FR2556635A1 - Electric arc-welding method and apparatus and welded workpieces in accordance with the said method - Google Patents

Abstract

The invention relates to welding. The welding method forming the subject of the invention is characterised especially in that the spiralled consumable electrode 3 is formed during its advance towards the welding-arc zone 7, by twisting together the electrode-wires 2 around the axis of advance of the electrode, the said electrode undergoing, during the said twisting, a helical rotation and translation movement about and along the said axis of advance, each of the wires 2 of the spiralled consumable electrode 3 still moving along the same trajectory upon entering the welding-arc zone still at the same point. The invention can be used for welding and overlaying with submerged arc, under a shielding gas, with consumable solid electrodes or powder electrodes.

Description

 The present invention relates to the field of electric welding of metals and in particular relates to an electric arc welding process, a welding device for the implementation of this process, as well as the parts welded in accordance with said process.

 The invention can be used in the development of materials for welding and recharging under flux, under shielding gas or their mixtures with solid fusible electrodes and powder electrodes, as well as for welding with special electrodes which do not require not the use of flux and shielding gas in the welding area.

The invention is particularly applicable to mechanized welding devices with advance of the electrode in guide channels of increased length.
The current trend to increase the dimensions of welded steel structures, as well as the wide use of high quality steel sheets, determine the constant search for means likely to increase the efficiency of welding processes and to ensure a reduction in the cost price of welded constructions while maintaining a high quality of welds. One of these processes satisfying the requirements of modern industry is electric arc welding with fused compound or bundle electrodes, consisting of two or more of two bare solid electrode wires (without insulation), of the same diameter or of different diameters, arranged one along the other. Arc welding with beam electrodes provides a higher efficiency of the welding process than that of traditional processes with a single electrode, which is especially important for the execution of recharges.

In addition, electric arc welding with beam electrodes easily ensures the possibility of additionally alloying the metal of the weld bead thanks to the fact that at least one of the electrode wires of the beam electrode can be made of sintered alloy. It should also be noted that, thanks to the absence of insulation on the bare electrode wires of the bundled electrode and thanks to the fact that they touch, all the electrode wires can be supplied from a single source of welding current.

 An electric arc welding process is known (see for example British patent NO 1280147 published on July 7, 1972), according to which the welding operation is carried out with a beam electrode composed of at least two separate electrode wires having no insulating coating and supplied from a common source of welding current, said electrode wires being arranged in the electrode in a bundle parallel to one another without being mechanically linked together by any special means .

 However, this latter circumstance means that, when this arc welding method is used to perform a mechanized welding operation, when the fusible electrode is brought to the place of welding along the guide channel - wire of the welding device using a push-type mechanism, it proves impossible to ensure, with a single mechanism of this type, the same speed of advance towards the welding zone for all This is explained by the fact that during the displacement of the wires of such a bundled electrode in the wire guide channel, said wires, being in no way linked to one another, are freely arranged along the entire section. internal of this channel, which has the consequence that the electrode wires are subjected, according to their mutual arrangements and their positions relative to the inner surface of the wire guide channel and its end piece, to different friction resistances. The difference between the friction resistances to which the different electrode wires are subjected increases even more if the electrode wires differ from each other by their diameter. As a result of the difference in the speeds of advance of the electrode wires towards the welding zone, the normal course of the welding process is disturbed, in particular, due to the disordered displacements of the initiated welding arc, so that the quality of the weld bead obtained deteriorates greatly. This is why it is not easy to widely use the method described above for carrying out mechanized electric arc welding, which is carried out in most cases with wire guide channels.

 An arc welding process is also known, according to which the welding process is carried out with a fused beam electrode (see for example the USSR author's certificate published on September 21, 1971 under the number 314610). According to this process, the beam electrode, composed of several bare electrode wires arranged in parallel, is previously clamped on all sides using special rollers, then brought to the welding area.

 Although this method has a certain advantage over the method described above, an advantage which is that the slippage of the electrode wires with respect to each other is eliminated, which is obtained by the mentioned tightening of the wires forming the '' bundled electrode, however, the friction resistance between the bundled electrode and the inner walls of the wire guide, if such a bundled electrode is advanced in a very long wire guide channel, remains relatively high and irregular over time. This causes random variations in the output speed of the bundle electrode from the tip of the wire guide, which in this case also leads to disordered movements of the welding arc, which take place mainly during the welding performed under low intensity welding current regimes.

 An arc welding process is also known, according to which the welding operation is carried out with a fusible electrode in twisted beam (see for example Japanese patent NO 53-118154). According to this method, the twisted beam electrode, which is in the form of a multi-threaded screw with a number of inputs determined by the number of bare electrode wires it contains, is gradually brought into the ignition zone of the welding arc at an angle of 5 to 10 degrees relative to the longitudinal axis of the weld bead.

 Although this arc welding process has a number of advantages, one of which is that the welding arc is rotated as the fusion is made. beam electrode composed of two wires twisted together, which in turn contributes to better stirring of the weld pool and good fusion of the edges of the joint to be welded, it is however very difficult, in this process also, to ensure uniform advancement of the electrode to the welding area with a single push mechanism. In this process, when it is necessary to advance the twisted electrode in a long guide wire channel, it proves necessary either to increase the pushing force acting on the electrode, or to use intermediate means additional voltage. However, these measurements do not ensure a constant output speed of the twisted electrode from the tip, because, during the progressive advancement of said electrode, the friction resistance between the surfaces of the wires of the electrode and the internal walls of the wire guide channel are distributed irregularly over time and along the length of the wire guide channel.

 With regard to the rotation of the welding arc mentioned above, it should be noted that in the presence of this effect, it is impossible to carry out the welding operations at high speeds, because the speed of said rotation is low. .

 In addition, this arc welding method can only be used for a relatively limited range of regimes of the welding process, since the total area of the cross section of the electrode 2 cannot exceed 9.1 mut2,, the welding current must be within the limits of 450 to 500 A, and the welding speed must be maintained within the limits of 15 to 23 centimeters per minute.

Arc welding equipment is well known
electric using the principle of lt clean advancement is a single fusible electrode, or a fusible electrode in a beam in a wire guide channel to bring them to the welding area. One of these devices (see for example the patent USA publish on May 6, 1958 under N 2 833 912) is composed of a welding torch produced in the form of a welding gun provided with a tip bringing the current to the electrode, and connected by means of a flexible sheath, playing the role of wire guide channel to bring the electrode to the welding zone, to a mechanism ensuring the advancement of the electrode This advancement mechanism includes a reduction gear installed in a portable box and equipped with a drive motor and rotary feed rollers connected kinematically to the shaft of the drive motor.

 This electric arc welding device allows, when the flexible wire guide is not too long, to bring the fusible electrode used towards the welding zone fairly uniformly and with sufficient safety. However, this device cannot ensure safe and regular advancement of the electrode used in a very long wire guide sheath with a single advance mechanism of the pusher type.

This is due to the fact that, to accomplish the advancement of the electrode in a very long wire guide sheath, it is necessary, as said above, to be considerably increased the force pushing the electrode into the thread guide, or use additional intermediate tensioning mechanisms arranged at determined intervals along the length of said thread guide sheath. The increase in the force pushing the electrode can be obtained, in this device, either by increasing the force exerted on the electrode by the feed rollers forming part of the device, or by increasing the number of said rollers. the first case, this results in a deformation of the electrode used and in particular by the formation of recesses on its surface, the dimensions of these recesses increasing as the forces exerted by the feed rollers increase ; in the second case, this leads to a complication and to an increase in the overall dimensions of the device. This latter effect is also due to the use of intermediate tension mechanisms. The formation of depressions on the welding electrode used in turn causes an increase in the friction forces resulting in the need to further increase the forces pushing the electrode. It should also be noted that, when the progressive advancement of an electrode is effected by pushing said electrode into the sheath of the wire guide with a high force, the current supply nozzle used in such an apparatus, nozzle which is generally made of a relatively soft metal to low electrical resistance, is subject to high wear and has a short service life, because, to ensure the necessary contact between said tip and the electrode, it is generally pressed against the electrode by forces directed perpendicular to the axis of advancement of the Eleetrode.

 Thus, all the methods of arc welding and all the apparatuses for carrying out these methods, which are known today, do not ensure a uniform advancement of the fuse-beam electrode towards the welding zone in long guide wire channels, in the case where said advancement is carried out using a single advancement mechanism, while the irregularity of the advancement of the electrode reduces the reliability of said advancement and, by Consequently, it affects the quality of the weld bead obtained.

 The present invention therefore relates to an electric arc welding process and a simple welding apparatus for implementing this process, which would ensure, by means of a single advance mechanism, the uniform advancement of a twisted fuse electrode, composed of several wires, to the welding zone in wire guide channels of greater length than that of the wire guides currently used in known welding equipment, and would at the same time allow such welding retaining a high quality of the joints, which can be in space in various positions and having chamfered edges in a manner analogous to that of all traditional welding processes, and being able to accomplish the welding at speeds, cross-sectional areas cross-section of the electrode and ordinary as well as high welding current values.

To solve this problem, the invention proposes a method of electric arc welding with advancement, towards the zone of the electric arc, of a twisted fusible electrode composed of at least two electrode wires without insulation and having under the shape of a screw with multiple threads and a number of inputs determined by the number of external electrode wires forming the thread of said screw, said advancement being effected with the possibility of adjusting the dimensions of the weld bead obtained, this process being characterized, according to the invention, in that the twisted fuse electrode is formed during its advance towards the region of the electric arc by twisting together electrode wires around the axis of advance, the fuse electrode performing during this twisting a hOllcoïdal movement of translation and rotation around and along the axis of advance, while each of the wires of the twisted fusible electrode always moves according to the same trajectory and enters the area of the arc so Always at the same point, the advancement speed of the twisted fuse electrode in the area of the welding arc being determined by the expression:
V = prn, where V is the advancing speed of the fuse electrode
twisted,
p is the pitch of the electrode wires,
r is the number of turns made by the fuse electrode
twisted per unit of time,
n is the number of external electrode wires to twist.

 The proposed arc welding method completely excludes, by twisting the electrode wires into a twisted beam electrode, the difference in the speeds of movement of the separate electrode wires, and ensures, thanks to the translational and rotational movement of the twisted electrode, the regular exit of said electrode from the tip of the welding torch, thereby allowing safe advancement of the electrode towards the welding zone.

 The electric arc welding method according to the invention is further characterized by the fact that the dimensions of the weld bead are adjusted, obtained by using a twisted fusible electrode composed of two electrode wires, by change, in the area of the welding arc, of the orientation of the end face of the twisted fusible electrode with respect to the longitudinal axis of the weld bead in a plane perpendicular to the axis of advance of said electrode.

 In a variant of such an adjustment, the change, in the area of the welding arc, of the orientation of the end face of the twisted fuse electrode relative to the longitudinal axis of the weld bead in the plane perpendicular to the axis of advance of said twisted fuse electrode, is produced by varying the span of the twisted fuse electrode along its axis of advance within the limits of f 0.5 of the twist pitch of the longitudinal profile of said electrode.

 In another variant of the adjustment, the orientation of the end face of the twisted fused electrode is changed in the welding zone relative to the longitudinal axis of the weld bead in the plane perpendicular to the 'axis of advance of said twisted fuse electrode, by turning the electrode in question around its axis of advance by an angle between 0 and 90 degrees.

 The adjustment of the dimensions of the weld bead obtained by the aforementioned means is simple and ensures, if necessary, the variation of the dimensions of said bead within fairly wide limits. The first variant of the adjustment, that is to say that which is carried out by varying the span of the electrode, offers more convenience in the case of manual arc welding, especially in hard to reach places.

For automatic arc welding, the two mentioned adjustment variants are suitable, the choice of the variant being determined by the particular conditions of execution of the welding process.

 The problem set out above is also solved by means of a welding apparatus for implementing the proposed method of electric arc welding, comprising a welding torch provided with a current supply nozzle and connected by means of '' a flexible wire guide tube, used to bring the fusible electrode into the welding zone, to a feed mechanism composed of a housing in which are contained a reducer equipped with a drive motor and rollers rotary feed, used to move the fusible electrode in the direction of its axis of advance and rigidly fixed on shafts connected to the shaft of the drive motor, said apparatus being characterized1 according to the invention, in that each feed rollers of the advance mechanism is made in the form of a cylinder having a thread with several threads on its peripheral surface with a pitch equal to that of the thread of the twisted fuse electrode being formed, the reduction mechanism of the advance includes a first transmission ission which ensures the rotation of the feed rollers around their axes in the same direction and comprises two driven members, each secured on the ends of the shafts and feed rollers, on the same side of said feed rollers, and a drive member kinematically connected to the driven members of said first transmission and to the shaft of the drive motor, as well as a second transmission which ensures the synchronous rotation of the two feed rollers around the axis of advance of the twisted fuse electrode and comprises a driven member, installed freely on the ends of the shafts of the feed rollers, on the same side of said feed rollers, and a drive member kinematically connected to the driven member of said second transmission and to the shaft of the drive motor, while the current supply endpiece is composed of a contact socket with an internal contact channel, on the surface of which is threaded with several threads with a diameter , a pitch and a number of inputs equal respectively to the diameter, to the pitch and to the number of inputs of one twisted fused electrode which has formed and which passes through the current supply nozzle.

 The apparatus proposed for carrying out electric arc welding simultaneously ensures the twisting of several electrode wires into a twisted electrode having the shape of a screw and the advancement of said electrode in a flexible wire guide pipe in the direction required by means of a single advance mechanism. Because the advance mechanism forces it to move in translation and rotation during advancement of the twisted electrode, at the electrode significant forces to push it into the flexible guide wire without any appreciable deformation of its surface, thanks to which it becomes possible to pass the twisted electrode, and this, with a regular speed, in guide pipes wires having a length appreciably greater than that of the guide-wire hoses which are used in known welding devices comprising a single advance mechanism.

 In one of the variant embodiments of the apparatus for implementing the proposed method of electric arc welding, the current-supplying tip of the welding torch may comprise an additional box, embracing the socket contact, on which housing is fixed an elastic element in contact with one of the ends of the contact sleeve and producing a force directed along the axis of advance of the twisted fuse electrode, force which ensures the tightening of the thread of the contact channel of the contact sleeve against the helical surface of said electrode.

 The use of an elastic element in the current supply tip of the welding torch that creates a force directed along the axis of advance of the twisted electrode gives the possibility, in the event of use of short wire guide pipes, to make up for the play between the helical surfaces of the twisted electrode and the contact sleeve of said end piece, play which inevitably appears due to the wear of the contact sleeve at during the operation of the arc welding apparatus.

 In another alternative embodiment of the apparatus for implementing the proposed method of electric arc welding, the current supply tip of the welding torch comprises an additional housing which embraces the contact socket provided an external thread on its peripheral surface, the internal surface of said housing having a thread having a diameter and a pitch equal respectively to the diameter and to the pitch of the external thread of the contact sleeve and meshed with the external thread of the contact sleeve contact.

The presence of a thread on the peripheral surface of the contact sleeve and a corresponding thread on the sur
inside face of the housing embracing the contact socket allows to vary at will, within wide limits, the va
their of the pressure force of the thread of the contact channel of this socket against the helical surface of the electrode
twisted, to make up for the above play. The use of the clamping means will be described in the following with more
details.

The external thread of the tip contact socket
current supply and threading on the surface
inside the housing of said current supply nozzle, file
tage which meshes with the first, may have a pitch less than that of the thread of the contact channel inside the contact sleeve.

Making the external thread of the cone socket
tact meshed with the thread of the housing of the current supply nozzle with such a pitch ensures the possibility of
select pressure force more gradually
and precise.

The invention will be better understood and other objects, details and advantages thereof will appear more clearly in the light of the explanatory description which will follow of various embodiments given solely by way of nonlimiting examples, with references to the drawings which are not annexed limitative in which
- Figure 1 shows, in a simplified way, a
welding installation illustrating the welding process
the electric arc according to the invention
- Figure 2 shows the mutual arrangement diagram of the working part of a fusible electrode formed of two wires twisted together and parts to be welded for a given length of span of said electrode, this diagram illustrating one of the adjustment modes dimensions of the weld bead according to the invention
- Figure 3 is a cross section of one electrode formed of two wires twisted together along line III-III of Figure 2
- Figure 4 shows a cross section of the weld bead obtained when the electrode is in the position shown in Figure 2;
- Figure 5 shows the mutual arrangement diagram of the working part of a fusible electrode formed by two wires twisted together and the parts to be welded for a span length of said electrode different from the length shown in Figure 2; ;
- Figure 6 is a cross section of the electrode shown in Figure 5 along line VI-VI;
- Figure 7 shows a cross section of the weld bead obtained when Zselecrode is in the position indicated in Figure 5;
- Figure 8 shows the mutual arrangement diagram of the working part of a fusible electrode formed by two wires twisted together and parts to be welded for a given orientation of said electrode, this diagram illustrating another mode of adjusting the dimensions of the weld bead according to the invention;
- Figure 9 shows a cross section of l2dle- ctrode of Figure 3 along the line IX-IXg
- Figure 10 is a cross section of the weld bead obtained when the electrode is in the position shown in Figure 8;
- Figure II represents the layout diagram of the working part of a fusible electrode formed by two wires twisted together and parts to be welded for another orientation of said electrode, different from the orientation indicated in Figure 8 ;
- Figure 12 is a cross section of the electrode shown in Figure II along the line XIIXXII ;;
- Figure 13 is a cross section of the weld bead obtained when the electrode is in the position shown in Figure II;
- Figure 14 is a sectional view of an electric arc welding apparatus carrying out the method proposed during such welding, according to the invention;
- Figure 15 shows the first transmission of the advance mechanism, in section along the line XV-XV of Figure 14;
- Figure 16 shows the second transmission of the advance mechanism, in section along line XVI-XVI of Figure 14;
- Figure 17 shows a cross section along the line XVII-XI W of Figure 14, the feed rollers of the advance mechanism, with partial cutaway;
- Figure 18 illustrates the receptor socket of the advance mechanism, in section along line XVIII-XVIII of Figure 14;
- Figure 19 shows the transverse ccupe of another variant of the receiving sleeve of the advance mechanism shown in Figure 14;
- Figure 20 shows the contact socket of the current supply nozzle of the welding torch, seen in section through a plane passing through the axis of said socket;
- Figure 21 is a view corresponding to Figure 20, in cross section along the line XXI-XXI of Figure 14;
- Figure 22 illustrates the contact sockets of the current supply tip of the welding torch, used for twisted electrodes composed of a various number of electrode wires (end view); and
- Figure 23 shows another design of the current supply tip of the welding torch, seen in section through a plane crossing the axis of said tip.

 It goes without saying that the attached drawings are only schematic representations and only serve to illustrate the present invention without any limitation of the dimensions of the constituent members of the proposed apparatus for electric arc welding, of the relationships of dimensions of these organs, etc. The same members in different drawings are marked with the same reference numbers.

The arc welding method according to the present invention consists of the following
Before the execution of the welding operation, there are introduced into the advancing mechanism 1 (FIG. 1) of a welding apparatus, solid electrode wires 2 without insulation, for example three wires, as shown in the figure, and the said mechanism is started up 1. Under the action of the mechanism 1, the fuse electrode 3 is advanced in a flexible wire guide pipe 4 and then through the nozzle 5 for supplying current from the welding torch 6 to the area of the welding arc 7, which starts when the fusible electrode 3 touches the surface of the parts 8 to be welded after the supply of a voltage appropriate electrical using a conductor 9 connected to the nozzle 5 for supplying current and a conductor 10 connected to the parts 8 to be welded. After the ignition of the welding arc 7, the electrode 3 and the metal of the parts 8 melt, and, by moving the welding torch 6 along the surface of the parts 8 to be welded according to a given trajectory, a weld bead 11 is produced.

According to the present invention, the advancement of the electrode of 3 fuse towards the area of the welding arc 7 is associated, in the proposed method, with the formation of said electrode, during which the electrode wires 2 take the form of a twisted beam electrode. Said twisted bundle electrode 3 is formed by twisting together the electrode wires 2 during its advancement; during twisting, the twisted bundle electrode 3 performs a helical movement of translation and rotation along and around its axis of advance, each of the wires 2 of said electrode always moving along the same trajectory and always entering a same location in the area of the welding arc 7. As a result of the twisting of the electrode wires 2 around the feed axis, which is performed without causing plastic deformation in said electrode wires 2, the twisted fuse electrode 3 turns into a long multi-threaded screw with a number of inputs determined by the number of external electrode wires 2 used, forming the thread, or the helical surface, of said screw. the fusible electrode 3 twisted towards the area of the welding arc 7 is determined according to the method by the following relation:
V = prn where V is the advancing speed of the fuse electrode 3
twisted, expressed in meters per minute,
p is the twist pitch of the electrode wires 2, in
meters,
r is the number of turns made by the fuse electrode
3 twisted in one minute,
n is the number of external electrode wires 2 to be twisted.

 it is obvious, for a person skilled in the art, that the proposed method of electric arc welding can be implemented with a twisted fusible electrode 3 composed of any reasonable number of electrode wires 2. In the case of a twisted fuse electrode 3 formed of several wires electrodes 2, for example of five wires or more, and when these wires are arranged in the electrode 3 in layers (considering the cross section of the electrode 3), the helical surface of the said electrode can only be formed by the wires 2 which are in the outer layer, and it is for this reason that they have been called above "external wires". On the other hand, the fused electrode 3 twisted can be formed by electrode wires 2 having both the same diameter and different diameters, but in the latter case, in the wire bundle 2, the external wires 2 forming the helical surface of the twisted electrode 3 must all have the same diameter.

 Concrete but nonlimiting examples of implementation of the proposed arc welding method are given below, which illustrate its aptitude for the use of twisted fused electrodes formed from different numbers of electrode wires. application of various execution regimes of the welding process and the use of wire guides 4 of different lengths.

Example 1
A fusible electrode 3 (FIG. 1) made up of two 1.0 mm diameter low alloy steel electrode wires 2 twisted together was used, using the arc welding method described above, to the welding area of parts 8, also of low alloy steel, which were the parts of the superstructure of a dry cargo ship. As a source of power for the welding arc 7, an ordinary welding rectifier with a rigid external voltage-current characteristic was used.

The protection of the welding area was carried out using carbon dioxide. Electric arc welding was performed under the following conditions:
- the pitch of the electrode wires was 3 millimeters;
- the speed of rotation of the electrode to be twisted around its axis of advance was 833.3 revolutions per minute,
- the speed of advance of the twisted electrode towards the welding zone was 5 meters per minute,
- the welding current was 200 A,
- the arc voltage was 21 V,
- the welding speed was 0.5 meters per minute.

 Under these conditions, the welding process was stable and the weld beads 11 obtained in various positions in space satisfied all the requirements imposed on the weld beads produced under carbon dioxide.

Example 2
Was brought to the welding area of the pieces to be welded from Example 1, according to the diagram shown, a fusible electrode 3 twisted by two electrode wires 2 of low alloy steel 1.8 mm in diameter. The arc welding process was carried out under the following conditions
- the pitch of the electrode wires was 6 millimeters,
the speed of rotation of the electrode to be twisted around its axis of advance was equal to 691.6 revolutions per minute,
- the speed of advance of the twisted electrode towards the welding zone was equal to 8.3 meters per minute,
- the welding current was equal to 600 A,
- the arc voltage was 42 V,
- the welding speed was 0.5 meters per minute.

 Under these conditions, the welding process was stable and the weld seams produced under carbon dioxide satisfied all the requirements imposed on the seams under such conditions.

Example 3
In this example, parts of a ship's hull were brought to the welding area, according to the same diagram as above, a fusible electrode 3 composed of three electrode wires 2 of low alloy steel of 6.0 millimeters in diameter, twisted together. The welding area was protected in this case using a manganese and silicon flux. Arc welding has been performed under the following conditions
- the pitch of twist of the electrode wires was equal to 30 millimeters;
- the rotational speed of the electrode to be twisted around its axis of advance was 20 revolutions per minute,
- the speed of advance of the twisted electrode towards the welding zone was 1.2 meters per minute,
- the welding current was equal to 4.200 A,
- the arc voltage was 24 V,
- the welding speed was 3 meters per minute.

 As a source of power for the electric arc, a powerful welding rectifier was used, specially designed for high speed welding.

 Under these conditions, the welding process was also very stable and the weld seams produced satisfied all the requirements imposed on the seams executed under a flux layer.

 The use of the arc welding method according to the present invention makes it possible to carry out the welding of assemblies arranged in various places in space and located at great distances from the advance mechanism 1, the length of the guide pipes -wires 4 flexible according to the proposed method can be increased from 2 to 10 times, and in some cases, even more, compared to the length of such wire guides used to effect the advancement of the electrode in the traditional methods of electric arc welding. The length of the wire guide channels depends on their construction and on the material used to construct them, as well as on the total cross-sectional area of the twisted electrode 3, on the number of electrode wires 2 which compose it and on the material of these In addition, while retaining the same flexibility of the wire guide pipe 4, it is possible, according to the proposed welding process, to advance a twisted electrode 3 with a total cross-sectional area of 1.5 to 2. times larger than that of twisted electrodes that can be advanced in known methods.

 Hereinafter are given concrete but nonlimiting examples of execution of the electric arc welding process according to the present invention, illustrating the possible lity of increasing the length of the flexible wire guide pipes 4.

Example 4
A flexible guide wire 4 of ordinal construction re guarantees, in traditional welding processes, the stability of the speed of supply to the welding zone, of a single electrode having a diameter of the order of 1.4 millimeter, over a distance of approximately 3.5 meters.

Using the proposed welding process, it became possible to make use of a flexible wire guide tube 4 twice as long, by passing therein a twisted electrode 3 formed of two electrode wires 2 of 1.0 mm diameter and having a cross-sectional area roughly equal to that of a single electrode 1.4 mm in diameter. The speed of supply of the twisted electrode to the area of the arc 7 was sufficiently stable.

 Example 5.

 In the area of the welding arc 7 a fusible electrode 3 has been brought formed of two electrode wires 2 of 1.8 millimeters in diameter twisted together. In this case, it was possible to increase the length of the wire guide tube 4 up to 14 meters (that is to say four times compared to that used for the ordinary advancement of a single electrode ) without affecting the stability of the speed of supply of the twisted electrode 3 to the area of the welding arc 7.

Example 6
In the electric arc welding zone, a fusible electrode 3 was formed, formed by three electrode wires 2 of 2.0 millimeters in diameter, twisted together. In this case, the twisted electrode 3 was brought using a wire guide pipe 4 over a distance equal to 35 meters and entered at a stable speed into the area of the welding arc 7, without visible alteration. the elasticity of the wire guide hose 4.

 The arc welding process according to the present invention can be carried out with adjustment of the dimensions of the weld bead 11 (FIG. 1). Said adjustment can be carried out both by ordinary variation of the welding speed or of the electrical parameters of the speed of the welding operation, and in particular of the welding current and of the voltage of the welding arc 7, as well as by change of the position of 11 fused electrode 3 twisted relative to the weld bead 11, that is to say by mechanical adjustment. According to the method of the invention, the mechanical adjustment of the dimensions of the weld bead obtained therefrom a twisted fusible electrode 3, formed of two electrode wires 2 and performing during its advancement rotational and translational movements around and along its axis of advance, is achieved by the change, in the area of the arc welding 7, the orientation of the end face 12 of the electrode 3 with respect to the longitudinal axis of the weld bead 11 in a plane perpendicular to the axis of advance of said electrode and passing through face to face 12.

 According to a mode of mechanical adjustment of the dimensions of the weld bead 11, the change, in the area of the welding arc 7, of the orientation of the end face 12 of the twisted fuse electrode 3-relative to the tudinal long axis of the weld bead it in the plane perpendicular to the axis of advance of the electrode 3 is effected by variation of the span length of the electrode 3, that is to say of the length of the part of the electroa.e 3 going from the place of its exit from the E end piece 5 for supplying current to its end face 12, within the limits of + 0.5 of the helical pitch of the longitudinal profile of said electrode.

 More precisely, the dimensions of the weld bead 11 are adjusted according to the mode considered as follows. For given values of the parameters of the welding regime and in order to obtain a weld bead 11 of minimum width with a maximum depth of the molten metal in the parts 8 to be welded, the twisted electrode 3 is arranged, during the execution of the welding operation, above the longitudinal axis of the weld bead 11 in the region of the welding arc 7 so that the line connecting the centers of the ends of the two wires which form the electrode 3 is arranged along the longitudinal axis of the weld bead 11. The arrangement of the twisted electrode 3, in this case, is illustrated more clearly by FIGS. 2, 3 and 4. On FIG. 2 is shown a twisted electrode having a twisting pitch T and a range B1 with respect to the nozzle 5 for supplying current. In FIG. 3 is shown a cross section of the twisted electrode 3, the wires 2 of which are arranged in the same way as on the end face of said electrode. Therefore, the line L indicated in this drawing, which connects the centers of the sections of the wires 2, is directed strictly in the same direction as the analog line which connects the centers of the wires 2 on the end face 12 of the electrode 3, and this is why, in what follows, to simplify the description and for greater clarity, we will characterize 17 orientation of the end face 12 of the electrode 3 by the arrangement of said line L. For the selected length El of the range of the twisted electrode 3 indicated on Figure 2 and with the arrangement of the line L shown in Figure 3, the weld bead It obtained has the shape shown in Figure 4 (the longitudinal axis of the bead 11 in Figure 4 is perpendicular to the drawing plane) In this case, the weld bead 11 has a minimum width designated by l has reference W1.

 If it is necessary to obtain a weld bead 11 having a maximum width and a minimum depth of molten metal from the parts 8 to be welded, it is necessary to increase or decrease the range of the electrode 3 twisted by half of its helical pitch T. This can be obtained by raising or lowering the nozzle 5 for supplying current or the whole welding torch 6 with respect to the parts 8 to be welded by half the helical pitch T of the electrode 3. Such a case is illustrated by FIGS. 5, 6 and 7. FIG. 5 represents a twisted electrode 3 having the same helical pitch T and a new shorter length B2, of the range of the elec trode which is obtained by lowering the torch of welding 6.

In this case, the line L indicated in FIG. 6 is arranged perpendicular to the longitudinal axis of the weld bead it represented in FIG. 7, which ensures the dispersion of the heat released by the welding arc 7 and a decrease in heat intake concentration along the longitudinal axis of this bead. In this case, the weld bead obtained there has a maximum width W2 and a minimum depth of the weld bead.

 In the event of variations in the length of the span of the twisted electrode 3 less than half of the heli-cotidal pitch T of the electrode 3, intermediate values of the width W and the depth of the weld bead can be obtained 11 , lying between the values quoted above.

 Below are given concrete but nonlimiting examples of how to adjust the dimensions of the weld bead 11, which is carried out, according to the proposed method of electric arc welding, by varying the span length of the electrode 3 twisted.

Example 7
A fusible electrode 3 formed by two electrode wires 2 4 mm in diameter twisted together was brought, by carrying out its rotational and translational movement, to the place of welding of low alloy steel parts, the line L and the similar line which connects the centers of the ends of the electrode wires 2 being disposed along the longitudinal axis of the weld bead 11. For the supply of the welding arc 7 an ordinary welding rectifier with external voltage characteristic was used -current rigid. Arc welding has been performed under the following conditions
- welding current 1200 A,
- arc voltage 32 V,
- welding speed 100 meters per hour,
- Manganese and silicon protective flux.

The bead 11 obtained satisfied all the requirements imposed on the weld beads executed under flux and had the following main dimensions
- cord width 13 mm,
- depth of the weld bead 7 mm,
- height of the cord bead 3.3 mm.

Example 8
Without changing the welding speed, the length of the span of the twisted fuse electrode 3 having the parameters given above has been reduced by a quarter of the helical pitch T, which has resulted in the line L was placed at an angle of 45 degrees relative to the longitudinal axis of the weld bead 11.

After the execution of the welding operation, a bead 11 was obtained satisfying all the requirements imposed on the weld beads produced under flux, but with other dimensions, namely
- width of the cord 17 mm,
- depth of the weld bead 5.5 mm,
- height of the cord bead 2.5 mm.

Example 9
While maintaining the same welding conditions, the length of span of said electrode has been reduced by a further quarter of the helical pitch T of electrode 3, which has resulted in the line L becoming perpendicular to the longitudinal axis of the weld bead 11.

At the end of the welding, a bead 11 was obtained which satisfied all the requirements imposed on the weld seams produced under flux, but having, compared to the two previous examples, a greater width, a lesser depth of the weld bead and a lower height of cord bead:
- cord width 21 mm,
- depth of the weld bead 4.5 mm
- height of the bead of the cord 2 mm.

 In another variant of the mechanical adjustment of the dimensions of the weld bead it (FIG. 1), the change, in the region of the welding arc 7, of the orientation of the end face 12 of the fusible electrode 3 twisted with respect to the longitudinal axis of the weld bead 11 in a plane perpendicular to the axis of advance of the electrode 3 is effected by rotating said electrode around its axis of advance by an angle between 0 and 90 degrees.

 In a more detailed manner, the adjustment of the dimensions of the weld bead 11 according to this variant is effected in the following manner. For given values of the parameters of the welding regimes and in order to obtain a weld bead It of minimum width and maximum depth of the molten metal of the parts 8 to be welded, the electrode 3 is twisted above the longitudinal axis of the weld bead it in the area of 17 welding arc 7 so that the line which connects the centers of the ends of the two wires 2 forming said electrode 3 is disposed along said longitudinal axis The arrangement of electrode 3 twisted in such a case is more clearly illustrated in FIGS. 8, 9 and 10. FIG. 8 represents an electrode 3 twisted with a helical pitch T and a span length BI. When the 3 tor saded electrode is positioned with respect to the clamps 8 to be welded and the line L is arranged as shown in FIG. 92, a weld bead 11 is obtained having a cross section whose shape is shown in FIG. 10 (on this figure, the longitudinal axis of the bead 11 is perpendicular to the plane of the drawing), the width of said weld bead 11 being minimal and designated in Wl.

If it is necessary to obtain a weld bead 11 having a maximum width and a minimum depth of the molten metal of the parts 8 to be welded, the twisted electrode 3 is made to rotate around its axis of advance. That
obtained by turning the welding torch 6 clockwise or counterclockwise. This case is illustrated in FIGS. 11, 12 and 13. FIG. 11 represents an electrode 3 twisted with the same helical pitch T and the same bearing B1, but deflected by 900 relative to the position of said electrode indicated in FIG. 8 In this case, the line L shown in FIG. 12 is arranged, as in the previous variant for adjusting the dimensions of the weld bead 11, perpendicular to the longitudinal axis of the weld bead 11 shown in FIG. 13. The weld bead obtained in this case has a maximum width W2 and a minimum depth.

 By changing the angular position of the electrode 3 twisted around its axis within the limits of O0 to 900, one can obtain intermediate values of the width W2 and the depth of the weld bead 11, lying between the values indicated above .

 Below are given concrete but non-limiting examples of how to adjust the dimensions of the weld bead 11 carried out, according to the proposed method of electric arc welding, by rotation of the electrode 3 twisted around its axis of advanced.

Example 10
A fusible electrode 3 formed by two electrode wires 2 of steel 4 mm in diameter twisted together, was brought, by performing a rotational and translational movement, to the place of welding of low alloy steel parts, the line L being disposed along the axis of the weld bead 11. To supply the welding arc 7, an ordinary welding rectifier with external voltage-current rigid characteristic was used. Arc welding has been performed under the following conditions
- welding current 1200 A,
- arc voltage 32 V,
- welding speed 100 meters per hour,
- Manganese and silicon protective flux.

The weld bead 11 obtained by this welding process satisfied all the requirements imposed on the weld beads executed under flux and had the following main dimensions
- cord width 13 mm,
- depth of the weld bead 7 mm,
- height of the cord bead 3.3 mm.

Example 11
Without changing the welding conditions and the span length of the twisted fusible electrode 3 having the parameters which have been given previously, an angle of 450 was established between the longitudinal axis of the weld bead 11 and said electrode by making it rotate around its axis, so that the line L was also arranged, with respect to said longitudinal axis, at an angle of 45 degrees.

The weld bead 11 obtained by this welding process satisfied all the requirements imposed on the weld beads produced under flux, but had other dimensions, namely:
- its width was equal to 17 mm,
- the depth of the weld bead was 5.5mu,
- the height of the bead of the cord was 2.5 mm.

Example 12
Under the same welding conditions and with the same electrode parameters as those of the previous example, an angle of 900 between the longitudinal axis was established by rotating the fused electrode 3 twisted around its axis. the weld bead 11 and said electrode, so that the line L was also arranged at an angle of 90 degrees relative to said longitudinal axis. The weld bead 11 obtained by this welding process satisfied all the requirements imposed on the cords of weld produced under flux, but had, in comparison with the two previous examples, a greater width, a lesser depth of the weld bead and a lower height of the bead of the bead, namely
- the width of the cord was equal to 21 mm,
- the depth of the weld bead was equal to
4.5 mm,
- the height of the bead of the cord was 2 mm.

 Thus, the variants of the mechanical adjustment of the dimensions of the weld bead that have just been described give the same results and, what is essential, ensures an effective influence on the dimensions of the bead. Thus, the factor for regulating the width of the weld bead in the examples relating to the two adjustment variants has a value greater than 1.5. The two variants of mechanical adjustment are quite simple, which is especially important for the welding of assemblies located in difficult to reach places and at various points in space, and lend themselves to the adjustment of welding machines as well before that during the execution of this process.

 Referring to Figure 14, it can be seen that the apparatus performing the proposed arc welding method described above, which apparatus is intended to be installed in shipbuilding workshops and is used for semi-automatic welding various parts of the shell made of low alloy steel, comprises a feed mechanism 1 connected by means of a flexible wire guide pipe 4 to a welding torch 6. The feed mechanism 1 is composed of 'a housing 13 which houses a drive motor 14 with a shaft 15, said drive motor being an electric motor, a reduction gear 16 comprising two gear transmissions and two feed rollers (17a and 17b) fitted respectively on shafts 18a and 18b connected by means of these gear transmissions to the shaft 15 of the drive motor 14. The feed rollers 17 serve to move the fused electrode 3 twisted along its axis of advance, designated by X.

 The first gear transmission of the reducer 16, ensuring the rotation of the feed rollers around their own axes in the same direction, comprises a drive member 19 in the form of a flared element provided with a cylindrical tenon central 20, extending outward and having an axial opening opening 21 and two circular rows of teeth, one of which (the outer row 22) is formed on the outer surface of said element, and the other (the row 23), on its inner surface. This transmission also comprises two driven members 24a and 24b, which are cylindrical toothed wheels having a diameter less than that of the drive member 19, these wheels being arranged inside the latter, meshed with the internal row 23 of teeth of this member and rigidly fixed on the end parts of the shafts 18a and 18b, respectively, of the respective feed rollers 17a and 17b, the driven members 24 being, as seen onthe drawing, arranged on the same side of said feed rollers 17.

 The central tenon 20 of the drive member 19 is installed in a sliding bearing 25 inserted by pressure into an orifice 26 drilled in the lower wall (according to the drawing) of the housing 13, the axis of this cotn- cidante orifice with the advance X axis mentioned above. Therefore, the drive member 19 can move around said axis X. The drive member 19 is kinematically connected to the shaft 15 of the drive motor 14 by an intermediate cylindrical wheel 27, fitted on the shaft 15 and meshed with the outer row 22 of teeth of the drive member 19. The mutual position of the drive member 19, the driven members 24 and the intermediate cylindrical wheel 27 in the plane of their gear is illustrated in Figure 15, in which all of the listed items are shown in section along line XV-XV in Figure 14.

 Thus, thanks to the connections described, during the rotation of the drive member 19 of the first transmission of the reduction gear 16, the feed rollers 17 (FIG. 14) can move around their axes in the same direction.

The second gear transmission of the reduction gear 16 which ensures the synchronous rotation of the two feed rollers 17 around the axis X of advance of the electrode 3 comprises a drive member 28 in the form of a wheel cylindrical fitted on the shaft 15 of the input motor 14, and a driven member 29, also a cylindrical wheel which is meshed with the drive member 28 and in the body of which are drilled an axial orifice opening 30 and two through holes 31a and 31b arranged diametrically. In the orifices 31a and 31b are inserted in the press sliding bearings 32a and 32b in which the shafts 18a and 18b of the respective feed rollers 17a and 17b are freely installed. The arrangement of the through orifices 31 in the driven member 29 and the mutual position of the drive member 28 and the driven member 29 in the plane of their gear are illustrated in FIG. 16, in which these elements are shown in section along the line
XVI-XVI of figure 14.

 The end parts of the shafts 18 (FIG. 14), which are on the side of the feed rollers 17 opposite to that on which these shafts are installed in the bearings 32, are freely connected to a disc 33, these end parts of the shafts 18a and 18b being mounted in the body of said disc 33 by means of sliding bearings 34a and 34b inserted by the press in orifices 35a and 35b arranged diametrically on said disc. it goes without saying that the distance between the orifices 35 and the axis of the disc 33 is the same as the distance which separates the orifices 31 from the axis of the driven member 29. Because one of the ends of each shaft 18 of the feed rollers 17 is installed in the driven member 29, and the other, in the disc 33, the driven member 29 and the disc 33 are connected in a single assembly.

 The disc 33 is provided with a central cylindrical tenon 36 having an axial orifice opening 37 and installed in a sliding bearing 38. This is inserted with the press in a through opening 39 drilled in the upper part (according to the drawing) of the housing 13, the axis of this orifice coinciding with the axis X in advance. Thus, thanks to the fact that the disc 33 and the driven member 29 are connected by means of the shafts 18 of the feed rollers 17 as a whole, and that the axis of the assembly obtained coincides with the axis X in advance, the feed rollers 17 can perform, during the rotation of the drive member 28 of the second transmission of the reduction gear 16, a synchronous movement of rotation about this axis.

 it is obvious to a person skilled in the art that the reduction gear 16 of the advance mechanism 1, as described here, is not the only possible one. Thus, the gear transmissions of the reducer 16 can be formed in another way and have wheels of other types. In addition, instead of the gear transmissions used, other types of gear transmissions can be used, as well as friction transmissions. Only the essential operating principle of the reducer must be preserved, consisting in that the transmissions used therein must simultaneously ensure the rotation of the feed rollers 17 around their own axes in the same direction and the synchronous rotation of these rollers around the feed axis X at the desired speeds.

 Each of the feed rollers 17 is a cylinder having on its peripheral surface a thread with multiple threads produced in the form of adjacent grooves 40 of cross section in the shape of a semicircle. This thread with multiple threads has a pitch equal to that of the twisted electrode 3 in formation. A person skilled in the art will readily understand that the number of entries of this thread with multiple threads must be different in each particular case and that it is mainly determined by the diameter of the feed rollers 17, the diameter of the electrode wires 2 and l 'helix angle of the electrode 3 to be formed. The feed rollers 17 are arranged, one with respect to the other, with a clearance 41 (FIG. 17) between their peripheral surfaces, the value of said clearance 41 being determined by the total diameter of the twisted electrode 3. This game ensures the wrapping of the electrode 3 by the threading of the rollers.

 In the upper part (according to the drawing) of the housing 13 (FIG. 14) of the advance mechanism 1, above the central cylindrical tenon 36 of the disc 33, is installed a receiving sleeve 42 fixed to said housing 13. The orifice opening 43 formed in the socket 42 and used to pass the electrode wires 2 into the advance mechanism 1 (the axis of this orifice coinciding with the advance X axis) has the shape of a truncated cone with grooves guide 44 (Figure 18) on its surface. The guide grooves 44 do not allow the electrode wires 2 passing through the receiving bush 42 to move in the orifice 43 around the axis of the bush. The number of guide grooves 44 is equal to the number of electrode wires 2 used for the formation of the twisted electrode 3.

 The receiving sleeve 42 can also be produced in the form of a cylinder in which, instead of the through hole 43 and guide grooves 44, are open through guide holes 45 for each electrode wire 2 (FIG. 19 ) arranged in the body of this cylinder around its axis at a certain angle relative to this axis, the number of orifices 45 also being equal to the number of electrode wires used. In the simplest case, the opening orifice 43 (FIG. 14) of the receiving socket 42 can be produced in the form of a slot having a width corresponding to the diameter of the electrode wires 2 which pass through this socket.

 Thus, owing to the fact that the axes of the orifice 43 of the receiving sleeve 42, of the axial laori.fice opening out 30 from the drive member 29 and the axial opening opening out 21 from the drive member 19 are arranged on a same line, called above axis X of advance, the orifices listed form a single channel of the advance mechanism 1. From this channel, the fusible electrode 3, arriving at its input in the form of independent electrode wires , comes out in the form of a twisted beam electrode.

 The lower part (according to the drawing) of the housing 13 of the advance mechanism 1 is connected through a transition element 46 to a central opening orifice 47 having a diameter corresponding to the diameter of the axial loris fice 21 of the drive member 19 and whose axis coincides with the feed axis X and is connected to a flexible guide wire 4 of ordinary type used to bring the fused electrode 3 twisted to the place of welding.

The flexible wire guide pipe 4 is a spiral wound three times in a steel wire of round or rectangular cross section and externally provided with an envelope which prevents it from stretching and with a protective layer arranged concentrically. to the envelope If the diameter of the electrode wires 2 forming the twisted electrode 3 is of the order of 2 mm, the flexible wire guide pipe 4 can have a length of up to 35 meters.

 The flexible wire guide pipe 4 ends at its other end with a welding torch 6 equipped with a nozzle 5 for supplying current. According to the invention, tip 5 of the current supply comprises a contact socket 48 with an internal contact channel 49 on the surface of which is formed: a thread with multiple threads having a diameter, a pitch and a number of inputs equal respectively to the diameters, to the pitch and to the number of inputs of the twisted electrode 3 which passes through said end piece, In the apparatus described, the number of inputs of the thread of the contact channel 49, like that of the electrode 3 twisted, is equal to 3.

We can get a more precise idea of the shape of the contact channel 49 by examining FIG. 20 in which the contact socket 48 is shown in longitudinal section along a plane passing through the axis of this socket, and FIG. 21, on which the contact sleeve 48 is shown in cross section. In other words, the helical surface of the contact channel 49 repeats the helical surface of the twisted electrode 3. Such a profile of the contact socket 49 is possible only if the twisted electrode 3 passing through the current-supply nozzle 5 performs combined movements of rotation and translation.

 Figure 22 illustrates contact sockets (end view) for the described type of power supply tip, which should be used if the twisted fuse electrode is formed by two (Figure 22a), by three (Figure 22b ) or seven (figure 22c) electrode wires.

 In the embodiment of the tip 5 for supplying current shown in FIG. 14, this tip comprises a cylindrical body 50 which embraces the contact socket 48 which can move along the walls of this body. Inside the body 50 is installed an elastic element 51 which is a compressed cylindrical spring, mounted in the body 50 using a washer 52 fixed to the wall of this body. The elastic element 51 is in contact with the end of the contact sleeve 48 and thereby creates a force directed along the axis of advance of the twisted electrode 3, ensuring the tightening of the thread of the contact channel 49 against the helical surface of said electrode.

 In the embodiment of the end piece 5 shown in FIG. 23, this end piece also comprises a cylindrical body 50 which embraces the contact socket 48. However, in this case, the contact socket 48 is provided with a thread exterior 53 produced on the internal surface of the body 50.

The internal surface of the body 50 is also provided with a thread 54 having a diameter and a pitch equal respectively to the diameter and the pitch of the external thread 53 of the contact socket 48 and meshing with the external thread 53 of this socket, the pitch of the thread 53 and, therefore, of the thread 54 being smaller than the pitch of the thread of the internal contact channel 49 of the contact sleeve 48, in other words, of the helical surface of the twisted electrode 3.

 The apparatus for carrying out the proposed method of electric arc welding operates as follows.

 Before starting the advance mechanism 1 (FIG. 14), at the start of the welding operation, a part of each of the electrode wires 2 is unwound from the coils and their ends are passed through the opening opening 43 of the receiving sleeve 42 Then, passing the ends of the electrode wires 2 through the axial opening opening 34 of the cylindrical lug 36 of the disc 33, they are introduced into the clearance 41 between the feed rollers 17a and 17b. Then the drive motor 14 of the reducer 16 is started. As a result of the rotation of the arc 15 of the drive motor 14, toothed drive member. 28 and the toothed wheel 27, fitted on said shaft 15, start to rotate.

 The rotation of the drive member 28, forming part of the second gear transmission of the reducer 16, causes the rotation of the driven member 29 of said transmission, which is meshed with said drive member 28, around the axis X in advance, as well as the rotation of the disc 33 and the feed rollers 17 connected to the driven member 29. As shown in FIG. 16, if the drive member 28 rotates clockwise, the driven member 29 rotates in the opposite direction. Because, on the one hand, the electrode wires 2 (FIG. 14) cannot move in the axial orifice 43 of the receiving sleeve 42 around the axis of this orifice (coinciding with the axis X in advance) and that, on the other hand, the ends of the electrode wires 2 are clamped in play 41 between the feed rollers 17, the electrode wires 2 are twisted together in a twisted electrode 3 in the space between the receiving sleeve 42 and the feed rollers 17.

 At the same time, the rotation of the toothed wheel 27 of the first gear transmission of the reducer 16 rotates the drive member 19. The rotation of the latter causes the rotation of the driven members 24 fitted on the shafts 18 of the rollers supply 17 and meshed with the internal row 23 of teeth of the drive member 19, so that the rollers 17 begin to move around their own axes in the same direction. As shown in FIG. 15, if the toothed wheel 27 rotates clockwise, the drive member 19 and the driven members 24 rotate counterclockwise. As a result of the rotation of the feed rollers 17 (FIG. 14 ) around their axes, these, which have a thread with multiple threads on their peripheral surfaces, screw into the set 41 existing between them the electrode wires 2 to be twisted and drive them out of this game in the form of a twisted electrode 3 completed, which performs a combined movement, composed of a rotational movement and a translational movement.

 Thus, it emerges from the foregoing description that the second transmission of the reduction gear 16, composed of the drive member 28 and the driven member 29, causing the rotation of the feed rollers 17 around the axis X a in advance, ensures the stranding of the wires 2 into electrode 3, while the first transmission of the reducer 16, composed of the drive member 19 and the driven member 24, causing the rotation of the rollers d brought around their axes, ensure in this way the advancement of the electrode 3 twisted in the necessary direction The operation of the reducer 16 resembles to a certain extent the well known function of a planetary mechanism, the role of the wheel central of it being played by the member 19, the role of the satellites, by the members 24, and the role of the satellite carrier, by the member 29.

 The electrode 3 emerging from the clearance 41 between the feed rollers 17 passes successively, making a helical movement along the axis v in advance, through the orifices these 30, 21 and 47 and enters the guide pipe - 4 flexible wire.

After the twisted electrode 3 has passed said wire guide 4, it is introduced into the current supply nozzle 5 of the welding torch 6, more precisely in the contact channel 49 of the contact socket 48. L electrode 3 is screwed into said channel 49 so that almost all the points on its external surface (of course1 the points which lie within the limits of the length of channel 49) enter into good sliding contact with the inner surface of this channel. The safety of the electrical contact between the contact socket 48 and the twisted electrode 3 is further ensured by the action of the elastic element 51 generating a constant force directed along the advance axis of the electrode 3 and clamping the helical surface of the contact channel 49 against the helical surface of said electrode.

 An action similar in function to the action of the elastic element 51 is also exerted by a threaded assembly (see FIG. 23) formed by the external thread 53 of the contact sleeve 48 and the internal thread 54 of the body 50 which kiss that socket. In this variant, the constancy of the clamping force acting along the axis of advance of the twisted electrode 3 is ensured by the self-tightening effect of this thread assembly 6 created during. the rotational and translational movements of the electrode 3 and ensuring the fixing in position of the contact sleeve 48 relative to its stationary body 50.

The choice of the ratio between the pitch of the aforementioned thread assembly and the pitch of the thread of the contact sleeve is determined by the particular operating conditions of the nozzle 5 for supplying current, the diameter and the length of the wire guide tube 4 (Figure 14) and the twisted electrode, etc. However, it should be noted that it is not always necessary to use special means to tighten the electrode 3 in the end piece 5 for supplying current.

Indeed, the internal diameter of the wire guide pipe 4 is always somewhat greater than the maximum diameter of the twisted electrode 3, which is necessary to create normal conditions for the passage of said electrode 3 through said wire guide pipe . Therefore, and also because the electrode 3 is supported, in the nozzle 5 for supplying current, on the thread of the contact socket 48, the electrode 3, in the event of d4-use of a
electrode 3 and a sufficiently long wire guide pipe 4, is arranged in the wire guide pipe 4 so that its longitudinal profile takes a wavy shape.

That is to say, in this case, the length of the electrode 3 located inside the wire guide pipe 4 is always a little longer than the length of said pipe. If this difference in length is greater than the value of the pitch of the helical surface of the twisted electrode 3, the elastic force of the idea-shaped twisted electrode 3, which appears under these conditions, ensures for a fairly long time the necessary tightening of the electrode 3 against the surface of the contact socket 48, and therefore no clamping means are needed. Examples of such a case are welding by hand or semi-automatic welding
When a relatively short wire guide pipe 4 and a twisted electrode 3 are used, for example in the case of automatic welding, when the difference between the above-mentioned lengths is smaller than the pitch of the thread of the twisted electrode 3, or when said electrode 3 does not have a wavy shape, the clamping means described must be used. This is due to the fact that due to the wear inevitably resulting from friction during operation of the tip 5 for supplying current , there occurs in the couple formed by the twisted electrode 3 and the contact socket 48 a play resulting in a loss of electrical contact between the elements of this couple and, consequently, in a disturbance of the whole process welding.

 So the question of whether he. whether or not to use such or such a clamping means must be resolved according to the destination, the construction and the character of the use of the welding installation. Note also that, thanks to the helical shape of the contact channel 49, we can tolerate, even when using clamping means, a fairly large wear of its surface.

Wear can even be tolerated as long as there is still a surface resembling a helical surface and as long as it can still fulfill its role. This is why the service life of the current supply nozzle 5 of such a construction greatly exceeds the service life of the commonly used tips.

 This is very important in different applications of electric arc welding and especially when performing welds in production line conditions, when the change of a worn tip requires stopping the production line. necessarily entailing excessive production costs.

 The method and the apparatus for electric arc welding which is the subject of the invention have, in comparison with known methods and devices, the following advantages.

 It should first of all be indicated that thanks to the fact that, in the proposed method, the advancement of the fusible electrode in a bundle and the stranding of all the electrode wires into a twisted electrode carrying out a movement of translation and rotation are associated in a single operation, there is no longer any need to use the special complicated apparatuses for separately carrying out the prior stranding of the electrodes from several wires and the subsequent winding of the twisted electrodes on magazine boxes.

 The proposed method ensures an improvement in the conditions of pushing of the twisted electrode in the wire guide pipes due to the increase in the areas of the contact surfaces of the supply means with the electrode to be brought, which has the effect a strong increase in the pushing force applied to the electrode to push it into the pipe. This offers the possibility of successfully solving the problem of designing welding equipment with increased torch action using a single push-type advance mechanism.

 The proposed method also ensures a stable course of the welding process, because, on the one hand, the complete absence of sliding of the electrode in the advance mechanism in the whole range of welding regimes, the advancement from the electrode to the welding arc area takes place at a substantially constant speed, and on the other hand, the contact of the electrode with the current supply nozzle according to its helical surface, ensure a high reliability of the electrical contact of the electrode with the nozzle.

 In addition, the proposed method ensures a significant increase in the welding yield (especially when the welding is carried out in places which are difficult to access), thanks to the possibility of using twisted electrodes with large total areas of cross section up to 150 mm2, to use welding currents of 6000 A and more (depending on the cross-sectional area of the electrode), and to perform welding at speeds of up to 1000 meters per hour and even more. The process allows the welding and reloading of both ferrous and non-ferrous metals, as well as the welding of various alloys based on them, which welding can be performed both under shielding gas and under flux, ensuring high quality. welded seams previously chamfered, the chamfering being carried out in the same way as in all traditional welding processes.

 The proposed method, which lends itself well to the usual methods of adjusting the dimensions of the weld bead, allows simple and effective mechanical adjustment, which can be carried out within fairly wide limits. Such an adjustment does not require the welders to be highly qualified, since the service of the welding apparatus is considerably simplified. In addition, adjusting the dimensions according to the proposed method makes it possible to simplify and automate the monitoring of the dimensions of the weld bead during the execution of the welding operations and to carry out the welds in accordance with the variations in the chamfering dimensions of the welds. .

 The device according to the invention is simpler in construction, requires less metal and has a considerably increased service life.

 All this gives the possibility of fully automating welding and performing it with the advancement of twisted electrodes with large cross-sectional areas in long wire guide pipes without reducing their elasticity, as well as considerably enlarging the field of applications of automatic welding by reducing the dimensions of the welding torches, which can be obtained by installing the electrode advance mechanism in the immediate vicinity of the wire magazine boxes, which have a large capacity and its arranged at a great distance from the place of execution of the welding.

Claims (9)

 1.- Arc welding process, of the type consisting in bringing into the area of the welding arc a twisted fusible electrode, formed of at least two electrode wires without insulation and being in the form of a screw with multiple threads, the number of inputs of which is determined by the number of external electrode wires forming the thread of said screw, the supply of the electrode is effected so as to allow the dimensions of the weld bead to be adjusted. obtain, characterized in that the twisted fusible electrode (3) is formed during its advance towards the area of the welding arc (7), by twisting together the electrode wires (2) around the axis of advance of the electrode, said electrode performing during said twisting a helical movement of rotation and translation around and along said axis of advance, each of the wires (2) of the twisted fuse electrode (3) moving always following the same trajectory and entering the area of the welding arc always in the same point, the speed of supply of the twisted fuse electrode (3) to the area of the welding arc being determined by the expression  V = p.r.n, where V is the forward speed of the twisted fuse electrode,  p is the twist pitch of the electrode wires,  r is the number of turns of the twisted fuse electrode  per unit of time,  n is the number of external electrode wires to twist.  2. A method of electric arc welding according to claim 1, characterized in that the adjustment of the dimensions of the weld bead (11) obtained by using a twisted fusible electrode (3) formed by two electrode wires (2) , is achieved by changing, in the area of the welding arc (7), the orientation of the end face (12) of the twisted fuse electrode (3) relative to the longitudinal axis of the bead weld (11) in a plane perpendicular to the axis of advance of said electrode (3).  3.- Arc welding method according to one of claims 1 and 2, characterized in that said change, in the area of the welding arc (7), of the orientation of the end face (12) of the twisted fuse electrode (3) with respect to the longitudinal axis of the weld bead (11) in a plane perpendicular to the axis of advance of the twisted fuse electrode (3), is produced by varying the length of the span of the twisted fusible electrode (3) along its axis of advance within the limits of 0.5 of the twisting pitch of the longitudinal profile of said electrode (3).  4.- Arc welding method according to claim 1 and 2, characterized in that the change, in the area of the welding arc (7), of the orientation of the end face (12) of the twisted fuse electrode (3) with respect to the longitudinal axis of the weld bead (11) in the plane perpendicular to the axis of advance of the twisted fuse electrode (3), is produced by rotating said electrode (3), around its axis of advance, by an angle between 0 and 90 degrees.  5. Welding apparatus for implementing the electric arc welding process according to one of claims 1 to 4, of the type comprising a welding torch (6) provided with a tip (5) d current supply, and connected, using a flexible wire guide pipe (4) designed to bring the fusible electrode (3) into the welding zone, of a feed mechanism (a) which comprises a housing (13) in which are mounted a reduction gear (16) equipped with a drive motor (14) and rotary feed rollers (17) used to move the fusible electrode (3) along its axis of feed and rigidly fixed on shafts (18) connected to the shaft (15) of the drive motor (14), charac terized in that each of the feed rollers (17) of the feed mechanism (1) is produced in the form of a cylinder comprising on its peripheral surface a thread with several threads the pitch of which is equal to that of the thread of the twisted fusible electrode (3) being formed, the reducer (16) of the mete feed mechanism (1) being composed of a first transmission ensuring the rotation in the same direction of the feed rollers (17) about their respective axes, and comprising two driven members (24) each rigidly fixed at the end of the shaft (18) of the corresponding feed roller (17) and on the same side of the feed rollers (17), a drive member (19) kinematically connects to the driven members (24) of said first transmission and with shaft (15) of the input motor (14), and of a second transmission ensuring the synchronous rotation of the two feed rollers (17) around the axis of advance of the twisted fuse electrode (3 ), and comprising a driven member (29) mounted in free rotation on the end of the shaft (18) of the corresponding feed roller (17), on the same side of said feed rollers (17), and a drive member (28) kinematically connected to the driven member (29) of said second transmission and to the shaft (15) of the drive motor (14), the end piece (5) d current supply consisting of a contact socket (48) with an internal contact channel (49) on the surface of which a thread with several threads is made whose diameter, pitch and number of entries are respectively equal to diameter, pitch and number of inputs of the twisted fuse electrode (3) formed, passing through said nozzle (5).  6.- Welding apparatus according to claim 5, characterized in that the tip (5) for current supply to the welding torch comprises an additional housing (50) embracing the contact socket (48) and on which is fixed an elastic element (51) which is in contact with one of the faces of the contact socket (48) and generates a force directed along the axis of advance of the twisted fuse electrode (3) and ensuring tightening the thread of the contact channel (49) of the contact sleeve (48) against the helical surface of the electrode (3)  7.- Welding apparatus according to claim 5, characterized in that the tip (5) for current supply to the welding torch (6) comprises an additional housing (50) embracing the contact socket (48) provided on its peripheral surface of an external thread (53), the internal surface of said housing having a thread (54) whose diameter and pitch are respectively equal to the diameter and pitch of the external thread (53) of the contact sleeve ( 48) and which is in engagement with said external thread (53) of the contact sleeve (48).  8. Welding apparatus according to claim 7, characterized in that the external thread (53) of the contact sleeve (48) of the nozzle (5) for current supply and the thread (54) produced on the inner surface of the housing (50) of the end piece (5) and engaging the thread (53) have a pitch smaller than the pitch of the thread of the inner contact channel (49) of the contact sleeve (48 ).  9. Welded parts and assemblies, characterized in that they are obtained by the process according to any of claims 1,2,3 and 4.