Method for residual stress reduction of a welded joint and residual stress reduction device for a welded joint

Abstract

This disclosure relates to a method and apparatus for reducing weld residual stress in steel structures with weld lines. Specifically, the method for reducing weld residual stress includes the steps of: plastically deforming a target deformation region by contacting a disk with the target deformation region and applying a compressive load to the target deformation region by means of a rotating disk, the target deformation region being a base material region near the interface between the weld bead of the weld line and the base material; and conveying the steel structure or disk such that the indentation caused by the plastic deformation extends in the target deformation region along the weld line in a continuous linear shape.

Description

Technical Field

[0001] This disclosure relates to apparatus and method for reducing residual stress in welded joints. Background Technology

[0002] Residual stress, which inevitably arises after welding, is caused by differences in localized heating and cooling, and this residual stress affects the fracture properties of the weld joint, such as fatigue fracture. Typically, post-weld heat treatment is used to reduce residual stress, in which the welded components are heated in a furnace for an extended period to reduce the relative deformation between the base metal and the weld metal. However, the application of post-weld heat treatment is significantly limited by furnace size constraints.

[0003] For example, the recently much-discussed tank for liquefied carbon dioxide carriers (Type C) Storage tanks are being designed with significantly increased dimensions and manufactured using high-strength steel (YS690 grade) to improve transport capacity. However, the expansion of furnace size is limited, and even when furnace size increases, there are issues with the high cost of stress-relief heat treatment and the difficulty in meeting the heat treatment standards stipulated by classification societies. Summary of the Invention

[0004] Technical issues

[0005] One aspect of this disclosure is to provide methods and apparatus for mitigating residual stress in welding.

[0006] One aspect of this disclosure is to provide methods and apparatus for mitigating residual welding stress, regardless of the dimensions of the steel structure.

[0007] One aspect of this disclosure is to provide a method and apparatus for rapidly and accurately reducing residual welding stress in welded joints.

[0008] One aspect of this disclosure is to provide methods and apparatus for mitigating residual welding stress in welded joints of each base material, even when the base materials being welded to each other have different physical properties.

[0009] The subject matter of this disclosure is not limited to the foregoing. Other objects of the invention will be readily apparent to those skilled in the art from the content of this specification.

[0010] Solution to the problem

[0011] According to one aspect of this disclosure, a method for reducing welding residual stress in a steel structure having a weld line includes: plastically deforming the target deformation region by contacting a disk with the target deformation region and applying a compressive load to the target deformation region by rotating the disk, the target deformation region being a base material region near the interface between the weld bead of the weld line and the base material; and conveying the steel structure or the disk in the target deformation region such that the indentation caused by the plastic deformation extends along the weld line in a continuous linear form.

[0012] During plastic deformation, the target area for deformation can be heated at least by the frictional heat generated by the rotation of the disk.

[0013] The depth of the indentation can be controlled by the heating temperature of the target area of ​​deformation and the compressive load applied by the disk.

[0014] The diameter of the disk can be 100 mm or larger.

[0015] The edge of the disk can be tapered, rounded, or eccentric.

[0016] The disk can be perpendicular to the surface of the deformed target area to form an indentation, or tilted at an angle of 65° or less.

[0017] By using n (where n is a natural number from 2 to 5) disks spaced apart from each other in the width direction of the welding line, n indentations can be formed in the deformation target area.

[0018] The two disks can be arranged spaced apart from each other with the welding line placed between them, such that an indentation is formed in each deformation target area on both sides of the welding line.

[0019] A first disk group comprising j (where j is a natural number from 2 to 5) disks spaced apart from each other in the width direction of the weld line, and a second disk group comprising k (where k is a natural number from 2 to 5) disks spaced apart from each other in the width direction of the weld line, may be arranged such that the weld line is placed between the first disk group and the second disk group, such that j indentations are formed in one deformation target area and k indentations are formed in the other deformation target area on both sides of the weld line.

[0020] The method may also include arranging l (where l is a natural number from 2 to 4) disks spaced apart from each other in the longitudinal direction of the welding line.

[0021] The third disk group, comprising l disks, and the fourth disk group, comprising m disks (where m is a natural number from 2 to 4) arranged spaced apart from each other in the longitudinal direction of the welding line, can be arranged spaced apart from each other such that the welding line is placed between the third disk group and the fourth disk group, such that at least two indentations overlap in each deformation target area on both sides of the welding line.

[0022] The disks forming the disk assembly may be the same or different in at least one of the following factors: disk diameter, disk thickness, disk edge shape, disk tilt angle, compressive load applied to the disk, and disk rotation speed.

[0023] The deformation target area can be the region within 0.1 cm to 20 cm from the interface toward the parent material.

[0024] Frictional heat can be applied to the deformed target area that has residual welding heat.

[0025] The method may further include: after completing the formation of continuous linear indentations, annealing the steel structure on which the indentations are formed, and after annealing, performing a surface treatment step to remove surface irregularities caused by the indentations.

[0026] Steel structures can be fluid storage containers, ship structures, marine structures, offshore wind power monopiles, or automobile bodies.

[0027] According to one aspect of this disclosure, an apparatus for reducing welding residual stress in a steel structure having weld lines includes: a deformation unit comprising a disk rotatable while in contact with a base material in a deformation target region, the deformation target region being a base material region near the interface between the weld bead of the weld line and the base material; a load application unit that applies an axial load to the disk of the deformation unit in the direction of the base material; and a conveying unit that conveys the steel structure in the longitudinal direction of the weld line such that the disk is located within the deformation target region.

[0028] According to one aspect of this disclosure, an apparatus for reducing welding residual stress in a steel structure with weld lines includes: a deformation unit comprising a disk rotatable while in contact with a base material in a deformation target region, the deformation target region being a base material region near the interface between the weld bead of the weld line and the base material; a load application unit that applies an axial load to the disk of the deformation unit in the direction of the base material; and a conveying unit that conveys the deformation unit along the weld line in the longitudinal direction of the weld line such that the disk is located within the deformation target region.

[0029] The deformation unit may include two disks, which are spaced apart from each other with a welding line placed between them and each contacting the deformation target area on both sides of the welding line.

[0030] The deformation unit may include a first disk group and a second disk group, which are arranged spaced apart from each other with a welding line placed between them and each contacting the deformation target area on both sides of the welding line. The first disk group may include j (where j is a natural number from 2 to 5) disks arranged spaced apart from each other in the width direction of the welding line, and the second disk group may include k (where k is a natural number from 2 to 5) disks arranged spaced apart from each other in the width direction of the welding line.

[0031] The deformation unit may include a third disk group and a fourth disk group, which are spaced apart from each other with a welding line placed between them and each contacting the deformation target area on both sides of the welding line. The third disk group may include l (where l is a natural number from 2 to 4) disks spaced apart from each other in the longitudinal direction of the welding line, and the fourth disk group may include m (where m is a natural number from 2 to 4) disks spaced apart from each other in the longitudinal direction of the welding line.

[0032] The device may also include a control unit that controls one or more factors selected from the rotational speed of the disk, the conveying speed of the conveying unit, and the load applied to the disk by the load applying unit.

[0033] Advantages of the invention

[0034] According to one aspect of the method disclosed herein, residual welding stress around the weld line can be rapidly reduced by mechanical deformation.

[0035] According to one aspect of the apparatus of this disclosure, welding residual stress can be mitigated by rapidly inducing highly controlled compressive residual stress in the target area.

[0036] The various and beneficial advantages and effects of this disclosure are not limited to those described above, and can be more readily understood in the process of describing specific exemplary embodiments of this disclosure. Attached Figure Description

[0037] Figure 1 This diagram illustrates a cross-section perpendicular to the weld line in a steel structure with weld lines, and the distribution of residual stress according to location.

[0038] Figure 2 This is a schematic diagram illustrating the process steps of forming an indentation in a deformation target area in a method for reducing welding residual stress according to an exemplary embodiment.

[0039] Figure 3The illustration shows a cross-section of the weld line perpendicular to the steel structure after indentation is formed and depicts a schematic diagram of the residual stress distribution according to location in a method for reducing welding residual stress according to an exemplary embodiment.

[0040] Figure 4 This is a schematic diagram illustrating the process steps of an indentation continuously extending in a linear shape in the deformation target area in a method for reducing welding residual stress according to an exemplary embodiment.

[0041] Figure 5 It is a cross-sectional view of the edge shape of the disk and a schematic diagram illustrating the indentation shape formed by the disk having each edge shape in the deformation target area in a method for reducing welding residual stress according to an exemplary embodiment.

[0042] Figure 6 This is a schematic diagram illustrating the process of forming an indentation in a deformation target area by rotating a disk in a method for reducing welding residual stress according to an exemplary embodiment.

[0043] Figure 7 This is another schematic diagram illustrating the process of forming an indentation in the target deformation area by rotating a disk in a method for reducing residual welding stress according to an exemplary embodiment.

[0044] Figures 8 to 11 This is yet another schematic diagram illustrating the process of forming an indentation in the target deformation area by rotating a disk in a method for reducing residual welding stress according to an exemplary embodiment. Detailed Implementation

[0045] Exemplary embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, the exemplary embodiments of the present disclosure can be modified in many different ways, and the scope of the present disclosure should not be limited to the exemplary embodiments set forth herein.

[0046] Furthermore, these exemplary implementations are provided so that this disclosure will be thorough and complete, and will fully convey the concepts of this disclosure to those skilled in the art.

[0047] In the accompanying drawings, the shape and size of the parts may be enlarged for clarity.

[0048] In the description of exemplary embodiments of this disclosure, well-known technologies are not described in detail to avoid unnecessary detail that could obscure the description. Furthermore, the following terms are defined in consideration of the functionality in this disclosure and may be interpreted in different ways depending on the intent of the user and operator. Therefore, the definitions of these terms should be interpreted based on the entire contents of this specification. The terms used in the detailed description are only for describing exemplary embodiments of this disclosure and should in no way be limiting. Unless otherwise expressly stated, the singular form includes the meaning of the plural form.

[0049] In this specification, expressions such as “comprising” or “including” are intended to indicate certain features, numbers, steps, operations, elements, some of them or combinations thereof, and should not be construed as excluding the presence or possibility of one or more other features, numbers, steps, operations, elements, components or combinations thereof besides those described.

[0050] Unless otherwise stated in this specification, the unit "%" refers to weight.

[0051] The connection between any two components includes the case where the two components are directly connected to each other and the case where the two components are indirectly connected to each other through other elements inserted between them.

[0052] The present disclosure will now be described in detail through each exemplary embodiment or example. It should be noted that each exemplary embodiment or example described in this specification is not limited to a single exemplary embodiment or example, but may be combined with other exemplary embodiments or examples. Therefore, references to claims in the claims are merely examples of exemplary embodiments, and the technical concept of the present disclosure should not be construed as being limited only to combinations with the referenced claims. Combinations with various claims also fall within the scope of the technical concept of the present disclosure.

[0053] The terminology used in this disclosure is for the purpose of describing the disclosure and not for limiting it. Furthermore, the singular forms used herein include the plural forms unless the relevant definitions explicitly indicate otherwise.

[0054] The word "including" as used in the specification means that the component is specified, but does not exclude the presence or addition of other components.

[0055] Unless otherwise specified, all terms used herein, including technical and scientific terms, shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. Terms as defined in dictionaries are interpreted as having meanings consistent with relevant technical literature and current disclosure.

[0056] In this specification and the appended claims, "steel structure" means a structure in which at least two steel members are joined together by welding.

[0057] In this specification and the appended claims, "weld bead" refers to the weld metal formed by welding and joining two steel components together. Weld metal is metal that is melted by welding energy during welding and then solidifies.

[0058] In this specification and the appended claims, "weld line" refers to a weld bead that is produced by continuous welding and has a macroscopically linear shape.

[0059] In this specification and the appended claims, "base material" refers to the material of the component to be welded. Base material includes not only the raw material of the component to be welded, but also the material whose microstructure and mechanical properties are altered by the welding heat.

[0060] Figure 1 This diagram illustrates a cross-section perpendicular to the weld line in a steel structure with weld lines, and also illustrates the distribution of residual stress σ as a function of position Y. In this diagram, the boundary (interface) between the weld and the base material in the cross-section is defined as the origin 0 of the Y-axis, and the direction from the boundary towards the base material is defined as the increasing direction of the Y-axis. Although the steel structure is formed by welding two steel members together, these two members are collectively referred to as the base material 100 without distinction.

[0061] As in Figure 1 In one example shown, the steel structure includes a base material 100 and a weld bead 210 formed by welding. In the direction from the interface IL between the weld bead 210 and the base material 100 toward the base material, similar to the distribution of weld residual stress applied to the base material, the maximum tensile residual stress is formed at the interface IL, and compressive residual stresses capable of counteracting the tensile residual stress are formed in areas outside the weld-affected zone. Figure 1 In the schematic cross-sectional view, the region of high tensile residual stress near the interface IL is also illustrated as "TRSZ".

[0062] Specifically, after welding, when the weld bead and base metal become a single continuous body, residual welding stress is generated as the base metal (unaffected by welding heat) restricts the shrinkage of the weld bead and heat-affected zone, which have reached higher temperatures. In other words, residual welding stress is the stress generated after welding when the base metal restricts the shrinkage of the weld bead, whose temperature immediately rises to a molten state. This indicates a state where the base metal tightly restricts the shrinkage of the weld bead. Therefore, residual welding stress is essentially tensile residual stress. Figure 1The distribution of welding residual stress in the weld results in the maximum tensile residual stress at the interface IL between the weld and the base metal. Compressive residual stress, corresponding to the force balance of the tensile residual stress, is generated in the base metal outside the weld heat-affected zone. In a specific example, in the case of low-carbon steel, a maximum tensile residual stress equivalent to the yield stress of the low-carbon steel can be generated at the interface between the weld and the base metal, which is low-carbon steel.

[0063] This disclosure relates to a method for reducing residual stress that can mechanically alleviate welding residual stress, particularly welding tensile residual stress formed in weld joints including the weld line and the weld heat-affected zone.

[0064] A residual stress reduction method according to a disclosure includes the following steps: bringing a disk into contact with a target deformation region—the target deformation region being a base material region near the interface between the weld bead of the weld line and the base material in a steel structure with weld lines, and applying a compressive load to the target deformation region using a rotating disk to cause plastic deformation of the target deformation region; and transferring the steel structure or the disk to the target deformation region such that the indentation caused by plastic deformation extends along the weld line in a continuous linear manner.

[0065] In a specific example, the deformation target area can be a region within 0.1 cm to 20 cm from the interface between the base material and the weld bead (weld line) toward the base material (one base material side), specifically a region within 1 cm to 10 cm from the interface toward the base material.

[0066] Figure 2 This is a schematic process diagram illustrating the step of forming an indentation 410 in a deformation target region 110 by applying a compressive load to the deformation target region 110 using a rotating disk 310, according to a specific example of a method for reducing residual welding stress. In this case, the compressive load can be applied towards the rotation axis ra of the disk.

[0067] The disk 310 can contact the deformation target area 110 near the interface IL between the weld bead 210 of the welding line and the base material 100. The disk 310 can contact the deformation target area 110 while rotating, or it can rotate after contacting the deformation target area 110.

[0068] The deformable target area 110 in contact with the disk 310 can be heated by the frictional heat generated by the rotation of the disk 310. By applying a compressive load (as indicated by the arrow in 310) to the heated deformable target area 110 by the rotating disk 310, the rotating disk 310 can embed itself into the deformable target area 110 and cause plastic deformation of the deformable target area 110, thereby forming an indentation 410 at the area in contact with the disk 310.

[0069] As described above, the method for reducing welding residual stress according to the example embodiment can be achieved by heating the target deformation area with a rotating disk and applying a compressive load almost simultaneously to induce plastic deformation in the target deformation area. By heating the target deformation area with a disk and inducing plastic deformation in the target deformation area, the designed compressive stress can be generated quickly and accurately in the target deformation area, and this compressive stress can be used to alleviate welding (tensile) residual stress.

[0070] Figure 3 The diagram illustrates a cross-section perpendicular to the weld line in a steel structure after plastic deformation (indentation) caused by a compressive load applied by a rotating disk. It also shows the distribution of residual stress σ as a function of position Y, where the boundary (interface, IL) between weld 210 and the base material 100 is the origin O of the Y-axis, and the direction pointing towards the base material where the indentation is formed is the increasing direction of the Y-axis. In this case, the cross-section perpendicular to the weld line refers to the cross-section of the steel structure perpendicular to the longitudinal direction of the weld line, and the weld line in the cross-section is called the weld bead, which is described in detail. The width direction of the weld line is the same as the width direction of the weld bead. The width direction of the weld bead at a point along the weld line can be a direction perpendicular to the longitudinal direction of the weld line at that corresponding point. The longitudinal direction of the weld line is the same as the direction of extension of the weld bead.

[0071] exist Figure 3 In the residual stress σ distribution, the residual stress caused by welding is shown with solid lines, and the residual stress caused by plastic deformation due to compressive load is shown with dashed lines. In addition, the area with high compressive residual stress around the indentation is marked as "CRSZ".

[0072] As in Figure 3 As illustrated in the example of residual stress distribution, the tensile residual stress formed by conventional welding can be offset by the compressive residual stress caused by plastic deformation, thereby reducing the welding residual stress.

[0073] During plastic deformation, the target area of ​​deformation can be heated, at least by the frictional heat generated by the rotation of the disk, and the depth of the indentation produced by plastic deformation can be controlled by compressive load.

[0074] A rotating disk can contact the base material over a large area, allowing the disk to rapidly heat a relatively large area of ​​the base material to the target temperature. In this case, the frictional heat generated by the rotating disk can be controlled by one or more factors, selected from the disk's diameter and rotational speed, as well as the compressive load applied to the disk.

[0075] By rapidly heating a relatively large area of ​​the base material to the target temperature, compressive residual stress can be generated over a wider range with a smaller compressive load (smaller indentation). The depth of the indentation and the resulting compressive residual stress can be easily controlled by adjusting the magnitude of the compressive load applied through the disc.

[0076] Furthermore, even if the disk or steel structure moves while the disk is rotating and applying a compressive load to the base material, the surface of the base material that comes into new contact with the disk due to the movement will be heated through heat conduction. Therefore, by moving the rotating disk or steel structure rapidly or continuously, the tensile residual stress in the deformation target area can be reduced along the weld line.

[0077] To reliably achieve the above-mentioned effects, the diameter of the disk is preferably 100 mm or larger, more preferably 200 mm or larger, and even more preferably 250 mm or larger. The diameter of the disk can be approximately 500 mm or smaller, but this disclosure is not limited to an upper limit on the disk diameter.

[0078] The element "transmitted," or "moved," in the step of extending the indentation can be a steel structure, a disk, or both. Since "motion" is a relative concept, even if both the steel structure and the disk move, when the moving speed of the steel structure differs from that of the disk, the faster-moving element can be interpreted as moving relative to the slower-moving element.

[0079] As stated above, since "motion" arises from the difference in relative motion between the steel structure and the disk, the disk is assumed to be the moving object (the conveyed element) in the following detailed description of the method for reducing welding residual stress. However, the following description remains essentially the same even if the moving object is the steel structure rather than the disk. Furthermore, the following description remains essentially the same even if both the disk and the steel structure move, when there is a net motion due to the difference in conveying speed. For example, when the disk is the moving object, the disk moves (is conveyed) along the weld line within the deformation target area. This corresponds to the case where the steel structure is the moving object and moves (is conveyed) such that the area of ​​the steel structure in contact with the disk moves along the weld line within the deformation target area.

[0080] Figure 4 This is a schematic diagram illustrating the following process: a disk (a rotating disk, 310) moves within the deformation target area 110 along the weld line 200, and an indentation extends along the weld line 200 in a continuous linear shape. Hereinafter, this linearly extending indentation may also be referred to as the indentation line 400. Figure 4 In the schematic diagram, the direction of movement of disk 310 is indicated by arrows.

[0081] like Figure 4As shown in the schematic diagram, the disk 310 can move along the welding line 200 within the deformation target area 110. Specifically, the disk 310 can move along the longitudinal direction of the welding line 200 within the deformation target area 110.

[0082] The disk 310 can rotate while moving, and simultaneously apply a compressive load to the base material 100. As the disk 310 moves, indentations can extend along the continuous linear trajectory of the disk 310. Therefore, indentation lines can be formed within the deformation target area 110, which contact or are spaced from the weld line and have a shape corresponding to at least a portion of the weld line. Here, the shape of the weld line is more accurately interpreted as the shape of the line obtained by replacing the weld line with a simple line in the steel structure, rather than the three-dimensional shape of the weld line.

[0083] Figure 5 It is a cross-sectional view illustrating the edge shape of the disk 310, and a schematic diagram illustrating the shape of the indentation 410 that can be formed by the disk 310 having various edge shapes in the deformation target area.

[0084] Figure 5 Example 'a' is a disk 310 with a tapered edge. Due to the tapered edge shape, an indentation 410 with a tapered shape that is deeply recessed on one side and the depth of the recess continuously decreases can be formed in the deformation target area. When using a disk 310 with a tapered edge, the size of the indentation 410, the depth of the indentation 410, and / or the degree of tapering of the indentation can be controlled by adjusting one or more factors selected from the thickness of the disk 310, the tapering angle θ, and the compressive load applied to the disk 310.

[0085] Figure 5 Figure b illustrates an example of a disk 310 with rounded edges. Due to the gently curved and raised edge shape, a gently curved and recessed indentation 410 can be formed in the deformation target area. When using a disk 310 with rounded edges, the size of the indentation 410, the depth of the indentation 410, and / or the level of curvature of the indentation can be controlled by adjusting one or more factors selected from the thickness of the disk 310, the curvature of the rounded edges, and the compressive load applied to the disk 310.

[0086] Figure 5 Figure c illustrates an example of a disk 310 with an eccentric edge, and Figure 5 Figure c illustrates an example of a disk 310 with an eccentric edge, the edge having both smoothly curved raised portions and smoothly curved recessed portions. When using a disk 310 with such an eccentric edge, by controlling the depth to which the disk 310 is pressed in, a gently curved indentation similar to a rounded edge can be formed (as shown in Figure c). Figure 5Various indentation shapes are available in the range from those shown in c to those with eccentric edges (not shown).

[0087] When only the gently curved protrusion at the eccentric edge is pressed into the base material, controlling the degree of the protrusion and its location allows for more precise control over both the depth of the indentation within the target deformation area and its location. Furthermore, the eccentric edge functions essentially the same as a rounded edge whose thickness corresponds to the thickness of the protrusion. In other words, a disk with an eccentric edge can form a narrower indentation, almost independent of the disk's thickness.

[0088] When the gently curved recessed portion of the eccentric edge is pressed into the base material, the shape of the indentation can be precisely controlled by the size of the deep recess, the depth of the deep recess, the size of the shallow recess, and the degree of the shallow recess. This precise control over the shape of the indentation means that the distribution of compressive residual stress formed in the base material, including the area targeted for deformation, can be precisely controlled.

[0089] Based on Figure 2 , Figure 4 and Figure 5 The detailed description of specific examples illustrates a disk perpendicular to the surface of the target deformation region, but this disclosure is not limited thereto. For example, as in Figure 6 In the example shown, the disk 310 can be perpendicular to the surface of the deformable target area where the indentation is formed, or it can be tilted at an angle β of 65° or less (within 65°). In this case, the tilt angle β is based on the angle (0°) when the disk is perpendicular to the surface of the deformable target area.

[0090] Based on the above Figure 5 The described edge shape or not based on the above Figure 5 In the case of the described edge shape, the size, shape, and maximum indentation depth of the indentation formed in the deformation target area can all be controlled by the tilt angle itself. This means that, in addition to the compressive load applied to the parent material by the disk, the distribution of compressive residual stress formed in the parent material, including the deformation target area, can be precisely controlled by controlling the tilt angle and the edge shape, or by controlling the tilt angle even when the edge shape is the same.

[0091] Figure 7 The diagram illustrates a specific example of a method for reducing residual welding stress, wherein the process involves forming continuous indentations 310A and 310B on each deformation target area 110A and 110B by positioning disks 310A and 310B on deformation target areas 110A and 110B on both sides of the welding line 200, respectively.

[0092] Since interfaces IL relative to the base material 100 are formed on both sides of the weld line 200, the deformation target regions 110A and 110B can be located on each side of the weld line 200 in the steel structure.

[0093] like Figure 7 As illustrated in the example, disks 310A and 310B are positioned for each deformation target region 110A and 110B, thereby allowing compressive residual stress to form substantially simultaneously in both deformation target regions 110A and 110B around the weld line 200. Figure 7 As shown, by substantially simultaneously generating compressive residual stress in the deformation target region where welding tensile residual stress needs to be reduced, the time required for residual stress reduction can be significantly shortened, and productivity can be improved.

[0094] When the disks are positioned for each deformation target area, the two disks 310A and 310B may be identical in one or more factors, selected from the applied compressive load, the shape of the disk edge, the thickness of the disk, the tilt angle of the disk, the diameter of the disk, and the rotational speed of the disk. Alternatively, the one or more factors may differ from each other.

[0095] As mentioned above, the compressive load, the edge shape, thickness, and tilt angle of the disk are the main factors affecting the distribution of compressive residual stress. The compressive load, as well as the diameter and rotational speed of the disk, are also major factors affecting the degree of frictional heat generation. This variation means that, depending on the target deformation area and the intended purpose and design, the indentation (indentation line) can be formed such that the indentation is heated to different temperatures and has different distributions of compressive residual stress.

[0096] Variations in one or more factors, selected from the diameter and rotational speed of the disk—whether they vary along with or independently of the compressive load—mean that the frictional heat generated by each disk can be different.

[0097] When components made of different base materials (first base material and second base material) are welded to form a steel structure, the distribution of welding residual stress formed on the first base material side centered on the weld line and the distribution of welding residual stress formed on the second base material side will inevitably be different.

[0098] According to a specific example, a method for reducing residual welding stress can be achieved, either together with or independently of compressive loads, by independently adjusting the diameter and / or rotation speed of a disk located in the deformation target region on the opposite side of the weld line, thereby controlling the degree of heating in the deformation target region on the opposite side of the weld line in different ways depending on the properties of the base material, even when the base materials on the opposite sides of the weld line are different and have different material properties.

[0099] Furthermore, the method for reducing welding residual stress according to the example embodiment can reduce different welding residual stresses substantially simultaneously by independently adjusting the compressive load, the edge shape, thickness, and tilt angle of each disk in the deformation target area located on both sides of the weld line, even when the base materials on both sides of the weld line are different and therefore have different distributions of welding tensile residual stress.

[0100] Figure 7 The example shown illustrates a steel structure with a single weld line 200. However, this disclosure is not limited thereto. The steel structure may have multiple weld lines. When the steel structure has Q weld lines (where Q is a natural number greater than or equal to 1), 2Q deformation target areas can be defined. In this case, the disk is positioned in each of the 1 to 2Q deformation target areas, thereby allowing indentations (lines) to be formed substantially simultaneously in the 1 to 2Q deformation target areas.

[0101] Figures 2 to 7 The specific example illustration depicts a single disk positioned within a single deformation target region. However, the method for reducing residual welding stress according to the example embodiment includes not only positioning a single disk within a single deformation target region, but also positioning multiple disks within the same deformation target region.

[0102] In a specific example, n indentations can be formed in the deformation target area by arranging n (where n is a natural number from 2 to 5) disks spaced apart from each other along the width of the weld line. In this case, it should be understood that when the distance between adjacent indentations is very close, adjacent indentations can be connected, and from the perspective of physical continuity, these n indentations can be represented as a single indentation.

[0103] Figure 8 The diagram illustrates a specific example of a method for reducing residual welding stress, which involves creating three indentations by positioning three disks in a single deformation target area.

[0104] As in Figure 8 As illustrated in the example, multiple disks 321, 322, and 323 are arranged spaced apart from each other along the width direction W of the weld bead 210 and can be positioned within the deformation target area 110. Figure 8 In the example, as an example of different compressive loads applied to each disk, the magnitude of the compressive load applied to the disk is illustrated by the length of the arrow.

[0105] By positioning multiple disks 321, 322, and 323 within the deformation target region 110, and for each disk paired with a load selected from compressive loads (such as... Figure 8As shown, the thickness of the disk, the edge shape of the disk, the tilt angle of the disk, the diameter of the disk, and the rotation speed of the disk can be independently adjusted to form a wider and more precise distribution of compressive residual stress under the temperature distribution controlled by the frictional heat controlled by each disk.

[0106] The tensile residual stress formed by welding can vary depending on the material of the base metal, welding conditions, and the physical shape of the weld joint. Therefore, in order to reduce the tensile residual stress in the weld joint, it is necessary to precisely control the stress distribution of the resulting compressive residual stress.

[0107] As described above, by controlling one or more factors selected from the thickness of the disk, edge shape, tilt angle, diameter, rotational speed, and compressive load (i.e., indentation depth), the size (width), shape, and depth of each of the n indentations formed in the deformation target area can be controlled.

[0108] This means that the distribution of compressive residual stress generated by each of the n indentations can be independently controlled. In this case, the n compressive residual stress distributions generated by the n indentations accumulate to form the final compressive residual stress distribution in the parent material, including the deformation target area.

[0109] Figure 9 This diagram illustrates an example of a first tray group 320A and a second tray group 320B arranged spaced apart from each other with a weld line 200 placed between them, such that j indentations are formed in one deformation target region 110A and k indentations are formed in the other deformation target region 110B on both sides of the weld line 200. The first tray group 320A includes j (where j is a natural number from 2 to 5) arranged spaced apart from each other in the width direction of the weld line (the width direction of the weld bead). Figure 9 In the example, j=3) disks, the second disk group 320B includes k disks (where k is a natural number from 2 to 5) arranged spaced apart from each other in the width direction of the weld line. Figure 9 In the example, there are k=2 disks.

[0110] The j disks constituting the first disk group 320A can be adapted to compressive loads selected from those applied to each disk. Figure 9 (As one example), the thickness, edge shape, tilt angle, diameter, and rotational speed of the disk have the same or different values. Additionally, independent of the first disk group 320, the k disks constituting the second disk group 320B are subjected to a compressive load selected from those applied to each disk (…). Figure 9 (One example) and one or more factors such as the thickness of the disk, edge shape, tilt angle, diameter, and rotation speed may have the same or different values.

[0111] As in Figure 9 As illustrated in the example, by positioning the first disc group 320A and the second disc group 320B in the deformation target areas 110A and 110B on both sides of the welding line and forming indentations, a wider and more precisely controlled distribution of compressive residual stress can be generated under a controlled temperature distribution in each deformation target area, while significantly reducing the time required for residual stress reduction and improving productivity.

[0112] In addition, such as in Figure 8 and Figure 9 As illustrated in the example, it is advantageous to position an assembly of disks, comprising multiple disks spaced apart from each other in the width direction of the weld line, in the target deformation region, even when the indentation is shallow, because the target compressive residual stress distribution can still be achieved.

[0113] Considering the intended use of steel structures with welded lines, the depth of indentations may need to be controlled to a level that will not significantly adversely affect the intended use. For example, when the steel structure is a fluid storage container holding pressurized fluid, a maximum indentation depth of 100 μm is advantageous. However, when the indentation depth is controlled, it may be difficult to achieve the target level of compressive residual stress using a single disk to form a single indentation. However, when a disk assembly comprising multiple disks spaced apart from each other in the width direction is positioned, multiple shallow indentations can be formed. The compressive residual stress distribution of each indentation can accumulate to form compressive residual stress (the final compressive residual stress applied to the parent material). Therefore, this helps to achieve the target level of compressive residual stress even with shallow indentations.

[0114] In a specific example, l (l is a natural number from 2 to 4) disks spaced apart from each other along the longitudinal direction of the weld line can be positioned within the deformation target area.

[0115] Figure 10 The diagram illustrates the following process: In a method for reducing residual welding stress according to a specific example, two disks 341 and 342 are positioned within the deformation target area 110, but spaced apart from each other along the longitudinal direction of the weld line 200.

[0116] In this case, based on the motion directions of disks 341 and 342 (e.g. Figure 10 (As shown by the arrow in the image), the motion trajectories of the front disk 341 and the rear disk can overlap.

[0117] Since the motion trajectories of disks 341 and 342 overlap, in the deformation target area 110, the first indentation line 510 can be formed first by the preceding disk 341, and then the second indentation line 520 can be formed to at least partially overlap with the first indentation line 510, thereby forming an indentation line 500 with the final designed cross-sectional shape.

[0118] Figure 10 The example illustration shows an example where the width of the first crease line 510 is greater than the width of the second crease line 520, and thus the second crease line 520 is formed again within the pre-formed first crease line 510, but this disclosure is not limited thereto.

[0119] By overlapping the first indentation line 510 and the second indentation line 520 to form the final indentation line 500, the distribution of compressive residual stress formed in the base material can be controlled more precisely compared to forming the indentation line 500 with a single disk.

[0120] For example, the width of the first indentation line can be narrower than the width of the second indentation line. In extreme cases, the second indentation line may be so wide and deep that, when only the physical shape of the final indentation line is observed, it appears as if only the second indentation line exists. However, even when the first indentation line is formed beforehand and the second indentation line is subsequently formed to cover the first indentation line, causing any trace of the first indentation line to disappear, the distribution of compressive residual stress ultimately formed in the parent material due to the pre-formed first indentation line may differ from the distribution of compressive residual stress generated solely by the second indentation line.

[0121] Furthermore, when the first indentation line 510 is pre-formed, the target deformation area is heated by frictional heat between the disk 341 forming the first indentation line 510 and the base material 100. Then, the disk 342 forming the second indentation line 520 can again generate frictional heat. In other words, while a wide area of ​​the base material is heated by the preceding disk 341, the area where a deep indentation is to be formed can be selectively and additionally heated by the following disk 642. This heat control allows the disks to move more quickly while simultaneously preventing excessive heat from being applied to the base material area other than the intended area.

[0122] Figure 11 This is a process diagram illustrating an example of how a third disc group 340A and a fourth disc group 340B are spaced apart from each other in the longitudinal direction of the weld line 200 and form indentation lines 500A or 500B in each of the deformation target areas 110A and 110B on both sides of the weld line 200, wherein the third disc group 340A includes l (where l is a natural number from 2 to 4, in Figure 11 In the example, l=2) disks 341A and 342A, disks 341A and 342A are spaced apart from each other in the longitudinal direction of welding line 200, and the fourth disk group 340B includes m (where m is a natural number from 2 to 4, in Figure 11 In the example, m=2) disks 341B and 342B, disks 341B and 342B are spaced apart from each other in the longitudinal direction of the weld line 200, and in the indentation lines 500A or 500B, at least two or more indentations overlap each other.

[0123] As in Figure 11 As shown in the example, a disk assembly comprising multiple disks spaced apart from each other in the longitudinal direction is positioned in each deformation target area with a weld line placed therebetween to form an indentation line, thereby creating a more precisely controlled distribution of compressive residual stress and rapidly reducing weld residual stress under controlled heat distribution.

[0124] like Figure 10 and Figure 11 As the example shows, even when multiple disks are arranged spaced apart from each other in the longitudinal direction of the weld line, the compressive load applied to each disk, as well as the thickness, edge shape, tilt angle, and diameter of the disk ( Figure 10 and Figure 11 (As shown in the example) and one or more factors such as rotation speed can be different or the same. Furthermore, one or more selected factors can be controlled for each disk.

[0125] Figure 8 and Figure 9 The example illustration shows multiple disks spaced apart from each other along the width of the weld line in a deformable target area, and Figure 10 and Figure 11 The example illustration shows multiple disks spaced apart from each other along the longitudinal direction of the weld line within a deformable target area. However, the spacing direction of the disks is not limited to the width direction or the longitudinal direction.

[0126] When the plurality of disks (disc groups) are arranged spaced apart from each other in a deformable target area, the spacing may include: a spacing in the width direction of the weld line; a spacing in the longitudinal direction of the weld line; and / or a spacing in both the width direction and the longitudinal direction of the weld line.

[0127] "The spacing in the width direction and the spacing in the longitudinal direction of the weld line" can refer to the disk assembly comprising disks spaced apart from each other in the width direction of the weld line relative to disk A and disks spaced apart in the longitudinal direction of the weld line relative to disk A. At the same time or independently, "the spacing in the width direction and the spacing in the longitudinal direction of the weld line" can indicate that the disk assembly comprises at least one disk spaced apart by a predetermined distance in the width direction of the weld line relative to disk A and also spaced apart by a predetermined distance in the longitudinal direction of the weld line.

[0128] When the disk assembly is located within the target deformation area, the moving speed of each disk forming the disk assembly can be at least substantially the same. Furthermore, the moving speeds of the first and second disk assemblies can be substantially the same; however, depending on the target objective, the moving speeds of the first and second disk assemblies can be controlled differently.

[0129] At the point where the indentation is formed by the disc or a group of discs, the temperature in the deformation target region allows for the achievement of the target compressive residual stress distribution and enables the application of a significantly reduced compressive load. However, it is preferable that the temperature (maximum temperature) in the deformation target region is higher than an undesirable phase transformation temperature, etc., without adversely affecting the base material. For example, when the steel is a high-strength steel with high yield strength (e.g., YS690 grade), it is preferable to control the temperature (maximum temperature) in the deformation target region below the eutectoid transformation point (Al transformation point). As a practical and non-limiting example, in the case of high-strength steel with high yield strength (e.g., YS690 grade), the maximum temperature in the deformation target region (the area where the disc contacts the deformation target region) can be 500°C to 600°C.

[0130] Considering the material properties of steel, the moving speed of the disc or disc assembly can be any speed sufficient to form the desired indentation line. As a practical and non-limiting example, when the steel is a high-strength steel with a high yield strength (e.g., YS690 grade), the moving speed can be, but is not limited to, 10 cm / min to 60 cm / min.

[0131] Considering the materials used, the thickness of the disk is sufficient to ensure stable rotation, prevent bending, and achieve the desired edge shape. As a practical and non-limiting example, when the disk is made of carbon steel, the thickness can range from 1 mm to 10 mm, but is not limited to this. Furthermore, as mentioned above, depending on the edge shape, the thickness of the disk and the size of the indentation can be substantially independent.

[0132] By considering the specific properties of the base material, the weld structure (joint configuration), the size of the area in the target deformation region where compressive residual stress will form, and the specific arrangement within the disk assembly during its construction, the rotational speed of the disk can be any speed sufficient to achieve the target heat distribution. As a practical and non-limiting example, when a single disk with a diameter of 100 mm or greater is located in the target deformation region and the steel is a high-strength steel with high yield strength (e.g., YS690 grade), the rotational speed can range from 10 rpm to 600 rpm. It should be noted that the rotational speed can vary outside the specified range depending on the type of disk assembly used and the specific arrangement within it.

[0133] By considering the specific characteristics of the base material, the edge shape of the disk, the tilt angle of the disk, the target temperature distribution in the deformation target area, the distribution of welding residual stress formed in the deformation target area, the welding structure (joint configuration), and the specific arrangement within the disk assembly when it is constructed, the compressive load applied to the disk can be a compressive load that can form the target compressive residual stress distribution. As a practical and non-limiting example, when a single disk is located in the deformation target area, is a butt joint, and is welded using single-pass submerged arc welding (SAW), the disk has rounded edges and a tilt angle of 0° (perpendicular to the surface of the deformation target area), and the steel is a high-strength steel with high yield strength (e.g., YS690 grade), by considering the contact area between the disk and the base material, the compressive load applied to the disk can be a load that applies a pressure of 250 MPa to 350 MPa to the base material.

[0134] According to a specific example, the above-described method for reducing welding residual stress can be performed during welding between base materials after the welding process.

[0135] In this configuration, the frictional heat generated by the disk is added to the deformation target area, which has residual welding heat, and the temperature distribution in the deformation target area can be controlled. The residual welding heat significantly reduces the amount of frictional heat generated by the disk, allowing the disk to move faster and making the heating of the target area (with additional heating via frictional heat) more precise and selective.

[0136] According to a specific example, a method for reducing welding residual stress may also include the following steps: annealing the steel structure after forming continuous linear indentations, and performing a surface treatment step after annealing to remove surface irregularities caused by the indentations.

[0137] Annealing aims to relieve stress in areas where plastic deformation occurs due to the disk, and can be performed by applying heat of approximately 200°C or lower, or essentially 100°C to 200°C, to the area located by the indentation line. In this case, heat can be applied by thermal radiation, including near-infrared or infrared radiation, the application of hot air, contact with a heating element, loading into a constant-temperature space, etc., but this disclosure is not limited to a specific annealing method.

[0138] Surface treatment can include, but is not limited to, physical surface treatments such as grinding.

[0139] The methods described above for reducing welding residual stress are particularly useful when the specific application of the steel structure makes tensile residual stress have a detrimental effect. Examples of steel structure applications where tensile residual stress has a detrimental effect include fluid storage containers, such as high-pressure gas or high-pressure liquid containers, ship structures, marine structures, offshore wind turbine monopiles, and automobile bodies. However, this disclosure is not limited to applications of steel structures.

[0140] The following describes in detail an apparatus for reducing residual welding stress in steel structures with weld lines.

[0141] In the device for reducing welding residual stress, the weld line, steel structure, base material, interface between weld bead and base material, target deformation area, disk, disk assembly, indentation, indentation line, formation of indentation line, compressive load (axial load), and distribution of compressive residual stress formed in the base material are similar to or the same as those described in the methods for reducing welding residual stress. Therefore, the device for reducing welding residual stress includes all of the contents described in the methods for reducing welding residual stress.

[0142] According to one disclosure, an apparatus for reducing welding residual stress in a steel structure with weld lines includes: a deformation unit comprising a disk capable of rotating while in contact with the base material in a deformation target area, the deformation target area being a base material region near the interface between the weld bead of the weld line and the base material; a load application unit applying an axial load to the disk of the deformation unit in the direction of the base material; and a conveying unit I conveying the deformation unit along the weld line in the longitudinal direction of the weld line, such that the disk is positioned within the deformation target area.

[0143] According to another disclosure, an apparatus for reducing welding residual stress in a steel structure with weld lines includes: a deformation unit comprising a disk rotatably disposed and in contact with the base material in a deformation target area, the deformation target area being the base material region near the interface between the weld bead of the weld line and the base material; a load application unit applying an axial load (compressive load) to the disk of the deformation unit in the direction of the base material; and a conveying unit II conveying the steel structure along the longitudinal direction of the weld line such that the disk is located within the deformation target area.

[0144] As mentioned above, the equipment for reducing welding residual stress includes two modes: the case where the component conveyed by the conveying unit is a steel structure and the case where the deformation unit is a deformation unit.

[0145] The deformation unit may include conventional rotating devices capable of rotating the disk. For example, the deformation unit may include: a magnetically based rotating device that is fixed by a magnetic connection and can be rotated by a rotating magnetic field; or a mechanical rotating device that includes a rotating shaft that is rotated by a mechanical force such as an electric motor or air pressure.

[0146] To achieve precise and simple independent rotational speed control for each disk, the rotating device can be magnetically driven. The magnetically driven rotating device can include a driving magnet and a rotating magnet, which intersects the driving magnet at a 90° angle with a predetermined gap. The rotating magnet rotates via the attractive and repulsive forces generated between it and the driving magnet. The disk can be connected to the rotating magnet via a rotating shaft, allowing the disk to rotate integrally with the rotating magnet.

[0147] The load application unit may include a conventional pressurizing device configured to apply pressure to a disk, specifically to the disk's axis of rotation, causing the disk to apply a compressive load to the base material. Examples of pressurizing devices include, but are not limited to, pneumatic drives, hydraulic drives, and mechanical displacement drives.

[0148] The conveying unit I may include a conventional conveying device I that allows a deformation unit, including a disk, to move along the weld line of the steel structure. The specific conveying device I can be determined and provided by considering the physical shape of the weld line within the steel structure. For example, when the weld line is straight, the conveying device I may include a forward-backward operating X-axis unit. As another example, when the weld line is a curve in a plane, the conveying device I may include a left-right operating Y-axis unit, a forward-backward operating X-axis unit, and a rotating unit that rotates horizontally about a rotation axis. As yet another example, when the weld line has a three-dimensional curved profile, the conveying device I may include a forward-backward operating X-axis unit, a left-right operating Y-axis unit, a up-down operating Z-axis unit, and a rotating unit that rotates horizontally about a rotation axis. In this case, regardless of the physical shape of the weld line, the conveying device I may include a Z-axis unit, and the lifting and lowering of the deformation unit can be controlled by this Z-axis unit. That is, when the residual stress reduction device is operating, the deformation unit can move via the Z-axis unit to contact the target deformation area, and when the residual stress reduction device is terminated, the deformation unit can move via the Z-axis unit to avoid contact with the target deformation area.

[0149] The conveying unit II may include a conventional conveying device II that allows the target area of ​​the steel structure to move along the weld line below the deformation unit, which includes a disc fixed at a predetermined position. The specific conveying device II can be determined and provided by considering the physical shape of the weld line within the steel structure. For example, when the weld line is straight or curved, the conveying unit may include a belt conveyor or roller conveyor driven by a power source. As another example, when the weld line has a three-dimensional curved profile, the conveying device II may include a forward-backward operating X-axis unit, a left-right operating Y-axis unit, a vertical operating Z-axis unit, and a rotating unit that rotates horizontally about a rotation axis. The weld residual stress reduction device may also include a lifting member that moves the deformation unit up and down while the conveying unit conveys the steel structure. The lifting member can control the lifting and lowering of the deformation unit and can contact / separate the deformation unit from the steel structure during operation / termination of the equipment.

[0150] Based on the above Figure 7 The method is similar or identical. The deformation unit may include two disks that are spaced apart from each other with a welding line placed between them, and the two disks respectively contact the deformation target area on both sides of the welding line.

[0151] Based on the above Figure 8 and Figure 9 Similar or identical, the deformation unit includes a first disk group and a second disk group, the first disk group and the second disk group are arranged spaced apart from each other with a welding line placed between the first disk group and the second disk group and contact the deformation target area on both sides of the welding line. The first disk group may include j (where j is a natural number from 2 to 5) disks arranged spaced apart from each other in the width direction of the welding line, and the second disk group may include k (where k is a natural number from 2 to 5) disks arranged spaced apart from each other in the width direction of the welding line.

[0152] With based Figure 10 and Figure 11 The above-mentioned deformation units are similar or identical. The deformation unit includes a third disk group and a fourth disk group. The third disk group and the fourth disk group are arranged apart from each other with the welding line placed between the third disk group and the fourth disk group and respectively contact the deformation target area on both sides of the welding line. The third disk group may include l (where l is a natural number from 2 to 4) disks spaced apart from each other in the longitudinal direction of the welding line, and the fourth disk group may include m (where m is a natural number from 2 to 4) disks spaced apart from each other in the longitudinal direction of the welding line.

[0153] If necessary, the device may also include a tilting unit that tilts the disk at a predetermined angle.

[0154] In one specific example embodiment, the device may also include a control unit. The control unit may control the rotational speed of each disk by operating mechanical or magnetic rotating devices, control the conveying speed of the deformation unit or steel structure via conveying device I and conveying device II, and / or control the load applied to each disk via a load applying unit.

[0155] While exemplary embodiments have been shown and described above, it will be apparent to those skilled in the art that modifications and variations may be made without departing from the scope of this disclosure as defined by the appended claims.

[0156] Explanation of reference numerals in the attached figures

[0157] 100: Base Material

[0158] 110, 110A, 110B: Deformation target areas

[0159] 210: Weld bead

[0160] 200: Welding line

[0161] 310, 310A, 310B, 321, 322, 323, 341, 342: Disks

[0162] 320A, 320B, 340A, 340B: Panel Sets

[0163] 410: Indentation

[0164] 400, 400A, 400B, 500A, 500B: Indentation lines

Claims

1. A method for reducing residual welding stress in a steel structure with weld lines, the method comprising: Plastic deformation of the target area is achieved by bringing a disk into contact with the target area and applying a compressive load to the target area by rotating the disk. The target area is the base material area near the interface between the weld bead of the weld line and the base material. as well as The steel structure or the disk is transferred within the target deformation region such that the indentation caused by the plastic deformation extends along the weld line in a continuous linear manner.

2. The method according to claim 1, wherein, During the plastic deformation, the target deformation region is heated at least by the frictional heat generated by the rotation of the disk.

3. The method according to claim 2, wherein, The depth of the indentation is controlled by the heating temperature of the deformable target area and the compressive load applied by the disk.

4. The method according to claim 2, wherein, The diameter of the disk is 100 mm or greater.

5. The method according to claim 2, wherein, The edge of the disk is tapered, rounded, or eccentric.

6. The method according to claim 1, wherein, The disk is perpendicular to the surface of the deformation target area where the indentation is formed, or the disk is tilted at an angle of 65° or less.

7. The method according to claim 1, wherein, n indentations are formed in the deformation target area by means of n (where n is a natural number from 2 to 5) disks spaced apart from each other in the width direction of the weld line.

8. The method according to claim 1, wherein, Two disks are arranged spaced apart from each other with the welding line placed between them, such that an indentation is formed in each of the deformation target areas on both sides of the welding line.

9. The method according to claim 1, wherein, A first disk group comprising j (where j is a natural number from 2 to 5) disks spaced apart from each other in the width direction of the weld line, and a second disk group comprising k (where k is a natural number from 2 to 5) disks spaced apart from each other in the width direction of the weld line, are arranged such that the weld line is placed between the first disk group and the second disk group, such that j indentations are formed in one deformation target region and k indentations are formed in the other deformation target region on both sides of the weld line.

10. The method according to claim 1, further comprising: l (where l is a natural number from 2 to 4) disks are arranged spaced apart from each other in the longitudinal direction of the welding line.

11. The method according to claim 10, wherein, The third disk group, comprising the l disks, and the fourth disk group, comprising m (where m is a natural number from 2 to 4) disks spaced apart from each other in the longitudinal direction of the welding line, are arranged such that the welding line is placed between the third disk group and the fourth disk group, such that at least two indentations are overlapped in each of the deformation target areas on both sides of the welding line.

12. The method according to claim 9 or 11, wherein, The disks forming the disk assembly are the same or different in at least one of the following factors: disk diameter, disk thickness, disk edge shape, disk tilt angle, compressive load applied to the disk, and disk rotation speed.

13. The method according to claim 1, wherein, The deformation target area is the region within 0.1 cm to 20 cm from the interface toward the parent material.

14. The method according to claim 2, wherein, The frictional heat is applied to the deformable target region that has residual welding heat.

15. The method according to claim 1, further comprising: After completing the formation of continuous linear indentations, The steel structure with the indentations is annealed; and After the annealing, a surface treatment step is performed to remove surface irregularities caused by the indentations.

16. The method according to claim 1, wherein, The steel structure can be a fluid storage container, a ship structure, a marine structure, an offshore wind power monopile, or a car body.

17. An apparatus for reducing residual welding stress in a steel structure with weld lines, the apparatus comprising: A deformation unit, comprising a disk capable of rotating while in contact with the base material in a deformation target area, wherein the deformation target area is the base material region near the interface between the weld bead of the welding line and the base material; A load application unit applies an axial load to the disk of the deformation unit along the direction of the parent material; as well as A conveying unit conveys the steel structure in the longitudinal direction of the welding line, such that the disk is located within the deformation target area.

18. An apparatus for reducing residual welding stress in a steel structure with weld lines, the apparatus comprising: A deformation unit, comprising a disk capable of rotating while in contact with the base material in a deformation target area, wherein the deformation target area is the base material region near the interface between the weld bead of the welding line and the base material; A load application unit applies an axial load to the disk of the deformation unit along the direction of the parent material; as well as A conveying unit conveys the deformation unit along the longitudinal direction of the welding line, such that the disk is located within the deformation target area.

19. The device according to claim 17 or 18, wherein, The deformation unit includes two disks, which are spaced apart from each other with the welding line placed between them, and each disk contacts the deformation target area on both sides of the welding line.

20. The device according to claim 17 or 18, wherein, The deformation unit includes a first disk group and a second disk group, which are arranged spaced apart from each other with the welding line placed between them, and each disk group contacts the deformation target area on both sides of the welding line. The first disk group comprises j disks (where j is a natural number from 2 to 5) arranged at intervals from each other in the width direction of the weld line, and The second disk group comprises k disks (where k is a natural number from 2 to 5) arranged at intervals from each other in the width direction of the welding line.

21. The device according to claim 17 or 18, wherein, The deformation unit includes a third disk group and a fourth disk group, which are arranged spaced apart from each other with the welding line placed between them, and each disk group contacts the deformation target area on both sides of the welding line. The third disk group comprises l disks (where l is a natural number from 2 to 4) arranged at intervals from each other in the longitudinal direction of the welding line. The fourth disk group comprises m disks (where m is a natural number from 2 to 4) arranged at intervals from each other in the longitudinal direction of the welding line.

22. The device according to claim 17 or 18, further comprising: A control unit that controls one or more factors selected from the rotational speed of the disk, the conveying speed of the conveying unit, and the load applied to the disk by the load applying unit.

Images