JP4528683B2 - Narrow groove welding method, welded structure, and welding apparatus therefor - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a narrow bead welding method, a welded structure, and a welding apparatus thereof for improving a backside bead portion on the back side generated by one-side welding of a pipe member or a plate member of a groove joint and a residual stress in the vicinity thereof to compressive stress. .

  Austenitic stainless steel materials used in welded structures such as containers, pipes, and components of nuclear power plants and thermal power plants tend to precipitate Cr carbide at the grain boundaries due to welding, and a Cr-deficient layer near the grain boundaries. The cracking susceptibility (material sensitization) to corrosion increases due to the formation of. Further, a high tensile residual stress exists in the welded portion (welded metal portion and adjacent heat-affected zone), and stress corrosion cracking is likely to occur because it is used in a severe corrosive environment such as high-temperature water. In order to prevent this stress corrosion cracking, it is necessary to remove one factor from the three factors of sensitization of the material, tensile stress, and corrosive environment. For this reason, in particular, there is a strong demand to improve or greatly reduce the tensile stress remaining in and near the surface of the welded part exposed to corrosive environments such as high-temperature water, and several welding methods and equipment have been proposed. ing.

  In the piping system heat treatment method described in Patent Document 1 (Japanese Patent Publication No. 53-38246), cooling water is present inside the pipe after the welding assembly, and the outside of the pipe is heated so that the pipe inner surface and the pipe outer surface It has been proposed that a temperature difference be generated during this period, the inner surface of the tube be tensile yielded, and the outer surface of the tube be compressed and yielded.

  In the preventive maintenance method and apparatus for an austenitic stainless steel welded part described in Patent Document 2 (Japanese Patent Laid-Open No. 2001-141629), a high-frequency heating coil is moved while following a linear welded part, It has been proposed to have a procedure for heating the welded part to a temperature higher than the temperature of the stress yield point, and a procedure for rapidly cooling the jet region by jetting cooling water into the overheated region.

  In the method and apparatus for joining metal parts described in Patent Document 3 (Japanese Patent Publication No. 9-512485), welding material is continuously supplied near the tip of the electrode tip that runs at a selected speed (127 cm / min or more). A step of continuously melting the welding material in the groove by a discharge current from the tip, and forming a weld bead, wherein the electrodes are joined and electrically connected to the tip. It has been proposed to achieve a final residual stress state that has a non-circular cross-section blade and that is compressible over a predetermined number of weld passes, without an external heat sink medium.

  Patent Document 4 (Japanese Patent Publication No. 9-512486) describes a method of relaxing residual stress in a weld metal part using a high torch travel speed. During the cap pass (final finish welding), the far surface (groove surface side) of the welded joint is heated (melted) at a torch travel speed faster than 254 mm (10 inches) per minute, and the near surface (groove bottom side) ) And a far surface, and a step of cooling the far surface and generating a compressive stress or a small tensile stress on the near surface without heat sink (water cooling) on the inner surface side. It has been proposed.

  Moreover, in the piping improvement method described in Patent Document 5 (Japanese Patent Laid-Open No. 2-258190), the welding heat affected zone is formed with a heat input in the range of 1 to 30 kJ / cm while holding the reactor water in the pressure vessel. It has been proposed to divide into a heating area and a heating area of the welding heat affected zone with a heat input in the range of 1 to 5 kJ / cm.

  In addition, in the method for welding stainless steel materials described in Patent Document 6 (Japanese Patent Publication No. 59-21711), a corrosion-resistant material is previously deposited on the surface in contact with the corrosive fluid near the weld joint, It has been proposed to melt the adjacent portion and the portion in contact with the corrosive fluid under a heat input condition of 5 kJ / cm or less, and then form a groove in the joint and weld it.

  Furthermore, in the multi-layer welding method for narrow groove joints of austenitic stainless steel described in Patent Document 7 (Japanese Patent Publication No. 62-19953), an austenitic filler material is used for the layer closer to the deepest groove. It has been proposed to weld (weld) and weld at least one outer layer adjacent to the layer using a martensitic filler material.

  Moreover, in the welding method and welding material described in Patent Document 8 (Japanese Patent Laid-Open No. 11-138290), a martensitic transformation is caused in the weld metal generated by welding in the cooling process after welding, and the weld metal is at room temperature. It has been proposed to make a state of expansion from the start temperature of martensitic transformation (for example, less than 250 ° C. and 170 degrees or less).

Further, in the TIG welding method and solid wire for TIG welding of high-strength steel described in Patent Document 9 (Japanese Patent Application Laid-Open No. 9-253860), the martensitic transformation start temperature of all weld metals is 400 ° C. or less, Welding using solid wire with 7.5 to 12% Ni, C 0.1% or less and H 2ppm or less, with wire feed rate 5-40g / min. It has been proposed to do.

Japanese Patent Publication No. 53-38246 (Patent No. 957324) JP 2001-141629 A Japanese National Patent Publication No. 9-512485 (Patent No. 3215427) Japanese National Patent Publication No. 9-512486 (Patent No. 3137985) JP-A-2-258190 (Japanese Patent No. 2865749) Japanese Patent Publication No.59-21711 (patent 1248914) Japanese Examined Patent Publication No. 62-19953 (Patent No. 1415054) JP 11-138290 A (Patent No. 3350726) JP-A-9-253860

  In the case of the above-mentioned Patent Document 1, it is an effective method for changing the tensile residual stress on the inner surface of the pipe generated during welding assembly into a compressive residual stress, but a large-scale high-frequency heating equipment different from the welding equipment is required. After the completion of welding, work man-hours and costs for heating the outer peripheral portion at a high temperature while supplying cooling water to the inner peripheral portion of the pipe are required.

  In the case of the above-mentioned Patent Document 2, a device for reducing the tensile residual stress has been devised. However, after welding is completed, high-temperature heating is performed by a high-frequency coil that moves on the surface of the linear weld site, and the overheated region is cooled with water. Therefore, mobile heating and water cooling facilities are required, and work man-hours and costs for implementing this high-temperature heating and rapid cooling are required.

  On the other hand, in the case of the above-mentioned Patent Document 3, there is a device for reducing the tensile residual stress and the welding strain by using the heat self-cooling effect of the high heat efficiency welding construction and the narrow groove joint without using the heat sink medium outside. Has been. However, since the amount of heat input at the time of important welding is not specified, there is a high possibility that the tensile residual stress will not be changed to the compressive residual stress. In addition, since a thin electrode formed in a non-cylindrical shape (non-circular cross section) different from an inexpensive tungsten electrode rod with a circular cross section is used, the manufacturing cost of this thin electrode becomes high, and it is inserted into the groove. Thus, the electrode replacement cost accompanying the consumption of the electrode tip that occurs when arc welding is also increased.

Moreover, in the case of the said patent document 4, it is thought that it is one method effective in the residual stress reduction of groove welding whose plate | board thickness and pipe diameter are comparatively small. However, in groove welding where the base metal plate is thick, the temperature gradient of the inner and outer surfaces of the pipe (front and back surfaces of the base material) is small, so that the residual stress on the back side can be obtained only with a cap pass (final finish welding) that heats and melts the front side. There is a high possibility that it will not be drastically reduced. Moreover, although the traveling speed is emphasized, the amount of heat input at the time of important welding is not prescribed. Further, as in the case of Patent Document 3, a thin electrode formed in a non-cylindrical shape (non-circular cross section) different from an inexpensive tungsten electrode rod having a circular cross section is used, so that the manufacturing cost of the thin electrode becomes high. In addition, the cost of electrode replacement accompanying wear of the electrode tip that occurs when arc welding is performed by inserting the groove into the groove increases.

  Further, in the case of the above-mentioned Patent Document 5, although it is one method effective for reforming the metal structure and improving the corrosion resistance, the heat-affected zone that has already been welded is subjected to a heat treatment (melting treatment) under predetermined heat input conditions. is doing. This heat treatment is directed to the welding heat-affected zone on the reverse side opposite to the main welding portion, and is not only completely different from the main welding construction, but the outside is forcibly water-cooled with furnace water.

  Moreover, in the case of the above-mentioned patent document 6, although it is one method effective for reforming the metal structure and improving the corrosion resistance, overlay welding on the back side to be applied before the main welding or heat affected zone by this overlay welding is performed. Therefore, a great number of man-hours and costs are required for the melting process and the subsequent groove processing. Moreover, although the heat input conditions for melting the heat affected zone are set at 5 kJ / cm or less, there is no description at all about the heat input conditions and welding method for forming a groove and performing main welding thereafter. . Furthermore, since the groove shape at this time is wide, the main welding is likely to be performed using a heat input amount several times higher than the heat input condition of the overlay welding.

  Furthermore, in the case of the above-mentioned patent document 7, in order to reduce the tensile residual stress on the inner surface of the pipe, welding is performed using austenite wire and martensite wire that are the same quality as the material of the groove joint. Although effective in reducing the tensile residual stress, the tensile stress still remains and has not yet been changed to a compressive stress. The martensitic wire is used only for the weld portion of the intermediate layer in the groove, and is not used for the weld portion of the final layer on the groove surface. In addition, since the groove joint has a wide angle, when welding a thick groove joint, the groove cross-sectional area to be welded and the groove shoulder width increase, making it difficult to weld one layer at a time for each pass. 1 and multipass multi-layer welding is required, and there is a high possibility that tensile residual stress and shrinkage deformation increase. The welding method is unknown, but assuming from the examples, there is a high possibility of an arc welding method using a welding wire (a filler metal) as an electrode rather than an arc welding method using non-consumable tungsten as an electrode. .

  Furthermore, in the case of the said patent document 8, in order to improve the fatigue strength of a welded joint, it welds using the welding material (it corresponds to a welding wire) which produces a martensitic transformation. Welding objects are mainly welded structures of low-alloy steel materials (such as high-strength steel materials) and cannot be applied to welding austenitic stainless steel materials of different materials. In addition, the place where the tensile residual stress generated by welding is reduced is the welded surface part of fillet joints, T joints and cross joints, or the surface part of double-sided welding of X groove joints. It does not apply to the weld back surface portion that is required for single-sided welding such as a point joint. Furthermore, the welding method is an arc welding method using a welding wire as an electrode, and not an arc welding method using non-consumable tungsten as an electrode.

  Further, in the case of Patent Document 9, it is considered effective for preventing weld cracking of high-tensile steel, but it cannot be applied to welding of stainless steel materials of different materials. In addition to this, several welding methods have been proposed in which welding is performed using a welding wire that causes martensitic transformation, but it is mainly intended for welding high-tensile steel materials, and not for austenitic stainless steel materials. It is. Similarly to Patent Document 6, the portion of the tensile residual stress that is reduced by welding is the weld surface portion, and the weld back surface that is required for single-sided welding such as a narrow groove joint having a different joint shape and penetration shape. The part is not targeted.

  The object of the present invention is effective in preventing the stress corrosion cracking by improving the backside bead portion on the back side generated by one-side welding of the pipe member or plate member of the groove joint and the residual stress in the vicinity thereof to compressive stress. It is an object of the present invention to provide a narrow groove welding method, a welded structure, and a welding apparatus therefor.

The narrow groove welding method of the present invention that solves the above-mentioned problems is austenitic by non-consumable electrode type arc welding from the bottom to the top of a groove joint formed by abutting a pipe member or plate member made of austenitic stainless steel. In the narrow groove welding method that improves the residual stress on the back side of the groove bottom by this single-sided welding, a back bead is formed on the back side of the groove bottom. First layer back welding process, and after this first layer back welding process, after the first layer welding process, the first layer welding process for performing the layer welding in the first heat input range up to a specific layer bead height, and after the first layer welding process And laminating in the second heat input range from the remaining groove portion to the final layer at the upper portion of the groove using one or more heat input conditions smaller than the plurality of heat input conditions used in the first lamination welding process. welding And a second lamination welding process that is characterized in that to form a compressive residual stress on the back bead and heat affected portion in the vicinity thereof of the back side.

  According to the narrow groove welding method, welded structure, and welding apparatus of the present invention, stress corrosion cracking is prevented in actual machine operation by improving the residual stress on the back inner bead portion and the vicinity thereof to compressive stress. Can contribute to longer life.

  As described above, the characteristics of the welding method of the present invention are characterized in that, in the lamination welding, the first lamination welding process for lamination welding in the first heat input range and the second lamination welding for lamination welding in the second heat input range. And a process. As a result, squeezing deformation that occurs on the weld surface side is suppressed to a small extent, compressive stress remains in the back bead portion on the reverse side and the vicinity thereof, and stress corrosion cracking can be prevented.

  In addition, a second laminate that is laminated and welded from the remaining groove portion to the final layer above the groove using one or more heat input conditions smaller than the plurality of heat input conditions used in the first laminate welding process. It is characterized in that a welding process is performed. As described above, even if compressive stress remains in the back bead portion on the back surface side and the vicinity thereof, even if applied in a corrosive environment, use stress corrosion cracking can be prevented. In addition, there is no need to water-cool the inner surface during welding, or to install an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be done, manufacturing costs can be reduced, and good welding quality is ensured In addition, the amount of wire used and the time required for welding can be reduced.

In particular, the first heat input range used in the first lamination welding process is 4 kJ / cm or more and 12 kJ / cm or less, and the second heat input range used in the second lamination welding process is 1 kJ / cm or more 6
It is good that it is below kJ / cm. If the first heat input is less than 4 kJ / cm, the compressive stress applied to the back bead portion on the back side and the vicinity thereof does not increase due to the melting region being too small and the shrinkage deformation in the groove width direction being insufficient. On the other hand, if this heat input is larger than 12 kJ / cm, the compressive stress applied to the back bead portion on the back side and the vicinity thereof is suppressed and reduced due to the excessive melting region and the increase in shrinkage deformation in the groove width direction. This is not preferable. The second heat input range is 1 kJ / cm or more and 6 kJ / cm or less, and it is preferable that the final layer above the groove is laminated and welded. If the heat input is less than 1 kJ / cm, welding cannot be performed. On the other hand, if the heat input amount is too large, it is not preferable because the wrinkling deformation is increased and the tensile stress applied to the back bead portion and the vicinity thereof is increased and remains.

  In the second lamination welding process, by making the heat input amount for each welding pass as small as possible, the progress of the wrinkling deformation occurring on the welding surface side can be suppressed to be small. By suppressing the wrinkle-squeezing deformation, the tensile stress applied to the back bead portion on the reverse side and the vicinity thereof is suppressed, and the compressive stress can be left in the back bead portion and the vicinity thereof after the completion of welding.

  The first heat input range and the second heat input range may each be laminated and welded to a specific range of stacked bead heights using one or more heat input conditions or welding conditions corresponding thereto.

  The specific laminated bead height may be in the range of 3/10 to 7/10 of the plate thickness. The compressive stress applied to the back bead portion and the vicinity thereof greatly varies depending on the height of the laminated bead that is laminated and welded in the groove, the amount of heat input, the groove shape, and the plate thickness, and the shrinkage deformation in the groove width direction converges. It becomes maximum around the height of the laminated bead. The laminated bead height at which the shrinkage deformation converges is approximately half or near the plate thickness of the groove joint to be welded. Therefore, the maximum compressive stress can be most effectively obtained by laminating and welding up to the above-mentioned specific range of laminated bead heights in an appropriate heat input range corresponding to the groove shape and plate thickness.

  The groove joint may be formed so that the groove bottom width is in the range of 3 mm to 7 mm and the groove angle is in the range of 2 degrees to 8 degrees. As a result, lamination welding with the above low heat input can be performed, and at the same time, the groove cross-sectional area to be welded can be reduced, shrinkage deformation and squeezing deformation due to welding can be suppressed, and the amount of welding wire used can be reduced. Preferably, the groove bottom width is formed in the range of 4 mm to 6 mm, and the groove angle is set in the range of 4 degrees to 6 degrees.

  In the welding process, it is preferable to perform lamination welding by distributing to a plurality of passes in the course of laminating welding one layer at a time or laminating welding one layer at a time. As a result, even under low heat input conditions, the groove wall surface can be reliably melted, and good weld beads having no defects up to the final layer above the groove can be obtained. At the same time, squeezing deformation that occurs on the weld surface side is suppressed to a small extent, and compressive stress remains in the back bead portion on the reverse side and the vicinity thereof, and even when applied in a corrosive environment, stress corrosion cracking can be prevented.

  In the welding process, non-consumable electrode type pulse arc welding or direct current arc welding may be performed, and a welding wire may be supplied and welded to the arc welding portion in the groove. As a result, it is possible to form a beautiful weld bead having no weld spatter from the groove bottom to the groove top.

  The welding wire may be the same type of welding wire as the pipe member or plate member. For example, when the tube member or plate member is an austenitic stainless material, an austenite wire of the same type as the tube member or plate member may be used. As a result, even in the case of a stainless steel material or a low carbon steel material, the inside of the groove to be welded can be filled with the same kind of welding wire as the pipe member or the plate member and reliably filled.

  Furthermore, when the tube member or plate member is an austenitic stainless material, an inconel wire or martensite wire of a nickel alloy can be used in the second lamination welding step. In the case of Inconel wires, the compressive stress remaining in the back bead portion on the back side and in the vicinity thereof can be increased by the effect of suppressing welding deformation caused by deviation of the linear expansion coefficient from the pipe member or plate member, and stress corrosion cracking can be achieved. Can be prevented. In addition, a martensitic wire can be used, and the deformation suppression action and the expansion action work on the weld metal part that causes the deviation of the average linear expansion coefficient and the martensite transformation, further increasing the compressive stress remaining in the back bead part and its vicinity. Can do.

  The non-consumable electrode may be used by inserting a non-consumable tungsten electrode rod having a narrow diameter and a circular cross section narrower than the groove width into the groove. As a result, arc welding in the groove can be properly performed without using an expensive flat-shaped (non-circular cross-section) special electrode. In addition, the small-diameter electrode having a circular cross section is inexpensive and easy to use, and can be reused by simply repolishing the electrode tip of the consumable part even when replacing the electrode.

  In the narrow groove welding method of the present invention, a desired back bead is formed on the back side which is important in one-side welding of a pipe member joint or a plate member joint by a first layer back wave welding process in which a back bead is formed on the back side of the groove bottom. Can be reliably formed. In addition, after the first layer backside welding process, the shrinkage deformation (plastic deformation) in the groove width direction is appropriately progressed by the first laminating welding process in which the laminating welding is performed in the first heat input range up to a specific laminated bead height. The tensile deformation remaining in the back bead portion on the back side and in the vicinity thereof can be changed to a maximum compressive stress by the plastic deformation that progresses appropriately.

  Further, the welding wire is supplied and welded to the arc welding portion without energization, or the welding wire is supplied and welded to the arc welding portion while being heated and energized, so that the inside of the groove to be welded can be obtained. It can be filled with the required weld metal, and it is possible to increase the amount of welding and improve the welding efficiency by heating the wire.

  Further, the present invention is a welded structure in which a groove joint is formed by abutting a pipe member or a plate member to achieve the above object, and is welded on one side from the bottom to the top thereof. A first layer weld metal part having a back bead formed on the back surface side, and a first layer weld metal formed by layer welding in a first heat input range from a portion in contact with the first layer weld metal part to a specific laminate bead height And a second laminated weld metal portion formed by lamination welding in the second heat input range from the remaining groove portion in contact with the first laminated weld metal portion to the final layer at the upper portion of the groove. Propose that feature and welded structure.

  In particular, lamination is performed from the remaining groove portion in contact with the first laminated weld metal part to the final layer at the upper part of the groove using one or more heat input conditions smaller than the plurality of heat input conditions used in the lamination welding. It is preferable to include a second laminated weld metal portion formed by welding. The first heat input range is 4 kJ / cm or more and 12 kJ / cm or less, preferably 4 kJ / cm or more and 10 kJ / cm or less. As a result, shrinkage deformation (plastic deformation) in the groove width direction is appropriately advanced, and the tensile stress remaining in the back bead portion on the back side and in the vicinity thereof can be changed to a maximum compressive stress.

  The second heat input range is preferably 1 kJ / cm or more and 6 kJ / cm or less. The specific laminated bead height may be in the range of 3/10 to 7/10 of the plate thickness.

  Thus, by laminating and welding up to the final layer at the upper part of the groove using one or a plurality of heat input conditions or welding conditions corresponding thereto, as described above, the wrinkling deformation generated on the weld surface side is suppressed to a small level. In addition, even if compressive stress remains in the back bead portion on the back side on the opposite side and in the vicinity thereof, stress corrosion cracking can be prevented even when applied in a corrosive environment.

  In addition, the weld metal portion may be laminated and welded to a plurality of passes in the course of laminating welding one layer at a time or laminating welding one layer per pass. As a result, it is possible to obtain a good weld bead cross-section that is stacked in order from the bottom to the top of the groove joint.

  Further, the amount of deformation of the wrinkle on the surface side (the amount of dents) is preferably 1.5 mm or less. Further, the back bead portion on the back surface side and the base material heat-affected portion in the vicinity thereof may be formed within the compression side range from the yield stress of the material.

  In addition, the shape of the portion where the first laminated weld metal portion and the second laminated weld metal portion are in contact with each other, or the weld cross-section in the vicinity thereof or a weld cross-section similar thereto, is changed. It can be bead width change, penetration change, laminate ripple change, metal structure change, etc.

  Further, the remaining groove portion contacting the second laminated weld metal portion with the first laminated weld metal portion using one or more heat input conditions smaller than the plurality of heat input conditions used in the laminate welding. To the final layer at the top of the groove.

  With such a configuration, compressive stress remains in and around the back bead portion on the back side due to suppression of welding deformation and suppression of tensile stress, and even when applied in a corrosive environment, stress corrosion cracking can be prevented and long life is achieved. Contributes to In addition, there is no need to water-cool the inner surface during welding, or to install an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be done, manufacturing costs can be reduced, and good welding quality is ensured In addition, the amount of wire used and the time required for welding can be reduced.

  In addition, the present invention is a welding apparatus that can perform one-side welding from the bottom to the top of a groove joint formed by abutting a pipe member or a plate member, and achieves the above-mentioned object, and is capable of attaching and detaching non-consumable electrodes. A welding torch, and a welding carriage that can arbitrarily move the welding torch in the welding line direction, up and down, left and right directions of the groove joint, supply a welding wire to the welding torch tip part or arc welding part, and adjust the vertical and horizontal positions. Selection of pulse arc welding or DC arc welding, TIG welding power source capable of controlling output of predetermined welding conditions, setting of heat input range conditions used in the first layer backside welding process, lamination up to a specific laminated bead height after the first layer welding The condition setting of the first heat input range used in the first laminating welding process to be welded, and then the condition setting of the second heat input range used in the second laminating welding process of laminating and welding up to the final layer are performed. Condition setting means, and driving control of the welding carriage in accordance with instructions of the condition setting means, output control of the TIG welding power source, and adjustment of the horizontal and vertical positions of the welding torch, the welding wire feed amount and the horizontal and vertical positions And a welding control device that performs the welding control.

  As a result, the first layer back wave welding process for forming a back bead on the back side of the groove bottom, the first layer welding process for layer welding to a specific stack height, and the final layer from the remaining groove part to the top of the groove It is possible to reliably perform the second laminating welding process for laminating and welding.

  Hereinafter, the contents of the present invention will be described in detail with reference to the embodiments shown in FIGS.

FIG. 1 is an explanatory view showing an embodiment of a narrow groove welding method and a welding procedure outline of the welded structure according to the present invention, in which (1) in FIG. Welding cross section when wave welding,
(2) is a welded cross section when laminated welded to a specific laminated bead height Hb, and (3) is a welded cross section when laminated welded from the remaining groove portion to the final layer above the groove. FIG. 2 is an explanatory view showing an example of the stress analysis result of the back bead portion that changes in the welding process of the groove joint. In the figure, a plurality of heat input amounts and stress changes when the respective heat input is switched and welded are shown. Moreover, FIG. 3 is another Example, and has shown the stress change when each joint with which plate | board thickness differs is welded.

  As shown in FIG. 1, in the first groove-shaped manufacturing step 51, a joint member to be welded is machined to a predetermined size, transported to a welding site, and the processed members and parts are assembled. It is a process. The joint members 1 and 2 are pipe members or plate members such as thick plate pipes and containers mainly used in nuclear power plants, thermal power plants, and chemical plants. It is necessary to weld one side to the top. At the same time, it is necessary to improve the stress remaining in the back bead 15 portion on the back side and the vicinity thereof to compressive stress. The next welding preparation step 52 is a step of attaching a welding carriage, welding torch, wire, etc., starting up a welding power source and a welding control device, and preparing for a welding operation.

  In the first layer back welding process 53, as shown in FIG. 1 (1), 21 first layer back welding (P = 1) is performed to form a back bead width B in an appropriate range on the back surface side of the groove bottom. It is a process. Moreover, you may make it perform the tack welding without a wire which melt | dissolves a groove bottom part shallowly and joins before this first layer back wave welding. The back bead width B in the proper range is preferably 4 to 7 mm, for example. Preferably it is 4-6 mm. In the first layer back wave welding that requires the formation of the back bead, the heat input condition of the arc that can be melted to the back surface side of the groove bottom or the welding condition corresponding to this is output, and the width B of the back bead 15 is formed in an appropriate range. One or more condition factors (e.g., peak current or base current or average welding current, peak voltage or average arc voltage or arc length, wire feed rate, welding speed) may be adjusted or controlled. The amount of heat input required for forming the back bead varies depending on the thickness of the groove bottom (root face f), width w, and material, but it can be formed in the range of 4 to 20 kJ / cm. However, it may be preferably 6 to 12 kJ / cm. Note that the heat input Q (kJ / cm) per unit length is a relational expression {Q = Ia * between the average welding current Ia (A), the average arc voltage Ea (V) and the welding speed V (mm / s). Ea / (100 * V)}.

  In the next first laminating welding step 41, as shown in FIG. 1 (2), after the first layer back wave welding step 53, laminating welding is performed in the first heat input range Q1 up to the laminating bead height Hb in a specific range. It is a process. By this first laminating welding step 41, shrinkage deformation (plastic deformation) in the groove width direction is moderately progressed, and the tensile stress remaining in the back bead portion on the back side and in the vicinity thereof due to this moderately progressing plastic deformation. The maximum compression stress can be changed. Laminated bead height Hb in a specific range is 3/10 or more and 7/10 or less of plate thickness T of joint members 1 and 2 to be welded. Further, the first heat input range Q1 is preferably 4 kJ / cm or more and 12 kJ / cm or less. By using one or more heat input conditions from this heat input range Q1 or welding conditions corresponding thereto, it is preferable to perform lamination welding to the laminated bead height Hb in the specific range. For example, several passes after the first layer welding are welded under a heat input condition of about 8 kJ / cm, and then the heat input is reduced to 4 to 5 kJ / cm and laminated to a laminated bead height Hb of about half the plate thickness. It can also be welded. Further, the welding after the first layer welding can be laminated and welded up to a specific range of laminated bead height Hb under a constant heat input condition of about 5 kJ / cm or 6 kJ / cm.

  Moreover, in this 1st lamination | stacking welding process 41, it specifies by carrying out the lamination | stacking welding for 1 layer 1 pass at a time using one or more heat input conditions of the said 1st input heat quantity range Q1, or the welding conditions applicable to this. A good nuclear weld bead having no defects up to the height of the laminated bead can be obtained. At the same time, as described above, the shrinkage deformation (plastic deformation) in the groove width direction is appropriately advanced, and the tensile stress remaining in the back bead portion on the back side and the vicinity thereof can be changed to the maximum compressive stress. In the first lamination welding step 41, one or more heat input conditions in the first input heat quantity range Q1 or one or more welding conditions corresponding thereto are used, and one pass is assigned to a plurality of passes in the middle of the lamination welding. It is also possible to laminate and weld.

As shown in FIG. 1 (3), the next second lamination welding process 42 is performed after the first lamination welding process 41, from the remaining groove portion to the final layer 39 (P = N) on the groove upper portion. This is a step of performing lamination welding using heat input conditions in the second heat input range Q2 or welding conditions corresponding thereto. This second laminating welding step 42 suppresses wrinkle deformation that occurs on the welding surface side, and compressive stress remains on the back bead portion on the back side on the opposite side and in the vicinity thereof, even if applied in a corrosive environment. , Stress corrosion cracking can be prevented. The second heat input range Q2 used in the second lamination welding process 42 is smaller than the heat input Q1 used in the first lamination welding process, and is 1 kJ / cm or more and 6 kJ / cm or less. Preferably they are 2 kJ / cm or more and 4 kJ / cm or less. From this heat input amount range Q2, one or a plurality of heat input conditions or welding conditions corresponding thereto may be laminated and welded to the final layer above the groove. For example, a heat input condition of about 4 kJ / cm or a welding condition corresponding to this can be selected and laminated welding can be performed to the final layer. Further, the heat input condition can be reduced during the lamination welding, and the final layer and several passes in the vicinity thereof can be laminated. Note that if the heat input Q2 used in the second lamination welding step 42 (second half welding) is smaller than 1 kJ / cm, it is not preferable because welding cannot be performed and a fusion failure may occur. On the contrary, if the heat input Q2 is more than 6 kJ / cm, it is not preferable because the squeezing deformation increases and the tensile stress applied to the back bead portion and its vicinity increases and remains.

The heat input conditions during welding are the average current Ia (A) and average arc voltage Ea to be set or output.
(V), which is closely related to the condition factor of the welding speed V (mm / s), and the relational expression {Q = Ia * Ea / (100 * V) so that a specific heat input Q (kJ / cm) is obtained. } May be used to determine appropriate values of Ia, Ea, and V. Further, although the arc voltage during DC arc welding changes slightly, an approximate average value may be adopted. Further, the current and arc voltage during pulse arc welding repeat high peak current (peak voltage) and low base current (base voltage), but an approximate average value may be adopted. Also, the control of the heat input Q (or heat input condition) can be easily achieved by increasing / decreasing the average current Ia or increasing / decreasing the welding speed.

  Further, in the second lamination welding step 42, one or more layers are welded one by one using one or more of the heat input conditions of the second input heat quantity range Q2 or the welding conditions corresponding thereto. Each welded weld bead can be reliably melted even under low heat input conditions, with no defects up to the final layer 39 above the groove, by performing multiple welding in multiple passes during the lamination welding. Can be obtained. At the same time, squeezing deformation that occurs on the weld surface side is suppressed to a small extent, and compressive stress remains in the back bead portion on the reverse side and the vicinity thereof, and even when applied in a corrosive environment, stress corrosion cracking can be prevented. In addition, there is no need to water-cool the inner surface during welding, or to install an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be done, manufacturing costs can be reduced, and good welding quality is ensured In addition, the amount of wire used and the time required for welding can be reduced.

  As shown in FIGS. 2 and 3, tensile stress is first generated by shrinkage deformation in the back bead portion formed by the first layer back wave welding. This tensile stress tends to increase as the heat input increases. Further, in the first lamination welding step 41 (first welding in (b)) that is laminated after the first layer welding, a large compressive stress is applied to the back bead portion by the progress of the shrinkage deformation (plastic deformation) in the groove width direction. Moreover, the analysis results show that the maximum value of the compressive stress changes depending on the amount of heat input and the thickness of the plate. In particular, the compressive stress applied to the back bead portion and the vicinity thereof greatly varies depending on the stack bead height Hb, heat input Q, plate thickness T, and groove shape in the groove, and in the groove width direction. The shrinkage deformation is maximized around the height of the laminated bead that converges. In addition, the maximum value of the compressive stress shifts in a direction in which the ratio Hb / T of the stacked bead height increases as the plate thickness T increases. For example, when the plate thickness T is 20 mm, the maximum value is about 0.4. In the case of 40 mm, the position has changed to around 0.6.

  Therefore, in (b) the first half welding, the most effective effect is achieved by laminating and welding each of the heat input conditions within the appropriate heat input range up to the laminated bead height Hb corresponding to each plate thickness T or the welding conditions corresponding thereto. In particular, a maximum compressive stress can be obtained. The laminated bead height Hb is in the range of approximately 3/10 to 7/10 (0.3 * T ≦ Hb ≦ 0.7 * T) of the plate thickness T, preferably 2/5 of the plate thickness T. It is good to set it as the range of 3/5 or less (0.4 * T <= Hb <= 0.6 * T). If the heat input Q1 used in the first laminating welding process 41 is less than 4 kJ / cm, the back bead portion on the back side and the vicinity thereof are caused by the melt region being too small and the shrinkage deformation in the groove width direction being insufficient. Since the applied compressive stress may not increase, it is not preferable. On the other hand, if the heat input Q1 is larger than 12 kJ / cm, the compressive stress applied to the back bead portion on the back side and the vicinity thereof is suppressed due to excessive melting area and increased shrinkage deformation in the groove width direction. Since it may become small, it is not preferable.

  In addition, as shown in FIGS. 2 and 3, in the second lamination welding step 42 ((c) second-half welding) in which lamination is performed from the remaining groove portion to the final layer at the upper portion of the groove, flaws generated on the welding surface side. With the progress of the squeezing deformation, a reaction tensile stress is generated in the back bead portion on the back surface side and in the vicinity thereof. This tensile stress mainly depends on the amount of heat input and the thickness of the plate, and tends to increase as the plate thickness T decreases. At the same time, the analysis results can be suppressed by welding with low heat input. . Therefore, in the latter half welding (c), by switching to low heat input conditions and performing lamination welding, even if the plate thickness T is different, compressive stress can be reliably left in the back bead portion and the vicinity thereof. When the plate thickness is 40 mm, (b) the first half welding and (c) the second half welding can be performed under substantially the same specific heat input conditions, and the compressive stress can be left in the back bead portion and the vicinity thereof. However, it is possible to reliably obtain a high compressive stress by performing the lamination welding with the low heat input switching at the time of the latter half of the welding (c). In particular, since the back bead part on the back side and the base heat affected part in the vicinity are formed in the range from the yield stress of the material to the compression side, stress corrosion cracking can be prevented even when applied in a corrosive environment. Contributes to longer life.

As shown in FIG. 1, in the first layer backside welding step 53, the first and second lamination welding steps 41 and 42, non-consumable electrode type pulse arc welding or DC arc welding is performed, and the inside of the groove is formed. By supplying and welding a welding wire to the arc welded portion, it is possible to form a beautiful weld bead without welding spatter from the groove bottom to the groove top. The welding wire 5 uses a welding wire of the same type as the joint members 1 and 2 in the first lamination welding process 41 and the second lamination welding process 42, so that the inside of the groove to be welded is a pipe member or a plate member. It can be reliably filled by filling with the same kind of welding wire. In particular, when the joint members 1 and 2 are austenitic stainless steel materials (for example, SUS304 series and SUS316 series), the same kind of austenitic wires as the joint members 1 and 2 (for example, Y308 series and Y316 series wires). May be used in the first lamination welding process 41 and the second lamination welding process 42. Further, by using an inconel wire of nickel alloy in the second lamination welding step 42 instead of the austenitic wire, the effect of suppressing welding deformation caused by the deviation of the linear expansion coefficient from the joint members 1 and 2 is achieved. The compressive stress remaining in the back bead portion on the back surface side and in the vicinity thereof can be increased.

  FIG. 4 is an explanatory view of an embodiment showing a groove shape and apparatus schematic configuration relating to the narrow groove welding method and welded structure of the present invention, (1) is a groove cross section of a joint member before welding, (2) is a groove cross section in which an insert material is provided at the center of the groove bottom, and (3) shows a schematic configuration of the welding apparatus and a weld cross section during welding. FIG. 5 is a weld cross section of an embodiment showing an outline of welding of the narrow gap welding method and welded structure of the present invention. (1) is a welding in which the heat input is switched and the layers are welded one by one for each pass. Section (2) shows a welded section in which the layers are welded in a plurality of passes while being laminated and welded one layer at a time.

As shown in FIGS. 4 (1) and 2 (2), the joint members 1 and 2 are made of containers, pipes or the like that require single-sided welding to be laminated from the back surfaces 1b and 2b of the groove lower portion to the upper portions of the groove surfaces 1a and 2a It is a narrow groove joint in which a thick plate tube member or plate member such as a guide tube is abutted. Moreover, it is a narrow groove joint in which the insert material 19 is provided at the groove bottom center. In particular, it is a joint member for welded structures used in nuclear power plants, thermal power plants, chemical plants, etc., and requires single-sided welding, and the residual stress generated in the back bead 15 on the back side and in the vicinity thereof. It is necessary to improve the compressive stress. The material of the joint members 1 and 2 is mainly austenitic stainless steel (for example, SUS304 series, SUS316 series). Moreover, the other austenitic stainless steel (For example, SUS309 type | system | group, SUS321 type | system | group, SUS347 type | system | group) different from this material may be sufficient. Furthermore, low carbon steel and low alloy steel different from stainless steel may be used.

  Moreover, when welding the groove joint of a pipe member, this pipe member itself becomes a restraint body, and can suppress the warp deformation and the wrinkle squeezing deformation which occur in the welding process. In the case of welding the groove joint of the plate member, the deformation can be suppressed by providing a deformation restraining jig for restraining warpage deformation and wrinkle squeezing deformation generated in the welding process and a restraining member corresponding thereto.

  The groove width w including the groove width w of the groove bottom or the width of the insert material 19 provided at the center of the groove bottom is a dimension range of 3 mm to 7 mm, and the groove angle to the groove upper portion (single-side angle θ (Doubled angle) is formed in the range of 2 to 8 degrees, preferably the groove bottom width w is in the range of 4 mm to 6 mm, and the groove angle is in the range of 4 to 6 degrees. As a result, the above-mentioned laminated welding with low heat input switching can be reliably performed, and at the same time, the groove cross-sectional area to be welded is greatly reduced, shrinkage deformation due to welding and crimping deformation are suppressed, and the amount of welding wire used is reduced. Can be reduced. When the groove bottom width w becomes smaller than 3 mm, the gap between the outer surface of the electrode 6 inserted into the groove 3 and the wall surface of the groove 3 is extremely narrow, and the first layer welding and the subsequent layer welding are performed. The entire groove width contracts due to the contraction deformation caused by the above, and contact of the electrode 6 with the groove wall surface and arcing are likely to occur, and it is difficult to perform lamination welding up to the upper part of the groove. On the other hand, when the groove bottom width w is wider than 7 mm, the number of welding passes and the amount of wire welding increase due to an increase in the groove cross-sectional area, and the shrinkage deformation and the wrinkle tightening deformation due to welding increase. Therefore, the range of the groove bottom width w was specified as 3 mm or more and 7 mm or less.

  The root face f at the bottom of the groove can be easily melted to the back side by forming it in the range of about 1 to 2.5 mm, preferably about 1.5 mm. In addition, by providing the insert material 19 in the center of the groove bottom, it is possible to alleviate the effects of steps and gaps that are likely to occur at the butt portion of the groove bottom. A good back bead width can be obtained.

In arc welding, as shown in FIG. 4 (3), power is supplied from a TIG welding power source 8 between the tip of the non-consumable electrode 6 provided on the welding torch 7 (TIG torch) and the joint members 1 and 2. Then, the arc 10 is generated in the groove, and the wire 5 is fed and melted to the welding portion of the arc 10 for welding. The TIG welding power source 8 is a welding power source capable of switching between pulse arc welding and DC arc welding by a switch for selecting a welding mode. When pulsed arc welding is selected, each condition value such as high peak current, low base current, and arc voltage required for power supply for pulsed arc welding can be output arbitrarily, and pulse frequency can be arbitrarily changed (for example, 1 Hz to maximum 500 Hz) ) Is also possible. For example, low pulse welding in the 1-10 Hz region,
Medium pulse welding in the 100 Hz region and high pulse welding in the 100 to 500 Hz region can be performed. When DC arc welding is selected, desired DC current and arc voltage (average arc voltage) corresponding to the average welding current can be output.

  The welding control device 9a controls the traveling of the welding carriage 4 (omitted) on which the welding torch 7 and the wire 5 are mounted, the output of the TIG welding power source 8, and the vertical and horizontal positions of the welding torch 7 (electrode 6). Moreover, the command control which adjusts the vertical and horizontal positions of the wire 5 of the wire supply device 11 that supplies the wire 5 to the arc 10 welding portion is performed. Further, the operation pendant 9b is connected to the welding control device 9a and incorporates welding condition adjusting means, torch position and wire position adjusting means.

  In the control device, each welding condition can be set, or these condition values can be interrupted and adjusted during welding. Especially when pulse arc welding is selected, peak current and peak time, base current and base time, or time ratio of pulse frequency and peak current, peak voltage or base used for electrode height control (AVC control) Voltage or average arc voltage, peak wire feed and base wire feed, welding speed or running speed corresponding to this welding speed, and if DC arc welding is selected, control of average welding current and electrode height (AVC control) The average arc voltage or arc length, wire feed speed, welding speed, or traveling speed corresponding to this welding speed used in the above is adjusted as appropriate.

  Furthermore, the positional deviation of the welding torch 7 (electrode 6) and the positional deviation of the wire 5 can be adjusted by the torch position and wire position adjusting means.

  Further, a welding apparatus for performing narrow groove welding for switching heat input includes a welding torch 7 capable of attaching / detaching a non-consumable electrode 6 to be inserted into the groove 3 and a welding line direction of the groove joint. , Arbitrary movement in the vertical and horizontal directions, supply of the welding wire 5 to the tip portion of the welding torch 7 or the welding portion of the arc 10 and selection of a welding cart (omitted) capable of adjusting the vertical and horizontal positions, pulse arc welding or DC arc welding, TIG welding power source 8 capable of controlling the output of predetermined welding conditions, setting of conditions of heat input range used in first layer back wave welding process 53, first lamination for laminating and welding up to a specific laminated bead height Hb after first layer welding A condition setting means capable of setting conditions for the first heat input range used in the welding step 41, and thereafter setting conditions for the second heat input range used in the second layer welding step 42 for laminating and welding to the final layer; This article A welding control device 9a for driving and controlling the welding carriage in accordance with an instruction from a setting means, controlling the output of the TIG welding power source 8, and adjusting the horizontal and vertical positions of the welding torch 7, the feed amount of the welding wire 5 and the horizontal and vertical positions; Can also be provided.

  From the welding apparatus having such a configuration, the first layer back wave welding step of forming a back bead on the back side of the groove bottom, the first layer welding step of layer welding to a specific layer height, and the remaining groove portion It is possible to reliably perform the second lamination welding process in which the lamination welding is performed up to the final layer above the groove. As described above, this series of welding operations suppresses the wrinkling deformation that occurs on the welding surface side, and the compressive stress remains in the back bead portion on the back side on the opposite side and in the vicinity thereof, and is applied in a corrosive environment. However, stress corrosion cracking can be prevented. In addition, there is no need to water-cool the inner surface during welding, or to install an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be done, manufacturing costs can be reduced, and good welding quality is ensured In addition, the amount of wire used and the time required for welding can be reduced.

As the shielding gas 33 flowing through the arc 10 welding portion in the groove 3, a mixed gas containing Ar + several percent H ₂ or a mixed gas containing Ar + several tens percent He may be used. For example, when a mixed gas containing Ar + 3 to 7% H ₂ is used, energy density and arc concentration are increased as compared with inert pure Ar gas, the molten state and penetration can be improved, and the welding speed is improved.

Further, the electrode 6 is a non-consumable tungsten electrode rod having a narrow diameter and a circular cross section narrower than the groove bottom width w, and is made of a high melting point material containing La ₂ O _3, W containing Y ₂ O ₃ , ThO _2. It is only necessary to use a W-shaped electrode rod. For example, by inserting an electrode rod having a circular cross section with an outer diameter φ2.4 or φ1.6 narrower than the groove bottom width w (an electrode with only the electrode tip processed into a conical shape) into the groove, Even if the electrode is not an expensive electrode having a flat cross section (non-circular cross section), arc welding in the groove can be properly performed. In addition, the small-diameter electrode having a circular cross section is inexpensive and easy to use, and can be reused by simply repolishing the electrode tip of the consumable part even when replacing the electrode.

  As shown in FIG. 5, the welded parts of the joint members 1 and 2 are identified from the first layer weld metal part 410 in which the back bead 15 is formed on the back side of the groove bottom part and the part in contact with the first layer weld metal part 410. The first laminated weld metal portion 411 formed by lamination welding in the first heat input range Q1 up to the laminated bead height Hb, and the groove from the remaining groove portion in contact with the first laminated weld metal portion 411 A second laminated weld metal part 422 formed by lamination welding in the second heat input range Q2 up to the upper final layer 39.

  The second laminated weld metal part 422 is opened from the portion in contact with the first laminated weld metal part 411 using one or more heat input conditions smaller than the plurality of heat input conditions used in the laminate welding. The tip part is formed by laminating and welding up to the final layer 39 at the upper part of the groove.

  As a result, squeezing deformation that occurs on the welding surface side is suppressed to a small extent, and compression stress remains in the back bead portion on the back side on the opposite side and its vicinity due to suppression of welding deformation and suppression of tensile stress. However, it can prevent stress corrosion cracking and contribute to longer life.

  In addition, there is no need to water-cool the inner surface during welding, or to install an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be done, manufacturing costs can be reduced, and good welding quality is ensured In addition, the amount of wire used and the time required for welding can be reduced.

  As described above, the laminated bead height Hb in the specific range is 3/10 or more and 7/10 or less of the plate thickness T of the joint members 1 and 2 to be welded. The thickness T is preferably 2/5 or more and 3/5 or less. The first heat input range Q1 may be 4 kJ / cm or more and 12 kJ / cm or less. The first laminated weld metal part 411 may be formed by laminating and welding up to the specific range of the laminated bead height Hb using one or more heat input conditions from the heat input range Q1. The second heat input range Q2 is 1 kJ / cm or more and 6 kJ / cm or less, preferably 2 kJ / cm or more and 4 kJ / cm or less. By laminating and welding from this heat input range Q2 to the final layer at the upper part of the groove using one or a plurality of heat input conditions, the second laminated weld metal part 422 is formed as described above. Compressive stress remains on the back bead portion on the back side and in the vicinity thereof due to suppression of tensile stress and suppression of tensile stress, and even when applied in a corrosive environment, stress corrosion cracking can be prevented, contributing to a longer life.

  Further, when the joint members 1 and 2 to be welded are austenitic stainless steel materials (for example, SUS304 series, SUS316 series), at least the first laminated weld metal part 411 or the first layer welded metal part 410 and the first laminated weld. The metal part is formed on the inner surface side or the bottom surface side exposed to a corrosive environment such as high-temperature water by welding an austenitic wire of the same type as the material of the joint members 1 and 2 (for example, a Y308 series wire or a Y316 series wire). From the weld back surface portion to a specific lamination height, it can be filled with the same kind of austenitic weld metal as the joint material, and at the same time, compressive stress can remain in the back bead portion and the vicinity thereof. Also for the second laminated weld metal portion 422, the austenite wire of the same type as the material of the joint members 1 and 2 may be welded. Further, if the joint members 1 and 2 to be welded are other austenitic stainless steel materials different from the austenitic stainless steel materials (for example, SUS309 series, SUS321 series, SUS347 series), the same kind of austenitic wire ( For example, Y309 series and Y347 series wires) may be welded. Furthermore, if the joint member is a low carbon steel or low alloy steel different from stainless steel, the same type of wire as the joint member may be used.

  Further, the first laminated weld metal part 411 is laminated and welded one layer at a time using one or more welding conditions of the first input heat quantity range Q1, and the second laminated weld metal part 422 is Low heat input can be achieved by using one or more welding conditions in the second heat input calorie range Q2 and performing layer-by-layer welding for each layer or layer-by-layer welding with one pass for each layer. Even under the conditions, the groove wall surface can be reliably melted, and good weld beads without defects can be obtained from the bottom of the joint members 1 and 2 to the final layer at the top of the groove. In addition, as described above, by suppressing welding deformation and suppressing tensile stress, compressive stress remains in the back bead portion and its vicinity on the back side, and even when applied in a corrosive environment, stress corrosion cracking can be prevented, and long Contributes to longer life.

  Further, the welding wire can be supplied and welded to the arc welding portion without energization, or the welding wire can be supplied and welded to the arc welding portion while being heated. It is possible to increase the welding amount and improve the welding efficiency due to the wire heating energization.

  FIG. 6 is a weld cross section of another embodiment showing an outline of welding of a narrow groove welding method and a welded structure according to the present invention. The main difference from FIG. 5 is that a nickel alloy inconel wire or martensite wire is used in the second lamination welding. Others are the same as FIG. Moreover, FIG. 7 is explanatory drawing which shows the relationship between temperature and the average linear expansion coefficient of each material.

  As shown in FIG. 6, when the joint members 1 and 2 are austenitic stainless materials, the first laminated weld metal part 411 or the first layer weld metal part 410 and the first laminate weld metal part 411 An austenitic wire 61 of the same type as the material of the members 1 and 2 is welded, and a nickel alloy inconel wire 62 or martensitic wire 63 is welded to the second laminated weld metal portion 422 laminated on the upper part. Yes. By welding in this way, the compressive stress remaining in the back bead portion on the back side and in the vicinity thereof can be increased due to the effect of suppressing the welding deformation caused by the deviation of the linear expansion coefficient and the martensitic transformation.

  In addition, the second laminated weld metal part 422 is laminated and welded one layer at a time, or is divided into a plurality of passes and laminated welded one layer at a time. However, it is possible to reliably melt the groove wall surface and obtain each weld bead having no defects up to the final layer above the groove. At the same time, as described above, the effect of suppressing welding deformation caused by the deviation of the linear expansion coefficient can increase the compressive stress remaining in the back bead portion and its vicinity on the back side, contributing to a longer life by preventing stress corrosion cracking. To do.

Further, the second laminated weld metal part 422 is laminated and welded with a smaller heat input than the first laminated weld metal part 411, so that the first laminated weld metal part 411, the second laminated weld metal part 422, It is possible to change the shape of the welded cross section in the vicinity of the contact portion or the vicinity thereof. This shape change may be any one or more of bead width change, penetration change, laminate ripple change, and metallographic change. For example, cross-section observation is facilitated by the denseness of laminated ripples, and the quality is improved by miniaturizing the metal structure.

  Further, the amount of deformation (dent) on the welding surface side remaining after the final layer is welded varies depending on the plate thickness, heat input, and groove shape, but is preferably about 1.5 mm or less. Preferably it is 1.0 mm or less. By suppressing the wrinkle-squeezing deformation to a small extent, the tensile stress generated on the back side can be suppressed to a small level, and compressive stress can be left in the back bead portion and the vicinity thereof. For example, if the back bead part on the back side and the base metal heat-affected part in the vicinity of the back layer can be formed on the compression side from the yield stress of the material after welding of the final layer, even a welded structure used in a corrosive environment Can prevent stress corrosion cracking.

As shown in FIG. 7, the average linear expansion coefficient (square line) of an Inconel wire (for example, Inconel 82 wire) is, for example, about 13.4 (× 10 ⁻⁶ / ° C.) at about 100 ° C. SUS304 material (line of ◇) is 3.9 (× 10 ⁻⁶ / ° C.) smaller than about 17.3 (× 10 ⁻⁶ / ° C.). In addition, it is about 2.6 (× 10 ⁻⁶ / ° C.) smaller than the average linear expansion coefficient (Δ line) of the SUS316L wire. Due to the deviation of the average linear expansion coefficient, a deformation suppressing action acts on the weld metal portion 422, and the compressive stress remaining in the back bead portion and the vicinity thereof becomes high.

  In addition, the average linear expansion coefficient (O line) of martensite wire is smaller than the average linear expansion coefficient of other materials, and has a characteristic of further drastically decreasing when the temperature is lowered. The martensitic wire is a martensitic stainless wire that has good fusion properties with the welded joint material of austenitic stainless steel, and contains at least 8 to 12% by weight of Ni of chemical composition and 8 to 12% by weight of Cr. A martensitic stainless wire having a martensitic transformation start temperature of 100 ° C. or higher and 300 ° C. or lower may be used. Therefore, the second laminated weld metal part 422 can be laminated and welded using a martensite wire instead of the Inconel wire. By laminating with this martensite-based wire, the deformation of the average metal expansion coefficient and the weld metal part that causes martensitic transformation have a deformation suppressing action and an expanding action, and the compressive stress remaining in the back bead portion and its vicinity can be further increased. .

  Table 1 is an example of welding conditions, and is a welding condition that can be used in the first layer back wave welding and the first and second laminated weldings shown in FIG. 1, FIG. 5, FIG. 6, and FIG. .

  FIG. 8 is an example showing a cross-sectional photograph of pipe welding performed by the narrow groove welding method of the present invention. FIG. 9 is an explanatory diagram showing the relationship between the stacking height in the pipe welding shown in FIG. 8 and the heat input amount for each welding pass, the groove shoulder width, the shrinkage amount on the back side, and the dent amount due to the front side squeezing. The pipe of the welded joint is SUS304 stainless steel with an outer diameter of 314 mm, a plate thickness of 29.5 mm, and a material. Moreover, the austenitic wire (Y308L) of the same kind as a piping member is used for the welding wire. The cumulative number of passes that are laminated and welded from the first layer to the last layer is 31 layers and 31 passes, but varies depending on differences in the groove cross-sectional area to be laminated and welded, the amount of heat input for each welding pass, the amount of wire welding, and the like.

As shown in FIGS. 8 and 9, in (a) first layer welding (back bead formation welding, first layer weld metal part 410) after tack welding, a back bead 15 is formed on the back surface side. In the first laminated welding after the first layer welding ((b) first half welding, first weld metal part 411), the specific heat input condition (4 ≦ Q1 ≦ 12 kJ / cm) in the first heat input range Q1 or Lamination welding is performed using a plurality of specific welding conditions corresponding to this. Further, in the second laminated welding ((c) second-half welding, second welded metal portion 422), the first entry is made at a point where the laminated bead height Hb (Σh + f) reaches about half of the plate thickness T. Switch to the specific heat input condition (2 ≦ Q2 ≦ 5 kJ / cm) in the second heat input range Q2 (2 ≦ Q2 ≦ 5 kJ / cm) smaller than the heat input condition used in the heat amount range Q1 or the welding condition corresponding thereto, or the specific welding condition corresponding thereto Lamination welding is performed up to the final layer at the top of the groove. The shoulder width w on the groove upper surface and the shrinkage ΔL2 on the back surface side (shrinkage of a predetermined length L) are mainly due to the progress of shrinkage deformation in the groove width direction that occurs in the process of the first layer welding and the first laminated welding. It has increased. In addition, the amount of depression Δc due to wrinkling generated on the front side of the welding (claw drawing deformation) is a result generated in the progress of the second laminated welding. By performing welding in this way, a good weld cross section as shown in FIG. 8 can be obtained. Further, by forming the surface-side dent amount Δc remaining after the end of welding, the tensile stress generated on the back side can be suppressed small, and the compressive stress can remain in the back bead portion and its vicinity. Here, pipe welding is shown as an example, but welding of plate members having different joint shapes may be used.

  FIG. 10 shows an example of the residual stress measurement result on the inner surface of the pipe after welding, and the welding is as described in FIGS. 8 and 9. Residual stress measurement is based on the strain gauge opening method (a strain gauge is attached to the measurement point inside the pipe, the strip-cut primary cut-open process goes through the final slit cut-out tertiary open process, and the open strain value in the circumferential direction. This is a result of measurement using a calculation result of circumferential residual stress σθ and axial residual stress from the measurement result of εθ and the axial open strain value εz. As shown in FIG. 10, the residual stress in the back bead portion on the back side and the vicinity thereof is a compressive stress having a maximum axial residual stress σz in the direction perpendicular to the weld line (circled line) of about −35 MPa. The circumferential residual stress σθ (line marked with ◆) in the weld line direction is a compressive stress of about −138 MPa at the maximum. The above compressive stress is the value at the bead central portion, and higher compressive stress is obtained at the bead boundary and weld heat affected zone, which are the most important for preventing stress corrosion cracking.

  In this way, if the narrow groove welding method of the present invention is applied, the backside bead portion on the back side and the residual stress in the vicinity thereof can be improved to compressive stress, and even when applied in a corrosive environment, stress corrosion cracking is prevented. Can contribute to longer life. In addition, there is no need to water-cool the inner surface during welding, or to install an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be done, manufacturing costs can be reduced, and good welding quality is ensured In addition, the amount of wire used and the time required for welding can be reduced.

It is explanatory drawing which shows one Example of the welding procedure outline | summary of the narrow groove welding method and its welded structure of this invention. It is explanatory drawing which shows one Example of the stress analysis result of the back bead part which changes in the welding process of a groove joint. It is explanatory drawing which shows another Example of the stress analysis result of the back bead part which changes in the welding process of a groove joint. It is explanatory drawing of one Example which shows the groove shape and apparatus schematic structure regarding the narrow groove welding method and welding structure of this invention. It is a welding cross section of one Example which shows the welding outline of the narrow groove welding method of this invention, and a welded structure. It is the welding cross section of another Example which shows the welding outline | summary of the narrow groove welding method and welding structure of this invention. It is explanatory drawing which shows the relationship between temperature and the average linear expansion coefficient of each material. It is one Example which shows the cross-sectional photograph of the piping welding constructed | assembled with the narrow groove welding method of this invention. It is explanatory drawing which shows the relationship between the lamination | stacking height in the pipe welding shown in FIG. 8, the amount of heat inputs for every welding path, a groove shoulder width, the shrinkage | contraction amount of a back side, and the amount of dents by the front side squeezing. It is one Example of the residual stress measurement result of the piping inner surface after welding construction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 2 ... Joint member, 1b, 2b ... Groove back surface, 3 ... Inside groove, 4 ... Welding cart, 5 ... Wire, 6 ... Electrode, 7 ... Welding torch, 8 ... TIG welding power supply, 9a ... Welding control apparatus 9b: Operation pendant, 10: Arc, 11: Wire feed motor, 15: Back bead, 19: Insert material, 21: Bead section of first layer welding, 39: Bead section of final layer, 41: First layer Welding step, 42 ... second lamination welding step, 51 ... groove shape manufacturing step, 52 ... weld preparation step, 53 ... first layer backside welding step, 56 ... first heat input range Q1, 57 ... second Heat input range Q2, 61 ... austenitic wire, 62 ... inconel wire, 63 ... martensite wire,
410 ... first layer weld metal part, 411 ... first weld metal part, 422 ... second weld metal part, T ... plate thickness, Hb ... laminated bead height, w ... groove bottom width, f ... root face, 2θ: groove angle.

Claims (11)

From the bottom to the top of a groove joint formed by abutting a pipe member or plate member made of austenitic stainless steel, one-side welding while welding austenitic stainless steel wire in the groove by arc welding of non-consumable electrode method In the narrow groove welding method for improving the residual stress on the back surface side of the groove bottom by the one-side welding,
A first layer back welding process for forming a back bead on the back side of the groove bottom, and a first layer welding for performing a layer welding in a first heat input range up to a specific layer bead height after the first layer back welding process And after the first laminating welding step, the remaining groove portion is connected to the upper portion of the groove using one or more heat input conditions smaller than the plurality of heat input conditions used in the first laminating welding process . A second laminating process for laminating and welding in the second heat input range up to the final layer ,
A narrow groove welding method, wherein compressive residual stress is formed in a back bead portion on the back surface side and a heat-affected portion in the vicinity thereof . 2. The narrow gap welding method according to claim 1, wherein a first heat input range used in the first laminating welding process is 4 kJ / cm or more and 12 kJ / cm or less, and the first laminating welding process uses the first heat input range. The heat input range of No. 2 is 1 kJ / cm or more and 6 kJ / cm or less, and uses a heat input condition smaller than the heat input condition used in the first laminating welding process. . 2. The narrow groove welding method according to claim 1, wherein the specific laminated bead height is in a range of 3/10 to 7/10 of a plate thickness . 2. The narrow groove welding method according to claim 1, wherein the groove joint is formed with a groove bottom width in a range of 3 mm to 7 mm and a groove angle in a range of 2 degrees to 8 degrees. Narrow groove welding method. 2. The narrow gap welding method according to claim 1, wherein in the first laminating welding step, laminating welding is performed one layer at a time using heat input conditions in the first heat input range, and the second laminating process is performed. In the welding process, one layer per layer is laminated and welded using a heat input condition smaller than the heat input condition used in the first laminating welding process, or a plurality of passes are laminated and laminated welded at an upper layer portion in the middle. A narrow groove welding method characterized by The narrow gap welding method according to claim 1 or 5, wherein in the second laminating step, the austenitic stainless wire is replaced with an inconel wire or martensitic wire of a nickel alloy, and the replaced wire A narrow groove welding method, wherein welding is performed while welding in the groove. One-sided welding is performed by welding austenitic stainless steel wire into the groove by arc welding using a non-consumable electrode method from the bottom to the top of the groove joint formed by abutting a pipe member or plate member made of austenitic stainless steel. In addition, in the welded structure in which the residual stress on the back side of the groove bottom is improved by the one-side welding,
A first-layer weld metal part having a back bead formed on the back side of the groove bottom part, and a first weld formed by laminating and welding in a first heat input range from a portion in contact with the first-layer weld metal part to a specific laminate bead height And a groove upper portion from the remaining groove portion in contact with the first laminated weld metal portion using at least one heat input condition smaller than the plurality of heat input conditions used in the laminate welding. A second laminated weld metal part formed by laminating and welding up to the final layer of
A welded structure in which compressive residual stress is formed in a back bead portion on the back surface side and a heat-affected portion in the vicinity thereof. The welded structure according to claim 7, wherein the first heat input range is 4 kJ / cm or more and 12 kJ / cm or less, the second heat input range is 1 kJ / cm or more and 6 kJ / cm or less, and A welded structure obtained by performing lamination welding using a heat input condition smaller than the heat input condition used for forming the first laminated weld metal part. 8. The welded structure according to claim 7, wherein the specific laminated bead height is in a range of 3/10 to 7/10 of a plate thickness. 8. The welded structure according to claim 7, wherein the amount of deformation (dent) on the front side is 1.5 mm or less. 8. The welded structure according to claim 7, wherein at least a portion where the first laminated weld metal portion and the second laminated weld metal portion are in contact with each other, a weld cross section in the vicinity thereof, or a weld cross section similar thereto is formed. A welded structure characterized in that the shape change is at least one of a bead width change, a penetration change, a laminate ripple change, and a metallographic change .

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