Core metal tool and method for manufacturing pipe

Abstract

To provide a core metal tool by which it is possible to enhance matching accuracy of both ends of a blank member during pipe-making welding, thereby reducing poor welding.SOLUTION: A core metal tool for pipe-making welding of a pipe has an approximately columnar shape whose outer diameter is an inner diameter of the pipe to be made, in which a central member, an outer peripheral member, an upper surface member, and a lower surface member, each being a separate body, are integrated by fastening. The central member has a tapered shape. The outer peripheral member is disposed in contact with a lateral surface of the central member, and is configured with an outer peripheral piece member divided in 3-6 pieces in top view. The upper surface member and the lower surface member are individually disposed on the central member and an upper surface side and a lower surface side of the outer peripheral member, and can be disassembled by undoing the fastening.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a core wire jig, and more particularly to a core wire jig for pipe welding, which improves butt welding accuracy and prevents poor welding in pipe welding, in which both ends of a blank material rolled into a cylindrical shape are butt welded to form a pipe. [Background technology]

[0002] A known method for manufacturing pipes is a pipe-making welding method in which a plate-shaped blank is wrapped around the blank, and the ends of the cylindrical blank are butt-welded together. Conventional wrapping methods, such as those described in Patent Document 1, involve wrapping the plate-shaped blank by passing it between a metal roll and an elastic resin roll (hereinafter also referred to as urethane roll forming). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 8-197285 Summary of the Invention [Problem to be solved by the invention]

[0004] Figure 6 is an explanatory diagram (schematic diagram) explaining the process of urethane roll foaming. As shown in Figure 6, in urethane roll foaming, a plate-shaped blank material is passed between a metal roll (steel roll) and an elastic resin roll (urethane roll) to form it into a cylindrical shape.

[0005] The blank material processed into a cylindrical shape is then clamped and pressed from the outside with a mold (outer mold) so that both ends are butted together, and the butt joints are welded in this state to produce a pipe, as shown in Figure 7.

[0006] However, in this type of urethane roll foaming, both ends of the blank (the beginning and end of the winding) can bite into the resin, resulting in insufficient winding. Figure 8 is a schematic diagram showing the processing state of the tip of the blank when the blank is wound using urethane roll foaming. As shown in Figure 8, in urethane roll foaming, the tip of the blank can bite into the urethane roll, resulting in insufficient winding (R processing) at the tip. In particular, when the blank is made of a hard material, the tip of the blank can easily be insufficiently wound.

[0007] When both ends of the blank are welded together in this state (pipe welding), steps and gaps are likely to occur at the butt joint, resulting in poor welding. Figure 9 is a schematic diagram showing examples of defects at the butt joint. Figure 9(a) shows an example of a gap at the butt joint, Figure 9(b) shows an example of an overlap at the butt joint, Figure 9(c) shows an example of a gap at the butt joint due to sagging or burrs in the shear cross section of the blank, and Figure 9(d) shows an example of a step at the butt joint.

[0008] The causes of such defects in the butt joints include not only insufficient winding, as mentioned above, but also warping or twisting of the blank material, and shear quality such as sagging or burrs on the end surface of the blank material.

[0009] When a pipe is manufactured by welding a butt joint with such defects, the pipe is likely to have a defective shape or poor material quality. Furthermore, in such a butt joint, not only does the cross-sectional shape of the welded portion become poor, but the heat input must be increased to ensure sufficient penetration in the weld, which can lead to holes due to burn-through and the heat effect can be widespread, causing problems in terms of the pipe's strength and corrosion resistance after welding.

[0010] When welding a butt joint, it is desirable to weld both ends of the blank together so that there are no steps or gaps at the butt joint. To ensure this, a common method is to clamp and press the blank together with a die, as shown in Figure 7, to ensure accurate butt joints at both ends. However, even when the die pressure is optimized, gaps or steps may remain at the butt joint. In such cases, a method is used in which the heat input during welding is increased to a level that does not cause burn-through, thereby melting a wide area, including the area with poor butt joint accuracy. However, this method results in a thick weld bead and a wide heat-affected zone (HAZ), which can lead to material defects.

[0011] The present invention has been made in consideration of the above circumstances, and aims to provide a core metal jig that can improve the butt joint accuracy of both ends of a blank material during pipe welding and reduce welding defects. [Means for solving the problem]

[0012] The present invention has the following configuration. [1] A core metal jig for pipe welding, The core metal jig is The pipe making machine is generally cylindrical in shape, with its outer diameter being the same as the inner diameter of the pipe to be made, and is configured by a central member, an outer peripheral member, an upper surface member, and a lower surface member, each of which is separate and is fastened together to form a single unit; the central member has a tapered shape; the outer peripheral member is arranged in contact with a side surface of the central member and is further configured by outer peripheral piece members divided into three to six pieces in top view, the upper surface member and the lower surface member are disposed on the upper surface side and the lower surface side of the central member and the outer peripheral member, respectively; The core metal jig can be disassembled by releasing the fastening. [2] The core metal jig according to [1], wherein the central member has a substantially truncated cone shape or a truncated polygonal pyramid shape. [3] The core metal jig according to [1] or [2], wherein the core metal jig has a groove on the side surface that is parallel to the axial direction. [4] A method for manufacturing a pipe, comprising manufacturing a pipe using the core metal jig according to any one of [1] to [3] above. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a core metal jig that can improve the butt joint accuracy of both ends of a blank material during pipe welding and reduce welding defects.

[0014] By using the core metal jig of the present invention, when butting together the ends of a blank material wound into a cylindrical shape, not only is the pipe pressed from the outside with a mold, but the core metal jig contacts the inside of the pipe to support its shape, making it less likely that steps or gaps will occur at the butt joint and improving butt joint accuracy. Then, by welding the butt joint with improved butt joint accuracy into a pipe, pipe shape defects and material defects are reduced. Furthermore, laser welding with a relatively low heat input is possible, suppressing the occurrence of welding defects such as underfill and voids. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic view showing one embodiment of a core metal jig of the present invention. [Figure 2] FIG. 2 is an exploded view (schematic view) of the core metal jig shown in FIG. [Figure 3] FIG. 3 is a schematic diagram showing an example of forming a butted portion by butting both ends of a blank material together using the core metal jig of the present invention. [Figure 4] FIG. 4 is a schematic view showing another embodiment of the core metal jig of the present invention. [Figure 5] FIG. 5 is an exploded view of the core metal jig shown in FIG. [Figure 6] FIG. 6 is an explanatory diagram (schematic diagram) illustrating the steps of urethane roll foam processing. [Figure 7] FIG. 7 is an explanatory diagram (schematic diagram) for explaining the process of butting together both ends of a blank material using a die. [Figure 8]FIG. 8 is a schematic diagram showing the processed state of the tip of the blank material when it is wound by urethane roll foam processing. [Figure 9] FIG. 9 is a diagram showing a schematic example of a case where a defect occurs at the butted portion. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, the core metal jig of the present invention will be described with reference to exemplary embodiments, but the present invention is not limited to the following embodiments.

[0017] (Core jig) Fig. 1 is a schematic diagram showing a core metal jig 1 according to one embodiment of the present invention. As shown in Fig. 1, the core metal jig 1 has an approximately cylindrical outer shape. Here, the approximately cylindrical shape includes not only a column whose cross section perpendicular to the axial direction is a perfect circle, but also an elliptical column, and also includes cases where grooves or the like exist on the surface of these columns. As will be described later, the core metal jig 1 is composed of a central member 2, an outer peripheral member 3, an upper surface member 4, and a lower surface member 5, which are fastened together to form a single unit.

[0018] The mandrel jig of the present invention has an outer diameter that is the same as the inner diameter of the pipe to be produced. That is, as described below, when a pipe is produced using the mandrel jig of the present invention, the outer circumference of the mandrel jig of the present invention matches the inner circumference of the pipe in a cross section perpendicular to the axial direction. The size of the mandrel jig is appropriately determined depending on the shape of the pipe to be produced. The applicable size is preferably an outer diameter (diameter, or major axis in the case of an elliptical shape) of the mandrel jig of approximately 30 to 300 mm and a height (length) of approximately 50 to 500 mm. This is primarily because the present invention is intended to be used as a cylindrical blank material obtained by winding a plate-shaped blank material using urethane roll foaming. That is, due to the nature of the urethane roll foaming process, it is not suitable for processing small diameter pipes or long pipes where the metal roll (steel roll) is prone to bending. Therefore, the lower limit of the diameter of the mandrel jig is approximately 30 mm, and the upper limit of the height (length) is approximately 500 mm. Furthermore, if the diameter of the pipe to be manufactured is large, the core jig will also become large and heavy, making it difficult to handle, so it is preferable to limit the diameter of the core jig to approximately 300 mm. Furthermore, if the length of the pipe is short, it is relatively easy to butt the two ends of the cylindrical pipe together without using a core jig, so it is preferable that the lower limit of the height (length) of the core jig of the present invention is approximately 50 mm. As will be described later, when a pipe is manufactured using the core jig of the present invention, a pipe with excellent shape precision is obtained. Therefore, the core jig of the present invention can be suitably used when manufacturing pipes that require high shape precision, and is particularly suitable for use when manufacturing pipes for automotive parts.

[0019] FIG. 2 is an exploded view (schematic diagram) of the core metal jig 1. As shown in FIG. 2, the core metal jig 1 has a central member 2, an outer peripheral member 3, an upper surface member 4, and a lower surface member 5, each of which is formed as a separate body. Furthermore, the outer peripheral member 3 is composed of three divided outer peripheral piece members (outer peripheral piece members 31, 32, and 33). These members are then fastened together to form the core metal jig 1 shown in FIG. 1. For ease of explanation, in this specification, the side of the core metal jig 1 on which the upper surface member 4 is arranged will be referred to as the upper surface side, and the side on which the lower surface member 5 is arranged will be referred to as the lower surface side.

[0020] Next, each member will be described.

[0021] <Central member> The central member has a tapered shape. The tapered shape refers to a shape in which the cross section of the central member perpendicular to the axial direction continuously reduces in diameter from the upper surface side to the lower surface side. As shown in FIG. 2 , in this embodiment, the central member 2 has a truncated cone shape. A through hole 2a is formed in the center of the central member 2, penetrating the central member 2 in the axial direction. As will be described later, the through hole 2a is a hole for passing a bolt, which is a fastening member. In this embodiment, the central member 2 has a truncated cone shape, but is not limited to this. For example, the central member may have an approximately truncated cone shape. Here, the approximately truncated cone shape refers to a shape that includes not only a truncated cone shape, but also an elliptical truncated cone shape and an oblique truncated cone shape.

[0022] <Peripheral parts> The outer peripheral member is disposed in contact with the side surface of the central member. When the outer peripheral member is integrated with other members, it constitutes the outer peripheral portion of the core metal jig body of the present invention. In other words, when the outer peripheral member is integrated with other members, the outer peripheral surface of the outer peripheral member becomes the side surface of the core metal jig body.

[0023] In the core metal jig of the present invention, the outer peripheral member is composed of a plurality of divided members (outer peripheral piece members). As shown in FIG. 2, the outer peripheral member 3 in this embodiment is composed of three divided outer peripheral piece members (31, 32, 33) in top view. The outer peripheral piece members 31, 32, and 33 each have a circular sector-shaped cross section in top view. When these are integrated to form the outer peripheral member 3, the cross section becomes annular. Furthermore, when the outer peripheral piece members 31, 32, and 33 are integrated to form the outer peripheral member 3, a space corresponding to the shape of the central member 2 is formed inside. When the outer peripheral member 3 and the central member 2 are integrated, the central member 2 is disposed in that space. Note that the outer peripheral portion of the core metal jig 1 may be formed by the outer peripheral piece members 31, 32, and 33 without any gaps between them, or, as described below, by providing gaps between them to form the outer peripheral portion of the core metal jig 1. By providing gaps between them to form the outer peripheral portion of the core metal jig, grooves can be formed on the side surfaces of the core metal jig. In this embodiment, the number of outer peripheral piece members constituting the outer peripheral member is three, but this is not limited to this. In the present invention, the number of outer peripheral piece members can be three or more and six or less. If the number of outer peripheral piece members is three or more, as described below, when manufacturing a pipe using the core wire jig of the present invention and disassembling the core wire jig, it becomes easier to disassemble into each component, and it also becomes easier to extract each component from the pipe. If the number of outer peripheral piece members is six or less, the manufacturability of the outer peripheral piece members is improved, and it is possible to prevent the number of outer peripheral piece members from becoming too large and making handling cumbersome.

[0024] <Top and bottom components> As shown in Fig. 2, the upper surface member 4 is disposed on the upper surface side of the central member 2 and the outer peripheral member 3, and the lower surface member 5 is disposed on the lower surface side of the central member 2 and the outer peripheral member 3. In this embodiment, the upper surface member 4 and the lower surface member 5 are each disk-shaped, and the diameters of the upper surface member 4 and the lower surface member 5 are the same as the diameter of the main body of the core metal jig 1 formed by the central member 2 and the outer peripheral member 3. Furthermore, through holes 4a and 5a are formed in the centers of the upper surface member 4 and the lower surface member 5, respectively. As will be described later, the through holes 4a and 5a are holes for passing bolts, which are fastening members.

[0025] In this embodiment, the upper surface member 4 and the lower surface member 5 are each disk-shaped, but this is not limiting. The shapes of the upper surface member and the lower surface member may be any shape that allows them to be integrated with the central member and the outer peripheral member by fastening to form the core metal jig. For example, the diameters of the upper surface member and the lower surface member may be smaller than the diameter of the core metal jig body. In this case, as will be described later, when the core metal jig is disassembled into its individual components, it becomes easier to remove it from the pipe. Furthermore, the upper surface member and the lower surface member do not have to be perfectly circular, and may be, for example, elliptical or polygonal. Furthermore, the shapes of the upper surface member and the lower surface member may be the same or different.

[0026] (Method of fastening and disassembling the core metal jig) The core metal jig of the present invention is configured by fastening together the central member, outer peripheral member, upper surface member, and lower surface member, which are separate members as described above. Here, "fastening" means, for example, that the central member, outer peripheral member, upper surface member, and lower surface member are integrated by a fastening force. Such fastening force can be applied, for example, by a fastening member (not shown). Examples of fastening members include, but are not limited to, bolts, nuts, screws, pins, keys, etc. Furthermore, the fastening may be performed by, for example, fastening the above-mentioned members together using magnetic force.

[0027] The core metal jig 1 shown in FIG. 1 integrates the components shown in FIG. 2 by fastening them together using bolts and nuts (not shown). When fastening the components together, the outer peripheral component 3 (outer peripheral piece components 31, 32, and 33) is positioned so that it contacts the side surface of the central component 2. In the core metal jig 1, the heights (axial lengths) of the central component 2 and the outer peripheral component 3 are the same. When the outer peripheral component 3 (outer peripheral piece components 31, 32, and 33) is positioned so that it contacts the side surface of the central component 2 as described above, the upper surface of the central component 2 and the upper surface of the outer peripheral component 3 are flush with each other, and the lower surface of the central component 2 and the lower surface of the outer peripheral component 3 are flush with each other. Then, the upper surface component 4 and the lower surface component 5 are positioned so that they contact the flush surfaces. Then, in this state, bolts are passed through the through holes 4a, 2a, and 5a of the upper surface component 4, central component 2, and lower surface component 5, and tightened with nuts to fasten these components together. Moreover, the core metal jig 1 can be disassembled into the individual components shown in FIG. 2 by loosening the fastening of the bolts and nuts, removing the bolts and nuts, and then releasing the fastening.

[0028] (Pipe manufacturing method) Next, a method for manufacturing a pipe using the core metal jig of the present invention will be described. Here, a method for manufacturing a pipe using the core metal jig 1 shown in FIG.

[0029] First, a plate-shaped blank material is wound into a cylindrical blank material. The winding method is not particularly limited, and may be, for example, a conventional urethane roll foaming method as shown in FIG.

[0030] Next, a core metal jig 1 (core metal jig 1 in a fastened state) is inserted into the cylindrical blank. Figure 3 is a schematic diagram showing the state in which the core metal jig 1 is inserted into the cylindrical blank and clamped between concave outer dies on both sides. The outer diameter of the core metal jig 1 corresponds to the inner diameter of the pipe to be made. Then, the blank is clamped between concave outer dies with a semicircular cross-section and the same diameter as the outer diameter of the pipe to be made. In this state, the blank is pressed with the dies, and both ends of the blank are butted together to form a butt joint.

[0031] As shown in Figure 3, by using the mandrel jig of the present invention, when the cylindrical blank is pressed from the outside with a mold, the mandrel jig comes into contact with the inside of the cylindrical blank to support its shape, allowing both ends of the blank to be butted together with high precision. In other words, by using the mandrel jig of the present invention, when welding a pipe into shape, it is possible to butt both ends of the blank together without creating steps or gaps at the butt joints, thereby improving butt joint precision.

[0032] Then, by performing pipe welding (laser welding) along the butt joints of the blank ends in this state, a pipe with a good cross-sectional shape can be manufactured. Furthermore, the heat input during welding is not increased more than necessary, which causes burn-through, and the impact of heat on the material is kept to a minimum. This reduces defects in the pipe shape and material quality. Furthermore, the occurrence of welding defects such as underfill and voids is suppressed.

[0033] Furthermore, after pipe welding, the core metal jig must be removed from the pipe. At this time, it is not easy to remove the core metal jig, which remains fastened together, from the pipe that has been clamped and welded with a concave outer die. Attempting to forcibly remove the core metal jig not only causes quality problems such as scratches on the inside of the pipe, but also causes problems such as deformation of the pipe or, in severe cases, breakage of the welded portion due to the unexpected load applied when removing the core metal jig.

[0034] The core metal jig of the present invention can be disassembled into its individual components (top surface component, bottom surface component, central component, and outer peripheral component) by releasing the fastening, so that it can be easily removed from the pipe. That is, to remove the core metal jig from the pipe, first release the fastening and remove the top surface component and the bottom surface component. Next, lightly tap the central component to remove it. In this case, since the central component of the present invention has a tapered shape, it can be easily removed by simply tapping it lightly from the underside. Furthermore, by utilizing the space created by removing the central component, the outer peripheral component (outer peripheral piece component) can also be easily removed. Therefore, it is possible to prevent damage to the inside of the pipe, deformation of the pipe, and destruction of the welded portion when removing the core metal jig from the pipe.

[0035] The mandrel jig of the present invention may also have grooves on its side surface that are parallel to the axial direction. Such grooves can be formed, for example, by forming grooves on the outer peripheral surface of the outer peripheral member (outer peripheral piece member). As described above, the grooves may also be formed by providing gaps corresponding to the grooves between the outer peripheral piece members that form the outer peripheral portion when integrated.

[0036] As described above, by forming a groove on the side of the core metal jig and welding the butt joint in line with the groove (i.e., aligning the groove with the weld line), welding of the welded portion and the core metal jig due to the heat input of the welding can be prevented. However, forming a groove as described above is not necessarily required. For example, when the core metal jig is made of a metal material such as steel, copper, or brass, it is preferable to form a groove on the side of the core metal jig to avoid welding at the welded portion of the pipe. On the other hand, when the core metal jig is made of a high-melting point material such as ceramic, or a material such as wood or thermosetting resin that is not likely to weld to the welded portion of the pipe, there is no need to form a groove on the side of the core metal jig.

[0037] Furthermore, even if the mandrel jig is made of metal, if the pipe is spot-welded (not continuous or temporary), the possibility of welding is considered low even without forming grooves on the side. Therefore, in such cases, there is no need to deliberately form grooves on the side of the mandrel jig. On the other hand, even if the material is not susceptible to welding, it is considered preferable to form grooves on the side if it is necessary to avoid contamination (adhesion of foreign matter) on the inner surface of the pipe, taking into account the intended use of the product. As such, the need for grooves on the side of the mandrel jig is determined by various factors, such as the material of the mandrel jig, the welding method, and the intended use of the product.

[0038] When forming a groove on the side of the core metal jig, the shape of the groove is not particularly limited, but as an example, the groove width can be 3 mm or more. Also, as an example, the groove width can be 10 mm or less. Also, as an example, the groove depth can be 5 mm or more. By making the groove width 3 mm or more, adhesion during welding can be more easily suppressed. By making the groove width 10 mm or less, the inner surface of the blank material can be more easily supported when manufacturing a pipe. Also, by making the groove depth 5 mm or more, adhesion during welding can be more easily suppressed.

[0039] (Other embodiments) Fig. 4 is a schematic diagram showing another embodiment of the core metal jig of the present invention, and Fig. 5 is its exploded view (schematic diagram). The core metal jig 10 shown in Fig. 4 has a substantially cylindrical shape with an outer diameter equal to the inner diameter of the pipe to be made, similar to the above-mentioned embodiment.

[0040] As shown in Fig. 5, the core metal jig 10 has a central member 20, an outer peripheral member 30, an upper surface member 40, and a lower surface member 50, which are each formed as separate bodies. Furthermore, the outer peripheral member 30 is made up of four divided outer peripheral piece members (outer peripheral piece members 301, 302, 303, and 304). These members are then fastened together to form the core metal jig 10.

[0041] As shown in FIG. 5 , in this embodiment, the central member 20 of the core metal jig 10 has a truncated quadrangular pyramid shape, and accordingly, the shape and number of divisions of the outer peripheral member 30 differ from those of the core metal jig 1 described above. Note that, although the central member 20 has a truncated quadrangular pyramid shape in this embodiment, this is not limiting. For example, the central member may have a polygonal truncated pyramid shape other than a truncated quadrangular pyramid, as long as it has a tapered shape. Furthermore, in the core metal jig 10, the components are fastened together using screws (not shown). For example, a known configuration can be used for fastening using screws. While details are omitted, as shown in FIG. 5 , screw holes 40a and 50a are formed in the top surface member 40 and the outer peripheral member 50, respectively, and the top surface member 40 and the outer peripheral member 50 are screwed together with the outer peripheral member 30 (outer peripheral piece members 301, 302, 303, and 304). The core metal jig 10 allows the components to be fastened and disassembled using these screws.

[0042] The method for manufacturing a pipe using the core metal jig 10 is the same as that using the above-described core metal jig 1. The core metal jig 10 of this embodiment also provides the same effects as the above-described core metal jig 1. [Explanation of symbols]

[0043] 1, 10 Core jig 2, 20 Central member 3, 30 Peripheral member 4, 40 Upper surface member 5, 50 Bottom member 31, 32, 33 Peripheral piece members 301, 302, 303, 304 Peripheral piece members

Claims

1. A core metal jig for pipe welding, The core metal jig has a generally cylindrical shape with an outer diameter equal to the inner diameter of the pipe to be manufactured, and is configured by a central member, an outer peripheral member, an upper surface member, and a lower surface member, each of which is separate, and which are integrated by fastening together; the central member has a tapered shape; the outer peripheral member is arranged in contact with a side surface of the central member and is further configured by outer peripheral piece members divided into three to six pieces in top view, the upper surface member and the lower surface member are disposed on the upper surface side and the lower surface side of the central member and the outer peripheral member, respectively; The core metal jig can be disassembled by releasing the fastening.

2. The core metal jig according to claim 1 , wherein the central member has a substantially truncated cone shape or a substantially truncated polygonal pyramid shape.

3. The core metal jig according to claim 1 , wherein the core metal jig has a groove on a side surface thereof that is parallel to the axial direction.

4. The core metal jig according to claim 2 , wherein the core metal jig has a groove on a side surface thereof that is parallel to the axial direction.

5. A method for manufacturing a pipe, comprising manufacturing a pipe using the core metal jig according to any one of claims 1 to 4.

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