Welding methods, welding support programs, and railway vehicle structures

Abstract

This invention provides a welding method that suppresses liquefaction cracking when welding together components with different plate thicknesses. [Solution] A welding method in which a first member and a second member having a thicker plate thickness than the first member are overlapped and welded together, wherein the welding conditions for the actual welding work are determined from the test results accumulated from prior welding tests, and the actual welding work is performed.

Description

Technical Field

[0001] The present invention relates to a welding method, a welding support program, and a railway vehicle structure when welding members with different plate thicknesses in combination.

Background Art

[0002] In a lap joint that is fabricated by overlapping members with different plate thicknesses as welding bases and welding the overlapping portion, generally, the base material with a thinner plate thickness tends to melt easily, while the base material with a thicker plate thickness tends to be difficult to melt. As a method of lap welding members with different plate thicknesses, there is Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When welding using an aluminum-based material that has a lower melting point than steel materials and has a high thermal conductivity, specific heat, and latent heat of fusion as the base material, if the heat input to the welded portion is excessive, the base material is likely to melt and fall off. If the heat input is insufficient, it becomes difficult for heat to accumulate and local melting becomes difficult.

[0005] Among aluminum-based materials, the 6000 series, which is an aluminum alloy for welded structures, is known to be more likely to develop welding cracks compared to the 5000 series and 7000 series of other aluminum alloys for welded structures. The 5000 series, 6000 series, 7000 series, etc. are based on the provisions of JIS and ISO.

[0006] Here, welding cracks tend to form in the heat-affected zone around the penetration portion formed in the plate thickness direction of the base material, and the cracks are classified as liquation cracks. It also occurs that a large number of minute cracks occur around the welded portion.

[0007] When welding 6000 series aluminum alloys with different thicknesses, excessive penetration into the thinner base metal may occur, potentially leading to liquefaction cracking in the heat-affected zone. Conversely, insufficient penetration into the thicker base metal may result in unwelded areas.

[0008] Patent Document 1 discloses a welding method in which a first bead is formed in advance on a base material with a small thickness, and then the first bead is welded to a base material with a large thickness, thereby reducing the difference in heat capacity between the base materials and increasing the joint strength. However, this method focuses on the weld bead that is formed in a convex shape on the surface of the base material, and it is unclear whether it has the effect of suppressing the occurrence of liquefaction cracking, which is affected by the state of penetration into the base material.

[0009] Therefore, one of the objectives of the present invention is to provide a welding method that suppresses welding cracks when welding members with different plate thicknesses.

[0010] Further objectives of the present invention will become apparent throughout the entire specification. [Means for solving the problem]

[0011] A welding method in which a first member and a second member having a thicker plate thickness than the first member are overlapped and welded together, wherein the welding conditions for the actual welding work are determined from the test results accumulated from prior welding tests, and the actual welding work is performed. [Effects of the Invention]

[0012] According to the present invention, a welding method is available that suppresses liquefaction cracking in lap fillet welding of members with different plate thicknesses.

[0013] Further means and effects of the present invention will become apparent throughout the entire specification below. [Brief explanation of the drawing]

[0014] [Figure 1] This is a flowchart of the welding method in one embodiment. [Figure 2] It is a flowchart of a welding method in another embodiment. [Figure 3] It is an explanatory diagram of a welded part. [Figure 4] It is a diagram of test results on a test piece. [Figure 5] It is a configuration diagram of a welding support device. [Figure 6] It is a configuration diagram of a welding support program. [Figure 7] It is an explanatory diagram of a railway vehicle structure.

Mode for Carrying Out the Invention

[0015] In the evaluation research on liquation cracking that occurs in the heat-affected zone near the welded part during fillet welding construction for a lap fillet weld joint using a 6000 series aluminum alloy with a plate thickness difference, the present inventors focused on the relationship between the information of the penetration formed in the base material with the thinner plate thickness and the length of the liquation cracking. The present invention has been completed based on this finding.

[0016] Hereinafter, embodiments of the present invention will be described while referring to the drawings.

Example

[0017] FIG. 1 shows an example of a welding method. It may also be referred to as an example of a lap fillet welding method. It is intended to overlap a first member and a second member with a plate thickness difference and perform fillet welding on the overlapping portion, and is composed of a pre-welding test and actual welding work.

[0018] First, a pre-welding test is carried out to check whether there are any problems with the welding work content and the quality of the welded part, and welding conditions serving as criteria for determining the quality of the welding work content and the welded part are determined.

[0019] A pre-welding test is carried out at S1. This is a welding test on a test piece. In order to prevent the occurrence of defects and rework as a result of directly welding the welding object, a pre-welding test is carried out on a small test piece.

[0020] In S2, the suitability of the welding process is clarified through a detailed analysis of the welded portion of the test specimen. This detailed analysis includes, if necessary, destructive testing to cut a cross-section of the weld and a detailed evaluation of the presence or absence of liquefaction cracking through microscopic observation. If a suitable welding condition is found, proceed to S3. If a problem is found, return to S1 and continue testing under different conditions. To save time, welding tests may be conducted on multiple test specimens under different conditions, and the detailed analysis may be performed on them all at once. In that case, these steps are also included in S1 and S2 in Figure 1.

[0021] In S3, the welding conditions are determined. Based on the results of the pre-welding test, the welding conditions for the manufactured object are determined. At that time, information on the plate thickness of the thinner component and information on the penetration formed in the thinner component by welding are obtained and used to determine the welding conditions.

[0022] In S4, the actual welding work is carried out using the welding conditions determined in S3.

[0023] In S5, after the actual welding work, a weld inspection is conducted to check for any quality issues with the weld.

[0024] If there are no problems with the results of the actual welding work in S6, the actual welding work is completed in S7. If there are problems, corrective work is performed to re-weld the welded area, and the actual welding work in S4 is repeated.

[0025] In this embodiment, by applying a manufacturing method consisting of a two-stage configuration of a pre-welding test and actual welding work, it is possible to provide a manufacturing method that can suppress liquefaction cracking.

[0026] Next, I will explain the results of further consideration.

[0027] Figure 3 is a schematic diagram illustrating the welded joint between the first member 1 and the second member 2, corresponding to the cross-section of the weld. In Figure 3, the first member 1 is shown as a thin member and the second member 2 as a thick member, illustrating the difference in wall thickness between the two. The first member 1 and the second member 2 were overlapped and fillet welded together. Both the first member 1 and the second member 2 were made of 6000 series aluminum alloy.

[0028] The specific welding method used was MIG welding, a type of consumable electrode arc welding. We also used 5000 series welding wire for MIG welding.

[0029] For the MIG welding method, the welding conditions were set as follows: welding current, welding voltage, welding speed (welding torch movement speed), welding torch tilt angle, and welding torch forward angle.

[0030] Furthermore, the corner position of the overlapping section between the first member 1 and the second member 2 was used as the reference point for the welding target position. A distance was set to offset the welding target position vertically along the second member 2 of the upper plate, and a distance was set to offset the welding target position horizontally along the first member 1 of the lower plate. These were referred to as the vertical offset distance and the horizontal offset distance, respectively.

[0031] By combining these welding conditions, various welding tests were conducted on the test specimens. Then, the welded test specimens were subjected to detailed analysis to confirm the condition of the welded joints.

[0032] The penetration depth of the lower plate into the first member 1 differs depending on whether the welding was successful or unsuccessful. When the welding was unsuccessful, the width, depth, and area of ​​the penetration were larger.

[0033] A detailed analysis of the penetration depth revealed that when welding was not performed correctly, numerous minute cracks occurred at the grain boundaries of the HAZ (heat-affected zone) near the molten boundary line in the first member 1, which is the lower plate.

[0034] 6000 series aluminum alloys have a wider brittle temperature range in the high-temperature region compared to 5000 series and 7000 series. Therefore, it is known that welded joints using 6000 series aluminum alloys are more susceptible to liquefaction cracking in the heat-affected zone (HAZ) of the base material when the heat input during welding is excessive or the welding conditions are not appropriate, compared to other aluminum alloys. Based on this, the crack in question can be identified as liquefaction cracking.

[0035] From the above, it was suggested that there is a relationship between the state of penetration into the first member 1, which is the lower plate, and the occurrence of liquefaction cracks.

[0036] Liquefaction cracking is a welding defect that reduces the strength characteristics of welds and welded joints. Therefore, it is necessary to select welding conditions that suppress the occurrence of liquefaction cracking.

[0037] As described above, it was suggested that the occurrence of liquefaction cracking is related to the state of penetration into the lower plate, the first member 1. Therefore, as shown in Figure 3, the plate thickness T of the first member 1 was denoted by reference numeral 3, the penetration width W into the first member 1 was denoted by reference numeral 4, and the penetration area S into the first member 1 was denoted by reference numeral 5. In addition, the lateral leg length K of the first member 1, which is one of the indicators of the strength characteristics of lap fillet welded joints, was denoted by reference numeral 6.

[0038] Then, the total length of the numerous minute liquefaction cracks measured by microscopic observation was added together and defined as the total liquefaction crack length L. The relationship between this total liquefaction crack length L and welding was then investigated.

[0039] Figure 4 shows the test results for the test specimens.

[0040] The horizontal axis represents S / (W·T).

[0041] The vertical axis represents L / K. This is one of the indicators of the strength characteristics of lap fillet welded joints, representing the ratio of the total length of liquefaction cracks L to the lateral leg length K of the first member.

[0042] This is a summary of the results obtained by performing MIG welding on various test specimens using various welding conditions.

[0043] The dashed line in the figure represents y = 0.4638x + 0.0387, R 2 This corresponds to =0.7241. y is the horizontal axis, x is the vertical axis, R 2 This is the correlation coefficient. From the value of the correlation coefficient, it can be seen that the dashed line in the figure is a reasonably reliable line.

[0044] The occurrence of liquefaction cracking was reduced by half when the L / K ratio on the vertical axis was generally 0.2 or less. The horizontal axis that satisfies this condition is generally 0

[0045] By incorporating the above findings in S3 of Figure 1, it became possible to determine welding conditions that further suppressed the occurrence of liquefaction cracking.

[0046] In this embodiment, a manufacturing method is provided that suppresses the occurrence of liquefaction cracking. [Examples]

[0047] Figure 2 corresponds to Figure 1 of Example 1 and shows a manufacturing method that includes further detailed determination of conditions.

[0048] A pre-welding test is performed in S11. This is a welding test on a test piece. To prevent defects and rework that may occur as a result of directly welding the workpiece, a pre-welding test is performed on a small test piece. Compared to S1, S11 incorporates information on penetration and insights from Figure 4, and includes methods and conditions related to welding operations and welding torch operation that result in good weld quality.

[0049] In S12, the welding process is clarified through a detailed analysis of the welded section of the test specimen to determine if there are any problems with the welding procedure. This detailed analysis allows for the accumulation of methods and conditions related to welding procedures and welding torch operation that result in good weld quality.

[0050] ​If satisfactory welding conditions are found, proceed to S13. If problems are found, return to S11 and continue testing under different conditions. To save time, welding tests may be performed on multiple specimens under different conditions and then a detailed analysis may be conducted on them together. In this case, the results are also included in S11 and S12 of Figure 2.

[0051] In S13, the welding conditions are determined. These welding conditions include the conditions set in S3, as well as methods and conditions related to the operation of the welding torch.

[0052] In S14, the actual welding work is carried out using the welding conditions determined in S13.

[0053] In S15, during the actual welding operation, it is determined whether the welding torch operation is correct. The quality of the welding work is judged, and if the welding torch operation is judged to be good, the welding torch operation is allowed to continue. If the welding torch operation is judged to be unsatisfactory, correction is prompted. In this way, welding defects can be identified and corrected at an early stage of the actual work.

[0054] The worker complies with the prompting instructions for welding torch operation, and the assessment of whether the welding torch operation is acceptable continues in S15. Visual sensors, position sensors, etc., may be used as means of notifying the operator of the continuation or correction of welding torch operation. The system checks whether the welding torch movement speed, welding torch height, welding torch angle, and welding target position are changing and notifies the operator.

[0055] When all welding is completed on the welding area to be constructed, the actual welding work is finished in S16.

[0056] After the work is completed, a weld inspection is performed in S17, similar to S5. In S18, based on the inspection results, it is determined whether the actual welding work is problem-free. If there are problems, corrective actions are taken to fix them, and the actual welding work is restarted in S14. If there are no problems, the process is completed in S19.

[0057] In this embodiment, by incorporating welding torch operation into Example 1, it is possible to provide a manufacturing method that further suppresses the occurrence of liquefaction cracking. [Examples]

[0058] Figure 5 is a configuration diagram of a welding support device applicable to Example 1 or Example 2. It includes an input device 20, a CPU 21, an output device 22, and a database 23. The database 23 is composed of devices such as memory or an SSD.

[0059] The results of the pre-welding tests in Example 1 or Example 2, along with their conditions, are input from the input device 20 and stored in the database 23. In S3 of Example 1, or S13 of Example 2, the CPU 21 determines the welding conditions based on the information of the object to be welded during the actual work and the information stored in the database 23. In the case of Example 2, the stored information includes various information related to the welding torch.

[0060] The determined welding conditions are output from the output device 22. The output format is not limited. It can be displayed on a screen, printed as a specification sheet for the operator, or, in the case of automatic welding, directly transmitted as instructions to the welding equipment; it encompasses a variety of output formats.

[0061] By applying the welding support device of this embodiment to either Embodiment 1 or Embodiment 2, a manufacturing method that suppresses the occurrence of liquefaction cracking can be provided. Furthermore, a welding support device capable of suppressing the occurrence of liquefaction cracking can be provided. [Examples]

[0062] Figure 6 is a diagram showing the configuration of the welding support program executed in the welding support device of Example 3.

[0063] Unit 30 is a test result storage unit that receives input of the results of the pre-welding test and stores them in database 23 in Figure 4.

[0064] 31 is a welding target input unit, which receives information about the workpiece to be welded during the actual welding operation. This includes the wall thickness of the first member 1 and the second member 2, as well as various other information such as the welding area and length.

[0065] Unit 32 is a welding condition calculation unit. Based on the information stored in the database 23 in Figure 4 and the information of the workpiece to be welded from the welding target input unit 31, it determines the welding conditions for the actual welding operation.

[0066] Unit 33 is a welding condition output unit. It outputs the working conditions for the actual welding operation determined by the welding condition calculation unit 32. The output format is not specified. It can be displayed on a screen, printed out to the operator as a specification sheet, or, in the case of automated welding, directly transmitted as instructions to the welding equipment. It encompasses a variety of output formats.

[0067] According to this embodiment, welding conditions can be determined based on the results of preliminary tests, thus providing a welding support program that can suppress the occurrence of liquefaction cracking. [Examples]

[0068] This embodiment describes a railway vehicle having a welded structure using any of Embodiments 1 to 4.

[0069] Figure 7 is an explanatory diagram of a railway vehicle structure. 51 is the railway vehicle, 52 is the wheel, 53 is the door, 54 is the window, 55 is the railway vehicle structure, and 56 is the pantograph.

[0070] At the welding stage, the railway vehicle body 55 is in a state where the wheels 52, doors 53, windows 54, pantographs 56, etc., have not yet been attached.

[0071] When using aluminum alloy from the 6000 series for railway vehicle structures, it was customary to keep the difference in wall thickness between the first member 1 and the second member 2 at welded points, such as in the double-skin structure of the side plates, to less than five times. This was a design principle based on empirical knowledge to avoid the fact that larger wall thickness differences increase the likelihood of liquefaction cracking and thus increase welding defects.

[0072] However, by using the manufacturing method, welding support device, and welding support program described in Examples 1 to 4, it became possible to more actively suppress liquefaction cracking. As a result, it became possible to manufacture railway vehicle structures even when the difference in wall thickness between the first member 1 and the second member 2 at the welded location was in the range of 5 to 8 times.

[0073] By increasing the thickness difference, the thickness of the skin can be significantly reduced relative to the thickness of the structure, which has the advantage of achieving weight reduction. In addition, by reducing the amount of material used, it is possible to reduce the environmental impact and the power consumption during vehicle operation. For this reason, increasing the thickness difference has long been desired, but it has long been impossible to realize in railway vehicle structures due to the risk of liquefaction cracking. However, by welding the railway vehicle structure using any of Examples 1 to 4, it has become possible to increase the thickness difference while suppressing the risk of liquefaction cracking.

[0074] Furthermore, if the welding ratio exceeds 8 times, there is a risk of insufficient penetration and non-welding in the thicker base material, the second member 2. Therefore, it was determined that 8 times is the practical upper limit with current welding technology.

[0075] In this embodiment, a railway vehicle structure with an increased difference in wall thickness can be realized.

[0076] Note that the above-described embodiments and experimental examples are for the purpose of assisting the understanding of the present invention, and the present invention is not limited to the specific configurations described. For example, a part of the configuration of the embodiment can be replaced with the configuration of the common technical knowledge of those skilled in the art, and the configuration of the common technical knowledge of those skilled in the art can also be added to the configuration of the embodiment. That is, for a part of the configuration of the embodiments and experimental examples in this specification, the present invention can be deleted, replaced with other configurations, or added with other configurations without departing from the technical idea of the invention.

[0077] Also, an example of the invention of the present application described using each of the above embodiments can be expressed as follows.

[0078] <Part 1> In a welding method of overlapping and welding a first member and a second member having a greater plate thickness than the first member, welding conditions for actual welding work are determined from test results accumulated through prior welding tests, and a welding method for performing actual welding work. <Part 2> The welding method according to <Part 1>, wherein the test results include information on the plate thickness and information on the penetration into the first member. <Part 3> The welding method according to <Part 2>, wherein the prior welding test includes conditions for welding torch operation. <Part 4> The welding method according to <Part 3>, wherein during the actual welding work, the welding torch operation is confirmed, and based on the determination of its quality, continuation or correction of the welding torch operation is notified. <Part 5> The welding method according to <Part 2>, when the plate thickness of the first member is T, the penetration width into the first member is W, and the penetration area into the first member is S, satisfying 0 < S / (W·T) < 0.4. <Part 6> The welding method according to <Part 5>, wherein the first member is a 6000 - series aluminum alloy. <Part 7> In a welding support program for supporting welding work, It has a test result storage unit, a welding target input unit, a welding condition calculation unit, and a welding condition output unit. The test result storage unit receives and stores the results of a preliminary welding test. The welding target input unit receives the information of the welded body to be the target of the actual welding work. Based on the information stored in the test result storage unit and the information from the welding target input unit, the welding condition calculation unit determines the welding conditions for the actual welding work. A welding support program that outputs the working conditions of the actual welding work by the welding condition output unit. <Item 8> The welding support program according to <Item 7>, wherein the results of the welding test include the information of the plate thickness and the information of the penetration. <Item 9> The welding support program according to <Item 8>, wherein the results of the welding test include the conditions of the welding torch operation. <Item 10> The welding support program according to <Item 9>, which checks the welding torch operation during the actual welding work and notifies the continuation or correction of the welding torch operation based on the determination of its quality. <Item 11> The welding support program according to <Item 10>, which presents the welding conditions that satisfy 0 < S / (W·T) < 0.4, where T is the plate thickness, W is the penetration width, and S is the penetration area, for the member with the thinner plate thickness among the two members to be welded. <Item 12> The welding support program according to <Item 11>, which is applied when the member with the thinner plate thickness among the two members to be welded is a 6000 - series aluminum alloy. <Item 13> A railway vehicle structure made of a 6000 - series aluminum alloy, having a welded part between a first member and a second member with a thicker plate thickness than the first member, and the plate thickness difference between the first member and the second member is 5 times or more and 8 times or less in the vicinity of the welded part. <Item 14> When the plate thickness of the first member is T, the penetration width into the first member is W, and the penetration area into the first member is S, the railway vehicle structure according to <the 13th item> satisfies 0 < S / (W · T) < 0.4.

Explanation of symbols

[0079] 1: First member 2: Second member 3: Plate thickness T of the first member 4: Penetration width W into the first member 5: Penetration area S into the first member 6: Lateral leg length K of the first member 20: Input device 21: CPU 22: Output device 23: Database 30: Test result accumulation unit 31: Welding target input unit 32: Welding condition calculation unit 33: Welding condition output unit 51: Railway vehicle 52: Wheel 53: Door 54: Window 55: Railway vehicle structure 56: Pantograph

Claims

1. In a welding method in which a first member and a second member having a thicker plate thickness than the first member are overlapped and welded together, A welding method in which welding conditions for the actual welding work are determined based on test results accumulated through prior welding tests, and then the actual welding work is performed.

2. The welding method according to claim 1, wherein the test results include information on plate thickness and information on penetration into the first member.

3. The welding method according to claim 2, wherein the aforementioned prior welding test includes conditions for welding torch operation.

4. The welding method according to claim 3, wherein the welding torch operation is checked during the actual welding work, and the welding torch operation is notified to continue or correct based on the judgment of whether it is good or bad.

5. The welding method according to claim 2, where T is the thickness of the first member, W is the penetration width into the first member, and S is the penetration area into the first member, and the condition 0 < S / (W・T) < 0.4 is satisfied.

6. The welding method according to claim 5, wherein the first member is a 6000 series aluminum alloy.

7. In a welding support program that assists with welding operations, It has a test result storage unit, a welding target input unit, a welding condition calculation unit, and a welding condition output unit. The aforementioned test result storage unit receives and stores the input of the results of the pre-welding test. The welding target input unit receives input of information about the workpiece to be welded, which is the subject of the actual welding work. The welding condition calculation unit determines the welding conditions for the actual welding operation based on the information stored in the test result storage unit and the information from the welding target input unit. A welding support program that outputs the working conditions for actual welding operations using the welding condition output unit.

8. The welding support program according to claim 7, wherein the results of the welding test include information on plate thickness and information on penetration.

9. The welding support program according to claim 8, wherein the results of the welding test include conditions for welding torch operation.

10. The welding support program according to claim 9, which checks the welding torch operation during the actual welding work and notifies the user to continue or correct the welding torch operation based on a judgment of its quality.

11. A welding support program according to claim 10, which provides welding conditions for the thinner of two members to be welded, where T is the plate thickness, W is the penetration width, and S is the penetration area, such that 0 < S / (W・T) < 0.

4.

12. The welding support program according to claim 11, applicable when the thinner of two members to be welded is made of a 6000 series aluminum alloy.

13. A railway vehicle body made of aluminum alloy in the 6000 series, having a welded joint between a first member and a second member having a plate thickness greater than that of the first member, wherein the difference in plate thickness between the first member and the second member near the welded joint is 5 times or more and 8 times or less.

14. A railway vehicle structure according to claim 13, where T is the thickness of the first member, W is the penetration width into the first member, and S is the penetration area into the first member, and the condition 0 < S / (W・T) < 0.4 is met.

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