JP7530077B2 - Joint structure and manufacturing method thereof - Google Patents

Description

The present invention relates to a bonded structure and a manufacturing method thereof, and more specifically to a bonded structure in which a titanium member is bonded to a member made of a metal other than titanium, and a manufacturing method thereof.

It has been a common practice to join a titanium member to a member made of a metal other than titanium by brazing. For example, Patent Document 1 discloses a method for manufacturing a fin tube in which an aluminum hoop-shaped fin material is spirally wound around the outer periphery of a titanium heat transfer tube, and the starting end of the fin material is brazed to the heat transfer tube.

JP 2005-7433 A

However, when the above brazing is performed by applying heat instantaneously with a TIG welder, there is a risk that the heat transfer tube or fin material may melt and cause holes due to misalignment of the arc, and this poses the problem of requiring skill in the work. On the other hand, when a gas burner is used as the heat source for brazing, there is also a risk that holes may be caused by melting when the thin fin material is heated for a long period of time.

In addition to brazing, soldering using a solder material that melts at a lower temperature than the brazing material is also known as a method for joining metal components. This can prevent the fin material from melting, but there is a problem in that soldering to heat transfer tubes made of titanium is extremely difficult.

The present invention aims to provide a joint structure that can easily and reliably join a titanium member to a member made of a metal other than titanium, and a method for manufacturing the same.

The object of the present invention is achieved by a joined structure in which a first member made of titanium is joined to a second member made of a metal other than titanium, wherein the second member is joined to a first joint formed on a surface of the first member using a brazing material made of a metal other than titanium via a second joint made of a solder material , and the first joint is a joined structure containing silver brazing .

This joint structure can be configured such that the second member is a band-shaped fin material made of aluminum and is spirally wrapped around the surface of the first member, which is a heat transfer tube. In this configuration, it is preferable that the first joint is disposed adjacent to both sides of the second member along the axial direction of the first member.

In addition, the object of the present invention is achieved by a method for manufacturing the above-mentioned joined structure, comprising a first step of melting a brazing material made of a metal other than titanium on a surface of the first member to form the first joint, and a second step of forming the second joint by soldering the second member to the first joint, wherein the first joint contains silver brazing .

The bonded structure and manufacturing method of the present invention make it possible to easily and reliably bond a titanium member to a member made of a metal other than titanium.

1 is a front view of a joint structure according to one embodiment of the present invention; 2 is a plan view of a main portion for explaining a method for manufacturing the joint structure shown in FIG. 1.

One embodiment of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a front view of a joint structure according to one embodiment of the present invention. As shown in FIG. 1, the joint structure 1 of this embodiment is a fin tube used in air-cooled heat exchangers and the like, and is configured by joining a first member 2 made of a titanium heat transfer tube and a second member 3 made of an aluminum fin material. In this specification, titanium and aluminum include alloys in addition to the respective pure metals.

The second member 3 is generally band-shaped, has an L-shaped cross section, and includes a base 3a and fins 3b standing up from the base 3a. The second member 3 is spirally wrapped around the surface of the first member 2 so that the base 3a abuts against the first member 2 and the fins 3b protrude outward from the first member 2.

On the surface of the first member 2, first joints 6, 7 made of silver solder are formed in a raised shape on both sides of the second member 3 along the axial direction of the first member 2. The silver solder may contain other elements such as Cu, Sn, Ni, and Li for the purposes of improving the joint strength, lowering the melting point, improving wettability, etc. In this embodiment, BAg-4 silver solder is used.

Second joints 8, 9 made of a solder material are interposed between the first joints 6, 7 and both sides of the second member 3. More specifically, one second joint 8 is formed so as to be in close contact with one first joint 6, the base 3a, and the fins 3b, and the other second joint 9 is formed so as to be in close contact with the other first joint 7 and the fins 3b.

The solder material constituting the second joints 8, 9 is not particularly limited, but examples include low-temperature solders for aluminum such as Sn-Pb and Sn-Zn, and other elements such as Cd, Bi, Cu, Al, and Sb may be added. The melting point of the solder material is less than 450°C, which is sufficiently lower than the melting point of silver solder (about 800°C). Therefore, even if the thickness of the fin 3b of the second member 3 is thin (for example, 0.4 mm), there is no risk of holes being formed in the second member 3 due to melting, and the second member 3 can be easily joined. In addition, the second joints 8, 9 made of a solder material are joined to the first member 2 made of titanium via the first joints 6, 7 made of silver solder, so that the joint strength between them can be maintained well.

Next, a method for manufacturing the joined structure 1 having the above configuration will be described. First, the second member 3 is spirally wound around the surface of the first member 2, and both ends of the second member 3 are fixed to adjacent parts of the second member 3 along the first member 2 with fixing members 4, 5 (see FIG. 1) such as staples. This maintains the state in which the second member 3 is wound around the first member 2.

Next, first joints 6, 7 are formed in a raised shape on both sides of the second member 3 on the surface of the first member 2 (first step). This first step can be performed, for example, by injecting an inert gas such as argon gas into the tube of the first member 2, applying titanium flux to the surface of the first member 2, and then pressing silver solder onto the surface of the first member 2 while heating the first member 2, or by pressing silver solder onto the surface of the first member 2 and heating the silver solder and flux to melt the silver solder on the surface of the first member 2.

Figure 2 (a) is a plan view of the main part showing the vicinity of one of the first joints 6 formed on the surface of the first member 2. The shape of the first joint 6 is not particularly limited, but in this embodiment, it is formed in a spot shape with a size required for joining. The other first joint 7 shown in Figure 1 is also formed in the same manner as the one of the first joints 6.

Next, the surface of the first member 2 is washed with water or the like to remove any burnt flux, and then flux is applied to the second member 3 and the first joints 6 and 7. The flux used here is preferably a solder flux, but it is also possible to use an iron flux for the second member 3 and an aluminum flux for the first joints 6 and 7.

Then, the second joints 8, 9 are formed by soldering the second member 3 to the first joints 6, 7 (second step). This second step can be performed, for example, by heating the first joints 6, 7 to attach a solder material to the first joints 6, 7, and then extending the solder material to the heated portion of the second member 3 to join the first joints 6, 7 and the second member 3.

Figure 2(b) is a plan view of the main part showing the vicinity of one of the second joints 8 formed on the surface of the first member 2. The second joint 8 is formed to be in close contact with the fin 3b and the first joint 6 of the second member 3 along the axial direction of the first member 2, and to cover the base 3a of the second member 3. The other second joint 9 shown in Figure 1 is also formed to be in close contact with the fin 3b and the second joint 7 of the second member 3 along the axial direction of the first member 2.

The manufacturing method of the joined structure 1 is not necessarily limited to this embodiment, and the joined structure 1 may be manufactured by other methods. For example, the joined structure 1 can be manufactured by fixing one end of the belt-like second member 3 to the surface of the first member 2 via the first joint 6 and the second joint 8, winding the second member 3 spirally around the surface of the first member 2, and then fixing the other end of the belt-like second member 3 to the surface of the first member 2 via the first joint 7 and the second joint 9. In this embodiment, the second member 3 is formed with an L-shaped cross section including the base 3a and the fin 3b, but it may be configured with only the fin 3b without the base 3a, and the fin 3b can be supported in an upright state by fixing both ends of the belt-like fin 3b to the first member 2 via the first joints 6, 7 and the second joints 8, 9.

The specific configuration and use of the joined structure 1 are not limited to this embodiment, and the present invention can be applied to various joined structures. The shape of the first member 2 is not particularly limited as long as it is made of titanium, and it may be, for example, plate-like or column-like in addition to tubular. The second member 3 is suitable for a thin member (e.g., 0.5 mm or less) like the fin material of this embodiment, but the shape of the second member 3 is also not particularly limited.

The present invention is preferably applicable when the second member 3 is made of a material with a low melting point, such as aluminum, but the present invention can also be applied when the second member 3 is made of other metals that can be soldered other than titanium, such as iron, copper, or alloys of these metals, or stainless steel, in addition to aluminum.

In this embodiment, the first joints 6, 7 are made of silver solder, taking into consideration compatibility with titanium and ease of use, but the first joints 6, 7 may also be made of solder materials containing one or more metals other than titanium, such as aluminum solder, copper solder, gold solder, nickel solder, etc., and can be appropriately selected taking into consideration the material of the second member 3, etc.

Reference Signs List 1: Joined structure 2: First member 3: Second member 6, 7: First joint 8, 9: Second joint

Claims (4)

A joined structure in which a first member made of titanium and a second member made of a metal other than titanium are joined,
the second member is joined to a first joint portion formed on a surface of the first member by using a brazing material made of a metal other than titanium via a second joint portion made of a solder material ;
The first joint portion includes silver solder . The joint structure according to claim 1 , wherein the second member is a band-shaped fin material made of aluminum and is spirally wound around a surface of the first member made of a heat transfer tube. The joint structure according to claim 2 , wherein the first joint portions are disposed adjacent to both sides of the second member along the axial direction of the first member. A method for manufacturing the joint structure according to any one of claims 1 to 3 , comprising the steps of:
a first step of melting a brazing material made of a metal other than titanium on a surface of the first member to form the first joint;
and a second step of forming the second joint portion by soldering the second member to the first joint portion ,
A method for manufacturing a joint structure , wherein the first joint portion contains silver solder .

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