Manufacturing method for welded structures

Abstract

To provide a manufacturing method for a welded structure that makes it possible to manufacture a welded structure in which a difference in quality between welded portions is small.SOLUTION: A manufacturing method for a welded structure includes a step of preparing a plurality of metal plates, a step of sandwiching the plurality of metal plates between a first electrode and a second electrode, and a step of energizing between the first electrode and the second electrode. The preparing step is performed so that a first metal plate including aluminum or an aluminum alloy as a component material is included in the plurality of metal plates. The sandwiching step is performed so that the first metal plate and the first electrode are in contact with each other. The energizing step includes a first energizing process and a second energizing process. The first energizing process is performed under an energization condition in which the plurality of metal plates is not welded to each other and in which a component material of the first metal plate adheres to a surface of the first electrode, and the second energizing process is performed under an energization condition in which the plurality of metal plates are welded to each other.SELECTED DRAWING: Figure 2

Description

Technical Field

[0004] , , ,

[0001] The present invention relates to a method for manufacturing a welded structure in which a plurality of metal plates are welded by spot welding.

Background Art

[0002] Patent Document 1 discloses spot welding. Spot welding sandwiches a plurality of panels with a pair of electrodes facing each other and passes an electric current between the pair of electrodes to weld the plurality of panels.

Prior Art Documents

Patent Documents

[0006] One of the objectives of the present invention is to provide a method for manufacturing a welded structure that can produce a welded structure in which the quality difference between multiple welds is small. [Means for solving the problem]

[0007] A method for manufacturing a welded structure according to one aspect of the present invention is: The process of preparing multiple metal plates, A step of sandwiching the plurality of metal plates between the first electrode and the second electrode, The process includes a step of applying current between the first electrode and the second electrode, The aforementioned preparation step involves preparing the plurality of metal plates so that a first metal plate, whose constituent material is aluminum or an aluminum alloy, is included in the plurality of metal plates. The clamping step is performed so that the first metal plate and the first electrode are in contact. The process of applying power includes a first power application process and a second power application process. The first energizing process is carried out under energizing conditions in which the plurality of metal plates are not welded together and the constituent material of the first metal plate adheres to the surface of the first electrode. The second energizing process is carried out under energizing conditions that allow the plurality of metal plates to be welded together. [Effects of the Invention]

[0008] In the above-described method for manufacturing the welded structure, the first energizing process in the first spot welding is performed using an electrode on which no material adhering to the surface of the first metal plate is present. Even if an electrode on which no material adhering to the surface of the first metal plate is present is used in the first energizing process, the damage to the first electrode is relatively small compared to the case where an electrode on which no material adhering to the surface of the first metal plate is present is used in the second energizing process. This is because the energizing conditions on which the material adhering to the first metal plate is present place less load on the first electrode compared to the energizing conditions on which multiple metal plates are welded. Furthermore, in the above-described method for manufacturing the welded structure, the second energizing process in the first spot welding can be performed using a first electrode on which the material adhering to the first metal plate is present and which suffers relatively little damage. Since the material adhering to the first metal plate is present on the first electrode, the damage to the electrode is small even in the second energizing process in the first spot welding. In the above-described method for manufacturing the welded structure, in spot welding from the second spot onward, both the first and second energizing processes can be performed using a first electrode on which the material adhering to the first metal plate is present and which suffers little damage. In other words, the above method for manufacturing a welded structure allows the second energizing process in the first spot weld and the second energizing process in subsequent spot welds to be carried out using a first electrode with substantially the same surface properties. Therefore, even if the energizing conditions are the same for the first spot weld and subsequent spot welds, it is unlikely that there will be a difference in the quality of the weld formed by the first spot weld and the weld formed by subsequent spot welds. Consequently, the above method for manufacturing a welded structure can produce a welded structure with minimal differences in the quality of multiple welds. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an explanatory diagram illustrating a method for manufacturing a welded structure according to an embodiment. [Figure 2]Figure 2 is a graph illustrating the process of applying electricity in the manufacturing method of a welded structure according to the embodiment. [Modes for carrying out the invention]

[0010] 《Embodiment》 [Method for manufacturing welded structures] A method for manufacturing a welded structure according to the embodiment will be described below with reference to Figures 1 and 2. The method for manufacturing a welded structure according to the embodiment is a method for manufacturing a welded structure by welding a plurality of metal plates 1 together by spot welding. The method for manufacturing a welded structure according to the embodiment comprises the following steps A to C. Step A involves preparing multiple metal plates 1. The multiple metal plates 1 include a first metal plate 10 whose constituent material is aluminum or an aluminum alloy. Step B involves sandwiching multiple metal plates 1 between the first electrode 100 and the second electrode 200. The sandwiching of the multiple metal plates 1 is carried out so that the first metal plate 10 and the first electrode 100 are in contact. Step C involves applying current between the first electrode 100 and the second electrode 200. One of the features of the manufacturing method for a welded structure according to this embodiment is that, as shown in Figure 2, process C includes a specific first energizing process F and a second energizing process S. Figure 2 is a graph showing the relationship between the energizing time and the energizing current in process C. The horizontal axis represents the energizing time (cycle), and the vertical axis represents the energizing current value (kA). One cycle is 1 / 60 of a second. When forming multiple welds, processes A through C are repeated.

[0011] [Process A] The multiple metal plates 1 prepared in step A include a first metal plate 10 and a second metal plate 20. The constituent material of the first metal plate 10 is aluminum or an aluminum alloy. The constituent material of the second metal plate 20 is the same as the constituent material of the first metal plate 10, or different from the constituent material of the first metal plate 10. "Same constituent material" means that the types of constituent elements are the same and the content of those elements is the same. "Different constituent material" means that the types of constituent elements are different, or the types of constituent elements are the same and the content of those elements is different. The second metal plate 20 is, for example, a plate whose constituent material is one selected from the group consisting of aluminum, aluminum alloy, iron, and iron alloy. In this embodiment, the multiple metal plates 1 consist of two plates: the first metal plate 10 and the second metal plate 20. Unlike this embodiment, the multiple metal plates 1 may consist of three or more plates. That is, in addition to the first metal plate 10 and the second metal plate 20, the multiple metal plates 1 may include one or more metal plates other than the first metal plate 10 and the second metal plate 20. The constituent materials of metal plates other than the first metal plate 10 and the second metal plate 20 can be the same as the constituent materials of the first metal plate 10 or the second metal plate 20.

[0012] [Process B] In step B, multiple metal plates 1 are sandwiched between the first electrode 100 and the second electrode 200 such that the first electrode 100 and the first metal plate 10 are in contact, and the second electrode 200 and the second metal plate 20 are in contact. Specifically, the first electrode 100 and the second electrode 200 sandwich a laminated region in which the first metal plate 10 and the second metal plate 20 are overlapped. If there are three or more metal plates 1, one or more metal plates other than the first metal plate 10 and the second metal plate 20 are placed between the first metal plate 10 and the second metal plate 20. Electrodes commonly used in spot welding can be used for the first electrode 100 and the second electrode 200. The constituent material of the first electrode 100 and the second electrode 200 is, for example, copper. No grooves or the like are provided on the surfaces of the first electrode 100 and the second electrode 200 in this embodiment. The pressure applied when sandwiching multiple metal plates 1 between the first electrode 100 and the second electrode 200 is, for example, 450 kgf (approximately 4.4 kN) or less.

[0013] [Process C] The first energization process F of process C is carried out under the first energization conditions. The first energization conditions are conditions under which the plurality of metal plates 1 are not welded to each other and the constituent material of the first metal plate 10 adheres to the surface of the first electrode 100. The first energization conditions are, for example, that the energization current value is less than 10 kA and the energization time is less than 5 cycles. The energization current value of the first energization process F may be constant within the above range as shown in FIG. 2, or may not be constant as long as it is within the above range although illustration is omitted. For example, the energization current value of the first energization process F may be increased step by step.

[0014] The second energization process S of process C is carried out under the second energization conditions. The second energization conditions are conditions under which the plurality of metal plates 1 are welded to each other. The second energization conditions are, for example, that the energization current value is 10 kA or more and 15 kA or less, and the energization time is 6 cycles or more and 11 cycles or less. The difference between the energization current values of the first energization process F and the second energization process S may be, for example, 3 kA or more and 9 kA or less, further 3.5 kA or more and 8.5 kA or less, particularly 4 kA or more and 8 kA or less. The energization current value of the second energization process S may be constant within the above range, or may not be constant as long as it is within the above range. For example, the energization current value of the second energization process S may be increased step by step. When the energization current value of the second energization process S is not constant, the difference between the energization current values of the first energization process F and the second energization process S refers to the difference between the energization current value of the first energization process F and the smallest energization current value of the second energization process S. FIG. 2 shows an example in which the energization current value of the second energization process S is increased in two stages of the first half process S1 and the second half process S2. The difference between the energization current values of the first half process S1 and the second half process S2 may be, for example, 2 kA or more and 5 kA or less, further 2.5 kA or more and 4.5 kA or less, particularly 3 kA or more and 4 kA or less.

[0015] The total number of cycles of the first energization process F and the second energization process S is, for example, 10 cycles or more and 15 cycles or less.

[0016] In this embodiment, the first energizing process F and the second energizing process S are performed consecutively. Continuous energizing, in which the first energizing process F and the second energizing process S are performed consecutively, is preferable because it shortens the cycle time compared to discontinuous energizing, in which the first energizing process F and the second energizing process S are not performed consecutively. Furthermore, continuous energizing is preferable because, compared to discontinuous energizing, it places less load on, for example, the timer contactor. The timer contactor is, for example, a control device that controls the energizing power and the energizing time.

[0017] In continuous energization, the current value does not return to zero after the first energization process F, but increases from the current value in the first energization process F to the current value in the second energization process S. In discontinuous energization, the current value becomes zero after the first energization process F. Then, at the start of the second energization process S, the current value increases from zero to the current value in the second energization process S. The load on the timer contactor increases when the current value is increased from zero. Continuous energization requires the current value to be increased from zero fewer times than discontinuous energization. Therefore, continuous energization places less load on the timer contactor than discontinuous energization.

[0018] The first energization process F in the spot welding of one dot is performed by an electrode to which the constituent material of the first metal plate 10 does not adhere on the surface. Even if an electrode to which the constituent material of the first metal plate 10 does not adhere on the surface is used in the first energization process F, compared with the case where an electrode to which the constituent material of the first metal plate 10 does not adhere on the surface is used in the second energization process S, the damage to the first electrode is relatively small. This is because the load on the first electrode 100 is smaller under the energization conditions where the constituent material of the first metal plate 10 adheres than under the energization conditions where a plurality of metal plates 1 are welded. And the manufacturing method of the welded structure can perform the second energization process S in the spot welding of one dot by the first electrode 100 to which the constituent material of the first metal plate 10 adheres and which has relatively little damage. Since the constituent material of the first metal plate 10 adheres to the first electrode 100, even in the second energization process S in the spot welding of one dot, the damage to the electrode is small. The manufacturing method of the welded structure can perform both the first energization process F and the second energization process S in the spot welding after the second dot by the first electrode 100 to which the constituent material of the first metal plate 10 adheres and which has little damage in the spot welding after the second dot. That is, the manufacturing method of the welded structure can perform the second energization process S in the spot welding of one dot and the second energization process S in the spot welding after the second dot using the first electrode 100 having substantially the same surface properties. Therefore, even if the spot welding of one dot and the spot welding after the second dot have the same energization conditions, it is difficult for a difference to occur between the quality of the welded portion formed by the spot welding of one dot and the quality of the welded portion formed by the spot welding after the second dot. Therefore, the manufacturing method of the welded structure can manufacture a welded structure with a small difference in the quality of a plurality of welded portions without using an expensive spot welding device that can conduct a large current under high pressure.

[0019] 《Test Example》 [Sample No. 1 to Sample No. 6] In Sample No. 1 to Sample No. 6, a welded structure in which the first metal plate 10 and the second metal plate 20 are spot welded was manufactured by performing steps A to C similar to the manufacturing method of the welded structure of the embodiment.

[0020] [Step A] A plate made of aluminum was prepared for the first metal plate 10. A plate made of iron was prepared for the second metal plate 20. The thickness of the first and second metal plates was 1 mm.

[0021] [Process B] In the process of sandwiching the first metal plate 10 and the second metal plate 20 between the first electrode 100 and the second electrode 200, the first electrode 100 and the first metal plate 10 were in contact, and the second electrode 200 and the second metal plate 20 were in contact. Specifically, a laminated region in which the first metal plate 10 and the second metal plate 20 were stacked was sandwiched between the first electrode 100 and the second electrode 200. The pressure applied to the first electrode 100 and the second electrode 200 was 30 kgf (approximately 0.294 kN).

[0022] [Process C] In the process of applying current between the first electrode 100 and the second electrode 200, the first current application process F and the second current application process S were performed consecutively, as shown in Figure 2. The current value (kA) and current application time (cycle) in the first current application process F and the current value (kA) and current application time (cycle) in the second current application process S are shown in Table 1. As shown in Figure 2, the current value was kept constant in the first current application process F. As shown in Figure 2, in the second current application process S, the current application conditions were different for the first half process S1 and the second half process S2. The current value in the second half process S2 was made larger than the current value in the first half process S1. The current application conditions in the first half process S1 are shown in the upper part of Table 1, and the current application conditions in the second half process S2 are shown in the lower part of Table 1. The first half process S1 and the second half process S2 were performed consecutively.

[0023] 〔evaluation〕 The first and second plug-out diameters (mm) of each sample were measured as follows: The first metal plate 10 was peeled off from the second metal plate 20. The smallest diameter of the remaining weld on the first metal plate 10 or the second metal plate 20 was measured. The first plug-out diameter is the smallest diameter of the weld formed at the first weld point using the unused first electrode 100 and second electrode 200. The second plug-out diameter is the smallest diameter of any weld from the second weld point onward, formed using the first electrode 100 and second electrode 200 after performing process C at least once. The first and second plug-out diameters of each sample are shown in Table 1.

[0024] [Table 1]

[0025] As shown in Table 1, the first and second plug-out diameters in the welded structures of Samples No. 1 to No. 6 were sufficiently large relative to the plate thickness. Therefore, the welded structures of Samples No. 1 to No. 6 have sufficient joint strength. In particular, in Samples No. 2 to No. 6, both the first and second plug-out diameters were 3 mm or larger. The welded structures of Samples No. 2 to No. 6 have superior joint strength compared to the welded structure of Sample No. 1.

[0026] In samples No. 1 to No. 6, the difference between the plug removal diameter at the first weld point and the plug removal diameter at the second weld point is small. In other words, in the welded structures of samples No. 1 to No. 6, welds formed using unused first electrodes 100 and second electrodes 200 and welds formed using first electrodes 100 and second electrodes 200 that have undergone process C at least once were of equivalent quality.

[0027] The present invention is not limited to these examples, but is intended to include all modifications within the meaning and scope equivalent to the claims as shown by the claims. [Explanation of symbols]

[0028] 1 Multiple metal plates, 10 First metal plate, 20 Second metal plate 100 first electrode, 200 second electrode F First energization process S second energization process, S1 first half process, S2 second half process

Claims

[Claim 1] The process of preparing multiple metal plates, A step of sandwiching the plurality of metal plates between the first electrode and the second electrode, The process includes a step of applying current between the first electrode and the second electrode, The aforementioned preparation step involves preparing the plurality of metal plates so that a first metal plate, whose constituent material is aluminum or an aluminum alloy, is included in the plurality of metal plates. The clamping step is performed so that the first metal plate and the first electrode are in contact. The process of applying power includes a first power application process and a second power application process. The first energizing process is carried out under energizing conditions in which the plurality of metal plates are not welded together and the constituent material of the first metal plate adheres to the surface of the first electrode. The second energizing process is carried out under energizing conditions in which the plurality of metal plates are welded together. The first energizing process and the second energizing process are performed in succession. A method for manufacturing welded structures.

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