ARC WELDING METHOD AND LONGITUDINAL ARC WELDING MEANS

Abstract: The invention relates to an arc welding method and an elongate arc welding means to make a long weld seam or a column of weld seams. According to the invention at least one elongate welding electrode (4) in the welding means, as a welding bar or rod, is supported in a position spaced from the welding object (3) and in register with it essentially straightly inside an at least partly flexible shell portion (1), by which the welding means is supported and engaged over the welding object (3). To maintain an even and continuous electric arc and to form a uniform weld seam each welding electrode is forced from the position spaced from the welding object (3) gradually and/or continuously the end part (41) ahead in a slanting angle, which is advantageously between 5 DEG ...50 DEG , to the welding object (3).

Description: Arc welding method and longitudinal arc welding means. The present invention relates to the arc welding method according to the introductory part of the claim 1 and to the arc welding means to form one or more uniform long weld seams according to the introductory part of the claim 11. The traditional manually effected welding by welding electrodes requires great professional skill, which is further emphasized, when welding must be carried out in exceptional circumstances, as under water. Due to troublesome working conditions a tendency has prevailed to provide a welding means which, when automatically brought to the object and located on it, could produce a high class weld seam without the need of a welder. A weld joint, not however of as good quality as a weld seam satisfying the requirements of f.ex. classification societies, can be provided by a rodlike or bandlike welding electrode, placed longitudinally to the welding object, whereby the welding current is conducted to this electrode from its other end. In this case the most prominent disadvantages are: - the uncontrolled progress of the electric arc, - local breakdowns of the electric current, due to which the weld seam becomes uneven and contains slag inclusions and edge wounds. Moreover, the weld penetration into the base material varies, because of the uneven arc. The first object of the present invention is therefore to provide a novel, improved welding method and welding means, by which it is possible to essentially reduce the disadvantages and weaknesses connected with the traditional production of a weld seam, and at the same time to enable the manufacture of a uniform long weld seam or weld seam rows by one welding action without changing the welding electrode. The second essential object of the invention is to provide a welding method and a welding means particularly suitable for underwater conditions. These goals have been achieved by the arc welding method and means mentioned above, the characteristic features of which have been described in the enclosed claims. The invention is thus based on the ingenious basic realization, that at least one elongate welding electrode in the welding means, as welding bar or rod, is supported essenitially straightly in the position spaced from the welding object and register with it, and that each welding electrode is forced fro this position gradually and/or continuously the end part ahead move towards the welding object to form at least one uniform w seam. In this way it is possible to ensure on the one hand, that no meaningless breakdonws can happen between the basic material and the electrode. Additional advantages include the fact, that welding can be performed in any orientation, and that the progress of the welding process can, if needed, be followed and even controlled in such a way, that the feeding rate of the welding electrode in relation to the progress rate of the electric arc in the object can be selected quite freely to correspond optimally each conditions and/or needs. The invention will be described in the following by some advantageous embodiments thereof with reference to the accompanying drawings, in which: - Figure 1 shows a longitudinal cross section of the welding means according to one advantageous embodiment of the invention - Figure 2 shows a sectional view taken along the line II-II of Fig. 1; - Figure 3 shows a sectional view taken along the line III-III Fig. I; - Figure 4 shows a longitudinal cross section of the welding means according to a second advantageous embodiment of the invention; - Figure 5 shows a longitudinal cross section of the welding means accroding to a third advantageous embodiment of the invention; and - Figure 6 shows a sectional view taken along the line VI-VI of Fig. 5; - Figure 7 shows a longitudinal cross section of the welding means according to a fourth advantageous embodiment of the invention; and - Figure 8 shows a perspective view of a fifth advantageous embodiment of the invention. The arc welding means according to the invention comprises a mantle type shell portion 1 made of at least partly flexible material and supporting the welding means and being open at one long side thereof. To the edges of the open side of the shell portion 1 has been placed, as shown in the drawings, fixing means 2, e.g. magnet pieces, bands etc. , to fasten the welding means and to keep it longitudinally over the welding object 3 with the open side towards the welding object. The size or shape of the welding object itself impose no limitation concerning the invention; the object can be for example a V-channel between two metal plates, a rupture in the metal plate or the like. The arc welding means includes also an elongate welding electrode 4, advan;tageously a welding bar or rod, extending to the whole length of the welding means and suspended inside the shell portion 1, so that when the welding means has been adapted to the welding object 3, the welding electrode is parallel with the welding object, i.e. the welding seam to be formed, and in register with it. To guarantee safety during the underwater use of the welding means and to facilitate the placing of the welding means to the welding object, it is advantageous to make the shell portion 1 from a non conductive flexible material, for instance polyamide material, whereby the setting of the welding means, especially the one provided with a flexible core wire, to any twisted or angular welding object can easily be done. As already stated before, the weld seam is formed according to the basic principle of the invention to the welding object 3 in such a way, that the end part 41 of the welding electrode 4, which before commencing the welding process has been supported along the whole length thereof at a distance from the welding object 3, is bent and laterally oriented by an angle, which advantageously is between 5°...50°, towards the welding object 3, whereas only the end part 41 forced to the immediate proximity of the welding object 3, is located at a distance from the welding object 3, which enables the appearance of the electric arc. After the arc has been formed, the welding electrode 4 is bent further on to form the weld seam from the position apart from the welding object 3 gradually the free end ahead to the welding object 3. According to the first advantageous embodiment of the invention shown in figures 1...3, in order to bend the welding electrode connected with the welding current supply, from the position at distance from the welding object 3 diagonally the end part 41 ahead to the welding object, a press arrangement 5 fastened inside the shell portion 1 to the internal top wall 11 and thus placed between the shell portion 1 and the welding electrode 4, is used in the welding means. In the first embodiment the press arrangement 5 comprises a series of press means 51 arranged one after another and supporting the welding electrode, each of whi means 51 has a spring means 52 and a retainer means 53. In orde to have the welding electrode at a distance from the welding object, the retainer means 53 keeps the spring means 52 and thereby the whole press means 51 compressed. To bend the weldin electrode the retainer means 53 can one at a time and alternate be transformed as non-retaining, whereby the spring means 52 is released from the compressed condition, so that it presses the end part 41 of the welding electrode down to the welding object 3. Then the welding electrode 4 is pressed with the free end 41 ahead to the arc area by the press arrangement 5 provided with the spring means 52 in several subsequent phases following each other. To transform the retainer means 53, fastened by its ends between the shell portion 1 and the press means 51 of the welding electrode 4, as non-retaining, it is shaped as a flanged pin made of a material yielding by thermal influence, preferably plastic, and provided with an internal electric resistance 54, by which the retainer means 53 can be heated up, whereby the retainer means 53 is softened and yields under the load directed to it by the spring means 52. Then the spring means, when it is released from the compressed condition, forces the welding electrode 4 to bend to the welding object 3. As is more clearly visible in the figure 3, the activating means for the electrical resistance are also connected with the push button press arrangement 5 according to this embodiment. These activating means comprise advantageously several current switches 9 located close to the edges of the open side of the shell portion 1, whereat these switches 9 when contacted with the press means 51 transferred towards the welding object 3, shut off the circuit flowing through the electrical resistance element 54 of the other press means 51 next in order, which heats up the electrical resistance element 54 and softens the retainer means, generating in this way a continuous welding process, in which the welding electrode 4 is serially bent to the welding object 3. According to the second advantageous embodiment of the inventio shown in figure 4, in order to bend the welding electrode 4 connected with the welding current supply from the position spaced from the welding object 3 diagonally the end part 41 ahe to the welding object, a press arrangement 5 is used in the welding means, adapted to be transferable inside the shell portion 1 between the inner top wall 11 of the shell portion an the welding electrode 4. The welding electrode 4 is gradually a continuously bent to the welding object 3 mechanically by an advantageously ball-type (as in figure 4) or wedge-type press piece 57 formed by the press arrangement, which piece 57 is transfered as supported to the welding electrode 4 and, in orde to maintain an even electric arc, by the speed corresponding the progress rate of the arc. When an electrode is used as the welding electrode, the outermost layer of which is conductive, as a so-called core filling wire, the welding current can be conducted for instance from a current rail extending to the whole length of the welding means to the welding electrode 4 by the conductive, advantageously metal press piece 57 of the press arrangement, whereby the conduction path of electricity to the welding electrode 4 will always be as short as possible. In the third advantageous embodiment of the invention, shown in figures 5 and 6, the welding electrode 4 coupled to the welding current supply is bent from a position spaced from the welding object continuously and gradually to the welding object by a press arrangement comprising a hollow means 56, most advantageously an elastic tube, for liquid medium flow, and an advantageously wedge-shaped expanding press piece 57 adapted onto the hollow means 56, the guiding surface of which, being diagonally curved towards the welding object, is supported against the welding electrode 4. The medium flow taking place in the tube expands the tube at least in the transversal direction in relation to the length of the welding electrode 4, whereby the expansion caused by the medium flow in the tube 56 forces the press piece 57 to move ahead thereof along the tube 56. In figure 5 an alternative or complementary solution to transfer the press piece 57 along the tube 56 has been illustrated by a dashed line. As can be seen in figure 5, an expansion piece 58 can be inserted in the tube to progress in the tube ahead the medium flow and to move thus the press piece 57. In order that the movement of the press piece 57 would happen f bending of the welding electrode 4 and for proper forming of the weld seam in the interior side walls of the shell portion 1, rail shaped guide projections 10 extend to the whole length of the shell portion to determine the course of the press piece 57. Also a support piece 8 clamped to the side walls of the shell portion 1 inside thereof in the immediate proximity of its top wall 11 supports the welding electrode 4 and the elastic tube 56 above it. The support piece 8 has been made by elastic plastic material, so that when the load generated by the expansion of the elastic tube and directed towards the welding object is applied to it, the skirts supporting the welding electrode 4 are opened detaching the end part 41 of the welding elecjtrod 4 from its suspension and allowing its movement in a slanting position guided by the wedge shaped press piece 57 to the welding object 3. In connection with the second and the third advantageous embodiments it must be emphasized, that it is possible to use in them a feedable welding electrode, whereby the feeding rate thereof can be regulated in relation to the progress speed of the electric arc between the welding electrode and the welding object in the welding means and thus enable also the welding of large cracks in one work phase. In the fourth and fifth advantageous embodiments shown in figures 7 and 8 the welding electrode coupled to the welding current supply by the press arrangement 5 is bent continuously and gradually from the position spaced from the welding object a slanting position the end part 41 ahead to the welding object by the above mentioned press arrangement in such a way, that th needed bending is achieved only by increasing the dimensions of the hollow means 56 belonging to the press arrangement 5 in the transversal direction in relation to the length of the welding electrode 4. The press arrangement 5 according to the fourth advantageous embodiment (figure 7) of the invention consists of a channel element made of conductive material, connected to the current supply and conductively coupled- to the welding electrode 4.To o channel of the channel element, i.e. the upper channel connected with the top wall 11 of the shell portion, has been adapted a conductor cable, and the side walls 59 defining the other channel of the channel element, i.e. the lower channe connected with the welding electrode 4, have been made as yielding in the transversal direction in rela;tion to the lengt of the welding electrode 4. Yielding of the side walls has in this embodiment realized so, that the side walls 59 are made of alloyed metal, whereby by stretching the side walls 59 the welding electrode is forced to bend the end part 41 ahead towar the welding object 3. To stretch the side walls 59 the press piece 57 is moved in the channel defined by these walls, the dimensions of the press piece 57 being at least in the transversal direction relation to the length of the welding electrode greater than th corresponding inner diameter of the unstretched channel. Ε- τ moving the press piece 57 in the channel most advantageous / wi a speed exactly corresponding the progress rate of the arc, the welding electrode 4 is bent according to the stretch of the sid walls and its end part 41 is directed in a slanting position to the welding object 3. In figure 8 has been shown the operational principle of the welding means according to the fifth advantagous embodiment of the invention and the feeding of the welding current to the welding electrode 4 has been realized in the same way as shown above in connection with the fourth advantageous embodiment of the invention. The press arrangement 5 comprises thus a conductive, advantagously metal channel element, having a first channel 6 to conduct the welding current and a second channel, whose side walls 59 are yielding. The difference compared with the fourth advantageous embodiment of the invention is that the channel, lower in the figure connected with the welding electrode, is full of medium 7 expanding under heat. Then this heat-expandable medium 7 stretches the side walls 59 and thus bends the welding electrode in order to direct the end part 41 thereof diagonally to the welding object 3. The way, by which the welding current is conducted to the press arrangement, is not the most essential factor considering the operation of the invention. The welding current can be conducted in the most simple way so, that a conductor cable has been adapted into the upper channel 6, or this channel is fille by conductive medium, e.g. mercury. The current feeding effecte by the press arrangement includes the advantage, that the conduction path of the current is always as short as possbile, which tends to stabilize the generated electric arc and thus to improve the quality of the weld seam produced. Especially in connection with the underwater use of the arc welding means according to the invention it can be stated, that it is advantagous to fill the interior of the shell portion 1 by an organic pastelike additive. For instance the additives described in the Finnish Patents Nos. 64903 and 72906 are suitable, by which it is possible to prevent the penetration of water to the arc area and thus obstruct the direct contact between the welding electrode and water, and which being under the influence of the electric arc form over the weld seam a slag layer with great heat capacity, delaying thus cooling of the weld seam and preventing the appearance of welding errors, as edge wounds, slag inclusions etc. Also, when a welding rod is used as the welding electrode with an outside coating, it is preferable, that the coating is prepared so, that it does not absorb water. The invention has been described above only by some advantageo embodiments thereof. This is not, of course, meant to limit the invention and as a person skilled in the artocan understand, the basic principle of the invention, i.e. bending from the position spaced from the welding object to the welding object, can be adapted and varied very broadly within the scope of the appended claims.

Claims: CLAIMS 1. An arc welding method to form a weld seam to the welding object by an arc welding means to be placed longitudinally thereto, c h a r a c t e r i z e d in that at least one elongate welding electrode, as welding bar or rod, in the welding means is supported essentially straightly in the position spaced from the welding object and in register therewith, and that each welding electrode is forced from this position gradually and/or continuously the end part ahead towards the welding object to form at least one uniform weld seam. 2. Arc welding method as claimed in claim 1, c h a r a c t e ¬ r i z e d in that the end part of the welding electrode is bent to be orientated diagonally side;ways at an angle, advantageousl between 5° ... 50° , towards the welding object, whereby only the above mentioned end part of the welding electrode forced to the immediate proxjimity of the welding object is at a distance from the welding object enabling the appearance of an electric arc. 3. Arc welding method as claimed in claims l or 2,c h a r a c t e r i z e d in that the welding electrode is pressed the free end part thereof ahead to the arc area by a press arrangement with spring means in several subsequent phases following each other, whereby to keep the welding electrode at a distance from the welding object, the spring means of each press means of the press arrangement , except the press means closest to the arc area in the direction of propagation of the electric arc, is kep in a prestressed compressed state by a retaining means, and whereby in order to press the free end part of the welding electrode to the welding object, the spring means of the press means of the press arrangement closest to the arc area in the direction of propagation of the electric arc is released from the prestressed state by tranforming the retaining means as non retaining. 4. Arc welding method as claimed in claim 3,c h a r a c t e r z d in that the retaining means is made of a material yieldi under heat, whereby the retaining means is heated up to transfo it as non retaining and thereby " to release the spring means. 5. Arc welding method as claimed in claims 1 or 2,c h a r a c t e r i z e d in that the welding electrode is bent gradually and continuously with the free end part thereof ahead to the ar area by a press arrangement moved in the direction of the weldi electrode essentially with the speed corresponding the propagation rate of the electric arc. 6. Arc welding method as claimed in claim 5,c h a r a c t e r z e d in that the welding electrode is bent mechanically to th welding object, advantageously by a ball shaped or wedge shaped press means. 7. Arc welding method as claimed in claim 6,c h a r a c t e r z e d in that the welding current is conducted to the welding electrode by a conductive press means. 8. Arc welding means as claimed in claims 1 or 2,c h a r a c t e r i z e d in that the welding electrode is bent gradually an continuously the free end thereof ahead to the arc area by a press arrangement, the dimensions of which are increased in the transversal direction in relation to the length of the welding electrode. 9. Arc welding method as claimed in any of claims 5...8,c h a r a c t e r i z e d in that the feeding rate of the welding electrode is regulated in relation to the propagation speed of the electric arc between the press arrangement or the welding electrode and the welding object. 10. Arc welding method as claimed in claims 1 or 2, c h a r a t e r i z e d in that the welding electrode is bent against th welding object by expanding gradually and continously a hollow means supporting the welding electrode at a distance from the welding object and serving as a press arrangement in the transversal direction in relation to the length of the welding electrode, and that the welding-current is conducted to the welding electrode by a conductive press arrangement. 11. Elongate arc welding means intended to be placed longitudinally onto a welding object and comprising: - an at least partly flexible mantle shaped shell portion (1) open in one long side and advantageously provided with fixing means (2) to fasten the welding means longitudinally to the welding object in register with it, said open side towards the welding object (3), and - an elongate at least partly flexible welding electrode (4), as a welding bar or rod, suspended inside the shell portion (1) in such a way, that when the welding means has been adapted to the welding object (3), the welding electrode (4) is essentially parallel and in register with the welding object, i.e. the weld seam to be formed,c h a r a c t e r i z e in that the welding electrode (4) is suspended inside the shell portion (1) at a distance from the open side of the shell porti (1) and provided with a press arrangement (5) to force the welding electrode (4) gradually and/or continuously from the suspension position thereof at a distance from said welding object (3) the end part (41) ahead diagonally sideways at an angle, advan;tageously between 5 ...5C , towards the welding object (3). 12. Arc welding means as claimed in claim ll,c h a r a c t e - r i z e d in that a press arrangement (5) has been adapted inside the shell portion (1) between the internal top wall (11) of the shell portion and the welding electrode (4), and that th press arrangement comprises a series of subsequently in line arranged press means (51) supporting the welding electrode and having each a spring means (52)' and a retaining means (53), whi in order to keep the welding electrode (4) at a distance from t welding object keeps the spring means (51) and thus the press means (51) compressed, and that the retaining means (53) of the press arrangement (5) can, advantageously one by one and alternately, . be transformed as non-retaining, whereby the spring means (52) is released from the compressed state and presses the welding electrode (4) towards the welding object (3). 13. Arc welding means as claimed in claim 12, c h a r a c ¬ t e r i z e d in that the retaining means (53) has an inter;nal electrical resistance element (54), and that the body part of the retining means (53) has been made of a material yielding or softening under heat, whereby by activating the resistance element (54) the retaining means (53) can be transformed as non retaining. 14. Arc welding means as claimed in any of claims 11...13, c h a r a c t e r i z e d in that several current switches (9) have been arranged in the side walls of the shell portion (1) close to the edges of the open side thereof to activate the electrical resistance element (54) of the second press means (51) next in order from the press means (51) trans;fered towards the welding object (3) . 15. Arc welding means as claimed in claim 11,c h a r a c t e ¬ i z e d in that the press arrangement (5) consists of a wedge shaped or ball shaped press piece (57) transferable betv.'ee the internal top wall (11) of the shell portion (1) and the welding electrode (4) to bend the welding electrode in a slanting position the end part (41) ahead to the welding object (3). 16. Arc welding means as claimed in claim 15,c h a r a c t e - r i z e d in that the press piece (57) comprises a wedge v/ith an arcuate running surface pressable against the welding electrode (4) to bend the end part (41) of the welding electrode (4) to the desired angle, which is advantageously between 5° ...50° . 17. Arc welding means as claimed in claim ll,c h a r a c t - r i z e d in that the press arrangement ( 5 ) has been adapted inside the shell portion (1) between the internal top wall (11) of the shell portion and the welding electrode (4) , and that th press arrangement includes a hollow means (56) to bend the end part (41) of the welding electrode (4) at least in the transversal direction in relation to the length of the welding electrode (4) . 18. Arc welding means as claimed in claim ^c h a r a c t e ¬ r i z e d in that the hollow means (56) comprises an elastic tube, inside which has been transferably adapted a press piece (57) essentially greater in its dimension than the inside diameter of the tube, at least in the transversal direction in relation to the length of the welding electrode (4) , whereby b transfering the press piece (57) in the tube means (56) with t speed corresponding the propagation rate of the electric arc t end part (41) of the welding electrode can be bent in a slanti position towards the welding object (3). 19. Arc welding means as claimed in claim 17,c h a r a c t e r i z e d in that the hollow means (56) comprises an elastic tube for a liquid medium flow, and that over the tube has been adapted an advantageously wedgelike expanding press piece ( 57) pressable against the welding electrode (4) and moving along t tube forced either by the liquid medium flowing directly in th tube and exjpanding it or by a expansion piece (58) pushed ahe by the medium. 20. Arc welding means as claimed in claims 15, 16 and 19,c h r a c t e r i z e d in that advantageously rail-shaped guide projections (10) have been provided in the sidewalls of the sh portion (12) to determine the course of the press piece (57). 21. Arc welding means as claimed in claim 17,c h a r a c t e r i z e d in that the hollow means (56) comprises an elongate channel element made of conductive material and conductively connected with the welding element, and that at least one side walls (59) of this channel element yield in the transversal direction in relation to the length of the welding electrode, whereby by stretching the side walls (59) the welding electrode (4) can be forced the end part (41) ahead in a slanting position towards the welding object (3) . 22. Arc welding means as claimed in claim 21,c h a r a c t e ¬ i z e d in that the press arrangement comprises a multi channel element, the first channel (6) of which is for conduction of the welding current, and the second channel of thi element with the side walls (59) thereof being alloyed as yielding has been filled by heat-expandable medium (7) to stretc the side walls (59) and thus to force the welding electrode (4) gradually and continuously towards the welding object (3) . 23. Arc welding means as claimed in claim 22,c h a r a c t e ¬ r i z e d in that a conductor cable has been adapted to the first channel (6) or this channel has been filled with a conductive medium, e.g. mercury. 24. Arc welding means as claimed in any of the preceding claims 11...23, c h a r a c t e r i z e d in that the press arrangement (5) or the welding electrode (4) has been supported inside the shell portion (1) in the upper part thereof by a supporting means (8) clamped to the side walls (12) of the shell portion (1) . 25. Arc welding means as claimed in any of the preceding claims 11...24, c h a r a c t e r i z e d in that the interior of the shell portion (1) has been filled by a pastelike additive to insulate the arc area and the welding electrode (4) from water.

Inventors: NIINIVAARA ENSI KYOESTI JUHANI, NIINIVAARA, ENSI, KYOESTI, JUHANI
Applicants: GSS GENERAL SEA SAFETY LTD OY, OY GSS GENERAL SEA SAFETY LTD
Application year: 1987
Main classification: B23K9
IPC codes: B23K9