JPH0216190B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of welding a wrought aluminum member to an aluminum die-cast member, and is particularly intended to enable airtight attachment by MIG (Metal Inert Gas) welding. Since die casting involves flowing the molten metal into the mold cavity at high speed and high pressure, air enters 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 aforementioned air entrainment, 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 cavities described above commonly occur in light alloy die-castings, but they also occur in aluminum die-casting parts, and there are unique problems when performing MIG welding on such areas. occurs. In other words, the aluminum base metal is melted to a considerable depth by the arc from the welding wire, and at this time, high-pressure microbubbles are heated and aggregated and then rapidly released, causing bubbles to form in the weld bead. Blowholes may occur due to rupture, 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 pressure vessels and flow pipes. Furthermore, such bursting of bubbles disturbs the flow of the shielding gas, making the original shielding function insufficient and causing irregularities in the shape of the arc itself, making it impossible to obtain uniform, high-quality beads. It becomes a problem. This invention was devised in view of the above-mentioned problems, and achieves proper airtight installation by organically combining the following points. (1) The gas content in the MIG welding area of aluminum die-cast parts should be reduced as much as possible to maintain base material quality suitable for MIG welding. (2) The material of the mating member to be welded to the aluminum die-casting member is a wrought aluminum material, which has good compatibility with the aluminum die-casting member. (3) We created a unique joint structure between die-cast aluminum parts and wrought aluminum parts, and optimized the movement points of the welding wire to create special phenomena in the heating distribution and melting zone. thing. This invention provides a method for attaching a lid plate made of wrought aluminum to a die-cast aluminum container when MIG welding a pipe made of wrought aluminum to a pipe member made of die-cast aluminum.
It can be applied to various things such as MIG welding. The embodiment described below corresponds to the latter case, and is a surge tank for an intake system of an internal combustion engine, which will be explained with reference to FIGS. 1 to 4. The surge tank 1 is made by MIG welding a cover plate 3 made of expanded aluminum to a tank body 2 made of die-cast aluminum, and welding is performed by bringing a MIG torch 4 close to the position shown in Figure 3. , a weld bead 5 as shown in FIG. 2 is formed. When the cover plate 3 is aligned with the tank body 2, the positional relationship between the two must be set to a predetermined relationship as described later.
A stepped portion 6 is provided as shown in the figure. Figure 4 shows the step 6.
This is a case where the support protrusion 7 is provided on the inner surface of the tank body 2 instead. An inlet pipe 8 is integrally formed in the tank body 2, and an outlet hole 9 is formed in the cover plate 3, and intake pipes 10 and 11 are connected to each of the outlet holes 9. The dimensions of surge tank 1 are 210mm wide and 180mm tall.
The depth is 55 mm, the tank body 2 has a wall thickness of 4.5 mm, and the cover plate 3 has a wall thickness of 4 mm. Moreover, FIG. 5 is an enlarged cross-sectional view of the welding local area, and the dimensions of each part are a=
4.5mm, b=4mm, c=3mm, d=1mm, e=8
mm, f=7 mm. The reason why we set e = 8 mm and f = 7 mm and formed the part indicated by reference numeral 12 in the thick part is to set a large thermal mass in this part and reduce the amount of melting on the die-casting member side. be. The problem of gas contained in the aluminum die-casting base material is as described above, but the gas content in the local area where welding is performed must be minimized as much as possible. In this specification, the gas content, that is, the degree of cavities and bubbles, is expressed by the specific gravity of the die-casting base material. According to the inventors' studies, ordinary die-casting, rather than methods such as oxygen-atmosphere die-casting, can be applied to products that require high quality in terms of strength and rigidity, such as automobile clutch housings and transmission cases. The specific gravity is between 2.70 and 2.73, and it has been found that the negative effects caused by bubble bursting cannot be eliminated if the specific gravity is around this level. specific gravity
If it is 2.73, a considerable number of qualified products can be obtained, but from the standpoint of mass production economics, the passing rate is still insufficient. In order to make the specific gravity of the welding local part, that is, the thick part indicated by the reference numeral 12 in FIG.
The casting method shown in Figs. and 7 was adopted. FIG. 6 is a longitudinal cross-sectional view schematically showing a commonly used die casting mold, including a movable die main mold 13, a movable die insert 14, and a fixed die main mold 1.
5. It is mainly composed of a fixed die insert 16, and both inserts 14 and 16 form a cavity 17, a runner 18, a pool 19, a gas vent passage 20, etc. of the tank body. A large number of extrusion pins 21
extends toward a portion corresponding to the thick wall portion 12 of the article, and a drive means 24 is connected to the support plates 22, 23 thereof. As a means, easy
Various mechanisms have been adopted, such as a pinion mechanism, hydraulic drive system, and movable die interlocking system, but the one shown is a hydraulic cylinder drive rod. In addition,
In the figure, 25 is a guide sleeve, 26 is a spout, and 27
is a plunger. In order to increase the specific gravity of the thick walled portion 12, the ventilation functions of the well-known hot water pool 19 and extrusion pin 21 are combined in a special manner as shown in FIG. 7, so that a high specific gravity can be obtained. That is, a large number of tundish pools 19 are arranged at as short intervals as possible, and the intermediate portions of the tundish pools 19 are made to correspond to the extrusion pins 21. By doing this, the air in the cavity 17 is discharged through the hot water pool 19 and the gas venting passage 20, and the movable die main mold 1 is discharged from the sliding gap of the extrusion pin 21.
It is also discharged to the right side of 3. The thick part 12 has a hot water pool 19 arranged at short intervals and an extrusion pin 21 in the middle thereof.
Since the air is discharged uniformly over the entire length of the thick wall, the amount of trapped air bubbles is significantly reduced. The specific gravity obtained in this way is in the range of 2.74 to 2.85, but under normal production management conditions,
It is 2.78-2.80. The aluminum alloy used for tank body 2 is
ADC12 (JIS H5302) with aluminum casting scraps added, Cu2.37%, Si9.7%, Mg0.22%, Zn0.7%,
Fe0.70%, Mn0.23%, Ni0.06%, Sn0.10%
(each % by weight), in the case of the chemical component with the balance being Al,
While the specific gravity was 2.92 in the defect-free state without containing gas, the specific gravity in the thick portion 12 was 2.80. This result means that the specific gravity has been significantly increased when referring to the case of the clutch housing described above. In addition, the tank body 2 was heated to 500℃.
When heated in a furnace for hours, approximately 3 to 5 blisters were observed in the bottom plate portion 28 (see Fig. 7), but no blisters were generated in the thick wall portion 12, and there were almost no bubbles or Even if there is heat, it is judged to be extremely minute. As mentioned above, the state of the gas in the aluminum die-casting material is so minute that it can hardly be called a bubble, but as a method of numerically evaluating it, it is evaluated here using the specific gravity value. It is now contained in a 1 cm ³ aluminum base material. If the gas is reduced and the weight is increased by 0.01 to 0.03 grams, that is a significant reduction in the amount of gas contained. From this point of view, the above-mentioned improvement in specific gravity is not noticeable numerically, but it is actually an important factor. Note that the specific gravity was measured by immersing the die-cast piece in a specific gravity measurement solution prepared in advance. Next, to explain the joint shape of the local welding part, when the cover plate 3 is aligned as shown in FIG. The positional relationship between the two is set so as to be close to the MIG torch 31 side. Therefore, a height difference of g=1 mm is provided. Although the MIG torch 31 in FIG. 5 is in a position away from the item, its welding wire 32
As is clear from the weld bead 5 in FIG. 2, the trajectory was set so that it moved on the surface 29 near and along the outer periphery of the cover plate 3. The position of this trajectory changes slightly depending on various conditions, but in this example, h=1 mm. The surge tank is set in such a manner that the local part of the weld is in a horizontal state. The conditions for MIG welding in this example are as follows. Arc current 120A Arc voltage 20V Arc pulse 60 cycles Wire Diameter 1.2mm Material JIS A4043 shielding gas flow rate 20/min Torch movement speed (average) 60cm/min The above specifications are very normal, and the shielding gas is also 100% Ar, 85% Ar + 15% He or 98%
A very common gas such as Ar + 2% O ₂ may be used.
In addition, examples of wire materials include Cu0.8%, Si5.0
%, Mg0.05%, Zn0.10%, Fe0.8%, Mn0.05%,
Ti0.20% (each % by weight), balance Al, JIS Z3232
It is equivalent to A4043 in . As mentioned above, the cover plate 3 is made of aluminum wrought material, and its chemical composition is Cu0.05%, Si0.25%,
Mg0.05%, Zn0.05%, Fe0.40%, Mn0.05%,
Al99.50% or more (each % by weight), equivalent to A1050P in JIS H4000. The state of change in the welding local area will be explained with reference to FIGS. 8 to 10. At the initial stage of melting as shown in FIG. 8, the molten pool is a relatively narrow region and the amount of metal melted is small. What is particularly noteworthy is that since the movement locus of the welding wire 32 is at a position as shown in FIG.
remains within the range. As the melting progresses further and the molten pool 33 becomes wider and deeper, the amount of molten metal also increases as shown in FIG. in this case,
Since the surface 29 of the cover plate is closer to the MIG torch side than the surface 30 of the thick portion, the water flows down to the lower surface 30 and partially covers the surface 30. In this state, since the amount of heat directed toward the thick portion 12 is small, the surface 30 has not yet reached the level of melting. As such welding action further progresses, the surface 30 side also melts as shown in FIG. 10, metal is also supplied from the welding wire, and it gradually solidifies into a cross-sectional shape as shown in the same figure. Figures 8 to 10 are shown for ease of understanding.
Although shown simply and exaggeratedly, when the cross section of the welded portion is observed in FIG. 11, the joining form as shown in FIG. 10 is basically recognized. According to the present invention, a height difference is provided between the surfaces of both parts at the welding local area, and the welding wire is installed and moved on the aluminum wrought material side.
Dissolution begins smoothly from the side of the expanded material that does not contain air bubbles.
Sufficient melting heat will be input to the wrought material side. As a result, the wrought material, which has increased fluidity, flows down toward the lower die-casting material and melts a portion of the die-casting material, but since the welding wire is positioned as described above, The amount of heat transferred to the die-casting material side is relatively small, so the amount of melting on the die-casting side is kept to a small amount. Due to this small amount of dissolution and high specific gravity, even if bubble bursting occurs, it will be extremely small and will not cause any disturbance in the shielding gas or impede the stability of the arc. Furthermore, even if a blowhole occurs due to bubble bursting, the wrought material and welding wire, which have received sufficient melting heat and do not contain bubbles, will flow down with good fluidity and form the blowhole. It plays the role of filling in small cavities and crevices, ultimately resulting in a highly airtight weld. As described above, the present invention includes installing a member made of wrought aluminum material at a higher position, setting the movement locus position of the welding wire on the side of the wrought aluminum material,
The aim is to preferentially melt a large amount of aluminum wrought material that does not contain air bubbles to create a flow phenomenon, to minimize the amount of melting on the die-casting material side, and as an important preliminary step, to reduce the specific gravity of the die-casting material. Various factors such as keeping it high are compounded,
Good welding of both parts was achieved. 2 that does not seem to have been given the same consideration as the present invention.
Fillet welding (MIG welding) on two aluminum die-cast plates
12 and 13 show the cases in which this was done. According to this, it is clearly observed that gases scattered in the die-cast plate melt and aggregate to form visible bubbles, which then burst or expand to form large spaces and solidify. . When compared with FIG. 11 according to the present invention, the difference between the two is very obvious. In addition, when we conducted an underwater inspection by applying an air pressure of 1 kg/cm ² to the obtained surjinks, we found that 3% of the tanks had poor airtightness at the weld bead, and the defective state could easily be repaired by repair welding. It was as good as possible. Furthermore, if the position of the MIG torch is set so that the dimension h is zero in FIG. 5, the amount of melting on the die-casting material side will be excessive, which is inappropriate for minimizing the influence of gas. Also,
If the dimension g becomes zero, it is impossible to obtain a falling phenomenon of a high quality aluminum wrought material, which is not favorable for the surface smoothness of the bead. The results of testing by changing each of these specifications are shown in the table below. In the table, the ○ mark indicates a passing product, the △ mark indicates a passing grade but the defective rate is too high, and the × mark indicates a rejected product.

[Table] According to the present invention, as explained above, due to the organic composite action of each constituent factor, MIG of an aluminum die-cast member and a wrought aluminum member is achieved with high airtightness. Welding can be achieved satisfactorily, and it can be put to practical use in a wide range of product fields including tubular bodies and other products, including the container-shaped articles of the embodiment.

[Brief explanation of drawings]

1 to 11 show embodiments of the present invention. FIG. 1 is a side view of the surge tank, FIG. 2 is a plan view of the surge tank, and FIGS. 3 is a sectional view, FIG. 5 is an enlarged sectional view of the welding area, FIG. 6 is a simplified longitudinal sectional view of the die-casting mold, and FIG. 7 is a partial plan view showing the tank body taken out from the mold. Figures 8 to 10 are cross-sectional views showing the melting process of the weld local area, Figure 11 is a cross-sectional view showing a good welding state, and Figure 12 is an external view of a defective weld bead.
FIG. 13 is a cross-sectional view of that of FIG. 12. 2... Parts made of aluminum die-casting, 3... Parts made of wrought aluminum material, 29... Surface of parts made of wrought material, 3
0...Surface of die-cast parts, 31...MIG
Torch, 32...Welding wire.

Claims (1)

[Claims] 1 Aluminum die-casting parts at least
The MIG welding area is cast in such a way that the gas content is reduced, and a wrought aluminum member is matched to the MIG welding area, and the positional relationship between the two is such that the surface of the wrought aluminum member is lower than the surface of the die-casting member. The welding wire from the MIG torch is moved near the outer periphery of the wrought material member and on the surface side of the wrought material member. A method of welding parts made of wrought timber.