Welding method

Abstract

To provide a welding method for efficiently welding a column member while securing a quality.SOLUTION: In a welding method, end parts of two columns 11 and 12 provided with a plurality of election pieces 11e and 12e and vertically arranged are welded using a welding robot. First and second weld regions Wa1 and Wa2 including two opposing corner parts of the columns 11 and 12 are welded first. then the erection pieces 11e and 12e are removed, and remaining third and fourth weld regions Wa3 and Wa4 are welded second. In the first welding and in the second welding, passes in the welding are welded by heat input of 5 kJ / cm or more and less than 15 kJ / cm at a temperature of 450°C or lower.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a welding method for welding a joint portion of column members constituting a steel column of a building.

Background Art

[0002] Conventionally, a steel column of a building is configured by welding a plurality of steel pipes in the vertical direction. In the welding operation of these steel pipes, a welding robot may be used (see, for example, Patent Document 1). In the welding system described in Patent Document 1, a guide rail using a corner unit having a straight portion and a curved portion is attached to the outer periphery of a square steel pipe to be welded. Further, a welding robot is provided slidably on the guide rail. When the position of the center of curvature of the welding portion and the position of the center of curvature of the position where the welding robot is located are different, the control unit of the control device controls the moving speed of the welding robot so that the length of the welding portion per unit time (welding speed) becomes constant.

[0003] Conventionally, since the welded portion involves rapid solidification shrinkage, thermal history, and strain history, it may cause welding defects such as material changes in the base metal portion, thermal stress, deformation, and cracking (see, for example, Non-Patent Document 1). As shown in this Non-Patent Document 1, neither slow cooling nor rapid cooling is preferable for the welded portion. FIG. 14 shows an appropriate construction region between slow cooling and rapid cooling described in Non-Patent Document 1.

[0004] Conventionally, welding temperature control was performed using the heat input and interpass temperature (temperature between passes in multi-layer welding) to ensure that the cooling rate of the welded area fell within the appropriate welding range. This is because the mechanical properties of the weld metal vary greatly depending on the welding conditions, even when using the same welding material. In particular, heat input and interpass temperature have a significant impact on the strength and toughness of the weld metal (see, for example, Non-Patent Documents 2 and 3). Non-Patent Document 2 shows the relationship between heat input of 15 kJ / cm to 50 kJ / cm, stress, and absorbed energy. Non-Patent Document 3 describes the main wire usage categories in steel frame buildings when the heat input is 15 kJ / cm to 30 kJ / cm (or 40 kJ / cm). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2018-58078 [Non-patent literature]

[0006] [Non-Patent Document 1] Edited by the Japan Welding Society, "New Edition: Personal Theories on Welding and Joining Technology," Sanpo Publishing, March 1, 2005, pp. 360-361. [Non-Patent Document 2] Edited by the Editorial Committee for the 2018 Cold-Formed Square Steel Pipe Design and Construction Manual, "2018 Cold-Formed Square Steel Pipe Design and Construction Manual," published by the Japan Building Center, supervised by the National Institute for Land and Infrastructure Management, February 28, 2018, pp. 146-150. [Non-Patent Document 3] "JIS Z 3312:2009 (JWES / JSA) Solid Wires for MAG Welding and MIG Welding for Mild Steel, High-Tensile Steel, and Low-Temperature Steel," published by the Japanese Standards Association, February 20, 2009, p. 40. [Overview of the project] [Problems that the invention aims to solve]

[0007] When welding is performed using a welding robot, "sideways welding" is sometimes used, where the tip of the welding torch of the welding robot contacts the welding area from the side. In this "sideways welding" method, compared to downward welding, more molten metal tends to drip from the welding area, so the amount of molten metal is reduced by lowering the heat input.

[0008] However, the aforementioned Non-Patent Documents 2 and 3 only describe heat inputs of 15 kJ / cm or more. Therefore, conditions for using heat of less than 15 kJ / cm are not considered. [Means for solving the problem]

[0009] A welding method that solves the above problem is a welding method for welding the ends of two column members arranged vertically, wherein the interpass temperature of the welding is 450°C or less, and the welding is performed with a heat input of 5 kJ / cm or more and less than 15 kJ / cm. [Effects of the Invention]

[0010] According to the present invention, quality can be ensured and column members can be welded efficiently. [Brief explanation of the drawing]

[0011] [Figure 1] This is a perspective view illustrating the state in which a welding robot for performing the welding method of the embodiment is attached. [Figure 2] This is a top view showing a welding robot attached to perform the welding method of the embodiment. [Figure 3] This is an explanatory diagram illustrating the welding method of the embodiment, where (a) shows the state after welding the opposing corners, (b) shows the state after removing the erection piece, and (c) shows the state after welding the remaining part. [Figure 4] This is an explanatory diagram illustrating the regions of each weld line and the arrangement of thermocouples in the test specimen according to the embodiment. [Figure 5]It is a graph showing the temperature change and heat input according to time in the welding line 2A in the embodiment. [Figure 6] It is a graph showing the temperature change and heat input according to time in the welding line 3A in the embodiment. [Figure 7] It is a graph showing the temperature change and heat input according to time in the welding line NA in the embodiment. [Figure 8] It is a graph showing the temperature change and heat input according to time in the welding line 2B in the embodiment. [Figure 9] It is a graph showing the temperature change and heat input according to time in the welding line 3B in the embodiment. [Figure 10] It is a graph showing the temperature change and heat input according to time in the welding line NB in the embodiment. [Figure 11] It is a graph showing the yield point with respect to the maximum inter-pass temperature in the embodiment, where (a) shows the case where the welding wire is YGW18 and (b) shows the case where the welding wire is G59JA1UC 3M1T. [Figure 12] It is a graph showing the tensile strength with respect to the maximum inter-pass temperature in the embodiment, where (a) shows the case where the welding wire is YGW18 and (b) shows the case where the welding wire is G59JA1UC 3M1T. [Figure 13] It is a graph showing the Charpy value with respect to the maximum inter-pass temperature in the embodiment, where (a) shows the case where the welding wire is YGW18 and (b) shows the case where the welding wire is G59JA1UC 3M1T. [Figure 14] It is a graph showing the cooling rate of the welded part and the soundness of the joint in the prior art.

Mode for Carrying Out the Invention

[0012] Hereinafter, an embodiment in which the welding method is embodied will be described with reference to FIGS. 1 to 13. In this embodiment, the welding method when joining a plurality of square steel pipes (columns) in the vertical direction to form the same single column will be described.

[0013] FIG. 1 is a perspective view in which a guide rail 30 and a welding robot 40 are installed on a column 12 disposed above a column 11, and FIG. 2 is a plan view thereof. In this embodiment, the columns 11 and 12 to be welded have the same shape and, for example, have a length corresponding to three floors. These columns 11 and 12 are annular steel pipes (square cross-section) having four corners in the shape of a quarter circle.

[0014] At the center of each side of the upper and lower ends of the columns 11 and 12, erection pieces 11e and 12e are provided at the upper and lower ends. A plurality of through holes are formed in a row in the erection pieces 11e and 12e. The erection pieces 11e and 12e of the upper and lower columns 11 and 12 are sandwiched between two splice plates 20 and aligned in a straight line. Then, the erection pieces 11e and 12e are fixed by bolts inserted through the through holes of the splice plate 20 and nuts screwed thereto. Thereby, the upper and lower columns 11 and 12 are aligned in a straight line. In addition, a beveled portion is formed at the lower end of the column 12 disposed on the upper side.

[0015] (Configuration of Guide Rail 30 and Welding Robot 40) In this embodiment, in the upper column 12, a guide rail 30 is attached in the vicinity of the lower end. This guide rail 30 has an annular shape surrounding the outer periphery of the columns 11 and 12 to be welded. Specifically, the guide rail 30 includes four corner units 31 corresponding to each corner of the columns 11 and 12. Each corner unit 31 has a quarter-circle arc-shaped curved portion corresponding to the corner of the columns 11 and 12 and two straight portions respectively connected to both ends of this curved portion. Here, when the size of the columns 11 and 12 is large, a linear rail can be additionally provided between each corner unit 31 to form a guide rail 30 adapted to the size of the columns 11 and 12.

[0016] Furthermore, the guide rail 30 includes a plurality of mounting portions 35 that are spaced apart on the outer circumference of the upper column 12. These mounting portions 35 fix the guide rail 30 to the outer circumference of the column 12 by tightening bolts, which press the tips of the bolts against the outer surface of the column 12.

[0017] The welding robot 40 is slidably mounted on the guide rail 30. In this embodiment, two welding robots 40 are mounted on the guide rail 30. The welding robot 40 used is the "Ishimatsu Multilayer Welding Robot" from MHI Solution Technologies Co., Ltd.

[0018] The welding robot 40 comprises a trolley 41, a control cable 42, a conduit cable 44, and a welding torch 45. The trolley 41 is attached to the guide rail 30. The trolley 41 slides along the guide rail 30 at a speed corresponding to a control signal from a control device (not shown) via the control cable 42. A welding wire passes through the conduit cable 44 and supplies the welding wire to the welding torch 45. The tip of the welding torch 45 is positioned so as to face the welding portion located below the guide rail 30. In this case, the tip of the welding torch 45 is positioned horizontally offset from the welding portion. Therefore, the welding robot 40 performs welding on the welding portion in a lateral direction using the welding wire.

[0019] (Welding method) Next, the welding method of this embodiment will be described. In this embodiment, welding is performed with the interpass temperature set to 450°C or lower and the heat input to the intermediate layer set to 5kJ / cm to 15kJ / cm.

[0020] Specifically, first, as shown in Figure 1, column 12 is placed and fixed on top of column 11. Specifically, the erection pieces 11e and 12e of columns 11 and 12 are aligned in a straight line, sandwiched between splice plates 20, and fixed with bolts and nuts.

[0021] Next, as shown in Figure 3(a), each welding robot 40 is used to weld the first welding area Wa1 and the second welding area Wa2 of the welding target area of ​​columns 11 and 12, respectively. The first and second welding regions Wa1 and Wa2 are the regions between the upper surface of the lower column 11 and the groove of the upper column 12. Furthermore, these first and second welding regions Wa1 and Wa2 each include the corner regions of columns 11 and 12, and are regions that are point-symmetrical with respect to the central axis C1 of columns 11 and 12. The first and second welding regions Wa1 and Wa2 are located between adjacent erection pieces 11e and 12e in the welding target region (all around). In this embodiment, with the erection pieces 11e and 12e arranged, the welding robot 40 sets the maximum range that can be welded (by normal welding operation) as the first and second welding regions Wa1 and Wa2.

[0022] In this embodiment, welding in the first and second welding regions Wa1 and Wa2 is performed using multiple passes with multi-layer welds. The interpass temperature is kept below 450°C. In this case, temperature measurement is performed using thermal chalk. Specifically, before starting the formation of each welding pass, the base material (the upper surface of the lower column 11 and the groove of the upper column 12) at the starting position of the passes in the first and second welding regions Wa1 and Wa2 is marked with thermal chalk that melts at 450°C or higher. If this thermal chalk melts, the temperature measurement is repeated until the chalk stops melting.

[0023] Then, when the thermal choke stops melting, the formation of the welding pass begins. Furthermore, in this case, the arc current, welding current, and welding speed are adjusted so that the heat input is between 5 kJ / cm and less than 15 kJ / cm. Subsequently, welding of the first welding area Wa1 and the second welding area Wa2 is completed by the formation of multiple welding passes.

[0024] Next, as shown in Figure 3(b), the erection pieces 11e and 12e are removed. Specifically, the bolts, nuts, and splice plates 20 are removed from the erection pieces 11e and 12e. Then, the erection pieces 11e and 12e are cut from the columns 11 and 12 by gas cutting or the like. In this case, the columns 11 and 12 are joined at the welded portions of the first welding area Wa1 and the second welding area Wa2.

[0025] Then, as shown in Figure 3(c), the third welding area Wa3 and the fourth welding area Wa4 are welded using each welding robot 40. These third and fourth welding areas Wa3 and Wa4 each include corners and are opposing unwelded portions, and are adjacent to the first welding area Wa1 and the second welding area Wa2, respectively.

[0026] Welding of the third and fourth welding regions Wa3 and Wa4 is carried out in the same manner as for the first and second welding regions Wa1 and Wa2. That is, the arc current, welding current, and welding speed are adjusted so that the interpass temperature is 450°C or less, and the heat input is 5 kJ / cm or more but less than 15 kJ / cm. After that, welding of the third and fourth welding regions Wa3 and Wa4 is completed by forming multiple passes. As a result, the upper end of the lower column 11 and the lower end of the upper column 12 are joined together by welding, and the upper and lower columns 11 and 12 are integrated into one unit.

[0027] <Evaluation of the validity of welding methods> The welding method described above was evaluated for validity based on the following experimental results. (Test specimens and experimental methods used in the test) Figure 4 shows column 50, the test specimen used in the experiment. Column 50 is made of BCP385 and measures 800 mm in length and width and 40 mm in thickness. The size and thickness are exaggerated in Figure 4.

[0028] In the experiment, a column made of BCP325 with dimensions of 700mm x 25mm in thickness and a column made of BCP385 with dimensions of 650mm x 50mm in thickness were also used as test specimens. Two types of welding wire were used: YGW18 and G59JA1UC 3M1T (formerly YGW21).

[0029] Then, the welding line around the entire circumference of column 50 was divided into six sections and welded. Here, a guide rail 30 with the configuration shown in Figures 1 and 2 is attached to the test specimen (column 50, etc.), and then two welding robots 40 with the above-described configuration are attached to the guide rail 30. Welding is then performed by lateral welding using these welding robots 40. Specifically, first, two welding robots 40 were used to pre-weld welding lines 2A and 3A simultaneously. Next, weld line NA was welded first, while weld line 2B was welded later. Finally, welding lines 3B and NB were welded simultaneously as a follow-up weld.

[0030] In this experiment, thermocouple T1 was placed 10 mm from the center of the opening at the end of weld lines 2A, 2B, 3A, 3B, NA, and NB. Weld lines 2A and 2B were welded at an interpass temperature of 250°C or less, and weld lines 3A and 3B were welded at an interpass temperature of 350°C or less. Weld lines NA and NB were welded without interpass temperature control. Slag removal was performed after each layer for weld lines 2A and 2B, and after every two layers for the other weld lines.

[0031] Figures 5 to 10 show the temperature and heat input history for weld lines 2A, 3A, NA, 2B, 3B, and NB of column 50. In these figures, the dotted line represents the total temperature history, the circles (〇) represent the interpass temperature, the lines extending vertically from the circles represent the temperature during welding, the lines extending horizontally represent the heat input for each welding pass, and HIave represents the average heat input of the intermediate layer. In addition, ITmax in Figures 7 and 10, which show weld lines NA and NB, represents the highest interpass temperature.

[0032] Here, comparing "2A, 3A, NA" and "3B, NB," which have the same weld length, the higher the interpass temperature, the shorter the welding time. However, there was no significant difference in welding time between interpass temperatures below 350°C and uncontrolled temperatures. This trend was similar for the cross-sections of the columns and welding wires of the other test specimens. Furthermore, in this test, all three types of test specimens, including the case with no temperature control, showed good weld appearance. Table 1 below shows the average heat input to the intermediate layer. Here, the intermediate layer is the layer excluding the initial and final layers. The average heat input to the intermediate layer is the average of the heat inputs when forming all the paths that make up the intermediate layer.

[0033] [Table 1]

[0034] As shown in Figures 5 to 10, the heat input for the first pass of the initial layer of each weld line 2A to NB was approximately 20 to 25 kJ / cm. The heat input for the second pass of the initial layer of weld line NA also exceeded 15 kJ / cm. However, the majority of the other passes had a heat input of less than 15 kJ / cm. The average heat input for the intermediate layer was approximately 12 kJ / cm, as shown in Table 1. The final pass used a low heat input (5 to 7 kJ / cm) for surface finishing.

[0035] (Evaluation of strength) A tensile test of the weld metal was performed using the test specimens described above. The results of the weld metal tensile test in this case are shown in Table 2.

[0036] [Table 2]

[0037] In each column of Table 2, the interpass temperature control values ​​are shown in the order of "250°C or less / 350°C or less / no control". In this test, the maximum interpass temperature reached approximately 450°C in the case of no temperature control. However, as shown in Table 2, the yield point σy, tensile strength σu, and elongation at break EL for all test specimens satisfied the standard values ​​for each welding wire.

[0038] Figures 11 and 12 show the relationship between the maximum interpass temperature and the yield point σy or tensile strength σu. The circled numbers in Figures 11 and 12 correspond to the circled numbers in Table 2, respectively. Note that the gray areas in Figures 11 and 12 indicate the results for corners. Figures 11(a) and 12(a) show the case for YGW18 welding wire, and Figures 11(b) and 12(b) show the case for G59JA1UC 3M1T welding wire. In Figures 11 and 12, the dotted line indicated by the top vertex of the black upward-pointing triangle indicates the lower limit of the specification, and the dotted line indicated by the bottom vertex of the black downward-pointing triangle in Figure 12 indicates the upper limit of the specification.

[0039] Figure 11 shows that the yield point σy decreases as the maximum interpass temperature ITmax increases. In particular, for the G59JA1UC 3M1T welding wire, the yield point σy was lower at the corners compared to the flat sections. However, even at 450°C, the lowest yield point σy in Figure 11(a), the lower limit of the specification was satisfied.

[0040] On the other hand, Figure 12 shows that, with respect to tensile strength σu, the decrease in strength with increasing ITmax is more gradual than that with respect to yield strength σy. At ITmax = 350℃, the ratio of yield strength σy / tensile strength σu to the lower limit of the specification was 1.10~1.25 (average 1.18) / 1.03~1.11 (average 1.07) for YGW18 and 1.13~1.40 (average 1.29) / 1.09~1.20 (average 1.17) for G59JA1UC 3M1T. Therefore, the welding wire G59JA1UC 3M1T comfortably satisfied the lower limit of the specification. Furthermore, the elongation at break satisfied the lower limit of the specification in all cases.

[0041] (Evaluation of toughness) Toughness was evaluated using Charpy impact tests, macroscopic cross-sectional tests, and Vickers hardness tests. For this test, the Charpy impact test was performed using a V-notch specimen as specified in JIS Z2242. Table 3 below shows a summary of the weld metal tensile test results.

[0042] [Table 3]

[0043] In Table 3, the Charpy values ​​are shown in the order of interpass temperature control values: "250°C or less / 350°C or less / no control". Here, the results for YGW18 at 0°C and G59JA1UC 3M1T at -5°C show that both welding wires satisfied the specified Charpy values.

[0044] Figure 13 shows the relationship between the Charpy absorption energy at 0°C and the maximum interpass temperature. Here, the circled numbers in Figure 13 correspond to the circled numbers in Table 3. Figures 13(a) and 13(b) show the cases where the welding wires are YGW18 and G59JA1UC 3M1T, respectively.

[0045] Figure 13 shows that, for YGW18 welding wire, the Charpy value remains approximately the same as at ITmax = 250°C even as ITmax increases. However, for G59JA1UC 3M1T welding wire, the decrease in the Charpy value becomes significant when ITmax exceeds 350°C.

[0046] In Table 3, locations "3" and "9" represent the Charpy values ​​of test specimens taken from the HAZ (heat-affected zone). These test specimens also showed high Charpy values, equivalent to or higher than the base metal's Charpy value of 264 J. Furthermore, the 0°C Charpy values ​​of the DEPO (weld metal) at ITmax = 350°C were 120 J or higher for both types of wire (YGW18 and G59JA1UC 3M1T).

[0047] Furthermore, 12 test specimens were taken from the flat and corner sections of column 50, spaced apart, and macroscopic cross-sectional tests were performed. The test results showed that all test specimens satisfied the approval test criteria of JASS6. In other words, they were defect-free regardless of ITmax, and no influence of ITmax was observed.

[0048] Furthermore, Vickers hardness tests were performed using macroscopic cross-sectional specimens from the corners of column 50. The results of these tests showed that the Vickers hardness was 350 Hv or less at all measurement points. Moreover, regardless of the ITmax or the measurement location (front, center, or back), the maximum hardness was approximately 220-260 Hv. As mentioned above, all toughness tests satisfied the conventional lower limit of the specifications.

[0049] (action) Welding is performed with an interpass temperature of 450°C or lower and a heat input of 5 kJ / cm or more but less than 15 kJ / cm. This allows welding to be performed with the same quality as conventional methods, even when starting pass welding at a higher temperature than before. Therefore, quality can be ensured and welding can be completed in a shorter time.

[0050] According to this embodiment, the following effects can be obtained. (1) In this embodiment, the interpass temperature is set to 450°C or lower, and the first to fourth welding regions (Wa1 to Wa4) are welded using a heat input of 5 kJ / cm or more and less than 15 kJ / cm. Even in this case, the strength (yield point σy and tensile strength σu) and toughness of the welded portion are equivalent to those of conventional interpass temperatures. Therefore, since the maximum interpass temperature can be increased to form the passes, the welding time can be shortened.

[0051] (2) In this embodiment, the welding robot 40 performs welding in a horizontal position with the heat input set to less than 15 kJ / cm. By lowering the heat input, the amount of molten metal can be reduced, thereby suppressing the dripping of molten metal from the welded area. As a result, a clean weld can be performed.

[0052] (3) In this embodiment, the first to fourth welding regions (Wa1 to Wa4) are welded by the welding robot 40. The welding robot 40 travels at a speed corresponding to the control signal from the control device, so the speed can be kept almost constant. Therefore, the heat input can be kept constant, and welding can be performed efficiently.

[0053] This embodiment can be implemented with the following modifications. This embodiment and the following modifications can be combined with each other to the extent that they do not contradict each other technically. In the above embodiment, the first and second welding areas Wa1 and Wa2, which include the two opposing corners of columns 11 and 12, were pre-welded, then the erection pieces 11e and 12e were removed, and the remaining third and fourth welding areas Wa3 and Wa4 were subsequently welded. The welding method is not limited to this two-corner pre-welding method. For example, a square pre-welding method may be used, in which the four corners of the column are pre-welded, then the erection pieces are removed, and the remaining straight section is subsequently welded. Furthermore, the range of pre-welding and subsequent welding may be changed depending on the position of the erection pieces in the column.

[0054] In the above embodiment, the temperature was measured using a thermal chalk before the path formation began. The instrument used for temperature measurement is not limited to a thermal chalk; for example, a non-contact temperature sensor may be used.

[0055] In the above embodiment, the first to fourth welding regions (Wa1 to Wa4) of columns 11 and 12 were welded with a heat input set to 5 kJ / cm or more and less than 15 kJ / cm. It is not necessary to set this heat input for the formation of all passes in welding; it is sufficient to set it for the formation of some passes in welding. For example, the first pass or the last pass may be formed using a heat input of 15 kJ / cm or more. Then, when forming other passes, if a heat input of 5 kJ / cm or more and less than 15 kJ / cm is used, the interpass temperature should be 450°C or lower. Alternatively, the passes constituting the first and second layers may be formed using a heat input of 15 kJ / cm or more. Then, the passes constituting the intermediate and final layers may be welded at an interpass temperature of 450°C or lower, using a heat input of 5 kJ / cm or more and less than 15 kJ / cm. Furthermore, in the above embodiment, the heat input was set to 5 kJ / cm or more and less than 15 kJ / cm to form the paths. However, it is not limited to setting the heat input when forming each path to 5 kJ / cm or more and less than 15 kJ / cm; for example, paths may be formed such that the average heat input of multiple paths is 5 kJ / cm or more and less than 15 kJ / cm.

[0056] In the above embodiment, two welding robots 40 were used to weld the joint portion of columns 11 and 12. The number of welding robots 40 used is not limited to two; one or more may be used. In the above embodiment, welding was performed using "sideways welding," in which the tip of the welding torch 45 of the welding robot 40 contacts the welding portion from the side (horizontally). Sideways welding can be performed by contacting the welding portion from the side (a position shifted horizontally), or by contacting it from an oblique angle that is shifted vertically. Furthermore, if a heat input of 5 kJ / cm or more and less than 15 kJ / cm is used, it is not limited to "sideways welding," but can also be applied to, for example, upward welding or downward welding. Moreover, it is not limited to welding with the welding robot 40, but can also be done manually.

[0057] In the above embodiment, the ends of columns 11 and 12, which are arranged vertically, are welded together. The column members, whose upper and lower ends are welded together, are not limited to columns (square steel pipes). For example, this method can also be used when welding column members of circular steel pipes or welded box-section columns vertically.

[0058] Next, the technical concepts that can be understood from the above embodiments and alternative examples are described below. (a) A welding method for welding the ends of two column members arranged vertically, A welding method characterized by performing the welding with an interpass temperature of 450°C or less and an average heat input of 5 kJ / cm or more and less than 15 kJ / cm. (b) The welding method according to (a), characterized in that the welding is performed by lateral welding.

[0059] (c) The welding method according to 1, 2, (a) or (b), characterized in that the welding is performed by a welding robot attached to the column member.

[0060] In welding of rectangular steel pipes, welding may be performed at temperatures below 450°C in the flat sections, but exceeding the conventional maximum interpass temperature (350°C), and welding may be performed at temperatures below 450°C in the corner sections, but within the conventional maximum interpass temperature range (250°C). (d) A welding method characterized in that the column member is a rectangular steel pipe, and in the flat portion of the rectangular steel pipe, welding is performed at an interpass temperature in the range of 350°C to 450°C, and in the corner portion of the rectangular steel pipe, welding is performed at an interpass temperature in the range of 250°C to 450°C. Furthermore, in welding square steel pipes, welding may be performed at temperatures below 450°C, but exceeding the conventional maximum interpass temperature (350°C), without distinguishing between flat and square sections. (e) The column member is a rectangular steel pipe, and the welding method is characterized in that welding is performed even in an interpass temperature range of over 350°C and up to 450°C. [Explanation of symbols]

[0061] C1...Central axis, NA, NB, 2A, 2B, 3A, 3B...Weld line, T1...Thermocouple, Wa1...First welding area, Wa2...Second welding area, Wa3...Third welding area, Wa4...Fourth welding area, 11, 12, 50...Column, 11e, 12e...Erection piece, 20...Splice plate, 30...Guide rail, 31...Corner unit, 35...Mounting part, 40...Welding robot, 41...Cart, 42...Control cable, 44...Conduit cable, 45...Welding torch.

Claims

1. A welding method for welding the ends of two column members arranged vertically, A welding method characterized by performing the welding with an interpass temperature of more than 250°C and 450°C or less, and a heat input of 5 kJ / cm or more and less than 15 kJ / cm.

2. The welding method according to claim 1, characterized in that the welding is performed by lateral welding.

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