cylindrical electrodes 13.14, it is also possible to soften the thickness of the weld in the solidifying weld seam 10 at the location 17 using methods known per se, i. by contact rolls or non-contact using ultrasonic or radiation absorption measurements. In both cases, the electrical measurement signal sent by the corresponding sensors will pass to the evaluation circuit (not shown) where the measured value will be automatically registered, displayed and evaluated for quality monitoring. When performing this evaluation, it is usually useful to make an average of the instantaneous values over the entire length of the weld (workpiece length) or a part thereof (e.g., compressed parts at the beginning and end), or to evaluate them statistically for quality control. For a number of workpieces and / or operating parameters, respective functional correlations predetermined can be stored in large data tables, allowing them to be retrieved at any time as required for computer processing.

Although the above embodiments of the method relate to the relationship between the seam thickness and the offset width, it is well possible to use predetermined relationships between ts and other working variables (e.g., F, v, I) in a similar manner.

Claims (8)

Patent claims Method for monitoring weld quality in fusion seam welding of a sheet of metal between cylindrical electrodes (13,14), where the set values are determined at least for the following working variables: thrust force (F) of the cylindrical electrodes (13,14), feed rate ( v), the intensity of the current (I) during welding, the arrow (b) offset of the edges of the sheet metal sheet, characterized in that the seam weld thickness (ts) during the welding operation is determined and the weld quality criterion is derived based on a predetermined relationship between the seam thickness (ts) and one of the above working variables. Method according to claim 1, characterized in that the criterion is derived by comparing the value of the seam thickness (ts) with the second working variable determined from this relationship. Method according to claim 1, characterized in that the criterion is derived by comparing the actual and set values of the seam weld thickness measured (s) as such. Method according to claim 1, characterized in that the tolerance range (T) for the seam thickness value (ts) is determined. Method according to claim 1, characterized in that the distance of the cylindrical electrodes (13, 14), which indicates the seam thickness (ts), is measured. Method according to claim 1, characterized in that the seam weld thickness (ts) is measured on the workpiece itself. Method according to claim 1, characterized in that the seam weld thickness values (ts) are averaged and / or statistically evaluated over at least a portion of the seam length. Method according to claims 1 to 7, characterized in that a predetermined relationship between the seam thickness (ts) and the offset width (b) is used to derive the weld quality criterion. Method according to claim 8, characterized in that the actual value of the offset width (b) is determined on the basis of a predetermined relationship. 91 / HER M-42