JP2016016413A - Method of manufacturing dissimilar material joined body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a dissimilar material joined body, by means of which stable arc is generated and preferable bead appearance can be obtained.SOLUTION: The method of manufacturing a dissimilar material joined body comprises a step of forming a joint by means of aluminum alloy material and steel material and a step of performing TIG welding by generating arc from a welding torch provided with a non-consumable electrode while supplying a filler metal to a weld position between the aluminum alloy material and the steel material. In the method, the non-consumable electrode is connected to an anode of a DC power source and, at the same time, the filler metal is connected to a cathode of the DC power source and thus, the non-consumable electrode and the filler metal are electrically conducted, TIG welding is performed and the dissimilar material joined body is manufactured. In the method of manufacturing the dissimilar material joined body, a gas nozzle provided in the welding torch may be connected to the cathode of the DC power source and the aluminum alloy material may be connected to the cathode of the DC power source.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a method for producing a dissimilar material joined body. More specifically, the present invention relates to a technique for forming a joint with an aluminum alloy material and a steel material and joining the aluminum alloy material and the steel material by performing TIG welding.

  2. Description of the Related Art In recent years, weight reduction has been demanded from the viewpoint of reducing environmental burden and fuel consumption in structures and building structures of transportation equipment such as automobiles, railways, ships, and aircraft. On the other hand, in the body of an automobile, etc., it is also pursued to improve safety at the time of a collision, and it is considered to improve safety in combination with weight reduction. For this reason, various studies have been made to partially apply aluminum alloy materials that are lightweight and excellent in energy absorption in addition to steel materials to automobile body structures and the like.

  When dissimilar joining of an aluminum alloy material and a steel material is performed by welding, formation of an intermetallic compound layer of highly brittle Fe and Al occurs at the joint interface between the aluminum alloy material and the steel material. In some cases, sufficient bonding strength may not be obtained.

  In such a situation, for example, Patent Document 1 discloses that “a joint in which an aluminum alloy material is stacked on a steel material is formed, the aluminum alloy material is used as a positive electrode, and a flux cored wire is used for direct current TIG welding. A technique relating to “a method of joining different materials by wire joining” is disclosed. In the technique disclosed in Patent Document 1, high bonding strength and the like are to be obtained by specifying the shape of the tungsten electrode used for TIG welding and the orientation during welding.

JP 2012-183570 A

  When the present inventors form a joint with an aluminum alloy material and a steel material and perform TIG welding, the arc generated from the welding torch used for TIG welding fluctuates or fluctuates, resulting in a problem of instability. I found out. And the present inventors acquired the knowledge that a favorable bead appearance cannot be obtained when an aluminum alloy material and a steel material are joined by TIG welding in which such an unstable arc is generated.

  Then, this invention makes it the main purpose to provide the manufacturing method of the dissimilar-material joined body which can generate | occur | produce a stable arc and can obtain a favorable bead appearance.

The present invention generates an arc from a welding torch having a non-consumable electrode while supplying a filler material to a welding position between the aluminum alloy material and the steel material, and forming a joint between the aluminum alloy material and the steel material. And TIG welding, and connecting the non-consumable electrode to the negative electrode of the DC power source and connecting the filler material to the positive electrode of the DC power source to conduct the current, thereby performing the TIG welding. A manufacturing method is provided.
The welding torch may include a gas nozzle, and the TIG welding may be performed by connecting the gas nozzle to a positive electrode of the DC power source.
The aluminum alloy material may be connected to the positive electrode of the DC power source to perform the TIG welding.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the dissimilar-material joined body which generate | occur | produces the stable arc and can obtain a favorable bead appearance can be provided.

It is a flowchart for demonstrating the manufacturing method of the dissimilar-material joined body which concerns on embodiment of this invention. It is a figure which shows the example of 1 structure for demonstrating the manufacturing method of the dissimilar-material joined body which concerns on embodiment of this invention. It is a figure for demonstrating one structural example of the joint shape of an aluminum alloy material and steel materials, and is the top view which looked at the dissimilar material joined body which joined the aluminum alloy material and steel materials by TIG welding from the upper direction. It is a figure for demonstrating one structural example of the joint shape of an aluminum alloy material and steel materials, and the side surface which looked at the dissimilar-material joined body which joined the aluminum alloy material and steel materials by TIG welding from the block arrow A direction in FIG. 3A FIG. It is a figure for demonstrating arrangement | positioning of the filler material which can be employ | adopted in the manufacturing method of the dissimilar-material joined body which concerns on embodiment of this invention. It is a figure for demonstrating the advance angle of the non-consumable electrode (welding torch) which can be employ | adopted in the manufacturing method of the dissimilar-material joined body which concerns on embodiment of this invention. It is a figure for demonstrating the bevel angle | corner of the non-consumable electrode (welding torch) which can be employ | adopted in the manufacturing method of the dissimilar-material joined body which concerns on embodiment of this invention. It is a figure for demonstrating the shape and dimension of the aluminum alloy material and steel material which were used in the Example and the comparative example, and those joint shapes, and the dissimilar material joined body which joined aluminum alloy material and steel material by TIG welding from the upper part FIG. It is a figure for demonstrating the shape and dimension of the aluminum alloy material and steel material which were used in the Example and the comparative example, and those joint shapes, and shows the dissimilar material joined body which joined the aluminum alloy material and the steel material by TIG welding. It is the side view seen from the inside block arrow A direction. 4 is a drawing-substituting photograph in which the bead appearance of the dissimilar material joined body manufactured in Example 1 is photographed. 6 is a drawing-substituting photograph in which an appearance of a bead of the dissimilar material joined body produced in Example 2 is photographed. 4 is a drawing-substituting photograph in which a cross section of a joint portion of a dissimilar material joined body manufactured in Example 2 is photographed. FIG. 6 is a drawing-substituting photograph in which a bead appearance of a product according to Comparative Example 1 is photographed. It is a figure for demonstrating the state where the arc generated from a welding torch is not stabilized. It is a figure showing an example of the bead appearance of the dissimilar-material joined body at the time of performing TIG welding with an aluminum alloy material and steel materials by the unstable arc as shown in FIG.

  First, a schematic process until the inventors complete the present invention will be described with reference to FIGS. FIG. 11 is a diagram for explaining a state where the arc 7a generated from the welding torch 5 used for TIG welding is not stable, and FIG. 12 shows an aluminum alloy due to the unstable arc 7a as shown in FIG. It is a figure showing an example of the bead appearance of dissimilar material joined object 1a at the time of performing TIG welding of material 2 and steel material 3.

As shown in FIG. 11, the present inventors, when TIG welding the aluminum alloy material 2 and the steel material 3, arc 7a generated from a welding torch 5 including a non-consumable electrode 51 and a gas nozzle 52 used for TIG welding. It was found that the problem of instability occurs due to shaking and wobbling. The generation of the unstable arc 7a is considered to be caused by welding of dissimilar metals such as the aluminum alloy material 2 and the steel material 3.
Then, when the aluminum alloy material 2 and the steel material 3 are joined by TIG welding in which such an unstable arc 7a is generated, the inventors spread or shift the bead as shown in FIG. Thus, it was found that a good bead appearance could not be obtained, and furthermore, a good bonding strength could not be obtained.

  Therefore, the present inventors change various welding conditions such as the welding posture of TIG welding, the arrangement of the filler metal, and the magnitude of the current in order to solve the problem that the unstable arc 7a is generated. Etc. earnestly researched and repeated trial and error. As a result, the inventors of the present invention unexpectedly generated an arc generated from the welding torch by connecting the filler material, which was not connected to the DC power source, to the positive electrode of the DC power source in the conventional common sense. The inventors have found that the present invention is stable and have completed the present invention.

  That is, the manufacturing method of the dissimilar material joined body of the present invention includes a step of forming a joint between an aluminum alloy material and a steel material, and a non-consumable electrode while supplying a filler material to a welding position between the aluminum alloy material and the steel material. And a step of performing TIG welding by generating an arc from the welding torch, and connecting the non-consumable electrode to the negative electrode of the DC power supply and connecting the filler material to the positive electrode of the DC power supply to conduct electricity and perform TIG welding. Is.

  EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated in detail, referring drawings. Note that the present invention is not limited to the embodiments described below. In the drawings used in the description of the following embodiments, the same components may be denoted by the same reference numerals and description thereof may be omitted.

  In the method for manufacturing the dissimilar material joined body 1 according to the embodiment of the present invention (dissimilar material joining method), a welding torch 5 and a filler material 6 each having a non-consumable electrode 51 are formed by forming a joint between the aluminum alloy material 2 and the steel material 3. The used TIG welding is performed, and the dissimilar material joined body 1 in which the aluminum alloy material 2 and the steel material 3 are joined is manufactured. Hereinafter, the aluminum alloy material 2 and the steel material 3 may be collectively referred to as the welded materials 2 and 3.

  FIG. 1 is a flowchart for explaining a method of manufacturing the dissimilar material joined body 1 of the present embodiment. FIG. 2 is a view showing a configuration example for explaining a method of manufacturing the dissimilar material joined body 1. FIG. 3 is a diagram for explaining one configuration example of the joint shape of the aluminum alloy material 2 and the steel material 3, and is a diagram showing the dissimilar material joined body 1 in which the aluminum alloy material 2 and the steel material 3 are joined by TIG welding. is there. 3A is a plan view of the dissimilar material assembly 1 as viewed from above, and FIG. 3B is a side view of the dissimilar material assembly 1 as viewed from the direction of the block arrow A in FIG. 3A. Hereinafter, the manufacturing method of the dissimilar-material joined body 1 of this embodiment is demonstrated, referring drawings.

  As shown in FIG. 1, in the manufacturing method of the dissimilar-material joined body 1 of this embodiment, the process of forming a joint with the aluminum alloy material 2 and the steel material 3 (hereinafter, sometimes referred to as “joint formation process”) S1. And a step of performing TIG welding for joining the aluminum alloy material 2 and the steel material 3 (hereinafter also referred to as “TIG welding step”) S2.

[Joint formation process]
In the joint forming step S1, the aluminum alloy material 2 and the steel material 3 are combined to form a welded joint. In the manufacturing method of the dissimilar-material joined body 1 of this embodiment, since it is the method of trying to obtain a favorable bead appearance by generating the stable arc 7 in the case of TIG welding, a joint shape is not specifically limited.

  Examples of the joint shape include a butt joint, a lap joint, a fillet joint, a T joint, a cross joint, a corner joint, a lip joint, a metal fitting joint, a flare joint, a scarf joint, and a glue joint. 3A and 3B, as in the so-called flare joint, the aluminum alloy material 2 and the steel material 3 which are bent are used, respectively, and groove-shaped welding made by providing a step between the outer surfaces of the bent corners is performed. An example of a joint is shown.

(Material to be welded)
As an aluminum alloy material 2 used as a material to be welded, 3000 series, 5000 series, 6000 series, and 7000 series defined by JIS or AA standards according to the required characteristics of the vehicle body structure to be applied such as strength, molding, and corrosion resistance. An aluminum alloy such as can be used. However, from the viewpoint of reducing the thickness of the aluminum alloy material 2 in response to the demand for weight reduction of the vehicle body such as an automobile, it is preferable to use the aluminum alloy material 2 having high strength and excellent formability among these aluminum alloy materials 2. .

  Further, Si such as 6N01, 6016, 6111, 6022 in which the mass ratio of Si to Mg (Si / Mg) in the component composition of the aluminum alloy material 2 is 1 or more and Si is excessively contained with respect to the Mg content. It is preferable to use an excess type 6000 series aluminum alloy material 2. The joints after welding using these 6000 series aluminum alloy materials 2 were subjected to artificial aging treatment at a low temperature of 160 to 180 ° C. and for a short time of about 10 to 50 minutes, whereby the strength once decreased due to the influence of welding heat. It is also possible to recover the growth. The aluminum alloy material 2 is subjected to solution treatment and quenching treatment (quality symbol T4), subsequent aging treatment (quality symbol T6), overaging treatment (quality symbol T7) after cold rolling or hot extrusion. ) May be used.

  As the steel material 3 used as the material to be welded, various steel plates or shaped steels such as mild steel, high-tensile steel (high-tensile steel), and stainless steel cold-rolled steel plate can be used. In addition, the steel material 3 may be a member and a part (for example, a vehicle body member) formed by processing these materials into a predetermined shape.

Although the aluminum alloy material 2 and the steel material 3 illustrated the bent plate shape which has a bending corner in FIG.2 and FIG.3, it is not limited to this shape, A flat plate shape may be sufficient. Further, the aluminum alloy material 2 and the steel material 3 may be members and parts (for example, vehicle body members) formed and processed into a predetermined shape.
The thicknesses of the plate-like portions of the aluminum alloy material 2 and the steel material 3 are not particularly limited. From the viewpoint of ensuring the strength and rigidity necessary for the application to which the dissimilar material joined body 1 obtained by the manufacturing method of the present embodiment is applied, the thickness of the plate-like portion of the aluminum alloy material 2 is preferably 0.5 mm or more. 0.7 mm or more is more preferable, and 1 mm or more is more preferable. Similarly, the thickness of the steel material 3 is preferably 0.1 mm or more, more preferably 0.3 mm or more, and further preferably 0.5 mm or more. Further, from the viewpoint of easily performing TIG welding, the thickness of the plate-like portions of the aluminum alloy material 2 and the steel material 3 is preferably 5 mm or less, and more preferably 3 mm or less.

[TIG welding process]
In the TIG welding step S2, while supplying the filler metal 6 to the welding position between the aluminum alloy material 2 and the steel material 3, the arc 7 is generated from the welding torch 5 including the non-consumable electrode 51, and the aluminum alloy material 2 and the steel material TIG welding with 3 is performed. At this time, the welded materials 2, 3 and the filler material 6 are melted by the heat generated by the arc 7 generated from the welding torch 5, and the molten metal 41 (see FIG. 2) is a joint of the welded materials 2, 3. A weld metal 4 (see FIG. 3) is formed by being provided at a portion (welding position) and then solidified, and the aluminum alloy material 2 and the steel material 3 are joined.

(Fused material)
The filler material 6 used for TIG welding is not particularly limited, but it is preferable to use a flux cored wire (hereinafter sometimes referred to as “FCW”) as the filler material 6. As this FCW, a commercially available FCW used for joining different materials between the aluminum alloy material 2 and the steel material 3 can be used. In such FCW, a flux is filled as a core material in a tubular skin material made of an aluminum alloy such as A4047 or A4043 containing Si, for example.

  As the FCW wire diameter, a FCW having a small diameter of about 0.8 to 1.8 mm, which is widely used as high-efficiency fully automatic welding or semi-automatic welding, can be used. The composition of the flux is not particularly limited, and for example, a flux having a composition containing a fluorine compound, an oxide (such as aluminum oxide), and an aluminum alloy powder can be used.

(Welding torch)
As shown in FIG. 2, the welding torch 5 used for TIG welding includes a non-consumable electrode 51. A tungsten electrode is used as the non-consumable electrode 51. As the electrode material of the tungsten electrode, pure tungsten, tungsten containing thorium oxide, tungsten containing lanthanum oxide and tungsten containing cerium oxide, tungsten containing yttrium oxide and tungsten containing zirconium oxide, etc., as defined in JIS Z 3233 are used. be able to.

  Further, the welding torch 5 may include a gas nozzle 52 as shown in FIG. 2, similarly to a welding torch generally used in TIG welding. The non-consumable electrode 51 is disposed inside the gas nozzle 52. An inert gas such as argon gas or helium gas is supplied into the gas nozzle 52, and the inert gas is ejected as a shielding gas from the opening 521 of the gas nozzle 52 during the TIG welding (the gas nozzle 52 in FIG. 2). (See arrow shown inside).

(DC power supply)
In the present embodiment, the DC power supply 8 is used as a power supply for supplying current to the non-consumable electrode 51 and the like. The melting range of the aluminum alloy material 2 can be reduced by direct current TIG welding using the direct current power supply 8 as compared with the case of using an alternating current power supply generally used for welding aluminum alloy materials. Thereby, it becomes possible to perform TIG welding efficiently and can contribute to formation of a favorable bead appearance.

(Connection to DC power supply)
In the manufacturing method of the dissimilar material joined body 1 of the present embodiment, the non-consumable electrode 51 is connected to the negative electrode 81 of the DC power supply 8 and the filler material 6 is connected to the positive electrode 82 of the DC power supply 8 and energized to perform TIG welding. Do. When a current from the DC power supply 8 flows through the non-consumable electrode 51 and the filler material 6, it is possible to generate a stable arc 7 from the welding torch 5. By this stable arc 7, the aluminum alloy material 2 and the steel material 3 are welded, so that a good bead appearance can be obtained.

  Moreover, in the manufacturing method of the dissimilar-material joined body 1 of this embodiment, although it is not necessary to connect the gas nozzle 52 with which the welding torch 5 is provided to the DC power supply 8, as shown in FIG. It is preferable to connect the gas nozzle 52. By connecting the gas nozzle 52 to the positive electrode 82 of the DC power supply 8, it is possible to narrow down while suppressing the spread of the arc 7 generated from the welding torch 5. This narrowed arc 7 reduces the melting range of the aluminum alloy material 2, thereby enabling efficient TIG welding and contributing to the formation of a good bead appearance.

  Further, in the present embodiment, the aluminum alloy material 2 that is the material to be welded does not necessarily need to be connected to the DC power source 8, but the aluminum alloy material 2 is connected to the positive electrode 82 of the DC power source 8 as shown in FIG. 2. It is preferable to do. By connecting the aluminum alloy material 2 to the positive electrode 82 of the DC power source 8, the arc 7 can be more concentrated toward the aluminum alloy material 2. Although not shown, the steel material 3 that is a material to be welded may be connected to the positive electrode 82 of the DC power supply 8.

  The magnitude of the current (welding current) energized when performing TIG welding, the welding speed, the flow rate of the shielding gas, etc. are not particularly limited, and the material and thickness of the materials 2 and 3 to be welded, the groove shape, and the joint shape Depending on the material and diameter of the filler material, the material and electrode diameter of the non-consumable electrode, etc., it can be set as appropriate. For example, the welding current can be set in the range of 30 to 100A, and preferably 50 to 100A. Moreover, when performing TIG welding with an automatic welder, the welding speed can be set in the range of 200 to 1000 mm / min, and preferably 300 to 600 mm / min. Argon gas or helium gas is preferably used as the working gas, shield gas, and back shield gas, and the shield gas may contain hydrogen gas of about several percent. The flow rate of the working gas may be set in the range of, for example, 0.3 to 1.5 L / min, the flow rate of the shield gas in the range of, for example, 5 to 40 L / min, and the flow rate of the back shield gas in the range of, for example, 1 to 10 L / min. Is possible.

  Although the feeding position of the filler metal 6 in TIG welding is not particularly limited, it is preferably supplied from the welding progress direction side. The feeding position of the filler material 6 is, for example, as shown in FIG. 4, when the non-consumable electrode 51 and the filler material 6 are viewed from the same plane. The feeding position of the filler material 6 may be set so that the distance d between the extension line of the central axis and the tip position of the filler material 6 is preferably about 1 to 10 mm, more preferably about 2 to 8 mm. it can. The supply angle of the filler material 6 is not particularly limited. For example, as shown in FIG. 4, the non-consumable electrode 51 when the non-consumable electrode 51 (welding torch 5) and the filler material 6 are viewed from the same plane. The filler material 6 is supplied so that the angle θ1 between the perpendicular to the center axis of the (welding torch 5) and the center axis of the filler material 6 is preferably 5 to 40 °, more preferably 10 to 30 °. Can do.

In performing the TIG welding, as shown in FIG. 5A, it is preferable to provide the advance angle θ2 to the non-consumable electrode 51 with respect to the welding direction (see the block arrow B in FIG. 5A). The advancing angle θ2 is expressed by the angle formed between the center axis of the perpendicular line and the non-consumable electrode 51 with respect to the weld line W _L when the welding line W _L is viewed from the side of the workpieces M such that the left-right direction . When the advance angle θ2 is provided, the advance angle θ2 is preferably set to 5 to 40 °, more preferably 10 to 30 °, from the viewpoint of generating a good arc and suppressing the occurrence of sputtering.

Moreover, when performing TIG welding, it is preferable to provide the non-consumable electrode 51 with a bevel angle θ3 as shown in FIG. 5B. The angle θ3 is in a plan view viewed workpieces M from the top, represented by the angle between the projection line of the central axis of the welding line W _L and a non-consumable electrode 51. When this bevel angle θ3 is provided, the bevel angle θ3 is preferably set to 10 to 45 °, more preferably 15 to 40 ° from the viewpoint of generating a good arc and suppressing the occurrence of sputtering.

  According to the manufacturing method of the dissimilar material joined body 1 of the present embodiment described in detail above, in the direct current TIG welding of the aluminum alloy material 2 and the steel material 3, the non-consumable electrode 51 used for the welding is connected to the negative electrode 81 of the direct current power source 8. At the same time, the melt 6 is connected to the positive electrode 82 of the DC power source 8 and energized to perform TIG welding, so that a stable arc 7 can be generated (see FIG. 2). And the manufacturing method of the dissimilar-material joined body 1 of this embodiment can obtain the dissimilar-material joined body 1 in which a favorable bead appearance is formed by the stable arc 7 (see FIG. 3).

  Hereinafter, the effects of the present invention will be specifically described with reference to Examples and Comparative Examples of the present invention. First, materials, apparatuses, and welding conditions used in Examples and Comparative Examples will be described. Note that, in the following examples and comparative examples, components in the drawings that are used in the description of the above-described embodiment are referred to in parentheses with reference numerals in the drawings.

[Material to be welded]
6A and 6B are diagrams for explaining the shapes and dimensions of the aluminum alloy material 20 and the steel material 30 used in the examples and comparative examples, and the joint shapes thereof.
As the aluminum alloy material 20, an aluminum alloy plate 20 having a thickness of 1.2 mm made of AA6022 which is a 6000 series aluminum alloy material was used. As the steel material 30, a steel plate 30 having a thickness of 0.7 mm made of SPC270, which is a cold-rolled steel plate, was used. The aluminum alloy plate 20 and the steel plate 30 were of the shape shown in FIGS. 6A and 6B and bent. Moreover, as shown in the same figure, the shape of the welded joint is a joint that welds a groove shape that is formed by providing a step between the outer surfaces of the bending corners of the aluminum alloy plate 20 and the steel plate 30. .

[Fused material]
As the filler material (6), a flux cored wire (FCW) having a wire diameter of 1.2 mm was used. As this FCW, Si is 2.3% by mass, Ti is 0.2% by mass, and the aluminum alloy skin material is substantially Al. The AlF ₃ is 10% by mass and the remaining is substantially KAlF. FCW containing a flux of 10% at a filling rate was used.

[Welding equipment]
For TIG welding of the aluminum alloy plate 20 and the steel plate 30, a transition arc type plasma welding machine manufactured by Fronius (power source for welding: MW / TT 5000 manufactured by Fronius, plasma module: Plasma Module 10 manufactured by Fronius) TIG welding was performed by automatic welding in which the welding torch (5) was driven by a 6-axis articulated robot.

[Welding conditions]
TIG welding performed in Examples and Comparative Examples was performed under conditions in the range shown in Table 1 below.

  In addition, TIG welding performed in Examples and Comparative Examples is as follows. As the feeding position of the filler material (6), θ1 shown in FIG. 4 is 20 °, d is 5 mm, and the inclination of the welding torch (5) is shown. The advance angle θ2 shown in 5A was 25 °, and the bevel angle θ3 shown in FIG. 5B was 30 °.

Example 1
In Example 1, the non-consumable electrode (51) of the welding torch (5) is connected to the negative electrode (81) of the DC power supply (8), and the gas nozzle (52) and filler material (6) of the welding torch (5). Was connected to the positive electrode (82) of the DC power source (8) and energized, and the aluminum alloy material 20 and the steel material 30 were TIG welded without being connected to the DC power source (8).
The TIG welding conditions at this time were as follows: the working gas flow rate was set to 0.3 mL / min, the welding current was set to 70 A, and the FCW feed speed was set to 2.0 m / min, and the welding speed was set to 400 to 1000 mm / min. It was controlled to be within the range.
In the TIG welding of Example 1, it was confirmed that the arc (7) generated from the welding torch (5) was stable. Further, FIG. 7 shows a drawing-substituting photograph in which the bead appearance of the dissimilar material joined body 10 manufactured in Example 1 is taken. As shown in FIG. 7, in the dissimilar material joined body 10 manufactured in Example 1, a bead having a good appearance was formed.

(Example 2)
In Example 2, the non-consumable electrode (51) of the welding torch (5) is connected to the negative electrode (81) of the DC power source (8), the gas nozzle (52) of the welding torch (5), and the filler material (6). The aluminum alloy material 20 was connected to the positive electrode (82) of the DC power source (8) and energized, and the steel material 30 was TIG welded without being connected to the DC power source (8).
TIG welding conditions at this time were set such that the flow rate of working gas was 0.3 mL / min, the welding current was 80 A, the welding speed was 400 mm / min, and the FCW feed speed was 3.5 m / min.
In TIG welding in Example 2, it was confirmed that the arc (7) generated from the welding torch (5) was stable. FIG. 8 shows a drawing substitute photograph in which the bead appearance of the dissimilar material joined body 10 manufactured in Example 2 is photographed. FIG. 9 shows a drawing substitute photograph in which a cross section of the weld metal 40 of the dissimilar material joined body 10 is photographed. As shown in FIG. 8, in the dissimilar material joined body 10 manufactured in Example 2, a bead having a good appearance is formed. As shown in FIG. 9, the aluminum alloy material 20 and the steel material 30 are formed. It was confirmed that the weld metal 40 entered and joined into the groove formed by the joint shape. Incidentally, FIG. 9, as shown in FIG. 6A, it was taken were taken test piece TP ₁ of 15 mm × 20 mm for cross section observation.

(Comparative Example 1)
In Comparative Example 1, the non-consumable electrode (51) of the welding torch (5) is connected to the negative electrode (81) of the DC power source (8), and the gas nozzle (52) and the aluminum alloy material 20 of the welding torch (5) are connected to the DC. The positive electrode (82) of the power source (8) was connected and energized, and the filler metal (6) and the steel material 30 were TIG welded without being connected to the DC power source (8).
The TIG welding conditions at this time are as follows: the working gas flow rate is set to 0.5 mL / min, the welding speed is set to 600 mm / min, the welding current is in the range of 90 to 100 A, and the FCW feeding speed is 1.2 to Control was performed so as to be within the range of 2.0 m / min.
In TIG welding in Comparative Example 1, it was confirmed that an unstable arc (7a) was generated from the welding torch (5). In addition, FIG. 10 shows a drawing-substituting photograph in which the bead appearance of the product according to Comparative Example 1 is photographed. As shown in FIG. 10, in Comparative Example 1, a good bead could not be formed, and the aluminum alloy material 20 and the steel material 30 were hardly joined.

About the dissimilar material joined body 10 of Example 1 and 2 in which a bead having a good appearance was formed, as shown in FIG. 6A, test pieces TP ₂ , TP ₃ , TP ₄ having a width of 20 mm and a length of 100 mm for a tensile test were provided. The sample was collected and subjected to a tensile test (n = 3) in which the test piece was pulled in the length direction. The average of the three measurement results is taken as the evaluation result, and the result is shown in Table 2. In addition, although the width dimension of each test piece TP ₂ , TP ₃ , TP ₄ was sampled by the standard of 20 mm as described above, due to the influence at the time of sampling, the width of each test piece was 19 mm as shown in Table 2. The value was used in the calculation of the breaking force.

  From the above results, the non-consumable electrode used for TIG welding was connected to the negative electrode of the DC power source, and the gas nozzle of the welding torch and the filler material were connected to the positive electrode of the DC power source to energize the aluminum alloy material and the steel material. It was confirmed that a stable arc can be generated by welding. This also suggested that a dissimilar material bonded body having a good bead appearance and high bonding strength can be obtained.

DESCRIPTION OF SYMBOLS 1 Dissimilar material joined body 2 Aluminum alloy material 3 Steel material 4 Weld metal 41 Molten metal 5 Welding torch 51 Non-consumable electrode 52 Gas nozzle 6 Filler material 7 Arc 8 DC power supply 81 Negative electrode 82 Positive electrode

Claims (3)

Forming a joint with an aluminum alloy material and a steel material;
A step of performing TIG welding by generating an arc from a welding torch having a non-consumable electrode while supplying a filler metal to a welding position between the aluminum alloy material and the steel material,
The manufacturing method of the dissimilar-material joined body which connects the said non-consumable electrode to the negative electrode of DC power supply, connects the said filler material to the positive electrode of said DC power supply, and supplies with electricity, and performs said TIG welding. The welding torch includes a gas nozzle,
The manufacturing method of the dissimilar-material joining body of Claim 1 which connects this gas nozzle to the positive electrode of the said DC power supply, and performs the said TIG welding.   The manufacturing method of the dissimilar-material joined body of Claim 1 or 2 which connects the said aluminum alloy material to the positive electrode of the said DC power supply, and performs the said TIG welding.