JP5237231B2 - Brazing material, metal member joining structure, and metal member joining method - Google Patents

Description

  The present invention relates to a brazing material, a joining structure of metal members, and a joining method of metal members, and in particular, a brazing material applied to joining dissimilar metal members using Fe-based metal members and Al-based metal members as metal members. Regarding improvements.

  The joining structure of metal members such as various joints is manufactured by joining dissimilar metal members. In joining dissimilar metal members, brazing is performed by heating a brazing material interposed between the metal members by laser irradiation. Thereby, the joining structure of a metal member is manufactured by forming a joined part between different metal members.

  For example, when using an Fe-based metal member made of an Fe-based material and an Al-based metal member made of an Al-based material as the dissimilar metal member, a Zn—Al-based brazing material is used as the brazing material (see, for example, Patent Document 1). ). This is because Zn does not form a compound layer but forms a eutectic structure with Al of the Al-based metal member which is a low melting point base material in a wide range.

Japanese Patent No. 3740858

  However, at the boundary between the Fe-based metal member and the joint, the brazed metal part has a Zn-Al-based structure containing Al of the eutectic-melted Al-based metal member. The Fe—Al-based intermetallic compound layer was formed with the Al and Fe-based metal member, and the Fe—Al-based intermetallic compound layer was fragile, and there was a possibility that fracture would occur there. As a result, the strength of the joint structure of different metal members was much lower than that of the joint structure of the same metal members.

  Therefore, the present invention provides a brazing material capable of obtaining a joining structure of dissimilar metal members having substantially the same strength as the joining structure of similar metal members, a method of joining metal members using the same, and a product obtained thereby. It aims at providing the joining structure of a metal member.

  The present inventor has intensively studied a brazing material applied to dissimilar metal joining using an Fe-based metal member and an Al-based metal member as metal members. Conventionally, when Si is added to Zn, as shown in FIG. 9A, the melting point of the material rises as Si is added and increases to about 600 to 900 ° C. Therefore, Si is a Zn-based brazing material. It has not been studied as an additive element. As an additive element of the Zn-based brazing filler metal, Al that lowers the melting point of the brazing filler metal by eutectic with Zn as shown in FIG. 9B is usually used. 9A is a binary equilibrium diagram of ZnSi, and FIG. 9B is a binary equilibrium diagram of ZnAl (Source: Binary Alloy Phase Diagrams, ASM International, Materials Park).

On the other hand, the present inventor uses a Zn—Si based brazing material containing Si as an additive element, thereby providing an Fe—Al based intermetallic compound layer at the boundary between the Fe based metal member and the joint. Was found not formed. That is, the brazing material of the present invention is a brazing material used for joining an Fe-based metal member made of an Fe-based material and an Al-based metal member made of an Al-based material, and Si: 0.25 to 2.5 weight %, With the balance being Zn and inevitable impurities.

  In the brazing material of the present invention, by using a Zn-Si based brazing material containing Si as an additive element, a dissimilar metal member of an Fe based metal member made of Fe based material and an Al based metal member composed of Al based material Since joining is performed, an Fe—Al based intermetallic compound layer is not formed at the boundary between the Fe based metal member and the joint. Conventionally, since the Fe-Al intermetallic compound layer at the boundary between the Fe-based metal member and the joint is fragile, the strength of the joint structure is reduced. In the present invention, the Fe-based metal member A layer containing Si as a main component is formed at the boundary between the metal and the joint, and this layer prevents the inflow of Al into the Fe-based metal member and the inflow of Fe into the brazing material layer. The problematic Fe-Al intermetallic compound layer is not formed. Therefore, since the strength of the boundary portion between the Fe-based metal member and the joint portion can be achieved, it is possible to obtain a joint strength substantially equivalent to that of the same-type metal member joint.

Brazing material of the present invention, Si: 0.25 to 2.5 containing wt%, since the balance being Zn and unavoidable impurities, it is possible to further improve the bonding strength (in particular peel strength).

The brazing material of the present invention is used in the method for joining metal members of the present invention. That is, the metal member joining method of the present invention includes a Fe-based metal member and an Al-based metal with a brazing material interposed between the Fe-based metal member made of Fe-based material and the Al-based metal member composed of Al-based material. A joining method for joining members, wherein the brazing material contains Si: 0.25 to 2.5% by weight, and the balance is made of Zn and inevitable impurities. Since the brazing material of the present invention is used in the method for joining metal members of the present invention, the same effects as those obtained by the brazing material of the present invention can be obtained.

  The metal member joining method of the present invention can employ various configurations. For example, the Fe-based metal member of the bonded portion can be heated at a temperature equal to or higher than the melting point of the Fe-based material. In this aspect, since the bonded portion of the Fe-based metal member made of the Fe-based material is heated at a temperature equal to or higher than the melting point of the Fe-based material, a keyhole can be formed in the bonded portion of the Fe-based metal member during bonding. . The keyhole is a cavity formed by melting a metal member. Moreover, a to-be-joined part represents the joining plan part of an Fe-type metal member and an Al-type metal member, and a joining part represents the joining plan part after joining.

  In the heating by laser irradiation, since the laser beam is multiply reflected in the keyhole, the energy density is increased in the keyhole, and the entire surface from the upper side to the lower side in the keyhole is heated substantially uniformly. As a result, the molten Zn—Si brazing material that has entered the keyhole after heating the welded portion can uniformly react with the entire surface of the keyhole. Therefore, since the strength of the boundary portion between the Fe-based metal member and the joint portion can be further increased, the joint strength of the joint structure can be further improved.

  In addition, the Zn-based material and the Fe—Zn-based material are vaporized. Thereby, regardless of the type of plating such as GA plating or GI plating, the plated portion applied to the Fe-based material is vaporized, so that a good joint can be obtained regardless of the type of plating. Furthermore, since the oxide film on the surface of the Fe-based material is removed by the vapor pressure during melting and vaporization due to overheating, the dissimilar metal member can be satisfactorily bonded without using a flux.

The metal member bonding structure of the present invention is a bonding structure manufactured by the metal member bonding method of the present invention. That is, in the joining structure of the metal member of the present invention, the Fe-based metal member made of Fe-based material and the Al-based metal member made of Al-based material contain Si: 0.25 to 2.5% by weight, and the balance is A metal member bonding structure formed by bonding with a brazing material composed of Zn and inevitable impurities, wherein a bonding portion is formed between an Fe-based metal member and an Al-based metal member, and the bonding portion is formed of an Al-based material. Adjacent to the metal member and containing Zn as a main component and the balance containing Al, and adjacent to the Fe-based metal member and containing Fe as the main component and the remainder containing Zn And a third layer containing Si as a main component. The second layer is formed between the first layer and the second layer.

  In the joint structure of the metal member of the present invention, the boundary portion between the joint portion and the Fe-based metal member contains Si as a main component. As described above, the inflow of Al into the Fe-based metal member and the first Fe Since the third layer for preventing inflow into the layer (the brazing filler metal layer) is formed, there is a problem of the prior art between the Fe-based material (Fe-based metal member and the second layer) and the first layer. The Fe—Al-based intermetallic compound layer is not formed, and the Fe-based material and the brazing filler metal layer are directly joined. Therefore, it is possible to improve the bonding strength as described above.

  According to the brazing material, metal member joining structure, or metal member joining method of the present invention, a fragile Fe-Al based intermetallic compound layer is not formed at the boundary between the Fe based metal member and the joint. In addition, the strength of the boundary between the Fe-based metal member and the joint can be achieved, and as a result, the joint structure can obtain an effect such as being able to obtain substantially the same joint strength as the same kind of metal member joint. it can.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic structure of the state which manufactures a joining structure by the joining method of the metal member of one Embodiment concerning this invention is represented, (A) is a perspective view, (B) is a side view. It is sectional drawing showing the structure of the to-be-joined part in which the keyhole was formed at the time of the joining of the metal member of one Embodiment which concerns on this invention. An example of the joining structure obtained by the joining method of the metal member of one embodiment concerning the present invention is expressed, (A) is a section lineblock diagram and (B) is the elements on larger scale of (A). (A) is a SEM photograph (left photograph) of a joint part of a joint structure obtained using a Zn—Si brazing material (Si content 1.0 wt%), and an Fe-based metal member and joint part in the photograph. (B) is an EPMA map analysis photograph of the boundary portion shown in the enlarged photograph of (A). It is a SEM photograph of the boundary part of a Fe-type metal member and a junction part, (A) is a 3000 times SEM photograph, (B) is a 15000 times SEM photograph. (A) is an enlarged SEM photograph of the boundary portion between the Fe-based metal member and the joint, (B) is an enlarged SEM photograph of a portion indicated by a frame X in (A), and (C) is It is an EPMA map analysis photograph of the part shown by the enlarged SEM photograph of (B). (A)-(E) are EPMA map analysis photographs of each element in the portion shown in FIG. 6 (C), where (A) is O, (B) is Al, (C) is Si, (D ) Is an EPMA map analysis photograph of Fe and (E) is Zn. It is a SEM photograph of the junction part of the junction structure obtained using Zn-Si system brazing material (Si content 1.0wt%). 9 is a TEM photograph (magnification: 30000 times) of a portion indicated by a frame Y in FIG. 8. 9 is an enlarged TEM photograph (magnification: 150,000 times) of a portion indicated by a frame Y in FIG. 8. (A), (B) is a schematic sectional block diagram of the joining structure body for demonstrating the method of a flare tensile strength test and a peel strength test. It is a graph showing the intensity | strength of each sample obtained by the flare tensile strength test. It is a graph showing the intensity | strength of each sample obtained by the peel strength test. (A) is a binary equilibrium diagram of ZnSi, and (B) is a binary equilibrium diagram of ZnAl.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration in a state where bonding is performed using a metal member bonding method according to an embodiment of the present invention, (A) is a schematic perspective view, and (B) is a front view.

  As a method for joining metal members, for example, an arrangement for producing a flare joint is used. As the metal member, an Fe-based metal member 1 made of Fe-based material and an Al-based metal member 2 made of Al-based material are used. The Fe-based metal member 1 and the Al-based metal member 2 have curved portions 11 and 12. In the arrangement of the Fe-based metal member 1 and the Al-based metal member 2, the curved portions 11, 12 face each other, and a groove shape 13 is formed by the curved portions 11, 12. In this case, a step is provided at the facing portion between the Fe-based metal member 1 and the Al-based metal member 2.

In the metal member joining method of the present embodiment, the wire-shaped Zn—Si brazing material 3 is fed to the center of the groove shape 13 through the wire guide 101, and the tip of the Zn—Si based brazing material 3 is sent. Irradiation with a laser beam 102 is performed. Zn-Si based brazing material 3, Si is contained 0.25 to 2.5 wt%, the balance being Zn and unavoidable impurities.

  In the irradiation with the laser beam 102, it is preferable to heat the bonded portions of the Fe-based metal member 1 and the Al-based metal member 2 at a temperature equal to or higher than the melting point of the Fe-based material. FIG. 2 is a cross-sectional view illustrating a schematic configuration of a bonded portion in which the keyhole 5 is formed when the Fe-based metal member 1 and the Al-based metal member 2 are bonded. In the bonded portion, the material is melted and evaporated by heating, and the keyhole 5 is formed by the evaporation reaction force (arrow in the figure) due to the evaporated material. In this case, the molten Zn—Si brazing material exists around the laser irradiation part. In such a keyhole 5, the laser beam 102 is multiply reflected as shown by dotted lines in the figure, so that the energy density is increased in the keyhole 5, and the entire surface from the upper side to the lower side in the keyhole 5. Is heated substantially uniformly. As a result, the molten Zn—Si brazing material that enters the keyhole 5 after passing through the laser beam 102 can uniformly react with the entire surface of the keyhole 5.

  By performing heating by irradiation of such a laser beam 102 from the near side to the far side in FIG. 1 along the extending direction of the groove shape 13, as shown in FIGS. 3 (A) and 3 (B), Fe The joining structure 10 of the metal system member 1 and the Al system metal member 2 can be manufactured. 3A is a cross-sectional configuration diagram of the bonded structure 10, and FIG. 3B is a partial enlarged view of the boundary portion 40 on the Fe-based metal member 1 side in the bonded portion 4 shown in FIG.

  The joint structure 10 includes an Fe-based metal member 1 and an Al-based metal member 2, and a joint 4 is formed between the Fe-based metal member 1 and the Al-based metal member 2. As shown in FIG. 3B, the bonding portion 4 includes a brazing filler metal layer 41 (first layer) adjacent to the Al-based metal member 2, a reaction layer 42 (second layer) adjacent to the Fe-based metal member 1, An Si enriched layer 43 (third layer) formed between the brazing material layer 41 and the reaction layer 42 is provided. The brazing filler metal layer 41 contains Zn as a main component, and the remainder contains Al. The reaction layer 42 contains Fe as a main component, and the remainder contains Zn. The Si enriched layer 43 contains Si as a main component. Since the Si enriched layer 43 prevents the inflow of Al into the Fe-based metal member 1 and the inflow of Fe into the brazing filler metal layer 41, the Fe-based material (Fe-based metal member 1 and the reaction layer 42) and the brazing filler metal layer 41. The Fe—Al-based intermetallic compound layer, which has been a problem of the prior art, is not formed between the Fe-based material and the brazing material layer 41.

  In the joint portion 4, it is preferable that Si grains are scattered in the matrix and the particle diameter is smaller. Specifically, the Si particle size is preferably a size that does not inhibit the mechanical elongation of Zn (for example, 10 μm or less). The atomization of Si grains is presumed to be performed by cutting the crystal grains during the extrusion process in the production of the brazing material.

  In this embodiment, since the dissimilar metal member joining of the Fe-based metal member 1 and the Al-based metal member 2 is performed using the Zn—Si based brazing material 3, Si is formed at the boundary between the Fe-based metal member and the joint. Is formed as a main component, and the diffusion of Al into the Fe-based metal member is prevented by the layer, so that the Fe—Al-based intermetallic compound layer, which has been a problem of the prior art, is not formed. Therefore, since the strength of the boundary portion between the Fe-based metal member 1 and the joint portion 4 can be improved, the joint structure 10 can obtain substantially the same joint strength as that of the same-type metal member joint. In particular, as the Zn—Si-based brazing material 3, Si: 0.25 to 2.5 wt% is contained, and the remainder is made of a brazing material composed of Zn and inevitable impurities. Further improvement can be achieved.

  Moreover, since the molten Zn—Si brazing material that has entered the keyhole 5 formed in the bonded portion of the Fe-based metal member 1 after heating can react uniformly with the entire surface of the keyhole 5. Further, the strength of the boundary portion between the Fe-based metal member 1 and the joint portion 4 can be further increased. As a result, the joint strength of the joint structure 10 can be further improved.

  In addition, the Zn-based material and the Fe—Zn-based material are vaporized. Thereby, regardless of the type of plating such as GA plating or GI plating, the plated portion applied to the Fe-based material is vaporized, so that a good joint can be obtained regardless of the type of plating. Furthermore, since the oxide film on the surface of the Fe-based material is removed by the vapor pressure during melting and vaporization due to overheating, the dissimilar metal member can be satisfactorily bonded without using a flux.

  Hereinafter, the present invention will be described in more detail with reference to specific examples.

  In the example, an Fe-based metal member and an Al-based metal member were disposed in the same manner as in the arrangement form shown in FIG. 1, and a groove shape was formed by the curved portions of these metal members. And the laser beam was irradiated to the front-end | tip part of the Zn-Si type | system | group brazing material, sending the wire-like Zn-Si type brazing material through the wire guide to the center part of the groove shape. Thereby, a bonded structure of metal members having a flare joint shape was manufactured.

  Regarding the bonding conditions, the focused diameter of the laser beam was 1.8 mm, the laser output was 1.4 kW, the bonding speed was 1 m / min, and the wire speed was 3.2 m / min. A steel plate (JAC270, plate thickness 1.0 mm, longitudinal length 200 mm, lateral length 80 mm in FIG. 1) was used as the Fe-based metal member, and Al plate (A6022-T4, plate thickness) as the Al-based metal member. 1.2 mm, the vertical length in FIG. 1 is 200 mm, and the horizontal length is 80 mm).

  In the joining of the metal members as described above, Zn—Si brazing materials having different Si contents (Si contents of 0.25 wt%, 1.0 wt%, 2.5 wt%) are prepared, and each Zn—Si is prepared. The metal member was joined using the brazing filler metal to obtain a metal member joining structure corresponding to each Zn-Si brazing filler metal. And each joining structure was cut | disconnected in strip shape in the direction orthogonal to a joining direction, and the several test piece was obtained. Note that the wire diameter of all the Zn—Si brazing materials was 1.2 mm. Various evaluations were performed using the test piece of the bonded structure as described above.

[Elemental analysis and observation of boundary between Fe metal member and joint]
(1) Low-magnification elemental analysis and SEM observation First, elemental analysis and observation were performed at a low magnification at the boundary between the Fe-based metal member and the joint. About the test piece of the joined structure obtained using the Zn-Si type | system | group brazing material whose Si content is 1.0 wt%, the elemental analysis was performed by the electron beam microprobe analyzer (EPMA) at low magnification. FIG. 4A is an SEM photograph (left photograph) of the joint portion of the joint structure and an enlarged SEM photograph (right photograph) of the boundary between the Fe-based metal member and the joint portion in the photograph. It is the EPMA map analysis photograph (Zn, Al, Fe, Si) of the boundary part shown by the enlarged SEM photograph of (A).

  Moreover, about the test piece of the same joining structure body, the boundary part of a Fe-type metal member and a junction part was observed with the scanning electron microscope (SEM). The result is shown in FIG. FIG. 5 is an SEM photograph of the boundary between the Fe-based metal member and the joint, (A) is a 3000 times SEM photograph, and (B) is a 15000 times SEM photograph.

  As shown in FIG. 4A, an Fe—Al-based intermetallic compound layer formed of a conventional bonded structure is observed at the boundary between the Fe-based metal member and the bonded portion of this example. First, in the EPMA element map analysis shown in FIG. 4B, Si was uniformly dispersed, and the interface between Fe and Zn (that is, the interface between the Fe-based metal member and the joint) was clearly observed. Al is a solution in which Al of an Al-based metal member is dissolved and diffused into the joint by welding. In addition, as shown in the 3000 times SEM photograph of FIG. 5A and the 15000 times SEM photograph of FIG. 5B, the Fe-based metal member of this example The Fe—Al-based intermetallic compound layer formed in the conventional bonded structure was not observed at the boundary with the bonded portion.

  As a result of the above-mentioned EPMA element map analysis and SEM observation, the conventional bonded structure (Zn-Al brazing material was bonded to the boundary between the Fe-based metal member and the bonded portion of the example of the present invention. It was confirmed that there was no fragile Fe—Al-based intermetallic compound layer formed in the bonded structure.

(2) High-magnification elemental analysis and TEM observation Next, in order to investigate in detail the boundary part between the Fe-based metal member and the joint part without the Fe-Al-based intermetallic compound layer, the Fe-based metal member and the joint part Elemental analysis and observation were carried out at a high magnification at the boundary part. About the test piece of the joining structure obtained using the Zn-Si type | system | group brazing material whose Si content is 1.0 wt%, elemental analysis was performed by EPMA with high magnification. 6A is an SEM photograph of the boundary portion between the Fe-based metal member and the joint, and FIG. 6B is an enlarged SEM photograph of a portion indicated by a frame X in FIG. 6A. (C) is an EPMA map analysis photograph of the portion shown in the enlarged SEM photograph of FIG. 6 (B). In FIG. 6B, the red portion indicates Fe, the green portion indicates Zn, the yellow portion indicates Si, and the light blue portion indicates Al. 7 (A) to (E) are EPMA map analysis photographs of each element in the portion shown in FIG. 6 (C), where (A) is O, (B) is Al, (C) is Si, (D) is an EPMA map analysis photograph of Fe and (E) is Zn.

  As can be seen from the EPMA element map analysis, a layer containing Zn and Al (brazing material layer) is observed on the Al-based metal member side, and a layer containing Fe and Zn (reaction layer) on the Fe-based metal member side. Was observed, and a layer containing Si (Si enriched layer) was observed between the brazing filler metal layer and the reaction layer. The width of the Si enriched layer was about 50 to 200 nm. As shown in FIGS. 7B, 7C, and 7E, the Si enriched layer was confirmed to contain Si at a high concentration without containing Zn and Al. As shown in FIG. 7 (B), it was confirmed not to be contained not only in the Si enriched layer but also in the reaction layer. With respect to the brazing material layer, the composition ratio, material, and crystal structure were obtained as shown in Table 1 by analyzing various data obtained by a transmission electron microscope (TEM) at a point P11 shown in FIG.

  In order to investigate in detail the boundary between the Fe-based metal member on which the Si-enriched layer is formed and the joint as described above, it is obtained by using a Zn-Si-based brazing material having a Si content of 1.0 wt%. About the test piece of the joined structure, the boundary part between the Fe-based metal member and the joined part was observed by TEM. 8 is an SEM photograph of a joint portion of the joint structure, FIG. 9 is a TEM photograph (magnification: 30000 times) of a portion indicated by a frame Y in FIG. 8, and FIG. 10 is an enlarged TEM photograph of the joint portion of FIG. (Magnification: 150,000 times).

  In the part indicated by points P21 to 25 in the TEM photograph (magnification: 30000 times) in FIG. 9, the composition ratio, material, and crystal structure were obtained by analyzing various data obtained by TEM. The results are shown in Table 2.

The portion of the point P21 in the brazing material layer was Zn having an hcp structure. The part of the point P22 in the brazing material layer was Zn-Al having an fcc structure. The part of the point P23 in the reaction layer was αFe (solid solution) having a bcc structure, and the part of the point P24 was Fe ₃ Zn ₁₀ (Zn plating) having a bcc structure. Unlike the brittle Fe—Al intermetallic compound layer (for example, a layer made of orthorhombic Fe ₂ Al ₅ ), which is a conventional problem, the reaction layer is made of Fe (solid solution) and Zn plating. It was found to be a fine mixed layer, which is a layer formed entirely by metal lattice bonding. The width of the reaction layer was about 1 μm. The point P25 portion in the Fe-based metal member was Fe having a bcc structure. In this case, it was found that Fe was not a rolled structure but a crystal refined.

  In the above 30,000 times TEM analysis, the presence of Si could not be confirmed, so in order to investigate the presence of Si, a TEM photograph (FIG. 10) was obtained at a magnification of 150,000 times. Table 3 shows the composition ratios obtained by TEM analysis in the portions indicated by points P31 to P33 in the TEM photograph of FIG. Regarding the point P33, in addition to the weight concentration (wt%), the atomic concentration (at%) is also shown.

  The portion of the point P31 in the brazing material layer was Zn having an hcp structure. The portion of point P32 in the reaction layer was αFe (solid solution) having a bcc structure. It was found that Si was concentrated and present at the point P33 in the Si concentrated layer. The width of the Si enriched layer was about 50 nm. Since the Si enriched layer is formed between the Fe-based material (Fe-based metal member and reaction layer) and the brazing filler metal layer, it acts as a reaction barrier for those materials (= Al to the Fe-based metal member) Inflow and the action of preventing the inflow of Fe into the brazing filler metal layer). It is considered that the intermetallic compound layer was not formed and the Fe-based material and the brazing material layer were directly joined. As shown in Table 3, the Si enriched layer indicated by the point P33 is rich in Al, unlike the EPMA map analysis shown in FIGS. 7B, 7C, and 7E. This is due to the following reasons. That is, in the chemical composition analysis of each part by TEM analysis, the test piece is cut, but the Si-enriched layer part having a narrow layer width was analyzed including the part of the brazing filler metal layer adjacent thereto. It is considered that a large amount of Al was detected in the chemical composition analysis of the concentrated layer.

[Joint strength evaluation of metal joint structure]
Flare tensile strength test and peel strength test were performed on test pieces of each joint structure obtained using Zn-Si brazing filler metals having Si content of 0.25 wt%, 1.0 wt%, and 2.5 wt%. It was. As the test piece, two pieces on the center side of the joint structure and four pieces on both end sides are allocated for each strength test. 1 piece and 2 pieces (total 3 pieces) on both ends were used.

  In the flare tensile strength test, as shown in FIG. 11 (A), with respect to the laterally extending portions of the Fe-based metal member 21 and the Al-based metal member 22 that are T-shaped on the surface side where the joint 23 is formed. Applied forces in opposite directions. In the flare tensile strength test, stress is most applied at the portions indicated by arrows A and B.

  The results (flare tensile strength value and fracture location) are shown in Table 4 and FIG. In Table 4, the test results of the test pieces of the joint structure corresponding to the Zn—Si brazing material having the Si content of 0.25 wt%, 1.0 wt%, and 2.5 wt% are shown as Samples 11 to 13. Table 4 also shows the results of Comparative Samples 11 and 12. The comparative sample 11 is a test piece of a joined structure of an Fe-based metal member and an Al-based metal member obtained using a Zn—Al-based brazing material having an Al addition amount of 6 wt% as a brazing material. The comparative sample 12 is a test piece of a joined structure of Al-based metal members obtained using a commercially available brazing material as the brazing material. The test pieces of the comparative samples 11 and 12 are obtained by cutting the obtained bonded structure into strips like the samples 11 to 13. In FIG. 12, the average value of the flare tensile strength of each sample and the fracture location are also shown.

  The strength reference value (the one-dot chain line in FIG. 12) of the flare tensile strength test is set as follows. The joint length of continuous welding equivalent to one spot welding spot was set to 20 mm, and the spot welding of Al in JIS Z3140 was used as a standard. Thereby, the tensile strength standard of spot welding in which the plate thickness of Al is 1.2 mm is 1.86 kN / 20 mm.

  As shown in Table 4 and FIG. 12, the tensile strength of Samples 11 to 13 of the present invention, which is a joined structure of dissimilar metal members, exceeded the strength reference value. In addition, the tensile strength of the samples 11 to 13 of the present invention is higher than the tensile strength of the comparative sample 11 which is a bonded structure of different metal members, and the comparative sample 12 which is a bonded structure of the same metal members. It was higher than the tensile strength. Then, it was confirmed that the tensile strength was greatly improved with a small amount of Si content (0.25 wt%). Moreover, in the samples 11-13 of this invention, it confirmed that it fractured | ruptured with the Al type metal member unlike the comparative sample 11 fractured | ruptured in the boundary part of a Fe-type metal member and a junction part.

  In the peel strength test, as shown in FIG. 11B, the lateral extension of the Fe-based metal member 21 and the Al-based metal member 22 having a T-shape on the surface opposite to the surface on which the joint 23 is formed. Forces in opposite directions were applied to the existing part. In such a peel strength test, the strength of the joint boundary can be measured by concentrating high stress on the joint boundary (location indicated by arrow C).

  The results (peel tensile strength value and fracture mode) are shown in Table 5 and FIG. In Table 5, the test results of the test pieces of the joint structure corresponding to the Zn—Si brazing material having the Si content of 0.25 wt%, 1.0 wt%, and 2.5 wt% are shown as Samples 21 to 23. Table 5 also shows the results of Comparative Samples 21 and 22. The comparative sample 21 is a test piece of a joined structure of an Fe-based metal member and an Al-based metal member obtained by using a Zn—Al-based brazing material having an Al content of 6 wt% as a brazing material. The comparative sample 22 is a test piece of a joined structure of Al-based metal members obtained by using a commercially available brazing material as a brazing material. The test pieces of Comparative Samples 21 and 22 are obtained by cutting the obtained bonded structure into strips like Samples 21 to 23. In FIG. 13, the average value of the peel strength of each sample and the broken part are shown.

  The strength reference value of the peel strength test (the one-dot chain line in FIG. 13) is a test of comparative sample 22 (joint structure of Al-based metal member) which is a joint structure of the same kind of metal member obtained using a commercially available brazing material. 80% of the peel strength value of the piece.

  As shown in Table 5 and FIG. 13, in the samples 21 to 23 of the present invention, which are joined structures of different metal members, the peel strength exceeded the strength standard. In addition, the peel strength of the samples 21 to 23 of the present invention was significantly improved with a small amount of Si content (0.25 wt%) as compared with the comparative sample 11 which is a bonded structure of dissimilar metal members. It was confirmed. Also, in the samples 21 and 22 of the present invention, unlike the comparative sample 21 fractured at the boundary between the Fe-based metal member and the joint, the Al-based metal member is similar to the comparative sample 22 that is a joint structure of the same kind of metal member. It was confirmed that it broke. Note that in the sample 23 of the present invention, the peel boundary width is reduced due to the decrease in wettability, so that the peel strength is slightly reduced as compared with the samples 21 and 22 of the present invention, and the boundary between the Fe-based metal member and the joint portion. It is presumed that the part broke.

  As described above, the strength of the sample of the present invention, which is a joined structure of dissimilar metal members using a Zn-Si brazing material having a Si content of 0.25 wt% to 2.5 wt%, exceeds the strength reference value. It was. In addition, the strength of the sample of the present invention was found to be significantly improved with a small amount of Si content (0.25 wt%) by comparison with a comparative sample that is a joint structure of the same dissimilar metal member. In particular, in the sample of the present invention which is a joined structure of dissimilar metal members using a Zn-Si brazing material having a Si content of 0.25 wt% to 1.0 wt%, the boundary portion between the Fe metal member and the joint portion It was found that a strong joint structure such as a joint structure of the same kind of metal member can be obtained.

  DESCRIPTION OF SYMBOLS 1 ... Fe type | system | group metal member, 2 ... Al type | system | group metal member, 3 ... Zn-Si type | system | group brazing material, 4 ... Junction part, 5 ... Keyhole, 40 ... Boundary part (Boundary part by the side of the Fe type metal member in a junction part) 41 ... brazing material layer (first layer), 42 ... reaction layer (second layer), 43 ... Si enriched layer (third layer)

Claims (4)

In a brazing material used for joining an Fe-based metal member made of an Fe-based material and an Al-based metal member made of an Al-based material,
A brazing material characterized by containing Si: 0.25 to 2.5% by weight, the balance being Zn and inevitable impurities. An Fe-based metal member made of Fe-based material and an Al-based metal member made of Al-based material contain Si: 0.25 to 2.5% by weight, and the balance is joined by a brazing material made of Zn and inevitable impurities. In the joining structure of the formed metal member,
A joint is formed between the Fe-based metal member and the Al-based metal member,
The joint is
A first layer that is adjacent to the Al-based metal member, contains Zn as a main component, and contains Al in the balance;
A second layer that is adjacent to the Fe-based metal member, contains Fe as a main component, and contains Zn in the balance;
A metal member bonding structure characterized by comprising a third layer formed between the first layer and the second layer and containing Si as a main component. In a joining method for joining the Fe-based metal member and the Al-based metal member by interposing a brazing material between an Fe-based metal member made of Fe-based material and an Al-based metal member composed of an Al-based material,
The brazing material contains Si: 0.25 to 2.5% by weight, and the balance is made of Zn and inevitable impurities. The method for joining metal members according to claim 3 , wherein the portion to be joined of the Fe-based metal member is heated at a temperature equal to or higher than the melting point of the Fe-based material.

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