Joined body and joining method

Abstract

To provide a joined body of aluminum-based material and different material which has sufficient joint strength and is formed by high pressure die casting.SOLUTION: Provided is a joined body in which a first member made of an aluminum-based material formed by high-pressure die casting (HPDC) and a second member made of material different from that of the first member are joined to each other, in which the first member has a melted and solidified portion which is solidified after melting and has a gas content lower than that of an unmelted portion, and the first member has a joint portion to be joined to the second member on one end side of the melted and solidified portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a bonded body and a bonding method. [Background technology]

[0002] In recent years, there has been a demand for reducing CO2 emissions and improving energy efficiency. One way to achieve this is to reduce the weight of various components. One way to reduce the weight of components is to use dissimilar materials, in which some of the components made of relatively high-strength, heavy materials such as steel plates are replaced with relatively lighter materials such as aluminum or magnesium.

[0003] As a technique for joining dissimilar materials, a method for hybrid welding of aluminum-based workpieces and iron-based workpieces without using brazing filler metal or flux has been disclosed (see Patent Document 1). Also disclosed is a laser welding method in which a plurality of metal plates, including at least one metal plate on which a surface treatment layer is formed, are overlapped, and a laser that scans along the weld shape of each metal plate is irradiated onto each metal plate, thereby melting each metal plate and vaporizing the surface treatment layer, thereby joining the metal plates (see Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-281279 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-115876 Summary of the Invention [Problem to be solved by the invention]

[0005] One known material to be welded is an aluminum-based material (hereinafter referred to as "HPDC aluminum material") formed by high-pressure die casting (HPDC). High-pressure die casting is a manufacturing process in which molten metal is fed into a mold and solidified to obtain the desired part. It is widely used because it offers advantages such as the ability to realize complex shapes and high production efficiency. However, HPDC aluminum material generally contains a high amount of gas (such as hydrogen), which can cause numerous blowholes (porosity) in the weld zone. Therefore, there is a problem in that sufficient joint strength cannot be obtained when joining dissimilar materials.

[0006] Cited Document 1 discloses a method using a first heat source to heat the surface of a ferrous workpiece from the aluminum workpiece side, and a second heat source to heat the surface of the aluminum workpiece in the overlapping portion. The first heat source melts only the zinc-based coating layer near the edge of the overlapping portion, and then the second heat source melts the zinc-based coating layer and the aluminum workpiece in the overlapping portion. However, when this method is applied to HPDC aluminum, the heat source that melts the zinc-based coating layer cannot melt the HPDC aluminum, and the gas-rich state cannot be resolved. If a heat source capable of melting HPDC aluminum were used, the melting point of the aluminum would decrease due to the melting of the HPDC aluminum and zinc-based coating near the overlapping portion. This could result in aluminum flowing into the newly formed surface, potentially resulting in excessive intermetallic compound formation.

[0007] The technology described in Patent Document 2 describes a method for removing blowholes that occur when the plating layer vaporizes during welding, but does not describe a means for removing gas contained in the base material.

[0008] The present invention has been made in view of the above, and has an object to provide a joined body of an aluminum-based material and a dissimilar material formed by high-pressure die casting, which has sufficient joint strength. [Means for solving the problem]

[0009] (1) A joined body formed by joining a first member made of an aluminum-based material formed by high-pressure die casting (HPDC) with a second member made of a material different from the first member, wherein the first member has a melted and solidified portion that solidifies after melting and has a lower gas content than an unmelted portion, and the first member has a joining portion that is joined to the second member on one end side of the melted and solidified portion.

[0010] According to the invention (1), it is possible to provide a joint having sufficient joint strength, which is formed by high pressure die casting and is made of an aluminum-based material and a dissimilar material.

[0011] (2) The joined body according to (1), wherein the second member is made of an iron material and has a base material and a plating layer formed on the surface of the base material, the boiling point of the plating layer is higher than the melting point of the base material, and the joint is joined to a solid solution layer in which at least a part of the material constituting the plating layer is solid-solved in the base material.

[0012] According to the invention of (2), the HPDC aluminum material is joined to the solid solution layer, resulting in a weld between aluminum and iron, making it easier to produce a joint than when directly welding to a plating layer.

[0013] (3) The joined body according to (1) or (2), wherein the first member and the second member are separated from each other at least in a portion of the joint side, other than the joint.

[0014] According to the invention of (3), it is possible to prevent a part of the molten and solidified portion from flowing into the solid solution layer during manufacturing, which would otherwise cause excessive intermetallic compounds to be generated and reduce the strength of the joint.

[0015] (4) The bonded body according to any one of (1) to (3), wherein the first member has a stepped shape formed so that the cross-sectional area of ​​the one end side is smaller than the cross-sectional area of ​​the other end side.

[0016] According to the invention of (4), it is possible to prevent a part of the molten and solidified portion from flowing into the solid solution layer during manufacturing, which would otherwise cause excessive intermetallic compounds to be generated and reduce the strength of the joint.

[0017] (5) A joining method for joining a first member made of an aluminum-based material formed by high-pressure die casting (HPDC) to a second member made of a material different from the first member, the joining method comprising: a first step of melting one end of the first member; and a second step of melting an end portion of the first member further to one end than the first molten portion melted in the first step, and joining the second molten portion of the first member melted in the second step to the second member.

[0018] According to the invention of (5), it is possible to manufacture a joint of an aluminum-based material and a dissimilar material formed by high-pressure die casting, which has sufficient joint strength.

[0019] (6) The joining method described in (5), wherein the second member is made of an iron material and has a base material and a plating layer formed on the surface of the base material, the boiling point of the plating layer is higher than the melting point of the base material, the first step is to dissolve at least a part of the material constituting the plating layer in the base material to form a solid solution layer, and the second step is to join the second molten portion to the solid solution layer.

[0020] According to the sixth aspect of the present invention, the HPDC aluminum material is joined to the solid solution layer, which results in a weld between aluminum and iron, making it easier to produce a joined body compared to welding with a plated layer. Furthermore, by simultaneously melting the plated layer and forming the first fusion zone in the first step, dissimilar material welding between a high-melting-point plated material and HPDC aluminum material, which is difficult to weld, can be performed in two melting steps.

[0021] (7) The joining method according to (6), wherein the second step joins the second molten portion to the solid solution layer after the surface temperature of the solid solution layer has reached a melting point or lower.

[0022] According to the invention (7), it is possible to prevent excessive formation of intermetallic compounds between iron and aluminum materials. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a cross-sectional view showing an outline of a bonded body according to a first embodiment. [Figure 2] FIG. 10 is a cross-sectional view showing an outline of a bonded body according to a second embodiment. [Figure 3] 3A to 3C are diagrams illustrating a manufacturing process of the bonded body according to the first embodiment. [Figure 4] 3A to 3C are diagrams illustrating a manufacturing process of the bonded body according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0024] <zygote> [First embodiment] As shown in FIG. 1 , the joined body 1 according to this embodiment is a joined body obtained by joining a first member 3, which is an aluminum-based material formed by high-pressure die casting (HPDC), and a second member 2, which is made of a material different from the first member 3. The first member 3 has a melted and solidified portion 32a that is melted and solidified and has a lower gas content than the unmelted portion. The first member 3 has a joint portion 32b, which is joined to the second member 2, at an end portion closer to one end than the melted and solidified portion 32a. Due to the manufacturing process, HPDC aluminum material may contain hydrogen and other gases inside. However, because the first member 3 is joined to the second member 2 at an end portion closer to the end than the melted and solidified portion 32a, which has a lower gas content, the joined body 1 has favorable joint strength.

[0025] (First member) 1, the first member 3 includes a base material 31 and one end portion 32. The one end portion 32 includes a melt-solidified portion 32a and a joint portion 32b. As shown in FIG. 1, the joint portion 32b is formed closer to the one end side than the melt-solidified portion 32a (the second member 2 side of the first member 3).

[0026] The molten and solidified portion 32a is a portion in which the internal gas content has been reduced by being re-melted after being formed by high-pressure die casting (HPDC). The gas content of the molten and solidified portion 32a is lower than that of the unmelted portion (base material 31), and may be, for example, less than 5 cc per 100 g of aluminum weight.

[0027] The joint portion 32b is a portion that is melted and joined to the second member 2. By providing the joint portion 32b closer to one end than the melt-solidified portion 32a, which has a low gas content, it is possible to improve the strength of not only the joint portion 32b but also the surrounding area, thereby obtaining a preferable joint strength of the joined body 1. The joint portion 32b is preferably joined to a solid solution layer 23 of the second member 2, which will be described later.

[0028] The joint portion 32b may be a part of the base material 31, or may be made of a material different from that of the base material 31. The joint portion 32b may be, for example, a brazing material (aluminum-based wire, etc.).

[0029] (Second member) The second member 2 is made of a material different from that of the first member 3. The second member 2 is, for example, an iron material having a plating layer 22 on the surface of a base material 21. The plating layer 22 is not particularly limited, but is preferably a high-melting-point plating layer having a boiling point higher than the melting point of the base material 21. As a result, the plating layer 22 does not melt in the second step described below. This prevents, for example, when the plating layer 22 is Zn-plated, the components constituting the plating layer 22 from mixing with the components constituting the first member 3, which can prevent a eutectic reaction from occurring, causing a decrease in the melting point of aluminum constituting the first member 3. If the melting point of aluminum were to decrease, aluminum would flow into the solid solution layer 23 formed in the second step, potentially resulting in excessive intermetallic compound formation.

[0030] An example of the plating layer 22 is an Fe—Al layer. An example of a steel material having an Fe—Al layer is a high-tensile steel plate having an aluminum-based plating (such as an Al—Si alloy) on its surface. The aluminum-based plating formed on the surface of the high-tensile steel plate is heated by hot stamping or the like, thereby forming an Fe—Al layer on the surface.

[0031] The Fe-Al layer may be a layer containing an intermetallic compound. The intermetallic compound is not particularly limited, but examples thereof include Al-Si-Fe intermetallic compounds. The Fe-Al layer may contain an alloy other than the intermetallic compound, such as an Fe-Al alloy. The thickness of the plating layer 22 in the second member 2 other than the joint portion is not particularly limited. The thickness of the plating layer 22 may be, for example, 10 to 50 μm, or 20 to 40 μm.

[0032] The melting point of the Fe—Al layer is not particularly limited, but is, for example, approximately 1280 to 1480°C. The melting point of the Fe—Al layer is closer to the melting point of iron (base material 21) (approximately 1560°C) compared to, for example, the melting point of zinc-based plating. Therefore, when attempting to melt only the Fe—Al layer and join it to the first member 3, it is necessary to adjust the melting temperature to a temperature between the melting points of the Fe—Al layer and the base material 21, making temperature control difficult. In this embodiment, the Fe—Al layer is melted together with the base material 21 to form a solid solution layer 23, and the solid solution layer 23 is joined to the first member 3. This facilitates temperature control during the production of the joined body 1.

[0033] The solid-solution layer 23 is a layer in which at least a portion of the material constituting the plating layer 22 is solid-solved in the base material 21. For example, it is a layer in which aluminum contained in the Fe-Al layer of the plating layer 22 is solid-solved. Joining the HPDC aluminum material to the solid-solution layer 23 results in welding between the HPDC aluminum material and the surface layer of the iron material that does not have the plating layer 22. This makes it easier to produce the joined body 1 compared to directly welding the plating layer 22 and the first member 3. The solid-solution layer 23 is a layer that extends in the thickness direction of the second member 2 to the position where the base material 21 is present. The proportion of aluminum that is solid-soluble in iron in the solid-solution layer 23, i.e., the proportion of aluminum to iron in the solid-solution layer 23, is preferably 10 mass% or less. By setting the proportion of aluminum in the solid-solution layer 23 within the above range, it is possible to prevent aluminum from forming an intermetallic compound due to its inability to dissolve, thereby preventing a decrease in the strength of the second member.

[0034] By joining the joint 32b to the solid solution layer 23, a thin intermetallic compound 4 may be formed between the first member 3 and the second member 2. The thickness of this intermetallic compound 4 is thinner than the thickness of the plating layer 22 in areas other than the joint. The above-mentioned thickness difference is particularly evident at the toe 32c and root 32d of the joint 32b in FIG. 1. From the above, it can be inferred that the material (aluminum) contained in the plating layer 22 has formed a solid solution in the base material 21.

[0035] 1, it is preferable that only a thin intermetallic compound layer 4 exists at the interface between the solid solution layer 23 and the joint 32b. That is, it is preferable that the joint 32b and the solid solution layer 23 are diffusion bonded by a diffusion reaction. If a plating layer 22 of the same thickness as that of the portion other than the joint exists at the interface between the joint 32b and the solid solution layer 23, the diffusion reaction (atomic movement) is inhibited, making it difficult to achieve diffusion bonding.

[0036] 1, it is preferable that the first member 3 and the second member 2 are separated by a predetermined distance G at least in a portion on the side of the joining portion 32b among portions other than the joining portion 32b. This makes it possible to prevent the first molten portion 32a1 from flowing into the solid solution layer 23 and excessive generation of intermetallic compounds in the first step described below. As shown in FIG. 1, the first member 3 and the second member 2 may be separated from each other in all portions except for the one end portion 32.

[0037] [Second embodiment] Next, the configuration of the bonded body 1a according to the second embodiment will be described with reference to Fig. 2. The same components as those in the first embodiment are denoted by the same reference numerals in the drawings, and the description thereof may be omitted.

[0038] As shown in FIG. 2, the bonded body 1a includes a first member 3 having a step shape 31a. The step shape 31a is formed so that the cross-sectional area of ​​one end side (the second member 2 side) is smaller than that of the other end side (the base material 31 side). This allows the first member 3 and the second member 2 to be separated by a predetermined distance G. Since the first member 3 has the step shape 31a, the first member 3 and the second member 2 can be easily maintained in a separated state when they are bonded together. To achieve the above effect, the step shape 31a preferably has a flat portion that comes into contact with the second member 2.

[0039] <Joining method> Next, a joining method for joining the first member 3 and the second member 2 to obtain the joined body 1 will be described with reference to Figures 3 and 4. The joining method according to this embodiment includes a first step of melting one end of the first member, and a second step of melting an end portion of the first member that is further toward the end than the first molten portion melted in the first step, and joins the second molten portion melted in the second step to the second member.

[0040] In the first step, one end of the first member 3 is melted to form a first molten zone 32a1, thereby converting gas present inside the HPDC aluminum material into blowholes. The first molten zone 32a1 is cooled and solidified after the second step to form the molten and solidified zone 32a of the joined body 1. The heat source for melting the one end of the first member in the first step is not particularly limited, but is preferably a laser beam B1, as shown in FIG. 3 . The laser beam B1 is irradiated onto the one end of the first member from a laser beam irradiation device 51, for example. In the following description, the heat source is described as a laser beam; however, the heat source is not limited to this, and known heat sources used in welding, such as an arc or an electron beam, can also be used.

[0041] In the first step, it is preferable to melt one end of the first member 3 and at least a portion of the plating layer 22 on the surface of the second member 2. That is, in the first step, as shown in FIG. 3 , the first member 3 and the second member 2 are preferably overlapped at a joining position and heated by irradiating with a laser beam or the like so that heat is transmitted from the first member 3 to a portion of the second member 2. This allows the plating layer 22 to dissolve in the base material 21 with a single irradiation, forming a solid-solution layer 23. Moreover, heat is not easily transmitted to the portion of the plating layer 22 overlapping with the first fusion portion 32a1, making melting less likely. Furthermore, the high melting point of the plating layer 22 further reduces melting. Furthermore, the first member 3 and the second member 2 are separated by a predetermined distance G. Therefore, the first fusion portion 32a1 flows into the plating layer 22, preventing excessive intermetallic compound formation.

[0042] The amount of heat in the first step is preferably an amount that is sufficient to melt the first member 3 and form the solid-solution layer 23. For example, when the plating layer 22 is an Fe—Al layer, the volumes of the molten plating layer 22 and the base material 21 are preferably adjusted so that the content of aluminum derived from the Fe—Al layer in the solid-solution layer 23 is within 10 mass % of Fe. This suppresses the formation of intermetallic compounds and improves the strength of the joined body 1. The adjustment can be made, for example, by adjusting the temperature and irradiation time of the laser beam B1. Note that even when a single laser beam is used, differences in heat absorption occur due to differences in the materials of the first member 3 and the second member 2. Therefore, when the second member 2 is made of iron, the temperature of the iron material is more likely to rise than that of the first member 3. The heating temperature of the first member 3 in the first step may be, for example, approximately 800°C, and the heating temperature of the second member 2 may be, for example, approximately 1500 to 2000°C.

[0043] In the first step, the cross-sectional area of ​​one end side of the first member 3 may be made smaller than other portions so that the one end side is more likely to melt.

[0044] A cooling step for cooling the first molten portion 32a1 may be performed after the first step and before the second step. The cooling step allows blowholes formed in the first molten portion 32a1 in the first step to solidify (accumulate above the molten portion 32a1). This makes it easier for the blowholes to be released in the second step. Furthermore, by performing the cooling step, the melting range of the first member 3 due to heating in the second step can be reduced, and the generation of new blowholes can be suppressed. This improves the quality of the bonded body 1. The cooling step is performed by providing a period between the first and second steps during which no heat is applied by a laser beam or the like, or the amount of heat applied is reduced (for example, by increasing the distance from the laser beam irradiation device).

[0045] The second step is a step of melting an end portion of the first member 3 that is closer to one end than the first molten portion 32a1 to form the second molten portion 32b1. The second molten portion 32b1 is cooled and solidified after the second step to become the joining portion 32b of the joined body 1. In this embodiment, the first molten portion 32a1 is provided at the end portion of the first member 3, and an aluminum-based wire is further introduced into the end portion and melted to form the second molten portion 32b1. However, the present invention is not limited to the above, and the second molten portion 32b1 may be formed by melting a portion of the base material 31.

[0046] In the second step, the second molten zone 32b1 is formed, and the gas in the solidified blowhole B of the first molten zone 32a1 is released to the outside. This reduces the gas content in the molten and solidified zone 32a, and improves the joint strength.

[0047] The heat source for forming the second fusion zone 32b1 is not particularly limited, but is preferably a laser beam B2. Like the laser beam B1, the laser beam B2 is irradiated onto the second fusion zone 32b1 from, for example, a laser beam irradiation device 52. As the heat source, a known heat source used in welding, such as an arc or an electron beam, can also be used instead of a laser beam.

[0048] In the second step, after forming the second fusion zone 32b1, the second fusion zone 32b1 is joined to the second member 2. The joining of the second fusion zone 32b1 is preferably performed to the solid solution layer 23. Furthermore, the joining is preferably performed after the surface temperature of the solid solution layer 23 has fallen below its melting point. This makes it possible to suppress the excessive generation of intermetallic compounds. The joining is preferably performed under a shielding gas to prevent oxidation of the surface of the second member 2.

[0049] Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and modifications and improvements within the scope of achieving the object of the present invention are included in the present invention. [Explanation of symbols]

[0050] 1, 1a zygote 2 Second member 21 Base material 22 plating layer 23 Solid solution layer 3 First member 31a Step shape 32a Melting and solidifying section 32a1 First fusion zone 32b Joint 32b1 Second fusion zone

Claims

1. a first member made of an aluminum-based material formed by high pressure die casting (HPDC); A joined body in which the first member and a second member made of a material different from the first member are joined, the first member has a melted and solidified portion that is melted and then solidified and has a lower gas content than an unmelted portion, The first member has a joining portion joined to the second member on one end side of the melt-solidified portion.

2. the second member is made of an iron material and has a base material and a plating layer formed on a surface of the base material; the boiling point of the plating layer is higher than the melting point of the base material; The joined body according to claim 1 , wherein the joint is joined to a solid solution layer in which at least a part of the material constituting the plating layer is solid-solved in the base material.

3. The joined body according to claim 1 , wherein the first member and the second member are separated from each other at least in a portion of the joint side of the first member and the second member other than the joint.

4. The bonded body according to claim 3 , wherein the first member has a stepped shape formed so that the cross-sectional area of ​​the one end side is smaller than the cross-sectional area of ​​the other end side.

5. a first member made of an aluminum-based material formed by high pressure die casting (HPDC); A joining method for joining a first member and a second member made of a material different from the first member, comprising: a first step of melting one end side of the first member; a second step of melting an end portion of the first member that is further on one end side than the first molten portion melted in the first step, a joining method, wherein a second molten portion of the first member melted in the second step is joined to the second member.

6. the second member is made of an iron material and has a base material and a plating layer formed on a surface of the base material; the boiling point of the plating layer is higher than the melting point of the base material; the first step includes forming a solid solution layer by dissolving at least a part of a material constituting the plating layer in the base material; The joining method according to claim 5 , wherein the second step joins the second molten portion to the solid solution layer.

7. The joining method according to claim 6 , wherein the second step joins the second molten portion to the solid solution layer after the surface temperature of the solid solution layer has reached a melting point or lower.

Images