Manufacturing method of the joint

Abstract

The present invention provides a method for manufacturing a joined body that allows welding to be performed by setting a current pattern that can suppress the generation of spatter without monitoring the resistance change of the workpiece during welding. [Solution] The method for manufacturing a joined body includes: sandwiching a plurality of metal workpieces to be measured between a first electrode and a second electrode, passing a constant current between the electrodes, and measuring the resistance value between the electrodes from the current value and the voltage value between the electrodes; and, using a plurality of metal workpieces of the same combination as the measurement target as the welding target, sandwiching the plurality of metal workpieces to be welded between the first electrode and the second electrode, and passing a welding current between the electrodes, the current value of which changes over time in the same way as the measured resistance value, to weld the plurality of metal workpieces.

Description

Technical Field

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[0001] The present disclosure relates to a manufacturing method for manufacturing a joined body by resistance welding.

Background Art

[0002] In Patent Document 1, as a resistance welding control method, when performing resistance welding by supplying a welding current to a welded member, the welding current and voltage are detected, and the change in resistance of the welded member is monitored, so that the occurrence of spatter during welding is learned and memorized over time.

[0003] And in this control method, based on the stored data, a current pattern during welding is obtained so as to lower the welding current immediately before the occurrence of spatter, and welding is performed with this current pattern after the next time, thereby preventing the occurrence of spatter (hereinafter referred to as sputter).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the resistance welding control method described in Patent Document 1, it is necessary to detect the welding current and voltage while welding the welded member and monitor the change in resistance of the welded member. Therefore, there is a problem that the control becomes complicated due to the calculation processing therefor.

[0006] An aspect of the present disclosure aims to provide a manufacturing method for a joined body that can set a current pattern capable of suppressing the occurrence of spatter and perform welding on a welded member without monitoring the change in resistance of the welded member while performing welding.

Means for Solving the Problems

[0007] A method for manufacturing a joint according to one aspect of this disclosure is: The method involves sandwiching multiple metal workpieces between a first electrode and a second electrode, passing a constant current between the first and second electrodes, and measuring the resistance between the electrodes from the current value and the voltage value between the electrodes. The process involves welding multiple metal workpieces of the same combination as the measurement target, sandwiching the multiple metal workpieces between a first electrode and a second electrode, and passing a welding current between the electrodes, the current value of which changes over time in the same way as the measured resistance value, to weld the multiple metal workpieces. Includes.

[0008] As described above, in the manufacturing method of this disclosure, multiple metal workpieces of the same combination as the workpiece to be welded are sandwiched between a first electrode and a second electrode, and a constant current is passed through them to measure the resistance between the electrodes. This is because, by passing a constant current, the rate of heat generation of the multiple metal workpieces to be welded, the initial heat generation timing, the timing of the heat generation starting resistance peak, and the degree of subsequent current loss (shutting) can be measured as changes in resistance (waveform).

[0009] Then, when welding multiple metal workpieces to be welded, the welding current is changed over time, similar to the resistance value measured earlier. Therefore, according to the manufacturing method of this disclosure, welding conditions for constant-resistance welding can be set so that the resistance value between electrodes during welding remains almost constant, without monitoring the resistance change of the workpiece while welding is being performed. Thus, the process of setting the welding conditions can be made extremely easy, and the processing load of the control during welding can be reduced.

[0010] Here, a welding apparatus capable of controlling the welding current with a time resolution of milliseconds may be used for welding multiple metal workpieces to be welded. In this way, when welding multiple metal workpieces, the welding current can be controlled with a time resolution of milliseconds. This allows the welding current to be precisely changed in response to changes in the resistance value measured before welding. Therefore, constant resistance welding can be achieved more effectively.

[0011] Furthermore, the constant current supplied between the electrodes during resistance measurement may be set to a current value that does not cause welding spatter. In this way, the resistance value used to set the welding current is measured in such a way that spatter does not occur when current is passed between the electrodes. As a result, the welding current is also set in a way that does not produce spatter, thereby improving the welding quality of multiple metal workpieces being welded. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic diagram showing the configuration of the welding apparatus according to the embodiment. [Figure 2] This is an explanatory diagram showing the current waveform of the welding current that is applied during welding. [Figure 3] This is an explanatory diagram showing the measurement results of the resistance value measured to set the welding current. [Figure 4] This is a flowchart illustrating the resistance measurement process performed when measuring resistance values. [Figure 5] This is an explanatory diagram showing the state of the workpiece during welding. [Modes for carrying out the invention]

[0013] Exemplary embodiments of the present disclosure are described below with reference to the drawings. [composition] The welding apparatus 1 shown in Figure 1 is configured to weld a workpiece W, which consists of multiple overlapping metal workpieces P1 and P2, using resistance spot welding. In other words, the welding apparatus 1 is used to manufacture a joint of multiple metal workpieces P1 and P2 by welding the workpiece W.

[0014] Among the plurality of metal workpieces P1 and P2, at least one is a high-tensile steel sheet with a tensile strength of 590 MPa (megapascals) or more, such as a hot press material or a high-tensile material. For example, the first metal workpiece P1 can be a hot-dip galvanized steel sheet and a high-tensile steel sheet with a tensile strength of 590 MPa or more. Also, the first metal workpiece P1 may be a high-tensile steel sheet with a tensile strength of 980 MPa or more, that is, a so-called ultra-high-tensile material.

[0015] Also, the second metal workpiece P2 may be, for example, a hot-dip galvanized steel sheet like the first metal workpiece P1, but is not limited to high-tensile steel sheets. That is, the second metal workpiece P2 may be a steel sheet with a tensile strength lower than that of high-tensile steel sheets, or may be a high-tensile steel sheet or an ultra-high-tensile material similar to the first metal workpiece P1.

[0016] In the present embodiment, at least one of the metal workpieces P1 and P2 to be welded is made into a high-tensile steel sheet because the higher the tensile strength of the metal workpieces P1 and P2, the greater the electrical resistance (hereinafter simply referred to as resistance) at the overlapping portion before welding.

[0017] That is, since the welding apparatus 1 of the present embodiment is suitable for welding high-tensile steel sheets with a large resistance at the overlapping portion, at least one of the metal workpieces P1 and P2 to be welded is made into a high-tensile steel sheet.

[0018] However, the welding apparatus 1 of the present embodiment can also be used to weld steel sheets with a tensile strength lower than that of high-tensile steel sheets. Also, in the present embodiment, it is described that two metal workpieces P1 and P2 are welded as the welding targets, but the welding apparatus 1 can also be used to weld three or more metal workpieces by overlapping them.

[0019] The welding apparatus 1 has a resistance welding machine 20. The resistance welding machine 20 welds a plurality of metal workpieces P1, P2 arranged as a workpiece W in the stacking direction by resistance spot welding. Note that the stacking direction is the direction in which the plurality of metal workpieces P1, P2 are arranged by overlapping, and corresponds to the normal direction of the surfaces of the metal workpieces P1, P2, in other words, the thickness direction of the metal workpieces P1, P2.

[0020] The resistance welding machine 20 includes a first electrode 21 and a second electrode 22. The first electrode 21 is disposed below the workpiece W. The second electrode 22 is disposed above the workpiece W so as to sandwich the workpiece W in the stacking direction together with the first electrode 21. The first electrode 21 is movable relative to the second electrode 22 in the vertical direction.

[0021] The first electrode 21 and the second electrode 22 each contact the workpiece W during welding. The first electrode 21 contacts the metal workpiece P2 located below the workpiece W. The second electrode 22 contacts the metal workpiece P1 located above the workpiece W. The first electrode 21 and the second electrode 22 sandwich the workpiece W so as to apply pressure to both sides in the stacking direction.

[0022] In this state, the resistance welding machine 20 supplies a welding current between the first electrode 21 and the second electrode 22. The workpiece W is welded by resistance heat generation caused by the welding current supplied from the resistance welding machine 20.

[0023] Note that the resistance welding machine 20 is configured to be able to control the welding current with a time resolution in milliseconds. This is to enable the following welding control unit 50 to control the welding current along a preset current waveform.

[0024] The welding apparatus 1 includes a resistance measurement unit 30, a current waveform generation unit 40, and a welding control unit 50 as a control system for the welding current. Of these, the welding control unit 50 is configured to control the welding current flowing between the first electrode 21 and the second electrode 22 when the workpiece W is welded by the resistance welding machine 20. That is, as illustrated in Figure 2, the welding control unit 50 controls the welding current by changing the current value of the welding current over time in accordance with a preset current waveform.

[0025] The welding current waveform controlled by the welding control unit 50 is divided into two phases: the initial high-current phase TA, when current is supplied to the workpiece W via each electrode 21, 22, and the main current phase TB, which is performed after the high-current phase TA by supplying the main current.

[0026] The high-current period TA is the period during which a high current, higher than the main current required for welding the workpiece W, is applied to blow away impurities from the metal workpieces P1 and P2. The main current period TB is the period after the high-current period TA when the main current is applied and welding is performed.

[0027] During the high-current period TA, the current supplied to the workpiece W gradually decreases from the maximum current immediately after the start of energization to the main current during the main current period, and during the main current period TB, the current value of the main current is set to decrease more slowly compared to the high-current period TA.

[0028] Next, the current waveform generation unit 40 is configured to set the current waveform of the welding current controlled by the welding control unit 50. The resistance measurement unit 30 is configured to measure the resistance value between the first electrode 21 and the second electrode 22 by performing the resistance measurement process shown in Figure 4, and to measure waveform data that the current waveform generation unit 40 uses to set the current waveform of the welding current.

[0029] The resistance measurement unit 30 and the current waveform generation unit 40 described above are for setting the current waveform of the welding current controlled by the welding control unit 50. This welding current waveform only needs to be set by the time the resistance welding machine 20 performs welding on the workpiece W to be welded under the control of the welding control unit 50 and production of the joined body begins.

[0030] Therefore, the resistance measurement unit 30 and the current waveform generation unit 40 may be provided together with the welding control unit 50 as a function of one welding apparatus 1, as shown in Figure 1, or they may be provided as a function of a second welding apparatus configured separately from welding apparatus 1. The second welding apparatus shall be equipped with a resistance welding machine 20, a first electrode 21, and a second electrode 22, similar to welding apparatus 1 shown in Figure 1.

[0031] In this case, the second welding apparatus may be installed together with welding apparatus 1 in a production plant that welds workpieces W to manufacture a jointed body, or it may be installed in a production plant separate from welding apparatus 1. Furthermore, the second welding apparatus may be installed in a control facility that manages the welding conditions of multiple welding apparatuses 1 installed in one or more production plants.

[0032] Next, the functions of the resistance measurement unit 30 and the current waveform generation unit 40 are realized by performing the resistance measurement process shown in Figure 4 in the welding apparatus 1 or the second welding apparatus. This resistance measurement process is performed with multiple metal workpieces P1 and P2 of the same combination as the workpiece W to be welded, sandwiched between the first electrode 21 and the second electrode 22 as the measurement targets.

[0033] As shown in Figure 4, in the resistance measurement process, at S110 (where S represents a step), current control is initiated to supply a preset constant current for measurement between the first electrode 21 and the second electrode 22 via the resistance welding machine 20. The constant current for measurement is set to a current value that does not generate spatter when a constant current is supplied to the workpiece W.

[0034] Then, in S120, the resistance value between the first electrode 21 and the second electrode 22 is repeatedly measured until a predetermined measurement time has elapsed and the measurement is determined to be complete in S130. This resistance value is measured by obtaining the inter-electrode voltage between the first electrode 21 and the second electrode 22 from the resistance welding machine 20, and calculating the resistance value from that inter-electrode voltage and a constant current.

[0035] Next, when it is determined that the measurement is complete in S130, the process moves to S140, where the constant current is stopped, and a current waveform of the welding current is generated based on the time-series data of the resistance values ​​that were repeatedly measured in S120.

[0036] In other words, in S140, as shown in Figure 3, the waveform of resistance change is obtained from the time-series data of resistance measured in S120. Then, the welding current waveform shown in Figure 2 is set so that the welding current changes over time at the same rate as the waveform of resistance change, and this is stored as welding current control data in a storage medium such as flash memory or hard disk.

[0037] The process in S140 functions as a current waveform generation unit 40. After storing the welding current waveform in the storage medium in S140, the resistance measurement process is terminated. The welding current waveform stored in the memory medium in S140 is used by the welding control unit 50 to control the welding current flowing between the first electrode 21 and the second electrode 22 via the resistance welding machine 20. The welding control unit 50 allows the user to appropriately tune the welding current flowing during welding of the workpiece W based on the current waveform set by the resistance measurement process.

[0038] [effect] As described above, in the welding apparatus 1 of this embodiment, the resistance measuring unit 30 measures the resistance value between the electrodes by passing a constant current between the electrodes while the workpiece W to be measured is sandwiched between the first electrode 21 and the second electrode 22.

[0039] This is because, by applying a constant current, the rate of heat generation of the workpiece W, the initial heat generation timing, the peak resistance timing at the heat generation initiation point, and the subsequent degree of current loss (shutting) can be measured as waveforms of changes in resistance value.

[0040] Then, when welding metal workpieces P1 and P2 that are the same combination as the workpiece W whose resistance value was measured by the resistance measurement unit 30, the welding control unit 50 changes the welding current over time at the same rate of change as the waveform of the change in resistance value measured by the resistance measurement unit 30.

[0041] Therefore, according to the welding apparatus 1 of this embodiment, constant resistance welding can be achieved, as shown in Figure 2, in which the resistance value between electrodes during welding is kept almost constant, without monitoring the resistance change of the workpiece W while welding is being performed.

[0042] Furthermore, the welding conditions for this constant-resistance welding can be easily set by resistance measurement processing by the resistance measurement unit 30 and the current waveform generation unit 40, and the processing load on the welding control unit 50 during welding can be reduced.

[0043] Furthermore, since the resistance welding machine 20 is configured to control the welding current with a time resolution of milliseconds, the welding control unit 50 can accurately control the welding current in accordance with the waveform of the change in resistance value measured by the resistance measurement unit 30. As a result, constant resistance welding can be achieved more effectively.

[0044] Furthermore, the constant current that the resistance measuring unit 30 supplies between the electrodes when measuring resistance is set to a current value that does not generate spatter during welding. Therefore, the welding current that the welding control unit 50 supplies between the electrodes during welding is also set to prevent spatter from occurring, thereby improving the welding quality of the workpiece W to be welded.

[0045] Next, the current waveform of the welding current set by the resistance measurement process shown in Figure 4 is divided into a high-current period TA at the beginning of welding and a main current period TB after the high-current period TA, as shown in Figure 2. During the high-current period TA, a high current higher than the main current is applied as the welding current.

[0046] Therefore, impurities can be blown away from the workpiece W to be welded during the high-current period TA, thereby suppressing the generation of spatter caused by impurities during welding with this current. In addition, by applying a high current during the high-current period TA, the surface of the workpiece W to be welded can be flattened, which also suppresses the generation of spatter.

[0047] Furthermore, by passing a large current greater than the main current during the high-current period TA, heat is introduced into the workpiece W, and as shown in Figure 5A, a gap GA is created between the metal workpieces P1 and P2 around the welding point M sandwiched between the first electrode 21 and the second electrode 22. As a result, the welding current can be concentrated at the welding point M, and current loss caused by current flowing between the metal workpieces P1 and P2 around the welding point M can be reduced.

[0048] Furthermore, during the high-current period TA and the main current period TB, the welding current decreases in a curved manner in response to the change in resistance values ​​measured as described above. However, as shown in Figure 5B, this welding current flows through the area around the welding point M where the metal workpieces P1 and P2 are in contact. This is because the resistance increases in the central part of the welding point M due to the melting of the workpiece W.

[0049] As the welding current flows in this manner, current loss is eliminated, and a weld nugget is formed on the workpiece W. The diameter of the weld nugget can be controlled by shifting the welding current up or down while maintaining the current waveform shown in Figure 2.

[0050] [Differentiation] Although a welding apparatus 1 for realizing the manufacturing method of the joint of the present disclosure has been described above, the manufacturing method of the present disclosure is not limited to the welding apparatus 1 of the above embodiment, and can take various forms. For example, the welding apparatus 1 described above may be used for welding a workpiece W in which three or more metal workpieces are stacked.

[0051] Furthermore, the function of one component in the above embodiment may be distributed among multiple components. The functions of multiple components may be integrated into one component. Some parts of the configuration of the above embodiment may be omitted. At least some parts of the configuration of the above embodiment may be added to or replaced with the configuration of other above embodiments. Any aspect of the technical concept specified by the wording of the claims constitutes an embodiment of the present disclosure.

[0052] [Technical Concept Disclosed in This Specified Specification] This specification discloses the following technical concepts: [Item 1] A manufacturing method for producing a joint by resistance welding, Multiple metal workpieces to be measured are sandwiched between a first electrode and a second electrode, a constant current is passed between the first electrode and the second electrode, and the resistance value between the electrodes is measured from the value of the current and the voltage value between the electrodes. The welding process involves using multiple metal workpieces of the same combination as the measurement target as the welding target, sandwiching the multiple metal workpieces to be welded between the first electrode and the second electrode, and passing a welding current between the electrodes, the current value of which changes over time in the same way as the measured resistance value, to weld the multiple metal workpieces. A method for manufacturing a composite body, including the above.

[0053] [Item 2] A method for manufacturing a joint according to claim 1, A method for manufacturing a joined body, wherein a welding apparatus capable of controlling the welding current with a time resolution of milliseconds is used for welding the plurality of metal workpieces.

[0054] [Item 3] A method for manufacturing a joint according to claim 1 or claim 2, A method for manufacturing a joined body, wherein the current supplied between the electrodes when measuring the resistance value is set to a current value that does not generate spatter due to welding. [Explanation of symbols]

[0055] 20... Resistance welding machine, 21... First electrode, 22... Second electrode, 30... Resistance measurement unit, 50... Welding control unit, P1, P2... Metal workpiece.

Claims

1. A manufacturing method for producing a joint by resistance welding, Multiple metal workpieces to be measured are sandwiched between a first electrode and a second electrode, a constant current is passed between the first electrode and the second electrode, and the resistance value between the electrodes is measured from the current value and the voltage value between the electrodes. The welding process involves using multiple metal workpieces of the same combination as the measurement target as the welding target, sandwiching the multiple metal workpieces to be welded between the first electrode and the second electrode, and passing a welding current between the electrodes, the current value of which changes over time in the same way as the measured resistance value, to weld the multiple metal workpieces. A method for manufacturing a composite body, including the above.

2. A method for manufacturing a joint according to claim 1, A method for manufacturing a joined body, wherein a welding apparatus capable of controlling the welding current with a time resolution in milliseconds is used for welding the plurality of metal workpieces.

3. A method for manufacturing a joint according to claim 1 or claim 2, A method for manufacturing a joined body, wherein the current supplied between the electrodes when measuring the resistance value is set to a current value that does not generate spatter due to welding.

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