Dissimilar metal joint

Abstract

The present invention provides a high-strength dissimilar metal joint in a dissimilar material joint in which a first member comprising a steel plate and a second member comprising an aluminum-based material or a magnesium-based material are joined. The present invention is provided with a first member comprising a steel plate, a second member comprising an aluminum-based material or a magnesium-based material, and a joining part for joining the first member and the second member, the first member having a through-hole facing the plate thickness direction of an overlapping surface that overlaps the second member. The joint part is a welding metal filled in the through-hole and welded to the second member, the surface reinforcement is formed on at least the surface of the first member, the diameter of the through-hole is 3.0-15.0 mm, the diameter of the surface reinforcement is d-5.0 d when the diameter of the through-hole is d, and the diameter of the second member is d when the diameter of the through-hole is d. When the plate thickness of the second member is set to t2, the height of the excess weld metal on the surface is set to 0.1 t2 or more and 5.0 t2 or less.

Description

Technical Field

[0001] The present invention relates to a dissimilar metal joining joint. Background Art

[0002] For transportation equipment represented by automobiles, the improvement of driving fuel efficiency is always sought for the purpose of suppressing various factors such as (a) the consumption of petroleum fuel as a limited resource, (b) CO2 as a global warming gas generated by combustion, and (c) driving costs. As a solution, in addition to the improvement of power system technology such as the use of electric drive, lightweighting of the vehicle body is also one of the improvement measures. In lightweighting, there is a solution to replace steel, which will become the current main material, with aluminum alloys, magnesium alloys, carbon fibers, etc. as lightweight raw materials. However, when all of them are replaced with these lightweight raw materials, there are problems such as high cost and insufficient strength. Therefore, as a solution, the so-called multi-material design method that combines steel and lightweight raw materials in their proper places has attracted attention.

[0003] As a conventional dissimilar material joining technology of steel and aluminum or magnesium, there is known a dissimilar material joining technology described in Patent Document 1, which includes an aluminum lower plate, a steel upper plate provided with a hole facing an overlapping surface overlapping with the lower plate, and an aluminum joining auxiliary member having a hollow portion and inserted into the hole of the upper plate, and the lower plate and the upper plate are joined by arc welding by filling the hollow portion of the joining auxiliary member with welding metal, thereby utilizing the restraining force of the aluminum. Similarly, as a dissimilar material joining technology for joining a steel lower plate and an aluminum upper plate using an iron welding wire, there is known, for example, Patent Document 2.

[0004] In addition, Patent Document 3 discloses the so-called flat head rivet method as follows: a steel material and an aluminum material having through holes pre-arranged along a welding line are overlapped with each other, and while the welding torch is set at a back angle and moves along the welding line, an aluminum welding wire is used to melt and fill the through holes arranged on the steel side with aluminum welding material, and a weld bead is formed to perform arc welding.

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2021-171765

[0008] Patent Document 2: WO2018 / 030272

[0009] Patent Document 3: Japanese Patent No. 4944923

[0010] The technology described in Patent Document 1 is to provide a through hole formed in a steel material serving as an upper plate with a joining auxiliary member made of an aluminum material or a magnesium material having a hollow portion that passes through in the plate thickness direction, and the purpose is to shorten the welding time. In this case, there are problems such as the cost of manufacturing the joining auxiliary member that fits into the through hole and the time and effort of inserting the manufactured joining auxiliary member into the through hole. In addition, the technology of Patent Document 2 is a technology that sets a steel plate as a lower plate and joins an upper plate made of an aluminum alloy or a magnesium alloy, which is different from the technology of joining a steel upper plate to an aluminum alloy lower plate. In addition, according to the technology of Patent Document 3, it is characterized in that a plurality of preparatory holes are continuously filled by line welding, so there is a problem that the steel is excessively melted, cracks are easily generated in the weld metal, and the joint strength is easily reduced. Summary of the invention

[0011] Problems to be solved by the invention

[0012] The present invention has been made in view of the above-mentioned situation, and an object of the present invention is to provide a high-strength dissimilar metal joint in a dissimilar metal joint that joins a first member made of a steel plate and a second member made of an aluminum-based material or a magnesium-based material.

[0013] Solutions to Solve Problems

[0014] The above-mentioned object of the present invention is achieved by the following structure.

[0015] [1] A dissimilar material joint, characterized in that:

[0016] The dissimilar material joint comprises:

[0017] A first member, which is composed of one or more steel plates;

[0018] a plate-shaped second member composed of one or more aluminum-based materials or one or more magnesium-based materials; and

[0019] a joining portion that joins the first member and the second member,

[0020] The first member has a through hole in the plate thickness direction facing the overlapping surface with the second member,

[0021] The joining portion is a weld metal filled in the through hole and welded to the second member, and has a surface relief arranged on the surface of the first member.

[0022] The relationship among the diameter d of the through hole, the width W1 of the surface excess, the height H1 of the surface excess, and the plate thickness t2 of the second member satisfies the following equation:

[0023] 3.0mm≤d≤15.0mm

[0024] d <W1≤5.0d

[0025] 0.1t2≤H1≤5.0t2.

[0026] [2] The dissimilar metal joint according to [1], characterized in that:

[0027] The dissimilar material joint has a rear surface excess height on the rear surface of the second member,

[0028] The relationship among the diameter d of the through hole, the width W2 of the back surface excess, the height H2 of the back surface excess, and the plate thickness t2 of the second member satisfies the following equation:

[0029] W2≤3.0d

[0030] H2≤5.0t2.

[0031] [3] A method for manufacturing a dissimilar metal joint, wherein the dissimilar metal joint is the dissimilar metal joint described in [1] or [2], wherein:

[0032] The method for manufacturing the dissimilar material joint comprises:

[0033] A hole-opening step of opening the through hole in the first component;

[0034] an overlapping step of overlapping the first component and the second component; and

[0035] a welding step of filling the through hole with a welding metal formed by melting a welding material and welding the welding metal to the second member;

[0036] The welding material is melted by using at least one heat source selected from electric arc, plasma and laser.

[0037] [4] The method for manufacturing a dissimilar metal joint according to [3], wherein:

[0038] The method for manufacturing a dissimilar metal joint includes, before the welding step, a step of bringing a backing member in contact with the second member into contact with the backing member.

[0039] Effects of the Invention

[0040] According to the present invention, in a dissimilar material joint having a first component formed of a steel plate, a second component formed of an aluminum-based material or a magnesium-based material, and a joint portion that joins the first component and the second component, a high-strength dissimilar material joint can be obtained by reducing the surface excess height of the joint portion to a specified size. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 (A) is a diagram showing a hole-forming step in the method for manufacturing a dissimilar metal joint according to the present embodiment, Figure 1 (B) is a diagram showing a welding step in the method for manufacturing the dissimilar metal joint according to the present embodiment.

[0042] Figure 2 It is a model diagram showing the shape of the joint portion.

[0043] Figure 3 (A) is a diagram showing an example in which a plurality of plate-like members are provided as an upper plate. Figure 3 (B) is a diagram in which a tapered portion is provided in the through hole and becomes wider toward the lower plate. Figure 3 (C) is a diagram in which a tapered portion whose width becomes narrower toward the lower plate is provided in the through hole.

[0044] Figure 4 (A) is a diagram showing a contacting step using a first backing member in the method for manufacturing a dissimilar metal joint according to the present embodiment, Figure 4 (B) is a diagram showing a contacting step using a second backing member in the method for manufacturing a dissimilar metal joint according to the present embodiment, Figure 4 (C) is a diagram showing a contacting step using a third backing member in the method for producing a dissimilar metal joint according to the present embodiment.

[0045] Figure 5 (A) is a cross-sectional photograph of the weld corresponding to No. 1 in Table 1. Figure 5 (B) is a cross-sectional photograph of the weld corresponding to No. 7 in Table 1. Figure 5 (C) is a cross-sectional photograph of the welded portion corresponding to No. 9 in Table 1. Figure 5 (D) is a cross-sectional photograph of the welded portion corresponding to No. 22 in Table 1.

[0046] Description of Reference Numerals

[0047] 10 Upper plate (first component)

[0048] 11 Through hole

[0049] 11A Through hole

[0050] 11B Through hole

[0051] 20 Lower plate (second member)

[0052] 30 Joint

[0053] 31 Surface reinforcement

[0054] 32 Back reinforcement

[0055] 40A First backing member

[0056] 40B Second backing member

[0057] 40C Third backing member

[0058] 41 First recess

[0059] 42 Second recess

[0060] d Diameter of through hole

[0061] t1 The thickness of the upper plate

[0062] t2 Thickness of lower plate

[0063] H1 Height of surface reinforcement

[0064] H2 Height of the back side

[0065] W1 Width of surface reinforcement

[0066] W2 Width of back reinforcement

[0067] θ1 First contact angle

[0068] θ2 Second contact angle. DETAILED DESCRIPTION

[0069] Hereinafter, a dissimilar metal joined joint and a method for manufacturing the dissimilar metal joined joint according to an embodiment of the present invention will be described with reference to the drawings. Figure 1 (A) is a diagram showing a hole-forming step in the method for manufacturing a dissimilar metal joint according to the present embodiment, Figure 1 (B) is a diagram showing a welding step in the method for manufacturing the dissimilar metal joint according to the present embodiment. Figure 2 This is a model diagram showing the shape of a dissimilar material joint.

[0070] The dissimilar material joining joint of the present embodiment includes an upper plate 10 (first member), a lower plate 20 (second member), and a joining portion 30 .

[0071] The upper plate 10 is a steel plate-shaped member having a through hole 11 formed therein. The lower plate 20 is a plate-shaped member made of an aluminum alloy or a magnesium alloy and is arranged to overlap the lower surface of the upper plate 10. The joint 30 is formed by filling the through hole 11 with molten welding metal made of an aluminum alloy or a magnesium alloy by arc spot welding. Figure 2 Better.

[0072] <Method for manufacturing a dissimilar material joint>

[0073] First, a hole drilling process is performed on the upper plate 10 to form a through hole 11 that penetrates the upper plate 10 in the plate thickness direction and faces the overlapping surface of the lower plate 20. Figure 1 In the hole forming step, the through hole 11 is formed in the upper plate 10 by cutting with a rotary tool such as an electric drill or a drilling machine, punching with a punch, or punching with a die.

[0074] Next, a stacking step of stacking the upper plate 10 and the lower plate 20 is performed.

[0075] Next, a welding process is performed in which the molten metal formed by melting the welding material is filled into the through hole and the welding metal is welded to the lower plate 20 by using any of the arc welding methods described below, including (a) consumable electrode type gas shielded arc welding method, (b) non-gas shielded arc welding method, (c) tungsten inert gas shielded arc welding method, (d) plasma arc welding method, and (e) covering arc welding method. At this time, in arc welding, the welding material is melted under welding conditions that substantially do not melt the upper plate 10. Thus, a joint 30 is formed in which the upper plate 10 and the lower plate 20 are joined. This structure refers to Figure 1 (B) is better.

[0076] That is, the welding material is melted by any of the above-mentioned arc welding methods, and the generated welding metal is filled into the through hole 11 of the upper plate 10, so that a flange-shaped surface reinforcement 31 is formed on the surface of the upper plate 10. The surface reinforcement 31 is also called reinforcement. Then, the welding metal is melted into the lower plate 20 until the back surface reinforcement 32 is formed, and the upper plate 10 and the lower plate 20 are joined. It should be noted that the back surface reinforcement is also called weld leak.

[0077] In other words, the weld metal filled in the through-hole 11 forms the joint portion 30 having the surface relief 31 and the back relief 32 .

[0078] It should be noted that the welding materials may be any materials that can be welded to the lower plate 20 using the above-mentioned arc welding method, and include welding wires, welding rods, fillers, consumables, and other materials commonly used in welding.

[0079] Hereinafter, each arc welding method will be described.

[0080] (a) The gas shielded arc welding method using a consumable electrode is a welding method generally referred to as MAG (metal active gas welding) or MIG (metal inert gas welding), and is a method in which a solid wire or a flux-cored wire is used as a filler and also as an arc-generating consumable electrode, and a shielding gas such as CO2, Ar, or He is used to block the weld from the atmosphere to form a sound weld.

[0081] (b) Gas-free arc welding is also called self-shielded arc welding, and is a method of using a special flux-cored wire as a filler and arc-generating melting electrode, while not requiring a shielding gas to form a sound weld.

[0082] (c) Gas tungsten arc welding is a type of gas shielded arc welding, but it is a non-melting electrode type, and is also commonly referred to as TIG (tungsten inert gas welding). The shielding gas uses an inactive gas such as Ar or He. An arc is generated between the tungsten electrode and the base material, and the filler wire is fed from the side to the arc. Usually, the filler wire is not energized, but there is also a hot wire method TIG that increases the melting speed by energizing. In this case, no arc is generated in the filler wire.

[0083] (d) Plasma arc welding is a welding method that uses the same principle as TIG, but uses double systematization and high speed of gas to narrow the arc and increase the arc force.

[0084] (e) Covered arc welding is an arc welding method in which a covered arc welding rod having a metal core wire coated with flux is used as a filler, and shielding gas is not required.

[0085] It should be noted that the welding method for generating the weld metal is not limited to the above-mentioned arc welding method, and may be a welding method that melts the weld metal using at least one heat source selected from arc, plasma, and laser. For example, in the case of mixing laser and arc, the welding time can be shortened. It should be noted that the welding method is preferably arc welding (MIG or TIG), and more preferably MIG.

[0086] When using MIG or TIG as a welding method, welding can be performed without moving the welding torch while aiming at the center of the through hole 11, or the welding torch can be raised over time, or swung inside or around the through hole 11, or a combination of these can be used.

[0087] In addition, the welding torch may not be brought close vertically to the upper plate 10 and the lower plate 20, but may be tilted for welding. In addition, the welding torch may be used for welding not only in a downward orientation but also in a horizontal orientation or an upward orientation.

[0088] Next, based on Figure 2 as well as Figure 3 (A)~ Figure 3 (C) The specific shape of the dissimilar material joining joint is described. Figure 3 (A) is a diagram showing an example in which a plurality of plate-like members are provided as an upper plate. Figure 3 (B) is a diagram in which a tapered portion is provided in the through hole and becomes wider toward the lower plate. Figure 3(C) is a diagram in which a tapered portion whose width becomes narrower toward the lower plate is provided in the through hole.

[0089] <Shape of the joint for joining dissimilar materials>

[0090] First, regarding the upper plate 10, the lower plate 20, and the joint 30 constituting the dissimilar material joint, the thickness of the upper plate 10 is referred to as t1, the thickness of the lower plate 20 is referred to as t2, the diameter of the through hole 11 is referred to as d, the width of the surface reinforcement 31 is referred to as W1, the height of the surface reinforcement 31 is referred to as H1, the width of the back reinforcement 32 is referred to as W2, and the height of the back reinforcement is referred to as H2. In addition, the contact angle between the upper plate 10 and the surface reinforcement 31 is referred to as θ1, and the contact angle between the lower plate 20 and the back reinforcement 32 is referred to as θ2. This structure refers to Figure 2 It should be noted that the width W1 of the surface reinforcement 31 refers to the width of the shortest portion of the width in the plane direction of the surface reinforcement 31. Similarly, the width W2 of the back reinforcement 32 refers to the width of the shortest portion of the width in the plane direction of the back reinforcement 32.

[0091] The plate thickness t1 of the upper plate 10 is preferably usually 0.5 mm to 3.0 mm, and more preferably 1.0 mm to 2.0 mm. However, the plate thickness t1 of the upper plate 10 may be out of the above range.

[0092] In addition, the upper plate 10 is not limited to only one sheet, and may be a first plate group formed by overlapping a plurality of sheets. In this case, the diameters of the through holes 11A and 11B may be different. When the diameters of the through holes 11A and 11B are different, the diameter of the through hole 11A and 11B with the smallest diameter is set as the diameter d of the through hole 11. Figure 3 (A) is better.

[0093] It should be noted that the upper plate 10 has no restrictions on the type of steel plate and whether or not the surface treatment is performed. No matter what strength grade of steel is used, it can be used as long as the through hole 11 can be formed. That is, the upper plate 10 can be stainless steel or a nickel-based alloy. In addition, the upper plate 10 can also be subjected to alloying hot-dip galvanizing (GA), hot-dip galvanizing (GI), aluminum plating, etc.

[0094] The thickness t2 of the lower plate 20 is not particularly limited but is preferably 0.5 mm to 8.0 mm. The lower plate 20 is not limited to one sheet, but may be a second sheet set (not shown) formed by stacking a plurality of sheets, and the thickness t2 may be out of the above range.

[0095] The upper limit of the plate thickness t2 of the lower plate 20 is more preferably 7.0 mm or less, more preferably 5.0 mm or less, and more preferably 3.0 mm or less.

[0096] The lower limit of the plate thickness t2 of the lower plate 20 is more preferably 0.65 mm or more, and more preferably 0.8 mm or more.

[0097] It should be noted that there is no limitation on the type of aluminum alloy or magnesium alloy for the lower plate 20. As aluminum alloys used for the lower plate 20, for example, there are 5000 series, 6000 series, 7000 series alloys, etc., all of which can be used. In addition, the lower plate 20 is not limited to a plate-shaped member, and any aluminum material such as an extruded material or a die casting can also be used.

[0098] The thickness ratio t1 / t2 of the upper plate 10 and the lower plate 20 is preferably in the range of 0.5 to 2.0 from the viewpoint of ease of welding work. The thickness ratio may be out of the above range if welding conditions are set so that the shape of the welded portion falls within a preferred range.

[0099] The diameter d of the through hole 11 is preferably 3.0 mm to 15.0 mm.

[0100] When the diameter d of the through hole 11 is too small, it is difficult to fill the welding material by arc welding, and the joint strength of the joint 30 is also reduced. Therefore, the lower limit of the diameter d of the through hole 11 is preferably 3.0 mm or more, more preferably 4.0 mm or more, and more preferably 5.0 mm or more.

[0101] On the other hand, when the diameter d of the through hole 11 is too large, it is difficult to fill the through hole 11 with weld metal, and the welding time becomes longer. In addition, the consumption of welding materials increases, and there is a concern that cracks in the lower plate 20 and the weld metal may be caused by excessive heat input to aluminum. Therefore, the diameter d of the through hole 11 is preferably 15.0 mm or less, more preferably 13.0 mm or less, and more preferably 11.0 mm or less.

[0102] The through hole 11 may be elliptical or polygonal, but preferably has no corners such as a circle or an ellipse from the viewpoint of stress concentration on the joint 30 and the upper plate 10. The through hole 11 may be chamfered, but the presence or absence of burrs is not limited.

[0103] In addition, the through hole 11 may not be a hole perpendicular to the plate thickness direction, but may have a taper. The taper formed in the through hole 11 may be a taper 11a that narrows toward the plate thickness surface direction, or a taper 11b that narrows toward the plate thickness back side (interface) direction. In this case, the diameter of the smallest diameter portion is set as the diameter d of the through hole 11. This structure refers to Figure 3 (B) and Figure 3 (C) is better.

[0104] When the diameter of the through hole 11 is d, the width W1 of the surface reinforcement 31 is preferably larger than the diameter d of the through hole and is 5.0d or less (d <W≤5.0d)。

[0105] Basically, the larger the width W1 of the surface reinforcement 31 is, the better the effect on the joint strength is. However, when the width W1 of the surface reinforcement 31 is too large, it is considered that the welding time is prolonged, the consumption of consumable materials is increased, and the steel is excessively melted and mixed into the weld metal in large quantities, causing embrittlement and thermal deformation. Therefore, the upper limit of the width W1 of the surface reinforcement 31 is preferably 5.0d or less, more preferably 4.5d or less, and more preferably 4.0d or less.

[0106] On the other hand, in order to obtain a desired anchoring effect, the lower limit of the width W1 of the surface reinforcement 31 is preferably larger than the diameter d of the through hole 11 , and more preferably 1.2d or more.

[0107] The height H1 of the surface reinforcement 31 is preferably not less than 0.1t2 and not more than 5.0t2 when the plate thickness of the lower plate 20 is t2.

[0108] Basically, the higher the height H1 of the surface reinforcement 31 is, the better the effect on the joint strength is. However, even if the height H1 of the surface reinforcement 31 is too high, the joint strength cannot be improved accordingly. On the other hand, it is easy to interfere with other parts, or the welding time is prolonged, or the consumption of consumable materials is increased. Therefore, the upper limit of the height H1 of the surface reinforcement 31 is preferably 5.0t2 or less, more preferably 4.5t2 or less, and more preferably 4.0t2 or less.

[0109] On the other hand, when the lower limit of the height H1 of the surface reinforcement 31 is too low, the joint 30 is easily broken by the external force in the peeling direction. Therefore, it is preferably 0.1t2 or more, more preferably 0.2t2 or more, more preferably 0.3t2 or more, and more preferably 0.4t2 or more.

[0110] When the diameter of the through hole 11 is d, the width W2 of the rear surface reinforcement 32 is preferably 0≤W2≤3.0d.

[0111] When the plate thickness of the lower plate 20 is set to t2, the height H2 of the back surface reinforcement 32 is preferably 0≤H2≤5.0t2.

[0112] That is, even if there is no back reinforcement 32, sufficient joint strength can be obtained, and the joint 30 can be lightweight. In the case of forming the back reinforcement 32, the larger the back reinforcement 32 is, the better the joint strength is. However, in the case where the width W2 and height H2 of the back reinforcement 32 are too large, it is considered that the back reinforcement 32 interferes with other parts, or the consumption of consumable materials increases, or the weight increases more than necessary. Therefore, the width W2 of the back reinforcement 32 is preferably less than 3.0d, more preferably less than 2.5d, and the height H2 of the back reinforcement 32 is preferably less than 5.0t2, more preferably less than 4.0t2.

[0113] It should be noted that a rear face excess 32 may be additionally formed in order to reinforce the joint portion 30 .

[0114] The contact angle θ1 may be any value between 0 and 180° as long as it satisfies the conditions of the width W1 and the height H1 of the surface excess height 31. However, when the contact angle θ1 exceeds 120°, there is a possibility that insufficient heat input may weaken the connection between the upper plate 10 and the connection portion 30, so it is preferably less than 120°.

[0115] Since the same metals are usually in contact, the contact angle θ2 is preferably 0 to 90°. However, this is not limited to the case of interference with a spacer member or other components described later, when alloy elements are significantly different, or when the lower plate 20 is surface treated.

[0116] When the width W1 and height H1 of the surface relief 31 and the width W2 and height H2 of the back relief 32 of the joint 30 are out of the prescribed range, the joint 30 may be repaired by grinding or re-welding to be within the prescribed range.

[0117] In addition, if the above conditions are met, a certain gap may exist between the upper plate 10 and the lower plate 20. Specifically, even if there is a gap of about 2 mm between the upper plate 10 and the lower plate 20, sufficient bonding strength by the bonding portion 30 can be obtained.

[0118] In addition, the upper plate 10 and the lower plate 20 may be welded with adhesive or sealant applied thereon for the purpose of preventing openings between the plates, improving rigidity, waterproofing, etc. However, it is desirable that the adhesive or sealant be applied within a range that does not cause influence due to heat.

[0119] In addition, the connection between the upper plate 10 and the lower plate 20 is a connection between steel and aluminum, so there is a concern about dissimilar metal contact corrosion (electrochemical corrosion). In order to prevent this corrosion, it is preferred that after the joint 30 is made, the dissimilar material contact portion including the joint 30 is covered by a sealant, a film, an electrodeposition coating, etc. in a manner so that moisture that becomes a cause of corrosion does not invade the dissimilar material contact portion including the joint 30.

[0120] Next, the weld metal constituting the joint portion 30 will be described in detail.

[0121] <Weld Metal>

[0122] As long as the welding material that becomes the weld metal is a welding material that becomes an aluminum alloy or a magnesium alloy, a commonly used welding wire can be applied, and it can be appropriately selected according to the joint 30 and the welding conditions. For example, there are 5000 series, 4000 series, and 1000 series welding wires in circulation, and any of them can be used. More specifically, for example, there are A5356, A5183, A5554, A4043, A4047, A1100, A1070, etc.

[0123] The weld metal constituting the joint 30 may be made by melting a part of the iron of the upper plate 10 and mixing it into the weld metal. Generally, the mixed iron makes the weld metal embrittled, but it has been found that a small amount of iron has the effect of improving the strength of the weld metal, and it effectively acts on improving the strength of the joint 30. The average Fe concentration in the weld metal constituting the joint 30 is preferably 10% or less.

[0124] When a joining auxiliary member (not shown) having a hollow portion is provided in the through hole 11 of the upper plate 10, the upper plate 10 is hardly melted, and thus the iron constituting the upper plate 10 is hardly mixed into the joint portion 30. Therefore, in the present embodiment, in order to melt a portion of the upper plate 10 during welding and mix it, it is necessary to allow the weld metal to flow directly into the through hole 11 without using a joining auxiliary member.

[0125] Next, based on Figure 4 Another embodiment of the method for manufacturing the dissimilar metal joint will be described. Figure 4 (A) is a diagram showing a contacting step using a first backing member in the method for manufacturing a dissimilar metal joint according to the present embodiment, Figure 4 (B) is a diagram showing a contacting step using a second backing member in the method for manufacturing a dissimilar metal joint according to the present embodiment, Figure 4 (C) is a diagram showing a contacting step using a third backing member in the method for producing a dissimilar metal joint according to the present embodiment.

[0126] <Method for Manufacturing Dissimilar Material Joint Using Backing Member>

[0127] The manufacturing method of the dissimilar metal joint of the present embodiment may also include a step of abutting the backing members 40A, 40B, 40C before the welding step, in which the back side of the lower plate 20 where the through hole 11 is arranged in the plate thickness direction is abutted. In other words, by performing the above-mentioned arc welding using the backing members 40A, 40B, 40C, it is possible to eliminate the back side excess height 32, limit the size of the back side excess height 32, or correct the shape of the back side excess height 32. As the material of the backing members 40A, 40B, 40C, a metal material such as copper or copper alloy having a higher melting point than the weld metal, or a heat-resistant non-metal material such as ceramics is used.

[0128] The backing members 40A, 40B, and 40C will be described in detail.

[0129] The first backing member 40A is provided as a plate-shaped member that is in surface contact with the entire portion of the lower plate 20 where the back relief 32 is formed. Thus, it is possible to restrict the back relief 32 from protruding from the lower plate 20. Figure 4 (A) is better.

[0130] The second backing member 40B is a plate-shaped member having a first recess 41 of a predetermined depth formed at a portion of the lower plate 20 where the back relief 32 is formed. This can prevent the height H2 and width W2 of the back relief 32 formed on the lower plate 20 from increasing beyond a predetermined value. Figure 4 (B) is better.

[0131] The third backing member 40C is a plate-shaped member having a predetermined dome-shaped second recess 42 formed at a portion of the lower plate 20 where the back relief 32 is formed. Thus, the back relief 32 formed on the lower plate 20 can be formed into a smooth dome shape, and the height H2 and width W2 of the back relief 32 can also be the desired values. Figure 4 (C) is better.

[0132] Example

[0133] Hereinafter, examples of the dissimilar metal joining joint and the method for manufacturing the dissimilar metal joining joint according to the present embodiment will be described in detail. However, the present invention is not limited thereto.

[0134] like Figure 1 (A) and Figure 1As shown in (B), an aluminum alloy lower plate 20 is overlapped and arranged under an upper plate 10 which is a steel plate having a through hole 11. Next, a power source is connected to the welding wire W and the lower plate 20, and the welding wire W is brought into contact with the lower plate 20 in the through hole 11, and MIG arc welding is performed. It should be noted that in MIG arc welding, 100% Ar gas is used as a shielding gas. Thus, the through hole 11 is filled with molten welding metal to form a joint portion 30, forming a dissimilar material joint joint that joins the upper plate 10 and the lower plate 20.

[0135] In this embodiment, the type of the upper plate 10 (S1 to S4), the type of the lower plate 20 (A1 to A4), the type of the welding wire W (W1, W2), the plate thickness t1 of the upper plate 10, the plate thickness t2 of the lower plate 20, the diameter d of the through hole 11, and the shape and size of the joint 30 (surface excess 31 and back surface excess 32) are appropriately changed to manufacture the dissimilar material joint. The types of the upper plate 10, the lower plate 20, and the welding wire W used are as follows.

[0136] (Type of upper plate)

[0137] S1: 270MPa grade cold rolled steel

[0138] S2: 270MPa grade cold rolled steel GA plated steel sheet

[0139] S3: 270MPa grade cold rolled steel GI plated steel plate

[0140] S4: 1500MPa grade cold rolled steel

[0141] (Type of lower plate)

[0142] A1: 6000 series aluminum alloy plate (tensile strength 240MPa)

[0143] A2: 5000 series aluminum alloy plate (tensile strength 270MPa)

[0144] A3: 7000 series alloy extrusion material (tensile strength 365MPa)

[0145] A4: Aluminum die casting material (tensile strength 310MPa)

[0146] A5: 5000 series aluminum alloy plate (tensile strength 230MPa)

[0147] (Type of welding wire)

[0148] W1: JIS Z3232 A5356-WYφ1.2mm

[0149] W2: JIS Z3232 A4043-WYφ1.2mm

[0150] <Evaluation of dissimilar material joints>

[0151] Next, for each of the obtained dissimilar material joints, the joint strength was evaluated by measuring the joint strength in the peeling direction in which the shape of the dissimilar material joint has a great influence.

[0152] (Joint strength in peeling direction)

[0153] As the joint strength of each dissimilar material joint, the joint strength in the peeling direction (CTS: Cross retention strength) based on the cross tensile test described in JIS Z3137 was measured, and the measured joint strength was compared with the reference strength (the relative reference strength was calculated) for evaluation.

[0154] The reference strength of the joint strength in the peeling direction (CTS) is set to 50% of the reference strength of the joint strength in the shearing direction (TSS). The reference strength of the joint strength in the shearing direction (TSS) is based on the minimum value of the tensile shear load B and BF grades of the WES7302 spot welding work standard (aluminum and aluminum alloys).

[0155] When showing a specific example, in the case of a 6000 series aluminum alloy plate (A1) having a plate thickness of 2.0 mm and a tensile strength of 240 MPa, the reference strength is calculated as follows.

[0156] 240×1 / 98×1.000×0.5=1.2kN

[0157] Table 1 shows the types and sizes of materials used in manufacturing each dissimilar material joint together with the joint strength, and the size of the joint 30. The size of the joint 30 was calculated by scanning the weld shape using a laser displacement meter.

[0158] [Table 1]

[0159]

[0160] As shown in Table 1, it can be confirmed that when the diameter d of the through hole 11 of the dissimilar metal joint is greater than 3.0 mm and less than 15.0 mm, d≤surface excess width W1≤5.0d, and 0.1t2≤surface excess height H1≤5.0t2 are satisfied, the joint strength of the dissimilar metal joint is greater than the reference strength.

[0161] In addition, No. 20 is a case where two upper plates 10 are stacked, and the total plate thickness t1 is 2.8 mm. No. 22 is a comparative example having a strength lower than the reference strength.

[0162] It should be noted that Figure 5(A) is a cross-sectional photograph of the weld corresponding to No. 1 in Table 1. Figure 5 (B) is a cross-sectional photograph of the weld corresponding to No. 7 in Table 1. Figure 5 (C) is a cross-sectional photograph of the welded portion corresponding to No. 9 in Table 1. Figure 5 (D) is a cross-sectional photograph of the welded portion corresponding to No. 22 in Table 1.

[0163] like Figure 5 (A)~ Figure 5 As shown in (D), in the welding method of this embodiment, even if the back side excess height 32 is not shown, as long as the joint 30 is joined to the lower plate 20, a practically sufficient joint strength can be obtained. On the other hand, it is necessary to control the welding conditions so that the welding metal does not melt too deeply and the joint 30 and the lower plate 20 do not melt through.

[0164] It should be noted that Figure 5 The example shown in (D) is a comparative example having a strength lower than the reference strength.

[0165] It should be noted that the present invention is not limited to the above-mentioned embodiments, and the combination of the various structures of the embodiments and the changes and applications made by those skilled in the art based on the description in the specification and known technologies are also intended by the present invention and included in the scope of protection requested.

[0166] As described above, the following matters are disclosed in this specification.

[0167] (1) A dissimilar material joint, characterized in that:

[0168] The dissimilar material joint comprises:

[0169] A first member, which is composed of one or more steel plates;

[0170] a plate-shaped second member composed of one or more aluminum-based materials or one or more magnesium-based materials; and

[0171] a joining portion that joins the first member and the second member,

[0172] The first member has a through hole in the plate thickness direction facing the overlapping surface with the second member,

[0173] The joining portion is a weld metal filled in the through hole and welded to the second member, and has a surface relief arranged on the surface of the first member.

[0174] The relationship among the diameter d of the through hole, the width W1 of the surface excess, the height H1 of the surface excess, and the plate thickness t2 of the second member satisfies the following equation:

[0175] 3.0mm≤d≤15.0mm

[0176] d <W1≤5.0d

[0177] 0.1t2≤H1≤5.0t2.

[0178] According to this configuration, by making the surface relief of the joining portion formed by the weld metal smaller than a predetermined dimension, a high-strength dissimilar metal joining joint can be obtained.

[0179] (2) The dissimilar metal joint according to (1), characterized in that:

[0180] The dissimilar material joint has a rear surface excess height on the rear surface of the second member.

[0181] The relationship among the diameter d of the through hole, the width W2 of the back surface excess, the height H2 of the back surface excess, and the plate thickness t2 of the second member satisfies the following equation:

[0182] W2≤3.0d

[0183] H2≤5.0t2.

[0184] According to this configuration, by making the rear face excess height formed by the weld metal smaller than a predetermined dimension, a high-strength dissimilar metal joint can be obtained.

[0185] (3) A method for manufacturing a dissimilar metal joint, wherein the dissimilar metal joint is the dissimilar metal joint described in (1) or (2), wherein:

[0186] The method for manufacturing the dissimilar material joint comprises:

[0187] A hole-opening step of opening the through hole in the first component;

[0188] an overlapping step of overlapping the first component and the second component; and

[0189] a welding step of filling the through hole with a welding metal formed by melting a welding material and welding the welding metal to the second member;

[0190] The welding material is melted by using at least one heat source selected from electric arc, plasma and laser.

[0191] According to this configuration, the molten metal constituting the joining portion can be smoothly generated from the welding material, and thus the dissimilar metal joining joint can be manufactured more stably.

[0192] (4) The method for manufacturing a dissimilar metal joint according to (3), wherein:

[0193] The method for manufacturing a dissimilar metal joint includes, before the welding step, a step of bringing a backing member in contact with the second member into contact with the backing member.

[0194] According to this structure, the size and shape of the rear surface excess formed in the second member can be adjusted arbitrarily.

Claims

1. A dissimilar material joint, It is characterized in that The dissimilar material joint comprises: A first member, which is composed of one or more steel plates; A plate-shaped second member, which is composed of one or more aluminum-based materials or one or more magnesium-based materials; as well as a joining portion that joins the first member and the second member, The first member has a through hole in the plate thickness direction facing the overlapping surface with the second member, The joining portion is a weld metal filled in the through hole and welded to the second member, and has a surface relief arranged on the surface of the first member. The diameter d of the through hole and the width W of the surface excess height 1 , the height H of the surface excess height 1 and the thickness t of the second member 2 The relationship satisfies the following formula, 3.0mm≤d≤15.0mm <h2 style=";text-align:left;direction:ltr">d<W<h2 style=";text-align:left;direction:ltr"> 1 <h2 style=";text-align:left;direction:ltr"> ≤5.0d 0.1t 2 ≤H 1 ≤5.0t 2 。 2. The dissimilar material joint according to claim 1, It is characterized in that The dissimilar material joint has a rear surface excess height on the rear surface of the second member. The diameter d of the through hole and the width W of the back side height 2 , the height H of the back side residual height 2 and the thickness t of the second member 2 The relationship satisfies the following formula, IN 2 ≤3.0d H 2 ≤5.0t 2 。 3. A method for manufacturing a dissimilar material joint, wherein the dissimilar material joint is the dissimilar material joint according to claim 1 or 2, in, The method for manufacturing the dissimilar material joint comprises: A hole-opening step of opening the through hole in the first component; an overlapping step of overlapping the first component and the second component; and a welding step of filling the through hole with a welding metal formed by melting a welding material and welding the welding metal to the second member; The welding material is melted by using at least one heat source selected from electric arc, plasma and laser.

4. The method for manufacturing a dissimilar material joint according to claim 3, in, The method for manufacturing a dissimilar metal joint includes, before the welding step, a step of bringing a backing member in contact with the second member into contact with the backing member.

Images