FR2812227A1 - Laser welding of a pipeline, uses multiple laser beams delivered through optic fibers to focussing head, supplied by generator and source unit running alongside pipe - Google Patents

Abstract

The laser welding joins sections tube (2a,2b) to form a pipeline, using multiple laser beams (6) transmitted by optic fibers (7) to one or more focusing heads (9), mounted on a mobile carriage running alongside the pipe. An electric generator (3) is mounted on a vehicle (4) which runs alongside the pipe. The laser source is also mounted on the vehicle, or can be on a separate vehicle.

Description

The invention relates to a method of laser welding tubes, as well as

  the installation for implementing the process.

  More particularly, the invention relates to a method of welding tubes for producing a pipeline of the pipeline type by means of one or

  several laser beams transmitted by optical fiber.

  Processes for welding pipelines using lasers are already known.

  o10 Patent application EP 706 849 describes in particular an external welding process of pipeline by laser. The laser source is mounted on a carriage which is itself mounted on a rail which surrounds the pipeline. However, the carriage cannot support high loads so that it is incompatible with high power laser sources. The applicants have observed that the laser welding of

  pipeline required the use of high laser powers.

  US Patents 4,429,211 and US 4,533,814 describe laser welding methods in which only the laser beam focusing device is placed on a carriage rotatably mounted around the pipeline. The laser source is moved away from the carriage and is guided towards the focusing device by several mirrors.

  These methods however require precise and meticulous adjustment of the mirrors.

  In addition, in order to ensure good transmission of the laser beam, the mirrors must be protected from the external environment as well as from impact. They have

  otherwise sensitive to climatic conditions.

  The invention aims to propose a laser welding process which does not have the drawbacks of existing processes, and which makes it possible to weld pipeline sections by laser under optimal conditions both in terms of

  of quality only in terms of speed and implementation.

  To this end, the invention describes a method for welding together sections of steel or aluminum alloy tubes, in particular for producing a pipeline of the pipeline type, said tubes having a thickness greater than 4 mm, this

  process consisting in joining the two ends of said sections of tubes.

  Said method is characterized in that said ends are welded by means of one or more laser beams transmitted by optical fiber (s), the power of the laser beam (s) being greater than or equal to 3 kW, the welding being obtained by orbital displacement of the laser beam (s) around said tube sections, said beam (s) being guided axially and radially to follow the joint plane formed by the two ends of said beams

sections of tubes.

  The use of a laser beam with a power greater than 4 kW makes it possible to weld large thicknesses of metal, which is the case with pipelines, under conditions allowing implementation much faster than

  in the case of conventional welding processes.

  The use of a fiber optic link between the laser source and the emission head makes it possible to arrange the laser source and the generator supplying it with

  outside and away from the pipeline.

  These provisions make the laser welding process fully operational

  whatever the terrain and climatic conditions.

  In one version, a chamfer is produced on the ends of the sections of tubes to be welded, the two chamfered ends are joined so as to create a groove between these two ends, the groove thus created having a depth less than the thickness of the tube, the ends of the tube sections being in contact with each other in the zone between the bottom of the groove and the interior surface of the tube sections by planar surfaces, said zone being welded by means of a or several laser beams, by moving said laser beam (s) in said groove along the line of intersection

  between the bottom of the groove and said flat surfaces in contact.

  These provisions make it possible to weld together sections of pipeline in

  which the metal has a very high thickness.

  Alternatively, said groove has a substantially U-shaped section or the like. Thanks to this U-shape, the lateral faces of the groove are located at a certain distance from the laser beam, which prevents any alteration of these faces.

side by beam.

  The laser beam (s) have a power of between 4 and 12 kW.

  This power is sufficient to obtain good quality welds for the thicknesses of metal generally encountered in pipelines. This

  power can be obtained by combining several laser sources.

  In the process according to the invention, the laser beam (s) is rotated at a continuous speed around the two sections of tubes to be welded, along

said line of intersection.

  A continuous weld is thus obtained, distributed evenly along the

  joint plane of the two sections of tubes.

  Furthermore, the gaseous protection of the weld is advantageously ensured

by a neutral gas flow.

  According to one embodiment of the invention, after carrying out the laser welding of said flat surfaces in contact with the two sections of tubes, the welding joint is completed by filling said groove using a conventional method of arc welding with a filler metal or using

other welding methods.

  The invention also relates to an installation for implementing the method, comprising an electric power generator group of power greater than 300 kW mounted on a towed vehicle or which can be placed on the ground along the pipe to be produced. , said vehicle or another vehicle connected to said vehicle also transporting a source of production of laser radiation transmitted by optical fiber (s) to one or more laser beam (s) emission and focusing heads ), characterized in that the said head or heads are mounted in rotation on guide means

  circumferentials surrounding the two sections of tubes to be welded.

  In one embodiment, said circumferential guide means cooperate with said joint plane to allow the laser beam (s) to

  very precisely follow said parting line.

  The said head (s) can also be guided during their movement on the said circumferential guide means by a member cooperating with one of the lateral faces of the said groove in order to be able to precisely follow the said line

  intersection between the bottom of the groove and said flat surfaces in contact.

  Other features and advantages of the invention will become apparent in the

description below.

  In the accompanying drawings given by way of nonlimiting examples: - Figure 1 is a diagram representing the laser source according to the invention connected by optical fiber (s) to the carriage, the latter carrying the emission head and focusing, the pipeline being shown in cross section; - Figure 2 schematically shows two portions of the sections of tubes to be welded in longitudinal section according to a first variant of the invention; - Figure 3 shows schematically two portions of the sections of tubes to be welded in longitudinal section according to a second variant of the invention; - Figures 4a and 4b schematically represent the path of the laser beam from the source to its focus for welding using two optical fibers (Figure 4a) or only one (Figure 4b); - Figure 5 shows schematically the end of the emission and focusing head; - Figures 6a to 6c show the impact points of two laser beams relative to the joint plane; - Figure 7 shows the guide means according to a first mode of

realization of the invention.

  The installation 1 is intended to implement the method according to the invention in order to

  to produce a pipeline 2 of the pipeline type by laser welding of two sections 2a, 2b of tubes.

  The sections 2a, 2b of tubes are made of steel or aluminum alloy and have

a thickness greater than 4 mm.

  Installation I comprises: - an electrical energy generator group 3 of power greater than 300 kW mounted on a vehicle 4; a source 5 for producing laser radiation 6 mounted on the vehicle 4 or on another similar vehicle (not shown) connected or not to the vehicle 4; one or more optical fibers 7; - circumferential guide means 8 surrounding the two sections 2a, 2b of tubes to be welded; one or more heads 9 for emitting and focusing laser beam (s)

  mounted on the guide means 8.

  Vehicle 4 can be towed or can be placed on the ground along the

  pipeline to be made. It can also be a motor vehicle.

  The power generator and the laser source can thus be easily moved along the line 2. In particular, large laser sources

  large and high power can be used and moved.

  Depending on the laser powers required one or more laser sources 5 can

  be used, as well as one or more generators 3.

  The laser radiation 6 is transmitted to the emission head (s) 9 by means of optical fiber (s) 7. The length of optical fiber (s) 7 is sufficient to connect the laser source 5 placed on the vehicle 4 to sections of tubes 2a and 2b to be welded, and to allow the emitting head or heads 9 to follow the complete periphery of these

sections.

  These optical fibers are externally protected by a flexible sheath. This flexible sheath makes the optical fibers usable whatever the conditions

  geographic and climatic conditions of the welding site.

  The use of optical fibers eliminates all the adjustment or protection problems inherent in a mirror transmission and simplifies the connection between

  a laser source 5 and an emission head 9.

  The circumferential guide means 8 cooperate with said joint plane 10 to allow the laser beam (s) 6 to follow said plane very precisely

seal 10.

  The joint plane 10 is defined as the transverse contact surface

  between the two sections of tubes 2a, 2b placed side by side to be welded.

  In one embodiment, the guide means 8 comprise a rail 11 fixed on the periphery of one of the two (or two) sections of tubes 2a, 2b on

  which are mounted one or more carriages 12.

  Each carriage 12 has guide rollers 13 placed in opposition on each side of the rail 11, so that the carriage 12 can go around completely

of the two sections of tubes 2a, 2b.

  A motorization system of the carriage 12 makes it possible to move the latter on

  all around the tube sections.

  This motorization system, shown in FIG. 7, comprises for example a motor 23 mounted on the carriage 12. This motor 23 drives a pinion 24 which cooperates with a rack 25 disposed along the rail 11. The motor can

  be remotely controlled automatically.

  The emitting and focusing heads 9 are mounted on the

carts 12.

  In a variant, the guide means comprise optical means, such as a camera (9a) enabling the laser beam (s) 6 to follow very closely.

  precisely said joint plane 10.

  In another variant, the guide means comprise mechanical means, such as guide rollers, allowing the laser beam (s) 6, guided axially and radially, to follow said axis very precisely.

parting line 10.

  Other types of suitable sensors can also be used to

  detect the position of the joint plane 10.

  The two sections 2a, 2b of tubes to be welded are maintained by supports at a sufficient distance from the ground so that a carriage 12 can easily

  go around the said sections.

  In one embodiment, the ends of the two sections of tubes 2a and 2b to be welded are chamfered, as shown in FIG. 3, so that

  create a groove 14 between these two ends.

  The ends of the sections 2a, 2b of tubes are then in contact with each other in the zone between the bottom of the groove and the interior surface

  sections of tubes by flat surfaces.

  The bottom of the groove 14 has a width greater than the diameter of the laser beam (s) 6 at their impact on the line of intersection 15 between the bottom of the

  groove and said flat surfaces in contact.

  Thus, the laser beam (s) 6 do not risk altering the walls of the groove 14. This width can for example be two millimeters greater than the diameter

  of the laser beam (s) 6 at its impact.

  In the example shown, the groove 14 has a section substantially in

U shape or the like.

  The thickness of the area between the bottom of the groove and the internal face of the tube sections is between 2 and 12 mm. Preferably, it is

between 4 and 6 mm.

  The said emission head (s) 9 can then be guided during their movement on said circumferential guide means 8 by a member (not shown) cooperating with one of the lateral faces of said groove 14 in order to be able to precisely follow said line of intersection 15 between the bottom of the

  groove and said flat surfaces in contact.

  This member may for example be one or more guide rollers according to the

lateral faces of the groove 14.

  The laser source 5 is now described in detail.

  The laser radiation 6 (or the laser beam (s)) is produced from a

  solid-state laser 16 whose wavelengths are transmissible by optical fiber.

  In one embodiment, the solid-state laser 16 is a neodymium: YAG (Yttrium - Aluminum - Garnet) bar laser excited by means of lamps or

of diodes.

  In Figure 4, the bar 17 of the laser is shown. He is excited by a lamp

18, for example neon.

  In another embodiment not shown, the solid-state laser 16 is a Ytterbium disc laser: YAG (Yttrium - Aluminum - Garnet) excited by means

of diodes.

  To this end, the high-power YAG lasers manufactured and marketed by the

  TRUMPF company may be perfectly suitable.

  The laser radiation 6 thus produced has a power greater than 4

  kW, it can for example be between 5 and 10 kW.

  The laser radiation 6 emitted by the excited solid rod 17 (or the disc) is transported by optical fiber (s) 7 to one or more emission heads 9 and

of focus.

  The emission and focusing head 9 comprises a collimating lens 19 followed by a focusing lens 20. This arrangement of lenses, known to a person skilled in the art, allows the laser beam to be concentrated in one or more

impact points.

  The end of the emitting and focusing head 9 is provided with a protective glass 22 located just after the focusing lens 20, as shown

in Figure 5.

  The focal diameter dl of the beam then corresponds to the narrowest diameter of the

  laser beam 6, at a working distance d2 from the protective glass 22.

  The diameter dl of the laser beam at its impact on the intersection zone of

  two sections of tubes 2a, 2b to be welded is between 0.3 and 2 mm.

  In FIG. 4a, two laser beams are emitted by two optical fibers 7 and focused by the lenses at two points of impact. We then define as the diameter of the laser beams, the distance a (FIG. 4a) between the two impact points of the beams. Two impact points can also be obtained from a single optical fiber 7 by inserting a wedge 21 between the two lenses 19 and 20, such as

  shown in FIG. 4b, which makes it possible to split the laser beam 6.

  The impact points at the joint plane 10 of the two laser beams 6 obtained are shown in Figures 6a to 6c. The plan of the figures is

  perpendicular to the joint plane 10.

  In FIG. 6a, the two laser beams are juxtaposed along an inclined axis

  at an angle to said joint plane 10.

  In FIG. 6b, the two laser beams are juxtaposed along an axis

  perpendicular to said joint plane 10.

  In FIG. 6c, the two laser beams are juxtaposed along an axis

  confused with said joint plane 10.

  The process of welding the two sections of tubes 2a, 2b is now

described in detail.

  The two ends of the sections of tubes 2a and 2b are joined, and the rail 11 supporting the carriage 12 is fixed to one or both of the sections

sections at a time.

  1'1 The vehicle 4, supporting the generator 3 and the laser source 5, is brought to

proximity of the sections to be welded.

  The carriage 12 carrying one or more emission and focusing heads 9 is then placed on the rail 11. The optical fiber or fibers 7 coming from the source

  laser 5 are connected to the head (s) 9.

  Once the laser source 5 is started, the motor of the carriage 12 is started so that the carriage moves at a continuous speed around the

  sections of tubes, along the line of intersection of the latter.

  The speed of movement of the carriage 12 and therefore of the laser beam (s) 6 is between 0.5 and 6 m per minute. Preferably, it is understood

between 2 and 4 m per minute.

  This speed makes it possible to obtain a good quality, regular and

  ensuring a substantial time saving compared to existing processes.

  In order to reduce the welding time, two carriages 12 can be placed

welding on the rail 11.

  Throughout the weld, the weld is protected from corrosion by a flow of

  neutral gas, such as for example argon.

  When the ends of the tube sections 2a, 2b are chamfered, after completion of the laser welding, the welding joint is completed by filling the groove 14 using a conventional method of arc welding with a filler metal or using other welding methods. We

  can for example use a laser to melt the filler metal.

  This gives a smooth and regular junction surface between the two

sections of tubes.

Claims (25)

  1. A method of welding together sections (2a, 2b) of steel or aluminum alloy tubes, in particular for producing a pipeline (2) of the pipeline type, said tubes having a thickness greater than 4 mm, this method consisting in joining the two ends of said sections (2a, 2b) of tubes, characterized in that said ends are welded by means of one or more laser beams (6) transmitted by optical fiber (s) (7), the power of the laser beam (s) being greater than or equal to 4 kW, the weld being obtained by orbital displacement of the laser beam (s) (6) around said sections (2a, 2b) of tubes, the beam (s) (6) being axially guided and radially to follow the parting line (10)   formed by the two ends of said sections (2a, 2b) of tubes.   2. Method according to claim 1, characterized in that a chamfer is produced on the ends of the sections (2a, 2b) of tubes to be welded, the two chamfered ends are joined so as to create a groove (14 ) between these two ends, the groove (14) thus created having a depth less than the thickness of the tube, the ends of the sections (2a, 2b) of tubes being in contact with each other in the zone between the bottom of the groove (14) and the inner surface of the sections of tubes by flat surfaces, said zone being welded by means of one or more laser beams (6), by moving the said beam (s) ( x) laser (s) in said groove (14) along the line of intersection (15) between the bottom of the groove   (14) and said planar surfaces in contact.   3. Method according to one of claims 1 or 2, characterized in that   said groove (14) has a substantially U-shaped section or the like.   4. Method according to one of claims 2 or 3, characterized in that   the bottom of the groove (14) has a width greater than two millimeters than the diameter of the laser beam (s) (6) at its impact on said intersection line (15).   5. Method according to one of claims 1 to 4, characterized in that the   or the laser beam (s) (6) have a power of between 4 and 12 kW.   6. Method according to one of claims 1 to 5, characterized in that the   diameter (dl, a) of the laser beam (s) (6) focused to its sound (s)   impact on said intersection zone is between 0.3 and 2 mm.   7. Method according to one of claims 1 to 6, wherein one uses at   at least two laser beams (6), characterized in that the two laser beams (6) are juxtaposed along an axis perpendicular to said joint plane (10).   8. Method according to one of claims 1 to 6, wherein one uses at   at least two laser beams (6), characterized in that the two laser beams (6) are juxtaposed along an axis coincident with said joint plane (1).   9. Method according to one of claims 1 to 6, wherein one uses at   at least two laser beams (6), characterized in that the two laser beams (6) are juxtaposed along an axis inclined by an angle a to said plane of seal (10).   10. Method according to one of claims 1 to 9, characterized in that   rotates the laser beam (s) (6) at a continuous speed around the two sections (2a, 2b) of tubes to be welded, along said line intersection (15).   11. Method according to claim 10, characterized in that the speed of movement of the laser beam (s) (6) is between 0.5 and 6 m per minute.   12. Method according to claim 11, characterized in that the speed of movement of the laser beam (s) (6) is between 2 and 4 m per minute.   13. Method according to one of claims 2 to 12, characterized in that   the thickness of the area between the bottom of the groove (14) and the face   internal sections (2a, 2b) of tubes is between 2 and 12 mm.   14. Method according to claim 13, characterized in that said   thickness is between 4 and 6 mm.   15. Method according to one of claims 1 to 14, characterized in that   the laser beam (s) (6) are produced from a solid-state laser (16)   whose wavelengths are transmissible by optical fiber.   16. The method of claim 15, characterized in that the laser to   solid (16) is a neodymium bar laser: YAG (Yttrium - Aluminum -   Garnet) excited by lamps or diodes.   17. The method of claim 15, characterized in that the laser to   solid (16) is a Ytterbium disc laser: YAG (Yttrium - Aluminum - Garnet) excited by diodes.   18. Method according to one of claims 1 to 17, characterized in that   the laser radiation (6) emitted by said excited solid is transported by optical fiber (s) (7) to one or more emission heads (9) of said (of said) laser beam (s).   19. Method according to one of claims I to 18, characterized in that   the gas protection of the weld is ensured by a neutral gas flow.   20. Method according to one of claims 2 to 19, characterized in   that after carrying out the laser welding of said planar surfaces in contact with the two sections (2a, 2b) of tubes, the welding joint is completed by filling said groove using a conventional method of arc welding with a metal d or by using other welding methods. 21. Installation (1) for implementing the process in accordance with one of the   Claims 1 to 20, comprising an energy generator group (3)   electric power greater than 300 kW mounted on a vehicle (4) towed or able to be placed on the ground along the pipe (2) to be produced, said vehicle (4) or another vehicle connected to said vehicle (4) also carrying a source (5) of production of laser radiation (5) transmitted by optical fiber (s) (7) to one or more heads (9) for emitting and focusing laser beam (s) ), characterized in that the said head (s) (9) are rotatably mounted on guide means   circumferential (8) surrounding the two sections (2a, 2b) of tubes to be welded.   22. Installation according to claim 21, characterized in that said circumferential guide means (8) cooperate with said joint plane (10) to allow the laser beam (s) (6) to follow very precisely said joint plane (10).   23. Installation according to claim 22, characterized in that said   circumferential guide means (8) are optical means.   24. Installation according to claim 22, characterized in that said   circumferential guide means (8) are mechanical means.   25. Installation according to claim 24, characterized in that the said head or heads (9) are further guided during their movement on said circumferential guide means (8) by a member cooperating with one of the lateral faces of said groove (14) to be able to precisely follow said line of intersection (15) between the bottom of the groove (14) and said flat surfaces in contact.