JP2010099672A - Method of joining different kind of metal between casting product and sheet, and joining structure of different kind of metal thereby - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of joining different kinds of metal between a casting product and a sheet, a method in which discharge of an eutectic melting reaction product from a joining boundary can be enhanced, even if pressurization is insufficient during the joining, so that a sound joined part can be obtained, in joining by using eutectic fusion a casting member which has a rib with pressurization possible only from one side and a planar member which is composed of a material different from the casting member. <P>SOLUTION: On the non-rib side of the casting member C comprising aluminum alloy and having ribs R, a galvanized steel sheet 1 as the planar member is piled up, with pressurization and energization performed by an electrode E from the side of the steel sheet 1 for resistance spot welding of the two members. In this welding, eutectic fusion is produced between the zinc contained in the galvanization layer 1p of the steel sheet 1 and aluminum, and the reaction product W produced on the joining boundary with the eutectic fusion is discharged into the recesses R which are formed on the reverse side of the ribs of the casting member C because of shrinks during the casting. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method of joining a cast member having ribs and a plate-like member made of a metal different from the cast member, and a dissimilar metal joining structure of a cast material and a plate material obtained by such a joining method. is there.

In recent years, automotive body components have been changed from conventional iron (cast) and steel members to light alloy members such as aluminum alloys and magnesium alloys as part of measures to improve fuel efficiency with a view to preventing pollution of the global environment. The weight of the car body has been reduced by the replacement.
Therefore, in the vehicle body assembly process, the joining frequency of such light alloy members and steel members is increased, and from the viewpoint of avoiding further increase in weight, different metal members are used as fastening members such as bolts, nuts and rivets. There is an urgent need to establish a technique that allows direct bonding without any problems.

In such dissimilar metal bonding, since a dense and strong oxide film is formed on the surface of the aluminum alloy material, it is necessary to administer a large amount of heat at the time of bonding in order to remove it. A thick intermetallic compound grows, resulting in a decrease in bonding strength.
Further, a strong oxide film also exists on the surface of the magnesium alloy material, and further, an oxide film on the steel surface grows during the heating process at the time of bonding, so that bonding in the air becomes difficult. In addition, the Fe-Mg binary phase diagram is known to exhibit a two-phase separation type, and since the mutual solubility limit is very small, the above-mentioned materials mainly composed of these metals are directly bonded to each other. This is extremely difficult metallurgically.

  Therefore, when joining a material having such an oxide film and steel, for example, Zn (zinc) is interposed at the joint interface, and eutectic melting is caused between Al or Mg and Zn at the time of joining. There has been proposed a method of discharging from a bonding interface at a low temperature together with a crystal melt (for example, see Patent Document 1).

On the other hand, a member made of an aluminum alloy or a magnesium alloy is not only a wrought material but also a cast product. In the case of such a cast member, a rib is provided to ensure the rigidity of the member. Often a complex three-dimensional shape.
When welding a steel plate and a complicatedly shaped cast member made of such an aluminum alloy or magnesium alloy to the cast member, the unevenness due to ribs or the like cannot be inserted on the cast member side, so the electrodes cannot be inserted. A welding method (indirect method) in which the material is disposed on one side of the material to be joined must be employed.
WO2006 / 046608

  However, when the method described in Patent Document 1 is carried out by the indirect method, the applied pressure is insufficient as compared with a normal welding method in which pressure is applied from both sides. There is a problem in that it cannot be sufficiently discharged from the wastewater, and the strength is lowered by the remaining of these.

  This invention is made | formed in view of the said subject in the dissimilar metal joining of such a cast member and a plate-shaped member. And the purpose is to increase the discharge property of the eutectic melt reaction product from the bonding interface, and to obtain a sound bonded part even if the applied pressure during bonding is insufficient. Another object of the present invention is to provide a dissimilar metal joining method between a metal plate and a plate material and a high strength dissimilar metal joining structure.

  As a result of intensive investigations aimed at achieving the above object, the present inventors pay attention to the fact that a recess is formed on the back side of the rib of the cast member due to shrinkage during casting, and this recess is actively used. As a result, the inventors have found that the above problems can be solved, and have completed the present invention.

  That is, the present invention is based on the above knowledge, and the method for joining dissimilar metals between a casting and a plate material according to the present invention includes metal B as a main component on the opposite rib side of a cast member having metal A as a main component and ribs. When the two plate members are stacked and pressed from the plate member side to join the two members, heating is performed with a third material containing metal C interposed between the two members, and metal A And eutectic melting between at least one of B and metal C, and the reaction product generated along with the eutectic melting is formed in the recess formed on the back surface of the rib of the cast member due to shrinkage during casting. It is characterized by discharging.

  Moreover, the dissimilar metal joining structure of the casting and the plate material of the present invention is obtained by the above method, and the new surfaces of the cast member and the plate-like member are joined directly or via a compound layer containing an intermetallic compound, The reaction product produced along with the eutectic melting flows into a recess formed on the rear surface of the rib of the cast member.

  According to the present invention, the recess formed on the back surface of the rib of the cast member due to the shrinkage is positively utilized, and the eutectic melt reaction product including the oxide film is caused to flow into the recess during bonding. Even when the applied pressure at that time is low, the reaction product can be quickly discharged from the bonding interface, and a decrease in bonding strength due to remaining can be prevented.

  Below, the dissimilar metal joining method of the casting of this invention and a board | plate material, and the joining structure obtained by this are demonstrated still in detail and concretely. In the present specification, “%” represents mass percentage unless otherwise specified.

FIG. 1 is an overall view showing a resistance welding apparatus by an indirect method and its point as an example of heating / pressurizing means used for joining different kinds of metals according to the present invention, and FIG. FIG. 1 (b) shows a point of seam welding for joining in a linear manner with a roller electrode.
The joining means used in the joining method of the present invention is not limited to resistance welding as long as heating and pressurization can be performed. For example, an apparatus combining a laser beam irradiation head and a pressure roller is used. It is also possible to use a roller to press immediately after the laser beam irradiation position.

  That is, in the dissimilar metal joining of the present invention, as shown in FIG. 1, ribs R and R are formed on the casting member C side in order to ensure rigidity as a member. Thus, the electrode cannot be disposed on the casting member C side. Therefore, as shown in the drawing, both the electrodes E, E (in the case of seam welding, the roller electrodes Er, Er) are all arranged on the plate-like member P side, and both members are attached from the plate-like member P side. The indirect method of applying pressure is adopted.

  In the present invention, as described above, on the opposite side of the cast member (for example, made of an aluminum alloy containing Al as a main component) that includes the metal A as a main component and having a rib, a plate containing the metal B as a main component. A third member containing metal C (for example, Zn) between the two members when the two members are joined by pressing from the side of the plate-like member by stacking the member (for example, a steel plate mainly composed of Fe). A reaction product generated by eutectic melting by heating in the state of interposing the material, causing eutectic melting between at least one of metals A and B and metal C (for example, between Al and Zn). Is discharged into a recess formed on the rear surface of the rib of the cast member due to shrinkage during casting.

Here, “shrinkage” is also referred to as casting shrinkage, cast stagnation, etc., and is a type of casting defect that occurs in a portion where solidification is delayed from the surroundings, such as a crossing portion or a thick portion of the meat, due to shrinkage during solidification of the molten metal, In the present invention, the recess due to such a defect generated on the back side of the rib is effectively used as a means for improving the discharge of the reaction product.
In the present invention, the “main component” means a component that is contained most in the material.

Next, regarding eutectic melting, an Al—Zn alloy will be described based on the above-described material examples (metal A = Al, metal B = Fe (steel), metal C = Zn).
That is, FIG. 2 shows an Al—Zn binary phase diagram, and as shown in the figure, the eutectic point (T _E ) in the Al—Zn system is 655 K, which is higher than the melting point 933 K of Al. Eutectic reactions occur at much lower temperatures. Therefore, by using the eutectic points shown in the figure to create eutectic melting of Al and Zn, and using them for bonding actions such as oxide film removal and interdiffusion during bonding of aluminum materials, low temperature bonding can be performed. Therefore, the growth of the Fe—Al intermetallic compound at the bonding interface can be extremely effectively suppressed.

Here, eutectic melting is melting using a eutectic reaction, and when the composition of an interdiffusion region formed by mutual diffusion of two metals (or alloys) becomes a eutectic composition, the holding temperature If is higher than the eutectic temperature, a liquid phase is formed by the eutectic reaction. For example, in the case of aluminum and zinc, the melting point of aluminum is 933 K, the melting point of zinc is 692.5 K, and this eutectic metal melts at 655 K which is lower than the respective melting points.
Therefore, a reaction occurs when the clean surfaces of both metals are brought into contact and heated to 655K or higher. This is called eutectic melting, and Al-95% Zn has a eutectic composition, but the eutectic reaction itself is a constant change unrelated to the alloy components, and the alloy composition only increases or decreases the amount of eutectic reaction. Absent.

On the other hand, a strong oxide film is present on the surface of the aluminum material, which is physically destroyed by plastic deformation of the aluminum material caused by energization and pressurization during resistance welding.
That is, since microscopic convex portions on the surface of the material are rubbed with each other by pressurization, eutectic melting occurs from a portion where aluminum and zinc are in contact with each other due to local destruction of some oxide films. By the generation of the liquid phase, the nearby oxide film is crushed and decomposed, and further, eutectic melting spreads over the entire surface, thereby promoting the oxide film destruction and joining via the liquid phase.

  Since the eutectic composition is spontaneously achieved by interdiffusion, it is not necessary to control the composition. An indispensable condition is that a low melting eutectic reaction exists between two kinds of metals or alloys. In the case of eutectic melting of aluminum and zinc, for example, when using Zn-Al alloy instead of zinc. Must have a composition with at least 95% zinc.

Here, as means for interposing zinc between both members, for example, an insert material containing zinc can be inserted, or at least one member can be plated with a material containing zinc in advance, It is desirable to employ plating. As a result, the step of sandwiching the insert material can be omitted, the working efficiency is improved, and after the plating layer melted by the eutectic reaction is discharged together with the surface impurities to the periphery of the joint portion, from below the plating layer. An extremely clean new surface will appear and a stronger bond will be possible.
In this case, it is desirable to use a galvanized steel sheet provided with a galvanized layer. This makes it possible to use ordinary commercially available steel materials (for example, stipulated in JIS G 3302 and G 3313) that are galvanized for the purpose of preventing rust as they are, without any special preparation, and can be used very simply and inexpensively. .

FIGS. 3A to 3E are schematic views showing a joining process between the aluminum material and the steel material described above.
First, as shown in FIG. 3 (a), a galvanized steel sheet 1 and an aluminum alloy material 2 provided with a galvanized layer 1p are prepared on the surface, and as shown in FIG. The plated steel plate 1 and the aluminum alloy material 2 are overlapped so that the galvanized layer 1p is inside. At this time, an oxide film 2 f is formed on the surface of the aluminum alloy material 2.

  Next, in the case of pressurization and heating, for example, resistance welding, local contact at the microscopic contact portion of the material surface by pressurization by the electrode and heating by energization from the electrode as shown in FIG. The destruction of the typical oxide film 2c is caused.

As a result, local contact between zinc and aluminum occurs, and eutectic melting of zinc and aluminum occurs as shown in FIG. 3 (d) according to the temperature state at that time. The reaction product including 2f and impurities at the bonding interface becomes discharged W and is discharged to the outside of the bonded portion as indicated by an arrow.
Therefore, a predetermined bonding area is ensured, and as a result, as shown in FIG. 3E, the new surfaces of aluminum and steel are directly bonded to each other, and a strong metal bonding between the steel plate 1 and the aluminum alloy material 2 is obtained. become.

In the combination of the steel sheet and the aluminum alloy material 2 described above, the example in which Zn is used as the metal C interposed between the two materials has been described. However, as long as it is a metal that forms a low melting point eutectic with Al, it is particularly Zn. For example, Cu (copper), Sn (tin), Ag (silver), Ni (nickel), or the like can be used in addition to the above-described Zn.
That is, the eutectic metal of these metals and Al melts at a temperature below the melting point of the base aluminum alloy material, so that the oxide film can be removed at a low temperature, and a steel material that easily generates fragile intermetallic compounds. Even in the joining of aluminum alloy materials, the formation of intermetallic compounds is suppressed and strong joining is possible.

  4 (a) to 4 (c) show a resistance spot welding process by an indirect method (see FIG. 1 (a)) of an aluminum alloy cast member C according to the method of the present invention and a galvanized steel sheet 1 as a plate-like member. FIG.

As shown in FIG. 4 (a), the cast member C made of an aluminum alloy is provided with ribs R and R in the vicinity of both sides of the joining portion in order to ensure rigidity as the member, and these back surfaces. On the joint surface side, recesses D and D are formed by shrinkage due to solidification shrinkage during casting, respectively. Needless to say, a strong oxide film (not shown) is formed on the surface of the cast member C.
On the other hand, a galvanized layer 1p is formed on a galvanized steel sheet 1 as a plate-like member.

Next, as shown in FIG. 4 (b), the galvanized steel sheet 1 is overlaid on the opposite rib side of the cast member C, that is, on the surface where the recesses D and D are formed so that the galvanized layer 1p is on the inner side. Then, the electrode R is brought into contact with the galvanized steel sheet 1 and energization and pressurization are performed. At this time, the other electrode is in contact with the cast member C at a portion not shown in the figure, so that a current-carrying state with the galvanized steel sheet 1 is ensured.
As the resistance spot joining condition, it is not necessary to apply a special condition. Depending on the thickness of the galvanized steel sheet 1 and the thickness of the joint portion of the cast member C, the welding current is 10000 to 40000 A, and the energizing time is 50 msec. The pressure can be selected within a range of about 500 msec and a pressing force of about 50 to 1200 kgf.

  When the oxide film is destroyed by the pressurization and current heating by the electrodes and local contact between zinc and aluminum occurs, eutectic melting occurs as described above, and the oxide film and impurities at the joint interface coexist. Together with the crystal molten metal, the material becomes discharged W and is discharged from the joint, and both members are joined.

At this time, a gap is formed between the two members due to the recesses D and D formed on the back surfaces of the ribs R and R, and as shown in FIG. Since it flows into the inside, the discharge from the bonding interface becomes extremely smooth, and the waste W is prevented from remaining in the bonding portion.
Therefore, the new surfaces of the cast member C made of the steel plate 1 and the aluminum alloy are directly joined to each other, and strong dissimilar metal joining between the casting and the plate material is achieved.

In the present invention, as described above, the concave portion D formed on the back surface side of the rib R by shrinkage at the time of casting is used, and the rib R is not necessarily on both sides of the joining portion, but only on one side. Needless to say, it should be on both sides if possible. Further, if the distance from the joint portion of the rib R is too large, the discharge W will lose its fluidity due to a temperature drop before reaching the recess D, so it is desirable that the distance is as close as possible.
From this point of view, as long as the original function of the product is not hindered, the position of the joint is adjusted according to the rib position, or the position and number of the ribs R of the cast member C are changed according to the joint position. Design changes are possible.

  Further, in the present invention, the plate-like member is not necessarily limited to a wrought material by plastic working such as rolling or extrusion, and a flat surface that does not have an unevenness on the anti-joining surface side becomes an obstacle to the electrode. It may be a casting as long as it is a plate-shaped member.

FIG. 5 shows a resistance seam welding result by the indirect method (see FIG. 1B) of the similar cast member C and the galvanized steel sheet 1. The electrode E in FIG. 4C is a roller electrode Er. There is basically no change except that the electrode and both members are moved relative to each other and joined in a linear shape.
There is no need to apply special conditions for the resistance seam joining, and welding current is 10000 to 40000 A depending on the thickness of the galvanized steel sheet 1 and the thickness of the joint of the cast member C. It can be appropriately selected within a range of conditions of 50 to 1500 kgf and a joining speed of about 1 to 9 m / min.

Next, the joining of magnesium alloy material and steel material using the same eutectic melting (metal A = Mg, metal B = Fe (steel), metal C = Zn) will be described.
That is, FIG. 6 shows an Mg—Zn-based binary phase diagram. As shown in the figure, the Mg—Zn-based material has two eutectic points (Te1 and Te2), which are 341 ° C. and The eutectic reaction occurs at a temperature of 364 ° C., much lower than the melting point of magnesium, 650 ° C.

Therefore, if the eutectic point of Mg and Zn is created using the eutectic point shown in the figure and used to remove the oxide film during bonding, the magnesium oxide film that inhibits bonding can be formed at a low temperature by the same principle. It can be surely removed and the interface temperature at the time of bonding can be kept more uniform.
However, as described above, the Fe-Mg binary phase diagram shows a two-phase separation type, and since the mutual solubility limit is very small, it is extremely difficult to directly bond these metal-based materials. Therefore, it is necessary to add in advance to the bonding interface Al that forms an intermetallic compound with both metals.

FIGS. 7A to 7E are schematic process diagrams showing a joining process between a magnesium alloy material and a steel material (galvanized steel sheet).
First, as shown in FIG. 7 (a), a galvanized steel sheet 1 having a zinc-plated layer (third material) 1p containing zinc as a metal that forms a eutectic with Mg at least on the surface on the bonding interface side. A magnesium alloy material 2 is prepared.

  And as shown in FIG.7 (b), these galvanized steel plates 1 and the magnesium alloy material 5 are piled up so that the galvanized layer 1p may become an inner side. Note that an appropriate amount of Al (for example, about 6%) is added to the magnesium alloy material 5 in advance, and an oxide film 5f is formed on the surface. Note that Al can also be added to the third material. For this purpose, a Zn—Al alloy-plated steel sheet can be used instead of the galvanized steel sheet 1.

Next, as shown by arrows in FIG. 7B, in the case of heating and pressurization, for example, resistance welding, when the electrode pressurization and the plastic deformation due to current heating are applied, the oxide film 5f is formed. Locally destroyed.
When the oxide film 1f is broken in this way, local contact between Mg and Zn occurs, and when the oxide film 1f is maintained at a predetermined temperature state, as shown in FIG. A phase is generated, and the oxide film 5f on the surface of the magnesium alloy material 5 is effectively removed sequentially from the bonding interface.

  Then, as shown in FIG. 7 (d), the oxide film 5f and impurities at the bonding interface together with the eutectic liquid phase become discharge W and are discharged around the bonded portion by pressing. At this time, Mg is preferentially melted and discharged together with Zn by eutectic melting at the bonding interface. As a result, the Al component added in the magnesium alloy is left behind, and a relatively Al-rich phase is formed only at the bonding interface. Further, this Al atom reacts with Fe and Mg, and Al-Mg or Fe-Al A compound layer 6 containing the intermetallic compound is formed.

  Furthermore, when the joining time has elapsed, as shown in FIG. 7E, the Mg—Zn eutectic fusion reaction product formed at the interface is completely discharged. As a result, a compound layer 6 containing an Al—Mg-based and / or Fe—Al-based intermetallic compound is formed at the bonding interface, and mutual diffusion is possible even in the combination of magnesium alloy and steel that are difficult to metallurgically bond directly. Thus, the strong bonding between the galvanized steel sheet 1 and the magnesium alloy material 5 is completed.

  In the dissimilar metal bonding method of the present invention, when a magnesium alloy material and a steel material are bonded, it is necessary that Al be present at the bonding interface as described above. It is necessary to add Al to at least one of the three materials in advance.

Examples of magnesium alloy materials containing Al include ASTM (American Society for Testing and Materials) AZ31 (about 3% Al), AZ61 (about 6% Al), AZ81 (about 8% Al), AZ91 (about 9% Al). Al-Zn magnesium alloys such as AZ101 (about 10% Al) and Al-Mn magnesium alloys such as AM60 (about 6% Al) and AM100 (about 10% Al) are defined.
Therefore, by using these alloys as the magnesium alloy material, an Al-containing magnesium alloy material can be obtained at a low cost and applied to the present invention without preparing an alloy again.

  On the other hand, a plated steel sheet having a surface plated with a Zn—Al alloy is defined in JIS G 3317 (Zn-5% Al) and G 3321 (55% Al—Zn). It can also be used as, and can be applied to joining with a magnesium alloy containing no Al.

  8 (a) to 8 (c) show a resistance spot welding process by an indirect method (see FIG. 1 (a)) of a cast member C made of magnesium alloy according to the method of the present invention and a galvanized steel sheet 1 as a plate-like member. FIG.

  As shown in FIG. 8A, ribs R and R are similarly formed in the vicinity of both sides of the joining portion in the cast member C made of an Al-containing magnesium alloy, and the back side of these ribs R and R , Recesses D and D are formed by shrinkage during casting, respectively, and an oxide film (not shown) is provided on the surface thereof.

And as shown in FIG.8 (b), the galvanized steel plate 1 is similarly piled up on the anti-rib side surface of the casting member C, the electrode R is contact | abutted to the galvanized steel plate 1, and electricity supply and pressurization are started. .
In addition, when the cast member C is made of an alloy not containing Al, it is desirable to use a plated steel sheet plated with a Zn-Al alloy as the Al addition means.

When jointing dissimilar metals using eutectic melting, high strength cannot be obtained unless the reaction product at the joint interface is quickly and forcibly discharged between the aluminum alloy and steel, so the tip curvature is small. It is desirable to use an R-type electrode (for example, R50 or less when the plate thickness is 1.2 mm). On the other hand, in the joining of a magnesium alloy having a large specific resistance value and steel, the temperature distribution and the applied pressure distribution in the joining surface become non-uniform, and it may be difficult to obtain high joint strength with the same concept.
On the other hand, in the joining of the magnesium alloy and the steel, the reaction product is removed from the joining interface by utilizing the low melting point eutectic (341 ° C., 364 ° C.) of the Mg—Zn alloy (381 ° C. for the Al—Zn alloy). It can be easily discharged. Therefore, in the case of joining a magnesium alloy and steel, it is desirable to use an R-type electrode having a larger tip curvature, which can increase the effective nugget diameter by dispersing and homogenizing the current density and the applied pressure, A high-strength dissimilar material joint can be realized.

The oxide film on the surface of the cast member C is destroyed by pressurization and electric heating by the electrode, eutectic melting occurs due to local contact between zinc and magnesium, and the reaction product containing oxide film and impurities at the bonding interface is generated. It becomes the discharge | emission material W, is discharged | emitted smoothly from a junction part, and flows in into the recessed parts D and D as shown in FIG.8 (c).
At this time, an Al—Mg-based intermetallic compound (Al ₃ Mg ₂ ) or an Fe—Al-based intermetallic compound (FeAl ₃ ) is generated at the bonding interface, and the steel plate is interposed via the compound layer 6 containing these intermetallic compounds. 1 and the new surfaces of the cast member C are joined to each other, and a strong dissimilar metal joining between the casting and the plate material becomes possible.

Similarly, it is possible to perform resistance seam welding between the cast member C made of a magnesium alloy and the galvanized steel sheet 1 by the indirect method (see FIG. 1B).
That is, as shown in FIG. 9, a cast member C made of a similar magnesium alloy and a galvanized steel sheet 1 are joined linearly via a compound layer 6 containing an intermetallic compound such as Al ₃ Mg ₂ or FeAl _3. be able to.

  Hereinafter, as examples, specific examples of dissimilar metal joining of a casting and a plate material according to the present invention will be shown. The present invention is not limited to these examples.

Example 1
As shown in FIG. 4, on the aluminum alloy casting C (AC2A) provided with ribs R having a thickness of 3 mm at the joint and 3 mm thick ribs R on both sides of the joint at an interval of 8 mm, a plate A 0.8 mm thick galvanized steel sheet 1 was placed. And resistance spot welding was implemented by welding current 30000A, energization time 0.24S (240 ms), and applied pressure 600kgf using the alternating current type resistance spot welding apparatus as shown to Fig.1 (a).
After joining is completed, the joint is cut and the periphery is observed. As a result, the eutectic reaction product containing oxide film and impurities at the joint interface flows into the recess on the back of the rib without remaining at the joint interface. The formation of a sound joint portion in which the new surfaces of both members were directly joined was confirmed.

(Example 2)
The galvanized steel sheet 1 was placed on an aluminum alloy casting C having the same shape and dimensions as those of Example 1 and made of ADC12 material, and resistance spot welding was performed under the same conditions.
And similarly, as a result of observing the periphery of a junction part, it was confirmed that the reaction product has flowed into the recessed part of a rib back surface, and the same healthy junction part was formed.

(Example 3)
As shown in FIG. 8, a magnesium alloy casting C (AZ31: containing 3% Al) having a thickness of 3 mm at the joint and two ribs R with a thickness of 3 mm on both sides of the joint at intervals of 8 mm. A galvanized steel sheet 1 having a thickness of 0.8 mm was placed on the top. And resistance spot welding was implemented by welding current 28000A, energization time 0.24S (240ms), and applied pressure 600kgf using the alternating current type resistance spot welding apparatus as shown to Fig.1 (a).
After joining is completed, the joint is cut and the periphery is observed. As a result, the eutectic reaction product containing oxide film and impurities at the joint interface flows into the recess on the back of the rib without remaining at the joint interface. It was confirmed that both members were satisfactorily bonded via a compound layer containing an intermetallic compound of Al.

Example 4
The galvanized steel sheet 1 is placed on a magnesium alloy casting C having the same shape and dimensions as those of Example 1 and made of AZ61 material (containing 6% Al), and resistance spot welding is performed under the same conditions. Carried out.
Similarly, as a result of observing the periphery of the joint, the reaction product flows into the recess on the back surface of the rib, and a healthy joint is formed through the same compound layer without remaining at the joint interface. It was confirmed that

(Example 5)
A similar galvanized steel sheet 1 is placed on the same aluminum alloy casting C (AC2A) as in Example 1, and welding is performed using an AC type resistance seam welding apparatus as shown in FIG. Resistance seam welding as shown in FIG. 5 was performed under the conditions of a current of 32000 A, a joining speed of 5 m / min, and a pressing force of 800 kgf.
After joining is completed, the joint is cut and the periphery is observed. As a result, the reaction product flows into the recesses on the back surface of the rib without remaining at the joint interface, and the new surfaces of both members are joined directly. It was confirmed that a healthy joint was formed.

(Example 6)
The galvanized steel sheet 1 was placed on the same aluminum alloy casting C (ADC12) as in Example 2, and resistance seam welding as shown in FIG. 5 was performed under the same conditions as in Example 5.
And similarly, as a result of observing the periphery of a junction part, it was confirmed that the reaction product has flowed into the recessed part of a rib back surface, and the healthy junction part is formed similarly.

(Example 7)
A similar galvanized steel sheet 1 is placed on the same magnesium alloy casting C (AZ31) as in Example 3, and welding is performed using an AC type resistance seam welding apparatus as shown in FIG. Resistance seam welding as shown in FIG. 5 was performed under the conditions of a current of 30000 A, a joining speed of 5 m / min, and a pressing force of 800 kgf.
After joining is completed, the joint is cut and the periphery thereof is observed. As a result, the reaction product does not remain at the joint interface and flows into the recesses on the back surface of the rib, and both members contain an intermetallic compound of Al. It was confirmed that the material was satisfactorily bonded via the compound layer.

(Example 8)
The galvanized steel sheet 1 was placed on the same magnesium alloy casting C (AZ61) as in Example 4, and resistance seam welding as shown in FIG. 5 was performed under the same conditions as in Example 7.
As a result of similarly observing the periphery of the joint, the reaction product flows into the recess on the back surface of the rib without remaining at the joint interface, and a healthy joint is formed through the same compound layer. It was confirmed that

It is the schematic which shows the point of the resistance spot welding (a) and resistance seam welding (b) by an indirect method. It is a graph which shows the eutectic point in an Al-Zn type binary phase diagram. (A)-(e) is process drawing which shows roughly the dissimilar metal joining process of the aluminum alloy and steel using eutectic melting. (A)-(c) is process drawing which shows the resistance spot welding process of the aluminum alloy casting member and steel plate by this invention. It is the schematic which shows the resistance seam welding result of the aluminum alloy casting member and steel plate which were obtained by this invention. It is a graph which shows the eutectic point in a Mg-Zn type binary phase diagram. (A)-(e) is process drawing which shows roughly the dissimilar metal joining process of the magnesium alloy and steel using eutectic melting. (A)-(c) is process drawing which shows the resistance spot welding process of the magnesium alloy casting member and steel plate by this invention. It is the schematic which shows the resistance seam welding result of the magnesium alloy casting member and steel plate which were obtained by this invention.

Explanation of symbols

1 Galvanized steel sheet (plate member)
1p Zinc plating layer (third material)
C Casting member (aluminum alloy, magnesium alloy)
R Rib D Recess W W Emission (Reaction product)
6 Compound layer

Claims (10)

  When a plate-shaped member having metal B as a main component is superimposed on the opposite rib side of a cast member having metal A as a main component and provided with ribs, both members are joined by pressurizing from the plate-shaped member side. Between the metal A and B and the metal C to cause eutectic melting, which was accompanied by eutectic melting. A method for joining different types of metal between a casting and a plate, wherein the reaction product is discharged into a recess formed on the back surface of the rib of the cast member due to shrinkage during casting.   The dissimilar metal joining method according to claim 1, wherein the cast member is made of an aluminum alloy, the plate member is a steel plate, and the metal C is zinc, and eutectic melting is caused between aluminum and zinc.   The dissimilar metal joining method according to claim 2, wherein the plate-like member is a galvanized steel sheet provided with a plating layer containing zinc as the metal C.   The cast member is made of a magnesium alloy, the plate member is a steel plate, the metal C is zinc, and eutectic melting occurs between magnesium and zinc, and one or each of Mg and Fe as the main components of both members And an intermetallic compound between the cast member and / or Al previously added in the third material, and the two members are joined via a compound layer containing the intermetallic compound. The dissimilar metal joining method according to claim 1.   The dissimilar metal joining method according to claim 4, wherein the plate-like member is a galvanized steel sheet provided with a plating layer containing zinc as the metal C.   The dissimilar metal joining method according to any one of claims 1 to 5, wherein the joining is performed intermittently by resistance spot welding.   The dissimilar metal joining method according to any one of claims 1 to 5, wherein the joining is continuously performed by resistance seam welding.   It is a joining structure obtained by the method according to any one of claims 1 to 7, wherein the new surfaces of the two members are joined directly or via a compound layer containing an intermetallic compound, and eutectic melting occurs. A dissimilar metal joining structure between a casting and a plate material, characterized in that a reaction product generated along with it flows into a recess formed on a rib back surface of the casting member.   The dissimilar metal joint structure according to claim 8, wherein the cast member is made of an aluminum alloy, the plate-like member is a steel plate, and the new surfaces of the two members are directly joined to each other.   The casting member is made of a magnesium alloy, the plate-like member is a steel plate, and the new surfaces of the two members are joined via a compound layer containing an Al—Mg-based and / or Fe—Al-based intermetallic compound. The dissimilar metal junction structure according to claim 8.

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