JP5730139B2 - Butt welding method for steel - Google Patents

Description

  The present invention relates to a steel butt welding method that eliminates the need for special heat treatment for removing a hardened portion generated after welding and removing residual stress.

  When welding thick carbon steels or low-alloy steels, or between carbon steels or low-alloy steels and stainless steels, the weld is generally reheated to improve weld residual stress after the end of welding. Heat treatment after welding is performed. However, in order to weld a welded joint that is difficult to heat-treat after welding for structural reasons, or to shorten the manufacturing period and cost, there is a welding method that omits the heat-treating after welding while ensuring good joint quality. is necessary.

  In Patent Document 1, in the overlay welding method for a carbon steel material or the like, a plurality of weld beads protruding from the periphery are formed in parallel and adjacent to the overlay recess of the base material, and overlap metal covering the entire overlay recess A build-up welding method is disclosed in which a layer is formed and the hardened portion in the base metal structure is softened and removed by the previous overlap metal layer by heat of the overlap metal layer formed later.

  In Patent Document 2, when welding a carbon steel pipe base material and an austenitic stainless steel pipe base material, at least two or more layers of low carbon welding materials of the same quality as the carbon steel base material are formed only on the inner surface of the groove portion on the carbon steel pipe side. After overlaying, a joint welding method is disclosed in which austenitic stainless steel welding material is used to laminate the entire groove surface until there is no influence of dilution of the components of the carbon steel base material, and then joint welding between austenitic stainless steels is disclosed. .

  Further, in Patent Document 3, in order to eliminate the need for tempering after welding when butt welding a clad pipe formed of carbon steel or low alloy steel as an outer layer and stainless steel or high alloy steel as an inner layer at the laying site, Prior to butt welding at the laying site, a build-up part is formed on the end surface of the outer layer using a stainless steel or high alloy steel welding rod, and a tempering treatment is performed on the outer layer part of the base material that has been cured by the heat effect of welding, A welding method is disclosed in which welding is performed by butting the built-up portions of stainless steel or high alloy steel at the laying site.

  Further, in Patent Document 4, a second cylindrical body is erected on the upright first cylindrical body, and a welding torch that emits a laser beam of a YAG laser is rotated horizontally in the circumferential direction of the cylindrical body. A welding method is disclosed in which the laser beam is emitted substantially horizontally from a welding torch toward a groove formed in a facing portion of a cylindrical body, and the first and second cylindrical bodies are circumferentially welded.

  Furthermore, Patent Document 5 discloses carbon steel and high-restraint welded joints such as welding repair of a rolling roll shaft for iron making or partial repair of a furnace core of a smelting furnace such as a blast furnace and a converter. In a welded joint having a degree of restraint of 5000 (N / (mm · mm)) or more for joining between steel materials made of at least one of low alloy high strength steels, the carbon content is low as less than 0.1 mass as a welding material. A welded joint using carbon austenitic stainless steel is disclosed.

JP-A-8-323473 Japanese Patent Laid-Open No. 61-266188 Japanese Patent Laid-Open No. 7-24577 JP 2000-176663 A Japanese Patent No. 4304892

  In the above-described prior art, the overlay welding method of Patent Document 1 is a welding method for overlaying a concave portion of a base material, and is different from the butt welding method of the present invention. In addition, the hardened part in the structure of the heat affected zone can be softened, but the tensile residual stress of the post-weld base metal may increase due to multilayer welding heat and solidification shrinkage. Not listed.

  The welding method of Patent Document 2 does not describe the narrow groove shape, the residual stress after welding, and the heat treatment after welding.

  In the butt welding method of Patent Document 3, a tempering process at the laying site is not necessary because the hardened part is tempered after overlay welding. However, there is no description other than the clad steel, and it is assumed that tempering is performed after overlay welding, and the narrow groove shape is not described.

  Since the welding method of Patent Document 4 has little heat input to the cylindrical body, there is a possibility that the post-weld heat treatment for removing residual stress and preventing delayed cracking accompanying embrittlement of the material may be simplified. However, the weld heat affected zone of carbon steel or low alloy steel, which is a thick plate by laser welding, may have a martensitic structure because of its high cooling rate.

  The welding method of patent document 5 welds carbon steel and a low alloy high-tensile steel directly with an austenitic stainless steel welding material.

  Thick carbon steel or low alloy steel welded joints, carbon steel / stainless steel dissimilar welded joints or low alloy steel / stainless steel dissimilar welded joints require post-weld heat treatment to reduce residual stress There is. However, if the product has a welded structure that cannot be heat treated after welding, or if the heat treatment after welding is omitted in order to shorten the manufacturing period or reduce costs, the integrity of the base material after welding and the welded part Ensuring is an issue.

  The present invention aims to provide a novel welding method that pays attention to the above-mentioned problems and eliminates the post-weld heat treatment by making the welded part good joint quality.

The present invention relates to a steel butt welding method in which a pair of base materials made of steel are made of carbon steel or low alloy steel, and a weld surface of the base material is grooved to make butt welding. A step of forming a groove surface on a base material made of steel, and overlay welding of a stainless steel or nickel base alloy by arc welding on the groove surface of a base material made of carbon steel or low alloy steel. A step of forming, a step of groove machining a build-up weld of a base material made of carbon steel or low alloy steel, and a step of butt welding a pair of base materials using stainless steel or a nickel-based alloy as a weld metal It is characterized by having.

  Further, in the butt welding method of steel materials, the height of the weld overlay formed by overlay welding of stainless steel or nickel base alloy by arc welding on the groove surface of the base material made of carbon steel or low alloy steel. The heat-affected zone of the base material has a predetermined height or more at which no hardened portion is formed.

  Moreover, in the butt welding method of steel materials, the height of the build-up weld portion is set to 4 mm or more.

  Further, in the butt welding method of steel materials, the overlay welding of stainless steel or nickel is performed following the step of overlay welding stainless steel or nickel base alloy on the groove surface of the base material made of carbon steel or low alloy steel. A heat treatment after welding is performed on the base alloy.

  Moreover, in the butt welding method of steel materials, a step of performing preheating of 100 degrees or more before the step of overlay welding stainless steel or nickel base alloy on the groove surface of the base material made of carbon steel or low alloy steel is performed. It is characterized by having.

  Further, in the butt welding method of steel materials, the groove angle in the step of groove processing the build-up weld portion of the base material made of carbon steel or low alloy steel is narrow groove processing of 30 degrees or less. To do.

  Further, in the butt welding method of steel materials, the step of butt welding the pair of base materials using stainless steel or nickel-base alloy as a weld metal is characterized by using arc welding.

  Further, in the butt welding method of steel materials, the step of butt welding the pair of base materials using stainless steel or nickel base alloy as a weld metal is characterized by using hot wire TIG welding.

  Further, in the butt welding method of steel materials, the step of butt welding the pair of base materials using stainless steel or a nickel base alloy as a weld metal uses laser welding.

  Moreover, in the butt welding method of steel materials, the step of butt welding the pair of base materials using stainless steel or nickel base alloy as a weld metal is characterized by performing hot wire TIG welding after performing laser welding.

  Further, the present invention is characterized by a radioactive substance storage container manufactured by the butt welding method of the steel material. The storage container is welded between the upper lid and the closing lid sandwiching the neutron shielding material and between the lower lid having the neutron shielding material and the sealed storage container main body by the butt welding method of the steel material.

  In particular, the present invention performs post-weld heat treatment by overlay welding stainless steel or nickel-base alloy on the groove surface of carbon steel or low alloy steel, and then butt welding with stainless steel or nickel-base alloy. There is provided a welding method capable of obtaining a sound welded portion even without it.

  Overlay welding uses the above-mentioned welding materials, and adopts the overlay welding method by arc welding having a build-up lamination with a small thickness and a constant thickness of carbon steel and low alloy steel. If the weld bead exceeds a certain thickness, the post-weld bead will improve the microstructure of the pre-weld bead, and heat treatment effect due to heat input of the lamination welding will occur, and no hardened layer will be formed in the heat affected zone of carbon steel or low alloy steel . Also, in order to prevent the heat input during butt welding in the subsequent process from adversely affecting the structure of the carbon steel and low alloy steel in the vicinity of the overlay melting boundary line, overlaying of a certain thickness or more is required. Become.

  Furthermore, a tensile residual stress resulting from butt welding in a subsequent process is generated in the overlay weld metal. In the present invention, a small tensile residual stress or a compressive residual stress is generated in the carbon steel and the low alloy high-strength steel in the vicinity of the melting boundary line, and the post-weld heat treatment is unnecessary. By making the groove shape at the time of butt welding adopted in the welding method of the present invention a narrow groove shape, the residual stress after welding can be further reduced.

  In the present invention, the tensile region of the welding residual stress is applied to the weld metal of stainless steel, and a small tensile residual stress or compressive residual stress is generated in the carbon steel or low alloy steel, so that post-weld heat treatment is not required. Furthermore, by performing narrow groove welding, the residual stress can be reduced without being restricted by the degree of restraint of the joint.

  According to the present invention, in a butt welding method for steel materials in which a pair of base materials made of steel materials are made of carbon steel or low alloy steel, and a weld surface of the base material is grooved and butt welded, carbon steel or A step of forming a groove surface on a base material made of low alloy steel, and overlay welding of the stainless steel or nickel base alloy on the groove surface of the base material made of carbon steel or low alloy steel by arc welding. A step of forming a portion, a step of groove-working a build-up weld of a base material made of carbon steel or low alloy steel, and a step of butt welding a pair of base materials using stainless steel or a nickel-based alloy as a weld metal Even if it has a welded structure that cannot be heat-treated after welding due to the characteristics of the product, or when the heat treatment after welding is omitted to shorten the manufacturing period and reduce costs, the welded portion is excellent. It is possible to provide a welding method for hand quality.

The schematic diagram which shows the butt-welding part in Example 1 of this invention. The flowchart which shows the butt-welding method in Example 1 of this invention. The schematic diagram which shows the hot wire TIG welding machine in Example 1 of this invention. The schematic diagram which shows the residual stress of a base material, an overlay welding part, and a butt welding part. The graph which shows the residual stress distribution of a butt weld part. The flowchart which shows the butt welding method in Example 2 of this invention. The schematic diagram which shows the butt-welding part in Example 3 of this invention. The schematic diagram which shows the modification of the butt-welding part in Example 3 of this invention. The schematic diagram which shows the 2nd modification of the butt-welding part in Example 3 of this invention. The schematic diagram which shows the butt-welding part in Example 4 of this invention. The A section enlarged view in FIG. The B section enlarged view in FIG.

  Hereinafter, modes for carrying out the present invention will be described with reference to examples and drawings.

  First, in Example 1, a welding method for performing butt welding by overlaying stainless steel on a base material will be described. In FIG. 1, a build-up weld 2 made of stainless steel is formed on a pair of base materials 1 provided on both sides, and a butt weld 3 is formed by butt welding using a stainless steel weld metal. The base material 1 is made of carbon steel or low alloy steel, and has a built-up groove surface at the tip. Overlay welding of stainless steel is performed on the buildup groove surface to form the buildup weld 2, and groove processing is performed on the surface to form a narrow groove surface. G is an overlay melting boundary line. The base material 1 may be carbon steels or low alloy steels, or a combination of both.

Next, the execution procedure of the welding method of Example 1 is demonstrated using the flowchart of FIG. First, in step S1, stainless steel is build-up welded to the build-up groove portion of the base material 1. At this time, for the build-up welding, there is a build-up lamination with a certain thickness by a weld bead, and arc welding with a low dilution rate of carbon steel or low alloy steel is used. The reason why the stacking thickness is more than a certain thickness is
(1) By making the weld bead with a certain thickness or more, heat treatment effect due to heat input of lamination welding occurs, and no hardened layer is formed in the heat-affected zone of the base metal (2) Input during butt welding in the subsequent process Two points are that overlaying of a certain thickness or more is necessary to prevent heat from adversely affecting the structure of the base metal in the vicinity of the overlaying boundary.

  In S1 of FIG. 2, since a favorable weld structure is obtained on the carbon steel side by performing preheating at 100 ° C. or higher during welding, heat treatment after build-up welding can be omitted. If a good weld structure is obtained on the carbon steel side without preheating, preheating can be omitted.

  Next, groove processing of the butt portion is performed by the processing machine M in S2. Here, in order to obtain good welding quality, the narrow groove is processed at an accurate angle.

  Finally, butt welding is performed in S3 using a stainless steel weld metal. The narrow groove shape butt welding of S3 does not adversely affect the structure of the base material 1 in the vicinity of the build-up melting boundary line G because of the build-up weld portion 2 having a constant thickness. In addition, since the residual tensile stress caused by the butt weld 3 in S3 is applied to the build-up weld 2 of stainless steel, a small tensile residual is present in the carbon steel and the low alloy high-strength steel near the build-up melting boundary line G. Only stress or compressive residual stress is generated and no post-weld heat treatment is required.

  In Example 1, the heat treatment after welding is not performed between steps S1 and S2. Further, no post-weld heat treatment is performed after S3.

  As the welding method of the present invention, arc welding with a low dilution rate of carbon steel or low alloy steel is used, and hot wire TIG automatic welding is used for overlay welding and butt welding as arc welding having particularly high construction efficiency. Since these products have a low dilution rate, the quality of the weld metal part can be improved by reducing the influence of the base metal on the weld metal part, or the amount of shrinkage of the weld metal can be reduced by reducing the number of laminated butt weld parts. Residual stress can be suppressed.

  FIG. 3 shows the structure of a hot wire TIG automatic welder. The wire 9 fed by the wire feeding device 14 passes through the power feeding chip 15 and is heated by the wire heating power source 13 connected to the power feeding chip 15. The welding torch 10 melts the material to be welded with electric power from the welding power source 11 to form a molten pool. At this time, the power feed tip 15 is fixed together with the welding torch 10 at a position where the wire 9 enters the molten pool. The welding carriage 12 guides the power feed tip 15 and the welding torch 10 so as to follow a predetermined locus.

  As shown in FIG. 4, in the butt welds between the overlay welds, the tensile residual stress that normally occurs in the vicinity of the butt weld line is applied to the overlay weld 2 of stainless steel, The tensile residual stress or compressive residual stress generated in carbon steel is reduced. Furthermore, since the butt groove in the present invention has a narrow groove shape, these residual stresses can be further reduced.

  FIG. 5 shows a graph of residual stress distribution when stainless steels are welded together by covering arc welding, narrow groove TIG welding, and laser welding. The groove angles are 60 ° for coated arc welding, 20 ° for narrow groove TIG welding, and 5 ° for laser welding, respectively.

  It is clear that the value of the tensile residual stress of the narrow groove TIG welding and the laser welding is small and the width of the tensile region in the vicinity of the weld metal center line is narrow as compared with the coated arc welding.

  If the lamination height of the build-up weld 2 is 10 mm or more, the residual stress on the carbon steel side shows a low value. In the case of laser welding, since the lowest maximum tensile residual stress is shown as shown in FIG. 6, the stacking height of the overlay welding 2 can be further reduced. For example, in Example 1, the stacking height of the build-up weld 2 is set to 4 mm or more so that the base material is in a temperature range that is not affected by the heat of butt welding (AC1 transformation point of carbon steel is 727 ° C. or less). In consideration of actual construction work, the groove angle is set to 30 ° or less.

  Next, in Example 2, after forming the build-up welded portion 2 of stainless steel on the build-up groove surface of the base material 1, welding such as dilution rate of the base material, magnitude of heat input, stacking height, preheating, etc. The execution procedure of the welding method which is not limited by the conditions is shown in the flowchart of FIG.

  In FIG. 6, after performing build-up welding with a constant thickness in step S10, a good weld structure is obtained on the carbon steel side by performing heat treatment after build-up welding in S20. Next, groove processing of the butt portion is performed in S30.

  Finally, butt welding is performed in S40. Since there is the build-up weld portion 2 having a constant thickness, the narrow groove butt welding in S40 does not adversely affect the structure of the base material 1 in the vicinity of the build-up melting boundary line G. Further, since the tensile residual stress resulting from the butt welding of S40 is applied to the weld overlay 2 of stainless steel, a small tensile residual stress or compressive residual stress is applied to the carbon steel and low alloy high-strength steel in the vicinity of the melting boundary line. Only occurs and no post-weld heat treatment is required.

  Next, in Example 3, the case where laser welding is used as a butt welding method is shown in FIG. Moreover, the modification at the time of combining laser welding and hot wire TIG welding is shown in FIG. Furthermore, FIG. 9 shows another modification example in the case of using hot wire TIG welding.

  In the welding method using only laser welding shown in FIG. 7, after forming the weld overlay 2 of stainless steel on the base material, the groove is processed into a narrow groove shape for laser welding. Thus, the laser weld 17 is formed.

  Further, in the welding method shown in FIG. 8, in which the butt welding is a combination of laser welding and arc welding according to the necessity on the product structure, after forming the laser welded portion 17 by laser welding to one or more layers and a predetermined layer, The hot wire TIG weld 16 is formed by hot wire TIG welding of the remaining layer.

  Further, as in the butt welding method shown in FIG. 9, after forming the weld overlay 2 of stainless steel on the base material 1, the groove is formed into a narrow groove shape for hot wire TIG contact, The butt weld 16 in one layer and one pass can also be formed by TIG welding. In any welding method, post-weld heat treatment after butt welding is not required.

  Although the welding material of Example 3 uses stainless steel, a nickel-base alloy welding material may be used in the same manner.

  FIG. 10 illustrates a fourth embodiment of the present invention. Example 4 shows an example in which the welding method of the present invention is applied to a welded part structure used in a radioactive substance storage container. The radioactive substance storage container 21 has a substantially cylindrical shape, and a neutron absorber 19 is attached between the upper lid 18 and the closing lid 20 and the lower lid 22, and is generally 150 in order to maintain neutron absorption performance. It is necessary to manage heat input at a temperature below ℃.

  Since both the butt weld of the upper lid 18 and the closing lid 20 and the butt weld of the radioactive substance storage container 21 and the lower lid 22 are butt welded after the neutron absorber 19 is attached, preheating and welding are performed during butt welding. Post-heat treatment is not possible. Therefore, preheating and post-welding heat treatment are not required by overlay welding stainless steel on the base material of the butt portion and then performing butt welding described in Examples 1 to 3. As a groove shape of arc welding, a groove angle is set to 30 degrees or less.

  FIG. 11 is an enlarged view of part A in FIG. The build-up weld 2 and the butt weld 3 are formed between the upper lid 18 and the closing lid 20 by the welding method described in the first to third embodiments.

  FIG. 12 is an enlarged view of a portion B in FIG. The build-up weld 2 and the butt weld 3 by the welding method described in the first to third embodiments are formed in the butt weld of the radioactive substance storage container 21 and the lower lid 22.

  The welding method of the present invention is a solution in the case where there is a heat input restriction on the constituent members, and is frequently used because it can be applied to a wide range of welded structures. Further, since the present invention greatly contributes to shortening the process, the effect of the present invention is very large. In particular, containers that store radioactive materials often have heat input limitations due to the use of neutron absorbers, which is an effective means for manufacturing products.

DESCRIPTION OF SYMBOLS 1 ... Base material 2 ... Overlay welding part 3 ... Butt welding part 16 ... Hot wire TIG welding part 17 ... Laser welding part 18 ... Upper lid 19 ... Neutron shielding material 20 ... Closed lid 21 ... Radioactive substance storage container 22 ... Lower lid G ... Overlay melting boundary line

Claims (11)

In a butt welding method for steel materials, a pair of base materials made of steel materials are made of carbon steel or low alloy steel, and the welding surface of the base material is grooved and butt welded.
Forming a groove surface in the base material made of carbon steel or low alloy steel;
Forming a build-up weld by overlay welding stainless steel or nickel-base alloy by arc welding on the groove surface of the base material made of carbon steel or low alloy steel;
A step of groove forming the build-up weld of the base material made of the carbon steel or the low alloy steel;
Butt welding the pair of base materials with stainless steel or nickel base alloy as a weld metal, and arcing stainless steel or nickel base alloy on the groove surface of the base material made of carbon steel or low alloy steel. A steel butt welding method characterized in that a height of a build-up weld portion formed by overlay welding by welding is set to a predetermined height or more at which a hardened portion is not formed in a heat-affected zone of a base material . 2. The steel butt welding method according to claim 1 , wherein a height of the build-up weld is 4 mm or more. The method of butt welding of steel materials according to claim 1 , wherein the overlay welding is performed following the step of overlay welding stainless steel or nickel base alloy to a groove surface of a base material made of carbon steel or low alloy steel. A butt welding method for steel, characterized by performing post-weld heat treatment on the stainless steel or nickel-base alloy. 2. The butt welding method for a steel material according to claim 1 , wherein before the step of overlay welding the stainless steel or the nickel base alloy to the groove surface of the base material made of the carbon steel or the low alloy steel, the temperature is 100 degrees or more. A method of butt welding of steel materials, comprising a step of preheating. In butt welding process of the steel according to any one of claims 1 to 4, the included angle of 30 degrees in the step of grooving the overlay weld part of the base material made of the carbon steel or low alloy steel A steel butt welding method characterized by the following narrow groove processing. In butt welding process of the steel according to any one of claims 1 to 5, the step of welding butt the pair of base material stainless steel or nickel-based alloy as weld metal, the use of arc welding A characteristic butt welding method for steel. In butt welding process of the steel according to any one of claims 1 to 5, the step of welding butt the pair of base material stainless steel or nickel-based alloy as weld metal, using a hot wire TIG welding A butt welding method for steel materials. In butt welding process of the steel according to any one of claims 1 to 5, the step of welding butt the pair of base material stainless steel or nickel-based alloy as weld metal, the use of laser welding A characteristic butt welding method for steel. In butt welding process of the steel according to any one of claims 1 to 5, the step of welding butt the pair of base material stainless steel or nickel-based alloy as weld metal, after the laser welding A butt welding method for steel materials, characterized by performing hot wire TIG welding. Container of radioactive material, characterized in that it is manufactured by butt welding method of the steel according to any one of claims 1 to 9. The storage container of radioactive material of claim 10, between the lower lid and the closed container body having between upper lid and the closure cap across the neutron shielding material and a neutron shielding material, any one of claims 1 to 9 A radioactive substance storage container welded by the butt welding method of steel materials described in 1.

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