JP2010104999A - Composite material for brazing and brazed product - Google Patents

Abstract

Disclosed is a brazing composite material which suppresses material surface oxidation and corrosion during long-term storage in the atmosphere and has good brazing properties.
A base material 2 and a brazing layer 3 are combined and integrated, and in the brazing composite material 1 for brazing and joining to other members via the brazing layer 3, the base material 2 is Fe or an Fe-based alloy. The brazing layer 3 is composed of a Cu layer 4 formed on the surface of the substrate 2 and a Cu—Ni alloy layer 5 formed on the surface of the Cu layer 4.
[Selection] Figure 1

Description

  The present invention relates to a brazing composite material and a brazing product that can improve brazing performance, and can improve heat resistance and oxidation resistance performance, particularly in a brazing composite material (composite for brazing processing).

  A heat exchanger such as an oil cooler for automobiles is mainly composed of stainless steel as a base material, and has a multilayer structure from the viewpoint of thermal efficiency. When assembling a heat exchanger from a stainless steel plate, the pressed stainless steel plates are stacked and joined by brazing heat treatment. As the brazing material, Cu brazing paste and Cu foil are mainly used. These brazing operations require an operation of applying or sandwiching a brazing material for each of the stainless steel brazing portions to be laminated. If the number of laminations is large, the labor of the operation increases and the production efficiency decreases.

In order to simplify these operations, a clad material in which Cu, which functions as a brazing material, is clad and joined to the stainless steel plate surface in advance has been developed and applied. When this clad material is used, it is possible to omit the trouble of applying a Cu brazing or inserting a Cu foil for brazing and simplify the process. For example, Patent Document 1 describes a method for producing a Cu / stainless steel / Cu clad material.
JP-A-10-180464 International Publication No. 2005/061167 Pamphlet JP 2006-272364 A JP 2006-272363 A JP 2006-43749 A JP 2003-117686 A

  However, the conventional clad material using Cu / stainless steel has the following problems.

  Since the material constituting the heat exchanger has a complicated structure, a processing method such as a multistage press is used for the shape processing. Since the material is continuously supplied during processing, the clad material is prepared as a coil-shaped continuous material.

  When a material that is not flowing into the process is stored in the atmosphere for a long time, Cu on the surface of the material is gradually oxidized and discolored. Especially in places close to the sea, corrosion of the material surface by sea breeze proceeds at the same time, both of which have a problem that the appearance of the material is greatly impaired and the brazing property at the time of product application is deteriorated.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a brazing composite material and a brazing product that suppresses material surface oxidation and corrosion during long-term storage in the atmosphere and has good brazing properties.

  The present invention, which was created to achieve the above object, is a brazing composite material in which a base material and a brazing layer are composite-integrated and brazed to another member via the brazing layer. Is a Fe or Fe-based alloy, and the brazing layer is a brazing composite material comprising a Cu layer formed on the surface of the substrate and a Cu-Ni alloy layer formed on the surface of the Cu layer. is there.

  The thickness of the Cu—Ni alloy layer is preferably 1 μm or more.

  The Cu-Ni alloy layer may contain 10 to 30% by mass of Ni.

  The entire brazing layer preferably contains 3% by mass or less of Ni.

  The base material may be stainless steel.

  Moreover, this invention is the brazing product assembled using the said composite material for brazing.

  According to the present invention, it is possible to obtain an effect of enabling good brazing joining without damaging the appearance even when stored in the atmosphere for a long period of time and without significantly increasing the brazing temperature as compared with the prior art.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of a brazing composite material showing a preferred embodiment of the present invention.

  As shown in FIG. 1, the brazing composite material 1 according to the present embodiment mainly includes a heat exchanger (for example, an automobile oil cooler, an exhaust gas recirculation (EGR) cooler, and a fuel cell reformer cooler). Etc.) or as a fuel cell member.

  When the brazing composite material 1 is used in a heat exchanger, a base material such as rolled stainless steel becomes a plate that defines a flow path of the heat exchanger, and what joins the plates becomes a brazing layer.

  For example, after processing the brazing composite material 1 into an appropriate shape, the brazing composite material 1 is overlapped to form a heat exchanger assembly, which is heated and held at a high temperature of 1150 ° C. or lower in a heating furnace. And cool. As a result, the portions (brazing layer) where the brazing composite material 1 is in contact with each other are heated and melted and brazed. In FIG. 1, an example in which a brazing layer is combined with a plate-like base material such as a plate used in a heat exchanger as the brazing composite material 1 will be described.

  The brazing composite material 1 forms a brazing layer (brazing material) 3 formed by laminating two metal layers on the surface of a base material (base material) 2. The layer 3 is combined and integrated. Each metal layer of the brazing layer 3 includes a Cu layer 4 formed on the surface of the substrate 2 and a Cu—Ni alloy layer 5 as an outermost layer formed on the surface of the Cu layer 4.

  The base material 2 is formed in a plate shape with Fe or an Fe-based alloy. For example, an austenitic stainless steel such as SUS304 or a ferritic stainless steel such as SUS430 may be used as the Fe alloy. Other than SUS304 and SUS430, other stainless steels such as SUS310 and SUS316 can also be used.

  Since the Cu-Ni alloy has a higher melting point than Cu, the brazing composite material 1 has a higher brazing temperature than the conventional composite material composed of only a stainless steel plate and a Cu layer. Therefore, it is advisable to limit the Ni concentration and the thickness of the Cu—Ni alloy layer 5 so that the brazing temperature does not increase significantly compared to the conventional case.

  The Ni concentration (Ni ratio) contained in the entire brazing layer 3 composed of the Cu layer 4 mainly functioning as the brazing material and the Cu—Ni alloy layer 5 is 3% by mass or less, preferably 0.5 to 2.5. It is good that it is mass%, More preferably, it is 0.8-2.3 mass%. If the Ni concentration contained in the entire brazing layer exceeds 3% by mass, the melting point of the entire brazing layer rises by 15 ° C. or more, the brazing temperature exceeds 1150 ° C., and the heat load on the brazing heat treatment furnace increases. This leads to a reduction in the life of the furnace. Moreover, the function of the Cu-Ni alloy layer 5 for preventing surface oxidation and surface corrosion is not fully exhibited as the Ni concentration contained in the entire brazing layer is less than 0.5% by mass.

  The Ni concentration (Ni ratio) of the outermost Cu—Ni alloy layer 5 is 10 to 30% by mass, preferably 10 to 20% by mass, and more preferably 10 to 15% by mass. If the Ni concentration of the Cu—Ni alloy layer is less than 10% by mass, the effect of improving corrosion resistance is small, and if it exceeds 30% by mass, the difference in mechanical properties with the Cu layer 4 becomes large, and the clad bonding processability deteriorates. On the other hand, when the Ni concentration in the Cu—Ni alloy layer exceeds 30 mass%, the corrosion resistance becomes excessive, and the cost of the brazing composite material itself increases.

  The thickness of the outermost Cu—Ni alloy layer 5 is arbitrary, but is 1 μm or more, preferably 1 to 10 μm, and more preferably 1.1 to 6.0 μm. When the thickness of the Cu—Ni alloy layer is less than 1 μm, there is a high possibility that the oxidation and corrosion received during storage reach the inner Cu layer 4 at a portion where the thickness is further reduced during press working. The thickness of the Cu—Ni alloy layer 5 is preferably 1/10 or less of the entire thickness of the brazing layer 3 in relation to the entire brazing layer 3.

  The thickness of the entire brazing layer 3 is arbitrary as long as it is designed in a range that meets the above-mentioned conditions, but it is preferably 100 μm or less in consideration of dimensional changes during melting of the brazing.

  The operation of this embodiment will be described.

  The brazing composite material 1 is obtained by clad-bonding a Cu layer 4 and a Cu—Ni alloy layer 5 to a base material 2 and rolling them to form a brazing layer 3. When the brazing composite material 1 is used for a heat exchanger, the brazing composite material 1 and another member (bonded member) are heated and melted so that the brazing composite material 1 and the other member are in contact with each other. The part (the brazing layer 3) is heated and melted and brazed. The other member may be another brazing composite material or another base material.

  At the time of brazing, the brazing layer 3 is alloyed by mutual diffusion between the base material 2 and the metal layers constituting the brazing layer 3, and the entire brazing layer 3 is melted and solidified. A member is brazed and a brazing material is obtained. Furthermore, if this brazing material is assembled by processing it into a predetermined shape, for example, a brazed product such as a heat exchanger or a fuel cell member can be obtained.

  Since the outermost surface layer of the brazing composite material 1 is the Cu—Ni alloy layer 5, the progress of surface oxidation and surface corrosion of the brazing layer 3 is slow compared to the case where only Cu is used as the brazing material. Therefore, the composite material 1 for brazing has the characteristics that there is little surface discoloration compared with the case where only Cu is used for brazing, and the appearance is not impaired. Further, in the case where only Cu is used as the brazing material, the oxidation progresses and the ratio of copper oxide on the Cu surface increases, so that the brazing flowability at the time of brazing is deteriorated. Flowability deterioration can be suppressed and a good brazing state can be maintained.

  Furthermore, since the brazing composite material 1 contains not only Cu but also a Ni component in the brazing material portion after brazing, there is an advantage that the corrosion resistance of the brazing material surface is improved.

  Thus, in the brazing composite material 1, the Cu—Ni alloy layer 5 is superior in corrosion resistance and oxidation resistance as compared to pure Cu-based materials, so that the atmosphere is highly corrosive, such as in the air and further in the sea breeze. There is little material surface corrosion and oxidation during long-term storage under, and the appearance is not easily damaged.

  The Cu—Ni alloy layer 5 formed on the outermost surface has a higher melting point than Cu, but is sufficiently thinner than the thickness of the Cu layer 4 of the inner layer (second layer) that mainly functions as a brazing material. Since it is formed, the brazing composite material 1 has an increase in brazing temperature of less than 15 ° C., which is negligible compared to pure Cu.

  In addition, since the brazing composite material 1 finally contains a trace amount of Ni component melted and contained in the brazing material after brazing, the corrosion resistance and oxidation resistance of the brazing material after brazing are only Cu. Compared to brazing filler metal.

  Therefore, according to the composite material 1 for brazing, the surface corrosion resistance and the surface oxidation resistance in the state before brazing can be greatly improved, the appearance is not impaired even when stored for a long time in the atmosphere, and compared with the conventional case. Thus, the effect of enabling good brazing and joining without greatly increasing the brazing temperature can be obtained.

  In particular, the brazing composite material 1 is preferably used in a usage environment in which the usage environment after brazing is relatively harsh, and even when only Cu is used as the brazing material. In such a use environment, the brazing composite material 1 can sufficiently ensure surface corrosion resistance and surface oxidation resistance even if the amount of Ni contained in the alloy component after brazing is as small as 3% by mass or less. . For this reason, the brazing composite material 1 does not require a corrosion-resistant metal such as Cr, which has a high material cost, and the material cost is lower.

  In the above-described embodiment, the example in which the brazing layer 3 is combined and integrated on the surface of the base material 2 has been described, but the brazing layer 3 may be clad-bonded to both surfaces of the base material 2 and integrated.

  In addition, a brazing layer having a two-layer structure of a Cu layer and a Cu—Ni alloy layer in order on the outer periphery of a rod-like (a form in which the base material is a core material) or a wire-like base material is plated or by a pipe making method. It may be combined and integrated. These bar-like or wire-like brazing composites are for further strengthening the brazing of the joint portion by being arranged at the joint portion during brazing.

Example 1
Coiled Cu—Ni alloy plate (Cu-15 mass% Ni) with a thickness of 0.17 mm and a coiled Cu plate with a thickness of 2.0 mm are superposed to form a total of two layers, and cold rolled to obtain a plate thickness A 1.0 mm clad plate was obtained. Subsequently, a clad plate having a thickness of 0.1 mm was finished by cold rolling. The clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Cu surface of the clad material and the base material are in contact with each other, and are clad by a cold rolling method. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

(Example 2)
A coiled Cu—Ni alloy plate (Cu-10 mass% Ni) with a thickness of 0.6 mm and a coiled Cu plate with a thickness of 2.0 mm are stacked to form a total of two layers, and cold rolled to obtain a plate thickness A 1.0 mm clad plate was obtained. Subsequently, a clad plate having a thickness of 0.1 mm was finished by cold rolling. The clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Cu surface of the clad material and the base material are in contact with each other, and are clad by a cold rolling method. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

(Example 3)
A coiled Cu—Ni alloy plate (Cu-15 mass% Ni) with a plate thickness of 0.11 mm and a coiled Cu plate with a plate thickness of 2.0 mm are superposed to form a total of two layers, and cold rolled to obtain a plate thickness A 1.0 mm clad plate was obtained. Subsequently, a clad plate having a thickness of 0.1 mm was finished by cold rolling. The clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Cu surface of the clad material and the base material are in contact with each other, and are clad by a cold rolling method. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

Example 4
A coiled Cu—Ni alloy plate (Cu-10 mass% Ni) with a plate thickness of 0.35 mm and a coiled Cu plate with a plate thickness of 2.0 mm are stacked to form a total of two layers, and cold rolled to obtain a plate thickness A 1.0 mm clad plate was obtained. Subsequently, a clad plate having a thickness of 0.1 mm was finished by cold rolling. The clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Cu surface of the clad material and the base material are in contact with each other, and are clad by a cold rolling method. Furthermore, it cold-rolled and produced the brazing composite material 1 of thickness 0.5mm.

(Comparative Example 1)
A coiled Cu—Ni alloy plate (Cu-3 mass% Ni) having a plate thickness of 1.33 mm and a coiled Cu plate having a plate thickness of 2.0 mm are overlapped to form a total of two layers, and cold rolled to obtain a plate thickness A 1.0 mm clad plate was obtained. Subsequently, a clad plate having a thickness of 0.1 mm was finished by cold rolling. The clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Cu surface of the clad material and the base material are in contact with each other, and are clad by a cold rolling method. Furthermore, it cold-rolled and produced the composite base material of thickness 0.5mm.

(Comparative Example 2)
A coiled Cu—Ni alloy plate (Cu-2 mass% Ni) with a plate thickness of 0.86 mm and a coiled Cu plate with a plate thickness of 2.0 mm are superposed to form a total of two layers, and cold rolled to obtain a plate thickness A 1.0 mm clad plate was obtained. Subsequently, a clad plate having a thickness of 0.1 mm was finished by cold rolling. The clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Cu surface of the clad material and the base material are in contact with each other, and are clad by a cold rolling method. Furthermore, it cold-rolled and produced the composite base material of thickness 0.5mm.

(Comparative Example 3)
A coiled Cu—Ni alloy plate (Cu-15 mass% Ni) with a plate thickness of 1.0 mm and a coiled Cu plate with a plate thickness of 2.0 mm are stacked to form a total of two layers, and cold rolled to obtain a plate thickness A 1.0 mm clad plate was obtained. Subsequently, a clad plate having a thickness of 0.1 mm was finished by cold rolling.

  The clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Cu surface of the clad material and the base material are in contact with each other, and are clad by a cold rolling method. Furthermore, it cold-rolled and produced the composite base material of thickness 0.5mm.

(Comparative Example 4)
A coiled Cu—Ni alloy plate (Cu-10 mass% Ni) having a plate thickness of 1.33 mm and a coiled Cu plate having a plate thickness of 2.0 mm are overlapped to form a total of two layers, and cold rolled to obtain a plate thickness A 1.0 mm clad plate was obtained. Subsequently, a clad plate having a thickness of 0.1 mm was finished by cold rolling.

  The clad material and the stainless steel strip (SUS304, thickness 2.5 mm) are arranged so that the Cu surface of the clad material and the base material are in contact with each other, and are clad by a cold rolling method. Furthermore, it cold-rolled and produced the composite base material of thickness 0.5mm.

(Conventional example)
A coiled Cu plate having a plate thickness of 2.0 mm and a stainless steel strip (SUS304, thickness 2.5 mm) were arranged and cold-rolled to obtain a clad plate having a plate thickness of 1.4 mm. Subsequently, a clad plate having a thickness of 0.5 m was finished by a cold rolling method.

  The brazing composite material 1 produced in Examples 1 to 4 above, Comparative Examples 1 to 4 and the composite material produced in the conventional example were sampled, and a half year exposure experiment was conducted in a place where the wind from the sea was directly blown. Went. The appearance of the sample surface after the exposure test was observed.

  Next, the sample subjected to the exposure test was cut into a size of 25 mm × 20 mm, and a metal pipe (made of SUS304, outer diameter φ6 mm (thickness 1 mm) × 15 mm) 21 (see FIG. 2) was placed in the center of the surface. Fixed and brazed. FIG. 2 shows a schematic cross-sectional view of a sample used for evaluation. Brazing heat treatment conditions were 1150 ° C. × 15 min and the degree of vacuum was 0.5 Pa. The appearance of the sample after the brazing test was observed, and a cross-sectional investigation was further conducted. The ratio of the cross-sectional area of the fillet formed by the flow of the braze after brazing as a numerator was evaluated as an index of brazing performance (fillet-forming ability). It can be determined that the greater the numerical value (the closer it is to 1), the higher the brazing property.

  Here, the fret forming ability will be briefly described. As shown in FIGS. 3 (a) and 3 (b), the fillet (brazing fillet) 31 includes a joined object and an object to be joined (in FIG. 3 (a) and FIG. 3 (b), a metal pipe 21). The solder accumulated in the contact portion forms a concave portion with a gentle curvature due to surface tension, and strictly speaking, depending on the shape, the greater the amount of brazing, the better the joint strength.

  The relationship between fillet forming ability and hot water flowability will be briefly described. Strictly speaking, “hot water flowability” is a broad meaning that indicates the ease of flow of wax, and “fillet forming ability” is appropriate for the viscosity and wettability (related to the magnitude of surface tension) of wax flow and wax. There is a nuance that the right balance determines its performance. It can be interpreted that “fillet forming ability” is an index of “hot water flowability”. However, “the flowability of the hot water is good” means that the wax flows and fills the gaps in the joint, and further, fillets are formed and sufficient joining is performed, which means “high fillet forming ability”. Is almost equivalent.

  Table 1 shows the appearance observation results and the brazing test results after the exposure test in each of the examples, comparative examples, and conventional examples.

  According to Table 1, since the Ni concentration in the Cu-Ni alloy is as low as less than 10% by mass in the comparative examples 1 and 2 and the conventional example, the surface after the exposure test undergoes intense oxidation and corrosion, resulting in significant surface discoloration. It was observed. On the other hand, Examples 1-4 and Comparative Examples 3 and 4 had little surface discoloration and the surface gloss was also maintained.

  In Comparative Examples 3 and 4, since the Ni concentration in the entire brazing layer is as large as more than 3 mass%, the fillet forming ability is as small as 0.5 or less, and sufficient brazing joining is not performed. On the other hand, in Examples 1 to 4, Comparative Examples 1 and 2, and the conventional example, it can be judged that the fillet forming ability is 0.7 or more and the brazing joint is sufficiently performed.

  Accordingly, the overall evaluation is as shown in Table 1, and Examples 1 to 4 have good appearance observation results after the corrosion test and high brazing fillet-forming ability, so compared with Comparative Examples 1 to 4 and the conventional example. Thus, the appearance discoloration is small, and sufficient brazing joining is possible without significantly increasing the conventional brazing temperature.

It is a cross-sectional view which shows an example of the composite material for brazing which shows suitable embodiment of this invention. It is a cross-sectional view of the sample (before brazing) for evaluating a brazing state using the brazing composite material shown in FIG. FIG. 3A is an external view of a sample (after brazing) for evaluating the brazing state, and FIG. 3B is a cross-sectional view thereof.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Composite material for brazing 2 Base material 3 Brazing layer 4 Cu layer 5 Cu-Ni alloy layer

Claims (6)

  In a brazing composite material in which a base material and a brazing layer are combined and integrated, and brazing and joining to another member via the brazing layer, the base material is Fe or an Fe-based alloy, and the brazing layer includes: A brazing composite material comprising a Cu layer formed on the surface of the base material and a Cu-Ni alloy layer formed on the surface of the Cu layer.   The brazing composite material according to claim 1, wherein the Cu—Ni alloy layer has a thickness of 1 μm or more.   The brazing composite material according to claim 1 or 2, wherein the Cu-Ni alloy layer contains 10 to 30% by mass of Ni.   The brazing composite material according to any one of claims 1 to 3, wherein the entire brazing layer contains 3 mass% or less of Ni.   The brazing composite material according to any one of claims 1 to 4, wherein the base material is stainless steel.   A brazed product assembled using the brazing composite material according to any one of claims 1 to 5.

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