JP2003117679A - Composite brazing filler metal and composite material for brazing and brazing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel composite brazing filler metal which has an excellent heat resistance and corrosion resistance, good brazing workability and excellent joining strength and toughness and a composite material for brazing and a brazing method. SOLUTION: The brazing filler metal for brazing base materials 5 to each other is formed by composing >=2 kinds of metals in order to lower the melting point and is so constituted that the structure after brazing thereof attains a phase consisting of a face centered cubic lattice (Fcc) or a phase consisting of the face centered cubic lattice and an intermetallic compound. As a result, the excellent heat resistance and corrosion resistance can be exhibited and the brazing workability is good and the excellent joining strength and toughness can be exhibited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite brazing material suitable for producing a brazing product such as a cooler for an exhaust gas recirculation system or a member for a fuel cell, which is required to have particularly excellent heat resistance and corrosion resistance. The present invention relates to a brazing composite material and a brazing method.

[0002]

2. Description of the Related Art Conventionally, a stainless base clad material has been used as a brazing member constituting a heat exchanger such as an oil cooler for an automobile. This is one in which one or both sides of a stainless steel plate that is the base material is clad with copper as a brazing material, and the brazing material at the joint of the members is heated above its melting point and welded to braze the base materials together. It is designed to be combined with each other.

As a brazing material for members made of stainless steel, Ni-based or Co-based alloys, various Ni brazing materials having excellent corrosion resistance at joints are specified by the JIS standard. Further, as this Ni brazing material, powdered Ni is used.
A powdered Ni brazing material obtained by adding 4 to 22% by weight of a metal powder selected from Ni, Cr, or a Ni—Cr alloy to the brazing material has also been proposed (JP 2000-107A).
883).

[0004]

By the way, these conventional brazing materials or composite materials for brazing are directly exposed to a high temperature and highly corrosive gas or liquid such as a heat exchanger, for example, an exhaust gas recirculation device (hereinafter referred to as "exhaust gas recirculation device"). EGR (Exhaust Gas Recirculat
ion)) or a cooler for reforming a fuel cell, it cannot exhibit sufficient heat resistance and corrosion resistance. Is significantly reduced.

On the other hand, various Ni as shown in JIS standards
Although the brazing material can exhibit excellent heat resistance and corrosion resistance as compared with the above stainless steel-based clad material, its form is powdery, so it requires a great deal of labor to apply it to each joint each time it is used. There is a problem that the required work is required, the productivity of the brazed product is remarkably lowered, and the manufacturing cost is increased.

Therefore, the present inventors have proposed a so-called brazing composite material having a brazing layer formed by alloying titanium or nickel with a metal such as copper or iron on the surface of stainless steel or the like as a base material. did. That is, although nickel and titanium can exhibit excellent corrosion resistance, their melting points are extremely high (about 1450 ° C. and 1690 ° C.), so it is difficult to function as a brazing material with only these metals. Approximately 1 by alloying metals such as iron and iron
Since the melting point can be lowered to about 200 ° C., excellent corrosion resistance and brazing function can be imparted.

However, when such a corrosion-resistant metal such as titanium or nickel is combined with another metal, depending on the combination, after brazing, the brazed portion is very brittle with the phase of the body-centered cubic lattice (Bcc). It was found that the phases composed of intermetallic compounds are formed, and the appearance of these phases significantly reduces the bonding strength and toughness (mechanical strength) of the brazed portion, and in the worst case, cracks and cracks occur.

Therefore, the present invention has been devised to solve the above problems, and its purpose is not only to exhibit excellent heat resistance and corrosion resistance but also to have good brazing workability and bonding strength. And a novel composite brazing material excellent in toughness, a composite material for brazing, and a brazing method.

[0009]

In order to achieve the above object, the first invention is, as shown in claim 1, a brazing material for brazing base materials to each other, which comprises two or more kinds in order to lower the melting point. And a structure after the brazing process is composed of a face-centered cubic lattice (Fcc) phase or a face-centered cubic lattice and intermetallic compound phase. Is a composite brazing material.

As a result, excellent heat resistance and corrosion resistance can be exhibited, the flowability of the brazing filler metal is better than that of titanium or nickel alone, and the handling is easier than that of powdery ones. Of course, the resulting structure after brazing becomes a phase composed of a face-centered cubic lattice (Fcc) or a coexistence of two phases of a phase composed of Fcc and a phase composed of an intermetallic compound. Therefore, excellent bonding strength and toughness can be exhibited.

Further, as described in claim 2, by suppressing the ratio of the intermetallic compound phase to 30% by volume or less,
Since the structure can be prevented from becoming hard and brittle, excellent bonding and toughness (mechanical strength) can be exhibited.

A second aspect of the present invention is a composite material for brazing, which is characterized in that these composite brazing materials are bonded to the surface of the base material in advance, as described in claim 3. Productivity can be improved.

A third aspect of the present invention is, in a brazing method for brazing base materials to each other by using these composite brazing materials, as set forth in claim 4, wherein the brazing material is heated from a molten state to 100%. The brazing method is characterized by cooling at a cooling rate of not more than ° C / sec. That is, by suppressing the cooling rate to 100 ° C./second or less, it is possible to suppress the production amount of the intermetallic compound in the brazed portion as described later, and it is possible to exhibit excellent bonding strength and toughness.

Further, as described in claim 5, even when the brazing composite materials are used together, if the so-called brazing composite materials are cooled at a cooling rate of 100 ° C./second or less from the molten state at the time of brazing, the same result is obtained. It is possible to suppress the amount of the intermetallic compound generated in the brazed portion, and it is possible to exhibit excellent bonding strength and toughness.

By adopting such a brazing method, a brazed product having excellent mechanical strength and high reliability can be manufactured with high productivity. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the accompanying drawings.

First, FIG. 1 shows an embodiment of a composite brazing material 1 according to the present invention.

As shown in the figure, this composite brazing material 1 has a plate-shaped nickel layer made of nickel or a nickel alloy and a non-nickel layer 3 made of titanium, a titanium alloy, copper, a copper alloy, iron or an iron alloy. It is composed of a laminated body.

Here, this laminate has, for example, a thickness of 0. A few meters
A strip of nickel or a nickel alloy having a strip shape of m and a non-nickel metal of the same strip are superposed and repeatedly rolled to obtain a desired thickness easily. Further, the lamination ratio (thickness) of the nickel layer 2 and the non-nickel layer 3 is not particularly limited, and by changing the ratio arbitrarily, the melting point temperature can be lowered to a desired melting point temperature (brazing temperature and heat resistant temperature). It can have a melting point. For example, when the ratio of the nickel layer 2 to the non-nickel layer 3 is about 1: 1 in such a form, the melting point temperature decreases to about 1200 ° C., and the heat resistance and brazing temperature (melt flow) in the vicinity thereof
Can be demonstrated.

However, as described above, when titanium is used as the non-nickel layer 3, the ratio is 40 w of the total.
It is suppressed to t% or less. That is, when the proportion of titanium exceeds 40 wt%, the structure of the brazed portion after brazing is almost always the phase of the intermetallic compound and the body-centered cubic lattice (B
This is because there is a possibility that it will become a phase of cc) and that the joint strength and toughness of the brazed portion will be significantly reduced.

Then, such a composite brazing material 1 of the present invention
Since it can be used as a brazing filler metal for heat exchangers exposed to high temperature and highly corrosive gases and liquids such as those mentioned above, for example, EGR coolers and fuel cell reforming coolers, it can exhibit excellent heat resistance and corrosion resistance. Since it can maintain excellent bond strength over a long period of time, has better flowability of molten metal than nickel or titanium brazing filler metal, and is easier to handle than powdered brazing filler metal. It is possible to significantly improve the property.

Further, since the formation structure of the brazed portion after brazing is the phase composed of the face-centered cubic lattice (Fcc) or the phase composed of Fcc and the intermetallic compound, as will be described later, this results in excellent bonding strength. And mechanical strength can be exerted.

As another embodiment of the present invention, FIG.
, The nickel layer 2 is formed into a bar or wire,
A laminated body having a circular cross section whose periphery is covered with the non-nickel layer 3 may be used. In addition, phosphorus is added to the nickel layer 2 in an amount of 0.
If it is contained in an amount of 02 to 10% by weight, or if it is further compounded with nickel-phosphorus plating to contain 0.02 to 10% by weight of phosphorus, the hot water flowability, wettability and oxidation resistance are remarkably improved. It is also possible to do. Here, the content of phosphorus is limited to 0.02 to 10% by weight. When the content of phosphorus is less than 0.02% by weight, the flowability of the molten metal cannot be improved, and when it exceeds 10% by weight, the brazing layer becomes brittle. This is because the vibration fatigue characteristics and the bonding strength are significantly reduced.
It is in the range of 8% by weight. Further, as shown in FIGS. 3 and 4, the non-nickel layer 3 may be formed by further two metal layers, for example, a titanium layer 3a made of titanium or a titanium alloy and a copper layer 3b made of copper or a copper alloy. The same effect as the above can be exhibited.

Next, FIG. 5 shows an embodiment of the brazing composite material 4 according to the second invention.

As shown, this brazing composite material 4
Is a composite brazing material 1 previously joined to the surface of a base material 5 made of a stainless steel plate or the like so as to be composited. Such brazing composite materials 4 or the brazing composite material If 4 and other base materials are brazed to each other, the brazing productivity is significantly improved in addition to the same effect as described above.

As another embodiment of the present invention, as shown in FIG. 6, the base material 5 may be rod-shaped or wire-shaped, and as shown in FIG. Three
It may be formed of two or more layers as shown in
Further, as shown in FIG. 8, the brazing layer 3 may be bonded not only to one surface but also to both surfaces depending on the application site.

[0027]

EXAMPLES Specific examples of the present invention will be described below together with comparative examples and conventional examples. (Example 1) First, SUS304 strips (thickness 2.5 mm)
After sequentially stacking copper strips (thickness 0.09 mm) and nickel strips (thickness 0.20 mm) by clad by a rolling method to stack the layers, the rolling is repeated and the total thickness of the brazing layers made of copper and nickel is increased. The thickness was 70 μm. Then, the composite material is heated in a vacuum furnace at 1200 ° C. to melt the brazing layer, and then the formation structure of the brazing portion, the proportion of the metal plan compound occupying the brazing layer, the cooling rate after brazing, the bonding strength, and the brazing strength. The processing characteristics after brazing and the brazing productivity were evaluated. The results are shown in Table 1.

Here, the determination of the formed structure after brazing and the proportion thereof were measured by analyzing the cross section of the brazing layer portion after brazing using a micro X-ray analyzer and observing with a metallographic microscope. The joint strength was evaluated by a vibration fatigue test. Further, the processing characteristics after brazing are as shown in FIG.
The base material 5 was bent at a right angle so that it was on the outside, and the appearance was evaluated by observing the appearance of cracks or cracks in the brazing layer 1 at the bent portions. (Example 2) A titanium strip (thickness 0.13 mm) and a nickel strip (thickness 0.10 mm) were clad by a rolling method in this order from the surface of the SUS304 strip (thickness 2.5 mm) and laminated, The same treatment as in Example 1 was performed, and the same evaluation was performed on the characteristics. (Example 3) Iron strips (thickness 0.10 mm), titanium strips (thickness 0.12 mm), nickel strips (thickness 0.15 mm) are rolled in this order from the surface of SUS304 strips (thickness 2.5 mm). The same treatment as in Example 1 was performed except that the layers were clad and laminated, and the same evaluation was performed on the characteristics. (Example 4) First, 304 SUS strips (thickness: 2.5 mm)
Iron strips (thickness 0.13 mm), titanium strips (thickness 0.02 mm), nickel strips (thickness 0.10 m)
m) was clad by a rolling method to be laminated, and rolling was repeated to obtain a total thickness of the brazing layer of iron, titanium and nickel of 70 μm. This composite is then
After heating in a vacuum furnace at 0 ° C. to melt the brazing layer, the brazing layer is cooled at a cooling rate of 85 ° C./sec to determine the proportion of the intermetallic compound in the formed structure after brazing and the brazing layer after brazing. It investigated by the method similar to Example 1. The results are shown in Table 2. (Examples 5 and 6) After melting the brazing layer, the same composite material as in Example 4 was formed except that the brazing layer was cooled at a cooling rate of 120 ° C / sec and 500 ° C / sec, respectively. went. (Comparative Example 1) A nickel strip (thickness 0.15 mm) was directly clad on the surface of SUS304 strip (thickness 2.5 mm) by a rolling method, and rolling was repeated to obtain a nickel thickness of 70 μm.
After setting m, this was heated in a vacuum furnace at 1200 ° C. to melt the brazing layer, and the characteristics thereof were evaluated by the same method as in Example 1. (Comparative Example 2) A copper strip (thickness: 0.05 mm) and a titanium strip (thickness: 0.
(20 mm) was compounded by a rolling method so that the total thickness of titanium and nickel was 70 μm, and the evaluation was performed in the same manner as in Example 1. (Comparative Example 3) A composite material similar to Comparative Example 2 was formed except that a copper strip was used instead of the iron strip shown in Comparative Example 2, and the characteristics thereof were evaluated by the same method as in Example 1. (Conventional Example 1) A commercially available powdered Ni brazing material melted with a synthetic resin binder is applied to one side of a SUS304 strip to form a brazing layer, which is then heated to 1200 ° C. in a vacuum furnace to form the brazing layer. After melting, the characteristics were evaluated in the same manner as in Example 1.

[0029]

[Table 1]

[0030]

[Table 2]

As a result, as is clear from Table 1, in Examples 1 to 3 according to the present invention, the produced tissue after brazing is a phase composed of Fcc or a phase composed of Fcc and an intermetallic compound. We were able to demonstrate excellent joint strength, workability, and brazing productivity. In particular, in Example 1 in which almost no intermetallic compound was formed, although the molten metal flowability was slightly inferior, the bonding strength and workability superior to any of the other Examples could be exhibited. Moreover, in Examples 4 to 6 in which the proportion of titanium was suppressed to 40 wt% or less,
As shown in Table 2, it was confirmed that the produced tissue after brazing was a phase composed of Fcc and an intermetallic compound, as in the above Examples. It was also found that the production rate of this intermetallic compound becomes smaller as the cooling rate after melting becomes slower, and especially at 100 ° C./sec or less, it can be seen that it can be reduced to such an extent that the bonding strength and toughness are hardly affected. It was

On the other hand, in Comparative Example 1 using nickel alone as the brazing material, it did not melt at the brazing temperature of 1200 ° C. and did not function as a brazing material. Further, in Comparative Examples 2 and 3 in which the proportion of titanium in the brazing layer exceeds 40 wt%, the formation structure after brazing is a phase composed of Bcc and an intermetallic compound, and the bonding strength is low. Moreover, cracks and cracks occur, making it difficult to put into practical use.

On the other hand, in Conventional Example 1 which has been conventionally used as a heat exchanger for automobile oil coolers and the like, its composition is a phase composed of Fcc and an intermetallic compound as in the case of this Example, and excellent bonding is achieved. Although it was possible to exert strength and workability, improvement in brazing productivity cannot be expected.

From the above results, in order to obtain sufficient bonding strength and processing characteristics after brazing, the proportion of the intermetallic compound showing the brazing layer after brazing is preferably 30% by volume or less, but more preferably Is 5 to 20% by volume. That is, when the intermetallic compound is scarcely generated or the ratio of the intermetallic compound is less than 5% by volume, the melting point of the brazing layer is not sufficiently lowered, and the flowability of the molten metal deteriorates. Is hard and brittle, and vibration fatigue characteristics and bonding strength are significantly reduced.

[0035]

In summary, according to the present invention, not only it has excellent corrosion resistance and heat resistance, but it also has excellent toughness and the processing characteristics after brazing are greatly improved. As a result, the production efficiency of the brazed product is improved, the manufacturing cost can be reduced, and the brazed product of high reliability and high quality can be obtained. .

[Brief description of drawings]

FIG. 1 is an enlarged sectional view showing an embodiment of a composite brazing material according to the present invention.

FIG. 2 is an enlarged sectional view showing another embodiment of the composite brazing material according to the present invention.

FIG. 3 is an enlarged sectional view showing another embodiment of the composite brazing material according to the present invention.

FIG. 4 is an enlarged cross-sectional view showing another embodiment of the composite brazing material according to the present invention.

FIG. 5 is an enlarged sectional view showing an embodiment of a brazing composite material according to the present invention.

FIG. 6 is an enlarged cross-sectional view showing another embodiment of the brazing composite material according to the present invention.

FIG. 7 is an enlarged sectional view showing another embodiment of the brazing composite material according to the present invention.

FIG. 8 is an enlarged sectional view showing another embodiment of the brazing composite material according to the present invention.

FIG. 9 is an explanatory diagram showing a processing characteristic evaluation method adopted in this embodiment.

[Explanation of symbols]

1 Composite brazing material 2 Nickel layer 3 Non-nickel layer 3a titanium layer 3b iron layer 4 Composite material for brazing 5 base materials

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayoshi Aoyama             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd. (72) Inventor Shirai Kaku             1-6-1, Otemachi, Chiyoda-ku, Tokyo             Standing Wire Co., Ltd.

Claims (6)

[Claims] 1. A brazing material for brazing base materials, which comprises a composite of two or more metals for lowering the melting point, and the texture after brazing is a face-centered cubic lattice (Fcc). A composite brazing material, characterized in that it is configured to be a phase composed of or a face-centered cubic lattice and a phase composed of an intermetallic compound. 2. The proportion of the intermetallic compound phase is 30% by volume.
The composite brazing material according to claim 1, wherein: 3. A composite material for brazing, comprising the composite brazing material according to claim 1 or 2 bonded to a surface of a base material. 4. A brazing method for brazing substrates together using the composite brazing material according to claim 1 or 2, wherein the brazing material is 100 ° C. /
A brazing method characterized by cooling at a cooling rate of less than a second. 5. A brazing method for brazing the brazing composite materials according to claim 3 or the brazing composite material and the base material together, wherein the brazing material is melted during brazing. A brazing method comprising cooling from a state at a cooling rate of 100 ° C./second or less. 6. A brazed product produced by the brazing method according to claim 4 or 5.