JPH0370585B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for welding an aluminum alloy die-cast member to an aluminum alloy die-cast member. More specifically, the present invention relates to a welding method that employs a welded joint shape that allows the two members to be welded with good airtightness.

[Prior Art] In addition to being a wrought material, aluminum alloys are widely used in various fields as cast products by gravity casting or low pressure casting, die cast products, and the like.

However, while each of these aluminum alloy products has advantages, it also has disadvantages.

For example, die-cast products have advantages over cast products, such as higher productivity, better dimensional accuracy, less post-processing, smoother casting surfaces, and the ability to cast thinner walls, but they are extremely difficult to weld. It has the disadvantage of being

That is, since die casting involves flowing welding material into the mold cavity at high speed and high pressure, air intrudes into the molten metal during the transition period of the inflow, which causes the formation of blowholes. Other causes include the gas generated from the mold release agent, but the main cause is the air entrainment mentioned above, most of which is scattered in a minute state that cannot be seen with the naked eye or a microscope. Its internal pressure has also become extremely high.

The above-mentioned blowholes generally occur in light alloy die-cast products, but they also occur in aluminum alloy die-cast products, and unique problems occur when performing inert gas arc welding on such products. do. In other words, the aluminum base metal is melted to a considerable depth by the arc, and at this time, high-pressure microbubbles are heated, aggregated, and then rapidly released, resulting in blowholes due to bubble bursting at the weld bead. This may occur, or beads that should run smoothly may break.
When such a phenomenon occurs at a pipe joint or a welded part of a container lid, the airtightness of the welded part is impaired, resulting in weld defects in cases such as pressure vessels and inflow pipes.

Furthermore, such bubble bursting disturbs the flow of the shielding gas, making the original shielding function insufficient and causing abnormalities in the shape of the arc itself, making it difficult to obtain a uniform and good bead. There is a problem that I want to do.

On the other hand, aluminum alloy cast products have disadvantages such as lower productivity and poor dimensional accuracy compared to die-cast products, but on the other hand, they have the advantage of not containing high-pressure microbubbles like die-cast products and are easy to weld. are doing.

[Problems to be Solved by the Invention] The present inventors took advantage of the respective advantages of aluminum alloy die-cast products and cast products to produce die-cast members and cast members, and welded and joined them to each other. I tried.

However, even when attempting to weld a die-cast member and a cast member, it has not been possible to successfully weld and join these two members due to the aforementioned poor weldability of the die-cast member.

However, as a result of further intensive research into the welding of the two members, the present inventors have discovered a welding joint shape that can suppress the generation of blowholes due to the opening of microscopic bubbles in the die-casting member, and the positional relationship between this and the welding arc. They discovered this and completed the present invention.

[Means for Solving the Problems] That is, the present invention provides a method for joining a die-cast aluminum alloy member B to a cast aluminum alloy member A by inert gas arc welding. The welding part B is gradually thinned toward its tip to form an inclined surface, and the tip has a cross-sectional shape cut off almost perpendicularly with respect to the mating surface of the two members, and The angle (α) formed by the inclined surface is 30 to 60 degrees, the height H of the almost vertically cut tip surface is 1.0 to 2.0 mm, and the welding torch is connected to the tip surface of the member A and the welding torch. Aluminum is welded by directing the welding arc toward the surface of the member A slightly away from the end surface of the member B while moving the aluminum while holding it so that the parallel distance D between the electrode and the electrode is 1.5 mm or less. The present invention relates to a method for welding an aluminum alloy die-cast member to an alloy cast member.

[Function] By making the shape of the welding part of the aluminum alloy die-casting member to be welded to the aluminum alloy casting member into a specific shape as described above to reduce the heat capacity of the welding part, the side of the casting member is reduced. Even if the amount of penetration is sufficiently increased, the portion of the die-cast member can be selectively melted with a small amount of heat input, thereby welding with a reduced amount of penetration on the side of the die-cast member. As a result, the occurrence of blowholes is suppressed and a defect-free welded part with high airtightness is obtained.

[Example] The welding method of the present invention is applied to inert gas arc welding of an aluminum alloy die-cast member and an aluminum alloy cast member. Here, the aluminum alloy cast members refer to gravity cast products and low pressure cast products. In addition, inert gas arc welding includes MIG (Metal Inert Gas) welding,
Examples include TIG (Tungsten Inert Gas) welding using filler metal, but it is particularly preferably applied to MIG welding.

Next, the present invention will be explained using an example in which a cooling water passage cover plate made of die-cast aluminum alloy is welded to a main body made of cast aluminum alloy by MIG welding in an intake manifold of an internal combustion engine.

Figure 1 is a plan view of the intake manifold, Figure 2 is a plan view of the intake manifold.
3 is a sectional view taken along the line A-A in FIG. 1, FIG. 4 is a partially enlarged bottom view of the intake manifold, FIG. 5 is an enlarged plan view of the cooling water passage cover plate, and FIG. The figure is a sectional view taken along the line B--B in FIG. 5, and FIG. 7 shows a state in which the cover plate is attached to the intake manifold for welding.

In the drawings, 1 is an intake manifold body made of aluminum alloy casting. A mounting seat 2 for the carburetor is formed on the top surface of the main body 1.
An air-fuel mixture collecting section 3 communicating with the carburetor and three branch passages 4, 5, and 6 extending from the collecting section 3 toward the intake ports of each cylinder of the internal combustion engine are provided inside. 7 is a flange for attaching the main body 1 to an internal combustion engine.

A substantially cylindrical peripheral wall 8 is integrally provided on the lower surface of the main body 1 at a portion corresponding to the lower part of the gathering portion 3, and the lower surface of the peripheral wall 8 constitutes a mating surface 9 with a cover plate described later. are doing. The inside of the peripheral wall 8 constitutes a housing 10 which is open at the bottom, and has an inlet opening into which cooling water from the cooling water jacket of the internal combustion engine flows. A baffle wall 12 is provided in the housing 10 to protrude in order to form a zigzag flow path for the cooling water.

Reference numeral 20 denotes a cover plate made of die-cast aluminum alloy for closing the housing 10, and is made slightly smaller than the outer circumference of the peripheral wall 8 of the main body 1.

The outer circumference of the cover plate 20 has a rising shape, and the upper surface of the rising part is connected to the main body 1.
It constitutes a mating surface 21 with. The cover plate 20 has a baffle wall 2 corresponding to the baffle wall 12 of the main body 1.
2 is provided, and an outlet pipe 23 for draining the cooling water that has flowed into the housing 10 is also integrally provided.

Note that positioning pieces 13 and 14 are integrally formed on the inner peripheral surface of the peripheral wall 8 of the main body 1 at opposing positions, and on the other hand, the cover plate 20 has positioning pieces 13 and 14 that correspond to the positioning pieces 13 and 14 of the main body 1. A pair of protruding pieces 24a and 24b, and 2
5a and 25b are integrally formed. Then, when fitting the cover plate 20 to the main body 1,
By fitting the positioning piece 13 between a pair of protrusions 24a and 24b and the positioning piece 14 between the other pair of protrusions 25a and 25b, the cover plate 20 is positioned on the main body 1. be done.

The main body 1 is a cast product, and the cover plate 2
Since the main body 1 is a die-cast product, in particular, the dimensions and positional accuracy of the positioning pieces 13 and 14 of the main body 1 are not high, so it is difficult to perform accurate positioning using only the positioning means using the above-mentioned fitting method. Therefore, more accurate positioning is also used. That is, a pair of cylindrical bosses 26a and 26b are integrally provided on the lower surface of the cover plate 20 (this surface becomes the upper surface during welding), and after positioning the cover plate 20 on the main body 1 using the temporary positioning means. The accuracy of the cover plate 20 is maintained by fitting a pair of clamp pins that are accurately positioned with respect to a preset moving trajectory of the welding wire into the boss holes of the bosses 26a and 26b of the cover plate 20. positioning.

Next, the shape of the welded joint, which is a feature of the present invention, will be explained in detail.

In the embodiment described above, the cover plate 20 is fitted to the main body 1 as shown in FIG. 7, and the entire outer circumference of the cover plate 20 is MIG-welded to the main body 1.

FIG. 8 is an enlarged sectional view of the welded portion (for example, an enlarged partial sectional view taken along the line CC in FIG. 7). 8th
As shown in the figure, the welding part of the cover plate 20 made of aluminum alloy die-casting which is overlapped with the mating surface 9 of the main body 1 made of aluminum alloy casting is gradually thinned toward the tip, and the tip is The mating surface 9 has a cross-sectional shape cut off almost vertically. During welding, the welding wire 31 of the MIG torch 30 moves on a surface connected to the mating surface 9 of the main body 1, which is slightly away from the tip surface 27 of the cover plate 20.

Next, a specific example of MIG welding is shown.

The height H of the tip surface 27 of the cover plate 20 is
1.5mm, the angle α between the inclined surface 28 and the mating surface 9 is 45
degree, the parallel distance D between the tip surface 27 and the welding wire 31
was set to 1.0mm. As the cover plate 20
ADC12 (JIS H5302) equivalent product, Cu2.3%,
Si9.6%, Mg0.29%, Zn0.65%, Fe0.75%,
An aluminum alloy with a chemical composition of 0.27% Mn, 0.06% Mi, 0.1% Sn, and the balance Al was die-cast and had a specific gravity of 2.73. The main body 1 is equivalent to AC4B (JIS H5202).
Cu2.2%, Si8.9%, Mg0.45%, Zn0.63%, Fe0.73
%, Mn 0.30%, and the balance aluminum was low-pressure cast.

The conditions for MIG welding are as follows.

Arc current: 130A Arc voltage: 16V Arc pulse: None Welding wire diameter: 1.2mm Shielding gas: 100% Ar Flow rate 25/min Torch movement speed (average): 70cm/min The wire material is A5356 (JIS Z3232)
Equivalent products: Si0.06%, Mg5.03%, Fe0.09%,
A chemical composition consisting of 0.12% Mn, 0.08% Ti, 0.10% Cr, a trace amount of Cu, a trace amount of Zn, and the balance Al was used.

Figure 9 shows a photographic sketch of the cross section of the welded part obtained by MIG welding under the above conditions. As shown in FIG. 9, no blowholes were observed in the weld bead 40. For the 50 products obtained, an airtightness test was conducted underwater by applying an air pressure of 2 kg/cm ² inside the housing 10.
I passed all the exams.

When using the welded joint shape of the present invention, a welded part with high airtightness is obtained without defects such as blowholes as described above.The reason is as follows.
10th to 12th diagrams schematically showing changing states of local welding parts
This will be explained based on the diagram. In the present invention,
The welding wire 31 of the MIG torch 30 is connected to the main body 1 slightly apart from the tip surface 27 of the cover plate 20.
The first
As shown in Figure 0, at the initial stage of heating any welding part, only the surface of the main body 1, which is a cast member, is melted to form a molten pool 41, and the cover plate 20, which is a die-cast member, is not yet melted. Not yet. As the heating progresses, as shown in FIG. 11, the amount of penetration of the main body 1 increases and the molten pool becomes deeper, but the tip of the cover plate 20 melts only slightly. As the heating progresses further, as shown in FIG. 12, the cover plate 20 is also melted due to a portion of the sufficient amount of heat input to the main body 1, but as described above, the cover plate 20 is melted in the distal direction. Since the wall is gradually made thinner, the thin wall portion is selectively melted with a small amount of heat input, and the amount of penetration is kept to a small amount. In this way, the main body 1 and the cover plate 20 are penetrated, and by supplying metal from the welding wire, a welded part as shown in FIG. 9 is finally obtained.

In the present invention, as described above, it is desirable to sufficiently increase the amount of penetration of the cast member, while minimizing the amount of penetration of the die-cast member containing bubbles to the extent that it does not impair the fusion and integration of both members. I can do it,
Therefore, the occurrence of blowholes is reduced as much as possible, and a welded part with high airtightness can be obtained.

In the case of a welded joint shape in which the above-mentioned consideration is not taken in the present invention, for example, the welded joint shape shown in FIGS. 15 to 18, the cast member 10
0 and the die-cast member 101, it is necessary to increase the amount of heat input and the amount of penetration into the die-cast member 101, which will cause blowholes to occur. There will be more.

In the welded joint shape of the present invention, the inclination angle (α) of the die-cast member, the height H of the tip surface 27,
The distance D between the tip surface 27 and the welding wire 31, etc.
It depends on the MIG welding conditions, etc., and it is difficult to determine it unambiguously, so it is preferable to determine it experimentally. To achieve the effect of suppressing the occurrence of blowholes as much as possible and obtaining a highly airtight welded part by minimizing the amount of penetration of die-cast parts without impairing the fusion and integration of both parts. are selected from the following ranges:

Inclination angle (α): 30 to 60 degrees Height of tip surface H: 1.0 to 2.0 mm Distance D: 1.5 mm or less Note that the inclined surface 28 of the die-cast member 20 does not have to be flat, and may be somewhat convex. It may also be concave. Further, the tip end surface 27 does not necessarily have to be perpendicular to the mating surface of both members, and may be slightly inclined from the perpendicularity.

There is no particular restriction on the material of the cast aluminum alloy member used in the present invention, and the above-mentioned
In addition to AC4B, AC2A, AC2B, AC3A,
AC4A, AC4C, AC4D, etc. are used.

In addition, there are no particular restrictions on the material of the aluminum alloy die-casting member, and in addition to the above-mentioned ADC12,
ADC1, ADC10, etc. are used. Note that the specific gravity of aluminum alloy die-cast products varies over a wide range depending on the bubble content, but in the present invention, even die-cast products with a relatively high bubble content in the range of 2.69 to 2.73 can be used without any problems. can do.

In addition to the above-mentioned A5356, there are also welding wires available.
A4063, A5556, A5654, A5183, etc. are used. In addition to 100% Ar as a shielding gas, 85
Normal such as %Ar + 15% He, 98% Ar + 2% _O2
MIX welding shielding gas is used in both cases.

In the present invention, as described above, the intake manifold body 1 is made of aluminum alloy casting.
When creating an airtight structure by welding a cover plate 20 made of aluminum alloy die-casting to a metal plate, it has been found that a more complete airtight mechanism can be achieved by placing the welding start and end points at specific locations. Served.

FIG. 19 is a cross-sectional view of the case where welding is started from an arbitrary point P on the peripheral wall 8 of the main body 1 in FIG. Since the main body 1 at point P is cold, the amount of penetration of the main body 1 is too small, making it difficult to achieve good fusion between the main body 1 and the cover plate 20, and leakage is likely to occur at this portion. If you try to increase the penetration amount of main body 1, cover plate 2
The amount of heat input to 0 increases, making blowholes more likely to occur.

Therefore, as shown in FIG. 20, the inventors increased the wall thickness of the peripheral wall 8 at the welding start point (end point), and moved a point Q away from the outer peripheral edge of the cover plate 20 to the welding start point (end point). ), but in this case, although the body 1 at the welding area is preheated to some extent by the heat generated during the formation of the sacrificial bead 50, the body 1 at the welding area
Since the heat capacity itself is increasing, the amount of penetration of the main body 1 at the welding site is still small.

As a result of intensive research in view of the above points, we have found that when MIG welding an aluminum alloy die-cast member to an aluminum alloy cast member, the welding start and end parts (hereinafter referred to as welding start and end parts)
The above problem can be solved by setting the groove on the side of the cast aluminum alloy member and away from the welding area of both members, and by providing a groove between the welding start/end part and the welding area. It was found that

FIG. 13 is a cross-sectional view showing an example of the embodiment, and corresponds to the partial cross-sectional view taken along the line DD in FIG. 7. In this embodiment, a boss 15 is used as a welding start and end point for a harness clamp provided on the intake manifold body 1, and a groove 16 is formed between the boss 15 and the peripheral wall 8. By providing this groove 16,
A corner 17 with a small heat capacity is formed between the groove 16 and the tip of the cover plate 20.

To explain how to perform MIG welding when such a welding start and end part is provided separately, as shown in FIG. The torch 30 is advanced toward the tip of the cover plate 20. When the torch 30 crosses the groove 16, the corner 17 of the main body 1 is heated, but since this part has a small heat capacity and melts with a relatively small amount of heat input, the amount of heat input to the cover plate 20 is maintained at an appropriate amount. At the same time, penetration of the main body 1 can be ensured, and airtightness at this part is ensured.

Then, the MIG torch 30 is moved around the outer periphery of the cover plate 20 once while forming a welding bead 40, and then crosses the groove 16 again to finish welding near the starting point Q on the boss 15.

In the present invention, the cross-sectional shape of the groove 16 is not particularly limited as long as the corner portion 17 with a small heat capacity is formed, and can take various shapes such as a U-shape, a V-shape, a semicircular shape, and a square shape. be. Groove 1
The depth of the cover plate 20 varies depending on how the cross-sectional area of the corner portion 17 (which approximately determines the amount of penetration of the main body 1) is determined.
If the dimensions are as in the above-mentioned embodiment, a suitable value is about 3 to 5 mm.

In the embodiment described above, the boss 15 was used as the welding start/end part, but a dedicated one may be provided separately. In that case, the surface of the welding start/end part is body 1.
It is preferable to make the welding surface substantially flush with the mating surface of the cover plate 20 from the viewpoint of easy welding operation.

In addition, it is necessary to provide the welding start and end portions at locations that do not affect airtightness. For example, it is necessary to provide the welding start and end portions at locations where the welding start and end portions are the surface of the cover plate 20. This is not preferable because a blowhole will occur and the airtightness of the area will be reduced accordingly.

The present invention has been described above using an example in which a cooling water passage cover plate, which is a die-cast aluminum alloy member, is MIG-welded to an intake manifold body, which is a cast aluminum alloy member, but the present invention is not limited to such an example. It is suitable for use in cases where both parts are MIG or TIG welded to create an airtight structure (for example, various types of closed containers, tube bodies through which fluids flow, etc.).

[Effects of the Invention] By setting the joint shape to the above-mentioned specific shape when inert gas arc welding an aluminum alloy casting member and an aluminum alloy die casting member, blowing due to the release of high pressure air bubbles contained in the die casting member can be achieved. The occurrence of holes is reduced as much as possible, and a welded part with high airtightness is obtained.

[Brief explanation of drawings]

FIG. 1 is a plan view showing an example of an intake manifold to which the present invention is applied, FIG. 2 is a front view thereof,
3 is a sectional view taken along the line A-A in FIG. 1, FIG. 4 is a partially enlarged bottom view of the intake manifold, FIG. 5 is an enlarged plan view of the cooling water passage cover plate, and FIG. 7 is a plan view showing a state in which the cover plate is fitted to the intake manifold, FIG. 8 is an enlarged partial sectional view taken along line C-C of FIG. 7, and FIG. 10 to 12 are sectional views showing the welding state of the welded part, FIG. 13 is a sectional view showing another embodiment of the present invention, and FIG. 14 is the same as that of FIG. 13. 15 to 18 are cross-sectional views showing examples of welded joint shapes outside the scope of the present invention, and Figures 19 to 20 are cross-sectional views showing welded joint shapes outside the scope of the present invention, respectively. FIG. 7 is a cross-sectional view showing yet another example. (Main symbols in the drawing), 1: Intake manifold body made of aluminum alloy casting, 20: Cover plate made of aluminum alloy die casting, 30:
MIG torch, 31: welding wire, 40: welding bead.

Claims (1)

[Claims] 1. When joining aluminum alloy die-cast member B to aluminum alloy die-cast member A by inert gas arc welding, the welding area of member B that is superimposed on the surface of the welding area of member A,
A sloping surface is formed with a gradually thinner wall toward the tip, and the tip has a cross-sectional shape cut off almost perpendicularly to the mating surface of the two members,
And the angle (α) between the mating surface and the inclined surface is
30 to 60 degrees, the height H of the nearly vertically cut off tip surface is 1.0 to 2.0 mm, and the welding torch is set at a parallel distance D between the tip surface of the member A and the electrode of the welding torch.
The welding arc is directed toward the surface of member A slightly distant from the tip surface of member B while holding and moving the aluminum alloy so that the tip surface is 1.5 mm or less. A method of welding alloy die-cast parts.