CS443390A3 - Process of welding metallic tubular jacket inside a metallic tube by employing a laser beam and apparatus for making same - Google Patents

Abstract

This relates to a process and an apparatus for welding together two metal parts by means of a laser beam. The apparatus comprises an optical fibre (10) for transmitting the beam and a welding head (9) comprising means (29) for focusing the beam issuing from the optical fibre, means (37) for deflecting the beam issuing from the focusing means (29) in order to focus the deflected beam onto the parts to be welded, a clearance zone (42) separating the deflection means (37) and the focal point (39) of the beam and means (14) for scavenging this clearance zone by means of a scavenging gas. <IMAGE>

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to a device for welding two metal beam beam beams consisting of an optical fiber for beam beam welding beams and a welding head comprising a beam of laser beams emanating from an optical fiber.

The invention also relates to a method for welding a tubular metal sheath of a beam-like beam inside a small inner diameter metal tube, for example from 10 to 50 mm ·

The device according to the invention is used in particular, though not exclusively, for the repair of passable tubes of a tubular plate heat exchanger, wherein the heat exchange takes place between the primary reactor cooler, for example a pressurized water reactor or REP and liquid phase water and a steam generating secondary cooler.

The point is that when repairing the exchanger tubes, any contamination of the secondary circuit, which must be unconditional, is prevented by the primary circuit filled with radioactive elements.

Repairing a passable heat exchanger tube, however damaged or cracked at the root of its attachment points to the tubular plate, is difficult · The internal diameter of the heat exchanger tube at the tubular plate connected to the nuclear reactor cooling circuit is actually of the order of 20 mm ·

The drawbacks of the known welding devices are that they occupy and / or consume a lot of energy and therefore cause serious deformations at the level of the tubular plate and the tube provided with the repair casing. than the existing welding equipment and methods, in terms of welding equipment in order to require little space, was very strong and made possible to carry out high quality welds and, in terms of execution, to achieve energy consumption than in known ways.

A two-metal welding machine with a beam of laser beams of an optical fiber for beam transmission and a welding head containing an axially elongated body parallel to the beam axis of the laser beam radiating from the optical fiber. The welding head comprises a beam beam emitting means emanating from the optical fiber, a beam beam deflecting means exiting the focusing means directed at the welded portion, and a beam deflecting means comprising a straight mirror for reflecting the beam of beams to be welded.

The essence of the invention is that the welding head comprises an inner outlet zone separating the reflecting mirror and the focusing point of the beam, -? : reflector / mirror beam-positioned, relative to point. (focusing at a distance of approximately equal to or greater than the distance separating the set-off heads from the point of focus, and the gas-flushing device of the output section arranged to remove metal vapors exiting the melt from the metal during welding from the deflection means. the laser beams within the optical fiber metal tube and for beam transmission and the welding head comprising a cylindrical body parallel to the axis of the beam of laser beams emanating from the optical fiber The welding head is operatively connected to the interior of the tube and includes means for focusing the beam of radiating radiation fiber optics and beam beam deflecting means exiting the focusing means, directed to a part of the casing to be welded » the beam bundles include a straight mirror to reflect the beam of a portion of the shell to be welded.

The present invention is based on the fact that the welding head comprises an exit zone separating the reflecting mirror and the focusing point of the beam, the upper cross-section of which is greater than or equal to the half-internal cross-section of the cylindrical body and the flushing device of the outlet gas of the scrubbing gas arranged to remove metal vapors , emerging from the metal melt during welding from the region of the deflection means · In both embodiments of the welding device, the smallest distance separating the deflection means from the focusing point is less than 30 mm »

The end of the optical fiber, from which the beam of beams radiates, is fixed in the axis of the welding head and the beam beam focusing means comprise deflecting optical beam means with respect to the beam head for guiding the beam to the reflecting mirror. beams located successively on the optical path of the optical fiber beam of meniscus, the flattened lens and the optical beam deflection means, the optical deflecting means being a part of a spherical flat convex lens, a cylindrical profiled lens thereof, wherein the Λ oda of the second spherical flattened lens is parallel to the axis of the first spherical waxy lens »

The gas flushing apparatus comprises deflectors formed by a wall-like arrangement symmetrically with respect to a plane passing through the axis of the welding head 4 and arranged to increase the gas velocity in the exit zone and the dynamic pressure applied to the welding zone.

In addition, the welding apparatus in both embodiments includes laser beam control and control means emitted in sequential pulse radiation from 10 to 50 milliseconds. • The laser beam source used is a compact YAG® laser beam source.

The welding head is provided with means for automatically rotating the axis around it and means for automatically moving the welding head along its axis arranged for longitudinally displacing the welding head relative to the welded components.

The gas flushing device comprises bypasses formed in part by circular orifices recessed in the inner surface of the cylindrical body about the beam-focusing means.

The method of welding a tubular metal casing inside a metal tube with an inside diameter of less than 50 mm consists in inserting the casing to be inserted into the tube into which the welding head of the elongate rod is inserted up to a predetermined position with respect to the casing to be welded into the systemic fiber coupled with a welding head, a beam of laser beams »focused on a part of the housing to be welded by means of deflection means attached to the welding head is transmitted» whereby the jacket is weighted to the metal tubes and the welding head rotates about its axis and performs a circular or intermittent weld of the shell to the inner tube wall ·

SUMMARY OF THE INVENTION The laser beam beam is emitted in pulses. At the same time as the beam of laser beams is transmitted, the welded region is flushed with flushing gas injected 5 inside the welding head and guided between the deflecting means and the weld zone. , are removed outside the deflection means and simultaneously drawn into the empty interior. . the tubes and the conduit opposite the end of the tube, through which the welding head, enters the neutral purge gas, injected into the welding head.

The invention overcomes the aforementioned drawbacks and provides further advantages of being used to wash neutral gas, preferably argon.

The smallest distance separating the deflection means from the focusing point is small, of the order of 30 mm, preferably in the range of 5 to 10 mm. The end of the optical fiber from which the laser beam emanates is fixed in the axis of the welding head and the beam beam sharpening means comprise optical means deflecting beam of rays from. . the axis of the welding head and focus it on the reflective mirror ·

The invention will be explained in more detail in the following description of specific embodiments, but the invention is not limited thereto

1 shows a diagram of the principle of the welding apparatus for carrying out the method according to the invention used in the repair of the tube of the heat exchanger, FIG. 2 shows a schematic diagram of the principle of the part of the optical system of the device according to FIG. FIGS. 4a, 4b show a front and sectional view of a beam deflecting means belonging to the focusing means of the device according to the invention; FIG. 5 is a schematic sectional view showing a portion of the welding head of the apparatus according to the invention with the side reflectors; FIG. 7 shows a partial vertical section in a plane VII-VII in FIG. 2; FIG. 8 is a partial schematic axial sectional view of an enlarged end of the welding head in another embodiment of the invention; FIG. FIG. 9 is a schematic perspective view of the welding heads and housings in the tube usable in the invention; Fig. 1O is a cross-sectional view of another * φ. an embodiment of the fastening means and the bypass of the welding head lenses according to FIG. obr ·. 11 is a cross-sectional view of the XI-XI of FIG.

The heat exchanger shown schematically in Figure 1 is a common type used for water pressure reactors. It consists of a shell J. comprising a bundle of U2 tubes whose end portions 3 extend through the tubular plate 4. The diameter of the tube 2 in FIG. The plate 4 is cut through the partition 5 by a cold water tank S-tank and the water tank is provided with a supply pipe and a tank 7 of the primary reactor coolant (not shown). the insulated and emptied part of the exchanger lying between the tubes 2 and the casing 7 in a known manner is filled with the secondary coolant reactor and therefore belongs to the secondary circuit.

The device according to a more detailed embodiment of the invention consists of a welding head, for example cylindrical, lying in an extension of the axis and connected to one of its ends to an optical fiber IQ for transferring the beam of laser beams. Optical fiber IQ is a mono-fiber of 500a 1500 Jjun. however, other types of multi-fiber bundles (multi-fiber bundles) can also be used. · The fiber, or bundle, is connected to the source 12 of continuous radiation emitted by the laser of the second type.

Typically, the laser is a solid, known type YAG (length of orderumicron wave) containing ND ions. 7

The radiation density of the triggered laser source in the device according to the invention is in the range of 0.1 to 5 MW per cm, preferably of the order of 0.3 MW / cm.

The welding head 9 is connected by a flushing gas 13 to a flushing gas flushing device 14, for example an arcon containing a pressurized argon tank and means for regulating the gas doses injected into the welding head 9

The welding apparatus comprises means for automatically rotating the welding head 9 about its axis and means for longitudinal automatic movement of the welding head 9 along its axis.

The rotating means (not shown) are located outside the welding head 9. They are arranged on the surface of the tube 2 to be repaired and are formed in a known manner, for example by two pinions, one of which is fixed to the welding head 9, the other to the support 15, while the two parallel to each other. the longitudinal displacement means, which are not also shown, are of the known type and comprise an end thread fixedly connected to the welding head 9 cooperating with the nut fixed to the support 15 and driven by stepper motor · The support 15 is formed, for example, of a device commonly used in the inspection and maintenance of a nuclear reactor and to which the welding head 9 and its rotary and sliding means are easily adaptable. SpiderM · Possible designs of these devices are described, for example, in US - A - 4 018 345 and FR A - 2 309 314 ·

The inner tube vacuum means 16 comprises a head 17, which is tightly attached to the opposite end 3 of the tube 2, into which the welding head 9 is seated.

The rotating and sliding means 9, the laser source 12, the flushing device 14 and the vacuum means 16 are controlled by the control and monitoring means 17a. The means 17a includes, for example, a programmable aftcma and enable the device to function as described below.

Fig. 2 is an axial section of the welding head 9 of the device according to the invention;

The welding head 9 consists of a metal cylindrical casing 20, for example of stainless steel with a longitudinal axis 21 · The outer diameter of the casing 2 is, for example, 19 mm of order · Accordingly, the metal cylindrical casing 20 is suitable for co-operation with the interior of the exchanger tube 2 whose internal diameter is of the order 20 mm, which allows self-centering of the welding head 9 in the tube 2. Specific self-centering means of the known type or means further described in connection with the embodiments shown in Figs.

The metal cylindrical casing 20 is at one end 22 thereof and at the other end 23 is provided with a metal plug 24 punctured through the passages 25 of the purging gas whose path is shown in FIG. 2 inside the welding head 9 by arrows 26 &quot; 21 and their number is, for example, six or eight. The welding head 9 is connected to the optical fiber 10 for converting the laser beam 27 by the end 28 of the optical fiber 10 attached to the plug 24 in the axis 21 of the welding head.

As shown in FIGS. 2, 3, the welding head 9 comprises focusing means 29 of the bundle 27, formed, for example, by a spherical meniscus 30, a spherical embossed lens 31, and optical beam deflecting means 32 of a beam-shaped semicircle extending from the cut-off cylindrical edge of the plane-shaped lens with the large diameter indicated in FIG. - 9 - you

Figures 4a and 4b show more precisely the embodiment of the deflection means 32 ' formed by the lens 35 with the axis 35 &apos; extending from the cylindrical log, or the bore of the spherical plane lens 36 with the axis 36 &apos;, the axis 35 &apos; being parallel to the axis 36 &apos;

The deflection means 37 (see FIG. 2) is formed by a flat mirror 37 &apos; located in a plane perpendicular to the beam and inclined by an angle of 20 to 60 &apos;

The mirror 37 * deflects the beam 38 and focuses the deflected beam 40 at the focusing point 39 lying on the parts to be welded in the example exchanger tube 2 and the cylindrical housing 41 which is in close contact with the inner tube wall 2 to which has been previously inserted, to which it has been fixed, for example, by a roll, expansion or hydraulic grooving. The angles of deflection of the laser beam 40 between incident corresponding reflected angles are in the range of 80 to 10 °. The inclination of the mirror 37 relative to the axis 21 and the distance between the mirror 37 * and the focus point 39 are determined. The deflected beam 40 forms a cone whose point is the point 39 of the focus. The deflection means 32 and the mirror 37 are, for example, arranged so that the axis of the beam of the beam 40 with the tangent plane intended to be welded, the angle of incidence ranging between 30 and 0 ° (normal impact), which favorably influences good penetration of the weld. According to the invention, the welding head 9 has an exit zone 42 separating the mirror 37 * from the focusing point 39 of the beams.

This inward or outwardly disposed outlet zone 42, in part within the welding head 9, represents a nominal gas passage through the flushing device 14 due to the closure 20 closes more or less above the mirror 37. is generally greater than or equal to half the inner cross section of the cylinder 20, which is because the reflection of the beam 27 is completely positioned relative to the point 39 of the focus at a distance equal to or greater than the distance d1 of the welding head 21 from the focus point 39 The distance d of the plane parallel to the axis 21 and reaching the upper stop of the mirror 37 * or more generally dotted, including the point of the deflection means 37 lying closest to the point 39, is equal to or greater than d 0 0.

In the welding apparatus according to the invention, in the embodiment described, the distance d is of the order of 10 mm * 0 ........ To allow the gas injected into the welding head 9 to be accessed by feed passages 25 &apos; located opposite to the exit zone 42 located near one end of the welding head 9, the flushing devices 14 comprise gas bypasses 43 around the focusing means 29. in the inner surface of the cylinder head 20 of the welding head 9 »

The device according to the invention is provided with a second cylindrical housing 44 for securing the focusing means 29 and the deflecting means 37 · The second cylindrical housing 44 permits the passage of the purge gas and is in contact with the first housing 20 in which it can rotate with little friction. the housing 44 at the point of bypass 43 forms the second part of the bypass means ·

Gas follows the path marked on ofcr. 2 Arrows 26 ·

Still further embodiments of these attachment means and bypasses 43 of the lenses 30, 31, 32 are possible. For example, as shown in Fig. 10, 11, the lens 60 is mounted in a cylindrical body 61 which is in contact with the inner cylinder housing 20 in which a cylindrical body 61 i is mounted, the outer diameter of which is, for example, of the order of 16 mm, consisting of a first portion 62 with a first inner diameter and a second portion 63 with a second inner diameter greater than the first inner diameter and forming an annular shoulder 64 on which the lens 60 abuts;

Two cylindrical holes 65 of, for example, 8 mm in diameter are transverse, along and perpendicular to the axis of the cylindrical body 61 and form bypass means 66 as known.

See Fig. 10. Such an arrangement permits a wide passage through the lens of the lens 60, which is advantageously manifested by the cooling of the gas and the reduction of its loss.

The welding head flushing device 14 further comprises deflectors 46 formed by straight walls positioned symmetrically with respect to the plane passing 21 of the welding head 9 and fixed to each other by a longitudinal stop 47 (FIG. 7) forming a V-shaped angle whose internal surfaces are in contact with the beam 38. (Fig. 2). starting from the focusing means of the lens 30, 31, 32 · The stop 46 (FIG. 7) is provided with a laser-beam-permeable aperture 47 for the components to be welded ·

Another embodiment of the deflector 46 is shown in FIGS. 5, 6. The deflectors 46 are formed by curved walls symmetrical with respect to the plane passing through 21 and tapering to form a venturi tube for guiding and accelerating the gassing point 39 of focusing and welding.

As mentioned, the welding apparatus (see Fig. 2) comprises means (not shown) located outside the welding head 9 for automatically rotating the welding head 9 about axis 21. These means allow rotation of the cylindrical shell 44 and at the same time different parts of the welding head 9 which are to the fastening means 24, namely the stoppers 24 of the focusing means 29, the mirrors 37, the deflectors 46 inside the cylindrical housing 20 of the welding head 9 · The ring 50 attached to the housing 20 and comprising a sealing joint 51 of a known type (e.g.

provides for tightness with casing 2 (¾ to prevent leakage of injected gas into the welding head 9 through passageways 25)

The apparatus is also provided with means for longitudinal automatic shifting of the welding head 9 in the tube 2 to be repaired. They comprise a sealing portion 52 of the hood branch, the base of which is provided with a sealing joint 53 with a tubular plate 4. Welding Heads 9o Hatch-shaped sealing portion 52 Lining jackets 20 are movable relative to each other Touching the sealing seal 54 # The hatch-shaped sealing portion 52 is held under pressure on the tubular plate 4 by known means not shown.

Fig. 8 shows another embodiment of the end of the welding head 9 according to the invention with the increased action of the washing gas near the point 39 of the sharpening #

The end 70 of the welding head 9 has a smaller outer diameter than the inner diameter of the shell 71 to which it is inserted. The leading edge 72 is attached to the cylindrical shell 73 of the welding head 9 in front of the mirror 74 facing the path of the laser beam.

The mirror 74 is positioned completely below the axial plane 77 of the welding head 9 with respect to the focusing point 83 # A flat surface 78 is formed on the leading edge 72, at a lower gas 79 inclined towards the mirror 74, e.g.

The first leading edge 72 is also provided with a rear wall 80, curved partially conical, partly in a flat shape, the direction of which is almost parallel to the closest line 81 of the conical beam of laser beams focused to point 83 #

Above the mirror 74, there is a second gas guide leading 84 forming a bevel 85 between the rear wall 80 of the first leading edge 72 and the front wall 86 of the second leading edge 84 &apos; This front wall 86 is, for example, flat or partially conical and is almost parallel to the nearest forming ρrr. For example, the height of the mirror 74 of the second leading 84 and the upper washing zone 88 are approximately equal, preferably equal to one third of the inner diameter of the welding head 9. extending the dynamic action by blowing the dust generated during welding into the jet and into the extension of the welding head 9 In the embodiment described, the sealing head 9 at its end 89 is fully open »

For example, at this end, self-centering means 90 are attached, which will be further described in connection with the description of the embodiment shown in FIGS.

These means comprise, for example, three flexible metal, 2 mm wide and 5 cm long lamellas 91, which may also form a cylindrical trivet, wherein the individual lamellas 91 are secured to one another by one end 92 and form a foot plate. The angle 95 is inserted round the circular brush with radial-tube or straw flexible bristles 96. The diameter of the wheel 95 is somewhat larger, for example, a few tenths of a millimeter than the inner diameter. the sheaths 71 »The bristles 96 are individual or arranged in tufts from each other separated by gaps 97 to allow a smooth flow of gases 79»

For example, in a casing with a diameter of 16 mm, a wheel diameter of 95 mm, the metalwork is from one end to the other 16 mm 3 tenths of a mm, the bristles are divided into eight tufts, each with ten flexible bristles with 3 to 4 ths. Next, the operation of the welding apparatus according to the invention, which was used to repair a small diameter tube, more precisely for the repair of a nuclear reactor tube heat exchanger, will be described.

First, the tube 2 to be repaired is first found, then inserted into the tube to be welded, for example, near the tube plate 4, and then the supporting head 15 of the welding head 9 is mounted in the housing 6 facing the tube 2. for repair • The welding head 9 is then introduced into the pipe 2 up to a position relative to the cylindrical housing 41 with which the pipe 2 is to be welded, for example, to abut a cylindrical housing 41 as shown in FIG. the operation is performed remotely and is controlled by controllers. by means of vacuum means 16, the sealing head 17, which was previously attached to the second end piece 2, for repair, air into the housing 7

Thereafter, a flushing gas, such as a known neutral gas, argon or nitrogen, is injected into the welding head 9 under the pressure of several bars (HPa). The gas entering the welding head 9 through the passages 25 'follows the path indicated in FIGS. wash under pressure equal to the injection gas pressure loss output zone 42 · Deflectors 45 increase produc velocity through the outlet zone 42 and direct its path to focus point 39 · The flushing gas outlet is facilitated by suction inside the pipe 2 in the direction of the welding head 9 by a vacuum pump 16 ·

The gas circuit commissioned emits a continuous beam of 12 Nd: YAG laser beams of the order of several hundred watts ·

The transmission preferably takes place impulsively, wherein the pulse emission time varies between 5 and 100 ms, for example 20 ms for energy from 10 to 50 Y at a rate of 1 to 10 shocks per second, for example 6 / s · ________ _____-14 -______________________

The laser beam emitted by the radiation source 12 is transmitted in a condensed manner by the condenser 12f (FIG. 3) »by the optical fiber 28 and then focused by means 29 and then deflected by the mirror 37, controlled and sharpened by the steep impact of the near-cylindrical cylindrical sheath 4 ' 2 · The focus point diameter 39, achieved by the device according to the invention, decreases, for example to 50 microns, whereby a perfect weld penetration, for example 1.5 mmo, is achieved During the welding, metal vapors (vapor and liquid droplets) are emitted towards the mirror 3¾ Flushing the exit zone 42 with a gas, for example a minimum upper section or equal to a half of the section of the welding head 9, e.g.

The boiling heads 9 open towards an important part of the surface, allow conveying vapor outside the mirror region 37 forward of the tube 2 and into the extension of the welding head 9, thereby preventing contamination of the mirror 37 which would otherwise be immediately covered by the recondensed metal vapors.

The dynamic pressure acting on the welding point, however, limits itself to the formation of metal vapors.

Thereafter, the upper portion of the welding head 9 is brought into rotational movement of the axis around it for the purpose of discontinuous or continuous welding of the cylindrical shell 41 with the tube 2 containing it. All these operations have been programmed and controlled by the control and control means 17a &apos;, for example, they are performed either automatically or semi-automatically.

As is clear, and as is clear from the foregoing, the invention is not limited to the embodiments described. In particular, it includes the case where the surface of the rear part of the mirror 37 has a bowl shape profiled to support the laminar -15 - the flushing gas outlet in the direction of the outlet zone 42 »flushing gas may be guided by another bypass design. for example, a conduit extending along the welding head 9 through which the purge gas is injected directly into the outlet zone 42 »

Claims (3)

- 1ζ '^ ΐΐ'-ΫΌΓ PATENT OVENAROKY 1 · Device for welding two metal parts with a beam of laser beams, consisting of an optical beam for transferring the beam and a welding head comprising an axially elongated body parallel to the axis of the beam of laser beams emitting from the optical fiber the welding head comprises focusing means of the beam emitting from the optical fiber, and the beam beam deflecting means exiting the focusing means and directed to the welded components and the beam beam deflecting means comprising a straight mirror for reflecting the beam on the components to be welded, characterized in that the welding head (9) comprises an inner outlet zone (42) separating the reflecting mirror (37 *) and the beam-focusing point (39), wherein the reflector beam (37 *) is completely positioned with respect to the focusing point (39) at a distance approximately equal to or greater than the distance (dQ) separating the axis (2l) of the welding head (9) from the focusing point (39) and the gas flushing device (14) of the exit zone (42) arranged for stripping vapors exiting the metal melt during welding from the deflection area (37) o 2 · Device for welding a metal tube shell inside a metal tube consisting of an optical beam transfer beam from a welding head containing a cylindrical body whose axis is parallel to the axis a beam of laser beams emanating from an optical fiber, wherein the welding head is operatively connected to the interior of the tube and comprises means for focusing a beam of radiation emanating from the optical fiber and deflecting means of the beam beam extending from the focusing means directed to a portion of the shell to be welded , the beam beam means TJ> · Oc <c · i 5- <'<· c ί LO O Comprising a straight mirror (37 *) for reflecting a beam of a beam to be welded, characterized in that the welding head (9) comprises an exit zone (42) separating the reflector (37 *) and the beam focusing point (39) spokes, the upper cross-section of which is greater than or equal to half the inner cross-section of the cylindrical body (20), and the flushing apparatus (14) of the discharge zone (42) for flushing gas are disposed to remove metal vapors exiting the metal melt during welding from the region of the deflection means (37) 3. A welding apparatus according to claim 1, characterized in that the smallest distance separating the deflecting means (37) from the focusing point (39) is finer than 30 mm. ............................. 4. A welding apparatus according to any one of claims 1 to 3, wherein the end of the optical fiber (28) from which the laser beam emanates is fixed in the axis (21) of the welding head (9) and the beam beam focusing means (29) comprises a deflecting optical beam. for the beam bundle (32) with respect to the axis (21) of the welding head (9) for guiding the beam to the reflecting mirror (37 *). The welding device according to claim 4, wherein the focusing means (29) the beam stack, located successively on the optical path of the beams emanating from the optical fiber (28), comprises a meniscus (30), a first pad-shaped lens (3l) and optical means (32) for deflecting the beams, the optical deflecting means (32) being formed in part the spherical flattened lens, its cylindrical profiling, wherein the second spherical flattened lens is parallel to the first spherical axis flattened lenses (31) · 6. Welding device according to claim 1, characterized in that the glazing device (14) comprises deflectors (45) formed by walls, arranged symmetrically with respect to the plane passing through the axis (2l) of the welding head (9). ., ........ _. 18 and arranged to increase the gas velocity in the outlet zone (42) and the dynamic pressure applied to the welding zone. 7. The welding device of claims 1 to 6, further comprising control and monitoring means (17) for laser beam welding. radiated in successive pulses from 10 to 50 milliseconds. 8. A welding apparatus according to any one of claims 1 to 7, wherein the source of the laser beam used is a compact YAG laser source. 9. Welding device according to claim 8, characterized in that the welding head (9) is provided with means for automatically rotating about its axis (21) and means for automatically moving the welding head (9) along its axis (21), arranged in a longitudinal displacement. the welding head (9) relative to the components to be welded. Welding apparatus according to Claims 1 to 9, characterized in that the flushing gas is neutral. 11. A welding apparatus according to any one of claims 1 to 10, characterized in that the gassing device (14) comprises bypasses (43) formed in part by circular orifices hollowed in the inner surface of the cylindrical body (20) around the focusing means (29). Method of welding a tubular metal casing inside a metal tube with an inside diameter of less than 50 mm by a beam of laser beams, according to which the casing is inserted into the tube into which the welding head of the elongated insert is inserted up to a position relative to the casing to be welded , a beam of laser beams is focused on the part of the housing to be welded by means of deflecting means attached to the welding head, into the system optic fiber connected to the welding head, thereby welding the jacket to the tube of the molten metal, and the welding head rotating about its axis to form a circular continuous or a continuous weld of the shell to the inner wall of the tube, characterized in that the laser beam is emitted in pulses while the laser beam is flushed with the flushing gas injected inside the welding head and guided between the deflecting means and the welded region. the metal vapors formed by the melting of the metal are diverted out of the region of the deflection means while being sucked into the empty interior of the tube and discharged by the end of the tube opposite the end of the tube entering the welding head, the neutral flushing gas injected in the welding head * Representative: A '/ u / - ---- ς r · / ř ř 30 30 30 30 30 96 Z 3096 14.11.1990