DE102015219450B4 - Method and device for welding at least two metal strips - Google Patents

Abstract

Method for welding at least two metal strips (1, 2), comprising the steps a) arranging the at least two metal strips (1, 2) in parallel, b) switching on a welding current (I), welding the metal strips (1, 2) in sections using a welding head (3), which is moved along a weld seam (4) with a first feed movement (A), and switching off the welding current (I), c) executing a movement (B) in the opposite direction to the first feed movement (A) with the welding head (3) and the metal strips (1, 2) by essentially the same distance (x, y), d) repeating steps b) and c) until the metal strips (1, 2) are completely welded together, characterized in that Welding current (I) is gradually increased at least in sections up to a first predetermined value (11) when switched on during the first feed movement (A) and/or gradually reduced at least in sections to a second predetermined value (I2) when switched off during the first feed movement (A). becomes.

Description

The invention relates to a method for welding at least two metal strips, in which the at least two metal strips are arranged parallel to one another in step a) and a welding current is switched on in step b), the metal strips with the aid of a welding head, which with a first feed movement along a weld seam is moved, sections are welded and the welding current is then switched off again. In a step c), a movement in the opposite direction to the first feed movement is carried out with the welding head and the metal strips by essentially the same distance. Steps b) and c) are repeated until the metal strips are completely welded together. In addition, the invention also relates to a metal strip that is produced using a method of the type mentioned above. Finally, the invention also relates to a device for welding at least two metal strips, comprising a welding head and means for carrying out a first feed movement and a movement in the opposite direction thereto with the welding head.

A method, a device and a metal strip of the type mentioned above are known in principle. For example, such a method and such a device are used to longitudinally weld comparatively long metal strips to one another, for example when the metal strips are not available or cannot be produced in the required width. In order to keep the work area small, the weld is made in sections, which means that the weld ultimately consists of pieces or sections lined up next to each other. The problem here is that the weld seam is constructed inhomogeneously according to the known methods and, in particular at the ends of the individual sections, has a different structure compared to the rest of the weld seam and is also different with regard to the geometric dimensions. Widening or "bumps" often occur at the ends of the individual sections, i.e. where the individual pieces of the weld seam meet.

In many applications, these inhomogeneities and distributions do not cause any problems. For certain applications, however, welded metal strips with a very high surface quality are required, for example when they are used for the production of plate-shaped or film-like materials, in particular for films for photography, LCD screens or artificial stone ("engineered stone"). A liquid or pasty material is applied to a driven/moving belt and the at least partially solidified material is lifted off. The surface finish of the product made with such a metal strip is directly related to the surface finish of the metal strip.

The DE 10 125 830 A1 also discloses a method for producing a welded connection between the ends of two metal strips using a TIG welding torch that can be moved transversely to the longitudinal direction of the metal strips. Before welding, pieces of sheet metal are attached to the longitudinal sides of the metal strips in the area of the subsequent weld seam, with the TIG welding torch being ignited on one of the pieces of sheet metal and placed on the other piece of sheet metal to weld the metal strips. After welding, the pieces of sheet metal are removed from the metal strips.

The DE 103 22 450 A1 also discloses a method for welding coated metal sheets, in which the length of a weld seam is kept so short that the vapor pressure of the coating, which evaporates during welding, which builds up as the length of the weld seam increases, does not exceed the critical eruption limit.

The JP H09-136159 A also discloses a method for resuming a longitudinal pipe welding operation after it has been previously interrupted. In this case, the welding head is moved, starting from an original position, in the direction of a feed direction of the tube, with the tube being temporarily stopped. The tube is subsequently welded by moving the welding head against said feed direction until a position at a distance from the original position is reached. As a result, the welding current is temporarily stopped, the welding head is moved to the original position and the longitudinal welding is continued in the normal way.

The DE 295 08 656 U1 finally discloses a strap welding device for welding endless straps to be joined together with at least one strap holder arranged on a base plate for receiving the strap ends, with a cutting device for trimming the strap ends and with a welding device for connecting the strap ends. The cutting device releases the plane of the strip during and/or after trimming of the strip ends, after which the welding device connects the strip ends at the released point.

An object of the invention is now to specify an improved method, an improved device and an improved metal strip. In particular, inhomogeneities and pulp Welding seams at the ends of the individual sections/pieces can be avoided or at least reduced.

The object of the invention is achieved with a method of the type mentioned at the outset, in which the welding current is gradually increased, at least in sections, to a first predetermined value when switched on during the first feed movement and/or to a second predetermined value when switched off during the first feed movement is gradually reduced to zero, at least in sections.

The object of the invention is also achieved with a metal strip that is produced using a method of the type mentioned above.

Finally, the object of the invention is also achieved with a device of the type mentioned at the outset, which has a controller/regulator that is set up to gradually increase the welding current, at least in sections, during a first advance movement up to a first predetermined value and/or when switched off during the first feed movement to a second predetermined value, in particular to zero, to be reduced at least in sections successively.

With the help of the proposed measures, smooth transitions between the individual sections of the weld seam are created, which affects the structure on the one hand and the geometric dimensions on the other. The weld seam therefore essentially appears as a whole or unit. Ideally, the boundaries between the individual sections of the weld seam are no longer perceptible or verifiable.

In general, in addition to the successively changing or constant sections, the course of the current can also have jumps, particularly at low current values at which there is no appreciable influence on the weld seam. As a rule, it is advisable to increase the welding current quickly, and if necessary with a step function, to a value from which the weld seam is significantly affected. The welding current can also be reduced from such a value to zero quickly or with the aid of a step function.

Basically, it should be noted that a gradual change in the current profile or a continuous section can also be made up of smaller individual stages, especially if digital control or regulation is used. Such a stage should be disregarded for the purposes of the invention if its height remains below 10% of the maximum current that occurs during welding. Other preferred values are less than 5% and less than 1%. In reality, the stages specified by a digital control or regulation are often so severely ground that they are no longer perceptible, in particular due to inductances in the welding circuit.

In general, the statement “substantially” in the context of the invention means in particular a deviation of up to 10%. With regard to the difference between the distance traveled by the welding head and the distance traveled by the metal strips during the movement in the opposite direction to the first feed movement, the indication "substantially" means in particular a deviation of a maximum of 10% in relation to the distance traveled by the welding head during the first feed movement . Further preferred values are a maximum of 5% and a maximum of 2%.

It is favorable if the distance by which the metal strips are moved in step c) is shorter by a differential distance than the distance covered by the welding head. In this way, the adjoining sections of the weld seam overlap one another, and a particularly homogeneous course of the same can be realized.

It is also favorable if the sections along which the welding current is successively increased or decreased at least in sections when switching on and off are of the same length. In this way, a homogeneous progression of the weld seam can be achieved even better. This applies in particular when the distances over which the welding current is successively increased or reduced at least in sections when switching on and/or off essentially correspond to the difference distance mentioned above.

It is also advantageous if the speed of the first advance movement is gradually increased at least in sections when the welding current is switched on up to a third predetermined value and/or is gradually reduced at least in sections when it is switched off to a fourth predetermined value (in particular to zero). This provides another parameter for influencing the welding result. In particular, the variation of the feed rate is advantageous when the welding current cannot be varied to the necessary extent, for example when the method for producing the metal strip is to be carried out with an existing welding current source which however, the requirements are not fully met. Like the course of the welding current, the course of the feed speed can also show jumps.

In addition, it is favorable if the successive increase/decrease in the welding current and/or the feed rate takes place linearly, exponentially, logarithmically, along a half sine wave or along a quarter sine wave. As a result, particularly gentle transitions between the individual sections of the weld seam can be achieved.

It is also particularly advantageous if the gradual increase/decrease of the welding current and the feed speed takes place in such a way that the energy introduced into the weld seam per unit of travel changes linearly, exponentially, logarithmically, along a half sine wave or along a quarter sine wave. In this variant of the manufacturing process, the course of the energy introduced into the weld seam is considered, which essentially results from the course of the welding current and the feed rate. With the same welding current, a low feed rate leads to a higher energy input per travel unit than a high feed rate.

It is also advantageous if alternating components are superimposed on the constant values of the welding current and/or the feed rate. This may promote welding and/or stability of the arc.

Finally, it is advantageous if the device for welding the metal strips has means for carrying out a movement of the metal strips in the opposite direction to the first feed movement. In this way, the production of the metal strip can take place completely automatically, and there is no need for the metal strips to be advanced manually.

At this point it is noted that the variants disclosed for the production method and the advantages resulting therefrom relate equally to the disclosed device and vice versa.

For a better understanding of the invention, it is explained in more detail with reference to the following figures.

• 1 eine schematisch dargestellte Anordnung zum Verschweißen zumindest zweier Metallbänder in Seitenansicht;
• 2 die Anordnung aus 1 in Draufsicht;
• 3 wie 1, jedoch mit einem beispielhaften Verlauf des Schweißstroms;
• 4 einen weiteren beispielhaften Verlauf für den Schweißstrom beziehungsweise die Vorschubgeschwindigkeit mit stufenförmigen Abschnitten;
• 5 weitere beispielhafte Verläufe für Schweißstrom und Vorschubgeschwindigkeit;
• 6 ein Beispiel, bei dem einem konstanten Wert des Schweißstrom / der Vorschubgeschwindigkeit Wechselanteile überlagert sind;
• 7 beispielhafte Verläufe für Schweißstrom, Vorschubgeschwindigkeit und in die Schweißnaht eingebrachte Energie und
• 8 eine beispielhafte Vorrichtung zum Verschweißen zweier Metallbänder.

They each show in a greatly simplified, schematic representation:

• 1 a schematically illustrated arrangement for welding at least two metal strips in side view;
• 2 the arrangement 1 in top view;
• 3 How 1 , but with an exemplary course of the welding current;
• 4 another example curve for the welding current or the feed rate with stepped sections;
• 5 further example curves for welding current and feed speed;
• 6 an example in which alternating components are superimposed on a constant value of welding current/feed speed;
• 7 exemplary curves for welding current, feed speed and energy introduced into the weld seam and
• 8th an exemplary device for welding two metal strips.

As an introduction, it should be noted that in the differently described embodiments, the same parts are provided with the same reference numbers or the same component designations, it being possible for the disclosures contained throughout the description to be applied to the same parts with the same reference numbers or the same component designations. The position information selected in the description, such as top, bottom, side, etc., refers to the figure directly described and shown and must be transferred to the new position in the event of a change of position. Furthermore, individual features or combinations of features from the different exemplary embodiments shown and described can also represent independent, inventive solutions or solutions according to the invention.

The 1 and 2 show a greatly simplified and schematically illustrated arrangement for welding at least two metal strips 1, 2, with the aid of a welding head 3 along a weld seam 4 in a side view ( 1 ) and top view ( 2 ). The metal strips 1, 2 are welded in sections. Concretely, the sections or segments C1 .. C4 are welded one after the other. In a first step a) of the method carried out here, the metal strips 1, 2 are aligned parallel to one another. In a further step b), a welding current I is switched on and the metal strips 1, 2 are welded together in sections, with the welding head 3 being moved along the weld seam 4 with a first feed movement A and with the welding current I being switched off at the end of section C1 ..C4 becomes. Then, in a step c), two movements are executed, either simultaneously or one after the other or at different times puts. The metal strips 1, 2 perform a movement B that runs in the opposite direction to the first feed movement A, specifically by the distance x. The welding head 3 also performs a movement B in the opposite direction to the first feed movement A, covering a distance y that is essentially the same length as the distance x. Steps b) and c) are carried out recursively in sequence until the metal strips 1, 2 are completely welded to one another, ie the sections C1 .. C4 are welded one after the other. The 1 and 2 show a state in which section C2 is being welded, ie step b) is being carried out for the second time. In this way, even relatively long metal strips 1, 2 can be welded over their entire length in a very limited space.

In order to create a smooth transition between the individual segments C1..C4 and thus a homogeneous strip surface, the welding current I is gradually increased at least in sections during the first feed movement A up to a first specified value when switching on and/or when switching off during the first Feed movement A to a second predetermined value at least in sections successively lowered, in particular to zero. Advantageously, the distance x by which the metal strips 1, 2 are moved in step c) is shorter by a differential distance d than the distance y covered by the welding head 3, as is shown in FIGS 1 and 2 is shown. This results in an overlapping of the adjoining sections C1..C4 during welding.

The 3 shows an illustrative course of the welding current I, which is successively increased at the beginning of a segment C1..C4 or when switching on and is successively reduced at the end of a segment C1..C4 or when switching off. It is also conceivable to successively increase the current I only when switching on or to successively reduce it only when switching off. A step would then result accordingly at the beginning or end of the current curve. In the example shown, the welding current is reduced linearly from zero to a constant value and linearly from this value to zero. However, this is not a mandatory condition, as will be shown in the following 4 until 7 is explained.

The overlap and the gradual change in the welding current I result in a particularly gentle transition between the segments C1 . It is advantageous if the distances z1, z2, on which the welding current I is successively increased or decreased at least in sections when switching on and off, as in FIG 3 shown, are of the same length and also (substantially) correspond to the differential distance d, which is formed by the difference between the distances yx. However, this is not mandatory. In principle, the distances z1 and z2 can also be of different lengths and do not have to correspond to the difference distance d.

4 shows a somewhat more general curve of the welding current I, from which it can be seen that the welding current I does not necessarily have to be increased successively over the entire distance z1 or reduced successively over the entire distance z2, but that steps or jumps in the current curve can also be provided . In the concrete, purely illustrative example of 4 if the welding current I is suddenly increased to a value I3 when switched on, then remains constant for a while and is then increased linearly to the value I1. When switching off, the welding current I is first reduced linearly to a value I2 on the distance z2, then remains constant for a while and is then abruptly reduced to the value zero. Such a course is advantageous in that welding currents I have almost zero influence on the weld seam 4 . However, the proposed measures quickly reach a level for the welding current I at which the weld seam 4 is influenced.

In the example shown, the welding current I can be related to the distance s or the time t. In particular, if the speed v of the first feed movement A is constant, the curve is practically congruent. However, the speed v is not necessarily constant, but can be successively increased at least in sections up to a third predetermined value v1 when the welding current I is switched on and/or gradually reduced to a fourth predetermined value v2 at least in sections when it is switched off. In principle, steps or jumps in the speed profile are also possible. In the 4 an example of the speed curve v is shown, which has the same shape as the current curve I. However, it is noted at this point that it is of course by no means necessary for the current curve I to be the same as the speed curve v, but that they can sometimes even differ greatly from each other. For example, the welding current I could have a curve as shown in 4 shown and for the velocity v a curve as in 3 be provided shown.

Up to now, linear or step-like progressions have been assumed. However, these are by no means the only options. 5 shows further examples in which, in addition to a linear increase (solid line), an exponential curve (dashed line), a logarithmic curve (dash-dot line), a curve along a half-sine wave (dotted line) or along a quarter-sine wave (dash-dot line) Point line) for the welding current I and the feed rate v are shown.

It is also conceivable that alternating components are superimposed on the constant values of the welding current I and/or the feed speed v, as is the case in FIG 6 is shown. For example, a triangular curve, a rectangular curve or a sinusoidal curve could be superimposed on the constant value.

In a further advantageous variant, the successive increase/decrease in the welding current I and the feed speed v takes place in such a way that the energy E introduced into the weld seam 4 per unit of travel changes linearly, exponentially, logarithmically, along a half sine wave or along a quarter sine wave. 7 shows an example in which the welding current I runs exponentially and the feed rate v logarithmically, as a result of which the energy input E into the weld seam 4 runs linearly or approximately linearly here.

8th finally shows an exemplary and schematically illustrated device 5 for welding at least two metal strips 1, 2, comprising a welding head 3 connected to a welding power source 6, which is mounted on a carriage 7, which is guided on rails 8 and can be moved by a drive 9 . In this example, the carriage 7, the rails 8 and the drive 9 thus form means for carrying out a first feed movement A and a movement B running in the opposite direction thereto with the welding head 3. In addition, the device 5 comprises a controller/regulator 10 which is set up for this purpose to gradually increase the welding current I when switching on during a first feed movement A up to a first predetermined value I1 at least in sections and/or to gradually reduce it to a second predetermined value I2 at least in sections when switching off during the first feed movement A. In addition, the control / regulation 10 is also connected to the drive 9, so that both the welding current I and the feed speed v can be increased / decreased successively, whereby, for example, in the 4 until 7 shown courses can be realized.

In addition, the device 5 also includes a machine table 11 and two drives 12, 13, which in the example shown form means for executing a movement B of the metal strips 1, 2 in the opposite direction to the first feed movement A. In this example, the drives 12 and 13 are also connected to the control/regulation 10, as a result of which the sequence comprising steps a) to d) for welding two metal strips 1, 2 can be implemented.

In general, it should be noted that in particular for the feed rate v, due to the mass inertia of the welding head 3, the carriage 7 and the drive 9, not any curves can be realized. In particular, maximum gradients for the speed, corresponding to the maximum achievable accelerations, are predetermined by the system. With the help of the proposed measures, a curve can be set for the welding current I that matches the curve of the feed rate v, so that the weld seam 4 has a homogeneous appearance.

Furthermore, it is noted that in particular the means 7 . For example, the welding head 3 can also be attached to the arm of an articulated arm robot. The means 12, 13 for moving the metal strips 1, 2 can of course also be designed differently.

The exemplary embodiments show possible embodiment variants of a manufacturing method for a metal strip 1, 2, it being noted at this point that the invention is not limited to the specifically illustrated embodiment variants of the same(s), but rather also various combinations of the individual embodiment variants with one another are possible and this possibility of variation due to the teaching on technical action through the present invention lies within the ability of the person skilled in the art working in this technical field. All conceivable design variants that are possible through combinations of individual details of the illustrated and described design variant are also included in the scope of protection.

In particular, it is also stated that the devices shown can in reality also include more or fewer components than shown and are sometimes shown in the figures in a greatly simplified manner.

Finally, for the sake of order, it should be pointed out that the devices shown and their components are sometimes shown not to scale and/or enlarged and/or reduced in order to better understand their structure.

Reference List

1

metal strap

1

metal strap

3

welding head

4

Weld

5

welding device

6

welding power source

7

Dare

8th

rail

9

Drive for welding head

10

control

11

machine table

12

Drive for metal belt

13

Drive for metal belt

A

feed motion

B

reset movement

C1..C4

welding section

i.e

differential feed path

E

energy

I

welding current

s

Away

t

Time

v

speed

x

Feed path metal strip

y

Feed path welding head

z1

switch-on path

z2

switch-off path

Claims (10)

Method for welding at least two metal strips (1, 2), comprising the steps of a) arranging the at least two metal strips (1, 2) in parallel, b) switching on a welding current (I), welding the metal strips (1, 2) in sections using a Welding head (3), which is moved along a weld seam (4) with a first feed movement (A), and switching off the welding current (I), c) executing a movement (B) in the opposite direction to the first feed movement (A) with the welding head (3 ) and the metal strips (1, 2) by substantially the same distance (x, y), d) repeating steps b) and c) until the metal strips (1, 2) are completely welded together, characterized in that the welding current (I) when switched on during the first feed movement (A) up to a first predetermined value (11) at least in sections gradually increased and/or when switched off during the first feed movement (A) to a second predetermined value (I2) at least in sections successively is lowered. procedure after claim 1 , characterized in that the distance (x) by which the metal strips (1, 2) are moved in step c) is shorter by a differential distance (d) than the distance (y) covered by the welding head (3). procedure after claim 1 or 2 , characterized in that the sections (z1, z2) on which the welding current (I) is successively increased or decreased at least in sections when switching on and off are of equal length. procedure after claim 2 or 3 , characterized in that the distances (z1, z2) over which the welding current (I) is successively increased or reduced at least in sections when switching on and/or off, each essentially correspond to the differential distance (d). Procedure according to one of Claims 1 until 4 , characterized in that the speed (v) of the first feed movement (A) when the welding current (I) is switched on is gradually increased up to a third predetermined value (v1) at least in sections and/or to a fourth predetermined value (v2) at least when switched off gradually reduced in sections. Procedure according to one of Claims 1 until 5 , characterized in that the successive increase/decrease of the welding current (I) and/or the feed speed (v) takes place linearly, exponentially, logarithmically, along a half sine wave or along a quarter sine wave. Procedure according to one of Claims 1 until 6 , characterized in that the successive increase/decrease of the welding current (I) and the feed speed (v) takes place in such a way that the energy (E) introduced into the weld seam (4) per unit of travel increases linearly, exponentially, logarithmically, along a half-sine wave or changes along a quarter sine wave. Procedure according to one of Claims 1 until 7 , characterized in that alternating components are superimposed on constant values of the welding current (11, 12) and/or the feed rate (v1, v2). Device (5) for welding at least two metal strips (1, 2), comprising a welding head (3) and means (7, 8, 9) for performing a first feed movement (A) and a movement (B) running in the opposite direction thereto with the welding head ( 3), characterized by a control/regulation (10) which is set up to successively increase the welding current (I) at least in sections during a first feed movement (A) up to a first predetermined value (11) and/or at Turning off during the first feed movement (A) to a second predetermined value (I2) at least in sections to lower successively. Device (5) after claim 9 , characterized by means (12, 13) for executing a movement (B) of the metal strips (1, 2) in the opposite direction to the first feed movement (A).

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