DE2048215C3 - Process for the electrical welding, in particular by arc compression welding, of coated sheets or metal bodies - Google Patents

Description

The invention relates to a method for electrical welding, in particular by arc pressure welding, of coated sheets or metal bodies by introducing a welding current into the parts to be welded together and by their mutual pressure in the welding area, after in Welding area on the opposing surfaces of the parts to be welded together Coatings removed and linear contact bumps forming a current path be milled out.

A method of this type is known from FR-OS 20 08 060. There serve the mutual pressure Plastic-coated sheets or other bodies to be joined together in the welding area either electrodes, which are pressed onto the outside of the parts via stripped zones and thus at the same time establish the circuit for the welding current; or there are de-energized pressure indicators used, which are pressed onto the coating, with the connection for the welding current on the side Cut edges are made, i.e. without local redeployment the outer coating to make / ti. in the

The welding area is created by local removal of the coating on those facing each other Surfaces of the parts to be connected to one another created a cavity, the Grur.d- and top surface - is represented by the then exposed, bare metal. To bridge this free distance, either a deformation of at least one of the parts to be connected to one another under the influence of the electrode pressure or stamp printing provided, or ίο welding inserts are inserted that profiled the shape or smooth wires, disks or the like.

In the case of the arc pressure welding mentioned in this prior publication, an arc is first formed between the parts to be connected, in order to then reduce the arc discharge To compress pasted surfaces of the parts to be joined together.

From DE-OS 15 65810 it is known for Joining a thin sheet to a thick metal body on the surface of the thick metal body to form in any way and any shaped ribs or relief lines, so that the welding current conventional resistance pressure welding on these contact surfaces with the thin sheet metal concentrated and the connection is only established in these areas of contact. From CH-PS 3 35 772 it is for conventional resistance pressure welding known, by means of a. Embossing tool at an angle to the later Pressing knurled grooves running through the weld seam into a sheet metal, so that after folding the Sheet metal the original knurling along the intended weld seam to a number of intersecting short lines, with the result that the resistance welding along the crossing points takes place.

From CH-PS 3 75 458 it is known for resistance butt welding to press the one against the other Roughen the end faces of the butt to be welded objects, so that when first mutual contact initially only a few point-like contacts with large transition resistance form; these lead to correspondingly high local preheating, and then also using hand tools to be able to produce the butt weld connection without applying great pressure.

For resistance roller seam welding of superimposed Sheets it is known from DE-OS 15 65 696, the sheets in the area of the intended To deform the weld seam in such a way that, similar to projection welding, elevations are formed, lengthways which the resistance pressure weld takes place. This makes it possible to give roller electrodes a long service life use; because the width of the weld seam is no longer over the printing width of the electrode rollers limited, but solely by the shape of the elevations.

From US-PS 10 39 137 it is known in the planar welding of superimposed sheets Use welding spacers to create the active weld joint area below the welding electrodes to extend to the largest possible cross-sectional area.

The present invention has the object basis, in the process of the above-mentioned To the contact surveys so / u that they ■■ jh due to their shape on the one hand for resistance pressure welding in the manner of classic projection welding, but on the other hand in particular also for

Use of arc pressure welding is suitable.

According to the invention, this object is achieved in that Jaß by directly adjacent concave Milled grooves acute-angled contact elevations were formed over which the to be worn At the beginning of the welding, part one another along these elevations or with crossing elevations touch; the aforementioned problem on which the invention is based is an alternative to this solution on the other hand, however, it is also achieved in that, prior to the removal of the coating, strip-shaped surfaces be embossed and by removing the coating through concave milled grooves, acute-angled Contact bumps are formed.

Milled grooves of this type that end at an acute angle result in an extremely high contact resistance the first time it is touched while the circuit is switched on, and immediately after the somewhat irregular The melting of the contact edges sets in arcing discharges, which are now the area Heat the larger material cross-section progressively, whereupon the compression of the displayed Partial areas can be made in order to establish the desired, quasi-planar welded connection. Here you can these concave groove cutouts both in the case of overlap connections and - namely in the case of sufficient Sheet metal thickness - made for butt joints of sheet metal or other metal bodies will. The alternative solution according to the present invention, namely the milled grooves only after the Make formation of manifestations has the particular advantage that the destruction of the Coating on the metal parts to be joined is limited to a minimal region, via which the welded connection is made anyway afterwards.

If, especially with thick sheet metal and thick metal bodies with comparatively thick coatings, by local removal of these coatings in the intended welding area in the surfaces of the coated parts are provided with milled cavities, it can be from manufacturing technology and thus from For reasons of cost, it should be expedient, not the face and base of these cavities with the concave To provide groove cutouts to the acute-angled gables of these elevations for the first contact create; rather, in these cases, it is expedient to use the first-mentioned solution according to the invention to the use of welding inserts known as such made use of those with corresponding acute-angled elevations as a result of curved groove millings at least one of its surfaces can be formed.

In the following description of preferred devices shown in simplified form in the drawing and shows measures for practicing the inventive method

Fig. 1 two sheets coated on both sides, which are provided in an overlap area for a Weld are processed,

Fig. 2 two superimposed, to be welded together sheets, of which the upper has strip-like knockouts,

Fig. i two metal sheets arranged one above the other, the layers of which are to be welded to one another are stripped of the coating by means of immediately successive, spherical cutouts.

Fig. 4 the welding of locally stripped Sheets with a Schweiijemlegestukkes in between with acute-angled edge region,

FIG. 5 shows a strip-shaped welding insert for use in accordance with FIG. 4,

F i g. 6 a butt weld using an insert piece placed in between,

7 shows the butt weld with a hollow cutout of the opposite end faces and

8 shows a further development of the measures according to

lu Fig. 7 for larger parts to be connected to one another Strength.

Fig. 1 shows an upper sheet 1 with an upper coating la and a lower coating 16, its edge 1c with an edge strip 2c of a metal sheet 2 with an upper coating 2a and a lower coating 26VeHChWeJBt. For this purpose, the upper sheet 1 with the part resting on the stripped edge strip 2c of the sheet 2 with three slightly upwards curved grooves 4 milled out. This creates acute-angled, linearly protruding points of contact 5 with the stripped edge strip of the Sheet 2 down. By a resilient pressure bar 6, the edge strip Ic of the sheet 1 is during the Melting the acute-angled webs 5 printed against the edge strip 2c of the lower sheet. as A table 3 serves as a base. The weld can be a pure resistance weld, or it can be with appropriate dimensioning of the acute-angled webs through correspondingly fine millings of the webs

i »5 melt these away and through arcing a more or less large area weld of the edge part Ic of the sheet 1 take place. To the latter Capacitor discharge welding currents are particularly suitable.

i "> The welding current is introduced into the upper sheet metal and diverted via the lower sheet metal. This makes it possible to leave the upper decorative layer 1 a and the lower decorative layer 2 b intact despite the welding process when the millings and the welding pa-

I »parameters are appropriately matched to one another.

It is also possible, by stripping the coating la and the coating 2b , to apply welding rollers above or below the welding point and thus to carry out the welding. the

■ »'> The welding current is shown schematically, where "5" means a secondary coil.

FIG. 2 shows an upper sheet 1 with strip-like knockouts 7 towards sheet 2. These knockouts can be carried out on sheet metal 1 coated on both sides

">" will be. The pre-embossed strips are milled out with disc milling cutters, which have curved working surfaces, with a hollow upward curve, leaving strip-shaped coatings Ib. Sheet metal 2 can also coincide in a strip-like manner

■ Ί> are decoated and in these decoated places 2d the acute-angled linear web parts 5 of the arched milled strips are inserted. Here, too, resilient pressure plates or strips or stamps are arranged and then the current is introduced into the "" surface of the sheet 1 and via the acute-angled linear contact webs 5 in sheet 2 and diverted through it 1. By leaving directly adjacent, coated, strip-shaped areas in place, when thermoplastics are used, the two plastic layers are welded to one another at the same time, so that the weld areas are hermetically sealed

to be hermetically sealed to the outside.

Here, too, with an appropriate design of the acute-angled webs and dimensioning of the welding parameters, the outer coatings 1 a, 2 b can be preserved intact.

F i g. 3 shows two superposed sheets 1 and 2 with coatings la and 2b, which together / u welded surfaces are stripped by means of directly successive rillenförmige.s milling. The stripping can also take place in advance. The two metal sheets are profiled in the same way at the welds in the shape of a sleeve. The metal sheets are placed crosswise on top of one another with these acute-angled webs 5 and 8, so that they only touch each other at the Kreiimngsniinkten. This makes it possible to weld large areas to one another at points with a relatively low expenditure of energy. This takes place completely independently of the thickness of the individual sheets and can also be carried out in such a way that the two outer coatings 1 a and 2 b remain undamaged despite the welding process. The height of the curvature and thus the height of the acute-angled webs and the distance between the webs can be chosen quite arbitrarily.

F i g. 4 shows an upper sheet 1 with coatings 1 a, 1 b and a lower sheet 2 with coatings 1 a. 2a, 25 and provided with circular or groove-shaped desizing coinciding welds 11, 12 of the two sheets to one another. A welding insert 14 is inserted into this welding point, which is milled or embossed with a hollow arched shape from both sides and thereby has acute-angled edge parts I4a upwards and downwards. The high electrical resistance of these acute-angled edge parts 14a or edge webs enables welding without the outer coatings being thermally damaged.

Fig. 5 shows the same insert 15 in strip form with an acute-angled edge 15a.

I i g. 6 shows a vertical section through two juxtaposed ones on roller conveyors 23. 23.Ϊ. Sheets 1 and 2 coated on both sides, the cut edges Io and 2c of which are welded to one another via an interposed insert 24 and a stream of visual welding guided through it. The insert or Si'hweißstück 24 is arched from both sides, so that only the edge parts are acute-angled

ίο protrude and touch the cut edges of the two sheets. In order that the metal sheets remain in the plane they occupy under the pressure of special pressure lines P that act against one another, a pressure ram 25, also provided with rollers, is provided above (see FIG. 7).

Fig. 7 shows in vertical section two sheets 1 and 2 which are welded together and whose cut edges Ie 2c are hollowed out with a disc milling cutter with a curved work surface, so that only acute-angled edge parts of the cut edges protrude against one another. If the stream of visual white is sent through the metal sheet, the tips melt and the sheets fall together under the resilient, mutually directed pressure of pressure means P.

τ> F i g. 8 shows an embodiment corresponding to FIG. 7, however, with regard to the greater thicknesses dci both sheets 1 and 2, the arched millings ar of each cutting edge Ie, 2e are made twice.

The well-known welding machines of various types are used for welding, depending on requirements according to the welds to be carried out. F. «can also in special cases capacitor Welding machines are applied.

For this purpose 2 sheets of drawing uncertainties

Claims (3)

f - claims. 1. A method for electrical welding, in particular by arc pressure welding, of coated sheets or metal bodies by introducing a welding current into the one another parts to be welded and by their mutual pressure in the welding area after in Welding area on the opposing surfaces of the parts to be welded together Part away the coatings and make a contacting linear current path Contact surveys are milled out, thereby characterized in that by directly adjacent concave milled grooves Acute-angled contact bumps were formed over which the parts to be welded to each other at the beginning of the welding along these elevations or with intersecting elevations touch. 2. Process for electrical welding, in particular by arc pressure welding, of Beschichieten sheets or metal bodies by introducing a welding current into them parts to be welded and by their mutual pressure in the welding area after in Welding area on the opposing surfaces of the parts to be welded together Part away the coatings and make a contacting linear current path Contact bumps were milled out, characterized in that before removing the Coating strip-shaped surfaces are embossed and by removing the coating concave groove cutouts acute-angled contact elevations are formed. 3. The method according to claim 1, characterized in that the acute-angled contact bumps be formed on intermediate weld pieces, which are milled into the coatings cavities be inserted.