Arc welding method and method for checking the welding strength of a joint welded using the arc welding method

Abstract

The arc welding method of the present application is an arc welding method for joining at least a part of a workpiece made by overlapping a plurality of non-ferrous metal plates. Also, the workpiece has a machining hole at a welding site, the machining hole is a non-through hole made by reaching a non-ferrous metal plate on the farthest side from an arc welding machine through the non-ferrous metal plate on the arc irradiation side and locally recessing the non-ferrous metal plate on the farthest side, an arc is irradiated from the opening side of the machining hole, and the back surface of the non-ferrous metal plate on the farthest side is melted without using a back pad jig on the side opposite to the opening side of the workpiece, and welding is performed, and thus, an arc welding method can be provided in which welding can be performed without using a back pad jig, and even when the space on the back surface side of the workpiece has a limitation, welding can be performed.

Description

TECHNICAL FIELD

[0001] The present application relates to an arc welding method and a welding strength inspection method for a joined body welded using the arc welding method, and more particularly to an arc welding method for joining non-ferrous metal sheets to each other and a welding strength inspection method for a joined body welded using the arc welding method. BACKGROUND

[0002] As an arc spot welding method, there is known a method in which, when joining a plurality of sheets by welding, a machining hole is formed in a sheet on the arc welding machine side of a work in which the sheets are overlapped, and the sheets are joined by arc spot welding using a welding wire feeding type.

[0003] In Patent Document 1, it is described that, in the case where arc spot welding is performed by melting the inner wall of the machining hole formed in the sheet, the melting depth of the lower sheet becomes deep, and burn-through occurs, and therefore, a back pad tool is brought into contact with the lower sheet.

[0004] Prior art documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. H06-039542 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] However, in actual production sites, there are cases where the shape of the work and the space on the back side of the work are limited, and the back pad tool cannot be used in many cases.

[0009] The present application has been made in view of the problems of the related art, and an object thereof is to provide an arc welding method in which arc spot welding can be performed even in the case where the space on the back side of the work is limited, without using a back pad tool.

[0010] SOLUTION TO PROBLEM

[0011] The present inventors have intensively studied in order to achieve the above object, and as a result, have found the following solution, thereby completing the present application: a machining hole is formed not only in the sheet on the arc welding machine side but also in the sheet on the side farthest from the arc welding machine, and thereby the above object can be achieved.

[0012] That is, the arc welding method of the present application is an arc welding method in which at least a part of a work in which a plurality of non-ferrous metal sheets are overlapped is melted to join the sheets.

[0013] Further, the workpiece has a machining hole at the welding site, the machining hole is a non-through hole that reaches the non-ferrous metal plate on the side farthest from the arc welder and makes a portion of the non-ferrous metal plate on the farthest side concave, and the arc is irradiated from the opening side of the machining hole, and the back surface of the non-ferrous metal plate on the farthest side is melted without using a back pad jig on the side of the workpiece opposite to the opening side, and welding is performed.

[0014] Further, the welding strength inspection method of the present application is a method of inspecting the welding strength of a joined body welded by the arc welding method.

[0015] Further, the welding strength is estimated from the diameter of the melted portion appearing on the back surface of the non-ferrous metal plate on the farthest side.

[0016] Effects of the Invention

[0017] According to the present application, by forming a machining hole 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 provide an arc welding method in which welding can be performed without using a back pad jig, even when the space on the back surface side of the workpiece is limited. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 is a main part cross-sectional view that explains the arc welding method of the present application.

[0019] Figure 2 is a main part cross-sectional view of a joined body welded by the arc welding method of the present application.

[0020] Figure 3 is a chart showing the relationship between the plate thickness of the machining hole formation site of the non-ferrous metal plate on the side farthest from the arc welder and the presence or absence of burn-through at the joint site when the machining hole diameter is 4 mm.

[0021] Figure 4 is a chart showing the relationship between the plate thickness of the machining hole formation site of the non-ferrous metal plate on the side farthest from the arc welder and the presence or absence of burn-through at the joint site when the machining hole diameter is 8 mm.

[0022] Figure 5 is a chart showing the relationship between the machining hole diameter of the melted portion formed in the joined body and the strength.

[0023] Figure 6 is a chart showing the relationship between the tensile strength of the joined body and the diameter of the melted portion appearing on the back surface of the non-ferrous metal plate on the side farthest from the arc welder. DETAILED DESCRIPTION

[0024] The arc welding method of the present invention will be described in detail.

[0025] The arc welding method of the present invention is a welding method for joining a plurality of overlapping non-ferrous metal plates by melting at least a portion of the workpiece using an arc.

[0026] The workpiece 2 formed by overlapping a plurality of non-ferrous metal plates is preliminarily provided with a processing hole 21 at the welding position. Figure 1 As shown, the above-mentioned processed hole is a non-through hole that penetrates the entire non-ferrous metal plate 3 (hereinafter sometimes referred to as the "front side plate") that is arranged at a position closer to the above-mentioned welding machine side than the non-ferrous metal plate 4 (hereinafter sometimes referred to as the "back plate") that is farthest from the arc welding machine 1, reaches the back plate 4, and makes a part of the above-mentioned back plate 4 concave.

[0027] Furthermore, the arc is irradiated by aiming at the inner peripheral surface of the processing hole 21 from the opening side of the processing hole 21, and the welding torch is rotated to melt the inner peripheral surface of the processing hole 21 together with the welding wire. At the same time, the bottom surface of the processing hole 21 melts. Once it melts to the back surface of the back plate 4, the arc irradiation is stopped and solidification is performed, thereby joining the overlapping multiple non-ferrous metal plates to each other.

[0028] In addition, the number of the front side plates 3 is not limited to one, and a plurality of them may be stacked.

[0029] The arc welding method of the present invention forms a recessed processing hole in a part of the back plate, and the inner peripheral side of the processing hole is also formed in the back plate, and the back plate is also melted together with the surface side plate adjacent in the in-plane direction of the joint interface, so there is no need for a backing device.

[0030] In other words, regardless of the bonding strength, when only the back plate is bonded to the adjacent front side plate, the bonding interface must be melted. If the back plate is not concave but flat, the back plate cannot melt toward the bonding interface unless the bottom surface of the processed hole melts. Therefore, in order to bond the back plate to the adjacent front side plate, the back plate must first be melted in the thickness direction. In contrast, as long as the back plate is partially concave, the back plate can immediately melt toward the bonding interface. Therefore, even if the bottom surface of the back plate does not melt, the back plate and the adjacent front side plate can be bonded.

[0031] In this way, the arc welding method of the present invention can melt the workpiece in the in-plane direction of the joining interface even if the workpiece formed by overlapping non-ferrous metal plates is not melted in the thickness direction. Therefore, the vicinity of the joining interface can be melted as early as possible and the back plate and the front side plate can be joined before the bottom surface of the processed hole is burned through.

[0032] Furthermore, by irradiating the arc, as the workpiece is melted toward the bonding interface, the workpiece is also melted in the thickness direction of the workpiece until the back surface of the back plate is melted, thereby Figure 2As shown, the molten portions sufficiently expand in the in-plane direction of the joint interface, and by filling the machining hole with molten metal from the welding wire, the joint strength can be ensured by the molten portions formed due to their solidification.

[0033] Further, the molten portion near the joint interface can be formed early, and thus the welding energy input to the workpiece can be reduced, and not only the deformation of the workpiece can be suppressed, but also the amount of smoke and dust generated can be reduced.

[0034] Further, in the Figure 1 , the welding is performed by irradiating the arc from above the machining hole formed in the workpiece, but the workpiece can be rotated by 90° so that the opening of the machining hole faces sideways, and the welding can be performed by irradiating the arc from the side.

[0035] The welding energy input to the workpiece depends not only on the material of the non-ferrous metal plate and the thickness of the non-ferrous metal plate, but also on the depth and diameter of the machining hole, but the current is preferably 50 to 350 A (amperes), and the current time is preferably 0.5 to 5 seconds.

[0036] If the welding energy input to the workpiece becomes too much, the molten metal separates from the joint portion, the volume of the molten portion formed by the solidification of the molten metal decreases, and the joint strength decreases.

[0037] The thickness of the recessed portion (machining hole forming portion) of the back plate is preferably thicker than 1 / 20 of the diameter of the machining hole.

[0038] The relationship between the thickness of the back plate at the machining hole forming portion when a machining hole with a diameter of 4 mm is formed in a 5000 series aluminum alloy plate and the cross tensile strength (CTS) is shown in Figure 3 , and in addition, the relationship between the thickness of the back plate at the machining hole forming portion when a machining hole with a diameter of 8 mm is formed and the cross tensile strength (CTS) is shown in Figure 4 .

[0039] From Figure 3 , 4 it can be seen that since the thickness of the recessed portion of the back plate is thicker than 1 / 20 of the diameter of the machining hole, the burn-through of the molten metal can be prevented, and the decrease in the volume of the molten portion can be prevented.

[0040] In addition, as long as the depth of the recess formed in the back plate is 0.1 mm or more, the back plate of the joint interface can be molten in the direction of the joint interface.

[0041] The machining hole is preferably cylindrical. The inner peripheral surface of the machining hole formed in the back plate and the adjacent surface side plate is flush, and at the joint interface between the back plate and the surface side plate, the back plate and the surface side plate can be molten at the same time, and thus the molten portion is easily molten in the direction of the joint interface.

[0042] The diameter of the processing hole is also dependent on the required joint strength, but is preferably greater than three times the thickness of the thinnest non-ferrous metal sheet constituting the workpiece. In the case where the diameter of the processing hole is less than three times the thickness of the thinnest non-ferrous metal sheet constituting the workpiece, the processing hole volume is small, and thus even if the molten metal fills the processing hole, the amount of heat possessed is small. As a result, heat is easily discharged to the surrounding base material, and it is difficult to melt in the joint interface direction, resulting in poor welding such as incomplete fusion.

[0043] The welding strength when a plurality of sheets are overlapped and welded is determined by the welding strength of the thinnest sheet, and as shown in Figure 5 , the welding strength has a correlation with the diameter of the processing hole.

[0044] For example, in the case where the thickness of the thinnest sheet is 1 mm and the required strength as a product is 2.0 kN, by setting the processing hole to a diameter of 4.5 mm or more, a strength of 2.5 kN or more can be ensured.

[0045] The arc welding method described above can be applied to the welding of non-ferrous metal sheets, and as the metal forming the non-ferrous metal sheet, for example, in addition to aluminum, magnesium, titanium, alloys containing these metals can also be listed.

[0046] A method for checking the welding strength of a joint body welded using the arc welding method of the present application will be described.

[0047] Generally, the welding strength of a joint body is determined by the diameter of the joint interface 51 of the two sheets of the molten portion 5, and thus in order to know the welding strength of the joint body, the diameter of the joint interface 51 of the molten portion 5 needs to be measured. However, it is difficult to measure the diameter of the joint interface 51 of the molten portion 5 from the outside.

[0048] The arc welding method of the present application can form a processing hole 21 that penetrates the joint interface 51 at the welding site as described above, and the edge of the joint interface 51 is exposed, and thus the vicinity of the joint interface can be directly melted by the processing hole 21, and even if the bottom surface of the processing hole 21 is not melted, the vicinity of the joint interface can be melted. Thus, as long as the molten portion 5 is formed to the back surface 41 of the back sheet 4, the diameter of the molten portion of the joint interface 51 is greater than the diameter 52 of the molten portion that appears on the back surface 41.

[0049] Thus, the welding strength of the joint body welded using the arc welding method of the present application can be inferred from the diameter 52 of the molten portion that appears on the back surface 41 of the back sheet 4.

[0050] In Figure 6 , the relationship between the diameter of the molten portion that appears on the back surface of the back sheet of a joint body welded using the arc welding method of the present application and the tensile shear strength is shown. Thus, the welding strength of the joint body welded using the arc welding method of the present application can be inferred from the diameter 52 of the molten portion that appears on the back surface 41 of the back sheet 4.

[0051] From Figure 6 It is known that there is a correlation between the tensile strength of the joint and the diameter of the molten portion appearing on the back surface of the back plate, and for a joint welded using the arc welding method of the present application, the welding strength of the joint can be inferred by measuring the diameter of the molten portion appearing on the back surface of the back plate.

[0052] Thus, the welding strength inspection method for the joint can simply infer the welding strength of the joint by measuring the diameter of the molten portion appearing on the back surface of the visually recognizable back plate, and therefore, instead of performing sample inspection, the entire number of joints can be inspected.

[0053] Explanation of Reference Numerals

[0054] 1, arc welder; 2, workpiece; 21, machined hole; 22, plate thickness of back plate at machined hole formation site; 3, non-ferrous metal plate on arc welder side (front side plate); 4, non-ferrous metal plate on side farthest from arc welder (back plate); 41, back surface; 5, molten portion; 51, joint interface; 52, diameter of molten portion appearing on back surface.

Claims

1. An arc welding method for joining workpieces formed by overlapping a plurality of non-ferrous metal plates by melting at least parts of the workpieces, characterized in that: The workpiece has a machined hole at the welding position, The processed hole is a non-through hole that penetrates the non-ferrous metal plate on the arc irradiation side and reaches the non-ferrous metal plate on the side farthest from the arc welding machine, and is formed by partially recessing the non-ferrous metal plate on the farthest side. An arc is irradiated from the opening side of the machined hole, and welding is performed by melting the non-ferrous metal plate on the back side of the farthest side on the side opposite to the opening side of the workpiece without using a backing jig.

2. The arc welding method according to claim 1, wherein: The processed hole is cylindrical.

3. The arc welding method according to claim 2, characterized in that 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 processed hole.

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

5. A method for inspecting the weld strength of a joint body welded by the arc welding method according to any one of claims 1 to 4, wherein: The welding strength is estimated from the diameter of the molten zone appearing on the back surface of the non-ferrous metal plate on the farthest side.

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