JP4724644B2 - Steel pipe pile manufacturing method and steel pipe sheet pile manufacturing method excellent in joint fastening performance - Google Patents

Description

  The present invention relates to a method for manufacturing a steel pipe pile and a method for manufacturing a steel pipe sheet pile, which are excellent in joint fastening performance by welding a mechanical joint to a steel pipe body to form a steel pipe pile or a steel pipe sheet pile.

  Steel pipe piles and steel pipe sheet piles used for ground improvement and stabilization, for example, have a wide application range in the case of airport maintenance. Therefore, widening and high yield strength are required, and the diameter of the steel pipe body is increased. Moreover, a depth may be 50 m or more, and a steel pipe pile and a steel pipe sheet pile are divided | segmented up and down and constructed from the problem on conveyance and construction. Depending on the ground conditions, steel pipe piles and steel pipe sheet piles may be divided into upper, middle and lower parts.

  Steel pipe piles and steel pipe sheet piles have been joined in the vertical direction by welded joints such as arc welding. However, in recent years, the machine is simplified from the viewpoint of not requiring special skills such as construction simplification, speedup, and welding. Type fittings are being considered. In the following description, for example, joints that mechanically fasten a steel pipe pile and a steel pipe sheet pile, such as a screw-type mechanical joint, a box joint, and a pin joint, are collectively referred to as a mechanical joint.

  The mechanical joint may be formed by directly machining the end of the steel pipe body, but it is difficult to machine the end of a large-diameter and / or long steel pipe pile and steel pipe sheet pile. Therefore, it is common to weld the manufactured mechanical joint separately to the steel pipe body. As described above, when the mechanical joint is welded to the steel pipe main body, there is a problem that deformation occurs due to welding thermal deformation and welding residual stress, and in particular, the roundness of the end portion is lowered.

  As a method for solving the deformation at the time of welding the mechanical joint for a steel pipe pile described above, a technique for preventing a screw fitting failure in a threaded mechanical joint has been proposed (for example, Patent Document 1). reference.). Specifically, in the screw joint for landslide suppression piles described in Patent Document 1, the shoulder portion is disposed only between the different diameter parallel threads, and the outer diameter of the joint portion is substantially equal to the different diameter of the pipe. . Moreover, the mechanical coupling which can fasten a steel pipe pile more simply than a screw-type mechanical coupling is also proposed (for example, refer patent documents 2 and 3). In the pile described in Patent Document 2, a convex portion is formed on the inner peripheral surface of the box joint material, and a concave portion is formed on the outer peripheral surface of the pin joint material. And the pin joint material are coupled to each other. Further, in the mechanical joint described in Patent Document 3, a key groove is provided in the pin joint material and the box joint material, and after fitting these joint materials, the key is inserted into the key groove as a joint. The proof stress is maintained.

  On the other hand, in a steel pipe sheet pile, since a sheet pile part is welded to the side surface of a steel pipe main body, there also exists a problem that a steel pipe main body becomes a drum shape by welding deformation. Therefore, in order to prevent deformation of the steel pipe main body when welding the sheet pile portion to the side surface of the steel pipe main body, a strain imparting member is inserted inside the steel pipe main body, and a method of pre-distorting the steel pipe main body (for example, Patent Document 4), a method of welding while cooling the steel pipe body from the inner surface (for example, refer to Patent Document 5), and a method of welding with a load applied to the joint according to the residual stress of the steel pipe body (for example, , See Patent Document 6).

JP-A-11-218270 JP 2004-346660 A JP 2005-48583 A JP-A-53-146238 JP-A-4-284970 JP-A-4-309464

  However, the conventional techniques described above have the following problems. That is, as the outer diameter of the steel pipe main body increases, deformation due to welding also increases. However, in the fastening method using the stepped parallel screw proposed in Patent Document 1, when the steel pipe main body has a large diameter, the fitting of the screw is not possible. There is a problem that it becomes difficult. Similarly, the techniques described in Patent Documents 2 and 3 also have a problem that, when the outer diameter of the steel pipe body is increased, when a mechanical joint is welded to the steel pipe body, deformation due to welding thermal deformation and welding residual stress occurs. is there. In particular, in the case of a mechanical joint that fits a box joint and a pin joint, if the deformation becomes large, the pin cannot be inserted into the box, or even if it can be inserted, the key will not fit in the field construction. There is. Such interruption of work due to poor fitting at the site causes a significant total cost increase, and is one of the problems that must be solved.

  Furthermore, although the technique of patent documents 4-6 is a method for preventing the deformation | transformation which arises when welding a joint to a steel pipe main body, these methods make the joint used as a sheet pile part the longitudinal direction of a steel pipe main body. Since the purpose is to reduce, prevent, or correct deformation at the time of welding, it is impossible to prevent deformation of the mechanical joint that is welded to the end of the steel pipe body in the circumferential direction. For this reason, although the technique of patent documents 4-6 can prevent the deformation | transformation by sheet pile welding, it cannot prevent the deformation | transformation of the mechanical coupling at the time of welding to a large diameter pipe, and cannot obtain the outstanding joint fastening property. There is a problem.

  The present invention has been made in view of the above-described problems, and is used to manufacture a steel pipe pile or a steel pipe sheet pile by welding a mechanical joint to a steel pipe body having an outer diameter of 1000 mm or more. It aims at providing the manufacturing method of the steel pipe sheet pile excellent in the joint fastening property which can reduce the deformation | transformation of a joint, and can prevent a joint fitting defect, and the manufacturing method of a steel pipe pile.

  The method of manufacturing a steel pipe pile excellent in joint fastening performance according to the present invention is a method of manufacturing a steel pipe pile in which a mechanical welded joint is temporarily attached to the end of a steel pipe main body at a plurality of locations in the circumferential direction and then main welding is performed. The steel pipe body has an outer diameter D (mm) of 1000 mm or more, and the tack welding has a range in which the maximum angle θ (°) with respect to the central axis of the steel pipe body is defined by the following mathematical formula (1): It is characterized by being performed at intervals.

  Moreover, in the manufacturing method of the steel pipe pile excellent in this joint fastening property, it is preferable to tack-wel at least the position where the diameter of the said steel pipe main body becomes the largest.

  Furthermore, the mechanical joint may be, for example, a box joint or a pin joint having a structure that can be fitted to each other.

  The manufacturing method of a steel pipe sheet pile excellent in joint fastening performance according to the present invention is a method of manufacturing a steel pipe sheet pile that performs main welding after temporarily welding a plurality of mechanical welded joints to the end of a steel pipe body in the circumferential direction. The steel pipe body has an outer diameter D (mm) of 1000 mm or more, and the tack welding has a range in which the maximum angle θ (°) with respect to the central axis of the steel pipe body is defined by the above formula (1). It is characterized by being performed at intervals.

  Moreover, it is preferable that the manufacturing method of the steel pipe sheet pile excellent in this joint fastening property carries out tack welding at least the position where the diameter of the said steel pipe main body becomes the maximum.

  In the manufacturing method of the steel pipe sheet pile excellent in the joint fastening property, the mechanical joint can be a box joint or a pin joint having a structure that can be fitted to each other.

  According to the present invention, since the temporary attachment interval when welding the mechanical joint to the steel pipe body is optimized, the deformation of the mechanical joint due to welding is suppressed even if the outer diameter of the steel pipe body is 1000 mm or more. Therefore, when the manufactured steel pipe piles or steel pipe sheet piles are connected to each other up and down via mechanical joints, it is possible to prevent the occurrence of poor fitting and to obtain excellent fastening properties.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. The manufacturing method of the steel pipe pile or steel pipe sheet pile excellent in the joint fastening property of the present invention is a mechanical joint in the steel pipe main body in the process of manufacturing the steel pipe pile or steel pipe sheet pile whose outer diameter D (mm) is 1000 mm or more. The joint deformation is prevented by specifying the tacking interval when welding the steel.

  A spiral steel pipe or a UOE steel pipe is usually used for a steel pipe pile and a steel pipe sheet pile having an outer diameter of 1000 mm or more as the object of the present invention. The UOE steel pipe is a U-shaped steel plate formed by a special press machine, shaped into an O-shape, arc welded at the joint, and expanded (E) from the inside with an expander. It is a steel pipe finished in dimensions. Further, as the base material of the steel pipe main body, SKY490 or the like is used for the steel pipe sheet pile, and SM490 or SM590 or the like is used for the thicker steel pipe pile.

  On the other hand, raw pipes used in mechanical joints for joining steel pipe piles or steel pipe sheet piles in the longitudinal direction are often manufactured by forging, and have higher strength than steel pipe main bodies of steel pipe piles or steel pipe sheet piles. These heat treatment materials are used. Such mechanical joints are machined and then joined by welding to the ends of steel pipe piles or steel pipe sheet piles. Submerged arc welding, semi-automatic welding, or manual arc welding is often employed as the type of welding at that time. Further, in the case of submerged arc welding and semi-automatic welding, one layer is often formed from the inner surface and one layer from the outer surface.

  Here, as an example, a method of welding a mechanical joint to an end portion of a steel pipe body by submerged arc welding will be described. First, a groove is formed in the joint surface of the steel pipe body and the mechanical joint by machining. At that time, when the submerged arc welding is performed one layer at a time from the inner surface and the outer surface, it is preferable to employ an X groove as the groove shape. Next, the steel pipe body and the root surface of the mechanical joint are put together to perform tack welding. Note that tack welding is often performed by manual arc welding from the outer surface. Thereafter, shield welding is performed on the entire circumference, and main welding is performed by submerged arc welding from the inner surface and the outer surface. Thereby, a mechanical joint is welded to the edge part of a steel pipe main body, and a steel pipe sheet pile or a steel pipe pile is completed.

  In the manufacturing process of the steel pipe pile or the steel pipe sheet pile described above, when the outer diameter of the steel pipe main body in the steel pipe pile or the steel pipe sheet pile becomes 1000 mm or more, the influence of welding deformation becomes large, and the frequency of poor fitting also increases. In addition, when the sheet pile portion is welded to the outer surface of the steel pipe main body, the flatness of the end of the steel pipe deteriorates when the steel pipe main body becomes elliptical and the roundness deteriorates. It has been found that welding deformation is promoted.

  Furthermore, when a fitting test was performed on a steel pipe sheet pile completed by this manufacturing method, in the case of a mechanical joint that mutually connects a box joint material and a pin joint material as described in Patent Document 2, There are some that cannot be inserted into the box after welding despite being able to fit before welding, and in the type of joint that inserts a key as described in Patent Document 3, There are some cases where the key cannot be inserted into the keyway after welding. Furthermore, when a screw type mechanical joint is welded to a steel pipe body having an outer diameter of 1000 mm or more, when welding deformation occurs, the parallel screw causes a significant increase in tightening torque, and the taper screw does not reach the predetermined fastening completion position. It turned out that it cannot fit.

Therefore, in order to investigate the direct cause of the poor fitting of the mechanical joint as described above, the inventors of the present invention have roundness and flatness of the mechanical joint after welding to a steel pipe body having an outer diameter of 1600 mm and a wall thickness of 24 mm. Investigated. FIG. 1A is a diagram schematically showing a method for obtaining roundness, and FIG. 1B is a diagram schematically showing a method for obtaining flatness. As shown in FIG. 1 (a), circularity, the maximum value of the inner diameter of the mechanical coupling 1 (maximum inner diameter _{r max),} the minimum value the difference between the (minimum inner diameter _{r min) (r max -r min} ) I asked for it. At that time, the inner diameter of the mechanical joint 1 was measured with a micrometer internal gauge. Further, as shown in FIG. 1B, the flatness is determined by pressing the end surface of the mechanical joint 1 against the smooth surface plate 2, and using the gap gauge, the deflection amount of the end surface of the mechanical joint 1, that is, the mechanical joint. The gap x between the end face of 1 and the surface of the smooth surface plate 2 was measured, and the value was defined as flatness.

  FIG. 2 is a graph showing the relationship between roundness and flatness of a mechanical joint, with the roundness on the horizontal axis and the flatness on the vertical axis. As shown in FIG. 2, the roundness and flatness of the mechanical joint are generally in a positive proportional relationship, and the variation between samples was found to be 12 mm at maximum in roundness and 2 mm at maximum in flatness. . When the result of the fitting test was collated, it was found that when the roundness was larger than 6 mm, there was a pin / box insertion failure in which the pin could not be inserted into the box. Moreover, among the samples in which the pins could be inserted into the box, those having a flatness greater than 1 mm could not be inserted into the mechanical joint. It has been clarified that when the steel pipe main body is welded in this way, the roundness and flatness of the mechanical joint deteriorate, leading to poor fitting.

  Next, the inventor of the present application attempted sensitivity analysis by FEA (Finite Element Analysis) in order to clarify the factors causing the roundness and flatness to vary. FIG. 3 is a view showing an example of an FEA model when a mechanical joint is welded to a steel pipe sheet pile having a steel pipe body having an outer diameter of 1600 mm and a wall thickness of 24 mm. FIG. 4 shows the relationship between the mechanical joint 12 and the steel pipe body 11. FIG. 3 is an enlarged view of a joint portion 16. Using the model shown in FIGS. 3 and 4, a mechanical joint 12 is attached to the end of a steel pipe sheet pile 11 in which a sheet pile portion 14 is provided on the outer surface of the steel pipe main body 13 and a cross-shaped rib 15 is provided inside. After temporarily attaching a plurality of locations to the circumferential position, unsteady heat conduction analysis and stress analysis were performed assuming that the inner surface and the outer surface were welded one by one while moving in the circumferential direction. At that time, as the influencing factors, the interval between the tack welded portions, the roundness and flatness of the steel pipe body 13, the main welding start position, the presence or absence of the sheet pile portion 14, the presence or absence of the cross-shaped rib 15 and the like were examined. Note that, as with the roundness and flatness of the mechanical joint 12, the roundness and flatness of the steel pipe body 13 can also be evaluated by the shape of the end of the steel pipe body 13.

  As a result of individually analyzing these factors, it has been found that the interval between the tack welds has the greatest influence on the roundness and flatness of the mechanical joint 12, and the influence of other factors is small. FIG. 5 shows changes in the roundness and flatness of the mechanical joint when the horizontal position is taken along the circumferential direction and the vertical axis is displaced, and the four positions are tack-welded by shifting 90 ° in the circumferential direction. FIG. As shown in FIG. 5, the roundness and flatness of the mechanical joint both have a sine curve for one wavelength with the tack welded joint as a node, and the roundness distribution and the flatness distribution are synchronized. I understood. Furthermore, when the generation time was analyzed, it was found that it was close to the final distribution at the end of tack welding.

  From the above analysis results, it is assumed that when the period of the sine curve in the roundness and flatness displacement is shortened, the amplitude is assumed to be small. The same analysis was performed by changing the interval between them. FIG. 6 shows changes in the roundness and flatness of the mechanical joint when the horizontal position is circumferential and the vertical axis is displaced, and six points are tack-welded by shifting by 60 ° in the circumferential direction. FIG. As shown in FIG. 6, in a cross section perpendicular to the central axis of the steel pipe main body, the maximum angle (hereinafter referred to as a temporary attachment interval) θ formed by two adjacent tack welds and the central axis of the steel pipe main body is 60. In the case of °, both roundness and flatness were superior compared to when the tacking interval θ was 90 °.

  FIG. 7 is a graph showing the relationship between the tacking interval θ and the roundness and flatness of the mechanical joint, where the horizontal axis represents the tacking interval θ and the vertical axis represents the roundness and flatness. . As shown in FIG. 7, both roundness and flatness start to decrease sharply when the tacking interval θ is less than 90 °. On the other hand, even if the tacking interval θ is set to 40 ° or less, the effect is not so great. Further, when the tacking interval θ is 0 °, it means an ideal state in the FEA analysis, and the main welding is started without performing tacking, or continuously in the circumferential direction as in shield welding. Although it means welding, in actual welding, a large-sized fixing jig for fixing a mechanical joint having a large weight is required, which is not practical. From these results, in view of cost effectiveness, the inventor of the present application is most preferable to set the temporary attachment interval θ to 30 to 60 ° and perform temporary attachment of 12 to 6 points in the circumferential direction at equal intervals. I found out.

  Based on the above knowledge, a mechanical joint is actually welded to a steel pipe body having an outer diameter of 1600 mm and a wall thickness of 24 mm by changing the tacking interval θ from 30 ° to 120 °. The roundness and flatness of the joint were measured and their fitting test was performed. FIG. 8 is a graph showing the relationship between the tacking interval and the roundness of the mechanical joint, where the horizontal axis represents the tacking interval θ and the vertical axis represents the roundness, and FIG. FIG. 5 is a graph showing the relationship between the tacking interval θ and the flatness of a mechanical joint, with the tacking interval θ taken and the vertical axis taken flatness. As a result, as shown in FIGS. 8 and 9, as predicted by FEA, as the tacking interval θ increases, the roundness and flatness of the mechanical joint both deteriorate, and at a tacking interval of 90 ° or more. Misfit samples started to appear. On the other hand, when the tacking interval θ was 60 ° or less, all of them could be fitted well, and the joint fastening performance was excellent.

  Next, this inventor decided to investigate the influence of the outer diameter of a steel pipe main body (henceforth only a pipe outer diameter). As shown in FIGS. 8 and 9, when a mechanical joint is welded to a steel pipe body having an outer diameter of 1600 mm, it can be understood that a stable fitting is possible if the temporary attachment interval θ is 60 ° or less. The predicted value of flatness of the mechanical joint by FEA is about 0.4 mm. Therefore, if the flatness of the mechanical joint is 0.4 mm, it is considered that stable fitting is possible.

  Based on the above consideration, assuming a case where a mechanical joint is welded to a steel pipe body having various outer diameters, a temporary attachment interval at which the predicted flatness of the mechanical joint is 0.4 mm was obtained by FEA. FIG. 10 is a graph showing the result of predicting the relationship between the pipe outer diameter D and the limit tacking interval by FEA, with the tube outer diameter D on the horizontal axis and the tacking interval θ on the vertical axis. Furthermore, in order to demonstrate the size dependency regarding the outer diameter D of the steel pipe main body shown in FIG. 10, the temporary attachment interval is changed with respect to the steel pipe main body having the outer diameter D of 800 to 2000 mm, and the limit of the occurrence of poor fitting. The tacking interval was determined. At that time, three tests were conducted, and a case where a pin / box insertion failure or a key insertion failure in a keyway occurred in one or more samples was defined as a fitting failure. FIG. 11 is a graph showing the results of confirming the relationship between the outer diameter D of the steel pipe body and the limit tacking interval by experiment, with the outer diameter D of the steel pipe body on the horizontal axis and the tacking interval θ on the vertical axis. It is.

  As shown in FIGS. 10 and 11, for a steel pipe main body having an outer diameter D of 1000 mm or more, if the temporary attachment interval θ is narrower than the FEA prediction limit (θ = 97400 / D), there is a poor fitting. It never happened. On the other hand, for a steel pipe body having an outer diameter of 800 mm, even if the temporary attachment interval θ is wider than the FEA prediction limit (θ = 97400 / D), a fitting failure does not occur, and the temporary attachment interval θ is 180 °. Thus, even when two opposing locations were temporarily attached, they could be fitted. From these results, the inventors of the present application have found that the range in which the effect of the present invention for solving the problem of welding deformation is obtained is when the outer diameter of the steel pipe body is 1000 mm or more. In addition, as shown in FIG.10 and FIG.11, the same effect is acquired even when the outer diameter D of a steel pipe main body is 2000 mm.

  Next, the inventor of the present application paid attention to the ellipse direction of the steel pipe main body at the time of temporary attachment and the relationship between the root gap and the circumferential position at the start of temporary attachment. In particular, in the case of a steel pipe sheet pile, when the sheet pile part is welded to the side surface of the steel pipe main body (sheet pile welding), the cross section of the steel pipe main body is deformed into an elliptical shape, and the position where the sheet pile welding is performed becomes the major axis direction of the ellipse. In order to suppress such deterioration of the roundness of the steel pipe body as much as possible, conventionally, the steel pipe body has been press-corrected after sheet pile welding, or a cross-shaped rib is installed near the end of the steel pipe. The deterioration of the roundness and flatness of the end of the main body has been prevented. However, when the diameter of the steel pipe main body becomes large, particularly costs and time are required to suppress the deformation of the steel pipe main body by sheet pile welding and maintain the shape as it is. For this reason, it is necessary to circumferentially weld the mechanical joint in a state in which the deformation due to sheet pile welding of the steel pipe body is allowed to some extent.

  Since the steel pipe body is deformed into a drum shape by sheet pile welding, the cross section is deformed into an ellipse, and in particular, a gap is generated in the root surface of the welding groove when welding the mechanical joint at the long diameter position on the end face. It was found that the deformation of the steel pipe main body due to this sheet pile welding remains even after press correction, and is reflected in the flatness of the end face of the joint after circumferential welding.

  FIG. 12 is a graph showing the effect of the tacking position on the flatness of the mechanical joint, with the tacking interval θ on the horizontal axis and the flatness on the vertical axis. The values shown in FIG. 12 are tested for each of three cases of a steel pipe main body having an outer diameter of 1600 mm when tack welding is performed at an arbitrary position, and when at least two points having a major axis position are tack welding. The average value. As shown in FIG. 12, in any of the tacking intervals, the flatness was improved by placing a tacking point at the position of the major axis.

  Next, this inventor examined the screw type mechanical coupling among mechanical couplings. FIG. 13 is a graph showing the relationship between the pipe outer diameter D and the tacking interval θ when a threaded mechanical joint is welded with the pipe outer diameter D on the horizontal axis and the tacking interval θ on the vertical axis. It is. In the data shown in FIG. 13, the case where the screw cannot be fastened to a predetermined position by human power is regarded as a poor fitting. As shown in FIG. 13, even when a screw type mechanical joint is welded, the temporary attachment interval θ is smaller than the FEA prediction limit (θ = 97400 / D), that is, with respect to the central axis of the steel pipe body. Any of those that were tack welded at intervals of (97400 / D) ° or less were able to fit well, and the joint fastening properties were excellent.

  The present invention has been made on the basis of the above-described findings, and a steel pipe pile or a steel pipe sheet pile is manufactured by welding a mechanical weld joint to the end of a steel pipe body having an outer diameter D (mm) of 1000 mm or more. First, the maximum angle θ (°) with respect to the central axis of the steel pipe body is an interval that falls within the range defined by the following formula (2), that is, the temporary attachment interval θ is within the range defined by the following formula (2). As a result, a plurality of locations are temporarily welded in the circumferential direction, and then the main welding is performed.

  At this time, when the tacking interval θ is larger than (97400 / D) °, deformation occurs in the mechanical welded joint after joining, and when the steel pipe piles or the steel pipe sheet piles are joined to each other, poor fitting of the joint occurs. To do. On the other hand, in the steel pipe pile manufacturing method or the steel pipe sheet pile manufacturing method of the present invention, the deformation of the mechanical joint when welding to the steel pipe body can be suppressed, so the machine welded to the end of one steel pipe body. Fastening between the joint and the mechanical joint joined to the end of the other steel pipe body is improved, and the steel pipe piles or steel pipe sheet piles can be connected well. Therefore, according to the present invention, it is possible to manufacture a steel pipe pile or a steel pipe sheet pile having excellent joint fastening properties.

  Moreover, in the manufacturing method of the steel pipe pile of this invention, or the manufacturing method of a steel pipe sheet pile, it is preferable to tack-wel at least 2 places which oppose the direction where the long diameter of a steel pipe main body extends. Thereby, a deformation | transformation of a mechanical coupling is suppressed, flatness increases, and a joint fastening property can be improved more.

  Further, examples of the mechanical joint welded to the steel pipe main body include a box joint and a pin joint having structures that can be fitted to each other. Since the manufacturing method of the steel pipe pile or the manufacturing method of the steel pipe sheet pile of the present invention can suppress the deformation of the mechanical joint when welding to the steel pipe body, the pin joint welded to the end of one steel pipe body is used. The box joint joined to the end of the other steel pipe main body can be satisfactorily fitted.

  In the present embodiment, the case where the mechanical joints are tack welded at equal intervals is described as an example. However, the present invention is not limited to this, and the temporary tack interval θ is (97400 / If it is in the range of D) ° or less, the same effect can be obtained even if it is not temporarily attached at regular intervals.

  Hereinafter, the effects of the present invention will be specifically described with reference to examples of the present invention and comparative examples that are out of the scope of the present invention. First, as a first embodiment of the present invention, a mechanical joint of JIS G3221 SFCM880R is a condition within the scope of the present invention at the end of a steel pipe sheet pile of JIS A 5530 SKY490 whose outer diameter D of the steel pipe body is 1000 to 2000 mm. After tack welding with, the main welding was performed by submerged arc welding, and the roundness, flatness and joint fastening property of the mechanical joint were evaluated. At that time, tack welding was performed by manual arc welding from the outer surface at equal intervals. Moreover, this welding performed the shield welding to the perimeter after the tack welding, and performed the submerged arc welding from the inner surface and the outer surface. Furthermore, the evaluation is performed for three pieces under the same conditions, and the roundness and flatness of the mechanical joint are averaged, and the joint fastening performance is evaluated based on the possibility of fitting, and all three pieces are fitted. What was made was considered good. On the other hand, as a comparative example, the conditions of tack welding and main welding are the same as those of the above-described embodiment, the number of tack welding is reduced and the mechanical joint is welded, and the roundness, flatness and joint of the mechanical joint are welded. The fastening property was evaluated. The above results are shown in Tables 1 and 2 below. In addition, the tacking interval θ (°) shown in the following Table 1 and Table 2 is the maximum value of the angle formed between the central axis of the steel pipe main body and the adjacent tack welding weld, and the limit tacking interval is the steel pipe main body. The value obtained based on the outer diameter D (mm) (= 97400 / D).

  As shown in Table 1 above, Example No. 1 in which the tacking interval θ is equal to or less than the limit tacking interval (97400 / D) °. 1-No. All of the 23 steel pipe sheet piles were able to fit the joints normally. On the other hand, as shown in Table 2, the comparative example No. in which the tacking interval θ exceeds the limit tacking interval (97400 / D) °. 1-No. As for the 17 steel pipe sheet pile, roundness and flatness deteriorated, and the fitting failure that the insertion of the pin into the box and the insertion of the load transmission key after the insertion was not possible occurred.

  Next, as a second embodiment of the present invention, a threaded joint made of HT780 steel is applied to a steel pipe pile made of JIS G 3106 SM490 steel having an outer diameter of a steel pipe body of 1000 to 1600 mm, within the scope of the present invention. After tack welding with, carbon dioxide arc welding was used to evaluate the roundness, flatness, and joint fastness of the mechanical joint. At that time, tack welding was performed by manual arc welding from the outer surface at equal intervals. In addition, the main welding was performed by performing shield welding on the entire circumference and carbon dioxide arc welding from the inner surface and the outer surface. Further, the evaluation was performed three by three in the same manner as in Example 1 described above. On the other hand, as a comparative example, the conditions of tack welding and main welding are the same as those of the above-described embodiment, the number of tack welding is reduced and the mechanical joint is welded, and the roundness, flatness and joint of the mechanical joint are welded. The fastening property was evaluated. The above results are summarized in Table 3 below.

  As shown in Table 3 above, Example No. welded within the scope of the present invention was used. 24-No. 29 steel pipe piles were able to fit screw joints manually. On the other hand, comparative example No. in which the tacking interval θ exceeds the limit tacking interval (97400 / D) °. 18-No. As for 20 steel pipe sheet piles, the roundness and flatness of the joint were deteriorated, and the threaded joint could not be manually fitted.

  Next, as a third embodiment of the present invention, a mechanical joint of JIS G3221 SFCM880R is attached to a steel pipe sheet pile of JIS A 5530 SKY490 whose outer diameter is 1600 mm, and the position of the tack welding is changed by submerged arc welding. Were circumferentially welded, and the flatness of the mechanical joint and the fastening performance of the joint were evaluated. The conditions for tack welding and main welding and the evaluation method were the same as in Example 1 described above. The above results are shown in Table 4 below.

  As shown in Table 4 above, Example No. 30-No. In each of the 35 steel pipe sheet piles, the tacking interval θ is the limit tacking interval 97400 / D or less. 30-No. The steel pipe sheet pile of 32 is obtained by temporarily welding the major axis position of the steel pipe main body. 33-No. The 35 steel pipe sheet piles are those in which the major axis position is not tack welded. In addition, Example No. No. 30 steel sheet pile and No. No. 33 steel pipe sheet pile, Example No. No. 31 steel sheet pile and No. 34 steel pipe sheet pile, Example No. 32 steel pipe sheet piles and The 35 steel pipe sheet piles are circumferential welds under the same size and the same welding conditions, but the welded part of the steel pipe main body is tack welded at the other position. The flatness was improved.

(A) is a figure which shows typically the method of calculating | requiring roundness, (b) is a figure which shows typically the method of calculating | requiring flatness. It is a graph which shows the relationship between roundness and flatness of a mechanical joint by taking roundness on a horizontal axis and taking flatness on a vertical axis. It is a figure which shows an example of a FEA model when a mechanical coupling is welded to the steel pipe sheet pile which has a steel pipe main body of outer diameter 1600mm and thickness 24mm. It is an enlarged view which shows the junction part 16 of the mechanical coupling 12 and the steel pipe main body 13 in the FEA model shown in FIG. It is a figure which shows the change of roundness and flatness of a mechanical joint when taking a position in the circumferential direction on the horizontal axis and taking displacement on the vertical axis and shifting by 90 ° in the circumferential direction at four locations. . It is a figure which shows the change of the roundness and flatness of a mechanical joint when taking a circumferential position on a horizontal axis and taking displacement on a vertical axis and shifting by 60 ° in the circumferential direction and tacking six places. . FIG. 5 is a graph showing the relationship between the tacking interval θ and the roundness and flatness of a mechanical joint, with the tacking interval θ on the horizontal axis and the roundness and flatness on the vertical axis. FIG. 5 is a graph showing the relationship between the tacking interval θ and the roundness of the mechanical joint, with the tacking interval θ on the horizontal axis and the roundness on the vertical axis. It is a graph which shows the relationship between the tacking space | interval (theta) and the flatness of a mechanical joint by taking the tacking space | interval (theta) on a horizontal axis and taking flatness on a vertical axis | shaft. It is a graph which shows the result of having predicted the relationship between the outer diameter D of a steel pipe main body, and a limit temporary attachment space | interval by taking the outer diameter D of a steel pipe main body on a horizontal axis, and taking the temporary attachment space | interval (theta) on a vertical axis | shaft. It is a graph which shows the result of having confirmed the relationship between the outer diameter D of a steel pipe main body, and a limit temporary attachment space | interval by taking the outer diameter D of a steel pipe main body on a horizontal axis, and taking temporary attachment space | interval (theta) on a vertical axis | shaft. It is a graph which shows the effect which a tacking position has on the flatness of a mechanical joint, taking the tacking interval θ on the horizontal axis and taking the flatness on the vertical axis. It is a graph which shows the relationship between pipe outer diameter D and temporary attachment space | interval (theta) at the time of taking pipe outer diameter D on a horizontal axis, and taking temporary attachment space | interval (theta) on a vertical axis | shaft, and welding a screw type mechanical coupling.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,12 Mechanical joint 2 Smooth surface plate 11 Steel pipe sheet pile 13 Steel pipe main body 14 Sheet pile part 15 Cross-shaped rib 16 Joint part

Claims (6)

A steel pipe pile manufacturing method in which main welding is performed after temporarily welding a plurality of mechanical weld joints to the end of a steel pipe body in the circumferential direction,
The steel pipe body has an outer diameter D (mm) of 1000 mm or more,
The tack welding is performed at intervals in which the maximum angle θ (°) with respect to the central axis of the steel pipe body is within a range defined by the following formula (A). Method.

  The method for producing a steel pipe pile excellent in joint fastening performance according to claim 1, wherein at least a position where the diameter of the steel pipe main body is maximum is tack welded.   The joint according to claim 1 or 2, wherein the mechanical joint is a box joint or a pin joint, and has a structure in which the box joint and the pin joint can be fitted to each other. Manufacturing method of steel pipe pile. A steel pipe sheet pile manufacturing method for performing main welding after temporarily welding a plurality of mechanical weld joints to the end of a steel pipe body in the circumferential direction,
The steel pipe body has an outer diameter D (mm) of 1000 mm or more,
The tack welding is performed at intervals in which the maximum angle θ (°) with respect to the central axis of the steel pipe main body is within a range defined by the following mathematical formula (A). Method.

  The method for producing a steel pipe sheet pile excellent in joint fastening performance according to claim 4, wherein at least a position where the diameter of the steel pipe main body is maximum is tack welded.   The joint according to claim 4 or 5, wherein the mechanical joint is a box joint or a pin joint, and has a structure in which the box joint and the pin joint can be fitted to each other. Manufacturing method of steel pipe sheet pile.

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