Arc welding method and method for inspecting weld strength of joints welded by said arc welding method

Abstract

An arc welding method according to the present invention includes fusing and joining at least part of a workpiece in which a plurality of non-ferrous metal sheets are stacked.　The workpiece has a processing hole at a welding site. The processing hole is a non-through-hole that passes through an arc-radiation-side non-ferrous metal sheet and extends to a non-ferrous metal sheet on the side farthest from an arc welding implement, at least part of the farthest-side non-ferrous metal sheet being recessed. The processing hole is irradiated with an arc from the open side, and the arc-radiation-side non-ferrous metal sheet is fused and welded to the back surface of the farthest-side non-ferrous metal sheet without using a backing jig on the side opposite from the workpiece. It is therefore possible to provide an arc welding method with which it is possible to carry out welding without using a backing tool and moreover to carry out welding even when there are constraints on a back-surface-side gap in a workpiece.

Description

[Technical field]

[0001] The present invention relates to an arc welding method and a method for inspecting the weld strength of a joint welded by the arc welding method, and more particularly to an arc welding method for joining non-ferrous metal plates together and a method for inspecting the weld strength of a joint welded by the arc welding method. [Background technology]

[0002] 2. Description of the Related Art When joining a plurality of plate materials by welding, a known arc spot welding method involves forming a machining hole in the plate material on the arc welder side of a workpiece in which the plate materials are stacked, and joining the plate materials by wire-fed arc spot welding.

[0003] Patent Document 1 describes that when arc spot welding is performed by melting the inner wall of a machined hole formed in the above-mentioned plate material, the melt depth of the lower plate material becomes deep and burn-through occurs, so a backing tool is abutted against the lower plate material. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 06-039542 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in actual production sites, there are cases where there are limitations on the shape of the workpiece or on the space on the back side of the workpiece, and it is often not possible to use a backing tool.

[0006] The present invention has been made in consideration of the problems associated with the conventional technology, and an object of the present invention is to provide an arc welding method that does not require a backing jig and enables arc spot welding even when there is limited space on the back side of the workpiece. [Means for solving the problem]

[0007] As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that the above-mentioned objective could be achieved by forming a machining hole that reaches not only the plate material on the arc welding machine side, but also the plate material furthest from the arc welding machine, and thus completed the present invention.

[0008] That is, the arc welding method of the present invention is an arc welding method in which at least a portion of a workpiece made of a plurality of overlapping non-ferrous metal plates is melted and joined. The workpiece has a machined hole at the welding site, the machined hole being a blind hole that penetrates the non-ferrous metal plate on the arc irradiated side to reach the non-ferrous metal plate furthest from the arc welding machine and is partially recessed, and an arc is irradiated from the opening side of the machined hole, and melted and welded to the back surface of the non-ferrous metal plate furthest from the arc welding machine without using a backing jig on the opposite side of the workpiece.

[0009] The weld strength inspection method of the present invention is a method for inspecting the weld strength of a joint welded by an arc welding method. The method is characterized in that the weld strength is estimated from the diameter of the molten portion appearing on the back surface of the non-ferrous metal plate on the farthest side. Effect of the Invention

[0010] According to the present invention, since a machining hole is formed that reaches not only the plate material on the side of the arc welder, but also the plate material farthest from the arc welder, it is possible to weld without using a backing tool, and it is possible to provide an arc welding method that allows welding even when there is limited space on the back side of the workpiece. [Brief description of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view of a main portion illustrating an arc welding method according to the present invention. [Diagram 2] 1 is a cross-sectional view of a main portion of a joint welded by the arc welding method of the present invention. [Diagram 3]1 is a graph showing the relationship between the plate thickness at the location where a hole is formed in the non-ferrous metal plate farthest from the arc welder and the presence or absence of burn-through at the welded portion when the diameter of the hole is 4 mm. [Figure 4] 1 is a graph showing the relationship between the plate thickness at the location where a machined hole is formed in the non-ferrous metal plate farthest from the arc welder and the presence or absence of burn-through at the welded portion when the diameter of the machined hole is 8 mm. [Diagram 5] 1 is a graph showing the relationship between the diameter of a processed hole and the strength of a fusion zone formed in a joint. [Figure 6] 1 is a graph showing the relationship between the tensile strength of a joint and the diameter of a fusion zone that appears on the back surface of a non-ferrous metal plate that is farthest from an arc welder. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The arc welding method of the present invention will now be described in detail. The arc welding method of the present invention is a welding method in which at least a portion of a workpiece is melted by an arc to join a plurality of overlapping non-ferrous metal plates together.

[0013] The workpiece 2, which is made up of multiple overlapping non-ferrous metal plates, has a machined hole 21 formed in advance at the welding site. As shown in Figure 1, the machined hole is a blind hole that penetrates all of the non-ferrous metal plate 3 (hereinafter sometimes referred to as the "front plate") that is arranged on the welding machine side rather than the non-ferrous metal plate 4 (hereinafter sometimes referred to as the "back plate") that is farthest from the arc welding machine 1, reaching the back plate 4 and recessing a part of the back plate 4.

[0014] Then, the welding torch is rotated to irradiate the inner circumferential surface of the machined hole 21 from the opening side of the machined hole 21, and the inner circumferential surface of the machined hole 21 is melted together with the wire. As a result, the bottom surface of the machined hole 21 melts, and when the melting reaches the back surface of the back plate 4, the arc irradiation is stopped and the wire is solidified, thereby joining the multiple overlapping non-ferrous metal plates together. The number of front panels 3 is not limited to one, and multiple panels may be stacked on top of each other.

[0015] In the arc welding method of the present invention, a hole is formed that is recessed into part of the back plate, so that the inner side surface of the hole is also formed in the back plate, and the back plate melts together with the adjacent front plate in the in-plane direction of the joint interface, eliminating the need for a backing tool.

[0016] In other words, when simply joining a back plate and an adjacent front plate, apart from the point of view of the joining strength, the joining interface needs to melt, and if the back plate is not concave and is flat, the back plate cannot melt in the direction of the joining interface unless the bottom of the machined hole melts, so in order to join the back plate and the adjacent front plate, the back plate must first melt in its thickness direction. On the other hand, if a part of the back plate is concave, the back plate can immediately melt in the direction of the joining interface, so it is possible to join the back plate and the adjacent front plate even if the bottom of the back plate does not melt.

[0017] In this way, the arc welding method of the present invention can melt the workpiece consisting of overlapping non-ferrous metal plates in the in-plane direction of the joint interface without melting it in the thickness direction, so that the vicinity of the joint interface can be melted early and the back plate and the front plate can be joined before the bottom surface of the machined hole melts through.

[0018] As the workpieces are melted in the direction of the joint interface, they are also melted in the thickness direction of the workpieces. By irradiating the arc until the back surface of the back plate is melted, the molten part spreads sufficiently in the in-plane direction of the joint interface as shown in Figure 2, and the molten metal from the welding wire fills the machining hole. The molten part formed by solidifying these parts ensures the joint strength.

[0019] In addition, because the area near the joint interface can be melted early, the welding energy input to the workpiece is reduced, and not only can deformation of the workpiece be suppressed, but the amount of fumes and dust generated can also be reduced.

[0020] In addition, in Figure 1, a form of welding is shown in which an arc is applied from above the machined hole formed in the workpiece, but it is also possible to rotate the workpiece 90 degrees so that the opening of the machined hole faces to the side and weld by applying an arc from the side.

[0021] The welding energy input to the workpiece depends on the material and thickness of the non-ferrous metal plate as well as the depth and diameter of the hole to be machined, but it is preferable that the current is 50 to 350 A (amperes) and the current time is 0.5 to 5 seconds.

[0022] If too much welding energy is input to the workpiece, the molten metal will drop and separate from the joint, reducing the volume of the molten part where the molten metal solidifies, and the joint strength will decrease.

[0023] The thickness of the recessed portion of the back plate (where the machined hole is formed) is preferably thicker than 1 / 20 of the diameter of the machined hole.

[0024] FIG. 3 shows the relationship between the thickness of the back plate at the location where the drilled hole is formed and the cross tensile strength (CTS) when a 4 mm diameter hole is formed in a 5000 series aluminum alloy plate, and FIG. 4 shows the relationship between the thickness of the back plate at the location where the drilled hole is formed and the cross tensile strength (CTS) when a 8 mm diameter hole is formed.

[0025] From Figures 3 and 4, it can be seen that by making the thickness of the recessed part of the back plate thicker than 1 / 20 of the diameter of the drilled hole, the molten metal is prevented from burning through and the volume of the molten part is prevented from decreasing.

[0026] Furthermore, if the depth of the recess formed in the back plate is 0.1 mm or more, the back plate at the joining interface can be melted in the direction of the joining interface.

[0027] The above-mentioned machined hole is preferably cylindrical. Since the inner peripheral surface of the machined hole formed in the front plate adjacent to the back plate is flush with the back plate, the back plate and the front plate can be melted simultaneously at the joining interface between the back plate and the front plate, which makes it easier to melt in the direction of the joining interface.

[0028] The diameter of the machined hole depends on the required joining strength, but is preferably greater than three times the thickness of the thinnest non-ferrous metal plate among the non-ferrous metal plates constituting the workpiece. If the diameter of the machined hole is smaller than three times the thickness of the thinnest non-ferrous metal plate among the non-ferrous metal plates constituting the workpiece, the volume of the machined hole is small, so even if the molten metal fills the machined hole, the amount of heat it possesses is small. As a result, heat is easily dissipated by the surrounding base material, it is difficult to melt in the direction of the joining interface, and welding defects such as non-welding occur.

[0029] When multiple plates are stacked and welded together, the weld strength is determined by the weld strength of the thinnest plate, and this weld strength correlates with the diameter of the drilled hole, as shown in FIG. 5.

[0030] For example, when the thickness of the thinnest sheet material is 1 mm, if the required strength of the product is 2.0 kN, a strength of 2.5 kN or more can be guaranteed by making the machined hole diameter 4.5 mm or more.

[0031] The above-mentioned arc welding method can be applied to the welding of non-ferrous metal plates, and examples of the metals constituting the non-ferrous metal plates include aluminum, magnesium, titanium, and alloys containing these metals.

[0032] A method for inspecting the weld strength of a joint welded by the above-mentioned arc welding method of the present invention will now be described.

[0033] Generally, the weld strength of a joint is determined by the diameter of the joint interface 51 of the two plate materials in the fusion zone 5, and therefore, in order to know the weld strength of the joint, it is necessary to measure the diameter of the joint interface 51 of the fusion zone 5. However, it is difficult to measure the diameter of the joint interface 51 of the fusion zone 4 from the outside.

[0034] In the arc welding method of the present invention, as described above, machined hole 21 penetrating joint interface 51 is formed in the welded portion, and the edge of joint interface 51 is exposed, so that the vicinity of the joint interface can be directly melted through machined hole 21, and the vicinity of the joint interface can be melted without melting the bottom surface of machined hole 21. Therefore, if fusion zone 5 is formed up to back surface 41 of the back plate 4, the diameter of the fusion zone at joint interface 51 will be larger than diameter 52 of the fusion zone appearing on back surface 41.

[0035] Therefore, the weld strength of a joint welded by the arc welding method of the present invention can be estimated from the diameter 52 of the fusion zone appearing on the rear surface 41 of the back plate 4.

[0036] FIG. 6 shows the relationship between the diameter of the fusion zone appearing on the back surface of the back plate and the tensile shear strength of a joint welded by the arc welding method of the present invention.

[0037] From FIG. 6, it can be seen that there is a correlation between the tensile strength of the joint and the diameter of the fusion zone appearing on the back surface of the back plate. For joints welded by the arc welding method of the present invention, it is possible to estimate the weld strength of the joint by measuring the diameter of the fusion zone appearing on the back surface of the back plate.

[0038] In this way, the welding strength inspection method for the joint requires only measuring the diameter of the molten part that appears on the visible back surface of the back plate, and the welding strength of the joint can be easily estimated, making it possible to inspect all the joints rather than just conducting sample inspections. [Explanation of symbols]

[0039] 1. Arc welding machine 2 Work 21 Machining hole 22 Thickness of back plate at hole forming location 3. Non-ferrous metal plate (front plate) on the arc welding machine side 4. The non-ferrous metal plate (back plate) furthest from the arc welding machine 41 Back side 5 Welding section 51 Joint interface 52 Diameter of the fusion zone on the back side

Claims

1. An arc welding method for melting and joining at least a portion of a workpiece having a plurality of overlapping non-ferrous metal plates, comprising: The workpiece has a processed hole at a welding site, The processed hole is a non-through hole that penetrates the non-ferrous metal plate on the arc irradiation side to reach the non-ferrous metal plate on the side farthest from the arc welding machine and is partially recessed, This is an arc welding method characterized by irradiating an arc from the opening side of the machined hole and melting and welding the back surface of the non-ferrous metal plate on the farthest side without using a backing jig on the opposite side of the workpiece.

2. The method of claim 1, wherein the hole is cylindrical.

3. 3. The arc welding method according to claim 2, wherein the thickness of the recessed portion of the non-ferrous metal plate on the farthest side is greater than 1 / 20 of the diameter of the hole.

4. 4. The arc welding method according to claim 3, wherein the diameter of the machined hole is greater than three times the thickness of the thinnest of the non-ferrous metal plates constituting the workpiece.

5. A method for inspecting weld strength of a joint welded by the arc welding method according to any one of claims 1 to 4, comprising the steps of: A weld strength inspection method characterized in that the weld strength is estimated from the diameter of the molten zone that appears on the back surface of the non-ferrous metal plate that is the furthest away.

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