JP6512880B2 - Shield nozzle and shield method - Google Patents

Description

  The present invention relates to a gas shield nozzle and a gas shield method used in narrow gap welding for thick plate butt joints and other joints.

  Conventionally, in order to facilitate the welding operation and to improve the quality of the welded joint, groove welding has been performed in which a groove is provided on a welding surface of a base material in butt welding or the like. When performing groove welding on thick plates such as steel materials and nickel-based alloys, the groove cross-sectional area increases as the thickness of the base material increases, and the welding efficiency decreases, or deformation or welding distortion occurs. There is a tendency for the weld quality to deteriorate due to the increase of For this reason, there is an increasing demand for narrow groove welding which narrows the groove and reduces the groove cross-sectional area, and the progress of welding technology in recent years makes the output of the heat source, focusing when the heat source is laser light or Along with the remarkable improvement of directivity, development is actively promoted.

  It is a well-known fact that it is important to replace oxygen-containing air in the weld with a shielding gas so that welding defects such as pores and cracks do not occur in the weld in various welding methods, and the weld The importance of the gas shield is the same for thick plate narrow gap welding.

  Although there is a method (for example, patent document 1) etc. which spray shield gas from the circular opening of a shield nozzle and spray it on the surface of a base material as a method of carrying out gas shielding of a welding part etc. It is necessary to gas shield the welds in the groove rather than the surface of the material. When the shield gas is injected from the outside of the groove toward the welded portion in the groove, the shield gas becomes turbulent and entrains the outside air, and the air in the groove is not efficiently replaced. In addition, the laser beam may be irradiated before the shield gas supplied from the outside of the groove reaches the bottom of the groove, and sufficient welding quality may not be guaranteed. For this reason, a method (for example, Patent Document 2) has also been developed in which a shield nozzle is inserted into a groove in order to gas-shield a weld in the groove. However, when the shield nozzle is inserted into the groove in thick plate narrow groove welding, the spatter generated during welding adheres to the wall surface of the groove, or the groove is shrunk due to heat input, etc. It is not practical to insert a shield nozzle into the groove, as it may cause damage due to interference with the groove. In addition, the larger the thickness of the base material or the smaller the groove angle, the more difficult it is to insert the shield nozzle into the groove, so the practicality in thick plate narrow groove welding is low.

  Moreover, in welding performed by moving the heat source continuously, for example, when the laser light is used as the heat source, the shield nozzle moves along with the movement of the irradiation part of the laser light, but not only the irradiation part but the welding planned part It is preferable to form a shield atmosphere also at a welding completion portion (that is, a portion located rearward to the welding direction with respect to the irradiation portion) (that is, a portion located forward in the welding direction with respect to the irradiation portion) Since a wide range including a weld completion part is not gas-shielded depending on the shield nozzle of a small diameter pipe usually adopted, the shield nozzle (for example, patent documents 3) provided with a plurality of shield gas jets is also developed. In order to form a sufficient shield atmosphere in the vicinity of the weld portion in the groove in the groove welding, some measures such as the shape of the shield nozzle and the shield gas jet are still required.

Japanese Patent Application Publication No. 2003-154476 JP, 2011-5533, A Japanese Patent Application Publication No. 2003-181676

  The present invention has been made in view of the above-described problems of the conventional method, and in a shield narrow gap welding, a shield nozzle and a shield method capable of forming a sufficient shield atmosphere in a weld portion in a groove Intended to provide. Another object of the present invention is to provide a shield nozzle and a shield method capable of supplying shield gas in the vicinity of a weld, including a portion to be welded and a weld completion portion in a high temperature state.

  The present inventors have found that by supplying shield gas from the outside of the groove into the groove in a uniform flow, that is, in a laminar flow state, a high gas shielding effect can be obtained at the weld in the groove. I found it.

That is, the shield nozzle according to the first aspect of the invention is a gas shield nozzle used for thick plate narrow groove laser welding, and is disposed between the laser light source and the weld so as to cover the weld at the groove. the laser paths that the laser beam passes, the shielding gas possess and supplying layer flow generation section, in a state of laminar flow in the weld from the groove outside, the laser light source side of said laser paths, ejection of compressed air It has an air nozzle which prevents outside air from flowing into the groove and / or leakage of shielding gas from the groove .
The shield nozzle according to the second aspect of the present invention is a gas shield nozzle used for thick plate narrow groove laser welding, and is disposed between the laser light source and the weld so as to cover the weld at the groove. A laser flow path through which the laser light passes, and a laminar flow generation unit for supplying shield gas from the outside of the groove to the weld in a laminar flow state, and the laminar flow generation unit is a laminar flow opposed to the weld It has an exit surface, the distance from the laminar flow release surface to the groove bottom is H, the welding feed rate is V _w , the gas flow rate is V _g , and the time for cooling to a temperature at which oxidation of the weld completion part is suppressed is t. when the laminar flow length of the welding direction ahead of the center of the laser path of the emission surface L ₁ and welding direction behind the length L ₂ is to satisfy the following equation.
L ₁ HH × V _w / V _g -Equation (1)
L ₂ VV _w × t − equation (2)

The shield nozzle according to the third aspect of the present invention further includes a wire passage through which a welding wire can be inserted when supplying the welding wire to the welding portion in the configuration of the first or second aspect of the invention.
The shield nozzle according to a fourth aspect of the present invention is characterized in that, in the configuration according to any of the first to third aspects, the laminar flow generation portion is made of a porous sintered body through which a shield gas can pass.

A shielding method according to a fifth aspect of the present invention is a gas shielding method used for thick plate narrow groove laser welding, which comprises a laser passage through which laser light passes and a shield nozzle capable of emitting a shielding gas, a laser light source Is disposed between the weld and the weld so as to cover the weld at the groove, and shield gas is supplied from the outside of the groove to the weld in a laminar flow state using the shield nozzle, and the shield nozzle is used as the shield nozzle Using a shield nozzle having a laminar flow emitting surface facing the weld, the length in front of the direction of welding from the center of the laser passage in the laminar flow emitting surface is L ₁ , the length behind the welding in the direction of welding L ₂ , distance H from flow discharge surface to the groove bottom portion, when the time for oxidation of the welding completion portion is cooled to a temperature which is suppressed to a t, the welding feed speed V _w and the gas flow velocity V _g And performing condition setting equation.
V _g H H × V _w / L ₁ -Equation (3)
V _w ≦ L ₂ / t − equation (4)

According to the configurations of the first and fifth inventions, the shield nozzle supplies the shield gas from the outside of the groove to the weld in a laminar flow. The laminar shielding gas flows into the groove without entraining external air and pushes out the oxygen-containing air present in the groove. The air in the groove is gradually replaced by the shielding gas to form a high shielding atmosphere in the groove. Since the shield nozzle has the laser passage, the laser beam is not blocked even if the shield nozzle is disposed between the laser light source and the weld so as to cover the weld at the groove.

Since the shield nozzle according to the third aspect of the present invention has the wire passage, it does not prevent the feeding of the welding wire even if it is disposed between the laser light source and the welding portion so as to cover the welding portion at the groove. .

The shield nozzle according to the first aspect of the present invention includes an air nozzle for injecting compressed air, and the injected compressed air serves as an air curtain (air knife). That is, the outside air flows into the laser communication path or RaHiraku destination unit or prevents shielding gas or leaking laser communication path or al. Furthermore, the air curtain (air knife) of the compressed air jetted from the air nozzle also plays a role of preventing the plume and spatter generated at the weld from spouting and damaging the welding apparatus such as the laser light source.

According to the configurations of the second and fifth inventions, the length L ₁ forward in the welding direction from the center of the laser passage in the laminar flow surface, the length L ₂ backward in the welding direction, the laminar flow surface to the groove bottom The welding planned portion (that is, the welding scheduled portion (i.e., as described later) because the distance H of the welding feed velocity V _w , the gas flow velocity V _g , and the time t for cooling to the temperature at which oxidation of the weld completion portion is suppressed satisfy the following equation. The shield gas can be supplied in the vicinity of the weld including the weld progress direction (forward) and the weld completion portion (that is, the weld progress direction backward) in a high temperature state.

L ₁ / V _w HH / V _g −Equation (5)
L ₂ / V _w tt − equation (6)
Formulas (1) and (3) described in claims 2 and 5 are obtained by modifying Formula (5) and placing L ₁ or V _g on the left side, and Formula (2) and Formula (4) is obtained by modifying the equation (6) and placing L ₂ or V _w on the left side.

It is a schematic cross section showing the example of the state of performing thick plate narrow gap welding by applying the present invention. It is a schematic diagram of thick plate narrow gap welding which is the object of the present invention. It is a perspective sectional view of a shield nozzle concerning the present invention. It is a perspective view of a shield nozzle concerning the present invention. It is a top view of a shield nozzle concerning the present invention. It is a bottom view of a shield nozzle concerning the present invention. It is a schematic diagram which shows the example which a shield nozzle does not have a wire passage. It is a schematic diagram which shows the example which a shield nozzle has a wire channel. It is a figure and a graph which show example 1 of an experiment. It is a figure and graph which show the comparative example 1. FIG. It is a figure and a graph which show comparative example 2. FIG. It is a figure and graph which show Experimental Examples 2-4. It is a figure and graph which show Experimental example 5-7.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 2 is a schematic view of thick plate narrow gap welding which is the object of the present invention. In FIG. 3, 1 is a thick plate of a base material, and a groove 2 is formed on the welding surface. In the present invention, a space around the groove 2 on the surface side of the thick plate 1 is referred to as a groove. Reference numeral 3 denotes laser light, which is emitted from a laser light source (not shown) and collected inside the groove 2. A shield nozzle 4 is disposed between the laser light source and the welding portion so as to cover the welding portion at the groove portion, and supplies the shielding gas 5 to the welding portion in the groove 2. Here, in the present invention, a thick plate refers to a steel plate or steel material having a plate thickness of 50 mmt or more, and any thick plate up to about 200 mmt can be an object of the present invention. Further, in the present invention, the narrow groove means a groove having a route width of 5 mm or less and a groove angle of 4 ° or less on one side.

The configuration of the shield nozzle 4 according to the present invention will be described with reference to FIGS. 3 and 4.
The shield nozzle 4 has a shield gas supply port 6, a case 7, a laser passage 8, and a laminar flow generation unit 9. The laminar flow generation unit 9 faces the weld portion and directs the shield gas 5 toward the weld portion. It has a laminar flow release surface 10 to release. The shield gas 5 supplied from a gas cylinder or the like flows into the case 7 of the sealed structure through the shield gas supply port 6, is laminarized by the laminar flow generation unit 9, and is released from the laminar flow emission surface 10. The material, shape, size, position and the like of the shield gas supply port 6 are not particularly limited, and known nozzles and conduits can be used. The material, shape, position, and the like of the case 7 are not particularly limited, and a rectangular or circular metal frame can be used.

  The laminar flow generation unit 9 is a means for laminarizing the shield gas 5 in the case 7 and supplying the laminar flow to the weld portion. The laminar flow generation unit 9 is a sinter having pores of a diameter of several tens of μm to 100 μm through which the shield gas 5 can pass. It can be formed of metal mesh, ceramic, sintered metal, etc. in addition to the solid. It can also be formed by disposing steel wool in the case 7 and supporting it by a metal mesh.

  The laser passage 8 is formed to penetrate the case 7 and the laminar flow generator 9 along the optical axis so that the laser light 3 can pass through. Specifically, the laser passage 8 may be a through hole, a cylindrical or truncated glass, or the like.

  Further, the shield nozzle 4 may have a wire passage 11 through which a welding wire can be inserted when supplying the welding wire to the welding portion. The wire passage 11 may be any as long as a welding wire can be inserted therethrough, and a slit having a width of about several millimeters may be employed.

The sides of the laser passage 8 and the wire passage 11 need to be closed so that the shield gas 5 in the case 7 does not leak.
Furthermore, the shield nozzle 4 is moved away from the laser passage 8 and / or the wire passage 11 to the laser light source side, by injection of compressed air to the outside air flowing into the groove and / or shielding gas from the groove 5 The air nozzle 12 may be provided to prevent the leakage of In order to form an air curtain (air knife) on the surface of the laser passage 8 or the wire passage 11 facing the laser light source, the air nozzle 12 has a mounting position, a jetting direction, a shape, a size, and the number of mountings. It can be adjusted appropriately. For example, when the laser passage 8 is a through hole, the wire passage 11 is provided at a position away from the laser passage 8 at a position away from the laser light source. If both the laser passage 8 and the wire passage 11 are open facing the laser light source, it is preferable to provide a plurality of air nozzles 12 and an air nozzle 12 capable of injecting compressed air over a wide area. The air nozzle 12 is provided at a position away from the laser passage 8 and / or the wire passage 11 to the laser light source side to such an extent that the compressed air does not affect the flow of the shield gas 5 released from the laminar flow generation unit 7 Should be

  Subsequently, FIG. 1 will be referred to. The shield nozzle and the shield method according to the present invention can be used for various welding methods such as lamination welding, butt welding, build-up welding, etc. The types of groove and joint are not limited either, but the drawings were referred The following description relates to the embodiment in laminated welding of V-groove butt joints. 1 and 7 to 13, the front in the welding progress direction (left direction in the drawing) is front, the rear in the welding progress direction is rear, the paper front is left, the paper back is right, the upper direction is up, the lower in the drawing. Although the directions are downward, these directions are for convenience, and the implementation of the present invention is not limited to these directions.

  The shield nozzle 4 is disposed so that the laminar flow emission surface 10 of the laminar flow generation unit 9 covers the weld at the groove and is parallel to the surface of the thick plate 1. The laser light 3 is emitted from an upper laser light source (not shown), passes through the laser passage 8, and is condensed inside the groove 2 with a spot diameter of about 0.5 to 2.0 mm. The laser beam 3 may move forward at a predetermined welding feed speed and weave in the lateral direction at a predetermined frequency, and may move in the vertical direction as the lamination progresses. The shield nozzle 4 moves in synchronization with the laser beam 3 to cover the weld at the groove. Specifically, the shield nozzle 4 is supported and moved by a device synchronized with the movement of the laser light 3.

  In FIG. 1, reference numeral 13 denotes a welding wire, and the welding wire 13 is supplied from the front or rear of the shield nozzle 4 to the weld in the groove 2. A commercially available small diameter wire or the like may be used as the welding wire 13. In addition to the small diameter wire, it is also possible to use a large diameter wire, a band-like wire or the like in order to improve the welding efficiency. The reference numeral 14 denotes a melting bead, which is formed at a weld completion portion, which is aft of the welding portion to which the welding wire 13 is supplied.

The shield gas 5 that has flowed into the case 7 from the shield gas supply port 6 in the shield nozzle 4 is laminarized by the laminar flow generation unit 9 and the weld portion in the groove 2 from the laminar flow release surface 10 facing the weld portion Released towards. The laminar shielding gas 5 flows into the groove 2 and displaces the air in the groove 2 to form a shielding atmosphere. A commercially available gas can be used as the shielding gas 5, and the type and flow rate of the active gas such as CO ₂ , the inert gas such as Ar, N ₂ , He, Ar-CO ₂ mixed gas, etc. depend on the welding conditions. It may be determined appropriately.

In the figure, L ₁ [mm] is the length of the laminar emission surface 10 forward of the center of the laser passage 8 and L ₂ [mm] is the length of the laminar flow emission surface 10 rearward of the center of the laser passage 8 H [mm] is the distance from the laminar flow surface 10 to the bottom of the groove 2. V _w [mm / sec] is the welding feed rate, and V _g [mm / sec] is the gas flow rate, that is, the gas flow rate [mm ³ / sec] supplied from the shield gas supply port 6. Divided by the area [mm ² ] of

It takes about H / _Vg [sec] at the maximum until the laminar flow of the shielding gas 5 supplied by the shielding nozzle 4 reaches the weld in the groove 2. Therefore, it is preferable to preflow the shielding gas 5 also to the welding planned portion ahead of the welding advancing direction, and the time L ₁ / from the start of the preflowing to the welding planned portion to the actual irradiation of the laser light 3 It is necessary that the shield gas 5 has reached the bottom of the groove 2 within V _w [sec]. That is,
L ₁ / V _w HH / V _g −Equation (5)
If the relationship between the dimension (shape) of the laminar flow release surface 10 of the laminar flow generation unit 9 and the welding conditions does not satisfy the above equation (5), before the shield gas 5 is supplied to the weld in the groove 2, that is, The laser beam 3 may be irradiated before a sufficient shield atmosphere is formed to start welding.

Equations (1) and (3) below are variations of Equation (5), and each has a length L of the laminar emission surface 10 forward of the center of the laser passage 8 for performing sufficient preflow. The minimum value of _{1 and} the minimum value of the gas flow velocity V _g are determined.

L ₁ HH × V _w / V _g -Equation (1)
V _g H H × V _w / L ₁ -Equation (3)
Generally, the weld completion portion at the rear of the weld portion is easily oxidized when the temperature is high, and the oxidation is suppressed when the temperature is below a certain temperature. The temperature at which oxidation is suppressed varies depending on the composition of the base material and the like, but is about 300 to 550 ° C., about 500 ° C. or less for iron and about 350 ° C. or less for titanium. The time t required for the weld completion portion to be cooled to the temperature at which oxidation is suppressed is determined by the laser output, the welding feed rate, etc. For example, in the experimental example of the present invention, the laser output is 6 kW, the welding feed rate 5 mm / In the case of sec, it takes about 15 seconds for the weld completion portion to be cooled to 500 ° C. or less. It is preferable to perform afterflow of the shielding gas 5 until it is cooled to a temperature where oxidation is suppressed, that is,
L ₂ / V _w tt − equation (6)
When the relationship between the dimension (shape) of the laminar flow emission surface 10 of the laminar flow generation unit 9 and the welding conditions does not satisfy the above equation (6), the shielding property at the welding completion part in the high temperature state becomes insufficient and the welding completion part May be oxidized.

Equations (2) and (4) below are variations of Equation (6), and the length of the laminar emission surface 10 behind the center of the laser passage 8 for sufficient afterflow, respectively The minimum value of L _{2 and} the maximum value of the welding feed speed V _w are determined.

L ₂ VV _w × t − equation (2)
V _w ≦ L ₂ / t − equation (4)
The difference due to the presence or absence of the wire passage 11 according to the second invention is shown with reference to FIGS. 7 and 8, and the effect of the shield nozzle 4 having the wire passage 11 will be described. FIG. 7 and FIG. 8 show that the lamination proceeds from the groove bottom to the upper side in the layer welding of the groove butt joint and welding near the surface of the thick plate 1 is performed. The case of feeding at a feed angle of 45 ° from the front (the angle between the welding wire 13 and the surface of the thick plate 1) is shown. FIGS. 7 and 8 respectively show cases where the shield nozzle 4 has the wire passage 11 when the shield nozzle 4 does not have the wire passage 11.

  When welding at the bottom of the groove 2 or near the bottom, interference between the welding wire 13 inserted into the groove 2 and the shield nozzle 4 disposed outside the groove 2 does not pose a problem, but the lamination When the welding wire 13 is fed closer to the surface of the plank 1, the upper portion of the welding wire 13 interferes with the laminar flow emission surface 10 of the shield nozzle 4. It is difficult to avoid interference with the shield nozzle 4 by adjusting the feed angle of the welding wire 13, and there is a limit to lowering the feed angle of the welding wire 13. In this case, it is necessary to raise the shield nozzle 4.

As shown in FIG. 7, in the case where the wire passage 11 is not formed in the shield nozzle 4, the shield nozzle 4 is provided so that the portion ahead of the laser passage 8 of the shield nozzle 4 and the upper portion of the welding wire 13 do not interfere with each other. Need to be lifted upwards. When the feed angle of the welding wire 13 is 45 °, the distance between the surface of the thick plate 1 and the laminar flow emitting surface 10 of the laminar flow generating portion 9 is the length of the laminar flow emitting surface 10 ahead of the center of the laser passage 8 It is necessary to make the same as L ₁ or more. When the shield nozzle 4 having the same size as that of the experimental example described later is used, the laminar flow emission surface 10 of the laminar flow generation unit 9 needs to be disposed about 50 mm above the surface of the thick plate 1. When the laminar flow release surface 10 is moved away from the welding portion, the released shield gas 5 may not be efficiently supplied into the groove 2, which may cause deterioration of the welding quality. On the other hand, as shown in FIG. 8, in the case where the wire passage 11 is formed in the shield nozzle 4, the lamination proceeds and even if the welding wire 13 needs to be supplied near the surface of the thick plate 1, the shield nozzle 4 It is not necessary to lift up the welding wire 13 and the welding wire 13 can be fed to the welding portion in the groove 2 while maintaining high shieldability of the welding portion, and high quality laminated welding can be performed.

Hereinafter, the present invention will be described in more detail based on experimental examples and comparative examples.
[Experimental Example 1]
This example is an example using a shield nozzle and a shield method according to the present invention as shown in FIG.

  A thick plate 1 having a thickness of 100 mm was prepared, and a V-shaped groove 2 having a root width of 3 mm and 2 ° on one side was formed on the welding surface, and a backing was attached. The shield nozzle 4 was disposed so that the laminar flow emission surface 10 of the laminar flow generation unit 9 was located 8 mm above in parallel with the surface of the thick plate 1. At this time, the distance from the laminar flow release surface 10 to the groove 2 bottom was 108 mm.

A 150 x 100 x 20 mm t rectangular metal frame is used as the case 7 of the shield nozzle 4, and the case 7 is penetrated as the laser passage 8 so that the front length is 45 mm and the rear length is 105 mm. A hole (φ 30 mm) was formed. The welding wire 13 used the commercially available thing of (phi) 1.2 mm, and in order to supply the welding wire 13 from the welding advancing direction front, the slit-like wire channel | path 11 of width 5 mm was formed in case 7. FIG. The lower surface of the shield nozzle 4 is the laminar flow emitting surface 10 except for the laser passage 8 and the wire passage 11. The laminar flow generation portion 9 is made of stainless particles of 3 μm in diameter and several tens of μm in diameter. A porous sintered body was used. CO ₂ was used as the shield gas 5 and supplied at a constant flow rate of 50 L / min (= 8.33 × 10 ⁵ mm ³ / sec). As the air nozzle 12, a flat nozzle having a nozzle width of 40 mm was disposed at a position 30 mm above the laser passage 8 so as to form an air curtain (air knife) crossing the optical axis of the laser beam 3. The flow velocity of the compressed air injected from the air nozzle 12 was 20 m / sec.

  The laser beam 3 in the figure is for convenience to show the welded portion, and actual welding is not performed. However, when the laser output is 6 kw and the welding feed rate is 5 mm / sec, the dimension of the laminar flow emission surface 10 ( The relationship between the shape) and the welding conditions satisfied the aforementioned equations (5) and (6).

The graph in FIG. 9 shows the results of measuring the oxygen concentration at the bottom of the groove 2 when the laser light 3 was not irradiated, at intervals of 10 to 20 mm along the welding progress direction.
As shown in the graph, the oxygen concentration was maintained at 0% over a wide area from the front to the rear of the weld, indicating high shielding properties over a wide area.
[Comparison 1]
As a conventional example, FIG. 10 shows a case where a large diameter pipe shield nozzle 15 formed by connecting three large diameter pipes is disposed outside the groove 2. The welding conditions and measurement contents other than the shield nozzle were the same as those of Experimental Example 1. The graph also shows the oxygen concentration when the flow rate of the shielding gas 5 is changed to 30 L / min (= 5.0 × 10 ⁵ mm ³ / sec).

  The large diameter pipe used in this example is a square pipe having a square cross section with a side of 15 mm, and when one end of the square pipe is inclined 45 ° from the horizontal direction, the end face is cut parallel to the surface of the base material Then it was used as a gas spout. Three large diameter pipes are connected to form a large diameter pipe shield nozzle 15, and the end of the gas nozzle close to the welding portion is located 108 mm behind the welding portion and 8 mm above the thick plate 1 surface Placed in

As shown in the graph, the injected shielding gas 5 mainly reaches only the weld and the range of 30 mm around and around the weld, and the oxygen concentration at the bottom of the groove 2 is 4% or more even within 30 mm before and after the weld The
[Comparison 2]
As a conventional example, FIG. 11 shows a case where a small diameter pipe shield nozzle 16 formed by connecting ten small diameter pipes is inserted into the groove 2. The welding conditions and measurement contents other than the shield nozzle were the same as those of Experimental Example 1. The graph also shows the oxygen concentration when the flow rate of the shielding gas 5 is changed to 30 L / min (= 5.0 × 10 ⁵ mm ³ / sec).

  The small diameter pipe used in this example is a round pipe having a diameter of 3 mm, and a pipe in which ten pipes are connected is used as a small diameter pipe shield nozzle 16. Insert the small diameter pipe shield nozzle 16 at a position 45 mm from the horizontal direction and 30 mm above the bottom of the groove 2 in the groove 2 and weld the end of the gas nozzle close to the weld. It was arranged to be located 30 mm behind the section.

As shown in the graph, the injected shield gas 5 mainly reached only in the range of 20 to 60 mm behind the weld, that is, in the vicinity of the jet nozzle of the thin pipe shield nozzle 16. The oxygen concentration at the weld is 2 to 4%, and the oxygen concentration at the bottom of the groove 2 is 0% only near the spout, and the shielding atmosphere is sufficient over a wide area at the bottom of the groove 2 It was not formed.
[Experimental examples 2 to 4]
Experimental Examples 2 to 4 are for showing the case where the wire passage 11 is not formed in the shield nozzle 4 in the present invention as shown in FIG. The graph also shows the difference in the oxygen concentration at the bottom of the groove 2 depending on the presence or absence of the air nozzle 12 when the wire passage 11 is not formed. Under the welding conditions of Experimental example 1, assuming that the feed angle of the welding wire 13 is 45 °, the laminar flow release surface 10 of the laminar flow generation portion 9 is positioned 50 mm above the parallel surface of the thick plate 1 Arranged as.

  Experimental Example 2 is an example in which the wire passage 11 is not formed, the laser passage 8 is a through hole, and the air nozzle 12 is not provided. Experimental Example 3 is an example in which the wire passage 11 is not formed, the laser passage 8 is a through hole, and the air nozzle 12 is provided above the laser passage 8. Experimental Example 4 is an example in which the wire passage 11 is not formed, the laser passage 8 is closed by a material that transmits the laser light 3, and the air nozzle 12 is not provided.

When the wire passage 11 is not formed in the shield nozzle 4, the distance between the shield nozzle 4 and the weld portion is long, so the oxygen concentration in the vicinity of the weld portion at the bottom of the groove 2 is as shown in the graph in FIG. In Experimental Example 2 in which the air nozzle 12 was not used, it was 4% or more, and in Experimental Example 3 in which the air nozzle 12 was used, it was 2% or more.
[Experimental Examples 5 to 7]
Experimental Examples 5 to 7 are for showing the effect of the air nozzle 12 in the present invention as shown in FIG. In order to make it easy to see the effect of using the air nozzle 12 under the welding conditions of Experimental Example 1, the shield nozzle 4 was disposed 20 mm above the surface of the base material, and the supply of the shield gas 5 and the measurement of the oxygen concentration were performed.

  Experimental Example 5 is an example in which the wire passage 11 is formed, the laser passage 8 is a through hole, and the air nozzle 12 is not provided. Experimental Example 6 is an example in which the wire passage 11 is formed, the laser passage 8 is a through hole, and the air nozzle 12 is provided above the laser passage 8. The experiment example 7 is an example in which the wire passage 11 is formed, the laser passage 8 is closed by the material that transmits the laser light 3, and the air nozzle 12 is not provided.

  As shown in the graph in FIG. 14, by using the air nozzle 12, the oxygen concentration at the bottom of the groove 2 was lowered, and high shielding performance was realized.

  The present invention can be used in narrow gap welding for thick butt joints and other joints, and can also be used for welding in extremely narrow gaps. Furthermore, in addition to the laser welding as described above, the present invention may also be used in narrow gap welding such as arc welding that does not use a laser.

Reference Signs List 1 thick plate 2 groove 3 laser beam 4 shield nozzle 5 shield gas 6 shield gas supply port 7 case 8 laser passage 9 laminar flow generation unit 10 laminar flow emission surface 11 wire passage 12 air nozzle 13 welding wire 14 melting bead 15 large diameter pipe Shield nozzle 16 Small diameter pipe shield nozzle

Claims (5)

A gas shield nozzle used for thick plate narrow groove laser welding, which is disposed between a laser light source and a weld so as to cover a weld at a bevel and through which laser light passes, and a shield gas possess and supplying layer flow generation section, in a state of laminar flow in the weld from the groove outside, the laser light source side of said laser paths, the inflow of the outside air into the groove portion by injection of compressed air and / Or the shield nozzle characterized by having an air nozzle which prevents the leak of shield gas from a groove part . A gas shield nozzle used for thick plate narrow groove laser welding, which is disposed between a laser light source and a weld so as to cover a weld at a bevel and through which laser light passes, and a shield gas possess a supplying layer flow generation section in a state of laminar flow in the weld from the groove outside, the laminar flow generating unit has a laminar flow emitting surface facing the weld, open from the laminar flow emitting surface Assuming that the distance to the front bottom is H, the welding feed rate is V _w , the gas flow rate is V _g , and the time for cooling to a temperature at which oxidation of the weld completion portion is suppressed t, the laser passage of the laminar flow emission surface shield nozzle length of welding direction ahead of the center L ₁ and welding direction behind the length L ₂ is to satisfy the following equation.
L ₁ HH × V _w / V _g -Equation (1)
L ₂ VV _w × t − equation (2) Further comprising, according to claim 1 or 2 shield nozzle according to wire passage capable of inserting the welding wire in supplying welding wire to the weld. The shield nozzle according to any one of claims 1 to 3 , wherein the laminar flow generation portion is made of a porous sintered body through which a shield gas can pass. A gas shield method used for thick plate narrow groove laser welding, which has a laser passage through which a laser beam passes and a shield nozzle capable of releasing a shield gas, is opened between the laser light source and the welding portion. The shield nozzle is disposed so as to cover the weld in the tip, and shield gas is supplied from the outside of the groove to the weld in a laminar flow state using the shield nozzle, and the shield nozzle is a laminar flow release surface facing the weld. The length from the center of the laser passage of the laminar flow emitting surface to the welding advancing direction L ₁ , the length from the welding advancing direction L ₂ , the distance from the laminar flow emitting surface to the groove bottom wherein H, when the time for oxidation of the welding completion portion is cooled to a temperature which is suppressed to a t, that setting a condition of the following equation for the welding feed speed V _w and the gas flow velocity V _g Cie Rudo way.
V _g H H × V _w / L ₁ -Equation (3)
V _w ≦ L ₂ / t − equation (4)

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