WO1998000265A9 - WELDING PROCESS WITH NARROW SLOT BY ARC WELDING - Google Patents

Abstract

The invention relates to a narrow slot welding method in which the welding device (SE) is guided in the welding groove and at least one fusion wire electrode (DE) guided through a contact tube (KR). is conveyed to the welding zone with a protective gas supply at a forward speed of said predefined wire electrode (DVG). Obtaining a good quality of the weld passes by the formation of an electric arc (RLB) alternately passing from one side of the room to the other, which is produced between the electrode wire (DE) and the room. Until now, this has been achieved by mechanical deflection of the electrode wire (DE) or electric arc autorotation (RLB), provided that certain welding parameters are met. These two possibilities are, however, limited in terms of the bridging width of the welding grooves. In order to be able to bridge larger widths of welding grooves inherent in the manufacture, it is provided according to the invention to superimpose on the autorotation of the electric arc (RLB), a mechanical deflection of the end of the wire. electrode (DE), in particular a mechanical rotational movement (RO) of the end of the electrode wire (DE). Curiously, a stable electric arc autorotation (RLB) is obtained, despite constant changes in the position of the electrode wire (DE).

Description

 description

Engraving process using the MAG welding process

The invention relates to a method for narrow gap welding with the MAG welding method in which the welding device is guided in the weld joint while at least one guided by a contact tube melting wire electrode is supplied under protective gas at a predetermined wire feed speed to the welding area, and in which the parameters welding current, Elektrodendrah Feed and contact tube distance can be adjusted so that forms a rotating arc at the end of the wire electrode.

MAG welding is one of the most widely used arc fusion welding processes due to its versatility, good mechanizability and high productivity. The economy of this known method can be further improved if the required joint cross-section is reduced and passed over to narrow-gap welding. However, in the deep and narrow welds, introducing the welder into the joint and positioning the consumable wire electrode to the workpiece flanks to be joined presents problems. The risk of binding errors on the workpiece flanks is thereby relatively high, in particular in the case of flame-cut workpiece flanks and the resulting large gap tolerances.

In narrow gap welding with the MAG welding process, the wire electrode and workpiece should be generated

Form arc alternately to both workpiece edges. This has hitherto been realized by a mechanical deflection of the wire electrode, a distinction being made here between static and dynamic process principles. In the static process principles, two wire electrodes are plastically deformed or mechanically guided such that the ends of the wire electrodes in each case to a workpiece flank are deflected out. In the case of dynamic process principles, the ends of a wire electrode swing back and forth between the two workpiece flanks, or two twisted wire electrodes are fed, which then assume different positions with respect to the workpiece flanks during melting. From Narrow Gap Welding-The State-of-the-Art in Japan, The Japan Welding Soc, Tokyo, 1986, pages 65 to 73 is another known to dynamic process principles variant is known in which the wire electrode by a rotating wire funnel to a helix is plastically deformed and thus results by the AbschmelzVorgang a rotational movement of the end of the wire electrode.

From EP-A-0 557 757 a method for narrow gap welding of the type mentioned in the introduction is known in which the parameters welding current, electrode extension and contact tube distance are set in such a way that the usual axial material transition is achieved by a rotating electrode Material transition is replaced with a rotating arc.

Both in narrow gap welding with a deflected wire electrode as well as narrow gap welding with a self-rotation of the arc, the bridgeable weld joint width is limited, so that there is a risk of Flankenbindefehlern at production-related larger gap widths.

The invention has for its object to provide a method for narrow gap welding with the MAG welding method, in which even with larger gap widths and especially in production-related gap tolerances safe edge detection can be guaranteed.

This object is achieved in a generic method for narrow gap welding according to the invention that the self-rotation of the arc is superimposed on a mechanical deflection of the end of the wire electrode. It is surprising to those skilled in the art that despite the mechanical deflection of the end of the wire electrode and the consequent permanent change in position of the electrode end an arc with stable self-rotation can weren formed. The superposition of the mechanical deflection and the self-rotation of the arc leads to a wider arc range, whereby the desired and necessary melting of the workpiece flanks is guaranteed even with larger joint widths with certainty.

Advantageous embodiments of the invention are specified in the subclaims.

According to claim 2, it is particularly advantageous to superimpose the self-rotation of the arc on a dynamic deflection of the end of the wire electrode. According to claim 3, for example, the self-rotation of the arc can be superimposed on a pendulum movement of the end of the wire electrode. However, according to claim 4, it is also possible to superimpose a rotational movement of the wire electrodes by means of twisting the wire electrodes using two melting wire electrodes of self-rotation.

In a particularly preferred embodiment of the method according to the invention, a rotational movement of the end of the wire electrode is superposed according to claim 5 of the self-rotation of the arc. The overlapping of both rotations results here in an additional stabilization of the rotating arc. Occasional reversals of rotation, such as occur during welding without mechanical rotation, are barely observed here. Due to the superimposition of the two rotations, the power can even be significantly reduced compared to welding without mechanical rotation, without jeopardizing the stability of the self-rotation. The combination of both rotations thus enables the application of narrow neck welding after the MAG welding process, even for heat-sensitive materials. In the superposition of the self-rotation of the arc and a mechanical rotation latter is generated according to claim 6 with little effort by a coiling of the wire electrode. In this case, according to claim 7, a preparation of the spiraling by a rotating wire set has proven to be particularly economical.

In the following, embodiments of the invention will be explained in more detail with reference to the drawing.

Show it

Figure 1, the narrow gap welding with two plastically deformed wire electrodes and an additional self-rotation of the forming at the end of the wire electrodes arc.

FIG. 2 shows the narrow gap welding with two mechanically deflected wire electrodes and an additional self-rotation of the arc forming at the end of the wire electrodes,

Figure 3, the narrow gap welding with a reciprocating wire electrode and an additional self-rotation of forming at the end of the wire electrode arc

FIG. 4 shows the narrow gap welding with a mechanically deflected, reciprocating wire electrode and an additional self-rotation of the arc forming at the end of the wire electrode,

FIG. 5 shows the narrow gap welding with two twisted wire electrodes and an additional self-rotation of the arc forming at the end of the wire electrodes,

FIG. 6 shows the narrow gap welding with a wire electrode plastically deformed into a helix and an additional internal rotation of the arc forming at the end of the wire electrode, and FIG Figure 7 shows the narrow gap welding according to the variant shown in Figure 6 in detail.

FIGS. 1 to 6 show a highly simplified schematic representation of different variants of narrow gap welding using the MAG welding method. In each case two thick sheets BL are to be welded together. Below the welding gap SF formed between the two sheets BL a base plate GB is arranged. In all variants, the consumable wire electrodes DE are supplied to the welding region through a contact tube KR under protective gas. By appropriate selection of the parameters welding current, electrode wire feed and contact tube distance is formed at each end of a wire electrode DE a rotating arc RLB. Under contact pipe distance is understood to mean the distance between the lower end of the contact tube KR and the uppermost weld bead. As further parameters that may play a role in the formation of an arc RLB with stable self-rotation, the nature of the protective gas and the diameter of the wire electrode DE may be mentioned.

FIGS. 1 and 2 show two static process principles in which two wire electrodes DE are fed in each case. In the embodiment shown in Figure 1 variant, the two wire electrode DE are fed into ^'the welding gap SF consecutively arranged contact tubes KR two, the wire electrode DE are curved by plastic deformation of the workpiece flanks out. In the variant shown in Figure 2, the ends of the wire electrodes DE are mechanically deflected by appropriately bent contact tubes KR to the workpiece edges.

FIGS. 3 to 6 show various dynamic process principles. In the variant according to FIG. 3, the desired alternating formation of the rotating electric arc RLB on both workpiece flanks is made possible by a reciprocating pendulum movement P. In the variant according to FIG. 4 this effect is made possible by a bent contact tube KR, which is also reciprocated in the direction of rotation DR.

Figure 5 shows a variant with two twisted, guided by a common contact tube KR wire electrode DE. Here, the self-rotation of the arc RLB is superimposed by a rotational movement of the ends of the wire electrodes DE caused by the melting process.

Finally, FIG. 6 shows a variant in which the rotational movement R of the end of the wire electrode DE is superimposed on the intrinsic rotation of the arc RLB. Here, the wire electrode DE is plastically deformed into a helix and guided in this helical shape through the contact tube KR. The mechanical rotation R then results during melting of the end of the wire electrode DE.

FIG. 7 shows the variant according to FIG. 6 in detail. The plastic deformation of the wire electrode DE into a helix takes place through a rotating wire set RD, which has three deflection rollers UR. The plane plastic deformation of the wire electrode DE supplied by the three deflection rollers UR becomes a spatial helical form due to the superimposed rotation RO of the entire set of wire straighteners RD.

In addition to the rotating wire straightener RD, the welding device, designated overall by SE, comprises a protective gas nozzle SGD in which the contact tube KR is arranged concentrically.

Due to the superimposition of the internal rotation of the arc RLB and the mechanical rotation R caused by the helix, production-related, larger gap widths can be bridged when constructing the individual weld beads or welding layers SL in the welding joint SF. The superposition of both rotations leads to a wider arc range, whereby the desired and necessary detection of both joints Flanks are guaranteed even with changing joint widths with certainty.

Example: In MAG narrow gap welding with that shown in FIG

Arrangement, the following conditions and welding parameters were realized:

Joint shape: I-joint

Sheet thickness: 200 mm Slit width: 15 - 18 mm

Inert gas: 13% C0 ₇ 14% 0 ₇ tstAr

Inert gas quantity: 201 / min

Diameter of the wire electrode: 1, 0 mm

Contact tube distance: 30 mm Wire feed: 30 m / min

Amperage: 325 A

Voltage: 43V

Welding speed: 30 cm / min

Melting rate: 11.0 Kg / h of path energy: 28 kJ / cm

Track number: 41

With the above-mentioned parameters and conditions, a high-quality welded connection between the individual flange ring segments of a gas turbine was realized. Due to the superimposition of the self-rotation of the arc and the mechanical rotation of the electrode end, tolerance-related changing joint widths did not cause any difficulties. In a subsequent examination, the weld seam profile of 200 mm throat thickness did not reveal any irregularities. The uniform, cup-shaped penetration with good flank detection confirmed the high quality of the welded joint. The fully mechanical continuous multi-layer welding leads compared to the previously known methods to improve quality and minimize the risk of binding errors at the seam beginning. The manufacturing security is increased and the physical load significantly minimized by the welder.

Claims

claims 1. A method for narrow gap welding using the MAG welding method, in which the welding device (SE) guided in the welding joint (SF) while at least one by a contact tube (KR) guided melting wire electrode (DE) under inert gas at a predetermined wire feed speed (DVG ) is supplied to the welding area, and in which the parameters welding current, wire electrode feed and contact tube pitch are set such that at the end of the wire electrode (DE) forms a rotating arc (RLB), characterized in that the self-rotation of the arc ( RLB) a mechanical deflection of the end of the wire electrode (DE) is superimposed. 2. Method according to claim 1, characterized in that the self-rotation of the arc (RLB) is superimposed on a dynamic deflection of the end of the wire electrode ((DE). 3. Method according to claim 2, characterized in that the self-rotation of the arc (RLB) is superimposed on a pendulum movement (P, DR) of the end of the wire electrode (DE). 4. The method according to claim 2, characterized in that, by using two melting wire electrodes (DE) of the self-rotation of the arc (RLB) by a Vver- twisting of the wire electrodes (DE) a rotational movement of the end of the wire electrodes (DE) is superimposed. 5. The method according to claim 2, characterized in that the self-rotation of the arc (RLB) is superimposed by a rotational movement (R) of the end of the wire electrode (DE). 6. Method according to claim 5, characterized in that the mechanical rotational movement (R) of the end of the wire electrode (DE) is generated by a helix of the wire electrode (DE). 7. Method according to claim 6, characterized in that the helix of the wire electrode (DE) is produced by a rotating wire set (RD).