JP4538394B2 - Residual stress improvement welding method and welded structure - Google Patents

Description

  The present invention relates to a residual stress improving welding method and a welded structure for improving a residual stress in a back bead portion on a back surface side and a vicinity thereof generated by one-side welding of a pipe member or a plate member of a groove joint.

  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. It is known that crack formation (sensitization of material) against corrosion is enhanced by the formation of the above. 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 when 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 significantly reduce the tensile stress remaining on and near the surface of the welded portion exposed to a corrosive environment such as high-temperature water to a compressive stress.

  Conventionally, several welding methods and welding apparatuses for reducing the tensile residual stress of the welded material portion have been proposed. For example, 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 welding assembly, and the outside of the pipe is heated so that the inner surface of the pipe and the pipe are heated. It has been proposed to generate a temperature difference with the outer surface, to cause tensile yielding of the inner surface of the tube, and compression yielding of the outer surface of the tube.

  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), the high-frequency heating coil is moved while following the linear welded part, and this high-frequency heating is performed. It has been proposed to have a procedure for heating a welded part to a temperature higher than the stress yield point temperature by a coil, and a procedure for rapidly cooling a jet of cooling water in an overheated region.

  On the other hand, in the method and apparatus for joining metal parts described in Patent Document 3 (Japanese Patent Publication No. 9-512485), the welding material is continuously applied in the vicinity of the tip of the electrode tip that travels at a selected speed (127 cm / min or more). A welding current is continuously melted in the groove by a discharge current from the tip, and a weld bead is formed, and the electrode is joined and electrically connected to the tip. It has been proposed to achieve a final residual stress state that is compressible over a predetermined number of weld passes and is generated without an external heat sink medium.

  Patent Document 4 (Japanese Patent Publication No. 9-512486) is filed by the same applicant as Patent Document 3. In the method of reducing the residual stress in the weld metal part using the high torch running speed described in Patent Document 4, the torch running speed is faster than 254 mm (10 inches) per minute during the cap pass (final finish welding). Heating (melting) the far surface (groove surface side) of the welded joint to generate a temperature distribution between the near surface (groove bottom surface side) and the far surface; cooling the far surface and compressing It has been proposed that the step of generating stress or a small tensile stress on the near surface is performed without a heat sink (water cooling) on the inner surface side.

  Moreover, in the piping improvement method described in Patent Document 5 (Japanese Patent Application 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.

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)

  In the case of the said patent document 1, it is thought that it is an effective method for changing the tensile residual stress of the piping inner surface which had arisen at the time of welding assembly into a compressive residual stress. However, not only large-scale high-frequency heating equipment different from the welding equipment is required, but also 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 after welding is required. Become.

  Moreover, in the case of the said patent document 2, the device for reducing a tensile residual stress is made | formed. However, after completion of welding, high-temperature heating is performed by a high-frequency coil that moves on the surface of the linear welding site, and the superheated area is rapidly cooled by jetting cooling water, so that mobile heating and water-cooling facilities are required. In addition, 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 possible to drastically reduce. 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. In addition, 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. .

  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 to provide a welding method for improving residual stress and a welded structure thereof.

The welding method for improving residual stress according to the present invention is a welding method for improving residual stress that improves the backside bead portion on the back side generated by one-side welding of a groove joint formed by abutting a pipe member or a plate member and the residual stress in the vicinity thereof. In this welding process, welding wire supplied to the arc welding part in the groove is welded by arc welding using a non-consumable electrode method, and a back bead is formed on the back side of the groove bottom by first layer welding. after allowed to until laminated bead height of 2/5 or 3/5 or less of the range of the plate thickness by laminating welded at 4 kJ / cm or more 12 kJ / cm or less in the heat input range, thereafter, the groove from the rest of the groove portions Switch to welding conditions with a heat input smaller than the heat input range up to the final layer of the upper layer and perform laminar welding to form compressive residual stress in the back bead part and the heat affected part in the vicinity thereof, or a part of the back bead the following 100MPa The compressive residual stress Zhang stresses are mixed, characterized in that to form the heat-affected portion.

Further, the welded structure of the present invention is a welded structure that improves the backside bead portion on the back side generated by single-sided welding of a groove joint formed by abutting a pipe member or a plate member and the residual stress in the vicinity thereof. Heat input range from 4kJ / cm to 12kJ / cm from the part contacting the first layer weld metal part where the back bead is formed on the back side of the bottom to the laminated bead height in the range of 2/5 to 3/5 of the plate thickness Welding with a heat input smaller than the heat input range from the first groove weld metal part formed by lamination welding in step 1 and the remaining groove part in contact with the first metal weld weld part to the final layer on the groove upper part. A second laminated welded metal part formed by laminating and switching to conditions, and forming a compressive residual stress in the back bead part and the heat affected part in the vicinity thereof, or a part of the back bead of 100 MPa or less Compression residue with mixed tensile stress Characterized in that to form the stress on the heat affected portion.

That is, in the residual stress improving welding method of the present invention, after a back bead is formed on the back side of the groove bottom by first layer welding, a heat input range of 4 kJ / cm or more and 12 kJ / cm or less up to a specific laminated bead height. After that, welding is performed with a heat input smaller than the above heat input range from the remaining groove portion to the final layer at the top of the groove , and compression residual is applied to the back bead portion and the heat affected portion in the vicinity thereof. Even if it is applied in a corrosive environment, stress corrosion cracking can be prevented by forming stress or forming a compressive residual stress in the heat-affected zone where a slight tensile stress is mixed in a part of the back bead. it can. In addition, there is no need to water-cool the inner surface during welding, or to provide an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be performed, the production cost can be reduced, good welding Quality can be ensured and the amount of wire used and the time required for welding can be reduced.

  In addition, the groove joint can be formed into a laminated bottom with a low heat input by forming a groove bottom width in a range of 4 mm to 7 mm and a groove angle in a range of 2 degrees to 8 degrees, It is possible to reduce the groove cross-sectional area to be welded, suppress shrinkage deformation and squeezing deformation due to welding, and reduce the amount of welding wire used. 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.

  Also, in the above welding, non-consumable electrode type pulse arc welding or direct current arc welding is performed, and welding is performed by supplying a welding wire to the arc welding portion in the groove to weld it from the groove bottom to the groove top. It is possible to form a beautiful weld bead that does not generate spatter. Furthermore, the welding wire uses the same kind of welding wire as the pipe member or plate member, so that even in a stainless steel material or a low carbon steel material, the inside of the groove to be welded is the same kind as the pipe member or plate member. It can be filled reliably with a welding wire. 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. In addition, by using nickel alloy inconel wire instead of the austenite wire in the latter half of the lamination welding, the effect of suppressing welding deformation caused by deviation of the linear expansion coefficient from the pipe member or plate member can be reduced. A large compressive residual stress is formed in the back bead portion and the heat affected zone in the vicinity thereof, and stress corrosion cracking can be prevented in advance.

  The specific laminated bead height is in the range of 2/5 or more and 3/5 or less of the plate thickness, and laminated welding is performed within a predetermined heat input range (4 kJ / cm or more and 12 kJ / cm or less) up to the laminated bead height. By doing so, shrinkage deformation (plastic deformation) in the groove width direction progresses appropriately, and the residual stress in the back bead portion and its vicinity can be changed from tensile stress to maximum compressive stress. This compressive stress changes greatly depending on the height of the laminated beads, heat input, groove shape, and plate thickness, which are laminated and welded in the groove, and becomes maximum around the height of the laminated beads where the shrinkage deformation in the groove width direction converges. . The laminated bead height at which the shrinkage deformation converges is approximately half of the plate thickness of the groove joint to be welded or the vicinity thereof. Therefore, the maximum compressive stress can be obtained most effectively by laminating and welding up to a specific range of laminated bead heights within the appropriate heat input range corresponding to the groove shape and plate thickness. On the other hand, in the latter layer welding, one or a plurality of heat input conditions in the heat input range of 2 kJ / cm or more and 6 kJ / cm or less from the remaining groove part to the final layer on the groove upper part or welding conditions corresponding thereto. By performing laminating welding using, it is possible to suppress the progress of wrinkling deformation that occurs on the welding surface side. The tensile stress applied to the back bead portion on the reverse side on the opposite side and the vicinity thereof is suppressed by the suppression of the wrinkle deformation, and a compressive residual stress is formed on the back bead portion and the heat affected zone in the vicinity thereof after the welding is completed. A compressive residual stress in which a slight tensile stress is mixed in a part of the back bead can be formed in the heat-affected portion.

In the welded structure of the present invention, the heat input range is 4 kJ / cm or more and 12 kJ / cm or less from the part contacting the first layer weld metal part where the back bead is formed on the back side of the groove bottom part to the specific laminated bead height. Laminate welding with a heat input smaller than the above heat input range from the first groove weld metal part formed by lamination welding and the remaining groove portion in contact with the first metal weld weld part to the final layer on the groove upper part A compressive residual in which a compressive residual stress is formed in the back bead portion and a heat-affected portion in the vicinity thereof, or a slight tensile stress is mixed in a part of the back bead. By forming stress in the heat-affected zone, stress corrosion cracking can be prevented even when applied in a corrosive environment.

  As described above, according to the residual stress improving welding method and its welded structure of the present invention, stress corrosion cracking can be prevented even when applied in a corrosive environment such as a power plant or a chemical plant. In addition, there is no need to water-cool the inner surface during welding, or to provide an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be performed, the production cost can be reduced, good welding Quality can be ensured and the amount of wire used and the time required for welding can be reduced.

  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 diagram showing an example of the residual stress improvement method of the present invention and the stress analysis result of the back bead portion that changes during the welding process in the welded structure. Moreover, FIG. 2 is another Example and has shown the stress change when each is welded by several heat input and heat input switching. Furthermore, FIG. 3 is explanatory drawing which shows one Example of the welding-process outline | summary of the residual stress improvement method and its welded structure of this invention, (1) in the figure is the first layer in the groove bottom part of a groove joint. Welding cross section when reverse wave welding is performed, (2) is the welding cross section when laminating and welding to a specific laminated bead height Hb, and (3) is when laminating and welding from the remaining groove portion to the final layer above the groove It is a welding cross section.

  As shown in FIGS. 1 and 2, when a back bead is formed on the back side of the groove lower portion by initial layer welding, tensile stress is first generated in the back bead portion due to shrinkage deformation. This tensile stress tends to increase as the heat input increases. The amount of heat input required for forming the back bead varies depending on the thickness of the groove bottom (root face f), the width w, and the material, but it can be formed in a heat input range of approximately 4-20 kJ / cm. Preferably, it may be 6 to 12 kJ / cm. Note that the heat input Q (kJ / cm) per unit length is a relational expression of the average welding current Ia (A), average arc voltage Ea (V) and welding speed V (mm / s) {Q = Ia * Ea / (100 * V)}.

In the first laminated welding ((ii) first half welding) laminated after the first layer welding, as shown in FIGS. 1 and 2, the back bead portion is formed by the progress of shrinkage deformation (plastic deformation) in the groove width direction. In this analysis result, a large compressive stress is applied, and 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 heat-affected portion in the vicinity thereof varies greatly depending on the stack bead height Hb, the heat input Q, the plate thickness T, and the groove shape, which are laminated and welded in the groove. The shrinkage deformation in the tip width direction is maximized around the height of the laminated bead where convergence is reached. Further, the maximum value of the compressive stress shifts in the direction in which the ratio Hb / T of the laminated 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. position,
In the case of 40 mm, the position has changed to about 0.6. Therefore, in the above-mentioned (ii) first half welding, up to the laminated bead height Hb corresponding to each plate thickness T, multiple-pass laminating welding is performed under a heat input condition of an appropriate heat input amount range Q1 or a welding condition corresponding thereto, The maximum compressive stress can be obtained most effectively. The appropriate heat input range Q1 is 4 kJ / cm or more and 12 kJ / cm or less. Further, the specific laminated bead height Hb is approximately 3/10 to 7/10 of the plate thickness T (0.3 *
T ≦ Hb ≦ 0.7 * T), preferably 2/5 or more and 3/5 or less of the plate thickness T (0.4 * T ≦ Hb ≦ 0.6 * T). If the heat input Q1 used in the first laminating welding is less than 4 kJ / cm, it is added to the back bead portion on the back side and the vicinity thereof due to the melting region being too small and the shrinkage deformation in the groove width direction being insufficient. This is not preferable because the compressive stress may not increase. On the contrary, if this heat input Q1 is more than 12 kJ / cm, the compressive stress applied to the back bead portion on the back side and the heat affected portion in the vicinity thereof due to excessive melting region and increased shrinkage deformation in the groove width direction. Is not preferable because it may be suppressed and become smaller.

  Further, as shown in FIGS. 1 and 2, in the second lamination welding ((iii) second half welding), a low heat input (2 ≦ Q2 ≦ 6 kJ / second) from the remaining groove portion to the final layer on the groove upper portion. In order to reduce compressive deformation on the weld surface side and to suppress reaction tensile stress in the back bead part on the back side and the heat affected part in the vicinity, compressive residual stress is formed. Is done. The tensile stress generated in the back bead portion and the vicinity thereof mainly depends on the amount of heat input and the thickness of the plate, and tends to increase as the plate thickness T decreases. The analysis result is that the stress is suppressed and the compressive residual stress is formed. Therefore, in the above-mentioned (iii) second-half welding, even if the plate thickness T is changed by switching to a low heat input condition, even if the plate thickness T is different, compressive residual stress can be formed in the back bead portion and the heat affected portion in the vicinity thereof. it can. If the plate thickness is 40mm, (ii) the first half welding and (iii) second half welding can be applied under almost the same specific heat input conditions to leave compressive stress in the back bead and its vicinity. However, even if (iii) the lamination welding with low heat input switching is applied during the latter half welding, as described above, the compressive residual stress is reliably formed, and even if applied in a corrosive environment, the stress corrosion cracking Can be prevented, and can contribute to a longer life. In addition, it is not preferable that the heat input Q2 used in the (iii) second half welding is smaller than 2 kJ / cm because welding may not be possible and poor fusion may occur. On the other hand, if the heat input Q2 is more than 6 kJ / cm, it is preferable because the wrinkling deformation increases and the tensile stress applied to the back bead portion and the heat affected portion in the vicinity thereof increases and remains. Absent.

  As described above, in the residual stress improving welding method of the present invention, the back bead is formed on the back surface side of the groove bottom portion in the first layer welding, and then the specific laminated bead height is 4 kJ / cm or more and 12 kJ / cm or less. Lamination welding is performed in the heat input range, and then lamination welding is performed in the heat input range of 2 kJ / cm or more and 6 kJ / cm or less from the remaining groove portion to the final layer above the groove, and the back bead portion and its vicinity Even if it is applied in a corrosive environment by forming a compressive residual stress in the heat-affected zone or by forming a compressive residual stress in the heat-affected zone in which a small amount of tensile stress is mixed in a part of the back bead, stress corrosion Cracking can be prevented. In addition, there is no need to water-cool the inner surface during welding, or to provide an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be performed, the production cost can be reduced, good welding Quality can be ensured and the amount of wire used and the time required for welding can be reduced.

  On the other hand, as shown in FIG. 3, in the first groove shape manufacturing step 51, the joint member to be welded is machined to a predetermined size, transported to the 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, a welding torch, a wire, etc., starting up a welding power source and a welding control device, and preparing a welding operation.

  In the first layer backside welding step 53, as shown in FIG. 3 (1), the first layer backside welding 21 (P = 1) is performed to form a back bead width B in an appropriate range on the back 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 21 that requires the formation of the back bead, the heat input condition of the arc that can be melted up to the back surface side of the groove bottom or the welding condition corresponding thereto is output, and the width B of the back bead 15 is within the proper range. One or more condition factors (eg, 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 to form.

  As shown in FIG. 3 (2), the next first laminating welding step 41 has a specific heat input range Q1 (4 ≦ Q1 ≦) up to a specific lamellar bead height Hb after the initial layer backside welding step 53. 12 kJ / cm). By this first laminating welding step 41, shrinkage deformation (plastic deformation) in the groove width direction progresses moderately, and the moderately progressing plastic deformation causes residual on the back bead portion on the back side and the heat-affected portion in the vicinity thereof. The tensile stress to be changed can be changed to a maximum compressive stress. As described above, the specific laminated bead height Hb to be welded is 2/5 or more and 3/5 or less of the plate thickness T of the joint members 1 and 2, and one or more pluralities from the heat input range Q1. Lamination welding may be performed using heat input conditions or welding conditions corresponding thereto. For example, several passes after the initial layer welding are welded under a heat input condition of 7 to 8 kJ / cm, and then the heat input is reduced to 4 to 5 kJ / cm to a laminated bead height Hb of about half the plate thickness. Lamination welding is also possible. Further, the welding after the first layer welding can be laminated and welded to the specific laminated bead height Hb under a constant heat input condition of about 5 kJ / cm.

  Further, in the first laminating welding step 41, a specific laminating process is performed by laminating and welding one layer at a time using one or more heat input conditions of the specific heat input calorie range Q1 or welding conditions corresponding thereto. A good nuclear weld bead having no defects up to the bead height 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. Further, in the first laminating welding step 41, a plurality of passes in the course of laminating and welding one layer at a time using one or more heat input conditions of the specific input heat quantity range Q1 or welding conditions corresponding thereto. It is also possible to perform lamination welding with sorting.

  As shown in FIG. 3 (3), the next second lamination welding step 42 is the final layer 39 (P = N) from the remaining groove portion to the upper part of the groove after the first lamination welding step 41. Up to this point, it is a step of performing lamination welding using the heat input condition in the second heat input range Q2 (2 ≦ Q2 ≦ 6 kJ / cm) or the welding conditions corresponding thereto. By this second laminating welding step 42, the wrinkling and squeezing deformation that occurs on the welding surface side is suppressed to a small extent, and a compressive residual stress is formed in the back bead portion on the opposite back surface side and the heat-affected portion in the vicinity thereof, or Even if a compressive residual stress in which a slight tensile stress (for example, 100 MPa or less) coexists in a part of the bead is formed in the heat-affected portion and applied in a corrosive environment, stress corrosion cracking can be prevented. In the second lamination welding step 42, lamination welding may be performed from the second heat input range Q2 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. For example, a heat input condition of about 4 kJ / cm or a welding condition corresponding to the heat input condition can be selected and laminated welding can be performed up 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.

The heat input conditions for each welding pass are closely related to the condition factors of the average current Ia (A), average arc voltage Ea (V), and welding speed V (mm / s) to be set or output. Using the relational expression {Q = Ia * Ea / (100 * V)} so that the heat quantity Q (kJ / cm), the appropriate Ia,
What is necessary is just to determine the value of Ea and V. Further, although the arc voltage during DC arc welding changes slightly, an approximate average value may be adopted. 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 the increase / decrease control of the average current Ia or the increase / decrease control of 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 welding surface side is suppressed to a small extent, and compressive residual stress is formed in the back bead part on the opposite side and the heat affected part in the vicinity. Cracking can be prevented. In addition, there is no need to water-cool the inner surface during welding, or to provide an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be performed, the production cost can be reduced, good welding Quality can be ensured and the amount of wire used and the time required for welding can be reduced.

As shown in FIG. 3, in the first layer back wave welding process 53, the first and second lamination welding processes 41 and 42, non-consumable electrode type pulse arc welding or direct current 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 having no weld 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 instead of the austenite wire in the second lamination welding step 42, 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 the heat-affected portion in the vicinity thereof can be increased.

  FIG. 4 is an explanatory view of an embodiment showing a groove shape and an apparatus schematic configuration relating to a residual stress improving method and a welded structure according to 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 in the center of the groove bottom, and (3) is a schematic configuration of the welding apparatus and a weld cross section during welding. FIG. 5 is a welded cross section of an embodiment showing an outline of welding of a residual stress improving method and a welded structure according to the present invention. (1) is a welded cross section obtained by switching the heat input and laminating and welding one layer at a time. , (2) shows a welded cross-section welded by laminating and welding to a plurality of passes in the course of laminating and welding one pass at a time.

As shown in FIGS. 4 (1) and 2 (2), the joint members 1 and 2 are containers, pipes, and guides that require single-side welding to be laminated from the back surfaces 1b and 2b of the groove bottom to the top of the groove surfaces 1a and 2a. It is a narrow groove joint in which a thick plate tube member or a plate member such as a tube is abutted. Moreover, it is a narrow groove joint in which the insert material 19 is provided at the groove bottom center. Particularly, it is a joint member of a welded structure used in a nuclear power plant, a thermal power plant, a chemical plant, etc., and it is necessary to perform one-side welding, and on the back bead 15 on the back side and the heat-affected portion in the vicinity thereof. It is necessary to improve the resulting residual stress to compressive stress. The material of the joint members 1 and 2 is mainly austenitic stainless steel (for example, SUS304 series, SUS316 series). Also, other austenitic stainless steels (for example, SUS309 series, SUS321 series, SUS347 series) different from this material may be used. Furthermore, low carbon steel and low alloy steel different from stainless steel may be used.

  Moreover, when welding the joint members 1 and 2 of the groove | channel of a pipe member, this pipe member itself becomes a restraint body and can suppress the curvature deformation | transformation and wrinkle squeezing deformation which arise in a welding process. When welding the joint members 1 and 2 of the groove of the plate member, by providing a deformation restraining jig or a restraining member corresponding to the deformation restraining jig for suppressing warpage deformation or scissor deformation occurring in the welding process, Deformation can be suppressed.

  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 top (the one-side angle θ is 2). By forming the groove bottom width w in the dimension range of 4 mm to 6 mm and the groove angle in the dimension range of 4 degrees to 6 degrees. , Lamination welding with low heat input switching as described above can be performed reliably, and at the same time, the groove cross-sectional area to be welded is significantly reduced, shrinkage deformation due to welding and crimping deformation are suppressed, and the amount of welding wire used is reduced. can do. When the groove width w is 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 lamination welding are performed. The entire groove width contracts due to the contraction, and the electrode 6 is easily contacted with the groove wall surface and an arc is easily generated. On the other hand, when the groove width w is larger 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 squeezing deformation due to welding increase. Therefore, the range of the groove width w is specified as 3 mm or more and 7 mm or less. The root face f at the groove bottom 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. Further, 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. Thus, a substantially uniform back bead width can be obtained satisfactorily.

  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 pulse arc welding is selected, each of the condition values such as high peak current, low base current, and arc voltage necessary for power supply of the pulse arc welding can be arbitrarily output, and the pulse frequency can be arbitrarily changed (for example, 1 Hz to The maximum frequency is 500 Hz). For example, low pulse welding in the 1 to 10 Hz region, medium pulse welding in the 10 to 100 Hz region, and high pulse welding in the 100 to 500 Hz region can be performed. Further, when DC arc welding is selected, a 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 travel of the welding carriage 4 (omitted) on which the welding torch 7 and the wire 5 are mounted, controls the output of the TIG welding power source 8, and controls the left and right positions of the welding torch 7 (electrode 6), The vertical position is command-controlled as necessary, and the wire supply device 11 that supplies the wire 5 to the arc 10 welding part is command-controlled to adjust the horizontal position and vertical position of the wire 5 as necessary. 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.

  When pulse arc welding is selected, the peak current and its peak time, the base current and its base time, or the time ratio between the pulse frequency and peak current, the peak voltage used for electrode height control (AVC control) or Set each condition value of base voltage or average arc voltage, peak wire feed and base wire feed, welding speed or running speed corresponding to this welding speed, or adjust these conditions by interrupting them during welding be able to. When DC arc welding is selected, it corresponds to the average welding current, average arc voltage or arc length used for electrode height control (AVC control), wire feed speed, welding speed, or this welding speed. Each condition value of traveling speed can be set, or these condition values can be interrupted and adjusted during welding. Further, the position deviation of the welding torch 7 (electrode 6) and the position deviation of the wire 5 can be adjusted by the torch position and wire position adjusting means. Furthermore, 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.

  In addition, a welding apparatus for performing narrow groove welding includes a welding torch 7 capable of attaching / detaching a non-consumable electrode 6 to be inserted into the groove 3, and welding the welding torch 7 to the joint members 1 and 2 at the groove. Arbitrary movement in the line direction, up / down / left / right direction, welding wire 5 is supplied to the tip of the welding torch 7 or arc 10 welding part, and the welding cart (omitted) which can adjust the up / down / left / right position, pulse arc welding or direct current arc welding Selection, TIG welding power source 8 capable of controlling output of predetermined welding conditions, setting of heat input range condition used in first layer back wave welding process 53, first welding to be laminated to specific laminated bead height Hb after first layer welding Setting of conditions for the first heat input range used in the laminating welding step 41, and setting of the conditions for the second heat input range used in the second laminating welding step 42 for laminating and welding to the final layer thereafter Means and this A welding control device 9a that drives and controls the welding carriage in accordance with instructions from the setting means, controls the output of the TIG welding power source 8, and adjusts 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 up to a specific layer height, and the remaining groove portion The 2nd lamination welding process of carrying out lamination welding to the last layer of a groove upper part can be constructed reliably. By this series of welding operations, as described above, the wrinkle squeezing deformation that occurs on the weld surface side is suppressed to a small extent, and a compressive residual stress is formed on the back bead portion on the back side on the opposite side and the heat-affected portion in the vicinity thereof, or Even if a compressive residual stress in which a slight tensile stress is mixed in a part of the back bead is formed in the heat-affected portion and 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 provide an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be performed, the production cost can be reduced, good welding Quality can be ensured and 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, the 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 can be increased. . The electrode 6 is a non-consumable tungsten electrode rod having a narrow diameter and a circular cross section narrower than the groove width w, and W containing La ₂ O _3, W containing Y ₂ O ₃ and W containing ThO _2. A W electrode rod may be used. For example, a special shape can be obtained by inserting and using an electrode rod having a circular cross section with an outer diameter φ2.4 or φ1.6 narrower than the groove width w (an electrode in which only the electrode tip is processed into a conical shape) into the groove. Even if it is not an expensive electrode with 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.

  Further, in the welded structure of the present invention, as shown in FIG. 5, from the portion in contact with the first layer weld metal portion 410 having the back bead 15 formed on the back side of the groove bottom portion to a specific laminated bead height Hb, 4 kJ Of the first laminated weld metal part 411 formed by lamination welding in a heat input range Q1 of not less than / cm and not more than 12 kJ / cm, and from the remaining groove part in contact with the first laminated weld metal part 411 to the upper part of the groove And a second laminated weld metal part 422 formed by laminating and welding in the heat input range Q2 of 2 kJ / cm to 6 kJ / cm up to the final layer 39, and compressive residual in the back bead part and the heat affected part in the vicinity thereof Stress corrosion cracking even when applied in a corrosive environment by forming stress in the heat-affected zone by forming stress or by forming a compressive residual stress in the back bead with a slight tensile stress (for example, 100 MPa or less). Can prevent Can contribute to longer life. In addition, there is no need to water-cool the inner surface during welding, or to provide an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be performed, the production cost can be reduced, good welding Quality can be ensured and the amount of wire used and the time required for welding can be reduced.

As described above, the specific laminated bead height Hb is 2/5 or more and 3/5 or less of the plate thickness T of the joint member, and one or more heat input conditions from the heat input range Q1 or this It is good to carry out lamination welding using the welding conditions corresponding to. Further, when the joint members 1 and 2 to be welded are austenitic stainless steel materials (for example, SUS304 series and SUS316 series), the first laminated weld metal part is the same kind of austenite wire as the material of the joint members 1 and 2. (For example,
Y308 series and Y316 series wire), the austenitic weld metal of the same type as the joint material from the inner or bottom welded back surface exposed to a corrosive environment such as high-temperature water to a specific stacking height. At the same time, compressive residual stress can be formed in the back bead portion and the heat affected portion in 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 input heat quantity range Q1, and the second laminated weld metal part 422 is the second welded metal part 422. By using one or more welding conditions in the input heat quantity range Q2, one layer and one pass are laminated, or one layer and one pass are laminated. However, it is possible to reliably melt the groove wall surface, and it is possible to obtain good weld beads without defects from the bottom of the joint members 1 and 2 to the final layer at the top of the groove. Further, as described above, compressive residual stress is formed in the back bead portion on the back side and the heat-affected portion in the vicinity thereof due to suppression of welding deformation and suppression of tensile stress, or slight tensile stress in a part of the back bead. Even if a compressive residual stress containing a mixture is formed in the heat-affected portion and is applied in a corrosive environment, stress corrosion cracking can be prevented, which can contribute to a longer life.

  FIG. 6 is a weld cross-section of another embodiment showing the residual stress improvement method of the present invention and a welding outline of a welded structure. The main difference from FIG. 5 is that a nickel alloy Inconel wire is used in the second lamination welding, and the other points are the same as FIG. That is, as shown in FIG. 6, when the joint members 1 and 2 are austenitic stainless steel, 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 an inconel wire 62 made of nickel alloy is welded to the second laminated weld metal portion 422 laminated on the upper part. By welding in this way, the compressive residual stress formed in the back bead part on the back side and the heat affected part in the vicinity thereof can be increased by the effect of suppressing welding deformation caused by the deviation of the linear expansion coefficient, as described above. Thus, even if it is applied in a corrosive environment, stress corrosion cracking can be prevented and it can contribute to a long life.

  In addition, the second laminated weld metal part 422 is subjected to a low heat input condition by being laminated and welded into a plurality of passes in the course of laminating welding one layer at a time or laminating welding one layer at a time. However, it is possible to reliably melt the groove wall surface, and to obtain each good weld bead having no defects up to the final layer above the groove. 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 and 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 can be facilitated by densely stacking ripples, and quality can be 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. Welding structure that is used in corrosive environment because the tensile stress generated on the back side is suppressed by suppressing this wrinkling deformation to a small extent, compressive residual stress is formed in the back bead part and the heat affected part in the vicinity. Even if it is a thing, a stress corrosion crack can be prevented and it can contribute to lifetime improvement.

  Table 1 shows an example of welding conditions, which are welding conditions that can be used in the first layer back wave welding and the first and second laminated weldings shown in FIGS.

  FIG. 7 is an example showing a cross-sectional photograph of pipe welding performed by the residual stress improvement method of the present invention. FIG. 8 is an explanatory diagram showing the relationship between the stacking height in the pipe welding shown in FIG. 7 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. The welding wire uses the same type of austenitic wire (Y308L) as the piping member or plate member. 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. 7 and 8, in (i) 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 ((ii) 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 ((iii) second-half welding, second welded metal portion 422), at the point where the laminated bead height Hb (Σh + f) reaches about half of the plate thickness T, the first welding is performed. 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 corresponding welding condition 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 amount ΔL2 on the back surface side (shrinkage of a predetermined length L) are mainly caused by shrinkage deformation in the groove width direction that occurs in the process of the first layer welding and the first laminated welding. Has increased by. Further, the dent amount Δc (俵 strangling deformation) due to wrinkling generated on the front side of the weld is a result generated in the progress of the second laminated welding. By performing welding in this way, a weld cross section as shown in FIG. 7 can be obtained satisfactorily. 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 to be small, and the compressive stress can remain in the back bead portion and the vicinity thereof. Here, pipe welding is shown as an example, but welding of plate members having different joint shapes may be used.

  FIG. 9 is 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. 7 and 8. 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 circumferential residual stress σθ and an axial residual stress calculated from a measurement result of εθ and an open strain value εz in the axial direction. As shown in FIG. 9, the backside bead portion on the backside and the residual stress in the vicinity thereof are compressive stresses having a maximum axial residual stress σz (circled line) in the direction perpendicular to the weld 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, by applying the residual stress improvement method of the present invention, the residual 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. It can also contribute to longer life. In addition, there is no need to water-cool the inner surface during welding, or to provide an expensive heat treatment device after the completion of welding, or to perform heat treatment, only welding work can be performed, the production cost can be reduced, good welding Quality can be ensured and the amount of wire used and the time required for welding can be reduced.

It is explanatory drawing which shows one Example of the stress analysis result of the back bead part which changes in the welding process in the residual stress improvement method of this invention, and its welding structure. It is explanatory drawing which shows another Example of the stress analysis result of the back bead part which changes in a welding process. It is explanatory drawing which shows one Example of the welding procedure outline | summary of the residual-stress improvement method and its welded structure of this invention. It is explanatory drawing of one Example which shows the groove shape and apparatus schematic structure regarding the residual stress improvement method of this invention, and a welded structure. It is the welding cross section of one Example which shows the welding stress improvement method of this invention, and the welding outline | summary of a welded structure. It is the welding cross section of other one Example which shows the welding stress improvement method of this invention, and the welding outline | summary of a welded structure. It is one Example which shows the cross-sectional photograph of the piping welding constructed | assembled by the residual stress improvement method of this invention. It is explanatory drawing which shows the relationship between the lamination | stacking height in the pipe welding shown in FIG. 7, the amount of heat inputs for every welding pass, a groove shoulder width, the shrinkage | contraction amount of a back side, and the amount of dents by the front side wrinkle tightening. 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 feeder, 15 ... back bead, 19 ... insert material, 21 ... first layer back wave welding, 39 ... bead cross section of final layer, 41 ... first lamination welding step 42 ... second laminating welding process, 51 ... groove shape manufacturing process, 52 ... welding preparation process, 53 ... first layer backside wave welding process, 56 ... first heat input range Q1, 57 ... second input Calorific range Q2, 61 ... austenitic wire, 62 ... inconel wire, 410 ... first layer weld metal part, 411 ... first weld metal part, 422 ... second weld metal part, T ... plate thickness, Hb ... lamination Bead height, w ... groove bottom width, f ... root face, 2θ Included angle.

Claims (2)

It is a residual stress improvement welding method for improving the residual bead on the back side and its vicinity, which occurs in one side welding of a groove joint formed by abutting a pipe member or a plate member,
In the welding construction, a welding wire to be supplied to the arc welding portion in the groove is welded by arc welding of a non-consumable electrode method, and a back bead is formed on the back side of the groove bottom portion by first layer welding, and then the plate Laminate welding is performed at a heat input range of 4 kJ / cm to 12 kJ / cm up to a laminated bead height in the range of 2/5 to 3/5 , and then from the remaining groove to the final layer above the groove Then, the welding condition is switched to the welding condition of the heat input smaller than the heat input range, and the lamination welding is performed to form a compressive residual stress in the back bead part and the heat affected part in the vicinity thereof, or a tensile force of 100 MPa or less is applied to a part of the back bead. A welding method for improving residual stress characterized by forming a compressive residual stress mixed with stress in the heat-affected portion. In a welded structure that improves the backside bead portion on the back side generated by one-side welding of a groove joint formed by abutting a pipe member or a plate member and the residual stress in the vicinity thereof,
Heat input of 4 kJ / cm or more and 12 kJ / cm or less from the part contacting the first layer weld metal part where the back bead is formed on the back side of the groove bottom to the laminated bead height in the range of 2/5 or more and 3/5 or less of the plate thickness. A first laminated weld metal portion formed by laminating welding in a range, and a remaining heat input amount smaller than the 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. A second laminated welded metal part formed by laminating and switching to welding conditions, and forming a compressive residual stress in the back bead part and the heat-affected part in the vicinity thereof or a part of the back bead of 100 MPa or less A welded structure characterized by forming a compressive residual stress in which the tensile stress is mixed in the heat-affected portion.

Images